Influence of light exposure during early life on the age of onset of bipolar disorder

Background: Environmental conditions early in life may imprint the circadian system and influence response to environmental signals later in life. We previously determined that a large springtime increase in solar insolation at the onset location was associated with a younger age of onset of bipolar disorder, especially with a family history of mood disorders. This study investigated whether the hours of daylight at the birth location affected this association. Methods: Data collected previously at 36 collection sites from 23 countries were available for 3896 patients with bipolar I disorder, born between latitudes of 1.4N and 70.7N, and 1.2S and 41.3S. Hours of daylight variables for the birth location were added to a base model to assess the relation between the age of onset and solar insolation. Results: More hours of daylight at the birth location during early life was associated with an older age of onset, suggesting reduced vulnerability to the future circadian challenge of the springtime increase in solar insolation at the onset location. Addition of the minimum of the average monthly hours of daylight during the first 3 months of life improved the base model, with a significant positive relationship to age of onset. Coefficients for all other variables remained stable, significant and consistent with the base model. Conclusions: Light exposure during early life may have important consequences for those who are susceptible to bipolar disorder, especially at latitudes with little natural light in winter. This study indirectly supports the concept that early life exposure to light may affect the long term adaptability to respond to a circadian challenge later in life.

Dietary habits are major determinants of the plasma antioxidant status in healthy elderly subjects

Previous studies indicate that regular consumption of a diet rich in fruits and vegetables is associated with a lower risk for age-related diseases. The aim of the present study was to evaluate whether the often-reported age-related decrease of plasma antioxidants in man depends on differences in dietary intake or on other age- and gender-related factors. In this observational case-control study, thirty-nine community-dwelling healthy subjects aged 65 years and older consuming high intakes of fruits and vegetables daily (HI) and forty-eight healthy subjects aged 65 and older consuming low intakes of fruit and vegetables daily (LI) were enrolled. Plasma levels of retinol, tocopherols, carotenoids and malondialdehyde (MDA) as well as content of protein carbonyls in Ig G were measured. Plasma levels of retinol, tocopherols and carotenoids were significantly higher in group HI than in group LI subjects independent of age and gender. MDA levels were inversely correlated with vitamin A and α-carotene. Protein carbonyls were inversely correlated with γ-tocopherol. In the elderly, a higher daily intake of fruits and vegetables is associated with an improved antioxidant status in comparison to subjects consuming diets poor in fruits and vegetables. Modification of nutritional habits among other lifestyle changes should be encouraged to lower prevalence of disease risk factors in later life. © The Authors 2005.

Could lichens grow on Mars?

Lichens meet some but not all of the criteria that must be fulfilled by inhabitants of Mars. They could withstand many aspects of the hostile environment especially if they live within the rocks as they do in the dry valleys of Antarctica. Lichens, however, are dual organisms and we have to presuppose the successful establishment of a variety of microorganisms on Mars and especially algae and fungi. To date, the evidence for the existence of microorganisms in Martian meteorites is controversial and there is no conclusive evidence of present life on the surface. In addition, if endolithic lichens have evolved on Mars and are alive today they would be subjected to a considerably more hostile environment than the extreme environments on Earth, which are regarded as at the limit of tolerance of present day lichens. The lack of liquid water over most of the surface and the problem of obtaining sufficient nitrogen resources are particular problems for Martian lichens. Further landings on Mars, scheduled for 2005 and future missions are likely to increase substantially our knowledge of the Martian surface and the possibilities for life by attempting to bring back samples of rock and minerals. In addition, the use of techniques such as Laser Raman technology and the development of gas chromatographic methods for use in space increase the probability that an answer to the question of whether lichens have existed on Mars will be obtained in the near future.

Ecological studies on:(a) the use of colonisation samplers in relation to biological surveillance of river water quality (b) the requirements of freshwater gastropoda

Some of the factors affecting colonisation of a colonisation sampler, the Standard Aufwuchs Unit (S. Auf. U.) were investigated, namely immersion period, whether anchored on the bottom or suspended, and the influence of riffles. It was concluded that a four-week immersion period was best. S. Auf. U. anchored on the bottom collected both more taxa and individuals than suspended ones. Fewer taxa but more individuals colonised S. Auf. U. in the potamon zone compared to the rhithron zone with a consequent reduction in the values of pollution indexes and diversity. It was concluded that a completely different scoring system was necessary for lowland rivers. Macroinvertebrates colonising S. Auf. U. in simulated streams, lowland rivers and the R. Churnet reflected water quality. A variety of pollution and diversity indexes were applied to results from lowland river sites. Instead of these, it was recommended that an abbreviated species - relative abundance list be used to summarise biological data for use in lowland river surveillance. An intensive study of gastropod populations was made in simulated streams. Lynnaea peregra increased in abundance whereas Potamopyrgas jenkinsi decreased with increasing sewage effluent concentration. No clear-cut differences in reproduction were observed. The presence/absence of eight gastropod taxa was compared with concentrations of various pollutants in lowland rivers. On the basis of all field work it appeared that ammonia, nitrite, copper and zinc were the toxicants most likely to be detrimental to gastropods and that P. jenkinsi and Theodoxus fluviatilis were the least tolerant taxa. 96h acute toxicity tests of P. jenkinsi using ammonia and copper were carried out in a flow-through system after a variety of static range finding tests. P. jenkinsi was intolerant to both toxicants compared to reports on other taxa and the results suggested that these toxicants would affect distribution of this species in the field.

The impact of architecture on the performance of artificial neural networks

A number of researchers have investigated the impact of network architecture on the performance of artificial neural networks. Particular attention has been paid to the impact on the performance of the multi-layer perceptron of architectural issues, and the use of various strategies to attain an optimal network structure. However, there are still perceived limitations with the multi-layer perceptron and networks that employ a different architecture to the multi-layer perceptron have gained in popularity in recent years, particularly, networks that implement a more localised solution, where the solution in one area of the problem space does not impact, or has a minimal impact, on other areas of the space. In this study, we discuss the major architectural issues affecting the performance of a multi-layer perceptron, before moving on to examine in detail the performance of a new localised network, namely the bumptree. The work presented here examines the impact on the performance of artificial neural networks of employing alternative networks to the long established multi-layer perceptron. In particular, networks that impose a solution where the impact of each parameter in the final network architecture has a localised impact on the problem space being modelled are examined. The alternatives examined are the radial basis function and bumptree neural networks, and the impact of architectural issues on the performance of these networks is examined. Particular attention is paid to the bumptree, with new techniques for both developing the bumptree structure and employing this structure to classify patterns being examined.

Beyond power:unbridging Foucault and Weber

Today, very few would doubt that there are plenty of reasons to liken Weber’s and Foucault’s theories of power. Nevertheless, their respective works have divergent ethical and ontological preoccupations which should be reconsidered. This paper explores Foucault’s account of a historical episode in Discipline and Punish and Weber’s theory of life spheres, uncovering evidence that there is a need to reassess the conceptual bridges which have been built so far. The exploration reveals a radical difference between a monological theory of power (Foucault) and a multidimensional approach to power (Weber). Yet by unbridging the two thinkers and focusing on other aspects of their theories along with their ideas about power, we also find that alternative links between the two frameworks may offer a more promising critical theory.

A study of fatigue failure in vulcanized rubber

Some aspects of fatigue failure in rubbers have been examined. Scanning electron micrographs of the surface exposed by the failure confirm the incremental, crack-propagation nature, of the fatigue process. Many other features of the failure surface have been identified and related to this process. The complicating effect of a reinforcing filler has also been investigated. The fatigue resistance of rubber test-pieces deformed in simple tension was measured as a function of frequency and temperature. This showed that an increase in frequency was equivalent to a decrease in temperature; for an amorphous unfilled rubber the time and temperature effects of crystallisation and fillers on the validity of this transformation is considered. This transformation indicates that hysteresis plays an important part in the fatigue process. Torsional pendulum measurements were used to demonstrate the dependence of the fatigue life on the mechanical damping. An apparatus was developed to measure the hysteresial energy loss directly at deformations, rates of deformation and temperatures consistent with a typical fatigue test. Measurements made with this apparatus are compared with fatigue values and a quantitative relationship is suggested describing fatigue, in terms of the energy lost per unit energy input in a cycle of a fatigue test.

Estimating direct and indirect effects of foreign direct investment on firm productivity in the presence of interactions between firms

We implement a method to estimate the direct effects of foreign-ownership on foreign firms' productivity and the indirect effects (or spillovers) from the presence of foreign-owned firms on other foreign and domestic firms' productivity in a unifying framework, taking interactions between firms into account. To do so, we relax a fundamental assumption made in empirical studies examining a direct causal effect of foreign ownership on firm productivity, namely that of no interactions between firms. Based on our approach, we are able to combine direct and indirect effects of foreign ownership and calculate the total effect of foreign firms on local productivity. Our results show that all these effects vary with the level of foreign presence within a cluster, an important finding for the academic literature and policy debate on the benefits of attracting foreign owned firms.