cometadata/datacite-rtg-text-other-reclassification-records huggingface dataset:
Spatial Modeling Approach for Dynamic Network Formation and Interactions
Creators: name: Han, Xiaoyi
name: Hsieh, Chih-Sheng
name: Ko, Stanley I. M.
Publisher: name: Taylor & Francis
Year: 2019
Subjects: subject: 69999 Biological Sciences not elsewhere classified
subject: FOS: Biological sciences
subject: 80699 Information Systems not elsewhere classified
subject: FOS: Computer and information sciences
subject: 19999 Mathematical Sciences not elsewhere classified
subject: FOS: Mathematics

description: This study primarily seeks to answer the following question: How do social networks evolve over time and affect individual economic activity? To provide an adequate empirical tool to answer this question, we propose a new modeling approach for longitudinal data of networks and activity outcomes. The key features of our model are the inclusion of dynamic effects and the use of time-varying latent variables to determine unobserved individual traits in network formation and activity interactions. The proposed model combines two well-known models in the field: latent space model for dynamic network formation and spatial dynamic panel data model for network interactions. This combination reflects real situations, where network links and activity outcomes are interdependent and jointly influenced by unobserved individual traits. Moreover, this combination enables us to (1) manage the endogenous selection issue inherited in network interaction studies, and (2) investigate the effect of homophily and individual heterogeneity in network formation. We develop a Bayesian Markov chain Monte Carlo sampling approach to estimate the model. We also provide a Monte Carlo experiment to analyze the performance of our estimation method and apply the model to a longitudinal student network data in Taiwan to study the friendship network formation and peer effect on academic performance. Supplementary materials for this article are available online.
Estimates for the ergodic measure and polynomial stability of plane stochastic curve shortening flow
Creators: name: Es-Sarhir, Abelhadi
name: von Renesse, Max
name: Stannat, Wilhelm
Publisher: name: arXiv
Year: 2010
Subjects: subject: Probability (math.PR)
subject: FOS: Mathematics
subject: 47D07, 60H15, 35R60

description: We establish moment estimates for the invariant measure of a stochastic partial differential equation describing motion by mean curvature flow in (1+1) dimension, leading to polynomial stability of the associated Markov semigroup. We also prove maximal dissipativity for the related Kolmogorov operator.
Power-Law Decay of Standing Waves on the Surface of Topological Insulators
Creators: name: Wang, Jing
name: Li, Wei
name: Cheng, Peng
name: Song, Canli
name: Zhang, Tong
name: Deng, Peng
name: Chen, Xi
name: Ma, Xucun
name: He, Ke
name: Jia, Jin-Feng
name: Xue, Qi-Kun
name: Zhu, Bang-Fen
Publisher: name: arXiv
Year: 2011
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: FOS: Physical sciences

description: We propose a general theory on the standing waves (quasiparticle interference pattern) caused by the scattering of surface states off step edges in topological insulators, in which the extremal points on the constant energy contour of surface band play the dominant role. Experimentally we image the interference patterns on both Bi$_2$Te$_3$ and Bi$_2$Se$_3$ films by measuring the local density of states using a scanning tunneling microscope. The observed decay indices of the standing waves agree excellently with the theoretical prediction: In Bi$_2$Se$_3$, only a single decay index of -3/2 exists; while in Bi$_2$Te$_3$ with strongly warped surface band, it varies from -3/2 to -1/2 and finally to -1 as the energy increases. The -1/2 decay indicates that the suppression of backscattering due to time-reversal symmetry does not necessarily lead to a spatial decay rate faster than that in the conventional two-dimensional electron system. Our formalism can also explain the characteristic scattering wave vectors of the standing wave caused by non-magnetic impurities on Bi$_2$Te$_3$.
description: 4 pages, 3 figures
CFD-DEM simulation of locomotive sanders
Creators: name: Aishwarya, Gautam
Publisher: name: University of British Columbia
Year: 2018

description: This study presents the development and results of a numerical model of a locomotive sander system. Locomotive sanders are used to optimize traction between the train wheels and railhead by spraying sand into the interface. It has been previously shown that a large fraction of sand sprayed by the sanders does not make it through the wheel-rail nip, leading to sand wastage and thereby increasing the cost and refilling effort. In this project, pneumatic conveying of sand through the wheel-rail nip is numerically modelled through coupled Computational Fluid Dynamics and Discrete Element Method simulations. The gas phase, discrete phase and coupled two-phase flows are separately validated against literature, and the parameters effecting the deposition of sand through the nip- relating to both aerodynamics of the particle laden jet and interaction with geometry are independently analyzed pertaining to their effects on sander efficiency. The aerodynamics associated with the particle laden jet play a critical role in optimizing the amount of sand going through the wheel-rail interface, with the particle velocities being directly correlated with the sander efficiency. Particle-geometry interactions are found to have a negligible effect on the deposition. In the absence of crosswinds, it is recommended to either employ smaller particles, or particles with a higher surface area to volume ratio to enhance the sander efficiency. Furthermore, a larger airflow rate through the nozzle is suggested. It is also found that the presence of crosswinds strongly negatively affects sander efficiency, which can be mitigated, to some extent, by reducing the nip-nozzle distance as much as safety regulations will allow, and using coarser grain particles.
Betriebliches Gesundheitsmanagement in Zeiten einer sich verändernden Arbeitswelt (BGM im Wandel)
Creators: name: Pfister, Samuel
Publisher: name: Zenodo
Year: 2020

description: Die Arbeitswelt befindet sich im stetigen Wandel. Doch wie sieht die Arbeitswelt von morgen aus? Und welche Auswirkungen hat die Arbeitswelt von morgen auf ein Betriebliches Gesundheitsmanagement (BGM) der Zukunft, welches weiterhin erfolgreich das positive Gesundheits-empfinden der Mitarbeitenden ins Zentrum seines Handelns stellen will? Mit der vorliegenden Master-Arbeit wird anhand einer Literaturrecherche aufgezeigt, wie Entwicklungen in den zentralen Bereichen Gesellschaft, Wirtschaft und Technik die Arbeitswelt der Schweiz in den nächsten zehn Jahren beeinflussen können. Zwecks Strukturierung der vielfältigen Aspekte erfolgt eine Unterteilung der Arbeitswelt in die Dimensionen „Arbeitnehmende“, „Arbeitsformen und Arbeitsverhältnisse“ sowie „Arbeitsweise“. Aus den einzelnen Aspekten zukünftiger Arbeitswelt-Szenarien werden die daraus resultierenden Auswirkungen für das BGM abgeleitet. Die Ableitung für das BGM erfolgt entlang der BGM-Qualitätskriterien zur Erlangung des Labels Friendly Work Space. Theoretische Bezüge zur systemischen Prävention dienen als Grundlage zur Klärung von Begrifflichkeiten sowie Zusammen-hängen und liefern dem BGM auch das Rüstzeug, in einer Arbeitswelt der Zukunft anschlussfähige Massnahmen zu planen. Aus den Ergebnissen der vorliegenden Master-Arbeit lassen sich für Organisationen im Hinblick auf das BGM der Zukunft fünf zentrale Handlungsfelder ableiten.
description: + Code Diss LU: hslusa mas bgm + Fussnote: Master-Arbeit MAS Betriebliches Gesundheitsmanagement, Hochschule Luzern – Soziale Arbeit, 2020 + NL-Code: NLLUHSA202012
The continuum intensity as a function of magnetic field I. Active region and quiet Sun magnetic elements
Creators: name: Kobel, P.
name: Solanki, S. K.
name: Borrero, J. M.
Publisher: name: arXiv
Year: 2011
Subjects: subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: FOS: Physical sciences

description: Small-scale magnetic fields are major contributors to the solar irradiance variations. Hence, the continuum intensity contrast of magnetic elements in the quiet Sun (QS) network and in active region (AR) plage is an essential quantity that needs to be measured reliably. By using Hinode/SP disk center data at a constant, high spatial resolution, we aim at updating results of earlier ground-based studies of contrast vs. magnetogram signal, and to look for systematic differences between AR plages and QS network. The field strength, filling factor and inclination of the field was retrieved by Milne-Eddington inversion (VFISV). As in earlier studies, we performed a pixel-by-pixel study of 630.2 nm continuum contrast vs. apparent (i.e. averaged over a pixel) longitudinal magnetic field over large fields of view in ARs and in the QS. The contrast of magnetic elements reaches larger values in the QS (on average 3.7%) than in ARs (1.3%). This could not be attributed to any systematic difference in the chosen contrast references. At Hinode's spatial resolution, the relationship between contrast and apparent longitudinal field strength exhibits a peak at around 700 G in both the QS and ARs, whereas earlier lower resolution studies only found a peak in the QS and a monotonous decrease in ARs. We attribute this discrepancy both to our careful removal of the pores and their close surroundings affected by the telescope diffraction, as well as to the enhanced spatial resolution and very low scattered light of the Hinode Solar Optical Telescope. According to our inversions, the magnetic elements producing the peak of the contrast curves have similar properties (field strength, inclination, filling factor) in ARs and in the QS, so that the larger brightness of magnetic elements in the QS remains unexplained.
description: 8 figures, 14 pages
Forecasting Inflation in a Data-Rich Environment: The Benefits of Machine Learning Methods
Creators: name: C. Medeiros, Marcelo
name: Vasconcelos, Gabriel F. R.
name: Veiga, Álvaro
name: Zilberman, Eduardo
Publisher: name: Taylor & Francis
Year: 2019
Subjects: subject: Medicine
subject: 69999 Biological Sciences not elsewhere classified
subject: FOS: Biological sciences
subject: 80699 Information Systems not elsewhere classified
subject: FOS: Computer and information sciences
subject: 19999 Mathematical Sciences not elsewhere classified
subject: FOS: Mathematics
subject: 110309 Infectious Diseases
subject: FOS: Health sciences

description: Inflation forecasting is an important but difficult task. Here, we explore advances in machine learning (ML) methods and the availability of new datasets to forecast US inflation. Despite the skepticism in the previous literature, we show that ML models with a large number of covariates are systematically more accurate than the benchmarks. The ML method that deserves more attention is the random forest model, which dominates all other models. Its good performance is due not only to its specific method of variable selection but also the potential nonlinearities between past key macroeconomic variables and inflation.
Fast elliptic solvers in cylindrical coordinates and the Coulomb collision operator
Creators: name: Pataki, Andras
name: Greengard, Leslie
Publisher: name: arXiv
Year: 2011
Subjects: subject: Numerical Analysis (math.NA)
subject: FOS: Mathematics
subject: 31A30, 82D10, 65N35, 65R20, 65T99

description: In this paper, we describe a new class of fast solvers for separable elliptic partial differential equations in cylindrical coordinates $(r,θ,z)$ with free-space radiation conditions. By combining integral equation methods in the radial variable $r$ with Fourier methods in $θ$ and $z$, we show that high-order accuracy can be achieved in both the governing potential and its derivatives. A weak singularity arises in the Fourier transform with respect to $z$ that is handled with special purpose quadratures. We show how these solvers can be applied to the evaluation of the Coulomb collision operator in kinetic models of ionized gases.
description: 20 pages, 5 figures
Spatial Modeling Approach for Dynamic Network Formation and Interactions
Creators: name: Han, Xiaoyi
name: Hsieh, Chih-Sheng
name: Ko, Stanley I.M.
Publisher: name: Taylor & Francis
Year: 2019
Subjects: subject: 69999 Biological Sciences not elsewhere classified
subject: FOS: Biological sciences
subject: 80699 Information Systems not elsewhere classified
subject: FOS: Computer and information sciences
subject: 19999 Mathematical Sciences not elsewhere classified
subject: FOS: Mathematics

description: This study primarily seeks to answer the following question: How do social networks evolve over time and affect individual economic activity? To provide an adequate empirical tool to answer this question, we propose a new modeling approach for longitudinal data of networks and activity outcomes. The key features of our model are the inclusion of dynamic effects and the use of time-varying latent variables to determine unobserved individual traits in network formation and activity interactions. The proposed model combines two well-known models in the field: latent space model for dynamic network formation and spatial dynamic panel data model for network interactions. This combination reflects real situations, where network links and activity outcomes are interdependent and jointly influenced by unobserved individual traits. Moreover, this combination enables us to (1) manage the endogenous selection issue inherited in network interaction studies, and (2) investigate the effect of homophily and individual heterogeneity in network formation. We develop a Bayesian Markov chain Monte Carlo sampling approach to estimate the model. We also provide a Monte Carlo experiment to analyze the performance of our estimation method and apply the model to a longitudinal student network data in Taiwan to study the friendship network formation and peer effect on academic performance. Supplementary materials for this article are available online.
A variant of Peres-Mermin proof for testing noncontextual realist models
Creators: name: Pan, Alok Kumar
Publisher: name: arXiv
Year: 2010
Subjects: subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: For any state in four-dimensional system, the quantum violation of an inequality based on the Peres-Mermin proof for testing noncontextual realist models has experimentally been corroborated. In the Peres-Mermin proof, an array of nine holistic observables for two two-qubit system was used. We, in this letter, present a new symmetric set of observables for the same system which also provides a contradiction of quantum mechanics with noncontextual realist models in a state-independent way. The whole argument can also be cast in the form of a new inequality that can be empirically tested.
description: 3 pages, To be published in Euro. Phys. Lett
Smoothing Quantile Regressions
Creators: name: Fernandes, Marcelo
name: Guerre, Emmanuel
name: Horta, Eduardo
Publisher: name: Taylor & Francis
Year: 2019
Subjects: subject: Space Science
subject: Neuroscience
subject: Physiology
subject: FOS: Biological sciences
subject: Biotechnology
subject: 59999 Environmental Sciences not elsewhere classified
subject: FOS: Earth and related environmental sciences
subject: Ecology
subject: 19999 Mathematical Sciences not elsewhere classified
subject: FOS: Mathematics

description: We propose to smooth the objective function, rather than only the indicator on the check function, in a linear quantile regression context. Not only does the resulting smoothed quantile regression estimator yield a lower mean squared error and a more accurate Bahadur–Kiefer representation than the standard estimator, but it is also asymptotically differentiable. We exploit the latter to propose a quantile density estimator that does not suffer from the curse of dimensionality. This means estimating the conditional density function without worrying about the dimension of the covariate vector. It also allows for two-stage efficient quantile regression estimation. Our asymptotic theory holds uniformly with respect to the bandwidth and quantile level. Finally, we propose a rule of thumb for choosing the smoothing bandwidth that should approximate well the optimal bandwidth. Simulations confirm that our smoothed quantile regression estimator indeed performs very well in finite samples. Supplementary materials for this article are available online.
High redshift X-ray cooling-core cluster associated with the luminous radio loud quasar 3C186
Creators: name: Siemiginowska, Aneta
name: Burke, D. J.
name: Aldcroft, Thomas L.
name: Worrall, D. M.
name: Allen, S.
name: Bechtold, Jill
name: Clarke, Tracy
name: Cheung, C. C.
Publisher: name: arXiv
Year: 2010
Subjects: subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: FOS: Physical sciences

description: We present the first results from a new, deep (200ks) Chandra observation of the X-ray luminous galaxy cluster surrounding the powerful (L ~10^47 erg/s), high-redshift (z=1.067), compact-steep-spectrum radio-loud quasar 3C186. The diffuse X-ray emission from the cluster has a roughly ellipsoidal shape and extends out to radii of at least ~60 arcsec (~500 kpc). The centroid of the diffuse X-ray emission is offset by 0.68(+/-0.11) arcsec (5.5+/-0.9 kpc) from the position of the quasar. We measure a cluster mass within the radius at which the mean enclosed density is 2500 times the critical density, r_2500=283(+18/-13)kpc, of 1.02 (+0.21/-0.14)x10^14 M_sun. The gas mass fraction within this radius is f_gas=0.129(+0.015/-0.016). This value is consistent with measurements at lower redshifts and implies minimal evolution in the f_gas(z) relation for hot, massive clusters at 01. We measure cooling times for the X-ray emitting gas at radii of 50 kpc and 25 kpc of 1.7(+/-0.2)x10^9 years and 7.5(+/-2.6)x 10^8 years, as well as a nominal cooling rate (in the absence of heating) of 400(+/-190)M_sun/year within the central 100 kpc. In principle, the cooling gas can supply enough fuel to support the growth of the supermassive black hole and to power the luminous quasar. The radiative power of the quasar exceeds by a factor of 10 the kinematic power of the central radio source, suggesting that radiative heating may be important at intermittent intervals in cluster cores.
description: 15 pages, 9 figures, ApJ in press
A New Method for Measuring Edge Tensions and Stability of Lipid Bilayers: Effect of Membrane Composition
Creators: name: Portet, Thomas
name: Dimova, Rumiana
Publisher: name: arXiv
Year: 2011
Subjects: subject: Biological Physics (physics.bio-ph)
subject: Soft Condensed Matter (cond-mat.soft)
subject: FOS: Physical sciences

description: We report a new and facile method for measuring edge tensions of lipid membranes. The approach is based on electroporation of giant unilamellar vesicles and analysis of the pore closure dynamics. We applied this method to evaluate the edge tension in membranes with four different compositions: egg phosphatidylcholine (EggPC), dioleoylphosphatidylcholine (DOPC), and mixtures of the latter with cholesterol and dioleoylphosphatidylethanolamine (DOPE). Our data confirm previous results for EggPC and DOPC. The addition of 17 mol % cholesterol to the DOPC membrane causes an increase in the membrane edge tension. On the contrary, when the same fraction of DOPE is added to the membrane, a decrease in the edge tension is observed, which is an unexpected result considering the inverted-cone shape geometry of the molecule. Presumably, interlipid hydrogen bonding lies in the origin of this behavior. Furthermore, cholesterol was found to lower the lysis tension of DOPC bilayers. This behavior differs from that observed on bilayers made of stearoyloleoylphosphatidylcholine, suggesting that cholesterol influences the membrane mechanical stability in a lipid-specific manner.
Improved background subtraction for the Sloan Digital Sky Survey images
Creators: name: Blanton, Michael R.
name: Kazin, Eyal
name: Muna, Demitri
name: Weaver, Benjamin A.
name: Price-Whelan, Adrian
Publisher: name: arXiv
Year: 2011
Subjects: subject: Instrumentation and Methods for Astrophysics (astro-ph.IM)
subject: FOS: Physical sciences

description: We describe a procedure for background subtracting Sloan Digital Sky Survey (SDSS) imaging that improves the resulting detection and photometry of large galaxies on the sky. Within each SDSS drift scan run, we mask out detected sources and then fit a smooth function to the variation of the sky background. This procedure has been applied to all SDSS-III Data Release 8 images, and the results are available as part of that data set. We have tested the effect of our background subtraction on the photometry of large galaxies by inserting fake galaxies into the raw pixels, reanalyzing the data, and measuring them after background subtraction. Our technique results in no size-dependent bias in galaxy fluxes up to half-light radii of 100 arcsec; in contrast, for galaxies of that size the standard SDSS photometric catalog underestimates fluxes by about 1.5 mag. Our results represent a substantial improvement over the standard SDSS catalog results and should form the basis of any analysis of nearby galaxies using the SDSS imaging data.
description: accepted by the Astronomical Journal
Predicted Colors and Flux Densities of Protostars in the Herschel PACS and SPIRE Filters
Creators: name: Ali, Babar
name: Tobin, J. J.
name: Fischer, W. J.
name: Poteet, C. A.
name: Megeath, S. T.
name: Allen, L.
name: Hartmann, L.
name: Calvet, N.
name: Furlan, E.
name: Osorio, M.
Publisher: name: arXiv
Year: 2010
Subjects: subject: Astrophysics of Galaxies (astro-ph.GA)
subject: FOS: Physical sciences

description: Upcoming surveys with the Herschel Space Observatory will yield far-IR photometry of large samples of young stellar objects, which will require careful interpretation. We investigate the color and luminosity diagnostics based on Herschel broad-band filters to identify and discern the properties of low-mass protostars. We compute a grid of 2,016 protostars in various physical congurations, present the expected flux densities and flux density ratios for this grid of protostars, and compare Herschel observations of three protostars to the model results. These provide useful constraints on the range of colors and fluxes of protostar in the Herschel filters. We find that Herschel data alone is likely a useful diagnostic of the envelope properties of young stars
description: Part of HOPS KP papers to the Herschel special A&A issue
Bias-Corrected Common Correlated Effects Pooled Estimation in Dynamic Panels
Creators: name: De Vos, Ignace
name: Everaert, Gerdie
Publisher: name: Taylor & Francis
Year: 2019
Subjects: subject: Biochemistry
subject: Cell Biology
subject: Genetics
subject: FOS: Biological sciences
subject: Molecular Biology
subject: Ecology
subject: 19999 Mathematical Sciences not elsewhere classified
subject: FOS: Mathematics
subject: 110309 Infectious Diseases
subject: FOS: Health sciences

description: This article extends the common correlated effects pooled (CCEP) estimator to homogenous dynamic panels. In this setting, CCEP suffers from a large bias when the time span (T) of the dataset is fixed. We develop a bias-corrected CCEP estimator that is consistent as the number of cross-sectional units (N) tends to infinity, for T fixed or growing large, provided that the specification is augmented with a sufficient number of cross-sectional averages, and lags thereof. Monte Carlo experiments show that the correction offers strong improvements in terms of bias and variance. We apply our approach to estimate the dynamic impact of temperature shocks on aggregate output growth.
Loewner equation for Laplacian growth: A Schwarz-Christoffel-transformation approach
Creators: name: Durán, M.
name: Vasconcelos, G. L.
Publisher: name: arXiv
Year: 2010
Subjects: subject: Pattern Formation and Solitons (nlin.PS)
subject: Fluid Dynamics (physics.flu-dyn)
subject: FOS: Physical sciences

description: The problem of Laplacian growth is considered within the Loewner-equation framework. A new method of deriving the Loewner equation for a large class of growth problems in the half-plane is presented. The method is based on the Schwarz-Christoffel transformation between the so-called `mathematical planes' at two infinitesimally separated times. Our method not only reproduces the correct Loewner evolution for the case of slit-like fingers but also can be extended to treat more general growth problems. In particular, the Loewner equation for the case of a bubble growing into the half-plane is presented.
description: 8 pages, 4 figures. To appear in Journal of Physics Conference Series
Smoothing quantile regressions
Creators: name: Fernandes, Marcelo
name: Guerre, Emmanuel
name: Horta, Eduardo
Publisher: name: Taylor & Francis
Year: 2019
Subjects: subject: Space Science
subject: Neuroscience
subject: Physiology
subject: FOS: Biological sciences
subject: Biotechnology
subject: 59999 Environmental Sciences not elsewhere classified
subject: FOS: Earth and related environmental sciences
subject: Ecology
subject: 19999 Mathematical Sciences not elsewhere classified
subject: FOS: Mathematics

description: We propose to smooth the objective function, rather than only the indicator on the check function, in a linear quantile regression context. Not only does the resulting smoothed quantile regression estimator yield a lower mean squared error and a more accurate Bahadur-Kiefer representation than the standard estimator, but it is also asymptotically differentiable. We exploit the latter to propose a quantile density estimator that does not suffer from the curse of dimensionality. This means estimating the conditional density function without worrying about the dimension of the covariate vector. It also allows for two-stage efficient quantile regression estimation. Our asymptotic theory holds uniformly with respect to the bandwidth and quantile level. Finally, we propose a rule of thumb for choosing the smoothing bandwidth that should approximate well the optimal bandwidth. Simulations confirm that our smoothed quantile regression estimator indeed performs very well in finite samples.
Philippe Meirieu, Una scuola per l'emancipazione. Libera dalle nostalgie dei vecchi metodi e da suggestioni alla moda, Armando Editore, Roma, ISBN 9788869926679, 280 pagine, 2020
Creators: name: Tripi, Maura
Publisher: name: Encyclopaideia
Year: 2020

description: Encyclopaideia, Vol. 24 No. 58 (2020)
The Ultraviolet-X-ray connection in AGN outflows
Creators: name: Costantini, Elisa
Publisher: name: arXiv
Year: 2010
Subjects: subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: FOS: Physical sciences

description: In this paper I review the recent progress in understanding the physics of the gas outflowing from active galactic nuclei and its impact on the surrounding environment, using the combined information provided by multiwavelength Ultraviolet-X-ray campaigns.
description: 13 pages, 4 figures. Invited talk at the "High-resolution X-ray spectroscopy: past, present, and future" conference, Utrecht, March 15-17 2010. Accepted for publication in Space Science Reviews
From Local to Global: External Validity in a Fertility Natural Experiment
Creators: name: Dehejia, Rajeev
name: Pop-Eleches, Cristian
name: Samii, Cyrus
Publisher: name: Taylor & Francis
Year: 2019
Subjects: subject: Pharmacology
subject: Biotechnology
subject: Ecology
subject: FOS: Biological sciences
subject: Sociology
subject: FOS: Sociology
subject: 69999 Biological Sciences not elsewhere classified
subject: 19999 Mathematical Sciences not elsewhere classified
subject: FOS: Mathematics
subject: Science Policy
subject: Plant Biology

description: We study issues related to external validity for treatment effects using over 100 replications of the Angrist and Evans natural experiment on the effects of sibling sex composition on fertility and labor supply. The replications are based on census data from around the world going back to 1960. We decompose sources of error in predicting treatment effects in external contexts in terms of macro and micro sources of variation. In our empirical setting, we find that macro covariates dominate over micro covariates for reducing errors in predicting treatments, an issue that past studies of external validity have been unable to evaluate. We develop methods for two applications to evidence-based decision-making, including determining where to locate an experiment and whether policy-makers should commission new experiments or rely on an existing evidence base for making a policy decision.
Essays on foreign firms listed in the United States
Creators: name: Zhang, Lei (Ray)
Publisher: name: University of British Columbia
Year: 2018

description: This thesis is a collection of two essays on US listed foreign firms, which represent a significant proportion of firms trading in US markets. These firms, like listed US firms, are subject to the litigation system in the US and are subject to monitoring by the US regulators, such as the Securities Exchange Commission (SEC) and the Public Company Accounting Oversight Board (PCAOB). Because of US regulators’ tripartite mission to protect investors, maintain efficient markets, and facilitate capital formation, it is not obvious how the US regulators monitoring of foreign firms compares with US firms. In addition, it is not trivial how the foreign auditors react to the legal environment in the US compared with the US auditors. The first chapter of this thesis explores whether SEC’s monitoring activities differ for US versus foreign firms and whether monitoring varies based on attributes of the home country’s institutions. We find that, on average, SEC monitors foreign firms with less frequency and SEC provides increased monitoring for those foreign firms where SEC monitoring is most valuable to US. In addition, SEC reduces monitoring when it can rely on public and private enforcement in the foreign firm’s home country. Our study highlights the heterogeneity in SEC monitoring of foreign firms. The second chapter examines the effects of cross-listings in the United States on the pricing and quality of foreign auditors. The Bonding hypothesis suggests that foreign auditors can leapfrog their home countries’ weak legal institutions and provide quality similar to US auditors for their cross-listed clients because they abide by U.S. legal requirements. However, recent evidence, such as the first chapter of these essays, suggests that the U.S. legal enforcement is weaker for foreign entities because U.S. regulators focus their resources on domestic firms. This study finds that despite the nuances of the functional convergence hypothesis, foreign auditors are found to provide quality at least as good as the U.S. non-Big4 auditors. The findings of this paper can mitigate some recent concerns about the quality of foreign auditors practicing in the U.S. cross-listing market.
Herschel ATLAS: The angular correlation function of submillimetre galaxies at high and low redshift
Creators: name: Maddox, S. J.
name: Dunne, L.
name: Rigby, E.
name: Eales, S.
name: Cooray, A.
name: Scott, D.
name: Peacock, J. A.
name: Negrello, M.
name: Smith, D. J. B.
name: Benford, D.
name: Amblard, A.
name: Auld, R.
name: Baes, M.
name: Bonfield, D.
name: Burgarella, D.
name: Buttiglione, S.
name: Cava, A.
name: Clements, D.
name: Dariush, A.
name: de Zotti, G.
name: Dye, S.
name: Frayer, D.
name: Fritz, J.
name: Gonzalez-Nuevo, J.
name: Herranz, D.
name: Ibar, E.
name: Ivison, R.
name: Jarvis, M. J.
name: Lagache, G.
name: Leeuw, L.
name: Lopez-Caniego, M.
name: Pascale, E.
name: Pohlen, M.
name: Rodighiero, G.
name: Samui, S.
name: Serjeant, S.
name: Temi, P.
name: Thompson, M.
name: Verma, A.
Publisher: name: arXiv
Year: 2010
Subjects: subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: FOS: Physical sciences

description: We present measurements of the angular correlation function of galaxies selected from the first field of the H-ATLAS survey. Careful removal of the background from galactic cirrus is essential, and currently dominates the uncertainty in our measurements. For our 250 micron-selected sample we detect no significant clustering, consistent with the expectation that the 250 micron-selected sources are mostly normal galaxies at z
description: Accepted for publication in the A&A Herschel Special issue. 5 pages, 3 figures.
The foreign exchange market: return distributions, multifractality, anomalous multifractality and Epps effect
Creators: name: Drozdz, Stanislaw
name: Kwapien, Jaroslaw
name: Oswiecimka, Pawel
name: Rak, Rafal
Publisher: name: arXiv
Year: 2010
Subjects: subject: Statistical Finance (q-fin.ST)
subject: Data Analysis, Statistics and Probability (physics.data-an)
subject: FOS: Economics and business
subject: FOS: Physical sciences

description: We present a systematic study of various statistical characteristics of high-frequency returns from the foreign exchange market. This study is based on six exchange rates forming two triangles: EUR-GBP-USD and GBP-CHF-JPY. It is shown that the exchange rate return fluctuations for all the pairs considered are well described by the nonextensive statistics in terms of q-Gaussians. There exist some small quantitative variations in the nonextensivity q-parameter values for different exchange rates and this can be related to the importance of a given exchange rate in the world's currency trade. Temporal correlations organize the series of returns such that they develop the multifractal characteristics for all the exchange rates with a varying degree of symmetry of the singularity spectrum f(alpha) however. The most symmetric spectrum is identified for the GBP/USD. We also form time series of triangular residual returns and find that the distributions of their fluctuations develop disproportionately heavier tails as compared to small fluctuations which excludes description in terms of q-Gaussians. The multifractal characteristics for these residual returns reveal such anomalous properties like negative singularity exponents and even negative singularity spectra. Such anomalous multifractal measures have so far been considered in the literature in connection with the diffusion limited aggregation and with turbulence. We find that market inefficiency on short time scales leads to the occurrence of the Epps effect on much longer time scales. Although the currency market is much more liquid than the stock markets and it has much larger transaction frequency, the building-up of correlations takes up to several hours - time that does not differ much from what is observed in the stock markets. This may suggest that non-synchronicity of transactions is not the unique source of the observed effect.
The low frequency of dual AGNs versus the high merger rate of galaxies: A phenomenological model
Creators: name: Yu, Qingjuan
name: Lu, Youjun
name: Mohayaee, Roya
name: Colin, Jacques
Publisher: name: arXiv
Year: 2011
Subjects: subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: Astrophysics of Galaxies (astro-ph.GA)
subject: FOS: Physical sciences

description: Dual AGNs are natural byproducts of hierarchical mergers of galaxies in the LambdaCDM cosmogony. Recent observations have shown that only a small fraction (~ 0.1%-1%) of AGNs at redshift z
description: 8 pages, 3 figures
Herschel-ATLAS: blazars in the SDP field
Creators: name: González-Nuevo, J.
name: De Zotti, G.
name: Andreani, P.
name: Barton, E. J.
name: Bertoldi, F.
name: Birkinshaw, M.
name: Bonavera, L.
name: Buttiglione, S.
name: Cooke, J.
name: Cooray, A.
name: Danese, G.
name: Dunne, L.
name: Eales, S.
name: Fan, L.
name: Jarvis, M. J.
name: Klöckner, H-R.
name: Hatziminaoglou, E.
name: Herranz, D.
name: Hughes, D. H.
name: Lapi, A.
name: Lawrence, A.
name: Leeuw, L.
name: López-Caniego, M.
name: Massardi, M.
name: Mauch, T.
name: Michalowski, M. J.
name: Negrello, M.
name: Rawlings, S.
name: Rodighiero, G.
name: Samui, S.
name: Serjeant, S.
name: Vieira, J. D.
name: White, G.
name: Amblard, A.
name: Auld, R.
name: Baes, M.
name: Bonfield, D. G.
name: Burgarella, D.
name: Cava, A.
name: Clements, D. L.
name: Dariush, A.
name: Dye, S.
name: Frayer, D.
name: Fritz, J.
name: Ibar, E.
name: Ivison, R. J.
name: Lagache, G.
name: Maddox, S.
name: Pascale, E.
name: Pohlen, M.
name: Rigby, E.
name: Sibthorpe, B.
name: Smith, D. J. B.
name: Temi, P.
name: Thompson, M.
name: Valtchanov, I.
name: Verma, A.
Publisher: name: arXiv
Year: 2010
Subjects: subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: FOS: Physical sciences

description: To investigate the poorly constrained sub-mm counts and spectral properties of blazars we searched for these in the Herschel-ATLAS (H-ATLAS) science demostration phase (SDP) survey catalog. We cross-matched 500$μ$m sources brighter than 50 mJy with the FIRST radio catalogue. We found two blazars, both previously known. Our study is among the first blind blazar searches at sub-mm wavelengths, i.e., in the spectral regime where little is still known about the blazar SEDs, but where the synchrotron peak of the most luminous blazars is expected to occur. Our early results are consistent with educated extrapolations of lower frequency counts and question indications of substantial spectral curvature downwards and of spectral upturns at mm wavelengths. One of the two blazars is identified with a Fermi/LAT $γ$-ray source and a WMAP source. The physical parameters of the two blazars are briefly discussed.These observations demonstrate that the H-ATLAS survey will provide key information about the physics of blazars and their contribution to sub-mm counts.
description: 5 pages, 2 figures, accepted for publication in A&A (Herschel special issue)
Testing Serial Correlation and ARCH Effect of High-Dimensional Time-Series Data
Creators: name: Ling, Shiqing
name: Tsay, Ruey S.
name: Yang, Yaxing
Publisher: name: Taylor & Francis
Year: 2019
Subjects: subject: Cell Biology
subject: Molecular Biology
subject: 39999 Chemical Sciences not elsewhere classified
subject: FOS: Chemical sciences
subject: Ecology
subject: FOS: Biological sciences
subject: Immunology
subject: FOS: Clinical medicine
subject: 19999 Mathematical Sciences not elsewhere classified
subject: FOS: Mathematics
subject: Cancer
subject: Science Policy
subject: Plant Biology

description: This article proposes several tests for detecting serial correlation and ARCH effect in high-dimensional data. The dimension of datap=p(n)may go to infinity when the sample sizen→∞. It is shown that the sample autocorrelations and the sample rank autocorrelations (Spearman’s rank correlation) of the L1-norm of data are asymptotically normal. Two portmanteau tests based, respectively, on the norm and its rank are shown to be asymptotically χ2-distributed, and the corresponding weighted portmanteau tests are shown to be asymptotically distributed as a linear combination of independent χ2 random variables. These tests are dimension-free, that is, independent of p, and the norm rank-based portmanteau test and its weighted counterpart can be used for heavy-tailed time series. We further discuss two standardized norm-based tests. Simulation results show that the proposed test statistics have satisfactory sizes and are powerful even for the case of small n and large p. We apply the tests to two real datasets. Supplementary materials for this article are available online.
The Evolution of M_*/M_BH Between z=2 and z=0
Creators: name: Trakhtenbrot, Benny
name: Netzer, Hagai
Publisher: name: arXiv
Year: 2010
Subjects: subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: FOS: Physical sciences

description: We propose a novel method to estimate M_*/M_BH, the ratio of stellar mass (M_*) to black hole mass (M_BH), at various redshifts using two recent observational results: the correlation between the bolometric luminosity of active galactic nuclei (AGN) and the star formation rate (SFR) in their host galaxies, and the correlation between SFR and M_* in star-forming (SF) galaxies. Our analysis is based on M_BH and L_bol measurements in two large samples of type-I AGN at z~1 and z~2, and the measurements of M_*/M_BH in 0.05
description: 5 pages 3 figures, accepted for publication in MNRAS Letters
From Local to Global: External Validity an A Fertility Natural Experiment
Creators: name: Dehejia, Rajeev
name: Pop-Eleches, Cristian
name: Samii, Cyrus
Publisher: name: Taylor & Francis
Year: 2019
Subjects: subject: Pharmacology
subject: Biotechnology
subject: Ecology
subject: FOS: Biological sciences
subject: Sociology
subject: FOS: Sociology
subject: 69999 Biological Sciences not elsewhere classified
subject: 19999 Mathematical Sciences not elsewhere classified
subject: FOS: Mathematics
subject: Science Policy
subject: Plant Biology

description: We study issues related to external validity for treatment effects using over 100 replications of the Angrist and Evans (1998) natural experiment on the effects of sibling sex composition on fertility and labor supply. The replications are based on census data from around the world going back to 1960. We decompose sources of error in predicting treatment effects in external contexts in terms of macro and micro sources of variation. In our empirical setting, we find that macro covariates dominate over micro covariates for reducing errors in predicting treatments, an issue that past studies of external validity have been unable to evaluate. We develop methods for two applications to evidence-based decision-making, including determining where to locate an experiment and whether policy-makers should commission new experiments or rely on an existing evidence base for making a policy decision.
Testing Serial Correlation and ARCH Effect of High-Dimensional Time-Series Data
Creators: name: Ling, Shiqing
name: Tsay, Ruey S.
name: Yang, Yaxing
Publisher: name: Taylor & Francis
Year: 2019
Subjects: subject: Cell Biology
subject: Molecular Biology
subject: 39999 Chemical Sciences not elsewhere classified
subject: FOS: Chemical sciences
subject: Ecology
subject: FOS: Biological sciences
subject: Immunology
subject: FOS: Clinical medicine
subject: 19999 Mathematical Sciences not elsewhere classified
subject: FOS: Mathematics
subject: Cancer
subject: Science Policy
subject: Plant Biology

description: This paper proposes several tests for detecting serial correlation and ARCH effect in high-dimensional data. The dimension of data p=p(n) may go to infinity when the sample size n→∞. It is shown that the sample autocorrelations and the sample rank autocorrelations (Spearman’s rank correlation) of the L1-norm of data are asymptotically normal. Two portmanteau tests based, respectively, on the norm and its rank are shown to be asymptotically χ2-distributed, and the corresponding weighted portmanteau tests are shown to be asymptotically distributed as a linear combination of independent χ2 random variables. These tests are dimension-free, i.e. independent of p, and the norm rank-based portmanteau test and its weighted counterpart can be used for heavy-tailed time series. We further discuss two standardized norm-based tests. Simulation results show that the proposed test statistics have satisfactory sizes and are powerful even for the case of small n and large p. We apply the tests to two real data sets.
Characterizing a Quantum Cascade Meta-Surface Amplifier at Terahertz Frequencies
Creators: name: Hatfield, Kassidon
name: Bundy, Briston
Publisher: name: Unknown
Year: 2023
Subjects: subject: Optical engineering
subject: Amplifiers (Electronics)
subject: Astronomy
subject: amplification
subject: terahertz
subject: quantum
subject: cascade
subject: metasurface
subject: amplifier
subject: Giant Molecular Clouds
subject: GMC
subject: Astronomy
subject: heterodyne
subject: receiver
subject: Jet Propulsion Laboratory
subject: JPL
subject: waveguide
subject: optical
subject: optical test bed
subject: test bed
subject: mirror block
subject: mirror
subject: ellipsoidal
subject: ellipsoidal mirror

description: The objective of this project is to measure amplification from a terahertz quantum
cascade metasurface amplifier. In this project an optical testbed was designed to accomplish this
objective. This will aid in the study of Giant Molecular Clouds (GMCs). GMCs have been an
area of great interest for astronomers and the current technology being used for this, the THz
heterodyne receiver, could be improved using an amplifier in the signal path between the sky and
the mixer as is done for lower frequency heterodyne receivers. Although other projects have
demonstrated amplifiers based on quantum cascade gain materials, they could not be
implemented into heterodyne receivers because their output signals could not be coupled to the
next element in the receiver chain. A recently designed amplifier at the Jet Propulsion
Laboratory uses a quantum cascade metasurface in place of the previously used waveguide
structure that can overcome this challenge. To design the optical test bed, a mirror block was
designed to focus light from the source to the meta-surface and subsequently focus the amplified
light from the meta-surface onto a detector. This mirror block and the testbed had their geometry,
structure, and placement calculated using a python script written for that purpose. This design
was simulated in SolidWorks to make sure the components would all fit in the area allotted. The
resulting testbed design achieved an angle of incidence of 5.08 degrees and a theoretical beam
radius of 0.3993 mm and a beam diameter of 0.7986 mm at the metasurface. The design met the
requirements, and the design was tested at JPL in June. The experimental beam diameter was 1.2
mm; however, we measured an amplification of 6 dB at 2.48 THz. We consider this a success,
but future projects will try to reduce the beam size to fit the original requirement.
Ο πληθυσμός της Ελλάδας μειώνεται συνεχώς μετά το 2010, οι μεταβολές του όμως σε περιφερικό επίπεδο διαφέρουν σημαντικά: ο ρόλος των Φυσικών και των Μεταναστευτικών Ισοζυγίων. (The population of Greece is constantly decreasing, but changes at regional level differ significantly: the role of natural increase and net migration.) DIRAP, FLASH NEWS 4, 2021
Creators: name: KOTZAMANIS, BYRON
name: Pappas, Vassilis
Publisher: name: figshare
Year: 2021
Subjects: subject: 160399 Demography not elsewhere classified
subject: FOS: Sociology

description: The population of Greece has been constantly declining after 2010, and the next census will confirm it as the resident population at the end of 2021 will be, if the coverage of the population in these two censuses will not differ significantly, 450.-500.00 less than in 2011. Waiting for the results of the 2021 census, and limiting to a nine year period (1/1/2011-1/1/2020), during which the population decrease has been estimated at 400 thousand, our interest lies in the following questions: Does this decrease apply to all regions? Does the population growth differ significantly between them? How did the natural increase and the net migration contribute to this? We will answer the above questions using the data (population estimates, birth records, and deaths) provided by the Hellenic Statistical Authority for this period.

Ο πληθυσμός της Ελλάδας μειώνεται συνεχώς μετά το 2010 και η απογραφή που θα διεξαχθεί θα το επιβεβαιώσει καθώς πιθανότατα οι μόνιμοι κάτοικοι στα τέλη του 2021 θα είναι κατά 450.-500.00 λιγότεροι από αυτούς που απεγράφησαν τον Μάιο του 2011 (υπό την προϋπόθεση ότι η κάλυψη του πληθυσμού στις δυο αυτές απογραφές δεν θα διαφοροποιείται σημαντικά). Σε αναμονή των αποτελεσμάτων της απογραφής αυτής, θα περιορισθούμε στην περίοδο 2011-2020, στη διάρκεια της οποίας η μείωση ανέρχεται σε 400 περίπου χιλιάδες και θα απαντήσουμε στα εξής ερωτήματα: ι) η μείωση αυτή αφορά όλες τις περιοχές; ιι) η ένταση των μεταβολών είναι περίπου ή ίδια ή αντιθέτως υπάρχουν σημαντικές διαφοροποιήσεις ; ιι) Πως εξελίχθηκαν τα Φυσικά Ισοζύγια (γεννήσεις- θάνατοι) και πως τα Μεταναστευτικά (είσοδοι – έξοδοι) και ειδικότερα πως αυτά συνέβαλαν στις μεταβολές του πληθυσμού της περίοδού 1/1/2011-1/1/2020; Στα προαναφερθέντα ερωτήματα θα απαντήσουμε αξιοποιώντας τα στοιχεία της Ελληνικής Στατιστικής Αρχής (ΕΛΣΤΑΤ) για την εννεαετή αυτή περίοδο (εκτιμήσεις για τον πληθυσμό, δεδομένα ληξιαρχείων για τις γεννήσεις και τους θανάτους)