We present new approaches to define and analyze geometric graphs. The region-counting distances, introduced by Demaine, Iacono and Langerman, associate to any pair of points (p,q) the number of items of a dataset S contained in a region R(p,q) surrounding (p,q). We define region-counting disks and circles, and study the complexity of these objects. Algorithms to compute epsilon-approximations of region-counting distances and approximations of region-counting circles are presented. We propose a definition of the locality for properties of geometric graphs. We measure the local density of graphs using the region-counting distances between pairs of vertices, and we use this density to define local properties of classes of graphs. We illustrate the locality by introducing the local diameter of geometric graphs: we define it as the upper bound on the size of the shortest path between any pair of vertices, expressed as a function of the density of the graph around those vertices. We determine the local diameter of several well-studied graphs such as the Theta-graph, the Ordered Theta-graph and the Skip List Spanner. We also show that various operations, such as path and point queries using geometric graphs as data structures, have complexities which can be expressed as local properties. A family of proximity graphs, called Empty Region Graphs (ERG) is presented. The vertices of an ERG are points in the plane, and two points are connected if their neighborhood, defined by a region, does not contain any other point. The region defining the neighborhood of two points is a parameter of the graph. This family of graphs includes several known proximity graphs such as Nearest Neighbor Graphs, Beta-Skeletons or Theta-Graphs. We concentrate on ERGs that are invariant under translations, rotations and uniform scaling of the vertices. We give conditions on the region defining an ERG to ensure a number of properties that might be desirable in applications, such as planarity, connectivity, triangle-freeness, cycle-freeness, bipartiteness and bounded degree. These conditions take the form of what we call tight regions: maximal or minimal regions that a region must contain or be contained in to make the graph satisfy a given property. We show that every monotone property has at least one corresponding tight region; we discuss possibilities and limitations of this general model for constructing a graph from a point set. We introduce and analyze sigma-local graphs, based on a definition of locality by Erickson, to illustrate efficient construction algorithm on a subclass of ERGs.

No description available.

Wir untersuchen, welchen Einfluss die Verankerung von langen, hydrophilen Polymeren in Lipidmembranen auf deren elastische Eigenschaften ausübt. Theoretisch werden zwei Grenzbereiche für die spontane Krümmung der Membran erwartet: <br /> i) bei kleinen Oberflächenkonzentrationen des Polymers (Pilzgebiet) sollte die spontane Krümmung linear von der Oberflächendichte des verankerten Polymers abhängen;<br /> ii) bei hoher Bedeckung (Bürstengebiet) sollte die Abhängigkeit quadratisch sein. Wir versuchen, Vorhersagen für das Bürstengebiet zu prüfen, indem wir die morphologischen Veränderungen beobachten, die bei Riesen (Giant)- Vesikeln hervorgerufen werden. <br /> <br /> Als lange Polymere verwenden wir fluoreszenzmarkierte &#955;-Phage DNA Moleküle, die durch eine Biotin-Avidin-Biotin Verbindung an biotinhaltigen Lipidvesikeln befestigt sind. Wir kontrollieren die Oberflächenkonzentration der Anker durch Variation der Menge an biotinhaltigem Lipid in der Membran. Die Menge der an der Membran verankerten DNA wird durch Fluoreszenzmessungen quantifiziert. Änderungen in den elastischen Eigenschaften der Membran bei Anbindung der DNA, werden über eine Analyse der Vesikel-Fluktuationen kontrolliert. Die spontane Krümmung der Membran steigt mit der Oberflächenbeladung. Bei höheren Verankerungen bilden die Vesikel Knospen (budding). Die Größe der Knospen kann ebenfalls zur Bestimmung der Krümmung der Membran verwendet werden. Der Einfluss auf die Biegesteifigkeit ist Thema weiterer Untersuchungen. / We study the effect on the elastic properties of lipid membranes induced by anchoring of long hydrophilic polymers. Theoretically, two limiting regimes for the membrane spontaneous curvature are expected : <br /> i) at low surface polymer concentration (mushroom regime) the spontaneous curvature should scale linearly with the surface density of anchored polymers; <br /> ii) at high coverage (brush regime) the dependence should be quadratic. We attempt to test the predictions for the brush regime by monitoring the morphological changes induced on giant vesicles.<br /> <br /> As long polymers we use fluorescently labeled &#955;-phage DNA molecules which are attached to biotinylated lipid vesicles with a biotin-avidin-biotin linkage. By varying the amount of biotinylated lipid in the membrane we control the surface concentration of the anchors. The amount of anchored DNA to the membrane is quantified with fluorescence measurements. Changes in the elastic properties of the membrane as DNA grafts to it are monitored via analysis of the vesicle fluctuations. The spontaneous curvature of the membrane increases as a function of the surface coverage. At higher grafting concentrations the vesicles bud. The size of the buds can also be used to assess the membrane curvature. The effect on the bending stiffness is a subject of further investigation.

No description available.

Recent advances in experimental and computational methods have opened up new directions in graphene fundamental studies. In addition to understanding the basic properties of this material and its quasi-one dimensional structures, significant efforts are devoted to describing their long ranged dispersive interactions. Other two-dimensional materials, such as silicene, germanene, and transition metal dichalcogenides, are also being investigated aiming at finding complementary to graphene systems with other "wonder" properties. The focus of this work is to utilize first principles simulations methods to build our basic knowledge of structure-interaction relations in two-dimensional materials and design their properties. In particular, mechanical folding and extended defects in zigzag and armchair graphene nanoribbons can be used to modulate their electronic and spin polarization characteristics and achieve different stacking patterns. Our simulations concerning zigzag silicene nanoribbons show width-dependent antiferromagnetic-ferromagnetic transitions unlike the case of zigzag graphene nanoribbons, which are always antiferromagnetic. Heterostructures, build by stacking graphene, silicene, and MoS$_2$, are also investigated. It is found that hybridization alters the electronic properties of the individual layers and new flexural and breathing phonon modes display unique behaviors in the heterostructure compositions. Anchored to SiC substrate graphene nanoribbons are also proposed as possible systems to be used in graphene electronics. Our findings are of importance not only for fundamental science, but they could also be used for future experimental developments.

No description available.

<p> Studies examining the characteristics of membranes that facilitate and affect fusion are central to understanding the intricacies of inter- and intra-cellular fusion processes and expanding the existing knowledge of other roles membranes may have. In this thesis a model membrane system, using Sendai Virus and Egg phosphatidylcholine (EggPC) liposomes containing the receptor glycophorin A (proteoliposomes), was used in examining different fusion with proteoliposomes prepared by different methods. For the first time glycophorin A was incorporated into EggPC liposomes vectorially. This was accomplished separately with two detergents: octylglucoside and CHAPS. Fusion of Sendai Virus with the reconstituted proteoliposomes revealed that octylglucoside reconstituted proteoliposomes exhibited lower fusion compared with CHAPS reconstituted proteoliposomes. Efforts to determine the basis for this difference, using either proteinase K or O-glycosidase digestion and subsequent fragment analysis using SDS-PAGE and silver-staining, were inconclusive. A separate study examined the ability of large membrane-anchored biopolymers (chosen in virtue of their large hydrophilic domains) to sterically stabilize Egg PC liposomes. Glycophorin A, the lipophosphoglycan (LPG) from Leishmania donovani, and a polyethyleneglycol-conjugated phospholipid (PEG5000-PE) were incorporated into Egg PC liposomes. In each case, binding of a soluble fluorescent probe, NeutrAvidin Oregon Green, to liposomes containing biotin-conjugated lipid was restricted. This supports the idea that large membrane-anchored biopolymers are able to sterically stabilize liposomes.</p> / Thesis / Master of Science (MSc)

Objectives: Discuss use of a linear incision for placement of a magnetically coupled bone anchored hearing implant. Methods: Case series. Results: Two patients underwent placement of magnetically coupled bone-anchored hearing implants (BAHI) through linear incisions. The first, a 40-year-old female with congenital single-sided deafness, previously had successful implantation of a percutaneous bone anchored hearing implant through a linear incision; unfortunately, she developed pain and intermittent drainage at her abutment site with time, resulting in a request for removal of her device. As an alternative to complete removal, we offered to replace the percutaneous implant with a magnetically coupled BAHI, employing the same linear incision previously. The second patient, a 53-year-old obese female with limited neck mobility and mixed hearing loss, underwent primary placement of a magnetically coupled BAHI through a linear incision. Limitations in neck mobility and patient body habitus precluded use of a traditional C-shaped incision. Both patients underwent surgery successfully, healed without incident, had their devices activated 6 weeks after their procedures, and are able to wear their implants more than 8 hours per day without discomfort. Conclusion: Surgical techniques for bone-anchored implants continue to evolve. Though manufacturers of magnetically coupled devices recommend using C-shaped incisions with large skin flaps, our first reported cases suggest that a small linear incision immediately overlying the implant magnet may be an acceptable alternative. Potential benefits include a smaller incision, less hair removal, smaller flap, decreased surgical time, and less postoperative pain.

Les travaux décris dans cette thèse rapportent la conception de Metal-Organic Frameworks (MOFs) photoactifs et leur immobilisation sur surface dans le but d’obtenir et d’étudier des SurMOFs (Surface anchored Metal-Organic Frameworks) propices aux processus photoinduits dans le cadre de la photosynthèse artificielle. Pour accomplir cela, nous avons synthétisé différents ligands photoactifs et réalisé leur immobilisation sur surface à l’aide de la croissance épitaxiale en phase liquide. Ainsi, différents SurMOFs à base de zinc(II), présentant tous une structure de type SurMOF-2, ont été préparés avec succès. Les premiers matériaux obtenus à base de ligands rylènes (naphtalène dimide : NDI et pérylène diimide : PDI) ont mis en avant de fortes interactions  entre les chromophores au sein du SURMOF, causant une perte de la luminescence. Une deuxième génération de ligands plus encombrés a été synthétisée. Ils ont conduit à des SurMOFs luminescents et siège de transferts d’énergie interligands. Ces premiers travaux ont mis en avant l’impact de la disposition des ligands dans le matériau sur les propriétés photoniques. Par ailleurs, des SurMOFs constitués de ligands dicétopyrrolopyrrole (DPP) et d’anthracène (ADP) ont été synthétisés. L’étude de leurs propriétés photoniques alliée à des calculs théoriques ont montré que le transfert d’énergie au sein de ce SurMOF ne se fait pas de manière isotrope. Enfin, un SurMOF à partir de ligand DPP portant des fonctions réactives (azoture) a été synthétisé et nous avons pu greffer différentes molécules par réaction de cyclo-addition de type Huisgen, dont un accepteur d’électron, à sa périphérie par modification post-synthétique. / The aim of this thesis was the development of photoactive Metal-Organic Frameworks (MOFs) and their immobilizations on surface to obtain and study SurMOFs (Surface anchored Metal-Organic Frameworks) to investigate photoinduced processes in the context of the artificial photosynthesis. Towards this goal, we have synthesized photoactive ligands and immobilized them on surfaces using liquid phase epitaxy (LPE) in a layer-by-layer (LbL) fashion. Thus, different zinc (II) based SurMOFs, featuring a SurMOF-2 structure, were successfully prepared. The first rylene- (naphthalene diimide: NDI and perylene diimide: PDI) based SurMOFs described in this thesis showed strong  interactions between the chromophores within the MOF, causing the quenching of the luminescence. A second generation of ligands, sterically hindered, was then synthesized. They lead to luminescent SurMOFs showing efficient ligand-to-ligand energy transfer. These first results highlight the impact of linker arrangement within the material on its photonic properties. Furthermore, diketopyrrolopyrrole (DPP) and anthracene (DPA) based SurMOFs were prepared. The study of their photonic properties coupled with theoretical calculations showed that energy transfers, occurring within SurMOF-2 type materials, were not isotropic. Finally, a SurMOF, made out of a DPP ligand bearing reactive moieties (azide), was synthesized and was functionalized with different kinds of molecules, including an electron acceptor, at the periphery by post-synthetic modification using the Huisgen cycloaddtion reaction.

The purpose of this study was to evaluate the effectiveness of a mathematics enrichment activity used to improve the mathematics performance of students relative to participation in the State Agricultural Mechanics Career Development Event (CDE) and in mandated assessments. The treatment group (13 schools, 43 students) participated in a mathematics enrichment activity situated in an agricultural mechanics context. The control group (16 schools, 56 students) did not participate in the enrichment activity. Both groups, as part of the CDE, were tested with a 100-question word problem examination, completed a individual skill and team activity, and completed a demographic instrument regarding participation in agricultural mechanics CDEs, scholastic performance, use of graphing calculators, enrollment in STEM, agricultural science, and fine arts courses, and other information. After the survey was conducted, schools were asked to provide TAKS exit scores on participating students. These scores were compared between schools and against statewide TAKS scores. Results of the study showed a significant improvement in scores on the individual written examination and teams scores for the agricultural mechanics CDE and on the TAKS exit level mathematics assessment. Mean written examination scores for the treatment group were 69.53; non-cooperators were 57.16. Mean total team scores for cooperating teams were 420.39; non-cooperators had a mean score of 368.13. Mean TAKS exit level mathematics scores for cooperators were 2336.78; non-cooperators had a mean TAKS exit level score of 2331.77. Participation in the enrichment activity improved both CDE and mathematics achievement scores.