Journal articles on the topic 'Textual morphogenesis'

Differentiating tension wood was observed in order to analyse the changes occurring during cell wall morphogenesis. Specimens were taken from trees in Guyana. Wall texture was analysed by means of ultrastructural cytochemistry. Modifications were encountered in fibre and vessel walls of tension wood when compared to typical wood. The changes were twofold: variation in the layering of polylamellate walls, and the deposition of a gelatinous layer in the fibre cell walls. Results are discussed in terms of variations in the rhythmic nature of cell wall deposition. Data confirm that the morphogenesis of the wall is a modular process allowing the cells to adapt to growth constraints.

This article presents an abstract computation model of the evolution of camouflage in nature. The 2D model uses evolved textures for prey, a background texture representing the environment, and a visual predator. A human observer, acting as the predator, is shown a cohort of 10 evolved textures overlaid on the background texture. The observer clicks on the five most conspicuous prey to remove (“eat”) them. These lower-fitness textures are removed from the population and replaced with newly bred textures. Biological morphogenesis is represented in this model by procedural texture synthesis. Nested expressions of generators and operators form a texture description language. Natural evolution is represented by genetic programming (GP), a variant of the genetic algorithm. GP searches the space of texture description programs for those that appear least conspicuous to the predator.

In this communication, we report a facile nanotopographical control over a stainless steel surface via an electrophoretic deposition of colloidal amphiphilic chitosan for preferential growth, proliferation or migration of vascular smooth muscle cells (VSMCs) and human umbilical vein endothelial cells (HUVECs). Atomic force microscopy revealed that the colloidal surface exhibited a deposition time-dependent nanotopographical evolution, wherein two different nanotopographic textures indexed by ‘kurtosis’ ( R kur ) value were easily designed, which were termed as ‘sharp’ (i.e. high peak-to-valley texture) surface and ‘flat’ (i.e. low peak-to-valley texture) surface. Cellular behaviour of VSMCs and HUVECs on both surfaces demonstrated topographically dependent morphogenesis, adherent responses and biochemical properties in comparison with bare stainless steel. The formation of a biofunctionalized surface upon a facile colloidal chitosan deposition envisions the potential application towards numerous biomedical devices, and this is especially promising for cardiovascular stents wherein a new surface with optimized texture can be designed and is expected to create an advantageous environment to stimulate HUVEC growth for improved healing performance.

Correct orientation of cell division is extremely important in the maintenance, regeneration, and repair of continuously proliferating tissues, such as the epidermis. Regulation of the axis of division of epidermal cells prevents the apoptosis-induced compensatory proliferation, and eventually the cancer. Thus, the orientation of cell division is critical for maintaining the tissue architecture. In this study, we investigated the effects of S. europaea extract on the texture of human skin and the behavior of these cells during skin morphogenesis. In sun-exposed skin, S. europaea improved the texture. A multilayered, highly differentiated in vitro skin model indicated that, S. europaea extract suppressed the UVB-induced changes in the morphology of basal keratinocytes. Orientation of cell division was determined by measuring the axis of mitosis in the vertical sections of our experimental model. Analyses of the digital images revealed that S. europaea preserved the axis of division of basal keratinocytes from UVB-induced perturbations. Our findings uncover a new mechanism by which S. europaea responds to the spindle misorientation induced by UVB.

Localized deformation patterns are a common motif in morphogenesis and are increasingly finding applications in materials science and engineering, in such instances as mechanical memories. Here, we describe the emergence of spatially localized deformations in a minimal mechanical system by exploring the impact of growth and shear on the conformation of a semi-flexible filament connected to a pliable shearable substrate. We combine numerical simulations of a discrete rod model with theoretical analysis of the differential equations recovered in the continuum limit to quantify (in the form of scaling laws) how geometry, mechanics and growth act together to give rise to such localized structures in this system. We find that spatially localized deformations along the filament emerge for intermediate shear modulus and increasing growth. Finally, we use experiments on a 3D-printed multi-material model system to demonstrate that external control of the amount of shear and growth may be used to regulate the spatial extent of the localized strain texture.

The wing scales of the Green Hairstreak butterfly Callophrys rubi consist of crystalline domains with sizes of a few micrometers, which exhibit a congenitally handed porous chitin microstructure identified as the chiral triply periodic single-gyroid structure. Here, the chirality and crystallographic texture of these domains are investigated by means of electron tomography. The tomograms unambiguously reveal the coexistence of the two enantiomeric forms of opposite handedness: the left- and right-handed gyroids. These two enantiomers appear with nonequal probabilities, implying that molecularly chiral constituents of the biological formation process presumably invoke a chiral symmetry break, resulting in a preferred enantiomeric form of the gyroid structure. Assuming validity of the formation model proposed by Ghiradella H (1989) J Morphol 202(1):69–88 and Saranathan V, et al. (2010) Proc Natl Acad Sci USA 107(26):11676–11681, where the two enantiomeric labyrinthine domains of the gyroid are connected to the extracellular and intra-SER spaces, our findings imply that the structural chirality of the single gyroid is, however, not caused by the molecular chirality of chitin. Furthermore, the wing scales are found to be highly textured, with a substantial fraction of domains exhibiting the <001> directions of the gyroid crystal aligned parallel to the scale surface normal. Both findings are needed to completely understand the photonic purpose of the single gyroid in gyroid-forming butterflies. More importantly, they show the level of control that morphogenesis exerts over secondary features of biological nanostructures, such as chirality or crystallographic texture, providing inspiration for biomimetic replication strategies for synthetic self-assembly mechanisms.

The area of investigation lies between Maneri and Gangnani along the Bhagirathi river in the lesser and central Himalayan block of Garhwal Himalayas. The rocks of Garhwal group are represented by quartzites, sericite quartzite’s and talc chlorite schist intruded by metabasics, whereas the Central crystallines are constituted by gneisses, schists, migmatites and amphibolites. For the purpose of drainage basin morphometric analysis 100 third order drainage basins were marked. Drainage basin morphometric parameters of 100 basins were calculated. On the basis of lithology and tectonic setup,the area was divided into three morphogenetic units viz Central crystallines, Thrust zone and Garhwal group. The basins which were situated below 2500 mts are categorized under low altitudes and above 2500 as basins of higher altitudes.The relationship between deainage basinmorphometric parameters and altitude suggest that basins situated at higher altitude have higher value of stream frequency, number of first and second order streams,fine texture and low drainage density.

Cell wall microfibril alignment in the tubular portion of Equisetum hyemale root hairs is helicoidal. Lamellae of helicoidal texture are deposited from tip to base; thus, different microfibril orientations are aligned with the plasma membrane successively. Zones with constant mean microfibril orientation are about 300 μm long. In any such zone of dry-cleaned, shadowed preparations, the frequency of microfibrils at the proximal end is 5 to 7 microfibrils per micrometre, which decreases to 0 at the distal end. The orientation of microfibrils of the underlying lamella, the microfibril frequency of which is 5 to 7/μm throughout, is the same as the microfibril orientation of the neighbouring distal lamella. Microfibrils of the cell wall are randomly oriented in the hair dome. Microtubule alignment in these root hairs was examined by means of freeze substitution. In the extreme tip of the root hair, microtubules run parallel to the plasma membrane and transverse to the long axis of the hair; the hemisphere of the hair contains randomly oriented microtubules. From extreme tip to base of the hair dome, microtubules become more and more axially aligned, and remain axially oriented in the hair tube. Further down the hair, where microfibril alignment is transverse and microfibrils are actively being deposited, microtubules still run in the axial direction. The observations emphasize the involvement of microtubles in root hair tip morphogenesis, but not in determining the alignment of the microfibrils in the hair tube.

The paper establishes the general features of the soil morphogenesis in ravined forests of Dnieper Prysamaria and genetic relationships of forest soils with zonal chernozem under herbaceous associations based on the detection of morphological properties that are «lithogenic», that is inherited from deluvial material and «pedogenic» features formed directly in the forest soil. The study area is located on the Dnieper Prysamaria (Dnipropetrovsk region) within the area of the steppes. The trial areas are incorporated in the upper Deep ravine, located in the upland part of watershed landscape. Catena is represented by five typical sections – between edging of the ravined forest and the field in the middle thirds of the slopes of the northern and southern exposures and in the thalweg of the ravine. Samples for meso-morphological studies were selected by genetic horizons, samples for soil horizons were selected using a soil drill. Basic morphological characteristics were determined in the laboratory (except for the hardness index). The mathematical processing of the results was carried out by methods of nonparametric statistics (method K-means). It was found that, despite the temporal and spatial disorder of deluvial material deposition processes and the differences of the water regime in the thalweg on the slopes, in the ravined biogeocenoses the forest soils are formed with common features of morphological organization of the genetic profile of the individual and morphological properties. The uniformity of the general structure is shown in a set sequence and the power of the genetic horizons, polycyclic and texture eluvial-illuvial differentiation of the genetic profile. The uniformity of the changes in the profile of the individual morphological properties is shown in the form of colour options of genetic horizons (due to humus content talus deposits), changing the particle size distribution of horizons in accordance with the general differentiation profile on eluvial and illuvial (due lessivage) part, changes in the morphology and dimensions of structural units related to changes in the structure of hardness horizons intensive leaching of carbonates from the profile of forest soils. The necessity of research processes clayization profile in situ, their role in the morphogenesis of compacted horizons are noted. There are two groups of properties that make it possible to analyze the micromorphology level communication between the soils in the catena. The first – a lithogenic conditionally or diluvial material properties, which persist for a long time in a forest soil – granulometry and less coloration horizons. The second – a pathogenic properties, sharply differing in the studied soils associated with the peculiarities of morphogenesis of a particular genetic profile and specific genetic horizon. These include the level of occurrence of carbonates in the profile and intensity of effervescence, the morphology of the structural units, the hardness of the genetic horizons, the level of spot colour. Cluster analysis identified a statistically illustrates the differences between the morphological structure of the soil catena, combining in one cluster the ravined soils on deluvial deposits under forest vegetation, and in the other – the soils on the loess under herbaceous vegetation. The contrast of differences increases down the profile.

Placental chorionic surface vascular networks (PCSVNs) are essential high-capacitance, low-resistance distribution and drainage networks, and are hence important to placental function and to fetal and newborn health. It was hypothesized that variations in the PCSVN structure may reflect both the overall effects of genetic and environmentally regulated variations in branching morphogenesis within the conceptus and the fetus’s vital organs. A critical step in PCSVN analysis is the extraction of blood vessel structure, which has only been done manually through a laborious process, making studies in large cohorts and applications in clinical settings nearly impossible. The large variation in the shape, color, and texture of the placenta presents significant challenges to both machine and human to accurately extract PCSVNs. To increase the visibility of the vessels, colored paint can be injected into the vascular networks of placentas, allowing PCSVNs to be manually traced with a high level of accuracy.This paper provides a proof-of-concept study to explain the geometric differences between manual tracings of paint-injected and un-manipulated PCSVNs under the framework of a shape-context model. Under this framework, paint-injected and un-manipulated tracings of PCSVNs can be matched with nearly 100% accuracy. The implication of our results is that the manual tracing protocol yields faithful PCSVN representations modulo a set of affine transformations, making manual tracing a reliable method for studying PCSVNs. Our work provides assurance to a new pre-processing approach for studying vascular networks by ways of dye-injection in medical imaging problems.

ABSTRACT Vernonia condensata Baker has been traditionally used in folk medicine for the treatment of several inflammatory and infectious processes. Overexploitation of this plant species has drastically reduced its population in its natural habitat (Cerrado). Therefore, tissue culture tools, such as somatic embryogenesis, can be used as an alternative method for rapid and large-scale plant regeneration. The objectives of this study were to induce callogenesis in Vernonia condensata from different types of explants and to evaluate the structural aspects of the development of pro-embryogenic masses of this species by means of histological analyses. The formation of calli was induced from leaf explants and internodal segments, which were inoculated in EME medium supplemented with 50 g L-1 sucrose, 0.5 g L-1 malt extract and 2.68 μM NAA, plus varying concentrations of BAP (0.00, 2.22, 4.44 or 8.88 μM). After 40 days, the following morphogenetic traits were evaluated: intensity of callus formation, intensity of oxidation, callus texture, and morphogenesis. The calli with embryogenic masses were analyzed by light and scanning electron microscopy. Both types of explants were responsive regarding callogenesis, with the BAP concentration of 4.44 μM promoting the formation of friable calli associated with a larger percentage of calli with embryogenic masses. Cells from leaf explants and internodal segments were able to dedifferentiate and change into embryonic structures.

Wet agglomeration of granular materials is widely carried out in many industrial fields, such as the pharmaceutical and food industries. This process must be optimized in terms of yields and quality of the final product. A lot of studies have shown that agglomeration occurs under capillary, viscous and frictional forces and can be divided into four steps: nucleation, consolidation, growth and rupture. This general description of agglomeration does not take into account the simultaneous changes of agglomerates size, texture and saturation degree with respect to the increase in water content. The aim of this work is to propose a description of the agglomeration based on experimental observations and to take into account the aforementioned aspects to propose a model. In this study, experiments are carried out on kaolin in a low shear mixer for various operating conditions: three speeds of blade rotation, two wetting modes. The evolution of agglomerates granulometric and textural parameters is taken into account by image analysis and immersion in paraffin, respectively. This study makes it possible to highlight an increase in agglomerates size associated with a solid volume fraction reduction when there is an increase in water content. A power law connects solid volume fraction and median diameter of agglomerates making it possible to identify a fractal growth process between the grain and pasty-like scale. This well-know approach in colloidal aggregation is new in the powder agglomeration field. Fractal dimension defined this way is mainly affected by the drop size generated during wetting. These experiments highlight the weak influence of the other process parameters tested. For a wetting mode, an equation leading to the direct determination of the desired size of agglomerates with water content is proposed. Applied to agglomeration, fractal morphogenesis should become a potential tool in product engineering.

The soils of Agoi-Ibami in central Cross River State of Nigeria were evaluated for their mechanical and textural compositions in the field. The objective was to present to small scale, subsistence farmers, with limited access to external farm-inputs for time consuming and expensive laboratory analysis, soil data for on-site and field land use and management decisions. Three profile pits were sunk, along three well defined and selected toposequences, on three landscape elements of crest, middleslope and valley bottom in three land use types of forest (FS), rubber (RS), and arable (AS). Relevant environmental properties were inventorized and the profiles described in the moist state. Their textures were determined by the feel method in the field among other morphological properties. The field investigation showed the soils to be predominatly loamy soils. After the field investigation, soil samples were collected from the morphogenetic horizons for determination of their mechanical composition in the laboratory to supplement the field investigation. Their loamy textures and mechanical composition inferred from their loamy texture impact unique physical and chemical properties like good water holding capacity, good drainage, fertile and productive soils and good for irrigation. Loamy soils exhibit properties intermediate between sandy and clayey soils. Loamy soils are considered best for agricultural production because they hold more water and nutrients than sandy soils and have better drainage, aeration and tillage properties than clayey soils. They have slight plastic and sticky workable properties ideal for crop growth and crop productivity. Therefore knowing the texture of soils and their mechanical composition in the field their properties can be inferred and land use and management decisions can be taken on-site without recourse to expensive and time consuming laboratory analyses which are beyond the capacity of resource poor small-scale and subsistence farmers in developing countries and or sub-Saharan Africa. The land use and management decisions are taken after mutual adaptation and adjustments of the description of the land use and the increasingly known soil qualities in the field.

O comportamento do U e do Th foi analisado durante a evolução pedogeoquímica e morfogenética de paisagens tropicais úmidas, sobre rocha granítica com teores normais desses elementos, visando estabelecer relações entre rocha-mãe e anomalias de U e de Th, tipos de solos residuais e geoformas resultantes dessa evolução. Em uma vertente caracterizada pelo sistema de transformação Latossolo-Solo Podzólico, anomalias de U e de Th de grande expressão geográfica e intensidade ocorrem na paisagem eluvial, parte superior da vertente onde se verificam declividades entre 0 e 8%. Tais radioanomalias são de natureza relativa/residual predominante e com baixa proporção de U adsorvido, e situam-se no topo do horizonte B dos Latossolos. As anomalias radioativas mais intensas, porém de menor expressão geográfica, localizam-se na paisagem transeluvial, parte mediana das vertentes com declividades entre 8 e 45%. São em parte residuais e em parte absolutas, resultantes da podzolização dos Latossolos, e associam-se ao topo do horizonte B textural dos Solos Podzólicos. Radioanomalias de menor intensidade, e essencialmente uraníferas, situam-se na paisagem supraqual, parte inferior e com baixas declividades da vertente. São de caráter absoluto, com o U fixado principalmente por adsorção às fases argilo-orgânica e óxido dos horizontes A0 e A1 dos Solos Hidromórficos. Nessa paisagem, em áreas de influência da atual rede de drenagem, pode existir desequilíbrio radioativo entre os radionuclídeos da série do 238 U, com reflexos negativos nas intensidades das radiações gama emitidas. Isto se deve à pouca idade de deposição do U nesses locais durante a podzolização, entre 100.000 e 500.000 anos. Então, no contexto enfocado, a transformação de rochas com teores normais em U e em Th pode resultar em materiais secundários, com concentrações nesses radionuclídeos mais elevadas que as existentes nas rochas inalteradas. A atuação dos processos geoquímicos responsáveis pela redistribuição do U e do Th ocorreu concorrentemente com a dos processos pedogenéticos, morfogenéticos e hidrogeológicos, durante a evolução das paisagens. Os principais tipos de anomalias de U e de Th, paisagens geoquímicas elementares, tipos e horizontes de solos residuais e geoformas estão cronológica e espacialmente relacionados. GEOCHEMICAL ANOMALIES OF U AND TH, RESIDUAL SOILS AND GEOFORMS IN HUMID TROPICAL LANDSCAPES OVER GRANITE Extended Abstract The geochemical behavior of U and Th during the evolution of humid tropical landscapes was analysed, with the objective to establishing relationships between parent rock, and the resulting U and Th anomalies, types of residual soils and geoforms. In one slope over granite with normal contents of U and Th, and characterized by the soil association Latosol-Podzolic, the pedologic horizons providers and receivers of these radionuclides during the processes of latolization and podzolization were evaluated. Studies were carried out on the main characteristics of the radioanomalies that took place in each landscape, mainly the concentration levels and the secondary hosting phases of U and Th, and their impact on the ratio Th/U and Us/Ut (soluble uranium/total uranium), and on their relative gammaradiometric intensities. Multi and interdisciplinary studies were done, making use of the various data and concepts from worldwide scientific literature, specifically in the fields of geochemistry and pedology. In the first case, emphasis was placed on the characteristics of the primary concentrations of U and Th (table 1), and on the geochemical concepts of element abundance, gradients, migration, flows and geochemical barriers, and of elementary landscape geochemistry (figure 1). In the field of pedology, the concept of transformational pedologic system and the cronology of the main pedogenetic phases were addressed. Moreover, concepts and elements of the areas of geomorphology, hydrogeology of the phreatic aquifer system and the nuclear physics of the series of 238 U and 232 Th were used and approached from a tridimensional and systemic perspective. The analyses were carried out in short space-temporal limits, according to the dimensions of the slopes and, regarding time specifics, the pedologic scale was found to be the most relevant. In the context studied, the Latosols occur in the eluvial landscape, associated to older, more stable and higher surfaces of the slope, where declivities between 0 and 8% can be observed. In this landscape, the geochemical environment is oxidizing and the pH is acid. The main concentrations of U and Th are due to resistant minerals containing U and Th, insoluble compounds of Th, and U and Th fixed to Fe and Al oxyhydroxides and clays by adsorption. These anomalies are characterized by low Us/Ut and high Th/U ratios, and intense gamma countings (table 2 and 3). They are relative and residual in nature, and are located on the top of latosolic B horizon (figure 2). The Podzolic Soils are of lesser geographic occurrence than the Latosols. Found in the transeluvial landscape, they are related to younger surfaces in intermediate altitudes of the slope, where the declivities are between 8 and 45 %. In this landscape, a strong control of the local parameters of the environment over the configuration and spacial distribution of the soil profiles and their physical properties has been observed. The geochemical environment is oxidizing and the pH is acid on the superficial horizons, changing to reducing toward the B textural horizon (Bt), where the pH levels are higher. The main concentrations of U and Th, being the result of the reworking of those associated with the Latosols, by podzolization, and located on the top of horizon Bt (figure 2 and table 4), present higher levels and higher proportions of soluble U in relation to the total contents. These anomalies show higher Us/Ut and lower Th/U ratios compared to the same ratios in the Latosols and more intense gamma manifestations (table 2). They are partially relative and partially absolute, depending on the migration of radionuclides, inclusively in colloidal solution, due to the eluviation-illuviation processes which take place during podzolization. The Hydromorphic Soils predominate in superaqual landscape, where the aeration zone of the aquifer is either thinner or inexistent, and the water-table outcrops or is present at a shallow depth. The geochemical environment works as a reducing agent due to the frequent saturation of the soils and the presence of organic matter (OM), and the pH , in general, ranges from neutral to alkaline. Besides OM, clay phases and Fe compounds with a high cationic exchange capacity are frequently encountered, making up favorable factors for the fixation by adsorption of U originated from eluvial and transeluvial landscapes during latolization and podzolization. The main concentrations are uraniferous and absolute, associated to horizons A0 and A1 of the soils (figure 2), resulting in high ratios Us/Ut, and decreases in Th/U. The gamma radiation emissions are moderate in intensity (table 2). In this landscape, radioactive disequilibrium in the decay series of 238 U, with a negative impact for the gamma radiation intensity, may occur in places near the drainage system. This happens due to the young age of 238 U deposition in these areas, mainly during the podzolization of the Latosols, between 100,000 and 500,000 years, insufficient time for the re-establishment of the secular radioactive equilibrium in the referred series. Hence, the transformation by the action of supergenic processes, mainly the pedogeochemical ones, of rocks with normal contents of U and Th, may result in materials with different distributions and concentrations of these radionuclides, considerably higher than the ones in unaffected rocks (table 3). Even the intensively leached soils, such as the ones of the association Latosol-Podzolic, present a relative increase in the U and Th values, due to the concentration of resistant minerals and their association with oxide, clay and carbon phases of the soils. U and Th distribution and levels of concentration reveal the nature of fixation of these radionuclides in their original hosting phases and their real mobilities in the different geochemical landscapes along the slope. In conclusion, in the present study, the landscapes which show the highest probability of containing high anomalies of U and Th are the transeluvial landscape, on the top of the textural B horizon of the Podzolic Soils, and the eluvial, on the top of the latosolic B horizon of the Latosols. In the superaqual landscape, the anomalies are uraniferous and associated with horizons A0 and A1 of the Hydromorphic Soils (figure 2 and table 2). Consequently, in the referred climatic environment, the action of the geochemical processes which lead to the re-distribution of U and Th, took place concomitantly with the pedogenetic, morphogenetic and hydrogeological ones, throughout the evolution of the landscapes. The main types of U and Th anomalies, types and horizons of the residual soils, elementary geochemical landscapes and geoforms are cronologically and spatially related.

Foram estabelecidas e analisadas as principais relações entre intensidades de exalação de radônio ( 222Rn e 220Rn) e os elementos morfológicos e dinâmicos de paisagens tropicais úmidas, com o objetivo de elaborar modelos de exalação de Rn adaptados a este tipo de paisagens, e aplicáveis na escala de pequenos núcleos habitacionais. Em uma vertente sobre rocha granítica com teores normais em U e Th, e caracterizada pela associação Latossolo-Solo Podzólico, os produtos de atuação dos processos supergênicos, com destaque para a transição de latolização em podzolização, e o atual regime hídrico do aqüífero freático, foram relacionados aos processos radioativos de geração, emanação e migração de Rn, verificando-se como tais inter-relações afetam a sua exalação nas paisagens. Tal abordagem foi fundamentada nos conceitos de sistema pedológico de transformação e de geoquímica de paisagens, além de conceitos da física e geologia nucleares e elementos climatológicos e hidrogeológicos do macroambiente, num enfoque interdisciplinar, tridimensional e sistêmico. Às vertentes configuradas em paisagens elementares; eluvial, transeluvial e supraqual associam-se diferentes geoformas, tipos e espessuras de solos residuais e radioanomalias com diferentes intensidades e formas de hospedagem de U e de Th. Com base em tais elementos, suas relações espaciais com o sistema freático, e considerando a umidade dos solos na capacidade de campo, as possibilidades de maiores taxas de exalação de Rn, sobretudo 222Rn, são nas paisagens supraqual e transeluvial. Na paisagem eluvial, a despeito da existência de intensas anomalias gama, devido principalmente ao acúmulo de minerais resistatos com U e Th e compostos de Th, os fluxos de Rn são menos significativos. Assim, no contexto enfocado, os produtos da alteração supergênica, organizados num sistema vertente, são materiais em que as taxas de exalação de radônio são mais elevadas do que as medidas na rocha inalterada subjacente. O entendimento do comportamento do U, Th, Ra e Rn no ambiente superficial tornou possível estabelecer modelos previsionais de exalação de Rn adaptados às paisagens elementares, em escalas compatíveis com pequenos núcleos habitacionais ou em unidades residenciais. RADON EXHALATION MODELS IN HUMID TROPICAL LANDSCAPES OVER GRANITE Extended Abstract The main relationships between radon ( 222 Rn and 220 Rn) exhalation intensities and the morpho-dynamic elements of humid tropical landscapes have been established and analyzed, aiming at elaborating Rn exhalation models adapted to this type of landscapes, to be used in the scale of small habitational nuclei. The present research revolved around the understanding of two distinct phases, each one presenting their own processes and time durations. The first one covers the modelling and internal constitution of a drainage basin slopes, during the geologic and pedologic times. The second one refers to the slope morphological system, structure of which is the result of previous processes, allowing for the current radioactive processes of Rn generation, emanation (figure 1), migration and exhalation, some of which affected by rain, temperature, pressure and winds. Such elements have proven to be relevant in the water regimen of the phreatic aquifer. Multi and interdisciplinary studies about the different areas approached were done, making use of several data, information and concepts from worldwide scientific literature. The focus of the study has been a slope over granite containing normal levels of U and Th, and characterized by the soil association Latosol-Podzolic (figure 2). The analyses were carried out in short spatial-temporal limits, according to the dimensions of the slopes, and, regarding time specifics, the pedologic scale was found to be the most relevant. Several aspects have been evaluated, namely the role of the supergenic processes on the evolution of the landscapes, the impact of this evolution on the efficiency of the radioactive processes mentioned, on the different soils and under different aquifer hydric regimens in these landscapes. In the studied soil, emphasis was placed on the concept of the transformation pedologic system and on the relative cronology of the main pedogenetic phases involved, namely latolization and podzolization. In the dispersion of radionuclides, fundamental concepts of surface geochemistry have been used, main emphasis on the ones of elementary landscape geochemistry (figure 2), and of element abundance, migration, flows, and geochemical barriers, backed up by the use of Th/U and Us/Ut (exchageable U/total U) ratios. Moreover, several concepts of nuclear physics, main focus on the 238 U and 232 Th decay series, and hydrogeologic and climatological elements of the environment have been addressed. In regard to the spatial-temporal dimensions stressed in this study, the chronology of the main pedogeochemical processes responsible for the re-distribution of U and Th, and the nature of their secondary hosting phases, it was assumed that the radionuclides of the series mentioned are in secular radioactive equilibrium. Such an approach allowed for the use of U and Th as indicators of the distribution of Ra, Rn precursor, which, in this study, is symbolized by the notation U and Th (Ra). In the models presented, the supergenic processes configurate the slopes in the eluvial, transeluvial, superaqual and aqual landscapes, this last one not considered in this study. Each of these landscapes is characterized by different geoforms, types and thickness of the residual soils and their permea-porosities, and associated to different radionuclides U and Th (Ra) concentrations and their respective hosting phases, as well as different water regimens of the phreatic aquifer (figure 2). The eluvial landscape is the place where Latosols mostly occur. In this case, the main U and Th (Ra) anomalies are located on the top of latosolic B horizon, and they are due to the relative accumulation of resistate minerals, insoluble Th compounds, and U and Th fixed to Fe and Al oxihydroxides and clays by adsorption. In this landscape, the aeration zone of the aquifer presents its maximum thickness, and the groundwater flows are vertical downward. In the transeluvial landscape, the dominant soils are the Podzolic, originated from the podzolization of the pre-existant Latosols. Moreover, the Latosol-Podzolic transformation system comprises a second generation of radioanomalies, more intense and with higher proportions of adsorbed U, and resultant from the reworking of the anomalies associated with the Latosols. Such a transforming phase is also responsible for the change in the existant versant slope angle and “permea-porosities”, forming a perched sub-system phreatic aquifer in this landscape (figure 2). The main concentrations of U and Th (Ra) are partly relative and partly absolute, and are located on the top of textural B horizon of the Podzoloic Soils, in hosting phases similar to the ones from the previous landscape, and containing organic matter as well. The groundwater flows are essentially lateral, the most superficial ones canalized through the A and E pedologic horizons of the perched sub-system aquifer. In the superaqual landscape, the radioanomalies are primarily uraniferous and absolute in nature, with U adsorbed to clays, organic matter and oxides of A0 and A1 horizons of the Hydromorphic Soils (figure 2), the migration of uraniferous solutions occurring in two principal phases. The first one, longer and older than 1 My, took place during latolization. The second phase, younger and affecting more limited geographic areas, occurred during the Latosols podzolization, between 100,000 and 500,000 years, having part of the solutions drained into the current drainage system. In this landscape, the groundwater flows are predominantly lateral during the rainy seasons, and vertical upward during dry seasons. Hence, the supergenic alteration products, organized on a slope system, are materials in which the rates of radon exhalation are higher than the ones measured on unaffected subjacent rock. Based on the secondary concentrations and hosting phases of U and Th (Ra), on the “permea-porosities” of the soils and their spatial relationships with the phreatic system, and considering the soil moisture content near the field capacity, the higher rates of Rn exhalation, mainly 222 Rn, are likely to happen in Hydromorphic Soils in the superaqual landscape and in Podzolic Soils in transeluvial landscape (table 1 and 2 and figure 2). This Rn exhalation rates are conditioned by a positive combination between Rn generation and emanation. Exceptions occur in areas under the influence of the current drainage system of the superaqual landscape, where 238 U younger than 1 My is in radioactive disequilibrium with their daughters, which causes a negative impact on Rn generation. In the eluvial landscape, despite the existance of high content of U and Th (Ra) associated with the Latosols, due to the accumulation of resistates with U and Th, Th compounds, and U and Th adsorbed in oxihydroxides and clays, the Rn fluxes are less important, and are controlled by the low emanation of most of the hosting phases mentioned (table 1). It is important to note that other soil moisture contents may affect the intensities of Rn fluxes significantly (table 2). At last the approach which has been used has led to an evaluation of Rn exhalation conditioning factors while referring to humid tropical landscapes. All kinds of parameters, climatic, geochemical, weathering, pedogenetic, morphogenetic and hydrogeologic parameters could be integrated into the scale of elementary landscape slope, and they all can be integrated among themselves and also to the radioactive processes of Rn generation, emanation, migration and exhalation, by means of an interdisciplinary, tridimensional and systemic viewpoint. U, Th, Ra and Rn behaviors have been fully investigated, making it possible to establish previsional models of Rn exhalation in scales compatible to dimensions of small habitational nuclei or even unitary dwellings.