Home About us Contact
|
Home About us Contact | ||
|
|
||
Ratio Used (ratio + used)
Selected AbstractsMass spectrometric characterization of covalent modification of human serum albumin by 4-hydroxy- trans -2-nonenalJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 9 2006Giancarlo Aldini Abstract Several pieces of evidence indicate that albumin modified by HNE is a promising biomarker of systemic oxidative stress and that HNE-modified albumin may contribute to the immune reactions triggered by lipid peroxidation-derived antigens. In this study, we found by HPLC analysis that HNE is rapidly quenched by human serum albumin (HSA) because of the covalent adduction to the different accessible nucleophilic residues of the protein, as demonstrated by electrospray ionization mass spectrometry (ESI-MS) direct infusion experiments (one to nine HNE adducts, depending on the molar ratio used, from 1 : 0.25 to 1 : 5 HSA : HNE). An LC-ESI-MS/MS approach was then applied to enzymatically digested HNE-modified albumin, which permitted the identification of 11 different HNE adducts, 8 Michael adducts (MA) and 3 Schiff bases (SB), involving nine nucleophilic sites, namely: His67 (MA), His146 (MA), His242 (MA), His288 (MA), His510 (MA), Lys 195 (SB), Lys 199 (MA, SB), Lys525 (MA, SB) and Cys34 (MA). The most reactive HNE-adduction site was found to be Cys34 (MA) followed by Lys199, which primarily reacts through the formation of a Schiff base, and His146, giving the corresponding HNE Michael adduct. These albumin modifications are suitable tags of HNE-adducted albumin and could be useful biomarkers of oxidative and carbonylation damage in humans. Copyright © 2006 John Wiley & Sons, Ltd. [source] A heterogeneous acid-catalyzed process for biodiesel production from enzyme hydrolyzed fatty acidsAICHE JOURNAL, Issue 1 2008Chia-Hung Su Abstract In this work, biodiesel synthesis via fatty acids esterification with methanol is conducted by using a heterogeneous catalyst made from cation-exchange resin. The kinetics of esterification is studied at the different levels of catalyst loading (3.65,53.6%, w/w), reaction temperature (333,353 K) and molar ratio of methanol to fatty acids (1:1 to 20:1). The reaction rate and fatty acids conversion increased with increases in catalyst loading, reaction temperature and molar ratio of feeding reactants. A pseudo-homogeneous kinetic model coupling the effect of catalyst loading, reaction temperature and methanol/fatty acids molar ratio used for describing the process gave a correlation coefficient of 0.95 between experimental and predicted data. The proposed model was further used to predict the optimal operating condition for obtaining equilibrium conversion of 0.99. A reaction temperature of 372.15 K, molar ratio of feeding reactants of 14.9:1 and reaction time of 9.5 h was numerically calculated as the optimal operating condition. Under this optimal operating condition, an experimental verification was carried out and a satisfactory match was observed between experimental data and model prediction. © 2007 American Institute of Chemical Engineers AIChE J, 2008 [source] Influence of Diaspore Seeding and Chloride Concentration on the Transformation of "Diasporic" Precursors to CorundumJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2001Richard L. Smith "Diasporic" precursors derived from sols formed by the controlled hydrolysis of aluminum sec-butoxide in the presence of HCl yielded mixtures of corundum and amorphous alumina when calcined between 500° and 800°C. The fraction of corundum in the calcined products depended on the HCl/alkoxide ratio used during hydrolysis and was maximized at 64 wt% when the molar ratio was 1. Precursors formed from sols hydrolyzed in the presence of HNO3 rather than HCl yielded only amorphous products or transition aluminas when treated below 900°C. The corundum yield of the precursors was enhanced when they were seeded with diaspore (,-AlOOH) crystals. Precursors synthesized with an HCl/alkoxide ratio of 1 and seeded with 7.6 × 1016 diaspore seeds/(mol of Al2O3) were transformed to phase-pure corundum within 12 h at 700°C. Based on studies of the phase evolution of the precursors during calcining, it was concluded that the diaspore seeds promoted conversion by acting as corundum nuclei once they decomposed at ,450°C. [source] Effect of clay/water ratio during bentonite clay organophilization on the characteristics of the organobentonites and its polypropylene nanocompositesPOLYMER ENGINEERING & SCIENCE, Issue 9 2009Suédina M.L. Silva A sodium bentonite (montmorillonite-based layered silicate clay) was organically modified with cetyl trimethyl ammonium bromide (cetrimide), using different clay/water ratios,but the same clay/cetrimide ratio,to suspend the bentonite clay and perform its organophilization. Infrared spectroscopy and thermogravimetric analysis indicated the incorporation of organic modifier into the bentonite. Wide-angle X-ray scattering showed that the incorporation of surfactant significantly increased the interlayer spacing in the bentonite for all concentrations studied. It was found that clay/water ratio employed during the modification affects neither the amount of organic salt incorporated nor the interlayer spacing in the organobentonites, but influences its degree of structural disorder. Lower clay/water ratios resulted in a more disorderly structure, as established by the decrease of the areas under the X-ray peaks as the clay/water ratio diminishes. The modified bentonites were melt compounded with maleic anhydride-grafted polypropylene. X-ray diffraction patterns of the hybrids revealed that the more disorderly organobentonites were better dispersed in the polymer matrix, indicating that, in the present system, the structure of polymer nanocomposites obtained were affected by the clay/water ratio used in organobentonite preparation. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers [source] TOWARDS A UNIFORM CONCEPT FOR THE COMPARISON AND EXTRAPOLATION OF ROCKWALL RETREAT AND ROCKFALL SUPPLYGEOGRAFISKA ANNALER SERIES A: PHYSICAL GEOGRAPHY, Issue 1 2007MICHAEL KRAUTBLATTER ABSTRACT. Rates of rockwall retreat and rockfall supply are fundamental components of sediment budgets in steep environments. However, the standard procedure of referencing rockwall retreat rates using only lithology is inconsistent with research findings and results in a variability that exceeds three orders of magnitude. The concept proposed in this paper argues that the complexity inherent in rockfall studies can be reduced if the stages of (i) backweathering, (ii) filling and depletion of intermediate storage on the rock face and (iii) final rockfall supply onto the talus slopes are separated as these have different response functions and controlling factors. Backweathering responds to preweathering and weathering conditions whereas the filling and depletion of intermediate storage in the rock face is mainly a function of internal and external triggers. The noise apparent in backweathering rates and rockfall supply can be reduced by integrating the relevant controlling factors in the response functions. Simple conceptual models for the three stages are developed and are linked by a time-dependent ,rockfall delivery rate', which is defined as the difference between backweathering and rockfall supply, thus reflecting the specific importance of intermediate storage in the rock face. Existing studies can be characterized according to their ,rockfall delivery ratio', a concept similar to the ,sediment delivery ratio' used in fluvial geomorphology. Their outputs can be qualified as trigger-dependent rockfall supply rates or backweathering rates dependent on (pre-)weathering conditions. It is shown that the existing quantitative backweathering and rockfall supply models implicitly follow the proposed conceptual models and can be accommodated into the uniform model. Suggestions are made for how best to incorporate non-linearities, phase transitions, path dependencies and different timescales into rockfall response functions. [source] Selective and frequency dependent predation of aquatic mosquito predator Diplonychus indicus Venkatesan & Rao (Hemiptera: Belostomatidae) on immature stages of three mosquito speciesENTOMOLOGICAL RESEARCH, Issue 6 2009Narayanasamy SIVAGNANAME Abstract Frequency dependent mosquito larval size (II and IV instars) and species selection by the water bug Diplonychus indicus against three mosquito species Culex quinquefasciatus, Aedes aegypti and Anopheles stephensi was studied in the laboratory. The different frequencies used for each species selection were 20:30:50, 30:50:20, 50:20:30, 25:35:40, 35:40:25 and 40:25:35 of fourth instars of the respective three prey species. All nymphal water bugs (I,V instars) selected IV instar mosquito larvae and the mean proportion of late (larger) larvae eaten by the predator instars was significantly higher than the mean proportion of early (smaller) larvae eaten (F= 2.28; P < 0.001). In all six ratios used to determine the frequency dependent mosquito species selection, all the stages of the water bug selected Ae. aegypti over the other two species (F= 452.43; P < 0.001). The mean number of mosquito larvae eaten increased as its density increased based on various ratios of larvae offered. The study indicated that the predatory efficiency of D. indicus was high when Ae. aegypti was offered as prey, suggesting the utility of this mosquito predator in the control of dengue vectors. [source] Price relations among hog, corn, and soybean meal futuresTHE JOURNAL OF FUTURES MARKETS, Issue 5 2005Qingfeng "Wilson" Liu This paper examines the relations among hog, corn, and soybean meal futures price series using the Perron (1997) unit root test and autoregressive multivariate cointegration models. Accounting for the significant seasonal factors and time trends, we find the three series are cointegrated with one single cointegrating vector, whose coefficients are comparable to the ratios used by the United States Department of Agriculture (USDA). Ex-post trading simulations that utilize the cointegration results generate significant profits, suggesting that market expectations may not fully incorporate the mean-reverting tendencies as indicated by the cointegration relations, and that inefficiency exists in these three commodity futures markets. Results from our ex-ante trading simulations that employ the USDA ratios also provide some evidence in this regard. © 2005 Wiley Periodicals, Inc. Jrl Fut Mark 25:491,514, 2005 [source] | |||||||||||||