DSC combined with chemiluminescence for studying polymer oxidation

The oxidation of (Ti,W)C ceramics have been studied as a part of the program to investigate of properties of powder materials. Thermogravimetry, derivative thermogravimetry (TG-DTG), and differential thermal analysis DSC have been used in the non-isothermal study of powder oxidation (Ti,W)C in dry air atmosphere. The powder of crystalline carbide cermets with a ratio of W:Ti equals 0.3 was used in this study. The diagrams were recorded on a sample mass 3.42 mg on the Setaram apparatus in temperatures ranging from 25 to 1000°C. Seven different heating rates were used. The analytical techniques SEM, WDX, EDX and XRD were used in the research. The kinetics of the oxidation process was followed by the integral method by applying the Coats-Redfern's approximation. The kinetic models of particular stages of (Ti,W)C oxidation were evaluated from the dynamic mass losses data. The values of apparent activation energy E and the pre-exponential factor A of each stage of the oxidation were calculated. This revised version was published online in July 2006 with corrections to the Cover Date.     

Influence of Cyclodextrins on the Kinetics of Oxidation of Amino Acids and BSA by Hydrazyl Radicals

The kinetics of oxidation of amino acids (Arg, His, Lys, Phe, Thr and Tyr), a dipeptide (Gly-His), and BSA (bovine serum albumin) by two persistent water soluble free radicals of the hydrazyl type has been studied.The rate decreases in the order Arg>Lys>Tyr>Thr>HisBSAPheGly-His with bothfree radicals. Addition to the reaction mixture of - and -cyclodextrin decreases the oxidation rate, probably due to amino acidencapsulation in the cyclodextrin cavity. -Cyclodextrin protects more efficiently against oxidation than -cyclodextrin.     

The microscopic investigation of structures of moving flux lines by neutron and muon techniques

We have used a variety of microscopic techniques to reveal the structure and motion of flux line arrangements, when the flux lines in low T _c type II superconductors are caused to move by a transport current. Using small-angle neutron scattering by the flux line lattice (FLL), we are able to demonstrate directly the alignment by motion of the nearest-neighbor FLL direction. This tends to be parallel to the direction of flux line motion, as had been suspected from two-dimensional simulations. We also see the destruction of the ordered FLL by plastic flow and the bending of flux lines. Another technique that our collaboration has employed is the direct measurement of flux line motion, using the ultra-high-resolution spectroscopy of the neutron spin-echo technique to observe the energy change of neutrons diffracted by moving flux lines. The muon spin rotation (μSR) technique gives the distribution of values of magnetic field within the FLL. We have recently succeeded in performing μSR measurements while the FLL is moving. Such measurements give complementary information about the local speed and orientation of the FLL motion. We conclude by discussing the possible application of this technique to thin film superconductors.     

Eine Ab?nderung der Kjeldahlschen Stickstoffbestimmungsmethode

Ohne Zusammenfassung