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Search Results: 1 - 10 of 298365 matches for " J. Parker "
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Psychotropic prescribing in HIV
J Parker
Southern African Journal of HIV Medicine , 2009,
Abstract: The use of psychiatric medication in patients with HIV infection is a complex area, but given the high rates of psychiatric disorder in this population – possibly as high as 50%1 – it deserves further consideration. A number of issues need to be thought about, including the nature of both the psychiatric illness and the HIV infection, the use of antiretroviral therapy (ART), and patient-related factors.
Simple tools for assembling and searching high-density picolitre pyrophosphate sequence data
Nicolas J Parker, Andrew G Parker
Source Code for Biology and Medicine , 2008, DOI: 10.1186/1751-0473-3-5
Abstract: A set of tools is provided to search a large data set of pyrophosphate sequence reads under a "live" CD version of Linux on a standard PC that can be used by anyone without prior knowledge of Linux and without having to install a Linux setup on the computer. The tools permit short lengths of de novo assembly, checking of existing assembled sequences, selection and display of reads from the data set and gathering counts of sequences in the reads.Demonstrations are given of the use of the tools to help with checking an assembly against the fragment data set; investigating homopolymer lengths, repeat regions and polymorphisms; and resolving inserted bases caused by incomplete chain extension.The additional information contained in a pyrophosphate sequencing data set beyond a basic assembly is difficult to access due to a lack of tools. The set of simple tools presented here would allow anyone with basic computer skills and a standard PC to access this information.The introduction of micro-fabricated high-density picolitre reactor pyrophosphate sequencing [1,2] by the company 454 Life Sciences (454 Life Sciences Corp., 20 Commercial Street, Branford, Connecticut 06405, USA; hereafter referred to as 454 sequencing) makes available for the first time large quantities of sequence data at reasonable cost. The continual reduction in sequencing cost will encourage sequencing by small groups or individual researchers with modest computer resources and limited experience of bioinformatics tools.The nature of the data from pyrophosphate sequencing is however both qualitatively and quantitatively different from that generated by Sanger sequencing [3] using fluorescent chain-terminating nucleotide analogues [4]. Instead of receiving a single consensus sequence with associated chromatogram (scf) file, this form of pyrophosphate sequencing generated for us 300 000 short sequence reads, around 100 bases long [5], assembled into several hundred contigs. However the normal system of ch
Del estado actual de los estudios quechuas
Parker, Gary J
Bulletin de l'Institut Francais d'études Andines , 1972,
Abstract: -
A micro-pool model for decision-related signals in visual cortical areas
Andrew J. Parker
Frontiers in Computational Neuroscience , 2013, DOI: 10.3389/fncom.2013.00115
Abstract: The study of sensory signaling in the visual cortex has been greatly advanced by the recording of neural activity simultaneously with the performance of a specific psychophysical task. Individual nerve cells may also increase their firing leading up to the particular choice or decision made on a single psychophysical trial. Understanding these signals is important because they have been taken as evidence that a particular nerve cell or group of nerve cells in the cortex is involved in the formation of the perceptual decision ultimately signaled by the organism. However, recent analyses show that the size of a decision-related change in firing in a particular neuron is not a secure basis for concluding anything about the contribution of a single neuron to the formation of a decision: rather the size of the decision-related firing is expected to be dominated by the extent to which the activation of a single neuron is correlated with the firing of the pool of neurons. The critical question becomes what defines membership of a population of neurons. This article presents the proposal that groups of neurons are naturally linked together by their connectivity, which in turn reflects the previous history of sensory stimulations. When a new psychophysical task is performed, a group of neurons relevant to the judgment becomes involved because the firing of some neurons in that group is strongly relevant to the task. This group of neurons is called a micro-pool. This article examines the consequences of such a proposal within the visual nervous system. The main focus is on the signals available from single neurons, but it argued that models of choice-related signals must scale up to larger numbers of neurons because MRI and MEG studies also show evidence of similar choice signals.
Probing brown dwarf formation mechanisms with Gaia
Richard J. Parker
Physics , 2014,
Abstract: One of the fundamental questions in star formation is whether or not brown dwarfs form in the same way as stars, or more like giant planets. If their formation scenarios are different, we might expect brown dwarfs to have a different spatial distribution to stars in nearby star-forming regions. In this contribution, we discuss methods to look for differences in their spatial distributions and show that in the only nearby star-forming region with a significantly different spatial distribution (the Orion Nebula Cluster), this is likely due to dynamical evolution. We then present a method for unravelling the past dynamical history of a star-forming region, and show that in tandem with Gaia, we will be able to discern whether observed differences are due to distinct formation mechanisms for brown dwarfs compared to stars.
Dynamics versus structure: breaking the density degeneracy in star formation
Richard J. Parker
Physics , 2014, DOI: 10.1093/mnras/stu2054
Abstract: The initial density of individual star-forming regions (and by extension the birth environment of planetary systems) is difficult to constrain due to the "density degeneracy problem": an initially dense region expands faster than a more quiescent region due to two-body relaxation and so two regions with the same observed present-day density may have had very different initial densities. We constrain the initial densities of seven nearby star-forming regions by folding in information on their spatial structure from the $\mathcal{Q}$-parameter and comparing the structure and present-day density to the results of $N$-body simulations. This in turn places strong constraints on the possible effects of dynamical interactions and radiation fields from massive stars on multiple systems and protoplanetary discs. We apply our method to constrain the initial binary population in each of these seven regions and show that the populations in only three - the Orion Nebula Cluster, $\rho$ Oph and Corona Australis - are consistent with having evolved from the Kroupa universal initial period distribution and a binary fraction of unity.
Clustered Star Formation: A Review
Richard J. Parker
Physics , 2012, DOI: 10.1007/978-3-319-03041-8_86
Abstract: In this contribution I present a review of star formation in clusters. I begin by discussing the various definitions of what constitutes a star cluster, and then compare the outcome of star formation (IMF, multiplicity, mass segregation and structure and morphology) in different star-forming regions. I also review recent numerical models of star formation in clusters, before ending with a summary of the potential effects of dynamical evolution in star clusters.
Audio Interaction in Computer Mediated Games
J. R. Parker,John Heerema
International Journal of Computer Games Technology , 2008, DOI: 10.1155/2008/178923
Abstract: The use of sound in an interactive media environment has not been advanced, as a technology, as far as graphics or artificial intelligence. This discussion will explore the use of sound as a way to influence the player of a computer game, will show ways that a game can use sound as input, and will describe ways that the player can influence sound in a game. The role of sound in computer games will be explored some practical design ideas that can be used to improve the current state of the art will be given.
Haemodynamic optimisation: are we dynamic enough?
Sophie J Parker, Owen Boyd
Critical Care , 2011, DOI: 10.1186/cc10480
Abstract: Over time theoretical advances and critical investigation have expanded our knowledge of how to manage patients. Clinical practise is constantly changing, whether due to a single signature study or an increasing body of evidence - but are physicians aware of this information, and do they have the tools to allow them to undertake new procedures and protocols? In the previous issue of Critical Care, Cannesson and colleagues explore attitudes and practices surrounding current haemodynamic management of high-risk surgical patients in Europe and the United States [1].Over 20 years, haemodynamic optimisation - also known as goal-directed haemodynamic therapy (GDHT) - in high-risk surgical patients has been documented to improve postoperative outcomes such as decreasing complication rates and shortening both intensive care and hospital lengths of stay [2,3]. There are also numerous systematic data analyses showing improvements with GDHT, some of them quite recent [4,5].Hamilton and colleagues published data from over two decades that showed haemodynamic optimisation could result in a significant reduction in mortality [4]. In addition, subgroup analysis revealed that this increase was specifically in studies that used pulmonary artery catheters as their mode of cardiac output monitoring, those that used fluids plus inotropes rather than fluids alone, those that measured either cardiac index or oxygen delivery and those that aimed for supranormal parameters. A further reduction in complication rates was shown in all subgroups that had haemodynamic optimisation. These observations were all despite dwindling numbers of modern trials showing in-study mortality benefit [4]. We suspect that this decline is largely because studies are no longer powered for this but rather are aimed at decreasing hospital stay and promoting the use of enhanced recovery protocols [6].Gurgel and Nascimento also showed that studies using the pulmonary artery catheters significantly reduced mortality
Heritable Transmission of Stress Resistance by High Dietary Glucose in Caenorhabditis elegans
Arnaud Tauffenberger,J. Alex Parker
PLOS Genetics , 2014, DOI: doi/10.1371/journal.pgen.1004346
Abstract: Glucose is a major energy source and is a key regulator of metabolism but excessive dietary glucose is linked to several disorders including type 2 diabetes, obesity and cardiac dysfunction. Dietary intake greatly influences organismal survival but whether the effects of nutritional status are transmitted to the offspring is an unresolved question. Here we show that exposing Caenorhabditis elegans to high glucose concentrations in the parental generation leads to opposing negative effects on fecundity, while having protective effects against cellular stress in the descendent progeny. The transgenerational inheritance of glucose-mediated phenotypes is dependent on the insulin/IGF-like signalling pathway and components of the histone H3 lysine 4 trimethylase complex are essential for transmission of inherited phenotypes. Thus dietary over-consumption phenotypes are heritable with profound effects on the health and survival of descendants.
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