Hard x-ray photoelectron spectroscopy of bulk and thin films of Heusler compounds

X-ray photoemission spectroscopy (XPS) is one of the most universal and powerful tools for investigation of chemical states and electronic structures of materials. The application of hard x-rays increases the inelastic mean free path of the emitted electrons within the solid and thus makes hard x-ray photoelectron spectroscopy (HAXPES) a bulk sensitive probe for solid state research and especially a very effective nondestructive technique to study buried layers.rnThis thesis focuses on the investigation of multilayer structures, used in magnetic tunnel junctions (MTJs), by a number of techniques applying HAXPES. MTJs are the most important components of novel nanoscale devices employed in spintronics. rnThe investigation and deep understanding of the mechanisms responsible for the high performance of such devices and properties of employed magnetic materials that are, in turn, defined by their electronic structure becomes feasible applying HAXPES. Thus the process of B diffusion in CoFeB-based MTJs was investigated with respect to the annealing temperature and its influence on the changes in the electronic structure of CoFeB electrodes that clarify the behaviour and huge TMR ratio values obtained in such devices. These results are presented in chapter 6. The results of investigation of the changes in the valence states of buried off-stoichiometric Co2MnSi electrodes were investigated with respect to the Mn content α and its influence on the observed TMR ratio are described in chapter 7.rnrnMagnetoelectronic properties such as exchange splitting in ferromagnetic materials as well as the macroscopic magnetic ordering can be studied by magnetic circular dichroism in photoemission (MCDAD). It is characterized by the appearance of an asymmetry in the photoemission spectra taken either from the magnetized sample with the reversal of the photon helicity or by reversal of magnetization direction of the sample when the photon helicity direction is fixed. Though recently it has been widely applied for the characterization of surfaces using low energy photons, the bulk properties have stayed inaccessible. Therefore in this work this method was integrated to HAXPES to provide an access to exploration of magnetic phenomena in the buried layers of the complex multilayer structures. Chapter 8 contains the results of the MCDAD measurements employing hard x-rays for exploration of magnetic properties of the common CoFe-based band-ferromagnets as well as half-metallic ferromagnet Co2FeAl-based MTJs.rnrnInasmuch as the magnetoresistive characteristics in spintronic devices are fully defined by the electron spins of ferromagnetic materials their direct measurements always attracted much attention but up to date have been limited by the surface sensitivity of the developed techniques. Chapter 9 presents the results on the successfully performed spin-resolved HAXPES experiment using a spin polarimeter of the SPLEED-type on a buried Co2FeAl0.5Si0.5 magnetic layer. The measurements prove that a spin polarization of about 50 % is retained during the transmission of the photoelectrons emitted from the Fe 2p3/2 state through a 3-nm-thick oxide capping layer.rn

Die Isolierung und Aufreinigung der Metalloendopeptidase LysN und die Evaluierung der Spezifität der LysN E157D-Mutante und ihr Einsatz in der Proteomik und die Mechanismen der Bildung von “dendritic cell aggresome- like induced structures“ (DALIS)

Der proteolytische Verdau von Proteinen in Peptide ist ein wichtiger Schritt in der Tandem-Massenspektrometrie. Dabei werden Peptide fragmentiert und die sich ergebenden Fragmentionen geben Aufschluss über die Aminosäuresequenz des zu untersuchenden Proteins. Dabei sind für die Fragmentierung sowohl Länge und Sequenz, als auch der Ladungszustand des Peptids ungemein wichtig. Diese Parameter bedingen sich durch Endoproteasen, die für den proteolytischen Verdau eingesetzt werden. Eine Voraussetzung hierfür ist die Spezifität der Protease. Trypsin ist bei weitem die gebräuchlichste Protease zur massenspektrometrischen Probenvorbereitung. Allerdings bietet Trypsin keine Komplettlösung. Je nach Fragestellung und Applikation müssen weitere Proteasen eingesetzt werden, um eine komplette Sequenzabdeckung zu gewährleisten und möglichst alle posttranslationalen Modifikationen nachzuweisen, oder bestimmte Proteomklassen (z.B Phosphoproteom

Spins, moments and radii of cd isotopes

The complex nature of the nucleon-nucleon interaction and the wide range of systems covered by the roughly 3000 known nuclides leads to a multitude of effects observed in nuclear structure. Among the most prominent ones is the occurence of shell closures at so-called ”magic numbers”, which are explained by the nuclear shell model. Although the shell model already is on duty for several decades, it is still constantly extended and improved. For this process of extension, fine adjustment and verification, it is important to have experimental data of nuclear properties, especially at crucial points like in the vicinity of shell closures. This is the motivation for the work performed in this thesis: the measurement and analysis of nuclear ground state properties of the isotopic chain of 100−130Cd by collinear laser spectroscopy.rnrnThe experiment was conducted at ISOLDE/CERN using the collinear laser spectroscopy apparatus COLLAPS. This experiment is the continuation of a run on neutral atomic cadmium from A = 106 to A = 126 and extends the measured isotopes to even more exotic species. The required gain in sensitivity is mainly achieved by using a radiofrequency cooler and buncher for background reduction and by using the strong 5s 2S1/2 → 5p 2P3/2 transition in singly ionized Cd. The latter requires a continuous wave laser system with a wavelength of 214.6 nm, which has been developed during this thesis. Fourth harmonic generation of an infrared titanium sapphire laser is achieved by two subsequent cavity-enhanced second harmonic generations, leading to the production of deep-UV laser light up to about 100 mW.rnrnThe acquired data of the Z = 48 Cd isotopes, having one proton pair less than the Z = 50 shell closure at tin, covers the isotopes from N = 52 up to N = 82 and therefore almost the complete region between the neutron shell closures N = 50 and N = 82. The isotope shifts and the hyperfine structures of these isotopes have been recorded and the magnetic dipole moments, the electric quadrupole moments, spins and changes in mean square charge radii are extracted. The obtained data reveal among other features an extremely linear behaviour of the quadrupole moments of the I = 11/2− isomeric states and a parabolic development in differences in mean square nuclear charge radii between ground and isomeric state. The development of charge radii between the shell closures is smooth, exposes a regular odd-even staggering and can be described and interpreted in the model of Zamick and Thalmi.

Nanoparticular iron complex drugs for parenteral administration - physicochemical characterization, biological distribution and pharmacological safety

Iron deficiency is the most common deficiency disease worldwide with many patients who require intravenous iron. Within the last years new kind of parenteral iron complexes as well as generic preparations entered the market. There is a high demand for methods clarifying benefit to risk profiles of old and new iron complexes. It is also necessary to disclose interchangeability between originator and intended copies to avoid severe anaphylactic and anaphylactoid side reaction and assure equivalence of therapeutic effect.rnrnThe investigations presented in this work include physicochemical characterization of nine different parenteral iron containing non-biological complex drugs. rnWe developed an in-vitro assay, which allows the quantification of labile iron in the different complexes and thus it is a useful tool to estimate the pharmaclogical safety regarding iron related adverse drug events. This assay additionally allowed the estimation of complex stability by evaluation of degradation kinetics at the applied conditions.rnrnAn in-ovo study was performed to additionally compare different complexes in respect to body distribution. This in combination with complex stability information allowed the risk estimation of potential local acute and chronic reactions to iron overload.rnrnInformation obtained by the combination of the methods within this work are helpful to estimate the safety and efficacy profile of different iron containing non-biological complex drugs. rnrnPhysicochemical differences between the complexes were demonstrated in respect to size of the inorganic fraction, size and size distribution of the complete particles, structure of the inorganic iron fraction, morphology of the complexes and charge of the complexes. And furthermore significant differences in the biological behavior of different complexes were demonstrated. rnrnThe combination of complex stability and biodistribution as well as the combination of structure, size and stability represent helpful tools for the physicochemical characterization of iron containing non-biological complex drugs and for the estimation of pharmacological safety. This work thus represents an up to date summary of some relevant methods for the characterization of intravenous iron complex drugs in respect to pharmaceutical quality, pharmacological safety and aspects of efficacy. rnrnProspectively, it is worthwhile that the methods within this work will contribute to the development and/or characterization of iron containing nanoparticular formulations with beneficial efficacy and safety profiles.rn