N-(α-Ketoacyl)anthranilic acids were prepared by oxidative ring opening of 3-hydroxyquinoline-2,4(1H,3H)-diones by using paraperiodic acid (H5IO6) or sodium periodate (NaIO4). The optimisation of the reaction conditions is described as well as the utilisation of N-(α-ketoacyl)anthranilic acids in the preparation of anthranilic acid hydrochlorides. 相似文献
AbstractFe3O4@SiO2@NH2 nanocomposite was prepared for highly effective adsorption of two anionic dyes one of which is triarylmethane dye (light green, LG) and the other is azo dye (brilliant yellow, BY). The characterization results demonstrated that superparamagnetic Fe3O4 nanoparticles were covered with silica and functionalized with amino groups successfully without losing magnetic character. The effects of adsorbent dosage, contact time, pH, temperature, and dye molecular structure on the adsorption were investigated. Acidic pH was better for both LG and BY, on the other hand, alkaline pH was favorable to some extent for LG in comparison with BY due to the contribution of stacking effect in addition to electrostatic attraction. Kinetic data demonstrated that the driving force for adsorption process could be explained by pseudo-second order mechanism in both systems. The equilibrium data were more compatible with Langmuir isotherm than those of Freundlich isotherm and the maximum adsorption capacities of Fe3O4@SiO2@NH2 calculated from Langmuir isotherm model for LG and BY at 30?°C and natural pH of the solution were 40.2 and 35.5?mg g?1. Thermodynamic calculations related to temperature dependence demonstrated that the adsorption process was spontaneous and exothermic. 相似文献
A new series of lactic acid derivatives has been prepared with molecular cores consisting of two laterally substituted biphenyls connected by an ester group. The compounds exhibited the TGBA phase in a broad temperature range. In addition, for some compounds, a narrow blue phase was found above the TGBA phase on cooling from the isotropic phase. Except for the compound with the shortest chain, the TGBC phase appeared below the TGBA phase. The low temperature SmC* phase existed within the interval up to 80 K, including the overcooled state, which was down to room temperature. In the compounds studied a strong pre-transitional phenomenon took place manifested as a broad peak on the differential scanning calorimetry plot in the isotropic phase. The phases were established on the basis of a planar sample and free-standing film microscope observation. Small angle X-ray diffraction measurements provided information about layer spacing, d, and confirmed the phase assignment. Dielectric spectroscopy revealed the soft and Goldstone modes in the respective TGBA and SmC* phases. 相似文献
In this paper we focused on cold plasma treatment of oxidized cellulose haemostat. Oxidized cellulose was modified in inert argon plasma. The changes of surface composition were examined by XPS and FTIR. Surface morphology of fibres was studied by SEM. Gravimetry was used to study ablation and water absorption. Antibacterial effect of pristine and plasma treated samples was examined by growth of Escherichiacoli and Staphylococcusepidermidis. Behaviour of pristine and plasma treated samples in water, physiological saline solution and phosphate buffered saline was observed by changes in the pH of their solutions. Modification of oxidized cellulose by inert argon plasma caused significant changes in the chemical composition of its surface layers as well as changes in morphology of those layers while maintaining or improving the antibacterial properties. We found out that modification by inert argon plasma improves the properties necessary for haemostatic function of oxidized cellulose. 相似文献
A new method involving matrix solid-phase dispersion (MSPD) extraction and UPLC in conjunction with photodiode array detection was developed for the rapid and simple determination of Sudan dyes in chili powder. Separation of Sudan I, Sudan II, Sudan III, and Sudan IV was achieved within 2 min on the 1.7 μm Acquity UPLC BEH C18 column by using gradient elution with a mobile phase consisting of acetonitrile–water at a flow rate of 0.5 mL min−1. Optimization of MSPD extraction parameters, such as type of solid sorbent and elution solvent were carried out. Optimal conditions selected for MSPD extraction were 0.25 g of sample, 0.5 g of silica gel as solid sorbent, and 7 mL of acetonitrile–methanol (9:1, v/v) as eluting solvent. Limits of detection ranged between 0.25 and 0.30 mg kg−1 depending on the dye involved. All analytes provided average recoveries from spiked (at 1, 1.5, and 2 mg kg−1) chili powder samples ranging from 81 to 106%. The method was applied to the analysis of chili powder samples obtained from different countries.
The polarographic behavior of thiamethoxam (a neonicotinoid insecticide) was studied by direct current and differential pulse
polarography. Depending on the pH thiamethoxam exhibited one or two well-defined cathodic polarographic waves. The characteristics
of the electrode reaction were investigated and it was found that at pH > 5.0 the target molecule captures four electrons
in the first step, and two in the second. Based on the reduction behavior of the target molecule on the mercury electrode,
a differential pulse polarographic method was elaborated for the rapid determination of thiamethoxam at pH 8.0. With the optimized
method, a linear response for thiamethoxam was found in the concentration range of 31.1 − 470 ng cm−3, the relative standard deviation did not exceed 1.6%, and the detection and quantitation limits were found to be 9.3 ng cm−3 and 31.1 ng cm−3, respectively. The method was applied to the determination of thiamethoxam in commercial formulations and real samples (potato
and maize). The procedure is simple, fast, sensitive, and compares well with comparative spectrophotometric and chromatographic
(HPLC/DAD) methods. 相似文献
M4,5 subshells average fluorescence yields (ϖM4,5) have been determined for thorium and uranium using M4,5 X-ray production cross-sections at 5.96 keV incident photon energy. The measurements have been performed using a 55Fe annular source and an Ultra-LEGe detector. The present values are compared with calculated theoretical values and theoretical
average M shell fluorescence yields (ϖM). Fair agreement (to within 22–27%) is typically obtained between present average fluorescence yields (ϖM4,5) and calculated theoretical values. 相似文献
Fe(III) ions may form ordered domains wherein the EPR resonance extends to the whole particle volume, leading to a major increase
of spectral line intensities. This phenomenon of “strong exchange“ is known as ferromagnetic resonance (fmr). The authors
observed another type of exchange, a weak one, characterized by drastically reduced resonances. Interestingly, both exchanges
run parallel (up- or downwards) with the catalytic activity of iron oxide nano-particles as catalysts in the N2O-mediated selective oxidation of benzene. 相似文献
Single crystal ZnO nanowires with lengths and diameters ranging from 2 to 30 μm and 100 to 300 nm, respectively, have been grown by the vapor transport method on SiO2/Si substrates using Au as catalyst. Their Raman and emission properties under different excitation wavelengths have been studied at the nanoscale. Whereas Raman measurements on nanowires corroborate the well-known ZnO phonon characteristics, their photoluminescence spectra exhibit a very broad emission band, mainly in the visible region from 450 to 800 nm, which corresponds to different defect-related recombination processes. Spectrally resolved scanning near-field optical microscopy, SNOM, of single ZnO nanowires have also been performed for a direct imaging of the photoluminescence emission with high spatial resolution below 100 nm, establishing a relationship with the simultaneously acquired topography. 相似文献
In this article, we compared seven statistical methods for detecting outbreaks of infectious disease; Historical limits, English
model, SPOTv2, CuSums, Bayesian predictive model, RKI method and Serfling model. We used simulated data and real data to compare
those seven methods. Simulated data have parameters such as trend, seasonality, mean and standard deviation. Among these methods,
SPOTv2 shows the best performance with a balance between sensitivity and positive predictive value and short time lag. But
in datasets having strong trends, Bayesian predictive model, English model and Serfling model perform better than SPOTv2.
These methods are also compared through real numerical example. 相似文献