970 resultados para Spatial Proximity
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The correlation between vegetation patterns (species distribution and richness) and altitudinal variation has been widely reported for tropical forests, thereby providing theoretical basis for biodiversity conservation. However, this relationship may have been oversimplified, as many other factors may influence vegetation patterns, such as disturbances, topography and geographic distance. Considering these other factors, our primary question was: is there a vegetation pattern associated with substantial altitudinal variation (10-1,093m a.s.l.) in the Atlantic Rainforest-a top hotspot for biodiversity conservation-and, if so, what are the main factors driving this pattern? We addressed this question by sampling 11 1-ha plots, applying multivariate methods, correlations and variance partitioning. The Restinga (forest on sandbanks along the coastal plains of Brazil) and a lowland area that was selectively logged 40years ago were floristically isolated from the other plots. The maximum species richness (>200 spp. per hectare) occurred at approximately 350m a.s.l. (submontane forest). Gaps, multiple stemmed trees, average elevation and the standard deviation of the slope significantly affected the vegetation pattern. Spatial proximity also influenced the vegetation pattern as a structuring environmental variable or via dispersal constraints. Our results clarify, for the first time, the key variables that drive species distribution and richness across a large altitudinal range within the Atlantic Rainforest. 2013 Springer Science+Business Media Dordrecht.
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This paper develops an interactive approach for exploratory spatial data analysis. Measures of attribute similarity and spatial proximity are combined in a clustering model to support the identification of patterns in spatial information. Relationships between the developed clustering approach, spatial data mining and choropleth display are discussed. Analysis of property crime rates in Brisbane, Australia is presented. A surprising finding in this research is that there are substantial inconsistencies in standard choropleth display options found in two widely used commercial geographical information systems, both in terms of definition and performance. The comparative results demonstrate the usefulness and appeal of the developed approach in a geographical information system environment for exploratory spatial data analysis.
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History tells that institutions evolve gradually over time, pushing new ideas across borders and cultures. Globalisation is argued to accelerate this process. We examine the spatial links of different political institutions across borders. Applying various tests for spatial proximity, we do not find evidence of contemporaneous spatial links. This result is robust to various measures of distance and of cultural proximity across countries. Instead, when we analyse long run dynamics diffusion of institutions seems to occur only gradually.
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The intensity of regional specialization in specific activities, and conversely, the level of industrial concentration in specific locations, has been used as a complementary evidence for the existence and significance of externalities. Additionally, economists have mainly focused the debate on disentangling the sources of specialization and concentration processes according to three vectors: natural advantages, internal, and external scale economies. The arbitrariness of partitions plays a key role in capturing these effects, while the selection of the partition would have to reflect the actual characteristics of the economy. Thus, the identification of spatial boundaries to measure specialization becomes critical, since most likely the model will be adapted to different scales of distance, and be influenced by different types of externalities or economies of agglomeration, which are based on the mechanisms of interaction with particular requirements of spatial proximity. This work is based on the analysis of the spatial aspect of economic specialization supported by the manufacturing industry case. The main objective is to propose, for discrete and continuous space: i) a measure of global specialization; ii) a local disaggregation of the global measure; and iii) a spatial clustering method for the identification of specialized agglomerations.
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This paper develops an Internet geographical information system (GIS) and spatial model application that provides socio-economic information and exploratory spatial data analysis for local government authorities (LGAs) in Queensland, Australia. The application aims to improve the means by which large quantities of data may be analysed, manipulated and displayed in order to highlight trends and patterns as well as provide performance benchmarking that is readily understandable and easily accessible for decision-makers. Measures of attribute similarity and spatial proximity are combined in a clustering model with a spatial autocorrelation index for exploratory spatial data analysis to support the identification of spatial patterns of change. Analysis of socio-economic changes in Queensland is presented. The results demonstrate the usefulness and potential appeal of the Internet GIS applications as a tool to inform the process of regional analysis, planning and policy.
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Az innovatv vllalati kapcsolatokkal foglalkoz vizsglatok sokasga az innovcis folyamatok kettssgrl ad szmot. Egyrszt felrtkeldtt a trbeli kzelsg szerepe, emiatt az innovatv vllalkozsok, intzmnyek trben koncentrldnak, fleg a nagyvrosokban. Msrszt szertegaz hlzatok jttek ltre a klnbz orszgokban mkd innovatv vllalatok, intzetek kztt, amelyek tbbsge a nagy tvolsgok ellenre is sikeres. Mindezen megfigyelsek arra utalnak, hogy pontostani kell a kzelsg s tvolsg zleti szereprl vallott ismereteket a vltoz globalizcis felttelekhez igaztva. A szerzk tanulmnyukban ttekintik a trbeli kzelsg szerepnek fbb jellemzit az innovatv tevkenysgeken alapul vllalati egyttmkdsek kialakulsban s fenntartsban. A hagyomnyos felfogsok rvid ismertetse utn a hlzati kzelsg, mskppen kapcsolati kzelsg (relational proximity) egyes tpusait elemzik. Rszletesen kitrnek a regionlis klaszterek s a loklis innovatv mili fbb jellemzire, amelyek a trbeli s a kapcsolati kzelsgekbl ered elnyket egyarnt hasznostjk. Ezek a mrvad nemzetkzi tapasztalatok itthon is alkalmazhatk az egyetemi s vllalati egyttmkdsek, illetve a helyi gazdasgfejlesztsi s vllalkozsfejlesztsi programok kidolgozsakor. ________ Multiple studies of innovative business relations give an account about the double character of innovative processes. On the one hand, the role of proximity has been appreciated, for this reason, the innovative companies, institutes are concentrated in space, especially in big cities. On the other hand extensive networks have been established among innovative companies, institutes operating in the different countries, most of which are successful in spite of the long distance. All these observations suggest there is a need to clarify business skills on the role of proximity and distance, tailored to the changing conditions of globalization. In their study the authors review the role of the main features of spatial proximity in formation and maintenace of corporate cooperation based on innovative activities. After a brief description of traditional concepts certain types of network proximity otherwise relational proximity are analyzed. They cover main features of regional clusters and the local innovative environment which utilize advantages coming both from spatial and relational proximities. This leading international experience are applicable at home as well when elaborating academic and corporate cooperation resp. local development programs for the economy and corporations.
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A anlise das relaes de similaridade florstica entre comunidades geralmente conduz ao estabelecimento de padres, condicionados por fatores diversos que determinam a ocorrncia ou no das espcies em diferentes locais. Em busca de tais padres, foram analisadas as relaes de similaridade florstica entre comunidades florestais localizadas na regio do Planalto de Ibina, estado de So Paulo, Brasil. Incluram-se na anlise 21 fragmentos florestais e seis stios em uma Reserva Florestal contnua, sendo que a composio florstica e a estrutura da comunidade arbrea (DAP mnimo 5 cm) em cada local foram amostradas pelo mtodo de quadrantes. Aplicaram-se dois mtodos de anlises multivariadas: 1) Anlise de Correspondncia Destendenciada (DCA), com base no ndice de similaridade de Srensen; e 2) Diviso Hierrquica Dicotmica (TWINSPAN). A similaridade florstica foi mais elevada entre comunidades em estdios sucessionais semelhantes, especialmente se estivessem geograficamente prximas. H um gradiente florstico associado latitude, indicando tratar-se de uma regio de transio entre biomas. Nos stios situados na face norte da regio de estudo esto presentes espcies que tambm ocorrem no cerrado e em floresta estacional semidecidual, enquanto nos stios situados na face sul prevalecem espcies caractersticas da floresta ombrfila densa.
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Lychnophora pohlii Sch. Bip. (Asteraceae), known as "Arnica mineira", is widely used in folk medicine and very abundant in the altitude vegetation of rocky grassland. The aim of this work was to study the density of this species and its relationship with soil parameters in rocky grassland in Diamantina, in the Upper Jequitinhonha region, Minas Gerais. Ten contiguous 20 x 50 m plots were marked (total sampled area 10,000 m) on the campus Juscelino Kubitschek of the Federal University of Jequitinhonha and Mucuri Valleys (UFVJM). The plants in these plots were evaluated for frequency, dominance and density. The relationship between the density of this species with nine soil physical and chemical properties was analyzed by means of canonical correspondence analysis (CCA). The highest plant abundance (I) of the species Lychnophora pohlii Sch. Bip. was found in the vegetation sampling areas: plot 6 with 255 plants, plot 7 with 173, plot 8 with 189, plot 9 with 159, and plot 1 with 151 plants. In these areas, the floristic soil characteristics were similar, resulting in spatial proximity in the ACC diagrams. The density of Lychnophora pohlii was higher in plots with higher pH, P-rem and base saturation, the variables most strongly correlated with the first axis of canonical correspondence analysis.
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Understanding the structure of interphase chromosomes is essential to elucidate regulatory mechanisms of gene expression. During recent years, high-throughput DNA sequencing expanded the power of chromosome conformation capture (3C) methods that provide information about reciprocal spatial proximity of chromosomal loci. Since 2012, it is known that entire chromatin in interphase chromosomes is organized into regions with strongly increased frequency of internal contacts. These regions, with the average size of ∼1 Mb, were named topological domains. More recent studies demonstrated presence of unconstrained supercoiling in interphase chromosomes. Using Brownian dynamics simulations, we show here that by including supercoiling into models of topological domains one can reproduce and thus provide possible explanations of several experimentally observed characteristics of interphase chromosomes, such as their complex contact maps.
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Horses (Equus caballus) belong to the group of seasonally polyestrous mammals. Estrous cycles typically start with increasing daylight length after winter, but mares can differ greatly in the timing of onset of regular estrus cycles. Here, we test whether spatial proximity to a stallion also plays a role. Twenty-two anestrous mares were either exposed to one of two stallions (without direct physical contact) or not exposed (controls) under experimental conditions during two consecutive springs (February to April). Ovarian activity was monitored via transrectal ultrasound and stallion's direct contact time with each mare was determined three times per week for one hour each. We found that mares exposed to a stallion ovulated earlier and more often during the observational period than mares that were not exposed to stallions. Neither stallion identity nor direct contact time, mare age, body condition, size of her largest follicle at the onset of the experiment, or parasite burden significantly affected the onset of cyclicity. In conclusion, the timing of estrous cycles and cycle frequency, i.e., crucial aspects of female reproductive strategy, strongly depend on how the mares perceive their social environment. Exposing mares to the proximity of a stallion can therefore be an alternative to, for example, light programs or elaborated hormonal therapies to start the breeding season earlier and increase the number of estrous cycles in horses.
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The interaction of the product of H2O2 and (PhSe)2 with delta-aminolevulinate dehydratase (delta-ALA-D) from mammals and plants was investigated. (PhSe)2 inhibited rat hepatic delta-ALA-D with an IC50 of 10 M but not the enzyme from cucumber leaves. The reaction of (PhSe)2 with H2O2 for 1 h increased the inhibitory potency of the original compound and the IC50 for animal delta-ALA-D inhibition was decreased from 10 to 2 M. delta-ALA-D from cucumber leaves was also inhibited by the products of reaction of (PhSe)2 with H2O2 with an IC50 of 4 M. The major product of reaction of (PhSe)2 with H2O2 was identified as seleninic acid and produced an intermediate with a lambdamax at 265 nm after reaction with t-BuSH. These results suggest that the interaction of (PhSe)2 with mammal delta-ALA-D requires the presence of cysteinyl residues in close proximity. Two cysteine residues in spatial proximity have been recently described for the mammalian enzyme. Analysis of the primary structure of plant delta-ALA-D did not reveal an analogous site. In contrast to (PhSe)2, seleninic acid, as a result of the higher electrophilic nature of its selenium atom, may react with additional cysteinyl residue(s) in mammalian delta-ALA-D and also with cysteinyl residues from cucumber leaves located at a site distinct from that found at the B and A sites in mammals. Although the interaction of organochalcogens with H2O2 may have some antioxidant properties, the formation of seleninic acid as a product of this reaction may increase the toxicity of organic chalcogens such as (PhSe)2.
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La prsente thse examine les liens entre le sommeil, la mmoire pisodique et les rves. Dans une premire tude, nous utilisons les technologies de la ralit virtuelle (RV) en liaison avec un paradigme de privation de sommeil paradoxal et de collecte de rve en vue d'examiner l'hypothse que le sommeil paradoxal et le rve sont impliqus dans la consolidation de la mmoire pisodique. Le sommeil paradoxal a t associ au rappel des aspects spatiaux des lments motionnels de la tche RV. De la mme faon, l'incorporation de la tche RV dans les rves a t associe au rappel des aspects spatiaux de la tche. De plus, le rappel des aspects factuels et perceptuels de la mmoire pisodique, form lors de la tche VR, a t associ au sommeil aux ondes lentes. Une deuxime tude examine l'hypothse selon laquelle une fonction possible du rve pourrait tre de crer de nouvelles associations entre les lments de divers souvenirs pisodiques. Un participant a t rveill 43 fois lors de l'endormissement pour fournir des rapports dtaills de rves. Les rsultats suggrent qu'un seul rve peut comporter, dans un mme contexte spatiotemporel, divers lments appartenant aux multiples souvenirs pisodiques. Une troisime tude aborde la question de la cognition lors du sommeil paradoxal, notamment comment les aspects bizarres des rves, qui sont forms grce aux nouvelles combinaisons d'lments de la mmoire pisodique, sont perus par le rveur. Les rsultats dmontrent une dissociation dans les capacits cognitives en sommeil paradoxal caractrise par un dficit slectif dans l'apprciation des lments bizarres des rves. Les rsultats des quatre tudes suggrent que le sommeil aux ondes lentes et le sommeil paradoxal sont diffremment impliqus dans le traitement de la mmoire pisodique. Le sommeil aux ondes lentes pourrait tre implique dans la consolidation de la mmoire pisodique, et le sommeil paradoxal, par l'entremise du rve, pourrais avoir le rle d'introduire de la flexibilit dans ce systme mnmonique.
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Purpose This paper examines the role of location-specific (L) advantages in the spatial distribution of multinational enterprise (MNE) R&D activity. The meaning of L advantages is revisited. In addition to L advantages that are industry-specific, the paper emphasises that there is an important category of L advantages, referred to as collocation advantages. Design/methodology/approach Using the OLI framework, this paper highlights that the innovation activities of MNEs are about interaction of these variables, and the essential process of internalising L advantages to enhance and create firm-specific advantages. Findings Collocation advantages derive from spatial proximity to specific unaffiliated firms, which may be suppliers, competitors, or customers. It is also argued that L advantages are not always public goods, because they may not be available to all firms at a similar or marginal cost. These costs are associated with access and internalisation of L advantages, and especially in the case of R&D are attendant with the complexities of embeddedness. Originality/value The centralisation/decentralisation, spatial separation/collocation debates in R&D location have been mistakenly viewed as a paradox facing firms, instead of as a trade-off that firms must make.
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Analysis of floristic similarity relationships between plant communities can detect patterns of species occurrence and also explain conditioning factors. Searching for such patterns, floristic similarity relationships among Atlantic Forest sites situated at Ibiuna Plateau, Sao Paulo state, Brazil, were analyzed by multivariate techniques. Twenty one forest fragments and six sites within a continuous Forest Reserve were included in the analyses. Floristic composition and structure of the tree community (minimum dbh 5 cm) were assessed using the point centered quarter method. Two methods were used for multivariate analysis: Detrended Correspondence Analysis (DCA) and Two-Way Indicator Species Analysis (TWINSPAN). Similarity relationships among the study areas were based on the successional stage of the community and also on spatial proximity. The more similar the successional stage of the communities, the higher the floristic similarity between them, especially if the communities are geographically close. A floristic gradient from north to south was observed, suggesting a transition between biomes, since northern indicator species are mostly heliophytes, occurring also in cerrado vegetation and seasonal semideciduous forest, while southern indicator species are mostly typical ombrophilous and climax species from typical dense evergreen Atlantic Forest.
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Analyzing and modeling relationships between the structure of chemical compounds, their physico-chemical properties, and biological or toxic effects in chemical datasets is a challenging task for scientific researchers in the field of cheminformatics. Therefore, (Q)SAR model validation is essential to ensure future model predictivity on unseen compounds. Proper validation is also one of the requirements of regulatory authorities in order to approve its use in real-world scenarios as an alternative testing method. However, at the same time, the question of how to validate a (Q)SAR model is still under discussion. In this work, we empirically compare a k-fold cross-validation with external test set validation. The introduced workflow allows to apply the built and validated models to large amounts of unseen data, and to compare the performance of the different validation approaches. Our experimental results indicate that cross-validation produces (Q)SAR models with higher predictivity than external test set validation and reduces the variance of the results. Statistical validation is important to evaluate the performance of (Q)SAR models, but does not support the user in better understanding the properties of the model or the underlying correlations. We present the 3D molecular viewer CheS-Mapper (Chemical Space Mapper) that arranges compounds in 3D space, such that their spatial proximity reflects their similarity. The user can indirectly determine similarity, by selecting which features to employ in the process. The tool can use and calculate different kinds of features, like structural fragments as well as quantitative chemical descriptors. Comprehensive functionalities including clustering, alignment of compounds according to their 3D structure, and feature highlighting aid the chemist to better understand patterns and regularities and relate the observations to established scientific knowledge. Even though visualization tools for analyzing (Q)SAR information in small molecule datasets exist, integrated visualization methods that allows for the investigation of model validation results are still lacking. We propose visual validation, as an approach for the graphical inspection of (Q)SAR model validation results. New functionalities in CheS-Mapper 2.0 facilitate the analysis of (Q)SAR information and allow the visual validation of (Q)SAR models. The tool enables the comparison of model predictions to the actual activity in feature space. Our approach reveals if the endpoint is modeled too specific or too generic and highlights common properties of misclassified compounds. Moreover, the researcher can use CheS-Mapper to inspect how the (Q)SAR model predicts activity cliffs. The CheS-Mapper software is freely available at http://ches-mapper.org.
