This thesis primarily deals with two concepts in painting that I explored during my Graduate studies at the University of New Orleans. Both concepts are similar in execution but have two distinctly different results.

Accurate distribution of genetic material is critical for the formation of functional cells and their proliferation. During cell division, sister chromatids separate from each other and segregate to opposite poles. To ensure accurate chromosome segregation all sister chromatids should be attached to microtubules from opposite spindle poles, known as bi-orientation. Cohesin is a protein complex that holds sister chromatids together from the time of its replication in S phase until anaphase onset, and it is required for proper chromosome segregation both in mitosis and in meiosis. It is distributed intermittently along the full length of chromosomes with significant enrichment in the region surrounding the centromere, known as the pericentromere. This chromosome domain was shown to be crucial for chromosome bi-orientation. In my PhD I studied how the establishment of tension between sister chromatids in the process of bi-orientation affects the distribution of different pericentromeric proteins on budding yeast chromosomes. It was known that levels of cohesin at the pericentromere are decreased in response to the establishment of tension. I demonstrate that other proteins, such as subunits of condensin, members of the Chromosome Passenger Complex (CPC) and others, exhibit similar dynamics, and suggest a model to explain this phenomenon. Out of all studied proteins, Shugoshin (Sgo1) was the only one that was completely removed from the pericentromere in response to spindle tension establishment. There is evidence that Sgo1 plays a role in sensing spindle tension and halting the cell cycle until this has been achieved but how it does so is not known. Therefore, removal of Shugoshin from the pericentromere might be a signal for the cell that bi-orientation occurred. I then found that spindle tension itself is not sufficient for Sgo1 re-localization from the pericentromere, and there are other factors that affect it. I showed that deletion of RTS1, a highly conserved regulatory subunit of Protein Phosphatase 2A (PP2A), results in substantial enrichment of Shugoshin at the pericentromere in the situation when spindle tension is absent. In addition, Bub1 kinase, a protein that is required for Sgo1 localization, was found to be removed from the centromere in response to spindle tension as well as Sgo1. The role of Bub1 the in localization of Shugoshin is to phosphorylate histone H2A, which then becomes a mark for Sgo1 loading. Therefore, we assume that Sgo1 dynamics and, potentially, its role in sensing bi-orientation, are regulated through the array of phosphorylation and de-phosphorylation events at the pericentromeric area. Finally, I have also found that budding yeast Sgo1 undergoes the posttranslational modification as sumoylation. I showed that sumoylation of Shugoshin is not required for its removal from the pericentromere during biorientation. However, it might be important for the regulation of Sgo1 degradation and its role in the metaphase to anaphase transition in mitosis.

Nous présentons une méthode pour caractériser des nanocapacités sub-10 nm de diamètre et des nanotransistors par Interferometric Scanning Microwave Microscope (ISMM), avec lequel nous avons réussi, de non seulement optimiser la résolution latérale qui permet de connaitre leur topographie, mais aussi de les caractériser quantitativement à l’échelle de l’attofarad. La caractérisation quantitative des nanocapacités dans la gamme de l’attofarad est réalisée en utilisant une série de capacités d’une cal kit intégrées sur une même puce. Des capacités à l'échelle nanométrique et des diodes à barrière tunnel ont été détectées par les variations de l'amplitude et de la phase du signal haute fréquence réfléchi S11. En ce qui concerne les nanotransistors mesurés à l’aide du montage IDPMM, l’évolution de la tension de seuil a été étudiée par deux approches : les mesures de courant I_d (V_tip) et les mesures de courbes dS_11/dV. Les résultats obtenus par ces deux approches coïncident sauf l’apparition d’un ‘splitting’ à fort V_bg qui est seulement observé par l’ISMM. Une cartographie 2D de la tension de seuil avec deux grilles pour les nanotransistors a été établie pour la première fois. En résumé, cette étude montre que l’ISMM est un outil alternatif fiable pour la caractérisation électrique de nanocomposants émergents. / We present a method to characterize sub-10 nm capacitors and nanotransistors by Interferometric Scanning Microwave Microscopy (ISMM), with which we are able to not only optimize the lateral resolution which related to the topography, but also quantitatively characterize across the attofarad range. Quantitative impedance characterization of attofarad range capacitors is achieved using an “on-chip” calibration kit facing thousands of nanodevices. Nanoscale capacitors and tunnel barriers were detected through variations in the amplitude and phase of the reflected microwave signal, respectively. With the banc IDPMM (Interferometric Doping Profile Measurement Module), the change of threshold voltage of nanotransistor is observed by two methods: the measurement of current I_d (V_tip) and the spectroscopy curves S_11/dV. The curves obtained by two approaches coincide except for a ‘splitting’ at high V_bg. In addition, a precise 2D mapping of threshold voltage in dual gate operation for nanotransistor is established for the first time. In brief, this study indicates that ISMM is a reliable alternative tool for electrical characterization of emerging nanocomponents.

The migration of keratinocytes across wound beds is a key step in dermal wound healing. In aged human skin, wound healing rates decrease, and reactive oxygen species damage accumulation increases, but it is unclear if these factors relate specifically to migration of human skin keratinocytes (HSKs). In this study, two concentrations of oxygen (4% and 21%) were used to model low and high oxidative stress to produce varying levels of reactive oxygen species. When migration of HSKs from young and old primary skin were compared by scratch assay, those from old skin migrated faster in high oxygen tension than did young HSKs, which was an opposite trend from that seen in young skin. An intense increase in reactive oxygen species at margins immediately after scratching was seen in both young and old HSKs, but reactive oxygen species disappeared from young skin at 21% oxygen most quickly. These cells also had the slowest migration. These findings suggest that old and young keratinocytes respond differently to oxidative stress, and that migration of keratinocytes--a key step in re-epithelialization of wounds, is effected by the efficacy of reactive oxygen species removal.

Barley is one of the important crops in many of the irrigated regions of the world. It is an important crop in Iran for both human consumption and livestock feed. In the United States and Europe it is used for livestock feed and beverages. The income from this crop is moderate in comparison to that from other major agricultural products. Barley production has a definite place in the economy of the region, because it requires only a small amount of care. It can be readily grown on poor lands. One of the factors contributing to the increased acreage of barley in many countries is the tolerance and adaptability of this plant to salt and poor or second class land. Yields have been increased materially in recent years with the development of new varieties superior to the standard varieties previously used. Better cultural practices are improving yields, but much remains to be done in this phase of the work.

Recently, surface tension has been shown to be important in emerging high technologies, such as in pumping and control of flow in microfluidic devices, in microchemical analysis of complex fluids, and in rapid DNA screening, etc. Advances in these new technologies will depend strongly on the availability of flexible methods for controlling surface tension. Photo-control using a photoresponsive surfactant is a potentially attractive route to accomplishing many of the tasks required in these processes. Photoresponsive surfactants typically incorporate an azobenzene group as the functional unit which experiences reversible trans-to-cis photoisomerization under different irradiation conditions. The photoisomerization usually causes a change in surface tension. Obviously, a large change in surface tension under different illumination conditions will be highly desirable in practical applications. However, the largest change in surface tension as reported in the literature is only 3 mN/m which is too small to generate any significant effect. In this presentation, we report a new class of photoresponsive surfactants which exhibit excellent performance in surface tension control. Under different illumination conditions, the change in surface tension can be as large as 11.0 mN/m. Experimental results are presented for two new photoresponsive surfactants. A discussion of experimental results follows. / Singapore-MIT Alliance (SMA)

The static stability of a Tension Leg Platform (TLP) with an intact tendon system is principally provided by its tendons and hence quite different from those of a conventional ship or even a floating structure positioned by its mooring system. Because small deformations in tendons are capable of providing sufficient righting moment to a TLP, the contribution from the inclination of its hull is relatively insignificant, especially when its tendon system is intact. When the tendon system of a TLP is completely damaged, the static stability of a TLP behaves and is calculated in a similar manner as those of a conventional ship. In the case of a TLP with a partially damaged tendon system, the stability of a TLP may be provided by the deformation of its tendons and to a certain extent the inclination of its hull. Several hurricanes in recent years have raised concerns about the feasibility and the robustness of the TLP concept in the deep water Gulf of Mexico. To the best of our knowledge, existing publications on the research of static stability of TLPs are limited. This study investigates the static stability of different types of TLPs representing those deployed in the Gulf of Mexico, under three different scenarios. That is, a TLP with 1) an intact tendon system, 2) a partially damaged tendon system, and 3) a completely damaged tendon system. The four different types of TLP chosen for this study are 1) a conventional four-leg TLP, 2) three-leg mini TLP, 3) extended four-leg TLP and 4) mini four-leg TLP. To avoid buckling and yielding occurring in a tendon, we define that the maximum righting moment provided by an intact or partially damaged tendon system is reached when the tension in one or more tendons on the down tension leg becomes zero or when the tension in one or more tendons on the up tension leg starts to yield. This definition leads us to identify the most dangerous (or vulnerable) directions of met-ocean conditions to a TLP with an intact or partially damaged tendon system. Hence, our finding may also be used in the study on the pitch/roll dynamic stability of a TLP. The righting moments of each TLP in the three different scenarios are respectively computed and compared with related wind-induce static upsetting moment at certain velocities. By comparing their ratios, the static stability of a TLP and the redundancy of its tendon system may be revealed, which has important implication to the design of a TLP.

Ce travail présente une étude du piégeage dune "goutte-sessile" en évaporation. Deux cas sont considérés : une goutte sur une surface hydrophile et sur une surfaces hydrophobe. Dans ces deux cas, lancrage de la ligne ( piégeage ) se fait entre langle de contact davancée et celui de reculée. La constance du rayon de la gouttelette est observée. Cette phase met en évidence trois régimes dévaporation : étalement, piégeage de la ligne triple et amorçage de la rétraction. Les paramètres suivants ont été étudiés par une technique dimagerie avec une résolution de 10?m/pixel : le volume, le rayon et langle de contact, leurs évolutions temporelles et les comportements du profil géométrique des gouttelettes. Deux diagrammes caractéristiques sont présentés : (i) langle de contact en fonction du volume et (ii) langle de contact en fonction du rayon. Ce dernier graphique met en évidence le piégeage de la ligne. Les grandeurs fondamentales de la dynamique dévaporation, qui caractérisent la richesse dune goutte sur substrat solide à surface horizontale, ont été quantifiées : 0,4 à 1,33?m/s pour la vitesse de rétraction de la ligne de contact, 640 à 937 ?rad/s pour le taux de décroissance de langle de contact sur substrats hydrophiles, 1 à 2,5 nl/s pour le taux dévaporation, et 0,71 à 1,09 nrad/s2 pour le taux de décélération pour les gouttes évaporées sur les substrats hydrophobes. Le comportement de langle de contact en fonction du temps est linéaire aux temps courts dans le cas des surfaces hydrophiles et aux temps larges pour les hydrophobes. La longueur de la constance du rayon est équivalente à la signature dhystérésis. Les substrats solides homogènes utilisés sont : (i) surface fakir et téflon pour les hydrophobes et (ii) porcelaine et nylon pour les hydrophiles en raison de la signature dhystérésis. Lénergie de piégeage est évaluée à ? 25?J/m pour les hydrophobes et à ? 30?J/m pour les hydrophiles. Le comportement de la goutte en évaporation dépend de manière dont on la pose "gonflée - posée". Le comportement de la ligne triple est observé. Un tel comportement nest pas trivial. Des modèles numériques sont mis au point afin dillustrer ce processus physique dapparence simple et de comprendre le piégeage. Ces modèles reproduisent de manière très réaliste la dynamique de lévaporation dune goutte allant des conditions initiales jusquau séchage complet. La cohérence entre ces modèles numériques et nos résultats expérimentaux avec effet mémoire dans les conditions naturelles valide un critère justifié jusquici par un formalisme analytique.

The growth of energy demand in the world requires addressing the increasing power requirements of industrial and residential consumers. Optimizing the design of new and existing large power producing systems can efficiently increase energy supply to meet the growing demand. Hydrogen as an energy carrier is a promising sustainable way to meet the growing energy demand, while protecting the environment. This thesis investigates the efficient production of hydrogen from the electrolysis of copper chloride, by predicting entropy production as a result of diffusive mass transfer. Also, this thesis investigates the possibility of producing electrical energy from waste heat produced by industrial or other sources. The thermocapillary motion of fluid droplet in a closed rectangular microchannel is used to generate electrical energy from waste heat in a piezoelectric membrane by inducing mechanical deformation as a result of the droplet motion. Modeling, fabrication, and experimental measurement of a micro heat engine (MHE) are investigated in this study. Analytical and experimental results are reported for both circular and rectangular microchannels. A novel fabrication technique using lead zirconate titanate (PZT) as substrate in microfluidic application is presented in this study. This thesis develops a predictive model of the entropy production due to thermal and fluid irreversibilities in the microchannel. Thermocapillary pressure and friction forces are modelled within the droplet, as well as surface tension hysteresis during start-up of the droplet motion. A new analytical model is presented to predict the effect of transient velocity on the voltage production in the MHE. In order to predict the effect of the applied stress on voltage, the different layers of deposition are considered for thin film laminates. The highest efficiency of the system from simulated taking into iv account the electromechanical coupling factor is about 1.6% with a maximum voltage of 1.25mV for the range of displacement considered in this study. In addition, new experimental and analytical results are presented for evaporation and de-pinning of deionised water and toluene droplets in rectangular microchannels fabricated from Su-8 2025 and 2075. / UOIT

Surface tension of a polymer melt in a supercritical fluid is a principal factor in determining cell nucleation and growth in polymer microcellular foaming. Previous work has presented the surface tension of the amorphous polymer, polystyrene (PS), in supercritical CO2 determined by Axisymmetric Drop Shape Analysis-Profile (ADSA-P), together with theoretical calculations for a corresponding system. The dependences of the surface tension on temperature, pressure and polymer molecular weight were discussed and the physical mechanisms for three main experimental trends were explained using Self Consistent Field Theory (SCFT). This thesis introduces recent work on the surface tension measurement of the crystalline polymer, high density polyethylene (HDPE), in supercritical N2 under various temperatures and pressures. The surface tension was determined by ADSA-P and the results were compared with those of the amorphous polymer PS. The dependence of the surface tension on temperature and pressure, at temperatures above the HDPE melting point, ~125°C, was found to be similar to that of PS; that is, the surface tension decreased with increasing temperature and pressure. Below 125°C and above 100°C, HDPE underwent a process of crystallization, where the surface tension dependence on temperature was different from that above the melting point, i.e., decreased with decreasing temperature. Differential Scanning Calorimetry (DSC) characterization of the polymer was carried out to reveal the process of HDPE crystallization and relate this to the surface tension behavior. It was found that the amount of the decrease in surface tension was related to the rate of temperature change and hence the extent of polymer crystallization. In the second part of the thesis, surface tension dependences on temperature, pressure and clay concentrations were studied for HDPE nano-clay composites (HNC) and compared with pure HDPE. It was found the trends with temperature and pressure were the same with PS in CO2 and HDPE in N2; that is, the surface tension decreased with increasing temperature and pressure. In all nanocomposite samples, the surface tension decreased compared with pure HDPE. This could be a good explanation for the better polymer foaming quality with the addition of clay in the polymer. A minimum surface tension was found with the sample at ~3% concentration of clay. The degree of crystallinity of HNC was analyzed by Differential Scanning Calorimetry (DSC) at different clay concentrations. A minimumz crystallinity was also found at the clay concentration of 3%. The possible relationship between surface tension and polymer crystallinity was discussed.