Some properties of a measure of resolution in gel electrophoresis and capillary zone electrophoresis

The most commonly used measure of resolution for chromatographic and electrophoretic separations does not take into account the possibility of there being different amounts of each of the molecular species. A modification of a measure of resolution recently suggested by Aldroubi and Garner (BioTechniques 1992, 13, 620-624) can incorporate this effect explicitly. Their criterion for resolution is based on the time to observe a valley of specified magnitude separating two peaks. We examine how this measure depends on different physically relevant parameters that characterize the system.     

The relative stability of a mercury stain at room temperature and liquid helium temperature

Observations of the localization of the mercurial stain TAMM [tetrakis (acetoxymercuri) methane] have been made at room temperature and liquid helium temperature. Mercurial stains do not maintain a fixed position at room temperature in the electron microscope. In order to record room temperature micrographs with the minimum possible dose, a special single-electron-counting electron microscope system was used. Micrographs were taken at liquid helium temperature using a prototype microscope with a superconducting electron objective lens. Tropomyosin paracrystals were chosen as a convenient test object. At room temperature the fine banding pattern of the paracrystals was barely resolvable or not resolvable at all. At liquid helium temperature the fine banding pattern of the paracrystals was easily observed and more than one micrograph could be taken before the banding pattern faded. These observations indicate that this mercurial stain is more stable in position at liquid helium temperature than at room temperature.     

Asymmetric double-quantum-well phase modulator using surfaceacoustic waves

An AlGaAs-GaAs asymmetric double-quantum-well (DQW) optical phase modulator using surface acoustic waves is investigated theoretically. The optimization steps of the DQW structure, which so far have not been reported in detail, are discussed here. The optimized phase modulator structure is found to contain a five-period QDW active region. A surface acoustic wave induces a potential field which provides the phase modulation. Analysis of the modulation characteristics show that by using the asymmetric DQW, the large change of the induced potential at the surface and thus large modification of the quantum-well (QW) structure can be utilized. The modification of each QW structure is consistent, although this consistency is not always preserved in typical surface acoustic wave devices. Consequently, the change of refractive index in each of the five DQW's is almost identical. Besides, the change of effective refractive index is ten times larger here in comparison to a modulator with a five-period single QW as the active region and thus produces a larger phase modulation. In addition, a long wavelength and a low surface acoustic wave power required here simplify the fabrication of surface acoustic wave transducer and the acoustooptic phase modulator     

What do Israeli Jewish and Arab adolescents know about drinking and driving?

This article describes a study, which is the first in Israel to investigate knowledge concerning drinking and driving among a large group of 2408 adolescents of four religions in the north of Israel, in the winter of 1995. The article analyses the results by referring to general scores and to five areas in the “drinking and driving” domain: legal blood alcohol concentration (BAC) limit, minimal number of drinks prohibited by the law before driving, common myths, main effects of alcohol on driving ability and youth vulnerability. The article emphasizes differences between the Jewish group and the non-Jewish (Arab) group. The average score of the sample was 2.06 (out of 5). Jews received the highest score (2.30) and Moslems got the lowest score (1.45). No differences were found among those who had a driving license and those who had not, and between the group of respondents from the north of Israel and a sample of participants from the center of the country. Lack of knowledge was revealed especially concerning knowledge about the BAC limit and youth vulnerability. Arabs tended to exaggerate the amount of drinks allowed to be consumed before driving according to the law, to hold common myths more than Jews and to get lower scores concerning alcohol main effects on driving skills. However, they tended to be more aware than Jews to youth vulnerability.     

Modeling of mechanical dysfunction in regional stunned myocardium of the left ventricle

Reversible mechanical dysfunction of the myocardium after a single or multiple episode(s) of coronary artery occlusion has been observed in previous studies and is termed myocardial stunning. The hypothesis that stunning could be represented by a decrease in maximum available muscle force in the stunned region was examined by means of a mathematical model that incorporates series viscoelastic elements. A canine experimental model was also employed to demonstrate depressed contractility and a consistent delay of shortening in the stunned region. The mechanical model of the left ventricle was designed to include a normal and stunned region, for which the stunned region was allowed to have variable size. Each region consisted of a volume and time dependent force generator in parallel with a passive elastic force element. The passive elastic element was placed in series with a constant viscosity component and a series elastic component. The model was solved by means of a computer. Passive and active properties of each region could be altered independently. The typical regional measures of muscle performance such as percent shortening, percent bulge, percent thickening, delay of shortening, percent increase in end-diastolic length and other hemodynamic measures were computed. These results were similar to those observed in animal models of stunning. In addition, a nearly linear relationship with end-diastolic length and delay of shortening was predicted by the model. It was concluded that a decrease in the peak isovolumic elastance and augmentation of viscosity effect of creep during stunning can explain mechanical abnormalities of stunned myocardium.     

Design for smelling

On our best days-without head colds, for example-and with a time out between sniffs, we can note the presence of and distinguish among 10000 airborne molecules or molecular compounds, sometimes when they amount to only a few molecules per trillion. Here, the authors present a quick tour of the route from molecule to smell. They correlate many of the discrete physiological steps with engineering ones, ranging from sampling, signal processing and amplification all the way to neural net computation     

Bulk deformation of Ti-6.8Mo-4.5Fe-1.5Al (timetal LCB) alloy

Recently, a low-cost near-β titanium alloy (Timetal LCB Ti-6.8Mo-4.5Fe-l.5Al wt %) containing iron and molybdenum has been developed. This alloy is cold formable in the β microstructure and can be aged to high strengths by precipitating the a phase. Due to its combination of cold formability and high strength, the alloy is a potential replacement for steel components in the automotive industry. The current study was undertaken to evaluate the cold bulk forming characteristics of Timetal LCB for use in lightweight automotive applications. Room-temperature compression tests conducted over a strain-rate range of 0.01 to 5/s indicate that the bulk cold compression of the alloy is affected by two factors: the microstructure and the length-to-diameter aspect ratio of the specimen. In the aged condition, when the microstructure has a-phase particles distributed along flow lines in the β-phase matrix, the alloy has the propensity for shear failure when deformed in compression in a direction parallel to the flow lines. In the solution-heat-treated condition, the microstructure consists of β grains with athermal ω phase. In this condition, the alloy can be cold compressed to 75 % reduction in height using specimens with aspect ratio of 1.125, but fails by shear for a larger aspect ratio of 1.5. Plastic deformation of the material occurs initially by single slip in most grains, but changes to multiple slip at true plastic strains larger than about 0.15. At a slow strain rate, the deformation is uniform, and the material work hardens continuously. At high strain rates, shear bands develop, and the localized deformation and temperature rise due to deformation heating leads to flow softening during compression. Although there is a considerable rise in temperature (200 to 500 °) during deformation, precipitation of the a phase was not observed.     

Histopathologic evaluation of feline inflammatory liver disease

The aim of this paper is to present methods for a fully computerised analysis of spermatocyte movement. The technique were designed for processing pure images of spermatozoa captured from a light microscope. The techniques described allowed for the reduction of background light inhomogeneity and for the correct detection of moving cells and involved densitometric equalization of background inhomogeneity and implementation of the dynamic threshold, adopted for the recognition of objects. The method for relating cells (found in each frame processed) to movement trajectories used heuristic rules, describing the behaviour of moving cells. This permitted samples containing high numbers of spermatocytes within the observed area to be processed with maximum accuracy.