Radio Astronomical Polarimetry and the Lorentz Group

In radio astronomy the polarimetric properties of radiation are often modified during propagation and reception. Effects such as Faraday rotation, receiver cross-talk, and differential amplification act to change the state of polarized radiation. A general description of such transformations is useful for the investigation of these effects and for the interpretation and calibration of polarimetric observations. Such a description is provided by the Lorentz group, which is intimately related to the transformation properties of polarized radiation. In this paper the transformations that commonly arise in radio astronomy are analyzed in the context of this group. This analysis is then used to construct a model for the propagation and reception of radio waves. The implications of this model for radio astronomical polarimetry are discussed.Comment: 10 pages, accepted for publication in Astrophysical Journa

High resolution characterisation of microstructural evolution in Rbx_{x}Fe2−y_{2-y}Se2_{2} crystals on annealing

The superconducting and magnetic properties of phase-separated A$_x$Fe$_{2-y}$Se$_2$ compounds are known to depend on post-growth heat treatments and cooling profiles. This paper focusses on the evolution of microstructure on annealing, and how this influences the superconducting properties of Rb$_x$Fe$_2-y$Se$_2$ crystals. We find that the minority phase in the as-grown crystal has increased unit cell anisotropy (c/a ratio), reduced Rb content and increased Fe content compared to the matrix. The microstructure is rather complex, with two-phase mesoscopic plate-shaped features aligned along {113} habit planes. The minority phase are strongly facetted on the {113} planes, which we have shown to be driven by minimising the volume strain energy introduced as a result of the phase transformation. Annealing at 488K results in coarsening of the mesoscopic plate-shaped features and the formation of a third distinct phase. The subtle differences in structure and chemistry of the minority phase(s) in the crystals are thought to be responsible for changes in the superconducting transition temperature. In addition, scanning photoemission microscopy has clearly shown that the electronic structure of the minority phase has a higher occupied density of states of the low binding energy Fe3d orbitals, characteristic of crystals that exhibit superconductivity. This demonstrates a clear correlation between the Fe-vacancy-free phase with high c/a ratio and the electronic structure characteristics of the superconducting phase.Comment: 6 figures v2 is exactly the same as v1. The typesetting errors in the abstract have been correcte

Concealed concern: Fathers' experience of having a child with Juvenile Idiopathic Arthritis

Despite increased research into families of chronically ill children, more needs to be known about the father’s experience. We address this issue through asking: ‘What is it like to be the father of a child with juvenile idiopathic arthritis?’ (JIA). Four members of eight families with an adolescent diagnosed with JIA, including seven fathers, were interviewed and transcripts analyzed using grounded theory. This study suggests that fathers of children with JIA experience several severe losses which are exacerbated through comparisons they make between their own situation and that of fathers of healthy children. In addition, the fathers faced several constraints which reduced their opportunities to communicate with their ill child through shared activities. Fathers appeared to conceal their distress by adopting strategies of denial and distraction however their adjustment was facilitated, to some extent, by social support. They could also develop greater acceptance of their situation over time as the care of their ill child became assimilated into family life and constraints upon their life gradually reduced through the increased maturity of their son or daughter with JIA. These findings have implications for healthcare professionals and voluntary organizations

Repair of Failing Spirit Lake Outlet Tunnel at Mount St. Helens

The 18 May 1980 eruption of Mount St. Helens resulted in one of the largest debris avalanches recorded in history. The debris avalanche blocked the natural outlet of Spirit Lake. To prevent an uncontrolled and catastrophic lake break-out, the U.S. Army Corps of Engineers (USACE) constructed the Spirit Lake Outlet Tunnel from 1984 to 1985. Because Spirit Lake is located in the Mount St. Helens National Volcanic Monument, the project was transferred to the U.S. Forest Service (USFS) for ownership and management. During original tunnel construction, the most difficulty occurred within the 90-m-wide Julie and Kathy L. shear zone complex. In 1996, tunnel walls within this complex experienced significant convergence, which required major repair along a 30 m segment. During inspections in 2014 and 2015, a 10 m segment at the upstream end of the complex, which had experienced slow heave in the past, was observed to have experienced an increase in heave of approximately 0.6 m, which decreased the hydraulic capacity of the tunnel below acceptable limits. The USACE, in accordance with and with funding from the USFS, designed a repair based on the rib set-shotcrete support system that was used for the 1996 repair. In addition to removing and arresting the heave, the 2015 repair was sized to be compatible with a future potential rehabilitation involving stabilizing and re-grading the invert profile of the Julie and Kathy L. shear zone complex. The 2015 repair construction contract was awarded in September 2015 for $3 million

Study of a Large NaI(Tl) Crystal

Using a narrow band positron beam, the response of a large high-resolution NaI(Tl) crystal to an incident positron beam was measured. It was found that nuclear interactions cause the appearance of additional peaks in the low energy tail of the deposited energy spectrum

High Purity Pion Beam at TRIUMF

An extension of the TRIUMF M13 low-energy pion channel designed to suppress positrons based on an energy-loss technique is described. A source of beam channel momentum calibration from the decay pi+ --> e+ nu is also described.Comment: 5 page

Is there still a place for the concept of therapeutic regression in psychoanalysis?

The author uses his own failure to find a place for the idea of therapeutic regression in his clinical thinking or practice as the basis for an investigation into its meaning and usefulness. He makes a distinction between three ways the term ‘regression’ is used in psychoanalytic discourse: as a way of evoking a primitive level of experience; as a reminder in some clinical situations of the value of non-intervention on the part of the analyst; and as a description of a phase of an analytic treatment with some patients where the analyst needs to put aside normal analytic technique in order to foster a regression in the patient. It is this third meaning, which the author terms “therapeutic regression” that this paper examines, principally by means of an extended discussion of two clinical examples of a patient making a so-called therapeutic regression, one given by Winnicott and the other by Masud Khan. The author argues that in these examples the introduction of the concept of therapeutic regression obscures rather than clarifies the clinical process. He concludes that, as a substantial clinical concept, the idea of therapeutic regression has outlived its usefulness. However he also notes that many psychoanalytic writers continue to find a use for the more generic concept of regression, and that the very engagement with the more particular idea of therapeutic regression has value in provoking questions as to what is truly therapeutic in psychoanalytic treatment