3D modelling of epidermal nerve fiber patterns

Neuropathical disorders, such as diabetic neuropathy, damage the nerve structure in the epidermis. This thesis presents statistical analyses and models for the epidermal nerve fibers (ENFs). The main objective is to improve our understanding regarding the three dimensional ENF structure and for this purpose, stochastic models are constructed. The ENF data are treated as point process configurations in three dimensional boxes, and samples from mild diabetic subjects and healthy volunteers are considered. In Paper I, the structure of the nerve trees is analyzed by comparing distributional properties of the first and later nerve tree segments. Using tools from spatial point process theory, second order properties of the underlying processes are examined and compared. We also defined a new measure, called epidermal active territory, to measure the volume of the epidermis covered by the nerves. Further, a three dimensional point process model for the nerve structure, is developed and evaluated using spatial summary statistics. The two dimensional version of the model captured the planar spatial structure, however, the complete model was unable to capture the attraction between the nerve fiber endings in the data. Therefore, a pairwise interaction Markov model allowing neighboring end points to interact was proposed in Paper II. Due to the anisotropic nature of the data, directional summary statistics were used to assess the goodness of fit of the models. The model was able to capture the attraction between the nerve fiber endings in the data

Terrorism Shocks and Public Spending: Panel VAR Evidence from Europe

Based on a trivariate panel VAR and utilizing Generalized Impulse Responses, we explored the dynamic impacts of terrorism and crime risks on public order and safety spending across European countries during the period 1994-2006. Our findings suggest that both a shock in terrorism risk or in crime, significantly increase the subsequent trajectory of public order and safety spending. As a by-product we find that public spending is ineffective in reducing observed crime or terrorism risks.Panel VAR, Public Order and Safety Spending, Terrorism Activity

Seismolosical studies of magma injection processes: volcano monitoring and imaging of magma chambers

The processes associated with magma injection at shallow depths within the crust have been the topic of many geophysical studies, some investigating the seismicity that accompanies volcanic activity and others attempting to map the subsurface extent and geometry of the resulting magma bodies. The aim of this study is to obtain a better understanding of these processes by investigating the nature of seismic signals that accompany volcanic eruptions and by seismically imaging a magma body beneath a mid-ocean ridge, both located on, or adjacent to Iceland. The seismic phenomena associated with the 1996 Vatnajӧkull subglacial eruption in central Iceland, have been studied using data recorded by both temporary (HOTSPOT) and permanent (SIL) seismic networks. These networks comprise 60 broadband and short-period three-component seismographs and cover most parts of the country. Two very active volcanic systems, Bárdarbunga and Grimsvӧtn, are situated underneath the Vatnajokull ice cap. The volcanoseismic signals recorded there were categorised according to their waveform shape and frequency content, into three groups: (a) low-frequency events (1-2 Hz); (b) mixed-frequency events (1-4 Hz); and (c) volcanic tremor. The eruption was preceded by intense seismic activity which began with a = 5.6 earthquake located at the Bárdarbunga volcanic system. The epicentres of the earthquake swarm that followed the M(_w), = 5.6 event initially delineated the Bárdarbunga caldera rim and then migrated towards Grimsvӧtn, to a place where a fissure was later observed. Pre-eruptive tremor started at least two days before the eruption as a harmonic signal around five narrow frequency bands (0.5-0.7, 1.6, 2.2, 2.8 and 3.2 Hz). Co-eruptive tremor started as a broadband, continuous signal which evolved into low-amplitude background tremor interrupted by high-amplitude, cigar-shaped bursts. Further analysis revealed that continuous tremor and the cigar-shaped bursts had all the characteristics of low- dimensional chaotic signals. Geophysical and geochemical evidence suggest that a lateral migration of magma from Bárdarbunga facilitated the rupture of the roof of a magma chamber, situated at the fissure area, which subsequently erupted as tephra on the glacier. The second phase of the RAMESSES (Reykjanes Ridge Axial Melt Experiment: Structural Synthesis from Electromagnetic and Seismics) experiment involved the acquisition of multichannel seismic reflection data from 39 along- and across-axis lines shot over the magmatically active 57º 45'N axial volcanic ridge. The data from one along-axis line were processed using a variety of techniques that mainly aimed at reducing the large amount of coherent noise present, a result of scattered energy at the rough seabed. The final processed section revealed a number of reflection events that could be interpreted as intra-crustal reflections, originating from the interface between pillow lavas and sheeted dykes, and from the top part of a thin melt lens

Landau Level Physics in a Quantum Well: new singular features in Magnetization and violations of de Haas - van Alphen periodicities

Analytical calculations based on a Landau Level (LL) picture are reported for an interface (with a finite-width Quantum Well (QW)) and for a fully three-dimensional charged quantum electronic system in an external magnetic field. They lead to a sequence of previously unnoticed singular features in global magnetization and magnetic susceptibility that lead to nontrivial corrections to the standard de Haas - van Alphen periods. Additional features due to Zeeman splitting are also reported (such as new energy minima that originate from the interplay of QW, Zeeman and LL Physics) that are possibly useful for the design of quantum devices. A corresponding calculation in a Composite Fermion picture leads to new predictions on magnetic response properties of a fully-interacting electron liquid in a finite-width interface.Comment: 5 pages, 9 figures, brief report submitted for the Proceedings of the ICMM-2010 Conference (Kolkata, October 2010

Thickness-induced violation of de Haas-van Alphen effect through exact analytical solutions at a one-electron and a one-Composite Fermion level

A systematic study of the energetics of electrons in an interface in a magnetic field is reported with exact analytical calculations based on a Landau Level (LL) picture, by serious consideration of the finite thickness of the Quantum Well (QW). The approach is physically transparent and subtly different in its line of reasoning from standard methods avoiding any semi-classical approximation. We find "internal" phase transitions (at partial LL filling) for magnetisation and susceptibility that are not captured by other approaches and that give rise to nontrivial violations of the standard de Haas-van Alphen periods, in a manner that reproduces the exact quantal astrophysical behaviours in the limit of full three-dimensional (3D) space. Upon inclusion of Zeeman splitting, additional features are also found, such as global energy minima originating from the interplay of QW, Zeeman and LL Physics, while a corresponding calculation in a Composite Fermion picture with {\Lambda}-Levels, leads to new predictions on magnetic properties of an interacting electron liquid. By pursuing the same line of reasoning for a topologically nontrivial system with a relativistic spectrum, we find evidence that similar effects might be operative in the dimensionality crossover of 3D strong topological insulators to 2D topological insulator quantum wells.Comment: 59 pages, many figures. An extensive treatment of the not-so-harmless role of thickness (but mostly at a one-particle level). Based on arXiv:1209.5102. Accepted for publication in European Physical Journal B. arXiv admin note: substantial text overlap with arXiv:1209.510

Terrorism Shocks and Public Spending: Panel VAR Evidence from Europe

Based on a trivariate panel VAR and utilizing Generalized Impulse Responses, we explored the dynamic impacts of terrorism and crime risks on public order and safety spending across European countries during the period 1994-2006. Our findings suggest that both a shock in terrorism risk or in crime, significantly increase the subsequent trajectory of public order and safety spending. As a by-product we find that public spending is ineffective in reducing observed crime or terrorism risks