Degree of Flocculation and Interparticles Charges of Conditioned Municipal Activated Sludge using Mixed Polymers

The present research work focuses on a new conditioning and flocculation mechanism of municipal fresh activated sludge using a dual polymer system combining cationic and anionic polyelectrolytes. Various pairs of three different types of polyelectrolytes, low molecular weight cationic polyacrylamide (CPAM-10), high molecular weight cationic polyacrylamide (CPAM-80) and an anionic polyacrylamide (APAM-30), were selected, being used either individually or as cationic-anionic pairs. The results of use of the dual systems indicated that using mixed polymers for conditioning gave lower turbidity with better settling when compared to that of using individual pure polymers. The mixed polymers improved the sludge volume index (SVI) by 62%. The zeta potentials of the supernatant and solid-like samples of conditioned activated sludge were measured. Slight increases in zeta potential, from –12 to –9, of the mixed polymers for all supernatants were observed. On the other hand, zeta measurements showed that the sludge solid-like particles retained their negative charges despite the addition of the individual cationic polymers in the mixture. This phenomenon was explained in terms of the addition of the polyelectrolytes attracting, primarily, the carboxylic groups of the fine suspended sludge particles, while hydrogen bonds between the larger sludge particles resulted in attraction in accordance with the Van der Waals mechanism, and both attractions caused an immediate dewatering that led to flocculation, but with low compactness. As a result of retaining negative charges on the large sludge particles, dissolved metals were partially attracted, causing reduction in conductivities of the supernatants of 10% to 15% for all pairs. Rheological tests showed that the formed flocs had low shear stress resistances, ranging between 0.2 and 0.4 Pa, and weak flocs strength.     

An ab initio and density functional theory study of keto-enol equilibria of hydroxycyclopropenone in gas and aqueous solution phase

Keto-enol tautomerism in hydroxycyclopropenone (2-hydroxy-2-cyclopropen-1-one) has been studied using ab initio methods, the B3LYP functional of density functional theory, as well as complete basis set (CBS-QB3 and CBS-APNO) and G3 methods. Absolute and relative energies were calculated with each of the methods, whereas computations of geometries and harmonic frequencies for hydroxycyclopropenone and 1,2-cyclopropanedione were computed in the gas phase but were limited to HF, MP2 and CCSD levels of theory, and the B3LYP functional, in combination with the 6-31++G** basis set. Using the MP2/6-31++G** gas phase optimized structure, each species was then optimized fully in aqueous solution by employing the polarizable continuum model (PCM) self-consistent reaction field approach, in which HF, MP2 and B3LYP levels of theory were utilized, with the same 6-31++G** basis set. In both gas and aqueous solution phases, the keto form is higher in energy for all of the model chemistries considered. The presence of the solvent, however, is found to have very little effect on the bond lengths, angles and harmonic frequencies. From the B3LYP/6-31++G** Gibbs free energy, the keto-enol tautomeric equilibrium constant for 2-hydroxy-2-cyclopropen-1-one <==> 1,2-cyclopropanedione is computed to be K(T)(gas) = 2.35 x 10(-6), K(T)(aq) = 5.61 x 10(-14). It is concluded that the enol form is overwhelmingly predominant in both environments, with the effect of the solvent shifting the direction of equilibrium even more strongly in the favor of hydroxycyclopropenone. The almost exclusive nature of this species is attributed to stabilization resulting from aromaticity. Confirmation is provided by comparison of the simulated vibrational spectra of hydroxycyclopropenone with the measured infrared spectrum in an argon matrix.     

A U(3) nonet scheme for leptons

Introducing six new heavy leptons, we construct a U(3) scheme for leptons. The leptonic U(3) is exactly parallel to the hadronic U(3). One may also introduce quark-like leptonic triplets. A “natural” value of 60° emerges for the mixing angle with m_w = 53 GeV in a theory of weak and electromagnetic interaction based on this U(3) symmetry. There are no neutral ΔS_l = 0 neutrino currents.     

Quantum dynamics calculations using symmetrized, orthogonal Weyl-Heisenberg wavelets with a phase space truncation scheme. III. Representations and calculations

In a previous paper [J. Theo. Comput. Chem. 2, 65 (2003)], one of the authors (B.P.) presented a method for solving the multidimensional Schrodinger equation, using modified Wilson-Daubechies wavelets, and a simple phase space truncation scheme. Unprecedented numerical efficiency was achieved, enabling a ten-dimensional calculation of nearly 600 eigenvalues to be performed using direct matrix diagonalization techniques. In a second paper [J. Chem. Phys. 121, 1690 (2004)], and in this paper, we extend and elaborate upon the previous work in several important ways. The second paper focuses on construction and optimization of the wavelength functions, from theoretical and numerical viewpoints, and also examines their localization. This paper deals with their use in representations and eigenproblem calculations, which are extended to 15-dimensional systems. Even higher dimensionalities are possible using more sophisticated linear algebra techniques. This approach is ideally suited to rovibrational spectroscopy applications, but can be used in any context where differential equations are involved.     

Algebraic methods for the Natanzon potentials

It is shown that the Schrödinger equation can be solved by means of spectrum-generating algebra techniques for the most general class of Natanzon potentials based on the SO(2, 1) algebra. This paper describes in detail thelinear spectrum generating algebra method which is then applied to solve the Natanzon confluent potentials, and it is extended to one example with spin-orbit coupling. Further, the method is used to explain in detail how to find the energy spectrum for the Dirac equation with a Coulomb potential. Afterwards thequadratic spectrum generation algebra method is presented, and it is used to solve the most general hypergeometric Natanzon potential: The bound state problem and the corresponding wave functions are given. A simple example further illustrates the use of the quadratic method.Partially supported by grant FONDECYT 90-1240.     

Revisiting non-perturbative effects in the jet broadenings

We show that taking into account the interplay between perturbative and non-perturbative effects, the power-suppressed shift to the broadening distributions becomes B dependent, and the non-perturbative contribution to the mean values becomes proportional to . The new theoretical treatment greatly improves the consistency of the phenomenology with the notion of the universality of confinement effects in jet shapes.This work was supported in part by the EU Fourth Framework Programme ‘Training and Mobility of Researchers’, Network ‘Quantum Chromodynamics and the Deep Structure of Elementary Particles’, contract FMRX-CT98-0194 (DG 12-MIHT).     

Estimation of parameter matrices based on measured data

Finite element structural updating based on measured data may inherent significant errors due to uncertainties in the updated physical parameter matrices. This study presents analytical equations to estimate the change in the physical parameter matrices based on the measured modal data of dynamic systems and the measured displacement data of static systems. The equations for the parameter estimation are derived by minimizing cost functions in the satisfaction of the eigenvalue equation, the mode shape orthogonality requirements for the dynamic system, and the satisfaction of the measured displacement data for the static systems. The proposed method utilizes the Moore–Penrose inverse for the inverse of the rectangular matrices without using Lagrange multipliers. Comparing the analytical results with Berman & Nagy’s method and Yang & Chen’s method, this study demonstrates that the derived equations take simpler forms and produce more accurate results. The proposed method can be widely utilized in predicting static or dynamic parameter matrices for the design and analysis of any structure.     

Characterization of Volatile Components of Chassalia chartacea and Its Acetylcholinesterase Inhibitory Activity

Chemistry of Natural Compounds -