cometadata/datacite-rtg-text-other-reclassification-records huggingface dataset:
Lattice stability and high pressure melting mechanism of dense hydrogen up to 1.5 TPa
Creators: name: Geng, Hua Y.
name: Hoffmann, R.
name: Wu, Q.
Publisher: name: arXiv
Year: 2016
Subjects: subject: Materials Science (cond-mat.mtrl-sci)
subject: Statistical Mechanics (cond-mat.stat-mech)
subject: Chemical Physics (physics.chem-ph)
subject: Computational Physics (physics.comp-ph)
subject: FOS: Physical sciences

description: Lattice stability and metastability, as well as melting, are important features of the physics and chemistry of dense hydrogen. Using ab initio molecular dynamics (AIMD), the classical superheating limit and melting line of metallic hydrogen are investigated up to 1.5 TPa. The computations show that the classical superheating degree is about 100 K, and the classical melting curve becomes flat at a level of 350 K when beyond 500 GPa. This information allows us to estimate the well depth and the potential barriers that must be overcome when the crystal melts. Inclusion of nuclear quantum effects (NQE) using path integral molecular dynamics (PIMD) predicts that both superheating limit and melting temperature are lowered to below room temperature, but the latter never reach absolute zero. Detailed analysis indicates that the melting is thermally activated, rather than driven by pure zero-point motion (ZPM). This argument was further supported by extensive PIMD simulations, demonstrating the stability of Fddd structure against liquefaction at low temperatures.
description: 27 pages, 6 figures, with Supplementary Information (with 16 pages)
title: Εκτίμηση της επίδρασης της πανδημίας COVID-19 στις πρακτικές αποτίμησης κινδύνου
title: Evaluating the effects of the COVID-19 pandemic on risk assessment
titleType: AlternativeTitle
Creators: name: Γκιάλπης, Δημήτριος
Publisher: name: Πανεπιστήμιο Πειραιώς
Year: 2023
Subjects: subject: COVID-19
subject: Solvency
subject: Φερεγγυότητα ΙΙ
subject: Ασφαλίσεις
subject: Θνησιμότητα

description: Στην συγκεκριμένη εργασία μελετάται η επιρροή της πανδημίας COVID-19, ως ακραίο υγειονομικό και κοινωνικό φαινόμενο, στις ασφαλίσεις στην Ελλάδα. Επιπλέον γίνεται έλεγχος της ετοιμότητας καθώς και της δυνατότητας πρόβλεψης και επιμέτρησης αντίστοιχων μελλοντικών γεγονότων. Αρχικά, γίνεται ανάλυση του πλαισίου της Φερεγγυότητας ΙΙ που αποτελεί το πλαίσιο λειτουργίας και εποπτείας των ασφαλιστικών επιχειρήσεων στην ΕΕ. Μέσα από την ανάλυση αυτή ο αναγνώστης αποκτά μια εικόνα για τη πολυπλοκότητα των κινδύνων στους οποίους βρίσκεται εκτεθειμένη μια ασφαλιστική εταιρεία, την ποσοτική και την ποιοτική ανάλυση που οφείλει να κάνει για αυτούς καθώς και ποια είναι η σύνδεση μεταξύ των κίνδυνων αυτών και ενός φαινομένου όπως η πανδημία COVID-19. Έπειτα, μελετάται η επίδρασης της πανδημίας COVID-19 στα επίπεδα της θνησιμότητας στην Ελλάδα. Πραγματοποιείται ανάλυση της υπερβάλλουσας θνησιμότητας κατά τα έτη της πανδημίας και εκτίμηση των επιπέδων της θνησιμότητας λόγω COVID-19. Στη συνέχεια ακολουθεί λεπτομερής ανάλυση των αποτελεσμάτων των ασφαλίσεων στην Ελλάδα κατά την περίοδο αυτή, σε επίπεδο ασφαλιστικού κλάδου. Σκοπός της ανάλυσης αυτής είναι να διαπιστωθεί η ακριβής επιρροή της πανδημίας στις ασφαλίσεις. Τέλος, συνδυάζοντας τα αποτελέσματα των προηγούμενων αναλύσεων με συμπεράσματα από αντίστοιχες έρευνες στο εξωτερικό προσπαθούμε να συμπεράνουμε ποια ήταν η συνολική επίδραση της πανδημίας COVID-19 στις Ελληνικές ασφαλιστικές εταιρείες.
Gap solitons for the repulsive Gross-Pitaevskii equation with periodic potential: coding and method for computation
Creators: name: Alfimov, Georgy L.
name: Kizin, Pavel P.
name: Zezyulin, Dmitry A.
Publisher: name: arXiv
Year: 2016
Subjects: subject: Pattern Formation and Solitons (nlin.PS)
subject: Quantum Gases (cond-mat.quant-gas)
subject: Mathematical Physics (math-ph)
subject: Chaotic Dynamics (nlin.CD)
subject: FOS: Physical sciences
subject: 35Q55, 35C08, 34C41, 37B10, 65P99

description: The paper is devoted to nonlinear localized modes ("gap solitons") for the spatially one-dimensional Gross-Pitaevskii equation (1D GPE) with a periodic potential and repulsive interparticle interactions. It has been recently shown (G. L. Alfimov, A. I. Avramenko, Physica D, 254, 29 (2013)) that under certain conditions all the stationary modes for the 1D GPE can be coded by bi-infinite sequences of symbols of some finite alphabet (called "codes" of the solutions). We present and justify a numerical method which allows to reconstruct the profile of a localized mode by its code. As an example, the method is applied to compute the profiles of gap solitons for 1D GPE with a cosine potential.
description: 24 pages, 10 figures; accepted for DCDS-B
FIB synthesis of Bi2Se3 1D nanowires demonstrating the co-existence of Shubnikov-de Haas oscillations and linear magnetoresistance
Creators: name: Bhattacharyya, Biplab
name: Sharma, Alka
name: Awana, V P S
name: Senguttuvan, T. D.
name: Husale, Sudhir
Publisher: name: arXiv
Year: 2016
Subjects: subject: Materials Science (cond-mat.mtrl-sci)
subject: FOS: Physical sciences

description: Since the discovery of topological insulators (TI), there are considerable interests in demonstrating metallic surface states, their shielded robust nature to the backscattering and study their properties at nanoscale dimensions by fabricating nanodevices. Here we address an important scientific issue related to TI whether one can clearly demonstrate the robustness of topological surface states (TSS) to the presence of disorder that does not break any fundamental symmetry. The simple straightforward method of FIB milling was used to synthesize nanowires of Bi2Se3 which we believe an interesting route to test robustness of TSS and obtained results are new compared to many of the earlier papers on quantum transport in TI demonstrating robustness of metallic SS to gallium doping. In presence of perpendicular magnetic field, we have observed the co-existence of Shubnikov de Haas oscillations and linear magnetoresistance which was systematically investigated at different channel lengths indicating the Dirac dispersive surface states. The transport properties and estimated physical parameters shown here demonstrate the robustness of SS to the fabrication tools triggering flexibility to explore new exotic quantum phenomena at nanodevice level.
description: Accepted in JPCM
Absorption spectroscopy of xenon and ethylene-noble gas mixtures at high pressure: Towards Bose-Einstein condensation of vacuum ultraviolet photons
Creators: name: Wahl, Christian
name: Brausemann, Rudolf
name: Schmitt, Julian
name: Vewinger, Frank
name: Christopoulos, Stavros
name: Weitz, Martin
Publisher: name: arXiv
Year: 2016
Subjects: subject: Atomic Physics (physics.atom-ph)
subject: FOS: Physical sciences

description: Bose-Einstein condensation is a phenomenon well known for material particles as cold atomic gases, and this concept has in recent years been extended to photons confined in microscopic optical cavities. Essential for the operation of such a photon condensate is a thermalization mechanism that conserves the average particle number, as in the visible spectral regime can be realized by subsequent absorption re-emission processes in dye molecules. Here we report on the status of an experimental effort aiming at the extension of the concept of Bose-Einstein condensation of photons towards the vacuum ultraviolet spectral regime, with gases at high pressure conditions serving as a thermalization medium for the photon gas. We have recorded absorption spectra of xenon gas at up to 30 bar gas pressure of the $5p^6 - 5p^56s$ transition with a wavelength close to 147 nm. Moreover, spectra of ethylene noble gas mixtures between 155 and 180 nm wavelength are reported.
description: 9 pages, 5 figures
On the quantum principles of cognitive learning
Creators: name: de Castro, Alexandre
Publisher: name: arXiv
Year: 2016
Subjects: subject: Neurons and Cognition (q-bio.NC)
subject: FOS: Biological sciences

description: Pothos & Busemeyer's (P&B's) query about whether quantum probability can provide a foundation for the cognitive modeling embodies so many underlying implications that the subject is far from exhausted. In this brief commentary, however, I suggest that the conceptual thresholds of the meaningful learning give rise to a typical Boltzmann's weighting measure, which indicates a statistical verisimilitude of quantum behavior in the human cognitive ensemble.
Rotation sensing with trapped ions
Creators: name: Campbell, W. C.
name: Hamilton, P.
Publisher: name: arXiv
Year: 2016
Subjects: subject: Atomic Physics (physics.atom-ph)
subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: We present a protocol for using trapped ions to measure rotations via matter-wave Sagnac interferometry. The trap allows the interferometer to enclose a large area in a compact apparatus through repeated round-trips in a Sagnac geometry. We show how a uniform magnetic field can be used to close the interferometer over a large dynamic range in rotation speed and measurement bandwidth without losing contrast. Since this technique does not require the ions to be confined in the Lamb-Dicke regime, thermal states with many phonons should be sufficient for operation.
description: 13 pages, 2 figures
Job Satisfaction and Its Determinants in Addis Ababa: Evidence from Public Employees
Creators: name: Sisay, Fassil
Publisher: name: African Journal of Leadership and Development
Year: 2016

description: For decades, job satisfaction has been an object of interest for many. More recently, public managers find it difficult to disregard the issue of job satisfaction as it directly affects productivity and turnover of the workers. The main purpose of this research is to investigate determinants that influence the job satisfaction and analyze the level of job satisfaction of civil servants in Addis Ababa city administration. To achieve the research objective, information was gathered through questionnaires from 372 randomly selected public servants in five sub-cities (Bole, Arada, Yeka, Gulele, and Kirkos) during summer 2015. In order to analyze job satisfaction, an ordered probit model was utilized. After the analysis, some attention-grabbing findings have come into sight. To begin with, women are more satisfied with their jobs than men. It also shows an inverted U-shaped relationship between age and job satisfaction. The best and least trained are less satisfied relative to intermediately educated. Married are more satisfied than non-married. Moreover, family characteristics found to have no significant effect on job satisfaction of workers; health problems do not significantly affect job satisfaction; and living in rental house have lower job satisfaction than living in own house. With respect to job related characteristics, civil servants who are living in their own house, working in a conducive working environment, believe to have a secured job, commute for short distance, and worked for less than 5 years in present organization report higher level of job satisfaction. What is more, individuals working for Bole sub-city administration as well as those working in land administration sector have higher job satisfaction. Finally, this paper recommends the city administration to improve working environment; facilitate paths to homeownership for civil servants; device a mechanism to make them car owners; improve their earnings; and regularly assess job satisfaction.
description: African Journal of Leadership and Development, Vol. 1 No. 1 (2016): Public Sector Reform Leadership
Networked MIMO with Fractional Joint Transmission in Energy Harvesting Systems
Creators: name: Gong, Jie
name: Zhou, Sheng
name: Zhou, Zhenyu
Publisher: name: arXiv
Year: 2016
Subjects: subject: Information Theory (cs.IT)
subject: FOS: Computer and information sciences

description: This paper considers two base stations (BSs) powered by renewable energy serving two users cooperatively. With different BS energy arrival rates, a fractional joint transmission (JT) strategy is proposed, which divides each transmission frame into two subframes. In the first subframe, one BS keeps silent to store energy while the other transmits data, and then they perform zero-forcing JT (ZF-JT) in the second subframe. We consider the average sum-rate maximization problem by optimizing the energy allocation and the time fraction of ZF-JT in two steps. Firstly, the sum-rate maximization for given energy budget in each frame is analyzed. We prove that the optimal transmit power can be derived in closed-form, and the optimal time fraction can be found via bi-section search. Secondly, approximate dynamic programming (DP) algorithm is introduced to determine the energy allocation among frames. We adopt a linear approximation with the features associated with system states, and determine the weights of features by simulation. We also operate the approximation several times with random initial policy, named as policy exploration, to broaden the policy search range. Numerical results show that the proposed fractional JT greatly improves the performance. Also, appropriate policy exploration is shown to perform close to the optimal.
description: 33 pages, 7 figures, accepted by IEEE Transactions on Communications
Double quantum dot Cooper-pair splitter at finite couplings
Creators: name: Hussein, Robert
name: Jaurigue, Lina
name: Governale, Michele
name: Braggio, Alessandro
Publisher: name: arXiv
Year: 2016
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: Strongly Correlated Electrons (cond-mat.str-el)
subject: Superconductivity (cond-mat.supr-con)
subject: FOS: Physical sciences

description: We consider the sub-gap physics of a hybrid double-quantum dot Cooper-pair splitter with large single-level spacings, in the presence of tunnelling between the dots and finite Coulomb intra- and inter-dot Coulomb repulsion. In the limit of a large superconducting gap, we treat the coupling of the dots to the superconductor exactly. We employ a generalized master-equation method which easily yields currents, noise and cross-correlators. In particular, for finite inter- and intra-dot Coulomb interaction, we investigate how the transport properties are determined by the interplay between local and nonlocal tunneling processes between the superconductor and the dots. We examine the effect of inter-dot tunneling on the particle-hole symmetry of the currents with and without spin-orbit interaction. We show that spin-orbit interaction in combination with finite Coulomb energy opens the possibility to control the nonlocal entanglement and its symmetry (singlet/triplet). We demonstrate that the generation of nonlocal entanglement can be achieved even without any direct nonlocal coupling to the superconducting lead.
description: 12 pages, 7 figures
A VLA Survey For Faint Compact Radio Sources in the Orion Nebula Cluster
Creators: name: Sheehan, Patrick D.
name: Eisner, Josh A.
name: Mann, Rita K.
name: Williams, Jonathan P.
Publisher: name: arXiv
Year: 2016
Subjects: subject: Astrophysics of Galaxies (astro-ph.GA)
subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: FOS: Physical sciences

description: We present Karl G. Janksy Very Large Array (VLA) 1.3 cm, 3.6 cm, and 6 cm continuum maps of compact radio sources in the Orion Nebular Cluster. We mosaicked 34 square arcminutes at 1.3 cm, 70 square arcminutes at 3.6 cm and 109 square arcminutes at 6 cm, containing 778 near-infrared detected YSOs and 190 HST-identified proplyds (with significant overlap between those characterizations). We detected radio emission from 175 compact radio sources in the ONC, including 26 sources that were detected for the first time at these wavelengths. For each detected source we fit a simple free-free and dust emission model to characterize the radio emission. We extrapolate the free-free emission spectrum model for each source to ALMA bands to illustrate how these measurements could be used to correctly measure protoplanetary disk dust masses from sub-millimeter flux measurements. Finally, we compare the fluxes measured in this survey with previously measured fluxes for our targets, as well as four separate epochs of 1.3 cm data, to search for and quantify variability of our sources.
description: 13 pages, 6 figures, 4 tables, ApJ, in press
A landscape of main sequence cool stars activity
Creators: name: Degott, Lucie
name: Baudin, Frederic
name: Samadi, Réza
name: Damiani, Cilia
name: Perri, Barbara
name: Pinçon, Charly
Publisher: name: Zenodo
Year: 2023
Subjects: activity
solar-type

description: Stellar activity remains poorly understood: we need to improve our understanding of spot characteristics (total area, lifetime...), of magnetic cycles and its dependence on the internal structure of stars and more generally the different stellar parameters and their evolution. We propose to characterize this activity using the signature of the magnetic structures in the light curves of the Kepler mission, in the Fourier domain. For this, we revisit the model of Harvey et al. (1985) in order to take into account all the components present in the power spectra (surface covered by the spots, their lifetime, the transits...). After validating this model with simulated light curves, we present the results from thousands of Kepler light curves of main-sequence stars used by McQuillan (2014). The results show the emergence of different regimes of activity related to rotation period, mass, Rossby number, with very good statistics. This opens new perspectives for the study of stellar activity in the frame of the future PLATO mission thanks to its capacities in photometric precision and stellar characterization.
Gaia FGK Benchmark Stars
Creators: name: Soubiran, Caroline
Publisher: name: Zenodo
Year: 2023

description: The Gaia Benchmark stars (GBS) are reference stars which have been carefully selected for the calibration and the validation of atmospheric parameters massively determined from Gaia data and from spectroscopic surveys. They define the fundamental scale for Teff and logg which are determined independently of spectroscopy, through the fundamental relations based on angular diameters directly measured by interferometry, on bolometric flux (Fbol) measured by SED fitting, on parallax and on mass, the mass being the only quantity having a dependency on theoretical assumptions. GBS are chosen to cover as well as possible the HR diagram in the FGK range, including dwarfs, subgiants, and giants of all metallicities, representative of the different stellar populations of the Milky Way probed by Gaia and other large surveys. After the initial version of 34 stars by Heiter+ 2015, we now present the third version which includes nearly 200 stars. The precision of fundamental (Teff, logg) significantly improved thanks to the exquisite quality of Gaia data reflecting on distances and Fbol. This set of well-characterised stars is also important to improve stellar models.
Diophantine approximation in angular domains
Creators: name: Roy, Damien
Publisher: name: arXiv
Year: 2016
Subjects: subject: Number Theory (math.NT)
subject: FOS: Mathematics
subject: 11J13

description: Let $α$ and $β$ be real numbers such that $1$, $α$ and $β$ are linearly independent over $\mathbb{Q}$. A classical result of Dirichlet asserts that there are infinitely many triples of integers $(x_0,x_1,x_2)$ such that $|x_0+αx_1+βx_2| < \max\{|x_1|,|x_2|\}^{-2}$. In 1976, W. M. Schmidt asked what can be said under the restriction that $x_1$ and $x_2$ be positive. Upon denoting by $γ\cong 1.618$ the golden ratio, he proved that there are triples $(x_0,x_1,x_2) \in \mathbb{Z}^3$ with $x_1,x_2>0$ for which the product $|x_0 + αx_1 + βx_2| \max\{|x_1|,|x_2|\}^γ$ is arbitrarily small. Although Schmidt later conjectured that $γ$ can be replaced by any number smaller than $2$, N. Moshchevitin proved very recently that it cannot be replaced by a number larger than $1.947$. In this paper, we present a construction showing that the result of Schmidt is in fact optimal.
description: 15 pages
An efficient way to compute dense and accurate grids of stellar models including the effect of radiative accelerations
Creators: name: Moedas, Nuno
name: Bossini, Diego
name: Deal, Morgan
Publisher: name: Zenodo
Year: 2023
Subjects: Diffusion - Turbulence - Stars: abundances - Stars: evolution - Asteroseismology

description: The chemical transport mechanisms are key ingredients in stellar evolution. However, the
 computation of stellar models, used to characterize stars, often includes a simple atomic dif-
 fusion treatment, ignoring other additional processes, like the radiative accelerations. This is
 mainly due to their high computational costs. But this approximation should not be applied
 to F-type stars because of the large surface depletion of chemical elements that the use of
 the gravitational settling only would induce.
 With the incoming data from PLATO, the incomplete physics in stellar models would pre-
 vent us from extending the requirements imposed by this mission for G-type stars to hotter
 types, speci cally in terms of accuracy in age and mass. Hence, it is fundamental to include
 other competing transport processes for a better characterization of such stars.
 In this talk, we present an ecient way to overcome this issue in stellar models. First,
 we show how to avoid the over-variations of surface abundances by introducing a turbulent
 mixing coecient that can reproduce the e ects of extra chemical transport processes, in-
 cluding radiative accelerations, parametrized on the surface iron abundance. Secondly, we
 will show the results of the implementation of a more ecient way to compute radiative
 accelerations by using the Single-Valued Parameter (SVP) approximation in MESA. As a
 test, we present the impact of our prescriptions on the characterization of Kepler stars.
 With our work we manage to retrieve the surface chemical abundances of many elements,
 mimicking also the e ect of radial acceleration in its complete implementation. This develop-
 ment allows a fast computation of a large number of stellar models including these processes,
 permitting us to produce more accurately the stellar fundamental properties (especially the
 ages) for F-type and hotter stars. The methods we present here can be adapted to any stellar
 evolution code selected to compute the grids used in the PLATO pipeline.
Spin relaxation and the Kondo effect in transition metal dichalcogenide monolayers
Creators: name: Rostami, Habib
name: Moghaddam, Ali G.
name: Asgari, Reza
Publisher: name: arXiv
Year: 2016
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: Strongly Correlated Electrons (cond-mat.str-el)
subject: FOS: Physical sciences

description: We investigate the spin relaxation and Kondo resistivity caused by magnetic impurities in doped transition metal dichalcogenides monolayers. We show that momentum and spin relaxation times due to the exchange interaction by magnetic impurities, are much longer when the Fermi level is inside the spin split region of the valence band. In contrast to the spin relaxation, we find that the dependence of Kondo temperature $T_K$ on the doping is not strongly affected by the spin-orbit induced splitting, although only one of the spin species are present at each valley. This result, which is obtained using both perturbation theory and poor man's scaling methods, originates from the intervalley spin-flip scattering in the spin-split region. We further demonstrate the decline in the conductivity with temperatures close to $T_K$ which can vary with the doping. Our findings reveal the qualitative difference with the Kondo physics in conventional metallic systems and other Dirac materials.
description: 20 pages, 5 figures
Analysis of Link Formation, Persistence and Dissolution in NetSense Data
Creators: name: Bahulkar, Ashwin
name: Szymanski, Boleslaw K.
name: Lizardo, Omar
name: Dong, Yuxiao
name: Yang, Yang
name: Chawla, Nitesh V.
Publisher: name: arXiv
Year: 2016
Subjects: subject: Social and Information Networks (cs.SI)
subject: Physics and Society (physics.soc-ph)
subject: FOS: Computer and information sciences
subject: FOS: Physical sciences

description: We study a unique behavioral network data set (based on periodic surveys and on electronic logs of dyadic contact via smartphones) collected at the University of Notre Dame.The participants are a sample of members of the entering class of freshmen in the fall of 2011 whose opinions on a wide variety of political and social issues and activities on campus were regularly recorded - at the beginning and end of each semester - for the first three years of their residence on campus. We create a communication activity network implied by call and text data, and a friendship network based on surveys. Both networks are limited to students participating in the NetSense surveys. We aim at finding student traits and activities on which agreements correlate well with formation and persistence of links while disagreements are highly correlated with non-existence or dissolution of links in the two social networks that we created. Using statistical analysis and machine learning, we observe several traits and activities displaying such correlations, thus being of potential use to predict social network evolution.
High Latitude Sea-Surface Skin Temperatures Derived from Saildrone Infrared Measurements
Creators: name: Jia, Chong
Publisher: name: Zenodo
Year: 2022

description: Short abstract From 15th May to 11th October 2019, six Saildrone autonomous surface vehicles (ASVs) were deployed for 150-day cruises collecting a suite of atmospheric and oceanographic measurements from Dutch Harbor, Alaska, transiting the Bering Strait into the Chukchi Sea. Two Saildrones funded by NASA (the National Aeronautics and Space Administration), SD-1036 and SD-1037, were equipped with infrared pyrometers in a “unicorn” structure on the deck for the determination of the ocean sea-surface skin temperature (SSTskin). We present an algorithm to derive SSTskin from the downward- and upward-looking radiometers and estimate the main contributions to inaccuracy of the SSTskin. After stringent quality control of data and eliminating measurements influenced by sea ice and precipitation, and restricting the acceptable tilt angle of the ASV based on line-by-line radiative transfer model (LBLRTM) simulations, SSTskin can be derived to an accuracy of 0.12 K. The error budget of the derived SSTskin is developed and the largest component comes from the instrumental uncertainties assuming the viewing geometry is adequately determined. Thus, Saildrones equipped with these sensors could provide sufficiently accurate SSTskin retrievals for studying the physics of the thermal skin effect, in conjunction with accurate sub-surface thermometer measurements, and for validating satellite-derived SSTskin at high latitudes.
Dépression et antidépresseurs, facteurs de risque dans l’ostéoporose.
Creators: name: Bengana, Bilal
Publisher: name: figshare
Year: 2024
Subjects: classificationCode: 320223
subject: Rheumatology and arthritis

description: L’ostéoporose est un problème de santé publique, générant des répercussions à l’échelle de l’individu comme à celles d’une société et entrainant ainsi un coût économique important et une morbidité augmentée dans la population, sans omettre le retentissement psychologique non négligeable chez les personnes qui en souffrent. C’est justement ces mêmes désordres psychologiques qui peuvent provoquer ou entretenir une telle pathologie, parmi eux l’anxiété et la dépression qui peuvent constituer des facteurs de risque de fragilité osseuse, ainsi que les traitements consommés pour traiter ces dernières, responsables d’une baisse conséquente de la densité minérale osseuse et exposant à un risque accru de fractures ostéoporotiques. Il est important pour tout praticien de savoir dépister l’ostéoporose chez une population avec des facteurs de risque comme ceux qui présentent une dépression et/ou consomment des traitements neuroleptiques ou antidépresseurs, et qui peuvent avoir un retentissement sur la force de l’os. Il est nécessaire aussi aux médecins psychiatres et rhumatologues de travailler étroitement pour savoir prendre en charge rapidement les sujets à risque.
Gibbs states defined by biorthogonal sequences
Creators: name: Bagarello, Fabio
name: Trapani, Camillo
name: Triolo, Salvatore
Publisher: name: arXiv
Year: 2016
Subjects: subject: Mathematical Physics (math-ph)
subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: Motivated by the growing interest on PT-quantum mechanics, in this paper we discuss some facts on generalized Gibbs states and on their related KMS-like conditions. To achieve this, we first consider some useful connections between similar (Hamiltonian) operators and we propose some extended version of the Heisenberg algebraic dynamics, deducing some of their properties, useful for our purposes.
description: In press in Journal of Physics A
Entanglement is an inevitable feature of any non-classical theory
Creators: name: Richens, Jonathan G.
name: Selby, John H.
name: Al-Safi, Sabri W.
Publisher: name: arXiv
Year: 2016
Subjects: subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: One of the most striking features of quantum theory is the existence of entangled states, responsible for Einstein's so called "spooky action at a distance". These states emerge from the mathematical formalism of quantum theory, but to date we do not have a clear idea of which physical principles give rise to entanglement. Why does quantum theory have entangled states? Would any theory superseding classical theory have entangled states, or is quantum theory special? We demonstrate that without entanglement, non-classical degrees of freedom cannot reversibly interact. We present two postulates, no-cloning / no-broadcasting and local transitivity, either of which are sufficient to imply the existence of entangled states in any non-classical theory with reversible interactions. Therefore we argue that entanglement is an inevitable feature of a non-classical universe.
description: 7 pages including appendices
2o Coloquio Internacional de Gobernanza Metropolitana y II Reunión General de la Red Gobernanza Metropolitana
Creators: name: Navarrete Ulloa, Carlos Alberto
name: Guevara Castillo, Álvaro Ángel
Publisher: name: Zenodo
Year: 2018
Subjects: gobernanza metropolitana
redes temáticas
grupos de investigación

description: El 2o Coloquio Internacional de Gobernanza Metropolitana y II Reunión General de la Red Gobernanza Metropolitana se realizó en las instalaciones de El Colegio de Jalisco del 14 al 16 de noviembre de 2018. Las principales actividades consistieron en: Conferencia Magistral: 12 de nov. 10 a.m.: Dr. Luis F. Aguilar Villanueva, Director del Instituto de Investigación en Políticas Públicas y Gobierno de la UdeG 13 de nov. 10 a.m.: Mtro. Sergio Graff, Medio Ambiente y Desarrollo Territorial en el Estado de Jalisco. Organización de la II-ReGobM: 90 ponentes / 15 Grupos de Trabajo / 32 instituciones mexicanas y 11 de procedencia internacional. Celebraremos 2 Conferencias Magistrales, 5 Conversatorios especializados, 8 presentaciones de libros y 3 Talleres de talla internacional. La convocatoria se dirige a: sociedad civil organizada, académicos, sector empresarial, cámaras y colegios de profesionistas, funcionarios públicos. Con invitación especial a rectores de las principales Universidades de Jalisco, lideres sociales, la CMIC, Colegio de Arquitectos del Estado de Jalisco, Colegio de Urbanistas, Colegio de Ingenieros del Estado de Jalisco, presidentes municipales de la ZMG, académicos y estudiantes, entre otros. Semana de la Gobernanza Metropolitana: 12 y 13 de noviembre II-ReGobM; 14, 15 y 16 Seminario Gobernanza Metropolitana y talleres Hechos metropolitanos, Metro-game y Distritos Creativos y Digitales.
description: La Red Gobernanza Metropolitana es la articulación de múltiples actores en espacios de reflexión e interacción para ampliar la comprensión, retos y oportunidades de las ciudades metropolitanas en México.
Influence of tangential displacement on the force of adhesion between a parabolic profile and plane surface
Creators: name: Popov, Valentin L.
name: Lyashenko, Iakov A.
name: Filippov, Alexander E.
Publisher: name: arXiv
Year: 2016
Subjects: subject: Soft Condensed Matter (cond-mat.soft)
subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: FOS: Physical sciences
subject: 74A05, 74A10

description: The force of adhesion of a rotationally symmetric indenter and an elastic half-space is analyzed analytically and numerically using an extension of the method of dimensionality reduction (MDR) for superimposed normal/tangential adhesive contacts. In particular, the dependency of the critical adhesion force on the simultaneously applied tangential force is obtained and the relevant dimensionless parameters of the problem are identified. The developed method is applicable straightforwardly to adhesive contacts of any bodies of revolution.
description: 12 pages, 3 figures
title: Deep learning in shallow waters: solution of shallow water equations using physics-informed neural networks
title: Μηχανική μάθηση σε ρηχά νερά: Επίλυση των εξισώσεων ρηχών υδάτων χρησιμοποιώντας φυσιογνωστικά νευρωνικά δίκτυα
Creators: name: Μαλαμας Ηλιας
Publisher: name: Technical University of Crete
Year: 2024

description: In this thesis we use Physics-informed Neural Networks (PINNs) to solve the Shallow Water Equations (SWE). We provide some insight into the novel idea of PINNs, which constitute a deviation from the rigorous context of the supervised learning paradigm, in the sense that no experimental or simulation data are necessary to train the neural network to solve the SWE, making them the solver of choice in cases where the production of labelled data is costly, time-consuming, or even impossible. We first provide an outline of the system of Partial Differential Equations (PDEs), that describe the SWEs and include some principal properties. We then introduce the idea of using the PINNs as an “unconventional” solver to those PDEs. In order to validate the solver, we engage the PINNs in several benchmark problems of increasing numerical difficulty, in order to prove the adequacy of the PINN idea as a SWE solver. In the sequel, we focus on the effect of the sampling strategy of the training points (domain and boundary) that are used to train the PINN, on the performance of the PINN, in an effort to shed some light on this aspect of the PINN training, when they are used to solve the SWE, applied on a demanding, Riemann problem.
description: Σε αυτήν την εργασία χρησιμοποιούμε τα Φυσιογνωστικά Νευρωνικά Δίκτυα (ΦυΓΝεΔ) για την επίλυση των Εξισώσεων Αβαθών Νερών (ΕΑΝ). Παρέχουμε μια επιγραμματική παρουσίαση της καινοτόμου ιδέας των ΦυΓΝεΔ, τα οποία συνιστούν περίπτωση που αποκλίνει από το αυστηρό πλαίσιο του παραδείγματος της επιβλεπόμενης μάθησης, με την έννοια ότι για την εκπαίδευση του νευρωνικού δικτύου για την επίλυση των ΕΑΝ, δεν είναι απαραίτητα δεδομένα από πειράματα ή εξομοιώσεις, ιδιότητα η οποία τα καθιστά τη μόνη επιλογή σε περιπτώσεις όπου η παραγωγή σεσημασμένων δεδομένων είναι δαπανηρή, χρονοβόρα, ή ακόμα και αδύνατη. Σε πρώτη φάση παρέχουμε ένα περίγραμμα του συστήματος Διαφορικών Εξισώσεων Μερικών Παραγώγων (ΔΕΜΠ), οι οποίες περιγράφουν τις ΕΑΝ και δίνουμε και μερικές βασικές ιδιότητές τους. Κατόπιν, εισάγουμε την ιδέα της χρήσης των ΦυΓΝεΔ ως έναν «μη-συμβατικό» επιλύτη αυτών των ΔΕΜΠ. Προκειμένου να επικυρώσουμε τον επιλύτη, χρησιμοποιούμε τα ΦυΓΝεΔ σε ορισμένα προβλήματα αναφοράς, αυξανόμενης αριθμητικής δυσκολίας, προκειμένου να αποδείξουμε την επάρκεια των ΦυΓΝεΔ ως επιλύτη των ΕΑΝ. Στη συνέχεια, εστιάζουμε στην απόδοση των ΦυΓΝεΔ και στην επίδραση της στρατηγικής της δειγματοληψίας των σημείων εκμάθησης (τόσο του πεδίου όσο και των ορίων) που χρησιμοποιούνται στην εκπαίδευση των ΦυΓΝεΔ, σε μια προσπάθεια να φωτίσουμε αυτήν την πλευρά της εκπαίδευσης των ΦυΓΝεΔ, όταν αυτά χρησιμοποιούνται στην επίλυση των ΕΑΝ, σε ένα απαιτητικό πρόβλημα Riemann.
Signatures of metal-free star formation in Planck 2015 Polarization Data
Creators: name: Miranda, V
name: Lidz, Adam
name: Heinrich, Chen He
name: Hu, Wayne
Publisher: name: arXiv
Year: 2016
Subjects: subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: FOS: Physical sciences

description: Standard analyses of the reionization history of the universe from Planck cosmic microwave background (CMB) polarization measurements consider only the overall optical depth to electron scattering ($τ$), and further assume a step-like reionization history. However, the polarization data contain information beyond the overall optical depth, and the assumption of a step-like function may miss high redshift contributions to the optical depth and lead to biased $τ$ constraints. Accounting for its full reionization information content, we reconsider the interpretation of Planck 2015 Low Frequency Instrument (LFI) polarization data using simple, yet physically-motivated reionization models. We show that these measurements still, in fact, allow a non-negligible contribution from metal-free (Pop-III) stars forming in mini-halos of mass $M \sim 10^5-10^6 M_\odot$ at $z \gtrsim 15$, provided this mode of star formation is fairly inefficient. Our best fit model includes an early, self-regulated phase of Pop-III star formation in which the reionization history has a gradual, plateau feature. In this model, $\sim$20\% of the volume of the universe is ionized by $z \sim 20$, yet it nevertheless provides a good match to the Planck LFI measurements. Although preferred when the full information content of the data is incorporated, this model would spuriously be disfavored in the standard analysis. This preference is driven mostly by excess power from E-mode polarization at multipoles of $10 \lesssim \ell \lesssim 20$, which may reflect remaining systematic errors in the data, a statistical fluctuation, or signatures of the first stars. Measurements from the Planck High Frequency Instrument (HFI) should be able to confirm or refute this hint and future cosmic-variance limited E-mode polarization surveys can provide substantially more information on these signatures
description: likelihood code available on request
Une version effective du théorème de Lindemann-Weierstrass par des méthodes d'indépendance algébrique
Creators: name: Roy, Damien
Publisher: name: arXiv
Year: 2016
Subjects: subject: Number Theory (math.NT)
subject: FOS: Mathematics
subject: 11J85

description: We present a new completely effective proof of the Lindemann-Weierstrass theorem based on algebraic independence methods. Although it is slightly weaker than the best known estimate due to A. Sert, it improves the best estimate due to M. Ably obtained by such methods. The novelty of the proof lies in the simplicity of the construction of auxiliary functions, a fact that we exploit to introduce the non-specialist to methods of algebraic independence.
description: in French
Diagonal-preserving gauge-invariant isomorphisms of graph $C^*$-algebras
Creators: name: Carlsen, Toke Meier
name: Rout, James
Publisher: name: arXiv
Year: 2016
Subjects: subject: Operator Algebras (math.OA)
subject: FOS: Mathematics

description: We study graph $C^*$-algebras equipped with generalised gauge actions, and characterise in terms of groupoids and groupoid cocycles when two graph $C^*$-algebras are isomorphic by a diagonal-preserving isomorphism that intertwines the generalised gauge actions. We apply this characterisation to show that two Cuntz-Krieger algebras are isomorphic by a diagonal-preserving isomorphism that intertwines the gauge actions if and only if the corresponding one-sided subshifts are eventually conjugate, and that the stabilisation of two Cuntz-Krieger algebras are isomorphic by a diagonal-preserving isomorphism that intertwines the gauge actions if and only if the corresponding two-sided subshifts are conjugate.
description: 12 pages
title: The study of some physical properties of selected rare Earth compounds
Creators: name: Westall, William Alexander
Publisher: name: University of Kent
Year: 2023

description: The work set out in this thesis relates to studies of europium(II) and europium(III) containing solids. The primary mode of study was Mossbauer spectroscopy supported where useful, by information from chemical analysis, x-ray diffractometry, electrical conductivity, thermogravimetry, infra-red and mass spectrometry. The thermal dehydration of EuCl3.6H2O and EuBr3.6H2O and subsequent conversion to oxyhaliae and oxide was studied initially by thermogravimetry to define stable intermediates; these were afterwards prepared in amounts enabling their characterization. The chloride system gave a sequence of well-defined intermediate hydrates; but those for the bromide system were less well-defined. Neither anhydrous europium(III) halide was observed in contrast with previous reports. However in the absence of oxygen the thermal decomposition of the hydrated bromide resulted in the formation of some europium(II) at temperatures above 300°C. The non-stoichiometric phase formed in the initial stages of the thermal reaction EuBr3 —» EuBr2 + 1/2 Br2 has been studied. The temperature dependent Mossbauer spectra are consistent with an "electron hopping" mechanism similar to that involved previously to describe non-stoichiometric EuCl3. Electrical conductivity measurements on both chloride and bromide systems revealed two regions for each system; they were separated by a characteristic temperature of 198 - 2K and 222 - 2K respectively. Below these temperatures charge ordering in the lattice is considered to occur while above, electron hopping predominates. Activation energies calculated for electron hopping from spectral and conductivity data are in agreement. Several europium-mercury compounds (EuHg where x = 0.8,1,2,3,3.6) have been prepared and studied. Correlation was found between the europium isomer shift and (n/v) where n is the number of europium ions in a unit cell of volume v. The electron density at the europium nucleus together with an approximate electron configuration of the europium ion core have been determined for each of the samples. The compounds were found to be metallic in nature with some degree of normal valence character in bonding. The ionic core of europium was found to be divalent with the conduction electron density at the nucleus decreasing with decreasing europium concentration in the crystal lattice.
Wave emission and absorption at spectral singularities
Creators: name: Wang, P.
name: Jin, L.
name: Zhang, G.
name: Song, Z.
Publisher: name: arXiv
Year: 2016
Subjects: subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: We studied the critical dynamics of spectral singularities. The system investigated is a coupled resonator array with a side-coupled loss (gain) resonator. For a gain resonator, the system acts as a wave emitter at spectral singularities. The reflection probability increased linearly over time. The rate of increase is proportional to the width of the incident wave packet, which served as the spectral singularity observer in the experiment. For a lossy resonator, the system acts as a wave absorber. The emission and absorption states at spectral singularities coalesce in a finite parity-time (PT ) symmetric system that combined by the gain and loss structures cut from corrresponding scattering systems at spectral singularities; in this case, the PT -symmetric system is at an exceptional point with a 2 * 2 Jordan block. The dynamics of the PT -symmetric system exhibit the characteristic of exceptional points and spectral singularities.
Supplementary document for Natural exceptional points in the excitation spectrum of a light-matter system - 6458763.pdf
Creators: name: Opala, Andrzej
name: Furman, Magdalena
name: Król, Mateusz
name: Mirek, Rafal
name: Tyszka, Krzysztof
name: Seredynski, Bartlomiej
name: Pacuski, Wojciech
name: Szczytko, Jacek
name: Matuszewski, Michal
name: Pietka, Barbara
Publisher: name: Optica Publishing Group
Year: 2023
Subjects: Uncategorized

description: Analysis of linear excitations and collective excitation spectrum
$PT$-symmetric graphene under a magnetic field
Creators: name: Bagarello, Fabio
name: Hatano, Naomichi
Publisher: name: arXiv
Year: 2016
Subjects: subject: Mathematical Physics (math-ph)
subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: FOS: Physical sciences

description: We propose a $PT$-symmetrically deformed version of the graphene tight-binding model under a magnetic field. We analyze the structure of the spectra and the eigenvectors of the Hamiltonians around the $K$ and $K'$ points, both in the $PT$-symmetric and $PT$-broken regions. In particular we show that the presence of the deformation parameter $V$ produces several interesting consequences, including the asymmetry of the zero-energy states of the Hamiltonians and the breakdown of the completeness of the eigenvector sets. We also discuss the biorthogonality of the eigenvectors, which {turns out to be} different in the $PT$-symmetric and $PT$-broken regions.
description: in press in Proceedings of the Royal Society A
Computation and validation of two-dimensional PSF simulation based on physical optics
Creators: name: Tayabaly, K.
name: Spiga, D.
name: Sironi, G.
name: Canestrari, R.
name: Lavagna, M.
name: Pareschi, G.
Publisher: name: arXiv
Year: 2016
Subjects: subject: Instrumentation and Methods for Astrophysics (astro-ph.IM)
subject: FOS: Physical sciences

description: The Point Spread Function (PSF) is a key figure of merit for specifying the angular resolution of optical systems and, as the demand for higher and higher angular resolution increases, the problem of surface finishing must be taken seriously even in optical telescopes. From the optical design of the instrument, reliable ray-tracing routines allow computing and display of the PSF based on geometrical optics. However, such an approach does not directly account for the scattering caused by surface microroughness, which is interferential in nature. Although the scattering effect can be separately modeled, its inclusion in the ray-tracing routine requires assumptions that are difficult to verify. In that context, a purely physical optics approach is more appropriate as it remains valid regardless of the shape and size of the defects appearing on the optical surface. Such a computation, when performed in two-dimensional consideration, is memory and time consuming because it requires one to process a surface map with a few micron resolution, and the situation becomes even more complicated in case of optical systems characterized by more than one reflection. Fortunately, the computation is significantly simplified in far-field configuration, since the computation involves only a sequence of Fourier Transforms. In this paper, we provide validation of the PSF simulation with Physical Optics approach through comparison with real PSF measurement data in the case of ASTRI-SST M1 hexagonal segments. These results represent a first foundation stone for future development in a more advanced computation taking into account microroughness and multiple reflection in optical systems.
description: Preprint version. The fully published paper can be found at https://doi.org/10.1117/12.2187534