2,124 research outputs found
Solving the Dirac equation with nonlocal potential by Imaginary Time Step method
The Imaginary Time Step (ITS) method is applied to solve the Dirac equation
with the nonlocal potential in coordinate space by the ITS evolution for the
corresponding Schr\"odinger-like equation for the upper component. It is
demonstrated that the ITS evolution can be equivalently performed for the
Schr\"odinger-like equation with or without localization. The latter algorithm
is recommended in the application for the reason of simplicity and efficiency.
The feasibility and reliability of this algorithm are also illustrated by
taking the nucleus O as an example, where the same results as the
shooting method for the Dirac equation with localized effective potentials are
obtained
Efficient quantum direct communication with authentication
Two protocols of quantum direct communication with authentication [Phys. Rev.
A 73, 042305(2006)] were recently indicated to be insecure against the
authenticator Trent's attacks [Phys. Rev. A 75, 026301(2007)]. We present two
efficient protocols by using four Pauli operations, which are secure against
inner Trent's attacks as well as outer Eve's attacks. Finally, we generalize
them to multiparty quantum direction communication.Comment: 4 pages, 4 table
\u3ci\u3eAuricularia auricula\u3c/i\u3e polysaccharides attenuate obesity in mice through gut commensal \u3ci\u3ePapillibacter cinnamivorans\u3c/i\u3e
Introduction: Auricularia auricula is a well-known traditional edible and medical fungus with high nutritional and pharmacological values, as well as metabolic and immunoregulatory properties. Nondigestible fermentable polysaccharides are identified as primary bioactive constituents of Auricularia auricula extracts. However, the exact mechanisms underlying the effects of Auricularia auricula polysaccharides (AAP) on obesity and related metabolic endpoints, including the role of the gut microbiota, remain insufficiently understood.
Methods: The effects of AAP on obesity were assessed within high-fat diet (HFD)-based mice through obesity trait analysis and metabolomic profiling. To determine the mechanistic role of the gut microbiota in observed anti-obesogenic effects AAP, faecal microbiota transplantation (FMT) and pseudo-germ-free mice model treated with antibiotics were also applied, together with 16S rRNA genomic-derived taxonomic profiling.
Results:High-fat diet (HFD) murine exposure to AAP thwarted weight gains, reduced fat depositing and enhanced glucose tolerance, together with upregulating thermogenesis proteomic biomarkers within adipose tissue. Serum metabolome indicated these effects were associated with changes in fatty acid metabolism. Intestine-dwelling microbial population assessments discovered that AAP selectively enhanced Papillibacter cinnamivorans, a commensal bacterium with reduced presence in HFD mice. Notably, HFD mice treated with oral formulations of P. cinnamivorans attenuated obesity, which was linked to decreased intestinal lipid transportation and hepatic thermogenesis. Mechanistically, it was demonstrated that P. cinnamivorans regulated intestinal lipids metabolism and liver thermogenesis by reducing the proinflammatory response and gut permeability in a JAK-STAT signaling-related manner.
Conclusion: Datasets from the present study show that AAP thwarted dietary-driven obesity and metabolism-based disorders by regulating intestinal lipid transportation, a mechanism that is dependent on the gut commensal P. cinnamivorans. These results indicated AAP and P. cinnamivorans as newly identified pre- and probiotics that could serve as novel therapeutics against obesity
Cosmological Constraints on the Undulant Universe
We use the redshift Hubble parameter data derived from relative galaxy
ages, distant type Ia supernovae (SNe Ia), the Baryonic Acoustic Oscillation
(BAO) peak, and the Cosmic Microwave Background (CMB) shift parameter data, to
constrain cosmological parameters in the Undulant Universe. We marginalize the
likelihood functions over by integrating the probability density . By using the Markov Chain Monte Carlo (MCMC) technique, we
obtain the best fitting results and give the confidence regions on the
plane. Then we compare their constraints. Our results show
that the data play a similar role with the SNe Ia data in cosmological
study. By presenting the independent and joint constraints, we find that the
BAO and CMB data play very important roles in breaking the degeneracy compared
with the and SNe Ia data alone. Combined with the BAO or CMB data, one
can improve the constraints remarkably. The SNe Ia data sets constrain
much tighter than the data sets, but the data
sets constrain much tighter than the SNe Ia data sets. All these results
show that the Undulant Universe approaches the CDM model. We
expect more data to constrain cosmological parameters in future.Comment: 10 pages,6 figures, 2 tables, accepted for publication in Research in
Astronomy and Astrophysic
Large-scale Graphitic Thin Films Synthesized on Ni and Transferred to Insulators: Structural and Electronic Properties
We present a comprehensive study of the structural and electronic properties
of ultrathin films containing graphene layers synthesized by chemical vapor
deposition (CVD) based surface segregation on polycrystalline Ni foils then
transferred onto insulating SiO2/Si substrates. Films of size up to several
mm's have been synthesized. Structural characterizations by atomic force
microscopy (AFM), scanning tunneling microscopy (STM), cross-sectional
transmission electron microscopy (XTEM) and Raman spectroscopy confirm that
such large scale graphitic thin films (GTF) contain both thick graphite regions
and thin regions of few layer graphene. The films also contain many wrinkles,
with sharply-bent tips and dislocations revealed by XTEM, yielding insights on
the growth and buckling processes of the GTF. Measurements on mm-scale
back-gated transistor devices fabricated from the transferred GTF show
ambipolar field effect with resistance modulation ~50% and carrier mobilities
reaching ~2000 cm^2/Vs. We also demonstrate quantum transport of carriers with
phase coherence length over 0.2 m from the observation of 2D weak
localization in low temperature magneto-transport measurements. Our results
show that despite the non-uniformity and surface roughness, such large-scale,
flexible thin films can have electronic properties promising for device
applications.Comment: This version (as published) contains additional data, such as cross
sectional TEM image
Supermassive Black Holes with High Accretion Rates in Active Galactic Nuclei. IV. H Time Lags and Implications for Super-Eddington Accretion
We have completed two years of photometric and spectroscopic monitoring of a
large number of active galactic nuclei (AGNs) with very high accretion rates.
In this paper, we report on the result of the second phase of the campaign,
during 2013--2014, and the measurements of five new H time lags out of
eight monitored AGNs. All five objects were identified as super-Eddington
accreting massive black holes (SEAMBHs). The highest measured accretion rates
for the objects in this campaign are , where
,
is the mass accretion rates, is the Eddington luminosity and
is the speed of light. We find that the H time lags in SEAMBHs are
significantly shorter than those measured in sub-Eddington AGNs, and the
deviations increase with increasing accretion rates. Thus, the relationship
between broad-line region size () and optical luminosity at
5100\AA, , requires accretion rate as an additional
parameter. We propose that much of the effect may be due to the strong
anisotropy of the emitted slim-disk radiation. Scaling by
the gravitational radius of the black hole, we define a new radius-mass
parameter () and show that it saturates at a critical accretion rate of
, indicating a transition from thin to slim
accretion disk and a saturated luminosity of the slim disks. The parameter
is a very useful probe for understanding the various types of accretion onto
massive black holes. We briefly comment on implications to the general
population of super-Eddington AGNs in the universe and applications to
cosmology.Comment: 53 pages, 12 figures, 7 tables, accepted for publication in The
Astrophysical Journa
High Stability Positron Beam Generation Based on Ultra-intense Laser
Relativistic positron beams were generated by laser wakefield electrons bombarding on solid target. Very stable positron beams were generated in our experiments. The total yield of positrons is about 4.4 x 10(8)/shot. The energy spectra of positrons and electrons obey quasi-Maxwell distribution. Compared with the direct method, the indirect method produces positrons (38.5 MeV) and electrons (50.5 MeV) with much higher slope temperature
Generation of subcycle isolated attosecond pulses by pumping ionizing gating
We present a novel approach named as pumping ionizing gating (PIG) for the
generation of isolated attosecond pulses (IAPs). In this regime, a short laser
is used to ionize a pre-existing gas grating, creating a fast-extending plasma
grating(FEPG) having an ionization front propagating with the velocity of
light. A low-intensity long counterpropagating pump pulse is then reflected by
a very narrow region of the ionization front, only where the Bragg conditions
for resonant reflection is satisfied. Consequently, the pump reflection is
confined within a sub-cycle region called PIG, and forms a wide-band coherent
IAP in combination with the frequency up-conversion effect due to the plasma
gradient. This approach results in a new scheme to generate IAPs fromlong
picosecond pump pulses. Three-dimensional (3D) simulations show that a 1.6-ps,
1-{\mu}m pump pulse can be used to generate a 330 as laser pulse with a peak
intensity approximately 33 times that of the pump and a conversion efficiency
of around 0.1%.These results highlight the potential of the PIG method for
generating IAPs with high conversion efficiency and peak intensity.Comment: It provides a new way to generate isolated attosecond pulse(IAP) by a
picosecond pump, which has a protential to boost the IAP energy to joule
leve
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