Home About us Contact
|
Home About us Contact | ||
|
|
||
Multicomponent Systems (multicomponent + system)
Selected AbstractsChemInform Abstract: Combining Multi-Catalysis and Multicomponent Systems for the Development of One-Pot Asymmetric Reactions: Stereoselective Synthesis of Highly Functionalized Bicyclo[4.4.0]decane-1,6-diones.CHEMINFORM, Issue 47 2008Dhevalapally B. Ramachary Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Synergistic effect of chemical preservatives with ethanol on the microbial shelf life of bread by factorial designINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 2 2008George Katsinis Summary The shelf life, particularly the mould-free shelf life (MFSL) of bread, was evaluated either by adding a conventional chemical preservative or by spraying the surface of bread, in which a chemical preservative was added. As bread making is a complex process and bread is a multicomponent system, the investigation was based on statistical design experiments. Using first-order factorial designs, reliable models were constructed, revealing the effects of some common ingredients of bread (such as salt, sugar, glycerol, potassium sorbate, calcium propionate) and their interactions on the MFSL (optimisation parameter) with and without ethanol surface spraying. The effectiveness of preservation was ranked as potassium sorbate + ethanol > calcium propionate + ethanol > potassium sorbate > calcium propionate. Ethanol addition led to MFSL prolongation of 43.5% and 38.5% compared with MFSL of potassium sorbate and calcium propionate, respectively, when all the factors were fixed to their basic levels. [source] Working memory and Down syndromeJOURNAL OF INTELLECTUAL DISABILITY RESEARCH, Issue 12 2007A. Baddeley Abstract A brief account is given of the evolution of the concept of working memory from a unitary store into a multicomponent system. Four components are distinguished, the phonological loop which is responsible for maintaining speech-based information, the visuospatial sketchpad performing a similar function for visual information, the central executive which acts as an attentional control system, and finally a new component, the episodic buffer. The buffer comprises a temporary multidimensional store which is assumed to form an interface between the various subsystems of working memory, long-term memory, and perception. The operation of the model is then illustrated through an account of a research programme concerned with the analysis of working memory in Down syndrome. [source] Thermodynamic Reassessment of ZrO2,CaO SystemJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 5 2009Kun Wang In this work, several thermodynamic assessments adopted widely for ZrO2,CaO system are reviewed and examined, the existing discrepancies are summarized, and a new assessment is carried out based on the formation enthalpy of two compounds (CaZr4O9 and Ca6Zr19O44) and experimental activity data concerning cubic solid solution. The thermodynamic parameters of all phases have been optimized by the least squares minimization procedure, a self consistent set of the optimized Gibbs energy parameters has been derived, which can be safely used to extrapolate into the multicomponent system. Compared with experimental data and the results in this work as well as the results reported previously, it is demonstrated that the present thermodynamic assessment is in better agreement with most of the experiments. [source] Viscous behaviour of quaternary fluid solutions at 298.15,KTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 5 2009R. K. Shukla Abstract Assuming a quaternary fluid solution to be made up of six binaries, a statistical approach of Flory has been extended to develop the expression for dynamic viscosity of multicomponent system using the concept of absolute rate and free volume approaches of liquid state. A reasonable agreement has been achieved between theory and the experiment for n -hexadecane,+,carbon tetrachloride,+,benzene,+,n -hexane quaternary system at 298.15 over a wide range of composition. An attempt has also been made to explain the nature of the molecular interactions, involved in the light of excess thermodynamic functions whose sign and magnitude depend upon the chain length and size of the component liquids. En supposant une solution de fluide quaternaire composée de six binaires, on a généralisé l'approche statistique de Flory dans le but d'établir l,expression pour la viscosité dynamique du système multicomposant à l,aide du concept de taux absolu et de l,approche des volumes libres de l,état liquide. Un accord raisonnable a été trouvé entre la théorie et l,expérience pour le système quaternaire n-hexadécane,+,tétrachlorure de carbone,+,benzène,+,n-hexane à 298,15 pour une vaste gamme de composition. On a également tenté d'expliquer la nature des interactions moléculaires, intervenant à la lumière des fonctions thermodynamiques d'excès dont le signe et la grandeur dépendent de la longueur de chaîne et de la quantité des composants liquides. [source] Density Measurements of Fluids and Their Mixtures at High PressureCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 6 2007A. M. F. Palavra Abstract The principles of the isochoric method are described, as well as the different variants of this method that can be considered according to the technique used to determine the amount of fluid inside the high pressure cell. An automated isochoric apparatus to measure the density of binary mixtures is presented. Accurate isochoric measurements of density of pure fluids, involving molecules like methanol, and mixtures, such as nitrogen plus methane and a multicomponent system with a composition representative of the U.S.A. commercial Gulf Coast natural gas, are analyzed. Moreover, the effect of the thermal degradation of fluids at high temperatures on the accuracy of the density measurements is also discussed. [source] Multicomponent Supramolecular Devices: Synthesis, Optical, and Electronic Properties of Bridged Bis-dirhodium and -diruthenium Complexes,EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 19 2006Anne Petitjean Abstract Four ruthenium- and rhodium-based metal,metal-bonded multicomponent systems have been synthesized, and their absorption, redox, spectroelectrochemical and structural properties have been studied. The absorption spectra of the four bis-dimetallic compounds M2LM2, where L is a bridging ligand and M is rhodium or ruthenium, exhibit very strong bands in the UV, visible and, for the diruthenium species, near-IR region. The low-energy absorption bands are assigned to charge-transfer transitions involving a metal,metal bonding orbital as the donor and an orbital centered on the bis-tetradentate aromatic ligands as the acceptor (metal,metal to ligand charge transfer, M2LCT). Each compound exhibits reversible bridging-ligand-centered reductions at mild potentials and several reversible oxidation processes. The oxidation signals of the two equivalent dimetallic centers of each bis-dimetallic compound are split, with the splitting , a measure of the electronic coupling , depending on both the metal and bridging ligand. The mixed-valence species of the dirhodium species was investigated, and the electronic coupling matrix element calculated from the experimental intervalence band parameters for one of them (86 cm,1) indicates a significant inter-component electronic interaction which compares well with good electron conducting anionic bridges such as cyanides. Although none of these compounds is luminescent, the M2LCT excited state of one of the bis-dirhodium complexes is relatively long-lived (about 6 ,s) in degassed acetonitrile at room temperature. The results presented here are promising for the development of linear poly-dimetallic complexes built on longer naphthyridine-based strands, with significant long-range electronic coupling and molecular-wire-like behavior. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Seasonal and pandemic influenza surveillance considerations for constructing multicomponent systemsINFLUENZA AND OTHER RESPIRATORY VIRUSES, Issue 2 2009Lynnette Brammer Abstract, Surveillance for influenza is essential for the selection of influenza vaccine components and detection of human infections with novel influenza A viruses that may signal the start of a pandemic. Virologic surveillance provides the foundation from which this information can be obtained. However, morbidity and mortality data are needed to better understand the burden of disease, which, in turn, can provide useful information for policy makers relevant to the allocation of resources for prevention and control efforts. Data on the impact of influenza can be used to identify groups at increased risk for severe influenza-related complications, develop prevention and control policies, and monitor the effect of these policies. Influenza surveillance systems frequently monitor outpatient illness, hospitalizations, and deaths, but selection of influenza surveillance components should be based on the surveillance goals and objectives of the jurisdiction. [source] PRIMUS: a Windows PC-based system for small-angle scattering data analysisJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 5 2003Petr V. Konarev A program suite for one-dimensional small-angle scattering data processing running on IBM-compatible PCs under Windows 9x/NT/2000/XP is presented. The main program, PRIMUS, has a menu-driven graphical user interface calling computational modules to perform data manipulation and analysis. Experimental data in binary OTOKO format can be reduced by calling the program SAPOKO, which includes statistical analysis of time frames, averaging and scaling. Tools to generate the angular axis and detector response files from diffraction patterns of calibration samples, as well as binary to ASCII transformation programs, are available. Several types of ASCII files can be directly imported into PRIMUS, in particular, sasCIF or ILL-type files are read without modification. PRIMUS provides basic data manipulation functions (averaging, background subtraction, merging of data measured in different angular ranges, extrapolation to zero sample concentration, etc.) and computes invariants from Guinier and Porod plots. Several external modules coupled with PRIMUSvia pop-up menus enable the user to evaluate the characteristic functions by indirect Fourier transformation, to perform peak analysis for partially ordered systems and to find shape approximations in terms of three-parametric geometrical bodies. For the analysis of mixtures, PRIMUS enables model-independent singular value decomposition or linear fitting if the scattering from the components is known. An interface is also provided to the general non-linear fitting program MIXTURE, which is designed for quantitative analysis of multicomponent systems represented by simple geometrical bodies, taking shape and size polydispersity as well as interparticle interference effects into account. [source] High-dimensional solid-liquid phase diagrams involving compounds and polymorphsAICHE JOURNAL, Issue 10 2002Christianto Wibowo A systematic procedure for the generation and visualization of high-dimensional isobaric phase diagrams for systems exhibiting compound formation and/or polymorphism is presented. Such phase diagrams are useful in synthesizing crystallization-based separation processes for systems involving compounds and polymorphs, which are common in the production of pharmaceuticals. Polythermal as well as isothermal phase diagrams of multicomponent systems can be generated. Examples are provided to illustrate the procedure. [source] Representation of high-dimensional, molecular solid-liquid phase diagramsAICHE JOURNAL, Issue 12 2000Ketan D. Samant A generic framework for the representation of multicomponent molecular solid-liquid phase diagrams in the form of digraphs is presented. Pure components, eutectic points, and saturation points in the solid-liquid composition space are represented as vertices of the digraph. These vertices are connected to form edges on the basis of the adjacency matrix, which is constructed by following a set of generic rules derived from the Gibbs phase rule. These edges form the boundaries of high-dimensional saturation varieties. Included in the framework is a procedure for plotting high-dimensional isobaric and isothermal isobaric phase behavior in the form of projections and cuts. With this framework, solid-liquid phase behavior of multicomponent systems can be easily represented and studied. Applications include facilitation of experimental development of high-dimensional phase diagrams and synthesis of crystallization-based separation processes. The latter is illustrated with the separation of a quinary mixture. [source] Thermodynamic characterization of hybrid polymer blend systemsPOLYMER ENGINEERING & SCIENCE, Issue 6 2009Amos Ophir A thermodynamic model was used to predict the morphology of hybrid multicomponent polymer blend systems. Two systems were studied, both including two noncompatible polymers, a third compatibilizer polymer and layered, organo-treated clays. The polar and nonpolar contributions of the surface energies of the components of the systems were calculated using measurements of the contact angles. The morphology of the multicomponent systems and the relative position of the organo-clays within them, were predicted by calculating the interaction energies between the different components of the system and evaluating these values according to the Vaia and Giannelis thermodynamic model for polymer melt intercalation in organically modified layered silicates. The experimental results show good correlation with the prediction that the organo-clays will have higher affinity to the compatibilizer polymer component situated at the interface between the two noncompatible blend components. In addition, the presence of the organo-clays in this interface was found to have a significant additional compatibilizing effect between the two polymer phases. The results presented in this work support the idea that hybrid formation via polymer melt intercalation depends mostly on energetic factors that can be determined from surface energies of polymers and organo-modified layered silicates, also in the case of multiphase polymer system. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers [source] Regulation, necessity, and the misinterpretation of knockoutsBIOESSAYS, Issue 8 2009Jamie Davies Abstract Much contemporary biology consists of identifying the molecular components that associate to perform biological functions, then discovering how these functions are controlled. The concept of control is key to biological understanding, at least of the physiological kind; identifying regulators of processes underpins ideas of causality and allows complicated, multicomponent systems to be summarized in relatively simple diagrams and models. Unfortunately, as this article demonstrates by drawing on published articles, there is a growing tendency for authors to claim that a molecule is a ,regulator' of something on evidence that cannot support the conclusion. In particular, gene knockout experiments, which can demonstrate only that a molecule is necessary for a process, are all too frequently being misinterpreted as revealing regulation. This logical error threatens to blur the important distinction between regulation and mere necessity and therefore to weaken one of our strongest tools for comprehending how organisms work. [source] | ||||||||||||||||