Chemistry (intrinsic) and inclusion (extrinsic) effects on the toughness and Weibull modulus of Fe-based bulk metallic glasses

Systematic changes in composition were employed to increase the notch toughness of a variety of Fe-based Bulk Metallic Glasses (BMGs). The Fe₅₀Mn₁₀Mo₁₄Cr₄C₁₆B₆ BMG possessed very high hardness (e.g. 12 GPa) but very low notch toughness (e.g. 5.7 MPa m^1/2) at room temperature, consistent with fracture surface observations of brittle features. Many of the other Fe-BMG variants, created to change the Poisson's ratio via systematic changes in alloy chemistry, exhibited higher toughness but more scatter in the data, reflected in a lower Weibull modulus. SEM examination revealed fracture initiation always occurred at inclusions in samples exhibiting lower toughness and/or Weibull modulus for a given chemistry. Implications of these observations on reliability of BMGs are discussed.     

Comparison of quasicrystalline (T2) and crystalline (R) structures in AlCuLi using high-resolution X-ray diffraction

Abstract

A high-resolution X-ray scattering experiment has been performed on quasicrystalline (T2) and crystalline (R) phases of AlCuLi alloys. Peak widths determined from the diffraction profile of the R phase are found to scale with momentum transfer G, similar to the strain-broadening effect seen in conventional crystals with small unit cells. A narrowing of peak widths on annealing is also observed. On the other hand, diffraction peak widths in I-phase samples obtained by rapid solidification are found to scale with phason momentum G ₁, similar to that observed in large faceted crystals. Thermal annealing of the I phase is found to have no effect on peak widths. Our findings are discussed in the light of models for crystals and quasicrystals.     

A three-stage estimation procedure for structural equation models with polytomous variables

This paper is concerned with the analysis of structural equation models with polytomous variables. A computationally efficient three-stage estimator of the thresholds and the covariance structure parameters, based on partition maximum likelihood and generalized least squares estimation, is proposed. An example is presented to illustrate the method.This research was supported in part by a research grant DA01070 from the U.S. Public Health Service. The production assistance of Julie Speckart is gratefully acknowledged.     

Influence analysis of ranking data

This paper develops diagnostic measures to identify those observations in Thurstonian models for ranking data which unduly influence parameter estimates that are obtained by the partition maximum likelihood approach of Chan and Bentler (1998). Diagnostic measures are constructed by employing the local influence approach that uses geometric techniques to assess the effect of small perturbations on a postulated statistical model. Very little additional effort is required to compute the proposed diagnostic measures, because all of the necessary building blocks are readily available after a usual fit of the model. The work described in this paper was partially supported by the grants from the Research Grants Council of the Hong Kong Special Administrative Region, China (RGC Ref. No. CUHK4186/98P and RGC Direct Grant ID2060178). The authors are grateful to the Editor and four anonymous referees for their helpful comments.     

Thomas: The Apostle of Scientists

Richard Dawkins suggests that the way “doubting Thomas” demanded evidence for Jesus’ resurrection should endear him to scientists. A close reading of Chapter 20 of John’s Gospel suggests that Thomas’ confession of Jesus’ divinity does indeed resonate with how scientists make progress, but not because he demanded evidence. Rather, the similarity lies in the way he went beyond the immediate evidence to reach a bold conclusion, the implications of which took a lifetime to work out. A comparison with the way J. J. Thomson discovered the first sub-atomic particle, the electron, shows that this is also how breakthroughs in science happen.     

Person theories: their temporal stability and relation to intertrait inferences

This article tests whether individual differences in inferring one trait from another (intertrait inferences) can be linked to lay beliefs about the malleability of personality (person theories). It finds that holding the belief that personality is malleable (incremental theory) rather than fixed (entity theory) at the time of inferences is associated with less extreme inferences involving semantically related (but not unrelated) traits. Although person theories have been assumed to be stable over time, existing short-term test-retest coefficients do not capture their instability over a longer period. These results can illuminate interrater discrepancies in assessments of personality pathology and job performance, enrich understanding of such phenomena as stereotyping and impression formation, refine the interpretation of past research involving person theories, and inform research planning.     

Contextual Adult Life Span Theory for Adapting Psychotherapy with Older Adults

Our aging population is growing in size and diversity. To integrate different views on aging and make explicit the role of culture as a contextual factor, we modified Knight’s (Psychotherapy with older adults, 2004) Contextual, Cohort-based, Maturity, Specific Challenge (CCMSC) model of psychotherapy with older adults into the Contextual Adult Lifespan Theory for Adapting Psychotherapy (CALTAP). This article describes various components of the CALTAP, which serves as a meta-theoretical framework in guiding an integrated psychotherapy approach for the aging population. The interaction between environmental factors like cohort differences and socio-cultural contexts and individual factors such as maturation and age-related specific challenges not only shapes the experience and presentation of older adults in clinical settings, but also highlights special considerations in adapting psychotherapy for older adults.