The interactions between cholesterol and other membrane molecules determine important membrane properties. It was shown that even small changes in the molecular structure of cholesterol have a crucial influence on these interactions. We recently reported that in addition to alterations in the tetracyclic ring structure, the iso-branched side chain of cholesterol also has a significant impact on membrane properties (Scheidt H. et al. 2013 Angew. Chem. Int. Ed. Engl. 52, 12848-12851). Here we used synthetic cholesterol analogs to investigate the influence of an unbranched aliphatic side chain of different length. The 2H NMR order parameter of the phospholipid chains and therefore the molecular packing of the phospholipid molecules shows a significant dependence on the sterol’s alkyl side chain length, while , membrane permeation studied by a dithionite ion permeation assay and lateral diffusion measured by 1H MAS pulsed field gradient NMR are less influenced. To achieve the same molecular packing effect similar to that of an iso-branched aliphatic side chain, a longer unbranched side chain (n-dodecyl instead of n-octyl) at C17 of cholesterol is required. Obviously, sterols having a branched iso- alkyl chain with two terminal methyl groups exhibit altered cholesterol-phospholipid-interactions compared to analogous molecules with a straight unbranched chain.

Sewage exfiltration from a sanitary and combined sewer systems and its percolation into porous medium results in a clogged or colmation layer in the nearby soil. In order to develop a comprehensive understanding of raw sewage transport mechanisms in porous media, investigations were carried out on the micro-scale properties of the multiphase system. In our laboratory experiments, the role of surfactants as a major organic chemical compound in wastewater was evaluated by using a surfactant solution as an artificial wastewater percolating into a porous media, represented by using columns and Plexiglas model. We studied flows of water and surfactants solution in saturated porous medium to detect the dynamic effects by means of measuring pressure and permeability as well as by visualization of flow regions and consequence for porosity along interfaces between water and surfactants solution. The tests revealed that mechanisms at interfaces between fluids and solids as well as between water and surfactants solution (i.e. wastewater) are significantly influencing the flow behavior. At the interfaces surfactant molecules are adsorbed or accumulate, respectively, and subsequently inducing electrical charges to those layers, altering the properties of fluids and these interfaces. Depending on the conditions, channels might be narrowed and thus decreasing the flow rate with a later erosion and increase of flow rates, or the flow and thus the erosive capacity might become intensified along the interface between surfactants solution and neighbouring water. In conclusion, the results of tests proved the surfactants to be an important controlling factor in the hydraulic properties of wastewater percolating into soil.

Die Dissertation analysiert die Auswirkungen der internationalen Diskussion zum lebenslangen Lernen als bildungspolitischem Reformkonzept auf die institutionelle Ausgestaltung des deutschen Hochschulwesens. Sie besteht aus einem einleitenden Kapitel und 14 Teilstudien, die zusammen eine multiperspektivische Fallstudie bilden. Über bereits vorliegende Bestandsaufnahmen geht die vorliegende Untersuchung durch ihre Multi¬perspektivität sowie die historische, theoretische und international ver¬gleichende Einordnung der Befunde hinaus. Die theoretische Basis bilden Konzepte zur Entstehung und zum Wandel von Institutionen. Hierbei kommt der Perspektive des Historischen Institutionalismus eine besondere Bedeutung zu. In den Teilstudien werden vier Dimensionen von Durchlässigkeit behandelt, die sich aus den im internationalen Rahmen diskutierten Reformkonzepten ergeben: (1.) die soziale Durchlässigkeit im Sinne der Beteiligung von unterrepräsentierten Personengruppen an hochschulischer Bildung, (2.) die institutionelle Durchlässigkeit zwischen den Systemen der beruflichen und der akademischen Bildung, (3.) die Realisierung eines Arbeitswelt- bzw. Praxisbezugs durch flankierende curriculare und/oder didaktische Initiativen sowie (4.) eine flexible Studienorganisation, die aus – ebenfalls flankierenden – organisatorischen Maßnahmen resultiert. Insgesamt konnte gezeigt werden, dass die seit den 1960er Jahren andauernde inter-nationale Diskussion um lebenslanges Lernen in Deutschland auf eine geringe Resonanz gestoßen ist. Dies gilt insbesondere für den Hochschulbereich. Seit einigen Jahren ist in Politik und Hochschulen jedoch ein Umdenken festzustellen, das seinen Ausdruck unter anderem in Veränderungen bei den Zugangsmöglichkeiten zum Hochschul¬studium gefunden hat. Die (potenziellen) Auswirkungen der aktuellen Entwicklungen auf die künftige institutionelle Ausgestaltung des deutschen Hochschulwesens sind allerdings kaum abzuschätzen. / This dissertation deals with the international discussion on lifelong learning as a political concept to reform the education system and analyses its impact on the institutional structure of the German higher education system. This doctoral thesis by publication is composed of an introductory chapter and 14 substudies providing an in-depth examination of various aspects applying various methods. The diverse parts form a multiperspectival case study. The present study exceeds existing research not only by its multitude of perspectives, but also by explaining the results from a historical, theoretical and internationally comparative point of view. Concepts concerning the emergence and change of institutions make up the theoretical basis of the thesis at hand. Special emphasis is put on the theoretical approach of historical institutionalism. The substudies focus on four dimensions of permeability emerging from international discussions about lifelong learning: (1.) social mobility of underrepresented groups with regard to the higher education system, (2.) institutional permeability between the systems of vocational education and higher education, (3.) implementation of requirements of the world of work and society in curricular and didactical concepts, and (4.) a flexible organisation of study programs resulting from organisational and operative measures. The present study concludes that the ideas of lifelong learning, which have been under discussion on an international level since the late 1960s, have only met with little response in Germany. This holds particularly true for the higher education system. However, a change of thinking in politics and higher education institutions has been noticeable in recent years. This has led to changes, among others, in the way of admission to study programs. (Potential) impacts of recent developments on the future institutional structure of the German higher education system can hardly be predicted at the present time.

The interactions between cholesterol and other membrane molecules determine important membrane properties. It was shown that even small changes in the molecular structure of cholesterol have a crucial influence on these interactions. We recently reported that in addition to alterations in the tetracyclic ring structure, the iso-branched side chain of cholesterol also has a significant impact on membrane properties (Scheidt H. et al. 2013 Angew. Chem. Int. Ed. Engl. 52, 12848-12851). Here we used synthetic cholesterol analogs to investigate the influence of an unbranched aliphatic side chain of different length. The 2H NMR order parameter of the phospholipid chains and therefore the molecular packing of the phospholipid molecules shows a significant dependence on the sterol’s alkyl side chain length, while , membrane permeation studied by a dithionite ion permeation assay and lateral diffusion measured by 1H MAS pulsed field gradient NMR are less influenced. To achieve the same molecular packing effect similar to that of an iso-branched aliphatic side chain, a longer unbranched side chain (n-dodecyl instead of n-octyl) at C17 of cholesterol is required. Obviously, sterols having a branched iso- alkyl chain with two terminal methyl groups exhibit altered cholesterol-phospholipid-interactions compared to analogous molecules with a straight unbranched chain.

Sewage exfiltration from a sanitary and combined sewer systems and its percolation into porous medium results in a clogged or colmation layer in the nearby soil. In order to develop a comprehensive understanding of raw sewage transport mechanisms in porous media, investigations were carried out on the micro-scale properties of the multiphase system. In our laboratory experiments, the role of surfactants as a major organic chemical compound in wastewater was evaluated by using a surfactant solution as an artificial wastewater percolating into a porous media, represented by using columns and Plexiglas model. We studied flows of water and surfactants solution in saturated porous medium to detect the dynamic effects by means of measuring pressure and permeability as well as by visualization of flow regions and consequence for porosity along interfaces between water and surfactants solution. The tests revealed that mechanisms at interfaces between fluids and solids as well as between water and surfactants solution (i.e. wastewater) are significantly influencing the flow behavior. At the interfaces surfactant molecules are adsorbed or accumulate, respectively, and subsequently inducing electrical charges to those layers, altering the properties of fluids and these interfaces. Depending on the conditions, channels might be narrowed and thus decreasing the flow rate with a later erosion and increase of flow rates, or the flow and thus the erosive capacity might become intensified along the interface between surfactants solution and neighbouring water. In conclusion, the results of tests proved the surfactants to be an important controlling factor in the hydraulic properties of wastewater percolating into soil.