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Vor dem Hintergrund zunehmender Wärmedämmmaßnahmen im Wohnungsbau, das heißt sinkender Heizlasten, und gleichzeitigem Bestreben nach Netzausbau und –verdichtung steht die Fernwärmeversorgung neuen Problemstellungen gegenüber. Es gilt Lösungsansätze für das Spannungsfeld niedriger Liniendichten, steigender Brennstoffpreise und der Forderung nach erneuerbaren Energien in der Wärmeversorgung zu entwickeln. Die vorliegende Arbeit untersucht in einer vergleichenden Simulationsstudie diverse Fahrweisen der Fernwärmeversorgung auf unterschiedlichen Temperaturniveaus. Befindet sich die Fernwärmevorlauftemperatur unter der aus Gründen des Legionellenschutzes notwendigen Temperatur der Trinkwassererwärmung, erfolgt eine dezentrale Nacherwärmung. Diese geschieht innerhalb der sogenannten LowEx-Fahrweise mittels elektrischen Heizstabs oder einem Wärmepumpen-Speicherladesystem mit Wärmequelle Fernwärme. Als Referenzsysteme finden die als Konventionelle-Fahrweise mit Speicherladesystem und die als Niedertemperatur-Fahrweise mit Wohnungsanschlussstation im Durchflussprinzip bezeichneten Betriebsweisen Anwendung. Neben der Senkung der Netzwärmeverluste und ggf. einer Steigerung der Erzeugungswirkungsgrade ermöglicht die LowEx-Fahrweise die dezentrale Einspeisung von Abwärme oder erneuerbaren Energien bei effizientem Betrieb der Energiebereitstellungsanlagen. Das Fernwärmenetz dient damit der gekoppelten Wärmeversorgung und auch Wärmeentsorgung. Beispielhaft wird die Abwärmeeinspeisung von Klimakälteprozessen mit sowohl Kompressionskälteanlagen als auch Absorptionskältenlagen untersucht. Anhand Solarthermie wird das Für und Wider der Einspeisung erneuerbarer Energien hinsichtlich der Senkung des Primärenergiebedarfs und der Verdrängung von Kraft-Wärme-Kopplungsanlagen diskutiert. Die Analysen erfolgen mit Hilfe modifizierter und neu entwickelter Modelle in der Simulationsumgebung TRNSYS-TUD.

The three main components of wood, namely, cellulose, hemicellulose, and lignin, can be used in various areas. However, since lignin covalently crosslinks with wood polysaccharides creating networks that is an obstacle for extraction, direct extraction of different wood components in high yield is not an easy matter. One potential approach to overcome such obstacles is to treat the wood with specific enzymes that degrade the networks by specific catalysis. However, the structure of wood is so compact that the penetration of the wood fibers by large enzyme molecules is hindered. Thus, the pretreatment of wood prior to the application of enzymes is necessary, for “opening” the structure. One pretreatment method that was performed in this thesis is based on kraft pulping, which is a well-established and industrialized technique. For untreated wood, the wood fibers cannot be attacked by the enzymes. A relatively mild pretreatment was sufficient for wood polysaccharides hydrolyzed by a culture filtrate. A methanol-alkali mixture extraction was subsequently applied to the samples that were pretreated with two types of hemicellulases, Gamanase and Pulpzyme HC, respectively. The extraction yield increased after enzymatic treatment, and the polymers that were extracted from monocomponent enzyme-treated wood had a higher degree of polymerization. Experiments with in vitro prepared lignin polysaccharide networks suggested that the increased extraction was due to the enzymatic untying. However, the relatively large loss of hemicellulose, particularly including (galacto)glucomannan (GGM), represents a problem with this technique. To improve the carbohydrate yield, sodium borohydride (NaBH4), polysulfide and anthraquinone were used, which increased the yields from 76.6% to 89.6%, 81.3% and 80.0%, respectively, after extended impregnation (EI). The additives also increased the extraction yield from approximately 9 to 12% w/w wood. Gamanase treatment prior to the extraction increased the extraction yield to 14% w/w wood. Sodium dithionite (Na2S2O4) is an alternative reducing agent for the preservation of hemicelluloses because it is less expensive than metal hydrides and only contains sodium and sulfur, which will not introduce new elements to the recovery system. Moreover, Na2S2O4has the potential to be generated from black liquor. Na2S2O4 has some preservation effect on hemicelluloses, and the presence of Na2S2O4 also contributed to delignification. The extraction yield increased to approximately 15% w/w wood. Furthermore, Na2S2O4 has been applied in the kraft pulping process of spruce. The yield and viscosity increased, while the Klason lignin content and kappa number decreased, which represents a beneficial characteristic for kraft pulp. The brightness and tensile strength of the resulting sheets also improved. However, the direct addition of Na2S2O4 to white liquor led to greater reject content. This problem was solved by pre-impregnation with Na2S2O4 and/or mild steam explosion (STEX) prior to the kraft pulping process. Following Na2S2O4 pre-impregnation and mild STEX, the obtained kraft pulp had substantially better properties compared with the properties exhibited after direct addition of Na2S2O4 to the white liquor. The wood structure opening efficiency of mild STEX alone was also tested. The accessibility of the wood structure to enzymes was obtained even at very modest STEX conditions, according to a reducing sugar analysis, and was not observed in untreated wood chips, which were used as a reference. The mechanical effect of STEX appears to be of great importance at lower temperatures, and both chemical and mechanical effects occur at higher STEX temperatures. / <p>QC 20140903</p>

Azyklische Beinstreckbewegungen stellen mit der Erzeugung hoher Absprunggeschwindigkeiten in vielen Sportarten wesentliche Teilleistungen dar, die durch Gelenkleistungen der unteren Extremitäten limitiert werden. An maximal willentlich ausgeführten Beinstreckbewegungen mit dem Ziel größtmöglicher Endbeschleunigung des Körperschwerpunkts hat die kniestreckende Muskulatur den größten Anteil. Mit geeigneten Muskelparametern lässt sich das Kontraktionsverhalten und damit die mechanische Antriebsleistung von Muskeln unter verschiedenen Arbeitsbedingungen kennzeichnen und das Training wirksam steuern. In dieser Arbeit wurde ein Instrumentarium zur individuellen Bestimmung von Muskelparametern der Kraft-Geschwindigkeit-Längen-Relation für die Kniestrecker entwickelt. Dies beinhaltete ein isokinetisches Testprogramm das die von antagonistischen Einflüssen isolierte Kraftdiagnose der kniestreckenden Muskulatur gewährleistet. Mit den in den Tests erhobenen Eingangsdaten konnten mit einem wirklichkeitsnahen Geometriemodell, inverser Dynamik und einem Optimierungsverfahren plausible Muskelparameter, u. a. die maximale Muskelleistung, für sechs Kadersportler berechnet werden. Am Beispiel eines Strecksprungs ohne Sprunggelenkeinsatz wurde gezeigt, dass die berechneten Parameter zur muskelkraftgesteuerten Simulation in Muskel-Skelett-Modellen geeignet sind und so die Optimierung der sportlichen Technik unter Berücksichtigung der individuell limitierten Antriebsleistung im Kniegelenk möglich ist.

Microtubules are a part of the cell cytoskeleton that performs different functions, such as providing the mechanical support for the shape of a cell, acting as tracks along which the motor protein move organelles from one part of the cell to another, or the forming mitotic spindle during the cell division. The microtubules are dynamic structures, namely they can grow and shrink. The phase of microtubule growth alternates with the phase of shrinkage that results in the dynamic microtubule network in the cell. However, to form stable and spatially well-defined structures, such as a mitotic spindle, the cell needs to control this stochastic process. This is done by microtubule-associated proteins (MAPs). One class of MAPs is the proteins of XMAP216/Dis1 family, which are microtubule polymerases. The founding member of this family is X. laevis XMAP215. XMAP215 is a processive polymerase acting on the microtubule plus end. XMAP215 binds either directly or reaches the microtubule plus end by the diffusion along the microtubule lattice. Being at the microtubule plus-end XMAP215 stays there transiently and helps to incorporate up to 25 tubulin dimers into microtubule lattice before it dissociates and, therefore, it processively tracks the growing microtubule end during polymerization. There are two hypothesis of microtubule assembly promotion: (i) XMAP215 repeatedly releases an associated tubulin dimer into the microtubule growing plus end or (ii) structurally stabilizes a polymerized tubulin intermediate at the growing plus end and, therefore, preventing depolymerization events. The first way results into the increase of on-rate of tubulin dimers at the microtubule end, whereas the second way results into the decrease of off-rate of tubulin dimers at the microtubule end. Here, I show the study of the mechanism of microtubule growth acceleration by XMAP215 and the dependence of XMAP215 polymerization activity on the applied force. To answer these questions, I investigated the addition of tubulin dimers to the plus end of the microtubule by XMAP215 and how this addition depends on the applied force. XMAP215 remains at the microtubule end for several rounds of tubulin addition surfing both growing and shrinking microtubule ends. Therefore, if one could track the position of the XMAP215 molecules at the very tip of a microtubule with sufficient resolution, it would provide the information about the dynamics of the microtubule end. The technique, which can detect the position of the object of interest with high spatial and temporal resolution in addition to being able to exert a force, is an optical trap. A calibrated optical trap not only provides a good measure of displacement but also enables force measurements. To monitor the position of the molecules of interest, the molecules of interest are usually attached to a microsphere. Hence, I tethered XMAP215 to a microsphere held by an optical trap, and used XMAP215 as a handle to interact with the microtubule tip. When the microtubule grows, the XMAP215 coated microsphere will move in the optical trap and this movement can be detected with high temporal and spatial resolution. My work demonstrates that cooperatively working XMAP215 molecules can not only polymerize microtubule but also harness the energy of microtubule polymerization or depolymerization to transport some cargo. There is an evidence that orthologues of XMAP215 in budding yeasts, fission yeasts and Drosophila localize on the kinetochores. Therefore, the ability of the bearing some load during microtubule polymerization could be potentially important for the XMAP215 functioning during cell division. I also showed the influence of external force applied to the XMAP215 molecules. Pointing toward microtubule growth, a force of 0.5 pN applied to the microtubule tip-coupled XMAP215-coated microsphere increases XMAP215 polymerization activity. However, the force of the same magnitude but applied against microtubule growth does not affect XMAP215 polymerization activity. This result can be explained by the fact, that the force acting in the direction of microtubule growth constrains XMAP215 to be at the very microtubule tip. Hence, XMAP215 can not diffuse away from plus-end and there is higher chance to incorporate tubulin dimers into the microtubule plus-end. The on- and off-rate of tubulin dimers at the microtubule end are both decreased when the external force applied either in direction of microtubule growth or opposite to it. The external force affects the off-rate slightly stronger than on-rate of tubulin dimer. Taking together, my study gives new insights into the mechanism of microtubule polymerization by XMAP215 and shows some novel properties of this protein.

Fernwärme ist aufgrund der verstärkten Förderung der Bundesregierung in den letzten Jahren wieder stärker in den Fokus der Energiewirtschaft gerückt. In Hinblick auf einen wirtschaftlich und energetisch effizienten Betrieb von Fernwärmesystemen ist nicht nur der Einsatz der Wärmeerzeuger mittels einer Einsatzplanung sorgfältig zu organisieren, sondern auch das Betriebsverhalten des Wärmeverteilnetzes selbst zu berücksichtigen. So führen ständig auftretende Änderungen der thermischen Last, der Vorlauftemperatur am Einspeisepunkt oder der Rücklauftemperaturen der Abnehmer zu instationären Betriebszuständen im Fernwärmenetz. Die damit verbundene zeitliche Entkopplung der zentralen Wärmeeinspeisung von der dezentralen Wärmeentnahme induziert eine Speicherung thermischer Energie in dem in den Rohrleitungen befindlichen Wasser und in den Rohren selbst. In den seltensten Fällen wird dieser Vorgang der Wärmespeicherung aktiv genutzt, er tritt vielmehr als eher unerwünschter Nebeneffekt auf. Bei Kenntnis der thermodynamischen Zusammenhänge hingegen lässt sich das Fernwärmenetz durch zielgerichtete Steuerung der Vorlauftemperatur analog einem thermischen Heißwasserspeicher als Wärmespeicher nutzen. Dies ist wiederum für die Betriebs- und Gewinnoptimierung interessant, da so weitere Speicherkapazitäten nutzbar gemacht werden können, um Lastspitzen zu verschieben und KWK-Anlagen zu betreiben ohne zusätzliche Investitionen tätigen zu müssen. In dieser Arbeit wird eine Methode vorgestellt, in der die Netzspeicherleistung mit Hilfe eines thermo-hydraulischen Simulationsprogrammes bestimmt wird, wobei dynamische Effekte wie die veränderliche Vorlauftemperaturen am Einspeisepunkt oder die stark schwankenden Lastanforderungen der Abnehmer in der Berechnungsmethodik realitätsnah abgebildet werden. Für eine aktive Nutzung des Fernwärmenetzes als Wärmespeicher muss der Verlauf der Vorlauftemperatur an die jeweilig gewünschte Netzspeicherleistung angepasst werden. Dazu wird in dieser Arbeit ein vereinfachter Funktionsansatz für die Netzspeicherleistung bestimmt, der zunächst mittels Regressionsanalyse aus den Ergebnissen gezielter thermo-hydraulischer Simulationen ermittelt und anschließend so in eine Einsatzplanung integriert wird, sodass die Vorlauftemperatur als zu optimierende Variable in die Gesamtoptimierung einfließt. Anhand eines realen Anwendungsfalls werden die Möglichkeiten und Grenzen der aktiven Nutzung der Speicherfähigkeit von Fernwärmenetzen aufgezeigt. Insbesondere werden monetäre Gewinnpotentiale bei Anwendung der aktiv gesteuerten Netzspeicherung in durch KWK-Anlagen versorgten Fernwärmenetzen bei gleichzeitigem Stromhandel auf dem Spotmarkt abgeschätzt.

Scaling in green liquor handling systems is a persistent problem in many kraft mills. Scaling is commonly believed to be the result of pirssonite (Na2Ca(CO3)2∙2H2O) deposition. In this work, scale characterization was performed by analyzing 12 scale samples obtained from 10 kraft mills. Only 4 samples were identified as pirssonite while the remaining consisted of CaCO3. The predominant presence of CaCO3 in the scale samples was found to be the result of selective dissolution of Na2CO3 from pirssonite scale, leaving CaCO3 behind. Experimental studies were also conducted to study pirssonite solubility under green liquor conditions. Results obtained from these studies were used to create and validate a database for pirssonite in the OLI Systems® software to predict its formation. This database was used to generate a family of pirssonite solubility curves that can be used by the kraft mills as operational guidelines to prevent pirssonite precipitation.

Scaling in green liquor handling systems is a persistent problem in many kraft mills. Scaling is commonly believed to be the result of pirssonite (Na2Ca(CO3)2∙2H2O) deposition. In this work, scale characterization was performed by analyzing 12 scale samples obtained from 10 kraft mills. Only 4 samples were identified as pirssonite while the remaining consisted of CaCO3. The predominant presence of CaCO3 in the scale samples was found to be the result of selective dissolution of Na2CO3 from pirssonite scale, leaving CaCO3 behind. Experimental studies were also conducted to study pirssonite solubility under green liquor conditions. Results obtained from these studies were used to create and validate a database for pirssonite in the OLI Systems® software to predict its formation. This database was used to generate a family of pirssonite solubility curves that can be used by the kraft mills as operational guidelines to prevent pirssonite precipitation.

This thesis focused on the modelling of a pulping process. The purpose was to see if an accurate model can be crated based on relatively simple premises and if the errors can be identified or analysed. To realise this, the authors conducted a literature study to identify the current state of the art regarding the chemical pulping process. In addition, flow charts and sample data from a case study were examined. Based on the literature review and case study, model assumptions were derived. The model is divided into sixteen components. Where mixing occurs, lumped conditions are assumed. The model has five validation points, four of which are temperatures and a mass flowrate. These are shown as deviations from the measured values. In conclusions, it was the model could produce stable results over a narrow time frame. More so if the transition period at the start of the simulation is overlooked. Several new model assumptions are presented with the purpose to increase accuracy e.g. account for the components ability to store mass.