Galactic Potentials

The information contained in galactic rotation curves is examined under a minimal set of assumptions. If emission occurs from stable circular geodesic orbits of a static spherically symmetric field, with information propagated to us along null geodesics, observed rotation curves determine galactic potentials without specific reference to any metric theory of gravity. Given the potential, the gravitational mass can be obtained by way of an anisotropy function of this field. The gravitational mass and anisotropy function can be solved for simultaneously in a Newtonian limit without specifying any specific source. This procedure, based on a minimal set of assumptions, puts very strong constraints on any model of the "dark matter".Comment: A somewhat longer form of the final version to appear in Physical Review Letters.Clarification and further reference

Introduction:navigating secrecy in security research

This introduction presents an overview of the key concepts discussed in the subsequent chapters of this book. The book offers a rich set of analyses of the challenges of secrecy in security research, and sets out practical ways to navigate, encircle and work with secrecy. It aims to offer not just a conceptual reflection on the dynamics of secrecy, but also practical, hands-on methodological guidance for qualitative fieldwork in the security domain. The book describes new ways of conceptualising secrecy in relation to fieldwork, by understanding secrecy as more than a barrier to be overcome. It shows how secrecy itself can be made productive to the analysis: mapping secrecies and sensitivities in the field can itself be revealing; navigating obfuscation is co-productive of research design and data. The book focuses on reconceptualising secrecy as a complex practice and mode of power

Changes in Social Comparison Orientation over the Life-span

Background: Social comparison is a basic human process, which may change dependent of one’s age. The purpose of this study was to examine how Social Comparison Orientation (SCO), i.e., the tendency to engage in social comparisons, varied across the lifespan. Method: A representative sample of 1613 adults from the Netherlands filled out the widely used 11-item scale for Social Comparison Orientation (SCO). Age was categorized in terms of decades, including both 19 years or younger and 80 years or older as categories. Results: The results showed a strong curvilinear effect of age: SCO was highest among people 19 years or younger, decreased substantially with increasing age until the age of 60, after which it increased moderately. Women were somewhat higher in SCO than men. Conclusion: The tendency to engage in social comparisons changes considerably over the life span, which may be due to the different challenges and insecurities that people may face in different stages of the life span

Modeling the Gas Flow in the Bar of NGC 1365

We present new observations of the strongly-barred galaxy NGC 1365, including new photometric images and Fabry-Perot spectroscopy, as well as a detailed re-analysis of the neutral hydrogen observations from the VLA archive. We find the galaxy to be at once remarkably bi-symmetric in its I-band light distribution and strongly asymmetric in the distribution of dust and in the kinematics of the gas in the bar region. The velocity field mapped in the H-alpha line reveals bright HII regions with velocities that differ by 60 to 80 km/s from that of the surrounding gas, which may be due to remnants of infalling material. We have attempted hydrodynamic simulations of the bar flow to estimate the separate disk and halo masses, using two different dark matter halo models and covering a wide range of mass-to-light ratios (Upsilon) and bar pattern speeds (Omega_p). None of our models provides a compelling fit to the data, but they seem most nearly consistent with a fast bar, corotation at sim 1.2r_B, and Upsilon_I simeq 2.0 +- 1.0, implying a massive, but not fully maximal, disk. The fitted dark halos are unusually concentrated, a requirement driven by the declining outer rotation curve.Comment: 43 pages, 15 figures, accepted to appear in Ap

Halo Geometry and Dark Matter Annihilation Signal

We study the impact of the halo shape and geometry on the expected weakly interacting massive particle (WIMP) dark matter annihilation signal from the galactic center. As the halo profile in the innermost region is still poorly constrained, we consider different density behaviors like flat cores, cusps and spikes, as well as geometrical distortions. We show that asphericity has a strong impact on the annihilation signal when the halo profile near the galactic center is flat, but becomes gradually less significant for cuspy profiles, and negligible in the presence of a central spike. However, the astrophysical factor is strongly dependent on the WIMP mass and annihilation cross-section in the latter case.Comment: 5 pages, 4 figures, PR

The early identification of risk factors on the pathway to school dropout in the SIODO study:A sequential mixed-methods study

BACKGROUND: School dropout is a persisting problem with major socioeconomic consequences. Although poor health probably contributes to pathways leading to school dropout and health is likely negatively affected by dropout, these issues are relatively absent on the public health agenda. This emphasises the importance of integrative research aimed at identifying children at risk for school dropout at an early stage, discovering how socioeconomic status and gender affect health-related pathways that lead to dropout and developing a prevention tool that can be used in public health services for youth. METHODS/DESIGN: The SIODO study is a sequential mixed-methods study. A case–control study will be conducted among 18 to 24 year olds in the south of the Netherlands (n = 580). Data are currently being collected from compulsory education departments at municipalities (dropout data), regional public health services (developmental data from birth onwards) and an additional questionnaire has been sent to participants (e.g. personality data). Advanced analyses, including cluster and factor analyses, will be used to identify children at risk at an early stage. Using the quantitative data, we have planned individual interviews with participants and focus groups with important stakeholders such as parents, teachers and public health professionals. A thematic content analysis will be used to analyse the qualitative data. DISCUSSION: The SIODO study will use a life-course perspective, the ICF-CY model to group the determinants and a mixed-methods design. In this respect, the SIODO study is innovative because it both broadens and deepens the study of health-related determinants of school dropout. It examines how these determinants contribute to socioeconomic and gender differences in health and contributes to the development of a tool that can be used in public health practice to tackle the problem of school dropout at its roots

Computing automorphic forms on Shimura curves over fields with arbitrary class number

We extend methods of Greenberg and the author to compute in the cohomology of a Shimura curve defined over a totally real field with arbitrary class number. Via the Jacquet-Langlands correspondence, we thereby compute systems of Hecke eigenvalues associated to Hilbert modular forms of arbitrary level over a totally real field of odd degree. We conclude with two examples which illustrate the effectiveness of our algorithms.Comment: 15 pages; final submission to ANTS I

The maximum number of minimal codewords in an [n,k]−[n,k]-code

Upper and lower bounds are derived for the quantity in the title, which is tabulated for modest values of $n$ and $k.$ An application to graphs with many cycles is given.Comment: 6 pp. Submitte