Water adsorption on SrTiO3(001): I. Experimental and simulated STM

Density functional theory-based simulations of scanning tunneling micrographs were used for comparison to published experimental images of reconstructed SrTiO₃(001) surfaces. It was found that the addition of dissociatively adsorbed H₂O to the presently accepted structural solution of the 2 × 1 reconstruction is more consistent with the experimental data. A proposed model for the c(4 × 4) reconstruction, based on the hydrated 2 × 1 structure, agrees well with experiment and is consistent with a formation process consisting of the simple dehydration of a wet 2 × 1 structure.     

c(4 × 2) and related structural units on the SrTiO3(001) surface: scanning tunneling microscopy, density functional theory, and atomic structure

Density functional theory is used to simulate high-bias, constant-current scanning tunneling micrographs for direct comparison with experimental images. Coupled to previous spectroscopic data, these simulations are used to determine the atomic structure of Ti-rich nanostructures on strontium titanate (001) surfaces. These nanostructures have three consecutive TiO(x) surface layers and exploit the distinctive structural motif of the c(4 × 2) reconstruction as their main building block. A structural model of a characteristic triline defect is also proposed.     

Solvent effects upon reactions between ions: hexacyanoferrate(II)-peroxodisulphate and sulphite-hexacyanoferate(III)

Summary Different approaches to the interpretation of solvent effects on reactions between ionic reactants are analysed, taking as a basis the kinetic data corresponding to the sulphite-hexacyanoferrate(III) and peroxodisulphate-hexacyanoferrate(III) oxidations. It is concluded that the approach based on the use of solvent parameters is the more promising, although knowledge of the transfer chemical potentials of the reactants may also be useful in the interpretation of kinetic behaviour.     

Study of the lithiated phenylacetonitrile monoanions and dianions formed according to the lithiated base used (LHMDS,LDA, or n-BuLi). 1. Evidence of heterodimer ("Quadac") or dianion formation by vibrational spectroscopy

It is evidenced through vibrational spectroscopy that a heterodimer or "Quadac" is formed when an excess of base (LHMDS, LDA, or n-BuLi) is added to PhCH(2)CN in THF, THF-hexane, or THF-toluene solution. The amount of heterodimer increases with the pK(H)(a) of the lithiated base. A dianionic species may be formed through decomposition of this heterodimer if the pK(H)(a) of the base is sufficiently high, as in the case of n-BuLi. With LDA, only a very small amount of dianion is observed, and with LHMDS, no dianion is detected. The predominant dianionic species observed are the linear and bridged separated ion pairs of the dilithiated dianion. The presence of the amine in the medium is of paramount importance. The PhCHCNLi monomer-dimer equilibrium is entropy driven toward the dimer solvated by the amine.     

Medium effects on the ligand field bands of hexathiocyanato- chromate(III)

Transition Metal Chemistry - The wavelengths of absorption maxima are reported for two ligand field bands of hexathiocyanatochromate(III), $ {? Cr(NCS)_{6}^{3-}} $, over a range of...     

Epicatechin,procyanidins, and phenolic microbial metabolites after cocoa intake in humans and rats

Proanthocyanidins, flavonoids exhibiting cardiovascular protection, constitute a major fraction of the flavonoid ingested in the human diet. Although they are poorly absorbed, they are metabolized by the intestinal microbiota into various phenolic acids. An analytical method, based on an optimized 96-well plate solid-phase extraction (SPE) procedure and liquid chromatography tandem mass spectrometry (SPE-LC-MS/MS) for the analysis of 19 phenolic microbial metabolites and monomeric and dimeric flavanols in urine samples, was developed and validated. Human urine samples were obtained before and after ingestion of an acute consumption of 40 g of soluble cocoa powder and rat urines before and after the prolonged administration (2 weeks) of different diets composed of natural cocoa powder. The mean recovery of analytes using the new SPE-LC-MS/MS method ranged from 87% to 109%. Accuracy ranged from 87.5% to 113.8%, and precision met acceptance criteria (<15% relative standard deviation). Procyanidin B2 has been detected and quantified for the first time in human and rat urine after cocoa consumption. Changes in human and rat urinary levels of microbial phenolic acids and flavanols were in the range of 0.001–59.43 nmol/mg creatinine and of 0.004–181.56 nmol/mg creatinine, respectively. Major advantages of the method developed include reduction of laboratory work in the sample preparation step by the use of 96-well SPE plates and the sensitive measurement of a large number of metabolites in a very short run time, which makes it ideal for use in epidemiological studies. ^a INGENIO-CONSOLIDER Program, Fun-c-food CSD2007-063 ^b CIBER 06003 Physiopathology of Obesity and Nutrition (CIBEROBN), and RETICS RD06/0045/0003, Instituto de Salud Carlos III     

Integration of block copolymer-wrapped single-wall carbon nanotubes into a trifunctional epoxy resin. Influence on thermal performance

Novel nanocomposite materials were prepared by incorporating block copolymer-wrapped single-wall carbon nanotubes (SWCNTs) into a trifunctional epoxy resin. The work was focused on the study of the influence of the SWCNTs and the block copolymer based on ethylene oxide and propylene oxide, Pluronic F68, on the thermal and thermo-oxidative cleavage reactions of the resin. A nanocomposite sample containing 2 wt% Pluronic-wrapped SWCNTs was prepared and its behaviour compared with that of Pluronic/epoxy and SWCNT/epoxy composites. Their thermal performance in both oxidative and inert atmospheres was evaluated by different techniques including thermogravimetric analysis (TGA), mass spectrometry and infrared spectroscopy. A kinetic study of the TGA data in both atmospheres based on the Vyazovkin’s advanced isoconversional method showed differences in the activation energies. Infrared spectroscopy of residues extracted at various steps during dynamic heating indicated a common degradation mechanism for all samples, and improved thermo-oxidative performance in the nanocomposite containing Pluronic-wrapped SWCNTs.     

Large deviations for Brownian motion in a random scenery

We prove large deviations principles in large time, for the Brownian occupation time in random scenery . The random field is constant on the elements of a partition of ^d into unit cubes. These random constants, say consist of i.i.d. bounded variables, independent of the Brownian motion {B_s,s0}. This model is a time-continuous version of Kesten and Spitzer's random walk in random scenery. We prove large deviations principles in ``quenched' and ``annealed' settings.Mathematics Subject Classification (2000):60F10, 60J55, 60K37     

PHOTODYNAMIC LIPID PEROXIDATION BY THE PHOTOSENSITIZING NONSTEROIDAL ANTIINFLAMMATORY DRUGS SUPROFEN AND TIAPROFENIC ACID

Abstract The photochemistry of the photosensitizing nonsteroidal antiinflammatory drugs tiaprofenic acid and suprofen involves the intermediacy of short-lived species ( i.e. radicals). The data obtained in the present work strongly suggest that such intermediates may be responsible for the phototoxicity of 2-arylpropionic acids by inducing photodynamic lipid peroxidation at drug concentrations likely to be reached in the skin. This has been investigated using linoleic acid as a model lipid and determining the amount of hydroperoxides by measuring the spectrophotometric absorption at 233 nm, associated with the formation of dienic hydroperoxides. The major photoproducts of tiaprofenic acid and suprofen are derivatives bearing an ethyl side chain. Photoproducts of this type, due to the lack of polar moieties, are highly lipophilic and likely to accumulate in the lipid bilayer of cell membranes. Taking into account their ability to induce photodynamic lipid peroxidation and their marked photostability, it is conceivable that such photoproducts can participate in many catalytic cycles, playing a significant role in the mechanism of photosensitizatinn by tiprofenic acid and suprofen.     

QSAR of copper(II) complexes with cytotoxic properties

Summary A QSAR based on a multiple regression analysis for 15 copper(II) semi- and thiosemicarbazone complexes with cytotoxic properties is presented. In vitro cytotoxicity was selected as the dependent variable and Van der Waals volumes (Vm), octanol- water partition coefficients (logP), specific rate constants of the copper(II) complexes towards superoxide radicals (k _s ) and variation in C=N vibration bands (CN) in IR spectra of the complexes with respect to the free ligands were selected as the independent variables. The stepwise regression procedure and the all possible regressions were practiced in the analysis of the data. The orthogonality analysis proved noncollinearity among the variables. According to the obtained equation the two best copper(II) complexes were submitted to a broad in vivo screening study and resulted to be active against La, P-388 and L-1210 leukemias.

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QSAR von Kupfer(II)-Komplexen mit cytotoxischen Eigenschaften

Zusammenfassung Es wird eine quantitative Struktur-Aktivitäts-Beziehung basierend auf einer multiplen Regressionsanalyse für 18 Kupfer(II)-Semi- und Thiosemicarbazon-Komplexe präsentiert. Die in vitro-Cytotoxizität wurde als die abhängige Variable und Van-der-Waals-Volumina (Vm), Octanol-Wasser-Verteilungskoeffizienten (logP), spezifische Geschwindigkeitskonstanten der Kupfer(II)-Komplexe gegenüber Superoxid-Radikalen (k _s ) und die Variationen der C=N-Vibrationsbanden (CN) in den IR-Spektren der Komplexe gegenüber den freien Liganden als unabhängige Variablen eingeführt. Es wurde stufenweise Regression und die alle möglichen Regressionen-Prozedur in der Analyse der Daten verwendet. Die Orthogonalitätsanalyse zeigte Nichtkolinearität der Variablen an. Entsprechend den erhaltenen Gleichungen wurden die beiden besten Kupfer(II)-Komplexe einem breiten in vivo-Screening unterworfen. Sie waren gegenüber La, P-388 und L-1210 Leukemie aktiv.