Urinary monitoring of saccharin and acesulfame-K as biomarkers of exposure to these additives

A method was developed to determine the levels of two intense sweeteners, saccharin and acesulfame-K, in human urine. Measurement of these two analytes in urine allowed an assessment to be made of dietary exposure to the sweeteners using intake/excretion curves. This paper describes an intake/excretion study in which 22 volunteers consumed known amounts of saccharin and acesulfame-K at five different levels ranging between 1.4 and 70mg of saccharin (0.7- 30% of the ADI for a 60kg person) and 2.2-102mg of acesulfame-K (0.4-19% of the ADI for a 60kg person). Urine collections were then carried out by the volunteers for 24 h after each dose. The data obtained from this study were used to construct intake/excretion curves for both sweeteners. To test the methodology developed, 188 volunteers aged between 3 and 74 years were asked to carry out a 24-h urine collection whilst keeping a 48-h food diary. Comparison of the intake data obtained using the biomarker approach with the questionnaire-based results was generally good, although discrepancies due to the format and assessment of the questionnaire data were noticed.     

A microfabricated wedge-shaped adhesive array displaying gecko-like dynamic adhesion,directionality and long lifetime

Gecko adhesion has become a paradigmatic example of bio-inspired engineering, yet among the many gecko-like synthetic adhesives (GSAs), truly gecko-like performance remains elusive. Many GSAs have previously demonstrated one or two features of the gecko adhesive. We present a new wedge-shaped GSA that exhibits several gecko-like properties simultaneously: directional features; zero force at detachment; high ratio of detachment force to preload force; non-adhesive default state; and the ability to maintain performance while sliding, even after thousands of cycles. Individual wedges independently detach and reattach during sliding, resulting in high levels of shear and normal adhesion during drag. This behaviour provides a non-catastrophic failure mechanism that is desirable for applications such as climbing robots where sudden contact failure would result in serious falls. The effects of scaling patch sizes up to tens of square centimetres are also presented and discussed. Patches of 1 cm² had an adhesive pressure of 5.1 kPa while simultaneously supporting 17.0 kPa of shear. After 30 000 attachment/detachment cycles, a patch retained 67 per cent of its initial adhesion and 76 per cent of its initial shear without cleaning. Square-based wedges of 20 μm and 50 μm are manufactured in a moulding process where moulds are fabricated using a dual-side, dual-angle lithography process on quartz wafers with SU-8 photoresist as the mould material and polydimethylsiloxane as the cast material.     

Novel in situ measurements of relative humidity in a polymer electrolyte membrane fuel cell

Miniature temperature/humidity sensors are incorporated into the graphite flowplates of a single cell polymer electrolyte membrane fuel cell (PEMFC) in order to measure the humidity profile along the serpentine channels of both anode and cathode in real time. The sensors show robust performance and importantly are able to recover after saturation. The key observation is a significant increase in relative humidity along the anode gas channel due to back diffusion of water from cathode to anode. Such measurements may be used to determine the water balance in the cell under a range of operating conditions to facilitate model validation and system optimisation.     

Accuracy of parental reporting of secondhand smoke exposure: The National Health and Nutrition Examination Survey III.

The accuracy of parental reports of youth secondhand smoke exposure has received limited attention in the research literature. Such reports were compared to serum cotinine levels among participants of the National Health and Nutrition Examination Survey III who were aged 4-16 years. Likely smokers with serum cotinine values of 14 ng/ml or more and self-reported tobacco users were excluded from the analysis (n = 87), leaving 2,524 youth participants. One adult guardian, typically the parent, was asked to identify household smokers and estimate the number of cigarettes smoked in the home. Using cotinine levels of at least 0.2 ng/ml as the criterion, we found the sensitivity and specificity of any reported smokers in the home to be .65 and .92, respectively. Spearman correlations between cotinine levels and the number of smokers and the number of cigarettes consumed in the household were .67 and .68, respectively, and varied little across subgroups, including age, gender, and ethnicity of the child as well as household poverty status and educational attainment of the parent. Parental reports of household smoking alone fail to capture all youth secondhand smoke exposures, but they correlate well with cotinine levels when expressed as the number of household smokers or the number of cigarettes smoked in the household. Additional research is needed to determine whether reliance on parental reports of secondhand smoke exposure leads to bias in studies examining health outcomes in children and adolescents. Also, additional research is needed to better determine the level of secondhand smoke exposure that is biologically important in children and adolescents.     

Statistical methods in psychology journals: Guidelines and explanations.

In the light of continuing debate over the applications of significance testing in psychology journals and following the publication of J. Cohen's (1994) article, the Board of Scientific Affairs (BSA) of the American Psychological Association (APA) convened a committee called the Task Force on Statistical Interference (TFSI) whose charge was "to elucidate some of the controversial issues surrounding applications of statistics including significance testing and its alternatives; alternative underlying models and data transformation; and newer methods made possible by powerful computers" (BSA, personal communication, February 28, 1996). After extensive discussion, the BSA recommended that publishing an article in American Psychologist, as a way to initiate discussion in the field about changes in current practices of data analysis and reporting may be appropriate. This report follows that request. Following each guideline are comments, explanations, or elaborations assembled by L. Wilkinson for the task force and under its review. The report is concerned with the use of statistical methods only and is not meant as an assessment of research methods in general. The title and format of the report are adapted from an article by J. C. Bailar and F. Mosteller (1988). (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Performance of Reed-Muller codes and a maximum-likelihood decodingalgorithm for OFDM

The performance of Reed-Muller encoding and a maximum-likelihood decoding algorithm for orthogonal frequency-division multiplexing is presented. The example codes have a tightly bounded peak-to-mean envelope power ratio, while simultaneously enabling powerful error correction. We present a maximum-likelihood decoder that makes use of a distance-preserving map and multiple fast Hadamard transforms. Its operation is described in detail and its performance is assessed under realistic channel conditions     

Stoichiometry of ozonation of environmentally relevant olefins in saturated hydrocarbon solvents

The double bond-to-ozone reaction stoichiometry was quantified for ozonation of several environmentally relevant unsaturated fatty acids and monoterpenes in saturated hydrocarbon solvents. Olefins with initial concentrations from 30 microM to 3mM were injected in a solvent (n-hexadecane, nonane, or cyclohexane) while an ozone-oxygen mixture was slowly bubbled through the solution. The number of ozone molecules consumed by the injection was quantified in the outgoing flow, and the expected 1:1 double bond-to-ozone reaction stoichiometry was observed only under subambient temperature conditions (T < 250 K). At room temperature, the effective number of double bonds oxidized by each ozone molecule increased to 2-5, with a higher degree of oxidation occurring at lower initial olefin concentrations. The observed enhancement in the stoichiometry is consistent with a competition between direct ozonation and free radical initiated oxidation of double bonds, with free radicals being produced by slow reactions between dissolved ozone and solvent molecules.     

Role of sigma B factor in the alkaline tolerance response of Listeria monocytogenes 10403S and cross-protection against subsequent ethanol and osmotic stress

Many of the considerable abilities of Listeria monocytogenes to persist and grow in a wide range of adverse environmental conditions are thought to be at least partly under the control of the alternative sigma factor (sigmaB), encoded by the sigB gene. However, little is known about the role of this master regulon in the impressive ability of Listeria to persist and grow under conditions of alkaline pH. In this study, Northern blot analysis of parent Listeria mRNA revealed that alkali adaptation (pH 9.5 for 1 h) significantly increased the expression of sigB-derived mRNA. The study included a comparison of the relative survival of mid-exponential populations of adapted and nonadapted parent type (sigmaB expressing) and mutant (not sigmaB expressing, deltasigB) Listeria strains during subsequent alkaline (pH 12.0), osmotic (25% NaCl, wt/vol), or ethanol (16.5%) stress. Alkali-adapted parent strains were more resistant to pH 12.0 than were adapted deltasigB type strains, but both alkali-adapted parent and deltasigB strains were more resistant to pH 12.0 than were nonadapted strains. Alkali-adapted parent strains were more resistant to osmotic stress than were adapted deltasigB type strains. No significant differences in viability were observed between alkali-adapted parent and deltasigB strains after ethanol stress, suggesting that cross-protection against osmotic stress is mediated by sigmaB whereas cross-protection against ethanol is sigmaB independent. Overall, alkali-induced cross-protection against osmotic and ethanol challenges may have serious implications for food safety and human health because such stress conditions are routinely used as part of food preservation and surface cleaning processes.     

全球光伏电池片、组件供应商排行榜中国企业均居榜首

根据IMS Research 2010年年底最新的光伏电池和组件季度报告,2010年第三季度,中国晶体硅光伏巨头一尚德和晶澳太阳能,分别位居全球光伏组件出货量、光伏电池生产量排行榜第一位。尚德光伏组件出货量以令人注目的25%的环比增幅继续保持首位,同年第二季度该公司首次问鼎