Investigations of high altitude geomagnetic phenomena using rubidium vapour systems

Imperial Users onl

A feasibility study towards ultra-thin PV solar cell devices by MOCDV based on a p-i-n structure incorporating pyrite

FeSx layers were deposited onto aluminosilicate glass substrates over a temperature range of 180°C to 500°C using a horizontal AP-MOCVD reactor. Fe(CO)5 was used as the Fe source in combination with t-Bu2S2 or t-BuSH as S precursor to control the rate of reaction and film stoichiometry. The Fe and S partial pressures were kept at 7.5 x 103 and 3.0 mbar, giving a gas phase S/Fe ratio of 400. Reactions followed a non-Arrhenius relationship at higher temperatures. XRD revealed mixed FeSx phases in the layers, which consisted mainly of FeS and Fe1-xS. Post growth annealing of the FeSx films using S powder in a static argon atmosphere and temperatures ranging from 250°C to 400°C was carried out using a 30 minute soak time. Characterisation by XRD confirmed a transitional phase change to FeS2 for the S anneal at 400°C. These films were highly absorbing in the visible region of the solar spectrum, which extended into the NIR. Devices with a p-i-n structure were produced using either a sulphurised or non-sulphurised FeSx i-layer, and compared to p-n devices without an i-layer. A non-sulphurised p-i-n device had the best I-V results, which was attributed to reduced lateral inhomogeneity across the device relative to the thinner p-n device structures. Devices with sulphurised FeSx i-layers performed least efficiently which is suspected to be due to a less defined FeSx/CdS junction caused by severe conditions during the S annealing process

Examination of adipocere formation in a cold water environment

Adipocere is a late-stage postmortem decomposition product that forms from the lipids present in soft tissue. Its formation in aquatic environments is typically related to the presence of a moist, warm, anaerobic environment, and the effect of decomposer microorganisms. The ideal temperature range for adipocere formation is considered to be 21-45°C and is correlated to the optimal conditions for bacterial growth and enzymatic release. However, adipocere formation has been reported in cooler aquatic environments at considerable depths. This study aimed to investigate the chemical process of adipocere formation in a cold freshwater environment in Lake Ontario, Canada. Porcine tissue was used as a human tissue analogue and submerged at two depths (i.e., 10 and 30 feet) in the trophogenic zone of the lake. Samples were collected at monthly postmortem submersion intervals and analysed using diffuse reflectance infrared Fourier transform spectroscopy to provide a qualitative profile of the lipid degradation and adipocere formation process. Early stage adipocere formation occurred rapidly in the cold water environment and proceeded to intermediate stage adipocere formation by the second month of submersion. However, further adipocere formation was inhibited in the third month of the study when temperatures approached the freezing point. The depth of submergence did not influence the chemical conversion process as similar stages of adipocere formation occurred at both depths investigated. The study demonstrated that adipocere can form rapidly, even on small amounts of soft tissue, which may be representative of dismembered or disarticulated limbs discovered in an aquatic environment. © 2010 Springer-Verlag

Seasonal variation of fatty acid profiles from textiles associated with decomposing pig remains in a temperate Australian environment

© 2018 Elsevier B.V. A methodology to examine the human post-mortem decomposition process has been developed through the monitoring of chemical changes to decomposition fluids absorbed by clothing. Model surface burials using clothed pigs were established during summer and winter seasons in a temperate region of Australia. Three clothing materials were investigated: cotton, polyester and cotton-polyester. Lipid decomposition products were extracted from the textiles and the fatty acid composition measured as a function of burial time using gas chromatography – mass spectrometry (GC-MS). Two derivatisation methods for the fatty acids were compared to establish the most effective approach and it was established that a trimethylsilylation derivatisation method is the optimal preparation technique. The summer trials revealed two rates of transformation of fatty acids from unsaturated to saturated forms, with a faster rate of change occurring earlier in the trials. A different pattern of behaviour was observed for the fatty acids detected during the winter trial, with a decrease in saturated fatty acids initially observed, followed by the conversion of unsaturated to saturated fatty acids until the end of trial. The initial change observed during the winter trial was attributed to a dehydrogenation process caused by microbiological enyzymatic activity. The study has demonstrated the feasibility of examining lipid decomposition products collected in clothing from burials to provide insight into the conditions and length of burial

Nanowire and core-shell-structures on flexible Mo Foil for CdTe solar cell applications

CdTe films, nanowires, film-nanowire combinations and CdS-CdTe core-shell structures have been fabricated in a preliminary survey of growth methods that will generate structures for PV applications. Selectivity between film, nanowire and film plus nanowire growth was achieved by varying the pressure of N2 gas present during Au-catalysed VLS growth of CdTe, on either Mo or Si substrates. Metamorphic growth of CdTe nanowires on sputtered CdTe films, deposited on glass substrates, was demonstrated. Coating of CdTe nanowires with CBD CdS gave conformal coverage whereas coating with MOCVD (Cd,Zn)S yielded highly crystallographic dendritic growth on the wires

Predicting success in graduate entry medical students undertaking a graduate entry medical program (GEM)

Background: Success in undergraduate medical courses in the UK can be predicted by school exit examination (A level) grades. There are no documented predictors of success in UK graduate entry medicine (GEM) courses. This study looks at the examination performance of GEM students to identify factors which may predict success; of particular interest was A level score. Methods: Data was collected for students graduating in 2004, 2005 and 2006, including demographic details (age and gender), details of previous academic achievement (A level total score and prior degree) and examination results at several points during the degree course. Results: Study group comprised 285 students. Statistical analyses identified no significant variables when looking at clinical examinations. Analysis of pass/fail data for written examinations showed no relationship with A level score. However, both percentage data for the final written examination and the analysis of the award of honours showed A level scores of AAB or higher were associated with better performance (p < 0.001). Discussion: A prime objective of introducing GEM programs was to diversify admissions to medical school. In trying to achieve this, medical schools have changed selection criteria. The findings in this study justify this by proving that A level score was not associated with success in either clinical examinations or passing written examinations. Despite this, very high achievements at A level do predict high achievement during medical school. Conclusions: This study shows that selecting graduate medical students with the basic requirement of an upper-second class honours degree is justifiable and does not disadvantage students who may not have achieved high scores in school leaver examinations