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Book reviews

     

Zur konstruktion bewerteter dicksonscher fastkörper

Zusammenfassung  After a short introduction to the valuation theory of nearfields, we give criteria for when a valuation of a skewfield F is also a valuation of the Dickson nearfield F^K which is derived from F by the coupling K on F. For the construction of examples, a rational function field F =K(t) is given. The set of all prolongations of a valuation v on K to F is well known. Sufficient conditions are given which guarantee that couplings K on F and elements are in this sense compatible so that w is a valuation of the Dickson nearfield F^K. Examples demonstrate the results.

     

Box-modeling of bone and tooth phosphate oxygen isotope compositions as a function of environmental and physiological parameters*

A time-dependent box model is developed to calculate oxygen isotope compositions of bone phosphate as a function of environmental and physiological parameters. Input and output oxygen fluxes related to body water and bone reservoirs are scaled to the body mass. The oxygen fluxes are evaluated by stoichiometric scaling to the calcium accretion and resorption rates, assuming a pure hydroxylapatite composition for the bone and tooth mineral. The model shows how the diet composition, body mass, ambient relative humidity and temperature may control the oxygen isotope composition of bone phosphate. The model also computes how bones and teeth record short-term variations in relative humidity, air temperature and δ¹⁸O of drinking water, depending on body mass. The documented diversity of oxygen isotope fractionation equations for vertebrates is accounted for by our model when for each specimen the physiological and diet parameters are adjusted in the living range of environmental conditions.     

On the Behavior of the Solutions for Certain Linear Autonomous Difference Equations

Certain linear autonomous delay as well as neutral delay difference equations are considered. A class of linear autonomous delay difference equations with continuous variable is also considered. Some results on the behavior of the solutions are established via two distinct positive roots of the corresponding characteristic equation.     

CuSO4/sodium ascorbate catalysed synthesis of benzosuberone and 1,2,3-triazole conjugates: Design,synthesis and in vitro anti-proliferative activity

A novel series of conjugates of benzosuberone and 1,2,3-triazole i.e. 3-(4-phenyl-1H-1,2,3-triazol-1-yl)propyl-9-chloro-2,3-dimethyl-6,7-dihydro-5H-benzo[7]annulene-8-carboxylic acids (8a-j) were synthesized in good to excellent yields catalysed by CuSO₄ under milder reaction conditions and evaluated for their anti-proliferative activity. The structural elucidation of the prepared compounds was carried out using IR, ¹H NMR, ¹³C NMR and Mass spectral analysis. The newly synthesized derivatives (8a-j) were evaluated for their anti-proliferative activity against four human cell lines and the novel derivatives showed moderate to excellent activity. The obtained results suggest that these compounds can be considered as new hits for anti-proliferative drug development programme and further SAR studies can help obtain better anticancer agents.     

Enhanced photoactivity of antimony phosphates by substitution of H+, Cu2+ and N3− in the K3Sb3P2O14·xH2O crystal lattice

Research on Chemical Intermediates - Substitutional doping of framework heteroatoms in photocatalysis is one of the approaches for harvesting visible light. Tunnel structure potassium antimony...     

Pressure induced phase transition behaviour in f-electron based dialuminides

The rare-earth and actinide based compounds are endowed with several exotic physical and chemical properties due to the presence of f-electrons. These properties exhibit interesting changes under the action of various thermodynamic fields and hence continues to be a subject of extensive research. For instance, under pressure, the nature of f-electrons can be changed from localized to itinerant, leading to a variety of changes in their structural, physical and chemical properties. The present review on the high pressure phase transition behaviour of dialuminides of rare earths and actinides is an outcome of research in our laboratory during the last five years using a unique combination of a Guinier diffractometer and a diamond anvil cell built in-house. To bring out the correlations between the compressibility and structural behaviour with the electronic structure, we have also carried out electronic structure calculation. Further, the usefulness of Villars’ three parameter structure maps in predicting pressure induced structural transitions has been explored and this has been illustrated with the available phase transition data.     

Spectroelectrochemical cell for in situ studies of solid oxide fuel cells

Solid oxide fuel cells (SOFCs) are able to produce electricity and heat from hydrogen‐ or carbon‐containing fuels with high efficiencies and are considered important cornerstones for future sustainable energy systems. Performance, activation and degradation processes are crucial parameters to control before the technology can achieve breakthrough. They have been widely studied, predominately by electrochemical testing with subsequent micro‐structural analysis. In order to be able to develop better SOFCs, it is important to understand how the measured electrochemical performance depends on materials and structural properties, preferably at the atomic level. A characterization of these properties under operation is desired. As SOFCs operate at temperatures around 1073 K, this is a challenge. A spectroelectrochemical cell was designed that is able to study SOFCs at operating temperatures and in the presence of relevant gases. Simultaneous spectroscopic and electrochemical evaluation by using X‐ray absorption spectroscopy and electrochemical impedance spectroscopy is possible.     

Intermixed terpyridine-functionalized monolayers on gold: nonlinear relationship between terpyridyl density and metal ion coordination properties

Aiming at the functionalization of surfaces with terpyridine anchors for the coordinative deposition of additional layers, mixed self-assembled monolayers (SAMs) were prepared from binary solutions of 12-(2,2':6',2″-terpyridine-4'-yl)dodecane-1-thiol (TDT) and 1-decanethiol (DT). The SAMs and the order of the constituting molecules were analyzed by X-ray photoelectron spectroscopy (XPS), near-edge X-ray absorption fine structure spectroscopy (NEXAFS), and time-of-flight-secondary ion mass spectrometry (ToF-SIMS). The composition of the (TDT/DT)-SAMs and with it the surface density of terpyridyl groups correlates linearly with the relative concentrations of the two compounds in the solution used for depositing them. In marked contrast, the amount of terpyridine-coordinated Pd(II) ions significantly deviates from this trend with an optimum at a 1:3 ratio of TDT/DT. This indicates a major fraction of the terpyridines in TDT-rich SAMs not to be accessible for Pd(II) ion coordination. In agreement, NEXAFS spectroscopy reveals the alkyl backbones in TDT-rich SAMs not to be ordered, while they are preferentially upright oriented in the optimal 1:3-(TDT/DT)-SAMs. We interpret this in terms of terpyridine backfolding in TDT-rich SAMs, while they are located in accessible positions on top of the SAM in the 1:3-(TDT/DT)-SAM. While the alkyl backbones in the 1:3-(TDT/DT)-SAM are ordered, NEXAFS spectroscopy shows the terpyridyl groups not to have a preferential orientation in this SAM and thus retain enough flexibility to adjust to molecules that are deposited on top of the mixed SAM. In conclusion, the novel SAM does not undergo phase separation and consists predominantly of intermixed phases with adjustable surface density of quite flexible terpyridine anchor groups. The terpyridine-Pd(II) anchors are not only available for a future deposition of the next layer, but the metal ions also represent a sensitive probe for the accessibility of the terpyridyl groups.     

Successive coordination of palladium(II)-ions and terpyridine-ligands to a pyridyl-terminated self-assembled monolayer on gold

The deposition of palladium on a novel, reversibly protonatable, pyridyl-terminated self-assembled monolayer on gold substrates has been studied by X-ray photoelectron spectroscopy (XPS), near-edge X-ray absorption fine structure spectroscopy (NEXAFS spectroscopy) and time of flight-secondary ion mass spectrometry (ToF-SIMS). For this purpose, 12-(pyridin-4-yl)dodecane-1-thiol, consisting of a surface-active head group, an unfunctionalized hydrocarbon backbone and a terminal pyridyl group, has been synthesized and deposited on gold surfaces. Coordination of Pd(II) ions to the pyridyl group was examined. Furthermore, a reversible protonation/deprotonation cycle has been applied, and the relation between protonation and the amount of complexed palladium was studied. Investigation of the SAM by angle-resolved NEXAFS spectroscopy revealed the aliphatic backbone to be preferentially upright oriented with the aromatic head group being not preferentially oriented. The palladium layer was further coordinated with a CF₃-labeled terpyridine ligand in order to prove the accessibility of the Pd(II) ions to further complexation and the platform useful for deposition of further layers toward a multi-layered system.