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This study reports the use of microfluidics, which intrinsically has a large surface-to-volume ratio, toward rapid antimicrobial susceptibility testing at the point of care. By observing the growth of uropathogenic Escherichia coli in gas permeable polymeric microchannels with different dimensions, we demonstrate that the large surface-to-volume ratio of microfluidic systems facilitates rapid growth of bacteria. For microchannels with 250 [micro]m or less in depth, the effective oxygenation can sustain the growth of E. coli to over [10.sup.9] cfu/mL without external agitation or oxygenation, which eliminates the requirement of bulky instrumentation and facilitates rapid bacterial growth for antimicrobial susceptibility testing at the point of care. The applicability of microfluidic rapid antimicrobial susceptibility testing is demonstrated in culture media and in urine with clinical bacterial isolates that have different antimicrobial resistance profiles. The antimicrobial resistance pattern can be determined as rapidly as 2 h compared to days in standard clinical procedures facilitating diagnostics at the point of care. 10.1021/ac9022764

BACKGROUND: Groundwater contaminated with arsenic imposes a big challenge to human health worldwide. Using natural compounds to subvert the detrimental effects of arsenic represents an attractive strategy. The transcription factor [...]

A mixture of drugs is often more effective than using a single effector. However, it is extremely challenging to identify potent drug combinations by trial and error because of the large number of possible combinations and the inherent complexity of the underlying biological network. With a closed-loop optimization modality, we experimentally demonstrate effective searching for potent drug combinations for controlling cellular functions through a large parametric space. Only tens of iterations out of one hundred thousand possible trials were needed to determine a potent combination of drugs for inhibiting vesicular stomatitis virus infection of NIH 3T3 fibroblasts. In addition, the drug combination reduced the required dosage by [approximately equal to] 10-fold compared with individual drugs. In another example, a potent mixture was identified in thirty iterations out of a possible million combinations of six cytokines that regulate the activity of nuclear factor kappa B in 293T cells. The closed-loop optimization approach possesses the potential of being an effective approach for manipulating a wide class of biological systems. combinatory drug therapy | drug cocktail | drug resistance | feedback control | viral infection

We have studied the behavior of failure in lifetime acceleration test of TMR prototype with performance meeting 100 Gb/[in.sup.2] recording. The failure mode is identified to be same as extrinsic breakdown of the AlOx barrier, while failure due to magnetic change is not observed. The extrinsic breakdown is further found to be the increase in pinhole conduction in the barrier, involving thermal energy from ambient and read current. Results also suggest the existence of a critical voltage below which pinhole is not enlarged. Furthermore, we will discuss our hypothesis in the formation of pinholes and the role of charge traps in the barrier. Finally, we will discuss a method for screening out heads with relatively short lifetime, which is feasible for mass production. The screening allows a guarantee of lifetime well enough for drive application. Index Terms--Breakdown, charge trapping, lifetime, recording head, TMR.

Bioprocessors for concentrating bioparticles, such as cells and molecules, are commonly needed in bioanalysis systems. In this microfluidic processor, a global flow field generated by ac electroosmosis transports the embedded particles to the regions near the electrode surface. The processor then utilizes electrophoretic and dielectrophoretic forces, which are effective in short range, to trap the target cells and molecules on the electrode surface. By optimizing the operating parameters, we have concentrated various biological objects in a large range of sizes, including Eseheriehia coli bacteria, [lambda] phage DNA, and single-stranded DNA fragments as small as 20 bases that have a radius of gyration of only 3 nm.

In this paper, we introduce chemical etching-based processes for fabricating micromanipulators from fused silica microcapillary tubing. The resulting devices are capable of manipulating individual cells and can be used for intracytoplasmic injection. Two types of micromanipulating tools: single-cell trappers and micro-injectors, were fabricated with two single-step etching processes. These etching mechanisms, which are either surface tension controlled or diffusion rate limited, are discussed in detail with experimental verifications. The fabrication processes are reproducible and amenable to mass production due to their simplicity and low fabrication cost. Single cell capture and intracytoplasmic injection have been successfully demonstrated on brassica oleracea protoplasts. Index Terms--Cell trapping, intracytoplasmic injection, micro-manipulator, photobleaching.

Internal shunting is introduced on tunneling magnetoresistive heads to enhance device anti-static robustness and external high-frequency noise pickup immunity. The details of the shunting scheme and the mechanism leading to both anti-static robustness and reduced high-frequency noise pickup are discussed. Index Terms--Direct charged device model (DCDM), electrostatic discharge (ESD), noise immunity, shunting.

Byline: Pak-Kin Wong, Chi-Man Vong, Lap-Mou Tam, Ke Li Modern automotive engines are controlled by the Electronic Control Unit (ECU). The engine ECU calibration is done empirically through tests on the dynamometer because no exact mathematical engine model is yet available. With Least Squares Support Vector Machines (LS-SVM), the approximate engine power performance model can be determined by training the sample data acquired from the dynamometer. Besides, Kernel Principal Components Analysis (KPCA) is proposed to transform unimportant adjustable variables into a compact subset for shortening model construction time and improving model accuracy. Experimental results show that KPCA+LS-SVM can really improve the training time and accuracy of an engine model.

A model based on the domain structure of the electrodes in ferromagnet-insulator-ferromagnet tunnel junctions is derived. It provides an explicit expression of the junction magnetoresistance (MR) in terms of the magnetization of the ferromagnetic layers. The response in magnetic field of junctions with very high and very low MR are simulated, and the lack of fringing field coupling is proposed to be a reason for low MR. The effect of temperature on junction MR is discussed briefly in the context of the model. Index Terms--Magnetic tunnel junctions.