The 87Rb 49s->48s Rydberg state transition was rendered insensitive to electric field fluctuations about a 1V/cm dc electric field. This was accomplished by applying a non-resonant 38.445GHz microwave field to modify the electric dipole moment difference between the two states involved. This effect can be used to preserve the coherence of Rydberg state qubits in the presence of varying electric fields.

In this dissertation, we study properties of quantum interaction phenomena in two-dimensional (2D) and one-dimensional (1D) electronic systems in p-GaAs micro- and nano-scale devices. We present low-temperature magneto-transport data from three forms of low-dimensional systems 1) 2D hole systems: in order to study interaction contributions to the metallic behavior of 2D systems 2) Bilayer hole systems: in order to study the many body, bilayer quantum Hall state at nu = 1 3) 1D hole systems: for the study of the anomalous conductance plateau G = 0.7 ???? 2e2/h The work is divided into five experimental studies aimed at either directly exploring the properties of the above three interaction phenomena or the development of novel device structures that exploit the strong particle-particle interactions found in p-GaAs for the study of many body phenomena. Firstly, we demonstrate a novel semiconductor-insulator-semiconductor field effect transistor (SISFET), designed specifically to induced 2D hole systems at a ????normal???? AlGaAs-on-GaAs heterojunction. The novel SISFETs feature in our studies of the metallic behavior in 2D systems in which we examine temperature corrections to ????xx(T) and ????xy(T) in short- and long-range disorder potentials. Next, we shift focus to bilayer hole systems and the many body quantum Hall states that form a nu = 1 in the presence of strong interlayer interactions. We explore the evolution of this quantum Hall state as the relative densities in the layers is imbalanced while the total density is kept constant. Finally, we demonstrate a novel p-type quantum point contact device that produce the most stable and robust current quantization in a p-type 1D systems to date, allowing us to observed for the first time the 0.7 structure in a p-type device.

Synchrotron light source are accelerating research and development and fueling innovation in a wide range of research disciplines and industries worldwide. The third-generation synchrotron radiation facilities such as Advanced Photon Source (APS), produce ultra-brilliant x-rays using insertion devices consisting mainly of undulators, which provide exciting opportunities for advanced research into materials, earth science, life science, and medicine. Using high brightness x-ray radiation with high spatial coherence, unique coherence-based experiments are now becoming possible: coherence imaging techniques such as phase contrast imaging, holography, and tomography, are under intensive development, opening up a range of new areas of investigation. At the same time some useful optical elements used in the synchrotron radiation system have been created rapidly. Crucial to the development of all these fields is some knowledge of the spatial coherence of the light produced by these sources. In other words, the characterization of spatial coherence is a high priority. / The aim of this project is to develop a theoretical and experimental program to allow the measurement of the spatial coherence of synchrotron radiation. A technique to measure the spatial coherence of x-rays from undulators is presented. The essence of the coherence measurement technique is based on the interpretation of a complex diffraction pattern. We measure the spatial coherence function of a 7.9 keV x-ray beam from an undulator at a third-generation synchrotron (APS) using a sophisticated diffracting aperture known as a Uniformly Redundant Array (URA). The URA was also used to measure the spatial coherence function for soft x-rays at the APS. When a traditional Young’s double-slit experiment is used to test the degree of coherence, the separations of the two-slit have to be changed repeatedly to full map the spatial coherence function. The URA is a complex aperture consisting of many slits, (or, for a two-dimensional array, pinholes), organized such that all possible slit separations occur, and do so with exactly the same frequency. One might regard the URA as able to simultaneously perform many Young’s experiments a precisely equal number of times across the full range of slit separations permitted by the overall size of the URA. Therefore one experiment using a one-dimensional (1D) URA can perform the equivalent of multiple double-slit experiments. The diffraction theory developed in this thesis a convenient theoretical basis for interpreting this diffraction pattern.

SUMMARY Introduction: There has recently been a great deal of interest in the role of synchronous high-frequency gamma oscillations in brain function. This interest has been motivated by an increasing body of evidence, that oscillations which are synchronous in phase across separated neuronal populations, may represent an important mechanism by which the brain binds or integrates spatially distributed processing activity which is related to the same object. Many models of schizophrenia suggest an impairment in the integration of brain processing, such as a loosening of associations, disconnection, defective multiple constraint organization, or cognitive dysmetria. This has led to recent speculation that abnormalities of high-frequency gamma synchronization may reflect a core dimension of the disturbance underlying this disorder. However, examination of the phase synchronization of gamma oscillations in patients with schizophrenia has never been previously undertaken. Method: In this thesis a new method of analysis of gamma synchrony was introduced, which enables the phase relationships of oscillations in a specific frequency band to be examined across multiple scalp sites as a function of time. This enabled, for the first time, the phase synchronization of gamma oscillations across widespread regions, to be studied in electrical brain activity measured at the scalp in humans. Gamma synchrony responses were studied in electroencephalographic (EEG) data acquired during a commonly employed conventional auditory oddball paradigm. The research consisted of two sets of experiments. In the first set of experiments, data from 100 normal subjects, consisting of 10 males and 10 females in each age decade from 20 to 70, was examined. These experiments were designed to characterize the gamma synchonizations that occurred in response to target and background stimuli and their functional significance in normal brain activity, and to exclude the possibility of these findings being due to electromyogram (EMG) or volume conduction artifact. The examination of functional significance involved the development of an additional new analysis technique. In the second set of experiments, data acquired from 35 patients with schizophrenia and 35 matched normal controls was analyzed. The purpose of these experiments was to determine whether patients showed disturbances of gamma synchrony compared to controls, and to establish the relationship of any such disturbances to medication levels, symptom profiles, duration of illness, and a range of psychophysiological variables. Results: In the 100 normals, responses to target stimuli were characterized by two bursts of synchronous gamma oscillations, an early (evoked) and a late (induced) synchronization, with different topographic distributions. Only the early gamma synchronization was seen in response to background stimuli. The main variable modulating the magnitude of these gamma synchronizations from epoch to epoch was pre-stimulus EEG theta (3-7 Hz) and delta (1-3 Hz) power. Early and late gamma synchrony were also associated with N1 and P3 ERP component amplitude across epochs. Across subjects, the early gamma synchronization was associated with shorter latency of the ERP components P2, N2 and P3, smaller amplitude of N1 and P2, and smaller pre-stimulus beta power. The control analyses showed that these gamma responses were specific to a narrow frequency range (37 to 41 Hz), and were not present in adjacent frequency bands. The responses were not generated by EMG contamination or volume conduction. In the 35 patients with schizophrenia, significant abnormalities of both the early and late synchronizations were observed compared to the 35 normal controls, with distinctive topographic characteristics. In general, early gamma synchrony was increased in patients compared to controls, and late gamma synchrony was decreased. These gamma synchrony disturbances were not related to medication level or the four summed symptom profile scores (positive, negative, general and total). They were, however, associated with duration of illness, becoming less severe the longer the patient had suffered from the disorder. The disordered gamma synchrony in patients was not secondary to abnormalities in other psychophysiological variables, but appeared to represent a primary disturbance. Discussion: The early synchronization may relate to the binding of object representations in early sensory processing, or, given that a constant inter-stimulus interval was employed, may be anticipatory and related to active memory. The late response is probably involved in binding in relation to activation of the internal contextual model involved in late expectancy/contextual processing (context updating or context closure) for target stimuli. The across epochs effects may relate to whether the focus of attention immediately prior to stimulus presentation is internal or is directed at the task. The across subjects effects suggest that a larger magnitude of the early gamma synchronization might indicate that the subject maintains a more stable and less ambiguous internal representation of the environment, that reduces the complexity of input and facilitates target/background discrimination and subsequent processing. The early gamma synchronization findings in patients with schizophrenia suggest that anticipatory processing involving active memory and forward-prediction of the environment is subject to over-binding or the formation of inappropriate associations. The late synchronization disturbances may reflect a fragmentation of contextual processing, and an inability to maintain contextual models of the environment intact over time. Conclusion: This research demonstrates the potential importance of integrative network activity as indexed by gamma phase synchrony in relation to normal cognition, and the possible broad relevance of such activity in psychiatric disorders. In particular, the application in this study to patients with schizophrenia showed that an impairment of brain integrative activity (missing links) might be a key feature of this illness.

Thesis (Ph. D.)--Ohio State University, 2008. / Title from first page of PDF file. Includes bibliographical references (p. 219-230).

Thesis (Ph. D.)--Duke University, 2008. / Includes bibliographical references.

<p>I Sverige insjuknar ca 30 000 personer årligen i stroke. Stroke är den vanligaste orsaken till neurologiska funktionshinder, som ofta innebär ett stort lidande för individen. I nuläget finns endast lite forskning kring de faktorer som påverkar <em>känslan av sammanhang </em>hos individer som genomlidit en stroke. Syftet med studien var att utifrån självbiografier ta reda på vad som bidrar till individens ökade känsla av sammanhang. Studien utgick från en kvalitativ ansats baserat på fyra självbiografier. Utifrån analysen uppstod fyra teman och tolv kategorier baserat på individernas viktigaste upplevelser av vad som bidrog till ökad <em>känsla av sammanhang</em>. Resultatet presenterades med hjälp av citat från självbiografierna. Det som bidrog till ökad känsla av sammanhang och som framkom i resultatet var <em>Möjlighet till stöd</em>, där stödet från närstående, vänner, sjukvårdspersonal och inte minst logoped var mycket betydelsefullt. Att <em>komma framåt, vardagslivet</em> och <em>livet efter stroke</em>, tar upp vikten av att finna mening och nya utmaningar och mål i livet. Det är viktigt för sjuksköterskan att förstå att stroke är en individuell sjukdom och att alla individer finner olika sätt till att anpassa sig till sin nya livssituation. Detta för att kunna anpassa omvårdnaden till varje enskild individ.</p> / <p> </p><p>Each year, about 30 000 people in Sweden suffer a stroke. It is the most common cause to neurological dysfunction and implicates much suffering for the individual. Few studies have been made about the factors that could conduce to the individuals’ sense of coherence. The aim of this study was to, based on autobiographies, find out which factors there are that contribute to the individuals sense of coherence. The study was based on a qualitative approach. The result was presented in four themes and twelve categories that arouse when reading the materials. Each team and category where described with the help of quotations from the autobiographies. The most important things for the individuals’ sense of coherence were; Possibility for <em>support</em>, the support from friends, relatives, healthcare stuff and speech therapist meant a lot for the individuals’ wellbeing. To <em>head forward</em>, <em>everyday life, Life after stroke</em> and finding new meaning where other factors that turned out to have a great value for the individuals. It’s important that the nurse understands the individuality of stroke and that each individual finds his or her own way to adapt the new life situation, this because the nurse has to adjust the care that is given.</p>

Optical Coherence Tomography (OCT) is a catheter‐based imaging method that employs near‐infrared light to produce high‐resolution cross sectional intravascular images. Α new segmentation technique is implemented for automatic lumen area extraction and stent strut detection in intravascular OCT images for the purpose of quantitative analysis of neointimal hyperplasia (NIH). Also a graphical user interface (GUI) is designed based on the employed algorithm. Methods: Four clinical dataset of frequency‐domain OCT scans of the human femoral artery were analysed. First, a segmentation method based on Fuzzy C Means (FCM) clustering and Wavelet Transform (WT) was applied towards inner luminal contour extraction. Subsequently, stent strut positions were detected by utilizing metrics derived from the local maxima of the wavelet transform into the FCM membership function. Results: The inner lumen contour and the position of stent strut were extracted with very high accuracy. Compared with manual segmentation by an expert physician, the automatic segmentation had an average overlap value of 0.917 ± 0.065 for all OCT images included in the study. Also the proposed method and all automatic segmentation algorithms utilised in this thesis such as k‐means, FCM, MRF – ICM and MRF – Metropolis were compared by means of mean distance difference in mm and processing time in sec with the physician’s manual assessments.. The strut detection procedure successfully identified 9.57 ± 0.5 struts for each OCT image. Conclusions: A new fast and robust automatic segmentation technique combining FCM and WT for lumen border extraction and strut detection in intravascular OCT images was designed and implemented. The proposed algorithm may be employed for automated quantitative morphological analysis of in‐stent neointimal hyperplasia. / Η τομογραφία οπτικής συνοχής (OCT) είναι μια απεικονιστική μέθοδος βασισμένη στον καθετηριασμό και χρησιμοποίει υπέρυθρο φως για να παράγει ένδo‐αγγειακές εικόνες – εγκάρσιας τομής με υψηλή ανάλυση. Σε αυτήν την διατριβή, μια νέα τεχνική τμηματοποίησης υλοποιήθηκε για την αυτόματη εξαγωγή της περιοχής του αυλού καθώς και για την ανίχνευση των «strut» στις ένδo‐ αγγειακές OCT εικόνες με σκοπό την ποσοτική ανάλυση της υπερπλασίας. Επίσης ένα εύκολο στην χρήση περιβάλλον γραφικών για καθημερινή κλινική χρήση σχεδιάστηκε με τον υλοποιημένο αλγόριθμο. Μέθοδοι: Τέσσερις OCT κλινικές εξετάσεις πεδίου‐συχνότητας της ανθρώπινης μηριαίας αρτηρίας αναλύθηκαν. H προτεινόμενη μέθοδος τμηματοποίησης για την εξαγωγή του εσωτερικού περιγράμματος αυλού, είναι βασισμένη στον Fuzzy CMeans (FCM) clustering και τον μετασχηματισμό κυματιδίου. Στη συνέχεια, οι θέσεις των «strut» εντοπίστηκαν χρησιμοποιώντας διάφορες τοπικές παραμέτρους που προέρχονται από τα τοπικά μέγιστα του μετασχηματισμού κυματιδίων εντός της FCM συνάρτησης. Αποτελέσματα: Το εσωτερικό περίγραμμα αυλού και η θέση των «strut» εξήχθηκαν με πολύ μεγάλη ακρίβεια. Σε σύγκριση με την ποσοτική αξιολόγηση από έναν ειδικό ιατρό, η αυτόματη τμηματοποίηση είχε μέση τιμή επικάλυψης 0,917±0,065 για όλες τις OCT εικόνες που περιλαμβάνονται στη μελέτη. Επίσης, έγινε σύγκριση με τους k‐means, FCM, ICM και Μetropolis αυτόματους αλγόριθμους τμηματοποίησης για εξαγωγή του εσωτερικού περιγράμματος αυλού και επέδειξε υψηλής ακρίβειας αποτελέσματα στον μικρότερο δυνατό χρόνο επεξεργασίας. Η διαδικασία ανίχνευσης «strut» προσδιόρισε επιτυχώς 9.57± 0,5 «strut» για κάθε OCT εικόνα. Συμπεράσματα: Μια νέα αποτελεσματική και γρήγορη αυτόματη τεχνική τμηματοποίησης που συνδυάζει FCM και WT για την εξαγωγή των ορίων του αυλού και την ανίχνευση των «strut» στις ένδο‐αγγειακές εικόνες OCT σχεδιάστηκε και υλοποιήθηκε. Ο προτεινόμενος αλγόριθμος μπορεί να χρησιμοποιηθεί για την αυτοματοποιημένη ποσοτική μορφολογική ανάλυση της υπερπλασίας.

<p>Beamforming of ultrasound signals in the presence of clutter, or partial aperture blockage by an acoustic obstacle can lead to reduced visibility of the structures of interest and diminished diagnostic value of the resulting image. We propose new beamforming methods to recover the quality of ultrasound images under such challenging conditions. Of special interest are the signals from large apertures, which are more susceptible to partial blockage, and from commercial matrix arrays that suffer from low sensitivity due to inherent design/hardware limitations. A coherence-based beamforming method designed for suppressing the in vivo clutter, namely Short-lag Spatial Coherence (SLSC) Imaging, is first implemented on a 1-D array to enhance visualization of liver vasculature in 17 human subjects. The SLSC images show statistically significant improvements in vessel contrast and contrast-to-noise ratio over the matched B-mode images. The concept of SLSC imaging is then extended to matrix arrays, and the first in vivo demonstration of volumetric SLSC imaging on a clinical ultrasound system is presented. The effective suppression of clutter via volumetric SLSC imaging indicates it could potentially compensate for the low sensitivity associated with most commercial matrix arrays. The rest of the dissertation assesses image degradation due to elements blocked by ribs in a transthoracic scan. A method to detect the blocked elements is demonstrated using simulated, ex vivo, and in vivo data from the fully-sampled 2-D apertures. The results show that turning off the blocked elements both reduces the near-field clutter and improves visibility of anechoic/hypoechoic targets. Most importantly, the ex vivo data from large synthetic apertures indicates that the adaptive weighing of the non-blocked elements can recover the loss of focus quality due to periodic rib structure, allowing large apertures to realize their full resolution potential in transthoracic ultrasound.</p> / Dissertation

Esta dissertação parte do pressuposto de que os operadores argumentativos e os conectivos, que, aqui, chamamos genericamente de operadores, estão correlacionados com a tessitura textual e pretende verificar se a freqüência relativa da ocorrência deles influi no grau de coesão e coerência que se atribui ao texto no momento da sua leitura. O substrato de trabalho é constituído por um conjunto de redações produzidas para as atividades propostas em diversas disciplinas que envolvem a prática de redação. As redações foram avaliadas por três professores de Língua Portuguesa de Ensino Médio e Ensino Superior de acordo com critérios em que o grau de coesão e coerência é o requisito mais relevante para averiguação. Procuramos, então, constatar a dependência entre a freqüência relativa de operadores e a nota fornecida pelos avaliadores. Os resultados sugerem a existência dessa dependência, mesmo quando os operadores selecionados não se apresentam corretamente empregados segundo as operações lógicas usuais previstas pela sintaxe. / This dissertation begins with connective and argumentative operators, called here, generally, as operators, which are related to textual texture and intends to check if the relative frequency of their occurrence influences on the degree of cohesion and coherence that attributes to the text at the moment of its reading. The substrate of the work is constituted by a group of compositions produced for the proposal activities in several subjects, which involves composition practice. Three Portuguese Language of High School and College teachers according to the criteria in which the degree of cohesion and coherence is the most important requisite for checking evaluated the compositions. We look for to verify the dependence between the relative frequency of operators and the grade attributed by the professors. The results suggest the existence of this dependence, even when the selected operators don´t present themselves correctly used according to the usual and normal operations required by syntax.