3,384 research outputs found

    A new gravitational N-body simulation algorithm for investigation of cosmological chaotic advection

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    Recently alternative approaches in cosmology seeks to explain the nature of dark matter as a direct result of the non-linear spacetime curvature due to different types of deformation potentials. In this context, a key test for this hypothesis is to examine the effects of deformation on the evolution of large scales structures. An important requirement for the fine analysis of this pure gravitational signature (without dark matter elements) is to characterize the position of a galaxy during its trajectory to the gravitational collapse of super clusters at low redshifts. In this context, each element in an gravitational N-body simulation behaves as a tracer of collapse governed by the process known as chaotic advection (or lagrangian turbulence). In order to develop a detailed study of this new approach we develop the COsmic LAgrangian TUrbulence Simulator (COLATUS) to perform gravitational N-body simulations based on Compute Unified Device Architecture (CUDA) for graphics processing units (GPUs). In this paper we report the first robust results obtained from COLATUS.Comment: Proceedings of Sixth International School on Field Theory and Gravitation-2012 - by American Institute of Physic

    Chorangioma and John Clarke

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    Perinatal mortality is a relevant indicator of a country health status. Through the centuries, measures have been promoted to reduce modifiable risk factors or to treat installed diseases. That was the example of the English medical doctor John Clarke (1758/1760?-1851), who dedicated his life to mother-child health care [1]. Among his contributions is the report of a placental tumour in 1798, named Chorangioma placenta (CP) [2]. It may occur in primiparas or multiparas, apparently increasing with the mother’s age, with association to the mother’s hypertension or diabetes mellitus [3]. Chorangioma may appear in single or multiple pregnancies and may lead to foetal heart failure, hydrops, or sudden intra-uterine death [3]. The authors report the case of a 2 cm diameter chorangioma (Fig. 1A), which ended in premature death of the male foetus in utero at 35 weeks and 5 days, in a multiparous mother. Histopathological examination confirmed the macroscopic suspicion by disclosing a benign vascular capillary proliferation (Fig. 1B) positive for endothelial markers CD34/CD31 (Fig. 1C). Its current incidence ranges from 0.5% to 1% of analysed placentas [4] and may represent a primitive angioblastic tissue malformation, aggravated with hypoxia and/or haemodynamic changes during pregnancy. To conclude, we highlight the relevance of chorangioma as a cause of perinatal death, which is around 30% [4]info:eu-repo/semantics/publishedVersio

    Ultrasonic pulse technique for evaluation of mechanical damage in processed coffee beans.

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    The knowledge of the physical characteristics of the coffee bean allows the transition from the conventional storage model in bags to the silo storage, and as an indirect measure of the improvement and conservation of the quality of the stored grain. The elastic modulus allows comparisons on the strength of material. The variations of this occur due to its chemical composition, microstructures and material defects, being able to be used as indicator of the physical integrity of the grain. The ultrasonic pulse technique is an alternative to obtain the elastic modulus in a simple and non-destructive way. In this context, it was proposed the development of a non-destructive methodology that will perform the quality evaluation by determining the elastic modulus of the coffee beans. For this purpose, a reference silo was constructed, reproducing the storage conditions, and the elastic modulus values were determined. The values obtained by the Stress Wave Timer apparatus are between 2.54 and 4.23 MPa, with a maximum load of 8.32 kN, and a calculated vertical pressure of 1,526 kPa. To evaluate the impact of the storage conditions and the loads applied during the non-destructive test, laboratory tests applied in seeds were performed, and the tetrazolium test was the only one able to differentiate the samples. It was concluded that Stress Wave Timer was able to determine the elastic modulus values for the coffee bean mass and could be used as an indicative of the quality.Título em português: Técnica de pulso ultrassônico para avaliação de danos mecânicos em grãos de café beneficiados

    A FREE BOUNDARY ISOPERIMETRIC PROBLEM IN HYPERBOLIC 3-SPACE BETWEEN PARALLEL HOROSPHERES

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    We investigate the isoperimetric problem of finding the regions of prescribed volume with minimal boundary area between two parallel horospheres in hyperbolic 3-space (the part of the boundary contained in the horospheres is not included). We reduce the problem to the study of rotationally invariant regions and obtain the possible isoperimetric solutions by studying the behavior of the profile curves of the rotational surfaces with constant mean curvature in hyperbolic 3-space. We also classify all the connected compact rotational surfaces M of constant mean curvature that are contained in the region between two horospheres, have boundary partial derivative M either empty or lying on the horospheres, and meet the horospheres perpendicularly along their boundary.244112

    Study, design and development of a new add-on function for the FRICTORQ® - Friction Test Instrument

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    The assessment of handle properties is of utmost importance in materials in our everyday life. There is a wide range of materials there are used in contact with the human skin, which may cause several unpleasant skin reactions. The FRICTORQ® is a laboratory equipment developed by the authors to measure the friction coefficient in fabrics, to enable a quantitative assessment of touch/handle, in order to predict the comfort behaviour of 2D/3D structures when used or touched by humans. In a further development, the FRICTORQ® was redesigned to accommodate a new testing kit function to determine the friction coefficient of fabrics in a liquid environment. This new design will be explained and the results obtained while testing different swimwear fabrics and hospital garments will be also presented and discussed
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