The spectrum of Trp- mutants isolated as 5-fluoroanthranilate-resistant clones in Saccharomyces bayanus, S. mikatae and S. paradoxus

5-Fluoroanthranilic acid (FAA)-resistant mutants were selected in homothallic diploids of three Saccharomyces species, taking care to isolate mutants of independent origin. Mutations were assigned to complementation groups by interspecific complementation with S. cerevisiae tester strains. In all three species, trp3, trp4 and trp5 mutants were recovered. trp1 mutants were also recovered if the selection was imposed on a haploid strain. Thus, FAA selection may be more generally applicable than was previously described.     

Predicting Success in a Minority Engineering Program

The purpose of this study was to investigate two frequently used selection variables, high school grade point average (GPA) and ACT composite test score, as predictors of success in the Increasing Diversity in Engineering Academics (IDEAs) minority engineering program (MEP) at The University of Akron. Data from 48 minority students who participated in the MEP were used in the analysis. The only significant predictor of graduation with an engineering degree was high school GPA. Both high school GPA and ACT scores were significantly correlated with undergraduate GPA. Although they could not be statistically analyzed, both the completion of the first calculus course and number of hours attending mandatory study halls were critical to success in the IDEAs program.     

Attitudes and expectations of 1995 gastroenterology graduates about gastroenterology

OBJECTIVE: To learn more about current attitudes and expectations of recent (June 1995) graduates of gastroenterology fellowship programs, why they chose either a private practice or academic career, and what impact managed care or health care reform had in their decision. METHODS: Between April and June 1995, and 8-page, 35-question survey questionnaire was mailed to graduating fellows and returned for evaluation. RESULTS: Graduates believed managed care had an impact on job availability, but it was not a factor in their job choice. Forty percent of the respondents reported that finding a job was either difficult or very difficult. The majority of respondents (67%) are pursuing a career in private practice. Most private practice physicians (PP) trained in 2-yr programs whereas academic physicians (AC) trained for the most part in 3-yr programs. The principal criteria on which decisions regarding job selection were based were similar between the two groups: co-workers, geographic location, access to patient care, and ability to perform endoscopy. Respondents in PP and AC expected to work 50-70 h/wk, care for patients with similar diseases, and have ample time for family. They would choose GI again as a career and believed that there is a future in GI. Salary expectations varied markedly between the two groups, and AC physicians were more concerned about their future financial needs. Twenty percent of PP physicians and 71% of AC physicians plan to participate in clinical research. CONCLUSIONS: Recent graduates of gastroenterology fellowship programs continue to have high expectations of their future careers. Although some had difficulty finding a job and stated that, although managed care had an impact on the job market, it had not yet become a major factor in their job selection.     

The effects of depressed pH on oogenesis in flagfish Jordanella floridae

Mature female flagfish Jordanella floridae were continuously exposed to pH levels of 6.7, 6.0, 5.5, 5.0 and 4.5 during a 20-d period. Quantitative histological analysis of oocyte numbers in six arbitrarily assigned stages of development indicates that the ability of oocytes to form mature eggs is reduced at all pH values tested to 20.7, 15.8, 2.1 and 8.2% respectively, when compared with control. This reduction is primarily produced by the loss of ability of oocytes to deposit secondary yolk within the cytoplasm. At pH 4.5 both primary and secondary yolk deposition is severely affected. Retardation of oocyte growth in Stages 2, 3, 4 and 5 is evident at all pH levels below 6.7, reflecting disturbances in protein production. This technique offers a method of assessing the reproductive capacity of fish from ovaries of mature breeding adults within the population.     

High-temperature superconducting delay lines and filters onsapphire and thinned LaAlO3 substrates

The very low microwave surface resistance of high-temperature-superconductor (HTS) thin films allows the realization of microwave devices with performance superior to those made by conventional technology. Superconducting delay lines, for example, have very low propagation loss and dispersion. Long, low-loss, superconducting delay lines on both thinned LaAlO₃ and sapphire substrates are presented. Delay lines with 27- and 44-ns delay have been made, for the first time, on 5-cm-diameter 254- and 127-μm-thick LaAlO₃ substrates, respectively. The insertion losses at 77 K and 6 GHz are 6 and 16 dB, respectively. Delay lines with 9-ns delay have, for the first time, been produced on M-plane sapphire substrates and demonstrate, at 77 K, an insertion loss of 1.0 dB at 6 GHz. A 2.5%-bandwidth 10 GHz four pole edge-coupled bandpass filter on M-plane sapphire substrates is also reported. The filter has minimum insertion loss of less than 0.5 dB at 9.75 GHz and 71 K     

Selected microcomputer applications for hospital management engineers

Hospital management engineering projects require a series of time consuming steps: data collection, data reduction and analysis, report preparation, and presentation. Hospital managers need information on a timely basis to help them provide quality patient care at optimum costs through an effective decision support system. Microcomputers can help management engineers and managers in these areas. Spreadsheet, data base, and standard computer language programs are three categories of microcomputer software reviewed in this paper with case studies to illustrate the application, the conditions for their selection, and potential benefits. In addition, specific points to assist with succesfful use of the computer are listed.     

Measuring the Electron’s Charge and the Fine-Structure Constant by Counting Electrons on a Capacitor

The charge of the electron can be determined by simply placing a known number of electrons on one electrode of a capacitor and measuring the voltage, V_s, across the capacitor. If V_s is measured in terms of the Josephson volt and the capacitor is measured in SI units then the fine-structure constant is the quantity determined. Recent developments involving single electron tunneling, SET, have shown bow to count the electrons as well as how to make an electrometer with sufficient sensitivity to measure the charge.     

Generation of large scale circulation in turbulent convection

In a horizontal layer of fluid heated below and cooled above, cellular convection with horizontal length scale comparable to the layer depth occurs in a certain range of Rayleigh numbers. As the Rayleigh number is increased, cellular flow disappears and is replaced by a random array of transient plumes. Upon further increase, these plumes drift in one direction near the bottom and in the opposite direction near the top of the layer with the axes of the plumes tilted in such a way that horizontal momentum is transported upwardsvia the Reynolds stress. With the onset of this large-scale horizontal flow, the largest scale of motion increases from a scale comparable to the layer depth to a scale comparable to the layer width. The conditions for the occurrence and the determination of the direction of this largescale circulation are described in this paper. A simple mathematical model is also described which, like the experiment, has the feature of spontaneous generation of a large-scale horizontal flow,u. A truncated Fourier representation of the streamfunction and temperature field is taken, which allows the possibility of a large-scale flow. The bifurcations of the resulting equations have been studied. The first bifurcation is from the conduction state to steady cellular convection. The second is from steady cellular convection to a steady tilted cell convection which has an Eulerian (but not Lagrangian) horizontal mean velocity,u. The third bifurcation is from steady tilted cells to an oscillatory flow, which may be described as consisting of transient, drifting, tilted plumes. The flow in this regime does have a net Lagrangian horizontal mean velocity. Embedded in this regime are also regions of hysteretic and other regions of chaotic flow. A qualitative similarity to the observed flows is noted.     

ZnO nanostructures as efficient antireflection layers in solar cells

An efficient antireflection coating (ARC) can enhance solar cell performance through increased light coupling. Here, we investigate solution-grown ZnO nanostructures as ARCs for Si solar cells and compare them to conventional single layer ARCs. We find that nanoscale morphology, controlled through synthetic chemistry, has a great effect on the macroscopic ARC performance. Compared with a silicon nitride (SiN) single layer ARC, ZnO nanorod arrays display a broadband reflection suppression from 400 to 1200 nm. For a tapered nanorod array with average tip diameter of 10 nm, we achieve a weighted global reflectance of 6.6%, which is superior to an optimized SiN single layer ARC. Calculations using rigorous coupled wave analysis suggest that the tapered nanorod arrays behave like modified single layer ARCs, where the tapering leads to impedance matching between Si and air through a gradual reduction of the effective refractive index away from the surface, resulting in low reflection particularly at longer wavelengths and eliminating interference fringes through roughening of the air-ZnO interface. According to the calculations, we may further improve ARC performance by tailoring the thickness of the bottom fused ZnO layer and through better control of tip tapering.