Microwave studies of the fractional Josephson effect in HgTe-based Josephson junctions

The rise of topological phases of matter is strongly connected to their potential to host Majorana bound states, a powerful ingredient in the search for a robust, topologically protected, quantum information processing. In order to produce such states, a method of choice is to induce superconductivity in topological insulators. The engineering of the interplay between superconductivity and the electronic properties of a topological insulator is a challenging task and it is consequently very important to understand the physics of simple superconducting devices such as Josephson junctions, in which new topological properties are expected to emerge. In this article, we review recent experiments investigating topological superconductivity in topological insulators, using microwave excitation and detection techniques. More precisely, we have fabricated and studied topological Josephson junctions made of HgTe weak links in contact with two Al or Nb contacts. In such devices, we have observed two signatures of the fractional Josephson effect, which is expected to emerge from topologically-protected gapless Andreev bound states. We first recall the theoretical background on topological Josephson junctions, then move to the experimental observations. Then, we assess the topological origin of the observed features and conclude with an outlook towards more advanced microwave spectroscopy experiments, currently under development.Comment: Lectures given at the San Sebastian Topological Matter School 2017, published in "Topological Matter. Springer Series in Solid-State Sciences, vol 190. Springer

Об использовании элементов метода ветвей и границ в схемах динамического программирования

Рассматривается возможный способ повышения эффективности алгоритмов по методу динамического программирования при решении условных экстремальных задач с аддитивными целевыми функциями, заданными на дискретных множествах. Основной идеей рассматриваемого способа является сокращение областей определения экстремума при решении рекуррентных уравнений Беллмана путем сравнения текущих значений функции Беллмана с рекордом, аналогично схеме метода ветвей и границ

Moving from contractor to owner operator: Impact on safety culture; a case study

Purpose – The purpose of this paper is to investigate whether a change in staffing contractual arrangements, specific training in hazard identification, mentoring of supervisors and the introduction of a robust safety system could improve an organisation\u27s safety culture. How safety conditions change under contracted out labour compared to direct labour and the influence that contracting out has on organisational safety culture is explored. Design/methodology/approach – The study used a case study methodology to detail how the change occurred over a six month period in 2011. As part of the analysis a model of the change process and push-pull factors is offered. Findings – As a result of the change, all areas saw some improvement. Work-related injury statistics dropped significantly, supervisors were clear of their roles, actively monitoring their crews to ensure they worked in a safer manner than before, and staff were actively addressing work-place hazards. With the safety system in place the organisation should be deemed compliant and diligent by the state auditing authorities. This study has also shown that using contractor workers together with in-house workers that are managed under different safety regimes is problematic. The problems don’t occur due to the contractor\u27s safety systems being less robust than the parent company\u27s or that contract workers are themselves less safe; it is the added complexity of managing multiple safety regimes and the lack of trust of the robustness of each system that create conflict. Research limitations/implications – The paper reports on the change process of one mining organisation in Western Australia as a case study from a managerial sample and is thereby limited. Practical implications – This study demonstrates the difficulties in changing safety culture in an underground mining organisation. The paper argues the need for specialised training in identifying hazards by the staff, the mentoring of supervisory staff and the adoption of a robust safety system to support improved safety culture. Originality/value – There is little research conducted in the resources sector researching changes in human resource supply and OHS management, in particular moving from contracted labour to hiring in-house. This case provides an insight into how a change in staffing hiring arrangements, together with specific safety initiatives, has a positive impact on safety performance

Brazilian cave heritage under siege

info:eu-repo/semantics/publishe

Thermal stability of the 'cave' mineral ardealite Ca2(HPO4)(SO4).4H2O

Thermogravimetry combined with evolved gas mass spectrometry has been used to characterise the mineral ardealite and to ascertain the thermal stability of this ‘cave’ mineral. The mineral ardealite Ca2(HPO4)(SO4)•4H2O is formed through the reaction of calcite with bat guano. The mineral shows disorder and the composition varies depending on the origin of the mineral. Thermal analysis shows that the mineral starts to decompose over the temperature range 100 to 150°C with some loss of water. The critical temperature for water loss is around 215°C and above this temperature the mineral structure is altered. It is concluded that the mineral starts to decompose at 125°C, with all waters of hydration being lost after 226°C. Some loss of sulphate occurs over a broad temperature range centred upon 565°C. The final decomposition temperature is 823°C with loss of the sulphate and phosphate anions

Thermal stability of crandallite CaAl3(PO4)2(OH)5.(H2O) A 'Cave' mineral from the Jenolan Caves

Thermogravimetry combined with evolved gas mass spectrometry has been used to characterise the mineral crandallite CaAl3(PO4)2(OH)5•(H2O) and to ascertain the thermal stability of this ‘cave’ mineral. X-ray diffraction proves the presence of the mineral and identifies the products after thermal decomposition. The mineral crandallite is formed through the reaction of calcite with bat guano. Thermal analysis shows that the mineral starts to decompose through dehydration at low temperatures at around 139°C while dehydroxylation occurs over the temperature range 200 to 700°C with loss of OH units. The critical temperature for OH loss is around 416°C and above this temperature the mineral structure is altered. Some minor loss of carbonate impurity occurs at 788°C. This study shows the mineral is unstable above 139°C. This temperature is well above the temperature in caves, which have a maximum temperature of 15°C. A chemical reaction for the synthesis of crandallite is offered and the mechanism for the thermal decomposition is given