cometadata/datacite-rtg-text-other-reclassification-records huggingface dataset:
Experimentally Validated Hopping-Transport Model for Energetically Disordered Organic Semiconductors
Creators: name: Upreti, Tanvi
name: Wang, Yuming
name: Zhang, Huotian
name: Scheunemann, Dorothea
name: Gao, Feng
name: Kemerink, Martijn
Publisher: name: arXiv
Year: 2021
Subjects: subject: Materials Science (cond-mat.mtrl-sci)
subject: FOS: Physical sciences

description: Charge transport in disordered organic semiconductors occurs by hopping of charge carriers between localized sites that are randomly distributed in a strongly energy dependent density of states. Extracting disorder and hopping parameters from experimental data like temperature dependent current-voltage characteristics typically relies on parametrized mobility functionals that are integrated in a drift-diffusion solver. Surprisingly, the functional based on the extended Gaussian disorder model (eGDM) has been extremely successful at this, despite it being based on the assumption of nearest neighbor hopping (nnH) on a regular lattice. We here propose a variable range hopping (VRH) model that has been integrated in a freeware drift-diffusion solver. The mobility model has been calibrated using kinetic Monte Carlo calculations and shows good agreement with the Monte Carlo calculations over the experimentally relevant part of the parameter space. The model is applied to temperature-dependent space charge limited current (SCLC) measurements of different systems. In contrast to the eGDM, the VRH model provides a consistent description of both p-type and n-type devices. We find a critical ratio of aNN/$α$ (mean inter-site distance / localization radius) of ~3 below which hopping to non-nearest neighbors becomes important around room temperature and the eGDM cannot be used for parameter extraction. Typical (Gaussian) disorder values in the range 45-120 meV are found, without any clear correlation with photovoltaic performance when the same active layer is used in an organic solar cell.
title: Kovarianzfunktionen der 1. und 2. Ableitungen des Schwerepotentials in der Ebene
Creators: name: Keller, W.
name: Meier, S.
Publisher: name: Zentralinstitut für Physik der Erde
Year: 1980

description: Ausgehend von der Kovarianzfunktion der Schwere (Schwereanomalie) und aufbauend auf den Arbeiten von GRAFAREND (1971, a-d, 1972, 1975), JORDAN (1972) und MORITZ (1974, 1975, 1976) werden die Autokovarianzfunktionen (AKF) der 1. und 2. Ableitungen des Schwerepotentials (Störpotentials) sowie sämtliche Kreuzkovarianzfunktionen (KKF) zwischen ihnen mit den Regeln der Kovarianzfortpflanzung in ebenen, homogenen, isotropen und differenzierbaren Zufallsfeldern abgeleitet. Das quadratische, bezüglich der Hauptdiagonale (AKF) symmetrische AKF-KKF-Schema umfaßt 9 x 9 = 81 Funktionen: 9 AKF der 1. und 2. Ableitungen des Schwerepotentials und 72 KKF zwischen ihnen. Davon sind 44 Funktionen (8 AKF, 36 KKF) durch Transformationen zu gewinnen. Als Ausgangsmodelle werden verallgemeinerte HIRVONEN-Modelle (MORITZ-, HIRVONEN- und POISSON-Modelle), das GAUSS-Modell sowie als Schwingungstyp die Spaltfunktion benutzt. Die abgeleiteten Funktionen lassen sich, in Polarkoordinaten-Schreibweise, als Skalarprodukte von Vektoren gewisser entfernungsabhängiger und winkelabhängiger Kompositionsfunktionen darstellen. Sie sind, anwendungsorientiert, in Tabellen zusammengefaßt. Die entfernungsabhängigen Kompositionsfunktionen sind für alle Modelle graphisch dargestellt. Im Grenzfall verschwindender Entfernungsdifferenz ergeben sich vollständige Varianz-Kovarianz-Schemata für einunddemselben Punkt der Ebene. Die benutzten mathematischen Grundlagen der Kovarianzfortpflanzung im (ebenen) Schwerefeld sind im Anhang behandelt.
description: Veröffentlichungen des Zentralinstituts für Physik der Erde; 60; ISSN 05148790
Low-threshold bistability of slow light in photonic-crystal waveguides
Creators: name: Mingaleev, Sergei F.
name: Miroshnichenko, Andrey E.
name: Kivshar, Yuri S.
Publisher: name: arXiv
Year: 2008
Subjects: subject: Optics (physics.optics)
subject: FOS: Physical sciences

description: We analyze the resonant transmission of light through a photonic-crystal waveguide side coupled to a Kerr nonlinear cavity, and demonstrate how to design the structure geometry for achieving bistability and all-optical switching at ultra-low powers in the slow-light regime. We show that the resonance quality factor in such structures scales inversely proportional to the group velocity of light at the resonant frequency and thus grows indefinitely in the slow-light regime. Accordingly, the power threshold required for all-optical switching in such structures scales as a square of the group velocity, rapidly vanishing in the slow-light regime.
description: LaTeX, 6 pages, 4 figures
Asynchronous and Multiprecision Linear Solvers - Scalable and Fault-Tolerant Numerics for Energy Efficient High Performance Computing
Creators: name: Anzt, Hartwig
Publisher: name: Karlsruher Institut für Technologie (KIT)
Year: 2012
Subjects: Asynchronous Relaxation
Energy-Efficient Numerics
GPU-Computing

description: Asynchronous methods minimize idle times by removing synchronization barriers, and therefore allow the efficient usage of computer systems. The implied high tolerance with respect to communication latencies improves the fault tolerance. As asynchronous methods also enable the usage of the power and energy saving mechanisms provided by the hardware, they are suitable candidates for the highly parallel and heterogeneous hardware platforms that are expected for the near future.
EVALUATING MONETARY POLICY'S ROLE IN DRIVING ECONOMIC GROWTH IN NIGERIA
Creators: name: Samuel, Ikenna Eze
Publisher: name: AYDEN JOURNAL
Year: 2024
Subjects: Monetary Policy Variables, Real Sector Growth, Monetary Policy Rate, Treasury Bill Rate

description: This study examined the relationship between monetary policy variables and growth of the real sector in Nigeria. Time series data were sourced from Central Bank of Nigeria statistical bulletin from 1987-2021.  Manufacturing sector gross domestic product was used as dependent variables while open market operation, monetary policy rate, Treasury bill rate and real interest rate were used as independent variables. Multiple regressions with econometrics view statistical package were used as data analysis techniques. Co-integration, Granger Causality Test and Augmented Unit Root Test were used to determine the long and the short run relationship that exist among the variables.  The adjusted R2 from the model proved that the independent variables can explain 73 percent changes on the growth of manufacturing sector. The study conclude that open market operation have positive and significant relationship with growth of the manufacturing sector, that monetary policy rate have positive and significant relationship with growth of the manufacturing sector, that treasury bill rate have positive and significant relationship with growth of the manufacturing sector while real interest rate have negative and significant relationship with growth of the manufacturing sector. The study recommend that the monetary authority should devise measures of managing the variation in indirect monetary policy variables. The regulatory authorities should strengthen its operational structure to enhance the operational efficiency of the financial market to attract foreign investors. The monetary authorities should strengthen indirect monetary policy variables as well as macroeconomic environment that encourages stability in the variables. Government through Central Bank of Nigeria should strengthen existing policies on the monetary policy instruments so as to increase and stabilize money supply in the economy
Brain tumour segmentation using a triplanar ensemble of U-Nets
Creators: name: Sundaresan, Vaanathi
name: Griffanti, Ludovica
name: Jenkinson, Mark
Publisher: name: arXiv
Year: 2021
Subjects: subject: Image and Video Processing (eess.IV)
subject: Computer Vision and Pattern Recognition (cs.CV)
subject: FOS: Electrical engineering, electronic engineering, information engineering
subject: FOS: Computer and information sciences

description: Gliomas appear with wide variation in their characteristics both in terms of their appearance and location on brain MR images, which makes robust tumour segmentation highly challenging, and leads to high inter-rater variability even in manual segmentations. In this work, we propose a triplanar ensemble network, with an independent tumour core prediction module, for accurate segmentation of these tumours and their sub-regions. On evaluating our method on the MICCAI Brain Tumor Segmentation (BraTS) challenge validation dataset, for tumour sub-regions, we achieved a Dice similarity coefficient of 0.77 for both enhancing tumour (ET) and tumour core (TC). In the case of the whole tumour (WT) region, we achieved a Dice value of 0.89, which is on par with the top-ranking methods from BraTS'17-19. Our method achieved an evaluation score that was the equal 5th highest value (with our method ranking in 10th place) in the BraTS'20 challenge, with mean Dice values of 0.81, 0.89 and 0.84 on ET, WT and TC regions respectively on the BraTS'20 unseen test dataset.
Gambling and COVID-19: Initial Findings from a UK Sample.
Creators: name: Sharman, Steve
name: Roberts, Amanda
name: Bowden-Jones, Henrietta
name: Strang, John
Publisher: name: Apollo - University of Cambridge Repository
Year: 2021
Subjects: Gambling
Disordered Gambling
Behavioural Addiction
Lockdown
Covid-19

description: In response to the COVID-19 pandemic, the UK Government placed society on 'lockdown', altering the gambling landscape. This study sought to capture the immediate lockdown-enforced changes in gambling behaviour. UK adults (n = 1028) were recruited online. Gambling behaviour (frequency and weekly expenditure, perceived increase/decrease) was measured using a survey-specific questionnaire. Analyses compared gambling behaviour as a function of pre-lockdown gambling status, measured by the Brief Problem Gambling Scale. In the whole sample, gambling participation decreased between pre- and during-lockdown. Both gambling frequency and weekly expenditure decreased during the first month of lockdown overall, but, the most engaged gamblers did not show a change in gambling behaviour, despite the decrease in opportunity and availability. Individuals whose financial circumstances were negatively affected by lockdown were more likely to perceive an increase in gambling than those whose financial circumstances were not negatively affected. Findings reflect short-term behaviour change; it will be crucial to examine, at future release of lockdown, if behaviour returns to pre-lockdown patterns, or whether new behavioural patterns persist.
Mid-Infrared interferometry of dust around massive evolved stars
Creators: name: Rajagopal, Jayadev
name: Menut, Jean-Luc
name: Wallace, D.
name: Danchi, W. C.
name: Chesneau, O.
name: Lopez, B.
name: Monnier, J. D.
name: Ireland, M.
name: Tuthill, P. G.
Publisher: name: arXiv
Year: 2007
Subjects: subject: Astrophysics (astro-ph)
subject: FOS: Physical sciences

description: We report long-baseline interferometric measurements of circumstellar dust around massive evolved stars with the MIDI instrument on the Very Large Telescope Interferometer and provide spectrally dispersed visibilities in the 8-13 micron wavelength band. We also present diffraction-limited observations at 10.7 micron on the Keck Telescope with baselines up to 8.7 m which explore larger scale structure. We have resolved the dust shells around the late type WC stars WR 106 and WR 95, and the enigmatic NaSt1 (formerly WR 122), suspected to have recently evolved from a Luminous Blue Variable (LBV) stage. For AG Car, the protoypical LBV in our sample, we marginally resolve structure close to the star, distinct from the well-studied detached nebula. The dust shells around the two WC stars show fairly constant size in the 8-13 micron MIDI band, with gaussian half-widths of ~ 25 to 40 mas. The compact dust we detect around NaSt1 and AG Car favors recent or ongoing dust formation. Using the measured visibilities, we build spherically symmetric radiative transfer models of the WC dust shells which enable detailed comparison with existing SED-based models. Our results indicate that the inner radii of the shells are within a few tens of AU from the stars. In addition, our models favor grain size distributions with large (~ 1 micron) dust grains. This proximity of the inner dust to the hot central star emphasizes the difficulty faced by current theories in forming dust in the hostile environment around WR stars. Although we detect no direct evidence for binarity for these objects, dust production in a colliding-wind interface in a binary system is a feasible mechanism in WR systems under these conditions.
description: 21 pages, 4 tables, 13 figures. Accepted for publication in the Astrophysical Journal
Phase Diagram of the Dirac Spectrum at Nonzero Chemical Potential
Creators: name: Osborn, J. C.
name: Splittorff, K.
name: Verbaarschot, J. J. M.
Publisher: name: arXiv
Year: 2008
Subjects: subject: High Energy Physics - Lattice (hep-lat)
subject: FOS: Physical sciences

description: The Dirac spectrum of QCD with dynamical fermions at nonzero chemical potential is characterized by three regions, a region with a constant eigenvalue density, a region where the eigenvalue density shows oscillations that grow exponentially with the volume and the remainder of the complex plane where the eigenvalue density is zero. In this paper we derive the phase diagram of the Dirac spectrum from a chiral Lagrangian. We show that the constant eigenvalue density corresponds to a pion condensed phase while the strongly oscillating region is given by a kaon condensed phase. The normal phase with nonzero chiral condensate but vanishing Bose condensates coincides with the region of the complex plane where there are no eigenvalues.
description: 17 pages, 3 figures
Massive planet migration: Theoretical predictions and comparison with observations
Creators: name: Armitage, Philip J.
Publisher: name: arXiv
Year: 2007
Subjects: subject: Astrophysics (astro-ph)
subject: FOS: Physical sciences

description: We quantify the utility of large radial velocity surveys for constraining theoretical models of Type II migration and protoplanetary disk physics. We describe a theoretical model for the expected radial distribution of extrasolar planets that combines an analytic description of migration with an empirically calibrated disk model. The disk model includes viscous evolution and mass loss via photoevaporation. Comparing the predicted distribution to a uniformly selected subsample of planets from the Lick / Keck / AAT planet search programs, we find that a simple model in which planets form in the outer disk at a uniform rate, migrate inward according to a standard Type II prescription, and become stranded when the gas disk is dispersed, is consistent with the radial distribution of planets for orbital radii 0.1 AU < a < 2.5 AU and planet masses greater than 1.65 Jupiter masses. Some variant models are disfavored by existing data, but the significance is limited (~95%) due to the small sample of planets suitable for statistical analysis. We show that the favored model predicts that the planetary mass function should be almost independent of orbital radius at distances where migration dominates the massive planet population. We also study how the radial distribution of planets depends upon the adopted disk model. We find that the distribution can constrain not only changes in the power-law index of the disk viscosity, but also sharp jumps in the efficiency of angular momentum transport that might occur at small radii.
description: ApJ, in press. References updated to match published version
Late Medieval Climate Changes in the Tropical Atlantic and Interannual Variability Documented in Northeastern Caribbean Corals
Creators: name: Xu, Yuanyuan
Publisher: name: Digital Repository at the University of Maryland
Year: 2014
Subjects: subject: Geochemistry
subject: FOS: Earth and related environmental sciences

description: Tropical sea surface temperature (SST) has been implicated as a driver of climate changes during the Medieval Climate Anomaly (MCA, 950-1300 CE) but little data exist from the tropical oceans for this time period.  I collected multiple Diploria strigosa coral colonies from Anegada, British Virgin Islands (18.73°N, 63.33°W) in order to reconstruct climate in the northeastern Caribbean and tropical North Atlantic during the MCA.  My Sr/Ca-temperature calibration results derived from three modern Diploria strigosa corals suggest that the temperature sensitivity for Diploria strigosa is -0.048 (±0.001) mmol/mol°C-1.  My reconstruction of MCA climate suggests cooler and wetter conditions in the northeastern Caribbean during the late MCA, indicating that a Pacific La Niña-type climate pattern may have influenced local conditions.  Additional analysis indicates that the North Atlantic Oscillation (NAO) was the principal driver of interannual climate variability during the late MCA.
Warming the early Earth - CO2 reconsidered
Creators: name: von Paris, P.
name: Rauer, H.
name: Grenfell, L.
name: Patzer, B.
name: Hedelt, P.
name: Stracke, B.
name: Trautmann, T.
name: Schreier, F.
Publisher: name: arXiv
Year: 2008
Subjects: subject: Astrophysics (astro-ph)
subject: FOS: Physical sciences

description: Despite a fainter Sun, the surface of the early Earth was mostly ice-free. Proposed solutions to this so-called "faint young Sun problem" have usually involved higher amounts of greenhouse gases than present in the modern-day atmosphere. However, geological evidence seemed to indicate that the atmospheric CO2 concentrations during the Archaean and Proterozoic were far too low to keep the surface from freezing. With a radiative-convective model including new, updated thermal absorption coefficients, we found that the amount of CO2 necessary to obtain 273 K at the surface is reduced up to an order of magnitude compared to previous studies. For the late Archaean and early Proterozoic period of the Earth, we calculate that CO2 partial pressures of only about 2.9 mb are required to keep its surface from freezing which is compatible with the amount inferred from sediment studies. This conclusion was not significantly changed when we varied model parameters such as relative humidity or surface albedo, obtaining CO2 partial pressures for the late Archaean between 1.5 and 5.5 mb. Thus, the contradiction between sediment data and model results disappears for the late Archaean and early Proterozoic.
description: 53 pages, 4 tables, 11 figures, published in Planetary and Space Science
Statistical properties of fast radio bursts elucidate their origins: magnetars are favoured over gamma-ray bursts
Creators: name: Cui, Xiang-Han
name: Zhang, Cheng-Min
name: Wang, Shuang-Qiang
name: Zhang, Jian-Wei
name: Li, Di
name: Peng, Bo
name: Zhu, Wei-Wei
name: Strom, Richard
name: Wang, Na
name: Wu, Qingdong
name: Ye, Chang-Qing
name: Wang, De-Hua
name: Yang, Yi-Yan
name: Diao, Zhen-Qi
Publisher: name: arXiv
Year: 2021
Subjects: subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: FOS: Physical sciences

description: Fast radio bursts (FRBs) are extremely strong radio flares lasting several milliseconds, most of which come from unidentified objects at a cosmological distance. They can be apparently repeating or not. In this paper, we analyzed 18 repeaters and 12 non-repeating FRBs observed in the frequency bands of 400-800 MHz from CHIME. We investigated the distributions of FRB isotropic-equivalent radio luminosity, considering the K correction. Statistically, the luminosity distribution can be better fitted by Gaussian form than by power-law. Based on the above results, together with the observed FRB event rate, pulse duration, and radio luminosity, FRB origin models are evaluated and constrained such that the gamma-ray bursts (GRBs) may be excluded for the non-repeaters while magnetars or neutron stars (NSs) emitting the supergiant pulses are preferred for the repeaters. We also found the necessity of a small FRB emission beaming solid angle (about 0.1 sr) from magnetars that should be considered, and/or the FRB association with soft gamma-ray repeaters (SGRs) may lie at a low probability of about 10%. Finally, we discussed the uncertainty of FRB luminosity caused by the estimation of the distance that is inferred by the simple relation between the redshift and dispersion measure (DM).
description: 12 pages, 2 figures, 2 tables. Accepted in Research in Astronomy and Astrophysics (RAA)
Electron waves in chemically substituted graphene
Creators: name: Peres, N. M. R.
name: Klironomos, F. D.
name: Tsai, S. -W.
name: Santos, J. R.
name: Santos, J. M. B. Lopes dos
name: Neto, A. H. Castro
Publisher: name: arXiv
Year: 2007
Subjects: subject: Materials Science (cond-mat.mtrl-sci)
subject: Strongly Correlated Electrons (cond-mat.str-el)
subject: FOS: Physical sciences

description: We present exact analytical and numerical results for the electronic spectra and the Friedel oscillations around a substitutional impurity atom in a graphene lattice. A chemical dopant in graphene introduces changes in the on-site potential as well as in the hopping amplitude. We employ a T-matrix formalism and find that disorder in the hopping introduces additional interference terms around the impurity that can be understood in terms of bound, semi-bound, and unbound processes for the Dirac electrons. These interference effects can be detected by scanning tunneling microscopy.
description: 4 pages, 7 figures
Polynomial Structure of the (Open) Topological String Partition Function
Creators: name: Alim, M.
name: Laenge, J. D.
Publisher: name: arXiv
Year: 2007
Subjects: subject: High Energy Physics - Theory (hep-th)
subject: FOS: Physical sciences

description: In this paper we show that the polynomial structure of the topological string partition function found by Yamaguchi and Yau for the quintic holds for an arbitrary Calabi-Yau manifold with any number of moduli. Furthermore, we generalize these results to the open topological string partition function as discussed recently by Walcher and reproduce his results for the real quintic.
description: 15 pages
A SYSTEMATIC APPROXIMATION TO THE NEURAL MOTOR CONTROL OF FORWARD, BACKWARD AND LATERAL TOE-TAPPING IN CHILDREN AND ADULTS
Creators: name: Karim, Mohammad Ehsanul
Publisher: name: Digital Repository at the University of Maryland
Year: 2014
Subjects: subject: Neurosciences
subject: FOS: Clinical medicine
subject: Biomechanics
subject: Kinesiology
subject: Toe tapping
subject: Uncontrolled Manifold

description: The neural motor control of forward, backward and lateral toe-tapping of typically developing adults, 6- and 10-year-old children was investigated using the uncontrolled manifold technique. Our results indicate that the central nervous system (CNS) controls or stabilizes three functional variables (center of mass, toe and head position) by organizing the overall joint variability structure, more than the individual joints. Results reveal: (1) children control forward and backward stepping more than adults, and (2) adults' forward stepping is more controlled than backward or lateral stepping. The relative ranking defining the approximate neural motor control of toe-tapping is: center of mass, toe and head position; indicating the CNS focuses on balance and foot placement. The observed invariance of this structure across movement phase, tap direction, and age, reinforces the idea that the CNS controls multi-directional toe-tap motion using similar neural control strategy.
The Discovery of Water Maser Emission from Eight Nearby Galaxies
Creators: name: Braatz, J. A.
name: Gugliucci, N. E.
Publisher: name: arXiv
Year: 2008
Subjects: subject: Astrophysics (astro-ph)
subject: FOS: Physical sciences

description: Using the Green Bank Telescope, we conducted a ``snapshot'' survey for water maser emission toward the nuclei of 611 galaxies and detected eight new sources. The sample consisted of nearby (v < 5000 km/s) and luminous (M_B < -19.5) galaxies, some with known nuclear activity but most not previously known to host AGNs. Our detections include both megamasers associated with AGNs and relatively low luminosity masers probably associated with star formation. The detection in UGC 3789 is particularly intriguing because the spectrum shows both systemic and high-velocity lines indicative of emission from an AGN accretion disk seen edge-on. Based on six months of monitoring, we detected accelerations among the systemic features ranging from 2 to 8 km/s/yr, the larger values belonging to the most redshifted systemic components. High-velocity maser lines in UGC 3789 show no detectable drift over the same period. Although UGC 3789 was not known to be an AGN prior to this survey, the presence of a disk maser is strong evidence for nuclear activity, and an optical spectrum obtained later has confirmed it. With follow up observations, it may be possible to measure a geometric distance to UGC 3789.
description: to appear in Astrophysical Journal, 1 May 2008
China’s Policy of Noninterference in Nigeria
Creators: name: MODESTUS, Queen
name: YANG，Mingxing
Publisher: name: Apollo - University of Cambridge Repository
Year: 2020
Subjects: Sino-Nigeria
Non-Interference
Diplomatic Discourse
Human Right
Sovereignty

description: This article examines the emerging diplomatic discourse in Sino-Nigeria relations with emphasis on China’s foreign policy of non-interference. The current paper is based on the premise that China’s principle of non-interference is a current debated issue in the International Community. International observers have argued on the implications of this principle for democracy and human rights in the country with some -the revisionist- calling on China to revise the stance, especially, in the face of human rights violations. While others -the conservative- have pointed out that Beijing has made a sharp but stylish U-turn from the policy of non-interference into that of systemic involvement and calls on China to maintain the policy - in words and practices - in order to protect the divine laws of sovereignty. Therefore, this paper, with specific emphasis on Nigeria, seeks to examine the ‘conservative’ and ‘revisionist’ approach of this principle in China’s contemporary relations with the country. It analyzes the current debate and its implications for the policy of non-interference, especially as stipulated in international law, and on what ground is a state permitted to interfere in the domestic affairs of another state. The study revealed that China’s application of non-interference principle in its relationship with Nigeria has been consistent and that political and economic investment in the country does not equal to interference. Although international law allows for interference in the face of human rights violations, however, China still maintains its stance even in such situations as it believes that human rights are subjective and interference on such grounds could be easily abused by super powers. Finally, the author using the conservative and revisionist approach revisits the current debate surrounding China’s policy of non-interference with the revisionist calling on China to be more sensitive to the internal dynamics while the conservative points to the the divine doctrine of sovereignty which they claim is repugnant to interference
ATLAS sensitivity to Wtb anomalous couplings in top quark decays
Creators: name: Aguilar-Saavedra, J. A.
name: Carvalho, J.
name: Castro, N.
name: Onofre, A.
name: Veloso, F.
Publisher: name: arXiv
Year: 2007
Subjects: subject: High Energy Physics - Phenomenology (hep-ph)
subject: FOS: Physical sciences

description: We study the sensitivity of the ATLAS experiment to Wtb anomalous couplings in top pair production with semileptonic decay, pp -> t tbar -> W+ b W- bbar, with one of the W bosons decaying leptonically and the other hadronically. Several observables are examined, including the W helicity fractions and new quantities recently introduced, such as the ratios of helicity fractions and some angular asymmetries defined in the W rest frame. The dependence on anomalous couplings of all these observables has been previously obtained. In this work we show that some of the new observables also have smaller systematic uncertainties than the helicity fractions, with a dependence on anomalous couplings similar or stronger than for helicity fractions. Consequently, their measurement can significantly improve the limits on anomalous couplings. Moreover, the most sensitive measurements can be combined. In this case, the precision achieved in the determination of Wtb anomalous couplings can be of a few percent in the semileptonic channel alone.
description: LaTeX 22 pages. ATLAS scientific note SN-ATLAS-2007-064. Final version to appear in EPJC
Association between meteorological factors and COVID-19: a systematic review
Creators: name: Chen, Sujuan
name: Huang, Lin
name: Cai, Dongjie
name: Li, Bixia
name: Yang, Jun
Publisher: name: Taylor & Francis
Year: 2022
Subjects: Medicine
Environmental Sciences not elsewhere classified
Biological Sciences not elsewhere classified
Science Policy

description: The outbreak of coronavirus disease in 2019 has become a serious threat to human health. Whether meteorological conditions could influence the transmission and virulence of COVID-19 remains controversial. In this study, we systematically reviewed the impact of temperature and humidity on the replication, morbidity, and mortality of COVID-19. We also discussed the main factors underlying the inconsistency across studies. Pubmed, Web of Science, Embase, and Scopus were used to identify papers published up to 7 December 2020. We initially identified 3515 papers, and 28 articles met the inclusion criteria after screening. Most studies showed high temperature and high humidity can partly reduce the reproduction, morbidity, and mortality of COVID-19. But the rest papers failed to identify a significant association. The discrepant results may be related to the difference in the climate context, study design, exposure assessment, policy intervention, socioeconomic status, and public health service.
Topology-driven ordering of flocking matter
Creators: name: Chardac, Amélie
name: Hoffmann, Ludwig A.
name: Poupart, Yoann
name: Giomi, Luca
name: Bartolo, Denis
Publisher: name: arXiv
Year: 2021
Subjects: subject: Soft Condensed Matter (cond-mat.soft)
subject: FOS: Physical sciences

description: When interacting motile units self-organize into flocks, they realize one of the most robust ordered state found in nature. However, after twenty five years of intense research, the very mechanism controlling the ordering dynamics of both living and artificial flocks has remained unsettled. Here, combining active-colloid experiments, numerical simulations and analytical work, we explain how flocking liquids heal their spontaneous flows initially plagued by collections of topological defects to achieve long-ranged polar order even in two dimensions. We demonstrate that the self-similar ordering of flocking matter is ruled by a living network of domain walls linking all $\pm 1$ vortices, and guiding their annihilation dynamics. Crucially, this singular orientational structure echoes the formation of extended density patterns in the shape of interconnected bow ties. We establish that this double structure emerges from the interplay between self-advection and density gradients dressing each $-1$ topological charges with four orientation walls. We then explain how active Magnus forces link all topological charges with extended domain walls, while elastic interactions drive their attraction along the resulting filamentous network of polarization singularities. Taken together our experimental, numerical and analytical results illuminate the suppression of all flow singularities, and the emergence of pristine unidirectional order in flocking matter.
description: 14 pages, 5 figures
Lichens in Diverse Landscapes: EREN-NEON Flexible Learning Project
Creators: name: Dudley, Leah
Publisher: name: QUBES Educational Resources
Year: 2021

description: This project makes use of publicly-available datasets on lichen presence and abundance and wet deposition, paired with geospatial data on air quality, tree canopy cover, and locally collected field data, to better understand how lichens respond to changes
Comparing equilibration schemes of high-molecular-weight polymer melts with topological indicators.
Creators: name: Tubiana, Luca
name: Kobayashi, Hideki
name: Potestio, Raffaello
name: Dünweg, Burkhard
name: Kremer, Kurt
name: Virnau, Peter
name: Daoulas, Kostas
Publisher: name: Apollo - University of Cambridge Repository
Year: 2021
Subjects: Paper
Multiscale Simulation Methods for Soft Matter Systems
multiscale simulations
polymer modelling
polymer melts
topological properties
molecular knots

description: Recent theoretical studies have demonstrated that the behaviour of molecular knots is a sensitive indicator of polymer structure. Here, we use knots to verify the ability of two state-of-the-art algorithms-configuration assembly and hierarchical backmapping-to equilibrate high-molecular-weight (MW) polymer melts. Specifically, we consider melts with MWs equivalent to several tens of entanglement lengths and various chain flexibilities, generated with both strategies. We compare their unknotting probability, unknotting length, knot spectra, and knot length distributions. The excellent agreement between the two independent methods with respect to knotting properties provides an additional strong validation of their ability to equilibrate dense high-MW polymeric liquids. By demonstrating this consistency of knotting behaviour, our study opens the way for studying topological properties of polymer melts beyond time and length scales accessible to brute-force molecular dynamics simulations.
KMOS study of the mass accretion rate from Class I to Class II in NGC 1333
Creators: name: Fiorellino, Eleonora
name: Manara, Carlo Felice
name: Nisini, Brunella
name: Ramsay, Suzanne
name: Antoniucci, Simone
name: Giannini, Teresa
name: Biazzo, Katia
name: Alcalà, Juan
name: Fedele, Davide
Publisher: name: arXiv
Year: 2021
Subjects: subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: FOS: Physical sciences

description: The mass accretion rate is the fundamental parameter to understand the process of mass assembly that results in the formation of a low-mass star. This parameter has been largely studied in Classical TTauri stars in star-forming regions with ages of 1-10Myr. However, little is known about the accretion properties of young stellar objects (YSOs) in younger regions and early stages of star formation, such as in the Class0/I phases. We present new NIR spectra of 17 ClassI/Flat and 35 ClassII sources located in the young (<1Myr) NGC1333 cluster, acquired with the KMOS instrument at the VLT. Our goal is to study whether the mass accretion rate evolves with age, as suggested by the widely adopted viscous evolution model, by comparing the properties of the NGC1333 members with samples of older regions. We measured the stellar parameters and accretion rates of our sample, finding a correlation between accretion and stellar luminosity, and between mass accretion rate and stellar mass. Both correlations are compatible within the errors with the older Lupus star-forming region, while only the latter is consistent with results from ChamaeleonI. The ClassI sample shows larger accretion luminosities with respect to the ClassII stars of the same cloud. However, the derived accretion rates are not sufficiently high to build up the inferred stellar masses, assuming steady accretion during the ClassI lifetime. This suggests that the sources are not in their main accretion phase and that most of their mass has already been accumulated during a previous stage and/or that the accretion is an episodic phenomenon. We show that some of the targets originally classified as Class I through Spitzer photometry are in fact evolved or low accreting objects. This evidence can have implications for the estimated protostellar phase lifetimes. Further observations are needed to determine if this is a general result.
Bordered Riemann surfaces in C^2
Creators: name: Forstneric, Franc
name: Wold, Erlend Fornaess
Publisher: name: arXiv
Year: 2007
Subjects: subject: Complex Variables (math.CV)
subject: Algebraic Geometry (math.AG)
subject: FOS: Mathematics
subject: 32C22, 32E10, 32H05, 32M17 (Primary); 14H55 (Secondary)

description: One of the oldest open problems in the classical function theory is whether every open Riemann surface admits a proper holomorphic embedding into C^2. In this paper we prove the following Theorem: If D is a bordered Riemann surface whose closure admits an injective immersion in C^2 that is holomorphic in D, then D admits a proper holomorphic embedding in C^2. The most general earlier results are due to J. Globevnik and B. Stensones (Math. Ann. 303 (1995), 579-597) and E. F. Wold (Internat. J. Math. 17 (2006), 963-974). We give an explicit and elementary construction that does not require the Teichmuller space theory, and we also indicate another possible proof using the latter theory.
description: 24 pages, 2 figures. To appear in J. Math. Pure Appl
Co-training for Deep Object Detection: Comparing Single-modal and Multi-modal Approaches
Creators: name: Gómez, Jose L.
name: Villalonga, Gabriel
name: López, Antonio M.
Publisher: name: arXiv
Year: 2021
Subjects: subject: Computer Vision and Pattern Recognition (cs.CV)
subject: Machine Learning (cs.LG)
subject: FOS: Computer and information sciences

description: Top-performing computer vision models are powered by convolutional neural networks (CNNs). Training an accurate CNN highly depends on both the raw sensor data and their associated ground truth (GT). Collecting such GT is usually done through human labeling, which is time-consuming and does not scale as we wish. This data labeling bottleneck may be intensified due to domain shifts among image sensors, which could force per-sensor data labeling. In this paper, we focus on the use of co-training, a semi-supervised learning (SSL) method, for obtaining self-labeled object bounding boxes (BBs), i.e., the GT to train deep object detectors. In particular, we assess the goodness of multi-modal co-training by relying on two different views of an image, namely, appearance (RGB) and estimated depth (D). Moreover, we compare appearance-based single-modal co-training with multi-modal. Our results suggest that in a standard SSL setting (no domain shift, a few human-labeled data) and under virtual-to-real domain shift (many virtual-world labeled data, no human-labeled data) multi-modal co-training outperforms single-modal. In the latter case, by performing GAN-based domain translation both co-training modalities are on pair; at least, when using an off-the-shelf depth estimation model not specifically trained on the translated images.
Critical behavior of the 2d scalar theory: resumming the ${\rm N}^8{\rm LO}$ perturbative mass gap
Creators: name: Heymans, Gustavo O.
name: Pinto, Marcus Benghi
Publisher: name: arXiv
Year: 2021
Subjects: subject: High Energy Physics - Theory (hep-th)
subject: Other Condensed Matter (cond-mat.other)
subject: High Energy Physics - Phenomenology (hep-ph)
subject: FOS: Physical sciences

description: We apply the optimized perturbation theory (OPT) to resum the perturbative series describing the mass gap of the bidimensional $ϕ^4$ theory in the $\mathbb{Z}_2$ symmetric phase. Already at NLO (one loop) the method is capable of generating a quite reasonable non-perturbative result for the critical coupling. At order-$g^7$ we obtain $g_c = 2.779(25)$ which compares very well with the state of the art ${\rm N}^8{\rm LO}$ result, $g_c = 2.807(34)$. As a novelty we investigate the supercritical region showing that it contains some useful complimentary information that can be used in extrapolations to arbitrarily high orders.
description: For more accuracy some sentences have been rephrased in this v2. 16 pages, 6 figures
Signatures of Pseudoscalar Photon Mixing in CMB Radiation
Creators: name: Agarwal, Nishant
name: Jain, Pankaj
name: McKay, Douglas W.
name: Ralston, John P.
Publisher: name: arXiv
Year: 2008
Subjects: subject: High Energy Physics - Phenomenology (hep-ph)
subject: Astrophysics (astro-ph)
subject: FOS: Physical sciences

description: We model the effect of photon and ultra-light pseudoscalar mixing on the propagation of electromagnetic radiation through the extragalactic medium. The medium is modelled as a large number of magnetic domains, uncorrelated with one another. We obtain an analytic expression for the different Stokes parameters in the limit of small mixing angle. The different Stokes parameters are found to increase linearly with the number of domains. We also verify this result by direct numerical simulations. We use this formalism to estimate the effect of pseudoscalar-photon mixing on the Cosmic Microwave Background (CMB) polarization. We impose limits on the model parameters by the CMB observations. We find that the currently allowed parameter range admits a CMB circular polarization up to order $10^{-7}$.
description: 17 pages, 5 figures
How robust are the constraints on cosmology and galaxy evolution from the lens-redshift test?
Creators: name: Capelo, Pedro R.
name: Natarajan, Priyamvada
Publisher: name: arXiv
Year: 2007
Subjects: subject: Astrophysics (astro-ph)
subject: FOS: Physical sciences

description: The redshift distribution of galaxy lenses in known gravitational lens systems provides a powerful test that can potentially discriminate amongst cosmological models. However, applications of this elegant test have been curtailed by two factors: our ignorance of how galaxies evolve with redshift, and the absence of methods to deal with the effect of incomplete information in lensing systems. In this paper, we investigate both issues in detail. We explore how to extract the properties of evolving galaxies, assuming that the cosmology is well determined by other techniques. We propose a new nested Monte Carlo method to quantify the effects of incomplete data. We apply the lens-redshift test to an improved sample of seventy lens systems derived from recent observations, primarily from the SDSS, SLACS and the CLASS surveys. We find that the limiting factor in applying the lens-redshift test derives from poor statistics, including incomplete information samples, and biased sampling. Many lenses that uniformly sample the underlying true image separation distribution will be needed to use this test as a complementary method to measure the value of the cosmological constant or the properties of evolving galaxies. Planned future surveys by missions like the SNAP satellite or LSST are likely to usher in a new era for strong lensing studies that utilize this test. With expected catalogues of thousands of new strong lenses, the lens-redshift test could offer a powerful tool to probe cosmology as well as galaxy evolution.
description: 17 pages, 10 figures, 3 tables. Invited contribution to the "Gravitational Lensing" Focus Issue of the New Journal of Physics. Minor revisions to match accepted version by the journal
Dynamic region proposal networks for semantic segmentation in automated glaucoma screening
Creators: name: Shah, Shivam
name: Kasukurthi, Nikhil
name: Pande, Harshit
Publisher: name: arXiv
Year: 2021
Subjects: subject: Computer Vision and Pattern Recognition (cs.CV)
subject: Machine Learning (cs.LG)
subject: Image and Video Processing (eess.IV)
subject: FOS: Computer and information sciences
subject: FOS: Electrical engineering, electronic engineering, information engineering

description: Screening for the diagnosis of glaucoma through a fundus image can be determined by the optic cup to disc diameter ratio (CDR), which requires the segmentation of the cup and disc regions. In this paper, we propose two novel approaches, namely Parameter-Shared Branched Network (PSBN) andWeak Region of Interest Model-based segmentation (WRoIM) to identify disc and cup boundaries. Unlike the previous approaches, the proposed methods are trained end-to-end through a single neural network architecture and use dynamic cropping instead of manual or traditional computer vision-based cropping. We are able to achieve similar performance as that of state-of-the-art approaches with less number of network parameters. Our experiments include comparison with different best known methods on publicly available Drishti-GS1 and RIM-ONE v3 datasets. With $7.8 \times 10^6$ parameters our approach achieves a Dice score of 0.96/0.89 for disc/cup segmentation on Drishti-GS1 data whereas the existing state-of-the-art approach uses $19.8\times 10^6$ parameters to achieve a dice score of 0.97/0.89.
Spatiotemporal correlations of earthquakes in the continuum limit of the one-dimensional Burridge-Knopoff model
Creators: name: Mori, Takahiro
name: Kawamura, Hikaru
Publisher: name: arXiv
Year: 2008
Subjects: subject: Other Condensed Matter (cond-mat.other)
subject: FOS: Physical sciences

description: Spatiotemporal correlations of the one-dimensional spring-block (Burridge-Knopoff) model of earthquakes, either with or without the viscosity term, are studied by means of numerical computer simulations. The continuum limit of the model is examined by systematically investigating the model properties with varying the block-size parameter a toward a\to 0. The Kelvin viscosity term is introduced so that the model dynamics possesses a sensible continuum limit. In the presence of the viscosity term, many of the properties of the original discrete BK model are kept qualitatively unchanged even in the continuum limit, although the size of minimum earthquake gets smaller as a gets smaller. One notable exception is the existence/non-existence of the doughnut-like quiescence prior to the mainshock. Although large events of the original discrete BK model accompany seismic acceleration together with a doughnut-like quiescence just before the mainshock, the spatial range of the doughnut-like quiescence becomes narrower as a gets smaller, and in the continuum limit, the doughnut-like quiescence might vanish altogether. The doughnut-like quiescence observed in the discrete BK model is then a phenomenon closely related to the short-length cut-off scale of the model.
Route to nonlocal cosmology
Creators: name: Calcagni, Gianluca
name: Montobbio, Michele
name: Nardelli, Giuseppe
Publisher: name: arXiv
Year: 2007
Subjects: subject: High Energy Physics - Theory (hep-th)
subject: Astrophysics (astro-ph)
subject: General Relativity and Quantum Cosmology (gr-qc)
subject: FOS: Physical sciences

description: An analytic approach to phenomenological models inspired by cubic string field theory is introduced and applied to some examples. We study a class of actions for a minimally coupled, homogeneous scalar field whose energy density contains infinitely many time derivatives. These nonlocal systems are systematically localized and an algorithm to find cosmological solutions of the dynamical equations is provided. Our formalism is able to define the nonlocal field in regions of the parameter space which are inaccessible by standard methods. Also, problems related to nonlocality are reinterpreted under a novel perspective and naturally overcome. We consider phenomenological models living on a Friedmann-Robertson-Walker background with power-law scale factor, both in four dimensions and on a high-energy braneworld. The quest for solutions unravels general features of nonlocal dynamics indicating several future directions of investigation.
description: 20 pages, 3 figures. v2: references addded, typos corrected, discussion improved; v3: matches the published version