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Search Results: 1 - 10 of 11791 matches for " Jonathan Levin "
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Wound healing with honey - a randomised controlled trial
Ronald Ingle, Jonathan Levin, Krijn Polinder
South African Medical Journal , 2006,
Abstract: Objectives. To compare honey and IntraSite Gel as woundhealing agents, to record side-effects, gauge patient satisfaction and calculate the cost-effectiveness of the honey used. Design and setting. A prospective, randomised, double-blind controlled trial was carried out among goldmine workers. Outcome measures. Outcome measures were healing times of shallow wounds and abrasions; side-effects; patient satisfaction with treatment; and amount of honey and IntraSite Gel used. Results. The mean healing times of shallow wounds treated with honey or with IntraSite Gel did not differ significantly (p = 0.75, 95% confidence interval (CI): -5.41; 7.49 days). When adjusted for wound size, the 2.8-day difference in favour of honey was not significant (p = 0.21, 95% CI: -2.41; 8.09). In the case of abrasions there was also no significant difference (p = 0.83, 95% CI: -4.98; 6.19 days). When adjusted for wound size, the difference of 0.22 days in favour of IntraSite Gel was not significant (p = 0.94, 95% CI: -5.72; 6.15.4). Of patients treated with honey, 27% and 10% respectively experienced itching and pain, and 2 experienced burning for a short time after application. Of patients treated with IntraSite Gel, 31% experienced itching. All patients in both treatment groups were either satisfied or extremely satisfied with treatment. The average cost of treatment per patient was R0.49 with honey and R12.03 with with IntraSite Gel. Conclusions. A distinction should be made between shallow wounds and abrasions when wound healing is being measured. There was no evidence of a real difference between honey and IntraSite Gel as healing agents. Honey is a safe, satisfying and effective healing agent. Natural honey is extremely costeffective. South African Medical Journal Vol. 96(9) 2006: 831-835
On State-Space Reduction in Multi-Strain Pathogen Models, with an Application to Antigenic Drift in Influenza A
Sergey Kryazhimskiy ,Ulf Dieckmann,Simon A Levin,Jonathan Dushoff
PLOS Computational Biology , 2007, DOI: 10.1371/journal.pcbi.0030159
Abstract: Many pathogens exist in phenotypically distinct strains that interact with each other through competition for hosts. General models that describe such multi-strain systems are extremely difficult to analyze because their state spaces are enormously large. Reduced models have been proposed, but so far all of them necessarily allow for coinfections and require that immunity be mediated solely by reduced infectivity, a potentially problematic assumption. Here, we suggest a new state-space reduction approach that allows immunity to be mediated by either reduced infectivity or reduced susceptibility and that can naturally be used for models with or without coinfections. Our approach utilizes the general framework of status-based models. The cornerstone of our method is the introduction of immunity variables, which describe multi-strain systems more naturally than the traditional tracking of susceptible and infected hosts. Models expressed in this way can be approximated in a natural way by a truncation method that is akin to moment closure, allowing us to sharply reduce the size of the state space, and thus to consider models with many strains in a tractable manner. Applying our method to the phenomenon of antigenic drift in influenza A, we propose a potentially general mechanism that could constrain viral evolution to a one-dimensional manifold in a two-dimensional trait space. Our framework broadens the class of multi-strain systems that can be adequately described by reduced models. It permits computational, and even analytical, investigation and thus serves as a useful tool for understanding the evolution and ecology of multi-strain pathogens.
High-Content Neurite Development Study Using Optically Patterned Substrates
Jonathan M. Bélisle, Leonard A. Levin, Santiago Costantino
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0035911
Abstract: The study of neurite guidance in vitro relies on the ability to reproduce the distribution of attractive and repulsive guidance molecules normally expressed in vivo. The identification of subtle variations in the neurite response to changes in the spatial distribution of extracellular molecules can be achieved by monitoring the behavior of cells on protein gradients. To do this, automated high-content screening assays are needed to quantify the morphological changes resulting from growth on gradients of guidance molecules. Here, we present the use of laser-assisted protein adsorption by photobleaching (LAPAP) to allow the fabrication of large-scale substrate-bound laminin-1 gradients to study neurite extension. We produced thousands of gradients of different slopes and analyzed the variations in neurite attraction of neuron-like cells (RGC-5). An image analysis algorithm processed bright field microscopy images, detecting each cell and quantifying the soma centroid and the initiation, terminal and turning angles of the longest neurite.
Flame Propagation on the Surfaces of Rapidly Rotating Neutron Stars during Type I X-ray Bursts
Yuri Cavecchi,Anna L. Watts,Jonathan Braithwaite,Yuri Levin
Physics , 2012, DOI: 10.1093/mnras/stt1273
Abstract: We present the first vertically resolved hydrodynamic simulations of a laterally propagating, deflagrating flame in the thin helium ocean of a rotating accreting neutron star. We use a new hydrodynamics solver tailored to deal with the large discrepancy in horizontal and vertical length scales typical of neutron star oceans, and which filters out sound waves that would otherwise limit our timesteps. We find that the flame moves horizontally with velocities of order $10^5$ cm s$^{-1}$, crossing the ocean in few seconds, broadly consistent with the rise times of Type I X-ray bursts. We address the open question of what drives flame propagation, and find that heat is transported from burning to unburnt fuel by a combination of top-to-bottom conduction and mixing driven by a baroclinic instability. The speed of the flame propagation is therefore a sensitive function of the ocean conductivity and spin: we explore this dependence for an astrophysically relevant range of parameters and find that in general flame propagation is faster for slower rotation and higher conductivity.
Rotational effects in thermonuclear Type I Bursts: equatorial crossing and directionality of flame spreading
Yuri Cavecchi,Anna L. Watts,Yuri Levin,Jonathan Braithwaite
Physics , 2014, DOI: 10.1093/mnras/stu2764
Abstract: In a previous study on thermonuclear (type I) nursts on accreting neutron stars we addressed and demonstrated the importance of the effects of rotation, through the Coriolis force, on the propagation of the burning flame. However, that study only analysed cases of longitudinal propagation, where the Coriolis force coefficient $2\Omega\cos\theta$ was constant. In this paper, we study the effects of rotation on propagation in the meridional (latitudinal) direction, where the Coriolis force changes from its maximum at the poles to zero at the equator. We find that the zero Coriolis force at the equator, while affecting the structure of the flame, does not prevent its propagation from one hemisphere to another. We also observe structural differences between the flame propagating towards the equator and that propagating towards the pole, the second being faster. In the light of the recent discovery of the low spin frequency of burster IGR~J17480-2446 rotating at 11 Hz (for which Coriolis effects should be negligible) we also extend our simulations to slow rotation.
Fast and slow magnetic deflagration fronts in Type I X-ray bursts
Yuri Cavecchi,Yuri Levin,Anna L. Watts,Jonathan Braithwaite
Physics , 2015,
Abstract: Type I X-ray bursts are produced by thermonuclear runaways that develop on accreting neutron stars. Once one location ignites, the flame propagates across the surface of the star. Flame propagation is fundamental in order to understand burst properties like rise time and burst oscillations. Previous work quantified the effects of rotation on the front, showing that the flame propagates as a deflagration and that the front strongly resembles a hurricane. However the effect of magnetic fields was not investigated, despite the fact that magnetic fields strong enough to have an effect on the propagating flame are expected to be present on many bursters. In this paper we show how the coupling between fluid layers introduced by an initially vertical magnetic field plays a decisive role in determining the character of the fronts that are responsible for the Type I bursts. In particular, on a star spinning at 450 Hz (typical among the bursters) we test seed magnetic fields of $10^{7} - 10^{10}$ G and find that for the medium fields the magnetic stresses that develop during the burst can speed up the velocity of the burning front, bringing the simulated burst rise time close to the observed values. By contrast, in a magnetic slow rotator like IGR J17480--2446, spinning at 11 Hz, a seed field $\gtrsim 10^9$ G is required to allow localized ignition and the magnetic field plays an integral role in generating the burst oscillations observed during the bursts.
Epidemic Enhancement in Partially Immune Populations
Juliet R.C. Pulliam, Jonathan G. Dushoff, Simon A. Levin, Andrew P. Dobson
PLOS ONE , 2007, DOI: 10.1371/journal.pone.0000165
Abstract: We observe that a pathogen introduced into a population containing individuals with acquired immunity can result in an epidemic longer in duration and/or larger in size than if the pathogen were introduced into a naive population. We call this phenomenon “epidemic enhancement,” and use simple dynamical models to show that it is a realistic scenario within the parameter ranges of many common infectious diseases. This finding implies that repeated pathogen introduction or intermediate levels of vaccine coverage can lead to pathogen persistence in populations where extinction would otherwise be expected.
Mortality in an antiretroviral therapy programme in Jinja, south-east Uganda: a prospective cohort study
Barbara Amuron, Jonathan Levin, Josephine Birunghi, Geoffrey Namara, Alex Coutinho, Heiner Grosskurth, Shabbar Jaffar
AIDS Research and Therapy , 2011, DOI: 10.1186/1742-6405-8-39
Abstract: Participants starting ART between February 2005 and December 2006 in The AIDS Support (TASO) clinic in Jinja, Uganda, were enrolled into a cluster-randomised trial of home versus facility-based care and followed up to January 2009. The trial was integrated into normal service delivery with patients managed by TASO staff according to national guidelines. Rates of survival, virological failure, hospital admissions and CD4 count over time were similar between the two arms. Data for the present analysis were analysed using Cox regression analyses.1453 subjects were enrolled with baseline median count of 108 cells/μl. Over time, 119 (8%) withdrew and 34 (2%) were lost to follow-up. 197/1453 (14%) died. Mortality rates (95% CI) per 100 person-years were 11.8 (10.1, 13.8) deaths in the first year and 2.4 (1.8, 3.2) deaths thereafter. The one, two and three year survival probabilities (95% CI) were 0.89 (0.87 - 0.91), 0.86 (0.84 - 0.88) and 0.85 (0.83 - 0.87) respectively. Low baseline CD4 count, low body weight, advanced clinical condition (WHO stages III and IV), not being on cotrimoxazole prophylaxis and male gender were associated independently with increased mortality. Tuberculosis, cryptococcal meningitis and diarrhoeal disease were estimated to be major causes of death.Practical and affordable interventions are needed to enable earlier initiation of ART and to reduce mortality risk among those who present late for treatment with advanced disease.Antiretroviral therapy (ART) has been scaled-up rapidly. About 4 million people in Africa are now on ART [1]. Various studies have shown that mortality during the first 6 months or so after initiating ART is much higher than in developed countries and retention of patients in programmes is poor [2,3]. However, most longitudinal studies conducted in Africa have been either short-term or have involved small numbers of participants. A recent randomised trial conducted in Uganda and Zimbabwe comparing clinical with laboratory dri
Mortality and loss-to-follow-up during the pre-treatment period in an antiretroviral therapy programme under normal health service conditions in Uganda
Barbara Amuron, Geoffrey Namara, Josephine Birungi, Christine Nabiryo, Jonathan Levin, Heiner Grosskurth, Alex Coutinho, Shabbar Jaffar
BMC Public Health , 2009, DOI: 10.1186/1471-2458-9-290
Abstract: HIV-infected subjects presenting at The AIDS Support Clinic in Jinja, SE Uganda, were assessed for antiretroviral therapy (ART). Eligible subjects were given information and counselling in 3 visits done over 4–6 weeks in preparation for treatment. Those who did not complete screening were followed-up at home. Survival analysis was done using poisson regression.4321 HIV-infected subjects were screened of whom 2483 were eligible for ART on clinical or immunological grounds. Of these, 637 (26%) did not complete screening and did not start ART. Male sex and low CD4 count were associated independently with not completing screening. At follow-up at a median 351 days, 181 (28%) had died, 189 (30%) reported that they were on ART with a different provider, 158 (25%) were alive but said they were not on ART and 109 (17%) were lost to follow-up. Death rates (95% CI) per 100 person-years were 34 (22, 55) (n.18) within one month and 37 (29, 48) (n.33) within 3 months. 70/158 (44%) subjects seen at follow-up said they had not started ART because they could not afford transport.About a quarter of subjects eligible for ART did not complete screening and pre-treatment mortality was very high even though patients in this setting were well informed. For many families, the high cost of transport is a major barrier preventing access to ART.Antiretroviral therapy has been scaled-up rapidly in Africa and elsewhere [1]. Early reports suggest that mortality of HIV-infected on ART is typically between about 6 to 12 deaths per 100 person-years [2-7], which is substantially better than in the pre-ART era [8] but higher than in developed countries [6]. One reason for the higher mortality in Africa is that patients in Africa present late for treatment, typically at 100–150 × 106/l CD4 cell count lower than in developed countries and with advanced disease [9]. Mortality in Africa is especially high during the first year after initiation of ART[10]. Retention of subjects in ART programmes in Afric
Good adherence to HAART and improved survival in a community HIV/AIDS treatment and care programme: the experience of The AIDS Support Organization (TASO), Kampala, Uganda
Andrew M Abaasa, Jim Todd, Kenneth Ekoru, Joan N Kalyango, Jonathan Levin, Emmanuel Odeke, Charles AS Karamagi
BMC Health Services Research , 2008, DOI: 10.1186/1472-6963-8-241
Abstract: The study was a retrospective cohort of 897 patients who initiated HAART at TASO clinic, Kampala, between May 2004 and December 2006. A total of 7,856 adherence assessments were performed on the data. Adherence was assessed using a combination of self-report and pill count methods. Patients who took ≤ 95% of their regimens were classified as non-adherent. The data was stratified at a CD4 count of 50 cells/mm3. Kaplan Meier curves and Cox proportional hazards regression models were used in the analysis.A total of 701 (78.2%) patients had a mean adherence to ART of > 95%. The crude death rate was 12.2 deaths per 100 patient-years, with a rate of 42.5 deaths per 100 patient-years for non-adherent patients and 6.1 deaths per 100 patient-years for adherent patients. Non-adherence to ART was significantly associated with mortality. Patients with a CD4 count of less than 50 cells/mm3 had a higher mortality (HR = 4.3; 95% CI: 2.22–5.56) compared to patients with a CD4 count equal to or greater than 50 cells/mm3 (HR = 2.4; 95% CI: 1.79–2.38).Our study showed that good adherence and improved survival are feasible in community HIV/AIDS programmes such as that of TASO, Uganda. However, there is need to support community HAART programmes to overcome the challenges of funding to provide sustainable supplies particularly of antiretroviral drugs; provision of high quality clinical and laboratory support; and achieving a balance between expansion and quality of services. Measures for the early identification and treatment of HIV infected people including home-based VCT and HAART should be strengthened.The introduction of HAART has greatly improved the survival of HIV/AIDS infected people. HAART reduces morbidity and mortality by suppression of viral replication, restoration and preservation of immune function, and prevention of drug resistance [1-4]. Mortality among patients on HAART is associated with high baseline levels of HIV RNA [5]; WHO stage III or IV at the beginning of trea
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