ΛCDM cosmology is described in terms of general relativity and the Robertson-Walker metric. The evolution of the observable universe, currently dominated by dark energy (Λ) and cold dark matter (CDM), is presented in terms of its thermal history. CDM is extended to include an inflation epoch that accelerates the early expansion rate to near exponential levels. It is shown that inflation solves several problems in CDM and produces perturbations in the metric that lead to the observed anisotropies in the Cosmic Microwave Background and the formation of large scale cosmological structures. Various theories of inflation are explored. Predictions of inflation theories are compared to observations published by the Planck Collaboration. The paper concludes with an examination of “𝜶-attractor” theories of inflation based on a modified form of gravity.

The concept of faster than light travel in general relativity is examined, starting with a review of the Alcubierre metric. This spacetime, although incredible in its implications, has certain unavoidable problems which are discussed in detail. It is demonstrated that in order to describe faster than light travel without any ambiguities, a coordinate independent description is much more convenient. An alternative method of describing superluminal travel is then proposed, which has similarities to the Krasnikov tube.

<p>The purpose of this thesis was to investigate different methods do measure velocity of pistons in pneumatic cylinders at Bosch Rexroth Teknik AB. Through information of velocity the adjustment of a cylinders damping can be done easier.</p><p>A future transducer will be used by salesmen, service personnel and customers. This requires a sensor that is easy to apply and use. It is also desirable that the sensor is cheap. A number of possible methods to measure velocity have been presented. In general, the requirements above have been difficult to fulfill.</p><p>In almost all pneumatic cylinders, magnets are mounted on the piston. Magnetic sensors are then used for proximity sensing to detect its extreme positions. A similar way can be used for velocity sensing. Assume that two magnetic sensors are placed on a fixed distance between each other, along the pistons direction of motion. The time to travel between the sensors is an expression for the velocity of the piston.</p><p>One way to solve the problem has been chosen and the accuracy of this method has been verified. This has been done under the assumption that the errors due to mounting is neglected and that the direction of sensitivity is idealistic.</p>

The purpose of this thesis was to investigate different methods do measure velocity of pistons in pneumatic cylinders at Bosch Rexroth Teknik AB. Through information of velocity the adjustment of a cylinders damping can be done easier. A future transducer will be used by salesmen, service personnel and customers. This requires a sensor that is easy to apply and use. It is also desirable that the sensor is cheap. A number of possible methods to measure velocity have been presented. In general, the requirements above have been difficult to fulfill. In almost all pneumatic cylinders, magnets are mounted on the piston. Magnetic sensors are then used for proximity sensing to detect its extreme positions. A similar way can be used for velocity sensing. Assume that two magnetic sensors are placed on a fixed distance between each other, along the pistons direction of motion. The time to travel between the sensors is an expression for the velocity of the piston. One way to solve the problem has been chosen and the accuracy of this method has been verified. This has been done under the assumption that the errors due to mounting is neglected and that the direction of sensitivity is idealistic.

Syftet med detta arbete är att försöka komma fram till hur elever som läser tekniskt och naturvetenskapligt program på gymnasiet uppfattar ämnet fysik. En enkät ligger till grund för undersökningen. Enligt eleverna blir ämnet tråkigt när det är för mycket teori och muntlig undervisning. Däremot blir ämnet intressantare när eleverna får ägna sig åt laborationer och experiment. En viktig faktor för både undervisningen och trivseln i klassrummet är läraren. Resultatet av undervisningen påverkas också positivt om eleverna har roligt när de undervisas. Överlag är fysikämnet intressant enligt eleverna och det finns ett tydligt intresse för att få förståelse för olika fenomen samtidigt som flertalet elever ser valet av gymnasieprogram som en framtidsinvestering.

Bristande kompetensnivå när studenterna når mer avancerade kurser inom optik tyder på att universitetet har ett problem i upplägget av detta ämne. Denna studie djupdyker in i den första optikkursen som ges på Uppsala Universitet, “Vågor och Optik” för Fysikkandidater och Civilingenjörer i vissa program. Genom att delta på laborationer, analysera kursutvärderingar och uppgifter som ges under kursens gång kan tydliga problem identifieras och bland annat ge en insikt i studenternas eget perspektiv på kursen.  För att sedan åtgärda dessa problem undersöks ett antal alternativa sätt att bedriva undervisningen med ett speciellt intresse av digitala hjälpmedel då denna studie bidrar med en vetenskaplig grund till ett parallellt projekt att utveckla en pedagogisk app för att ytterligare förbättra utbildningen. Studien avslutas sedan med sju steg för att förbättra kursen genom att åtgärda de problem som identifierats i kursen.

The aim of this report is to introduce the reader to the field of integrability in classical and quantum physics. The report begins with a reminder of Hamiltonian mechanics and explains the notion of Liouville integrability. The introduction of the Lax formalism is then used to show a method for generating conserved quantities that lends itself well to a generalisation to classical field theory. In this context, the fundamental concepts of r-matrix, monodromy and transfer matrix are presented. To close the section on classical integrability, the classical inverse scattering method is presented on the example of the Korteweg - de Vries equation. Solving the spin chain XXX 1/2 using the coordinate Bethe ansatz is then used to open the door to the field of quantum integrability. The generalisation of the classical concepts introduced previously to the quantum domain will allow us to implement the algebraic Bethe ansatz method, which is a more general approach. Using this procedure, the examples of the spin chains XXX s and XXZ s are treated, clearly highlighting the importance of symmetries in the field of integrability. Finally, a brief overview of the Gauge/Bethe correspondence is presented.

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.

<p>²²⁶Ra is a radionuclide of much concern since it poses a high risk of radio-toxicity when ingested and is well known for its invariably long half life of 1600 years. As such ²²⁶Ra concentrations were measured in whole body tissue of fathead minnows (Pimephales promelas) in an experimental set up. Fathead minnows obtained were about two months old and fed on a Radium-226 spiked diet until 115 days. A simple and direct method to determine ²²⁶Ra ingested by fish using a homogeneous liquid scintillation counting was developed. The study consisted of three groups; a sham, Radium treatment and acid treatment. Fathead minnows were sampled 75 and 115 days after feeding, and the following end points; mass (w/w), length, specific growth rate, condition factor and radionuclide measurements obtained. Mean end point results were (0.24 ± 0.03 g), (2.78 ± 0.1 cm), (1.75 ± 0.13 % day^-1), (1.10 ± 0.06 g cm^-3) and (577.06 ± 572.13 mBq g^-1) respectively. Also mean total ²²⁶Ra level was calculated as (1911.43 ± 868.64 mBq g^-1) while the activity in sham and acid treatment resulted in levels below the Minimum Detectable Activity of 7.46 mBq g^-1. The mean rate of ²²⁶Ra accumulation, known as the concentration factor, by the fathead minnows was determined as 0.35 ± 0.19. Assuming that the ²²⁶Ra Isotope is evenly distributed in the fish whole body, the derived dose rate was found to be 5.26 μGy h^-1.</p> / Master of Science (MSc)

<p>Intensity-Modulated Radiation Treatment (IMRT) requires patient-specific quality assurance measurements, which can benefit from the convenience of using an Electronic Portal Imaging Device (EPID) for dose verification. However, EPIDs have limitations stemming from the non-uniform backscatter due to the support-arm as well as from scatter, glare, and an increased sensitivity to low-energy photons. None of these effects is typically accounted for in a treatment planning system (TPS) model, resulting in errors in calculated EPID response of up to 6%. This work addresses the non-uniform backscatter by directly incorporating a support-arm backscatter region into the TPS geometry. The shape of the backscatter region is adjusted iteratively until the TPS-calculated flood-field planar dose matches the flood-field EPID image The scatter, glare and increased low-energy response are addressed by using a radially-dependent Point-Spread Function (Kernel). The kernel is fitted using a least-squares method so that it best reproduces the EPID-acquired image for a checkerboard field. The backscatter-correction method is implemented for a Varian Clinac equipped with a 40 cm x 30 cm (512 x 384 pixel) EPID and a Pinnacle³ TPS and tested for several rectangular and IMRT fields. The scatter, glare and energy-response correction kernel is implemented and tested for a simulated checkerboard field and a simulated IMRT field. Agreement between the EPID-measured image and TPS-calculated planar dose map is seen to improve from 6% to 2% when the backscatter region is added to the Pinnacle³ model. Agreement between the simulated EPID images and simulated TPS images is improved from 14% to approx. 1% when the radially-dependent kernel is used. Simultaneous application of both the backscatter region and Point-Spread Function is a promising direction for future investigations.</p> / Master of Science (MSc)