A comparison of logarithmic overconvergent de Rham-Witt and log-crystalline cohomology for projective smooth varieties with normal crossing divisor

This is the author accepted manuscript. The final version is available from Università di Padova via the DOI in this record.In this note we derive for a smooth projective variety X with normal crossing divisor Z an integral comparison between the log-crystalline cohomology of the associated log-scheme and the logarithmic overconvergent de Rham–Witt cohomology de fined by Matsuue. This extends our previous result that in the absence of a divisor Z the crystalline cohomology and overconvergent de Rham–Witt cohomology are canonically isomorphic

Overconvergent Wittvectors

Copyright © 2012 by Walter de Gruyter. The final publication is available at www.degruyter.comLet A be a finitely generated algebra over a field K of characteristic p > 0. We introduce a subring W†(A) ⊂ W(A), which we call the ring of overconvergent Witt vectors, and prove its basic properties. In a subsequent paper we use the results to define an overconvergent de Rham–Witt complex for smooth varieties over K whose hypercohomology is the rigid cohomology

Overconvergent de Rham-Witt cohomology

Copyright © 2011 Société mathématique de FranceThe goal of this work is to construct, for a smooth variety X over a perfect field k of finite characteristic p > 0, an overconvergent de Rham-Witt complex WyX=k as a suitable sub-complex of the de Rham-Witt complex of Deligne-Illusie. This complex, which is functorial in X, is a complex of etale sheaves and a differential graded algebra over the ring Wy( OX) of Overconvergent Witt-vectors. If X is affine one proves that there is a isomorphism between Monsky-Washnitzer cohomology and (rational) overconvergent de Rham-Witt cohomology. Finally we define for a quasiprojective X an isomorphism between the rational overconvergent de Rham-Witt cohomology and the rigid cohomology

Mechanical spectroscopy of retina explants at the protein level employing nanostructured scaffolds

Development of neuronal tissue, such as folding of the brain, and formation of the fovea centralis in the human retina are intimately connected with the mechanical properties of the underlying cells and the extracellular matrix. In particular for neuronal tissue as complex as the vertebrate retina, mechanical properties are still a matter of debate due to their relation to numerous diseases as well as surgery, where the tension of the retina can result in tissue detachment during cutting. However, measuring the elasticity of adult retina wholemounts is difficult and until now only the mechanical properties at the surface have been characterized with micrometer resolution. Many processes, however, such as pathological changes prone to cause tissue rupture and detachment, respectively, are reflected in variations of retina elasticity at smaller length scales at the protein level. In the present work we demonstrate that freely oscillating cantilevers composed of nanostructured TiO2 scaffolds can be employed to study the frequency-dependent mechanical response of adult mammalian retina explants at the nanoscale. Constituting highly versatile scaffolds with strong tissue attachment for long-term organotypic culture atop, these scaffolds perform damped vibrations as fingerprints of the mechanical tissue properties that are derived using finite element calculations. Since the tissue adheres to the nanostructures via constitutive proteins on the photoreceptor side of the retina, the latter are stretched and compressed during vibration of the underlying scaffold. Probing mechanical response of individual proteins within the tissue, the proposed mechanical spectroscopy approach opens the way for studying tissue mechanics, diseases and the effect of drugs at the protein level

Optical intensity interferometry lab tests in preparation of stellar diameter measurements at IACTs at GHz photon rates

Astronomical intensity interferometry enables quantitative measurements of the source geometry by measuring the photon fluxes in individual telescopes and correlating them, rather than correlating the electromagnetic waves' amplitudes. This simplifies realization of large telescope baselines and high angular resolutions. Imaging Atmospheric Cherenkov Telescopes (IACTs), intended to detect the optical emission of $\gamma$-ray induced air showers, are excellent candidates to perform intensity correlations in the optical at reasonable signal-to-noise ratios. The detected coherence time is on the scale of $10^{-12}$ to $10^{-15}$~seconds - depending on the optical bandwidth of the measurement - which challenges the detection system to work in a stable and accurate way. We developed an intensity interferometry setup applicable to IACTs, which measures the photo currents from photomultipliers and correlates them offline, and as such is designed to handle the very large photon rates provided by the telescopes. We present measurements in the lab simulating starlight using a xenon lamp and measured at different degrees of temporal and spatial coherence. Necessary calibration procedures are described with the goal of understanding the measurements quantitatively. Measured coherence times between $5\,$femtoseconds (corresponding signal-to-background ratio $5\cdot10^{-7}$) and $110\,$femtoseconds (signal-to-background ratio $10^{-5}$) are in good agreement with expectations, and so are the noise levels in the correlations, reaching down to $6 \cdot 10^{-8}$, after measurements between $30\,$minutes and $1\,$ hour

Arbeit – ein Schlüssel für soziale Gerechtigkeit!? Bericht zum 21. Forum Sozialethik (05.–07.09.2011) in der Katholischen Akademie Schwerte

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Influence of substituents of Perylenebisimides on the surface energy and wettability: A systematic structure–property relationship analysis

This paper seeks to elucidate the influence on the surface wettability of a variety of substituents located in different positions of the perylene bisimide (PBI) core (ortho versus imide) with distinct electron-donor or -withdrawing character and diverse steric demand, using for this more than 20 planar PBIs. The correlation between the polarity of the individual functional group on the PBI and the surface wettability has been addressed by means of substituent descriptors in terms of Hansch-Fujita π parameter, Hammett σmeta and σpara constants, and steric parameters (Taft-Dubois Es’ and Charton υ). With these parameters, a quantitative structure–property relationship (QSPR) analysis has been performed using multivariable linear regression (MLR) fittings. The relationship of Surface Energy, determined by the static contact angle method with three different solvents, to structural properties of PBIs is described. As well, the polar and dispersive contributions have been determined. For planar PBIs, a predominant influence of the substituents in the imide position on the surface wettability has been found despite of the electronic nature and steric hindrance of the substituents simultaneously located in ortho positions. This effect is more pronounced with the longer alkyl substituents at the imide position. This study paves the way for a rational chromophore design considering the on surface behavior, which will ultimately condition the contact and thus their performance in optoelectronic devices

Employing Nanostructured Scaffolds to Investigate the Mechanical Properties of Adult Mammalian Retinae Under Tension

Numerous eye diseases are linked to biomechanical dysfunction of the retina. However, the underlying forces are almost impossible to quantify experimentally. Here, we show how biomechanical properties of adult neuronal tissues such as porcine retinae can be investigated under tension in a home-built tissue stretcher composed of nanostructured TiO2 scaffolds coupled to a self-designed force sensor. The employed TiO2 nanotube scaffolds allow for organotypic long-term preservation of adult tissues ex vivo and support strong tissue adhesion without the application of glues, a prerequisite for tissue investigations under tension. In combination with finite element calculations we found that the deformation behavior is highly dependent on the displacement rate which results in Young’s moduli of (760–1270) Pa. Image analysis revealed that the elastic regime is characterized by a reversible shear deformation of retinal layers. For larger deformations, tissue destruction and sliding of retinal layers occurred with an equilibration between slip and stick at the interface of ruptured layers, resulting in a constant force during stretching. Since our study demonstrates how porcine eyes collected from slaughterhouses can be employed for ex vivo experiments, our study also offers new perspectives to investigate tissue biomechanics without excessive animal experiments. © 2020 by the authors. Licensee MDPI, Basel, Switzerland