Applications of the Bethe-Salpeter equation in nuclear physics

This work reports the study of techniques for solving the Bethe-Salpeter equation with a confinement kernel and reports the foundation of a program for constructing a relativistic model of the hadrons based upon the Bethe-Salpeter equation. The techniques described here represent a solution of the problem of constructing a relativistic model for the mesons. General methods are given for defining a confinement kernel in momentum space, of transforming the confinement kernel into an integrodifferential operator, and for solving the integral equations which result from applying these procedures to the Bethe-Salpeter equation;Momentum space eigenfunctions for charmonium are obtained and found to be large out to momentum values of order 1GeV/c. The expectation values of both a relativistic and non-relativistic velocity operator are found to be greater than 0.48c for all of the states of charmonium investigated. The Lorentz structure of the confinement kernel is determined by a fit to the heavy meson spectra where it is found that inclusion of coupling of positive and negative frequency states appears to rule out a linear confinement kernel which contains a significant vector or pseudoscalar portion

Relativistic Meson Spectroscopy and In-Medium Effects

We extend our earlier model of $q\bar q$ mesons using relativistic quasipotential (QP) wave equations to include open-flavor states and running quark-gluon coupling effects. Global fits to meson spectra are achieved with rms deviations from experiment of 43-50 MeV. We examine in-medium effects through their influence on the confining interaction and predict the confining strength at which the masses of certain mesons fall below the threshold of their dominant decay channel.Comment: 12 Pages, 2 Postscript figures (appended at the end with instructions, available also from [email protected]

Natural succession and clearcutting as drivers of environmental heterogeneity and beta diversity in North American boreal forests

<div><p>Clear-cutting alters natural ecosystem processes by reducing landscape heterogeneity. It is the dominant harvesting technique across the boreal zone, yet understanding of how environmental heterogeneity and beta diversity are structured in forest ecosystems and post-clear cut is lacking. We use ground-dwelling arthropods as models to determine how natural succession (progression from deciduous to mixed to coniferous cover types) and clear-cutting change boreal forests, exploring the role of environmental heterogeneity in shaping beta diversity across multiple spatial scales (<i>between-cover types</i> and <i>between-stands of the same cover type</i> (1600 to 8500 m), <i>between-plots</i> (100 to 400 m) and <i>within-plots</i> (20 to 40 m)). We characterise environmental heterogeneity as variability in combined structural, vegetational and soil parameters, and beta diversity, as variability in assemblage composition. Clear-cutting homogenised forest environments across all spatial scales, reducing total environmental heterogeneity by 35%. Arthropod beta diversity reflected these changes at larger scales suggesting that environmental heterogeneity is useful in explaining beta diversity both <i>between-cover types</i> and <i>between-stands</i> of the same cover type. However, at smaller scales, <i>within-</i> and <i>between-plots</i> spider beta diversity reflected the lower environmental heterogeneity in regenerating stands, whereas staphylinid and carabids assemblages were not homogenised 12 years post-harvest. Differences in environmental heterogeneity and staphylinid beta diversity between cover types were also important at small scales. In regenerating stands, we detected a subtle yet notable effect of pre-felling cover type on environmental heterogeneity and arthropods, where pre-felling cover type accounted for a significant amount of variance in beta diversity, indicating that biological legacies (e.g. soil pH reflecting pre-harvest conditions) may have a role in driving beta diversity even 12 years post-harvest. This study highlights the importance of understanding site history when predicting impacts of change in forest ecosystems. Further, to understand drivers of beta diversity we must identify biological legacies shaping community structure.</p></div

Gender differences in perceived environmental correlates of physical activity

BACKGROUND: Limited research has been conducted on gender differences in perceived environmental correlates of physical activity (PA). The purpose of this study was to explore the potential role of gender in the link between perceived environment and PA. METHODS: Using a telephone-administered survey, data was collected on leisure time physical activity (LTPA), perceptions of the neighbourhood environment, and self-efficacy in a representative sample of 1209 adults from the province of Alberta, Canada. LTPA was regressed on ten measures of perceived neighbourhood environment and self-efficacy in a series of logistic regressions. RESULTS: Women were more likely than men to perceive their neighbourhood as unsafe to go for walks at night (χ(2 )= 67.46, p < 0.001) and to report seeing people being active in their neighbourhood (χ(2 )= 6.73, p < 0.01). Conversely, women were less likely to perceive easy access to places for PA (χ(2 )= 11.50, p < 0.01) and availability of places to buy things within easy walking distance from home (χ(2 )= 4.30, p < 0.05). Adjusting for age, education, income, and place of residence, access to places for PA (OR = 2.49) and interesting things to look at in the neighbourhood (OR = 1.94), were associated with higher levels of LTPA in men. Access to places for PA (OR = 2.63) and reporting seeing people being active (OR = 1.50) were associated with increased LTPA among women. After controlling for sociodemographic variables and self-efficacy, the presence of shops and places to buy things within easy walking distance from home (OR = 1.73), interesting things to look at in the neighbourhood (OR = 1.65), and access to places for PA (OR = 1.82) were associated with higher levels of LTPA in men. Among women, no significant relationships were observed between perceived environment and LTPA after adjusting for self-efficacy. CONCLUSION: The results provide additional support for the use of models in which gender is treated as a potential moderator of the link between the perceived environment and PA. Further, the results suggest the possibility of differential interventions to increase PA based on factors associated with gender

Supramolecular Chemistry: A Capstone Course

A fourth-year capstone course offers students an opportunity to integrate topics covered in the core disciplinary courses, to learn an advanced interdisciplinary topic, and to approach unfamiliar problems and literature. This article describes a fourth-year capstone course designed to incorporate components of faculty lectures, student seminars, and original, hands-on research projects in order to cover the topic of supramolecular chemistry in one semester with unusual depth. This approach should be applicable to other advanced topics in chemistry

Evidence for the intense exchange of MazG in marine cyanophages by horizontal gene transfer

Background: S-PM2 is a phage capable of infecting strains of unicellular cyanobacteria belonging to the genus Synechococcus. S-PM2, like other myoviruses infecting marine cyanobacteria, encodes a number of bacterial-like genes. Amongst these genes is one encoding a MazG homologue that is hypothesized to be involved in the adaption of the infected host for production of progeny phage. Methodology/Principal Findings: This study focuses on establishing the occurrence of mazG homologues in other cyanophages isolated from different oceanic locations. Degenerate PCR primers were designed using the mazG gene of S-PM2. The mazG gene was found to be widely distributed and highly conserved among Synechococcus myoviruses and podoviruses from diverse oceanic provinces. Conclusions/Significance: This study provides evidence of a globally connected cyanophage gene pool, the cyanophage mazG gene having a small effective population size indicative of rapid lateral gene transfer despite being present in a substantial fraction of cyanophage. The Prochlorococcus and Synechococcus phage mazG genes do not cluster with the host mazG gene, suggesting that their primary hosts are not the source of the mazG gene

Moths and Butterflies (Lepidoptera) of the Boreal Mixedwood Forest near Lac La Biche, Alberta, Including New Provincial Records

Lepidoptera were collected, primarily via UV light trap, for three seasons in the boreal mixedwood forest near Lac La Biche, Alberta. A total of 11,111 specimens were collected, representing 41 families and 438 species. A species list with flight times is presented. The total Lepidoptera community was estimated to be 546 ± 23.34 species. Abundance and species richness peaked in late July. Thirty-five species constitute new records for Alberta, while one species, Acanthopteroctetes bimaculata, is a new record for Canada, and the first record of the family Acanthopteroctetidae in Canada

The influence of self-efficacy and outcome expectations on the relationship between perceived environment and physical activity in the workplace

BACKGROUND: Recent research and commentary contends that ecological approaches may be particularly useful for understanding and promoting physical activity participation in various settings including the workplace. Yet within the physical activity domain there is a lack of understanding of how ecological environment factors influence behaviour. Thus, the purpose of this study was to examine the relationships between perceived environment, social-cognitive variables, and physical activity behaviour. METHODS: Participants (N = 897) were employees from three large worksites who completed self-report inventories containing measures of self-efficacy, outcome expectations, perceptions of the workplace environment (PWES), and physical activity behaviour during both leisure-time and incorporated throughout the workday. RESULTS: Results of both bivariate and multiple regression analyses indicated the global PWES scores had a limited association with leisure-time physical activity (R(2)adj =.01). Sequential regression analyses supported a weak association between physical activity incorporated in the workplace and PWES (R(2)adj = .04) and the partial mediation of self-efficacy on the relationship between PWES and workplace physical activity (variance accounted for reduced to R(2)adj = .02 when self-efficacy was controlled). CONCLUSION: Overall, the results of the present investigation indicate that self-efficacy acted as a partial mediator of the relationship between perceived environment and workplace physical activity participation. Implications of the findings for physical activity promotion using ecological-based approaches, and future directions for research from this perspective in worksite settings are discussed