7,714 research outputs found
Form Factors for Lambda_b -> Lambda Transitions in SCET
We present a systematic discussion of Lambda_b -> Lambda transition form
factors in the framework of soft-collinear effective theory (SCET). The
universal soft form factor, which enters the symmetry relations in the limit of
large recoil energy, is calculated from a sum-rule analysis of a suitable SCET
correlation function. The same method is applied to derive the leading
corrections from hard-collinear gluon exchange at first order in the strong
coupling constant. We present numerical estimates for form factors and
form-factor ratios and their impact on decay observables in Lambda_b -> Lambda
mu^+ mu^- decays.Comment: 2+29 pages, 9 figures. Corrections in Sections 3.2 and 4 and Appendix
D.1. Conclusions do not change. Erratum to appear in PR
Exchange-Rate Systems and Interest-Rate Behaviour: The Experience of Hong Kong and Singapore
The Currency Board System in Hong Kong and the monitoring band system in Singapore are important benchmarks for two different exchange-rate systems. In this paper we consider the implications of the two exchange-rate systems on the interest-rate behaviour of the two economies. We examine the domestic-US interest differentials under the two exchange-rate regimes during the Asian Financial Crisis as well as the pre- and post-crisis periods. Using a bivariate generalized autoregressive conditional heteroscedasticity model, we also investigate whether there is any change in the correlation between the domestic and US interest rates due to the Asian Financial Crisis.
A frailty model for detecting number of faults in a system
A frailty model for failure data is proposed to estimate the total number of faults in a system. The Littlewood model and Jelinski-Moranda are the two particular cases of the proposed formulation. The two-stage estimating procedure, a conditional likelihood and a Horvitz-Thompson estimator, is found to be efficient. Simulation studies are given to assess the performance of the estimator. Two examples are also presented.published_or_final_versio
Supragingival calculus: Formation and control
Dental calculus is composed of inorganic components and organic matrix. Brushite, dicalcium phosphate dihydrate, octacalcium phosphate, hydroxyapatite, and whitlockite form the mineral part of dental calculus. Salivary proteins selectively adsorb on the tooth surface to form an acquired pellicle. It is followed by the adherence of various oral micro-organisms. Fimbriae, flagella, and some other surface proteins are essential for microbial adherence. Microbial co-aggregation and co-adhesion enable some micro-organisms, which are incapable of adhering, to adhere to the pellicle-coated tooth surface. Once organisms attach to the tooth surface, new genes could be expressed so that mature dental plaque can form and biofilm bacteria assume increased resistance to antimicrobial agents. Supersaturation of saliva and plaque fluid with respect to calcium phosphates is the driving force for plaque mineralization. Both salivary flow rate and plaque pH appear to influence the saturation degree of calcium phosphates. Acidic phospholipids and specific proteolipids present in cell membranes play a key role in microbial mineralization. The roles of crystal growth inhibitors, promoters, and organic acids in calculus formation are discussed. Application of biofilm culture systems in plaque mineralization is concisely reviewed. Anti-calculus agents used - centering on triclosan plus polyvinyl methyl ether/maleic acid copolymer, pyrophosphate plus polyvinyl methyl ether/maleic acid copolymer, and zinc ion - in commercial dentifrices are also discussed in this paper.published_or_final_versio
A Gibbs-sampler approach to estimate the number of faults in a system using capture-recapture sampling
A new recapture debugging model is suggested to estimate the number of faults in a system, ν, and the failure intensity of each fault, φ. The Gibbs sampler and the Metropolis algorithm are used in this inference procedure. A numerical illustration suggests a notable improvement on the estimation of ν and φ compared with that of a removal debugging model.published_or_final_versio
Inert-states of spin-5 and spin-6 Bose-Einstein condensates
In this paper we consider spinor Bose-Einstein condensates with spin f=5 and
f=6 in the presence and absence of external magnetic field at the mean field
level. We calculate all of so-called inert-states of these systems.
Inert-states are very unique class of stationary states because they remain
stationary while Hamiltonian parameters change. Their existence comes from
Michel's theorem. For illustration of symmetry properties of the inert-states
we use method that allows classification of the systems as a polyhedron with 2f
vertices proposed by R. Barnett et al., Phys. Rev. Lett. 97, 180412 (2006).Comment: 19 pages, 4 figure
Light-Cone Distribution Amplitudes for Heavy-Quark Hadrons
We construct parametrizations of light-cone distribution amplitudes (LCDAs)
for B-mesons and Lambda_b-baryons that obey various theoretical constraints,
and which are simple to use in factorization theorems relevant for
phenomenological applications in heavy-flavour physics. In particular, we find
the eigenfunctions of the Lange-Neubert renormalization kernel, which allow for
a systematic implementation of renormalization-group evolution effects for both
B-meson and \Lambda_b-baryon decays. We also present a new strategy to
construct LCDA models from momentum-space projectors, which can be used to
implement Wandzura-Wilczek--like relations, and which allow for a comparison
with theoretical approaches that go beyond the collinear limit for the
light-quark momenta in energetic heavy-hadron decays.Comment: 39 pages, 11 figure
Validation of the Chinese version of the Reynolds' suicidal ideation questionnaire: psychometric properties and its short version
BACKGROUND: This study aims to validate the Chinese version of the Reynolds' Suicidal Ideation Questionnaire (SIQ) in a Chinese society and explore a convenient short version. METHODS: A sample of 711 cases was derived from two territory-wide surveys of Hong Kong adolescents aged between 15 and 19 years old. RESULTS: The SIQ and the Suicidal Ideation Questionnaire-Junior (SIQ-JR) demonstrated good reliability and concurrent validity among Hong Kong adolescents. However, the factor structure for both SIQ and SIQ-JR appeared to be unclear. A four-item short form of the SIQ-JR, namely, SIQ-JR-4, was proposed. CONCLUSION: The SIQ-JR-4 is an ideal substitute of the SIQ/SIQ-JR for future quick assessment of suicidal ideation in Chinese young adolescents
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