Impact of Background Oxygen Pressure on the Pulsed-Laser Deposition of ZnO Nanolayers and on Their Corresponding Performance as Electron Acceptors in PbS Quantum-Dot Solar Cells

ZnO films are commonly employed as n-type semiconductors in heterojunctions with PbS colloidal quantum-dot (CQDs) films because of their outstanding optical transparency and electron acceptor properties, yet studies of the impact of ZnO film microstructure, composition, and defect qualities on the solar-cell performance are quite limited. Here we report on the fabrication of ZnO films via pulsed-laser deposition and use these films to investigate how different morphologies affect the PbS CQD solar-cell performance. By modification of the background gas O2 pressures during the ZnO deposition process, the device performance approaching a 7.8% energy conversion efficiency is achieved with an O2 pressure of 100 mTorr. Higher or lower O2 pressures led to significantly lower device efficiency. We employ various materials and device characterizations to highlight the differences in the physical properties introduced by the fabrication oxygen pressure. In particular, we have found that the differences in the type and density of ZnO oxygen defects are the key factors behind the dispersion in solar-cell performances

How to Argue about Health Care

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68919/2/10.1177_107755878704400102.pd

Staffing and Training Aspects of Hospital Management: Some Issues for Research

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68624/2/10.1177_107755878904600205.pd

Influence of psychological factors in food risk assessment - A review

Background: Typically, food-related risk assessments are carried out within a four step, technical framework, as detailed by the Codex Alimentarius Commission (World Health Organization/ Food and Agricultural Organization of the United Nations, 2015). However, the technical framework presumes a level of ‘objective risk’ and does not take into account that risk is complex and psychologically constructed, something which is rarely acknowledged within risk analysis as a whole. It is well documented that people's perceptions of risk are based on more than merely probability of occurrence, but reflect other non-technical psychological factors (e.g., risk origin, severity, controllability, familiarity). Moreover, the basis of these risk perceptions is largely similar for experts and non-experts. Scope and approach: In this review, we consider each stage of the risk assessment process from a psychological perspective, reviewing research on non-technical factors which could affect assessments of risk and subsequent risk management decisions, with a particular focus on food safety. Key Findings and Conclusions: We identify 12 factors from the psychological literature which could potentially influence how risks are assessed and characterised. Drawing on insights from this research, we propose a number of recommendations to standardise approaches in risk assessment. Acknowledging and working with the subjectivity of risk is key to ensuring the efficacy of the wider risk analysis process

The developmental pattern of homologous and heterologous tRNA methylation in rat brain differential effect of spermidine

Using S -adenosyl- L -[Me- 14 C] methionine, rat cerebral cortex methyltransferase activity was determined during the early postnatal period in the absence of added Escherichia coli tRNA and in its presence. [Me- 14 C] tRNA was purified from both systems and its [Me- 14 C] base composition determined. The endogenous formation of [Me- 14 C] tRNA (homologous tRNA methylation) was totally abolished in the presence of 2.5 mM spermidine, whereas E. coli B tRNA methylation (heterologous methylation) was markedly stimulated. Only [Me- 14 C] 1-methyl guanine and [Me- 14 C] N 2 -methyl guanine were formed by homologous methylation, there being an inverse shift in their relative proportions with age. Heterologous tRNA methylation led, additionally, to the formation of [Me- 14 C] N 2 2 -dimethyl guanine, 5-methyl cytosine, 1-methyl adenine, 5-methyl uracil, 2-methyl adenine, and 1-methyl hypoxanthine. A comparison of heterologous tRNA methylation between the whole brain cortex (containing nerve and glial cells) and bulk-isolated nerve cell bodies revealed markedly lower proportions of [Me- 14 C] N 2 -methyl and N 2 2 -dimethyl guanine and significantly higher proportions of [Me- 14 C] 1-methyl adenine in the neurons. The present findings suggest (1) that homologous tRNA methylation may provide developing brain cells with continuously changing populations of tRNA and (2) that neurons are enriched in adenine residue-specific tRNA methyltransferases that are highly sensitive to spermidine.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/45399/1/11064_2004_Article_BF00966229.pd