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General Scheme (general + scheme)
Selected AbstractsCompetition between Host Aggregates and Isolated Guest Chromophores in Trapping Excitons in Polybenzazole Copolymers and BlendsMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 24 2006Shanfeng Wang Abstract Summary: Host,guest systems have been prepared using the blends and copolymers consisting of the host molecule poly(p -phenylene benzobisoxazole) (PBO) with a higher bandgap of 2.93 eV and the guest molecule poly(2,5-thienylbenzobisoxazole) (PBOT) with a lower bandgap of 2.57 eV. These systems have been investigated using photoluminescence (PL) spectra and time-resolved PL decay dynamics. Both PBOT-PBO copolymers and PBOT/PBO blends with the PBOT compositions less than 20% demonstrate higher intensities and narrower bandwidths in solid-state emission compared to that of PBOT, as well as larger fractions of the shorter lifetime component in PL decay dynamics. A general scheme on intrachain and interchain exciton migration and trapping mechanism has been proposed to interpret the phenomena in both solutions and thin films. Particularly, a competition in trapping exciton between PBO aggregates and isolated PBOT chromophores has been revealed. General scheme of exciton migration and trapping paths for host (D: donor),guest (A: acceptor) systems involving the isolated chromophores (A and D) and aggregates (AA and DD) in both ground state and excited state marked without or with an asterisk. [source] Hyperbranched macromolecules through donor-acceptor type copolymerization of allyl,vinylene bifunctional monomers,POLYMER INTERNATIONAL, Issue 10 2002O Rzaev, Zakir M Abstract Present review is an attempt to generalize and systematize the results accumulated in synthesis of cyclolinear and hyperbranched reactive macromolecules via radical alternating copolymerization of various bifunctional monomers containing donor and acceptor type double bonds. Synthesis of hyperbranched reactive macromolecules was carried out using complex-radical cyclocopolymerization of donor-acceptor type bifunctional monomers such as monoallyl ester of maleic acid (MAM), allyl acrylate (AA), allyl methacrylate (AM), allyl trans -cinnamate (AC), methylallylmaleate (MeAM), methylallylfumarate (MAF) and allyl-,-(N-maleimido)acetate (AMI), and maleic anhydride (MA) and styrene (St) as typical acceptor and donor comonomers, respectively. The kinetic parameters of these reactions, constants of cyclization, complex-formation and copolymerization, as well as the ratios of chain growth rates for the participation of monomeric charge transfer complexes and free monomers, were all determined. It was demonstrated that in the studied systems, copolymerizations predominantly proceed according to alternating mechanism with formation of macromolecules having cyclolinear structure in the steady-state and hyperbranched structure in the high conversion conditions. It was shown that formation of linear and hyperbranched macromolecules containing allyl or vinylene groups in the side chain occurs selectively carry out and depends on the nature of used comonomer. General schemes and proposed mechanism of hyperbranching and crosslinking reactions were also described. Some useful properties of synthesized reactive copolymers were discussed. © 2002 Society of Chemical Industry. [source] The Explainability of IntuitionsDIALECTICA, Issue 1 2004Nenad Mi Explaining intuitions in terms of "facts of our natural history" is compatible with rationally trusting them. This compatibilist view is defended in the present paper, focusing upon nomic and essentialist modal intuitions. The opposite, incompatibilist view alleges the following: If basic modal intuitions are due to our cognitive make-up or "imaginative habits" then the epistemologists are left with a mere non-rational feeling of compulsion on the side of the thinker. Intuitions then cannot inform us about modal reality. In contrast, the paper argues that there are several independent sources of justification which make the feeling of compulsion rational: the prima-facie and a priori ones come from the obviousness of our basic modal intuitions and our not being able to imagine things otherwise, others, a posteriori, from the epistemic success of these intuitions. Further, the general scheme of evolutionary learning is reliable, reliability is preserved in the resulting individual's cognitive make-up, and we can come to know this a posteriori. The a posteriori appeal to evolution thus plays a subsidiary role in justification, filling the remaining gap and removing the residual doubt. Explaining modal intuitions is compatible with moderate realism about modality itself. [source] Macroscopically Aligned Ionic Self-Assembled Perylene-Surfactant Complexes within a Polymer Matrix,ADVANCED FUNCTIONAL MATERIALS, Issue 13 2008Ari Laiho Abstract Ionic self-assembled (ISA) surfactant complexes present a facile concept for self-assembly of various functional materials. However, no general scheme has been shown to allow their overall alignment beyond local polydomain-like order. Here we demonstrate that ionic complexes forming a columnar liquid-crystalline phase in bulk can be aligned within polymer blends upon shearing, taken that the matrix polymers have sufficiently high molecular weight. We use an ISA complex of N,N,-bis(ethylenetrimethylammonium)perylenediimide/bis(2-ethylhexyl) phosphate (Pery-BEHP) blended with different molecular weight polystyrenes (PS). Based on X-ray scattering studies and transmission electron microscopy the pure Pery-BEHP complex was found to form a two-dimensional oblique columnar phase where the perylene units stack within the columns. Blending the complex with PS lead to high aspect ratio Pery-BEHP aggregates with lateral dimension in the mesoscale, having internal columnar liquid-crystalline order similar to the pure Pery-BEHP complex. When the Pery-BEHP/PS blend was subjected to a shear flow field, the alignment of perylenes can be achieved but requires sufficiently high molecular weight of the polystyrene matrix. The concept also suggests a simple route for macroscopically aligned nanocomposites with conjugated columnar liquid-crystalline functional additives. [source] Coupling electrical and mechanical effects in discrete element simulationsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 2 2008M. Renouf Abstract When investigating the electrical characteristics of granular assemblies under dynamical solicitations (powder, steel bead assemblies, etc.), it is difficult to distinguish between effects that are purely electrical and those that are strongly dependent on mechanical effects. Although numerous experimental works have permitted better understanding of the static electrical behaviour of such media, it is difficult to determine the effects control the multi-physical behaviour of the medium, especially under dynamical solicitations. In the present paper, numerical investigations of the electrical characteristics of granular material are proposed. Moreover, it presents the formulation of a new model, embedded in the general scheme of discrete element methods, that couples electrical and mechanical effects and takes into account the oxidation phenomenon. Numerical simulations on the basis of experimental works are performed to validate the model, and the results of dynamical simulations are discussed. Copyright © 2007 John Wiley & Sons, Ltd. [source] Generation and adaptation of computational surface meshes from discrete anatomical dataINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 6 2004Pascal J. FreyArticle first published online: 27 MAY 200 Abstract Fast and accurate scanning devices are nowadays widely used in many engineering and biomedical fields. The resulting discrete data is usually directly converted into polygonal surface meshes, using ,brute-force' algorithms, often resulting in meshes that may contain several millions of polygons. Simplification is therefore required in order to make storage, computation and display possible if not efficient. In this paper, we present a general scheme for mesh simplification and optimization that allows to control the geometric approximation as well as the element shape and size quality (required for numerical simulations). Several examples ranging from academic to complex biomedical geometries (organs) are presented to illustrate the efficiency and the utility of the proposed approach. Copyright © 2004 John Wiley & Sons, Ltd. [source] The N -particle wave function as a homogeneous functional of the densityINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 14 2007Tamás Gál Abstract It is shown that requiring consistency with the structure of the equation that determines the wave function associated to a density ,() by density-functional theory, yields the N -particle wave function as a degree-half homogeneous functional of the density, and leads to a separation A[N, ,] of N dependence (with N = ,,() d) of density functionals A[,] = A[,,, ,] for which A[,,, ,,] = , A[,, ,]; as a consequence of the linearity of quantum mechanical operators. This implies that the ground-state value of any quantum mechanical observable arises naturally as a degree-one homogeneous N -particle density functional. This general scheme for the structure of density functionals can be considered as the conceptual generalization of the Weizsäcker functional, which is the exact degree-one homogeneous one-particle kinetic-energy density functional. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2007 [source] Theoretical study of the reaction of alkynes with furan catalyzed by AuCl3 and AuClINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 2 2007Hassan Rabaâ Abstract A general scheme for the endo- and exo-cyclization of furan reactivity with [L -AuIII, IClx] with (x = 3, 1 and L -acetylene and vinylidene) complexes is investigated using density functional theory (DFT) code. Two conceivable mechanisms via a [4 + 2] Diels,Alder process or carbene complex are analyzed. According to the activation energy values of the gold (III and I) catalyst, the first mechanism, which implies the Diels,Alder reaction of AuIII, is thermodynamically favored and gives more evidence of the intramolecular addition of the furan with the alkynes. The second mechanism, presumably assisted by the spontaneous formation of the exo-vinylidene complexes and intermediates of gold (III, I) by forming the carbene complex, is kinetically favored. Additionally, we compare our results with other structures with intramolecular additions that exhibit the quasi-similarity of gold analogue structures. Differences in activation energies are observed, according to the functional used. Finally, we probe the solvent effects, which decrease the energy barrier in the path. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007 [source] The Differential Susceptibility of Specific Neuronal Populations: Insights from Huntington's DiseaseIUBMB LIFE, Issue 6 2003Ian Mitchell Abstract Recent successes in identifying the genes and associated proteins underlying several familial neurodegenerative conditions have not always resulted in accounts as to why the associated patterns of neuronal damage are so specific and limited. Here, with reference to Huntington's disease, we present a general scheme to show how the mutant protein could interact with associated proteins to form an aggregation product. This could lead to neuronal death by direct actions on caspases, or by raising the levels of intracellular calcium ions and reactive oxygen species above a threshold that cannot be resisted by the protection normally conferred by endogenous factors such as calcium binding proteins, free radical scavengers and trophic factors. The local distributions of vulnerability and protective factors could ultimately dictate the pattern of damage induced by the mutant gene. IUBMB Life, 55: 293-298, 2003 [source] Synthesis of deuterated 4,4,-diaminodiphenylsulfone (Dapsone) and related analogsJOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 2 2003Peter M. Gannett Abstract A general scheme for the synthesis of 4,4,-diaminodiphenylsulfone-d5 (Dapsone) from aniline-d5 is described. The method may have general application and the preparation of the related analogs, 4,4,-dimethylaminodiphenyl sulfone from aniline-d5 and 4,4,-dimethoxydiphenyl sulfone from phenol-d5, is also described. Copyright © 2002 John Wiley & Sons, Ltd. [source] Competition between Host Aggregates and Isolated Guest Chromophores in Trapping Excitons in Polybenzazole Copolymers and BlendsMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 24 2006Shanfeng Wang Abstract Summary: Host,guest systems have been prepared using the blends and copolymers consisting of the host molecule poly(p -phenylene benzobisoxazole) (PBO) with a higher bandgap of 2.93 eV and the guest molecule poly(2,5-thienylbenzobisoxazole) (PBOT) with a lower bandgap of 2.57 eV. These systems have been investigated using photoluminescence (PL) spectra and time-resolved PL decay dynamics. Both PBOT-PBO copolymers and PBOT/PBO blends with the PBOT compositions less than 20% demonstrate higher intensities and narrower bandwidths in solid-state emission compared to that of PBOT, as well as larger fractions of the shorter lifetime component in PL decay dynamics. A general scheme on intrachain and interchain exciton migration and trapping mechanism has been proposed to interpret the phenomena in both solutions and thin films. Particularly, a competition in trapping exciton between PBO aggregates and isolated PBOT chromophores has been revealed. General scheme of exciton migration and trapping paths for host (D: donor),guest (A: acceptor) systems involving the isolated chromophores (A and D) and aggregates (AA and DD) in both ground state and excited state marked without or with an asterisk. [source] A mathematical model for a spatial predator,prey interactionMATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 11 2002Annunziata Palumbo A predator,prey model is proposed within the general scheme of extended thermodynamics. An additional equation of balance is needed to account for the flux of the number density of the predator as an independent field variable. Copyright © 2002 John Wiley & Sons, Ltd. [source] Long-term monitoring in IC4665: fast rotation and weak variability in very low mass objectsMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 3 2009Alexander Scholz ABSTRACT We present the combined results of three photometric monitoring campaigns targeting very low mass (VLM) stars and brown dwarfs in the young open cluster IC4665 (age ,40 Myr). Each of our observing runs covers time-scales of ,5 d in the seasons 1999, 2001 and 2002, respectively. In all three runs, we observe ,100 cluster members, allowing us for the first time to put limits on the evolution of spots and magnetic activity in fully convective objects on time-scales of a few years. For 20 objects covering masses from 0.05 to 0.5 M,, we detect a periodic flux modulation, indicating the presence of magnetic spots co-rotating with the objects. The detection rate of photometric periods (,20 per cent) is significantly lower than in solar-mass stars at the same age, which points to a mass dependence in the spot properties. With two exceptions, none of the objects exhibits variability and thus spot activity in more than one season. This is contrary to what is seen in solar-mass stars and indicates that spot configurations capable of producing photometric modulations occur relatively rarely and are transient in VLM objects. The rotation periods derived in this paper range from 3 to 30 h, arguing for a lack of slow rotators among VLM objects. The periods fit into a rotational evolution scenario with pre-main sequence contraction and moderate (40,50 per cent) angular momentum losses due to wind braking. By combining our findings with literature results, we identify two regimes of rotational and magnetic properties, called C- and I-sequence. Main properties on the C-sequence are fast rotation, weak wind braking, H, emission and saturated activity levels, while the I-sequence is characterized by slow rotation, strong wind braking, no H, emission and linear activity-rotation relationship. Rotation rate and stellar mass are the primary parameters that determine in which regime an object is found. We outline a general scheme to understand rotational evolution for low-mass objects in the context of these two regimes and discuss the potential as well as the problems of this picture. [source] Introduction to the programming of deep brain stimulatorsMOVEMENT DISORDERS, Issue S3 2002Jens Volkmann MD Abstract The clinical success of deep brain stimulation (DBS) for treating Parkinson's disease, tremor, or dystonia critically depends on the quality of postoperative neurologic management. Movement disorder specialists becoming involved with this therapy need to acquire new skills to optimally adapt stimulation parameters and medication after implantation of a DBS system. In clinical practice, the infinite number of possible parameter settings in DBS can be reduced to few relevant combinations. In this article, the authors describe a general scheme of selecting stimulation parameters in DBS and provide clinical and neurophysiological arguments for such a standardized algorithm. They also describe noninvasive technical trouble shooting by using programming features of the commercially available neurostimulation devices. © 2002 Movement Disorder Society [source] Exploiting the anisotropy of anomalous scattering boosts the phasing power of SAD and MAD experimentsACTA CRYSTALLOGRAPHICA SECTION D, Issue 7 2008Marc Schiltz The X-ray polarization anisotropy of anomalous scattering in crystals of brominated nucleic acids and selenated proteins is shown to have significant effects on the diffraction data collected at an absorption edge. For conventionally collected single- or multi-wavelength anomalous diffraction data, the main manifestation of the anisotropy of anomalous scattering is the breakage of the equivalence between symmetry-related reflections, inducing intensity differences between them that can be exploited to yield extra phase information in the structure-solution process. A new formalism for describing the anisotropy of anomalous scattering which allows these effects to be incorporated into the general scheme of experimental phasing methods using an extended Harker construction is introduced. This requires a paradigm shift in the data-processing strategy, since the usual separation of the data-merging and phasing steps is abandoned. The data are kept unmerged down to the Harker construction, where the symmetry-breaking is explicitly modelled and refined and becomes a source of supplementary phase information. These ideas have been implemented in the phasing program SHARP. Refinements using actual data show that exploitation of the anisotropy of anomalous scattering can deliver substantial extra phasing power compared with conventional approaches using the same raw data. Examples are given that show improvements in the phases which are typically of the same order of magnitude as those obtained in a conventional approach by adding a second-wavelength data set to a SAD experiment. It is argued that such gains, which come essentially for free, i.e. without the collection of new data, are highly significant, since radiation damage can frequently preclude the collection of a second-wavelength data set. Finally, further developments in synchrotron instrumentation and in the design of data-collection strategies that could help to maximize these gains are outlined. [source] A family of hyperbolic spin Calogero-Moser systems and the spin Toda latticesCOMMUNICATIONS ON PURE & APPLIED MATHEMATICS, Issue 6 2004L.-C. Li In this paper, we continue to develop a general scheme to study a broad class of integrable systems naturally associated with the coboundary dynamical Lie algebroids. In particular, we present a factorization method for solving the Hamiltonian flows. We also present two important classes of new examples, a family of hyperbolic spin Calogero-Moser systems and the spin Toda lattices. To illustrate our factorization theory, we show how to solve these Hamiltonian systems explicitly. © 2004 Wiley Periodicals, Inc. [source] | ||||||||||||||||