Gamma-induced trapping levels in si with and without gold doping

Because gold doping can be used to suppress ionization-induced photocurrents in Si devices exposed to radiation environments, it is of interest to know whether or not radiation-induced mobile defects interact with Au to form deep level defect complexes. Trapping level studies have been undertaken using the technique of deep level transient spectroscopy (DLTS) prior to and following Co-60 gamma irradiation and thermal annealing of p⁺/n Si junctions doped with 3-6 × 10¹⁴ Au/cm³ and 1-3 × 10¹³ Au/cm³ , and of non-Au doped p⁺ /n and n⁺ /p junctions. Prior to irradiation, the Au acceptor level at E_c - 0.57 eV is observed in the gold doped junctions. During irradiation, five additional levels at E_c - 0.18 eV, E_c - 0.20 eV, E_c - 0.46 eV, E_v +0.17 eV, and E_v + 0.39 eV grow in linearly with gamma dose. None of these levels are associated with Au because they are observed at equal concentrations in the non-Au doped and Audoped junctions, and because the Au concentration as monitored by the E_c - 0.57 eV level does not change even when defect concentrations are of the same order. Isochronal annealing studies also indicate that the Au acceptors are inert to defect re-ordering effects which occur during annealing. This work was supported by the United States Department of Energy (DOE) under contract number DE-AC04-76-DP00789. A United States Department of Energy Facility.     

The effect of gamma irradiation and forward bias on the 76 K electroluminescence spectrum of GaP:Zn,O

Both the effects of gamma irradiation and high-current forward bias on the low temperature electroluminescence (EL) spectra of GaP:Zn,O light emitting diodes (LEDs) have been studied by measuring constant current (1 mA) 76 K EL spectra below 1000 nm. The LEDs were divided into two sets: a control set which was subjected only to forward bias, and a set exposed to gamma irradiation and forward bias. The EL spectra reveal the growth of sharp, bound exciton emission bands (Z lines) in the range 580 nm to 620 nm following extended high current bias at 300 K of irradiated LEDs and, more weakly, in control LEDs which show pre-bias evidence of these lines. The emergence of these lines is tenatively associated with the recombination-enhanced motion of a defect, possibly the Zn interstitial, which can be introduced by irradiation and is sometimes present in unirradiated LEDs. This article sponsored by the U. S. Department of Energy (DOE) under Contract No. DE-AC04-76-DP00789. A United States Department of Energy Facility.     

Simulations of the Field-Reversed Configuration with the NIMROD Code

The recently formed Plasma Science and Innovation Center (PSI-Center) is refining the NIMROD code to simulate field-reversed configurations (FRCs). The NIMROD code can resolve highly anisotropic heat conduction and viscosity. This, combined with its ability to include two-fluid effects, allows us to capture more detailed physics than previous calculations. Some initial simulations are focused on 2D (n = 0 only) non-linear two-fluid simulations. We present initial validations of a translating FRC and note good conservation of density and magnetic flux. As a validation of the effects of anisotropic thermal conduction, we present a comparison of an FRC with standard thermal transport to one with anisotropic conduction. Two-fluid simulations are shown which produce significant spin-up due to the end-shorting boundary condition. Finally, simulations of the tilt instability are presented, which show that Hall physics significantly retards, but does not eliminate the growth rate.     

Depletion layer effects in the open-circuit- voltage-decay lifetime measurement

There is a renewal of interest in open circuit voltage decay as a technique for determining the base region minority carrier lifetime in semiconductor diodes. Although the existing theory of open circuit voltage decay provides a substantial foundation for interpreting the experimental data, major features of the decay curves of real silicon diodes cannot be satisfactorily explained unless depletion layer effects are taken into account. Theoretical decay curves are calculated to show the effects of depletion layer capacitance and recombination current on the otherwise ideal open circuit voltage decay. From these and from experimental decay curves, it is shown that each of these depletion layer effects is significant only below a threshold junction voltage that depends upon material parameters of the device.     

Why review articles on the health effects of passive smoking reach different conclusions

OBJECTIVE: To determine whether the conclusions of review articles on the health effects of passive smoking are associated with article quality, the affiliations of their authors, or other article characteristics. DATA SOURCES: Review articles published from 1980 to 1995 were identified through electronic searches of MEDLINE and EMBASE and from a database of symposium proceedings on passive smoking. ARTICLE SELECTION: An article was included if its stated or implied purpose was to review the scientific evidence that passive smoking is associated with 1 or more health outcomes. Articles were excluded if they did not focus specifically on the health effects of passive smoking or if they were not written in English. DATA EXTRACTION: Review article quality was evaluated by 2 independent assessors who were trained, followed a written protocol, had no disclosed conflicts of interest, and were blinded to all study hypotheses and identifying characteristics of articles. Article conclusions were categorized by the 2 assessors and by one of the authors. Author affiliation was classified as either tobacco industry affiliated or not, based on whether the authors were known to have received funding from or participated in activities sponsored by the tobacco industry. Other article characteristics were classified by one of the authors using predefined criteria. DATA SYNTHESIS: A total of 106 reviews were identified. Overall, 37% (39/106) of reviews concluded that passive smoking is not harmful to health; 74% (29/39) of these were written by authors with tobacco industry affiliations. In multiple logistic regression analyses controlling for article quality, peer review status, article topic, and year of publication, the only factor associated with concluding that passive smoking is not harmful was whether an author was affiliated with the tobacco industry (odds ratio, 88.4; 95% confidence interval, 16.4-476.5; P<.001). CONCLUSIONS: The conclusions of review articles are strongly associated with the affiliations of their authors. Authors of review articles should disclose potential financial conflicts of interest, and readers of review articles should consider authors' affiliations when deciding how to judge an article's conclusions.     

How much of the hippocampus can be explained by functional constraints?

In the spirit of Marr, we discuss an information-theoretic approach that derives, from the role of the hippocampus in memory, constraints on its anatomical and physiological structure. The observed structure is consistent with such constraints, and, further, we relate the quantitative arguments developed in earlier analytical studies to experimental measures extracted from neuronal recordings in the behaving rat.     

Expression of human cathepsin K in Pichia pastoris and preliminary crystallographic studies of an inhibitor complex

Cathepsin K is a cysteine protease of the papain family, which is predominantly expressed in osteoclasts, and is regarded as a key protease in bone remodeling. To facilitate structural studies of the protein, the wild-type sequence of the protease has been mutated so as to replace a potential N-glycosylation site. We have expressed the mutant human cathepsin K to 190 mg/5 L using the Pichia pastoris expression system. Cathepsin K was inactivated with the mechanism-based inhibitor, APC3328, and crystallized from magnesium formate. A 2.2 A X-ray data set has been collected on crystals belonging to space group P2(1)2(1)2(1), with a = 41.66 A, b = 51.41 A, and c = 107.72 A. There is most likely one molecule per asymmetric unit.     

Reactivation of hippocampal ensemble activity patterns in the aging rat.

In young rats, the pattern of neuronal ensemble activity correlations expressed among hippocampal pyramidal cells during behavior persists during subsequent quiet wakefulness and slow-wave sleep, a process that may facilitate the consolidation of episodic memories. The present study explored the hypothesis that age-related changes in this process might contribute to memory impairments observed during normal aging. Neuronal activity was recorded from CA1 pyramidal cells, and in both young and old rats, there was a strong similarity between the resting epoch activity patterns and those from the preceding behavior epoch. This similarity was strongest during sharp-wave events. There were no detectable differences in the reactivation process or the decay rate between the young and old age groups. Thus, age differences in spatial memory do not appear to be explainable by differences in the spontaneous reactivation of familiar patterns within the hippocampus during the immediate postbehavior period. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Design methodology management

Design methodology management is an emerging technology in the world of electrical computer aided design. It has spawned considerable research over the past decade, and a firm belief in many people's minds that it is the key to significant productivity enhancements in the next. How close are we to seeing this belief fulfilled? In this paper, we define the concepts that are important to design methodology management systems and explain how these systems relate to CAD frameworks. We then examine and characterize 23 notable design methodology management systems of the last 15 years in order to understand the state of the art. Finally, we describe and analyze the trends we have seen in these systems and propose where this technology is headed