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1579 Publications visible to you, out of a total of 1579
Premelting Anomalies in Pyromellitic Dianhydride: Negative Thermal Expansion, Accelerated Radiation Damage, and Polymorphic Phase Transition

Abstract (Expand)

We have established a comprehensive approach to evaluate the structure–property relationships in solid pyromellitic dianhydride (PMDA) at high temperature. Synchrotron single-crystal X-ray diffraction … experiments have yielded structural models for this volatile compound up to 250 °C. PMDA exhibits negative thermal expansion around 145 °C, which is correlated to geometrical changes in the intermolecular carbonyl–carbonyl interactions. A reversible phase transition above ca. 210 °C was detected by differential scanning calorimetry and is associated with the lowering of the molecular symmetry, as indicated by Raman spectroscopy. X-ray powder and single-crystal diffraction data confirm the formation of a new high-temperature monoclinic phase, with two symmetry-independent anhydride groups in the asymmetric unit. The influence of pyromellitic acid impurities on the formation temperature of the new phase has been investigated, and thermodynamic parameters of pure pyromellitic dianhydride have been revaluated. Additionally, the analysis of the temperature- and time-dependent variations in the diffraction patterns allowed us to track the augmented radiation-driven decarboxylation upon heating. Significantly, the formation of a high-temperature low-symmetry phase in PMDA may challenge the solid-state polymerization that aims for highly oriented materials.

Authors: Tomasz Porȩba, Marcin Świa̧tkowski, Michelle Ernst, Giorgia Confalonieri

Date Published: 5th May 2022

Publication Type: Journal

Improving coreference resolution with word formation

Abstract

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Authors: Wei Zhao, Kevin Mathews, Haixia Chai

Date Published: 5th May 2022

Publication Type: InProceedings

A proposal for explicit word formation annotation in discourse corpora

Abstract

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Author: Mark-Christoph Müller

Date Published: 5th May 2022

Publication Type: InProceedings

Towards Effortless Navigation of Scientific-Literature Screen Reading for Biocuration

Abstract

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Authors: Sucheta Ghosh, Wolfgang Müller, Ulrike Wittig, Maja Rey

Date Published: 5th May 2022

Publication Type: InProceedings

Martini 3 coarse-grained force field for poly(para-phenylene ethynylene)s.

Abstract (Expand)

Poly(<i>para</i>-phenylene ethynylene)s, or short PPEs, are a class of conjugated and semi-flexible polymers with a strongly delocalized π electron system and increased chain stiffness. Due … to this, PPEs have a wide range of technological applications. Although the material properties of single-chains or mixtures of few PPE chains have been studied in detail, the properties of large assemblies remain to be fully explored. Here, we developed a coarse-grained model for PPEs with the Martini 3 force field to enable computational studies of PPEs in large-scale assembly. We used an optimization geometrical approach to take the shape of the π conjugated backbone into account and also applied an additional angular potential to tune the mechanical bending stiffness of the polymer. Our Martini 3 model reproduces key structural and thermodynamic observables of single PPE chains and mixtures, such as persistence length, density, packing and stacking. We show that chain entanglement increases with the expense of nematic ordering with growing PPE chain length. With the Martini 3 PPE model at hand, we are now able to cover large spatio-temporal scales and thereby to uncover key aspects for the structural organization of PPE bulk systems. The model is also predicted to be of high applicability to investigate out-of-equilibrium behavior of PPEs under mechanical force.

Authors: Matthias Brosz, Nicholas Michelarakis, Uwe H F Bunz, Camilo Aponte-Santamaría, Frauke Gräter

Date Published: 4th May 2022

Publication Type: Journal

Opportunities and challenges in machine learning‐based newborn screening—A systematic literature review

Abstract

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Authors: Elaine Zaunseder, Saskia Haupt, Ulrike Mütze, Sven F. Garbade, Stefan Kölker, Vincent Heuveline

Date Published: 1st May 2022

Publication Type: Journal

TESS asteroseismology of the Kepler red giants

Abstract (Expand)

ABSTRACT Red giant asteroseismology can provide valuable information for studying the Galaxy as demonstrated by space missions like CoRoT and Kepler. However, previous observations have been limited …d to small data sets and fields of view. The TESS mission provides far larger samples and, for the first time, the opportunity to perform asteroseimic inference from full-frame images full-sky, instead of narrow fields and pre-selected targets. Here, we seek to detect oscillations in TESS data of the red giants in the Kepler field using the 4-yr Kepler results as a benchmark. Because we use 1–2 sectors of observation, our results are representative of the typical scenario from TESS data. We detect clear oscillations in ∼3000 stars with another ∼1000 borderline (low S/N) cases. In comparison, best-case predictions suggest ∼4500 detectable oscillating giants. Of the clear detections, we measure Δν in 570 stars, meaning a ∼20 per cent Δν yield (14 per cent for one sector and 26 per cent for two sectors). These yields imply that typical (1–2 sector) TESS data will result in significant detection biases. Hence, to boost the number of stars, one might need to use only νmax as the seismic input for stellar property estimation. However, we find little bias in the seismic measurements and typical scatter is about 5–6 per cent in νmax and 2–3 per cent in Δν. These values, coupled with typical uncertainties in parallax, Teff, and [Fe/H] in a grid-based approach, would provide internal uncertainties of 3 per cent in inferred stellar radius, 6 per cent in mass, and 20 per cent in age for low-luminosity giant stars. Finally, we find red giant seismology is not significantly affected by seismic signal confusion from blending for stars with Tmag ≲ 12.5.

Authors: Dennis Stello, Nicholas Saunders, Sam Grunblatt, Marc Hon, Claudia Reyes, Daniel Huber, Timothy R Bedding, Yvonne Elsworth, Rafael A García, Saskia Hekker, Thomas Kallinger, Savita Mathur, Benoit Mosser, Marc H Pinsonneault

Date Published: 1st May 2022

Publication Type: Journal

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