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

Ultracold Atoms as a Target: Absolute Scattering Cross-Section Measurements

We report on a new experimental platform for the measurement of absolute scattering cross-sections. The target atoms are trapped in an optical dipole trap and are exposed to an incident particle beam. The exponential decay of the atom number directly yields the absolute total scattering cross-section. The technique can be applied to any atomic or molecular species that can be prepared in an optical dipole trap and provides a large variety of possible scattering scenarios

Impact of nutrition education on diabetes knowledge and attitudes of adults with type 2 diabetes living in a resource-limited setting in South Africa: a randomised controlled trial

Objective: To evaluate the effect of a nutrition education (NE) programme on diabetes knowledge and attitudes of adults with type 2 diabetes mellitus (T2DM).Methods: Eighty-two adults (40–70 years) with poorly controlled T2DM (HbA1c ≥ 8%) and attending two community health centres in Moretele, North West Province (South Africa) participated in a one-year randomised controlled trial. Participants were randomised to the intervention group (n = 41; 8 weekly group education (2 2.5 hours); follow-up meetings and education materials) or control group (education materials only). Diabetes Knowledge Form B assessed knowledge about diabetes. Diabetes Attitudes Scale-III assessed the attitudes towards diabetes and treatment. Assessments were done at 6 and 12 months. Analysis of co-variance compared the groups (baseline, age, gender and clinic adjustments). An intention to-treat analysis was employed.Results: The intervention group had higher mean diabetes knowledge scores + 0.95 (p = 0.033) and + 2.05 (p < 0.001) at 6 and 12 months respectively. However, the scores were below 50%. Patient autonomy for diabetes attitudes was the only score significantly higher in the intervention group + 0.27 (p = 0.028) at 12 months.Conclusion: NE significantly improved diabetes knowledge in the intervention group, though not satisfactorily, but had limited effects on the attitudes towards diabetes.Keywords: attitudes, diabetes knowledge, nutrition education, South Africa, type 2 diabete

Fast nonadiabatic dynamics of many-body quantum systems

Modeling many-body quantum systems with strong interactions is one of the core challenges of modern physics. A range of methods has been developed to approach this task, each with its own idiosyncrasies, approximations, and realm of applicability. However, there remain many problems that are intractable for existing methods. In particular, many approaches face a huge computational barrier when modeling large numbers of coupled electrons and ions at finite temperature. Here, we address this shortfall with a new approach to modeling many-body quantum systems. On the basis of the Bohmian trajectory formalism, our new method treats the full particle dynamics with a considerable increase in computational speed. As a result, we are able to perform large-scale simulations of coupled electron-ion systems without using the adiabatic Born-Oppenheimer approximation

Stakeholders’ perceptions of dietary and related self-management challenges and education programme preferences for type 2 diabetes adults

Objective: To inform the adaptation of an intervention from a primary healthcare setting to a tertiary setting, the dietary and related self-management challenges and education programme preferences of adults with type 2 diabetes (T2DM) were explored.Setting: A study was undertaken in a tertiary teaching hospital in Gauteng Province, South Africa.Methods: A qualitative approach was employed. Data were collected via focus-group discussions and open-ended selfadministered questionnaires from a convenient purposive sample of T2DM patients (n = 28; 40–70 years) and health professionals (n = 10) respectively. Data were analysed using a thematic framework method.Results: Participants revealed diabetes-related knowledge deficits and struggle with adhering to diet, exercise, medication and appointment keeping as problems affecting patients. They also perceived multiple barriers to effective self-management (financial constraints, unsupportive social and physical environments and personal factors). Patients perceived the challenges to greatly impact on their quality of life and consequently the motivation to self-care appropriately. Participants desired an education programme in the form of monthly group meetings with approaches to enhance learning (e.g. use of examples from peers and the provision of education materials). Strategies for motivating and sustaining programme participation (e.g. testimonials from successful participants) were perceived as necessary. Involving family was seen as a key support for positive behaviour change.Conclusion: In adapting the intervention, the participants’ preferences for education need to be considered and the unique challenges addressed. In particular, strategies for enhancing the patients’ motivation and the self-efficacy to effectively selfmanage are essential

Ion structure in warm dense matter: benchmarking solutions of hypernetted-chain equations by first-principle simulations

We investigate the microscopic structure of strongly coupled ions in warm dense matter using ab initio simulations and hypernetted chain (HNC) equations. We demonstrate that an approximate treatment of quantum effects by weak pseudopotentials fails to describe the highly degenerate electrons in warm dense matter correctly. However, one-component HNC calculations for the ions agree well with first-principles simulations if a linearly screened Coulomb potential is used. These HNC results can be further improved by adding a short-range repulsion that accounts for bound electrons. Examples are given for recently studied light elements, lithium and beryllium, and for aluminum where the extra short-range repulsion is essential

All-optical formation of a Bose-Einstein condensate for applications in scanning electron microscopy

We report on the production of a F=1 spinor condensate of 87Rb atoms in a single beam optical dipole trap formed by a focused CO2 laser. The condensate is produced 13mm below the tip of a scanning electron microscope employing standard all-optical techniques. The condensate fraction contains up to 100,000 atoms and we achieve a duty cycle of less than 10s.Comment: 5 pages, 4 figure

Comparison of UV and ELS detectors in HSPEC analysis of natural organic matter in dam water

This project arose out the need for a simple method to analyse natural organic matter (NOM) on a routine basis. Water samples were obtained from the Vaal Dam. Analysis was preceded by separating the NOM into the humic and non-humic fractions. The humic portion was separated further into two fractions by employing a non-ionic DAX-8 resin to separate humic acid from fulvic acid. High-performance size-exclusion chromatography (HPSEC), equipped with a UV detector and an evaporative light scattering detector (ELSD) was used to obtain information on the molecular weight distribution and concentration levels of the two acids. Mixed standards of polyethylene oxide/glycol were employed for calibration. The molecular weight distributions (MWDs) of the isolated fractions of humic and fulvic acids were determined with ELSD detection as weight-average (Mw), number-average (Mn) and polydispersity (ρ) of individual NOM fractions. The Mw/Mn ratio was found to be less than 1.5 in all fractions, indicating that they have a low and narrow size fraction. It is noted that the ELSD detector proved to be far more capable than the UV detector. A finding of interest is that 40% of the total organic carbon in the dam water samples could be attributed to humic substances. The developed method successfully separated the humic substances from water and further separated the humic substances into the component acids, namely, humic and fulvic acids. Molecular weight distribution of these compounds is a powerful indication of how much DOM was present in the dam water. Even though the UV method was useful in characterizing these substances, the ELS detector is recommended because it detects all the organic species present.Keywords: Natural organic matter, dam water, determination, ELS

An adaptive model for the optical properties of excited gold

We study the temperature-dependent optical properties of gold over a broad energy spectrum covering photon energies below and above the interband threshold. We apply a semi-analytical Drude-Lorentz model with temperature-dependent oscillator parameters. Our approximations are based on the distribution of electrons over the active bands with a density of states provided by density functional theory. This model can be easily adapted to other materials with similar band structures and can also be applied to the case of occupational nonequilibrium. Our calculations show a strong enhancement of the intraband response with increasing electron temperature while the interband component decreases. Moreover, our model compares well with density functional theory-based calculations for the reflectivity of highly excited gold and reproduces many of its key features. Applying our methods to thin films shows a sensitive nonlinear dependence of the reflection and absorption on the electron temperature. These features are more prominent at small photon energies and can be highlighted with polarized light. Our findings offer valuable insights for modeling ultrafast processes, in particular, the pathways of energy deposition in laser-excited samples

Structure of strongly coupled, multi-component plasmas

We investigate the short-range structure in strongly coupled fluidlike plasmas using the hypernetted chain approach generalized to multicomponent systems. Good agreement with numerical simulations validates this method for the parameters considered. We found a strong mutual impact on the spatial arrangement for systems with multiple ion species which is most clearly pronounced in the static structure factor. Quantum pseudopotentials were used to mimic diffraction and exchange effects in dense electron-ion systems. We demonstrate that the different kinds of pseudopotentials proposed lead to large differences in both the pair distributions and structure factors. Large discrepancies were also found in the predicted ion feature of the x-ray scattering signal, illustrating the need for comparison with full quantum calculations or experimental verification