Determination of very low concentrations of polyacrylamide and polyethyleneoxide flocculants by nephelometry

A method is described for the analytical determination of low concentrations of polyacrylamide or polyethyleneoxide flocculants in water, in the range 0–10 parts/10⁶. It depends on measuring the turbidity produced by mixing the polymer solution with a dilute solution of tannic acid in the presence of 1 m NaCl. With a sensitive nephelometer, as little as 0.1 parts/10⁶ of flocculant can be detected.     

A simplified recursive formulation for the dynamic analysis of planar mechanisms

Summary In the present paper, a numerical method for generating the equations of motion of planar mechanisms with only revolute joints is presented. The method rests upon the idea of replacing the rigid body by a dynamically equivalent constrained system of particles. For the open loop case, the equations of motion are generated recursively along the open chains. Geometric constraints that fix the distance between the particles are introduced. For the closed loop case, the system is transformed to open loops by cutting suitable kinematic joints with the addition of kinematic constraints. The method is conceptually easy and suitable for computer implementation. It eliminates the necessity of distributing the external forces and moments over the particles and uses the concepts of linear and angular momentums to generate the rigid body equations of motion without introducing any rotational coordinates. An example with closed loops is chosen to demonstrate the generality and simplicity of the proposed method.     

Use of dual polarization interferometry as a diagnostic tool for protein crystallization

The use of dual polarization interferometry (DPI) as a tool for probing the different possible outcomes of protein crystallization experiments is described. DPI is a surface analytical technique used for the characterization of structure and interactions of molecular layers on an optical waveguide surface for a wide range of applications, including protein-protein interactions and conformational changes. The application of this technique provides a "signature" of crystallization events, thus predicting if there will be protein crystal formation, amorphous precipitate, or clear solution. The technique was demonstrated on a number of model proteins, and it also produced meaningful results in the case of two problematic target proteins. DPI in conjunction with a dialysis setup, allows changes in the protein solution above the waveguide surface to be monitored simultaneously with continuous control of its precipitant content. DPI has the potential to be used as a powerful method for discovering crystallization conditions, for obtaining information on the crystallization process, and as an aid in crystal optimization. It has also provided what is, to the best of our knowledge, the most direct observation to date of salting-in behavior in a protein-salt solution.     

Effects of ripening and parching on the quality characteristics,the chemical composition and the nutritive value of chickpea (Cicer arietinum L)

Physical properties and various chemical constituents of chickpea seeds were determined before and after ripening (malana and dry seeds of Giza 1 cultivar) and before and after parching (dry and parched seeds of Giza 2 cultivar). The raw dry seeds of Giza 2 were much smaller, lighter in mass and higher in seed coat percentage than those of Giza 1. Malana (green seeds at physiological maturity) seeds were large and uniform in size; they became smaller with much variation in seed size upon ripening. Parching significantly reduced the seed mass, but increased the seed volume. Marked differences in the chemical composition of the raw dry seeds were observed between the two cultivars which were grown under different environmental conditions. Ripening resulted in significant decreases in crude protein and polyphenol content but significant increases in nonreducing sugars, raffinose, neutral detergent fibre (NDF), add detergent fibre, cellulose, and phytic acid content. A considerable increase in Ca and Cu, a significant increase in in-vitro protein digestibility, but significant reductions in NDF, trypsin inhibitor activity and phytic acid content occurred upon parching.     

Chemical composition and functional properties of Ulva lactuca seaweed collected in Tunisia

The chemical composition and some functional properties of the dried “Ulva lactuca” algae, collected from the littoral between the Taboulba and Sayada area, were determined. The dried “U. lactuca” algae were investigated for their soluble, insoluble and total dietary fibre content, mineral amount, amino acid and fatty acid profiles, swelling capacity (SWC), water holding capacity (WHC) and oil holding capacity (OHC). Results showed that “U. lactuca” alga powder was characterised by a high content of fibres (54.0%), minerals (19.6%), proteins (8.5%) and lipids (7.9%). The neutral fibres contain hemicellulose (20.6%), cellulose (9.0%) and lignin (1.7%). The proteinic fraction analysis indicated the presence of essential amino acids, which represent 42.0% of the total amino acids. The fatty acids profile was dominated by the palmitic acid, which represents about 60.0% of the total fatty acids, followed by oleic acid (16.0%). The study of the functional properties proved that SWC, WHC and OHC of this alga varied with temperatures and that were comparable to those of some commercial fibre rich products.     

Corrosion inhibition of mild steel in aqueous solutions using nonionic surfactants

Protection of Metals and Physical Chemistry of Surfaces - The inhibiting effect of nonionic surfactant of Tween-20 and 60 on the corrosion of mild steel in 0.5 M HCl was studied by weight loss,...     

Book reviews

ENVIRONMENTAL MODELLING FOR DEVELOPING COUNTRIES edited by Asit K. Biswas, T.N. Khoshoo and Ashok Khosla Tycooly Publishing, London and New York, 1990, 166 pp.

COMPUTATIONAL METHODS IN SURFACE HYDROLOGY Edited by G. Gambolati, A. Rinaldo, C.A. Brebbia, W.G. Gray and G.F. Pinder Computational Mechanics Publication, Southampton and Boston. Co‐published with Springer‐Verlag, Berlin, 1990, 556 pp.

GROUNDWATER MONITORING edited by Lorne G. Everett Genium Publication, Schenectady, 1987, 440pp.

WATER POLLUTION IN INDIA by Bharat Desai Lancer Books, New Delhi, 1990, 282pp.     

Estimation of the reliability function using the delay-time models

The reliability model developed by Christer is used in which the notion of delay-time is involved, which is the span of time from when a defect is first detected upon inspection to when it is considered to have failed. In this paper, a new simplified formula for the reliability function is obtained, in which the delay time and the time to failure densities are exponential distributions. The MLE of the reliability function are also obtained. A numerical procedure is used to solve the results for the new model.     

Thermodynamic effect on the bending response of elastic foundation FG plate by using a novel four variable refined plate theory

This article deals with the study of the thermodynamic behavior of functionally graded material plates resting on two-parameter elastic foundation. An analytical solution based on a new shear refined deformation theory is presented. The displacement field used in the present refined theory contains undetermined integral forms and involves only four unknowns to derive. The plate is assumed simply supported and subjected to two different temperatures fields across its thickness. The mechanical characteristics of the plate are assumed to be varied across the thickness according to a simple exponential law distribution. The governing equations and boundary conditions are derived using the principle of virtual displacements and Navier solution technique is adopted to derive analytical solutions. A detailed numerical study of the present new refined theory is carried out to examine the influence of the time’s parameter, foundation’s parameters and deflection on the bending response of the FG plate.