In this thesis the colonization factor antigen I (CFA/I) of the enterotoxicogenic Escherichia coli (ETEC) is characterized biophysically with an optical tweezers. ETEC is the causative agent of travellers’ diarrhoea. The CFA/I is an adherence organelle, often named pili, mediating attachment to the epithelia of the small intestine, essential for infection. An optical tweezers were used to unfold the pili showing a steady state force of about 8 pN during unfolding. Also, the force dependence on unfolding velocity was studied. At velocities above 1.75 μm/s, the force increased linearly with the logarithmic velocity, in line with results from UPEC associated E. coli. The resulting force of CFA/I differs significantly from previously studied type 1, P and S pili which are in the range 25-30 pN. This is supposed to reflect differences in the host environment, i.e. the difference between gastrointestinal and urinary tract. The general behaviour however, seem to be the same for the different pili, in accordance with the similar macromolecular structure. In addition, the steady state force of the F1C pili of Escherichia coli was estimated to 28pN.

This thesis investigates a novel way to simulate cracks as an extension of the Mate- rial Point Method (MPM). Previous methods, like CRAMP (CRAcks with Material Points), often use an explicit crack representation to define the material crack. We use an implicit crack representation defined as the intersection between pieces of the original specimen created by a pre-fracture process. Material chunks are there- after forced together using massless particle constraints. The method has proven successful in tearing scenarios, and the main benefits are: (1) minor computational overhead compared to the initial MPM algorithm; (2) simple to implement and scales well in 3 dimensions; (3) gives easy and controllable setup phase for desired material failure mode. The development of the crack extension has required a fully general MPM solver that can handle arbitrarily many distinct bodies connected in the same simulation. Current collision schemes for MPM exists, however these are often focused on two-body collisions and does not scale well for additional objects due to inaccuracies in contact normal calculations. We present a method that uses an iterative pair-wise comparison scheme to resolve grid collisions that extends to any number of collision objects.

We are accustomed to think the phase of single particle states does not matter. After all, the phase cancels out when calculating physical observables. However, the geometric phase can cause interference even in single particle states and can be measured. Berry’s phase is a geometric phase the system accumulates as its time-dependent Hamiltonian is subjected to closed adiabatic excursion in parameter space. In this report, we explore how Berry’s phase manifests itself in various fields of physics, both classical and quantum mechanical. The Hannay angle is a classical analogue to Berry’s phase and they are related by a derivative. The Aharonov-Bohm effect is a manifestation of Berry’s phase. Net rotation of deformable bodies in the language of gauge theory can be translated as a Berry phase. The well-known BornOppenheimer approximation is a molecular Aharonov-Bohm effect and is another manifestation of Berry’s Phase.

In the present thesis, we offer an introduction to type IIB string compactifications on $\mathbb{T}^{d}/\Gamma$ toroidal orbifolds. We first describe the technical method to construct these spaces and reduce the string background on it. We will have (non)-geometrical fluxes arising from these spaces which decorate with discrete deformations our four $\mathcal{N}=1$ dimensional supergravity theory. Solving its equations of motion, we find several families of supersymmetric AdS vacua with fixed moduli, which can be related through a set of  $SL(2,\mathbb{Z})$ symmetries.

Calculations on stress, strain and deformation are typically made using finite element methods (FEM). An alternative to this is a rigid bodydynamics approach also called lumped element method (LEM). LEM implements deformation by replacing single rigid bodies with multiple subbodies, which are in turn connected with joints (also called constraints) that allow movement between the sub-bodies. If instead of FEM, a lumped element method is used to simulate deformable objects, sufficient accuracy can be obtained at a much lower cost, complexity-wise. A lumped element method-approach could for example achieve real-time simulationspeed. The purpose of this thesis is to expand upon previous work into LEM, analyzing how the rigid bodies and constraints should be configured to produce accurate results for a wider range of objects. Specifically, beams of varying cross section and curved beam axis, as well as other test cases. The simulated values are compared with the analytic predictions given by Euler-Bernoulli beam theory. These simulations are implemented using the AGX Dynamics physics engine from Algoryx Simulation AB. One intended application area of LEM is crane arms. This motivates the focus on analyzing how LEM behaves when simulating beams, as they represent the most basic version of crane arms. Simulation and testing of full crane objects was unfortunately not accomplished, partly due to a lack of convenient testing data. Further work is needed to confirm that LEM behaves well for these expanded cases as well. In addition to the analysis section above, the purpose is also to implement a pipeline for automatic conversion of a CAD-model to a lumped element version in AGX. Specifically, a CAD-model given in the 3D-modeling software SpaceClaim.

The tree amplitudes of string theory low-energy effective actions admit a diagrammatic expansion in terms of higher-than-cubic contact terms. These tree amplitudes can be used to build loop amplitudes using unitary cuts or the forward limit. In this thesis we study the possibility of constructing four-point cubic representations for the resulting one-loop contact terms that obey the Bern-Carrasco-Johansson (BCJ) color-kinematics relation. From the string theory effective action we study the contact terms carrying ζ2, ζ3, ζ4, and ζ5. For the even ζ2 and ζ4 cases we find that the cubic representations are incompatible with the BCJ relations, as expected from their disappearance in the closed-string effective action. We find a unique, local set of numerators at ζ3 that obey the BCJ relations. For ζ5 we find two choices of representations: one obeys BCJ but requires non-trivial contributions for the tadpole; the other contains no tadpoles but breaks one of the BCJ relations.

No description available.

<p>QC 20150603</p>

Denna studie behandlar energibegreppet i geografiämnet. Energibegreppet är komplext, inte minst för att det behandlas i olika kontexter med olika betydelser. Som lärare i naturvetenskapsämnena vill man förstå elevernas lärande om naturvetenskapliga begrepp, även om lärandet ligger utanför de egna ämnena. Syftet med studien är därför att kvalitativt undersöka hur energibegreppet behandlas i geografiämnet för att få en djupare förståelse för hur naturvetenskapsundervisningen och geografiundervisningen kan komplettera varandra. Sex samhällskunskapslärare i årkurserna 4–6 intervjuades om deras användning av energibegreppet. Deras uttalanden tematiserades och jämfördes med de fyra nyckelidéer om energibegreppet som Duit lyfter fram som centrala ur ett naturvetenskapligt perspektiv. Tre nyckelidéer kunde identifieras i lärarnas beskrivningar av hur de behandlar energibegreppet i geografiämnet. Tre teman kunde också urskiljas i datan. Studien pekar på att energibegreppet behandlas i geografiämnet med viss förankring till energiomvandling och energiöverföring. Vilket gör det möjligt att arbeta med ämnesövergripande undervisning gällande energibegreppet. / This study deals with the energy concept in the school subject of geography. The energy concept is complex, not least because it is treated in different contexts with different meanings. As a science teacher, you want to understand the students' learning about science concepts, also such learning that is outside their subject. The aim of the qualitative study is therefore to investigate how the energy concept is treated in the subject of geography in order to gain a deeper understanding of how science teaching and geography teaching can complement each other. Six social science teachers in middle school were interviewed about their use of the energy concept. Their statements were thematized and compared with the four key ideas about the energy concept that Duit highlights as central from a scientific perspective. Three key ideas could be identified in the teachers' descriptions of how they treat the energy concept in the subject of geography. Three themes could also be distinguished in the data. The study indicates that the energy concept is treated in the subject of geography with some base in energy transformation and energy transfer. That makes it possible to work interdisciplinary regarding the energy concept.

In many engineering applications, one is interested in structures with elastic properties which undergo deformation due to external loads. This interest has motivated a deep study of the equations underlying the deformation and how to solve them during the two last centuries. In this thesis, we propose a method that allows us to construct exact solutions to these equations. We prove that the partial differential equation governing the deformation is equivalent to the well-studied Cauchy-Riemann equation on the unit disk. Furthermore, we prove sufficient conditions for when the exact solutions to the Cauchy-Riemann equation on the unit disk can be used to construct solutions to the physical problem. We end the thesis by outlining a method for solving the elasticity equation in a general simply connected domain with a known conformal mapping to the unit disk. This method simplifies the formulas of Kolosov and Muskhelishvili, which are constructed by complex potentials in a similar, but more indirect way. It also allows us to obtain solutions in domains where standard numerical methods, such as e.g. the finite element method, proves difficult or even impossible to apply.