Cellular automaton model of precipitation/dissolution coupled with solute transport

Precipitation/dissolution reactions coupled with solute transport are modelled as a cellular automaton in which solute molecules perform a random walk on a regular lattice and react according to a local probabilistic rule. Stationary solid particles dissolve with a certain probability and, provided solid is already present or the solution is saturated, solute particles have a probability to precipitate. In our simulation of the dissolution of a solid block inside uniformly flowing water we obtain solid precipitation downstream from the original solid edge, in contrast to the standard reaction-transport equations. The observed effect is the result of fluctuations in solute density and diminishes when we average over a larger ensemble. The additional precipitation of solid is accompanied by a substantial reduction in the relatively small solute concentration. The model is appropriate for the study of the r\^ole of intrinsic fluctuations in the presence of reaction thresholds and can be employed to investigate porosity changes associated with the carbonation of cement.Comment: LaTeX file, 13 pages. To appear in Journal of Statistical Physics (Proceedings of Lattice Gas'94, June 1994, Princeton). Figures available from author. Requests may be submitted by E-mail ([email protected]) or ordinary mail (Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland

OCCUPATIONAL EXPOSURE TO EXTERNAL RADIATION IN SWITZERLAND.

Individual monitoring for both external and internal exposures is well regulated in Switzerland. The article gives an overview on the occupational exposure to external radiation of workers based on the data collected in the Swiss national dose registry (NDR) in 2013. The NDR records the monthly doses of radiation workers since the introduction of ICRP 60 recommendations and is manifested in the Swiss ordinance since 1994. Annual dose limits for effective dose are typically exceeded once a year in Switzerland, mostly in medicine. The NDR is a useful optimisation tool to identify and characterise areas with the highest exposures. While exceeded dose limits were often related to accidental acute exposure in the past, they are now more related to continuous exposure during normal work, especially in medicine

Origin of the Critical Thickness in Improper Ferroelectric Thin Films

Improper ferroelectrics are expected to be more robust than conventional ferroelectrics against depolarizing field effects and to exhibit a much-desired absence of critical thickness. Recent studies, however, revealed the loss of ferroelectric response in epitaxial improper ferroelectric thin films. Here, we investigate improper ferroelectric hexagonal YMnO3 thin films and find that the polarization suppression, and hence functionality, in the thinner films is due to oxygen off-stoichiometry. We demonstrate that oxygen vacancies form on the film surfaces to provide the necessary charge to screen the large internal electric field resulting from the positively charged YMnO3 surface layers. Additionally, we show that by modifying the oxygen concentration of the films, the phase transition temperatures can be substantially tuned. We anticipate that our findings are also valid for other ferroelectric oxide films and emphasize the importance of controlling the oxygen content and cation oxidation states in ferroelectrics for their successful integration in nanoscale applications.ISSN:1944-8244ISSN:1944-825

Current practice of transitional care for adolescents and young adults in Swiss paediatric and adult rheumatology centres.

About half of all children with rheumatic diseases need continuous medical care during adolescence and adulthood. A good transition into adult rheumatology is essential. Guidelines for a structured transition process have therefore been recommended by the European League Against Rheumatism (EULAR) and the Paediatric Rheumatology European Society (PReS). However, implementation of these guidelines requires resources often not available in a busy clinical practice. To assess the current practice of transitional care in Switzerland in relation to EULAR/PReS recommendations and to describe gaps and challenges in following the recommendations. All paediatric Swiss rheumatology centres and their collaborating adult centres offering a transition service to adult care were invited to participate in this survey. The responsible paediatric and adult rheumatologist of each centre was interviewed separately using a structured manual addressing the EULAR/PReS transitional care recommendations. All 10 paediatric and 9 out of 10 adult rheumatologists agreed to participate. Centres varied in the number of patients in transition, from n = 0 to n = 111. The following EULAR/PReS recommendations were implemented and applied in most centres: continuity in the healthcare team, consultations focused on adolescents and young adults, joint consultations between the paediatric and adult rheumatologist, and access to the EULAR website. Only rarely did a centre have a written transition policy or evaluate their transitional care programme. The vast majority of the interviewees had no specific training in adolescent health. Most centres rated their transitional care performance as very good. Transition in Switzerland is not uniform and consequently the implementation of the EULAR/PReS recommendations is variable in Swiss rheumatology centres. Skills of healthcare professionals, continuity between clinical settings, size of the centres, and hospital focus on the needs of adolescents and young adults may represent key predictors of successful transitional care for patients with chronic rheumatic diseases. Future studies should examine these variables

Development of High-Specificity Fluorescent Probes to Enable Cannabinoid Type 2 Receptor Studies in Living Cells

Pharmacological modulation of cannabinoid type 2 receptor (CB2R) holds promise for the treatment of numerous con-ditions, including inflammatory diseases, autoimmune disorders, pain, and cancer. Despite the significance of this re-ceptor, researchers lack reliable tools to address questions concerning the expression and complex mechanism of CB2R signaling, especially in cell-type and tissue-dependent context. Herein, we report for the first time a versatile ligand platform for the modular design of a collection of highly specific CB2R fluorescent probes, used successfully across ap-plications, species and cell types. These include flow cytometry of endogenously expressing cells, real-time confocal microscopy of mouse splenocytes and human macrophages, as well as FRET-based kinetic and equilibrium binding assays. High CB2R specificity was demonstrated by competition experiments in living cells expressing CB2R at native levels. The probes were effectively applied to FACS analysis of microglial cells derived from a mouse model relevant to Alzheimer's disease