Mesoscopic Interactions in Complex Photonic Media

Mesoscale optics provides a framework for understanding a wide range of phenomena occurring in a variety of fields ranging from biological tissues to composite materials and from colloidal physics to fabricated nanostructures. When light interacts with a complex system, the outcome depends significantly on the length and time scales of interaction. Mesoscale optics offers the apparatus necessary for describing specific manifestations of wave phenomena such as interference and phase memory in complex media. In-depth understanding of mesoscale phenomena provides the required quantitative explanations that neither microscopic nor macroscopic models of light-matter interaction can afford. Modeling mesoscopic systems is challenging because the outcome properties can be efficiently modified by controlling the extent and the duration of interactions. In this dissertation, we will first present a brief survey of fundamental concepts, approaches, and techniques specific to fundamental light-matter interaction at mesoscopic scales. Then, we will discuss different regimes of light propagation through randomly inhomogenous media. In particular, a novel description will be introduced to analyze specific aspects of light propagation in dense composites. Moreover, we will present evidence that the wave nature of light can be critical for understanding its propagation in unbounded highly scattering materials. We will show that the perceived diffusion of light is subjected to competing mechanisms of interaction that lead to qualitatively different phases for the light evolution through complex media. In particular, we will discuss implications on the ever elusive localization of light in three-dimensional random media. In addition to fundamental aspects of light-matter interaction at mesoscopic scales, this dissertation will also address the process of designing material structures that provide unique scattering properties. We will demonstrate that multi-material dielectric particles with controlled radial and azimuthal structure can be engineered to modify the extinction cross-section, to control the scattering directivity, and to provide polarization-dependent scattering. We will show that dielectric core-shell structures with similar macroscopic sizes can have both high scattering cross-sections and radically different scattering phase functions. In addition, specific structural design, which breaks the azimuthal symmetry of the spherical particle, can be implemented to control the polarization properties of scattered radiation. Moreover, we will also demonstrate that the power flow around mesoscopic scattering particles can be controlled by modifying their internal heterogeneous structures. Lastly, we will show how the statistical properties of the radiation emerging from mesoscopic systems can be utilized for surface and subsurface diagnostics. In this dissertation, we will demonstrate that the intensity distributions measured in the near-field of composite materials are direct signatures of the scale-dependent morphology, which is determined by variations of the local dielectric function. We will also prove that measuring the extent of spatial coherence in the proximity of two-dimensional interfaces constitutes a rather general method for characterizing the defect density in crystalline materials. Finally, we will show that adjusting the spatial coherence properties of radiation can provide a simple solution for a significant deficiency of near-field microscopy. We will demonstrate experimentally that spurious interference effects can be efficiently eliminated in passive near-field imaging by implementing a random illumination

CMS physics technical design report : Addendum on high density QCD with heavy ions

Peer reviewe

CMS ECAL Barrel. The Worst Combination of Loads

Linear superposition of responses of a structure to different load cases delivered by linear analysis methods can be used to obtain its response to any linear combination of those load cases. this way extreme response values can be investigated when the magnitudes of the interacting loads ( their load factors) vary within specified ranges. The load factors can be regarded as the co-ordinates of a combined load case in a vectorial load space. In this paper, for the case of correlated load factors in the load space, the Lagrangean Multiplicator method is applied to determine extreme response values and the corresponding load factors. Not only summable response quantities such as components of displacements, stresses, forces and moments, but also the Von Mises stress, the buckling load factor and the modal frequency of a pre-stressed structure are addressed

Concepts and case studies of interactive technologies integrated in physical space

Abweichender Titel laut Übersetzung der Verfasserin/des VerfassersZsfassung in engl. SpracheDer Computer der Zukunft soll uns in allen Lebenslagen und Alltagssituationen unterstützen, indem er uns ununterbrochen mit nützlichen Informationen versorgt. Die Verwirklichung dieser Vision, die Ende der achtziger Jahre zum ersten Mal entstand, scheint mit den heutigen Hochleistungscomputern und -netzwerken sowie mit dem Fortschritt in Sensorik in greifbare Nähe gerückt zu sein. Viele Forschungsarbeiten werden diesem Thema gewidmet (Ubiquitous Computing, Pervasive Computing, Context-aware Computing, Disappearing Computing, Ambient Intelligence, Smart Spaces, etc.). Die moderne Art der Informationstechnologie fordert eine neue Art der Mensch-Maschine-Interaktion, daher stehen in der weiteren Entwicklung der Computertechnologie nicht mehr die klassischen Kriterien wie die Netzwerkgeschwindigkeit im Vordergrund. Vielmehr muss sich die Forschung auf die Benutzerschnittstelle konzentrieren. Der "unsichtbare" Computer der Zukunft wird vollständig in den uns umgebenden Räumen und Alltagsgegenständen integriert sein, wodurch explizite Input-Outputs über klassische Schnittstellen überflüssig werden. Die Verwendung von Raum und Alltagsgegenständen als eine optimale Schnittstelle ist naheliegend, da Menschen den Umgang mit diesen Objekten als natürlich empfinden. Aus diesem Grund konzentrieren sich viele multidisziplinäre Forschungsarbeiten unter anderem auf die Untersuchung des menschlichen Verhaltens in seinen diversen Lebensräumen. In dieser Arbeit beschreibe ich verschiedene Aspekte der oben genannten Vision, eine Reihe von angewandten Technologien für deren Realisierung, und ein paar Beispiele für die Integration interaktiver Technologie in den Raum. Zudem gehe ich ausführlich auf das Thema der Wahrnehmung des Raums durch Menschen und seine Wechselwirkung mit der Mensch-Maschine-Interaktion ein.The Computer of future shall support us in all situations of our everyday life through continuous supply of valuable information. The realisation of this vision, which has first emerged at the end of the eighties, seems to take concrete shape, considering today's high performance computers and networks, as well as the advances in the sensor technology. This very topic and related fields have also been subject to enormous dedicated research (Ubiquitous Computing, Pervasive Computing, Context-aware Computing, Disappearing Computing, Ambient Intelligence, Smart Spaces, etc.).The modern "everyday computing" requires a novel form of human-computer-interaction. Accordingly, the design of an appropriate interface between the human and the computer will be of eminent importance. The "disappearing" computer of future will be fully integrated in the physical spaces of our daily life, such that any explicit input-output via traditional interfaces will not be needed anymore. The leverage of space and objects of everyday life as an optimal interface is quite straight forward, since human beings deal with such objects fully naturally and with ease. Therefore, a considerable amount of multidisciplinary research focuses on studying the human behaviour in his various physical environments. In this work, I discuss different aspects of the above mentioned vision along with a number of applied technologies for its realisation, as well as few examples for the integration of the interactive technology in the physical space. Furthermore, I elucidate the issue of human perception of the physical space and its interplay with the human-computer-interaction.8

From Mosques and Coffeehouses to Squares and Cafés: the Production and Transformation of Political Public Spaces and Social Life in Modern Tehran

Why did the spaces of protest in Tehran, the capital of Iran, shift from sacred spaces of the city, two mosques and a holy shrine during the 1905 and 1906 Constitutional Revolution, to the streets and squares of the northern city in the 1940s and the early 1950s? Through extensive archival research in Iran, including examination of old Iranian periodicals, memoirs, travelogues, maps, and the like, I found that this spatial transformation was the tip of an iceberg; it was closely related to the transformations of urban society, social life, and social spaces in Tehran that had been brewing for decades. Nineteenth-century Iranian urban society was largely a classless society; it consisted of numerous smaller communities. Social life and the social spaces of Tehran –takīyyihs, zūrkhānihs, mosques, bathhouses, and coffeehouses –were highly shaped by communal identities. In this context, the main sacred spaces of the city were the only sites that could transcend communal diversities and brought people together for a common political cause. However, Iranian urban society underwent massive transformations during the first half of the twentieth century. Two new urban classes, the modern middle and the urban working classes, developed in Iranian cities, particularly Tehran, which were free from the bonds of communal life. The city’s social spaces and social life transformed alongside urban society. A new spatial discourse that was incubated in Iranian society for a century became the main force transforming Iranian cities, particularly Tehran. Moreover, new types of social spaces after European models –cinemas, theaters, cafés, restaurants, and sport clubs –became the centers of social life for the modern middle class. This class became the main political social force in the city. It rejected traditional and religious spaces and defined a new way of life for itself. In this context, the newly built network of streets and squares of the northern section of Tehran substituted the sacred spaces of the city as the primary political public spaces. Alongside the main historical element of the dissertation, there is also a theoretical deliberation. Through the examination of various instances of social movements and their social forces, I investigate the relationship between the public sphere and political public spaces in a context beyond the conventional geographic scope of western urban and political theories. My research suggests that the current models of the public sphere, including Habermas’s bourgeois public sphere, do not map onto Iranian society. Instead, my research suggests a new model based on the particularities of Iranian urban society during the nineteenth and the early twentieth centuries, but potentially applicable to cases far beyond Tehran as well. In this model, I introduce the communal sphere as the main construct of segmented Iranian urban society in the nineteenth century, mediated between the private and public spheres. In this context, the public sphere formed as the outcome of coming together of various communal spheres through the binding force of religion and political activities of a new urban bourgeoisie, the propertied middle class, at the turn of the twentieth century. Also, I found that the public sphere and political public spaces are deeply interconnected; they share certain commonalities that can be investigated through the socio-historical analysis

Phase Transitions In The Diffusion Of Light

We demonstrate a new phenomenon occurs in the propagation of light through random media. Due to different mechanisms of interaction, recurrent scattering of onshell propagating fields is impeded by strongly localized evanescent couplings

Phase Transitions In The Diffusion Of Light

We demonstrate a new phenomenon occurs in the propagation of light through random media. Due to different mechanisms of interaction, recurrent scattering of onshell propagating fields is impeded by strongly localized evanescent couplings

Phase Transitions In Diffusion Of Light

It has been a long time belief that, with increasing the scattering strength of multiple scattering media, the transport of light gradually slows down and, eventually, comes to a halt corresponding to a localized state. Here we present experimental evidence that different stages emerge in this evolution, which cannot be described by classical diffusion with conventional scaling arguments. A microscopic model captures the relevant aspects of electromagnetic wave propagation and explains the competing mechanisms that prevent the three-dimensional wave localization. We demonstrate that strong evanescent-field couplings hinder the localization of wave resonances and, therefore, impede the slowing down of diffusion. The emerging out of equilibrium steady-state process resembles the diffusion of classical particles in spatially correlated random potentials and the thermalization of matter waves due to atomic collisions