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Parameters Relevant (parameter + relevant)
Selected AbstractsMATING DENSITY AND THE STRENGTH OF SEXUAL SELECTION AGAINST DELETERIOUS ALLELES IN DROSOPHILA MELANOGASTEREVOLUTION, Issue 4 2008Nathaniel P. Sharp Deleterious alleles constantly enter populations via mutation. Their presence reduces mean fitness and may threaten population persistence. It has been suggested that sexual selection may be an efficient way by which deleterious alleles are removed from populations but there is little direct experimental evidence. Because of its potential role in mutational meltdowns, there is particular interest in whether the strength of sexual selection changes with density. For each of eight visible markers in Drosophila melanogaster we have compared the strength of sexual selection at two densities. We find evidence of strong sexual selection against most but not all of these alleles. There is no evidence that sexual selection tends to be stronger (or weaker) at high density relative to low density. In addition, we also measure the effects of these mutations on two key parameters relevant to population productivity,juvenile viability and female fecundity. In most cases, sexual selection is as strong or stronger than these other forms of selection. [source] ESTIMATING A GEOGRAPHICALLY EXPLICIT MODEL OF POPULATION DIVERGENCEEVOLUTION, Issue 3 2007L. Lacey Knowles Patterns of genetic variation can provide valuable insights for deciphering the relative roles of different evolutionary processes in species differentiation. However, population-genetic models for studying divergence in geographically structured species are generally lacking. Since these are the biogeographic settings where genetic drift is expected to predominate, not only are population-genetic tests of hypotheses in geographically structured species constrained, but generalizations about the evolutionary processes that promote species divergence may also be potentially biased. Here we estimate a population-divergence model in montane grasshoppers from the sky islands of the Rocky Mountains. Because this region was directly impacted by Pleistocene glaciation, both the displacement into glacial refugia and recolonization of montane habitats may contribute to differentiation. Building on the tradition of using information from the genealogical relationships of alleles to infer the geography of divergence, here the additional consideration of the process of gene-lineage sorting is used to obtain a quantitative estimate of population relationships and historical associations (i.e., a population tree) from the gene trees of five anonymous nuclear loci and one mitochondrial locus in the broadly distributed species Melanoplus oregonensis. Three different approaches are used to estimate a model of population divergence; this comparison allows us to evaluate specific methodological assumptions that influence the estimated history of divergence. A model of population divergence was identified that significantly fits the data better compared to the other approaches, based on per-site likelihood scores of the multiple loci, and that provides clues about how divergence proceeded in M. oregonensis during the dynamic Pleistocene. Unlike the approaches that either considered only the most recent coalescence (i.e., information from a single individual per population) or did not consider the pattern of coalescence in the gene genealogies, the population-divergence model that best fits the data was estimated by considering the pattern of gene lineage coalescence across multiple individuals, as well as loci. These results indicate that sampling of multiple individuals per population is critical to obtaining an accurate estimate of the history of divergence so that the signal of common ancestry can be separated from the confounding influence of gene flow,even though estimates suggest that gene flow is not a predominant factor structuring patterns of genetic variation across these sky island populations. They also suggest that the gene genealogies contain information about population relationships, despite the lack of complete sorting of gene lineages. What emerges from the analyses is a model of population divergence that incorporates both contemporary distributions and historical associations, and shows a latitudinal and regional structuring of populations reminiscent of population displacements into multiple glacial refugia. Because the population-divergence model itself is built upon the specific events shaping the history of M. oregonensis, it provides a framework for estimating additional population-genetic parameters relevant to understanding the processes governing differentiation in geographically structured species and avoids the problems of relying on overly simplified and inaccurate divergence models. The utility of these approaches, as well as the caveats and future improvements, for estimating population relationships and historical associations relevant to genetic analyses of geographically structured species are discussed. [source] Axial Rotation of the Lower Human Spine by Rhythmic Torques Automatically Generated at the Resonant FrequencyEXPERIMENTAL PHYSIOLOGY, Issue 3 2003E. Geoffrey Walsh Subjects sat on a ,Balans' chair supported by the shaft of a large torque generator. The lower but not the upper part of the body was free to make to/fro movements maintained by feeding back a modified velocity signal to the generator. The stiffness could be increased by the use of a position signal. Using the equations for a torsion pendulum the good linearity observed in relationship to the applied forces allowed stiffness, inertia, damping, critical damping and the damping factor to be determined in absolute terms. The method enables parameters relevant to back function and problems to be evaluated. Eleven adults acted as subjects. [source] Use of pharmacokinetics in the coagulation factor treatment of patients with haemophiliaHAEMOPHILIA, Issue 6 2005A. D. Shapiro Summary., Dosing decisions for replacement coagulation factors in patients with haemophilia should be made on an individual patient basis, with the required dose dependent on factors including the clinical situation, the severity of the factor deficiency, and the location and extent of bleeding. Moreover, there is considerable variability in the pharmacokinetics of coagulation products that needs to be considered; in particular, with both factor (F) IX and FVIII products, there is considerable inter-patient variability in in vivo recovery and terminal half-life values. In the present report, we provide a practical guide to calculating and applying pharmacokinetic parameters relevant to the optimal dosing of coagulation products. We discuss the conduct of a pharmacokinetic study in an individual patient, how to calculate pharmacokinetic values from raw data and clinical situations where an individual pharmacokinetic study is helpful. We highlight the importance of considering an individual pharmacokinetic study in all patients starting a new coagulation product. [source] Cell resilience in species life spans: a link to inflammation?AGING CELL, Issue 4 2010Caleb E. Finch Summary Species differences in life span have been attributed to cellular survival during various stressors, designated here as ,cell resilience'. In primary fibroblast cultures, cell resilience during exposure to free radicals, hypoglycemia, hyperthermia, and various toxins has shown generally consistent correlations with the species characteristic life spans of birds and mammals. However, the mechanistic links of cell resilience in fibroblast cultures to different species life spans are poorly understood. We propose that certain experimental stressors are relevant to somatic damage in vivo during inflammatory responses of innate immunity, particularly, resistance to reactive oxygen species (ROS), low glucose, and hyperthermia. According to this hypothesis, somatic cell resilience determines species differences in longevity during repeated infections and traumatic injuries in the natural environment. Infections and injury expose local fibroblasts and other cells to ROS generated by macrophages and to local temperature elevations. Systemically, acute phase immune reactions cause hypoglycemia and hyperthermia. We propose that cell resilience to somatic stressors incurred in inflammation is important in the evolution of longevity and that longer-lived species are specifically more resistant to immune-related stressors. This hypothesis further specifies Kirkwood's disposable soma theory. We suggest expanding the battery of stressors and markers used for comparative studies to additional cell types and additional parameters relevant to host defense and to their ecological specificities. [source] MODELING HEAT EFFICIENCY, FLOW AND SCALE-UP IN THE COROTATING DISC SCRAPED SURFACE HEAT EXCHANGERJOURNAL OF FOOD PROCESS ENGINEERING, Issue 4 2002ALAN FRIIS ABSTRACT A comparison of two different scale corotating disc scraped surface heat exchangers (CDHE) was performed experimentally. The findings were compared to predictions from a finite element model. We find that the model predicts well the flow pattern of the two CDHE's investigated. The heat transfer performance predicted by the model agrees well with experimental observations for the laboratory scale CDHE whereas the overall heat transfer in the scaled-up version was not in equally good agreement. The lack of the model to predict the heat transfer performance in scale-up leads us to identify the key dimensionless parameters relevant for scale-up. [source] Erythropoietin improves neurodevelopmental outcome of extremely preterm infantsANNALS OF NEUROLOGY, Issue 5 2010Achim-Peter Neubauer MD Objective Erythropoietin has been reported to possess neuroprotective properties in animal studies. No previous studies have investigated the neurodevelopmental outcome of extremely low birth weight (ELBW) infants treated with recombinant human erythropoietin (rEpo) and evaluated it at school age. Methods Of 200 ELBW infants treated from 1993 to 1998, 171 (86%) survived, and 148 (87%) were followed up to the age of 10 to 13 years. The neurodevelopmental and school outcome of the ELBW infants receiving rEpo treatment for stimulation of erythropoiesis in the first weeks of life (n = 89) was compared to that of untreated children (n = 57). To test for a neuroprotective effect of erythropoietin therapy, analyses of variance (ANOVAs) were conducted with erythropoietin treatment and intraventricular hemorrhage (IVH) as independent variables and Hamburg-Wechsler Intelligence Test for Children-III (HAWIK-III) intelligence quotient (IQ) scores as dependent variables. Results The rEpo group scored significantly better than untreated children in the overall developmental assessment (55% vs 39% normally developed, p < 0.05) as well as in the psychological examination (mean composite HAWIK-III IQ score, 90.8 vs 81.3, p < 0.005). The results of ANOVAs show that these differences were ascribable to children with IVH. Whereas those children with IVH treated with rEpo scored significantly better than untreated children (52% vs 6% normally developed, composite HAWIK-III IQ score, 90.3 vs 67.0), treated and untreated children without IVH did not differ in their outcome. The treatment and control groups were comparable in perinatal parameters relevant to prognosis. Interpretation The results of our observational study confirm the hypothesis of a neuroprotective effect of rEpo in ELBW infants with IVH. This offers a promising preventative therapeutic option for the treatment of these high-risk infants. ANN NEUROL 2010;67:657,666 [source] Satellite radar observation of tropical peat swamp forest as a tool for hydrological modelling and environmental protectionAQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 3 2007Dirk H. Hoekman Abstract 1.Tropical peat swamp forests may contain as much as 20% of the global soil carbon stock. They are threatened by large-scale deforestation and canal drainage. Oxidation and forest fire cause enormous carbon emissions. Most remaining areas are located in Indonesia. These are becoming increasingly important for maintaining biodiversity. 2.Time series of historical JERS-1 SAR data reveal the extent and nature of recent disturbances, such as those caused by excess drainage and severe ENSO events. Examples are given for a number of peat swamp forest areas in Sumatra and Borneo. 3.Peat swamp hydrology is studied along a 23-km transect, which crosses a complete peat dome. First results show the relevance of surface runoff and peat soil roughness in the description of flooding events, and have been used to produce an improved hydrological description. 4.Since the dynamics of flooding events can potentially be observed by the ALOS PALSAR instrument (yet to be launched), this new hydrological model can be used to infer parameters relevant for detection of ecosystem disturbance and evaluation of restoration efforts. Copyright © 2007 John Wiley & Sons, Ltd. [source] | |||||||||||||