Crystal Growth in Gels at Elevated Pressures: The Upper Limit of Temperature for Metastable Formation of Aragonite

Both rapid precipitation and diffusion controlled gel growth were applied to crystallize calcium carbonate at temperatures in the range of 100 °C to 270 °C. The amount of aragonite was determined by means of X-ray diffraction data. The morphology of the aragonite crystals are described. Metastable formation of aragonite was observed only at temperatures below 270 °C.     

Effects of diclofenac on EPC liposome membrane properties

In this work the interaction of a non-steroidal anti-inflammatory drug (NSAID), diclofenac, with egg yolk phosphatidylcoline (EPC) liposomes, used as cell-membrane models, was quantified by determination of the partition coefficient. The liposome/aqueous phase partition coefficient was determined by derivative spectrophotometry, fluorescence quenching, and measurement of zeta-potential. Theoretical models based on simple partition of the diclofenac between two different media, were used to fit the experimental data, enabling the determination of K_p. The three techniques used yielded similar results. The effects of the interaction on the membranes characteristics were further evaluated, either by studying membrane potential changes or by effects on membrane fluidity. The liposome membrane potential and the size and size-homogeneity of liposomes were measured by light scattering. The effects of diclofenac on the internal viscosity or fluidity of the membrane were determined by use of spectroscopic probes—a series of n-(9-anthroyloxy) fatty acids in which the carboxyl terminal group is located at the interfacial region of the membrane and the fluorescent anthracene group is attached at different positions along the fatty acid chain. The location of the diclofenac on the membrane was also evaluated, by fluorescence quenching using the same series of fluorescent probes. Because the fluorescent anthracene group is attached at different positions along the fatty acid chain, it is possible to label at a graded series of depths in the bilayer. The interactions between the drug and the probe are a means of predicting the location of the drug on the membrane.     

Quasicrystalline epitaxial single element monolayers on icosahedral Al-pd-mn and decagonal Al-ni-co quasicrystal surfaces

Single element quasicrystalline monolayers were prepared by deposition of antimony and bismuth on the fivefold surface of icosahedral Al71.5Pd21Mn8.5 and the tenfold surface of decagonal Al71.8Ni14.8Co13.4. Elastic helium atom scattering and low energy electron diffraction of the monolayers show Bragg peaks at the bulk derived positions of the clean surfaces, revealing highly ordered quasicrystalline epitaxial films. Their adatom densities of (0.9+/-0.2)x10(15) cm(-2) and (0.8+/-0.2)x10(15) cm(-2) on Al-Pd-Mn and Al-Ni-Co, respectively, correspond to roughly one adatom per Al atom of the quasicrystalline substrate surfaces.     

X-ray absorption and X-ray photoelectron spectroscopy of a rhodium colloid

Transition metal colloids are potential precursors of heterogeneous catalysts with application to selective chemical reactions. Sample preparation techniques are described. Experimental details are given of the characterization of these often air-sensitive particles by X-ray photoelectron and X-ray absorption spectroscopy. First results obtained with both techniques for a Rh-colloid show that the metal is mainly present in the zerovalent chemical state. But the spectra indicate further chemical states of Rh which can be assigned to the outermost metal atoms of the colloid interacting with organic ligands or to the educt Rh-halides.     

η3-Allyl[1,2-bis(diphenylphosphino)ethan]tricarbonylvanadium(0)-komplexe

The preparation, properties and spectroscopic investigation (IR, ¹H NMR, ³¹P NMR, MS) of η³-allyl[1,2-bis(diphenylphosphino)ethan]tricarbonylvanadium(0) compounds are reported.     

Organoarsen-Verbindungen : XXIV. Zur synthese der perhydro-1,3-azarsenine

The reaction of NaAsHR with ClCH₂CH₂CH₂NH₂ yields the corresponding secondary 3-aminopropylarsines, RAs(H)CH₂CH₂CH₂NH₂, which with aldehydes and ketones form the perhydro-1,3-azarsenines. The properties and reactivity of these heterocyclic compounds are described.     

An axiomatic scheme more general than quantum theory

An axiomatic scheme generalizing the operational approach to quantum theory is described. Only quite general axioms ensuring the existence of well-behaved probabilities are postulated. The space-time location of macroscopic apparatus interacting with the object is explicitly taken into consideration. The states and observables are defined and their time development is considered. The classification of physical processes with respect to their reversibility or irreversibility in time is given. The conditions of Lorentz and translational invariance are formulated. Linear transformations corresponding to operations on the object are introduced. In the case of reversible processes these transformations form an algebra and linear representations of the Poincaré group arise naturally. These results are, in general, invalid for irreversible processes. The position of quantum theory in the scheme described is clarified.     

A Statistical Model for Describing Spectral Diffusion Effects in Electron Spin Echo (ESE) and Electron Nuclear Double Resonance (ENDOR) Experiments

A statistical model for an EPR line broadened by dipolar electron-nuclear interaction is proposed. This makes it possible for the effect of spectral diffusion on the width and intensity of ENDOR signals to be determined from electron spin echo experiments. In this paper, various ENDOR mechanisms are discussed in addition to a calculation of the variation in both Boltzmann factor and spin temperature due to the spectral diffusion effect.