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Diffuse Optical Tomography is a diagnostic imaging modality where optical parameters such as absorption coefficient, scattering coefficient and refractive index distributions are recovered to form the internal tissue metabolic image. Near-infrared (NIR) light has the potential to be used as a noninvasive means of diagnostic imaging within the human breast. Due to the diffusive nature of light in tissue, computational model-based methods are required for functional imaging. The main goal is to recover the spatial variation of optical properties which shed light on the different metabolic states of tissue and tissue like media. This thesis addresses the issue of quantitative recovery of optical properties of tissue-mimicking phantom and pork tissue using diffuse optical tomography (DOT). The main contribution of the present work is the development of robust, efficient and fast optical property reconstruction algorithms for a direct 3-D DOT imaging system. There are both theoretical and experimental contributions towards the development of an imaging system and procedures to minimize accurate data collection time, overall system automation as well as development of computational algorithms. In nurturing the idea of imaging using NIR light into a fully developed direct 3-D imaging system, challenges from the theoretical and computational aspects have to be met. The recovery of the optical property distribution in the interior of the object from the often noisy boundary measurements on light, is an ill-posed ( and nonlinear) problem. This is particularly true, when one is interested in a direct 3-D image reconstruction instead of the often employed stacking of 2-D cross-sections obtained from solving a set of 2-D DOT problems. In order to render the DOT, a useful diagnostic imaging tool and a robust reconstruction procedure giving accurate and reliable parameter recovery in the scenario, where the number of unknowns far outnumbers the number of independent data sets that can be gathered (for example, the direct 3-D recovery mentioned earlier) is essential. Here, the inversion problem is often solved through iterative methods based on nonlinear optimization for the minimization of a data-model misfit function. An interesting development in this direction has been the development of Broyden’ s and adjoint Broyden’ s methods that avoids direct Jacobian computation in each iteration thereby making the full 3-D a reality. Conventional model based iterative image reconstruction (MoBIIR) algorithm uses Newton’ s and it’s variant methods, where it required repeated evaluation of whole Jacobian, which consumes bulk time in reconstruction process. The explicit secant and adjoint information based fast 2-D/3-D image reconstruction algorithms without repeated evaluation of the Jacobian is proposed in diffuse optical tomography, where the computational time has been decreased many folds by updating the Jacobian successively through low rank update. An alternative route to the iterative solution is attempted by introducing an artificial dynamics in the system and treating the steady-state response of the artificially evolving dynamical system as a solution. The objective is to consider a novel family of pseudo-dynamical 2-D and 3-D systems whose numerical integration in time provides an asymptotic solution to the inverse problem at hand. We convert Gauss-Newton’ s equation for updates into a pseudo-dynamical (PD) form by explicitly adding a time derivative term. As the pseudo-time integration schemes do not need such explicit matrix inversion and depending on the pseudo-time step size, provides for a layer of regularization that in turn helps in superior quality of 2-D and 3-D image reconstruction. A cost effective frequency domain Matlab based 2-D/3-D automated imaging system is designed and built. The complete instrumentation (including PC-based control software) has been developed using a single modulated laser source (wavelength 830nm) and a photo-multiplier tube (PMT). The source and detector fiber change their positions dynamically allowing us to gather data at multiple source and detector locations. The fiber positions are adjusted on the phantom surface automatically for scanning variable size phantoms. A heterodyning scheme was used for reading out the measurement using a lock-in-amplifier. The Matlab program carries out sequence of actions such as instrument control, data acquisition, data organization, data calibration and reconstruction of image. The Gauss-Newton’ s, Broyden’ s, adjoint Broyden’ s and pseudo-time integration algorithms are evaluated using the simulation data as well as data from the experimental DOT system. Validation of the system and the reconstruction algorithms were carried out on a real tissue, a pork tissue with an embedded fat inhomogeneity. The results were found to match the known parameters closely.

Measurement of tissue hemodynamics provides vital information for the assessment of tissue viability. This thesis reports three noninvasive near-infrared diffuse optical systems for spectroscopic measurements and tomographic imaging of tissue hemodynamics in vulnerable tissues with the goal of disease diagnosis and treatment monitoring. A hybrid near-infrared spectroscopy/diffuse correlation spectroscopy (NIRS/DCS) instrument with a contact fiber-optic probe was developed and utilized for simultaneous and continuous monitoring of blood flow (BF), blood oxygenation, and oxidative metabolism in exercising gastrocnemius. Results measured by the hybrid NIRS/DCS instrument in 37 subjects (mean age: 67 ± 6) indicated that vitamin D supplement plus aerobic training improved muscle metabolic function in older population. To reduce the interference and potential infection risk on vulnerable tissues caused by the contact measurement, a noncontact diffuse correlation spectroscopy/tomography (ncDCS/ncDCT) system was then developed. The ncDCS/ncDCT system employed optical lenses to project limited numbers of sources and detectors on the tissue surface. A motor-driven noncontact probe scanned over a region of interest to collect boundary data for three dimensional (3D) tomographic imaging of blood flow distribution. The ncDCS was tested for BF measurements in mastectomy skin flaps. Nineteen (19) patients underwent mastectomy and implant-based breast reconstruction were measured before and immediately after mastectomy. The BF index after mastectomy in each patient was normalized to its baseline value before surgery to get relative BF (rBF). Since rBF values in the patients with necrosis (n = 4) were significantly lower than those without necrosis (n = 15), rBF levels can be used to predict mastectomy skin flap necrosis. The ncDCT was tested for 3D imaging of BF distributions in chronic wounds of 5 patients. Spatial variations in BF contrasts over the wounded tissues were observed, indicating the capability of ncDCT in detecting tissue hemodynamic heterogeneities. To improve temporal/spatial resolution and avoid motion artifacts due to a long mechanical scanning of ncDCT, an electron-multiplying charge-coupled device based noncontact speckle contrast diffuse correlation tomography (scDCT) was developed. Validation of scDCT was done by imaging both high and low BF contrasts in tissue-like phantoms and human forearms. In a wound imaging study using scDCT, significant lower BF values were observed in the burned areas/volumes compared to surrounding normal tissues in two patients with burn. One limitation in this study was the potential influence of other unknown tissue optical properties such as tissue absorption coefficient (µa) on BF measurements. A new algorithm was then developed to extract both µa and BF using light intensities and speckle contrasts measured by scDCT at multiple source-detector distances. The new algorithm was validated using tissue-like liquid phantoms with varied values of µa and BF index. In-vivo validation and application of the innovative scDCT technique with the new algorithm is the subject of future work.

<p>The optical properties of biological tissue provide quantitative information about the physiological structure and chemical composition of a tissue sample. The investigation of tissue optical properties through Diffuse Reflectance Spectroscopy (DRS) is a rapid, non-invasive technique with extensive applications in healthcare diagnostics and therapeutics. Breast conservation surgery, a clinical practice performed for nearly 15,000 patients annually, requires accurate diagnosis of the tissue margin, the healthy layer of tissue surrounding the excised tumor. This margin assessment has traditionally been performed via post-operative pathology through one of multiple time-intensive processes that are performed after the surgery is completed. However, the margin assessment can also be rapidly performed by DRS, leading towards pathological evaluations concurrent with the excision surgery. </p><p>Presently, DRS probe designs are limited to laboratory settings. They include illumination and collection optical fibers, spectrometers, and CCD detectors, which all add to the complexity, cost, and size of a diagnostic system. Recently, DRS probes have been designed with Silicon photodetectors (Si PDs), including detector arrays that enable simultaneous DRS imaging of multiple tissue sites. The Si PDs reduce probe system complexity by replacing the cumbersome fiber-based collection probes and CCD detectors. </p><p>However, these monolithic Si PD probes are rigid and flat. When imaging non-planar tissue samples, a rigid probe may experience reduced accuracy from uneven tissue pressure and loss of contact with the tissue surface. A physically flexible DRS probe can improve sensing accuracy by conforming to a tissue surface with arbitrary curvature.</p><p>This thesis presents the design, fabrication, and test of flexible DRS Si PD probes constructed with thin film single crystalline silicon heterogeneously bonded to a flexible polymer substrate. The PDs have dark currents and responsivities comparable to high performance standard thickness Si PDs. The responsivity and zero bias dark current of the flexible PDs were evaluated while flat and while curved up to a 10 mm radius of curvature, with measured variations in responsivity (±0.61%) and dark current (±3 pA).</p><p>The flexible DRS probe was evaluated on benign and malignant breast tissue representative liquid phantoms. DRS measurements were performed with the flexible DRS probe on both liquid phantoms over a wavelength range of 470 – 600 nm at five radii of curvature: flat, 50 mm, 25 mm, 15 mm, and 10 mm. The optical contrast between the benign and malignant phantom DRS measurements ranged from 4.0-13.6% across all measured wavelengths for the flat test case and 5.9-15.5% while curved. For both phantoms at all wavelengths, the DRS signal increased in response to increasing curvature. The increase in reflectance signal ranged from 4.8-12.3% when the liquid phantom curvature was brought from flat to a 10 mm radius of curvature. The experimental results were then compared to theoretical reflectance values generated through a forward Monte Carlo model. The mean error between experiment and theory was 2.33% for the benign phantom and 1.23% for the malignant phantom. </p><p>Pixel-to-pixel crosstalk, the portion of diffusely reflected light that enters the tissue near one PD but is detected at a different PD, was also evaluated using the same test setup as for the DRS signal. The crosstalk signal also increases due to curvature, with an increase of 33.2-40.0% across all measured wavelengths for the benign phantom. The experimental crosstalk signal for the benign phantom was compared to a forward Monte Carlo model with mean error of 4.85%. The crosstalk could not be measured on the malignant phantom due to lower reflected light levels that were below the noise floor of the PD. </p><p>The flexible Si PD probe presented herein shows promising results for optical tissue analysis and feature extraction on both flat and curved tissue surfaces. This flexible probe technology facilitates conformal tissue DRS imaging, potentially in a clinical diagnostic device.</p> / Dissertation

Academic performance of first year university students in the international arena as well as locally, has been a point of concern for all stakeholders because of high dropout rates and failure. Although many explanations for this have been offered and accepted, all have located the problem external to the individual. This study examined the interplay between interpersonal and intrapersonal factors on academic performance of first year university students in South Africa. A sociocognitive perspective was employed by an investigation of student identity processing styles as a means to explain academic performance. A mixed sample of 419 first year psychology students at a South African university was randomly chosen. Berzonsky’s Identity Style Inventory (ISI3) was used to categorise students’ identity processing styles which was then correlated to students’ mid-year examination results. Although similar research was conducted overseas, the findings of the present study did not match previous results. Unlike any other known study the correlation between normative processing style and academic performance of first year university students was statistically significant but was negative. There was significant difference only between informational and normative identity processing styles on academic performance and between informational and diffuse-avoidant processing styles on academic performance. It was found in this study that culture and race played a role in student identity processing styles and in turn influenced student academic performance in the first year of university. A discussion of results, educational implications of findings, limitations of the study and recommendations for future research are included at the end of this study.

In recent years, different renewable energy sources have been on the rise. Among these, solar power has shown great potential in both small and big scale. Since solar irradiance is the main input for solar power systems, it is of great importance to examine how much of the solar irradiance actually reaches a certain location, and how much of the total solar irradiance consists of direct (beam), diffuse and reflected irradiance. This is usually done with expensive measurement meters, such as pyranometers and pyrheliometers. In this thesis, incident solar irradiance data from a cheap sensor network is analyzed, a new proposed model for estimating beam and diffuse fraction is examined and the results are compared to another estimation model, namely Erbs model. The comparison between the two models shows high correlation for beam irradiance, regardless of weather conditions, whereas the correlation for diffuse irradiance shows a highly varying result, much dependent on the weather conditions. It is difficult to motivate how well the proposed model is performing on a broader scale, since the study is limited to a specific area during a short period of time.

O trabalho foi desenvolvido para analisar a aplicabilidade do princípio da insignificância aos crimes que tutelam bens jurídicos difusos. O conceito de bem jurídico é o único elemento prévio à legislação com capacidade de limitar materialmente o poder punitivo estatal, sendo inaceitável o seu abandono, relativização ou flexibilização. O bem jurídico difuso é tutelado tendo em vista a proteção e o pleno desenvolvimento do ser humano, e suas características favorecem a tipificação de crimes de perigo abstrato e de crimes cumulativos, sendo inaceitáveis crimes de mera desobediência. O princípio da insignificância é uma ferramenta interpretativa do tipo penal e deve ser dividido em insignificância absoluta, hipótese em que a conduta sequer afeta o bem jurídico abstratamente considerado, apresentando uma ofensividade reduzidíssima e carecendo de tipicidade material; e insignificância relativa, hipótese em que se exclui a culpabilidade do agente no caso de ser diminuta a lesão ao bem jurídico individualizado e reduzidíssima a reprovabilidade do agente, devendo o fato ser considerado axiologicamente irrelevante, não havendo necessidade ou merecimento de pena. As lesões ao bem jurídico difuso atingem apenas indiretamente o indivíduo, ainda que socialmente tomado, e quando o reflexo da lesão ao bem jurídico difuso atingir o indivíduo (de hoje ou do futuro) de forma reduzida, deve ser ela considerada insignificante, sendo a insignificância relativa o instrumento mais compatível com a análise das condutas que se subsumem a crimes de perigo abstrato e a crimes cumulativos. / This work was developed to analyze the applicability of the insignificance principle to the crimes that protect the diffuse juridical chattels. The juridical chattel is the only element previews to the legislation capable of limiting the punishing power of the State, and it is unacceptable to abandon it, to relativize it or to loosen it. The diffuse juridical chattel is protected to preserve the human being and its full development, and its characteristics facilitate the creation of abstract danger crimes and cumulating crimes, but it is unacceptable crimes of mere disobedience. The insignificance principle is a interpretative tool for the criminal type and must be divided into absolute insignificance, which occurs when the action do not affect the juridical chattel abstractly considered, having a very reduced offensiveness, lacking of material typicality, and relative insignificance, which excludes the culpability when it entail a small damage to the juridical chattel individually taken, what makes this action axiologically irrelevant, and the punishment unnecessary and undeserved. The damages to the juridical chattel strike only indirectly the individual, even when socially taken, and when the reflex of the damage to the juridical chattel strikes the individual (of the present or of the future) in a reduced way, it must be considered insignificant, and the relative insignificance is the most compatible tool to analyze the insignificance of the action that may be considered an abstract danger crime or a cumulating crime.

Runoff from paved surfaces in the urban environment is recognised as a major contributing source to deteriorated water quality. In stormwater, both various metals and organic compounds can be present and the quality of stormwater is dependent on e.g. the characteristics of the surfaces that the runoff encounters. Diffuse pollution sources, i.e. anthropogenic emissions from e.g. traffic or constructions, has been pointed out by the European Water Framework Directive to significantly contribute to pollution of stormwater receivers. In order to create and obtain a sustainable, liveable and aesthetical urban environment it is critical to be able to mitigate stormwater pollution, not least considering the increasing amount of stormwater due to climate change.The aim of this master’s thesis was to evaluate the potential release of inorganic- and organic stormwater pollutants from conventional roofing materials by laboratory leaching experiments. The study was mainly aimed to serve as a first screening on the roofing materials, in order to be able to select a number of materials for further investigation later on. The organic compounds included in this study were polycyclic aromatic hydrocarbons, nonylphenols and -ethoxylates, phthalates and herbicides. Previous research on stormwater pollution has mainly focused on metals and there is therefore a knowledge gap on organic compounds in urban runoff. The leaching experiments were designed considering previous similar studies. Synthetic rainwater was prepared based on measurements of rainwater quality in Sweden. Duplicates of 16 commonly used roofing materials were prepared and immersed in beakers of synthetic rainwater. The beakers were agitated on an orbital shaking device for 24 hours and pH as well as conductivity was recorded in the leachates before sending the samples to the contracted laboratory for analysis. Metals were analysed on all materials and the organic compound analyses were performed on selected materials based on each material’s composition and was limited with the substance’s probability to release from each material.From the analysis results, mean values for the leached concentrations of all duplicates were calculated. The annual potential release of substances from materials was estimated based on the leached concentrations and data on the average annual precipitation in Sweden, in order to get an indication of the order of magnitude of the pollutant release. The results showed a potential release of a number of the included substances from many of the studied roofing materials, in varying order of magnitude. The shingle roofing was the material that showed the ability to release the largest number of pollutants. Some materials e.g. the clay tile also showed potential to adsorb substances on the material surface. Metals were mainly released in dissolved form from most materials. Phthalates were not present in concentrations above report limits in the leachates from any of the studied materials. The results also indicate a significant different in the release potential from materials that were considered similar in their composition and expected to have similar leaching behaviour prior to the laboratory experiments, e.g. two similar felt roof materials from different manufacturers. / <p>Validerat; 20150715 (global_studentproject_submitter)</p>

Heat dissipation is a critical bottleneck for microelectronic device performance and longevity. At micrometer and nanometer length scales heat carriers scatter at the boundaries of the material reducing its thermal conductivity. Additionally, thermal boundary conductance across dissimilar material interfaces becomes a dominant factor due to the increase in surface area relative to the volume of device layers. Therefore, techniques for monitoring spatially varying temperature profiles, and methods to improve thermal performance are critical to future device design and optimization. The first half of this thesis focused on frequency domain thermoreflectance (FDTR) to measure thermal transport in nanometer-thick polymer films and across an organic-inorganic interface. Hybrid structures of organic and inorganic materials are widely used in devices such as batteries, solar cells, transistors, and flexible electronics. The Langmuir-Blodgett (LB) technique was used to fabricate nanometer-thick polymer films ranging from 2 - 30 nm. FDTR was then used to experimentally determine the thermal boundary conductance between the polymer and solid substrates. The second half of the thesis focused on developing a fundamental understanding of thermal transport in wide-bandgap (WBG) materials, such as GaN, and ultrawide-bandgap (UWBG) materials, such as diamond, to improve thermal dissipation in power electronic devices. Improvements in WBG materials and device technologies have slowed as thermal properties limit their performance. UWBG materials can provide a dramatic leap in power electronics technologies while temporarily sidestepping the problems associated with their WBG cousins. However, for power electronic devices based on WBG- and UWBG-materials to reach their full potential the thermal dissipation issues in these hard-driven devices must be understood and solved. FDTR provides a comprehensive pathway towards fully understanding the physics governing phonon transport in WBG- and UWBG-based devices. By leveraging FDTR imaging and measuring samples as a function of temperature, defect concentration, and thickness, in conjunction with transport models, a well-founded understanding of the dominant thermal-carrier scattering mechanisms in these devices was achieved. With this knowledge we developed pathways for their mitigation.

<p>The flower is debatably the most complex of the plant organs, composed of far more tissues than any other plant organ system, and, as such, the molecular mechanisms that govern tissue specification and development have only just begun to be explored. One tissue that has seen little research is the stigma. The stigma is the apical-most part of the gynoecium and is designed to trap pollen grains on specialized cells called stigma papillae and provide the means for them to germinate. Using a forward genetic screen, many mutants which exhibit defects in stigma development were identified. The identification of the genes with the causative mutations will uncover new genes involved in stigma development which can be linked to previously discovered genes to build a more comprehensive gene regulatory network of stigma specification. Over the course of the screen, a new mutant, <i>lily</i>, was identified which has open buds throughout most of flower development. This valuable genetic tool allows microscopy and chemical applications at younger stages than emasculation allows. Here, <i>lily</i> was used to show the importance of reactive oxygen species in stigma specification and identity maintenance. In addition to specification, the morphological differentiation of stigma papillae was investigated. Using reverse and chemical genetics, live-imaging, and morphometrics, it was found that stigma papillae grow via an anisotropic diffuse growth mechanism. Collectively, these findings constitute a substantial breaking of ground for stigma research, providing a solid foundation for future investigation.</p>