Isotope effect on the E2g phonon and mesoscopic phase separation near the electronic topological transition in Mg1-xAlxB2

We report the boron isotope effect on the E2g phonon mode by micro-Raman spectroscopy on the ternary Mg1-xAlxB2 system, synthesized with pure isotopes 10B and 11B. The isotope coefficient on the phonon frequency is near 0.5 in the full range decreasing near x = 0. The intraband electron-phonon (e-ph) coupling, for the electrons in the sigma band, has been extracted from the E2g line-width and frequency softening. Tuning the Fermi energy near the electronic topological transition (ETT), where the sigma Fermi surface changes from 2D to 3D topology the E2g mode, shows the known Kohn anomaly on the 2D side of the ETT and a splitting of the E2g phonon frequency into a hard and soft component from x = 0 to x = 0.28. The results suggest a minor role of the intraband phonon mediated pairing in the control of the high critical temperature in Mg1-xAlxB2. The common physical features of diborides with the novel multigap FeAs-based superconductors and cuprates is discussed.Comment: 19 pages, 6 figure

Experimental observation of controllable kinetic constraints in a cold atomic gas

Many-body systems relaxing to equilibrium can exhibit complex dynamics even if their steady state is trivial. In situations where relaxation requires highly constrained local particle rearrangements, such as in glassy systems, this dynamics can be difficult to analyze from first principles. The essential physical ingredients, however, can be captured by idealized lattice models with so-called kinetic constraints. While so far constrained dynamics has been considered mostly as an effective and idealized theoretical description of complex relaxation, here we experimentally realize a many-body system exhibiting manifest kinetic constraints and measure its dynamical properties. In the cold Rydberg gas used in our experiments, the nature of the kinetic constraints can be tailored through the detuning of the excitation lasers from resonance. The system undergoes a dynamics which is characterized by pronounced spatial correlations or anticorrelations, depending on the detuning. Our results confirm recent theoretical predictions, and highlight the analogy between the dynamics of interacting Rydberg gases and that of certain soft-matter systems

Mechanical properties of Ti-6Al-4V selectively laser melted parts with body-centred-cubic lattices of varying cell size

Significant weight savings in parts can be made through the use of additive manufacture (AM), a process which enables the construction of more complex geometries, such as functionally graded lattices, than can be achieved conventionally. The existing framework describing the mechanical properties of lattices places strong emphasis on one property, the relative density of the repeating cells, but there are other properties to consider if lattices are to be used effectively. In this work, we explore the effects of cell size and number of cells, attempting to construct more complete models for the mechanical performance of lattices. This was achieved by examining the modulus and ultimate tensile strength of latticed tensile specimens with a range of unit cell sizes and fixed relative density. Understanding how these mechanical properties depend upon the lattice design variables is crucial for the development of design tools, such as finite element methods, that deliver the best performance from AM latticed parts. We observed significant reductions in modulus and strength with increasing cell size, and these reductions cannot be explained by increasing strut porosity as has previously been suggested. We obtained power law relationships for the mechanical properties of the latticed specimens as a function of cell size, which are similar in form to the existing laws for the relative density dependence. These can be used to predict the properties of latticed column structures comprised of body-centred-cubic (BCC) cells, and may also be adapted for other part geometries. In addition, we propose a novel way to analyse the tensile modulus data, which considers a relative lattice cell size rather than an absolute size. This may lead to more general models for the mechanical properties of lattice structures, applicable to parts of varying size

Here and now: perceptions of Indian Ocean islanders on the climate change and migration nexus

Empirical studies exploring the links between climate change and migration are increasing. Often, perceptions are not fully explored from the people most affected by the climate change and migration nexus. This article contributes to filling this gap by eliciting and analyzing perceptions regarding climate change and migration from an understudied population labelled as being amongst those most immediately and directly affected by climate change: Indian Ocean islanders. Open-ended, semi-structured interviews were conducted in two case study communities in Maldives (Kaafu Guraidhoo with 17 interviews and Raa Dhuvafaaru with 18 interviews) and two case study communities in Lakshadweep, India (Kavaratti with 35 interviews and Minicoy with 26 interviews). The results present the interviewees’ perceptions of climatic variability and change that they experience; how they perceive the causes of these changes; and links to migration decisions. The interviews demonstrate that perceptions of climate change, of migration, and of the links or lack thereof between the two are centred on the interviewees’ own experiences, their own locations, and the immediate timeframe. External information and direction has limited influence. Their perceptions are framed as being the ‘here and now’ through topophilia (here) and tempophilia (now). The islanders’ views do not avoid, but rather encompass, long-term livelihoods and the future. Such a future might be in another location, but the anchor is expressing future hopes and aspirations through the here and now. It is not linked to the wide-scale, long-term issue of climate change

Moral disengagement strategies in sex offenders

Sexual abuse is a heterogeneous phenomenon. The literature on sexual offenders considers risk factors in the individual and familial history as well as precursors such as cognitive distortions, defence mechanisms and moral disengagement (MD) mechanisms. This study investigates the MD in sex offenders and non-sex offenders in a sample of 362 males comprising a control group of 268 non-offenders, a group of 42 detained sex offenders and a group of 52 detained non-sex offenders. Participants were administered a semi-structured interview and the Moral Disengagement Scale (MDS). The results show a significant difference between the jailed participants (non-sex offenders and sex offenders) and controls; offenders were found to generally display overall higher levels of MD. Among the jailed participants, sex offenders seem to make more use of MD mechanisms than non-sex offenders

Variation in beliefs about 'fracking' between the UK and US

In decision-making on the politically-contentious issue of unconventional gas development, the UK Government and European Commission are attempting to learn from the US experience. Although economic, environmental, and health impacts and regulatory contexts have been compared cross-nationally, public perceptions and their antecedents have not. We conducted similar online panel surveys of national samples of UK and US residents simultaneously in September 2014 to compare public perceptions and beliefs affecting such perceptions. The US sample was more likely to associate positive impacts with development (i.e., production of clean energy, cheap energy, and advancing national energy security). The UK sample was more likely to associate negative impacts (i.e., water contamination, higher carbon emissions, and earthquakes). Multivariate analyses reveal divergence cross-nationally in the relationship between beliefs about impacts and support/opposition – especially for beliefs about energy security. People who associated shale gas development with increased energy security in the UK were over three times more likely to support development than people in the US with this same belief. We conclude with implications for policy and communication, discussing communication approaches that could be successful cross-nationally and policy foci to which the UK might need to afford more attention in its continually evolving regulatory environment

The BCC Unit Cell for Latticed SLM Parts; Mechanical Properties as a Function of Cell Size

The existing framework describing the mechanical properties of lattices places strong emphasis on one important property, the relative density of the repeating cells. In this work, we explore the effects of cell size, attempting to construct more complete models for the performance of lattices. This was achieved by examining the elastic modulus and ultimate tensile strength of latticed parts with a range of unit cell sizes and fixed density. The parts were produced by selective laser melting (SLM). The examined cell type was body-centred-cubic (BCC), a cell of high relevance for SLM because of its self-supporting structure. We obtained power law relationships for the mechanical properties of our latticed specimens as a function of cell size, which are similar in form to the existing laws for the density dependence. These can be used to predict the properties of latticed column structures comprised of BCC cells, and may be easily amended for other situations. In addition, we propose a novel way to analyse the elastic modulus data, which may lead to more general models, applicable to parts of varying size. Lastly, our general methodology may be of use in future studies which explore the other parameters that determine lattice performance; the choice of cell type, the global shape of the lattice structure and the type of stress.Mechanical Engineerin