The antioxidant and anticorrosive properties of crude glycerol fraction from biodiesel production

BACKGROUND: Raw glycerol fractions as the waste material from biodiesel production were investigated for its antioxidant and anticorrosive properties. For comparison raw glycerol fractions and biodiesel fuels together with different oil feedstocks (as an input material for the transesterification process) were measured by means of electron paramagnetic resonance (EPR) spectroscopy. Additionally glycerol fractions were subjected to corrosivity testing (Herbert method). RESULTS: 1,2,3‐Propanetriol‐containing fractions exhibited high free radical scavenging properties, in comparison with biodiesel and oil material. Additionally, the Herbert test proved the anticorrosive ability of the crude glycerol fractions investigated. Radical scavenging (antioxidant) properties obtained from EPR spectroscopy paralleled the anticorrosive investigations, with samples having the highest quenching abilities giving the best results in the Herbert tests. CONCLUSION: The anticorrosive activity of glycerol fractions examined in this paper generates a new application in lubricant manufacturing. The results show new ways of utilising raw glycerol fraction without very costly and time‐consuming purification. Copyright © 2009 Society of Chemical Industry     

Stereochemical course of Escherichia coli RNase H

A new enzymatic method has allowed the assignment of the stereochemistry of E. coli RNase-H-assisted hydrolysis of RNA labelled within the scissile bond with (R(p))-phosphorothioate. This method is based on a stereospecific, two-step enzymatic conversion of cytidine 5'-[(18)O]phosphorothioate into the corresponding 5'-alpha-[(18)O]thiotriphosphate, which is then further used for stereospecific transfer of cytidine 5'-[(18)O]phosphorothioate to the 3'-OH group of a short oligonucleotide with the aid of terminal deoxyribonucleotidyl transferase. Matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry of the resulting elongated primer revealed that RNase-H-assisted hydrolysis proceeds with inversion of configuration at the phosphorus atom. This result is discussed in the context of current knowledge of the architecture of the active site of the enzyme.     

Storage of ammonia in old sewer sediments

Nitrogen sources in combined sewers are briefly summarised. Some evidence of biodegradation including the ammonification of sewer sediment has been found from a new interpretation of field experimental data known from the literature. Gravel and sand sediments in combined sewers were found to be potential sources of ammonia, which is discharged through overflows.     

Elimination of Constraint Violation and Accuracy Aspects in Numerical Simulation of Multibody Systems

Multibody systems are often modeled as constrained systems, and theconstraint equations are involved in the dynamics formulations. To makethe arising governing equations more tractable, the constraint equationsare differentiated with respect to time, and this results in unstablenumerical solutions which may violate the lower-order constraintequations. In this paper we develop a methodology for numerically exactelimination of the constraint violations, based on appropriatecorrections of the state variables (after each integration step) withoutany modification in the motion equations. While the elimination ofviolation of position constraints may require few iterations, theviolation of velocity constraints is removed in one step. The totalenergy of the system is sometimes treated as another measure of theintegration process inaccuracy. An improved scheme for one-stepelimination of the energy constraint violation is proposed as well. Theconclusion of this paper is, however, that the energy conservation is ofminor importance as concerns the improvement of accuracy of numericalsimulations. Some test calculations are reported.     

Physical shape functions in finite element analysis of moderately thick plates

A new rectangular finite element for moderately thick plates is presented. The element is based on the concept of physical shape functions, i.e. functions which contain in themselves physical and geometrical properties of the element. The analytic formulae of stiffness, geometric stiffness and mass matrices are presented for isotropic material. The element is free from locking and zero energy modes not corresponding to rigid body motions. Several examples are presented for static, initial stability and free vibration problems.     

Transient analysis and simulation of nonuniform lossy transmission lines

A new formulation of equations of the nonuniform lossy transmission line, in the form of integral equations based on the method of characteristics, has been introduced. Two methods of solution of these equations are presented, the first based on discretization of the integrals and, the second, a method of successive approximations, are presented and the results are compared. The presented integral equations of the line have interesting circuit representations and exhibit wave processes such as reflection, distortion, and attenuation. © 1992 John Wiley & Sons, Inc.     

A method of calculating the concentration of deposit around an injection well

From the equations analogous to the Herzig-Leclerc-Le Goff equations an inequality is derived. This inequality can be used for calculating the concentration of deposit around an injection well. The full balance equation for solid particles and the kinetic equation in the general form are taken into consideration. The maximum relative error of the method is calculated. The deep radial filtration through the uniform and non-uniform porous media is considered.     

Mathematical model of heat and mass transfer processes in evaporative condensers

This study presents a new mathematical model of heat and mass transfer processes in evaporative condensers. The model consists of four ordinary differential equations with their boundary conditions and some associated algebraic equations. The model was formulated for steady-state heat and mass transfer conditions. A simulation computer program based on the model was written. It was devised for heat calculations in condensers built from bare tubes. The quality of the model was calculated by comparing the results obtained by running the program with experimental results achieved by other authors. The computed results show a good degree of conformity with experimental results. The differences are less than 20% (but in one case, 30%). The computer program may be used to determine heat performance of evaporative condensers of horizontal in-line and staggered bundle systems (if S_q > 2d_z).     

Computations of (α, k)-machines

In this paper we study the properties of computations of an (α, k)-machine, which is a special case of k-machine introduced by Grodzki [7]. Some sufficient conditions for convergence, divergence and boundedness of computations are given. The problem of the existence of a cyclic computation, the length of which is equal to any given positive integer, generated by an (α, k)-machine is presented.