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Jabre, Saline. "Impact of mechanical stress on nucleus morphology and transcription on skeletal muscle". Electronic Thesis or Diss., Sorbonne université, 2022. http://www.theses.fr/2022SORUS561.
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La réponse du noyau aux contraintes mécaniques impliquent les lamines de type A mais aussi la chromatine et les modifications post-traductionnelles des histones. Cette réponse est essentielle à l’adaptation des cellules aux contraintes mécaniques, notamment dans les tissus soumis à des contraintes mécaniques importantes comme le muscle squelettique. Cependant les mécanismes impliqués restent mal connus. Le premier objectif de ma thèse était de déterminer l'impact de la différenciation musculaire sur les caractéristiques nucléaires de cellules musculaires. Les objectifs suivants étaient d’analyser l’effet de l’expression des protéines de l'enveloppe nucléaire (lamines A/C, SUN1 et SUN2) et de la compaction de la chromatine sur la réponse nucléaire aux contraintes mécaniques. J’ai caractérisé la forme nucléaire et des marqueurs d’histone dans des cellules précurseurs musculaires (MuSC) immortalisées obtenus chez des patients sains et dans des myotubes (72h de différenciation). Les marqueurs d’histones suivants ont été analysés : 1-La tri-méthylation de la lysine4 de l'histone H3 (H3K4me3) et l'acétylation de H3K4 (H3K4ac), associés aux gènes activement transcrits 2- H3K27me3, un marqueur de l'hétérochromatine facultative, régulé par le développement 3- et H3K9me3, un marqueur de l'hétérochromatine constitutive. La différenciation en myotubes est associée à une élongation et à une réduction significative du volume nucléaire. De plus, l'intensité du marquage nucléaire H3K27me3 est significativement plus faible dans les myotubes par rapport aux MuSC alors que les intensités nucléaires H3K9me3 et H3K4me3 sont plus élevées. Ces résultats sont compatibles avec les modifications attendues de l'accessibilité de la machinerie transcriptionnelle avec la différenciation myogénique. Dans les myotubes, la déficience en lamines A/C entraîne une déformation nucléaire qui est majorée par le stretch mécanique (étirement cyclique de 10%, 4h) Le stretch est associé à une augmentation significative du volume nucléaire dans les myotubes témoins, qui est abolie dans les myotubes déficients en lamines A/C. Dans les myotubes témoins, le stretch augmente l'intensité du marquage H3K27me3 et réduit l'intensité du marquage H3K4me3 et H3K4ac. Dans les myotubes déficients en lamines A/C, l’intensité des marqueurs actifs de la chromatine est plus élevée en conditions statiques et stretch s’accompagne d’une augmentation paradoxale de H3K4me3 après. L’inhibition spécifique des histones désacétylases de classe I et II par la trichostatine A induit également une augmentation de H3K4ac en conditions statique et après stretch par rapport au myotubes témoins. A l’inverse, dans les myotubes déficients en SUN2 ou SUN1, l'étirement réduit l'intensité de H3K4me3, alors que l'augmentation de l'intensité nucléaire de H3K27me3 est abolie dans les myotubes déficients en SUN2 étirés. Par ailleurs, la déficience en lamines A/C s’accompagne d’une dérégulation majeure des gènes régulant les marqueurs d’histone. Dans l'ensemble, notre étude met en évidence des modifications importantes des marqueurs post-traductionnels des histones au cours de la différenciation musculaire et lors d'un stress mécanique. Les lamines de type A semblent cruciales pour prévenir l'activation anormale des marqueurs actifs de la chromatine dans les myotubes soumis à un défi mécanique. Nos résultats suggèrent que la mécano-réponse chromatinienne est étroitement régulée par les protéines de l'enveloppe nucléaire dans le muscle squelettiqueThe lamina, and specifically A-type lamins, are major contributors to nuclear stiffness and deformations. However, chromatin and its histone modification states also contribute to nuclear mechanics independently of A-type lamins. How A-type lamins and chromatin-mediated mechanoresponse contribute to mechanical load-mediated adaptation in normal and pathological skeletal muscle remains unknown. We sought to determine how muscle differentiation impacts nuclear characteristics in muscle cell precursors (MuSCs) and myotubes. Then, we investigated the respective roles of nuclear envelope proteins (lamin A/C, SUN1 and SUN2) and drug-modulated chromatin compaction on the mechanical load-mediated nuclear response in myonuclei. We used immortalized MuSCs obtained from healthy patients and analyzed nuclear shape and chromatin characteristics in MuSCs and myotubes obtained after 72h of differentiation. Histone modifications were analyzed: a) histone H3 lysine4 tri-methylation (H3K4me3) and H3K4 acetylation (H3K4ac), associated with transcriptionally active genes, b) H3K27 tri-methylation (H3K27me3), a chromatin repression marker, associated with facultative heterochromatin and c) H3K9 tri-methylation (H3K9me3), a chromatin repression marker associated with constitutive heterochromatin and mainly located at the nuclear periphery. Myotube differentiation was associated with nuclear elongation and significant reduction in nuclear volume. In addition, the relative intensity of nuclear H3K27me3 (chromatin repression marker) labelling was significantly lower in myotubes compared to MuSCs, whereas nuclear H3K9me3 and H3K4me3 (chromatin active marker) intensities were higher in myotubes compared to MuSCs, thereby showing that myogenic differentiation is modulating the accessibility of the transcriptional machinery. Myotubes were silenced for LMNA expression with silencing mRNA strategies and submitted to a cyclic stretch (10%,4hours) to investigate A-type lamin’ roles in nuclear shape and chromatin organization during mechanical stress. A-type lamin deficient myotubes had abnormal nuclear shape in static conditions and nuclear deformations further increased after cyclic stretch. Cyclic stretch was associated with a significant increase in nuclear volume in control myotubes that was abolished in A-type lamin deficient myotubes. In addition, stretching increased the intensity of the H3K27me3 and reduced H3K4me3 and H3K4ac intensities of labelling in nuclei from control myotubes. Importantly, A-type lamin deficiency was associated with higher intensity in chromatin active markers at baseline and a paradoxical increased in H3K4me3 after stretch. Consistent modifications in histone modifications were obtained by western-blots in control and A-type deficient myotubes. Interesting, stretch reduced H3K4me3 intensity both in SUN2 or SUN1-deficient myotubes while the increase in the nuclear intensity of the H3K27me3 was abolished in stretched SUN2-deficient myotubes. Transcriptomic changes associated with A-type lamin deficiency support these results. Trichostatin A (TSA) is a powerful and specific Class I and II histone deacetylase inhibitor (HDACi), widely used to increase the expression of genes silenced by chromatin condensation, thereby favoring chromatin decompaction. TSA increased nuclear volume without affecting nuclear shape both in static and stretched conditions. In addition, TSA decreased H3K27me3 and H3K9me3 intensities in static myotubes but did not prevent the stretch-induced increase in H3K27me3 intensity. Overall, our study highlights crucial changes of histone post-translational markers during muscle differentiation and upon mechanical challenge. A-type lamins appear crucial to prevent abnormal activation of chromatin active markers in mechanically challenged myotubes. Moreover, our results suggest that the nuclear mechano-response is tightly regulated by nuclear envelope proteins in skeletal muscle
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Meaders, Johnathan Lee. "Growth, Morphology, and Positioning of Microtubule Asters in Large Zygotes:". Thesis, Boston College, 2020. http://hdl.handle.net/2345/bc-ir:109018.
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Thesis advisor: David R. BurgessMicrotubule (MT) asters are radial arrays of MTs nucleated from a microtubule organizingcenter (MTOC) such as the centrosome. Within many cell types, which display highly diverse size and shape, MT asters orchestrate spatial positioning of organelles to ensure proper cellular function throughout the cell cycle and development. Therefore, asters have adopted a wide variety of sizes and morphologies, which are directly affects how they migrate and position within the cell. In large cells, for example during embryonic development, asters growth to sizes on the scales of hundreds of microns to millimeters. Due to this relatively enormous size scale, it is widely accepted that MT asters migrate primarily through pulling mechanisms driven by dynein located in the cytoplasm and/or the cell cortex. Moreover, prior to this dissertation, significant contributions from pushing forces as a result of aster growth and expansion against the cell cortex have not been detected in large cells. Here we have reinvestigated sperm aster growth, morphology, and positioning of MT asters using the large interphase sperm aster of the sea urchin zygote, which is historically a powerful system due to long range migration of the sperm aster to the geometric cell center following fertilization. First, through live-cell quantification of sperm aster growth and geometry, chemical manipulation of aster geometry, inhibition of dynein, and targeted chemical ablation, we show that the sperm aster migrates to the zygote center predominantly through a pushing-based mechanism that appears to largely independent of proposed pulling models. Second, we investigate the fundamental principles for how sperm aster size is determined during growth and centration. By physically manipulating egg size, we obtain samples of eggs displaying a wide range of diameters, all of which are at identical developmental stages. Using live-cell and fluorescence microscopy, we find strong preliminary evidence that aster diameter and migration rates show a direct, linear scaling to cell diameter. Finally, we hypothesize that a collective growth model for aster growth, or centrosome independent MT nucleation, may explain how the sperm aster of large sea urchin zygotes overcomes the proposed physical limitations of a pushing mechanism during large aster positioning. By applying two methods of super resolution microscopy, we find support for this collective growth model in the form of MT branching. Together, we present a model in which growth of astral MTs, potentially through a collective growth model, pushes the sperm aster to the zygote center
Thesis (PhD) — Boston College, 2020
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Biology
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Russell-Mergenthal, Helen. "Qualitative and quantitative morphology of lateral rectus motoneurons of the principal abducens nucleus". VCU Scholars Compass, 1985. https://scholarscompass.vcu.edu/etd/5602.
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Nine lateral rectus motoneurons of the principal abducens nucleus, intracellularly stained with HRP, were morphometrically analyzed by light microscopy using a new method for determining motoneuron size. Particular emphasis was placed on devising a method of estimating total dendrite size from the proximal dendritic diameter alone.
The dendrites of these cells were divided into three types. One type, the microdendrites, had a consistent diameter of l micrometer, variable but short lengths, and added very little to the overall cell size. The majority of the dendrites on these cells (83) were standard in appearance but they could be separated into two further types. Six dendrites differed from the other 77 in that they were tapering processes which branched minimally, had both a rostrally and a caudally directed secondary dendrite and showed a larger ratio for the sum of the secondary dendrite diameters to the proximal dendrite diameter. The remaining 77 branched extensively and traveled either rostral or caudal in the brainstem. However, the most significant difference was quantitative. The tapering dendrites were approximately 2X the size of the prevalent branching dendrites based on proximal diameter measurements. Correlation coefficients of the relation between proximal diameter and surface area or volume of the entire dendrite increased when the correlations were separated into two types. Therefore, to insure the most accurate total size calculations, the regression lines used for estimating dendrite size were of the separate correlations. Total neuron size was calculated by adding the soma and dendrite surface areas. An intraneuronal comparison of size indicated that the size of the soma was not indicative of the size of the cell and it constituted between 2% to 7% of the total cell size. Comparison of the motoneuron size to the mechanical properties of their muscle units was inconclusive. However, a general tendency for small motoneurons to innervate muscle units of lower force output was observed. The smaller motoneurons were generally more dorsally located in the nucleus.
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Zhao, Min. "Morphology and physiology of neurons in the young rat's ventral nucleus of the lateral lemniscus". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/mq36947.pdf.
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Fukui, Iwao. "Developmental changes in membrane excitability and morphology of neurons in the nucleus angularis of the chick". Kyoto University, 2003. http://hdl.handle.net/2433/148720.
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Chen, Baiyu, i 陳白羽. "Suprachiasmatic nucleus projecting retinal ganglion cells in golden hamsters development, morphology and relationship with NOS expressingamacrine cells". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2006. http://hub.hku.hk/bib/B37238218.
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Chen, Baiyu. "Suprachiasmatic nucleus projecting retinal ganglion cells in golden hamsters development, morphology and relationship with NOS expressing amacrine cells". Click to view the E-thesis via HKUTO, 2006. http://sunzi.lib.hku.hk/hkuto/record/B37238218.
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Graham, Cathy D. "Chemosensitive Neurons of the Locus Coeruleus and the Nucleus Tractus Solitarius: Three Dimensional Morphology and Association with the Vasculature". Wright State University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=wright1409665728.
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Mazzuca, Lisa Marie. "Morphology, star formation, and kinematics of nuclear rings". College Park, Md. : University of Maryland, 2006. http://hdl.handle.net/1903/3805.
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Thesis (Ph. D.) -- University of Maryland, College Park, 2006.Thesis research directed by: Astronomy. 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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Yeung, R. R. "Nuclear spin relaxation and morphology of solid polyolefins". Thesis, University of East Anglia, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.356619.
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Poulet, Axel. "Study of the role of plant nuclear envelope and lamina-like components in nuclear and chromatin organisation using 3D imaging". Thesis, Oxford Brookes University, 2016. http://www.theses.fr/2016CLF22703/document.
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Le complexe linker of nucleoskeleton and cytoskeleton (LINC) est un complexe protéique conservé au cours de l’évolution, reliant les compartiments cytoplasmiques et nucléaires au travers la membrane nucléaire. Bien que les données récentes montrent une de ce complexe dans la régulation de la morphologie nucléaire et de la méiose, son implication dans l’organisation de la chromatine a été moins étudié chez les plantes. Le premier objectif de ce travail était de développer un plugin NucleusJ ImageJ dédié à la caractérisation de la morphologie nucléaire et de l’organisation de la chromatine en 3D. NucleusJ calcul 15 paramètres, y compris la forme et la taille des noyaux ainsi que des objets intra-nuclaires et leur position dans le noyau. Une documentation pour ce programme est disponible pour son utilisation, ainsi que des qu’un jeu données de noyaux pour tester ce programme. Plusieurs améliorations sont en cours pour développer une nouvelle version de ce plugin. Dans une deuxième partie de ce travail, des méthodes d’imagerie 3D ont été utilisées pour étudier la morphologie nucléaire et l’organisation de la chromatine dans les noyaux interphasiques chez Arabidopsis thaliana dans lequel les domaines d’htrochromatique sont groupés en régions detectable appelés chromocentres. Ces chromocentres forment un environnement répressif contribuant la rpression transcriptionnelle de séquences répétées permettant la stabilité du génome. Des mesures quantitatives de la position 3D de chromocentres dans le noyau montrent que la plupart chromocentres sont situés proximité de la périphérie du noyau, mais que cette distance peut être modifiée par le volume nucléaire ou dans certains mutants affectant le complexe LINC. Ce complexe LINC est proposé pour contribuer l’organisation de la chromatine et à son positionnement, de plus la mutation de ce complexe est associée une dérégulation l’inactivation de la transcription, ainsi qu’a une décompaction des séquences hétérochromatiques. La dernière partie de ce travail tire profit de séquences gnomiques disponibles et les données de RNA-seq pour explorer l’évolution des protines de la NE chez les plantes. Au Final, le travail réalisé durant cette thèse associe la génétique, la biologie moléculaire, la bioinformatique et de l’imagerie afin de mieux comprendre la contribution de l’enveloppe nucléaire dans l’organisation de la morphologie du noyaux et de la chromatine et suggère l’implication fonctionnelle du complexe LINC dans ces processusThe linker of nucleoskeleton and cytoskeleton (LINC) complex is an evolutionarily well-conserved protein bridge connecting the cytoplasmic and nuclear compartments across the nuclear membrane. While recent data supports its function in nuclear morphology and meiosis, its implication for chromatin organisation has been less studied in plants. The first aim of this work was to develop NucleusJ a simple and user-friendly ImageJ plugin dedicated to the characterisation of nuclear morphology and chromatin organisation in 3D. NucleusJ quantifies 15 parameters including shape and size of nuclei as well as intra-nuclear objects and their position within the nucleus. A step-by-step documentation is available for self-training, together with data sets of nuclei with different nuclear organisation. Several improvements are ongoing to release a new version of this plugin. In a second part of this work, 3D imaging methods have been used to investigate nuclear morphology and chromatin organisation in interphase nuclei of the plant model Arabidopsis thaliana in which heterochromatin domains cluster in conspicuous chromatin regions called chromocentres. Chromocentres form a repressive chromatin environment contributing to the transcriptional silencing of repeated sequences a general mechanism needed for genome stability. Quantitative measurements of 3D position of chromocentres in the nucleus indicate that most chromocentres are situated in close proximity to the periphery of the nucleus but that this distance can be altered according to nuclear volume or in specific mutants affecting the LINC complex. Finally, the LINC complex is proposed to contribute at the proper chromatin organisation and positioning since its alteration is associated with the release of transcriptional silencing as well as decompaction of heterochromatic sequences. The last part of this work takes advantage of available genomic sequences and RNA-seq data to explore the evolution of NE proteins in plants and propose a minimal requirement to built the simplest functional nuclear envelope. Altogether, work achieved in this thesis associate genetics, molecular biology, bioinformatics and imaging to better understand the contribution of the nuclear envelope in nuclear morphology and chromatin organisation and suggests the functional implication of the LINC complex in these processes
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Mayer, Jürgen. "Investigation of the biophysical basis for cell organelle morphology". Master's thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2010. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-26600.
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It is known that fission yeast Schizosaccharomyces pombe maintains its nuclear envelope during mitosis and it undergoes an interesting shape change during cell division - from a spherical via an ellipsoidal and a peanut-like to a dumb-bell shape. However, the biomechanical system behind this amazing transformation is still not understood. What we know is, that the shape must change due to forces acting on the membrane surrounding the nucleus and the microtubule based mitotic spindle is thought to play a key role. To estimate the locations and directions of the forces, the shape of the nucleus was recorded by confocal light microscopy. But such data is often inhomogeneously labeled with gaps in the boundary, making classical segmentation impractical. In order to accurately determine the shape we developed a global parametric shape description method, based on a Fourier coordinate expansion. The method implicitly assumes a closed and smooth surface. We will calculate the geometrical properties of the 2-dimensional shape and extend it to 3-dimensional properties, assuming rotational symmetry.
Using a mechanical model for the lipid bilayer and the so called Helfrich-Canham free energy we want to calculate the minimum energy shape while respecting system-specific constraints to the surface and the enclosed volume. Comparing it with the observed shape leads to the forces. This provides the needed research tools to study forces based on images.
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Mayer, Jürgen. "Investigation of the biophysical basis for cell organelle morphology". Master's thesis, Max-Planck-Institut für Molekulare Zellbiologie und Genetik, 2008. https://tud.qucosa.de/id/qucosa%3A25225.
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It is known that fission yeast Schizosaccharomyces pombe maintains its nuclear envelope during mitosis and it undergoes an interesting shape change during cell division - from a spherical via an ellipsoidal and a peanut-like to a dumb-bell shape. However, the biomechanical system behind this amazing transformation is still not understood. What we know is, that the shape must change due to forces acting on the membrane surrounding the nucleus and the microtubule based mitotic spindle is thought to play a key role. To estimate the locations and directions of the forces, the shape of the nucleus was recorded by confocal light microscopy. But such data is often inhomogeneously labeled with gaps in the boundary, making classical segmentation impractical. In order to accurately determine the shape we developed a global parametric shape description method, based on a Fourier coordinate expansion. The method implicitly assumes a closed and smooth surface. We will calculate the geometrical properties of the 2-dimensional shape and extend it to 3-dimensional properties, assuming rotational symmetry.
Using a mechanical model for the lipid bilayer and the so called Helfrich-Canham free energy we want to calculate the minimum energy shape while respecting system-specific constraints to the surface and the enclosed volume. Comparing it with the observed shape leads to the forces. This provides the needed research tools to study forces based on images.
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He, Dandan. "Effect of Radiation on the Morphology of Lithium-ion Battery Cathodes". The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1405677300.
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Sharma, Osheen. "Segmentation of cancer epithelium using nuclei morphology with Deep Neural Network". Thesis, KTH, Skolan för kemi, bioteknologi och hälsa (CBH), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-280383.
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Bladder cancer (BCa) is the fourth most commonly diagnosed cancers in men and the eighth most common in women. It is an abnormal growth of tissues which develops in the bladder lining. Histological analysis of bladder tissue facilities diagnosis as well as it serves as an important tool for research. To bet- ter understand the molecular profile of bladder cancer and to detect predictive and prognostic features, microscopy methods, such as immunofluorescence (IF), are used to investigate the characteristics of bladder cancer tissue. For this project, a new method is proposed to segment cancer epithelial us- ing nuclei morphology captured with IF staining. The method is implemented using deep learning algorithms and performance achieved is compared with the literature. The dataset is stained for nuclei (DAPI) and a marker for cancer epithelial (panEPI) which was used to create the ground truth. Three popu- lar Convolutional Neural Network (CNN) namely U-Net, Residual U-Net and VGG16 were implemented to perform the segmentation task on the tissue mi- croarray dataset. In addition, a transfer learning approach was tested with the VGG16 network that was pre-trained with ImageNet dataset. Further, the performance from the three networks were compared using 3fold cross-validation. The dice accuracies achieved were 83.32% for U-Net, 88.05% for Residual U-Net and 82.73% for VGG16. These findings suggest that segmentation of cancerous tissue regions, using only the nuclear morphol- ogy, is feasible with high accuracy. Computer vision methods better utilizing nuclear morphology captured by the nuclear stain, are promising approaches to digitally augment the conventional IF marker panels, and therefore offer im- proved resolution of the molecular characteristics for research settings.
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Goulbourne, Christopher Nicholas. "The effect of farnesylated prelamin A accumulation on nuclear morphology and function". Thesis, University of Oxford, 2011. http://ora.ox.ac.uk/objects/uuid:3a578fbd-3223-42a8-87fd-f20fd7ef3e1e.
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Failure to process prelamin A, by the enzyme ZMPSTE24, leads to the build up of farnesylated prelamin A, which has been implicated in causing the symptoms experienced in laminopathies and HIV therapy. A common feature to these conditions is the development of an irregular nuclear boundary, often including deep invaginations that form a nucleoplasmic reticulum. Additionally, dysregulated lipid synthesis is frequently associated with improper lamin A processing and I set out to address the molecular mechanisms behind these two features that could explain lipoatrophy experienced in patients. By using siRNA targeted against Zmpste24 I utilised an array of biochemical, molecular and imaging techniques to uncover a mechanism that leads to the production of a nucleoplasmic reticulum that was dependent on both the farnesylated tail of prelamin A and the phosphatidylcholine synthesising enzyme CCTα. The morphology of this structure consisted of an invagination of both the inner and outer nuclear membranes with a cytoplasmic core or just invagination of the inner nuclear membrane. Serial section dual axis electron tomography provided a new insight into the ultrastructural changes at the nuclear periphery that revealed novel structural features. The dysregulation of lipid synthesis was assessed by investigating the effects farnesylated prelamin A has on the distribution and dynamics of the transcription factor SREBP-1 and assessment of the downstream consequences this has on its targets that regulate adipocyte differentiation potential. Finally, the metabolomic profile of an HIV protease inhibitor that leads to prelamin A build up was generated and revealed increases in lipolysis, glycolysis and mediators of inflammation. The research presented offers a new insight into the development of a convoluted nuclear boundary and nucleoplasmic reticulum, in the context of lamin A mutants and how dysregulated lipid synthesis, caused by farnesylated prelamin A, leads to lipoatrophy.
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Pompea, Stephen Mark. "The relationship of galaxy morphology to nuclear star formation in noninteracting spiral galaxies". Diss., The University of Arizona, 1989. http://hdl.handle.net/10150/184893.
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Three specific questions concerning the relationship between galaxian morphology and infrared properties were addressed for non-interacting galaxies: (1) Why are high infrared luminosity (L > 10¹⁰ L(⊙)) Sa galaxies scarce compared to Sb and Sc galaxies; (2) Is there a relationship between the bulge to total luminosity and the infrared properties of early type spirals; and (3) Are bars essential to nuclear star formation processes in non-interacting galaxies? These questions were answered using IRAS data, CO (1-0) measurements, 2 μm, 10 μm, and visible CCD observations. Only 4% of Sa's in the Revised Shapley-Ames Catalog (RSAC) with B(Γ) < 12 have infrared luminosities > 10¹⁰ L(⊙), 1/6 of the ratio for Sb's and Sc's. Less than three Sa's of 166 in the RSAC have nuclear starbursts not associated with interactions or active nuclei. A comparison of neutral hydrogen fluxes and CO fluxes with infrared fluxes implies that molecular cloud formation is inhibited in Sa's, leading to the lack of infrared activity. An investigation of the role of bulges in suppressing star formation in Sa through Sb spirals relied on the photometric observations of Kent, Kodaira, and Cornell and on IRAS infrared observations. The bulge to total luminosity is uncorrelated with the ratio of infrared to blue flux, 60 μm/100 μm fluxes, or infrared luminosity. These results indicate that disk star formation is relatively unaffected by bulge size. The hypothesis that high far-infrared luminosities in non-interacting galaxies are dependent on material fed into their nuclei by bars was tested by near infrared imaging of a sample of 15 optically unbarred galaxies in a search for hidden bars. These galaxies were non-interacting, non-Seyfert galaxies with far infrared luminosities > 10¹⁰ L(⊙) and hot colors between 60 and 100 μm (S₆₀/S₁₀₀ > 0.5, indicative of nuclear starbursts). At least 8 of these galaxies do not appear to have bars. Strong bars therefore are not an absolute requirement for high infrared luminosity.
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Rangel, Julio Cesar Ferreira 1963. "Pipe wall damage morphology measurement methodology development for flow assisted corrosion evaluation". Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/84750.
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Thesis (Nucl.E.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering; and, (S.M.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1999.Includes bibliographical references (leaves 103-110).
by Julio Cesar Ferreira Rangel.
S.M.
Nucl.E.
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Tzou, Der-Lii M. "Solid state 13C NMR studies of the Morphology and orientational order of polymer fibers". Diss., Georgia Institute of Technology, 1991. http://hdl.handle.net/1853/30276.
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Nasreddine, Victor Fuad. "Solid state nuclear magnetic resonance spectroscopy of polymer thin films : chain conformation, dynamics, and morphology". Thesis, McGill University, 2002. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=83081.
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This dissertation presents solid-state NMR studies of the chain conformation, dynamics and morphology of three adsorbed polymer systems: two random semi-crystalline copolymers, poly(ethylene-co-acrylic acid) (PEA) and poly(propylene-co-acrylic acid) (PPA), and an amorphous homopolymer, poly(n-butyl methacrylate) (PnBMA). Zirconia (ZrO2) was chosen as the substrate for all three polymers since the binding of carboxylic acids to this metal oxide is well understood. The choice of polymers was based on their particular bulk conformational and dynamic properties as well as their common use in polymer coatings. These studies are motivated by the general lack of a microscopic picture of adsorbed polymers, which can be provided by NMR, and the relevance of chain conformation and dynamics to important polymer film properties such as adhesion.First the chain conformation and surface binding of adsorbed PEA as a function of acrylic acid content are characterized by 13C cross polarization - magic angle spinning (CP-MAS), 2D 1H- 13C wideline separation (WISE) and 1H spin diffusion NMR experiments and FTIR-PAS (Fourier transform infrared photoacoustic spectroscopy) measurements. The most important finding is that the chain conformation of adsorbed PEA is determined primarily by the sticker group density rather than the surface coverage. The second study of PEA concerns the chain dynamics in the bulk and adsorbed states. Variable temperature NMR experiments provide evidence that ethylene segments of adsorbed PEA form partially folded loops rather than flat extended trains. Finally 129Xe NMR studies, used to probe the morphology of adsorbed PEA, show a bulk-like signal only for the highest loadings.
The second system investigated, PPA, is another semi-crystalline random copolymer which binds to zirconia via carboxylate linkages. The 13 C CP-MAS NMR spectra of adsorbed PPAC unexpectedly show splittings normally associated with chain-chain packing in the crystalline regions of bulk polypropylene (PP). The splittings in the spectra of adsorbed PPAC, which are more resolved than in bulk PPA, are proposed to arise from recrystallization of the PP segments between sticker groups.
Finally the interfacial properties of an amorphous homopolymer, PnBMA were studied using 13C and 129Xe NMR to characterize adsorbed and filled samples. PnBMA binds to zirconia via the partial hydrolysis of the ester side chains. The remaining ester chains of adsorbed PnBMA are found to segregate to the polymer/air interface. Both adsorbed and ZrO 2-filled PnBMA show enhanced local segmental mobility. However, the 129Xe NMR measurements of the filled samples are consistent with restricted motion on a larger length scale which may be due to particle bridging.
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Marin, Frédéric. "The complex morphology of radio-quiet active galactic nuclei : multi-wavelength radiative transfer and polarization". Phd thesis, Université de Strasbourg, 2013. http://tel.archives-ouvertes.fr/tel-01001920.
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When probing the inner structures of unresolved astrophysical sources, spectropolarimetry has proven to be a solid tool, both independent and complementary to spectral and timing analyses. In this thesis, I theoretically explore the polarization of Active Galactic Nuclei (AGN), which are powered by accretion onto supermassive black holes and often reveal significant mass outflows. Their emission is strongly anisotropic and the standard model of AGN postulates that the anisotropy is caused by a confinement of the radiation in the funnel of an obscuring body of circumnuclear dust; the radiation is thus forced to escape along the funnel where it photo-ionizes conically shaped outflows. The asymmetrical configuration explains an observational dichotomy where AGN properties are characterized according to the observer's line-of-sight. However, AGN observations differ significantly from one waveband to another and the broadband validity of the unified model has to be tested by a method that gives strong constraints on the AGN morphology. In this thesis, I subsequently investigate how morphological and composition constraints on the different substructures in thermal, radio-quiet Active Galactic Nuclei can be deduced from optical, UV and X-ray polarization properties.
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Morrish, Dru, i DruMorrish@gmail com. "Morphology dependent resonance of a microscope and its application in near-field scanning optical microscopy". Swinburne University of Technology. Centre for Micro-Photonics, 2005. http://adt.lib.swin.edu.au./public/adt-VSWT20051124.121838.
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In recent times, near-field optical microscopy has received increasing attention for its
ability to obtain high-resolution images beyond the diffraction limit. Near-field optical
microscopy is achieved via the positioning and manipulation of a probe on a scale less
than the wavelength of the incident light.
Despite many variations in the mechanical design of near-field optical microscopes almost all rely on direct mechanical access of a cantilever or a derivative form to probe the sample. This constricts the study to surface examinations in simple sample environments. Distance regulation between the sample surface and the delicate probe
requires its own feedback mechanism. Determination of feedback is achieved through
monitoring the shift of resonance of one arm of a 'tuning fork', which is caused by the interaction of the probes tip with the Van der Waals force. Van der Waals force emanates from atom-atom interaction at the top of the sample surface. Environmental contamination of the sample surface with additional molecules such as water makes accurate measurement of these forces particularly challenging. The near-field study of
living biological material is extremely difficult as an aqueous environment is required for its extended survival. Probe-sample interactions within an aqueous environment that
result in strong detectable signal is a challenging problem that receives considerable
attention and is a focus of this thesis.
In order to increase the detectible signal a localised field enhancement in the probing region is required. The excitation of an optically resonant probe by morphology dependent resonance (MDR) provides a strong localised field enhancement. Efficient MDR excitation requires important coupling conditions be met, of which the localisation of the incident excitation is a critical factor.
Evanescent coupling by frustrated total internal reflection to a MDR microcavity provides an ideal method for localised excitation. However it has severe drawbacks if the probe is to be manipulated in a scanning process. Tightly focusing the incident illumination by a high numerical aperture objective lens provides the degree of freedom to enable both MDR excitation and remote manipulation. Two-photon nonlinear excitation is shown to couple efficiently to MDR modes due to the high spatial localisation of the incident excitation in three-dimensions. The dependence of incident excitation localisation by high numerical aperture objective on MDR efficiency is thoroughly examined in this thesis. The excitation of MDR can be enhanced by up to 10 times with the localisation of the incident illumination from the centre of the
microcavity to its perimeter.
Illuminating through a high numerical aperture objective enables the remote noninvasive
manipulation of a microcavity probe by laser trapping. The transfer of photon momentum from the reflection and refraction of the trapping beam is sufficient enough to exert piconewtons of force on a trapped particle. This allows the particle to be held and scanned in a predictable fashion in all three-dimensions. Optical trapping
removes the need for invasive mechanical access to the sample surface and provides a means of remote distance regulation between the trapped probe and the sample. The femtosecond pulsed beam utilised in this thesis allows the simultaneous induction of two-photon excitation and laser trapping. It is found in this thesis that a MDR microcavity can be excited and translated in an efficient manner. The application of this technique to laser trapped near-field microscopy and single molecule detection is of particular interest.
Monitoring the response of the MDR signal as it is scanned over a sample object enables a near-field image to be built up. As the enhanced evanescent field from the propagation of MDR modes around a microcavity interacts with different parts of the sample, a measurable difference in energy leakage from the cavity modes occurs. The definitive spectral properties of MDR enables a multidimensional approach to imaging and sensing, a focus of this thesis. Examining the spectral modality of the MDR signal
can lead to a contrast enhancement in laser trapped imaging. Observing a single MDR mode during the scanning process can increase the image contrast by up to 1:23 times compared to that of the integrated MDR fluorescence spectrum.
The work presented in this thesis leads to the possibility of two-photon fluorescence
excitation of MDR in combination with laser trapping becoming a valuable tool in near-
field imaging, sensing and single molecule detection in vivo. It has been demonstrated
that particle scanned, two-photon fluorescence excitation of MDR, by laser trapping 'tweezers' can provide a contrast enhancement and multiple imaging modalities. The spectral imaging modality has particular benefits for image contrast enhancements.
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Williams, Joshua Steven. "WHEN MOLECULES AND MORPHOLOGY CLASH: REVISITING SPECIES TREE RECONSTRUCTION OF AMBYSTOMATID SALAMANDERS USING MULTIPLE NUCLEAR LOCI". UKnowledge, 2012. http://uknowledge.uky.edu/biology_etds/3.
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The analysis of diverse data sets can yield different phylogenetic estimates that challenge systematists to explain the source of discordance. The Ambystomatidae are a classic example of this phylogenetic conflict. Previous attempts to resolve the ambystomatid species tree using allozymic, morphological, and mitochondrial sequence data have yielded different estimates, making it unclear which data source best approximates ambystomatid phylogeny. We present the first multi-locus DNA sequencebased phylogenetic study of the Ambystomatidae. Because independent loci can contain discordant gene tree histories, concatenating unlinked loci into a single data matrix can lead to strongly supported and erroneous results. Therefore, we utilized a range of analyses, including coalescent-based methods of phylogenetic estimation that account for incomplete lineage sorting and concordance-based methods that estimate the proportion of sampled loci that support a particular clade. We repeated these analyses with the removal of individual loci to determine if any locus has a disproportionate effect on our phylogenetic results. Many deep and relatively shallow clades within Ambystoma were robustly resolved. Analyses that excluded loci produced overlapping posterior distributions, suggesting no disproportionate influence of any particular locus. Our estimates differ from previous hypotheses, although there was greater similarity with previous molecular estimates, relative to morphological estimates.
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後藤, 千恵子. "植物における核膜形態維持の分子機構". 京都大学 (Kyoto University), 2014. http://hdl.handle.net/2433/189653.
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Woller, Kevin Benjamin. "Characterization of the dynamic formation of nano-tendril surface morphology on tungsten while exposed to helium plasma". Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/112365.
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Thesis: Sc. D., Massachusetts Institute of Technology, Department of Nuclear Science and Engineering, 2017.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 133-140).
Tungsten undergoes surface morphology changes on the nanometer scale when subjected to low energy helium ion bombardment. This is due in part to the ion bombardment causing tungsten atoms to move on the surface, but also because of helium implantation and bubble development in the near surface at a depth < 30 nm. At high enough surface temperatures, T/TM >/~ 0.2, where TM is the melting temperature, nanoscale tendrils form on the surface and grow longer with additional bombardment by helium, but will decompose at the same temperature without helium bombardment. A tungsten surface that develops a densely packed layer of nano-tendrils over macroscopic areas greater than the grain size is referred to as tungsten fuzz, and is under intense study in fusion energy research, both for better understanding of how tungsten fuzz forms and of how tungsten fuzz affects the performance of plasma-facing components. The necessity of helium irradiation of the surface to induce nano-tendril growth motivates investigation into the dynamic process of helium implantation and accumulation in the surface. In this thesis, in situ elastic recoil detection is developed and used to measure the dynamic concentration of helium within a tungsten surface during the active growth of tungsten fuzz. During the development of in situ elastic recoil detection analysis, a variant of tungsten nano-tendril growth was discovered featuring drastically isolated bundles of nano-tendrils that grow at a higher rate than tungsten fuzz. The variation in nano-tendril morphology is correlated with incident helium ion energy modulation. The dependence on ion energy modulation and isolated nature of the nano-tendril bundles reveals clearly that nano-tendril growth is sensitive to surface kinetic effects. In this thesis, the structure and parameter space of the newly discovered nano-tendril bundle growth is analyzed with a suite of electron-based surface science techniques.
by Kevin Benjamin Woller
Sc. D.
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Sabatini, Giovanni. "Unveiling the inner morphology and gas kinematics of NGC 5135 with ALMA". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2017. http://amslaurea.unibo.it/14062/.
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Active galactic nuclei are thought to play a major role in the formation and evolution of galaxies, providing mechanisms for feedback from the supermassive black hole (SMBH) to its hosting galaxy and the intergalactic medium. In co-evolutionary scenarios, the SMBH properties are strictly connected to those of the host galaxy, in either high redshift quasars and in local Seyfert nuclei. Local Seyfert galaxies hosting both SMBHs and star forming regions, can be considered as the nearest counterparts of high redshift sub-mm heavily dust obscured star forming galaxies, where a significant fraction of the optical and UV photons are absorbed by dust are re-emitted in the IR and sub-mm bands. In the absence of major merging events and companions, the mechanisms that link the star formation (SF) and the accretion onto the black hole (BH) lie in the inner galactic regions (within ~1 kpc from the BH) and are responsible for the feeding of the BH and the quenching of the SF through feedback mechanisms from the BH itself. On the one hand, high resolution observations in the sub-mm band suggest that feeding might happen through the formation of bars at the inner end of the spiral galactic arms. On the other hand, outflows from the SMBHs have been observed and seem to be responsible for halting the gas infall and the SF in the inner galactic regions.
Fuelling and outflows seem to constitute a self-regulating combination of processes on the small scales that determine the galaxy morphology and dynamics. How the small scales dynamics influences the overall galaxy morphology, what is the timescale on which different processes happen, and if the different evolutionary stages justify the different observed morphologies, are still open questions.
This thesis project develops within the above astrophysical context, with the main goal of studying the morphology, the kinematics and the physical processes at play in the inner regions of the nearby Seyfert 2 galaxy NGC 5135 with ALMA.
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Arnold, Timothy. "The dependence of the fraction of active galactic nuclei in groups and clusters on host galaxy morphology". Connect to resource, 2008. http://hdl.handle.net/1811/35988.
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Kha, Stephanie Tieu. "An Investigation of Cellular Proliferation and Nuclear Morphology in the Multi-Step Progression of Cutaneous Squamous Cell Carcinoma". Thesis, The University of Arizona, 2015. http://hdl.handle.net/10150/579258.
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With 3.5 million cases diagnosed in more than 2 million people in the United States annually, skin cancer leads as a frequent and devastating disease carrying a large public health burden. Understanding the multi-step disease progression is crucial for developing interventional strategies that can reduce the incidence as well as the risk of recurrence for non-melanoma skin cancers. In this study of 40 tissue samples, cellular proliferation is quantified and analyzed in four categories that represent the stages of progression for SCC carcinogenesis: Normal, Sun-exposed, Actinic Keratosis, and Squamous Cell Carcinoma. The results in this study show an exponential increase in levels of Proliferative Cell Nuclear Antigen (PCNA) expression with each progressed category, as well as a positive association with nuclear morphology feature values related to sun-damaged nuclei that were published in a previous study. These findings support the utility of investigative techniques from the field of immunohistochemistry in studying the UV-induced skin carcinogenesis model for the multi-step disease progression of cutaneous squamous cell carcinoma. Furthermore, this study elucidates the complexities involved in clinical histological diagnoses for non-melanoma skin cancers.
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Koay, J. Y., M. Vestergaard, H. E. Bignall, C. Reynolds i B. M. Peterson. "Parsec-scale radio morphology and variability of a changing-look AGN: the case of Mrk 590". OXFORD UNIV PRESS, 2016. http://hdl.handle.net/10150/621462.
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We investigate the origin of the parsec-scale radio emission from the changing-look active galactic nucleus (AGN) of Mrk 590, and examine whether the radio power has faded concurrently with the dramatic decrease in accretion rates observed between the 1990s and the present. We detect a compact core at 1.6 and 8.4 GHz using new Very Long Baseline Array observations, finding no significant extended, jet-like features down to similar to 1 pc scales. The flat spectral index (alpha(8.4)(1.6) = 0.03) and high brightness temperature (T-b similar to 10(8) K) indicate self-absorbed synchrotron emission from the AGN. The radio to X-ray luminosity ratio of log(L-R/L-X) similar to -5, similar to that in coronally active stars, suggests emission from magnetized coronal winds, although unresolved radio jets are also consistent with the data. Comparing new Karl G. Jansky Very Large Array measurements with archival and published radio flux densities, we find 46 per cent, 34 per cent, and (insignificantly) 13 per cent flux density decreases between the 1990s and the year 2015 at 1.4 GHz, 5 GHz and 8.4 GHz, respectively. This trend, possibly due to the expansion and fading of internal shocks within the radio-emitting outflow after a recent outburst, is consistent with the decline of the optical-UV and X-ray luminosities over the same period. Such correlated variability demonstrates the AGN accretion-outflow connection, confirming that the changing-look behaviour in Mrk 590 originates from variable accretion rates rather than dust obscuration. The present radio and X-ray luminosity correlation, consistent with low/hard state accretion, suggests that the black hole may now be accreting in a radiatively inefficient mode.
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Nakajima, Naoki. "GATA6-positive lung adenocarcinomas are associated with invasive mucinous adenocarcinoma morphology, hepatocyte nuclear factor 4α expression, and KRAS mutations". Kyoto University, 2020. http://hdl.handle.net/2433/253168.
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Aime, Mary Catherine. "Generic concepts in the Crepidotaceae as inferred from nuclear large subunit ribosomal DNA sequences, morphology, and basidiospore dormancy patterns". Thesis, Virginia Tech, 1998. http://hdl.handle.net/10919/32285.
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The Crepidotaceae (Imai) Singer (Basidiomycetes: Agaricales) represents a proposed family of saprophytic fungi containing five agaricoid (Crepidotus, Tubaria, Melanomphalia, Simocybe, Pleurotellus) and four cyphelloid (Episphaeria, Phaeosolenia, Pellidiscus, Chromocyphella) genera. Several contemporary classification systems exist that delegate some or all of these genera to other agaric families. Phylogenetic relationships for the most prevalent genera in the Crepidotaceae were investigated using nuclear large subunit ribosomal DNA (LSU rDNA) sequences. Parsimony analysis of the molecular data supports the Singer classification of Crepidotus, Melanomphalia, and Simocybe as a single monophyletic unit within the Agaricales. The affinities of the genus Tubaria remain uncertain.
Crepidotus (Fr.) Staude is the largest and most phenotypically variable genus in the Crepidotaceae. Sequencing of the LSU rDNA region for a cross-section of morphologically diverse species suggests that Crepidotus is not a monophyletic genus. Analysis of morphological characters for 23 Crepidotus taxa shows that characters traditionally applied for infrageneric classification of Crepidotus are homoplasic in origin, but that less commonly emphasized characters such as spore shape and ultrastructure of spore wall ornamentation may be indicative of monophyletic clades for this complex.
A unique pattern of basidiospore dormancy and germination, unknown in any other species of agaric, is reported for 11 species of Crepidotus. Similar patterns were also encountered in species of Simocybe and Melanomphalia. In these species an endogenous period of spore dormancy of four to six months is followed by an activation period where the factors necessary for subsequent germination appear to involve a minimal nutritional component, water, and exposure to light.Master of Science
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Pehu, Eija. "Analysis of anther-derived plants of Solanum phureja: variation in ploidy, photosynthetic efficiency and structure of the nuclear genome". Diss., Virginia Polytechnic Institute and State University, 1986. http://hdl.handle.net/10919/71169.
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The ultimate goal of the· breeding scheme, of which the present study is a part, is to introduce exotic germplasm into existing cultivars of Solanum tuberosum through· 4x X 2x crosses using the South American diploid potato species Solanum phureja as the pollen parent. The first phase of this program includes the 'reconstruction' of a highly heterozygous diploid, pollen parent by .first : reducing the chromosome number of the S. phureja clones to the monoploid level and subsequently fusing genomes of two unrelated monoploid plants either by somatic hybridization or by cross-pollination between fertile doubled monoploids.
Within this framework, the objectives of this research were to analyze variation among anther-derived plants of Solanum phureja regarding their: 1) ploidy level and morphology, 2) net photosynthesis and its biochemical components, and 3) nuclear genomic structure, particularly with regard ·to the amplification of rRNA genes as influenced by the anther-culture process.
Based on the analysis of several morphological characters of the anther-derived plants by canonical discriminant function, four characters (anther length, number of chloroplasts/pair of guard cells, leaf width, corolla width) were selected for most effective assignment of plants to their ploidy groups by clustering procedures. Clustering of the anther-derived plants proved to be an efficient means of separating monoploids from higher ploidy levels.
To assess the impact of the process of anther-culture on the physiology of the resulting plants and to evaluate the possibility of selecting anther-derived genotypes for further breeding efforts, monoploid, diploid and tetraploid anther-derived plants were studied regarding their net photosynthesis and its component characteristics. Leaf area, net photosynthesis and chlorophyll content increased with increasing ploidy' Among .the. monoploids I. Rubisco activity and concentration displayed a. significant genotypic effect; whereas in the diploid group variation among genotypes was significant for total protein content and maximum specific activity of ribulose bisphosphate carboxylase. Among the tetraploid genotypes, significant differenc.es were found with respect to net photosynthesis and specific leaf weight. Two exceptional genotypes were identified: a monoploid with an increase of 28% fcfr maximum activity of ribulose bisphosphate carboxylase and a tetraploid with an increase of 30% for net photosynthesis over the anther-donor plant.
To evaluate DNA variation among the anther-derived plants, the nuclear genomes of anther-derived monoploid and diploid plant were studied by DNA reassociation kinetics. It was found that the nuclear genome of the monoploid has undergone differential replication resulting in an increase of sequences consisting of highly· repetitive DNA. Free solution RNA-DNA hybridization showed that the monoploid DNA contained 30% more rDNA sequences than the diploid. Southern blot analysis using rRNA as the probe revealed variation for copy number of certain restriction fragments and for restriction enzyme cleavage sites.Ph. D.
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Bowen, James M. "Physicochemical characterization of discrete weapons grade plutonium metal particles originating from the 1960 BOMARC incident". University of Cincinnati / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1384850163.
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Souza, André Alves de. "Estudo da morfologia e dinâmica molecular de filmes de MEH-PPV via espalhamento de raios-x de alto ângulo e ressonância magnética nuclear do estado sólido". Universidade de São Paulo, 2007. http://www.teses.usp.br/teses/disponiveis/88/88131/tde-12042007-171750/.
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A morfologia e dinâmica e filmes de MEH-PPV preparados pela técnica casting com os solventes tolueno e clorofórmio foram estudados utilizando Espalhamento de Raios-X de Alto Ângulo (WAXS) e técnicas de Ressonância Magnética Nuclear do Estado Sólido (RMN), respectivamente. Evidências do aumento da agregação foram obtidas por WAXS, que revelou uma tendência de aumento na ordem molecular sob tratamento térmico. Essas tendências foram suportadas pelas medidas de RMN que mostrou uma diminuição da mobilidade das cadeias laterais do MEH-PPV sob tratamento térmico, principalmente para os filmes feitos com o solvente tolueno. Ainda, a dependência das medidas de WAXS e RMN com a temperatura revelou que as mudanças na fotoluminescência dos filmes de MEH-PPV estão relacionadas às mudanças no ambiente molecular induzidas pelas dinâmicas dos segmentos. As medidas de espectroscopia de fluorescência (PL) com os dois tratamentos térmicos, 90 ºC por 12 horas e 150 ºC por uma hora, revelou que a banda da segunda emissão, relacionada ao aumento na agregação dos filmes, é aumentada sob os tratamentos térmicos, com forte dependência com as temperaturas dos tratamentos térmicos. Ambas as temperaturas foram escolhidas por estarem acima da temperatura de transição vítrea do MEH-PPV (Tg = 75 ºC), assim promovendo total relaxação das cadeias que constituem o polímero.The morphology and dynamic of MEH-PPV films prepared by casting from toluene and chloroform were studied using Wide-Angle X-ray Scattering (WAXS) and Solid-State Nuclear Magnetic Resonance (NMR) techniques, respectively. Evidences of the increase in the aggregation were obtained by WAXS, which revealed a tendency of increasing in the molecular ordering upon thermal treatment. This tendency was supported by NMR measurements that showed the decrease in the mobility of the MEH-PPV side-chains upon thermal treatment, mainly from films cast from toluene. Moreover, the temperature dependence of the WAXS and NMR signals revealed that the changes in the MEH-PPV photoluminescence films are related to the changes in the molecular environment induced by the segmental dynamics. The Fluorescence Spectroscopy (PL) measured at two different thermal treatments, 90 ºC by 12 hours and 150 ºC by one hour, revealed that the second emission band, related to the increase in the aggregation of the films, is increased upon thermal treatments, with strong dependency with the thermal treatment temperatures. All the temperatures were away from the glass transition temperature of the MEH-PPV (Tg = 75 ºC), thus providing total relaxation stages to the polymer chains.
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Oliveira, Ana Filipa Martins. "Microglial clearance function: dependence on phenotypes". Master's thesis, Faculdade de Ciências e Tecnologia, 2011. http://hdl.handle.net/10362/6715.
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Dissertação para obtenção do Grau de Mestre em
Genética Molecular e BiomedicinaMicroglia are active sensors of the brain and respond promptly to even minor disturbance in their microenvironment. A feature of this response is the accumulation of these cells at the site of lesion. Neonatal jaundice is a common condition of the newborn and may determine injury to neurons and glial cells, such as microglia, when levels of unconjugated bilirubin (UCB) are excessive. With the objective to evaluate whether microglia have a protective or deleterious role, we decided to assess, using the Boyden chamber, the chemotactic effect of free unbound UCB (fUCB), as well as the migration ability of UCB-treated microglia in the absence or in the presence of chemotatic compounds, such as ATP and S100B. Also, we intended to evaluate the effect of glycoursodeoxycholic acid (GUDCA) as a modulator. To characterize our usual model of microglia isolation, phenotypic evaluation of cultures with different days in vitro (DIV) was performed by estimating cell morphology, nuclear factor-kappaB (NF-κB) activation and phagocytic ability. We observed that fUCB did not act as a chemotactic compound for microglia and that cells treated with UCB showed decreased migration ability. Co-incubation with GUDCA prevented this effect and enhanced microglia migration. However, reduced effects were observed in the presence of ATP and abolished when using S100B. Isolated microglia with 2 DIV showed features of activation, but presentedramified morphology of the “resting” state, less NF-κB activation and increased phagocytosis at 13 DIV. Data indicate that microoglia exposure to UCB leads to a reduced migration ability and that co-incubation with GUDCA prevents this deleterious effect, resulting in an increased migration. Characterization of microglia phenotypes, along the time in culture, point to 13 DIV cells as the most suitable for studies intended to evaluate microglia reactivity to UCB, and probably to other stimuli.
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Weirich, Timothy Douglas. "Evaluating the Potential for Atmospheric Corrosion of 304 Stainless Steel Used for Dry Storage of Spent Nuclear Fuel". The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1557098372186951.
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Dutour, Provenzano Gaëlle. "Role of intermediate filaments in mechanotransduction". Electronic Thesis or Diss., Sorbonne université, 2021. http://www.theses.fr/2021SORUS364.
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Les cellules s'adaptent en permanence à leur microenvironnement. En particulier, elles modifient leur morphologie, leur croissance, leur division et leur motilité en fonction des propriétés biochimiques et physiques de la matrice extracellulaire (MEC). Elles sont équipées de structures adhésives appelées plaques d’adhérences, permettant aux cellules d'interagir avec les protéines de la MEC via les protéines transmembranaires appelées intégrines et de détecter la nature et la rigidité de la MEC. Le signal est transduit par les protéines des plaques d’adhérences et résulte par exemple en une modification de la tension mécanique induite par l'acto-myosine. Les voies de signalisation en aval peuvent également atteindre le noyau. L'expression des gènes peut alors être modifiée, ce qui peut en retour affecter la composition des plaques d’adhérences et de la MEC pour une réponse cellulaire adaptative. Nous avons émis l'hypothèse qu'en plus des voies de signalisation, un couplage mécanique direct entre les événements se produisant à la périphérie de la cellule et le noyau pourrait participer à la transmission de signaux mécaniques. Bien que les filaments intermédiaires (FIs) aient des propriétés mécaniques extrêmement intéressantes et résistent à des charges de tension élevées, leur implication dans les voies de mécanotransduction est encore mal connue. En utilisant l'astrocyte comme modèle, en raison de sa combinaison spécifique de FIs : vimentine, GFAP, nestine et synémine, nous avons d'abord étudié l'effet de la rigidité du substrat sur la morphologie, la structure et les fonctions du noyau, ainsi que sur l'organisation des FIs autour du noyau. Nous avons ensuite étudié l’impact de l’absence de FI les changements nucléaires observés en réponse à la rigidité du substrat. En utilisant une combinaison de techniques de microfabrication, de méthodes biochimiques et de microscopie, nous avons montré que la rigidité du substrat affecte la forme, le volume du noyau, la structure de la chromatine et le recrutement des facteurs de transcriptions (YAP). Nos résultats suggèrent que les FI forment une structure en forme de cage autour du noyau d'une manière dépendante de la rigidité : un substrat plus rigide induit la formation d’une cage de vimentine et de nestine. Cette interaction avec le noyau pourrait expliquer les modifications nucléaires observées en réponse à la rigidité du substrat. Au total, les résultats obtenus au cours de notre étude permettent de mieux comprendre le rôle des filaments intermédiaires dans les réponses nucléaires aux propriétés mécaniques du substratCells continuously adapt to their microenvironment. In particular, they modulate their morphology, growth, division, and motility according to the biochemical and physical properties of the extracellular matrix (ECM). Cells are equipped with adhesive structures called FAs, allowing them to interact with ECM proteins through the core transmembrane proteins called integrins and to sense the nature and the rigidity of the ECM. This information are transduced by FA proteins and lead, for instance, to changes in acto-myosin-mediated mechanical tension. Downstream signalling pathways also reach the nucleus; gene expression is then modified and may, in return, affect the composition of FAs or of the ECM proteins for adaptative cell response. Here, we hypothesized that, in addition to signalling pathways, a direct mechanical coupling between the events occurring at the cell periphery and the nucleus may participate in the transmission of mechanical cues and the regulation of nuclear functions. Although intermediate filaments (IFs) have extremely interesting mechanical properties and resist high tension load, their involvement in mechanotransduction pathways remains elusive. Using astrocyte as a model, due to its specific combination of IFs: vimentin, GFAP, nestin, and synemin, we studied first the effect of substrate rigidity on the nucleus morphology and function, and on the organisation of IFs around the nucleus. Then, we investigated the role of IFs in rigidity-induced nuclear changes. Using a combination of microfabrication techniques, biochemical and microscopy methods, we showed that substrate rigidity affects the nucleus shape, volume, and structure of the chromatin and the recruitment of transcription factor (YAP) and IFs are mediating these changes. Our results suggest that IFs form a cage-like structure around the nucleus in a rigidity-dependent manner: stiffer substrates promote the formation of a cage of vimentin and nestin. In the absence of IFs, the nuclear changes induced by rigidity are different than with IF. The nucleus increases its size in soft substrate, together with an increase in tension measured by YAP localising in the nucleus. The structure of the chromatin is changed. Altogether, the results obtained during our investigation give a better understanding of the role of intermediate filaments in the mechanosensitive nuclear responses
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Clarke, Nicholas Paul. "Neuronal microcircuits of the entopenuncular nucleus and subthalamic nucleus". Thesis, University of Oxford, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.388564.
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Adamczyk, Anne Marie. "Electromagnetic nucleus - nucleus cross sections using energy dependent branching ratios". Worcester, Mass. : Worcester Polytechnic Institute, 2009. http://www.wpi.edu/Pubs/ETD/Available/etd-042109-191434/.
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Zager, Eric Louis. "The impact of TeV nucleus-nucleus simulations on JACEE results /". Thesis, Connect to this title online; UW restricted, 2002. http://hdl.handle.net/1773/9757.
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Alalawi, Huda. "INVESTIGATION OF NUCLEAR COMPRESSION IN THE AMPT MODELOF NUCLEUS-NUCLEUS COLLISIONS". Kent State University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=kent1543405727739039.
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El, Haj Kacem Maher. "Visco-plasticité de transformation de phase diffusive : modélisation numérique et caractérisation des effets de la viscosité". Thesis, Rouen, INSA, 2016. http://www.theses.fr/2016ISAM0007.
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Dans cette étude, nous analysons les conséquences mécaniques des transformations de phase diffusives, particulièrement la plasticité de transformation ou TRIP (TRansformation Induced Plasticity) ainsi que le comportement élasto-viscoplastique. Cette plasticité de transformation, explicable par le mécanisme de Greenwood-Johnson, est souvent décrite avec le modèle de Leblond qui fait l'hypothèse d'un comportement élastoplastique. Dans ce modèle comme dans la majorité des analyses expérimentales et des modélisations (analytiques, par éléments finis, FFT ou encore champ de phase), une des hypothèses principales est de ne pas prendre en compte le caractère visqueux du comportement. Or plusieurs études récentes montrent que le comportement des deux phases (parente et produite) peut être très sensible au taux de déformation imposé, particulièrement à haute température. D'où l'intérêt de développer une modélisation rendant compte des effets visqueux présents lors de certaines transformations. Pour ce faire, nous adoptons une modélisation numérique où le comportement de chaque phase est décrit par une loi élasto-viscoplastique à écrouissage mixte associée à la loi de Norton ; la cinétique de transformation est imposée et le problème d'interactions mécaniques entre phases est traité par la méthode des éléments finis. D'une part, la contribution de la viscosité au TRIP est quantifiée pour différents taux de déformation imposés durant la transformation de phase. D'autre part, l'effet du taux de transformation (configuration arbitraire) sur la prédiction du TRIP est évalué et caractérisé. Une extension des modèles existants (à cinétique périodique et aléatoire) est proposée. Elle consiste d'abord à étudier et évaluer l'effet de la morphologie de germe ainsi que l'anisotropie de croissance sur la prédiction du TRIP. Ensuite, une amélioration avec un modèle anisotherme, basé sur des mesures expérimentales existantes, a été introduite. Elle consiste principalement à tenir compte de la variation des propriétés mécaniques en fonction de la température. Les analyses montrent que la prise en compte de la viscosité peut conduire à des effets importants sur la prédiction du TRIP par rapport aux résultats obtenus avec un modèle élastoplastique classique. Elles montrent en particulier, en configuration anisotherme, une amélioration de la prédiction du TRIP mesuré expérimentalement lors de la transformation perlitique d'un acier 100Cr6 [Tahimi, 2012]. Cette étude permet par ailleurs de dégager des tendances évidentes dans les relations entre le TRIP et l'histoire de la transformation : chargement mécanique et cinétique de transformation, morphologie des germes et anisotropie de croissance. Ces résultats pourront contribuer à l'élaboration d'un modèle analytique simple prenant en compte la viscositéIn this study, the mechanical consequences of phase transformations in steel, particularly, the TRansformation Induced Plasticity TRIP as well as the elasto-viscoplastic behavior has been analyzed. This transformation plasticity, due to the Greenwood-Johnson mechanism, is often described with the model of Leblond with the assumption of an elastoplastic behavior. Moreover, in the majority of experimental analysis or numerical finite elements modeling FEM or phase field modeling PFM, the viscous criteria were not considered. However, several recent studies have demonstrated that both phases (parent and product) show high strain-rate sensitivity at elevated temperatures. Hence, the principal interests using the FEM modeling to extend these main reference models of [Leblond, 89] and [Taleb-Sidoroff, 2003], with taking into account the viscous effects, which are present during some phase transformations, especially at high temperatures. To do this, the behavior of each phase is described by an elasto-viscoplastic law with mixed hardening associated to the Norton law. The transformation kinetics is imposed and the problem of mechanical interactions between phases is processed by the finite element method. On the one hand, the contribution from viscosity to TRIP was quantified for different strain-rate during phase transformation. On the other hand, the effect of an arbitrarily-set of transformation-rate in the FEM simulations was evaluated and characterized. An extension of the existing models (for periodic and random kinetics) is proposed. It consists at first in studying and in evaluating the effect of both the morphology of nuclei and the growth anisotropy, on the prediction of TRIP. Then, an improvement with non-isothermal model, based on existing experimental measures, was introduced. It consists mainly in taking into account the variation of the mechanical properties of the mixture of both phases, according to the temperature. The predictions show that in such cases, the consideration of the viscosity can lead to major changes of the estimated TRIP compared with results obtained from a classic plastic model. Also, the prediction of TRIP can be significantly influenced by the choice of the morphology of germs and by the type of growth: isotropic or anisotropic. These improvements, particularly with the non-isothermal configuration, show a good agreement with experimental measures of TRIP on the 10006 steel during pearlite phase transformation [Tahimi, 2012]. This study allows besides, releasing obvious trends in the relations between the TRIP and the history of the phase transformation: mechanical loading and kinetics of transformation, morphology of nuclei and growth anisotropy. These results can contribute to the elaboration of a simple analytical model taking into account the viscous criteria
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Rathbun, Kevin David. "Electron and positron production in 14.6 A · GeV/c nucleus-nucleus collisions". Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/12142.
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Alhomaidhi, Sultan Mohammad A. "Search for Maximum Nuclear Compression in a Model of Nucleus-Nucleus Collisions". Kent State University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=kent1448216380.
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Monsivais, Pablo. "GABAergic inhibition of nucleus magnocellularis and laminaris by the superior olivary nucleus /". Thesis, Connect to this title online; UW restricted, 2001. http://hdl.handle.net/1773/10635.
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Jones, K. L. "The unbound nucleus 13Be". Thesis, University of Surrey, 2000. http://epubs.surrey.ac.uk/843687/.
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The fragmentation of a 133 pps beam of 14Be ions at 35 MeV/A on targets of carbon and lead has been used to study the structure of the unbound nucleus 13Be. Neutrons and 12Be reaction products were measured in the DeMoN array and a detector telescope placed at 0° respectively. These coincidence measurements were used to reconstruct the 13Be particles. The beam energy was measured on a particle by particle basis from the time of flight. This was essential for momentum measurements which were made in the reference frame of the projectile. A significant contribution to the experimental background came from reactions in the detector telescope, which had to be subtracted. Relative velocity (arithmetic velocity difference) and invariant mass analyses both signify the existance of significant strength close to the 12Be + n threshold. Simulations including an experimental filter clearly show that this includes strength that is localised below 500 ke V in relative energy. Momentum distributions for 12Be, 10Be, neutrons and the reconstructed 13Be particle in the longitudinal direction have been measured. The 13Be distribution displays evidence for a two component structure. Calculations of the neutron stripping from 14Be have shown that this structure requires s-wave stripping to explain the narrow component. The wider component is consistent with d- wave stripping, and additional contributions from p-wave stripping cannot be excluded. The angular distribution of neutrons from 12Be + n breakup, measured in the 13Be reference frame is essentially isotropic. There is evidence for a weak asymmetry which could be due to broad over-lapping states of both positive and negative parity at energies below 2 MeV. This would support the inclusion of a P½ resonance in the low-lying structure of 13Be.
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Persram, Declan. "Delta production in nucleon-nucleon scattering and pion production in nucleus-nucleus collisions". Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=23931.
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We present a calculation of $ Delta$ production cross section in the one-boson-exchange model for the reaction $NN to N Delta.$ Our calculation is in quantitative agreement with a previous calculation by Huber and Aichelin (1). The effect of the $NN to N Delta$ anisotropic differential cross section on $ pi$ production in Au + Au collisions at a kinetic energy of $1{GeV over A}$ is studied. We find that there is no large effect on the final $ pi$ transverse momentum spectra.
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Blaszczak, Joanna, Stefanie Dipper, Gisbert Fanselow, Shinishiro Ishihara, Svetlana Petrova, Stavros Skopeteas, Thomas Weskott i Malte Zimmermann. "Morphology". Universität Potsdam, 2007. http://opus.kobv.de/ubp/volltexte/2008/2224/.
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The guidelines for morphological annotation contain the layers that are necessary for understanding the structure of the words in the object language: morphological segmentation, glossing, and annotation of part-of-speech.
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Jeu, Marcel Theodorus Gerardus de. "Electrophysiology of the suprachiasmatic nucleus". [S.l. : Amsterdam : s.n.] ; Universiteit van Amsterdam [Host], 2001. http://dare.uva.nl/document/59002.
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Atherton, Jeremy Francis. "Neurophysiology of the subthalamic nucleus". Thesis, University of Edinburgh, 2001. http://hdl.handle.net/1842/29793.
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Possibly as many as half the neurones in the STN have an axon collateral with branches off from the main axon and reinnervates the nucleus. This suggests that rather than working autonomously as was previously thought, the neurones of the STN can operate together as a network. Computer models of the STN showed that the level of interconnectivity within the STN would be huge, even if each axon collateral only contacted a small number of the total neurones with dendritic fields that overlapped with it. A network model showed that such a system was capable of switch-like behaviour. At low levels of activity the neurones would act autonomously. However, excitatory inputs could increase the degree of non-synchronous correlation between the activity of neurones in the STN leading them all to enter a high activity state. A single cell model was then developed in order to look at how this high activity state could be terminated. An interesting problem arose in the construction of this model; no known kinetics for the voltage-gated sodium and potassium channels could replicate the high frequency (500Hz) firing rates that are obtained by STN neurones. Intracellular recordings were made in vitro to investigate the mechanisms underlying high-frequency firing in the STN. Using a two-pulse protocol the speed of recovery from inactivation was measured giving an estimate of the inactivation characteristics of the ion channels in these neurones. These experiments showed that the neurones have very slow inactivation kinetics suggesting that STN neurones may have a much shortened refractory period, enabling high frequency firing. Such a mode of operation requires a large, fast potassium current. A potential candidate for this current is the Kv3.l potassium channel, which is strongly expressed by STN neurones.