On characterization of Hamiltonian graphs

A necessary and a sufficient condition are derived for a graph to be non-Hamiltonian

The metabolic profiles of HIV-infected and non-infected women in Mangaung, South Africa

Objective: To determine the biochemical nutritional status of HIV-infected women in Mangaung.Design: Cross-sectional.Setting: The community of Mangaung, Free State, South Africa.Subjects: A representative group of 500 black women (25–44 years) was selected randomly to participate.Outcome measures: Biochemical analyses were performed for total  lymphocytes, serum protein, serum albumin, plasma fibrinogen, serum insulin, serum glucose, serum triglycerides and serum cholesterol using standard methodology. Values were compared to standard references, and between HIV-infected and HIV-uninfected women.Results: After screening for eligibility, 488 women qualified. Sixty-one per cent of the younger women (25–34 years) and 38% of the older women (35–44 years) were HIV-infected. HIV-infected women had significantly lower median blood values for total lymphocytes (p = 0.0001 and p = 0.02 for younger and older group respectively) and serum albumin (p = 0.0001 for both age groups), but significantly higher median concentrations of serum protein (p = 0.0001 for both age groups) than uninfected women. Plasma fibrinogen and serum insulin concentrations were significantly lower in HIV-infected younger women than in their uninfected counterparts (p = 0.002 for both parameters). Older HIV-infected women had significantly lower total serum cholesterol values (p = 0.01) than older HIV-uninfected women. Serum glucose and serum triglycerides did not differ significantly between HIV-infected and HIV-uninfected women.Conclusions: The results indicate a possible impact of HIV infection on serum protein and serum albumin, which may adversely affect biochemical nutritional status and the course of HIV progression. Future research into the causes and possible treatment of metabolic changes in women in this community should be prioritised

Work functioning among young adults:the role of mental health problems from childhood to young adulthood

OBJECTIVES: Mental health problems (MHPs) during childhood and adolescence are negatively associated with having a paid job in young adulthood. Yet, little is known about how young adults function at work, that is, do they experience difficulties in meeting their job demands given their health state. This longitudinal study aims to examine the impact of MHPs from childhood to young adulthood on young adults’ work functioning (WF). METHODS: Data were used from 1004 participants in the TRacking Adolescents’ Individual Lives Survey, a Dutch prospective cohort study with 18-year follow-up. MHP trajectories, including 11, 13.5, 16, 19, 22 and 26 age points, were identified using growth mixture models. WF was assessed at age 29 with the Work Role Functioning Questionnaire 2.0 (WRFQ). Regression analyses were conducted to examine the association between MHP trajectories and WF. RESULTS: Young adults with high-stable trajectories of internalising and externalising problems reported lower WF (mean WRFQ scores of 70.5 and 70.7, respectively) than those with low-stable trajectories (78.4 and 77.2), that is, they experience difficulties in meeting the work demands for more than one work day per full-time work week. Young adults with moderate-stable or decreasing MHP trajectories reported lower WF scores compared with those with low-stable trajectories. CONCLUSIONS: Both persistent high and elevated levels of MHPs from childhood to young adulthood are associated with lower WF scores in young adulthood compared with low-level MHPs. Occupational healthcare professionals should support young workers with a history of MHPs to optimise their work functioning

Low-Dissipation Simulation Methods and Models for Turbulent Subsonic Flow

The simulation of turbulent flows by means of computational fluid dynamics is highly challenging. The costs of an accurate direct numerical simulation (DNS) are usually too high, and engineers typically resort to cheaper coarse-grained models of the flow, such as large-eddy simulation (LES). To be suitable for the computation of turbulence, methods should not numerically dissipate the turbulent flow structures. Therefore, energy-conserving discretizations are investigated, which do not dissipate energy and are inherently stable because the discrete convective terms cannot spuriously generate kinetic energy. They have been known for incompressible flow, but the development of such methods for compressible flow is more recent. This paper will focus on the latter: LES and DNS for turbulent subsonic flow. A new theoretical framework for the analysis of energy conservation in compressible flow is proposed, in a mathematical notation of square-root variables, inner products, and differential operator symmetries. As a result, the discrete equations exactly conserve not only the primary variables (mass, momentum and energy), but also the convective terms preserve (secondary) discrete kinetic and internal energy. Numerical experiments confirm that simulations are stable without the addition of artificial dissipation. Next, minimum-dissipation eddy-viscosity models are reviewed, which try to minimize the dissipation needed for preventing sub-grid scales from polluting the numerical solution. A new model suitable for anisotropic grids is proposed: the anisotropic minimum-dissipation model. This model appropriately switches off for laminar and transitional flow, and is consistent with the exact sub-filter tensor on anisotropic grids. The methods and models are first assessed on several academic test cases: channel flow, homogeneous decaying turbulence and the temporal mixing layer. As a practical application, accurate simulations of the transitional flow over a delta wing have been performed

Branching of the Falkner-Skan solutions for λ < 0

The Falkner-Skan equation f'" + ff" + λ(1 - f'^2) = 0, f(0) = f'(0) = 0, is discussed for λ < 0. Two types of problems, one with f'(∞) = 1 and another with f'(∞) = -1, are considered. For λ = 0- a close relation between these two types is found. For λ < -1 both types of problem allow multiple solutions which may be distinguished by an integer N denoting the number of zeros of f' - 1. The numerical results indicate that the solution branches with f'(∞) = 1 and those with f'(∞) = -1 tend towards a common limit curve as N increases indefinitely. Finally a periodic solution, existing for λ < -1, is presented.

Virtual Special Issue on Corporate Governance and Ethics: What’s Next?

Corporate governance (CG) is a key area of management with important implications for business ethics. The interface of CG and business ethics is populated with rich intellectual debates on the role of ethics in governance from a multi-disciplinary perspective. Within these debates, the relationship between CG and outcomes for business and society, and the role of CG structures and processes and their comparative aspects across institutional settings are discussed. Despite a proliferation of research at the interface of CG and ethics, we observe that an engagement with topics, methodologies, and expected outcomes drawing on established frames and theories of CG tends to the ignoring or even the preclusion of an explicit engagement with debates in business ethics. Through this VSI, we as section editors showcase previously published papers in the Journal that proactively explore the explicit linkages and interfaces between CG and ethical societal challenges, with the aim of inspiring further such CG research

Correction: Mental Health Problems and Educational Attainment in Adolescence:9-Year Follow-Up of the TRAILS Study (vol 9, e101751, 2014)

Background: This study examines if mental health problems at age 11 and changes in mental health problems between age 11 and 16 predict educational attainment of adolescents at age 19, overall and stratified by gender.Methods: Data from 1711 adolescents (76.8% from initial cohort) of the Tracking Adolescents' Individual Lives Survey (TRAILS), a Dutch prospective cohort study with 9year follow-up, were used. Mental health problems (externalizing, internalizing and attention problems) were measured by the Youth Self Report and the Child Behavior Checklist at ages 11 and 16. Difference scores for mental health problems between age 11 and 16 were calculated. Educational attainment was assessed at age 19.Results: Externalizing, internalizing and attention problems at age 11 were significantly associated with low educational attainment at age 19 (crude model). When adjusted for demographic variables and the other mental health problems, only the association for attention problems remained significant (odds ratio (OR), 95% confidence interval: 3.19, 2.11-4.83). Increasing externalizing problems between age 11 and 16 also predicted low educational attainment at age 19 (OR 3.12, 1.83-5.32). Among girls, increasing internalizing problems between age 11 and 16 predicted low educational attainment (OR 2.21, 1.25-3.94). For boys, no significant association was found for increasing internalizing problems and low educational attainment. For increasing attention problems between age 11 and 16 no significant association with low educational attainment was found.Conclusions: Externalizing, internalizing and attention problems at age 11 and an increase of these problems during adolescence predicted low educational attainment at age 19. Early treatment of these mental health problems may improve educational attainment, and reduce socioeconomic health differences in adulthood.</p