868 resultados para spatial point pattern


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Montado decline has been reported since the end of the nineteenth century in southern Portugal and increased markedly during the 1980s. Consensual reports in the literature suggest that this decline is due to a number of factors, such as environmental constraints, forest diseases, inappropriate management, and socioeconomic issues. An assessment on the pattern of montado distribution was conducted to reveal how the extent of land management, environmental variables, and spatial factors contributed to montado area loss in southern Portugal from 1990 to 2006. A total of 14 independent variables, presumably related to montado loss, were grouped into three sets: environmental variables, land management variables, and spatial variables. From 1990 to 2006, approximately 90,054 ha disappeared in the montado area, with an estimated annual regression rate of 0.14 % year-1. Variation partitioning showed that the land management model accounted for the highest percentage of explained variance (51.8 %), followed by spatial factors (44.6 %) and environmental factors (35.5 %). These results indicate that most variance in the large-scale distribution of recent montado loss is due to land management, either alone or in combination with environmental and spatial factors. The full GAM model showed that different livestock grazing is one of the most important variables affecting montado loss. This suggests that optimum carrying capacity should decrease to 0.18–0.60 LU ha-1 for livestock grazing in montado under current ecological conditions in southern Portugal.

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The objective of this paper was to determine changes in the spatial distribution of tree species in a logged compared to an unlogged forest of the Tapajos National Forest in the municipality of Belterra, State of Para, Brazil, over an eight-year period. The distribution pattern was determined for trees> 5 cm dbh and, also, for trees > 30 cm dbh. The relationship (a quadrate method) discussed by McGinnis was selected to be used in this study. Forty-seven percent of species with trees > 5 cm dbh showed clumped distribution in the studied forests. Geissospermwn sericeunz Benth & Hook., Minquartia guianensis Aubl., Poureria bilocularis (H. Winkler) Bachni, Protium guacayantan Cuatrec, Sclerolobium chrysophyllunz Poepp. et Endl. and the Sapotaceae family (9 species) occurred in clumps of small trees (5 cm 5 dbh < 30 cm) and big trees (dbh > 30 cm) in both the logged and undisturbed forest. Trees in all sizes of these species certainly have aggregation characteristics in different light condition's during the whole growth-cycle. Only Sclerolobium cizzysophylltan out of fourteen species that occurred aggregated in all forest conditions was light demanding. The shade-tolerant Lecythis lurida (Miers) Mori and Manilkara huberi (Ducke) Stand!. showed also aggregated distribution for small and big trees in the unlogged forest. An aggregated distribution is not always directly correlated to abundance, considering that most of the clumped species had less than seven trees per hectare.

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Field infestation and spatial distribution of introduced Bactrocera carambolae Drew and Hancock and native species of Anastrepha in common guavas [Psidium guajava (L.)] were investigated in the eastern Amazon. Fruit sampling was carried out in the municipalities of Calc¸oene and Oiapoque in the state of Amapa, Brazil. The frequency distribution of larvae in fruit was fitted to the negative binomial distribution. Anastrepha striata was more abundant in both sampled areas in comparison to Anastrepha fraterculus (Wiedemann) and B. carambolae. The frequency distribution analysis of adults revealed an aggregated pattern for B. carambolae as well as for A. fraterculus and Anastrepha striata Schiner, described by the negative binomial distribution. Although the populations of Anastrepha spp. may have suffered some impact due to the presence of B. carambolae, the results are still not robust enough to indicate effective reduction in the abundance of Anastrepha spp. caused by B. carambolae in a general sense. The high degree of aggregation observed for both species suggests interspecific co-occurrence with the simultaneous presence of both species in the analysed fruit. Moreover, a significant fraction of uninfested guavas also indicated absence of competitive displacement.

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Introduction: Brazil, is one of the main agricultural producers in the world ranking 1st in the production of sugarcane, coffee and oranges. It is also 2nd as world producer of soybeans and a leader in the harvested yields of many other crops. The annual consumption of mineral fertilizers exceeds 20 million mt, 30% of which corresponds to potash fertilizers (ANDA, 2006). From this statistic it may be supposed that fertilizer application in Brazil is rather high, compared with many other countries. However, even if it is assumed that only one fourth of this enormous 8.5 million km2 territory is used for agriculture, average levels of fertilizer application per hectare of arable land are not high enough for sustainable production. One of the major constraints is the relatively low natural fertility status of the soils which contain excessive Fe and Al oxides. Agriculture is also often practised on sandy soils so that the heavy rainfall causes large losses of nutrients through leaching. In general, nutrient removal by crops such as sugarcane and tropical fruits is much more than the average nutrient application via fertilization, especially in regions with a long history of agricultural production. In the recently developed areas, especially in the Cerrado (Brazilian savanna) where agriculture has expanded since 1980, soils are even poorer than in the "old" agricultural regions, and high costs of mineral fertilizers have become a significant input factor in determining soybean, maize and cotton planting. The consumption of mineral fertilizers throughout Brazil is very uneven. According to the 1995/96 Agricultural Census, only in eight of the total of 26 Brazilian states, were 50 per cent or more of the farms treated "systematically" with mineral fertilizers; in many states it was less than 25 per cent, and in five states even less than 12 per cent (Brazilian Institute for Geography and Statistics; Censo Agropecuario1995/96, Instituto Brazileiro de Geografia e Estadistica; IBGE, www.ibge.gov.br). The geographical application distribution pattern of mineral fertilizers may be considered as an important field of research. Understanding geographical disparities in fertilization level requires a complex approach. This includes evaluation of the availability of nutrients in the soil (and related soil properties e.g. CEC and texture), the input of nutrients with fertilizer application, and the removal of nutrients by harvested yields. When all these data are compiled, it is possible to evaluate the balance of particular nutrients for certain areas, and make conclusions as to where agricultural practices should be optimized. This kind of research is somewhat complicated, because it relies on completely different sources of data, usually from incomparable data sources, e.g. soil characteristics attributed to soil type areas, in contrast to yields by administrative regions, or farms. A priority tool in this case is the Geographical Information System (GIS), which enables attribution of data from different fields to the same territorial units, and makes possible integration of these data in an "inputoutput" model, where "input" is the natural availability of a nutrient in the soil plus fertilization, and "output" export of the same nutrient with the removed harvested yield.

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Este avance de investigación pretende ofrecer una visión preliminar de un fenómeno bastante reciente que se está dando en Costa Rica y particularmente en el Valle Central: la urbanización del espacio agrícola. Este proceso se está desarrollando más allá del espacio suburbano y presenta una especialidad diferente, ya que aquí la organización social campesina y las actividades agropecuarias siguen siendo predominantes. Sin embargo, esta extremadamente vinculado con el proceso de metropolizacion que surge en el país. Se está asistiendo, pues, a una reubicación de los espacios residenciales de las clases de mejores ingresos, las cuales influenciadas tal vez por un modelo ideológico importado, buscan poder disfrutar de las ventajas que ofrece el espacio rural pero con la posibilidad de seguir trabajando en la ciudad y seguir gozando de los servicios urbanos. La  rural-urbanización dentro de una estrategia global de estructuración del espacio puede ser considerada como un mecanismo de selección y una apropiación de los mejores lugares donde se dará la futura de expansión urbana. Desde esta perspectiva, resulta interesante llamar la atención de cómo ciertos sectores sociales están proyectando desde ahora la futura expansión del espacio metropolitano.   SUMMARY This preliminary investigative report presents a viewpoint about a very recent phenomenon that is occurring in Costa Rica and especially in the Central Valley: the urbanization of the agrarian space. This process is developing beyond the suburban areas and presents a different spacial structure because in these areas, the rural social structures and the livestock and agricultural activities are still predominant. Nevertheless, such activities are very much related to the urbanization process occurring in the country. As such, we are witnessing a reubication of the residential structure of the high-income classes, of which, influenced perhaps by an improved idiologic model, hope to enjoy the advantages offered by a rural area but also taking advantage of the convenience offered by the urban benefits; plus the opportunity to keep working in the city. The process of rural urbanization conceived in a global strategy of spatial structures, can be considered as a selection and appropriation mechanism of the best areas for the future urban expansion. From this perspective, it is interesting to call attention to the process by which certain social sectors are now projecting the future organization of the metropolitan area.  In reference to the real-estate capital invested in the study areas, and specifically to Costa Rica capital, this investment in the promotion of real-estate, acts as a shelter sector, by changing the course of direction of the capital accumulated in the other economic sectors, especially considering that the real-estate sector insures more secure profits in spite of the relatively insignificant recuperation rate of the capital investment comparison to the industrial sector, where more capital risks occur, above all during an economic crisis.  At present, the zones influenced by rural urbanization are affected by a modification in their productive structure, in other words, what were once agricultural zones, are now converted to residential zones. This produces spectacular changes in the composition of the work force by producing service-oriented employment that leads to the following abandonment of the agricultural activities.  From a social point of view, this rural urbanization pattern provokes a marked spatial segregation, in which an exclusive high income social group with a particularly consuming life style is noted at one level, and on the other, social groups that inhered patterns of rural life with more traditional lifestyles. In reference to the community level in the study areas, localized conflicts have emerged between local people and the new residents. These conflicts are highly conditioned by the insertion in the communities of these new residents.       RESUME   Ce document préliminaire décrit un phénomène assez récent au Costa Rica, qui affecte plus particulièrement la « Vallée Centrale ». il s’agit de l’urbanisation de l’espace agricole.  Ce sont des espaces franchement ruraux, bien au-delà des banlieues, qui sont affectés par ce processus qui, en conséquence, montre des caractères différents: comme se maintien de la organisation social liée aux activités agricoles; en face l’infiltration d’un autre mode de vie dû à sa transformation en espace résidentiel pour classes aux revenus élevés qui, peut-être, influencées par un modèle culturel importé, préfèrent une localisation qui puisée leus offrir à  la fois les avantages de vivre dans un espace rural avec ceux de la ville, lieu de travail suffisamment proche dont elles continuent à pouvoir utiliser ses services. Ce modèle culturel doit être considère en fonction du processus de métropolitain apparu dan le pays. L’urbanisation de l’espace rural, dans une stratégie globale de structuration de l’espace peut se considérer comme un mécanisme de sélection et d’appropriation des meilleurs sites de l’expansion urbaine future.  Dans cette perspective, il est intéressant de constater qu’il existe déjà, de la part certains secteurs sociaux, un projet d’organisation de l’espace métropolitain futur. Le foncier est considéré comme un secteur refuge pour les capitaux nationaux d’où l’intérêt de la spéculation pour ces zones. En effet, ce placement, plus sûr, malgré un plus faible taux de récupération du capital, est préfère à d’ autres- comme l’investissement industriel- plus rentables, mais plus risqués, surtout en temps de crise. L’urbanisation de l’espace rural s’accompagne d’une modification des structures productives : moins d’agriculture et évolution de l’emploi vers le tertiaire liée à la présence de nouveaux résidents. Du point de vue social, cette situation se traduit par une très nette ségrégation spatiale. D’un côte, un group socio-économique aux revenus élèves représentant  la société de consommation ; de l’autre, les ruraux au style de vie plus traditionnel. Il en résulte une certaine tension entre les deux groupes.

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Introduction. This is a pilot study of quantitative electro-encephalographic (QEEG) comodulation analysis, which is used to assist in identifying regional brain differences in those people suffering from chronic fatigue syndrome (CFS) compared to a normative database. The QEEG comodulation analysis examines spatial-temporal cross-correlation of spectral estimates in the resting dominant frequency band. A pattern shown by Sterman and Kaiser (2001) and referred to as the anterior posterior dissociation (APD) discloses a significant reduction in shared functional modulation between frontal and centro-parietal areas of the cortex. This research attempts to examine whether this pattern is evident in CFS. Method. Eleven adult participants, diagnosed by a physician as having CFS, were involved in QEEG data collection. Nineteen-channel cap recordings were made in five conditions: eyes-closed baseline, eyes-open, reading task one, math computations task two, and a second eyes-closed baseline. Results. Four of the 11 participants showed an anterior posterior dissociation pattern for the eyes-closed resting dominant frequency. However, seven of the 11 participants did not show this pattern. Examination of the mean 8-12 Hz amplitudes across three cortical regions (frontal, central and parietal) indicated a trend of higher overall alpha levels in the parietal region in CFS patients who showed the APD pattern compared to those who did not have this pattern. All patients showing the pattern were free of medication, while 71% of those absent of the pattern were using antidepressant medications. Conclusions. Although the sample is small, it is suggested that this method of evaluating the disorder holds promise. The fact that this pattern was not consistently represented in the CFS sample could be explained by the possibility of subtypes of CFS, or perhaps co-morbid conditions. Further, the use of antidepressant medications may mask the pattern by altering the temporal characteristics of the EEG. The results of this pilot study indicate that further research is warranted to verify that the pattern holds across the wider population of CFS sufferers.

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Enterprise Application Integration (EAI) is a challenging area that is attracting growing attention from the software industry and the research community. A landscape of languages and techniques for EAI has emerged and is continuously being enriched with new proposals from different software vendors and coalitions. However, little or no effort has been dedicated to systematically evaluate and compare these languages and techniques. The work reported in this paper is a first step in this direction. It presents an in-depth analysis of a language, namely the Business Modeling Language, specifically developed for EAI. The framework used for this analysis is based on a number of workflow and communication patterns. This framework provides a basis for evaluating the advantages and drawbacks of EAI languages with respect to recurrent problems and situations.