Percolative model of proton conductivity of Nafion membranes

A model is proposed for the simulation of Nafion^® proton conductivity, where it is assumed that proton conduction occurs only in the water present in the membrane pores. Water is considered to be present in the pores due to two different phenomena: adsorption and capillary condensation. In the latter case, the pore is flooded and proton conduction occurs throughout the whole pore section. The conditions under which capillary condensation occurs are simulated in the model through the Kelvin–Cohan equation for condensation. The Kelvin–Cohan equation is a function of RH, temperature and the pore radius; the larger the pore, the higher the RH for which capillary condensation takes place. If the conditions for capillary condensation are not satisfied, then water is present in the pore due to adsorption under the form of a water layer which covers the pore walls and provides a path for proton conduction. In this case, the modified Brunauer–Emmet–Teller (BET) equation has been used in the model to simulate the thickness of the water layer.     

A mammographic evaluation of the morphostructural variations of the breast during hormone-replacement therapy in the postmenopause

OBJECTIVE: To compare i.v. ketorolac with i.v. prochlorperazine as the initial treatment of migraine headaches in the ED. METHODS: A prospective, double-blind comparison study was performed, using a convenience sample of 64 patients suffering from migraine headaches presenting to the ED at a tertiary care university teaching hospital. Patients were randomly assigned to receive either 10 mg of prochlorperazine i.v. or 30 mg of ketorolac i.v.. Patients scored the severity of their headaches using a 10-cm visual analog pain scale. An initial mark was made on the scale at the time of entry into the study and later another mark was made on a new unmarked pain scale 1 hour after medication administration. Changes in pain scores within each treatment group and between groups were analyzed using the Wilcoxon rank sum test. RESULTS: Prior to treatment, the patients assigned to receive prochlorperazine had a median score of 9.2 cm (mean +/- SD pain score of 8.3 cm +/- 2.1 cm), while the patients receiving ketorolac had a median score of 9.0 (mean pain score of 8.4 cm +/- 1.7 cm). There was no significant difference between the pain scores of the participants in the 2 groups prior to treatment (p = 0.80). One hour after medication administration, the patients in the prochlorperazine group had a median score of 0.5 cm (mean 2.1 +/- 3.2 cm), while those patients receiving ketorolac had a median pain score of 3.9 (mean 4.0 +/- 3.3 cm). The decrease in pain score was significant for both groups of patients (p = 0.0001). The change in pain score for the patients in the prochlorperazine group (median 7.1) was significantly greater than the change in pain score for the patients in the ketorolac group (median 4.0; p = 0.04). CONCLUSION: Although both drugs were associated with a significant reduction in pain scores, benefit over a placebo agent was not tested. Furthermore, the patients who received prochlorperazine i.v. for migraine headaches had a statistically significant greater decrease in their pain scores than did those receiving ketorolac i.v.     

EFFECTS OF SOLID FRICTIONAL INTERACTIONS ON THE APPLICABILITY OF THE FLUID-DYNAMIC SCALING RULES FOR FLUIDISATION

Experimental results are reported which confirm the validity of the fluid dynamic scaling rules for gas-solid fluidised beds operated in the bubbling regime, regardless of the particle and wall roughness. These rules still apply for shallow beds operated in the slugging regime for cases in which the ratio (H_mt/D_t) of inital bed height to bed diameter is less than the tangent of the angle of internal friction of the particles; however, for higher values of H_mt/D_t, which permit the formation of fully developed dense-phase slugs, the scaling rules become invalid. This is considered to be due to particle-particle and particle-wall interactions, and evidence is reported for both these effects in the slugging regime.     

Iron and nickel doped alkaline-earth catalysts for biomass gasification with simultaneous tar reformation and CO2 capture

The tar reforming catalytic activity of iron and nickel based catalysts supported on alkaline-earth oxides CaO, MgO and calcined dolomite [a (CaMg)O solid solution] has been investigated in a fixed bed reactor operating at temperatures ranging from 650 to 850 °C; toluene and 1-methyl naphthalene were used as model compounds for tar generated during biomass gasification. The CO₂ absorption capacities of Fe/(CaMg)O and Ni/(CaMg)O were also investigated at the lower temperature condition (650 °C) at which the sorption process is thermodynamically favoured. It was found that iron and nickel may be optimised in the substrate particles to enhance both the catalytic activity and the carbon deposition resistance during catalytic tests, at the same time reducing critical limitations on CO₂ capture capacity.     

Waste gas biofiltration: advances and limitations of current approaches in microbiology

As confidence in gas biofiltration efficacy grows, ever more complex malodorant and toxic molecules are ameliorated. In parallel, for many countries, emission control legislation becomes increasingly stringent to accommodate both public health and climate change imperatives. Effective gas biofiltration in biofilters and biotrickling filters depends on three key bioreactor variables: the support medium; gas molecule solubilization; and the catabolic population. Organic and inorganic support media, singly or in combination, have been employed and their key criteria are considered by critical appraisal of one, char. Catabolic species have included fungal and bacterial monocultures and, to a lesser extent, microbial communities. In the absence of organic support medium (soil, compost, sewage sludge, etc.) inoculum provision, a targeted enrichment and isolation program must be undertaken followed, possibly, by culture efficacy improvement. Microbial community process enhancement can then be gained by comprehensive characterization of the culturable and total populations. For all species, support medium attachment is critical and this is considered prior to filtration optimization by water content, pH, temperature, loadings, and nutrients manipulation. Finally, to negate discharge of fungal spores, and/or archaeal and/or bacterial cells, capture/destruction technologies are required to enable exploitation of the mineralization product CO(2).     

Fatty acid and positional selectivities of gastric lipase from premature human infants:in vitro studies

Gastric lipase activity in aspirates from premature human infants was tested for fatty acid and positional selectivity using racemic diacid triacylglycerols (TG) as substrates. The resulting free fatty acids and monoacylglycerols (MG) were recovered and analyzed. Octanoic acid (8∶0) and decanoic acid (10∶0) were hydrolyzed with a preference of 61.5∶1 and 2.4∶1 compared to palmitic acid (16∶0) fromrac-16∶0–8∶8∶0 andrac-16∶0–10∶0–10∶0, respectively. The ratio of lauric acid (12∶0) to oleic acid (18∶1) hydrolyzed fromrac-18∶1–12∶0 was 13∶1. Myristic acid (14∶0), 18∶1 and linoleic acid (18∶2) were released at similar rates. These data and the composition of the MG suggest that,in vitro, the lipase is selective for shorter chain fatty acids and for fatty acids on the primary positions of the TG backbone.     

Environmental implications of crop insurance subsidies in Southern Italy

The changing environment affects agriculture with uncertainty. On the other hand, policies to cope with risks may have strong impacts on the environment. We evaluate the effects of public risk management programmes, such as subsidized crop insurance, fertilizer use and land allocation to crops. We implement a mathematical programming model of a representative wheat–tomato farm in Puglia, a Southern Italy region. The results show that under the current crop insurance programmes, tomato production is expected to expand and will require larger amounts of fertilizer, whereas the opposite is true for wheat production. Policy and environmental implications are discussed.