Renal proliferative and phenotypic changes in rats with two-kidney, one-clip Goldblatt hypertension

Previous research in this laboratory has shown that preweaning and postweaning juvenile meadow voles, Microtus pennsylvanicus, can acquire a spatial task, the Morris water-maze task. The present study examined the influence of age of juvenile acquisition ("before weaning" (BW; Day 10 and 15 after birth) and "after weaning" (AW; Day 20 and 25 after birth)) of a spatial task on subsequent re-acquisition of the same hidden-platform spatial water-maze task. This study also compared sex differences and litter sex-ratio effects on reacquisition performance. Fifteen litters of adults were re-tested in the same water maze 6 weeks after being initially tested as juveniles. All analyses were conducted using a covariate that removed the group differences in the original task performance. Adult voles from female-biased litters, that had previously learned the task at an older juvenile age (AW), reacquired the same task faster than adults that had previously learned the task at a younger juvenile age (BW). In the adult BW group there was also a significant litter sex-ratio effect such that voles born into a female-biased litter re-acquired the task more slowly than did voles born into a male-biased litter. There were no significant sex or litter sex-ratio effects on spatial learning in the AW group. These results show that adult meadow voles can require a spatial task more quickly if they initially learned the task at an older juvenile age, suggestive of a period of infantile amnesia. In addition, these results indicate that the litter sex-ratio can affect adult spatial performance, suggesting that the relative amount of androgens in utero may influence the development of sexually-dimorphic spatial ability in adulthood.     

Transmission electron microscopy study of a dental gallium alloy

Analytical transmission electron microscopy (TEM) studies of a dental gallium alloy have been carried out. This commercial Ga alloy was made by triturating a Ag-Sn-Cu-rich alloy powder with a liquid Ga alloy containing Ga, In and Sn. Ga alloys are of increasing interest as an alternative to amalgam. The dental material studied in the present work was found to be a composite consisting of remaining, undissolved particles from the Ag-based alloy powder in a matrix of reaction products with the liquid Ga alloy. The phases in the matrix and the remaining Ag-based alloy particles have been identified by electron diffraction, high resolution electron microscopy and energy dispersive X-ray spectroscopy. the following phases were identified: orthorhombic Ag₃Sn, cubic -Cu₉Ga₄, cubic Ag₉In₄, tetragonal -Sn and hexagonal Ag₂Ga. In addition to these well-known phases Ga-rich regions of Cu-Ga were observed consisting of an intergrowth of the tetragonal CuGa₂ and one of the cubic -Cu₉Ga₄ phases.     

Psychosomatic disease and the problem of causation

Despite its impressive rate of growth in the past decades, an increasing amount if dissatisfaction with the area of psychosomatic medicine is reflected in recent literature. The discipline's failures relate to concepts of pathogenesis and therapeutic application of research findings. These failures are explained as a necessary consequence of the philosophical tenet of mind-body dualism which underlies medical theory. It is urged that advocates of psychosomatic medicine give the concept of "holism" meaning at the most fundamental level by establishing a rational basis for theory, or else forsake this line of research for others which yield causal relationships conductive to effective therapy.     

Shot-noise limited,supercontinuum-based optical coherence tomography

We present the first demonstration of shot-noise limited supercontinuum-based spectral domain optical coherence tomography (SD-OCT) with an axial resolution of ...     

High-frequency scattering by a conducting circular cylinder coatedwith a lossy dielectric of nonuniform thickness

A closed-form expression for the field produced by a plane wave incident on an infinitely long conducting cylinder, coated with a lossy dielectric of nonuniform thickness, is obtained using perturbation theory. This approximate series solution is later evaluated asymptotically for electrically large cylinder sizes. The scattered fields are interpreted using geometric optics and creeping waves. The fields are calculated using the exact series, the approximate perturbation series, and the high-frequency asymptotic solutions, and compared for different angles of incidence     

Radiation due to a convex curvature discontinuity of adielectric-coated perfect conductor

Surface waves radiate energy at discontinuities in the curvature of the guiding structure. By reciprocity, surface waves will be excited by plane waves incident upon such a discontinuity. Here, the problem of the radiation of a surface wave on a flat dielectric-coated perfect conductor incident upon an abrupt change to a dielectric-coated cylindrical conductor with a large radius of curvature is considered. The problem is formulated as an integral equation over the aperture of the discontinuity. Since the change in curvature is modest, an approximate perturbation solution to the integral equation is derived and the radiated field due to the discontinuity is found. This radiated field reduces to published results for an impedance surface approximation when that approximation is valid. The problem of mode conversion and associated radiation near higher mode cutoffs is also studied. It is found that near mode cutoffs, the higher order mode dominates the radiation pattern and causes the overall radiation pattern due to the discontinuity in curvature to be narrow and end fire. Away from cutoff, when all of the propagating bound modes are more tightly bound to the surface, the radiation pattern is less narrow and less end fire. For very tightly bound modes the pattern is nearly uniform. For dielectrics characterized by small permitivities, the changes in radiation pattern should be measurable     

Inactivating microorganisms using a pulsed electric fieldcontinuous treatment system

High-voltage pulsed electric fields (PEFs) can be used to inactivate microorganisms in liquids. Applying PEF technology to food pasteurization is a promising nonthermal method, which may radically change food preservation processes and provide consumers with microbiologically safe, minimally processed, fresh-like products. A continuous-flow system in a laboratory-size prototype was constructed for the nonthermal pasteurization of liquid foods with PEF technology. Major components in the prototype include a high-voltage repetitive pulse generator, a coaxial liquid food treatment chamber, a fiber-optic temperature sensing instrument and a data acquisition system. Microbial inactivation tests were conducted in the continuous PEF treatment system. Repetitive high-voltage pulses with an exponential decaying waveshape were applied to the liquid food which was pumped through the treatment chamber. Test microorganisms selected for inactivation were Escherichia coli, Staphylococcus aureus and Saccharomyces cerevisiae. Over 6-order-of-magnitude reductions in the viability of selected microorganisms were achieved while the food temperature was maintained below 40°C     

Heat conduction in microbes exposed to pulsed electric fields

Nonthermal pasteurization of liquid foods by intense pulsed electric fields results in advantages over conventional heat pasteurization. Thermal damage to liquid foods can adversely affect the flavor and taste and result in loss of nutrients. Numerical modeling of heating parameters near the microbe during exposure to these intense electric fields is described. Boundary conditions at membrane interfaces included the continuity of temperature and continuity of heat flow. Temperature, heat flow vector, and heat source were included in the one-dimensional model. Two simulations are reported here. Simulation 1 consisted of a 0.5 μm wide microbe suspended in liquid with conductivity of 0.01 S/m and was treated with an applied electric field of 40 kV/cm for 375 ns. Simulation 2 contained a 1.0 μm wide microbe suspended in liquid with conductivity of 0.1 S/m and was treated with an applied electric field of 40 kV/cm for 1 μs. Comparison is made with a uniform conductivity model (ohmic), and it is shown that significant differences exist in the heating parameters between the two models. For the parameters used in these one-dimensional simulations, conditions for electroporation were found to exist without a significant temperature rise in the microbe     

Statistics of differential rain attenuation on adjacent earth-space propagation paths

Forty hours of observations of the three-dimensional radar reflectivity structure of rain in the Montreal area were used to simulate the centimetre-wavelength attenuations occurring simultaneously over a multitude of earth-space propagation paths. The same data base had been used in a previous study which confirmed that the radar estimates of attenuation statistics are in good agreement with attenuation distributions measured independently by passive radiometers. Differences between the attenuations occurring simultaneously over pairs of paths to a common point at the ground were tabulated as a function of angular path separation, viewing direction, radio frequency, and system margin. These data are required for evaluating the possibility of interference at an earth station caused by a signal from an adjacent satellite. In this study, values of angular separation from 2 to 9 degrees, radio frequencies from 11 to 30 GHz, elevation angles from 5 to 30 degrees, and system margins from 2 to 10 dB were considered. It was found that the cumulative distributions of differential attenuation could be characterized effectively by the attenuation difference occurring during 1 % of the time that the carrier signal suffered some attenuation, but not an attenuation exceeding the system margin. It was also found that this characteristic differential attenuation could be expressed to good approximation as a simple analytical function of the system parameters.