In this thesis, plasma parameters including plasma and floating potentials, electron energy distribution function (EEDF) plasma density and electron temperature are studied in a high power pulsed magnetron (HPPM) discharge at different Argon (Ar) gas pressures and different magnetron powers. It is reported that the EEDF during and shortly after the pulse can be represented by a bi-Maxwellian distribution indicating two energy groups of electrons.

Furthermore, we report on the variation of the plasma parameters and electron energy distribution function with gas pressure in the pressure range 0.5-20 mtorr. At a high pressure (> 10 mTorr) two density peaks are present, the second of which occurs hundreds of microseconds after the pulse is switched off. It shows that the second peaks occurrence depends on the target material used as well as the chamber pressure and the magnetron power. It is found that the electron density is very high (up to 10¹⁹ m^-3, during the whole of the measured 2000 µs, indicating the importance of the second density peak in maintaining the high plasma density.

Measurements on the electron temperature show that this does not exceed 3 eV while the pulse is on, and that it is no more than 0.5 after the pulse is off. A movie is constructed using Langmuir probe measurements data, showing the temporal evolution of the plasma at 20 mTorr argon pressure and 11 J pulse energy. Analysis shows the existence of a magnetic trap underneath the center of the target. Furthermore, the electron flux in the substrate vicinity 10 - 12 cm from the target is found to be homogeneous. Ti thin films are grown along the sidewalls of a hole, 1 cm² in area and 2 cm in depth, using both de magnetron and HPPM sputtering. Secondary electron microscopy shows that the film grown by de magnetron sputtering shows clear columnar growth, while a dense and flat film was produced using the HPPM sputtering technique.

The increasing power consumption due to the high integration rate of VLSI digital CMOS circuits has become a major concern. Many important design issues and parameters are strongly dependent on the power dissipation and the accuracy of its estimated value during the design exploration. Among these issues we identify particularly the operation time per battery pack, the computational capacity and performance of the mobile electronic products, as well as more general aspects such as circuit reliability, cost for packaging and power supplies. In this thesis, some issues on power estimation and development of low-power circuit techniques, aimed for medium and high speed operations, are addressed.

The complex impact of Miller capacitance on power and performance of digital CMOS circuits is investigated. Significant enhancements in characterization and modeling of the Miller effects compared to the existing conclusions, which are based on simplified rules, are achieved.

A novel estimation technique for the relatively involved average short-circuit power consumption has been developed. Compared to the existing, time-consuming technique, the proposed technique provides a fast estimation with a reasonable accuracy, and has a potential to be used for real measurement.

A significant portion of the total power consumption in VLSI circuits is due to the capacitance of the interconnections, however, estimating the interconnect length and its RC property at early stages in a large-scale top-down design flow is a hard task. Existing, simplified interconnection length estimation techniques are unacceptably inaccurate and unable to give a useful feedback during the design verification and simulation.

A new design-sensitive interconnection length estimation technique and a corresponding algorithm has been developed. The technique has the unique quality to estimate the length of each interconnection separately, and therefore detects and localizes most of the potentially long interconnects. The result of the estimation can directly be used to add the important RC properties of the interconnects to the power estimators or circuit simulators, consequently yielding a significant increase in estimation accuracy.

An investigation on generic low-power circuit techniques aimed for main-stream design styles has been made and various suggestions are proposed. The result has later been used to adapt the design of cell libraries to low power requirements.

High fan-in dynamic gates can result in lower power consumption, fewer logic levels and very compact layout. Two major disadvantages, which reduce the practical use of such wide gates, are the relatively long propagation delay and the large leakage currents, which are due to the increasing subthreshold current in today's and future submicron devices. For speeding up the wide gates, new and simple sensing elements are proposed, which results in faster gates and lower power consumption compared to the alternative solutions. The issues related to large subthreshold leakage currents is also addressed and a leakage-tolerant multi-phase keeper circuit is presented. The new keeper holds the dynamic output of the wide domino gates statically, with a greater driving strength than that in the conventional solution. Furthermore, an increase in robustness is achieved without any significant delay penalty.

Large capacitive loads resulting from long on-chip interconnects and the corresponding driver-receiver circuits can consume a significant portion of the total power consumption of a CMOS chip. A low-power, high-speed and robust driver-receiver circuit is proposed. The new bus architecture utilizes a precharge-to-low interconnect and a fast and simple level converter as receiver, which together reduce the power consumption up to 70% below that of a conventional precharged bus architecture without any delay penalty.

The protein folding problem is one of the most important issues to be solved in the field of molecular biology. The subject of this thesis mainly deals with various aspects of the folding process.

In Paper I, near-UV CD kinetic measurements on mutants, in which one tryptophan (Trp) residue had been replaced, were performed to probe the development of asymmetric environments around specific Trp residues during the refolding of human carbonic anhydrase II (HCA II). The development of the individual (Trp) CD spectra during refolding was obtained by subtracting the CD spectrum of the mutant lacking one Trp from that of HCA II at different time points. The same method was used for the particular Trp residues to obtain the kinetic CD traces monitored at a specific wavelength (270 nm). Three Trp residues were analyzed, each probing different structural regions of the native structure. The investigated Trp residues develop their native CD bands at different rates, showing that formation of native-like tertiary structure is occurring with varying rates indifferent regions of the protein.

The same approach was applied to the extracellular domain of human tissue factor (sTF), which contains four Trp residues (Paper II). The individual Trp CD spectra showed that all four residues contributed to the CD spectrum in almost the entire wavelength region investigated, including the far-UV region. This leads to uncertain predictions of the amounts of various types of secondary structure. Accordingly, the best prediction of secondary sTF structure content was achieved using a hypothetical Trp-free CD spectrum. The kinetic refolding results suggest that the compact asymmetric environments of the individual Trp residues in sTF are formed simultaneously, leading to the conclusion that the native tertiary structure of the whole protein is formed in a cooperative manner.

In Paper III, the role of the metal ion cofactor for the refolding of bovine carbonic anhydrase II (BCA II) was studied from the molten globule to the native state. Refolding was possible to achieve by mere addition of the metal ion to the apomolten-globule, because the apoenzyme was less stable than the holoenzyme. The cofactor-effected refolding can be summarized as follows: 1) initially, the metal ion binds to the molten globule; 2) compaction of the metal-binding site region is then induced by the metal ion binding; 3) a functioning active center is formed; 4) finally, the native tertiary structure is generated in the outer parts of the protein.

In paper IV the aim was to determine the nature of the tetramer contact of human extracellular superoxide dismutase (hEC-SOD). We chose a strategy in which we mapped the subunit interaction interface by studying effects of twelve different mutations in the N-terminal domain fused to HCA II. The results show that the hydrophobic side of a predicted amphiphatic a-helix (formed by residues 14-32) in the N-terminal domain is essential for the subunit interaction.

Physical phenomena related to the growth of alumina, A1₂O₃, are investigated by experiments and ab initio calculations. Alumina is a well studied material with applications in a variety of areas, due to its many beneficial properties. For example, the α and κ phases are widely used as wear-resistant coatings due to their hardness and thermal stability, while, e.g., the γ and θ phases find applications as catalysts or catalyst supports, since they have large surface areas.

Alumina growth at low temperatures usually results in one of the metastable phases. These are involved in transition sequences, which all irreversibly end in the transformation to the thermodynamically stable α phase at about 1050°C. Thus, the metastable aluminas can be grown at low temperatures but cannot be used in high temperature applications, while formation of the stable α phase typically require high temperatures, prohibiting the use of temperature sensitive substrates.

In the experimental part of this work, single-phase α-alumina thin films were grown at temperatures down to 280°C. This was achieved by pre-depositing a chromia template layer, which is shown to promote formation of α-alumina. The results demonstrate that low-temperature α-alumina growth is possible once initial nucleation has occurred.

In the second part of this work, the effect of additives on the phase stability of α- and θ-alumina is investigated by density functional theory calculations. The studied alumina dopants are 5 at.% of Cr, Mo, Co, or As, which substitute for Al in the lattices, and 5 at.% of N or S, substituting for O. We predict that most tested dopants tend to reverse the stability between α- and θ-alumina, so that, e.g., Mo-doping makes the θ phase energetically favored. The exception is Co, which instead gives a slight increase in the relative stability of the α phase. The stability of some of these compounds is also studied by calculating their energies of formation from their constituents, i.e., related dopant oxides, pure metals, and molecules. The results show that the Cr-, Mo-, and Co-doped aluminas are higher in energy than phase separations into pure alumina and other phases, containing the dopants. Thus, the doped aluminas seem to be metastable and will most likely phase separate at high temperatures.

The studies presented in this thesis were part of a pan-European project, and they describe the research performed to develop a method for comparing amphetamine samples. The work included the following: optimisation of a method for profiling of amphetamine by gaschromatography (GC); optimisation of a technique for preparing samples for GC analysis; testing and evaluation of the abilities of a number of distance metrics to discern links between amphetamine samples originating from the same batch of synthesis analysed using the method developed in the current studies.

Street amphetamine contains hundreds of different by-products (target compounds), many of which have been identified and found to come from the different conditions used in the manufacturing process. Therefore, the main objective of developing the GC method was to optimise separation and quantification of the target compounds. The best separation was achieved using a DB-35MS capillary column. For quantification, mass spectrometry (MS) in the scan mode employing one target ion seemed to perform best, because this technique provided superior selectivity, and also made it possible to use mass spectra to identify target compounds. In addition, MS detection proved to offer excellent between-laboratory reproducibility.

The conditions used to prepare amphetamine samples for liquid-liquid extraction (LLE) andsolid-phase extraction (SPE) were also optimised. The sample preparation methods gave similar results but it was easier to use LLE, hence it was chosen for further sample preparation.

The ability of various numerical methods to find links between amphetamine samples was tested on GC-MS data of 26 target compounds that had been transformed by various pretreatment techniques. The best results were obtained when using Pearson correlation applied to data transformed by normalisation followed by applying fourth root.

It was also demonstrated that the amphetamine profiling method developed in the current studies was superior to a procedure already in use in a number of forensic laboratories in Europe.

This thesis describes the design, synthesis and characterization of synthetic receptor molecules for the recognition and binding of proteins with applications in bioseparation and biosensing. A 42-residue polypeptide, designed to fold into a helix-loop-helix motif and dimerize in solution to form a four-helix bundle, was used as the scaffold. In the first part of the thesis it was functionalized by the incorporation of three substituents at the side chains of lysine residues. A library of 343 receptors was created and screened for affinity towards the human IgG fab fragment using SPR technology. The scaffold was reacted in a stepwise and combinatorial procedure with seven active esters in a pH controlled site-selective acylation reaction to form amides at the side chains of three lysine residues. Four receptor candidates were found to have 0.1 mM affinities and were selected for further investigation.

Both the unfunctionalized scaffold and the four selected receptors were found to bind well also to HCA II and the molecular interactions with this target protein were studied in detail. NMR studies of their interactions with ¹⁵N-labeled HCA II revealed that the peptides bound to a hydrophobic patch near the active site cleft, and SPR studies of modified receptor polypeptides led to the conclusion that mainly hydrophobic interactions were involved in binding.

In the second part of the thesis two scaffolds were functionalized with a benzenesulfonamide ligand linked to the scaffold by a series of aliphatic spacers of varying length. Benzenesulfonamide is a known inhibitor of HCA II with a dissociation constant of 1.5 µM and it was found that the overall affinity of the functionalized peptide was enhanced by increasing the length of the ligand spacer due to cooperativity between the scaffold and the ligand in the binding to HCA II. The receptor with a seven methylene group spacer bound HCA II with a dissociation constant of 4 n M. It was also shown that the sequence of the scaffold polypeptide strongly affected the overall affinity of the peptide conjugate for the target protein.

In this work various aspects of data preprocessing are discussed. Preprocessing of data from multivariate sensor data systems is often necessary to extract relevant information or remove disturbances. Depending on the sensor type different preprocessing techniques have to be used. A number of important problems face the user e.g. drifting sensor data which results in very short-lived calibration models, and complex models with a very high number of variables. A systematic approach to handle and analyse data is necessary. In this work different preprocessing techniques are elaborated to reduce these problems.

Drift is a gradual change in any quantitative characteristic that is supposed to remain constant. Thus, a drifting chemical sensor does not give exactly the same response even if it is exposed to exactly the same environment for a long time. Drift is a common problem for all chemical sensors, and thus needs to be considered as soon as measurements are made for a long period of time. Drift reduction methods try to compensate for the changes in sensor performance using mathematical models and thus maintaining the identification capability of the chemical sensor. The problem with drifting sensor data and thereby short-lived calibration models is overcome using reference samples and smart algorithms utilizing the relation between the reference measurements and the measurements from the samples. This has been studied in two of the papers in this thesis. Two new approaches have been developed and tested using data from real measurements from the electronic nose and tongue.

In industry and science more and more variables are used to describe the process under study which lead to complex models and calculations. In order to increase the interpretability of the measurements, decrease the calculation demand on the computer, and/or to reduce noise an alternative, more compact, representation of the measurement can be made which describes the important features of the measurement well but with a much smaller vector. This data reduction is the topic of three of the papers in this thesis. Two different methods have been used: A double exponential model has been developed to approximate electronic tongue data. The parameters from this model describe the signal and are used as inputs to multivariate models. Secondly, the more general approach wavelet compression with different strategies for selection of wavelet coefficients has also been studied for variable reduction of both electronic tongue data and X-ray powder diffraction data.

Bioprocess engineering, the technology that is focused on the exploitation of the metabolic potential of biological agents, has attracted growing interest throughout the past 50 years from both scientific and industrial communities. The products that have been brought to market range from pharmaceuticals and enzymes to food products and vitamins. The quality of human life has been improved through these efforts in many ways.

Despite a strong research effort and the fact that microbial transformations often reach yields close to the theoretical maximum. many bioprocesses still operate at relatively low yields. One of the obstacles in effective operation is the extraction of useful information from the bioprocess. Sensors that acquire real-time information about the cells' state and their interaction with the environment in the bioreactor are seldom available. Hence, the implementation of sophisticated process control is prevented.

In this thesis a new approach of non-invasive on-line bioprocess monitoring is evaluated. Chemical multisensor arrays (i.e. electronic noses) are used to extract information from the composition of volatiles emitted from the cell culture. The focus is on two specific areas: (i) monitoring of key variables in the bioreactor environment and (ii) monitoring of cell states and physiological events. The overall concern is, besides the increase of yield and reproducibility, the safety operation of bioprocesses.

To cover a comprehensive area of modern bioprocessing, several organisms are investigated under different modes of operation in laboratory- and production scale processes. In repeated batch cultivations of recombinant Escherichia coli it is shown that an electronic nose can monitor biomass and specific growth rate with high accuracy. Glucose and ethanol concentration are monitored in batch cultivations of Saccharomyces cerevisiae. Bioproduct monitoring is presented in production-scale mammalian cell cultivation. The concentration of a therapeutic protein is monitored on-line in this long-term bioprocess thereby also outlining the stability of the sensor technique.

In production-scale mammalian cell culture it is possible to follow cell transition states and monitor the reproducibility of the process. The physiological state of the cell population is revealed in laboratory-scale cultivations. It is shown that microbial contamination can be identified earlier than with conventional methods. Finally, the metabolic burden imposed on bacterial cells through strong overexpression of recombinant protein is monitored in fed-batch cultivation.

When implants are inserted into the human body cascades of events become started that will determine the outcome of wound healing and ultimately the success of the implantation. The events start with the adsorption of small molecules, and proteins that may be activated (enzymes) or are able to activate cells of the immune defense and the healing process. In the biomaterials research that is conducted in our group we often ask two questions: "How much?" and "What?" proteins adsorb to a specific surface after incubation in serum or plasma. In the first two papers in this thesis I studied how well we are able to determine the answer to the first question. In the latter two works I tried to answer both questions for two model biomaterial surfaces: oligo(ethylene glycol) terminated self assembled monolayers on gold and chitosan coated silicon.

In many null ellipsometric studies the protein film refractive, N_film, is assumed to be close to 1.5. In the first paper we analyzed if the assumption of N_film = 1.465 is satisfactory for the determination of the surface mass density of a submonolayer thin protein film. Human serum albumin (HSA) was labeled with ¹²⁵I and mixed with non-labeled HSA, and hydrophobic and hydrophilic silicon pieces were incubated in the solutions. The surface mass densities on all pieces determined by both ellipsometry and gamma counter measurements, and was pair-wise compared. The above assumption regarding the value of N_film for the agreement between the methods was satisfactory, although precautions have to be made not to overestimate the surface mass density when studying radiolabelled proteins, especially at rough surfaces.

Are the assumptions made in Paper I also true for up to 100 nm thick protein films or do we have to use a different protein film refractive index and do the ellipsometric model still hold? Human serum albumin (HSA) and polyclonal anti-HSA were labeled with ¹²⁵I and mixed with unlabelled proteins. Hydrophobic silicon pieces were alternatingely incubated in the two protein solutions. Again the surface mass density was quantified with null ellipsometry and a gamma counter and the methods compared. The thickest protein layers were also gently scratched and the thickness measured by AFM. It appeared that a protein film refractive index N_film = 1.5 was a good choice for the determination of the protein film thickness. However, in order to obtain a good methods agreement for the adsorbed mass density a linear correction term was needed in the Cuypers surface mass density formula for ellipsometry. The physical interpretation of the correction term is presently unclear.

Self assembled monolayers (SAMs) containing oligo (ethyleneglycol) end groups (OEG) have been successfully used to minimize protein adsorption from single protein solutions. We investigated the protein resistance in a fibrinogen solution, serum and plasma of OEG-SAMs with an increasing number of OEG units and with different end groups. It turned out that the adsorbed amounts after 10 minutes of plasma incubation and 15 minutes of fibrinogen incubation decreased with an increasing number of EG units. In serum, the total deposition and subsequent deposition of antibodies towards complement proteins (C3c, C3d and properdin) did not depend on the number of EG units. In summary, the investigated OEG-SAMs were not protein resistant in complex solutions, although the adsorbed amounts varied with the number of EG units and the terminal chemical group. Complement deposition was observed at OEG surfaces.

For the last 50 odd years different polysaccharides, such as heparin and cellulose have been used for clinical applications and in recent years also chitin and its deacetylated form chitosan have gained increasing attention as potential biomaterials. Previous studies on complement activation by chitosan derivatives have focused on the soluble complement factors and not the surface bound ones that may be important for the binding of cells to surfaces. In our study about 10 nm thick chitosan films were incubated in plasma or serum and subsequently in polyclonal antibodysolutions. The films did not activate complement and the intrinsic pathway of coagulational though fibrinogen was detectable after plasma incubations. When the chitosan film was acetylated it became a strong alternative complement pathway activator in serum and fibrinogen was then no longer antibody detectable after plasma incubations.

The ecology of the red-listed butterfly Lopinga achine was studied in partly open woodlands in the province of Östergotland, Sweden. Detailed autoecological research is essential for successful conservation of a species, and the present investigation focused on the initial aspects of such work, namely, choice of host plant, habitat selection, and dispersal ability. The effects of patch area, isolation, and successional stages of studied sites were also examined.

The results indicate that L. achine depends on a single host plant, Carex montana. The females preferred to oviposit near this sedge, and most of the larvae (> 80%) were found on C. montana in the field. Egg-laying females and larvae were restricted to C. montana growing in a narrow zone along the edges of glades. This restriction to forest edges is probably the cause for the dependence of L. achine on a restricted stage of canopy cover. More specifically, no L. achine occurred at sites with less than 60% canopy cover, and population densities decreased sharply with more than 90% cover. Eighty-six percent of the studied sites that were occupied are unmanaged, thus the most important aspect of long-term conservation of L. achine is probably the deterministic changes of its woodland habitat. If the sites remain unmanaged, the system of populations will most likely collapse within 20-40 years. Populations of both L. achine and C. montana increased in size at experimentally managed sites where new glades were created. However, an important prerequisite of successful restoration appears to be the presence of C. montana along the edges of new glades from the start, because the rate of C. montana colonisation was slow.

Most of the populations (50 of 79) were small (< 500 adults; none larger than 4,500) and seemed to show synchronous interannual fluctuation. The probability that a patch would be occupied increased with increasing patch area and decreasing distance to the nearest occupied patch. This was presumably due to different probabilities of extinctions, colonisations, and survival of the inhabiting populations. All but two of the sites with ≥ 3 individuals were within 740 m of the nearest neighbour. Patch size is also a key factor for occurrence: compared to larger patches, small patches are more dependent on neighbour populations.

The majority of the movements were small and within sites, although in many cases the distance to other sites was less than 100 m. Only 56 individuals (4.0% of those recaptured) moved between sites. It seems that habitat patches of L. achine should be less than 700 m from each other to ensure inter-population contact. Fifteen to 20 wellconnected populations have been stated as a lower limit for a viable metapopulation.Based on these criteria, there are two groups of viable populations in the studied area,and these two groups will be given priority in future conservation work.

This thesis had two objectives: the first objective was to evaluate the response of forest ground vegetation to selected forestry operations, i.e. cutting of different intensities and scarification; the second objective was to compare the use of survey data in vegetation research with that of more traditional research using field trials - i.e. can survey data be used and produce results that comply with those emerging from field trials? Here, the results from an analysis of survey data has been compared with results emerging from a field trial.

Survey data was analysed from the National Forest Inventory (NFI), using 789 sample plots in central and northern Sweden visited twice at an interval of 10-11 years, 294 of which had been subjected to logging between inventories. This was compared with a field trial in central Sweden: a complete block design with four replicates - three treatments and conventional harvesting as the control.

The cutting intensity was found to have an impact on the ground-layer flora, the change being mostly differences in abundance rather than change in species richness. Those increasing were early successional species, i.e. crustose lichens, Deschampsia flexuosa. In contrast, Vaccinium myrtillus was decreasing substantially in response to increased cutting intensity. A number of species appeared to be indifferent to cutting, i.e. Vaccinium vitisidaea, Trientalis europaea.

Scarification had a different impact on the flora than cutting: only Polytrichum spp. increased substantially, while many decreased.

For those effects that were possible to compare in both studies, the results from survey data comply with those from the field trial, indicating that survey data is possible to use in forest vegetation research.

Chemical sensors based on the selective absorption of gas/vapors in polymer layers rely on molecular interactions. Details of the mechanisms involved can be obtained by studying the adsorption on well defined model organic surfaces. In this thesis, the adsorption of dimethylmethylphosphonate (DMMP), a model molecule for the nerve gas, sarin, and the influence of humidity on the interaction, have been studied. Well defined organic interfaces were obtained by solution self assembly of long chain co-substituted thiol molecules, SH-(CH₂)_m-X, on gold surfaces. The interfacial properties are given by the tail group X and the following three different functional groups, -CH₃, -OH, -COOH, have been analyzed.

In the first paper, the properties of the self assembled monolayers (SAMs) were examined. The monolayers form ordered semi-crystalline layers with the tail groups defining the chemical properties of the interfaces. In mixed monolayers the surface concentration of the OH and CH₃ terminated thiols corresponds to that of the preparation solution and no signs of macroscopic phase separation could be observed.

The equilibrium adsorption of DMMP was analyzed under sensor conditions by a surface acoustic wave sensor (SAW), sensitive to changes in surface mass, and infrared reflection absorption spectroscopy (IRAS). It was found that DMMP interacts with hydrogen bond donating groups and that the lone pair electrons of the P=O oxygen is the main interacting part of the molecule. Both the temperature programmed desorption of DMMP adsorbed at 100 K and the SAW results from room temperature measurements indicate that the strongest interaction is on the -COOH surface followedby -OH and -CH₃. For the -OH surface there is also a surface coverage dependent in the strength of interaction.

The influence of humidity on the interaction was studied as DMMP was allowed to adsorb at different levels of relative humidity. For the -OH surface, an increase in the DMMP coverage proportional to the relative humidity was observed both with the SAW and with IRAS. A closer examination, however, revealed that a loss of water occurred during adsorption of DMMP. The conclusion from this experiment is that SAW results and other mass sensitive devices must be corrected if competing adsorption takes place. For the -COOH surface, low humidities tend to increase the DMMP coverage but at higher humidities a clear loss was registered by IRAS and the SAW sensor even after compensation for changes in water coverage. As water is present, the increased interaction can be explained by hydrogen bonding to free OH of the water. On the -COOH surface, the adsorption sites become blocked by water, which is more tightly bound on this surface. In the mixed (OH / CH₃) monolayers water vapor starts to influence the DMMP adsorption above a critical concentration of OH groups of 0.6. This is also the OH concentration above which total wetting with DMMP occurs.

The well defined organic monolayers formed by solution self-assembly was found to be suitable for interaction studies of the hydrogen bond accepting DMMP molecule and the influence of humidity on the interaction. The complementary information resulting from the chosen analytical techniques can be used for both qualitative and quantitative evaluation of the adsorption. For example, an optimal composition for the mixed (OH/CH₃) SAM has been identified, where the number of adsorption sites and the interaction is sufficiently high, and the influence from humidity still low.

This thesis deals with van der Waals and Casimir forces near metal films. Thick, thin and strictly two-dimensional metal films will be investigated. For many applications one can model a double quantum-well structure with two strictly two-dimensional metallic sheets. The correlation energy of such structures changes when the carriers in the two sheets drift relative each other. This change in the van der Waals energy gives rise to a current drag. We found that the dragged current varies with separation as d^-3.5, this is the same as the separation dependence found for the van der Waals force between thin metal films. We have used both optical data and model dielectric functions to investigate the retarded van der Waals interaction between thin and thick metal films. Usually the correct separation dependence of the van der Waals interaction can be found from simple summation of pair-interactions. Thin metallic sheets are an exception to this general rule. To find the correct separation dependence the longitudinal collective excitations must be accounted for. Using optical data and numerical methods we examined the validity of asymptotic results.

The extension of the van der Waals interaction between macroscopic objects to finite temperatures is the Helmholz free energy of attraction. We have investigated the temperature dependence of the Casimir attraction between a pair of quantum wells. For many small objects found in nature, thermal effects will be a dominating source of attraction. This is also true for quantum well structures. Thermal corrections will be important already at temperatures less than 1 K. At zero temperature the retarded van der Waals energy has three separation regions. At separations of the order of the Thomas-Fermi screening length and smaller both single-particle and collective excitations contribute; in the intermediate range the collective longitudinal excitations dominate and give rise to the van der Waals forces; at large separations the collective transverse modes dominate and the result is identical to the Casimir attraction. The zero frequency part of the Helmholz free energy gives contributions at all finite temperatures. This part of the interaction will dominate at smaller and smaller separations with increasing temperatures. The interaction between thin metal films has one more conceptually interesting property. We have found that there is a possibility that the retarded van der Waals energy between two thin metal films may be larger than the corresponding non-retarded van der Waals energy. The interaction between two 20 Å gold sheets may constitute a candidate to observe this phenomenon. This is related to an unusually large relative contribution from transverse electric modes. When retardation is neglected these modes do not give any contributions at all. This anomalous effect vanishes with increasing dissipation and with increasing film thickness.

In a comment on a recent calculation of the zero temperature Casimir force between imperfect conductors we corrected a few errors in the treatment of optical data. We have further investigated the temperature dependence of the Casimir force between real metal surfaces. This thesis presents result from calculations performed on both the real and imaginary frequency axis. The result is the same regardless of integration path. Using both optical data and the Drude dielectric function with dissipation included, we found a long-range high temperature asymptote in agreement with the corresponding asymptote for the interaction between quantum wells. This asymptote is in agreement with the result obtained by E. M. Lifshitz for general dielectric surfaces. It is on the other hand half as large as the result obtained by J. Schwinger and coworkers for perfect conductors. This later result has been used in comparison with experiments. It has very recently been argued that one should ignore the physical behaviour of the dielectric function in such a way as to get agreement between the high temperature asymptotes of real and ideal metals. This can be obtained if a plasma model with no dissipation is used for the dielectric response of the metals. We regard it to be a weak proof to simply claim that the correct thermal corrections to the Casimir force of a real material and an idealisation have to be identical. There is however at least one good reason why one can not simply disregard this argument. The experimental data of a recent experiment seems to agree better with this idealisation. As discussed in this thesis one should have in mind that the experimental data are found after a very large electrostatic contribution is subtracted. We have in particular found that the thermal corrections in the limit of low temperatures and small separations are substantially larger than previously assumed. We consider the disagreement between our theoretical results and the experimental ones by Lamoreaux to be intriguing and we hope that it will act as an inspiration for new experimental and theoretical efforts.

In article 6 the retarded van der Waals energy of an atom between thin silver sheets was investigated. Film thickness, temperature, and retardation influence this interaction. Nienhaus et al. recently used ultra thin (∼50 Å) Ag films on a Si surface to detect hydrogen gas. Dimensionality effects are important for metallic films of this size. Our result is not relevant for that work, but could be important in other cases where atoms interact with ultra thin metal films.

We have finally calculated the wetting angle as function of doping concentration for water on ln₂0₃:Sn (ITO) and determined the critical concentration for spreading. One has tried to overcome the problem of ice on car windscreens by coating the outer surface of the windshield with ITO. ITO is a both transparent and conducting material. Unfortunately, it turns out that one runs into another problem. The material wets too much. Our calculation relies on the dielectric properties of water and the doped semiconductor. We have modelled these properties.

The research reported in this thesis is concerned with a new type of semiconductor device that can be realised by using thin films of semiconducting polymers, or conjugated polymers. In this thesis only one family of these conjugated polymers is studied, namely poly-(para-phenylene vinylene) and derivatives thereof.

This thesis focuses on how a change in the interface conditions between electrodes and polymer affects the performance of the devices. Especially on how low workfunction metals, e.g. calcium, magnesium interact with poly-(para-phenylene vinylene), and derivatives thereof. Those low workfunction metals are often used as the negative electrode for polymer light emitting devices. This type of light emitting device is described in this thesis and the issues off charge injection and transport is discussed in detail. Also the difference between the ideal theoretical models and real life system is in focus.

Studies of different types of degradation mechanisms in the polymer light emitting devices are also included. The degradation of the polymer material due to low energy electrons from the thermal electron beam evaporator during fabrication has been studied in detail. Also included is an investigation and comparison of used and unused polymer light emitting devices that has been done with the help of sputtered depth profile analysis with surface sensitive Auger spectrometry.

In plasma assisted thin film growth control over the energy and direction of the incoming species is desired. If the growth species are ionized this can be achieved by the use of a substrate bias. ions may be accelerated by an applied potential, whereas neutral particles may not. Thin films grown by ionized physical vapor deposition (I­PVD) have lately shown promising results regarding film structure and adhesion. high power pulsed magnetron sputtering (HPPMS) is a newly developed technique, which relies on the creation of a dense plasma in front of the sputtering target to produce a large fraction of ions of the sputtered material.

High power pulses of length ~100 µs are applied to a conventional planar magnetron. The highly energetic nature of the discharge, which involves power densities of several kW per cm² creates a very dense plasma in front of the target. Previous measurements on the plasma properties indicate peak plasma densities in the order of 10¹⁹-10²⁰ electrons per m³ and average electron energies of a few eV in a close vicinity to the target. This allows a large fraction of the sputtered material to be ionized.

This work is focused onto two areas: 1. the ionization fraction of the sputtered material and the ionization process itself and 2. how the highly energetic discharge and the plasma dynamics affects the magnetic environment of the magnetron. Knowledge and control of the process is of interest in thin film growth when relating film properties to process parameters.

Optical emission spectroscopy (OES) measurements of the plasma indicate that the degree of ionization of sputtered Ti is very high, over 90 % in the peak of the pulse. Even at relatively low applied target power (~200 Wcm^-2 peak power) the recorded spectrum is totally dominated by radiation from ions. The distribution of electronically excited states roughly follows a Boltzmann distribution, with a characteristic temperature of 0.6 eV in the case of Ta. This indicates that the distribution of excited states differs significantly from the distribution of ionized states within Ta. We expect a high degree of ionization of the sputtered material, this requires a significant amount of electrons with energies over the ionization potential, which is between 6 and 7 eV for many metals. Sputtered material is ionized close to the target to be transported into a cooler plasma region. The recorded HPPMS spectra were compared to a spectrum taken from a d.c. magnetron discharge, showing a completely different appearance. The dependence on the choice of target material is also discussed, and is assumed to strongly affect the fraction of ions.

Magnetic measurements performed with a coil type probe show significant deformation in the magnetic field of the magnetrons during the pulse. Spatially resolved measurements show evidence of a dense azimuthally Ex B drifting current. Circulating currents mainly flow within 2 away cm from the target surface in an early part of the pulse, to later diffuse axially into the chamber and decrease in intensity. We record peak current densities of the ExB drift to be in the order of 10⁵ A/m². Comparisons between Langmuir probe measurements and the magnetic field deformation also indicates that the expanding highly energetic plasma creates diamagnetic and paramagnetic changes of the magnetic field.

Ecological communities are often exposed to different kind of disturbances of varied magnitude. The response to disturbances can be affected by, among other factors, the strength of interactions between species within the community. The main purpose of this thesis is the study of the relation between interaction strength (distribution and positioning of strong and weak links) and the response of model communities to disturbances. Additionally, we wish to identify keystone species and keystone links and to recognize species vulnerable to secondary extinctions with respect to the interaction strength concept.

The first part of this study (paper I) deals with species removal from model ecological communities. The number of secondary extinctions following the loss of one species measures the response to this disturbance. The loss of the following species categories triggered, on average, the largest number of secondary extinctions: a) rare resources strongly interacting with many consumers b) abundant intermediate consumer species strongly interacting with many resources and c) abundant weakly interacting resources. Species vulnerable to secondary extinctions were mainly weakly interacting consumers and strongly interacting resources (excluding primary producers). This vulnerability to secondary extinctions was not only dependent on characteristics of the species themselves but also on which species was initially removed. Some species were facing a high probability of extinction after the deletion of a wide range of species categories, while others were vulnerable only to the deletion of few species categories.

The second part (paper II) deals with less severe disturbances; small changes in the intrinsic growth rate of species and small changes in the interaction strength of links. In this way the importance of both species and links was revealed. The response of the community was measured as the effect of these changes on the resilience of the system. Overall, the resilience of the model communities was more sensitive to changes in weakly interacting species or weak links.

The main message of this work is that keystone species and keystone links could be context dependent, both with respect to characteristics of the community and the stability criterion used. Studying the effects of severe disturbances, such as species loss, and using the number of secondary extinctions to measure the community's response, the disturbance of strongly interacting species affected the community most. On the contrary, by applying small perturbations to community parameters and measuring the response as the effect on resilience, the perturbation of weakly interacting species and weak links affected the community most. Thus, both strong and weak agents of the community can be important for stability properties under different regimes of disturbance.

The obstacles to overcome low reproducibility and stability of bioprocesses are numerous. Underlying biochemical processes are inherently non-linear, complex and subject to shifting initial conditions. Problems with high variability are also associated to production strains and scale-up of a bioprocess to largescale bioreactors. Reliable on-line monitoring of key process variables is still a challenging task and hinders the closed-loop control of these key process variables. In this thesis, methods for stabilization of bioprocesses by means of multivariate on-line monitoring, modelling and control are studied.

The foundation was laid with the development of integrated multivariate bioprocess monitoring, modelling and control within a real-time knowledge-based expert system. Thereby, a large number of signals from different advanced on-line analyzers ranging from mass spectroscopy via on-line HPLC to nearinfrared spectroscopy and electronic noses, could be used in combination with a variety of multivariate modelling and control tools for a flexible development of methods for stabilization of bioreactor processes. Subsequently, it could be shown how problems related to the initial conditions of a bioprocess can be solved by a multivariate assessment of the preculture quality. Furthermore, it was demonstrated how qualitative and quantitative key process variables can be made available and applied for process supervision; here, multivariate statistical process modelling and neural network sensor fusion from on-line monitoring of bioprocesses with advanced on-line analyzers were used. Finally, a closed-loop control method was presented, showing how feedback control of a multivariate key process variable trajectory can improve adherence to the specifications of the bioprocess. As model systems, aerobic fed-batch cultivations using recombinant Escherichia coli and anaerobic yoghurt batch fermentations have been used. The results provide general methods for multivariate stabilization of bioprocesses in precultivation steps, laboratory-scale and production-scale. They show that multivariate monitoring, modelling and control can provide a functional and versatile framework for reduced batch-tobatch variation and stabilization of bioprocesses with possible implications on product quality and process economics.

The design, synthesis, and structure-activity relationships analysis of some potential protease inhibitors are outlined in this thesis. In particular, the serine protease thrombin and the malarial aspartic proteases plasmepsin I and II (Plm I and II) are described in regard to the roles they play in living organisms, and that is followed by discussions concerning the design, synthesis, and biological test results of inhibitors of these enzymes.

A topic considered is why it is sometimes necessary to pharmacologically regulate the blood-coagulating capacity of thrombin. Moreover, various aspects of malaria arediscussed, including the geographical distribution of the disease, the biological features of the malaria parasites, and the consequences of malaria infection.

The problems associated with designing enzyme inhibitors in general are briefly explained. Furthermore, the design of inhibitors of thrombin and Pim I and II is considered in greater detail, and the task of designing the novel potential inhibitors reported in the papers underlying this thesis is addressed.

The synthesis of thrombin inhibitors based on tartaric acid and malic acid, and the synthesis of newly designed plasmepsin inhibitors based on a novel reversed-statine core are described in detail. The utilization of solid support chemistry in the work on plasmepsin inhibitors is explained thoroughly. Additionally, there are discussions extensively covering the challenges encountered regarding the syntesis of all types of inhibitors in this thesis, and alternative synthetic strategies are addressed. Biological test results of the synthesized target compounds are analyzed, and structure-activity relationships (SAR) discussions are conducted as thoroughly as possible.

Semiconductor compound materials from groups III and V in the periodic table have attracted much interest during recent years, due to promising properties for optoelectronic devices such as lasers and light emitting diodes. Most of these devices are fabricated from quantum well (QW) structures. This thesis is based on optical studies on quantum wells and modulation doped heterostructures in some important III-V material systems: InGaAs/lnP, InGaN/GaN and GaN/AlGaN. The experimental investigations involve photoluminescence (PL), PL excitation (PLE) and time-resolved PL spectroscopy. Simple theoretical models have been used in some cases to compare with and identify experimental data.

In the InGaAs/lnP material system, the dependence of the electronic structure on both In content (and thereby built-in strain) and well width has been studied by means of Fourier transform (FT) PL and FTPLE for a set of QW samples. The reduced effective masses for the same set of samples have been determined by applying external magnetic fields and fitting the experimental data to Landau levels. Similar experiments have also been performed on a set of modulation doped heterostructures, where a self-consistent calculation enabled peak identification as well as a suggestion for a probable potential profile.

Electronic structure and optical transitions have been studied in a modulation doped GaN/AlGaN QW and compared to calculations based on a simple model. Also, the recombination processes involved in the PL from InGaN/GaN multi QW samples have been investigated. The In content and the growth condition for the barriers were varied. In a set of Si doped samples with different doping concentrations, the screening of the strain induced piezoelectric field was studied.

This PhD thesis is focused on strain-related phenomena in group-III nitride layers and heterostructures. Key issues in material properties as phonon mode behavior, structure and lattice parameters of AlN, InN and GaN, as well as of AlN/GaN superlattices are addressed in order to give answers to some open questions. The research is motivated by the enormous technological application potential of the group-III nitride materials for optoelectronic devices and high temperature, and high power devices. Due to the lack of native substrates, the group-III nitrides are typically grown on foreign substrates resulting inbuilt-in strain in the films, as well as, in misorientation and defect formation. Substantial efforts have been concentrated on the research of strain-related fundamental properties of group-III nitrides. However, some of the strain-related structural and vibrational properties of these materials remain unclear and this gap has to be filled in order to fully explore the possibilities for applications.The thesis contributes to the knowledge of the strain-related phenomena ingroup-III nitrides by concentrating on the following: i) lattice parameters and strain relaxation in GaN, AlN, InN films with different thicknesses, as well as free-standing GaN quasi-substrates; ii) phonon mode behavior and deformation potentials of AlN and InN; iii) structural evolution in AlN and GaN; iv)phonon mode behavior and strain evolution in AlN/GaN superlattices. The layers studied were grown by a variety of growth techniques and nucleation schemes aiming at establishing of a comprehensive understanding of the material properties.

The thesis is organized as follows: In the first part a general description of the basic properties of group-III nitrides is given with a special emphasis on the structural and vibrational properties. The vibrational properties of lowdimensional group-III nitrides are also reviewed. After that, basic concepts of strain phenomenon in group-III nitrides, as well as the strain effects on phonons and on structural properties are discussed. Finally, the experimental techniques used are introduced.

The second part of the thesis consists of six papers providing informationon specific strain-related structural and vibrational properties of III-nitride layers and superlattices.

The lattice parameters of GaN films grown by two different techniques on a-plane sapphire are the subject of Paper I. We have determined two different values of the in-plane lattice parameter of the GaN layers in contrast to only one in the case of films grown on c-plane sapphire. We suggest that the observed distortion of the hexagonal symmetry can be attributed to the presence of anisotropic in-plane strain in the films. A new approach to determination of lattice parameters has been proposed.

Paper II deals with the lattice parameters of GaN quasi-substrates grown by hydride vapor phase epitaxy using two nucleation schemes. The lattice parameters of both, Ga- and N-polar faces of the quasi-substrates were determined and compared. The strain relaxation phenomena in such free-standing layers and the concept of strain-free lattice parameters are discussed.

Papers III and IV are devoted to the deformation potentials of the E 1 (TO)mode in AlN, and the E1 (TO) and E2 modes in InN, where a combination of infraredellipsometry, infrared reflection, Raman scattering and x-ray diffractionstudies was used. The reported results in Paper III present the first experimentalvalues for the E₁ (TO) deformation potentials of AlN and the results for the InN deformation potentials in Paper IV are the first ever reported.

The strain evolution and its effect on the structural and vibrational properties of thin epitaxial AlN layers with different thicknesses have been studied in Paper V. A model of the strain evolution with film thickness and related defect structure is suggested and it is successfully used in the infrared ellipsometry data analysis.

Paper VI is focused on the strain evolution in AlN/GaN superlattices withdifferent periods and its effect on their phonon properties. The presence of phonons originating from the superlattice constituents was revealed and their nature is discussed.

Doping with rare earth element erbium (Er) in Si has recently attracted a lot of research interest due to potential applications in Si-based opto-electronics. By using molecular beam epitaxy (MBE), precipitate-free Er-doping in Si has been made together with other co-dopants, e.g., oxygen (0) and fluorine (F), up to a level ∼10²⁰ cm^-3. Together with other capabilities of high quality growth of layered structures with desired doping profiles and heterojunctions offered by MBE, several types of dedicated Er-doped Si and Si/SiGe light emitting devices have been designed, processed, and characterized, aiming at finding a possible solution for efficient Sibased light emitters.

During the thesis work, mainly three types of Er-doped Si light emitting devices: Schottky-type light emitting diode (LED), p-i-n LED, and heterojunction bipolar transistor (HBT), have been studied for light emission from either the surface or an edge. Three kinds of Er-containing sources, namely Er₂O₃ , ErF₃ , and elementa lEr together with SiO were used for doping. In order to get comparative results from electroluminescence (EL) and photoluminescence (PL) measurements using the same sample, Schottky-type LEDs using Er/O structures were fabricated and characterized, where Er³⁺ ions can be excited using an impact process of hot electrons generated in the depletion region at reverse bias. A number of grown Si:Er:O and Si:Er:F p-i-n structures were processed into LEDs, and EL from these devices was studied both at forward bias and reverse bias conditions. The light emission from forward biased p-i-n diodes was concluded to be due to the carrier-recombination-mediated energy transfer process, however, luminescence could not persist to room temperature (RT) due to the strong quenching process induced by the energy back transfer process and other nonradiative processes. For reverse biased p-i-n diodes, especially for the structure designed favoring the electron tunneling, intense EL was observed via direct carrier impact excitation process, which persisted up to RT or even higher. In order to have independent control over the injection current and the applied bias, and de-couple their influence on the EL intensity, Si/SiGe/Si:Er:O-HBTs with Er³⁺ ions incorporated in the collector have been fabricated with layered structures prepared by differential MBE growth. Careful EL studies have been carried out by operating an HBT in a linear regime prior to the avalanche breakdown. The effective Er impact cross-section has shown a 100-fold increase compared with conventional Si:Er-LEDs. The temperature dependent EL measurements on different types of devices have indicated that an Er-induced defect level located at 150 meV below the conduction band is mainly responsible for thermal quenching of the luminescence intensity, which is the same value as obtained in PL measurements. Time-resolved EL measurements have exhibited that Auger-carrier de-excitation plays an important role in reducing EL intensity. Moreover, it has revealed that not only ionized equilibrium carriers but also injected excess carriers act as Auger de-excitation centers. Finally, the results of the thesis work suggest that if the HBT structure can be combined with a high optical activation of Er³⁺ ions, an efficient Si-based light emitter is possible.