The research programme studied the cure reaction of a phenolic novolak resin and the effects of various additives and fillers on the reaction. The programme utilised the recently developed thermal analysis technique of temperature-modulated differential scanning calorimetry (TMDSC) performed in conjunction with other available thermal analysis techniques. TMDSC enables the signal for the heat of reaction to be separated from the underlying specific heat change in the resin. This meant that the reaction could be studied without interference from any physical changes in the resin. The manufacture of composite brake materials required the use of numerous additives and fillers to produce the desired properties. The influence of such additives on the cure rate and final properties of the resin was known to occur but had not previously been measured due to the difficulties presented by the presence of opaque additives. Some additives also underwent thermally induced physical changes in the temperature range of the cure. The final properties and the processing of new brake materials undergoing development often required trial and error adjustments to compensate for changes in cure rate. An understanding of the influence of additives would enable more rapid commercial development of brake materials through an improvement in the ability to predict both the properties of the product and the optimal processing parameters. Processing efficiency could also be improved through detailed knowledge of the kinetics. Moulding cycle times and post-baking times and temperatures were longer than necessary in order to ensure adequate cure at the end of each stage because of the lack of kinetic data. The cure of phenolic resin has been shown to be highly complicated with numerous alternate and competing reactions. For the manufacture of composite materials, knowledge of the kinetic parameters of individual reactions is not considered to be important; rather the overall kinetic parameters are required for prediction. Therefore the kinetic model parameters that best described the observed behaviour were chosen even though the model had no basis in the molecular interaction theory of reaction. Rather it served as a convenient tool for predictions. Characterisation of the resin proved to be difficult due to the presence of overlapping peaks, and volatile reaction products. TMDSC was successfully used to determine the reaction kinetics of the pure resin and the influence of certain additives on the reaction kinetics. The determination of the kinetic parameters using TMDSC agreed well with the traditional Differential Scanning Calorimetry isothermal and non-isothermal techniques. Both the Perkin-Elmer and TA Instruments were utilised for the research and were found to provide reasonably good agreement with each other. The capabilities and limitations of the individual instruments were critically examined, frequently beyond the manufacturers' specifications. TMDSC suffers from a limitation in the heating rate of the sample compared to DSC. However, it was observed that valuable information could still be obtained from TMDSC despite using heating rates that were higher than specified by manufacturers. Hot Stage Microscopy and thermogravimetry were additional experimental techniques used to aid in the characterisation of the resin. Some inhomogeneity of the resin was identified as well as differences in the behaviour of the cure between open (constant pressure) and closed (constant volume) environments were observed. A novel method of determining the orders of the cure reactions and their kinetic parameters was utilised. Reaction models for the overall cure reactions were postulated and tested by fitment to sections of experimental data in temperature regions which appeared to be free of interference from overlapping peaks. Once an individual peak was reasonably well modelled, adjacent overlapping peaks were able to be modelled both individually and in combinations by fitment to experimental data. The Solver function in Microsoft Excel was utilised to find the best fitting model parameters for the experimental data. The model parameters were able to be refined as overlapping peaks were progressively incorporated into the calculations. This method produced results that agreed well with the traditional method of analysing reaction peak temperatures at multiple scanning rates. Model fitment was shown to be of benefit where overlapping reactions occur. Various model scenarios could be tested and optimised to particular sections of experimental data. This enabled the researcher to easily identify areas of possible anomalies and postulate alternative scenarios. The accuracy of the postulated model was able to be determined by its successful fitment to experimental data from experiments run under different conditions.

In this thesis a new approach for characterisation of digital mobile radio channels is investigated. The new approach is based on recognition of the fact that while the fading which is characteristic of the mobile radio channel is very rapid, the processes underlying this fading may vary much more slowly. The comparative stability of these underlying processes has not been exploited in system designs to date. Channel models are proposed which take account of the stability of the channel. Estimators for the parameters of the models are proposed, and their performance is analysed theoretically and by simulation and measurement. Bounds are derived for the extent to which the mobile channel can be predicted, and the critical factors which define these bounds are identified. Two main applications arise for these channel models. The first is the possibility of prediction of the overall system performance. This may be used to avoid channel fading (for instance by change of frequency), or compensate for it (by change of the signal rate or by power control). The second application is in channel equalisation. An equaliser based on a model which has parameters varying only very slowly can offer improved performance especially in the case of channels which appear to be varying so rapidly that the convergence rate of an equaliser based on the conventional model is not adequate. The first of these applications is explored, and a relationship is derived between the channel impulse response and the performance of a broadband system.

<p>Stora volymer förorenade sediment kommer att behöva tas om hand under de kommande åren då bottensediment i svenska farleder, hamn- och kustområden under lång tid har konta–minerats av både tungmetaller och organiska föroreningar. I examensarbetet studeras fyra möjligheter för hantering av förorenade muddermassor. De tre traditionella metoderna är <em>tippning till havs</em>, <em>utfyllnad i vik</em> eller <em>deponering på land</em>. <em>Stabilisering/solidifiering</em> (s/s) är ytterligare ett alternativ som innebär att muddermassorna kan nyttiggöras i geokonstruktioner genom att massornas hållfasthet ökas. Metoden går ut på att muddermassorna blandas med bindemedel och de eventuella föroreningarna binds då in i matrisen genom kemisk reaktion och fysikalisk inneslutning.  Syftet med examensarbetet är att, utifrån ett platsspecifikt perspektiv, undersöka hur föroreningsrisker kan jämföras mellan de fyra olika huvud–alternativen för hantering av muddermassor. Jämförelsen är tänkt att utgöra <em>en del</em> av ett beslutsunderlag som ska ligga till grund för valet av hanteringsalternativ.</p><p>Arbetet har fokuserat på miljöriskanalys och främst på hur risker kan <em>kategoriseras, värderas</em> och <em>jämföras</em>. Metoden inkluderar en litteraturstudie, en undersökning av tillstånds–ansökningar för hamnutbyggnad, en fallstudie där användning av LCA-metodik, ”ekotoxicitetspotential” och Naturvårdsverkets riktvärdesmodell testats för att jämföra föroreningsrisker mellan olika hanteringsalternativ i Oxelösunds hamn. Avslutningsvis genomfördes en serie intervjuer kring temat karaktärisering och jämförelser av risk i en s.k. Stakeholder Opinion Assessment (SOA).</p><p>I studien av tillståndsansökningarna för hamnutbyggnad konstaterades att jämförelser av platsspecifika föroreningsrisker mellan olika hanteringsalternativ för förorenade mudder–massor <em>inte görs.</em> Istället är det andra aspekter, t.ex. ekonomi, som avgör vilket alternativ som väljs. Varken ekotoxicitetspotential eller Naturvårdsverkets riktvärdesmodell visade sig vara lämpliga metoder för att beskriva och jämföra risker i det aktuella fallet. Av intervjuerna i SOA:n framgår att det råder delade meningar om hur risker ska beskrivas och på vilket sätt de kan jämföras och det finns ett stort behov av att utveckla nya sätt att beskriva och jämföra föroreningsrisker mellan olika alternativ och olika platser.</p><p>Arbetet har visat att det finns ett behov av att utveckla miljöriskanalysens avslutande steg, riskkaraktärisering och riskvärdering, eftersom det idag inte finns några konkreta metoder för att jämföra föroreningsrisker mellan olika hanteringsalternativ för förorenade muddermassor. För att förbättra beslutsunderlag föreslås därför en tydligare problemformulering och att övergripande platsspecifika scenarion för de olika alternativen tas fram. Viktigt aspekter att tydliggöra är skyddsobjekt, tidsskala, spridning och exponering. Jämförelsen av platsspecifika föroreningsrisker får inte heller bli allt för detaljerad, eftersom den bara är en del av ett större beslutsunderlag.</p> / <p>Large amounts of contaminated sediment has to be taken care of within the next few years since the sediment in Swedish sea lanes, ports and coastal areas have been contaminated by both heavy metals and organic pollutants over a long time period. Four options for handling contaminated dredged material were studied within this master thesis project. The three traditional methods are dumping the dredged material at sea, filling a bay with dredged material or putting the dredged material on a land disposal. Stabilization/solidification (s/s) is another option, where the contaminated dredged sediments are mixed with a binder that gives them greater strength, while immobilizing contaminants through chemical reactions or physical confinement in the structure. The aim of this thesis is to examine how risks of contamination can be compared between the four main options for management of dredged materials, in a site-specific perspective.</p><p>The main tool in the project has been environmental risk assessment with special focus on how risks can be categorized, measured and compared. The study includes a literature review, an examination of permit applications for port development, a case study where the LCA methodology, "potential eco-toxicity" and the Swedish Environmental Protection Agency's guideline value model was tested in order to compare the risks of contamination from the various management options in the port of Oxelösund. Finally a Stakeholder Opinion Assessment (SOA), by the theme risk characterization and risk comparison, was made.</p><p>The study of permit applications for port expansion has shown that the site-specific risks of contamination are not considered when choosing between management options of dredged materials. Instead other aspects, such as economy, determine the option chosen. Neither potential of eco-toxicity or the Swedish Environmental Protection Agency's guideline value model proved to be appropriate methods in order to describe and compare the risks associates with this case. The interviews in the SOA show that people disagree on how risks should be described and compared. There is a demand for new methods of describing and comparing risks associated with different management options for dredged materials at different sites.</p><p>This work has shown that well-known methods on how to compare risks of contamination between the different management options for contaminated dredged materials do not exist. There is also a need of developing the latter steps in the environmental risk assessment. To develop a better decision basis, a more explicit definition of the problem is proposed. It is particularly important to make site-specific descriptions of the various systems to be compared. The comparison of the site-specific risks of contamination should not be too detailed, since it is part of a larger decision support.</p> / Stabcon

This thesis is focused on the novel wood chip refining process called AdvancedThermomechanical Pulp (ATMP) refining. ATMP consists of mechanical pretreatmentof chips in Impressafiner and Fiberizer prior to first stage refining atincreased intensity. Process chemicals (this study was concentrated on hydrogenperoxide and magnesium hydroxide) are introduced into the first stage refiner.It is known that the use of chemicals in TMP process and first stage refining atelevated intensity can reduce the energy demands of refining. The downside is thatthey also alter the character of the produced pulp. Reductions in fibre length andtear index are usually the consequences of refining at elevated intensity. Additionof chemicals usually leads to reduction of the light scattering coefficient. Usingstatistical methods it was shown that it is possible to maintain the TMP character ofthe pulp using the ATMP process. This is explained by a separation of thedefibration and the fibre development phases in refining. This separation allowsdefibration of chips to fibres and fibre bundles without addition of chemicals orincrease in refining intensity. Chemicals are applied in the fibre developmentphase only (first stage refiner). The energy demand in refining to reach tensileindex of 25 Nm/g was reduced by up to 1.1 MWh/odt (42 %) using the ATMPprocess on Loblolly pine. The energy demand in refining of White spruce, requiredto reach tensile index of 30 Nm/g, was reduced by 0.65 MWh/odt (37%).Characterizations of individual fibre properties, properties of sheets made fromlong fibre fractions and model fibre sheets with different fines fractions werecarried out. It was established that both the process equipment configuration (i.e.the mechanical pre‐treatment and the elevated refining intensity) and the additionof process chemicals in the ATMP process influence fibre properties such as external and internal fibrillation as well as the amount of split fibres. Improvementof these properties translated into improved properties of sheets, made from thelong fibre fractions of the studied pulps. The quality of the fines fraction alsoimproved. However, the mechanisms of improvement in the fines quality seem tobe different for fines, generated using improved process configuration andaddition of process chemicals. The first type of fines contributed to better bondingof model long fibre sheets through the densification of the structure. Fines whichhave been influenced by the addition of the process chemicals seemed in additionto improve bonding between long fibres by enhancing the specific bond strength.The improved fibre and fines properties also translated into better airpermeability and surface roughness of paper sheets, properties which areespecially important for supercalendered (SC) printing paper. The magnitude offibre roughening after moistening was mainly influenced by the processequipment configuration while the addition of process chemicals yielded lowestfinal surface roughness due to the lowest initial surface roughness. There was nodifference in how fines fractions from the studied processes influenced the fibreroughening. However, fines with better bonding yielded model fibre sheets withhigher PPS, probably due to their consolidation around fibre joints. Hence, thedecrease in PPS can probably be attributed to the improvements in the long fibrefraction properties while the improvement of fines quality contributed to thereduction of air permeability.The process chemicals, utilized in the ATMP process (Mg(OH)2 and H2O2) alsoproved to be an effective bleaching system. Comparable increases in brightnesscould be reached using the ATMP process and conventional tower bleaching.Maximum brightness of the pulp was reached after approximately 10 minutes ofhigh‐consistency storage after refining or 40 minutes of conventional bleaching.This study was conducted using a pilot scale refiner system operated as a batchprocess. Most of the experiments were performed using White spruce (Piceaglauca). In Paper I, Loblolly pine (Pinus taeda) was used. It is believed that theresults presented in this thesis are valid for other softwood raw materials as well,but this limitation should be considered.

This study is aimed at investigating the feasibility of using the radiometric technique as an alternative to traditional methods for determining soil physico-chemical parameters which are important for terroir characterization. In-situ and ex-situ radiometric analyses of soil from three vineyard blocks of Simonsig Wine Estate in the Stellenbosch district (Western Cape, South Africa) were studied. A mobile MEDUSA gamma-ray detection system comprising a CsI(Na) crystal (length 15 cm, diameter 7 cm) and associated electronics mounted on a portable trolley were used for partial terroir characterisation. Thereafter activity concentrations of 40K, 232Th series and 238U series in soil (top ~30 cm) from the measured MEDUSA spectra (0 – 3 MeV) were extracted by means of the full-spectrum analysis (FSA) method. A lead-shielded HPGe detector was used for analyzing collected soil samples while soil physico-chemical parameters were analysed using standard methods at research and commercial laboratories.

New and future telecommunication networks are and will be broadband type. The existing terrestrial and space radio communication infrastructures might be supplemented by new wireless networks that make and will make use of aeronautics-technology. Our study/contribution is referring to radio communications based on radio stations aboard a stratospheric platform named, by ITU-R, HAPS (High Altitude Platform Station). These new networks have been proposed as an alternative technology within the ITU framework to provide various narrow/broadband communication services. With the possibility of having a payload for Telecommunications in an aircraft or a balloon (HAPS), it can be carried out radio communications to provide backbone connections on ground and to access to broadband points for ground terminals. The latest implies a complex radio network planning. Therefore, the radio coverage analysis at outdoors and indoors becomes an important issue on the design of new radio systems. In this doctoral thesis, the contribution is related to the HAPS application for terrestrial fixed broadband communications. HAPS was hypothesised as a quasi-static platform with height above ground at the so-called stratospheric layer. Latter contribution was fulfilled by approaching via simulations the outdoor-indoor coverage with a simple efficient computational model at downlink mode. This work was assessing the ITU-R recommendations at bands recognised for the HAPS-based networks. It was contemplated the possibility of operating around 2 GHz (1820 MHz, specifically) because this band is recognised as an alternative for HAPS networks that can provide IMT-2000 and IMT-Advanced services. The global broadband radio communication model was composed of three parts: transmitter, channel, and receiver. The transmitter and receiver parts were based on the specifications of the IEEE Std 802.16TM-2009 (with its respective digital transmission techniques for a robust-reliable link), and the channel was subjected to the analysis of radio modelling at the level of HAPS and terrestrial (outdoors plus indoors) parts. For the channel modelling was used the two-state characterisation (physical situations associated with the transmitted/received signals), the state-oriented channel modelling. One of the channel-state contemplated the environmental transmission situation defined by a direct path between transmitter and receiver, and the remaining one regarded the conditions of shadowing. These states were dependent on the elevation angle related to the ray-tracing analysis: within the propagation environment, it was considered that a representative portion of the total energy of the signal was received by a direct or diffracted wave, and the remaining power signal was coming by a specular wave, to last-mentioned waves (rays) were added the scattered and random rays that constituted the diffuse wave. At indoors case, the variations of the transmitted signal were also considering the following matters additionally: the building penetration, construction material, angle of incidence, floor height, position of terminal in the room, and indoor fading; also, these indoors radiocommunications presented different type of paths to reach the receiver: obscured LOS, no LOS (NLOS), and hard NLOS. The evaluation of the feasible performance for the HAPS-to-ground terminal was accomplished by means of thorough simulations. The outcomes of the experiment were presented in terms of BER vs. Eb/N0 plotting, getting significant positive conclusions for these kind of system as access network technology based on HAPS.

Stora volymer förorenade sediment kommer att behöva tas om hand under de kommande åren då bottensediment i svenska farleder, hamn- och kustområden under lång tid har konta–minerats av både tungmetaller och organiska föroreningar. I examensarbetet studeras fyra möjligheter för hantering av förorenade muddermassor. De tre traditionella metoderna är tippning till havs, utfyllnad i vik eller deponering på land. Stabilisering/solidifiering (s/s) är ytterligare ett alternativ som innebär att muddermassorna kan nyttiggöras i geokonstruktioner genom att massornas hållfasthet ökas. Metoden går ut på att muddermassorna blandas med bindemedel och de eventuella föroreningarna binds då in i matrisen genom kemisk reaktion och fysikalisk inneslutning.  Syftet med examensarbetet är att, utifrån ett platsspecifikt perspektiv, undersöka hur föroreningsrisker kan jämföras mellan de fyra olika huvud–alternativen för hantering av muddermassor. Jämförelsen är tänkt att utgöra en del av ett beslutsunderlag som ska ligga till grund för valet av hanteringsalternativ. Arbetet har fokuserat på miljöriskanalys och främst på hur risker kan kategoriseras, värderas och jämföras. Metoden inkluderar en litteraturstudie, en undersökning av tillstånds–ansökningar för hamnutbyggnad, en fallstudie där användning av LCA-metodik, ”ekotoxicitetspotential” och Naturvårdsverkets riktvärdesmodell testats för att jämföra föroreningsrisker mellan olika hanteringsalternativ i Oxelösunds hamn. Avslutningsvis genomfördes en serie intervjuer kring temat karaktärisering och jämförelser av risk i en s.k. Stakeholder Opinion Assessment (SOA). I studien av tillståndsansökningarna för hamnutbyggnad konstaterades att jämförelser av platsspecifika föroreningsrisker mellan olika hanteringsalternativ för förorenade mudder–massor inte görs. Istället är det andra aspekter, t.ex. ekonomi, som avgör vilket alternativ som väljs. Varken ekotoxicitetspotential eller Naturvårdsverkets riktvärdesmodell visade sig vara lämpliga metoder för att beskriva och jämföra risker i det aktuella fallet. Av intervjuerna i SOA:n framgår att det råder delade meningar om hur risker ska beskrivas och på vilket sätt de kan jämföras och det finns ett stort behov av att utveckla nya sätt att beskriva och jämföra föroreningsrisker mellan olika alternativ och olika platser. Arbetet har visat att det finns ett behov av att utveckla miljöriskanalysens avslutande steg, riskkaraktärisering och riskvärdering, eftersom det idag inte finns några konkreta metoder för att jämföra föroreningsrisker mellan olika hanteringsalternativ för förorenade muddermassor. För att förbättra beslutsunderlag föreslås därför en tydligare problemformulering och att övergripande platsspecifika scenarion för de olika alternativen tas fram. Viktigt aspekter att tydliggöra är skyddsobjekt, tidsskala, spridning och exponering. Jämförelsen av platsspecifika föroreningsrisker får inte heller bli allt för detaljerad, eftersom den bara är en del av ett större beslutsunderlag. / Large amounts of contaminated sediment has to be taken care of within the next few years since the sediment in Swedish sea lanes, ports and coastal areas have been contaminated by both heavy metals and organic pollutants over a long time period. Four options for handling contaminated dredged material were studied within this master thesis project. The three traditional methods are dumping the dredged material at sea, filling a bay with dredged material or putting the dredged material on a land disposal. Stabilization/solidification (s/s) is another option, where the contaminated dredged sediments are mixed with a binder that gives them greater strength, while immobilizing contaminants through chemical reactions or physical confinement in the structure. The aim of this thesis is to examine how risks of contamination can be compared between the four main options for management of dredged materials, in a site-specific perspective. The main tool in the project has been environmental risk assessment with special focus on how risks can be categorized, measured and compared. The study includes a literature review, an examination of permit applications for port development, a case study where the LCA methodology, "potential eco-toxicity" and the Swedish Environmental Protection Agency's guideline value model was tested in order to compare the risks of contamination from the various management options in the port of Oxelösund. Finally a Stakeholder Opinion Assessment (SOA), by the theme risk characterization and risk comparison, was made. The study of permit applications for port expansion has shown that the site-specific risks of contamination are not considered when choosing between management options of dredged materials. Instead other aspects, such as economy, determine the option chosen. Neither potential of eco-toxicity or the Swedish Environmental Protection Agency's guideline value model proved to be appropriate methods in order to describe and compare the risks associates with this case. The interviews in the SOA show that people disagree on how risks should be described and compared. There is a demand for new methods of describing and comparing risks associated with different management options for dredged materials at different sites. This work has shown that well-known methods on how to compare risks of contamination between the different management options for contaminated dredged materials do not exist. There is also a need of developing the latter steps in the environmental risk assessment. To develop a better decision basis, a more explicit definition of the problem is proposed. It is particularly important to make site-specific descriptions of the various systems to be compared. The comparison of the site-specific risks of contamination should not be too detailed, since it is part of a larger decision support. / Stabcon

Es wurden die Zusammenhänge zwischen den Herstellungsbedingungen und dem nanostrukturellen Aufbau von Multischichten, mit Rücksicht auf das mechanische Verhalten aufgeklärt. Dazu wurden durch plasmaunterstützte Gasphasenabscheidung (PACVD) Hartmetallsubstrate mit Viellagen beschichtet und vorrangig mittels analytischer Transmissionselektronenmikroskopie (TEM) charakterisiert. Als Schichkomponenten wurden hauptsächlich TiN und Al2O3 untersucht, daneben aber auch Schichtsysteme der Komponenten AlON, (TiAl)N, und (Ti,Al)ON. Darüber hinaus wurden noch TiC-aC (TiC mit amorphem Kohlenstoffanteil)-Schichten einbezogen. Ziel waren gleichmäßige Multischichten mit Korngrößen von einigen Nanometern, geringer Testur und geringer Mikrorissdichte, die hart sind und gut haften. Die TEM-Untersuchungen dienten insbesondere der Aufklärung der Nanostruktur in den Interface-Bereichen der Schichtsysteme, wobei an Hand der Elektronenenergie-Verlustspektroskopie (EELS) sowohl element- als auch phasenspezifische Signale ausgewertet wurden. Zur verbesserten Bewertung der anfallenden Datenmengen wurden z. T. faktoranalytische Methoden eingesetzt. Je nach Prozessführung der Schichtherstellung kommt es in den Interface-Bereichen zur Durchmischung der Komponenten. Insbesondere führt diffundierender Sauerstoff zur Bildung von TiO2, was sich nachteilig auf die Qualität der Schichten auswirkt. Die Tiefe der &amp;quot;gestörten&amp;quot; Zonen begrenzt die wünschenswerte Verringerung der Einzelschichtdicken. Als wirkungsvolle Gegenmaßnahme hat sich der Einbau von Kohlenstoff erwiesen, wodurch sich dünnere Einzelschichten verwirklichen lassen.

Abstract: Micro­Raman Spectroscopy Investigation of Hard Coatings Diamond, silicon carbide, and boron nitride have attracted great interest in the last years, due to their excellent material properties. Especially the extreme hardness and the high thermal con­ ductivity of these materials favour them as protective layers. The very large hardness gave these materials, deposited as films on various substrates, their name: hard coatings. In contrast to di­ amond, silicon carbide and boron nitride can be n­ as well as p­doped, making them promising candidates for high speed and high temperature electronic applications. Contrarily to the materials mentioned above, carbon nitride was obtained in crystalline form just very recently. Up to now the deposited films mainly consist of amorphous or nanocrystalline, carbon­rich material. For all these material systems inelastic light scattering (Raman spectroscopy) has been already applied for the material properties investigation. However, these investigations usually were restricted to only one of the various Raman spectroscopy tools, described in this work: Incident laser light energy varia­ tion, temperature variation, utilizing the selection rules, measurements at varying sample positions, two­dimensional mappings and one­dimensional scans in the conventional plane­view and the addi­ tional cross­sectional sample geometry. In contrast to this, this work demonstrates the improvement of the information about the investigated material and/or the sample heterostructure obtained by using the combination of all the above mentioned techniques. In the case of the diamond material system, films deposited on silicon substrates were investigated and an interfacial graphitic layer of 2nm thickness was found by scanning across the interface, which was obscured in the conven­ tional plane­view sample geometry. Similar to this an ultra­thin top layer and buried intermixed regions were identified in the silicon carbide material system utilizing the cross­sectional sample geometry. In addition to this, the temperature and the incident laser light energy dependences for 5 SiC polytypes (3C, 4H, 6H, 15R, and 21R) were measured. A resonance enhancement for the 3C and the 21R polytype was found corresponding to their fundamental bandgaps at 2.46eV and ß2.8eV, respectively. For the other polytypes no resonance enhancement was found, due to their larger fundamental bandgap. In the boron nitride material system the spatial correlation model for Raman lineshape analysis was applied for the first time and the values of the asymmetric broad­ ening and the frequency downshift for decreasing crystal sizes were evaluated. This was measured for single crystals of different size and for films deposited on silicon substrates. The correlation lengths in the ten nanometer region found for the deposited films corroborate the nanocrystalline nature of these films. Additionally incident laser light energy was measured, revealing the 488.0nm (Ar + ) and 482.5nm (Kr + ) laser lines as the optimum laser lines for the boron nitride investigation. Furthermore the dependence of the phonon feature parameters was investigated depending on the incident laser light power. A maximum power of 5­10mW for the micro­Raman spectroscopy setup was found to avoid any laser light induced heating of the investigated material. Two­dimensional mappings of the deposited boron nitride films were performed to improve the information about the material system. In the case of carbon nitride for the first time distinct phonon features were measured in a wide spectral range contrarily to most of the other investigations, which usually show only broad bands.

In der Milchindustrie spielt die Auswahl der Starterkulturen eine wichtige Rolle bei der Herstellung fermentierter Produkte mit gewünschter Textur und entsprechenden sensorischen Eigenschaften. Milchsäurebakterien mit der Fähigkeit extrazelluläre Polysaccharide (EPS) zu synthetisieren sind von besonderem Interesse, da auf Grund der in situ gebildeten Hydrokolloide der Einsatz von Zusatzstoffen vermieden werden kann. Die Wirkung von EPS auf die Produkt-eigenschaften ist in der Literatur bereits mehrfach beschrieben, wird jedoch auf Grund der Vielzahl an unterschiedlichen Stämmen und Fermentationsparametern bzw. einer fehlenden Systematisierung immer noch sehr kontrovers diskutiert. Des Weiteren stellt die wissenschaftliche Aufklärung der komplexen Struktur-Funktionsbeziehungen und der Wechselwirkungen mit anderen Produktkomponenten eine große Herausforderung dar. Um die Zusammenhänge besser verstehen zu können, wurde in dieser Arbeit ein neuer Ansatz gewählt: isolierte und aufgereinigte EPS wurden der Milch vor der Säuerung zugesetzt und die daraus hergestellten Milchgele mit jenen mit in situ produzierten EPS verglichen. In Milchgelen aus Einzelstammkulturen von Streptococcus thermophilus oder Lactobacillus delbrueckii ssp. bulgaricus wurden EPS‑Gehalte von 40 - 150 mg/kg ermittelt. Die Gele unterschieden sich hinsichtlich ihrer Viskosität und ihres fadenziehenden Charakters, was erste Hinweise auf die Art der gebildeten EPS liefert. Die Synthese größerer Mengen an EPS zur Charakterisierung und Untersuchung ihrer Funktionalität erfolgte entkoppelt von der Produkt­herstellung mit ausgewählten Stämmen in Batch-Fermentationen mit konstantem pH in komplexen oder semidefinierten Medien. S. thermophilus ST‑143 produzierte ~ 300 mg/L fadenziehende EPS, die durch entsprechende Aufreinigungsschritte als drei EPS‑Fraktionen gewonnen werden konnten: freie EPS (EPSf), kapsuläre EPS (EPSk) und ein Gemisch aus beiden (EPSf+k). EPSf haben eine höhere Molekülmasse (M = 2,6 x 10^6 Da) und eine höhere intrinsische Viskosität (1,14 mL/mg) im Vergleich zu EPSk (M = 7,4 x 10^3 Da, 1,4 x 10^5 Da; intrinsische Viskosität = 0,06 mL/mg) und führten bereits in geringen Mengen zu rheologischen Veränderungen. Allerdings scheinen die EPSk Wechselwirkungen zwischen EPSf Molekülen zu unterstützen. In chemisch gesäuerten Milchgelen konnte durch den definierten Zusatz aufgereinigter Fraktionen von EPSf und EPSf+k vor der Säuerung (c = 0 - 0,35 mg/g) erstmals eine konzentrationsabhängige Wirkung aufgezeigt werden. Mit EPSf stieg der maximale Speichermodul der Milchgele als Maß für die Gelsteifigkeit linear an (457 - 722 Pa). EPSk zeigten hingegen keinen Einfluss. Als Modellpolysaccharid wurde vergleichend das gut beschriebene, ebenfalls ungeladene und nicht gelbildende Homopoly­saccharid Dextran herangezogen (c = 0 - 300 mg/g). EPSf und Dextran veränderten die Gelbildung, erhöhten die Steifigkeit stichfester Gele und die Viskosität gerührter Gele in ähnlichem Maße, es waren jedoch deutlich unterschiedliche Konzentrationen notwendig. Die in den Milchgelen beschriebenen Einflüsse können unter anderem auf Depletionseffekte zwischen gleichgeladenen Polymeren (hier Proteine und Polysaccharide) zurückgeführt werden. / The selection of suitable starter cultures for the production of fermented milk with a desired texture and corresponding sensory attributes is of great importance for the dairy industry. Lactic acid bacteria with the ability to synthesise extracellular polysaccharides (EPS) are of particular interest, because these in situ produced hydrocolloids may allow to omit the use of additives. Many effects of EPS on product properties are already described in the scientific literature, but are still discussed controversially because of the multitude of different strains and fermentation parameters and, hence, a lack of systematisation. Furthermore, research on the mechanisms behind the structure-function relationship and interactions with other product components is a challenging area. To obtain a deeper understanding of this complex system, a new approach was chosen for the present study: EPS were isolated, purified and added to the milk prior to acidification, and the respective milk gels were compared with those with in situ produced EPS. In milk gels acidified by single strains of Streptococcus thermophilus or Lactobacillus delbrueckii ssp. bulgaricus, EPS contents of 40 - 150 g/kg were determined. The gels differed in viscosity and their ropy character, which is a first indicator for the type of the EPS. To allow for their chemical and technofunctional characterisation, the synthesis of higher amounts of EPS was performed by batch-fermentation at constant pH and decoupled from the product manufacturing with selected strains in complex or semidefined media. S. thermophilus ST‑143 synthesised ~ 300 mg/L ropy EPS, which were isolated as three different EPS fractions by applying particular purification steps: free EPS (EPSf), capsular derived EPS (EPSk) and a mixture of both EPS (EPSf+k). EPSf had a higher molecular mass (M = 2.6 x 10^6 Da) and a higher intrinsic viscosity (1.14 mL/mg) compared to EPSk (M = 7.4 x 10^3 Da, 1.4 x 10^5 Da; intrinsic viscosity = 0.06 mL/mg) and affected the rheological properties of aqueous solutions already at low concentration. However, EPSk appear to support interactions between the EPSf molecules. In chemically acidified milk gels a concentration dependent impact of EPSf and EPSf+k, which were added to the milk prior to acidification (c = 0 - 0,35 mg/g), was described for the first time. The maximum of the storage modulus as a measure for stiffness of the milk gels linearly increased with EPSf content (457 - 722 Pa). With EPSk no effects were observed. For the purpose of comparison dextran, a well described also uncharged and non gelling homopolysaccharide, was used as a model polysaccharide (0 - 300 mg/g). EPSf and dextran affected the gelation, increased gel stiffness of set gels and viscosity of stirred gels to a similar way, but the concentrations needed for that found to be completely different. The effects described for milk gels can be ascribed among others to depletion interactions between similar charged polymers (here proteins and polysaccharides).