5,072 research outputs found

    Near-field Response in Lossy Media with Exponential Conductivity Inhomogeneity

    Get PDF
    Abstract-This paper examines the near-field response to source currents in lossy media with exponential conductivity inhomogeneity. The motivation for this work is to understand the modification of the polar ionosphere D region (50-90 km altitude) by powerful high frequency transmitters. The transmitted waves heat the D region plasma, causing a localized conductivity perturbation. In the presence of the DC electric field of the polar electrojet, the conductivity perturbation produces a current perturbation referred to as "antenna current" that can drive extremely/very low frequency radiation. Here we seek to understand the production of antenna current in a strongly inhomogeneous plasma. In the lower D region, the static approximation is valid, and we solve using a scalar potential description. In the upper D region, we use the magnetoquasistatic approximation and solve using a vector potential approach

    Gender, age and the MBA: An analysis of extrinsic and intrinsic career benefits

    Get PDF
    Against the background of an earlier UK study, this paper presents the findings of a Canadian based survey of career benefits from the MBA. Results indicate firstly that gender and age interact to influence perceptions of career outcomes (young men gain most in terms of extrinsic benefits of career change and pay), and secondly that both men and women gain intrinsic benefits from the MBA. However, intrinsic benefits vary by gender: men in the study were more likely to say they gained confidence from having a fuller skill set while women were more likely to say they gained confidence from feelings of self worth; men emphasised how they had learned to give up control while women argued that they had gained a ‘voice’ in the organization. The role of the MBA in career self- management and the acquisition of key skills are examined as well as the implications for the design of programmes in meeting the varied need of men and women in different age groups

    Aboriginal Children and Their Caregivers Living with Low Income: Outcomes from a Two-Generation Preschool Program

    Get PDF
    The development of preschool children of Aboriginal heritage is jeopardized by the inter-generational transmission of risk that has created, and continues to create, social disadvantage. Early intervention programs are intended to mitigate the impact of social disadvantage. Yet, evidence of the effectiveness of these programs for children of Aboriginal heritage is limited. The purpose of this study was to examine the effects of a two-generation, multi-cultural preschool program on 45 children of Aboriginal heritage and their caregivers. We used a single-group, pretest (program intake)/posttest (program exit) design with follow-up when the children were 7 years old. We used an observational measure of child receptive language (Peabody Picture Vocabulary Test–III) and caregiver-reported measures of child development (Nipissing District Developmental Screen), risk for child maltreatment (Adult-Adolescent Parenting Inventory; AAPI), parenting stress (Parenting Stress Index; PSI), self-esteem (Rosenberg Self-Esteem scale; RSE), and life skills (Community Life Skills scale; CLS). Using paired t-tests we found statistically significant increases in child receptive language scores between intake and exit, and repeated-measures ANOVA showed that these improvements were maintained up to age 7 years. For caregivers, Pearson’s correlations demonstrated that risk for child maltreatment, parenting stress, self-esteem, and life skills were stable over time. Results of this study suggest that children of Aboriginal heritage can benefit from participation in a two-generation, multi-cultural preschool program. Their caregivers may have received greater benefit if issues of intergenerational transmission of the negative influences of residential schools were addressed as part of programming

    Sexual selection drives weak positive selection in protamine genes and high promoter divergence, enhancing sperm competitiveness

    Get PDF
    Phenotypic adaptations may be the result of changes in gene structure or gene regulation, but little is known about the evolution of gene expression. In addition, it is unclear whether the same selective forces may operate at both levels simultaneously. Reproductive proteins evolve rapidly, but the underlying selective forces promoting such rapid changes are still a matter of debate. In particular, the role of sexual selection in driving positive selection among reproductive proteins remains controversial, whereas its potential influence on changes in promoter regions has not been explored. Protamines are responsible for maintaining DNA in a compacted form in chromosomes in sperm and the available evidence suggests that they evolve rapidly. Because protamines condense DNA within the sperm nucleus, they influence sperm head shape. Here, we examine the influence of sperm competition upon protamine 1 and protamine 2 genes and their promoters, by comparing closely related species of Mus that differ in relative testes size, a reliable indicator of levels of sperm competition. We find evidence of positive selection in the protamine 2 gene in the species with the highest inferred levels of sperm competition. In addition, sperm competition levels across all species are strongly associated with high divergence in protamine 2 promoters that, in turn, are associated with sperm swimming speed. We suggest that changes in protamine 2 promoters are likely to enhance sperm swimming speed by making sperm heads more hydrodynamic. Such phenotypic changes are adaptive because sperm swimming speed may be a major determinant of fertilization success under sperm competition. Thus, when species have diverged recently, few changes in gene-coding sequences are found, while high divergence in promoters seems to be associated with the intensity of sexual selection

    Longitudinal associations of importance of religion and frequency of service attendance with depression risk among adolescents in Nova Scotia

    Get PDF
    Objective: To examine the directionality of associations between self-reported religious importance or worship attendance and depression among adolescents, and to determine whether social supports or general self-efficacy are mechanisms of observed associations. Method: A cohort (n = 976) of Canadian high school students were surveyed in Grade 10 (2000 to 2001) and 2 years later (2002 to 2003). Logistic regression was conducted separately among adolescents with and without elevated depressive symptoms to examine associations between baseline religious attendance and religious importance with later depression, adjusting for confounding factors. Effects of reverse causation were also assessed, determining associations between baseline depression and follow-up religious attendance and importance. Results: Girls who were not depressed at baseline and who attended religious services had lower odds of later depression (adjusted odds ratio [AOR] 0.46; 95% CI 0.22 to 0.95, P < 0.05), which was accounted for by general self-efficacy. Boys who were depressed at baseline who attended religious services had lower odds of still being depressed at followup (AOR 0.23; 95% CI 0.06 to 0.80, P < 0.01). Depression at baseline predicted lower attendance at follow-up among boys (AOR 0.26; 95% CI 0.09 to 0.75, P < 0.01). Conclusions: Religious attendance independently predicts lower depression at followup among girls, and may do so by increasing self-efficacy. Among boys with depression, religious attendance predicts a lower likelihood of still being depressed at follow-up. The relation between religious attendance and depression in boys is bidirectional

    Imprisonment and internment: Comparing penal facilities North and South

    Get PDF
    Recent references to the ‘warehouse prison’ in the United States and the prisión-depósito in Latin America seem to indicate that penal confinement in the western hemisphere has converged on a similar model. However, this article suggests otherwise. It contrasts penal facilities in North America and Latin America in terms of six interrelated aspects: regimentation; surveillance; isolation; supervision; accountability; and formalization. Quantitatively, control in North American penal facilities is assiduous (unceasing, persistent and intrusive), while in Latin America it is perfunctory (sporadic, indifferent and cursory). Qualitatively, North American penal facilities produce imprisonment (which enacts penal intervention through confinement), while in Latin America they produce internment (which enacts penal intervention through release). Closely entwined with this qualitative difference are distinct practices of judicial involvement in sentencing and penal supervision. Those practices, and the cultural and political factors that underpin them, represent an interesting starting point for the explanation of the contrasting nature of imprisonment and internment

    Evaluation and Comparison of a Habitat Suitability Model for Postdrift Larval Lake Sturgeon in the St. Clair and Detroit Rivers

    Full text link
    We evaluated composition and spatial distribution of riverine nursery habitat for larval Lake Sturgeon Acipenser fulvescens in the Middle Channel of the St. Clair River, Michigan, and Fighting Island Channel of the Detroit River, Ontario, using a habitat suitability model (HSM) and fish collections. Although model outputs indicated similar portions of high‐quality habitat in the Middle Channel (16.9%) and Fighting Island Channel (15.7%), larval abundance and dispersal patterns varied between these systems. Analysis with Akaike’s information criterion indicated that a regression model using sand–silt substrate performed best at predicting the observed water‐volume‐standardized CPUE (number of larvae·h−1·m−3) in the Middle Channel. Of 93 larvae that were collected in the Middle Channel, most were found to cluster at three distinct areas of high‐ and moderate‐quality habitat, which was composed predominately of sand–silt substrate. Lengths of larvae varied by as much as 9 mm, and the degree of yolk sac absorption also varied, indicating that larvae in the Middle Channel remained within the channel after a short drift downstream. Of the 25 larvae that were collected in Fighting Island Channel, distribution was sporadic, and occurrence did not significantly correlate with measured habitat variables. Larvae were relatively homogeneous in size and yolk sac stage, indicating that newly emerged larvae did not utilize available habitat in Fighting Island Channel but instead drifted into the main channel of the Detroit River. Dispersal patterns indicate variability in young Lake Sturgeon ecology, which is dependent on local habitat conditions—most notably, substrate composition. Furthermore, modeled larval–habitat associations found in this study were compared to a similar study on larval Lake Sturgeon from the North Channel of the St. Clair River. Model outputs from all three systems accurately accounted for observed larval dispersal patterns among both rivers. This supports the transferability of an HSM parameterized for Lake Sturgeon from individual river reaches within two large river systems.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/146299/1/nafm10217.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/146299/2/nafm10217_am.pd

    Youth’s narratives about family members smoking: parenting the parent- it’s not fair!

    Get PDF
    <p>Abstract</p> <p>Background</p> <p>Successful cancer prevention policies and programming for youth must be based on a solid understanding of youth’s conceptualization of cancer and cancer prevention. Accordingly, a qualitative study examining youth’s perspectives of cancer and its prevention was undertaken. Not surprisingly, smoking (i.e., tobacco cigarette smoking) was one of the dominant lines of discourse in the youth’s narratives. This paper reports findings of how youth conceptualize smoking with attention to their perspectives on parental and family-related smoking issues and experiences.</p> <p>Methods</p> <p>Seventy-five Canadian youth ranging in age from 11–19 years participated in the study. Six of the 75 youth had a history of smoking and 29 had parents with a history of smoking. Youth were involved in traditional ethnographic methods of interviewing and photovoice. Data analysis involved multiple levels of analysis congruent with ethnography.</p> <p>Results</p> <p>Youth’s perspectives of parents and other family members’ cigarette smoking around them was salient as represented by the theme: <it>It’s not fair.</it> Youth struggled to make sense of why parents would smoke around their children and perceived their smoking as an unjust act. The theme was supported by four subthemes: <it>1) parenting the parent about the dangers of smoking; 2) the good/bad parent; 3) distancing family relationships; and 4) the prisoner</it>. Instead of being <it>talked to</it> about smoking it was more common for youth to share stories of <it>talking to</it> their parents about the dangers of smoking. Parents who did not smoke were seen by youth as the good parent, as opposed to the bad parent who smoked. Smoking was an agent that altered relationships with parents and other family members. Youth who lived in homes where they were exposed to cigarette smoke felt like a trapped prisoner.</p> <p>Conclusions</p> <p>Further research is needed to investigate youth’s perceptions about parental cigarette smoking as well as possible linkages between youth exposed to second hand smoke in their home environment and emotional and lifestyle-related health difficulties. Results emphasize the relational impact of smoking when developing anti-tobacco and cancer prevention campaigns. Recognizing the potential toll that second-hand smoke can have on youth’s emotional well-being, health care professionals are encouraged to give youth positive messages in coping with their parents’ smoking behaviour.</p
    corecore