Probing the Structure and Energetics of Dislocation Cores in SiGe Alloys through Monte Carlo Simulations

We present a methodology for the investigation of dislocation energetics in segregated alloys based on Monte Carlo simulations which equilibrate the topology and composition of the dislocation core and its surroundings. An environment-dependent partitioning of the system total energy into atomic contributions allows us to link the atomistic picture to continuum elasticity theory. The method is applied to extract core energies and radii of 60 degrees glide dislocations in segregated SiGe alloys which are inaccessible by other methods.Comment: 5 pages, to be published in Physical Review Letter

Thermally controlled widening of droplet etched nanoholes

We describe a method to control the shape of nanoholes in GaAs (001) which combines the technique of local droplet etching using Ga droplets with long-time thermal annealing. The cone-like shape of inverted nanoholes formed by droplet etching is transformed during long-time annealing into widened holes with flat bottoms and reduced depth. This is qualitatively understood using a simplified model of mass transport incorporating surface diffusion and evaporation. The hole diameter can be thermally controlled by varying the annealing time or annealing temperature which provides a method for tuning template morphology for subsequent nanostructure nucleation. We also demonstrate the integration of the combined droplet/thermal etching process with heteroepitaxy by the thermal control of hole depth in AlGaAs layers

Asymmetric coalescence of reactively wetting droplets

Coalescence of droplets during reactive wetting is investigated for the liquid Ga/GaAs(001) system. In situmirror electron microscopy reveals that coalescence predominantly involves the motion of one reactive droplet relative to the other. This behaviour differs significantly from coalescence in non-reactive systems and is associated with contact line pinning at a ridge/etch pit edge which is identified using atomic force microscopy and selective etching. A simple geometrical model is presented to describe the pinning

On the sensitivity of convergent beam low energy electron diffraction patterns to small atomic displacements

Multiple scattering simulations are developed and applied to assess the potential of convergent beam low-energy electron diffraction (CBLEED) to distinguish between various reconstructions of the Si(001) surface. This is found to be readily achievable through changes in pattern symmetry. A displacement R-factor approach is used to incorporate the angular content of CBLEED discs and identify optimal energy ranges for structure refinement. Defining a disc R-factor, optimal diffraction orders are identified which demonstrate an enhanced sensitivity to small atomic displacements. Using this approach, it was found that respective dimer height and length displacements as small as ±0.06 Å and ±0.20 Å could be detected

Asymmetric coalescence of reactively wetting droplets

Coalescence of droplets during reactive wetting is investigated for the liquid Ga/GaAs(001) system. In situmirror electron microscopy reveals that coalescence predominantly involves the motion of one reactive droplet relative to the other. This behaviour differs significantly from coalescence in non-reactive systems and is associated with contact line pinning at a ridge/etch pit edge which is identified using atomic force microscopy and selective etching. A simple geometrical model is presented to describe the pinning

Pharmacists in Pharmacovigilance: Can Increased Diagnostic Opportunity in Community Settings Translate to Better Vigilance?

The pharmacy profession has undergone substantial change over the last two to three decades. Whilst medicine supply still remains a central function, pharmacist’s roles and responsibilities have become more clinic and patient focused. In the community (primary care), pharmacists have become important providers of healthcare as Western healthcare policy advocates patient self-care. This has resulted in pharmacists taking on greater responsibility in managing minor illness and the delivery of public health interventions. These roles require pharmacists to more fully use their clinical skills, and often involve diagnosis and therapeutic management. Community pharmacists are now, more than ever before, in a position to identify, record and report medication safety incidents. However, current research suggests that diagnostic ability of community pharmacists is questionable and they infrequently report to local or national schemes. The aim of this paper is to highlight current practice and suggest ways in which community pharmacy can more fully contribute to patient safety

The National Criticality Experiments Research Center and its role in support of advanced reactor design

The National Criticality Experiments Research Center (NCERC) located at the Nevada National Security Site (NNSS) in the Device Assembly Facility (DAF) and operated by Los Alamos National Laboratory (LANL) is the only general purpose critical experiments facility in the United States. Experiments from subcritical to critical and above prompt critical are carried out at NCERC on a regular basis. In recent years, NCERC has become more involved in experiments related to nuclear energy, including the Kilopower/KRUSTY demonstration and the recent Hypatia experiment. Multiple nuclear energy related projects are currently ongoing at NCERC. This paper discusses NCERC’s role in advanced reactor design and how that role may change in the future

Support for people who use Anabolic Androgenic Steroids: A Systematic Scoping Review into what they want and what they access.

BACKGROUND: Since there is a paucity of research on support for people using Anabolic Androgenic Steroids (AAS), we aimed to identify and synthesise the available evidence in this field. Gaining an understanding of the support both accessed and wanted by recreational AAS users will be of use to professionals who provide services to intravenous substance users and also to those working in the fields of public health and social care, with the aim to increase engagement of those using AAS. METHODS: A systematic scoping review of the literature to explore and identify the nature and scope of information and support both accessed and wanted by non-prescribed AAS users. Any support services or information designed to help people who use AAS were considered. RESULTS: We identified 23 papers and one report for review, which indicated that AAS users access a range of sources of information on: how to inject, substance effectiveness, dosages and side effects, suggesting this is the type of information users want. AAS users sought support from a range of sources including medical professionals, needle and syringe programmes, friends, dealers, and via the internet, suggesting that, different sources were used dependent on the information or support sought. DISCUSSION: AAS users tended to prefer peer advice and support over that of professionals, and access information online via specialist forums, reflecting the stigma that is experienced by AAS users. These tendencies can act as barriers to accessing services provided by professionals. CONCLUSIONS: Support needs to be specific and targeted towards AAS users. Sensitivity to their perceptions of their drug-use and the associated stigma of being classified in the same sub-set as other illicit drug users is relevant to facilitating successful engagement

Running droplets of gallium from evaporation of gallium arsenide

High-temperature annealing of gallium arsenide in vacuum causes excess evaporation of arsenic, with accumulation of gallium as liquid droplets on the surface. Using real-time in situ surface electron microscopy, we found that these droplets spontaneously run across the crystal surface. Running droplets have been seen in many systems, but they typically require special surface preparation or gradient forces. In contrast, we show that noncongruent evaporation automatically provides a driving force for running droplets. The motion is predicted and observed to slow and stop near a characteristic temperature, with the speed increasing both below and above this temperature. The same behavior is expected to occur during the evaporation of similar III-V semiconductors such as indium arsenide