On approximation rates for boundary crossing probabilities for the multivariate Brownian motion process

Motivated by an approximation problem from mathematical finance, we analyse the stability of the boundary crossing probability for the multivariate Brownian motion process, with respect to small changes of the boundary. Under broad assumptions on the nature of the boundary, including the Lipschitz condition (in a Hausdorff-type metric) on its time cross-sections, we obtain an analogue of the Borovkov and Novikov (2005) upper bound for the difference between boundary hitting probabilities for "close boundaries" in the univariate case. We also obtained upper bounds for the first boundary crossing time densities.Comment: 15 page

Country differences in the diagnosis and management of coronary heart disease : a comparison between the US, the UK and Germany

Background The way patients with coronary heart disease (CHD) are treated is partly determined by non-medical factors. There is a solid body of evidence that patient and physician characteristics influence doctors' management decisions. Relatively little is known about the role of structural issues in the decision making process. This study focuses on the question whether doctors' diagnostic and therapeutic decisions are influenced by the health care system in which they take place. This non-medical determinant of medical decision-making was investigated in an international research project in the US, the UK and Germany. Methods Videotaped patients within an experimental study design were used. Experienced actors played the role of patients with symptoms of CHD. Several alternative versions were taped featuring the same script with patients of different sex, age and social status. The videotapes were shown to 384 randomly selected primary care physicians in the three countries under study. The sample was stratified on gender and duration of professional experience. Physicians were asked how they would diagnose and manage the patient after watching the video vignette using a questionnaire with standardised and open-ended questions. Results Results show only small differences in decision making between British and American physicians in essential aspects of care. About 90% of the UK and US doctors identified CHD as one of the possible diagnoses. Further similarities were found in test ordering and lifestyle advice. Some differences between the US and UK were found in the certainty of the diagnoses, prescribed medications and referral behaviour. There are numerous significant differences between Germany and the other two countries. German physicians would ask fewer questions, they would order fewer tests, prescribe fewer medications and give less lifestyle advice. Conclusion Although all physicians in the three countries under study were presented exactly the same patient, some disparities in the diagnostic and patient management decisions were evident. Since other possible influences on doctors treatment decisions are controlled within the experimental design, characteristics of the health care system seem to be a crucial factor within the decision making process

‘What’s it like to have ME?’ The discursive construction of ME in computer-mediated communication and face-to-face interaction

ME/CFS (chronic fatigue syndrome) is a debilitating illness for which no cause or medical tests have been identified. Debates over its nature have generated interest from qualitative researchers. However, participants are difficult to recruit because of the nature of their condition. Therefore, this study explores the utility of the internet as a means of eliciting accounts. We analyse data from focus groups and the internet in order to ascertain the extent to which previous research findings apply to the internet domain. Interviews were conducted among 49 members of internet (38 chatline, 11 personal) and 7 members of two face-to-face support groups. Discourse analysis of descriptions and accounts of ME/CFS revealed similar devices and interactional concerns in both internet and face-to-face communication. Participants constructed their condition as serious, enigmatic and not psychological. These functioned to deflect problematic assumptions about ME/CFS and to manage their accountability for the illness and its effects

Gamma-ray bursts and terrestrial planetary atmospheres

We describe results of modeling the effects on Earth-like planets of long-duration gamma-ray bursts (GRBs) within a few kiloparsecs. A primary effect is generation of nitrogen oxide compounds which deplete ozone. Ozone depletion leads to an increase in solar UVB radiation at the surface, enhancing DNA damage, particularly in marine microorganisms such as phytoplankton. In addition, we expect increased atmospheric opacity due to buildup of nitrogen dioxide produced by the burst and enhanced precipitation of nitric acid. We review here previous work on this subject and discuss recent developments, including further discussion of our estimates of the rates of impacting GRBs and the possible role of short-duration bursts.Comment: 12 pages including 5 figures (4 in color). Added discussion of GRB rates and biological effects. Accepted for publication in New Journal of Physics, for special issue "Focus on Gamma-Ray Bursts

‘He's a Cracking Wee Geezer from Pakistan’: Lay Accounts of Refugee Integration Failure and Success in Scotland

Previous research on the integration of asylum seekers and refugees has aimed to develop conceptual frameworks for understanding integration or to measure the extent to which people are integrated. However, this research tends to pay insufficient attention to the rhetorical functions of integration discourse. The current study addresses this gap through a discursive analysis of ‘lay’ accounts of asylum seeker and refugee integration in Glasgow, Scotland. The analysis highlights that accounts of integration ‘failure’ may support ‘two-way’ conceptions of integration while still blaming asylum seekers for any lack of integration. Furthermore, accounts of integration ‘success’ may reinforce assimilationist policies or otherwise function to reinforce the view that adult asylum seekers generally do not integrate. The analysis highlights the importance of attending to the rhetorical functions of integration discourse in order to understand how particular policies and practices are supported or criticised at the community level at which integration takes place

Sources of Variation in Physician Adherence with Clinical Guidelines: Results from a Factorial Experiment

BACKGROUND: Health services research has documented the magnitude of health care variations. Few studies focus on provider level sources of variation in clinical decision making-for example, which primary care providers are likely to follow clinical guidelines, with which types of patient. OBJECTIVES: To estimate: (1) the extent of primary care provider adherence to practice guidelines and the unconfounded influence of (2) patient attributes and (3) physician characteristics on adherence with clinical practice guidelines. DESIGN: In a factorial experiment, primary care providers were shown clinically authentic video vignettes with actors portrayed different “patients” with identical signs of coronary heart disease (CHD). Different types of providers were asked how they would manage the different “patients” with identical CHD symptoms. Measures were taken to protect external validity. RESULTS: Adherence to some guidelines is high (over 50% of physicians would follow a third of the recommended actions), yet there is low adherence to many of them (less than 20% would follow another third). Female patients are less likely than males to receive 4 of 5 types of physical examination (p < .03); older patients are less likely to be advised to stop smoking (p < .03). Race and SES of patients had no effect on provider adherence to guidelines. A physicians’ level of experience (age) appears to be important with certain patients. CONCLUSIONS: Physician adherence with guidelines varies with different types of “patient” and with the length of clinical experience. With this evidence it is possible to appropriately target interventions to reduce health care variations by improving physician adherence with clinical guidelines

Ocean acidification of a coastal Antarctic marine microbial community reveals a critical threshold for CO2 tolerance in phytoplankton productivity

© 2017 Author. High-latitude oceans are anticipated to be some of the first regions affected by ocean acidification. Despite this, the effect of ocean acidification on natural communities of Antarctic marine microbes is still not well understood. In this study we exposed an early spring, coastal marine microbial community in Prydz Bay to CO2 levels ranging from ambient (343μatm) to 1641μatm in six 650 L minicosms. Productivity assays were performed to identify whether a CO2 threshold existed that led to a change in primary productivity, bacterial productivity, and the accumulation of chlorophyll a (Chl a) and particulate organic matter (POM) in the minicosms. In addition, photophysiological measurements were performed to identify possible mechanisms driving changes in the phytoplankton community. A critical threshold for tolerance to ocean acidification was identified in the phytoplankton community between 953 and 1140μatm. CO2 levels ≥1140μatm negatively affected photosynthetic performance and Chl a-normalised primary productivity (csGPP14C), causing significant reductions in gross primary production (GPP14C), Chl a accumulation, nutrient uptake, and POM production. However, there was no effect of CO2 on C VN ratios. Over time, the phytoplankton community acclimated to high CO2 conditions, showing a down-regulation of carbon concentrating mechanisms (CCMs) and likely adjusting other intracellular processes. Bacterial abundance initially increased in CO2 treatments ≥953μatm (days 3-5), yet gross bacterial production (GBP14C) remained unchanged and cell-specific bacterial productivity (csBP14C) was reduced. Towards the end of the experiment, GBP14C and csBP14C markedly increased across all treatments regardless of CO2 availability. This coincided with increased organic matter availability (POC and PON) combined with improved efficiency of carbon uptake. Changes in phytoplankton community production could have negative effects on the Antarctic food web and the biological pump, resulting in negative feedbacks on anthropogenic CO2 uptake. Increases in bacterial abundance under high CO2 conditions may also increase the efficiency of the microbial loop, resulting in increased organic matter remineralisation and further declines in carbon sequestration