A quotient of the Lubin-Tate tower II

In this article we construct the quotient M_1/P(K) of the infinite-level Lubin-Tate space M_1 by the parabolic subgroup P(K) of GL(n,K) of block form (n-1,1) as a perfectoid space, generalizing results of one of the authors (JL) to arbitrary n and K/Q_p finite. For this we prove some perfectoidness results for certain Harris-Taylor Shimura varieties at infinite level. As an application of the quotient construction we show a vanishing theorem for Scholze's candidate for the mod p Jacquet-Langlands and the mod p local Langlands correspondence. An appendix by David Hansen gives a local proof of perfectoidness of M_1/P(K) when n = 2, and shows that M_1/Q(K) is not perfectoid for maximal parabolics Q not conjugate to P.Comment: with an appendix by David Hanse

On topological cyclic homology

Topological cyclic homology is a refinement of Connes--Tsygan's cyclic homology which was introduced by B\"okstedt--Hsiang--Madsen in 1993 as an approximation to algebraic $K$-theory. There is a trace map from algebraic $K$-theory to topological cyclic homology, and a theorem of Dundas--Goodwillie--McCarthy asserts that this induces an equivalence of relative theories for nilpotent immersions, which gives a way for computing $K$-theory in various situations. The construction of topological cyclic homology is based on genuine equivariant homotopy theory, the use of explicit point-set models, and the elaborate notion of a cyclotomic spectrum. The goal of this paper is to revisit this theory using only homotopy-invariant notions. In particular, we give a new construction of topological cyclic homology. This is based on a new definition of the $\infty$-category of cyclotomic spectra: We define a cyclotomic spectrum to be a spectrum $X$ with $S^1$-action (in the most naive sense) together with $S^1$-equivariant maps $\varphi_p: X\to X^{tC_p}$ for all primes $p$. Here $X^{tC_p}=\mathrm{cofib}(\mathrm{Nm}: X_{hC_p}\to X^{hC_p})$ is the Tate construction. On bounded below spectra, we prove that this agrees with previous definitions. As a consequence, we obtain a new and simple formula for topological cyclic homology. In order to construct the maps $\varphi_p: X\to X^{tC_p}$ in the example of topological Hochschild homology we introduce and study Tate diagonals for spectra and Frobenius homomorphisms of commutative ring spectra. In particular we prove a version of the Segal conjecture for the Tate diagonals and relate these Frobenius homomorphisms to power operations

Evidence of estrogenic mixture effects on the reproductive performance of fish

The official published version can be obtained from the link below - Copyright @ 2007 American Chemical SocietyRecent research into the effects of mixtures of estrogenic chemicals has revealed the capacity for similarly acting chemicals to act in combination, according to the principles of concentration addition. This means that, collectively, they may pose a significant environmental risk, even when each component is present at a low and individually ineffective concentration. The aim of this study was to investigate the ecological significance of mixture effects at low-effect concentrations by assessing the combined effect of estrogenic chemicals on the reproductive performance of fish. Pairs of fathead minnows were exposed to five estrogenic chemicals. Endpoints analyzed included fecundity, the expression of male secondary sexual characteristics, somatic indices, and vitellogenin induction. In the first phase of the study, a concentration-response analysis was performed to investigate the relative sensitivity of these endpoints. In the second phase, mixture effects at low-effect concentrations were explored by exposing fish to each of the mixture components, individually and in combination. Data from these experiments provide evidence of mixture effects on fitness and fecundity, demonstrating the capacity for chemicals to act together to affect reproductive performance, even when each component is present belowthe threshold of detectable effects. This has important implications for hazard assessment and contributes to our understanding of mixture effects at increasing levels of biological complexity.This work was funded by the European Commission, under contract EVK1-2001-00091

Genotoxic mixtures and dissimilar action: Concepts for prediction and assessment

This article has been made available through the Brunel Open Access Publishing Fund. This article is distributed under the terms of the creative commons Attribution license which permits any use, distribution, and reproduction in any medium, provided the original author(s)and the source are credited.Combinations of genotoxic agents have frequently been assessed without clear assumptions regarding their expected (additive) mixture effects, often leading to claims of synergisms that might in fact be compatible with additivity. We have shown earlier that the combined effects of chemicals, which induce micronuclei (MN) in the cytokinesis-block micronucleus assay in Chinese hamster ovary-K1 cells by a similar mechanism, were additive according to the concept of concentration addition (CA). Here, we extended these studies and investigated for the first time whether valid additivity expectations can be formulated for MN-inducing chemicals that operate through a variety of mechanisms, including aneugens and clastogens (DNA cross-linkers, topoisomerase II inhibitors, minor groove binders). We expected that their effects should follow the additivity principles of independent action (IA). With two mixtures, one composed of various aneugens (colchicine, flubendazole, vinblastine sulphate, griseofulvin, paclitaxel), and another composed of aneugens and clastogens (flubendazole, doxorubicin, etoposide, melphalan and mitomycin C), we observed mixture effects that fell between the additivity predictions derived from CA and IA. We achieved better agreement between observation and prediction by grouping the chemicals into common assessment groups and using hybrid CA/IA prediction models. The combined effects of four dissimilarly acting compounds (flubendazole, paclitaxel, doxorubicin and melphalan) also fell within CA and IA. Two binary mixtures (flubendazole/paclitaxel and flubendazole/doxorubicin) showed effects in reasonable agreement with IA additivity. Our studies provide a systematic basis for the investigation of mixtures that affect endpoints of relevance to genotoxicity and show that their effects are largely additive.UK Food Standards Agenc

Sea bass (Dicentrarchus labrax) : a model organism for the screening of estrogenic chemicals in marine surface waters?

Society of Environmental Toxicology and Chemistry - SETAC Europe 14th Annual Meeting, Prague, Czech Republic, April 2004.There is growing concern that aquatic wildlife in surface waters of the European Union is exposed to natural and man-made chemicals that have the ability to mimic estrogens and lead to reproductive dysfunction. Estrogenic responses in fish are the net result of complex chains of events involving the uptake, distribution and metabolism of test agents until they interact with their target sites. Typically these aspects cannot be modelled in short-term cell-based assays, only studies with vertebrates offer the opportunity to assess potential interactions of test compounds at higher organisational levels. However, studies with endocrine disrupting chemicals have been performed mainly with freshwater organisms. The sensitivity of a marine fish species to different estrogenic chemicals was investigated under chronic exposure conditions. This work is part of a study focusing on the combination effects of mixtures of estrogenic chemicals in marine and freshwater organisms (ACE, EVK1-CT-2001-100). As test organism the sea bass (Dicentrarchus labrax) was selected, a common species in European marine systems. Juveniles were exposed under a flow-through system for 14 days for a set of reference chemicals (17Ã -estradiol, ethynylestradiol, nonylphenol, octylphenol, bisphenol A). Effects at subcellular level were analysed using vitellogenesis as endpoint. Its relevance is evaluated by further investigations about the individual fitness (condition factor, hepatossomatic index), as well as the liver cytochrome P450 activity. The general suitability of the sea bass as a model organism for the screening of estrogenic chemicals in the marine environment is discussed.Comissãoo Europeia (CE) - ACE, EVK1-CT-2001-100

Capacitance-conductance investigation on the phase transitions in Ga nanoparticles

We have reported on coupled capacitance-conductance measurements on Ga nanoparticles embedded in vitreous matrices. The melting of nanoparticles was clearly detected as an abrupt increase in the capacitance vs. temperature scans. The influence of the embedding matrix and of the frequency of the applied field on the dielectric response was checked. The presence of a hysteresis cycle between melting and solidification has been detected. The technique allows the identification of the various solid phases of confined Ga

Antagonistic Activities of Sox2 and Brachyury Control the Fate Choice of Neuro-Mesodermal Progenitors

The spinal cord and mesodermal tissues of the trunk such as the vertebral column and skeletal musculature derive from neuro-mesodermal progenitors (NMPs). Sox2, Brachyury (T), and Tbx6 have been correlated with NMP potency and lineage choice; however, their exact role and interaction in these processes have not yet been revealed. Here we present a global analysis of NMPs and their descending lineages performed on purified cells from embryonic day 8.5 wild-type and mutant embryos. We show that T, cooperatively with WNT signaling, controls the progenitor state and the switch toward the mesodermal fate. Sox2 acts antagonistically and promotes neural development. T is also involved in remodeling the chromatin for mesodermal development. Tbx6 reinforces the mesodermal fate choice, represses the progenitor state, and confers paraxial fate commitment. Our findings refine previous models and establish molecular principles underlying mammalian trunk development, comprising NMP maintenance, lineage choice, and mesoderm formation