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Several Datasets (several + dataset)
Selected AbstractsVARIATION OF SHELL SHAPE IN THE CLONAL SNAIL MELANOIDES TUBERCULATA AND ITS CONSEQUENCES FOR THE INTERPRETATION OF FOSSIL SERIESEVOLUTION, Issue 2 2000Sarah Samadi Abstract., Interpreting paleontological data is difficult because the genetic nature of observed morphological variation is generally unknown. Indeed, it is hardly possible to distinguish among several sources of morphological variation including phenotypic plasticity, sexual dimorphism, within-species genetic variation or differences among species. This can be addressed using fossil organisms with recent representatives. The freshwater snail Melanoides tuberculata ranks in this category. A fossil series of this and other species have been studied in the Turkana Basin (Kenya) and is presented as one of the best examples illustrating the punctuated pattern of evolution by the tenants of this theory. Melanoides tuberculata today occupies most of the tropics. We studied variation of shell shape in natural populations of this parthenogenetic snail using Raup's model of shell coiling. We considered different sources of variation on estimates of three relevant parameters of Raup's model: (1) variation in shell shape was detected among clones, and had both genetic and environmental bases; (2) sexual dimorphism, in those clones in which males occur, appeared as an additional source of shell variation; and (3) ecophenotypic variation was detected by comparing samples from different sites and years within two clones. We then tested the performance of discriminant function analyses, a classical tool in paleontological studies, using several datasets. Although the three sources of variation cited above contributed significantly to the observed morphological variance, they could not be detected without a priori knowledge of the biological entities studied. However, it was possible to distinguish between M. tuberculata and a related thiarid species using these analyses. Overall, this suggests that the tools classically used in paleontological studies are poorly efficient when distinguishing between important sources of within-species variation. Our study also gives some empirical bases to the doubts cast on the interpretation of the molluscan series of the Turkana Basin. [source] A sparse marker extension tree algorithm for selecting the best set of haplotype tagging single nucleotide polymorphismsGENETIC EPIDEMIOLOGY, Issue 4 2005Ke Hao Abstract Single nucleotide polymorphisms (SNPs) play a central role in the identification of susceptibility genes for common diseases. Recent empirical studies on human genome have revealed block-like structures, and each block contains a set of haplotype tagging SNPs (htSNPs) that capture a large fraction of the haplotype diversity. Herein, we present an innovative sparse marker extension tree (SMET) algorithm to select optimal htSNP set(s). SMET reduces the search space considerably (compared to full enumeration strategy), and therefore improves computing efficiency. We tested this algorithm on several datasets at three different genomic scales: (1) gene-wide (NOS3, CRP, IL6 PPARA, and TNF), (2) region-wide (a Whitehead Institute inflammatory bowel disease dataset and a UK Graves' disease dataset), and (3) chromosome-wide (chromosome 22) levels. SMET offers geneticists with greater flexibilities in SNP tagging than lossless methods with adjustable haplotype diversity coverage (,). In simulation studies, we found that (1) an initial sample size of 50 individuals (100 chromosomes) or more is needed for htSNP selection; (2) the SNP tagging strategy is considerably more efficient when the underlying block structure is taken into account; and (3) htSNP sets at 80,90% , are more cost-effective than the lossless sets in term of relative power, relative risk ratio estimation, and genotyping efforts. Our study suggests that the novel SMET algorithm is a valuable tool for association tests. Genet. Epidemiol. 29:336,352, 2005. © 2005 Wiley-Liss, Inc. [source] Measuring disability in older adults: The International Classification System of Functioning, Disability and Health (ICF) frameworkGERIATRICS & GERONTOLOGY INTERNATIONAL, Issue 1 2008W Jack Rejeski Background: Despite the importance of disability to geriatric medicine, no large scale study has validated the activity and participation domains of the International Classification System of Functioning, Disability, and Health (ICF) in older adults. The current project was designed to conduct such as analysis, and then to examine the psychometric properties of a measure that is based on this conceptual structure. Methods: This was an archival analysis of older adults (n = 1388) who had participated in studies within our Claude D Pepper Older Americans Independence Center. Assessments included demographics and chronic disease status, a 23-item Pepper Assessment Tool for Disability (PAT-D) and 6-min walk performance. Results: Analysis of the PAT-D produced a three-factor structure that was consistent across several datasets: activities of daily living disability, mobility disability and instrumental activities of daily living disability. The first two factors are activities in the ICF framework, whereas the final factor falls into the participation domain. All factors had acceptable internal consistency reliability (>0.70) and test,retest (>0.70) reliability coefficients. Fast walkers self-reported better function on the PAT-D scales than slow walkers: effect sizes ranged from moderate to large (0.41,0.95); individuals with cardiovascular disease had poorer scores on all scales than those free of cardiovascular disease. In an 18-month randomized clinical trial, individuals who received a lifestyle intervention for weight loss had greater improvements in their mobility disability scores than those in a control condition. Conclusion: The ICF is a useful model for conceptualizing disability in aging research, and the PAT-D has acceptable psychometric properties as a measure for use in clinical research. [source] Role of land cover changes for atmospheric CO2 increase and climate change during the last 150 yearsGLOBAL CHANGE BIOLOGY, Issue 8 2004Victor Brovkin Abstract We assess the role of changing natural (volcanic, aerosol, insolation) and anthropogenic (CO2 emissions, land cover) forcings on the global climate system over the last 150 years using an earth system model of intermediate complexity, CLIMBER-2. We apply several datasets of historical land-use reconstructions: the cropland dataset by Ramankutty & Foley (1999) (R&F), the HYDE land cover dataset of Klein Goldewijk (2001), and the land-use emissions data from Houghton & Hackler (2002). Comparison between the simulated and observed temporal evolution of atmospheric CO2 and ,13CO2 are used to evaluate these datasets. To check model uncertainty, CLIMBER-2 was coupled to the more complex Lund,Potsdam,Jena (LPJ) dynamic global vegetation model. In simulation with R&F dataset, biogeophysical mechanisms due to land cover changes tend to decrease global air temperature by 0.26°C, while biogeochemical mechanisms act to warm the climate by 0.18°C. The net effect on climate is negligible on a global scale, but pronounced over the land in the temperate and high northern latitudes where a cooling due to an increase in land surface albedo offsets the warming due to land-use CO2 emissions. Land cover changes led to estimated increases in atmospheric CO2 of between 22 and 43 ppmv. Over the entire period 1800,2000, simulated ,13CO2 with HYDE compares most favourably with ice core during 1850,1950 and Cape Grim data, indicating preference of earlier land clearance in HYDE over R&F. In relative terms, land cover forcing corresponds to 25,49% of the observed growth in atmospheric CO2. This contribution declined from 36,60% during 1850,1960 to 4,35% during 1960,2000. CLIMBER-2-LPJ simulates the land cover contribution to atmospheric CO2 growth to decrease from 68% during 1900,1960 to 12% in the 1980s. Overall, our simulations show a decline in the relative role of land cover changes for atmospheric CO2 increase during the last 150 years. [source] | ||||||||||