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Search Results: 1 - 10 of 424005 matches for " Robert M. Perkins "
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Transfusion, erythropoiesis-stimulating agent therapy, and kidney transplant wait time  [PDF]
Robert M. Perkins, H. Lester Kirchner, Rajesh Govindasamy
Open Journal of Internal Medicine (OJIM) , 2012, DOI: 10.4236/ojim.2012.21001
Abstract: Aim: Anemia is highly prevalent among patients wait-listed for renal transplant, and management with blood transfusion or erythropoietin stimulating agents may impact transplant wait time. The purpose of this study was to examine the impact of blood transfusion and erythropoiesis stimulating agent therapy on renal transplant wait time. Methods: We retrospectively analyzed all adult patients listed for first deceased donor kidney transplantation at two transplant centers in Central Pennsylvania between 2004 and 2008. The exposures of interest were blood transfusion and erythropoietin stimulating agent therapy. Cox proportional hazards were used to model time to deceased donor kidney transplant. Results: Among 407 patients listed for transplant, 84 received a deceased donor kidney during a median follow-up of 26.3 months. In an adjusted Cox proportional hazards model, with erythropoiesis stimulating agent and transfusion both treated as time-dependent exposures, UNOS inactive status at listing date (hazard ratio [HR] 0.81; 95% CI 0.73 - 0.89; P < 0.001) and transfusion during the wait list period (HR 0.27; 95% CI 0.11 - 0.69; P = 0.01) independently predicted longer transplant wait time. Erythropoiesis stimulating agent use prior to or after transplant wait listing date did not independently predict wait time. Conclusion: Blood transfusion while waitlisted for kidney transplant is strongly associated with prolonged wait time.
Comparing the Sensitivity of the MMPI-2 Clinical Scales and the MMPI-RC Scales to Clients Rated as Psychotic, Borderline or Neurotic on the Psychodiagnostic Chart  [PDF]
Robert M. Gordon, Ronald W. Stoffey, Bethany L. Perkins
Psychology (PSYCH) , 2013, DOI: 10.4236/psych.2013.49A1003
Abstract:

The purpose of this study was to assess the differences between the MMPI-2 and the MMPI-RC scales in sensitivity to levels of psychopathology. Ninety-eight clients from forensic, disability and psychotherapy evaluations were evaluated on the MMPI-2 and RC scales and rated for personality organization (neurotic, borderline or psychotic) on the Psychodiagnostic Chart. The results over-all showed support that most of the MMPI-2 scales have more clinical sensitivity than the RC scales at all levels of psychopathology and particularly at the less pathological levels. K correction does not account for the elevation differences. Most of the RC scales add little to no incremental validity to the MMPI-2 Clinical scales except for RC 1, RC 2, and RC 9 and these may be used as supplemental scales.

Renal Replacement Therapy in Austere Environments
Christina M. Yuan,Robert M. Perkins
International Journal of Nephrology , 2011, DOI: 10.4061/2011/748053
Abstract: Myoglobinuric renal failure is the classically described acute renal event occurring in disaster environments—commonly after an earthquake—which most tests the ingenuity and flexibility of local and regional nephrology resources. In recent decades, several nephrology organizations have developed response teams and planning protocols to address disaster events, largely focusing on patients at risk for, or with, acute kidney injury (AKI). In this paper we briefly review the epidemiology and outcomes of patients with dialysis-requiring AKI after such events, while providing greater focus on the management of the end-stage renal disease population after a disaster which incapacitates a pre-existing nephrologic infrastructure (if it existed at all). “Austere” dialysis, as such, is defined as the provision of renal replacement therapy in any setting in which traditional, first-world therapies and resources are limited, incapacitated, or nonexistent. 1. Introduction Austere renal replacement therapy (RRT) describes the provision of renal replacement therapy in any setting in which traditional, first-world therapies and resources are limited, incapacitated, or nonexistent. The provision of RRT in an austere environment is very different from that in a routine situation in a first-world country. In the latter case, the following apply (1) the environment is secure from violence and physical risk to the providers and patients; (2) the transportation infrastructure is functioning; (3) there are plentiful and stable sources of electricity, RRT supplies, and potable water; (4) engineering systems are in place for the production of pure water; (5) sophisticated equipment is available; (6) adequate equipment maintenance and nursing/technician staff support exist; (7) patient acuity and numbers are predictable and stable. In an austere situation, some or all of these components may be inadequate or completely absent. If austere environment RRT is to be successful, the provider must identify the components that are lacking and attempt to offer reasonably safe and effective substitutes for them if they cannot be controlled or repaired. This requires flexibility, the ability to triage, and a thorough understanding of the engineering and physiologic principals of RRT. Moreover, specific advance planning is necessary, especially in an environment or geographic area where certain disasters are likely to occur (particularly true for storms and earthquakes). Every dialysis unit should have a disaster plan. Moreover, it is important during planning and implementation not to
Improved Efficacy of a Gene Optimised Adenovirus-based Vaccine for Venezuelan Equine Encephalitis Virus
Amanda J Williams, Lyn M O'Brien, Robert J Phillpotts, Stuart D Perkins
Virology Journal , 2009, DOI: 10.1186/1743-422x-6-118
Abstract: Following administration of this vaccine to Balb/c mice, an approximately ten-fold increase in antibody response was elicited and increased protective efficacy compared to an ad-based vaccine containing non-optimised genes was observed after challenge.This study, in which the utility of optimising genes encoding the structural proteins of VEEV is demonstrated for the first time, informs us that including optimised genes in gene-based vaccines for VEEV is essential to obtain maximum immunogenicity and protective efficacy.Venezuelan equine encephalitis virus (VEEV) is a positive-stranded, enveloped, RNA virus of the genus Alphavirus in the family Togaviridae. VEEV causes a disease in humans characterized by fever, headache, and occasionally encephalitis. It is the cause of recent outbreaks in South America [1] and is considered to be a potential biological weapon [2-6].There is a complex variety of different serogroups of VEEV. Only serogroup I varieties A/B and C have caused major outbreaks involving hundreds of thousands of equine and human cases [1]. Serogroups II through VI and serogroup I varieties D, E and F are enzootic strains, relatively avirulent in equines and not usually associated with major equine outbreaks, although they do cause human illness which can be fatal [7].There is currently no vaccine licensed for human use to protect against infection with VEEV, although two vaccines have been used under Investigational New Drug status in humans. TC-83, a live-attenuated vaccine, and C-84, a formalin-inactivated version of TC-83, are not considered suitable for use because of poor immunogenicity and safety [8]. A further live-attenuated vaccine, V3526, derived by site-directed mutagenesis from a virulent clone of the IA/B Trinidad Donkey (TrD) strain of VEEV has recently been developed. V3526 has been shown to be effective in protecting rodent and nonhuman primates against virulent challenge [9-11] but demonstrated a high level of adverse events in phase I c
Biodegradation of Dispersed Oil in Arctic Seawater at -1°C
Kelly M. McFarlin, Roger C. Prince, Robert Perkins, Mary Beth Leigh
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0084297
Abstract: As offshore oil and gas exploration expands in the Arctic, it is important to expand the scientific understanding of arctic ecology and environmental impact to mitigate operational risks. Understanding the fate of oil in arctic seawater is a key factor for consideration. Here we report the chemical loss due to the biodegradation of Alaska North Slope (ANS) crude oil that would occur in the water column following the successful dispersion of a surface oil slick. Primary biodegradation and mineralization were measured in mesocosms containing Arctic seawater collected from the Chukchi Sea, Alaska, incubated at ?1°C. Indigenous microorganisms degraded both fresh and weathered oil, in both the presence and absence of Corexit 9500, with oil losses ranging from 46?61% and up to 11% mineralization over 60 days. When tested alone, 14% of 50 ppm Corexit 9500 was mineralized within 60 days. Our study reveals that microorganisms indigenous to Arctic seawater are capable of performing extensive biodegradation of chemically and physically dispersed oil at an environmentally relevant temperature (?1°C) without any additional nutrients.
Aspects of classical backgrounds and scattering for affine Toda theory on a half-line
P. Bowcock,M. Perkins
Physics , 1999, DOI: 10.1088/1126-6708/2003/02/016
Abstract: In this paper we study various aspects of classical solutions to the affine Toda equations on a half-line with integrable boundary conditions. We begin by finding conditions that the theory has a stable vacuum by finding a Bogomolny bound on the energy, and analysing the possible singularities of the field at the boundary. Using these constraints and extensive numerical investigations we classify the vacuum configurations and reflection factors for A_r^(1) Toda theories up to r=5.
Assessing Chemical Mixtures and Human Health: Use of Bayesian Belief Net Analysis  [PDF]
Anindya Roy, Neil J. Perkins, Germaine M. Buck Louis
Journal of Environmental Protection (JEP) , 2012, DOI: 10.4236/jep.2012.36056
Abstract: Background: Despite humans being exposed to complex chemical mixtures, much of the available research continues to focus on a single compound or metabolite or a select subgroup of compounds inconsistent with the nature of human exposure. Uncertainty regarding how best to model chemical mixtures coupled with few analytic approaches remains a formidable challenge and served as the impetus for the study. Objectives: To identify the polychlorinated biphenyl (PCB) congener(s) within a chemical mixture that was most associated with an endometriosis diagnosis using novel graphical modeling techniques. Methods: Bayesian Belief Network (BBN) models were developed and empirically assessed in a cohort comprising 84 women aged 18 - 40 years who underwent a laparoscopy or laparotomy between 1999 and 2000; 79 (94%) women had serum concentrations for 68 PCB congeners quantified. Adjusted odds ratios (AOR) for endometriosis were estimated for individual PCB congeners using BBN models. Results: PCB congeners #114 (AOR = 3.01; 95% CI = 2.25, 3.77) and #136 (AOR = 1.79; 95% CI = 1.03, 2.55) were associated with an endometriosis diagnosis. Combinations of mixtures inclusive of PCB #114 were all associated with higher odds of endometriosis, underscoring its potential relation with endometriosis. Conclusions: BBN models identified PCB congener 114 as the most influential congener for the odds of an endometriosis diagnosis in the context of a 68 congener chemical mixture. BBN models offer investigators the opportunity to assess which compounds within a mixture may drive a human health effect.
Birthday Inequalities, Repulsion, and Hard Spheres
Will Perkins
Mathematics , 2015,
Abstract: We study a birthday inequality in random geometric graphs: the probability of the empty graph is upper bounded by the product of the probabilities that each edge is absent. We show the birthday inequality holds at low densities, but does not hold in general. We give three different applications of the birthday inequality in statistical physics and combinatorics: we prove lower bounds on the free energy of the hard sphere model and upper bounds on the number of independent sets and matchings of a given size in d-regular graphs. The birthday inequality is implied by a repulsion inequality: the expected volume of the union of spheres of radius r around n randomly placed centers increases if we condition on the event that the centers are at pairwise distance greater than r. Surprisingly we show that the repulsion inequality is not true in general, and in particular that it fails in 24-dimensional Euclidean space: conditioning on the pairwise repulsion of centers of 24-dimensional spheres can decrease the expected volume of their union.
Random k-SAT and the Power of Two Choices
Will Perkins
Computer Science , 2012,
Abstract: We study an Achlioptas-process version of the random k-SAT process: a bounded number of k-clauses are drawn uniformly at random at each step, and exactly one added to the growing formula according to a particular rule. We prove the existence of a rule that shifts the satisfiability threshold. This extends a well-studied area of probabilistic combinatorics (Achlioptas processes) to random CSP's. In particular, while a rule to delay the 2-SAT threshold was known previously, this is the first proof of a rule to shift the threshold of k-SAT for k >= 3. We then propose a gap decision problem based upon this semi-random model. The aim of the problem is to investigate the hardness of the random k-SAT decision problem, as opposed to the problem of finding an assignment or certificate of unsatisfiability. Finally, we discuss connections to the study of Achlioptas random graph processes.
Implementing Arithmetic and Other Analytic Operations By Transcriptional Regulation
Sean M. Cory,Theodore J. Perkins
PLOS Computational Biology , 2008, DOI: 10.1371/journal.pcbi.1000064
Abstract: The transcriptional regulatory machinery of a gene can be viewed as a computational device, with transcription factor concentrations as inputs and expression level as the output. This view begs the question: what kinds of computations are possible? We show that different parameterizations of a simple chemical kinetic model of transcriptional regulation are able to approximate all four standard arithmetic operations: addition, subtraction, multiplication, and division, as well as various equality and inequality operations. This contrasts with other studies that emphasize logical or digital notions of computation in biological networks. We analyze the accuracy and precision of these approximations, showing that they depend on different sets of parameters, and are thus independently tunable. We demonstrate that networks of these “arithmetic” genes can be combined to accomplish yet more complicated computations by designing and simulating a network that detects statistically significant elevations in a time-varying signal. We also consider the much more general problem of approximating analytic functions, showing that this can be achieved by allowing multiple transcription factor binding sites on the promoter. These observations are important for the interpretation of naturally occurring networks and imply new possibilities for the design of synthetic networks.
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