Effect of the primary particle morphology on the micromechanical properties of nanostructured alumina agglomerates

Depending on the application of nanoparticles, certain characteristics of the product quality such as size, morphology, abrasion resistance, specific surface, dispersibility and tendency to agglomeration are important. These characteristics are a function of the physicochemical properties, i.e. the micromechanical properties of the nanostructured material. The micromechanical properties of these nanostructured agglomerates such as the maximum indentation force, the plastic and elastic deformation energy and the strength give information on the product properties, e.g. the efficiency of a dispersion process of the agglomerates, and can be measured by nanoindentation. In this study a Berkovich indenter tip was used for the characterisation of model aggregates out of sol–gel produced silica and precipitated alumina agglomerates with different primary particle morphologies (dimension of 15–40 nm). In general, the effect of the primary particle morphology and the presence or absence of solid bonds can be characterised by the measurement of the micromechanical properties via nanoindentation. The micromechanical behaviour of aggregates containing solid bonds is strongly affected by the elastic–plastic deformation behaviour of the solid bonds and the breakage of solid bonds. Moreover, varying the primary particle morphology for similar particle material and approximately isotropic agglomerate behaviour the particle–particle interactions within the agglomerates can be described by the elementar breaking stress according to the formula of Rumpf.     

Convenient synthesis and characterization of molecules containing multiple β-keto ester units

Three compounds containing two β-keto ester units and one containing three were obtained in good yields from sebacyl, terepthaloyl, isophthaloyl, and trimesoyl chlorides. In this one pot procedure the acid chlorides were first treated with ethyl acetoacetate and barium oxide and then with ethyl alcohol. The aliphatic ester exists mainly as keto ester with a very small amount of the enol tautomer. In the case of aromatic esters, all possible tautomers were found in considerable concentrations in deuterochloroform solution. Theoretical chemical shifts were estimated from GIAO/WP04/aug—cc-pVDZ/SCRF calculations, for a probable signal assignation for the corresponding tautomeric species. Our theoretical results are in agreement with experimental findings and account for negligible stability differences between the tautomers of each aromatic compound.     

Unusual nonoctahedral geometry with molybdenum oxoimido complexes containing η2-pyrazolate ligands

The preparation and oxygen-atom-transfer (OAT) reactivity of oxoimido complexes [MoO(N-t-Bu)(t-Bu(2)-4-Rpz)(2)] [where R = H (1), Br (2), and Me (3); t-Bu(2)pz = 3,5-di-tert-butylpyrazolate] are reported. The reaction of the potassium salt of the respective pyrazolate ligands and the molybdenum oxoimido precursor, [MoO(N-t-Bu)Cl(2)(dme)] (dme = dimethoxyethane), in toluene afforded complexes 1-3 in good yields. The complexes were fully characterized by (1)H and (13)C NMR and IR spectroscopy, mass spectrometry, elemental analysis, and single-crystal X-ray crystallography. The solid-state structures reveal that, in each case, the molybdenum center is coordinated by one oxo, one N-t-Bu group, and two sterically demanding pyrazolate ligands via their two adjacent nitrogen atoms in an η(2) fashion. Coordination around the metal center is severely distorted from octahedral and might be seen as closely approaching a distorted trigonal-prismatic geometry, which is relevant to the active site of dimethyl sulfoxide reductase in its oxidized form. The potential utility of all of the complexes 1-3 for OAT reactivity toward PMe(3) at room temperature is examined, and plausible mechanistic pathways are explored by density functional theory calculations. Furthermore, the complexes reported here open a new and convenient entry into mixed oxoimidomolybdenum complexes.     

Coupling of 3D Boundary Elements with Curved Finite Shell Elements

The mixed-dimensional coupling of finite shells and 3D boundary elements is presented. A stiffness formulation for the boundary element domain is generated by the Symmetric Galerkin Boundary Element Method and is assembled to the global finite element system. Multipoint constraints are derived in an integral sense by equating the work at the coupling interface. They are evaluated numerically during the analysis and avoid spurious stress concentrations also for curved interfaces. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

The Chemistry of Cyborgs—Interfacing Technical Devices with Organisms

The term “cyborg” refers to a cybernetic organism, which characterizes the chimera of a living organism and a machine. Owing to the widespread application of intracorporeal medical devices, cyborgs are no longer exclusively a subject of science fiction novels, but technically they already exist in our society. In this review, we briefly summarize the development of modern prosthetics and the evolution of brain–machine interfaces, and discuss the latest technical developments of implantable devices, in particular, biocompatible integrated electronics and microfluidics used for communication and control of living organisms. Recent examples of animal cyborgs and their relevance to fundamental and applied biomedical research and bioethics in this novel and exciting field at the crossroads of chemistry, biomedicine, and the engineering sciences are presented.     

Charge-symmetry-breaking nucleon form factors

A quantitative understanding of charge-symmetry breaking is an increasingly important ingredient for the extraction of the nucleon??s strange vector form factors. We review the theoretical understanding of the charge-symmetry-breaking form factors, both for single nucleons and for ⁴He.     

The study of the lipophilicity of some aminoalkanol derivatives with anticonvulsant activity

A series of new (phenoxyethyl)aminoalkanol derivatives were synthesized and evaluated for their anticonvulsant activity. The most promising compound seemed to be (R,S)‐1N‐[(2,6‐dimethyl)phenoxyethyl]amino‐2‐butanol, which displayed anti‐MES activity (in mice, i.p.) with protective index (TD₅₀/ED₅₀) of 5.712, corresponding to that of phenytoin (6.6), carbamazepine (4.9) and valproate (1.7). The lipophilicity of compounds 1–17 exhibiting anticonvulsant activity was investigated. Their lipophilicities (R_M0) were determined using reversed‐phase thin‐layer chromatography (RP‐TLC) with a mixture of acetone and water as mobile phases. The partition coefficients of 1–17 (logP) were also calculated using two computer programs (Pallas and ALOGPS) and compared with R_M0. The relationship between anticonvulsant activity and lipophilicity of the tested substances was estimated. Copyright © 2010 John Wiley & Sons, Ltd.     

Kinetics and mechanisms of the reaction of OH radicals with dimethyl sulfide

The rate constant of the reaction of OH with DMS has been measured relative to OH + ethene in a 420 l reaction chamber at 760 torr total pressure and 298 ± 3 K in N₂ + O₂ buffer gas using the 254 nm photolysis of H₂O₂ as the OH source. In agreement with a recent absolute rate determination of the reaction the measured effective rate constant was found to increase with increasing partial pressure of O₂ in the system, for 760 torr air a rate constant of (8.0 ± 0.5) × 10^?12 cm³ s^?1 was obtained. Product studies have been performed on the reaction in air using FTIR absorption spectrometry for detection of reactants and products. On a molar basis, SO₂ was formed with a yield of 70% and dimethyl sulfone (CH₃SO₂CH₃) with a yield of approximately 20%. These results are considerably different to those obtained in other product studies which were carried out in the presence of NO_x. These differences are compared and their relevance for the atmospheric oxidation mechanisms of DMS is discussed.