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71.
Valerie V. Sheares Lifen Wu Yunxiao Li Tatania K. Emmick 《Journal of polymer science. Part A, Polymer chemistry》2000,38(22):4070-4080
The bulk free‐radical polymerization of 2‐[(N,N‐dialkylamino)methyl]‐1,3‐butadiene with methyl, ethyl, and n‐propyl substituents was studied. The monomers were synthesized via substitution reactions of 2‐bromomethyl‐1,3‐butadiene with the corresponding dialkylamines. For each monomer the effects of the polymerization initiator, initiator concentration, and reaction temperature on the final polymer structure, molecular weight, and glass‐transition temperature (Tg) were examined. Using 2,2′‐azobisisobutyronitrile as the initiator at 75 °C, the resulting polymers displayed a majority of 1,4 microstructures. As the temperature was increased to 100 and 125 °C using t‐butylperacetate and t‐butylhydroperoxide, the percentage of the 3,4 microstructure increased. Differential scanning calorimetry indicated that all of the Tg values were lower than room temperature. The Tg values were higher when the majority of the polymer structure was 1,4 and decreased as the percentage of the 3,4 microstructure increased. The Diels–Alder side products found in the polymer samples were characterized using NMR and gas chromatography‐mass spectrometry methods. The polymerization temperature and initiator concentration were identified as the key factors that influenced the Diels–Alder dimer yield. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 4070–4080, 2000 相似文献
72.
73.
Qualitative operators for reasoning maps: Evaluating multi-criteria options with networks of reasons
Cognitive/causal maps have been widely used as a powerful way of capturing decision-makers’ views about a problem, representing it as a cause–effect discourse. Several ways of making causal inferences from this type of model have been proposed in the Operational Research and Artificial Intelligence literatures, but none, as far as we are aware, has attempted to use a causal map structure to perform a multi-criteria evaluation of decision alternatives. Recently, we have proposed a new multi-criteria method, denominated as a Reasoning Map, which permits the use of decision-makers’ reasoning, structured as a network of means-and-ends (a particular type of causal map) to perform such an evaluation. In this manner, the model resembles the way that people talk and think about decisions in practice. The method also pays explicit attention to the cognitive limitations of decision-makers in providing preference information. Thus it employs qualitative assessment of preferences, utilises aggregation operators for qualitative data and provides also qualitative outputs. In this paper we discuss and evaluate possible ways of aggregating qualitative performance information in Reasoning Maps. 相似文献
74.
The suspended particle size distribution in slurries can, in principle, be estimated from measured ultrasonic wave attenuation across a frequency band in the 10s of MHz range. The procedure requires a computational model of wave propagation which incorporates scattering phenomena. These models fail at high particle concentrations due to hydrodynamic effects which they do not incorporate. This work seeks an effective viscosity and density for the medium surrounding the particles, which would enable the scattering model predictions to match experimental data for high solids loading. It is found that the required viscosity model has unphysical characteristics leading to the conclusion that a simple effective medium modification to the ECAH/LB is not possible. The paper confirms the successful results which can be obtained using core–shell scattering models, for smaller particles than had previously been studied, and outlines modifications to these which would permit rapid computation of sufficient stability to support fast particle sizing procedures. 相似文献
75.
Rodgers MA Villareal VA Schaefer EA Peng LF Corey KE Chung RT Yang PL 《Journal of the American Chemical Society》2012,134(16):6896-6899
Hepatitis C virus (HCV) infection has been clinically associated with serum lipid abnormalities, yet our understanding of the effects of HCV on host lipid metabolism and conversely the function of individual lipids in HCV replication remains incomplete. Using liquid chromatography-mass spectrometry metabolite profiling of the HCV JFH1 cell culture infection model, we identified a significant steady-state accumulation of desmosterol, an immediate precursor to cholesterol. Pharmacological inhibition or RNAi-mediated depletion of DHCR7 significantly reduced steady-state HCV protein expression and viral genomic RNA. Moreover, this effect was reversed when cultures were supplemented with exogenous desmosterol. Together, these observations suggest an intimate connection between HCV replication and desmosterol homeostasis and that the enzymes responsible for synthesis of desmosterol may be novel targets for antiviral design. 相似文献
76.
Yaroslav O. Mezhuev Alexander V. Varankin Anna L. Luss Valerie A. Dyatlov Aristides M. Tsatsakis Antonios K. Stratidakis Yuri V. Korshak 《国际化学动力学杂志》2020,52(8):520-525
The kinetic curves for oxidation of dopamine hydrochloride in aqueous solution in the presence of ammonium peroxydisulfate were obtained by UV–vis spectroscopy and potentiometry. It was shown that the reaction follows the first-order kinetic equation and proceeds at a low rate. The values for the activation energy and the preexponential factor were determined as 75 kJ × mol−1 and 4 × 108 s−1, respectively. The activation entropy was found having a negative value of −89 J × mol−1 × K−1. The first reaction order, the low preexponential factor and the negative activation entropy value for the reaction between the 2-(3,4-dihydroxyphenyl)ethanammonium cation and the peroxydisulfate anion were explained by the formation of ionic associates, which slowly enter into the internal redox reaction. 相似文献
77.
In this paper, we answer the question of when the subcategory of semi-stable representations is the same for two rational vectors for an acyclic quiver. This question has been previously answered by Ingalls, Paquette, and Thomas in the tame case in [14]. Here we take a more invariant theoretic approach, to answer this question in general. We recover the known result in the tame case. 相似文献
78.
Valerie Belton 《The Journal of the Operational Research Society》1985,36(4):265-274
The use of a simple multiple-criteria model to assist in decision making is described. The model, a hierarchical additive weighted value-function, was used as a part of a decision-making process to select, from a shortlist of three, the company with which to place a contract for the development of a computerized financial management system. The multiple-criteria model and its use are described in detail. To conclude, there is a discussion on the contribution of the model to the decision-making process as perceived by the decision-making group. 相似文献
79.
Silvia Coniglio Sandro Colagioia Fabrizio D'Alessandro Valerio D'Elia Valerie Orlando 《Tetrahedron letters》2004,45(28):5375-5378
A new, simple and efficient procedure for the preparation of secondary amides through internal condensation of acylmethanesulfonamides ammonium salts is described. The selective acylation of mixed primary-secondary amines could be an attractive application of the new method. 相似文献
80.
Lourdes Ventol Valerie Metivaud Laura Bays Raül Benages Miquelngel Cuevas‐Diarte Teresa Calvet Denise Mondieig 《Helvetica chimica acta》2006,89(9):2027-2039
Complementary techniques had to be applied to investigate the binary system tetradecanedioic acid (C14H26O4)–hexadecanedioic acid (C16H30O4), because all the forms observed have the same space group (P21/c; Z = 2). We studied the polymorphism of the two single compounds and of their mixtures by X‐ray powder diffraction, differential‐scanning calorimetry (DSC), infrared spectroscopy (IR), scanning electron microscopy (SEM), and thermo‐optical microscopy (TOM). The two diacids were found to be isopolymorphic. At low temperature, they crystallize in the same ordered C‐form, and, on heating, adopt the ordered Ch‐form, 1° below their melting point. In contrast to similar compounds (unbranched alkanes, alkanols, and fatty acids), the solid–solid and solid–liquid phase‐transition temperatures decrease with increasing chain length. At low temperature, a new monoclinic form, Ci, appears as a result of the disorder of composition in the mixed samples. There are two [C + Ci]‐type solid–solid domains. On heating, the solid domains are related to solid–liquid domains by a peritectic invariant for compositions rich in C14H26O4, and by a eutectic invariant for compositions rich in C16H30O4. At higher temperature, there appears a second peritectic invariant for compositions rich in C14H26O4, together with a metatectic invariant for compositions rich in C16H30O4. All the solid forms observed in this binary system are isostructural. Nevertheless, the equilibrium between them is complex near the melting point, and their miscibility in the solid state is reduced. 相似文献