2,077 research outputs found
Conectividade Estrutural do Cérebro: Diferenças entre um Cérebro Normal e um Cérebro com Patologia
RESUMO: Perceber a rede estrutural formada pelos neurĂłnios no cĂ©rebro a nĂvel da macro escala Ă© um desafio atual na ĂĄrea das neurociĂȘncias. Neste estudo analisou-se a conectividade estrutural do cĂ©rebro em 22 indivĂduos saudĂĄveis e em dois doentes com epilepsia pĂłs-traumĂĄtica. Avaliaram-se as diferenças entre estes dois grupos. TambĂ©m se pesquisaram diferenças a nĂvel do gĂ©nero e idade no grupo de indivĂduos
saudĂĄveis e os que tĂȘm valores mĂ©dios mais elevados nas mĂ©tricas de caracterização da rede. Para tal, desenvolveu-se um protocolo de anĂĄlise recorrendo a diversos softwares especializados e usaram-se mĂ©tricas da Teoria dos Grafos para a caracterização da conectividade estrutural entre 118 regiĂ”es encefĂĄlicas distintas. Dentro do grupo dos indivĂduos saudĂĄveis concluiu-se que os homens, no geral, sĂŁo os que tĂȘm mĂ©dia mais alta para as mĂ©tricas de caracterização da rede estrutural. Contudo, nĂŁo se observaram diferenças significativas em relação ao gĂ©nero nas mĂ©tricas de caracterização global do cĂ©rebro. Relativamente Ă idade, esta correlaciona-se negativamente, no geral, com as mĂ©tricas de caracterização da rede estrutural. As regiĂ”es onde se observaram as diferenças mais importantes entre indivĂduos saudĂĄveis e doentes sĂŁo: o sulco rolĂąndico, o hipocampo, o prĂ©-cuneus, o tĂĄlamo e o cerebelo bilateralmente. Estas diferenças sĂŁo consistentes com as imagens radiolĂłgicas dos doentes e com a literatura estudada sobre a epilepsia pĂłs-traumĂĄtica. Preveem-se desenvolvimentos para o estudo da conectividade estrutural do cĂ©rebro humano, uma vez que a sua potencialidade pode ser combinada com outros mĂ©todos de modo a caracterizar as alteraçÔes dos circuitos cerebrais.info:eu-repo/semantics/publishedVersio
In plane quantification of in vivo muscle elastic anisotropy factor by steered ultrasound pushing beams
Skeletal muscles are organized into distinct layers and exhibit anisotropic
characteristics across various scales. Assessing the arrangement of skeletal
muscles may provide valuable biomarkers for diagnosing muscle related
pathologies and evaluating the efficacy of clinical interventions. In this
study, we propose a novel ultrafast ultrasound sequence constituted of steered
pushing beams was proposed for ultrasound elastography applications in
transverse isotropic muscle. Based on the propagation of the shear wave
vertical mode, it is possible to fit the experimental results to retrieve in
the same imaging plane, the shear modulus parallel to fibers as well as the
elastic anisotropy factor. The technique was demonstrated in vitro in phantoms
and ex vivo in fusiform beef muscles. At last, the technique was applied in
vivo on fusiform muscles (biceps braachi) and mono-penate muscles
(gastrocnemius medialis) during stretching and contraction. This novel sequence
provides access to new structural and mechanical biomarkers of muscle tissue,
including the elastic anisotropy factor, within the same imaging plane.
Additionally, it enables the investigation of multiples parameters during
muscle active and passive length changes
Constraint-based analysis of gene interactions using restricted boolean networks and time-series data
Abstract\ud
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Background\ud
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A popular model for gene regulatory networks is the Boolean network model. In this paper, we propose an algorithm to perform an analysis of gene regulatory interactions using the Boolean network model and time-series data. Actually, the Boolean network is restricted in the sense that only a subset of all possible Boolean functions are considered. We explore some mathematical properties of the restricted Boolean networks in order to avoid the full search approach. The problem is modeled as a Constraint Satisfaction Problem (CSP) and CSP techniques are used to solve it.\ud
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Results\ud
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We applied the proposed algorithm in two data sets. First, we used an artificial dataset obtained from a model for the budding yeast cell cycle. The second data set is derived from experiments performed using HeLa cells. The results show that some interactions can be fully or, at least, partially determined under the Boolean model considered.\ud
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Conclusions\ud
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The algorithm proposed can be used as a first step for detection of gene/protein interactions. It is able to infer gene relationships from time-series data of gene expression, and this inference process can be aided by a priori knowledge available.This work was supported by FAPESP (Fundação de Amparo Ă Pesquisa do Estado de SĂŁo Paulo), CNPq (Conselho Nacional de Desenvolvimento CientĂfico e TecnolĂłgico), and CAPES (Coordenação de Aperfeiçoamento de Pessoal de NĂvel Superior).This work was supported by FAPESP (Fundação de Amparo Ă Pesquisa do Estado de SĂŁo Paulo), CNPq (Conselho Nacional de Desenvolvimento CientĂfico e TecnolĂłgico), and CAPES (Coordenação de Aperfeiçoamento de Pessoal de NĂvel Superior).This article has been published as part of BMC Proceedings Volume 5 Supplement 2, 2011: Proceedings of the 6th International Symposium on Bioinformatics Research and Applications (ISBRA10). The full contents of the supplement are available online at http://www.biomedcentral.com/17536561/5?issue=S2.This article has been published as part of BMC Proceedings Volume 5 Supplement 2, 2011: Proceedings of the 6th International Symposium on Bioinformatics Research and Applications (ISBRA'10). The full contents of the supplement are available online at http://www.biomedcentral.com/1753-6561/5?issue=S2
Lutzomyia adiketis sp. n. (Diptera: Phlebotomidae), a vector of Paleoleishmania neotropicum sp. n. (Kinetoplastida: Trypanosomatidae) in Dominican amber
<p>Abstract</p> <p>Background</p> <p>Amber fossils can be used to trace the history of disease-vector associations because microorganisms are preserved "in situ" inside the alimentary tract and body cavity of blood-sucking insects.</p> <p>Results</p> <p><it>Lutzomyia adiketis </it>sp. n. (Phlebotomidae: Diptera) is described from Dominican amber as a vector of <it>Paleoleishmania neotropicum </it>sp. n. (Kinetoplastida: Trypanosomatidae). The fossil sand fly differs from all previously described extinct and extant members of the genus by the following combination of characters: Sc forked with the branches meeting the costa and radius veins; wing L/W value of 4.1; a ÎŽ value of 18; a ratio ÎČ/α value of 0.86, and the shape and size of the spatulate rods on the ninth sternite. The trypanosomatid is characterized by the structure of its promastigotes, amastigotes and paramastigotes and its transmission by an extinct species of sand fly.</p> <p>Conclusion</p> <p>Morphological characters show that the fossil sand fly is a new extinct species and that it is host to a digenetic species of trypanosomatid. This study provides the first fossil evidence that Neotropical sand flies were vectors of trypanosomatids in the mid-Tertiary (20â30 mya).</p
Fracturing ranked surfaces
Discretized landscapes can be mapped onto ranked surfaces, where every
element (site or bond) has a unique rank associated with its corresponding
relative height. By sequentially allocating these elements according to their
ranks and systematically preventing the occupation of bridges, namely elements
that, if occupied, would provide global connectivity, we disclose that bridges
hide a new tricritical point at an occupation fraction , where
is the percolation threshold of random percolation. For any value of in the
interval , our results show that the set of bridges has a
fractal dimension in two dimensions. In the limit , a self-similar fracture is revealed as a singly connected line
that divides the system in two domains. We then unveil how several seemingly
unrelated physical models tumble into the same universality class and also
present results for higher dimensions
Decomposition and nutrient release of leguminous plants in coffee agroforestry systems.
Leguminous plants used as green manure are an important nutrient source for coffee plantations, especially for soils with low nutrient levels. Field experiments were conducted in the Zona da Mata of Minas Gerais State, Brazil to evaluate the decomposition and nutrient release rates of four leguminous species used as green manures (Arachis pintoi, Calopogonium mucunoides, Stizolobium aterrimum and
Stylosanthes guianensis) in a coffee agroforestry system under two different climate conditions. The initial N contents in plant residues varied from 25.7 to 37.0 g kg-1 and P from 2.4 to 3.0 g kg-1. The lignin/N, lignin/polyphenol and(lignin+polyphenol)/N ratios were low in all residues studied. Mass loss rates were highest in the first 15 days, when 25 % of the residues were decomposed. From 15 to 30 days, the decomposition rate decreased on both farms. On the farm in Pedra Dourada (PD), the decomposition constant k increased in the order C. mucunoides < S. aterrimum < S. guianensis < A. pintoi. On the farm in Araponga (ARA), there was no difference in the decomposition rate among leguminous plants. The N release rates varied from 0.0036 to 0.0096 d-1. Around 32 % of the total N content in the plant material was released in the first 15 days. In ARA, the N concentration in the S. aterrimum residues was always significantly higher than in the other residues. At the end of 360 days, the N released was 78 % in ARA and 89 % in PD of the initial content. Phosphorus was the most rapidly released nutrient (k values from 0.0165 to 0.0394 d-1). Residue decomposition and nutrient release did not correlate with initial residue chemistry and biochemistry, but differences in climatic conditions between the two study sites modified the decomposition rate constants
Computational Physics on Graphics Processing Units
The use of graphics processing units for scientific computations is an
emerging strategy that can significantly speed up various different algorithms.
In this review, we discuss advances made in the field of computational physics,
focusing on classical molecular dynamics, and on quantum simulations for
electronic structure calculations using the density functional theory, wave
function techniques, and quantum field theory.Comment: Proceedings of the 11th International Conference, PARA 2012,
Helsinki, Finland, June 10-13, 201
LOFAR discovery of a double radio halo system in Abell 1758 and radio/X-ray study of the cluster pair
Radio halos and radio relics are diffuse synchrotron sources that extend over Mpc-scales and are found in a number of merger galaxy clusters. They are believed to form as a consequence of the energy that is dissipated by turbulence and shocks in the intra-cluster medium (ICM). However, the precise physical processes that generate these steep synchrotron spectrum sources are still poorly constrained. We present a new LOFAR observation of the double galaxy cluster Abell 1758. This system is composed of A1758N, a massive cluster hosting a known giant radio halo, and A1758S, which is a less massive cluster whose diffuse radio emission is confirmed here for the first time. Our observations have revealed a radio halo and a candidate radio relic in A1758S, and a suggestion of emission along the bridge connecting the two systems which deserves confirmation. We combined the LOFAR data with archival VLA and GMRT observations to constrain the spectral properties of the diffuse emission. We also analyzed a deep archival Chandra observation and used this to provide evidence that A1758N and A1758S are in a pre-merger phase. The ICM temperature across the bridge that connects the two systems shows a jump which might indicate the presence of a transversal shock generated in the initial stage of the merger
A hypothetico-deductive approach to assessing the social function of chemical signalling in a non-territorial solitary carnivore
The function of chemical signalling in non-territorial solitary carnivores is still relatively unclear. Studies on territorial solitary and social carnivores have highlighted odour capability and utility, however the social function of chemical signalling in wild carnivore populations operating dominance hierarchy social systems has received little attention. We monitored scent marking and investigatory behaviour of wild brown bears Ursus arctos, to test multiple hypotheses relating to the social function of chemical signalling. Camera traps were stationed facing bear âmarking treesâ to document behaviour by different age sex classes in different seasons. We found evidence to support the hypothesis that adult males utilise chemical signalling to communicate dominance to other males throughout the non-denning period. Adult females did not appear to utilise marking trees to advertise oestrous state during the breeding season. The function of marking by subadult bears is somewhat unclear, but may be related to the behaviour of adult males. Subadults investigated trees more often than they scent marked during the breeding season, which could be a result of an increased risk from adult males. Females with young showed an increase in marking and investigation of trees outside of the breeding season. We propose the hypothesis that females engage their dependent young with marking trees from a young age, at a relatively âsafeâ time of year. Memory, experience, and learning at a young age, may all contribute towards odour capabilities in adult bears
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