Search results for " variability"
showing 10 items of 853 documents
A hierarchical analysis of genetic structure and variability in patchily distributed coexisting Chiastocheta species (Diptera:Anthomyiidae)
1996
The pattern of genetic variation in four coexisting fly species of the genus Chiastocheta was studied by allozyme electrophoresis. The fly species are confined to patches of one plant, Trollius europaeus, and thus experience very similar habitat fluctuations. Collection sites were chosen in a hierarchical fashion and F-statistics were estimated at three levels: intraregion, inter-region and total population. Population characteristic genetic parameters were compared within and among species and were related to the hierarchical level. The species were used as replicate experiments for inference of habitat history, and the hierarchical levels were used as inference for specific gene flow patt…
Genetic variability in the endemic Leucojum valentinum
2009
The genetic variability of Leucojum valentinum Pau (Amaryllidaceae), a vulnerable endemic species restricted to a small area in the region of Valencia (Eastern Spain), has been studied using random amplified polymorphic DNA (RAPD) markers. A total of 197 individuals from eleven populations were studied using 13 RAPD primers. Our results show high variability for the species, low differentiation among populations and uncorrelated levels of genetic variability and population size. Four groups in which three populations (SAG, PUG and COL) are separated from all the others were found, but without connection to geographical location.
Genetic Variability of Hepatitis C Virus before and after Combined Therapy of Interferon plus Ribavirin
2008
We present an analysis of the selective forces acting on two hepatitis C virus genome regions previously postulated to be involved in the viral response to combined antiviral therapy. One includes the three hypervariable regions in the envelope E2 glycoprotein, and the other encompasses the PKR binding domain and the V3 domain in the NS5A region. We used a cohort of 22 non-responder patients to combined therapy (interferon alpha-2a plus ribavirin) for which samples were obtained before initiation of therapy and after 6 or/and 12 months of treatment. A range of 25-100 clones per patient, genome region and time sample were sequenced. These were used to detect general patterns of adaptation, t…
Homologous recombination as a mechanism of genetic changes in bovine parainfluenza-3 virus
2021
Bovine parainfluenza-3 virus (BPIV-3) is one of the main viruses associated with bovine respiratory disease complex (BRDC) worldwide. BPIV-3 infect the bovine respiratory tract causing from subclinical infections to severe pneumonia with significant economic losses in the cattle industry. BPIV-3 is a RNA virus with high genetic variability, nevertheless, the contribution of recombination events to its variability has not been assessed so far. In this study the 25 complete genome sequences (CGS) reported so far and 215 partial sequences of different viral genes of BPIV-3 were analyzed to determine their genotypes and subgenotypes, distribution, and the existence of potential recombination ev…
Informational analysis of forest landscape spatial heterogeneity
1999
Summary Under the perspective of forest ecosystem management, landscape is interpreted as a functioning structure. From an inventory and monitoring operational point of view, such an approach implies wise use of geographic information systems and remote sensing techniques enabling a global view of the territorial mosaic. From a methodological point of view, landscape ecology theory may be used as the assessment framework. Remotely sensed data provide excellent opportunities for the involved analyses, using both vegetation density measures and spatial statistics. The objective of this paper was to assess landscape spatial heterogeneity using an analysis method based on Shannon's information …
Wind speed spatial estimation for energy planning in Sicily: A neural kriging application
2008
Abstract One of the first steps for the exploitation of any energy source is necessarily represented by its estimation and mapping at the aim of identifying the most suitable areas in terms of energy potential. In the field of renewable energies this is often a very difficult task, because the energy source is in this case characterized by relevant variations over space and time. This implies that any temporal, but also spatial, estimation model has to be able to incorporate this spatial and temporal variability. The paper deals with the spatial estimation of the wind fields in Sicily (Italy) by following a data-driven approach. Starting from the results of a preliminary study, a novel tech…
Intraseasonal rainfall variability over Madagascar
2016
International audience; Using daily rain-gauge records for Madagascar and nearby islands, this paper investigates rainfall intraseasonal variability at local and regional scales during the austral summer season (November–February), as well as the respective influences of recurrent convective regimes over the South-West Indian Ocean (SWIO) and the Madden-Julian Oscillation (MJO). Our results show a general consistency between local-scale rainfall variability in Madagascar and regional-scale features of climate variability. The influence of Tropical-Temperate Troughs in their mature phase and/or their easternmost locations is first underlined. The development of such systems over Southern Afr…
Modelling the spatial-temporal progression of the 2009 A/H1N1 influenza pandemic in Chile
2016
A spatial-temporal transmission model of 2009 A/H1N1 pandemic influenza across Chile, a country that spans a large latitudinal range, is developed to characterize the spatial variation in peak timing of that pandemic as a function of local transmission rates, spatial connectivity assumptions for Chilean regions, and the putative location of introduction of the novel virus into the country. Specifically, a metapopulation SEIR (susceptible-exposed-infected-removed) compartmental model that tracks the transmission dynamics of influenza in 15 Chilean regions is calibrated. The model incorporates population mobility among neighboring regions and indirect mobility to and from other regions via th…
Source Detection in an Outbreak of Legionnaire’s Disease
2006
Spatial statistics have broadly been applied, developed and demanded from the field of epidemiology. The point process theory is an appropriate framework to analyse the spatial variation of risk of disease from information at individual level.
Downy-oak woods of Italy: phytogeographical remarks on a controversial taxonomic and ecologic issue
2014
The importance of downy oak as an integral component of the "submediterranean" woods has been underscored by many studies. Nevertheless, terms like "submediterranean" and "downy oak" are some of the most poorly understood concepts in European phytogeographic and taxonomic research. Downy oak is well known to be a problematic taxon. The name "Quercus pubescens" (= Q. humilis) combines populations characterized by increasing phenotypic and genomic polymorphisms along north-south gradients, which is explained as the result of a "founder effect" produced by a relatively fast post-glacial re-colonization of the northern areas through rare long-distance dispersal events. On the other hand, polymo…