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Search Results: 1 - 10 of 545015 matches for " Dennis A. V. Brown "
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The Use of Life Narrative and Living Standard Measurement Survey Data in the Study of Poverty in the Caribbean: A Resolution of Conflicting Epistemologies  [PDF]
Dennis A. V. Brown
Sociology Mind (SM) , 2013, DOI: 10.4236/sm.2013.33030
Abstract:

The paper examines the compatibility or usefulness of fit between epistemologically disparate quantitative survey data and qualitative life narrative data gleaned in the study of poverty in the Caribbean. It aims to find out whether or not the different approaches to the understanding of reality on which the two methodologies are based preclude the integration of their findings as a means of furthering understanding of the dynamics of Caribbean poverty. The analysis draws on Country Poverty Studies conducted in the territory of Grenada in the Eastern Caribbean. It is centered on the demographic measure of fertility, a measure of chronic illnesses by socioeconomic status and life narrative interviews conducted around the themes of poverty, family and life experiences with select poor households across the country. Fertility was measured using parity of women aged <15 - 30+. Statistical analyses were done using cross tabulations. The findings indicate that the hermeneutic understanding of the life narratives, and the causal explanatory accounts provided by the positivist quantitative data, allow for understanding of negative health seeking behaviour on the part of the poor, not provided by the quantitative data by themselves. They also provide insight into the synergy between family, reproductive behaviour, labour market status and chronic poverty in the Caribbean region that would not have been possible through the use of the positivist quantitative method by itself.

Protease Activated Receptor Signaling Is Required for African Trypanosome Traversal of Human Brain Microvascular Endothelial Cells
Dennis J. Grab ,Jose C. Garcia-Garcia,Olga V. Nikolskaia,Yuri V. Kim,Amanda Brown,Carlos A. Pardo,Yongqing Zhang,Kevin G. Becker,Brenda A. Wilson,Ana Paula C. de A. Lima,Julio Scharfstein,J. Stephen Dumler
PLOS Neglected Tropical Diseases , 2009, DOI: 10.1371/journal.pntd.0000479
Abstract: Background Using human brain microvascular endothelial cells (HBMECs) as an in vitro model for how African trypanosomes cross the human blood-brain barrier (BBB) we recently reported that the parasites cross the BBB by generating calcium activation signals in HBMECs through the activity of parasite cysteine proteases, particularly cathepsin L (brucipain). In the current study, we examined the possible role of a class of protease stimulated HBMEC G protein coupled receptors (GPCRs) known as protease activated receptors (PARs) that might be implicated in calcium signaling by African trypanosomes. Methodology/Principal Findings Using RNA interference (RNAi) we found that in vitro PAR-2 gene (F2RL1) expression in HBMEC monolayers could be reduced by over 95%. We also found that the ability of Trypanosoma brucei rhodesiense to cross F2RL1-silenced HBMEC monolayers was reduced (39%–49%) and that HBMECs silenced for F2RL1 maintained control levels of barrier function in the presence of the parasite. Consistent with the role of PAR-2, we found that HBMEC barrier function was also maintained after blockade of Gαq with Pasteurella multocida toxin (PMT). PAR-2 signaling has been shown in other systems to have neuroinflammatory and neuroprotective roles and our data implicate a role for proteases (i.e. brucipain) and PAR-2 in African trypanosome/HBMEC interactions. Using gene-profiling methods to interrogate candidate HBMEC pathways specifically triggered by brucipain, several pathways that potentially link some pathophysiologic processes associated with CNS HAT were identified. Conclusions/Significance Together, the data support a role, in part, for GPCRs as molecular targets for parasite proteases that lead to the activation of Gαq-mediated calcium signaling. The consequence of these events is predicted to be increased permeability of the BBB to parasite transmigration and the initiation of neuroinflammation, events precursory to CNS disease.
Airway Microbiota and Pathogen Abundance in Age-Stratified Cystic Fibrosis Patients
Michael J. Cox,Martin Allgaier,Byron Taylor,Marshall S. Baek,Yvonne J. Huang,Rebecca A. Daly,Ulas Karaoz,Gary L. Andersen,Ronald Brown,Kei E. Fujimura,Brian Wu,Diem Tran,Jonathan Koff,Mary Ellen Kleinhenz,Dennis Nielson,Eoin L. Brodie,Susan V. Lynch
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0011044
Abstract: Bacterial communities in the airways of cystic fibrosis (CF) patients are, as in other ecological niches, influenced by autogenic and allogenic factors. However, our understanding of microbial colonization in younger versus older CF airways and the association with pulmonary function is rudimentary at best. Using a phylogenetic microarray, we examine the airway microbiota in age stratified CF patients ranging from neonates (9 months) to adults (72 years). From a cohort of clinically stable patients, we demonstrate that older CF patients who exhibit poorer pulmonary function possess more uneven, phylogenetically-clustered airway communities, compared to younger patients. Using longitudinal samples collected form a subset of these patients a pattern of initial bacterial community diversification was observed in younger patients compared with a progressive loss of diversity over time in older patients. We describe in detail the distinct bacterial community profiles associated with young and old CF patients with a particular focus on the differences between respective “early” and “late” colonizing organisms. Finally we assess the influence of Cystic Fibrosis Transmembrane Regulator (CFTR) mutation on bacterial abundance and identify genotype-specific communities involving members of the Pseudomonadaceae, Xanthomonadaceae, Moraxellaceae and Enterobacteriaceae amongst others. Data presented here provides insights into the CF airway microbiota, including initial diversification events in younger patients and establishment of specialized communities of pathogens associated with poor pulmonary function in older patient populations.
Singular loci of Bruhat-Hibi toric varieties
Justin A. Brown,V. Lakshmibai
Mathematics , 2007,
Abstract: For the toric variety X associated to the Bruhat poset of Schubert varieties in a minuscule G/P, we describe the singular locus in terms of the faces of the associated polyhedral cone. We further show that the singular locus is pure of codimension 3 in X.
Singular loci of Grassmann-Hibi toric varieties
Justin A. Brown,V. Lakshmibai
Mathematics , 2006,
Abstract: For the toric variety X associated to the Bruhat poset of Schubert varieties in the Grassmannian, we describe the singular locus in terms of the faces of the associated polyhedral cone. We also determine the tangent cones at the maximal singularities of X. These turn out to be again toric varieties. In the case of X being associated to the Bruhat poset of Schubert varieties in the Grassmannian of 2-planes in a n-dimensional vector space (over the base field), we also prove a certain product formula relating the multiplicities at certain singular points.
Calculation of centrality bias factors in $p$+A collisions based on a positive correlation of hard process yields with underlying event activity
Dennis V. Perepelitsa,Peter A. Steinberg
Physics , 2014,
Abstract: Hard scattering yields in centrality-selected proton-- and deuteron--nucleus ($p$+A) collisions are generally compared to nucleon--nucleon ($NN$) cross-sections scaled to the appropriate partonic luminosity using geometric models derived from an analysis of minimum bias $p$+A interactions. In general, these models assume that hard process rates and the magnitude of the soft event activity in the underlying $NN$ collisions is uncorrelated. When included, these correlations influence the measured yield in a nominal centrality interval, an effect typically referred to as a "centrality bias". In this work, the impact of a positive correlation between the hard scattering yield and the underlying event activity in individual $NN$ collisions is investigated. This correlation is incorporated into the centrality calculations used by ATLAS and PHENIX, both based on a similar Monte Carlo Glauber approach but with different models of the per-collision or per-participant event activity. It is found that the presence of this correlation tends to increase the yield measured in more central events and decrease it in peripheral events. Numerical factors to correct measured yields for the centrality bias effect are calculated for $p$+A collisions at RHIC and the LHC. Reasonable agreement with a previous calculation of these factors by PHENIX is found, despite differences in the implementation of the underlying bias.
Estimating species richness of arthropods in azorean pastures: the adequacy of suction sampling and pitfall trapping
Borges, P. A. V.,Brown, V. K.
Graellsia , 2003,
Abstract: Se han investigado las ventajas del uso combinado de técnicas de succión (Vortis) y trampas de caída, a la hora de estimar la riqueza de especies de artrópodos en pastizales antrópicos y seminaturales de tres islas oceánicas de las Azores de origen geológico reciente. Se ha comprobado, además, la capacidad de las trampas de caída y de succión para describir la composición faunística y la riqueza de especies según distintos grupos taxonómicos y ecológicos. Teniendo en cuenta el porcentaje de especies colectado sobre el total estimado, ambas técnicas de muestreo resultaron fiables en lo que se refiere a su eficacia, ofreciendo buenas estimas de la riqueza de especies de artrópodos. Usando los dos métodos a la vez, se obtuvieron valores de eficacia cercanos al 90% para algunos grupos taxonómicos. Las técnicas de succión o de caída por separado fueron fiables para estimar la riqueza de especies de artrópodos predadores (todas las especies) y ara as. Sin embargo, ambas técnicas son necesarias para conseguir estimaciones fiables en el caso de los grupos herbívoros. En términos de presencia-ausencia, los grupos que se alimentan de savia, los chupadores y los herbívoros masticadores mostraron diferentes patrones, con una proporción de colecta más alta en los primeros mediante las técnicas de succión, mientras que la mayoría de las especies masticadoras se pudieron colectar mediante las trampas de caída. Un patrón similar fue obtenido en el caso de las ara as, en donde las especies tejedoras fueron colectadas solo gracias a las técnicas de succión, mientras que la mayoría del resto de las especies se capturaron gracias al uso de trampas de caída. Se concluye que estos dos métodos de colecta deben considerarse complementarios y no alternativos. Por tanto, en estudios realizados en pastizales y sistemas agrícolas, se recomienda el uso simultáneo de ambas técnicas a fin de obtener estimas fiables de la riqueza de especies y la composición taxonómica de artrópodos.
Differential, Phosphorylation Dependent Trafficking of AQP2 in LLC-PK1 Cells
William L. Rice, Yan Zhang, Ying Chen, Toshiyuki Matsuzaki, Dennis Brown, Hua A. Jenny Lu
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0032843
Abstract: The kidney maintains water homeostasis by modulating aquaporin 2 (AQP2) on the plasma membrane of collecting duct principal cells in response to vasopressin (VP). VP mediated phosphorylation of AQP2 at serine 256 is critical for this effect. However, the role of phosphorylation of other serine residues in the AQP2 C-terminus is less well understood. Here, we examined the effect of phosphorylation of S256, S261 and S269 on AQP2 trafficking and association with recycling pathway markers. We used LLC-PK1 cells expressing AQP2(S-D) or (S-A) phospho mutants and a 20°C cold block, which allows endocytosis to continue, but prevents protein exit from the trans Golgi network (TGN), inducing formation of a perinuclear AQP2 patch. AQP2-S256D persists on the plasma membrane during cold block, while wild type AQP2, AQP2-S256A, S261A, S269A and S269D are internalized and accumulate in the patch. Development of this patch, a measure of AQP2 internalization, was most rapid with AQP2-S256A, and slowest with S261A and S269D. AQP2-S269D exhibited a biphasic internalization profile with a significant amount not internalized until 150 minutes of cold block. After rewarming to 37°C, wt AQP2, AQP2-S261A and AQP2-S269D rapidly redistributed throughout the cytoplasm within 20 minutes, whereas AQP2-S256A dissipated more slowly. Colocalization of AQP2 mutants with several key vesicular markers including clathrin, HSP70/HSC70, EEA, GM130 and Rab11 revealed no major differences. Overall, our data provide evidence supporting the role of S256 and S269 in the maintenance of AQP2 at the cell surface and reveal the dynamics of internalization and recycling of differentially phosphorylated AQP2 in cell culture.
The HPV Vaccination Strategy: Could Male Vaccination Have a Significant Impact?
V. Brown,K. A. J. White
Computational and Mathematical Methods in Medicine , 2010, DOI: 10.1080/17486700903486613
Abstract: We investigate the potential success of the human papilloma virus (HPV) vaccine, taking into consideration possible waning immunity and the influence of behavioural parameters. We use a compartmental, population-level ordinary differential equation (ODE) model. We find the effective reproductive value for HPV, R 0 e , which measures the threshold for infection outbreak in a population that is not entirely susceptible, together with infection prevalence. We study the effects of different parameters on both of these quantities. Results show that waning immunity plays a large part in allowing infection to persist. The proportion of the population not sexually active when vaccination occurs affects R 0 e , as does the rate at which individuals become sexually active. In several cases, infection persists as a result of an infection reservoir in the male cohort. To explore this further, we introduce male vaccination and find the conditions for which vaccination of males could be considered appropriate.
Dispelling the curse of the neutron skin in atomic parity violation
B. A. Brown,A. Derevianko,V. V. Flambaum
Physics , 2008, DOI: 10.1103/PhysRevC.79.035501
Abstract: We perform calculations for the neutron skin of nuclei and its contribution to atomic parity non-conservation (PNC) in many isotopes of Cs, Ba, Sm, Dy, Yb, Tl, Pb, Bi, Fr, Ra. Three problems are addressed: i) Neutron-skin induced errors to single-isotope PNC, ii) Possibility to measure neutron skin using atomic PNC, iii) Neutron-skin induced errors for ratios of PNC effects in different isotopes. In the latter case the correlations in the neutron skin values for different isotopes lead to cancelations of the errors; this makes the isotopic ratio method a competitive tool in a search for new physics beyond the standard model.
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