Munin: Blar i publiseringsdato Doktorgradsavhandlinger (NT-fak)

Studies of ionospheric parameters by means of electron plasma lines observed by EISCAT

Guio, Patrick (Doctoral thesis; Doktorgradsavhandling, 18-des-1998)

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Sammendrag:

This work presents a study of the electron plasma lines observed by the incoherent scatter radar EISCAT. The work is focusing on two parts. On one hand, the design of a plasma line experiment for the EISCAT system with an improved spatial resolution. On the other hand, the comparison of the plasma line data collected with the EISCAT radar with an improved model for the intensity and the Doppler frequency shift of the plasma lines. In order to improve the spatial resolution of the plasma line experiment we have designed the first experiment that implements the recent technique of alternating code. The experiment has been run successfully with an altitude resolution of 3kmas opposed to 40– 50km obtained with the conventional techniques. Because it is very difficult to construct a self-consistent model of the velocity distribution function encompassing all of the relevant energy range, we have made an ad hoc model by separating the distribution into two parts: the thermal and the supra-thermal population. The thermal population is represented by the Spitzer function that takes into account the effect of an electric field and/or a temperature gradient. The supra-thermal population is derived from the angular energy flux of the supra-thermal electrons calculated by a numerical electron transport model. A numerical code has been developed to calculate the dielectric function and the reduced one-dimensional velocity distribution for any arbitrary two-dimensional velocity distribution which are needed to model the intensity and the Doppler frequency shift of the plasma lines. We have been able to reproduce peculiar features of the intensity as well as the Doppler shift of the plasma lines with data collected with the EISCAT VHF radar. Especially, two sharp peaks in the supra-thermal distribution were identified as the signature of photo-ionisation of N2and Oand were observed in the measured data. The effect of the temperature gradient—which produces a decisive correction to the Doppler shift of the plasma lines—was taken into accountmore accurately than previously by numerical evaluation of the singular integrals rather than by the use of the first terms of a series expansion as done in other studies. This is important because it has allowed a model for the first time to reproduce accurately the intensity and the Doppler shift of the plasma line as measured by actual experiment.

URI:

http://hdl.handle.net/10037/2976

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article_2.pdf (1.308Mb)

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Low-frequency noise characterization of silicon-germanium resistors and devices

Johansen, Jarle Andre (Doctoral thesis; Doktorgradsavhandling, 03-jun-2004)

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Sammendrag:

The main topic of this thesis is experimental low-frequency electrical noise characterization of semiconductor devices. In particular, we concentrate on applications of the silicon-germanium alloy (SiGe). Low-frequency electrical noise is a sensitive measure of defects and non-idealities in semiconductor devices, which directly or indirectly impact device performance and reliability. Thus, it is of prime importance to be able to characterize the noise in semiconductor devices. We compare the low-frequency noise from poly-crystalline silicon-germanium thin film resistors with different germanium content, film thickness and doping level. The noise level decreases with increasing doping density. We find that the germanium content and film thickness have little influence on the noise level. The noise was found to stem from mobility fluctuations in the depletion region of the grains. We compare the low-frequency noise of silicon based field-effect transistors with poly-crystalline gates, made from silicon and silicon-germanium. The output noise level for N-MOSFETs is independent of the gate material, whereas for P-MOSFETs the silicon-germanium gate material results in lower noise. Analysis of fluctuating physical quantities, points towards mobility fluctuations for P-MOS, and number fluctuations for N-MOS. We present results from measurement of the low-frequency electrical noise in Al- GaInP QuantumWell Lasers. Experimental evidence of a connection between the noise and device reliability is found, and hence, low-frequency noise measurements can be used as a non-destructive reliability indicator for laser diodes. The low-frequency noise in state-of-the-art silicon-germanium Heterojunction Bipolar Transistors (HBTs) is explored. Device geometrical down-scaling induces a deviceto- device noise variation, caused by small sets of noise generating traps, that are different from device to device. We use proton irradiation to introduce additional traps, and find that it can reduce the noise variation without increasing the noise level significantly. Aggressive down-scaling normally results in higher low-frequency noise. However, we find that the latest generation of SiGe HBTs (> 200 GHz) breaks this trend, and only a residual background noise remains, resulting in record values of low-frequency noise level and noise corner frequency. We present, and apply, recent statistical tools to probe for non-linear coupling between frequency components in a noise signal. These tools are applied to low-frequency noise time series with Random Telegraph Signal (RTS) noise from small geometry SiGe HBTs. The noise in small HBTs is shown to be non-Gaussian and non-linear. The nonlinearity is shown to originate from the RTS component of the noise.

URI:

http://hdl.handle.net/10037/345

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thesis.pdf (2.912Mb)

Angles as tool for grasping space. Teaching of angles based on students’ experiences with physical activities and body movement

Fyhn, Anne Birgitte (Doctoral thesis; Doktorgradsavhandling, 13-jun-2007)

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Sammendrag:	The thesis enlightens how the choice of context as well as the approach to mathematics is important in introducing the concepts of angles. The analyses indicate that students should not be introduced to measuring angles before they are able to sort out angles according to their sizes. Angles can be introduced by use of the students’ bodies in a climbing context, where the word angle refers to bent shape. Climbing is an activity which to a large extent is experienced as exciting and fun. The idea is to base the teaching on the students’ talk about climbing. The teacher’s job is to guide the students to build up their understanding of angles as a tool for improved climbing technique. The students’ use of drawing and text in describing and explaining angles in a climbing context is analysed. These analyses indicate that the teaching should point out differences between narrative and analytical text and drawing and then the students’ analytical drawings can function as basis for their further work with geometry. The thesis focuses on students’ mathematising of climbing and on how the participating teachers relate to this activity. The analyses indicate that the teachers need some experience with inductive teaching of mathematics in some practical context before they are able to grasp the value of their students’ mathematising. Thus two DVDs are made. The first one shows how inductive physical geometry activities can function as basis for written and oral tasks in mathematics. The second DVD shows how students can mathematise climbing with respect to angles, and how experiences from one climbing situation can function as basis for adapting the teaching of angles to the students’ different levels of understanding.
Beskrivelse:	DVD 1, which is part of the thesis introduction, is not made available in Munin due to restrictions in the Personal Data Act.
URI:	http://hdl.handle.net/10037/994

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Quality of service aware binding in open systems

Hanssen, Øyvind (Doctoral thesis; Doktorgradsavhandling, 07-feb-2008)

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Sammendrag:	This thesis addresses negotiation of bindings in QoS aware open systems and in particular how to characterize possible contracts, requirements and capabilities of heterogeneous environments. Our approach is (1) to use trading of policies as the principle for negotiation and (2) the use of declared or rule-based conformance for QoS statements to be used in negotiation and (3) a middleware binding framework supporting negotiable bindings. A policy is an architectural entity which encapsulates a potential QoS contract plus a resource and implementation configuration to enforce the contract. The contract part (profile) consists of an obligation to be matched with requirements and an expectation to be matched with descriptions of the environment. A policy may encapsulate how implementation components and properties of environments are combined to achieve a QoS level. Policy trading is the proposed principle for negotiation. Potential contracts may be orthogonal to interfaces and interface types, and are associated with some trading service. Negotiation is essentially to collect requirements and environment descriptions from participants and match these with policies. We investigate an approach to contract matching based on declared conformance. An important contribution is the development of a declarative expression language for profiles, requirement and environment descriptions used in negotiation at run-time. We propose to define conformance as rule bases. Such rule bases can be compiled to efficient conformance checking code. We propose two composition operators to combine expressions at run-time and develop the foundations of a generic conformance checking algorithm for profile expressions. A prototype binding framework is developed, supporting activation of bindings, pluggable binder and activator components. The framework is extended to support negotiation using policy trading and profile expressions. The approach is validated by examples and proof of concept implementations. A profile model compiler, a policy trader and the binding framework are implemented and applied to example applications.
Beskrivelse:	The trial lecture of the thesis defence is available in Munin at http://hdl.handle.net/10037/2840.
URI:	http://hdl.handle.net/10037/1350

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appendix.pdf (5.377Mb)

thesis.pdf (1.284Mb)

Higher-order SCF response functions in a quasi-energy formulation

Thorvaldsen, Andreas J. (Doctoral thesis; Doktorgradsavhandling, 30-sep-2008)

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Sammendrag:	This thesis is concerned with computer modelling of molecules interacting with electromagnetic radiation (light, radio waves, etc.), static electric and magnetic fields (in the laboratory), as well as approximate treatments of the motions of the molecules' atomic nuclei (vibration). Compared to interactions between electrons or between electron and nucleus, these interactions are small, and well approximated by perturbation theory. Perturbation of isolated molecules in their ground state by time-dependent electromagnetic fields is known as 'response theory' (response functions), and permits study of both ground and excited states. For the 'self-consistent field' (SCF) class of electronic structure models, which includes the popular Kohn-Sham DFT models, this thesis presents a full hierachy of new formulas for response functions. Although there are several equivalent formulas for a given response function, one specific is typically preferable due to computational considerations. The derived formulas are expressed in terms of the atomic-orbital (AO) density matrix, and take into account time- and perturbation dependence of the AOs, such as magnetic-field-dependent 'London AOs' or 'gauge-including AOs', which are employed to obtain gauge-origin independent results with improved basis set convergence. The density matrix has an advantage over the more common molecular orbital (MO) parameterization in that it typically decays rapidly with the distance between atoms. For large molecules one may therefore truncate the density matrix. This can lead to great computational savings. We formulate response theory by applying perturbation theory to 'Floquet theory' (sometimes called optical Bloch equations), which is a semi-classical quantum field theory. The central quantity in Floquet theory is the 'quasi-energy', and this is therefore the 'quasi-energy formalism' of response theory. We have implemented the response function formulas in a local version of the DALTON quantum chemistry program, and demonstrate applications to the Cotton-Mouton birefringence, coherent anti-Stokes Raman scattering, electric-field-gradient induced birefringence, and to the vibrational corrections to hyperpolarizabilities.
Beskrivelse:	Papers number 2,3 and 5 of the thesis are not available in Munin due to publishers' restrictions: 2. Thorvaldsen AJ, Ferrighi L, Ruud K, Ågren H, Coriani S, Jørgensen P.:"Analytic ab initio calculations of Coherent anti-Stokes Raman Scattering (CARS)." Physical Chemistry Chemical Physics 2009; 11: 2293-2304 (Royal Society of Chemistry). Available at http://dx.doi.org/10.1039/b812045e 3. Thorvaldsen AJ, Ruud K, Jaszunski M.:"Analytic calculations of vibrational hyperpolarizabilities in the atomic orbital basis."Journal of Physical Chemistry A 2009; 356(1-3): 177-186 (Elsevier) Available at http://dx.doi.org/10.1016/j.chemphys.2008.10.033 5. Shcherbin D, Thorvaldsen AJ, Ruud K, Rizzo A, Coriani S.:" Analytical calculations of nonlinear mixed electric and magnetic frequency-dependent molecular properties using London atomic orbitals: Buckingham birefringence." Physical Chemistry Chemical Physics 2009; 11: 816-825. (Royal Society of Chemistry). Available at http://dx.doi.org/10.1039/b815752a
URI:	http://hdl.handle.net/10037/2136

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paper_I.pdf (457.0Kb)

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Changing circumstances : implications for trophic dynamics and species conservation in the Fennoscandian tundra

Henden, John-André (Doctoral thesis; Doktorgradsavhandling, 16-mar-2009)

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Sammendrag:	A special case of population fluctuation is multi-annual population cycles. While such population cycles exist in several ecosystems, they are more prominent in northern (e.g.tundra) ecosystems, especially among key stone herbivore species. These herbivores providean important ecosystem function in the sense of pulsed flows of resources (i.e. for predators) and disturbances (i.e. for vegetation) throughout the ecosystem. However, the circumstances on the tundra are changing. For instance, large scale collapse of population cycles of many herbivors has been reported, as well as northward expansion of novel predators (e.g. red fox). These changes, heavily connected to climate changes, are capable of disrupting the function and structure of such systems. Overall this thesis aims to outline and evaluate the recent dramatic changes in multi-annual population cycles of many herbivores and the possible implications of such changes on the trophic dynamics and species conservation in the Fennoscandinavian tundra ecosystem. First I show that the recent collapse of multi-annual population cyclles are now a widespread phenomenon, extending several species and ecosystem barriers. Next I show, based on long time series of fox bounty data, that these recent changes have some historical analogies. Specifically, I show that the highly publicized patterns (e.g. geographic gradients, large scale synchrony) in Fennoscandian small rodent cycle have been buject to large spatio-temporal trensitions in their patterns, being highly non-stationary. I also demonstrate that collapse of cycles similar to the recent events, though on a smaller spatial extent, have occurred earlier and that these incidents seem to concur with shifts between cold and warm climatic periods. Then I demonstrate wich aspects of the recent changes in the dynamics of key prey species is likely to heavily affect the viability and existence of tundra predatirs strongly adapted to the pulsed flow of resources provided bycyclically fluctuating prey populations. Furthermore, the effect of recent and future projections of climate change may facilitate the establishment of novel predator species, which may act as dominant competitors for native species for habitat and prey. I here show that increased competition with red fox may be detrimental to arctic fox viability, especially if subsidies (e.g. reindeer carcasses) are available to the dominant competitor. Finally, I show that attempts to conserve native predators, such as the arctic fox, should take into account the factors that govern their demography and thus population dynamics. I show thet the effect of management action is highly dependent onthe phase of the demographic cycle of arctic fox. This means that management intervantion should be continous, but most focused to moments in time where the effect is expected to be most pronounced.
Beskrivelse:	Papers number 1,2 and 3 of the thesis are not available in Munin due to publishers' restrictions. 1.Rolf A. Ims, John-André Henden, Siw T. Killengreen.: "Collapsing population cycles." Trends in Ecology & Evolution; 23(2): 79-86 (Science Direct). Available at http://dx.doi.org/10.1016/j.tree.2007.10.010 2.John-André Henden, Rolf A. Ims, Nigel G. Yoccoz.: "Nonstationary spatio-temporal small rodent dynamics: evidence from long-term Norwegian fox bounty data." Journal of Animal Ecology; 78(3): 636-645 (Wiley). Available at http://dx.doi.org/10.1111/j.1365-2656.2008.01510.x 3.John-André Henden , Bård-Jørgen Bårdsen, Nigel G. Yoccoz, Rolf A. Ims.: " Impacts of differential prey dynamics on the potential recovery of endangered arctic fox populations." Journal of Applied Ecology Journal of Applied Ecology; 45(4): 1086-1093 (Wiley). Available at http://dx.doi.org/10.1111/j.1365-2664.2008.01515.x
URI:	http://hdl.handle.net/10037/2585

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POP-cocktails : hangover threats for seabirds? The response of three seabird species to exposure to persistent organic pollutants in the Barents Sea

Sagerup, Kjetil (Doctoral thesis; Doktorgradsavhandling, 11-jun-2009)

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Sammendrag:	The overall aim of the thesis was to study immunological effects of pollutants in Barents Sea. The Glaucous gull (Larus hyperboreus), black-legged kittiwake (Rissa tridactyla) and Atlantic puffin (Fratercula arctica) were studied. The apex predatory glaucous gull have high levels of persistent organic pollutants (POPs), while the fish eating black-legged kittiwake and Atlantic puffin are located lower in the food-chain and have lower levels of POPs. In breeding glaucous gulls, positive correlations between levels of intestinal nematode and organochlorine (OC) levels were observed. The intestinal parasite intensities could be seen as an end result of the immune system’s battle against the establishment and survival of the parasites. An increased infection with increased OC levels might be explained by immune suppression activity of OCs. The influence of the Barents Sea’s POP-cocktails on the developing immune system was studied on laboratory-raised glaucous gull chicks. The polluted group that simulated “naturally” polluted glaucous gull chicks responded less well to an influenza vaccine and had lower levels of circulating immunoglobulin-G (IgG) and IgM than the control group. The hypothesis of a POP-induced immune suppression was also investigated in the less polluted black-legged kittiwake and Atlantic puffin. The predictions of an altered level of circulating IgG with OCP, PCB or PBDE levels were tested. The results show no indication of correlations between the IgG and pollutant levels. Naturally dead glaucous gulls were studied in an attempt to evaluate whether pollutants contribute to the death. Autopsies and POP analyses reveal that the brain levels of pesticides and PCBs were the same as in a sample of dead glaucous gulls from 1989, while the liver levels were significantly lower. The brain levels thereby strengthen the theory that an additional stress provided from elevated pollutant levels could be deadly.
Beskrivelse:	Papers number 1,2 and 3 of the thesis are not available in Munin due to publishers' restrictions. Paper 4 is a manuscript, and not available in Munin. 1. Sagerup, K., Henriksen, E.O., Skorping, A. Skaare, J.U., Gabrielsen G.W.: "Intensity of parasitic nematodes is associated with organochlorine levels in the glaucous gull (Larus hyperboreus)." Jornal of Applied Ecology 2000; 37: 532-239 (British Ecology Society). Available at http://dx.doi.org/10.1046/j.1365-2664.2000.00521.x 2. Sagerup, K., Larsen, H.J.S., Skaare, J.U., Johansen, G.M., Gabrielsen, G.W.: "The toxic effects of multiple persistent organic pollutant exposures on the post-hatch immunity maturation of glaucous gulls." Journal of Toxicology and Environmental Health - Part A 2009; 72: 1-14 (Taylor & Francis). Available at http://dx.doi.org/10.1080/15287390902959516 3. Sagerup, K., Savinov, V., Savinova, T., Kuklin, V.V., Muir, D.C.G., Gabrielsen, G.W.: "Persistent organic pollutants, heavy metals and parasites in the glaucous gull (Larus hyperboreus) on Spitsbergen." Environmental Pollution 2009; 157(8-9): 2282-2290 (Elsevier). Available at http://dx.doi.org/10.1016/j.envpol.2009.03.031 4. Sagerup, K., Åsbakk, K., Polder A., Skaare, J.U., Gabrielsen, G.W., Barrett, R.T.: "The effect of persistent organic pollutants (POPs) on the immune system of black-legged kittiwakes and Atlantic puffins in the Barents Sea." Manuscript.
URI:	http://hdl.handle.net/10037/2244

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thesis.pdf (1.273Mb)

Behavioral and energetic response of Arctic-breeding seabirds to environmental variability.

Welcker, Jorg (Doctoral thesis; Doktorgradsavhandling, 16-jun-2009)

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Sammendrag:	Knowledge about the extent to which organisms inhabitating the Arctic are able to adjust to environmental variability is essential in order to predict the impact of future climate change. In this context, the flexibility og two Acrtic-breeding seabirds, the little Auk (Alle alle) and the kittiwake (Rissa tridactyla), in foraging behavior and energy expenditure in response to environmental variability. Analysis of the foraging behavior of little auks revealed the during chick-rearing this species adopts a bimodal foraging strategy in which they alternate single foraging trips of long duration with several trips of short length. This stereotyped pattern was found to be highly flexivle and adjusted to psatial and temporal variation in foraging conditions. However, behavioral modifications led to reduced chick feeding rates and lower reproductive success, indicating the adjustments did not allow birds to fully compensate for costs incurred by unfavorable conditions. Adjustment and limitation of energy expenditure differed remarkably between the two study species. Metabolic rate in little auks was flexible and adjusted in response to variation in food availability. Birds increased energy expenditure when food was abundant. Elevated metabolism was associated with increased chick provisioning, resulting in enhanced chick surival, and increased resource allocation to self-maintenance, associated with higher body mass and a higher return rate of individuals the subsquent season. In contrast, kittiwakes did not adjust their metabolic rate in response to environmental variability. In this species, metabolic rate was similar across five study years despite large variation in foraging conditions. Instead, kittiwakes seemed to operate close to an energetic ceiling which seemed independent of extrinsic factors. This study suggested a limited ability of Arctic seabirds to compensate for large variation to environmental conditions.
Beskrivelse:	Papers number 1, 2 and 3 of the thesis are not available in Munin due to publishers' restrictions. Papers 4 and 5 are manuscripts, and not available in Munin. 1. Jorg Welcker, Ann M. A. Harding, Nina J. Karnovsky, Harald Steen, Hallvard Strøm and Geir W. Gabrielsen: "Flexibility in the bimodal foraging strategy of a high Arctic alcid, the little auk Alle alle." Journal of Avian Biology 2009; 40(4): 388-399 (Wiley). Available at http://dx.doi.org/10.1111/j.1600-048X.2008.04620.x 2. Jorg Welcker, Harald Steen, Ann M. A. Harding and Geir W. Gabrielsen: "Sex-specific provisioning behaviour in a monomorphic seabird with a bimodal foraging strategy." Ibis 2009; 151(3): 502-513 (Wiley). Available at http://dx.doi.org/10.1111/j.1474-919X.2009.00931.x 3. Jorg Welcker, Ann M. A. Harding, Alexander S.Kitaysky, John R. Speakman and Geir W. Gabrielsen: "Daily energy expenditure increases in response to low nutritional stress in an Arctic-breeding seabird with no effect on mortality." Functional Ecology 2009; 23(6): 1081-1090 (Wiley). Available at http://dx.doi.org/10.1111/j.1365-2435.2009.01585.x 4. Jorg Welcker, Børge Moe, Claus Bech, Jannik Schultner, John R. Speakmana and Geir W. Gabrielsen: "Evidence for an energetic ceilinf in free-ranging kittiwakes (Rissa tridactyla)". Manuscript 5. Jannic Schultner, Jorg Welcker, John R. Speakman, Erling S. Nordøy and Geir W. Gabrielsen: "Application of the two-sample doubly-lebeled water method alters behavior and affects estimates of energy expenditure in black-legged kittiwakes". Manuscript
URI:	http://hdl.handle.net/10037/2598

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thesis.pdf (3.297Mb)

Particle precipitation : effects on selected ionospheric phenomena

Lunde, June (Doctoral thesis; Doktorgradsavhandling, 26-nov-2009)

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Sammendrag:	The motivation behind this thesis has been to study particle precipitation from the Sun into the Earth’s upper atmosphere and its effects on selected ionospheric phenomena. Particles from the solar wind can enter the Earth's magnetosphere through magnetic merging, either at the sub-solar point, or at higher latitudes, depending on the configuration of the interplanetary magnetic field. This interaction can be studied from the ground at Svalbard, due to its fortuitous location beneath the magnetospheric cusp region on the dayside, and its location inside the polar cap during night-time. It has been studied how these precipitating particles act on the aurora and ion-acoustic waves in the ionized part of the atmosphere. The studies have been conducted using various methods, including extracting data from databases, running different experiments and building new instrumentation. The latter was a radiation detector for measuring Bremsstrahlung X-rays. The main instrument used for this study has been the EISCAT (European Incoherent SCATtering) radar located at Svalbard, together with an assortment of other ground based instruments such as photometers, riometers and magnetometers. In addition, particle instruments onboard satellites have been used as well as an X-ray instrument mounted on a balloon launched from Longyearbyen. Primarily, it is the effect of particle precipitation on large ion-acoustic waves that has been studied. These waves can be observed by advanced radar facilities, both from Svalbard and Tromsø (EISCAT) in the form of spectra known as natural enhanced ion acoustic lines (NEIALs). It has been found that the most energetic particle precipitation causes ion-acoustic waves which mainly propagate downward, while the less energetic part of the particle precipitation is related to ion-acoustic waves which propagate upward. In this project, large ion-acoustic waves have been discovered during night-time at very high latitudes where they were not expected to occur. Previously, these phenomena have only been observed during daytime at Svalbard. Furthermore, in this work, the infrared atomic oxygen emission line (844.6 nm) has been introduced as a new possible method to detect NEIALs in optical data. Particle precipitation sometimes cause flickering aurora, hence intensity variation and the apparent motion of flickering spots in the aurora have been studied. Finally, precipitating particles typically consists of electrons and ions, and in this study, an example is given on of how the merging of the Earth’s and Sun’s magnetic fields guide the precipitation.
Beskrivelse:	Papers 2 and 4 are not available in Munin: 2. T. Grydeland, B. Gustavsson, L. Baddeley, J. Lunde, and E. M. Blixt: 'Conditional integration of Incoherent Scattering in relation to flickering aurora', Journal of Geophysical Research (2008), vol.113, A08305, 8pp. Available at http://dx.doi.org/doi:10.1029/2008JA013039 4. B. Gustavsson, J. Lunde, and E. M. Blixt: 'Optical observations of flickering aurora and its spatio-temporal characteristics', Journal of Geophysical Research (2008), vol.113, A12317, 8pp. Available at http://dx.doi.org/10.1029/2008JA013515
URI:	http://hdl.handle.net/10037/4221

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thesis.pdf (7.645Mb)

The few touch digital diabetes diary : user-involved design of mobile self-help tools for peoplewith diabetes

Årsand, Eirik (Doctoral thesis; Doktorgradsavhandling, 10-des-2009)

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Sammendrag:	Paradoxically, the technological revolution that has created a vast health problem due to a drastic change in lifestyle also holds great potential for individuals to take better care of their own health. The first consequence is not addressed in this dissertation, but the second represents the focus of the work presented, namely utilizing ICT to support self-management of individual health challenges. As long as only 35% of the patients in Norway achieve the International Diabetes Federation‟s goal for blood glucose (HbA1c), actions and activities to improve blood glucose control and related factors are needed. The presented work focuses on the development and integration of alternative sensor systems for blood glucose and physical activity, and a fast and effortless method for recording food habits. Various user-interface concepts running on a mobile terminal constitute a digital diabetes diary, and the total concept is referred to as the “Few Touch application”. The overall aim of this PhD project is to generate knowledge about how a mobile tool can be designed for supporting lifestyle changes among people with diabetes. Applying technologies and methods from the informatics field has contributed to improved insight into this issue. Conversely, addressing the concrete use cases for people with diabetes has resulted in the achievement of ICT designs that have been appreciated by the cohorts involved. Cooperation with three different groups of patients with diabetes over several years and various methods and theories founded in computer science, medical informatics, and telemedicine have been combined in design and research on patient-oriented aids. The blood glucose Bluetooth adapter, the step counter, and the nutrition habit registration system that have been developed were all novel and to my knowledge unique designs at the time they were first tested, and this still applies to the latter two. Whether it can be claimed that the total concept presented, the Few Touch application, will increase quality of life, is up to future research and large-scale tests of the system to answer. However, results from the Type 2 diabetes half-year study showed that several of the participants did adjust their medication, food habits and/or physical activity due to use of the application.
Beskrivelse:	Paper number 2, 4, 5 and 7 are not available in Munin, due to publishers' restrictions: 2. Årsand E, and Demiris G.: "User-Centered Methods for Designing Patient-Centric Self-Help Tools", Informatics for Health and Social Care, 2008 Vol. 33, No. 3, Pages 158-169 (Informa Healthcare). Available at http://dx.doi.org/10.1080/17538150802457562 4. Årsand E, Olsen OA, Varmedal R, Mortensen W, and Hartvigsen G.: "A System for Monitoring Physical Activity Data Among People with Type 2 Diabetes", pages 173-178 in S.K. Andersen, et.al. (eds.) "eHealth Beyond the Horizon - Get IT There", Proceedings of MIE2008, Studies in Health Technology and Informatics, Volume 136, May 2008, ISBN: 978-1-58603-864-9 5. Årsand E, Tufano JT, Ralston J, and Hjortdahl P.: "Designing Mobile Dietary Management Support Technologies for People with Diabetes", Journal of Telemedicine and Telecare, 2008 Volume 14, Number 7, Pp. 329-332 (Royal Society of Medicine Press). Available at http://dx.doi.org/10.1258/jtt.2008.007001 7. Årsand E, Walseth OA, Andersson N, Fernando R, Granberg O, Bellika JG, and Hartvigsen G.: "Using Blood Glucose Data as an Indicator for Epidemic Disease Outbreaks", pages 199-204 in R. Engelbrecht et.al. (eds.): "Connecting Medical Informatics and Bio-Informatics", Proceedings of MIE2005, Studies in Health Technology and Informatics, Volume 116, August 2005, ISBN: 978-1-58603-549-5. Check availability
URI:	http://hdl.handle.net/10037/2762

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Statistical Analysis of Multilook Polarimetric Radar Images with the Mellin Transform

Anfinsen, Stian Normann (Doctoral thesis; Doktorgradsavhandling, 19-mai-2010)

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Sammendrag:

This thesis presents methods for statistical analysis of the probability distributions used to model multilook polarimetric radar images. The methods are based on a matrix-variate version of Mellin's integral transform. The proposed theoretical framework is referred to as Mellin kind statistics. It is an extension of a theory recently developed for single polarisation amplitude and intensity data to the complex matrix-variate case describing multilook polarimetric images. This generalisation is made possible by the rediscovery of a generalised Mellin transform, which is defined for functions of positive definite Hermitian matrices. The domain makes it suited for application to the distributions used to model the polarimetric covariance and coherency matrix. The analysis tools include the matrix-variate Mellin kind characteristic function, which is defined with the Mellin transform in place of the conventional Fourier transform. Matrix log-moments and matrix log-cumulants are retrieved from this function. The matrix log-cumulants are used in a moment based approach to parameter estimation of the distribution parameters. The estimators make efficient use of all the statistical information in the polarimetric covariance matrix, and are superior to all known alternatives. The matrix log-cumulants are also used to construct the first known goodness-of-fit test for matrix distributions based on the multilook polarimetric product model. The algorithms are interpreted by means of a highly informative graphical visualisation tool displaying a space spanned by certain matrix log-cumulants. It is demonstrated that the matrix-variate Mellin transform is the natural tool for analysing multilook polarimetric radar images. This conclusion is based on the simple and elegant mathematical expressions obtained, the superb statistical properties of developed estimators, as well as the intuitive interpretations offered by the Mellin kind statistics.

URI:

http://hdl.handle.net/10037/2471

Tilhørende fil(er): 5

paper_1.pdf (5.533Mb)

paper_2.pdf (613.3Kb)

paper_3.pdf (1.662Mb)

thesis_entire.pdf (9.069Mb)

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Relative sea level, deglaciation and tsunami history deduced from isolation basins

Romundset, Anders (Doctoral thesis; Doktorgradsavhandling, 15-okt-2010)

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Sammendrag:	NORSK SAMANDRAG: Denne avhandlinga tek for seg endringane i relativt havnivå – strandforskyvinga – dei siste vel 11.500 åra på kysten av Finnmark og i midtre Hardanger. Ei stor mengd kjerneprøver frå avsettingane i innsjøar som ein gong låg under havnivået, er henta inn og analysert. Grenser mellom sediment som vart avsett i salt- eller ferskvatn er bestemt ved å analysere både kiselalgar og restar etter daude dyr og planter, og tidfest ved hjelp av radiokarbondatering. I lag med presist oppmålte høgder på innsjøtersklane, gjer desse data det mogleg å rekonstruere havnivåendringane i høg detalj. Her blir det presentert havnivåkurver som syner utviklinga i fire område; Tørvikbygd i Hardanger, Sørøya og Rolvsøya i vest-Finnmark og Nordkinnhalvøya i aust-Finnmark. Desse dokumenterer samspelet mellom landheving og havnivåstiging – stort sett har landhevinga vore sterkast, men i tida mellom ca. 9-7000 år sidan var det motsette tilfelle på finnmarkskysten – da vart fleire innsjøar atter oversvømt etter å ha lege fleire tusen år over havnivået. På Rolvsøya steig havnivået opp over ein innsjø men nådde ikkje den neste som ligg rett attmed, berre omlag 60 cm høgare. Her stabiliserte det seg i meir enn tre tusen år, fram til for ca. 5000 år sidan. Etter det har havnivået falle fleire meter fram til i dag. Ei liknande utvikling er òg funne på Sørøya og Nordkinnhalvøya, men i Tørvikbygd er historia ei anna. Her vart landet mykje hardare nedpressa mot slutten av siste istid, og landhevinga har vore tilsvarande sterk, særleg det fyrste tusenåret etter at isen forsvann – da datt strandlina gjennomsnittleg med meir enn 5 cm i året. Breen som dekte Barentshavet under siste istid, smelta vekk tidlegare enn isen over Finnmark. Dette førte til sterk heving av havbotnen som også virka inn på tidleg isfrie område av ytterkysten og medførte at spranget mellom marin grense og yngre strandliner er langt større her enn langs andre delar av norskekysten. I tillegg er bidraget til hevinga frå Barentshavet, truleg i lag med ein slakare profil på innlandsisen, årsaka til at dei heva strandlinene i Finnmark hallar mindre enn dei gjer t.d. på Vestlandet. Det er funne klåre spor etter ein tsunami i fem av innsjøane på Finnmarkskysten. Dateringar syner at dette må ha vore Storeggatsunamien, som vart utløyst av eit enormt undersjøisk skred utafor Mørekysten for om lag 8100-8200 år sidan. Bølgja slo opp i alle fall 3-4 meter i høgda, og mange hundre meter innover land. Erosjonen var sterkast nært sjøen der tsunamien grov sed ned i meir enn 3000 år eldre avleiringar. Over erosjonskontakten ligg nedst eitt sandlag, fylgd av mellom anna opprivne torvbitar og gytjeklumpar som tydeleg har rulla i sanda. Den valdsamme erosjonen og dei sorterte avsettingane tilseier at tsunamien må ha råka 17 innsjøar som ikkje var islagte, og på denne tida var klimaet vesentleg kaldare enn i dag. Dette gjer det truleg at både Storeggaskredet og tsunamien hende ein gong mellom april og oktober.
Beskrivelse:	Paper number 1 of the thesis is not available in Munin due to publisher's restrictions: 1. Romundset, A., Lohne, Ø.S., Mangerud, J. & Svendsen, J.I.: «The first Holocene relative sea-level curve from the middle part of Hardangerfjorden, western Norway», Boreas 39(2010), 87-104 (Wiley). Available at http://dx.doi.org/10.1111/j.1502-3885.2009.00108.x
URI:	http://hdl.handle.net/10037/2703

Tilhørende fil(er): 3

paper_2.pdf (6.899Mb)

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thesis.pdf (878.2Kb)

Signal processing techniques for the enhancement of marine seismic data

Sanchis, Charlotte Juliette (Doctoral thesis; Doktorgradsavhandling, 12-nov-2010)

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Sammendrag:

This thesis presents several signal processing techniques applied to the enhancement of marine seismic data. Marine seismic exploration provides an image of the Earth's subsurface from reflected seismic waves. Because the recorded signals are contaminated by various sources of noise, minimizing their effects with new attenuation techniques is necessary. A statistical analysis of background noise is conducted using Thomson’s multitaper spectral estimator and Parzen's amplitude density estimator. The results provide a statistical characterization of the noise which we use for the derivation of signal enhancement algorithms. Firstly, we focus on single-azimuth stacking methodologies and propose novel stacking schemes using either enhanced weighted sums or a Kalman filter. It is demonstrated that the enhanced methods yield superior results by their ability to exhibit cleaner and better defined reflected events as well as a larger number of reflections in deep waters. A comparison of the proposed stacking methods with existing ones is also discussed. We then address the problem of random noise attenuation and present an innovative application of sparse code shrinkage and independent component analysis. Sparse code shrinkage is a valuable method when a noise-free realization of the data is generated to provide data-driven shrinkages. Several models of distribution are investigated, but the normal inverse Gaussian density yields the best results. Other acceptable choices of density are discussed as well. Finally, we consider the attenuation of flow-generated nonstationary coherent noise and seismic interference noise. We suggest a multiple-input adaptive noise canceller that utilizes a normalized least mean squares alg orithm with a variable normalized step size derived as a function of instantaneous frequency. This filter attenuates the coherent noise successfully when used either by itself or in combination with a time-frequency median filter, depending on the noise spectrum and repartition along the data. Its application to seismic interference attenuation is also discussed.

URI:

http://hdl.handle.net/10037/2794

Tilhørende fil(er): 3

thesis.pdf (30.12Mb)

thesis-sanchis-1.pdf (11.77Mb)

thesis-sanchis-2.pdf (18.49Mb)

Characterization of sub-seabed fluid flow and hydrate systems at Nyegga, offshore mid- Norway : integration of seismic imaging and velocity modeling

Plaza-Faverola, Andreia Aletia (Doctoral thesis; Doktorgradsavhandling, 12-nov-2010)

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Sammendrag:	What causes the escape of natural gases to the seafloor and how significant this escape has been along the mid-Norwegian continental margin? These are questions that guided the doctoral thesis. The thesis is part of a research project supported by the European Commission and the Norwegian Research Council, which aims at quantifying geological processes that control fluid flow and gas hydrate formation along the Norwegian-Barents-Svalbard margin. The thesis was divided in three stages according to the following three main objectives: (1) to assess the distribution of shallow gas reservoirs and paths for fluid migration from deep sources; (2) to investigate the internal structure of a vertical fluid escape feature (chimney) through implementation of high resolution travel-time reflection tomography modeling; and (3) to infer a time scale for fluid escape in the region through detailed seismic characterization of depositional settings and sediment deformation of sediments deposited during the last three major glaciations and their inter-glacial cycles. The methodology implemented consists in the integration of velocity analysis techniques and seismic imagine applied to different resolution seismic data sets. The thesis presents results from four articles that together bring us closer to the overall understanding of fluid flow related systems in Nyegga, offshore mid-Norway. While each article has separate and specific aims, the problems and results covered by the four articles are nevertheless guided by a single motive: to access geophysical and geological indications of sub-seabed fluid flow processes by the implementation of non-invasive methods. Two of the most important results encountered are first, that gas hydrates are at present hindering catastrophic escapes of fluids towards the seafloor; and second that fluid escape in the margin has seemingly been episodically. Fluid escape periods seem to be related to overpressure generation during the last three glaciations.
Beskrivelse:	Paper number 1 and 2 of the thesis are not available in Munin due to publishers' restrictions: 1. Plaza-Faverola, A., S. Bünz, and J. Mienert (2010). "Fluid distributions inferred from Pwave velocity and reflection seismic amplitude anomalies beneath the Nyegga pockmark field of the mid-Norwegian margin", Marine and Petroleum Geology, 27(1): 46-60 2. Plaza-Faverola, A., G. K. Westbrook, K. Stephan, R. Exley, A. Gailler, T. Minshull and K. Broto, (2010). "Evidence from tomographic investigation of Vp variation for accumulation of substantial methane hydrate in a fluid-escape chimney in the Nyegga pockmark field, offshore Norway". JGR solid earth. v. doi:10.1029/2009JB007078, in press.
URI:	http://hdl.handle.net/10037/2812

Tilhørende fil(er): 3

paper-3.pdf (1.402Mb)

paper-4.pdf (1.854Mb)

thesis.pdf (1.368Mb)

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Sammendrag:	To contribute to the fundamental picture of the electronic structure of low-coordinate transition metal complexes, we have carried out a series of DFT studies on mono-imido and nitrosyl complexes for different metal ions (Mn^II/III, Fe^II/III/IV, Co^II/III) and different systems of basal ligands. These studies reveal striking similarities of the electronic structure for these systems. The distinction of bent versus linear NO units is attributed to the ranking of the dz2 and dxz/yz parentage MOs relative to each other. Without a ligand trans to the NO group, the antibonding metal dz2- NO σ orbital interaction is lessened by mixing in metal pz, causing the MO to shift away from the NO ligand. This exact same orbital interaction appears to explain the existence of middle to late first-row transition metal imido complexes.
Beskrivelse:	The four papers of the thesis are not available in Munin, due to publishers' restrictions: 1. Tangen, E.; Svadberg, A.; Ghosh, A. "Toward Modeling H-NOX Domains: A DFT Study of Heme-NO Complexes as Hydrogen Bond Acceptors," Inorganic Chemistry 2005, 44, 7802-7805. (American Chemical Society) Available at http://dx.doi.org/10.1021/ic050486q 2. Tangen, E.; Conradie, J.; Ghosh, A. "The Challenge of Being Straight: Explaining the Linearity of a Low-Spin {FeNO}⁷ Unit in a Tropocoronand Complex," Inorganic Chemistry 2005, 44, 8699-8706. (American Chemical Society) Available at http://dx.doi.org/10.1021/ic050781a 3. Conradie, J.; Tangen, E.; Ghosh, A. "Trigonal bipyramidal iron(III) and manganese(III) oxo, sulfido, and selenido complexes. An electronic-structural overview," Journal of Inorganic Biochemistry 2006, 100, 707-715. (Elsevier Science) Available at http://dx.doi.org/10.1016/j.jinorgbio.2006.01.029 4. Tangen, E.; Conradie, J.; Ghosh, A. "Bonding in Low-Coordinate Environments: Electronic Structure of Pseudotetrahedral Iron-Imido Complexes," J. Chem. Theory Comput. 2007, 3, 448-457. (American Chemical Society) Available at http://dx.doi.org/10.1021/ct600318n
URI:	http://hdl.handle.net/10037/1725