Self Organising Maps for variable selection: Application to human saliva analysed by nuclear magnetic resonance spectroscopy to investigate the effect of an oral healthcare product

SOMs (Self Organising Maps) are derived from the machine learning literature and serve as a valuable method for representing data. In this paper, the use of SOMs as a technique for determining the most significant variables (or markers) in a dataset is described. The method is applied to the NMR spectra of 96 human saliva samples, half of which have been treated with an oral rinse formulation and half of which are controls, and 49 variables consisting of bucketed intensities. In addition, three simulations, two of which consist of the same number of samples and variables as the experimental dataset and a third that contains a much larger number of variables, are described. Two of the simulations contain known discriminatory variables, and the remaining is treated as a null dataset without any specific discriminatory variables added. The described SOM method is contrasted to Partial Least Squares Discriminant Analysis, and a list of the markers determined to be most significant using both approaches was obtained and the differences arising are discussed. A SOM Discrimination Index (SOMDI) is defined, whose magnitude relates to how strongly a variable is considered to be a discriminator. In order to ensure that the model is stable and not dependent on the random starting point of the SOM, one hundred iterations were performed and variables that were consistently of high rank were selected. A variety of approaches for data representation are illustrated, and the main theoretical principles of employing SOMs for determining which variables are most significant are outlined. Software used in this paper was written in-house, allowing greater flexibility over existing packages, and tailored for the specific application in hand.     

High hydrogen production from glycerol or glucose by electrohydrogenesis using microbial electrolysis cells

The use of glycerol for hydrogen gas production was examined via electrohydrogenesis using microbial electrolysis cells (MECs). A hydrogen yield of 3.9 mol-H₂/mol was obtained using glycerol, which is higher than that possible by fermentation, at relatively high rates of 2.0 ± 0.4 m³/m³ d (E_ap = 0.9 V). Under the same conditions, hydrogen was produced from glucose at a yield of 7.2 mol-H₂/mol and a rate of 1.9 ± 0.3 m³/m³ d. Glycerol was completely removed within 6 h, with 56% of the electrons in intermediates (primarily 1,3-propanediol), with the balance converted to current, intracellular storage products or biomass. Glucose was removed within 5 h, but intermediates (mainly propionate) accounted for only 19% of the electrons. Hydrogen was also produced using the glycerol byproduct of biodiesel fuel production at a rate of 0.41 ± 0.1 m³/m³ d. These results demonstrate that electrohydrogenesis is an effective method for producing hydrogen from either pure glycerol or glycerol byproducts of biodiesel fuel production.     

Corrosion control enhancement from a dolomite-amended slow sand filter

The associated decrease of pH in slow sand filters, due to CO2 conversion and biological activity, may produce effluent that is slightly corrosive to downstream distribution pipe material. This pilot study examined the use of a 3-cm crushed dolomite limestone media layer placed within the filter column of a slow sand filter to enhance effluent corrosion control by the introduction of beneficial dolomite dissolution products, without impacting turbidity removal efficiencies. Turbidity removal, calcium concentration, pH, conductivity, total hardness and alkalinity changes were calculated for the filter during a 60-day pilot study, and water chemistry values were used to estimate the changes of the saturation index (SI) throughout the filter run. Total hardness change through the filter was compared to change calculated by a derived equation for hardness using calcium concentrations to determine if the media was dissolving in stoichiometric proportions, and mineral service life in the filter was estimated using an assumption of stoichiometric dissolution at a constant flow rate. Effluent SI was raised an average of 30%, alkalinity was increased by 19%, and effluent pH averaged 7.7. Filter effluent complied with current turbidity regulatory requirements for the provision of potable water, and mineral service life was estimated between 7.5 and 9.5 years.     

The perceived utility of human and automated aids in a visual detection task

Although increases in the use of automation have occurred across society, research has found that human operators often underutilize (disuse) and overly rely on (misuse) automated aids (R. Parasuraman & V. Riley, 1997). Nearly 275 Cameron University students participated in 1 of 3 experiments performed to examine the effects of perceived utility (M. T. Dzindolet, H. P. Beck, L. G. Pierce, & L. A. Dawe, 2001) on automation use in a visual detection task and to compare reliance on automated aids with reliance on humans. Results revealed a bias for human operators to rely on themselves. Although self-report data indicate a bias toward automated aids over human aids, performance data revealed that participants were more likely to disuse automated aids than to disuse human aids. This discrepancy was accounted for by assuming human operators have a "perfect automation" schema. Actual or potential applications of this research include the design of future automateddecision aids and training procedures for operators relying on such aids.     

Physician decision making and cardiac risk: Effects of knowledge, risk perception, risk tolerance, and fuzzy processing.

Despite training, professionals sometimes make serious errors in risky decision making. The authors investigated judgments and decisions for 9 hypothetical patients at 3 levels of cardiac risk, comparing student and physician groups varying in domain-specific knowledge. Decisions were examined regarding whether they deviated from guidelines, how risk perceptions and risk tolerances determined decisions, and how the latter differed for knowledge groups. More knowledgeable professionals were better at discriminating levels of risk according to external correspondence criteria but committed similar errors in disjunctive probability judgments, violating internal coherence criteria. Also, higher knowledge groups relied on fewer dimensions of information than did lower knowledge groups. Consistent with fuzzy-trace theory, experts achieved better discrimination by processing less information and made sharper all-or-none distinctions among decision categories. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

THE BREAKING OF TERNARY ACETATE-ALCOHOL-WATER AZEOTROPES BY EXTRACTIVE DISTILLATION

The breaking of seven ternary acetate-alcohol-water azeotropes by extractive distillation was accomplished. They are n-propyl acetate-n-propanol-water, isopropyl acetate-isopropanol-water, n-butyl acetate-n-butanol-water, 2-butyl acetate-2-butanol-water, isobutyl acetate-isobutanol-water, n-amyl acetate-n-amyl alcohol-water and n-hexyl acetate-n-hexanol-water. The acetates, usually the highest boiling constituents, are obtained as overhead product as a two-phase mixture with water. The most effective agents are glycols and dimethylsulfoxide. Solubility parameters were found to be a qualitative indication for selecting extractive distillation agents. When the formation of a chemical complex is dominant, solubility parameter does not explain solution behavior satisfactorily.     

Do routine antibiotics after loop diathermy excision reduce morbidity?

AIMS: To determine functional results after unilateral and bilateral cataract surgery in children with different aphakic optical correction. METHODS: In this retrospective study, we evaluated visual acuity and binocular vision in 107 children who underwent cataract surgery during the 10 year period from 1985 to 1995. Aphakia was corrected by an intracapsular intraocular lens (IOL), spectacles or contact lenses. RESULTS: Mean visual acuity was > 20/40 (< 0.3 log MAR) with normal binocular vision in 58 children over 7 months of age operated on for bilateral cataracts. Pseudophakic eyes regained visual acuity > 20/63 (< 0.5 log MAR) more often (90%) than aphakic eyes (46%) (p < 0.001). Binocular vision was also achieved more often after IOL implantation (p < 0.001). Visual outcome of early bilateral cataracts was less satisfactory in children with abnormal foveolar function. For 49 children who had surgery for unilateral cataracts, prognosis was poor when surgery was performed before the age of 7 months. For cataract surgery in older children (> or = 7 months) mean visual acuities were better with IOL implantation (p < 0.05). CONCLUSION: Cataract surgery with unilateral and bilateral IOL implantation can provide a beneficial effect on final visual outcome in children who are operated on before abnormal foveolar function develops.