712 research outputs found
Analysis of genetic structure of white croaker usin amplified fragment length polymorphism (AFLP) markers
No Abstrac
Spatially resolved pump-probe study of single-layer graphene produced by chemical vapor deposition
Carrier dynamics in single-layer graphene grown by chemical vapor deposition
(CVD) is studied using spatially and temporally resolved pump-probe
spectroscopy by measuring both differential transmission and differential
reflection. By studying the expansion of a Gaussian spatial profile of carriers
excited by a 1500-nm pump pulse with a 1761-nm probe pulse, we observe a
diffusion of hot carriers of 5500 square centimeter per second. We also observe
that the expansion of the carrier density profile decreases to a slow rate
within 1 ps, which is unexpected. Furthermore, by using an 810-nm probe pulse
we observe that both the differential transmission and reflection change signs,
but also that this sign change can be permanently removed by exposure of the
graphene to femtosecond laser pulses of relatively high fluence. This indicates
that the differential transmission and reflection at later times may not be
directly caused by carriers, but may be from some residue material from the
sample fabrication or transfer process.Comment: 9 pages, 3 figure
Differences in Mode of Action of Cochinchinenin A and B on Tetrodotoxin-Resistant Sodium Channels
Purpose: To explore the mechanism of antagonistic interaction between cochinchinenin A and B in modulating tetrodotoxin-resistant (TTR-X) sodium currents.Methods: The time variation of the effects induced by cochinchinenin A and B on the TTX-R sodium currents in dorsal root ganglion (DRG) neurons of rats were observed using whole-cell patch clamp technique. Based on pharmacological fundamental theory, the modes of action of cochinchinenin A and B on TTX-R channels were distinguished.Results: The scatter diagram which reflected the time variation of inhibition effect on TTX-R sodium currents induced by cochinchinenin A fitted well with occupancy theory equation (goodness of fit test, p > 0.05), while that of cochinchinenin B fitted well with rate theory equation (p > 0.05). The rate constants for combination and dissociation between cochinchinenin A and TTX-R sodium channel were (198.7 ± 39.9) x 10-3 and (41.1 ± 6.2) x 10-3 respectively; while corresponding values for combination andassociation between cochinchinenin B and TTX-R sodium channel were (99.9 ± 16.8) x 10-3 and (5.3 ± 0.4) x 10-3 respectively.Conclusion: The main cause of the antagonistic interaction between cochinchinenin A and B may be attributed to the different modes of their action on TTX-R sodium channels.Keywords: Cochinchinenin, Tetrodotoxin-resistant sodium channel, Antagonistic interaction, Occupancy theory, Rate theor
Effect of mechanical stimulation on the degradation of poly(lactic acid) scaffolds with different designed structures
Biodegradability is one of the required scaffold functions for bone tissue engineering, and it is influenced by the mechanical micro-environment after scaffold implantation into body. This paper aimed to develop a mathematical model to numerically study the mechanical impact on the degradation of poly (lactic acid) (PLA) scaffolds with different designed structures. In addition, the diffusion-governed autocatalysis on the scaffold degradation was also included, and the scaffold collapse time by an author-developed algorithm was determined. The results showed that an increase in mechanical stimulation led to an increase in the scaffold degradation rate. Moreover, different structures with a similar porosity shared a degradation tendency but had different collapse times, which was very sensitive to the diffusion coefficient of the scaffold. The present study could be helpful to understand the dynamic degradation process of PLA scaffolds, and guide the design of PLA material and scaffold structure. It may be also used as a tool for the evaluation of the in vitro and in vivo degradation performance of scaffolds.</p
Internal friction and Jahn-Teller effect in the charge-ordered La1-xCaxMnO3 (0.5<x<0.87)
The Jahn-Teller effect in the charge-ordered (CO) state for La1-xCaxMnO3
(0.5<x<0.87) was studied by measuring the low-temperature powder x-ray
diffraction, internal friction, and shear modulus. We find that the
electron-lattice interaction with the static Jahn-Teller distortion is the
strongest near x=0.75 in the CO state. It was particularly observed that a
crossover of the Jahn-Teller vibration mode from Q2 to Q3 near x=0.75 induces
crossovers of the crystal structure from tetragonally compressed to
tetragonally elongated orthorhombic, and of the magnetic structure from CE-type
to C-type near x=0.75. The experimental results give strong evidence that the
Jahn-Teller effect not only plays a key role in stabilizing the CO state, but
also determines the magnetic and crystal structures in the CO state for
La1-xCaxMnO3.Comment: 13 pages, 3 figures, PD
Intermittent QPO properties of MAXI J1820+070 revealed by Insight-HXMT
We investigate the dynamical properties of low frequency quasi-periodic
oscillations (QPOs) observed from the black hole X-ray binary MAXI J1820+070
during the early part of its 2018 outburst, when the system was in a bright
hard state. To this aim, we use a series of observations from the Hard X-ray
Modulation Telescope Insight-HXMT, and apply a wavelet decomposition (weighted
wavelet Z-transforms) to the X-ray light-curve. We find that the QPO phenomenon
is intermittent within each individual observation, with some sub-intervals
where the oscillation is strongly detected (high root-mean-square amplitude)
and others where it is weak or absent. The average life time of individual QPO
segments is ~ 5 oscillation cycles, with a 3 sigma tail up to ~ 20 cycles.
There is no substantial difference between the energy spectra during intervals
with strong and weak/absent QPOs. We discuss two possible reasons for the
intermittent QPO strength, within the precessing jet model previously proposed
for MAXI J1820+070. In the rigid precession model, intermittent QPOs are
predicted to occur with a coherence Q ~ a few when the disk alignment
time-scale is only a few times the precession time-scale. Alternatively, we
suggest that changes in oscillation amplitude can be caused by changes in the
jet speed. We discuss a possible reason for the intermittent QPO strength,
within the precessing jet model previously proposed for MAXI J1820+070: we
suggest that changes in oscillation amplitude are caused by changes in the jet
speed. We argue that a misaligned, precessing jet scenario is also consistent
with other recent observational findings that suggest an oscillation of the
Compton reflection component in phase with the QPOs.Comment: 8 pages, 4 figure
Comparative Plasma Lipidome between Human and Cynomolgus Monkey: Are Plasma Polar Lipids Good Biomarkers for Diabetic Monkeys?
10.1371/journal.pone.0019731PLoS ONE65
A single residue substitution in the receptor-binding domain of H5N1 hemagglutinin is critical for packaging into pseudotyped lentiviral particles
© 2012 Tang et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.Background: Serological studies for influenza infection and vaccine response often involve microneutralization and hemagglutination inhibition assays to evaluate neutralizing antibodies against human and avian influenza viruses, including H5N1. We have previously characterized lentiviral particles pseudotyped with H5-HA (H5pp) and validated an H5pp-based assay as a safe alternative for high-throughput serological studies in BSL-2 facilities. Here we show that H5-HAs from different clades do not always give rise to efficient production of H5pp and the underlying mechanisms are addressed.
Methodology/Findings: We have carried out mutational analysis to delineate the molecular determinants responsible for efficient packaging of HA from A/Cambodia/40808/2005 (H5Cam) and A/Anhui/1/2005 (H5Anh) into H5pp. Our results demonstrate that a single A134V mutation in the 130-loop of the receptor binding domain is sufficient to render H5Anh the ability to generate H5Anh-pp efficiently, whereas the reverse V134A mutation greatly hampers production of H5Cam-pp. Although protein expression in total cell lysates is similar for H5Anh and H5Cam, cell surface expression of H5Cam is detected at a significantly higher level than that of H5Anh. We further demonstrate by several independent lines of evidence that the behaviour of H5Anh can be explained by a stronger binding to sialic acid receptors implicating residue 134.
Conclusions: We have identified a single A134V mutation as the molecular determinant in H5-HA for efficient incorporation into H5pp envelope and delineated the underlying mechanism. The reduced binding to sialic acid receptors as a result of the A134V mutation not only exerts a critical influence in pseudotyping efficiency of H5-HA, but has also an impact at the whole virus level. Because A134V substitution has been reported as a naturally occurring mutation in human host, our results may have implications for the understanding of human host adaptation of avian influenza H5N1 virusesThis work was supported by grants from the Research Fund for the Control of Infectious Diseases of Hong Kong (RFCID#08070972), the Area of
Excellence Scheme of the University Grants Committee (grant AoE/M-12/-06 of the Hong Kong Special Administrative Region, China), the French Ministry of Health, and the RESPARI project of the Institut Pasteur International Network
SYNTHESIS AND CHARACTERIZATION OF ASYMMETRIC ULTRAFILTRATION MEMBRANE MADE WITH RECYCLED POLYSTYRENE FOAM AND DIFFERENT ADDITIVES
Disappearance of plasmaspheric hiss following interplanetary shock
Abstract Plasmaspheric hiss is one of the important plasma waves controlling radiation belt dynamics. Its spatiotemporal distribution and generation mechanism are presently the object of active research. We here give the first report on the shock-induced disappearance of plasmaspheric hiss observed by the Van Allen Probes on 8 October 2013. This special event exhibits the dramatic variability of plasmaspheric hiss and provides a good opportunity to test its generation mechanisms. The origination of plasmaspheric hiss from plasmatrough chorus is suggested to be an appropriate prerequisite to explain this event. The shock increased the suprathermal electron fluxes, and then the enhanced Landau damping promptly prevented chorus waves from entering the plasmasphere. Subsequently, the shrinking magnetopause removed the source electrons for chorus, contributing significantly to the several-hours-long disappearance of plasmaspheric hiss
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