High voltage power supply

A high voltage power supply is formed by three discrete circuits energized by a battery to provide a plurality of concurrent output signals floating at a high output voltage on the order of several tens of kilovolts. In the first two circuits, the regulator stages are pulse width modulated and include adjustable ressistances for varying the duty cycles of pulse trains provided to corresponding oscillator stages while the third regulator stage includes an adjustable resistance for varying the amplitude of a steady signal provided to a third oscillator stage. In the first circuit, the oscillator, formed by a constant current drive network and a tuned resonant network included a step up transformer, is coupled to a second step up transformer which, in turn, supplies an amplified sinusoidal signal to a parallel pair of complementary poled rectifying, voltage multiplier stages to generate the high output voltage

An improved soft X-ray photoionization detector

Photoionization detector with an alumina shell, a beryllium foil window, and a xenon gas fill measures small incident photon fluxes from soft X rays. It has high spectral selectivity and quantum efficiencies, and a long shelf life. It minimizes electrical leakage and recontamination, and will hold a high vacuum

Publications of the planetary biology program for 1975: A special bibliography

The Planetary Biology Program of the National Aeronautics and Space Administration is the first and only integrated program to methodically investigate the planetary events which may have been responsible for, or related to, the origin, evolution, and distribution of life in the universe. Research supported by this program is divided into the seven areas listed below: (1) chemical evolution, (2) organic geochemistry, (3) life detection, (4) biological adaptation, (5) bioinstrumentation, (6) planetary environments, and (7) origin of life. The arrangement of references in this bibliography follows the division of research described above. Articles are listed alphabetically by author under the research area with which they are most closely related. Only those publications which resulted from research supported by the Planetary Biology Program and which bear a 1975 publication date have been included. Abstracts and theses are not included because of the preliminary and abbreviated nature of the former and the frequent difficulty of obtaining the latter

A soft X-ray photoionization detector

Direct current xenon-filled ceramic ionization chamber used as radiation detector in solar and astrophysical observations from rockets and satellite

Literacy Access through Storytime: An Ethnographic Study of Public Library Storytellers in a Low-Income Neighborhood

While early literacy achievement continues to be stratified by social class in the United States, public libraries often offer programs such as “storytime” in order to bolster the literacy development of youth in their communities. The purpose of the present ethnographic study was to explore how storytellers recruited and maintained participation in this free literacy program in a lower-income neighborhood. Via participant observations, semi-structured interviews, and artifact collection, storytellers recruited new patrons to storytime by (1) appealing to community members to enter the physical space of the library and (2) appealing to library patrons to attend storytime. Once patrons attended storytime, storytellers acted in order to maintain storytime attendance by (1) facilitating meaningful learning experiences, (2) fostering enjoyment through participation, (3) developing nurturing relationships, and (4) offering flexibility in storytime expectations. By exploring a contextualized account of the work of storytellers, the findings suggest important avenues through which public programs may contribute to more equitable access to literacy learning