cometadata/datacite-rtg-text-other-reclassification-records huggingface dataset:
What is the stiffness of a bent book?
Creators: name: Poincloux, Samuel
name: Chen, Tian
name: Audoly, Basile
name: Reis, Pedro
Publisher: name: arXiv
Year: 2020
Subjects: subject: Soft Condensed Matter (cond-mat.soft)
subject: FOS: Physical sciences

description: We study the bending of a book-like system, comprising a stack of elastic plates coupled through friction. The behavior of this layered system is rich and nontrivial, with a non-additive enhancement of the apparent stiffness and a significant hysteretic response. A dimension reduction procedure is employed to develop a centerline-based theory describing the stack as a non-linear planar rod with internal shear. We consider the coupling between the nonlinear geometry and the elasticity of the stacked plates, treating the interlayer friction perturbatively. This model yields predictions for the stack's mechanical response in three-point bending that are in excellent agreement with our experiments. Remarkably, we find that the energy dissipated during deformation can be rationalized over three orders of magnitude, including the regimes of a thick stack with large deflection. This robust dissipative mechanism could be harnessed to design new classes of low-cost and efficient damping devices.
description: 5 pages, 3 figures, and Supplementary Information
The role of interactions in spin-polarised atomic Fermi gases at unitarity
Creators: name: Recati, A.
name: Lobo, C.
name: Stringari, S.
Publisher: name: arXiv
Year: 2008
Subjects: subject: Other Condensed Matter (cond-mat.other)
subject: FOS: Physical sciences

description: We study the zero temperature properties of a trapped polarized Fermi gas at unitarity by assuming phase separation between an unpolarized superfluid and a polarized normal phase. The effects of the interaction are accounted using the formalism of quasi-particles to build up the equation of state of the normal phase with the Monte Carlo results for the relevant parameters. Our predictions for the Chandrasekhar-Clogston limit of critical polarization and for the density profiles, including the density jump at the interface, are confirmed with excellent accuracy by the recent experimental results at MIT. The role of interaction on the radial width of the minority component, on the gap of the RF transition and on the spin oscillations in the normal phase is also discussed. Our analysis points out the Fermi liquid nature of these strongly interacting spin polarized configurations.
description: Revisitedc version accepted for pubblication. 1 figure added, 1 figure correted, typos corrected, references updated
Spectroscopic Binary Mass Determination using Relativity
Creators: name: Zucker, Shay
name: Alexander, Tal
Publisher: name: arXiv
Year: 2006
Subjects: subject: Astrophysics (astro-ph)
subject: FOS: Physical sciences

description: High-precision radial-velocity techniques, which enabled the detection of extrasolar planets are now sensitive to relativistic effects in the data of spectroscopic binary stars (SBs). We show how these effects can be used to derive the absolute masses of the components of eclipsing single-lined SBs and double-lined SBs from Doppler measurements alone. High-precision stellar spectroscopy can thus substantially increase the number of measured stellar masses, thereby improving the mass-radius and mass-luminosity calibrations.
description: 10 pages, 1 figure, accepted for publication by the Astrophysical Journal Letters
Nanoseconds field emitted current pulses from ZrC needles and field emitter arrays
Creators: name: Ganter, R.
name: Bakker, R. J.
name: Betemps, R.
name: Dehler, M.
name: Gerber, T.
name: Gobrecht, J.
name: Gough, C.
name: Johnson, M.
name: Kirk, E.
name: Knopp, G.
name: Pimpec, F. Le
name: Li, K.
name: Paraliev, M.
name: Pedrozzi, M.
name: Rivkin, L.
name: Sehr, H.
name: Schulz, L.
name: Wrulich, A.
Publisher: name: arXiv
Year: 2006
Subjects: subject: Accelerator Physics (physics.acc-ph)
subject: FOS: Physical sciences

description: The properties of the electron source define the ultimate limit of the beam quality in linear accelerators like Free Electron Lasers (FEL). The goal is to develop an electron gun delivering beam emittance lower than current state of the art. Such a gun should reduce the cost and size of an X-ray Free Electron Laser (XFEL). In this paper we present two concepts of field emitter cathodes which could potentially produce low emittance beam. The first challenging parameter for such cathode is to emit peak current as high as 5 A. This is the minimum current requirement for the XFEL concept from Paul Scherrer Institut.1 Maximum current of 0.12 A and 0.58 A have been reached respectively with field emitter arrays (FEA) and single needle cathodes. Laser assisted field emission gave encouraging results to reach even higher peak current and to pre-bunch the beam.
description: 23 pages, 1 table, 9 figures Accepted for publication in JVST B
The state space for two qutrits has a phase space structure in its core
Creators: name: Baumgartner, Bernhard
name: Hiesmayr, Beatrix C.
name: Narnhofer, Heide
Publisher: name: arXiv
Year: 2006
Subjects: subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: We investigate the state space of bipartite qutrits. For states which are locally maximally mixed we obtain an analog of the ``magic'' tetrahedron for bipartite qubits--a magic simplex W. This is obtained via the Weyl group which is a kind of ``quantization'' of classical phase space. We analyze how this simplex W is embedded in the whole state space of two qutrits and discuss symmetries and equivalences inside the simplex W. Because we are explicitly able to construct optimal entanglement witnesses we obtain the border between separable and entangled states. With our method we find also the total area of bound entangled states of the parameter subspace under intervestigation. Our considerations can also be applied to higher dimensions.
description: 3 figures
Analyzing Cyber-Attack Intention for Digital Forensics Using Case-Based Reasoning
Creators: name: Al-Mousa, Mohammad Rasmi
Publisher: name: arXiv
Year: 2021
Subjects: subject: Cryptography and Security (cs.CR)
subject: FOS: Computer and information sciences

description: Cyber-attacks are increasing and varying dramatically day by day. It has become challenging to control cyber-attacks and to identify the perpetrators and their intentions. In general, the analysis of the intentions of cyber-attacks is one of the main challenges in digital forensics. In many cases of cyber-attacks, the analysis of the intent of the attacks determines the strategy and tools used in the attack, thus facilitating the process of identifying the perpetrator of the attack with greater accuracy. In this paper a model will be proposed to analyze the intentions of cyber-attacks. In this proposal, a set of steps will be conceived by linking them with a case-based reasoning methodology. This model will be examined by analyzing the intent of attacks for some cases and comparing the results with other methods of analyzing the intent of attacks. Hopefully the results will determine the intent of cyber-attacks more accurately.
description: 6 pages
Na-O Anticorrelation and Horizontal Branches. V. The Na-O anticorrelation in NGC 6441 from Giraffe spectra
Creators: name: Gratton, R. G.
name: Lucatello, S.
name: Bragaglia, A.
name: Carretta, E.
name: Cassisi, S.
name: Momany, Y.
name: Pancino, E.
name: Valenti, E.
name: Caloi, V.
name: Claudi, R.
name: D'Antona, F.
name: Desidera, S.
name: François, P.
name: James, G.
name: Moehler, S.
name: Ortolani, S.
name: Pasquini, L.
name: Piotto, G.
name: Recio-Blanco, A.
Publisher: name: arXiv
Year: 2007
Subjects: subject: Astrophysics (astro-ph)
subject: FOS: Physical sciences

description: We present an analysis of FLAMES-Giraffe spectra for several bright giants in NGC 6441, to investigate the presence and extent of the Na-O anticorrelation in this anomalous globular cluster. The field of NGC 6441 is very crowded, with severe contamination by foreground (mainly bulge) field stars. Appropriate membership criteria were devised to identify a group of 25 likely cluster members among the about 130 stars observed. Combined with the UVES data obtained with the same observations, high dispersion abundance analyses are now available for a total of 30 stars in NGC 6441, 29 of them having data for both O and Na. The spectra were analyzed by a standard line analysis procedure; care was taken to minimize the impact of the differential interstellar reddening throughout the cluster, and to extract reliable information from crowded, and moderately high S/N (30-70), moderately high resolution (R ~ 23,000) spectra. NGC 6441 is very metal-rich ([Fe/H]=$-0.34\pm 0.02\pm0.04$ dex). There is no clear sign of star-to-star scatter in the Fe-peak elements. The alpha-elements Mg, Si, Ca, and Ti are overabundant by rather large factors, suggesting that the cluster formed from material enriched by massive core collapse SNe. The O-Na anticorrelation is well defined, with about 1/4 of the stars being Na-rich and O-poor. One of the stars is a Ba-rich and moderately C-rich star. The distribution of [Na/O] ratios among RGB stars in NGC 6441 appears similar to the distribution of colors of stars along the horizontal branch. The fraction of Na-poor, O-rich stars found in NGC 6441 agrees well with that of stars on the red horizontal branch of this cluster (in both cases about 80%), with a sloping distribution toward lower values of [O/Na] (among RGB stars and bluer colors (among HB stars).
description: 33 pages, 10 figures. A&A Accepted
Studies of the microwaves surface resistance of pure, zinc, and nickel doped YBCO crystals
Creators: name: Zhang, Kuan
Publisher: name: University of British Columbia
Year: 2009

description: An apparatus utilizing a superconducting cavity resonator has been developed for the systematic study of the microwave surface resistance of high purity (twinned and untwinned), zinc and nickel doped YBa₂Cu₃O₇₋₈ single crystals at 35 GHz. The objective was to obtain the intrinsic microwave properties of high temperature superconductors. By using our highly sensitive apparatus to study the effects of twinning and doping, we have been able to confirm that what we have obtained is indeed the intrinsic properties of YBa₂Cu₃O₇₋₈. The results show that the intrinsic microwave properties of YBa₂Cu₃O₇₋₈ are very different from that of conventional s-wave BCS superconductors. Firstly, the quasiparticle scattering rate is strongly temperature dependent, and drops rapidly below the transition temperature, which implies a quasiparticle-quasiparticle scattering mechanism. Secondly, both the surface resistance and the real part of the conductivity vary linearly with T below 35K (except for the zinc doped crystals), suggesting an unconventional superconducting pairing state with line nodes in the order parameter. Thirdly, the real part of the conductivity when extrapolated to the OK is very small, in contrast to previously existing data, and approaches the limit predicted for a d-wave superconductor. A practical result of our studies is that we have shown that the microwave loss of high temperature superconductors can be reduced by doping with certain impurities. This is an important result in the area of microwave applications, where one generally wants as low a surface resistance as possible
Control of multiatom entanglement in a cavity
Creators: name: Mandilara, A.
name: Akulin, V. M.
name: Kolar, M.
name: Kurizki, G.
Publisher: name: arXiv
Year: 2006
Subjects: subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: We propose a general formalism for analytical description of multiatomic ensembles interacting with a single mode quantized cavity field under the assumption that most atoms remain un-excited on average. By combining the obtained formalism with the nilpotent technique for the description of multipartite entanglement we are able to overview in a unified fashion different probabilistic control scenarios of entanglement among atoms or examine atomic ensembles. We then apply the proposed control schemes to the creation of multiatom states useful for quantum information.
description: 11 pages, 1 figure. Finalized version
Stepwise Chirping of Chiral Sculptured Thin Films for Bragg Bandwidth Enhancement
Creators: name: Lakhtakia, Akhlesh
Publisher: name: arXiv
Year: 2020
Subjects: subject: Optics (physics.optics)
subject: FOS: Physical sciences

description: A stepwise chirping of the periodicity of a chiral sculptured thin film is shown to considerably enhance the bandwidth of the Bragg regime, thereby extending the frequency range of operation as a circular{polarization filter.
Σύνθεση πουρινικών δεοξυαπιοθειονουκλεοζιτών μέσω της αντίδρασης Pummerer
Creators: name: Σιτσανίδης, Ευστράτιος Δημητρίου
Publisher: name: Aristotle University of Thessaloniki
Year: 2014
Subjects: Αντίδραση Pummerer
θειονουκλεοζίτες
απιονουκλεοζίτες
Pummerer reaction
thionucleosides
apionucleosides

description: Οι τροποποιημένοι νουκλεοζίτες αποτελούν αντικείμενο εκτεταμένης έρευνας, εξαιτίας κυρίως της πολυποίκιλης βιολογικής τους δράσης. Ο στόχος της συγκεκριμένης μεταπτυχιακής εργασίας ήταν η σύνθεση των οπτικά καθαρών εναντιομερών νουκλεοζιτών, του τροποποιημένου με θείο, σακχάρου απιόζης, χρησιμοποιώντας αζωτούχες βάσεις πουρίνης, μέσω της αντίδρασης μετάθεσης Pummerer. Ειδικότερα, μελετήθηκε η αποδοτικότητα και στερεοεκλεκτικότητα της αντίδρασης Pummerer κατά τη σύζευξη της αζωτούχας πουρινικής βάσης με το θειοσάκχαρο και διερευνήθηκαν οι συνθήκες αποπροστασίας των προστατευμένων νουκλεοζιτών, στο καθοριστικό πλέον στάδιο παραλαβής των τελικών προϊόντων. Ιδιαίτερη βαρύτητα δόθηκε στη διευκρίνιση της δομής, τόσο των ενδιάμεσων όσο και των τελικών προϊόντων, ώστε να προταθεί ένας μηχανισμός που να επεξηγεί ικανοποιητικά τα πειραματικά αποτελέσματα. Τέλος, όλοι οι τροποποιημένοι απιονουκλεοζίτες αναμένεται να δοκιμαστούν ως προς τη βιολογική τους δράση.
description: Modified nucleosides are subject of extensive research, mainly because of their diverse biological activity. The objective of this thesis was the synthesis of optically pure enantiomers of nucleosides consisted of a thioapiose sugar moiety and purine bases, via the Pummerer rearrangement reaction. More specifically, we studied the efficiency and stereoselectivity of the Pummerer reaction during the coupling of the purine base with the thiosugar moiety and we investigated the conditions of deprotection of the protected nucleosides. In addition, we emphasized on the structure clarification of both the intermediate and final products in order to propose a mechanism and to explain sufficiently the experimental results. Finally, all the modified apiothionucleosides will be tested for their biological activity.
Momentum-resolved surface enhanced Raman scattering from a nanowire-nanoparticle junction cavity
Creators: name: Vasista, Adarsh B.
name: Chaubey, Shailendra K.
name: Gosztola, David J.
name: Wiederrecht, Gary P.
name: Gray, Stephen K.
name: Kumar, G. V. Pavan
Publisher: name: arXiv
Year: 2020
Subjects: subject: Optics (physics.optics)
subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: Applied Physics (physics.app-ph)
subject: FOS: Physical sciences

description: Herein we report experimental evidence of directional SERS from molecules situated inside a single nanowire-nanoparticle junction cavity. The emission was confined to a narrow range of wavevectors perpendicular to the axis of the cavity. In addition to this, the molecules excite multiple guided modes of the nanowire which were imaged using leakage radiation Fourier microscopy. We further characterize the emission wavevectors as a function of output polarization. The excited guided modes of the wire show interesting polarization signatures. All the results were corroborated using finite element method based numerical simulations. Essentially, we provide an important connection between gap-cavity enhanced Raman scattering and its directionality of emission. The results may be of relevance in understanding the cavity electrodynamics at the nanoscale and molecular coupling to extremely small gaps between a one dimensional and a zero-dimensional plasmonic nanostructure.
Magnetic Moments of Heavy $Ξ_{Q}$ Baryons in Light Cone QCD Sum Rules
Creators: name: Aliev, T. M.
name: Azizi, K.
name: Ozpineci, A.
Publisher: name: arXiv
Year: 2008
Subjects: subject: High Energy Physics - Phenomenology (hep-ph)
subject: FOS: Physical sciences

description: The magnetic moments of heavy $Ξ_{Q}$ baryons containing a single charm or bottom quark are calculated in the framework of light cone QCD sum rules method. A comparison of our results with the predictions of the quark models is presented.
description: 26 Pages, 8 Figures and 1 Table
Experimental study of exclusive $^2$H$(e,e^\prime p)n$ reaction mechanisms at high $Q^2$
Creators: name: Egiyan, K. S.
name: Collaboration, the CLAS
Publisher: name: arXiv
Year: 2007
Subjects: subject: Nuclear Experiment (nucl-ex)
subject: FOS: Physical sciences

description: The reaction $^2$H$(e,e^\prime p)n$ has been studied with full kinematic coverage for photon virtuality $1.75
description: 6 pages, 4 figures
Wedge Products and Cotensor Coalgebras in Monoidal Categories
Creators: name: Ardizzoni, A.
Publisher: name: arXiv
Year: 2006
Subjects: subject: Category Theory (math.CT)
subject: Quantum Algebra (math.QA)
subject: FOS: Mathematics
subject: 18D10, 18A30

description: The construction of the cotensor coalgebra for an "abelian monoidal" category $\M$ which is also cocomplete, complete and AB5, was performed in [A. Ardizzoni, C. Menini and D. Ştefan, \emph{Cotensor Coalgebras in Monoidal Categories}, Comm. Algebra, to appear]. It was also proved that this coalgebra satisfies a meaningful universal property which resembles the classical one. Here the lack of the coradical filtration for a coalgebra $E$ in $\M$ is filled by considering a direct limit $\widetilde{D}$ of a filtration consisting of wedge products of a subcoalgebra $D$ of $E$. The main aim of this paper is to characterize hereditary coalgebras $\widetilde{D}$, where $D$ is a coseparable coalgebra in $\M$, by means of a cotensor coalgebra: more precisely, we prove that, under suitable assumptions, $\widetilde{D}$ is hereditary if and only if it is formally smooth if and only if it is the cotensor coalgebra $T^c_{D}(D\w D/D)$ if and only if it is a cotensor coalgebra $T^c_{D}(N)$, where $N$ is a certain $D$-bicomodule in $\M$. Because of our choice, even when we apply our results in the category of vector spaces, new results are obtained.
Manifestations of Drag Reduction by Polymer Additives in Decaying, Homogeneous, Isotropic Turbulence
Creators: name: Perlekar, Prasad
name: Mitra, Dhrubaditya
name: Pandit, Rahul
Publisher: name: arXiv
Year: 2006
Subjects: subject: Chaotic Dynamics (nlin.CD)
subject: Soft Condensed Matter (cond-mat.soft)
subject: Fluid Dynamics (physics.flu-dyn)
subject: FOS: Physical sciences

description: The existence of drag reduction by polymer additives, well established for wall-bounded turbulent flows, is controversial in homogeneous, isotropic turbulence. To settle this controversy we carry out a high-resolution direct numerical simulation (DNS) of decaying, homogeneous, isotropic turbulence with polymer additives. Our study reveals clear manifestations of drag-reduction-type phenomena: On the addition of polymers to the turbulent fluid we obtain a reduction in the energy dissipation rate, a significant modification of the fluid energy spectrum especially in the deep-dissipation range, a suppression of small-scale intermittency, and a decrease in small-scale vorticity filaments.
description: 4 pages, 3 figures
Youth political participation and inequalities: comparing European countries and different repertoires of engagement
Creators: name: Lello, Elisa
name: Bazzoli, Nico
Publisher: name: De Europa
Year: 2023

description: In recent years, research on Western democracies has shown that younger generations are less involved in political activities than a few decades ago. Several scholars have disputed claims of apathy or retirement into the private sphere of the younger generations, underlining that they prefer to engage in unconventional forms of activism and protest, or associations and voluntary work.


At the same time, research has revealed a contraction of youth participation over time also concerning its non-institutionalized forms, showing that these practices of activism are not overrepresented among younger generations in comparison with adults.


Our work investigates the most recent youth political participation dynamics by analysing data from the 9th edition (2018) of the European Social Survey. The first aim is to explore the differences in youth political engagement levels among EU countries. On the other hand, the transformations involving the very nature of political participation also affect the relationship between socio-economic inequalities and political engagement. The second objective, therefore, is to assess the impact of socio-economic inequalities on political engagement based on a quantitative and comparative approach, comparing younger cohorts with older ones, and electoral participation with unconventional engagement.


Keywords:


youth political participation – European youth – social and economic inequalities – conventional/unconventional participation – social centrality – class.
description: De Europa, V. 6 N. 2 (2023)
VLTI/AMBER interferometric observations of the recurrent Nova RS Oph 5.5 days after outburst
Creators: name: Chesneau, Olivier
name: Nardetto, N.
name: Millour, F.
name: Hummel, Ch.
name: De Souza, A. Domiciano
name: Bonneau, D.
name: Vannier, M.
name: Rantakyro, F. T.
name: Spang, A.
name: Malbet, F.
name: Mourard, D.
name: Bode, M. F.
name: O'brien, T. J.
name: Skinner, G.
name: Petrov, R.
name: Stee, Ph.
name: Tatulli, E.
name: Vakili, F.
Publisher: name: arXiv
Year: 2006
Subjects: subject: Astrophysics (astro-ph)
subject: FOS: Physical sciences

description: We report on interferometric AMBER/VLTI observations of the recurrent nova RS Oph five days after its outburst on 2006 Feb 12. Using three baselines from 44 to 86m, and a spectral resolution of 1500, we measured the extension of the emission in the K band continuum and in the BrG and HeI2.06 micron lines. The continuum visibilities were interpreted by fitting simple geometric models consisting of uniform and Gaussian ellipses, ring and binary models. The visibilities and differential phases in the BrG line were interpreted using skewed ring models aiming to perform a limited parametric reconstruction of the extension and kinematics of the line forming region. The limited uv coverage does not allow discrimination between filled models and rings. Binary models are discarded because the measured closure phase in the continuum is close to zero. The visibilities in the lines are at a low level compared to their nearby continuum, consistent with a more extended line forming region for HeI2.06 than BrG. The ellipse models for the continuum and for the lines are highly flattened and share the same position angle. Two radial velocity fields are apparent in the BrG line: a 'slow' expanding ring-like structure (v~1800km/s), and a 'fast' structure extended in the E-W direction (v~2500-3000km/s). These results confirm the basic fireball model, contrary to the conclusions of other interferometric observations conducted by Monnier et al. (2006).
description: Accepted in A&A
An X-ray look at the Seyfert 1 Galaxy Mrk 590: XMM-Newton and Chandra reveal complexity in circumnuclear gas
Creators: name: Longinotti, A. L.
name: Bianchi, S.
name: Santos-Lleo, M.
name: Rodriguez-Pascual, P.
name: Guainazzi, M.
name: Cardaci, M.
name: Pollock, A. M. T.
Publisher: name: arXiv
Year: 2007
Subjects: subject: Astrophysics (astro-ph)
subject: FOS: Physical sciences

description: This paper reports on a partially simultaneous observation of the bright Seyfert 1 Galaxy Mrk590, performed by XMM-Newton and Chandra. The long exposure (~100 ks) allows to investigate with great detail the Fe K complex at 6-7 keV and the presence of soft X-ray spectral features. We have analysed XMM-Newton data from the European Photon Imaging Camera (EPIC) in the 0.5-12 keV band and from the Reflection Grating Spectrometer (RGS) in the 0.35-2.5 keV band, and data from the High Energy Transmission Gratings (HETGs) onboard Chandra. UV and optical data from the Optical Monitor (OM) onboard XMM-Newton are also included in the analysis. The broad band spectrum is well described by an unabsorbed power law and three unresolved Fe~K lines in the 6-7 keV range. The presence of a Compton reflection component and a narrow Fe K line at 6.4 keV is consistent with an origin via torus reflection. The ionised Fe lines at ~6.7 and 7 keV are instead most likely originated by scattering on a warm and ionised gas. The soft X-ray spectrum appears to be almost featureless due to the very bright continuum emission, except for one emission line identified as OVIII Ly alpha detected at ~19 Angstrom by both RGS and Chandra-MEG. The emerging picture consists of an active nucleus seen directly on a "clean" line of sight without intervening material, surrounded by photoionised circumnuclear gas at a high ionisation level. We also study three serendipitous sources in the field of view of Chandra and XMM-Newton. One of these sources may be identified with an ULX of L_{0.3-10 keV}~10^{40} ergs/s.
description: 10 pages, 13 figures, accepted for publication on A&A including referee's comments
An Extension of the Athena++ Framework for Fully Conservative Self-Gravitating Hydrodynamics
Creators: name: Mullen, P. D.
name: Hanawa, Tomoyuki
name: Gammie, C. F.
Publisher: name: arXiv
Year: 2020
Subjects: subject: Instrumentation and Methods for Astrophysics (astro-ph.IM)
subject: FOS: Physical sciences

description: Numerical simulations of self-gravitating flows evolve a momentum equation and an energy equation that account for accelerations and gravitational energy releases due to a time-dependent gravitational potential. In this work, we implement a fully conservative numerical algorithm for self-gravitating flows, using source terms, in the astrophysical magnetohydrodynamics framework Athena++. We demonstrate that properly evaluated source terms are conservative when they are equivalent to the divergence of a corresponding "gravity flux" (i.e., a gravitational stress tensor or a gravitational energy flux). We provide test problems that demonstrate several advantages of the source-term-based algorithm, including second order convergence and round-off error total momentum and total energy conservation. The fully conservative scheme suppresses anomalous accelerations that arise when applying a common numerical discretization of the gravitational stress tensor that does not guarantee curl-free gravity.
description: 34 pages, 9 figures
Proposed E-payment Process Model to Enhance Quality of Service through Maintaining the Trust of Availability
Creators: name: AL-Qawasmi, Khaled
name: AL-Mousa, Mohammad
name: yousef, Mohammad
Publisher: name: arXiv
Year: 2021
Subjects: subject: Cryptography and Security (cs.CR)
subject: Software Engineering (cs.SE)
subject: FOS: Computer and information sciences

description: The use of the Internet has become an urgent necessity in various fields and activities. One of such important fields could be electronic business (E-Business). E-business includes all operations and activities related to Internet commerce, including e-commerce, e-marketing, eservices, e-payment, and electronic transfer. This proposal focuses on two perspectives that are under e-commerce umbrella where many e-payment process models suffer from the lack of clarity in the special procedures of the verification of the quality of services. This proposal, therefore, proposes a new E-payment process model to enhance the quality of service through maintaining availability. The proposed model focuses on the concepts of electronic payment model dimensions, which includes integrity, non-repudiation, authenticity, confidentiality, privacy, and availability. Accordingly, the proposed model implements the availability dimension in order to improve the quality of services that are provided to the consumer.
description: 5 pages
Degrees of hostility towards migrant solidarity: the case of Ceuta and Melilla
Creators: name: Marconi, Valentina
Publisher: name: De Europa
Year: 2023

description: While European borders have increasingly hardened since the so-called 2015 refugee crisis, practices of migrant assistance and solidarity by civil society actors have become a feature of contemporary border politics. On the one hand, across the European Union, local and international initiatives have often responded to needs of newcomers, by playing a pivotal role in doing humanitarian work; on the other hand, both organisations and individuals engaged in migrant solidarity and assistance have become the target of policies and practices of criminalisation. My analysis takes the Spanish enclaves of Ceuta and Melilla as a case-study, drawing on data collected during a 2019-2020 fieldwork. The paper argues that in the Spanish enclaves’ local humanitarians belonging to a range of civil society actors face different forms of intimidation and indirect pressure, both by governmental and non-governmental actors. I show how the lack of acceptance of the work of local humanitarians among some sectors of the local population lies with feelings of ‘fear’ and rejection towards some specific groups of migrants, such as unaccompanied minors from Morocco and young male migrants from Sub-Saharan countries. In addition, I describe how, along this EU external border, cases of harsher forms of criminalisation have been recorded as well. The paper concludes that tensions and hurdles that local humanitarians face in these EU border localities partially reflect a broader European trend and are a ‘sub-product’ of larger process of criminalisation of migrants and refugees travelling through irregular routes.


 Humanitarian border – Migrant solidarity - Civil society organisations – Ceuta – Melilla – Criminalisation
description: De Europa, V. 6 N. 2 (2023)
Full counting statistics of chaotic cavities with many open channels
Creators: name: Novaes, Marcel
Publisher: name: arXiv
Year: 2007
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: Chaotic Dynamics (nlin.CD)
subject: FOS: Physical sciences

description: Explicit formulas are obtained for all moments and for all cumulants of the electric current through a quantum chaotic cavity attached to two ideal leads, thus providing the full counting statistics for this type of system. The approach is based on random matrix theory, and is valid in the limit when both leads have many open channels. For an arbitrary number of open channels we present the third cumulant and an example of non-linear statistics.
description: 4 pages, no figures; v2-added references; typos corrected
Utilizing a Database of Simulated Geometric Albedo Spectra for Photometric Characterization of Rocky Exoplanet Atmospheres
Creators: name: Smith, Adam J. R. W.
name: Mandell, Avi M
name: Villanueva, Geronimo L
name: Moore, Michael Dane
Publisher: name: arXiv
Year: 2020
Subjects: subject: Earth and Planetary Astrophysics (astro-ph.EP)
subject: Instrumentation and Methods for Astrophysics (astro-ph.IM)
subject: FOS: Physical sciences

description: In anticipation of future flagship missions focused on the goal of achieving direct imaging of rocky exoplanets, we have developed a database of models to help the community examine the potential spectral characteristics of a broad range of rocky planet atmospheres. Using the publicly available Planetary Spectrum Generator (PSG), we have computed a grid of 141,600 rocky exoplanet geometric albedo spectra across a 7-dimensional parameter space. Using this grid, we have performed a color-color analysis seeking to identify the most useful near-ultraviolet and red or near-infrared photometric followup channels to combine with a green-optical (discovery) spectral channel. We found that a combination of filters at 0.4 um, 0.58 um, and (approx) 0.8um were able to distinguish between atmospheres with moderate-to-high concentrations of four different dominant absorbing constituents, given at least 10 hours of observation on a star at 10 parsec with a 15-meter-class space telescope; however, more moderate abundances similar to those of Solar System rocky bodies would be more challenging to detect. We recommend that future missions seeking to characterize directly imaged rocky exoplanets by colors alone further consider multi-band photometry as a first discriminator for planetary characteristics.
description: 15 pages, 10 figures. Accepted by AJ as of 9/2/2020
Citizenship in Times of Crises – Crisis of Citizenship?
Creators: name: Parreira Do Amaral, Marcelo
name: Zelinka, Jozef
name: Benasso, Sebastiano
name: König, Joseph
Publisher: name: De Europa
Year: 2023

description: The article discusses recent developments that are impacting the understandings of citizenship in late modern societies. During the past decades, citizenship has been discussed in terms of its contributions to tackling effects of political, social and economic crises. Most prominent are those challenges deriving from processes of Europeanization and globalization, but also, digital technologies are said to impinge new requirements on individuals, thus calling for European, global or digital citizenship. Well beyond simply changing the traditional orientation towards a nation-state, new conceptualizations of citizenship gravitate heavily towards individual dispositions and subjective competencies, while legal-juridical features remain untouched and largely unrelated. This explains the strong emphasis on the role of education in cultivating – global, European, digital – citizenship among individuals. The contribution asks whether and if so, how changed understandings of citizenship may lead to ‘performative citizenship’, where individuals are burdened with the requirement of constantly enacting ‘good’ and ‘worthy’ citizenship. The paper is organized along three sections: First, we revisit the mainstream literature on citizenship and discuss the main elements in historical-systematic manner. Second, based on a thorough literature review we discuss recent developments that call for updated meanings and representations of citizenship, before, third, the paper deliberates on the performative nature on newer conceptions of citizenship by examining recent examples of so-called global universities. The article closes with a discussion of research avenues for the topic, including crucial questions as to the status, role and function of citizenship in times of crises.
description: De Europa, V. 6 N. 2 (2023)
Desenvolvimento de Vouacapoua americana Aubl. (Fabaceae): Influência da biometria de sementes e diferentes níveis de luz
Creators: name: Karolina Motta de Campos
name: Rairys Cravo Herrera
name: Hevely Ueda Silveira Prates
name: Lucas de Oliveira Lima
name: Israeli Ingrid Costa Debrito
name: Cassiele Fonseca da Cruz
name: Magali Gonçalves Garcia
name: Guilherme Coelho Britto
Publisher: name: Zenodo
Year: 2024

description: There are records about the influence of seed size on seedling establishment, while during seedling development,environmental resources are the main factors. The objective of this work was to evaluate the relationship between seed biometry, radiance and canopy openness in the establish-ment and development of Vouacapoua americana. For this, shoot height, stem diameter, number of leaves, leaflets, leaf area, chlorophyll a and b at 60 and 180 days after sowing were evaluated. After transplanting, survival, regrowth and growth of seedlings were measured. Emergence was influ-enced by biometrics at 30 and 60 days. At 140 days, growth variables were positively related to seed biometry. A high percentage (88.88%) of survival and regrowth (63.63%) was observed in thefield. Survival was positively affected by canopy openness. It was concluded that seeds with greater bi-ometry of V. americanapromote greater emergence after 30 days and more developed seedlings. The association of evaluations of biometric characteristicsof seeds and environmental factors contribute to the planning of production programs for seedlings of V. americana.
School integration of refugee minors: An analysis of the barriers of education quality and continuity in Italian and Greek school systems
Creators: name: Ince-Beqo, Gül
name: Roussakis, Yiannis
name: Sergi, Vittorio
Publisher: name: De Europa
Year: 2023

description: In recent years, the number of minor migrants, both accompanied and unaccompanied, arriving in European countries increased significantly. The impact of newcomers on the school systems of various European countries has highlighted problems in education continuity and in the accomplishment of educational goals. Relying on the preliminary data from the Erasmus+ KA2 project “Continugee” in Italy and Greece, this paper analyses the current policies and practices used in refugee children education. In addition to policy analysis, interviews with families, teachers and professionals operating in migrant shelters and schools were conducted, aimed to address both institutional and relational dimensions of schooling and to point out good practices in educational incorporation of refugee youth. Research shows that – notwithstanding a common concern throughout Europe, national and local regulations, and local practices do affect their access to quality education. Age limits, gender gaps, location of shelters, lack of adequate institutional educational facilities and of professional training make effective educational placement and continuity difficult. Schools have a very different level of effectiveness and European policy innovation is often jeopardized by lack of resources and staff motivation. Recognition of qualifications and skills, a supported participation into mainstream education, and a participatory approach with families and guardians are essential for effective school integration.


Keywords: refugee, minors, education, training, policy, European


 
description: De Europa, V. 6 N. 2 (2023)
AstroSat observations of long-duration X-ray superflares on active M-dwarf binary EQ Peg
Creators: name: Karmakar, Subhajeet
Publisher: name: Zenodo
Year: 2021
Subjects: stars: activity
stars: coronae
stars: flare
EQ Peg
stars: low-mass
stars: magnetic field

description: We present a comprehensive study of three large long-duration flares detected on an active M-dwarf binary EQ Peg using Soft X-Ray Telescope of the AstroSat observatory. The peak X-ray luminosities of the flares in the 0.3 -- 7 keV band are found to be within ~4-10 × 10^{30} erg s^{-1}. Spectral analysis indicates the presence of three temperature corona with the first two plasma temperatures remain constant during all the flares and the post-flare. The flare-temperature peaked at 56, 40, and 31 MK, which are 2.5, 1.8, and 1.4 times more than the minimum value, respectively. The peak emission measures are found to be 1.16 -- 5.64 × 10^{53} cm^{-3}, whereas the abundances peaked at 0.7 -- 1.2 times the solar abundances. Using quasi-static loop modeling, we derive loop-lengths for all the flares as 2.7 ± 1.4 × 10^{11}, 3.9 ± 1.5 × 10^{11}, and 6.4 ± 2.4 × 10^{11} cm, respectively. The estimated energies of all three flares are >10^{33-35} erg, putting them in the category of Superflare. All three superflares are also found to be the longest duration flares ever observed on EQ Peg.
Two dimensional foam rheology with viscous drag
Creators: name: Janiaud, E.
name: Weaire, D.
name: Hutzler, S.
Publisher: name: arXiv
Year: 2006
Subjects: subject: Soft Condensed Matter (cond-mat.soft)
subject: FOS: Physical sciences

description: We formulate and apply a continuum model that incorporates elasticity, yield stress, plasticity and viscous drag. It is motivated by the two-dimensional foam rheology experiments of Debregeas et al. [G. Debregeas, H. Tabuteau, and J.-M. di Meglio, Phys. Rev. Lett. 87, 178305 (2001)] and Wang et al [Y. Wang, K. Krishan, and M. Dennin, Phys. Rev. E 73, 031401 (2006)], and is successful in exhibiting their principal features an exponentially decaying velocity profile and strain localisation. Transient effects are also identified.
description: accepted version (to appear in PRL). Some parts of the paper have been rewritten (mainly introduction and final discussion)
On the theory of superfluidity
Creators: name: Yu, Yongle
Publisher: name: arXiv
Year: 2006
Subjects: subject: Statistical Mechanics (cond-mat.stat-mech)
subject: FOS: Physical sciences

description: We investigate the properties of dispersion spectra of one-dimensional periodic Bose systems with repulsive interparticle interactions. These systems with sufficient large interactions can support metastable supercurrent states, which correspond to the local minima of the dispersion spectra at non-zero momenta. The existence of local minima in the spectra and the energy barriers, which separate the minima, can be explained in terms of Bose exchange symmetry. We extend our study to the case of higher dimensional Bose systems. We suggest that superfluidity could be understood as a Bose exchange effect.
description: simplified version; added references; 6 pages, 6 figures
Ανθρωποκεντρική ανάλυση στερεοσκοπικού βίντεο.
Creators: name: Τσιγγαλής, Ιωάννης Αργυρίου
Publisher: name: Aristotle University of Thessaloniki
Year: 2014
Subjects: Βαθμονόμηση σημαντικότητας αντικειμένων
Αναγνώριση πλάνων βίντεο
Ανάλυση κοινωνικών μέσων δικτύωσης
Object saliency rate
Shot type detection
Social network analysis

description: Σε αυτή τη διπλωματική ασχοληθήκαμε με τη σημασιολογική περιγραφή βίντεο. Επίσης, πραγματοποιήθηκε στατιστική ανάλυση δεδομένων κοινωνικής δικτύωσης τα οποία ανακτήθηκαν μέσω του YouTube API. Πρέπει να σημειώσουμε ότι τόσο για τη σημασιολογική περιγραφή βίντεο όσο και για την ανάλυση κοινωνικών δικτύων χρησιμοποιήθηκαν τρισδιάστατα βίντεο. Πιο συγκεκριμένα, σχετικά με τη σημασιολογική περιγραφή του βίντεο ασχοληθήκαμε με δύο θέματα. Αρχικά, μέσω συγκεκριμένης μεθοδολογίας που αναπτύξαμε, προσπαθήσαμε να βαθμολογήσουμε περιοχές ενδιαφέροντος οι οποίες εμφανίζονται στα πλαίσια εικονοσειρών. Ειδικότερα, μια περιοχή ενδιαφέροντος πλαισιώνεται από ένα κουτί και περιέχει ένα πρόσωπο. Οι περιοχές αυτές βαθμολογήθηκαν αυτόματα ως ``καθόλου σημαντικές'', ``ελάχιστα σημαντικές'', ``μέτρια σημαντικές '' και ``πολύ σημαντικές''. Το δεύτερο θέμα με το οποίο ασχοληθήκαμε στη σημασιολογική περιγραφή βίντεο ήταν η αναγνώριση συγκεκριμένων τύπων πλάνων. Συγκεκριμένα, ασχοληθήκαμε με την αναγνώριση πλάνων στα οποία ένας ηθοποιός έχει στραμμένη την πλάτη στην κάμερα ενώ η κάμερα καταγράφει ότι κοιτάει αυτός ο ηθοποιός. Η κάμερα, επίσης, καταγράφει ένα κομμάτι της πλάτης του κεφαλιού του ηθοποιού. Η αγγλική ονομασία αυτού του πλάνου είναι ``Over-The-Shoulder (OTS)''. Για την επίλυση αυτού του προβλήματος αναπτύχθηκε σχετική μέθοδος αυτόματης αναγνώρισης. Τέλος, ασχοληθήκαμε με στατιστική ανάλυση δεδομένων τα οποία συλλέχθηκαν μέσω του YouTube API. Σε αυτά τα δεδομένα προσπαθήσαμε να ανιχνεύσουμε ``Power-law'' συμπεριφορές. Επίσης, μελετήσαμε τις ``Lorenz'' καμπύλες για αυτά τα δεδομένα.
description: On this thesis, we present two methods for semantic stereoscopic video analysis. The first method ranks specific Regions of Interest (ROIs) according to their importance. Three labels of importance can be assigned to each ROI: ``non-salient'', ``low-salient'', ``medium-salient'' and ``high-salient''. A method that assigns these labels automatically is presented. The second method detects Over-The-Shoulder (OTS) shots. In an OTS shot, the camera is placed behind the shoulder of an actor and captures whatever it is pointing at, usually another actor. This configuration is used to place the viewer in the first actor's perspective. It is usually employed in shots with tension. The proposed method applies only stereoscopic information and returns promising results. Finally, we conclude this thesis by making a small statistical study on YouTube. We work only with stereoscopic videos. Concepts like the Power-Law and the Lorenz curve are discussed.
Young Stars in Taurus: The K2 View
Creators: name: Cody, Ann Marie
name: Hillenbrand, Lynne A.
Publisher: name: Zenodo
Year: 2021
Subjects: Young stars
Young star variability

description: Young stars with circumstellar disks are highly variable sources on many timescales. Accretion, dust obscuration, and rotational modulation of stellar spots are thought to be the main contributors to this variability, although the physical drivers are not understood in detail. Over the past few years, space missions have returned exquisite light curves of young stars (YSOs) across the sky, enabling new analyses of their flux behavior from minute to several month timescales. The Kepler telescope's K2 Mission contributed to this endeavor with observations of several star-forming regions, including Upper Scorpius, rho Ophiuchus, the Lagoon Nebula, and Taurus. Here we present a newly processed set of light curves for all 100 disk-bearing stars observed during K2 Campaign 13 encompassing the ~1 Myr Taurus region. We apply statistical metrics to classify the morphology of each ~80-day light curve and ultimately correlate time domain behavior with stellar and circumstellar properties, including spectral type, disk evolutionary state, and multiplicity. We compare our results with those previously published for the older Upper Scorpius star formation region, finding that quasi-periodic obscuration events appear to become more common at slightly older age.
description: {"references": ["Rebull, Luisa, et al. (2020)", "Cody, Ann Marie, & Hillenbrand, Lynne (2018)"]}
Οπτική ανίχνευση φωνητικής δραστηριότητας
Creators: name: Πατρώνα, Φωτεινή Παύλου
Publisher: name: Aristotle University of Thessaloniki
Year: 2014
Subjects: Οπτική ανίχνευση φωνητικής δραστηριότητας
Ανίχνευση κίνησης
Μηχανές εδραίων αναζήτησης
Visual voice activity detection
Action recognition
Support vector machines

description: Στα πλαίσια της παρούσας εργασία ασχοληθήκαμε με το πρόβλημα της Οπτικής Ανίχνευσης Φωνητικής Δραστηριότητας. Μία νέα βάση δεδομένων που διαφέρει από τις υπάρχουσες και μπορεί να χρησιμοποιηθεί εκτός των άλλων και για έλεχγο μεθόδων που στοχεύουν στην Οπτική Ανίχνευση Φωνητικής Δραστηριότητας δημιουργήθηκε, μελετήθηκαν οι επιδόσεις μίας προϋπάρχουσας μεθόδου σε δύο βάσεις δεδομένων που χρησιμοποιούνται στη βιβλιογραφία, καθώς και στη νέα βάση που δημιουργήθηκε, εντοπίστηκαν τα βασικά της προβλήματα και υιοθετήθηκε η προσέγγιση του προβλήματος της Οπτικής Ανίχνευσης Φωνητικής Δραστηριότητας σαν πρόβλημα αναγνώρισης κίνησης. Εφαρμόστηκαν τεχνικές εξαγωγής χαρακτηριστικών, αναπαράστασης και κατηγοριοποίησης εικοσειράς κυρίαρχες στο χώρο της αναγνώρισης κίνησης, και βάσει των αποτελεσμάτων που αυτές έδωσαν στη νέα βάση δεδομένων διαπιστώθηκε ότι μπορούν να εφαρμοστούν με επιτυχία και σε αυτό το πρόβλημα.
description: Visual Voice Activity Detection was the main problem under research in this thesis. A new dataset, considerably different from all the already existing ones and usable for testing methods aiming at solving the problem of Visual Voice Activity Detection was constructed, a preexisting method introduced by AUTH researchers was tested on two publicly available datasets as well as on the new one and its drawbacks were detected. Finally, action recognition techniques for feature extraction, video description and classification were adopted and proved to be appropriate for this problem, based on experiments conducted on the new dataset constructed.