Locating saddle points using gradient extremals on manifolds adaptively revealed as point clouds.

Steady states are invaluable in the study of dynamical systems. High-dimensional dynamical systems, due to separation of time scales, often evolve toward a lower dimensional manifold M. We introduce an approach to locate saddle points (and other fixed points) that utilizes gradient extremals on such a priori unknown (Riemannian) manifolds, defined by adaptively sampled point clouds, with local coordinates discovered on-the-fly through manifold learning. The technique, which efficiently biases the dynamical system along a curve (as opposed to exhaustively exploring the state space), requires knowledge of a single minimum and the ability to sample around an arbitrary point. We demonstrate the effectiveness of the technique on the Müller-Brown potential mapped onto an unknown surface (namely, a sphere). Previous work employed a similar algorithmic framework to find saddle points using Newton trajectories and gentlest ascent dynamics; we, therefore, also offer a brief comparison with these methods.

Principles for the safety evaluation of cosmetic powders.

Consumer exposure to cosmetic (personal care) products is mostly by dermal contact, however additional considerations with regards to potential inhalation exposure from some cosmetics, such as sprays and powders, may be needed for a robust and reliable safety assessment. To get a deeper understanding of the exposure to airborne particles and droplets during product application, a team of international experts was founded under the umbrella of the European Association of the Cosmetic Industry "Cosmetics Europe" (CE) in Brussels. This expert team has worked out a pragmatic strategy how small and medium sized enterprises (SMEs), but also relevant authorities, could handle the safety evaluation of cosmetic powder products. Sufficient information on the aerodynamic diameter of sprayed droplets and here specifically of airborne particles is essential in addition to knowing the exposure after typical product application. The current article is focused on the determination of inhalation exposure to solids, and the derivation of safe exposure levels for cosmetic powder products found in the market. The principles described herein are very similar to spray products as published earlier and should be applied in a similar way (Steiling et al., 2014). Prediction models for the best estimate of inhalation exposure, developed with data from computer simulation programs, individual real-time measurements or finally by experience from the market were introduced and applied. Safety assessment approaches for exposure from powder spray products were developed and have been already considered in regulatory guidelines like the EC Cosmetics Regulation.

Maintaining abstinence from cigarette smoking: effectiveness of group counselling and factors predicting outcome.

The aim of the study was to assess the effectiveness of worksite group counselling interventions designed to prevent smoking relapse after abstinence has been achieved following 3 months therapy using group support and/or transdermal nicotine replacement therapy. After 3 months, abstinent subjects were randomly allocated either to a counselling group led by professional psychologists (PG), to a counselling group led by former smokers (SG) or to no intervention group (NG). The 3 and 12 months abstinence were defined, respectively, as a sustained smoking cessation during the last month, and the last 9 months. Complete abstinence was confirmed by expired carbon monoxide and by urine cotinine concentrations. The abstinence rate at 3 months was 35.1%. After 12 months abstinence rates were not statistically different in the PG, the SG and the NG (respectively 57.8, 53.4 and 49.6% of those randomised). In multivariate analyzes, baseline variables associated with 12 months abstinence were non-smoking family, gender (male), lower daily intake of nicotine and better psychological adjustment. Mean weight gain at 3 months in abstinent versus relapsed subjects, was respectively, 4.1 and 2.4 kg. Baseline variables associated with weight gain at 3 months were higher Fagerström score, gender (male) and professional status (blue collar worker). Group support after abstinence has been achieved did not significantly improve the abstinence. This study shows the difficulty of preventing smoking relapse with monthly group counselling. The results indicate the need to investigate further specific programmes focusing on factors such as gender, family, nicotine dependence, psychological and weight concerns/issues which may precipitate relapse.

Improving cancer prevention at the worksite: how are Belgian companies dealing with smoking regulations?

Little is known about the impact of smoking policy on companies' policies related to smoking in Belgium. The study was designed in order to compare the companies' policies related to smoking (CPRS) in 1990 and in 1993. During this 3 year period, numerous information and regulation inputs (media, brochures) were aimed at companies to regulate smoking behavior in the workplace, so as to reduce the risks of passive smoking. A short questionnaire was mailed to 3543 Belgian companies in October 1990 and in June 1993 to assess: designation of smoke free areas (SFA); willingness to offer a worksite information program (WIP); willingness to offer a worksite smoking cessation program (WSCP); willingness to subsidize a WSCP; willingness to offer a WSCP during working hours; willingness to offer a meeting room for a WSCP and actual organization of a WSCP. In 1990, 773 companies (22%) and in 1993, 890 companies (25%) responded to the questionnaire. The results showed that small companies and companies with a high blue/white collar ratio were less able to implement health policy recommendations. A total of 325 (9%) companies responded to the 1990 and 1993 questionnaires. Comparison of 1990 and 1993 dataset showed that during this 3 year period, no major changes occurred for a majority of companies. Amongst the small positive changes, only the designation of smoke free areas and the organization of a small number of WSCP was observed. The conclusion is that despite inputs, little impact on smoking policies is noticeable. Strategies designed to intensify inputs and to promote implementation of regulation of WSCP should therefore further be studied.