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71.
Boutin A Coasne B Fuchs AH Galarneau A Di Renzo F 《Langmuir : the ACS journal of surfaces and colloids》2012,28(25):9526-9534
We report experimental nitrogen adsorption isotherms of organics-coated silicas, which exhibit a low-pressure desorption branch that does not meet the adsorption branch upon emptying of the pores. To address the physical origin of such a hysteresis loop, we propose an equilibrium thermodynamic model that enables one to explain this phenomenon. The present model assumes that, upon adsorption, a small amount of nitrogen molecules penetrate within the organic layer and reach adsorption sites that are located on the inorganic surface, between the grafted or adsorbed organic molecules. The number of accessible adsorption sites thus varies with the increasing gas pressure, and then we assume that it stays constant upon desorption. Comparison with experimental data shows that our model captures the features of nitrogen adsorption on such hybrid organic/inorganic materials. In particular, in addition to predicting the shape of the adsorption isotherm, the model is able to estimate, with a reasonable number of adjustable parameters, the height of the low-pressure hysteresis loop and to assess in a qualitative fashion the local density of the organic chains at the surface of the material. 相似文献
72.
Meta M. Bloksma Renzo M. Paulus Huub P. C. van Kuringen Friso van der Woerdt Hanneke M. L. Lambermont‐Thijs Ulrich S. Schubert Richard Hoogenboom 《Macromolecular rapid communications》2012,33(1):92-96
The monomers 2‐methyl‐2‐oxazine (MeOZI), 2‐ethyl‐2‐oxazine (EtOZI), and 2‐n‐propyl‐2‐oxazine (nPropOZI) were synthesized and polymerized via the living cationic ring‐opening polymerization (CROP) under microwave‐assisted conditions. pEtOZI and pnPropOZI were found to be thermoresponsive, exhibiting LCST behavior in water and their cloud point temperatures (TCP) are lower than for poly(2‐oxazoline)s with similar side chains. However, comparison of poly(2‐oxazine) and poly(2‐oxazoline)s isomers reveals that poly(2‐oxazine)s are more water soluble, indicating that the side chain has a stronger impact on polymer solubility than the main chain. In conclusion, variations of both the side chains and the main chains of the poly(cyclic imino ether)s resulted in a series of distinct homopolymers with tunable TCP. 相似文献
73.
We present in this paper a modification of the selection procedure, within the CIPSI algorithm, specifically intended for
the calculation of one-electron properties. In this new procedure the determinants are selected following their contribution
to a certain one-electron property. As test cases we report the calculation of the electric dipole of carbon monoxide and
of the hyperfine coupling constants of the CH3 radical.
Received: 20 August 2000 / Accepted: 2 October 2000 / Published online: 21 December 2000 相似文献
74.
Renzo Cini 《Acta Crystallographica. Section C, Structural Chemistry》2001,57(10):1171-1173
The title compound, [Co(C23H29N3O4)]·0.5C2H6O or [CoII{(4-MeO-sal)2Medpt}]·0.5CH3CH2OH [(4-MeO-sal)2Medpt is N,N′-(4-methyl-4-azaheptane-1,7-diyl)bis(4-methoxysalicylideniminate)], obtained through the reaction of H2[(4-MeO-sal)2Medpt] and Co(CH3COO)2 in refluxing ethanol under an atmosphere of ultrapure nitrogen, has the usual pseudo-trigonal-bipyramidal coordination arrangement previously found for this class of (sal)2Rdpt compounds. The O—Co—O bond angle [120.4 (1)°] is significantly smaller than the corresponding values previously found for most non-O2-bound [CoII{(sal)2Medpt}]-type molecules (observed range 126.9–138.6°), whereas the equatorial Co—N bond [2.185 (3) Å] is relatively long. 相似文献
75.
Paola Falsini Roberto Pini Renzo Salimbeni Matteo Vannini A.F.M.Yusuf Haider Roberto Buffa 《Optics Communications》1985,53(6):421-424
A simple combination of a lens-based unstable resonator and an inverted telescope coupling geometry working in a XeCl laser pumped H2 Raman cell are presented. Raman spectrum optimization is achieved by varying the pump beam numerical aperture. 70% pump depletion and energy conversion efficiencies as high as 66% and 7.8% have been obtained for S1, S2 and S3 respectively. 相似文献
76.
The C2H2 isothermal dissociation rate on Ni(111) was measured by following, with HREEL spectroscopy, the intensity of the CH stretching peak as a function of time. By repeating the experiment at several different temperatures we have obtained an activation energy of 1.2 ± 0.1 eV/molecule and a pre-exponential factor of 1014±1 s−1 for the first step of the C2H2 dissociation reaction. 相似文献
77.
The behaviour of orbits of the action of the group of smooth gauge transformations on connections for a principal bundle P(M, G) is discussed with and without compactness assumption on M and G. In the case of compact M and with suitable conditions on G a stratification structure for the space of orbits is established. A natural tame weak Riemannian metric is given on each stratum. 相似文献
78.
The electrochemical behaviour of a series of iron(II) complexes with the tetradentate ligand NN′-1,2-phenylenebis(salicylideneimine), [Fe(II)L], was studied in non-aqueous solvents. The redox properties of the complexes were related to the nature of the substituents in the aromatic rings. Attention was devoted to dioxygen reactivity of the complexes. The electrode activity of the catechol—[NN′-1,2-phenylenebis(salicylidene-iminato) iron(III)] system, [Fe(III)L(catH)], was also studied; the results gave evidence that both the electrochemical oxidation and the chemical oxidation by dioxygen of [Fe(II)L] in the presence of catechol lead to the complex [Fe(III)L(catH)]. 相似文献
79.
The paper focuses on the problem of long-range dependence when analysing time series of hydrological data. Three time series are analysed: the monthly rainfall in the town of Florence, Italy; the daily minimum temperatures in the same town; and, finally, the daily water inflow to Lake Maggiore, Italy. Heuristic methods and maximum likelihood estimation of a parametric model are used to investigate the Hurst phenomena and to detect whether long-range dependence is present in any of the time series. We found that long-range dependence is not present in the first series but it is present in the last two. The daily water inflow to Lake Maggiore was modelled by a fractionally differenced arima model (farima) which contains a long-range dependence component. It is shown that the fit is much better than the one provided by more traditional arima models that do not have such a component.
Sommario Lo studio considera il problema dell'identificazione dei fenomeni di dipendenza a lungo termine (long range dependence) nelle serie temporali di dati idrologici. Allo scopo sono state analizzate tre serie temporali, rispettivamente quella dei totali mensili di precipitazione rilevati alla stazione dell'Osservatorio Ximeniano de Firenze, quella delle temperature minime giornaliere per la stessa stazione e quella degli afflussi giornalieri al Lago Maggiore. Per identificare la presenza di fenomeni di dipendenza long range, attraverso la valutazione della consistenza del fenomeno di Hurst, sono stati utilizzati sia metodi euristici, sia la stima a massima verosimiglianza di un modello parametrico. Due delle tre serie analizzate sono risultate caratterizzate da tale dipendenza. Per la serie degli afflussi al Lago Maggiore, si è inoltre proceduto alla simulazione attraverso un modello arima a differenziazione frazionaria (farima), la cui struttura contiene una componente long-range. I risultati ottenuti, mostrano che tale modello fornisce risultati significativamente migliori dei tradizionali modelli arima, privi di tale componente.相似文献
80.