The Study of Exciton-Polariton Phase Transitions Through Spontaneous Vortices and First-Order Correlation

Phase transitions are among the most fascinating phenomena discovered in the last century, with collective molecular dynamics leading to novel observations such as superconductivity and superfluidity. Yet even in the highly-ordered state of such systems, defects could still form and persist. Investigating the behavior of such defects is not just a matter of fundamental interest, but also valuable in applications where macroscopic order is important. Our studies of order and defects make use of an exciton-polariton (polaritons hereafter) system. These are quasi-particles with part-matter and part-light components, with a bosonic nature that allows for observation of macroscopic quantum phenomena typically seen in conventional atomic condensates. Their low effective mass allows for such observations at relatively high temperatures (10K - 300K), and the photonic component allows for experimental access using standard table-top optical techniques. These factors have generated much interest in the field of polaritonics over the past two decades. In a two-dimensional system like the polaritons, defects appear in phase transitions as spontaneously-formed vortices. While such vortices have been observed, their reported behaviors were influenced by sample properties or pump configurations. Formation and behaviors in which phase-transition mechanisms and polariton hydrodynamics are primary contributing factors have yet to be observed. Such observations would allow for comparisons with analogous results in atomic condensates and allow for deeper studies in universality. In this thesis, I present efforts taken towards the realization of such observations. I will propose the design of a Compact Mirroring Mach-Zehnder interferometer (CoMMZI) for the detection of photonic orbital angular momentum (OAM) states. The observation of such states would be an unequivocal indication of spontaneously-formed quantum vortices. I will demonstrate that the proposed interferometer is capable of detecting OAM states with a low number of photons, thereby making it suitable for the detection of moving vortices in a single-shot realization of a polariton condensate. I will then discuss how the interferometer was tested with vortex states formed with a spatial light modulator and continuous-wave lasers. I will show that the interferometer is capable of detecting vortex phases and present techniques to increase the chances of successful detection. I will also show preliminary experiments with a polariton condensate formed with non-resonant pump configurations. OAM states within an optically-induced ring trap have been detected. Finally, I will show spectrometric and temporal first-order correlation functions for polaritons within an optically-induced ring trap, a potential system for the observation of vortices. I will show the presence of three population fractions with coherence times spanning three orders of magnitude and briefly discuss possible implications for vortex-detection experiments. The efforts in this thesis demonstrate the possibilities and challenges associated with the detection of spontaneously-formed vortices within a single instance of a polariton condensate, providing insight for attempts at experimental realizations.PHDPhysicsUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/163142/1/lhofai_1.pd

The Mediterranean Sea Regime Shift at the End of the 1980s, and Intriguing Parallelisms with Other European Basins

Background: Regime shifts are abrupt changes encompassing a multitude of physical properties and ecosystem variables, which lead to new regime conditions. Recent investigations focus on the changes in ecosystem diversity and functioning associated to such shifts. Of particular interest, because of the implication on climate drivers, are shifts that occur synchronously in separated basins. Principal Findings: In this work we analyze and review long-term records of Mediterranean ecological and hydro-climate variables and find that all point to a synchronous change in the late 1980s. A quantitative synthesis of the literature (including observed oceanic data, models and satellite analyses) shows that these years mark a major change in Mediterranean hydrographic properties, surface circulation, and deep water convection (the Eastern Mediterranean Transient). We provide novel analyses that link local, regional and basin scale hydrological properties with two major indicators of large scale climate, the North Atlantic Oscillation index and the Northern Hemisphere Temperature index, suggesting that the Mediterranean shift is part of a large scale change in the Northern Hemisphere. We provide a simplified scheme of the different effects of climate vs. temperature on pelagic ecosystems. Conclusions: Our results show that the Mediterranean Sea underwent a major change at the end of the 1980s that encompassed atmospheric, hydrological, and ecological systems, for which it can be considered a regime shift. We further provide evidence that the local hydrography is linked to the larger scale, northern hemisphere climate. These results suggest that the shifts that affected the North, Baltic, Black and Mediterranean (this work) Seas at the end of the 1980s, that have been so far only partly associated, are likely linked as part a northern hemisphere change. These findings bear wide implications for the development of climate change scenarios, as synchronous shifts may provide the key for distinguishing local (i.e., basin) anthropogenic drivers, such as eutrophication or fishing, from larger scale (hemispheric) climate drivers

Molecular Characterization of the Ro/SS-A Autoantigens

AbstractMolecular techniques have recently revealed that there are several immunologically distinct Ro/SS-A antigens. Three genes encoding putative Ro/SS-A protein antigens with calculated masses of 46, 52, and 60 kD have been isolated. The encoded amino acid sequence of each is quite dissimilar. The 46-kD antigen is calreticulin (CR), a highly conserved calcium-binding protein that resides predominately in the endoplasmic reticulum where it may be involved in protein assembly. Although CR has recently been confirmed to be a new human rheumatic disease-associated autoantigen, its relationship to the other components of the Ro/SS-A ribonucleoprotein has become somewhat controversial owing predominately to the fact that recombinant forms of calreticulin have not displayed the same pattern of autoantibody reactivity possesse by the native form of this protein.The 52-kD antigen most likely resides in the nucleus and may be involved in the regulation of gene expression. The cellular location and function of the 60-kD antigen is uncertain but studies indicate that it is a RNA-binding protein.The 46- and 60-kD antigens share homology with foreign polypeptides, suggesting that an immune response initially directed against a foreign protein may give rise to the autoimmune response directed at cross-reacting self proteins

Annual report GLE o.p.s. 2012

Výroční zpráva organizace za rok 2012, shrnutí a vyhodnocení aktivit organizace a účetní závěrka

Synthèse de copolymères à architectures complexes à base de POE utilisés en tant qu'électrolytes polymères solides pour une application dans les batteries lithium métal-polymère

Dans le contexte d'un développement durable, les véhicules électriques apparaissent comme une solution incontournable dans le futur. Parmi les dernières évolutions sur les batteries, les systèmes constitués d'une électrode au lithium (technologie lithium métal) présente des performances remarquables en termes de densité d'énergie. L'inconvénient majeur de cette méthodologie est lié à la formation de dendrites lors de la recharge susceptibles d'occasionner des courts-circuits conduisant à l'explosion de la batterie. C'est dans cet axe que s'inscrit mon sujet de thèse dont l'objectif est de développer un électrolyte polymère solide présentant une conductivité ionique élevée (2.10-4 S.cm-1 à40°C) et une tenue mécanique suffisante (30 MPa) pour limiter les phénomènes de croissance dendritique. Pour cela, la polymérisation contrôlée par les nitroxydes (NMP) a été utilisée pour synthétiser des copolymères à blocs avec un bloc possédant des groupes d'oxyde d'éthylène –CH2-CH2-O- permettant la conduction des ions lithium et un bloc de polystyrène assurant la tenue mécanique de l'électrolyte final. Le bloc assurant la conduction ionique des architectures ainsi synthétisées sont constituées soit de POE sous forme linéaire soit de POE sous forme de peigne.In the context of sustainable development, electric vehicles appear to be a major solution for the future. Among the lastest technologies, the Lithium Metal Polymer battery has presented very interesting performances in terms of energy density. The main drawback of this system is the formation of lithium dendrites during the refill of the battery that could cause short circuits leading to the explosion of the battery. The aim of my PhD is to develop a Solid Polymer Electrolyte showing a high ionic conductivity (2.10-4 S.cm-1 at 40°C) and a high mechanical strength (30 MPa) to prevent dendritic growth. For that purpose, Nitroxide Mediated Polymerization is used to synthesize block copolymers with a PEO moiety for ionic conduction –CH2-CH2-O- and polystyrene for mechanical strength. Different kind of architectures have been synthesized : block copolymer with linear PEO moiety or with grafted PEO moiety

The Dynamic Lateral Response of Deep Foundations.

A field testing procedure was developed and the dynamic lateral response of eleven full-scale pipe piles was obtained experimentally. Steady-state vibration and plucking tests were conducted on piles embedded in both cohesive and granular soils at three separate sites. Two piles in cohesive soils were retested with either a conventional compacted granular soil or a cement-stabilized granular soil replacing the insitu surficial soil. Dynamic soil properties adjacent to the piles were determined by suitable field and laboratory testing techniques. The theoretical dynamic response was predicted using a two-degree-of-freedom analysis with stiffness and damping parameters obtained from the computer program, PILAY, developed by Novak and Aboul-Ella. The theoretical predictions for the dynamic response curves were compared with the observed field testing results. Damping ratios evaluated by the plucking technique were slightly higher than those observed for the steady-state vibration tests. A decrease in damping with increasing force level for the steady-state vibration tests indicated a reduction of the geometric damping for the soil-pile-mass system at higher amplitudes. This occurred irrespective of the soil type surrounding the head of the pile. The decrease in damping was attributed to a soil-pile separation caused by the large number of cyclic repetitions experienced by the soil. No significant decrease in damping was observed for the higher amplitude plucking tests. The observed resonant frequency and damping are significantly overestimated if the stiffness and damping predicted by PILAY are used. The difference is likely related to the soil-pile contact condition. Observed response amplitudes were typically 1.5 to 2 times greater than predicted for frequencies beyond the translation resonance. Modification of the rocking parameter could not account for the difference.Ph.D.Civil engineeringUniversity of Michiganhttp://deepblue.lib.umich.edu/bitstream/2027.42/158639/1/8204657.pd