Ce travail de thèse s’intéresse à l’introduction de méthodologies électrochimiques dans la problématique de la caractérisation du transport de peptides pénétrants (CPPs) à travers des membranes phospholipidiques. Malgré leur charge électrique globalement positive, ces peptides sont en effet capables de traverser les bicouches lipidiques de cellules réelles ou artificielles (liposomes) et il n’existe pas à ce jour de mécanisme d’internalisation universellement admis. Dans ce contexte, nous avons dans un premier temps développé des méthodologies visant à détecter des peptides pénétrants marqués par des sondes rédox en optimisant les conditions de volume et de confinement à l’électrode. Parallèlement, nous avons tenté d’observer le passage transmembranaire de ces peptides en utilisant un dispositif dérivé du patch-clamp, dans lequel un morceau (patch)de membrane lipidique est excisé d’une vésicule géante et le suivi du passage assuré par une détection ampérométrique sur ultramicro-électrode à proximité de la membrane. La sensibilité de la technique ampérométrique et le flux de CPP s’avérant faibles, nous nous sommes tournés vers une stratégie associant fluorescence (pour la sensibilité) et commande électrochimique (pour l’extinction de la fluorescence). Dans la mesure où les phospholipides constituent la barrière dynamique à travers laquelle doivent passer les CPPs, nous avons d’abord étudié l’extinction électrochimique de phospholipides marqués par une sonde à la fois rédox et fluorescente, le NBD. Observée sur des vésicules géantes au microscope confocale, la réduction électrochimique a permis l’extinction sélective des phospholipides situés sur le feuillet externe de la vésicule, un résultat que ne permettent ni la réduction par des agents chimiques (dithionite), ni les techniques de « photobleaching ». Cette propriété a été confirmée cette fois-ci pour des CPPs marqués par le NBD qui ont été mis à incuber en présence de vésicules géantes et pour lesquels un essai préliminaire semble confirmer une extinction de fluorescence essentiellement pour les peptides associés au feuillet externe de la vésicule. / This PhD work was aimed at introducing electrochemical strategies in the general topic devoted to the characterization of the passage of cell penetrating peptides (CPPs) across phospholipidic membranes. Although positively charged, CPPs are prone to cross lipidic bilayers of real and artificial cells (liposomes) and there is no commonly admitted internalization mechanism so far. Therefore, we first developed electrochemical setups aimed at improving the amperometric detection of redox-taggedCPPs, through optimization of volume and confinement. Additionally, we have made attempts to use patch-clamp inspired setups to monitor the passage of CPPs across a membrane patched from a giant vesicle using ultramicro-electrodes in the close vicinity of the patched membrane. Since the amperometric technique displayed poor sensibility and the flux of CPP was too narrow, we changed our strategy for a methodology coupling fluorescence (for the sensitivity) and an electrochemical command (to achieve fluorescence extinction). Considering that phospholipids are forefront actors of CPP internalization, we first focused on the electrochemical quenching of phospholipids tagged with a probe displaying both redox and fluorescent properties (NBD). Observed on giant unilamellar vesicles (GUVs) with confocal microscopy, the electrochemical reduction of the NBD probe led to the selective extinction of the phospholipids located on the outer leaflet of the vesicle, a selectivity which is not observed using chemical quenchers such as dithionite or photobleaching methods. That property was extended to NBD-tagged CPPs, previously incubated with unlabeled Guvs and that preliminary experiment confirmed that the electrochemical extinction mostly concerned peptides associated to the outer leaflet of the liposome.

No description available.

In this work we first introduce the basics of surface study and than we get acquainted with three basic types of surfaces of computer graphics, Bézier, rational Bézier and B-spline surfaces. This is to prepare the reader for the study of the fourth type of surfaces - NURBS. All types of introduced surfaces are accompanied by examples and algorithms with programs implemented in MatLab environment. When studying the NURBS surfaces properties we also introduce the associated important geometric tools. With this base of knowledge we concentrate on examples of common surfaces represented as NURBS, that are again accompanied with representation in programs. i

Master of Science / Department of Biology / Brett K. Sandercock / Grassland birds are declining throughout their native range. The Flint Hills of eastern Kansas and Oklahoma contain large tracts of tallgrass prairie, but intensification of agricultural practices may be contributing to ongoing population declines. Common rangeland management practices include annual burning coupled with heavy grazing by cattle. This system, known as intensive early stocking and burning, promotes homogeneous utilization of forage by cattle but may not provide habitat for some grassland bird species. Patch-burn grazing is an alternative management system that aims to restore heterogeneity on rangelands by recreating the fire-grazing interaction that would have historically occurred throughout the Great Plains. From 2011-2013, we examined responses of grassland birds to traditional rangeland management and patch-burn grazing by conducting vegetation surveys, line transect surveys, and nest monitoring on privately-owned pastures in Chase County and Greenwood County, Kansas. Vegetative heterogeneity was higher on patch-burned pastures, with unburned patches having higher visual obstruction and less bare ground. Densities of grassland birds differed by species and among habitat strata. Unburned patches on patch-burned pastures were associated with increased densities of Dickcissels (Spiza americana), Eastern Meadowlarks (Sturnella magna) and Grasshopper Sparrows (Ammodramus savannarum). Henslow’s Sparrows (A. henslowii) were only detected on patch-burned pastures. Nest survival of grassland songbirds was similar among management systems but varied by year. Probability of nest parasitism by Brown-headed Cowbirds (Molothrus ater) varied among years and between treatments for Dickcissels and Grasshopper Sparrows, with overall lower rates on burned areas and during drought years. For Dickcissels and Grasshopper Sparrows, there was a significant reduction in host clutch size between parasitized versus unparasitized nests. Overall, nest survival of grassland songbirds in managed rangelands was low. Patch-burn grazing improved rangeland conditions and provided habitat for more species of birds, but did not increase nest survival. Drought conditions in 2012 and 2013 may have influenced the results of this study, as many landowners were unable to burn as planned. Further study is needed to determine underlying factors driving variation in nest success and parasitism rates for grassland birds, particularly on private lands which make up the vast majority of remnant tallgrass prairies.

Aging is the main risk factor for cognitive decline. The hippocampus, a brain region critical for learning and memory formation, is especially vulnerable to normal and pathological age-related cognitive decline. Dysregulation of both insulin and intracellular Ca2+ signaling appear to coexist and their compromised actions may synergistically contribute to neuronal dysfunction with aging. This dissertation focused on the interaction between insulin, Ca2+ dysregulation, and cognition in hippocampal neurons by examining the contributions of insulin to Ca2+ signaling events that influence memory formation. I tested the hypothesis that insulin would increase cognition in aged animals by altering Ca2+-dependent physiological mechanisms involved in learning. The possible effects of insulin on learning and memory in young and aged rats were studied. In addition, the effects of insulin on the Ca2+-dependent afterhyperpolarization in CA1 pyramidal hippocampal neurons from young and aged animals were compared. Further, primary hippocampal cultures were used to examine the possible effects of insulin on voltage-gated Ca2+ channel activity and Ca2+-induced Ca2+-release; mechanisms known to influence the AHP. We found that intranasal insulin improved memory in aged F344 rats. Young and aged F344 rats were treated with Humalog®, a short-acting insulin analog, or Levemir®, a long-acting insulin analog. The aged rats performed similar to young rats in the Morris Water Maze, a hippocampal dependent spatial learning and memory task. Electrophysiological recordings from CA1 hippocampal neurons revealed that insulin reduced the age-related increase in the Ca2+-dependent afterhyperpolarization, a prominent biomarker of brain aging that is associated with cognitive decline. Patch clamping recording from hippocampal cultured neurons showed that insulin reduced Ca2+ channel currents. Intracellular Ca2+ levels were also monitored using Fura-2 in response to cellular depolarization. Results indicated that a reduction in Ca2+-induced Ca2+-release from intracellular stores occurred in the presence of insulin. These results suggest that increasing brain insulin levels in aged rats may have improved memory by reducing the AHP and intracellular Ca2+concentrations. This study indicates a possible mechanism responsible for the beneficial effects of intranasal insulin on cognitive function absorbed in selective Alzheimer’s patients. Thus, insulin therapy may reduce or prevent age-related compromises to Ca2+ regulatory pathways typically associated with cognitive decline.

Un canal chlorure de 10 pS de la membrane basolatérale des cellules intercalaires du canal connecteur présente des propriétés proches de celles de ClC-K2. Nos données de patch clamp montrent que son activité et le nombre de canaux actifs (N) augmentent avec (i) la dépolarisation membranaire (ii) la concentration en calcium externe et (iii) l’alcalinisation extra et intracellulaire. L’alcalinisation extracellulaire déplace la dépendance au voltage vers des potentiels négatifs, alors que l’alcalinisation intracellulaire augmente leur activité à des potentiels négatifs. Ces données suggèrent que le Ca2+ extracellulaire et le pH modulent l’activité des canaux ClC-K2 via une action sur la porte commune plutôt que sur les protopores des autres canaux ClC. Nous avons cherché à établir le rôle et l’identité moléculaire des canaux potassiques basolatéraux du tubule contourné proximal (PCT), peu connus. Nos résultats montrent la présence d’ARNm codant pour les sous-unités Kir4.2 et Kir5.1 dans le PCT et, par western blot et par immunohistochimie, leur expression sur la membrane basolatérale du PCT. Un canal potassique, étudié par patch-clamp, présente des propriétés semblables à celles des canaux hétérotétramériques Kir4.2/Kir5.1 sur la membrane basolatérale du PCT de souris : il présente une conductance de 47 pS, une rectification entrante induite par le Mg2+ intracellulaire, une dépendance de son activité au pHi et un blocage par le Ba2+ extracellulaire. Cependant, un phénotype rénal chez des souris invalidées pour le gène Kcnj15 codant pour Kir4.2 n’a pas pu être mis en évidence. / A 10 pS chloride channel at the basolateral side of connecting duct intercalated cells shares properties with the cloned ClC-K2 channel. Patch-clamp experiments show that its activity and the number of active channels increase with (i) membrane depolarization (ii) external calcium concentration and (iii) external and internal alkalinization. External alkalinization also shifts the voltage-dependence curve towards negative voltages while internal alkalinization flattens the voltage-dependence curve thereby raising channel activity at negative potentials. These data suggest that extracellular calcium and both extra and intracellular protons modulate ClC-K2 channels activity through an action on the common gate rather than on the protopores present in others ClC channels.The role and the molecular identity of basolateral potassium channels of the proximal convoluted tubule (PCT) are not very well known. RT-PCR results revealed the presence of mRNA encoding the Kir4.2 and Kir5.1 potassium channels subunits in mouse PCT tubular cells, and western blot and immunohistochemistry experiments showed that both proteins are expressed at the basolateral membrane of these cells. The most frequent channel observed by patch-clamp on the basolateral membrane of PCT presents a conductance of 47 pS, an inward rectification induced by intracellular Mg2+, an inhibition by extracellular Ba2+ and an activity dependent on intracellular pH. These electrophysiological properties are consistent with the presence of heteromeric Kir4.2/Kir5.1 channels in the basolateral membrane of mouse PCT. The study of mice knocked out for the Kir4.2-encoding gene Kcnj15 did not highlight a renal phenotype.

Approved for public release; distribution is unlimited / The Numerical Electromagnetics Code (NEC) was used to evaluate the admittance, average power gain, and the electric near and far field of a monopole antenna mounted on a cubical box over a perfectly conducting ground plane. Two models of the box, employing surface patches and wire grids, were evaluated. The monopole was positioned at the center, the edge, and at a corner of the box's top surface. Admittance and average power gain of the antenna were calculated. NEC results were examined and compared with experimental data and with results from "PATCH", another independent electromagnetic modeling code. The near electric field was calculated for both models. Computer graphics techniques were presented for plotting NEC near field results using DISSPLA (Display Integrated Software System and Plotting Language), a commercial graphics package. Contour and 3-D amplitude, and phase plots of the near electric fields were presented. Radiation patterns were calculated to relate far field and near field behavior of the antenna. Surface patch and wire grid models are compared and conclusions were presented. / Naval Ocean Systems Center / http://archive.org/details/investigationofn00elli / O&MN, Direct Funding / Lieutenant, Hellenic Navy

Master of Science / Department of Biology / Alice Boyle / Species extinctions over the past two centuries have mainly been caused by habitat destruction. Landscape change typically reduces habitat area, and can fragment contiguous habitat into remnant patches that are more subject to anthropogenic disturbance. Furthermore, changes in the landscape matrix and land-use intensification within remaining natural areas can reduce habitat quality and exacerbate the consequences of habitat loss and fragmentation. Accordingly, wildlife conservation requires an understanding of how landscape structure influences habitat selection. However, most studies of habitat selection are conducted at fine spatial scales and fail to account for landscape context. Temperate grasslands are a critically endangered biome, and remaining prairies are threatened by woody encroachment and disruptions to historic fire-grazing regimes. Here, I investigated the effects of habitat area, fragmentation, woody cover, and rangeland management on habitat selection by two species of declining grassland-obligate sparrows: Henslow’s Sparrows (Ammodramus henslowii) and Grasshopper Sparrows (A. savannarum). I conducted >10,000 bird surveys at sites located throughout eastern Kansas, home to North America’s largest remaining tracts of tallgrass prairie, during the breeding seasons of 2015 and 2016. I assessed the relative importance of different landscape attributes in determining occurrence and within-season site-fidelity of Henslow’s Sparrows using dynamic occupancy models. The species was rare, inhabited <1% of sites, and appeared and disappeared from sites within and between seasons. Henslow’s Sparrows only settled in unburned prairie early in spring, but later in the season, inhabited burned areas and responded to landscape structure at larger scales (50-ha area early in spring vs. 200-ha during mid-season). Sparrows usually settled in unfragmented prairie, strongly favored Conservation Reserve Program (CRP) fields embedded within rangeland, avoided trees, and disappeared from hayfields after mowing. Having identified fragmentation as an important determinant of Henslow’s Sparrow occurrence, I used N-mixture models to test whether abundance of the more common Grasshopper Sparrow was driven by total habitat area or core habitat area (i.e. grasslands >60 m from woodlands, croplands, or urbanized areas). Among 50-ha landscapes containing the same total grassland area, sparrows favored landscapes with more core habitat, and like Henslow’s Sparrows, avoided trees; in landscapes containing ~50–70% grassland, abundance decreased more than threefold if half the grassland area was near an edge, and the landscape contained trees. Effective conservation requires ensuring that habitat is suitable at spatial scales larger than that of the territory or home range. Protecting prairie remnants from agricultural conversion and woody encroachment, promoting CRP enrollment, and maintaining portions of undisturbed prairie in working rangelands each year are critical to protecting threatened grassland species. Both Henslow’s Sparrows and Grasshopper Sparrows were influenced by habitat fragmentation, underscoring the importance of landscape features in driving habitat selection by migratory birds. As habitat loss threatens animal populations worldwide, conservation efforts focused on protecting and restoring core habitat could help mitigate declines of sensitive species.

When an electrically small antenna is conceived, designed, simulated, and tested, the main emphasis is usually placed immediately on its impedance bandwidth and radiation efficiency. All too often it is assumed that its directivity will only be that of a Hertzian dipole and, hence, its directivity becomes a minor consideration. This is particularly true if such a compact antenna radiates in the presence of a large ground plane. Attention is typically focused on the radiator and its size, while the ground plane is forgotten. This has become a too frequent occurrence when antennas, such as patch antennas that have been augmented with metamaterial structures, are explored. In this paper, it is demonstrated that while the ground plane has little impact on the resonance frequency and impedance bandwidth of patch antennas or metamaterial-inspired three-dimensional magnetic EZ antennas, it has a huge impact on their directivity performance. Moreover, it is demonstrated that with both a metamaterial-inspired two-element array and a related Huygens dipole antenna, one can achieve broadside-radiating electrically small systems that have high directivities. Several common and original designs are used to highlight these issues and to emphasize why a fundamental figure of merit such as directivity should never be overlooked.

The invention of closed circuit television (CCTV) has initiated a new trend in high security by video surveillance. More recently, CCTV cameras have been incorporating wireless LAN technology for data transfer purposes by using on chip memory storage until the time of update. In this thesis, short range communication such as Bluetooth low energy (Bluetooth smart) is used in order to perform simple I/O applications. The two important components of the project are the camera and the Bluetooth module box. An external antenna is designed for the connectivity box and the operating range of the box is deduced by using link budget. The blue cool connectivity box is assessed by defining the capabilities of the box, i.e., simple I/O operations. Field test measurements for the designed antenna provide optimum communication range. The thesis also reviews software simulation tools that are essential for antenna design and path loss modelling. The efficiency of simulated measurements versus real-time measurements are also assessed. The primary target of the thesis is to detail the design of a cost-effective antenna based on link budget calculations and perform basic I/O tasks wirelessly between the blue cool connectivity box and the camera. It is concluded that in future works, advanced operations can be added on to the existing model. It is also suggested that a model for multi floor communication can be designed.