Characterization of Al2O3-ZrO2 mixed oxide catalytic supports prepared by the sol-gel method

A series of Al₂O₃-ZrO₂ mixed oxides was prepared by the sol-gel method with variable amounts of ZrO₂ between pure alumina and pure zirconia. Textural, bulk and surface characterization of the samples was carried out by nitrogen physisorption (S_BET, porosity), surface acidity, zero point charge (ZPC), thermal analysis (DSC, TGA), X-ray diffraction (XRD) and FT-Raman spectroscopy. The textural results show that at low zirconia contents, higher surface areas than those of pure alumina are obtained, and that the mixed oxides samples show a bimodal pore size distribution different from that of a mechanical mixture of the pure oxides. Also, in the zirconia-rich samples, higher surface areas than for pure zirconia are stabilized. The ZPC results indicate the formation of a surface composition equivalent to the bulk composition of the two oxides. The acidity measurements show that, as the density of acid sites in the mixed oxides increases steadily with zirconia content, a sharp increase is observed between the zirconia-rich mixed oxides and the pure ZrO₂. It appears possible then to tune the acidity of the mixed oxide by changing its composition. The XRD and FT-Raman results show that the incorporation of alumina in the support stabilizes the metastable cubic and tetragonal zirconia phases, possibly by a matrix effect which constrains the size of the ZrO₂ particles below the critical size beyond which the crystallization and transformation process to a more stable zirconia phase occurs.     

Beverage cloud stability with isolated soy protein

The purpose of this study was to optimise the use of isolated soy protein (ISP) as a clouding agent for beverages. ISP was fractionated by hydrophobic interaction chromatography (HIC) using 2 M KCl in a step gradient manner. A hydrophilic and a hydrophobic fraction were collected. The proteins therein were separated by SDS-PAGe. Each fraction was combined with citrus pectin in nine different ratios at pH 3·7 and subjected to cloud stability and turbidity studies for 28 days at 4°C. The molecular weight patterns of the two fractions were different, indicating separation in the HIC column. Analysis of variance with repeated measures found no significant difference in cloud stability between the two fractions (P<0·05). Empirically, the hydrophilic fraction acted as a better clouding agent. Significant differences in cloud stability and cloud turbidity were found between different ratios of pectin: protein (P<0·05). No correlation was found between the initial cloud composition and cloud stability. Hydrophilic fraction in pectin: protein ratios 1: 2 and 4:1 gave optimum cloud stability. This study reiterated the usefulness of ISP as a clouding agent. © 1998 Society of Chemical Industry.     

Separation of Deformation Components in Polymer Textile Materials

Fibre Chemistry - The deformation occurring in polymeric textile materials can be conditionally separated into three components: elastic, highly elastic, and plastic. However, distinguishing...     

Criteria for Confidence Prediction of Relaxation Processes of Polymer Textile Materials

Fibre Chemistry - The article considers the questions of adequacy of mathematical modelling of relaxation processes of polymer textile materials. The developed integral criteria for confidence...     

SBA-15 supports modified by Ti and Zr grafting for NiMo hydrodesulfurization catalysts

A series of Ti- and Zr-containing mesoporous SBA-15 supports and their respective NiMo catalysts were prepared to study the effect of the Ti and Zr loading into the support on the characteristics of Ni and Mo surface species and their catalytic activity in the 4,6-dimethyldibenzothiophene hydrodesulfurization (HDS). Ti and Zr-containing SBA-15 solids with different metal loading (up to 19 wt.% of TiO₂ or 22 wt.% of ZrO₂) were prepared by chemical grafting. The solids prepared were characterized by N₂ physisorption, X-ray diffraction (XRD), UV–vis diffuse reflectance spectroscopy (DRS), temperature-programmed reduction (TPR), chemical analysis and HRTEM. The results show that Ti- and Zr-SBA-15 supports with highly dispersed Ti and Zr species can be obtained without substantial loss of SBA-15 characteristics. Zr grafted species showed somewhat better dispersion on the SBA-15 surface than the corresponding Ti counterparts. It was found that TiO₂ and, especially, ZrO₂ incorporation in the SBA-15 support leads to stronger interaction of Mo and Ni species with the support providing better dispersion to the oxidic and sulfided metal species (XRD, TPR, HRTEM). NiMo catalysts supported on Ti- and Zr-containing SBA-15 showed high activity in 4,6-dimethyldibenzothiophene HDS. It can be concluded therefore that SBA-15 materials grafted with Ti or Zr species show promising features as supports for Mo-based hydrotreating catalysts.     

Binding of Kingella kingae RtxA Toxin Depends on Cell Surface Oligosaccharides,but Not on β2 Integrins

The Gram-negative coccobacillus Kingella kingae is increasingly recognized as an important invasive pediatric pathogen that causes mostly bacteremia and skeletal system infections. K. kingae secretes an RtxA toxin that belongs to a broad family of the RTX (Repeats in ToXin) cytotoxins produced by bacterial pathogens. Recently, we demonstrated that membrane cholesterol facilitates interaction of RtxA with target cells, but other cell surface structures potentially involved in toxin binding to cells remain unknown. We show that deglycosylation of cell surface structures by glycosidase treatment, or inhibition of protein N- and O-glycosylation by chemical inhibitors substantially reduces RtxA binding to target cells. Consequently, the deglycosylated cells were more resistant to cytotoxic activity of RtxA. Moreover, experiments on cells expressing or lacking cell surface integrins of the β₂ family revealed that, unlike some other cytotoxins of the RTX family, K. kingae RtxA does not bind target cells via the β₂ integrins. Our results, hence, show that RtxA binds cell surface oligosaccharides present on all mammalian cells but not the leukocyte-restricted β₂ integrins. This explains the previously observed interaction of the toxin with a broad range of cell types of various mammalian species and reveals that RtxA belongs to the group of broadly cytolytic RTX hemolysins.     

Comparative Analysis for the Presence of IgG Anti-Aquaporin-1 in Patients with NMO-Spectrum Disorders

Detection of IgG anti-Aquaporin-4 (AQP4) in serum of patients with Neuromyelitis optica syndrome disorders (NMOSD) has improved diagnosis of these processes and differentiation from Multiple sclerosis (MS). Recent findings also claim that a subgroup of patients with NMOSD, serum negative for IgG-anti-AQP4, present antibodies anti-AQP1 instead. Explore the presence of IgG-anti-AQP1 using a previously developed cell-based assay (CBA) highly sensitive to IgG-anti-AQP4. Serum of 205 patients diagnosed as NMOSD (8), multiple sclerosis (94), optic neuritis (39), idiopathic myelitis (29), other idiopathic demyelinating disorders of the central nervous system (9), other neurological diseases (18) and healthy controls (8), were used in a CBA over fixed HEK cells transfected with hAQP1-EGFP or hM23-AQP4-EGFP, treated with Triton X-100 and untreated. ELISA was also performed. Analysis of serum with our CBA indicated absence of anti-AQP1 antibodies, whereas in cells pretreated with detergent, noisy signal made reliable detection impossible. ELISA showed positive results in few serums. The low number of NMOSD serums included in our study reduces its power to conclude the specificity of AQP1 antibodies as new biomarkers of NMOSD. Our study does not sustain detection of anti-AQP1 in serum of NMOSD patients but further experiments are expected.     

Formal methods of situational analysis: Experience from their use

The problems of sociological data and knowledge representation for the situational analysis of labour relations are described. It is suggested that the technologies for searching for empirical laws are described step by step by the JSM method for the automated generation of hypotheses using the research material that was obtained by a group of authors on two firms. Conclusions are made as to the potentialities and scope of the method.