The Road to Stueckelberg's Covariant Perturbation Theory as Illustrated by Successive Treatments of Compton Scattering

We review the history of the road to a manifestly covariant perturbative calculus within quantum electrodynamics from the early semi-classical results of the mid-twenties to the complete formalism of Stueckelberg in 1934. We chose as our case study the calculation of the cross-section of the Compton effect. We analyse Stueckelberg's paper extensively. This is our first contribution to a study of his fundamental contributions to the theoretical physics of twentieth century.Comment: This paper is a "working-physicist" version of a paper to be published in Studies in History and Philosophy of Modern Physic

Angiotensin II type 1 receptor antagonists alleviate muscle pathology in the mouse model for laminin-alpha2-deficient congenital muscular dystrophy (MDC1A)

BACKGROUND: Laminin-alpha2-deficient congenital muscular dystrophy (MDC1A) is a severe muscle-wasting disease for which no curative treatment is available. Antagonists of the angiotensin II receptor type 1 (AT1), including the anti-hypertensive drug losartan, have been shown to block also the profibrotic action of transforming growth factor (TGF)-beta and thereby ameliorate disease progression in mouse models of Marfan syndrome. Because fibrosis and failure of muscle regeneration are the main reasons for the severe disease course of MDC1A, we tested whether L-158809, an analog derivative of losartan, could ameliorate the dystrophy in dyW/dyW mice, the best-characterized model of MDC1A. METHODS: L-158809 was given in food to dyW/dyW mice at the age of 3 weeks, and the mice were analyzed at the age of 6 to 7 weeks. We examined the effect of L-158809 on muscle histology and on muscle regeneration after injury as well as the locomotor activity and muscle strength of the mice. RESULTS: We found that TGF-beta signaling in the muscles of the dyW/dyW mice was strongly increased, and that L-158809 treatment suppressed this signaling. Consequently, L-158809 reduced fibrosis and inflammation in skeletal muscle of dyW/dyW mice, and largely restored muscle regeneration after toxin-induced injury. Mice showed improvement in their locomotor activity and grip strength, and their body weight was significantly increased. CONCLUSION: These data provide evidence that AT1 antagonists ameliorate several hallmarks of MDC1A in dyW/dyW mice, the best-characterized mouse model for this disease. Because AT1 antagonists are well tolerated in humans and widely used in clinical practice, these results suggest that losartan may offer a potential future treatment of patients with MDC1A

Geodetic displacements and aftershocks following the 2001 M_w = 8.4 Peru earthquake: Implications for the mechanics of the earthquake cycle along subduction zones

We analyzed aftershocks and postseismic deformation recorded by the continuous GPS station AREQ following the M_w = 8.4, 23 June 2001 Peru earthquake. This station moved by 50 cm trenchward, in a N235°E direction during the coseismic phase, and continued to move in the same direction for an additional 15 cm over the next 2 years. We compare observations with the prediction of a simple one-dimensional (1-D) system of springs, sliders, and dashpot loaded by a constant force, meant to simulate stress transfer during the seismic cycle. The model incorporates a seismogenic fault zone, obeying rate-weakening friction, a zone of deep afterslip, the brittle creep fault zone (BCFZ) obeying rate-strengthening friction, and a zone of viscous flow at depth, the ductile fault zone (DFZ). This simple model captures the main features of the temporal evolution of seismicity and deformation. Our results imply that crustal strain associated with stress accumulation during the interseismic period is probably not stationary over most of the interseismic period. The BCFZ appears to control the early postseismic response (afterslip and aftershocks), although an immediate increase, by a factor of about 1.77, of ductile shear rate is required, placing constraints on the effective viscosity of the DFZ. Following a large subduction earthquake, displacement of inland sites is trenchward in the early phase of the seismic cycle and reverse to landward after a time t i for which an analytical expression is given. This study adds support to the view that the decay rate of aftershocks may be controlled by reloading due to deep afterslip. Given the ratio of preseismic to postseismic viscous creep, we deduce that frictional stresses along the subduction interface account for probably 70% of the force transmitted along the plate interface

Social Competence, Transition Plans and Children with Learning Disabilities

Social competence is the ability to use the appropriate social skills in every aspect of life. For children with learning disabilities, it is a difficult skill to master. These children have trouble with communicating, following directions, listening and completing a task, which can cause problems in the classroom and in adulthood. Yet, these skills are rarely addressed on the individual education and transition plans for these students. The purpose of this paper is to explore the characteristics of children who have learning disabilities and social competence deficits. The difficulties of social competence are examined through the definition of this skill, classroom implications, complications in adolescence/adulthood and a discussion of the importance of adding social skills training to the curriculum

Workmen\u27s Compensation

Covers cases on a wife\u27s loss of consortium under destruction of common law remedies, on the limitation of the time to file a claim related to a doctor\u27s duty to inform an injured worker of his rights, and on the immunity provision of an employer that has no employees and the right to subscribe to benefits

Retaining Students to Completion: A Qualitative Study of Institutional Factors

Retaining students until they complete their qualifications is one of the main aims of many higher education institutions. Retention of students is also looked at from different perspectives in the literature. This small, exploratory, narrative enquiry research looks into the experiences of twenty-one domestic students during their first year and a half of a three-year bachelor’s degree at a New Zealand university. The same researcher conducted all the interviews, which were recorded, transcribed and imported to Nvivo for thematic analysis. The researcher attempted to draw comparisons between the students who withdrew from the university within the first year and a half and those who did not in order to gain a deeper understanding of the institutional factors which may be involved in retention of students. Four main themes were found in the interview data, relating to expectations for student effort, guidance provided by instructors, feedback provided on assignments and consistency, which seemed to be significant to the university experience for many students

Quantum κ\kappa-Poincare in Any Dimensions

The $\kappa$-deformation of the D-dimensional Poincar\'e algebra $(D\geq 2)$ with any signature is given. Further the quadratic Poisson brackets, determined by the classical $r$-matrix are calculated, and the quantum Poincar\'e group "with noncommuting parameters" is obtained.Comment: (PLAIN TeX, 10 pp.

Bicrossproduct structure of κ\kappa-Poincare group and non-commutative geometry

We show that the $\kappa$-deformed Poincar\'e quantum algebra proposed for elementary particle physics has the structure of a Hopf agebra bicrossproduct U(so(1,3))\cobicross T. The algebra is a semidirect product of the classical Lorentz group $so(1,3)$ acting in a deformed way on the momentum sector $T$. The novel feature is that the coalgebra is also semidirect, with a backreaction of the momentum sector on the Lorentz rotations. Using this, we show that the $\kappa$-Poincar\'e acts covariantly on a $\kappa$-Minkowski space, which we introduce. It turns out necessarily to be deformed and non-commutative. We also connect this algebra with a previous approach to Planck scale physics.Comment: 12 pages. Revision: minor typos correcte