Structural effects on diffusion in metallic glasses: The pressure dependence of Ni diffusion in as-quenched and relaxed Co42Zr58

In order to clarify the role of thermal defects in diffusion in metallic glasses, we have measured the temperature and pressure dependences of diffusion of Ni, a probe for Co, in relaxed and non-relaxed amorphous Co₄₂Zr₅₈ alloys by means of the tracer technique in combination with secondary-ion mass spectroscopy. For the relaxed state, the activation energy and the pre-factor are Q _{= (}1:65=0:08₎ eV and D _{0 =} 2:4+3:9 10-6m2 s-1 respectively. The pressure - 1:9 dependence yields an activation volume V _{act = (}0:66 0:15₎Omega, with Omega being the average atomic volume of the alloy. This value is similar to activation volumes in crystalline materials and is indicative of diffusion via thermally generated defects. Unlike monovacancies in crystals, these defects appear to be spread out, judging from recent isotope-effect measurements. Comparison with literature data shows that the activation volume and hence the diffusion mechanism in metallic glasses clearly depend on the structure and composition even for the very same component. The activation volume in the as-quenched state was found to be _{( )} ^{0:93 0:25 Omega.}     

Daily relations between social perceptions and physical activity among college women

ObjectivesThere is a need to develop more effective physical activity (PA) promotion programs for college women. Theory and evidence suggest that perceptions of the social environment play a role in college women’s PA, though little is known about how these perceptions are associated with PA at the day level. The goal of this study was to examine relations between changes in college women’s daily social perceptions and objectively assessed PA over seven days.DesignDaily diary method.MethodCollege women (n = 80, M_Age = 20, M_BMI = 23.1 kg/m²) wore Fitbit wristbands and completed daily self-reports of (1) the quantity and perceived intensity of their social interactions (positive/negative), and (2) the occurrence of social comparisons (based on appearance/health/status) for seven days.ResultsMultilevel models showed daily variability in predictors and outcomes (ps < 0.0001), as well as relations between within-person changes in social perceptions and PA. Increases in negative interactions (particularly those with friends) were consistently associated with decreases in daily PA, whereas increases in positive interactions showed limited relations (srs = −0.22-0.34). Days with health comparisons were days with greater PA for women who had stronger overall interest in comparisons, but were days with less PA for women with weaker overall interest (srs = 0.22–0.33). PA did not differ between days with vs. without appearance comparisons.ConclusionsSocial perceptions show meaningful day-to-day variability and relations with college women’s daily PA, and specific associations may be useful for improving tailored interventions for college women.     

Nucleation of He bubbles in amorphous FeBSi alloy irradiated with He ions

It is interesting to investigate the formation of He bubbles in amorphous alloys because point defects do not exist in amorphous materials. In the present study, the microstructural evolution of amorphous Fe₇₉B₁₆Si₅ alloy, either irradiated with 5?keV He⁺ ions or implanted with 150?eV He⁺ ions without causing displacement damage, and then annealed at a high temperature, was investigated using transmission electron microscopy (TEM). Vacancy-type defects were formed in the amorphous alloy after irradiation with 5?keV He⁺ ions, and He bubbles formed during annealing the irradiated samples at high temperature. On the other hand, for samples implanted with 150?eV He⁺ ions, although He atoms are also trapped in the free volume, no He bubbles were observed during annealing the samples even up to 873?K. In conclusion, the formation of He bubbles is related to the formation and migration of vacancy-type defects even in amorphous alloys.     

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.     

Identification of planar defects in D019 phases using high-resolution transmission electron microscopy

An analysis based on crystal symmetry and high-resolution transmission electron microscopy (HRTEM) is presented as a general methodology to identify planar defects on the basal planes of D0₁₉ compounds. As a starting point, the possible (close-packing preserving) planar defects are classified in accordance with their visibility, and the magnitude of the displacement vector on prismatic projections. Analysis of experimental HRTEM images, obtained under two different viewing conditions, followed by matching with simulated images, enables unambiguous identification to be made. The methodology is applied to planar defects observed in D0₁₉ Co₃     

The roles of exercise tolerance and resilience in the effect of physical activity on emotional states among college students

Background/objectiveNegative emotional states, such as depression, anxiety, and stress challenge health care due to their long-term consequences for mental disorders. Accumulating evidence indicates that regular physical activity (PA) can positively influence negative emotional states. Among possible candidates, resilience and exercise tolerance in particular have the potential to partly explain the positive effects of PA on negative emotional states. Thus, the aim of this study was to investigate the association between PA and negative emotional states, and further determine the mediating effects of exercise tolerance and resilience in such a relationship.MethodIn total, 1117 Chinese college students (50.4% female, M_age=18.90, SD=1.25) completed a psychosocial battery, including the 21-item Depression Anxiety Stress Scale (DASS-21), the Connor-Davidson Resilience Scale (CD-RISC), the Preference for and Tolerance of the Intensity of Exercise Questionnaire (PRETIE-Q), and the International Physical Activity Questionnaire short form (IPAQ-SF). Regression analysis was used to identify the serial multiple mediation, controlling for gender, age and BMI.ResultsPA, exercise intensity-tolerance, and resilience were significantly negatively correlated with negative emotional states (Ps<.05). Further, exercise tolerance and resilience partially mediated the relationship between PA and negative emotional states.ConclusionsResilience and exercise intensity-tolerance can be achieved through regularly engaging in PA, and these newly observed variables play critical roles in prevention of mental illnesses, especially college students who face various challenges. Recommended amount of PA should be incorporated into curriculum or sport clubs within a campus environment.     

Indice d’aptitude général et indice de compétence cognitive pour le WISC-IV : normes empiriques versus normes statistiques

IntroductionThe General Ability Index (GAI) was developed within the WISC-III to measure general cognitive ability. The GAI can be used as a substitute for the FSIQ. Recently, the Cognitive Proficiency Index (CPI) was developed. The GAI and CPI tables for the French WISC-IV were recently created using statistical approximation. However, it has been suggested that tables created with statistical approximation were less proficient than tables created using samples.ObjectiveThe objective of this study was to compare GAI and CPI normative tables of the French WISC-IV which use a statistical approximation procedure, to tables based on a sample.MethodTo explore the validity of the GAI and ICC scores, we studied 182 children aged from 8 to 12-years-old.ResultsCorrelations between both types of tables were 0,997 for GAI and 0,999 for CPI, and the absolute mean difference was 5.38 points and 2.24, respectively. For the children presenting a GAI_S lower than 89, GAI_E suggested that it is likely that their scores are lower about 8-10 points than that indicated by GAI_S.ConclusionResults of this study support the use of GAI and CPI to provide different views of children's cognitive abilities.     

Retention and thermal desorption of helium in amorphous and crystalline FeBSi alloys

Helium retention in metals is related to their atomic structure and the type of defects they contain. In order to investigate the dependence of helium retention on structure, amorphous Fe₇₉B₁₆Si₅ and crystalline FeBSi alloys were irradiated by helium ions at room temperature. In the crystalline alloy irradiated with 5 keV He⁺ ions, three types of helium trapping sites were found: surface defects produced by the irradiation, interstitial-type dislocation loops, and voids. Although these defects did not exist in the amorphous FeBSi alloy, we did observe thermal desorption peaks related to all three types. In addition, helium was released during the crystallization of amorphous FeBSi that had been irradiated by He⁺ ions.     

Morphological study of micropits formed by anodic etching of an Al-Pd-Mn icosahedral quasicrystal

Faceted micropits obtained by electrochemical etching of a single quasicrystal of an Al-Pd-Mn icosahedral phase have been examined by optical and electron microscopy. Anodic etching of the flat surface of a fivefold plane in a solution composed of CH₃OH and HNO₃(3:1 in volume ratio) reveals a variety of icosahedrally faceted micropits which originated from pre-existing microvoids and etch pits of pentagonal pyramid shape due to the other origins, probably structural defects inside the specimen. As the dissolution progresses, the micropits make successive changes in their shapes, ending in pentagonal pyramids before they vanish.     

Ab initio investigation of electron-phonon interaction in LaSn3 and CaSn3

ABSTRACT

We present results for the structural, electronic, vibrational, and electron-phonon coupling properties of LaSn₃ and CaSn₃ adopting the simple cubic AuCu₃-type structure obtained using the the generalised gradient approximation of the density functional theory and plane wave ab initio pseudopotential method. Our electronic results show that both materials display metallic character with several bands, which have mainly Sn 5p character, crossing the Fermi level. The calculated phonon spectrum of LaSn₃ accords very well with reported experimental measurements. The weights of the peaks in the Eliashberg spectral function of both compounds are enhanced with the use of experimental lattice constant in our electron-phonon calculation, increasing the value of average electron phonon coupling parameter from 0.876 to 0.937 for LaSn₃ (by 7%) and from 0.642 to 0.725 for CaSn₃ (by 13%). The use of experimental lattice constant also improves the agreement between theoretical and experimental values of the superconducting temperature for both compounds.     

Sol-gel-hydrothermal growth of oxide thin films at low temperatures

Lead zirconate titanate (PZT) (Pb(Zr_0.52Ti_0.48)O₃) and barium titanate (BaTiO₃) thin films have been successfully prepared using a novel sol-gel- hydrothermal (SG-HT) technique at low temperatures, which involves a combination of the conventional sol-gel process and a hydrothermal method. Highly (111)-oriented PZT thin films with a single perovskite phase and polycrystalline BaTiO thin films with well developed crystallites were obtained at a processing temperature as low as 160⁰C. The microstructural characteristics demonstrate that the SG-HT-derived PZT and BaTiO₃ thin films with good crystallinity and surface morphology are converted from the amorphous phase to the desired perovskite phase on platinum-coated and bare silicon substrates at a low processing temperature of 100-200 C. These results suggest that the SGHT technique, which is of great significance because of its low processing temperature, will become a potential and promising process for fabricating PZT, BaTiO₃ and other oxide thin films.     

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.     

Self-ratings of positive and negative affect and retrieval of positive and negative affect memories

Abstract

Based on analysis of self-ratings of mood, positive affect (PA) and negative affect (NA) have been proposed as basic, orthogonal mood dimensions (Watson & Tellegen, 1985). The present study asked subjects (N = 61) to not only provide self-ratings of PA and NA terms but also to retrieve personal memories associated with those terms. Self-rated PA was associated with latency to retrieve PA- but not NA-related memories; self-rated NA was associated with latency to retrieve NA- but not PA-related memories. Self-ratings of PA and NA were not significantly correlated, nor were retrieval latencies for PA and NA memories. Individual item correlations also revealed a strong direct relationship between self-ratings and retrieval latency. The dissociations involving a non-self report measure strengthen the distinction between PA and NA, and the individual item correlations are interpreted as showing that self-ratings of affect are based upon the ease of retrieval of personal memories.     

Determinants of mechanical efficiency trajectories from childhood to adolescence: Findings from the QUALITY cohort

PurposeTo estimate the shape and number of mechanical efficiency (ME) trajectories from childhood to adolescence; and verify whether ME trajectory membership can be predicted by sex, biological maturation, body weight, body composition and physical activity (PA) in childhood.MethodsData from QUALITY, an ongoing cohort study on the natural history of obesity, were used. Participants attended a baseline visit (8–10 years, n = 630) and follow-up visits two years (n = 564), and seven years (n = 377) later. ME was assessed by an incremental cycling test at 50w (ME_50w, %) and at VO_2peak (ME_VO2peak, %). Group-based trajectory analysis for ME and a logistic regression were performed.ResultsMean age of the 454 participants (boys = 54%) was 9.7 ± 0.9 years at baseline. Two distinct ME_50w trajectories were identified and all tended to decrease. No distinct trajectories emerged for ME_VO2peak; average ME_VO2peak increased over time. Thus, the difference between ME_VO2peak (∆) at baseline and follow-up was calculated for correlation analysis. Trajectory groups were labeled “Low-Decreaser” and “High-Decreaser” (Reference) for ME_50w, describing the starting point and slope. High-Decreasers were mostly prepubertal girls, had lower body weight and fat free mass index, lower PA and lower VO_2peak at baseline (χ²or t-test, p < 0.05). Girls were less likely to be Low-Decreasers (OR = 0.56, 95%CI = 0.42–0.74), while having overweight/obesity predicted a greater likelihood of classification in the Low-Decreaser trajectory (OR = 2.38, 95%CI = 1.16–4.88). Those with higher PA were more likely to be Low-Decreasers (OR = 1.02, 95%CI = 1.01–1.04). Finally, concerning ME_VO2peak, sex, biological maturation, body weight, zBMI, fat free mass index, PA and VO_2peak were positively correlated with ∆ ME_VO2peak.ConclusionsWe found evidence that excess weight at baseline predicts low levels of ME in childhood and adolescence. Additionally, higher PA at baseline is not related to higher ME_50w levels. More research is needed to identify different approaches to explore this measure in transition to adulthood.     

Thermomagnetic study of devitrification in Fe-Si-B-Cu-Nb(-X) alloys

Thermomagnetic measurements have been used to study the magnetic and structural changes occurring at the two steps of the crystallization process of Fe_73.5Si_13.5B₉Cu₁Nb₁X₂ (X = Zr, Nb, Mo and V) alloys. Alloying raises the thermal stability of the amorphous phase against nanocrystallization in the order V < Mo < Nb < Zr and some differences in the final crystalline phases are found. The Curie temperature of the amorphous phase increases (about 15K) during structural relaxation. In the course of nanocrystallization a further increase of about 30K in the Curie temperature of the amorphous intergranular is observed for samples with X = Zr, Nb and Mo, but only of about 15K for samples containing V. The observed increase in the Curie temperature of the Fe-Si phase between the end of the first crystallization process and the end of the second crystallization process is associated with a reduction in the Si content, in agreement with X-ray diffraction results.     

Thermomagnetic gravimetric study of the crystallization process in amorphous Fe-Si-B-Cu alloys

The thermal properties of amorphous Fe_84-xSi₆B₁₀Cu_x and Fe_77.5-xSi_13.5B₉Cu_x alloys have been investigated using thermomagnetic gravimetry (TMG). After electronically cancelling the sample weight, an apparent weight (AW) was applied by placing a magnet beneath the sample pan. Heating was then carried out to detect the formation of ferromagnetic crystallization-induced phases. In both Cu-free Fe₈₄Si₆B₁₀ and Fe_77:7Si_13:5B₉ alloys, a two-stage increase in AW was observed on the TMG curve. The addition of Cu to these alloys caused a decrease in the crystallization temperatures as well as a marked increase in AW in the above two-stage process. It is presumed that such behaviour originates from the lack of metalloid elements in the amorphous matrix, which is caused by their distribution to Cu-enriched clusters.     

Qualitative elicitation of affective beliefs related to physical activity

ObjectivesBased on previous research that has identified affective attitude as a distinct predictor of physical activity (PA) behavior, the purpose of this pilot study was to elicit affective beliefs toward physical activity using qualitative data generated through specific open-ended questions.MethodsA sample of 126 undergraduate students participated in this study. Four open-ended questions based on the theory of planned behavior were posed to elicit affective beliefs. A content analysis was used to categorize and code data by theme based on common responses that emerged in the elicitation. A frequency count of the responses falling into each category was then conducted to establish which affective beliefs were the most common. The themes were established by two researchers and reviewed for internal homogeneity and external heterogeneity by a third party.ResultsThe results highlight key beliefs related to affective attitude. In descending rank order; Social Involvement, Pleasant Body States, Esteem, Improved Psychological Outcome, and General Enjoyment were the most common affective beliefs for PA involvement. Feelings arising from Time Issues/Conflict, Physical Unpleasantness, PA Environment, and Necessity/Obligation were the most common negative affective beliefs.ConclusionsThe results suggest that promoting enjoyment rather than necessity of PA and encouraging variety in PA may be effective. Addressing the importance of aesthetically pleasing environments and highlighting social interaction as a strategy rather than merely a norm or a form of support in behavioral research may be important.     

Formation of ductile Al-based metallic glasses without rare-earth elements

Al₇₅Cu₁₇Mg₈ is a eutectic composition according to the ternary phase diagram, which can be quenched into a fully amorphous phase by adding 2-8at.% Ni, but the addition of a similar percentage of Gd failed to form the amorphous phase. The amorphous alloys obtained exhibit two broad diffuse peaks in the X-ray diffraction curves and, correspondingly, two halo rings in the electron diffraction patterns, implying that two types of local atom configuration exist. Thermal analysis of the amorphous alloys indicates that the primary crystallization peak shifts to higher temperatures with increasing Ni content. The occurrence of a nucleation and crystal growth peak during isothermal crystallization reveals the amorphous nature of the quenched ribbon alloys. The quenched amorphous ribbons do not break after bending by 180°. Mechanical testing yielded a tensile strength of 810MPa for (Al₇₅Cu₁₇Mg₈)₉₅Ni₅, and a vein structure, characteristic of amorphous fracture, is apparent in scanning electron micrographs. The different effects of Ni and Gd on the glass formation indicate that the large atomic size of Gd is not critical to the glass formation.     

A 15-year longitudinal test of the theory of planned behaviour to predict physical activity in a randomized national sample of Canadian adults

BackgroundThere have been very limited long-term prospective studies examining social-cognitive models in the PA domain with large, representative population samples.ObjectiveThe primary objective was to examine the Theory of Planned Behaviour's (TPB) ability to explain PA behaviour in a randomly selected national sample of Canadian adults over a 15-year period. A secondary objective was to test the moderating effects of gender on TPB.DesignThe study employed a longitudinal design.MethodsA cohort of 1427 randomly-selected adults reported TPB constructs and PA behaviour in 1988, and again in 2003. Structural equation modelling techniques were employed to test TPB.ResultsThe full model including both 1988 and 2003 TPB measures accounted for 29% and 21% of the variance in intention, and 9% and 22% of the variance in PA in 1988 and 2003, respectively. Gender moderated aspects of the TPB in the full model. The core predictive model (1988 TPB constructs predicting 2003 PA behaviour) explained 13% of the variance in 2003 PA behaviour.ConclusionsThe TPB's long-term ability to predict PA behaviour is modest.     

A pilot study exploring the use of a telephone-assisted planning intervention to promote parental support for physical activity among children and youth with disabilities

Parent support is an important contributor to physical activity (PA) among children and youth with disabilities (CYD). Although many parents of CYD are motivated to provide parent PA support, CYD remain insufficiently active. The multi-process action control model has been applied to understand parent PA support and highlights behavioral regulation strategies such as action and coping planning as critical for translating intentions into behavior. Parents may struggle to create and carryout planning without support. There is no known research examining telephone support as a tool to promote planning and subsequent parent PA support behavior.MethodParents (43 mothers and 6 fathers) of CYD (child M_age = 12.53 years ± 5.53; 75% male; 38.6% developmental disability) completed a baseline questionnaire and were subsequently randomized to a telephone-assisted planning experimental group twice over four weeks (n = 23) or a control group who had access to planning tools but no telephone assistance (n = 26).ResultsNo significant main or interaction effects emerged for parent PA support behavior. However, a significant time × condition interaction was found for behavioral regulation strategies (i.e., action and coping planning and self-monitoring; F(1,44) = 5.05, p = 0.03) indicating a significant increase in the use of behavioral regulation strategies for parent PA support from baseline, for parents assigned to the telephone-assisted intervention.ConclusionThese findings suggest potential for planning support as a tool to enhance behavioral regulation strategies related to parent PA support among parents of CYD.