@article{15079, abstract = {Large complex systems tend to develop universal patterns that often represent their essential characteristics. For example, the cumulative effects of independent or weakly dependent random variables often yield the Gaussian universality class via the central limit theorem. For non-commutative random variables, e.g. matrices, the Gaussian behavior is often replaced by another universality class, commonly called random matrix statistics. Nearby eigenvalues are strongly correlated, and, remarkably, their correlation structure is universal, depending only on the symmetry type of the matrix. Even more surprisingly, this feature is not restricted to matrices; in fact Eugene Wigner, the pioneer of the field, discovered in the 1950s that distributions of the gaps between energy levels of complicated quantum systems universally follow the same random matrix statistics. This claim has never been rigorously proved for any realistic physical system but experimental data and extensive numerics leave no doubt as to its correctness. Since then random matrices have proved to be extremely useful phenomenological models in a wide range of applications beyond quantum physics that include number theory, statistics, neuroscience, population dynamics, wireless communication and mathematical finance. The ubiquity of random matrices in natural sciences is still a mystery, but recent years have witnessed a breakthrough in the mathematical description of the statistical structure of their spectrum. Random matrices and closely related areas such as log-gases have become an extremely active research area in probability theory. This workshop brought together outstanding researchers from a variety of mathematical backgrounds whose areas of research are linked to random matrices. While there are strong links between their motivations, the techniques used by these researchers span a large swath of mathematics, ranging from purely algebraic techniques to stochastic analysis, classical probability theory, operator algebra, supersymmetry, orthogonal polynomials, etc.}, author = {Erdös, László and Götze, Friedrich and Guionnet, Alice}, issn = {1660-8933}, journal = {Oberwolfach Reports}, number = {4}, pages = {3459--3527}, publisher = {European Mathematical Society}, title = {{Random matrices}}, doi = {10.4171/owr/2019/56}, volume = {16}, year = {2020}, } @inproceedings{15082, abstract = {Two plane drawings of geometric graphs on the same set of points are called disjoint compatible if their union is plane and they do not have an edge in common. For a given set S of 2n points two plane drawings of perfect matchings M1 and M2 (which do not need to be disjoint nor compatible) are disjoint tree-compatible if there exists a plane drawing of a spanning tree T on S which is disjoint compatible to both M1 and M2. We show that the graph of all disjoint tree-compatible perfect geometric matchings on 2n points in convex position is connected if and only if 2n ≥ 10. Moreover, in that case the diameter of this graph is either 4 or 5, independent of n.}, author = {Aichholzer, Oswin and Obmann, Julia and Patak, Pavel and Perz, Daniel and Tkadlec, Josef}, booktitle = {36th European Workshop on Computational Geometry}, location = {Würzburg, Germany, Virtual}, title = {{Disjoint tree-compatible plane perfect matchings}}, year = {2020}, } @inproceedings{15086, abstract = {Many communication-efficient variants of SGD use gradient quantization schemes. These schemes are often heuristic and fixed over the course of training. We empirically observe that the statistics of gradients of deep models change during the training. Motivated by this observation, we introduce two adaptive quantization schemes, ALQ and AMQ. In both schemes, processors update their compression schemes in parallel by efficiently computing sufficient statistics of a parametric distribution. We improve the validation accuracy by almost 2% on CIFAR-10 and 1% on ImageNet in challenging low-cost communication setups. Our adaptive methods are also significantly more robust to the choice of hyperparameters. }, author = {Faghri, Fartash and Tabrizian, Iman and Markov, Ilia and Alistarh, Dan-Adrian and Roy, Daniel and Ramezani-Kebrya, Ali }, booktitle = {Advances in Neural Information Processing Systems}, isbn = {9781713829546}, location = {Vancouver, Canada}, publisher = {Neural Information Processing Systems Foundation}, title = {{Adaptive gradient quantization for data-parallel SGD}}, volume = {33}, year = {2020}, } @article{15142, abstract = {Bacteria and archaea employ CRISPR (clustered, regularly, interspaced, short palindromic repeats)-Cas (CRISPR-associated) systems as a type of adaptive immunity to target and degrade foreign nucleic acids. While a myriad of CRISPR-Cas systems have been identified to date, type I-C is one of the most commonly found subtypes in nature. Interestingly, the type I-C system employs a minimal Cascade effector complex, which encodes only three unique subunits in its operon. Here, we present a 3.1 Å resolution cryo-EM structure of the Desulfovibrio vulgaris type I-C Cascade, revealing the molecular mechanisms that underlie RNA-directed complex assembly. We demonstrate how this minimal Cascade utilizes previously overlooked, non-canonical small subunits to stabilize R-loop formation. Furthermore, we describe putative PAM and Cas3 binding sites. These findings provide the structural basis for harnessing the type I-C Cascade as a genome-engineering tool.}, author = {O’Brien, Roisin E. and Santos, Inês C. and Wrapp, Daniel and Bravo, Jack Peter Kelly and Schwartz, Evan A. and Brodbelt, Jennifer S. and Taylor, David W.}, issn = {2041-1723}, journal = {Nature Communications}, keywords = {General Physics and Astronomy, General Biochemistry, Genetics and Molecular Biology, General Chemistry, Multidisciplinary}, publisher = {Springer Nature}, title = {{Structural basis for assembly of non-canonical small subunits into type I-C Cascade}}, doi = {10.1038/s41467-020-19785-8}, volume = {11}, year = {2020}, } @article{15152, abstract = {Transcription factors (TFs) regulate gene expression through chromatin where nucleosomes restrict DNA access. To study how TFs bind nucleosome-occupied motifs, we focused on the reprogramming factors OCT4 and SOX2 in mouse embryonic stem cells. We determined TF engagement throughout a nucleosome at base-pair resolution in vitro, enabling structure determination by cryo–electron microscopy at two preferred positions. Depending on motif location, OCT4 and SOX2 differentially distort nucleosomal DNA. At one position, OCT4-SOX2 removes DNA from histone H2A and histone H3; however, at an inverted motif, the TFs only induce local DNA distortions. OCT4 uses one of its two DNA-binding domains to engage DNA in both structures, reading out a partial motif. These findings explain site-specific nucleosome engagement by the pluripotency factors OCT4 and SOX2, and they reveal how TFs distort nucleosomes to access chromatinized motifs.}, author = {Michael, Alicia Kathleen and Grand, Ralph S. and Isbel, Luke and Cavadini, Simone and Kozicka, Zuzanna and Kempf, Georg and Bunker, Richard D. and Schenk, Andreas D. and Graff-Meyer, Alexandra and Pathare, Ganesh R. and Weiss, Joscha and Matsumoto, Syota and Burger, Lukas and Schübeler, Dirk and Thomä, Nicolas H.}, issn = {1095-9203}, journal = {Science}, number = {6498}, pages = {1460--1465}, publisher = {American Association for the Advancement of Science }, title = {{Mechanisms of OCT4-SOX2 motif readout on nucleosomes}}, doi = {10.1126/science.abb0074}, volume = {368}, year = {2020}, } @article{15153, abstract = {Mammalian circadian rhythms are generated by a transcription-based feedback loop in which CLOCK:BMAL1 drives transcription of its repressors (PER1/2, CRY1/2), which ultimately interact with CLOCK:BMAL1 to close the feedback loop with ~24 hr periodicity. Here we pinpoint a key difference between CRY1 and CRY2 that underlies their differential strengths as transcriptional repressors. Both cryptochromes bind the BMAL1 transactivation domain similarly to sequester it from coactivators and repress CLOCK:BMAL1 activity. However, we find that CRY1 is recruited with much higher affinity to the PAS domain core of CLOCK:BMAL1, allowing it to serve as a stronger repressor that lengthens circadian period. We discovered a dynamic serine-rich loop adjacent to the secondary pocket in the photolyase homology region (PHR) domain that regulates differential binding of cryptochromes to the PAS domain core of CLOCK:BMAL1. Notably, binding of the co-repressor PER2 remodels the serine loop of CRY2, making it more CRY1-like and enhancing its affinity for CLOCK:BMAL1.}, author = {Fribourgh, Jennifer L and Srivastava, Ashutosh and Sandate, Colby R and Michael, Alicia Kathleen and Hsu, Peter L and Rakers, Christin and Nguyen, Leslee T and Torgrimson, Megan R and Parico, Gian Carlo G and Tripathi, Sarvind and Zheng, Ning and Lander, Gabriel C and Hirota, Tsuyoshi and Tama, Florence and Partch, Carrie L}, issn = {2050-084X}, journal = {eLife}, keywords = {General Immunology and Microbiology, General Biochemistry, Genetics and Molecular Biology, General Medicine, General Neuroscience}, publisher = {eLife Sciences Publications}, title = {{Dynamics at the serine loop underlie differential affinity of cryptochromes for CLOCK:BMAL1 to control circadian timing}}, doi = {10.7554/elife.55275}, volume = {9}, year = {2020}, } @article{15220, abstract = {A new window is opening in high-energy astronomy: X-ray polarimetry. With many missions currently under development and scheduled to launch as early as 2021, observations of the X-ray polarization of accreting X-ray pulsars will soon be available. As polarization is particularly sensitive to the geometry of the emission region, the upcoming polarimeters will shed new light on the emission mechanism of these objects, provided that we have sound theoretical models that agree with current spectroscopic and timing observation and that can make predictions of the polarization parameters of the emission. We here present a new model for the polarized emission of accreting X-ray pulsars in the accretion column scenario that for the first time takes into account the macroscopic structure and dynamics of the accretion region and the propagation of the radiation towards the observer, including relativistic beaming, gravitational lensing, and quantum electrodynamics. In this paper, we present all the details of the model, while in a companion paper, we apply our model to predict the polarization parameters of the bright X-ray pulsar Hercules X-1.}, author = {Caiazzo, Ilaria and Heyl, Jeremy}, issn = {1365-2966}, journal = {Monthly Notices of the Royal Astronomical Society}, keywords = {Space and Planetary Science, Astronomy and Astrophysics}, number = {1}, pages = {109--128}, publisher = {Oxford University Press}, title = {{Polarization of accreting X-ray pulsars. I. A new model}}, doi = {10.1093/mnras/staa3428}, volume = {501}, year = {2020}, } @article{15221, abstract = {We employ our new model for the polarized emission of accreting X-ray pulsars to describe the emission from the luminous X-ray pulsar Hercules X-1. In contrast with previous works, our model predicts the polarization parameters independently of spectral formation, and considers the structure and dynamics of the accretion column, as well as the additional effects on propagation due to general relativity and quantum electrodynamics. We find that our model can describe the observed pulse fraction and the pulse shape of the main peak, as well as the modulation of the cyclotron line with phase. We pick two geometries, assuming a single accretion column or two columns at the magnetic poles, that can describe current observations of pulse shape and cyclotron modulation with phase. Both models predict a high polarization fraction, between 60 and 80 per cent in the 1–10 keV range, that is phase and energy dependent, and that peaks at the same phase as the intensity. The phase and energy dependence of the polarization fraction and of the polarization angle can help discern between the different geometries.}, author = {Caiazzo, Ilaria and Heyl, Jeremy}, issn = {1365-2966}, journal = {Monthly Notices of the Royal Astronomical Society}, keywords = {Space and Planetary Science, Astronomy and Astrophysics}, number = {1}, pages = {129--136}, publisher = {Oxford University Press}, title = {{Polarization of accreting X-ray pulsars – II. Hercules X-1}}, doi = {10.1093/mnras/staa3429}, volume = {501}, year = {2020}, } @article{15223, abstract = {Using photometry collected with the Zwicky Transient Facility, we are conducting an ongoing survey for binary systems with short orbital periods ( with the goal of identifying new gravitational-wave sources detectable by the upcoming Laser Interferometer Space Antenna (LISA). We present a sample of 15 binary systems discovered thus far, with orbital periods ranging from 6.91 to 56.35 minutes. Of the 15 systems, seven are eclipsing systems that do not show signs of significant mass transfer. Additionally, we have discovered two AM Canum Venaticorum systems and six systems exhibiting primarily ellipsoidal variations in their lightcurves. We present follow-up spectroscopy and high-speed photometry confirming the nature of these systems, estimates of their LISA signal-to-noise ratios, and a discussion of their physical characteristics.}, author = {Burdge, Kevin B. and Prince, Thomas A. and Fuller, Jim and Kaplan, David L. and Marsh, Thomas R. and Tremblay, Pier-Emmanuel and Zhuang, Zhuyun and Bellm, Eric C. and Caiazzo, Ilaria and Coughlin, Michael W. and Dhillon, Vik S. and Gaensicke, Boris and Rodríguez-Gil, Pablo and Graham, Matthew J. and Hermes, JJ and Kupfer, Thomas and Littlefair, S. P. and Mróz, Przemek and Phinney, E. S. and Roestel, Jan van and Yao, Yuhan and Dekany, Richard G. and Drake, Andrew J. and Duev, Dmitry A. and Hale, David and Feeney, Michael and Helou, George and Kaye, Stephen and Mahabal, Ashish. A. and Masci, Frank J. and Riddle, Reed and Smith, Roger and Soumagnac, Maayane T. and Kulkarni, S. R.}, issn = {1538-4357}, journal = {The Astrophysical Journal}, keywords = {Space and Planetary Science, Astronomy and Astrophysics}, number = {1}, publisher = {American Astronomical Society}, title = {{A systematic search of Zwicky transient facility data for ultracompact binary LISA-detectable gravitational-wave sources}}, doi = {10.3847/1538-4357/abc261}, volume = {905}, year = {2020}, } @article{15224, abstract = {When a star exhausts its nuclear fuel, it either explodes as a supernova or more quiescently becomes a white dwarf, an object about half the mass of our Sun with a radius of about that of the Earth. About one-fifth of white dwarfs exhibit the presence of magnetic fields, whose origin has long been debated as either the product of previous stages of evolution or of binary interactions. We here report the discovery of two massive and magnetic white-dwarf members of young star clusters in the Gaia second data release (DR2) database, while a third massive and magnetic cluster white dwarf was already reported in a previous paper. These stars are most likely the product of single-star evolution and therefore challenge the merger scenario as the only way to produce magnetic white dwarfs. The progenitor masses of these stars are all above 5 solar masses, and there are only two other cluster white dwarfs whose distances have been unambiguously measured with Gaia and whose progenitors' masses fall in this range. This high incidence of magnetic white dwarfs indicates that intermediate-mass progenitors are more likely to produce magnetic remnants and that a fraction of magnetic white dwarfs forms from intermediate-mass stars.}, author = {Caiazzo, Ilaria and Heyl, Jeremy and Richer, Harvey and Cummings, Jeffrey and Fleury, Leesa and Hegarty, James and Kalirai, Jason and Kerr, Ronan and Thiele, Sarah and Tremblay, Pier-Emmanuel and Villanueva, Michael}, issn = {2041-8213}, journal = {The Astrophysical Journal Letters}, keywords = {Space and Planetary Science, Astronomy and Astrophysics}, number = {1}, publisher = {American Astronomical Society}, title = {{Intermediate-mass stars become magnetic white dwarfs}}, doi = {10.3847/2041-8213/abb5f7}, volume = {901}, year = {2020}, } @inproceedings{15228, abstract = {We describe a new implementation of a broad-band soft X-ray polarimeter, substantially based on a previous design. This implementation, the Pioneer Soft X-ray Polarimeter (PiSoX) is a SmallSat, designed for NASA’s call for Astrophysics Pioneers, small missions that could be CubeSats, balloon experiments, or SmallSats. As in REDSoX, the grating arrangement is designed optimally for the purpose of polarimetry with broad-band focussing optics by matching the dispersion of the spectrometer channels to laterally graded multilayers (LGMLs). The system can achieve polarization modulation factors over 90%. For PiSoX, the optics are lightweight Si mirrors in a one-bounce parabolic configuration. High efficiency, blazed gratings from opposite sectors are oriented to disperse to a LGML forming a channel covering the wavelength range from 35 Å to 75 Å (165 - 350 eV). Upon satellite rotation, the intensities of the dispersed spectra, after reflection and polarizing by the LGMLs, give the three Stokes parameters needed to determine a source’s linear polarization fraction and orientation. The design can be extended to higher energies as LGMLs are developed further. We describe examples of the potential scientific return from instruments based on this design.}, author = {Marshall, Herman L. and Heine, Sarah and Garner, Alan and Gullikson, Eric and Guenther, Moritz and Leitz, Christopher and Masterson, Rebecca and Miller, Eric and Zhang, William and Boissay Malaquin, Rozenn and Caiazzo, Ilaria and Chakrabarty, Deepto and Davidson, Rosemary and Gallo, Luigi and Heilmann, Ralf K. and Heyl, Jeremy and Kara, Erin and Marscher, Alan and Schulz, Norbert}, booktitle = {Space Telescopes and Instrumentation 2020: Ultraviolet to Gamma Ray}, isbn = {978-151063675-0}, issn = {1996-756X}, location = {Virtual}, publisher = {SPIE}, title = {{A small satellite version of a soft x-ray polarimeter}}, doi = {10.1117/12.2562811}, volume = {11444}, year = {2020}, } @inproceedings{15229, abstract = {We propose a high-time-resolution, high-spectral-resolution X-ray telescope that uses transition-edge sensors (TES) as detectors and collector optics to direct the X-rays onto the focal plane, providing a large effective area in a small satellite. The key science driver of the instrument is to study neutron stars and accreting black holes. The proposed instrument is built upon two technologies that are already at high TRL: TES X-ray detectors and collector optics.}, author = {Heyl, Jeremy and Caiazzo, Ilaria and Gallagher, Sarah and Hoffman, Kelsey and Safi-Harb, Samar}, booktitle = {Space Telescopes and Instrumentation 2020: Ultraviolet to Gamma Ray}, isbn = {978-151063675-0}, issn = {1996-756X}, location = {Virtual}, publisher = {SPIE}, title = {{The Colibrì high-resolution x-ray telescope}}, doi = {10.1117/12.2562625}, volume = {11444}, year = {2020}, } @article{15286, author = {Fäßler, Florian and Dimchev, Georgi A and Hodirnau, Victor-Valentin and Zens, Bettina and Möhl, Christoph and Bradke, Frank and Schur, Florian KM}, issn = {1435-8115}, journal = {Microscopy and Microanalysis}, keywords = {Instrumentation}, number = {S2}, pages = {2518--2519}, publisher = {Oxford University Press}, title = {{Cryo-electron tomography workflows for quantitative analysis of actin networks involved in cell migration}}, doi = {10.1017/s1431927620021881}, volume = {26}, year = {2020}, } @inproceedings{10556, abstract = {In this paper, we present the first Asynchronous Distributed Key Generation (ADKG) algorithm which is also the first distributed key generation algorithm that can generate cryptographic keys with a dual (f,2f+1)-threshold (where f is the number of faulty parties). As a result, using our ADKG we remove the trusted setup assumption that the most scalable consensus algorithms make. In order to create a DKG with a dual (f,2f+1)- threshold we first answer in the affirmative the open question posed by Cachin et al. [7] on how to create an Asynchronous Verifiable Secret Sharing (AVSS) protocol with a reconstruction threshold of f+1