Electromigration of Single-Layer Clusters

Single-layer atom or vacancy clusters in the presence of electromigration are studied theoretically assuming an isotropic medium. A variety of distinctive behaviors distinguish the response in the three standard limiting cases of periphery diffusion (PD), terrace diffusion (TD), and evaporation-condensation (EC). A general model provides power laws describing the size dependence of the drift velocity in these limits, consistent with established results in the case of PD. The validity of the widely used quasistatic limit is calculated. Atom and vacancy clusters drift in opposite directions in the PD limit but in the same direction otherwise. In absence of PD, linear stability analysis reveals a new type of morphological instability, not leading to island break-down. For strong electromigration, Monte Carlo simulations show that clusters then destabilize into slits, in contrast to splitting in the PD limit. Electromigration affects the diffusion coefficient of the cluster and morphological fluctuations, the latter diverging at the instability threshold. An instrinsic attachment-detachment bias displays the same scaling signature as PD in the drift velocity.Comment: 11 pages, 4 figure

Non-conserved dynamics of steps on vicinal surfaces during electromigration-induced step bunching

We report new results on the non-conserved dynamics of parallel steps on vicinal surfaces in the case of sublimation with electromigration and step-step interactions. The derived equations are valid in the quasistatic approximation and in the limit $f^{-1}\gg l_D\gg l_{\pm} \gg l_i$, where $f$ is the inverse electromigration length, $l_D$ the diffusion length, $l_{\pm}$ the kinetic lengths and $l_i$ the terrace widths. The coupling between crystal sublimation and step-step interactions induces non-linear, non-conservative terms in the equations of motion. Depending on the initial conditions, this leads to interrupted coarsening, anticoarsening of step bunches or periodic switching between step trains of different numbers of bunches.Comment: 11 pages, 4 figures; revised and extended versio

On the mechanisms governing gas penetration into a tokamak plasma during a massive gas injection

A new 1D radial fluid code, IMAGINE, is used to simulate the penetration of gas into a tokamak plasma during a massive gas injection (MGI). The main result is that the gas is in general strongly braked as it reaches the plasma, due to mechanisms related to charge exchange and (to a smaller extent) recombination. As a result, only a fraction of the gas penetrates into the plasma. Also, a shock wave is created in the gas which propagates away from the plasma, braking and compressing the incoming gas. Simulation results are quantitatively consistent, at least in terms of orders of magnitude, with experimental data for a D 2 MGI into a JET Ohmic plasma. Simulations of MGI into the background plasma surrounding a runaway electron beam show that if the background electron density is too high, the gas may not penetrate, suggesting a possible explanation for the recent results of Reux et al in JET (2015 Nucl. Fusion 55 093013)

Velocity-space sensitivity of the time-of-flight neutron spectrometer at JET

The velocity-space sensitivities of fast-ion diagnostics are often described by so-called weight functions. Recently, we formulated weight functions showing the velocity-space sensitivity of the often dominant beam-target part of neutron energy spectra. These weight functions for neutron emission spectrometry (NES) are independent of the particular NES diagnostic. Here we apply these NES weight functions to the time-of-flight spectrometer TOFOR at JET. By taking the instrumental response function of TOFOR into account, we calculate time-of-flight NES weight functions that enable us to directly determine the velocity-space sensitivity of a given part of a measured time-of-flight spectrum from TOFOR

Relationship of edge localized mode burst times with divertor flux loop signal phase in JET

A phase relationship is identified between sequential edge localized modes (ELMs) occurrence times in a set of H-mode tokamak plasmas to the voltage measured in full flux azimuthal loops in the divertor region. We focus on plasmas in the Joint European Torus where a steady H-mode is sustained over several seconds, during which ELMs are observed in the Be II emission at the divertor. The ELMs analysed arise from intrinsic ELMing, in that there is no deliberate intent to control the ELMing process by external means. We use ELM timings derived from the Be II signal to perform direct time domain analysis of the full flux loop VLD2 and VLD3 signals, which provide a high cadence global measurement proportional to the voltage induced by changes in poloidal magnetic flux. Specifically, we examine how the time interval between pairs of successive ELMs is linked to the time-evolving phase of the full flux loop signals. Each ELM produces a clear early pulse in the full flux loop signals, whose peak time is used to condition our analysis. The arrival time of the following ELM, relative to this pulse, is found to fall into one of two categories: (i) prompt ELMs, which are directly paced by the initial response seen in the flux loop signals; and (ii) all other ELMs, which occur after the initial response of the full flux loop signals has decayed in amplitude. The times at which ELMs in category (ii) occur, relative to the first ELM of the pair, are clustered at times when the instantaneous phase of the full flux loop signal is close to its value at the time of the first ELM

Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries

Background Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres. Methods This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries. Results In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia. Conclusion This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries

ЭНДОПРОТЕЗИРОВАНИЕ ГОЛЕНОСТОПНОГО СУСТАВА (ОБЗОР ЛИТЕРАТУРЫ)

Ankle joint replacement remains the most promising but at the same time one of the most challenging fields of orthopedics. In this article the authors analyzed the history of ankle joint replacement development with meticulous details of the prosthesis structure as well as complications occurring with different generations of the prosthesis. Major tendencies of development and improvements of the prosthesis are described while taking into account the complicated biomechanics of the ankle joint. Based on the completed analysis the conclusion was made that using new materials in combination with improved structure allows for major improvements in the ankle joint replacement.Эндопротезирование голеностопного сустава на сегодняшний день является одним из перспективных, но мало изученных направлений. Представлена история развития эндопротезов голеностопного сустава с подробным анализом конструкций, типов, а также осложнений, возникающих при использовании разных поколений эндопротезов. Описаны основные тенденции развития и пути совершенствования эндопротезов, учитывающих всю сложность биомеханики голеностопного сустава. Использование новых материалов в сочетании с усовершенствованной конструкцией позволило заметно улучшить результаты эндопротезирования голеностопного сустава

Rate-determining stage in NO SCR with propane on low-exchanged Cu-ZSM-5 catalyst

The kinetics of the NO SCR with propane has been studied on a low-exchanged Cu-ZSM-5 catalyst. The study of the kinetics of individual reaction stages (2-nitrosopropane isomerization to acetone oxime and reaction of adsorbed acetone oxime with gaseous NO) has shown that the NO reaction with acetone oxime is the rate-determining stage in the whole chain of transformations leading to the formation of molecular nitrogen in the low-temperature region below 300 °C. The kinetic analysis of the reaction has revealed that at the temperatures above 300 °C propane plays a more important role

FTIR study of aceton oxime interaction with H-ZSM-5 and Cu-ZSM-5

Copper based catalysts are of great importance as catalysts for NO removal from exhaust industrial gases. Earlier authors have shown that NO reaction with acetone oxime (AO) is the rate determining step of NO catalytic reduction by propane over Cu-ZSM-5 catalyst at temperatures below 300°C. Aim of the present work is to clarify the peculiarities of acetone oxime coordination over surface of H-ZSM-5 zeolite and that doped with Cu(II) and Cu(I)-cations. We studied AO coordination in CCl4 solutions and then data obtained were used for analysis of spectra of AO adsorbed on pure zeolite and that dopped with Cu (I) and Cu (II) cations. It was shown that there are monomers and several associates of AO in CCl4 solution differing in size and type of bonding with their own characteristic bands in IR spectra. The spectrum of acetone oxime adsorbed on pure zeolite includes non symmetrical band at 1710 cm-1 due to AO strongly bonded with zeolite surface through H-bond. There are four AO adspecies on zeolite dopped with copper with two different types of AO coordination to Cu(I) or to Cu(II) cations: one with participation of O atom and another one with N atom. Complexes of AO with Cu(I) ions are much more stable then those with Cu(II) ions.</p