Laser ultrasonics system for measurement of speed of sound in gases

In this work we developed a setup to measure the speed of sound in gases using a laser ultrasonics system. The mentioned setup is an all optical system composed by a Q-switched Nd:YAG laser to generate the sound waves, and a fiber optical microphone to detect them. The Nd:YAG provided a laser pulse of approximately 420 mJ energy and 9 ns of pulse width, at the wavelength of 1064 nm. The pulsed laser beam, focused by a positive lens, was used to generate an electrical breakdown (in the gas) which, in turn, generates an sound wave that traveled through a determined distance and reached the fiber optical microphone. The resulting signal was acquired in an oscilloscope and the time difference between the optical pulse and the arrival of the sound waves was used to calculate the speed of sound, since the distance was known. The system was initially tested to measure the speed of sound in air, at room pressure and temperature and it presented results in agreement with the theory, showing to be suitable to measure the speed of sound in gases. © 2012 American Institute of Physics.

Planificación del transporte en países de América Latina

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Formulación de proyectos agropecuarios, extractivos, de transporte y energético

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Congelação de espermatozoides epididimários de gatos utilizando o diluidor Botu-crio® após refrigeração por 24 h em contêiner de transporte de sêmen Botu-tainer®

The possibilities of using the sperm collected from the epididymis have been widely used because the fertilizing capacity sperm preservation and the possibility of using it for wild cats. But in the process of cryopreservation, some studies show a decrease in the quality of the sperm when left under cooling before frozen for some time. This study aimed to assess the quality of the epididymal sperm obtained from domestic cats after cryopreservation using a diluent based on egg yolk and glycerol (Botu-crio®), comparing the morphofunctional characteristics after cooling for 24 hours in a container of semen transport (Botu-tainer®). We use eight cats submitted to elective orchiectomy, aging from eight months, without racial determination, and good nutritional status. These sperm characteristics were: motility, vigor, concentration, membrane integrity and morphology. It has been found, after statistical analysis, that the container of semen was able to maintain sperm viability, even for 24h. We also observed a significant decrease on all parameters after frozen, consequential, probably to thermal stress that occurs in processing. However, the percentage of membrane integrity after thawing shows good employability of the Botu-crio®, which viability is possible to perform in vitro fertilization, requiring higher ratings.

Planificación del transporte en los países del Cono Sur: evaluación comparativa de las metodologías aplicadas en cinco países

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Precios sombra en los estudios integrados de transporte: la experiencia argentina

Explica la significacion de los precios sombra en la evaluacion de proyectos en el contexto de America Latina y resume algunos metodos para derivarlos, citando el caso de la primera fase del Plan nacional de Transporte de Argentina.

Institucionalización de la planificación de transporte: la experiencia de la República Federativa del Brasil

Describe la Empresa Brasilena del Planeamiento de Transporte (GEIPOT), sus origenes, evolucion historica, caracteristicas, organizacion, recursos humanos, actividades, y clientes.

Papel de los estudios integrados en la planificación del transporte: la experiencia uruguaya

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Coordinación del transporte vial con los demas medios de transporte internacional en Sudamérica = Co-ordination of road transport with other international transport media in South America

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El transporte urbano en América Latina: consideraciones acerca de su igualdad y eficiencia

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Cómo mejorar el transporte urbano de los pobres

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¿Por qué las inversiones en el transporte público no reducen la congestión de tránsito urbano?

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La evolución del papel del Estado en la regulación del transporte terrestre

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Las concesiones y la optimización del transporte vial y ferroviario

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Self-trapping of Fermi and Bose gases under spatially modulated repulsive nonlinearity and transverse confinement

We show that self-localized ground states can be created in the spin-balanced gas of fermions with repulsion between the spin components, whose strength grows from the center to periphery, in combination with the harmonic-oscillator (HO) trapping potential acting in one or two transverse directions. We also consider the ground state in the noninteracting Fermi gas under the action of the spatially growing tightness of the one- or two-dimensional (1D or 2D) HO confinement. These settings are considered in the framework of the Thomas-Fermi-von Weizsäcker (TF-vW) density functional. It is found that the vW correction to the simple TF approximation (the gradient term) is nearly negligible in all situations. The properties of the ground state under the action of the 2D and 1D HO confinement with the tightness growing in the transverse directions are investigated too for the Bose-Einstein condensate with the self-repulsive nonlinearity. © 2013 American Physical Society.