Measurement of thermophysical properties of polyvinyl alcohol complexed with some metal ions

Polyvinyl alcohol (PVA)-Cu(II) and PVA-Cr(III) complexes were prepared with different concentrations of CuC1₂ and Cr(NO₃)₃ salts. The structures of the obtained complexes were investigated using UV spectroscopy and x-ray analysis. The thermal properties (volumetric heat capacity, thermal diffusivity, and thermal conductivity) of aqueous solutions of PVA-metal complexes have been measured using the hot-wire (and strip) technique as a function of temperature (20°-80°C). The results show that the values of the thermal properties depend on the type and the concentration of metal ions bound to the polymeric chains of PVA and the temperatures. However, a considerable increase in the values of the thermal properties was observed for PVA-Cu(II) complex. The type of metal salt under investigation affects the structure of PVA. The complex of PVA-Cr(III) is more thermally stable than the complex of PVA with Cum. However, both polymer-metal complexes showed good properties which may make them acceptable for some practical uses.     

Spectrofluorimetric determination of warfarin sodium by using N1-methylnicotinamide chloride as a fluorigenic agent

A spectrofluorimetric method is described for the determination of drugs containing active methylene groups adjacent to carbonyl groups. The method was applied successfully to the determination of warfarin sodium in laboratory-prepared mixtures, in commercial tablets, and in spiked human plasma samples. Finally, the method was applied to the determination of the steady-state concentration of warfarin sodium in the blood of a hospitalized patient. The method involves the reaction of warfarin sodium with 0.2 ml (0.4 x 10(-3)M) N1-methylnicotinamide chloride reagent in the presence of 3 mL 1.0N NaOH and cooling in ice for 8 min, followed by adjustment of the pH to 2.0, using formic acid and heating for 4 min, whereby a highly fluorescent reaction product is produced. The optimal wavelengths of excitation and emission were determined by using a synchronous wavelength search and found to be 284 and 354 nm, respectively. The standard curves were linear over a concentration range of 50-1500 ng/mL in both aqueous solutions and spiked human plasma samples. The mean recoveries (+/- standard deviation) were 101.157 (+/-1.33) and 95.73 (+/-1.88%) for aqueous solutions and spiked human plasma samples, respectively. The method showed good specificity and precision. The proposed method is simple and economical because of its minimal instrumentation and chemicals requirements. Nevertheless, it is highly sensitive, specific, and reproducible. Accordingly, it is suitable for quality-control applications, drug monitoring, and bioavailability and bioequivalency studies.     

Unimolecular reactivity of uracil-Cu(2+) complexes in the gas phase.

The gas-phase interaction of copper(II) ions with uracil are studied by means of mass spectrometry and B3LYP/6-311+G(2df,2p)//B3LYP/6-31G(d) calculations. Positive-ion electrospray spectra show that the reaction of uracil with copper(II) gives rise to singly charged species, whereby the [Cu(uracil--H)](+) complex is the most intense ion in the spectra at low concentration. Mass spectrometry/mass spectrometry (MS/MS) experiments show that the loss of HNCO and NCO are the dominant fragmentation processes, accompanied by a minor loss of CO. A systematic study of the spectra obtained with different labeled species, namely, 2-(13)C- (m/z 175), 2-(13)C,1,3-(15)N(2)- (m/z 177) and 3-(15)N-uracil (m/z 175), concludes unambiguously that both the loss of HNCO and NCO involve exclusively C2 and N3, whereas only C4 is involved in the loss of CO. Suitable mechanisms for these fragmentation processes are proposed through a theoretical survey of the corresponding potential energy surface. In these mechanisms, pi complexes, which lie high in energy with respect to the global minimum, play a significant role in the loss of NCO; this explains why both products, HNCO and NCO involve the same atoms of the ring.     

Polymerization of N-aryl maleimides

Overall rates of polymerization of ring-substituted-N-phenylmaleimides were measured, mainly in dioxane. Rate equations were deduced. The rate of polymerization increased on addition of ZnCl₂; the effect was attributed to the interaction of the Lewis acid and the π-cloud of the growing maleimide radical. The effect of solvent on the rate of polymerization was also investigated.     

Catalytic properties of Fe ion-exchanged mordenite toward the ethanol transformation: influence of the methods of preparation

The transformation of ethanol on Fe ion-exchanged mordenite was compared in the temperature range of 200–400 °C for samples prepared in the solution and solid states. Ethane and methane were found as rather major products, compared to acetaldehyde and acetone. Diethyl ether was also detected as a dehydration product. The conversion was found to increase monotonically (to 96%) with increasing the Fe content (to 100%) and reaction temperature to 400 °C. The selectivity towards acetaldehyde and acetone was found maximum at the temperature 300 °C. Decrease in the catalyst Brönsted acidity due to ion-exchange in solution caused a marked increase in the selectivity toward acetaldehyde at 300 °C. At variance, Fe ion-exchanged in the solid state resulted in a higher Brönsted acidity catalyst of higher selectivity to acetone. The solid state exchanged catalyst formed more coke at 400 °C. The higher zeolite acidity catalyzes the ethane propagation into the coke precursors. The extraordinary formation of ethane as a dominant transformation product (in the absence of H₂ gas supply) is explained mainly to the O-abstracting affinity of the Fe³⁺ ion. Methane may be formed as a result of decomposition reaction at high temperatures. Mössbauer and XRD were applied for characterizing different Fe species involved as active sites in the reaction. Coke deposited on the catalysts was measured by TGA. Other helpful information was obtained from BET of N₂-adsorption and FT–IR of NH₃-adsorption. Fair correlation between the active sites responsible for formation of the various products and the zeolite acidity is discussed along with a possible role for the surface area and pore structure in the reaction activity and selectivity.     

Simultaneous sensing system for identical long-period gratings sensors using subcarrier multiplexing

A novel system based on subcarrier multiplexing is presented for simultaneous sensing of identical long-period grating sensor array. The experimental results show that the system facilitates excellent discrimination of two sensors at identical resonance wavelength.     

Spectrofluorimetric determination of drugs containing active methylene group using N1-methyl nicotinamide chloride as a fluorigenic agent

A spectrofluorimetric method was described for the determination of drugs containing active methylene groups adjacent to carbonyl groups. The method was applied successfully to the determination of three life saving cardiovascular drugs, with narrow therapeutic indices: pentoxifylline (I), propafenone hydrochloride (II) and acebutolol hydrochloride (III), in laboratory-prepared mixtures, in commercial tablets and in plasma samples. The method involved the reaction of each of the tested drugs with N1-methyl nicotinamide chloride (NMNCl) in the presence of alkali, followed by addition of formic acid, where highly fluorescent reaction products were produced. The produced fluorescence were measured quantitatively at 472 nm (lambdaex 352 nm), 409 nm (lambdaex 310 nm) and 451 nm (lambdaex 266 nm) for (I), (II), and (III) respectively. The method was linear over concentration ranges of 10-1000 microg/ml , 0.2-12 microg/ml and 0.08-10 microg/ml in standard solutions for (I), (II), and (III) respectively. In spiked human plasma samples, calibration graphs were linear over concentration ranges of 20-1000 microg/ml, 0.2-15 microg/ml and 0.08-10 microg/ml for (I), (II), and (III) respectively. The method showed good accuracy, specificity and precision in both laboratory-prepared mixtures and spiked human plasma samples. The proposed method is simple, with low instrumentation requirements, suitable for quality control application, bioavailability and bioequivalency studies.     

数字图像相关方法若干关键问题研究进展

本文报道了作者及其所在课题组近期在数字图像相关(DIC)测量方法上取得的重要研究进展。主要包括:(1)通过对DIC方法中反向组合高斯-牛顿算法的理论误差分析,提出了新的理论误差公式,进一步证明了反向组合高斯-牛顿算法在提高计算速度和测量精度方面的综合优势;(2)采用提出的理论误差公式,发展了数字散斑场的优化及制作方法,保证了测量结果的一致性和正确性;(3)基于相机阵列和图像拼接技术,发展了超分辨率数字图像相关方法,大大提高了DIC测量方法的应变测量分辨率;(4)提出了大视场条件下的三维系统标定方法,实现了三维测量系统的外参实时标定和多相机测量系统中相机位姿的自动矫正;(5)研制了便携式原位三维测量仪和多尺度DIC测量系统,实现了三维实时数字图像相关测量,进一步满足了DIC方法在工业在线检测和医学领域中的应用需求。     

Removal of dyes from colored textile wastewater by orange peel adsorbent: equilibrium and kinetic studies

The use of low-cost and ecofriendly adsorbents has been investigated as an ideal alternative to the current expensive methods of removing dyes from wastewater. Orange peel was collected from the fields of orange trees in the north of Iran and converted into a low-cost adsorbent. This paper deals with the removal of textile dyes from aqueous solutions by orange peel. Direct Red 23 (DR23) and Direct Red 80 (DR80) were used as model compounds. The adsorption capacity Q0 was 10.72 and 21.05 mg/g at initial pH 2. The effects of initial dye concentration (50, 75, 100, 125 mg/l), pH, mixing rate, contact time, and quantity of orange peel have been studied at 25 degrees C. The Langmuir and Freundlich models were used for this study. It was found that the experimental results show that the Langmuir equation fit better than the Freundlich equation. The results indicate that acidic pH supported the adsorption of both dyes on the adsorbent. Orange peel with concentrations of 8 and 4 g/l has shown adsorption efficiencies of about 92 and 91% for DR23 and DR80, respectively. Furthermore, adsorption kinetics of both dyes was studied and the rates of sorption were found to conform to pseudo-second-order kinetics with a good correlation (R > or = 0.998). Maximum desorption of 97.7% for DR23 and 93% for DR80 were achieved in aqueous solution at pH 2. Finally, the effect of adsorbent surface was analyzed by scanning electron microscope (SEM). SEM images showed reasonable agreement with adsorption measurements.     

Transmetallation of beta-allenyl silanes: efficient synthesis of dienyl chlorostannanes and chlorostibines

The reaction of 1-trimethylsilylbuta-2,3-diene with tin tetrachloride, antimony trichloride or antimony pentachloride gave the corresponding buta-1,3-dien-2-yl halostannane or stibine derivatives; this ligand exchange was extended to other beta-allenylsilanes.