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[en] This work deals with the role of polar interactions on the viscosity and sedimentation behaviors of magnetorheological suspensions with micro-sized magnetic particles dispersed in oil carriers. The oleic acid and dimer acid were employed to make an adjustment of the hydrophobicity of iron particles, in the interest of performing a comparative evaluation of the contributions of the surface polarity. The viscosity tests show that the adsorbed surfactant layer may impose a hindrance to the movement of iron particles in the oil medium. The polar attractions between dimer acid covered particles gave rise to a considerable increase in viscosity, indicating flocculation structure developed in the suspensions. The observed plateau-like region in the vicinity of 0.1 s"−"1 for MRF containing dimer acid is possibly due to the flocculation provoked by the carboxylic polar attraction, in which the structure is stable against fragmentation. Moreover, a quick recovery of the viscosity and a higher viscosity-temperature index also suggest the existence of particle-particle polar interaction in the suspensions containing dimer acid. The sedimentation measurements reveal that the steric repulsion of oleic acid plays a limited role in the stability of suspensions only if a large quantity of surfactant was used. The sedimentation results observed in the dimer acid covered particles confirm that loose and open flocculation was formed and enhanced sedimentation stability. - Highlights: • Surfactants were employed to make adjustments of the hydrophobicity of particles. • Polar attractions between particles increased the viscosity considerably. • Loose and open flocculation was formed in CI/DA suspension. • The steric repulsion of oleic acid played a limited role in the stability.
[en] The solid complexes of uranyl and thorium nitrates with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol(5-Br-PADAP) have been synthesized in acetone medium. Composition of complexes are determined by elemental analysis as following: UO2(NO3)2(HL)2; Th(NO3)3L · HL(HL = 5-Br-PADAP). The complexes have been characterized by infrared spectra, ultraviolet-visible spectra, solubility and molar conductance determination, thermogravimetric(TG) and differential thermal analysis(DTA), and X-ray powder diffraction
[en] We have developed a resin phase spectrophotometric method to determine the amount of beryllium by detecting a change in absorbance of the resin phase. 8-Hydroxynaphthalene-3,6-disulphonic acid-(1-azo-2')-1',8'-dihydroxynaphthalene-3',6'-disulphonic acid tetrasodium salt (beryllon II) immobilized by a strong base anion-exchange resin on the end of a bifurcated optical fibre bundle was chosen as a material sensitive to beryllium. Experiments were made using a home-made optical fiber spectrophotometer. The properties of the resin phase proved to be good for continual use of 350 times during a month. The reaction order between immobilized beryllon II and beryllium in solution was determined by kinetic theory and experiments. This method was also used to determine the amount of beryllium in beryllium-copper alloy; the response was linear from 0.43 to 2.60 μg/ml at pH 12.5 and 676 nm. The effect of interfering ions on the determination of beryllium was studied at the same time. (Author)
[en] The relationship was studied between the relative mobility of a group of 19 chlorophenols in different buffers modified by eight kinds of different organic additives in capillary zone electrophoresis and a set of 10 molecular descriptors calculated by semi-empirical quantum chemical method PM3 implemented in HyperChem. Using multiple linear regression (MLR), we obtained an empirical function which included five descriptors. The performance of radial basis function neural network (RBFNN) was evaluated and proved better than MLR
[en] The influence of enhanced UV-B radiation (approximating a 15% ozone layer reduction) on competitive interaction between spring wheat (Triticum aestivum) and wild oat (Avena fatua) was examined in the field. The density-dependent mortality of both wheat and wild oat did not exhibit a significant difference between control and UV-B treatment conditions. A relatively high degree of competitive stress enhanced the effects of UV-B stress on biomass reduction. The relative competitive status of wheat in terms of total biomass increased under UV-B enhancement while it decreased when based upon grain production. Shifts in competitive balance occurred with significant changes in total biomass, especially when plants grew at higher densities in monocultures and mixtures. The sensitivity of wild oat to intensification of UV-B radiation at higher densities in mixtures was greater than that at lower densities. At all densities examined, wheat grown in mixture was significantly less sensitive to UV-B radiation than that in monoculture, and just the opposite for wild oat. The density of monocultures did not alter the response index (RI) of wheat and wild oat to enhanced UV-B radiation. (author)
[en] The determination of proteins with 2-(4-chloro-2-phosphonophenylazo)-7-(4-iodophenylazo) -1,8-dihydroxynaphthalene-3,6-disulfonic acid (CPA-pI) by Rayleigh light scattering (RLS) was studied in this paper. The weak RLS of CPA-pI and BSA can be enhanced greatly by the addition of Al3+ at the pH 5.6 and an enhanced RLS signal was produced at 365-385 nm. Based on the reaction of CPA-pI, Al3+ and proteins, a new quantitative determination method for proteins has been developed. The effect of three variables for the determination of proteins was optimized by means of artificial neural networks (ANNs) using extended delta-bar-delta (EDBD) algorithms with the optimal network structure of 3-5-1. This method is very sensitive (2.5-35.4 μg/ml for bovine serum albumin (BSA)), rapid (<2 min), simple (one step) and tolerance of most interfering substances. Six samples of protein in human serum were determined and the maximum relative error is no more than 2% and the recovery is between 95% and 105%
[en] The binding properties of diprophylline (DPP) to lysozyme (Lys) were investigated using fluorescence spectroscopy in combination with UV-vis absorption techniques under simulative physiological conditions. Results of fluorescence measurement indicated that the intrinsic fluorescence of Lys was strongly quenched by DPP. The binding constants and the number of binding sites at different temperatures (298, 310, and 318 K) calculated with the data obtained from fluorescence quenching experiments via the modified Stern-Volmer equation were 8.61x104 L mol-1 and 1.34; 10.36x104 L mol-1 and 1.22; 12.85x104 L mol-1 and 1.11, respectively. Positive values of ΔH0 and ΔS0 obtained according to the Van't Hoff equation for the formation of the DPP-Lys complex implied that typical hydrophobic interactions might play a significant role during the binding process. Furthermore, the effect of DPP on the conformation change of Lys was analyzed using synchronous fluorescence measurement. The effects of common co-ions on the interaction of DPP with Lys were also discussed. - Research highlights: → The quenching mechanism of DPP on Lys was mainly a static quenching procedure. → Complex formation with one binding site and hydrophobic interaction as main forces were observed. → The binding process occurred spontaneously, and was an exothermic reaction.
[en] In this paper, a new kind of fluorescent nanomaterial with morin modified alumina core and silica shell was prepared. Samples were characterized by transmission electron microscope (TEM), X-ray diffraction (XRD), Fourier transform infrared spectra (FT-IR), photoluminescent (PL) spectroscopy and fluorescence microscope. TEM results indicated that this material could be synthesized in nanometer range. PL spectra suggested that this new synthesized material was photostable and it showed nearly no dye leakage. This was because the dye molecules could form stable complex with the reactive aluminum cations on the surfaces of the alumina particles. The excitation and emission maxima of this new luminescent material were located at 420 and 493 nm, respectively. This new kind of luminescent nanomaterial was prepared by morin, AlCl3 and tetraethyl orthosilicate, which was very important for the large-scale and economic preparation luminescent nanoparticles because these precursors were inexpensive and the preparation process was convenient.
[en] The accurate non-linear quantitive structure-property relationship model for predicting the adsorption constant of volatile and semivolatile organic vapors in soil was firstly developed based on support vector machine (SVM) by using the compounds' molecular descriptors calculated from the structure alone and the features of soil and air. Multiple linear regression (MLR) was used to build the linear QSPR model. Both the linear and non-linear models can give satisfactory prediction results: the correlation coefficient R was 0.953 and 0.995, the mean square error (MSE) was 0.0517 and 0.0057, respectively, for the whole dataset. The prediction result of the SVM model was better than that obtained by the MLR model, which proved non-linear model can simulate the relationship between the structural descriptors, the environmental condition and the soil/air distribution more accurately as well as SVM was a useful tool in the prediction of the adsorption constant of compounds. - The model we built can be used to predict a given molecule's adsorption characteristics, and also allow a more accurate determination of its environmental fate
[en] This paper reports on the preparation of a new multifunctional nanocomposite that consists of superparamagnetic core and rhodamine B (Rh B) doped silica shell. The final products were characterized by x-ray powder diffraction (XRD), transmission electron microscopy (TEM), vibration sample magnetometer (VSM), photoluminescence (PL) spectra and Fourier transform infrared spectra (FT-IR). The resultant multifunctional nanoparticles were superparamagnetic with a saturation magnetization of about 10 emu g-1, their sizes were smaller than 150 nm and they possessed an emission peak at 568 nm with an excitation wavelength of 520 nm. This new material holds considerable promise in magneto-optical materials and biological applications