913 resultados para Nearest Neighbor


Relevância:

10.00% 10.00%

Publicador:

Resumo:

Vols. 1-6 translated by Mary Hanford Ford; v. 7-21, 24-25, by Edith M. Norris; v. 22, by Arthur S. Martin; v. 23, by Arthur S. Martin and Edith M. Norris.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Vols. 1-6 translated by Mary Hanford Ford: v. 7-21, 24-25, by Edith M. Norris; v. 22, by Arthur S. Martin; v. 23, by Arthur S. Martin and Edith M. Norris.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Title from cover.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Thesis (Master's)--University of Washington, 2016-06

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Thesis (Master's)--University of Washington, 2016-06

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Isothermal-isobaric (NPT) molecular dynamics simulation has been performed to investigate the layering behavior and structure of nanoconfined quaternary alkylammoniums in organoclays. This work is focused on systems consisting of two clay layers and a number of alkylammoniums, and involves the use of modified Dreiding force field. The simulated basal spacings of organoclays agree satisfactorily with the experimental results in the literature. The atomic density profiles in the direction normal to the clay surface indicate that the alkyl chains within the interlayer space of montmorillonite exhibit an obvious layering behavior. The headgroups of long alkyl chains are distributed within two layers close to the clay surface, whereas the distributions of methyl and methylene groups are strongly dependent on the alkyl chain length and clay layer charge. Monolayer, bilayer, and pseudo-trilayer structures are found in organoclays modified with single long alkyl chains, which are identical to the structural models based on the measured basal spacings. A pseudo-quadrilayer structure, for the first time to our knowledge, is also identified in organoclays with double long alkyl chains. In the mixture structure of paraffin-type and multilayer, alkyl chains do not lie flat within a single layer but interlace, and also jump to the next layer in pseudo-trilayer as well as next nearest layer in pseudo-quadrilayer.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Childhood obesity is a serious public health problem because of its strong association with adulthood obesity and the related adverse health consequences. The published literature indicates a rising prevalence of childhood obesity in both developed and developing countries. However no data exists on the prevalence in Northeast Thailand, one of the poorest regions of the country and one that has experienced a recent economic transition. The objective of this study was to estimate the prevalence of obesity in seven to nine year old children in urban Khon Kaen, Northeast Thailand. A cross-sectional school based survey was conducted to determine the prevalence of obesity in children of urban Khon Kaen, Thailand. Multi-staged cluster sampling was used to select 12 school clusters of 72 children each between the ages of 7 and 9 years, in primary school grades 1, 2 and 3 from government, private and demonstration schools. A total of 864 seven to nine year old school children were studied. Anthropometric measurements of standing height and weight were taken for all subjects to the nearest tenth of a centimetre and tenth of a kilogram respectively. Childhood obesity was defined as a weight-for-height Z-score above 2.0 standard deviations of the National Center for Health Statistics/World Health Organisation reference population median. The prevalence of childhood obesity was 10.8% (95% CI: 7.6, 13.9). Obesity was significantly more prevalent in boys than girls. The biggest difference was observed between the three school types, with the highest prevalence of obesity found at teacher training demonstration schools and the lowest at the government schools. This study provides the first data on childhood obesity prevalence in Northeast Thailand. The prevalence of 10.8 per cent is lower than that found in two other urban areas of Thailand but slightly higher than expected for this relatively poor region. If this prevalence rate increases, as observed in other countries in economic transition, the incidence of non-communicable diseases associated with obesity is also likely to increase, thus raising cause for concern and reason for intervention to both control and prevent obesity during childhood.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Genetic diversity and population structure were investigated across the core range of Tasmanian devils (Sarcophilus laniarius; Dasyuridae), a wide-ranging marsupial carnivore restricted to the island of Tasmania. Heterozygosity (0.386-0.467) and allelic diversity (2.7-3.3) were low in all subpopulations and allelic size ranges were small and almost continuous, consistent with a founder effect. Island effects and repeated periods of low population density may also have contributed to the low variation. Within continuous habitat, gene flow appears extensive up to 50 km (high assignment rates to source or close neighbour populations; nonsignificant values of pairwise F-ST), in agreement with movement data. At larger scales (150-250 km), gene flow is reduced (significant pairwise F-ST) but there is no evidence for isolation by distance. The most substantial genetic structuring was observed for comparisons spanning unsuitable habitat, implying limited dispersal of devils between the well-connected, eastern populations and a smaller northwestern population. The genetic distinctiveness of the northwestern population was reflected in all analyses: unique alleles; multivariate analyses of gene frequency (multidimensional scaling, minimum spanning tree, nearest neighbour); high self-assignment (95%); two distinct populations for Tasmania were detected in isolation by distance and in Bayesian model-based clustering analyses. Marsupial carnivores appear to have stronger population subdivisions than their placental counterparts.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

We studied thalamic projections to the visual cortex in flying foxes, animals that share neural features believed to resemble those present in the brains of early primates. Neurones labeled by injections of fluorescent tracers in striate and extrastriate cortices were charted relative to the architectural boundaries of thalamic nuclei. Three main findings are reported: First, there are parallel lateral geniculate nucleus (LGN) projections to striate and extrastriate cortices. Second, the pulvinar complex is expansive, and contains multiple subdivisions. Third, across the visual thalamus, the location of cells labeled after visual cortex injections changes systematically, with caudal visual areas receiving their strongest projections from the most lateral thalamic nuclei, and rostral areas receiving strong projections from medial nuclei. We identified three architectural layers in the LGN, and three subdivisions of the pulvinar complex. The outer LGN layer contained the largest cells, and had strong projections to the areas V1, V2 and V3. Neurones in the intermediate LGN layer were intermediate in size, and projected to V1 and, less densely, to V2. The layer nearest to the origin of the optic radiation contained the smallest cells, and projected not only to V1, V2 and V3, but also, weakly, to the occipitotemporal area (OT, which is similar to primate middle temporal area) and the occipitoparietal area (OP, a third tier area located near the dorsal midline). V1, V2 and V3 received strong projections from the lateral and intermediate subdivisions of the pulvinar complex, while OP and OT received their main thalamic input from the intermediate and medial subdivisions of the pulvinar complex. These results suggest parallels with the carnivore visual system, and indicate that the restriction of the projections of the large- and intermediatesized LGN layers to V1, observed in present-day primates, evolved from a more generalized mammalian condition. (C) 2004 IBRO. Published by Elsevier Ltd. All rights reserved.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

A number of very small isolated H II regions have been discovered at projected distances up to 30 kpc from their nearest galaxy. These H II regions appear as tiny emission-line objects in narrowband images obtained by the NOAO Survey for Ionization in Neutral Gas Galaxies (SINGG). We present spectroscopic confirmation of four isolated H II regions in two systems; both systems have tidal H I features. The results are consistent with stars forming in interactive debris as a result of cloud-cloud collisions. The Halpha luminosities of the isolated H II regions are equivalent to the ionizing flux of only a few O stars each. They are most likely ionized by stars formed in situ and represent atypical star formation in the low-density environment of the outer parts of galaxies. A small but finite intergalactic star formation rate will enrich and ionize the surrounding medium. In one system, NGC 1533, we calculate a star formation rate of 1.5 x 10(-3) M-. yr(-1), resulting in a metal enrichment of similar to 1 x 10(-3) solar for the continuous formation of stars. Such systems may have been more common in the past and a similar enrichment level is measured for the metallicity floor'' in damped Lyalpha absorption systems.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Sequences of small-subunit rRNA genes were determined for Dermocystidium percae and a new Dermocystidium species established as D. fennicum sp. n. from perch in Finland. On the basis of alignment and phylogenetic analysis both species were placed in the Dermocystidium-Rhinosporidium clade within Ichthyosporea, D. fennicum as a specific sister taxon to D. salmonis, and D. percae in a clade different from D. fennicum. The ultrastructures of both species well agree with the characteristics approved within Ichthyosporea: walled spores produce uniflagellate zoospores lacking a collar or cortical alveoli. The two Dermocystidium species resemble Rhinosporidium seeberi (as described by light microscope), a member of the nearest relative genus, but differ in that in R. seeberi plasmodia have thousands of nuclei discernible, endospores are discharged through a pore in the wall of the sporangium, and zoospores have not been revealed. The plasmodial stages of both Dermocystidium species have a most unusual behaviour of nuclei, although we do not actually know how the nuclei transform during the development. Early stages have an ordinary nucleus with double, fenestrated envelope. In middle-aged plasmodia ordinary nuclei seem to be totally absent or are only seldom discernible until prior to sporogony, when rather numerous nuclei again reappear. Meanwhile single-membrane vacuoles with coarsely granular content, or complicated membranous systems were discernible. Ordinary nuclei may be re-formed within these vacuoles or systems. In D. percae small canaliculi and in D. fennicum minute vesicles may aid the nucleus-cytoplasm interchange of matter before formation of double-membrane-enveloped nuclei. Dermocystidium represents a unique case when a stage of the life cycle of an eukaryote lacks a typical nucleus.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

This paper proposes a theoretical explanation of the variations of the sediment delivery ratio (SDR) versus catchment area relationships and the complex patterns in the behavior of sediment transfer processes at catchment scale. Taking into account the effects of erosion source types, deposition, and hydrological controls, we propose a simple conceptual model that consists of two linear stores arranged in series: a hillslope store that addresses transport to the nearest streams and a channel store that addresses sediment routing in the channel network. The model identifies four dimensionless scaling factors, which enable us to analyze a variety of effects on SDR estimation, including (1) interacting processes of erosion sources and deposition, (2) different temporal averaging windows, and (3) catchment runoff response. We show that the interactions between storm duration and hillslope/channel travel times are the major controls of peak-value-based sediment delivery and its spatial variations. The interplay between depositional timescales and the travel/residence times determines the spatial variations of total-volume-based SDR. In practical terms this parsimonious, minimal complexity model could provide a sound physical basis for diagnosing catchment to catchment variability of sediment transport if the proposed scaling factors can be quantified using climatic and catchment properties.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Adsorption of pure nitrogen, argon, acetone, chloroform and acetone-chloroform mixture on graphitized thermal carbon black is considered at sub-critical conditions by means of molecular layer structure theory (MLST). In the present version of the MLST an adsorbed fluid is considered as a sequence of 2D molecular layers, whose Helmholtz free energies are obtained directly from the analysis of experimental adsorption isotherm of pure components. The interaction of the nearest layers is accounted for in the framework of mean field approximation. This approach allows quantitative correlating of experimental nitrogen and argon adsorption isotherm both in the monolayer region and in the range of multi-layer coverage up to 10 molecular layers. In the case of acetone and chloroform the approach also leads to excellent quantitative correlation of adsorption isotherms, while molecular approaches such as the non-local density functional theory (NLDFT) fail to describe those isotherms. We extend our new method to calculate the Helmholtz free energy of an adsorbed mixture using a simple mixing rule, and this allows us to predict mixture adsorption isotherms from pure component adsorption isotherms. The approach, which accounts for the difference in composition in different molecular layers, is tested against the experimental data of acetone-chloroform mixture (non-ideal mixture) adsorption on graphitized thermal carbon black at 50 degrees C. (C) 2005 Elsevier Ltd. All rights reserved.