Composition and magnetic character of nanometre-size Cu precipitates in reactor pressure vessel steels: Implications for nuclear power plant lifetime extension

The sensitivity of positrons to nanometre-size Cu precipitates in Fe alloys has enabled us to apply a novel spin-polarized element-specific method to probe the composition and magnetic character of the precipitates responsible for reactor pressure vessel (RPV) steel embrittlement. The results clearly show that the precipitates are non-magnetic and place an upper limit of about 10at% on their Fe content. The practical implication of this result is that the Cu precipitate contribution to RPV steel embrittlement saturates is not expected to contribute further during lifetime extension. Our study demonstrates that polarized positrons can be used as a powerful probe of the magnetic character of nanoscale materials, even those embedded in a strongly magnetic host.     

Analysis of a displacive superlattice in nickel arsenide

Abstract

The structural analysis by convergent-beam electron diffraction is described for a weak orthorhombic superlattice observed in both mineral and synthetic samples of NiAs. The three equivalent directions for the commensurate wavevector, q = ?(a? + b?), defined a domain structure within the hexagonal subcell. Within a single domain, the symmetry around the c axis was reduced from 6mm to 2mm. The internal structure of higher-order Laue-zone reflections in diffraction patterns recorded at 100 K was used to associate a specific phonon eigenvector or condensed soft mode with the atomic displacement pattern.     

Anisotropic grain growth kinetics in nanocrystalline nickel

ABSTRACT

Intriguing properties exhibited by nanocrystalline metals, including a high level of mechanical strength, arise from their nanometer-scale grain sizes. It is critical to determine the evolution of grain size of nanocrystalline materials at elevated temperature, as this process can drastically change the mechanical properties. In this work, a nanocrystalline Ni foil with grain size ～ 25?nm was annealed in situ in an X-ray diffractometer. X-ray diffraction peaks were analysed to determine the grain growth kinetics. The grain growth exponents obtained were ～ 2–4 depending upon the crystallographic direction, indicating the anisotropic nature of the grain growth kinetics.     

The Relation of Lifetime Cognitive Activity and Lifetime Access to Resources to Late-life Cognitive Function in Older African Americans

ABSTRACT

Research in older Caucasians has demonstrated that cognitive activity is related to cognitive function in late adulthood. Knowledge of this association is limited in older minority populations. We examined the relation of cognitive activity and access to cognitive resources, with cognitive function in a group of 108 older African Americans. We constructed two scales to measure the frequency of cognitive activity and the presence of resources that promote cognitive activity during early and late life. Both measures had high internal consistency and the cognitive activity scale had adequate temporal stability over a 4-week interval. In analyses that controlled for age and education, more frequent lifetime cognitive activity was related to current cognitive function, but lifetime cognitive resources only approached significance. The results suggest that both measures are psychometrically sound in a minority population and that lifetime cognitive activity may contribute to current cognitive function in African Americans.     

A comparison between American and Chinese college students on suicide-related behavior parameters

Background/ObjectiveThe United States (US) and China are the two largest economies, but recent and directly comparable studies on suicide-related behaviors in the two countries are lacking. By using the Suicidal Behaviors Questionnaire-Revised (SBQ-R), item-level comparison was performed in assessing self-reported suicide-related behaviors between the US and Chinese undergraduates.MethodThis study involved a total of 3,185 college students aged between 18 to 24 years (1,185 US college students, and 2,000 Chinese students who were randomly selected from a large sample of 11,806 Chinese college students). Participants filled out the 4-item SBQ-R.ResultsParticipants’ responses were compared by country and sex. There was a higher overall risk of suicide-related behaviors among US students (24.3%) compared to Chinese students (17.0%). US students also reported higher lifetime attempt, past-year ideation, and lifetime threat. US female college students reported the highest suicide-related behaviors compared to other sub-groups.ConclusionsThere is a need to tailor specific interventions to alleviate college students’ suicide-related behaviors in the US and China, with a particular focus on US females.     

Postreading Questioning and Middle School Students’ Understanding of Literature

Bibliopower can be used effectively to develop positive attitudes about reading and writing among reluctant readers and writers. The purpose of this study was to identify Newbery and Caldecott Medal books which possess bibliopower. Suggestions are made for the classroom use of these books to help students build lifetime commitments to reading and writing.     

The role of lifetime periods in the organisation of episodic memories

ABSTRACT

Research on the nature of episodic memory associations has suggested that episodic memories are associated by conceptual knowledge, where memories cluster around the same content (e.g. memories about the same people) or general-event knowledge, where memories cluster around extended events (e.g. a holiday in London), repeated events (e.g. Sunday walks in the park), or causally related events (i.e. where one event leads to another). Research has also suggested that episodic memories are associated by lifetime periods (e.g. when I was in high school), where memories cluster within lifetime periods. However, it is unclear whether episodic memories can be associated solely by lifetime periods, or if such associations are subordinate to conceptual or general-event associations. To answer this question, we reanalysed a large sample of involuntary memory chains (Mace, J. H., Clevinger, A. M., & Bernas, R. S. (2013). Involuntary memory chains: What do they tell us about autobiographical memory organisation? Memory, 21, 324–335). The results of this analysis suggested that lifetime periods associations are subordinate to conceptual and general-event associations, as lifetime periods were found to cluster within the latter two associations. The potential functions of this organisation are discussed.     

Nano-undulations of nickel thin films on a substrate under compressive stress

Nickel thin films on a substrate have been studied in situ by atomic force microscopy during deformation. Undulations have been observed on the debonding regions, of very low amplitude and of periodicity of the order of 1mum. Attempts are made to compare these experimental results with previous models of buckling instabilities of thin plates.     

Phase stability of Al3Nb as a function of nickel additions

Abstract

Phase stability of the intermetallic compound Al₃Nb is investigated as a function of nickel additions by band structure calculations based on an extended Hueckel tight-binding method. With this method, the electronic structure and total energies of the Al_6-n -Ni _n Nb₂ compounds (where n is an integer from 0 to 6) are calculated for both D0₂₂ and L1₂ structures under the assumption that nickel substitutes for aluminium. The electronic total energies obtained from integration of the energy states of all electrons considered have shown that the D0₂₂ structure is stable in the binary Al₃Nb compound as compared with the L1₂ structure; conversely, the L1₂ structure is stable for compounds with n values greater than 1. These calculations are in good agreement with X-ray diffraction results reported by Schubert and co-workers. Differences in the electronic total energy per atom between D0₂₂ and L1₂ are - 0·79 eV and 0·56 eV for n equal to 0 and 2, respectively.     

Multilayered phase formation after high-fluence implantation of nickel into aluminium

The formation of crystalline and amorphous layers has been observed in Al crystals after 5MeV Ni implantation up to a fluence of 7.6 10 17 Ni atomscm -2 . The layers are structured into sublayers perpendicular to the implantation direction with sharp interfaces between the phases and almost symmetrically arranged to both sides of the maximum of the implantation profile. The sublayers of thickness of the order of 100nm were analysed by transmission electron microscopy. They consist of polycrystalline Al 3 Ni, crystalline Al 3 Ni precipitates and small amorphous zones, depending on the local Ni implantation concentration.     

Strain localization in nickel single crystals cyclically deformed at 77 K

Nickel monocrystals oriented for single slip have been cyclically deformed at 77 K at plastic strain amplitude between 5 x 10^-4 and 1 x 10^-2 up to saturation of the stress amplitude. After unloading from maximum compression, the slip markings on the surface of the specimens were removed and the deformation continued for one half cycle in tension. As previously observed for room-temperature deformation, the plastic strain was found to be localized in narrow slip bands (SBs). Using atomic force microscopy at a given imposed strain amplitude, a wide spectrum of local plastic strains was found. The averaged resolved shear strain of the SBs was found to be independent of the imposed plastic strain amplitude and turned out to be a factor of three larger than the upper plateau strain limit of the cyclic stress-strain curve.     

On the microstructures of equilibrated and quenched spinel-containing nickel titanates

Electron microscopy has been used to study the microstructures of equilibrated and quenched NiO-TiO₂ mixtures containing 5, 10, 15, 20 and 25wt% TiO₂. All the specimens contained rocksalt- and spinel-structured phases on a nanometre scale. The microstructure suggests that a nonstoichiometric spinel decomposed during quenching. The 25wt% TiO₂ specimen exhibited a lamellar microstructure composed of NiTiO₃ and spinelNiO. These phases had the usual orientation relationships, i.e., (111)_cubic||(0001)_hex and (110)_cubic|| (1100>_hex. Faceted NiO solid-solution regions with coherent cube-on-cube interfaces with the spinel were found in the four specimens of lower TiO₂ contents. When large (15 and 20wt% TiO₂), these regions were faceted cuboidal particles. With lower TiO₂ contents, these regions were no longer equiaxed and could be interconnected. The specimens were chemically homogeneous on a length scale of about 1mum. Morphological evidence is presented to explain which part of the microstructure most probably already existed in this form during equilibration. In particular, the large-scale NiTiO₃ and the spinel lamella in the 25wt% TiO₂ material form during long-term equilibration.     

Positron lifetime study of an Al-1.7at.% Mg-1.1at.% Cu alloy

The behaviour of vacancies during isothermal ageing following quenching of an Al-1.7at.% Mg-1.1at.% Cu alloy has been studied by positron annihilation lifetime spectroscopy. The positron lifetime parameters vary in parallel with the Vickers hardness of the alloy, suggesting simultaneous migration of vacancies and changes in the size and concentration of vacancies containing clusters and dislocation loops. The results also explain the long hardness plateau observed previously in ageing experiments carried out between 100 and 240°C in terms of a continuous growth of Mg-Cu-vacancy clusters during ageing. The vacancy concentration of the clusters increases gradually until the setting in of the cluster Guinier-Preston-Bagaryatsky zone transformation.     

Associations between childhood adversity and daily suppression and avoidance in response to stress in adulthood: can neurobiological sensitivity help explain this relationship?

Background and objectives: Although it has been postulated that psychological responses to stress in adulthood are grounded in childhood experiences in the family environment, evidence has been inconsistent. This study tested whether two putative measures of neurobiological sensitivity (vagal flexibility and attentional capacity) moderated the relation between women’s reported exposure to a risky childhood environment and current engagement in suppressive or avoidant coping in response to daily stress.

Design and methods: Adult women (N?=?158) recruited for a study of stress, coping, and aging reported on early adversity (EA) in their childhood family environment and completed a week-long daily diary in which they described their most stressful event of the day and indicated the degree to which they used suppression or avoidance in response to that event. In addition, women completed a visual tracking task during which heart rate variability and attentional capacity were assessed.

Results: Multilevel mixed modeling analyses revealed that greater EA predicted greater suppression and avoidance only among women with higher attentional capacity. Similarly, greater EA predicted greater use of suppression, but only among women with greater vagal flexibility.

Conclusion: Childhood adversity may predispose individuals with high neurobiological sensitivity to a lifetime of maladaptive coping.     

Brain-derived neurotrophic factor Val66met polymorphism and plasma levels in road traffic accident survivors

Background: Alterations in brain-derived neurotrophic factor (BDNF) expression and release may play a role in the pathogenesis of post-traumatic stress disorder (PTSD). Design: This study evaluated road traffic accident (RTA) survivors to determine whether PTSD and trauma-related factors were associated with plasma BDNF levels and BDNF Val66Met carrier status following RTA exposure. Methods: One hundred and twenty-three RTA survivors (mean age 33.2 years, SD?=?10.6 years; 56.9% male) were assessed 10 (SD?=?4.9) days after RTA exposure. Acute stress disorder (ASD), as assessed with the Acute Stress Disorder Scale, was present in 50 (42.0%) of the participants. Plasma BDNF levels were measured with enzyme-linked immunosorbent assay and BDNF Val66Met genotyping was performed. PTSD, as assessed with the Clinician-Administered PTSD Scale, was present in 10 (10.8%) participants at 6 months follow-up. Results: Neither BDNF Val66Met genotype nor plasma BDNF was significantly associated with the presence or severity of ASD or PTSD. Plasma BDNF levels were, however, significantly correlated with the lifetime number of trauma exposures. Conclusions: In RTA survivors, plasma BDNF levels increased with increasing number of prior trauma exposures. Plasma BDNF may, therefore, be a marker of trauma load.     

Exploring religious and/or spiritual identities: part 1 – assessing relationships with health

ABSTRACT

There is considerable debate about the distinction between being religious and being spiritual. It is time to move beyond this issue to an examination of the health-related implications of being religious and/or spiritual. Three health outcomes are used in this study: self-rated health, depressive symptoms, and alcohol use. The data are from a large nationwide random probability survey of adults of all ages who reside in the United States (N?=?2,876–2,883). Four self-identified categories of religiousness/spirituality are examined: religious and spiritual, spiritual only, not religious/not spiritual, and religious only. Tests are performed to see if membership in each category offsets the noxious effects of lifetime trauma on the health-related outcomes. A clear pattern emerges from the data. Lifetime trauma is associated with less favourable health ratings, more symptoms of depression, and greater alcohol consumption. However, these relationships are substantially stronger among people who say they are religious only.     

Birth,death and Ruth: an essay in memory of Emmanuel Chukwudi Eze

abstract

The birth of a particular individual is contingent even though the docRine of creation out of nothing teaches otherwise. Birth is an ontological invitation alerting the individual to inevitable death. In the intervening period along the path to death the individual is locked in the existential quest for Ruth. During his lifetime Emmanuel Chukwudi Eze, was engaged in the complex quest for Ruth. His engagement in the search of the Ruth of and about Africa elevated him to the status of one of the distinguished philosophers Africa has ever produced. This essay is in memory of Eze as an African philosopher, a philosopher engaged in the Ruth of and about post-colonial Africa.     

The Impact of Sexual Assault on College Students’ Daily Occupations: A Phenomenological Approach

Abstract

Sexual assault is associated with a high degree of Posttraumatic Stress Disorder (PTSD) severity. Three in ten survivors of campus sexual assault develop PTSD over their lifetime. Occupational therapists treat veterans with PTSD, but limited research exists addressing college student survivors of sexual assault and occupational therapy. A phenomenological approach was used to understand meanings of sexual assault for college student survivors. Semi-structured interviews yielded rich data and themes of disruption and reduced quality of life. The author concludes there is potential for occupational therapists to play a collaborative role on college campuses.     

Mental ghosts and the process of grief

Abstract

Grieving the death of a loved one is an experience that many people will face at least once in their lifetime, but the lack of widely accepted guidelines as to what constitutes “normal” grieving results in mourning being a common experience with little universality. Memories may keep the deceased alive in the minds of the survivor and may even interfere with the formation of new relationships. This article considers the process of grieving the loss of a spouse and some of the individual factors, such as age, sex, and personal beliefs, that may account for variability in grief experiences. While several modeh detailing the grief process are discussed, the inappropriateness of establishing expectations for the nature and duration of grief is argued for.     

Measurement of the size effect in the yield strength of nickel foils

There is a growing consensus that materials become stronger in small volumes and in the presence of large strain gradients. It has not been clear whether this is due to increased resistance to the motion of dislocations, fewer dislocations, or increased difficulty of multiplying dislocations in these situations. A classic experiment by Stölken and Evans (J.S. Stölken and A.G. Evans, Acta metall. 46 5109 (1998)) showed that thin nickel foils under bending display increased strengthening at large plastic strain values and, correspondingly, large plastic strain gradients. We have adapted their technique to small strains, and report preliminary data for the stress–strain curves of thin nickel foils through the elastic–plastic transition. These data show unambiguously that the yield strength is greater in the thinner foils. The strengthening is additive to the Hall–Petch effect, and is consistent with a size effect at the onset of plastic deformation.