Molecular imprinting polymerization by Fenton reaction

The aim of this study is the preparation of molecularly imprinted polymers by employing a redox pair as initiator system. Bulk molecularly imprinted polymers were synthesized by using Fenton reagents as initiator system. Theophylline, methacrylic acid, and ethylene glycol dimethacrylate were employed as model template, functional monomer, and crosslinking agent, respectively. Conventional imprinted polymers were also prepared by using 2,2′-azoisobutyronitrile in order to evaluate the efficiency of the proposed initiator system. Redox molecularly imprinted polymers and conventional molecularly imprinted polymers were characterized by water uptake measurement, while the imprinting effect of synthesized polymers were evaluated by performing binding experiments in organic (acetonitrile) and in water (buffered water solution at pH = 7.4) media.     

Mechanism of the Asymmetric Autocatalytic Soai Reaction Studied by Density Functional Theory

The mechanism of the Soai reaction has been thoroughly investigated at the M05‐2X/6‐31G(d) level of theory, by considering ten energetically distinct paths. The study indicates the fully enantioselective catalytic cycle of the homochiral dimers to be the dominant mechanism. Two other catalytic cycles are shown to both be important for correct understanding of the Soai reaction. These are the catalytic cycle of the heterochiral dimer and the non‐enantioselective catalytic cycle of the homochiral dimers. The former has been proved to be not really competitive with the principal cycle, as required for the Soai reaction to manifest chiral amplification, whereas the latter, which is only slightly competitive with the principal one, nicely explains the experimental enantioselectivity observed in the reaction of 2‐methylpyrimidine‐5‐carbaldehyde. The study has also evidenced the inadequacy of the B3LYP functional for mechanistic investigations of the Soai reaction.     

Formation of Superoxo Species by Interaction of O2 with Na Atoms Deposited on MgO Powders: A Combined Continuous‐Wave EPR (CW‐EPR), Hyperfine Sublevel Correlation (HYSCORE) and DFT Study

The formation of O₂^? radical anions by contact of O₂ molecules with a Na pre‐covered MgO surface is studied by a combined EPR and quantum chemical approach. Na atoms deposited on polycrystalline MgO samples are brought into contact with O₂. The typical EPR signal of isolated Na atoms disappears when the reaction with O₂ takes place and new paramagnetic species are observed, which are attributed to different surface‐stabilised O₂^? radicals. Hyperfine sublevel correlation (HYSCORE) spectroscopy allows the superhyperfine interaction tensor of O₂^?Na⁺ species to be determined, demonstrating the direct coordination of the O₂^? adsorbate to surface Na⁺ cations. DFT calculations enable the structural details of the formed species to be determined. Matrix‐isolated alkali superoxides are used as a standard to enable comparison of the formed species, revealing important and unexpected contributions of the MgO matrix in determining the electronic structure of the surface‐stabilised Na⁺? O₂^? complexes.     

Indirect control of corporations

We consider situations in which shares ofn firms are held by the samen firms as well as by individual investors. The probelm is to determine the actual control of the firms by the individual investors.In part 1, we develop the mathematical model, and explain the basic notions of clutter and of effective reduction. In part 2 we introduce the idea of a consistent reduction, prove existence of such, and show the relation between consistent and effective reductions. In part 3 we introduce multilinear extensions and show how these can be used to calculate the effective and consistent reductions. Several examples are worked out in detail.     

Unexpected high ordering of a [60]Fullerene nitroxide in the nematic phase of 4-4'-azoxyanisole

A nitroxide [60]fullerene adduct containing a pyrrolidine-1-oxyl group has been synthesized. Its orientational order in the nematic phase of the liquid crystal solvent 4,4'-azoxyanisole (PAA) has been measured from the variation of the EPR spectral parameters on passing from the isotropic to the nematic phase. Highly resolved EPR lines allow for precise evaluation of the shifts of the g , a N and a H values. Since the g and the hyperfine tensors are known, the order matrix could be obtained. This is compared with the one calculated with a theoretical model based on short range solute-solvent interactions, which predicts a considerable degree of orientation of the molecular axes, despite the almost spherical shape of the molecule. The agreement with experimental findings is quite good and it is further improved if a bent structure of the pyrrolidine ring is taken into account.     

Ulrich bundles on blowing up (and an erratum)

We deal with the behaviour of Ulrich bundles with respect to push-forward and pull-back via blowing-up points. We also correct a wrong statement in [11].     

Numerical method for evaluating the response of rotating shafts to excitation

Summary To obtain an accurate forecast of the behaviour of a shaft rotating on lubricated bearings under excitation, an adequate model must be introduced to represent the response of the bearings; a linear model of the response is sufficient for many practical purposes, but allowance must be made for the variation of film stiffness, cross-stiffness, etc., with direction. As a consequence the shaft must be assumed to move in an elliptical, rather than circular, whirl. The phenomenon which must be analyzed is thus more complex than that envisaged in König's study, for instance, see Ref. [2]. We show here nevertheless that it is possible to devise an appropriate generalization of the Myklestad-Holzer method, so that the problem can be solved by matrix manipulations.

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Sommario Per prevedere con accuratezza l'ampiezza di vibrazione di un asse lievemente sbilanciato che ruoti su supporti lubrificati è necessario rappresentare adeguatamente il comportamento dei supporti stessi.Un modello lineare è sufficiente per molti scopi pratici purchè si tenga conto che la risposta non ha generalmente simmetria assiale. Di conseguenza è necessario poter considerare casi nei quali la traiettoria di ciascun punto dell'asse è ellittica piuttosto che circolare. Perciò si richiede una generalizzazione del metodo di König; generalizzazione che è indicata nel presente lavoro. Il metodo proposto fa però ancora uso di semplici operazioni matriciali.

     

Anelastic deformation as an internal parameter

Summary We consider continua for which a local configuration exists, whence the instantaneous elastic strain must be measured. Relations involving stress, strain and strain rate are indicated, which are compatible with objectivity and with the Clausius-Duhem inequality. Definitions and a theorem of Coleman and Gurtin regarding continua with internal parameters are adapted to advantage.

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Sommario Si studiano continui per i quali esiste una configurazione locale (variabile nel tempo) e a partire dalla quale va misurata istante per istante la deformazione elastica. Si specificano le relazioni permesse dalla disguaglianza di Clausius Duhem e dal principio di obbiettività e si adattano al caso alcune definizioni ed un teorema di Coleman e Gurtin sui continui con parametri interni.

     

Synthesis of hydrophilic microspheres with LCST close to body temperature for controlled dual‐sensitive drug release

Novel stimuli‐responsive hydrophilic microspheres were prepared by free radical polymerization of hydroxyethyl methacrylate (HEMA) and methacrylic acid (MA), as hydrophilic monomers, and N‐isopropylacrylamide (NIPAAm) and N,N′‐ethylenebisacrylamide (EBA), as thermo‐sensitive monomer and crosslinker, respectively. Hydrophilic comonomers were introduced in the macromolecular network to synthesize materials with tunable thermal behavior. In addition, by introducing in the polymerization feed both a hydrophilic and a pH‐sensitive monomer, such as MA, dual stimuli‐responsive (pH and temperature) hydrogels were synthesized. The incorporation of monomers in the network was confirmed by infrared spectroscopy, while the network density and the shape of hydrogels was found to strictly depend on the concentration of monomers in the polymerization feed. Thermal analyses showed negative thermo‐responsive behavior with pronounced water affinity of microspheres at a temperature lower than lower critical solution temperature (LCST). In our experiment, the LCST values of the hydrogels were in the range 34.6–37.5°C, close to the body temperature, and the amount of hydrophilic moieties in the polymeric network allows to collect shrinking/swelling transition temperatures higher than the LCST of NIPAAm homopolymers. In order to test the preformed materials as drug carriers, diclofenac diethylammonium salt (DDA) was chosen and drug entrapment percent was determined. Drug release profiles, in media at different temperature and pH, depend on hydrogels crosslinking degree and drug–bead interactions. By using semi‐empirical equations, the release mechanism was extensively studied and the diffusional contribute was evaluated. Copyright © 2010 John Wiley & Sons, Ltd.