Metal-support interaction: titania-supported nickel-iron catalysts

The influence of the titania support and metal particle size on the performance of nickel-iron catalysts in the Fischer-Tropsch synthesis has been studied by varying the nickel-iron loading and, consequently, varying the nickel-iron particle size. Low-loaded titania-supported nickel-iron catalysts (2 wt%) turned out to be more selective towards higher hydrocarbons than high-loaded nickel-iron catalysts (20 wt%), which produce much more methane. From temperature-programmed hydrogenation experiments, magnetic measurements and Mössbauer spectroscopy it followed that different types of carbon are present on the catalysts depending on the metal loading. These types of carbon could be related to the selectivity in Fischer-Tropsch synthesis and to the deactivation of the catalysts with time on stream. These differences in catalytic behaviour are most likely due to the presence of TiO _x species on the surface of the active phase, which species decrease the CO and H₂ adsorption properties of the catalyst, but increase the dissociation of CO.     

The influence of an intermediate MoO3 layer on the solid state reaction of cobalt oxide withγ-Al2O3

In view of the importance for Co_xO_y,-MoO₃/-Al₂O₃ hydrodesulphurization (HDS) catalysts, the reactivity of cobalt oxide layers towards cobalt aluminate formation was investigated on both MoO₃-covered and bare -Al₂O₃ substrates. Co₃O₄/MoO₃/-Al₂O₃ and Co₃O₄/-Al₂O₃ systems were prepared by vapour-deposition of MoO₃ (12 × 10¹⁵ Mo atoms/cm²) and Co (400 × 10¹⁵ Co atoms/cm²) layers onto a -Al₂O₃ substrate, followed by oxidation of the Co layer to Co₃O₄. After annealing at 800°C for 40 h, the interfacial reaction to cobalt aluminate was assessed using Rutherford backscattering spectrometry. The presence of molybdenum oxide appeared to enhance cobalt aluminate formation. The Mo atoms, which spread out over the entire cobalt-containing layer, presumably caused a high defect density, which explains the observed higher reaction rate. The amount of MoO₃ was much too low to stabilize all cobalt atoms by cobalt molybdate formation.     

The effect of steam treatment on MeO/Al2O3 model catalysts (Me = Ni,Co, Cu,Fe)

To study the influence of steam on the solid state reaction between MeO (Me = Ni, Co, Cu or Fe) and Al₂O3, MeO/-Al₂O₃ and MeO/-Al₂O₃ model catalysts were kept in either N₂/20% O₂ or N₂/O₂/30% H₂O at 500–1000°C. The samples were subsequently analyzed with RBS and FTIR. Surprisingly, nickel, cobalt and copper volatilized when MeO/-Al₂O₃ or MeAl₂U₄/-Al₂O₃ samples were annealed in the presence of 0.3 atm steam at 1000°C. Especially copper was found to volatilize very rapidly in the presence of steam, even at a temperature as low as 800°C. FTIR spectra of steam-treated NiO/-Al₂O₃ samples showed the incorporation of hydroxyl groups in the nickel oxide layer. This observation and an excellent agreement with thermochemical calculations support our conclusion that the volatile species are metal hydroxides. The solid state reaction of MeO with-Al₂O₃ was found to proceed at a much higher rate in the presence of 0.3 atm steam at 500–800°C, presumably as a result of an enhanced surface mobility of Me and Al ions along the grain boundaries and the surfaces of the internal pores of the-Al₂O₃ support, when steam is present.     

BASF NanoSelect? Technology: Innovative Supported Pd- and Pt-based Catalysts for Selective Hydrogenation Reactions

An innovative BASF catalyst manufacturing technology (NanoSelect?) is introduced which allows production of heterogeneous catalysts with excellent control over metal crystallite sizes. NanoSelect? technology enabled the development of Pd catalysts which are lead-free Lindlar catalyst replacements in alkyne-to-cis-alkene hydrogenations. NanoSelect? Pt catalysts showed excellent chemoselectivity in substituted nitro-arene hydrogenation reactions without build-up of hydroxylamine intermediates. All NanoSelect? produced catalysts show markedly higher activity per gram of metal leading to ten-fold less use of precious metal.     

Expression of CD2 on porcine B lymphocytes

BACKGROUND/AIMS: Deposition of paramagnetic substances in basal ganglia, resulting in increased signals in T1-weighted magnetic resonance images (bright basal ganglia), is frequently seen in liver cirrhosis. The present study describes the prevalence of bright basal ganglia and its clinical significance in patients with long-standing portal vein thrombosis in the absence of liver cirrhosis. METHODS: Six patients with angiographically proven complete portal vein thrombosis and cavernomatous transformation without signs of acute or chronic liver disease were studied by magnetic resonance imaging of the brain, neuropsychiatric evaluation, psychometric tests, electroencephalography, and determination of arterial ammonia levels and of serum manganese concentrations from peripheral venous blood. RESULTS: Five out of six patients demonstrated increased signal intensity in the basal ganglia. Overt portal-systemic encephalopathy was not noted prior to or at the time of evaluation. Normal EEG results were recorded in all patients. Only one of the six patients had pathological results in at least two out of four psychometric tests. This latter patient had had a large right-sided brain infarction. Arterial ammonia concentrations were normal in four of the six patients; one patient with increased ammonia levels had concomitant renal insufficiency with azotemia. The other four patients had no relevant concomitant diseases. Serum manganese levels were non-significantly increased compared with a control group (p=0.06), but they were significantly correlated to basal ganglia signal intensity (R=0.88; p=0.02). CONCLUSIONS: Our results demonstrate that bright basal ganglia primarily represent shunt-induced alterations. They are not directly associated with disturbed liver function nor with portal-systemic encephalopathy.     

纺粘和熔喷技术的未来

自纺粘法和熔喷法技术问世以来，它们就紧紧和一个特殊领域——卫生学联系在了一起。由于市场不断增大，以及婴儿、女性卫生护理、医疗等一次性用品的发展，纺粘和非织造材料的市场占有率取得了持续增长。     

The effect of muscle repair on postoperative facial skeletal growth in children with bilateral cleft lip and palate

Systems for testing genetic toxicology are components of carcinogenic and genetic risk assessment. Present routine genotoxicity-testing is based on at least 20 years of development during which many different test systems have been introduced and used. Today, it is clear that no single test is capable of detecting all genotoxic agents. Therefore, the usual approach is to perform a standard battery of in-vitro and in-vivo tests for genotoxicity. Work-groups of the European Union (EU), the Organization for Economic Co-operation and Development (OECD), and, very recently, the work-group of the International Conference on Harmonization of Technical Requirements for Registration of Pharmaceuticals for Human Use (ICH) have defined such standard battery tests. These and some currently used supplementary or confirmatory tests are briefly discussed here. Additional test systems for the assessment of genotoxic and carcinogenic hazard and risk are seriously needed. These tests must be more relevant to man than are current assays and less demanding in respect of cost, time and number of animals. Another aspect for reassessment derives from the actual situation in the pharmaceutical industry. Companies have to prepare for the world economy of the 21st century. Therefore, pharmaceutical research is speeding up tremendously by use of tools such as genomics, combinatorial chemistry, high throughput screening and proteomics. Toxicology and genotoxicology need to re-evaluate their changing environment and must find ways to respond to these needs. In conclusion, genetic toxicology needs to answer questions coming from two major directions: hazard and risk identification and high throughput testing.     

Assessment of the free surface area of magnesia-supported magnesium ferrite particles using selective oxygen chemisorption

The free surface area of iron oxide catalysts supported on magnesium oxide has been determined using selective oxygen chemisorption at room temperature. The oxygen chemisorption experiments were performed on reduced catalysts. It has appeared to be essential that the iron oxide phase, which is present as MgFe₂O₄ in the fresh calcined catalysts, is reduced uniquely to FeO, prior to the chemisorption experiment. Crystallite sizes typically in the range of 20–23 nm have been found independent of the catalyst loading and the type of precursors. A higher iron loading does not lead to larger crystallites, but rather to more crystallites of about the same average size. Results are in very good agreement with those obtained by X-ray line broadening and electron microscopy.     

Individual differences in P300 amplitude: a genetic study in adolescent twins

Three experiments, using temporal generalization and verbal estimation methods, studied judgements of durations of auditory (500-Hz tone) and visual (14-cm blue square) stimuli. With both methods, auditory stimuli were judged longer, and less variable, than visual ones. The verbal estimation experiments used stimuli from 77 to 1183 msec in length, and the slope of the function relating mean estimate to real length differed between modalities (but the intercept did not), consistent with the idea that a pacemaker generating duration representations ran faster for auditory than for visual stimuli. The different variability of auditory and visual stimuli was attributed to differential variability in the operation of a switch of a pacemaker-accumulator clock, and experimental data suggested that such switch effects were separable from changes in pacemaker speed. Overall, the work showed how a clock model consistent with scalar timing theory, the leading account of animal timing, can address an issue derived from the classical literature on human time perception.