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First principles investigations are performed to understand the spin-polarized transport in Magnetic Tunnel Junctions (MTJs) consisting of an out-of-plane graphene sheet as a barrier in between two CrO 2 Half-Metallic-Ferromagnetic (HMF) electrodes. Upon comparison of the results with the results of in-plane graphene based MTJs reported in the past, it is observed that out-of-plane structures offer a high TMR of ∼100% and the transport phenomenon is tunneling since there are no transmission states near the Fermi level. However, in in-plane structures, the transport phenomenon cannot be tunneling since there are a significant number of transmission states near the Fermi level, although a high Magneto Resistance (MR) of ∼90% is observed. Both the TMR and Spin Injection Efficiency η (Spin-Filtration) are higher in out-of-plane structures in comparison to in-plane structures, which is due to the graphene sheet acting as a perfect barrier in out-of-plane structures, which results in negligible spin down current (I↓) in both the Parallel Configuration (PC) and Antiparallel Configuration (APC).
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Enhancing TMR and spin-filtration by using out-of-plane graphene insulating barrier in MTJs.
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Physical chemistry chemical physics : PCCP
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chemistry
| 2,148 | 13 |
Metal clusters have drawn continuous interest because of their high potential for the assembly of matter with special properties that may significantly differ from the corresponding bulk. Controlled combination of particular elements in one nanoparticle can increase the options for the creation of new materials for photonic, catalytic, or electronic applications. Superfluid helium droplets provide confinement and ultralow temperature, i.e. an ideal environment for the atom-by-atom aggregation of a new nanoparticle. This perspective presents a review of the current research progress on the synthesis of tailored metal and metal oxide clusters including core-shell designs, their characterization within the helium droplet beam, deposition on various solid substrates, and analysis via surface diagnostics. Special attention is given to the thermal properties of mixed metal clusters and questions about alloy formation on the nanoscale. Experimental results are accompanied by theoretical approaches employing computational chemistry, molecular dynamics simulations and He density functional theory.
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Metal clusters synthesized in helium droplets: structure and dynamics from experiment and theory.
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Physical chemistry chemical physics : PCCP
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chemistry
| 2,148 | 13 |
Control of the interfacial structures of ionic liquids (ILs) at charged interfaces is important to many of their applications, including in energy storage solutions, sensors and advanced lubrication technologies utilising electric fields. In the case of the latter, there is an increasing demand for the study of non-halogenated ILs, as many fluorinated anions have been found to produce corrosive and toxic halides under tribological conditions. Here, the interfacial structuring of a series of four imidazolium ILs ([CnC1Im]) of varying alkyl chain lengths (n = 5, 6, 7, 10), with a non-halogenated borate-based anion ([BOB]), have been studied at charged interfaces using sum frequency generation (SFG) spectroscopy and neutron reflectivity (NR). For all alkyl chain lengths, the SFG spectra show that the cation imidazolium ring responds to the surface charge by modifying its orientation with respect to the surface normal. In addition, the combination of SFG spectra with electrochemical NR measurements reveals that the longest alkyl chain length (n = 10) forms a bilayer structure at all charged interfaces, independent of the ring orientation. These results demonstrate the tunability of IL interfacial layers through the use of surface charge, as well as effect of the cation alkyl chain length, and provide valuable insight into the charge compensation mechanisms of ILs.
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Interfacial structuring of non-halogenated imidazolium ionic liquids at charged surfaces: effect of alkyl chain length.
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Physical chemistry chemical physics : PCCP
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chemistry
| 2,148 | 13 |
In this work we study mechanisms of solvent-mediated ion interactions with charged surfaces in ionic liquids by molecular dynamics simulations, in an attempt to reveal the main trends that determine ion-electrode interactions in ionic liquids. We compare the interfacial behaviour of Li(+) and K(+) at a charged graphene sheet in a room temperature ionic liquid, 1-butyl-3-methylimidazolium tetrafluoroborate, and its mixtures with lithium and potassium tetrafluoroborate salts. Our results show that there are dense interfacial solvation structures in these electrolytes that lead to the formation of high free energy barriers for these alkali metal cations between the bulk and direct contact with the negatively charged surface. We show that the stronger solvation of Li(+) in the ionic liquid leads to the formation of significantly higher interfacial free energy barriers for Li(+) than for K(+). The high free energy barriers observed in our simulations can explain the generally high interfacial resistance in electrochemical storage devices that use ionic liquid-based electrolytes. Overcoming these barriers is the rate-limiting step in the interfacial transport of alkali metal ions and, hence, appears to be a major drawback for a generalised application of ionic liquids in electrochemistry. Some plausible strategies for future theoretical and experimental work for tuning them are suggested.
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Molecular origin of high free energy barriers for alkali metal ion transfer through ionic liquid-graphene electrode interfaces.
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Physical chemistry chemical physics : PCCP
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chemistry
| 2,148 | 13 |
Gradient metasurfaces have attracted much attention due to intriguing wavefront and polarization manipulation. Here, a bilayer gradient metasurface is constructed by use of a rectangular nanorod layer and its complementary nanoaperture. It reveals asymmetric anomalous reflection and symmetric anomalous transmission for two counter-propagating directions. The dependence of the anomalous reflection and transmission phenomena on nanostructure thickness are numerically studied in optical frequencies. The increasing metallic layer thickness of the gradient metasurface greatly enhances anomalous reflection of the left-handed circularly polarized wave (LCP) for the nanorod side and suppresses anomalous reflection for the other side. Both resonant frequencies of anomalous reflection and transmission linearly shift with the refractive index. The bilayer gradient metasurface is important for realizing wavefront modulation and optical sensing.
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Large asymmetric anomalous reflection in bilayer gradient metasurfaces.
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Optics express
|
physics
| 2,034 | 56 |
One of the fascinating topological phenomena is the edge state in one-dimensional system. In this work, the topological photonics in the dimer chains composed by the split ring resonators are revealed based on the Su-Schrieffer-Heeger model. The topologically protected photonic edge state is observed directly with the in situ measurements of the local density of states in the topological nontrivial chain. Moreover, we experimentally demonstrate that the edge state localized at both ends is robust against a varied of perturbations, such as losses and disorder. Our results not only provide a versatile platform to study the topological physics in photonics but also may have potential applications in the robust power transfer.
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Experimental demonstration of the robust edge states in a split-ring-resonator chain.
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Optics express
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physics
| 2,034 | 56 |
We consider the generation of photon pairs by spontaneous four-wave mixing in ring resonators, as described by Clemmen et al. in Opt. Express17, 16558 (2009). We show that the theoretical limit predicted for the generation rate in their Erratum-Opt. Express 18, 14107 (2010)-is far too large due to an incorrect definition of a field enhancement factor.
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Continuous wave photon pair generation in silicon-on-insultator waveguides and ring resonators and erratum: comment.
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Optics express
|
physics
| 2,034 | 56 |
A measurement method that can be used to extract the relative intensity noise of a nanolaser is introduced and analyzed. The method is based on optical injection of emission from a nanolaser, serving as a master oscillator, transferring its intensity fluctuations to a low-noise semiconductor laser serving as a slave oscillator. Using the stochastic rate equation formalism, we demonstrate that the total relative intensity noise of the system is a weighted superposition of the relative intensity noise of individual lasers. We further discuss the analytical relations that can be used to extract the relative intensity noise spectrum of a nanolaser. Finally, we use mutual correlation as a mathematical tool to quantify the degree of resemblance between the injected and extracted intensity fluctuations, theoretically confirming that the spectra are at least 97% correlated within the 3-dB bandwidth when an injection strength is chosen properly.
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Intensity noise and bandwidth analysis of nanolasers via optical injection.
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Optics express
|
physics
| 2,034 | 56 |
Computer-generated holography at high resolutions is a computationally intensive task. Efficient algorithms are needed to generate holograms at acceptable speeds, especially for real-time and interactive applications such as holographic displays. We propose a novel technique to generate holograms using a sparse basis representation in the short-time Fourier space combined with a wavefront-recording plane placed in the middle of the 3D object. By computing the point spread functions in the transform domain, we update only a small subset of the precomputed largest-magnitude coefficients to significantly accelerate the algorithm over conventional look-up table methods. We implement the algorithm on a GPU, and report a speedup factor of over 30. We show that this transform is superior over wavelet-based approaches, and show quantitative and qualitative improvements over the state-of-the-art WASABI method; we report accuracy gains of 2dB PSNR, as well improved view preservation.
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Accelerated computer generated holography using sparse bases in the STFT domain.
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Optics express
|
physics
| 2,034 | 56 |
For an on-orbit lasercom receiver, the space thermal environment, microgravity environment and the adjustment error will deform the optical antenna, distorting the received wavefront and deteriorating the system performance. The axial non-confocal antenna is a deformed antenna caused by the despace of the secondary or primary mirror. Based on the simplified combination method of ray tracing and diffraction theory (simplified CMRD, or SCMRD), the calculation model of the normalized intensity distribution (NID) and the normalized received power (NRP) is established for an axial non-confocal antenna. The numerical results show that, the axial non-confocal antenna will flatten the received light spot, causing interruption of the communication link and deterioration of the bit error rate (BER) performance. The quantitative relations of the NID versus the axial non-confocal distance and the NRP versus the axial non-confocal distance would provide a reference for optical design, structural design, thermal design, assembly and adjustment accuracy design and detector selection. Besides, the numerical results are compared to those calculated by the wavefront fitting method and CMRD. The pros and cons of all methods are discussed. This work would advance the development of extending the SCMRD to analyze other deformed antennas' impact on an on-orbit lasercom receiver.
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Impact of an axial non-confocal antenna on the on-orbit lasercom receiver analyzed by the simplified combination method of ray tracing and diffraction theory.
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Optics express
|
physics
| 2,034 | 56 |
We demonstrate optically induced crossover from a weak to a strong coupling regime in a single photonic system consisting of propagating surface plasmon polaritons (SPPs) on a planar silver film and ultraviolet (UV)-switchable photochromic molecules. A gradual increase is observed in the vacuum Rabi splitting upon increasing UV exposure, along with intriguing behavior, where the reflectivity initially decreases due to increased losses at the weak coupling regime, and then increases due to the emergence of strongly coupled modes and the associated band gap formation at the resonance frequency of the uncoupled states. This work explicitly demonstrates the optical tunability of the degree of hybridization of the SPP and exciton modes, spanning the range from weak to intermediate and finally to the strong coupling regime.
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Optically induced crossover from weak to strong coupling regime between surface plasmon polaritons and photochromic molecules.
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Optics express
|
physics
| 2,034 | 56 |
We study and demonstrate the efficient parametric amplification of spectrally incoherent broadband nanosecond pulses to high energies. Signals composed of mutually incoherent monochromatic lines or amplified spontaneous emission are amplified in a sequence of optical parametric amplifiers pumped at 526.5 nm, with the last amplifier set in a collinear geometry. This configuration results in 70% conversion efficiency from the pump to the combined signal and idler, with a combined energy reaching 400 mJ and an optical spectrum extending over 60 nm around 1053 nm. The spatial, spectral, and temporal properties of the amplified waves are investigated. The demonstrated high conversion efficiency, spectral incoherence, and large bandwidth open the way to a new generation of high-energy, solid-state laser drivers that mitigate laser-plasma instabilities and laser-beam imprint via enhanced spectral bandwidth.
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High-energy parametric amplification of spectrally incoherent broadband pulses.
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Optics express
|
physics
| 2,034 | 56 |
An improved moth-flame optimization (IMFO) algorithm is proposed to increase the location accuracy of a vision measurement system. This algorithm can optimize the initial pose parameters by improving a series of random solutions to the required precision. A measurement experiment system of space manipulator is designed to precision test. The IMFO algorithm is evaluated on 23 benchmark functions and measurement experiments for pose, and the results are verified by a comparative study with self-adaptive differential evolution (SaDE), moth-flame optimization (MFO), and proactive particle swarm optimization (PPSO). The statistical results of the benchmark functions show that the IMFO algorithm can provide very promising and competitive results. Additionally, the experimental results of pose measurement show that the accuracy of the IMFO algorithm is approximately twice higher than that of other three algorithms. All in all, the experiments indicate that the IMFO algorithm has a good optimization ability to complete the visual identification accurately.
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Application of vision measurement model with an improved moth-flame optimization algorithm.
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Optics express
|
physics
| 2,034 | 56 |
THz conductivity of large area MoS 2 and MoSe 2 monolayers as well as their vertical heterostructure, MoSe 2 MoS 2 is measured in the 0.3-5 THz frequency range. Compared to the monolayers, the ultrafast THz reflectivity of the MoSe 2 MoS 2 heterobilayer is enhanced many folds when optically excited above the direct band gap energies of the constituting monolayers. The free carriers generated in the heterobilayer evolve with the characteristic times found in each of the two monolayers. Surprisingly, the same enhancement is recorded in the ultrafst THz reflectivity of the heterobilayer when excited below the MoS 2 bandgap energy. A mechanism accounting for these observations is proposed.
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Enhancement in optically induced ultrafast THz response of MoSe2MoS2 heterobilayer.
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Optics express
|
physics
| 2,034 | 56 |
A novel membrane-based tunable liquid aspherical lens design capable of dynamically reducing spherical aberration over certain focal length tuning range is presented. Different from conventional treatment using elastic membrane with uniform thickness, in current case, the membrane's cross-section is designed to be a plano-convex shape with well-defined aspherical contour. A brand new design flow combining optical ray-tracing and mechanical finite element analysis is especially developed, in which through properly selecting the initial focal length and the center membrane thickness with respect to particularly designed figure of merit (FOM), the membrane can be flexibly optimized to achieve dynamic spherical aberration correction capability over the desired focal length range. For proof of concept demonstration, a tunable aspherical lens with clear aperture of 4 mm is designed. Compared with conventional counterpart, after being individually optimized using current design strategy, lenses with distinctly reduced spherical aberration have been successfully achieved over different focal length tuning ranges. Besides, no special refractive index matching between the filling liquid and the membrane is required, making current design more practical in real applications.
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Universal membrane-based tunable liquid lens design for dynamically correcting spherical aberration over user-defined focal length range.
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Optics express
|
physics
| 2,034 | 56 |
We demonstrate an air-core single-mode hollow hybrid waveguide that uses Bragg reflector structures in place of the vertical metal walls of the standard rectangular waveguide or via holes of the so-called substrate integrated waveguide. The high-order modes in the waveguide are substantially suppressed by a modal-filtering effect, making the waveguide operate in the fundamental mode over more than one octave. Numerical simulations show that the propagation loss of the proposed waveguide can be lower than that of classic hollow metallic rectangular waveguides at terahertz frequencies, benefiting from a significant reduction in Ohmic loss. To facilitate fabrication and characterization, a proof-of-concept 20 to 45 GHz waveguide is demonstrated, which verifies the properties and advantages of the proposed waveguide. A zero group-velocity dispersion point is observed at near the middle of the operating band, which is ideal for reducing signal distortion. This work offers a step towards a hybrid transmission-line medium that can be used in a variety of functional components for multilayer integration and broadband applications.
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Substrate integrated Bragg waveguide: an octave-bandwidth single-mode hybrid transmission line for millimeter-wave applications.
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Optics express
|
physics
| 2,034 | 56 |
We theoretically and experimentally examined the effects of the different positions between receiving lens (RL) and detector, namely, defocus, off-axis, and tilt, on the time-domain pulsed echo laser profile (TDPELP). Results show that distortions including saturation and broadening of TDPELP are obtained, regardless of the position between RL and detector. Thus, we adjust the focal length of RL to successfully obtain an optimal TDPELP using tunable lens under extreme situations, such as too strong or too weak intensity of the TDPELP.
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Improving the performance of time-domain pulsed echo laser profile using tunable lens.
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Optics express
|
physics
| 2,034 | 56 |
We demonstrate a technique to continuously tune center frequency and repetition rate of optical frequency combs generated in silicon microring modulators and bandwidth scale them. We utilize a drive frequency dependent, microwave power induced shifting of the microring modulator resonance. In this work, we demonstrate center frequency tunability of frequency combs generated in silicon microring modulators over a wide range (∼8nm) with fixed number of lines. We also demonstrate continuously tunable repetition rates from 7.5GHz to 15GHz. Further, we use this effect to demonstrate a proof-of-principle experiment to bandwidth scale an 8-line (20dB band) comb generated from a single ring modulator driven at 10GHz to a comb with 12 and 15 lines by cascading two and three ring modulators, respectively. This is accomplished by merging widely spaced ring modulator resonances to a common location, thus coupling light simultaneously into multiple cascaded ring modulators.
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Microwave power induced resonance shifting of silicon ring modulators for continuously tunable, bandwidth scaled frequency combs.
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Optics express
|
physics
| 2,034 | 56 |
Time multiplexing is a super-resolution technique that sacrifices time to overcome the resolution reduction obtained because of diffraction. There are many super resolution methods based on time multiplexing, but all of them require a priori knowledge of the time changing encoding mask, which is projected on the object and used to encode and decode the high-resolution information. In this paper, we present a time multiplexing technique that does not require the a priori knowledge on the projected encoding mask. First, the theoretical concept of the technique is demonstrated; then, numerical simulations and experimental results are presented.
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Time multiplexing super-resolved imaging without a priori knowledge of the spatial distribution of the encoding structured illumination.
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Optics express
|
physics
| 2,034 | 56 |
Based on an integrated silicon platform, we present an ultracompact structure to generate optical orbital angular momentum (OAM) modes, where only a waveguide with a specially designed trench is involved. Single-trench waveguide can support two orthogonal LP-like modes whose optical axes are rotated by around 45° with respect to the horizontal and vertical directions. By optimizing the structure parameters, OAM modes with topological charges of + 1 and -1 can be selectively generated by combining two orthogonal LP-like modes with different propagation constants. We study the structure parameters for both x- and y-polarizations over a wide wavelength range from 1.45 µm to 1.65 µm. The average mode purities are close to 90% for x- and y-polarizations. Moreover, we design an on-chip OAM modes (de)multiplexer (OAM 0 , OAM ± 1 ) for x-polarization based on trench silicon waveguides. It is shown that the mode extinction ratio can achieve approximately 20 dB from 1.52 µm to 1.58 µm.
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On-chip orbital angular momentum modes generator and (de)multiplexer based on trench silicon waveguides.
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Optics express
|
physics
| 2,034 | 56 |
To develop new efficient phosphors for LEDs based on multifunctional applications, a series of Ce 3+ /Mn 2+ activated Ca 7 (PO 4 ) 2 (SiO 4 ) 2 (CPS) samples were prepared by solid-state reaction method. Upon 365 nm excitation, a broad emission band around 439 nm in the Ce 3+ -single-doped CPS was observed. The optimal Ce 3+ concentration was determined to be 3%, for which the quantum efficiency was obtained to be 90.4%, higher than that of the commercial BAM phosphor. By monitoring 458 nm, an intense and broad excitation band was found from 240 to 400 nm, which can match well with the near-ultraviolet (NUV) LED chip. For Ce 3+ -Mn 2+ codoped CPS, a new red emission band belonging to Mn 2+ appeared and an energy transfer from Ce 3+ to Mn 2+ was confirmed. It was also found that the emission spectra of Ce 3+ /Mn 2+ could well cover the optical absorption bands of plants. The fabrication of the phosphors on NUV LED chip indicates that the present phosphors could be promising in solid lighting and plants growth.
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Ce3+/Mn2+-activated Ca7(PO4)2(SiO4)2: efficient luminescent materials for multifunctional applications.
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Optics express
|
physics
| 2,034 | 56 |
We demonstrate a simple and robust method to write a phase-shifted helical long-period fiber grating (HLPG), where an equivalent phase-shift is formed by changing the local period of the grating during the fabrication process. Furthermore, we propose and demonstrate a simple method to characterize the phase-shift formed in a HLPG, which is realized by directly analyzing the imaging pattern of the fabricated HLPG using a stereo microscope under a white light illumination. Unlike the previous methods which are indirectly realized either by measuring the transmission spectrum of the fabricated HLPG or by analyzing the differential interference contrast (DIC) microscopic images of the fabricated HLPG, the proposed method can be used to well estimate the grating period as well as the phase-shift inserted in the HLPG in situ, which could considerably facilitate the fabrication technique of the HLPG by using CO<sub>2</sub> laser.
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Phase-shifted helical long-period fiber grating and its characterization by using the microscopic imaging method.
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Optics express
|
physics
| 2,034 | 56 |
By using the transfer matrix method, we analyze the optical properties of periodically sparse patterned microring resonators in the resonator-waveguide system. The dispersion relation of a periodically sparse patterned microring is investigated theoretically. Two kinds of modes supported by the periodically sparse patterned microring resonators, traveling modes and stationary modes, are found. We also derive the reflectivity of the microring resonator side-coupled to a waveguide and find that just the stationary modes lead to total reflections. Traveling modes do not reflect, which can be used to extend free spectral range. All the transmission properties are confirmed by the finite-difference time-domain method numerically.
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Transmission properties of periodically sparse patterned microring resonators.
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Optics express
|
physics
| 2,034 | 56 |
We report the study of the resistance of archetypal MOFs (MILs, HKUST-1, UiO-66, and ZIF-8) under gamma irradiation. The different porous solids were irradiated with doses up to 1.75 MGy. All the MOFs constructed with transition metals (Cu 2+ , Zn 2+ , Zr 4+ ) exhibit an evident destruction of the framework, whereas the compounds constructed with aluminium remain intact.
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Stability of metal-organic frameworks under gamma irradiation.
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Chemical communications (Cambridge, England)
|
chemistry
| 540 | 13 |
By using an electrochemical strategy, we demonstrated that ferrous ions are capable of decreasing bacterial EET activity in a certain potential range where the conduction-band edge of natural abundant iron(III) oxides is located. It is proposed that ferrous ions enable alteration of the formal potential of outer membrane c-type cytochromes, a crucial protein involved in the EET process.
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Ferrous ion regulated extracellular electron transfer: towards self-suppressed microbial iron(III) oxide reduction.
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Chemical communications (Cambridge, England)
|
chemistry
| 540 | 13 |
Development of reliable and affordable quantitative methods for miRNAs with high specificity and sensitivity is a central challenge to make miRNA testing a routine part of medical care with respect to cancer. Herein, we propose a strategy for glucoamylase-encapsulated liposome-encoded magnetic beads initiated by padlock exponential rolling circle amplification (P-ERCA) for portable and accurate quantification of miRNA by using a glucometer readout.
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Liposome-encoded magnetic beads initiated by padlock exponential rolling circle amplification for portable and accurate quantification of microRNAs.
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Chemical communications (Cambridge, England)
|
chemistry
| 540 | 13 |
This review describes how one can perform nanometer (nm)-scale SECM experiments through advances in tip fabrication and positioning and instrumentation design. Basic SECM methodology including instrumentation and feedback and generation/collection modes are discussed. Aspects of nanoscale SECM including fabrication of nm-sized electrodes and nano SECM instrumentation are also described. State of the art applications related to nanogaps (i.e., rapid homogeneous reactions and short-lived intermediates; heterogeneous electron transfer kinetics; nanoparticles (NPs) and clusters) and nanoscale imaging (e.g., single NPs, single biological samples, combined methods) are described. Future possibilities and prospects are suggested that might lead to even better resolution, thus introducing SECM electrochemical imaging to the single atom level.
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Scanning electrochemical microscopy at the nanometer level.
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Chemical communications (Cambridge, England)
|
chemistry
| 540 | 13 |
This paper reports that the bulk polymerization of l-aspartic acid diethyl ester catalyzed by immobilized CAL-B at 80 °C for 24 h gives primarily (∼95%) α-linked poly(l-aspartate) in 70% yield with DP avg = 50 and regioselectivity (α/β) = 94 : 6. Plots of log{[M] 0 /[M] t } vs. time and DP avg vs. conversion indicate that this polymerization proceeds in a controlled manner by a chain-growth mechanism up to 90% conversion. Thereafter, competition occurs between chain growth and step mechanisms.
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CAL-B catalyzed regioselective bulk polymerization of l-aspartic acid diethyl ester to α-linked polypeptides.
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Chemical communications (Cambridge, England)
|
chemistry
| 540 | 13 |
The reaction of (Cp*Al) 4 with a series of fluoro(hetero)arenes has been investigated and C-F bond activation was observed with perfluorotoluene, pentafluoropyridine as well as 1,2,3,4-tetrafluoro-, pentafluoro- and hexafluorobenzene. The reaction mechanism has been probed by means of DFT calculations and the computational findings are in good agreement with the experimental observations.
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C-F bond activation by pentamethylcyclopentadienyl-aluminium(i): a combined experimental/computational exercise.
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Chemical communications (Cambridge, England)
|
chemistry
| 540 | 13 |
Here, a low-cost perovskite solar cell using CuI and ZnO as the respective inorganic hole and electron transport layers is introduced. Copper foil is chosen as a cheap and low-weight conductive substrate which has a similar work function to ITO. Besides, copper foil is an interesting copper atom source for the growth of the upper cuprous iodide layer on copper foil. A spray coating of a transparent silver nanowire electrode is used as a top contact. The prepared device shows a maximum power conversion efficiency of 12.80% and long-term durability providing an environmentally and market friendly perovskite solar cell.
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All-inorganic large-area low-cost and durable flexible perovskite solar cells using copper foil as a substrate.
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Chemical communications (Cambridge, England)
|
chemistry
| 540 | 13 |
Photoactive nano TiO2 particles with fluorescent properties have attracted great attention because of their potential applications in photodynamic therapy. Herein we report first a simple method to prepare water soluble fluorescent nano titanium oxide particles from titanium-oxo-clusters (TOCs). The nano material was characterized as an aggregate of titanium-oxo-clusters, which can be used directly in aqueous systems for investigations in biomedical fields.
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Bio-compatible fluorescent nano TiO materials prepared from titanium-oxo-cluster precursors.
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Chemical communications (Cambridge, England)
|
chemistry
| 540 | 13 |
An efficient one-pot approach for the controllable synthesis of trifluoromethyl/gem-difluoromethylene substituted cyclobutene derivatives has been developed. The mechanism may involve visible light-induced [2+2]-cycloaddition of quinolinones with 1-bromo-1-trifluoromethylethene, followed by base-promoted dehydrobromination, [1,3]-H shift and further dehydrofluorination. A variety of CF3/CF2-substituted cyclobutenes that are currently difficult to obtain are afforded in good yields in this protocol, which may find its way into future fluorinated cyclobutene preparation.
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Visible light-induced one-pot synthesis of CF3/CF2-substituted cyclobutene derivatives.
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Chemical communications (Cambridge, England)
|
chemistry
| 540 | 13 |
A fluorescent liquid pyrene derivative with a high fluorescence quantum yield (65%) in the bulk state is reported. With this as the sole oil phase, stable luminescent oil-in-water microemulsions have been prepared. Increasing the loading of liquid pyrene swells the droplets, as detected by small-angle neutron scattering. These larger droplets have a greater proportion of pyrene excimer emission contribution in their photoluminescence spectra, which leads to a red shift in the chromaticity of the emission.
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Fluorescent liquid pyrene derivative-in-water microemulsions.
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Chemical communications (Cambridge, England)
|
chemistry
| 540 | 13 |
A novel and efficient iron-catalyzed sp 3 carbon-hydrogen bond functionalization of benzoxazinone derivatives has been developed. For the first time, benzoxazin-2-ones were used as substrates in an oxidative dehydrogenative coupling reaction. The experiments were performed under mild reaction conditions to construct alkyl-aryl C(sp 3 )-C(sp 2 ) bonds. The application of this method to the gram-scale synthesis of natural product cephalandole A has been accomplished in a 3-step sequence. A plausible one electron oxidation involved mechanism is proposed.
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Iron-catalyzed oxidative sp3 carbon-hydrogen bond functionalization of 3,4-dihydro-1,4-benzoxazin-2-ones.
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Chemical communications (Cambridge, England)
|
chemistry
| 540 | 13 |
We report an empirical correlation between the blocking temperature of large energy barrier SMMs and the relaxation time at the point where the Raman and Orbach relaxation mechanisms have the same rate; this supports the idea that the ability to retain magnetisation is controlled by the Raman relaxation process in these materials.
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Correlating blocking temperatures with relaxation mechanisms in monometallic single-molecule magnets with high energy barriers (Ueff > 600 K).
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Chemical communications (Cambridge, England)
|
chemistry
| 540 | 13 |
Inspired by nature, supramolecular nanoparticles based on complementary nucleobase interactions have aroused wide interest. In our study, two kinds of fluorophores were conjugated at the end of nucleobase containing homopolymers, which can be used to confirm the binding state and calculate the binding constants among different nucleobase pairs. Furthermore, we describe a facile synthesis of nucleobase-functionalized amphiphilic polymers with rigid and flexible backbones using RAFT polymerization. Spindle-like or telophase-like supramolecular self-assemblies were formed by different components of such synthetic amphiphilic polymers.
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Spindle-like and telophase-like self-assemblies mediated by complementary nucleobase molecular recognition.
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Chemical communications (Cambridge, England)
|
chemistry
| 540 | 13 |
Oxidative nucleophilic α-hydrogen substitution is a direct method for BODIPY functionalization. However, it was hampered by the low reactivity of BODIPYs toward weak nucleophiles. Herein, we develop a cation radical accelerated oxidative nucleophilic α-hydrogen substitution reaction between BODIPY dyes and a variety of alcohols. This direct C-H alkoxylation presented a wide substrate scope and high site selectivity, providing a series of α-alkoxylated BODIPYs with diverse functional groups. Moreover, a BODIPY derivative with a pyridinium ion was developed as a new mitochondria-targeting fluorescent probe with favorable photophysical properties.
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Direct C-H alkoxylation of BODIPY dyes via cation radical accelerated oxidative nucleophilic hydrogen substitution: a new route to building blocks for functionalized BODIPYs.
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Chemical communications (Cambridge, England)
|
chemistry
| 540 | 13 |
A novel and air-stable organo(hydro)diborane featuring a five-membered aryl ring supported bridging B-C-B three-centre-two-electron (3c-2e) bond has been reported. Pyrido[1,2- a ]isoindole was found to undergo a stepwise BH 3 addition reaction, during which a mono-BH 3 adduct was formed from a electrophilic addition at the C γ in pyrido[1,2- a ]isoindole. A molecule of hydrogen was eliminated throughout the second step of addition reaction. DFT calculations indicate that the H 2 evolution is concerted to the second BH 3 addition rather than forming BC before the second BH 3 attack.
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Formation of an air-stable diborane via a stepwise BH3 addition of pyrido[1,2-a]isoindole with H2 evolution.
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Chemical communications (Cambridge, England)
|
chemistry
| 540 | 13 |
Recently, we found that the Raman optical activity (ROA) technique can be used to monitor even a weak lanthanide luminescence including circular polarization. In the present study we compare circularly polarized luminescence (CPL) spectra of Eu(iii), Sm(iii), and Er(iii) induced by aqueous solution of sialic acid. For Eu providing the strongest signal a chelation model was proposed where the carboxyl adopts the axial conformation and carboxyl oxygen is attached to Eu(iii).
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Specific circularly polarized luminescence of Eu(iii), Sm(iii), and Er(iii) induced by N-acetylneuraminic acid.
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Chemical communications (Cambridge, England)
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chemistry
| 540 | 13 |
A fundamental boron cluster, [closo-B 12 H 12 ] 2- , mainly known as an inert agent for boron neutron capture therapy, can also serve as a bi-functional reductant and a capping agent for the formation of monodispersed size-controlled gold nanoparticles (AuNPs) under mild reaction conditions. The obtained AuNPs remained thermo-dynamically stable over 3 months, and exhibited high performance in phase transfer and sensing of heavy metal ions.
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From boron clusters to gold clusters: new label-free colorimetric sensors.
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Chemical communications (Cambridge, England)
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chemistry
| 540 | 13 |
Alkenes bearing a stereocenter in the allylic position were found to undergo Kulinkovich hydroxycyclopropanation with good diastereoselectivity. For the isomerization of the resulting cyclopropanols to diastereomerically enriched α-methyl ketones, a new mild regioselective method has been developed. A sequence of stereoselective cyclopropanation and cyclopropanol ring opening was successfully employed for the construction of the C20 stereocenter in steroids.
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Stereoselective synthesis of α-methyl and α-alkyl ketones from esters and alkenes via cyclopropanol intermediates.
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Chemical communications (Cambridge, England)
|
chemistry
| 540 | 13 |
A new, highly porous acylamide-functionalized MOF with a (3,24)-connected rht-type network (HNUST-5) has been synthesized and structurally determined using powder X-ray diffraction. HNUST-5 exhibits a high BET surface area of 3643 m 2 g -1 , and a large CO 2 uptake capability (38.9 mmol g -1 under 36 bar) with an excellent selectivity of CO 2 /CH 4 (7.3) and CO 2 /N 2 (32.5) at 273 K.
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A highly porous rht-type acylamide-functionalized metal-organic framework exhibiting large CO2 uptake capabilities.
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Chemical communications (Cambridge, England)
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chemistry
| 540 | 13 |
Previous studies have shown that habitual physical activity improves postprandial appetite regulation. We evaluated the direct association between physical activity level (PAL) and postprandial appetite regulation, and the effect of day-to-day variations in PAL on improving postprandial appetite regulation in lean young males. Fourteen young male adults wore a triaxial accelerometer for at least 6 consecutive days to evaluate their PAL. Two random liquid preload tests were performed on separate days to evaluate the competence of postprandial appetite regulation. In the preload test, participants ate sandwiches ad libitum 75 min after drinking one of two liquids containing different energy densities. When a participant had an adequate regulation of their postprandial appetite, the difference in energy intake from sandwiches was expected to be close to the energy gap between both liquids. Average daily PAL ( r = -0.558, p < 0.05), but not the SD of PAL, which is indicative of the day-to-day variations in PAL ( r = -0.437, p > 0.1), correlated with the difference in energy intake from the sandwiches. In addition, higher average PAL was closer to the energy gap between the two liquids. These results suggest that average daily PAL, rather than day-to-day variations in PAL, predicts inter-individual variation in postprandial appetite regulation, at least for lean young males.
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Association of Day-to-Day Variations in Physical Activity with Postprandial Appetite Regulation in Lean Young Males.
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Nutrients
|
food
| 2,004 | 27 |
The purpose was to examine the effects of creatine supplementation during resistance training sessions on skeletal muscle mass and exercise performance in physically active young adults. Twenty-two participants were randomized to supplement with creatine (CR: n = 13, 26 ± 4 yrs; 0.0055 g·kg -1 post training set) or placebo (PLA: n = 9, 26 ± 5 yrs; 0.0055 g·kg -1 post training set) during six weeks of resistance training (18 sets per training session; five days per week). Prior to and following training and supplementation, measurements were made for muscle thickness (elbow and knee flexors/extensors, ankle plantarflexors), power (vertical jump and medicine ball throw), strength (leg press and chest press one-repetition maximum (1-RM)) and muscular endurance (one set of repetitions to volitional fatigue using 50% baseline 1-RM for leg press and chest press). The creatine group experienced a significant increase ( p < 0.05) in leg press, chest press and total body strength and leg press endurance with no significant changes in the PLA group. Both groups improved total body endurance over time ( p < 0.05), with greater gains observed in the creatine group. In conclusion, creatine ingestion during resistance training sessions is a viable strategy for improving muscle strength and some indices of muscle endurance in physically active young adults.
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Effects of Creatine Supplementation during Resistance Training Sessions in Physically Active Young Adults.
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Nutrients
|
food
| 2,004 | 27 |
Inflammation-modulating elements are recognized periodontitis (PD) risk factors, nevertheless, the association between dietary inflammatory index (DII) and PD has never been appraised. We aimed to assess the association between DII and PD and the mediation effect of DII in the association of PD with systemic inflammation. Using the National Health and Nutrition Examination Survey 2009-2010, 2011-2012 and 2013-2014, participants who received periodontal exam and provided dietary recall data were included. The inflammatory potential of diet was calculated via DII. PD was defined according to the 2012 case definition. White blood cells (WBC), segmented neutrophils and C-reactive protein (CRP) were used as proxies for systemic inflammation. The periodontal measures were regressed across DII values using adjusted multivariate linear regression and adjusted mediation analysis. Overall, 10,178 participants were included. DII was significantly correlated with mean periodontal probing depth (PPD), mean clinical attachment loss (CAL), thresholds of PPD and CAL, WBC, segmented neutrophils and DII ( p < 0.01). A linear regression logistic adjusted for multiple confounding variables confirmed the association between DII and mean PPD (B = 0.02, Standard Error [SE]: 0.02, p < 0.001) and CAL (B = -0.02, SE: 0.01, p < 0.001). The association of mean PPD and mean CAL with both WBC and segmented neutrophils were mediated by DII (from 2.1 to 3.5%, p < 0.001). In the 2009-2010 subset, the association of mean CAL with serum CRP was mediated by DII (52.0%, p < 0.01). Inflammatory diet and PD may be associated. Also, the inflammatory diet significantly mediated the association of leukocyte counts and systemic inflammation with PD.
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Association between Dietary Inflammatory Index and Periodontitis: A Cross-Sectional and Mediation Analysis.
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Nutrients
|
food
| 2,004 | 27 |
Probiotics are reported to improve gastrointestinal (GI) function via regulating gut microbiota (GM). However, exactly how probiotics influence GM and GI function in elders is poorly characterized. Therefore, in this study, we assessed the effect of the probiotic Lacticaseibacillus paracasei PS23 (LPPS23) on the GM and GI function of aged mice. There were four groups of senescence-accelerated mouse prone-8 (SAMP8) mice ( n = 4): a non-treated control group, a saline control group, a low dose LPPS23 group (1 × 10 8 colony-forming unit (CFU)/mouse/day), and a high dose LPPS23 group (1 × 10 9 CFU/mouse/day). Non-treated mice were euthanized at 16 weeks old, and others were euthanized at 28 weeks old. The next-generation sequencing results revealed that LPPS23 enriched Lactobacillus and Candidatus_Saccharimonas , while the abundance of Lachnospiraceae _UCG_001 decreased in aged mice given LPPS23. The abundance of Lactobacillus negatively correlated with the abundance of Erysipelotrichaceae . Moreover, LPPS23 improved the GI function of aged mice due to the longer intestine length, lower intestinal permeability, and higher phagocytosis in LPPS23-treated mice. The ELISA results showed that LPPS23 attenuated the alterations of pro-inflammatory factors and immunoglobulins. The abundance of LPPS23-enriched Lactobacillus was positively correlated with healthy GI function, while Lachnospiraceae _UCG_001, which was repressed by LPPS23, was negatively correlated with a healthy GI function in the aged mice according to Spearman's correlation analysis. Taken together, LPPS23 can effectively modulate GM composition and improve GI function in aged SAMP8 mice.
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Lacticaseibacillus paracasei PS23 Effectively Modulates Gut Microbiota Composition and Improves Gastrointestinal Function in Aged SAMP8 Mice.
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Nutrients
|
food
| 2,004 | 27 |
Sensitization and allergy to legumes can be influenced by different factors, such as exposure, geographical background, and food processing. Sensitization and the allergic response to legumes differs considerably, however, the reason behind this is not yet fully understood. The aim of this study is to investigate if there is a correlation between legume protein consumption and the prevalence of legume sensitization. Furthermore, the association between sensitization to specific peanut allergens and their concentration in peanut is investigated. Legume sensitization data (peanut, soybean, lupin, lentil, and pea) from studies were analyzed in relation to consumption data obtained from national food consumption surveys using the European Food Safety Authority (EFSA), Global Environment Monitoring System (GEMS), and What We Eat in America-Food Commodity Intake Database (WWEIA-FCID) databases. Data were stratified for children <4 years, children 4⁻18 years, and adults. Sufficient data were available for peanut to allow for statistical analysis. Analysis of all age groups together resulted in a low correlation between peanut sensitization and relative peanut consumption ( r = 0.407), absolute peanut consumption ( r = 0.468), and percentage of peanut consumers ( r = 0.243). No correlation was found between relative concentrations of Ara h 1, 2, 3, 6, 7, and 8 in peanut and sensitization to these peanut allergens. The results indicate that the amount of consumption only plays a minor role in the prevalence of sensitization to peanut. Other factors, such as the intrinsic properties of the different proteins, processing, matrix, frequency, timing and route of exposure, and patient factors might play a more substantial role in the prevalence of peanut sensitization.
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Legume Protein Consumption and the Prevalence of Legume Sensitization.
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Nutrients
|
food
| 2,004 | 27 |
Fulminant hepatic failure (FHF) is a rare, life-threatening liver disease with a poor prognosis. Administration of D-galactosamine (GalN) and lipopolysaccharide (LPS) triggers acute liver injury in mice, simulating many clinical features of FHF in humans; therefore, this disease model is often used to investigate potential therapeutic interventions to treat FHF. Recently, suppression of the nucleotide-binding domain and leucine-rich repeat related (NLR) family, pyrin domain containing 3 (NLRP3) inflammasome, was shown to alleviate the severity of GalN/LPS-induced liver damage in mice. Therefore, the goal of this study was to find dietary exosome-like nanoparticles (ELNs) with therapeutic potential in curbing FHF by suppressing the NLRP3 inflammasome. Seven commonly consumed mushrooms were used to extract ELNs. These mushrooms were found to contain ELNs composed of RNAs, proteins, and lipids. Among these mushroom-derived ELNs, only shiitake mushroom-derived ELNs (S-ELNs) substantially inhibited NLRP3 inflammasome activation by preventing inflammasome formation in primary macrophages. S-ELNs also suppressed the secretion of interleukin (IL)-6, as well as both protein and mRNA levels of the Il1b gene. Remarkably, pre-treatment with S-ELNs protected mice from GalN/LPS-induced acute liver injury. Therefore, S-ELNs, identified as potent new inhibitors of the NLRP3 inflammasome, represent a promising class of agents with the potential to combat FHF.
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Protective Role of Shiitake Mushroom-Derived Exosome-Like Nanoparticles in D-Galactosamine and Lipopolysaccharide-Induced Acute Liver Injury in Mice.
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Nutrients
|
food
| 2,004 | 27 |
Intermittent fasting has become popular in recent years and is controversially presented as a possible therapeutic adjunct. A bibliographic review of the literature on intermittent fasting and obesity, diabetes, and multiple sclerosis was carried out. The scientific quality of the methodology and the results obtained were evaluated in pairs. Intermittent fasting has beneficial effects on the lipid profile, and it is associated with weight loss and a modification of the distribution of abdominal fat in people with obesity and type 2 diabetes as well as an improvement in the control of glycemic levels. In patients with multiple sclerosis, the data available are too scarce to draw any firm conclusions, but it does appear that intermittent fasting may be a safe and feasible intervention. However, it is necessary to continue investigating its long-term effects since so far, the studies carried out are small and of short duration.
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Intermittent Fasting and the Possible Benefits in Obesity, Diabetes, and Multiple Sclerosis: A Systematic Review of Randomized Clinical Trials.
|
Nutrients
|
food
| 2,004 | 27 |
There are numerous and diverse factors enabling the overconsumption of foods, with the sense of taste being one of these factors. There are four well established basic tastes: sweet, sour, salty, and bitter; all with perceptual independence, salience, and hedonic responses to encourage or discourage consumption. More recently, additional tastes have been added to the basic taste list including umami and fat, but they lack the perceptual independence and salience of the basics. There is also emerging evidence of taste responses to kokumi and carbohydrate. One interesting aspect is the link with the new and emerging tastes to macronutrients, with each macronutrient having two distinct perceptual qualities that, perhaps in combination, provide a holistic perception for each macronutrient: fat has fat taste and mouthfeel; protein has umami and kokumi; carbohydrate has sweet and carbohydrate tastes. These new tastes can be sensed in the oral cavity, but they have more influence post- than pre-ingestion. Umami, fat, kokumi, and carbohydrate tastes have been suggested as an independent category named alimentary. This narrative review will present and discuss evidence for macronutrient sensing throughout the alimentary canal and evidence of how each of the alimentary tastes may influence the consumption of foods.
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Macronutrient Sensing in the Oral Cavity and Gastrointestinal Tract: Alimentary Tastes.
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Nutrients
|
food
| 2,004 | 27 |
Nutritional status affects the survival of patients with sepsis. This retrospective study analyzed the impact of body mass index (BMI) and modified nutrition risk in critically ill (mNUTRIC) scores on survival of these patients. Data of 1291 patients with sepsis admitted to the intensive care unit (ICU) were extracted. The outcomes were mortality, duration of stay, ICU stay, and survival curve for 90-day mortality. Logistic regression analysis was performed to examine the risk factors for mortality. Cytokine and biomarker levels were analyzed in 165 patients. The 90-day survival of underweight patients with low mNUTRIC scores was significantly better than that of normal-weight patients with low mNUTRIC scores (70.8% vs. 58.3%, respectively; p = 0.048). Regression model analysis revealed that underweight patients with low mNUTRIC scores had a lower risk of mortality (odds ratio = 0.557; p = 0.082). Moreover, normal-weight patients with low mNUTRIC scores had the lowest human leukocyte antigen DR (HLA-DR) level on days 1 (underweight vs. normal weight vs. overweight: 94.3 vs. 82.1 vs. 94.3, respectively; p = 0.007) and 3 (91.8 vs. 91.0 vs. 93.2, respectively; p = 0.047). Thus, being underweight may not always be harmful if patients have optimal clinical nutritional status. Additionally, HLA-DR levels were the lowest in patients with low survival.
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Impact of Body Mass Index on the Survival of Patients with Sepsis with Different Modified NUTRIC Scores.
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Nutrients
|
food
| 2,004 | 27 |
Branched-chain amino acids (BCAAs: leucine, isoleucine, valine) account for 35% of skeletal muscle essential amino acids (AAs). As such, they must be provided in the diet to support peptide synthesis and inhibit protein breakdown. Although substantial evidence has been collected about the potential usefulness of BCAAs in supporting muscle function and structure, dietary supplements containing BCAAs alone may not be effective in controlling muscle protein turnover, due to the rate-limiting bioavailability of other AAs involved in BCAAs metabolism. We aimed to evaluate the in vivo/ex vivo effects of a 4-week treatment with an oral formulation containing BCAAs alone (2:1:1) on muscle function, structure, and metabolism in a murine model of physiological exercise, which was compared to three modified formulations combining BCAAs with increasing concentrations of L-Alanine (ALA), an AA controlling BCAAs catabolism. A preliminary pharmacokinetic study confirmed the ability of ALA to boost up BCAAs bioavailability. After 4 weeks, mix 2 (BCAAs + 2ALA) had the best protective effect on mice force and fatigability, as well as on muscle morphology and metabolic indices. Our study corroborates the use of BCAAs + ALA to support muscle health during physiological exercise, underlining how the relative BCAAs/ALA ratio is important to control BCAAs distribution.
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Ergogenic Effect of BCAAs and L-Alanine Supplementation: Proof-of-Concept Study in a Murine Model of Physiological Exercise.
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Nutrients
|
food
| 2,004 | 27 |
Nutritional compounds may have an influence on different OMICs levels, including genomics, epigenomics, transcriptomics, proteomics, metabolomics, and metagenomics. The integration of OMICs data is challenging but may provide new knowledge to explain the mechanisms involved in the metabolism of nutrients and diseases. Traditional statistical analyses play an important role in description and data association; however, these statistical procedures are not sufficiently enough powered to interpret the large integrated multiple OMICs (multi-OMICS) datasets. Machine learning (ML) approaches can play a major role in the interpretation of multi-OMICS in nutrition research. Specifically, ML can be used for data mining, sample clustering, and classification to produce predictive models and algorithms for integration of multi-OMICs in response to dietary intake. The objective of this review was to investigate the strategies used for the analysis of multi-OMICs data in nutrition studies. Sixteen recent studies aimed to understand the association between dietary intake and multi-OMICs data are summarized. Multivariate analysis in multi-OMICs nutrition studies is used more commonly for analyses. Overall, as nutrition research incorporated multi-OMICs data, the use of novel approaches of analysis such as ML needs to complement the traditional statistical analyses to fully explain the impact of nutrition on health and disease.
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Statistical and Machine-Learning Analyses in Nutritional Genomics Studies.
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Nutrients
|
food
| 2,004 | 27 |
There are limited data on the fluid balance characteristics and fluid replenishment behaviors of high-performance adolescent athletes. The heterogeneity of hydration status and practices of adolescent athletes warrant efficient approaches to individualizing hydration strategies. This study aimed to evaluate and characterize the hydration status and fluid balance characteristics of high-performance adolescent athletes and examine the differences in fluid consumption behaviors during training. In total, 105 high-performance adolescent athletes (male: 66, female: 39; age 14.1 ± 1.0 y) across 11 sports had their hydration status assessed on three separate occasions-upon rising and before a low and a high-intensity training session (pre-training). The results showed that 20-44% of athletes were identified as hypohydrated, with 21-44% and 15-34% of athletes commencing low- and high-intensity training in a hypohydrated state, respectively. Linear mixed model (LMM) analyses revealed that athletes who were hypohydrated consumed more fluid (F (1.183.85)) = 5.91, ( p = 0.016). Additional K-means cluster analyses performed highlighted three clusters: "Heavy sweaters with sufficient compensatory hydration habits," "Heavy sweaters with insufficient compensatory hydration habits" and "Light sweaters with sufficient compensatory hydration habits". Our results highlight that high-performance adolescent athletes with ad libitum drinking have compensatory mechanisms to replenish fluids lost from training. The approach to distinguish athletes by hydration characteristics could assist practitioners in prioritizing future hydration intervention protocols.
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Hydration Status and Fluid Replacement Strategies of High-Performance Adolescent Athletes: An Application of Machine Learning to Distinguish Hydration Characteristics.
|
Nutrients
|
food
| 2,004 | 27 |
Infancy is a time of plasticity in development of taste preference. Complementary feeding (CF) may be a "sensitive period" for learning new taste preferences and establishing healthy dietary behaviors that may track later in life. Among 1162 children in the U.S. prospective cohort study Project Viva, we aimed to identify patterns of CF behaviors around 1 year and examine associations with diet quality in early childhood (median age 3.1y). We identified patterns of CF using latent class analysis (LCA) and examined later diet quality based on scores on the Youth Healthy Eating Index (YHEI). We identified four distinct CF patterns (latent classes). Later YHEI scores were highest in the class characterized by "breast milk and delayed sweets and fruit juice" and lowest in the "picky eaters" class. The classes defined as "late flavor introduction and delayed sweets" and "early flavor introduction and more fruit juice" had similar, moderate scores. Our results suggest that CF patterns that increase food acceptance and discourage the innate preference for sweetness may have persistent influences on diet quality.
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Patterns of Complementary Feeding Behaviors Predict Diet Quality in Early Childhood.
|
Nutrients
|
food
| 2,004 | 27 |
Myricetin is an effective antioxidant in the treatment of obesity and obesity-related metabolic disorders. The objective of this study was to explore the regressive effect of myricetin on pre-existing hepatic steatosis induced by high-fat diet (HFD). C57BL/6 mice were fed either a standard diet or a HFD for 12 weeks and then half of the mice were treated with myricetin (0.12% in the diet, w/w ) while on their respective diets for further 12 weeks. Myricetin treatment significantly alleviated HFD-induced steatosis, decreased hepatic lipid accumulation and thiobarbituric acid reactive substance (TBARS) levels, and increased antioxidative enzyme activities, including catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GPx) activities. Microarray analysis of hepatic gene expression profiles showed that myricetin significantly altered the expression profiles of 177 genes which were involved in 12 biological pathways, including the peroxisome proliferator activated receptor (PPAR) signaling pathway and peroxisome. Further research indicated that myricetin elevated hepatic nuclear Nrf2 translocation, increased the protein expression of heme oxygenase-1 (HO-1) and NAD(P)H quinone dehydrogenase 1 (NQO1), reduced the protein expression of PPARγ, and normalized the expressions of genes that were involved in peroxisome and the PPAR signaling pathway. Our data indicated that myricetin might represent an effective therapeutic agent to treat HFD-induced hepatic steatosis via activating the Nrf2 pathway and the PPAR signaling pathway.
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Regressive Effect of Myricetin on Hepatic Steatosis in Mice Fed a High-Fat Diet.
|
Nutrients
|
food
| 2,004 | 27 |
Celiac disease may present with a range of different symptoms, including abdominal problems in a broader sense, iron deficiency and "constant tiredness". All of these symptoms should consequently lead the clinicians to consider celiac disease as a potential etiopathogenetic cause. Although the pathophysiology of celiac disease is well documented, the actual mechanisms for disease presentation(s) are less well understood. We here address the topic of fatigue in celiac disease. A systematic literature search identified 298 papers of which five met the criteria for full evaluation. None of the reviewed papers were of high quality and had several methodological weaknesses. We conclude that there is an unmet need to study the contributing factors and management of fatigue in celiac disease.
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Fatigue as an Extra-Intestinal Manifestation of Celiac Disease: A Systematic Review.
|
Nutrients
|
food
| 2,004 | 27 |
Activation of the NOD-like receptor pyrin-domain containing 3 (NLRP3) inflammasome is associated with chronic low-grade inflammation in metabolic diseases such as obesity. Mechanistic studies have shown that β-hydroxybutyrate (OHB) attenuates activation of NLRP3, but human data are limited. In a randomized, double-blind, placebo-controlled crossover trial ( n = 11) we tested the hypothesis that acutely raising β-OHB by ingestion of exogenous ketones would attenuate NLRP3 activation in humans with obesity. Blood was sampled before and 30 min post-ingestion of a ketone monoester drink ((R)-3-hydroxybutyl (R)-3-hydroxybutyrate, 482 mg/kg body mass) or placebo. A 75 g oral glucose load was then ingested, and a third blood sample was obtained 60 min following glucose ingestion. NLRP3 activation was quantified by assessing monocyte caspase-1 activation and interleukin (IL)-1β secretion in ex vivo lipopolysaccharide (LPS)-stimulated whole-blood cultures. LPS-stimulated caspase-1 activation increased following glucose ingestion (main effect of time; p = 0.032), with no differences between conditions. IL-1β secretion did not differ between conditions but was lower 60 min post-glucose ingestion compared to the fasting baseline (main effect of time, p = 0.014). Plasma IL-1β was detectable in ~80% of samples and showed a decrease from fasting baseline to 60 min in the ketone condition only (condition × time interaction, p = 0.01). In individuals with obesity, an excursion into hyperglycemia following ingestion of a glucose load augments LPS-induced activation of caspase-1 in monocytes with no apparent impact of raising circulating β-OHB concentration via ingestion of exogenous ketones. Exogenous ketone supplementation may impact plasma IL-1β, but these findings require confirmation in studies with larger sample sizes.
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The Impact of Acute Ingestion of a Ketone Monoester Drink on LPS-Stimulated NLRP3 Activation in Humans with Obesity.
|
Nutrients
|
food
| 2,004 | 27 |
The liver plays a key role in whole-body, glucose and lipid homeostasis. Nutritional signals in response to fasting and refeeding regulate hepatic lipid synthesis. It is established that activation of mitogen-activated protein kinase (MAPK) phosphatase-1 (MKP-1) in response to overnutrition regulates MAPK-dependent pathways that control lipid metabolism in the liver. However, the regulatory mechanisms and the impact of the actions of MKP-1 in hepatic response to fasting remains unclear. We investigated the effect of fasting on the expression of MKP-1 and the impact on hepatic response to feeding. In this study, we demonstrate that fasting stress induced upregulation of hepatic MKP-1 protein levels with a corresponding downregulation of p38 MAPK and JNK phosphorylation in mouse livers. We found that MKP-1-deficient livers are resistant to fasting-induced hepatic steatosis. Hepatic MKP-1 deficiency impaired fasting-induced changes in the levels of key transcription factors involved in the regulation of fatty acid and cholesterol metabolism including Srebf2 and Srebf1c . Mechanistically, MKP-1 negatively regulates Srebf2 expression by attenuating p38 MAPK pathway, suggesting its contribution to the metabolic effects of MKP-1 deficiency in the fasting liver. These findings support the hypothesis that upregulation of MKP-1 is a physiological relevant response and might be beneficial in hepatic lipid utilization during fasting in the liver. Collectively, these data unravel some of the complexity and tissue specific interaction of MKP-1 action in response to changes in nutritional cues, including fasting and excess nutrients.
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Fasting-Induced Upregulation of MKP-1 Modulates the Hepatic Response to Feeding.
|
Nutrients
|
food
| 2,004 | 27 |
Aging is accompanied by profound changes in many physiological functions, leading to a decreased ability to cope with stressors. Many changes are subtle, but can negatively affect nutrient intake, leading to overt malnutrition. Poor oral health may affect food selection and nutrient intake, leading to malnutrition and, consequently, to frailty and sarcopenia. On the other hand, it has been highlighted that sarcopenia is a whole-body process also affecting muscles dedicated to chewing and swallowing. Hence, muscle decline of these muscle groups may also have a negative impact on nutrient intake, increasing the risk for malnutrition. The interplay between oral diseases and malnutrition with frailty and sarcopenia may be explained through biological and environmental factors that are linked to the common burden of inflammation and oxidative stress. The presence of oral problems, alone or in combination with sarcopenia, may thus represent the biological substratum of the disabling cascade experienced by many frail individuals. A multimodal and multidisciplinary approach, including personalized dietary counselling and oral health care, may thus be helpful to better manage the complexity of older people. Furthermore, preventive strategies applied throughout the lifetime could help to preserve both oral and muscle function later in life. Here, we provide an overview on the relevance of poor oral health as a determinant of malnutrition and sarcopenia.
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Poor Oral Health as a Determinant of Malnutrition and Sarcopenia.
|
Nutrients
|
food
| 2,004 | 27 |
Gastrointestinal (GI) health is an important aspect of general health. Gastrointestinal symptoms are of specific importance for the elderly, an increasing group globally. Hence, promoting the elderly's health and especially gastrointestinal health is important. Gut microbiota can influence gastrointestinal health by modulation of the immune system and the gut-brain axis. Diverse gut microbiota have been shown to be beneficial; however, for the elderly, the gut microbiota is often less diverse. Nutrition and physical activity, in particular, are two components that have been suggested to influence composition or diversity. In this study, we compared gut microbiota between two groups of elderly individuals: community-dwelling older adults and physically active senior orienteering athletes, where the latter group has less gastrointestinal symptoms and a reported better well-being. With this approach, we explored if certain gut microbiota were related to healthy ageing. The participant data and faecal samples were collected from these two groups and the microbiota was whole-genome sequenced and taxonomically classified with MetaPhlAn. The physically active senior orienteers had a more homogeneous microbiota within the group and a higher abundance of Faecalibacterium prausnitzii compared to the community-dwelling older adults. Faecalibacterium prausnitzii has previously shown to have beneficial properties. Senior orienteers also had a lower abundance of Parasutterella excrementihominis and Bilophila unclassified, which have been associated with impaired GI health. We could not observe any difference between the groups in terms of Shannon diversity index. Interestingly, a subgroup of community-dwelling older adults showed an atypical microbiota profile as well as the parameters for gastrointestinal symptoms and well-being closer to senior orienteers. Our results suggest specific composition characteristics of healthy microbiota in the elderly, and show that certain components of nutrition as well as psychological distress are not as tightly connected with composition or diversity variation in faecal microbiota samples.
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Differences in Gut Microbiome Composition between Senior Orienteering Athletes and Community-Dwelling Older Adults.
|
Nutrients
|
food
| 2,004 | 27 |
Impurity doping has been widely used to endow semiconductor nanocrystals with novel optical, electronic, and magnetic functionalities. Here, we introduce a new family of doped NCs offering unique insights into the chemical mechanism of doping, as well as into the fundamental interactions between the dopant and the semiconductor host. Specifically, by elucidating the role of relative bond strengths within the precursor and the host lattice, we develop an effective approach for incorporating manganese (Mn) ions into nanocrystals of lead-halide perovskites (CsPbX 3 , where X = Cl, Br, or I). In a key enabling step not possible in, for example, II-VI nanocrystals, we use gentle chemical means to finely and reversibly tune the nanocrystal band gap over a wide range of energies (1.8-3.1 eV) via postsynthetic anion exchange. We observe a dramatic effect of halide identity on relative intensities of intrinsic band-edge and Mn emission bands, which we ascribe to the influence of the energy difference between the corresponding transitions on the characteristics of energy transfer between the Mn ion and the semiconductor host.
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Mn2+-Doped Lead Halide Perovskite Nanocrystals with Dual-Color Emission Controlled by Halide Content.
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Journal of the American Chemical Society
|
biology
| 1,674 | 9 |
This study explores a bottom-up approach toward negatively curved carbon allotropes from octabenzo[8]circulene, a negatively curved nanographene. Stepwise chemical reduction reactions of octabenzo[8]circulene with alkali metals lead to a unique highly reduced hydrocarbon pentaanion, which is revealed by X-ray crystallography suggesting a local view for the reduction and alkali metal intercalation processes of negatively curved carbon allotropes. Polymerization of the tetrabromo derivative of octabenzo[8]circulene by the nickel-mediated Yamamoto coupling reaction results in a new type of porous carbon-rich material, which consists of a covalent network of negatively curved nanographenes. It has a specific surface area of 732 m 2 g -1 and functions as anode material for lithium ion batteries exhibiting a maximum capacity of 830 mAh·g -1 at a current density of 100 mA·g -1 . These results indicate that this covalent network presents the key structural and functional features of negatively curved carbon allotropes.
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Charging a Negatively Curved Nanographene and Its Covalent Network.
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Journal of the American Chemical Society
|
biology
| 1,674 | 9 |
Heterocyclic polymers have gained enormous attention for their unique functionalities and wide applications. In contrast with the well-studied polymer systems with five- or six-membered heterocycles, functional polymers with readily openable small-ring heterocycles have rarely been explored due to their large synthetic difficulty. Herein, a facile one-pot multicomponent polymerization to such polymers is developed. A series of functional polymers with multisubstituted and heteroatom-rich azetidine frameworks are efficiently generated at room temperature in high atom economy from handy monomers. The four-membered azetidine rings in the polymer skeletons can be easily transformed into amide and amidine moieties via a fast and efficient acid-mediated ring-opening reaction, producing brand-new polymeric materials with distinctive properties. All the as-prepared azetidine-containing polymers exhibit intrinsic visible luminescence in the solid state under long-wavelength UV irradiation even without conventionally conjugated structures. Such unconventional luminescence is attributed to the clusteroluminogens formed by through-space electronic interactions of heteroatoms and phenyl rings. All the obtained polymers show excellent optical transparency, high and tunable refractive indices, low optical dispersions and good photopatternability, which make them promising materials in various advanced electronic and optoelectronic devices. The ring-opened polymers can also function as a lysosome-specific fluorescent probe in biological imaging.
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Facile Multicomponent Polymerizations toward Unconventional Luminescent Polymers with Readily Openable Small Heterocycles.
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Journal of the American Chemical Society
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biology
| 1,674 | 9 |
The isoquinoline alkaloids isolated from the genus Corydalis possess potent and diverse biological activities. Herein, a concise, divergent, and enantioselective route to access these natural products is disclosed. Key transformations of our approach include a challenging Zn-ProPhenol-catalyzed asymmetric Mannich reaction to build a quaternary stereogenic center and a rapid cationic Au-catalyzed cycloisomerization to the common structural skeleton of these natural products. Subsequent late-stage oxidations and modifications allow efficient access to the targeted alkaloids. Overall, seven natural products have been successfully synthesized in 6 to 10 steps from readily available starting materials, including (+)-corynoline, (+)-anhydrocorynoline, (+)-12-hydroxycorynoline, (+)-12-hydroxycorynoloxine, (+)-corynoloxine, (+)-6-acetonylcorynoline, and (+)-bulleyanaline.
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Enantioselective Divergent Syntheses of (+)-Bulleyanaline and Related Isoquinoline Alkaloids from the Genus Corydalis.
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Journal of the American Chemical Society
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biology
| 1,674 | 9 |
If hydrogen can be stored and carried safely at a high density, hydrogen-fuel cells offer effective solutions for vehicles. The stable chemisorption of atomic hydrogen on single layer graphene (SLG) seems a perfect solution in this regard, with a theoretical maximum storage capacity of 7.7 wt %. However, generating hydrogenated graphene from H 2 requires extreme temperatures and pressures. Alternatively, hydrogen adatoms can easily be produced under mild conditions by the electroreduction of protons in solid/liquid systems. Graphene is electrochemically inert for this reaction, but H-chemisorption on SLG can be carried out under mild conditions via a novel Pt-electrocatalyzed "spillover-surface diffusion-chemisorption" mechanism, as we demonstrate using dynamic electrochemistry and isotopic Raman spectroscopy. The apparent surface diffusion coefficient (∼10 -5 cm 2 s -1 ), capacity (∼6.6 wt %, ∼85.7% surface coverage), and stability of hydrogen adatoms on SLG at room temperature and atmospheric pressure are significant, and they are perfectly suited for applications involving stored hydrogen atoms on graphene.
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Electrochemical Storage of Atomic Hydrogen on Single Layer Graphene.
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Journal of the American Chemical Society
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biology
| 1,674 | 9 |
A tetrahomoleptic, pseudotetrahedral U 4+ imidophosphorane complex, [U(NP(pip) 3 ) 4 ], 1-U(PN) , is reported. This complex can be oxidized by two electrons with either mesityl azide or nitrous oxide. This two-electron atom/group transfer oxidation is the first example observed at a homoleptic, tetravalent uranium complex. The mesityl imido compound [U(NMes)(NP(pip) 3 ) 4 ], 2-U(PN)NMes , exhibits a unique square pyramidal geometry in contrast to the expected trigonal bipyramidal geometry of the oxo complex [U(O)(NP(pip) 3 ) 4 ], 2-U(PN)O . The bonding driving the structural dichotomy of these structures and the absence of a structurally observable inverse trans -influence in 2-U(PN)NMes were examined by DFT and natural bonding orbital analysis.
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Two-Electron Oxidative Atom Transfer at a Homoleptic, Tetravalent Uranium Complex.
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Journal of the American Chemical Society
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biology
| 1,674 | 9 |
Ordered mesoporous materials (OMMs) have received increasing interest due to their uniform pore size, high surface area, various compositions and wide applications in energy conversion and storage, biomedicine and environmental remediation, etc. The soft templating synthesis using surfactants or amphiphilic block copolymers is the most efficient method to produce OMMs with tailorable pore structure and surface property. However, due to the limited choice of commercially available soft templates, the common OMMs usually show small pore size and amorphous (or semicrystalline) frameworks. Tailor-made amphiphilic block copolymers with controllable molecular weights and compositions have recently emerged as alternative soft templates for synthesis of new OMMs with many unique features including adjustable mesostructures and framework compositions, ultralarge pores, thick pore walls, high thermal stability and crystalline frameworks. In this Perspective, recent progresses and some new insights into the coassembly process about the synthesis of OMMs based on these tailor-made copolymers as templates are summarized, and typical newly developed synthesis methods and strategies are discussed in depth, including solvent evaporation induced aggregation, ligand-assisted coassembly, solvent evaporation induced micelle fusion-aggregation assembly, homopolymer assisted pore expanding and carbon-supported crystallization strategy. Then, the applications of the obtained large-pore OMMs in catalysis, sensor, energy conversion and storage, and biomedicine by loading large-size guest molecules (e.g., protein and RNA), precious metal nanoparticles and quantum dots, are discussed. At last, the outlook on the prospects and challenges of future research about the synthesis of large-pore OMMs by using tailor-made amphiphilic block copolymers are included.
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New Insight into the Synthesis of Large-Pore Ordered Mesoporous Materials.
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Journal of the American Chemical Society
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biology
| 1,674 | 9 |
The synthesis of a new anionic 3D metal-catecholate framework, termed MOF-1992, is achieved by linking tetratopic cobalt phthalocyanin-2,3,9,10,16,17,23,24-octaol linkers with Fe 3 (-C 2 O 2 -) 6 (OH 2 ) 2 trimers into an extended framework of roc topology. MOF-1992 exhibits sterically accessible Co active sites together with charge transfer properties. Cathodes based on MOF-1992 and carbon black (CB) display a high coverage of electroactive sites (270 nmol cm -2 ) and a high current density (-16.5 mA cm -2 ; overpotential, -0.52 V) for the CO 2 to CO reduction reaction in water (faradaic efficiency, 80%). Over the 6 h experiment, MOF-1992/CB cathodes reach turnover numbers of 5800 with turnover frequencies of 0.20 s -1 per active site.
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Three-Dimensional Phthalocyanine Metal-Catecholates for High Electrochemical Carbon Dioxide Reduction.
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Journal of the American Chemical Society
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biology
| 1,674 | 9 |
We address the double hydrogen transfer (DHT) dynamics of the porphycene molecule, a complex paradigmatic system in which the making and breaking of H-bonds in a highly anharmonic potential energy surface require a quantum mechanical treatment not only of the electrons but also of the nuclei. We combine density functional theory calculations, employing hybrid functionals and van der Waals corrections, with recently proposed and optimized path-integral ring-polymer methods for the approximation of quantum vibrational spectra and reaction rates. Our full-dimensional ring-polymer instanton simulations show that below 100 K the concerted DHT tunneling pathway dominates but between 100 and 300 K there is a competition between concerted and stepwise pathways when nuclear quantum effects are included. We obtain ground-state reaction rates of 2.19 × 10 11 s -1 at 150 K and 0.63 × 10 11 s -1 at 100 K, in good agreement with experiment. We also reproduce the puzzling N-H stretching band of porphycene with very good accuracy from thermostated ring-polymer molecular dynamics simulations. The position and line shape of this peak, centered at around 2600 cm -1 and spanning 750 cm -1 , stem from a combination of very strong H-bonds, the coupling to low-frequency modes, and the access to cis-like isomeric conformations, which cannot be appropriately captured with classical-nuclei dynamics. These results verify the appropriateness of our general theoretical approach and provide a framework for a deeper physical understanding of hydrogen transfer dynamics in complex systems.
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Elucidating the Nuclear Quantum Dynamics of Intramolecular Double Hydrogen Transfer in Porphycene.
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Journal of the American Chemical Society
|
biology
| 1,674 | 9 |
Chiral coordination cages feature both chirality and defined inner space, providing advanced molecular materials. A series of chiral 20-nucleus cobalt-imidazolate cages were synthesized by self-assembly of 72 subcomponents, featuring a novel tetartoid (tetragonal pentagonal dodecahedron) structure. Spontaneous resolution of racemic tetartoidal cages (Δ and Λ) into a conglomerate of homochiral crystals are observed, while both homochiral Δ and Λ tetartoidal cages can be obtained through chiral induction of (d)- and (l)-enantiomers of menthol, respectively. The 2-methyl substituent on imidazolyl is critical to the formation of a tetartoidal cage, and the absence of such steric effect will switch the final structure to a cubic cage.
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Self-Assembly of Chiral Metal-Organic Tetartoid.
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Journal of the American Chemical Society
|
biology
| 1,674 | 9 |
The isomalabaricanes comprise a large family of marine triterpenoids with fascinating structures that have been shown to be selective and potent apoptosis inducers in certain cancer cell lines. In this article, we describe the successful total syntheses of the isomalabaricanes stelletin A, stelletin E, and rhabdastrellic acid A, as well as the development of a general strategy to access other natural products within this unique family. High-throughput experimentation and computational chemistry methods were used in this endeavor. A preliminary structure-activity relationship study of stelletin A revealed the trans-syn-trans core motif of the isomalabaricanes to be critical for their cytotoxic activity.
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Synthetic Studies on Selective, Proapoptotic Isomalabaricane Triterpenoids Aided by Computational Techniques.
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Journal of the American Chemical Society
|
biology
| 1,674 | 9 |
Metal-organic frameworks and porous coordination cages have shown incredible promise as a result of their high tunability. However, syntheses pursuing precisely targeted mixed functionalities, such as multiple ligand types or mixed-metal compositions are often serendipitous, require postsynthetic modification strategies, or are based on complex ligand design. Herein, we present a new method for the controlled synthesis of mixed functionality metal-organic materials via the preparation of porous salts. More specifically, the combination of porous ionic molecules of opposite charge affords framework-like materials where the ratio between cationic cage and anionic cage is potentially tunable. The resulting doubly porous salt displays the spectroscopic signatures of the parent cages with increased gas uptake capacities as compared to starting materials. This approach will be widely applicable to all families of porous ions and represents a new and powerful method for the synthesis of porous solids with tailored functionalities.
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A Charged Coordination Cage-Based Porous Salt.
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Journal of the American Chemical Society
|
biology
| 1,674 | 9 |
Oxidative stress in depression is a prime cause of neurotransmitter metabolism dysfunction in the brain. Acetylcholinesterase (AChE), a key hydrolase in the cholinergic system, directly determines the degradation of neurotransmitters. However, due to the complexity of the brain and lack of appropriate in situ imaging tools, the mechanism underlying the changes in AChE activity in depression remains unclear. Hence, we generated a two-photon fluorescence probe (MCYN) for real-time visualization of AChE with excellent sensitivity and selectivity. AChE can specifically recognize and cleave the carbamic acid ester bond in MCYN, and MCYN emits bright fluorescence at 560 nm by two-photon excitation at 800 nm. By utilizing MCYN to monitor AChE, we discovered a significant increase in AChE activity in the brains of mice with depression phenotypes. Notably, with the assistance of a two-photon fluorescence imaging probe of the superoxide anion radical (O 2 •- ), in vivo visualization for the first time revealed the positive correlation between AChE and O 2 •- levels associated with depressive behaviors. This finding suggests that oxidative stress may induce AChE overactivation, leading to depression-related behaviors. This work provides a new and rewarding perspective to elucidate the role of oxidative stress regulating AChE in the pathology of depression.
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Observation of Acetylcholinesterase in Stress-Induced Depression Phenotypes by Two-Photon Fluorescence Imaging in the Mouse Brain.
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Journal of the American Chemical Society
|
biology
| 1,674 | 9 |
The translation of biological glycosylation in humans to the clinical applications involves systematic studies using homogeneous samples of oligosaccharides and glycoconjugates, which could be accessed by chemical, enzymatic or other biological methods. However, the structural complexity and wide-range variations of glycans and their conjugates represent a major challenge in the synthesis of this class of biomolecules. To help navigate within many methods of oligosaccharide synthesis, this Perspective offers a critical assessment of the most promising synthetic strategies with an eye on the therapeutically relevant targets.
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Oligosaccharide Synthesis and Translational Innovation.
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Journal of the American Chemical Society
|
biology
| 1,674 | 9 |
Density functional calculations have provided evidence that a Ag(I)-mediated deconstructive fluorination of N -benzoylated cyclic amines ( LH ) with Selectfluor [(F-TEDA)(BF 4 ) 2 ] begins with an association of the reactants to form a singlet state adduct {[( LH )-Ag]-[F-TEDA] 2+ }. The subsequent formation of an iminium ion intermediate, [ L + -Ag]-HF-[TEDA] + , is, formally, a Ag(I)-mediated hydride abstraction event that occurs in two steps: (a) a formal oxidative addition (OA) of [F-TEDA] 2+ to the Ag(I) center that is attended by an electron transfer (ET) from the substrate ( LH ) to the Ag center (i.e., OA + ET, this process can also be referred to as a F-atom coupled electron transfer), followed by (b) H-atom abstraction from LH by the Ag-coordinated F atom. The overall process involves lower-lying singlet and triplet electronic states of several intermediates. Therefore, we formally refer to this reaction as a two-state reactivity (TSR) event. The C-C bond cleavage/fluorination of the resulting hemiaminal intermediate via a ring-opening pathway has also been determined to be a TSR event. A competing deformylative fluorination initiated by hemiaminal to aldehyde equilibration involving formyl H-atom abstraction by a TEDA 2+ radical dication, decarbonylation, and fluorination of the resulting alkyl radical by another equivalent of Selectfluor may also be operative in the latter step.
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Key Mechanistic Features of the Silver(I)-Mediated Deconstructive Fluorination of Cyclic Amines: Multistate Reactivity versus Single-Electron Transfer.
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Journal of the American Chemical Society
|
biology
| 1,674 | 9 |
The power of cation-initiated cyclizations of polyenes for the synthesis of polycyclic terpenoids cannot be overstated. However, a major limitation is the intolerance of many relevant reaction conditions toward the inclusion in the substrate of polar functionality, particularly in unprotected form. Radical polycyclizations are important alternatives to bioinspired cationic variants, in part owing to the range of possible initiation strategies, and in part for the functional group tolerance of radical reactions. In this article, we demonstrate that Co-catalyzed MHAT-initiated radical bicyclizations are not only tolerant of oxidation at virtually every position in the substrate, oftentimes in unprotected form, but these functional groups can also contribute to high levels of stereochemical control in these complexity-generating transformations. Specifically, we show the effects of protected or unprotected hydroxy groups at six different positions and their impact on stereoselectivity. Further, we show how multiply oxidized substrates perform in these reactions, and finally, we document the utility of these reactions in the synthesis of three aromatic abietane diterpenoids.
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Stereocontrolled Radical Bicyclizations of Oxygenated Precursors Enable Short Syntheses of Oxidized Abietane Diterpenoids.
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Journal of the American Chemical Society
|
biology
| 1,674 | 9 |
A pure-supramolecular-linker (PSL) approach for the formation of metal-organic frameworks (MOFs) was initially given, which was demonstrated by syntheses of two highly connected and isostructural MOFs, {Fe 3 O(TPBTM 6- )(Cl)(H 2 O) 2 } ∞ (TPBTM = N , N ', N ″-tris(isophthalyl)-1,3,5-benzenetricarboxamide) (NJU-Bai52, NJU-Bai for Nanjing University Bai group) and {Sc 3 O(TPBTM 6- )(OH)(H 2 O) 2 } ∞ (NJU-Bai53). Very interestingly, they exhibit exceptional thermal stability, water stability, and highly selective CO 2 capture properties. In particular, NJU-Bai53 with higher uptakes (2.74 wt % at 0.4 mbar and 298 K, 7.67 wt % at 298 K and 0.15 bar) and higher selectivity may be an excellent candidate for CO 2 capture.
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Pure-Supramolecular-Linker Approach to Highly Connected Metal-Organic Frameworks for CO2 Capture.
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Journal of the American Chemical Society
|
biology
| 1,674 | 9 |
The interface of metal-oxide plays pivotal roles in catalytic reactions, but its catalytic function is still not clear. In this study, we report the high activity of nanostructured Ru/ceria (Ru-clusters/ceria) in the ethylene methoxycarbonylation (EMC) reaction in the absence of acid promoter. The catalyst offers 92% yield of MP with TOF of 8666 h -1 , which is about 2.5 times of homogeneous Pd catalyst (∼3500 h -1 ). The interfacial Lewis acid-base pair [Ru-O-Ce-Vö], which consists of acidic Ce-Vö (oxygen vacancy) site and basic interfacial oxygen of Ru-O-Ce linkage, acts as active site for the dissociation of methanol and the subsequent transfer of hydrogen to the activated ethylene, which is the key step in acid-promoter-free EMC reaction. The combination of 1 H MAS NMR, pyridine-IR and DFT calculations reveals the hydrogen species derived from methanol contains Brönsted acidity. The EMC reaction mechanism under acid-promoter-free condition over Ru-clusters/ceria catalyst is discussed.
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Acid-Promoter-Free Ethylene Methoxycarbonylation over Ru-Clusters/Ceria: The Catalysis of Interfacial Lewis Acid-Base Pair.
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Journal of the American Chemical Society
|
biology
| 1,674 | 9 |
γ-Secretase is a membrane-embedded aspartyl protease complex central in biology and medicine. How this enzyme recognizes transmembrane substrates and catalyzes hydrolysis in the lipid bilayer is unclear. Inhibitors that mimic the entire substrate transmembrane domain and engage the active site should provide important tools for structural biology, yielding insight into substrate gating and trapping the protease in the active state. Here, we report transmembrane peptidomimetic inhibitors of the γ-secretase complex that contain an N-terminal helical peptide region that engages a substrate docking exosite and a C-terminal transition-state analog moiety targeted to the active site. Both regions are required for stoichiometric inhibition of γ-secretase. Moreover, enzyme inhibition kinetics and photoaffinity probe displacement experiments demonstrate that both the docking exosite and the active site are engaged by the bipartite inhibitors. The solution conformations of these potent transmembrane-mimetic inhibitors are similar to those of bound natural substrates, suggesting these probes are preorganized for high-affinity binding and should allow visualization of the active γ-secretase complex, poised for intramembrane proteolysis, by cryo-electron microscopy.
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Design of Substrate Transmembrane Mimetics as Structural Probes for γ-Secretase.
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Journal of the American Chemical Society
|
biology
| 1,674 | 9 |
We present the results of an all-sky search for continuous gravitational-wave signals with frequencies in the 500-1700 Hz range targeting neutron stars with ellipticity of 10^{-8}. The search is done on LIGO O2 data using the Falcon analysis pipeline. The results presented here double the sensitivity over any other result on the same data [B. P. Abbott et al. (LIGO Scientific Collaboration and Virgo Collaboration), Phys. Rev. D 100, 024004 (2019)PRVDAQ2470-001010.1103/PhysRevD.100.024004, C. Palomba et al., Phys. Rev. Lett. 123, 171101 (2019)PRLTAO0031-900710.1103/PhysRevLett.123.171101]. The search is capable of detecting low-ellipticity sources up to 170 pc. We establish strict upper limits which hold for worst-case signal parameters. We list outliers uncovered by the search, including several which we cannot associate with any known instrumental cause.
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Results from the First All-Sky Search for Continuous Gravitational Waves from Small-Ellipticity Sources.
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Physical review letters
|
physics
| 2,149 | 56 |
The thermal properties of a material with a spatiotemporal modulation, in the form of a traveling wave, in both the thermal conductivity and the specific heat capacity are studied. It is found that these materials behave as materials with an internal convectionlike term that provides them with nonreciprocal properties, in the sense that the heat flux has different properties when it propagates in the same direction or in the opposite one to the modulation of the parameters. An effective medium description is presented which accurately describes the modulated material, and numerical simulations support this description and verify the nonreciprocal properties of the material. It is found that these materials are promising candidates for the design of thermal diodes and other advanced devices for the control of the heat flow at all scales.
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Nonreciprocal Thermal Material by Spatiotemporal Modulation.
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Physical review letters
|
physics
| 2,149 | 56 |
At the triple point of a repulsive screened Coulomb system, a fcc crystal, a bcc crystal, and a fluid phase coexist. At their intersection, these three phases form a liquid groove, the triple junction. Using confocal microscopy, we resolve the triple junction on a single-particle level in a model system of charged PMMA colloids in a nonpolar solvent. The groove is found to be extremely deep and the incommensurate solid-solid interface to be very broad. Thermal fluctuations hence appear to dominate the solid-solid interface. This indicates a very low interfacial energy. The fcc-bcc interfacial energy is quantitatively determined based on Young's equation and, indeed, it is only about 1.3 times higher than the fcc-fluid interfacial energy close to the triple point.
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Triple Junction at the Triple Point Resolved on the Individual Particle Level.
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Physical review letters
|
physics
| 2,149 | 56 |
We consider dipolar excitations propagating via dipole-induced exchange among immobile molecules randomly spaced in a lattice. The character of the propagation is determined by long-range hops (Levy flights). We analyze the eigenenergy spectra and the multifractal structure of the wave functions. In 1D and 2D, all states are localized, although in 2D the localization length can be extremely large leading to an effective localization-delocalization crossover in realistic systems. In 3D, all eigenstates are extended but not always ergodic, and we identify the energy intervals of ergodic and nonergodic states. The reduction of the lattice filling induces an ergodic to nonergodic transition, and the excitations are mostly nonergodic at low filling.
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Quantum Levy Flights and Multifractality of Dipolar Excitations in a Random System.
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Physical review letters
|
physics
| 2,149 | 56 |
Using parametric conversion induced by a Shapiro-type resonance, we produce and characterize a two-mode squeezed vacuum state in a sodium spin 1 Bose-Einstein condensate. Spin-changing collisions generate correlated pairs of atoms in the m=±1 Zeeman states out of a condensate with initially all atoms in m=0. A novel fluorescence imaging technique with sensitivity ΔN∼1.6 atom enables us to demonstrate the role of quantum fluctuations in the initial dynamics and to characterize the full distribution of the final state. Assuming that all atoms share the same spatial wave function, we infer a squeezing parameter of 15.3 dB.
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Probing Spin Correlations in a Bose-Einstein Condensate Near the Single-Atom Level.
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Physical review letters
|
physics
| 2,149 | 56 |
The ability to prepare nonclassical states in a robust manner is essential for quantum sensors beyond the standard quantum limit. We demonstrate that Bayesian optimal control is capable of finding control pulses that drive trapped Rydberg atoms into highly entangled Greenberger-Horne-Zeilinger states. The control sequences have a physically intuitive functionality based on the quasi-integrability of the Ising dynamics. They can be constructed in laboratory experiments, resulting in preparation times that scale very favorably with the system size.
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Bayesian Optimal Control of Greenberger-Horne-Zeilinger States in Rydberg Lattices.
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Physical review letters
|
physics
| 2,149 | 56 |
We study the physical properties of four-dimensional, string-theoretical, horizonless "fuzzball" geometries by imaging their shadows. Their microstructure traps light rays straying near the would-be horizon on long-lived, highly redshifted chaotic orbits. In fuzzballs sufficiently near the scaling limit this creates a shadow much like that of a black hole, while avoiding the paradoxes associated with an event horizon. Observations of the shadow size and residual glow can potentially discriminate between fuzzballs away from the scaling limit and alternative models of black compact objects.
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Fuzzball Shadows: Emergent Horizons from Microstructure.
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Physical review letters
|
physics
| 2,149 | 56 |
We investigate the emergence of orientational order among +1/2 disclinations in active nematic liquid crystals. Using a combination of theoretical and experimental methods, we show that +1/2 disclinations have short-range antiferromagnetic alignment, as a consequence of the elastic torques originating from their polar structure. The presence of intermediate -1/2 disclinations, however, turns this interaction from antialigning to aligning at scales that are smaller than the typical distance between like-sign defects. No long-range orientational order is observed. Strikingly, these effects are insensitive to material properties and qualitatively similar to what is found for defects in passive nematic liquid crystals.
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Orientational Correlations in Active and Passive Nematic Defects.
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Physical review letters
|
physics
| 2,149 | 56 |
We present a framework in which the transition between a many-body localized (MBL) phase and an ergodic one is symmetry breaking. We consider random Floquet spin chains, expressing their averaged spectral form factor (SFF) as a function of time in terms of a transfer matrix that acts in the space direction. The SFF is determined by the leading eigenvalues of this transfer matrix. In the MBL phase, the leading eigenvalue is unique, as in a symmetry-unbroken phase, while in the ergodic phase and at late times the leading eigenvalues are asymptotically degenerate, as in a system with degenerate symmetry-breaking phases. We identify the broken symmetry of the transfer matrix, introduce a local order parameter for the transition, and show that the associated correlation functions are long-ranged only in the ergodic phase.
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Many-Body Delocalization as Symmetry Breaking.
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Physical review letters
|
physics
| 2,149 | 56 |
We investigate the bulk photovoltaic effect, which rectifies light into electric current, in a collective quantum state with correlation driven electronic ferroelectricity. We show via explicit real-time dynamical calculations that the effect of the applied electric field on the electronic order parameter leads to a strong enhancement of the bulk photovoltaic effect relative to the values obtained in a conventional insulator. The enhancements include both resonant enhancements at sub-band-gap frequencies, arising from excitation of optically active collective modes, and broadband enhancements arising from nonresonant deformations of the electronic order. The deformable electronic order parameter produces an injection current contribution to the bulk photovoltaic effect that is entirely absent in a rigid-band approximation to a time-reversal symmetric material. Our findings establish that correlation effects can lead to the bulk photovoltaic effect and demonstrate that the collective behavior of ordered states can yield large nonlinear optical responses.
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Bulk Photovoltaic Effect Driven by Collective Excitations in a Correlated Insulator.
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Physical review letters
|
physics
| 2,149 | 56 |
We study the statistical-mechanical properties of intertwined double-helical DNAs (DNA braids). In magnetic tweezers experiments, we find that torsionally stressed stretched braids supercoil via an abrupt buckling transition, which is associated with the nucleation of a braid end loop, and that the buckled braid is characterized by a proliferation of multiple domains. Differences between the mechanics of DNA braids and supercoiled single DNAs can be understood as an effect of the increased bulkiness in the structure of the former. The experimental results are in accord with the predictions of a statistical-mechanical model.
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Nucleation of Multiple Buckled Structures in Intertwined DNA Double Helices.
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Physical review letters
|
physics
| 2,149 | 56 |
Hund's coupling is shown to generally favor, in a doped half-filled Mott insulator, an increase in the compressibility culminating in a Fermi-liquid instability towards phase separation. The largest effect is found near the frontier between an ordinary and an orbitally decoupled ("Hund's") metal. The increased compressibility implies an enhancement of quasiparticle scattering, thus favoring other possible symmetry breakings. This physics is shown to happen in simulations of the 122 Fe-based superconductors, possibly implying the relevance of this mechanism in the enhancement of the critical temperature for superconductivity.
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Hund's Induced Fermi-Liquid Instabilities and Enhanced Quasiparticle Interactions.
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Physical review letters
|
physics
| 2,149 | 56 |
We report on the strong coupling of surface plasmon polaritons and molecular vibrations in an organic-inorganic plasmonic hybrid structure consisting of a ketone-based polymer deposited on top of a silver layer. Attenuated-total-reflection spectra of the hybrid reveal an anticrossing in the dispersion relation in the vicinity of the carbonyl stretch vibration of the polymer with an energy splitting of the upper and lower polariton branch up to 15 meV. The splitting is found to depend on the molecular layer thickness and saturates for micrometer-thick films. This new hybrid state holds a strong potential for application in chemistry and optoelectronics.
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Strong Coupling between Surface Plasmon Polaritons and Molecular Vibrations.
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Physical review letters
|
physics
| 2,149 | 56 |
Much of the physical world around us can be described in terms of harmonic oscillators in thermodynamic equilibrium. At the same time, the far-from-equilibrium behavior of oscillators is important in many aspects of modern physics. Here, we investigate a resonating system subject to a fundamental interplay between intrinsic nonlinearities and a combination of several driving forces. We have constructed a controllable and robust realization of such a system using a macroscopic doubly clamped string. We experimentally observe a hitherto unseen double hysteresis in both the amplitude and the phase of the resonator's response function and present a theoretical model that is in excellent agreement with the experiment. Our work unveils that the double hysteresis is a manifestation of an out-of-equilibrium symmetry breaking between parametric phase states. Such a fundamental phenomenon, in the most ubiquitous building block of nature, paves the way for the investigation of new dynamical phases of matter in parametrically driven many-body systems and motivates applications ranging from ultrasensitive force detection to low-energy computing memory units.
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Parametric Symmetry Breaking in a Nonlinear Resonator.
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Physical review letters
|
physics
| 2,149 | 56 |
We report the first measurement of monoenergetic muon neutrino charged current interactions. MiniBooNE has isolated 236 MeV muon neutrino events originating from charged kaon decay at rest (K^{+}→μ^{+}ν_{μ}) at the NuMI beamline absorber. These signal ν_{μ}-carbon events are distinguished from primarily pion decay in flight ν_{μ} and ν[over ¯]_{μ} backgrounds produced at the target station and decay pipe using their arrival time and reconstructed muon energy. The significance of the signal observation is at the 3.9σ level. The muon kinetic energy, neutrino-nucleus energy transfer (ω=E_{ν}-E_{μ}), and total cross section for these events are extracted. This result is the first known-energy, weak-interaction-only probe of the nucleus to yield a measurement of ω using neutrinos, a quantity thus far only accessible through electron scattering.
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First Measurement of Monoenergetic Muon Neutrino Charged Current Interactions.
|
Physical review letters
|
physics
| 2,149 | 56 |
In a magnetically confined plasma with a stochastic magnetic field, the dependence of the perpendicular viscosity on the magnetic fluctuation amplitude is measured for the first time. With a controlled, ∼ tenfold variation in the fluctuation amplitude, the viscosity increases ∼100-fold, exhibiting the same fluctuation-amplitude-squared dependence as the predicted rate of stochastic field line diffusion. The absolute value of the viscosity is well predicted by a model based on momentum transport in a stochastic field, the first in-depth test of this model.
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Dependence of Perpendicular Viscosity on Magnetic Fluctuations in a Stochastic Topology.
|
Physical review letters
|
physics
| 2,149 | 56 |
Recent scanning tunneling microscopy (STM) experiments reported single-molecule fluorescence induced by tunneling currents in the nanoplasmonic cavity formed by the STM tip and the substrate. The electric field of the cavity mode couples with the current-induced charge fluctuations of the molecule, allowing the excitation of photons. We investigate theoretically this system for the experimentally relevant limit of large damping rate κ for the cavity mode and arbitrary coupling strength to a single-electronic level. We find that for bias voltages close to the first inelastic threshold of photon emission, the emitted light displays antibunching behavior with vanishing second-order photon correlation function. At the same time, the current and the intensity of emitted light display Franck-Condon steps at multiples of the cavity frequency ω_{c} with a width controlled by κ rather than the temperature T. For large bias voltages, we predict strong photon bunching of the order of κ/Γ where Γ is the electronic tunneling rate. Our theory thus predicts that strong coupling to a single level allows current-driven nonclassical light emission.
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Single-Photon Emission Mediated by Single-Electron Tunneling in Plasmonic Nanojunctions.
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Physical review letters
|
physics
| 2,149 | 56 |
We reformulate the projected imaginary-time evolution of the full configuration interaction quantum Monte Carlo method in terms of a Lagrangian minimization. This naturally leads to the admission of polynomial complex wave function parametrizations, circumventing the exponential scaling of the approach. While previously these functions have traditionally inhabited the domain of variational Monte Carlo approaches, we consider recent developments for the identification of deep-learning neural networks to optimize this Lagrangian, which can be written as a modification of the propagator for the wave function dynamics. We demonstrate this approach with a form of tensor network state, and use it to find solutions to the strongly correlated Hubbard model, as well as its application to a fully periodic ab initio graphene sheet. The number of variables which can be simultaneously optimized greatly exceeds alternative formulations of variational Monte Carlo methods, allowing for systematic improvability of the wave function flexibility towards exactness for a number of different forms, while blurring the line between traditional variational and projector quantum Monte Carlo approaches.
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Projector Quantum Monte Carlo Method for Nonlinear Wave Functions.
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Physical review letters
|
physics
| 2,149 | 56 |
We measured the electromagnetic stress-induced local strain distribution on a centimeter-sized parallel-plate metallic resonant unit illuminated with microwave radiation. Using a fiber interferometer, we found that the strain changes sign across the resonant unit, in agreement with theoretical predictions that the attractive electric and repulsive magnetic forces act at different locations. The enhancement of the corresponding maximum local electromagnetic stress is stronger than the enhancement of the net force, reaching a factor of >600 compared to the ordinary radiation pressure.
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Measurement of Mechanical Deformations Induced by Enhanced Electromagnetic Stress on a Parallel Metallic-Plate System.
|
Physical review letters
|
physics
| 2,149 | 56 |
The fast pyrolysis of waste lignin derived from biobutanol production process was performed to determine the optimal pyrolysis conditions and pyrolysis product properties. Four types of pyrolysis reactors, e.g.: micro-scale pyrolyzer-gas chromatography/mass spectrometry, lab and bench scale fixed bed (FB) reactors, and bench scale rotary kiln (RK) reactor, were employed to compare the pyrolysis reaction conditions and product properties obtained from different reactors. The yields of char, oil, and gas obtained from lab scale and bench scale reactor were almost similar compared to FB reactor. RK reactor produced desirable bio-oil with much reduced yield of poly aromatic hydrocarbons (cancer precursor) due to its higher cracking reaction efficiency. In addition, char agglomeration and foaming of lignin pyrolysis were greatly restricted by using RK reactor compared to the FB reactor.
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Production of bio-oil with reduced polycyclic aromatic hydrocarbons via continuous pyrolysis of biobutanol process derived waste lignin.
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Journal of hazardous materials
|
chemistry
| 1,530 | 13 |
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