Topotaxial formation of titanium-rich barium titanates during solid state reactions on (110) TiO2 (rutile) and (001) BaTiO3 single crystals

The orientation relationships of Ti-rich barium titanate phases formed by solid state reactions at high temperatures were studied using (110) TiO₂ (rutile) and (001) BaTiO₃ single-crystal substrates. Well-oriented Ba₆Ti₁₇O₄₀ islands were observed after a vapor–solid reaction of a BaO quantity equivalent to a nominal BaO film thickness of 1 nm with the TiO₂ substrate, whereas a thin film consisting of well-oriented BaTiO₃ and Ba₆Ti₁₇O₄₀ grains was formed after vapor–solid reaction of a BaO quantity equivalent to a nominal BaO film thickness of 50 nm with the rutile substrate. A topotaxial orientation relationship between Ba₆Ti₁₇O₄₀ and TiO₂ was found. Topotaxy is facilitated by a certain similarity in the oxygen sublattices of TiO₂ and Ba₆Ti₁₇O₄₀. The mechanism of the reaction occurring between BaO vapor and the TiO₂ surface at high temperature is discussed. On the other hand, several well-oriented Ba₄Ti₁₃O₃₀, Ba₆Ti₁₇O₄₀ and Ba₂Ti₅O₁₂ phases were observed to be embedded in the mainly forming Ba₂TiSi₂O₈ phase after a solid–solid reaction of amorphous SiO₂ thin films with (001) BaTiO₃ substrates at temperatures above 1000 °C. They were formed by a topotaxial reaction involving the transformation of (111) planes of BaTiO₃ into (001) planes of the Ti-rich phases by removal of BaO and insertion of TiO₂. Cross-sections of the interfaces between the substrates and the various reaction products are studied by (high-resolution) transmission electron microscopy.     

Zur Untersuchung von Weinbrand, Weindestillat und ?hnlichen Erzeugnissen

Ohne Zusammenfassung     

Design of a Genetic Algorithm for the Simulated Evolution of a Library of Asymmetric Transfer Hydrogenation Catalysts

Breeding new catalysts : A library of 1980 catalysts was designed for asymmetric hydrogen transfer to acetophenone. The library was submitted to evaluation and further simulated evolution experiments, based on a genetic algorithm (see scheme). We demonstrated that it was easily possible to get 5–6 of the ten best catalysts, while investigating only 10% of the library.

     

Hyphenation of atmospheric pressure chemical ionisation mass spectrometry to supercritical fluid chromatography for polar car lubricant additives analysis

Car lubricant additives are added to mineral or synthetic base stocks to improve viscosity and resistance to oxidation of the lubricant and to limit wear of engines. As they belong to various chemical classes and are added to a very complex medium, the base stock, their detailed chromatographic analysis is very difficult and time consuming. In a previous paper, it was demonstrated that supercritical fluid chromatography (SFC) allows the elution of common low-molecular-weight additives. Since their total resolution could not be achieved owing to the limited peak capacity of packed columns, the hyphenation of selective and informative detection methods such as atomic emission detection (AED) was required. Further to results obtained in SFC-AED, this work describes the hyphenation of SFC to atmospheric pressure chemical ionisation ion trap mass spectrometry (MS). SFC–MS hyphenation is detailed: temperature, flow rates of gas and mobile phase introduced in the source, position of the restrictor, ionisation additives and conditions of autotune are studied. Car lubricant monitoring requires negative and positive ionisation modes with or without the addition of ionisation auxiliary solvent according to the nature of additives. Moreover, when sensitivity is of major concern for a selected additive, the autotuning routine of the MS has to be performed in conditions as close as possible to analytical conditions, i.e. under subcritical conditions. Unambiguous identification and structure elucidation of several additives in formulated car lubricants are also presented.     

Silver(I) complexes of 9-anthracenecarboxylic acid and imidazoles: synthesis, structure and antimicrobial activity

[Ag(2)(9-aca)(2)] (1) (9-acaH = 9-anthracenecarboxylic acid) reacts with a series of imidazoles to give [Ag(imidH)(2.3)(CH(3)CN)(0.7)](9-aca) (3), [Ag(6)(imidH)(4)(9-aca)(6)(MeOH)(2)] (4), {[Ag(1-Me-imid)(2)](2)[Ag(4)(9-aca)(6)]} (5), {[Ag(1-Bu-imid)(2)](2)[Ag(4)(9-aca)(6)]} (6) and [Ag(apim)](9-aca)·H(2)O (7) (imidH = imidazole; 1-Me-imid = 1-methylimidazole; 1-Bu-imid = 1-butylimidazole; apim = 1-(3-aminopropyl)imidazole). The mononuclear complex 3, hexanuclear 4-6, and polymeric 7, were all characterised using X-ray crystallography. While many of the complexes possess excellent in vitro antifungal and antibacterial activities they are, unanimously, more effective against fungal cells. The insect, Galleria mellonella, can survive high doses of the Ag(i) complexes administered in vivo, and a number of the complexes offer significant protection to larvae infected with a lethal dose of pathogenic Candida albicans cells.     

Molecularly imprinted polymers: synthetic receptors in bioanalysis

Molecularly imprinted polymers (MIPs) are tailor-made synthetic materials possessing specific cavities designed for a target molecule. Since they recognise their target analyte with affinities and selectivities comparable to those of antibody–antigen, enzyme–substrate and ligand–receptor interactions, they are often referred to as synthetic receptors or plastic antibodies. In this review, we describe the great potential and recent developments of MIPs in affinity separations, with emphasis on their application to the solid-phase extraction (SPE) of analytes from complex matrices. Research efforts made in this field to obtain water-compatible polymers for their applicability in aqueous environments are described. We particularly discuss problems encountered in the use of MIPs in SPE and the attempts carried out to improve their efficiency.     

The role of stacking faults for the formation of shunts during potential‐induced degradation of crystalline Si solar cells

Mono‐ and multicrystalline solar cells have been stressed by potential‐induced degradation (PID). Cell pieces with PID‐shunts are imaged by SEM using the EBIC technique in plan view as well as after FIB cross‐section preparation. A linear shaped signature is found in plan‐view EBIC images at every potential‐induced shunt position on both mono‐ and multicrystalline solar cells. Cross‐sectional SEM and TEM images reveal stacking faults in a {111} plane. Combined TEM/EDX measurements show that the stacking faults are strongly decorated with sodium. Thus, the electric conductivity of stacking faults is assumed to arise under the influence of sodium ion movement through a high electric field across the SiN_x anti‐reflective layer, resulting in PID. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Ordinal pattern statistics for the assessment of heart rate variability

The recognition of all main features of a healthy heart rhythm (the so-called sinus rhythm) is still one of the biggest challenges in contemporary cardiology. Recently the interesting physiological phenomenon of heart rate asymmetry has been observed. This phenomenon is related to unbalanced contributions of heart rate decelerations and accelerations to heart rate variability. In this paper we apply methods based on the concept of ordinal pattern to the analysis of electrocardiograms (inter-peak intervals) of healthy subjects in the supine position. This way we observe new regularities of the heart rhythm related to the distribution of ordinal patterns of lengths 3 and 4.     

Effect of nanoparticle size on the extravasation and the photothrombic activity of meso(p-tetracarboxyphenyl)porphyrin

Particle size should be optimized to achieve targeted and extended drug delivery to the affected tissues. We describe here the effects of the mean particle size on the pharmacokinetics and photothrombic activity of meso-tetra(carboxyphenyl)porphyrin (TCPP), which is encapsulated into biodegradable nanoparticles based on poly(d,l-lactic acid). Four batches of nanoparticles with different mean sizes ranging from 121 to 343 nm, were prepared using the emulsification-diffusion technique. The extravasations of each TCPP-loaded nanoparticle formulation from blood vessels were measured, as well as the extent of photochemically induced vascular occlusion. These preclinical tests were carried out in the chorioallantoic membrane (CAM) of the chicken's embryo. Fluorescence microscopy showed that both the effective leakage of TCPP from the CAM blood vessels and its photothrombic efficiency were dependent on the size of the nanoparticle drug carrier. Indeed, the TCPP fluorescence contrast between the blood vessels and the surrounding tissue increased at the applied conditions, when the particle size decreased. This suggests that large nanoparticles are more rapidly eliminated from the bloodstream. In addition, after injection of a drug dose of 1mg/kg body weight and a drug-light application interval of 1 min, irradiation with a fluence of 10J/cm(2) showed that the extent of vascular damage gradually decreased when the particle size increased. The highest photothrombic efficiency was observed when using the TCPP-loaded nanoparticles batch with a mean diameter of 121 nm. Thus, in this range of applied conditions, for the treatment of for instance a disease like choroidal neovascularization (CNV) associated with age-related macular degeneration (AMD), these experiments suggest that the smallest nanoparticles may be considered as the optimal formulation since they exhibited the greatest extent of vascular thrombosis as well as the lowest extravasation.