Oberflächendiffusion auf oxidiertem Nickel

A porous electrode of sintered nickel powder was used as a separating diaphragm between two electrolyte-solution spaces and its flow resistance for the solution and the electrical diaphragm resistance was measured. By galvanostatic or potentiostatic oxidation the electrode was oxidized on the surface to Ni(OH)₂ and NiOOH, causing a decrease of pore volume indicated by an increase of flow resistance. In contrast under certain conditions the electrical diaphragm resistance simultaneously diminishes. Thus the electric current is now carried not only by the ions of the electrolyte in the pores of the electrode; there is now an additional charge transport, which is assumed to be proton diffusion on the oxidized nickel surface. The thickness of the diffusion layer, the diffusion coefficient and the temperature dependence of proton diffusion were measured.     

Gastrointestinal pH profiles in patients with inflammatory bowel disease

BACKGROUND: 5-Amino salicylic acid preparations are used in therapy for patients with inflammatory bowel diseases. The bioavailability of these drugs depends on their coating. AIM: To determine whether intraluminal pH is decreased by the presence of inflammation, thereby altering the release of 5-amino salicylic acid in the intestinal lumen. METHODS: Intraluminal gastrointestinal pH was measured by means of a radiotelemetry capsule in 12 healthy controls, in 12 patients with Crohn's disease (five with active disease), and in 11 patients with ulcerative colitis (seven with active disease). RESULTS: The median gastric pH values in the patient groups (Crohn's disease 2.4, range 1.5-4.1; ulcerative colitis 1.95, range 1.55-4.4) were significantly higher than those observed in the controls (1.55, range 0.95-2.6). In the small bowel and colonic segments, all the pH values of Crohn's disease patients were comparable to those of the controls, as were the pH values in the proximal small intestine and in the left colon in patients with ulcerative colitis. However, the latter group had higher pH values in the terminal ileum, the caecum and the right colon. Patients with active disease had comparable median gastrointestinal pH values to patients in remission. CONCLUSIONS: The luminal release of 5-amino salicylic acid might not be inhibited by low pH in patients with active inflammatory bowel diseases. This supports a safe disintegration of the slow release mesalazine preparations even in the presence of severe disease.     

Olsalazine versus mesalazine in the treatment of mild to moderate ulcerative colitis

AIM: To compare the efficacy and tolerability of olsalazine sodium with enteric-coated mesalazine in inducing endoscopic remission in patients with mild to moderate active ulcerative colitis. PATIENTS AND METHODS: Patients with mild to moderate active ulcerative colitis were randomized to receive either olsalazine sodium, 3 g/day (n = 88), or mesalazine, 3 g/day (n = 80), for up to 12 weeks. RESULTS: Of the patients treated with olsalazine sodium, 52.2% achieved endoscopic remission, compared with 48.8% of patients treated with mesalazine. This difference was not significant (P = 0.67). There was a nonsignificant trend for patients with left-sided colitis or a more severe endoscopic grade to achieve remission if they were treated with olsalazine sodium than if they were treated with mesalazine. Both treatments were comparable with respect to clinical activity index and an investigator's global assessment. Seventy patients reported one or more adverse events; adverse events were seen in 45% of olsalazine sodium-treated patients and in 36% of mesalazine-treated patients. Eleven patients treated with olsalazine sodium and nine patients treated with mesalazine withdrew from the study because of adverse events. One patient treated with olsalazine sodium compared with two treated with mesalazine stopped treatment because of diarrhoea. Serious adverse events occurred in three patients treated with olsalazine sodium and in four treated with mesalazine. CONCLUSION: Therapeutic effectiveness and tolerance to the treatment did not differ between olsalazine sodium, 3 g/day, and mesalazine, 3 g/day, in inducing endoscopic remission in patients with mild to moderate active ulcerative colitis within 12 weeks of treatment.     

On the long-term performance of depyrophorized and annealed titanium-containing raney-nickel catalysts for hydrogen anodes in alkaline fuel cells

In alkaline H₂O₂ fuel cells, Ti-containing Raney-nickel is employed as catalyst for hydrogen electrodes. The rate of anodic hydrogen conversion and the long-term performance have been increased markedly by annealing of the slowly air-oxidized catalyst samples in hydrogen atmosphere. The ageing rate of these annealed catalysts was found to be very small at polarizations below the “critical value” of about 50 mV, but it increases exponentially if the polarization surpasses 50 mV. The best catalyst with the lowest ageing rate under 15 μ V/h was prepared using a Raney-NiTi2 catalyst with 4–6 wt% initial Ni(OH)₂-content, which was heat treated in hydrogen atmosphere at 350°C for 5 min.     

A Complex Network Methodology for Travel Demand Model Evaluation and Validation

Networks and Spatial Economics - Travel demand can be viewed as a weighted and directed graph where nodes are the origins and destinations and links represent the trips between nodes. This paper...     

Impedance measurements of air-oxidized and H2-annealed Raney-Ni catalysts for alkaline fuel cells

The catalytic properties and the long-term performance of Raney-NiTi2 catalysts being used in H₂ electrodes of alkaline H₂---O₂ fuel cells can be significantly improved by slow air oxidation and subsequent annealing in an H₂ atmosphere at 300°C. Individual reaction steps are investigated by means of impedance measurements. Theoretical estimations, on the basis of a simple equivalent circuit of a supported electrode, result in a frequency-response relationship which is in very good agreement with the experimental data referring to the relevant frequency range of 10⁻³−10⁻¹ Hz. A method to evaluate the impedance spectra is described in some detail. Calculated and measured impedance data are in good agreement, thus indicating the validity of the charge transfer resistance, the diffusion resistance, as well as the chemisorption capacity and the double-layer capacity. Experiments on the influence of catalyst annealing in an H₂ atmosphere at 350°C show a strong increase in the charge transfer resistance and an obvious decrease in the diffusion resistance, depending on the annealing time. A similar influence on the chemisorption capacity and the double-layer capacity is not observed.     

An ultrasonic feeding mechanism for continuous aerosol generation from cohesive powders

The dispersion of dry, cohesive micro- and nanosized powders has wide applications ranging from medical and environmental science to manufacturing technology. Being able to disperse the dry powder at a stable concentration over periods of time (～hour to several hours) is challenging to achieve, which we attempt to address with a novel dry powder dispersion technology. A portable, cost effective and simple dry powder dispersion device that uses ultrasonic energy for continuous feeding of aerosol particles to a de-agglomeration device is developed and tested with commercially available powders. The study is performed using 5?µm polyamide powder and rutile TiO₂ powders of 500, 100, and 30?nm mean size of primary particles. The ultrasonic dispersion device proved to be able to disperse all of these powders, which represent low-density material to high-density metal oxides, with stable concentration over periods that extend to an hour. From aerosol measurements to obtain the size distribution of various size particles, it is seen that the highly agglomerated powder particles are not easy to de-agglomerate as we go to the lower (nominal) sized powders because of the stronger inter-particle adhesion forces between nanoparticles compared to microparticles. The scanning electron microscopy (SEM) images of particles in their native powder state and those collected after the dispersion showed significant difference in the agglomeration of the powder particles, which suggests partial success of the turbulent jet de-agglomeration employed.

Copyright © 2019 American Association for Aerosol Research     

Thermal stabilization of penicillolysin, a thermolabile 19 kDa Zn2+-protease, obtained by site-directed mutagenesis

Penicillolysin is a member of the clan MX and the family of M35 proteases. The enzyme is a thermolabile Zn(2+)- protease from Penicillium citrinum with a unique substrate profile. We expressed recombinant penicillolysin in Aspergillus oryzae and generated several site-directed mutants, R33E/E60R, A167E and T81P, with the intention of exploring thermal stabilization of this protein. We based our choice of mutations on the structures of homologous thermally stable enzymes, deuterolysin (EC 3.4.24.39) from A.oryzae and a peptidyl-Lys metallopeptidase (GfMEP) from the edible mushroom Grifora frondsa. The resulting mutant proteins exhibited comparable catalytic efficiency to the wild-type enzyme and some showed a higher tolerance to temperature.