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1
Raj, Kolupula Yuva Deva. « Chromatic Particulate Monitoring System ». Thesis, University of Liverpool, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.526954.
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Ker, Keong Alex Koh. « Chromatic driver fatigue monitoring system ». Thesis, University of Liverpool, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.494130.
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Sleep related vehicle accidents have been under publicised but remains as one of the main causes of road traffic accidents, as much as drink driving. This research aims to reduce this worldwide problem by developing a system to monitor fatigue driving. The thesis describes the research into the application of chromatic data processing techniques to detect early physiological and physical indicators of fatigue. Physiological factors that influence drivers are based on the duration of the drive, how much rest they have throughout the journey and the quality of sleep they had prior to the drive. The physiological indicator algorithm of the system is developed to take account of these factors and calculates the tiredness level. The chromatic technique is then used to analyse the results to establish trends and signatures of early fatigue situations where a warning system can be introduced. The chromatic signatures of fatigue have been established using results from 20 road tests conducted by professional drivers. Physical indicators such as early drowsy driving are detected by monitoring the behaviour of the vehicle. Micro sleep (e.g. head nodding, slow eye-blinking) can lead to lane drifting and vehicle swerving. These events are being regarded as early physical signs of sleepy driving. The main sensor for detecting the lateral yaw motion of the vehicle is a miniaturised gyroscope. Chromatic analysis is applied to the gyroscope output to identify and differentiate fatigue related events (e.g. swerves and lane drifting) from normal driving (e.g. left and right turning, roundabouts and bumpy roads) Combining the extracted information of the physiological and physical indicators, a Chromatic Fatigue Driving System can be developed as a tail safe system which monitors and alerts driver during critical fatigue conditions.
3
Hutchinson, S. J. « Spatio-chromatic interactions in the human visual system ». Thesis, Queen's University Belfast, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.411198.
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陳淸儀 et Ching-yi Chan. « Image retrieval system based on texture and chromatic features ». Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2000. http://hub.hku.hk/bib/B31223953.
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Chan, Ching-yi. « Image retrieval system based on texture and chromatic features ». Hong Kong : University of Hong Kong, 2000. http://sunzi.lib.hku.hk/hkuto/record.jsp?B22665249.
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Guizani, Sghaier. « Optical post chromatic dispersion compensation in an optical fiber communication system ». Thèse, Trois-Rivières : Université du Québec à Trois-Rivières, 2008. http://www.uqtr.ca/biblio/notice/resume/30055578R.pdf.
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Snelgar, Rosemary S. « Aspects of chromatic and temporal processing in normal and impaired human vision ». Thesis, Keele University, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.329085.
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COLVERO, CLAITON PEREIRA. « STUDY OF CHROMATIC DISPERSION AND NONLINEAR EFFECTS IN SHIFTED DISPERSION FIBER OPTIC SYSTEM ». PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2001. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=1553@1.
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AGÊNCIA NACIONAL DE PETRÓLEONeste trabalho é apresentado um estudo sobre a determinação matemática dos valores da dispersão cromática total, do zero de dispersão distribuído e efeitos não lineares em fibras ópticas de dispersão deslocada (DS). Uma metodologia para caracterização das dispersões cromáticas e para os zeros de dispersão local das fibras estudadas é elaborada com a utilização do modelo de fibra degrau equivalente e de aproximações entre as fibras ópticas dos enlaces trabalhados. A relação entre o diâmetro do campo modal e o zero de dispersão cromática distribuído segundo A. Rossaro [6] é discutida e comprovada através da realização de uma série de medidas práticas para a determinação dos efeitos não lineares das fibras de dispersão deslocada dos enlaces da Petrobrás. O objetivo deste trabalho é analisar estes efeitos prejudiciais a transmissão de sinais ópticos de alta velocidade apresentados nos cabos submarinos da Petrobrás entre o Porto de Imbetiba e as plataformas de Pargo I e Pampo I na Bacia de Campos, analisando os resultados obtidos e caracterizando as possibilidades de upgrade destes enlaces.
This work presents a study on the mathematical determination of the total chromatic dispersion, zero dispersion wavelength and nonlinear optical effects in dispersion shifted (DS) fiber optic system. A methodology to determine the chromatic dispersion and zero dispersion wavelength is proposed using the equivalent step index model and the similarity of the total chromatic dispersion measured in fibers of the links under study. The relationship between the mode field diameter and the zero dispersion wavelength according to A. Rossaro [6] is discussed and proven with a series of practical measurements for the determination of the nonlinear effects of the dispersion shifted optical fibers of Petrobras links Imbetiba - Pargo and Imbetiba - Pampo of the Campos Basin.
En este trabajo se presenta un estudio sobre la determinación matemática de los valores de dispersión cromática total, del cero de dispersión distribuido y los efectos no lineales en fibras ópticas de dispersión desplazada (DS). Se elabora una metodología para la caracterización de las dispersiones cromáticas y para los ceros de dispersión local de las fibras estudiadas; utililizando el modelo de fibra escalón equivalente y de aproximaciones entre las fibras ópticas de los enlace. Se discute la relación entre el diámetro del campo modal y el cero de dispersión cromática distribuido según A. Rosaro [6] se comprueba a través de la realización de una serie de medidas prácticas para la determinación de los efectos no lineales de las fibras de dispersión desplazada de los enlaces de la Petrobrás. EL objetivo de este trabajo es analizar los efectos perjudiciales a la transmisión de señales ópticos de alta velocidad que se presentan en los cables submarinos de la Petrobrás entre el Puerto de Imbetiba y las plataformas de Pargo I y Pampo I en la Bacia de Campos, analizando los resultados obtenidos y caracterizando las posibilidades de upgrade de estos enlaces.
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Hughes, Richard. « Determination of Chromatic and Luminance Channels in the Zebrafish Visual System Using an Increment Threshold Technique ». TopSCHOLAR®, 1996. http://digitalcommons.wku.edu/theses/803.
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It is well established that the primate visual system possesses anatomically separate chromatic and luminance channels; these pathways are responsible for the visual coding of color and brightness information, respectively. In lower vertebrates, such as the zebrafish (Danio rerio), there does not appear to be any anatomical separation of cell types mediating color and luminance information. However, several studies suggest that these vertebrates may be able to discriminate these attributes of a visual stimulus. The purpose of this study was to determine whether the zebrafish visual system possesses chromatic and luminance channels. In addition, the contribution of each cone photoreceptor type to the chromatic and luminance channels was determined. An increment threshold procedure was used to elicit electroretinogram (ERG) b-wave responses to monochromatic light under two different intensities of white background adaptation. From the ERG b-wave responses, a spectral sensitivity function was derived under low and high levels of white background. By examining spectral sensitivity functions under these two levels of white background adaptation, it was possible to determine if two functional channels exist for color and luminance in the zebrafish visual system. The results of this study suggest that zebrafish possess a chromatic channel, but do not seem to have a luminance channel. The low level of white background adaptation yielded a spectral sensitivity function that was similar to the spectral sensitivity function of the chromatic channel in the primate. Alternatively, the high level of white background produced a spectral sensitivity function which appears to represent neither a chromatic nor a luminance channel; rather, the high level of white background only suppressed the cone contributions to the spectral sensitivity function. In addition, the ultraviolet cones were found to contribute substantially to spectral sensitivity functions derived under both the high and low white background adaptation levels. In conclusion, the results of the present study suggest that anatomical separation may be required for separation of function. Furthermore, the finding that zebrafish possess only a chromatic channel, as well as substantial ultraviolet sensitivity, may be a reflection of the type of environment in which they are normally found.
10
Doi, Eizaburo. « A study of computational neural network models on spatio-chromatic properties of the early visual system ». 京都大学 (Kyoto University), 2003. http://hdl.handle.net/2433/148775.
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Ambardekar, Aditya. « Analysis of BER in optical direct detection DPSK system in the presence of SPM and chromatic dispersion ». abstract and full text PDF (UNR users only), 2008. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1460745.
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Xu, Tianhua. « Digital Dispersion Equalization and Carrier Phase Estimation in 112-Gbit/s Coherent Optical Fiber Transmission System ». Licentiate thesis, KTH, Optik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-34034.
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Coherent detection employing multilevel modulation format has become one of the most promising technologies for next generation high speed transmission system due to the high power and spectral efficiencies. With the powerful digital signal processing (DSP), coherent optical receivers allow the significant equalization of chromatic dispersion (CD), polarization mode dispersion (PMD), phase noise (PN) and nonlinear effects in the electrical domain. Recently, the realizations of these DSP algorithms for mitigating the channel distortions in the transmission system are the most attractive investigations. The CD equalization can be performed by the digital filters developed in the time and the frequency domain, which can suppress the fiber dispersion effectively. The PMD compensation is usually performed in the time domain with the adaptive least mean square (LMS) and constant modulus algorithms (CMA) equalization. Feed-forward and feed-back carrier phase estimation algorithms are employed to mitigate the phase noise from the transmitter and local oscillator lasers. The fiber nonlinearities are compensated by using the digital backward propagation methods based on solving the nolinear Schrodinger (NLS) equation and the Manakov equation. In this dissertation, we present a comparative analysis of three digital filters for chromatic dispersion compensation, an analytical evaluation of carrier phase estimation with digital equalization enhanced phase noise and a brief discussion for PMD adaptive equalization. To implement these investigations, a 112-Gbit/s non-return-to-zero polarization division multiplexed quadrature phase shift keying (NRZ-PDM-QPSK) coherent transmission system is realized in the VPI simulation platform. With the coherent transmission system, these CD equalizers have been compared by evaluating their applicability for different fiber lengths, their usability for dispersion perturbations and their computational complexity. Meanwhile, the bit-error-rate (BER) floor in carrier phase estimation using a one-tap normalized LMS filter is evaluated analytically, and the numerical results are compared to a differential QPSK detection system.QC 20110629
13
Mirzoyan, Rafayel. « Study of the coherent effects in rubidium atomic vapor under bi-chromatic laser radiation ». Phd thesis, Université de Bourgogne, 2013. http://tel.archives-ouvertes.fr/tel-00934648.
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The effect of electromagnetically induced transparency is observed, using nanocelland microcell. The EIT-resonance with good parameters (high contrast and small FWHM) is obtained in thick cells. The EIT-resonance splitting in magnetic field is observed for the cases of D1-line of 85Rb and 85Rb. The theoretical model, explaining the EIT-resonance components frequency shift dependence on magnetic field strength is presented. The theoretical and experimental results are compared and good agreement is shown. Also the EIT-resonance behavior in hyperfine Paschen-Back regime is presented and explained. For the first time the N-type resonance in microcell is observed. Good parameters of theN-type resonance in microcell are obtained. It allows us to observe the N-type resonance behavior in magnetic field. The N-resonance splitting in magnetic field is observed for the cases of 85Rb and 85Rb. The theoretical calculations of the N-resonance components frequency shift dependence on magnetic field is presented. The theoretical and experimental results are compared and good agreement is shown. Also the N-resonance behavior in hyperfine Paschen-Back regime is presented and explained. Simultaneous observation of N- and EIT-resonance is shown. Comparison of EIT- and N-resonance is made
14
Challa, Naveen K. « An electrophysiological study of chromatic processing in the human visual system. Using visual evoked potentials and electroretinograms to study cortical and retinal contributions to human trichromatic vision ». Thesis, University of Bradford, 2011. http://hdl.handle.net/10454/5343.
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The work in this thesis is concerned with examining the retinal and cortical contributions to human trichromatic colour vision. Chromatic processing at the cortex level was examined using visual evoked potentials (VEPs). These responses were elicited by chromatic spot stimuli, which were manipulated in order to selectively activate the chromatic processing system. Chromatic processing at the retinal level was examined using the electroretinograms (ERGs) for which cone isolating stimuli were used to assess the nature of L and M cone inputs to cone-opponent mechanisms.
The results from the VEP experiments suggest VEP morphology is dependent upon 1) chromatic and or luminance contrast content of the stimulus, 2) stimulus size, and 3) extent to which the chromatic stimulus activates either the L/M or S/(L+M) opponent mechanism. The experiments indicate that chromatic stimulation is indexed by large N1 component and small offset responses. Optimal stimulus size for chromatic isolation is 2-4 ° along L/M axes and 6° along S/(L+M) axis.
From the ERG experiments, It has been shown that the low (12Hz) and high (30Hz) temporal frequency flickering stimuli can isolate the chromatic and luminance processing mechanisms in the retina. For low temporal frequency ERGs, the L:M ratio was close to unity and L/M phase difference was close to 180°. For high temporal frequency ERGs, the L:M ratio was more than unity and L/M phase difference was close to 90°. In addition to this, the variation in L:M ratio across the retinal eccentricity was also examined. These results suggest, for the chromatic processing, L:M ratio is close to unity independent of retinal eccentricity and individuals. For the luminance processing, L:M ratio is more than unity and depends upon the region of the retina being stimulated. These findings indicate the maintenance of cone selective input for the chromatic processing across the human retina.
15
Challa, Naveen Kumar. « An electrophysiological study of chromatic processing in the human visual system : using visual evoked potentials and electroretinograms to study cortical and retinal contributions to human trichromatic vision ». Thesis, University of Bradford, 2011. http://hdl.handle.net/10454/5343.
Texte intégralRésumé :
The work in this thesis is concerned with examining the retinal and cortical contributions to human trichromatic colour vision. Chromatic processing at the cortex level was examined using visual evoked potentials (VEPs). These responses were elicited by chromatic spot stimuli, which were manipulated in order to selectively activate the chromatic processing system. Chromatic processing at the retinal level was examined using the electroretinograms (ERGs) for which cone isolating stimuli were used to assess the nature of L and M cone inputs to cone-opponent mechanisms. The results from the VEP experiments suggest VEP morphology is dependent upon 1) chromatic and or luminance contrast content of the stimulus, 2) stimulus size, and 3) extent to which the chromatic stimulus activates either the L/M or S/(L+M) opponent mechanism. The experiments indicate that chromatic stimulation is indexed by large N1 component and small offset responses. Optimal stimulus size for chromatic isolation is 2-4 ° along L/M axes and 6° along S/(L+M) axis. From the ERG experiments, It has been shown that the low (12Hz) and high (30Hz) temporal frequency flickering stimuli can isolate the chromatic and luminance processing mechanisms in the retina. For low temporal frequency ERGs, the L:M ratio was close to unity and L/M phase difference was close to 180°. For high temporal frequency ERGs, the L:M ratio was more than unity and L/M phase difference was close to 90°. In addition to this, the variation in L:M ratio across the retinal eccentricity was also examined. These results suggest, for the chromatic processing, L:M ratio is close to unity independent of retinal eccentricity and individuals. For the luminance processing, L:M ratio is more than unity and depends upon the region of the retina being stimulated. These findings indicate the maintenance of cone selective input for the chromatic processing across the human retina.
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Taddei, Rita de Cassia. « Alberto Nepomuceno, Artémis : um estudo de análise neorriemanniana ». Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/27/27157/tde-26052015-120059/.
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Este trabalho analisa a estruturação harmônica do episódio lírico Artémis, de Alberto Nepomuceno, buscando demonstrar que a técnica usada pelo compositor emprega sistematicamente os princípios da linguagem do cromatismo pós-wagneriano. Observa-se, inicialmente, que o projeto dessa obra encontra-se na vanguarda das estéticas de seu tempo, alinhando-se com as correntes progressistas do período. Nesse sentido verifica-se que, apesar de Nepomuceno ter sido identificado pela historiografia modernista como precursor do nacionalismo musical brasileiro, nesta obra prevalece sua inclinação cosmopolita. Para o desenvolvimento da pesquisa examinou-se inicialmente qual ferramenta de análise harmônica, dedicada ao repertório do cromatismo romântico do final do século XIX, seria mais adequada ao Artémis. Apresenta-se, por isso, uma introdução às teorias analíticas aplicáveis ao repertório com tonalidade expandida do século XIX, focando nos trabalhos de Hugo Riemann, Arnold Schoenberg e David Kopp. As teorias harmônicas de Riemann, sendo a matriz primordial dessas teorias, são extensamente investigadas. Comparamos, a seguir, as propostas dos três teóricos no que se refere a ferramentas de análise para peças com estrutura cromática. Discorrendo sobre aspectos positivos e negativos de cada teoria investigada, apontamos a recente teoria neorriemanniana de Kopp como a que melhor sistematizou, para nossos propósitos, os avanços acadêmicos no entendimento dos problemas harmônicos do repertório cromático do século XIX. Defendendo a importância de se atrelar, adequadamente, teoria, análise e repertório, confrontamos teoria e prática analítica, aplicando ao Artémis a sistemática das transformações cromáticas de Kopp. Conseguimos assim demonstrar, na prática do processo analítico, através de uma ferramenta de análise perfeitamente ajustada ao repertório proposto, resultados que atestam a coerência estrutural do texto musical abordado aos princípios transformacionais da harmonia cromática pós-wagneriana.This dissertation analyses the harmonic structure of the \"lyric episode\" Artémis, composed by Alberto Nepomuceno, aiming to demonstrate that the technique used by the composer employs, systematically, the principles of the post-Wagnerian chromatic language. We observe, initially, that the project of this piece fits the avant-garde aesthetics of its time, aligning itself to the progressive trends of the period. In this sense we verify - although Nepomuceno has been identified by the modernistic Brazilian historiography as a forerunner of the Brazilian musical nationalism - that his cosmopolitan inclinations prevailed in this composition. At first, for the adequate development of the research, we examined which tool of harmonic analysis, dedicated to the chromatic repertoire of the final of the XIX Century, would be more adequate to the music of Artémis. We present, therefore, an introduction to the analytical theories that might be useful to the repertoire of expanded tonality of the XIX Century, focusing in the texts of Hugo Riemann, Arnold Schoenberg and David Kopp. The harmonic theories of Riemann, as the matrix for all these theories, are extensively investigated. We compare, in the sequence, the proposals of three theoreticians that developed analytical tools for pieces with chromatic structures. Revealing the positive and negative aspects of each of these theories, we pointed out the recent neoriemannian theory by Kopp as the one that better systematizes, for our purposes, the academic advances in the understanding of the harmonic problems of the chromatic repertoire composed at the end of the XIX Century. Because we defend the importance of considering simultaneously theory, analysis and repertoire, we confront theory and practice, applying to Artémis, Kopp\'s chromatic transformations systematic theory. This way we were able to demonstrate, in the practice of the analytical process, through an analytic tool perfectly fit to proposed repertoire, results that attest the structural coherence of the studied musical text with the transformational principles of post-Wagnerian chromatic harmony.
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Xu, Shaoqiu. « Chromatic systems for the care community ». Thesis, University of Liverpool, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.406631.
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Aceves, Fernandez Marco Antonio. « Chromatic intelligent systems for pollution monitoring ». Thesis, University of Liverpool, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.427046.
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Barroqueiro, Sergio A. B. « Chromatic sensors for aircraft fuel systems ». Thesis, University of Liverpool, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.399038.
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Chatzis, Sokratis. « Chromatic monitoring with the use of embedded systems ». Thesis, University of Liverpool, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.539716.
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Glomon, Lhusak. « Source based chromatic methodology for optical fibre sensor systems ». Thesis, University of Liverpool, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.400231.
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Oliveira, Inês do Vale Marques. « Digital chromatic dispersion equalization in optical coherent transmission systems ». Master's thesis, Universidade de Aveiro, 2016. http://hdl.handle.net/10773/21735.
Texte intégralRésumé :
Mestrado em Engenharia Eletrónica e TelecomunicaçõesA crescente procura de largura de banda tem obrigado a área de comunicações óticas a explorar diferentes soluções, de forma a evitar a ”crise de capacidade” [1]. O investigadores têm trabalhado no sentido de atingir o equilíbrio entre os vários compromissos, repensando a forma como o sinal ótico é enviado e recebido, para que a perda de informação seja mínima ao longo do canal de propagação. No inıcio desta década, começaram a ser adotados formatos de modulação avançada, os quais apresentam elevada eficiência espetral, bem como deteção coerente, que permite extrair a informação da amplitude e da fase do campo ótico. Estas técnicas são complementadas pelo pós-processamento digital de sinal, que é atualmente muito importante na mitigação das distorções do sinal e imperfeiçoes do recetor. As distorções do sinal podem ser causadas, por exemplo, pela dispersão cromática na fibra. Esta dissertação engloba o estudo e simulação de um sistema de transmissão coerente PM-QPSK, bloco-a-bloco, fazendo uma abordagem detalhada dos conceitos supramencionados. O sistema foi então simulado na presença de dispersão cromática e de ruído, alternada e simultaneamente. Os resultados mostram que o sinal recebido apresenta uma distribuição quase Gaussiana em todos os casos. Com vista a recuperar o sinal transmitido, e no caso em que só se considerou o efeito da dispersão cromática, aplicou-se um filtro linear de resposta impulsional inversa à da fibra, conseguindo assim uma equalização digital perfeita do sinal recebido. Também foi implementado um filtro adaptado no receptor para minimizar o efeito do ruído, obtendo não uma equalização perfeita, mas ótima.
The crescent demand on high bandwidth has been compelling the optical communications area to explore di erent solutions, in order to avoid the \capacity crunch" of the optical bres [1]. Researchers have been working towards reaching the best tradeo s balance, rethinking the way as the optical signal is sent and received, so the loss of information is minimum throughout the propagation channel. Advanced modulation formats became adopted in the beginning of this decade, presenting high spectral e ciency, as well as coherent detection, which allows extracting information from the amplitude and phase of the optical eld. These techniques are complemented by post-digital signal processing, which is nowadays very important at mitigating signal distortions and receiver imperfections. Those impairments result, for instance, of the chromatic dispersion at the bre. This dissertation covers the study and simulation of a PM-QPSK transmission system, block-by-block, approaching in detail the concepts mentioned above. The system was then simulated with chromatic dispersion and with noise, alternately and simultaneously. The results show that the received signal presents an almost Gaussian distribution in every case. In order to retrieve the transmitted signal, and in the case that only chromatic dispersion's e ect was considered, a linear lter was applied with an inverse impulse response of the bre, achieving such a perfect digital equalization of the received signal. A matched lter was also implemented in the receptor to minimize the noise e ect, obtaining not a perfect equalization, but an optimal one.
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Henderson, Philip James. « Chromatic modulation systems for multiparameter measurement in physically demanding environments ». Thesis, University of Liverpool, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.257163.
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Schornstein, Nancy M. « Computing the chromatic number of t-(v, k, [lambda]) designs. / ». Online version of thesis, 1989. http://hdl.handle.net/1850/10617.
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Boroudjerdi, Hoda. « Charged polymer-macroion complexes ». Phd thesis, Universität Potsdam, 2005. http://opus.kobv.de/ubp/volltexte/2006/628/.
Texte intégralRésumé :
This work explores the equilibrium structure and thermodynamic phase behavior
of complexes formed by charged polymer chains (polyelectrolytes) and oppositely
charged spheres (macroions).
Polyelectrolyte-macroion complexes form a common pattern in soft-matter physics,
chemistry and biology, and enter in numerous technological applications as well.
From a fundamental point of view, such complexes are interesting in that
they combine the subtle interplay between electrostatic interactions and elastic as well as entropic
effects due to conformational changes of the polymer chain, giving rise
to a wide range of structural properties.
This forms the central theme of theoretical studies presented in this thesis, which
concentrate on a number of different problems
involving strongly coupled complexes, i.e. complexes that are characterized by
a large adsorption energy and small chain fluctuations.
In the first part, a global analysis of the structural phase behavior of a single polyelectrolyte-macroion complex is presented based on a dimensionless representation, yielding results that cover a wide range of realistic system parameters. Emphasize is made on the interplay between the effects due to the polyelectrolytes chain length, salt concentration and the macroion charge as well as the mechanical chain persistence length. The results are summarized into generic phase diagrams characterizing the wrapping-dewrapping behavior of a polyelectrolyte chain on a macroion. A fully wrapped chain state is typically obtained at intermediate salt concentrations and chain lengths, where the amount of polyelectrolyte charge adsorbed on the macroion typically exceeds the bare macroion charge leading thus to a highly overcharged complex.
Perhaps the most striking features occur when a single long polyelectrolyte chain is complexed with many oppositely charged spheres. In biology, such complexes form between DNA (which carries the cell's genetic information) and small oppositely charged histone proteins serving as an efficient mechanism for packing a huge amount of DNA into the micron-size cell nucleus in eucaryotic cells. The resultant complex fiber, known as the chromatin fiber, appears with a diameter of 30~nm under physiological conditions. Recent experiments indicate a zig-zag spatial arrangement for individual DNA-histone complexes (nucleosome core particles) along the chromatin fiber. A numerical method is introduced in this thesis based on a simple generic chain-sphere cell model that enables one to investigate the mechanism of fiber formation on a systematic level by incorporating electrostatic and elastic contributions. As will be shown, stable complex fibers exhibit an impressive variety of structures including zig-zag, solenoidal and beads-on-a-string patterns, depending on system parameters such as salt concentration, sphere charge as well as the chain contour length (per sphere). The present results predict fibers of compact zig-zag structure within the physiologically relevant regime with a diameter of about 30~nm, when DNA-histone parameters are adopted.
In the next part, a numerical method is developed in order to investigate the role of thermal fluctuations on the structure and thermodynamic phase behavior of polyelectrolyte-macroion complexes. This is based on a saddle-point approximation, which allows to describe the experimentally observed reaction (or complexation) equilibrium in a dilute solution of polyelectrolytes and macroions on a systematic level. This equilibrium is determined by the entropy loss a single polyelectrolyte chain suffers as it binds to an oppositely charged macroion. This latter quantity can be calculated from the spectrum of polyelectrolyte fluctuations around a macroion, which is determined by means of a normal-mode analysis. Thereby, a stability phase diagram is obtained, which exhibits qualitative agreement with experimental findings.
At elevated complex concentrations, one needs to account for the inter-complex interactions as well. It will be shown that at small separations, complexes undergo structural changes in such a way that positive patches from one complex match up with negative patches on the other. Furthermore, one of the polyelectrolyte chains may bridge between the two complexes. These mechanisms lead to a strong inter-complex attraction. As a result, the second virial coefficient associated with the inter-complex interaction becomes negative at intermediate salt concentrations in qualitative agreement with recent experiments on solutions of nucleosome core particles.
In dieser Arbeit werden Gleichgewichtsstrukturen und die thermodynamischen Phasen von Komplexen aus geladenen Polymeren (Polyelektrolyten) und entgegengesetzt geladenen Kugeln (Makroionen) untersucht. Polyelektrolyt-Makroion-Komplexe bilden ein grundlegendes und wiederkehrendes Prinzip in der Physik weicher Materie sowie in Chemie und Biologie. In zahlreichen technologischen Prozessen finden sich ebenfalls Anwendungsbeispiele für derartige Komplexe. Zusätzlich zu ihrem häufigen Auftreten sind sie aufgrund ihrer Vielfalt von strukturellen Eigenschaften von grundlegendem Interesse. Diese Vielfalt wird durch ein Zusammenspiel von elektrostatischen Wechselwirkungen sowie elastischen und entropischen Effekten aufgrund von Konformationsänderungen in der Polymerkette bedingt und bildet das zentrale Thema der theoretischen Studien, die mit dieser Arbeit vorgelegt werden. Verschiedene Strukturen und Prozesse, die stark gekoppelte Komplexe beinhalten - das sind solche, für die eine hohe Adsorptionsenergie und geringe Fluktuationen in den Polymerketten charakteristisch sind -, bilden das Hauptthema der Arbeit.
Basierend auf einer dimensionslosen Darstellung wird im ersten Teil der Arbeit in einer umfassenden Analyse das strukturelle Phasenverhalten einzelner Polyelektrolyt-Makroion-Komplexe behandelt. Der Schwerpunkt wird hier auf das Wechselspiel zwischen Effekten aufgrund der Polyelektrolytkettenlänge, ihrer mechanischen Persistenzlänge, der Salzkonzentration und der Ladung des Makroions gelegt. Die Ergebnisse werden in allgemeinen Phasendiagrammen zusammengestellt, das das Aufwickeln-Abwickeln-Verhalten der Polyelektrolytkette auf einem Makroion beschreibt. Ein Zustand mit komplett aufgewickelter Kette tritt typischerweise bei mittleren Salzkonzentrationen und Kettenlängen auf; häufig ist hier die auf dem Makroion adsorbierte Gesamtladung des Polyelektrolyts größ er als die Ladung des nackten Makroions, d.h. es findet in hohem Grad Ladungsinversion statt.
Äußerst bemerkenswerte Eigenschaften treten auf, wenn eine einzelne lange Polyelektrolytkette viele, ihr entgegengesetzt geladene Kugeln komplexiert. In biologischen Systemen findet man solche Komplexe zwischen DNS, die die genetische Information einer Zelle trägt, und kleinen, entgegengesetzt geladenen Histonproteinen. Diese Komplexe dienen als effizienter Mechanismus, die groß e Menge an DNS im Mikrometer-groß en Zellkern eukaryotischer Zellen zu komprimieren. Die dadurch erhaltene komplexe Faser, eine Chromatinfaser, hat unter physiologischen Bedingungen einen Durchmesser von nur etwa 30~nm. Neue Experimente haben gezeigt, dass eine räumliche Zickzack-Anordnung einzelner DNA-Histon-Komplexe entlang der Chromatinfaser vorliegt. In der hier vorgelegten Arbeit wird eine numerische Methode vorgestellt, die auf einem einfachen Ketten-Kugel-Zell-Modell basiert und die die systematische Untersuchung des Mechnismus zur Faserbildung ermöglicht, wobei sowohl elektrostatische als auch elastische Wechselwirkungen berücksichtigt werden. Es wird gezeigt, dass stabile Komplexfasern in Abhängigkeit von der Salzkonzentration, der Kugelladung und der Kettenkonturlänge eine Vielfalt von Strukturen aufweisen, darunter Zickzack-, Solenoid- und Perlenkettenformen. Für physiologisch relevante Bedingungen werden mit dieser Methode für DNA-Histon-Komplexe Fasern kompakter Zickzack-Struktur mit einem Durchmesser von etwa 30~nm erhalten.
Im folgenden Teil wird eine numerische Methode entwickelt, um den Einfluss thermischer Fluktuationen auf Struktur und thermodynamisches Phasenverhalten der Polyelektrolyt-Makroion-Komplexe zu untersuchen. Basierend auf der Sattelpunktsnäherung werden die experimentell beobachteten Reaktionsgleichgewichte in verdünnten Lösungen von Polyelektrolyten und Makroionen systematisch beschrieben. Das Gleichgewicht ist durch einen Verlust an Entropie für die einzelne Polyelektrolytkette durch die Bindung an das entgegengesetzt geladene Makroion gekennzeichnet. Diese Größ e wurde aus dem Spektrum der Polyelektrolytfluktuationen um das Makroion erhalten und mittels einer Analyse der Normalmoden berechnet. Hierüber wird ein Phasendiagramm zur Stabilität der Komplexe erhalten, das qualitativ gute Übereinstimmungen mit experimentellen Ergebnissen aufweist.
Bei höheren Komplexkonzentrationen müssen auch die Wechselwirkungen zwischen den Komplexen berücksichtigt werden. Es wird gezeigt, dass sich die Struktur der Komplexe bei kleinen Abständen so ändert, dass positiv geladene Bereiche eines Komplexes mit negativ geladenen auf einem Nachbarkomplex räumlich korrelieren. Weiterhin können einzelne Polyelektrolytketten als verbrückendes Element zwischen zwei Komplexen dienen. Dieser Mechanismus führt zu starker effektiver Anziehung zwischen den Komplexen. In Übereinstimmung mit kürzlich durchgeführten Experimenten ist als Folge davon der zweite Virialkoeffizient der Wechselwirkung zwischen Komplexen bei mittleren Salzkonzentrationen negativ.
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Dias, Jérôme. « Profondeur par la couleur : analyse spatio-spectrale d'un système chromatique ». Thesis, Grenoble, 2013. https://tel.archives-ouvertes.fr/tel-03210653.
Texte intégralRésumé :
La profondeur est une information importante en complément d'une image couleur, pour interpréter le contenu d'une scène. Nous proposons un système d'imagerie chromatique pour acquérir en simultané ces deux informations. Celui-ci se compose d'une optique présentant du chromatisme longitudinal qui a pour propriété d'effectuer un filtrage spatio-spectral, variable en fonction de la profondeur des objets qui composent la scène. Ce filtrage génère un flou image dépendant de la longueur d'onde et de la profondeur. Pour mesurer ce flou, on a généralement recours à un capteur d'image revêtu d'une mosaïque de filtres dite de Bayer, conçu pour l'acquisition d'image couleur. Il est montré qu'une analyse par couleur (RGB) de la dispersion spatiale d'une telle image, permet d'estimer la profondeur sans ambiguïté et de reconstituer l'image couleur nette correspondante. Cependant cette méthode est efficace pour reconstituer l'image couleur nette mais ne permet d'obtenir qu'une faible précision de profondeur. Pour améliorer cette précision, nous proposons un système d'imagerie chromatique différent, composé d'un capteur revêtu d'une mosaïque de filtres adaptée à l'acquisition d'une image spectrale.Nous avons établi un modèle spectral permettant de simuler l'image mosaïque acquise à partir d'un tel système. Puis nous avons mis en place une procédure d'analyse spatio-spectrale, afin d'estimer conjointement la profondeur et l'image couleur nette des objets de la scène correspondante. A partir de celle-ci nous avons établi deux algorithmes d'estimation basés sur un problème inverse. Le premier inclut les paramètres physiques du système alors que le second est appliqué de manière aveugle à partir d'une base de données d'images. Un démonstrateur système a été réalisé pour évaluer les performances expérimentales de ces méthodes, pour différents types de scènes.Les algorithmes développés montrent qu'il est possible d'améliorer la précision de l'estimation de profondeur d'un système chromatique, en effectuant une analyse multispectrale. Cette approche ne nuit pas à la qualité de l'image couleur reconstruite. De plus, le premier algorithme mis en place nous a permis d'établir un critère pouvant être utilisé pour optimiser les paramètres systèmes, en fonction de l'application souhaitéeLike color, depth is a very useful information to interpret the content of a scene. Depth can be estimated from an acquisition obtained with a chromatic imaging system. It consists of an optical system with an axial chromatic aberration. This aberration creates an image blur that depends on the wavelength and the depth. To measure this, an image sensor with a Bayer color filter array, particularly suitable for color image acquisition, is generally used. It has been shown that a color (RGB) analysis of the spatial dispersion of such image enabled unambiguous estimation of the depth map and a corresponding sharp color image of the given scene. However, this method is more suitable for EDOFs applications as it reconstructs a sharp color image and provides a low depth accuracy.To improve this technique we propose a different chromatic imaging system, consisting of an image sensor coated with a color customized filter array, suitable to acquire spectral image. In this perspective, we have established a spectral model to simulate the mosaic image. Then we have developed a procedure for spatio-spectral analysis applied to this image, to jointly estimate the depth and the sharp color image of the corresponding scene.From this, two estimation algorithms based on inverse problem solving have been proposed and implemented. The first includes the physical system parameters while the second is a blind approach applied learnt from an images database.An experimental system has been designed, qualified and built to evaluate the real performance of these two methods, for different scenes. The developed algorithms show that it is possible to improve the depth estimation accuracy with a chromatic imaging system, by performing a multispectral analysis. This approach does not affect the reconstructed sharp color image quality. In addition, the first algorithm allowed us to establish an optimization criterion to find the optimal system parameters, for a desired application
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Anupriya, Samadi. « Multi-sensor data fusion for aircraft fuel systems using chromatic processing ». Thesis, University of Liverpool, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.399129.
Texte intégral
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Lloyd, Charles J. C. « A human spatial-chromatic vision model for evaluating electronic displays ». Diss., Virginia Tech, 1990. http://hdl.handle.net/10919/29310.
Texte intégralRésumé :
This dissertation examines those attributes of full-color display systems (particularly color matrix displays) which degrade image quality. Based on this analysis, it is suggested that a comprehensive metric should measure image quality in terms of transmitted signal and noise modulation, both achromatic and chromatic. Moreover, it is suggested that these signal and noise measurements be weighted in terms of human spatial-chromatic visual characteristics.
A review of extant image quality metrics reveals several limitations of these metrics which make them unsuitable for the evaluation of color matrix displays. These limitations include the inability to account for chromatic modulation transfer and chromatic noise as well as the general inability to account for spatial and grey-scale sampling.
This work describes a new methodology for assessing image quality that can be applied to full-color as well as monochromatic, and sampled as well as continuous, display systems. Unlike most display quality metrics, the proposed methodology is not based on the tools of linear systems analysis. Rather, it is based on more veridical models of the human visual system (HVS), including multi-channel models of spatial vision, the zone theory of color vision, physiological models of retinal processes, and models of the optics of the eye.
A display evaluation system consisting of the HVS model used in conjunction with a display simulator is described. The HVS model employs nine image processing stages to account for nonlinear retinal processes, opponent color encoding, and multiple spatial frequency channels. A detailed procedure for using the HVS model to evaluate display systems is provided.
The validity of the HVS model was tested by conducting contrast detection, discrimination, and magnitude estimation experiments on the model. The results of these experiments correspond closely with published human performance data The utility of the display evaluation system was assessed by making image quality predictions for the display systems used in three image quality studies. Image quality predictions using the proposed system correlate strongly with ratings of image quality provided by human subjects. Results of these validation studies indicate that the proposed method of display evaluation is viable and warrants further development.Ph. D.
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Nott, A. « Nitric oxide induces chromatin remodelling in the developing central nervous system ». Thesis, University College London (University of London), 2009. http://discovery.ucl.ac.uk/15822/.
Texte intégralRésumé :
The development of the nervous system is a complex task that involves precise connections between billions of neurons. This is achieved, at least in part, by the overproduction of neurons and the survival of a select few that compete for limited survival and growth promoting factors, such as neurotrophic factors. The neurotrophin brain-derived neurotrophin factor (BDNF) has been shown to play an important role in proliferation and differentiation of cortical neuronal precursors (Bartkowska et al 2007). Moreover, BDNF induces binding of the transcription factor CREB to gene promoters in a nitric oxide (NO)-dependent manner (Riccio et al 2006). NO positively regulates a large number of transcription factors and genes in the nervous system (Hemish et al 2003; Dhakshinamoorthy et al 2007). I have demonstrated that NO achieves this broad level of gene regulation by influencing chromatin remodelling. My data also show that NO accumulates within the nucleus of cortical neurons upon BDNF stimulation, thereby inducing Snitrosylation of a wide array of nuclear proteins. S-nitrosylation of histone deacetylase 2 (HDAC2) decreases its affinity for chromatin, leading to increased histone acetylation levels. This NO-dependent regulation of HDAC2 promotes changes in endogenous gene expression and affects the dendritic length of cortical neurons.
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Mugada, Trilok Ranjan. « Superprimer chromate free coating system for DoD applications / ». Cincinnati, Ohio : University of Cincinnati, 2006. http://www.ohiolink.edu/etd/view.cgi?acc%5Fnum=ucin1145383075.
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MUGADA, TRILOK RANJAN. « SUPERPRIMER : CHROMATE FREE COATING SYSTEM FOR DoD APPLICATIONS ». University of Cincinnati / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1145383075.
Texte intégral
32
Lidon, Maria Sol. « Digital Pre-compensation of Chromatic Dispersion in QPSK high speed telecom systems ». Thesis, KTH, Skolan för informations- och kommunikationsteknik (ICT), 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-51039.
Texte intégralRésumé :
Chromatic dispersion (CD) is one of the most significant impairments in optical fiber communication systems. Since expensive and complex optical components are required to mitigate CD in the optical domain high-speed digital signal processing techniques are becoming an alternative to compensate electronically both non-linear and linear optical fiber degradations in the transmitter or receiver. This thesis investigates a new electronic dispersion compensation technique based on signal predistortion using an electro-optic modulator driven by signals previously filtered by a linear Finite Impulse Response filter. Moreover, since transmitter and local oscillator lasers phase noise has usually been assessedindependently without regard to the effect of chromatic dispersion on the phase noise in the system performance, a comparative study between pre- and postcompensation of chromatic dispersion influence on equalization enhanced phase noise (EEPN) in coherent multilevel systems is carried out. For that purpose, carrier phase estimation is implemented by a one-tap normalized least-meansquare filter. Simulations of chromatic dispersion equalization in the transmitter demonstrate that a 56-Gbit/s QPSK coherent system is able to compensate large amounts of fiber chromatic dispersion using a predistorting linear finite impulse response filter. Concerning impact of chromatic dispersion compensation on equalization enhanced phase noise, simulation results show for postcompensation scheme the local oscillator phase noise limits the EEPN influence in the system. However, when the CD equalization is performed in the transmitter, the transmitter laser phase noise is the limiting factor that determines the EEPN effect in the transmission system. Most of those constraints may be mitigated by performing CD compensation in optical domain in such a way that the EEPN influence could be neglected.
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Whittleston, Robert Andrew. « Bioremediation of chromate in alkaline sediment-water systems ». Thesis, University of Leeds, 2011. http://etheses.whiterose.ac.uk/2024/.
Texte intégralRésumé :
The poorly controlled disposal of chromium ore processing residue (COPR) is a globally widespread problem due to its potential to form chromium contaminated hyperalkaline (pH > 12) leachates. These highly oxidising leachates typically contain chromium in the Cr(VI) oxidation state as its chromate anion (CrO42-). This anion is highly mobile, toxic, carcinogenic, and exhibits a high degree of bioavailability. Under reducing conditions chromium exists in the non-toxic and poorly soluble Cr(III) oxidation state. Thus, the reduction of Cr(VI) to Cr(III) is often the goal of remediative strategies. In anaerobic subsurface environments where reducing conditions are established by the indigenous microbial population, chromium reduction can occur naturally. The microbial transformation of Cr(VI) to Cr(III) can be both a result of its direct use in microbial metabolism, or through its indirect reaction with microbially produced reduced species, e.g. Fe(II). This study has used a multidisciplinary approach to investigate the biogeochemical influences on the fate and stability of Cr(VI) leaching from a site of COPR in the north of England. Reducing sediments encountered directly beneath the COPR waste were found contain elevated concentrations of chromium. These sediments were shown to be able to remove aqueous Cr(VI) from solution when incubated with contaminated site groundwater in microcosm incubation experiments. This removal is likely a result of the abiotic reduction by soil associated microbially produced Fe(II), followed by precipitation as insoluble Cr(III) hydroxides. X-ray absorption spectroscopy (XAS) and electron microscopy confirms the association of chromium as Cr(III) with iron in these soils, hosted as a mixed Cr(III)-Fe(III) oxyhydroxide phase. Upon air oxidation, only minor amounts of chromium was remobilised from these sediments as Cr(VI). A diverse population of alkaliphilic microorganisms are indigenous to this horizon, capable of successful metabolism despite elevated pH values. This population was found to contain a consortium of microorganisms capable of iron reduction when incubated at pH 9 to 9.5. Microbial community analysis found taxonomic similarity to several known metal reducing alkaliphiles from the phylum Firmicutes. These results suggest that the novel action of iron reducing alkaliphiles indigenous to reducing sediments beneath COPR sites may provide zones of natural chromium attenuation via microbially mediated mechanisms of Cr(VI) transformation.
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Grenar, David. « Řešení nasazení DWDM systémů na 100G a 400G ». Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2016. http://www.nusl.cz/ntk/nusl-242064.
Texte intégralRésumé :
The aim of this master´s thesis is an explanation of the problem of transport optical networks with Dense Wavelength Division Multiplexing. DWDM principle, properties and limit of transmission system. Focus of thesis is also specification properties of migration transmission system to higher speed 40G, 100G and in future to 400G. Part of thesis is outlined the basic division of multiplexing system, there are discussed the basic solutions of wavelength multiplexes CWDM and DWDM, focus for the effects of nonlinear phenomena and parasitic modulation FWM, SPM and XPM in modulation DP-QPSK and 16-QAM. In practicle part we will make measurement of properties of 10G and then experimental measurement parameters on 100G.
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Holgate, Robert George Edward. « The use of the yeast two-hybrid system as a means of identifying protein interactors of the human protein, BMI-1 ». Thesis, University College London (University of London), 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.322737.
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Colì, Davide. « Magnetic Polymer Models for Epigenomic Spreading and Chromatin Organization ». Doctoral thesis, Università degli studi di Padova, 2020. http://hdl.handle.net/11577/3426255.
Texte intégralRésumé :
In this thesis we present a detailed investigation of the interplay between 3D organization of the chromatin and epigenomic spreading in Eukaryotic nuclei, via polymer physics models.
We begin with a review of the biology behind epigenetic processes, and of some basic physical models that have been proposed to describe them. We also examine the model presented in [1], and study in details its equilibrium and non-equilibrium dynamics via extensive molecular dynamic simulations. At equilibrium we confirm the existence of a first-order phase transition between a swollen and epigenetically disordered phase, and a compact ordered one. At non-equilibrium we prove the existence of two novel phases [2] where the polymer is organized in a compact-disordered or swollen-ordered fashion.
We extend the model by inserting “genomic bookmarking” [2], that is transcription factors permanently bound to the DNA and which enhance the positive feedback loop in the epigenetic machinerie. We also develop a more realistic, biologically inspired, model which successfully reproduces the distribution of epigenetic marks in a Drosophila chromosome.
We next discuss the model proposed in [1] and its relation with magnetic polymer models on a lattice [3]. We find a Landau-Ginzburg-like expression for the free-energy of a dense magnetic polymer in the mean-field approximation. The new free-energy, and ad hoc Montecarlo simulations, confirm the presence of a first-order phase transition between a swollen-disordered phase and a compact-ordered one at equilibrium. We also study the non-equilibrium kinetic of the mean-field model by employing a set of opportunely modified “Model A” equations.
At last, we develop a phenomenological mean-field model for a melt of chromatin fibers in a closed system akin to the Eukaryotic nuclei [4]. The phenomenological free-energy will depend on a conserved density field and a non-conserved magnetisation field. The equilibrium phases will be hence investigated analytically via a common-tangent construction construction, and include both uniform and demixed phases undergoing phase separation. The dynamics of the equilibrium phases is then studied via a set of “Model C” equations in order to estimate the critical coarsening exponents. Finally, we insert in the kinetic equations some non-equilibrium terms akin to a first-order reaction which arrest
the phase separation.
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Reddington, James Peter. « Role for the DNA methylation system in polycomb protein-mediated gene regulation ». Thesis, University of Edinburgh, 2012. http://hdl.handle.net/1842/8138.
Texte intégralRésumé :
Chromatin structure and epigenetic mechanisms play an important role in initiating and maintaining the intricate patterns of gene expression required for embryonic development. One such mechanism, DNA methylation (5mC), involves the chemical modification of cytosine bases in DNA and is implicated in maintaining patterns of transcription. However, many fundamental aspects of DNA methylation are not fully understood, including the mechanisms by which it influences transcriptional states. Recent data suggest functional links between DNA methylation and a second epigenetic mechanism that has important roles in transcriptional repression, the polycomb group (PcG) repressor system. Here, I suggest that an intact DNA methylation system is required for the repression of many PcG target genes by influencing the genomic targeting of the polycomb repressor 2 complex (PRC2) and its signature histone modification, H3K27me3 (K27me3). I demonstrate differential genomic localisation of K27me3 at gene promoter regions in hypomethylated mouse embryonic fibroblast (MEF) cells deficient for the major maintenance DNA methyltransferase, Dnmt1. Globally, Dnmt1-/- MEFs have a higher level of the K27me3 mark than controls, as assessed by western blot and immunofluorescence. I observe increased K27me3 at a relatively small number of gene promoters in Dnmt1-/- MEFs that often are associated with high levels of DNA methylation in wildtype MEFs, consistent with the notion that DNA methylation is capable of antagonising PRC2 binding at certain loci. Conversely, I show that a large number of developmentally important genes that are normally repressed and highly bound by K27me3, including classic polycomb targets, the Hox genes, display dramatically reduced association with K27me3 in Dnmt1-/- MEFs. Many of these genes, but not all, show reciprocal increases in promoter H3K4me3 modification and are transcriptionally de-repressed in Dnmt1-/- MEFs. I suggest that these genes are mostly associated with CpG-rich promoters with low levels of DNA methylation in wildtype cells, implying that their silencing is not dependent on the canonical role of DNA methylation. Consistent with the findings of recently published work, I suggest a working model where PRC2 binding in wildtype cells is restricted by CpG methylation. According to this model, the differential genomic location of K27me3 in hypomethylated Dnmt1-/- MEFs is explained by a redistribution of PRC2 to normally DNA methylated, unbound loci, resulting in a titration effect and coincident loss of K27me3 from normal targets. It was also apparent that certain PRC2-target genes, including the developmentally important Hox gene clusters, are strongly affected in Dnmt1-/- MEFs, displaying striking loss of K27me3. As intergenic transcription has been implicated in relief from polycomb silencing and abundant intergenic transcription has been reported within Hox clusters, I measured RNA expression at Hox clusters and a small number of other PcG target genes in Dnmt1-/- MEFs using highdensity tiling arrays. In Dnmt1-deficient MEFs, widespread increases in intergenic transcription were observed within Hox clusters. In addition, mapping of the elongatingpolymerase- associated H3K36me3 histone modification showed widespread increases in this mark at intergenic and promoter regions in Dnmt1-/- MEFs. Increased local intergenic RNA and H3K36me3 were found to correlate with K27me3 loss for this cohort of genes. I suggest a working model where increased intergenic transcription and H3K36me3 in Dnmt1-/- MEFs leads to accelerated loss of K27me3 at certain loci, including Hox clusters. Taken together with recently published data, this work suggests that a major role of DNA methylation is in shaping the PRC2/K27me3 landscape. The potential implications of this putative role for DNA methylation are widespread, including our knowledge of how DNA methylation influences transcriptional regulation, and the consequence of rearranged DNA methylation patterns that are observed in many diseases including cancers.
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FITTI, Matteo. « Non-contact smart measurement systems for in-line quality control of precision turned parts ». Doctoral thesis, Università Politecnica delle Marche, 2020. http://hdl.handle.net/11566/274500.
Texte intégralRésumé :
Questa tesi è il risultato del lavoro svolto nell'ambito del progetto europeo H2020 GO0D MAN e intende essere un contributo alla realizzazione del paradigma dell' Industry 4.0. In particolare, riguarda lo sviluppo di sistemi intelligenti di controllo qualità in linea.
Il lavoro presenta lo sviluppo di due sistemi: a) un sistema di misura automatizzato basato su un sensore cromatico confocale per controllare le dimensioni dei componenti metallici torniti e b) un sistema di controllo automatizzato basato su visione artificiale per verificare la presenza di bave dovute al processo di foratura sulle stesse parti.
Questi componenti metallici, costituiti da piccoli cilindri cavi con numerosi fori laterali, sono utilizzati nelle valvole idrauliche destinate all'industria automobilistica. Il controllo di qualità di queste parti richiede la verifica di tolleranze dimensionali rigorose e delle prestazioni funzionali.
L'obiettivo generale del progetto è realizzare un controllo di qualità in linea al 100% al fine di prevenire la generazione e la propagazione di difetti all'uscita della stazione di lavorazione di tornitura.
I due sistemi sviluppati presentano un comportamento intelligente, finalizzato alla gestione dell'incertezza di misura e alla riduzione del rischio di diagnosi errate. Il livello di automazione e l'approccio ottico senza contatto adottato consentono di estendere i controlli precedentemente effettuati su campioni statistici al 100% della produzione.
Dopo aver presentato i casi industriali, questa tesi discute la progettazione concettuale di ciascun sistema, i passaggi per la realizzazione dei prototipi, la loro caratterizzazione in condizioni di laboratorio e infine la dimostrazione in una vera linea di produzione.This thesis is the result of work carried out within the European project H2020 GO0D MAN and intends to be a contribution to realize the Industry 4.0 paradigm. In particular, it concerns the development of in-line smart quality control systems. The work presents the development of two systems: a) an automated measurement system based on a confocal chromatic sensor for checking the dimensions of turned metal components and b) an automated control system based on computer vision for checking the presence of burrs due to the drilling process on the same parts. These metal components, which consist of little hollow cylinders with several lateral holes, are used in hydraulic valves intended for use in the automotive industry. The quality control of these parts requires the verification of stringent dimensional tolerances and functional performances. The overall objective of the project is to realize an in-line 100% quality control in order to prevent the generation and propagation of defects at the exit of the turning processing station. The two systems developed exhibit smart behaviour, aimed at managing measurement uncertainty and reducing the risk of misdiagnosis. The automation level and the optical non-contact approach adopted allows to extend the controls previously made on statistical samples to 100% of the production. After presenting the industrial cases, this thesis discusses the conceptual design for each system, the steps for the realization of the prototypes, their characterization in laboratory condition and finally the demonstration in a real production line.
39
Xu, Tianhua. « DSP based Chromatic Dispersion Equalization and Carrier Phase Estimation in High Speed Coherent Optical Transmission Systems ». Doctoral thesis, KTH, Optik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-94835.
Texte intégralRésumé :
Coherent detection employing multilevel modulation formats has become one of the most promising technologies for next generation high speed transmission systems due to the high power and spectral efficiencies. Using the powerful digital signal processing (DSP), coherent optical receivers allow the significant equalization of chromatic dispersion (CD), polarization mode dispersion (PMD), phase noise (PN) and nonlinear effects in the electrical domain. Recently, the realizations of these DSP algorithms for mitigating the channel distortions in the coherent transmission systems are the most attractive investigations. The CD equalization can be performed by the digital filters developed in the time and the frequency domain, which can suppress the fiber dispersion effectively. The PMD compensation is usually performed in the time domain with the adaptive least mean square (LMS) and constant modulus algorithms (CMA) equalization. Feed-forward and feed-back carrier phase estimation (CPE) algorithms are employed to mitigate the phase noise (PN) from the transmitter (TX) and the local oscillator (LO) lasers. The fiber nonlinearities are compensated by using the digital backward propagation methods based on solving the nonlinear Schrödinger (NLS) equation and the Manakov equation. In this dissertation, we present a comparative analysis of three digital filters for chromatic dispersion compensation, a comparative evaluation of different carrier phase estimation methods considering digital equalization enhanced phase noise (EEPN) and a brief discussion for PMD adaptive equalization. To implement these investigations, a 112-Gbit/s non-return-to-zero polarization division multiplexed quadrature phase shift keying (NRZ-PDM-QPSK) coherent transmission system with post-compensation of dispersion is realized in the VPI simulation platform. In the coherent transmission system, these CD equalizers have been compared by evaluating their applicability for different fiber lengths, their usability for dispersion perturbations and their computational complexity. The carrier phase estimation using the one-tap normalized LMS (NLMS) filter, the differential detection, the block-average (BA) algorithm and the Viterbi-Viterbi (VV) algorithm is evaluated, and the analytical predictions are compared to the numerical simulations. Meanwhile, the phase noise mitigation using the radio frequency (RF) pilot tone is also investigated in a 56-Gbit/s NRZ single polarization QPSK (NRZ-SP-QPSK) coherent transmission system with post-compensation of chromatic dispersion. Besides, a 56-Gbit/s NRZ-SP-QPSK coherent transmission system with CD pre-distortion is also implemented to analyze the influence of equalization enhanced phase noise in more detail.QC 20120528
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Rallis, Ilias. « Intelligent chromatic fibre optic sensors and monitoring systems for enhancing useful by-products from anaerobic digestion ». Thesis, University of Liverpool, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.417968.
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Danh, Tu Thien. « ANALYSIS OF CHROMATIN ACCESSIBILITY OF THE HUMAN C-MYC REPLICATION ORIGIN ». Wright State University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=wright1449845546.
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Rieck, Daniel C. « MEMS fabricated nanopores and micropores functionalized with chromate-selective solvent polymeric membrane ». Pullman, Wash. : Washington State University, 2008. http://www.dissertations.wsu.edu/Thesis/Fall2008/d_rieck_012609.pdf.
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Thesis (M.S. in chemical engineering)--Washington State University, December 2008.Title from PDF title page (viewed on Apr. 10, 2009). "Department of Chemical Engineering." Includes bibliographical references.
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Airiau, Mecthilde. « Les mots et les usages de la couleur chez les peintres du Trecento florentin ». Electronic Thesis or Diss., Sorbonne université, 2025. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2025SORUL017.pdf.
Texte intégralRésumé :
Cette thèse s'attache à montrer les usages et les fonctions de la couleur dans la peinture sur panneau de bois florentine au Trecento. Il s'agit du premier travail sur la question qui, pour dépasser la seule analyse des teintes, s'appuie sur une méthode pluridisciplinaire convoquant la lexicographie, les études matérielles et les analyses visuelles. Afin de déterminer la place de la couleur dans la société florentine, la première partie donne lieu à une vaste enquête sur le vocabulaire de la couleur dans les langues italiennes du Trecento, qui permet de constater l'importance du rouge pour la société florentine, d'une part, et la neutralité des termes de couleur indépendamment de tout contexte d'autre part. La deuxième partie est l'occasion d'une synthèse sur l'étude des sources de l'histoire matérielle de la couleur et d'un panorama des matériaux employés et de leur mise en œuvre. Elle met en évidence la complexité inhérente à la technique de la tempera et la systématicité de mise en œuvre des pigments qui en résultent, ce qui n'exclut pas pour autant une certaine adaptabilité de la technique aux désirs des peintres. Enfin, la troisième partie examine le fonctionnement et les fonctions de la couleur dans les images, tant d'un point de vue iconographique que pictural. L'étude met ainsi au jour les systèmes qui gouvernent les choix des peintres en matière de couleur en montrant que, si on peut révéler certaines préférences individuelles, le déploiement des couleurs dans les peintures sur panneau de bois répond à des logiques iconographique, rhétoriques et fonctionnelles, elles-mêmes découlant du contexte intellectuel, religieux et artistique dans lequel elles s'inscriventThis thesis investigates the uses and functions of colour in Florentine panel painting of the Trecento. As the first study on this topic, it moves beyond a mere analysis of hues, using a multidisciplinary approach that incorporates lexicography, material studies, and visual analysis. To determine the role of colour within Florentine society, the first section undertakes a comprehensive examination of colour vocabulary in 14th-century Italian languages, revealing both the significance of red within Florentine culture and the neutrality of colour terms regardless of context. The second section provides a synthesis of previous studies on the material history of colour and an overview of the materials and their application techniques. It highlights the inherent complexity of tempera techniques and the systematic use of pigments, while also allowing for some adaptability to artists' preferences. Finally, the third section examines the functions of colour within images, from both iconographic and pictorial perspectives. This study brings to light the systems underpinning painter colour choices, showing that, while certain individual preferences may be identified, the use of colour in panel paintings follows iconographic, rhetorical, and functional rationales reflecting the intellectual, religious, and artistic context of the period
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Garinther, Wendy Irene. « Studies of the topoisomerase and cofactor requirements for nucleosome reconstitution in a yeast chromatin assembly system ». Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/mq22598.pdf.
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RANGEL, MÁRCIA MOREIRA. « CHROMATIC PROJECT FOR INFORMATION SYSTEMS : PROPOSAL FOR THE USE OF COLOR IN WAYFINDING FOR HEALTH CARE FACILITIES ». PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2016. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=31388@1.
Texte intégralRésumé :
PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROCOORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
PROGRAMA DE SUPORTE À PÓS-GRADUAÇÃO DE INSTS. DE ENSINO
A cor é inerente à experiência visual humana, sendo um atributo importante do projeto do ambiente construído nos Estabelecimentos Assistenciais de Saúde (EAS). Nos EAS a cor tem usos diversificados. Sob o viés funcional os códigos da linguagem cromática conformam a cor-informação com o sentido de auxiliar no desempenho do espaço. Ao tratar da orientação espacial do usuário, essa abordagem é pelo wayfinding, para o uso da cor-informação nos sistemas informacionais do ambiente construído – arquitetura, objetos e mensagens adicionais. Esses sistemas são pertinentes aos campos da Arquitetura, do Design de Interiores e do Design Gráfico. A partir do entendimento de que o potencial informacional da cor é condicionado pelas relações de diversas variáveis pertinentes ao seu contexto, esse estudo desenvolveu o modelo do Projeto Cromático para os Sistemas Informacionais (PCSI). O PCSI é uma proposta de encaminhamento de projeto que contempla as interações de aspectos fundamentais acerca da cor-informação no ambiente construído. Desenvolveram-se dois estudos de caso nos quais foram verificadas as questões apontadas no PCSI. Os dados mostram que a eficiência da cor-informação nos deslocamentos do usuário em EAS implica uma condição que envolve o atendimento dos seguintes aspectos: a ação interdisciplinar entre os projetistas ao longo dos processos dos projetos que envolvem o uso da cor no ambiente, o aporte teórico acerca dos fundamentos da cor, cor-informação, wayfinding e Ergonomia, integração da cor-informação aos sistemas informacionais e esses às necessidades do usuário real, aquele que irá interagir com o ambiente.
Color is inherent in the human visual experience and is therefore an important attribute in designing a built environment for Health Care Facilities (EAS). In this environment, color has varied uses. From a functional viewpoint, chromatic language codes conform with the color-information so as to assist in the performance of space. In dealing with the user s spatial orientation this approach is for wayfinding, for the use of color-information in the information systems of the built environment - architecture, objects and additional messages. These systems are relevant to projects in the fields of Architecture, Interior Design and Graphic Design. Based on the understanding that the informational potential of color is conditioned to the relation of several variables relevant to their context, this study developed the Chromatic Design model for Information Systems (PCSI). The PCSI is a project-forwarding proposal that includes the interactions of fundamental aspects of color-information in the built environment. Two case studies were developed in which the issues raised in the PCSI were checked. Data show that color-information efficiency in a user s movement through an EAS implies a condition that involves satisfying the following aspects: an interdisciplinary action between designers throughout the processes of the projects involving the use of color in the environment, the theoretical contribution of color basics, color-information, wayfinding and Ergonomics, integrating color-information to information systems and integrating these to the needs of the real user who will be interacting with the environment.
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Aitken, Sarah Jane. « The pathological and genomic impact of CTCF depletion in mammalian model systems ». Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/284403.
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CCCTC-binding factor (CTCF) binds DNA, thereby helping to partition the mammalian genome into discrete structural and regulatory domains. In doing so, it insulates chromatin and fine-tunes gene activation, repression, and silencing. Complete removal of CTCF from mammalian cells causes catastrophic genomic dysregulation, most likely due to widespread collapse of 3D chromatin looping within the nucleus. In contrast, Ctcf hemizygous mice with lifelong reduction in CTCF expression are viable but have an increased incidence of spontaneous multi-lineage malignancies. In addition, CTCF is mutated in many human cancers and is thus implicated as a tumour suppressor gene. This study aimed to interrogate the genome-wide consequences of a reduced genomic concentration of Ctcf and its implications for carcinogenesis. In a genetically engineered mouse model, Ctcf hemizygous cells showed modest but robust changes in almost a thousand sites of genomic CTCF occupancy; these were enriched for lower affinity binding events with weaker evolutionary conservation across the mouse lineage. Furthermore, several hundred genes concentrated in cancer-related pathways were dysregulated due to changes in transcriptional regulation. Global chromatin structure was preserved but some loop interactions were destabilised, often around differentially expressed genes and their enhancers. Importantly, these transcriptional alterations were also seen in human cancers. These findings were then examined in a hepatocyte-specific mouse model of Ctcf hemizygosity with diethylnitrosamine-induced liver tumours. Ctcf hemizygous mice had a subtle liver-specific phenotype, although the overall tumour burden in Ctcf hemizygous and wild-type mice was the same. Using whole genome sequencing, the highly reproducible mutational signature caused by DEN exposure was characterised, revealing that Braf(V637E), orthologous to BRAF(V600E) in humans, was the predominant oncogenic driver in these liver tumours. Taken together, while Ctcf loss is partially physiologically compensated, chronic CTCF depletion dysregulates gene expression by subtly altering transcriptional regulation. This study also represents the first comprehensive genome-wide and histopathological characterisation of this commonly used liver cancer model.
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Lepage, Sarah Isabelle Marie. « Analysis of the mechanism of maintenance of the H3K27 trimethylation mark using a novel chromatin targeting system ». Thesis, University of British Columbia, 2012. http://hdl.handle.net/2429/42161.
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Chromatin replication during cell division must be accurately orchestrated to ensure genetic and epigenetic information is transmitted to cell progeny. Upon cell division, newly synthesized histones assemble onto the newly formed chromatin to replace the disassociated parental histones. As these newly synthesized histones do not contain the same post-translational modifications as their adjacent parental histones, these modifications must be recapitulated after each cell division.
The trimethylation of lysine 27 (K27me3) on histone H3 is associated with transcriptional repression, and is deposited by EZH2, a member of the PRC2 complex. Using a Gal4 DNA binding domain (Gal4DBD) fused to EZH2 coupled with FLP/FRT-based deletion of a gal4 binding site cassette, I provide evidence that, once established, the maintenance of H3K27me3 does not require the presence of the DNA binding sites necessary for the initial deposition of this mark. These results suggest that the presence of specific histone marks may be sufficient to promote reiterative deposition of the same mark on nascent histones in association with DNA replication.
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Levenstein, Mark E. « Development and characterization of a highly defined, fully recombinant in vitro chromatin assembly system with Drosophila factors / ». Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2002. http://wwwlib.umi.com/cr/ucsd/fullcit?p3045785.
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Lim, Hui Jun. « Dynamic regulation of histone lysine methylation via the ubiquitin-proteasome system ». Thesis, Harvard University, 2013. http://dissertations.umi.com/gsas.harvard:11163.
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Lysine methylation is an important post-translational modification found on histones that is added and removed by histone lysine methyltransferases and demethylases, respectively. Lysine methylation occurs in a specific and well-regulated manner, and plays key roles in regulating important biological processes such as transcription, DNA damage and cell cycle. Regulation of the protein abundance of these methylation enzymes particularly by the ubiquitin-proteasome system has emerged as a key mechanism by which the histone methylation status of the cell can be regulated, allowing cells to respond rapidly to specific developmental and environmental cues. In my thesis, I focus on two histone lysine demethylases, KDM4A and PHF8, both of which appear to be regulated by E3 ligases; this regulation impacts their function in the cell. Chapter 2 shows that KDM4A is targeted for proteasomal degradation by the SCFFBXO22, and mis-regulation of KDM4A results in changes in global histone 3 lysine 9 and 36 (H3K9 and H3K36) methylation levels and impacts the transcription of a KDM4A target gene, ASCL2. Chapter 3 shows how PHF8 is targeted for proteasomal degradation by the APCCDC20 via a novel, previously unreported LxPKxLF motif on PHF8. I also found that similar to other APCCDC20 substrates like Cyclin B, PHF8 is an important G2-M regulator, loss of which results in cell cycle defects such as prolonged G2 and defective M phases. To further interrogate PHF8 biology, Chapter 4 describes the generation of a PHF8 conditional knockout mouse. PHF8 biology is interesting and relevant to human disease, as mutations are found in X-linked intellectual disability and autism. Complete loss of PHF8 by full body knockout in the mouse appears to be embryonically lethal, underscoring its key role in early development. This mouse model would allow us to extensively study the biochemistry and biology of PHF8 in the context of development and especially in brain function, where it is anticipated to play key roles. Overall, my dissertation work provides mechanistic and biological insights into how histone demethylases are dynamically regulated by the ubiquitin-proteasome system, providing an extra dimension to our understanding of how chromatin marks can be regulated.
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Bauer, Moritz 1987. « Integrative analysis of X-chromosome reactivation kinetics in a novel reprogramming system ». Doctoral thesis, Universitat Pompeu Fabra, 2020. http://hdl.handle.net/10803/668761.
Texte intégralRésumé :
The reactivation of the inactive X chromosome has the potential to provide a unique system to study the developmentally induced formation of euchromatin. However, insights into this process were hampered by the lack of adequate systems, which would allow the dissection of the process using high-throughput sequencing techniques. Here I describe the development of a novel induced pluripotent stem cell reprogramming system that allows the isolation of cells poised for X-reactivation, subsequently achieving near-deterministic efficiency of X-reactivation. Utilizing this novel system, we were able to reveal that the reactivation of silenced genes occurs rapidly and can be divided into distinct initiation and completion phases. Similarly, we could show that chromatin opening of the inactive X proceeds in a two-step fashion, initiating in close proximity to previously open regions, and possibly being initiated by pluripotency factors. Finally, we could show that mega-domains and TADs correspond to two different levels of three-dimensional genome organization superimposed on the Xi, independent of gene expression. We conclude that gene expression and chromatin accessibility during X-reactivation share similar kinetics, while genome organization might follow distinct principles.La reactivación del cromosoma X inactivo tiene el potencial de proporcionar un sistema único para estudiar la formación de eucromatina inducida por el desarrollo. Sin embargo, la comprensión de este proceso se vio obstaculizada por la falta de sistemas adecuados, lo que permitiría la disección del proceso utilizando técnicas de secuenciación de alto rendimiento. Aquí describo el desarrollo de un nuevo sistema de reprogramación de células madre pluripotentes inducidas que permite el aislamiento de células preparadas para la reactivación de X, logrando posteriormente la eficiencia casi determinista de la reactivación de X. Utilizando este novedoso sistema, pudimos revelar que la reactivación de genes silenciados ocurre rápidamente y puede dividirse en distintas fases de iniciación y finalización. Del mismo modo, podríamos mostrar que la apertura de cromatina de la X inactiva se realiza en dos pasos, iniciando en las proximidades de regiones previamente abiertas, y posiblemente iniciada por factores de pluripotencia. Finalmente, podríamos mostrar que los mega-domains y los TADs corresponden a dos niveles diferentes de organización del genoma tridimensional superpuestos en el Xi, independientemente de la expresión génica. Llegamos a la conclusión de que la expresión génica y la accesibilidad a la cromatina durante la reactivación X comparten una cinética similar, mientras que la organización del genoma podría seguir principios distintos.