Theoretical Analysis of Coagulation Kinetics in Brownian Disperse Systems

Analytical solution to the system of differential equations describing the coagulation kinetics in Brownian dilute disperse systems is obtained. The effect of the reversibility of aggregation in the secondary minimum on the coagulation kinetics in the primary minimum is analyzed. It is shown that experimental conditions can substantially affect the theoretical interpretation of experimental data.__________Translated from Kolloidnyi Zhurnal, Vol. 67, No. 3, 2005, pp. 381–391.Original Russian Text Copyright © 2005 by Mishchuk.     

On Line Determination of Perphenazine Using Flow Injection Analysis

An accurate specific flow injection spectrophotometric method for the determination of perphenazine in the range 50-250 ppm is introduced. In the method, 110 μl of the drug is injected through a stream of 0.2% (w/v) potassium dichromate in 0.25 M sulfuric acid flowing on line as a carrier stream. The drug is oxidized on the flow to the red monocation radical, the peak absorbance of which is monitored at 525 nm. A throughput of up to 300 samples per hour is attained. The mechanism of the reaction is suggested and the method is compared with the United States Pharmacopeia method.     

On the Possibility of Using Lithium-doped Copper Oxide in Lithium Cells

Lithium cells with cathodes based on lithium-doped copper oxide were studied.     

On the Effect of Interaction between Dispersed Phase Particles on the Rheology of Fractally Heterogeneous Disperse Systems

The microrheology of the aqueous solution of hydrolyzed polyacrylonitrile is studied by determining its optical characteristics in the process of flow. It is shown that the flow stability is lost in the region of the solution dilatancy; this loss is manifested in random oscillations of the system transparency. The structure of the system is fractal when the content of the polymer exceeds 1 wt %. The fractal dimension of the structural elements is determined.     

Shear Hardening in the Rheology of Structured Systems

Moscow University Chemistry Bulletin - A structural rheological model is presented that describes the phenomenon of shear solidification in structured systems, namely, in concentrated suspensions,...     

流动注射分析法响应曲线的方差和样品分散

根据串联釜模型，考察了响应曲线的方差与各变量（反应管长，载流流速和进样体积）间的关系以及方差与相应分散系数的关系。只有在载流流速和进样体积一定时，才能以方差表征分散系数。     

On the Possibility of Using UV Spectroscopy as a Measure of the Low-Barrier Hydrogen Bond

In many enzyme-catalyzed biochemical pathways, a short, strong hydrogen bond between an enzyme and substrate is an important structural feature. These bonds are termed low-barrier hydrogen bonds. In this paper, we show that UV spectra can be used as an experimental technique to determine if a system contains a low-barrier hydrogen bond (LBHB). We simulate, using the time-dependent view of UV spectroscopy, several different UV spectra: absorption, photodissociation, and emission, on systems containing a low-barrier hydrogen bond. We find several distinguishing spectral features in these UV spectra for systems that possess a LBHB.     

Coagulation and Flocculation Purification of Fat- and Protein-Containing Disperse Systems

Procedure for treatment of wastewater with a coagulant (aluminum sulfate) and anionic flocculants to remove fats and proteins was studied The purification efficiency was evaluated from the flocculation parameters.     

A Cell for Measuring Shear Strength of Powdered Disperse Systems

The design of a cell is described for shear thixotrometers allowing to measure the shear strength of powdered materials under compression loads of up to 1 MPa.     

Investigation of the Wall Slip Effect in Highly Concentrated Disperse Systems by Means of Non-Invasive UVP-PD Method in the Pressure Driven Shear Flow1

A novel in-line UVP-PD non-invasive rheological measuring technique was introduced for rheological analysis of highly concentrated disperse systems. The method is based on a combination of the Ultrasonic Pulsed Echo Doppler technique (UVP, Ultrasound Velocity Profiler) and the pressure difference (PD) method. The rheological properties were derived from simultaneous recording and on-line analysis of the velocity and related radial shear stress profiles across a circular channel. Wall slip velocity was extrapolated from the on-line fit and monitored on-line simultaneously with the flow index. Two effects were found and preliminarily analyzed. The first effect refers to a transition from strongly non-Newtonian to Newtonian flow velocity profile while increasing in the absolute flow velocity. The second flow effect refers to an abrupt reduction of the wall slip velocity while increasing the absolute flow velocity. Considerable discrepancy was found between the results of the in-line UVP-PD measurement in pressure driven shear flow and the results of the conventional rheometry.     

On the Possibility of Evanescent Wave Excitation Distal from a Solid-Liquid Interface Using Light Quenching

Abstract— Evanescent wave illumination with total internal reflection is often used to provide excitation near a quartz-water interface. We now show that evanescent illumination at one wavelength and incident angle, coupled with light quenching at a second wavelength and incident angle, can be used for selective excitation of fluorophores located up to 5000 Å into the aqueous phase. The displacement of the fluorophore population from the solid-liquid interface depends on the angles of incidence of the excitation and quenching beams and the optical power of the quenching beam. Light quenching with an evanescent wave was demonstrated to be experimentally possible using Pyridinez and a light-quenching wavelength of 736 nm. The use of combined evanescent wave excitation and evanescent wave quenching could provide selective excitation of fluorophores in the cytoplasmic region of cells and may provide improved response times for optical sensors based on evanescent excitation.     

On the Possibility of Using the Jellium Model as a Guide To Design Bimetallic Superalkali Cations

The potential application of the jellium model as guidance in the rational design of bimetallic superalkali cations is examined under gradient-corrected density functional theory for the first time. By using Li, Mg, and Al as atomic building blocks, a series of bimetallic cationic clusters with 2, 8, 20, and 40 valence electrons are obtained and investigated. As the corresponding neutral clusters tend to lose one valence electron to achieve closed-shell states in the jellium model, these studied cations exhibit much lower vertical electron affinities (EA_vert, 3.42–4.95 eV) than the ionization energies (IEs) of alkali metal atoms, indicating their superalkali identities. The high stability of these cationic clusters is guaranteed by their considerable HOMO–LUMO gaps and binding energies per atom. Moreover, the feasibility of using the designed superalkalis as efficient reductants to activate CO₂ and N₂ molecules and as stable building blocks to assemble ionic superatom compounds is explored. Therefore, this study may provide an effective method for obtaining various metallic superatoms with extensive applications on the basis of the simple jellium rule.     

On the Possibility of Using SPARK-1M Portable X-ray Spectrometer for Studying the Chemical Bond

The possibility of using SPARK-1M spectrometer for studying the shift of emission lines belonging to the K series of X-ray spectra of transition metals (chemical shift of the lines) was studied. The possibility of using the spectrometer for measuring the chemical shift and evaluating the relative amounts of transition metals in different oxidation states is analyzed.     

Change in the Rheological Properties of Oil Disperse Systems upon a Vibrational Treatment

The effect of a vibrational treatment on the rheological properties of highly structured oil disperse systems is studied. A maximal decrease in the rheological parameters is observed after 20-min vibrational treatment for paraffin-rich and highly resinous oils and after 5-min treatment for mazut. The vibrational treatment is shown to be the most effective for oils with an increased content of paraffins. It is revealed that the magnetic treatment decreases the congelation temperature of oil.     

Determination of Hydrogen Peroxide Concentrations By Flow Injection Analysis Based On the Enhanced Chemiluminescent Reaction Using Peroxidase

Abstract

The technique of flow injection analysis was employed in the determination of hydrogen peroxide. the method was based on the chemiluminescence reaction of luminol with H₂O₂ which is catalyzed by horseradish peroxidase and enhanced by p-iodophenol. Hydrogen peroxide was linearly detected in the range 10^?6M-10^?4M by measuring the maximum intensity of light emitted. the detection limit is about 1 · 10^?6M hydrogen peroxide. Transition metal cations at millimolar concentrations do not have any interference on the determination of hydrogen peroxide by FIA based on the enhanced chemiluminescent reaction. This technique is relatively rapid and simple, and permits measurement of up to 80 samples/hr using generally available equipment.     

Removal of Disperse Dyes from Water Using Surfactant Treated Alumina

An alumina surface was modified by adsorption of an anionic surfactant, sodium dodecyl sulfate (SDS). Typical S‐shaped isotherm of surfactant on alumina was observed. The adsorption of Disperse Red‐11, Disperse Blue‐26 and Disperse Red‐156 on alumina and surfactant treated alumina has been investigated. The enhancement in adsorption of these disperse dyes on surfactant treated alumina is observed, which may be attributed to their solubilization in surfactant aggregates formed at the solid/liquid interface. The effect of pH on adsorption has been studied. The adsorption is greatly influenced by pH of the medium. The applicability of the Langmuir model and the Dual‐Mode sorption model (DSM) were tested for equilibrium data.