Finite nilpotent semigroups of small coclass

The parameter coclass has been used successfully in the study of nilpotent algebraic objects of different kinds. In this paper a definition of coclass for nilpotent semigroups is introduced and semigroups of coclass 0, 1, and 2 are classified. Presentations for all such semigroups and formulae for their numbers are obtained. The classification is provided up to isomorphism as well as up to isomorphism or anti-isomorphism. Commutative and self-dual semigroups are identified within the classification.Comment: 11 page

Are tyrosine kinase inhibitors promising for the treatment of systemic sclerosis and other fibrotic diseases?

Tissue fibrosis causes organ failure and death in patients with systemic sclerosis (SSc), but clearly effective anti-fibrotic therapies are not available. The tyrosine kinase inhibitor (TKI) imatinib, which blocks the pro-fibrotic c-Abl kinase and PDGF receptor, is currently evaluated in clinical proof-of-concept trials for the treatment of patients with SSc. In experimental models, imatinib efficiently prevented and reduced tissue fibrosis. First clinical case studies demonstrated anti-fibrotic effects of imatinib in selected patients with SSc and other fibrotic diseases, and observational studies in sclerotic chronic graft-versus-host disease showed promising results. Besides imatinib, the two novel TKIs of c-Abl and PDGF receptor nilotinib and dasatinib have recently proven efficacy in experimental models of SSc. The potential of TKIs of the VEGF receptor (e.g., semaxinib, vatalanib, sutent, and sorafenib) and the EGF receptor (e.g., erlotinib, gefitinib, lapatinib, and canertinib) as anti-fibrotic treatments are also discussed in this review. Prior to clinical use, however, controlled trials need to address efficacy as well as tolerability of TKIs in patients with different fibrotic diseases

Deformed Quantum Cohomology and (0,2) Mirror Symmetry

We compute instanton corrections to correlators in the genus-zero topological subsector of a (0,2) supersymmetric gauged linear sigma model with target space P1xP1, whose left-moving fermions couple to a deformation of the tangent bundle. We then deduce the theory's chiral ring from these correlators, which reduces in the limit of zero deformation to the (2,2) ring. Finally, we compare our results with the computations carried out by Adams et al.[ABS04] and Katz and Sharpe[KS06]. We find immediate agreement with the latter and an interesting puzzle in completely matching the chiral ring of the former.Comment: AMSLatex, 30 pages, one eps figure. V4: typos corrected, final version appearing in JHE

Hidden Symmetry in Topological Gravity

Talk presented by P.N. at “Mathematics and Physics of Strings,” Berkeley and “Topology and Geometry in Theoretical Physics,” Turku (Finland), 1991

Semirigid Supergravity

We formulate two-dimensional topological gravity starting from local N = 2 superconformal geometry. The theory is free from the very beginning. The usual ‘‘twisting’’ of the N = 2 algebra emerges from symmetry breaking when we expand about a nonzero value for one of the ghost fields. The mysterious linear term in the supercurrent emerges automatically, as does a full superfield formalism for the whole system including ghosts. We analyze the moduli space of the ‘‘semirigid’’ super Riemann surfaces associated with this theory, including their allowed degenerations

Topological Couplings and Contact Terms in 2d Field Theory

In string theory and in topological quantum field theory one encounters operators whose effect in correlation functions is simply to measure the topology of 2d spacetime. In particular these \u27dilation\u27-type operators count the number of other operators via contact terms with the latter. While contact terms in general have a reputation for being convention-dependent, the ones considered here are perfectly well-defined by virtue of their simple geometrical meaning: They reflect the geometry of the stable-curve compactification. We give an unambiguous prescription for their evaluation which involves no analytic continuation in momenta

New Discrete States of Strings Near a Black Hole

We find the physical spectrum for the “black hole” solution recently proposed by E. Witten as an exact string background with a 2-dimensional target space. The spectrum contains some of the states found in studies of d = 1 non-critical string theory but, in addition, has new states not previously found in the d = 1 non-critical string. Along the way we find a remarkable “stringy” symmetry of the spectrum relating massive states to massless ones

The Dilaton Equation in Semirigid String Theory

We show how to obtain explicit integration measures on ordinary moduli space corresponding to the correlation functions of pure 2-dimensional topological gravity. In particular our prescription tells how to remove the zero modes of the βγ system. We then use our formula to derive the “dilaton equation” introduced by E. Verlinde and H. Verlinde,a relation between the N-point and (N − 1)-point correlations of this theory. Just as incritical string theory we use the fact that certain brst-exact states fail to decouple. Instead they build up ˇ Cech classes, in this instance the Euler class of an N-times punctured surface. Throughout we use the “semirigid” formulation of topological gravity. Thus theLiouville sector of other approaches never enters

Hidden Symmetry in Topological Gravity

Talk presented by P.N. at “Mathematics and Physics of Strings,” Berkeley and “Topology and Geometry in Theoretical Physics,” Turku (Finland), 1991

Frontiers of antifibrotic therapy in systemic sclerosis

Although fibrosis is becoming increasingly recognized as a major cause of morbidity and mortality in modern societies, targeted anti-fibrotic therapies are still not approved for most fibrotic disorders. However, intense research over the last decade has improved our understanding of the underlying pathogenesis of fibrotic diseases. We now appreciate fibrosis as the consequence of a persistent tissue repair responses, which, in contrast to normal wound healing, fails to be effectively terminated. Profibrotic mediators released from infiltrating leukocytes, activated endothelial cells and degranulated platelets may predominantly drive fibroblast activation and collagen release in early stages, whereas endogenous activation of fibroblasts due epigenetic modifications and biomechanical or physical factors such as stiffening of the extracellular matrix and hypoxia may play pivotal role for disease progression in later stages. In the present review, we discuss novel insights into the pathogenesis of fibrotic diseases using systemic sclerosis (SSc) as example for an idiopathic, multisystem disorder. We set a strong translational focus and predominantly discuss approaches with very high potential for rapid transfer from bench-to-bedside. We highlight the molecular basis for ongoing clinical trials in SSc and also provide an outlook on upcoming trials. This article is protected by copyright. All rights reserved