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排序方式: 共有439条查询结果,搜索用时 31 毫秒
31.
Xiayi Hu Enzo Mangano Daniel Friedrich Hyungwoong Ahn Stefano Brandani 《Adsorption》2014,20(1):121-135
A systematic study of the diffusion mechanism of CO2 in commercial 13X zeolite beads is presented. In order to gain a complete understanding of the diffusion process of CO2, kinetic measurements with a zero length column (ZLC) system and a volumetric apparatus have been carried out. The ZLC experiments were carried out on a single bead of zeolite 13X at 38 °C at a partial pressure of CO2 of 0.1 bar, conditions representative of post-combustion capture. Experiments with different carrier gases clearly show that the diffusion process is controlled by the transport inside the macropores. Volumetric measurements using a Quantachrome Autosorb system were carried out at different concentrations. These experiments are without a carrier gas and the low pressure measurements show clearly Knudsen diffusion control in both the uptake cell and the bead macropores. At increasing CO2 concentrations the transport mechanism shifts from Knudsen diffusion in the macropores to a completely heat limited process. Both sets of experiments are consistent with independent measurements of bead void fraction and tortuosity and confirm that under the range of conditions that are typical of a carbon capture process the system is controlled by macropore diffusion mechanisms. 相似文献
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The infrared spectra of single human normal and leukemic lymphocytes have been obtained by means of the microscope-FT-IR system. Substantial differences between the two kinds of cells have been observed at level of the O-P-O vibrations of the DNA and of the proteic components. This determination opens up the possibility in determining the early stages of leukemia, in following the course of patients under therapy, and in evaluation of the residual neoplastic disease. 相似文献
35.
Enzo Giannetti Giuseppe Martino Nicoletti Romano Mazzocchi 《Journal of polymer science. Part A, Polymer chemistry》1985,23(8):2117-2134
Homogeneous Ziegler-Natta systems for the ethylene polymerization, deriving from R2R2′M complexes (R = cyclopentadienyl; R′ = alkyl, aryl; M = Ti, Zr, Hf) and oligomeric oxoalane compounds, were studied. Further results concerning the methyl aluminoxane synthesis and the related chemistry are reported. On the basis of spectroscopic data a delocalized electronic structure could be inferred for these compounds. Results from polymerization experiments showed that the highest productivities are obtained only by oxoalane cocatalysts having a high degree of oligomerization. The catalytic activity of the systems under investigation was strongly affected also by changing both the σ-alkyl and the π-cyclo-pentadienyl ligands. Furthermore, it was found that in the presence of methyl aluminoxane, the homoleptic σ-alkyl derivatives of IVB transition metals, such as Zr(CH2C6H5)4, are also able to polymerize ethylene with a fairly high productivity. Active species containing Zr? O? Al bonds have been postulated. 相似文献
36.
Lorenzo?BertiniEmail author Emilio N.M.?Cirillo Enzo?Olivieri 《Communications in Mathematical Physics》2005,258(2):405-443
In this paper we develop a general theory which provides a unified treatment of two apparently different problems. The weak Gibbs property of measures arising from the application of Renormalization Group maps and the mixing properties of disordered lattice systems in the Griffiths’ phase. We suppose that the system satisfies a mixing condition in a subset of the lattice whose complement is sparse enough namely, large regions are widely separated. We then show how it is possible to construct a convergent multi-scale cluster expansion.The authors acknowledge the support of Cofinanziamento MIUR. 相似文献
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Pinkerton RG Barberi EA Menon RS 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2004,171(1):151-156
The use of multiple radiofrequency (RF) surface coil elements has applications in both fast parallel imaging and conventional imaging techniques. Through implementation of a simple magnetic decoupling network, 50 Omega matching can be achieved in both the transmitter and receiver chains, enabling the use of conventional RF power amplifiers and preamplifiers for transceive applications. Unlike phased array coil arrangements using low impedance preamplifiers for decoupling, the noise correlation between 50 Omega coils decoupled with discrete components has not been characterized. We have measured the dependence of coil quality factor (Q-factor) and noise correlation on coil separation and shown these quantities to be consistent with theoretical arguments, at least at 4 T (170 MHz). Our results suggest that a coil system for transmission and reception of NMR signals with 50 Omega coils can be built to take advantage of all the benefits of conventional array coils and with the added advantages of using conventional amplifiers. 相似文献
39.
Filippo Gazzola Hans-Christoph Grunau Enzo Mitidieri 《Transactions of the American Mathematical Society》2004,356(6):2149-2168
We show that the classical Hardy inequalities with optimal constants in the Sobolev spaces and in higher-order Sobolev spaces on a bounded domain can be refined by adding remainder terms which involve norms. In the higher-order case further norms with lower-order singular weights arise. The case being more involved requires a different technique and is developed only in the space .
40.
Benincasa C Maiuolo L Mazzotti F Perri E Sindona G Urso E 《Journal of mass spectrometry : JMS》2004,39(1):61-65
A method is presented which allows the identification and assay of a nucleoside in the presence of other analogues and homologues. The method is based on the conventional multiple reaction monitoring approach performed on the [M + H]+ ions of wild-type and modified nucleosides produced by the turbo ionspray ionization method on a triple-quadrupole mass spectrometer. The accuracy of the quantitative determination relies on the evaluation of a response factor rho, which takes into account the kinetics of dissociation of the parent ions into the protonated [B + 2H]+ nucleobase ions. The evaluation of the absolute concentration of each analyte in the examined mixture does not require any previous chromatographic separation. 相似文献