Abstract. We present results of experimental studies on the formation of gas hydrates (clathrates) at conditions of geophysical interest. Clathrate hydrates formed by a reaction of gas at ice Ih surfaces are always found to be mesoporous to macroporous with pores sizes between 100 to 400 nm and pore volumes of approximately 25-40% for CH4, Ar and N2 hydrate, and smaller pores of 20 to 100rim with a porosity of approximately 10-20% for CO2 hydrate. The three-dimensional sponge-like microstructure occurs in single crystalline grains of typically a few •um size and was observed by field-emission scanning electron microscopy. It forms over a wide range of p-T conditions below the ice Ih melting. The porous microstructure is stable for at least several months, even close to the clathrate decomposition, and is proposed to be formed by local differences in the energy balance between hydrate formation and ice decompositon. The results presented are considered of potential major importance for the understanding of the behaviour of natural gas hydrates found e.g. in polar ice sheets and permafrost regions, and also in some celestial bodies.

Data on the influence of opioid substitution therapy (OST) on skeletal health in men is limited. This cross-sectional study aimed to determine the prevalence of low bone mass in male drug users and to evaluate the relationship between endogenous testosterone and bone mass. We recruited 144 men on long-term opioid maintenance therapy followed in the Center of Addiction Medicine in Basel, Switzerland. Data on medical and drug history, fracture risk and history of falls were collected. Bone mineral density (BMD) was evaluated by densitometry and serum was collected for measurements of gonadal hormones and bone markers. 35 healthy age- and BMI-matched men served as the control group. The study participants received OST with methadone (69 %), morphine (25 %) or buprenorphine (6 %). Overall, 74.3 % of men had low bone mass, with comparable bone mass irrespective of OST type. In older men (≥40 years, n = 106), 29.2 % of individuals were osteoporotic (mean T-score -3.0 ± 0.4 SD) and 48.1 % were diagnosed with osteopenia (mean T-score -1.7 ± 0.4 SD). In younger men (n = 38), 65.8 % of men had low bone mass. In all age groups, BMD was significantly lower than in age-and BMI-matched controls. In multivariate analyses, serum free testosterone (fT) was significantly associated with low BMD at the lumbar spine (p = 0.02), but not at the hip. When analysed by quartiles of fT, lumbar spine BMD decreased progressively with decreasing testosterone levels. We conclude that low bone mass is highly prevalent in middle-aged men on long-term opioid dependency, a finding which may partly be determined by partial androgen deficiency.

Stabilitätsgrenzen der Eisphasen4.1.1 Eisverwandte Strukturen: Clathrat-Hydrate 4.1.2 Eisverwandte Strukturen: Gas-Hydrate 4.2 Das Phasendiagramm von Eis in Wechselwirkung mit Gasen 4.3 Experimentelle Untersuchung von Schmelzkurven im System Eis und Gas bis zu Gasdrücken von p~6.5kbar 4.3.1 Schmelzkurvenexperimente an Eis Ih 4.3.2 Schmelzkurvenexperimente an Eis im Druckbereich von p~2.5kbar bis p~6.5kbar 4.3.3 Eis V und Eis VI 4.3.4 Metastabiles Eis XII und Eis IV 5. Strukturuntersuchungen 5.1 Argon-Clathrat-Hydrat 5.2 Neue Phasen im System Wasser und Neon 5.2.1 Neon-Clathrat-Hydrat 5.2.2 Gas-Hydrate 5.2.3 Eis II-Neon-Hydrat 5.3 Strukturelle Untersuchungen an Eis Ih 5.3.1 Die mittlere Struktur von Eis Ih 5.3.2 Strukturelle Untersuchungen an D 2 O-Eis Ih in Wechselwirkung mit Gasen 5.4 Verfeinerungsstrategie und Verfeinerungsproblematiken der Strukturbestimmung und des Eis Ih-Gasinhaltes 5.5 Experimentelle Ergebnisse 5.5.1 Gitterkonstanten von Eis Ih unter Gaswechselwirkung als Funktion von Druck und Temperatur 5.5.2 Eis Ih-Struktur als Funktion des Druckes und der Temperatur 5.5.3 Eis Ih-Struktur unter Einfluss von Argongas 5.5.4 Eis Ih-Hydrat. Wechselwirkung von Eis Ih mit Helium-und Neongas 5.5.5 Gasinhalt in Eis Ih für Helium-und Neongas 5.5.6 Neon 5.5.7 Helium 5.5.8 Struktur von Eis Ih und Eis Ih-Hydrat. Experimentelle Ergebnisse im Vergleich 5.6 Sorptionssimulationen von Helium-und Neongas in Eis Ih-Hydrat 5.6.1 Ergebnisse der Sorptionssimulationen 6. Diskussion und Ausblick 207 7. Literaturverzeichnis L-1 8. Anhang 8.2.1 Experimentelle und theoretische Grundlagen -Die pVT-Apparatur: Schematische Zeichnung und Erläuterung des HD-Sticks A-1 8.2.1.3.1 GEM (General Material Diffraktometer) A-2 8.2.2.1 Experimentelle und theoretische Grundlagen -Rietveld-Strukturanalyse: Definition des thermischen Auslenkungsparameters U A-3 8.3.2 Die Herstellung von Eis Ih : Rekristallisation von Eis Ih A-4 8.3.3 Phasenübergänge von Hochdruckeisphasen in Eis Ic als transiente Phase: Stapelfehler und lokale Delokationen A-5 8.3.3.1 Strukturelle Untersuchungen an kubischem Eis Ic A-6 8.3.3.1.2 Strukturelle Untersuchungen an kubischem Eis Ic: Rietveld-Anpassungen A-8 8.3.3.1.3 Strukturelle Untersuchungen an kubischem Eis Ic: Peakprofilparameter A-12 8.3.3.1.4 Strukturelle Untersuchungen an kubischem Eis Ic: Quantitative Phasenanteile an kubischem Eis Ic mittels Einzelreflexfits A-12 8.3.3.2 Kinetik der Phasenübergänge in kubisches Eis Ic A-19 8.5.4 Verfeinerungsstrategie und Verfeinerungsproblematiken der Strukturbestimmung und des Eis Ih-Gasinhaltes A-24 8.5.5.1 Experimentelle Ergebnisse: Kompressibilitäten und Expansivitäten von Eis Ih A-26 Danksagung Lebenslauf * Abbildung 2.1: Schematischer Aufbau der pVT-Apparatur, * : Schematische Zeichnung und Erläuterung des HD-Stick vergl. Abbildung, Anhang 8.2.1