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991.
Mario Gleria Riccardo Po Giorgio Giannotta Luisa Fiocca Roberta Bertani Luca Fambri Francesco Paolo La Mantia Roberto Scaffaro 《Macromolecular Symposia》2003,196(1):249-270
The utilization of Cyclophosphazenes as polymer modifiers is reviewed, with particular concern to their exploitation as versatile chain extenders, possibly for recycle problems, crosslinkers, to enhance mechanical properties of polymeric materials, branchers, to selectively introduce ramifications in linear polymers, and compatibilizers, to favor the formation of blends between originally incompatible organic macromolecules. The great versatility of the synthetic methods put forward for these substrates, together with the ease of controlling their modification, functionalization and reactivity are important parameters for the evaluation of which type of use is more feasible for these trimers. The importance of cyclophosphazenes bearing organic polymeric chains, azide groups, 2-oxazoline derivatives and oxirane rings in connection with organic conventional macromolecules is critically highlighted. 相似文献
992.
993.
994.
Giorgio Papeschi Stefano Mancuso Anna Maria Marras 《Journal of Solid State Electrochemistry》2000,4(6):325-329
The electrochemical behaviour of a Cu/CuSe electrode was studied in order to define its selectivity towards cupric ions,
Nerstian response, limit of detection and response time. The chalcogenide electrode was prepared by cathodic deposition of
Se and subsequent formation of a thin layer of CuSe on a copper substrate. A Cu/CuSe microelectrode was prepared using copper
wire 75 μm in diameter. The dimensions and response time (<0.5 s) allowed use of this electrode in the “vibrating probe method”
with the aim of measuring net influxes as well as effluxes of copper(II) ions in Olea europaea roots. The electrode potential was measured along the root at a distance of 5 μm from the surface for 5 s, and then again
for 5 s at a distance of 55 μm, moving the microelectrode with respect to the root surface by steps with a frequency of 0.1 Hz.
The potentials measured at the two extremes of vibration were then converted to copper(II) concentrations. Substitution of
these values in Fick's law yields the flux, assuming the diffusion constant D for copper ions in aqueous solutions. The results enabled us to detect copper(II) fluxes as small as 0.05 pmol cm−2 s−1. Copper(II) influx showed marked spatial and temporal features: it was highest at about 1.5 mm from the root apex and exhibited
an oscillatory pattern in time.
Received: 29 September 1999 / Accepted: 11 January 2000 相似文献
995.
Giorgio Della Sala Alessandra Lattanzi Tania Severino Arrigo Scettri 《Journal of molecular catalysis. A, Chemical》2001,170(1-2):219-224
Investigations were carried out on the oxidation of sulfides to sulfoxides catalyzed by the commercial Cp2Ti(X)2 (X=Cl, OTf)/t-butyl hydroperoxide (TBHP). The asymmetric version of prochiral sulfides oxidation was achieved using Cp2TiCl2, as transition metal catalyst, in the presence of (+)-(R)-BINOL, as chiral ligand and activated 4 Å molecular sieves (m.s.). 相似文献
996.
The hydrodynamic stability of a low speed, plane, non-isothermal laminar wall jet at a constant temperature boundary condition was investigated theoretically and experimentally. The mean velocity and temperature profiles used in the stability analysis were obtained by implementing the Illingworth–Stewartson transformation that allows one to extend the classical Glauert solution to a thermally non-uniform flow. The stability calculations showed that the two unstable eigenmodes coexisting at moderate Reynolds numbers are significantly affected by the heat transfer. Heating is destabilizing the flow while cooling is stabilizing it. However, the large-scale instabilities associated with the inflection point of the velocity profile still amplify in spite of the high level of the stabilizing temperature difference. The calculated stability characteristics of the wall jet with heat transfer were compared with experimental data. The comparison showed excellent agreement for small amplitudes of the imposed perturbations. The agreement is less good for the phase velocities of the sub-harmonic wave and this is attributed to experimental difficulties and to nonlinear effects. 相似文献
997.
Stefania Villa Giacomo Luca Evoli Giorgio Cignarella Michela M. Curzu Grard A. Pinna 《Journal of heterocyclic chemistry》1999,36(2):485-492
Dehydrogenation and amination of 4,4a,5,6-tetrahydro and 5,6-dihydrobenzocinnolinones in refluxing hydrazine hydrate to give new benzo[h]cinnolinones and 4-aminobenzo[h]cinnolinones are reported, and reaction mechanisms proposed. Experiments were also extended to 4,4a-dihydro-5H-indenopyridazinone which underwent hydrazine induced dehydrogenation to 5H-indenopyridazin-3-one but not subsequent amination. 相似文献
998.
Alessandro Bertolini Giorgio Carelli Augusto Moretti Giovanni Moruzzi Franco Strumia 《International Journal of Infrared and Millimeter Waves》1999,20(5):759-768
With 228 known FIR laser emissions, hydrazine is the most prolific laser active molecules after methanol. But, due to the complexity of its rovibrational spectrum, only a few assignments of hydrizine FIR laser transitions are found in literature. Here we analyze 44 FIR laser lines of hydrazine excited by 20 different CO2 pumps. The pump transitions are compared to available assignments of IR amino-wagging transitions. We propose values for the J and K quantum numbers involved in 41 FIR laser transitions, for 22 of them we give also the symmetry species. 相似文献
999.
Giorgio Giardina Patrizia Rosi Antonella Ricci Claudio Lo Sterzo 《Journal of polymer science. Part A, Polymer chemistry》2000,38(14):2603-2621
The palladium‐catalyzed Stille coupling of an aromatic diiodide with half an equivalent of tributyl(ethynyl)tin results in a complex mixture containing the diethynylaromatic compound, the iodo(ethynyl)aromatic compound, unreacted diiodide and the tributyltin iodide side product. Addition of LDA to this mixture, while leaving the iodoaromatic moieties unaffected, causes deprotonation of the ethynyl functionalities, which immediately recombine with tributyltin iodide to form a mixture of bis(tributylethynyltin)aromatic, iodo(tributylethynyltin)aromatic, and unchanged diiodide. Being the palladium catalyst still active, it is sufficient to warm up this mixture to obtain the coupling of the tributylethynyltin and iodo moieties resulting in the formation of a poly(arylene ethynylene) polymer. Isolation of the polymer is easily and rapidly achieved by precipitation, while distillation of the mother liquor allows recovery of the tributyltin iodide side product. The latter can be utilized for the preparation of new tributyl(ethynyl)tin, thus allowing a convenient turnover of the tributyltin moiety. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2603–2621, 2000 相似文献
1000.