<p>Asymmetric multiple quantum wells (AMQWs) can provide broad and flat gain spectra. Broadly tunable diode lasers can be realized with AMQW active regions and without the need for antireflection coatings on cleaved facets.</p> <p> This thesis reports the application of AMQW broadly tunable lasers with uncoated facets for Fourier domain and synthesized optical coherence tomography (OCT). A depth resolution of 13 μm in air was obtained with a test bed OCT system that used diffractive optical elements, short external cavities, and AMQW InGaAsP/InP broadly tunable lasers as the light sources for the Fourier domain and the synthesized OCT measurements. The centre wavelengths of the broadly tunable sources were 1550 nm and the tunable ranges were ≤ 117 nm.</p> <p>The features of broad and flat gain spectra of AMQWs also make AMQWs ideal candidates for broad spectral width superluminescent diodes (SLDs). 1300 nm AMQW InGaAsP/InP SLDs were designed and fabricated for application to time domain OCT. For the design of the active region, it was found by simulation of gain and the comparison of two growths that the transition carrier density (TCD) has to be reasonably high to achieve high power SLDs. A transfer matrix method was used to solve for the modes of planar optical waveguides with arbitrary layers and the thicknesses of these layers were optimized with a Marquardt nonlinear fitting method. With the optimization of the optical waveguide and with AMQWs with high TCDs, the output power of SLDs could reach 2 mW with > 90 nm spectral width. It is shown by time domain OCT measurements that the depth resolution of the OCT measurements could reach 7.85 μmin air with double section SLDs.</p> <p>Two dimensional OCT images of a glass cover slip were built with the imageSC function in Matlab™. Image enhancement with blind/not-blind deconvolution was performed based on the measured point spread function (PSF) of the OCT setup. A Richardson-Lucy algorithm was used as the blind deconvolution method and a not-blind version of a Jansson-Van Cittert method was used.</p> / Thesis / Doctor of Philosophy (PhD)

Vad gäller sambandet mellan KASAM och psykiskt välbefinnande tyder tidigare forskning på en starkt positiv korrelation. Forskning som bedrivits avseende den religiösa trons påverkan på det psykiska välbefinnandet har däremot konstaterat både positiva och negativa samband. Studiens frågeställningar ämnar bland annat att undersöka korrelationen mellan psykisk hälsa och KASAM, religiös tro samt bakgrundsvariablerna ålder, kön och födelseland. Urvalet bestod av 86 deltagare i Sverige och data samlades in via enkäter. En Pearson-korrelationsanalys kunde påvisa signifikanta positiva samband mellan KASAM och psykiskt välbefinnande samt mellan religiös tro och psykiskt välbefinnande. En hierarkisk regressionsanalys påvisade att variationen i psykisk hälsa till störst del kunde förklaras av KASAM, samt att en mindre procent kunde förklaras av bakgrundsvariablerna och religiös tro. Utifrån studiens resultat kan det sammanfattas att både KASAM och religiös tro är faktorer som har en effekt på den psykiska hälsan. Dessa kan hävdas agera likt ett skyddsnät gentemot psykisk ohälsa.

Trots att de väletablerade begreppen Mening i livet (MIL) och Känsla av sammanhang (KASAM) är snarlika saknas forskning kring sambanden sinsemellan. Studiens syfte var att explorativt undersöka dessa samband samt om de korrelerar olika till motivation och coping. I studien ingick 191 universitetsstudenter varav 116 kvinnor. Enkäten utgjordes av ett antal bakgrundsvariabler och 4 skalor. Analysen visade att hanterbarhet som enskild komponent hos KASAM korrelerade svagast med samtliga MIL-komponenter samt att MIL förklarade 45% av variationen i inre motivation jämfört med KASAM som förklarade 26%. Analysen visade även att MIL förklarade en större del av konstruktiva copingstrategier och KASAM en större del av destruktiva strategier där hanterbarhet var en central komponent. MIL ser ut att omfatta en bredare dimension av motivation och coping men saknar en del aspekter som komponenten hanterbarhet innefattar såsom resurser för att hantera livets utmaningar. Detta tyder på att skalorna till viss del har olika användningsområden.

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<p>It has been observed by researchers that periodic auditory stimuli can cause the activities in different brain areas to be periodically synchronized. Fast auditory stimuli have been shown to cause the brain sources to synchronize at the rate of stimuli. Brain sources respond to them not only by increase in local synchronization, but also in the global synchronization of cortical regions often regarded as functional connectivity. Spectral power and coherence are often used to characterize such neural synchronization. Beta band oscillations have been reported to underlie the neural mechanism during repetitive auditory stimuli. Cortical generators of these underlying beta oscillations were investigated in several studies based on MEG measurements. This research is intended to investigate (1) EEG can be used to detect and localize neural sources changing in power and coherence and (2) beta oscillations underlie such neural synchronization during fast repetitive auditory stimuli based on EEG measurements. The procedure of this study consists of several steps. First, the minimum variance (MV) scalar beamformer, an adaptive spatial filter, is used to estimate the temporal signals in the brain source space, given EEG recordings. The analysis of the estimated source temporal signals then consists of two stages firstly the power analysis and secondly the coherence analysis. The dynamics of power and coherence is investigated instantaneously over time and in the lower beta frequency band [14,20Hz]. This is done by detecting the most prominent changes in the two spectral parameters through singular value decomposition (SVD). Two coherence measures imaginary component (IC) and magnitude-squared coherence (MSC) are employed and compared in terms of their performance both mathematically and experimentally. In the simulations, we show the capability of using EEG to detect and localize power co-variations and dynamic functional connectivity in the cortical regions. We also perform the procedure on the recorded real data from subjects passively listening to rhythmic auditory stimuli. Beta oscillations are found to underlie the neural activity to percept auditory stimuli. This is shown by localization of auditory cortices and detection of power co-variation in this frequency band. We demonstrate the feasibility of using EEG to identify coupled and co-activated brain sources similar to those obtained from MEG signals in the previous studies. These include auditory and motor regions which were found to be functionally coherent and have a functional role in the auditory perception. The superiority of IC over MSC measure is proven mathematically and validated in both simulations and real data experiments.</p> / Master of Applied Science (MASc)