cometadata/datacite-rtg-text-other-reclassification-records huggingface dataset:
Controlling the TiN electrode work function at the atomistic level: a first principles investigation
Creators: name: Calzolari, Arrigo
name: Catellani, Alessandra
Publisher: name: arXiv
Year: 2021
Subjects: subject: Materials Science (cond-mat.mtrl-sci)
subject: FOS: Physical sciences

description: The paper reports on a theoretical description of work function of TiN, which is one of the most used materials for the realization of electrodes and gates in CMOS devices. Indeed, although the work function is a fundamental quantity in quantum mechanics and also in device physics, as it allows the understanding of band alignment at heterostructures and gap states formation at the metal/semiconductor interface, the role of defects and contaminants is rarely taken into account. Here, by using first principles simulations, we present an extensive study of the work function dependence on nitrogen vacancies and surface oxidation for different TiN surface orientations. The results complement and explain a number of existent experimental data, and provide a useful tool to tailoring transport properties of TiN electrodes in device simulations.
description: 7 pages, 5 figures
The Nambu-Goto and Polyakov Strings via the Relativistic Particles
Creators: name: Kamani, Davoud
Publisher: name: arXiv
Year: 2006
Subjects: subject: High Energy Physics - Theory (hep-th)
subject: FOS: Physical sciences

description: We assume the bosonic string is a composite object of the relativistic particles. The behavior of the relativistic particles in a curve enables us to obtain the Nambu-Goto and the Polyakov actions of the bosonic string. We observe that the particles of these strings move with non-constant speeds along them.
description: 12 pages, Latex, no figure. In the revised version some changes have been introduced
Quantum random walk of two photons in separable and entangled state
Creators: name: Pathak, P. K.
name: Agarwal, G. S.
Publisher: name: arXiv
Year: 2006
Subjects: subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: We discuss quantum random walk of two photons using linear optical elements. We analyze the quantum random walk using photons in a variety of quantum states including entangled states. We find that for photons initially in separable Fock states, the final state is entangled. For polarization entangled photons produced by type II downconverter, we calculate the joint probability of detecting two photons at a given site. We show the remarkable dependence of the two photon detection probability on the quantum nature of the state. In order to understand the quantum random walk, we present exact analytical results for small number of steps like five. We present in details numerical results for a number of cases and supplement the numerical results with asymptotic analytical results.
Interpersonal differences in sociotropic and autonomous dysthymic subtypes
Creators: name: Bieling, Peter J.
Publisher: name: University of British Columbia
Year: 2008

description: The current study reviews theoretical and research evidence which links the concepts of sociotropy and autonomy to depression. The concepts of sociotropy and autonomy have been implicated as relevant factors in pre-disposing individuals to depression and as influencing the experience of depression; however, important postulated interpersonal differences have not been examined empirically. The current study explores theoretical interpersonal differences in sociotropic or autonomous dysthymic women. The motivational goals, interpersonal concerns, and other perceptions of sociotropic and autonomous individuals were assessed after an interpersonal interaction. Subjects who were found to be dysthymic and displayed excessive sociotropy or autonomy were asked to participate in a laboratory task with a confederate who acted either in a controlling or passive manner. Sociotropic subjects were more motivated by interpersonal goals in the interaction than autonomous subjects. Sociotropes were more dependent on their partners and felt that they had to rely on them to a greater extent for support, help, and advice; they also attempted to please their partner and were concerned about their partner's evaluation of them. These individuals felt their partner had evaluated them positively, was dependable, and was pleased with them. On the other hand, autonomous individuals felt that they were being intruded upon by their partner during the interaction, that their partner had acted in a controlling manner, and that their partner had perfectionistic standards. Perceptions of others was independent of actual behaviour of interaction partners. Moreover, sociotropic subjects were better liked by confederates than were autonomous subjects and confederates rated sociotropics as more likeable. These results indicate that sociotropic individuals are more interpersonally oriented than autonomous individuals and that these individuals not only perceive others differently, but are perceived differently by others. Implications for interpersonal models of depression are discussed and the possible impact of these differences on the experience of depression are examined.
TableSense: Spreadsheet Table Detection with Convolutional Neural Networks
Creators: name: Dong, Haoyu
name: Liu, Shijie
name: Han, Shi
name: Fu, Zhouyu
name: Zhang, Dongmei
Publisher: name: arXiv
Year: 2021
Subjects: subject: Information Retrieval (cs.IR)
subject: FOS: Computer and information sciences

description: Spreadsheet table detection is the task of detecting all tables on a given sheet and locating their respective ranges. Automatic table detection is a key enabling technique and an initial step in spreadsheet data intelligence. However, the detection task is challenged by the diversity of table structures and table layouts on the spreadsheet. Considering the analogy between a cell matrix as spreadsheet and a pixel matrix as image, and encouraged by the successful application of Convolutional Neural Networks (CNN) in computer vision, we have developed TableSense, a novel end-to-end framework for spreadsheet table detection. First, we devise an effective cell featurization scheme to better leverage the rich information in each cell; second, we develop an enhanced convolutional neural network model for table detection to meet the domain-specific requirement on precise table boundary detection; third, we propose an effective uncertainty metric to guide an active learning based smart sampling algorithm, which enables the efficient build-up of a training dataset with 22,176 tables on 10,220 sheets with broad coverage of diverse table structures and layouts. Our evaluation shows that TableSense is highly effective with 91.3\% recall and 86.5\% precision in EoB-2 metric, a significant improvement over both the current detection algorithm that are used in commodity spreadsheet tools and state-of-the-art convolutional neural networks in computer vision.
Hic sunt dracones! the modern unknown Data Dragons
Creators: name: Thiery, Florian
name: Trognitz, Martina
name: Gruber, Ethan
name: Wigg-Wolf, David
Publisher: name: Zenodo
Year: 2019
Subjects: Linked Data
Linked Open Data
Five Star Data
FAIR Data
Semantic Web
Data Dragon
CAA
Archaeology

description: The world of digital data is full of unknown data, with are not FAIR (Findable, Accessible, Interoperable and Reusable).
 This modern species of dragons on a (digital) map of the internet as sign for unknown and dangerous areas, the unknown
 digital data dragons, have to be resolved by digital techniques. We could use the Semantic Web and all of its ideas for this
 challenge. This paper focuses on data dragons in the humanities domain, especially in archaeology and proposes ideas to
 overcome the data dragons to achieve FAIR LOUD in archaeology!
On moment-density estimation in some biased models
Creators: name: Mnatsakanov, Robert M.
name: Ruymgaart, Frits H.
Publisher: name: arXiv
Year: 2006
Subjects: subject: Statistics Theory (math.ST)
subject: FOS: Mathematics
subject: 62G05 (Primary) 62G20 (Secondary)

description: This paper concerns estimating a probability density function $f$ based on iid observations from $g(x)=W^{-1} w(x) f(x)$, where the weight function $w$ and the total weight $W=\int w(x) f(x) dx$ may not be known. The length-biased and excess life distribution models are considered. The asymptotic normality and the rate of convergence in mean squared error (MSE) of the estimators are studied.
description: Published at http://dx.doi.org/10.1214/074921706000000536 in the IMS Lecture Notes--Monograph Series (http://www.imstat.org/publications/lecnotes.htm) by the Institute of Mathematical Statistics (http://www.imstat.org)
title: Η ναυτιλία στην εποχή του Covid-19 και οι συνέπειες στις χρηματοοικονομικές καταστάσεις των ναυτιλιακών εταιριών
title: Shipping during the Covid-19 era and the consequences on financial statements of shipping companies
Creators: name: Κωστας Σταυρος
Publisher: name: Technical University of Crete
Year: 2021

description: Σκοπός της διπλωματικής εργασίας είναι η χρηματοοικονομική πληγή αλλά και οι ευρύτερες χρηματοοικονομικές διαταραχές που προκάλεσε η πανδημία στον τομέα της ναυτιλίας. Η παραπάνω ανάλυση πραγματοποιήθηκε σε δέκα (10) ναυτιλιακές εταιρείες που δραστηριοποιούνται τόσο στον ελλαδικό όσο και στο διεθνή θαλάσσιο χώρο. Για την επιλογή των ναυτιλιακών εταιρειών καθοριστικό ρόλο αποτέλεσε η οικονομική κατάσταση καθώς και η κατηγορία πλοίων που απασχολεί κάθε επιχείρηση ώστε να γίνει αποτελεσματική συγκρίσεις μεταξύ τους. Επομένως, επιλέχθηκαν εταιρείες που διαθέτουν υγραεριοφόρα πλοία, μεταφορές επιβατών, πλοία με ξηρό φορτίο χύδην και τέλος μεταφορά εμπορευματοκιβωτίων. Η οικονομική ανάλυση έγινε με βάση τους χρηματοοικονομικούς αριθμοδείκτες οι οποίοι προέκυψαν από τις οικονομικές καταστάσεις των ναυτιλιακών εταιρειών για την τελευταία πενταετία, με στόχο την αξιόπιστη μελέτη για την οικονομική πορεία έως και την ολοκλήρωση των αυστηρών περιοριστικών μέτρων. Τέλος, με την μέθοδο τις οριζόντιας ανάλυσης πραγματοποιήθηκε η διαχρονική σύγκριση των εταιρειών ως προς το κεφάλαιο κίνησης, σε σχέση πάντα με το προηγούμενο έτος, αλλά και μεταξύ των εταιρειών που δραστηριοποιούνται σε όμοια είδη πλοίων.
description: The purpose of the dissertation is the financial wound but also the wider financial disturbancescausedby the pandemic in the shipping sector. The above analysis was performed in ten(10) shippingcompanies operating both in Greece and in the international maritime space. The financial situationaswell as the category of ships occupied by each company played a decisive role in the selectionoftheshipping companies in order to make effective comparisons between them. Therefore, companieswithLPG vessels, passenger transport, dry bulk carriers and finally container transport wereselected. Thefinancial analysis was based on the financial ratios that emerged from the financial statementsoftheshipping companies for the last five years, with the aim of a reliable study of the economic courseuntilthe completion of the strict restrictive measures. Finally, with the method of horizontal analysis, thetime comparison of the companies in terms of working capital was carried out, always inrelationtotheprevious year, but also between the companies that are active in similar types of ships.
Spin transfer torques in nonlocal lateral spin valve
Creators: name: Xu, Yuan
name: Xia, Ke
name: Ma, Zhongshui
Publisher: name: arXiv
Year: 2008
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: FOS: Physical sciences

description: We report a theoretical study on the spin and electron transport in the nonlocal lateral spin valve with non-collinear magnetic configuration. The nonlocal magnetoresistance, defined as the voltage difference on the detection lead over the injected current, is derived analytically. The spin transfer torques on the detection lead are calculated. It is found that spin transfer torques are symmetrical for parallel and antiparallel magnetic configurations, which is different from that in conventional sandwiched spin valve.
description: 7 papges, 5 figures
In-plane and transverse superconducting fluctuation diamagnetism in the presence of charge-density waves in 2H-NbSe2 single crystals
Creators: name: Soto, F.
name: Berger, H.
name: Cabo, L.
name: Carballeira, C.
name: Mosqueira, J.
name: Pavuna, D.
name: Vidal, F.
Publisher: name: arXiv
Year: 2006
Subjects: subject: Superconductivity (cond-mat.supr-con)
subject: FOS: Physical sciences

description: The fluctuation-diamagnetism (FD) above the superconducting transition was measured in 2H-NbSe2 single crystals. The moderate uniaxial anisotropy of this compound, and some experimental improvements, allowed to measure the superconducting fluctuation effects in the two main crystallographic directions. These results reveal that the nonlocal electrodynamic effects on the FD are highly anisotropic, and they also discard a possible contribution to the FD coming from the charge-density waves (CDW) appearing below $Tcdw > Tc in 2H-NbSe2, in agreement with a phenomenological estimate.
description: 7 pages, 5 figures
Historical Developments of the Theory of Transcendence and Algebraic Independence
Creators: name: Fernandes, Gwladys
Publisher: name: arXiv
Year: 2021
Subjects: subject: Number Theory (math.NT)
subject: FOS: Mathematics

description: Qu'est la majest{é} de ce qui finit, aupr{è}s des d{é}parts titubants, des d{é}sordres de l'aurore?. Let this question from the French writer Colette guide us to walk through the promising beginnings, fascinating evolutions and results, challenging open problems and perspectives of an exciting theory that is far from revealing all its secrets.
РАСЧЕТ ПОТЕРЬ В МНОГОСЛОЙНОМ КРУГЛОМ ПЛАЗМОННОМ ВОЛНОВОДЕ
Creators: name: Селина Н.В.
name: Хить Я.В.
name: Иващенко Н.Г.
Publisher: name: Математическое моделирование, компьютерный и натурный эксперимент в естественных науках
Year: 2023
Subjects: цилиндрический волновод
поверхностные плазмоны
многослойная оболочка

description: Разработан алгоритм расчета потерь в цилиндрическом волноводе. Приведен результат чис-ленного расчета таких структур, графический анализ результата подтверждает снижение потерь в многослойной плазмонной структуре.
Precise Coulomb wave functions for a wide range of complex l, eta and z
Creators: name: Michel, N.
Publisher: name: arXiv
Year: 2007
Subjects: subject: Computational Physics (physics.comp-ph)
subject: FOS: Physical sciences

description: A new algorithm to calculate Coulomb wave functions with all of its arguments complex is proposed. For that purpose, standard methods such as continued fractions and power/asymptotic series are combined with direct integrations of the Schrodinger equation in order to provide very stable calculations, even for large values of |eta| or |Im(l)|. Moreover, a simple analytic continuation for Re(z) < 0 is introduced, so that this zone of the complex z-plane does not pose any problem. This code is particularly well suited for low-energy calculations and the calculation of resonances with extremely small widths. Numerical instabilities appear, however, when both |eta| and |Im(l)| are large and |Re(l)| comparable or smaller than |Im(l)|.
An INTEGRAL monitoring of GRS 1915+105 using simultaneous space and ground based instruments
Creators: name: Rodriguez, Jerome
name: Pooley, Guy
name: Hannikainen, Diana
name: Lehto, Harry J.
name: Belloni, Tomaso
name: Cadolle-Bel, Marion
name: Corbel, Stephane
Publisher: name: arXiv
Year: 2006
Subjects: subject: Astrophysics (astro-ph)
subject: FOS: Physical sciences

description: We report the results of 3 observations of GRS 1915+105 during which the source is found to show the X-ray dips/spike sequences (cycles). These observations were performed simultaneously with \integral, RXTE, the Ryle and Nancay radio telescopes. They show the so-called $ν$, $λ$ and $β$ classes of variability during which a high level of correlated X-ray and radio variability is observed. We study the connection between the accretion processes seen in the X-ray behaviour, and the ejections seen in radio. By observing ejection during class $λ$, we generalise the fact that the discrete ejections in GRS 1915+105 occur after the cycles seen at X-ray energies, and identify the most likely trigger of the ejection through a spectral approach to our INTEGRAL data. We show that each ejection is very probably the result of the ejection of a Comptonising medium responsible for the hard X-ray emission seen above 15 keV with INTEGRAL. We study the rapid variability of the source, and observe the presence of Low Frequency Quasi Periodic Oscillations during the X-ray dips. The ubiquity of the former behaviour, and the following ejection may suggest a link between the QPO and the mechanism responsible for the ejection.
description: 10 pages, 7 figures, proceedings of the microquasar workshop held in Como, Italy, Sept. 18-22, 2006. Eds T. Belloni
Towards an Engineering Framework for Ultrafast Quantum Nonlinear Optics
Creators: name: Yanagimoto, Ryotatsu
name: Ng, Edwin
name: Onodera, Tatsuhiro
name: Mabuchi, Hideo
Publisher: name: arXiv
Year: 2021
Subjects: subject: Quantum Physics (quant-ph)
subject: Optics (physics.optics)
subject: FOS: Physical sciences

description: The advent of dispersion-engineered and highly nonlinear nanophotonics is expected to open up an all-optical path towards the strong-interaction regime of quantum optics by combining high transverse field confinement with ultra-short-pulse operation. Obtaining a full understanding of photon dynamics in such broadband devices, however, poses major challenges in the modeling and simulation of multimode non-Gaussian quantum physics, highlighting the need for sophisticated reduced models that facilitate efficient numerical study while providing useful physical insight. In this manuscript, we review our recent efforts in modeling broadband optical systems at varying levels of abstraction and generality, ranging from multimode extensions of quantum input-output theory for sync-pumped oscillators to the development of numerical methods based on a field-theoretic description of nonlinear waveguides. We expect our work not only to guide ongoing theoretical and experimental efforts towards next-generation quantum devices but also to uncover essential physics of broadband quantum photonics.
description: The first two authors contributed equally to this work; 11 pages, 2 figures
Additional file 1: of Non-ossifying fibroma with a pathologic fracture in a 12-year-old girl with tricho-rhino-phalangeal syndrome: a case report
Creators: name: Su, Weijuan
name: Shi, Xiulin
name: Lin, Mingzhu
name: Huang, Caoxin
name: Wang, Liying
name: Song, Haiqu
name: Zhuang, Yanzhen
name: Zhang, Haifang
name: Li, Nanzhu
name: Li, Xuejun
Publisher: name: figshare
Year: 2018
Subjects: subject: Medicine
subject: Genetics
subject: FOS: Biological sciences
subject: Biotechnology
subject: Sociology
subject: FOS: Sociology
subject: Biological Sciences not elsewhere classified
subject: Mathematical Sciences not elsewhere classified
subject: Developmental Biology
subject: Science Policy

description: Timeline. (DOCX 13 kb)
Evaluation of Deep-Learning-Based Voice Activity Detectors and Room Impulse Response Models in Reverberant Environments
Creators: name: Ivry, Amir
name: Cohen, Israel
name: Berdugo, Baruch
Publisher: name: arXiv
Year: 2021
Subjects: subject: Sound (cs.SD)
subject: Machine Learning (cs.LG)
subject: Audio and Speech Processing (eess.AS)
subject: FOS: Computer and information sciences
subject: FOS: Electrical engineering, electronic engineering, information engineering

description: State-of-the-art deep-learning-based voice activity detectors (VADs) are often trained with anechoic data. However, real acoustic environments are generally reverberant, which causes the performance to significantly deteriorate. To mitigate this mismatch between training data and real data, we simulate an augmented training set that contains nearly five million utterances. This extension comprises of anechoic utterances and their reverberant modifications, generated by convolutions of the anechoic utterances with a variety of room impulse responses (RIRs). We consider five different models to generate RIRs, and five different VADs that are trained with the augmented training set. We test all trained systems in three different real reverberant environments. Experimental results show $20\%$ increase on average in accuracy, precision and recall for all detectors and response models, compared to anechoic training. Furthermore, one of the RIR models consistently yields better performance than the other models, for all the tested VADs. Additionally, one of the VADs consistently outperformed the other VADs in all experiments.
description: Accepted to ICASSP 2020
СМЕЩЕНИЕ ПЕРЕТЯЖКИ ГАУССОВА ПУЧКА В МНОГОСЛОЙНОЙ МЕТАЛЛОДИЭЛЕКТРИЧЕСКОЙ СТРУКТУРЕ
Creators: name: Селина Н.В.
name: Хить Я.В.
name: Иващенко Н.Г.
Publisher: name: Математическое моделирование, компьютерный и натурный эксперимент в естественных науках
Year: 2023
Subjects: гауссов пучок
перетяжка гауссова пучка
многослойная линза Пендри

description: Предложен способ плавного изменения положения перетяжки гауссова пучка с использованием многослойной металлодиэлектрической двухкомпонентной структуры при соотношении диэлектрических проницаемостей металла и диэлектрика: ε_d≪|ε_m |.
A Large-Scale Study of the Twitter Follower Network to Characterize the Spread of Prescription Drug Abuse Tweets
Creators: name: Sequeira, Ryan
name: Gayen, Avijit
name: Ganguly, Niloy
name: Dandapat, Sourav Kumar
name: Chandra, Joydeep
Publisher: name: arXiv
Year: 2021
Subjects: subject: Social and Information Networks (cs.SI)
subject: FOS: Computer and information sciences

description: In this article, we perform a large-scale study of the Twitter follower network, involving around 0.42 million users who justify DA, to characterize the spreading of DA tweets across the network. Our observations reveal the existence of a very large giant component involving 99% of these users with dense local connectivity that facilitates the spreading of such messages. We further identify active cascades over the network and observe that the cascades of DA tweets get spread over a long distance through the engagement of several closely connected groups of users. Moreover, our observations also reveal a collective phenomenon, involving a large set of active fringe nodes (with a small number of follower and following) along with a small set of well-connected nonfringe nodes that work together toward such spread, thus potentially complicating the process of arresting such cascades. Furthermore, we discovered that the engagement of the users with respect to certain drugs, such as Vicodin, Percocet, and OxyContin, that were observed to be most mentioned in Twitter is instantaneous. On the other hand, for drugs, such as Lortab, that found lesser mentions, the engagement probability becomes high with increasing exposure to such tweets, thereby indicating that drug abusers engaged on Twitter remain vulnerable to adopting newer drugs, aggravating the problem further.
description: 13 pages, 9 figures, and accepted by IEEE Transactions on Computational Social Systems
Primordial helium recombination I: feedback, line transfer, and continuum opacity
Creators: name: Switzer, Eric R.
name: Hirata, Christopher M.
Publisher: name: arXiv
Year: 2007
Subjects: subject: Astrophysics (astro-ph)
subject: FOS: Physical sciences

description: Precision measurements of the cosmic microwave background temperature anisotropy on scales $\ell > 500$ will be available in the near future. Successful interpretation of these data is dependent on a detailed understanding of the damping tail and cosmological recombination of both hydrogen and helium. This paper and two companion papers are devoted to a precise calculation of helium recombination. We discuss several aspects of the standard recombination picture, and then include feedback, radiative transfer in HeI lines with partial redistribution, and continuum opacity from HI photoionization. In agreement with past calculations, we find that HeII recombination proceeds in Saha equilibrium, whereas HeI recombination is delayed relative to Saha due to the low rates connecting excited states of HeI to the ground state. However, we find that at $z<2200$ the continuum absorption by the rapidly increasing HI population becomes effective at destroying photons in the HeI $2^1P^o-1^1S$ line, causing HeI recombination to finish around $z\approx 1800$, much earlier than previously estimated.
description: 30 pages, 13 figures, to be submitted to PRD
Biosystematics of the annual species of the Mimulus guttatus species complex in British Columbia, Canada
Creators: name: Benedict, Beverly G.
Publisher: name: University of British Columbia
Year: 2008

description: The M. guttatus species complex consists of several morphologically and ecologically distinct taxa, which, for the most part, are able to intercross; this makes it both an evolutionarily fascinating group to study and a taxonomic nightmare. In this study I found that on one ecologically diverse hillside on Vancouver Island, British Columbia (B. C.), Canada, three distinct species of the M. guttatus species complex grow sympatrically. These three species included: 1) M. guttatus, a large flowered, facultatively annual diploid 2) M. nasutus, a small flowered, annual diploid, and 3) a small flowered, annual tetraploid to which a previous name could not be applied. This taxon has been named M. queue. In addition to the B.C. populations, M. nasutus and M. guttatus populations from California and M. queue populations from Oregon were also studied. Pre-zygotic crossing barriers reduce gene exchange between M. nasutus and M. guttatus. Both pre- and post-zygotic crossing barriers have effectively isolated M. queue from M. guttatus and M. nasutus. Under most growing conditions, the three taxa can be distinguished morphologically. However, when collected from dry habitats the two small flowered species are difficult to separate. Nineteen different measurements of the flower and calyx were taken. The ranges of all 19 measurements were overlapping for M. nasutus and M. queue. Medians were significantly different for calyx measurements, the difference between calyx length and pistil length and the difference in length of the upper and lower corollalobes. Boxplot comparisons of the B.C. and California populations of M. nasutus revealed no significant differences in the medians of the floral measurements. Only one floral measurement was found to be significantly different when the Oregon populations of M. queue were compared to the B. C. populations of M. queue. Discriminant and principle component analysis grouped individuals moderately wellinto the proper species. Discrimination was poorest when very small flowers were used. Enzyme electrophoresis indicated distinct differences in genetic diversity and in the compartmentalization of the diversity between the primarily autogamous M. queue and M. nasutus, and M. guttatus with its mixed mating system. The southern populations of M. nasutus and M. queue exhibited somewhat greater gene diversity than the northern populations. The presence of fixed heterozygosity in all populations of M. queue indicated that it is likely an allopolyploid. Whether the B.C. and Oregon populations are directly related or independently derived could not be determined from the present data. More collecting is required to determine the geographic distribution of M. queue and to shed light on its evolutionary past.
Ultra-cold WIMPs: relics of non-standard pre-BBN cosmologies
Creators: name: Gelmini, Graciela B.
name: Gondolo, Paolo
Publisher: name: arXiv
Year: 2008
Subjects: subject: Astrophysics (astro-ph)
subject: FOS: Physical sciences

description: Weakly interacting massive particles (WIMPs) are one of very few probes of cosmology before Big Bang nucleosynthesis (BBN). We point out that in scenarios in which the Universe evolves in a non-standard manner during and after WIMP kinetic decoupling, the horizon mass scale at decoupling can be smaller and the dark matter WIMPs can be colder than in standard cosmology. This would lead to much smaller first objects in hierarchical structure formation. In low reheating temperature scenarios the effect may be large enough as to noticeably enhance indirect detection signals in GLAST and other detectors, by up to two orders of magnitude.
description: Six pages, one figure- Extensive additions and rewriting with respect to v1. Figure changed
Radiation of twisted photons in elliptical undulators
Creators: name: Kazinski, P. O.
name: Ryakin, V. A.
Publisher: name: arXiv
Year: 2021
Subjects: subject: Accelerator Physics (physics.acc-ph)
subject: Optics (physics.optics)
subject: FOS: Physical sciences

description: The explicit expressions for the average number of twisted photons radiated by a charged particle in an elliptical undulator in the classical approximation as well as in the approach accounting for the quantum recoil are obtained. It is shown that radiation emitted by a particle moving along an elliptical helix which evolves around the axis specifying the angular momentum of twisted photons obeys the selection rule: $m+n$ is an even number, where $m$ is a projection of the total angular momentum of a twisted photon and $n$ is the harmonic number of the undulator radiation. This selection rule is a generalization of the previously known selection rules for radiation of twisted photons by circular and planar undulators and it holds for both classical and quantum approaches. The class of trajectories of charged particles that produce the twisted photon radiation obeying the aforementioned selection rule is described.
description: 9 pages
Primordial helium recombination II: two-photon processes
Creators: name: Hirata, Christopher M.
name: Switzer, Eric R.
Publisher: name: arXiv
Year: 2007
Subjects: subject: Astrophysics (astro-ph)
subject: FOS: Physical sciences

description: Interpretation of precision measurements of the cosmic microwave background (CMB) will require a detailed understanding of the recombination era, which determines such quantities as the acoustic oscillation scale and the Silk damping scale. This paper is the second in a series devoted to the subject of helium recombination, with a focus on two-photon processes in He I. The standard treatment of these processes includes only the spontaneous two-photon decay from the 2^1S level. We extend this treatment by including five additional effects, some of which have been suggested in recent papers but whose impact on He I recombination has not been fully quantified. These are: (i) stimulated two-photon decays; (ii) two-photon absorption of redshifted HeI line radiation; (iii) two-photon decays from highly excited levels in HeI (n^1S and n^1D, with n>=3); (iv) Raman scattering; and (v) the finite width of the 2^1P^o resonance. We find that effect (iii) is highly suppressed when one takes into account destructive interference between different intermediate states contributing to the two-photon decay amplitude. Overall, these effects are found to be insignificant: they modify the recombination history at the level of several parts in 10^4.
description: 19 pages, 11 figures, to be submitted to PRD
Τα μέσα κοινωνικής δικτύωσης ως εργαλείο πολιτικής επικοινωνίας
Creators: name: Βάθη, Χριστιάνα Σπύρου
Publisher: name: Aristotle University of Thessaloniki
Year: 2020
Subjects: Πολιτική Επικοινωνία
Εκλογές
Twitter
Political Communication
Elections

description: Στόχος της παρούσας διπλωματικής εργασίας είναι η μελέτη του ρόλου των μέσων κοινωνικής δικτύωσης στην πολιτική επικοινωνία. Πρόκειται για ένα ζήτημα το οποίο εντάσσεται στη γενικότερη επιστημονική συζήτηση σχετικά με το ρόλο των νέων μέσων ως εργαλείων πολιτικής επικοινωνίας. Στην παρούσα εργασία, συγκεκριμένα μελετάται η περίπτωση των τελευταίων βουλευτικών εκλογικών αναμετρήσεων που έλαβαν χώρα στην Ελλάδα την 7η Ιουλίου 2019. Για την εκπλήρωση αυτού του στόχου πραγματοποιείται έρευνα ποιοτικού χαρακτήρα, μέσα από την εξέταση του πολιτικού λόγου των δύο πολιτικών αρχηγών, του ΣΥΡΙΖΑ και της Νέας Δημοκρατίας, όπως αυτός διατυπώνεται προεκλογικά στο Twitter. Η εργασία χωρίζεται στο θεωρητικό και ο ερευνητικό μέρος. Στο θεωρητικό μέρος γίνεται μία προσπάθεια να αποδοθεί ο ρόλος της πολιτικής επικοινωνίας στις εκλογικές αναμετρήσεις των φιλελεύθερων και πλουραλιστικών δημοκρατικών συστημάτων, καθώς και η σχέση αυτής με τα ΜΜΕ και κυρίως με τα Νέα Μέσα και ιδιαίτερα με το Τwitter. Στο ερευνητικό μέρος, στο οποίο το βασικό αντικείμενο μελέτης είναι οι βουλευτικές εκλογές της 7ης Ιουλίου 2019 εξετάζεται ο προεκλογικός λόγος των Αλέξη Τσίπρα και Κυριάκου Μητσοτάκη, όπως αυτός συναντάται στους λογαριασμούς τους στο Twitter. Το ερευνητικό αντικείμενο είναι ιδιαίτερης σημασίας, αν αναλογιστούμε ότι πρόκειται για ένα ζήτημα ερευνητικά μη τετριμμένο και με πολλαπλές κοινωνικοπολιτικές συνέπειες.
description: The purpose of this master thesis is to study the role of social media in political communication. This subject is part of the general scientific discussion regarding the role of the New Media in political communication. Specifically the present thesis studies the case of the last parliament elections that took place in Greece the 7th of July 2019. For the accomplishment of this purpose the researcher actualized a qualitative survey, looking into the political speech of the two political leaders of Syriza and New Democracy, as it was captured electorally in Twitter. This thesis is divided in two parts, the theoretical and the empirical. The aim of the theoretical part is to show the connection between political communication and elections of liberal and pluralist democratic systems, as well as the association of political communication with Mass Media and especially with New Media and Twitter. The aim of the empirical part is to study the political speech of Alexis Tsipras and Kiriakos Mitsotakis in Twitter during the electoral time before the elections of the 7th of July 2019. The subject matter of this survey is important taking under consideration that it is not overused and it has multiple social and political consequences for the country of Greece.
Exact Quantum Loop Results in the Theory of General Relativity
Creators: name: Ward, B. F. L.
Publisher: name: arXiv
Year: 2006
Subjects: subject: High Energy Physics - Phenomenology (hep-ph)
subject: FOS: Physical sciences

description: We present a new approach to quantum general relativity based on the idea of Feynman to treat the graviton in Einstein's theory as a point particle field subject to quantum fluctuations just as any such field is in the well-known Standard Model of the electroweak and strong interactions. We show that by using resummation techniques based on the extension of the methods of Yennie, Frautschi and Suura to Feynman's formulation of Einstein's theory, we get calculable loop corrections that are even free of UV divergences. One further by-product of our analysis is that we can apply it to a large class of interacting field theories, both renormalizable and non-renormalizable, to render their UV divergences finite as well. We illustrate our results with applications of some phenomenological interest.
description: 26 pages, 3 figures; improved text; improved text;improved text; improved text to 31 pages, 4 figures
Ultralong temporal coherence in optically trapped exciton-polariton condensates
Creators: name: Orfanakis, K.
name: Tzortzakakis, A. F.
name: Petrosyan, D.
name: Savvidis, P. G.
name: Ohadi, H.
Publisher: name: arXiv
Year: 2021
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: Other Condensed Matter (cond-mat.other)
subject: FOS: Physical sciences

description: We investigate an optically trapped exciton-polariton condensate and observe temporal coherence beyond 1~ns duration. Due to the reduction of the spatial overlap with the thermal reservoir of excitons, the coherence time of the trapped condensate is more than an order of magnitude longer than that of an untrapped condensate. This ultralong coherence enables high precision spectroscopy of the trapped condensate, and we observe periodic beats of the field correlation function due to a fine energy splitting of two polarization modes of the condensate. Our results are important for realizing polariton simulators with spinor condensates in lattice potentials.
description: 8 pages, 7 figures
Parity doublers in chiral potential quark models
Creators: name: Kalashnikova, Yu. S.
name: Nefediev, A. V.
name: Ribeiro, J. E. F. T.
Publisher: name: arXiv
Year: 2006
Subjects: subject: High Energy Physics - Phenomenology (hep-ph)
subject: FOS: Physical sciences

description: The effect of spontaneous breaking of chiral symmetry over the spectrum of highly excited hadrons is addressed in the framework of a microscopic chiral potential quark model (Generalised Nambu-Jona-Lasinio model) with a vectorial instantaneous quark kernel of a generic form. A heavy-light quark-antiquark bound system is considered, as an example, and the Lorentz nature of the effective light-quark potential is identified to be a pure Lorentz-scalar, for low-lying states in the spectrum, and to become a pure spatial Lorentz vector, for highly excited states. Consequently, the splitting between the partners in chiral doublets is demonstrated to decrease fast in the upper part of the spectrum so that neighboring states of an opposite parity become almost degenerate. A detailed microscopic picture of such a "chiral symmetry restoration" in the spectrum of highly excited hadrons is drawn and the corresponding scale of restoration is estimated.
description: LaTeX2e, 4 pages, uses aipproc class, Talk given by A.Nefediev at the conference "Quark Confinement and the Hadron Spectrum VII", 2-7 September 2006, Acores, Portugal, to appear in Proceedings
Αξιολόγηση προσομοιώσεων του οπτικού βάθους αεροζόλ με το RegCM4 κατά το καλοκαίρι του 2013
Creators: name: Τσολάκη, Μαρία Χαραλάμου
Publisher: name: Aristotle University of Thessaloniki
Year: 2020
Subjects: Οπτικό βάθος αεροζόλ
Περιοχικό κλιματικό μοντέλο
Aerosol optical depth
Regional climate model

description: Σκοπός της εργασίας ήταν η αξιολόγηση των προσομοιώσεων του οπτικού βάθους αεροζολ κατά το καλοκαίρι του 2013 με χρήση του κλιματικού μοντέλου περιοχής RegCM4. Για το σκοπό αυτό χρησιμοποιήθηκαν δεδομένα από προσομοιώσεις του μοντέλου για τους μήνες Μάιο, Ιούνιο, Ιούλιο και Αύγουστο του 2013 για μια ευρύτερη περιοχή που περιλαμβάνει τη Μεσόγειο και την Αφρική. Από την επεξεργασία των δεδομένων προέκυψαν εκτιμήσεις για τις τιμές του οπτικού βάθους των αιωρούμενων σωματιδίων καθώς των πιθανών πηγών τους. Η αξιολόγηση έγινε με δεδομένα από το δίκτυο AERONET. Χρησιμοποιήθηκαν δεδομένα από συγκεκριμένους σταθμούς που παρουσίαζαν ενδιαφέρον με βάση τις προσομοιώσεις του μοντέλου αλλά και τα χαρακτηριστικά της περιοχής. Αξιολογήθηκαν οι ημερήσιες τιμές οπτικού βάθους και του εκθέτη Angstrom. Η σύγκριση μεταξύ των προσομοιώσεων του μοντέλου και των δεδομένων του δικτύου AERONET πραγματοποιήθηκε για τιμές οπτικού βάθους στα 550nm για κάθε σταθμό, για το σύνολο των σταθμών και για περιοχές που χωρίστηκαν ομαδοποιώντας τις τοποθεσίες των σταθμών. Διαπιστώθηκε μικρή συσχέτιση των προσομοιώσεων με τα δεδομένα. Εξαίρεση αποτελούν οι περιπτώσεις που εμφανίζονται ημέρες με «επεισοδιακά φαινόμενα» (πχ επίδραση σκόνης) ή συνολικά για τις περιοχές που είναι μεγαλύτερη η επίδραση φυσικής προέλευσης αιωρημάτων. Συμπεραίνεται, λοιπόν μια τάση του μοντέλου να υπερεκτιμά την επίδραση των αιωρημάτων με αυξημένες τιμές AOD ιδιαίτερα στις περιοχές με έντονη παρουσία πηγών ανθρωπογενών αιωρημάτων.
description: The purpose of this study was to evaluate the aerosol optical depth simulations in the summer of 2013 using the RegCM4 regional climate model. For this purpose, data from model simulations for the months of May, June, July and August 2013 were used for a wider region that includes the Mediterranean and Africa. The data processing resulted in estimates for the values of aerosol optical depth as well as their possible sources. The evaluation was performed with data from the AERONET network using data from specific stations that were of interest based on the model simulations and the characteristics of the area. The daily values of optical depth and the Angstrom exhibitor were evaluated. The comparison between the model simulations and the AERONET network data was performed for optical depth values at 550nm for each station, for all stations and for areas separated by grouping the station locations. The correlation of the simulations was small. Exceptions are cases that occur on days with "episodic effects" (eg dust effect) or overall for areas where the effect of natural suspensions is greater. This information led to the conclusion that there is a tendency of the model to overestimate the effect of suspensions with increased AOD values, especially in areas with a strong presence of anthropogenic suspension sources.
Flat Surfaces
Creators: name: Zorich, Anton
Publisher: name: arXiv
Year: 2006
Subjects: subject: Dynamical Systems (math.DS)
subject: Geometric Topology (math.GT)
subject: FOS: Mathematics

description: Various problems of geometry, topology and dynamical systems on surfaces as well as some questions concerning one-dimensional dynamical systems lead to the study of closed surfaces endowed with a flat metric with several cone-type singularities. Such flat surfaces are naturally organized into families which appear to be isomorphic to the moduli spaces of holomorphic one-forms. One can obtain much information about the geometry and dynamics of an individual flat surface by studying both its orbit under the Teichmuller geodesic flow and under the linear group action. In particular, the Teichmuller geodesic flow plays the role of a time acceleration machine (renormalization procedure) which allows to study the asymptotic behavior of interval exchange transformations and of surface foliations. This long survey is an attempt to present some selected ideas, concepts and facts in Teichmuller dynamics in a playful way.
description: (152 pages; 51 figures) Based on the lectures given by the author at the Les Houches School "Number Theory and Physics" in March of 2003 and at the workshop on dynamical systems in ICTP, Trieste, in July 2004. See "Frontiers in Number Theory, Physics and Geometry. Volume 1: On random matrices, zeta functions and dynamical systems'', P.Cartier; B.Julia; P.Moussa; P.Vanhove (Editors), Springer-Verlag (2006) for the entire collection (including, in particular, the complementary lectures of J.-C. Yoccoz). For a short version see the paper "Geodesics on Flat Surfaces", arXiv.math.GT/0609399
Cardiac Motion Modeling with Parallel Transport and Shape Splines
Creators: name: Guigui, Nicolas
name: Moceri, Pamela
name: Sermesant, Maxime
name: Pennec, Xavier
Publisher: name: arXiv
Year: 2021
Subjects: subject: Computer Vision and Pattern Recognition (cs.CV)
subject: Differential Geometry (math.DG)
subject: FOS: Computer and information sciences
subject: FOS: Mathematics

description: In cases of pressure or volume overload, probing cardiac function may be difficult because of the interactions between shape and deformations.In this work, we use the LDDMM framework and parallel transport to estimate and reorient deformations of the right ventricle. We then propose a normalization procedure for the amplitude of the deformation, and a second-order spline model to represent the full cardiac contraction. The method is applied to 3D meshes of the right ventricle extracted from echocardiographic sequences of 314 patients divided into three disease categories and a control group. We find significant differences between pathologies in the model parameters, revealing insights into the dynamics of each disease.
Identifying the optimal location for the facilitation of a retail store
Creators: name: Πέτρου, Αχιλλέας Δημητρίου
Publisher: name: Aristotle University of Thessaloniki
Year: 2020
Subjects: Τοποθεσία εγκαταστάσεων
Κατάστημα λιανικής
Διαδικασία αναλυτικής ιεράρχησης
Facility location
Retail store
Analytical hierarchy process

description: The identification of the optimal location is of the outmost importance for each business due to the high expenses and long-term commitment. The case examined refers to the identification of the optimal location for the establishment of a retail store for a nuts company. The study area in which the examination take place is the Prefecture of Attica. The investigation contains different approaches encompasses subjectivity (Weighted factor rating method), objectivity (Load distance technique) and mixed subjectivity and objectivity (Analytical Hierarchy Process). Two different solutions obtained by the application of the processes allowing to decision makers evaluate the optimal one based on their preferences.
description: Ο προσδιορισμός της βέλτιστης τοποθεσίας είναι ύψιστης σημασίας για κάθε επιχείρηση λόγω των υψηλών δαπανών και της μακροπρόθεσμης δέσμευσης. Η υπόθεση που εξετάστηκε αναφέρεται στον προσδιορισμό της βέλτιστης θέσης για τη δημιουργία λιανικού καταστήματος για μια εταιρεία ξηρών καρπών. Η περιοχή μελέτης όπου πραγματοποιήθηκε η έρευνα είναι ο Νομός Αττικής. Η έρευνα περιέχει διαφορετικές προσεγγίσεις που περιλαμβάνει την υποκειμενικότητα (μέθοδος βαθμολογίας σταθμισμένου παράγοντα), την αντικειμενικότητα (τεχνική απόστασης φορτίου) και τη μικτή υποκειμενικότητα και αντικειμενικότητα (αναλυτική διαδικασία ιεραρχίας). Η εφαρμογή των μεθόδων υπέδειξε δύο διαφορετικές λύσεις δίνοντας στον υπεύθυνο λήψης αποφάσεων να επιλέξει την πλέον συμφέρουσα βάσει των προτιμήσεων του.
Temporal Graph Signal Decomposition
Creators: name: McNeil, Maxwell
name: Zhang, Lin
name: Bogdanov, Petko
Publisher: name: arXiv
Year: 2021
Subjects: subject: Machine Learning (cs.LG)
subject: FOS: Computer and information sciences

description: Temporal graph signals are multivariate time series with individual components associated with nodes of a fixed graph structure. Data of this kind arises in many domains including activity of social network users, sensor network readings over time, and time course gene expression within the interaction network of a model organism. Traditional matrix decomposition methods applied to such data fall short of exploiting structural regularities encoded in the underlying graph and also in the temporal patterns of the signal. How can we take into account such structure to obtain a succinct and interpretable representation of temporal graph signals? We propose a general, dictionary-based framework for temporal graph signal decomposition (TGSD). The key idea is to learn a low-rank, joint encoding of the data via a combination of graph and time dictionaries. We propose a highly scalable decomposition algorithm for both complete and incomplete data, and demonstrate its advantage for matrix decomposition, imputation of missing values, temporal interpolation, clustering, period estimation, and rank estimation in synthetic and real-world data ranging from traffic patterns to social media activity. Our framework achieves 28% reduction in RMSE compared to baselines for temporal interpolation when as many as 75% of the observations are missing. It scales best among baselines taking under 20 seconds on 3.5 million data points and produces the most parsimonious models. To the best of our knowledge, TGSD is the first framework to jointly model graph signals by temporal and graph dictionaries.
description: 9 Main Pages 2 Supplement to be published in the research track in Proceedings of the 27th ACM SIGKDD Conference on Knowledge Discovery and Data Mining (KDD 2021), August 14 through August 18, 2021,Virtual Event, Singapore