Determination of rubidium in human serum

Field desorption mass spectrometry (FD-MS) combined with stable isotope dilution has been used to determine rubidium concentrations from human serum. Samples obtained from 110 healthy volunteers (50 males, 60 females) were examined. The rubidium concentrations found varied from 0.96 to 3.56 mumoles/l, the average value being 1.96 mumoles/l. The precision of the measurements within a batch was 0.8%. The time for 1 analysis, including sample preparation is about 30 min, the total sample consumption is 100-200 mul. The corresponding potassium concentrations were also determined from all these serum samples; a weak trend towards higher potassium levels with increasing rubidium concentration is found.     

Multi-model approaches to phylogenetics: Implications for idealization

Phylogenetic models traditionally represent the history of life as having a strictly-branching tree structure. However, it is becoming increasingly clear that the history of life is often not strictly-branching; lateral gene transfer, endosymbiosis, and hybridization, for example, can all produce lateral branching events. There is thus motivation to allow phylogenetic models to have a reticulate structure. One proposal involves the reconciliation of genealogical discordance. Briefly, this method uses patterns of disagreement – discordance – between trees of different genes to add lateral branching events to phylogenetic trees of taxa, and to estimate the most likely cause of these events. I use this practice to argue for: (1) a need for expanded accounts of multiple-models idealization, (2) a distinction between automatic and manual de-idealization, and (3) recognition that idealization may serve the meso-level aims of science in a different way than hitherto acknowledged.     

Abnormal development of cultured rat embryos in rat and human sera prepared after vitamin A ingestion

Summary Human and rat sera were assayed for teratogenic activity using a whole rat embryo culture technique. Sera prepared from blood withdrawn 1–5 h after the ingestion of vitamin A capsules caused developmental retardation and craniofacial abnormalities. Control sera permitted normal growth and differentiation.Financial support for this project was provided by Department of Energy contract EVO 3139 (Office of Health and Environmental Research), USA (Scientific contribution 940, Storrs Agricultural Experiment Station), and by the Medical Research Council, U.K.     

100 years of radiobiology: Implications for biomedicine and future perspectives

The development of radiobiology from the very early detection of the biological action of X-rays to the knowledge of today is described in sections on radiation chemistry and biochemistry, mutation and cancer induction, and embryonic damage, as well as the dependence of radiation response on radiation quality and temporal dose distribution (repair) and the interaction with other factors. For medicine radiobiology serves as a basis for radiotherapy and radiological protection. The effect of very low doses, and their possible biopositive effect (hormesis and adaptive response), is also discussed, as are the health hazard of radon, health risks after the Chernobyl accident, and space radiobiology. The radiobiology of the future will be concerned with biomolecular and genetic implications, problems of damage and repair, and connected problems like hormesis.     

Selenium toxicity: Effect of fluoride

Zusammenfassung Wenn junge Ratten gleichzeitig Selen und Fluor erhalten, sind die toxischen Eigenschaften von Selen nicht grösser, als in den Kontrollen, die nur Selenium erhielten. Dieses Resultat steht im Widerspruch zu früheren Feststellungen.     

Research on scientific journals: Implications for editors and authors

A review of editorial policies of leading journals and of research relevant to scientific journals revealed conflicts between‘science’and‘scientists’. Owing to these conflicts, papers are often weak on objectivity and replicability. Furthermore, papers often fall short on importance, competence, intelligibility, or efficiency. Suggestions were made for editorial policies such as: (1) structured guidelines for referees, (2) open peer review, (3) blind reviews, and (4) full disclosure of data and method. Of major importance, an author's‘Note to Referees’(describing the hypotheses and design, but not the results) was suggested to improve the objectivity of the ratings of importance and competence. Also, recommendations are made to authors for improving contributions to science (such as the use of multiple hypotheses) and for promoting their careers (such as using complex methods and obtuse writing).     

Lithium and rubidium: effects on the rhythmic swimming movement of jellyfish (Aurelia aurita).

The effects of adding LiCl, RbCl, KCl or NaCl to sea water at concentrations up to 30 mmoles/1 on the frequency of contraction of jellyfish (Aurelia aurita) suggest that studies on phylogenetically low animals with relatively simple nervous systems may be of use to determine mechanisms of action of lithium and rudidium on movements.     

Lithium and rubidium: Effects on the rhythmic swimming movement of jellyfish (Aurelia aurita)

Summary The effects of adding LiCl, RbCl, KCl or NaCl to sea water at concentrations up to 30 mmoles/1 on the frequency of contraction of jellyfish (Aurelia aurita) suggest that studies on phylogenetically low animals with relatively simple nervous systems may be of use to determine mechanisms of action of lithium and rubidium on movements.Acknowledgments. We thank P. Carl Petersens Fund and the Danish Medical Research Council for financial support and Henning Petersen for permission to carry out our experiments at Mols Laboratory.     

Costs and benefits of mycorrhizas: Implications for functioning under natural conditions

Summary It is paradoxical that most plants under natural conditions are infected with vesicular-arbuscular mycorrhizal fungi, yet that it is often difficult to demonstrate that infected plants receive any benefit from the association. The costs and benefits of infection are analysed and a hypothesis formulated that infection only yields benefits at times during the life cycle when P demand by the plant exceeds the capacity of the root system. A simulation model is described that suggests that infection density should be more or less constant below a threshold value of root P uptake rate, but that above this value roots should be non-mycorrhizal. More extensive study of mycorrhizas under field conditions is needed to test such predictions.     

Implications of ancient DNA for phylogenetic studies

The utility of DNA sequence characters from fossil specimens is examined from a phylogenetic perspective. Four ways that fossil characters can alter phylogenetic hypotheses are discussed. Two empirical examples and a third hypothetical example concerning amber-preserved insects are presented to illustrate these phenomena. Fossil DNA sequences as characters will be affected by the problem of missing data and missing taxa. In general, cladogram accuracy will be more greatly affected by missing taxa and cladogram resolution will be affected more acutely by missing data. Due to these points, an examination of the importance of the phylogenetic question being addressed, the utility of the fossil DNA sequences and the rarity of the fossil should be considered before damage of a fossil is undertaken.     

The dynamic and stochastic instability of betas: Implications for forecasting stock returns

The purpose of this paper is to simultaneously investigate several important issues that feature the dynamic and stochastic behavior of beta coefficients for individual stocks and affect the forecasting of stock returns. The issues include randomness, nonstantionarity, and shifts in the mean and variance parameters of the beta coefficient, and are addressed within the framework of variable-mean-response (VMR) random coefficients models in which the problem of heteroscedasticity is present. Estimation is done using a four-step generalized least squares method. The hypotheses concerning randomness and nonstationarity of betas are tested. The time paths, sizes, and marginal rates of mean shifts are determined. The issue of variance shift is examined on the basis of five special tests, called T*, B, S', G and W. Then the impacts of the dynamic and stochastic instability on the estimation of betas is tested by a nonparametric procedure. Finally, the VMR models' ability of forecasting stock returns is evaluated against the standard capital asset pricing model. The empirical findings shed new light on the continuing debate as to whether the beta coefficient is random and nonstationary and have important implications for modeling and forecasting the measurement of performance and the determination of stock returns.     

Seven components of judgmental forecasting skill: Implications for research and the improvement of forecasts

A decomposition of the Brier skill score shows that the performance of judgmental forecasts depends on seven components: environmental predictability, fidelity of the information system, match between environment and forecaster, reliability of information acquisition, reliability of information processing, conditional bias, and unconditional bias. These components provide a framework for research on the forecasting process. Selected literature addressing each component is reviewed, and implications for improving judgmental forecasting are discussed.