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1
Daivasagaya, Daisy. "CMOS contact and phase imaging of biochemical sensor microarray." Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=117067.
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In this Thesis, we present two systems for gaseous oxygen (O2) sensing. First, we describe a compact luminescent sensor microsystem that is based on the direct integration of sensor elements with a polymeric optical filter and placed on a low power Complementary Metal-Oxide Semiconductor (CMOS) imager Integrated Circuit (IC). The second system is a hand-held scale phase fluorometric system. This system is based on a new single-chip integrated circuit that can perform the activities of sinusoidal signal generation using Direct Digital Synthesis and phase angle extraction of the detection luminescence signal from the sensor films using Discrete Fourier Transform. For O2 sensing, the sensors operate on the measurement of excited-state emission intensity of O2-sensitive luminophores tris(4,7-diphenyl-1,10- phenanthroline) ruthenium(II) ([Ru(dpp)3]2+) encapsulated in sol-gel derived xerogel thin-films. For the compact luminescent sensor microsystem, we incorporate a polymeric optical filter that is made with polydimethylsiloxane (PDMS) that is mixed with color die Sudan-II. The surface of the PDMS filter is molded to incorporate arrays of pyramidal microstructures that serve to focus the optical sensor signals on to the photodetectors. The xerogel sensor arrays are contact printed on top of the PDMS pyramidal lens-like microstructures. The CMOS imager uses a 32x32 (1024 elements) array of active pixel sensors and each pixel includes a high-gain phototransistor to convert the detected optical signals into electrical currents. Correlated double sampling circuit, pixel address, digital control and signal integration circuits are also implemented on-chip. The CMOS imager data is read out as a serial coded signal. The developed CMOS sensor microsystems provide a useful platform for the development of miniaturized, analytically reliable, and accurate optical chemical gaseous and aqueous sensors.Dans cette thèse, nous présentons deux systèmes pour détecter l'oxygène gazeux (O2). Tout d'abord, nous décrivons un microsystème compact à senseur luminescent qui est basée sur l'intégration directe d'éléments de senseur avec un filtre optique polymère qui est placé sur un imageur circuits intégrés (CI) à faible énergie de type Complementary metal oxide semi-conductor (CMOS). Le second système est un système portatif qui permet de détecter la différence de phase fluorométrique. Ce système est basé sur un circuit intégré à puce unique qui permet de générer des signaux sinusoïdal en utilisant la synthèse directe de signaux digitaux et l'extraction de l'angle de phase du signal luminescent, provenant des films du senseur, en utilisant des transformées de Fourier discrète sur ce signal. Pour la détection du dioxygène, les senseurs mesure l'intensité d'émission des luminophores tris (4,7-diphényl-1, 10 - phénanthroline) ruthénium (II) ([Ru(dpp)3]2+) à l'état excité encapsulés dans des sol-gel provenant de micro film xérogel. Le microsystème compact à senseur luminescent comprend un filtre optique polymère à base de polydiméthylsiloxane (PDMS), qui est mélangée avec le colorant Soudan-II. La surface du filtre PDMS est moulée pour ainsi incorporer les réseaux de microstructures pyramidales qui servent à concentrer les signaux des senseurs optiques sur les photodétecteurs. Les réseaux de senseur à base de xérogel sont imprimés par contact sur le dessus des microstructures PDMS pyramidales qui agissant comme des lentilles. L'imageur CMOS utilise une matrice de 32x32 (1024 éléments) servant de pixels actifs et chaque un de ces pixels comporte un phototransistor à gain élevé pour convertir les signaux détectés optiques en courants électriques. La corrélation de circuit d'échantillonnage double, l'adresse de pixel, et les circuits de commande numérique d'intégration de signaux sont également résolue par la puce. Les données sont lues par l'imageur en tant que signaux codé en série. Les capteurs CMOS fournissent une plateforme utile pour le développement des systèmes miniaturisés pour l'analyse fiable et précis des composantes chimiques gazeuse et aqueuse par des moyens optiques.
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Ji, Honghao. "Integrated CMOS optical sensors for fluorescence detection and contact imaging." College Park, Md. : University of Maryland, 2006. http://hdl.handle.net/1903/3890.
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Thesis (Ph. D.) -- University of Maryland, College Park, 2006.Thesis research directed by: Electrical Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Simon, Kim. "Otherwise than seeing, negotiating distance and contact for an ethical imaging." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/MQ28661.pdf.
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Gan, Tat Hean. "New approaches to ultrasonic imaging using air-coupled and contact techniques." Thesis, University of Warwick, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.273503.
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Galan, Cherrez Andres Moroni. "Design and Evaluation of a CMOS Contact-Imaging System for Microfluidics." BYU ScholarsArchive, 2017. https://scholarsarchive.byu.edu/etd/7219.
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A CMOS contact-imaging system for microfluidics is presented. The microsystem integrates a five-layer PDMS microfluidic network and a CMOS image sensor fabricated in a standard 0.18 µm technology. The CMOS image sensor consists of two 10×1-pixel array, an amplifier, and a control logic. The imager is able to achieve a low dark signal of 1.67 mV/s, a maximum integration time of 514 s, and a high dynamic range of 75.2 dB at 1 s integration time. The microfluidic device integrates several actuated valve to achieve a fully automated lab-on-a-chip. This work also presents a quantitative comparison of the photomultiplier tube (PMT) and the CMOS contact-imaging system. The CMOS-microfluidic device is validated using an on-chip chemiluminescent analyte.
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Weisenfeld, Neil Ira 1969. "A non-contact, active stereo imaging system for intraoperative surface measurements." Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/87276.
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Petrack, Alec M. "Single-Pixel Camera Based Spatial Frequency Domain Imaging for Non-Contact Tissue Characterization." Wright State University / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=wright1596066982589817.
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Al-Khalidi, Farah Qais. "Development and evaluation of thermal imaging techniques for non-contact respiration monitoring." Thesis, Sheffield Hallam University, 2011. http://shura.shu.ac.uk/20616/.
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Respiration rate is one of the main indicators of an individual's health and therefore it requires accurate quantification. Its value can be used to predict life threatening conditions such as the child death syndrome and heart attacks. The current respiration rate monitoring methods are contact based, i.e. a sensing device needs to be attached to the person's body. Physically constraining infants and young children by a sensing device can be stressful to the individuals which in turn affects their respiration rate. Therefore, measuring respiration rate in a non-contact manner (i.e. without attaching the sensing device to the subject) has distinct benefits. Currently there is not any non-contact respiration rate monitoring available for use in medical field. The aim of this study was to investigate thermal imaging as a means for non-contact respiration rate monitoring. Thermal imaging is safe and easy to deploy. Twenty children were enrolled for the study at Sheffield Children Hospital; the children were from 6 month to 17 years old. They slept comfortably in a bed during the recordings. A high resolution high sensitivity (0.08 degree Kelvin) thermal camera (Flir A40) was used for the recordings. The image capture rate was 50 frames per second and its recording duration per subject was two minutes (i.e. 6000 image frames)A median digital lowpass filter was used to remove unwanted frequency spectrum of the images. An important issue was to localize and track the area centered on the tip of the nose (i.e. respiration region of interest, ROI). A number of approaches were developed for this purpose. The most effective approach was to identify use the warmest facial point (i.e. the point where the bridge of the nose meets the corner of one of the eyes). A novel method to analyse the selected ROI was devised. This involved segmenting the ROI into eight equal segments centred on the tip of nose. A respiration signal was produced for each segment across the 6000 recorded images from each subject. The study demonstrated that the process of dividing the ROI into eight segments improves determination of respiration rate. The respiration signals were processed both in the time and frequency domains to determine respiration rates for the 20 subjects included in the study. The respiration values obtained from the two domains were close. During each recording respiration rate was monitored using conventional contact methods (e.g. nostril thermistor, abdomen and chest movement sensor etc). There was a close correlation (correlation value 0.99) between respiration values obtained by thermal imaging and those obtained using conventional contact method. The novel aspects of the study relate to the development of techniques that facilitated thermal imaging as an effective non-contact respiration rate monitoring in both normal and patient subject groups.
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Wu, Wan-Chen (Wan-Chen Shane) 1974. "Tactile sensing of shape : biomechanics of contact investigated using imaging and modeling." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/35623.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2006.Includes bibliographical references (leaves 123-131).
The overall goal of this research effort is to improve the understanding of the biomechanics of skin as it pertains to human tactile sense. During touch, mechanoreceptors beneath the skin surface are mechanically loaded due to physical contact of the skin with an object and respond with a series of neural impulses. This neural population response is decoded by the central nervous system to result in tactile perception of properties such as the shape, surface texture and softness of the object. The particular approach taken in this research is to develop a realistic model of the human fingertip based on empirical measurements of in vivo geometric and material properties of skin layers, so that the mechanical response of the fingertip skin to different shapes of objects in contact can be investigated, to help identify the relevant mechanism that triggers the mechanoreceptors in tactile encoding of object shape. To obtain geometric data on the ridged skin surface and the layers underneath together with their deformation patterns, optical coherence tomography (OCT) was used to image human fingertips in vivo, free of load as well as when loaded with rigid indenters of different shapes.
(cont.) The images of undeformed and deformed finger pads were obtained, processed, and used for biomechanically validating the fingertip model. To obtain material properties of skin layers, axial strain imaging using high frequency ultrasound backscatter microscopy (UBM) was utilized in experiments on human fingertips in vivo to estimate the ratio of stiffnesses of the epidermis and dermis. By utilizing the data from OCT and UBM experiments, a multilayered three dimensional finite element model of the human fingertip composed of the ridged fingerpad skin surface as well as the papillary interface between the epidermis and dermis was developed. The model was used to simulate static indentation of the fingertip by rigid objects of different shapes and to compute stress and strain measures, such as strain energy density (SED), and maximum compressive or tensile strain (MCS, MTS), which have been previously proposed as the relevant stimuli that trigger mechanoreceptor response.
(cont.) The results showed that the intricate geometry of skin layers and inhomogeneous material properties around the locations of the SA-I and RA mechanoreceptors caused significant differences in the spatial distribution of candidate relevant stimuli, compared with other locations at the same depths or the predictions from previous homogeneous models of the fingertip. The distribution of the SED at the locations of SA-I mechanoreceptors and the distribution of MCS/MTS at the locations of RA mechanoreceptors under indentation of different object shapes were obtained to serve as predictions to be tested in future biomechanical and neurophysiological experiments.
by Wan-Chen Wu.
Ph.D.
10
Hall, Lee. "Use of imaging technology to better understand soft contact lens fit dynamics." Thesis, Aston University, 2014. http://publications.aston.ac.uk/24468/.
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The principal theme of this thesis is the identification of additional factors affecting, and consequently to better allow, the prediction of soft contact lens fit. Various models have been put forward in an attempt to predict the parameters that influence soft contact lens fit dynamics; however, the factors that influence variation in soft lens fit are still not fully understood. The investigations in this body of work involved the use of a variety of different imaging techniques to both quantify the anterior ocular topography and assess lens fit. The use of Anterior-Segment Optical Coherence Tomography (AS-OCT) allowed for a more complete characterisation of the cornea and corneoscleral profile (CSP) than either conventional keratometry or videokeratoscopy alone, and for the collection of normative data relating to the CSP for a substantial sample size. The scleral face was identified as being rotationally asymmetric, the mean corneoscleral junction (CSJ) angle being sharpest nasally and becoming progressively flatter at the temporal, inferior and superior limbal junctions. Additionally, 77% of all CSJ angles were within ±50 of 1800, demonstrating an almost tangential extension of the cornea to form the paralimbal sclera. Use of AS-OCT allowed for a more robust determination of corneal diameter than that of white-to-white (WTW) measurement, which is highly variable and dependent on changes in peripheral corneal transparency. Significant differences in ocular topography were found between different ethnicities and sexes, most notably for corneal diameter and corneal sagittal height variables. Lens tightness was found to be significantly correlated with the difference between horizontal CSJ angles (r =+0.40, P =0.0086). Modelling of the CSP data gained allowed for prediction of up to 24% of the variance in contact lens fit; however, it was likely that stronger associations and an increase in the modelled prediction of variance in fit may have occurred had an objective method of lens fit assessment have been made. A subsequent investigation to determine the validity and repeatability of objective contact lens fit assessment using digital video capture showed no significant benefit over subjective evaluation. The technique, however, was employed in the ensuing investigation to show significant changes in lens fit between 8 hours (the longest duration of wear previously examined) and 16 hours, demonstrating that wearing time is an additional factor driving lens fit dynamics. The modelling of data from enhanced videokeratoscopy composite maps alone allowed for up to 77% of the variance in soft contact lens fit, and up to almost 90% to be predicted when used in conjunction with OCT. The investigations provided further insight into the ocular topography and factors affecting soft contact lens fit.
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Fincke, Jonathan Randall. "Non-contact quantitative imaging of limbs, bone and tissue, using ultrasound tomographic techniques." Thesis, Massachusetts Institute of Technology, 2018. http://hdl.handle.net/1721.1/119342.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2018.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 123-131).
Non-contact and quantitative ultrasound images of bone and soft tissue are produced from original algorithms applied to observational data sets collected on two custom built ultrasound imaging systems for limb imaging. The images are quantitative in that the distribution of sound speeds and dimensionally accurate geometry of tissue structures are reconstructed. The first imaging system is based on laser generation and detection of ultrasound (LUS) and the second is a water immersion ultrasound tomography (UST) system. The LUS and UST systems and algorithms, in aggregate, can be used to generate large volume, quantitative 2D and traditional 2D ultrasound images. Existing medical ultrasound systems are unable to acquire or generate large volume, quantitative and clinically useful bone images. A medical ultrasound system with these capabilities would have significant clinical value. LUS and UST systems could improve the quality, cost and safety of osteoporosis diagnosis and tracking, prosthetic fitting, bone fracture detection and tracking, intraoperative imaging and volumetric imaging in intensive care units. The algorithms and systems established for this thesis contribute broadly to non-contact ultrasound imaging: LUS for medical imaging, and UST for bone and soft tissue imaging and quantification. Non-contact techniques are clinically valuable because they can deliver operator independent image quality and large volume imagery without making contact with the body and distorting the tissue. Quantitative ultrasound imaging techniques are clinically useful because they provide intrinsic information about tissue mechanical properties, such as stiffness and density. Successful bone and soft tissue quantification using UST techniques could yield an entirely new and radiation free means of assessing bone and soft tissue strength and health. The experiments completed with the LUS system demonstrate its capability to generate images without contacting or treating the skin surface. Further, soft tissue (weak reflector), as well as bone (strong reflectors) are resolved at skin safe optical exposures. To enhance the LUS system performance, the optical wavelength of the generation laser is studied and optimized to deliver the largest acoustic source possible while also meeting optical exposure thresholds for skin. Additionally, commercially available laser vibrometer technology optimized for detecting vibrations on rough surfaces, such as skin, is identified and tested. Three original algorithms yield images of bone and soft tissue geometry and sound speed when applied to experimental data from the UST device. The first algorithm is a backscatter/reflection adaptive imaging technique that enables high resolution, SNR and volumetric imagery of bone and soft tissue to be formed from a single, mechanically scanned ultrasound transducer. The second algorithm uses a travel-time sound speed inversion technique that estimates water, soft tissue and bone sound speed to within 10% of ground truth estimates. The performance of this algorithm is validated on multiple samples and a simulated data set. The third algorithm is a full waveform inversion (FWI) algorithm regularized with the level set technique to enable quantification of bone properties. This algorithm is validated on an animal tissue sample and simulated data sets. The FWI technique resolves the soft tissue spatial sound speed distribution with half to one-quarter wavelength (1 - 0.5 mm) resolution and average sound speed values are within 10% of ground truth measurements.
by Jonathan Randall Fincke.
Ph. D.
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de, León Izeppi Edgar. "Non-contact Methods for Detecting Hot-mix Asphalt Nonuniformity." Diss., Virginia Tech, 2006. http://hdl.handle.net/10919/29206.
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Segregation, or non-uniformity, in Hot Mix Asphalt (HMA) induces accelerated pavement distress(es) that can reduce a pavement's service life up to 50%. Quality Assurance procedures should detect and quantify the presence of this problem in newly constructed pavements. Current practices are usually based on visual inspections that identify non-uniform surface texture areas. An automatic process that reduces subjectivity would improve the quality-assurance procedures of HMA pavements.
Virginia has undertaken a focused research effort to improve the uniformity of hot-mix asphalt (HMA) pavements. A method using a dynamic (laser-based) surface macrotexture instrument showed great promise, but it revealed that it may actually miss significant segregated areas because they only measure very thin longitudinal lines. The main objective of this research is to develop a non-contact system for the detection of segregated HMA areas and for the identification of the locations of these areas along a road for HMA quality assurance purposes.
The developed system uses relatively low cost components and innovative image processing and analysis software. It computes the gray level co-occurrence matrix (GLCM) of images of newly constructed pavements to find various parameters that are commonly used in visual texture analysis. Using principal component analysis to integrate multivariable data into a single classifier, Hotelling's T2 statistic, the system then creates a list of the location of possible nonuniformities that require closer inspection.
Field evaluations of the system at the Virginia Smart Road proved that it is capable of discriminating between different pavement surfaces. Verification of the system was conducted through a series of field tests to evaluate the uniformity of newly constructed pavements. A total of 18 continuous road segments of recently paved roads were tested and analyzed with the system. Tables and plots to be used by inspection personnel in the field were developed. The results of these field tests confirmed the capability of the system to detect potential nonuniformities of recently completed pavements. The system proved its potential as a useful tool in the final inspection process.Ph. D.
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Asogan, Dhinesh. "A non-contact laser ablation cell for mass spectrometry." Thesis, Loughborough University, 2011. https://dspace.lboro.ac.uk/2134/11014.
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A common analytical problem in applying LA sampling concerns dealing with large planar samples, e.g. gel plates, Si wafers, tissue sections or geological samples. As the current state of the art stands, there are two solutions to this problem: either sub-sample the substrate or build a custom cell. Both have their inherent drawbacks. With sub-sampling, the main issue is to ensure that a representative is sample taken to correctly determine the analytes of interest. Constructing custom cells can be time consuming, even for research groups that are experienced or skilled, as they have to be validated before data can be published. There are various published designs and ideas that attempt to deal with the issue of large samples, all of which ultimately enclose the sample in a box. The work presented in this thesis shows a viable alternative to enclosed sampling chambers. The non-contact cell is an open cell that uses novel gas dynamics to remove the necessity for an enclosed box and, therefore, enables samples of any arbitrary size to be sampled. The upper size limit of a sample is set by the travel of the XY stages on the laser ablation system, not the dimensions of the ablation cell.
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Chihara, Hideo. "In vivo detection of atherosclerotic plaque using non-contact and label-free near-infrared hyperspectral imaging." Kyoto University, 2016. http://hdl.handle.net/2433/217737.
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Ausdenmoore, Benjamin D. "Synaptic contact localization in three dimensional space using a Center Distance Algorithm." Wright State University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=wright1320866829.
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Sorgato, Casares Verónica. "Novel multi-spectral imaging technique for the spatial quantification of optical properties." Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066284/document.
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La nouvelle technique 'Dual-Step' d'Imagerie Multispectrale qui a été développée a comme objectif de contribuer au diagnostic clinique des lésions superficielles, en procurant des cartes grand champ quantitatives des propriétés optiques endogènes telles que l'absorption et la diffusion. L'approche repose sur la combinaison d'une technique sans-contact de Spectroscopie de Réflectance Diffuse spatialement résolue (DRSsr) pour estimer la diffusion utilisée ensuite par une autre technique d'Imagerie Multispectrale (MSI) pour estimer l'absorption. Les bancs d'essai de chaque technique ont \'et\'e construits et caractérisés dans le cadre de ce travail. La quantification optimale des propriétés optiques s'appuie sur un nouvel algorithme de calibration ('ACA-Pro' ) qui atteint des erreurs d'estimation minimales et inférieures à 3.3% pour la diffusion et 5.3% pour l'absorption. La technique 'Dual-Step' a été validée sur des fantômes d'intralipide mais aussi sur des échantillons ex-vivo de peau humaine et des modèles in-vivo d'inflammation de peau de rats. Les résultats montrent la faisabilité de la technique 'Dual-Step' et son potentiel en diagnostic clinique grâce à son approche quantitative, grand champ et non-invasiveThe Novel 'Dual-Step' Multispectral Imaging Technique that has been developed intends to contribute to the clinical diagnosis of superficial lesions by providing non-invasively quantitative spatial wide field maps of absorption and scattering endogenous optical properties. The approach relies on the combination of a Non-Contact Spatially-resolved Diffuse Reflectance Spectroscopy (DRSsr) technique with a Multispectral Imaging (MSI) technique. Absolute quantification is based on the scattering estimation with Non-Contact DRSsr which is subsequently used by MSI to estimate wide field absorption. The instrumental setups of each technique are built and thoroughly characterized in this work. The optimal quantification of optical properties relies on a newly established calibration algorithm 'ACA-Pro' that achieves minimal estimation errors inferior to 3.3% for scattering and 5.3% for absorption. The developed 'Dual-Step' technique has been validated not only with an extensive intralipid phantom study but also with ex-vivo biological human skin samples and in-vivo inflammation skin models on rats. The results show the potential of the 'Dual-Step' technique as a valid quantitative, wide-field, and non-invasive clinical diagnosis approach
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Osman, Oglou Okan [Verfasser]. "First contact imaging of nanoparticular siRNA – From synthesis to application of a prodye concept / Okan Osman Oglou." Mainz : Universitätsbibliothek Mainz, 2015. http://d-nb.info/1073654451/34.
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Bousmat, Jonas. "Expériences et modèles du frottement élastomère sur chaussée en roulement/glissement." Thesis, Lyon, 2018. http://www.theses.fr/2018LYSEC011.
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Les enjeux de consommation d'énergie et de sécurité ont fait du frottement entre les pneumatiques et la chaussée une propriété importante lors de la conception de nouveaux pneumatiques. Pour mesurer ces efforts de frottement deux cinématiques sont couramment utilisées : la mise en glissement et le roulement/glissement. Les lois de frottement issues des expériences de mise en glissement sont assez bien interprétées. En revanche, le lien qui existe entre ces lois de frottement et le comportement en roulement/glissement est encore mal compris. En particulier, les modèles de roulement/glissement n'incorporent pas la transition entre frottement statique et frottement dynamique, bien que cette phénoménologie soit bien établie expérimentalement. Dans cette thèse, nous proposons différents modèles de frottement en roulement/glissement qui étendent ceux de la littérature en intégrant explicitement la transition de frottement statique/dynamique. Pour tester ces modéles dans le cas du contact pneu/chaussée, nous avons réalisé des expériences selon les deux cinématiques, sur un contact simplifié élastomère/chaussée. A partir des expériences de mise en glissement, les paramètres de la loi de frottement sont identifiés, en fonction de la force normale appliquée, de la vitesse de glissement et de la nature de la chaussée. Ces résultats sont implémentés dans nos modèles, pour produire des prédictions en roulement/glissement, qui sont finalement comparées avec les mesures obtenues en roulement/glissement. De plus, certaines hypothèses des modèles ont été testées par des expériences de visualisation in situ du contact. En particulier nous confirmons, sur une interface élastomère/verre, la présence simultanée d'une zone collée et d'une zone en glissement en conditions de roulement/glissementFor safety and energy consumption issues, tyre friction has become an important property when designing tyres. There are two main kinematic conditions which are commonly used to measure friction forces : the onset of sliding and the rolling/sliding. The friction laws which are extracted from the onset of sliding experiments are rather well interpreted. In contrast, the link between those frictions laws and the rolling/sliding behaviour remains incompletely understood. In particular, the rolling/sliding models do not take into account the transition between static friction and dynamic friction, although it is a well-established phenomenology. In this manuscript, we propose diérent models of friction in rolling/sliding, which extend those of the literature by explicitly integrating a static/dynamic friction transition. To test these models in the case of a tyre/road contact, we performed experiment in the two kinematic conditions, on a simpliéd elastomer/road contact. From the onset of sliding experiments, we identify the parameters of the friction law as functions of the applied normal force, the sliding speed and the type of road. These results are used as inputs in our models to predict the rolling/sliding behaviour, and are eventually compared with the corresponding experiments. In addition, we have tested several assumptions made in the models by performing in situ contact imaging experiments. In particular we con_rm, on an elastomer/glass interface, the simultaneous presence of a sticking and a slipping zone in rolling/sliding conditions
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Du, Lucy W. "Design of a constraint device for compliant bodies using quasi-conformal contact surfaces as applied to mouse imaging." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/104291.
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Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2016.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 99-101).
The purpose of this work is the modeling and prototyping of quasi-conformal constraint contacts and the investigation of their positioning ability for compliant bodies, specifically for the holding of mice in optical imaging setups. The direct application of this work is the restraint of laboratory mice for biological imaging of micron- and submicron-scale biological structures. No existing research has measured the shear stiffness of mouse facial tissue or modeled the effect of quasi-conformal contact constraints on nonlinear materials. The constraint devices and techniques currently available for mice have limitations that have prevented further exploration of their biological structures. The theoretical model, design rationale, and testing results of a prototype device utilizing quasi-conformal constraints are presented in this thesis. This device is capable of restraining anesthetized mice to sub-micron movement in all axes of translation, without additional surgery or discomfort to the mouse. With the findings presented in this thesis, the design of further optimized devices can be made-both for anesthetized and awake mice-enabling further studies in bone marrow and neural activity that are currently impossible. This could ultimately lead to breakthroughs in stem cell and neurobiological research.
by Lucy W. Du.
S.M.
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Fournstedt, Daniel. "Jämförelse mellan Scheimpflug imaging och anterior segment OCT i mätning av Corneal tjocklek." Thesis, Linnéuniversitetet, Institutionen för medicin och optometri (MEO), 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-44694.
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Purpose: The purpose of this study was to compare corneal thickness measured both centrally and midperipherally, between two instruments using different measuring principles. The study also looked at correlation between corneal thickness and intraocular pressure (IOP). Methods: Central and midperipheral corneal thickness was measured on the right eyes of 31 subjects with two different instruments. Instruments were Scheimpflug-camera from Bon Sirius and an AS/OCT from Optos. Measurements were taken on central cornea (CCT) and midperipheral (nasal (NCT), temporal (TCT), superior (SCT) and inferior (ICT)) at a distance of 1.75 mm from the apex. Mean age of the subjects was 23.6 ± 4.5 years. (19-44 years). A CT-80A non-contact tonometer (NonCT) from Topcon was used to measure the intraocular pressure (IOP). Results: A mean-value for central corneal thickness was calculated to 542.4 µm and 540.4 µm for Bon Sirius and AS/OCT repectively. Remaining measured points had mean-values for corneal thickness of, NCT: 577.7 µm & 558.5 µm. TCT: 555.0 µm & 545.2 µm. SCT: 585.7 µm & 554.5 µm. ICT: 563.0 µm & 548.9 µm, respectively. Mean-difference for CCT was 2.4 µm and it showed a significant difference between the two instruments with a p-value of 0.007. Remaining measured points all showed a significant difference of p<0.05. NCT: 19.2 µm. TCT: 9.8 µm. SCT: 31 µm. ICT: 14 µm. A correlation between IOP and CCT measured in both Sirius and AS/OCT was positive with r = 0.7 and p<0.05. Conclusion: The results showed that Sirius gives higher values for corneal thickness then ASOCT in all five measurement points. The results show that these instruments can be used interchangeably when measuring central corneal thickness. However, caution should be used when measuring midperipheral corneal thickness as the there is a significant differences between these two instruments.
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Sahli, Riad. "Mise en glissement des interfaces multicontacts élastomères : étude expérimentale par visualisation in situ." Thesis, Lyon, 2017. http://www.theses.fr/2017LYSEC012/document.
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La mise en glissement d’une interface de contact est un phénomène dont la dynamique spatiotemporelle est encore mal comprise. Dans cette thèse, nous avons développé et mis en oeuvre un dispositif expérimental original permettant de visualiser in situ les phénomènes locaux en jeu lors de la mise en glissement d’interfaces rugueuses élastomères, avec une bonne résolution temporelle. Nous avons mis en évidence une forte réduction de l’aire de contact réelle au sein d’une interface de contact sous cisaillement, et ce bien avant le début du glissement macroscopique. Cette réduction influence la valeur de la force de frottement statique de l’interface. Nous avons montré que le paramètre qui quantifie l’amplitude de la réduction vérifie une loi d’échelle valable largement, allant des monocontacts millimétriques jusqu’aux jonctions micrométriques impliquées dans les interfaces rugueuses. Nous avons ensuite montré que la contrainte de cisaillement critique de mise en glissement d’une interface n’est pas une constante pour un couple de matériaux en contact. En effet, en changeant systématiquement l’épaisseur d’un revêtement élastique sur l’un des corps en contact, on peut varier cette contrainte d’un facteur trois. Cet effet est interprété semi-quantitativement via un modèle couplant dissipation à l’interface et dans le volume des matériaux. Nous avons enfin montré que la dynamique spatio-temporelle de mise en glissement est influencée par le couple appliqué à l’interface par la force de frottement, lorsque celle-ci n’est pas exercée dans le plan de l’interface. En particulier, via une mesure du champ de déplacement par corrélation d’images, nous avons réalisé la première comparaison quantitative avec un modèle récent décrivant cet effet de coupleThe onset of sliding of a contact interface is a phenomenon the space-time dynamics of which are still poorly understood. In this thesis, we have developed and implemented an original experimental device allowing us to visualize in situ the local phenomena involved during the onset of sliding of rough elastomer interfaces, with a good temporal resolution. We have shown a strong reduction of the real contact area within a sheared contact interface, well before the beginning of macroscopic sliding. This reduction affects the value of the static friction force of the interface. We have shown that the parameter that quantifies the amplitude of the reduction obeys a well-defined scaling law ranging from millimetric mono-contacts to the micrometric junctions involved in rough interfaces. We have then shown that the shear strength of an interface is not a constant for a couple of materials in contact. Indeed, by systematically changing the thickness of an elastic coating on one of the bodies in contact, we could vary the value of the shear strength by a factor three. This effect is interpreted semi-quantitatively via a model incorporating dissipation both at the interface and in the bulk of the materials. We have finally shown that the space-time dynamics of the onset of sliding is influenced by the torque applied to the interface by the friction force, when the latter is not exerted in the plane of the interface. In particular, via a digital image correlation-based measurement, we performed the first quantitative comparison with a recent model describing this torque effect
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Ramamoorthy, Padmapriya. "HIGH MOLECULAR WEIGHT TEAR PROTEINS AND OCULAR SURFACE MUCINS IN CONTACT LENS-RELATED DRY EYE." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1316523981.
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Kiehl, Zachary Adam. "Measuring Pulse Rate Variability During Motion Artifact with a Non-Contact, Multi-Imager Photoplethysmography System." Wright State University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=wright1430403954.
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Nicodeme, Claire. "Evaluation de l'adhérence au contact roue-rail par analyse d'images spectrales." Thesis, Paris Sciences et Lettres (ComUE), 2018. http://www.theses.fr/2018PSLEM024/document.
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L’avantage du train depuis sa création est sa faible résistance à l’avancement du fait du contact fer-fer de la roue sur le rail conduisant à une adhérence réduite. Cependant cette adhérence faible est aussi un inconvénient majeur : étant dépendante des conditions environnementales, elle est facilement altérée lors d’une pollution du rail (végétaux, corps gras, eau, etc.). Aujourd’hui, les mesures prises face à des situations d'adhérence dégradée impactent directement les performances du système et conduisent notamment à une perte de capacité de transport. L’objectif du projet est d’utiliser les nouvelles technologies d’imagerie spectrale pour identifier sur les rails les zones à adhérence réduite et leur cause afin d’alerter et d’adapter rapidement les comportements. La stratégie d’étude a pris en compte les trois points suivants : • Le système de détection, installé à bord de trains commerciaux, doit être indépendant du train. • La détection et l’identification ne doivent pas interagir avec la pollution pour ne pas rendre la mesure obsolète. Pour ce faire le principe d’un Contrôle Non Destructif est retenu. • La technologie d’imagerie spectrale permet de travailler à la fois dans le domaine spatial (mesure de distance, détection d’objet) et dans le domaine fréquentiel (détection et reconnaissance de matériaux par analyse de signatures spectrales). Dans le temps imparti des trois ans de thèse, nous nous sommes focalisés sur la validation du concept par des études et analyses en laboratoire, réalisables dans les locaux de SNCF Ingénierie & Projets. Les étapes clés ont été la réalisation d’un banc d’évaluation et le choix du système de vision, la création d'une bibliothèque de signatures spectrales de référence et le développement d'algorithmes classification supervisées et non supervisées des pixels. Ces travaux ont été valorisés par le dépôt d'un brevet et la publication d'articles dans des conférences IEEEThe advantage of the train since its creation is in its low resistance to the motion, due to the contact iron-iron of the wheel on the rail leading to low adherence. However this low adherence is also a major drawback : being dependent on the environmental conditions, it is easily deteriorated when the rail is polluted (vegetation, grease, water, etc). Nowadays, strategies to face a deteriorated adherence impact the performance of the system and lead to a loss of transport capacity. The objective of the project is to use a new spectral imaging technology to identify on the rails areas with reduced adherence and their cause in order to quickly alert and adapt the train's behaviour. The study’s strategy took into account the three following points : -The detection system, installed on board of commercial trains, must be independent of the train. - The detection and identification process should not interact with pollution in order to keep the measurements unbiased. To do so, we chose a Non Destructive Control method. - Spectral imaging technology makes it possible to work with both spatial information (distance’s measurement, target detection) and spectral information (material detection and recognition by analysis of spectral signatures). In the assigned time, we focused on the validation of the concept by studies and analyses in laboratory, workable in the office at SNCF Ingénierie & Projets. The key steps were the creation of the concept's evaluation bench and the choice of a Vision system, the creation of a library containing reference spectral signatures and the development of supervised and unsupervised pixels classification. A patent describing the method and process has been filed and published
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Woollett, Katherine. "Multiple sports concussion in male rugby players : a neurocognitive and neuroimaging study." Thesis, University of Exeter, 2017. http://hdl.handle.net/10871/30302.
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Objective: Following a sport related concussion (SRC) visible symptoms generally dissipate in 7-10 days post-injury. However, little is known about the cumulative effects of SRCs both in terms of structural damage to the white matter of the brain and neurocognitive performance. To address this issue, the relationship between the number of SRCs (frequency), axonal white matter (WM) damage and neurocognitive performance was examined. There were three predictions. First, increases in SRC frequency will be associated with decreases in performance on neurocognitive tests. Second, the frequency of SRC will be associated with axonal injury measured three WM tracts: the corpus callosum, the fronto-occipital fasciculus and the inferior longitudinal fasciculus. Third, less accurate and slower performance on a response inhibition task (STOP-IT) will be associated with greater axonal injury. Methods: A cross-sectional correlational design was utilised. Participants were rugby players with a history of SRC, rugby players with no history of SRC and control athletes (N=40) who completed a neurocognitive test battery and had a DTI brain scan. The neurocognitive battery consisted of the following standardised tests: Speed and Capacity of Language Processing Test, CogState Electronic Battery, Stroop Colour and Word Test, Controlled Oral Word Association Test, the Trail Making Test and the experimental test STOP-IT Electronic Test. White matter axonal injury was measured by DTI using fractional anisotropy (FA) and mean diffusivity (MD) metrics. The DTI data was processed using FSL to extract FA and MD DTI metrics in three a-priori regions of interest. Results: Spearman’s correlation analyses did not find significant associations between SRC frequency and neurocognitive performance on the FAS (rs=0.053, 95% CI [-0.27, 0.36]), TMT-A (rs=0.058, 95% CI [-0.26, 0.37]), TMT-B (rs= -0.046, 95% CI [-0.27, 0.36]) and the Stroop Interference (rs= -0.25, 95% CI [-0.07, 0.52]). Similarly, no significant Spearman’s correlations were found between SRC frequency and the computerised neurocognitive tests STOP-IT-SSRT (rs= -0.04, 95% CI [-0.28, 0.35])), STOP-IT–Accuracy (rs= -0.05, 95% CI [-0.27, 0.36]), CogState Detection subtest (rs= -0.15, 95% CI [-0.17, 0.44]), CogState Identification subtest (rs= -0.065, 95% CI [-0.26, 0.37]), CogState One card learning subtest (rs= 0.24, 95% CI [-0.08, 0.52]) or the CogState One back task subtest (rs= 0.06, 95% CI [-0.26, 0.37]). In terms of the DTI data there were no significant associations between SRC frequency and axonal injury measured by FA values in the CC (rs= 0.005, 95% CI [-0.31, 0.32]), ILF (rs= 0.028, 95% CI [-0.29, 0.34]) or FOF (rs= -0.022, 95% CI [-0.30, 0.33]). The same was pattern was found for MD values in the CC (rs= 0.081, 95% CI [-0.24, 0.39]), ILF (rs= -0.16, 95% CI [-0.16, 0.45]) or FOF (rs= -0.15, 95% CI [-0.17, 0.44]) Finally, there were no significant Spearman’s correlations between axonal injury FA values and the STOP-IT SSRT in any of the ROIs: CC (rs= 0.005, 95% CI [-0.31, 0.32]), ILF (rs= 0.028, 95% CI [-0.29, 0.34]) or FOF (rs= -0.022, 95% CI [-0.30, 0.33]). Equally, there were no significant correlations between MD values STOP-IT SSRT in the CC (rs= -0.028, 95% CI [-0.29, 0.34]), ILF (rs= -0.16, 95% CI [-0.16, 0.45]) or FOF (rs= -0.15, 95% CI [-0.17, 0.44]). Likewise, there were no significant Spearman’s correlations between accuracy on the STOP-IT and FA values and in any of the ROIs: CC (rs= 0.19, 95% CI [-0.13, 0.48]), ILF (rs= -0.045, 95% CI [-0.27, 0.35]) and FOF (rs= -0.032, 95% CI [-0.29, 0.34]), or MD values in the CC (rs= -0.11, 95% CI [-0.21, 0.41]), ILF (rs= 0.017, 95% CI [-0.30, 0.33]) or FOF (rs= 0.082, 95% CI [-0.24, 0.39]). This study did not find support for the hypothesis that cumulative SRCs are associated with poorer performance on neurocognitive tests or with axonal injury as measured by FA and MD DTI metrics. Conclusion: The null findings suggest that there are no cumulative effects of SRCs. The current findings are inconsistent with previous cross-sectional research that indicates that there are long-term changes to diffusivity measures present after single SRCs as well as cumulative effects in contact sport athletes. Likewise they are at odds with evidence suggesting that after three SRCs neurocognitive performance can be affected. The study needs to be extended to include a larger sample to ensure the results are not due to low statistical power.
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Abd, El Kader Magdy Ezzat. "Application of Hot-Melt Ink Jet Processes for Imaging at Offset Printing Form Cylinder." Doctoral thesis, Universitätsbibliothek Chemnitz, 2004. http://nbn-resolving.de/urn:nbn:de:swb:ch1-200400092.
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The present work related to apply hot-melt ink-jet process for imaging at offset lithographic printing form, to utilise a reusable surface for many times and particularly related to validating thermal and ultrasonic erasing processes. This dissertation investigated systematically the role of certain factors towards affecting erasing image area process on print surfaces. Thermal erasing process approved to melt and suck the image area from the surface, the results were adopted by using contact angle measurements and scanning electron microscope. Ultrasonic erasing process permitted to solve the image area by choosing erasing chemistries, influence of selected erasing chemistries on printing surface, and evaluation the process, the results were tested by UV/Vis spectrometer, contact angle, profileometery and visual microscopeDer Fortschritt im Bereich von Charakterisierung und Verständnis für Hot-melt Ink Jet Prozesse zur Bebilderung von Offsetdruckform-Zylindern ist ein Ergebnis dieser Forschung. Die Systematik dieser Arbeit basiert auf einem theoretischen Teil, um einen geeigneten Löschprozess auszuwählen. Der Löschprozess hängt von den Eigenschaften des Hot-melt Ink Jet Materials und der genutzten Aluminiumdruckoberfläche ab. Diese werden systematisch im Labormaßstab experimentell untersucht. Der thermische Prozess wurde einerseits durch Benetzbarkeitsprüfungen und anderseites durch Rasterelektronmikroskopaufnahmen bewertet.Der Ultraschallprozess ist ein nasser Löschprozess. Die Untersuchungen wurden in vier Stufen systematisch durchgeführt - Auswahl vom geeigneten Lösungsmitteln - Einflüsse von ausgewählten Lösungsmitteln auf nicht beschichtete und beschichtete Aluminium platten - Evaluation eines Ultraschalllöschprozesses - Validation eines Löschprozesses; zur Bewertung des Löschprozesses wurden mehrere Druckplattenproben bebildert und gelöscht Die Ergebnisse wurden durch UV/Vis Spektrometer, Kontaktwinkel, Profiliometrie und Visuelle Mikroskopie getestet
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Liu, Taoming. "A MAGNETICALLY-ACTUATED ROBOTIC CATHETER FOR ATRIAL FIBRILLATION ABLATION UNDER REAL-TIME MAGNETIC RESONANCE IMAGING GUIDANCE." Case Western Reserve University School of Graduate Studies / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=case1484654444253783.
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Silva, Emerson Rodrigo da. "Estudo das propriedades do biospeckle e suas aplicações." Universidade de São Paulo, 2007. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-02102007-104941/.
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Esta dissertação é dedicada ao estudo de algumas das propriedades e aplicações do speckle dinâmico no monitoramento de atividade em tecidos biológicos. As estatísticas espaço-temporais de primeira e segunda ordem são discutidas em vias gerais. As principais técnicas para obtenção de dados a partir do granulado óptico são apresentadas, com especial destaque para a função de autocorrelação, as matrizes de co-ocorrência, o método de Fujii e a Análise de Contraste do Laser Speckle (LASCA). Uma nova metodologia de análise, baseada no estudo do contraste das correlações sucessivas, é proposta. Diversas simulações numéricas, utilizando diferentes funções densidade de probabilidade para as velocidades dos centros espalhadores, foram realizadas com intuito de testar os métodos de análise e fornecer subsídios para a interpretação de resultados in vivo. Tecidos vegetais e animais foram investigados, realizando-se o monitoramento do processo de senescência e mapas de vascularização em folhas, acompanhamento de frutos contaminados por fungos, mapeamento de atividade em flores e análise de cicatrização em ratos submetidos à cirurgia abdominal. Ensaios explorando o uso do biospeckle em microscopia são implementados. Por fim, é avaliado o potencial da técnica como ferramenta de diagnóstico em um caso de úlcera venosa crônica submetida a tratamento por meio de laserterapia de baixa intensidade. Os resultados encontrados revelaram o grande potencial em aplicações biológicas, através da construção de mapas que permitiram, por exemplo, a visualização detalhada da rede vascular de folhas vegetais. Também foi possível a identificação de áreas atacadas por micro organismos. Os estudos em tecidos animais e humanos apontaram perspectivas bastante promissoras do uso do biospeckle em ambiente clínico.This master thesis is devoted to the study of some properties and applications of dynamic speckles on monitoring of activity in biological tissues. The first and second order space-time statistics are dicussed in an overview perspective. The main techniques used to obtain information from grainy pattern are presented, with special prominence to autocorrelation function, co-occurrence matrices, Fujii's method and the Laser Speckle Contrast Analisys (LASCA). A new methodology, based on the study of the contrast of sucessive correlations, is proposed. Several numerical simulations, using different probability density functions to velocities of scatterers, are done in order to test the analysis methods and supply subsidies for interpretation of in vivo results. Vegetable and animal tissues are investigated by monitoring of senescence process and construction of vascularization maps of leaves, accompanying of fungi contamined fruits, mapping of activity in flowers and analysis of healing in rats undergone to abdominal surgery. Experiments using the biospeckle phenomenon in microscopy are carried out. At last, it is evaluated the potentiality of the technique as diagnosis tool in a chronic vein ulcer undergone to treatment through low intensity laser therapy. The found results showed the great potential in biological applications, through the construction of maps that maked possible, for example, the detailed visualization of the vascular net on leaves. It was allowed the identification of areas injured by micro organisms. The studies on animal and human tissues pointed very promising perspectives of the use of biospeckle in clinical environment.
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Petitdidier, Nils. "Système d'imagerie pour la caractérisation en couches de la peau par réflectance diffuse." Thesis, Strasbourg, 2018. http://www.theses.fr/2018STRAD048/document.
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Les travaux effectués au cours de cette thèse concernent le développement d’un instrument à faible coût et porté sur la personne permettant le suivi quantitatif des paramètres physiologiques de la peau in vivo et de manière non invasive. L’instrument est fondé sur la technique de Spectroscopie de Réflectance Diffuse résolue spatialement (srDRS). Cette technique fournit une quantification absolue des propriétés optiques endogènes d’absorption et de diffusion du tissu sondé et possède un potentiel pour la caractérisation de ces propriétés en couches de la peau.Afin de maximiser ce potentiel, notre approche repose sur l’utilisation d’un capteur matriciel placé en contact avec le tissu et permettant l’imagerie de réflectance diffuse à haute résolution spatiale. Les travaux présentés ici comprennent la spécification et la validation d’une architecture innovante permettant la mise en œuvre de l’approche proposée, l’implémentation d’un système porté sur la personne et bas coût basé sur cette architecture et l’évaluation des performances de ce système au travers d’expérimentations à la fois sur fantômes de peau et in vivo. Les résultats obtenus valident le potentiel de l’instrument développé pour le suivi quantitatif et non-invasif des propriétés de la peau. L’approche proposée est prometteuse pour l’analyse de milieux en couches tels que la peau et ouvre la voie au développement d’une nouvelle génération d’instruments portés sur la personne et bas coûts pour le suivi en continu des propriétés optiques des tissusThis work presents the development of a low-cost, wearable instrument for quantitative monitoring of skin physiological parameters toward non-invasive diagnostics in vivo. The instrument is based on the spatially resolved Diffuse Reflectance Spectroscopy (srDRS) technique, which provides absolute quantification of absorption and scattering endogenous properties of the probed tissue volume with a potential to discriminate between properties of individual skin layers. In the developed instrument, this potential is maximized by the use of a multi-pixel image sensor to perform contact, high resolution imaging of the diffuse reflectance. This study comprises the specification and validation of a novel srDRS system architecture based on the proposed approach, the implementation of this architecture into a low-cost, wearable device and the evaluation of the device performance both on tissue-simulating phantoms and in vivo. Results validate the potential of the instrument for the non-invasive, quantitative monitoring of tissue properties. The described approach is promising for addressing the analysis of layered tissue suchas skin and paves the way for the development of low-cost, wearable devices for continuous, passive monitoring of tissue optical properties
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Hamdan, Iyas. "Multimodal Image Registration in Image-Guided Prostate Brachytherapy." Thesis, Ecole nationale supérieure Mines-Télécom Atlantique Bretagne Pays de la Loire, 2017. http://www.theses.fr/2017IMTA0002/document.
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Le cancer de la prostate est le cancer le plus fréquent chez l'homme en France et aux pays occidentaux. Il est la troisième cause de décès liés au cancer, étant responsable d'environ 10% des morts. La curiethérapie, une technique de radiothérapie, est liée à une meilleure qualité de vie après le traitement, par rapport aux autres méthodes de traitement. La curiethérapie de la prostate consiste à insérer des sources radioactives dans la prostate afin de délivrer une dose d'irradiation localisée à la tumeur tout en protégeant les tissus sains environnants. L'imagerie multimodale est utilisée afin d'améliorer la précision du traitement. Les images Tomodensitométriques préopératoires, appelées Computed Tomography (CT), peuvent être utilisées pour calculer une distribution personnalisée et plus précise de dose. Pendant l'intervention, le chirurgien utilise un système de guidage temps-réel par l'Ultrason Transrectale, Transrectal Ultrasound (TRUS), pour placer correctement les sources radioactives dans leurs positions souhaitées. Par conséquent, si les positions des sources sont déterminées sur l'image CT, elles doivent être transférées à l'image US. Cependant, un recalage US/CT direct et robuste est difficilement envisageable parce que les tissus mous, telle que la prostate, offrent peu de contraste en CT et en US. En revanche, l'Imagerie par Résonance Magnétique (IRM) fournit un meilleur contraste et peut, potentiellement, améliorer le traitement en améliorant la visualisation. Donc, ces trois modalités (IRM, CT et US) doivent être correctement alignées. Pour compenser les déformations de la prostate, due au changement de taille et forme entre les différentes acquisitions, un recalage non-rigide est nécessaire. Une méthode de recalage entièrement automatique est nécessaire, afin de faciliter son intégration au bloc opératoire. Nous proposons dans un premier temps un recalage IRM/CT basé sur la maximisation de l'information mutuelle en combinaison avec un champ de déformation paramétré par B-Splines. Nous proposons de contraindre le recalage sur des volumes d'intérêt (VOIs) afin d'améliorer la robustesse et le temps de calcul. L'approche proposée a été validée sur des jeux de données cliniques. Une évaluation quantitative a montré que l'erreur de recalage est égale à 1.15±0.20 mm; qui répond à la précision clinique souhaitée. Ensuite, nous proposons un deuxième recalage US/IRM, où nous utilisons une approche multi-résolution pour éviter les minima locaux et améliorer le temps de calcul. Un critère de similarité, qui met en corrélation l'intensité de l'image US avec l'intensité ainsi que le gradient de l'image IRM, a été utilisé afin de trouver la transformation qui aligne les deux images. Cette méthode a été validée sur un fantôme de prostate dans un premier temps pour évaluer sa faisabilité. Ensuite, elle a été validée sur des jeux de données cliniques en utilisant des critères qualitatives et quantitatives. La distance Hausdorff a montré que l'erreur de recalage est égale à 1.44±0.06 mm. L'approche proposée dans ce travail permet d'aller vers un protocole de curiethérapie guidée par l'imagerie multimodale qui puisse améliorer la précision globale de cette procédure. Malgré ces résultats plutôt encourageants, les travaux futurs impliqueront une évaluation plus approfondie sur plus de jeux de données afin d'évaluer la fiabilité et l'efficacité de cette méthode avant de l'intégrer au bloc opératoireProstate cancer is the most common cancer in men in France and western countries. It is the third leading cause of death from cancer, being responsible for around 10% of deaths. Brachytherapy, a radiotherapy technique, is associated with a better health-related quality of life after the treatment, compared to other treatment techniques. Prostate brachytherapy involves the implantation of radioactive sources inside the prostate to deliver a localized radiation dose to the tumor while sparing the surrounding healthy tissues. Multi-modal imaging is used in order to improve the overall accuracy of the treatment. The pre-operative Computed Tomography (CT) images can be used to calculate a personalized and accurate dose distribution. During the intervention, the surgeon utilizes a real-time guiding system, Trasnrectal Ultrasound (TRUS), to accurately place the radioactive sources in their desired pre-planned positions. Therefore, if the positions of the sources were determined on CT, they need to be transferred to US. However, a robust and direct US/CT registration is hardly possible since they both provide low soft tissue contrast. Magnetic Resonance Imaging (MRI), on the other hand, has a superior contrast and can potentially improve the treatment planning and delivery by providing a better visualization. Thus, these three modalities (MRI, US and CT) need to be accurately registered. To compensate for prostate deformations, caused by changes in size and form between the different acquisitions, non-rigid registration is essential. Fully automatic registration methodology is necessary in order to facilitate its integration in a clinical workflow. At first, we propose a registration between pre-operative MR and CT images based on the maximization of the mutual information in combination with a deformation field parameterized by cubic B-Splines. We propose to constrain the registration to volumes of interest (VOIs) in order to improve the robustness and the computational efficiency. The proposed approach was validated on clinical patient datasets. Quantitative evaluation indicated that the overall registration error was of 1.15±0.20 mm; which satisfies the desired clinical accuracy. Then, we propose a second intra-operative US/MRI registration, where a multi-resolution approach is implemented to reduce the probability of local minima and improve the computational efficiency. A similarity measure, which correlates intensities of the US image with intensities and gradient magnitude of the MRI, is used to determine the transformation that aligns the two images. The proposed methodology was validated on a prostate phantom at first to assess its feasibility. Subsequently, the method was validated on clinical patient datasets and evaluated using qualitative and quantitative criteria, resulting in a registration error of 1.44±0.06 mm. The approach proposed in this work allows going towards a multimodal protocol for image-guided brachytherapy which can improve the overall accuracy of this procedure. Despite such encouraging results, future work will involve further evaluation on a larger number of datasets in order to assess the reliability and the efficiency of this methodology before integrating it in a clinical workflow
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Kumar, Charchit. "Quantitative and qualitative investigation of adhesion and friction on textured surfaces : inspiration from insect-plant interactions." Thesis, Strasbourg, 2019. http://www.theses.fr/2019STRAE008.
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L’adhérence et le frottement existent dans de nombreux systèmes techniques ainsi que dans les systèmes naturels. Ces deux phénomènes ont une influence importante sur la durabilité et l’efficacité des dispositifs techniques. Une approche reconnue pour ajuster précisément ces caractéristiques - outre le fait de modifier les propriétés physico-chimiques - est la texturation des surfaces en contact. Les surfaces de feuilles de plantes sont souvent décorées avec des morphologies de surface diverses, et présentent ainsi des fonctionnalités de surface remarquables. Cette thèse visait à réaliser une étude systématique de la mécanique de l’adhérence et du frottement sur des surfaces micro-structurées, répliquées à partir de surfaces de feuilles végétales, en contact avec une sonde qui s’inspire de l’organe adhérent d’un insecte. Les morphologies de surface de trois feuilles végétales différentes ont été directement transférées sur un polymère viscoélastique. Pour ce faire, trois approches différentes de reproduction ont fait l’objet d’une étude approfondie. La microscopie électronique à balayage et la microscopie confocale à balayage laser ont été utilisées pour l'évaluation qualitative et quantitative de la qualité de reproduction. Concernant l’étude de la mécanique du contact, un nano-indenteur a été modifié, permettant d’enregistrer les images in situ des contacts réels. Des tests de pull-off ont été menés afin d’évaluer quantitativement l’effet de la pré-charge sur la force d’adhésion et pour comprendre les modes distincts de collage/décollement. Des essais de frottement ont été effectués afin d’examiner l’effet de la charge normale et de la vitesse de glissement sur la force de frottement. Les résultats ont été discutés en fonction de la topographie de chaque surfaceAdhesion and friction exist in many technical systems as well as in natural ones. Both phenomena have a profound influence on the durability and efficiency of technical systems. A well-recognised way to tune these characteristics - besides altering the physicochemical properties - is the texturing of the interacting surfaces. Inspiringly, plant leaf surfaces are often decorated with diverse surface morphologies, and so show remarkable functionalities. This thesis aimed to perform a systematic investigation of adhesion and friction mechanics on micro-structured surfaces replicated from plant leaves, in contact with a probe, which was inspired from an insect’s adhesive pad. Surface morphologies of three different plant leaves were directly transferred onto a viscoelastic polymer. For this, three different replication approaches were comprehensively explored. Scanning electron microscopy and confocal laser scanning microscopy were used for the qualitative and quantitative evaluation of replication ability. For the contact mechanics investigation, a high-resolution nanoindenter was modified, with incorporating a unique feature to record the in-situ real-contact images. Pull-off tests were carried out to quantitatively evaluate the effect of pre-load on adhesion force characteristics and to understand distinct attachment-detachment modes. Friction investigations were performed to examine the effect of normal load and sliding speed on the friction force. Results were discussed with regard to each surface’s topography
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Ng, Victor. "Content enrichment for mobile context aware imaging applications with a social aspect." Thesis, McGill University, 2014. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=121246.
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With technological advancements in data collection techniques allowing increasing amounts of contextual metadata to be appended to everyday image files, it has become a daunting task to effectively display such supplemental data alongside original image content without overloading users with information. I propose a unique approach to actively display geo-tagged image content that embeds the images in a navigable 3D environment in a way that makes explicit the geographical context and spatiotemporal relationships between the images. This approach enhances the viewer's comprehension of the image's context and content thus supporting my hypothesis that context extracted from metadata can enhance image content absorption rather than hinder it. The 3D environment is built by mapping Google Street View images onto a spherical tessellation within which user image content is overlaid. The proposed geographical browser and social-networking system is implemented on an iPad, using the iPad's built-in compass, gyroscopes, and accelerometers to provide real-time gesture control and spatial orientation. User studies were performed on the proposed system as well as on a standard social-networking application for comparison purposes. The results were used to evaluate the relative performance of the system in enabling users to absorb and comprehend image information. Test subject were found to consistently answer questions more accurately on images viewed on the proposed system as compared to the images viewed on a typical social-networking application.Les avancées technologiques dans les techniques de collection de données augmentant la quantité de méta données contextuelles à associer aux images de tous les jours, afficher ces données supplémentaires de manière effective avec l'image originale est devenu une tâche ardue. Je propose une approche unique permettant d'afficher de manière active du contenu géo taggué qui renferme des images dans un environnement 3D navigable d'une manière qui rend explicite le contexte géographique et la relation spatiotemporelle entre les images. Cette approche augmente la compréhension du contexte et du contenu de l'image par l'observateur, supportant ainsi ma thèse selon laquelle le contexte extrait des métadonnées peut améliorer l'absorption du contenu de l'image plutôt que de le cacher. L'environnement 3D est construit en cartographiant des images de Google Street View dans une tessellation sphérique sur laquelle le contenu de l'image est superposé. Le navigateur géographique et outil de réseau social proposé est implémenté sur un iPad, utilisant la boussole intégrée à l'iPad, ses gyroscopes et accéléromètres pour fournir en temps-réel des contrôles par gestes et orientation spatiale. Des études utilisateurs ont été effectuées sur le système proposé, de même que sur une application de réseau social standard à fin de comparaisons. Les résultats ont été utilisés afin d'évaluer la performance relative du système à permettre aux utilisateurs d'absorber et comprendre l'information de l'image. Les sujets de test ont donné de manière consistante des réponses plus précise aux questions répondues sur des images observées sur le nouveau système comparé aux images observées sur une application typique de réseau social.
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Nouizi, Farouk. "Tomographie optique diffuse et de fluorescence préclinique : instrumentation sans contact, modélisation et reconstruction 3D résolue en temps." Phd thesis, Université Louis Pasteur - Strasbourg I, 2011. http://tel.archives-ouvertes.fr/tel-00658285.
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La Tomographie Optique Diffuse Résolue en Temps (TOD-RT) est une technique d'imagerie clinique et préclinique en pleine croissance. Elle fournit les cartes d'absorption et de diffusion optique des organes explorés, et les paramètres physiologiques associés. La Tomographie Optique Diffuse de Fluorescence Résolue en Temps (TODF-RT) est basée sur la détection de photons de fluorescence. Elle permet de déterminer les cartes de la concentration et du temps de vie de sondes fluorescentes et d'accéder à une imagerie métabolique et moléculaire très importante pour le diagnostic et le suivi thérapeutique, en particulier en cancérologie. L'objectif de cette thèse était de réaliser des images 3D de TOD/TODF-RT sur des rongeurs en utilisant une technologie optique résolue en temps, les acquisitions étant réalisées à l'aide de fibres optiques disposées autour de l'animal et sans contact avec sa surface. Le travail a été mené en quatre étapes : 1- mise en place d'un dispositif d'imagerie de la surface de l'animal et reconstruction de son contour 3D, 2- modélisation de l'approche sans contact pour la résolution du problème direct, 3- traitement des mesures prenant en compte la réponse impulsionnelle de l'appareil, 4- établissement d'une méthode de reconstruction des images basée sur une sélection de points judicieusement choisis sur les profils temporels. Ces travaux ont permis d'obtenir des images optiques 3D de bonne qualité en réduisant la diaphonie entre l'absorption et la diffusion. Ces améliorations ont été obtenues tout en diminuant le temps de calcul, par comparaison avec les méthodes utilisant la totalité des profils temporels.
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Melville, David O. S. "Planar Lensing Lithography: Enhancing the Optical Near Field." Thesis, University of Canterbury. Electrical and Computer Engineering, 2006. http://hdl.handle.net/10092/1091.
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In 2000, a controversial paper by John Pendry surmised that a slab of negative index material could act as a perfect lens, projecting images with resolution detail beyond the limits of conventional lensing systems. A thin silver slab was his realistic suggestion for a practical near-field superlens - a 'poor-mans perfect lens'. The superlens relied on plasmonic resonances rather than negative refraction to provide imaging. This silver superlens concept was experimentally verified by the author using a novel near-field lithographic technique called Planar Lensing Lithography (PLL), an extension of a previously developed Evanescent Near-Field Optical Lithography (ENFOL) technique. This thesis covers the computational and experimental efforts to test the performance of a silver superlens using PLL, and to compare it with the results produced by ENFOL. The PLL process was developed by creating metal patterned conformable photomasks on glass coverslips and adapting them for use with an available optical exposure system. After sub-diffraction-limited ENFOL results were achieved with this system additional spacer and silver layers were deposited onto the masks to produce a near-field test platform for the silver superlens. Imaging through a silver superlens was achieved in a near-field lithography environment for sub-micron, sub-wavelength, and sub-diffraction-limited features. The performance of PLL masks with 120-, 85-, 60-, and 50-nm thick silver layers was investigated. Features on periods down to 145-nm have been imaged through a 50-nm thick silver layer into a thin photoresist using a broadband mercury arc lamp. The quality of the imaging has been improved by using 365 nm narrowband exposures, however, resolution enhancement was not achieved. Multiple layer silver superlensing has also been experimentally investigated for the first time; it was proposed that a multi-layered superlens could achieve better resolution than a single layer lens for the same total silver thickness. Using a PLL mask with two 30-nm thick silver layers gave 170-nm pitch sub-diffraction-limited resolution, while for a single layer mask with the same total thickness (60 nm) resolution was limited to a 350-nm pitch. The proposed resolution enhancement was verified, however pattern fidelity was reduced, the result of additional surface roughness. Simulation and analytical techniques have been used to investigate and understand vi ABSTRACT the enhancements and limitations of the PLL technique. A Finite-Difference Time- Domain (FDTD) tool was written to produce full-vector numerical simulations and this provided both broad- and narrowband results, allowing image quality as a function of grating period to be investigated. An analytical T-matrix method was also derived to facilitate computationally efficient performance analysis for grating transmission through PLL stacks. Both methods showed that there is a performance advantage for PLL over conventional near-field optical lithography, however, the performance of the system varies greatly with grating period. The advantages of PLL are most prominent for multi-layer lenses. The work of this thesis indicates that the utilisation of plasmonic resonances in PLL and related techniques can enhance the performance of near-field lithography.
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Hoang, Vu Dinh. "Charge transport study of InGaAs two-color QWIPs." Thesis, Monterey California. Naval Postgraduate School, 2004. http://hdl.handle.net/10945/1574.
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Approved for public release, distribution is unlimitedIn this thesis, a series of experiments were performed to characterize the material properties of InGaAs/GaAs for use in a two-color quantum-well IR photodetector (QWIP) design. Results from room temperature studies using cathodoluminescence and photoluminescence indicated light emission at 858 nm and 1019 nm from GaAs and InGaAs, respectively. Using a direct transport imaging technique, an edge dislocation pattern was observed and shown to be confined to the InGaAs layer of the material. A dislocation density measurement was performed and was shown to be less than 2000 lines/cm. Quantitative intensity level measurements indicated fluctuation in the region of dislocations to be less than 30% of the signal to background level. Finally, a spot mode study using the direct transport imaging method was performed to evaluate the feasibility of using this technique for contact-less diffusion length measurements.
Civilian, Department of Air Force
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Jeger-Madiot, Nathan. "Conception d'un imageur ultrasonore dans l'air pour la mesure des ondes basses-fréquences en surface du corps humain." Thesis, Paris 6, 2017. http://www.theses.fr/2017PA066330/document.
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L'objectif des travaux présentés dans cette thèse est le développement d'un système d'imagerie ultrasonore fonctionnant dans l'air pour la mesure sans contact des mouvements vibratoires en surface du corps humain. L'étude des vibrations en surface de la peau ouvre plusieurs champs d'application. L'observation de la vitesse d'une onde de surface sur la peau à partir du film de propagation permet de caractériser l'élasticité de la couche superficielle ainsi que ses hétérogénéités. A partir de cette analyse, il est possible de détecter des objets cachés sur ou sous la peau, dans un objectif de sécurité. Une seconde application est l'observation des vibrations de surface engendrées par le battement cardiaque, la respiration et l'onde de pouls. La réalisation d'un premier dispositif monovoie a permis la mesure locale de vibrations de l'ordre de la dizaine de microns. A partir de ces premiers travaux, nous avons construit un imageur ultrasonore 2D dans l'air à haute cadence d'imagerie. Il est constitué d'un réseau carré de 256 microphones et de 12 émetteurs. La principale nouveauté de notre approche repose sur l'imagerie d'une surface spéculaire. En effet, la rugosité de la peau est négligeable comparée aux longueurs d'onde de travail, de l'ordre du centimètre pour limiter l'atténuation dans l'air. Pour répondre à cette contrainte, l'imagerie est réalisée à partir de la formation de voies émission/réception par synthèse d'ouverture en utilisant une émission séquentielle d'ondes sphériques. Après caractérisation du système, nous avons imagé la propagation d'une onde de surface sur un fantôme mimant le corps humain et l'interférence de cette onde avec un objet étranger. Une seconde version de l'imageur 2D, constituée de 36 émetteurs, a permis la mesure de la déformation du thorax lors du battement cardiaque ainsi que la propagation de l'onde de pouls au niveau de la carotideThe aim of the work presented in this dissertation is to develop an airborne ultrasonic system for the contactless measurement of vibrations on the human body surface. The vibration study of the skin surface opens several application fields. The visualization of the surface wave velocity on the skin from the propagation movie allows to characterize the superficial layer elasticity as well as its heterogeneities. From this analysis, objects hidden on or under the skin can be detected for a security purpose. A second application is the observation of the surface vibrations generated by the heartbeat, respiration and pulse wave.The implementation of a first single-channel device allowed the local measurement of vibrations about ten microns order. From this initial work, we developed a 2D airborne ultrasonic imager with high frame rate. It is composed by a 256 microphones square array and by 12 piezoelectric transducers. The main innovation of our approach is the specular surface imaging. Indeed, the skin roughness is negligible compared to the working wavelength, of the centimeter order to limit the air attenuation. To resolve this issue, the imaging process is carried out with an emission/reception beamforming using synthetic aperture and achieved by a sequential emission of spherical waves.After the system characterization, we imaged the surface wave propagation on a phantom mimicking the human body and the interference between this wave and a foreign object. A second version of the 2D imager, composed by 36 emitters, was applied to measure the deformation of the thorax during the heartbeat as well as the pulse wave propagation in the carotid artery
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Kengyelics, Stephen Mark. "Cardiac X-ray context sensitive imaging." Thesis, University of Leeds, 2017. http://etheses.whiterose.ac.uk/18217/.
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Over the past two decades there have been significant advances in the technology used in the field of cardiac X-ray imaging with the advent of fully digital X-ray detectors. However, the means by which the advantages of this technology are implemented at a systems level remain basic. Most modern cardiac X-ray imaging systems employ feedback control to maintain an adequate average output signal level to the X-ray detector based on the attenuation properties of the patient. This approach is not necessarily optimal over the range of clinical imaging tasks for an individual, or over an anthropomorphically heterogeneous population. Within this thesis methods are presented for extracting dynamic real-time information from within cardiac image sequences that are suitable for incorporation in automatic dose rate control systems that regulate their output based on clinically relevant image quality metrics. A framework is proposed that combines image quality metrics for contrast and noise on a per image frame basis to provide an overall indicator of image acceptability. These metrics are compared to the performance of experienced clinical observers. The methods presented have a wider applicability to other X-ray procedures that use dynamic imaging of blood vessels made visible by the use of contrast agents.
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Sigmundsson, Rúnar. "Subharmonic Imaging of Polymer-Shelled Contrast Agents." Thesis, KTH, Skolan för kemi, bioteknologi och hälsa (CBH), 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-233492.
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The harmonic generation due to the nonlinear behavior of Ultrasound Contrast Agents (UCAs) must be exploited for improved efficiency when imaging vascular targets in the neighborhood of highly echogenic tissue. One may even further improve the efficiency by focusing on the subharmonic generation of the UCAs, which is an even more exclusive property than the generation of higher harmonics, for improved Contrast-to-Tissue ratio (CTR). The aim of this work was first, the design of a set-up for nonlinear imaging of Poly-Vinyl Alcohol (PVA) based UCAs on The Verasonics Research System with special focus on nondestructive Subharmonic Imaging. The second part of the work addressed the evaluation of the subharmonic response provided by the agents in the developed setup. Six different imaging techniques were developed. These were Fundamental B-mode imaging (FB), Pulse Inversion imaging (PI), and a Contrast Pulse Sequence based on three pulses (CPS3), with and without a focus on the subharmonic component by the implementation of a Linear Bandpass Filter (LBF). Experiments were performed on a tissue mimicking flow phantom and the performance of the agents for each technique was determined in terms of CTR and CNR. The PVA agents provided a backscattering enhancement of the order of 23 dB through FB imaging. However, the performance of the FB technique was unsatisfactory in terms of CTR. The CPS3 sequence performed best of the six techniques with an improvement of 14 dB and 13 dB in CTR and CNR, respectively, compared with the FB technique. Combining the LBF around the subharmonic component with the multi-pulse techniques of PI and CPS3 resulted in a degraded CTR performance due to significant amount of signals from tissue around the subharmonic component and insufficient subharmonic detection from the PVA agents.
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Lin, Fanglue. "Ultrasound contrast imaging with multi-pulse transmission." Phd thesis, INSA de Lyon, 2013. http://tel.archives-ouvertes.fr/tel-01018646.
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In ultrasound imaging domain, nonlinear imaging has become an important branch. Nonlinear imaging can be divided into tissue harmonic imaging and contrast harmonic imaging, according to where the nonlinear signals come from. Contrast harmonic imaging emerges because contrast agents, which are intravenously injected to enhance the weak echoes backscattered from blood cells, can vibrate nonlinearly when they undergo an acoustic pressure. Then, these nonlinear signals backscattered by contrast agents are collected to form harmonic images. However, during the wave propagation in tissue, the harmonics of the transmitted wave are also generated in tissue. The presence of tissue harmonic signals degrades the image quality in contrast harmonic imaging. This thesis aims to better distinguish the echoes from contrast agents and the echoes from tissue, whether through designing new modalities, or investigating and optimizing the existing modalities. Our efforts are mainly focused on the multi-pulse techniques in ultrasound contrast imaging. Firstly, we propose a mathematical background to generalize most of the multi-pulse ultrasound imaging techniques that have been described in previous literatures. The formulation can be used to predict the nonlinear components in each frequency band and to design new transmission sequences to either increase or decrease specified nonlinear components in each harmonic band. Simulation results on several multi-pulse techniques are in agreement with the results given in previous literatures. Secondly, the techniques using multiple transmissions to increase the CTR are generally based on the response of static scatterers inside the imaged region. However, scatterer motion, for example in blood vessels, has an inevitable influence on the relevance of the techniques. It can either upgrade or degrade the technique involved. Simulations, in-vitro experiments from a single bubble and clouds of bubbles, and in-vivo experiments from rats show that the phase shift of the echoes backscattered from bubbles is dependent on the transmissions' phase shift, and that the bubble motion influences the efficiency of multi-pulse techniques. Furthermore, experimental results based on the second-harmonic inversion (SHI) technique reveal that bubble motion can be taken into account to optimize multi-pulse techniques. Besides, a new technique, called double pulse inversion (DPI), has also been proposed. The PI technique is applied twice before and after the arrival of the contrast agents to the region of interest. The resulting PI signals are substracted to suppress the tissue-generated harmonics and to improve CTR. Simulations and in-vitro experimental results have shown an improved CTR of DPI. However, the presence of tissue movements may hamper the effectiveness of this technique. In-vivo experimental results confirm that the tissue motion of the rat during the acquisition is an inevitable barrier of this technique.
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Yoo, Byunghee. "MOLECULAR IMAGING OF BREAST CANCER USING PARACEST MRI." Case Western Reserve University School of Graduate Studies / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=case1183658257.
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Williams, Jamie. "Imagined Contact Intervention with an American Muslim Target." TopSCHOLAR®, 2019. https://digitalcommons.wku.edu/theses/3152.
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Recent studies have shown that imagining contact with a member of a differing social group can reduce prejudice toward said group. This type of prejudice intervention, known as an imagined contact intervention, can be beneficial when direct contact with the outgroup is not feasible. This study adds to existing research on imagined contact interventions by replicating a simple version of the intervention by Husnu and Crisp (2010) and assessing attitudes toward an American Muslim out-group. This study extends the research of Husnu and Crisp (2010) by using American participants as opposed to British participants and also uses an online distribution for the intervention as opposed to a laboratory setting. The research question was: Will the imagined contact intervention significantly reduce prejudice toward the American Muslim out-group when compared to a control condition? Participants who reported socializing with the Muslim out-group less than three times in the past six months completed a form of the intervention online, responded to an out-group attitude index regarding the Muslim out-group, and completed demographics questions. In this study, there was no significant effect of the imagined contact intervention on out-group attitudes. Possible reasons for the intervention’s ineffectiveness, including the use of online distribution for the survey, are discussed along with directions for future research.
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Harris, Steven Scott. "Adiabatic pulse preparation for imaging iron oxide nanoparticles." Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/47555.
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Iron oxide nanoparticles are of great interest as contrast agents for research and potentially clinical molecular magnetic resonance imaging (MRI). Biochemically modifying the surface coatings of the particles with proteins and polysaccharides enhances their utility by improving cell receptor specificity, increasing uptake for cell labeling and adding therapeutic molecules. Together with the high contrast they produce in MR images, these characteristics promise an expanding role for iron oxide nanoparticles and molecular MR imaging for studying, diagnosing and treating diseases at the molecular level. However, these contrast agents produce areas of signal loss with traditional MRI sequences that are not specific to the nanoparticles and cannot easily quantify the contrast agent concentration. With the expanding role of iron oxide nanoparticles in molecular imaging, new methods are needed to produce a quantitative contrast that is specific to the iron oxide nanoparticle. This dissertation presents a new method for detecting and quantifying iron oxide nanoparticles using an adiabatic preparation pulse and the failure of the adiabatic condition for spins diffusing near the particles. In the first aim, the theoretical foundation of the work is presented, and a Monte Carlo simulation supporting the proposed mechanism of the contrast is described. Adiabatic pulse prepared imaging sequences are also developed for imaging at 3 Tesla and 9.4 Tesla to highlight the translational potential of the approach for clinical examinations and scientific research, and the linear correlation of the contrast with iron concentration ideal for quantification is presented. Further, the physical characteristics of the nanoparticles and the parameters of the MRI sequence are modified to characterize the approach. In the second aim, the contrast is characterized in more realistic phantoms and in vitro, and a method to more accurately quantify nanoparticle concentration in the presence of magnetization transfer is presented. Finally, accelerated imaging methods are implemented to acquire the adiabatic contrast in a time compatible with in vivo imaging, and the technique is evaluated in an in vivo model of quantitative iron oxide nanoparticle imaging. Together, these aims present a method using an adiabatic preparation pulse to generate an MR contrast based on the microscopic magnetic field gradients surrounding the iron oxide nanoparticles that is suitable for in vivo quantitative, molecular imaging.
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Ioannou, Maria. "Comparing direct and indirect forms of intergroup contact in Cyprus." Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:de6a7b58-79b1-40e9-bc1d-ee8dfdf1635d.
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This thesis examines and compares the effectiveness of direct and indirect types of contact in leading to short- or longer-term prejudice-reducing outcomes in Cyprus. Chapter 1 provides a background to the relations between Greek and Turkish Cypriots and Chapter 2 provides a theoretical introduction to the intergroup contact hypothesis (Allport, 1954) and to extended friendships (Wright, Aron, McLaughlin-Volpe, & Ropp, 1997), vicarious contact (Mazziotta, Mummendey, & Wright, 2011), and imagined contact (Crisp & Turner, 2009) which have been suggested to be alternatives and a stepping stone to direct contact when the latter is absent. Chapter 3 consists of three experiments assessing the relative effects of direct and vicarious contact (Experiments 1 and 2) and imagined contact (Experiment 3). The results show that direct, and to a weaker extent, vicarious contact lead to more positive outgroup attitudes, but that a week after contact this effect is lost. All types of contact yield less anxiety, an effect that endures in time, and direct and imagined contact yield more positive action tendencies, an effect that remains significant in time only for direct contact. Chapter 4 consists of two experiments further exploring the capacity of imagined contact to yield positive intergroup outcomes. Experiment 4 tests whether the induction of interpersonal and intergroup similarities and/or differences into a positive imagined contact scenario affects participants evaluation of the outgroup. The results show, in line with the Optimal Distinctiveness Theory (Brewer, 1971), that ‘balanced similarity’ which incorporates both similarities and differences yields more positive outgroup attitudes than the conditions focusing only on similarities or only on differences. Experiment 5 compares ‘balanced similarity’ with positive imagined contact and finds that only the former affects variables related to preparing individuals for future contact. Chapter 5 consists of a three-wave longitudinal study examining the temporal effects of direct and extended friendships on outgroup attitudes and their mediation. Both types of friendships yield a significant indirect effect on attitudes which is stronger for direct friendships and is mediated by intergroup anxiety for both types of friendships and also by ingroup norms for direct friendships. Chapter 6 presents and discusses the key findings, outlines the limitations of these studies, and suggests avenues for future research.
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Evangelou, Dimitrios. "Ultraharmonic Imaging of Polymer-shelled Microbubbles." Thesis, KTH, Skolan för kemi, bioteknologi och hälsa (CBH), 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-232975.
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Ultrasound has been established as one of the most widely used imaging modalities for diagnostic purposes, due to the several advantages it provides in comparison with other techniques. Hence, ways to further improve the confidence in diagnoses provided by ultrasound are constantly being investigated. One of them is the introduction of Ultrasound Contrast Agents, which can enhance the weak echoes produced by the small vessels, improving the imaging performance. In this study, a setup was created and six ultrasound imaging techniques were implemented by using the Verasonics Research System®, in order to take advantage of the different behavior between the tissue and the Polyvinyl-Alcohol microbubbles, when exposed to ultrasound. These were: Fundamental B-mode, Ultraharmonic, PulseInversion, Subharmonic Pulse Inversion, Ultraharmonic Pulse Inversion, Combination of the Sub- and Ultraharmonic Pulse Inversion. For the assessment of the bubbles’ response, the amplitude spectra were used, which showed a limited detection around the ultraharmonic region. For the evaluation of the imaging performance of the techniques, the Contrast-to-Tissue (CTR) and Contrast-to-Noise Ratios (CNR) were calculated. The Combination of the Sub- and Ultraharmonic Pulse Inversion reported the highest imaging performance among all the techniques. A comparison with previous articles provided a similar pattern in terms of CTR.Technology
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Nxumalo, Jochonia Norman. "Cross-sectional imaging of semiconductor devices using nanometer scale point contacts." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0007/NQ32010.pdf.
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Cheung, Shing-chung, and 張成忠. "Novel contrast agents for magnetic resonance imaging." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2009. http://hub.hku.hk/bib/B42841550.
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Cheung, Shing-chung. "Novel contrast agents for magnetic resonance imaging." Click to view the E-thesis via HKUTO, 2009. http://sunzi.lib.hku.hk/hkuto/record/B42841550.
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Garach, Ravindra Mahendrakumar. "Robust phase sensitive inversion recovery imaging." Texas A&M University, 2005. http://hdl.handle.net/1969.1/2574.
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Inversion Recovery (IR) is a powerful tool for contrast manipulation in Mag-
netic Resonance Imaging (MRI). IR can provide strong contrast between tissues with
different values of T1 relaxation times. The tissue magnetization stored at an IR
image pixel can take positive as well as negative values. The corresponding polarity
information is contained in the phase of the complex image. Due to numerous factors
associated with the Magnetic Resonance (MR) scanner and the associated acquisition
system, the acquired complex image is modulated by a spatially varying background
phase which makes the retrieval of polarity information non-trivial. Many commercial
MR scanners perform magnitude-only reconstruction which, due to loss of polarity
information, reduces the dynamic contrast range. Phase sensitive IR (PSIR) can
provide enhanced image contrast by estimating and removing the background phase
and retrieving the correct polarity information. In this thesis, the background phase
of complex MR image is modeled using a statistical model based on Markov Ran-
dom Fields (MRF). Two model optimization methods have been developed. The first
method is a computationally effcient algorithm for finding semi-optimal solutions
satisfying the proposed model. Using an adaptive model neighborhood, it can recon-
struct low SNR images with slow phase variations. The second method presents a
region growing approach which can handle images with rapid phase variations. Ex-
perimental results using computer simulations and in vivo experiments show that the
proposed method is robust and can perform successful reconstruction even in adverse
cases of low signal to noise ratios (SNRs) and high phase variations.
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Guimaraes, Alexander Savio Ramos. "Quantitative 1H N.M.R. chemical shift imaging of neuronal content." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/28128.
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Datar, Akshata. "HIGH CONTENT IMAGING ASSAYS ON MICROARRAY CHIP BASED PLATFORM." Cleveland State University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=csu1462795576.
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