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Search Results: 1 - 10 of 123732 matches for " Jeffrey T. Kuvin "
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Augmentation Index Derived from Peripheral Arterial Tonometry Correlates with Cardiovascular Risk Factors
Eshan Patvardhan,Kevin S. Heffernan,Jenny Ruan,Michael Hession,Patrick Warner,Richard H. Karas,Jeffrey T. Kuvin
Cardiology Research and Practice , 2011, DOI: 10.4061/2011/253758
Abstract: Background. Augmentation index (AIx) is traditionally obtained from pressure waveforms via arterial applanation tonometry. We sought to evaluate the association between AIx obtained from peripheral arterial tonometry (PAT) with cardiovascular risk factors (CRF) and coronary artery disease (CAD). Methods. 186 patients were enrolled in the study. The presence or absence of CRFs and CAD was assessed in each subject. AIx was calculated by an automated algorithm averaging pulse wave amplitude data obtained via PAT. Central blood pressures were assessed in a subset of patients undergoing clinically indicated cardiac catheterization. Results. An association was observed between AIx and age, heart rate, systolic blood pressure, mean arterial pressure, pulse pressure, body weight and body mass index. AIx was significantly lower in patients with <3 CRFs compared to those with >5 CRFs (=.02). CAD
Systemic Vascular Function Is Associated with Muscular Power in Older Adults
Kevin S. Heffernan,Angela Chalé,Cynthia Hau,Gregory J. Cloutier,Edward M. Phillips,Patrick Warner,Heather Nickerson,Kieran F. Reid,Jeffrey T. Kuvin,Roger A. Fielding
Journal of Aging Research , 2012, DOI: 10.1155/2012/386387
Abstract: Age-associated loss of muscular strength and muscular power is a critical determinant of loss of physical function and progression to disability in older adults. In this study, we examined the association of systemic vascular function and measures of muscle strength and power in older adults. Measures of vascular endothelial function included brachial artery flow-mediated dilation (FMD) and the pulse wave amplitude reactive hyperemia index (PWA-RHI). Augmentation index (AIx) was taken as a measure of systemic vascular function related to arterial stiffness and wave reflection. Measures of muscular strength included one repetition maximum (1RM) for a bilateral leg press. Peak muscular power was measured during 5 repetitions performed as fast as possible for bilateral leg press at 40% 1RM. Muscular power was associated with brachial FMD ( ?? = 0 . 4 3 , ?? < 0 . 0 5 ), PWA-RHI ( ?? = 0 . 4 2 , ?? < 0 . 0 5 ), and AIx ( ?? = ? 0 . 5 4 , ?? < 0 . 0 5 ). Muscular strength was not associated with any measure of vascular function. In conclusion, systemic vascular function is associated with lower-limb muscular power but not muscular strength in older adults. Whether loss of muscular power with aging contributes to systemic vascular deconditioning or vascular dysfunction contributes to decrements in muscular power remains to be determined. 1. Introduction As life expectancy in the United States continues to rise, the maintenance of physical independence of older adults has also emerged as a major clinical and public health priority. A critical factor in an older person’s ability to function independently is the ability to move without assistance. Older adults who lose mobility are less likely to remain in the community, have higher rates of mortality, and experience a poorer quality of life [1, 2]. Age-associated loss of muscular strength (the ability to generate maximal muscle force) and muscular power (the product of the force and velocity of muscle contraction) is an important determinant of this loss of physical function and progression to disability [3]. Interestingly, although muscular strength and power are associated, muscular power has been shown to be a stronger predictor of physical function than muscular strength in older adults [4, 5]. Poor muscular power is associated with a 3-fold greater risk for mobility impairment than poor muscle strength [6] and improving muscular power leads to improvements in physical function independent of changes in muscular strength [7]. Although numerous potential mechanisms have been put forth, no single common
Does the alpha cluster structure in light nuclei persist through the fusion process?
J. Vadas,T. K. Steinbach,J. Schmidt,Varinderjit Singh,C. Haycraft,S. Hudan,R. T. deSouza,L. T. Baby,S. A. Kuvin,I. Wiedenhover
Physics , 2015,
Abstract: [Background] Despite the importance of light-ion fusion in nucleosynthesis, a limited amount of data exists regarding the de-excitation following fusion for such systems. [Purpose] To explore the characteristics of alpha emission associated with the decay of light fused systems at low excitation energy. [Method] Alpha particles were detected in coincidence with evaporation residues (ER) formed by the fusion of 18O and 12C nuclei. Both alpha particles and ERs were identified on the basis of their energy and time-of-flight. ERs were characterized by their energy spectra and angular distributions while the alpha particles were characterized by their energy spectra, angular distributions, and cross-sections. [Results] While the energy spectra and angular distributions for the alpha particles are well reproduced by statistical model codes, the measured cross-section is substantially underpredicted by the models. Comparison with similar systems reveals that the fundamental quantity for the alpha cross-section is Ec.m. and not the excitation energy of the fused system. [Conclusion]The enhancement in the measured alpha cross-section as compared to the statistical model codes and its dependence with Ec.m. suggest that a coupling between pre-existing alpha cluster structure and the collision dynamics is responsible for the observed alpha cross-section.
Sub-barrier enhancement of fusion as compared to a microscopic method in 18O+12C
T. K. Steinbach,J. Vadas,J. Schmidt,C. Haycraft,S. Hudan,R. T. deSouza,L. T. Baby,S. A. Kuvin,I. Wiedenh?ver,A. S. Umar,V. E. Oberacker
Physics , 2014, DOI: 10.1103/PhysRevC.90.041603
Abstract: Measurement of the energy dependence of the fusion cross-sec on at sub-barrier energies provides an important test for theoretical models of fusion. To extend the measurement of fusion cross-sections in the sub-barrier domain for the 18O+12C system. Use the new experimental data to confront microscopic calculations of fusion. Evaporation residues produced in fusion of 18O ions with 12C target nuclei were detected with good geometric efficiency and identified by measuring their energy and time-of-flight. Theoretical calculations with a density constrained time dependent Hartree-Fock (DC-TDHF) theory include for the first time the effect of pairing on the fusion cross-section. Comparison of the measured fusion excitation function with the predictions of the DC-TDHF calculations reveal that the experimental data exhibits a smaller decrease in cross-section with decreasing energy than is theoretically predicted. The larger cross-sections observed at the lowest energies measured indicate a larger tunneling probability for the fusion process. This larger probability can be associated with a smaller, narrower fusion barrier than presently included in the theoretical calculations.
Tissue-specific circadian cycles
Jeffrey T Ehmsen
Genome Biology , 2002, DOI: 10.1186/gb-2002-3-8-reports0046
Abstract: Temporal patterns of gene expression in the suprachiasmatic nuclei and liver of C57BL/6J mice previously entrained to a standard dark-light cycle were examined by microarray analysis. Transcripts showing a cosine-like periodic variation of 20-28 hours were considered to be regulated in circadian fashion. Approximately 650 cycling transcripts were revealed, including at least eight previously identified as expressed with circadian periodicity. Only 28 of these genes overlapped between the SCN and liver, perhaps representing components of the circadian oscillator itself. Intriguingly, the remaining nonoverlapping cycling transcripts are generally expressed at much lower levels in the other tissue, suggesting tissue-specific circadian regulation of transcription relevant to the function of the particular organ. Examination of the functions of these transcripts suggests that circadian control of many pathways is probably exerted at biochemically rate-limiting steps. In the SCN, for example, circadian control of genes involved in the synthesis, processing and release of neurotransmitters or in regulating the levels of channel proteins and receptors could influence neuronal signaling. Tightly regulated synthesis and degradation of periodically expressed proteins is critical. Indeed, a majority of the cycling transcripts in the SCN are implicated in protein synthesis, including ribosomal components, proteins involved in folding and members of the ubiquitin-mediated protein-degradation pathway. In the liver, cycling levels of membrane channels, transporters and enzymes involved in nutrient metabolism could regulate the use and movement of metabolites. Peak expression of such transcripts is also correlated with the expected temporal activity of the relevant tissue, with peak expression of regulated genes in the SCN occurring at 10 and 22 hours in the circadian cycle, roughly anticipating dusk and dawn.A publicly accessible Database of circadian gene expression is provided by
Doubling up the genome
Jeffrey T Ehmsen
Genome Biology , 2002, DOI: 10.1186/gb-2002-3-8-reports0045
Abstract: Assuming that conserved syntenies between MHC regions in human and bony fish represent en bloc duplications that occurred before the Gnathostomata radiation, the authors cloned nine 'anchor genes' from an amphioxus cosmid library, sequenced 400 kilobases of regions flanking these genes, and ran a database search for similar sequences in the human genome. The 9 anchor genes and 22 surrounding genes and their counterparts in the human genome are considered to be orthologs, prompting the conclusion that duplications giving rise to the anchor-gene families occurred between 420 and 766 million years ago, after the divergence of cephalochordates and vertebrates but before the vertebrate radiation. The human orthologs of the genes surrounding the amphioxus anchor genes were mapped and their distribution within the four human MHC regions on chromosomes 1, 6, 9 and 19 were analyzed, revealing a statistically nonrandom organization indicative of an evolutionary link between the two genomes. To understand the development of the human MHC regions better, the authors used cloned amphioxus genes to reconstruct a 'proto-MHC region' ancestral to the Gnathostomata. In terms of organization and gene-substitution patterns, the human MHC paralogous region on chromosome 9 is conspicuously more similar to the predicted ancestral genomic region than the other three human MHC paralogous regions, suggesting that the entire region may for some reason be under negative selection.It will be instructive to look at other genomic regions that appear to have a duplication-based origin; this should become more straightforward as the sequenced genomes of other species become available. Such studies should make it possible to trace the type(s) of genome duplication that have occurred in vertebrate evolution - whether complete polyploidization or duplication of chromosomal segments. Further studies might also explore the implications of apparent negative selection pressures for maintaining gene organi
Selecting ELL Textbooks: A Content Analysis of L2 Learning Strategies
Jeffrey T LaBelle
Journal of Language Teaching and Research , 2010, DOI: 10.4304/jltr.1.4.358-369
Abstract: Although middle school teachers use a variety of ELL textbooks, many lack effective criteria to critically select materials that represent a wide range of L2 learning strategies. This study analyzed the illustrated and written content of 33 ELL textbooks to determine the range of L2 learning strategies represented. The researchers chose an intentional, convenience sample from each textbook to form the corpus they analyzed. They sought to answer the question: To what extent do middle school ELL texts depict frequency and variation of language learning strategies in illustrations and written texts? To measure the content, the researchers developed a coding instrument to track how frequently each of 15 language learning strategies was portrayed. They concluded that 6 of the 33 textbooks had a good to excellent range of L2 learning strategies in both illustrated and written representation. The study provides recommendations for teachers regarding selection of ELL textbooks appropriate for their students along with a sample coding instrument for their use.
Vietnamese American Experiences of English Language Learning: Ethnic Acceptance and Prejudice
Jeffrey T LaBelle
Journal of Southeast Asian American Education and Advancement , 2007,
Abstract: This article investigates the effects of ethnic acceptance and prejudice on English language learning among immigrant nonnative speakers. During 2004 and 2005, the author conducted participatory dialogues among six Vietnamese and Mexican adult immigrant English language learners. The researcher sought to answer five questions: (1) What are some nonnative English speakers’ experience regarding the way native speakers treat them? (2) How have nonnative English speakers’ experiences of ethnic acceptance or ethnic prejudice affected their learning of English? (3) What do nonnative English speakers think they need in order to lower their anxiety as they learn a new language? (4) What can native English speakers do to lower nonnative speakers’ anxiety? (5) What can nonnative English speakers do to lower their anxiety with native English speakers? Even though many of the adult immigrant participants experienced ethnic prejudice, they developed strategies to overcome anxiety, frustration, and fear. The dialogues generated themes of acceptance, prejudice, power, motivation, belonging, and perseverance, all factors essential to consider when developing English language learning programs for adult immigrants.
Biomedical Pollutants in the Urban Environment and Implications for Public Health: A Case Study
Jeffrey N. T. Squire
ISRN Public Health , 2013, DOI: 10.1155/2013/497490
Abstract: This study investigated the management of biomedical pollutants in the Accra Metropolitan Area in Ghana, using a qualitative case study approach involving interviews, focus-group discussions, and observation techniques. A state of precariousness was found to characterize the management of biomedical pollutants in the study area, culminating in the magnification of risks to the environment and public health. There is neither a single sanitary landfill nor a properly functioning incineration system in the entire metropolis, and most of the healthcare facilities surveyed lack access to suitable treatment technologies. As a result, crude burning and indiscriminate dumping of infectious and toxic biomedical residues were found to be widespread. The crude burning of toxic biomedical pollutants was found to provide environmental pathways for carcinogenic substances. These include polynuclear aromatic hydrocarbons (PAHs), polychlorinated dibenzofurans (PCDFs), polychlorinated dibenzo-para-dioxins (PCDDs), polychlorinated biphenyls (PCBs), hydrogen, lead, mercury, cadmium, chlorobenzenes, particulate matter, and chlorophenols. The improper disposal of biomedical pollutants in open dumps and unsanitary landfills also carries a risk of providing environmental entry points for volatile organic compounds (VOCs), inorganic macrocomponents, heavy metals, and xenobiotic organic compounds. 1. Introduction Biomedical pollutants generated during the course of healthcare delivery are known to carry greater risks to the environment and human health due to its infectious, hazardous, and toxic composition [1–3]. Some classes of biomedical pollutants can interfere with the metabolic processes of organisms, cause neurotoxic, nephrotoxic, and neurological effects on the human body, and stop or kill the growth of living cells [3]. Certain classes of biomedical pollutants are also known to be bioactive in aquatic ecosystems even at low concentrations and can have negative impacts on aquatic life in terms of reproduction and development [4–6]. In spite of the risks, the management of healthcare biomedical pollutants is not prioritized in many parts of the world especially in developing countries. In many developing countries, there are no effective policies in place regulating the management of biomedical pollutants, resulting in unsafe handling and disposal practices. In cases where there are policies in place, compliance and enforcement procedures are highly negligible [7–9]. Resultantly, the management of biomedical pollutants in many developing countries is characterized by
Expression of mitochondrial branched-chain aminotransferase and α-keto-acid dehydrogenase in rat brain: implications for neurotransmitter metabolism
Jeffrey T. Cole
Frontiers in Neuroanatomy , 2012, DOI: 10.3389/fnana.2012.00018
Abstract: In the brain, metabolism of the essential branched chain amino acids (BCAAs) leucine, isoleucine, and valine, is regulated in part by protein synthesis requirements. Excess BCAAs are catabolized or excreted. The first step in BCAA catabolism is catalyzed by the branched chain aminotransferase (BCAT) isozymes, mitochondrial BCATm and cytosolic BCATc. A product of this reaction, glutamate, is the major excitatory neurotransmitter and precursor of the major inhibitory neurotransmitter γ-aminobutyric acid (GABA). The BCATs are thought to participate in a α-keto-acid nitrogen shuttle that provides nitrogen for synthesis of glutamate from α-ketoglutarate. The branched-chain α-keto acid dehydrogenase enzyme complex (BCKDC) catalyzes the second, irreversible step in BCAA metabolism, which is oxidative decarboxylation of the branched-chain α-keto acid (BCKA) products of the BCAT reaction. Maple Syrup Urine Disease (MSUD) results from genetic defects in BCKDC, which leads to accumulation of toxic levels of BCAAs and BCKAs that result in brain swelling. Immunolocalization of BCATm and BCKDC in rats revealed that BCATm is present in astrocytes in white matter and in neuropil, while BCKDC is expressed only in neurons. BCATm appears uniformly distributed in astrocyte cell bodies throughout the brain. The segregation of BCATm to astrocytes and BCKDC to neurons provides further support for the existence of a BCAA-dependent glial-neuronal nitrogen shuttle since the data show that BCKAs produced by glial BCATm must be exported to neurons. Additionally, the neuronal localization of BCKDC suggests that MSUD is a neuronal defect involving insufficient oxidation of BCKAs, with secondary effects extending beyond the neuron.
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