Component-Mode Synthesis Method Variants in the Dynamics of Coupled Structures

The component-mode synthesis method is usually adopted in order to reduce the number of degrees-of-freedom of structures composed of two or more substructures without loosing the main physical characteristics of the whole structure. Many approaches of this method have been proposed in the literature. These approaches differ from each other for the boundary conditions which are imposed at the interface of the two substructures. In this paper four variants of interface boundary conditions are examined. For each set of conditions a suitable coordinate transformation, compatible with the conditions at the boundary degrees-of-freedom between the two substructures, is presented. Moreover, in the numerical applications a comparison between the four component-mode synthesis variants here proposed with respect to the same variants proposed in the literature is presented. The better accuracy of the proposed approach is shown.     

Enantioselective Cytotoxicity of Chiral Diphosphine Ruthenium(II) Complexes Against Cancer Cells

The chiral cationic complex [Ru(η¹-OAc)(CO)((R,R)-Skewphos)(phen)]OAc ( 2 ^R ), isolated from reaction of [Ru(η¹-OAc)(η²-OAc)(R,R)-Skewphos)(CO)] ( 1 ^R ) with phen, reacts with NaOPiv and KSAc affording [RuX(CO)((R,R)-Skewphos)(phen)]Y (X=Y=OPiv 3 ^R ; X=SAc, Y=OAc 4 ^R ). The corresponding enantiomers 2 ^S - 4 ^S have been obtained from 1 ^S containing (S,S)-Skewphos. Reaction of 2 ^R and 2 ^S with (S)-cysteine and NaPF₆ at pH=9 gives the diastereoisomers [Ru((S)-Cys)(CO)(PP)(phen)]PF₆ (PP=(R,R)-Skewphos 2 ^R -Cys; (S,S)-Skewphos 2 ^S -Cys). The DFT energetic profile for 2 ^R with (S)-cysteine in H₂O indicates that aquo and hydroxo species are involved in formation of 2 ^R -Cys. The stability of the ruthenium complexes in 0.9 % w/v NaCl solution, PBS and complete DMEM medium, as well as their n-octanol/water partition coefficient (logP), have been evaluated. The chiral complexes show high cytotoxic activity against SW1736, 8505 C, HCT-116 and A549 cell lines with EC₅₀ values of 2.8–0.04 μM. The (R,R)-Skewphos derivatives show higher cytotoxicity compared to their enantiomers, 4 ^R (EC₅₀=0.04 μM) being 14 times more cytotoxic than 4 ^S against the anaplastic thyroid cancer 8505 C cell line.     

A mathematical model of anorexia and bulimia

In this paper, we propose a mathematical model to study the dynamics of anorexic and bulimic populations. The model proposed takes into account, among other things, the effects of peers' influence, media influence, and education. We prove the existence of three possible equilibria that without media influences are disease‐free, bulimic‐endemic, and endemic. Neglecting media and education effects, we investigate the stability of such equilibria, and we prove that under the influence of media, only one of such equilibria persists and becomes a global attractor. Which of the three equilibria becomes global attractor depends on the other parameters. Copyright © 2014 John Wiley & Sons, Ltd.     

On the Ekman Equations for Ocean Currents Driven by a Stochastic Wind

The basic assumptions for the depth-dependent Ekman equations are presented. An analysis of three wind stress time series, from different geographical locations, is performed: The results lead to interpret the wind stress as a stochastic process, with components fluctuating with deterministic frequencies. The stochastic equations coupling wind stress and ocean currents are formulated; their solutions are stochastically bounded. Results of numerical simulations are given to show the main behaviors of the system.     

Antioxidant and spectroscopic studies of crosslinked polymers synthesized by grafting polymerization of ferulic acid

A novel, simple synthetic strategy for the preparation of crosslinked polymers with significant antioxidant properties is proposed. Ferulic acid (FA), a well‐known antioxidant compound, due to its reactivity toward free radical process, was inserted into a polymeric network with methacrylic acid (MAA) and ethylene glycole dimethacrylate acting as comonomer and crosslinker, respectively. All the reactants were simultaneously mixed in the polymerization feed and one‐pot radical reaction was carried out. Irregular microparticles were prepared by bulk polymerization and microspheres by precipitation polymerization. The materials were characterized by nuclear magnetic resonance–magic angle spinning (NMR‐MAS) studies, to verify effective FA insertion into polymeric networks, and by morphological, dimensional analyses, and water absorption measurement to study their superficial and swelling properties, respectively. Antioxidant properties of materials were evaluated by linoleic acid emulsion system–thiocyanate assay, determination of scavenging activity on DPPH radicals, determination of available phenolic groups in polymeric matrices, and determination of total antioxidant capacity. Copyright © 2009 John Wiley & Sons, Ltd.     

On the molecular origin of cold denaturation of globular proteins

A polypeptide chain can adopt very different conformations, a fundamental distinguishing feature of which is the water accessible surface area, WASA, that is a measure of the layer around the polypeptide chain where the center of water molecules cannot physically enter, generating a solvent-excluded volume effect. The large WASA decrease associated with the folding of a globular protein leads to a large decrease in the solvent-excluded volume, and so to a large increase in the configurational/translational freedom of water molecules. The latter is a quantity that depends upon temperature. Simple calculations over the -30 to 150 °C temperature range, where liquid water can exist at 1 atm, show that such a gain decreases significantly on lowering the temperature below 0 °C, paralleling the decrease in liquid water density. There will be a temperature where the destabilizing contribution of the polypeptide chain conformational entropy exactly matches the stabilizing contribution of the water configurational/translational entropy, leading to cold denaturation.     

Ground states of simple bodies that may undergo brittle fractures

Equilibrium states of elastic-brittle solids that may suffer nucleation of cracks in finite deformation setting are analyzed. Crack patterns are described in terms of appropriate Radon measures, namely curvature varifolds with boundary. A new form of the energy is presented: it includes terms associated with the curvature of margins and tips of possible cracks. Existence of minima of the energy is established in classes of pairs of deformation and families of varifolds. Configurational balances in weak form are determined with reference to generic curvature varifolds with boundary. They include non-standard terms associated with the curvatures involved in the energy. Pointwise balances of configurational actions are also evaluated in a special case: new pointwise balances at the tips and along the margins of the crack pattern emerge.     

Sequestration of some biogenic amines and poly(allyl)amine by high molecular weight polycarboxylic ligands in aqueous solution

The interactions of two high molecular weight polycarboxylic ligands [polyacrylic-co-maleic, MW = 70 kDa, and poly(methyl vinyl ether-co-maleic acid), MW = 15 kDa] with some polyamines [1,4-diaminobutane (or putrescine), histamine and poly(allyl)amine, MW = 15 kDa] were studied, at t = 25 °C and at low ionic strength (I = 0.015 mol L^? 1) by potentiometric measurements. For all investigated systems, the formation of (am)(L)H_i species was found (am = amine, L = polycarboxylic ligand, i = 1…4); the stability of polyammonium–polycarboxylate complexes is fairly high and the formation percentage of most species reaches ～ 90% in the experimental conditions (mmolar concentration of reactants). The dependence on temperature and ionic strength of the stability of polyamine–polycarboxylate species was studied using some semiempirical equations and enthalpy data for the protonation of both components. The sequestering ability of polyelectrolytes towards amines was modeled by a sigmoid Boltzman type equation and was defined by calculating the parameter pL₅₀ (the total ligand concentration, as ? log C_L, able to bind 50% of cation); this parameter gives an objective representation of this ability. The dependence of pL₅₀ on pH, ionic strength and temperature was studied too.     

A Density Functional Theory Study of Poly (vinyl chloride) (PVC) Free Radical Polymerization

Summary: Quantum chemistry was applied to the free radical polymerization of Vinyl Chloride with the aim of elucidating the reaction kinetics and especially the formation of structural defects and low molecular weight polymer. The radical reactions were studied using the Density Functional Theory. All calculations were performed with B3LYP functionals and in particular the 6-31G(d,p) basis set was selected to evaluate the exchange and correlation energies. The computational method was first validated by predicting the rate constant of the propagation step and comparing the calculated values to experimental ones. Then intramolecular chain transfer, β-scission and branching reactions were also investigated, due to their direct connection with the production of defects in the growing chains. A comparison of the evaluated kinetic constants of such secondary reactions with other computational evaluations and experimental data was finally made.