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61.
Anu Stella Mathews Dongjo Kim Youngkyoo Kim Il Kim Chang‐Sik Ha 《Journal of polymer science. Part A, Polymer chemistry》2008,46(24):8117-8130
Here, we report the synthesis and characterization of new soluble polyimides that are functionalized using carbazole moieties in their side chain. As a monomer for synthesizing the polyimides, 4″‐carbazole‐9‐yl‐[1,1′;2′,1″] terphenyl‐4‐4′‐diamine and 2‐(3‐carbazol‐9‐yl‐propyl)‐biphenyl‐4,4′‐diamine were synthesized and then characterized using 1H NMR, 13C NMR, FTIR, UV–visible and photoluminescence spectroscopy, differential scanning calorimetry (DSC), and elemental analysis. The polyimides synthesized via chemical imidization processes were characterized with X‐ray photoelectron spectroscopy, gel permeation chromatography, wide angle X‐ray diffraction, thermogravimetric analysis, DSC, tensile strength measurement, and dielectric property measurement. Results showed that the synthesized polyimides were soluble in a variety of organic solvents, optically transparent in a visible range, thermally stable, mechanically strong, and considerably low dielectric. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 8117–8130, 2008 相似文献
62.
R. Baldini-Celio M. Bozzo G. Capon R. Del Fabbro M. Grilli E. Iarocci M. Locci C. Mencuccuni G.P. Murtas M.A. Spano M. Spinetti V. Valente C. Bacci G. Penso B. Stella 《Physics letters. [Part B]》1975,58(4):471-474
The reactions e+e?→ hadrons and e+e+e?→e+e? have been studied at the J/gY (3100) resonance). The relative weights of the topological cross sections for fixed charged multiplicity are σ2=(32±5)%, σ4=(49±8)%, σ6=(18±3)%, and σ8=(1±0.6)%. The average pion multiplicities are 〈nch〉=3.8±0.3 and 〈nπo〉=3.1±0.8. The decay widths are Γe=(4.6±0.8) keV, Γh=(59±24) keV, and Γ=(68±26) keV. 相似文献
63.
Maria Stella Mongioví Silvana Romeo 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》1996,47(1):144-161
A dissipative model of helium II was built up in previous works, using a 13-field extended thermodynamic theory formulated by Liu and Müller. In this work a generalization of such model is presented, where an extended thermodynamics with 14 fields due to Kremer is used. It is shown that the fourteenth field is able to account for the experimental data concerning the second sound attenuation. Further, the proposed theory is able to explain the Osborne experiment. Finally, a comparison with the two-fluid model is performed, emphasizing the different ways in which the dissipative phenomena are explained by the two theories. 相似文献
64.
This paper shows that market equilibrium problems of production may generally be modelled as equilibrium flow problems in networks and that their equilibrium conditions can be visualized as a variational inequality. This connection would allow us to transplant directly elements of the well-developed theory of equilibrium flow in networks to the theory of market equilibrium. 相似文献
65.
Zingaretti L Mariano Correa N Boscatto L Chiacchiera SM Durantini EN Bertolotti SG Rivarola CR Silber JJ 《Journal of colloid and interface science》2005,286(1):245-252
The distribution of different aliphatic and aromatic amines: n-butylamine (n-BA), isobutylamine (i-BA), tert-butylamine (t-BA), piperidine (PIP), N,N-dimethylaniline (DMA) and N-methylaniline (MA) in water/sodium 1,4-bis(2-ethylhexyl)sulfosuccinate(AOT)/n-hexane reverse micelles was investigated by steady-state fluorescence measurements. The partition constants were measured by an indirect method based on the effect that amine partitioning exert on the bimolecular rate of the reaction between a microphase incorporated fluorophore (Ru(bpy)2+(3)) and the quencher, (Fe(CN)3-(6)). For MA, that can act as a quencher of the fluorophore a direct method was used. The results show that primary amines have larger partition constants than the secondary ones. For tertiary amines the distribution constants were practically negligible. Laser flash photolysis experiments confirmed that tertiary amines, both aliphatic and aromatic, are not incorporated to the micellar pseudophase. The effect of the amine structure on the partition constant was analyzed through linear solvation free energy relationships (LSER) using solute parameters and compared with those obtained for alcohols. Hydrogen bond interactions with the AOT polar heads appear to be the main driving force for the distribution of amines between the organic and micellar pseudophases, whereas the size of the alkyl or aromatic group tends to hinder it. 相似文献
66.
67.
68.
A. Borghesi Chen Chen-Jia G. Guizzetti F. Marabelli L. Nosenzo E. Reguzzoni A. Stella P. Ostoja 《Il Nuovo Cimento D》1985,5(3):292-303
Summary In this work reflectance (R) and thermoreflectance (TR) spectra in the infra-red of bulk P and B heavily doped silicon samples
are reported and discussed. The values of the scattering time and of the effective mass, as well as the temperature derivative
of the plasma frequency, scattering time and high-frequency dielectric constant are extracted from the data and analysed in
terms of free-carrier-photon and free-carrier-impurity interaction.
Riassunto In questo lavoro sono riportati e discussi gli spettri di riflettanza (R) e termoriflettanza (TR) in infrarosso di campioni di silicio drogati pesantemente per diffusione con P e B. Dai dati sono ricavati i valori dei tempi di rilassamento e della massa effettiva, come pure la derivata in temperatura della frequenza di plasma, del tempo di rilassamento e della costante dielettrica ad alta frequenza, che sono analizzati sulla base delle interazioni fra portatori liberi e fononi e fra portatori liberi e impurezze.相似文献
69.
In two experiments we explored the instructional value of a cross‐domain mapping between “number” and “line” in secondary school students' understanding of density. The first experiment investigated the hypothesis that density would be more accessible to students in a geometrical context (infinitely many points on a straight line segment) compared to a numerical context (infinitely many numbers in an interval). The participants were 229 seventh to eleventh graders. The results supported this hypothesis but also showed that students' conceptions of the line segment were far from that of a dense array of points. We then designed a text-based intervention that attempted to build the notion of density in a geometrical context, making explicit reference to the number-to-points correspondence and using the “rubber line” bridging analogy (the line as an imaginary unbreakable rubber band) to convey the no-successor principle. The participants were 149 eighth and tenth graders. The text intervention improved student performance in tasks regarding the infinity of numbers in an interval; the “rubber line” bridging analogy further improved performance successfully conveying the idea that these numbers can never be found one immediately next to the other. 相似文献
70.
Salvatore Stella 《Journal of Algebraic Combinatorics》2013,38(1):121-158
Motivated by the theory of cluster algebras, F. Chapoton, S. Fomin, and A. Zelevinsky associated to each finite type root system a simple convex polytope, called generalized associahedron. They provided an explicit realization of this polytope associated with a bipartite orientation of the corresponding Dynkin diagram. In the first part of this paper, using the parametrization of cluster variables by their g-vectors explicitly computed by S.-W. Yang and A. Zelevinsky, we generalize the original construction to any orientation. In the second part we show that our construction agrees with the one given by C. Hohlweg, C. Lange, and H. Thomas in the setup of Cambrian fans developed by N. Reading and D. Speyer. 相似文献