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Silicon carbide (SiC) has been discussed as a promising material for high power bipolar devices for almost twenty years. Advances in SiC crystal growth especially the development of chemical vapor deposition (CVD) have enabled the fabrication of high quality material. Much progress has further been achieved in identifying minority charge carrier lifetime limiting defects, which may be attributed to structural defects, surface recombination or point defects located in the band gap of SiC. Deep levels can act as recombination centers by interacting with both the valence and conduction band. As such, the defect levels reduce the minority charge carrier lifetime, which is of great importance in bipolar devices. Impurities in semiconductors play an important role to adjust their semiconducting properties. Intentional doping can introduce shallow defect levels to increase the conductivity or deep levels for achieving semi-insulating (SI) SiC. Impurities, especially transition metals generate defect levels deep in the band gap of SiC, which trap charge carriers and thus reduce the charge carrier lifetime. Transition metals, such as vanadium, are used in SiC to compensate the residual nitrogen doping. It has previously been reported that valence band edges of the different SiC polytypes are pinned to the same level and that deep levels related to transition metals can serve as a common reference level; this is known as the LANGER-HEINRICH (LH) rule. Electron irradiation introduces or enhances the concentration of existing point defects, such as the carbon vacancy (VC) and the carbon interstitial (Ci). Limiting the irradiation energy, Eirr, below the displacement energy of silicon in the SiC lattice (Eirr < 220 keV), the generated defects can be attributed to carbon related defects, which are already created at lower Eirr. Ci are mobile at low temperatures and using low temperature heat treatments, the annealing behavior of the introduced Ci and their complexes can be studied. Deep levels, which appear and disappear depending on the electrical, thermal and optical conditions prior to the measurements are associated with metastable defects. These defects can exist in more than one configuration, which itself can have different charge states. Capacitance transient investigations, where the defect’s occupation is studied by varying the depletion region in a diode, can be used to observe such occupational changes. Such unstable behavior may influence device performance, since defects may be electrically active in one configuration and inactive after transformation to another configuration. This thesis is focused on electrical characterization of deep levels in SiC using deep level transient spectroscopy (DLTS). The first part, papers 1-4, is dedicated to defect studies of both impurities and intrinsic defects in as-grown material. The second part, consisting of papers 5-7, is dealing with the defect content after electron irradiation and the annealing behavior of the introduced deep levels. In the first part, transition metal incorporation of iron (Fe) and tungsten (W) is discussed in papers 1 and 2, respectively. Fe and W are possible candidates to compensate the residual nitrogen doping in SiC. The doping with Fe resulted in one level in n-type material and two levels in p-type 4H-SiC. The capture process is strongly coupled to the lattice. Secondary ion mass spectrometry measurements detected the presence of B and Fe. The defects are suggested to be related to Fe and/or Fe-B-pairs. Previous reports on tungsten doping showed that W gives rise to two levels (one shallow and one deep) in 4H- and only one deep level in 6H-SiC. In 3C-SiC, we detected two levels, one likely related to W and one intrinsic defect, labeled E1. The W related energy level aligns well with the deeper levels observed in 4H- and 6H-SiC in agreement with the LH rule. The LH rule is observed from experiments to be also valid for intrinsic levels. The level related to the DLTS peak EH6=7 in 4H-SiC aligns with the level related to E7 in 6H-SiC as well as with the level related to E1 in 3C-SiC. The alignment suggests that these levels may originate from the same defect, probably the VC, which has been proposed previously for 4H- and 6H-SiC. In paper 3, electrical characterization of 3C-layers grown heteroepitaxially on different SiC substrates is discussed. The material was of high quality with a low background doping concentration and SCHOTTKY diodes were fabricated. It was observed that nickel as rectifying contact material exhibits a similar barrier height as the previously suggested gold. A leakage current in the low nA range at a reverse bias of -2 V was achieved, which allowed capacitance transient measurements. One defect related to DLTS peak E1, previously presented in paper 2, was detected and suggested to be related to an intrinsic defect. Paper 4 gives the evidence that chloride-based CVD grown material yields the same kind of defects as reported for standard CVD growth processes. However, for very high growth rates, exceeding 100 mm/h, an additional defect is observed as well as an increase of the Ti-concentration. Based on the knowledge from paper 2, the origin of the additional peak and the assumed increase of Ti-concentration can instead both be attributed to the deeper and the shallower level of tungsten in 4H-SiC, respectively. In the second part of the thesis, studies of low-energy (200 keV) electron irradiated as-grown 4H-SiC were performed. In paper 5, bistable defects, labeled EB-centers, evolved in the DLTS spectrum after the annihilation of the irradiation induced defect levels related to DLTS peaks EH1, EH3 and the bistable M-center. In a detailed annealing study presented in paper 6, the partial transformation of M-centers into the EB-centers is discussed. The transition between the two defects (M-centers → EB-centers) takes place at rather low temperatures (T ≈ 400 oC), which suggests a mobile defect as origin. The M-center and the EB-centers are suggested to be related to Ci and/or Ci complex defects. The EB-centers anneal out at about 700 oC. In paper 7, the DLTS peak EH5, which is observed after low- and high-energy electron irradiation is presented. The peak is associated with a bistable defect, labeled F-center. Configuration A exists unoccupied and occupied by an electron, whereas configuration B is only stable when filled by an electron. Reconfiguration temperatures for both configurations were determined and the reconfiguration energies were calculated from the transition kinetics. The reconfiguration B→A can also be achieved by minority charge carrier injection. The F-center is likely a carbon related defect, since it is already present after low-energy irradiation.

Laborationer i naturvetenskap har blivit en mer central del av undervisningen sedan nationella prov infördes i ämnet. Laborationer i naturvetenskap har fångat vårt intresse eftersom vi upplevt att syftet med laborationen sällan synliggjorts för eleverna, både från våra egna erfarenheter och vad vi sett när vi varit ute påverksamhetsförlagd utbildning. Syftet med vår kunskapsöversikt var att undersöka vad forskningen säger om lärares syften i relation till laborationer i naturvetenskap. Vi har sökt efter forskning och granskat den kritiskt för att besvara våra forskningsfrågor: Vad säger forskningen om vilka syften lärare har med att arbeta laborativt i naturvetenskap? och Vad säger forskningen om hur lärare synliggör sina syften för eleverna under laborativa moment? Vi fann bland annat att lärares syfte med laborativt arbete är att intressera och roa eleverna, utveckla förståelse för begrepp och händelser, tänka och reflektera och att koppla naturvetenskapen till vardagen. Det vi fått fram är att lärares syfte med laborativa moment synliggörs på olika sätt genom antingen introduktionen, instruktionen eller under lektionen. Vi föreslår att fortsatt forskning fördjupar sig på vilket sätt lärare ska synliggöra syftena under laborativa moment för eleverna. Men även fokusera på om det har någon inverkan på deras lärande om eleverna uppfattar syftena eller inte.

This thesis involves structure and interaction studies of the Fc fragment of human IgG. For this purpose, hIgG-Fc of different subclasses were cloned and expressed in the eukaryotic host Pichia pastoris, where relevant protein modification at the post-translational level can be obtained. Sometimes, changes in pH, temperature and salt concentration or addition of moderate amounts of denaturants to a protein solution are associated with the protein forming non-natively folded states, such as the molten globule or the A state. IgG and some parts thereof are capable of forming another, so called alternatively folded state, usually induced by acidification in the presence of anions. This state is in many aspects related to the molten globule and the A state but with distinguishing properties related mainly to chemical stability and formation of oligomeric structures. The first part of this thesis describes two different alternatively folded states of hIgG-Fc of subclass 4. One of them was induced by decreasing the pH of the protein solution. Observed structural changes were highly dependent on the concentration of sodium chloride. The alternatively folded protein showed drastic changes in its secondary structure compared to the native protein and significant tertiary structure was lost. Moreover, it displayed an apparently increased chemical stability and had surface exposed hydrophobic patches resulting in the formation of higher order assemblies. In addition, it was shown for the first time that thermal induction of an alternatively folded state is also possible, with similar, but not identical, properties as the acid-induced state. Heat incubation for 20 hours at neutral pH and at a physiological salt concentration further resulted in the formation of protein aggregates. The dye Congo red had affinity for these aggregates, and when viewed under polarized light, it showed green birefringence. They also displayed binding of Thioflavin T and had a typical fibril appearance in the transmission electron microscope. Hence, the formed aggregates share key properties with structures constituting amyloid. The second part of this thesis is focused on interactions of the Fc-fragment with respect to both Fcγ-receptors on monocytes and the IgG autoantibody rheumatoid factor. Immune complexes and their binding to Fcγ-receptors are of pathogenic interest to rheumatoid arthritis. A surface mimic presenting full IgG molecules was designed as an in vitro immune complex model. Utilizing self-assembled monolayers composed of alkanethiolates with different chemical functionalities, the lateral IgG density could be tuned, enabling control of monocyte interaction with the surface. Importantly, the IgG molecules were homogeneously oriented to expose the Fc-fragment. The protein repellent properties of these  surfaces ensured that only differences in IgG concentration determined variations in cellular adhesion. In a separate study the specificities of IgG rheumatoid factor with respect to the different subclasses of hIgG-Fc were investigated, using sera from patients with early rheumatoid arthritis. Strikingly high IgG-RF reactivity against hIgG2-Fc was observed, together with raised levels against hIgG1-Fc and hIgG4-Fc. No reactivity against hIgG3-Fc was found.

Avloppsslam är en restprodukt som skapas vid rening av avloppsvatten och består mest av organiskt material. Slammet är mycket näringsrikt men innehåller ofta höga halter av olika föroreningar som tungmetaller, läkemedelsrester etc. Stockholm Vatten AB är certifierade enligt REVAQ för att kunna använda avloppsslam som gödningsmedel på åkermarker. För att slammet fortsättningsvis ska genomgå certifiering måste föroreningshalterna minska. Silver är en av de metaller som avskiljs från avloppsvattnet till slammet och har en hög ackumuleringshastighet i mark. Vid spridning på åkermark kan en förhöjd koncentration inverka negativ på mikroorganismer i mark och naturliga vatten. Arbetet för att minska silverflödet till reningsverk sker genom uppströmsarbete, vilket innebär åtgärder direkt vid källan. Resultat från en provtagning genomförd av Stockholm Vatten AB på knutpunkter i sex delområden, vars ledningsnät går till Henriksdals reningsverk, användes för att beräkna flödet av silver genom provpunkterna samt också till att utvärdera mängden silver per person i varje delområde. I arbetet har även möjliga källor till silverutsläpp beaktats, dels punktkällor i form av industriella verksamheter men även diffusa källor som bidrag från hushåll. Resultaten visar på viss variation mellan delområdena. Loudden är det område som sticker ut mest, men inom området Loudden finns en större betydande källa känd sen tidigare. Koncentrationerna antyder att de boende i delområdena inte ger upphov till höga halter av silver, utan mängden silver per person är konstant oberoende av område, vilket indikerar att de högre halterna kommer från andra källor. Inventeringen visar på verksamheter som kan bidra med silver till avloppsvattnet. Sett ur ett historiskt perspektiv är verksamheterna idag mycket färre. Därutöver kan tidigare utsläpp av silver medfört en anrikning i de sedimentavlagringar som finns i ledningsnätet, vilket kan bidra med kontinuerligt utsläpp till avloppsvattnet. Dessa läckage kan vara bidragande till varför silverkoncentrationen i avloppsslam inte längre minskar. Hushåll, verksamheter och konsumtion av produkter med innehåll av silver kan också vara diffusa källor som kan bli viktiga för minskningen av silver i avloppsslam.

Denna undersökning har som syfte att ta reda på vad barnen i förskolan anser om att delta i kemiexperiment och vad som händer i barngruppen under experimenten. För att studera dessa frågor har jag gjort observationer med hjälp av videokamera och intervjuer av barnen som deltagit i experimenten. Barnen har visat stort intresse, engagemang, glädje och nyfikenhet vilket har genomsyrat experimenttillfällena. Resultaten i denna undersökning visar att kemiexperiment kan vara ett bra verktyg i förskolan. Barnen interagerar med varandra, associerar till tidigare erfarenheter i livet och ger uttryck för att uppleva, med många av sina sinnen.

Early adequate antimicrobial therapy improves outcome in septicemia. Rapid species identification (ID) from blood cultures is thus important. Matrix-assisted laser desorption-ionisation time of flight (MALDI-TOF) can provide species ID within an hour from blood culture (BC) vials. The present study aimed at comparing the performance and hands on time of two methods for preparing samples from BC vials prior to species ID using MALDI-TOF analysis: sample preparation with SepsityperTM kit and samples smeared from inoculated agar plates after 1-5 hours incubation. Aerobic and anaerobic BC vials, BacT/Alert and BacTEC, were inoculated in triplicates with five reference strains. Viable count was applied as a control of growth in the BC vials. Thereafter two methods were tested for species ID: sample preparation with the SepsityperTM kit (Bruker Daltonics) followed by Ethanol/Formic Acid Extraction and MALDI-TOF analysis as well as a plating method were 100μl of BC-suspension were inoculated on chocolate agar and incubated in CO2in 1, 2, 3, 4 and 5 h followed by MALDI-TOF analysis without extraction. Using the SepsityperTM all species were identified with ID score >2.0 from BacTEC, while none from the BacT/Alert vials. The time to result using the plating method was quite similar for BacT/Alert and BacTEC: Escherichia coli could be detected after 2h, Enterococcus faecalis and Pseudomonas aeruginosa after 3h. Staphylococcus aureus and Streptococcus agalactiae could not be identified. Sample preparation with the SepsityperTM kit followed by MALDI-TOF analysis allows a rapid ID from BacTEC vials with a hands on time of one hour for 12 samples. However, ID from the plating method is less laborious and seems as a promising alternative.

Cell-penetrating peptides (CPPs) have emerged as a group of remarkable delivery vectors for various hydrophilic macromolecules, otherwise excluded from cells due to the protective plasma membrane. Unbiased conclusions regarding e.g. uptake mechanism, intracellular distribution and cargo delivery efficacy is complicated by the use of different methodological parameters by different laboratories. The first paper in this thesis introduced unifying protocols enabling comparison of results from different research groups. One of these methods, HPLC, was used in paper II to investigate CPP uptake and degradation in yeasts. Both parameters varied depending on peptide and yeast species; however pVEC emerged as a promising delivery vector in yeast since it internalized into both species tested without concomitant degradation. Protein mimicry was another investigated phenomenon and in paper III a 22-mer peptide from the p14Arf protein (Arf (1-22)) was found to be sufficient for retaining its function as a tumor suppressor. This peptide comprised a combination of apoptogenic property and CPP in one unity, thus providing opportunity to conjugate cytotoxic agents boosting the tumoricidal activity. Surprisingly, a partially inverted control peptide to Arf (1-22), called M918, was found to be an extraordinary CPP. In paper IV, it was shown to be superior to well-established CPPs in delivery of both peptide nucleic acids and proteins. Albeit the promising results these two peptides displayed, their utility in vivo, as with all peptides, is hampered by rapid degradation. With the aim of improving their stability, Arf (1-22) and M918 were synthesized with D-amino acids in the reverse order, a modification called retro-inverso (RI) isomerization. Their cell-penetrating ability was retained, but the treated cells displayed unexpected morphological alterations indicative of apoptosis. The presented results demonstrate the versatility of CPPs, functioning as vectors in both yeast and mammalian cells and as protein mimicking peptides with biological activity. Their potential as drug delivery agents is obvious; however, peptide degradation is an issue that requires further improvements before clinical success is in reach. / At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 5: In press.

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