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Search Results: 1 - 10 of 211092 matches for " James D. Robinson "
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Causality and the Power Spectrum
James Robinson,Benjamin D. Wandelt
Physics , 1995, DOI: 10.1103/PhysRevD.53.618
Abstract: We find constraints on the generation of super-causal-horizon energy perturbations from a smooth initial state, under a simple physical scheme. We quantify these constraints by placing the upper limit $\lambda_c = 3.0 d_H$ on the wavelength at which the power spectrum turns over to $k^4$ behavior. This means that sub-horizon processes can generate significant power on scales further outside the horizon than one might naively expect. The existence of this limit may have important implications for the interpretation of the small scale power spectrum of the Cosmic Microwave Background.
Edges and Overlaps in Northwest Atlantic Phylogeography
Safra Altman,John D. Robinson,James M. Pringle,James E. Byers,John P. Wares
Diversity , 2013, DOI: 10.3390/d5020263
Abstract: As marine environments change, the greatest ecological shifts—including resource usage and species interactions—are likely to take place in or near regions of biogeographic and phylogeographic transition. However, our understanding of where these transitional regions exist depends on the defining criteria. Here we evaluate phylogeographic transitions using a bootstrapping procedure that allows us to focus on either the strongest genetic transitions between a pair of contiguous populations, versus evaluation of transitions inclusive of the entire overlap between two intraspecific genetic lineages. We compiled data for the Atlantic coast of the United States, and evaluate taxa with short- and long-dispersing larval phases separately. Our results are largely concordant with previous biogeographic and phylogeographic analyses, indicating strong biotic change associated with the regions near Cape Cod, the Delmarva Peninsula, and eastern Florida. However, inclusive analysis of the entire range of sympatry for intraspecific lineages suggests that broad regions—the Mid-Atlantic Bight and eastern Florida–already harbor divergent intraspecific lineages, suggesting the potential for ecological evaluation of resource use between these lineages. This study establishes baseline information for tracking how such patterns change as predicted environmental changes take place.
Cosmological constraints from the correlation function of galaxy clusters
James Robinson
Physics , 2000,
Abstract: I compare various semi-analytic models for the bias of dark matter halos with halo clustering properties observed in recent numerical simulations. The best fitting model is one based on the collapse of ellipsoidal perturbations proposed by Sheth, Mo & Tormen (1999), which fits the halo correlation length to better than 8 per cent accuracy. Using this model, I confirm that the correlation length of clusters of a given separation depends primarily on the shape and amplitude of mass fluctuations in the universe, and is almost independent of other cosmological parameters. Current observational uncertainties make it difficult to draw robust conclusions, but for illustrative purposes I discuss the constraints on the mass power spectrum which are implied by recent analyses of the APM cluster sample. I also discuss the prospects for improving these constraints using future surveys such as the Sloan Digital Sky Survey. Finally, I show how these constraints can be combined with observations of the cluster number abundance to place strong limits on the matter density of the universe.
Monitoring Procalcitonin in Febrile Neutropenia: What Is Its Utility for Initial Diagnosis of Infection and Reassessment in Persistent Fever?
James Owen Robinson,Frédéric Lamoth,Frank Bally,Marlies Knaup,Thierry Calandra,Oscar Marchetti
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0018886
Abstract: Management of febrile neutropenic episodes (FE) is challenged by lacking microbiological and clinical documentation of infection. We aimed at evaluating the utility of monitoring blood procalcitonin (PCT) in FE for initial diagnosis of infection and reassessment in persistent fever.
Relationship between parental estimate and an objective measure of child television watching
Jodie L Robinson, Dana D Winiewicz, Janene H Fuerch, James N Roemmich, Leonard H Epstein
International Journal of Behavioral Nutrition and Physical Activity , 2006, DOI: 10.1186/1479-5868-3-43
Abstract: Young children today are exposed to an abundance of sedentary activities that include television and movie watching, using the computer, and playing video games. National data and recent research both suggest that 3–7 year-old children watch an average of two [1-7] to three hours of television per day [2-9], with media related television activities such as video games and movies adding a half hour per day [6,10], and computer games adding another half hour per day [6,11].Television viewing is typically assessed by parental estimates, since young children cannot accurately self-report their own television viewing behaviors, but there is limited validity data of parental estimates of child television viewing time. Parents overestimated child television viewing by 1.1 hours/week to 5.3 hours/week in comparison to parental diaries [12], and parental diaries overestimated television viewing when compared with video observation by 3.2 hours/week [12]. Parents also underestimate child viewing hours versus Nielsen ratings (13.4 hours/week versus 27.8 hours/week, respectively) [9]. Nielsen Media Research measures estimates of audience viewing using an electronic monitoring system, called people meters, placed on each TV set in randomly selected homes. The people meters record what channel is being watched, and who is watching to provide national household and person estimates of TV viewing [9]. Parental estimates are influenced by how much opportunity parents have to observe their children engaging in these behaviors. Thirty-two to forty percent of children seven years old and younger have a television in their bedroom [6,10,13], which may limit the accuracy of parental observations on television watching. A television set in the child's bedroom is related to increased prevalence of obesity [13], higher overall viewing times [11,13-16], and greater sleep disturbances [15]. This study compared parental estimates of television and computer use with an objective measure for all
Retroperitoneal haemorrhage in renal angiomyolipoma causing hepatic functional decompensation: a case report
Julekha R Wajed, Simon D Taylor-Robinson, James E Jackson, Gordon WH Stamp
Journal of Medical Case Reports , 2007, DOI: 10.1186/1752-1947-1-82
Abstract: We present a case of retroperitoneal bleeding from a renal angiomyolipoma in a patient with known cirrhosis of the liver, which caused acute deterioration of liver function and consequent hepatic encephalopathy. Selective embolisation of the lesion was performed with a good subsequent outcome. Such functional hepatic decompensation has not previously been reported in this context and we suggest the use of prophylactic embolisation for incidental renal angiomyolipomata, regardless of size, in all patients with chronic liver disease to prevent this potentially life-threatening complication.Renal angiomyolipomata are incidental findings that usually remain clinically silent in the majority of cases [1]. However, in a small minority there have been reports of severe haemorrhage, which can be fatal if not treated promptly [2-6].There is a strong association with angiomyolipomata and tuberous sclerosis [2,4,7]. However, there are no case reports of renal angiomyolipomata in patients with chronic liver disease and the potential hepatic complications, if there is a spontaneous haemorrhage [8-10].There is an established risk of sudden bleeding from angiomyolipomata in lesions greater than 4 cm in maximal diameter, or during pregnancy from an increased haemodynamic flow. In some countries this has led to prophylactic embolisation beginning to become the recommended practice in such cases [4-6,11].This case report demonstrates the rare complication of a bleeding renal angiomyolipoma in association with chronic liver disease, which caused rapid decompensation and encephalopathy. We suggest the use of prophylactic embolisation of incidental angiomyolipomata, regardless of size, in all patients with chronic liver disease.A 59 year-old woman presented to her general practitioner in 2005 with a 2-month history of right-sided flank pain, haematuria, and weight loss. She was not diabetic or dyslipidaemic, and there was no significant past medical or family history. She did not take a
Distinct Structural Features of G Protein-Coupled Receptor Kinase 5 (GRK5) Regulate Its Nuclear Localization and DNA-Binding Ability
Laura R. Johnson, James D. Robinson, Katrina N. Lester, Julie A. Pitcher
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0062508
Abstract: G protein-coupled receptor kinases (GRKs) act to desensitize G protein-coupled receptors (GPCRs). In addition to this role at the plasma membrane, a nuclear function for GRK5, a member of the GRK4 subfamily of GRKs, has been reported. GRK5 phosphorylates and promotes the nuclear export of the histone deacetylase, HDAC5. Here we demonstrate that the possession of a nuclear localization sequence (NLS) is a common feature of GRK4 subfamily members (GRKs 4, 5 and 6). However, the location of the NLS and the ability of these GRKs to bind DNA in vitro are different. The NLSs of GRK5 and 6 bind DNA in vitro, whilst the NLS of GRK4 does not. Using mutants of GRK5 we identify the regions of GRK5 required for DNA-binding in vitro and nuclear localization in cells. The DNA-binding ability of GRK5 requires both the NLS and an N-terminal calmodulin (CaM)-binding site. A functional nuclear export sequence (NES), required for CaM-dependent nuclear export of the kinase, is also identified. Based on our observations we propose a model to explain how nuclear localization of GRK5 may be regulated. Notably, the nuclear localization of GRK5 and 6 is differentially regulated. These results suggest subfamily specific nuclear functions for the GRK4 subfamily members. Identification of GRK specific small molecule inhibitors of nuclear localization and/or function for the GRK4 subfamily may thus be an achievable goal.
Chronic Pravastatin but Not Atorvastatin Treatment Impairs Cognitive Function in Two Rodent Models of Learning and Memory
Sarah A. Stuart, James D. Robertson, Neil V. Marrion, Emma S. J. Robinson
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0075467
Abstract: Statins are some of the most commonly prescribed drugs and are used to reduce blood cholesterol. Recent evidence suggests that, in some patients, they may adversely influence cognitive function including causing memory impairments. These clinical observations have led to statin prescriptions now including a warning about possible cognitive impairments. In order to better understand the relationship between statin treatment and cognitive function, studies in animals are needed. The present study investigated the effects of chronic treatment with two statins, pravastatin and atorvastatin, in two rodent models of learning and memory. Adult rats were treated once daily with pravastatin (10mg/kg, orally) or atorvostatin (10mg/kg, orally) for 18 days. Before, during and after treatment, animals were tested in a simple discrimination and reversal learning task. On the last day of treatment and following one week withdrawal, animals were also tested in a task of novel object discrimination. Pravastatin tended to impair learning over the last few days of treatment and this effect was fully reversed once treatment ceased. In the novel object discrimination task, pravastatin significantly impaired object recognition memory. No effects were observed for atorvostatin in either task. These data suggest that chronic treatment with pravastatin impairs working and recognition memory in rodents. The reversibility of the effects on cessation of treatment is similar to what has been observed in patients, but the lack of effect of atorvostatin suggests that lipophilicity may not be a major factor influencing statin-induced cognitive impairments.
Using MapMyFitness to Place Physical Activity into Neighborhood Context
Jana A. Hirsch,Peter James,Jamaica R. M. Robinson,Kyler M. Eastman,Kevin D. Conley
Frontiers in Public Health , 2014, DOI: 10.3389/fpubh.2014.00019
Abstract: It is difficult to obtain detailed information on the context of physical activity at large geographic scales, such as the entire United States, as well as over long periods of time, such as over years. MapMyFitness is a suite of interactive tools for individuals to track their workouts online or using global positioning system in their phones or other wireless trackers. This method article discusses the use of physical activity data tracked using MapMyFitness to examine patterns over space and time. An overview of MapMyFitness, including data tracked, user information, and geographic scope, is explored. We illustrate the utility of MapMyFitness data using tracked physical activity by users in Winston-Salem, NC, USA between 2006 and 2013. Types of physical activities tracked are described, as well as the percent of activities occurring in parks. Strengths of MapMyFitness data include objective data collection, low participant burden, extensive geographic scale, and longitudinal series. Limitations include generalizability, behavioral change as the result of technology use, and potential ethical considerations. MapMyFitness is a powerful tool to investigate patterns of physical activity across large geographic and temporal scales.
Warming early Mars with CO2 and H2
Ramses M. Ramirez,Ravi Kopparapu,Michael E. Zugger,Tyler D. Robinson,Richard Freedman,James F. Kasting
Physics , 2014, DOI: 10.1038/ngeo2000
Abstract: The presence of valleys on ancient terrains of Mars suggest that liquid water flowed on the martian surface 3.8 billion years ago or before. The above-freezing temperatures required to explain valley formation could have been transient, in response to frequent large meteorite impacts on early Mars, or they could have been caused by long-lived greenhouse warming. Climate models that consider only the greenhouse gases carbon dioxide and water vapor have been unable to recreate warm surface conditions, given the lower solar luminosity at that time. Here we use a one-dimensional climate model to demonstrate that an atmosphere containing 1.3-4 bar of CO2 and water vapor, along with 5 to 20 percent H2, could have raised the mean surface temperature of early Mars above the freezing point of water. Vigorous volcanic outgassing from a highly reduced early martian mantle is expected to provide sufficient atmospheric H2 and CO2, the latter from the photochemical oxidation of outgassed CH4 and CO, to form a CO2-H2 greenhouse. Such a dense early martian atmosphere is consistent with independent estimates of surface pressure based on cratering data.
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