oalib

Publish in OALib Journal

ISSN: 2333-9721

APC: Only $99

Submit

Any time

2020 ( 55 )

2019 ( 446 )

2018 ( 635 )

2017 ( 637 )

Custom range...

Search Results: 1 - 10 of 450020 matches for " J. L. Roberts "
All listed articles are free for downloading (OA Articles)
Page 1 /450020
Display every page Item
Soft Pion Emission in Semileptonic $B$-Meson Decays
J. L. Goity,W. Roberts
Physics , 1994, DOI: 10.1103/PhysRevD.51.3459
Abstract: An analysis of semileptonic decays of $B$ mesons with the emission of a single soft pion is presented in the framework of the heavy-quark limit using an effective Lagrangian which implements chiral and heavy-quark symmetries. The analysis is performed at leading order of the chiral and inverse heavy mass expansions. In addition to the ground state heavy mesons some of their resonances are included. The estimates of the various effective coupling constants and form factors needed in the analysis are obtained using a chiral quark model. As the main result, a clear indication is found that the $0^{+}$ and $1^{+}$ resonances substantially affect the decay mode with a $D^{\ast}$ in the final state, and a less dramatic effect is also noticed in the $D$ mode. An analysis of the decay spectrum in the $D^{(\ast)}-\pi$ squared invariant mass is carried out, showing the main effects of including the resonances. The obtained rates show promising prospects for studies of soft pion emission in semileptonic $B$-meson decays in a $B$-meson factory where, modulo experimental cuts, about $10^5$ such decays in the $D$ meson mode and $10^4$ in the $D^{\ast}$ mode could be observed per year.
A relativistic chiral quark model for pseudoscalar emission from heavy mesons
J. L. Goity,W. Roberts
Physics , 1998, DOI: 10.1103/PhysRevD.60.034001
Abstract: The amplitudes for one-pion mediated transitions between heavy meson excited states are obtained in the framework of the relativistic chiral quark model. The effective coupling constants to pions and the decay widths of excited heavy mesons with l<=2 for non-radially excited, and the l=0 radially excited mesons are presented for both charmed and beauty mesons. We also discuss the allowed decays of strange excited heavy mesons by emission of a K-meson.
Radiative Transitions in Heavy Mesons in a Relativistic Quark Model
J. L. Goity,W. Roberts
Physics , 2000, DOI: 10.1103/PhysRevD.64.094007
Abstract: The radiative decays of $D^*$, $B^*$, and other excited heavy mesons are analyzed in a relativistic quark model for the light degrees of freedom and in the limit of heavy quark spin-flavor symmetry. The analysis of strong decays carried out in the corresponding chiral quark model is used to calculate the strong decays and determine the branching ratios of the radiative $D^*$ decays. Consistency with the observed branching ratios requires the inclusion of the heavy quark component of the electromagnetic current and the introduction of an anomalous magnetic moment for the light quark. It is observed that not only $D$, but also $B$ meson transitions within a heavy quark spin multiplet are affected by the presence of the heavy quark current.
Explaining First-Year Seedling Survival from Quality Distributions of Bare-Root Seedlings and Microsites in Industrial Plantations  [PDF]
Puskar N. Khanal, Thomas J. Dean, Scott D. Roberts, Donald L. Grebner, Thomas J. Straka
Open Journal of Forestry (OJF) , 2018, DOI: 10.4236/ojf.2018.83023
Abstract: First-year seedling survival impacts all subsequent management planning in plantation forestry. Descriptive statistics of first-year seedling survival data from the Louisiana Department of Agriculture and Forestry (LDAF) indicated that survival success reaches a plateau at between 79% - 85% under normal weather conditions. We provide an explanation for this plateau based on an analysis of seedling and microsite qualities involved in operational pine plantations by: 1) using a conceptual model demonstrating how variation in seedling quality and microsite quality interact to determine plantation survival, 2) presenting an example to characterize quality distributions of seedling and microsite qualities, and 3) comparing model outcomes based on measured distributions to realistic values of first-year survival. Simulation results indicated that consistent survival could result from random pairings of initial seedling and site quality distributions. LDAF data analysis indicated that 72% of seedlings were associated with the most frequent quality class that comprised seedlings with stem caliper between 3.2 to 4.7 mm and average stem height and volume of 25.75 cm and 3.43 cm3, respectively. Similarly, assessment of microsites at planting sites in Southeast Louisiana indicated that 48% of planted seedlings were associated with the most frequent microsite quality class which supported first-year height increment between 9 to 29 cm. Modelling of current operational practice indicated that using seedlings with larger caliper size would increase first year survival, but would result in higher establishment costs. The conceptual model could be modified to for use in other regions regardless of species types involved.
The Avian Encephalomyelitis Virus (AEV) 5’ Untranslated Region Contains an IRES with Similarity to the Hepatitis C Virus IRES
M Bakhshesh,L Roberts,G J Belsham
Iranian Journal of Public Health , 2005,
Abstract: Cap-independent internal initiation of protein synthesis has been shown to occur on a number of viral and cellular mRNAs. Initiation of protein synthesis is directed by an internal ribosome entry site (IRES) element within the 5’ untranslated region (UTR) of the mRNA. Avian encephalomyelitis virus (AEV) belongs to the picornavirus family and shares protein sequence similarity with hepatitis A virus (HAV). Because of this, it was assigned to the hepatovirus genus. We have demonstrated that the 494 nucleotide 5’ UTR of this virus genome contains an internal ribosome entry site (IRES) element. However, in contrast to the HAV IRES, the AEV IRES functions efficiently in the presence of cleaved eIF4G, suggesting functional differences exist. Furthermore, comparison of the AEV IRES sequence with that of the hepatitis C virus (HCV) IRES revealed areas of striking similarity, especially in the region of the ribosome binding site. The AEV IRES is thus very similar to the recently described IRES from the picornavirus porcine teschovirus; this IRES also shows similarity to the HCV IRES. These results suggest that these viruses may have exchanged sequences during evolution.
Some Tauberian theorems for Euler and Borel summability
J. A. Fridy,K. L. Roberts
International Journal of Mathematics and Mathematical Sciences , 1980, DOI: 10.1155/s0161171280000531
Abstract: The well-known summability methods of Euler and Borel are studied as mappings from ¢ “1 into ¢ “1. In this ¢ “ ¢ ’ ¢ “ setting, the following Tauberian results are proved: if x is a sequence that is mapped into ¢ “1 by the Euler-Knopp method Er with r>0 (or the Borel matrix method) and x satisfies ¢ ‘n=0 ¢ |xn ¢ ’xn+1|n< ¢ , then x itself is in ¢ “1.
Preliminary Evaluations of a Complex Amino Acid Supplement, Fatigue RevivaTM, to Reduce Fatigue in a Group of Professional Male Athletes and a Group of Males Recruited from the General Public  [PDF]
R. Hugh Dunstan, Diane L. Sparkes, Timothy K. Roberts, Benjamin J. Dascombe
Food and Nutrition Sciences (FNS) , 2014, DOI: 10.4236/fns.2014.52028
Abstract:

Fatigue RevivaTM was developed to provide a source of amino acids for rapid uptake by the body while avoiding the need for digestion of proteins. Complex amino acid formulations have significant palatability issues and thus new products require significant development and testing. An initial pilot study with 18 professional male athletes and 21 males recruited from the general public was undertaken to evaluate product palatability and tolerance over a 30 day period. This investigation found that Fatigue RevivaTM was well tolerated in terms of palatability and usage across 39 participants with only two of the 39 subjects reporting an issue with taste and five reporting an issue with flatulence. The professional athlete cohort reported a significantly lower level of fatigue compared with the general public group prior to commencement of supplementation. The general public group reported a significant reduction in fatigue following the use of Fatigue RevivaTM over the 30-day period. Compliance was extremely poor amongst the professional athlete group and as a result, changes in fatigue could not be statistically assessed for this group over the study period. Preliminary assessment of the product indicated that it has the potential to significantly reduce fatigue. Minor modifications to the product were identified for future development.

Representations of algebraic quantum groups and reconstruction theorems for tensor categories
M. Mueger,J. E. Roberts,L. Tuset
Mathematics , 2002,
Abstract: We give a pedagogical survey of those aspects of the abstract representation theory of quantum groups which are related to the Tannaka-Krein reconstruction problem. We show that every concrete semisimple tensor *-category with conjugates is equivalent to the category of finite dimensional non-degenerate *-representations of a discrete algebraic quantum group. Working in the self-dual framework of algebraic quantum groups, we then relate this to earlier results of S. L. Woronowicz and S. Yamagami. We establish the relation between braidings and R-matrices in this context. Our approach emphasizes the role of the natural transformations of the embedding functor. Thanks to the semisimplicity of our categories and the emphasis on representations rather than corepresentations, our proof is more direct and conceptual than previous reconstructions. As a special case, we reprove the classical Tannaka-Krein result for compact groups. It is only here that analytic aspects enter, otherwise we proceed in a purely algebraic way. In particular, the existence of a Haar functional is reduced to a well known general result concerning discrete multiplier Hopf *-algebras.
Multi-scale interactions between local hydrography, seabed topography, and community assembly on cold-water coral reefs
L.-A. Henry,J. Moreno Navas,J. M. Roberts
Biogeosciences (BG) & Discussions (BGD) , 2013, DOI: 10.5194/bg-10-2737-2013
Abstract: We investigated how interactions between hydrography, topography and species ecology influence the assembly of species and functional traits across multiple spatial scales of a cold-water coral reef seascape. In a novel approach for these ecosystems, we used a spatially resolved complex three-dimensional flow model of hydrography to help explain assembly patterns. Forward-selection of distance-based Moran's eigenvector mapping (dbMEM) variables identified two submodels of spatial scales at which communities change: broad-scale (across reef) and fine-scale (within reef). Variance partitioning identified bathymetric and hydrographic gradients important in creating broad-scale assembly of species and traits. In contrast, fine-scale assembly was related more to processes that created spatially autocorrelated patches of fauna, such as philopatric recruitment in sessile fauna, and social interactions and food supply in scavenging detritivores and mobile predators. Our study shows how habitat modification of reef connectivity and hydrography by bottom fishing and renewable energy installations could alter the structure and function of an entire cold-water coral reef seascape.
Multi-scale interactions between local hydrography, seabed topography, and community assembly on cold-water coral reefs
L.-A. Henry,J. Moreno Navas,J. M. Roberts
Biogeosciences Discussions , 2012, DOI: 10.5194/bgd-9-17885-2012
Abstract: We investigated how the interactive effects of hydrography, topography and intrinsic community dynamics influence the assembly of species and functional traits across multiple spatial scales of a cold-water coral reef seascape. In a novel approach for these ecosystems, we use a spatially resolved complex three-dimensional flow model of hydrography to help explain assembly patterns. Forward selection of distance-based Moran's eigenvector mapping (dbMEM) variables identified two submodels of spatial scales at which communities are structured: broad-scale (across reef) and fine-scale (within reef). Canonical variance partitioning revealed broad-scale structures created mainly by variability in bathymetry and hydrography across reefs, which manifest as relatively narrow environmental niches for predators and scavenging detritivores. Fine-scale assembly was related more to processes that create spatially autocorrelated patches of fauna within a reef due to restricted dispersal in sessile fauna but social mating interactions and food supply in more mobile organisms. Our study implies that perturbations such as habitat fragmentation and altered hydrodynamic regimes have the potential to induce significant changes in the structure and function of cold-water coral reef ecosystems at spatial scales that span the entire seascape.
Page 1 /450020
Display every page Item


Home
Copyright © 2008-2017 Open Access Library. All rights reserved.