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Im Rahmen der Bachelorarbeit wurden verschiedene Messungen am CH-Modell des Protonen - Linearbeschleunigers für FAIR durchgeführt.
Zu Beginn wurde die Wirkung der Tuner auf das elektrische Feld im Resonator und die Frequenz untersucht. Aus den systematischen Messungen konnte man feststellen, wie die Tuner das elektrische Feld beeinflussen. Außerdem konnte man sehen, dass die Tuner zu einer Erhöhung der Frequenz führen, was auch durch den theoretischen Hintergrund erwartet wurde. Aus den so gewonnenen Erkenntnissen konnte nun versucht werden, die Spaltspannungen an eine Vorgabe aus LORASR anzupassen. Dies nahm den Hauptteil der Bachelorarbeit ein. Die Anpassung konnte durch Variation der Tuner und der Spaltlängen erreicht werden. Die Abweichungen zur LORASR - Vorgabe lagen alle, bis auf einen Wert, im vorgegebenen Bereich. Allerdings waren die Messungen nicht perfekt reproduzierbar, da es bei der Störkörpermessung zu Fehlern kam. Der Motor, der den Störkörper durch die CH-Struktur ziehen sollte, war in diesem Zeitraum defekt, wodurch sich die gemessenen Spaltspannungen etwas veränderten.
Weiterhin wurde noch eine Sensibilitätsuntersuchung bei Erwärmung des Niederenergieteils des Resonators und eine Modenuntersuchung durchgeführt.
Durch die Erwärmung des Niederenergieteils konnte man sehen, dass das Feld im Inneren des Resonators auf Temperaturunterschiede reagiert. Dies hat aber keinen Einfluss auf die Betriebsfähigkeit des Resonators, da die zu erwartenden Einflüsse auf den Resonator im Betrieb sehr gering sind. Die Modenuntersuchung hat die vorherigen Annahmen bestätigt. Die Hochfrequenzleistung wird über die Linse hinweg störungsfrei weitergegeben und die ersten 4 Moden schwingen alle in dem Modell an und sind messbar, wenn man außen in den Tanks einkoppelt.
The Dagstuhl Perspectives Workshop "Online Privacy: Towards Informational Self-Determination on the Internet" (11061) has been held in February 6-11, 2011 at Schloss Dagstuhl. 30 participants from academia, public sector, and industry have identified the current status-of-the-art of and challenges for online privacy as well as derived recommendations for improving online privacy. Whereas the Dagstuhl Manifesto of this workshop concludes the results of the working groups and panel discussions, this article presents the talks of this workshop by their abstracts.
Stem cells are often referred to as potential candidates for the treatment of different pathologies. Their ability to differentiate into various tissue specific cell types offers the possibility to engineer cell systems or organs for replacement. One of the main questions in stem cell biology is how stemness properties are regulated and to what extend this regulation is intrinsic or conveyed by the direct microenvironment (‘niche’). In order to elucidate such regulatory processes, it is informative to analyze processes or molecules that are shared between different stem cell populations.
One such molecule that is expressed on a wide range of different embryonic and adult as well as tumor stem cells is the ABC transporter Abcg2. ABC transporters in general are transmembrane proteins that actively extrude endo- and exotoxins as well as xenobiotics, thereby protecting cells and organs. Additionally, ABC transporters are responsible for drug resistance in many cancers. A well-described characteristic of stem cells expressing Abcg2 is the formation of the ‘side population’ (SP) phenotype: An active Abcg2 transporter mediates the efflux of a particular fluorescent dye that is taken up by all cells, thus leading to a less brightly stained population. This phenomenon is widely used to characterize and isolate the most primitive stem cell subpopulation from embryonic and adult tissues, including tumors. Besides its role as toxin transporter little is known about the function of Abcg2 in stem cells. This is mainly due to the fact that its physiological substrate in stem cells remains unknown. The identification of such substrates is therefore of high interest because it would directly link the activity of ABC transporters to regulatory mechanisms in stem cell biology.
In the present study we wanted to test the hypothesis that the sphingolipid ceramide is a physiological substrate of the ABC transporter Abcg2. Sphingolipids are potent second messengers and are known to have regulatory functions in stem cells. In particular, the sphingolipid ceramide is described as a mediator of controlled cell death and inducer of differentiation. It is suggested that stem cells need to keep their intracellular ceramide content at low levels in order to prevent apoptosis or differentiation. We propose that Abcg2 and ceramide interact and that this interaction leads to changes in the absolute or relative amounts of ceramide. This in turn influences basic stem cell functions such as self renewal and differentiation.
We show that Abcg2 prevents cells from accumulating fluorescence labeled ceramide. Furthermore, exogenously applied ceramides inhibit the transport activity of Abcg2, measured by a decrease of the side population phenotype. This inhibitory effect is consistent with a competitive inhibition mechanism. Additionally, we show that active Abcg2 can increase the ceramide concentration in cell culture supernatant. Finally we demonstrate that Abcg2 protects from ceramide induced cytotoxicity in human cell lines. In summary, these in vitro results strongly suggest that Abcg2 has the ability to regulate ceramide levels.
Murine hematopoietic stem cells (HSCs) are the best characterized adult stem cell system so far. By using 7-colour fluorescence-activated cell sorting (FACS) we established the purification of the most primitive HSCs, reflected by their high engraftment capability when transplanted to lethally irradiated mice. By using this sorted cell populations it was in addition possible to establish a system to reproducibly manipulate HSCs ex vivo. This experimental system will serve in further elucidating the physiological consequences of Abcg2 mediated changes in ceramide levels on stem cells in vivo.
Taken together, this study shows that Abcg2 has the ability to regulate ceramide levels in cells. This in turn can lead to cellular protection from ceramide induced apoptosis. Additionally, the experimental techniques to further analyze the role of Abcg2 and ceramide in the most primitive hematopoietic stem cells were successfully established, enabling more detailed analysis in the future.
TRADITIONALLY, THE COST OF DEBT IS SOLELY SEEN DEPENDENT ON FIRM OR DEBT CHARACTERISTICS. HOWEVER, INCREASED PRICE TRANSPARENCY AS CAN BE FOUND IN THE U.S. CORPORATE BOND MARKET HAS REDUCED CORPORATE BOND YIELDS. THE OBJECTIVE OF THIS WORK IS TO MEASURE THE SPILL-OVER EFFECT OF INCREASED PRICE TRANSPARENCY IN CORPORATE BONDS ON THE COST OF CORPORATE BORROWING OF SYNDICATED LOANS BY MAKING USE OF A NATURAL EXPERIMENT, I.E., THE INTRODUCTION OF THE TRACE SYSTEM FOR BONDS.
Mountains, with their isolated position and altitudinal belts, are hotspots of biodiversity. Their flora and fauna have been observed worldwide since the days of Alexander von Humboldt, which has led to basic knowledge and understanding of species composition and the most important driving forces of ecosystem differentiation in such altitudinal gradients. Systematically designed analyses of changes in species composition with increasing elevation have been increasingly implemented since the 1990s. Since global climate change is one of the most important problems facing the world this century, a focus on such ecosystem studies is urgently needed. To identify the main future needs of such research we analyze the studies dealing with species changes of diverse taxonomical groups along altitudinal gradients (0 to 6,400 m a.s. l.) on all continents, published during the past one to two decades. From our study we can conclude that although mountains are powerful for climate change research most studies have to face the challenge of separating confounding effects driving species assemblages along altitudinal gradients. Our study therefore supports the view of the need of a global altitudinal concept including that (1) not only one or a few taxonomical groups should be analyzed, but rather different taxonomical groups covering all ecosystem functions simultaneously; (2) relevant site conditions should be registered to reveal direct environmental variables responsible for species distribution patterns and to resolve inconsistent effects along the altitudinal gradients; (3) transect design is appropriate for analyzing ecosystem changes in site gradients and over time; (4) both the study design and the individual methods should be standardized to compare the data collected worldwide; and (5) a long-term perspective is important to quantify the degree and direction of species changes and to validate species distribution models. (6) Finally we suggest to develop experimental altitudinal approaches to overcome the addressed problems of biodiversity surveys.
Neanderthal diets are reported to be based mainly on the consumption of large and medium sized herbivores, while the exploitation of other food types including plants has also been demonstrated. Though some studies conclude that early Homo sapiens were active hunters, the analyses of faunal assemblages, stone tool technologies and stable isotopic studies indicate that they exploited broader dietary resources than Neanderthals. Whereas previous studies assume taxon-specific dietary specializations, we suggest here that the diet of both Neanderthals and early Homo sapiens is determined by ecological conditions. We analyzed molar wear patterns using occlusal fingerprint analysis derived from optical 3D topometry. Molar macrowear accumulates during the lifespan of an individual and thus reflects diet over long periods. Neanderthal and early Homo sapiens maxillary molar macrowear indicates strong eco-geographic dietary variation independent of taxonomic affinities. Based on comparisons with modern hunter-gatherer populations with known diets, Neanderthals as well as early Homo sapiens show high dietary variability in Mediterranean evergreen habitats but a more restricted diet in upper latitude steppe/coniferous forest environments, suggesting a significant consumption of high protein meat resources.
If there is one thing to be learned from David Foster Wallace, it is that cultural transmission is a tricky game. This was a problem Wallace confronted as a literary professional, a university-based writer during what Mark McGurl has called the Program Era. But it was also a philosophical issue he grappled with on a deep level as he struggled to combat his own loneliness through writing. This fundamental concern with literature as a social, collaborative enterprise has also gained some popularity among scholars of contemporary American literature, particularly McGurl and James English: both critics explore the rules by which prestige or cultural distinction is awarded to authors (English; McGurl). Their approach requires a certain amount of empirical work, since these claims move beyond the individual experience of the text into forms of collective reading and cultural exchange influenced by social class, geographical location, education, ethnicity, and other factors. Yet McGurl and English's groundbreaking work is limited by the very forms of exclusivity they analyze: the protective bubble of creative writing programs in the academy and the elite economy of prestige surrounding literary prizes, respectively. To really study the problem of cultural transmission, we need to look beyond the symbolic markets of prestige to the real market, the site of mass literary consumption, where authors succeed or fail based on their ability to speak to that most diverse and complicated of readerships: the general public. Unless we study what I call the social lives of books, we make the mistake of keeping literature in the same ascetic laboratory that Wallace tried to break out of with his intense authorial focus on popular culture, mass media, and everyday life.
Barth und Benjamin verbindet ein radikales Bemühen, um ein neues Wort- und Sprachverständnis, das der eine gegen die traditionelle Theologie, der andere gegen eine positivistische Geisteswissenschaft vorbringt. Damit nehmen sie gewollt oder ungewollt eine prophetische Haltung ein, die sie zeitweise zu absonderlichen Einzelgängern und zu Protagonisten auf verlorenem Posten macht. Barths Diagnose der Erfahrungsarmut traditioneller Exegese für die Arbeit des Theologen ebenso wie Benjamins Sprachduktus und die teils surrealistisch anmutende Themenwahl seiner wissenschaftlichen Fragestellungen lassen vermuten, dass der prophetische Gestus ihres Selbstverständnisses die Ablehnung der Umwelt schon einbezieht und Benjamins Text "Der destruktive Charakter" den Keim einer Theorie der Prophetie 'en miniature' für beide bereitzuhalten scheint. Denn der "destruktive Charakter steht in der Front der Traditionalisten" (GS IV, 398), von denen sich Barth und Benjamin umgeben sahen. Und so könnte man sagen, der Prophet (ebenso wie der destruktive Charakter) zertrümmert nicht einfach das Überlieferte. Er erarbeitet "Trümmer [...] um des Weges willen, der sich durch sie hindurchzieht" (ebd.). "[N]ur eine Parole: Platz schaffen", schreibt Benjamin, "nur eine Tätigkeit: räumen ", in einem Bedürfnis "nach frischer Luft und freiem Raum" (396).
We present the analysis of the impact of convection on the composition of the tropical tropopause layer region (TTL) in West-Africa during the AMMA-SCOUT campaign. Geophysica M55 aircraft observations of water vapor, ozone, aerosol and CO2 during August 2006 show perturbed values at altitudes ranging from 14 km to 17 km (above the main convective outflow) and satellite data indicates that air detrainment is likely to have originated from convective cloud east of the flights. Simulations of the BOLAM mesoscale model, nudged with infrared radiance temperatures, are used to estimate the convective impact in the upper troposphere and to assess the fraction of air processed by convection. The analysis shows that BOLAM correctly reproduces the location and the vertical structure of convective outflow. Model-aided analysis indicates that convection can influence the composition of the upper troposphere above the level of main outflow for an event of deep convection close to the observation site. Model analysis also shows that deep convection occurring in the entire Sahelian transect (up to 2000 km E of the measurement area) has a non negligible role in determining TTL composition.
Diese kleine Auswahl an Ringfunden mit Bezug zu Deutschland oder Österreich soll über die interessanten, vielfältigen und teilweise auch überraschenden oder ungewöhnlichen Einblicke informieren, die heute noch durch die Vogelberingung gewonnen werden. Da die Angaben auf das Wesentliche reduziert wurden, sind diese Funddaten für die weitere Auswertung nicht in allen Fällen geeignet. Interessenten, die Ringfunde für Auswertungen verwenden möchten, wenden sich bitte an eine der drei deutschen Beringungszentralen.