The effect of electropulsing on dislocation structures in [233] coplanar double-slip-oriented fatigued copper single crystals

The effect of high-current-density electropulsing on dislocation structures in a coplanar double-slip-oriented copper single crystal that had previously been fatigued is reported. The results show that, after electropulsing, vein structures are transformed to cell structures with some dark regions. It is proposed that the thermal compressive stress caused by electropulsing activates a coplanar slip system and leads to strong dislocation interactions between primary and coplanar slip systems, thereby forming cell structures. Partial recrystallization may occur by electropulsing, leading to the appearance of some dark regions.     

Effect of local chemistry,structure and length scale of heterogeneities on the mechanical properties of a Ti45Cu40Ni7.5Zr5Sn2.5 bulk metallic glass

We report on distinct variations in local chemistry, structure and length scale of heterogeneous regions in Ti₄₅Cu₄₀Ni_7.5Zr₅Sn_2.5 fully glass rods of different diameters, i.e. rods subjected to different cooling rates. The present investigations indicate that the mechanical properties of the Ti₄₅Cu₄₀Ni_7.5Zr₅Sn_2.5 bulk metallic glass can be modified within a wide range of strength and plastic deformability by controlling the scale of the heterogeneous regions in the glass through appropriate variation of the cooling rate applied for solidification.     

Tunability of vortex-like patterns on 180o domain walls in ferroelectric PbTiO3

ABSTRACT

Vortices and antivortices are topological defects that could be exploited in high-density storage devices. Using first-principles calculations, we found vortex-like patterns around charged domain walls that are closely related to the tilt angles of charged 180° domain walls relative to the [100] direction. With decreasing tilt angle, the vortex-like patterns evolve from independent antivortices to vortex-antivortex pairs, and then to the inexistence of vortex or antivortex defects. These findings might promote to understand the atomic scale structures of 180° domain walls and open a new pathway to manipulating vortex structures to obtain novel properties.     

Dislocation arrangements and crystallographic characterization of deformation band in fatigued copper single crystal

This letter reveals the dislocation arrangements and crystallographic characterization of deformation bands (denoted DBII) in a copper single crystal fatigued at a high strain amplitude gamma_pl = 8 x 10^-3. The results show that the surface deformation morphology of the crystal displays the following features. (1) Primary slip bands (SBs) were formed after 2 x 10⁴ cycles and these carried a relatively homogeneous and small plastic strain. (2) Secondary slip bands did not operate during cyclic deformation. (3) Deformation bands (DBs) with a width of 50 mum were homogeneously distributed over the whole surface of the crystal and were perpendicular to the SBs. (4) Dislocation patterns within the SBs often consisted of irregular structures, which did not show a persistent feature. The results indicate that these SBs are not typical persistent slip bands (PSBs). (5) Within the DBII, the microstructure can be classified into two types. One type consists of regular 100% ladder-like parallel PSBs. The other type is full of dislocation walls parallel to DB direction, which have not been reported previously. By crystallographic analysis of the DBII, it is shown that the habit plane of the DBII should correspond to the (101) plane. Based on the observations above, it is suggested that the formation of DBII should be attributed to the local regularization of dislocation walls within primary slip bands.     

Interfacial reaction between silicon nitride and aluminium

Abstract

The microstructure of a silicon nitride/aluminium interface has been identified by analytical transmission electron microscopy. HIPed silicon nitride without any additive was bonded by pure aluminium at 800°C for 15 min. A thin (～ 5000 Å) reaction layer was recognized at the interface. It consisted of two regions. One an amorphous layer facing the aluminium; it contained aluminium, silicon and oxygen. The other was on the silicon nitride side and consisted of fine particles which were less than 100 Å in diameter. These particles were considered to have β'-sialon type structure.     

Do High- and Low-Active Adolescents Have Different Prototypes of Physically Active Peers?

The Psychological Record - Previous studies have investigated social images in health-risk behaviors, suggesting that these images are important factors in adolescents’ health-related...     

Different effects of eyelid blinks and target blanking on saccadic suppression of displacement

Displacements of visual stimuli during saccadic eye movements are often not noticed. We have demonstrated that saccadic suppression of image displacement can be eliminated by blanking the stimulus for a short period during and after the saccade (Deubel, Schneider, & Bridgeman, 1996). Here we report an experiment in which target visibility was interrupted after the saccade, either by distal target blanking or by voluntary eyeblink. The data show that the effect of blinking is different from blanking; interruption of vision due to a blink did not enable subjects to detect target displacements any better than they had done in the no-blank condition. The results provide evidence for an extraretinal signal that distinguishes between endogenous and exogenous sources of temporary object disappearance after the saccade.     

Physical activity-related well-being in older adults: social cognitive influences

In this study, the pattern and correlates of physical activity-related well-being in older adults (N = 174; men = 49, women = 125; mean age = 66 years) were examined across a 6-month exercise trial. Baseline levels of self-efficacy fitness, importance of physical activity, and social support and exercise participation across the trial were used as correlates of positive and negative feeling states. Psychological responses to physical activity were assessed on a bimonthly basis across the trial. Latent growth curve analyses indicated significant growth in positive well-being over the 6-month period, with increases reaching a threshold at 4 months. Self-efficacy was inversely related to change in positive well-being across the trial. Frequency of activity and increases in well-being over the trial were significant predictors of self-efficacy at program termination. Findings suggest the social cognitive context of the exercise experience may have influence on exercise-related well-being.