cometadata/datacite-rtg-text-other-reclassification-records huggingface dataset:
Calibration of quasi-static aberrations in exoplanet direct-imaging instruments with a Zernike phase-mask sensor. IV. Temporal stability of non-common path aberrations in VLT/SPHERE
Creators: name: Vigan, A.
name: Dohlen, K.
name: N'Diaye, M.
name: Cantalloube, F.
name: Girard, J.
name: Milli, J.
name: Sauvage, J. -F.
name: Wahhaj, Z.
name: Zins, G.
name: Beuzit, J. -L.
name: Caillat, A.
name: Costille, A.
name: Merrer, J. Le
name: Mouillet, D.
name: Tourenq, S.
Publisher: name: arXiv
Year: 2022
Subjects: subject: Instrumentation and Methods for Astrophysics (astro-ph.IM)
subject: FOS: Physical sciences

description: Coronagraphic imaging of exoplanets using ground-based instruments on large telescopes is intrinsically limited by speckles induced by uncorrected aberrations. These aberrations originate from the imperfect correction of the atmosphere by an extreme adaptive optics system; from static optical defects; or from small opto-mechanical variations due to changes in temperature, pressure, or gravity vector. More than the speckles themselves, the performance of high-contrast imagers is ultimately limited by their temporal stability, since most post-processing techniques rely on difference of images acquired at different points in time. Identifying the origin of the aberrations and the timescales involved is therefore crucial to understanding the fundamental limits of dedicated high-contrast instruments. We previously demonstrated the use of a Zernike wavefront sensor called ZELDA for sensing non-common path aberrations (NCPA) in VLT/SPHERE. We now use ZELDA to investigate the stability of the instrumental aberrations using 5 long sequences of measurements obtained at high cadence on the internal source. Our study reveals two regimes of decorrelation of the NCPA. The first, with a characteristic timescale of a few seconds and an amplitude of a few nanometers, is induced by a fast internal turbulence within the enclosure. The second is a slow quasi-linear decorrelation on the order of a few $10^{-3}$ nm rms/s that acts on timescales from minutes to hours. We use coronagraphic image reconstruction to demonstrate that these two NCPA contributions have a measurable impact on differences of images, and that the fast internal turbulence is a dominating term over to the slow linear decorrelation. We also use dedicated sequences where the derotator and atmospheric dispersion compensators emulate a real observation to demonstrate the importance of performing observations symmetric around the meridian.
description: 14 pages, 15 figures. Accepted for publication in A&A
Tracking the 3D evolution of a halo coronal mass ejection using the revised cone model
Creators: name: Zhang, Q. M.
Publisher: name: arXiv
Year: 2022
Subjects: subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: FOS: Physical sciences

description: This paper aims to track the 3D evolution of a full halo CME on 2011 June 21. The CME results from a non-radial eruption of a filament-carrying flux rope in NOAA active region 11236. The eruption is observed in EUV wavelengths by the EUVI on board the ahead and behind STEREO spacecrafts and the AIA on board SDO. The CME is observed by the COR1 coronagraph on board STEREO and the C2 coronagraph on board SOHO/LASCO. The revised cone model is slightly modified, with the top of the cone becoming a sphere, which is internally tangent to the legs. Using the multi-point observations, the cone model is applied to derive the morphological and kinematic properties of the CME. The cone shape fits nicely with the CME observed by EUVI and COR1 on board STEREO twin spacecraft and LASCO/C2 coronagraph. The cone angle increases sharply from 54$^{\circ}$ to 130$^{\circ}$ in the initial phase, indicating a rapid expansion. A relation between the cone angle and heliocentric distance of CME leading front is derived, $ω=130\degr-480d^{-5}$, where $d$ is in unit of $R_{\odot}$. The inclination angle decreases gradually from $\sim$51$^{\circ}$ to $\sim$18$^{\circ}$, suggesting a trend of radial propagation. The heliocentric distance increases gradually in the initial phase and quickly in the later phase up to $\sim$11\,$R_{\odot}$. The true speed of CME reaches $\sim$1140 km s$^{-1}$, which is $\sim$1.6 times higher than the apparent speed in the LASCO/C2 field of view. The revised model is promising in tracking the complete evolution of CMEs.
description: 7 pages, 11 figures, accepted for publication in A&A, comments are welcome
Algebraic fibre spaces with strictly nef relative anti-log canonical divisor
Creators: name: Liu, Jie
name: Ou, Wenhao
name: Wang, Juanyong
name: Yang, Xiaokui
name: Zhong, Guolei
Publisher: name: arXiv
Year: 2021
Subjects: subject: Algebraic Geometry (math.AG)
subject: Complex Variables (math.CV)
subject: Differential Geometry (math.DG)
subject: FOS: Mathematics
subject: 14E30, 14H30, 14J45, 32Q57, 53C22

description: Let $(X,Δ)$ be a projective klt pair, and $f:X\to Y$ a fibration to a smooth projective variety $Y$ with strictly nef relative anti-log canonical divisor $-(K_{X/Y}+Δ)$. We prove that $f$ is a locally constant fibration with rationally connected fibres, and the base $Y$ is a canonically polarized hyperbolic projective manifold. In particular, when $Y$ is a single point, we establish that $X$ is rationally connected. Moreover, when $\dim X=3$ and $-(K_X+Δ)$ is strictly nef, we prove that $-(K_X+Δ)$ is ample, which confirms the singular version of a conjecture of Campana-Peternell for threefolds.
description: 24 pages
Validation of e$^+$e$^-$ Pair Production Total Cross Sections for Monte Carlo Particle Transport
Creators: name: Basaglia, Tulio
name: Begalli, Marcia
name: Choi, Chansoo
name: Han, Min Cheol
name: Hoff, Gabriela
name: Kim, Chan Hyeong
name: Pia, Maria Grazia
name: Saracco, Paolo
Publisher: name: arXiv
Year: 2022
Subjects: subject: Computational Physics (physics.comp-ph)
subject: High Energy Physics - Phenomenology (hep-ph)
subject: FOS: Physical sciences

description: Several sources of total cross sections for e$^+$e$^-$ pair production by photon interaction with matter, used by major Monte Carlo codes for particle transport, are quantitatively evaluated with respect to experimental measurements collected from the literature. They include data libraries deriving from theoretical calculations and analytical formulae representing empirical fits to tabulations. Although most of these sources of cross sections are based on one theoretical reference, the statistical data analysis documented in the paper highlights differences in their compatibility with experiment. The cross sections collected in the 1997 version of the Evaluated Photon Data Library (EPDL) exhibit the lowest incompatibility with experiment; the paper details the validation results for all the examined cross section sources. The scarcity of experimental data does not allow the validation process to discern pair production in the field of the nucleus and in the field of atomic electrons; nevertheless, the paper documents relevant clues regarding the contribution of the latter to reproduce experimental measurements.
description: Accepted for publication in IEEE Transactions on Nuclear Science
Takagi Function Identities on Dyadic Rationals
Creators: name: Monroe, Laura
Publisher: name: arXiv
Year: 2021
Subjects: subject: Combinatorics (math.CO)
subject: Data Structures and Algorithms (cs.DS)
subject: Classical Analysis and ODEs (math.CA)
subject: Number Theory (math.NT)
subject: FOS: Mathematics
subject: FOS: Computer and information sciences
subject: 68R05 (Primary) 26A27 (Secondary), 05C05, 28A80

description: The number of unbalanced interior nodes of divide-and-conquer trees on $n$ leaves is known to form a sequence of dilations of the Takagi function on dyadic rationals. We use this fact to derive identities on the Takagi function and on the Hamming weight of an integer in terms of the Takagi function.
description: 11 pages, 1 figure. This paper is a small portion of arXiv:2108.11496 with some additions, split for publication. Version 2 adds references to another proof of the weight theorem and makes some notation changes. Version 3 is the published version
Strictly nef divisors on singular threefolds
Creators: name: Wang, Juanyong
name: Zhong, Guolei
Publisher: name: arXiv
Year: 2021
Subjects: subject: Algebraic Geometry (math.AG)
subject: FOS: Mathematics
subject: 14E30, 14J30

description: Let $X$ be a normal projective variety with only klt singularities, and $L_X$ a strictly nef $\mathbb{Q}$-divisor on $X$. In this paper, we study the singular version of Serrano's conjecture, i.e., the ampleness of $K_X+t L_X$ for sufficiently large $t\gg 1$. We show that, if $X$ is assumed to be a $\mathbb{Q}$-factorial Gorenstein terminal threefold, then $K_X+tL_X$ is ample for $t\gg 1$ unless $X$ is a weak Calabi-Yau variety (i.e., the canonical divisor $K_X\sim_\mathbb{Q}0$ and the augmented irregularity $q^\circ(X)=0$) with $L_X\cdot c_2(X)=0$.
description: 23 pages; this article is a revision of the previous version arXiv: 2105.07681; new results on singular weak Calabi-Yau threefolds are added in Section 5; comments are welcome! arXiv admin note: substantial text overlap with arXiv:2105.07681
New Fixed Figure Results with the Notion of $k$-Ellipse
Creators: name: Taş, Nihal
name: Aytimur, Hülya
name: Güvenç, Şaban
Publisher: name: arXiv
Year: 2021
Subjects: subject: Metric Geometry (math.MG)
subject: FOS: Mathematics
subject: 54H25, 47H09, 47H10

description: In this paper, as a geometric approach to the fixed-point theory, we prove new fixed-figure results using the notion of $k$-ellipse on a metric space. For this purpose, we are inspired by the Caristi type contraction, Kannan type contraction, Chatterjea type contraction and Ćirić type contraction. After that, we give some existence and uniqueness theorems of a fixed $k$-ellipse. We also support our obtained results with illustrative examples. Finally, we present a new application to the $S$-Shaped Rectified Linear Activation Unit ($SReLU$) to show the importance of our theoretical results.
Bicycling crash circumstances vary by route type: a cross-sectional analysis
Creators: name: Teschke, Kay
name: Frendo, Theresa
name: Shen, Hui
name: Harris, M. Anne
name: Reynolds, Conor C.
name: Cripton, Peter Alec, 1965-
name: Brubacher, Jeffrey
name: Cusimano, Michael D.
name: Friedman, Steven M.
name: Hunte, Garth
name: Monro, Melody
name: Vernich, Lee
name: Babul, Shelina
name: Chipman, Mary
name: Winters, Meghan
Publisher: name: BioMed Central
Year: 2015

description: Background: Widely varying crash circumstances have been reported for bicycling injuries, likely because of differing bicycling populations and environments. We used data from the Bicyclists’ Injuries and the Cycling Environment Study in Vancouver and Toronto, Canada, to describe the crash circumstances of people injured while cycling for utilitarian and leisure purposes. We examined the association of crash circumstances with route type. Methods Adult cyclists injured and treated in a hospital emergency department described their crash circumstances. These were classified into major categories (collision vs. fall, motor vehicle involved vs. not) and subcategories. The distribution of circumstances was tallied for each of 14 route types defined in an earlier analysis. Ratios of observed vs. expected were tallied for each circumstance and route type combination. Results Of 690 crashes, 683 could be characterized for this analysis. Most (74%) were collisions. Collisions included those with motor vehicles (34%), streetcar (tram) or train tracks (14%), other surface features (10%), infrastructure (10%), and pedestrians, cyclists, or animals (6%). The remainder of the crashes were falls (26%), many as a result of collision avoidance manoeuvres. Motor vehicles were involved directly or indirectly with 48% of crashes. Crash circumstances were distributed differently by route type, for example, collisions with motor vehicles, including “doorings”, were overrepresented on major streets with parked cars. Collisions involving streetcar tracks were overrepresented on major streets. Collisions involving infrastructure (curbs, posts, bollards, street furniture) were overrepresented on multiuse paths and bike paths. Conclusions These data supplement our previous analyses of relative risks by route type by indicating the types of crashes that occur on each route type. This information can guide municipal engineers and planners towards improvements that would make cycling safer.
The Role of the Magnetic Anisotropy in Atomic-Spin Sensing of 1D Molecular Chains
Creators: name: Wäckerlin, Christian
name: Cahlík, Aleš
name: Goikoetxea, Joseba
name: Stesovych, Oleksandr
name: Medvedeva, Daria
name: Redondo, Jesús
name: Švec, Martin
name: Delley, Bernard
name: Ondráček, Martin
name: Pinar, Andres
name: Blanco-Rey, Maria
name: Kolorenc, Jindrich
name: Arnau, Andres
name: Jelínek, Pavel
Publisher: name: arXiv
Year: 2022
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: Strongly Correlated Electrons (cond-mat.str-el)
subject: FOS: Physical sciences

description: One-dimensional metal-organic chains often possess a complex magnetic structure susceptible to be modified by a alteration of their chemical composition. The possibility to tune their magnetic properties provides an interesting playground to explore quasiparticle interactions in low-dimensional systems. Despite the great effort invested so far, a detailed understanding of the interactions governing the electronic and magnetic properties of the low-dimensional systems is still incomplete. One of the reasons is the limited ability to characterize their magnetic properties at the atomic scale. Here, we provide a comprehensive study of the magnetic properties of metal-organic one-dimensional (1D) coordination polymers consisting of 2,5-diamino-1,4-benzoquinonediimine ligands coordinated with Co or Cr atoms synthesized in ultra-high vacuum conditions on a Au(111) surface. A combination of an integral X-ray spectroscopy with local-probe inelastic electron tunneling spectroscopy corroborated by multiplet analysis, density functional theory, and inelastic electron tunneling simulations enable us to obtain essential information about their magnetic structure, including the spin magnitude and orientation at the magnetic atoms, as well as the magnetic anisotropy.
description: 35 pages, 8 Figures, 3 tables
Generating enhanced primordial GWs during inflation with intermittent violation of NEC and diminishment of GW propagating speed
Creators: name: Cai, Yong
name: Piao, Yun-Song
Publisher: name: arXiv
Year: 2022
Subjects: subject: General Relativity and Quantum Cosmology (gr-qc)
subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: High Energy Physics - Theory (hep-th)
subject: FOS: Physical sciences

description: We investigate both the null energy condition (NEC) violating scenario and the $c_T$-diminishing scenario for generating enhanced power spectrum of primordial gravitational waves (GWs) during inflation, where $c_T$ is the propagating speed of primordial GWs. Both of these two scenarios can be realized stably with theories beyond Horndeski, hence can be uniformly implemented within the framework of the effective field theory. We calculate the power spectrum of primordial GWs by assuming that the inflationary Universe undergoes three phases, where the violation of NEC or the diminishment of $c_T$ occurs in the intermediate phase. A template of the spectrum is given for the NEC-violating scenario. We also discuss the underlying relation and discrepancy between these two scenarios with a disformal transformation.
description: 28 pages, 11 figures; two typos were corrected
A new X-ray tidal disruption event candidate with fast variability
Creators: name: Hampel, J.
name: Komossa, S.
name: Greiner, J.
name: Reiprich, T. H.
name: Freyberg, M.
name: Erben, T.
Publisher: name: arXiv
Year: 2022
Subjects: subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: Astrophysics of Galaxies (astro-ph.GA)
subject: FOS: Physical sciences

description: During a close encounter between a star and a supermassive black hole, the star can get disrupted by the black hole's tidal forces, resulting in a tidal disruption event (TDE). The accretion of the star's material onto the black hole produces strong emission in different wavelength regimes. Here we report the discovery with ROSAT of an X-ray-selected transient source in an optically non-active galaxy. At the location RA: 13h31m57.66s and Dec: -32deg3arcmin19.7arsec a sudden rise in X-ray luminosity by a factor of 8 within 8 days has been observed. Additionally, a very soft X-ray spectrum with a black-body temperature kT=0.1 keV and a peak luminosity of at least 10^43 erg/s suggest a TDE interpretation, and the observed properties are very similar to previously identified soft X-ray (ROSAT) TDEs. An optical spectrum taken of the galaxy at the position of RXJ133157.6-324319.7 six years after the X-ray outburst does not show any emission lines as would be expected from a persistent active galactic nucleus (AGN). The redshift of the galaxy is determined to be 0.051 based on absorption lines. It is therefore likely a member of the galaxy cluster Abell 3560. The rise in X-ray luminosity happens within 8 days and thus appears to be fast for such an event. No X-ray emission was detected 170 days before and 165 days after the event, and none was detected 25 years later with the Neil Gehrels Swift Observatory. The change in X-ray luminosity is at least a factor of 40.
description: 11 pages, 5 figures, accepted for publication in "Research in Astronomy and Astrophysics" (RAA)
title: Discourses of Menstruation: Girls. Menarche and Psychology
Creators: name: Lovering, Kathryn Matthews
Publisher: name: Goldsmiths, University of London
Year: 1994

description: This thesis is an investigation into the discourses and practices of menarche in psychology, in British culture and among young adolescents. Part I discusses the findings and limitations of current psychological theory about and research on adolescent girls' knowledge and experiences of menstruation through a review of psychological literature and a research project with young adolescents. The research project consisted of three studies: a series of informal group discussions on "Growing up"; questionnaires on aspects of self-concept and attitudes to menstruation with' 80 boys and 87 girls; and interviews on expectations and experiences of menarche with 44 girls. The review and research demonstrate adolescents' negative attitudes to and lack of knowledge about menstruation and the limitations of 'traditional' psychological research. Neither traditional psychological practice nor a more feminist inductive content analysis were able to account for the patriarchal nature of menstrual knowledge, the meanings of menstruation for adolescents or girls' subjective experience of menstruation. Part II traces the emergence of patriarchal conceptions and practices of menstruation in British culture and Western psychology. This is done through a discursive analysis of: the female body, sexuality and menstruation from 1600 to 1850; the scientific debates about 'The Woman Question', the female body and menstruation from 1850 to 1914; and the emergence of the 'pre- and postmenarcheal girl' in 20th century psychology from 1937 to the present. Part III presents a feminist poststructuralist discourse analysis of the inscription of young British adolescents into menstrual discourses. This is done through an analysis of the group discussions and interviews with adolescents which discusses: the discourses available to young British adolescents to make sense of menstruation, what menstruation comes to mean to adolescents and how these discourses, practices, and meanings constitute girls' subjectivity.
On threefolds with the smallest nontrivial monodromy group
Creators: name: Lvovski, Serge
Publisher: name: arXiv
Year: 2022
Subjects: subject: Algebraic Geometry (math.AG)
subject: FOS: Mathematics
subject: 14D05, 14N30

description: Using an adjunction-theoretic result due to A.J.Sommese together with a proposition from SGA7, we obtain a complete list of smooth threefolds for which the monodromy group acting on $H^2$ of its smooth hyperplane section is $\mathbb Z/2\mathbb Z$. The possibility of such a classification was announced by F.L.Zak in 1991.
description: 22 pages, Section 5.3 substantially revised
Thermodynamics of non-linearly charged Anti-de Sitter black holes in four-dimensional Critical Gravity
Creators: name: Álvarez, Abigail
name: Bravo-Gaete, Moisés
name: Juárez-Aubry, María Montserrat
name: Rodríguez, Gerardo Velázquez
Publisher: name: arXiv
Year: 2022
Subjects: subject: General Relativity and Quantum Cosmology (gr-qc)
subject: High Energy Physics - Theory (hep-th)
subject: FOS: Physical sciences

description: In this work, we provide new examples of Anti-de Sitter black holes with a planar base manifold in four-dimensional Critical Gravity by considering nonlinear electrodynamics as a matter source. We find a general solution characterized by the presence of only one integration constant where, for a suitable election of coupling constants, we can show the existence of one or more horizons. Additionally, we compute its non-null thermodynamical quantities through a variety of techniques, testing the validity of the first law of thermodynamics as well as a Smarr formula. Finally, we analyze the local thermodynamical stability of the solutions. To our knowledge, these charged configurations are the first example with Critical Gravity where their thermodynamical quantities are not zero.
Effect of molecular and electronic geometries on the electronic density in FLO-SIC
Creators: name: Liebing, Simon
name: Trepte, Kai
name: Schwalbe, Sebastian
Publisher: name: arXiv
Year: 2022
Subjects: subject: Chemical Physics (physics.chem-ph)
subject: Computational Physics (physics.comp-ph)
subject: FOS: Physical sciences

description: Recently, Trepte et al. [J. Chem. Phys., vol. 155, 2021] pointed out the importance of analyzing dipole moments in the Fermi-Löwdin orbital (FLO) self-interaction correction (SIC) for cyclic, planar molecules. In this manuscript, the effect of the molecular and electronic geometries on dipole moments and polarizabilities is discussed for non-cyclic molecules. Computed values are presented for water, formaldehyde, and nitromethane. Continuing the work of Schwalbe et al. [J. Chem. Phys. vol. 153, (2020)], we reconfirm that systematic numerical parameter studies are essential to obtain consistent results in density functional theory (DFT) and SIC. In agreement with Trepte et al. [J. Chem. Phys., vol. 155, 2021], DFT agrees well with experiment for dipole moments, while SIC slightly overestimates them. A Linnett double-quartet electronic geometry is found to be energetically preferred for nitromethane.
description: 22 pages, 8 figures, 5 tables
SMART-Plant_IWARR2019_Sorting optimal WWTP configurations with resource recovery units under a multi-criteria decision making framework
Creators: name: Zivko Juznic-Zonta
name: Guisasola, Albert
name: Baeza, Juan Antonio
Publisher: name: Zenodo
Year: 2020
Subjects: DSS
wastewater
EBPR

description: Abstract: The effort to upgrade urban WWTP into bio-refineries capable to recover and produce valuable resources is hindered by the fact that technical, economical and environmental impact analysis are complex and time expensive. In the present work, we present a Decision Support System (DSS) that finds an optimal configuration of a WWTP given a set of resource recovery unit processes. For the case study, we consider seven innovative technologies that are tested into the SMART-Plant H2020 project (No.690323). These technologies are modelled and integrated inside a plant-wide model superstructure. We show how the DSS evaluates all the possible plant configurations and how these configurations are sorted by a Multi-Criteria Decision Making (MCDM) method. Plant design optimization is done under dynamic inflow conditions that depend on the local weather history, sewer characteristics and effluent limitations, while sorting accounts for economic, effluent quality and environmental impact multi-criteria.
The Astrometric Performance Test of 80-cm Telescope at Yaoan Station and Precise CCD Positions of Apophis
Creators: name: Guo, Bifeng
name: Peng, Qingyu
name: Chen, Ying
name: Zheng, Zhongjie
name: Shang, Yijia
name: Li, Dan
name: Chen, Xiao
Publisher: name: arXiv
Year: 2022
Subjects: subject: Instrumentation and Methods for Astrophysics (astro-ph.IM)
subject: FOS: Physical sciences

description: The 80-cm azimuthal telescope is newly mounted at Yaoan Station, Purple Mountain Observatory in 2018. The astrometric performance of the telescope is tested in the following three aspects. (a) The geometric distortion of its CCD attached. It is stable in both a single epoch and multi epochs. Eight distortion solutions are derived over about one year. The maximum values range from 0.75 to 0.79 pixel and the median values range from 0.14 to 0.16 pixel. (b) The limit magnitude of stars. About 20.5 magnitude (Gaia-G) stars can be detected with Johnson-V filter exposured in 300 seconds. The astrometric error of about 20.5 magnitude stars is estimated at 0.14 arcsec using the fitted sigmoidal function. (c) The astrometric accuracy and the precision of stacked fast-moving faint object. 24 stacked frames of the potentially hazardous asteroid (PHA) (99942) Apophis are derived on April 14 and 15, 2021 (fainter than 18 mag) based on the ephemeris shifts. During data reduction, the newest Gaia EDR3 Catalog and Jet Propulsion Laboratory Horizons ephemeris are referenced as theoretical positions of stars and Apophis, respectively. Our results show that the mean (O-C)s (observed minus computed) of Apophis are -0.018 and 0.020 arcsec in right ascention and declination, and the dispersions are estimated at 0.094 and 0.085 arcsec, respectively, which show the consistency of the stacked results by Astrometrica.
An innovative approach to managing geographical information system support for a large-scale indoor residual spraying campaign in Burundi
Creators: name: Matthey-Doret, Aude
name: Weza, Jean-Pierre
name: Lessard, Audrey
name: Ham, Frederic
name: Moeneclaey, David
Publisher: name: F1000 Research Limited
Year: 2020

description: An innovative approach to managing geographical information system support for a large-
scale indoor residual spraying campaign in Burundi presented at MSF Scientific Days International (London) Innovation Day, May 14, 2020 by Aude Matthey-Doret
Knowledge, attitudes, and practices regarding palliative care: a mixed-methods study from Bihar, India
Creators: name: Mohit Nair
name: Kumar, Pragya
name: Mahajan, Raman
name: Harshana, Amit
name: Karishma Krishna Kurup
name: Moreto-Planas, Laura
name: Burza, Sakib
Publisher: name: F1000 Research Limited
Year: 2020

description: Poster shared at MSF Scientific Days International (London), May 13/14, 2020.
Small ball probabilities for the stochastic heat equation with colored noise
Creators: name: Chen, Jiaming
Publisher: name: arXiv
Year: 2022
Subjects: subject: Probability (math.PR)
subject: FOS: Mathematics
subject: Primary, 60H15, Secondary, 60G60

description: We consider the stochastic heat equation on the 1-dimensional torus $\mathbb{T}:=\left[-1,1\right]$ with periodic boundary conditions: $$ \partial_t u(t,x)=\partial^2_x u(t,x)+σ(t,x,u)\dot{F}(t,x),\quad x\in \mathbb{T},t\in\mathbb{R}_+, $$ where $\dot{F}(t,x)$ is a generalized Gaussian noise, which is white in time and colored in space. Assuming that $σ$ is Lipschitz in $u$ and uniformly bounded, we estimate small ball probabilities for the solution $u$ when $u(0,x)\equiv 0$.
description: Published in Stochastic Processes and their Applications
X-ray fine structure of a limb solar flare revealed by Insight-HXMT, RHESSI and Fermi
Creators: name: Zhang, Ping
name: Wang, Wei
name: Su, Yang
name: Zhang, Shuangnan
name: Song, Liming
name: Lu, Fangjun
name: Zhang, Shu
Publisher: name: arXiv
Year: 2022
Subjects: subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: FOS: Physical sciences

description: We conduct a detailed analysis of an M1.3 limb flare occurring on 2017 July 3, which have the X-ray observations recorded by multiple hard X-ray telescopes, including Hard X-ray Modulation Telescope (Insight-HXMT), Ramaty High Energy Solar Spectroscopic Imager (RHESSI), and The Fermi Gamma-ray Space Telescope (FERMI). Joint analysis has also used the EUV imaging data from the Atmospheric Imaging Assembly (AIA) aboard the Solar Dynamic Observatory. The hard X-ray spectral and imaging evolution suggest a lower corona source, and the non-thermal broken power law distribution has a rather low break energy $\sim$ 15 keV. The EUV imaging shows a rather stable plasma configuration before the hard X-ray peak phase, and accompanied by a filament eruption during the hard X-ray flare peak phase. Hard X-ray image reconstruction from RHESSI data only shows one foot point source. We also determined the DEM for the peak phase by SDO/AIA data. The integrated EM beyond 10 MK at foot point onset after the peak phase, while the $>$ 10 MK source around reconnection site began to fade. The evolution of EM and hard X-ray source supports lower corona plasma heating after non-thermal energy dissipation. The combination of hard X-ray spectra and images during the limb flare provides the understanding on the interchange of non-thermal and thermal energies, and relation between lower corona heating and the upper corona instability.
description: 12 pages, 6 figures, Research in Astron. Astrophys. in press
Virtual focus groups: new frontiers in research
Creators: name: Turney, Lyn
name: Pocknee, Catherine
Publisher: name: Swinburne
Year: 2024

description: New information and communication technologies in the form of learning management systems provide unique and inventive opportunities for qualitative researchers. Their intrinsic ability to record discursive data in text format accurately and to provide safe, secure, and anonymous environments for participants makes them amenable for use as advanced research tools. In this article, the authors report on a collaborative project that tested the potential of online discussion boards for use in virtual focus groups. What the researchers found was that not only was the method theoretically sound, it actually enhanced their ability to connect with difficult-to-access populations that were disparately spread.
The E10 Wheeler-DeWitt operator at low levels
Creators: name: Kleinschmidt, Axel
name: Nicolai, Hermann
Publisher: name: arXiv
Year: 2022
Subjects: subject: High Energy Physics - Theory (hep-th)
subject: General Relativity and Quantum Cosmology (gr-qc)
subject: FOS: Physical sciences

description: We consider the Wheeler-DeWitt operator associated with the bosonic part of the Hamiltonian of D=11 supergravity in a formulation with only the spatial components of the three-form and six-form fields, and compare it with the E10 Casimir operator at low levels, to show that these two operators precisely match modulo spatial gradients up to and including gl(10) level two. The uniqueness of the E10 Casimir operator eliminates all ordering ambiguities in the quantum Hamiltonian, at least up to the level considered. Beyond level three the two operators are expected to start to differ from each other, as they do so for the classical expressions. We then consider truncations of the E10 Wheeler-DeWitt operator for various finite-dimensional subgroups of E10 in order to exhibit the automorphic properties of the associated wave functions and to show that physically sensible wave functions generically vanish at the cosmological singularity, thus providing new and more sophisticated examples of DeWitt's proposed mechanism for singularity resolution in quantum gravity. Our construction provides novel perspectives on several unresolved conceptual issues with the Wheeler-DeWitt equation, such as the question of observables in quantum gravity, or the issue of emergent space and time in a purely algebraic framework. We also highlight remaining open questions of the E10 framework.
description: 53 pages
The Canadian contribution to the otolaryngology literature: a five year bibliometric analysis
Creators: name: Gurberg, Joshua
name: Lin, June R
name: Akbari, Elaheh
name: White, Paul
name: Nunez, Desmond A
Publisher: name: BioMed Central
Year: 2016

description: Objectives: To assess the 2008–2012 Canadian contribution to the Otolaryngology literature. Methods: All articles published from January 2008 - December 2012 in 5 Otolaryngology journals were reviewed. Nationality, number of authors, and study type were extracted. The output, number of authors, and study type of Canadian papers were compared to International papers using Mantel-Haenszel Common Odds Ratio Estimate, Pearson’s Chi-Squared or Fishers exact tests. Results: 4519 papers were analyzed. There was a statistically significant decrease in Canadian authored papers from 12.8% in 2008–9 to 10.2% in 2011–12 (Fishers exact, p = .01). Multi-authorship increased in Canadian papers (χ2, p = .01). The types of studies published by Canadian Otolaryngologists did not change over the study period. Conclusions: Canadian authored papers in a sample of Otolaryngology journals decreased from 2008 to 2012. The increase in multiauthorship, whilst indicating increasing collaboration, suggests reduced per capita publication productivity. These findings warrant further study.
Antibiotics susceptibility patterns in hospitalized patients with advanced HIV in Bihar, India
Creators: name: Mahajan, Raman
name: Jiménez, Carolina
name: Moretó-Planas, Laura
name: Harshana, Amit
name: Vikash Kumar
name: Flevaud, Laurence
name: Burza, Sakib
Publisher: name: F1000 Research Limited
Year: 2020

description: Poster presented at MSF Scientific Days International (London), May 13/14, 2020.
Pressure-induced superconductivity reentrant in transition metal dichalcogenide TiSe2
Creators: name: Xia, Wei
name: Wu, Jiaxuan
name: Li, Zhongyang
name: Yuan, Jian
name: An, Chao
name: Wang, Xia
name: Yu, Na
name: Zou, Zhiqiang
name: Liu, Gang
name: Zhou, Chunyin
name: Feng, Jiajia
name: Zhang, Lili
name: Dong, Zhaohui
name: Chen, Bin
name: Yang, Zhaorong
name: Yu, Zhenhai
name: Chen, Hanghui
name: Guo, Yanfeng
Publisher: name: arXiv
Year: 2022
Subjects: subject: Superconductivity (cond-mat.supr-con)
subject: FOS: Physical sciences

description: Through either elements intercalation or application of pressure, transition metal dichalcogenide 1T-TiSe2 exhibits superconductivity in proximity to a charge density wave (CDW) quantum critical point (QCP), thus providing an ideal avenue to study the correlation between the two symmetry-breaking exotic quantum electronic states. We report herein that, in addition to the well-known superconducting dome that emerges within the low pressure range of 2 - 4 GPa and peaks with the maximal Tc of about 1.8 K, the pressure induces another separate superconducting transition starting around 15 GPa with a substantially higher Tc that reaches 5.6 K at about 21.5 GPa. The high-pressure X-ray diffraction and Raman spectroscopy measurements unveil that the superconductivity reentrant is caused by a first-order structural phase transition (from P-3m1 space group to Pnma space group), which is also supported by the density functional theory calculation. A comparative theoretical calculation also reveals that the conventional phonon-mediated mechanism can account for the superconductivity of 1T-TiSe2 under low pressure, while the electron-phonon coupling of 4O-TiSe2 under high pressure is too weak to induce the superconductivity with a Tc as high as 5.6 K. This implies that the emergent superconductivity in the 4O-TiSe2 may have an unconventional origin. Our finding would open a new window toward the discovery of more exotic quantum states in transition metal dichalcogenides via high pressure.
description: 15 pages, 4 figures
The sensitivity of GPz estimates of photo-z posterior PDFs to realistically complex training set imperfections
Creators: name: Stylianou, Natalia
name: Malz, Alex I.
name: Hatfield, Peter
name: Crenshaw, John Franklin
name: Gschwend, Julia
Publisher: name: arXiv
Year: 2022
Subjects: subject: Instrumentation and Methods for Astrophysics (astro-ph.IM)
subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: FOS: Physical sciences

description: The accurate estimation of photometric redshifts is crucial to many upcoming galaxy surveys, for example the Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST). Almost all Rubin extragalactic and cosmological science requires accurate and precise calculation of photometric redshifts; many diverse approaches to this problem are currently in the process of being developed, validated, and tested. In this work, we use the photometric redshift code GPz to examine two realistically complex training set imperfections scenarios for machine learning based photometric redshift calculation: i) where the spectroscopic training set has a very different distribution in colour-magnitude space to the test set, and ii) where the effect of emission line confusion causes a fraction of the training spectroscopic sample to not have the true redshift. By evaluating the sensitivity of GPz to a range of increasingly severe imperfections, with a range of metrics (both of photo-z point estimates as well as posterior probability distribution functions, PDFs), we quantify the degree to which predictions get worse with higher degrees of degradation. In particular we find that there is a substantial drop-off in photo-z quality when line-confusion goes above ~1%, and sample incompleteness below a redshift of 1.5, for an experimental setup using data from the Buzzard Flock synthetic sky catalogues.
description: 12 pages, 8 figures, accepted in PASP
Quantization: History and Problems
Creators: name: Carosso, Andrea
Publisher: name: arXiv
Year: 2022
Subjects: subject: History and Philosophy of Physics (physics.hist-ph)
subject: Mathematical Physics (math-ph)
subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: In this work, I explore the concept of quantization as a mapping from classical phase space functions to quantum operators. I discuss the early history of this notion of quantization with emphasis on the works of Schrödinger and Dirac, and how quantization fit into their overall understanding of quantum theory in the 1920's. Dirac, in particular, proposed a quantization map which should satisfy certain properties, including the property that quantum commutators should be related to classical Poisson brackets in a particular way. However, in 1946, Groenewold proved that Dirac's mapping was inconsistent, making the problem of defining a rigorous quantization map more elusive than originally expected. This result, known as the Groenewold-Van Hove theorem, is not often discussed in physics texts, but here I will give an account of the theorem and what it means for potential "corrections" to Dirac's scheme. Other proposals for quantization have arisen over the years, the first major one being that of Weyl in 1927, which was later developed by many, including Groenewold, and which has since become known as Weyl Quantization in the mathematical literature. Another, known as Geometric Quantization, formulates quantization in differential-geometric terms by appealing to the character of classical phase spaces as symplectic manifolds; this approach began with the work of Souriau, Kostant, and Kirillov in the 1960's. I will describe these proposals for quantization and comment on their relation to Dirac's original program. Along the way, the problem of operator ordering and of quantizing in curvilinear coordinates will be described, since these are natural questions that immediately present themselves when thinking about quantization.
description: 28 pages
Topological band structure via twisted photons in a degenerate cavity
Creators: name: Yang, Mu
name: Zhang, Hao-Qing
name: Liao, Yu-Wei
name: Liu, Zheng-Hao
name: Zhou, Zheng-Wei
name: Zhou, Xing-Xiang
name: Xu, Jin-Shi
name: Han, Yong-Jian
name: Li, Chuan-Feng
name: Guo, Guang-Can
Publisher: name: arXiv
Year: 2022
Subjects: subject: Optics (physics.optics)
subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: Synthetic dimensions based on particles' internal degrees of freedom, such as frequency, spatial modes and arrival time, have attracted significant attention. They offer ideal large-scale lattices to simulate nontrivial topological phenomena. Exploring more synthetic dimensions is one of the paths toward higher dimensional physics. In this work, we design and experimentally control the coupling among synthetic dimensions consisting of the intrinsic photonic orbital angular momentum and spin angular momentum degrees of freedom in a degenerate optical resonant cavity, which generates a periodically driven spin-orbital coupling system. We directly characterize the system's properties, including the density of states, energy band structures and topological windings, through the transmission intensity measurements. Our work demonstrates a novel mechanism for exploring the spatial modes of twisted photons as the synthetic dimension, which paves the way to design rich topological physics in a highly compact platform.
The preliminary statistical analysis of LAMOST DR8 low resolution AFGK stars
Creators: name: Chen, Yan hui
name: Li, Guang Wei
name: Shu, Hong
Publisher: name: arXiv
Year: 2022
Subjects: subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: FOS: Physical sciences

description: We download the LAMOST DR8 low resolution catalog 6,478,063 AFGK tpye stars and plot the figures of effective temperature, gravitational acceleration, and metal abundance. Some small and medium mass stars are evolved from pre-main sequence or main sequence stage to planetary nebula stage or white dwarf stage by the stellar evolution code \texttt{MESA}. We analyze the observed statistical data and model calculation results, and then obtain some basic conclusions preliminarily. Most red giant and asymptotic giant stars with log$g$ less than 0.85 have poor metal abundance. Most hot A type main-sequence stars are metal rich stars with log$g$ from 3.5 to 4.5. The conclusions are reasonable within a certain error range. The theory of a gap area in the H-R diagram for stellar evolutions of medium mass stars is reflected in the statistical figures. The central core hydrogen burning stage and the central core helium burning stage correspond to the peak structures in the gravitational acceleration statistical figures respectively. The metal abundances among A, F, G, and K type stars have a wide distribution. We can not simply replace the metal abundances of these stars with the metal abundance of the Sun when doing a fine research work.
description: 14 figures, accepted by RAA
MUSE spectroscopic observations of the Young Massive Cluster NGC1850
Creators: name: Sollima, A.
name: D'Orazi, V.
name: Gratton, R.
name: Carini, R.
name: Carretta, E.
name: Bragaglia, A.
name: Lucatello, S.
Publisher: name: arXiv
Year: 2022
Subjects: subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: Astrophysics of Galaxies (astro-ph.GA)
subject: FOS: Physical sciences

description: NGC1850 is the nearest Young Massive Cluster of the Local Group with a mass similar to those of Galactic globular clusters. Recent studies have revealed an extended morphology of its MSTO, which can be interpreted as a spread in either age or internal rotation. An accurate spectroscopic determination of its chemical properties is still missing. We analyse spectra obtained with MUSE in adaptive optics mode of 1167 stars in both components of this cluster (NGC1850A and NGC1850B). Thanks to this dataset, we measure an average metallicity of =-0.31 +/- 0.01, a mean Ba abundance of =+0.40 +/- 0.02 and a systemic radial velocity of =251.1 +/- 0.3 km/s. The dispersion of the radial velocities suggests a dynamical mass of log(M/Ms)=4.84 +/- 0.1, while no significant systemic rotation is detected. We detect a significant bimodality in OI line strength among the TO stars of NGC1850A with ~66% of stars with [O/Fe]~-0.16 and the rest with no detectable line. The majority of O-weak stars populate preferentially the red side of the MSTO and show H lines in emission, suggesting that they are Be stars rotating close to their critical velocity. Among normal MSTO stars, red stars have on average broader line profiles than blue ones, suggesting a correlation between colour and rotational velocity. The mean metallicity of this cluster lies at the metal-rich side of the metallicity distribution of the LMC following its age-metallicity relation. The Ba and O abundances agree with those measured in the bar of this galaxy. The observed spread in OI line width among its MS stars can be interpreted as an effect of rotational mixing occurring in the envelopes of O-weak stars. The correlation between line broadening and colour suggests that the observed colour spread among turn-off stars can be due to a wide range in rotational velocity covered by these stars.
description: 11 pages, 10 figures, acepted for publication by A&A
Improved iterative methods for solving risk parity portfolio
Creators: name: Choi, Jaehyuk
name: Chen, Rong
Publisher: name: arXiv
Year: 2022
Subjects: subject: Portfolio Management (q-fin.PM)
subject: FOS: Economics and business

description: Risk parity, also known as equal risk contribution, has recently gained increasing attention as a portfolio allocation method. However, solving portfolio weights must resort to numerical methods as the analytic solution is not available. This study improves two existing iterative methods: the cyclical coordinate descent (CCD) and Newton methods. We enhance the CCD method by simplifying the formulation using a correlation matrix and imposing an additional rescaling step. We also suggest an improved initial guess inspired by the CCD method for the Newton method. Numerical experiments show that the improved CCD method performs the best and is approximately three times faster than the original CCD method, saving more than 40% of the iterations.
Testing Feedback from Star Clusters in Simulations of the Milky Way Formation
Creators: name: Brown, Gillen
name: Gnedin, Oleg Y.
Publisher: name: arXiv
Year: 2022
Subjects: subject: Astrophysics of Galaxies (astro-ph.GA)
subject: FOS: Physical sciences

description: We present a suite of galaxy formation simulations that directly model star cluster formation and disruption. Starting from a model previously developed by our group, here we introduce several improvements to the prescriptions for cluster formation and feedback, then test these updates using a large suite of cosmological simulations of Milky Way mass galaxies. We perform a differential analysis with the goal of understanding how each of the updates affects star cluster populations. Two key parameters are the momentum boost of supernova feedback $f_{\mathrm{boost}}$ and star formation efficiency per freefall time $ε_{\mathrm{ff}}$. We find that $f_{\mathrm{boost}}$ has a strong influence on the galactic star formation rate, with higher values leading to less star formation. The efficiency $ε_{\mathrm{ff}}$ does not have a significant impact on the global star formation rate, but dramatically changes cluster properties, with increasing $ε_{\mathrm{ff}}$ leading to a higher maximum cluster mass, shorter age spread of stars within clusters, and higher integrated star formation efficiencies. We also explore the redshift evolution of the observable cluster mass function, finding that most massive clusters have formed at high redshift $z>4$. Extrapolation of cluster disruption to $z=0$ produces good agreement with both the Galactic globular cluster mass function and age-metallicity relation. Our results emphasize the importance of using small-scale properties of galaxies to calibrate subgrid models of star cluster formation and feedback.
description: Accepted for publication in MNRAS