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Characteristic Properties (characteristic + property)
Selected AbstractsHeterogeneous Plasma-Producing Structures at Current Implosion of a Wire ArrayCONTRIBUTIONS TO PLASMA PHYSICS, Issue 8 2005E. V. Grabovsky Abstract Characteristic properties of the plasma production process have been considered for the case of megampere currents flowing through hollow cylindrical wire arrays of the Angara-5-1 facility. In 3-4 nanoseconds after voltage applying to the wire surfaces there appear a plasma layer. The system becomes heterogeneous, i.e. consisting of a kernel of metal wires and a plasma layer. In several nanoseconds the current flow goes from metal to plasma, which results in reducing the electric field strength along the wire. The Joule heat energy delivered to the metal before the moment of complete current trapping by plasma is insufficient for the whole mass transition to a hot plasma state. The X-ray radiography techniques made it possible to detect and study dense clusters of substance of ,1g/cm3 at a developed discharge stage. The radial expansion velocity of ,104 cm/s measured at the 70-th nanosecond after the current start allows treating the dense core at a late stage in the form of a submicron heterogeneous structure from its liquid and slightly ionized gas phase. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Two-dimensional hydrogen atom confined in circles, angles, and circular sectorsINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 4 2005L. Chaos-Cador Abstract The Schrödinger equation for the 2D hydrogen atom is separable in circular coordinates (, = , , = tan,1y/x). In this article the energy eigenvalues and eigenfunctions of such an atom in three different situations of confinement inside (a) a circle (0 , , , ,0, 0 , , , 2,), (b) an angle (0 , , , ,, 0 , , , ,0), and (c) a circular sector (0 , , , ,0, 0 , , , ,0) are explicitly constructed. Characteristic properties of the atom in its ground state for each situation of confinement such as the polarizability for (a) and electric dipole moment for (b) and (c) are also evaluated. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005 [source] Cyclic polymers: Synthetic strategies and physical propertiesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 2 2010Hans R. Kricheldorf Abstract Syntheses of cyclic polymers including cyclic homopolymers, cyclic block copolymers, sun-shaped polymers, and tadpole polymers are discussed on the basis of a differentiation between synthetic methods and synthetic strategies (e.g., polycondensation, ring,ring equilibration, or ring-expansion polymerization). Furthermore, all synthetic methods are classified as kinetically or thermodynamically controlled reactions. Characteristic properties of cyclic polymers such as smaller hydrodynamic volume, lower melt viscosities, and higher thermostabilities are compared to the properties of their linear counterparts. Furthermore, the nanophase separation of cyclic diblock copolymers is discussed. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 251,284, 2010 [source] Unambiguous structural elucidation of base-modified purine nucleosides using NMRMAGNETIC RESONANCE IN CHEMISTRY, Issue 1 2008Raman Narukulla Abstract A general and unambiguous approach has been developed for structural elucidation of modified purine nucleosides using NMR spectroscopy. Systematic assignment of proton and carbon signals of modified nucleosides was firmly established by COSY and the anomerism of the glycosidic linkage of synthetic nucleosides clearly elucidated by NOESY experiments. Characteristic properties of 15N-isotopic labelling at specific positions of nucleosides were also employed for structural studies. The reported approach is applicable to other modified nucleosides and nucleotides, as well as nucleobases. Copyright © 2007 John Wiley & Sons, Ltd. [source] Diffraction imaging in depthGEOPHYSICAL PROSPECTING, Issue 5 2008T.J. Moser ABSTRACT High resolution imaging is of great value to an interpreter, for instance to enable identification of small scale faults, and to locate formation pinch-out positions. Standard approaches to obtain high-resolution information, such as coherency analysis and structure-oriented filters, derive attributes from stacked, migrated images. Since they are image-driven, these techniques are sensitive to artifacts due to an inadequate migration velocity; in fact the attribute derivation is not based on the physics of wave propagation. Diffracted waves on the other hand have been recognized as physically reliable carriers of high- or even super-resolution structural information. However, high-resolution information, encoded in diffractions, is generally lost during the conventional processing sequence, indeed migration kernels in current migration algorithms are biased against diffractions. We propose here methods for a diffraction-based, data-oriented approach to image resolution. We also demonstrate the different behaviour of diffractions compared to specular reflections and how this can be leveraged to assess characteristics of subsurface features. In this way a rough surface such as a fault plane or unconformity may be distinguishable on a diffraction image and not on a traditional reflection image. We outline some characteristic properties of diffractions and diffraction imaging, and present two novel approaches to diffraction imaging in the depth domain. The first technique is based on reflection focusing in the depth domain and subsequent filtering of reflections from prestack data. The second technique modifies the migration kernel and consists of a reverse application of stationary-phase migration to suppress contributions from specular reflections to the diffraction image. Both techniques are proposed as a complement to conventional full-wave pre-stack depth migration, and both assume the existence of an accurate migration velocity. [source] Glia-induced neuronal differentiation by transcriptional regulationGLIA, Issue 11 2007Christian Göritz Abstract There is increasing evidence that different phases of brain development depend on neuron,glia interactions including postnatal key events like synaptogenesis. To address how glial cells influence synapse development, we analyzed whether and how glia-derived factors affect gene expression in primary cultures of immunoisolated rat retinal ganglion cells (RGCs) by oligonucleotide microarrays. Our results show that the transcript pattern matched the developmental stage and characteristic properties of RGCs in vitro. Glia-conditioned medium (GCM) and cholesterol up- and downregulated a limited number of genes that influence the development of dendrites and synapses and regulate cholesterol and fatty acid metabolism. The oligonucleotide microarrays detected the transcriptional regulation of neuronal cholesterol homeostasis in response to GCM and cholesterol treatment. Surprisingly, our study revealed neuronal expression and glial regulation of matrix gla protein (Mgp). Together, our results suggest that glial cells promote different aspects of neuronal differentiation by regulating transcription of distinct classes of genes. © 2007 Wiley-Liss, Inc. [source] Influence of potassium sorbate on the growth of yeasts and moulds in yogurtINTERNATIONAL JOURNAL OF DAIRY TECHNOLOGY, Issue 2 2009MAHA A M AL-ASHMAWY Yeasts and moulds are little affected by low pH and may cause spoilage of yogurt during storage. In the present study, potassium sorbate was added as a preservative in concentrations of 0.05%, 0.1% and 0.2%. The unpreserved yogurt showed unfavourable characteristics: yeast and mould counts and acidity increased. The addition of potassium sorbate, however, inhibited yeast and mould levels, with normal characteristic properties extending more than 14 days. Potassium sorbate is thus seen as valuable for preserving yogurt. [source] Structures and stability of lithium monosilicide clusters SiLin (n = 4,16): What is the maximum number, magic number, and core number for lithium coordination to silicon?JOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 11 2008Ning He Abstract In the coordination, hypervalent and cluster chemistry, three important characteristic properties are the maximum coordination number, magic number, and core coordination number. Yet, few studies have considered these three numbers at the same time for an MLn cluster with n larger than 8. In this article, we systematically studied the three properties of SiLin (n = 4,16) clusters at the B3LYP/6-31G(d), B3LYP/6-311++G(2d), and CCSD(T)/6-311++G(3df)//B3LYP/6-311++G(2d) (for energy only) levels. Various isomeric forms with different symmetries were calculated. For each SiLin (n = 4,9), silicon cohesive energy (cE) from SiLin , Si + Lin reaction, vertical ionization potential (vIP), and vertical electron affinity (vEA) were obtained for the lowest-energy isomer. We found that the maximum Li-coordination number of Si is 9, which is the largest number among the known MLin clusters. All cE, vIP, and vEA values predicted that 6 is the magic Li-coordination number of Si. For small SiLin (n , 6) clusters, Li atoms favor direct coordination to Si, whereas for larger SiLin (n , 7) clusters, there is a core cluster that is surrounded by excessive Li atoms. The core Li-coordination number is 6 for SiLin (n = 7,8), 7 for SiLin (n = 9,10), 8 for SiLin (n = 11,15) and 9 for SiLin (n , 16). Through the calculations, we verified the relationship between the structure and stability of SiLin with the maximum coordination number, magic number, and core coordination number. © 2008 Wiley Periodicals, Inc. J Comput Chem, 2008 [source] Polymer Morphology: A Guide to Macromolecular Self-OrganizationMACROMOLECULAR SYMPOSIA, Issue 1 2004D.C. Bassett Abstract The study of polymer morphology continues to be the principal means of acquiring knowledge and understanding of macromolecular self-organization. Longstanding problems of the nature of melt-crystallized lamellae and spherulitic growth have been resolved, bringing understanding of how characteristic properties such as a broad melting range and spatially-varying mechanical response are inherent in spherulitic morphologies. This reflects the distinctive features of the crystallization of long molecules, i.e. that they impede each other and, for faster growth, form rough basal surfaces. Knowledge of morphology is an essential accompaniment to the informed development of advanced polymeric materials and a full understanding of their structure/property relations. [source] Species differences in enantioselective 2-oxidations of RS-8359, a selective and reversible MAO-A inhibitor, and cinchona alkaloids by aldehyde oxidaseBIOPHARMACEUTICS AND DRUG DISPOSITION, Issue 3 2006Kunio Itoh Abstract The 2-oxidation activity on the pyrimidine ring of RS-8359, a MAO-A inhibitor, is the major metabolic pathway catalysed by aldehyde oxidase. This study investigated the species differences in the 2-oxidation activity by using liver cytosolic fractions from rats, mice, guinea-pigs, rabbits, dogs, monkeys and humans. The Vmax/Km value for the (S)-enantiomer of RS-8359 was extremely high in monkeys and humans, moderate in guinea-pigs, and low in rats and mice. Dogs were deficient in 2-oxidation activity. The (R)-enantiomer was only oxidized at a very low rate in guinea-pigs, monkeys and humans, and not oxidized in rats, mice and rabbits. Thus, marked species differences and enantioselectivity were obvious for the 2-oxidation of the (S)-enantiomer of RS-8359. The in vitro results were in good accordance with previously reported in vivo excretion data of the 2-keto metabolite and the non-detectable plasma concentrations of the (S)-enantiomer in monkeys and humans after administration of racemic RS-8359. Enantioselectivity was also observed for the oxidation of cinchona alkaloids catalysed by aldehyde oxidase. Among the four cinchona alkaloids studied, the oxidation activity of cinchonidine, which has no substituents at the 6-hydroxy group but bears (8S,9R)-configurations, was highest. As opposed to the (S)-enantiomer, an extremely high catalytic activity of cinchonidine was confirmed in rabbits, but not in monkeys or humans. Rabbit liver aldehyde oxidase was suggested to have characteristic properties around the active site. Copyright © 2006 John Wiley & Sons, Ltd. [source] Modeling with a view to target identification in metabolic engineering: A critical evaluation of the available toolsBIOTECHNOLOGY PROGRESS, Issue 2 2010Jo Maertens Abstract The state of the art tools for modeling metabolism, typically used in the domain of metabolic engineering, were reviewed. The tools considered are stoichiometric network analysis (elementary modes and extreme pathways), stoichiometric modeling (metabolic flux analysis, flux balance analysis, and carbon modeling), mechanistic and approximative modeling, cybernetic modeling, and multivariate statistics. In the context of metabolic engineering, one should be aware that the usefulness of these tools to optimize microbial metabolism for overproducing a target compound depends predominantly on the characteristic properties of that compound. Because of their shortcomings not all tools are suitable for every kind of optimization; issues like the dependence of the target compound's synthesis on severe (redox) constraints, the characteristics of its formation pathway, and the achievable/desired flux towards the target compound should play a role when choosing the optimization strategy. © 2010 American Institute of Chemical Engineers Biotechnol. Prog., 2010 [source] Invariance and factorial modelsJOURNAL OF THE ROYAL STATISTICAL SOCIETY: SERIES B (STATISTICAL METHODOLOGY), Issue 2 2000P. McCullagh Two factors having the same set of levels are said to be homologous. This paper aims to extend the domain of factorial models to designs that include homologous factors. In doing so, it is necessary first to identify the characteristic property of those vector spaces that constitute the standard factorial models. We argue here that essentially every interesting statistical model specified by a vector space is necessarily a representation of some algebraic category. Logical consistency of the sort associated with the standard marginality conditions is guaranteed by category representations, but not by group representations. Marginality is thus interpreted as invariance under selection of factor levels (I -representations), and invariance under replication of levels (S -representations). For designs in which each factor occurs once, the representations of the product category coincide with the standard factorial models. For designs that include homologous factors, the set of S -representations is a subset of the I -representations. It is shown that symmetry and quasi-symmetry are representations in both senses, but that not all representations include the constant functions (intercept). The beginnings of an extended algebra for constructing general I -representations is described and illustrated by a diallel cross design. [source] 3D rheological model of transversal isotropic elastoplastic bodyPROCEEDINGS IN APPLIED MATHEMATICS & MECHANICS, Issue 1 2003Victor Naumov Dr.-Ing. A 3D theory of microplasticity for an anisotropic elastoplastic body is presented. This theory is proposed for the phenomenological description and analysis of deformation of a superconducting cable under the transversal cyclic loading. Obtained constitutive equations reflect the possibility to describe hysteresis loops during cyclic loading of the material. They reflect the fact that these hysteresis loops don't depend on the strain rate. Developed theory deals with phenomenological anisotropy of elastoplasticity which is a characteristic property of the superconducting cable. This cable consists of a large number of strands oriented in general along the cable axis. [source] Synthesis of copolymer from 1,3,5-trioxane and 1,3-dioxolane catalyzed by Maghnite-H+JOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2010Khadidja Beloufa Abstract Copolymers (polyoxymethylene) were prepared by cationic copolymerization of 1,3,5-trioxane (TOX) with 1,3-dioxolane (DOX) in the presence of Maghnite-H+ (Mag-H+) in solution. Maghnite is a Montmorillonite sheet silicate clay, with exchanged protons to produce Mag-H+. Various techniques, including 1H-NMR, 13C-NMR, FT-IR spectroscopy, and Ubbelohde viscometer were used to elucidate structural characteristics properties of the resulting copolymers. The influence of the amount of catalyst, of dioxolane (DOX), temperature, solvent, and time of copolymerization on yield and on intrinsic viscosity of copolymers was studied. The yield of copolymerization depends on the amount of Mag-H+ used and the reaction time. We also propose mechanisms involved in the synthesis of copolymer (polyoxymethylene). © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] | ||||||||||||||||