Ethnic differences in predictors of adolescent smoking onset and escalation: a longitudinal study from 7th to 12th grade.

The present study sought to determine whether risk factors for cigarette smoking onset have a stronger influence on Black versus White children, and whether those patterns differ for nonsmokers versus experimental smokers. As part of a larger study, 5,213 seventh graders were surveyed annually for 5 years. The survey instrument assessed cigarette smoking, along with a variety of background variables thought to influence smoking. Results indicated that rebelliousness predicted smoking onset for Black nonsmokers; peer modeling was more influential for Whites. For both ethnicities, socially isolated children were at increased risk. The variables that predicted the shift from experimental to regular smoking were for the most part different from those that predicted smoking onset. Specifically, youths who lived with smokers, viewed smoking as a means to a goal, and experienced few adverse physiological effects of smoking were more likely to increase their cigarette consumption. Overall, we found that, contrary to previous research, risk factors for smoking differed across ethnicity. Further, smoking onset appears to be shaped by forces different from those that accelerate consumption.     

The effects of shoe traction and obstacle height on lower extremity coordination dynamics during walking

This study aims to investigate the effects of shoe traction and obstacle height on lower extremity relative phase dynamics (analysis of intralimb coordination) during walking to better understand the mechanisms employed to avoid slippage following obstacle clearance. Ten participants walked at a self-selected pace during eight conditions: four obstacle heights (0%, 10%, 20%, and 40% of limb length) while wearing two pairs of shoes (low and high traction). A coordination analysis was used and phasing relationships between lower extremity segments were examined. The results demonstrated that significant behavioral changes were elicited under varied obstacle heights and frictional conditions. Both decreasing shoe traction and increasing obstacle height resulted in a more in-phase relationship between the interacting lower limb segments. The higher the obstacle and the lower the shoe traction, the more unstable the system became. These changes in phasing relationship and variability are indicators of alterations in coordinative behavior, which if pushed further may have lead to falling.     

Deposited Chromium as a Corrosion Preventative

Atmospheric corrosion tests of copper plus bright nickel plus microcracked chromium plate have shown that microcracked chromium produced by the post nickel strike method and having a minimum thickness of 0·3/μm provides corrosion resistance at least as good as microcracked chromium produced by other methods, which require a minimum thickness of 0·8 μm in order to ensure an adequate density of microcracking.     

Time-Line Interpolation Errors in Pipe Networks

An exact method of assessing numerical errors in analyses of unsteady flows in pipe networks is introduced. The assessment is valid for fixed-grid method of characteristics analyses using time-line interpolations. A pipe polynomial transfer matrix is developed and is analogous to transfer function matrices used in free oscillation theory. The influence of reachback is assessed by comparing exact numerical predictions using a polynomial transfer matrix with exact analytical predictions obtained using free oscillation theory. The investigation is part of a long-term project aimed at automating the selection of numerical grid sizes in unsteady flow analyses. The eventual goal is to enable users of unsteady flow software to prescribe required degrees of accuracy instead of specifying the numerical grid itself. This paper is only a first step toward the long-term aim, but it is a big step toward an intermediate objective of providing exact benchmarking data for the assessment of approximate methods of automatic grid selection.     

Potential sources of food hazards in emerging commercial aquaculture industry in sub-Saharan Africa: a case study for Uganda

A study was conducted to assess sources of food hazards in Uganda's emerging commercial aquaculture industry based on Hazard Analysis Critical Control Point (HACCP), focusing on inputs, their sources and farm-practices on ten representative commercial farms. Critical control points (CCPs) were identified to reveal potential hazards that would jeopardise any export trade. Site selection, water quality, fertiliser, fish seed, fish rearing facilities, feeds, and post-harvest practices were the main CCPs identified. Animal manure was used to generate plankton as pond fertiliser in nine of the ten surveyed farms and veterinary drugs were not found in any of the ten farms, which is starkly different from aquaculture in indutrialised countries. Potential sources of hazards from water were mainly: municipal waste flow which was more likely on five of the ten farms, domestic waste (four farms), agricultural run-off (three farms), and low water pH (three farms). Fish fry and fingerlings from other farms, feeds formulated on-farm from unapproved sources, chemical products, uncontrolled fish predators, and domestic animal and human activities were the other potential sources of hazards. A complete application of HACCP is recommended for producing safe products that meet the strict market standards of developed countries.     

Planning in partially-observable switching-mode continuous domains

Continuous-state POMDPs provide a natural representation for a variety of tasks, including many in robotics. However, most existing parametric continuous-state POMDP approaches are limited by their reliance on a single linear model to represent the world dynamics. We introduce a new switching-state dynamics model that can represent multi-modal state-dependent dynamics. We present the Switching Mode POMDP (SM-POMDP) planning algorithm for solving continuous-state POMDPs using this dynamics model. We also consider several procedures to approximate the value function as a mixture of a bounded number of Gaussians. Unlike the majority of prior work on approximate continuous-state POMDP planners, we provide a formal analysis of our SM-POMDP algorithm, providing bounds, where possible, on the quality of the resulting solution. We also analyze the computational complexity of SM-POMDP. Empirical results on an unmanned aerial vehicle collisions avoidance simulation, and a robot navigation simulation where the robot has faulty actuators, demonstrate the benefit of SM-POMDP over a prior parametric approach.