From the Signature Theorem to Anomaly Cancellation

We survey the Hirzebruch signature theorem as a special case of the Atiyah–Singer index theorem. The family version of the Atiyah–Singer index theorem in the form of the Riemann–Roch–Grothendieck–Quillen (RRGQ) formula is then applied to the complexified signature operators varying along the universal family of elliptic curves. The RRGQ formula allows us to determine a generalized cohomology class on the base of the elliptic fibration that is known in physics as (a measure of) the local and global anomaly. Combining several anomalous operators allows us to cancel the local anomaly on a Jacobian elliptic surface, a construction that is based on the construction of the Poincaré line bundle over an elliptic surface

Neuartige schaltbare columnare Flüssigkristalle

Columnare Flüssigkristalle sind durch die in den Mesophasen vorliegende hohe Leitfähigkeit entlang der Molekülstapel für Anwendungen in der Optoelektronik von Interesse. Ziel dieser Arbeit war die Synthese neuartiger columnarer Flüssigkristalle mit Strukturmerkmalen, die es ermöglichen sollten, an diesen Molekülen photochemisch, redox- oder Metallionen-induziert ablaufende Schaltvorgänge durchführen zu können. Weiterhin sollte untersucht werden, ob durch die genannten Prozesse eine Modifikation bzw. Induzierung von Mesophasen möglich ist. Im Rahmen der Arbeit gelang die Darstellung der ersten columnaren Flüssigkristalle mit Tetraphenylethen und Dibenzo-18-krone-6 als Zentralkernen sowie die Synthese von chiralen Triphenylenderivaten. Im Fall der Tetraphenylethenderivate wurde in Abhängigkeit der Verknüpfung zwischen Zentralkern und Peripherie der Moleküle unterschiedliches columnar mesogenes Phasenverhalten beobachtet. Durch eine oxidative Photocyclisierung der mesogenen Tetraphenylethene konnte gezeigt werden, dass auch Phenanthren als Zentralkern von columnaren Flüssigkristallen geeignet ist. Die durch Komplexierung mit Metallkationen induzierte Konformationsänderung der Kronenetherderivate führte zu einer Stabilisierung der von diesen Verbindungen gebildeten Mesophasen. Eine Dotierung von Hexaalkyloxytriphenylenen (HAT's) mit den nicht mesogenen, chiralen Triphenylenen hatte eine Modifikation der von den HAT's gebildeten columnaren Mesophasen zur Folge.Columnar liquid crystals are promising candidates for applications in the field of optoelectronics due to the high conductivity these compounds display along the stacks of molecules in the mesophases. This thesis describes the synthesis of novel columnar liquid crystals with structural properties which enable light, redox or metal ion induced switching processes in these molecules. Further research was conducted on whether these processes could lead to a modification or formation of mesophases. The first columnar liquid crystals with tetraphenylethene and dibenzo-18-crown-6 as cores were synthesised, as well as novel chiral triphenylene derivatives. In the case of the tetraphenylethene compounds, the phase behaviour varied with the connection between the core and periphery units of the molecules. An oxidative photocyclisation of the mesogenic tetraphenylethenes proved that molecules with phenanthrene as a core unit can also form columnar mesophases. A complexation with metal cations induced a change of conformation in the crown ether derivatives and thus led to a stabilisation of the mesophases formed by these compounds. Hexaalkyloxytriphenylenes (HATs) were doped with the chiral, non-mesogenic triphenylenes, resulting in a modification of the columnar mesophases formed by the pure HATs

Time Flies: Autophagy During Ageing in Drosophila

The process of ageing compromises the age-associated decrease in fertility, gradual loss of function, and increased vulnerability to disease, which progressively diminishes the capability of an organism to survive [1-3]. Unsurprisingly, in the past years it has been of great interest to understand which factors influence this inevitable and complex process. As a result a wide array of molecular and cellular damages has been identified and shown to accumulate during ageing. The lifelong accumulation of such damages will eventually result in frailty and disease [4]. The variety of identified age-dependent damages has given rise to different theories for molecular ageing mechanisms. These mechanisms include decreased cellular capacity to deal with DNA damage, and decline in cellular division capacity, which is linked to the progressive shortening of telomeres upon each cell cycle. Also an increased accumulation of damaged mitochondria and the involved increase in reactive oxygen species (ROS) production and decline in ATP synthesis has been shown to occur over time (reviewed in [5]). One of the phenotypic hallmarks of aged cells is the intracellular accumulation of damaged proteins and therefore protein turnover/protein degradation has attracted attention over the last years [2]. At the same time, forward genetics have allowed to investigate single gene alterations and their influence on lifespan of whole organisms. Even though the ageing process is without doubt influenced by stochastic and environmental factors, single gene mutations were shown to extend lifespan in worms, flies, and mice, suggesting the existence of a central process of ageing [6, 7]. Many of the genetic manipulations that alter longevity affect metabolism, nutrient sensing and stress response pathways. As all these pathways are connected to autophagy (an important player also in protein turnover), the question about the role of autophagy in ageing has come more and more to the fore. In this chapter we will focus on how research conducted in the excellent genetic model system Drosophila melanogaster has contributed to understand more about the interplay of autophagy and ageing

Die Äolsharfe als Klangkomposition?: Philosophische Bemerkungen zur Rolle des Subjekts in der Musik

Die Äolsharfe galt als Stimme der Natur, des Windes, ohne menschliches Zutun. Sich der Natur anzunähern führte bei den Romantikern und Impressionisten zu einer Musik, bei der Gestalten und Phrasenbildung zugunsten des ›Klanges‹ zurücktraten. Debussys Prélude Brouillards (Nebel), in Beziehung gesetzt zur chinesischen Landschaftsmalerei öffnet den Raum für philosophische Überlegungen über die Rolle des Subjekts in der Musik, in Auseinandersetzung mit der Philosophie von Theodor W. Adorno und François Jullien, sowie mit Klangkompositionen von John Cage und Alvin Lucier.The Aeolian harp was considered to be the voice of nature and of the wind, able to play without any human help. To get closer to nature, Romantic and Impressionist composers reduced the importance of figure and phrasing in favour of sound. The prélude »Brouillards« (fog) of Debussy, set in relation to Chinese landscapes paintings, opens the mind for philosophical reflections on the role of subjectivity in music, in light of the philosophy of Theodor W. Adorno and François Jullien and with sound compositions of John Cage and Alvin Lucier

The residual STL volume as a metric to evaluate accuracy and reproducibility of anatomic models for 3D printing: application in the validation of 3D-printable models of maxillofacial bone from reduced radiation dose CT images.

BackgroundThe effects of reduced radiation dose CT for the generation of maxillofacial bone STL models for 3D printing is currently unknown. Images of two full-face transplantation patients scanned with non-contrast 320-detector row CT were reconstructed at fractions of the acquisition radiation dose using noise simulation software and both filtered back-projection (FBP) and Adaptive Iterative Dose Reduction 3D (AIDR3D). The maxillofacial bone STL model segmented with thresholding from AIDR3D images at 100 % dose was considered the reference. For all other dose/reconstruction method combinations, a "residual STL volume" was calculated as the topologic subtraction of the STL model derived from that dataset from the reference and correlated to radiation dose.ResultsThe residual volume decreased with increasing radiation dose and was lower for AIDR3D compared to FBP reconstructions at all doses. As a fraction of the reference STL volume, the residual volume decreased from 2.9 % (20 % dose) to 1.4 % (50 % dose) in patient 1, and from 4.1 % to 1.9 %, respectively in patient 2 for AIDR3D reconstructions. For FBP reconstructions it decreased from 3.3 % (20 % dose) to 1.0 % (100 % dose) in patient 1, and from 5.5 % to 1.6 %, respectively in patient 2. Its morphology resembled a thin shell on the osseous surface with average thickness <0.1 mm.ConclusionThe residual volume, a topological difference metric of STL models of tissue depicted in DICOM images supports that reduction of CT dose by up to 80 % of the clinical acquisition in conjunction with iterative reconstruction yields maxillofacial bone models accurate for 3D printing

Technikbasiertes Spiel von Tagespflegebesuchern mit und ohne Demenz: Effekte, Heuristiken und Korrelate

Das Spiel von alten Menschen ist bislang relativ unbeachtet geblieben. Wir untersuchen dieses Thema mithilfe eines Tablet-Memory-Spiels wissenschaftlich auf 2 Ebenen: anhand einer psychologischen Beobachtung, die durch eine Spielprotokollanalyse ergänzt wird, und anhand einer deduktiv-induktiven Interpretation der kulturellen Spieltheorie