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Metal-oxide semiconductors are the most widely used gas-sensitive materials due to their numerous advantages such as high sensitivity to various gases with ease of production, high compatibility with other processes, low cost, simplicity of measurements along with minimal energy consumption. From this point of view, investigations of the morphological and electrical characteristics of metal-oxide materials, particularly based on tin(IV) oxide, and the determination of their sensitivity to organic compounds such as ethyl acetate and chlorobenzene are extremely important. In this work, tin(IV)-oxide nanostructures have been synthesized by chemical vapour deposition (CVD) technique and modified with argentum. Obtained samples have been investigated with electron microscopy, and as a result, it was found that, during the synthesis under different conditions, nanoparticles of zero- and mixed zero- and one-dimensional morphology were obtained. The study of electrical characteristics and sensitivity towards vapours of ethyl acetate and chlorobenzene has been carried out. The comparison of electrical properties and sensitivity to the vapours of organic substances of pure and modified 0D- and mix 0D + 1D-SnO2-samples is presented. It was found that morphology affects not only electrical properties of tin(IV)-oxide nanostructures, but also their sensing properties. It was shown that the addition of argentum has an ambiguous effect on the sensitivity depending on the morphology of the obtained samples; modification leads to increasing of 0D-sample sensitivity and decreasing of sensing response for 0D + 1D-SnO2-sample. [ABSTRACT FROM AUTHOR]

Hybridization between genetically distinct taxa is a complex evolutionary process. One challenge to studying hybrid populations is quantifying the degree to which non-native genes have become evenly mixed among individuals in the population. In this paper, we present a variance-based parameter, md, that measures the degree to which non-native genes are evenly distributed among individuals in a population. The parameter has a minimum value of 0 for populations in which individuals from multiple taxa are present but have not interbred, and a maximum value of 1 for populations in which all individuals have the same amount of non-native ancestry. A recurrence equation showed that relatively few generations of random mating are required for md to approach 1 (indicating a well-mixed population), and that md is independent of initial amounts of non-native ancestry. The parameter is mathematically equivalent to Fsyand we show how existing formulae for FST can be used to estimate md when diagnostic loci are available. Computer simulations showed this estimator to have very little bias for realistic amounts of data. [ABSTRACT FROM AUTHOR]

One of the primary goals of population genetics is to succinctly describe genetic relationships among populations, and the computer program STRUCTURE is one of the most frequently used tools for doing so. The mathematical model used by STRUCTURE was designed to sort individuals into Hardy-Weinberg populations, but the program is also frequently used to group individuals from a large number of populations into a small number of clusters that are supposed to represent the main genetic divisions within species. In this study, I used computer simulations to examine how well STRUCTURE accomplishes this latter task. Simulations of populations that had a simple hierarchical history of fragmentation showed that when there were relatively long divergence times within evolutionary lineages, the clusters created by STRUCTURE were frequently not consistent with the evolutionary history of the populations. These difficulties can be attributed to forcing STRUCTURE to place individuals into too few clusters. Simulations also showed that the clusters produced by STRUCTURE can be strongly influenced by variation in sample size. In some circumstances, STRUCTURE simply put all of the individuals from the largest sample in the same cluster. A reanalysis of human population structure suggests that the problems I identified with STRUCTURE in simulations may have obscured relationships among human populations-particularly genetic similarity between Europeans and some African populations. [ABSTRACT FROM AUTHOR]

We describe 12 diagnostic single nucleotide polymorphism (SNP) assays for use in species identification among rainbow and cutthroat trout: five of these loci have alleles unique to rainbow trout ( Oncorhynchus mykiss), three unique to westslope cutthroat trout ( O. clarkii lewisi) and four unique to Yellowstone cutthroat trout ( O. clarkii bouvieri). These diagnostic assays were identified using a total of 489 individuals from 26 populations and five fish hatchery strains. [ABSTRACT FROM AUTHOR]

The coefficient of variation of estimates of three genetic distances (standard genetic distance of Nei, chord distance, FST) was examined with computer simulation to determine if large samples (per population) are necessary to precisely estimate genetic distances at loci with high levels of polymorphism. These simulations showed that loci with high mutation rates produce estimates of genetic distance with lower coefficients of variation than loci with lower mutation rates-without requiring larger sample sizes from each population. In addition, the rate at which increasing sample sizes decreases the coefficient of variation of estimates of genetic distances was shown to be approximately determined by the value of FST between the populations being sampled. When FST was greater than 0.05, sampling fewer than 20 individuals (per population) should be sufficient. When FST was less than 0.01, sampling 100 individuals (per population) or more will be useful.Heredity (2005) 94, 33-36. doi:10.1038/sj.hdy.6800548 Published online 25 August 2004 [ABSTRACT FROM AUTHOR]