Wave-packet continuum discretization method for solving the three-body scattering problem

We generalize the wave-packet continuum discretization method previously developed for the scattering problem to the three-body system. For each asymptotic channel, we construct a basis of three-body wave packets given by square-integrable functions. We show that the projections of the channel resolvents on the subspace of three-body wave packets are determined by diagonal matrices, whose eigenvalues we find explicitly. We express the amplitudes of 2→2 processes explicitly in terms of “wave-packet” finite-dimensional projections of the full resolvent. To illustrate our formalism, we calculate the differential cross section of elastic deuteron scattering on a heavy nucleus above the three-body breakup threshold and the s-wave quartet (n-d)-scattering amplitude. The results of the calculations agree well with the results obtained by other methods. In terms of complexity, the proposed scheme for solving the three-body scattering problem is comparable to solving a similar problem for bound states. __________ Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 150, No. 3, pp. 473–497, March, 2007.     

Estimating the Parameters of the Arrhenius Equation

Estimation of the parameters of the Arrhenius equation often leads to multicollinearity, or, in other words, a degenerate set of equations in the least-squares procedure. This circumstance makes it difficult to estimate the unknown parameters. Simple expedients for model modification are suggested that reduce multicollinearity, thus allowing the parameters to be determined. Simulated and real examples are considered.__________Translated from Kinetika i Kataliz, Vol. 46, No. 3, 2005, pp. 329–332.Original Russian Text Copyright © 2005 by Rodionova, Pomerantsev.     

In-line prediction of drug release profiles for pH-sensitive coated pellets

A new method for the prediction of the drug release profiles during a running pellet coating process from in-line near infrared (NIR) measurements has been developed. The NIR spectra were acquired during a manufacturing process through an immersion probe. These spectra reflect the coating thickness that is inherently connected with the drug release. Pellets sampled at nine process time points from thirteen designed laboratory-scale coating batches were subjected to the dissolution testing. In the case of the pH-sensitive Acryl-EZE coating the drug release kinetics for the acidic medium has a sigmoid form with a pronounced induction period that tends to grow along with the coating thickness. In this work the autocatalytic model adopted from the chemical kinetics has been successfully applied to describe the drug release. A generalized interpretation of the kinetic constants in terms of the process and product parameters has been suggested. A combination of the kinetic model with the multivariate Partial Least Squares (PLS) regression enabled prediction of the release profiles from the process NIR data. The method can be used to monitor the final pellet quality in the course of a coating process.     

Exchange mechanism of dα interaction and vertex constants of <Superscript>6</Superscript>Li

In this work, we use a model for describing the dα interaction in a ⁶Li nucleus, in which the dα nuclear potential is written as the sum of the local folding potential and a nonlocal term originating from the deuteron exchange mechanism and corresponding to a three-deuteron component of the ⁶Li wave function. This model was used to calculate the nuclear vertex constants and the corresponding asymptotic normalization coefficients of ⁶Li in the dα channel. Both values L = 0 and L = 2 of relative dα orbital angular momentum L were considered. Calculations were performed with and without allowance for the Coulomb dα interaction.     

Dibaryon concept for nuclear force and its experimental evidence

Numerous theoretical and experimental arguments are presented in favor of the generation of intermediate σ-dressed dibaryon in NN interaction at middle and short distances. We argue that this intermediate dibaryon can be responsible for the strong middle-range attraction and the short-distance repulsion in the NN interaction, and also for the short-range correlations in nuclei. The suggested mechanism for the σ dressing of the dibaryon is identical to that which explains the Roper-resonance structure, its dominant decay modes, and its extraordinary low mass. A similar transformation mechanism from the glue to the scalar field was discovered in J/ψ decays. The new experimental data on 2π production in the scalar-isoscalar channel in pn and pd collisions and in, particular, the very recent data on γγ correlations in pC and dC scattering in the GeV region seems to corroborate the existence of the σ-dressed dibaryon in two- and three-nucleon interactions.     

Kinetic Model of Diclofenac Degradation Developed Using Multivariate Curve Resolution Method

This study presents the kinetic modeling of the natural long-term aging of the pharmaceutical substance as well as the intact tablets of Diclofenac. Datasets are collections of near-infrared spectra acquired from the intact tablets packed in plastic blisters and the spectra of the pure substance. Fresh samples and samples at different stages of degradation are analyzed. No methods of accelerated aging were applied. Multi-step application of MCR-ALS in its soft version followed by the kinetic modeling of the results helps to propose a generic degradation mechanism; which includes: a global kinetic model; approximations of the NIR spectra of the intermediate and product; rough estimates of rate constants. We study tablets in blister packs; exactly as they are presented in pharmacies; and this is important from a practical point of view.