Derivation and consistency of the partial functions of the ternary system involving interaction coefficients

The logarithm of activity coefficients of the components of the ternary system is derived based on the Maclaurin infinite series, which is expressed in terms of the integral property of the system and subjected to appropriate boundary conditions. The derivation of the functions involves extensive summation of various infinite series pertaining to the first-order interaction coefficients that have been shown completely to remove any truncational error. Since the conventional equations involving interaction coefficients are internally inconsistent, a consistent form of the partial functions is developed in the article using the technique just described. The thermodynamic consistency of the functions based on the Maxwell and the Gibbs-Duhem relations has been established. The derived values of the logarithmic activity coefficients of the components have been found to be in agreement with the thermodynamic data of the Fe-Cr-Ni system at 1873 K and have been found to be independent of the compositional paths.

Quinazoline�iodine interaction as studied by NMR in nematic solutions

The results of an NMR study of the interaction of quinazoline with iodine in the nematic phase indicate the formation of at least two different types of charge-transfer complexes. Significant changes in the molecular geometry of the quinazoline moiety were observed as a result of complexation with iodine. Detailed information on the formation of the charge-transfer complexes was derived from the changes in the molecular structure, order parameters and chemical shifts as functions of iodine concentration. The observed changes in the order parameters are interpreted in terms of bond interaction tensors.

Mutations in beta ` subunit of Escherichia coli RNA polymerase perturb the activator polymerase functional interaction required for promoter clearance

P>Transcription activator C employs a unique mechanism to activate mom gene of bacteriophage Mu. The activation process involves, facilitating the recruitment of RNA polymerase (RNAP) by altering the topology of the promoter and enhancing the promoter clearance by reducing the abortive transcription. To understand the basis of this multi-step activation mechanism, we investigated the nature of the physical interaction between C and RNAP during the process. A variety of assays revealed that only DNA-bound C contacts the beta' subunit of RNAP. Consistent to these results, we have also isolated RNAP mutants having mutations in the beta' subunit which were compromised in C-mediated activation. Mutant RNAPs show reduced productive transcription and increased abortive initiation specifically at the C-dependent mom promoter. Positive control (pc) mutants of C, defective in interaction with RNAP, retained the property of recruiting RNAP to the promoter but were unable to enhance promoter clearance. These results strongly suggest that the recruitment of RNAP to the mom promoter does not require physical interaction with C, whereas a contact between the beta' subunit and the activator, and the subsequent allosteric changes in the active site of the enzyme are essential for the enhancement of promoter clearance.

Interaction of Bacillus polymyxa with some oxide minerals with reference to mineral beneficiation and environmental control

Interaction of Bacillus polymyxa with calcite, hematite, corundum and quartz resulted in significant surface chemical changes not only of the cells but also in the minerals. Both the cell surfaces as well as quartz particles were rendered more hydrophobic after mutual interaction, whilst the rest of the minerals exhibited enhanced hydrophilicity after interaction with the bacteria. The bacteria were also observed to be capable of dissolving calcite, hematite and corundum and biosorbing the dissolved metal ions to varying extents. An excess of polysaccharides could be observed on biotreated calcite, hematite and corundum while the predominance of a protein-based metabolic product was evident on quartz surfaces. The utility of bioprocessing in the beneficiation of the above minerals through bioflotation and bioflocculation is demonstrated. (C) 1997 Elsevier Science Ltd.

New La2CuO4 derivatives La(2-2x)Sr(2x)Cu(1-x)M(x)O(4) (M=Ti, Mn, Fe, or Ru): A study of linear Cu-O-M electronic interaction in two dimensions

Oxides of the general formula La2-2xSr2xCu1-xII,M(x)(IV)O(4) (M = Ti, Mn, Fe, or Ru), crystallizing in the tetragonal K,NIF, structure, have been synthesized. For M=Ti, only the x=0,5 member could be prepared, while for M=Mn and Fe, the composition range is 0 Cu(III)-O-Fe(III) valence degeneracy. Increasing the strontium content at the expense of lanthanum in La2-2xSr2xCu1-xFexO4 for x less than or equal to 0.20 renders the samples metallic but not superconducting. (C) 1997 Academic Press.

Representation of thermodynamic properties of quaternary systems using interaction parameters

Integral excess free energy of a quaternary system has been expressed in terms of the MacLaurin infinite series. The series is subjected to appropriate boundary conditions and each of the derivatives correlated to the corresponding interaction coefficients. The derivation of the partial functions involves extensive summation of various infinite series pertaining to the first order and quaternary parameters to remove any truncational error. The thermodynamic consistency of the derived partials has been established based on the Gibbs-Duhem relations. The equations are used to interpret the thermodynamic properties of the Fe-Cr-Ni-N system.

The effect of temperature on the surface tension and adsorption functions of the Fe-S-O melts - an analysis based on interaction parameters

The present investigation analyses the thermodynamic behaviour of the surfaces and adsorption as a function of temperature and composition in the Fe-S-O melts based on the Butler's equations. The calculated-values of the surface tensions exhibit an elevation or depression depending on the type of the added solute at a concentration which coincides with that already present in the system. Generally, the desorption of the solutes as a function of temperature results in an initial increase followed by a decrease in the values of the surface tension. The observations are analyzed based on the surface interaction parameters which are derived in the present research.

Interaction of A beta peptide (1-40) with amino acid aluminium complexes: relevance to Alzheimer's disease

A beta (39-43 aminoacid residues) is the principal peptide component of amyloid deposits in Alzheimer's disease (AD). A beta peptide is derived from the amyloid precursor protein (APP) in which mutations give rise to many forms of familial AD. Aluminium is reported to play a key role in inducing conformational change in the synthetic beta-amyloid peptide (1-40)from alpha-helix to beta-pleated sheet, leading to aggregation and fibrillar formation. We have studied the interaction of amino acid-Al complexes such as D-Asp-Al and L-Glu-Al with A beta(1-40) in TFE/buffer (70% TFE and 30% H2O v/v pH 6.7) mixture using CD spectroscopy. The interaction of either of these amino acid complexes with A beta(1-40) results in loss of alpha-helical content and the peptide is more unstructured compared to free Al3+ in the solution. Our data strongly support the idea, that the Al3+ in the form of aminoacid-Al complexes is more effective in inducing random coil conformation in the A beta peptide than the free Al3+ present in the solution.

A game theoretical multiple resource interaction approach to resource allocation in an air campaign

In this paper we propose a multiple resource interaction model in a game-theoretical framework to solve resource allocation problems in theater level military campaigns. An air raid campaign using SEAD aircraft and bombers against an enemy target defended by air defense units is considered as the basic platform. Conditions for the existence of saddle point in pure strategies is proved and explicit feedback strategies are obtained for a simplified model with linear attrition function limited by resource availability. An illustrative example demonstrates the key features.

Non-resonant perturbation formula for interaction impedance measurement for a folded-waveguide SWS

The non-resonant perturbation formula for the measurement of interaction impedance of a folded-waveguide slow-wave structure was derived for the relevant electromagnetic field configuration at the axis of the beam-hole of the structure. Efficacy of the theory was benchmarked through virtual measurement using 3D electromagnetic modeling in CST-studio.

Dielectric barrier discharge plasma interaction with the airflow over an airfoil

The effect of various parameters on the velocity of the induced jet produced by a dielectric barrier discharge (DBD) plasma was studied experimentally. The glow discharge was created at atmospheric conditions by using a high voltage RF power supply. Flow visualization and photographic studies of the plasma were performed. The parametric investigation of the characteristics of the plasma show that the width of the plasma in the uniform glow discharge regime was an indication of the velocity induced under stagnant conditions. It was observed that the spanwise overlap of the two electrodes, dielectric thickness, voltage and frequency of the applied voltage are the major parameters that govern the velocity and the extent of plasma in the streamwise direction.

Real-time kinetic analysis of hCG-monoclonal antibody interaction using radiolabeled hCG probe: presence of two forms of Ag-mAb complex as revealed by solid phase dissociation studies

Real-time kinetics of ligand-ligate interaction has predominantly been studied by either fluorescence or surface plasmon resonance based methods. Almost all such studies are based on association between the ligand and the ligate. This paper reports our analysis of dissociation data of monoclonal antibody-antigen (hCG) system using radio-iodinated hCG as a probe and nitrocellulose as a solid support to immobilize mAb. The data was analyzed quantitatively for a one-step and a two-step model. The data fits well into the two-step model. We also found that a fraction of what is bound is non-dissociable (tight-binding portion (TBP)). The TBP was neither an artifact of immobilization nor does it interfere with analysis. It was present when the reaction was carried out in homogeneous solution in liquid phase. The rate constants obtained from the two methods were comparable. The work reported here shows that real-time kinetics of other ligand-ligate interaction can be studied using nitrocellulose as a solid support. (C) 2002 Elsevier Science B.V. All rights reserved.

Amino acid interaction preferences in helical membrane proteins

Membrane proteins are involved in a number of important biological functions. Yet, they are poorly understood from the structure and folding point of view. The external environment being drastically different from that of globular proteins, the intra-protein interactions in membrane proteins are also expected to be different. Hence, statistical potentials representing the features of inter-residue interactions based exclusively on the structures of membrane proteins are much needed. Currently, a reasonable number of structures are available, making it possible to undertake such an analysis on membrane proteins. In this study we have examined the inter-residue interaction propensities of amino acids in the membrane spanning regions of the alpha-helical membrane (HM) proteins. Recently we have shown that valuable information can be obtained on globular proteins by the evaluation of the pair-wise interactions of amino acids by classifying them into different structural environments, based on factors such as the secondary structure or the number of contacts that a residue can make. Here we have explored the possible ways of classifying the intra-protein environment of HM proteins and have developed scoring functions based on different classification schemes. On evaluation of different schemes, we find that the scheme which classifies amino acids to different intra-contact environment is the most promising one. Based on this classification scheme, we also redefine the hydrophobicity scale of amino acids in HM proteins.