Density-gradient analysis for density functional theory: Application to atoms

We present an analysis of local or semilocal density functionals for the exchange-correlation energy by decomposing them into their gradients r_s (local Seitz radius), ζ (relative spin polarization), and s (reduced density gradient). We explain the numerical method pertaining to this kind of analysis and present results for a few atoms and ions. The atomic shell structure is prominent, and only the ranges 0 < r_s < 10 and 0 < s < 3 are important. The low-density and large-gradient domains, where the approximations for the exchange-correlation energy are least trustworthy, have very little weight. © 1997 John Wiley & Sons, Inc.     

On conservation of energy and kinematic compatibility in dynamics of nonlinear velocity-based three-dimensional beams

Nonlinear Dynamics - In this paper, we present an original energy-preserving numerical formulation for velocity-based geometrically exact three-dimensional beams. We employ the algebra of...     

Site–site interactions in a polymer matrix: The effect of polymer backbone structure on the transformation of crosslinked resins with substituted hydrazines

Crosslinked chloromethylated polystyrene ( 1 ) and crosslinked copoly(styrene-p-nitro-phenylacrylate) ( 3 ) readily reacted with 1,1-dimethylhydrazine, but the course of the reaction was strongly dependent on the structure of the backbone. Monofunctionalization was observed with chloromethylated polystyrene ( 1 ) giving the 1,1,1-dimethylhydrazinium chloride derivative ( 2 ), while high degree of additional crosslinking took place with crosslinked copoly(styrene-p-nitrophenylacrylate) ( 3 ), and additional crosslinking was also observed in functionalization with N-aminopiperidine and N-aminomorpholine. The additional crosslinking suggested a higher backbone mobility in acrylate beads ( 3 ) compared to chloromethylated polystyrene ( 1 ). The type of transformation and the degree of additional crosslinking also depended on the starting crosslinking of copoly(styrene-p-nitrophenylacrylate) ( 3; 3a , 2% DVB; 3b , 4% DVB; 3c , 10% DVB). Replacement of p-nitrophenol groups in copoly(styrene-p-nitrophenylacrylate) ( 3 ) with hydrazino units resulted in enhanced swelling abilities of the hydrazine derivatives ( 4, 5, 6 ) in methanol, dimethylformamide, and chloroform, while formation of the hydrazinium chloride derivative ( 2 ) from chloromethylated polystyrene ( 1 ) caused enhancement of swelling in methanol but diminished it in toluene. The degree of crosslinking of copoly(styrene-p-nitrophenylacrylate) ( 3 ) also influenced the swelling abilities of 3 and its hydrazino derivatives, being higher with 2% cross-linked resins and lower with 4% and 10% crosslinked resins. © 1996 John Wiley & Sons, Inc.     

Ab initio calculation on the (Si2O7)6− bitetrahedra

The total energy surface of the (Si₂O₇)^6? ion is calculated from the bend and torsion angles in the SiOSi axis. The results are discussed and compared with the experimental data. The ab initio calculation of (SiO₄)^4?, as well as the calculation of the charge distributions for all species were made and discussed.     

A novel synergistic formulation between a cationic surfactant from lysine and hyaluronic acid as an antimicrobial coating for advanced cellulose materials

In this investigation, a novel coating for viscose fabric surface modification was developed using a synergistic formulation between a natural antimicrobial cationic surfactant from lysine (MKM) and a biopolymer hyaluronic acid (HA). The interaction between MKM and HA in aqueous solutions, as well as the interactions between their synergistic formulation (HA-MKM) and viscose fabric (CV) were studied using pH-potentiometric titrations’, turbidity measurements, the Kjeldahl method for the determination of nitrogen amounts, attenuated total reflectance fourier transform infrared spectroscopy, and scanning electron microscopy. The hydrophilic and antimicrobial properties of the functionalised CV were examined in order to evaluate its usages for medical applications. The results of the interaction studies showed that MKM and HA interact with each other by forming a precipitate when the binding sites of HA are saturated. The precipitate has a slightly positive charge at neutral pH due to excess binding of the MKM to HA. The excess positive charge was also detected on CV coated with HA-MKM. This was proven to be very beneficial for the antimicrobial properties of the functionalised CV. The antimicrobial tests showed exceptional antimicrobial activity of the functionalised CV against Escherichia Coli, Staphylococcus Aureus, Streptococcus Agalactiae, Candida Albicans, and Candida Glabrata, making the CV fabric highly interesting for potential use in medicine.     

Solvent-free iodination of organic molecules using the I(2)/urea-H(2)O(2) reagent system

Introduction of iodine under solvent-free conditions into several aromatic compounds activated toward electrophilic functionalization was found to proceed efficiently using elemental iodine in the presence of a solid oxidizer, the urea-H(2)O(2) (UHP) adduct. Two types of iodo-functionalization through an electrophilic process were observed: iodination of an aromatic ring, and side-chain iodo-functionalization in the case of arylalkyl ketones. Two reaction routes were established based on the required substrate : iodine : oxidizer ratio for the most efficient iodo-transformation, and the role of UHP was elucidated in each route. The first, requiring a 1 : 0.5 : 0.6 stoichiometric ratio of substrate to iodine to UHP, followed the atom economy concept in regard to iodine and was valid in the case of aniline, 4-t-Bu-phenol, 1,2-dimethoxy benzene, 1,3-dimethoxy benzene, 1,2,3-trimethoxy benzene, 1,2,4-trimethoxy benzene, 1,3,5-trimethoxy benzene, 1-indanone and 1-tetralone. The second reaction route, where a 1 : 1 : 1 stoichiometric ratio of substrate : I(2) : UHP was needed for efficient iodination, was suitable for side-chain iodo-functionalization of acetophenone and methoxy-substituted acetophenones. Moreover, addition of iodine to 1-octene and some phenylacetylenic derivatives was found to proceed efficiently without the presence of any oxidizer and solvent at room temperature.     

Site-Site Interactions in a Polymer Matrix. Functionalization of Pyridine Rings with Dibromoalkanes in Crosslinked Poly(Styrene-CO-4-Vinylpyridine)

Pyridine ring functionalization and additional crosslinking in crosslinked poly(styrene-co-4-vinylpyridine) with various dibromoalkanes depend on the chain length of the dibromoalkane, the solvent polarity, and the molar ratio between the pyridine rings and the dibromoalkane. the effect of chain length on additional crosslinking becomes more pronounced when the good swelling solvent dimethylformamide is replaced by dibromoalkane. on the other hand, the degree of crosslinking of poly(styrene-co-4-vinylpyridine) influences both the reactivity and the additional crosslinking.     

A brief and stereoselective synthesis of limonoid models, with antifeedant activity against Locusts migratoria

A short stereoselective preparation of havanensin-type limonoid models is reported. The synthesis is based on a radical domino reaction of an epoxyketone to a bicyclic hydroxyketone, and is achieved in six and nine steps from simple cyclohexenones. The epoxyhavanensin derivatives show significant antifeedant activity against Spodoptera littoralis and Spodoptera frugiperda, and the epoxyketone 21 shows potent antifeedant activity against Locusts migratoria.     

Effect of water on the functionalization of substituted anisoles with iodine in the presence of F-TEDA-BF4 or hydrogen peroxide

Water was found to be a convenient reaction medium for functionalization of substituted anisoles using iodine in the presence of Selectfluor F-TEDA-BF(4) or hydrogen peroxide as mediators and oxidizers. Two types of functionalization were observed: iodination or oxidation. In the iodination process, two reaction routes were established. In the case of the first route, a high iodine atom economy was achieved for selective and effective iodo functionalization with a stoichiometric ratio of substrate/iodine/(mediator/oxidizer) = 2:1:1.2. An electrophilic iodination reaction process was suggested for this route, with the oxidizer converting the liberated iodide anion to iodine. For the second reaction route, a stoichiometric ratio of substrate/iodine/(mediator/oxidizer) = 1:1:1 and a lower iodine atom economy were observed; in this case, ion radical formation in the first step of the reaction was suggested. Iodine was found to be an effective catalyst for the oxidation of a hydroxy benzyl functional group to benzaldehyde using F-TEDA-BF(4). Water is an effective medium for functionalization of anisole, p-methoxy benzyl alcohol, 1-(4-methoxyphenyl)ethanone, o-dimethoxy benzene, m-dimethoxy benzene, and p-dimethoxy benzene, whereas F-TEDA-BF(4) as a mediator/oxidizer could be replaced by hydrogen peroxide in the case of the functionalization of 1-(4-methoxyphenyl)ethanone, o-dimethoxy benzene, m-dimethoxy benzene, and p-dimethoxy benzene. Water changes the type of transformation of p-methoxy benzyl alcohol.