Behaviour of composite floor slabs under fire conditions

This paper is concerned with the ultimate behaviour of composite floor slabs during fire scenarios. Steel/concrete composite structures are increasingly common in the UK and worldwide, particularly for multi-storey construction. The popularity of this construction form is mainly due to the excellent efficiency offered in terms of structural behaviour, construction time and material usage all of which are attractive given the ever-increasing demands for improved sustainability in construction. In this context, the engineering research community has focused considerable effort in recent years towards understanding the response of composite structures during fires. In particular, the contribution made by the floor slab system is of crucial importance as its ability to undergo secondary load-carrying mechanisms (e.g. membrane action) once conventional strength limits have been reached may be the key to preventing disproportionate collapse of the overall structure. Researchers have focused on developing the fundamental understanding of the complex behaviour of floor slabs and also improving the methods of analysis. Building on this work, the current paper describes the development and validation of a finite element model which can simulate the response of floor slab systems until failure, both at ambient and elevated temperature. The model can represent the complexities of the behaviour including the temperature-dependent material and geometric nonlinearities. It is first developed at ambient temperature and validated using a series of experiments on isolated slab elements. The most salient parameters are identified and studied. Thereafter, the model is extended to include the effects of elevated temperature and is employed to investigate the behaviour under these conditions. Comparisons with current design procedures are assessed and discussed

Assessment of the ultimate response of composite slab panels

It has been shown that steel-concrete composite floor systems can withstand loads and deflections far greater than those calculated by the traditional methods of design under fire conditions. In recent years, there has been considerable research focus directed towards developing the fundamental understanding of the complex behaviour of floor slabs and also improving the methods of analysis. Building on this work, the current paper describes the development and validation of a finite element model, developed using the ABAQUS software, which is capable of simulating the load-displacement response until failure. The model can represent the complexities of the behaviour including both the material and geometric nonlinearities and has been developed in five phases, including (i) unrestrained isolated strips (ii) restrained isolated strips (iii) unrestrained slabs (iv) restrained slabs and (v) an arrangement of three by three slab panels. The first four phases have been validated using data from tests on isolated elements and the current paper focuses mainly on the response of unrestrained two-way spanning slabs. The most salient parameters including boundary conditions, continuity and various other material and geometric properties are identified and studied. Comparisons with current design procedures are also discussed. The results of this investigation offer detailed insights into the key factors that govern the ultimate behaviour of buildings with composite floor systems under extreme loading conditions, and provide the essential background to enable the development of more performance-based design expressions

Ebola virus disease epidemic in West Africa: Lessons learned and issues arising from West African countries

© Royal College of Physicians 2015. All rights reserved.The current Ebola virus disease (EVD) outbreak ravaging three nations in West Africa has affected more than 14,000 persons and killed over 5,000. It is the longest and most widely spread Ebola epidemic ever seen. At the time of this overview (written November 2014), having affected eight different nations, Nigeria and Senegal were able to control and eliminate the virus within a record time. Ghana has successfully, to date, kept the virus away from the country, despite economic and social relationships with affected nations. What lessons can we learn from Nigeria, Senegal and Ghana in the current epidemic? How can the world improve the health systems in low- and middle-income countries to effectively manage future outbreaks? Recently, the Royal College of Physicians launched a new partnership with the West African College of Physicians to curtail the effects of HIV/AIDS, malaria and tuberculosis in the region. We believe that strengthened health systems, skilled human resources for health and national ownership of problems are key to effective management of outbreaks such as EVD

Perceptions, Experiences and Expectations of Physicians Regarding the Role of the Pharmacist in an Iraqi Hospital Setting

Purpose: To investigate the perceptions, expectations, and experiences of physicians regarding hospital-based pharmacists in some Iraqi government hospitals.Methods: A cross-sectional study was conducted at four government hospitals in Baghdad and Erbil, Iraq from March to July 2012. A validated, self-administered questionnaire was hand-delivered to a random sample of 200 physicians. The questionnaire comprised four sections that probed the physicians' demographic characteristics as well as their perceptions of, expectations of, and experiences with hospital pharmacists.Results: Most participants (69.4 %) reported rarely interacting with pharmacists and that enquiring about the availability of medications was the main purpose (74.9 %) of any interactions. Physicians reported being comfortable with pharmacists preventing prescription error, treating minor illness, and suggesting prescription medication to physicians of 74, 75 and 67 %, respectively, but only 47 % were comfortable with pharmacists providing patient education. The perspective of physicians in Erbil differed from that of physicians in Baghdad (p < 0.05).Conclusion: Interactions between Iraqi physicians and pharmacists are still not optimal. Physicians are much more comfortable with traditional pharmacist functions than with the extended, patient-oriented pharmacy services currently being promoted. Great efforts are needed to enhance the Iraqi physician's attitude regarding the clinical services provided by pharmacists which in turn would result in more collaboration among healthcare professionals.Keywords: Physician, Pharmacist, Perception, Experience, Expectation, Patient-oriented, Pharmacy servic

Differentiation of Human Embryonic Stem Cells into Cells with Corneal Keratocyte Phenotype

Corneal transparency depends on a unique extracellular matrix secreted by stromal keratocytes, mesenchymal cells of neural crest lineage. Derivation of keratocytes from human embryonic stem (hES) cells could elucidate the keratocyte developmental pathway and open a potential for cell-based therapy for corneal blindness. This study seeks to identify conditions inducing differentiation of pluripotent hES cells to the keratocyte lineage. Neural differentiation of hES cell line WA01(H1) was induced by co-culture with mouse PA6 fibroblasts. After 6 days of co-culture, hES cells expressing cell-surface NGFR protein (CD271, p75NTR) were isolated by immunoaffinity adsorption, and cultured as a monolayer for one week. Keratocyte phenotype was induced by substratum-independent pellet culture in serum-free medium containing ascorbate. Gene expression, examined by quantitative RT-PCR, found hES cells co-cultured with PA6 cells for 6 days to upregulate expression of neural crest genes including NGFR, SNAI1, NTRK3, SOX9, and MSX1. Isolated NGFR-expressing cells were free of PA6 feeder cells. After expansion as a monolayer, mRNAs typifying adult stromal stem cells were detected, including BMI1, KIT, NES, NOTCH1, and SIX2. When these cells were cultured as substratum-free pellets keratocyte markers AQP1, B3GNT7, PTDGS, and ALDH3A1 were upregulated. mRNA for keratocan (KERA), a cornea-specific proteoglycan, was upregulated more than 10,000 fold. Culture medium from pellets contained high molecular weight keratocan modified with keratan sulfate, a unique molecular component of corneal stroma. These results show hES cells can be induced to differentiate into keratocytes in vitro. Pluripotent stem cells, therefore, may provide a renewable source of material for development of treatment of corneal stromal opacities. © 2013 Chan et al

Reduced loss of NH3 by coating urea with biodegradable polymers, palm stearin and selected micronutrients

In agricultural lands, the loss of NH3 from surface-applied urea and micronutrient deficiencies are the two most common problems, which can be solved by using coated urea with micronutrients and biodegradable natural materials. These coatings can improve the nutrient status in the soil and simultaneously reduce nitrogen loss from urea. To control ammonia loss and urea’s hydrolysis process, two laboratory studies were conducted to compare the effects of using coated urea with that of using only urea. Both studies consisted of consecutive incubation experiments that were conducted on the same Typic Paleudult soil (Serdang Series). Eight treatments (labeled as Urea, UPS1, UPS2, UPS3, UAG1%, UAG2%, UG1% and UG2%) in study 1 and six treatments (labeled U, UPSCu, UAGCu, UGCu, UCu, and UCuZn) in study 2 were prepared and used to determine the effects of various concentrations of natural materials and the inhibitory effects of micronutrients on both ammonia loss and the hydrolysis process. The NH3 loss was measured by forced draft techniques; the soil’s exchangeable ammonium, available nitrate and urea-N were determined by using standard procedures. The outcomes of the study did not show any significant difference among various concentrations ofnatural material. Coated urea treatments significantly reduced ammonia loss by 30 to 40% in study 1 and by 40 to 67% in study 2 in comparison to urea alone. The same observation was made with respect to urea hydrolysis. All of the coated urea treatments significantly slowed down the hydrolysis process in comparison to urea. The outcomes of the study may improve urea fertilizer by reducing the loss of NH3 volatilization.Key words: Biodegradable polymers, coated urea, CuSO4, NH3 volatilization loss, urease inhibitor, urea

Ventricular Conduction System Modeling for Electrophysiological Simulation of the Porcine Heart

Depolarization sequences triggering mechanical contraction of the heart are largely determined by the cardiac conduction system (CS). Many biophysical models of cardiac electrophysiology still have poor representations of the CS. This work proposes a semiautomatic method for the generation of an anatomically-realistic porcine CS that reproduces ventricular activation properties in swine computational models. Personalized swine biventricular models were built from magnetic resonance images. Electrical propagation was described by the monodomain model. The CS was defined from manually-determined anatomic landmarks using geodesic paths and a fractal tree algorithm. Two CS distributions were defined, one restricted to the subendocardium and another one by performing a subendo-to-intramyocardium projection based on histological porcine data. Depolarization patterns as well as left ventricular transmural and inter-ventricular delays were assessed to describe ventricular activation by the two CS distributions. The electrical excitations calculated using the two CS distributions were in good agreement with reported activation patterns. The pig-specific subendo-intramyocardial CS led to improved reproduction of experimental activation delays in ventricular endocardium and epicardium

The urinary diversion in children with bladder exstrophy and epispadias: alternative to primary bladder closure

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