cometadata/datacite-rtg-text-other-reclassification-records huggingface dataset:
title: Διερεύνηση συμπεριφοράς κόμβων σύνδεσης προκατασκευασμένων γεφυρών Bailey
titleType: AlternativeTitle
Creators: name: Kachrimanis, Alkaios
Publisher: name: National Technological University of Athens
Year: 2025
Subjects: Bailey
Κόπωση
Υπομοντέλα
Δυναμική απόκριση

description: Εθνικό Μετσόβιο Πολυτεχνείο--Μεταπτυχιακή Εργασία. Διεπιστημονικό-Διατμηματικό Πρόγραμμα Μεταπτυχιακών Σπουδών (Δ.Π.Μ.Σ.) “Δομοστατικός Σχεδιασμός και Ανάλυση των Κατασκευών”
An all-solid-state laser source at 671 nm for cold atom experiments with lithium
Creators: name: Eismann, Ulrich
name: Gerbier, Fabrice
name: Canalias, Carlota
name: Zukauskas, Andrius
name: Trénec, Gérard
name: Vigué, Jacques
name: Chevy, Frédéric
name: Salomon, Christophe
Publisher: name: arXiv
Year: 2011
Subjects: subject: Optics (physics.optics)
subject: Quantum Gases (cond-mat.quant-gas)
subject: Atomic Physics (physics.atom-ph)
subject: FOS: Physical sciences

description: We present an all solid-state narrow line-width laser source emitting $670\,\mathrm{mW}$ output power at $671\,\mathrm{nm}$ delivered in a diffraction-limited beam. The \linebreak source is based on a fre-quency-doubled diode-end-linebreak pumped ring laser operating on the ${^4F}_{3/2} \rightarrow {^4I}_{13/2}$ transition in Nd:YVO$_4$. By using periodically-poled po-tassium titanyl phosphate (ppKTP) in an external build-up cavity, doubling efficiencies of up to 86% are obtained. Tunability of the source over $100\,\rm GHz$ is accomplished. We demonstrate the suitability of this robust frequency-stabilized light source for laser cooling of lithium atoms. Finally a simplified design based on intra-cavity doubling is described and first results are presented.
Evaluation of FESOM2.0 Coupled to ECHAM6.3: Preindustrial and HighResMIP Simulations
Creators: name: Sidorenko, D.
name: Goessling, H.F.
name: Koldunov, N.V.
name: Scholz, P.
name: Danilov, S.
name: Barbi, D.
name: Cabos, W.
name: Gurses, O.
name: Harig, S.
name: Hinrichs, C.
name: Juricke, S.
name: Lohmann, G.
name: Losch, M.
name: Mu, L.
name: Rackow, T.
name: Rakowsky, N.
name: Sein, D.
name: Semmler, T.
name: Shi, X.
name: Stepanek, C.
name: Streffing, J.
name: Wang, Q.
name: Wekerle, C.
name: Yang, H.
name: Jung, T.
Publisher: name: FID GEO
Year: 2019

description: A new global climate model setup using FESOM2.0 for the sea ice-ocean component and ECHAM6.3 for the atmosphere and land surface has been developed. Replacing FESOM1.4 by FESOM2.0 promises a higher efficiency of the new climate setup compared to its predecessor. The new setup allows for long-term climate integrations using a locally eddy-resolving ocean. Here it is evaluated in terms of (1) the mean state and long-term drift under preindustrial climate conditions, (2) the fidelity in simulating the historical warming, and (3) differences between coarse and eddy-resolving ocean configurations. The results show that the realism of the new climate setup is overall within the range of existing models. In terms of oceanic temperatures, the historical warming signal is of smaller amplitude than the model drift in case of a relatively short spin-up. However, it is argued that the strategy of “de-drifting” climate runs after the short spin-up, proposed by the HighResMIP protocol, allows one to isolate the warming signal. Moreover, the eddy-permitting/resolving ocean setup shows notable improvements regarding the simulation of oceanic surface temperatures, in particular in the Southern Ocean.
Non-equilibrium quasiparticles and topological excitations in hybrid superconducting structures
Creators: name: Heimes, Andreas Franz
Publisher: name: Karlsruhe
Year: 2014

description: We discuss the properties of a hybrid single electron turnstile, involving a small superconducting island sandwiched between normal metal leads. We theoretically model the charge transport and non-equilibrium quasiparticle distribution and compare with recent experimental findings. In the second part of the thesis we theoretically investigate chains of magnetic atoms on top of superconducting substrates and discuss the ability of the hybrid setup to harbor Majorana fermion excitations.
Spatial quantum search in a triangular network
Creators: name: Abal, G.
name: Donangelo, R.
name: Forets, M.
name: Portugal, R.
Publisher: name: arXiv
Year: 2010
Subjects: subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: The spatial search problem consists in minimizing the number of steps required to find a given site in a network, under the restriction that only oracle queries or translations to neighboring sites are allowed. We propose a quantum algorithm for the spatial search problem on a triangular lattice with N sites and torus-like boundary conditions. The proposed algortithm is a special case of the general framework for abstract search proposed by Ambainis, Kempe and Rivosh [AKR05] (AKR) and Tulsi [Tulsi08], applied to a triangular network. The AKR-Tulsi formalism was employed to show that the time complexity of the quantum search on the triangular lattice is O(sqrt(N logN)).
description: 10 pages, 4 Postscript figures, uses sbc-template.sty, appeared in Annals of WECIQ 2010, III Workshop of Quantum Computation and Quantum Information
A General Framework for Transmission with Transceiver Distortion and Some Applications
Creators: name: Zhang, Wenyi
Publisher: name: arXiv
Year: 2010
Subjects: subject: Information Theory (cs.IT)
subject: FOS: Computer and information sciences

description: A general theoretical framework is presented for analyzing information transmission over Gaussian channels with memoryless transceiver distortion, which encompasses various nonlinear distortion models including transmit-side clipping, receive-side analog-to-digital conversion, and others. The framework is based on the so-called generalized mutual information (GMI), and the analysis in particular benefits from the setup of Gaussian codebook ensemble and nearest-neighbor decoding, for which it is established that the GMI takes a general form analogous to the channel capacity of undistorted Gaussian channels, with a reduced "effective" signal-to-noise ratio (SNR) that depends on the nominal SNR and the distortion model. When applied to specific distortion models, an array of results of engineering relevance is obtained. For channels with transmit-side distortion only, it is shown that a conventional approach, which treats the distorted signal as the sum of the original signal part and a uncorrelated distortion part, achieves the GMI. For channels with output quantization, closed-form expressions are obtained for the effective SNR and the GMI, and related optimization problems are formulated and solved for quantizer design. Finally, super-Nyquist sampling is analyzed within the general framework, and it is shown that sampling beyond the Nyquist rate increases the GMI for all SNR. For example, with a binary symmetric output quantization, information rates exceeding one bit per channel use are achievable by sampling the output at four times the Nyquist rate.
description: 32 pages (including 4 figures, 5 tables, and auxiliary materials); submitted to IEEE Transactions on Communications
Vorausschau im Produktentstehungsprozess - Das integrierte Produktentstehungs-Modell (iPeM) als Bezugsrahmen für Vorausschau am Beispiel von Szenariotechnik und strategischer Frühaufklärung = Foresight for Product Engineering Processes - Using the Integrated Product Engineering Model (iPeM) to align foresight - the example of scenario technique and strategic early warning
Creators: name: Meyer-Schwickerath, Ben
Publisher: name: Karlsruhe
Year: 2014
Subjects: Vorausschau
Foresight
PEP
Zielsystem
Szenariotechnik

description: In dieser Arbeit wird ein Modell vorgestellt, welches die Integration von Vorausschau in das Zielsystem von Produktentstehungsprozessen (PEP) ermöglicht. Die Arbeit fokussiert hierbei im Rahmen der Vorausschau auf die Szenariotechnik und die strategische Früherkennung.
Double Sivers effect asymmetries and their impact on transversity measurements at RHIC
Creators: name: Boer, Daniel
name: Dunnen, Wilco J. den
name: Kotzinian, Aram
Publisher: name: arXiv
Year: 2011
Subjects: subject: High Energy Physics - Phenomenology (hep-ph)
subject: FOS: Physical sciences

description: We study double transverse spin asymmetries in the Drell-Yan process at measured transverse momentum of the lepton pair. Contrary to what a collinear factorization approach would suggest, a nonzero double transverse spin asymmetry in the laboratory frame a priori does not imply nonzero transversity. TMD effects, such as the double Sivers effect, in principle form a background. Using the current knowledge of the relevant TMDs we estimate their contribution in the laboratory frame for Drell-Yan and W production at RHIC and point out a cross check asymmetry measurement to bound the TMD contributions. We also comment on the transverse momentum integrated asymmetries that only receive power suppressed background contributions.
description: 12 pages, 11 eps figures, minor changes, matches the published version
Burial and Origin of Permafrost-Derived Carbon in the Nearshore Zone of the Southern Canadian Beaufort Sea
Creators: name: Grotheer, H.
name: Meyer, V.
name: Riedel, T.
name: Pfalz, G.
name: Mathieu, L.
name: Hefter, J.
name: Gentz, T.
name: Lantuit, H.
name: Mollenhauer, G.
name: Fritz, M.
Publisher: name: FID GEO
Year: 2020

description: Detailed organic geochemical and carbon isotopic (δ13C and Δ14C) analyses are performed on permafrost deposits affected by coastal erosion (Herschel Island, Canadian Beaufort Sea) and adjacent marine sediments (Herschel Basin) to understand the fate of organic carbon in Arctic nearshore environments. We use an end-member model based on the carbon isotopic composition of bulk organic matter to identify sources of organic carbon. Monte Carlo simulations are applied to quantify the contribution of coastal permafrost erosion to the sedimentary carbon budget. The models suggest that ~40% of all carbon released by local coastal permafrost erosion is efficiently trapped and sequestered in the nearshore zone. This highlights the importance of sedimentary traps in environments such as basins, lagoons, troughs, and canyons for the carbon sequestration in previously poorly investigated, nearshore areas.
Width control on event-scale deposition and evacuation of sediment in bedrock-confined channels
Creators: name: Cook, Kristen L.
name: Turowski, Jens M.
name: Hovius, Niels
Publisher: name: FID GEO
Year: 2020

description: Abstract In mixed bedrock–alluvial rivers, the response of the system to a flood event can be affected by a number of factors, including coarse sediment availability in the channel, sediment supply from the hillslopes and upstream, flood sequencing and coarse sediment grain size distribution. However, the impact of along-stream changes in channel width on bedload transport dynamics remains largely unexplored. We combine field data, theory and numerical modelling to address this gap. First, we present observations from the Daan River gorge in western Taiwan, where the river flows through a 1 km long 20–50 m wide bedrock gorge bounded upstream and downstream by wide braidplains. We documented two flood events during which coarse sediment evacuation and redeposition appear to cause changes of up to several metres in channel bed elevation. Motivated by this case study, we examined the relationships between discharge, channel width and bedload transport capacity, and show that for a given slope narrow channels transport bedload more efficiently than wide ones at low discharges, whereas wider channels are more efficient at high discharges. We used the model sedFlow to explore this effect, running a random sequence of floods through a channel with a narrow gorge section bounded upstream and downstream by wider reaches. Channel response to imposed floods is complex, as high and low discharges drive different spatial patterns of erosion and deposition, and the channel may experience both of these regimes during the peak and recession periods of each flood. Our modelling suggests that width differences alone can drive substantial variations in sediment flux and bed response, without the need for variations in sediment supply or mobility. The fluctuations in sediment transport rates that result from width variations can lead to intermittent bed exposure, driving incision in different segments of the channel during different portions of the hydrograph. © 2020 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd
Relatively large theta13 and nearly maximal theta23 from the approximate S3 symmetry of lepton mass matrices
Creators: name: Zhou, Shun
Publisher: name: arXiv
Year: 2011
Subjects: subject: High Energy Physics - Phenomenology (hep-ph)
subject: FOS: Physical sciences

description: We apply the permutation symmetry S_3 to both charged-lepton and neutrino mass matrices, and suggest a useful symmetry-breaking scheme, in which the flavor symmetry is explicitly broken down via S_3 -> Z_3 -> nothing in the charged-lepton sector and via S_3 -> Z_2 -> nothing in the neutrino sector. Such a two-stage breaking scenario is reasonable in the sense that both Z_3 and Z_2 are the subgroups of S_3, while Z_3 and Z_2 only have a trivial subgroup. In this scenario, we can obtain a relatively large value of the smallest neutrino mixing angle, e.g., theta_{13} ~ 9^\circ, which is compatible with the recent result from T2K experiment and will be precisely measured in the ongoing Double Chooz and Daya Bay reactor neutrino experiments. Moreover, the maximal atmospheric mixing angle theta_{23} ~ 45^\circ can also be obtained while the best-fit value of solar mixing angle theta_{12} ~ 34^\circ is assumed, which cannot be achieved in previous S_3 symmetry models.
description: 15 pages, no figures, minor changes, matches the published version
title: Νευρωνικά δίκτυα γράφων γνώσης σε συστήματα συστάσεων
titleType: AlternativeTitle
title: Graph Neural Networks in Knowledge-Based Recommendation Systems
Creators: name: Karamargiou, Aikaterini
Publisher: name: National Technological University of Athens
Year: 2025
Subjects: Graphs
Recommender Systems
Graph Neural Networks
Neural Networks
Γράφοι
Συστήματα Συστάσεων
Νευρωνικά Δίκτυα Γράφων
Νευρωνικά Δίκτυα
Γράφοι Γνώσης
Knowledge Graphs

description: Εθνικό Μετσόβιο Πολυτεχνείο--Μεταπτυχιακή Εργασία. Διεπιστημονικό-Διατμηματικό Πρόγραμμα Μεταπτυχιακών Σπουδών (Δ.Π.Μ.Σ.) “Μαθηματική Προτυποποίηση σε Σύγχρονες Τεχνολογίες και στα Χρηματοοικονομικά”
Structure of heme d1-free cd1 nitrite reductase NirS
Creators: name: Klünemann, Thomas
name: Blankenfeldt, Wulf
Publisher: name: FID GEO
Year: 2020

description: A key step in anaerobic nitrate respiration is the reduction of nitrite to nitric oxide, which is catalysed by the cd1 nitrite reductase NirS in, for example, the Gram-negative opportunistic pathogen Pseudomonas aeruginosa. Each subunit of this homodimeric enzyme consists of a cytochrome c domain and an eight-bladed β-propeller that binds the uncommon isobacteriochlorin heme d1 as an essential part of its active site. Although NirS has been well studied mechanistically and structurally, the focus of previous studies has been on the active heme d1-bound form. The heme d1-free form of NirS reported here, which represents a premature state of the reductase, adopts an open conformation with the cytochrome c domains moved away from each other with respect to the active enzyme. Further, the movement of a loop around Trp498 seems to be related to a widening of the propeller, allowing easier access to the heme d1-binding side. Finally, a possible link between the open conformation of NirS and flagella formation in P. aeruginosa is discussed.
Classical Polylogarithms for Amplitudes and Wilson Loops
Creators: name: Goncharov, Alexander B.
name: Spradlin, Marcus
name: Vergu, C.
name: Volovich, Anastasia
Publisher: name: arXiv
Year: 2010
Subjects: subject: High Energy Physics - Theory (hep-th)
subject: Algebraic Geometry (math.AG)
subject: FOS: Physical sciences
subject: FOS: Mathematics

description: We present a compact analytic formula for the two-loop six-particle MHV remainder function (equivalently, the two-loop light-like hexagon Wilson loop) in N = 4 supersymmetric Yang-Mills theory in terms of the classical polylogarithm functions Li_k with cross-ratios of momentum twistor invariants as their arguments. In deriving our result we rely on results from the theory of motives.
description: 11 pages, v2: journal version, minor corrections and simplifications, additional details available at http://goo.gl/Cl0y
Superior Lithium Storage Capacity of α-MnS Nanoparticles Embedded in S-Doped Carbonaceous Mesoporous Frameworks
Creators: name: Ma, Yuan
name: Ma, Yanjiao
name: Kim, Guk-Tae
name: Diemant, Thomas
name: Behm, Rolf Jürgen
name: Geiger, Dorin
name: Kaiser, Ute
name: Varzi, Alberto
name: Passerini, Stefano
Publisher: name: FID GEO
Year: 2019

description: Abstract Herein, a Mn-based metal–organic framework is used as a precursor to obtain well-defined α-MnS/S-doped C microrod composites. Ultrasmall α-MnS nanoparticles (3–5 nm) uniformly embedded in S-doped carbonaceous mesoporous frameworks (α-MnS/SCMFs) are obtained in a simple sulfidation reaction. As-obtained α-MnS/SCMFs shows outstanding lithium storage performance, with a specific capacity of 1383 mAh g−1 in the 300th cycle or 1500 mAh g−1 in the 120th cycle (at 200 mA g−1) using copper or nickel foil as the current collector, respectively. The significant (pseudo)capacitive contribution and the stable composite structure of the electrodes result in impressive rate capabilities and outstanding long-term cycling stability. Importantly, in situ X-ray diffraction measurements studies on electrodes employing various metal foils/disks as current collector reveal the occurrence of the conversion reaction of CuS at (de)lithiation process when using copper foil as the current collector. This constitutes the first report of the reaction mechanism for α-MnS, eventually forming metallic Mn and Li2S. In situ dilatometry measurements demonstrate that the peculiar structure of α-MnS/SCMFs effectively restrains the electrode volume variation upon repeated (dis)charge processes. Finally, α-MnS/SCMFs electrodes present an impressive performance when coupled in a full cell with commercial LiMn1/3Co1/3Ni1/3O2 cathodes.
Thermoregeneration of Plastrons on Superhydrophobic Coatings for Sustained Antifouling Properties
Creators: name: Simovich, Tomer
name: Rosenhahn, Axel
name: Lamb, Robert N.
Publisher: name: FID GEO
Year: 2019

description: A popular and desirable function of superhydrophobic coatings is their remarkable ability to retain an entrapped layer of air, called a plastron, when submerged underwater. The drawback is that the air layer is short-lived due to solvation into the surrounding liquid. While manipulating the solubility of gases using temperature is a possible approach, it generally requires inefficiently heating large volumes of water. Following the demonstrated ability to maintain air bubbles on superhydrophobic surfaces for drag reduction, this article introduces a novel method of extracting gas from water to replenish and stabilize the plastron on superhydrophobic surfaces for sustained antifouling abilities. This method involves locally heating the liquid surrounding a superhydrophobic coating, reducing gas solubility, and causing the gas to nucleate at the liquid–air interface. The approach requires a relatively low energy input, due to the small volume of locally heated water. With a constant supply of equilibrated water and minimal energy input, the plastron can survive indefinitely without the need for a mechanical delivery of air. The thermoregenerating superhydrophobic samples were shown to exhibit excellent antifouling behavior and inhibited diatom attachment over a period of 5 days.
Mechanistic Aspects of the Electrocatalytic Oxygen Evolution Reaction over Ni−Co Oxides
Creators: name: Negahdar, Leila
name: Zeng, Feng
name: Palkovits, Stefan
name: Broicher, Cornelia
name: Palkovits, Regina
Publisher: name: FID GEO
Year: 2019

description: Abstract The electrocatalytic oxygen evolution reaction (OER) presents the key transformation in electrochemical water-splitting majorly determining energy efficiency and economics of hydrogen generation. In this study, the kinetics of the OER over Ni−Co oxide structured by KIT-6 templating and non-structured Ni−Co oxide catalysts in alkaline solution have been investigated aiming for insight with regard to the respective kinetically relevant surface reactions. Steady-state Tafel plot analysis and electrochemical impedance spectroscopy (EIS) were used to determine kinetic parameters, Tafel slopes and the order of reaction. A dual Tafel slope behavior was observed for both catalysts. Tafel slopes of ca. 40 and 120 mV dec−1 and 90 and 180 mV dec−1 at low and high overpotentials appear for structured and non-structured Ni−Co oxide, respectively. A reaction order of unity was observed for structured Ni−Co oxide, while non-structured Ni−Co oxide possessed a fractional reaction order in the high overpotential region. The kinetics of OER over structured Ni−Co oxide were governed by Langmuir adsorption with the rate-limiting step after primary adsorption of surface intermediates. In contrast, non-structured Ni−Co oxide obeyed the Temkin adsorption isotherm condition with the primary adsorption step being rate-limiting.
Nitride Spinel: An Ultraincompressible High-Pressure Form of BeP2N4
Creators: name: Vogel, Sebastian
name: Bykov, Maxim
name: Bykova, Elena
name: Wendl, Sebastian
name: Kloß, Simon D.
name: Pakhomova, Anna
name: Dubrovinskaia, Natalia
name: Dubrovinsky, Leonid
name: Schnick, Wolfgang
Publisher: name: FID GEO
Year: 2019

description: Abstract Owing to its outstanding elastic properties, the nitride spinel γ-Si3N4 is of considered interest for materials scientists and chemists. DFT calculations suggest that Si3N4-analog beryllium phosphorus nitride BeP2N4 adopts the spinel structure at elevated pressures as well and shows outstanding elastic properties. Herein, we investigate phenakite-type BeP2N4 by single-crystal synchrotron X-ray diffraction and report the phase transition into the spinel-type phase at 47 GPa and 1800 K in a laser-heated diamond anvil cell. The structure of spinel-type BeP2N4 was refined from pressure-dependent in situ synchrotron powder X-ray diffraction measurements down to ambient pressure, which proves spinel-type BeP2N4 a quenchable and metastable phase at ambient conditions. Its isothermal bulk modulus was determined to 325(8) GPa from equation of state, which indicates that spinel-type BeP2N4 is an ultraincompressible material.
Odd Parity Perturbations of the Self-Similar LTB Spacetime
Creators: name: Duffy, Emily M.
name: Nolan, Brien C.
Publisher: name: arXiv
Year: 2010
Subjects: subject: General Relativity and Quantum Cosmology (gr-qc)
subject: FOS: Physical sciences

description: We consider the behaviour of odd-parity perturbations of those self-similar Lemaître-Tolman-Bondi spacetimes which admit a naked singularity. We find that a perturbation which evolves from initially regular data remains finite on the Cauchy horizon. Finiteness is demonstrated by considering the behaviour of suitable energy norms of the perturbation (and pointwise values of these quantities) on natural spacelike hypersurfaces. This result holds for a general choice of initial data and initial data surface. Finally, we examine the perturbed Weyl scalars in order to provide a physical interpretation of our results. Taken on its own, this result does not support cosmic censorship; however a full perturbation of this spacetime would include even parity perturbations, so we cannot conclude that this spacetime is stable to all linear perturbations.
description: 36 pages
"We just wanna warm some bellies" : Food Not Bombs, anarchism, and recycling wasted food for protest
Creators: name: Fessenden, Sarah Grace
Publisher: name: University of British Columbia
Year: 2017

description: Within and against neoliberal systems Food Not Bombs serves hope. Food Not Bombs is a global anarchist-inspired (dis)organization that protests war—among other things—by giving away food for free. This dissertation is an ethnography about Food Not Bombs generally and the Vancouver chapter of Food Not Bombs in particular. It contributes to anthropologies of resistance, specifically those kinds of resistance practiced by Food Not Bombs and alter-globalization activists. Since Food Not Bombs offers a unique perspective on issues such as food-waste and hunger, I follow Food Not Bombs both in its critique of contemporary social life and in its production of alternative cultural forms. I begin by introducing the concepts direct action project and social movement (dis)organization to conceptually locate Food Not Bombs and groups like it. What is unique about direct action projects is that they explicitly weave together critique and hope; in other words, critique and hope are immanent in their direct action tactics. The manner of the critique itself (i.e. direct action) alleviates some of these harsh experiences of life under neoliberalism and, simultaneously, imagines/creates alternative cultural forms. Working with(in) global justice and alter-globalization movements, Food Not Bombs is a social movement (dis)organization, incorporating anarchistic logics and values to protest movements. Working in the interstices of capitalism, Food Not Bombs recovers wasted food, prepares it in collective kitchens using non-hierarchical organization, and serves it for free to anyone in want or need of it in public spaces. “We just wanna warm some bellies” not just in the moment but in such a way as to prefigure a world where people could freely feed themselves and help their neighbors do the same. Appadurai (2013) suggests a politics wherein we do not end with critique but with enacting a new vision for the future in the present. In this dissertation I describe Food Not Bombs as a direct action project that does the work of hope in the present by exploiting the cracks in capitalism and creatively producing new cultural forms as well as cooking up some food to share. In other words, “punk rock DIY belly feeding.”
A String Model for AdS Gravity and Higher Spins
Creators: name: Polyakov, Dimitri
Publisher: name: arXiv
Year: 2011
Subjects: subject: High Energy Physics - Theory (hep-th)
subject: FOS: Physical sciences

description: We construct a string sigma-model which low energy limit describes the anti de Sitter gravity and spin 3 massless fields in Vasiliev's frame-like formalism. The model is based on vertex operators generating vielbein and connection fields in the Mac Dowell - Mansoury - Stelle - West (MMSW) formulation of gravity. The structure of the vertex operators is based on the hidden symmetry generators in RNS superstring theory, realizing the isometry group of the AdS space. The beta-function equations in the sigma-model lead to equations of motion in the MMSW gravity with negative cosmological constant with the AdS geometry being the vacuum solution. Generalizations for the higher spin fields are analyzed and equations of motion for spin 3 fields in $d=3$ in frame-like formalism are obtained in the low energy limit of string theory. These equations correspond to those of $sl(3,R)$ truncated Chern-Simons action based on higher spin algebra $hs(1,1)$.
description: 21 pages typos corrected, few clarifications and references added
Electrochemical CO2 Reduction: Tailoring Catalyst Layers in Gas Diffusion Electrodes
Creators: name: Junge Puring, Kai
name: Siegmund, Daniel
name: Timm, Jana
name: Möllenbruck, Florian
name: Schemme, Steffen
name: Marschall, Roland
name: Apfel, Ulf-Peter
Publisher: name: FID GEO
Year: 2020

description: Abstract The electrochemical conversion of CO2 into commodity chemicals or fuels is an attractive reaction for sustainable CO2 utilization. In this context, the application of gas diffusion electrodes is promising due to efficient CO2 mass transport. Herein, a scalable and reproducible method is presented for polytetrafluoroethylene (PTFE)-bound copper gas diffusion electrodes (GDEs) via the dry-pressing method and compositional parameters are emphasized to alter such electrodes. The assembly of the catalytic layer plays a critical role in the electrode performance, as elevated bulk hydrophobicity coupled with good surface wettability is observed to offer highest performance in 0.5 m KHCO3. With optimized electrodes, formate, CO, and H2 are obtained at a current density of 25 mA cm−2 as main products in 1 m KOH in faradaic efficiencies (FEs) of 27%, 30%, and 36%. At 200 mA cm−2, an altered product composition with ethylene (33% FE) and ethanol (9% FE) along with H2 (33% FE) is observed. In addition, n-propanol is observed with 7% faradaic efficiency. The results indicate that the composition of the GDE has a severe influence on the electrode performance and setting proper hydrophobicity gradients within the electrode is key toward developing a successful electrochemical CO2 reduction.
Helical states of nonlocally interacting molecules and their linear stability: geometric approach
Creators: name: Benoit, Steve
name: Holm, Darryl D.
name: Putkaradze, Vakhtang
Publisher: name: arXiv
Year: 2010
Subjects: subject: Mathematical Physics (math-ph)
subject: Chaotic Dynamics (nlin.CD)
subject: FOS: Physical sciences

description: The equations for strands of rigid charge configurations interacting nonlocally are formulated on the special Euclidean group, SE(3), which naturally generates helical conformations. Helical stationary shapes are found by minimizing the energy for rigid charge configurations positioned along an infinitely long molecule with charges that are off-axis. The classical energy landscape for such a molecule is complex with a large number of energy minima, even when limited to helical shapes. The question of linear stability and selection of stationary shapes is studied using an SE(3) method that naturally accounts for the helical geometry. We investigate the linear stability of a general helical polymer that possesses torque-inducing non-local self-interactions and find the exact dispersion relation for the stability of the helical shapes with an arbitrary interaction potential. We explicitly determine the linearization operators and compute the numerical stability for the particular example of a linear polymer comprising a flexible rod with a repeated configuration of two equal and opposite off-axis charges, thereby showing that even in this simple case the non-local terms can induce instability that leads to the rod assuming helical shapes.
description: 34 pages, 9 figures
Supernova tests of the timescape cosmology
Creators: name: Smale, Peter R.
name: Wiltshire, David L.
Publisher: name: arXiv
Year: 2010
Subjects: subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: General Relativity and Quantum Cosmology (gr-qc)
subject: FOS: Physical sciences

description: The timescape cosmology has been proposed as a viable alternative to homogeneous cosmologies with dark energy. It realises cosmic acceleration as an apparent effect that arises in calibrating average cosmological parameters in the presence of spatial curvature and gravitational energy gradients that grow large with the growth of inhomogeneities at late epochs. Recently Kwan, Francis and Lewis [arXiv:0902.4249] have claimed that the timescape model provides a relatively poor fit to the Union and Constitution supernovae compilations, as compared to the standard Lambda CDM model. We show this conclusion is a result of systematic issues in supernova light curve fitting, and of failing to exclude data below the scale of statistical homogeneity, z < 0.033. Using all currently available supernova datasets (Gold07, Union, Constitution, MLCS17, MLCS31, SDSS-II, CSP, Union2), and making cuts at the statistical homogeneity scale, we show that data reduced by the SALT/SALT-II fitters provides Bayesian evidence that favours the spatially flat Lambda CDM model over the timescape model, whereas data reduced with MLCS2k2 fitters gives Bayesian evidence which favours the timescape model over the Lambda CDM model. We discuss the questions of extinction and reddening by dust, and of intrinsic colour variations in supernovae which do not correlate with the decay time, and the likely impact these systematics would have in a scenario consistent with the timescape model.
description: 21 pages, 9 figures; v2 small clarifications, figures and references added; accepted by MNRAS
Representation of Model Error in Convective-Scale Data Assimilation: Additive Noise Based on Model Truncation Error
Creators: name: Zeng, Yuefei
name: Janjic, Tijana
name: Sommer, Matthias
name: De Lozar, Alberto
name: Blahak, Ulrich
name: Seifert, Axel
Publisher: name: FID GEO
Year: 2019

description: To account for model error on multiple scales in convective-scale data assimilation, we incorporate the small-scale additive noise based on random samples of model truncation error and combine it with the large-scale additive noise based on random samples from global climatological atmospheric background error covariance. A series of experiments have been executed in the framework of the operational Kilometre-scale ENsemble Data Assimilation system of the Deutscher Wetterdienst for a 2-week period with different types of synoptic forcing of convection (i.e., strong or weak forcing). It is shown that the combination of large- and small-scale additive noise is better than the application of large-scale noise only. The specific increase in the background ensemble spread during data assimilation enhances the quality of short-term 6-hr precipitation forecasts. The improvement is especially significant during the weak forcing period, since the small-scale additive noise increases the small-scale variability which may favor occurrence of convection. It is also shown that additional perturbation of vertical velocity can further advance the performance of combination.
Analyzing Internal Variability and Forced Response of Subdaily and Daily Extreme Precipitation Over Europe
Creators: name: Wood, R. R.
name: Ludwig, R.
Publisher: name: FID GEO
Year: 2020

description: At regional to local scales internal variability is expected to be a dominant source of uncertainty in analyzing precipitation extremes and mean precipitation even far into the 21st century. A debated topic is whether a faster increase in subdaily precipitation extremes can be expected. Here we analyzed seasonal maximum precipitation in various time steps (3 hr, days, and 5 days) from a high-resolution 50-member large-ensemble (CRCM5-LE) and compared them to changes in mean precipitation over Europe. Our results show that the magnitude of change in extreme precipitation varies for season and duration. Subdaily extremes increase at higher rates than daily extremes and show higher scaling with temperature. Northern Europe shows widespread scaling above Clausius-Clapeyron of subdaily extremes in all seasons and for daily extremes in winter/spring. Scaling above Clausius-Clapeyron is also visible over Eastern Europe in winter/spring. For most regions and seasons the forced response emerges from the internal variability by midcentury.
Phyllotactic description of hard sphere packing in cylindrical channels
Creators: name: Mughal, Adil
name: Chan, Ho Kei
name: Weaire, Denis
Publisher: name: arXiv
Year: 2010
Subjects: subject: Soft Condensed Matter (cond-mat.soft)
subject: FOS: Physical sciences

description: We develop a simple analytical theory that relates dense sphere packings in a cylinder to corresponding disk packings on its surface. It applies for ratios R=D/d (where d and D are the diameters of the hard spheres and the bounding cylinder, respectively) up to R=1+1/sin(pi/5). Within this range the densest packings are such that all spheres are in contact with the cylindrical boundary. The detailed results elucidate extensive numerical simulations by ourselves and others by identifying the nature of all competing phases.
Floodwater harvesting to manage irrigation water and mesquite encroachment in a data-sparse river basin: an eco-hydrological approach
Creators: name: Babker, Zryab
name: Elagib, Nadir Ahmed
name: Al Zayed, Islam Sabry
name: Sulieman, Rayyan
Publisher: name: FID GEO
Year: 2020

description: This investigation attempts to understand the eco-hydrology of, and accordingly suggest an option to manage floodwater for agriculture in, the understudied and data-sparse ephemeral Baraka River Basin within the hyper-arid region of Sudan. Reference is made to the major feature of the basin, that is, the Toker Delta spate irrigation scheme. A point-to-pixel comparison of gridded and ground-based data sets is performed to enhance the estimates of rainfall. Analysis of remotely sensed land use/cover data is performed. The results show a significant reduction of the grassland and barren areas explained by a significant expansion of the cropland and open shrubland (invasive mesquite trees) areas in the delta. The cotton sown area is highly dependent on the flooded area and the discharge volume in the delta. However, the area of this major crop has declined since the early 1990s in favour of cultivation of more profitable food crops. Expansion of mesquite in the delta is problematic, taking hold under increased floodwater, and can only be manged by clearance to provide crop cultivation area. There is a great potential for floodwater harvesting during the rainfall season (June to September). A total seasonal runoff volume of around 4.6 and 10.8 billion cubic metres is estimated at 90 and 50% probabilities of exceedance (reliabilities), respectively. Rather than leaving the runoff generated from rainfall events to pass to the Red Sea or be consumed by mesquite trees, a location for runoff harvesting structure in a highly suitable area is proposed. Such a structure will support any policy shifts towards planning and managing the basin water resources for use in irrigating the agricultural scheme.
Combined X-ray and neutron single-crystal diffraction in diamond anvil cells
Creators: name: Grzechnik, Andrzej
name: Meven, Martin
name: Paulmann, Carsten
name: Friese, Karen
Publisher: name: FID GEO
Year: 2019

description: It is shown that it is possible to perform combined X-ray and neutron single-crystal studies in the same diamond anvil cell (DAC). A modified Merrill–Bassett DAC equipped with an inflatable membrane filled with He gas has been developed. It can be used on laboratory X-ray and synchrotron diffractometers as well as on neutron instruments. The data processing procedures and a joint structural refinement of the high-pressure synchrotron and neutron single-crystal data are presented and discussed for the first time.
A chorographical map of the Province of New York in North America : divided into counties, manors, patents and townships ; exhibiting likewise all the private grants of land made and located in that Province ; compiled from actual surveys deposited in the Patent Office at New York, by order of His Excellency Major General William Tryon
Creators: name: (:Unav)
Publisher: name: Columbia University
Year: 2015
Subjects: Real property--New York (State)--Maps.

description: Relief shown by hachures. Depths shown by form lines
Observation of the superconducting proximity effect and possible evidence for Pearl vortices in a candidate topological insulator
Creators: name: Zhang, Duming
name: Wang, Jian
name: DaSilva, Ashley M.
name: Lee, Joon Sue
name: Gutierrez, Humberto R.
name: Chan, Moses H. W.
name: Jain, Jainendra
name: Samarth, Nitin
Publisher: name: arXiv
Year: 2011
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: FOS: Physical sciences

description: We report the observation of the superconducting proximity effect in nanoribbons of a candidate topological insulator (Bi2Se3) which is interfaced with superconducting (tungsten) contacts. We observe a supercurrent and multiple Andreev reflections for channel lengths that are much longer than the inelastic and diffusive thermal lengths deduced from normal state transport. This suggests that the proximity effect couples preferentially to a ballistic surface transport channel, even in the presence of a coexisting diffusive bulk channel. When a magnetic field is applied perpendicular to the plane of the nanoribbon, we observe magnetoresistance oscillations that are periodic in magnetic field. Quantitative comparison with a model of vortex blockade relates the occurrence of these oscillations to the formation of Pearl vortices in the region of proximity induced superconductivity.
description: Submitted to Physical Review B (regular article)
Two-Dimensional Arrays of RF Ion Traps with Addressable Interactions
Creators: name: Kumph, Muir
name: Brownnutt, Michael
name: Blatt, Rainer
Publisher: name: arXiv
Year: 2011
Subjects: subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: We describe the advantages of 2-dimensional, addressable arrays of spherical Paul traps. They would provide for the ability to address and tailor the interaction strengths of trapped objects in 2D and could establish a valuable new tool for quantum information processing. Simulations of trapping ions are compared to first tests using printed circuit board trap arrays loaded with dust particles. Pair-wise interactions in the array are addressed by means of an adjustable radio-frequency (RF) electrode shared between trapping sites. By attenuating this RF electrode potential, neighboring pairs of trapped objects have their interaction strength increase and are moved closer to one another. In the limit of the adjustable electrode being held at RF ground, the two formerly spherical traps are merged into one linear Paul trap.
description: 23 pages, 13 figures
Expression, purification and crystal structure determination of a ferredoxin reductase from the actinobacterium Thermobifida fusca
Creators: name: Rodriguez Buitrago, Jhon Alexander
name: Klünemann, Thomas
name: Blankenfeldt, Wulf
name: Schallmey, Anett
Publisher: name: FID GEO
Year: 2020

description: The ferredoxin reductase FdR9 from Thermobifida fusca, a member of the oxygenase-coupled NADH-dependent ferredoxin reductase (FNR) family, catalyses electron transfer from NADH to its physiological electron acceptor ferredoxin. It forms part of a putative three-component cytochrome P450 monooxygenase system in T. fusca comprising CYP222A1 and the [3Fe–4S]-cluster ferredoxin Fdx8 as well as FdR9. Here, FdR9 was overexpressed and purified and its crystal structure was determined at 1.9 Å resolution. The overall structure of FdR9 is similar to those of other members of the FNR family and is composed of an FAD-binding domain, an NAD-binding domain and a C-terminal domain. Activity measurements with FdR9 confirmed a strong preference for NADH as the cofactor. Comparison of the FAD- and NAD-binding domains of FdR9 with those of other ferredoxin reductases revealed the presence of conserved sequence motifs in the FAD-binding domain as well as several highly conserved residues involved in FAD and NAD cofactor binding. Moreover, the NAD-binding site of FdR9 contains a modified Rossmann-fold motif, GxSxxS, instead of the classical GxGxxG motif.
Radiative decay of the X(3872) as a mixed molecule-charmonium state in QCD Sum Rules
Creators: name: Nielsen, M.
name: Zanetti, C. M.
Publisher: name: arXiv
Year: 2010
Subjects: subject: High Energy Physics - Phenomenology (hep-ph)
subject: FOS: Physical sciences

description: We use QCD sum rules to calculate the width of the radiative decay of the meson X(3872), assumed to be a mixture between charmonium and exotic molecular $[c\bar{q}][q\bar{c}]$ states with $J^{PC}=1^{++}$. We find that in a small range for the values of the mixing angle, $5^0\leqθ\leq13^0$, we get the branching ratio $Γ(X\to J/ψγ)/Γ(X\to J/ψπ^+π^-)=0.19\pm0.13$, which is in agreement, with the experimental value. This result is compatible with the analysis of the mass and decay width of the mode $J/ψ(nπ)$ performed in the same approach.
description: 7 pages, 9 figures; revised version accepted for publication in Phys. Rev. D
Simulation of small-angle X-ray scattering data of biological macromolecules in solution
Creators: name: Franke, Daniel
name: Hajizadeh, Nelly R.
name: Svergun, Dmitri I.
Publisher: name: FID GEO
Year: 2020

description: This article presents IMSIM, an application to simulate two-dimensional small-angle X-ray scattering patterns and, further, one-dimensional profiles from biological macromolecules in solution. IMSIM implements a statistical approach yielding two-dimensional images in TIFF, CBF or EDF format, which may be readily processed by existing data-analysis pipelines. Intensities and error estimates of one-dimensional patterns obtained from the radial average of the two-dimensional images exhibit the same statistical properties as observed with actual experimental data. With initial input on an absolute scale, [cm−1]/c[mg ml−1], the simulated data frames may also be scaled to absolute scale such that the forward scattering after subtraction of the background is proportional to the molecular weight of the solute. The effects of changes of concentration, exposure time, flux, wavelength, sample–detector distance, detector dimensions, pixel size, and the mask as well as incident beam position can be considered for the simulation. The simulated data may be used in method development, for educational purposes, and also to determine the most suitable beamline setup for a project prior to the application and use of the actual beamtime. IMSIM is available as part of the ATSAS software package (3.0.0) and is freely available for academic use (http://www.embl-hamburg.de/biosaxs/download.html).
Optimization of the Neutrino Factory, revisited
Creators: name: Agarwalla, Sanjib Kumar
name: Huber, Patrick
name: Tang, Jian
name: Winter, Walter
Publisher: name: arXiv
Year: 2010
Subjects: subject: High Energy Physics - Phenomenology (hep-ph)
subject: High Energy Physics - Experiment (hep-ex)
subject: Instrumentation and Detectors (physics.ins-det)
subject: FOS: Physical sciences

description: We perform the baseline and energy optimization of the Neutrino Factory including the latest simulation results on the magnetized iron detector (MIND). We also consider the impact of tau decays, generated by nu_mu to nu_tau or nu_e to nu_tau appearance, on the mass hierarchy, CP violation, and theta_{13} discovery reaches, which we find to be negligible for the considered detector. For the baseline-energy optimization for small theta_{13}, we qualitatively recover the results with earlier simulations of the MIND detector. We find optimal baselines of about 2500 km to 5000 km for the CP violation measurement, where now values of E_mu as low as about 12 GeV may be possible. However, for large theta_{13}, we demonstrate that the lower threshold and the backgrounds reconstructed at lower energies allow in fact for muon energies as low as 5 GeV at considerably shorter baselines, such as FNAL-Homestake. This implies that with the latest MIND analysis, low- and high-energy versions of the Neutrino Factory are just two different versions of the same experiment optimized for different parts of the parameter space. Apart from a green-field study of the updated detector performance, we discuss specific implementations for the two-baseline Neutrino Factory, where the considered detector sites are taken to be currently discussed underground laboratories. We find that reasonable setups can be found for the Neutrino Factory source in Asia, Europe, and North America, and that a triangular-shaped storage ring is possible in all cases based on geometrical arguments only.
description: 45 pages, 16 figures, 3 tables. V3: Comment on "bi-magic" baseline added in new App. C (not included in published version). Data files for the individual sites can be downloaded at http://www.phys.vt.edu/~pahuber/neutrino-factory-sites.html
Application of the differential maximum entropy method (DMaxEnt) for the solution of population balance equations.
Creators: name: Zacharioudakis, Emmanouil
Publisher: name: National Technological University of Athens
Year: 2025
Subjects: Crystallization
Maximum entropy
Population balance

description: Εθνικό Μετσόβιο Πολυτεχνείο--Μεταπτυχιακή Εργασία. Διεπιστημονικό-Διατμηματικό Πρόγραμμα Μεταπτυχιακών Σπουδών (Δ.Π.Μ.Σ.) “Υπολογιστική Μηχανική”