Testing conformal mapping with kitchen aluminum foil

We report an experimental verification of conformal mapping with kitchen aluminum foil. This experiment can be reproduced in any laboratory by undergraduate students and it is therefore an ideal experiment to introduce the concept of conformal mapping. The original problem was the distribution of the electric potential in a very long plate. The correct theoretical prediction was recently derived by A. Czarnecki (Can. J. Phys. 92, 1297 (2014))

Il cibo e gli inglesi: una tavola panculinaria

It is common knowledge that in great Britain table manners are more important than the food on the table, and that Britons consider it nobler to have a perfect etiquette than to find the time to cook. Someone could argue that people busy with the building of an Empire have little time to waste on such refined pastimes, but it is only a stereotype, like the one saying that Latins give great importance both to food and to the ways of sharing it. Bernard Shaw once observed that since the English can endure their own cooking, then they can endure absolutely everything. Although the English cuisine may not be a perfect example of culinary arts, according to the author, it can certainly become an emblematic case of the variety of ‘pan-culinary arts’. Being the coloniser, the British Empire brought raw materials and food from the colonies, and dedicated little time to cooking as a way of conquering the world, but it was indeed the colonised who ‘conquered’ the English population by tempting their taste buds. The cuisine resulting from these encounters is presented in the papers of the issue

Spatial confinement of muonium atoms

We report the achievement of spatial confinement of muonium atoms (the bound state of a positive muon and an electron). Muonium emitted into vacuum from mesoporous silica reflects between two SiO$_2$ confining surfaces separated by 1 mm. From the data, one can extract that the reflection probability on the confining surfaces kept at 100 K is about 90% and the reflection process is well described by a cosine law. This technique enables new experiments with this exotic atomic system and is a very important step towards a measurement of the 1S-2S transition frequency using continuous wave laser spectroscopy.Comment: 5 pages, 6 figure

El Taller lítico LY 041-La Divisoria (Departamento Pilcaniyeu, Provincia de Río Negro)

En el taller lítico LY 041-La Divisoria, situado en el sudoeste de la estepa rionegrina, se prepararon artefactos bifaciales en rocas dacíticas procedentes de la cercana cantera Paso Limay. Habría sido un satélite del alero Carriqueo, un pequeño sitio de vivienda muy próximo, del cual se habrían segregado algunas tareas de talla, que generan muchos desechos potencialmente molestos o peligrosos. Además, desde el sitio se tiene buena visibilidad del paisaje. Subsidiariamente, en LY 041-La Divisoria se habrían realizado algunas tareas de procesamiento de materiales orgánicos. Este sitio corrobora que para los cazadores-recolectores de la comarca, la cantera Paso Limay tuvo un papel central en el aprovisionamiento de roca para puntas de proyectil.LY 041-La Divisoria is a lithic workshop in the southwestern steppe of the Río Negro Province, Argentina, where dacite brought from the Paso Limay quarry was reduced bifacially. This workshop would have been a satellite of close-by Carriqueo rockshelter, a small living cite from which certain tasks were sometimes shifted because they generated encumbering refuse. LY 041-La Divisoria provided also a good view of the environment. Subsidiarily, some processing of organic materials was carried out. LY 041-La Divisoria corroborates that for the local hunter-gatherers, the Paso Limay quarry was of major importance for the provisioning of raw material for projectile-points.Fil: Crivelli Montero, Eduardo A. . Universidad de Buenos AiresFil: Ramos, Mariano S. . Universidad Nacional de Lujá

A new experiment to search for the invisible decay of the orthopositronium

We propose an experiment to search for invisible decays of orthopositronium (o-Ps) with a 90% confidence sensitivity in the branching ratio as low as $10^{-8}$. Evidence for this decay mode would unambigously signal new physics: either the existence of extra--dimensions or fractionally charged particles or new light gauge bosons. The experimental approach and the detector components of the proposed experiment are described.Comment: Based on a talk given at Workshop on Positronium Physics, Zurich, Switzerland, 30-31 May 200

Plus forts ensemble - Swiss School of Public Health

De vénérables écoles de santé publique ont fêté leur 100 e anniversaire au cours des 20 dernières années. En Suisse, la pandémie a pris au dépourvu une institution adolescente - un modèle innovant qui fête son 16 e anniversaire cette année. L'âge adulte a-t-il été atteint

A mathematical model for cell cycle-specific cancer virotherapy

Oncolytic viruses preferentially infect and replicate in cancerous cells, leading to elimination of tumour populations, while sparing most healthy cells. Here, we study the cell cycle-specific activity of viruses such as vesicular stomatitis virus (VSV). In spite of its capacity as a robust cytolytic agent,VSVcannot effectively attack certain tumour cell types during the quiescent, or resting, phase of the cell cycle. In an effort to understand the interplay between the time course of the cell cycle and the specificity of VSV, we develop a mathematical model for cycle-specific virus therapeutics. We incorporate the minimum biologically required time spent in the non-quiescent cell cycle phases using systems of differential equations with incorporated time delays. Through analysis and simulation of the model, we describe how varying the minimum cycling time and the parameters that govern viral dynamics affect the stability of the cancer-free equilibrium, which represents therapeutic success

An Improved Limit on Invisible Decays of Positronium

The results of a new search for positronium decays into invisible final states are reported. Convincing detection of this decay mode would be a strong evid ence for new physics beyond the Standard Model (SM): for example the existence of extra--dimensions, of milli-charged particles, of new light gauge bosons or of mirror particles. Mirror matter could be a relevant dark matter candidate. In this paper the setup and the results of a new experiment are presented. In a collected sample of about $(6.31\pm0.28) \times 10^6$ orthopositronium decay s, no evidence for invisible decays in an energy window [0,80] keV was found and an upper limit on the branching ratio of orthopositronium \invdecay could be set: \binvdecay<4.2\times 10^{-7} (90% C.L.) Our results provide a limit on the photon mirror-photon mixing strength $\epsilon \leq 1.55\times 10^{-7}$ (90% C.L.) and rule out particles lighter than the electron mass with a fraction $Q_x \leq 3.4 \times 10^{-5}$ of the electron charge. Furthermore, upper limits on the branching ratios for the decay of parapositronium $Br(p-Ps\to invisible)\leq 4.3 \times 10^{-7}$ (90% C.L.) and the direct annihilation $Br(e^+e^-\to invisible)\leq 2.1 \times 10^{-8}$ (90% C.L.) could be set.Comment: 17 pages, 7 figures, added references, fixed limit on millicharged particles and changed two plots accordingl

Influence of pre-strain and bake hardening on the static and fatigue strength of a DP600 steel sheet

The influence of pre-strain on the tensile and fatigue properties of a dual phase DP600 steel was studied. The material was pre-strained by uni-axial tension in rolling and transverse direction. Thereafter, specimens were cut from the deformed plates in parallel or orthogonal to pre-strain direction. It was found that pre-strain increases yield and tensile strength. Results suggested that strain path change primarily affects the elastic-plastic transition during early stage of reloading. Pre-strained specimens showed an increase in high cycle regimes as a consequence of yield strength increment, irrespective of imposed pre-straining direction. A modified stress life equation that accounts for pre-strain was proposed and showed good agreement with experimental data. Bake hardening enhanced both tensile and high cycle fatigue resistance. Walker equation was successfully fitted to account for tensile mean stress. In low cycle fatigue, negligible influence of pre-strain was observed due to cyclic softening and residual stress relaxation