Dependence of defect introduction on temperature and resistivity and some long-term annealing effects

The effort reported here represents data of lithium properties in bulk-silicon samples before and after irradiation for analytical information required to characterize the interactions of lithium with radiation-induced defects in silicon. A model of the damage and recovery mechanisms in irradiated-lithium-containing solar cells is developed based on making measurements of the Hall coefficient and resistivity of samples irradiated by 1-MeV electrons. Experiments on bulk samples included Hall coefficient and resistivity measurements taken as a function of: (1) bombardment temperature, (2) resistivity, (3) fluence, (4) oxygen concentration, and (5) annealing time at temperatures from 300 to 373 K

Shortcomings in ground testing, environment simulations, and performance predictions for space applications

This paper addresses the issues involved in radiation testing of devices and subsystems to obtain the data that are required to predict the performance and survivability of satellite systems for extended missions in space. The problems associated with space environmental simulations, or the lack thereof, in experiments intended to produce information to describe the degradation and behavior of parts and systems are discussed. Several types of radiation effects in semiconductor components are presented, as for example: ionization dose effects, heavy ion and proton induced Single Event Upsets (SEUs), and Single Event Transient Upsets (SETUs). Examples and illustrations of data relating to these ground testing issues are provided. The primary objective of this presentation is to alert the reader to the shortcomings, pitfalls, variabilities, and uncertainties in acquiring information to logically design electronic subsystems for use in satellites or space stations with long mission lifetimes, and to point out the weaknesses and deficiencies in the methods and procedures by which that information is obtained

Study to determine and improve design for lithium-doped solar cells Quarterly report, 1 Jan. - 31 Mar. 1971

Lithium donor density gradient measurements for prediction of lithium cell behavior after electron irradiation and recoverabilit

Action of lithium in radiation-hardened silicon solar cells Quarterly report, 16 Jul. - 15 Oct. 1968

Action of lithium in recovery of irradiated silicon solar cell

The Graduate Education Initiative: Description and Preliminary Findings

[Excerpt] In1991 the Andrew W. Mellon Foundation launched the Graduate Education Initiative (hereafter GEI) to improve the structure and organization of PhD programs in the humanities and social sciences. Such changes were seen as necessary to combat high rates of student attrition and long times-to-degree in these programs. While attrition and time-to-degree were deemed to be important in and of themselves, and of great significance to degree seekers, they were also seen more broadly as indicators of the effectiveness of graduate programs. Several characteristics of doctoral programs were earmarked as contributing to high attrition and long degree time, including: unclear expectations, a proliferation of courses, elaborate and sometimes conflicting requirements, intermittent supervision, epistemological disagreements on fundamentals and not least, inadequate funding. Projections that faculty shortages would occur in the late 1990s in the humanities made the goals of reducing student attrition and time-to-degree particularly timely if an adequate number of PhDs were to be available. This was far from the first such effort to reduce times-to degree-and rates of attrition. Earlier programs, which provided grants in aid to individual students or to graduate schools to distribute as they saw fit, had failed conspicuously. Based on data which showed that there were marked differences among departments and on a great deal of experience on the ground, the architects of the GEI determined that to improve graduate education would require departments to make changes in their PhD programs. As such, the Foundation shifted much of its support for doctoral education, which had previously gone directly to students, to block grants that would be awarded to departments within major universities

Action of lithium in radiation hardened silicon solar cells Quarterly report, 23 Apr. - 15 Jul. 1968

Recovery properties of lithium containing p-n silicon solar cells after radiation damag

Study to determine and improve design for lithium-doped solar cells Quarterly report, 1 Apr. - 30 Jun. 1970

Lithium action effects on spontaneous annealing of radiation damage in bulk silicon and silicon solar cell

Radiation damage in lithium-containing solar cells Final report, 21 Jun. 1966 - 20 Mar. 1968

Interaction of lithium with defects induced in silicon solar cells by one MeV electron bombardmen

Rapid progesterone actions on thymulin-secreting epithelial cells cultured from rat thymus

Many soluble factors of neural, endocrine, paracrine and autocrine origin are present in the thymus and modulate its function. Long-term effects of sex steroids have! been documented for thymocytes and cells of the thymic microenvironment. In this report we examine rapid actions of progesterone upon aspects of epithelial cell physiology. Progesterone (0.1-10 mu M) was applied to cultured thymulin-secreting thymic epithelial cells (TS-TEC) and changes in transmembrane potential, transmembrane current, intracellular calcium levels and thymulin secretion were assessed. Rapid changes in electrophysiology and intracellular calcium provide evidence for a membrane-bound progesterone receptor in these cells, in addition to classical cytoplasmic receptors. Application of progesterone to TS-TEC caused electrophysiological changes in 56% of cells (n = 40), activating an inward current (-24 +/- 9 pA at 1 mu M, n = 7, p < 0.02) and dose-dependent depolarization (7.1 +/- 1.8 mV at 1 mu M, n = 19, p < 0.01). Intracellular calcium levels, monitored by the ratiometric fluorescent calcium indicator fura-2, increased within seconds of progesterone (1 mu M) application. Progesterone(1 mu M) increased thymulin levels in supernatant, as measured by ELISA, above the levels in the preapplication period (142 +/- 16% of the preapplication period, n = 3, p < 0.02). This effect was reduced in the presence of cobalt chloride which blocks voltage-dependent calcium channels. In addition, TS-IEC in culture were immunoreactive to antibody AG7. This antibody was raised to a membrane-bound antigen involved in calcium influx subsequent to progesterone binding in sperm. thus we suggest that progesterone acts upon many aspects of TS-TEC physiology through both cytoplasmic and membrane-bound receptors

Prediction and measurement of radiation damage to CMOS devices on board spacecraft

The CMOS Radiation Effects Measurement (CREM) experiment is presently being flown on the Explorer-55. The purpose of the experiment is to evaluate device performance in the actual space radiation environment and to correlate the respective measurements to on-the-ground laboratory irradiation results. The experiment contains an assembly of C-MOS and P-MOS devices shielded in front by flat slabs of aluminum and by a practically infinite shield in the back. Predictions of radiation damage to C-MOS devices are based on standard environment models and computational techniques. A comparison of the shifts in CMOS threshold potentials, that is, those measured in space to those obtained from the on-the-ground simulation experiment with Co-60, indicates that the measured space damage is smaller than predicted by about a factor of 2-3 for thin shields, but agrees well with predictions for thicker shields