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51.
52.
Domenica Scarano Serena Bertarione Federico Cesano Giuseppe Spoto Adriano Zecchina 《Surface science》2004,570(3):155-166
Atomic force microscopy in contact, non-contact and in high resolution modes have been used to image MgO powder samples, obtained at different degree of sintering, starting from Mg(OH)2 decomposition or obtained in form of smoke. From high resolution AFM images of MgO smoke, the lattice periodicity on regular surfaces has been revealed for the first time, under ambient conditions. The high surface perfection of the microcrystals has been further confirmed by HRTEM analysis. To obtain more information on the local structure of the single faces, in terms of type and distribution of the surface active sites, the adsorption of a simple probe molecule (CO) on such surfaces has been investigated by means of FTIR spectroscopy. 相似文献
53.
A.K. Jain J.Y. Grossiord M. Chevallier P. Gaillard A. Guichard M. Gusakow J.R. Pizzi 《Nuclear Physics A》1973,216(3):519-540
The 6Li(d, 2d)4He and 6Li(d, dα)2H reactions were performed at 27 MeV. Analyses of these and the 42.8 and 55 MeV 6Li(α, 2α)2H reactions were performed using distorted wave and plane wave impulse approximations. The kinematic and potential coupling approximations to final state three-body Schrödinger equation and the post and prior form approximations to off-shell scattering cross section were studied for the three reactions. It was found that only the kinematic coupling and post form approximations could be used for the consistent analyses of the three reactions. The effects of distortions and localization of the reactions were investigated. Manifestations of deuteron cluster deformation were noticed in the analyses of the three reactions. 相似文献
54.
Emission of gases and degradation volatiles from polymeric wood constituents in friction welding of wood dowels 总被引:2,自引:0,他引:2
Analysis of volatile compounds and gases emitted as smoke at the welding interface during rotational wood dowel welding of a hardwood (beech) and of a softwood (Norway spruce) has shown that the compounds in such a smoke are water vapour, CO2, degradation compounds from wood polymeric carbohydrates and from amorphous lignin, as well as some volatile terpenes, these latter only for the softwood used, Norway spruce. The main carbohydrates contributing to the volatile compounds are xylans for beech and glucomannans for spruce. Numerous compounds, in very small proportions derived from the degradation and rearrangement reactions of lignin, have also been identified. The proportion of CO2 emitted is very low, and neither CO nor methane is emitted due to the relatively low temperature of dowel welding. Experiments at temperature slightly higher than that of dowel welding but prolonged in time have shown that the main component of the smoke produced during welding appears to be water vapour. 相似文献
55.
Diego Pizzi Ryan Worth Marco Giacinti Baschetti Giulio C. Sarti Ken-ichi Noda 《Journal of membrane science》2008
The permeability of hydrogen selective Pd-based membranes was tested in different experimental conditions. The membranes were obtained by depositing palladium–silver films onto ceramic porous supports, with film composition of about 20 wt% of silver and thicknesses of about 2.5 μm. Their permeance was measured at 400 °C at total trans-membrane pressures between 0.2 and 6 bar, using pure feeds of H2 and N2, as well as H2/N2 and H2/CO mixtures; the temperature dependence of permeability was investigated using pure H2 feeds at 300, 400 and 500 °C. The membranes exhibit a very attractive behavior, maintaining a virtually infinite selectivity throughout the testing, with permeance values among the highest values reported in literature for similar membranes. Permeation of pure hydrogen accurately follows Sieverts’ law and confirms the presence of a chemisorption–dissociation–diffusion mechanism, characterised by the transport of atomic hydrogen through the Pd–Ag layer as the limiting step. In the case of H2/N2 mixtures, the high membrane permeance originates also significant concentration polarization phenomena resulting in apparent deviations from Sieverts’ behavior; the presence of CO in the feed may reduce hydrogen permeability even by 75%, although this effect is shown to be fully reversible after a subsequent air treatment at 400 °C. The temperature dependence of the membrane permeability is of Arrhenius type, with an activation energy of about 17 kJ/mol, that is, close to what is reported for Pd–Ag membranes following Sieverts’ behavior. 相似文献
56.
Lorella Guadagnini Marco Giorgetti Domenica Tonelli 《Journal of Solid State Electrochemistry》2013,17(11):2805-2814
A glucose amperometric biosensor was developed. Glucose oxidase enzyme was immobilized by means of a Nafion membrane on glassy carbon modified with an electrochemically deposited mixed Cu and Pd hexacyanoferrate (CuPdHCF). According to the data provided by X-ray atomic spectroscopy measurements, this Cu- and Pd-based hexacyanoferrate is likely to be a mixture of single CuHCF and PdHCF pure phases. The biosensor performances were evaluated by recording the steady-state currents due to submillimolar additions of glucose to a potassium buffer solution (pH 5.5) and exploiting the electrocatalytic reduction of the enzymatically produced hydrogen peroxide. The CuPdHCF-based biosensor exhibited a sensitivity of 8.1?±?0.6 A M?1 m?2, a limit of detection of 1.4?×?10?5 M, and a linear response range extending between 5?×?10?5 and 4?×?10?4 M, with a dynamic response range up to 4?×?10?3 M glucose. Electrode sensitivity and signal stability resulted more satisfactory as compared to those of a CuHCF-based biosensor fabricated according to the same procedure. The selectivity was investigated through an interference study. The response to easily oxidizable species was found to be low enough to allow glucose determination in biological samples. 相似文献
57.
Aldo Arrais Eliano Diana Domenica Marabello Giuliana Gervasio Pier Luigi Stanghellini 《Journal of organometallic chemistry》2011,696(11-12):2299-2305
The synthesis of organometal complexes from chromium hexacarbonyl with 1-methyl-naphthalene ligand is reported. Two arene-chromium-tricarbonyl isomers are formed at competitive yields, featured with the metal fragment coordinated to both the methylated and the benzenic aromatic ring. A single-crystal X-ray diffraction measurement has been performed on the [(η6-5,6,7,8,9,10-C11H10)Cr(CO)3] isomer, which presents the metal carbonyl moiety attached to the benzenic arene ligand. The products of reaction have been studied by UV–VIS–NIR, fluorescence and 1H NMR spectroscopies. A detailed vibrational characterisation by mean of experimental FT-IR and Raman spectroscopy and DFT calculations is reported. The electron ligand donation to the metal carbonyl system, determined by FT-IR spectroscopy, has been related to the actual decrease of resonance energy of the aromatic hydrocarbon in the complex and compared with other chromium tricarbonyl complexes of different polycyclic aromatic hydrocarbons provided with the naphthalenic moiety. 相似文献
58.
Giorgetti M Guadagnini L Tonelli D Minicucci M Aquilanti G 《Physical chemistry chemical physics : PCCP》2012,14(16):5527-5537
A deep structural investigation predominantly by X-ray spectroscopic techniques is conducted on films of copper hexacyanoferrate (CuHCF) deposited under different conditions, aimed at establishing structure-properties relationships. We show that the potentiodynamic electrosynthesis of CuHCF on carbon-based surfaces produces a highly disordered material, with a variable amount of Prussian Blue (PB). The subsequent Cu(2+) intercalation induces the partial conversion of PB into CuHCF, which explains the improved electrocatalytic properties after the intercalation process. Both Cu and Fe K-edge data have been recorded. For the sample with the lower amount of PB, we could perform a multiple edge data analysis to determine the local atomic environment around both metal centres using the same set of structural parameters. The presence of high multiplicity Cu-N-C-Fe linear chains has allowed us to determine accurately the local environment of Fe while fitting the Cu K-edge data only. Using this approach we have retrieved structural information around Fe for those samples in which the concomitant presence of PB would have made impossible the analysis of the Fe K-edge. The Fe-C, C-N and Cu-N bond distances have been found in agreement with those of the bulk structures, but higher values of [Fe(CN)(6)] vacancies for the building blocks have been evidenced, reaching a value of ~45% in one sample. XANES, Raman and SEM data agree with the model proposed for each studied electrode. 相似文献
59.
Patterns consisting of strings with a bounded number of mismatches are central to coding theory and find multiple applications
in text processing and computational biology. In this latter field, the presence of over-represented patterns of this kind
has been linked, for instance, to modeling regulatory regions in biosequences. The study and computation of expected number
of occurrences and related scores for these patterns is made difficult by the sheer explosion of the roster of candidates
that need to be evaluated. In recent work, properties of pattern saturation and score monotonicity have proved capable to
mitigate this problem. In such a context, expectation and score monotonicity has been established within the i.i.d. model for all cases of interest except that of a fixed word length with a varying number of mismatches. The present paper
completes this investigation by showing that the expected number of occurrences in a textstring for such a word is bi-tonic,
that is, behaves as a unimodal function of the number of errors. This extends to this case the time and space savings brought
about by discovery algorithms based on pattern saturation.
Work Supported in part by the Italian Ministry of University and Research under the Bi-National Project FIRB RBIN04BYZ7, and
by the Research Program of Georgia Tech. An extended abstract related to this work was presented at the Dagstuhl Seminar Dagstuhl
on “Combinatorial and Algorithmic Foundations of Pattern and Association Discovery”, May 14-19, 2006 [3]. 相似文献
60.
Summary The Bu4N[Cr2H(CO)10] species reacts with hydrogen chloride in methanol to produce Bu4N[Cr(CO)5Cl].Analogous reactions using the complex K(phen)3Cr2H(CO)10 and K(bpy)2Cr2H(CO)10 salts (phen = 1,10-phenanthroline, bpy = 2,2-bipyridine) give the new (phen)2H[Cr2H(CO)10], phenH[Cr2H(CO)10], (phenH)2(Cl)[Cr2H(CO)10], and bpyH[Cr2H(CO)10] derivatives respectively. 相似文献