Disclinations and rotational deformation in fine-grained materials

A theoretical model is presented which describes a new mechanism of plastic deformation in fine-grained materials. In the framework of the model, rotational deformation occurs via motion of dipoles of grain-boundary disclinations and is associated with the emission of lattice dislocations from grain boundaries into adjacent grain interiors. Ranges of defect system parameters are identified in which the disclination motion is energetically favourable. It is shown that the mechanism can contribute to plastic flow in fine-grained materials prepared by highly non-equilibrium methods such as ball milling, severe deformation and high-pressure compaction.     

Nucleation of recrystallization in fine-grained materials: an extension of the Bailey–Hirsch criterion

Abstract

A new criterion for nucleation in the case of dynamic recrystallization is proposed in order to include the contribution of the grain boundary energy stored in the microstructure in the energy balance. Due to the nucleation events, the total surface area of pre-existing grain boundaries decreases, leading to a nucleus size smaller than expected by conventional nucleation criteria. The new model provides a better prediction of the nucleus size during recrystallization of pure copper compared with the conventional nucleation criterion.     

Clinical Issues with Gay Male Couples

SUMMARY

Although gay male couples share with all couples three essential tasks of couplehood-creating boundaries in order to form a couple identity, negotiating closeness and distance, and accommodating to their individual differences-gay male couples face special complications in each task. These complications, examined herein, are largely the result of the marginalization gay men experience from living in a homophobic culture, and male gender acculturation that makes male-to-male intimacy difficult. A model of brief couple therapy for gay men is presented that is designed to honor, as well as challenge, the relationship the men have co-constructed and specifically addresses the difficulties men have in maintaining intimate bonds. A case study illustrates the treatment of clinical issues presented by male couples.     

Epitaxial Ni-Al thin films on NaCl using a Ag buffer layer

Epitaxial nanoscale [001] films of Ni _x Al_100-x (x = 62.5) have been prepared by physical vapour deposition on to a thin film of Ag [001] on NaCl (001) faces with occasional hillocks. The Ag film contains numerous dislocations and stacking faults and has a rms surface roughness of 2 nm. The Ni-Al film is ordered in the B2 structure and reveals many dislocations as well as antiphase boundaries between ordered domains. The formation of subgrains in the Ni-Al film results in severe height variations up to 30 nm across the surface. A cross-sectional model for the growth of both films is presented.     

Fracture mechanisms of symmetrical tilt grain boundaries

The mechanisms of failure of symmetrical tilt boundaries have been investigated using an atomistic technique. The fracture process advances in steps that are related to the structural unit of the symmetrical tilt grain boundary. These boundaries are shown to fail through a combined mechanism involving dislocation emission in certain regions of the structural unit, followed by microcleavage, and again dislocation emission. The overall toughness of the boundaries is given by the combination of the toughness of these two processes.     

The order–dsorder transition at twin boundaries in Cu3Au as studied by TEM

Abstract

The order-disorder phase transition at ∑ = 3{111}- and {211}-type twin boundaries has been studied in the L1²-ordered alloy Cu³Au employing in situ heating in a transmission electron microscope. Evidence is presented for an order-disorder phase transition occurring in these boundaries prior to the bulk transition. The temperature difference ΔT between the transition temperature of both boundary types and the bulk is estimated as 0.5K <ΔT<2K. No difference in T _c for the twin boundaries can be established as yet. The nature of the order-disorder transition in both twin boundaries is presumably a second-order phase transition.     

Ethics,Identity and the Boundaries of the Person

Abstract

Ethical theories and theories of the person constrain each other, in that a proposition about the person may be a reason for or against an ethical proposition, and conversely. An important class of such propositions about the person concern the boundaries of the person. These boundaries enclose a person's defining properties, which constitute his identity. A person's identity may partly determine and partly be determined by his ethical judgments. An equilibrium between one's identity and one's ethical judgments is the counterpart, at the personal level, of the philosophical ideal of reflective equilibrium between a theory of the person and an ethical theory.     

Discontinuous precipitation initiated at interphase boundaries in a Zn-rich Zn-6.3 at.% Ag alloy

Discontinuous precipitation in a two-phase Zn-rich Zn-6.3at.%Ag alloy has been studied. It has been shown that the eta/epsilon interphase boundaries have the ability to initiate discontinuous precipitation as do the eta/eta grain boundaries. The back-polishing method is used to show the interconnection between a discontinuous precipitate colony and the eta/epsilon interphase boundary. The reaction front velocity of discontinuous precipitation initiated at the eta/eta grain boundary is 12-90% higher than that of discontinuous precipitation initiated at the eta/epsilon interphase boundary under various ageing temperatures.     

Approximant phases,phason planes and domain-boundary networks in Al−Ni−Rh alloys

Structurally complicated ξ′- and ξ-phases have been found, for the first time, in as-cast Al₇₃Ni₅Rh₂₂ and Al₇₅Ni₁₅Rh₁₀ alloys. The lattice parameters of these two phases were determined by means of electron diffraction and high-resolution transmission electron microscopy (HREM). These two phases have similar orthorhombic structures but with different lattice parameters of a?=?23.2?Å, b?=?16.4?Å, c?=?12.0?Å for the ξ′-phase and a?=?20.3?Å, b?=?16.4?Å, c?=?14.8?Å for the ξ-phase. A new two-dimensional domain-boundary network has also been observed in these two phases. Domain boundaries with normals closely parallel to the [001] direction are actually phason planes represented by a translation vector of r?=(1/2)a?+(1/2τ)c in the ξ′-phase and r=±(1/2τ²) a?+(τ/2)c in the ξ-phase, whereas the newly-found wide and zigzag boundaries perpendicular to the above set were attributed from the step-like boundary structures of domains related by a translation vector of r?=(1/τ)((1/2)a?+(1/2τ)c). The structural difference between the two types of planar faults is discussed.     

A Safe Space for Healing: Boundaries,Power and Vulnerability in Pastoral Care

Abstract

This article is a theological reflection on issues of power and vulnerability in relation to pastoral boundaries. It starts with a reflection on my experience in training ordinands and pastoral carers, and an awareness that mandatory training in safeguarding often seems to focus on regulations and procedures, rather than power dynamics and self-awareness. The article goes on to summarize recent literature relating to pastoral boundaries, before exploring the underlying concepts of power and vulnerability, using theologians such as Moltmann and Bonhoeffer on the vulnerability of God, and the feminist writings of Carter Heyward and Mary Grey on mutuality. It concludes by arguing that boundaries provide a safe space for the delicate balancing of vulnerability, risk and power in the pastoral relationship.     

Electron microscopy of grain boundaries: An application to RE-Fe-B (RE = Pr or Nd) magnetic materials

Abstract

To study the grain boundaries of the technologically important RE_13.75Fe_80.25B₆ (RE = Pr or Nd) permanent magnets, we developed a new method using small-angle dark-field imaging based on inner-potential differences at the grain boundaries, combined with high-resolution electron microscopy and nanoscale chemical analysis. In both the Pr- and Nd-based melt-quenched die-upset magnets we consistently observed a very thin Fe-rich amorphized intergranular phase at the boundaries, and this finding may have an impact on our understanding of the coercivity mechanism of these materials. Although the value of the method was demonstrated for transition metal-rare earth intermetallics, it may also be applied to grain-boundary studies in other materials.     

Texture and grain boundary character distribution (GBCD) in rapidly solidified and annealed Fe–6·5 mass% Si ribbons

Abstract

The type and frequency of grain boundaries, the so-called grain boundary character distribution (GBCD), has been determined in rapidly solidified and subsequently annealed Fe-6·5 mass% Si alloy ribbon by the scanning electron microscopy-electron channelling pattern (SEM-ECP) technique. High frequencies of low-angle boundaries and coincidence boundaries with Σ3, Σ9, Σ11, Σ17 and Σ19 were observed in a fully annealed ribbon with well defined {110} texture. The total frequency of low-angle boundaries and coincidence boundaries is almost one-half of all grain boundaries. The coincidence boundaries which occurred more frequently are exactly those predicted theoretically from the coincidence orientations for 〈110〉 rotation in cubic crystals, similar to those observed previously in {100} textured ribbons of the same alloy produced by the same processing method. The presence of a close relationship between the type of texture and GBCD has been confirmed by experiment on differently textured ribbons of the same material.     

Defect formation in Nd2Fe14B grains caused by Zn diffusion

Defect formation in Nd₂Fe₁₄B grains, caused by a low-pressure-pack-sublimation Zn coating process, has been investigated. The results indicate that, in the Zn-affected region, low-angle boundaries decorated with precipitates form within the Nd2Fe14B grains. Zn, which is almost insoluble in Nd₂Fe₁₄     

Guest Editorial: Conceptualizing Justice and Counter-Expertise

ABSTRACT

Systemic injustices exclude counter-experts from telling their stories and influencing the collective imagination. Four papers and some discussant essays illustrate the ways in which counter-experts cross boundaries to contest knowledge claims, legal institutions, and forms of data in order to resist various forms of injustice. Literature on counter-expertise, socio-technical imaginaries, and epistemic injustice highlights how marginalized groups are prevented from participating in the process of collective imagining. A definition of counter-expertise and a new typology of counter-expertise demonstrate how marginalized groups navigate boundaries to pursue epistemic justice. The four papers in the special issue exemplify the ways in which counter-experts navigate identity politics. To combat epistemic injustice within our field, STS scholars can be more inclusive with teaching, mentoring, reviewing and other forms of scholarly gatekeeping.     

Gestalt approach to family therapy

Abstract

Gestalt psychotherapy is presented as a synthesis of a number of psychological traditions. Two particular techniques are described in detail: the empty chair technique which is a strategy that focuses on the parents' internalized object relations which are played out between themselves and with their children; and the Gestalt experiment which is a strategy that focuses on the contact boundaries between family members.     

Verbal cues flexibly transform spatial representations in human memory

ABSTRACT

Humans possess a unique ability to communicate spatially-relevant information, yet the intersection between language and navigation remains largely unexplored. One possibility is that verbal cues accentuate heuristics useful for coding spatial layouts, yet this idea remains largely untested. We test the idea that verbal cues flexibly accentuate the coding of heuristics to remember spatial layouts via spatial boundaries or landmarks. The alternative hypothesis instead conceives of encoding during navigation as a step-wise process involving binding lower-level features, and thus subsequently formed spatial representations should not be modified by verbal cues. Across three experiments, we found that verbal cues significantly affected pointing error patterns at axes that were aligned with the verbally cued heuristic, suggesting that verbal cues influenced the heuristics employed to remember object positions. Further analyses suggested evidence for a hybrid model, in which boundaries were encoded more obligatorily than landmarks, but both were accessed flexibly with verbal instruction. These findings could not be accounted for by a tendency to spend more time facing the instructed component during navigation, ruling out an attentional-encoding mechanism. Our findings argue that verbal cues influence the heuristics employed to code environments, suggesting a mechanism for how humans use language to communicate navigationally-relevant information.     

Stacking-fault formation in [001] small-angle symmetric tilt grain boundaries in cubic zirconia bicrystals

Small-angle symmetric [001] tilt grain boundaries in cubic zirconia bicrystals with misorientation angles 2θ =1.0° and 2θ =5.0° have been fabricated by diffusion bonding. High-resolution electron microscopy observations revealed that the 1.0° boundary consists of a periodic array of mixed dislocations with Burgers vector b =( a /2)[101] or b = ( a /2)[101], while the 5.0° boundary consists of a periodic array of edge dislocations with Burgers vector b = ( a /2)[100], associated with stacking faults at alternate intervals. This suggests that there is a critical angle for structural transitions in the series of the [001] small-angle tilt grain boundaries.     

The ‘frame’ as a container for the erotic transference – A case study

Abstract

This paper discusses various aspects of the psychotherapeutic frame, and explores the importance of maintaining the boundaries of the frame especially when an erotic transferential relationship is present. Many now agree that erotic transference and counter-transference occur in most therapeutic relationships, and yet it is something that therapists often struggle to work with effectively. The author acknowledges her own difficulties in working with erotic transferences and demonstrates why the adherence to the frame is especially significant in these circumstances. A case study is used to illustrate the difficulties of working with the erotic transference within the constructs of a frame and short-term therapy, and how the author's own counter-transference affected the therapy as well as how this was dealt with in supervision.     

Toward a New Covenant: Embracing a Dialogue and Decision Culture to Address the Challenges of the Agoras of the 21st Century

Twenty-first century agoras, unlike their historical counterparts, are not comprised of villages populated by individuals who know each other and share the same past, environment, and culture. Contemporary agoras are diverse and global. Their dialogue is often conducted across geographical and cultural boundaries. Additionally, they often address challenges and issues that are far more complex than those of the early agoras. This article seeks to identify such challenges and summarize a variety of appropriate dialogue methodologies.