Positive muon diffusion in mixed Nb‐hydrides, NbHxDy

Positive muons have been used to monitor the proton and deuteron mobilities in mixed, concentrated NbH_xD_y hydrides, with x+y= constant. The mobility of the muons decreases linearly with increasing D‐content, which is expected if the protons and the deuterons move in an uncorrelated fashion. Combined with other evidence which suggests that such correlations exist, the present observation may be interpreted as due to a destruction of a correlated motion of H’s or D’s in the vicinity of the muons. This revised version was published online in August 2006 with corrections to the Cover Date.     

Abriß einer einheitlichen Theorie der Gamma- und der hypergeometrischen Funktionen

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Ratchet patterns sort molecular shuttles

Molecular shuttles based on microtubules propelled by motor proteins can be guided on surfaces by adsorbing motors in chemical patterns or by using open guiding channels. While chemical patterns can guide microtubules based on a Brownian ratchet mechanism, the rigidity of the microtubules limits guiding to features with dimensions on the order of their persistence length (5 mm). To achieve guiding on micron-scale dimensions, physical barriers are required which can exploit the forces exerted by multiple motors to bend tubules into tight radii of curvature. Microtubule guiding is illustrated for the case of a special ratchet pattern that is capable of sorting microtubules on the basis of the direction of their motion. Received: 3 December 2001 / Accepted: 11 February 2002 / Published online: 22 April 2002     

Ein Nomogramm zur Reduktion eines Resonators mit interner dünner Linse

Ohne ZusammenfassungDiese Arbeit wurde durch den Schweiz. Nationalfonds unterstützt.     

Hochauflösende Elektronenmikroskopie an Yttriumiodidcarbidoxiden

High Resolution Electron Microscopy on Yttrium Iodide Carbide Oxides An investigation on the real structure of the yttrium iodide carbide oxides has been carried out by means of HRTEM. In the structures planar layer fragments with the general composition Y₂I₂C are linked via chains of corner sharing Y₄O tetrahedra building corrugated layers. A sequence of compounds with the general formula (Y₂I₂C)_nYO can be derived where n denotes the number of linked octahedra chains in the plane sections, and thus represents their width. Irregularities concerning the width of the planar segments have been detected. Besides the so far known members of the series Y₇I₆C₃O und Y₉I₈C₄O, with n = 3 and 4, respectively, an additional ordered compound with alternating 3 and 4 octahedra chains has been found. The introduction of the samples, which are very sensitive to air and moisture, into the microscope has been realised using a specially designed transfer system.     

Preparation and analysis of heart and skeletal muscle specimens with LAMMA

Summary A technique is described to obtain shockfrozen tissue specimens from a beating heart in situ using liquid propane as cooling agent. The method allows to take up to 8 samples from the ischemic area of the left ventricle of a pig heart following acute coronary artery occlusion.A freeze-drying apparatus was developed in which, under a vacuum of 10^–6 mm Hg, the specimens remain for 10 days with the temperature slowly rising from initially –100 C to room temperature. Freezing damages in the tissues samples due to the formation of ice crystals either during shock-freezing or freeze-drying are usually below the spatial resolution of the microscope system employed in the LAMMA instrument. Already after a few minutes of ischemia, a considerable decrease of the intracellular K/Na relation was measured. LAMMA spectra from skeletal muscle were taken to check for possible ion redistribution which had eventually occurred during the various steps of the preparation procedure employed.Supported by Deutsche Forschungsgemeinschaft, SFB 68, A 10     

Buchbesprechung

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Zur fluorimetrischen Bestimmung von Oestrogenen im Harn

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