Effects of the electric field distribution on microchip valving performance

Valving characteristics on microfluidic devices were controlled through manipulation of the electric field strengths during both the sample loading and dispensing steps. Three sample loading profiles for the constant volume valve (pinched injection) in conjunction with four dispensing schemes were investigated to study valving performance. The sample confinement profiles for the sample loading step consisted of a weakly pinched sample, a medium pinched sample, and a strongly pinched sample. Four dispensing schemes varied the electric field strengths in the sample and sample waste channels relative to the analysis channel to control the volume of the sample dispensed from the valve. The axial extent of the sample plug decreased as the electric field strengths in the sample and sample waste channels were raised relative to the analysis channel. In addition, a trade-off existed between sample plug length and sensitivity.     

Study of structural and electronic transport properties of Ce-doped LaMnO3

The structural and electronic transport properties of La_1−x Ce _x MnO₃ (x=0.0–1.0) have been studied. All the samples exhibit orthorhombic crystal symmetry and the unit cell volume decreases with Ce doping. They also make a metal-insulator transition (MIT) and transition temperature increases with increase in Ce concentration up to 50% doping. The system La_0.5Ce_0.5MnO₃ also exhibits MIT instead of charge-ordered state as observed in the hole doped systems of the same composition.     

A fiber-optic cyclodextrin-based sensor

This paper describes the development of a fiber-optic cyclodextrin-based (FCD) sensor. The device uses laser excitation and fluorescence detection with beta-cyclodextrin as the reagent phase, immobilized at the tip of an optical fiber. The sensitivity of the FCD sensor is 14 times as great as that of a bare optical fiber when measurements are made with the fiber immersed in a buffer after a 10-min incubation period. The selectivity of the sensor is illustrated with pyrene as the model compound and 5,6-benzoquinoline as the interferent. An interference study with a contaminated environmental ground water sample is used to illustrate the usefulness of the FCD device.     

Two connected inverse spectral transforms

We establish a transformation which connects the potentials of the one-dimensional Dirac and Klein-Gordon operators. This transformation links the solutions of the nonlinear evolution equations solvable by means of the two inverse spectral transforms which use the Dirac and Klein-Gordon direct and inverse spectral problems.     

Multi-analyte analysis system using an antibody-based biochip

A multi-analyte detection system using a unique antibody (Ab) biochip is described. The Ab-based biochip, also referred to as the protein biochip, uses a sensor array based on a complementary metal oxide silicon (CMOS) integrated circuit. The Ab-biochip has a sampling platform of four-by-four microarrays of antibodies deposited onto a Nylon membrane substrate. The micro-arrayed antibodies can be interrogated simultaneously or sequentially using the biochip sensing array detector with the use of a diffractive optical element illuminating each antibody spot individually. The usefulness of the Ab biochip is illustrated by the measurements of immunoglobulin G (IgG) used as the model analyte system. The detection limit for Cy5-labeled IgG molecules was 13 pg.     

Estimating the Sensory Irritating Potency of Airborne Nonreactive Volatile Organic Chemicals and Their Mixtures

Abstract

This article describes the possibility of estimating whether or not a mixture of nonreactive volatile organic chemicals (NRVOC) is likely to elicit complaints of sensory irritation in humans. For this estimation we rely on: a) the sensory irritating potency of individual NRVOC can be estimated from a variety of physicochemical properties of these chemicals, b) at low exposure concentrations, the additivity rule can be applied using the potency of each chemical in a mixture and c) a threshold concentration exists below which no sensory irritation will occur. We used this estimating approach and we compared the results obtained with those obtained experimentally in humans exposed to a well defined mixture. The approach presented can be used to arrive at a decision as to whether or not exposure to a mixture of NRVOC is likely to result in sensory irritation complaints by humans, either in the general indoor air situation or for industrial workers.