A universal pattern of mortality decline in the G7 countries.

Human lifespan has increased enormously this century. But we remain uncertain about the forces that reduce mortality, and about the cost implications of ageing populations and their associated social burden. The poor understanding of the factors driving mortality decline, and the difficulty of forecasting mortality are due in part to the pronounced irregularity of annual to decadal mortality change. Here we examine mortality over five decades in the G7 countries (Canada, France, Germany, Italy, Japan, UK, US). In every country over this period, mortality at each age has declined exponentially at a roughly constant rate. This trend places a constraint on any theory of society-driven mortality decline, and provides a basis for stochastic mortality forecasting. We find that median forecasts of life expectancy are substantially larger than in existing official forecasts. In terms of the costs of ageing, we forecast values of the dependency ratio (that is, the ratio of people over 65 to working people) in 2050 that are between 6% (UK) and 40% (Japan) higher than official forecasts.

Sex acts, sex partners, and sex budgets: implications for risk factor analysis and estimation of HIV transmission probabilities.

Many epidemiological studies have identified the number of sex partners as a risk factor for the acquisition of HIV, but few studies have identified the number of sex acts as a risk factor. The seeming lack of importance of the number of sex acts as a risk factor has yet to be explained. In this report we conduct an exploratory data analysis to evaluate the relationship between the number of sex acts and the number of sex partners for heterosexuals. Our results indicate that it may be most appropriate to view sexual activity within a sex budget and resource allocation framework. We use the results (a) to suggest an explanation for why the results from some of the risk factor analysis studies have identified a per partnership but not a per act risk, and (b) to assess the implications of the relationship for the estimation of heterosexual transmission probabilities for HIV.

A new parallel plate dialyser. II. Description of design and in vitro performance.

Using a high efficiency membrane support pattern, described in the previous paper, a prototype of a new parallel plate dialyser has been developed. The new dialyser is designed in such a way that the number of components is reduced to one item per blood layer and the membrane is folded as a continuum. This permits a semiautomatic assembly of the unit, which reduces production costs. Furthermore this technique facilitates aseptic handling of the item. The in vitro performance has been tested and it compares favorably with commercially available disposable parallel plate dialysers.

A new parallel plate dialyser. I. Development and testing of membrane support.

The pattern of membrane support in the dialysate flow path of a dialyser is one of the most important parameters for high utlization of the membrane-area. 27 different injection moulded membrane support patterns were designed to approximate a pattern with the best overall properties. Only 15 of the patterns had acceptable properties in regard to 1) efficiency, 2) compliance, 3) flow resistance, 4) membrane rupture level, and 5) air retention at low flow values. A pattern with parallel interrupted ridges perpendicular to the direction of dialysate flow showed the best overall results although differences were marginal between the best patterns. The chosen support pattern was approximately 35% better in chloride clearance at low dialysate flow, and approximately 200% better at high flows than the conventional Kiil pattern.