Calorimetric study of the cubic mesogen, ACBC(6)

The heat capacity of the cubic mesogen ACBC(16) was measured between 16 and 500 K by adiabatic calorimetry. As well as the known condensed phases, a new crystalline phase was found to undergo a glass transition at around 165 K. Phase transitions between crystal, SmC, cubic, and isotropic liquid phases took place at 399.16, 431.15, and 474.30 K, respectively. As in the case of ANBC, a broad hump was observed in the heat capacity of the isotropic liquid phase. The first order nature of the SmC-cubic phase transition was confirmed for the first time by the observation of supercooling of the cubic phase. The broad hump in the isotropic liquid phase was shown to extend to a low temperature side if the isotropic liquid was supercooled, suggesting that the event occurring at the hump is not directly related to the cubic-isotropic liquid phase transition.     

Editorial: Molecular Magnets

Monatshefte für Chemie - Chemical Monthly -     

Influence on elemental status by hip-endoprostheses

For many clinical purposes various artificial devices are applied, which contact human tissue and can thus cause adverse reactions between prosthetic surfaces and body components. Of the many materials applied for orthopaedic joint replacements the most common are cobalt-chromium-molybdenum alloys. In these cases considerable amounts of cobalt-chromium-molybdenum wear particles are released from the prostheses which have to be regarded as a cause of long-time problems for the patient.Since these particles are dissolved in body fluids of the surrounding area they are distributed in the whole body via blood. Elevated metal concentrations have been found in blood and urine of persons with endoprostheses. Partly the metals are excreted via urine, but to some extend they accumulate in different organs.Therefore this study dealt with the development of an analytical method for the determination of seven relevant trace elements, namely Al, Co, Cr, Mo, Nb, Ni, and Ti in nine kinds of human tissue (brain, heart, kidney, liver, lung, muscle, lymphatic nodes, spleen, body fat) starting with drawing of the sample, sample work up and finally analysis by means of atomic spectrometry. The optimized method was then applied to determine the metal contents in organs of persons (post mortem) with total hip replacements with metal on metal bearing surfaces. Comparison of the data obtained with those of persons without hip-endoprostheses shows that brain and lung are the main targets for elemental accumulation in persons with hip-endoprostheses. Mo and Nb represent the elements with the highest tendency to be accumulated.     

Settling Behavior Characterization of Submicron Particles in Dilute and Concentrated Suspensions

In separation processes, the knowledge of particle size and density arc often not enough to describe the settling behaviour in a concentrated suspension. Therefore, a direct method for the characterization of the settling behavior of submicron particles in concentrated suspensions is introduced in a centrifugal field by a manometric sedimentation analysis. By means of this cumulative method in a homogeneous suspension, the analyses of both the interfacial settling rate and the settling rate of the particles within the concentrated suspension are possible. This permits a differential examination of settling processes in a broad concentration range. First, the influence of the solid concentration on the settling rate at the interface and within a monodisperse suspension with a range from 0.01 to 30 vol.% is represented. The relationship between the increase in settling rate through particles settling in a cluster and a concentration decrease in the suspension is also represented. Consideration of the possibilities of the analysis of polydisperse suspensions demonstrates the field of applications for this method.     

Controllability properties of nonlinear behaviors

This paper proposes a topological framework for the analysis of the time shift on behaviors. It is shown that controllability is not a property of the time shift, while chain controllability is. This also leads to a global decomposition of behaviors.

     

Chelating Complexes of Diethylzinc and ZnCl2 with 2,2‐Bipyridine and 1,6,7,12,13,18‐Hexaazatrinaphthylene (HATN) as Ligands

The 1,6,7,12,13,18‐hexaazatrinaphthylene (HATN) complex [(Et₂Zn)₃(μ₃‐HATN)] was synthesized and characterized by IR spectroscopy, UV/Vis spectroscopy, elemental analysis and ESI‐MS spectrometry. Attempts to prepare ZnCl₂ complexes of HATN leads only to the mononuclear [(Cl₂Zn)(HATN)] derivative, characterized by X‐ray diffraction, IR‐ and UV/Vis‐spectroscopy as well as ESI‐MS spectrometry. The bright red 2,2′‐bipyridine (bipy) complex [(Et₂Zn)(bipy)] ( 1 ) was synthesized and characterized by X‐ray diffraction and NMR spectroscopy. The UV/Vis‐spectra of the HATN‐complexes show absorptions in regions of far longer wavelengths than the corresponding 2,2′‐bipyridine or 1,10‐phenantroline complexes. Consequently the π*‐LUMO of HATN ( 5 ) is lower in energy than the π*‐LUMO of 2,2′‐bipyridine ( 2 ) or 1,10‐phenanthroline (phen).     

The influence of different evaluation techniques on the results of interlaboratory comparisons

The influence of different evaluation techniques on the results of an interlaboratory comparison for the determination of nutrients in ground- and surface water was investigated. The outlier-test procedure was found to influence the interlaboratory standard deviations (SDs), but not the averages. It was shown that even small differences in the numbers of outliers detected can change the SD severely. Comparing the outlier-test procedures of Hampel, Grubbs and Graf-Henning, it was found that Hampel's test detected the most outliers, thus generally resulting in smaller SDs between interlaboratory comparisons. The Graf-Henning test detected the fewest outliers and its application resulted in the highest SDs of the three test procedures investigated. The comparison of different summarising indices, namely the rescaled sum of z-scores, average of absolute z-scores and average deviation showed no comparability. Possibilities to improve the comparability of interlaboratory comparisons and to minimise misunderstandings are suggested.     

Development of reference materials for microbiological analysis

The reliability of reference materials (RMs) depends on properties such as fitness, robustness, commutability, stability and homogeneity. The development of RMs for microbiological analysis is especially challenged through questions around the stabilisation and recovery of viable cells, the dispersion of precise numbers of cells, matrix effects and, when using molecular techniques, the presence of nucleic acids (e.g. DNA) of dead and live target organisms. However, RMs are indispensable tools for quality control in microbiological analysis. The Institute for Reference Materials and Measurements (IRMM), as part of the European Commission, concentrates its efforts on the development of RMs to support the development, implementation and monitoring of EU legislation. A special focus is given to highly precise RMs for presence/absence and enumeration tests in microbiological food and water analysis. Another group of new RMs certified by the IRMM comprise DNA-based materials to control the identity of micro-organisms in qualitative assays. All of these activities serve to improve quality control in microbiological analysis. Presented at ‘BERM-10’, April 2006, Charleston, SC, USA.