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11.
M. Kaveh 《Physics letters. A》1976,58(5):329-331
The phonon-phonon scattering relaxation time for metals is derived by an analysis that explicitly incorporates the Peierls condition that normal phonon-phonon scattering cannot equilibrate the phonon system. Numerical results are presented for potassium. These results demonstrate that at low temperatures, the Peierls condition leads to a very significant reduction of phonon-phonon scattering. 相似文献
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G. H. Rounaghi E. Razavipanah F. Kaveh 《Journal of inclusion phenomena and macrocyclic chemistry》2010,68(3-4):245-252
The stability constants of 1:1 (M:L) complexes of benzo-15-crown-5 (B15C5) with Li+, Na+, K+ and NH4 + cations, the Gibbs standard free energies ( $ \Updelta {\text{G}}_{\text{c}}^{ \circ } $ ), the standard enthalpy changes ( $ \Updelta {\text{H}}_{\text{c}}^{ \circ } $ ) and standard entropy changes ( $ \Updelta {\text{S}}_{\text{c}}^{ \circ } $ ) for formation of these complexes in acetonitrile–methanol (AN–MeOH) binary mixtures have been determined conductometrically. The conductance data show that the stoichiometry of the complexes formed between the macrocyclic ligand and the studied cations is 1:1 (M:L). In most cases, addition of B15C5 to solutions of these cations, causes a continuous increase in the molar conductivities which indicates that the mobility of complexed cations is more than the uncomplexed ones. The stability constants of the complexes were obtained from fitting of molar conductivity curves using a computer program, GENPLOT. The results show that the selectivity order of B15C5 for the metal cations changes with the nature and composition of the binary mixed solvent. The values of standard enthalpy changes ( $ \Updelta {\text{H}}_{\text{c}}^{ \circ } $ ) for complexation reactions were obtained from the slope of the van’t Hoff plots and the changes in standard entropy ( $ \Updelta {\text{S}}_{\text{c}}^{ \circ } $ ) were calculated from the relationship $ \Updelta {\text{G}}_{{{\text{c}},298.15}}^{ \circ } = \Updelta {\text{H}}_{\text{c}}^{ \circ } - 298.15\Updelta {\text{S}}_{\text{c}}^{ \circ } $ . A non-linear behavior was observed between the stability constants (log Kf) of the complexes and the composition of the acetonitrile–methanol (AN–MeOH) binary solution. The results obtained in this study, show that in most cases, the complexes formed between B15C5 and Li+, Na+, K+ and NH4 + cations are both enthalpy and entropy stabilized and the values of these thermodynamic quantities change with the composition of the binary solution. 相似文献
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A simple, efficient and highly chemoselective method for tetrahydropyranylation of alcohols and phenols has been developed by their reaction with 3,4-dihydro-2H-pyran at room temperature in the presence of a catalytic amount of polystyrene supported AlCl3. The method is also highly selective for monoprotection of symmetrical diols. 相似文献
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Mwsleh Mwhmadi Mehdi Kamali Jamal Rashidiani Omid Rezai Kaveh Moradi Ashkan Faridi Khadijeh Eskandari 《Journal of Cluster Science》2014,25(6):1577-1587
NiO and CuO nanostructures were synthesized successfully via simple and fast microwave approach. Olive oil was chose as surfactant for stabilizing nanostructures. Different parameters such as microwave time and power and olive oil concentration were investigated on product size and morphology. The products were characterized with X-ray diffraction pattern, scanning electron microscopy, transmission electron microscopy and energy dispersive spectrometry analysis. 相似文献
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Haopeng Wang Ninghang Lin Kaveh Kahen Hamid Badiei Kaveh Jorabchi 《Journal of the American Society for Mass Spectrometry》2014,25(4):692-695
We present plasma-assisted reaction chemical ionization (PARCI) for elemental analysis of halogens in organic compounds. Organohalogens are broken down to simple halogen-containing molecules (e.g., HBr) in a helium microwave-induced plasma followed by negative mode chemical ionization (CI) in the afterglow region. The reagent ions for CI originate from penning ionization of gases (e.g., N2) introduced into the afterglow region. The performance of PARCI-mass spectrometry (MS) is evaluated using flow injection analyses of organobromines, demonstrating 5–8 times better sensitivities compared with inductively coupled plasma MS. We show that compound-dependent sensitivities in PARCI-MS mainly arise from sample introduction biases. Figure
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18.
Daniel Leibig Margarita Messerle Tobias Johann Christian Moers Farzaneh Kaveh Hans-Jürgen Butt Doris Vollmer Axel H. E. Müller Holger Frey 《Journal of polymer science. Part A, Polymer chemistry》2020,58(1):181-192
Well-defined polystyrene homopolymers with surface-adhesive triethoxysilyl end group were synthesized via living carbanionic polymerization, epoxide end-functionalization and subsequent hydrosilylation with triethoxysilane. Grafting-to performance of polymers with various molecular weight (Mn = 3000–14,000 g mol−1) to a silicon surface was examined in dependence of reaction time, polymer concentration, solvent and number of alkoxysilyl end groups. Crosslinkable polymers for surface modification were synthesized by statistical carbanionic copolymerization of 4-vinylbenzocyclobutene (4-VBCB) and styrene, followed by epoxide end-functionalization and triethoxysilane modification (Mn = 4000–14,000 g mol−1). The copolymers were characterized by 1H-NMR, THF-SEC, and matrix-assisted laser desorption and ionization time-of-flight mass spectrometry. In situ 1H-NMR kinetic studies in cyclohexane-d12 provided information regarding the monomer gradient in the polymer chains, with styrene being the more reactive monomer (rs = 2.75, r4-VBCB = 0.23). Thin polymer films on silicon wafers were prepared by grafting-to surface modification under conditions derived for the polystyrene homopolymer. The traceless, thermally induced crosslinking reaction of the benzocyclobutene units was studied by DSC in bulk as well as in 3–6 nm thick polymer films. Crosslinked films were analyzed by atomic force microscopy, ellipsometry, and nanoindentation, showing smooth polymer films with an increased modulus. © 2019 The Authors. Journal of Polymer Science published by Wiley Periodicals, Inc. J. Polym. Sci. 2020 , 58, 181–192 相似文献
19.
Monatshefte für Chemie - Chemical Monthly - In the present study, we demonstrated the synthesis of magnetic cyanoguanidine-modified chitosan (MCGC) as an efficient and green retrievable... 相似文献
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