A kinetic model for the anode of the direct methanol fuel cell (DMFC) is presented. The model is based on the generally accepted dual site mechanism of methanol oxidation, in aqueous solution, on well characterized Pt-Ru catalyst and it can predict the performance of the electrode as a function of cell temperature, anode potential and methanol concentration. In addition the model also generates data regarding the surface coverage of significant adsorbates involved in methanol oxidation on the dual site catalyst.The analysis of the initial complex model confirms that a simplification in anode modelling can be made and some of the kinetic parameter can be reliably neglected. Based on this approach a fast and simplified three parameter model is derived from the same complex kinetic mechanism. The kinetic parameters of both models are estimated from experimental anode polarisation data from a 9 cm(2) DMFC operating with various methanol feed concentrations and temperatures. The models were developed in Lab VIEW and this has greatly simplified the simulation process, giving a model with ca. 85-95% fit on the experimental data. Depending on the computational speed available, and the desired complexity of problem at hand, either of the models can be used to give accurate model simulations for methanol fuel cell polarisations. (C) 2007 Elsevier B.V. All rights reserved.

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Fuel cell-based automobiles have gained attention in the last few years due to growing public concern about urban air pollution and consequent environmental problems. From an analysis of the power and energy requirements of a modern car, it is estimated that a base sustainable power of ca. 50 kW supplemented with short bursts up to 80 kW will suffice in most driving requirements. The energy demand depends greatly on driving characteristics but under normal usage is expected to be 200 Wh/km. The advantages and disadvantages of candidate fuel-cell systems and various fuels are considered together with the issue of whether the fuel should be converted directly in the fuel cell or should be reformed to hydrogen onboard the vehicle. For fuel cell vehicles to compete successfully with conventional internal-combustion engine vehicles, it appears that direct conversion fuel cells using probably hydrogen, but possibly methanol, are the only realistic contenders for road transportation applications. Among the available fuel cell technologies, polymer-electrolyte fuel cells directly fueled with hydrogen appear to be the best option for powering fuel cell vehicles as there is every prospect that these will exceed the performance of the internal-combustion engine vehicles but for their first cost. A target cost of $ 50/kW would be mandatory to make polymer-electrolyte fuel cells competitive with the internal combustion engines and can only be achieved with design changes that would substantially reduce the quantity of materials used. At present, prominent car manufacturers are deploying important research and development efforts to develop fuel cell vehicles and are projecting to start production by 2005.

Results on the performance of a 25 cm2 liquid-feed solid-polymer-electrolyte direct methanol fuel cell (SPE-DMFC), operating under near-ambient conditions, are reported. The SPE-DMFC can yield a maximum power density of c. 200 mW cm−2 at 90°C while operating with 1 M aqueous methanol and oxygen under ambient pressure. While operating the SPE-DMFC under similar conditions with air, a maximum power density of ca. 100 mW cm−2 is achieved. Analysis of the electrode reaction kinetics parameters on the methanol electrode suggests that the reaction mechanism for methanol oxidation remains invariant with temperature. Durability data on the SPE-DMFC at an operational current density of 100 mA cm−2 have also been obtained.

Mixed-reactants solid-polymer-electrolyte direct methanol fuel cells (SPE-DMFCs) with a PtRu/C anode and a methanol-tolerant oxygen-reduction cathode catalyst have been assembled and have been subjected to galvanostatic polarisation studies. The oxygen-reduction cathode was either of the FeTMPP/C, CoTMPP/C, FeCoTMPP/C and RuSe/C. It was found that the SPE-DMFC with the RuSe/C cathode yielded the best performance. It has been possible to achieve power densities of approximately 50 and 20mW/cm2 while operating a mixed-reactants SPE-DMFC at 90°C with oxygen and air fed cathodes, respectively. Interestingly, these SPE-DMFCs exhibit no parasitic oxidation of methanol with oxygen.

Background: Opioids, although effective postoperative analgesics, are associated with undesirable side effects. In an attempt to determine whether adjuvant, nonopioid medication would permit a reduction of the amount of fentanyl required for postoperative analgesia, the efficacy of ketorolac, an injectable nonsteroidal antiinflammatory drug, was studied as an adjuvant to fentanyl patient-controlled epidural analgesia (PCEA) for postoperative pain management following radical retropubic prostatectomy.Methods: Forty patients were randomized into two groups to receive fentanyl PCEA and either ketorolac 30 mg intra-muscularly every 6 h after an initial dose of 60 mg (n = 20) or placebo (n = 20) for 72 h. Visual analogue scale pain scores (0-100 mm; 0 mm = no pain; 100 mm = worst pain), sedation, fentanyl usage, gastrointestinal function, complications, blood loss, and temperature were assessed four times each day.Results: Visual analogue scale (VAS) pain scores at rest were lower in the ketorolac group during the first 4 h (P < 0.01), but were similar thereafter. Global VAS pain scores with activity were lower in the ketorolac group on postoperative day 1 (23 +/- 4 vs. 39 +/- 6; P < 0.05) and postoperative day 2 (17 +/- 3 vs. 29 +/- 4; P < 0.05). Bladder spasm pain occurred less frequently in the ketorolac group (1 vs. 9 patients; P < 0.05). Fentanyl usage was less in the ketorolac group throughout the study (33 +/- 3 vs. 50 +/- 6 mug/h, 0-24 h; 20 +/- 2 vs. 36 +/- 6 mug/h, 24-48 h; 12 +/- 2 vs. 24 +/- 6 mug/h, 48-72 h; P < 0.05). Sedation scores and side effects were similar, except on postoperative day 3 when nausea was less frequent in the ketorolac group (0 vs. 6 patients; P < 0.05). Recovery of gastrointestinal function occurred sooner in the ketorolac group as determined hy first bowel sounds (26 +/- 3 vs. 38 +/- 4 h; P < 0.05), first clear liquids (51 +/- 2 vs. 65 +/- 3 h; P < 0.01), and first regular meal (95 +/- 4 vs. 110 +/- 4 h; P < 0.05). There was no significant difference in blood loss, transfusion requirement, hematocrit, platelet count, or temperature. There was high overall satisfaction in both groups, hut fewer patients in the ketorolac group rated pain with walking as usually or always painful (1 vs. 9 patients; P < 0.05).Conclusions: Ketorolac is a beneficial adjuvant to fentanyl PCEA for postoperative pain management after radical retropubic prostatectomy.

A 15-month-old phenotypic female was diagnosed as having 46XY gonadal dysgenesis following karyotyping for Turner-like features. Gonadectomy at the time of bilateral ureteral reimplantation for vesicoureteral reflux showed gonadoblastoma. This case, in which malignancy was already established at 15 months, indicates the need for early gonadectomy, which should be performed at the time of diagnosis.