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

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

Hot electron driven enhancement of spin-lattice coupling in 4f ferromagnets observed by femtosecond x-ray magnetic circular dichroism

Femtosecond x-ray magnetic circular dichroism was used to study the time-dependent magnetic moment of 4 fs electrons in the ferromagnets Gd and Tb, which are known for their different spin-lattice coupling. We observe a two-step demagnetization with an ultrafast demagnetization time of 750 fs identical for both systems and slower times which differ sizeably with 40 ps for Gd and 8 ps for Tb. We conclude that spin-lattice coupling in the electronically excited state is enhanced up to orders of magnitude compared to equilibrium.Comment: added reference 24, clarified the meaning of photo-induced, emphasized that XMCD probes the magnetic moment localized at 4f electron

Insights into the molecular mechanism of RGL2-mediated inhibition of seed germination in Arabidopsis thaliana

10.1186/1471-2229-12-179BMC Plant Biology12

The relevance of ERTS-1 data to the state of Ohio

There are no author-identified significant results in this report

Work-life conflicts and health among Swiss physicians--in comparison with other university graduates and with the general Swiss working population

QUESTION UNDER STUDY: The present study aimed to compare the prevalence of work-life conflicts and the health status of physicians, with a representative sample of university graduates as well as with a representative sample of the general Swiss working population. Furthermore, it aimed to analyse whether work-life conflicts correlate with the health of physicians, as it does in the general working population. METHODS: The present cross-sectional study analysed data from 2007 originating from the SwissMedCareer Study (a prospective cohort study of physicians who graduated in 2001; n = 543) and the Swiss Household Panel (a representative Swiss survey on living and working conditions; university graduates of the same age range: n = 172, general working population of the same age range: n = 670). Data were analysed with Chi2 tests, correlations and logistic regressions. RESULTS: Physicians reported strong time-based as well as strain-based work-life conflicts more frequently than university graduates and the general working population. Significantly more physicians reported "moderate" to "very poor" health than the other two samples. Surprisingly, on the other side of the scale ("very good" health), physicians outnumbered the other samples too. Strong associations between work-life conflict and self-rated health as well as various health complaints were found for physicians. CONCLUSION: The high prevalence of work-life conflicts may explain the comparably high prevalence of poor self-rated health in the physicians' sample

Dipolar interaction between two-dimensional magnetic particles

We determine the effective dipolar interaction between single domain two-dimensional ferromagnetic particles (islands or dots), taking into account their finite size. The first correction term decays as 1/D^5, where D is the distance between particles. If the particles are arranged in a regular two-dimensional array and are magnetized in plane, we show that the correction term reinforces the antiferromagnetic character of the ground state in a square lattice, and the ferromagnetic one in a triangular lattice. We also determine the dipolar spin-wave spectrum and evaluate how the Curie temperature of an ensemble of magnetic particles scales with the parameters defining the particle array: height and size of each particle, and interparticle distance. Our results show that dipolar coupling between particles might induce ferromagnetic long range order at experimentally relevant temperatures. However, depending on the size of the particles, such a collective phenomenon may be disguised by superparamagnetism.Comment: 11 pages, 5 figure