Catalytic Combustion of Model Carbon Particles (CPs) over Pt/β-SiC Catalyst

Platinum catalyst supported on a medium surface area -SiC was successfully used for the catalytic combustion of model carbon particles and compared to a catalyst supported on a low surface area -SiC. The -SiC-based catalyst showed no deactivation as a function of cycling tests while a strong deactivation was observed on the -SiC-based catalyst. This deactivation was attributed to the progressive encapsulation of the platinum particles by a layer of silica which built up during the combustion cycle. These results render possible the use of Pt/-SiC catalyst as a diesel carbon particle catalytic filter with continuous regeneration.     

Manufacturing of Mo-25 Re and Mo-50 Re Alloys by Means of Powder Sintering at Medium Temperatures

Powder mixtures of molybdenum and rhenium were sintered at various temperatures to fabricate Mo-25% Re and Mo-50% Re alloys. For this purpose, stoichiometric mixtures of the component powder metals with particle sizes of 1 to 5 μm average, were first homogenized in a planetary mill and then compacted at 300, 400, 500 and 600 MPa, to the shape of tablets and small billets for rolling to thin foils. The obtained pieces were subjected to sintering at various temperatures in the range of 1400 to 1700°C, under argon-hydrogen protecting atmosphere. The solid solution of rhenium in the molybdenum matrix was followed by means of x-ray diffraction. It was found that at all sintering temperatures rhenium was totally dissolved in theMo-25% Re alloy, while small amounts of an intermediate phase were detected in the case of the Mo-50% Re alloy, in good agreement with the corresponding phase diagram. The densification of sintered parts increased with temperature and compaction pressure up to values less than 90%. Owing to the fine particle size of the powders, the sintering temperature can be lower than those normally utilized in the refractory metals industry.     

Ribamidyl (ribavirin) as a modulator of the biological action of arabinosylcytosine and methotrexate

Administration of ribamidyl (Rb) prior to Ara-C to intact mice or mice with implanted tumours enhanced Ara-C toxicity. The growth of tumours (plasmacytoma MOPC-21, adenocarcinoma of the small intestine (strain AKATON), mammary adenocarcinoma 755 (Ca 755) resistant to Ara-C or Rb was inhibited after coadministration of these drugs. The augmentation of toxic and antitumour effects of Ara-C by Rb is similar to the described effect of high doses of thymidine. This is in accordance with the enhancement of the intracellular pool of thymidine phosphates under the action of Rb. The toxicity of methotrexate in vivo was increased by coadministration with Rb. This effect may be connected with a decrease in purine precursors pool under the action of Rb.     

Therapeutic effect of blastolysin in athymic mice with transplanted strains of human tumors

9 transplanted strains were used for the evaluation of antitumour effect of blastolysin. The short-term inhibition of the tumour growth was observed on the following models: breast cancer, stomach cancer, kidney cancer and chorionepithelioma.     

Influence of Alumina-Supported M–Pt Catalysts in DeNOx Reactions with M = Pd or Ir or Ru

To better understand N₂ formation in the selective catalytic reduction of NO _x by propene under oxidative atmosphere, we studied the catalytic behavior of bimetallics. Surface segregation phenomena may provoke geometric and electronic modifications of the catalytic active sites. To explain our results we invoked: (i) the facile way to oxidize the bimetallic aggregates, (ii) the presence of atoms with low coordination number able to be oxidized first and (iii) an eventual formation of like vic-diNO _x species on such bimetallics leading to N₂ formation.