Floquet topological transitions in a driven one-dimensional topological insulator

The Su-Schrieffer-Heeger model of polyacetylene is a paradigmatic Hamiltonian exhibiting non-trivial edge states. By using Floquet theory we study how the spectrum of this one-dimensional topological insulator is affected by a time-dependent potential. In particular, we evidence the competition among different photon-assisted processes and the native topology of the unperturbed Hamiltonian to settle the resulting topology at different driving frequencies. While some regions of the quasienergy spectrum develop new gaps hosting Floquet edge states, the native gap can be dramatically reduced and the original edge states may be destroyed or replaced by new Floquet edge states. Our study is complemented by an analysis of Zak phase applied to the Floquet bands. Besides serving as a simple example for understanding the physics of driven topological phases, our results could find a promising test-ground in cold matter experiments

Government and the Intelligence Community: A Case Study on Russia and the United States Government\u27s Effect on Intelligence Systems

The United States and Russia are two major superpowers with governments that are run in different manners. Central to a government\u27s and country\u27s defense is their intelligence systems. The intelligence systems of these two countries are run as part of the government and are integral to its functioning. The purpose of this thesis is to discuss how both the governments and intelligence systems are structured and do they coincide with their respective systems. Using a case study on the United States and Russia, their intelligence systems and governments a comparison was drawn. While looking at the history of both governments and communities and what they are like in the present day it was determined that there exist similarities in structures. As the countries grew and modernized so did their intelligence community. The history of how the intelligence community developed in their respective country and interacted with citizens both foreign and domestic showed striking similarities to the governments own workings. Another important find was the rules and restrictions that were involved in the government\u27s evolution was also paralleled in the intelligence communities evolution. In the United States there are regulations against intruding into the lives and properties of citizens and the intelligence community reflects this in executive order 12333 that states intelligence communities cannot collect information on citizens unless it is imperative to the safety and security of the country

Understanding SOA Migration Using a Conceptual Framework

Migration of legacy assets to SOA embodies a key software engineering challenge. Over a decade there has been an increasing interest in the approaches addressing SOA migration. These approaches mainly differ in `what is migrated' and `how the migration is performed'. Such differences aggravate achieving a general understanding of `what SOA migration entails'. We describe what such migration process entails and what distinct conceptual elements systematically define the process. Based on the comprising conceptual elements the framework which is considered as a basis for understanding and assessment of different approaches is proposed. Further, the role of the migration framework in positioning and assessing the existing methods, is discussed. Finally, the procedure for positioning and mapping of migration approaches on the framework is explained using two example migration processes

Near-infrared spectroscopy study of tourniquet-induced forearm ischaemia in patients with coronary artery disease

Near-Infrared Spectroscopy (NIR) can be employed to monitor local changes in haemodynamics and oxygenation of human tissues. A preliminary study has been performed in order to evaluate the NIRS transmittance response to induced forearm ischaemia in patients with coronary artery disease (CAD). The population consists in 40 patients with cardiovascular risk factors and angiographically documented CAD, compared to a group of 13 normal subjects. By inflating and subsequently deflating a cuff placed around the patient arm, an ischaemia has been induced and released, and the patients have been observed until recovery of the basal conditions. A custom LAIRS spectrometer (IRIS) has been used to collect the backscattered light intensities from the patient forearm throughout the ischaemic and the recovery phase. The time dependence of the near-infrared transmittance on the control group is consistent with the available literature. On the contrary, the magnitude and dynamics of the NIRS signal on the CAD patients show deviations from the documented normal behavior, which can be tentatively attributed to abnormal vessel stiffness. These preliminary results, while validating the performance of the IRIS spectrometer, are strongly conducive towards the applicability of the NIRS technique to ischaemia analysis and to endothelial dysfunction characterization in CAD patients with cardiovascular risk factors.Publisher PD

19F nuclear spin relaxation and spin diffusion effects in the single ion magnet LiYF4:Ho3+

Temperature and magnetic field dependences of the 19F nuclear spin-lattice relaxation in a single crystal of LiYF4 doped with holmium are described by an approach based on a detailed consideration of the magnetic dipole-dipole interactions between nuclei and impurity paramagnetic ions and nuclear spin diffusion processes. The observed non-exponential long time recovery of the nuclear magnetization after saturation at intermediate temperatures is in agreement with predictions of the spin-diffusion theory in a case of the diffusion limited relaxation. At avoided level crossings in the spectrum of electron-nuclear states of the Ho3+ ion, rates of nuclear spin-lattice relaxation increase due to quasi-resonant energy exchange between nuclei and paramagnetic ions, in contrast to the predominant role played by electronic cross-relaxation processes in the low-frequency ac-susceptibility.Comment: 27 pages total, 5 figures, accepted for publication, Eur. Phys. J.

Contribuição de poleiros naturais e artificiais para a recuperação de ecossistemas florestais.

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