Gewebezellen sammeln ständig Informationen über die mechanischen Eigenschaften ihrer Umgebung, indem sie aktiv an dieser ziehen. Diese Kräfte werden an Zell-Matrix-Kontakten übertragen, die als Mechanosensoren fungieren. Jüngste Experimente mit Zellen auf elastischen Substraten zeigen, dass Zellen sehr empfindlich auf Veränderungen der effektiven Steifigkeit ihrer Umgebung reagieren, die zu einer Reorganisation des Zytoskeletts führen können. In dieser Arbeit wird ein theoretisches Model entwickelt, um die Selbstorganisation von Zellen in weichen Materialien vorherzusagen. Obwohl das Zellverhalten durch komplexe regulatorische Vorgänge in der Zelle gesteuert wird, scheint die typische Antwort von Zellen auf mechanische Reize eine einfache Präferenz für große effektive Steifigkeit der Umgebung zu sein, möglicherweise weil in einer steiferen Umgebung Kräfte an den Kontakten effektiver aufgebaut werden können. Der Begriff Steifigkeit umfasst dabei sowohl Effekte, die durch größere Härte als auch durch elastische Verzerrungsfelder in der Umgebung verursacht werden. Diese Beobachtung kann man als ein Extremalprinzip in der Elastizitätstheorie formulieren. Indem man das zelluläre Kraftmuster spezifiziert, mit dem Zellen mit ihrer Umgebung wechselwirken, und die Umgebung selbst als linear elastisches Material modelliert, kann damit die optimale Orientierung und Position von Zellen vorhergesagt werden. Es werden mehrere praktisch relevante Beispiele für Zellorganisation theoretisch betrachtet: Zellen in externen Spannungsfeldern und Zellen in der Nähe von Grenzflächen für verschiedene Geometrien und Randbedingungen des elastischen Mediums. Dafür werden die entsprechenden elastischen Randwertprobleme in Vollraum, Halbraum und Kugel exakt gelöst. Die Vorhersagen des Models stimmen hervorragend mit experimentellen Befunden für Fibroblastzellen überein, sowohl auf elastischen Substraten als auch in physiologischen Hydrogelen. Mechanisch aktive Zellen wie Fibroblasten können auch elastisch miteinander wechselwirken. Es werden daher optimale Strukturen als Funktion von Materialeigenschaften und Zelldichte bzw. der Geometrie der Zellpositionen berechnet. Schließlich wird mit Hilfe von Monte Carlo Simulationen der Einfluss stochastischer Störungen auf die Strukturbildung untersucht. Das vorliegende Model trägt nicht nur zu einem besseren Verständnis von vielen physiologischen Situationen bei, sondern könnte in Zukunft auch für biomedizinische Anwendungen benutzt werden, um zum Beispiel Protokolle für künstliche Gewebe im Bezug auf Substratgeometrie, Randbedingungen, Materialeigenschaften oder Zelldichte zu optimieren. / Adherent cells constantly collect information about the mechanical properties of their extracellular environment by actively pulling on it through cell-matrix contacts, which act as mechanosensors. In recent years, the sophisticated use of elastic substrates has shown that cells respond very sensitively to changes in effective stiffness in their environment, which results in a reorganization of the cytoskeleton in response to mechanical input. We develop a theoretical model to predict cellular self-organization in soft materials on a coarse grained level. Although cell organization in principle results from complex regulatory events inside the cell, the typical response to mechanical input seems to be a simple preference for large effective stiffness, possibly because force is more efficiently generated in a stiffer environment. The term effective stiffness comprises effects of both rigidity and prestrain in the environment. This observation can be turned into an optimization principle in elasticity theory. By specifying the cellular probing force pattern and by modeling the environment as a linear elastic medium, one can predict preferred cell orientation and position. Various examples for cell organization, which are of large practical interest, are considered theoretically: cells in external strain fields and cells close to boundaries or interfaces for different sample geometries and boundary conditions. For this purpose the elastic equations are solved exactly for an infinite space, an elastic half space and the elastic sphere. The predictions of the model are in excellent agreement with experiments for fibroblast cells, both on elastic substrates and in hydrogels. Mechanically active cells like fibroblasts could also interact elastically with each other. We calculate the optimal structures on elastic substrates as a function of material properties, cell density and the geometry of cell positioning, respectively, that allows each cell to maximize the effective stiffness in its environment due to the traction of all the other cells. Finally, we apply Monte Carlo simulations to study the effect of noise on cellular structure formation. The model not only contributes to a better understanding of many physiological situations. In the future it could also be used for biomedical applications to optimize protocols for artificial tissues with respect to sample geometry, boundary condition, material properties or cell density.

This thesis details research performed in modeling, simulation, and rational design of porous SOFC cathodes via development, extension, and use of the key tools to aid in the fundamental understanding and engineering design of cathode materials. Phenomenological modeling of triple phase boundary (TPB) reactions and surface transport on La₁₋ₓSrₓMnO₃ (LSM) was conducted, providing insight into the role of the bulk versus surface oxygen reduction pathway and the role of sheet resistance in thin-film patterned electrode measurements. In response to observation of sheet resistance deactivation, a modeling study was conducted to design thin-film patterned electrodes with respect to sheet resistance. Additionally, this thesis outlines the application of phenomenological chemical kinetics to describe and explain the performance and stability enhancements resulting from surface modification of La₁₋ₓSrₓCo₁₋yFeyO₃₋delta (LSCF) with a conformal LSM coating. The analysis was performed in close coordination with electrochemical experiments and transmission electron microscopy. Finally, the thesis describes conformal modeling of porous cathode microstructures using chemical kinetics and transport models. A novel application of conservative point defect ensembles was developed to allow simulations with complicated chemical surface kinetics to be efficiently coupled with bulk transport within the porous structure. The finite element method was employed to simulate electrochemical response conformal to sintered porous ceramic structures using actual 3D microstructural reconstructions obtained using x-ray microtomography. Mesh refinement, linear, and nonlinear reaction rate kinetics were employed to study the bulk versus surface oxygen reduction pathways and the effect of near-TPB nanostructure.

This thesis work aims at a better understanding of magneto-optical properties of dilute nitrides and II-VI diluted magnetic semiconductor quantum structures. The thesis is divided into two parts. The first part gives an introduction of the research fields, together with a brief summary of the scientific results included in the thesis. The second part consists of seven scientific articles that present the main findings of the thesis work. Below is a short summary of the thesis. Dilute nitrides have been of great scientific interest since their development in the early 1990s, because of their unusual fundamental physical properties as well as their potential for device applications. Incorporation of a small amount of N in conventional Ga(In)As or Ga(In)P semiconductors leads to dramatic modifications in both electronic and optical properties of the materials. This makes the dilute nitrides ideally suited for novel optoelectronic devices such as light emitting devices for fiber-optic communications, highly efficient visible light emitting devices, multi-junction solar cells, etc. In addition, diluted nitrides open a window for combining Si-based electronics with III-V compounds-based optoelectronics on Si wafers, promising for novel optoelectronic integrated circuits. Full exploration and optimization of this new material system in device applications requires a detailed understanding of their physical properties. Papers I and II report detailed studies of effects of post-growth rapid thermal annealing (RTA) and growth conditions (i.e. presence of N ions, N2 flow, growth temperature and In alloying) on the formation of grown-in defects in Ga(In)NP. High N2 flow and bombardment of impinging N ions on grown sample surface is found to facilitate formation of defects, such as Ga interstitial (Gai) related defects, revealed by optically detected magnetic resonance (ODMR). These defects act as competing carrier recombination centers, which efficiently decrease photoluminescence (PL) intensity. Incorporation of a small amount of In (e.g. 5.1%) in GaNP seems to play a minor role in the formation of the defects. In GaInNP with 45% of In, on the other hand, the defects were found to be abundant. Effect of RTA on the defects is found to depend on initial configurations of Gai related defects formed during the growth. In Paper III, the first identification of an interfacial defect at a heterojunction between two semiconductors (i.e. GaP/GaNP) is presented. The interface nature of the defect is clearly manifested by the observation of ODMR lines originating from only two out of four equivalent <111> orientations. Based on its resolved hyperfine interaction between an unpaired electronic spin (S=1/2) and a nuclear spin (I=1/2), the defect is concluded to involve a P atom at its core with a defect/impurity partner along a <111> direction. Defect formation is shown to be facilitated by N ion bombardment. In Paper IV, the effects of post-growth hydrogenation on the efficiency of the nonradiative (NR) recombination centers in GaNP are studied. Based on the ODMR results, incorporation of H is found to increase the efficiency of the NR recombination via defects such as Ga interstitials. In Paper V, we report on our results from a systematic study of layered structures containing an InGaNAs/GaAs quantum well, by the optically detected cyclotron resonance (ODCR) technique. By monitoring PL emissions from various layers, the predominant ODCR peak is shown to be related to electrons in GaAs/AlAs superlattices. This demonstrates the role of the SL as an escape route for the carriers confined within the InGaNAs/GaAs single quantum well. The last two papers are within a relatively new field of spintronics which utilizes not only the charge (as in conventional electronics) but also the quantum mechanical property of spin of the electron. Spintronics offers a pathway towards integration of information storage, processing and communications into a single technology. Spintronics also promises advantages over conventional charge-based electronics since spin can be manipulated on a much shorter time scale and at lower cost of energy. Success of semiconductor-based spintronics relies on our ability to inject spin polarized electrons or holes into semiconductors, spin transport with minimum loss and reliable spin detection. In Papers VI and VII, we study the efficiency and mechanism for carrier/exciton and spin injection from a diluted magnetic semiconductor (DMS) ZnMnSe quantum well into nonmagnetic CdSe quantum dots (QD’s) by means of spin-polarized magneto PL combined with tunable laser spectroscopy. By means of a detailed rate equation analysis presented in Paper VI, the injected spin polarization is deduced to be about 32%, decreasing from 100% before the injection. The observed spin loss is shown to occur during the spin injection process. In Paper VII, we present evidence that energy transfer is the dominant mechanism for carrier/exciton injection from the DMS to the QD’s. This is based on the fact that carrier/exciton injection efficiency is independent of the width of the ZnSe tunneling barrier inserted between the DMS and QD’s. In sharp contrast, spin injection efficiency is found to be largely suppressed in the structures with wide barriers, pointing towards increasing spin loss.

Using the AdS/CFT correspondence, we study the anisotropic transport properties of both supersymmetric and non-supersymmetric matter fields on (2+1)-dimensional defects coupled to a (3+1)-dimensional N=4 SYM "heat bath". We address on the one hand the purely conformal defect where the only non-vanishing background field that we turn on is a "topological", parameter parametrizing the impact on the bulk. On the other hand we also address the case of a finite external background magnetic field, finite net charge density and finite mass. We find in the purely conformal limit that the system possesses a conduction threshold given by the wave number of the perturbation and that the charge transport arises from a quasiparticle spectrum which is consistent with an intuitive picture where the defect acquires a finite width in the direction of the SYM bulk. We also examine finite-coupling modifications arising from higher derivative interactions in the probe brane action. In the case of finite density, mass and magnetic field, our results generalize the conformal case. We discover at high frequencies a spectrum of quasiparticle resonances due to the magnetic field and finite density and at small frequencies a Drude-like expansion around the DC limit. Both of these regimes display many generic features and some features that we attribute to strong coupling, such as a minimum DC conductivity and an unusual behavior of the "cyclotron" and plasmon frequencies, which become correlated to the resonances found in the conformal case. We further study the hydrodynamic regime and the relaxation properties, in which the system displays a set of different possible transitions to the collisionless regime. The mass dependence can be cast in two regimes: a generic relativistic behavior dominated by the UV and a non-linear hydrodynamic behavior dominated by the IR. In the massless case, we also extend earlier results to find an interesting duality under the transformation of the conductivity and the exchange of density and magnetic field. Furthermore, we look at the thermodynamics and the phase diagram, which reproduces general features found earlier in 3+1 dimensional systems and demonstrates stability in the relevant phase.

The development and improvement of the functionality of metal oxides in heterogeneous catalysis and other surface chemical processes can greatly benefit from an atomic-level understanding of the surface chemistry. Atomistic calculations such as quantum mechanical (QM) calculations and molecular dynamics (MD) simulations can provide highly detailed information about the atomic and electronic structure, and constitute valuable complements to experimental surface science techniques. In this thesis, an embedded-cluster approach for quantum mechanical calculations has been developed to model the surface chemistry of metal oxides. In particular, CO adsorption on the MgO(001) and CeO2(110) surfaces as well as O vacancy formation at the CeO2(110) surface have been investigated. The cluster model has been thoroughly tested by comparison with electronic structure calculations for the periodic slab model. The chemical implications of distorted surface structures arising from the surface dynamics have been investigated by combining the QM embedded-cluster calculations with force-field based MD simulations. Here QM embedded-cluster calculations were performed using surface structures sampled from the MD simulations. This combined MD+QM embedded-cluster procedure was applied to the CO adsorption on MgO(001) at 50 K and the O vacancy formation on CeO2(110) at 300 K. Significant thermal variations of the CO adsorption energy and the O vacancy formation energy were observed. It was found that these variations could be estimated using the force field of the MD simulation as an interaction model. With this approach, the QM results were extrapolated to higher temperature and doped systems.

Automated visual inspection is an emerging multi-disciplinary field with many challenges; it combines different aspects of computer vision, pattern recognition, automation, and control systems. There does not exist a large body of work dedicated to the design of generalized visual inspection systems; that is, those that might easily be made applicable to different product types. This is an important oversight, in that many improvements in design and implementation times, as well as costs, might be realized with a system that could easily be made to function in different production environments. <br /><br /> This thesis proposes a framework for generalizing and automating the design of the defect classification stage of an automated visual inspection system. It involves using an expandable set of features which are optimized along with the classifier operating on them in order to adapt to the application at hand. The particular implementation explored involves optimizing the feature set in disjoint sets logically grouped by feature type to keep search spaces reasonable. Operator input is kept at a minimum throughout this customization process, since it is limited only to those cases in which the existing feature library cannot adequately delineate the classes at hand, at which time new features (or pools) may have to be introduced by an engineer with experience in the domain. <br /><br /> Two novel methods are put forward which fit well within this framework: cluster-space and hybrid-space classifiers. They are compared in a series of tests against both standard benchmark classifiers, as well as mean and majority vote multi-classifiers, on feature sets comprised of just the logical feature subsets, as well as the entire feature sets formed by their union. The proposed classifiers as well as the benchmarks are optimized with both a progressive combinatorial approach and with an genetic algorithm. Experimentation was performed on true colour industrial lumber defect images, as well as binary hand-written digits. <br /><br /> Based on the experiments conducted in this work, it was found that the sequentially optimized multi hybrid-space methods are capable of matching the performances of the benchmark classifiers on the lumber data, with the exception of the mean-rule multi-classifiers, which dominated most experiments by approximately 3% in classification accuracy. The genetic algorithm optimized hybrid-space multi-classifier achieved best performance however; an accuracy of 79. 2%. <br /><br /> The numeral dataset results were less promising; the proposed methods could not equal benchmark performance. This is probably because the numeral feature-sets were much more conducive to good class separation, with standard benchmark accuracies approaching 95% not uncommon. This indicates that the cluster-space transform inherent to the proposed methods appear to be most useful in highly dependant or confusing feature-spaces, a hypothesis supported by the outstanding performance of the single hybrid-space classifier in the difficult texture feature subspace: 42. 6% accuracy, a 6% increase over the best benchmark performance. <br /><br /> The generalized framework proposed appears promising, because classifier performance over feature sets formed by the union of independently optimized feature subsets regularly met and exceeded those classifiers operating on feature sets formed by the optimization of the feature set in its entirety. This finding corroborates earlier work with similar results [3, 9], and is an aspect of pattern recognition that should be examined further.

Using the AdS/CFT correspondence, we study the anisotropic transport properties of both supersymmetric and non-supersymmetric matter fields on (2+1)-dimensional defects coupled to a (3+1)-dimensional N=4 SYM "heat bath". We address on the one hand the purely conformal defect where the only non-vanishing background field that we turn on is a "topological", parameter parametrizing the impact on the bulk. On the other hand we also address the case of a finite external background magnetic field, finite net charge density and finite mass. We find in the purely conformal limit that the system possesses a conduction threshold given by the wave number of the perturbation and that the charge transport arises from a quasiparticle spectrum which is consistent with an intuitive picture where the defect acquires a finite width in the direction of the SYM bulk. We also examine finite-coupling modifications arising from higher derivative interactions in the probe brane action. In the case of finite density, mass and magnetic field, our results generalize the conformal case. We discover at high frequencies a spectrum of quasiparticle resonances due to the magnetic field and finite density and at small frequencies a Drude-like expansion around the DC limit. Both of these regimes display many generic features and some features that we attribute to strong coupling, such as a minimum DC conductivity and an unusual behavior of the "cyclotron" and plasmon frequencies, which become correlated to the resonances found in the conformal case. We further study the hydrodynamic regime and the relaxation properties, in which the system displays a set of different possible transitions to the collisionless regime. The mass dependence can be cast in two regimes: a generic relativistic behavior dominated by the UV and a non-linear hydrodynamic behavior dominated by the IR. In the massless case, we also extend earlier results to find an interesting duality under the transformation of the conductivity and the exchange of density and magnetic field. Furthermore, we look at the thermodynamics and the phase diagram, which reproduces general features found earlier in 3+1 dimensional systems and demonstrates stability in the relevant phase.

Rapporten beskriver en undersökning rörande två olika typer av inre fel, centrumfel och ytnära fel, på valsar. Examensarbete för högskoleingenjörsexamen i maskinteknik (22.5p) vid Instutitionen för ingenjörsvetenskap, fysik och matematik, Karlstad Universitet. Utfört på uppdrag av Scana Steel Björneborg AB. Scana Björneborg är en av Europas ledande producenter av tunga friformsmidda detaljer och har eget stålverk, egen smedja, värmebehandlingsanläggning och maskinpark. På Scana Björneborg gjuts göt av järnskrot, varpå de smids, värmebehandlas och maskinbearbetas till valsar. Efter maskinbearbetning kontrolleras valsarna med ultraljud för att hitta eventuella inre fel. Specifikationerna från kund för hur stora indikationer får vara är strama och stora kostnader uppstår i samband med reklamationer, kassationer, omarbeten och förseningar. Felen har blivit alltmer frekventa och Scana Björneborg har satt samman två projektgrupper för att få försöka få bukt på dem. Examensarbetet skall understödja båda dessa grupper och genom undersökningen skapa underlag för vidare beslut. Undersökningen delades in i tre olika moment: * Statistik och information som kunde användas för att hitta eventuella samband och orsaker till de olika feltyperna samlades i en databas. * Den samlade statistiken och informationen organiserades, förenklades och analyserades sedan med hjälp av programmet SIMCA, ett program gjort för multivariata analyser av stora datamängder. Eventuella samband granskades och analyserades därefter manuellt för att väga och gallra resultatet . * Sex ytnära fel i tre olika detaljer öppnades upp för kartläggning av vilken typ av defekter det rörde sig om, och en metallografisk undersökning i ljus- och svepelektronmikroskop och analys av defekternas sammansättning gjordes. SIMCA-analys av insamlad statistik med avseende på centrumfel och vidare granskning och analys av dess resultat antyder att hög smidesvikt, hög Vanadinhalt, stukning, hög nedsmidningsgrad och smidestid per ton i den följden är viktiga faktorer vid uppkomsten av centrumfel, och att en viss samverkan finns mellan dem. SIMCA-analys av insamlad statistik med avseende på ytnära fel och vidare granskning och analys av dess resultat antyder att ett samband mellan valda parametrar och uppkomsten av ytnära fel inte går att hitta. Metoden bedöms olämplig för vidare undersökning av ytnära fel. Den metallografiska undersökningen av öppnade ytnära defekter visade att samtliga sex defekter liknade varandra till utseende och sammansättning. Vanligaste beståndsdelarna i dessa inneslutningar var Aluminium tillsammans med förhöjda halter av Kol och Syre. Dessa ämnen är alla naturliga i stålet och därför bedöms inte de ytnära felen vara utifrån kommande. / The report describes an investigation concerning two types of internal defects, axis-centered defects and near-surface defects, in rolls. Thesis for bachelor’s degree in mechanical engineering (22.5p), at the institution for engineering, physics and mathematics, Karlstad University. Ordered by Scana Steel Björneborg AB. Scana Steel Björneborg AB is one of Europe’s leading producers of heavy free-form forgings and has its own steel plant, forge, heating treatment facility and machine park. Scana Steel Björneborg AB casts ingots from iron scrap. The ingots are then forged, heat treated and machined into rolls. After the machining the rolls are tested with ultrasonic testing equipment to look for indications of internal defects. The specifications on how big the indications are allowed to be from the client are rigid and large costs come up because of reclamations, discarding, reworking and delays. The defects have become increasingly more frequent and Scana Steel Björneborg AB has put together two groups to try and get control over the problem. The thesis is meant to support the two groups by investigating the internal defects, and to create a platform to take further decisions from. The investigation was made up of three parts: * Statistics and information that could be used to find connections and cause of the internal defects was gathered in a data base. * The gathered statistics and information was organized, simplified and analyzed with SIMCA, a computer software made for multivariate analyzing of large amounts of information. The results of the SIMCA-simulation were then checked further manually to weigh and lay down the fairness of the results. * Six near-surface defects in three parts were opened up to map the types of defects and a metallographic examination in optical microscope, scanning electron microscope and spectrometer analysis of the defects’ composition was made. The SIMCA analysis of gathered statistics concerning axis-centered defects and later manual analysis of the results showed that high forging weight, high Vanadium content, high degree of forging and low forging-time per tonne all relate to the creation of axis-centered defects, and that some interaction is present between them. The SIMCA analysis concerning near-surface defects showed that the chosen parameters do not relate with the creation of near-surface defects. The method is deemed unsuitable for further investigations. The metallographic examination of the six near-surface defects showed that all six defects resemble each other in appearance and composition. The most common elements in these inclusions are Aluminum and heightened contents of Carbon and Oxygen. These elements are all naturally occurring elements in the steel and because of this the inclusions are not thought to be exogenous.

Gelenkknorpel ist ein gefäßloses, hoch spezialisiertes Gewebe mit nur sehr begrenzter Regenerationsfähigkeit. Entstandene Läsionen werden bei natürlicher Heilung durch min-derwertigen Faserknorpel gefüllt. Ein vielversprechender Therapieansatz kommt aus dem Gebiet des Tissue Engineering. Dabei werden isolierte Chondrozyten in vitro vermehrt und anschließend in den Defekt eingebracht. In den letzten Jahren ist hier die 3 D-Kultivierung in patientenspezifischen Biomaterialien zunehmend in den Fokus der Forschung geraten. Ziel der hier vorgestellten Studie war es, die Tauglichkeit von Vollblut und Blutplasma als Aus-gangsmaterial für MACTs aufgrund makroskopischer Eigenschaften, Zellzahlentwicklung im Konstrukt, Zellvitalität und Syntheseleistung charakteristischer EZM-Marker zu untersuchen. Es wurde für diese Studie Knorpel aus den Fesselgelenken vier geschlachteter Pferde (2-16 Jahre) entnommen, mechanisch zerkleinert und anschließend mit Kollagenase A verdaut. Von einem 6 jährigen klinikeigenen Wallach wurde Vollblut in Citratröhrchen gewonnen, ein Teil zu Plasma weiterverarbeitet und beides bei -80 °C bis zur weiteren Verwendung Schock gefroren. Zur Herstellung der walzenförmigen Konstrukte mit den Maßen 9,6 cm2 x 4,7 mm, wurden 4,5 ml Vollblut bzw. Plasma mit je 3x106 Chondrozyten suspensiert und durch Zuga-be von CaCl2 zur Koagulation gebracht. Der Kultivierungszeitraum betrug 28 Tage in DMEM, angereichert mit 10% allogenem Serum und 1% Antibiotika. Die Konstrukte wurden an den Tagen 1, 14 und 28 auf Zellzahl, -vitalität und mithilfe qRT-PCR auf hyaline Knorpelmarker wie Kollagen Typ II und Aggrekan untersucht. Zudem wurden histologische und immunhisto-chemische Präparate der Konstrukte angefertigt. Die Zellvitalität betrug sowohl in den VB-, als auch in den BP-Konstrukten ≥95% bei steigen-der Zellzahl (bis zu 5x106 im Vollblutkonstrukt). Die MACTs beider Ausgangsmaterialien schrumpften auf eine Größe von 2 cm² x 2 mm. Histologisch konnten in beiden Konstruktar-ten mit der Alzianblaufärbung sGAG belegt werden. Darüber hinaus wurde der sGAG Gehalt mit dem DMMB Assay quantitativ ermittelt. Aggrekan, C-4-S, C-6-S und COMP wurden als wichtige Bestandteile der EZM immunhistochemisch angefärbt und waren ebenfalls in beiden Konstruktarten nachweisbar. Mit der qRT PCR konnte die Genexpression von Aggrekan, Kol II und Kol I über den zeitlichen Verlauf ermittelt werden. Es stellte sich heraus, dass sich sowohl die Genexpression von Aggrekan als auch die von Kol II, den beiden Indikatorprotei-nen EZMs des hyalinen Gelenkknorpels über den Kultivierungszeitraum absenkten. Dies deutet auf eine Dedifferenzierung der Chondrozyten hin. Die Expression von Kol I dagegen stieg um ein Vielfaches an. Auch das kennzeichnet eine Dedifferenzierung. Zieht man ande-re Studien heran, so ist die festgestellte Umstellung der Genexpression aber vergleichsweise niedrig, eine Dedifferenzierung weg vom chondrogenen Phänotyp in der hier vorliegenden Arbeit also weniger stark ausgebildet. Biokompatibilität mit und Abbaubarkeit im Empfängerorganismus konnten in dieser in vitro Untersuchung nicht evaluiert werden. Zusammenfassend kann man festhalten, dass VB und BP als Ausgangsbiomaterialien zur Herstellung von MACT geeignet sind. Inwieweit es gelingen wird, den chondrogenen Phäno-typ beispielweise durch mechanische Stimulation der eingesäten Zellen stärker zu erhalten, muss in folgenden Studien geklärt werden. Ebenfalls weiterer Forschungsbedarf ist bei den Eigenschaften Elastizität und Steifheit gegeben. Grundsätzlich gilt, dass MACTs auf VB- und BP-Basis einen einfachen, kostengünstigen und patientenspezifisch herstellbaren Therapie-ansatz für die Behandlung von Knorpeldefekten darstellen. / Articular cartilage is a vessel-free, highly specialized tissue with only very limited regenera-tive capacity. Resulting lesions are filled with inferior fibrocartilage by natural healing. A promising therapeutic approach comes from the field of tissue engineering. Therefore iso-lated chondrocytes are expanded in vitro and then placed into the defect. In the last few years the 3-D culturing in patient-specific biomaterials has come increasingly into the focus of research. Purpose of the present study was to evaluate the suitability of whole blood and blood plasma as a basic material for MACT based on macroscopic properties, development of cell number in the construct, cell viability and synthetic performance of characteristic markers. For this study cartilage from the four fetlock joints of slaughtered horses (2-16 years) were removed, crushed mechanically and then digested with Collagenase A. Whole blood was obtained in citrate tubes of a 6 year old gelding owned by the clinic, finished part to both plasma and shock frozen at -80°C until further use. To prepare the cylindrical constructs, measuring 9.6 cm2 x 4.7 mm, 4.5 ml of whole blood or plasma, each with 3x106 chondro-cytes were suspended and coagulated by the addition of CaCl2. The cultivation period was 28 days in DMEM supplemented with 10% allogenic serum and 1% antibiotics. The con-structs were evaluated on days 1, 14 and 28 on cell number, viability, and using qRT-PCR examination for hyaline cartilage markers such as collagen type II and aggrecan. In addition, histological and immunohistochemical preparations of the constructs were made. The cell vitality was in the WB, as well as in the BP constructs ≥ 95% with increasing cell number (up to 5x106 in whole blood construct). The MACTs of both basic materials shrink to a size of 2 cm x 2 mm². Histologically sGAG could be verified in both construct species by Alzianblau staining. In addition, the GAG content was determined with the DMMB assay quantitatively. Aggrecan, chondroitin-4-sulphate, chondroitin-6-sulphate and COMP as major components of the ECM were stained immunohistochemically and were also detectable in both types of constructs. Aggrecan, collagen II and collagen I were determined on the time course by qRT PCR gene expression. It turned out that the gene expressions of both, aggre-can and of collagen II, the two ECM protein indicators of hyaline cartilage lowered over the cultivation period. This indicates a dedifferentiation of chondrocytes. The expression of colla-gen I on the other hand increased to a multiple, also featuring a dedifferentiation. If one approached other studies, the observed change in gene expression is comparatively low. In the present work the dedifferentiation from the chondrogenic phenotype is less distinctive. Biocompatibility and biodegradability in the recipient organism could not be evaluated in this in vitro investigation. In summary, one should notice that VB and BP are suitable basic materials for the production of MACT. It has to be clarified by following studies, to what extent the chondrogenic pheno-type can be strengthened, for example by mechanical stimulation of cells sown. Also further research is needed on the given properties, e.g. elasticity and stiffness. Generally MACT based on WB and BP- is a simple, inexpensive and patient-specific produced therapeutic approach for the treatment of cartilage defects.

Optical properties of Tl4In3GaSe8, Tl4InGa3Se8, Tl4In3GaS8, Tl2InGaS4 and Tl4InGa3S8 chain and layered crystals were studied by means of photoluminescence (PL) and transmission-reflection experiments. Several emission bands were observed in the PL spectra within the 475-800 nm wavelength region. The results of the temperature- and excitation intensity-dependent PL measurements in 15-300 K and 0.13&times / 10-3-110.34 W cm-2 ranges, respectively, suggested that the observed bands were originated from the recombination of electrons with the holes by realization of donor-acceptor or free-to-bound type transitions. Transmission-reflection measurements in the wavelength range of 400-1100 nm revealed the values of indirect and direct band gap energies of the crystals studied. By the temperature-dependent transmission measurements in 10-300 K range, the rates of change of the indirect band gap of the samples with temperature were found to be negative. The oscillator and dispersion energies, and zero-frequency refractive indices were determined by the analysis of the refractive index dispersion data using the Wemple&ndash / DiDomenico single-effective-oscillator model. Furthermore, the structural parameters of all crystals were defined by the analysis of X-ray powder diffraction data. The determination of the compositional parameters of the studied crystals was done by energy dispersive spectral analysis experiments.