Electrical microfluidic pressure gauge for elastomer microelectromechanical systems

We report on an electrical microfluidic pressure gauge. A polydimethylsiloxane microvalve closes at a characteristic applied pressure determined by the material's properties and the valve's dimensions. Hence, when the same pressure is applied to all valves of a heterogeneous valve array, some valves close while others remain open. The state of the array is combined with knowledge of the respective characteristic closing pressures of the individual valves to yield an estimate of the applied pressure. The state of each valve is obtained by electrical measurements, since the electrical resistance of the respective underlying fluid-filled channel increases by at least two orders of magnitude as the valve closes and its insulating elastomer material interrupts the electrical circuit. The overall system functions as a pressure gauge with electrical readout. This device would be a critical component in active pressure-regulation loops in future integrated microfluidic systems

Experimentally validated quantitative linear model for the device physics of elastomeric microfluidic valves

A systematic experimental study and theoretical modeling of the device physics of polydimethylsiloxane “pushdown” microfluidic valves are presented. The phase space is charted by 1587 dimension combinations and encompasses 45–295 µm lateral dimensions, 16–39 µm membrane thickness, and 1–28 psi closing pressure. Three linear models are developed and tested against the empirical data, and then combined into a fourth-power-polynomial superposition. The experimentally validated final model offers a useful quantitative prediction for a valve's properties as a function of its dimensions. Typical valves (80–150 µm width) are shown to behave like thin springs

Vortex Formation by Interference of Multiple Trapped Bose-Einstein Condensates

We report observations of vortex formation as a result of merging together multiple $^{87}$Rb Bose-Einstein condensates (BECs) in a confining potential. In this experiment, a trapping potential is partitioned into three sections by a barrier, enabling the simultaneous formation of three independent, uncorrelated condensates. The three condensates then merge together into one BEC, either by removal of the barrier, or during the final stages of evaporative cooling if the barrier energy is low enough; both processes can naturally produce vortices within the trapped BEC. We interpret the vortex formation mechanism as originating in interference between the initially independent condensates, with indeterminate relative phases between the three initial condensates and the condensate merging rate playing critical roles in the probability of observing vortices in the final, single BEC.Comment: 5 pages, 3 figure

O que dizem as perspectivas brasileiras contemporâneas da publicidade sobre o publicitário?

El objetivo de esta investigación es identificar la presencia o ausencia y la naturaleza del papel del publicista en diez de las “perspectivas brasileñas contemporáneas sobre el fenómeno publicitario”. La metodología es cualitativa y los procedimientos están guiados por la investigación bibliográfica. Los resultados indican que la presencia del publicista es sutil en los recientes abordajes brasileños del fenómeno publicitario, dado que en pocos de ellos se menciona al profesional de la producción como protagonista del proceso, mientras que en la mayoría de las perspectivas el publicista es visto como un coproductor con el público consumidor, en el contexto de la comunicación y la cibercultura.The objective of the research is to identify the presence, or absence, and the nature of the advertiser’s role in ten of the contemporary Brazilian perspectives on the advertising phenomenon. The methodology is qualitative and the procedures are guided by bibliographical research. The results indicate that the presence of the advertiser is subtle in recent Brazilian approaches to the advertising phenomenon, given that in few of them the production professional is mentioned as a protagonist of the process, whereas in most perspectives the advertiser is seen as a co-producer with the public consumer in the context of communication and cyberculture.O objetivo da pesquisa é identificar a presença/ ausência e a natureza do papel do publicitário em dez das “perspectivas brasileiras contemporâneas sobre o fenômeno publicitário”. A metodologia é qualitativa e os procedimentos são orientados pela pesquisa bibliográfica. Os resultados apontam que a presença do publicitário é sutil nas abordagens brasileiras recentes sobre o fenômeno publicitário, dado que em poucas delas o profissional da produção é mencionado como um protagonista do processo, enquanto na maioria das perspectivas o publicitário é visto como um coprodutor junto do consumidor, no contexto de comunicação e cibercultura

O que dizem as perspectivas brasileiras contemporâneas da publicidade sobre o publicitário?

O objetivo da pesquisa é identificar a presença/ ausência e a natureza do papel do publicitário em dez das “perspectivas brasileiras contemporâneas sobre o fenômeno publicitário”. A metodologia é qualitativa e os procedimentos são orientados pela pesquisa bibliográfica. Os resultados apontam que a presença do publicitário é sutil nas abordagens brasileiras recentes sobre o fenômeno publicitário, dado que em poucas delas o profissional da produção é mencionado como um protagonista do processo, enquanto na maioria das perspectivas o publicitário é visto como um coprodutor junto do consumidor, no contexto de comunicação e cibercultura

H∞ and L2–L∞ filtering for two-dimensional linear parameter-varying systems

This is the post print version of the article. The official published version can be obtained from the link below - Copyright 2007 Wiley-BlackwellIn this paper, the H∞ and l2–l∞ filtering problem is investigated for two-dimensional (2-D) discrete-time linear parameter-varying (LPV) systems. Based on the well-known Fornasini–Marchesini local state-space (FMLSS) model, the mathematical model of 2-D systems under consideration is established by incorporating the parameter-varying phenomenon. The purpose of the problem addressed is to design full-order H∞ and l2–l∞ filters such that the filtering error dynamics is asymptotic stable and the prescribed noise attenuation levels in H∞ and l2–l∞ senses can be achieved, respectively. Sufficient conditions are derived for existence of such filters in terms of parameterized linear matrix inequalities (PLMIs), and the corresponding filter synthesis problem is then transformed into a convex optimization problem that can be efficiently solved by using standard software packages. A simulation example is exploited to demonstrate the usefulness and effectiveness of the proposed design method

Where Nanophotonics and Microfluidics Meet

A new generation of photonic devices has recently emerged that relies on using geometries of sub-wavelength microstructures within a high refractive index contrast materials system. These geometries are used to confine and manipulate light within very small volumes. High optical field densities can be obtained within such structures, and these in turn can amplify optical nonlinearities. Moreover, many of these structures, as for example photonic crystals and slotted waveguides, can be engineered for the efficient localization of light within the low-index regions of high index contrast microstructures. When such structures are back-filled nonlinear polymers or liquids, devices can be tuned and novel phenomena can be observed. In particular, such devices are very interesting when constructed from silicon on insulator (SOI) material in which the optical waveguide also serves as a transparent electrical contact. Here we show examples of the design, fabrication and testing of optical microstructures in which the electro-optic (χ2) and photorefractive (χ3) nonlinearities are used for electro-optic tuning, frequency mixing, optical rectification, and high-speed switching of light

Collisional-inhomogeneity-induced generation of matter-wave dark solitons

We propose an experimentally relevant protocol for the controlled generation of matter-wave dark solitons in atomic Bose-Einstein condensates (BECs). In particular, using direct numerical simulations, we show that by switching-on a spatially inhomogeneous (step-like) change of the s-wave scattering length, it is possible to generate a controllable number of dark solitons in a quasi-one-dimensional BEC. A similar phenomenology is also found in the two-dimensional setting of "disk-shaped" BECs but, as the solitons are subject to the snaking instability, they decay into vortex structures. A detailed investigation of how the parameters involved affect the emergence and evolution of solitons and vortices is provided.Comment: 8 pages, 5 Figures, Physics Letters A (in press

Relation between positional specific heat and static relaxation length: Application to supercooled liquids

A general identification of the {\em positional specific heat} as the thermodynamic response function associated with the {\em static relaxation length} is proposed, and a phenomenological description for the thermal dependence of the static relaxation length in supercooled liquids is presented. Accordingly, through a phenomenological determination of positional specific heat of supercooled liquids, we arrive at the thermal variation of the static relaxation length $\xi$, which is found to vary in accordance with $\xi \sim (T-T_0)^{-\nu}$ in the quasi-equilibrium supercooled temperature regime, where $T_0$ is the Vogel-Fulcher temperature and exponent $\nu$ equals unity. This result to a certain degree agrees with that obtained from mean field theory of random-first-order transition, which suggests a power law temperature variation for $\xi$ with an apparent divergence at $T_0$. However, the phenomenological exponent $\nu = 1$, is higher than the corresponding mean field estimate (becoming exact in infinite dimensions), and in perfect agreement with the relaxation length exponent as obtained from the numerical simulations of the same models of structural glass in three spatial dimensions.Comment: Revised version, 7 pages, no figures, submitted to IOP Publishin