Electron-deuteron scattering in a current-conserving description of relativistic bound states: formalism and impulse approximation calculations

The electromagnetic interactions of a relativistic two-body bound state are formulated in three dimensions using an equal-time (ET) formalism. This involves a systematic reduction of four-dimensional dynamics to a three-dimensional form by integrating out the time components of relative momenta. A conserved electromagnetic current is developed for the ET formalism. It is shown that consistent truncations of the electromagnetic current and the $NN$ interaction kernel may be made, order-by-order in the coupling constants, such that appropriate Ward-Takahashi identities are satisfied. A meson-exchange model of the $NN$ interaction is used to calculate deuteron vertex functions. Calculations of electromagnetic form factors for elastic scattering of electrons by deuterium are performed using an impulse-approximation current. Negative-energy components of the deuteron's vertex function and retardation effects in the meson-exchange interaction are found to have only minor effects on the deuteron form factors.Comment: 42 pages, RevTe

Relativistic three-body bound states and the reduction from four to three dimensions

Beginning with an effective field theory based upon meson exchange, the Bethe-Salpeter equation for the three-particle propagator (six-point function) is obtained. Using the one-boson-exchange form of the kernel, this equation is then analyzed using time-ordered perturbation theory, and a three-dimensional equation for the propagator is developed. The propagator consists of a pre-factor in which the relative energies are fixed by the initial state of the particles, an intermediate part in which only global propagation of the particles occurs, and a post-factor in which relative energies are fixed by the final state of the particles. The pre- and post-factors are necessary in order to account for the transition from states where particles are off their mass shell to states described by the global propagator with all of the particle energies on shell. The pole structure of the intermediate part of the propagator is used to determine the equation for the three-body bound state: a Schr{\"o}dinger-like relativistic equation with a single, global Green's function. The role of the pre- and post-factors in the relativistic dynamics is to incorporate the poles of the breakup channels in the initial and final states. The derivation of this equation by integrating over the relative times rather than via a constraint on relative momenta allows the inclusion of retardation and dynamical boost corrections without introducing unphysical singularities.Comment: REVTeX, 21 pages, 4 figures, epsf.st

Comparison of microanalytical methods for estimating H20 contents of silicic volcanic glasses

Three methods of estimating H20 contents of geologic glasses are compared: (1) ion microprobe analysis (secondary ion mass spectrometry), (2) Fourier-transform infrared spectroscopy (FTIR), and (3) electron microprobe analysis using the Na decay-curve method. Each analytical method has its own advantages under certain conditions, depending on the relative importance of analytical accuracy, precision, sensitivity, spatial resolution,and convenience, and each is capable of providing reasonably accurate estimates of the H20, or total volatile, content of geologic glasses. The accuracy of ion microprobe analyses depends critically on the availability of well-characterized hydrous standard glasses. Precision is often better than 0,2 wt% (10). The method provides good spatial resolution (-15 #m) and the capability to determine simultaneously the abundance of other volatile species of interest (e.g., F, B). FTIR spectroscopy provides excellent analytical sensitivity (-10 ppm), accuracy and precision «0.1 wt%), and the capability to determine the abundance of H20 and C02 species (H20, OH-, C02' eOj-) in analyzed glasses, although the spatial resolution (> 25-35 #m) is not as good as that of the ion microprobe. The main advantages of the estimation of H20 contents of hydrous glasses using the electron microprobe are excellent spatial resolution (- 10 #m) and analytical convenience. The disadvantages are that accuracy and precision (>0.5 wt%) are not as good as those associated with the other methods, but, for certain applications, these uncertainties may be acceptable for the estimation of H20 contents of H20-rich (> 1 wt%) samples

Becoming a (green) identity entrepreneur: learning to negotiate situated identities to nurture community environmental practice

This paper explores the relationship between ‘green’ identity and community environmental practice. It focuses on the ways in which professional community development facilitators and lead members of community groups attempt to actively shape how environmental projects are locally received. Drawing principally on identity, social sustainability and social practice theory scholarship, it reviews the often very personal and place-specific ways in which appeals to green identity are variously understood and applied, or are actively avoided, by community group leaders. Individuals who have become skilful in negotiating and influencing the presentation of environmental projects to the local community are understood here as (green) identity entrepreneurs. Arguably, it is the situated entrepreneurial skilfulness of lead individuals in negotiating the multiple and evolving (green) identities circulating through any one project, which plays a significant part in determining its subsequent impact and longevity. In understanding the contribution of (green) identity entrepreneurship, however, its relational association with everyday practices, routines and meanings of community and place is brought to the fore. The paper also considers how divergent external interpretations of what constitutes legitimate environmental practice at a local level further shape project identity. The discussion is informed by evidence drawn from a qualitative study of seventeen community groups and seven professional environmental support officers participating in a Welsh Government led programme aimed at facilitating 'community action on climate change'

Monitoring SO2 emission at the Soufriere Hills Volcano: implications for changes in erruptive conditions

FLWINinfo:eu-repo/semantics/publishe

Hot and cool executive function and its relation to theory of mind in children with and without autism spectrum disorder

Previous research has clearly demonstrated that Autism Spectrum Disorder (ASD) involves deficits in multiple neuropsychological functions, such as Executive Function (EF) and Theory of Mind (ToM). A conceptual distinction is commonly made between cool and hot EF. In ASD, continued attention has been paid to the cool areas of executive dysfunction. Cool EF has been strongly related to ToM but research has not taken into account the association between hot EF and ToM in ASD. The present study investigates the associations between hot and cool EF and ToM in 56 school-aged children with ASD and 69 controls on tasks tapping cool EF (i.e. working memory, inhibition, planning), hot EF (i.e. affective decision making, delay discounting), and ToM (i.e. mental state/ emotion recognition and false belief). Significant group differences in each EF measure support an executive dysfunction in both domains in ASD. Strong associations between delay discounting and ToM mental state/ emotion recognition are reported suggesting that hot EF makes a unique contribution to ToM above and beyond cool EF in typical development and ASD. This study improves understanding of the profile of higher-order cognitive deficits in children with ASD, which may inform diagnosis and intervention

Nonperturbative study of generalized ladder graphs in a \phi^2\chi theory

The Feynman-Schwinger representation is used to construct scalar-scalar bound states for the set of all ladder and crossed-ladder graphs in a \phi^2\chi theory in (3+1) dimensions. The results are compared to those of the usual Bethe-Salpeter equation in the ladder approximation and of several quasi-potential equations. Particularly for large couplings, the ladder predictions are seen to underestimate the binding energy significantly as compared to the generalized ladder case, whereas the solutions of the quasi-potential equations provide a better correspondence. Results for the calculated bound state wave functions are also presented.Comment: 5 pages revtex, 3 Postscripts figures, uses epsf.sty, accepted for publication in Physical Review Letter

Substantiating a political public sphere in the Scottish press : a comparative analysis

This article uses content analysis to characterize the performance of the media in a national public sphere, by setting apart those qualities that typify internal press coverage of a political event. The article looks at the coverage of the 1999 devolved Scottish election from the day before the election until the day after. It uses a word count to measure the election material in Scottish newspapers the Herald, the Press and Journal and the Scotsman, and United Kingdom newspapers the Guardian, the Independent and The Times, and categorizes that material according to discourse type, day and page selection. The article finds a number of qualities that typify the Scottish sample in particular, and might be broadly indicative of a political public sphere in action. Firstly, and not unexpectedly, it finds that the Scottish newspapers carry significantly more election coverage. Just as tellingly, though, the article finds that the Scottish papers offer a greater proportion of advice and background information, in the form of opinion columns and feature articles. It also finds that the Scottish papers place a greater concentration of both informative and evaluative material in the period before the vote, consistent with their making a contribution to informed political action. Lastly, the article finds that the Scottish sample situates coverage nearer the front of the paper and places a greater proportion on recto pages. The article therefore argues that the Scottish papers display features that distinguish them from the UK papers, and are broadly consistent with their forming part of a deliberative public sphere, and suggests that these qualities might be explored as a means of judging future media performance

Thermal expansion, heat capacity and magnetostriction of RAl3_3 (R = Tm, Yb, Lu) single crystals

We present thermal expansion and longitudinal magnetostriction data for cubic RAl3 (R = Tm, Yb, Lu) single crystals. The thermal expansion coefficient for YbAl3 is consistent with an intermediate valence of the Yb ion, whereas the data for TmAl3 show crystal electric field contributions and have strong magnetic field dependencies. de Haas-van Alphen-like oscillations were observed in the magnetostriction data of YbAl3 and LuAl3, several new extreme orbits were measured and their effective masses were estimated. Zero and 140 kOe specific heat data taken on both LuAl3 and TmAl3 for T < 200 K allow for the determination of a CEF splitting scheme for TmAl3