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111.
Photooxygenations of 2-(γ,ε-dihydroxyalkyl) furans in H(2)O followed by in situ reduction and ketalization affords, in one synthetic operation, DE-bicyclic ketals of the pectenotoxins. 相似文献
112.
Antonia M. Carro Diego García‐Rodríguez Paula Gonzalez‐Siso Rosa A. Lorenzo 《Journal of separation science》2012,35(21):2866-2874
Chemicals are widely used in aquaculture and one of the main recipients of these analytes is the aquatic environment. The aim of this work was to develop and validate a simple and sensitive method for the determination of multiclass chemotherapeutic agents in farmed fish and shellfish using matrix solid‐phase dispersion and liquid chromatography‐tandem mass spectrometry. Residues of azamethiphos, three avermectins, two carbamates, and two benzoylureas were extracted from samples using silica gel as clean‐up adsorbent and 0.5% acetic acid in acetonitrile as elution solvent. The extraction conditions were investigated and optimized using an experimental design. Mass spectrometry detection was carried out in positive electrospray ionization mode with multiple‐reaction monitoring scan (except for benzoylurea family). Matrix‐matched standards were used for the drugs quantification. Good linearity (R2 ≥ 0.996) was observed in the range of 5–500 μg kg?1. Limits of detection were in the range of 1.5–3.7 μg kg?1. Recoveries from salmon samples spiked with veterinary drugs were in the range 84.9–118%. Precision was satisfactory since relative standard deviations were lower than 10.6%. The method can be successfully applied for the analysis of fish and shellfish from aquaculture. 相似文献
113.
Maria J. Ortiz Antonia R. Agarrabeitia Gonzalo Duran-Sampedro Jorge Bañuelos Prieto Teresa Arbeloa Lopez Walter A. Massad Hernán A. Montejano Norman A. García Iñigo Lopez Arbeloa 《Tetrahedron》2012,68(4):1153-1162
A theoretical and experimental study on the iodination of BODIPY dyes with different degrees of substitution has been developed. Polyhalogenated BODIPYs synthesized in this work are the first examples of this type of dyes with more than two halogen atoms in the BODIPY core and they can be selectively functionalized. Surprisingly, the position in which halogen is attached has a marked effect in the photophysical properties and modulates the fluorescence capacity of the resulting BODIPY. These iodinated BODIPYs are efficient singlet oxygen generators. 相似文献
114.
Energy transfer between vibrational, rotational, and translational degrees of freedom of a molecule during a collision process is enhanced when the classical frequencies associated with the initial state are in the proximity of nonlinear resonance conditions. We present an analysis of the classical resonant effects in the collisions of light diatoms with periodic surfaces, and discuss the initial conditions in which these effects can be observed. In particular, we find that for grazing incidence and resonant initial values of the classical frequencies, corresponding to specific vibro-rotational molecular states and translational energies, an efficient energy transfer between the intramolecular vibro-rotational degrees of freedom and the translational degree of freedom along a symmetry direction on the surface can be found. This efficient energy transfer manifests itself in the emergence of specific peaks in the molecular diffraction patterns. The predictions of the resonance analysis are contrasted with the results of classical trajectory calculations obtained in a diatom-rigid surface collision model. 相似文献
115.
Antonia Vecchio 《Numerische Mathematik》2001,89(4):783-794
Summary. Conditions are proven which assure the summability of the first difference of the fundamental matrix of nonconvolution Volterra
discrete equations. These conditions are applied to the stability analysis of some linear methods for solving Volterra integral
equations of nonconvolution type.
Received July 25, 1999 / Revised version received February 14, 2000 / Published online April 5, 2001 相似文献
116.
117.
Maria Antonia Iat Rosalba Saija Arianna Giusto Paolo Denti Ferdinando Borghese Cesare Cecchi-Pestellini 《Journal of Quantitative Spectroscopy & Radiative Transfer》2006,100(1-3):157-164
We calculate the energy density distribution in the ultraviolet within small spheres containing concentric cavities, aimed at simulating interstellar dust grains. We explore the dependence on chemical composition by progressively changing, in an arbitrary way, the refractive index of the sphere material. We conclude that a significant fraction of the energy of the impinging radiation is trapped throughout the particle interior. 相似文献
118.
Evaluation of pozzolanic activity of natural and artificial pozzolans by thermal analysis 总被引:2,自引:0,他引:2
In this research, the pozzolanic activity of natural and artificial pozzolan used for preparation of restoration mortars was evaluated. For this purpose, several pastes were prepared, by mixing two artificial pozzolans and a natural one with commercial hydrated lime, in different ratios. The pastes were cured in standard conditions (RH = 98%, T = 25 °C). The pozzolanic activity was evaluated by using simultaneous differential thermal and thermogravimetric analysis (DTA/TG) after curing for 3, 7, 14, 28 days. The obtained results revealed that the various lime/pozzolan pastes displayed different reaction kinetics and therefore the various pozzolans present different reactivity, in proportion to its mineralogical, physical and chemical characteristics. 相似文献
119.
Lavinia Claudia Buruleanu Andreea Antonia Georgescu Florin Andrei Danet Radu Lucian Olteanu Cristina Mihaela Nicolescu 《Analytical letters》2018,51(7):1039-1059
The antioxidant activity, total phenolic content, and total flavonoid content of 10 edible mushrooms species, including cultivated (Pleurotus ostreatus, Agaricus bisporus white and brown) and wild (P. ostreatus, Macrolepiota procera, Cantharellus cibarius, Russula vesca, Russula alutacea, Boletus edulis and Agaricus campestris), were determined. The extraction was performed using water and 50% water–ethanol and the caps and stipe were investigated separately. Water was the most appropriate solvent for phenolic compounds regardless of the sample. In contrast, the presence of ethanol in the solvent increased the extraction of flavonoids for cultivated P. ostreatus (caps and stipe), and wild R. alutacea, R. vesca, A. campestris, P. ostreatus (only caps) and C. cibarius, M. procera (only stipe). Significant differences between the antioxidant activities of the samples were registered in relationship with the different solvents. The antioxidant activity of water extract of dried A. bisporus brown (cultivated) showed the strongest 1,1-diphenyl-2-picrylhydrazyl radicals-scavenging assay (88.64%), while the B. edulis hydroalcoholic extract contained 74.93%. A detailed investigation into the functional group of phenolics and other organic compounds responsible with the antioxidant activity has been performed using Fourier transform infrared spectroscopy. The infrared spectra showed that the solvent-type directly influences the extraction process and, hence, the antioxidant activity. The present study contributes to information concerning mushrooms as sources of biologically active compounds. To investigate the correlations between phytochemical characteristics (i.e., phenolics, flavonoids and antioxidant activity) closely related to nature of solvents, the statistical analysis was performed. 相似文献
120.
In self-preserving turbulent wall flows, both measurements and direct numerical simulations indicate that the mean square vorticity in the outer region does not depend only on and U
. It also depends on the Reynolds number.RAA is grateful to St. Francis Xavier University (Antigonish) for their support while on study leave there. The support of ARC is gratefully appreciated. 相似文献