Performance of Methanol Oxidation Catalysts with Varying Pt:Ru Ratio as a Function of Temperature

This paper describes the effects of varying the Pt to Ru ratio in carbon-supported catalysts for methanol oxidation as a function of temperature. Previously these effects were studied in isolation, but now it is shown that the composition of a given catalyst as a function of temperature is extremely important for its activity towards methanol oxidation. Platinum rich 3:2 atomic ratio catalysts perform better than a 1:1 catalyst at 25 °C, where only Pt is believed to be active towards methanol dehydrogenation, since this process is a highly thermally activated process on Ru sites. This result is reversed at 65 °C, where the 1:1 catalyst displays much higher currents across the entire range of polarization. This may result from methanol dehydrogenation occurring on both Ru and Pt sites at higher temperatures. At an intermediate temperature, 45 °C, the 3:2 catalyst is seen to perform better at lower current values, while the 1:1 catalyst is superior at higher current densities, with the crossover occurring at 62 A g^–1. As a consequence, when designing fuel cell catalysts, the composition of the catalyst employed should be tailored with respect to the exact operating conditions, in order to promote optimum fuel cell performance.     

Hydrogenation of methyl sorbate and soybean esters with polymer-bound metal catalysts

New polymer-bound hydrogenation catalysts were made by complexing PdCl₂, RhCl₃·3H₂O, or NiCl₂ with anthranilic acid anchored to chloromethylated polystyrene. The Pd(II) and Ni(II) polymers were reduced to the corresponding Pd(O) and Ni(O) catalysts with NaBH₄. In the hydrogenation of methyl sorbate, these polymer catalysts were highly selective for the formation of methyl 2-hexenoate. The diene to monoene selectivity decreased in the order: Pd(II), Pd(O), Rh(I), Ni(II), Ni(O). Kinetic studies support 1,2-reduction of the Δ4 double bond of sorbate as the main path of hydrogenation. In the hydrogenation of soybean esters, the Pd(II) polymer catalysts proved superior because they were more active than the Ni(II) polymers and produced lesstrans unsaturation than the Rh(I) polymers. Hydrogenation with Pd(II) polymers at 50~100 C and 50 to 100 psi H₂ decreased the linolenate content below 3% and increasedtrans unsaturation to 10~26%. The linolenate to linoleate selectivity ranged from 1.6 to 3.2. Reaction parameters were analyzed statistically to optimize hydrogenation. Recycling through 2 or 3 hydrogenations of soybean esters was demonstrated with the Pd(II) polymers. In comparison with commercial Pd-on-alumina, the Pd(II) polymers were less active and as selective in the hydrogenation of soybean esters but more selective in the hydrogenation of methyl sorbate. Presented at ISF-AOCS Meeting, New York, April 1980.     

Asymmetric reverse osmosis and ultrafiltration membranes prepared from sulfonated polysulfone

The concept of solubility parameter, developed by Hansen, has been applied to the determination of solubility diagram of polysulfone and sulfonated polysulfone. Data showing the effect of various parameters such as thermodynamic quality of the solvent, casting solution composition and viscosity, solvent evaporation period and precipitation bath composition, on membrane structure and performance have been presented. By adjusting these parameters a wide variety of sulfonated polysulfone membranes useful for both ultrafiltration and reverse osmosis applications could be obtained.     

纳米粒子/环氧树脂复合材料的固化动力学研究

在纳米Al2O3、Si3N4、SiC填充环氧树脂复合材料体系中,纳米粒子表面活性及粒子与环氧树脂之间的相互作用影响着环氧树脂的固化过程.本文利用傅立叶红外光谱表征了纳米粒子与环氧树脂之间的化学作用情况,并利用差视扫描量热仪研究了不同纳米粒子/环氧树脂复合材料的固化动力学.结果表明,具有相对最强表面活性的纳米Al2O3粒子与基体之间的相互作用最强,同时该粒子对环氧树脂固化过程的促进作用最显著.     

Zur personellen Verankerung der IT-Funktion im Vorstand börsennotierter Unternehmen: Ergebnisse einer inhaltsanalytischen Betrachtung

On the Rate of Board Members with IT Responsibilities in Firms Listed on the Stock Exchange: Results of a Content Analysis: This article reports on a content analysis that investigates the rate of board members with IT responsibilities in firms listed on the stock exchange in the German speaking countries. Furthermore, the study ascertains the correlation of six factors – which become evident through content analysis – with the rate of board members with IT responsibilities. A total of 679 annual reports of German, Austrian, and Swiss corporations have been analyzed. The results show that in Germany and Switzerland 26 percent of the firms investigated have a board member with IT responsibilities, in Austria the rate is 23 percent. Additionally, the results show that turnover and number of employees are highly positively correlated with the rate of board members with IT responsibilities. Furthermore, the data show a correlation between industry and the rate of board members with IT responsibilities.     

Computing presentations for subgroups of polycyclic groups and of context-free groups

Algorithms for solving uniform decision problems for algebraic structures crucially depend on the chosen finite presentations for the structures under consideration. Rewriting techniques have been used very successfully to solve uniform decision problems, when the presentations considered involve finite, noetherian, and ()-confluent rewriting systems. Whenever the class of algebraic structures considered is closed under the operation of taking finitely generated substructures, then the algorithms for solving the uniform decision problems can be applied to the substructures as well. However, since these algorithms depend on the form of the presentations, this involves the task of constructing a presentation of a certain form for a substructure given a presentation of this form for the structure itself and a finite set of generating elements for the substructure.This problem, which has received a lot of attention in algebra, is here investigated from an algorithmic point of view. The structures considered are the following two classes of groups, which have been studied extensively before: the polycyclic groups and the context-free groups.Finitely generated context-free groups can be presented by finite, monadic, and -confluent string-rewriting systems. Due to their nice algorithmic properties these systems provide a way to effectively solve many decision problems for context-free groups. Since finitely generated subgroups of context-free groups are again contextfree, they can be presented in the same way. Here we describe a process that, from a finite, monadic, and -confluent string-rewriting system presenting a context-free groupG and a finite subsetU ofG, determines a presentation of this form for the subgroup U ofG that is generated byU. For finitely presented polycyclic groups we obtain an analogous result, when we use finite confluent PCP2-presentations to describe these groups.This work was performed while this author was visiting at the Fachbereich Informatik, Universität Kaiserslautern, during his sabbatical 1991/92     

Premedication with oral midazolam in children--an assessment of psychomotor function, anxiolysis, sedation and pharmacokinetics

We studied 30 children, aged 4 to 12 years, undergoing elective circumcision, premedicated with midazolam 0.5 mg.kg-1 and atropine 0.02 mg.kg-1 by mouth. A modified postbox test and the coding component of the Wechsler intelligence scale (WISC-R) was used to assess the preoperative effect of premedication on psychomotor function. Mood and sedation were also scored and related to serum midazolam concentrations. The children showed a significant decline in psychomotor performance 30 and 60 minutes after premedication when compared with their best unmedicated performance recorded the previous evening. This decline in psychomotor performance was only weakly associated with serum midazolam concentrations (r = 0.1). The postbox toy ratio is a suitable measurement of psychomotor performance in children because of its simplicity and ease of use in the clinical environment, although it may suffer the "test-retest" limitations of similar types of assessment. The sedative and anxiolytic effects of midazolam provide a quiet environment for a smooth induction of anaesthesia.     

Providing the right stuff: feeding children with chronic renal failure

The progressive loss of renal function in children with chronic renal failure (CRF) has a negative influence on their nutritional status and statural growth. Supportive therapies with 1-25 dihydroxy-vitamin D3, recombinant erythropoietin and growth hormone have significantly improved the biochemical and clinical features but the success of these therapies is largely related to an appropriate diet, with adequate protein/caloric intakes. Children more than adults have minimal protein requirements to avoid malnutrition and growth impairment FAO/WHO and RDA recommendations save as guidelines for a correct diet in children with CRF. Following these allowances leads to a "normoproteic" diet, with a protein intake which is often half the unrestricted one in Western European countries, but which is still likely to be not enough to protect against renal deterioration. Indeed the European Study Group for Nutritional Treatment of CRF in children failed to show a significant effect of diet on the mean decline of glomerular filtration rate over two years.     

Cervical pain and proprioceptive sensitivity

With the intent of estimating the proprioceptive sensitivity of the cervical rachis, the Authors subjected 17 healthy volunteers and 20 patients suffering from various cervical disorders to a clinical head positioning test, which was previously experimented upon by several french Authors was modified under certain aspects by our equipe. The test, consists in flexion and extension of the head after maximal rotations to the left and right, then repositioning the head at the starting point "0" which corresponds to the crossing point of two orthogonal axis of a target. The positions are marked on the target by a laser beam situated on the helmet worn by the subject undergoing testing. The results obtained corresponding to the errors committed regarding point "0", permit us to confirm the reliability of the test and significant definitions between the control group and the patients suffering from cervical disorders.