110 research outputs found
Low compressible noble metal carbides with rock-salt structure: ab initio total energy calculations of the elastic stability
We have systematically studied the mechanical stability of all noble metal
carbides with the rock-salt structure by calculating their elastic constants
within the density function theory scheme. It was found that only four carbides
(RuC, PdC, AgC and PtC) are mechanically stable. In particular, we have shown
that RuC, PdC, and PtC have very high bulk modulus, which has been remarkably
observed by the most recent experiment for the case of PtC. From the calculated
density of states, we can conclude that these compounds are metallic, like the
conventional group IV and group V transition metal carbides.Comment: Appl. Phys. Lett. 89, 071913 (2006
Potential super-hard Osmium di-nitride with fluorite structure: First-principles calculations
We have performed systematic first-principles calculations on di-carbide,
-nitride, -oxide and -boride of platinum and osmium with the fluorite
structure. It is found that only PtN, OsN and OsO are
mechanically stable. In particular OsN has the highest bulk modulus of
360.7 GPa. Both the band structure and density of states show that the new
phase of OsN is metallic. The high bulk modulus is owing to the strong
covalent bonding between Os 5\textit{d} and N 2\textit{p} states and the dense
packed fluorite structure.Comment: Phys. Rev. B 74,125118 (2006
Restoration of Noradrenergic Function in Parkinson’s Disease Model Mice
Dysfunction of the central noradrenergic and dopaminergic systems is the primary neurobiological characteristic of Parkinson’s disease (PD). Importantly, neuronal loss in the locus coeruleus (LC) that occurs in early stages of PD may accelerate progressive loss of dopaminergic neurons. Therefore, restoring the activity and function of the deficient noradrenergic system may be an important therapeutic strategy for early PD. In the present study, the lentiviral constructions of transcription factors Phox2a/2b, Hand2 and Gata3, either alone or in combination, were microinjected into the LC region of the PD model VMAT2 Lo mice at 12 and 18 month age. Biochemical analysis showed that microinjection of lentiviral expression cassettes into the LC significantly increased mRNA levels of Phox2a, and Phox2b, which were accompanied by parallel increases of mRNA and proteins of dopamine β-hydroxylase (DBH) and tyrosine hydroxylase (TH) in the LC. Furthermore, there was considerable enhancement of DBH protein levels in the frontal cortex and hippocampus, as well as enhanced TH protein levels in the striatum and substantia nigra. Moreover, these manipulations profoundly increased norepinephrine and dopamine concentrations in the striatum, which was followed by a remarkable improvement of the spatial memory and locomotor behavior. These results reveal that over-expression of these transcription factors in the LC improves noradrenergic and dopaminergic activities and functions in this rodent model of PD. It provides the necessary groundwork for the development of gene therapies of PD, and expands our understanding of the link between the LC-norepinephrine and dopamine systems during the progression of PD
Fabrication of Chitosan/Silk Fibroin Composite Nanofibers for Wound-dressing Applications
Chitosan, a naturally occurring polysaccharide with abundant resources, has been extensively exploited for various biomedical applications, typically as wound dressings owing to its unique biocompatibility, good biodegradability and excellent antibacterial properties. In this work, composite nanofibrous membranes of chitosan (CS) and silk fibroin (SF) were successfully fabricated by electrospinning. The morphology of electrospun blend nanofibers was observed by scanning electron microscopy (SEM) and the fiber diameters decreased with the increasing percentage of chitosan. Further, the mechanical test illustrated that the addition of silk fibroin enhanced the mechanical properties of CS/SF nanofibers. The antibacterial activities against Escherichia coli (Gram negative) and Staphylococcus aureus (Gram positive) were evaluated by the turbidity measurement method; and results suggest that the antibacterial effect of composite nanofibers varied on the type of bacteria. Furthermore, the biocompatibility of murine fibroblast on as-prepared nanofibrous membranes was investigated by hematoxylin and eosin (H&E) staining and MTT assays in vitro, and the membranes were found to promote the cell attachment and proliferation. These results suggest that as-prepared chitosan/silk fibroin (CS/SF) composite nanofibrous membranes could be a promising candidate for wound healing applications
First Measurement of the Decay Asymmetry in the pure W-boson-exchange Decay
Based on of annihilation data collected at
the center-of-mass energies between and with the
BESIII detector at the BEPCII collider, the pure \textit{W}-boson-exchange
decay is studied with a full angular analysis.
The corresponding decay asymmetry is measured for the first time to be
. This
result reflects the non-interference effect between the - and -wave
amplitudes. The phase shift between - and -wave amplitudes has two
solutions, which are or
Measurement of the Electromagnetic Transition Form-factors in the decays
With a sample of events accumulated with
the BESIII detector, we analyze the decays
via the process
. The branching fractions are measured to be
and
,
and the ratio is
. In addition, by combining the
and
decays, the slope parameter of the electromagnetic transition form factor is
measured to be , which is
consistent with previous measurements from BESIII and theoretical predictions
from the VMD model. The asymmetry in the angle between the and
decay planes, which has the potential to reveal the -violation
originating from an unconventional electric dipole transition, is also
investigated. The asymmetry parameters are determined to be
and
,
implying that no evidence of -violation is observed at the present
statistics. Finally, an axion-like particle is searched for via the decay
, and upper limits of the
branching fractions are presented for the mass assumptions of the axion-like
particle in the range of
Measurements of electromagnetic form factors in the time-like region using the untagged initial-state radiation technique
The process is studied from
threshold up to 3.04 GeV/ via the initial-state radiation technique using
data with an integrated luminosity of 12.0 fb, collected at
center-of-mass energies between 3.773 and 4.258 GeV with the BESIII detector at
the BEPCII collider. The pair production cross sections and the effective form
factors of are measured in eleven
invariant mass intervals from threshold to 3.04 GeV/. The results are
consistent with the previous results from Belle and BESIII. Furthermore, the
branching fractions of the decays and
are determined and the obtained
results are consistent with the previous results of BESIII.Comment: 13 pages, 6 figure
Observation of the Singly Cabibbo-Suppressed Decay
The singly Cabibbo-suppressed decay is observed for the first time with a statistical
significance of by using 4.5 fb of collision data
collected at center-of-mass energies between 4.600 and 4.699 GeV with the
BESIII detector at BEPCII. The absolute branching fraction of
is measured to be in a model-independent approach. This is
the first observation of a Cabibbo-suppressed decay involving
in the final state. The ratio of branching fractions between
and the Cabibbo-favored decay
is calculated to be , where with the
Cabibbo mixing angle. This ratio significantly deviates from and
provides important information for the understanding of nonfactorization
contributions in decays.Comment: 8 pages, 2 figure
A New Look at the Scalar Meson via Decays
Using of collision data collected with the
BESIII detector at the center-of-mass energy of 3.773 GeV, we investigate the
semileptonic decays ( and ).
The decay is observed for the first time. By
analyzing simultaneously the differential decay rates of and in different
four-momentum transfer intervals, the product of the relevant hadronic form
factor and the magnitude of the
Cabibbo-Kobayashi-Maskawa matrix element is determined to be
for
the first time. With the input of from the global fit in the
standard model, we determine . The absolute branching fractions of and are determined as and . Combining these results with those of previous BESIII measurements on
their semielectronic counterparts from the same data sample, we test lepton
flavor universality by measuring the branching fraction ratios and , which are
compatible with the standard model expectation.Comment: Supplemental Materials added in this versio
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