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Selected AbstractsCyclometalated 2-phenylpyridine complex [RuII(o -C6H4 -py)(MeCN)4]PF6 as a tunable catalyst for living radical polymerizationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 12 2008F. Diaz Camacho Abstract The cyclometalated complex [RuII(o -C6H4 -py)(MeCN)4]PF6 (1) with a ,-RuC bond and four substitutionally labile acetonitrile ligands mediates radical polymerization of different vinyl monomers, viz. n -butyl acrylate, methyl methacrylate, and styrene, initiated by three alkyl bromides: ethyl 2-bromoisobutyrate, methyl 2-bromopropionate, and 1-phenylethyl bromide. The polymerization requires the presence of Al(OiPr)3 and occurs uncontrollably as a conventional radical process. The variation of the molar ratio of the components of the reaction mixture, such as initiator, Al(OiPr)3 and catalyst, affected the polymerization rates and the molecular weights but did not improve the control. A certain level of control has been achieved by adding 0.5 eq of SnCl2 as a reducing agent. Tin(II) chloride decreased the rate of polymerization and simultaneously the molecular weights became conversion-dependent and the polydispersities were also narrowed. Remarkably, the level of control was radically improved in the presence of excess of the poorly soluble catalyst (1), when the added amount of (1) was not soluble any more, i.e., under heterogeneous conditions, the system became adjustable and the living polymerization of all three monomers was finally achieved. Possible mechanisms of the (1)-catalyzed polymerization are discussed. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4193,4204, 2008 [source] Casein gelation under simultaneous action of transglutaminase and glucono-,-lactoneMOLECULAR NUTRITION & FOOD RESEARCH (FORMERLY NAHRUNG/FOOD), Issue 3 2004Orquídea Menéndez Abstract Casein solutions (5% w/v) were treated with microbial transglutaminase (MTG) and glucono-,-lactone (GDL) under varying conditions in order to obtain gels. Storage modulus (G ,) and gelation time of the gels were measured by oscillation rheometry, while protein cross-linking was determined by gel permeation chromatography. The addition of only GDL to milk resulted in very weak gels, while MTG on its own was not able to create gel networks. Simultaneous action of both ingredients led to gels, the firmness of which was linearly related to the added amount of MTG, but passed through a maximum with rising GDL concentrations. Using chromatographical analysis, increasing G , values were interrelated with the formation of MTG-induced oligomers. The gelation time was directly proportional to the GDL concentration but not influenced by the addition of MTG within the studied range of concentration. [source] In Vitro/in Vivo scaling of alprazolam metabolism by CYP3A4 and CYP3A5 in humansBIOPHARMACEUTICS AND DRUG DISPOSITION, Issue 2 2001Noriko Hirota Abstract We attempted to predict the in vivo metabolic clearance of alprazolam from in vitro metabolic studies using human liver microsomes and human CYP recombinants. Good correlations were observed between the intrinsic clearance (CLint) for 4-hydroxylation and CYP3A4 content and between the CLint for ,-hydroxylation and CYP3A5 content in ten human liver microsomal samples. Using the recombinant CYP isoforms expressed in insect cells, the CLint for CYP3A4 was about 2-fold higher than the CLint for CYP3A5 in the case of 4-hydroxylation. However, the CLint for CYP3A5 was about 3-fold higher than the CLint for CYP3A4 in the case of ,-hydroxylation. The metabolic rates for 4- and ,-hydroxylation increased as the added amount of cytochrome b5 increased, and their maximum values were 3- to 4-fold higher than those without cytochrome b5. The values of CLint, in vivo predicted from in vitro studies using human liver microsomes and CYP3A4 and CYP3A5 recombinants were within 2.5 times of the observed value calculated from literature data. The average CLint value (sum of 4- and ,-hydroxylation) obtained using three human liver microsomal samples was 4-fold higher than that obtained using three small intestinal microsomal samples from the same donors, indicating the minor contribution of intestinal metabolism to alprazolam disposition. The area under the plasma concentration-time curve (AUC) of alprazolam is reported to increase following co-administration of ketoconazole and the magnitude of the increase predicted from the in vitroKi values and reported pharmacokinetic parameters of ketoconazole was 2.30,2.45, which is close to the value observed in vivo (3.19). A quantitative prediction of the AUC increase by cimetidine was also successful (1.73,1.79 vs 1.58,1.64), considering the active transport of cimetidine into the liver. In conclusion, we have succeeded in carrying out an in vitro/in vivo scaling of alprazolam metabolism using human liver microsomes and human CYP3A4 and CYP3A5 recombinants. Copyright © 2001 John Wiley & Sons, Ltd. [source] Mineralization of organic contaminants in sludge-soil mixturesENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 4 2001Bo Gejlsbjerg Abstract The mineralization of 14C-labeled linear alkylbenzene sulfonate (LAS), nonylphenol (NP), nonylphenol-di-ethoxylate (NP2EO), di-(2-ethylhexyl)phthalate (DEHP), pyrene, and 1,4-dichlorobenzene (DCB) was investigated in different sludge-soil mixtures and soils. Under aerobic conditions, the mineralization of LAS, NP, and NP2EO was between 50 and 81% of the added amounts after two months, while DEHP and pyrene were mineralized more slowly. The mineralization of the model chemicals was indirectly affected by the amount of sludge in the test mixtures. A higher content of sludge in the mixtures reduced the overall concentration of oxygen, which resulted in a decrease of the mineralization of several of the model chemicals. In sludge-soil mixtures with predominantly anaerobic conditions, the mineralization was slower for all of the chemicals with the exception of DEHP and DCB. The mineralization of DCB was enhanced in mixtures with a high sludge content. No pronounced difference in the mineralization of the model chemicals (except DEHP) was observed when the sludge was mixed with three different agricultural soils. [source] HOW DO THE SIGNAL DETECTION INDICES REACT TO FREQUENCY CONTEXT BIAS FOR INTENSITY SCALING?JOURNAL OF SENSORY STUDIES, Issue 1 2001HYE-SEONG LEE ABSTRACT Stimulus frequency context effects were noted for stimuli with positive, negative and no skew, using aqueous NaCl stimuli of different concentrations as a model system and orange juice stimuli with added amounts of sucrose as a beverage system. The hypothesis that analysis by signal detection ,m values, rather than individually rated intensity values, would result in the absence of the context effect, was not confirmed. [source] Microwave Dielectric Properties of Sintered Alumina Using Nano-Scaled Powders of , Alumina and TiO2JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 5 2007Cheng-Liang Huang The microstructure and the microwave dielectric properties of nano-scaled , alumina (,-Al2O3) ceramics with various added amounts of nano-scaled TiO2 have been investigated. The sintering temperature of nano-scaled , alumina can be effectively lowered by increasing the TiO2 content. The Q×f values of nano-scaled , alumina could be tremendously boosted by adding an appropriate amount of TiO2. However, introducing excessive TiO2 into the alumina ceramics would instead lead to a decrease in the Q×f values. The phases of TiO2 and Al2TiO5 co-existed at 1350°C, and the maximum Q×f value appeared right after the eradication of TiO2 phase at 1400°C. Consequently, increasing the TiO2 content to 0.5 wt% yielded a Q×f value of 680 000 GHz (measured at 14 GHz) for nano-scaled , alumina prepared at 1400°C for duration of 4 h. In addition, a very low loss tangent (tan ,) of 2 × 10,5 was also obtained at 14 GHz. The ,f value is strongly correlated to the compositions and can be controlled through the existing phases. In fact, ,f could be adjusted to near zero by adding 8 wt% TiO2 to , alumina ceramics. A dielectric constant (,r) of 10.81, a high Q×f value of 338 000 GHz (measured at 14 GHz), and a temperature coefficient of resonant frequency (,f) of 1.3 ppm/°C were obtained for nano-scaled , alumina with 8 wt% TiO2 sintered at 1350°C for 4 h. Sintered ceramic samples were also characterized by X-ray diffraction and scanning electron microscopy. [source] Effects of rare-earth oxide additions and heat-treatment temperature on the transformation and microstructure of silicon nitridePHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 1 2003Jinhui Dai Abstract In this paper, mixtures of Si3N4 powder with different added amounts of single rare-earth oxide Re2O3 (Re = Ce, Nd, Sm, Eu, Gd, Dy, Er, Yb) were heat treated at 1600,1800 °C and the effects of Re2O3 on the transformation and the microstructure of Si3N4 were investigated. Compared with the original Si3N4 powder, the transformation ratio of the Si3N4 powders obviously increased and the phase transformation finishing temperatures decreased by about 100 °C when different rare-earth oxides were added. When the heat-treatment temperature was 1700 °C, the transformation ratio of the Si3N4 powder was about 100%. When the heat-treatment temperature was 1600 °C and the amount of Re2O3 addition was 3 mol%, an anomalous transformation ratio occurred. In addition, it was found that the transformation ratio of Si3N4 changed periodically with the increase of the atomic number of the lanthanide when the heat-treatment temperature was 1650 °C or less. The SEM image of the Si3N4 powders obtained at 1700 °C indicated that the heavy lanthanide oxides such as Er2O3 and Yb2O3 were very helpful to develop rod-like ,-Si3N4 particles. [source] | |||||||||||||