A study of deposition conditions and hydrogen motion in rf sputtered hydrogenated amorphous silicon

Three series of a-Si:H films were prepared by r.f. sputtering in He/H(,2), Ar/H(,2), and Xe/H(,2) atmospheres. The r.f. power used for deposition was varied from 0.27 W/cm(\u272) to 3.3 W/cm(\u272) for each of these three series. The films were characterized using mechanical thickness, optical transmission, infrared, and electron spin resonance measurements;The deposition rates of these films were found to vary linearly with deposition rates predicted from known sputtering yields. The total hydrogen concentration of the films as a function of deposition rate was found to agree with the predictions of a kinematic model for hydrogen incorporation. The concentration of silicon atoms bonded to more than one hydrogen atom was found to agree with a random statistical model, although, there were fluctuations away from this model\u27s predictions when high r.f. powers were used for deposition;The density of weak Si-Si bonds and the value of the Urbach edge coefficient were used to judge the quality of the films. It was found that samples prepared in an Ar/H(,2) atmosphere at high r.f. powers (\u3e2.2 W/cm(\u272)) were of the highest quality;Samples consisting of alternating layers of high and low hydrogen concentration were also prepared. These samples were confirmed to be multilayers through the use of x-ray, optical transmission, and reflected electron loss spectroscopy depth profiling measurements. Thermal annealing experiments performed on these samples demonstrated that hydrogen does not diffuse, but rather effuses out of the sample, at elevated temperatures. These experiments also;indicated that silicon-hydrogen bonds in r.f. sputtered a-Si:H are stronger than silicon-hydrogen bonds in glow discharge produced a-Si:H; *DOE Report IS-T-1309. This work was performed under contract No. W-7405-Eng-82 with the U.S. Department of Energy

Non-displaceable contact embeddings and infinitely many leaf-wise intersections

We construct using Lefschetz fibrations a large family of contact manifolds with the following properties: Any bounding contact embedding into an exact symplectic manifold satisfying a mild topological assumption is non-displaceable and generically has infinitely many leaf-wise intersection points. Moreover, any Stein filling has infinite dimensional symplectic homology.Comment: 11 pages, 4 figure

Patterns of sensory nerve conduction abnormalities in demyelinating and axonal peripheral nerve disorders

The pattern of an abnormal median-normal sural (AMNS) sensory response is associated with acute and chronic inflammatory demyelinating polyradiculoneuropathy (AIDP and CIDP) and considered unusual in other types of neuropathy, although specificity and sensitivity of this pattern have not been evaluated. We compared sensory responses (patterns and absolute values) in patients with AIDP, CIDP, diabetic polyneuropathy (DP), and motor neuron disease (MND). Using strict criteria, the AMNS pattern occurred more frequently in recent onset AIDP (39%) compared with CIDP (28%), DP (14%–23%), or MND (22%) patients. This pattern was found in 3% of control subjects. The extreme pattern of an absent median-present sural response occurred only in AIDP and CIDP patients and in no other groups. Abnormalities of both nerves were more common in long-standing polyneuropathies such as CIDP and DP compared with AIDP or MND. Median nerve amplitudes were reduced significantly in AIDP, CIDP, and DP patients compared with MND patients, whereas sural nerve amplitudes were significantly reduced only in DP and CIDP patients. These findings may reflect early distal nerve involvement particularly in AIDP patients which is highlighted by differences in median and sural nerve recording electrode placement. We conclude that, in the appropriate clinical setting, the AMNS pattern, an absent median-present sural response pattern, or a reduced median amplitude compared with the sural amplitude supports a diagnosis of a primary demyelinating polyneuropathy. © 1993 John Wiley & Sons, Inc.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/50157/1/880160304_ftp.pd

Many-body Electronic Structure of Metallic alpha-Uranium

We present results for the electronic structure of alpha uranium using a recently developed quasiparticle self-consistent GW method (QSGW). This is the first time that the f-orbital electron-electron interactions in an actinide has been treated by a first-principles method beyond the level of the generalized gradient approximation (GGA) to the local density approximation (LDA). We show that the QSGW approximation predicts an f-level shift upwards of about 0.5 eV with respect to the other metallic s-d states and that there is a significant f-band narrowing when compared to LDA band-structure results. Nonetheless, because of the overall low f-electron occupation number in uranium, ground-state properties and the occupied band structure around the Fermi energy is not significantly affected. The correlations predominate in the unoccupied part of the f states. This provides the first formal justification for the success of LDA and GGA calculations in describing the ground-state properties of this material.Comment: 4 pages, 3 fihgure

Hardware Acceleration in Genode OS Using Dynamic Partial Reconfiguration

Algorithms with operations on large regular data structures such as image processing can be highly accelerated when executed as hardware tasks in an FPGA fabric. The Dynamic Partial Reconfiguration (DPR) feature of new SRAM-based FPGA families allows a dynamic swapping and replacement of hardware tasks during runtime. Particularly embedded systems with processing chains that change over time or that are too large to be implemented in an FPGA fabric in parallel, benefit from DPR. In this paper we present a complete framework for hardware acceleration using DPR in the microkernel based Genode OS. This makes the DPR feature available not only for the high-performance computing field, but also for safety-critical applications. The new framework is evaluated for an exemplary imaging application running on a Xilinx Zynq-7000 SoC

Rewarding Properties of Social Defeat

Conditioned place preference (CPP) is a classical conditioning paradigm used to evaluate the rewarding or aversive properties of a stimulus. A stimulus can be an audio, visual, or sensory prompt but can also be stimuli associated with behaviors. Environments associated with sexual and aggressive encounters can become rewarding to both male and female Syrian hamsters regardless of social status. However, we have observed that individually-housed, non-aggressive hamsters find social interaction without aggression or sexual behaviors rewarding. Therefore, we expanded upon our previous experiments using CPP to test the hypothesis that group-housed, male hamsters (n=12) can develop a preference for a negative social experience such as social defeat. The CPP paradigm consisted of an initial preference test (15 min X 2), a conditioning phase (10 min X 5 days), and a final preference test (15 min). The hamster was placed into a CPP apparatus containing two main testing chambers, black and white, connected by a neutral, clear chamber. The pretest was conducted to establish a baseline for comparison to the posttest to determine changes in the amount of time spent in either (black/white) chamber. An individually-housed male (n=11) was paired with a group-housed male in their non-preferred chamber for conditioning. The order of placement in the chambers was alternated daily. Control animals (n=5) were used to evaluate effects of habituation across conditioning trials. The result of our experiment showed that group- housed animals developed a CPP for social defeat. We observed that the preference scores increased from 0.34 (± 0.01) to 0.41 (± 0.04), p = .08 and the difference scores decreased from 243.67 (± 21.72) to 171.25 (± 60.34), p \u3c .05. There were no significant differences between pretest and posttest scores for controls for both preference scores and for difference scores from pretest to posttest. The results of this experiment suggest that that our subjects developed a CPP for social defeat and that their response may have been influenced by the type of social defeat. We believe that an escapable defeat with different aggressors’ parings, as was conducted in our experiment, produced social interaction with novelty but with lower stress levels, leading the animals to develop a CPP for social defeat. The hamster’s reactions to the experiment conducted suggest that their response may have been influenced by the type of social defeat that was experienced. There are two types of social defeat models: inescapable and escapable. An inescapable defeat implies that an animal cannot avoid its aggressor whereas an escapable defeat implies that the animal can. Animals exposed to an inescapable defeat have been found to produce generalized aversion and avoidance towards not only a familiar aggressor but a novel, non-aggressive aggressor with the avoidance greater with the familiar aggressor than the unfamiliar; whereas, animals exposed to an escapable defeat only produce avoidance towards its previous aggressor. However, our previous and current research indicates that all Syrian hamsters regardless of social (aggressive/submissive) and housing (group/individual) status all formed a CPP for social behavior, albeit social aggression or social defeat. Our CPP experiment paradigm, similar to that of an inescapable defeat model in that the animal can avoid its aggressors, perhaps produced a positive CPP for social defeat because the hamsters found the controllability of the defeat with novel aggressors across the conditioning trials to be stimulating. While, the hamsters displayed a CPP for social defeat they were not completely resilient and demonstrated higher vigilance to their surroundings as evidenced by the increased duration in the neutral chamber following social defeat. The hamsters’ behaviors suggest that the conducted experiment produced a combination of mild social defeat with novel interactions that produced less aversion and perhaps lower generalized anxiety which was sufficient to develop a CPP for social defeat

Strain-Induced Conduction Band Spin Splitting in GaAs from First Principles Calculations

We use a recently developed self-consistent GW approximation to present first principles calculations of the conduction band spin splitting in GaAs under [110] strain. The spin orbit interaction is taken into account as a perturbation to the scalar relativistic hamiltonian. These are the first calculations of conduction band spin splitting under deformation based on a quasiparticle approach; and because the self-consistent GW scheme accurately reproduces the relevant band parameters, it is expected to be a reliable predictor of spin splittings. We also discuss the spin relaxation time under [110] strain and show that it exhibits an in-plane anisotropy, which can be exploited to obtain the magnitude and sign of the conduction band spin splitting experimentally.Comment: 8 pages, 4 figures, 1 tabl

Self-Adaptation for Availability in CPU-FPGA Systems Under Soft Errors

We introduce a model-based reliability estimation to preserve application availability in CPU-FPGA systems exposed to soft errors under varying environment conditions. The estimation is used as an in-system method to select a suitable configuration for changing radiation conditions. This allows systems to autonomously adapt their configuration in order to balance between reliability and performance. Such a self-adaptation goes beyond the state-of-the-art, where adaptation relies on preplanned reactive mode changes. By autonomously evaluating new configurations, our self-adaptation process is capable of increasing the availability by selecting the configuration with the desired application reliabilities for the current environment conditions

Reversal of spin polarization in Fe/GaAs (001) driven by resonant surface states: First-principles calculations

A minority-spin resonant state at the Fe/GaAs(001) interface is predicted to reverse the spin polarization with voltage bias of electrons transmitted across this interface. Using a Green's function approach within the local spin density approximation we calculate spin-dependent current in a Fe/GaAs/Cu tunnel junction as a function of applied bias voltage. We find a change in sign of the spin polarization of tunneling electrons with bias voltage due to the interface minority-spin resonance. This result explains recent experimental data on spin injection in Fe/GaAs contacts and on tunneling magnetoresistance in Fe/GaAs/Fe magnetic tunnel junctions