The biological function and the technological applications of semiflexible polymers, such as DNA, actin filaments and carbon nanotubes, strongly depend on their rigidity. Semiflexible polymers are characterized by their persistence length, the definition of which is the subject of the first part of this thesis. Attractive interactions, that arise e.g.~in the adsorption, the condensation and the bundling of filaments, can change the conformation of a semiflexible polymer. The conformation depends on the relative magnitude of the material parameters and can be influenced by them in a systematic manner. In particular, the morphologies of semiflexible polymer rings, such as circular nanotubes or DNA, which are adsorbed onto substrates with three types of structures, are studied: (i) A topographical channel, (ii) a chemically modified stripe and (iii) a periodic pattern of topographical steps. The results are compared with the condensation of rings by attractive interactions. Furthermore, the bundling of two individual actin filaments, whose ends are anchored, is analyzed. This system geometry is shown to provide a systematic and quantitative method to extract the magnitude of the attraction between the filaments from experimentally observable conformations of the filaments. / Die biologische Funktion und die technologischen Anwendungen semiflexibler Polymere, wie DNA, Aktinfilamente und Nanoröhren aus Kohlenstoff, werden wesentlich von deren Biegesteifigkeit bestimmt. Semiflexible Polymere werden charakterisiert durch ihre Persistenzlänge, mit deren Definition sich der erste Teil dieser Arbeit befasst. Anziehende Wechselwirkungen, wie sie z.B. bei der Adsorption, der Kondensation und der Bündelung von Filamenten auftreten, können die Konformation eines semiflexiblen Polymers verändern. Die Konformation ist dabei abhängig von der relativen Größe der Materialparameter und kann durch diese gezielt beeinflusst werden. Im Einzelnen werden hier die Morphologien semiflexibler Polymerringe, wie z.B. DNA oder ringförmiger Nanoröhren, untersucht, die auf drei verschieden strukturierten Substraten adsorbieren: (i) Ein topographischer Kanal, (ii) ein chemisch modifizierter Streifen und (iii) ein periodisches Muster topographischer Oberflächenstufen. Die Ergebnisse werden mit der Kondensation von Ringen durch anziehende Wechselwirkungen verglichen. Des Weiteren wird die Bündelung zweier Aktinfilamente, deren Enden verankert sind, untersucht. Diese Systemgeometrie liefert eine systematische Methode, um die Stärke der Anziehung zwischen den Filamenten aus experimentell beobachtbaren Konformationen zu berechnen.

This study investigated the use of lexical bundles in research articles written in English by Turkish scholars. For the purpose of the study, a corpus of published research articles produced by Turkish scholars in six different academic disciplines was collected. The four-word lexical bundles that appeared at least twenty times in this one million word corpus were identified and further analyzed both structurally and functionally based on the previous taxonomies developed by Biber, Johansson, Leech, Conrad and Finegan (1999) and Biber, Conrad and Cortes (2004). The results of this study revealed that the lexical bundles found have structural correlates as well as strong functional features that help to construct discourse in academic writing. The conclusions drawn from this study could be applied to the teaching of academic genres to researchers in English as a Foreign Language context and are expected to provide insights for further corpus-based studies in academic writing.

This thesis describes the development of a Mach-Zehnder interferometric filter based planar Doppler velocimetry (MZI-PDV) flow measurement technique. The technique uses an entirely new optical system, an unbalanced MZI incorporating glass blocks for wavefront-matching, to replace the iodine cell currently used in conventional PDV. The free spectral range of the interferometric filter can be selected by adjusting the optical path difference of the MZI. This allows the velocity measurement range, sensitivity and resolution to be varied. This system offers no restricts to the choice of laser wavelength of operation which is not the case with most techniques. Two techniques to process the interference fringe images are presented. The first uses the shift of the fringe pattern to determine the Doppler frequency shift along profiles. The second provides a full-field measurement by normalising the received light intensity at each pixel in the image. With the single camera MZI-PDV scheme, exact alignment of the two output images on the active area of the camera is automatic. This eliminates the pixel-matching problem in conventional two camera PDV systems. The technique allows the measurement of up to three components of the flow velocity across a plane defined by a laser light sheet. The construction of a single velocity component MZI-PDV system that incorporates a phase-locking system designed to stabilise the filter is described. Measurements are made on the velocity field of a rotating disc with maximum velocities of ~±70ms-1 and an axis-symmetric air jet (with a nozzle diameter of 20mm) with an exit velocity of ~85ms-1. Standard deviations in the measured velocities were found to be about 2.9 and 2ms-1 for the two processing methods respectively. The system was then modified to make 3-component velocity measurements using imaging fibre bundles to port multiple views to a single detector head, and the standard deviation of the velocity error is around ±3ms-1 for a maximum velocity of ~±30ms-1 in the field of view. The factors that will affect the quality of the interference fringe image are investigated including polarisation sensitivity of the two beam splitters and flatness of the optical components. The inclination angle and the optical path deviation have little effect on the contrast of the interference fringes since collimated light beams, rather than divergent ones, are used in the interferometer.

The present study considers steady laminar two-dimensional incompressible flow over both in-line and staggered flat tube bundles used in heat exchanger applications. The effects of various independent parameters, such as Reynolds number (Re), Prandtl number (Pr), length ratio (L/Da), and height ratio (H/Da), on the pressure drop and heat transfer were studied. A finite volume based FORTRAN code was developed to solve the governing equations. The scalar and velocity variables were stored at staggered grid locations. Scalar variables (pressure and temperature) and all thermophysical properties were stored at the main grid location and velocities were stored at the control volume faces. The solution to a one-dimensional convection diffusion equation was represented by the power law. The locations of grid points were generated by the algebraic grid generation technique. The curvilinear velocity and pressure fields were linked by the Semi-Implicit Method for Pressure Linked Equations (SIMPLE) algorithm. The line-by-line method, which is a combination of the Tri-Diagonal Matrix Algorithm (TDMA) and the Gauss-Seidel procedure, was used to solve the resulting set of discretization equations. The result of the study established that the flow is observed to attain a periodically fully developed profile downstream of the fourth module. The strength increases and the size of the recirculation gets larger as the Reynolds number increases. As the height ratio increases, the strength and size of the recirculation decreases because the flow has enough space to expand through the tube passages. The increase in length ratio does not significantly impact the strength and size of the recirculation. The non-dimesionalized pressure drop monotonically decreased with an increase in the Reynolds number. In general, the module average Nusselt number increases with an increase in the Reynolds number. The results at Pr = 7.0 indicate a significant increase in the computed module average Nusselt number when compared to those for Pr = 0.7. The overall performance of in-line configuration for lower height ratio (H/Da = 2) and higher length ratio (L/Da = 6) is preferable since it provides higher heat transfer rate for all Reynolds numbers except for the lowest Re value of 25. As expected the staggered configurations perform better than the in-line configuration from the heat transfer point of view.

We study the Hitchin component in the space of representations of the fundamental group of a Riemann surface into a split real Lie group in the rank 2 case. We prove that such representations are described by a conformal structure and class of Higgs bundle we call cyclic and we show cyclic Higgs bundles correspond to a form of the affine Toda equations. We also relate various real forms of the Toda equations to minimal surfaces in quadrics of arbitrary signature. In the case of the Hitchin component for PSL(3,R) we provide a new proof of the relation to convex RP²-structures and hyperbolic affine spheres. For PSp(4,R) we prove such representations are the monodromy for a special class of projective structure on the unit tangent bundle of the surface. We prove these are isomorphic to the convex-foliated projective structures of Guichard and Wienhard. We elucidate the geometry of generic 2-plane distributions in 5 dimensions, work which traces back to Cartan. Nurowski showed that there is an associated signature (2,3) conformal structure. We clarify this as a relationship between a parabolic geometry associated to the split real form of G₂ and a conformal geometry with holonomy in G₂. Moreover in terms of the conformal geometry we prove this distribution is the bundle of maximal isotropics corresponding to the annihilator of a spinor satisfying the twistor-spinor equation. The moduli space of deformations of a compact coassociative submanifold L in a G₂ manifold is shown to have a natural local embedding as a submanifold of H2(L,R). We consider G2-manifolds with a T^4-action of isomorphisms such that the orbits are coassociative tori and prove a local equivalence to minimal 3-manifolds in R^{3,3} = H²(T⁴,R) with positive induced metric. By studying minimal surfaces in quadrics we show how to construct minimal 3-manifold cones in R^{3,3} and hence G₂-metrics from equations that are a set of affine Toda equations. The relation to semi-flat special Lagrangian fibrations and the Monge-Ampere equation is explained.

No description available.

Wir studieren Moduln über Maximalordnungen auf glatten projektiven Flächen und ihre Modulräume. Wir untersuchen null- und zweidimensionale Modulräume auf K3 und abelschen Flächen für unverzweigte Ordnungen, den sogenannten Azumaya Algebren. Weiterhin untersuchen wir Modulräume für spezielle verzweigte Ordnungen auf der projektiven Ebene. Wir beweisen das diese Räume immer glatt sind. Mit Hilfe dieses Ergebnisses studieren wir die Deformationstheorie der betrachteten Moduln. Im letzten Kapitel konstruieren wir explizite Ordnungen und berechnen einige Modulräume.

Baigiamajame magistro darbe aprašyta apvaliosios medienos rietuvių fotonuotraukų analizė, siekiant įvertinti medienos rietuvių glaudumo koeficientą. Darbo tikslas – Įvertinti fotometrinio metodo taikymo apvaliosios medienos rietuvių glaudumo koeficiento nustatymui galimybes. Uždaviniai: • Įvertinti atsitiktinių ir sisteminių paklaidų dydžius, gaunamus apvaliosios medienos rietuvių glaudumo koeficientą, nustatant fotometriniu metodu. • Įvertinti fotometrinio metodo paklaidų priklausomybę nuo sortimentų rūšies. • Įvertinti paklaidų priklausomybę nuo medienos rietuvių glaudumo. Tyrimo objektas – į transporto priemonę sukrauti apvaliosios madienos popiermedžiai. Tyrimo metodika Darbe naudoti mokslinio tyrimo metodai: • Dokumentų analizė; • Vaizdų analizė; • Statistinė analizė; • Loginė analizė. Darbo rezultatai – mano pasirinktas fotometrinis metodas, apvaliosios madienos rietuvių glaudumo koeficientui įvertinti, gali būti taikomas. Paklaidos yra daromos tačiau jos nėra esminės. Iš pasirnktų trijų analizuojamojo vaizdo išskyrimo būdų tiksliausi rezultatai buvo stačiakampio forma išskirtas vaizdas. / Digital photographs of spruce and birch bundles were analised by photometric method using ArcView GIS 3.2. program to determine stacking coefficient of wood in the work. The main aim – to determine ability of photometric method to avaluate stacking coefficient of bundles. The main tasks: • To determine randon and systematic bias of photometric method to estimating stacking of wood bundles. • To determine volume of bias, using photometric method, dependents of roundwood species. • To aveluate dependense of errors in stacking coefficients of bundles volume. Research object. –solid wood which is loaded in a bundles of a truck. Methods: • Dokument analysis; • Image analysis; • Statistic analysis; • Logical analysis. Calculations were made using software ArcView GIS 3.2., STATISTICA v6.0 and EXCEL. The main results. photometric method can be applied to timber stacking precision ratios. Articularly accurate are obtained with the bundle of analyzing image maked rectangle.

The study presents a contrastive analysis of learner language which is represented by written English of the Lithuanian EFL learners and native speakers of English. The material for the study comes from three corpora of learner language: two Lithuanian corpora consist of student essays written by first-year students and third-/fourth-year students of English Philology while the native speaker corpus is a selection of argumentative essays from the LOCNESS corpus. The study involves structural and functional analyses of lexical bundles retrieved from the three corpora. The findings of the study show that written English produced by the learners of the lower proficiency levels bears more features typical of spoken English. As the level of proficiency increases, the number of verbal bundles gives way to bundles incorporating noun and prepositional phrases which are more characteristic of the written variety of the language. As regards the distribution of lexical bundles across the functional types, the study proves that the Lithuanian learners pay more attention to discourse organization and expression of stance while in the native speaker material the proportion of referential lexical bundles, used to express propositions, is much more prominent. The study also involves an analysis of phrasal expressions recurring in the lexical bundles. The conclusions and implications of the research may be particularly useful to the practice of ELT/EFL in Lithuania while certain insights of... [to full text] / Disertacijoje aprašomas gretinamasis leksinių samplaikų tyrimas lietuvių gimtosios kalbos vartotojų ir gimtakalbių anglų kalbos vartotojų rašytinėje anglų kalboje. Tyrime naudoti trys skirtingų kalbos mokėjimo lygių vartotojų anglų kalbos tekstynai: pirmakursių studentų ir vyresniųjų kursų studentų, kurių gimtoji kalba – lietuvių, rašiniai, bei anglų gimtosios kalbos vartotojų, t. y. įvairių Didžiosios Britanijos ir JAV universitetų studentų rašiniai. Leksinių samplaikų struktūrinė analizė parodė, jog žemesnio mokėjimo lygio mokinių kalboje dažniau pasitaiko veiksmažodinių samplaikų, o aukštesnio lygio mokinių kalboje – vardažodinių. Tai rodo, jog žemesnio mokėjimo lygio mokinių kalba artimesnė sakytinei anglų kalbai, kuriai būdingos veiksmažodinės leksinės samplaikos. Kylant kalbos mokėjimo lygiui, mokinių rašytinėje kalboje randasi daugiau vardažodinių leksinių samplaikų, kurios dažnesnės rašytiniame diskurse. Funkcinė leksinių samplaikų analizė atskleidė, jog kylant mokinių kalbos mokėjimo lygiui nuosekliai kinta ir tam tikrų kalbos funkcijų raiška: žemesnio lygio mokiniai daugiau dėmesio skiria diskurso organizavimo ir autoriaus pozicijos raiškai, o aukštesnio lygio mokinių kalboje dažnesni referentiniai pasakymai, perteikiantys teksto propozicinį turinį. Leksinių samplaikų analizė pagal jose realizuojamus frazinius junginius atskleidė lietuvių gimtosios kalbos vartotojams būdingų frazinių junginių vartojimo ypatumų. Tyrimo išvados ir taikomoji vertė siejamos su anglų... [toliau žr. visą tekstą]

<p>We introduce Hypoelliptic Diffusion Maps (HDM), a novel semi-supervised machine learning framework for the analysis of collections of anatomical surfaces. Triangular meshes obtained from discretizing these surfaces are high-dimensional, noisy, and unorganized, which makes it difficult to consistently extract robust geometric features for the whole collection. Traditionally, biologists put equal numbers of ``landmarks'' on each mesh, and study the ``shape space'' with this fixed number of landmarks to understand patterns of shape variation in the collection of surfaces; we propose here a correspondence-based, landmark-free approach that automates this process while maintaining morphological interpretability. Our methodology avoids explicit feature extraction and is thus related to the kernel methods, but the equivalent notion of ``kernel function'' takes value in pairwise correspondences between triangular meshes in the collection. Under the assumption that the data set is sampled from a fibre bundle, we show that the new graph Laplacian defined in the HDM framework is the discrete counterpart of a class of hypoelliptic partial differential operators.</p><p>This thesis is organized as follows: Chapter 1 is the introduction; Chapter 2 describes the correspondences between anatomical surfaces used in this research; Chapter 3 and 4 discuss the HDM framework in detail; Chapter 5 illustrates some interesting applications of this framework in geometric morphometrics.</p> / Dissertation