1,904 research outputs found

    The Ellipticity of the Disks of Spiral Galaxies

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    The disks of spiral galaxies are generally elliptical rather than circular. The distribution of ellipticities can be fit with a log-normal distribution. For a sample of 12,764 galaxies from the Sloan Digital Sky Survey Data Release 1 (SDSS DR1), the distribution of apparent axis ratios in the i band is best fit by a log-normal distribution of intrinsic ellipticities with ln epsilon = -1.85 +/- 0.89. For a sample of nearly face-on spiral galaxies, analyzed by Andersen and Bershady using both photometric and spectroscopic data, the best fitting distribution of ellipticities has ln epsilon = -2.29 +/- 1.04. Given the small size of the Andersen-Bershady sample, the two distribution are not necessarily inconsistent. If the ellipticity of the potential were equal to that of the light distribution of the SDSS DR1 galaxies, it would produce 1.0 magnitudes of scatter in the Tully-Fisher relation, greater than is observed. The Andersen-Bershady results, however, are consistent with a scatter as small as 0.25 magnitudes in the Tully-Fisher relation.Comment: 19 pages, 5 figures; ApJ, accepte

    Anomalous Spin Dynamics observed by High Frequency ESR in Honeycomb Lattice Antiferromagnet InCu2/3V1/3O3

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    High-frequency ESR results on the S=1/2 Heisenberg hexagonal antiferromagnet InCu2/3V1/3O3 are reported. This compound appears to be a rare model substance for the honeycomb lattice antiferromagnet with very weak interlayer couplings. The high-temperature magnetic susceptibility can be interpreted by the S=1/2 honeycomb lattice antiferromagnet, and it shows a magnetic-order-like anomaly at TN=38 K. Although, the resonance field of our high-frequency ESR shows the typical behavior of the antiferromagnetic resonance, the linewidth of our high-frequency ESR continues to increase below TN, while it tends to decrease as the temperature in a conventional three-dimensional antiferromagnet decreases. In general, a honeycomb lattice antiferromagnet is expected to show a simple antiferromagnetic order similar to that of a square lattice antiferromagnet theoretically because both antiferromagnets are bipartite lattices. However, we suggest that the observed anomalous spin dynamics below TN is the peculiar feature of the honeycomb lattice antiferromagnet that is not observed in the square lattice antiferromagnet.Comment: 5 pages, 5 figure

    Sexual harassment and abuse in sport: The research context

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    This special issue of the Journal of Sexual Aggression draws on the contributions to a Symposium on ‘Sexual Harassment in Sport – Challenges for Sport Psychology in the New Millennium’, held at the Xth Congress of the International Society for Sport Psychology, Skiathos, Greece from May 28th to June 2nd 2001. The symposium, which was organised by the authors of this editorial, was intended to move forward the international research agenda on sexual harassment and abuse in sport and to examine professional practice issues for sport psychologists. It was clear from the attendance of over 60 delegates at that symposium that international interest in this subject is growing. Further evidence of this came from the attendance of 26 members states – from Azerbaijan to Sweden - at a Council of Europe seminar on The Protection of Children, Young People and Women in Sport, held in Helsinki in September 2001

    Prenatal Environmental Exposure to Persistent Organic Pollutants and Reproductive Hormone Profile and Pubertal Development in Dutch Adolescents

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    Persistent organic pollutants (POPs), such as polychlorinated biphenyls (PCBs), may interfere with hormonal processes. Knowledge about the effects of prenatal exposure to PCBs and their hydroxylated metabolites (OH-PCBs) on pubertal development is limited. Therefore, the aim of the current study was to determine whether prenatal environmental PCB and OH-PCB exposure are associated with reproductive hormone levels and pubertal characteristics in 13- to 15-year-old children. In this Dutch observational cohort study, 194 mother-infant pairs were included (1998-2002). Maternal pregnancy serum levels of PCBs, OH-PCBs, and other POPs were measured. At follow-up (2014-2016), we measured serum or plasma levels of reproductive hormones in their children. We assessed Tanner stages and testicular volume (by clinician or standardized self-assessment), and participants completed questionnaires on pubertal onset. In total, 101 adolescents (14.4 ± 0.8 years; 53.7% of invited) participated, and 55 were boys. In boys, higher prenatal PCB levels were associated with higher testosterone levels, higher pubic hair stage, larger testicular volume, and younger age at onset of growth spurt and voice break. In girls, higher prenatal PCB levels were associated with higher stages for breast development. In conclusion, higher prenatal PCB exposure could be associated with more advanced pubertal development in 13- to 15-year-old children

    Phase diagram of a Heisenberg spin-Peierls model with quantum phonons

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    Using a new version of the density-matrix renormalization group we determine the phase diagram of a model of an antiferromagnetic Heisenberg spin chain where the spins interact with quantum phonons. A quantum phase transition from a gapless spin-fluid state to a gapped dimerized phase occurs at a non-zero value of the spin-phonon coupling. The transition is in the same universality class as that of a frustrated spin chain, which the model maps to in the anti-adiabatic limit. We argue that realistic modeling of known spin-Peierls materials should include the effects of quantum phonons.Comment: RevTeX, 5 pages, 3 eps figures included using epsf. Improved theories in adiabatic and non-adiabatic regimes give better agreement with DMRG. This version accepted in Physical Review Letter

    Implementation and evaluation of a physical activity counselling programme in primary care among cancer survivors:SoDA study protocol

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    INTRODUCTION: Physical activity (PA) favourably affects various health outcomes in cancer survivors, but little is known about how to implement a PA programme in primary care. We therefore aim to implement and evaluate such a programme for cancer survivors in general practice. METHODS AND ANALYSES: The Stimulation of Daily Activity study is an implementation study with a single-arm longitudinal design in 15 Dutch general practices. Patients aged ≥18 years who finished cancer treatment more than 6 months ago will be eligible for inclusion. The intervention will comprise six coaching sessions with the practice nurse in 9 months, seeking to increase PA in daily activities and using an activity tracker for goal setting and feedback. The Reach, Effectiveness, Adoption, Implementation and Maintenance framework will be used to evaluate implementation in terms of the health outcomes, extent of implementation and barriers and facilitators to implementation, using a mixed methods approach. Descriptive analyses and linear mixed model analyses will be performed on the quantitative data, while qualitative data from focus groups and interviews will be analysed by thematic analyses. ETHICS AND DISSEMINATION: The Medical Research Ethics Committee of the University Medical Centre Groningen, the Netherlands, concluded that this study was not subject to the Dutch Medical Research Involving Human Subjects Act (registration number: 201900586). The study results will be made available to patients and general practitioners via (inter)national publications and conferences, newsletters, public summaries and via (social) media

    Study trip as means of expanded learning

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    This article explores the study trip as an interconnected activity of work and play, constituting an extended means of teaching design studio in spatial design related disciplines. This study analyses the case of a cohort of about 200 students involved in a joint project in three cities, Athens, Tokyo and London, where groups were challenged with a common project brief. The students conducted empirical studies of the cities through play and enjoyment. The case study provides evidence of the benefits and issues emerging in this particular teaching and learning method of project-based and field work research in spatial design
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