<p>This thesis deals with relativistic membranes and, in particular, a limit called stretched membranes. The thesis also considers the relation of membranes to the conjectured M-theory and string theory. The thesis is divided into two parts. One introductory part where I introduce areas which are of relevance for the second part.</p><p>The second part consists of the scientific papers.</p><p>In the first part I make a general introduction to string theory. Furthermore, I discuss different limits of membrane theory. Then, I make a short review of the different conjectures of M-theory and briefly mention different consistency checks of these conjectures. The last subject in the first part concerns an area, which is not</p><p>in direct connection to the other chapters in the thesis. This is a short introduction to the general treatment of theories with constraints.</p><p>The second part of the thesis consists of the included articles. The common topic of these is that they give a new approach to the treatment of membranes. We here make a partial gauge-fixing of the constraints which, by choosing an appropriate limit, will yield a perturbation theory around a free string-like theory. The stringlike</p><p>theory is the usual string theory with an extra parameter dependence. This perturbation theory we solve by infinitesimal canonical transformations.</p><p>The corresponding quantum theory is also discussed. We show that a particular ordering gives critical dimensions 27 and 11 for the bosonic and fermionic case respectively.</p>

<p>The formation of thin films of polymer blends by spin-coating from solution is characterised by rapid solvent quenching, a process that results in non-equilibrium morphologies. Thin films of conjugated polymer blends are used as the active material in polymer solar cells, in which the morphology may have drastic effects on device performance.</p><p>In this thesis results from morphology studies are presented for spin-coated thin films of polyfluorenes and co-polymers of polyfluorene blended with the fullerene derivative [6,6]-phenyl-C61-butyric acid methyl ester (PCBM). The surface morphology was investigated by atomic force microscopy (AFM) and was found to depend on the blend ratio as well as the chemical structure of the blend components. The spin speed, which determines the thickness of the spin-coated thin films, was also found to influence the morphology. Secondary ion mass spectrometry (SIMS) was used for depth profiling of the chemical composition in thin films of poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-5,5-(4´,7´-di-2-thienyl-2´,1´,3´-benzothiadiazole)] (LBPF5) blended with PCBM. The films were found to be vertically phase separated with a four-fold multilayered structure.</p>

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The Gamma-ray Large Area Space Telescope (GLAST) is a space mission with anticipated launch in 2007. The aim is to study the gamma-ray sky in the energy range 10 keV – 300 GeV. The GLAST electromagnetic calorimeter is 8.6X0 deep and has a total of 1536 CsI(Tl) crystals each measuring 32.62.x2.67x1.99 cm3. The crystals are read out at both ends with PIN photodiodes. As a part of the quality control procedure during crystal production, samples from all CsI(Tl) boules were irradiated with gamma-rays from a 60Co source. The average decrease in light yield was found to be (13.4±0.7)% after 100 Gy, 5 times the expected dose during a 5 year mission. The correspondence between the radiation damage of boule samples and the full-sized crystals were examined. A full-size crystal was also irradiated with a 180 MeV proton beam, with a decrease in light yield of (22±5)% after a dose of 175 Gy. The induced radioactivity of the crystal was also studied and a number of radioactive nuclei could be identified. Detailed simulations of electron- and photon-induced showers in a segmented CsI calorimeter have been performed in the energy range 1 – 100 GeV, and for incident angles 0°, 30° and 60°. The energy distributions in the 1.99 cm (1.08X0) thick layers were found to change systematically along the shower, varying little with initial energy. Three probability distributions have been fitted to the data: negative binomial, log-normal and Gaussian distributions. The energy fluctuations generated from non-perpendicular incident were similar to those for perpendicular incidence. Two energy reconstruction methods were also studied, shower profile fitting and leakage correction. The latter gave better energy resolution, 5.1% and 7.6% (6.6% and 9.1%) for 1 GeV and 10 GeV electrons (photons) in the segmented 8.6X0 calorimeter. A third method, using a maximum likelihood method is also discussed. / <p>QC 20100630</p>

This thesis deals with relativistic membranes and, in particular, a limit called stretched membranes. The thesis also considers the relation of membranes to the conjectured M-theory and string theory. The thesis is divided into two parts. One introductory part where I introduce areas which are of relevance for the second part. The second part consists of the scientific papers. In the first part I make a general introduction to string theory. Furthermore, I discuss different limits of membrane theory. Then, I make a short review of the different conjectures of M-theory and briefly mention different consistency checks of these conjectures. The last subject in the first part concerns an area, which is not in direct connection to the other chapters in the thesis. This is a short introduction to the general treatment of theories with constraints. The second part of the thesis consists of the included articles. The common topic of these is that they give a new approach to the treatment of membranes. We here make a partial gauge-fixing of the constraints which, by choosing an appropriate limit, will yield a perturbation theory around a free string-like theory. The stringlike theory is the usual string theory with an extra parameter dependence. This perturbation theory we solve by infinitesimal canonical transformations. The corresponding quantum theory is also discussed. We show that a particular ordering gives critical dimensions 27 and 11 for the bosonic and fermionic case respectively.

The experimental setup SCANDAL, used for measurements of the differential cross section for elastic neutron scattering, has been upgraded with new Na doped CsI scintillating detectors for measurements at 175 MeV. Two experimental campaigns have been carried out, collecting data on three different nuclei: iron, bismuth and silicon. SCANDAL has also been used in an attempt to measure the proton content in ANITA, the white neutron beam at the The Svedberg Laboratory in Uppsala.This thesis describes the design of the new SCANDAL, and the details of the first experiment. Some of the characteristics of the new setup, such as energy resolution, are illustrated by the early steps in the analysis of the first experimental data, collected in January and February 2009.

The formation of thin films of polymer blends by spin-coating from solution is characterised by rapid solvent quenching, a process that results in non-equilibrium morphologies. Thin films of conjugated polymer blends are used as the active material in polymer solar cells, in which the morphology may have drastic effects on device performance. In this thesis results from morphology studies are presented for spin-coated thin films of polyfluorenes and co-polymers of polyfluorene blended with the fullerene derivative [6,6]-phenyl-C61-butyric acid methyl ester (PCBM). The surface morphology was investigated by atomic force microscopy (AFM) and was found to depend on the blend ratio as well as the chemical structure of the blend components. The spin speed, which determines the thickness of the spin-coated thin films, was also found to influence the morphology. Secondary ion mass spectrometry (SIMS) was used for depth profiling of the chemical composition in thin films of poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-5,5-(4´,7´-di-2-thienyl-2´,1´,3´-benzothiadiazole)] (LBPF5) blended with PCBM. The films were found to be vertically phase separated with a four-fold multilayered structure.

A quantum computer is an information processing machine, much like an ordinary classical computer, but its function is based on quantum mechanical principles. To be able to construct such a machine would be a fantastic accomplishment---to have total control over a quantum system is a dream for both physicists and science-fiction enthusiasts. The basic information unit in a quantum computer is the quantum bit, or qubit for short. A quantum computer consists of many coupled qubits. To get a single qubit to work properly, would be a major step towards building this machine. Here we study two different qubit ideas. The central element in both setups is the superconducting tunnel junction---the Josephson junction. By connecting the Josephson junctions to standard electronics in a clever way, a qubit can be realised. With these constructions it is in principle very easy to manipulate and read out the quantum probabilities, by varying voltages and currents in time. However, this ease of manipulation has a cost: strong interactions with uncontrolled degrees of freedom of the environment transfer information from the qubit. For superconducting qubits this decoherence is typically very fast. There are ways to deal with the decoherence. One way is to tune the circuit parameters so that the decoherence becomes minimal. Another way is to engineer the qubits so fast so that the effect of decoherence becomes small. In this thesis, we will apply both these strategies. Specifically, the measurement speed of the second qubit we study, turns out to be very sensitive to the topology of the phase space of the detector variables.

Solar radiation is the main driving force for the Earth’s weather and climate. It is also the prime source for renewable energy technologies.Solar energy technologies can satisfy the current energy demand and at the same time reduce anthropogenic greenhouse gas emissions. It follows from scientific and engineering research within the field that accurate terrestrial solar radiation data and derived models can improve the detection of longterm climate change, the validation of Earth radiation budget estimates, and the deployment of solar energy systems. But, accurate assessment of solar energy at the Earth’s surface is difficult due to spatial, temporal and angular variability. These variations emphasise the need for localised solar radiation measurements and models. In light of the above, this work has aimed at improving the quality of radiation data at two specific locations; one in Trondheim, Norway and the other in Durban, South Africa. This has entailed the development of an automatic data logging system, and frequent radiometer calibrations with traceability to the World Radiometric Reference. In addition, a radiometer called the Direct-Diffuse Solar Radiometer has been developed for the mapping of sky radiance. Supplementary work has been done to re-affirm the need for quality ground-based data. The work done is twofold, the first on the measurements of solar irradiance and the second on the implementation of solar radiation models. So, the presentation of the work is divided into two parts. Chapters 1 to 5 are included in Part A under the heading “Measurement of Solar Irradiance”. Chapters 6 is given in Part B, “Data Modelling”. Chapter 1 describes the concept of solar irradiance, discusses the components of solar radiation and introduces the radiometers in common use for the measurements of solar irradiance. Motivations for the development of the Direct-Diffuse Solar Radiometer are also included. Chapter 2 describes the radiation mapping at the two sites, with particular emphasis on methods implemented for higher accuracy sampling, data reliability and continuity. Regular radiometer calibration is necessary to ensure the data quality. Therefore the methodology for and results from calibration of the site radiometers are given in Chapter 3. The acquired direct and global data for the sites are presented in Chapter 4. Diurnal 1-minute variations are discussed along with estimates of monthly and annual trends, with particular emphasis on atmospheric transmittance and the clearness index. The last chapter in Part A, i.e. Chapter 5, presents the work done on the Direct-Diffuse Solar Radiometer (DDSR-1B). The instrument is designed for measuring sky irradiance as well as direct solar irradiance. The DDSR-1B is a prototype ground based instrument which is mounted on a remotely controlled solar tracker/sky positioner. The Chapter discusses the DDSR- 1B’s design, control, calibration and field tests in detail. Chapter 6 in Part B considers 2 available software products that can generate estimates of direct normal solar irradiances for any ground location. This chapter also concludes the work for this thesis by reemphasising the need for localised solar radiation measurements and models. Finally, Chapter 7 collects the major conclusions given through the course of this text.

The structure of the halo nucleus 6He has been investigated in a pionic fusion experiment at the CELSIUS storage ring facility in Uppsala. The 4He(d, 6He)π+ reaction was studied 0.6 - 5.0 MeV above threshold in the centre-of-mass frame with a deuteron beam incident on a 4He gas target. The 6He ions were detected in a ΔE - E solid-state detector telescope inserted into the CELSIUS ring. The results for the total and differential cross section are presented and compared to results for the analogue reaction producing the 3.56 MeV analogue state in 6Li. A simple model of the reaction gives results consistent with earlier findings of 6He as having a spatial extent considerably exceeding that of the alpha particle. It is also shown that information about the high momentum part of the halo wave function can be extracted from the results of this pionic fusion measurement.