Growth orientation of one-dimensional silicon nanowires prepared by thermal evaporation

One-dimensional silicon nanowires have been grown by thermal evaporation and their growth orientations determined by transmission electron microscopy studies. The nanowires, which are often highly curved in morphology and heavily twinned in microstructure, are crystallographically separated into several sections, each with a characteristic crystallographic orientation along the wire axis. Straight nanowires, or straight sections in a curved nanowire, are found to have non-unique crystallographic orientations when {111} twinning occurs.     

Multiple phase transitions in CuO

Electrical resistivity, thermoelectric power, magnetic susceptibility and calorimetric measurements were carried out on a single crystal of CuO. In addition the two known antiferromagnetic transitions between 210K and 230K, a new phase transition around 160K was found in CuO. The experimental results show that this new transition is related to changes in the electronic state of CuO.     

Survey of plateau behaviour in the cyclic stress-strain curve of copper single crystals

Experimental results relating to the plateau behaviour in the cyclic stress-strain (CSS) curve of copper single crystals located on different sides of the stereographic triangle are summarized. Unlike the situation for single-sliporiented crystals, the crystallographic orientation has a strong effect on the plateau behaviour in the CSS curves of double- and multiple-slip-oriented crystals. The existence or non-existence of a plateau in the CSS curves, as well as the corresponding plateau stress amplitude, depend not only on the modes and intensities of dislocation interactions among slip systems operating in the crystals but also on the slip deformation characteristics associated with crystal orientations. The plateau region in CSS curve disappears only when multiple slip plays a determining role during cyclic deformation.     

Crystallization behaviour of Al-based amorphous alloy and nanocomposites by rapid quenching

The microstructure and crystallization behaviour of melt-spun Al₈₈Ni₉Ce₂Fe₁ amorphous alloy and nanophase composites have been studied by means of X-ray diffraction, transmission electron microscopy and scanning and isothermal calorimetry. The diffraction patterns from Al₈₈Ni₉Ce₂Fe₁ amorphous alloys are diffuse, indicating a basically amorphous structure but contain two rings presumed to be associated with quenched-in nuclei. In the cases of Al₈₈Ni₉Ce₂Fe₁ nanophase composites, nanoscale precipitated particles are homogeneously dispersed in an amorphous matrix, and the crystallite diameter and volume fraction are sensitive to quenching conditions. During thermal crystallization, a two-step phase transformation occurs in the amorphous alloy and nanocomposites, which is characterized by a diffusion-controlled precipitation of nanoscale Al particles and the growth of a Al₃(Ni, Fe) nanophase prior to a Al₁₁Ce₃ nanophase. This study gives insight into structure-control for obtaining nanophases dispersed in an amorphous matrix by rapid quenching.     

Self-evaluation and self-perception: The role of attention in the experience of anxiety

Abstract

Self-awareness promotes the experience of anxiety in two ways. It does so directly, by enhancing awareness of the emotional state itself, and by initiating the self-evaluation process that is necessary for anxiety to occur. It also does so indirectly, by constraining some behaviors and inhibiting others. In particular, it increases accuracy of self-perception, and, in so doing, retards the process of self-delusion. This is important, because the latter process has been shown to have a salutary effect on mental health, acting as a buffer against dysphoric states such as depression and anxiety.     

Risk perception and risky choice: Situational, informational and dispositional effects

We investigated how situational (gain–loss), informational (opportunity–threat framing) and dispositional (achievement motive and avoidance motive) variables affected opportunity–threat perception and risky choice in managerial decision-making contexts. In Study 1, the risk preference of the participants showed a reflection effect due to situational differences (gain or loss) and a partial framing effect caused by presenting the same choice information in terms of either opportunities or threats. However, both effects were in the opposite direction of predictions from prospect theory. Gains and positive framing enhanced risk-seeking preference whereas losses and negative framing augmented risk-averse preference. Risk-seeking choices were mediated by opportunity perception whereas risk-averse choices were mediated by threat perception. In Study 2, the participants high in achievement motive perceived greater opportunities in a negative situation, and the participants high in avoidance motive perceived greater threats in a positive situation, suggesting that ambition (achievement motive) operates more significantly in the face of adversities whereas cautiousness (avoidance motive) functions more significantly in prosperity.     

Protection and vulnerability processes relevant for early onset of substance use: a test among African American children.

This research tested predictions from a self-regulation model of factors relevant for early onset of tobacco and alcohol use with a community sample of 889 African American children (mean age = 10.5 years). Criterion variables were peer substance use, willingness to use substances, and resistance efficacy (intention to refuse substance offers). Structural modeling indicated effects of temperament dimensions were mediated through self-control and risk-taking constructs, which were related to school involvement, life events, and perceived vulnerability to harmful effects of substances. Peer use was predicted by life events, poor self-control, and parent-child conflict; willingness was predicted by life events, risk taking, and (inversely) parental support; and resistance efficacy was predicted by perceived vulnerability and (inversely) poor self-control. Findings are discussed with reference to theoretical models of early protection and vulnerability processes.     

Perforant path activation modulates the induction of long-term potentiation of the schaffer collateral--hippocampal CA1 response: theoretical and experimental analyses

In one computational model of hippocampal function, the entorhinal cortical input to CA1 is hypothesized to play a key role in the ability of CA1 to decode CA3 recodings. Here, we develop a modification of this CA1 decoder hypothesis that is applicable to several computational theories of hippocampal function, and then we electrophysiologically investigate one assumption of this new hypothesis. First, using biologically realistic estimates, we calculate that CA3-induced CA1 excitation is too high and that inhibition plausibly plays a role in this CA1 decoder model. Thus motivated, we turn to a physiological demonstration to substantiate the plausibility of the proposed mechanism. Using the rat hippocampal slice, we examine an interlaminar interaction between the distal perforant path input to hippocampal CA1 stratum moleculare and the more proximal Schaffer collateral input to stratum radiatum. Perforant path activation provides sufficient inhibition to block homosynaptic long-term potentiation elicited by a suitably strong stratum radiatum input. For this interlaminar interaction to be most effective, perforant path activation must both precede and follow Schaffer collateral activation. Perforant path-evoked inhibition in CA1 can thus serve as a viable mechanism in the learned decoder theory of hippocampal CA1.