A Scanning Electron Microscope for Ultracold Atoms

We propose a new technique for the detection of single atoms in ultracold quantum gases. The technique is based on scanning electron microscopy and employs the electron impact ionization of trapped atoms with a focussed electron probe. Subsequent detection of the resulting ions allows for the reconstruction of the atoms position. This technique is expected to achieve a much better spatial resolution compared to any optical detection method. In combination with the sensitivity to single atoms, it makes new in situ measurements of atomic correlations possible. The detection principle is also well suited for the addressing of individual sites in optical lattices.Comment: 5 pages, 2 figure

A reduced coupled-mode description for the electron-ion energy relaxation in dense matter

We present a simplified model for the electron-ion energy relaxation in dense two-temperature systems that includes the effects of coupled collective modes. It also extends the standard Spitzer result to both degenerate and strongly coupled systems. Starting from the general coupled-mode description, we are able to solve analytically for the temperature relaxation time in warm dense matter and strongly coupled plasmas. This was achieved by decoupling the electron-ion dynamics and by representing the ion response in terms of the mode frequencies. The presented reduced model allows for a fast description of temperature equilibration within hydrodynamic simulations and an easy comparison for experimental investigations. For warm dense matter, both fluid and solid, the model gives a slower electron-ion equilibration than predicted by the classical Spitzer result

In situ surface coverage analysis of RuO₂-catalysed HCl oxidation reveals the entropic origin of compensation in heterogeneous catalysis

In heterogeneous catalysis, rates with Arrhenius-like temperature dependence are ubiquitous. Compensation phenomena, which arise from the linear correlation between the apparent activation energy and the logarithm of the apparent pre-exponential factor, are also common. Here, we study the origin of compensation and find a similar dependence on the rate-limiting surface coverage term for each Arrhenius parameter. This result is derived from an experimental determination of the surface coverage of oxygen and chlorine species using temporal analysis of products and prompt gamma activation analysis during HCl oxidation to Cl2 on a RuO2 catalyst. It is also substantiated by theory. We find that compensation phenomena appear when the effect on the apparent activation energy caused by changes in surface coverage is balanced out by the entropic configuration contributions of the surface. This result sets a new paradigm in understanding the interplay of compensation effects with the kinetics of heterogeneously catalysed processes

Biology : the ultimate science for teaching an understanding of scientific evidence.

Recent school science curriculum developments in many countries emphasise that scientists derive evidence for their claims through different approaches; that such practices are intimately bound up with disciplinary knowledge; and that the quality of data should be appreciated. This position paper focuses on the role of Biology to understand evidence, an essential component of ‘scientific practice’. Biology is an empirical science, using evidence to support claims. Yet biological practice is diverse – including, inter alia, observations, lab-based experimentation, field trials, ecological surveys, randomised controlled trials – so how can we teach, within the time-constraints of the curriculum, to help pupils really understand about evidence in biology? In this paper biology is shown to be the ultimate context for teaching about evidence and ‘scientific practice’. The paper draws on a body of research that presents an understanding of the validity of data as a set of conceptual relationships, shown on a concept map. Using examples from biological practice, the paper shows how teachers can illustrate the application of the network of all these ideas and their inter-relationships within the biology curriculum, to help pupils develop the necessary ‘thinking behind the doing’. The paper explores ways in which this understanding is inherently related to underpinning disciplinary ideas of biology

A Current Mode Detector Array for Gamma-Ray Asymmetry Measurements

We have built a CsI(Tl) gamma-ray detector array for the NPDGamma experiment to search for a small parity-violating directional asymmetry in the angular distribution of 2.2 MeV gamma-rays from the capture of polarized cold neutrons by protons with a sensitivity of several ppb. The weak pion-nucleon coupling constant can be determined from this asymmetry. The small size of the asymmetry requires a high cold neutron flux, control of systematic errors at the ppb level, and the use of current mode gamma-ray detection with vacuum photo diodes and low-noise solid-state preamplifiers. The average detector photoelectron yield was determined to be 1300 photoelectrons per MeV. The RMS width seen in the measurement is therefore dominated by the fluctuations in the number of gamma rays absorbed in the detector (counting statistics) rather than the intrinsic detector noise. The detectors were tested for noise performance, sensitivity to magnetic fields, pedestal stability and cosmic background. False asymmetries due to gain changes and electronic pickup in the detector system were measured to be consistent with zero to an accuracy of $10^{-9}$ in a few hours. We report on the design, operating criteria, and the results of measurements performed to test the detector array.Comment: 33 pages, 20 figures, 2 table

Strong-coupling effects in the relaxation dynamics of ultracold neutral plasmas

We describe a hybrid molecular dynamics approach for the description of ultracold neutral plasmas, based on an adiabatic treatment of the electron gas and a full molecular dynamics simulation of the ions, which allows us to follow the long-time evolution of the plasma including the effect of the strongly coupled ion motion. The plasma shows a rather complex relaxation behavior, connected with temporal as well as spatial oscillations of the ion temperature. Furthermore, additional laser cooling of the ions during the plasma evolution drastically modifies the expansion dynamics, so that crystallization of the ion component can occur in this nonequilibrium system, leading to lattice-like structures or even long-range order resulting in concentric shells

Adaptive risk-based targeted surveillance for foreign animal diseases at the wildlife-livestock interface

Animal disease surveillance is an important component of the national veterinary infrastructure to protect animal agriculture and facilitates identification of foreign animal disease (FAD) introduction. Once introduced, pathogens shared among domestic and wild animals are especially challenging to manage due to the complex ecology of spillover and spillback. Thus, early identification of FAD in wildlife is critical to minimize outbreak severity and potential impacts on animal agriculture as well as potential impacts on wildlife and biodiversity. As a result, national surveillance and monitoring programs that include wildlife are becoming increasingly common. Designing surveillance systems in wildlife or, more importantly, at the interface of wildlife and domestic animals, is especially challenging because of the frequent lack of ecological and epidemiological data for wildlife species and technical challenges associated with a lack of non-invasive methodologies. To meet the increasing need for targeted FAD surveillance and to address gaps in existing wildlife surveillance systems, we developed an adaptive risk-based targeted surveillance approach that accounts for risks in source and recipient host populations. The approach is flexible, accounts for changing disease risks through time, can be scaled from local to national extents and permits the inclusion of quantitative data or when information is limited to expert opinion. We apply this adaptive risk-based surveillance framework to prioritize areas for surveillance in wild pigs in the United States with the objective of early detection of three diseases: classical swine fever, African swine fever and foot-and-mouth disease. We discuss our surveillance framework, its application to wild pigs and discuss the utility of this framework for surveillance of other host species and diseases

Effectiveness of a structured, framework-based approach to implementation: the Researching Effective Approaches to Cleaning in Hospitals (REACH) Trial.

BACKGROUND:Implementing sustainable practice change in hospital cleaning has proven to be an ongoing challenge in reducing healthcare associated infections. The purpose of this study was to develop a reliable framework-based approach to implement and quantitatively evaluate the implementation of evidence-based practice change in hospital cleaning. DESIGN/METHODS:The Researching Effective Approaches to Cleaning in Hospitals (REACH) trial was a pragmatic, stepped-wedge randomised trial of an environmental cleaning bundle implemented in 11 Australian hospitals from 2016 to 2017. Using a structured multi-step approach, we adapted the integrated Promoting Action on Research Implementation in Health Services (i-PARIHS) framework to support rigorous and tailored implementation of the cleaning bundle intervention in eleven diverse and complex settings. To evaluate the effectiveness of this strategy we examined post-intervention cleaning bundle alignment calculated as a score (an implementation measure) and cleaning performance audit data collected using ultraviolet (UV) gel markers (an outcome measure). RESULTS:We successfully implemented the bundle and observed improvements in cleaning practice and performance, regardless of hospital size, intervention duration and contextual issues such as staff and organisational readiness at baseline. There was a positive association between bundle alignment scores and cleaning performance at baseline. This diminished over the duration of the intervention, as hospitals with lower baseline scores were able to implement practice change successfully. CONCLUSION:Using a structured framework-based approach allows for pragmatic and successful implementation of clinical trials across diverse settings, and assists with quantitative evaluation of practice change. TRIAL REGISTRATION:Australia New Zealand Clinical Trial Registry ACTRN12615000325505, registered on 4 September 2015

Integrated product and process models: towards an integrated framework and review

While product models and process models have a long standing transiting, there are few models that integrate the two type of models. Those that exist are research systems, which even if validated in industry do not have a broad uptake to date. This paper develops an integrated framework for product and process models based on the purpose the models are put it building on a model of Browning and Ramasesh. Selected integrated model are classified according to the framework. This revealed the no model to date gives equal weight to product and process models