Methodology for calculating turn-off transient of photoconductive circuit elements in picosecond optoelectronics

A methodology for calculating the transient following sudden removal of photon or mass-particle excitation is developed for semiconductor devices in which high hole-electron recombination rates, rather than short transit times, yield picosecond response time. We suggest the name photoconductive circuit element (PCE) for these optoelectronic transducers to emphasize their potential application to diverse circuit and system functions. The device consists of a nearly intrinsic active region that contains extremely high concentrations of deep-level states acting as recombination centers. Regions of semiconductors highly doped with shallow donor or acceptor atoms connected to metallic contacts border this active region. In calculating the turnoff transient, we set forth criteria that define nearly ideal ohmic-contact systems and the quasi-neutrality regime of the intrinsic region. If these criteria are met, the turn-off transient becomes a problem in photoconductive decay. For incremental variations in the electron and hole quasi-Fermi voltages much less than the thermal voltage, two characteristic times, assigned to each recombination-center energy level, rather than a single lifetime, describe electron-hole recombination. A computer algorithm accounting for incremental variations within suitably small time intervals then enables calculation of observables that may vary by many orders of magnitude, InP:Fe photoconductive circuit elements containing eight different Fe concentrations, excited by 780 and 600 nm laser-light pulses and 6 MeV electron pulses, showed a (1/e)-fall-time versus Fe-concentration in general accord with results calculated by the methodology. The capture cross sections and the energy distribution of the recombination-center energy levels receive attention. The InP:Fe transducers showed (1/e)-fall-times in the sub- 100-ps regime.     

Diurnal variation in subsidiary reaction time in a long-term driving task

Traffic accidents show a marked diurnal rhythm, which is a seldom investigated phenomenon. One possible background factor examined in the present study is the biological circadian rhythm. Eight subjects drove for 3 hr, beginning at 0300, 0900, 1500 and 2100. During each session a subsidiary reaction time task was used as an indirect measure of driving performance. Critical confounding factors, such as lighting conditions, traffic intensity, amount of sleep preceding the session and temperature in the car were considered. The results showed that there were small differences in the level of performance among the four sessions. However, differences in the rate of performance deterioration were not observed. From these results it was concluded that biological rhythm as a single variable has only a minor influence on this type of performance. Consequently the diurnal rhythm of traffic accidents must be attributed to other factors such as long hours of driving and/or sleep deprivation which culminate during the morning hours.     

Internship Workshops on Psychopathology: Bridging the Academic-Clinical Gap.

Reports on a brief orientation program designed to familiarize new interns with some of the major signs of psychopathology they will encounter and to help bridge gaps in training for individual interns. The orientation consists of four 1-day workshops focusing on the areas of depression, suicide and hospitalization, schizophrenia, and neuropsychological problems. Completing these intensive workshop experiences provides a brief overview of psychopharmacology and a short introduction to the evaluation process of child problems. The workshops are regarded as important both for the interns and the staff. As the interns become more curious and less defensive about beginning their clinical rotations, the staff become less frustrated about handling the interns' anxieties concerning their lack of preparation for the internship year. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dependence of reproducing gap null on head geometry

The spatial frequency response of reproduce heads with infinite depth, but finite pole length, is determined to very good accuracy by superposition of conformal map solutions for simpler geometries. This approach yields closed form approximations of the frequency response which are accurate to better than 7% for any head length-to-gap length ratio and any spatial frequency. In particular, the effect of this ratio on the location of the first gap null in the frequency response spectrum is explored for narrow pole length heads. The results lead to design considerations for extending the useful frequency range of thin film reproduce heads.     

Multivalent presentation of mannose on hyperbranched polyglycerol and their interaction with concanavalin A lectin

We describe the synthesis of multivalent mannose derivatives by using hyperbranched polyglycerols (hPG) as a scaffold with different linker structures. Grafting of protected mannose (Man) units is achieved by using Cu(I) -catalyzed Huisgen click chemistry with either an anomeric azide or propargyl ether onto complementarily functionalized alkyne or azido polymer surfaces. NMR spectroscopy, dynamic light scattering (DLS), IR spectroscopy, size-exclusion chromatography (SEC), and elemental analysis have been used to characterize the hPG-Man compounds. The surface availability and bioactivity of Man-modified polymers were evaluated by using a competitive surface plasmon resonance (SPR)-based binding assay by interactions of the glycopolymers with concanavalin A (Con A), a lectin that binds mannose containing molecules. The results indicated that the novel glycoarchitectures presented in this work are efficient inhibitors of Con A-mannose recognition and resulted in inhibitor concentrations (mean IC(50)) from the micro- to the nanomolar range, whereas the corresponding monovalent mannoside (methyl-Man) requires millimolar concentrations. The results provide an interesting structure-activity relationship for libraries of materials that differ in the linkage of the sugar moiety presented on a biocompatible polyglycerol scaffold.     

The use of intensity-dependent weight functions to “Weberize” $$L^2$$ L 2 -based methods of signal and image approximation

Optimization and Engineering - We consider the problem of modifying $$L^2$$ -based approximations so that they “conform” in a better way to Weber’s model of perception: Given a...     

Comparitative Research of Pollen Morphology of Common Flax Cultivars (Linum usitatissimum L., Linaceae)

Pollen morphology of 11 cultivars of different purpose use of Linum usitatissimum was studied with LM and SEM microscopy. On average, pollen grains were radially symmetrical, isopolar, and prolate spheroidal in shape, tricolpate and of large size. All grains were semitectate with discontinuous tectum due to partial fusion of heads of the clavae. The clavae were dimorphic, clearly differ in size, but morphologically similar. The smaller ones were dominant. All observed cultivars were very similar in pollen structure and the differences among their pollen grains were primarily quantitative.     

Simulation of hydrogen deflagration and detonation in a BWR reactor building

A systematic study was carried out to investigate the hydrogen behaviour in a BWR reactor building during a severe accident. BWR core contains a large amount of Zircaloy and the containment is relatively small. Because containment leakage cannot be totally excluded, hydrogen can build up in the reactor building, where the atmosphere is normal air. The objective of the work was to investigate, whether hydrogen can form flammable and detonable mixtures in the reactor building, evaluate the possibility of onset of detonation and assess the pressure loads under detonation conditions. The safety concern is, whether the hydrogen in the reactor building can detonate and whether the external detonation can jeopardize the containment integrity. The analysis indicated that the possibility of flame acceleration and deflagration-to-detonation transition (DDT) in the reactor building could not be ruled out in case of a 20 mm² leakage from the containment. The detonation analyses indicated that maximum pressure spike of about 7 MPa was observed in the reactor building room selected for the analysis.