Structure and dynamics of a Cariniana estrellensis (Lecythidaceae) population in a fragment of Atlantic Forest in Minas Gerais, Brazil

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Community structure of aquatic insects (Ephemeroptera, Plecoptera, and Trichoptera) in Cerrado streams of Paraguay, Paraná, and São Francisco river basins

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Husserl on Geometry and Spatial Representation

Husserl left many unpublished drafts explaining (or trying to) his views on spatial representation and geometry, such as, particularly, those collected in the second part of Studien zur Arithmetik und Geometrie (Hua XXI), but no completely articulate work on the subject. In this paper, I put forward an interpretation of what those views might have been. Husserl, I claim, distinguished among different conceptions of space, the space of perception (constituted from sensorial data by intentionally motivated psychic functions), that of physical geometry (or idealized perceptual space), the space of the mathematical science of physical nature (in which science, not only raw perception has a word) and the abstract spaces of mathematics (free creations of the mathematical mind), each of them with its peculiar geometrical structure. Perceptual space is proto-Euclidean and the space of physical geometry Euclidean, but mathematical physics, Husserl allowed, may find it convenient to represent physical space with a non-Euclidean structure. Mathematical spaces, on their turn, can be endowed, he thinks, with any geometry mathematicians may find interesting. Many other related questions are addressed here, in particular those concerning the a priori or a posteriori character of the many geometric features of perceptual space (bearing in mind that there are at least two different notions of a priori in Husserl, which we may call the conceptual and the transcendental a priori). I conclude with an overview of Weyl's ideas on the matter, since his philosophical conceptions are often traceable back to his former master, Husserl.

Population structure, distribution and abundance patterns of the patagonian smoothhound Mustelus schmitti Springer, 1939 (Chondrichthyes, Elasmobranchii, Triakidae) in the rio de La Plata and inner continental shelf , sw Atlantic ocean (34º30'-39º30'S)

Um total de 4824 Mustelus schmitti foi amostrado. As fêmeas apresentaram comprimento total de 25-93 cm na primavera e 28-90 cm no verão enquanto os machos apresentaram 34-82 e de 28-77 cm, respectivamente. A composição de comprimentos da população mostrou diferenças significativas entre primavera e verão sendo as fêmeas maiores do que os machos. A distribuição de comprimento total não variou significativamente entre cruzeiros. A densidade variou significativamente entre cruzeiros nos machos sendo que a variação não foi expressiva nas fêmeas. No cruzeiro da primavera, ambos os sexos ocorreram em profundidades menores do que 50 m, as fêmeas ocorrendo em toda a área de estudo, as adultas somente acima da latitude 35°30'S. Os machos adultos foram observados em toda a área sendo que os imaturos somente em dois arrastos na Bahia de Samborombón. O cruzeiro de verão mostrou uma distribuição descontínua da espécie ao longo da área de estudo, resultando na segregação espacial em dois grupos, com predominância de fêmeas imaturas em ambos.

Uncertainties in the prediction of spatial variability of soil CO2 emissions and related properties

A emissão de CO2 do solo apresenta alta variabilidade espacial, devido à grande dependência espacial observada nas propriedades do solo que a influenciam. Neste estudo, objetivou-se: caracterizar e relacionar a variabilidade espacial da respiração do solo e propriedades relacionadas; avaliar a acurácia dos resultados fornecidos pelo método da krigagem ordinária e simulação sequencial gaussiana; e avaliar a incerteza na predição da variabilidade espacial da emissão de CO2 do solo e demais propriedades utilizando a simulação sequencial gaussiana. O estudo foi conduzido em uma malha amostral irregular com 141 pontos, instalada sobre a cultura de cana-de-açúcar. Nesses pontos foram avaliados a emissão de CO2 do solo, a temperatura do solo, a porosidade livre de água, o teor de matéria orgânica e a densidade do solo. Todas as variáveis apresentaram estrutura de dependência espacial. A emissão de CO2 do solo mostrou correlações positivas com a matéria orgânica (r = 0,25, p < 0,05) e a porosidade livre de água (r = 0,27, p <0,01) e negativa com a densidade do solo (r = -0,41, p < 0,01). No entanto, quando os valores estimados espacialmente (N=8833) são considerados, a porosidade livre de água passa a ser a principal variável responsável pelas características espaciais da respiração do solo, apresentando correlação de 0,26 (p < 0,01). As simulações individuais propiciaram, para todas as variáveis analisadas, melhor reprodução das funções de distribuição acumuladas e dos variogramas, em comparação à krigagem e estimativa E-type. As maiores incertezas na predição da emissão de CO2 estiveram associadas às regiões da área estudada com maiores valores observados e estimados, produzindo estimativas, ao longo do período estudado, de 0,18 a 1,85 t CO2 ha-1, dependendo dos diferentes cenários simulados. O conhecimento das incertezas gerado por meio dos diferentes cenários de estimativa pode ser incluído em inventários de gases do efeito estufa, resultando em estimativas mais conservadoras do potencial de emissão desses gases.

Effect of addition of MTES on the structure of siloxane-PPG nanocomposites

Hybrid transparent and flexible siloxane-polypropyleneglycol (PPG) materials with covalent bonds between the inorganic (siloxane) and organic (polymeric) phases were prepared by sol-gel process. In order to improve the quality of the mechanical properties of these materials, different amounts of methyltriethoxysilane (MTES) were added to the initial sol. The effect of MTES addition on the structure of the composites was studied by Small-Angle X-Ray Scattering (SAXS) and Si-29 Nuclear Magnetic Resonance (Si-29 NMR). In absence of MTES, SAXS spectra exhibit a peak that is assigned to spatial correlation due to short range order between the siloxane clusters embedded in the polymeric phase. The experimental results indicate that, for low MTES concentrations ([MTES]/[O] less than or equal to 0.8, O: ether-type oxygen of PPG), the silicon species resulting from hydrolysis and condensation of MTES fill the open spaces between polymeric chains, interacting with the ether-type oxygens. For larger MTES content ([MTES]/[O] greater than or equal to 0.8), the number of free ether-type oxygen sites avalaible for reaction with such silicon species is not large enough. Consequently, a fraction of silicon species resulting from MTES addition graft to siloxane clusters formed by hydrolysis and condensation of the hybrid precursor. For all MTES concentrations the condensation degree of the siloxane phase, determined from Si-29 NMR spectroscopy, is high (> 69%), as expected under neutral pH synthesis conditions.

Structure of potentials with N higgs doublets

Extensions of the standard model with N Higgs doublets are simple extensions presenting a rich mathematical structure. An underlying Minkowski structure emerges from the study of both variable space and parameter space. The former can be completely parametrized in terms of two future lightlike Minkowski vectors with spatial parts forming an angle whose cosine is -(N-1)(-1). For the parameter space, the Minkowski parametrization enables one to impose sufficient conditions for bounded below potentials, characterize certain classes of local minima, and distinguish charge breaking vacua from neutral vacua. A particular class of neutral minima presents a degenerate mass spectrum for the physical charged Higgs bosons.

Silica-PEG hybrid ormolytes: structure and properties

The effect of lithium salt doping on the structure and ionic conduction properties of silica-polyethyleneglycol composites is reported. These materials, so called ormolytes (organically modified electrolytes), were obtained by the sol-gel process. They have chemical stability due to the covalent bonds between the inorganic (silica) and organic (polymer) phase. The structure of these hybrid materials was investigated by small-angle X-ray scattering (SAXS) as a function of lithium concentration [O]/[Li] (O being the oxygens of the ether type). The spectra have a well-defined peak attributed to the existence of a liquid-like spatial correlation of silica clusters. The ionic conductivity was studied by AC impedance spectroscopy and is maximum for [O]/[Li] = 15. This result is consistent with SAXS and thermo-mechanical analysis measurements and is due to the formation of cross-linking between the polymer chains for the larger lithium concentrations. These materials are solid, transparent, flexible and have an ionic conductivity up to 10(-4) S/cm. (C) 1999 Elsevier B.V. B.V. All rights reserved.

Prediction and spatial variability of soil dynamic properties in sugar cane fields of São Paulo State Brazil

The objective of this work was to model and diagnose the spatial variability of soil load support capacity (SLSC) in sugar cane crop fields, as well as to evaluate the management impact on São Paulo State soil structure. The investigated variables were: pressure preconsolidation (sigma(p)), apparent cohesion () and internal friction angle (). The conclusions from the results were that the models and spatial dependence maps constitute important tools in the prediction and location of the mechanical internal strength of soils cultivated with sugar cane. They will help future soil management decisions so that soil structure sustainability will not be compromised.

Microhabitat and plant structure of Compsopogon coeruleus (Compsopogonaceae, Rhodophyta) populations in streams from São Paulo State, southeastern Brazil

Microhabitat distribution was investigated in three populations of C. coeruleus to determine the distributional patterns and their controlling factors, as well as morphometric adaptations to varying conditions on a scale of a few centimetres. Morphometric variations and their relations with physical variables (current velocity, irradiance, depth and type of substratum) revealed some particular characteristics for each population and indicate particular adaptations. However, some trends were clear: 1) larger plants (length and/or diameter) produced a higher quantity of monosporangia in the three populations; 2) plant length and diameter were positively correlated in two populations; 3) plant diameter was positively correlated with current velocity in two populations; 4) higher percent cover was associated with substrata composed of macrophytes in two populations. C. coeruleus occurred under relatively wide microhabitat conditions and had high niche width values, suggesting a tolerance to considerable variation in physical variables. These characteristics contribute to the species' wide distribution in Brazilian streams, both spatial (at distinct scales) and seasonal. (C) ADAC / Elsevier, Paris.

Food web structure in a tropical stream ecosystem

This study investigated the structure and properties of a tropical stream food web in a small spatial scale, characterizing its planktonic, epiphytic and benthic compartments. The study was carried out in the Potreirinho Creek, a second-order stream located in the south-east of Brazil. Some attributes of the three subwebs and of the conglomerate food web, composed by the trophic links of the three compartments plus the fish species, were determined. Among compartments, the food webs showed considerable variation in structure. The epiphytic food web was consistently more complex than the planktonic and benthic webs. The values of number of species, number of links and maximum food chain length were significantly higher in the epiphytic compartment than in the other two. Otherwise, the connectance was significantly lower in epiphyton. The significant differences of most food web parameters were determined by the increase in the number of trophic species, represented mainly by basal and intermediate species. High species richness, detritus-based system and high degree of omnivory characterized the stream food web studied. The aquatic macrophytes probably provide a substratum more stable and structurally complex than the sediment. We suggest that the greater species richness and trophic complexity in the epiphytic subweb might be due to the higher degree of habitat complexity supported by macrophyte substrate. Despite differences observed in the structure of the three subwebs, they are highly connected by trophic interactions, mainly by fishes. The high degree of fish omnivory associated with their movements at different spatial scales suggests that these animals have a significant role in the food web dynamic of Potreirinho Creek. This interface between macrophytes and the interconnections resultant from fish foraging, diluted the compartmentalization of the Potreirinho food web.

The role of spatial and temporal descriptors for neotropical tadpole communities in southern Brazil

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Passive and active dispersers respond similarly to environmental and spatial processes: an example from metacommunity dynamics of tree hole invertebrates

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Microhabitat and plant structure of Batrachospermum (Batrachospermales, Rhodophyta) populations in four streams of São Paulo State, southeastern Brazil

Microhabitat and plant structure of seven Batrachospermum populations (four of Batrachospermum delicatulum (= Sirodotia delicatula), one of Batrachospermum macrosporum and two of the 'Chantransia' stage), including the influence of physical variables (current velocity, depth, irradiance and substratum), were investigated in four streams of São Paulo State, southeastern Brazil. The populations of B. delicatulum and the 'Chantransia' stage occurred under very diverse microhabitat conditions, which probably contributes to their wide spatial and seasonal distribution in Brazilian streams. Results suggest branch reconfiguration as a probable mechanism of adaptation to current velocity based on the occurrence of: (i) B. macrosporum (a large mucilaginous form with presumably little ability for branch reconfiguration) under lower current velocity than B. delicatulum; (ii) only dense plants in populations with high current velocities (> 60 cm s-1), whereas 53-77% of dense plants were seen in populations exposed to lower currents (< 40 cm s-1); (iii) positive correlations of plant length with internode length in populations under low current velocities and negative correlation in a population with high velocity (132 cm s-1); and (iv) negative correlations of current velocity with plant diameter and internode length in a population under high flow. This study, involving mainly dioecious populations, revealed that B. delicatulum displayed higher fertilization rates than B. macrosporum. A complementary explanation for a dioecious species to increase fertilization success was proposed consisting of outcrossing among intermingled male and female adjacent plants within an algal spot.

Foraging, diet and community structure in an epigaeic ant (Hymenoptera: Formicidae) assemblage: the role of recruitment

The significance of recruitment systems for community structure of epigaeic ants in a tropical upland forest in southern Brazil was evaluated by examining patterns of spatial occurrence at fixed points. Normal exploratory activity was evaluated with pitfall traps, while the effect of recruitment and diet was evaluated by using honey and sardine baits at the same points. Through techniques developed for environmental impact assessment, the significance of recruitment was evaluated following perturbation, or the placement of bait. Of the 46 species encountered, 15 were sufficiently frequent to study. Of these, only 6 showed significant spatial frequency changes at baits when compared with pitfall trap collections. In one analysis, monthly differences were important for a few smaller species, suggesting thermic limitations, while bait types either increased or decreased spatial point usage. The magnitude of spatial point variation is an index for the strength of recruitment in community organization. Bait types suggest nutritional possibilities of each species. Both recruitment and diet are probably functions of the species composition of the ant community.