Variational Formulation of Macro-Particle Models for Electromagnetic Plasma Simulations

A variational method is used to derive a self-consistent macro-particle model for relativistic electromagnetic kinetic plasma simulations. Extending earlier work [E. G. Evstatiev and B. A. Shadwick, J. Comput. Phys., vol. 245, pp. 376-398, 2013], the discretization of the electromagnetic Low Lagrangian is performed via a reduction of the phase-space distribution function onto a collection of finite-sized macro-particles of arbitrary shape and discretization of field quantities onto a spatial grid. This approach may be used with both lab frame coordinates or moving window coordinates; the latter can greatly improve computational efficiency for studying some types of laser-plasma interactions. The primary advantage of the variational approach is the preservation of Lagrangian symmetries, which in our case leads to energy conservation and thus avoids difficulties with grid heating. Additionally, this approach decouples particle size from grid spacing and relaxes restrictions on particle shape, leading to low numerical noise. The variational approach also guarantees consistent approximations in the equations of motion and is amenable to higher order methods in both space and time. We restrict our attention to the 1-1/2 dimensional case (one coordinate and two momenta). Simulations are performed with the new models and demonstrate energy conservation and low noise.Comment: IEEE Transaction on Plasma Science (TPS) Special Issue: Plenary and Invited Papers of the Pulsed Power and Plasma Science Conference (PPPS 2013

Joining wood by friction welding

At the Chair of Timber Constructions of the Swiss Federal Institute of Technology in Lausanne (EPFL) tests were carried out to join wooden work pieces by friction welding without any additional welding deposit. It could be determined that this kind of technology, which is mainly used for thermoplastics and metal, can also be applied to wood. Tests were carried out to determine the influence of the processing parameters like welding pressure, frequency and amplitude of the circular movement on the welding process and the input of energy at the interface. In addition, the resistance of the joint was examined. The development of the shear strength during solidification of the interface as well as the shear strength achievable after a complete solidification of the interface was the objective of the examinations. Furthermore, the microstructure of the welded joint was studied to reveal the manner in which the thermally decomposed wood forms the connection between the welded piece

Reliability Analysis of River Levees Using Logistic Regression Models – Abilities and Limitations

Source: ICHE Conference Archive - https://mdi-de.baw.de/icheArchiv

Möglichkeiten zur Attraktivitätssteigerung der Hausarztmedizin aus der Sicht junger Ärztinnen und Ärzte

Hintergrund: Ziel der Studie ist es zu untersuchen, welche berufliche Laufbahn junge Ärztinnen und Ärzte gegen Ende ihrer fachärztlichen Weiterbildung anstreben und welche Faktoren aus ihrer Sicht eine Tätigkeit in der ärztlichen Grundversorgung attraktiver machen könnten. Methodik: Im Rahmen einer seit 2001 laufenden Schweizer prospektiven Studie zu Determinanten der Karriereentwicklung nahmen 534 junge Ärztinnen und Ärzte im Jahr 2007 an der vierten Befragung teil. Sie machten Angaben zur angestrebten beruflichen Laufbahn, zum geplanten Praxismodell und Praxisstandort, ferner benannten sie Faktoren, die für bzw. gegen die Hausarztmedizin sprechen und welche die Attraktivität der Hausarztmedizin steigern würden. Ergebnisse: 84 Personen (42% Männer, 58% Frauen) streben eine Tätigkeit als Hausarzt/-ärztin an (60% spezialisieren sich in Allgemeinmedizin, 40% in Allgemeiner Innerer Medizin), 450 spezialisieren sich in einem anderen Fachgebiet. Von den 534 Studienteilnehmenden möchten 208 später in einer Praxis arbeiten, mehrheitlich in einer Gruppenpraxis (88%). 49% der zukünftigen Hausärzte planen eine Praxis in einer Stadt, von den Spezialisten sind es 77%. Als wesentliche Gründe gegen die Hausarztmedizin werden die unsichere Entwicklung der Hausarztmedizin und das niedrige Einkommen genannt, als positive Faktoren die Vielseitigkeit, das breite Patientenspektrum sowie die Kontinuität der Arzt-Patient-Beziehung. Um die Attraktivität der Hausarztmedizin zu steigern, müssten interdisziplinäre Gruppenpraxen gefördert und die finanziellen Rahmenbedingungen verbessert werden. Schlussfolgerung: Die Hausarztmedizin wird als interessantes Berufsfeld eingeschätzt, die gegenwärtigen Rahmenbedingungen für die Ausübung der hausärztlichen Tätigkeit wirken jedoch abschreckend

The Activity of the Serotonin Receptor 2C is Regulated by Alternative Splicing

The central nervous system-specific serotonin receptor 2C (5HT2C) controls key physiological functions, such as food intake, anxiety, and motoneuron activity. Its deregulation is involved in depression, suicidal behavior, and spasticity, making it the target for antipsychotic drugs, appetite controlling substances, and possibly anti-spasm agents. Through alternative pre-mRNA splicing and RNA editing, the 5HT2C gene generates at least 33 mRNA isoforms encoding 25 proteins. The 5HT2C is a G-protein coupled receptor that signals through phospholipase C, influencing the expression of immediate/early genes like c-fos. Most 5HT2C isoforms show constitutive activity, i.e., signal without ligand binding. The constitutive activity of 5HT2C is decreased by pre-mRNA editing as well as alternative pre-mRNA splicing, which generates a truncated isoform that switches off 5HT2C receptor activity through heterodimerization; showing that RNA processing regulates the constitutive activity of the 5HT2C system. RNA processing events influencing the constitutive activity target exon Vb that forms a stable double stranded RNA structure with its downstream intron. This structure can be targeted by small molecules and oligonucleotides that change exon Vb alternative splicing and influence 5HT2C signaling in mouse models, leading to a reduction in food intake. Thus, the 5HT2C system is a candidate for RNA therapy in multiple models of CNS disorders

Caging Targets for Destruction

Intracellular bacterial pathogens engage in a tug-of-war with innate host defenses. In this issue of Cell Host & Microbe, Mostowy et al. (2010) identify a role for the septin family of cytoskeletal proteins in targeting intracellular Shigella to the autophagy pathway

Optimization of delivery adherence based on capacity planning and bid pricing

Sales revenues of enterprises are often subject to seasonal fluctuation. This leads to high or low utilized resources and this in turn to revenue losses. Hence, the enterprises invest a high effort to improve long and short-term resource utilization. In this context, disregarding future capacity utilization within the process of quotation leads to short-timed capacity adjustments for instance, additional work hours across seasons. This paper presents an approach which focuses on dependencies between costs and capacity by linking cost pricing and production scheduling. A first evaluation at an MTO supplier shows that order delays can be reduced by up to 95% and total costs by 21% compared to using the most appropriate priority rule