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161.
A method based on immersed solid-phase microextraction (SPME) and gas chromatography mass spectrometry detection (GC-MS) for the determination of organophosphorous pesticides (OPPs) in aqueous samples was developed. A sol-gel based coating fiber was prepared using 3-(trimethoxysilylpropyl) amine as precursor. The synthesized fiber was prepared in a way to impart polar moiety into the coating network and would be more suitable for extracting polar and semi-polar organic pollutants. Important parameters influencing the extraction process were optimized and an extraction time of 40 min at 30 °C gave maximum peak area, when NaCl (20% w/v) was added to the aqueous sample. The linearity for disulfoton, phorate and sulfotep was in the concentration range of 0.01 to 5 ng mL− 1 and for parathion and O,O,O-triethylthiphosphate was in the range of 0.01 to 50 ng mL− 1. Limits of detection ranged from 1 ng L− 1, for parathion, to 0.05 ng L− 1, for disulfoton using time-scheduled selected ion monitoring (SIM) mode, and the RSD% values were all below 10.5% at the 1 ng mL− 1 level. The developed method was successfully applied to real water samples while the relative recovery percentages obtained for the spiked water samples were from 80 to 115%.  相似文献   
162.
An electrochemical sensor was developed for determination of hydrogen peroxide (HP) based on a carbon ceramic electrode modified with iron pentacyanonitrosylferrate (FePCNF). The surface of an iron-doped CCE was derivatized in a solution of PCNF by cycling the electrode potential between ?0.2 and +1.3 V for about 60 times. The morphology and the composition of the resulting electrode were characterized by scanning electron microscopy and Fourier transform infrared techniques. The electrode displayed excellent response to the electro-oxidation of HP which is linearly related to its concentration in the range from 0.5 μM to 1300 μM. The detection limit is 0.4 μM, and the sensitivity is 849 A M ?1?cm ?2. The modified electrode was used to determination of HP in hair coloring creams as real samples.  相似文献   
163.
Primary, secondary, tertiary, allylic, and benzylic halides are converted efficiently into symmetric disulfides in high yields using thiourea as the sulfur atom source. The reactions are odorless and are performed at 30-35 °C in wet PEG-200 using MnO2 as an oxidant.  相似文献   
164.
We give a new upper bound for the smallest eigenvalues of the Dirac operator on a Riemannian flow carrying transversal Killing spinors. We derive an estimate on both Sasakian and 3-dimensional manifolds, and partially classify those satisfying the limiting case. Finally, we compare our estimate with a lower bound in terms of a natural tensor depending on the eigenspinor.  相似文献   
165.
AlPW12O40 was found to be an effective catalyst for the selective acetylation of alcohols, thiols, and amines in the absence of solvent at room temperature.  相似文献   
166.
Consider a time-harmonic electromagnetic plane wave incident on a periodic (grating) structure. An inhomogeneous (subwavelength) object is placed inside the periodic structure. The scattering problem is to study the electromagnetic field distributions. The problem arises in the study of near-field optics and has many physical and biological applications. This work is devoted to modeling and analysis of a near-field optics problem. An integral representation approach is presented to solve the problem. It is shown particularly that the perturbation due to the object decays exponentially along the periodic direction of the structure, provided that no surface waves occur. Based on the approach, a general solution method is discussed and the well-posedness of the model problems are established.  相似文献   
167.
In this paper we are interested in the semilinear elliptic equations of the type u=u(,u), on bounded smooth domain of R n . We also treat existence of positive solution of u=p(x)f(u), which explodes near the boundary of (called large solutions). Our approach is based on potential theory.  相似文献   
168.
Summary Flow injection analysis with on-line ion-exchange preconcentration using a mini-column loaded with 8-quinolinol immobilized on controlled-pore glass, is described for the determination of iron(II)-enhanced chemiluminescent oxidation of luminol in alkaline hydrogen peroxide. The detection limit for iron(II) is 10–13 mol/l (in 3 ml of sample). The operating conditions are optimized, and the effect of interferents is studied. The analysis time was 5 min for each sample, including 2 min for sample loading.  相似文献   
169.
Summary A convenient and simple synthesis of 5-mercapto-3-phenyl-2-thioxo-2,3-dihydrothiazolo-[4,5-d]pyrimidin-7(6H-one(2) and its 5,7-dichloro (3), 5,7-diazido (4), 5,7-diamino (5), 5,7-dimerapto (6), 5,7-dimethylthio (7), and 6-methyl-5-methylthio (8) derivatives is described. The prepared compounds were screened for theirin vitro anti-HIV, anticancer, antibacterial and antifungal activities.
Kondensierte Thiazole, 1. Mitt.: Synthese von 5,7-disubstituierten Thiazolo[4,5-d]pyrimidinen als potentielle anti-HIV, anticancerogene und antimikrobielle Verbindungen
Zusammenfassung Die Synthese von 5-Mercapto-3-phenyl-2-thioxo-2,3-dihydrothiazolo[4,5-d-pyrimidin-7(6H)-on (2) und seiner 5,7-dichloro-(3), 5,7-diazido-(4), 5,7-dimanio-(5), 5,7-dimercapto-(6), 5,7-dimethylthio- (7) und 6-methyl-5-methylthio-Derivaten (8) wird beschrieben. Die hergestellten Verbindungen wurden auf ihrein vitro anti-HIV, anticancerogenen, antibakteriellen und antimykotischen Aktivitäten geprüft.
  相似文献   
170.
Phytochemical screening of nonpolar fractions from the methanol extract of the Bamboo shoot skin Phyllostachys heterocycla var. pubescens resulted in the isolation of a new sterol-glucoside-fatty acid derivative (6’-O-octadeca-8″,11″-dienoyl)-sitosterol-3-O-β-d-glucoside (1), together with six known compounds. The chemical structures of the pure isolated compounds were deduced based on different spectral data. The isolated compounds were assessed to determine their cytotoxic activity, and the results were confirmed by determining their apoptotic activity. Compound 1 was more cytotoxic against the MCF-7 cells (IC50 = 25.8 µM) compared to Fluorouracil (5-FU) (26.98 µM), and it significantly stimulated apoptotic breast cancer cell death with 32.6-fold (16.63% compared to 0.51 for the control) at pre-G1 and G2/M-phase cell cycle arrest and blocked the progression of MCF-7 cells. Additionally, RT-PCR results further confirmed the apoptotic activity of compound 1 by the upregulation of proapoptotic genes (P53; Bax; and caspases 3, 8, and 9) and downregulation of the antiapoptotic genes (BCL2). Finally, the identified compounds, especially 1, were found to have high binding affinity towards both tyrosine-specific protein kinase (TPK) and vascular endothelial growth factor receptor (VEGFR-2) through the molecular docking studies that highlight its mode of action.  相似文献   
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