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排序方式: 共有420条查询结果,搜索用时 15 毫秒
1.
CuPc molecules adsorbed on Au(1 1 0)-(1 × 2): growth morphology and evolution of valence band states
Fabrizio Evangelista A. RuoccoValdis Corradini M.P. DonzelloCarlo Mariani Maria Grazia Betti 《Surface science》2003,531(2):123-130
We present the growth morphology, the long-range ordering, and the evolution of the valence band electronic states of ultrathin films of copper phthalocyanine (CuPc) deposited on the Au(1 1 0)-(1 × 2) reconstructed surface, as a function of the organic molecule coverage. The low energy electron diffraction patterns present a (5 × 3) reconstruction from the early adsorption stages. High-resolution UV photoelectron spectroscopy data show the disappearance of the Au surface states related to the (1 × 2) reconstruction, and the presence of new electronic features related to the molecule-substrate interaction and to the CuPc molecular states. The CuPc highest occupied molecular orbital gradually emerges in the valence band, while the interface electronic states are quenched, upon increasing the coverage. 相似文献
2.
Jaime E. Muñoz Rivera Maria Grazia Naso 《Journal of Mathematical Analysis and Applications》2007,326(1):691-707
We study the asymptotic behavior of the solutions of a class of linear dissipative integral differential equations. We show in the abstract setting a necessary and sufficient condition to get an exponential decay of the solution. In the case of the lack of exponential decay, we find the polynomial rate of decay of the solution. Some examples are given. 相似文献
3.
G. Balducci L. Bencivenni G. De Rosa R. Gigli B. Martine S.Nunziante Cesaro 《Journal of Molecular Structure》1980
The infrared and Raman spectra of some cyclopentadienyl compounds of the transition metals, namely Ti(C5H5)Cl3 and M(C5H5)2Cl2 (M = Ti, Zr and Hf), are reported and discussed. The infrared spectra of the gaseous species isolated in argon matrices at 10 K provide structural information about the single molecules. Particular attention has been paid to the low-frequency region in order to achieve more reliable assignments for the internal-rotation modes. The structural data and the fundamental frequencies derived from the spectra are employed in a calculation of the thermodynamic functions for these compounds in the ideal gas state. 相似文献
4.
Benati L Bencivenni G Leardini R Minozzi M Nanni D Scialpi R Spagnolo P Zanardi G 《The Journal of organic chemistry》2005,70(8):3046-3053
Thermal reaction of various alpha-azido esters with Bu(3)SnH in refluxing benzene results in smooth production of 3-(tributylstannyl)-1-triazene adducts affording cyclized 1,2,3-triazol-4-ones in preference to reduced amines and thence provides a new useful method for the preparation of these triazole derivatives. In the presence of AIBN the occurrence of triazene products still remains important or even exclusive and, consequently, generation of the expected stannylaminyl radicals is seriously limited. With 2-azidomalonates and alpha-azido-beta-keto esters stannyltriazenes can similarly occur in the absence of the radical initiator, but in the latter cases the ensuing triazenes undergo preferential cyclization onto the ketone moiety to give reactive hydroxytriazolines. Contrary to alpha-azido esters, in the presence of AIBN alpha-azido-beta-keto esters as well as azidomalonates give rise only to the usual stannylaminyl radicals. A possible explanation for the different behavior of the mono- and dicarbonyl azides in the presence of AIBN is put forward. 相似文献
5.
Pozzoli L Bolzacchini E Van Dingenen R Hjiorth J Dentener F Perrone G Rindone B Librando V 《Annali di chimica》2003,93(4):447-456
The model BAGS (Boxmodel for Aerosol and Gasphase Simulations) has been developed. It is composed of two major modules: the first one describes the system of the chemical reactions in the gaseous phase, the second one calculates the aerosol chemical composition and the dimensional distribution of the particles. The boxmodel has been developed with the introduction of new chemical and physical processes, not previously included, in particular the formation of Secondary Organic Aerosol. The other implemented processes are a module for the dynamic of the particle population, nucleation, coagulation and dry deposition. The last phase of the work has been a check of the BAGS capabilities by a series of tests, that have permitted to compare it with other models (MAPS and MADM). The tests in particular have concerned the aerosol water content prediction, the photochemistry, the condensation of the inorganic compounds and the formation of Secondary Organic Aerosol. 相似文献
6.
Many abiotic and biotic factors can influence the partitioning equilibrium of heavy metals, thus influencing metal impact on aquatic environments. Unicellular algal species release soluble organic substances able to complex metals. In our laboratory a Cr-tolerant strain was selected and isolated from a wild type strain of Scenedesmus acutus. The exudates released by the two strains counteracted the growth inhibition caused by Cr(VI) and the exudates of the Cr-tolerant strain were more effective. On the contrary, the exudates did not reduce chromium toxicity to the cladoceran Daphnia magna. The reduction of chromium effect on algae seems the consequence of an algae-specific interaction among Cr(VI), exudates and algal cells. Chromium uptake resulted to be energy-dependent since bioaccumulation rate in subdued light condition was lower than at high light intensity. The effect of Cr(VI) on algae changed depending on metabolism of the cells and in particular it seemed to be related to the bioaccumulation rate. Tolerance in the selected strain could not be ascribed to a lower uptake of chromium. The difference in sensitivity to chromium between the two strains was exploited to evaluate if tolerance acquired by algae could have consequences for Daphnia. After treatment with Cr(VI), the two strains of S. acutus were used as food source for D. magna. The results indicate that chromium is accumulated by algae in a form not available for daphnids and that Cr tolerance acquired by the algae can be of some advantage to the consumer organism. 相似文献
7.
The molecular structure of gaseous CsReO4 has been studied by matrix isolation IR spectroscopy. The 18O substitution experiments indicate a bidentate structure of C2v symmetry in which the perrhenate anion is slightly distorted from the tetrahedral geometry. 相似文献
8.
Giorgini MG Arcioni A Polizzi C Musso M Ottaviani P 《The Journal of chemical physics》2004,120(10):4969-4979
We have investigated the Raman profiles of the nu(C[Triple Bond]N) and nu(C=O) vibrational modes of the nematic liquid crystal ME6N (4-cyanophenyl-4(')-hexylbenzoate) in the isotropic phase at different temperatures and used them as probes of the dynamics and structural organization of this liquid. The vibrational time correlation functions of the nu(C[Triple Bond]N) mode, rather adequately interpreted within the assumption of exponential modulation function (the Kubo-Rothschild theory), indicate that the system experiences an intermediate dynamical regime that gets only slightly faster with increasing temperature. However, this theory fails in predicting the non-exponential behavior that the time correlation functions manifest in the long time range (t>3 ps). For this reason we have additionally approached the interpretation of vibrational correlation functions in terms of the theory formulated by Rothschild and co-workers for locally structured liquids. The application of this theory reveals that the molecular dynamics in this liquid crystal in the isotropic phase is that deriving from a distribution of differently sized clusters, which narrows as the temperature increases. Even at the highest temperature reached in this study (87 degrees C above the nematic-isotropic transition), the liquid has not yet achieved the structure of the simple liquid and the dynamics has not reached the limit of the single channel process. The vibrational and orientational relaxations occur in very different time scales. The temperature independence of the orientational dynamics in the whole range from 55 degrees C to 135 degrees C has been referred to the nonhydrodynamic behavior of the system, arising when local pseudonematic structures persist for times longer than the orientational relaxation. The occurrence of the process of resonant vibrational energy transfer between the C=O groups of adjacent molecules has been revealed in the isotropic phase by a slightly positive Raman noncoincidence effect in the band associated with the nu(C=O) mode. A qualitative interpretation is tentatively given in terms of partial cancellation of contributions deriving from structures having opposite orientations of their C=O groups. 相似文献
9.
Gallo P Nasi A Vinci F Guadagnuolo G Brambilla G Fiori M Serpe L 《Rapid communications in mass spectrometry : RCM》2005,19(4):574-579
In this work we present a method for confirmatory analysis of chloramphenicol (CAP) in bovine and buffalo raw milk. CAP is extracted in acetonitrile and purified by affinity chromatography on an alpha-1-acid glycoprotein (AAG) column, then is identified and determined by ion-trap liquid chromatography/electrospray ionisation tandem mass spectrometry (LC/ESI-MS/MS) analysis in the negative ion mode. CAP was identified at the minimum required performance limit (MRPL) of 0.30 ppb, by monitoring the [M-H]- ion and at least two product ions, meeting the qualitative and quantitative criteria set by the European Commission in Decision 2002/657/EC for confirmation of prohibited veterinary drugs. The trueness and within-day and between-day repeatability data are also reported. Moreover, the loading capacity of affinity columns towards CAP was tested. This method, based on the molecular recognition between drug and AAG during the purification step to improve sample cleanup, represents a quantitative and repeatable procedure for confirmatory analysis, and fits the requirements for the routine official control of CAP residues in raw milk. 相似文献
10.
Fermo P Gilardoni S Jauni Simarro T Bolzacchini E Lasagni M Gianelle V Pozzoli L Perrone G Librando V 《Annali di chimica》2003,93(4):389-396
The carbonaceous component in the Milan urban particulate matter, i.e. the two components black carbon (BC) and organic carbon (OC), has been measured by means of a thermogravimetric analyzer combined with an infrared spectrophotometer (TGA/FT-IR). While black carbon may be considered a primary pollutant, organic carbon includes both primary emissions and secondary organic aerosols. Since carbonaceous aerosol (including a small quantity of inorganic carbon, too) makes up roughly from 25% to 50% of the average annual PM 2.5 mass concentration, a deeper understanding of this component is required. The TGA/FT-IR technique, employed for the first time to our knowledge for the quantification of the particulate matter carbonaceous component, allows, thought the results here presented are preliminary, to assess the two components BC and OC in a simple way especially if compared with the methods reported in the literature. The total carbon (TC) determinations performed by TGA/FT-IR on Milan urban particulate matter are in good agreement with the results obtained by a total organic carbon (TOC) analyzer operating directly on the solid sample. 相似文献