Activity of NiCuAl catalyst in methane decomposition studied using a thermobalance and the structural changes in the Ni and the deposited carbon

Activity measurements of a NiCuAl catalyst for the thermal decomposition of methane have been carried out in a thermobalance at different operating temperatures and partial pressures of methane and hydrogen. The thermobalance allows, by gravimetry, a continuous record of the evolution of the deposited carbon during and at the end of the test and the extraction of a sufficient amount of homogenous sample to study the involved structural changes in Ni and the structural properties of the deposited carbon by powder X-ray diffraction (XRD) and transmission electron microscopy (TEM). The effect of the operating temperature, mainly derived from thermal sintering, on Ni particles and on the deposited carbon is highly significant. The effect of methane as a reactant and hydrogen as a reaction product is mostly derived from its influence on the reaction rate. Additionally, methane and hydrogen reduce the effect of thermal sintering on Ni lowering the surface energy by chemisorption. The study also shows that the deposited carbon on the Ni leading face probably diffuses to the Ni trailing face superficially, and not through bulk Ni as assumed by the present kinetic models.     

Molecular dynamics study of cluster impact on the (0 0 1) and (1 1 0) surfaces of fcc metals

Molecular dynamics simulations of the impact deposition of metal clusters on fcc metal surfaces are presented. Two-dimensional elongated islands are formed when the incident cluster travels parallel to the surface. For perpendicular incidence the results of the impact event are very sensitive to the relative cohesive properties of the cluster and substrate atoms.     

Spectral sensitivity of cones in the goldfish, Carassius auratus

The spectral sensitivities of retinal cones isolated from goldfish (Carassius auratus) retinas were measured in the range 277-737 nm by recording membrane photocurrents with suction pipette electrodes (SPE). Cones were identified with lambda max (+/- S.D.) at 623 +/- 6.9 nm, 537 +/- 4.7 nm, 447 +/- 7.7 nm, and about 356 nm (three cells). Two cells (lambda max 572 and 576 nm) possibly represent genetic polymorphism. A single A2 template fits the alpha-band of P447(2), P537(2), and P623(2). HPLC analysis showed 4% retinal:96% 3-dehydroretinal. Sensitivity at 280 nm is nearly half that at the lambda max in the visible. The lambda max of the beta-band (in nm) is a linear function of the lambda max of the alpha-band and follows the same relation as found for A1-based cone pigments of a cyprinid fish.     

The Argentine radioactive waste respository: Basic criteria,preliminary siting and design conceptual basis

At the end of the seventies. The Argentine authorities decided to explore alternatives for disposing of the high-level radioactive wastes that would eventually be generated by the country's nuclear programme. This programme involves nuclear power reactors that will generate an integrated electrical energy of a fraction of a terawatt year by the end of the century (1). The country's programme also foresees the reprocessing of the spent fuel. The paper describes the basic criteria adopted by the Argentine authorities for the disposal of high-level wastes. On the basis of these criteria. a site in stable, unfractured granite was selected for detailed studies, near Gastre. Province of Chubut, out of about 200 potential sites. This site has been thoroughly investigated and its suitability has been validated. On the other hand, work has progressed on the design of the future repository.     

Occupational allergy in greenhouse workers: sensitization to Tetranychus urticae

BACKGROUND: Tetranychus urticae (TU) is a macroscopic mite which is found infesting a large number of plants of economic interest. It has rarely been described as a cause of occupational allergic disease in agricultural workers. OBJECTIVE: To describe TU sensitization in greenhouse workers attending the outpatient allergy unit and its clinical associations, and to characterize the allergens involved. MATERIALS AND METHODS: Twenty-four consecutive carnation greenhouse workers with allergy-related symptoms, referred to our outpatient clinic during a 6-month period, were included. We made the diagnostic extract from carnation leaves heavily infested with TU. Skin-prick test, specific IgE measurement and bronchial provocation test with TU extract were carried out in all subjects. Allergen characterization was achieved by SDS-PAGE (sodium dodecylsulfate-polyacrylamide gel electrophoresis) and immunoblotting. RESULTS: Sixteen patients (66%) presented positive skin-prick test and specific IgE and were diagnosed allergic to TU. Fifteen patients suffered from bronchial asthma, 14 rhinitis and five urticaria. Twelve exhibited positive bronchial provocation test to the TU extract. On RAST-inhibition studies, there was no evidence of crossreactivity between TU extract and D. pteronyssinus. An allergen at 19 kDa was determined in the TU extract by SDS-PAGE immunoblotting studies. CONCLUSION: TU could be an important occupational allergen in greenhouse workers showing allergic symptomatology. There is no crossreactivity between this mite and the house dust mite D. pteronyssinus.     

Extracts from various mite species contain cross-reactive and noncross-reactive IgE epitopes. A RAST inhibition study

PURPOSE: A low pregnancy rate in in vitro fertilization (IVF) patients of advanced maternal age may be caused by aneuploidies originating from non disjunction in the first or second meiotic divisions. We introduced genetic testing of oocytes by sampling and fluorescent in situ hybridization (FISH) analysis of the first and second polar bodies, to avoid fertilization and transfer of aneuploid oocytes in IVF patients of advanced maternal age. METHODS: Three hundred and sixty-three IVF patients 34 years and older participated in the study. Using micromanipulation procedures, the first and second polar bodies were removed following their extrusion from the oocytes and studied by FISH, using probes specific for chromosomes 13, 18, and 21 to detect oocytes with common aneuploidies. RESULTS: Of a total of 538 IVF cycles, 3250 oocytes were available for FISH analysis, with conclusive FISH results in 2742 oocytes (84.3%). As many as 1102 (40%) of oocytes were predicted to be aneuploid and not transferred. Of 1640 embryos predicted to be normal, 1145 were transferred in 467 treatment cycles, resulting in 107 pregnancies (23%), from which 67 healthy children have been born, 32 pregnancies spontaneously aborted, and 15 pregnancies are ongoing after being confirmed normal by prenatal diagnosis. CONCLUSIONS: Preimplantation diagnosis by first- and second-polar body FISH analysis allows us to avoid the age-related risk of common aneuploidies in IVF patients of advanced maternal age.     

Kinetic behaviour and reactivity of zinc ferrites for hot gas desulphurization

Different zinc ferrite samples have been prepared with varying Fe:Zn atomic ratios and preparation procedures in order to optimize their behaviour as hot gas desulphurization agents. Kinetic studies on metal oxide sulphidation were performed in a thermobalance and sulphur removal tests were conducted in a fixed-bed reactor. Fresh and exhausted samples were characterized by several physical techniques. The results show that reaction rate is mainly controlled by mass transfer processes of the reactant through the gas film in contact with the solid and through the sulphide layer. Bulk ferrites displayed the best performance for sulphur removal. Ferrites deposited on an alumina substrate by impregnation are highly dispersed, however they exhibited a very poor efficiency for sulphur removal. Solid-state reactions of single oxides at the alumina interface, i.e. zinc and/or iron aluminate formation, instead of pore occlusion by the active ingredient seem to be responsible for a low reactivity.     

p53 in breast cancer. Its relation to histological grade, lymph-node status, hormone receptors, cell-proliferation fraction (ki-67) and c-erbB-2. Immunohistochemical study of 153 cases

The mutation of the p53 gene is a common phenomenon in numerous human tumors, leading to the accumulation of nonfunctioning p53 protein in the cell nucleus, which can be detected by immunohistochemistry. In breast cancer, it has been suggested that the overexpression of p53 protein in the nucleus is an indicator of poor prognosis, which must be borne in mind in selecting coadjuvant treatment for each patient. This study is an immunohistochemical analysis of p53 expression in 153 cases of mammary carcinoma, correlating it with histological grade, axillary node status, hormone receptors, cell-proliferation fraction and expression of the c-erbB-2 oncoprotein. Of all the breast-cancer tissue analyzed, 43.79% was positive for p53. The overexpression of this protein bears a direct statistically significant relationship to histological grade, cell-proliferation fraction and c-erbB-2, and an inverse relationship to estrogen and progesterone receptors. No statistically significant relationship was found with axillary node status. The expression of p53 in poorly differentiated tumors-commonly receptor negative and with a high proliferation fraction-may indicate greater tumor aggressiveness and a high risk of relapse.     

Real time power supply quality measurement and monitoringmultichannel system

This paper describes a multi-channel system for measuring and monitoring electric power supply quality in real-time. The hardware is simple but powerful, because it is based on a PC with an acquisition card, and a development card with a single dedicated DSP (digital signal processor)     

Characterization of recombinant Mercurialis annua major allergen Mer a 1 (profilin)

Whether vitamin D receptor (VDR) gene polymorphisms are associated with osteoporosis is highly controversial. The relationship between VDR gene polymorphisms and bone mineral density (BMD) might, however, be modified by age-related and/or environmental factors. We studied the potential association between BMD and VDR genotypes in females from prepuberty to premenopause and prospectively investigated the interaction of VDR genotypes with dietary calcium and BMD changes during childhood. Bsm I VDR gene polymorphisms and BMD at the lumbar spine (LS) and femur (neck [FN] and midshaft [FS]) were assessed in 369 healthy Caucasian females, aged 7-56 years (143 prepubertal girls, 54 peri- and postpubertal adolescents, and 172 premenopausal adults). Femoral trochanter (FT) and distal radius BMD (metaphysis and diaphysis) were also measured in 101 of the prepubertal girls who participated in a 1-year, double-blind, randomized study of calcium supplementation (850 mg/day) versus placebo on bone mineral mass accrual. Among all females, 150 (40.7%) had bb, 167 (45.3%) Bb, and 52 (14%) BB VDR genotypes. In prepubertal and adolescent girls altogether, LS BMD (Z scores) was associated with VDR genotypes and was significantly lower in BB than in Bb or bb subjects. Trends for a similar difference were also detected at the FN level as well as on the mean BMD (Z scores) of the three sites measured (LS, FN, and FS). By contrast, no BMD differences were detectable among VDR genotypes in the adults. In 101 prospectively studied prepubertal girls, calcium supplementation significantly increased BMD at most skeletal sites, except LS. After segregation for VDR genotypes (40 bb, 47 Bb, and 14 BB), a significant calcium effect was present in Bb but not bb girls, whereas in BB girls there was a positive but nonsignificant trend for a calcium effect. Moreover, dietary calcium intake was significantly correlated with BMD changes at various independent bone sites in Bb girls but not in bb girls. In contrast, BMD gain in bb girls appeared to be higher than among the other genotypes when the dietary calcium intake was low, i.e., in the absence of calcium supplements. BMD was significantly associated with VDR gene polymorphisms only before puberty, BB girls having significantly lower BMD (Z scores) than the other genotypes. By increasing dietary calcium intake, BMD accrual was increased in Bb and possibly BB prepubertal girls, whereas bb subjects had the highest spontaneous BMD accrual and remained unaffected by calcium supplements. Taking into account complex interactions between VDR gene polymorphisms and environmental factors, including calcium intake, may thus help to understand the discordant relationships between BMD and VDR gene polymorphisms.