Improving Extractions of |Vcb| and the b Quark Mass from Semileptonic Inclusive B Decay

Recent advances in improving extractions of |Vcb| and m_b from spectra of semileptonic inclusive B decay are reported. Results of a general moment analysis of the lepton energy spectrum and the hadronic invariant mass spectrum are summarized. The calculation of the general O(\alpha_s) structure functions for semileptonic B decay is reported, which has allowed the calculation of the O(\alpha_s Lambda_{QCD} /m_b) terms for the hadronic invariant mass moments to be carried out. Recent theoretical advances and improvements in experimental data has allowed extractions of the CKM element |Vcb| to improve to the 2% level.Comment: 8 pages, 2 figures. Talk given at MRST2004, May 12-14, Concordia, Montrea

A mathematical understanding of how cytoplasmic dynein walks on microtubules

Cytoplasmic dynein 1 (hereafter referred to simply as dynein) is a dimeric motor protein that walks and transports intracellular cargos towards the minus end of microtubules. In this article, we formulate, based on physical principles, a mechanical model to describe the stepping behaviour of cytoplasmic dynein walking on microtubules from the cell membrane towards the nucleus. Unlike previous studies on physical models of this nature, we base our formulation on the whole structure of dynein to include the temporal dynamics of the individual subunits such as the cargo ( for example, an endosome, vesicle or bead), two rings of six ATPase domains associated with diverse cellular activities (AAAþ rings) and the microtubule-binding domains which allow dynein to bind to microtubules. This mathematical framework allows us to examine experimental observations on dynein across a wide range of different species, as well as being able to make predictions on the temporal behaviour of the individual components of dynein not currently experimentally measured. Furthermore, we extend the model framework to include backward stepping, variable step size and dwelling. The power of our model is in its predictive nature; first it reflects recent experimental observations that dynein walks on microtubules using a weakly coordinated stepping pattern with predominantly not passing steps. Second, the model predicts that interhead coordination in the ATP cycle of cytoplasmic dynein is important in order to obtain the alternating stepping patterns and long run lengths seen in experiments

The Self-Guided Horse Facility Analysis: A Proactive Safety Education Tool for Equine Facilities

Extension professionals who work with horse owners, barn managers, and other equine clientele often encounter resistance to new management ideas. There are several faulty theories that horse people often rely on with respect to safety in equine facilities. Exposing these flaws facilitates convincing horse owners to adopt safer standard operating procedures. The Self-Guided Horse Facility Analysis is a checklist-driven booklet designed to help clientele recognize the potential hazards in their facilities and to make a proactive change before an accident occurs

Flavour constraints on multi-Higgs-doublet models: Yukawa alignment

In multi-Higgs-doublet models, the alignment in flavour space of all Yukawa matrices coupling to a given right-handed fermion guarantees the absence of tree-level flavour-changing neutral couplings, while introducing new sources of CP violation. With N Higgs doublets (and no right-handed neutrinos) the Yukawa Lagrangian is characterized by the fermion masses, the CKM quark mixing matrix and 3(N-1) complex couplings. Quantum corrections break the alignment, generating a minimal-flavour-violation structure with flavour-blind phases. The aligned multi-Higgs-doublet models lead to a rich and viable phenomenology with an interesting hierarchy of flavour-changing neutral current effects, suppressing them in light-quark systems while allowing potentially relevant signals in heavy-quark transitions.Comment: 6 pages, 5 figures. Talk given in the "Third Workshop on Theory, Phenomenology and Experiments in Heavy Flavour Physics" (Capri, 5-7 July 2010

Level Crossings in Complex Two-Dimensional Potentials

Two-dimensional PT-symmetric quantum-mechanical systems with the complex cubic potential V_{12}=x^2+y^2+igxy^2 and the complex Henon-Heiles potential V_{HH}=x^2+y^2+ig(xy^2-x^3/3) are investigated. Using numerical and perturbative methods, energy spectra are obtained to high levels. Although both potentials respect the PT symmetry, the complex energy eigenvalues appear when level crossing happens between same parity eigenstates.Comment: 9 pages, 4 figures. Submitted as a conference proceeding of PHHQP

The Impact of Soil Disturbance on Soil Bacterial Community Composition

Soil bacterial communities are an important part of terrestrial ecosystems due to their roles in biogeochemical cycling processes. Consequently, understanding how soil disturbance affects the soil bacterial diversity is vital to understanding the entire ecosystem. In this study we examined the effects of soil disturbance (by mining) on the soil bacterial community composition from three sites on Bauxite Ridge in Southeast Tennessee compared to three undisturbed sites in a nearby location. The soil bacterial community was analyzed by 16S rDNA amplicon sequencing of total DNA extracted from the soil samples collected from each of the six sites. Characterization of the bacterial community of these six sites showed that soil disturbance does not appear to be correlated with the differences in the diversity of the bacterial community, though this does not correlate with previous research