This thesis has two focuses. The major focus is an investigation of the nature of high-velocity ~2 km/s)ionospheric flows occasionally detected by the King Salmon SuperDARN radar at relatively low magnetic latitudes of 65^0. The second focus is a validation work on the quality of SuperDARN convection measurements. As an alternative convection-monitoring instrument, an ion drift meter onboard the DMSP satellite was chosen for comparison with SuperDARN. This study includes a broad range of velocities of up to ~1.5 km/s. Consideration of very large velocities is fundamentally important for successful research on the major topic of the thesis.<p>The validation work is performed first. Two approaches are undertaken. The first approach considers data at the raw level. SuperDARN F region line-of-sight velocities are directly compared with DMSP cross-track ion drifts in approximately the same directions. More than 200 satellite passes over the fields of view of five Northern Hemisphere and four Southern Hemisphere radars are considered. It is shown that all radars exhibit overall consistency with DMSP measurements and a linear fit line to the data has a slope of 0.8 with a tendency for SuperDARN velocities to be smaller. Radar echo range effects and the role of spatial inhomogeneity and temporal variations of the convection pattern are investigated. SuperDARN convection maps were generated for select events for which SuperDARN l-o-s data agree almost ideally with DMSP measurements.<p>Convection maps were obtained using all Northern Hemisphere SuperDARN radars. The full convection vectors were found to be in reasonable agreement with the DMSP ion drifts, although a small deterioration (~10%) was noticed. The overall agreement between SuperDARN and DMSP measurements implies SuperDARN observations are reliable for velocity magnitudes of up to ~1.5 km/s, and SuperDARN radars are suitable instruments for studying extremely fast ionospheric flows. These results also imply that radar measurements can be merged with DMSP measurements into a common data set to provide more reliable convection maps.<p>For the main focus of the thesis, a statistical investigation of the King Salmon radar echoes was performed to determine typical echo characteristics and compare them with data from other SuperDARN radars. It is shown that King Salmon regularly observes high-velocity echoes in the dusk sector at ~21:00 MLT and ~65^0 MLat. Individual events are presented with line-of-sight velocities (observed with the L-shell aligned beams) as high as 2 km/s. Statistically, the enhanced flows are the largest and cover the greatest area in the winter and are the smallest and cover the least area in the summer. Similar fast flows were discovered in the Unwin radar data (in the Southern Hemisphere, lowest magnetic latitude ~57^0) that became available near the completion time of this thesis. It is also shown that statistically, the Stokkseyri radar, which observes in the auroral zone and has a similar azimuthal orientation as King Salmon, does not observe similar high-velocity echoes. Geophysical conditions for the onset of high-velocity King Salmon flows in several individual events are then investigated. It is shown that fast flows are excited in close association with substorm progression near the King Salmon field of view. By comparing SuperDARN data with optical images obtained from the IMAGE satellite and particle data from the DMSP satellites it is shown that velocity enhancement begins at substorm onset and peaks 20-50 minutes later over a range of latitudes including the auroral and sub-auroral regions. During the substorm recovery phase, as bright aurora shifts poleward, exceptionally fast flows can be excited at the equatorial edge of the electron auroral oval and these flows can be classified as sub-auroral polarization stream (SAPS) flows. Variability of SAPS flows and their relationship to auroral oval processes are discussed. Finally, several suggestions for further research are presented.

The aim of this thesis was to develop an objective and automatic method for identifying capillaries in microscope images of the skin. Furthermore, statistical data about the identified capillaries and the capillary distribution should be computed and stored in a database. The method was implemented using the platform independent programming language Java. An analysis of microscope improvement using various polarization filter setups and wavelength filtershas also been performed, as well as a pilot study of the effect of applying a local anaesthetic cream on the skin. The method is developed and aimed at research on various pathological skin conditions affecting the capillary distribution. Hypertension, diabetes, inflammation, ischemia, connective tissue disease, and erythromelalgia are all examples of diseases or pathological conditions which are supposed to affect the distribution of the skin capillaries.

The lateral spatial separation between the circular polarization components of a linearly polarized light beam impinging at off-normal incidence on an air-semiconductor interface is investigated experimentally and theoretically. This fundamental optical phenomenon is referred to as the Spin Hall effect of light (SHEL). An optical pump-probe technique is demonstrated to resolve in situ the nanometer size SHEL displacement of a beam transmitted inside an absorptive material. Three different types of optical interactions in silicon and GaAs demonstrate the technique’s general applicability. First, resonant ∼150 fs pump and probe pulses at λ = 820 nm resolve the SHEL displacement via free-carrier absorption in a 10 μm thick silicon sample. The measured SHEL displacements for a p-polarized probe beam are obtained between −10 to 150 nm as a function of the angle of incidence on the sample. Different angles of incidence are achieved by keeping a fixed angular separation between the pump and the probe beams while rotating the sample about the axis perpendicular to the plane of incidence. In another experiment, an optically thin (500 nm thick) GaAs sample allows one to use Pauli-blocking as an optical interaction to investigate the polarization and angular dependence of the SHEL in the probe beam. For such a polarization-dependent imaging technique, the SHEL displacement in the pump beam also contributes to the measured signal and is evaluated experimentally. A probe beam at normal incidence is used to measure a SHEL displacement of ∼180 nm in a transmitted p-polarized pump beam impinging on the sample with an angle of incidence of 55 degrees. Finally, two-photon absorption is used to resolve the SHEL in a (001) oriented 500 μm thick GaAs wafer using an optical source generating sub-bandgap radiation (λ = 1550 nm) with a pulse duration of 120 fs. Linearly p- and s- co-polarized pump and probe beams are also used to investigate the polarization dependence of the SHEL. All the experimental results obtained using these different optical interactions agree with the theory within the experimental error. Finally, analytical expressions of the shifts experienced by the circular components of a beam impinging at an interface between two optical media are also derived for an incident beam with an arbitrary spatial distribution.

Le but de ce projet est de développer de nouveaux outils pour explorer des processus d'organisation intracellulaire dynamique dans les cellules vivantes, avec une sensibilité sans précédent. Ce travail se concentre sur deux aspects principaux : le développement d'outils pour l'étude en molécule unique de la division cellulaire asymétrique, et la mise au point de sondes monovalentes qui permettent le suivi d'une protéine individuelle utilisant un nanocristal semiconducteur (ou quantum dot, QD). La division cellulaire asymétrique (DCA) est définie comme une division cellulaire dans laquelle une cellule mère donne naissance à deux cellules filles avec des destins différents (ce qui se manifeste à travers par exemple la taille, le contenu ou le profil d'expression). Notre étude se concentre sur la division cellulaire asymétrique dans les cellules souches neurales de Drosophila melanogaster, appelés neuroblastes. Au cours de la division asymétrique des neuroblasts, avant la séparation de la cellule-mère en deux cellules-filles, certaines molécules dans le cytoplasme se redistribuent de façon asymétrique (polarisée). Ce travail a montré la faisabilité de l'étude de la division cellulaire asymétrique à l'échelle de la molécule unique. Les méthodes ont été conçues et développées pour la conjugaison et la caractérisation des complexes QD-protéines. Nous avons réussi à cibler les protéines localisées de manière asymétrique dans des neuroblastes en division. Cela ouvre la voie à des études intracellulaires de ce phénomène, en utilisant des QDs individuels Ce travail a également mis en évidence la limite principale de ce système expérimental : la nature tridimensionnelle des mouvements. En raison de l'épaisseur de la neuroblate, les QDs sortent du plan focal très souvent. En conséquence, l'obtention des trajectoires suffisamment longues pour le calcul des paramètres de transport, devient très difficile. Toutefois, certaines informations peuvent encore être extraites des données que nous avons obtenues, en analysant la répartition spatiale de "courts-déplacements" dans les films obtenus. Les déplacements des QDs entre deux images consécutives sont regroupés et analysés en fonction de leur emplacement par rapport à une carte polaire normalisée d'un neuroblaste polarisé. Une telle analyse n'a pas besoin des trajectoires longues mais peut, quand même, révèler des differences dans la mobilité des protéines entre les differents domaines de la cellule. Cette analyse est actuellement en cours. Nous avons aussi réussi à produire des sondes monovalentes pour le suivi des proteines membranaires extracellulaires. Ces sondes sont basées sur un fragment de chaîne variable d'anticorp (ScFv). Ces sondes doivent avoir des nombreuses applications dans le suivi des diverses protéines membranaires, mais doivent être améliorées afin de répondre aux exigences rigoureuses du suivi intracellulaire.

The lateral spatial separation between the circular polarization components of a linearly polarized light beam impinging at off-normal incidence on an air-semiconductor interface is investigated experimentally and theoretically. This fundamental optical phenomenon is referred to as the Spin Hall effect of light (SHEL). An optical pump-probe technique is demonstrated to resolve in situ the nanometer size SHEL displacement of a beam transmitted inside an absorptive material. Three different types of optical interactions in silicon and GaAs demonstrate the technique’s general applicability. First, resonant ∼150 fs pump and probe pulses at λ = 820 nm resolve the SHEL displacement via free-carrier absorption in a 10 μm thick silicon sample. The measured SHEL displacements for a p-polarized probe beam are obtained between −10 to 150 nm as a function of the angle of incidence on the sample. Different angles of incidence are achieved by keeping a fixed angular separation between the pump and the probe beams while rotating the sample about the axis perpendicular to the plane of incidence. In another experiment, an optically thin (500 nm thick) GaAs sample allows one to use Pauli-blocking as an optical interaction to investigate the polarization and angular dependence of the SHEL in the probe beam. For such a polarization-dependent imaging technique, the SHEL displacement in the pump beam also contributes to the measured signal and is evaluated experimentally. A probe beam at normal incidence is used to measure a SHEL displacement of ∼180 nm in a transmitted p-polarized pump beam impinging on the sample with an angle of incidence of 55 degrees. Finally, two-photon absorption is used to resolve the SHEL in a (001) oriented 500 μm thick GaAs wafer using an optical source generating sub-bandgap radiation (λ = 1550 nm) with a pulse duration of 120 fs. Linearly p- and s- co-polarized pump and probe beams are also used to investigate the polarization dependence of the SHEL. All the experimental results obtained using these different optical interactions agree with the theory within the experimental error. Finally, analytical expressions of the shifts experienced by the circular components of a beam impinging at an interface between two optical media are also derived for an incident beam with an arbitrary spatial distribution.

In this Thesis the magnetic and structural properties of thin epitaxial Fe, Co, and Ni films are discussed. Some of the in-situ prepared samples were used to characterize the degree of circular polarization of the newly installed beamline D1011 at MAX-lab. By means of x-ray magnetic circular dichroism (XMCD) and utilizing the associated magneto optic sum rules, the orbital (ml) and spin (ms) moments are determined directly in mB/atom with elemental specificity. The extended x-ray absorption fine structure (EXAFS) measurements yield site specific information on the local crystallographic structure. These measurements were performed using the circular x-rays of several beamlines. The influence of the degree of spatial source coherence lspat of the x-rays was characterized by means of Fresnel diffractometry. A correlation between enhanced XAS white line intensities and higher values of lspat was established for 20 ML Fe, Co, and Ni films on Cu(100). The degree of circularly polarized x-rays (Pc) at beamline D1011 at MAX-lab was characterized by studying Fe films on Cu(100) by means of XMCD. The maximum value of Pc is experimentally determined to Pc =0.85. The Au/Co/Au trilayer system was studied as a function of Co thickness, temperature, and Au cap thickness. A 10 mono-layer (ML) Co film, with an Au cap of 20 Å, shows a spin reorientation transition (SRT) from an in-plane to an out-of-plane easy direction as the temperature is lowered from 300 K to 200 K. The magnetic properities of these Co films are very different to what is found for bulk samples due to, in particular, the broken symmetry at the interfaces. The thickness dependent spin reorientation transition in the Fe/Ag(100) system was characterized by means of XMCD and EXAFS measurements. 3 ML Fe films show an out-of-plane easy direction with an 125% enhanced orbital moment as compared to the 25 ML Fe in-plane film. Simulations of the Fe L-edge EXAFS indicate the bulk Fe bcc structure for film thicknesses of 6-25 ML Fe. For 3 ML Fe strong deviations from this bcc phase is observed. Ultrathin Co films deposited on flat and vicinal Cu(111) in the thickness region 1-25 ML were studied by means of XMCD and scanning tunneling microscopy (STM). The vicinal Cu(111) Co deposition leads to the formation of elongated islands preferentially oriented along the step edges. In connection to this particular Co growth mode we observe an increase of both the orbital and the spin moment on the vicinal Cu(111) of about 25% relative to what was observed for Co on flat Cu(111).

Definir los parámetros de polarización de la luz procedente de una muestra aporta una mayor información sobre las propiedades de ésta que la simple medida de la intensidad luminosa difundida. Cuando un haz luminoso sufre una perturbación debida a cualquier interacción con un medio, los campos electromagnéticos del haz incidente y el del haz emergente, expresados en términos de los parámetros de Stokes, pueden ser relacionados mediante la denominada matriz de Mueller. En este aspecto, el conocer la evolución de los parámetros de dicha matriz del sistema, nos permitiría definir cómo se comporta éste frente a la luz incidente. Para tal objetivo, se ha puesto a punto un polarímetro dinámico basado en técnicas de Transformada de Fourier, que permite determinar con una sola medida los 16 elementos de la matriz de Mueller. Ésta nos mostrará los cambios sufridos por la polarización del haz incidente debido a su interacción con una muestra problema.Aplicando el método de Descomposición Polar, se puede ver que cualquier sistema puro, con matriz de Mueller M, responde a la siguiente relación: M=R*D, donde R y D simbolizan las matrices de Mueller de un medio Retardador ideal y de un medio Diatenuador ideal, respectivamente. En una versión extendida de éste teorema, teniendo en cuenta que no todos los medios son ideales, sino que hay medios en los que aparecen efectos de despolarización, la descomposición de la matriz de Mueller daría lugar a: M=Z*R*D, tomando Z como la matriz de Mueller de un sistema despolarizante. De esta forma, utilizando algebra matricial, podemos descomponer la matriz de un sistema problema, en matrices de menor complejidad, con un estricto sentido físico.Partiendo de éstos resultados teóricos, y por medio del uso del polarímetro dinámico para la caracterización polarimétrica de los sistemas, se han analizado muestras de diversos tipos: superficies planas microestructuradas, para evaluar el efecto de la composición, tamaño e interacción; suspensiones de micropartículas y nanopartículas en coloide, para caracterizar su tamaño y composición; y sustancias quirales en medios turbios (en éste aspecto, recientemente ha sido demostrada la validez de éste método para el análisis in situ de tejidos biológicos). Asimismo, se han caracterizado componentes ópticos y polarimétricos por transmisión y reflexión, demostrando la validez del método. Finalmente se han llevado a cabo simulaciones computacionales a fin de estudiar patrones de comportamiento en sistemas complejos por medio del método de Descomposición Polar. / Polarization parameters of light scattered from a sample give more information about its properties than the light scattering intensity measurement. When a light beam interacts with an object or a medium, the electromagnetic fields of the incident and the emerging beam, both expressed in terms of Stokes parameters, can be related by the so-called Mueller matrix. In this respect, the matrix elements are associated to the physical system and define its behaviour. For the analysis of real systems, Mueller matrix must be experimentally obtained. For this purpose, a dynamic polarimeter (DRCP or Dual Rotating Compensator Polarimeter) based on Fourier Transform techniques has been developed, which allow us to determine the 16 elements of the Mueller matrix in a single cycle of measurements.Applying an algebraic tool, as the Polar Decomposition method (PD), we can see that any Mueller matrix corresponding to a pure system satisfies: M = R * D, where R and D are the Mueller matrices of an ideal Retarder and a Diattenuator, respectively. In an extended version of PD, taking into account that not all matrices are ideal, but there are systems in which depolarization effects occur, the decomposition of the Mueller matrix would lead to: M = Z * R * D, with Z representing the depolarization. Thus, using matrix algebra, we can decompose the matrix of a system, in a product of matrices with a strict physical sense.Based on these theoretical results and by using a polarimetric characterization of systems (through PDRC measurements), we have analyzed samples of different types: flat microstructured surfaces to evaluate the effect of the composition, size and interaction; suspensions of microparticles or nanoparticles to characterize their size and composition; chiral substances in turbid media (in this aspect has recently been demonstrated the validity of this method for the analysis of biological tissues "in situ"); characterization and study of polarimetric optics in transmission and reflection, demonstrating the validity of the method. Finally, we have carried out computer simulations to explore patterns in complex systems using PD.

La estructura y componentes del ojo humano hacen que los cambios que se producen sobre el estado de polarización de la luz que emerge de él, tras realizar un doble paso y sufrir una reflexión en la retina, sean complejos y a priori poco predecibles. Esos cambios pueden influir en los resultados obtenidos con dispositivos que analizan la luz reflejada en la retina. Para conocer mejor los cambios que el ojo origina sobre un haz que lo atraviesa y los fenómenos a los que da lugar, se ha llevado a cabo un estudio de la calidad de imagen retiniana en función de los estados de polarización, así como un estudio espacial de los distintos parámetros de polarización a partir del cálculo de matrices de Mueller. Teniendo como base el método de doble paso, se ha diseñado y construido un polarímetro de imagen que utiliza retardadores variables de cristal líquido en los brazos generador y analizador. Con este dispositivo se han registrado series de dieciséis imágenes de doble paso correspondientes a las combinaciones independientes de estados de polarización de entrada y salida. Los resultados para varios sujetos muestran que la calidad de imagen depende en gran medida del estado de polarización de salida. Sin embargo, la influencia de la polarización de entrada, calculada usando matrices de Mueller espacialmente resueltas, juega un papel poco significativo. Por otra parte, el estudio polarimétrico de las imágenes de doble paso muestra que (1) la parte central de las imágenes tiene un grado de polarización del 80% frente a un 25% en la periferia; (2) el retardo introducido depende del observador, aunque la birrefringencia que presenta el ojo es lineal; (3) el dicroísmo es coherente con la longitud de onda empleada y (4) el valor de la polarizancia indica la existencia de cierta birrefringencia circular. / The structure and components of the human eye make changes produced on the polarization state of the light emerging from it after a double-pass through ocular media and a reflection in the retina be complicated and hardly predectible. Those changes can influence on the results obtained with any device analyzing the light reflected in the retina. A study of the retinal image quality as a function of the polarization state has been performed. A spatially resolved polarimetric study of different polarization parameters using Mueller-matrices was also performed. An imaging polarimeter adapted to an ophthalmoscopic double-pass apparatus using two ellectronically controlled liquid-crystal variable retarders has been developed. Series of sixteen double-pass images corresponding to independent combinations generator-analyzer have been recorded. Results obtained for several subjects show that the estimation of the image quality depends strongly on the polarization state in the exit pathway. However, the influence of the entrance polarization, calculated using spatially resolved Mueller-matrices is nearly negligible. On the other hand, the polarimetric study of double-pass images shows that (1) the light forming the central part of the images presents a degree of polarization of 80% while this is reduced to around 25% for the light in the skirts; (2) the retardation introduced by the eye in a double-pass is quite dependent on observers, although the birefringence is linear; (3) the dicroism is coherent with the wavelength used, and (4) the value of the polarizance indicates the existency of circular birrefringence.

No description available.

This thesis describes the design, development, and implementation of a pulsed source of polarization-entangled photons using spontaneous parametric down-conversion in a Sagnac interferometer. A tangle of 0.9286 ± 0.0015, fidelity to the state (|10〉 + |01〉)/√2 of 0.9798 ± 0.0004 and a brightness of 597 pairs/s/mW were demonstrated. Spontaneous parametric down-conversion is a nonlinear optical process in which one photon is split into two lower-frequency photons while conserving momentum and energy, in this experiment nearly degenerate photons are produced. These photons are then interfered at the output beamsplitter of the interferometer, exchanging path entanglement for polarization entanglement and generating the desired polarization-entangled photon pairs.