Refine
Year of publication
- 2014 (222) (remove)
Document Type
- Doctoral Thesis (222) (remove)
Keywords
- Gammastrahlungsastronomie (4)
- data analysis (4)
- gamma-ray astronomy (4)
- Crab Nebula (3)
- Datenanalyse (3)
- Krebsnebel (3)
- Synchronisation (3)
- Systembiologie (3)
- synchronization (3)
- systems biology (3)
Institute
- Institut für Biochemie und Biologie (37)
- Institut für Physik und Astronomie (25)
- Institut für Geowissenschaften (19)
- Wirtschaftswissenschaften (15)
- Institut für Chemie (13)
- Historisches Institut (12)
- Institut für Informatik und Computational Science (10)
- Department Psychologie (9)
- Hasso-Plattner-Institut für Digital Engineering gGmbH (9)
- Institut für Ernährungswissenschaft (8)
Geometric electroelasticity
(2014)
In this work a diffential geometric formulation of the theory of electroelasticity is developed which also includes thermal and magnetic influences. We study the motion of bodies consisting of an elastic material that are deformed by the influence of mechanical forces, heat and an external electromagnetic field. To this end physical balance laws (conservation of mass, balance of momentum, angular momentum and energy) are established. These provide an equation that describes the motion of the body during the deformation. Here the body and the surrounding space are modeled as Riemannian manifolds, and we allow that the body has a lower dimension than the surrounding space. In this way one is not (as usual) restricted to the description of the deformation of three-dimensional bodies in a three-dimensional space, but one can also describe the deformation of membranes and the deformation in a curved space. Moreover, we formulate so-called constitutive relations that encode the properties of the used material. Balance of energy as a scalar law can easily be formulated on a Riemannian manifold. The remaining balance laws are then obtained by demanding that balance of energy is invariant under the action of arbitrary diffeomorphisms on the surrounding space. This generalizes a result by Marsden and Hughes that pertains to bodies that have the same dimension as the surrounding space and does not allow the presence of electromagnetic fields. Usually, in works on electroelasticity the entropy inequality is used to decide which otherwise allowed deformations are physically admissible and which are not. It is alsoemployed to derive restrictions to the possible forms of constitutive relations describing the material. Unfortunately, the opinions on the physically correct statement of the entropy inequality diverge when electromagnetic fields are present. Moreover, it is unclear how to formulate the entropy inequality in the case of a membrane that is subjected to an electromagnetic field. Thus, we show that one can replace the use of the entropy inequality by the demand that for a given process balance of energy is invariant under the action of arbitrary diffeomorphisms on the surrounding space and under linear rescalings of the temperature. On the one hand, this demand also yields the desired restrictions to the form of the constitutive relations. On the other hand, it needs much weaker assumptions than the arguments in physics literature that are employing the entropy inequality. Again, our result generalizes a theorem of Marsden and Hughes. This time, our result is, like theirs, only valid for bodies that have the same dimension as the surrounding space.
Atmospheric interactions with land surface in the arctic based on regional climate model solutions
(2014)
Wer wird Vater und wann?
(2014)
Synchronization is a fundamental phenomenon in nature. It can be considered as a general property of self-sustained oscillators to adjust their rhythm in the presence of an interaction.
In this work we investigate complex regimes of synchronization phenomena by means of theoretical analysis, numerical modeling, as well as practical analysis of experimental data.
As a subject of our investigation we consider chimera state, where due to spontaneous symmetry-breaking of an initially homogeneous oscillators lattice split the system into two parts with different dynamics. Chimera state as a new synchronization phenomenon was first found in non-locally coupled oscillators system, and has attracted a lot of attention in the last decade. However, the recent studies indicate that this state is also possible in globally coupled systems. In the first part of this work, we show under which conditions the chimera-like state appears in a system of globally coupled identical oscillators with intrinsic delayed feedback. The results of the research explain how initially monostable oscillators became effectivly bistable in the presence of the coupling and create a mean field that sustain the coexistence of synchronized and desynchronized states. Also we discuss other examples, where chimera-like state appears due to frequency dependence of the phase shift in the bistable system.
In the second part, we make further investigation of this topic by modeling influence of an external periodic force to an oscillator with intrinsic delayed feedback. We made stability analysis of the synchronized state and constructed Arnold tongues. The results explain formation of the chimera-like state and hysteric behavior of the synchronization area. Also, we consider two sets of parameters of the oscillator with symmetric and asymmetric Arnold tongues, that correspond to mono- and bi-stable regimes of the oscillator.
In the third part, we demonstrate the results of the work, which was done in collaboration with our colleagues from Psychology Department of University of Potsdam. The project aimed to study the effect of the cardiac rhythm on human perception of time using synchronization analysis. From our part, we made a statistical analysis of the data obtained from the conducted experiment on free time interval reproduction task. We examined how ones heartbeat influences the time perception and searched for possible phase synchronization between heartbeat cycles and time reproduction responses. The findings support the prediction that cardiac cycles can serve as input signals, and is used for reproduction of time intervals in the range of several seconds.
When azobenzene-modified photosensitive polymer films are irradiated with light interference patterns, topographic variations in the film develop that follow the electric field vector distribution resulting in the formation of surface relief grating (SRG). The exact correspondence of the electric field vector orientation in interference pattern in relation to the presence of local topographic minima or maxima of SRG is in general difficult to determine. In my thesis, we have established a systematic procedure to accomplish the correlation between different interference patterns and the topography of SRG. For this, we devise a new setup combining an atomic force microscope and a two-beam interferometer (IIAFM). With this set-up, it is possible to track the topography change in-situ, while at the same time changing polarization and phase of the impinging interference pattern. To validate our results, we have compared two photosensitive materials named in short as PAZO and trimer. This is the first time that an absolute correspondence between the local distribution of electric field vectors of interference pattern and the local topography of the relief grating could be established exhaustively. In addition, using our IIAFM we found that for a certain polarization combination of two orthogonally polarized interfering beams namely SP (↕, ↔) interference pattern, the topography forms SRG with only half the period of the interference patterns. Exploiting this phenomenon we are able to fabricate surface relief structures below diffraction limit with characteristic features measuring only 140 nm, by using far field optics with a wavelength of 491 nm. We have also probed for the stresses induced during the polymer mass transport by placing an ultra-thin gold film on top (5–30 nm). During irradiation, the metal film not only deforms along with the SRG formation, but ruptures in regular and complex manner. The morphology of the cracks differs strongly depending on the electric field distribution in the interference pattern even when the magnitude and the kinetic of the strain are kept constant. This implies a complex local distribution of the opto-mechanical stress along the topography grating. The neutron reflectivity measurements of the metal/polymer interface indicate the penetration of metal layer within the polymer resulting in the formation of bonding layer that confirms the transduction of light induced stresses in the polymer layer to a metal film.
Der Häftlingsfreikauf aus der DDR 1962/63 - 1989 : zwischen Menschenhandel und humanitären Aktionen
(2014)
Weltweit streben Anti-Doping Institute danach jene Sportler zu überführen, welche sich unerlaubter Mittel oder Methoden bedienen. Die hierfür notwendigen Testsysteme werden kontinuierlich weiterentwickelt und neue Methoden aufgrund neuer Wirkstoffe der Pharmaindustrie etabliert. Gegenstand dieser Arbeit war es, eine parallele Mehrkomponentenanalyse auf Basis von Antigen-Antikörper Reaktionen zu entwickeln, bei dem es primär um Verringerung des benötigten Probevolumens und der Versuchszeit im Vergleich zu einem Standard Nachweis-Verfahren ging. Neben der Verwendung eines Multiplex Ansatzes und der Mikroarraytechnologie stellten ebenfalls die Genauigkeit aller Messparameter, die Stabilität des Versuchsaufbaus sowie die Performance über einen Einfach-Blind-Ansatz Herausforderungen dar. Die Anforderung an den Multiplex Ansatz, keine falschen Signale trotz ähnlicher Strukturen zu messen, konnte durch die gezielte Kombination von spezifischen Antikörpern realisiert werden. Hierfür wurden neben Kreuzreaktivitätstests auf dem Mikroarray parallel erfolgreich Western Blot Versuche durchgeführt. Jene Antikörper, welche in diesen Versuchen die gesetzten Anforderungen erfüllten, wurden für das Ermitteln der kleinsten nachweisbaren Konzentration verwendet. Über das Optimieren der Versuchsbedingungen konnte unter Verwendung von Tween in der Waschlösung sowohl auf Glas als auch auf Kunststoff die Hintergrundfluoreszenz reduziert und somit eine Steigerung des Signal/Hintergrundverhältnisses erreicht werden. In den Versuchen zu Ermittlung der Bestimmungsgrenze wurde für das humane Choriongonadotropin (hCG-i) eine Konzentration von 10 mU/ml, für dessen beta-Untereinheit (hCG-beta) eine Konzentration von 3,6 mU/ml und für das luteinisierende Hormon (LH) eine Konzentration von 10 mU/ml bestimmt. Den ermittelten Wert im Serum für das hCG-i entspricht dem von der Welt-Anti-Dopin-Agentur (WADA) geforderten Wert in Urin von 5 mU/ml. Neben der Ermittlung von Bestimmungsgrenzen wurden diese hinsichtlich auftretender Matrixeffekte in Serum und Blut gemessen. Wie aus den Versuchen zur Ermittlung von Kreuzreaktivitäten auf dem Mikroarray zu entnehmen ist, lassen sich das LH, das hCG-i und hCG-β ebenfalls in Serum und Blut messen. Die Durchführung einer Performance-Analyse über einem Einfach-Blind-Ansatz mit 130 Serum Proben, wurde ebenfalls über dieses System realisiert. Die ausgewerteten Proben wurden anschließend über eine Grenzwertoptimierungskurve analysiert und die diagnostische Spezifität ermittelt. Für die Messungen des LH konnte eine Sensitivität und Spezifität von 100% erreicht werden. Demnach wurden alle negativen und positiven Proben eindeutig interpretiert. Für das hCG-β konnte ebenfalls eine Spezifität von 100% und eine Sensitivität von 97% erreicht werden. Die hCG-i Proben wurden mit einer Spezifität von 100% und eine Sensitivität von 97,5% gemessen. Um den Nachweis zu erbringen, dass dieser Versuchsaufbau über mehrere Wochen stabile Signale bei Vermessen von identischen Proben liefert, wurde ein über zwölf Wochen angesetzter Stabilitätstest für alle Parameter erfolgreich in Serum und Blut durchgeführt. Zusammenfassend konnte in dieser Arbeit erfolgreich eine Mehrkomponentenanalyse als Multiplex Ansatz auf einem Mikroarray entwickelt werden. Die Durchführung der Performance-Analyse und des Stabilitätstests zeigen bereits die mögliche Einsatzfähigkeit dieses Tests im Kontext einer Dopinganalyse.