Collective effects in light scattering from cold strontium clouds

A cold atomic cloud is a versatile object, because it offers many handles to control and tune its properties. This facilitates studies of its behavior in various circumstances, such as sample temperature, size and density, composition, dimensionality and coherence time. The range of possible experiments is constrained by the specifications of the atomic species used. In this thesis presents the work done in the experiment for laser cooling of strontium atoms, focusing on its stability, which should provide cold and ultracold samples for the study of collective effects in light scattering. From the initial apparatus, innumerous changes were performed. The vacuum system got improved and now reached lower ultra high vacuum due to the pre-baking done to its parts and adding a titanium-sublimation stage. The quadrupole trap were improved by the design and construction of a new pair of coils. The stability of the blue, green and red laser systems and the loss prevention of laser light were improved, giving rise to a robust apparatus. Another important point is the development of homemade devices to reduce the costs and to be used as a monitor of different parts of an cold atoms experiment. From this homemade devices, we could demonstrate a dramatic linewidth narrowing by injection lock of an low cost 461 nm diode laser and its application to our strontium experiment. In the end, this improved experimental apparatus made possible the study of a new scattering effect, the mirror assisted coherent back-scattering (mCBS).

CuH-ZSM-5 as Hydrocarbon Trap under Cold Start Conditions

Cold start tests are carried out to evaluate the performance of copper-exchanged zeolites as hydrocarbon traps under simulated gasoline car exhaust gases, paying special attention to the role of copper in the performance of these zeolites. It is concluded that the partial substitution of the protons in the parent H-ZSM-5 zeolite is highly beneficial for hydrocarbon trapping due to the formation of selective adsorption sites with specific affinity for the different exhaust components. However, it is also observed that uncontrolled exchanging process conditions could lead to the presence of CuO nanoparticles in the zeolite surface, which seem to block the pore structure of the zeolite, decreasing the hydrocarbon trap efficiency. Among all the zeolites studied, the results point out that a CuH-ZSM-5 with a partial substitution of extra-framework protons by copper cations and without any detectable surface CuO nanoparticles is the zeolite that showed the best performance under simulated cold start conditions due to both the high stability and the hydrocarbon retaining capacity of this sample during the consecutive cycles.

Sitting on the fence: Swedish defence policy and the Baltic Sea region. OSW Point of View Number 33, April 2013

Sweden finds itself in the midst of the most heated debates about defence policy and the direction of military reforms since the end of the Cold War, as Stockholm faces the challenge of finding a new military security formula. From the Swedish point of view, the post-Cold War strategic timeout in Europe is coming to an end. The international environment is reverting to a situation in which the use of force among states is no longer an improbable scenario. Stockholm cannot rule out the emergence of crises or conflicts in Northern Europe in the future, which could directly or indirectly affect Sweden. In this context, the transformations of Sweden’s defence policy over the past twenty years have become a problem. Sweden has moved from neutrality, i.e. non-involvement on any side of an armed interstate conflict, to non-alignment, whereby it stays outside military alliances and freely shapes its policies during wartime. It has joined the European Union and co-operates closely with NATO on foreign missions. Its ability to defend its own territory, however, has diminished.

Biological and environmental time series obtained from Point B, Bay of Villefranche

Ecological succession provides a widely accepted description of seasonal changes in phytoplankton and mesozooplankton assemblages in the natural environment, but concurrent changes in smaller (i.e. microbes) and larger (i.e. macroplankton) organisms are not included in the model because plankton ranging from bacteria to jellies are seldom sampled and analyzed simultaneously. Here we studied, for the first time in the aquatic literature, the succession of marine plankton in the whole-plankton assemblage that spanned 5 orders of magnitude in size from microbes to macroplankton predators (not including fish or fish larvae, for which no consistent data were available). Samples were collected in the northwestern Mediterranean Sea (Bay of Villefranche) weekly during 10 months. Simultaneously collected samples were analyzed by flow cytometry, inverse microscopy, FlowCam, and ZooScan. The whole-plankton assemblage underwent sharp reorganizations that corresponded to bottom-up events of vertical mixing in the water-column, and its development was top-down controlled by large gelatinous filter feeders and predators. Based on the results provided by our novel whole-plankton assemblage approach, we propose a new comprehensive conceptual model of the annual plankton succession (i.e. whole plankton model) characterized by both stepwise stacking of four broad trophic communities from early spring through summer, which is a new concept, and progressive replacement of ecological plankton categories within the different trophic communities, as recognised traditionally.

Mutations within the selectivity filter of the NMDA receptor-channel influence voltage dependent block by 5-hydroxytryptamine

Background and purpose: Voltage-dependent block by Mg2+ is a cardinal feature of NMDA receptors which acts as a coincidence detector to prevent the receptor from over-activation. Inhibition of NMDA receptor currents by 5-hydroxytryptamine (5-HT) indicated that 5-HT, similar to Mg2+, binds within the membrane electric field. In the present study, we assessed whether point mutations of critical asparagine residues located within the selectivity filter of NR1 and NR2A subunits of NMDA receptor-channel affect voltage-dependent block by 5-HT. Experimental approach: The mode of action of 5-HT and Mg2+ on wild-type and mutated NMDA receptor-channels expressed in Xenopus oocytes was investigated using the two-electrode voltage clamp recording technique. Key results: The mutation within the NR1 subunit NR1(N0S or N0Q) strongly reduced the voltage dependent block by 5-HT and increased the IC50. The corresponding mutations within the NR2 subunits NR2A(N0Q or N + 1Q) reduced the block by 5-HT to a lesser extent. This is in contrast to the block produced by external Mg2+ where a substitution at the NR2A(N0) and NR2A(N + 1) sites but not at the NR1(N0) site significantly reduced Mg2+ block. Conclusion and implications: The block of NMDA receptor-channels by 5-HT depends on the NR1-subunit asparagine residue and to a lesser extent on the NR2A-subunit asparagine residues. These data suggest that the interaction of 5-HT with functionally important residues in a narrow constriction of the pore of the NMDA receptor-channel provides a significant barrier to ionic fluxes through the open channel due to energetic factors governed by chemical properties of the binding site and the electric field.

Computer aided design and analysis of cold formed sections

The work reported in this thesis is concerned with the improvement and expansion of the assistance given to the designer by the computer in the design of cold formed sections. The main contributions have been in four areas, which have consequently led to the fifth, the development of a methodology to optimise designs. This methodology can be considered an `Expert Design System' for cold formed sections. A different method of determining section properties of profiles was introduced, using the properties of line and circular elements. Graphics were introduced to show the outline of the profile on screen. The analysis of beam loading has been expanded to beam loading conditions where the number of supports, point loads, and uniform distributive loads can be specified by the designer. The profile can then be checked for suitability for the specified type of loading. Artificial Intelligence concepts have been introduced to give the designer decision support from the computer, in combination with the computer aided design facilities. The more complex decision support was adopted through the use of production rules. All the support was based on the British standards. A method has been introduced, by which the appropriate use of stiffeners can be determined and consequently designed by the designer. Finally, the methodology by which the designer is given assistance from the computer, without constraining the designer, was developed. This methodology gives advice to the designer on possible methods of improving the design, but allows the designer to reject that option, and analyse the profile accordingly. The methodology enables optimisation to be achieved by the designer, designing variety of profiles for a particular loading, and determining which one is best suited.

100-Gb/s point-to-point solutions for long-reach passive optical networks in sparse rural and urban areas

Long reach-passive optical networks (LR-PON) are being proposed as a means of enabling ubiquitous fiber-to-the-home (FTTH) by massive sharing of network resources and therefore reducing per customer costs to affordable levels. In this paper, we analyze the chain solutions for LR-PON deployment in urban and rural areas at 100-Gb/s point-to-point transmission using dual polarization-quaternary phase shift-keying (DP-QPSK) modulation. The numerical analysis shows that with appropriate finite impulse response (FIR) filter designs, 100-Gb/s transmission can be achieved with at least 512 way split and up to 160 km total distance, which is sufficient for many of the optical paths in a practical situation, for point-to-point link from one LR-PON to another LR-PON through the optical switch at the metro nodes and across a core light path through the core network without regeneration.

Rigid and non-rigid point-based medical image registration

The primary goal of this dissertation is to develop point-based rigid and non-rigid image registration methods that have better accuracy than existing methods. We first present point-based PoIRe, which provides the framework for point-based global rigid registrations. It allows a choice of different search strategies including (a) branch-and-bound, (b) probabilistic hill-climbing, and (c) a novel hybrid method that takes advantage of the best characteristics of the other two methods. We use a robust similarity measure that is insensitive to noise, which is often introduced during feature extraction. We show the robustness of PoIRe using it to register images obtained with an electronic portal imaging device (EPID), which have large amounts of scatter and low contrast. To evaluate PoIRe we used (a) simulated images and (b) images with fiducial markers; PoIRe was extensively tested with 2D EPID images and images generated by 3D Computer Tomography (CT) and Magnetic Resonance (MR) images. PoIRe was also evaluated using benchmark data sets from the blind retrospective evaluation project (RIRE). We show that PoIRe is better than existing methods such as Iterative Closest Point (ICP) and methods based on mutual information. We also present a novel point-based local non-rigid shape registration algorithm. We extend the robust similarity measure used in PoIRe to non-rigid registrations adapting it to a free form deformation (FFD) model and making it robust to local minima, which is a drawback common to existing non-rigid point-based methods. For non-rigid registrations we show that it performs better than existing methods and that is less sensitive to starting conditions. We test our non-rigid registration method using available benchmark data sets for shape registration. Finally, we also explore the extraction of features invariant to changes in perspective and illumination, and explore how they can help improve the accuracy of multi-modal registration. For multimodal registration of EPID-DRR images we present a method based on a local descriptor defined by a vector of complex responses to a circular Gabor filter.

A generalized adaptive mathematical morphological filter for LIDAR data

Airborne Light Detection and Ranging (LIDAR) technology has become the primary method to derive high-resolution Digital Terrain Models (DTMs), which are essential for studying Earth's surface processes, such as flooding and landslides. The critical step in generating a DTM is to separate ground and non-ground measurements in a voluminous point LIDAR dataset, using a filter, because the DTM is created by interpolating ground points. As one of widely used filtering methods, the progressive morphological (PM) filter has the advantages of classifying the LIDAR data at the point level, a linear computational complexity, and preserving the geometric shapes of terrain features. The filter works well in an urban setting with a gentle slope and a mixture of vegetation and buildings. However, the PM filter often removes ground measurements incorrectly at the topographic high area, along with large sizes of non-ground objects, because it uses a constant threshold slope, resulting in "cut-off" errors. A novel cluster analysis method was developed in this study and incorporated into the PM filter to prevent the removal of the ground measurements at topographic highs. Furthermore, to obtain the optimal filtering results for an area with undulating terrain, a trend analysis method was developed to adaptively estimate the slope-related thresholds of the PM filter based on changes of topographic slopes and the characteristics of non-terrain objects. The comparison of the PM and generalized adaptive PM (GAPM) filters for selected study areas indicates that the GAPM filter preserves the most "cut-off" points removed incorrectly by the PM filter. The application of the GAPM filter to seven ISPRS benchmark datasets shows that the GAPM filter reduces the filtering error by 20% on average, compared with the method used by the popular commercial software TerraScan. The combination of the cluster method, adaptive trend analysis, and the PM filter allows users without much experience in processing LIDAR data to effectively and efficiently identify ground measurements for the complex terrains in a large LIDAR data set. The GAPM filter is highly automatic and requires little human input. Therefore, it can significantly reduce the effort of manually processing voluminous LIDAR measurements.

Rigid and Non-rigid Point-based Medical Image Registration

The primary goal of this dissertation is to develop point-based rigid and non-rigid image registration methods that have better accuracy than existing methods. We first present point-based PoIRe, which provides the framework for point-based global rigid registrations. It allows a choice of different search strategies including (a) branch-and-bound, (b) probabilistic hill-climbing, and (c) a novel hybrid method that takes advantage of the best characteristics of the other two methods. We use a robust similarity measure that is insensitive to noise, which is often introduced during feature extraction. We show the robustness of PoIRe using it to register images obtained with an electronic portal imaging device (EPID), which have large amounts of scatter and low contrast. To evaluate PoIRe we used (a) simulated images and (b) images with fiducial markers; PoIRe was extensively tested with 2D EPID images and images generated by 3D Computer Tomography (CT) and Magnetic Resonance (MR) images. PoIRe was also evaluated using benchmark data sets from the blind retrospective evaluation project (RIRE). We show that PoIRe is better than existing methods such as Iterative Closest Point (ICP) and methods based on mutual information. We also present a novel point-based local non-rigid shape registration algorithm. We extend the robust similarity measure used in PoIRe to non-rigid registrations adapting it to a free form deformation (FFD) model and making it robust to local minima, which is a drawback common to existing non-rigid point-based methods. For non-rigid registrations we show that it performs better than existing methods and that is less sensitive to starting conditions. We test our non-rigid registration method using available benchmark data sets for shape registration. Finally, we also explore the extraction of features invariant to changes in perspective and illumination, and explore how they can help improve the accuracy of multi-modal registration. For multimodal registration of EPID-DRR images we present a method based on a local descriptor defined by a vector of complex responses to a circular Gabor filter.

Social paranoia and absurdist fiction in Cold War America and Soviet Russia: a comparative study

This thesis explores the theme of social paranoia as depicted in the Absurdist fiction of Cold War America and Soviet Russia. The central hypothesis informing this research maintains that, despite the ideology of moral and cultural “Otherness” constructed and reinforced by both nations throughout much of twentieth century, the US and the Soviet Union more often than not functioned as mirror images of paranoia and suspicion. Much of the fiction produced in Russia from the Revolution onwards and in the US during the Cold War period highlights how these two ostensibly irreconcilable nations were consumed by similar fears and gripped by an equally pervasive paranoia. These parallel conditions of anxiety and mistrust led to a surprising congruity of literary responses, which transcended the ideological divide between capitalism and communism and, as such, underscored the homogeny of fear which lay beneath the façade of constructed difference. I contend that, because Soviet Russia and the America of the Cold War period were nations consumed by fear and suspicion, authors living in both countries became preoccupied by the mechanics of such deeply paranoid societies. Consequently, much of the fiction of the US and the Soviet Union during this period was preoccupied with the themes of paranoia, conspiracy, intensive bureaucracy and the politicisation of science, which resulted in the terror of the Nuclear Age. This thesis explores how these central themes unite apparently diverse literary texts and illustrate the uniformity of terror which transcended both the physical and ideological boundaries separating the United States and the Soviet Union. In doing so, this research focuses primarily on the multi-faceted manifestations of paranoia in selected works by Soviet authors Mikhail Bulgakov, Daniil Kharms and Yuli Daniel, and American authors Joseph Heller, Thomas Pynchon and Kurt Vonnegut. Focusing on key works by each author, this research considers these texts as products of two culturally diverse, yet equally paranoid societies and explores their preoccupation with issues of spying, infiltration and conspiracy. This thesis thus emphasises how these authors counter simplistic notions of Cold War Otherness by revealing two nations possessed by a similar sense of vulnerability and insecurity. Furthermore, this thesis examines how this social anxiety is reinforced by the way in which these authors position issues such as the mechanics of the bureaucratic system and clandestine scientific experimentation as the focal point of the paranoid imagination. Ultimately, by examining the concordance of paranoiac representation in America and the Soviet Union during this period, I demonstrate that these ostensibly divergent nations harboured similar fears and insecurities.

State-Selective Attachment of Helium to Molecular Ions in a New Cryogenic Ion Trap

Light is the main information about the interstellar medium accessible on Earth. Based on this information one can conclude on the composition of the region where the light originates from, as well as on its history. The requirement for this is that it is possible to identify the different absorption and emission features in the spectrum and assign them to certain molecules, atoms or ions. To enable the identification of the different species, precise spectroscopic investigations of the species in the laboratory are necessary. In this work a new spectroscopic method is presented, which can be used to record pure rotational spectra of mass selected, cold, stored molecular ions. It is based on the idea of state specific attachment of helium atoms to the stored molecular ions. The new technique has been made possible through the development and recent completion of two new 22-pole ion trap instruments in the work group of Laboratory Astrophysics at the University of Cologne. These new instruments have the advantage to reach temperatures as low as 4K compared to the 10K of the predecessor instrument. These low temperatures enable the ternary attachment of helium atoms to the stored molecular ions and by this make it possible to develop this new method for pure rotational spectroscopy. According to this, this work is divided into two parts. The first part deals with the new FELion experiment that was build and characterized in the first part of the thesis. FELion is a cryogenic 22-pole ion trap apparatus, allowing to generate, mass select, store and cool down, and analyze molecular ions. The different components of the instrument, e.g. the Storage Ion Source for generating the ions or the first quadrupole mass filter, are described and characterized in this part. Besides this also the newly developed control and data acquisitions system is introduced. With this instrument the measurements presented in the second part of the work were performed. The second part deals with the new action spectroscopic method of state-selective helium attachment to the stored molecular ions. For a deeper analysis of the new technique the systems of CD+ and helium and HCO+ and helium are investigated in detail. Analytical and numerical models of the process are presented and compared to experimental results. The results of these investigations point to a seemingly very general applicability of the new method to a wide class of molecular ions. In the final part of the thesis measurements of the rotational spectrum of l-C3H+ are presented. These measurements have to be high-lighted, since it was possible for the first time in the laboratory to unambiguously measure four low-lying rotational transitions of l-C3H+. These measurements (Brünken et al. ApJL 783, L4 (2014)) enabled the reliable identification of so far unidentified emision lines observed in several regions of the interstellar medium (Pety et al. Astron. Astrophys. 548, A68 (2012), McGuire et al. The Astrophysical Journal 774, 56 (2013) and McGuire et al. The Astrophysical Journal 783, 36 (2014)).