Antibiotic Sensitivity of Staph. aureus

Undergraduate Experimental Basi

Precautionary Saving and Social Insurance

Microdata studies of household saving often find a significant group in the population with virtually no wealth, raising concerns about heterogeneity in motives for saving. In particular, this heterogeneity has been interpreted as evidence against the life-cycle model of saving. This paper argues that a life-cycle model can replicate observed patterns in household wealth accumulation after accounting explicitly for precautionary saving and asset-based means- tested social insurance. We demonstrate theoretically that social insurance programs with means tests based on assets discourage saving by households with low expected lifetime income. In addition, we evaluate the model using a dynamic programming model with four state variables. Assuming common preference parameters across lifetime- income groups, we are able to replicate the empirical pattern that low-income households are more likely than high-income households to hold virtually no wealth. Low wealth accumulation can be explained as a utility-maximizing response to asset-based means-tested welfare programs.

Front contact Grid Design for Terrestrial III-V Concentrator Solar Cells

Photovoltaic devices can exhibit an increase in conversion efficiency as increasing power density is concentrated onto them. Design of the front contact grid is a major processing step that can govern the concentration at which the efficiency is at a peak. A series of equations provided by M. Green was used to design GaAs solar cells for concentrations of 1, 25, 50, 100, and 200 suns. The cells were processed and tested under a 1-sun calibrated AM1.5G spectrum, as well as a Large Area Pulsed Solar Simulator to measure device parameters under concentrated light. All devices—except the ones designed for 1-sun—exhibited increases in efficiency with increased concentration. Additionally, series resistance was shown to decrease with the increased concentration design

Glacier-like forms on Mars

More than 1300 glacier-like forms (GLFs) are located in Mars' mid-latitudes. These GLFs are predominantly composed of ice–dust mixtures and are visually similar to terrestrial valley glaciers, showing signs of downhill viscous deformation and an expanded former extent. However, several fundamental aspects of their behavior are virtually unknown, including temporal and spatial variations in mass balance, ice motion, landscape erosion and deposition, and hydrology. Here, we investigate the physical glaciology of martian GLFs. We use satellite images of specific examples and case studies to build on existing knowledge relating to (i) GLF current and former extent, exemplified via a GLF located in Phlegra Montes; (ii) indicators of GLF motion, focusing on the presence of surface crevasses on several GLFs; (iii) processes of GLF debris transfer, focusing on mapping and interpreting boulder trains on one GLF located in Protonilus Mensae, the analysis of which suggests a best-estimate mean GLF flow speed of 7.5 mm a−1; and (iv) GLF hydrology, focusing on supra-GLF gulley networks. On the basis of this information, we summarize the current state of knowledge of the glaciology of martian GLFs and identify future research avenues

What is the impact of diabetes mellitus on radiation induced acute proctitis after radical radiotherapy for adenocarcinoma prostate? A prospective longitudinal study

Background: Long-term complications of diabetes include cardiovascular disease, retinopathy, nephropathy, and neuropathy. Diabetic patients with prostate cancer could be at a high risk of radiation-induced acute proctitis following radical radiotherapy. Our aims were to analyse the incidence, severity, and duration of radiation proctitis in diabetic patients treated by radical radiotherapy and combined androgen deprivation for prostate cancer. Material and methods: On the bases of inclusion and exclusion criteria 716 patients with prostate cancer were retrospectively recruited. Patients were stratified into diabetic patients and non-diabetic patients. The incidence, severity, and duration of proctitis were the main outcomes. A polynomial ordered logistic regression was fitted to determine the influence of diabetes status, age, blood pressures medication, co-morbidities, Gleason score, PSA after treatment, and tumour stage on the grades of proctitis. Time to resolution per year was modelled as a negative binomial generalised linear model. Results: The overall mean age of patients was 67.44 (SD 6.77) years with a follow-up time of 3.36 (SD 2.05) years. Data exploratory analysis suggested that the only highly significant explanatory variable was the presence or absence of diabetes. Polynomial ordered logistic regression, however, showed that the presence (or not) of diabetes remained as the only significant predictor (t = −2.74; p = 0.0059) of severity of proctitis. A negative binomial generalised linear model showed that both grade of proctitis (z = −17.178; p < 0.001), and diabetes (z = −5.92; p < 0.001), were highly significant predictors of time to resolution. Conclusions: Diabetic patients were significantly more likely to have proctitis after radical radiation therapy for prostate cancer. Diabetes was significantly associated with an induced risk of radiation induced proctitis and also with deceleration of its resolution. Keywords: Prostate cancer, Diabetes mellitus, Proctitis, Radiotherap

Potential Dilution of Minority Voting Strength Not within Area of Constitutional Review.

Abstract Forthcoming

Magnetisation and Transport Studies of Carbon Based Nanostructures

This thesis presents investigations in to the properties of bulk graphite, graphitised silicon carbide and exfoliated graphene. The background physics and theory relevant to the investigations is detailed. This is followed by descriptions of the equipment and methods used during experiments presented within this thesis. Millikelvin de Haas-van Alphen and Shubnikov-de Haas experiments were performed for several types of graphite. These types included forms of natural, kish and highly orientated pyrolitic graphite. Oscillations for two sets of carriers (holes and electrons) were observed with varying strengths between the types. This suggests that the mobility of the charge carriers in graphite can vary significantly depending on the formation of the graphite bulk. Hall measurement results support this statement, as the electron to hole mobility ratio appears much greater in natural graphite than in highly orientated pyrolitic graphite. Analysis of the oscillations for each sample indicates that the electrons have a higher mobility than the holes, and that the effective mass of the holes is lower than that of the electrons. Depending on the sample, the mobility of the holes was found to vary between 1.07->1.42 m^2/Vs and the mobility of the electrons between 1.64->16.0 m^2/Vs. The effective masses of the charge carriers were found to be 0.031+-0.007 m0 and 0.046+-0.003 m0 for holes and electrons respectively. The nature of the carriers for the different types of graphite was determined. It was found in the de Haas-van Alphen experiments that the phase of the carriers varied between samples. However, in the majority of cases, the electrons were shown to be Dirac fermions. In Shubnikov-de Haas experiments, the electrons demonstrated an indeterminate nature. In both types of measurement, the holes were found to have an indeterminate nature. De Haas-van Alphen experiments were also performed on two graphitised silicon carbide samples. The sample fabricated at The University of Leeds exhibited a complicated background magnetisation. This is not characteristic of a carbon system and so indicates a lack of a carbon film. The sample fabricated by the Georgia Institute of Technology exhibited a magnetisation akin to ZYB grade highly orientated pyrolitic graphite. Sheet magnetoresistance measurements were also performed on a more recent graphitised silicon carbide sample, fabricated at The University of Leeds. Weak localisation was observed as well as a large number of non-oscillatory features. These features were attributed to the absence of a defined Hall-bar geometry and the presence of multiple graphene domains between surface contacts. Magnetotransport and activation energies of exfoliated graphene flakes were also investigated. The charge carrier mobilities at 240K for a particular sample were found to be 20,670+-30 cm^2/Vs for holes and 22,770+-40 cm^2/Vs for electrons. These mobilities rose to 25,600+-200 cm^2/Vs for holes and 25,900+-200 cm^2/Vs for electrons by 2.5K. This observation implies that the holes experience stronger phonon scattering than the electrons. The activation energies for filling factors nu=+-2 and nu=+-6 were found at several magnetic fields for the sample. The activation energies allowed for determination of the broadening of the Landau levels. The broadening of the nu=+-6$ levels were found to be constant as a function of magnetic field, with Gamma_{+-6}=260+-40 K. The nu=-2 level also showed a constant value for the broadening, Gamma_{-2}=620+-40 K. However, for nu=+2, the activation energy approached the bare Landau level separation at high magnetic fields. This implies a zero-energy Landau level that is narrower than the higher levels. Further to the mobility asymmetry at high temperatures, the difference in broadening between the nu=-2 and nu=+2 sides of the zeroth Landau level suggests that there is a form of scattering which affects the holes more than the electrons near the Dirac point