The concept of LR-nets was introduced and investigated firstly by H.P. Lotz in [27] and by F. Raebiger in [30]. Therefore we call such nets Lotz-Raebiger nets, shortly LR-nets. In this thesis we treat two problems on asymptotic behavior of these operator nets. First problem is to generalize well known theorems for Ces`aro averages of a single operator to LR-nets, namely to generalize the Eberlein and Sine theorems. The second problem is related to the strong convergence of Markov LR-nets on L1-spaces. We prove that the existence of a lower-bound functions is necessary and sufficient for asymptotic stability of LR-nets of Markov operators.

Prior to this study, to our best knowledge, no cast-in-place, older-type RC building has ever been subjected to near-field strong ground motions from three major earthquakes. This happened in an indirect way in Turkey over a time span of eleven years. Three identical buildings belonging to Ministry of Public Works and Resettlement (MPWR) that had been built to the same design templates, experienced March 13th 1992 Erzincan earthquake in Erzincan, November 12th 1999 D&uuml / zce earthquake in Bolu and May 1st 2003 Bing&ouml / l earthquake in Bing&ouml / l, respectively. The ground motion sensor stations were fortuitously nearby in an adjacent single-story building in Bolu and Bing&ouml / l. The station in Erzincan was in a single-story building about 2 km away from the case study building but we assume that the record applies to the building there. These three data represent characteristics of near-field ground motions and the distance of the sensor stations to the nearest fault trace was less than 10 km. The buildings sustained varying degrees of damage during the earthquakes and their damage survey was employed through site investigations. Given that the damage information, input motions, design drawings and material properties of the buildings are all known, this provided an opportunity to predict the structural damage to these buildings by proper modeling using the tools of current computational performance assessment procedures. In this circumstance, three dimensional (3D) analytical models of the MPWR buildings have been performed. Bi-directional excitations have been applied to the models by nonlinear time history analyses (NTHA). The results illustrate that NTHA are capable of indicating the occurrence of shear failure in captive columns / however, they overestimate the global damage level for all buildings. The overestimation is more significant in Erzincan case where the building sustained a pulse-type motion without significant distress.

This investigation address the effect that pressure, p, and temperature, T, have on 4f-states of the rare-earth elements in the isostructural YbRh2Si2, EuCo2Ge2, and EuCu2Ge2 compounds. Upon applying pressure, the volume of the unit cell reduces, enforcing either the enhancement of the hybridization of the 4f-localized electrons with the ligand or a change in the valence state of the rare-earth ions. Here, we probe the effect of a pressure-induced lattice contraction on these system by means of electrical resistivity, from room temperature down to 100 mK. At ambient pressure, the electrical resistivity of YbRh2Si2 shows a broad peak at 130 K related to the incoherent scattering on the ground state and the excited crystalline electrical field (CEF) levels. At T_N = 70 mK, YbRh2Si2 undergoes a magnetic phase transition. Upon applying pressure up to p_1 = 4 GPa , T_N increases monotonously while the peak in the electrical resistivity is shifted to lower temperatures. For p < p_1 a different behavior is observed; namely, T_N depends weakly on the applied pressure and a decomposition of the single peak in the electrical resistivity into several shoulders and peaks occurs. Above p_2 = 9 GPa, the electrical resistivity is significantly reduced for T < 50 K and this process is accompanied by a sudden enhancement of T_N. Thus, our results confirm the unexpected behavior of the magnetization as function of pressure reported by Plessel et al. The small value of the magnetic ordering temperature for p < p_2 and the strength of the mechanism that leads to the peaks and shoulders in the electrical resistivity suggest that the f-electrons are still screened by the conduction electrons. Therefore, the observed behavior for pressures lower than p_2 might be a consequence of the competition of two different types of magnetic fluctuations (seemingly AFM and FM). Furthermore, the results suggest that a sudden change of the CEF scheme occurs at pressures higher than p_1, which would have an influence on the ground state. Additionally, a comparison of the pressure dependent features in the electrical resistivity of YbRh2Si2 with similar maxima in other isostructural YbT2X2 (T = transition metal; X = Si or Ge) compounds was performed. For the comparison, a simple relation that considers the Coqblin-Schrieffer model and the hypothesis of Lavagna et al. is proposed. A systematic behavior is observed depending on the transition metal; namely, it seems that the higher the atomic radii of the T-atom the smallest the pressure dependence of the maximum in the electrical resistivity, suggesting a weaker coupling of localized- and conduction-electrons. It is also observed that an increase in the density of conduction electrons reduces the pressure dependence of the characteristic Kondo temperature. The mechanism responsible for the sudden enhancement of T_N in YbRh2Si2 at about p_2 is still unknown. However two plausible scenarios are discussed. The Eu-ions in EuCo2Ge2 and EuCu2Ge2 have a divalent character in the range 100 mK < T < 300 K. Therefore, these systems order magnetically at T_N = 23 K and T_N = 12 K, respectively. The studies performed on EuCo2Ge2 and EuCu2Ge2 as a function of pressure suggest that a change to a non-magnetic trivalent state of the Eu-ions might occur at zero temperature for pressures higher than 3 GPa and 7 GPa, respectively. A common and characteristic feature on EuCo2Ge2 and EuCu2Ge2 is the absence of a clear first order transition from the divalent to the trivalent state of the Eu-ions at finite temperature for p > 3 GPa and for p > 7 GPa, respectively. In other isostructural Eu-based compounds, a discontinuous and abrupt change in the thermodynamic and transport properties associated to the valence transition of the Eu-ions is typically observed at finite temperatures. In contrast, the electrical resistivity of EuCo2Ge2 and EuCu2Ge2 changes smoothly as a function of pressure and temperature. The analysis of the the electrical resistivity of EuCo2Ge2 suggest that a classical critical point might be close to the AFM-ordered phase, being a hallmark of this compound. The overall temperature dependence of the the electrical resistivity of EuCo2Ge2 changes significantly at 3 GPa; therefore, it seems that the system suddenly enters to a T-dependent valence-fluctuating regime. Additionally, the pressure-dependent electrical-resistivity isotherms show a step-like behavior. Thus, it is concluded that discontinuous change of the ground state might occur at 3 GPa. The electrical resistivity of EuCu2Ge2 at high pressure is characterized by a negative logarithmic T-dependence in the pressure range 5 GPa < p < 7 GPa for T > T_N and by a broad peak in the pressure dependent residual resistivity, whose maximum is located at 7.3 GPa. The first behavior resembles the incoherent scattering process typical for an exchange coupling mechanism between the localized electrons and the ligand. This and the peak effect in the local 4f susceptibility observed in NMR measurements are consistent with such a coupling mechanism. Thus, it would be for the first time that a dense Eu-based compound like EuCu2Ge2 show such a behavior. Combining the results of the experiment performed at high pressures on EuCu2Ge2 with the studies performed in the EuCu2(Ge1-xSix)2 series, a crossover from an antiferromagnetically ordered state into a Fermi-liquid state for pressures higher than 7.3 GPa may be inferred from the analysis. Therefore, it may be possible that the sudden depopulation of 4f-level occur mediated by quantum fluctuation of the charge due to a strong Coulomb repulsion between the localized-electrons and the ligand. This phenomenon would explain the broad peak in the residual resistivity. To our knowledge, this would be the first Eu-based compound, isostructural to ThCr2Si2, that show such a transition as function of pressure at very low temperatures.

The 1st strand transfer, a crucial step of reverse transcription involving the HIV-1 nucleocapsid protein (NC), relies on base pairing of the r sequence of strong-stop DNA (ssDNA) with the 3' R sequence of viral RNA (3' UTR) which forms the TAR and polyA stem-loops. The r sequence can form the cTAR and cpolyA stem-loops. Therefore, the transfer relies probably on annealing of folded molecules. This process is not well known at the molecular and structural level. The tools of molecular biology and three DNA-targeted probes were used to get insights into the annealing process. Our results were the following: 1) in the absence of NC, the cTAR DNA folds into two distinct conformations in equilibrium; 2) NC slightly shifts the equilibrium toward one conformation and binds tightly the internal loop of the cTAR hairpin; 3) NC is required for the formation of heteroduplex of the full-length ssDNA and 3' UTR; 4) the annealing of ssDNA to 3' UTR can be initiated from different sites in the presence of 0.2 mM MgCl2; 5) the full-length ssDNA folds into two conformations in equilibrium in 0.2 mM MgCl2 but mainly into one conformation in 2 mM MgCl2 ; 6) NC preferentially binds to the single-stranded region between the cTAR and cpolyA hairpins in ssDNA. This binding site probably plays an important role in the annealing of complementary DNA and RNA hairpins. This study helps us to gain insights into the reverse transcription process and the associated genetic recombination.

The narrative identity: Alexander Nehamas, Richard Rorty This work analyzes the problem of narrative identity developed in the works of Nehamas and Rorty. These two American philosophers work in the same – postnietzschean – paradigm. Both of them claim that the identity is not simply given to a person; rather, it is something one has to achieve if he/she wants to have one. A means both philosophers offer to such an achievement is to narrate a story about one’s person, one’s style of life and thus to create ones identity. Nehamas and Rorty assert that while creating identity one has to obey to some rules. However, the rules the philosophers announce are somewhat different. As to Nehamas, he claims that the project of the self-creation ought to be coherent and distinctive. These two criteria are to be achieved, otherwise the self-creation will fail. In addition, this project has to be accomplished in writing. Nehamas demonstrates how these criteria distinctiveness and coherence – are achieved in the writings of certain philosophers. These philosophers are Socrates, Plato, Montaigne, Nietzsche, Foucault and ultimately Nehamas himself. Nehamas suggests that all these philosophers belong to the tradition of the art of living and that all of them are primarily concerned with the projects of self-creation and self-perfection. As to Rorty, he asserts that the creator of oneself has to fulfil one major requirement. Like Nehamas, Rorty claims that the aim of self-creator, whom he... [to full text]

In this thesis, we describe linear codes over prime fields obtained from incidence designs of iterated line graphs of complete graphs Li(Kn) where i = 1, 2. In the binary case, results are extended to codes from neighbourhood designs of the line graphs Li+1(Kn) using certain elementary relations. Codes from incidence designs of complete graphs, Kn, and neighbourhood designs of their line graphs, L1(Kn) (the so-called triangular graphs), have been considered elsewhere by others. We consider codes from incidence designs of L1(Kn) and L2(Kn), and neighbourhood designs of L2(Kn) and L3(Kn). In each case, basic parameters of the codes are determined. Further, we introduce a family of vertex-transitive graphs 􀀀n that are embeddable into the strong product L1(Kn) ⊠ K2, of triangular graphs and K2, a class which at first sight may seem unnatural but, on closer look, is a repository of graphs rich with combinatorial structures. For instance, unlike most regular graphs considered here and elsewhere that only come with incidence and neighbourhood designs, 􀀀n also has what we have termed as 6-cycle designs. These are designs in which the point set contains vertices of the graph and every block contains vertices of a 6-cycle in the graph. Also, binary codes from incidence matrices of these graphs have other minimum words in addition to incidence vectors of the blocks. In addition, these graphs have induced subgraphs isomorphic to the family Hn of complete porcupines (see Definition 4.11). We describe codes from incidence matrices of 􀀀n and Hn and determine their parameters.

Fumonisins, carcinogenic mycotoxins produced by various Fusarium species, occur naturally in maize and maize-based food products. They are hazards for animal and human health as they cause cancer in rodents and have been associated with oesophageal cancer and neural tube defects in humans. The most abundant naturally occurring fumonisins analogues in maize are fumonisin B1, B2 and B3 (FB1, FB2 and FB3). For analytical determination, they mostly require suitable extraction, clean-up and pre or post-column derivatization together with reversed-phase HPLC separation. o- Phthaldialdehyde (OPA) had been adopted as the most widely used derivatization reagent for fumonisins as they lack useful chromophores or fluorophores. Alternative derivatization reagents, naphthalene-2,3- dicarboxaldehyde (NDA) and dansyl chloride (DnS-Cl), were investigated in this study

Dominated by Heisenberg's uncertainty principle, vacuum is not quantum mechanically an empty void, i.e. virtual pairs of particles appear and disappear persistently. This nonlinearity subsequently provokes a number of phenomena which can only be practically observed by going to a high-intensity regime. Pair production beyond the so-called Sauter-Schwinger limit, which is roughly the field intensity threshold for pairs to show up copiously, is such a nonlinear vacuum phenomenon. From the viewpoint of Dirac's front form of Hamiltonian dynamics, however, vacuum turns out to be trivial. This triviality would suggest that Schwinger pair production is not possible. Of course, this is only up to zero modes. While the instant form of relativistic dynamics has already been at least theoretically well-played out, the way is still open for investigating the front form. The aim of this thesis is to explore the properties of such a contradictory aspect of quantum vacuum in two different forms of relativistic dynamics and hence to investigate the possibility of finding a way to resolve this ambiguity. This exercise is largely based on the application of field quantization to light-front dynamics. In this regard, some concepts within strong field theory and light-front quantization which are fundamental to our survey have been introduced, the order of magnitude of a few important quantum electrodynamical quantities have been fixed and the basic information on a small number of nonlinear vacuum phenomena has been identified. Light-front quantization of simple bosonic and fermionic systems, in particular, the light-front quantization of a fermion in a background electromagnetic field in (1+1) dimensions is given. The light-front vacuum appears to be trivial also in this particular case. Amongst all suggested methods to resolve the aforementioned ambiguity, the discrete light-cone quantization (DLCQ) method is applied to the Dirac equation in (1+1) dimensions. Furthermore, the Tomaras-Tsamis-Woodard (TTW) solution, which expresses a method to resolve the zero-mode issue, is also revisited. Finally, the path integral formulation of quantum mechanics is discussed and, as an alternative to TTW solution, it is proposed that the worldline approach in the light-front framework may shed light on different aspects of the TTW solution and give a clearer picture of the light-front vacuum and the pair production phenomenon on the light-front.

High-order Harmonic Generation (HHG) is an extreme nonlinear process that can be intuitively understood as the sequence of 3 steps: i) tunnel ionization of the target atom/molecule, creating an electronic wave packet (EWP) in the continuum, ii) acceleration of the EWP by the strong laser field and iii) recombination to the core with emission of an attosecond burst of XUV coherent light. HHG thus provides a tunable ultrashort tabletop source of XUV/Soft X-ray radiation on attosecond time scale for applications ('direct' scheme). At the same time, it encodes coherently in the XUV radiation the structure and dynamical charge rearrangement of the radiating atoms/molecules ('self-probing' scheme or High Harmonic Spectroscopy). This thesis is dedicated to both application schemes in attophysics based on advanced characterization and control of the attosecond emission. In the so-called 'self-probing' scheme, the last step of HHG, the electron-ion re-collision can be considered as a probe process and the emission may encode fruitful information on the recombining system, including molecular structure and dynamics. In the first part, we performed high harmonic spectroscopy of N₂O and CO₂ molecules that are (laser-)aligned with respect to the polarization of the driving laser. We implemented two methods based on optical and quantum interferometry respectively in order to characterize the amplitude and phase of the attosecond emission as a function of both photon energy and alignment angle. We discovered new effects in the high harmonic generation, which could not be explained by the structure of the highest occupied molecular orbital (HOMO). Instead, we found that during the interaction with the laser field, two electronic states are coherently excited in the molecular ion and form a hole wave packet moving on an attosecond timescale in the molecule after tunnel ionization. We focused on exploring this coherent electronic motion inside the molecule, and compared the measurements in N₂O and CO₂. The striking difference in the harmonic phase behavior led us to the development of a multi-channel model allowing the extraction of the relative weight and phase of the two channels involved in the emission. An unexpected pi/4 phase shift between the two channels is obtained. Moreover, we studied the attosecond profile of the pulses emitted by these two molecules, and we proposed a simple but flexible way for performing attosecond pulse shaping. In the second part, high harmonic spectroscopy was extended to other molecular systems, including some relatively complex molecules, e.g., SF₆ and small hydrocarbons (methane, ethane, ethylene, acetylene). It revealed many interesting results such as phase distortions not previously reported. For the 'direct' scheme, we photoionized rare gas atoms using well characterized attosecond pulses of XUV coherent radiation combined with an infrared (IR) laser "dressing" field with controlled time delay, stabilized down to about ± 60 as. We evidenced marked differences in the measured angular distributions of the photoelectrons, depending on the number of IR photons exchanged. Joined to a theoretical interpretation, these observations bring new insights into the dynamics of this class of multi-color photoionization processes that are a key step towards studying photoionization in the time domain, with attosecond time resolution.

Graph partitioning is a fundamental optimization problem that has been intensively studied. Many graph partitioning formulations are important as building blocks for divide-and-conquer algorithms on graphs as well as to many applications such as VLSI layout, packet routing in distributed networks, clustering and image segmentation. Unfortunately such problems are notorious for the huge gap between known best known approximation algorithms and hardness of approximation results. In this thesis, we study approximation algorithms for graph partitioning problems using a strong hierarchy of relaxations based on semi-definite programming, called Lasserre Hierachy. Our main contribution in this thesis is a propagation based rounding framework for solutions arising from such relaxations. We present a novel connection between the quality of solutions it outputs and column based matrix reconstruction problem. As part of our work, we derive optimal bounds on the number of columns necessary together with efficient randomized and deterministic algorithms to find such columns. Using this framework, we derive approximation schemes for many graph partitioning problems with running times dependent on how fast the graph spectrum grows. Our final contribution is a fast SDP solver for this rounding framework: Even though SDP relaxation has nO(r) many variables, we achieve running times of the form 2O(r) poly(n) by only partially solving the relevant part of relaxation. In order to achieve this, we present a new ellipsoid algorithm that returns certificate of infeasibility.