3D magnetic configuration of the Halpha filament and X-ray sigmoid in NOAA AR 8151

We investigate the structure and relationship of an H $\alpha$ filament and an X-ray sigmoid observed in active region NOAA 8151. We first examine the presence of such structures in the reconstructed 3D coronal magnetic field obtained from the non-constant- $\alpha$ force-free field hypothesis using a photospheric vector magnetogram (IVM, Mees Solar Observatory). This method allows us to identify several flux systems: a filament (height 30 Mm, aligned with the polarity inversion line (PIL), magnetic field strength at the apex 49 G, number of turns 0.5-0.6), a sigmoid (height 45 Mm, aligned with the PIL, magnetic field strength at the apex 56 G, number of turns 0.5-0.6) and a highly twisted flux tube (height 60 Mm, magnetic field strength at the apex 36 G, number of turns 1.1-1.2). By searching for magnetic dips in the configuration, we identify a filament structure which is in good agreement with the H $\alpha$ observations. We find that both filament and sigmoidal structures can be described by a long twisted flux tube with a number of turns less than 1 which means that these structures are stable against kinking. The filament and the sigmoid have similar absolute values of $\alpha$ and Jz in the photosphere. However, the electric current density is positive in the filament and negative in the sigmoid: the filament is right-handed whereas the sigmoid is left-handed. This fact can explain the discrepancies between the handedness of magnetic clouds (twisted flux tubes ejected from the Sun) and the handedness of their solar progenitors (twisted flux bundles in the low corona). The mechanism of eruption in AR 8151 is more likely not related to the development of instability in the filament and/or the sigmoid but is associated with the existence of the highly twisted flux tube (~1.1-1.2 turns)

Chinese Soft Power Promotion in the United States: 2005-2014

This thesis focuses on two research questions regarding the impact of economic crises on states\u27 soft power strategies. Specifically, can economic crises lead states to abandon generating soft power within countries affected by the resulting economic changes? And, does a shift away from soft power promotion policies represent a change in a state\u27s foreign policy strategy? To answer these questions, this thesis utilizes a case study focusing on the People\u27s Republic of China (PRC) from 2005 to January 1, 2015, investigating soft power generating efforts by China in the United States before and after the 2007 Financial Crisis. Research into Chinese soft power promotion activities in the realms of economics, people-to-people exchanges, and the arts reveals no definitive trends as to whether states abandon soft power promotion strategies in response to economic crises and illustrates what was once considered soft power generating can be later regarded as reducing soft power

Correlation of Dental Plaque Acidogenicity and Acidurance with Caries Activity – Perspectives of the Ecological Plaque Hypothesis

The ecological plaque hypothesis for the aetiopathogenesis of caries implies a microbial shift towards a more acidogenic and aciduric dental plaque microflora, due to a frequent carbohydrate intake. Certain plaque bacteria exhibit metabolic activity, at a low pH. A correlation exists between the increased numbers of some aciduric bacterial species, e.g. mutans streptococci and lactobacilli, and caries activity. The aim of this study was to study the acidogenic (lactate production / mg plaque x min., at pH 7.0) and aciduric potential (lactate production at pH 5.5 / lactate production at pH 7.0) of dental plaque in relation to the caries activity. Samples of dental plaque were collected from fifteen caries free and fifteen caries active children. Plaque suspensions in Ringer’s solution containing 1% sucrose and buffered with 0.5 M MOPS (pH 7.0) or MES (pH 5.5) were incubated aerobically at 37 ºC for 10-20 min. The production of lactic acid in the suspensions was determined by an enzymatic assay. In caries free children, significantly lower acidogenic potential at both pHs were recorded than in caries active children. The highest difference between the groups was in the acidogenic activity at neutral pH. On the contrary, the aciduric potential was lower in the caries active group than in the caries free. Caries activity correlated with the acidogenic potentials of dental plaque at both pH 7.0 and 5.5. A new perspective of the ecological plaque hypothesis based on the increased catabolic ability of plaque is proposed

Density profiles and collective excitations of a trapped two component Fermi vapour

We discuss the ground state and the small-amplitude excitations of a degenerate vapour of fermionic atoms placed in two hyperfine states inside a spherical harmonic trap. An equations-of-motion approach is set up to discuss the hydrodynamic dissipation processes from the interactions between the two components of the fluid beyond mean-field theory and to emphasize analogies with spin dynamics and spin diffusion in a homogeneous Fermi liquid. The conditions for the establishment of a collisional regime via scattering against cold-atom impurities are analyzed. The equilibrium density profiles are then calculated for a two-component vapour of 40K atoms: they are little modified by the interactions for presently relevant values of the system parameters, but spatial separation of the two components will spontaneously arise as the number of atoms in the trap is increased. The eigenmodes of collective oscillation in both the total particle number density and the concentration density are evaluated analytically in the special case of a symmetric two-component vapour in the collisional regime. The dispersion relation of the surface modes for the total particle density reduces in this case to that of a one-component Fermi vapour, whereas the frequencies of all other modes are shifted by the interactions.Comment: 14 pages, 4 figure

Heat transfer and performance characteristics of axial cooling fans with downstream guide vanes

This study examines experimentally the effect of stators on the performance and heat transfer characteristics of small axial cooling fans. A single fan impeller, followed by nine stator blades in the case of a complete stage, was used for all the experimental configurations. Performance measurements were carried out in a constant speed stage performance test rig while the transient liquid crystal technique was used for the heat transfer measurements. Full surface heat transfer coefficient distributions were obtained by recording the temperature history of liquid crystals on a target plate. The experimental data indicated that the results are highly affected by the flow conditions at the fan outlet. Stators can be beneficial in terms of pressure drop and efficiency, and thus more economical operation, as well as, in the local heat transfer distribution at the wake of the stator blades if the fan is installed very close to the cooling object. However, as the separation distance increases, enhanced heat transfer rate in the order of 25% is observed in the case of the fan impelle

Medium-transparent MAC protocols for converged optical wireless networks

In order to address the explosive demand for high-capacity and omnipresent wireless access, modern cell-based wireless networks are slowly adopting two major solution roadmaps. The first is the employment of small-cell formations in order to increase the overall spectral efficiency, whereas the second is the employment of higher frequency bands, such as the mm-wave 60GHz band, that offers vast amounts of bandwidth. Depending on the specific application, the above solutions inevitably require the installation and operational management of large amounts of Base Stations (BSs) or Access Points (APs), which ultimately diminishes the overall cost-effectiveness of the architecture. In order to reduce the system cost, Radio over Fiber (RoF) technology has been put forward as an ideal candidate solution, due to the fact that it provides functionally simple antenna units, often termed as Remote Antenna Units (RAUs) that are interconnected to a central managing entity, termed as the Central Office (CO), via an optical fiber. Although extensive research efforts have been dedicated to the development of the physical layer aspects regarding RoF technologies, such as CO/RAU physical layer design and radio signal transport techniques over fiber, very limited efforts have con-centrated on upper layer and resource management issues. In this dissertation, we are concerned with access control and resource management of RoF-based mm-wave network architectures targeting the exploitation of the dual medium and its centralized control properties in order to perform optimal optical/wireless/time resource allocation. In this dissertation, we propose a Medium-Transparent MAC (MT-MAC) protocol that concurrently administers the optical and wireless resources of a 60GHz RoF based network, seamlessly connecting the CO to the wireless terminals through minimal RAU intervention. In this way, the MT-MAC protocol forms extended reach 60GHz WLAN networks offering connectivity amongst wireless devices that are attached to the same or different RAUs under both Line of Sight (LOS) and non LOS conditions. The notion of medium-transparency relies on two parallel contention periods, the first in the optical domain and the second in the wireless frequency and time domains, with nested dataframe structures. The MT-MAC operation is based on a proposed RAU design that allows for wavelength selectivity functions, thus being compatible with completely passive optical distribution network implementations that are predominately used by telecom operators today. Two variants of the MT-MAC protocol are considered. The first offers dynamic wavelength allocation with fixed time windows, whereas the second targets fairness-sensitive applications by offering dynamic wavelength allocation with dynamic transmission opportunity window sizes, based on the number of active clients connected at each RAU. Both variants of the protocol are evaluated by both simulation and analytical means. For the latter part, this thesis introduces two analytical models for calculating saturation throughput and non-saturation packet delay for the converged MT-MAC protocol. Finally, this thesis presents an extensive study regarding the network planning and formation of 60GHz Gigabit WLAN networks when the latter are deployed over existing Passive Optical Network (PON) infrastructures. Three possible architectures where studied: i) the RoF approach, ii) the Radio & Fiber approach and iii) the hybrid RoF-plus-R&F approach that combines the properties of both the aforementioned architectures. During the elaboration of this thesis, one major key conclusion has been extracted. The work proposed in this thesis considers that there is a fundamental requirement for implementing new converged optical/wireless MAC protocols, that have the complete overview of both available resources in order to effectively administer the hybrid Radio-over-Fiber networks.A fin de atender la demanda explosiva de alta capacidad y acceso inalámbrico omnipresente, las redes inalámbricas basadas en celdas están poco a poco adoptando dos principales guías de solución. La primera es el empleo de formaciones de celdas pequeñas con el fin de aumentar la eficiencia espectral global, mientras que la segunda es el empleo de bandas de frecuencia superior, como la banda de 60GHz, la cual ofrece una gran cantidad de ancho de banda. Dependiendo de la aplicación en específico, las soluciones anteriores inevitable-mente requieren de una instalación y una gestión operativa de grandes cantidades de Estaciones Base o Puntos de Acceso, que en última instancia disminuye la rentabilidad de la arquitectura. Para reducir el coste, la tecnología radioeléctrica por fibra (RoF) se presenta como una solución ideal debido al hecho de que proporciona unidades de antenas de sim-ple funcionamiento, a menudo denominadas Unidades de Antenas Remotas (RAUs), las cuales están interconectadas a una entidad central de gestión, denominada Oficina Central (CO), a través de la fibra óptica. A pesar de que se han dedicado muchos esfuerzos de investigación al desarrollo de varios aspectos de las capas física con respecto a las tecnologías RoF, muy pocos esfuerzos se han concentrado en la capa superior y cuestiones de gestión de recursos. En esta tesis, nos enfocando en el control de acceso y gestión de recursos de arquitecturas RoF y comunicaciones milimétricas, con el fin de aprovechar y explotar el medio dual y las propiedades para realizar una óptima asignación de los recursos ópticos, inalámbricos y temporales. Nosotros proponemos un protocolo Transparente al Medio MAC (MT-MAC) que simultáneamente administre los recursos ópticos e inalámbricos de una red RoF a 60GHz, conectando a la perfección el CO a los terminales inalámbricos a través de una mínima intervención RAU. El protocolo MT-MAC forma unas redes WLAN 60GHz de alcance extendido, ofreciendo así conectividad entre los dispositivos inalámbricos que están conectados al mismo o diferentes RAUs bajo con o sin Línea de Vista (condiciones LOS o NLOS) respectivamente. La noción de transparencia al medio se basa en dos períodos de contención para-lelos, el primero en el dominio óptico y el segundo en la frecuencia inalámbrica y dominio del tiempo, con estructuras de datos anidados. La operación MT-MAC se basa en proponer un diseño RAU que permita la selectividad de funciones de longitud de onda. Dos variantes del protocolo MT- MAC son considerados; el primer ofrece asignación de longitud de onda dinámica con ventanas de tiempo fijo, mientras que la segunda tiene como objetivo entornos de aplicaciones sensibles ofreciendo asignación de longitud de onda con tamaño de ventana de oportunidad de transmisión dinámico, basado en el número de clientes conectados en cada RAU. Ambas variantes del protocolo están evaluadas tanto por medios analíticos como de simulación. En la segunda parte, esta tesis introduce dos modelos analíticos para calcular el rendimiento de saturación y no saturación del retardo de paquetes para el protocolo MT-MAC convergente. Finalmente, esta tesis presenta un extenso estudio de la planificación de red y la formación de redes 60GHz Gigabit WLAN cuando esta se encuentra desplegada sobre las ya existente infraestructuras de Redes Ópticas Pasivas (PONs). Tres posibles arquitecturas han sido estudiadas: i) el enfoque RoF, ii) el enfoque Radio y Fibra , y iii) el enfoque híbrido, RoF más R&F el cual combina las propiedades de ambas arquitecturas anteriormente mencionadas. Durante la elaboración de esta tesis, se ha extraído una importante conclusión: hay un requerimiento fundamental para implementar nuevos protocolos ópticos/inalámbricos convergentes, que tengan una completa visión de ambos recursos disponibles para poder administrar efectivamente las redes de tecnología RoF.Postprint (published version

Zobrazení cizinců na královských reliéfech Staré říše

(česky) Cílem této práce je shromáždit královské reliéfy pojednávající o cizincích z různých míst tehdejšího starověkého Egypta a prozkoumat jednotlivé aspekty zobrazování cizinců a roli cizinců v dekorativním programu, královské propagandě nebo v rámci víry. Vzhledem k charakteru práce budou zpracovány pouze nástěnné a skalní reliéfy. V rámci výzkumu pak bude kladen důraz na: témata jednotlivých vyobrazení, etnické aspekty cizinců (pokud jsou vyobrazeny), toponyma, zapojení bohů a bohyní, provázanosti s dalšími scénami v okolí uvažovaných reliéfů a jejich umístění v rámci pohřebních komplexů nebo v rámci celého Egypta (v případě skalních reliéfů). Časovým rozpětím výzkumu je Stará říše (cca 2592-2120 př. n. l.).(in English): The present thesis aim is to collect royal reliefs dealing with foreigners from various locations throughout Ancient Egypt and examine separate aspects of depiction of foreigners and the role foreigners played in decorative program, royal propaganda or belief system. Due to the nature of the study only wall and rock reliefs will be processed. Within the research focus will be laid on: topics of reliefs, ethnical aspects (if depicted), toponyms, gods and goddesses involved, interconnection to other scenes in proximity and their location within the mortuary complex or the whole Egypt (in case of rock reliefs). The timespan of research is the Old Kingdom (ca. 2592-2120 BC).Český egyptologický ústavCzech Institute of EgyptologyFilozofická fakultaFaculty of Art

Fatigue during the COVID-19 pandemic – prevalence and predictors: findings from a prospective cohort study

The COVID-19 pandemic and consequent lockdowns had a substantial impact on mental health. Distress and fatigue are highly correlated. However, little is known about the determinants of fatigue in the general population during the pandemic. This study aimed to examine the prevalence and predictors of fatigue during the COVID-19 pandemic in the UK population. Online surveys were completed by a UK community cohort in April 2020 (wave 1), July-September 2020 (wave 2) and November-December 2020 (wave 3). In total, 3097 participants completed the wave 1 survey, and 1385 and 1087 participants (85.4% women) completed wave 2 and 3 surveys respectively. Fatigue was assessed using the Chalder Fatigue Scale at waves 2 and 3. Hair samples were provided by 827 participants (90.6% women) at wave 1 and wave 2, which were analyzed to indicate HairE (stress hormone). The mean total fatigue score during wave 2 was 14.7 (SD = 4.7), significantly higher than pre-pandemic levels observed in the community (mean difference 0.50, p = .003). At wave 2, 614 (44.3%) participants met the case definition for fatigue, only 15.6% of whom indicated that fatigue lasted for more than 6 months (suggesting it had started prior to the pandemic). Predictors of fatigue at wave 3 included being in a risk group, depression and belief in having COVID-19, which explained 23.8% of the variability in fatigue scores. Depression at wave 1 was the only significant predictor of remaining a fatigue case at wave 3. Fatigue was highly prevalent in the UK community during the COVID-19 pandemic and limited people’s daily function. Depression and sociodemographic variables were significant predictors of fatigue