Impact of experimental conditions on material response during forming of steel in semi-solid state

Semi-solid forming is an effective near-net-shape forming process to produce components with complex geometry and in fewer forming steps. It benefits from the complex thixotropic behaviour of semi-solids. However, the consequences of such behaviour on the flow during thixoforming, is still neither completely characterized and nor fully understood, especially for high melting point alloys. The study described in this paper investigates thixoextrusion for C38 low carbon steel material using dies at temperatures much lower than the slug temperature. Four different process parameters were studied: the initial slug temperature, the die temperature, the ram speed and the presence of a ceramic layer at the tool/material interface. The extruded parts were found to have an exact shape and a good surface state only if the temperature was below a certain value. This critical temperature is not an intrinsic material property since its value depends on die temperature and the presence of the Ceraspray©layer. Two kinds of flow were highlighted: a homogeneous flow controlled by the behaviour of the solid skeleton characterized by a positive strain rate sensitivity, and a non homogeneous flow (macro liquid/solid phase separation) dominated by the flow of the free liquid. With decreasing ram speed, heat losses increase so that the overall consistency of the material improves, leading to apparent negative strain rate sensitivity. Finally, some ways to optimise thixoforming are proposed

Special features of RAD Sequencing data:implications for genotyping

Restriction site-associated DNA Sequencing (RAD-Seq) is an economical and efficient method for SNP discovery and genotyping. As with other sequencing-by-synthesis methods, RAD-Seq produces stochastic count data and requires sensitive analysis to develop or genotype markers accurately. We show that there are several sources of bias specific to RAD-Seq that are not explicitly addressed by current genotyping tools, namely restriction fragment bias, restriction site heterozygosity and PCR GC content bias. We explore the performance of existing analysis tools given these biases and discuss approaches to limiting or handling biases in RAD-Seq data. While these biases need to be taken seriously, we believe RAD loci affected by them can be excluded or processed with relative ease in most cases and that most RAD loci will be accurately genotyped by existing tools

Influence de la vitesse de mise en forme et du cycle de chauffe sur le thixoforgeage des aciers

Analyse l’influence de la vitesse du coulisseau et de la température du lopin (fraction liquide) sur le comportement de l’acier à l’état semi-solide en utilisant un nouvel outillage de filage direct monté sur une presse hydraulique. Cette nouvelle conception évite la décélération du vérin rapide pendant la mise en forme. Il permet donc des essais à vitesse constante. Ce travail s’intéresse également à l’écoulement de la matière dans le cas du thixoforgeage de l’acier et montre l’importance d’un couplage entre la température initiale et la vitesse de déformation. Les différentes conditions permettant d’avoir un écoulement homogène et continu, avec un effort de mise en forme faible, sont étudiées et présentées.This paper analyses the influence of two parameters (tool axis speed and billet temperature) on semi-solid steel alloy behaviour. A new design of direct filling tool is proposed and adapted on hydraulic press. This concept avoids the speed decrease during forming process. This works shows thermal exchange influence in thixoforging process in function speed raw and initial temperature inside the billet by analysis forming loads and part geometries

Rheology of StelliteTM 21 Alloy in Semi-Solid State

The main objective of this study was to conduct an analysis of the rheological properties of StelliteTM 21 alloy in the semi-solid state, as the results could be used for identifying the appropriate temperature range for thixoforming of this alloy, and a secondary objective of the experimental work was the development of mathematical model of the alloy’s apparent viscosity. Such viscosity models are necessary for numerical simulations of the thixoforming processes. The StelliteTM 21 alloy exhibits high hardness and thus shaping in the semi-solid state is promising route of production of parts from this alloy. Within the confines of experimental work the measurement methods of the rheological properties at high temperatures was developed. They are based on the use of specially designed viscometer equipped with high temperature furnace. Keywords: thixoforming, rheological properties, viscosity, thixotropy, StelliteTM alloy

Ethnic differences in health in Scotland : the contrast between morbidity and mortality

In Scotland, most minority ethnic groups live longer than the White Scottish population but whether they report better health is unclear. Similarly, the international literature on ethnicity and health is divided between a strand that highlights the overall morbidity disadvantage in ethnic minorities and another strand that is puzzled by their mortality advantage. This thesis brings the two strands together by investigating whether ethnic patterns in morbidity and mortality align, based on a unique population source. The Scottish Health and Ethnicity Linkage Study links the Scottish Census 2001 to 12 years of hospitalisation and death records and provides a considerable sample size (4.6 million people) for this research. Therefore, this thesis makes a number of methodological contributions in addition to providing key empirical evidence of an ethnic morbidity-mortality paradox in Scotland. In particular, healthy life expectancy by sex and ethnicity is calculated for the first time in the UK using a direct method. Findings highlight the shortest healthy life expectancies in the Pakistani population contrasting with their mortality advantage. Hence, the Pakistani population experiences the highest number of years in poor health in Scotland. Indeed, the Pakistani population reports poorer health than the majority population which contrasts with their mortality advantage. This contrast persists beyond socio-economic circumstances and across migrant generations. Furthermore, using interaction analyses, this research demonstrates that reporting poorer health strongly predicts higher risks of mortality in minority ethnic groups but with greater strength for particular groups. Finally, findings show higher risks of (hospitalisation-based) multimorbidity in the Pakistani population which supports their morbidity disadvantage in Scotland. Diseases underlying this disadvantage include those related to the metabolic syndrome and respiratory disease. Policy makers should aim to improve the quality of life of the Pakistani population of Scotland while future research pinpoints the root causes of this morbidity-mortality paradox

The Transition to an Energy Sufficient Economy

Nigeria is an energy-rich nation with a huge energy resource base. The country is the largest reserves holder and largest producer of oil and gas in the African continent. Despite this, only about 40% of its 158 million people have access to modern energy services. Around 80% of its rural population depend on traditional biomass. This paper presents an overview of ongoing research to examine energy policies in Nigeria. The aims are: 1) to identify and quantify the barriers to sustainable energy development and 2) to provide an integrated tool to aid energy policy evaluation and planning. System dynamics modelling is shown to be a useful tool to map the interrelations between critical energy variables with other key sectors of the economy, and for understanding the energy use dynamics (impact on society and the environment). It is found that the critical factors are burgeoning population, lack of capacity utilisation, and inadequate energy investments. Others are lack of suitably trained manpower, weak institutional frameworks, and inconsistencies in energy policies. These remain the key barriers hampering Nigeria\u27s smooth transition from energy poverty to an energy sufficient economy

Quantitative genome re-sequencing defines multiple mutations conferring chloroquine resistance in rodent malaria

<p>Abstract</p> <p>Background</p> <p>Drug resistance in the malaria parasite <it>Plasmodium falciparum </it>severely compromises the treatment and control of malaria. A knowledge of the critical mutations conferring resistance to particular drugs is important in understanding modes of drug action and mechanisms of resistances. They are required to design better therapies and limit drug resistance.</p> <p>A mutation in the gene (<it>pfcrt</it>) encoding a membrane transporter has been identified as a principal determinant of chloroquine resistance in <it>P</it>. <it>falciparum</it>, but we lack a full account of higher level chloroquine resistance. Furthermore, the determinants of resistance in the other major human malaria parasite, <it>P. vivax</it>, are not known. To address these questions, we investigated the genetic basis of chloroquine resistance in an isogenic lineage of rodent malaria parasite <it>P. chabaudi </it>in which high level resistance to chloroquine has been progressively selected under laboratory conditions.</p> <p>Results</p> <p>Loci containing the critical genes were mapped by Linkage Group Selection, using a genetic cross between the high-level chloroquine-resistant mutant and a genetically distinct sensitive strain. A novel high-resolution quantitative whole-genome re-sequencing approach was used to reveal three regions of selection on chr11, chr03 and chr02 that appear progressively at increasing drug doses on three chromosomes. Whole-genome sequencing of the chloroquine-resistant parent identified just four point mutations in different genes on these chromosomes. Three mutations are located at the foci of the selection valleys and are therefore predicted to confer different levels of chloroquine resistance. The critical mutation conferring the first level of chloroquine resistance is found in <it>aat1</it>, a putative aminoacid transporter.</p> <p>Conclusions</p> <p>Quantitative trait loci conferring selectable phenotypes, such as drug resistance, can be mapped directly using progressive genome-wide linkage group selection. Quantitative genome-wide short-read genome resequencing can be used to reveal these signatures of drug selection at high resolution. The identities of three genes (and mutations within them) conferring different levels of chloroquine resistance generate insights regarding the genetic architecture and mechanisms of resistance to chloroquine and other drugs. Importantly, their orthologues may now be evaluated for critical or accessory roles in chloroquine resistance in human malarias <it>P. vivax </it>and <it>P. falciparum</it>.</p

Evidencing the gap between health expectancy and life expectancy for ethnic groups in Scotland

Background Recent evidence has shown that ethnic minorities live longer than the majority population in Scotland. This mortality advantage in ethnic minorities is not unique to Scotland. However, whether morbidity patterns by ethnicity align with mortality patterns by ethnicity is unknown. Thus, this study explores ethnic differences in health expectancies (HE) in Scotland and contrasts HE with life expectancy (LE) findings. Methods The Scottish Health and Ethnicity Linkage study anonymously links the Scottish Census 2001 for 4.6 million people to mortality records. The Scottish Census 2001 collected two measures of self-assessed health, self-declared ethnicity, age, and sex. Utilising the life tables used to calculate life expectancy by ethnicity and sex in Scotland, the Sullivan method was employed to calculate two measures of health expectancy (healthy life expectancy and disability-free life expectancy) by ethnicity and sex. 95% confidence intervals were calculated to detect significant differences compared to the majority White Scottish population, taken as reference. Results Longer health expectancies were found in males and females of Other White British, Other White, and Chinese origins as well as in Indian males compared to White Scottish populations. Any Mixed Background and Pakistani populations had the shortest healthy life expectancies. Patterns of health expectancy by ethnicity mostly aligned with patterns of life expectancy by ethnicity with the clear exception of the Pakistani population who showed among the longest life expectancies with the shortest health expectancies. Contrasting HE with LE findings, the number of years in an unhealthy state was greater in females than in males for each ethnic group. In relation to ethnicity, Pakistani and Indian populations had the highest number of years in an unhealthy state in Scotland. Pakistani females showed the strong-est disadvantage in this respect. Conclusion Pakistani populations had the shortest health expectancies contrasting with the longest life expectancies in Scotland. Future research should aim to understand why such a discrepancy occurs while policy makers ensure that fair and adapt-ed care is provided to offer better quality of life for the most vulnerable.Publisher PDFPeer reviewe

Assessment of health care, hospital admissions, and mortality by ethnicity : population-based cohort study of health-system performance in Scotland

This study was supported by the Chief Scientist's Office (grant number CZH/4/878) and supplementary funding from the UK National Health Service (NHS) Health Scotland. The Information Services Division of NHS National Services Scotland and the National Records of Scotland both made in-house contributions to the study. Additionally, SVK acknowledges funding from an NHS Research Scotland Senior Clinical Fellowship (SCAF/15/02), the Medical Research Council (MC_UU_12017/13 and MC_UU_12017/15), and the Chief Scientist's Office (SPHSU13 and SPHSU15).Background:  Ethnic minorities often experience barriers to health care. We studied six established quality indicators of health-system performance across ethnic groups in Scotland. Methods: In this population-based cohort study, we linked ethnicity from Scotland's Census 2001 (April 29, 2001) to hospital admissions and mortality records, with follow-up until April 30, 2013. Indicators of health-system performance included amenable deaths (ie, deaths avertable by effective treatment), preventable deaths (ie, deaths avertable by public health policy), avoidable deaths (combined amenable and preventable deaths), avoidable hospital admissions, unplanned readmissions, and length of stay. We calculated rate ratios and odds ratios (with 95% CIs) using Poisson and logistic regression, which we multiplied by 100, adjusting first for age-related covariates and then for socioeconomic-related and birthplace-related covariates. The white Scottish population was the reference (rate ratio [RR] 100). Findings:  The results are based on 4·61 million people. During the 50·5 million person-years of study, 1·17 million avoidable hospital admissions, 587 740 unplanned readmissions, and 166 245 avoidable deaths occurred. South Asian groups had higher avoidable hospital admissions than the white Scottish group, with the highest reported RRs in Pakistani groups (RR 140·6 [95% CI 131·9–150·0] in men; RR 141·0 [129·0–154·1] in women). There was little variation between ethnic groups in length of stay or unplanned readmission. Preventable and amenable mortality were higher in the white Scottish group than several ethnic minorities including other white British, other white, Indian, and Chinese groups. Such differences were partly diminished by adjustment for socioeconomic status, whereas adjustment for country of birth had little additional effect. Interpretation: These data suggest concerns about the access to and quality of primary care to prevent avoidable hospital admissions, especially for south Asians. Relatively high preventable and amenable deaths in white Scottish people, compared with several ethnic minority populations, were unexpected. Future studies should both corroborate and examine explanations for these patterns. Studies using several indicators simultaneously are also required internationally. Funding: Chief Scientist's Office, Medical Research Council, NHS Research Scotland, Farr Institute.Peer reviewe

Determinants of services expectations : an application to the airline industry

Understanding consumer expectations is a key to deliver superior services. The role of expectations has received attention in both satisfaction and perceived quality literature domains but no agreement has been reached concerning the nature and formation of expectations. The present study reviewed the antecedents of consumer expectations discussed in the literature and incorporated some of them into a model. Then it looked at the impact of individualism/collectivism on the formation of expectations. Regressions were conducted to see which antecedents influenced expectations. Two different types of expectations were found and results revealed that many antecedents related to external and internal sources of information, values, number of perceived alternatives and other personal characteristics influence one or the two types of expectations. Interesting theoretical and managerial implications were found concerning the proposed model. The study also revealed that differences exist between individualists and collectivists with regard to the formation of expectations; however, the differences were not as expected