Trefoils and hexafoils in 3-braids

We determine the cobordism distance between all positive 3-braid links and connected sums of trefoil knots, up to a constant error. This may be seen as a reinterpretation of Coxeter's finiteness result on the braid group on three strands modulo third powers of the generators. We go on to explore the limits of Coxeter's result, and find the cobordism distance between three strand torus links and almost all connected sums of two strand torus links, up to a constant error.Comment: 8 pages, 2 figures, comments welcom

Twisting braids and surfaces

This thesis covers two twisting notions, namely that of Dehn twists and that of Fox’s twist moves. More precisely, in the first part we characterise closed embedded discs in surfaces that are bounded by a circuit curve system in terms of a particular relation called the cycle relation between the associated Dehn twists. We also characterise bouquets of curves in a similar vein. In the process, we classify all circuits of curves in terms of whether the corresponding Dehn twists generate an Artin group. In the second part we relate Przytycky’s obstructions on the HOMFLY polynomial for two links to be related by twist moves to the crossing number and the braid index. We also estimate the cobordism distance between connected sum powers of trefoil or hexafoil links and three strand torus links

Heat-shock mediated overexpression of HNF1β mutations has differential effects on gene expression in the Xenopus pronephric kidney.

The transcription factor HNF1B, encoded by the TCF2 gene, plays an important role in the organogenesis of vertebrates. In humans, heterozygous mutations of HNF1B are associated with several diseases, such as pancreatic β-cell dysfunction leading to maturity-onset diabetes of the young (MODY5), defective kidney development, disturbed liver function, pancreas atrophy, and malformations of the genital tract. The African claw frog Xenopus laevis is an excellent model to study the processes involved in embryogenesis and organogenesis, as it can be manipulated easily with a series of methods. In the present study, we overexpressed HNF1β mutants in the developing Xenopus embryo to assess their roles during organogenesis, particularly in the developing pronephric kidney. Towards this goal, we developed a heat-shock inducible binary Cre/loxP system with activator and effector strains. Heat-shock activation of the mutant HNF1B variants P328L329del and A263insGG resulted in malformations of various organs and the affected larvae developed large edemas. Defects in the pronephros were primarily confined to malformed proximal tubules. Furthermore, the expression of the proximal tubule marker genes tmem27 and slc3a1, both involved in amino acid transport, was affected. Both P328L329del and A263insGG downregulated expression of slc3a1. In addition, P328L329del reduced tmem27 expression while A263insGG overexpression decreased expression of the chloride channel clcnk and the transcription factor pax2. Overexpression of two mutant HNF1B derivatives resulted in distinct phenotypes reflected by either a reduction or an enlargement of pronephros size. The expression of selected pronephric marker genes was differentially affected upon overexpression of HNF1B mutations. Based on our findings, we postulate that HNF1B mutations influence gene regulation upon overexpression in specific and distinct manners. Furthermore, our study demonstrates that the newly established Cre/loxP system for Xenopus embryos is an attractive alternative to examine the gene regulatory potential of transcription factors in developing pronephric kidney as exemplified here for HNF1B

Bouquets of curves in surfaces

We characterise embedded bouquets of simple closed curves in orientable surfaces, in terms of relations between the corresponding Dehn twists.Comment: 11 pages, 4 figures, comments welcom

The nephrogenic potential of the transcription factors osr1, osr2, hnf1b, lhx1 and pax8 assessed in Xenopus animal caps

<p>Abstract</p> <p>Background</p> <p>The three distinct types of kidneys, pronephros, mesonephros and metanephros, develop consecutively in vertebrates. The earliest form of embryonic kidney, the pronephros, is derived from intermediate mesoderm and the first expressed genes localized in the pronephros anlage are the transcription factors osr1, osr2, hnf1b, lhx1 and pax8, here referred to as the early nephrogenic transcription factors. However, the pathway inducing nephrogenesis and the network of theses factors are poorly understood. Treatment of the undifferentiated animal pole explant (animal cap) of Xenopus with activin A and retinoic acid induces pronephros formation providing a powerful tool to analyze key molecular events in nephrogenesis.</p> <p>Results</p> <p>We have investigated the expression kinetics of the early nephrogenic transcription factors in activin A and retinoic acid treated animal caps and their potential to induce pronephric differentiation. In treated animal caps, expression of osr1, osr2, hnf1b and lhx1 are induced early, whereas pax8 expression occurs later implying an indirect activation. Activin A alone is able to induce osr2 and lhx1 after three hours treatment in animal caps while retinoic acid fails to induce any of these nephrogenic transcription factors. The early expression of the five transcription factors and their interference with pronephros development when overexpressed in embryos suggest that these factors potentially induce nephrogenesis upon expression in animal caps. But no pronephros development is achieved by either overexpression of OSR1, by HNF1B injection with activin A treatment, or the combined application of LHX1 and PAX8, although they influenced the expression of several early nephrogenic transcription factors in some cases. In an additional approach we could show that HNF1B induces several genes important in nephrogenesis and regulates lhx1 expression by an HNF1 binding site in the lhx1 promoter.</p> <p>Conclusions</p> <p>The early nephrogenic transcription factors play an important role in nephrogenesis, but have no pronephros induction potential upon overexpression in animal caps. They activate transcriptional cascades that partially reflect the gene activation initiated by activin A and retinoic acid. Significantly, HNF1B activates the lhx1 promoter directly, thus extending the known activin A regulation of the lhx1 gene via an activin A responsive element.</p

From precarious conditions to permanent positions? Problems, responsible actors, and solutions for strengthening the academic mid-level staff in Switzerland

The precarious situation of doctoral and postdoctoral researchers, resulting from fixed-term contracts and the demanding working conditions of young researchers at Swiss universities, has been increasingly discussed in recent years by academic organizations, political actors, and the broader public. While discussions on various levels are intensifying, concrete measures remain largely absent, and young researchers find themselves in an environment of job insecurity and a lack of prospects. Therefore, we organized a panel discussion on why and how to create permanent positions in the Swiss academic system during this year’s annual conference of the Swiss Association of Communication and Media Research (SACM). The panel included presentations of preliminary results from a recent study analyzing the working conditions of young and emerging communication and media scholars in Switzerland as well as discussions with researchers and actors from science organizations regarding: 1) the need for improvement of the current working conditions and the future perspectives of mid-level staff at Swiss universities, 2) the responsibilities of different actors, and 3) alternatives to the status quo that help solve the precarious situation of young and emerging scholars in Switzerland and beyond. The discussion showed several reasons for establishing more permanent positions and inducing a systemic change. While there are manifold arguments for creating more permanent positions, these arguments must appeal to those with decision-making power