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Search Results: 1 - 10 of 334414 matches for " Jonathan S Karpelowsky "
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Outcome of HIV-exposed uninfected children undergoing surgery
Jonathan S Karpelowsky, Alastair JW Millar, Nelleke van der Graaf, Guido van Bogerijen, Heather J Zar
BMC Pediatrics , 2011, DOI: 10.1186/1471-2431-11-69
Abstract: A prospective study of children less than 60 months of age undergoing general surgery at a paediatric referral hospital from July 2004 to July 2008 inclusive. Children underwent age-definitive HIV testing and were followed up post operatively for the development of complications, length of stay and mortality.Three hundred and eighty children were enrolled; 4 died and 11 were lost to follow up prior to HIV testing, thus 365 children were included. Of these, 38(10.4%) were HIVe, 245(67.1%) were HIVn and 82(22.5%) were HIVi children.The overall mortality was low, with 2(5.2%) deaths in the HIVe group, 0 in the HIVn group and 6(7.3%) in the HIVi group (p = 0.0003). HIVe had a longer stay than HIVn children (3 (2-7) vs. 2 (1-4) days p = 0.02). There was no significant difference in length of stay between the HIVe and HIVi groups. HIVe children had a higher rate of complications compared to HIVn children, (9 (23.7%) vs. 14(5.7%) (RR 3.8(2.1-7) p < 0.0001) but a similar rate of complications compared to HIVi children 34 (41.5%) (RR = 0.6 (0.3-1.1) p = 0.06).HIVe children have a higher risk of developing complications and mortality after surgery compared to HIVn children. However, the risk of complications is lower than that of HIVi children.HIV-exposed uninfected (HIVe) children are a rapidly growing population. Programs for the prevention of mother to child transmission (PMTCT) have reduced the transmission rate of perinatal HIV infection to approximately 2% to 5% [1-3]. Such programs have therefore effectively reduced the number of HIV infected (HIVi)children but identified an increasing population of HIVe children [4].HIVe children have been overlooked as a group of children who may be at an increased risk of illness compared to HIV-unexposed (HIVn) children. Recently, increased morbidity and mortality in HIVe children compared to HIVn children has been reported [4-10]. Many factors may account for this including innate deficiencies in immunity [11-13], feeding practice
South African Burn Society burn stabilisation protocol
J S Karpelowsky, L Wallis, H Rode
South African Medical Journal , 2007,
Basic Principles in the Management of Thermal Injuries
JS Karpelowsky, H Rode
South African Family Practice , 2008,
Abstract: Although this article focuses predominantly on the management of paediatric burns, many of the principles and management protocols are universal and can be used for adults. Burns are defined as the coagulate destruction of tissue by thermal, chemical or electrical injury. This simplistic definition does, however, fail to incorporate the significant short- and long-term sequelae of these injuries, and the devastating social, functional and cosmetic consequences resulting from burn wounds. South African Family Practice Vol. 50 (3) 2008: pp. 24-31
Surgical Complications of Bacille Calmette-Guérin (BCG) Infection in HIV infected children
J Karpelowsky, A Alexander, SD Peek, A Millar, H Rode
South African Medical Journal , 2008,
Abstract: Aim. Bacille Calmette-Guérin (BCG) immunisation is well established as part of the South African national expanded programme for immunisation (EPI). The World Health Organization (WHO) currently recommends that BCG be given to all asymptomatic infants irrespective of HIV exposure at birth but does not recommend BCG vaccination for children with symptomatic HIV infection. This approach, however, has led to HIV-infected neonates who are asymptomatic at birth, developing severe vaccinerelated complications. We present a surgical case series, representative of a minority of the cases in circulation, in support of a change to the timing of BCG administration to HIV-exposed neonates. Methods. A case series of 17 HIV-infected patients with surgical complications of BCG vaccination. Results. Seventeen patients are presented. The first two illustrate disseminated systemic BCG infection, resulting in BCG infection of the lymph nodes, liver, spleen and tibia, and the second with gastrointestinal involvement causing bowel obstruction. The other 15 patients represent a series of severe ulcerating lymphadenitis secondary to BCG. Conclusion. The risks of BCG in HIV-infected infants are significant. Current recommendations are not satisfactory, and a change in policy is required to prevent the harmful effects of this vaccine in a high-risk group of patients. We believe that there is sufficient need to adequately stratify patients and vaccinate them according to a protocol that takes impaired immunity into consideration. South African Medical Journal Vol. 98 (10) 2008: pp. 801-804
Sensori-Motor Lateral Preferences of Amateur Motorsport Drivers
Jonathan S. Pointer
Research Journal of Medical Sciences , 2012,
Abstract: Vision-related aspects of motorsport activity have been little reported. We consider here oculo-visual influence upon hand and foot action for the kart racing driver as investigated through an assessment of patterns of sensori-motor lateral preference. Functional lateral preferences for eye, hand and foot were determined by a self-administered questionnaire, initially amongst a population of kart racing drivers (N = 60, 90% males, aged 10-52 years) and subsequently for a matched control group of optometric patients. Further comparative laterality data were located in a published study of healthy male subjects in the general population (N = 2,756, 94% aged 8-55 years). For each modality the kart drivers recorded no statistically significant difference in degree of right preference compared to either the matched control group or the larger general population; 70% were right-eyed, 85% right-footed and 90% right-handed. Lateral congruency of sensori-motor combinations was statistically similar in motorsport and non-participating individuals, being only slightly more ipsilateral than chance would predict. Patterns of lateral association between the sighting eye and the preferred upper/lower limbs of kart drivers were no different to those recorded for a non-motorsport population. This outcome is considered in the context of the physical restrictions imposed on the driver by the race equipment and the specific motion dynamics of competitive kart racing.
An Alternative Vision Test Stimulus: Orientation-Performance Isotropy Confirmed in Central Fixation for an Angular Broken Ring Test Target
Jonathan S. Pointer
Research Journal of Medical Sciences , 2012,
Abstract: Ophthalmologists and optometrists use charts displaying the Landolt broken ring stimulus instead of letters when testing the vision of specific patient groups. However, a degree of performance inequality versus stimulus orientation has been claimed in association with the use of the classic circular broken ring design. In recent years an angular version of the stimulus has found application in several clinical and vision-related studies. The present investigation was undertaken to assess whether testing with this alternative angular optotype design has any influence on orientation-performance anisotropy in central fixation. Ten normally-sighted subjects undertook an automated four-alternative forced-choice visual discrimination task under monocular foveal viewing conditions. Their error (orientation misidentification) performance was recorded in response to a randomised sequence of high-contrast single, variously sized, four-alternative orientation angular broken ring stimuli. Having first weighted the grouped error scores to counter orientation heterogeneity in stimulus presentation, statistical analysis indicated equality of performance across the four orientations of presentation. Subsidiary analysis failed to reveal any evidence of a systematic error bias associated with stimulus angular subtense. The angular design of the broken ring optotype tested here appears to have promoted isotropic orientation performance in central fixation for this group of normally-sighted adult subjects.
Jonathan S. Russ
Essays in Economic & Business History , 2001,
Abstract: This paper examines Honda of America Manufacturing and its experiences recruiting personnel in the U.S. during the l970s and 1980s. Honda’s Japanese management faced significant challenges hiring a workforce it considered capable of upholding the firm’s quality standards. In order to meet manufacturing goals, company officials adapted management practices successfully used in Japan to suit American cultural and legal environments. The challenges the firm faced in transferring its management model to the U.S. were at times anticipated, and at other times were not. Nevertheless, as a result of shrewd planning, flexibility, and difficult lessons drawn from experience, the firm prevailed in an American environment.
Classification of intended phoneme production from chronic intracortical microelectrode recordings in speech motor cortex
Jonathan S. Brumberg
Frontiers in Neuroscience , 2011, DOI: 10.3389/fnins.2011.00065
Abstract: We conducted a neurophysiological study of attempted speech production in a paralyzed human volunteer using chronic microelectrode recordings. The volunteer suffers from locked-in syndrome leaving him in a state of near-total paralysis, though he maintains good cognition and sensation. In this study, we investigated the feasibility of supervised classification techniques for prediction of intended phoneme production in the absence of any overt movements including speech. Such classification or decoding ability has the potential to greatly improve the quality-of-life of many people who are otherwise unable to speak by providing a direct communicative link to the general community. We examined the performance of three classifiers on a multi-class discrimination problem in which the items were 38 American English phonemes including monophthong and diphthong vowels and consonants. The three classifiers differed in performance, but averaged between 16 and 21% overall accuracy (chance-level is 1/38 or 2.6%). Further, the distribution of phonemes classified statistically above chance was non-uniform though 20 of 38 phonemes were classified with statistical significance for all three classifiers. These preliminary results suggest supervised classification techniques are capable of performing large scale multi-class discrimination for attempted speech production and may provide the basis for future communication prostheses.
piecewiseSEM: Piecewise structural equation modeling in R for ecology, evolution, and systematics
Jonathan S. Lefcheck
Quantitative Biology , 2015,
Abstract: Ecologists and evolutionary biologists are relying on an increasingly sophisticated set of statistical tools to describe complex natural systems. One such tool that has gained increasing traction in the life sciences is structural equation modeling (SEM), a variant of path analysis that resolves complex multivariate relationships among a suite of interrelated variables. SEM has historically relied on covariances among variables, rather than the values of the data points themselves. While this approach permits a wide variety of model forms, it limits the incorporation of detailed specifications. Here, I present a fully-documented, open-source R package piecewiseSEM that builds on the base R syntax for all current generalized linear, least-square, and mixed effects models. I also provide two worked examples: one involving a hierarchical dataset with non-normally distributed variables, and a second involving phylogenetically-independent contrasts. My goal is to provide a user-friendly and tractable implementation of SEM that also reflects the ecological and methodological processes generating data.
Methodology for Comparing Coupling Algorithms for Fluid-Structure Interaction Problems  [PDF]
Jason P. Sheldon, Scott T. Miller, Jonathan S. Pitt
World Journal of Mechanics (WJM) , 2014, DOI: 10.4236/wjm.2014.42007

The multi-physics simulation of coupled fluid-structure interaction problems, with disjoint fluid and solid domains, requires one to choose a method for enforcing the fluid-structure coupling at the interface between solid and fluid. While it is common knowledge that the choice of coupling technique can be very problem dependent, there exists no satisfactory coupling comparison methodology that allows for conclusions to be drawn with respect to the comparison of computational cost and solution accuracy for a given scenario. In this work, we develop a computational framework where all aspects of the computation can be held constant, save for the method in which the coupled nature of the fluid-structure equations is enforced. To enable a fair comparison of coupling methods, all simulations presented in this work are implemented within a single numerical framework within the deal.ii [1] finite element library. We have chosen the two-dimensional benchmark test problem of Turek and Hron [2] as an example to examine the relative accuracy of the coupling methods studied; however, the comparison technique is equally applicable to more complex problems. We show that for the specific case considered herein the monolithic approach outperforms partitioned and quasi-direct methods; however, this result is problem dependent and we discuss computational and modeling aspects which may affect other comparison studies.

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