Formation of icosahedral quasicrystals in an annealed Zr65Al7.5Ni10Cu12.5Ag5 metallic glass

The formation and thermal stability of an icosahedral quasicrystalline phase in an annealed Zr₆₅Al_7.5Ni₁₀Cu_12.5Ag₅ metallic glass have been investigated by X-ray diffraction and transmission electron microscopy analyses. It was found that the quasicrystalline phase can precipitate from the glassy state and the supercooled liquid of the alloy over a wide range of annealing temperatures. After optimizing the heat-treatment conditions, the volume fraction of the quasicrystalline phase in the alloy can reach as high as about 80%. Investigation of the thermal stability of the quasicrystalline phase demonstrates that it is very stable when the annealing temperature is below the glass transformation temperature T _g of the alloy.     

Sign determination of the 57 Fe electric-field gradient in Al-based crystals and icosahedral quasicrystals

Abstract

The icosahedral quasicrystals i-AIMn, isomorphically substituted by 28 at.% Fe or by a mixture of (CrFe) atoms, have been studied for the first time by in-field Mössbauer spectroscopy in order to determine the sign and asymmetry parameter of the dominant electric-field gradient (EFG) term. In addition, the orthorhombic o-Al(MnFe) and cubic α- and hexagonal β-Al(MnFe)Si crystalline phases have been studied. We show that the previous Mössbauer results are inadequate for determining whether there are two sites in the quasicrystalline structure in the ratio of the golden number. Our results for i-Al(MnFe) show that the dominant EFG is negative, with an asymmetry parameter of about 0·6. For i-Al(CrFe), essentially no deviations are found from the model of Czjzek or the Gaussian isotropic model. One crystalline phase, the hexagonal β phase, is found to have a very similar quadrupole effect to that found in i-Al(MnFe). In addition it is found that this phase undergoes a change which is at least partly of magnetic origin.     

Determination of the Burgers vector of dislocations in icosahedral quasicrystals by a high-resolution lattice-fringe technique

A technique for the determination of the full six-dimensional Burgers vector characterizing a dislocation in an icosahedral quasicrystal is presented. It is based on the lattice-fringe analysis of two high-resolution transmission electron microscopy images taken at two different sample orientations. As an example we present the analysis of a dislocation in a bent icosahedral Al-Pd-Mn quasicrystal. We obtained a Burgers vector B = A₀[-2,0,3,-2,3,0] where A₀ = 0.645nm is the six-dimensional hyperlattice constant. This result is consistent with previous results obtained by diffraction contrast analysis and convergent-beam electron diffraction techniques.     

Tension-compression-tension tertiary twins in coarse-grained polycrystalline pure magnesium at room temperature

Using electron backscatter diffraction, the microstructural features of tension–compression–tension (T–C–T) tertiary twins are studied in coarse-grained pure polycrystalline magnesium subjected to monotonic compression along the extrusion direction in ambient air. T–C–T tertiary twins are developed due to the formation of a compression–tension double twin inside a primary tension twin. All the observed T–C–T twin variants are of T_iC_jT_j type. T_iC_i+1T_i+1 (or T_iC_i?1T_i?1) variants are observed more frequently than T_iC_i+2T_i+2 (or T_iC_i?2T_i?2) variants. The number of tertiary twin lamellae increases with the applied compressive strain.     

Plasticity of GaAs(011) at room temperature under concentrated load

Indentations have been made on a (011) surface of GaAs single crystal at room temperature. The loading-unloading curves were compared with those obtained under the same experimental conditions on (001) surfaces. The indents formed were observed by transmission electron microscopy in plan view as well as in cross-sectional view in samples prepared by the focused-ion-beam technique. The gliding systems could be identified, providing a better understanding of the plastic flow under the indenter. The arrangements of dislocations generated by the indenter have been analysed and compared with results previously reported by Ning et al.     

Investigation of tensile deformation mechanisms at room temperature in a new Ni-based single crystal superalloy

The deformation microstructures of a new Ni-based single crystal superalloy, M 4706, have been characterized by transmission electron microscopy after interrupted tensile tests at room temperature. It is found that besides shearing of γ′ precipitates by strongly coupled dislocations, another unusual shearing process involving a single a/2 〈1?0?1〉 matrix dislocation as well as the formation of the isolated superlattice stacking fault and Shockley loop also operates actively during initial yielding. Based on experimental observations, occurrence of these different shearing processes is discussed.     

{111} Glide in Ni3Al at room temperature. In situ observations under weak-beam conditions

Abstract

In situexperiments are performed in Ni₃AL at room temperature. We observe reversible changes of antiphase boundary (APB) planes between {111} and {100}, and movements in {111} planes controlled by the crossing of sessile positions with the APB plane in {111}.     

Solid-phase epitaxy of implanted silicon at liquid nitrogen and room temperature induced by electron irradiation in the electron microscope

Abstract

Electron-beam-induced solid-phase epitaxy (SPE) has been obtained on cross-sections of implanted Si layers, by in situ irradiation in the electron microscope, with electrons of energies of 200, 250 and 300 keV, at both room and liquid-nitrogen temperature. The, absence of a transition from SPE to layer-by-layer amorphization (which is observed during ion-beam irradiation on decreasing the temperature below a certain critical value) and the athemal nature of the electron-induced crystallization process below room temperature, indicate that, although elastic displacement is the basic mechanism of both processes, the models which describe ion-beam-induced epitaxy in the temperature range 200≤T≤400°C cannot be extrapolated to explain the results of electron irradiation below room temperature.     

Perception of the length of an object through dynamic touch is invariant across changes in the medium

Rotational inertia—a mechanical quantity that describes the differential resistance of an object to angular acceleration in different directions—has been shown to support perception of the properties of that object through dynamic touch (wielding). The goal of the present study was to examine if perception of the length of an object through dynamic touch depends on its rotational inertia, independent of the medium in which it is wielded. The participants (n = 14) wielded 12 different objects held in air or completely immersed in water and reported perceived lengths of those objects. Each object consisted of a rod of a particular density with a particular number of stacked steel rings attached at a particular location along its length. Perceived length was invariant across medium. In addition, a single-valued function of the major eigenvalue, I ₁, and the minor eigenvalue, I ₃, of the rotational inertia, I, of the 12 objects predicted the perceived lengths of those objects in both air and water, and the perceived lengths were invariant across the two media. These results support the hypothesis that the informational support for perception of the length of an object through dynamic touch is invariant across changes in the medium.     

Operative castration in sexual delinquency--a survey of topical literature and an attempt at forming an opinion]

An attempt is made to form an opinion regarding the indication of operative castration for sexual delinquents, from a survey of recent literature dealing with methods of treatment for cases of sexual deviation/sexual delinquency (operative/medicinal castration, combined psychotherapy and medicinal castration, stereotactic operation on the hypothalamus).     

Changes with age and with exclusion of vision in performance at an aiming task

Forty industrial workers between 20 and 60 years of age took part in the experiment. Each sat facing a display in an enclosure. His task was to locate targets with a pointer, under two conditons: when he was able to make whatever use he chose of direct vision, and wearing a pair of red goggles through which only the diplay could be seen.

On the average, those over 40 years of age took more time than younger subjects over those portions of the task which were concerned with the initiation of a fresh action. V'hen unable t o make use of vision the older had far greater difficulty in locating the targets and attempted to supplement tactile and kinesthetic cues by making postural adjustments, turning their heads and often their bodies in the direction of the target at which they were aiming. These findings are discussed in relation to an earlier observation of the greater tendency for older people to look at what they are doing.     

Origin of the initial rapid age hardening in an Al-1.7 at.% Mg-1.1 at.% Cu alloy

The origin of the rapid hardening which occurs during the initial ageing stage of an Al-1.7 at.% Mg-1.1 at.% Cu alloy has been investigated by the threedimensional atom-probe (3DAP) and transmission electron microscopy techniques. Although the rapid hardening reaction occurs within 1 min at 150 degrees C, no evidence for solute clusters or Guinier-Preston-Bagaryatsky (GPB) zones was detected using the 3DAP after this ageing time. When a short-term aged specimen is deformed and then aged at 150 degrees C, further rapid hardening occurs. This suggests that the rapid hardening is associated with a solutedislocation interaction. Uniform dispersions of Cu-Mg co-clusters do not occur until closer to the end of the hardness plateau and it is thought that these evolve into GPB zones during the second stage of the age-hardening process.     

Correlates of parental control and autonomy support in an interdependent culture: A look at Ghana

It is unclear whether, similar to research findings in Western societies, autonomy support is associated with positive child outcomes, and forceful control with negative outcomes in collectivist societies. A two-part study (N = 190 Ghanaian sixth graders) examined the relations of parental structure, control, and autonomy support in Ghana with child outcomes, and whether autonomy support was at odds with Ghanaian children’s values of interdependence and respect for elders. Results showed that structure was related to cognitive perceived competence, parental control was related to controlled regulation around school work and decreased academic engagement, and autonomy support was negatively related to depression and positively related to autonomous forms of motivation, engagement in school, and interestingly, children’s endorsement of collectivist cultural values. The importance of distinguishing between parental control and provision of structure, and the implication of the findings for understanding the role of parental autonomy support in diverse cultures, are discussed.     

Personality features and cognitive level in patients at an early stage of Alzheimer’s disease

In this cross-sectional study, we explored the relationship between premorbid personality and its changes over 5 years, and cognitive deterioration in patients with mild Alzheimer’s disease. The cognitive level of 54 patients was compared with that of 64 control subjects using the Mini Mental State (MMSE). Family members completed the NEO-PI-R (form R) twice, once to evaluate the participants’ current personality and again to assess personality traits as they were remembered to be 5 years earlier. Furthermore, the family filled in the Informant Questionnaire on Cognitive Decline (IQCODE), the Activities of Daily Living (ADL), and the Instrumental Activities of Daily Living (IADL) scales to assess their proxies’ cognitive level and daily living functioning. Regarding the relationship between personality characteristics and cognitive status, we observed trends for premorbid personality and significant links for personality changes in the clinical group. Thus, changes in neuroticism and conscientiousness were associated with cognitive deterioration, whereas decreased openness to experience and conscientiousness over time predicted loss of independence in daily functioning in the clinical group. Our study suggests that premorbid features can be considered as latent traits linked to the neuropathology underlying the disease process, while personality changes are probably the consequences of the pathological process.     

The role of the body as the medium in child psychotherapy: snapshots of therapy with an 11-year-old,severely abused,multiply placed girl

In Victoria, Australia, children with a history of abuse and severe attachment difficulties, and who have experienced multiple carers and placements, have been traditionally viewed by mental health services as unsuitable for psychoanalytic psychotherapy. A number of factors, including the lack of integrated, long-term case planning; unstable residential placement; and the belief that psychotherapeutic treatment will be of an extended duration, have influenced the decision not to provide individual psychotherapy for these children. Currently, the movement within mental health services is towards responsive and briefer treatment models. The child psychotherapist is challenged to re-think theory, technique and practice. This paper identifies contextual constraints that have led to these children being precluded from accessing psychotherapy. An alternative model of intervention is discussed and illustrated with clinical material. The contributions of Alvarez, Trevarthen, Schore and other writers are drawn on to underpin the clinical work. This model involves a change in technique and role and the use of a time-limited intervention. Intrinsic to the model is the understanding of the child's psycho-biological experience of trauma and disrupted attachment. The child's experiences are conveyed in the pre-verbal, gestural domain to enable history to be given voice.     

Perception of affective prosody in patients at an early stage of relapsing–remitting multiple sclerosis

Cognitive dysfunction is well known in patients suffering from multiple sclerosis (MS) and has been described for many years. Cognitive impairment, memory, and attention deficits seem to be features of advanced MS stages, whereas depression and emotional instability already occur in early stages of the disease. However, little is known about processing of affective prosody in patients in early stages of relapsing–remitting MS (RRMS). In this study, tests assessing attention, memory, and processing of affective prosody were administered to 25 adult patients with a diagnosis of RRMS at an early stage and to 25 healthy controls (HC). Early stages of the disease were defined as being diagnosed with RRMS in the last 2 years and having an Expanded Disability Status Scale (EDSS) of 2 or lower. Patients and HC were comparable in intelligence quotient (IQ), educational level, age, handedness, and gender. Patients with early stages of RRMS performed below the control group with respect to the subtests ‘discrimination of affective prosody’ and ‘matching of affective prosody to facial expression’ for the emotion ‘angry’ of the ‘Tübingen Affect Battery’. These deficits were not related to executive performance. Our findings suggest that emotional prosody comprehension is deficient in young patients with early stages of RRMS. Deficits in discriminating affective prosody early in the disease may make misunderstandings and poor communication more likely. This might negatively influence interpersonal relationships and quality of life in patients with RRMS.