Diversified Portfolios in Continuous Time

We study a financial market containing an infinite number of assets, where each asset price is driven by an idiosyncratic random source as well as by a systematic noise term. Introducing 2 asymptotic assets" which correspond to certain infinitely well diversified portfolios we study absence of (asymptotic) arbiytrage, and in this context we obtain continuous time extensions of atemporal APT results. We also study completeness and derivative pricing, showing that the possibility of forming infinitely well diversified portfolios has the property of completing the market. It also turns out that models where the all risk is of diffusion type are qualitatively quite different from models where one risk is of diffusion type and the other is of Poisson type. We also present a simple martingale based theory for absence of asymptotic arbitrage.Large economies; diversifiable risk; APT; asymptotic arbitrage; completeness; martingales

Exchange rate variations and the behaviour of the purchasing department

When the risk of a devaluation is high this is likely to affect the purchasing behaviour of firms importing goods from abroad. A model is developed which shows optimal purchasing and inventory policies for firms in that situation. Another model is developed for the case when the value of a currency is changing gradually over time. The results derived in the first model are tested against empirical data from 23 large firms in Sweden and 23 subsidiaries of Swedish firms operating in different countries. The studies refer to the behaviour of the firms before and after the devaluation of the Swedish crown by 10% in August 1977.

Validation guidelines for PCR workflows in bioterrorism preparedness, food safety and forensics

The polymerase chain reaction (PCR) is the backbone of contemporary DNA/RNA analysis, ideally enabling detection of one or just a few target molecules. However, when analysing food or forensic samples the analytical procedure is often challenged by low amounts of poor quality template molecules and complex matrices. Applying optimised and validated methods in all steps of the analysis workflow, i.e. sampling, sample treatment, DNA/RNA extraction and PCR (including reverse transcription for RNA analysis), is thus necessary to ensure the reliability of analysis. In this paper, we describe how in-house validation can be performed for the different modules of the diagnostic PCR process, providing practical examples as tools for laboratories in their planning of validation studies. The focus is analysis of heterogeneous samples with interfering matrices, with relevance in food testing, forensic DNA analysis, bioterrorism preparedness and veterinary medicine. Our objective is to enable rational in-house validation for reliable and swift quality assurance when results are urgent, for example in the event of a crisis such as a foodborne outbreak or a crime requiring the analysis of a large number of diverse samples. To that end, we explain the performance characteristics associated with method validation from a PCR and biological sample matrix perspective and suggest which characteristics to investigate depending on the type of method to be validated. Also, we include a modular approach to validation within the PCR workflow, aiming at efficient validation and a flexible use of methods

The beneficial effect over 3 years by pictorial information to patients and their physician about subclinical atherosclerosis and cardiovascular risk : Results from the VIPVIZA randomized clinical trial.

Objective: Non-adherence to guidelines and preventive measures is a major challenge, particularly so to obtain long-term adherence to lifestyle changes and recommended medication. The objective was to investigate if pictorial information regarding subclinical carotid atherosclerosis provided to individuals and physicians gave sustained effects on cardiovascular risk beyond the previously reported effect after 1 year and up to 3 years. Methods: A Prospective Randomized Open Blinded End-point (PROBE) trial. Within a CVD prevention program in Västerbotten County, Sweden, 3532 healthy individuals aged 40, 50 or 60 years were enrolled and 1:1 randomized to intervention (n = 1749; pictorial information with additional prevention materials to participants and physicians) or control group (n = 1783; no pictorial information to participants and physicians). Preventive measures were managed within primary care. Participants were investigated at baseline during 2013-2016 and at follow-up after 1 and 3 years. Results: A beneficial effect on cardiovascular risk was observed at 3-year follow-up; Framingham Risk Score (FRS) was 13.38 for the intervention group and 14.08 for the control group (p = 0.047) and SCORE was 1.69 vs. 1.82 (p = 0.022). The effect observed at 1-year was sustained over 3 years after adjustment for sex and education and more pronounced among participants with a severe atherosclerotic picture at baseline. Conclusions: This study provides evidence of sustained beneficial effects on the adherence to prevention guidelines over 3 years of pictorial information about subclinical carotid atherosclerosis, resulting in lower cardiovascular risk regardless of sex and educational level. Direct visualization of the underlying still subclinical atherosclerotic disease, rather than just indirect information about risk factors and statistical risk of future myocardial infarction, stroke and death, is one way to tackle the problem of non-adherence to prevention of cardiovascular diseases