1,344 research outputs found
Theoretical study on decay and resonance
We present a theoretical study of resonance in the decay, where the weak interaction part proceeds
through the Cabibbo-favored process . Next, the
intermediate two mesons and one baryon state can be constructed with a pair of
with the vacuum quantum numbers. Finally, the is
mainly produced from the final state interactions of in
coupled channels, and it is shown in the invariant mass
distribution. Besides, the scalar meson and nucleon excited state
are also taken into account in the decaying channels
and , respectively. Within model parameters, the ,
and invariant mass distributions are
calculated, and it is found that our theoretical results can reproduce well the
experimental measurements, especially for the clear peak around MeV in
the spectrum. The proposed weak decay process and the interaction mechanism can provide valuable
information on the nature of the resonance.Comment: 9 pages, 5 figure
[(3aS,5aR,8aR,8bS)-2,2,7,7-TetraÂmethylÂtetraÂhydro-3aH-bisÂ[1,3]dioxolo[4,5-b:4â˛,5â˛-d]pyran-3a-yl]methyl (R)-N-(1-phenylÂethÂyl)sulfamate
In the title compound, C20H29NO8S, the two five-membered rings adopt envelope conformations (with an O atom at the flap in each case), while the six-membered pyran ring displays a twist-boat conformation. In the crystal, molÂecules are linked by NâHâŻO hydrogen bonds into a supraÂmolecular chain running along the a axis
Diffusion Mechanism of Lithium Ion through Basal Plane of Layered Graphene
International audienceCoexistence of both edge plane and basal plane in graphite often hinders the understanding of lithium ion diďŹusion mechanism. In this report, two types of graphene samples were prepared by chemical vapor deposition (CVD): (i) well-deďŹned basal plane graphene grown on Cu foil and (ii) edge plane-enriched graphene layers grown on Ni ďŹlm. Electrochemical performance of the graphene electrode can be split into two regimes depending on the number of graphene layers: (i) the corrosion-dominant regime and (ii) the lithiation-dominant regime. Li ion diďŹusion perpendicular to the basal plane of graphene is facilitated by defects, whereas diďŹusion parallel to the plane is limited by the steric hindrance that originates from aggregated Li ions adsorbed on the abundant defect sites. The critical layer thickness (lc) to eďŹectively prohibit substrate reaction using CVD-grown graphene layers was predicted to be âź6 layers, independent of defect population. Our density functional theory calculations demonstrate that divacancies and higher order defects have reasonable diďŹusion barrier heights allowing lithium diďŹusion through the basal plane but neither monovacancies nor Stone-Wales defect
Application of Traditional Chinese Medical Herbs in Prevention and Treatment of Respiratory Syncytial Virus
Respiratory syncytial virus (RSV) is a common viral pathogen of the lower respiratory tract, which, in the absence of effective management, causes millions of cases of severe illness per year. Many of these infections develop into fatal pneumonia. In a review of English and Chinese medical literature, recent traditional Chinese medical herb- (TCMH-) based progress in the area of prevention and treatment was identified, and the potential anti-RSV compounds, herbs, and formulas were explored. Traditional Chinese medical herbs have a positive effect on inhibiting viral attachment, inhibiting viral internalization, syncytial formation, alleviation of airway inflammation, and stimulation of interferon secretion and immune system; however, the anti-RSV mechanisms of TCMHs are complicated, which should be further investigated
High-performance silicon-based multicomponent battery anodes produced via synergistic coupling of multifunctional coating layers
Nanostructured Si-based materials are key building blocks for next-generation energy storage devices. To meet the requirements of practical energy storage devices, Si-based materials should exhibit high-power, low volume change, and high tap density. So far, there have been no reliable materials reported satisfying all of these requirements. Here, we report a novel Si-based multicomponent design, in which the Si core is covered with multifunctional shell layers. The synergistic coupling of Si with the multifunctional shell provides vital clues for satisfying all Si anode requirements for practical batteries. The Si-based multicomponent anode delivers a high capacity of similar to 1000 mA h g(-1), a highly stable cycling retention (similar to 65% after 1000 cycles at 1 C), an excellent rate capability (similar to 800 mA h g(-1) at 10 C), and a remarkably suppressed volume expansion (12% after 100 cycles). Our synthetic process is simple, low-cost, and safe, facilitating new methods for developing electrode materials for practical energy storage.open0
Laboratory observation of ion acceleration via reflection off laser-produced magnetized collisionless shocks
Fermi acceleration by collisionless shocks is believed to be the primary
mechanism to produce high energy charged particles in the Universe,where
charged particles gain energy successively from multiple reflections off the
shock front.Here,we present the first direct experimental evidence of ion
energization from reflection off a supercritical quasi perpendicular
collisionless shock,an essential component of Fermi acceleration in a laser
produced magnetized plasma. We observed a quasi monoenergetic ion beam with 2,4
times the shock velocity in the upstream flow using time of flight method. Our
related kinetic simulations reproduced the energy gain and showed that these
ions were first reflected and then accelerated mainly by the motional electric
field associated with the shock. This mechanism can also explain the quasi
monoenergetic fast ion component observed in the Earth's bow shock
Pathophysiologic Findings of Irritable Bowel Syndrome in China
The mechanism of irritable bowel syndrome (IBS) is still incompletely understood in the world although large amount of investigations have been carried out on it. There are many studies on the pathophysiology of IBS in China, which has huge amount of population suffering from IBS with special ethnicity and culture, including Mainland China, Hong Kong and Taiwan. We collected the literatures to show the results and discuss whether there were any differences in the pathophysiologic findings between China and other countries, whether there were any differences among different subtypes and how the pathophysiology correlated with the manifestations of patients. Gene polymorphism, disturbances of gastrointestinal motility, visceral hypersensitivity, intestinal infection and inflammation, psychological disturbances, food hypersensitivity and intolerance, and altered gut microflora were reviewed in this paper. Some conflicting outcomes between China and other countries were noted although most of them were similar
Search for rare quark-annihilation decays, B --> Ds(*) Phi
We report on searches for B- --> Ds- Phi and B- --> Ds*- Phi. In the context
of the Standard Model, these decays are expected to be highly suppressed since
they proceed through annihilation of the b and u-bar quarks in the B- meson.
Our results are based on 234 million Upsilon(4S) --> B Bbar decays collected
with the BABAR detector at SLAC. We find no evidence for these decays, and we
set Bayesian 90% confidence level upper limits on the branching fractions BF(B-
--> Ds- Phi) Ds*- Phi)<1.2x10^(-5). These results
are consistent with Standard Model expectations.Comment: 8 pages, 3 postscript figues, submitted to Phys. Rev. D (Rapid
Communications
X-ray emission from the Sombrero galaxy: discrete sources
We present a study of discrete X-ray sources in and around the
bulge-dominated, massive Sa galaxy, Sombrero (M104), based on new and archival
Chandra observations with a total exposure of ~200 ks. With a detection limit
of L_X = 1E37 erg/s and a field of view covering a galactocentric radius of ~30
kpc (11.5 arcminute), 383 sources are detected. Cross-correlation with Spitler
et al.'s catalogue of Sombrero globular clusters (GCs) identified from HST/ACS
observations reveals 41 X-rays sources in GCs, presumably low-mass X-ray
binaries (LMXBs). We quantify the differential luminosity functions (LFs) for
both the detected GC and field LMXBs, whose power-low indices (~1.1 for the
GC-LF and ~1.6 for field-LF) are consistent with previous studies for
elliptical galaxies. With precise sky positions of the GCs without a detected
X-ray source, we further quantify, through a fluctuation analysis, the GC LF at
fainter luminosities down to 1E35 erg/s. The derived index rules out a
faint-end slope flatter than 1.1 at a 2 sigma significance, contrary to recent
findings in several elliptical galaxies and the bulge of M31. On the other
hand, the 2-6 keV unresolved emission places a tight constraint on the field
LF, implying a flattened index of ~1.0 below 1E37 erg/s. We also detect 101
sources in the halo of Sombrero. The presence of these sources cannot be
interpreted as galactic LMXBs whose spatial distribution empirically follows
the starlight. Their number is also higher than the expected number of cosmic
AGNs (52+/-11 [1 sigma]) whose surface density is constrained by deep X-ray
surveys. We suggest that either the cosmic X-ray background is unusually high
in the direction of Sombrero, or a distinct population of X-ray sources is
present in the halo of Sombrero.Comment: 11 figures, 5 tables, ApJ in pres
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