Global existence of classical solutions to the Vlasov-Poisson system in a three dimensional, cosmological setting

The initial value problem for the Vlasov-Poisson system is by now well understood in the case of an isolated system where, by definition, the distribution function of the particles as well as the gravitational potential vanish at spatial infinity. Here we start with homogeneous solutions, which have a spatially constant, non-zero mass density and which describe the mass distribution in a Newtonian model of the universe. These homogeneous states can be constructed explicitly, and we consider deviations from such homogeneous states, which then satisfy a modified version of the Vlasov-Poisson system. We prove global existence and uniqueness of classical solutions to the corresponding initial value problem for initial data which represent spatially periodic deviations from homogeneous states.Comment: 23 pages, Latex, report #

The Impact of Financialization on Management and Employment Outcomes

This paper examines three questions: 1) How and why have financial models of doing business emerged in the last three decades? 2) What new forms of financial capitalism have become important in the current period? 3) How do new financial intermediaries, such as private equity, and the financial strategies of nonfinancial corporations affect the management of companies and employment outcomes? The paper describes how deregulation and institutional change created the conditions for a new, more powerful role for finance capital in the governance of U.S. companies, and it synthesizes the empirical evidence on the process and outcomes of financialization in large publicly traded corporations, as well as those taken over by private equity. Areas for future research are identified to examine how financialization affects management and employment relations in the postcrisis period

Existence of axially symmetric static solutions of the Einstein-Vlasov system

We prove the existence of static, asymptotically flat non-vacuum spacetimes with axial symmetry where the matter is modeled as a collisionless gas. The axially symmetric solutions of the resulting Einstein-Vlasov system are obtained via the implicit function theorem by perturbing off a suitable spherically symmetric steady state of the Vlasov-Poisson system.Comment: 32 page

Three-Dimensional Stationary Spherically Symmetric Stellar Dynamic Models DEpending on Local Energy

Three-Dimensional Stationary Spherically Symmetric Stellar Dynamic Models Depending on the Local Energy. Juergen Batt, Enno Joern, Alexander L. Skubachevskii The stellar dynamic models considered here are triples (f,rho,U) of three functions: the distribution function f=f(r,u), the local density rho=rho(r) and the Newtonian potential U=U(r), where r:=|x|, u:=|v| ((x,v) in R^3xR^3 are the space-velocity coordinates), and f is a function q of the local energy E=U(r)+u^2/2. Our first result is an answer to the following question: Given a (positive) function p=p(r) on a bounded interval [0,R], how can one recognize p as the local density of a stellar dynamic model of the given type ("inverse problem")? If this is the case, we say that p is "extendable" (to a complete stellar dynamic model). Assuming that p is strictly decreasing, we reveal the connection between p and F, which appears in the nonlinear integral equation p=FU[p] and the solvability of Eddington's equation between F and q. Second, we investigate the following question ("direct problem"): Which q induce distribution functions f of the form f=q(-E(r,u)-E0) of a stellar dynamic model? This leads to the investigation of the nonlinear equation p=FU[p] in an approximate and constructive way by mainly numerical methods. The paper extends preceding work on flat galaxies to the three-dimensional case. In particular, the present answer to the extendability problem is completely different as in [1]. The present paper also opens the way to further explicit solutions of the Vlasov-Poisson system beyond the classical known examples which are for instant given in [4]. Keywords: Vlasov-Poisson system, stationary solutions, numerical approximation, mathematical physic, galaxy astrophysics.Comment: 41 pages, 10 diagram

Consumer purchasing behaviour for fresh vegetables in Nanjing, China

With increasing income and growing concerns for food safety, consumer purchasing behaviour for fresh vegetables is changing in China. To gain a better understanding of consumer behaviour in Nanjing, 542 face-to-face interviews were conducted. Results show that most fresh vegetables are purchased from traditional wet markets several times per week. In evaluating the quality of the fresh vegetables respondents intended to purchase, the two key selection criteria were colour and freshness. Most respondents were aware of some recent food safety incident that had adversely affected the industry. Respondents were most concerned about the presence of pesticide residues. To reduce the possibilities of contamination, respondents chose to wash or soak the fresh vegetables they intended to eat and to buy from trusted suppliers. Consumers believed that farmers, vegetable processors and government should be responsible for the enhancing and maintaining the safety of the fresh vegetables offered for sale

Domestic Outsourcing in the United States: A Research Agenda to Assess Trends and Effects on Job Quality

The goal of this paper is to develop a comprehensive research agenda to analyze trends in domestic outsourcing in the United States—firms’ use of contractors and independent contractors—and its effects on job quality and inequality. In the process, we review definitions of outsourcing, the available scant empirical research, and limitations of existing data sources. We also summarize theories that attempt to explain why firms contract out for certain functions and assess their predictions about likely impacts on job quality. We then lay out in detail a major research initiative on domestic outsourcing, discussing the questions it should answer and providing a menu of research methodologies and potential data sources. Such a research investment will be a critical resource for policymakers and other stakeholders as they seek solutions to problems arising from the changing nature of work

Motive8!: feasibility of a text messaging intervention to promote physical activity in knee osteoarthritis

Aim: To develop and test the feasibility of using a SMS text messaging intervention to promote physical activity in patients with knee OA. Methods: 27 people (6 male, 21 female; aged 25-81 years) with knee osteoarthritis received 4 text messages per week, for 6 weeks. Telephone surveys were conducted at baseline and 6 weeks to measure physical activity levels and beliefs, including self-efficacy for exercise, barriers and benefits of exercise, social support and pain. Participants completed physical activity diaries. Process evaluation included participant perceptions of the intervention and 'real-time' data on intervention fidelity (automated collection of delivery and response data) and participant engagement (text response). Results: 648 messages were sent, 100% were accurately delivered. From baseline to 6 weeks, physical activity, self-efficacy for exercise, perceived benefits of exercise and social support significantly increased; reductions were observed in barriers to exercise and pain. Participants engaged with the intervention; 100% read the messages, 89% responded to texts requesting replies, 64% completed physical activity diaries with low attenuation (1.8% drop) by six weeks. Participants perceived messaging to be enjoyable (96%), personally relevant (85%), of appropriate frequency (100%) and duration (88%). Mobile phones, email and web were perceived to be most acceptable for health promotion compared with other forms of technology. Conclusions: People with knee osteoarthritis can engage meaningfully with an interactive mobile phone messaging intervention over a six-week period. Health communications promoting physical activity demonstrate potential for behaviour change and positive implications for perceptions of exercise and pain; this needs to be tested in a randomised trial. Data collected in 'real-time' can be used for process evaluation to demonstrate participant engagement and intervention fidelity

Spherically symmetric steady states of galactic dynamics in scalar gravity

The kinetic motion of the stars of a galaxy is considered within the framework of a relativistic scalar theory of gravitation. This model, even though unphysical, may represent a good laboratory where to study in a rigorous, mathematical way those problems, like the influence of the gravitational radiation on the dynamics, which are still beyond our present understanding of the physical model represented by the Einstein--Vlasov system. The present paper is devoted to derive the equations of the model and to prove the existence of spherically symmetric equilibria with finite radius.Comment: 13 pages, mistypos correcte

Active8! Technology-based intervention to promote physical activity in hospital employees

Purpose: Increase physical activity in healthcare employees using health messaging, and compare email with mobile phone short-message service (SMS) as delivery channels. Design: Randomised controlled trial Setting: UK hospital workplace Subjects: 296 employees (19-67 years, 53% of study website visitors) Intervention: 12-week messaging intervention designed to increase physical activity and delivered via SMS (n=147) or email (n=149); content tailored using Theory of Planned Behaviour (TPB) and limited to 160 characters. Measures: Baseline, 6, 12 and 16 weeks. Online measures included TPB constructs; physical activity behaviour on the Global Physical Activity Questionnaire; health-related quality of life on the Short-Form 12. Analysis: General linear models for repeated measures. Results: Increase in duration (mean hours/day) of moderate work-related activity and moderate recreational activity from baseline to 16 weeks. Short-lived increase in frequency (days/week) of vigorous recreational activity from baseline to 6 weeks. Increase in duration and frequency of active travel from baseline to 16 weeks. Emails generated greater changes than SMS in active travel and moderate activity (work and recreational). Conclusion: Minimal physical activity promotion delivered by SMS or email can increase frequency and duration of active travel, and duration of moderate-intensity physical activity at work and for leisure, which is maintained up to one-month after messaging ends. Both channels were useful platforms for health communication; emails were particularly beneficial with hospital employees