Home About us Contact
|
Home About us Contact | ||
|
|
||
Same Composition (same + composition)
Selected AbstractsMechanical properties of single crystalline and glassy lithium triborateCRYSTAL RESEARCH AND TECHNOLOGY, Issue 4 2008I. P. Shakhverdova Abstract Mechanical properties of LiB3O5 single crystal plates with different orientation as well as of glass with the same composition have been investigated. The nano- (H) and microhardness (HM), the reduced Young's modulus (Er) and the crack behaviour of the samples were studied. Both hardness and Young's modulus of glass appeared smaller in comparison to corresponding single crystal data (H , 7 , 8 GPa, HM , 6 GPa, Er , 70 , 80 GPa for glass and H , 10 , 15 GPa, HM , 6 ,11 GPa, Er , 93 , 155 GPa for single crystal). H, Er, and the plane of crack propagation proved orientation-dependent. Cracks in the glass sample were not observed up to 0.49 N microindentation load, whereas for the single crystal the cracks appeared already at 0.098N. In single crystals the observed cleavage planes {211} and/or {412} are oriented nearly parallel to planes of B-O rings. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Evaluating low level sequence identitiesFEBS JOURNAL, Issue 2 2001AROM homologous?, Are Aspergillus QUTA A review published several years ago [Hawkins, A.R. & Lamb, H.K. (1995) Eur. J. Biochem. 232, 7,18] proposed that genetic, biochemical and physiological data can override sequence comparison in the determination of homology in instances where structural information is unavailable. Their lead example was the hypothesis that the transcriptional activator protein for quinate catabolism in Aspergillus nidulans, QUTA, is derived from the pentafunctional AROM protein by a gene duplication followed by cleavage [Hawkins, A.R., Lamb, H.K., Moore, J.D. & Roberts, C.F. (1993) Gene136, 49,54]. We tested this hypothesis by a sensitive combination of position-specific log-odds scoring matrix methods. The position-specific log-odds scoring matrices were derived from a large number of 3-dehydroquinate synthase and 5- enolpyruvylshikimate-3-phosphate synthase domains that were proposed to be the domains from the AROM protein that gave rise to the transcriptional activator protein for quinate metabolism. We show that the degree and pattern of similarity between these position-specific log-odds scoring matrices and the transcriptional activator protein for quinate catabolism in A. nidulans is that expected for random sequences of the same composition. This level of similarity provides no support for the suggested gene duplication and cleavage. The lack of any trace of evidence for homology following a comprehensive sequence analysis indicates that the homology hypothesis is without foundation, underlining the necessity to accept only similarity of sequence and/or structure as evidence of evolutionary relatedness. Further, QUTA is homologous throughout its entire length to an extended family of fungal transcriptional regulatory proteins, rendering the hypothesized QUTA,AROM homology even more problematic. [source] Near-Net Shape ,-Si4Al2O2N6 Parts by Hydrolysis Induced Aqueous Gelcasting ProcessINTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 1 2009Ibram Ganesh In this paper, a new net-shaping process, an hydrolysis-induced aqueous gelcasting (GC) (GCHAS) has been reported for consolidation of ,-Si4Al2O2N6 ceramics from aqueous slurries containing 48,50 vol%,-Si3N4, ,-Al2O3, AlN, and Y2O3 powders mixture. Dense ceramics of same composition were also consolidated by aqueous GC and hydrolysis assisted solidification routes. Among three techniques used, the GCHAS process was found to be superior for fabricating defect-free thin wall ,-Si4Al2O2N6 crucibles and tubes. Before use, the as purchased AlN powder was passivated against hydrolysis. The sintered ,-Si4Al2O2N6 ceramics exhibited comparable properties with those reported for similar materials in the literature. [source] Effect of sequence distribution of PES/PEES random, block, and alternative copolymers on excimer formation in solutionJOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2007Xiao-Ming Zhou Abstract Three copolymers of poly(ether sulfone) and poly(ether ether sulfone) with the same composition but different sequence distribution were synthesized by three kinds of methods. Their molecular aggregation in dichloromethane was studied by fluorescence spectrophotometer and electron microscope. The experimental results revealed that the formation of intermolecular excimers in alternative copolymer (A50) dichloromethane solution were observed at a A50 concentration about 1.6 × 10,2 g/mL by the fluorescence analysis, but the formation of intermolecular excimers in dichloromethane were not found for random copolymer (R50) and block copolymer (B50). The electron micrograph of three copolymer films, heat-treated at 200°C for 7 days, presented a diffraction micrograph, which suggest that three copolymer molecular aggregation is changed from a randomly coiled amorphous phase to an ordered one, and the order structure of alternative copolymer (A50) was the most distinct in three copolymers. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 [source] Studies on the cell treatment conditions to elicit lipolytic responses from 3T3-L1 adipocytes to TCDD, 2,3,7,8-tetrachlorodibenzo-p-dioxinJOURNAL OF CELLULAR BIOCHEMISTRY, Issue 2 2007Wen Li Abstract Wasting syndrome is one of the hallmark symptoms of poisoning by TCDD (=dioxin), which is associated with the massive loss of adipose tissue and serum hyperlipidemia in vivo. Yet, the most widely used in vitro cell model 3T3-L1 adipocyte has not been useful for studying such an action of TCDD because of the difficulty of inducing their mature adipocytes to respond to TCDD to go through lipolysis. Here, we made efforts to find the right cell culture and treatment conditions to induce mature 3T3-L1 adipocytes to go through lipolysis, which is defined as events leading to reduction of lipids in adipocytes. The optimum condition was found to require 7-day differentiated adipocytes being subjected to DMEM medium containing TCDD (but without insulin) for 5 day incubation with two medium changes (the same composition) on incubation days 2 and 4. After 24 h, the early effect of TCDD on adipocytes was predominantly on inflammation, particularly induction of COX-2 and KC (IL-8), which is accompanied by upregulation of C/EBP, and ,. The sign of TCDD-induced lipolysis starts slowly and by incubation day 3, a few markers showed modestly significant changes. By day 5 of incubation, however, many markers show highly significant signs of lipolytic changes. Although this process could take place without exogenous macrophages or their cytokines, addition of exogenous TNF, considerably synergized this action of TCDD. In conclusion, under a right condition, 3T3-L1 adipocytes were found to respond to TCDD to go through lipolysis. The early trigger of such a response appears to be activation of COX-2, which is amplified by TNF,. J. Cell. Biochem. 102: 389,402, 2007. © 2007 Wiley-Liss, Inc. [source] Effect of inhibitory compounds on the anaerobic digestion performance of diluted wastewaters from the alimentary industryJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 11 2009Rafael Camarillo Abstract BACKGROUND: Up to now the effect of inhibitory compounds on the anaerobic digestion performance of urban and industrial wastewaters has been mostly studied in fluidized bed and upflowing anaerobic sludge blanket (UASB) bioreactors but not in upflow packed-bed biodigesters. RESULTS: In this paper, response surface methodology (RSM) was used to quantify the effect of various inhibitory compounds (olive oil, ethanol and phenol) on chemical oxygen demand (COD) removal and biogas production rate from synthetic solutions and real industrial wastewaters by anaerobic digestion. The synthetic solutions possessed the same composition in these inhibitory compounds as diluted effluents from olive oil mill and winery industries. The process was performed in a laboratory scale digester containing anaerobic sludge from the Urban Reclamation Station of Toledo (Spain). The comparison of both individual factors and interactions between factors showed that the addition of olive oil at moderate concentrations (up to 0.5% w/w) did not change the performance of the process in comparison with that observed when feeding to the system a model solution (51.5% COD removal, 0.65 L biogas day,1). However, low concentrations of ethanol or phenol (250 and 150 mg L,1, respectively) almost completely inhibited the methanogenic phase. Moreover, a strong interaction between ethanol and phenol concentrations on COD removal was observed. CONCLUSION: The experimental results showed quantitatively the importance of some inhibitory compounds on anaerobic treatment of both synthetic solutions and real wastewaters from olive oil mill and winery industries. Inhibitory effects are closely related to both the organic loads and the anaerobic bioreactor used. Copyright © 2009 Society of Chemical Industry [source] MECHANICAL PROPERTIES OF TWO-PHASE DISPERSE AGAR/GELATIN MIXED GELSJOURNAL OF TEXTURE STUDIES, Issue 3 2000KEIKO FUJII ABSTRACT Agar/gelatin mixed gels with the same composition but with a different two-phase disperse structure were prepared and their mechanical properties compared. The agar/gelatin mixture was first kept at temperature above the gelling temperature of gelatin but below that of agar and stirred for the selected period, before cooling it below the gelling temperature of gelatin. For the low rupture stress system the agar concentration was 0.7% (w/w), while the gelatin concentration was 4.5% (w/w) to achieve the same rupture stress as the agar gel. The mixing temperatures selected were 20 and 37C. For the high rupture stress system, the agar and gelatin concentration was 2.8 and 10.4% (w/w), respectively, to achieve the same rupture stress. The mixing temperatures selected were 37 and 40C. The both mixed gels prepared by this method consisted of a dispersed phase of agar and a continuous phase of gelatin. The rupture stress of the mixed gels decreased as the content of the dispersed phase increased. The rupture stress had a tendency to be lower as the size of the dispersed particles increased. These results suggest that the interface between the dispersed phase and the continuous phase plays an important role as Griffith's crack, with the rupture of mixed gels occurring from that place. [source] Screen Printing to Achieve Highly Textured Bi4Ti3O12JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 7 2010Michael R. Winter The focus of this paper is to explore the efficacy of screen printing to generate crystalline texture in bismuth titanate through the orientation of highly anisotropic seed crystals. Seed crystals were grown through a molten salt flux technique with aspect ratios of ,100:1, mixed with equiaxed powder of the same composition and oriented using screen printing, a high shear process. By printing on a flexible polymer substrate and using multiple print/dry cycles, it was possible to create pads with a thickness of several hundred micrometers and to remove the dried pads, creating free-standing samples. Upon sintering, the seed crystals grew at the expense of the matrix powder, a process known as templated grain growth. The degree of texture was analyzed using a variety of techniques including scanning electron microscopy, X-ray diffraction and electron backscatter diffraction. [source] A Potential Red-Emitting Phosphor BaGd2(MoO4)4:Eu3+ for Near-UV White LEDJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2009Chongfeng Guo Red-emitting phosphor BaGd2,xEux(MoO4)4 has been successfully synthesized by a simple sol,gel method. The process of phosphor formation is characterized by thermogravimetric-differential thermal analysis and X-ray diffraction. Field-emission scanning electronic microscopy is used to characterize the size and the shape of the phosphor particles. Photo-luminescent property of the phosphor is also performed at the room temperature. The effects of firing temperature and Eu3+ activator concentration on the photoluminescence (PL) properties are elaborated in detail. PL characterization reveals that the sample with the firing temperature at 800°C and the concentration of Eu3+ at 0.7 shows the most intense emission, and its intensity is about three times stronger than that of phosphor prepared by solid-state method with the same composition and firing temperature. The new red-emitting phosphor shows an intense absorption at 396 nm, which matches well with commercial near-UV light-emitting diode (LED) chips, therefore, it is a good candidate of red phosphor used for near-UV white LEDs. [source] Kinetic Model for Crystallization in White Ceramic GlazesJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 1 2001Agustin Escardino Theoretical equations have been developed for crystal growth rate in layers of small frit (glass) particles during firing. Throughout the process, the crystalline and the glassy phases have different compositions; therefore, the system can be considered a pseudo-two-component system consisting of a crystallizable component (structural unit) and a noncrystallizable mixture of several components. The concentration of the crystallizable component decreases in the residual glassy phase during the crystal growth process, on integrating at the surfaces of crystals having the same composition. Throughout the crystal growth process, a concentration gradient of the crystallizable component is therefore produced in the glassy phase, which results in mass transport by diffusion of this component from the bulk residual glassy phase to the surfaces of the crystals. Equations have been derived assuming that the diffusion step of the crystallizable component through the residual glassy phase is the overall crystal growth process rate-controlling step. [source] Preparing Low-Loss Low-Temperature Cofired Ceramic Material without Glass AdditionJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 11 2000Heli Jantunen A low-temperature cofired ceramic (LTCC) composition for radio-frequency purposes was accomplished without prior glass preparation. In this process, the formulation was made by mixing the glass-forming oxides (ZnO, SiO2, and B2O3) with the commercial microwave ceramic MgTiO3,CaTiO3. The sintering, microstructure, and microwave properties were compared to a formulation with exactly the same composition, but a conventional production route, including glass preparation. The novel preparation route resulted in improved firing properties of the mixture. Also, the densities, porosities, and phases of the samples were almost the same as those of the conventional samples, but the phase fractions were different. Finally, this preparation route produced better dielectric values. [source] Soy Protein Isolate versus Meat-Based Low-Protein Diet for Dogs with Congenital Portosystemic ShuntsJOURNAL OF VETERINARY INTERNAL MEDICINE, Issue 4 2009S. Proot Background: Both presurgical preparation and long-term support of nonoperable dogs with congenital portosystemic shunts (CPSS) require optimal dietary management. Studies suggested that protein source may play an important role, with vegetable and dairy protein sources having better effects on hepatic encephalopathy (HE) than meat proteins. Objectives: Determine whether a low-protein test diet with soy as its main protein source results in better scores than a control diet with the same composition but with poultry as its main protein source in dogs with CPSS. Methods: In a double-blind cross-over study, 16 dogs received each diet for 4 weeks. Dogs in group T first received the test diet and then the control diet, whereas dogs in group C were fed the diets in the opposite order. Different variables (body weight, body condition score, HE score, fecal score, CBC, plasma tests of liver function including NH3, and coagulation tests) were measured at the start of the study and after completion of each diet. Results: One-way repeated measures ANOVA was performed. Plasma NH3 was significantly lower after the test diet than after the control diet. The test diet also resulted in significantly higher fibrinogen concentrations and lower prothrombin times. The HE score improved with both diets, with no significant difference between the 2 diets. Conclusions: Both diets achieved a significant improvement in HE score. The influence of the soy-based diet on plasma NH3 concentration and coagulation parameters suggests that such a diet decreases the risk for HE and gives better support of liver function. [source] Growth kinetics of AlxGa1,xN layers (0 < x < 1) in plasma-assisted molecular beam epitaxyPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7-8 2010A. M. Mizerov Abstract Comparative study of growth kinetics of the AlxGa1-xN (x = 0-1) layers of different polarity, grown by plasma assisted molecular beam epitaxy (PA MBE) under different growth conditions (substrate temperature, group III to activated nitrogen and Al to Ga flux ratios) and on different buffer layers, is presented. The 60 °C higher temperature stability of N-face AlGaN layers is detected. The strong influence of elastic stress on growth kinetics of metal-polar AlxGa1-xN (x > 0.2) layers is observed and discussed. It was found that two-dimensional growth of AlGaN films of the same composition on different buffer layers at TS = 700 °C can be achieved at different group III surface enrichment, the AlGaN(0001)/c-Al2O3 films exhibiting the atomically smooth surface at group III to activated nitrogen flux ratio FIII/FN *gradually increased from 1.3 to 2 with the x variation from 0.1 to 0.8. In this case the alloy composition is controlled by the variation of Al flux only (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Poly(methyl methacrylate)/montmorillonite nanocomposites prepared by bulk polymerization and melt compoundingPOLYMER COMPOSITES, Issue 11 2009Krajnc, Matja This article focuses on structural, thermal, and mechanical properties of nanocomposites in dependence of preparation method and poly(methyl mathacrylate) (PMMA)/organically modified montmorillonite (OMMT) ratio. PMMA/OMMT nanocomposites were prepared by bulk polymerization and by melt compounding. Properties of nanocomposites of the same composition prepared by the two methods were compared. It was observed that nanocomposites prepared via melt compounding at 200°C had a highly oriented structure with lower interlayer spacing values than nanocomposites prepared via bulk polymerization. Two reasons for the observed smaller interlayer spacing obtained by melt compounding were identified. The first is enhanced PMMA penetration and/or formation between layers in the case of bulk polymerization, which was confirmed by determination of stronger interactions between OMMT and PMMA by Soxhlet extraction, infrared spectroscopy, and differential dynamic calorimery. The second reason for smaller interlayer spacing for nanocomposites prepared by melt compounding is organic modifier degradation during melt compounding process, which was confirmed by thermogravimetric analysis. Both reasons lead to the fracture of melt compounded nanocomposites on the OMMT-polymer interface, which was observed by scanning electron microscopy. For nanocomposites with disoriented structure and larger interlayer spacing prepared via bulk polymerization the fracture occurred in the polymer matrix. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers [source] Viscoelastic properties of extrusion cast sheets of natural and synthetic aliphatic polyestersPOLYMER ENGINEERING & SCIENCE, Issue 10 2005Mrinal Bhattacharya The objective of this study was to determine the viscoelastic properties of natural (starch and protein) blends and synthetic biodegradable aliphatic copolyester blends. Blends of natural and synthetic biodegradable poly(butylene succinate) were cast into sheets using a coathanger die and then subjected to stress relaxation and creep tests at various temperatures. The natural content was varied at 10%, 30%, and 50% by weight. In some formulations a small (5% by weight) amount of compatibilizer was added. The materials were blended using a twin screw-extruder, pelletized, and sheeted using a coathanger die. The decay of stress upon the imposition of constant strain showed two regions, an exponential and power law; the stresses relaxed sharply at the initial stage and then decayed at a reduced rate for the duration of the experiment. The addition of compatibilizers increased the time required for the stress to relax compared to uncompatibilized blends of the same composition. Similarly, as the natural content increased the time taken to relax to a specified stress level decreased. Increased temperature enhanced the relaxation process. The initial strain of the creep curves was affected by the natural content; the higher the natural content, the lower the initial strain for the samples upon imposition of a constant stress. Similarly, the presence of compatibilizer in the blend reduced the initial strain for samples containing the same natural content. As the natural content of the blend decreases, the time required to attain the plateau compliance is reduced. The equilibrium compliance increased with temperature. These behaviors are described in terms of blend morphology. The empirical Struik and power law models can be used to fit the compliance data well. POLYM. ENG. SCI., 45:1452,1460, 2005. © 2005 Society of Plastics Engineers [source] Relationship between segment structures and elastic properties of segmented poly(urethane-urea) elastic fibersPOLYMER ENGINEERING & SCIENCE, Issue 11 2003Nori Yoshihara Studies on segmented poly(urethane-urea) (SPUU) elastic fibers having various segment structures were done in terms of elastic recovery and stress-strain relationship (S-S). Three kinds of segment structures were used: 1) the same composition having different sequences of segment units, 2) the same length of soft segments having different molecular weights of polyol, and 3) different segment structures having almost the same stress at 350% elongation. The SPUU elastic fibers having higher sequence numbers of both soft and hard segment units, that is, greater block structures, show better elastic recovery properties, especially delayed elastic recovery. The SPUU elastic fibers showing better elastic recovery take an optimum value for the number-average molecular weight (Mn) of soft segments jointed with urethane bonds. Here the optimum Mn depends on the molecular weight of polytetramethyleneglycol (PTMG) as a starting material. The hysteresis loss in S-S for the pre-elongation decreases with an increase of Mn of PTMG. The SPUU elastic fibers having greater block structures show lower stress with lower 2C1 and 2C1 + 2C2 of Mooney-Rivilin plot constants for elastic fibers having the same composition. This indicates a lower density of crosslinks for finite deformation. An increase of the urea bonds or the molar ratio of urea bond to urethane bond raises the stress. It is found that the polymerization process, as well as composition, is important for design structures of SPUU elastic fibers. [source] Compatibilizers based on polypropylene grafted with itaconic acid derivatives.POLYMER ENGINEERING & SCIENCE, Issue 4 2003Effect on polypropylene/polyethylene terephthalate blends New types of compatibilizers based on functionalized polypropylene (PP) were synthesized by radical melt grafting either with monomethyl itaconate or dimethyl itaconate. The effect of these new modified PP compounds were tested as compatibilizers in PP/polyethylene terephthalate (PET) blends. Blends with compositions 15/85 and 30/70 by weight of PP and PET were prepared in a single-screw extruder. Morphology of the compatibilized blends revealed a very fine and uniform dispersion of the PP phase as compared with that of noncompatibilized blends of the same composition, leading to improved adhesion between the two phases. Whereas dimethyl itaconate derived agent showed less activity, the monomethyl itaconate parent compound showed an increase of the impact resistance of PET in PP/PET blend. This was attributed to the hydrophilic nature of the monomethyl itaconate part of this compatibilizer. The tensile strength of PET in noncompatibilized blends gradually decreases as the PP content increases, while blends containing functionalized PP exhibited higher values. [source] Plasma polymerization and deposition of glycidyl methacrylate on Si(100) surface for adhesion improvement with polyimidePOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 10 2001X. P. Zou Abstract Thin polymer films were deposited on Si(100) surfaces by plasma polymerization of glycidyl methacrylate (GMA) under different glow discharge conditions. The FT-IR, X-ray photoelectron spectroscopy (XPS), and amine treatment results suggested that the epoxide functional groups of the deposited films had been preserved to various extents, depending on the plasma deposition conditions. The use of a low radio frequency power (, 5 W) and a relatively high system pressure (100,400 Pa) readily resulted in the deposition of thin films having nearly the same composition of the epoxide functional groups as that of the GMA homopolymer. The plasma-polymerized GMA (PP-GMA) thin films deposited on the Ar plasma-pretreated Si(100) surfaces were retained to a large extent after acetone extraction, suggesting the presence of covalent bonding between the PP-GMA layer and the Si surface. Thermal imidization of the poly(amic acid) precursor of polyimide on the GMA plasma-polymerized Si(100) surface resulted in a strongly adhered polyimide film. The adhesion results further suggested that the GMA polymer had been grafted on the Si(100) surface and the epoxide functional groups had undergone reactive interaction (curing) with the carboxylic and amine groups of the poly(amic acid) during thermal imidization. Copyright © 2001 John Wiley & Sons, Ltd. [source] Incommensurate structure of InAl1,,,xTixO3,+,x/2 [x = 0.701,(1)]: comparison between modulated and composite modelsACTA CRYSTALLOGRAPHICA SECTION B, Issue 4 2008P. J. Bereciartua The structure of the monoclinic phase of the compound InAl1,,,xTixO3,+,x/2 with x = 0.701,(1) has been analyzed within the (3,+,1)-dimensional superspace formalism. Two different models were refined describing the structure as an incommensurate modulated layer and modulated composite, respectively. Both models include the same composition,structure relation. In the composite approach it is derived from the mismatching between the two subsystems. In the incommensurate modulated system, it is derived from a closeness condition between O atomic domains. The distribution and coordination of the cations is discussed and compared with previously proposed models for similar compounds. [source] A simple hydrogen-bonded chain in (3Z)-3-{1-[(5-phenyl-1H -pyrazol-3-yl)amino]ethylidene}-4,5-dihydrofuran-2(3H)-one, and a hydrogen-bonded ribbon of centrosymmetric rings in the self-assembled adduct (3Z)-3-{1-[(5-methyl-1H -pyrazol-3-yl)amino]ethylidene}-4,5-dihydrofuran-2(3H)-one,6-(2-hydroxyethyl)-2,5-dimethylpyrazolo[1,5- a]pyrimidin-7(4H)-one (1/1)ACTA CRYSTALLOGRAPHICA SECTION C, Issue 1 2010Jairo Quiroga (3Z)-3-{1-[(5-Phenyl-1H -pyrazol-3-yl)amino]ethylidene}-4,5-dihydrofuran-2(3H)-one, C15H15N3O2, (I), and the stoichiometric adduct (3Z)-3-{1-[(5-methyl-1H -pyrazol-3-yl)amino]ethylidene}-4,5-dihydrofuran-2(3H)-one,6-(2-hydroxyethyl)-2,5-dimethylpyrazolo[1,5- a]pyrimidin-7(4H)-one (1/1), C10H13N3O2·C10H13N3O2, (II), in which the two components have the same composition but different constitutions, are formed in the reactions of 2-acetyl-4-butyrolactone with 5-amino-3-phenyl-1H -pyrazole and 5-amino-3-methyl-1H -pyrazole, respectively. In each compound, the furanone component contains an intramolecular N,H...O hydrogen bond. The molecules of (I) are linked into a chain by a single intermolecular N,H...O hydrogen bond, while in (II), a combination of one O,H...N hydrogen bond, within the selected asymmetric unit, and two N,H...O hydrogen bonds link the molecular components into a ribbon containing alternating centrosymmetric R44(20) and R66(22) rings. [source] The in vitro Inhibitory Potential of Trade Herbal Products on Human CYP2D6-Mediated Metabolism and the Influence of EthanolBASIC AND CLINICAL PHARMACOLOGY & TOXICOLOGY, Issue 5 2007Bent H. Hellum Herbal components were extracted from commercially available products in a way that ensured the same composition of constituents in the extract as in the original trade products. c-DNA baculovirus expressed CYP2D6 was used with dextromethorphan as substrate. Quinidine was included as a positive control inhibitor. A validated high performance liquid chromatography methodology was used to quantify the formation of dextrorphan (product of dextromethorphan O-demethylation). Ethanol showed a biphasic effect on CYP2D6 metabolism, increasing initially the CYP2D6 activity with 175% of control up to a concentration of 1.1%, where after ethanol linearly inhibited the CYP2D6 activity. All the investigated herbs inhibited CYP2D6 activity to some extent, but only St. John's wort, common sage and common valerian were considered possible candidates for in vivo clinically significant effects. They showed IC50 values of 0.07 ± 7 × 10,3 mg/ml, 0.8 ± 0.05 mg/ml and 1.6 ± 0.2 mg/ml, respectively. St. John's wort inhibited CYP2D6-mediated metabolism in an uncompetitive manner, while common valerian and common sage in a non-competitive manner demonstrated interherb differences in inhibition patterns and differences when compared to the more homogenous competitive inhibitor quinidine. Common valerian was the only herb that showed a mechanistic inhibition of CYP2D6 activity and attention should be paid to a possible toxicity of this herb. [source] Stabilization of glucose oxidase in alginate microspheres with photoreactive diazoresin nanofilm coatingsBIOTECHNOLOGY & BIOENGINEERING, Issue 1 2005Rohit Srivastava Abstract The nanoassembly and photo-crosslinking of diazo-resin (DAR) coatings on small alginate microspheres for stable enzyme entrapment is described. Multilayer nanofilms of DAR with poly(styrene sulfonate) (PSS) were used in an effort to stabilize the encapsulation of glucose oxidase enzyme for biosensor applications. The activity and physical encapsulation of the trapped enzyme were measured over 24 weeks to compare the effectiveness of nanofilm coatings and crosslinking for stabilization. Uncoated spheres exhibited rapid loss of activity, retaining only 20% of initial activity after one week, and a dramatic reduction in effective activity over 24 weeks, whereas the uncrosslinked and crosslinked {DAR/PSS}-coated spheres retained more than 50% of their initial activity after 4 weeks, which remained stable even after 24 weeks for the two and three bilayer films. Nanofilms comprising more polyelectrolyte layers maintained higher overall activity compared to films of the same composition but fewer layers, and crosslinking the films increased retention of activity over uncrosslinked films after 24 weeks. These findings demonstrate that enzyme immobilization and stabilization can be achieved by using simple modifications to the layer-by-layer self-assembly technique. © 2005 Wiley Periodicals, Inc. [source] NOx storage and reduction with propylene on Pt/BaO/aluminaAICHE JOURNAL, Issue 10 2004Rachel L. Muncrief Abstract An experimental study was carried out of periodically operated NOx (NO + NO2) storage and reduction on a model Pt/BaO/Al2O3 catalyst powder. The effect of the reductant (propylene) injection policy on time-averaged NOx conversion was evaluated in terms of feed composition and temperature, reductant pulse duration, and overall cycle time. Conditions giving time-averaged NOx conversions exceeding 90% were identified. The reductant-to-oxidant ratio during the injection and the total cycle time are both found to be critical factors to achieve high conversion. The time-averaged conversion is bounded above and below by the steady-state conversions obtained with feeds having the same compositions as that during the rich and lean part of the cycle, respectively. For a fixed supply of propylene, short pulses of high concentration are much more effective than longer pulses of reduced concentration. The NOx conversion achieves a maximum value at an intermediate overall cycle time when the propylene pulse of fixed duty fraction is net reducing. High conversions are sustained over a wide temperature window (200,400°C). A simple storage,reduction cycle is proposed that elucidates the main findings in the study. The key factor for high NOx conversion is the temporal production of oxygen-deficient conditions coupled with high catalyst temperatures, both resulting from the intermittent catalytic oxidation of propylene. © 2004 American Institute of Chemical Engineers AIChE J, 50: 2526,2540, 2004 [source] | ||||||||||||||||||||||||||||||||||