Light‐Activated,Multi‐Semiconductor Hybrid Microswimmers

Using a dynamic fabrication process, hybrid, photoactivated microswimmers made from two different semiconductors, titanium dioxide (TiO₂) and cuprous oxide (Cu₂O) are developed, where each material occupies a distinct portion of the multiconstituent particles. Structured light‐activated microswimmers made from only TiO₂ or Cu₂O are observed to be driven in hydrogen peroxide and water most vigorously under UV or blue light, respectively, whereas hybrid structures made from both of these materials exhibit wavelength‐dependent modes of motion due to the disparate responses of each photocatalyst. It is also found that the hybrid particles are activated in water alone, a behavior which is not observed in those made from a single semiconductor, and thus, the system may open up a new class of fuel‐free photoactive colloids that take advantage of semiconductor heterojunctions. The TiO₂/Cu₂O hybrid microswimmer presented here is but an example of a broader method for inducing different modes of motion in a single light‐activated particle, which is not limited to the specific geometries and materials presented in this study.     

Pain threshold values during periodontal probing: assessment of maxillary incisor and molar sites

Probing pain threshold (PPT) assessments were conducted in the facial and oral sulci of maxillary central incisors and first molars of 10 periodontally healthy adults. All subjects were systemically healthy, free of pain, and reported no current medication usage. A computer-linked electronic probe, modified to deliver steadily increasing forces up to 200 grams, was used to collect the data. The system contained a subject operated "off-switch" which, upon activation, signaled the computer to record the subject's PPT. Assessments of each subject's PPTs were conducted on 3 separate occasions at 7-day intervals. Results indicated that the facial sulci of the incisors were the most pain sensitive. They displayed a mean PPT of 50.9 +/- 26.6 grams. The oral sulci of the incisors exhibited a mean PPT of 76.5 +/- 45.2 grams. Facial and oral sulci of the molars evidenced mean PPT values of 102.6 +/- 52.1 grams and 113.5 +/- 51.3 grams, respectively. These data suggest that sulci associated with incisor teeth are nearly twice as pain sensitive as sulci associated with molar teeth. In addition, facial sulci are significantly more pain sensitive than oral sulci. Data did not indicate a visit effect nor a side-of-mouth effect on PPT values.     

Decorating tokens to facilitate recognition of ambiguous language constructs

Software tools are fundamental to the comprehension, analysis, testing and debugging of application systems. A necessary first step in the development of many tools is the construction of a parser front‐end that can recognize the implementation language of the system under development. In this paper, we describe our use of token decoration to facilitate recognition of ambiguous language constructs. We apply our approach to the C++ language since its grammar is replete with ambiguous derivations such as the declaration/expression and template‐declaration/expression ambiguity. We describe our implementation of a parser front‐end for C++, keystone, and we describe our results in decorating tokens for our test suite including the examples from Clause Three of the C++ standard. We are currently exploiting the keystone front‐end to develop a taxonomy for implementation‐based class testing and to reverse‐engineer Unified Modeling Language (UML) class diagrams. Copyright © 2002 John Wiley & Sons, Ltd.     

Development of open-cathode polymer electrolyte fuel cells using printed circuit board flow-field plates: Flow geometry characterisation

Open-cathode air-breathing fuel cells have the advantage of reduced system complexity and simplified operation, as oxygen is taken directly from ambient air without the need for blowers/compressors. In this study, printed circuit boards (PCBs) are used as flow-field plates. The use of PCBs offers the potential for significant cost reduction due to their well-established manufacturing processing and low materials cost. This study investigates the effect of varying the cathode geometry (parallel and circular) and opening ratios (43%, 53% and 63%) on fuel cell performance using polarisation curves, electrochemical impedance spectroscopy (EIS) and thermal imaging. The results obtained indicate that circular openings afford lower Ohmic resistance than parallel flow-field designs, which helps improve contact between the gas diffusion layer and flow-field plate. However, flow-field plates with circular openings suffer from greater mass transport limitation effects. Likewise, greater opening ratios offer better mass transport but increased Ohmic resistance as a result of the reduced area of lands/ribs. The thermal imaging results reveal lower temperature in the middle of the fuel cell due to “bowing” of the printed circuit board flow field plates which reduces the local current density. A trade-off between these factors results in a design with a maximum area specific power density of 250 mW cm⁻².     

The effect of O2 enrichment on NOx formation in biomass co-fired pulverised coal combustion

Oxygen enrichment of the combustion air in pulverised coal combustion for power plant is seen as a possible retrofit measure to improve CO₂ scrubbing and capture. This technique produces a reduced volume of flue gas with higher CO₂ concentration than normal air combustion that will contributes to the enhancement of amine scrubbing plant efficiencies. We report in this article the results of a study at the small pilot scale into the effect of these combustion modifications on the formation of NO_x and associated carbon burnout changes. Experiments were performed using a Russian coal, typical of that used in some UK power stations with shea meal and Pakistani cotton stalk as biomass fuels co-fired at a fraction of 15%th. The down-fired pulverised coal combustor was operated at 20 kWth under air-staged conditions for NO_x control and the secondary and over-fire air flows were both enriched by up to 79% (100% O₂) for a range of splits giving a 35% overall O₂ concentration for full enrichment. When the same enrichment process was applied to biomass/coal combustion different behaviour was observed with respect to NO_x formation. We have shown that oxygen enrichment can achieve benefits of improved carbon burnout with a positive impact on NO_x emissions over and above the primary aim of increasing CO₂ concentration in the flue gas for enhanced capture efficiencies. With all other conditions of overall stoichiometry, OFA levels and O₂ enrichment levels remaining the same, NO_x levels at 22% OFA initially increased over the range of secondary air enrichment, particularly for shea meal/coal co-firing. At 31% OFA the trends were to lower NO_x at high enrichment levels. However, co-firing with shea meal initially showed an increase in NO_x emission at lower levels of enrichment (up to 40% O₂) followed by overall lower NOx emissions at 100% O₂ in the secondary air. The results show that NO_x emissions can either increase or decrease depending on the operating conditions. The differences in behaviour are attributed, not only to the effects of enrichment on the stoichiometry of the near-burner zone, but also on the flame dynamics and intensity of combustion related to the associated reductions in gas velocity and swirl intensity by the transition from air to pure O₂ in the secondary oxidant stream.     

Simultaneous reduction of NOx and SO2 emissions from coal combustion by calcium magnesium acetate

The potential of calcium magnesium acetate (CMA) as a medium for the simultaneous control of NO_x and SO_x emissions has been investigated using a pulverized coal combustion rig operating at 80 kW. A US and a UK coal of significantly different sulphur contents were used as primary fuel and CMA was injected in solution form into the combustion gases by horizontally opposed twin-fluid atomisers at temperatures of 1100-1200 °C. SO₂ reductions typically greater than 80 and 70% were found for initial SO₂ levels of 1000 and 1500 ppm, respectively, at Ca/S ratios greater than 2.5. There did not appear to be significant limitation on sulphation by pore blockage using CMA due to the open structure formed during calcination and there is clear potential for zero SO₂ emissions at higher Ca/S ratios. The Ca content of the CMA in the form of CaO, via a droplet drying/particle calcination process, absorbs SO₂ by sulphation processes by penetration into the open pore structure of these particles. The effect of primary zone stoichiometry (λ₁=1.05, 1.15 and 1.4) on NO_x reduction was investigated for a range of CMA feed rates up to a coal equivalent of 24% of the total thermal input. NO_x reductions of 80, 50 and 30% were achieved at a primary zone stoichiometry of λ₁=1.05, 1.15 and 1.4, respectively, for a reburn zone residence time of 0.8 s. At lower equivalent reburn fuel fractions, coal gave greater NO_x reductions than CMA but similar levels were achieved above Rff=18%. The mechanism for NO_x reduction involves the organic fraction of CMA which pyrolyses into hydrocarbon fragments (CH_i), but to a lesser degree than coal, which may then react with NO_x in a manner similar to a conventional ‘reburn’ mechanism where NO_x is partly converted to N₂ depending on the availability of oxygen.     

Microbiological characterization of randomly selected Portuguese raw milk cheeses with reference to food safety

Seventy raw milk cheeses made in different regions of Portugal, both hard and soft varieties, made with cow's, ewe's, or goat's milk or combinations of these, were sampled within their quoted shelf lives for microbiological safety. On the basis of the presence or numbers of Escherichia coli, E. coli O157, Staphylococcus aureus, Salmonella, and Listeria monocytogenes, cheeses were categorized as satisfactory, acceptable, unsatisfactory, or unacceptable and potentially hazardous. Twenty-two of the 70 cheeses were classified as satisfactory or acceptable. Thirty-seven of the cheeses were considered unsatisfactory because of the presence of E. coli, S. aureus, or both, while 11 of the cheeses were graded as unacceptable and potentially hazardous because of the presence of excessive numbers of S. aureus, E. coli, or L. monocytogenes and the presence of Salmonella in three of these. All cheeses graded as unacceptable and potentially hazardous were soft or semisoft cheeses made with ewe's and goat's milk, with the exception of two hard cheeses made with cow's milk. E. coli O157 was not detected in any of the cheeses. According to the present results, it seems that the presence or counts of pathogenic or indicator organisms in raw milk cheeses cannot be related to the processing conditions, milk type, or region of production.     

Facilitation of sociomoral reasoning in delinquents.

An intervention involving 60 incarcerated juvenile delinquents (ages 14–18 yrs) yielded significant gains in sociomoral reasoning that were attributable to a dilemma-discussions treatment. The treatment consisted of 8 weekly small-group discussions of sociomoral dilemmas. Ss were pretested on the Sociomoral Reflection Measure (SRM) and the Dilemma Decisions Survey and were assigned to either consensus dilemma-discussion, nonconsensus dilemma-discussion, or no-discussion groups. Pretest results show that Ss initially differed in both sociomoral stage and dilemma opinion. Of the dilemma-discussions Ss, 87.5% were pretested at Modal Stage 2 on the SRM and shifted to Modal Stage 3 on the posttest, whereas only 14.3% of the Modal Stage 2 control Ss did so. Pretest Modal Stage 3 Ss remained at Stage 3 on the posttest. Across the experimental groups, no difference was found between groups where a consensus was required for the discussion and groups having no consensus requirement. Investigations of the possible in-program and postrelease behavioral ramifications of the dilemma-discussions treatment are recommended. (40 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)