Home About us Contact
|
Home About us Contact | ||
|
|
||
Additional Populations (additional + population)
Selected AbstractsPositron lifetime evolution during room temperature ageing in Al-Zn-Mg-(Cu)PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 11 2009A. Dupasquier Abstract The effect on the formation of vacancy-solute clusters by the addition of small percentages of Cu to Al-Zn-Mg has been studied by positron annihilation lifetime spectroscopy. The results document the ability of Cu to increase the number of vacancies retained after quenching, by forming an additional population of vacancy-solute clusters in competition with pure Zn clusters. It has also been shown that Cu accelerates the decomposition of the alloy at 150°, thereby leaving a reduced supersaturation of the matrix after an early interruption. An unexpected result is that the curve positron lifetime vs, ageing time at RT displays the symptoms of a change in the nature of the coherent aggregates that occurs in about 10 hours of RT exposure. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Morphological changes in the shape of the non-pathological bony knee joint with age: a morphometric analysis of the distal femur and proximal tibia in three populations of known age at deathINTERNATIONAL JOURNAL OF OSTEOARCHAEOLOGY, Issue 4 2008S. D. Stevens Abstract This study examines possible morphological variation in the knee joint of Homo sapiens with increasing age in ostensively healthy and non-pathological distal femora and proximal tibiae. Throughout the lifetime of each individual, the hard tissue of the knee undergoes considerable remodelling as a response to biomechanical stresses, changes in bone microarchitecture and reduction of bone mineral content as a concomitant of ageing. The knee is also subject to greater levels of degenerative joint disease than any other joint. If death occurs whilst such diseases are in the earliest stages, initial bone changes may not be visually obvious in museum specimens. If such specimens are used for comparative analyses, it is hypothesised that changes might render it problematic if all ages are conglomerated into discrete samples. This study therefore investigates the degree to which the distal femur and proximal tibia change shape during ageing and, if changes are present, whether they are expressed similarly in males and females. It also examines whether changes are of greater magnitude than those morphological differences which might exist between populations. In an example population of African-Americans, results indicate that there is a statistically significant difference in shape between age groups and those differences become progressively greater between the youngest and oldest adults. Results also show that although morphological variation caused by ageing is apparent, those shape differences attributable to sexual dimorphism are more powerful. When two additional populations are analysed jointly with the African-Americans (Caucasian Americans and the European Spitalfields sample), results indicate that inter-population shape differences are considerably greater than differences caused by increasing age. Results imply that it is justifiable to combine specimens of all ages into discrete samples for comparative purposes. Copyright © 2007 John Wiley & Sons, Ltd. [source] Modeling distributions of disjunct populations of the Sierra Madre SparrowJOURNAL OF FIELD ORNITHOLOGY, Issue 3 2008Octavio R. Rojas-Soto ABSTRACT Sierra Madre Sparrows (Xenospiza baileyi) are among the least known of all bird species in Mexico. Recent surveys have discovered previously unknown populations and the current known distribution of Sierra Madre Sparrows consists of two populations separated by >800 km. We used available distributional information to develop ecological niche models that (1) predict much of the distribution potential of the species, (2) establish that the broad disjunction separating the two populations has ecological correlates that appear to be important to the distributional of these sparrows, and (3) illustrate the extremely restricted ecological distribution of the species. We used two sets of climatic and topographic variables, with one including all 22 variables available and the second with only six variables that were positively related to quality of distributional models. Although indications of differences between the two sets of populations were found based on the full 22-dimensional environmental dataset, such a highly dimensional analysis is vulnerable to over-fitting; models based on the reduced dataset indicated that the two populations occur in areas with similar ecological conditions. Our models also suggest that southern population of Sierra Madre Sparrows covers most of their potential range in that region. The potential range of the northern population, however, extends beyond known points of occurrence. To clarify the distribution of Sierra Madre Sparrows and evaluate their status and conservation opportunities, detailed searches for additional populations in areas identified by the model are needed. SINOPSIS El gorrión serrano (Xenospiza baileyi) se encuentra entre las especies menos conocidas de México. En un estudio reciente se descubrieron nuevas poblaciones, por lo que la distribución actual de esta ave está conformada por dos meta-poblaciones separadas por más de 800 km. Utilizamos la información disponible sobre su distribución para desarrollar modelos del nicho ecológico que: 1) predigan la mayor parte de la distribución potencial de la especie, 2) establezcan que la amplia separación de las dos poblaciones está correlacionada con condiciones ecológicas que parecen ser importantes para la distribución de la especie y 3) ilustren la extrema restricción ecológica que caracteriza la distribución de la especie. Para generar los modelos, utilizamos dos conjuntos de variables climatológicas y topográficas. Uno con 22 variables y el otro con las seis variables que estaban positivamente correlacionadas con la calidad de los modelos de distribución. Aunque se encontraron indicios de diferencias ecológicas entre las dos poblaciones con base en las 22 variables ambientales estudiadas, el análisis con tantas dimensiones es sensible a un efecto de sobre-ajuste. Los modelos producidos con el subconjunto de seis variables indicaron que las dos poblaciones se encuentran en áreas con condiciones ecológicas similares. Nuestros modelos sugieres que la población del sur ocupa la mayor parte de su área de distribución potencial en la región. No obstante, la distribución potencial de la población del norte es mucho más amplia que su distribución conocida. Es necesario realizar búsquedas minuciosas del gorrión serrano en los sitios identificados por el modelo propuesto para definir adecuadamente su distribución, evaluar su estatus y buscar oportunidades para su conservación. [source] A Comparison of Correlates of DSM-IV Alcohol Abuse or Dependence Among More Than 400 Sons of Alcoholics and ControlsALCOHOLISM, Issue 1 2001M. A. Schuckit Background: Alcohol dependence and abuse are defined as separate disorders. However, relatively few data are available about whether the same characteristics predict both syndromes. Methods: Complete data were available from the 15 year follow-up of 411 men who originally had been evaluated from a university population at about age 20. Both baseline data gathered prospectively and the retrospective ratings in six domains of life functioning were analyzed for their relationship to the development of alcohol abuse or dependence during the follow-up. Results: Baseline characteristics of a family history of substance use disorders, the quantity and frequency of drinking, the history of alcohol-related problems, and the level of response to alcohol all predicted future alcohol abuse or dependence, but only an alcoholic second-degree relative or a first-degree drug-dependent family member differentially predicted dependence. Logistic regression analyses revealed that similar baseline characteristics combined to predict dependence and, separately, abuse. When the domains of functioning during the 15 years were included, positive alcohol expectancies, poor coping mechanisms, low level of social support, and drinking in the environment contributed to both dependence and abuse, although the relationship was stronger for dependence. Conclusions: The predictors and correlates of alcohol abuse and dependence in this group of men were similar. Further research in additional populations and on other drugs is needed to determine if the two syndromes overlap sufficiently to be combined. [source] DNA barcoding Central Asian butterflies: increasing geographical dimension does not significantly reduce the success of species identificationMOLECULAR ECOLOGY RESOURCES, Issue 5 2009VLADIMIR A LUKHTANOV Abstract DNA barcoding employs short, standardized gene regions (5' segment of mitochondrial cytochrome oxidase subunit I for animals) as an internal tag to enable species identification. Prior studies have indicated that it performs this task well, because interspecific variation at cytochrome oxidase subunit I is typically much greater than intraspecific variation. However, most previous studies have focused on local faunas only, and critics have suggested two reasons why barcoding should be less effective in species identification when the geographical coverage is expanded. They suggested that many recently diverged taxa will be excluded from local analyses because they are allopatric. Second, intraspecific variation may be seriously underestimated by local studies, because geographical variation in the barcode region is not considered. In this paper, we analyse how adding a geographical dimension affects barcode resolution, examining 353 butterfly species from Central Asia. Despite predictions, we found that geographically separated and recently diverged allopatric species did not show, on average, less sequence differentiation than recently diverged sympatric taxa. Although expanded geographical coverage did substantially increase intraspecific variation reducing the barcoding gap between species, this did not decrease species identification using neighbour-joining clustering. The inclusion of additional populations increased the number of paraphyletic entities, but did not impede species-level identification, because paraphyletic species were separated from their monophyletic relatives by substantial sequence divergence. Thus, this study demonstrates that DNA barcoding remains an effective identification tool even when taxa are sampled from a large geographical area. [source] Common promoter deletion is associated with 3.9-fold differential transcription of ovine CCR5 and reduced proviral level of ovine progressive pneumonia virusANIMAL GENETICS, Issue 5 2009S. N. White Summary Chemokine (C-C motif) Receptor 5 (CCR5) is a chemokine receptor that regulates immune cell recruitment in inflammation and serves as a coreceptor for human immunodeficiency virus (HIV). A human CCR5 coding deletion (termed delta-32) results in strong resistance to HIV infection, and sequence variants in CCR5 regulatory regions have been implicated in delayed progression to acquired immune deficiency syndrome. Both ovine progressive pneumonia virus (OPPV), also known as maedi-visna, and HIV are macrophage-tropic lentiviruses, have similar genomic structures, and cause lifelong persistent host infection, suggesting CCR5 may have a role in regulating OPPV provirus levels. Therefore, the ovine CCR5 genomic sequence was determined, and sequence variants were obtained from the open reading frame and surrounding regulatory sites. One CCR5 variant contained a 4-base deletion within a binding site for octamer transcription factors in the promoter region. A test for differential transcription from each allele in heterozygous animals showed a 3.9-fold transcription difference (P < 0.0001). OPPV proviral levels were also measured in 351 naturally exposed Rambouillet, Polypay and Columbia sheep. Deletion homozygotes showed reduced OPPV proviral levels among these animals (P < 0.01). The association of this CCR5 promoter deletion with OPPV levels will need to be validated in additional populations before the deletion can be recommended for widespread use in marker-assisted selection. However, because of the large impact on transcription and because CCR5 has roles in inflammation, recruitment of effector cells, and cell-mediated immunity, this deletion may play a role in the control of infections of many diverse pathogens of sheep. [source] Distribution modelling to guide stream fish conservation: an example using the mountain sucker in the Black Hills National Forest, USAAQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 7 2008Daniel C. Dauwalter Abstract 1.Conservation biologists need tools that can utilize existing data to identify areas with the appropriate habitat for species of conservation concern. Regression models that predict suitable habitat from geospatial data are such a tool. Multiple logistic regression models developed from existing geospatial data were used to identify large-scale stream characteristics associated with the occurrence of mountain suckers (Catostomus platyrhynchus), a species of conservation concern, in the Black Hills National Forest, South Dakota and Wyoming, USA. 2.Stream permanence, stream slope, stream order, and elevation interacted in complex ways to influence the occurrence of mountain suckers. Mountain suckers were more likely to be present in perennial streams, and in larger, higher gradient streams at higher elevations but in smaller, lower gradient streams at lower elevations. 3.Applying the logistic regression model to all streams provided a way to identify streams in the Black Hills National Forest most likely to have mountain suckers present. These types of models and predictions can be used to prioritize areas that should be surveyed to locate additional populations, identify stream segments within catchments for population monitoring, aid managers in assessing whether proposed forest management will potentially have impacts on fish populations, and identify streams most suitable for stream rehabilitation and conservation or translocation efforts. 4.When the effect of large brown trout (Salmo trutta) was added to the best model of abiotic factors, it had a negative effect on the occurrence of mountain suckers. Negative effects of brown trout on the mountain sucker suggest that management of recreational trout fisheries needs to be balanced with mountain sucker conservation in the Black Hills. However, more spatially explicit information on brown trout abundance would allow managers to understand where the two species interact and where recreational fisheries need to be balanced with fish conservation. Copyright © 2008 John Wiley & Sons, Ltd. [source] The shared epitope hypothesis in rheumatoid arthritis: Evaluation of alternative classification criteria in a large UK Caucasian cohortARTHRITIS & RHEUMATISM, Issue 5 2008Ann W. Morgan Objective Many classification systems for the HLA,DRB1 allelic association with rheumatoid arthritis (RA) have been reported, but few have been validated in additional populations. We sought to evaluate 3 different DRB1 allele classification systems in a large cohort of Caucasian RA patients and control subjects in the UK. Methods HLA,DRB1 typing was undertaken in 1,325 Caucasian RA patients and 462 healthy Caucasian controls who were residents of the UK. Logistic regression analyses were performed to investigate the different classification systems. Results We confirmed the association between the susceptibility alleles S2 and S3P, as proposed by Tezenas du Montcel, and the presence of RA in UK Caucasians. A significant hierarchy of risk was observed within the S3P allele group. There was no evidence of a significant association between DRB1*1001 and RA. Our data did not support the hypothesis that an isoleucine at position 67 conferred protection against RA, other than in contrast to the susceptibility alleles. However, the presence of an aspartic acid at amino acid 70 did appear to confer some degree of protection. Conclusion We were unable to fully substantiate any of the 3 recent revisions of the shared epitope hypothesis in this large cohort of Caucasian RA patients and control subjects in the UK. This reinforces the importance of evaluating disease susceptibility alleles in different Caucasian populations as well as in other ethnic groups. In particular, it will be important to clarify the precise DRB1 association in a given population before DRB1 genotyping is incorporated into clinical diagnostic or treatment algorithms. [source] | |||||||||||||