NMR-Untersuchungen zur kollektiven Diffusion von Wasser und gelösten Ionen: Die dynamische Hydratationszahl und der Einfluss poröser Materialien

Gegenstand der Arbeit ist die Untersuchung der kollektiven Diffusion von Wasser und Ionen in wässrigen Elektrolytlösungen. Dabei wird insbesondere die Dynamik der Wassermoleküle innerhalb der Hydratationshüllen der Ionen und der Einfluss poröser Materialien untersucht. Nach einer Einführung zur Dynamik der Hydratationshülle folgen Grundlagen der NMR-Diffusometrie, welche genutzt wurde um die Selbstdiffusionskoefifizienten der Wassermolek\u7füle und der Ionen der Lösungen zu messen. Daraus wurden die dynamischen Hydratationszahlen der Ionen bestimmt, welche die Anzahl an Wassermolekülen angeben, die durch die Diffusion des Ions in ihrer translatorischen Bewegung beeinflusst sind. Der Einfluss poröser Materialien auf die Dynamik wird am Beispiel nanopor\u7föser Glasmonolithe und mikroporöser Li-LSX Kristalle untersucht

Water dynamics of LiCl solutions confined in nanopores

The self-diffusion of water in aqueous solutions of lithium chloride in bulk solutions and in these solutions confined to porous glass monoliths with bimodal pore structure has been studied by PFG NMR. The concentration dependent data for the bulk solutions are analyzed by the description of Sevrugin et al. [1], which yields information about the water dynamics within the ion’s hydration shell. For an application to confined diffusion, this description is extended by introducing a tortuosity factor. Whereas in the larger macropores no influence on the water dynamics within the hydration shell is detected, in the smaller mesopores, a significant increase of the mobility of the hydrating water molecules is observed

The kinematics in the pc-scale jets of AGN The case of S5 1803+784

We present a kinematic analysis of jet component motion in the VLBI jet of the BL Lac object S5 1803+784, which does not reveal long-term outward motion for most of the components. Understanding the complex kinematic phenomena can possibly provide insights into the differences between quasars and BL Lac objects. The blazar S5 1803+784 has been studied with VLBI at $\nu$ =1.6, 2.3, 5, 8.4, and 15 GHz between 1993.88 and 2005.68 in 26 observing runs. We (re)analyzed the data and present Gaussian model-fits. We collected the already published kinematic information for this source from the literature and re-identified the components according to the new scenario presented in this paper. Altogether, 94 epochs of observations have been investigated. A careful study of the long-term kinematics reveals a new picture for component motion in S5 1803+784. In contrast to previously discussed motion scenarios, we find that the jet structure within 12 mas of the core can most easily be described by the coexistence of several bright jet features that remain on the long-term at roughly constant core separations (in addition to the already known {\it stationary} jet component $\sim$ 1.4 mas) and one faint component moving with an apparent superluminal speed ($\sim$ 19c, based on 3 epochs). While most of the components maintain long-term roughly constant distances from the core, we observe significant, smooth changes in their position angles. We report on an evolution of the whole jet ridge line with time over the almost 12 years of observations. The width of the jet changes periodically with a period of $\sim$ 8 to 9 years. We find a correlation between changes in the position angle and maxima in the total flux-density. We present evidence for a geometric origin of the phenomena and discuss possible models.Comment: The manuscript will be published by A&

The Cosmological History of Accretion onto Dark Halos and Supermassive Black Holes

Aims: We investigate the cosmological growth of dark halos and follow the consequences of coeval growth for the accretion history of associated supermassive black holes. Methods: The Press-Schechter approximation is used to obtain an analytic expression for the mean rate of growth of dark matter halos. Dark halo accretion rates are compared with numerical work and the consequences for understanding AGN evolution are described. Results: The mean accretion rate onto dark matter halos is shown to have a simple analytic form that agrees with previous numerical work and that may easily be calculated for a wide range of halo mass, redshift and cosmological parameters. The result offers a significant improvement over published fitting formulae deduced from merger trees. We then consider the growth of associated supermassive black holes, and make a basic test of the simple hypothesis of `Pure Coeval Evolution' (PCE) in which, on average, black hole growth tracks dark halo growth. We demonstrate that both the absolute value of the integrated AGN bolometric luminosity density and its cosmological evolution derived from hard X-ray surveys are well-reproduced by PCE. Excellent agreement is found at z >~ 0.5, although the observed luminosity density drops by a factor 2 compared with PCE by z=0: black hole growth appears to decouple from halo growth at low redshifts, and this may be related to the phenomenon of `cosmic downsizing'. Overall, AGN evolution appears either to be caused by or to be closely linked to the slow-down in the growth of cosmic structure. We also discuss the mean Eddington ratio averaged over all galaxies, which is predicted to show strong evolution to higher values with redshift.Comment: 14 pages. Accepted for publication in Astronomy and Astrophysic

NMR-Untersuchungen zur kollektiven Diffusion von Wasser und gelösten Ionen: Die dynamische Hydratationszahl und der Einfluss poröser Materialien

Gegenstand der Arbeit ist die Untersuchung der kollektiven Diffusion von Wasser und Ionen in wässrigen Elektrolytlösungen. Dabei wird insbesondere die Dynamik der Wassermoleküle innerhalb der Hydratationshüllen der Ionen und der Einfluss poröser Materialien untersucht. Nach einer Einführung zur Dynamik der Hydratationshülle folgen Grundlagen der NMR-Diffusometrie, welche genutzt wurde um die Selbstdiffusionskoefifizienten der Wassermolek\u7füle und der Ionen der Lösungen zu messen. Daraus wurden die dynamischen Hydratationszahlen der Ionen bestimmt, welche die Anzahl an Wassermolekülen angeben, die durch die Diffusion des Ions in ihrer translatorischen Bewegung beeinflusst sind. Der Einfluss poröser Materialien auf die Dynamik wird am Beispiel nanopor\u7föser Glasmonolithe und mikroporöser Li-LSX Kristalle untersucht

Software Verification with Integrated Data Type Refinement for Integer Arithmetic

We present an approach to integrating the refinement relation between infinite integer types (used in specification languages) and finite integer types (used in programming languages) into software verification calculi. Since integer types in programming languages have finite ranges, in general they are not a correct data refinement of the mathematical integers usually used in specification languages. Ensuring the correctness of such a refinement requires generating and verifying additional proof obligations. We tackle this problem considering Java and UML/OCL as example. We present a sequent calculus for Java integer arithmetic with integrated generation of refinement proof obligations. Thus, there is no explicit..

Water dynamics of LiCl solutions confined in nanopores

The self-diffusion of water in aqueous solutions of lithium chloride in bulk solutions and in these solutions confined to porous glass monoliths with bimodal pore structure has been studied by PFG NMR. The concentration dependent data for the bulk solutions are analyzed by the description of Sevrugin et al. [1], which yields information about the water dynamics within the ion’s hydration shell. For an application to confined diffusion, this description is extended by introducing a tortuosity factor. Whereas in the larger macropores no influence on the water dynamics within the hydration shell is detected, in the smaller mesopores, a significant increase of the mobility of the hydrating water molecules is observed