Structures in superconducting YBa2Cu3O7−δ thin films investigated by magneto-optic technique

Using a reflection magneto-optic technique we have investigated natural inhomogeneities and artificial structures in YBCO thin films exposed to an external magnetic field. The artificial structures were mechanically scratched by scanning a diamond tip with different loading over the film surface. Alternatively planar structures with reduced oxygen content could be patterned by heating the YBCO film with a focused laser beam in nitrogen atmosphere. Depending on the laser annealing parameters different screening properties concerning the applied magnetic field could be achieved.As a magneto-optically active layer we used EuS films evaporated on glass as well as bismuth- and gallium-doped lutetium-iron-garnet films grown onto (111) oriented gadolinium-gal lium-gar net substrates by liquid phase epitaxy. In contrast to measurements with EuS films that show only weak faraday rotation for temperatures higher than 20 K the magneto-optic studies have been expanded to about 60 K by using the garnet films.     

How would an EU-membership of the Visegrád- countries affect Europe‘s economic geography?EU-membership of the Visegrád-countries

The question posed in the title of the paper is answered by simulating EU-integration of the Visegrád-countries by a spatial computable general equilibrium (SCGE) model. A two-sector model is calibrated for a system of almost 100 regions covering the whole area of Europe and a rest of world region. The sectors are a local sector, producing non-tradables under perfect competition, and a tradables sector, producing a large number of tradable varieties under monopolistic competition. Trade between regions is costly, with costs depending on geographic distance and national impediments to trade. The model is calibrated such that the equilibrium solution reproduces benchmark data about international trade and regional incomes. Economic integration is simulated by reducing impediments to trade between integrating countries and calculating a new counterfactual equilibrium.     

Complications following major abdominal surgery in cirrhotic patients

The morbidity and mortality associated with major abdominal surgical interventions in 34 histologically proven cirrhotic patients are analyzed by the authors. The surgical interventions were carried out as urgent, absolute and elective indications. Thirty-seven general and surgical complications were observed following major abdominal surgery in 34 cirrhotics. Seven out of 34 patients died, giving a mortality rate of 21%. Suture-line insufficiency, peritonitis, sepsis and other inflammatory processes turned out to be the most common complications. Statistical analysis showed that the Child criteria, prothrombin level and white blood cell count were useful prognostic factors.     

Cross sections of proton induced nuclear reactions on enriched 111Cd and 112Cd for the production of 111In for use in nuclear medicine

Proton induced nuclear reactions on enriched 111Cd and 112Cd have been studied up to 30 MeV in the context of routine production of the medically used isotope 111In with low and medium energy cyclotrons. The excitation functions of 111Cd(p,n)111m,gIn and 112Cd(p,2n)111m,gIn as production reactions and 111Cd(p,2n)110mIn, 111Cd(p,2n)110In, 111Cd(p,3n)109ml,m2,In, 112Cd(p,3n)110mIn, 112Cd(p,3n)110gIn as competing processes have been measured using the activation method involving the stacked-foil technique. The deduced thick target yields are compared with those obtained experimentally.     

Electrophilic chlorination of methane over superacidic sulfated zirconia

Catalytic chlorination of methane was studied over SO ₄ ^2– /ZrO₂, Pt/SO ₄ ^2– /ZrO₂, and Fe/Mn/SO ₄ ^2– /ZrO₂ solid superacid catalysts. The reactions were carried out in a continuous flow reactor under atmospheric pressure, at temperatures below 240°C, with a gaseous hourly space velocity of 1000 ml/g h and a methane to chlorine ratio of 4 to 1. At 200°C with 30% chlorine converted the selectivity in methyl chloride exceeds 90%. At more elevated temperatures, the selectivity decreases but stays above 80% in methyl chloride at 225°C using the sulfated zirconia catalysts. The selectivity can be enhanced by adding platinum to sulfated zirconia catalysts. An iron and manganese-doped catalyst exhibited excellent selectivities at somewhat lower conversions. Methyl chloride is obtained at 235°C in selectivities greater than 85%. No chloroform or carbon tetrachloride is formed. The electrophilic insertion involves electron-deficient metal-coordinated chlorine into the methane C-H bond.Catalysis by solid superacids, 29. For part 28 see ref. [14].     

Atomic force microscopy on polymers and polymer related compounds

Summary Surface morphology and molecular arrangement have been recorded by atomic force microscopy (AFM) on polytetrafluoroethylene (PTFE) and on polycarbonate (PC) films. In a thin layer of PTFE deposited by rubbing polymer on hot glass substrate unidirectional orientation of polymer has been revealed. Individual polymer chains have been visualized. An interchain distance of .53 nm and several periodicities along the chain contours have been found-.44 nm, .62 nm and .82 nm-in accordance with a 13/6 helix.The monitoring of surface changes during thermal treatment of amorphous-bis-phenol A-PC film has been realized by AFM. Different types of surface morphology were revealed. Spherulites are formed during polymer crystallization. In most cases, however, numerous nanocrystallites appeared after thermal treatment. On their surfaces well-ordered atomic scale AFM images have been received. The arrangement of AFM patterns can be characterized by periodicities of .50 nm and .52 nm in the orthogonal directions. Polycarbonate oligomers-as the product of surface degradation-effectively might form the observed nanocrystallites.Prof. Dr. G. Zachmann zum 60. Geburtstag herzlichst gewidmetThese results were given by us first in a lecture in Baltimore, at the 5th ISPAC Symposium on May 31, 1991, and in a lecture in Santa Barbara, at the Nanoscope Users Meeting on June 25, 1991     

Zur Reaktivität von Tanninen in Abhängigkeit vom Kambialalter

Ohne Zusammenfassung