42 research outputs found

    Nanofiller Fibre-Reinforced Polymer Nanocomposites

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    In this work, the technology of nano and micro-scale particle reinforcement concerning various polymeric fibre-reinforced systems including polyamides (PA), polyesters, polyurethanes, polypropylenes and high performance/temperature engineering polymers such as polyimide (PI), poly(ether ether ketone) (PEEK), polyarylacetylene (PAA) and poly p-phenylene benzobisoxazole (PBO) is reviewed. When the diameters of polymer fibre materials are shrunk from micrometers to submicrons or nanometers, there appear several unique characteristics such as very large surface area to volume ratio (this ratio for a nanofibre can be as large as 103 times of that of a microfibre), flexibility in surface functionalities and superior mechanical performance (such as stiffness and tensile strength) compared with any other known form of the material. However, nanoparticle reinforcement of fibre reinforced composites has been shown to be a possibility, but much work remains to be performed in order to understand how nanoreinforcement results in dramatic changes in material properties. The understanding of these phenomena will facilitate their extension to the reinforcement of more complicated anisotropic structures and advanced polymeric composite systems

    Polymer/montmorillonite nanocomposites with improved thermal properties: Part II. Thermal stability of montmorillonite nanocomposites based on different polymeric matrixes.

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    In previous part of this work factors influencing the thermal stability of polymer nanocomposite materials were indicated, such as chemical constitution of organic modifier, filler content, nanocomposites’ structure and the processing- dependent degree of homogenization of nanofiller, were presented. In this part the basic changes in thermal behaviour of different polymeric matrixes (e.g. polyolefins, polyamides, poly(vinyl chloride) and styrene-containing polymers) upon addition of montmorillonite have been described. Brief description of the kinetics of the decomposition process in inert and oxidative environment, as well as analysis of volatile and condensed products of degradation, have also been present

    Free vibration of a three-layered sandwich beam using the dynamic stiffness method and experiment

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    In this paper, an accurate dynamic stiffness model for a three-layered sandwich beam of unequal thicknesses is developed and subsequently used to investigate its free vibration characteristics. Each layer of the beam is idealised by the Timoshenko beam theory and the combined system is reduced to a tenth-order system using symbolic computation. An exact dynamic stiffness matrix is then developed by relating amplitudes of harmonically varying loads to those of the responses. The resulting dynamic stiffness matrix is used with particular reference to the Wittrick-Williams algorithm to carry out the free vibration analysis of a few illustrative examples. The accuracy of the theory is confirmed both by published literature and by experiment. The paper closes with some concluding remarks. (c) 2007 Elsevier Ltd. All rights reserved

    Clinical indicators of bacterial meningitis among neonates and young infants in rural Kenya

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    <p>Abstract</p> <p>Background</p> <p>Meningitis is notoriously difficult to diagnose in infancy because its clinical features are non-specific. World Health Organization (WHO) guidelines suggest several indicative signs, based on limited data. We aimed to identify indicators of bacterial meningitis in young infants in Kenya, and compared their performance to the WHO guidelines. We also examined the feasibility of developing a scoring system for meningitis.</p> <p>Methods</p> <p>We studied all admissions aged < 60 days to Kilifi District Hospital, 2001 through 2005. We evaluated clinical indicators against microbiological findings using likelihood ratios. We prospectively validated our findings 2006 through 2007.</p> <p>Results</p> <p>We studied 2,411 and 1,512 young infants during the derivation and validation periods respectively. During derivation, 31/1,031 (3.0%) neonates aged < 7 days and 67/1,380 (4.8%) young infants aged 7-59 days (p < 0.001) had meningitis. 90% of cases could be diagnosed macroscopically (turbidity) or by microscopic leukocyte counting. Independent indicators of meningitis were: fever, convulsions, irritability, bulging fontanel and temperature ≄ 39°C. Areas under the receiver operating characteristic curve in the validation period were 0.62 [95%CI: 0.49-0.75] age < 7 days and 0.76 [95%CI: 0.68-0.85] thereafter (P = 0.07), and using the WHO signs, 0.50 [95%CI 0.35-0.65] age < 7 days and 0.82 [95%CI: 0.75-0.89] thereafter (P = 0.0001). The number needed to LP to identify one case was 21 [95%CI: 15-35] for our signs, and 28 [95%CI: 18-61] for WHO signs. With a scoring system, a cut-off of ≄ 1 sign offered the best compromise on sensitivity and specificity.</p> <p>Conclusion</p> <p>Simple clinical signs at admission identify two thirds of meningitis cases in neonates and young infants. Lumbar puncture is essential to diagnosis and avoidance of unnecessary treatment, and is worthwhile without CSF biochemistry or bacterial culture. The signs of Meningitis suggested by the WHO perform poorly in the first week of life. A scoring system for meningitis in this age group is not helpful.</p

    Stress analysis at the interface of metal-to-metal adhesively bonded joints subjected to 4-point bending: finite element method.

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    This paper presents a study of stress states in two-dimensional models of metal-to-metal adhesively bonded joints subjected to 4-point flexural loading using the finite element (FE) method. The FE simulations were carried out on adhesive bonded joints of high support span to specimen thickness ratio undergoing extensive plastic deformations. Two different adhesive types with eight different adhesive layer thicknesses each varying between 50 ÎŒm and ÎŒm were considered. The lower interfaces in the brittle adhesive were observed to be under a lower stress state because of the constraint exerted by a relatively stiff lower adherend. The ductile adhesive layers were under a lower state of stress as a result of the lower elastic modulus. It is concluded that the degree of plastic deformation in the adhesive is dictated by the adherend stiffness and the load transfer along the interface. The effect of load and support pins is noticeable at all adhesive thicknesses. High stress localisation exists in the vicinity of the load pins. The constraint exerted by the adherends dictates the deformation gradient through thickness of the adhesive layer. Adhesive joint behaviour as determined by the adhesive properties is investigated and also experimentally validated. Conclusions were drawn by correlating the adhesive and adherend stress states

    Estimation of the national disease burden of influenza-associated severe acute respiratory illness in Kenya and Guatemala : a novel methodology

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    Background: Knowing the national disease burden of severe influenza in low-income countries can inform policy decisions around influenza treatment and prevention. We present a novel methodology using locally generated data for estimating this burden. Methods and Findings: This method begins with calculating the hospitalized severe acute respiratory illness (SARI) incidence for children <5 years old and persons ≄5 years old from population-based surveillance in one province. This base rate of SARI is then adjusted for each province based on the prevalence of risk factors and healthcare-seeking behavior. The percentage of SARI with influenza virus detected is determined from provincial-level sentinel surveillance and applied to the adjusted provincial rates of hospitalized SARI. Healthcare-seeking data from healthcare utilization surveys is used to estimate non-hospitalized influenza-associated SARI. Rates of hospitalized and non-hospitalized influenza-associated SARI are applied to census data to calculate the national number of cases. The method was field-tested in Kenya, and validated in Guatemala, using data from August 2009–July 2011. In Kenya (2009 population 38.6 million persons), the annual number of hospitalized influenza-associated SARI cases ranged from 17,129–27,659 for children <5 years old (2.9–4.7 per 1,000 persons) and 6,882–7,836 for persons ≄5 years old (0.21–0.24 per 1,000 persons), depending on year and base rate used. In Guatemala (2011 population 14.7 million persons), the annual number of hospitalized cases of influenza-associated pneumonia ranged from 1,065–2,259 (0.5–1.0 per 1,000 persons) among children <5 years old and 779–2,252 cases (0.1–0.2 per 1,000 persons) for persons ≄5 years old, depending on year and base rate used. In both countries, the number of non-hospitalized influenza-associated cases was several-fold higher than the hospitalized cases. Conclusions: Influenza virus was associated with a substantial amount of severe disease in Kenya and Guatemala. This method can be performed in most low and lower-middle income countries

    Clinical laboratory reference values amongst children aged 4 weeks to 17 months in Kilifi, Kenya: A cross sectional observational study

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    Reference intervals for clinical laboratory parameters are important for assessing eligibility, toxicity grading and management of adverse events in clinical trials. Nonetheless, haematological and biochemical parameters used for clinical trials in sub-Saharan Africa are typically derived from industrialized countries, or from WHO references that are not region-specific. We set out to establish community reference values for haematological and biochemical parameters amongst children aged 4 weeks to 17 months in Kilifi, Kenya. We conducted a cross sectional study nested within phase II and III trials of RTS, S malaria vaccine candidate. We analysed 10 haematological and 2 biochemical parameters from 1,070 and 423 community children without illness prior to experimental vaccine administration. Statistical analysis followed Clinical and Laboratory Standards Institute EP28-A3c guidelines. 95% reference ranges and their respective 90% confidence intervals were determined using non-parametric methods. Findings were compared with published ranges from Tanzania, Europe and The United States. We determined the reference ranges within the following age partitions: 4 weeks to <6 months, 6 months to less than <12 months, and 12 months to 17 months for the haematological parameters; and 4 weeks to 17 months for the biochemical parameters. There were no gender differences for all haematological and biochemical parameters in all age groups. Hb, MCV and platelets 95% reference ranges in infants largely overlapped with those from United States or Europe, except for the lower limit for Hb, Hct and platelets (lower); and upper limit for platelets (higher) and haematocrit(lower). Community norms for common haematological and biochemical parameters differ from developed countries. This reaffirms the need in clinical trials for locally derived reference values to detect deviation from what is usual in typical children in low and middle income countries

    Controlled Human Malaria Infection in Semi-Immune Kenyan Adults (CHMI-SIKA): a study protocol to investigate in vivo Plasmodium falciparum malaria parasite growth in the context of pre-existing immunity [version 2; peer review: 2 approved]

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    Malaria remains a major public health burden despite approval for implementation of a partially effective pre-erythrocytic malaria vaccine. There is an urgent need to accelerate development of a more effective multi-stage vaccine. Adults in malaria endemic areas may have substantial immunity provided by responses to the blood stages of malaria parasites, but field trials conducted on several blood-stage vaccines have not shown high levels of efficacy. We will use the controlled human malaria infection (CHMI) models with malaria-exposed volunteers to identify correlations between immune responses and parasite growth rates in vivo. Immune responses more strongly associated with control of parasite growth should be prioritized to accelerate malaria vaccine development. We aim to recruit up to 200 healthy adult volunteers from areas of differing malaria transmission in Kenya, and after confirming their health status through clinical examination and routine haematology and biochemistry, we will comprehensively characterize immunity to malaria using >100 blood-stage antigens. We will administer 3,200 aseptic, purified, cryopreserved Plasmodium falciparum sporozoites (PfSPZ Challenge) by direct venous inoculation. Serial quantitative polymerase chain reaction to measure parasite growth rate in vivo will be undertaken. Clinical and laboratory monitoring will be undertaken to ensure volunteer safety. In addition, we will also explore the perceptions and experiences of volunteers and other stakeholders in participating in a malaria volunteer infection study. Serum, plasma, peripheral blood mononuclear cells and whole blood will be stored to allow a comprehensive assessment of adaptive and innate host immunity. We will use CHMI in semi-immune adult volunteers to relate parasite growth outcomes with antibody responses and other markers of host immunity. / Registration: ClinicalTrials.gov identifier NCT02739763

    Track D Social Science, Human Rights and Political Science

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    Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/138414/1/jia218442.pd

    Late Presentation With HIV in Africa: Phenotypes, Risk, and Risk Stratification in the REALITY Trial.

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    This article has been accepted for publication in Clinical Infectious Diseases Published by Oxford University PressBackground: Severely immunocompromised human immunodeficiency virus (HIV)-infected individuals have high mortality shortly after starting antiretroviral therapy (ART). We investigated predictors of early mortality and "late presenter" phenotypes. Methods: The Reduction of EArly MortaLITY (REALITY) trial enrolled ART-naive adults and children ≄5 years of age with CD4 counts .1). Results: Among 1711 included participants, 203 (12%) died. Mortality was independently higher with older age; lower CD4 count, albumin, hemoglobin, and grip strength; presence of World Health Organization stage 3/4 weight loss, fever, or vomiting; and problems with mobility or self-care at baseline (all P < .04). Receiving enhanced antimicrobial prophylaxis independently reduced mortality (P = .02). Of five late-presenter phenotypes, Group 1 (n = 355) had highest mortality (25%; median CD4 count, 28 cells/”L), with high symptom burden, weight loss, poor mobility, and low albumin and hemoglobin. Group 2 (n = 394; 11% mortality; 43 cells/”L) also had weight loss, with high white cell, platelet, and neutrophil counts suggesting underlying inflammation/infection. Group 3 (n = 218; 10% mortality) had low CD4 counts (27 cells/”L), but low symptom burden and maintained fat mass. The remaining groups had 4%-6% mortality. Conclusions: Clinical and laboratory features identified groups with highest mortality following ART initiation. A screening tool could identify patients with low CD4 counts for prioritizing same-day ART initiation, enhanced prophylaxis, and intensive follow-up. Clinical Trials Registration: ISRCTN43622374.REALITY was funded by the Joint Global Health Trials Scheme (JGHTS) of the UK Department for International Development, the Wellcome Trust, and Medical Research Council (MRC) (grant number G1100693). Additional funding support was provided by the PENTA Foundation and core support to the MRC Clinical Trials Unit at University College London (grant numbers MC_UU_12023/23 and MC_UU_12023/26). Cipla Ltd, Gilead Sciences, ViiV Healthcare/GlaxoSmithKline, and Merck Sharp & Dohme donated drugs for REALITY, and ready-to-use supplementary food was purchased from Valid International. A. J. P. is funded by the Wellcome Trust (grant number 108065/Z/15/Z). J. A. B. is funded by the JGHTS (grant number MR/M007367/1). The Malawi-Liverpool–Wellcome Trust Clinical Research Programme, University of Malawi College of Medicine (grant number 101113/Z/13/Z) and the Kenya Medical Research Institute (KEMRI)/Wellcome Trust Research Programme, Kilifi (grant number 203077/Z/16/Z) are supported by strategic awards from the Wellcome Trust, United Kingdom. Permission to publish was granted by the Director of KEMRI. This supplement was supported by funds from the Bill & Melinda Gates Foundation