Eine alte Gattung neu erfunden: Die Apologi Centum des Leon Battista Alberti

Leon Battista Alberti′s short fable collection Apologi Centum (1437) marks a radical departure from the medieval understanding of the genre as well as from the newly discovered Greek collections of 'truly Aesopian′ fables. It defines the genre in a new way, and becomes a model in its own right for the following generations of Renaissance fabulists. The extreme conciseness of his Apologi, Alberti claims, inevitably makes them obscure and hard to understand the very contrary of the easy schooltexts fables are usually meant to be. This paper studies Alberti′s claim to novelty and the way he puts it into practice, naming and exemplifying a number of techniques by which he succeeds in creating pregnant, riddling fables for the educated, intelligent reade

In piscibus obsonatores et rhetores: Petr. 39.13

In piscibus (sc. nascuntur) obsonatores et rhetores: thus Trimalchio concludes the sign-by-sign interpretation he gives in Petr. 39 of the astrological repositorium that has been served some chapters before (35.1-5). While the obsonatores - ‘buyers of fish' (TLL 9.234.49-70), from ὀΨωνέω, ‘buy fish and other dainties' (LSJ s.v.) - pose no problem, the rhetores have mystified interpreters since Peter Burman, who frankly confessed: ‘Causam non video, cum pisces vulgo muti habeantur, rhetores vero loquaces. Fortasse corrupta vox. An vectores aut veteratores? Haereo.

Purification and Characterization of Retinoblastoma like Factor-containing Protein Complexes from Drosophila melanogaster

The Retinoblastoma protein (pRb) was the first tumor suppressor protein to be identified. It is the founding member of the so called pRb or pocket protein family, comprising two additional members (p107 and p130) in mammalian cells, and its best characterized function is the regulation of the E2F family of transcription factors. Today, the pRb-E2F network represents one of the best understood pathways implicated in cell cycle regulation and differentiation. Pocket proteins negatively regulate the transactivation properties of E2F proteins by two mechanisms: First, binding of pocket proteins to E2F masks the E2F transactivation domain and thereby impairs transcriptional activation. Second, pocket proteins interact with several chromatin modifying and chromatin binding proteins and recruit these proteins to E2F target genes, where they help to establish a repressive chromatin conformation. In this work, advantage was taken of the relative simplicity of the Drosophila melanogaster pRb-E2F network to purify and functionally characterize native pRb repressor complexes. Two related multisubunit complexes that only differ in their pocket protein subunit (RBF1 or RBF2) have been purified from Drosophila embryo nuclear extract. These complexes contain several novel pocket protein-associated polypeptides and localize to transcriptionally silent regions on Drosophila polytene chromosomes. Moreover, they specifically associate with deacetylated histone tails, which are a hallmark of transcriptionally silent chromatin. In cycling Drosophila S2 cells, the purified complexes redundantly repress the expression of a certain class of E2F target genes implicated in differentiation and development, whereas they do not control the expression of cell cycle-regulated E2F targets. Interestingly, the isolated complexes seem to be highly conserved between different organisms. Genes encoding the Caenorhabditis elegans homologs of the complex subunits act within the same genetic pathway involved in vulval cell fate determination and they functionally cooperate in different developmental processes. Furthermore, a complex with striking homology to the Drosophila complexes also exists in human cells. In the light of the specific repression of developmentally regulated E2F target genes in cycling Drosophila cells, it is conceivable that the complexes prevent the uncontrolled expression of genes important during differentiation. Since the C. elegans homologs of the complex subunits are also involved in cell fate determination, this might be a highly conserved feature of the isolated complexes

A Vanishing Act, Explained

In a paper in this issue of Developmental Cell, Shibutani et al. (2008) uncover the mechanism that underlies tightly regulated S-phase degradation of Drosophila E2F1 during development. They show that dE2F1 is degraded by the Cul4Cdt2 ubiquitin ligase in a manner that resembles the DNA replication-dependent turnover of Cdt1

Smectic and soap bubble optofluidic lasers

Soap bubbles are simple, yet very unique and marvelous objects. They exhibit a number of interesting properties such as beautiful interference colors and the formation of minimal surfaces. Various optical phenomena have been studied in soap films and bubbles, but so far they were not employed as optical cavities. Here we demonstrate, that dye doped soap or smectic liquid crystal bubbles can support whispering gallery mode lasing, which is observed in the spectrum as hundreds of regularly spaced peaks, resembling a frequency comb. The lasing enabled the measurement of size changes as small as 10 nm in a millimeter-sized, $\sim$100 nm thick bubble. Bubble lasers were used as extremely sensitive electric field sensors with a smallest measurable electric field of 110 Vm$^{-1}$Hz$^{-1/2}$. They also enable the measurement of pressures up to a 100 bar with a resolution of 1.5 Pa, resulting in a dynamic range of almost $10^7$. By connecting the bubble to a reservoir of air, almost arbitrarily low pressure changes can be measured while maintaining an outstanding dynamic range. The demonstrated soap bubble lasers are a very unique type of microcavities which are one of the best electric field and pressure microsensors to date and could in future also be employed to study thin films and cavity optomechanics