Catastrophic Fermi surface reconstruction in the shape-memory alloy AuZn

AuZn undergoes a shape-memory transition at 67 K. The de Haas van Alphen effect persists to 100 K enabling the observation of a change in the quantum oscillation spectrum indicative of a catastrophic Fermi surface reconstruction at the transition. Coexistence of both Fermi surfaces at low temperatures is suggestive of an intrinsic phase separation in the bulk of the material. In addition, a Dingle analysis reveals a sharp change in the scattering mechanism at a threshold cyclotron radius, which we suggest to be related to the underlying microstructure that drives the shape-memory effect.Comment: 4 pages, 4 figure

Size of Orbital Ordering Domain Controlled by the Itinerancy of the 3d Electrons in a Manganite Thin Film

An electronic effect on a macroscopic domain structure is found in a strongly correlated half-doped manganite film Nd$_{0.5}$Sr$_{0.5}$MnO3 grown on a (011) surface of SrTiO3. The sample has a high-temperature (HT) phase free from distortion above 180K and two low-temperature (LT) phases with a large shear-mode strain and a concomitant twin structure. One LT phase has a large itinerancy (A-type), and the other has a small itinerancy (CE-type), while the lattice distortions they cause are almost equal. Our x ray diffraction measurement shows that the domain size of the LT phase made by the HT-CE transition is much smaller than that by the HT-A transition, indicating that the difference in domain size is caused by the electronic states of the LT phases.Comment: 9 pages, 4 figure

"Cold Melting" of Invar Alloys

An anomalously strong volume magnetostriction in Invars may lead to a situation when at low temperatures the dislocation free energy becomes negative and a multiple generation of dislocations becomes possible. This generation induces a first order phase transition from the FCC crystalline to an amorphous state, and may be called "cold melting". The possibility of the cold melting in Invars is connected with the fact that the exchange energy contribution into the dislocation self energy in Invars is strongly enhanced, as compared to conventional ferromagnetics, due to anomalously strong volume magnetostriction. The possible candidate, where this effect can be observed, is a FePt disordered Invar alloy in which the volume magnetostriction is especially large

Fermi Surface as a Driver for the Shape-Memory Effect in AuZn

Martensites are materials that undergo diffusionless, solid-state transitions. The martensitic transition yields properties that depend on the history of the material and may allow it to recover its previous shape after plastic deformation. This is known as the shape-memory effect (SME). We have succeeded in identifying the primary electronic mechanism responsible for the martensitic transition in the shape-memory alloy AuZn by using Fermi-surface measurements (de Haas-van Alphen oscillations) and band-structure calculations. This strongly suggests that electronic band structure is an important consideration in the design of future SME alloys

Crystallographic structure of ultrathin Fe films on Cu(100)

We report bcc-like crystal structures in 2-4 ML Fe films grown on fcc Cu(100) using scanning tunneling microscopy. The local bcc structure provides a straightforward explanation for their frequently reported outstanding magnetic properties, i.e., ferromagnetic ordering in all layers with a Curie temperature above 300 K. The non-pseudomorphic structure, which becomes pseudomorphic above 4 ML film thickness is unexpected in terms of conventional rules of thin film growth and stresses the importance of finite thickness effects in ferromagnetic ultrathin films.Comment: 4 pages, 3 figures, RevTeX/LaTeX2.0

THE EFFECT OF AGE, SEX AND LEVEL OF INTAKE OF DIETARY FIBER FROM WHEAT ON LARGE-BOWEL FUNCTION IN 30 HEALTHY-SUBJECTS

1. To evaluate the effect of age, sex and level of intake on the colonic response to wheat fibre, thirty healthy volunteers aged 17–62 years (nineteen men, eleven women) recruited from a local industry, were divided into four groups and given a controlled diet for two 3-week periods. The diet contained white bread during one period or one of four different amounts of bran-enriched wholemeal bread during the other (30, 60, 110, 170 g/d). 2. Wide variation was observed between subjects in stool weight on the basal diet and in response to wheat fibre. Stepwise regression analysis showed that the variation in stool weight was significantly related to sex (t4.0, P <0.001) but not to age, height, weight or energy:fibre intakes on the basal diet. Stool weight in men (162(SE 11) g/d) was approximately double that in women (83(SE 11) g/d). Transit time and stool weight were closely related and the effect of sex on stool weight could be explained entirely by differences in transit. 4. Faecal carbohydrate excretion increased with the addition of bran mainly due to increased amounts of cellulose and pentose (arabinose+xylose), whilst digestibility of dietary non-starch polysaccharide fell from 77.6 (SE 2.3)% on the white bread diet to 65.6 (SE 2.4)% with the added bran (t 7.4, P < 0.01, n26). 5. Faecal pH was more acid in men than in women and was related to methane production. Methane producers had higher faecal pH than non-producers (7.06 (SE 0.1 1) v. 6.65 (SE O.1)), lower stool weight (g/d; 93 (SE 12) v. 156 (SE 13)) and slower transit times (h; 84.6 (SE 11.7) v. 48.6 (SE 6.6)). 6. These studies show that, when on similar diets, women have much lower stool weights and slower transit times than men. Furthermore, within the range of amounts of wheat fibre used in this and other published work, stool weight increases in linear proportion to the dose of fibre added to the diet. Methane excretion in breath is associated in this group of subjects with slow transit time and high faecal pH

Serum Concentrations of Organochlorine Pesticides and Growth among Russian Boys

Background: Limited human data suggest an association of organochlorine pesticides (OCPs) with adverse effects on children’s growth

The Moral Resilience of Young People Who Care

This paper draws on findings from a qualitative study of the social wellbeing of young people caring for a close family member. The research makes a novel contribution to the international literature by examining the moral resilience of young adult carers. Focus groups or individual, semi-structured interviews were undertaken with fifteen young people in South-East England during 2018–2019. The paper explores whether young people with a seriously ill or disabled family member define and conduct themselves in moral terms and how they respond to the moral challenges of a caring life. It was found that the participants saw moral value in their caring role and their actions reflected a desire to provide compassionate care. Previous research into young adult carers had indicated that the caring role stimulated their political consciousness, but this study suggests that the role also strengthens their moral consciousness. However, designating girls as carers in early life shifts the moral responsibility to females and compounds gender inequity in caring. Hence, there is a need to address social and gender inequalities in care. In addition, healthcare professionals should recognise when statutory input is necessary to facilitate young people’s broader lifeplans

MicroRNA132 Modulates Short-Term Synaptic Plasticity but Not Basal Release Probability in Hippocampal Neurons

MicroRNAs play important regulatory roles in a broad range of cellular processes including neuronal morphology and long-term synaptic plasticity. MicroRNA-132 (miR132) is a CREB-regulated miRNA that is induced by neuronal activity and neurotrophins, and plays a role in regulating neuronal morphology and cellular excitability. Little is known about the effects of miR132 expression on synaptic function. Here we show that overexpression of miR132 increases the paired-pulse ratio and decreases synaptic depression in cultured mouse hippocampal neurons without affecting the initial probability of neurotransmitter release, the calcium sensitivity of release, the amplitude of excitatory postsynaptic currents or the size of the readily releasable pool of synaptic vesicles. These findings are the first to demonstrate that microRNAs can regulate short-term plasticity in neurons