@phdthesis{Wang2011, author = {Wang, Long}, title = {X-tracking the usage interest on web sites}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-51077}, school = {Universit{\"a}t Potsdam}, year = {2011}, abstract = {The exponential expanding of the numbers of web sites and Internet users makes WWW the most important global information resource. From information publishing and electronic commerce to entertainment and social networking, the Web allows an inexpensive and efficient access to the services provided by individuals and institutions. The basic units for distributing these services are the web sites scattered throughout the world. However, the extreme fragility of web services and content, the high competence between similar services supplied by different sites, and the wide geographic distributions of the web users drive the urgent requirement from the web managers to track and understand the usage interest of their web customers. This thesis, "X-tracking the Usage Interest on Web Sites", aims to fulfill this requirement. "X" stands two meanings: one is that the usage interest differs from various web sites, and the other is that usage interest is depicted from multi aspects: internal and external, structural and conceptual, objective and subjective. "Tracking" shows that our concentration is on locating and measuring the differences and changes among usage patterns. This thesis presents the methodologies on discovering usage interest on three kinds of web sites: the public information portal site, e-learning site that provides kinds of streaming lectures and social site that supplies the public discussions on IT issues. On different sites, we concentrate on different issues related with mining usage interest. The educational information portal sites were the first implementation scenarios on discovering usage patterns and optimizing the organization of web services. In such cases, the usage patterns are modeled as frequent page sets, navigation paths, navigation structures or graphs. However, a necessary requirement is to rebuild the individual behaviors from usage history. We give a systematic study on how to rebuild individual behaviors. Besides, this thesis shows a new strategy on building content clusters based on pair browsing retrieved from usage logs. The difference between such clusters and the original web structure displays the distance between the destinations from usage side and the expectations from design side. Moreover, we study the problem on tracking the changes of usage patterns in their life cycles. The changes are described from internal side integrating conceptual and structure features, and from external side for the physical features; and described from local side measuring the difference between two time spans, and global side showing the change tendency along the life cycle. A platform, Web-Cares, is developed to discover the usage interest, to measure the difference between usage interest and site expectation and to track the changes of usage patterns. E-learning site provides the teaching materials such as slides, recorded lecture videos and exercise sheets. We focus on discovering the learning interest on streaming lectures, such as real medias, mp4 and flash clips. Compared to the information portal site, the usage on streaming lectures encapsulates the variables such as viewing time and actions during learning processes. The learning interest is discovered in the form of answering 6 questions, which covers finding the relations between pieces of lectures and the preference among different forms of lectures. We prefer on detecting the changes of learning interest on the same course from different semesters. The differences on the content and structure between two courses leverage the changes on the learning interest. We give an algorithm on measuring the difference on learning interest integrated with similarity comparison between courses. A search engine, TASK-Moniminer, is created to help the teacher query the learning interest on their streaming lectures on tele-TASK site. Social site acts as an online community attracting web users to discuss the common topics and share their interesting information. Compared to the public information portal site and e-learning web site, the rich interactions among users and web content bring the wider range of content quality, on the other hand, provide more possibilities to express and model usage interest. We propose a framework on finding and recommending high reputation articles in a social site. We observed that the reputation is classified into global and local categories; the quality of the articles having high reputation is related with the content features. Based on these observations, our framework is implemented firstly by finding the articles having global or local reputation, and secondly clustering articles based on their content relations, and then the articles are selected and recommended from each cluster based on their reputation ranks.}, language = {en} } @phdthesis{Voelker2011, author = {V{\"o}lker, Jan}, title = {{\"A}sthetik der Lebendigkeit : Kants dritte Kritik}, publisher = {Fink}, address = {Paderborn}, isbn = {978-3-7705-5161-3}, pages = {274 S.}, year = {2011}, language = {de} } @phdthesis{Vapenka2011, author = {V{\´a}penka, Aleš}, title = {Geschlechterstereotype und Geschlechtsidentit{\"a}t von M{\"a}nnern mit unterschiedlichem Verlauf der psychosexuellen Entwicklung}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-53175}, school = {Universit{\"a}t Potsdam}, year = {2011}, abstract = {Im Rahmen eines explorativen Vergleichsuntersuchungsplans wurde untersucht, inwieweit sich die durch biologische Faktoren bedingte unterschiedliche Lebenserfahrung sowie die Sozialisationsbedingungen in der psychosexuellen Entwicklung bei hetero-, homo- und postoperativen transsexuellen M{\"a}nnern (N = 191) auf die Integration der Geschlechterstereotypen in die kognitiven (Selbst-, Fremdwahrnehmung), emotionalen (Selbst- und Fremdbewertung) und verhaltensm{\"a}ßigen Aspekte (Normen der geschlechtsspezifischen Verhaltens) der Geschlechtsidentit{\"a}t auswirken und ob sich Identifikationsmuster der Entwicklung des geschlechtlichen Selbstkonzepts ableiten lassen. Die Messung der kognitiven Aspekte des geschlechtlichen Selbstkonzepts (Maskulinit{\"a}t und Femininit{\"a}t) erfolgte mittels der GERO-Skala von Brengelmann und Hendrich (1990). Zur Erfassung der emotionalen Aspekte und Identifikationsmuster der Entwicklung des geschlechtlichen Selbstkonzepts wurden die Werte f{\"u}r die Variablen Maskulinit{\"a}t und Femininit{\"a}t zuerst mittels der computergesteuerten Methodik IDEXMONO und IDEXIDIO, die auf der Identit{\"a}tsstrukturanalyse (Identity Structure Analysis) von Weinreich (2003) basiert, aufgearbeitet und weiter interferenzstatistisch ausgewertet. Weiterhin wurden der Fragebogen zur Messung normativer Geschlechtsrollenorientierung (NGRO) von Athenstaedt (2000) sowie ein ad hoc entworfener demographischer Fragebogen eingesetzt. Die Ergebnisse zeigen, dass der Verlauf der psychosexuellen Entwicklung einen starken Einfluss auf die Integration der Geschlechterstereotypen in die geschlechtliche Selbst- und Fremdwahrnehmung hat. Im kognitiven Bereich, bezogen auf die pers{\"o}nliche Identit{\"a}t (Grad der Selbstzuschreibung m{\"a}nnlicher und weiblicher Merkmale), stellt die Maskulinit{\"a}t eine stabile und erstrebenswerte Variable zur Herausbildung des geschlechtlichen Selbstkonzepts bei allen Gruppen dar. Die Femininit{\"a}t tr{\"a}gt am meisten zur Differenzierung zwischen den Hetero-, Homo- und Transsexuellen bei. Sie wird, je nach der Entwicklungsphase, unterschiedlich in das geschlechtliche Selbstkonzept integriert. Hinsichtlich der sozialen Identit{\"a}t (Zugeh{\"o}rigkeitsgef{\"u}hl) lassen sich die Gruppen bez{\"u}glich der wahrgenommenen {\"A}hnlichkeiten sowohl mit m{\"a}nnlichen als auch weiblichen Personen, je nach der Entwicklungsphase, unterscheiden. Die soziale Wahrnehmung von M{\"a}nnern und Frauen (Fremdwahrnehmung), ist bei Transsexuellen traditioneller als die der Hetero- und Homosexuellen. Bei der Selbst- und Fremdbewertung ergaben sich keine signifikanten Unterschiede. Bei der Internalisierung der sozialen Normen des geschlechtsspezifischen Verhaltens zeigt sich, dass Heterosexuelle der Aus{\"u}bung der Geschlechterrollen gegen{\"u}ber egalit{\"a}rer eingestellt sind als Trans- und Homosexuelle. Bei den Sozialisationsfaktoren ist hervorzuheben, dass generell weibliche Identifikationspersonen einen st{\"a}rkeren Einfluss auf die Herausbildung des geschlechtlichen Selbstkonzeptes hatten als m{\"a}nnliche Identifikationspersonen. Es scheint jedoch, dass Homosexuelle bei der Entwicklung ihres geschlechtlichen Selbstkonzepts st{\"a}rker unter dem Einfluss der Frauen stehen als die anderen zwei erforschten Gruppen. Zur Beantwortung der Frage, welche selbstkonzeptbezogenen Variablen und Entwicklungsfaktoren die gr{\"o}ßte statistische Bedeutung f{\"u}r die Trennung und Pr{\"a}diktion der einzelnen untersuchten Gruppen haben, wurde eine Diskriminanzanalyse berechnet. Die gr{\"o}ßte diskriminatorische Bedeutung besitzen die Variablen „Stereotypische Wahrnehmung der m{\"a}nnlichen Personen" und „Ego-Involvement mit weiblichen Personen" f{\"u}r die Diskriminanzfunktion 1 (Trennung der Transsexuellen von Hetero- und Homosexuellen) und die Variablen „Empathische Identifikation mit m{\"a}nnlichen Personen in der Vergangenheit" und „Zuwachs an empathischer Identifikation mit weiblichen Personen" f{\"u}r die Diskriminanzfunktion 2 (Trennung der Hetero- von Homosexuellen).}, language = {de} } @phdthesis{Vukicevic2011, author = {Vukicevic, Radovan}, title = {Iodine- and azide-terminated poly(vinylidene fluoride) as a building block for the preparation of hybrid materials and block copolymers}, address = {Potsdam}, pages = {122 S.}, year = {2011}, language = {en} } @phdthesis{Vosloh2011, author = {Vosloh, Daniel}, title = {Subcellular compartmentation of primary carbon metabolism in mesophyll cells of Arabidopsis thaliana}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-55534}, school = {Universit{\"a}t Potsdam}, year = {2011}, abstract = {Metabolismus in Pflanzenzellen ist stark kompartimentiert. Viele Stoffwechselwege haben Reaktionen in mehr als einem Kompartiment. Zum Beispiel wird w{\"a}hrend der Photosynthese in pflanzlichen Mesophyllzellen Kohlenstoff in Form von St{\"a}rke in den Chloroplasten synthetisiert, w{\"a}hrend es im Zytosol in Form von Sacharose gebildet und in der Vakuole gespeichert wird. Diese Reaktionen sind strikt reguliert um ein Gleichgewicht der Kohlenstoffpools der verschiedenen Kompartimente aufrecht zu erhalten und die Energieversorgung aller Teile der Zelle f{\"u}r anabolische Reaktionen sicher zu stellen. Ich wende eine Methode an, bei der die Zellen unter nicht-w{\"a}ssrigen Bedingungen fraktioniert werden und daher der metabolische Status der w{\"a}hrend der Ernte herrschte {\"u}ber den ganzen Zeitraum der Auftrennung beibehalten wird. Durch die Kombination von nichtw{\"a}ssriger Fraktionierung und verschiedener Massenspektrometrietechniken (Fl{\"u}ssigchromotagraphie- und Gaschromotagraphie basierende Massenspekrometrie) ist es m{\"o}glich die intrazellul{\"a}re Verteilung der meisten Intermediate des photosynthetischen Kohlenstoffstoffwechsels und der Produkte der nachgelagerten metabolischen Reaktionen zu bestimmen. Das Wissen {\"u}ber die in vivo Konzentrationen dieser Metabolite wurde genutzt um die {\"A}nderung der freien Gibbs Energie in vivo zu bestimmen. Mit Hilfe dessen kann bestimmt werden, welche Reaktion sich in einem Gleichgewichtszustand befinden und welche davon entfernt sind. Die Konzentration der Enzyme und der Km Werte wurden mit den Konzentrationen der Metabolite in vivo verglichen, um festzustellen, welche Enzyme substratlimitiert sind und somit sensitiv gegen{\"u}ber {\"A}nderungen der Substratkonzentration sind. Verschiedene Intermediate des Calvin-Benson Zyklus sind gleichzeitig Substrate f{\"u}r andere Stoffwechselwege, als da w{\"a}ren Dihyroxyaceton-phosphat (DHAP, Saccharosesynthese), Fructose 6-phosphat (Fru6P, St{\"a}rkesynthese), Erythrose 4-phosphat (E4P, Shikimat Stoffwechselweg) und Ribose 5-phosphat (R5P, Nukleotidbiosynthese). Die Enzyme, die diese Intermediate verstoffwechseln, liegen an den Abzweigungspunkten zu diesen Stoffwechselwegen. Diese sind Trisose phosphat isomerase (DHAP), Transketolase (E4P), Sedoheptulose-1,7 biphosphat aldolase (E4P) und Ribose-5-phosphat isomerase (R5P), welche nicht mit ihren Substraten ges{\"a}ttigt sind, da die jeweilige Substratkonzentration geringer als der zugeh{\"o}rige Km Wert ist. F{\"u}r metabolische Kontrolle bedeutet dies, dass diese Schritte am sensitivsten gegen{\"u}ber {\"A}nderungen der Substratkonzentrationen sind. Im Gegensatz dazu sind die regulierten irreversiblen Schritte von Fructose-1,6.biphosphatase und Sedoheptulose-1,7-biphosphatase relativ insensitiv gegen{\"u}ber {\"A}nderungen der Substratkonzentration. F{\"u}r den Stoffwechselweg der Saccharosesynthese konnte gezeigt werden, dass die zytosolische Aldolase eine geringer Bindeseitenkonzentration als Substratkonzentration (DHAP) aufweist, und dass die Konzentration von Saccharose-6-phosphat geringer als der Km Wert des synthetisierenden Enzyms Saccharose-phosphatase ist. Sowohl die Saccharose-phosphat-synthase, also auch die Saccharose-phosphatase sind in vivo weit von einem Gleichgewichtszustand entfernt. In Wildtyp Arabidopsis thaliana Columbia-0 Bl{\"a}ttern wurde der gesamte Pool von ADPGlc im Chloroplasten gefunden. Das Enzyme ADPGlc pyrophosphorylase ist im Chloroplasten lokalisiert und synthetisiert ADPGlc aus ATP und Glc1P. Dieses Verteilungsmuster spricht eindeutig gegen die Hypothese von Pozueta-Romero und Kollegen, dass ADPGlc im Zytosol durch ADP vermittelte Spaltung von Saccharose durch die Saccharose Synthase erzeugt wird. Basierend auf dieser Beobachtung und anderen ver{\"o}ffentlichten Ergebnissen wurde geschlußfolgert, dass der generell akzeptierte Stoffwechselweg der St{\"a}rkesynthese durch ADPGlc Produktion via ADPGlc pyrophosphorylase in den Chloroplasten korrekt ist, und die Hypothese des alternativen Stoffwechselweges unhaltbar ist. Innerhalb des Stoffwechselweges der Saccharosesynthsese wurde festgestellt, dass die Konzentration von ADPGlc geringer als der Km Wert des St{\"a}rkesynthase ist, was darauf hindeutet, dass das Enzym substratlimitiert ist. Eine generelle Beobachtung ist, dass viele Enzmye des Calvin-Benson Zyklus {\"a}hnliche Bindeseitenkonzentrationen wie Metabolitkonzentrationen aufweisen, wohingegen in den Synthesewegen von Saccharose und St{\"a}rke die Bindeseitenkonzentrationen der Enzyme viel geringer als die Metabolitkonzentrationen sind.}, language = {en} } @phdthesis{vonNicolai2011, author = {von Nicolai, Christina}, title = {The interplay of salt movements and regional tectonics at the passive continental margin of the South Atlantic, Kwanza Basin}, address = {Potsdam}, pages = {134 S.}, year = {2011}, language = {en} } @phdthesis{ValverdeSerrano2011, author = {Valverde Serrano, Clara}, title = {Self-assembly behavior in hydrophilic block copolymers}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-54163}, school = {Universit{\"a}t Potsdam}, year = {2011}, abstract = {Block copolymers are receiving increasing attention in the literature. Reports on amphiphilic block copolymers have now established the basis of their self-assembly behavior: aggregate sizes, morphologies and stability can be explained from the absolute and relative block lengths, the nature of the blocks, the architecture and also solvent selectiveness. In water, self-assembly of amphiphilic block copolymers is assumed to be driven by the hydrophobic. The motivation of this thesis is to study the influence on the self-assembly in water of A b B type block copolymers (with A hydrophilic) of the variation of the hydrophilicity of B from non-soluble (hydrophobic) to totally soluble (hydrophilic). Glucose-modified polybutadiene-block-poly(N-isopropylacrylamide) copolymers were prepared and their self-assembly behavior in water studied. The copolymers formed vesicles with an asymmetric membrane with a glycosylated exterior and poly(N-isopropylacrylamide) on the inside. Above the low critical solution temperature (LCST) of poly(N-isopropylacrylamide), the structure collapsed into micelles with a hydrophobic PNIPAM core and glycosylated exterior. This collapse was found to be reversible. As a result, the structures showed a temperature-dependent interaction with L-lectin proteins and were shown to be able to encapsulate organic molecules. Several families of double hydrophilic block copolymers (DHBC) were prepared. The blocks of these copolymers were biopolymers or polymer chimeras used in aqueous two-phase partition systems. Copolymers based on dextran and poly(ethylene glycol) blocks were able to form aggregates in water. Dex6500-b-PEG5500 copolymer spontaneously formed vesicles with PEG as the "less hydrophilic" barrier and dextran as the solubilizing block. The aggregates were found to be insensitive to the polymer's architecture and concentration (in the dilute range) and only mildly sensitive to temperature. Variation of the block length, yielded different morphologies. A longer PEG chain seemed to promote more curved aggregates following the inverse trend usually observed in amphiphilic block copolymers. A shorter dextran promoted vesicular structures as usually observed for the amphiphilic counterparts. The linking function was shown to have an influence of the morphology but not on the self-assembly capability in itself. The vesicles formed by dex6500-b-PEG5500 showed slow kinetics of clustering in the presence of Con A lectin. In addition both dex6500-b-PEG5500 and its crosslinked derivative were able to encapsulate fluorescent dyes. Two additional dextran-based copolymers were synthesized, dextran-b-poly(vinyl alcohol) and dextran-b-poly(vinyl pyrrolidone). The study of their self-assembly allowed to conclude that aqueous two-phase systems (ATPS) is a valid source of inspiration to conceive DHBCs capable of self-assembling. In the second part the principle was extended to polypeptide systems with the synthesis of a poly(N-hydroxyethylglutamine)-block-poly(ethylene glycol) copolymer. The copolymer that had been previously reported to have emulsifying properties was able to form vesicles by direct dissolution of the solid in water. Last, a series of thermoresponsive copolymers were prepared, dextran-b-PNIPAMm. These polymers formed aggregates below the LCST. Their structure could not be unambiguously elucidated but seemed to correspond to vesicles. Above the LCST, the collapse of the PNIPAM chains induced the formation of stable objects of several hundreds of nanometers in radius that evolved with increasing temperature. The cooling of these solution below LCST restored the initial aggregates. This self-assembly of DHBC outside any stimuli of pH, ionic strength, or temperature has only rarely been described in the literature. This work constituted the first formal attempt to frame the phenomenon. Two reasons were accounted for the self-assembly of such systems: incompatibility of the polymer pairs forming the two blocks (enthalpic) and a considerable solubility difference (enthalpic and entropic). The entropic contribution to the positive Gibbs free energy of mixing is believed to arise from the same loss of conformational entropy that is responsible for "the hydrophobic effect" but driven by a competition for water of the two blocks. In that sense this phenomenon should be described as the "hydrophilic effect".}, language = {en} } @phdthesis{Urieta2011, author = {Urieta, Kristin}, title = {Kinder in schwierigen {\"U}bergangssituationen vom Elementar- zum Prim{\"a}rbereich : eine biografieanalytische Studie}, publisher = {Curach Bh{\´a}n Publ}, address = {Berlin}, isbn = {978-3-942002-01-1}, pages = {235 S.}, year = {2011}, language = {de} } @phdthesis{Unterlass2011, author = {Unterlass, Miriam Margarethe}, title = {From monomer salts and their tectonic crystals to aromatic polyimides : development of neoteric synthesis routes}, address = {Potsdam}, pages = {147 S.}, year = {2011}, language = {en} } @phdthesis{Ulrich2011, author = {Ulrich, Mathias}, title = {Permafrost landform studies on Earth : Implications for periglacial landscape evolution and habitability on Mars}, address = {Potsdam}, pages = {VIII, 160 S.}, year = {2011}, language = {en} } @phdthesis{Taeger2011, author = {T{\"a}ger, Philipp}, title = {Der Schutz von Menschenrechten im internationalen Investionsrecht : unter besondere Beachtung der Rechte und Pflichten des Exportstaates}, series = {Studien zum internationalen Wirtschaftsrecht}, volume = {4}, journal = {Studien zum internationalen Wirtschaftsrecht}, publisher = {Nomos}, address = {Baden-Baden}, isbn = {978-3-8329-6731-4}, pages = {356 S.}, year = {2011}, language = {de} } @phdthesis{Tischer2011, author = {Tischer, Markus}, title = {Effizienzmessung im Sparkassensektor am Beispiel regionaler Cluster}, series = {Schriftenreihe Finanzierung und Banken}, volume = {18}, journal = {Schriftenreihe Finanzierung und Banken}, publisher = {Verl. Wiss. \& Praxis}, address = {Sternenfels}, isbn = {978-3-89673-601-7}, pages = {250 S.}, year = {2011}, language = {de} } @phdthesis{Tiller2011, author = {Tiller, Nadine}, title = {Plastid translation : functions of plastid-specific ribosomal proteins and identification of a factor mediating plastid-to-nucleus retrograde sifnalling}, address = {Potsdam}, pages = {122 S.}, year = {2011}, language = {en} } @phdthesis{Thiele2011, author = {Thiele, Sven}, title = {Modeling biological systems with Answer Set Programming}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-59383}, school = {Universit{\"a}t Potsdam}, year = {2011}, abstract = {Biology has made great progress in identifying and measuring the building blocks of life. The availability of high-throughput methods in molecular biology has dramatically accelerated the growth of biological knowledge for various organisms. The advancements in genomic, proteomic and metabolomic technologies allow for constructing complex models of biological systems. An increasing number of biological repositories is available on the web, incorporating thousands of biochemical reactions and genetic regulations. Systems Biology is a recent research trend in life science, which fosters a systemic view on biology. In Systems Biology one is interested in integrating the knowledge from all these different sources into models that capture the interaction of these entities. By studying these models one wants to understand the emerging properties of the whole system, such as robustness. However, both measurements as well as biological networks are prone to considerable incompleteness, heterogeneity and mutual inconsistency, which makes it highly non-trivial to draw biologically meaningful conclusions in an automated way. Therefore, we want to promote Answer Set Programming (ASP) as a tool for discrete modeling in Systems Biology. ASP is a declarative problem solving paradigm, in which a problem is encoded as a logic program such that its answer sets represent solutions to the problem. ASP has intrinsic features to cope with incompleteness, offers a rich modeling language and highly efficient solving technology. We present ASP solutions, for the analysis of genetic regulatory networks, determining consistency with observed measurements and identifying minimal causes for inconsistency. We extend this approach for computing minimal repairs on model and data that restore consistency. This method allows for predicting unobserved data even in case of inconsistency. Further, we present an ASP approach to metabolic network expansion. This approach exploits the easy characterization of reachability in ASP and its various reasoning methods, to explore the biosynthetic capabilities of metabolic reaction networks and generate hypotheses for extending the network. Finally, we present the BioASP library, a Python library which encapsulates our ASP solutions into the imperative programming paradigm. The library allows for an easy integration of ASP solution into system rich environments, as they exist in Systems Biology.}, language = {en} } @phdthesis{Thiele2011, author = {Thiele, Jan}, title = {Auslandseins{\"a}tze der Bundeswehr zur Bek{\"a}mpfung des internationalen Terrorismus : V{\"o}lker- und verfassungsrechtliche Aspekte}, series = {Studien zum {\"o}ffentlichen Recht, V{\"o}lker- und Europarecht}, volume = {20}, journal = {Studien zum {\"o}ffentlichen Recht, V{\"o}lker- und Europarecht}, publisher = {Lang}, address = {Frankfurt am Main}, isbn = {978-3-631-60597-4}, issn = {1437-2037}, pages = {393 S.}, year = {2011}, language = {de} } @phdthesis{tenBrummelhuis2011, author = {ten Brummelhuis, Niels}, title = {Self-assembly of cross-linked polymer micelles into complex higher-order aggregates}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-52320}, school = {Universit{\"a}t Potsdam}, year = {2011}, abstract = {The creation of complex polymer structures has been one of the major research topics over the last couple of decades. This work deals with the synthesis of (block co-)polymers, the creation of complex and stimuli-responsive aggregates by self-assembly, and the cross-linking of these structures. Also the higher-order self-assembly of the aggregates is investigated. The formation of poly-2-oxazoline based micelles in aqueous solution and their simultaneous functionalization and cross-linking using thiol-yne chemistry is e.g. presented. By introducing pH responsive thiols in the core of the micelles the influence of charged groups in the core of micelles on the entire structure can be studied. The charging of these groups leads to a swelling of the core and a decrease in the local concentration of the corona forming block (poly(2-ethyl-2-oxazoline)). This decrease in concentration yields a shift in the cloud point temperature to higher temperatures for this Type I thermoresponsive polymer. When the swelling of the core is prohibited, e.g. by the introduction of sufficient amounts of salt, this behavior disappears. Similar structures can be prepared using complex coacervate core micelles (C3Ms) built through the interaction of weakly acidic and basic polymer blocks. The advantage of these structures is that two different stabilizing blocks can be incorporated, which allows for more diverse and complex structures and behavior of the micelles. Using block copolymers with either a polyanionic or a polycationic block C3Ms could be created with a corona which contains two different soluble nonionic polymers, which either have a mixed corona or a Janus type corona, depending on the polymers that were chosen. Using NHS and EDC the micelles could easily be cross-linked by the formation of amide bonds in the core of the micelles. The higher-order self-assembly behavior of these core cross-linked complex coacervate core micelles (C5Ms) was studied. Due to the cross-linking the micelles are stabilized towards changes in pH and ionic strength, but polymer chains are also no longer able to rearrange. For C5Ms with a mixed corona likely network structures were formed upon the collapse of the thermoresponsive poly(N-isopropylacrylamide) (PNIPAAm), whereas for Janus type C5Ms well defined spherical aggregates of micelles could be obtained, depending on the pH of the solution. Furthermore it could be shown that Janus micelles can adsorb onto inorganic nanoparticles such as colloidal silica (through a selective interaction between PEO and the silica surface) or gold nanoparticles (by the binding of thiol end-groups). Asymmetric aggregates were also formed using the streptavidin-biotin binding motive. This is achieved by using three out of the four binding sites of streptavidin for the binding of one three-arm star polymer, end-functionalized with biotin groups. A homopolymer with one biotin end-group can be used to occupy the last position. This binding of two different polymers makes it possible to create asymmetric complexes. This phase separation is theoretically independent of the kind of polymer since the structure of the protein is the driving force, not the intrinsic phase separation between polymers. Besides Janus structures also specific cross-linking can be achieved by using other mixing ratios.}, language = {en} } @phdthesis{Tan2011, author = {Tan, Irene}, title = {Towards greener stationary phases : thermoresponsive and carbonaceous chromatographic supports}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-53130}, school = {Universit{\"a}t Potsdam}, year = {2011}, abstract = {Polymers which are sensitive towards external physical, chemical and electrical stimuli are termed as 'intelligent materials' and are widely used in medical and engineering applications. Presently, polymers which can undergo a physical change when heat is applied at a certain temperature (cloud point) in water are well-studied for this property in areas of separation chemistry, gene and drug delivery and as surface modifiers. One example of such a polymer is the poly (N-isopropylacrylamide) PNIPAAM, where it is dissolved well in water below 32 oC, while by increasing the temperature further leads to its precipitation. In this work, an alternative polymer poly (2-(2-methoxy ethoxy)ethyl methacrylate-co- oligo(ethylene glycol) methacrylate) (P(MEO2MA-co-OEGMA)) is studied due to its biocompatibility and the ability to vary its cloud points in water. When a layer of temperature responsive polymer was attached to a single continuous porous piece of silica-based material known as a monolith, the thermoresponsive characteristic was transferred to the column surfaces. The hybrid material was demonstrated to act as a simple temperature 'switch' in the separation of a mixture of five steroids under water. Different analytes were observed to be separated under varying column temperatures. Furthermore, more complex biochemical compounds such as proteins were also tested for separation. The importance of this work is attributed to separation processes utilizing environmentally friendly conditions, since harsh chemical environments conventionally used to resolve biocompounds could cause their biological activities to be rendered inactive.}, language = {en} } @phdthesis{Szecowka2011, author = {Szec{\´o}wka, Marek}, title = {Metabolic fluxes in photosynthetic and heterotrophic plant tissues}, address = {Potsdam}, pages = {XII, 145 S.}, year = {2011}, language = {en} } @phdthesis{Sun2011, author = {Sun, Xiaoliang}, title = {Towards understanding the dynamics of biological systems from -Omics data}, address = {Potsdam}, pages = {114 S.}, year = {2011}, language = {en} } @phdthesis{Stoyanov2011, author = {Stoyanov, Hristiyan}, title = {Soft nanocomposites with enhanced electromechanical response for dielectric elastomer actuators}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-51194}, school = {Universit{\"a}t Potsdam}, year = {2011}, abstract = {Electromechanical transducers based on elastomer capacitors are presently considered for many soft actuation applications, due to their large reversible deformation in response to electric field induced electrostatic pressure. The high operating voltage of such devices is currently a large drawback, hindering their use in applications such as biomedical devices and biomimetic robots, however, they could be improved with a careful design of their material properties. The main targets for improving their properties are increasing the relative permittivity of the active material, while maintaining high electric breakdown strength and low stiffness, which would lead to enhanced electrostatic storage ability and hence, reduced operating voltage. Improvement of the functional properties is possible through the use of nanocomposites. These exploit the high surface-to-volume ratio of the nanoscale filler, resulting in large effects on macroscale properties. This thesis explores several strategies for nanomaterials design. The resulting nanocomposites are fully characterized with respect to their electrical and mechanical properties, by use of dielectric spectroscopy, tensile mechanical analysis, and electric breakdown tests. First, nanocomposites consisting of high permittivity rutile TiO2 nanoparticles dispersed in thermoplastic block copolymer SEBS (poly-styrene-coethylene-co-butylene-co-styrene) are shown to exhibit permittivity increases of up to 3.7 times, leading to 5.6 times improvement in electrostatic energy density, but with a trade-off in mechanical properties (an 8-fold increase in stiffness). The variation in both electrical and mechanical properties still allows for electromechanical improvement, such that a 27 \% reduction of the electric field is found compared to the pure elastomer. Second, it is shown that the use of nanofiller conductive particles (carbon black (CB)) can lead to a strong increase of relative permittivity through percolation, however, with detrimental side effects. These are due to localized enhancement of the electric field within the composite, which leads to sharp reductions in electric field strength. Hence, the increase in permittivity does not make up for the reduction in breakdown strength in relation to stored electrical energy, which may prohibit their practical use. Third, a completely new approach for increasing the relative permittivity and electrostatic energy density of a polymer based on 'molecular composites' is presented, relying on chemically grafting soft π-conjugated macromolecules to a flexible elastomer backbone. Polarization caused by charge displacement along the conjugated backbone is found to induce a large and controlled permittivity enhancement (470 \% over the elastomer matrix), while chemical bonding, encapsulates the PANI chains manifesting in hardly any reduction in electric breakdown strength, and hence resulting in a large increase in stored electrostatic energy. This is shown to lead to an improvement in the sensitivity of the measured electromechanical response (83 \% reduction of the driving electric field) as well as in the maximum actuation strain (250 \%). These results represent a large step forward in the understanding of the strategies which can be employed to obtain high permittivity polymer materials with practical use for electro-elastomer actuation.}, language = {en} }