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Search Results: 1 - 10 of 456743 matches for " I. M. Newsome "
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The Young Solar Analogs Project: I. Spectroscopic and Photometric Methods and Multi-year Timescale Spectroscopic Results
R. O. Gray,J. M. Saken,C. J. Corbally,M. M. Briley,R. A. Lambert,V. A. Fuller,I. M. Newsome,M. F. Seeds,Y. Kahvaz
Physics , 2015,
Abstract: This is the first in a series of papers presenting methods and results from the Young Solar Analogs Project, which began in 2007. This project monitors both spectroscopically and photometrically a set of 31 young (300 - 1500 Myr) solar-type stars with the goal of gaining insight into the space environment of the Earth during the period when life first appeared. From our spectroscopic observations we derive the Mount Wilson $S$ chromospheric activity index ($S_{\rm MW}$), and describe the method we use to transform our instrumental indices to $S_{\rm MW}$ without the need for a color term. We introduce three photospheric indices based on strong absorption features in the blue-violet spectrum -- the G-band, the Ca I resonance line, and the Hydrogen-$\gamma$ line -- with the expectation that these indices might prove to be useful in detecting variations in the surface temperatures of active solar-type stars. We also describe our photometric program, and in particular our "Superstar technique" for differential photometry which, instead of relying on a handful of comparison stars, uses the photon flux in the entire star field in the CCD image to derive the program star magnitude. We present time series plots of our spectroscopic data for all four indices, and carry out extensive statistical tests on those time series demonstrating the reality of variations on timescales of years in all four indices. We also statistically test for and discover correlations and anti-correlations between the four indices. We discuss the physical basis of those correlations. As it turns out, the "photospheric" indices appear to be most strongly affected by continuum emission. We thus anticipate that these indices may prove to be useful proxies for monitoring continuum emission in the near ultraviolet.
Patterns of Hemodialysis Catheter Dysfunction Defined According to National Kidney Foundation Guidelines As Blood Flow <300?mL/min
Robert I. Griffiths,Britt B. Newsome,Geoffrey A. Block,Robert J. Herbert,Mark D. Danese
International Journal of Nephrology , 2011, DOI: 10.4061/2011/891259
Abstract: Blood flow rate (BFR) <300?mL/min commonly is used to define hemodialysis catheter dysfunction and the need for interventions to prevent complications. The objective of this study was to describe patterns of unplanned BFR <300?mL/min during catheter hemodialysis using data from DaVita dialysis facilities and the United States Renal Data System. Patients were included if they received at least eight weeks of hemodialysis exclusively through a catheter between 08/04 and 12/06, and catheter hemodialysis was the first treatment modality following diagnosis of end-stage renal disease (first access), or it immediately followed at least one 30-day period of dialysis exclusively through a fistula or graft (replacement access). Actual BFR <300?mL/min despite a planned BFR ≥300?mL/min defined catheter dysfunction during each dialysis session. There were 3,364 patients, 268,363 catheter dialysis sessions, and 19,118 (7.1%) sessions with catheter dysfunction. Almost two-thirds of patients had ≥1 catheter dysfunction session, and 30% had ≥1 catheter dysfunction session per month. Patients with catheter as a replacement access had a higher rate of catheter dysfunction than those with a catheter as first access (hazard ratio: 1.13; ). Catheter dysfunction affects almost one-third of catheter dialysis patients each month and two-thirds overall. 1. Introduction Hemodialysis catheter dysfunction often is defined as blood flow rate (BFR) <300?mL/min [1], including in the National Kidney Foundation’s Kidney Disease Outcome Quality Initiative (NKF-KDOQI) clinical practice guidelines [2]. Other definitions of catheter dysfunction reported in the literature include frequent arterial and venous pressure alarms, poor conductance, and poor dialysis efficiency based on urea reduction ratio or Kt/V calculations [3–8]. Among these definitions, the one recommended by NKF-KDOQI may be of particular significance to providers and payers. This is especially true in the United States, where NKF-KDOQI guidelines play a prominent role in shaping clinical practice, including through the Centers for Medicare and Medicaid Services’ (CMS) End-Stage Renal Disease (ESRD) Clinical Performance Measures Project [9]. Since the recommendation to define catheter dysfunction as BFR <300?mL/min was opinion based, concerns have been raised that it has been interpreted to mean BFR must be kept above 300?mL/min to maintain adequate dialysis. However, one recent study showed that mean blood flows <300?mL/min were not commonly associated with dialysis inadequacy [1], prompting the authors to conclude that
Anthropogenic Resource Subsidies Determine Space Use by Australian Arid Zone Dingoes: An Improved Resource Selection Modelling Approach
Thomas M. Newsome, Guy-Anthony Ballard, Christopher R. Dickman, Peter J. S. Fleming, Chris Howden
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0063931
Abstract: Dingoes (Canis lupus dingo) were introduced to Australia and became feral at least 4,000 years ago. We hypothesized that dingoes, being of domestic origin, would be adaptable to anthropogenic resource subsidies and that their space use would be affected by the dispersion of those resources. We tested this by analyzing Resource Selection Functions (RSFs) developed from GPS fixes (locations) of dingoes in arid central Australia. Using Generalized Linear Mixed-effect Models (GLMMs), we investigated resource relationships for dingoes that had access to abundant food near mine facilities, and for those that did not. From these models, we predicted the probability of dingo occurrence in relation to anthropogenic resource subsidies and other habitat characteristics over ~ 18,000 km2. Very small standard errors and subsequent pervasively high P-values of results will become more important as the size of data sets, such as our GPS tracking logs, increases. Therefore, we also investigated methods to minimize the effects of serial and spatio-temporal correlation among samples and unbalanced study designs. Using GLMMs, we accounted for some of the correlation structure of GPS animal tracking data; however, parameter standard errors remained very small and all predictors were highly significant. Consequently, we developed an alternative approach that allowed us to review effect sizes at different spatial scales and determine which predictors were sufficiently ecologically meaningful to include in final RSF models. We determined that the most important predictor for dingo occurrence around mine sites was distance to the refuse facility. Away from mine sites, close proximity to human-provided watering points was predictive of dingo dispersion as were other landscape factors including palaeochannels, rocky rises and elevated drainage depressions. Our models demonstrate that anthropogenically supplemented food and water can alter dingo-resource relationships. The spatial distribution of such resources is therefore critical for the conservation and management of dingoes and other top predators.
Impact of Hemodialysis Catheter Dysfunction on Dialysis and Other Medical Services: An Observational Cohort Study
Robert I. Griffiths,Britt B. Newsome,Grace Leung,Geoffrey A. Block,Robert J. Herbert,Mark D. Danese
International Journal of Nephrology , 2012, DOI: 10.1155/2012/673954
Abstract: Practice guidelines define hemodialysis catheter dysfunction as blood flow rate (BFR) <300?mL/min. We conducted a study using data from DaVita and the United States Renal Data System to evaluate the impact of catheter dysfunction on dialysis and other medical services. Patients were included if they had ≥8 consecutive weeks of catheter dialysis between 8/2004 and 12/2006. Actual BFR <300 mL/min despite planned BFR ≥300?mL/min was used to define catheter dysfunction during each dialysis session. Among 9,707 patients, the average age was 62,53% were female, and 40% were black. The median duration of catheter dialysis was 190 days, and the cohort accounted for 1,075,701 catheter dialysis sessions. There were 70,361 sessions with catheter dysfunction, and 6,33 1 (65.2%) patients had at least one session with catheter dysfunction. In multivariate repeated measures analysis, catheter dysfunction was associated with increased odds of missing a dialysis session due to access problems (Odds ratio [OR] 2.50; ), having an access-related procedure (OR 2.10; ), and being hospitalized (OR 1.10; ). Catheter dysfunction defined according to NKF vascular access guidelines results in disruptions of dialysis treatment and increased use of other medical services. 1. Background Blood flow rate (BFR) <300?mL/min often is used to define hemodialysis catheter dysfunction, including in the National Kidney Foundation’s (NKF) Kidney Disease Outcomes Quality Initiative (KDOQI) vascular access guidelines [1, 2], and in many research studies [3]. Causes of catheter dysfunction include mechanical kinking, malpositioning of the catheter tip, thrombus accumulation, and growth of a fibrin sheath [4]. Early dysfunction, which has been defined as occurring within the first two weeks of placement [2], is most often, but not exclusively, caused by mechanical problems. Delayed or late dysfunction is typically caused by thrombus accumulation, with or without the presence of a fibrin sheath [4], and is considered to be the most likely cause of low BFR overall [4–7]. Other definitions of catheter dysfunction reported in the literature include frequent arterial and venous pressure alarms, poor conductance, and poor dialysis efficiency based on urea reduction ratio or Kt/V calculations [4]: these have been applied when evaluating the impact of catheter dysfunction on clinical outcomes, economic expenditures, and patient quality of life [8–11]. However, the impact of catheter dysfunction using a BFR threshold, such as in the NKF-KDOQI guidelines, has received less attention. One notable exception
Perceptual “Read-Out” of Conjoined Direction and Disparity Maps in Extrastriate Area MT
Gregory C. DeAngelis,William T. Newsome
PLOS Biology , 2012, DOI: 10.1371/journal.pbio.0020077
Abstract: Cortical neurons are frequently tuned to several stimulus dimensions, and many cortical areas contain intercalated maps of multiple variables. Relatively little is known about how information is “read out” of these multidimensional maps. For example, how does an organism extract information relevant to the task at hand from neurons that are also tuned to other, irrelevant stimulus dimensions? We addressed this question by employing microstimulation techniques to examine the contribution of disparity-tuned neurons in the middle temporal (MT) visual area to performance on a direction discrimination task. Most MT neurons are tuned to both binocular disparity and the direction of stimulus motion, and MT contains topographic maps of both parameters. We assessed the effect of microstimulation on direction judgments after first characterizing the disparity tuning of each stimulation site. Although the disparity of the stimulus was irrelevant to the required task, we found that microstimulation effects were strongly modulated by the disparity tuning of the stimulated neurons. For two of three monkeys, microstimulation of nondisparity-selective sites produced large biases in direction judgments, whereas stimulation of disparity-selective sites had little or no effect. The binocular disparity was optimized for each stimulation site, and our result could not be explained by variations in direction tuning, response strength, or any other tuning property that we examined. When microstimulation of a disparity-tuned site did affect direction judgments, the effects tended to be stronger at the preferred disparity of a stimulation site than at the nonpreferred disparity, indicating that monkeys can selectively monitor direction columns that are best tuned to an appropriate conjunction of parameters. We conclude that the contribution of neurons to behavior can depend strongly upon tuning to stimulus dimensions that appear to be irrelevant to the current task, and we suggest that these findings are best explained in terms of the strategy used by animals to perform the task.
Perceptual “Read-Out” of Conjoined Direction and Disparity Maps in Extrastriate Area MT
Gregory C DeAngelis ,William T Newsome
PLOS Biology , 2004, DOI: 10.1371/journal.pbio.0020077
Abstract: Cortical neurons are frequently tuned to several stimulus dimensions, and many cortical areas contain intercalated maps of multiple variables. Relatively little is known about how information is “read out” of these multidimensional maps. For example, how does an organism extract information relevant to the task at hand from neurons that are also tuned to other, irrelevant stimulus dimensions? We addressed this question by employing microstimulation techniques to examine the contribution of disparity-tuned neurons in the middle temporal (MT) visual area to performance on a direction discrimination task. Most MT neurons are tuned to both binocular disparity and the direction of stimulus motion, and MT contains topographic maps of both parameters. We assessed the effect of microstimulation on direction judgments after first characterizing the disparity tuning of each stimulation site. Although the disparity of the stimulus was irrelevant to the required task, we found that microstimulation effects were strongly modulated by the disparity tuning of the stimulated neurons. For two of three monkeys, microstimulation of nondisparity-selective sites produced large biases in direction judgments, whereas stimulation of disparity-selective sites had little or no effect. The binocular disparity was optimized for each stimulation site, and our result could not be explained by variations in direction tuning, response strength, or any other tuning property that we examined. When microstimulation of a disparity-tuned site did affect direction judgments, the effects tended to be stronger at the preferred disparity of a stimulation site than at the nonpreferred disparity, indicating that monkeys can selectively monitor direction columns that are best tuned to an appropriate conjunction of parameters. We conclude that the contribution of neurons to behavior can depend strongly upon tuning to stimulus dimensions that appear to be irrelevant to the current task, and we suggest that these findings are best explained in terms of the strategy used by animals to perform the task.
Cooperatives, Green Behavior, and Environmental Protection
Mark P. Alavosius,William D. Newsome
Revista Latinoamericana de Psicología , 2012,
Abstract: Los comportamientos humanos relacionados con la degradación ambiental pueden ser la mejor oportunidad hasta ahora para la aplicación socialmente válida de la ciencia conductual a gran escala. Cambiar el comportamiento en la escala necesaria para hacer una diferencia a nivel global requerirá esfuerzos nunca antes vistos en las aplicaciones del análisis de la conducta. Incorporar principios conductuales de probada efectividad en los modelos organizacionales para alterar los comportamientos de cientos de millones de personas puede ser parte de la solución humana al problema del calentamiento global. Este trabajo considera el movimiento de cooperativas y como los estudiantes del comportamiento pueden usar las tecnologías actuales de comunicación, las redes sociales y la creciente comprensión de las contingencias entrelazadas y las redes verbales para proponer soluciones al problema climático a través del cambio conductual. Se proponen consideraciones para iniciativas prácticas.
Isolation of Primary Human Hepatocytes from Normal and Diseased Liver Tissue: A One Hundred Liver Experience
Ricky H. Bhogal,James Hodson,David C. Bartlett,Christopher J. Weston,Stuart M. Curbishley,Emma Haughton,Kevin T. Williams,Gary M. Reynolds,Phillip N. Newsome,David H. Adams,Simon C. Afford
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0018222
Abstract: Successful and consistent isolation of primary human hepatocytes remains a challenge for both cell-based therapeutics/transplantation and laboratory research. Several centres around the world have extensive experience in the isolation of human hepatocytes from non-diseased livers obtained from donor liver surplus to surgical requirement or at hepatic resection for tumours. These livers are an important but limited source of cells for therapy or research. The capacity to isolate cells from diseased liver tissue removed at transplantation would substantially increase availability of cells for research. However no studies comparing the outcome of human hepatocytes isolation from diseased and non-diseased livers presently exist. Here we report our experience isolating human hepatocytes from organ donors, non-diseased resected liver and cirrhotic tissue. We report the cell yields and functional qualities of cells isolated from the different types of liver and demonstrate that a single rigorous protocol allows the routine harvest of good quality primary hepatocytes from the most commonly accessible human liver tissue samples.
Revisiting Brain Atrophy and Its Relationship to Disability in Multiple Sclerosis
Navid Shiee, Pierre-Louis Bazin, Kathleen M. Zackowski, Sheena K. Farrell, Daniel M. Harrison, Scott D. Newsome, John N. Ratchford, Brian S. Caffo, Peter A. Calabresi, Dzung L. Pham, Daniel S. Reich
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0037049
Abstract: Background Brain atrophy is a well-accepted imaging biomarker of multiple sclerosis (MS) that partially correlates with both physical disability and cognitive impairment. Methodology/Principal Findings Based on MRI scans of 60 MS cases and 37 healthy volunteers, we measured the volumes of white matter (WM) lesions, cortical gray matter (GM), cerebral WM, caudate nucleus, putamen, thalamus, ventricles, and brainstem using a validated and completely automated segmentation method. We correlated these volumes with the Expanded Disability Status Scale (EDSS), MS Severity Scale (MSSS), MS Functional Composite (MSFC), and quantitative measures of ankle strength and toe sensation. Normalized volumes of both cortical and subcortical GM structures were abnormally low in the MS group, whereas no abnormality was found in the volume of the cerebral WM. High physical disability was associated with low cerebral WM, thalamus, and brainstem volumes (partial correlation coefficients ~0.3–0.4) but not with low cortical GM volume. Thalamus volumes were inversely correlated with lesion load (r = ?0.36, p<0.005). Conclusion The GM is atrophic in MS. Although lower WM volume is associated with greater disability, as might be expected, WM volume was on average in the normal range. This paradoxical result might be explained by the presence of coexisting pathological processes, such as tissue damage and repair, that cause both atrophy and hypertrophy and that underlie the observed disability.
A Switch in Hepatic Cortisol Metabolism across the Spectrum of Non Alcoholic Fatty Liver Disease
Adeeba Ahmed, Elizabeth Rabbitt, Theresa Brady, Claire Brown, Peter Guest, Iwona J. Bujalska, Craig Doig, Philip N. Newsome, Stefan Hubscher, Elwyn Elias, David H. Adams, Jeremy W. Tomlinson, Paul M. Stewart
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0029531
Abstract: Context Non alcoholic fatty liver disease (NAFLD) is the hepatic manifestation of the metabolic syndrome. NAFLD represents a spectrum of liver disease ranging from reversible hepatic steatosis, to non alcoholic steato-hepatitis (NASH) and cirrhosis. The potential role of glucocorticoids (GC) in the pathogenesis of NAFLD is highlighted in patients with GC excess, Cushing's syndrome, who develop central adiposity, insulin resistance and in 20% of cases, NAFLD. Although in most cases of NAFLD, circulating cortisol levels are normal, hepatic cortisol availability is controlled by enzymes that regenerate cortisol (F) from inactive cortisone (E) (11β-hydroxysteroid dehydrogenase type 1, 11β-HSD1), or inactivate cortisol through A-ring metabolism (5α- and 5β-reductase, 5αR and 5βR). Objective and Methods In vitro studies defined 11β-HSD1 expression in normal and NASH liver samples. We then characterised hepatic cortisol metabolism in 16 patients with histologically proven NAFLD compared to 32 obese controls using gas chromatographic analysis of 24 hour urine collection and plasma cortisol generation profile following oral cortisone. Results In patients with steatosis 5αR activity was increased, with a decrease in hepatic 11β-HSD1 activity. Total cortisol metabolites were increased in this group consistent with increased GC production rate. In contrast, in patients with NASH, 11β-HSD1 activity was increased both in comparison to patients with steatosis, and controls. Endorsing these findings, 11β-HSD1 mRNA and immunostaining was markedly increased in NASH patients in peri septal hepatocytes and within CD68 positive macrophages within inflamed cirrhotic septa. Conclusion Patients with hepatic steatosis have increased clearance and decreased hepatic regeneration of cortisol and we propose that this may represent a protective mechanism to decrease local GC availability to preserve hepatic metabolic phenotype. With progression to NASH, increased 11β-HSD1 activity and consequent cortisol regeneration may serve to limit hepatic inflammation.
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