Micro-Textured Black Silicon Wick for Silicon Heat Pipe Array

Planar, semiconductor heat arrays have been previously proposed and developed; however, this design makes use of a novel, microscale black silicon wick structure that provides increased capillary pumping pressure of the internal working fluid, resulting in increased effective thermal conductivity of the device, and also enables operation of the device in any orientation with respect to the gravity vector. In a heat pipe, the efficiency of thermal transfer from the case to the working fluid is directly proportional to the surface area of the wick in contact with the fluid. Also, the primary failure mechanism for heat pipes operating within the temperature range of interest is inadequate capillary pressure for the return of fluid from the condenser to the wick. This is also what makes the operation of heat pipes orientation-sensitive. Thus, the two primary requirements for a good wick design are a large surface area and high capillary pressure. Surface area can be maximized through nanomachined surface roughening. Capillary pressure is largely driven by the working fluid and wick structure. The proposed nanostructure wick has characteristic dimensions on the order of tens of microns, which promotes menisci of very small radii. This results in the possibility of enormous pumping potential due to the inverse proportionality with radius. Wetting, which also enhances capillary pumping, can be maximized through growth of an oxide layer or material deposition (e.g. TiO2) to create a superhydrophilic surface

Experiments in Nonsmooth Control of Distributed Manipulation

This paper describes an experimental modular distributed manipulation system upon which one can implement a variety of control schemes. We have shown elsewhere that when one includes the nonsmooth effects of friction into a model of distributed manipulation, nonsmooth feedback laws must generally be used to control distributed manipulators. We summarize results obtained with this experimental system that confirm the validity of control schemes proposed by the authors in recent papers (see [13, 14]). We describe the control algorithms in some detail and include specifics of the experimental set-up and experimental results

Mislocalization of mitochondria and compromised renal function and oxidative stress resistance in Drosophila SesB mutants

Mitochondria accumulate at sites of intense metabolic activity within cells, but the adaptive value of this placement is not clear. In Drosophila, sesB encodes the ubiquitous isoform of adenine nucleotide translocase (ANT, the mitochondrial inner membrane ATP/ADP exchanger); null alleles are lethal, whereas hypomorphic alleles display sensitivity to a range of stressors. In the adult renal tubule, which is densely packed with mitochondria and hence enriched for sesB, both hypomorphic alleles and RNA interference knockdowns cause the mitochondria to lose their highly polarized distribution in the tissue and to become rounded. Basal cytoplasmic and mitochondrial calcium levels are both increased, and neuropeptide calcium response compromised, with concomitant defects in fluid secretion. The remaining mitochondria in sesB mutants are overactive and maintain depleted cellular ATP levels while generating higher levels of hydrogen peroxide than normal. When sesB expression is knocked down in just tubule principal cells, the survival of the whole organism upon oxidative stress is reduced, implying a limiting role for the tubule in homeostatic response to stressors. The physiological impacts of defective ANT expression are thus widespread and diverse