Study of the Ternary Complex Formation between Vanadium(III)-Cysteine and Small Blood Serum Bioligands

The complex species formed between vanadium(III) cysteine and small blood serum bioligands: lactic, oxalic, citric and phosphoric acids were studied in aqueous solution by means of electromotive force measurements, Emf(H), at 25 °C and 3.0 mol⋅dm⁻³ KCl as the ionic medium. The ternary complexes were studied by potentiometric measurements and the data analyzed using the least-squares computational program LETAGROP to obtain the respective stability constants and stoichiometric coefficients. The UV-Vis spectrophotometric measurements were done in order to make a qualitative characterization of the complexes formed in aqueous solution.     

Noise-controlled self-replicating patterns

We present novel numerical evidence of spot self-replication controlled by noise in a simple autocatalytic reaction-diffusion system. The system dynamics exhibits a noise controlled transition from stripe growth to spot replication. The growth kinetics is also controlled by noise, and there is an optimal noise intensity for which the multiplication rate of spots is maximal. For larger noise intensities, the spots become unstable and the system is attracted by the trivial steady state. Some of the effects are reminiscent of both polymer chain and cell colony formation in random environments.     

Solving linear programs with finite precision: I. Condition numbers and random programs

We define a condition number (A,b,c) for a linear program min x s.t. Ax=b,x0 and give two characterizations via distances to degeneracy and singularity. We also give bounds for the expected value, as well as for higher moments, of log (A,b,c) when the entries of A,b and c are i.i.d. random variables with normal distribution. This work has been substantially funded by a grant from the Research Grants Council of the Hong Kong SAR (project number CityU 1085/02P)     

Algebraic Decay in Hierarchical Graphs

We study the algebraic decay of the survival probability in open hierarchical graphs. We present a model of a persistent random walk on a hierarchical graph and study the spectral properties of the Frobenius–Perron operator. Using a perturbative scheme, we derive the exponent of the classical algebraic decay in terms of two parameters of the model. One parameter defines the geometrical relation between the length scales on the graph, and the other relates to the probabilities for the random walker to go from one level of the hierarchy to another. The scattering resonances of the corresponding hierarchical quantum graphs are also studied. The width distribution shows the scaling behavior P()1/.     

Numerical methods for inferring phylogenies

Molecular phylogenies describe the study of evolution relationships between living beings, protein and genetic sequences and other molecular taxons. In recent years there has been increased interest in producing large and accurate phylogenies trees using some numerical computational methods approach. One class of molecular phylogenies is the distance matrices method, with the matrix whose entries represent the distinctions between the taxons under study. To construct large and accurate trees for a large number of taxons, the computational processing increases and parallel computing can be helpful. So far we have tested some methods to solve the linear systems, being driven to important conclusions, like which is the best tested method, and having also reached some questions about communication. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

A unified approach to the asymptotic almost-equivalence of evolution systems without Lipschitz conditions

We study the asymptotic behavior of almost-orbits of evolution systems in Banach spaces without any continuity assumptions on either the space or the time dependence. We establish, in a unified framework, standard convergence, ergodic convergence and almost-convergence of almost-orbits for both the weak and the strong topologies on the basis of the analogue behavior of orbits.     

Synthesis of 6-bromo-2-arylindoles using 2-iodobenzoic acid as precursor

The synthesis of 6-bromo-2-arylindoles starting from readily available 2-iodobenzoic acid is presented. Regioselective bromination of the latter was followed by Curtius rearrangement and trapping of the isocyanate with benzyl alcohol led to the benzyl carbamate of 2-iodo-5-bromoaniline. Chemoselective Sonogashira coupling of this compound with arylacetylenes followed by TBAF induced 5-endo-dig cyclization gave the desired bromo indoles. The method allows selective introduction of a bromine atom at the indole C-6 position.     

Predicting thermophysical properties of biodiesel fuel blends using the SAFT-VR approach

Modeling of thermophysical properties and phase equilibria of long-chain methylesters mixtures are presented, using the SAFT-VR approach for mixtures. Molecules are represented as chains of spherical segments that can associate due to the presence of short-ranged attractive sites, using previous molecular parameters obtained for pure fatty acid methyl esters. These attractive sites as well as the intermolecular interactions between monomers segments are modeled via variable-ranged square-well potentials. The cross-energy binary-interaction parameter of the extended Berthelot combining rule was fitted to liquid densities and speed of sound. Very good predictions are obtained for isochoric heat capacities and for binary and ternary phase diagrams.     

Complexation Equilibria and Determination of Stability Constants of Binary and Ternary Nickel(II) Complexes with Amino Acids (Glycine, α-Alanine, β-Alanine and Proline) and Dipicolinic Acid as Ligands

In this paper we report the formation of binary and ternary nickel(II) complexes involving dipicolinic acid (H₂Dipic) as the primary ligand and some selected amino acids {glycine (HGly), ?-alanine (H?-Ala), ??-alanine (H??-Ala) and proline (HPro)} as secondary ligands. These complexes were studied at 25?°C by means of electromotive force measurements, emf(H), using 1.0?mol?dm^?3 NaCl as the ionic medium. The experimental data were analyzed by means of the computational least-squares program LETAGROP, taking into account hydrolysis of the nickel(II) cation and the acid/base reactions of the ligands whose equilibrium constants were kept fixed during the analysis. In the study of the binary nickel(II)?Camino acids systems the species [NiL]⁺, NiL₂ and [NiL₃]^? were observed, and in the case of the ternary nickel(II)?Cdipicolinic acid?Camino acids systems the complexes Ni(Dipic)HL, [Ni(Dipic)L] ^? and [Ni(Dipic)L(OH)]^2? were observed. The respective stability constants were determined, and the species distribution diagrams, as a function of pH, are briefly discussed.     

Kinetic Modeling of Fructooligosaccharide Production Using Aspergillus oryzae N74

In this study, the kinetic for the bioconversion of sucrose to fructooligosaccharides (FOS) by free cells of Aspergillus oryzae N74 was modeled. In addition, the effect of immobilized glucose isomerase (IGI) on FOS production yield was evaluated and considered in the kinetic model. The selected kinetic models were based on a proposed reaction mechanism described by elementary rate equations and modified Michaelis?CMenten kinetic equations. The use of IGI allowed to increase the FOS production yield (FOS_Yield) and to decrease the glucose/fructose (G/F) ratio. At shake flask scale, the FOS_Yield was increased in 4.7?% (final yield 58.3?%), while the G/F ratio was reduced 6.2-fold. At bench scale, the FOS_Yield was increased in 2.2?% (final yield 57.3?%), while the G/F ratio was reduced 4.5-fold. The elementary rate equation model was the one that best adjusted experimental data for FOS production using either the fungus biomass or the mixture fungus biomass?CIGI, with an overall average percentage error of 7.2. Despite that FOS production yield was not highly improved by the presence of IGI in the reaction mixture, it favored the reduction of residual glucose in the mixture, avoiding the loss of material owe to glucose transformation to fructose that can be used in situ for FOS production by the fructosyltransferase.