Zur thermischen Zersetzung der hochkonzentrierten Salpetersäure

The thermal decomposition of highly concentrated nitric acid was observed at atmospheric pressure between 0 and 60 °C for up to 273 d. The decomposition of highly concentrated nitric acid $$2 HNO_3 \rightleftharpoons 2 NO_2 + H_2 O + {1 \mathord{\left/ {\vphantom {1 2}} \right. \kern-\nulldelimiterspace} 2} O_2 $$ is a second order reaction in nitric acid. The reversible reaction proceeds to equilibrium. The velocity and equilibrium constants were obtained by kinetic evaluation of the readings for HNO₃ and NO₂. The activation energy for decomposition was — 134 kJ/mol.     

A new synthetic cobalt tellurate: Co3TeO6

Single crystals of tricobalt(II) tellurium(VI) hexa­oxide, Co₃TeO₆, were synthesized via transport reactions using HCl as transporting agent. The compound crystallizes in the monoclinic system (space group C2/c). The Te atoms are positioned in 4b () and 8f positions, while the Co atoms are in 4e (2) and 8f positions. The structure consists of (100) oxygen layers packed in a hhchhc sequence, with Te^VI in octa­hedral coordination and Co^II in both octa­hedral and tetra­hedral coordination. The structure contains face‐sharing CoO₆ octa­hedra, as well as edge‐sharing CoO₄ tetra­hedra. Co₃TeO₆ is the first oxide that is isostructural with the β‐Li₃MF₆ family of compounds (M = Al, Cr, Ga, Ti and V).     

Deposition and aggregation of aspirin molecules on a phospholipid bilayer pattern

Aspirin and 1,2-dimyristoyl-sn-glycero-3-phosphoethanolamine (DMPE) are deposited from their alcoholic mixed solution onto highly oriented pyrolytic graphite (HOPG) by spin coating. The film structure and morphology are characterized by atomic force microscopy (AFM). The barely soluble DMPE forms a highly oriented stripe phase as a result of its one-dimensional epitaxy with the HOPG lattice. The bilayer stripe pattern exposes the cross section of the lipid bilayer lamellae and enables the direct visualization of the molecular interactions of drug or biological molecules with either the hydrophobic or the hydrophilic part of the phospholipid bilayer. The bilayer pattern affects the aspirin molecular deposition and aggregation. AFM shows that the aspirin molecules prefer to deposit and aggregate along the aliphatic interior part of the bilayer pattern, giving rise to parallel dimer rods in registry with the underlying pattern. The nonpolar interactions between aspirin and the phospholipid bilayer are consistent with the lipophilic nature of aspirin. The bilayer pattern not only stabilizes the rodlike aggregate structure of aspirin at low aspirin concentration but also inhibits crystallization of aspirin at high aspirin concentration. Molecular models show that the width of the DMPE aliphatic chain interior can accommodate no more than two aspirin dimers. The bilayer confinement may prevent aspirin from reaching its critical nucleus size. This study illustrates a general method to induce a metastable or amorphous form of an active pharmaceutical ingredient (API) by chemical confinement under high undercooling conditions. Metastable and amorphous solids often display better solubility and bioavailability than the stable crystalline form of the API.     

IR reflection spectra of monolayer films sandwiched between two high refractive index materials

Monolayer films adsorbed on substrates with high refractive indices such as metals or semiconductors yield strongly enhanced infrared reflection spectra when they are contacted with a transparent, high refractive index ambient medium and are probed with p-polarized light at high incidence angles. The sensitivity increase arises from the enhancement of the perpendicular electric field within a thin, low refractive index layer sandwiched between two high refractive index materials and gives rise to signal intensity gains up to 2 orders of magnitude in combination with an essentially exclusive detection of only perpendicular surface vibrations. Experimental spectra of ordered monolayer films of octadecanethiol on gold and of octadecylsiloxane on silicon in this sandwich configuration yield enhancement factors between 15 (on Si) and 30 (on gold) compared to conventional grazing incidence external reflection spectra and are governed by a common, simple surface selection rule, which allows immediate quantitative evaluation and comparison of the film structures on different substrates.     

Photometrische Bestimmung von Ozon im Trinkwasser

Zusammenfassung Als Reagens für die photometrische Ozonbestimmung wird N-N-N-N-Tetramethyl-p-phenylendiamin in citronensaurer Lösung vorgeschlagen. Zur Aufnahme der Eichkurve dient eine Apparatur zur kontinuierlichen Erzeugung eines Wassers mit konstantem Ozongehalt. Die jodometrische Titration dieser kleinen Konzentrationen wird beschrieben. Ozon reagiert mit zwei Äquivalenten unter Bildung des Farbstoffes. Die Störung durch salpetrige Säure kann durch Pufferung auf p_H 5 ausgeschlossen werden.     

Chromatographische Bestimmung kleiner Mengen o-Kresol in Kresolgemischen

Zusammenfassung Es wird eine Analysenmethode beschrieben zur Bestimmung kleiner Mengen o-Kresol in Mischungen mit m- und p-Kresol, welche außerdem noch kleine Mengen Phenol, o-Äthylphenol, sowie von Xylenolen enthalten können. Die Methode beruht auf folgender Grundlage. Die Phenole werden mit diazotiertem p-Nitranilin gekuppelt, das Farbstoffgemisch auf Al₂O₃-Säulen chromatographiert und der abgetrennte o-Kresolfarbstoff mit einem geeigneten Photometer gemessen. Mengen von einigen Prozenten o-Kresol bis herunter zu weniger als einem Zehntelprozent lassen sich mit dieser Methode exakt bestimmen, ohne daß die obengenannten Beimengungen stören.Der Verfasser dankt dem Leiter des Laboratoriums Herrn Dr. E. van Hulle für wertvolle Ratschläge, Herrn Dr. H. Hoyer für die ultrarotspektrographischen Bestimmungen mit dem Doppelstrahlapparat Modell 21 der Perkin-Elmer Corp. und Herrn Dr. A. Wadenklee für die Nachprüfung der übrigen Methoden, insbesondere die eingehende Bearbeitung der Kondensationsmethode mit Benzaldehyd.     

Switching the Stiffness of Polyelectrolyte Assembly by Light to Control Behavior of Supported Cells

Polyelectrolyte block copolymer micelles assembled thin film is switched in response to local photocatalytic reactions on titanium dioxide, resulting in a layer of variable height, stiffness in response to visible light irradiation. Preosteoblasts migrate toward stiffer side of the substrates.

     

On initial value problems for quaternionic valued functions

In [2], [6], [7], methods are discussed for solving initial value problems