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排序方式: 共有176条查询结果,搜索用时 15 毫秒
31.
32.
Daniele Bianchi Rossella Bortolo Rino D'Aloisio Marco Ricci 《Angewandte Chemie (International ed. in English)》1999,38(5):706-708
Effective and stable Pd catalysts for the biphasic synthesis of hydrogen peroxide from carbon monoxide, oxygen, and water [Eq. (a)] can be obtained by the right choice of bidentate nitrogen ligand. The best turnover numbers (578) for this reaction have been achieved with palladium complexes with 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline ligands. 相似文献
33.
Giovanna Gomez dAyala Emilia Di Pace Paola Laurienzo Diletta Pantalena Elvira Somma Maria Rossella Nobile 《European Polymer Journal》2009,45(11):3217-3229
Functionalization of polymers is a particular relevant approach in the field of biodegradable polymers, where modifications are often required to allow these materials to replace more conventional, not biodegradable polymers in a wider range of applications. This article will report on functionalization of poly(ε-caprolactone) with unsaturated monomers bearing either anhydride groups (PCL-g-(MA-GMA)) or tertiary amines (PCL-g-DMAEA), obtained through radical grafting in a Brabender mixer. Crystallization kinetics parameters have been determined with several techniques (rheology, optical microscopy and differential scanning calorimetry) and the results obtained are in good agreement. It was observed that the crystallization rate significantly increases in the case of the modified polymers. 相似文献
34.
Rossana Iervolino Elvira Somma Maria Rossella Nobile Xuming Chen Benjamin S. Hsiao 《Journal of Thermal Analysis and Calorimetry》2009,98(3):611-622
The flow-induced crystallization behavior of nanocomposites, containing isotactic poly(1-butene) (PB) and functionalized multi-walled
carbon nanotubes (MWNT), was investigated. Three different MWNT concentrations (0.1, 1, 5 wt%) were used to prepare the nanocomposites.
Effects of MWNT and shear flow on the crystallization parameters were evaluated separately. Rheological measurements based
on oscillatory shear revealed induction time and crystallization half-time at the quiescent state, where both parameters exhibited
the nucleating effect of MWNT on PB. Rheological measurements based on steady-state shear flow and short-time shear flow revealed
the evolution of molecular orientation, which was studied in both PB and its nanocomposites. A small increase in crystallization
kinetic was recorded in PB under shear having moderate values of the Weissenberg (We) number. On the other hand, a dramatic synergistic effect of MWNT and shear was detected under the same shear conditions
for nanocomposites. The optical microscopic images exhibited a clear transition from isotropic to row-like morphology in the
case of nanocomposites under shear. 相似文献
35.
Alcaro S Bolasco A Cirilli R Ferretti R Fioravanti R Ortuso F 《Journal of chemical information and modeling》2012,52(3):649-654
A computer-aided design of novel asymmetric pyrazoles with improved enantioselective properties was performed by docking experiments starting from a model of Chiralcel OJ chiral in the stationary phase. Synthesis and HPLC experiments confirmed the theoretical prediction and led to a detailed investigation of the enantioselective recognition process. For the first time, looking at the time spent by each enantiomer in contact with the CSP during long molecular dynamic simulations, the experimental analytical trend has been reproduced. 相似文献
36.
Beatriz Martín‐García Prof. M. Mercedes Velázquez Dr. Francesco Rossella Prof. Vittorio Bellani Prof. Enrique Diez Prof. Jose Luis García Fierro Jose Antonio Pérez‐Hernández Juan Hernández‐Toro Sergi Claramunt Prof. Albert Cirera 《Chemphyschem》2012,13(16):3682-3690
Films of a few layers in thickness of reduced graphite oxide (RGO) sheets functionalized by the zwitterionic surfactant N‐dodecyl‐N,N‐dimethyl‐3‐ammonio‐1‐propanesulfonate (DDPS) are obtained by using the Langmuir–Blodgett method. The quality of the RGO sheets is checked by analyzing the degrees of reduction and defect repair by means of X‐ray photoelectron spectroscopy, atomic force microscopy (AFM), field‐emission scanning electron microscopy (SEM), micro‐Raman spectroscopy, and electrical conductivity measurements. A modified Hummers method is used to obtain highly oxidized graphite oxide (GO) together with a centrifugation‐based method to improve the quality of GO. The GO samples are reduced by hydrazine or vitamin C. Functionalization of RGO with the zwitterionic surfactant improves the degrees of reduction and defect repair of the two reducing agents and significantly increases the electrical conductivity of paperlike films compared with those prepared from unfunctionalized RGO. 相似文献
37.
Ciminiello P Dell'Aversano C Dello Iacovo E Fattorusso E Forino M Grauso L Tartaglione L Guerrini F Pezzolesi L Pistocchi R Vanucci S 《Journal of the American Chemical Society》2012,134(3):1869-1875
Since 2005, the benthic dinoflagellate Ostreopsis cf. ovata has bloomed across the Mediterranean basin, provoking serious toxic outbreaks. LC/MS studies have identified a number of palytoxin-like compounds, termed ovatoxins, along with trace amounts of putative palytoxin as the causative agents of the O. cf. ovata -related human sufferings. So far, any risk assessment for ovatoxins as well as establishment of their allowance levels in seafood has been prevented by the lack of pure toxins. The present paper reports on the isolation, NMR-based structural determination, and preliminary mouse lethality evaluation of ovatoxin-a, the major toxic compound contained in O. cf. ovata extracts. Availability of pure ovatoxin-a will open the double prospect of fully evaluating its toxicity and preparing reference standards to be employed in LC/MS quantitative analyses. Elucidation of ovatoxin-a's complex structure will ultimately herald the understanding of the molecular bases of ovatoxins bioactivity. 相似文献
38.
Rossella Yivlialin Claudia Filoni Francesco Goto Alberto Calloni Lamberto Du Franco Ciccacci Gianlorenzo Bussetti 《Molecules (Basel, Switzerland)》2022,27(22)
Reflectance anisotropy spectroscopy (RAS) coupled to an electrochemical cell represents a powerful tool to correlate changes in the surface optical anisotropy to changes in the electrochemical currents related to electrochemical reactions. The high sensitivity of RAS in the range of the absorption bands of organic systems, such as porphyrins, allows us to directly correlate the variations of the optical anisotropy signal to modifications in the solid-state aggregation of the porphyrin molecules. By combining in situ RAS to electrochemical techniques, we studied the case of vacuum-deposited porphyrin nanocrystals, which have been recently observed dissolving through electrochemical oxidation in diluted sulfuric acid. Specifically, we could identify the first stages of the morphological modifications of the nanocrystals, which we could attribute to the single-electron transfers involved in the oxidation reaction; in this sense, the simultaneous variation of the optical anisotropy with the electron transfer acts as a precursor of the dissolution process of porphyrin nanocrystals. 相似文献
39.
40.
Giulia Samorì Chiara Samorì Rossella Pistocchi 《Applied biochemistry and biotechnology》2014,173(1):74-89
The objective of the present study was to evaluate the nutrient removal efficiency and the physiological responses in terms of growth, biochemical composition and photosynthetic activity of the autochthonous freshwater algal strain Desmodesmus communis. Microalgae were grown in a primary municipal effluent under different hydraulic retention times (HRTs) and in a two-phases process using both primary and secondary wastewater effluents. Semi-continuous cultures were operated for 7 day at 5-, 3- and 1.5-day HRT and the different dilution rate showed a greater influence on the biomass composition and nutrient removal efficiency. Removal of N-NH3 and P-PO4 was over 99 % and the highest accumulation of polysaccharides (57.2 wt.%) was obtained at high HRT (5 day); the maximum content of proteins (26.9 wt.%) was achieved at 1.5-day HRT, even if, under this condition, a clear inefficiency in terms of ammonia removal was observed. Moreover the accumulation of N-NH3 occurring at 1.5-day HRT caused the decrease of the photosynthetic response in terms of efficiency of light capture (α) and relative electron transport rate (rETR), both parameters extracted from the rapid light curves (RLC) measurements. No significant differences were observed for the total fatty acids (TFAs), with a content of 2–3.5 wt.% for each HRT condition. On the other hand, in the two-phases process, when a nutrient deprivation condition was induced by diluting the culture with the secondary wastewater effluent, the algal cells accumulated TFAs, achieving a maximum content of 9.7 wt.% and a great increment in terms of biomass (1.64?±?0.02 g L?1) due to the ability of this algal strain to accumulate intracellular N. The wide and accurate investigation of the different aspects related to the whole process represents a relevant point of novelty in this research field and suggests the operational conditions for the start-up of an open pond system for wastewater treatment and biomass production for further applications. 相似文献