The research work presented in this thesis deals with characterization ofdynamics of active photonic devices that are based on semiconductormaterials. The thesis contains an introduction and a collection of publishedarticles in peer reviewed international journals and conferences.The introduction starts with the physical background and a review of thesemiconductor material properties which both affects the design andfabrication of the devices and determine their performance in applicationssuch as wavelength, optical power and attenuation, drive current andvoltage, temperature sensitivity and modulation bandwidth.The next chapter of the introduction is dedicated to various kinds ofsemiconductor lasers. It describes the physical principles, steady stateoperation and the dynamical response. The laser is essentially an opticalcavity consisting of a material with optical gain inbetween two reflectivemirrors. Special attention is given to the spectral shape of the mirrorreflectivity and its effect on the laser dynamics and how these effects canbe distinguished from those of the gain material.In order to improve dynamic performance, it is common that the laser,instead of being directly modulated by varying the drive current, isconnected to a separate modulator. The next chapter is therefore devotedto electroabsorption modulators for high speed intensity modulation andtheir integration to lasers. In order to fully take advantage of the highintrinsic modulation bandwidth of these devices it is important to havea good microwave design to avoid electrical parasitics. A segmented paddesign to achieve this is briefly described.The last part of the introduction covers measurements techniques that wereimplemented to experimentally investigate above devices. A description ofthe measurement methods, including practical hints and methods forevaluation of the measured results are provided. / QC 20100707

Cellular homeostasis is the effort of all living cells to maintain their intracellular content when facing physiological change(s) in the extracellular environment. To date, cellular homeostasis is known to be regulated mainly by time-consuming active mechanisms and via multiple signaling pathways within the cells. The aim of this thesis is to show that time-efficient passive (physical) mechanisms also, under the control and regulation of bio-physical factors such as cell morphology and distribution and co-localization of transport proteins in the cell membrane, can regulate cellular homeostasis. This thesis has been developed in an interface between physics and biology and focuses on critical cases in which cells face physiologically unstable environments at their steady state and therefore may need a constituent effort to maintain their homeostasis. The main hypothesis here is that the cell geometry is oriented in such a way that cellular homeostasis is preserved in a given environment. For exploring these cases, comparative spatial models have been developed that combine transporting function of membrane proteins with simple versus complex geometries of cells. Models confirm the hypothesis and show that cell morphology, size of extracellular space and intercellular distances are important for a dynamic regulation of water and ion homeostasis at steady state. The main clue is the existence of diffusion limited space (DLS) in the bulk extracellular space (ECS). DLS can, despite being ECS, maintain its ionic content and water balance due a controlled function of transport proteins in the membrane facing part of DLS. This can significantly regulate cellular water and ion homeostasis and play an important role in cell physiology. In paper I, the role of DLS is explored in the kidney whereas paper II addresses the brain. The response of cells to change in osmolarity is of critical importance for water homeostasis. Cells primarily respond to osmotic challenge by transport of water via their membranes. As water moves into or out of cells, the volumes of intra- and extracellular compartments consequently change. Water transport across the cell membrane is enhanced by a family of water channel proteins (aquaporins) which play important roles in regulation of both cell and the extracellular space dimensions. Paper III explores a role for aquaporins in renal K+ transport. Experimentally this role is suggested to be different from bulk water transport. In a geometrical model of a kidney principal cell with several DLS in the basolateral membrane, a biophysical role for DLS-aquaporins is suggested that also provides physiological relevance for this study. The biophysical function of water channels is then extensively explored in paper IV where the main focus has been the dynamics of the brain extracellular space following water transport. Both modeling and experimental data in this paper confirmed the importance of aquaporin-4 expressed in astrocytes for potassium kinetics in the brain extracellular space. Finally, geometrically controlled transport mechanisms are studied on a molecular level, using silicon particles as a simplified model system for cell studies (paper V and VI). In paper V the role of electrostatic forces (around the nano-pores and in between the loaded material and the silicon surface) is studied with regard to transport processes.  In paper VI the roles of pore size and molecular weight of loaded material are studied. All together this thesis presents various modeling approaches that employ biophysical aspects of transport mechanisms combined with cell geometry to explain cell homeostasis and address cell physiology-based questions. / QC20100727

Electroacoustic technology has in many ways revolutionised the wireless telecommunication industry. The IC compatible fabrication technique of thin film electroacoustic devices has so far provided a considerable increase in device performance and reduction in size. At the moment, new areas where this technology can be of use is under investigation. In particular, thin film bulk acoustic wave resonators are promising candidates for biochemical and gravimetric sensor applications. For bulk acoustic waves, the thesis addresses a number of aspects in the design, fabrication, characterisation, and integration of thin film electroacoustic devices. The object of the studies conducted in the thesis has been to improve on design and thereby optimise the performance of the device to fit a particular application of interest. For high frequency and high power applications, a conceptually new design of the solidly mounted resonator has been investigated. A 1 GHz plate wave resonator with a much higher Q factor than its surface acoustic counterpart have also been fabricated. A multi-chip-module 2 GHz microwave oscillator featuring a monolithically integrated solidly mounted resonator and a flip chip transistor have been fabricated and characterised with a phase noise of -125 dBc/Hz at 100 kHz. For sensor applications, the fabrication of shear mode solidly mounted resonators featuring c-axis inclined AlN films has been studied. A process for the bonding of a microfluidic system on top of the resonator has been realised. Further, the effect of conductive liquids on the resonator performance has been investigated.For surface acoustic wave devices, acoustic manipulation of particles in microfluidic channels has been studied. Two functional devices have been fabricated by bonding piezoelectric substrates to glass or fused silica superstrates. By generating an interface acoustic wave, that propagates along the bonded interface, manipulation of sub-micrometer particles was realised. / wisenet

In this master thesis I have investigated one-dimensional nanostructures, so called quantum wires. The goal was to grow them in situ on a stepped silicon surface and thereafter do several kinds of measurements, like Scanning Tunneling Microscopy, Low-Energy Electron Diffraction and Photoemission. The surface that was used was a Si(332) surface and the metals used in the growth of the quantum wires were gold and silver. After the preparation and measurement of the stepped surface, evaporation of silver and gold was performed. The Scanning Tunneling Spectroscopy measurments were done on both Ag/Si(332) and Au/Si(332) surfaces. This gave information about the local density of stats on the surfaces and possible bandgaps. All experiments were performed in ultra high vacuum, except the sample cutting and the first cleaning of the surface, which was done after the Shiraki method.

We begin by recalling some basic definitions from Lie algebra theory to motivate our subsequent transition to the more general setting of category theory. Next, we develop a relatively self-contained introduction to those areas of category theory needed for an understanding of what follows. Here we also motivate and introduce the graphical calculus notations. We then state the definitions of a braided commutator algebra, a braided Lie algebra, and a braided commutator Lie algebra. We proceed to show that color Lie algebras and Lie superalgebras are examples of braided Lie algebras. Thus, we are interested in examining color Lie algebras and Lie superalgebras in the generalized setting of braided Lie algebras. So we end by examining the representation theory of braided Lie algebras and braided commutator Lie algebras. In paricular, we find analogues of the adjoint representation, the tensor product representation, and the contragredient representation.

Misconceptions in physics and especially mechanics have been the object of several studiessince the first half of the 20th century. These studies have determined which misconceptions are present. A few or none studies have been made on how the education counters these misconceptions. It is therefore important to investigate the differences in knowledge between pupils in the ages of 13 and 16 years. This study aims to investigate the knowledge of the concept of force amongst pupils in the age of 13 and 16 years, moreover to investigate if misconceptions are common with these pupils. The method selected for investigation was a survey with multiple choice questions and a few questions were the pupils were asked to draw arrows in pictures to represent forces. The result is shown in diagrams and interprets that they have a low level of understanding in this subject, it also shows that misconceptions are dominant. The difference in the results between the pupils aged 13 and 16 is not significant, and therefore the conclusion can be made that the education is performed in a wrong fashion. Moreover, the results interpret that the pupils in the ninth year of compulsory education do not meet the objectives of the Swedish curriculum, where the pupils should have knowledge about pressure, energy and the build-up of matter where force plays an important part. / Vardagsföreställningar inom fysik och i synnerhet mekanik har sedan 1900-talet första hälft hamnat i fokus i flera studier. Dessa studier har kartlagt vilka vardagsföreställningar som är förekommande. Få eller inga undersökningar har genomförts där man ställer undervisningen i fokus och hur den motverkar dessa vardagsföreställningar. Det är därför angeläget att undersöka hur skillnader ser ut mellan år sju och år nio på grundskolan. Det här arbetets syfte är att undersöka skillnaderna i förståelse för begreppet kraft mellan grundskoleelever i år sju och nio, dessutom undersöka om vardagsföreställningar är vanliga hos dessa elever. Datainsamlingsmetoden för undersökningen var en enkät med flervalsfrågor samt ett fåtal frågor där eleverna ombads rita kraftpilar i figurer. Resultaten är sammanställda och pressenteras i diagram och visar att eleverna har en låg kunskap och flera föreställningar är framträdande. Många har uppfattningen att krafter alltid verkar på kroppar som är i rörelse. Skillnaden i resultaten mellan år sju och år nio är inte betydande och slutsatsen kan därför dras att undervisningen sker på ett felaktigt sätt. Dessutom tyder resultaten på att måluppfyllelsen inte är tillräcklig för ett godkänt betyg för stora delar av eleverna i år nio, eftersom eleven enligt uppnåendemålen ska ha kunskap om tryck, energi och materiens uppbyggnad, där kraft spelar en väsentlig roll.

In this master thesis I have looked on two different kinds of representations of the Lie algebras su(2) and sl(2), and the tensor products of the representations. In the first case I looked at a tensor product involving a representation similar to one that appears in an article by A. van Tonder. This representation and tensor product was investigated mainly to get a good comprehension in the subject and to understand some of the problems that can arise. In the other case, which is the main problem in this thesis, I looked at a tensor product and representations that appears in an article by M. R. Gaberdiel. Here we deal with a tensor product of representations of su(2) with a specific value for the level at k = -4/3 and a specific eigenvalue of the Casimir operator at -2/9. This was done in the frame of finite dimensional Lie algebra and affine Lie algebra and not in the case of fusion rules as in the article by M. R. Gaberdiel. In both cases some of the calculations where done from in situ and the investigation of the representations behaviour due to the step operators, theirs eigenvalue and theirs weight system. Results and conclusions of the investigations are discussed in the last part of this thesis.

In this thesis the main purpose is to use extreme value theory and time series analysis to find modelsfor estimating the two risk measures for potential losses, value at risk and expected shortfall. Focus ison the time horizon needed to obtain predictions that are consistent with the actual outcome of anasset or a portfolio of assets. The extreme value based methods used are the Hill estimator and the peak over threshold method.The Hill estimator is also combined with a time series model. The time series model used is an AR(1)-GARCH(1,1) model. For extreme value theory based models the choice of threshold between the observations belongingto the tail and the observations belonging to the center of the distribution is crucial. In this study thethreshold is set to be 10% of the sample size, by conventional choice. There are additional methodsof choosing the threshold and some of them are presented in this paper. For each models different length of historical data is used when predictions of the risk measures aremade for different assets. The main result is that the best model and appropriate time horizon ofhistorical data to use for estimating value at risk and expected shortfall differs from dataset todataset. However, the methods that combine extreme value theory and time series models are themost flexible ones and those are the ones most likely to capture extreme events. The conditional Hillmethods with shorter time horizons seem preferable when estimating the risk measures for indices,while the Hill estimator with time horizon of three or four years is preferable for foreign exchangerates. In this study only models for single assets are evaluated, but the models could easily beimplemented on a time series of a portfolio. A multivariate case of the extreme value theory existsbut its complexity makes it disadvantageously to implement. So if for example the univariateextreme value models alone are considered inadequate to capture all the relations in a portfolio themodels could be used as a complement to the commonly used model based solely on historicalsimulation and thereby improve the risk analysis.

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