Modeling of Nanoplasmas Created from Finite Systems by Ultrafast Intense X‐ray Pulses

In this review we discuss various simulation methods for modeling nanoplasmas created from finite‐size samples after their irradiation with femtosecond, intense X‐ray pulses. Depending on the sample composition and its size, either a particle method or a transport method can be applied. Also, the observables of interest influence the choice of the simulation method. The current status of dedicated methods developed by the CFEL Theory Division at DESY in Hamburg and their possible extensions are presented together with some application examples. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Bis(tetraethylammonium) hydrogensulfate dihydrogenphosphate at 292 and 150 K

The title compound, 2C₈H₂₀N⁺·HSO₄⁻·H₂PO₄⁻, was crystallized in a desiccator over P₄O₁₀ from a water solution of stoichiometric amounts of tetraethyl­ammonium hydroxide and sulfuric and phosphoric acids. The compound is deliquescent. The structure contains two symmetry‐independent cations in nearly the same conformation, as well as two symmetry‐independent anions, the central atoms of which are equally occupied by P and S. The anions are interconnected by short O⃛O hydrogen bonds into one‐dimensional chains. The distances and angles between some of the methyl or methyl­ene groups and anionic O atoms indicate the presence of C—H⃛O hydrogen bonds. The structure was determined from data at 292 (2) and 150 (2) K. These room‐ and low‐temperature structures are virtually the same, with the exception of the localization of the H atoms that participate in the symmetry‐restricted O⃛O hydrogen bonds. A differential scanning calorimetry experiment indicated no phase transition below the temperature at which the compound started to decompose (353 K), down to 93 K.     

The use and accuracy of the ZAF correction procedure for the microanalysis of glasses

Summary Systematic series of glasses with varied content of Ca, Al, Mg and Na were prepared. The ZAF corrections were calculated. It was shown that the theoretically and experimentally determined coefficients are not identical, because the intensity of the characteristic X-ray depends linearly on concentration for nearly all the elements tested, but the calculated correction coefficients increase with increasing concentration. Correction coefficients calculated according to the present state of the ZAF method may be applied to a wider range of concentrations with only limited accuracy.

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Einsatz und Richtigkeit des ZAF-Korrekturverfahrens für die Mikroanalyse von Gläsern

Zusammenfassung Systematisch ausgewählte Versuchsreihen von Gläsern mit variablem Gehalt an Ca, AI, Mg und Na wurden hergestellt und die ZAF-Korrektur- faktoren berechnet. Es konnte gezeigt werden, daß die berechneten und die experimentell bestimmten Korrekturfaktoren voneinander abweichen, weil die Intensität der charakteristischen Röntgenstrahlung linear von der Konzentration nahezu aller Elemente abhängt, die berechneten Korrekturfaktoren aber mit zunehmender Konzentration größer werden. Daraus muß gefolgert werden, daß die nach den derzeit üblichen Methoden berechneten ZAF-Korrekturfaktoren bei Anwendung in einem größeren Konzentrationsbereich nur beschränkte Richtigkeit aufweisen.

     

The Reversible Proxibarbal-Valofan Isomerisation. Part I. Kinetic and thermodynamic studies in aqueous solutions

The tautomerisation between proxibarbal (I) and the two diastereoisomers of valofan, IIX and IIY , was investigated in aqueous solutions, and various rate and equilibrium caonstants were calculated by compartmental analysis. The proportion of I at equilibrium was found to increase with pH, and indeed, the two equilibrium constants are linear functions of pH. In contrast, the equilibrium-concentratio ratio of IIY/IIX was close to 63:37 and remained constant in the pH range investigated. The rate constants were also determined as a function of temperature, allowing calculation of the tehrmolynamic parameters. Under physiological conditions, the difference in free energy favouring I vs. IIX and IIY is 6.7 and 5.4KJ · mol^?1, respectively.     

The Reversible Proxibarbal-Valofan Isomerisation. Part II. Kinetic studies in a biphasic octanol/water system

The tautomerisation between proxibarbal (I) and the two diasterloisomers of valofan ( IIX and IIY ) was investigated at pH 7.4 in a biphasic octanol/H₂O system. The rate constants of isomerisation and the equilibrium constants of (partition coefficients) were calculated by compartmental analysis. The rate constants of isomerisation were comparable with those determined in monophasic aqueous solutions, whereas at pH 7.4 and 37° the duration necessary for a global equilibrium to be reached was 4–6 times longer in the biphasic system. These reduced rates and the higher lipophilicity of IIX and IIY as compared to I may be of pharmacokinetic and pharmacodynamic significance. They may also have relevance for a number of drugs known or suspected to form lactonic or lactamic metabolites.     

Change of energy profiles for muons upon lattice relaxation

Systematic calculations of potentials for muons and protons in various simple metals have been recently performed using local pseudopotentials in first-order perturbation theory. In the present contribution some results which are of particular interest forSR are discussed. The modification of the energy profiles with lattice relaxation is studied in Cu and Cs.     

Confocal fluorescence imaging of photosensitized DNA denaturation in cell nuclei

The double-stranded helical structure of DNA is maintained in part by hydrogen bonds between strands and by stacking interactions between adjacent purine and pyrimidine bases in one strand. The transition (denaturation) from a double-stranded (ds) to a single-stranded (ss) form can be induced in isolated DNA or fixed cells by exposure to elevated temperatures, alkali or acids, aprotic or nonpolar solvents or some drugs. We report here that DNA denaturation can occur in situ in cell nuclei as a result of interaction between light and an intercalated dye, acridine orange or ethidium bromide. This DNA photodenaturation was probed using metachromatic properties of acridine orange and imaged by fluorescence confocal microscopy. Furthermore, an empirical kinetic model was developed to separate changes of acridine orange luminescence intensities caused by photobleaching from those that were a result of DNA denaturation. We investigated the influence of oxygen on these phenomena and propose a mechanism by which photodenaturation may occur.     

Measurements of the heat capacity of diamond with different isotopic compositions

We report measurements of the heat capacity C_p of diamond with several isotopic compositions (¹²C_1−x¹³C_x) in the 20-280 K temperature range. The results, in particular the derivative of the specific heat with respect to the average isotopic mass, are compared with recent ab initio calculations. Agreement is good for T>150 K. At lower temperatures, the samples with isotopic compositions different from the natural one display an anomalous increase in C_p/T³ with decreasing temperature which is attributed to the presence of metallic inclusions stemming from the metal used as a solvent in the high-pressure high-temperature growth process.     

Revelation of Causes of Colour Change in Beryllium-Treated Sapphires

Blue sapphires are treated with Be in oxidizing atmosphere to change the blue colour into yellow. Untreated and Be-treated samples are examined using laser ablation inductively coupled-plasma-mass spectrometry （LA-ICP- MS）, electron spin resonance （ESR） and ultraviolet-visible （UV-vis） spectroscopy. The results show that the yellow colouration in Be-heated blue sapphires is not due to Be diffusion from the surface of sapphire. Be behaves as a sole catalyst in this process. We find that the charge transfer between the ferrous （Fe^2＋） and ferric （Fe^3＋） is the reason of the colour change. The above conclusions are confirmed by ESR measurements to determine the connections between the Fe3＋ ions before and after Be-treated heat treatments.