Morhell, N., and H. Pastoriza. "Power law fluid viscometry through capillary filling in a closed microchannel." Sensors and Actuators B: Chemical 227 (2016): 24–28.
Abstract: In this work we analyze the capillary filling dynamics of non-Newtonian fluids that can be modeled with a power law constitutive equation. We solve the Poiseuille equations for an hydrophilic closed channel where capillary pressures drives the fluid in until a rest position given by the barometric pressure is reached. We show that this dynamics can be used to measure both the coefficient k and exponent n, that describes the power law fluid viscosity and we ran tests on Soda Lime Glass microchannels. Using a simple experimental setup with a USB Microscope and a custom image processing software we were able to measure the power law parameters of whole blood, wall varnish and DI water. The exponents were also obtained from the velocity profiles inside the microchannel using a custom μPIV setup matching both results with those measured with a standard Brookfield Rotational Microviscometer.
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Morhell, N., and H. Pastoriza. "A single channel capillary microviscometer." Microfluidics and Nanofluidics 15, no. 4 (2013): 475–479. http://dx.doi.org/10.1007/s10404-013-1162-4 (accessed July 6, 2022).
Abstract: We have developed a microviscometer analyzing the fluid dynamics in a single
channel glass microfluidic chip with a closed end. The device is able to test sample
volumes of a few microliters by inserting one drop in the inlet. The fluid enters the
channel driven by capillary pressure and an optical sensor registers the motion. The
equation that describes the fluid dynamics is function of the channel geometry,
atmospheric pressure, fluid viscosity and capillary pressure. Knowing the first two the
last parameters can be obtained as fitting parameters from the meniscus position as a
function of time plot. We have successfully tested Newtonian fluids with different
viscosities and capillary pressure.
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Ogando, K., and H. Pastoriza. "Design of integration-ready metasurface-based infrared absorbers." Journal of Applied Physics 118, no. 4 (2015): 043109.
Abstract: We introduce an integration ready design of metamaterial infrared absorber, highly compatible with many kinds of fabrication processes. We present the results of an exhaustive experimental characterization, including an analysis of the effects of single meta-atom geometrical parameters and collective arrangement. We confront the results with the theoretical interpretations proposed in the literature. Based on the results, we develop a set of practical design rules for metamaterial absorbers in the infrared region.
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Ogando, K., N. La Forgia, J. J. Zárate, and H. Pastoriza. "Design and characterization of a fully compliant out-of-plane thermal actuator." Sensors and Actuators A: Physical 183 (2012): 95–100.
Abstract: This paper presents the design and characterization of an out-of-plane thermal actuator. The design optimizes the vertical displacement by concentrating elastic deformations in localized hinges allowing a full thermal expansion of the actuator arms. Heating is provided by Joule dissipation in the actuator itself.
A testing device was fabricated using the Memscap PolyMUMPs process. Characterization of the sensor was performed by white light optical profilometry for varying electric biasing and different atmospheres.
The presented design has the advantage that the moving direction of the actuator can be determined by the relative location of the hinges.
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Pastoriza, H. "Diagramas de fases de superconductores laminares: Estructuras de vórtices en monocristales de BiScCaCuO." Ph.D. thesis, Instituto Balseiro, 1994.
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Pastoriza, H. "Mediciones magnéticas en óxidos superconductores." Master's thesis, Instituto Balseiro, 1989.
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Pastoriza, H., S. Candia, and G. Nieva. "Anisotropic vortex dynamics in twined YBaCuO single crystals." Physica B 284-288, no. 2 (2000): 763–764.
Abstract: Rotating continuously the applied vortex force and measuring the vortex velocity vector, we were able to directly determine the role of twin boundaries in the vortex dynamics in YBa$2$Cu$3Ο_7$ single crystals with unidirectional twins. We show the different effect of these correlated pinning defects into the various vortex phases. In the entangled vortex liquid state, we observe a linear response but with an anisotropic viscosity. On the other hand, an anomalous guided motion by twin planes is found in the vortex solid.
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Pastoriza, H., S. Candia, and G. Nieva. "Role of twin boundaries on the vortex dynamics in YBaCuO single crystal." Phys. Rev. Lett. 83, no. 5 (1999): 1026–1029.
Abstract: By means of a novel technique of rotating the applied current we have directly measured the influence of twin boundaries on the vortex motion in a YBa2 Cu3 O7 single crystal. The results indicate that the effect of twin planes on the vortex dynamics starts to develop below a certain temperature, being responsible for an anisotropic viscosity in the vortex liquid state and a guided motion in the solid state.
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Pastoriza, H., F. de la Cruz, D. B. Mitzi, and A. Kapitulnik. "Two-step transition towards the reversibility region in Bi$2$Sr$2$CaCu$_2$O8-δ single crystals." Phys. Rev. B 46, no. 14 (1992): 9278–9281.
Abstract: We have performed magnetization measurements on Bi$2$Sr$2$CaCu$_2$O8-δ single crystals in the \bf c crystallographic direction for fields from 2 Oe up to 700 Oe. The results strongly suggest that the reversible thermodynamic region is achieved after the vortex flux structure shows an abrupt transition at a temperature lower than that determined by the irreversibility line.
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Pastoriza, H., M. F. Goffman, and F. de la Cruz. "Comment on ``Irreversibility line of monocrystaline {Bi$2$Sr$2$CaCu$2$O$8$}: Experimental evidence for a dimensional crossover of the vortex ensemble''." Phys. Rev. Lett. 72, no. 8 (1994): 1303.
Abstract: A Comment on the Letter by A. Schilling et al., Phys. Rev. Lett. \bf 71, 899 (1993).
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