Design and Characterization of Maltoheptaose-b-Polystyrene Nanoparticles,as a Potential New Nanocarrier for Oral Delivery of Tamoxifen

Tamoxifen citrate (TMC), a non-steroidal antiestrogen drug used for the treatment of breast cancer, was loaded in a block copolymer of maltoheptaose-b-polystyrene (MH-b-PS) nanoparticles, a potential drug delivery system to optimize oral chemotherapy. The nanoparticles were obtained from self-assembly of MH-b-PS using the standard and reverse nanoprecipitation methods. The MH-b-PS@TMC nanoparticles were characterized by their physicochemical properties, morphology, drug loading and encapsulation efficiency, and release kinetic profile in simulated intestinal fluid (pH 7.4). Finally, their cytotoxicity towards the human breast carcinoma MCF-7 cell line was assessed. The standard nanoprecipitation method proved to be more efficient than reverse nanoprecipitation to produce nanoparticles with small size and narrow particle size distribution. Moreover, tamoxifen-loaded nanoparticles displayed spherical morphology, a positive zeta potential and high drug content (238.6 ± 6.8 µg mL⁻¹) and encapsulation efficiency (80.9 ± 0.4 %). In vitro drug release kinetics showed a burst release at early time points, followed by a sustained release profile controlled by diffusion. MH-b-PS@TMC nanoparticles showed higher cytotoxicity towards MCF-7 cells than free tamoxifen citrate, confirming their effectiveness as a delivery system for administration of lipophilic anticancer drugs.     

R(30) rectangular rings in 2,5‐dioxopiperazine‐1,4‐di­acetic acid

Molecules of the title 2,5‐dioxopiperazinedione derivative, C₈H₁₀N₂O₆, occupy centres of symmetry in the crystal structure. The six‐membered ring has an almost planar conformation, with the substituent on nitrogen nearly perpendicular to the ring. The ideal geometry of the isolated mol­ecule, as determined by ab initio HF–LCAO quantum‐mechanical calculations, is slightly more puckered than that observed in the solid state. In the crystal structure, a strong hydrogen bond joins neighbouring mol­ecules, thus forming a network of rectangular (30) rings.     

Quantum-mechanical and molecular mechanics conformational analysis of 1,5-cyclooctadiene

The 1,5-cyclooctadiene (COD) molecule can easily form complexes with transition metals with the molecular structure of various of these complexes being proposed with the aid of X-ray diffraction methods. The fact that the complexes exhibit weak metal-COD bonds makes it very important in inorganic synthesis and catalysis. In this work the potential energy surface (PES) for the COD molecule was comprehensively investigated: first with molecular mechanics (using the MM3 force field); and, in a second stage, at the ab initio Hartree-Fock level of theory employing the 3-21G^*, 6-31G, and 6-31G^* basis sets and also including electron correlation effects at the Moller-Plesset second-order perturbation theory level. This work revealed that there are three distinct conformers of the COD molecule with the predicted lowest energy conformation being in agreement with the proposed structure based on experimental electron diffraction data. © 1997 by John Wiley & Sons, Inc.     

Modelling the Vapor–Liquid Equilibrium of Polymer Solutions Using a Cubic Equation of State

This work presents the vapor–liquid equilibrium calculations in an isothermal flash, applied to polymer solutions, using the Peng–Robinson cubic equation of state modified by Stryjek–Vera, and the mixing rule introduced by Wong–Sandler. This rule allows combining the rigid lattice thermodynamic model of Flory–Huggins to the Peng–Robinson–Stryjek–Vera equation of state. As the Gibbs free energy must be minimum in the equilibrium state, a stochastic optimization method, the simulated annealing algorithm, was used to find out the extreme of this thermodynamic potential.     

New blow-up criteria for local solutions of the 3D generalized MHD equations in Lei–Lin–Gevrey spaces

This paper determines the existence of a unique local solution for the 3D generalized magnetohydrodynamics equations. In order to be more precise, our solution is obtained by involving Lei–Lin–Gevrey spaces as well as Lei–Lin spaces. Furthermore, we present five new blow-up criteria for this same system when the maximal time of existence is finite. It is important to point out that one of these criteria is obtained by assuming fractional Laplacians with equal powers.