822 research outputs found
Hadronic B Decays to Charmed Baryons
We study exclusive B decays to final states containing a charmed baryon
within the pole model framework. Since the strong coupling for is larger than that for , the two-body charmful decay
has a rate larger than
as the former proceeds via the pole while the latter via the
pole. By the same token, the three-body decay receives less baryon-pole contribution than
. However, because the important charmed-meson
pole diagrams contribute constructively to the former and destructively to the
latter, has a rate slightly larger than
. It is found that one quarter of the rate comes from the resonant contributions. We discuss
the decays and
and stress that they are not color suppressed even though they can only proceed
via an internal W emission.Comment: 25 pages, 6 figure
Charmless Two-body Baryonic B Decays
We study charmless two-body baryonic B decays in a diagramatic approach.
Relations on decay amplitudes are obtained. In general there are more than one
tree and more than one penguin amplitudes. The number of independent amplitudes
can be reduced in the large m_B limit. It leads to more predictive results.
Some prominent modes for experimental searches are pointed out.Comment: 15 pages, 2 figures. To appear in Phys. Rev.
Do Chinese Stock Markets React To The Newspaper Recommendations?
This paper studies how the stock prices in Chinese stock markets react to the stock recommendations from a Chinese business newspaper Zhong Guo Zheng Quan Bao (China Security). Using event study methodology and market model as a benchmark, we calculate abnormal returns to ascertain the impact of published recommendations. We find that there are no statistically significant long-term abnormal returns associated with the published recommendations. However, there are profitable opportunities if investors act prior to the published recommendations. We also find that the recommendations from the newspaper causes a significant short term movement two days after the publication day, suggesting a delayed response from the investors who act on the recommendation. The delayed response shows the gradual dissemination of the information in Chinese stock markets. In summary, these results indicate that press recommendations of Chinese stocks contain no useful economic information for investors who act on the published recommendations. The possible abnormal returns for investors who buy the stocks before the recommendations are made public are evidence of a market that is strong-form inefficient and the delayed response from investors to the newspaper recommendations is most likely the evidence of a market that is semi-strong-form inefficient
Economic Growth And FDI In China
This paper studies the importance of foreign direct investment (FDI) in economic development in China. By analyzing the data from China and comparing China with other developed and developing countries, the paper finds that FDI becomes a force in economic growth, especially in the later stage of industrialization; Specifically, the paper finds that a country’s foreign trade is the engine in the initial stage of the economic development, while FDI is the main force in the post-industrialization stage
Why Are Social Networking Applications Successful: An Empirical Study Of Twitter
Social networking applications (SNAs) are among the fastest growing web applications of recent years. In this paper, we propose a causal model to assess the success of SNAs, grounded on DeLone and McLean’s updated information system (IS) success model. In addition to their original three dimensions of quality, i.e., system quality, information quality and service quality, we propose that a fourth dimension – networking quality – contributes to SNA success. We empirically examined the proposed research model with a survey of 139 Twitter users. The data validates the significant role of networking quality in determining the focal SNA’s success. This study also highlights the overwhelming impact of networking quality on user satisfaction compared to the influence from information quality and service quality. The theoretical and practical implications are discussed
Synthesis and evaluation of copper-supported titanium oxide nanotubes as electrocatalyst for the electrochemical reduction of carbon oxide to organics
Carbon dioxide (CO 2 ) is considered as the prime reason for the global warming effect and one of the useful ways to transform it into an array of valuable products is through electrochemical reduction of CO 2 (ERC). This process requires an efficient electrocatalyst with high faradaic efficiency at low overpotential and enhanced reaction rate. Herein, we report an innovative way of reducing CO 2 using copper-metal supported on titanium oxide nanotubes (TNT) electrocatalysts. The TNT support material was synthesized using alkaline hydrothermal process with Degussa (P-25) as a starting material. Copper nanoparticles were anchored on the TNT by homogeneous deposition-precipitation method (HDP) with urea as precipitating agent. The prepared catalysts were tested in a home-made H-cell with 0.5 M NaHCO3 aqueous solution in order to examine their activity for ERC and the optimum copper loading. Continuous gas-phase ERC was carried out in a solid polymer electrolyte (SPE) reactor. The 10% Cu/TNT catalysts were employed in the gas diffusion layer (GDL) on the cathode side with Pt-Ru/C on the anode side. Faradaic efficiencies for the three major products namely methanol, methane, and CO were found to be 4%, 3%, and 10%, respectively at -2.5 V with an overall current density of 120 mA/cm 2 . The addition of TNT significantly increased the catalytic activity of electrocatalyst for ERC. It is mainly attributed to their better stability towards oxidation, increased CO 2 adsorption capacity and stabilization of the reaction intermediate, layered titanates, and larger surface area (400 m 2 /g) as compared with other support materials. Considering the low cost of TNT, it is anticipated that TNT support electrocatalyst for ECR will gain popularity
Charmless Exclusive Baryonic B Decays
We present a systematical study of two-body and three-body charmless baryonic
B decays. Branching ratios for two-body modes are in general very small,
typically less than , except that \B(B^-\to p \bar\Delta^{--})\sim
1\times 10^{-6}. In general, due to
the large coupling constant for . For three-body modes we
focus on octet baryon final states. The leading three-dominated modes are with a branching ratio of
order for and
for . The penguin-dominated decays with strangeness
in the meson, e.g., and , have appreciable rates and the mass
spectrum peaks at low mass. The penguin-dominated modes containing a strange
baryon, e.g., , have
branching ratios of order . In contrast, the decay
rate of is smaller. We explain why some of
charmless three-body final states in which baryon-antibaryon pair production is
accompanied by a meson have a larger rate than their two-body counterparts:
either the pole diagrams for the former have an anti-triplet bottom baryon
intermediate state, which has a large coupling to the meson and the
nucleon, or they are dominated by the factorizable external -emission
process.Comment: 46 pages and 3 figures, to appear in Phys. Rev. D. Major changes are:
(i) Calculations of two-body baryonic B decays involving a Delta resonance
are modified, and (ii) Penguin-dominated modes B-> Sigma+N(bar)+p are
discusse
Nonleptonic Weak Decays of Bottom Baryons
Cabibbo-allowed two-body hadronic weak decays of bottom baryons are analyzed.
Contrary to the charmed baryon sector, many channels of bottom baryon decays
proceed only through the external or internal W-emission diagrams. Moreover,
W-exchange is likely to be suppressed in the bottom baryon sector.
Consequently, the factorization approach suffices to describe most of the
Cabibbo-allowed bottom baryon decays. We use the nonrelativistic quark model to
evaluate heavy-to-heavy and heavy-to-light baryon form factors at zero recoil.
When applied to the heavy quark limit, the quark model results do satisfy all
the constraints imposed by heavy quark symmetry. The decay rates and up-down
asymmetries for bottom baryons decaying into and
are calculated. It is found that the up-down asymmetry is negative except for
decay and for decay modes with in the final
state. The prediction for
is consistent with the recent CDF measurement. We also present
estimates for decays and compare with various model
calculations.Comment: 24 pages, to appear in Phys. Rev. Uncertainties with form factor q^2
dependence are discusse
Redox-Linked Domain Movements in the Catalytic Cycle of Cytochrome P450 Reductase
SummaryNADPH-cytochrome P450 reductase is a key component of the P450 mono-oxygenase drug-metabolizing system. There is evidence for a conformational equilibrium involving large-scale domain motions in this enzyme. We now show, using small-angle X-ray scattering (SAXS) and small-angle neutron scattering, that delivery of two electrons to cytochrome P450 reductase leads to a shift in this equilibrium from a compact form, similar to the crystal structure, toward an extended form, while coenzyme binding favors the compact form. We present a model for the extended form of the enzyme based on nuclear magnetic resonance and SAXS data. Using the effects of changes in solution conditions and of site-directed mutagenesis, we demonstrate that the conversion to the extended form leads to an enhanced ability to transfer electrons to cytochrome c. This structural evidence shows that domain motion is linked closely to the individual steps of the catalytic cycle of cytochrome P450 reductase, and we propose a mechanism for this
Charmless Three-Body Baryonic B Decays
Motivated by recent data on B-> p pbar K decay, we study various charmless
three-body baryonic B decay modes, including Lambda pbar pi, Sigma0 pbar pi, p
pbar pi, p pbar Kbar0, in a factorization approach. These modes have rates of
order 10^{-6}. There are two mechanisms for the baryon pair production,
current-produced and transition. The behavior of decay spectra from these
baryon production mechanisms can be understood by using QCD counting rules.
Predictions on rates and decay spectra can be checked in the near future.Comment: 26 pages, 9 figures; version to appear in Phys. Rev.
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