Metallic Magnets without Inversion Symmetry and Antiferromagnetic Quantum Critical Points

This thesis focusses on two classes of systems that exhibit non-Fermi liquid behaviour in experiments: we investigated aspects of chiral ferromagnets and of antiferromagnetic metals close to a quantum critical point. In chiral ferromagnets, the absence of inversion symmetry makes spin-orbit coupling possible, which leads to a helical modulation of the ferromagnetically ordered state. We studied the motion of electrons in the magnetically ordered state of a metal without inversion symmetry by calculating their generic band-structure. We found that spin-orbit coupling, although weak, has a profound effect on the shape of the Fermi surface: On a large portion of the Fermi surface the electron motion parallel to the helix practically stops. Signatures of this effect can be expected to show up in measurements of the anomalous Hall effect. Recent neutron scattering experiments uncovered the existence of a peculiar kind of partial order in a region of the phase diagram adjacent to the ordered state of the chiral ferromagnet MnSi. Starting from the premise that this partially ordered state is a thermodynamically distinct phase, we investigated an extended Ginzburg-Landau theory for chiral ferromagnets. In a certain parameter regime of the Ginzburg-Landau theory we identified crystalline phases that are reminiscent of the so-called blue phases in liquid crystals. Many antiferromagnetic heavy-fermion systems can be tuned into a regime where they exhibit non-Fermi liquid exponents in the temperature dependence of thermodynamic quantities such as the specific heat capacity; this behaviour could be due to a quantum critical point. If the quantum critical behaviour is field-induced, the external field does not only suppress antiferromagnetism but also induces spin precession and thereby influences the dynamics of the order parameter. We investigated the quantum critical behavior of clean antiferromagnetic metals subject to a static, spatially uniform external magnetic field. We studied how the interplay of precession and damping affects various thermodynamic and transport quantities. We found that the susceptibility d M/d B is the thermodynamic quantity which shows the most significant change upon approaching the quantum critical point and which gives experimental access to the (dangerously irrelevant) spin-spin interactions. Finally, we studied the quantum critical behaviour of two-dimensional antiferromagnetic metals. Going beyond an order parameter theory, we included the electronic quasiparticles as well as the fluctuating magnetization in a functional Renormalization Group calculation. Preliminary results indicate a divergence in the fRG-equations already at a finite distance from the quantum critical point - this is incompatible with the Hertz-Millis picture

Integrated collinear refractive index sensor with Ge PIN photodiodes

Refractive index sensing is a highly sensitive and label-free detection method for molecular binding events. Commercial implementations of biosensing concepts based on plasmon resonances typically require significant external instrumentation such as microscopes and spectrometers. Few concepts exist that are based on direct integration of plasmonic nanostructures with optoelectronic devices for on-chip integration. Here, we present a CMOS-compatible refractive index sensor consisting of a Ge heterostructure PIN diode in combination with a plasmonic nanohole array structured directly into the diode Al contact metallization. In our devices, the photocurrent can be used to detect surface refractive index changes under simple top illumination and without the aid of signal amplification circuitry. Our devices exhibit large sensitivities > 1000 nm per refractive index unit in bulk refractive index sensing and could serve as prototypes to leverage the cost-effectiveness of the CMOS platform for ultra-compact, low-cost biosensors.Comment: 21 pages, 6 figures, supporting information with 11 pages and 11 figures attache

Crystalline phases in chiral ferromagnets: Destabilization of helical order

In chiral ferromagnets, weak spin-orbit interactions twist the ferromagnetic order into spirals, leading to helical order. We investigate an extended Ginzburg-Landau theory of such systems where the helical order is destabilized in favor of crystalline phases. These crystalline phases are based on periodic arrangements of double-twist cylinders and are strongly reminiscent of blue phases in liquid crystals. We discuss the relevance of such blue phases for the phase diagram of the chiral ferromagnet MnSi.Comment: 6 pages, 5 figures (published version

Cylindrical Microparticles Composed of Mesoporous Silica Nanoparticles for the Targeted Delivery of a Small Molecule and a Macromolecular Drug to the Lungs: Exemplified with Curcumin and siRNA

The transport of macromolecular drugs such as oligonucleotides into the lungs has become increasingly relevant in recent years due to their high potency. However, the chemical structure of this group of drugs poses a hurdle to their delivery, caused by the negative charge, membrane impermeability and instability. For example, siRNA to reduce tumour necrosis factor alpha (TNF-α) secretion to reduce inflammatory signals has been successfully delivered by inhalation. In order to increase the effect of the treatment, a co-transport of another anti-inflammatory ingredient was applied. Combining curcumin-loaded mesoporous silica nanoparticles in nanostructured cylindrical microparticles stabilized by the layer-by-layer technique using polyanionic siRNA against TNF-α was used for demonstration. This system showed aerodynamic properties suited for lung deposition (mass median aerodynamic diameter of 2.85 ± 0.44 µm). Furthermore, these inhalable carriers showed no acute in vitro toxicity tested in both alveolar epithelial cells and macrophages up to 48 h incubation. Ultimately, TNF-α release was significantly reduced by the particles, showing an improved activity co-delivering both drugs using such a drug-delivery system for specific inhibition of TNF-α in the lungs

Cylindrical Microparticles Composed of Mesoporous Silica Nanoparticles for the Targeted Delivery of a Small Molecule and a Macromolecular Drug to the Lungs: Exemplified with Curcumin and siRNA

The transport of macromolecular drugs such as oligonucleotides into the lungs has become increasingly relevant in recent years due to their high potency. However, the chemical structure of this group of drugs poses a hurdle to their delivery, caused by the negative charge, membrane impermeability and instability. For example, siRNA to reduce tumour necrosis factor alpha (TNF-α) secretion to reduce inflammatory signals has been successfully delivered by inhalation. In order to increase the effect of the treatment, a co-transport of another anti-inflammatory ingredient was applied. Combining curcumin-loaded mesoporous silica nanoparticles in nanostructured cylindrical microparticles stabilized by the layer-by-layer technique using polyanionic siRNA against TNF-α was used for demonstration. This system showed aerodynamic properties suited for lung deposition (mass median aerodynamic diameter of 2.85 ± 0.44 µm). Furthermore, these inhalable carriers showed no acute in vitro toxicity tested in both alveolar epithelial cells and macrophages up to 48 h incubation. Ultimately, TNF-α release was significantly reduced by the particles, showing an improved activity co-delivering both drugs using such a drug-delivery system for specific inhibition of TNF-α in the lungs

Exploring the Aspects of Blogging as a Professional Activity and their Influence on Authenticity of the Author and Credibility of the Blog

Blogging has established itself as an important and influential part of the modern online media. At the dawn of the blogosphere people were publishing their diaries and life journals. Nowadays, some bloggers operate blogs that are hardly any different from online newspapers and magazines. On the one hand professional blogging is broadly accepted in the society, but on the other hand it is poorly understood. The purpose of this explorative study is to broaden the understanding of blogging as a professional activity. In particular, this study explores the aspects of professional blogging and the interplay between credibility, authenticity and monetisation in blogs. To understand blogging as a professional activity an extensive literature research is conducted. First, main concepts of blogging as a social activity are discussed. Then, the changes that come together with the transformation of a social activity into a professional activity of blogging are discussed. To look at the activity of blogging from an unusual perspective, a comprehensive qualitative survey is conducted with blog readers. The survey examines not only readers’ perception of blogging as a professional activity, but also motivations for reading blogs and attitude to monetising practices and labelling of monetised content in blogs. Information received from the survey is used to draw some conclusions about the state of the art of blogging as a professional activity, and challenges and opportunities blogging industry faces nowadays

Developing and analysing a curriculum map in Occupational- and Environmental Medicine

Background: During the last 5 years a fundamental curriculum reform was realized at the medical school of the Ludwig Maximilians University. In contrast to those efforts, the learning objectives were not defined consistently for the curriculum and important questions concerning the curriculum could not be answered. This also applied to Occupational and Environmental Medicine where teachers of both courses were faced with additional problems such as the low number of students attending the lectures. The aims of the study were to develop and analyse a curriculum map for Occupational and Environmental Medicine based on learning objectives using a web-based database. Furthermore we aimed to evaluate student perception about the curricular structure. Methods: Using a web-based learning objectives database, a curriculum map for Occupational and Environmental Medicine was developed and analysed. Additionally online evaluations of students for each course were conducted. Results: The results show a discrepancy between the taught and the assessed curriculum. For both curricula, we identified that several learning objectives were not covered in the curriculum. There were overlaps with other content domains and redundancies within both curricula. 53% of the students in Occupational Medicine and 43% in Environmental Medicine stated that there is a lack of information regarding the learning objectives of the curriculum. Conclusions: The results of the curriculum mapping and the poor evaluation results for the courses suggest a need for re-structuring both curricula

What are effects of a spaced activation of virtual patients in a pediatric course?

BACKGROUND: Virtual patients (VPs) have a long tradition in the curriculum of the medical faculty at the Ludwig-Maximilians-University (LMU) Munich. However, the pediatric VPs were not well integrated into the curriculum and hardly used by students. METHODS: Therefore we created and implemented a self-contained E-learning module based on virtual patients (VPs), which was embedded into the pediatric curriculum. Students taking this course were divided into two groups. For Group A the virtual patients were activated in a timed order (“spaced activation”), whereas Group B could work on all VPs from the beginning. We investigated the performance of these two groups concerning usage pattern including number of sessions and session duration, score on questions integrated into the VP and results of the intermediate exam. RESULTS: The integration of the VPs into the pediatric course was successful for both groups. The usage pattern for the spaced activation turned out to be more balanced, however we did not find any significant differences in the results of the intermediate exam, the score on questions included in the VPs nor in the time students spent working on the VPs. CONCLUSIONS: Our study showed that the spaced activation led to a more balanced VP usage pattern with a lower peak of sessions at the end of the course. Further studies will have to investigate whether a spaced activation of VPs leads to favorable long-term learning outcomes