1,919 research outputs found
Universal Thermoelectric Effect of Dirac Fermions in Graphene
We numerically study the thermoelectric transports of Dirac fermions in
graphene in the presence of a strong magnetic field and disorder. We find that
the thermoelectric transport coefficients demonstrate universal behavior
depending on the ratio between the temperature and the width of the
disorder-broadened Landau levels(LLs). The transverse thermoelectric
conductivity reaches a universal quantum value at the center of
each LL in the high temperature regime, and it has a linear temperature
dependence at low temperatures. The calculated Nernst signal has a peak at the
central LL with heights of the order of , and changes sign near other
LLs, while the thermopower has an opposite behavior, in good agreement with
experimental data. The validity of the generalized Mott relation between the
thermoelectric and electrical transport coefficients is verified in a wide
range of temperatures.Comment: 4 pages, 4 figures, published versio
Search for spin-dependent gravitational interactions at the Earth range
Among the four fundamental forces, only gravity does not couple to particle
spins according to the general theory of relativity. We test this principle by
searching for an anomalous scalar coupling between the neutron spin and the
Earth gravity on the ground. We develop an atomic gas comagnetometer to measure
the ratio of nuclear spin-precession frequencies between Xe and
Xe, and search for a change of this ratio to the precision of 10
as the sensor is flipped in the Earth gravitational field. The null results of
this search set an upper limit on the coupling energy between the neutron spin
and the gravity on the ground at 5.310~eV (95\% confidence
level), resulting in a 17-fold improvement over the previous limit. The results
can also be used to constrain several other anomalous interactions. In
particular, the limit on the coupling strength of axion-mediated
monopole-dipole interactions at the range of the Earth radius is improved by a
factor of 17.Comment: Accepted by Physical Review Letter
3-Carboxypyrazino[2,3-f][1,10]phenanthrolin-9-ium-2-carboxylate
In the title zwitterionic compound, C16H8N4O4, the dihedral angle between the carboxyl and carboxylate groups is 72.14 (2)°. In the crystal, molecules are linked by strong intermolecular O—H⋯O− and N+—H⋯O− hydrogen bonds into double chains extended along [001]. These chains are additionally stabilized by π–π stacking interactions between the pyridine and benzene rings [centroid–centroid distance = 3.5542 (8) Å]
Bilaterally Combined Electric and Acoustic Hearing in Mandarin-Speaking Listeners: The Population With Poor Residual Hearing
The hearing loss criterion for cochlear implant candidacy in mainland China is extremely stringent (bilateral severe to
profound hearing loss), resulting in few patients with substantial residual hearing in the nonimplanted ear. The main objective
of the current study was to examine the benefit of bimodal hearing in typical Mandarin-speaking implant users who have
poorer residual hearing in the nonimplanted ear relative to those used in the English-speaking studies. Seventeen Mandarinspeaking bimodal users with pure-tone averages of 80 dB HL participated in the study. Sentence recognition in quiet and in
noise as well as tone and word recognition in quiet were measured in monaural and bilateral conditions. There was no
significant bimodal effect for word and sentence recognition in quiet. Small bimodal effects were observed for sentence
recognition in noise (6%) and tone recognition (4%). The magnitude of both effects was correlated with unaided thresholds at
frequencies near voice fundamental frequencies (F0s). A weak correlation between the bimodal effect for word recognition
and unaided thresholds at frequencies higher than F0s was identified. These results were consistent with previous findings
that showed more robust bimodal benefits for speech recognition tasks that require higher spectral resolution than speech
recognition in quiet. The significant but small F0-related bimodal benefit was also consistent with the limited acoustic hearing
in the nonimplanted ear of the current subject sample, who are representative of the bimodal users in mainland China.
These results advocate for a more relaxed implant candidacy criterion to be used in mainland China
Association between regulatory T cell activity and sepsis and outcome of severely burned patients: a prospective, observational study
Silicon nitride metalenses for unpolarized high-NA visible imaging
As one of nanoscale planar structures, metasurface has shown excellent
superiorities on manipulating light intensity, phase and/or polarization with
specially designed nanoposts pattern. It allows to miniature a bulky optical
lens into the chip-size metalens with wavelength-order thickness, playing an
unprecedented role in visible imaging systems (e.g. ultrawide-angle lens and
telephoto). However, a CMOS-compatible metalens has yet to be achieved in the
visible region due to the limitation on material properties such as
transmission and compatibility. Here, we experimentally demonstrate a divergent
metalens based on silicon nitride platform with large numerical aperture
(NA~0.98) and high transmission (~0.8) for unpolarized visible light,
fabricated by a 695-nm-thick hexagonal silicon nitride array with a minimum
space of 42 nm between adjacent nanoposts. Nearly diffraction-limit virtual
focus spots are achieved within the visible region. Such metalens enables to
shrink objects into a micro-scale size field of view as small as a single-mode
fiber core. Furthermore, a macroscopic metalens with 1-cm-diameter is also
realized including over half billion nanoposts, showing a potential application
of wide viewing-angle functionality. Thanks to the high-transmission and
CMOS-compatibility of silicon nitride, our findings may open a new door for the
miniaturization of optical lenses in the fields of optical fibers,
microendoscopes, smart phones, aerial cameras, beam shaping, and other
integrated on-chip devices.Comment: 16 pages, 7 figure
Large-scale Kinetic Simulations of Colliding Plasmas within a Hohlraum of Indirect Drive Inertial Confinement Fusions
The National Ignition Facility has recently achieved successful burning
plasma and ignition using the inertial confinement fusion (ICF) approach.
However, there are still many fundamental physics phenomena that are not well
understood, including the kinetic processes in the hohlraum. Shan et al. [Phys.
Rev. Lett, 120, 195001, 2018] utilized the energy spectra of neutrons to
investigate the kinetic colliding plasma in a hohlraum of indirect drive ICF.
However, due to the typical large spatial-temporal scales, this experiment
could not be well simulated by using available codes at that time. Utilizing
our advanced high-order implicit PIC code, LAPINS, we were able to successfully
reproduce the experiment on a large scale of both spatial and temporal
dimensions, in which the original computational scale was increased by
approximately 7 to 8 orders of magnitude. When gold plasmas expand into
deuterium plasmas, a kinetic shock is generated and propagates within deuterium
plasmas. Simulations allow us to observe the entire progression of a strong
shock wave, including its initial formation and steady propagation. Although
both electrons and gold ions are collisional (on a small scale compared to the
shock wave), deuterium ions seem to be collisionless. This is because a
quasi-monoenergetic spectrum of deuterium ions can be generated by reflecting
ions from the shock front, which then leads to the production of neutrons with
unusual broadening due to beam-target nuclear reactions. This work displays an
unprecedented kinetic analysis of an existing experiment, shedding light on the
mechanisms behind shock wave formation. It also serves as a reference for
benchmark simulations of upcoming new simulation codes and may be relevant for
future research on mixtures and entropy increments at plasma interfaces
Treatment with gelsolin reduces brain inflammation and apoptotic signaling in mice following thermal injury
<p>Abstract</p> <p>Background</p> <p>Burn survivors develop long-term cognitive impairment with increased inflammation and apoptosis in the brain. Gelsolin, an actin-binding protein with capping and severing activities, plays a crucial role in the septic response. We investigated if gelsolin infusion could attenuate neural damage in burned mice.</p> <p>Methods</p> <p>Mice with 15% total body surface area burns were injected intravenously with bovine serum albumin as placebo (2 mg/kg), or with low (2 mg/kg) or high doses (20 mg/kg) of gelsolin. Samples were harvested at 8, 24, 48 and 72 hours postburn. The immune function of splenic T cells was analyzed. Cerebral pathology was examined by hematoxylin/eosin staining, while activated glial cells and infiltrating leukocytes were detected by immunohistochemistry. Cerebral cytokine mRNAs were further assessed by quantitative real-time PCR, while apoptosis was evaluated by caspase-3. Neural damage was determined using enzyme-linked immunosorbent assay of neuron-specific enolase (NSE) and soluble protein-100 (S-100). Finally, cerebral phospho-ERK expression was measured by western blot.</p> <p>Results</p> <p>Gelsolin significantly improved the outcomes of mice following major burns in a dose-dependent manner. The survival rate was improved by high dose gelsolin treatment compared with the placebo group (56.67% vs. 30%). Although there was no significant improvement in outcome in mice receiving low dose gelsolin (30%), survival time was prolonged against the placebo control (43.1 ± 4.5 h vs. 35.5 ± 5.0 h; P < 0.05). Burn-induced T cell suppression was greatly alleviated by high dose gelsolin treatment. Concurrently, cerebral abnormalities were greatly ameliorated as shown by reduced NSE and S-100 content of brain, decreased cytokine mRNA expressions, suppressed microglial activation, and enhanced infiltration of CD11b+ and CD45+ cells into the brain. Furthermore, the elevated caspase-3 activity seen following burn injury was remarkably reduced by high dose gelsolin treatment along with down-regulation of phospho-ERK expression.</p> <p>Conclusion</p> <p>Exogenous gelsolin infusion improves survival of mice following major burn injury by partially attenuating inflammation and apoptosis in brain, and by enhancing peripheral T lymphocyte function as well. These data suggest a novel and effective strategy to combat excessive neuroinflammation and to preserve cognition in the setting of major burns.</p
Multi-Target Screening and Experimental Validation of Natural Products from Selaginella Plants against Alzheimer's Disease
Alzheimer's disease (AD) is a progressive and irreversible neurodegenerative disorder which is considered to be the most common cause of dementia. It has a greater impact not only on the learning and memory disturbances but also on social and economy. Currently, there are mainly single-target drugs for AD treatment but the complexity and multiple etiologies of AD make them difficult to obtain desirable therapeutic effects. Therefore, the choice of multi-target drugs will be a potential effective strategy inAD treatment. To find multi-target active ingredients for AD treatment from Selaginella plants, we firstly explored the behaviors effects on AD mice of total extracts (TE) from Selaginella doederleinii on by Morris water maze test and found that TE has a remarkable improvement on learning and memory function for AD mice. And then, multi-target SAR models associated with AD-related proteins were built based on Random Forest (RF) and different descriptors to preliminarily screen potential active ingredients from Selaginella. Considering the prediction outputs and the quantity of existing compounds in our laboratory, 13 compounds were chosen to carry out the in vitro enzyme inhibitory experiments and 4 compounds with BACE1/MAO-B dual inhibitory activity were determined. Finally, the molecular docking was applied to verify the prediction results and enzyme inhibitory experiments. Based on these study and validation processes, we explored a new strategy to improve the efficiency of active ingredients screening based on trace amount of natural product and numbers of targets and found some multi-target compounds with biological activity for the development of novel drugs for AD treatment
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