cometadata/datacite-rtg-text-other-reclassification-records huggingface dataset:
The Properties of Short gamma-ray burst Jets Triggered by neutron star mergers
Creators: name: Murguia-Berthier, Ariadna
name: Ramirez-Ruiz, Enrico
name: Montes, Gabriela
name: De Colle, Fabio
name: Rezzolla, Luciano
name: Rosswog, Stephan
name: Takami, Kentaro
name: Perego, Albino
name: Lee, William H.
Publisher: name: arXiv
Year: 2016
Subjects: subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: General Relativity and Quantum Cosmology (gr-qc)
subject: FOS: Physical sciences

description: The most popular model for short gamma-ray bursts (sGRBs) involves the coalescence of binary neutron stars. Because the progenitor is actually hidden from view, we must consider under which circumstances such merging systems are capable of producing a successful sGRB. Soon after coalescence, winds are launched from the merger remnant. In this paper, we use realistic wind profiles derived from global merger simulations in order to investigate the interaction of sGRB jets with these winds using numerical simulations. We analyze the conditions for which these axisymmetric winds permit relativistic jets to breakout and produce a sGRB. We find that jets with luminosities comparable to those observed in sGRBs are only successful when their half-opening angles are below ~20°. This jet collimation mechanism leads to a simple physical interpretation of the luminosities and opening angles inferred for sGRBs. If wide, low luminosity jets are observed, they might be indicative of a different progenitor avenue such as the merger of a neutron star with a black hole. We also use the observed durations of sGRB to place constraints on the lifetime of the wind phase, which is determined by the time it takes the jet to breakout. In all cases we find that the derived limits argue against completely stable remnants for binary neutron star mergers that produce sGRBs.
description: 6 pages, 5 figures, Submitted to ApJL
On the theory of solitons of fluid pressure and solute density in geologic porous media, with applications to shale, clay and sandstone
Creators: name: Caserta, A.
name: Kanivetsky, R.
name: Salusti, E.
Publisher: name: arXiv
Year: 2016
Subjects: subject: Geophysics (physics.geo-ph)
subject: Pattern Formation and Solitons (nlin.PS)
subject: FOS: Physical sciences

description: In this paper we propose the application of a new model of transients of pore pressure p and solute density \r{ho} in geologic porous media. This model is rooted in the non-linear waves theory, the focus of which is advection and effect of large pressure jumps on strain (due to large p in a non-linear version of the Hooke law). It strictly relates p and \r{ho} evolving under the effect of a strong external stress. As a result, the presence of quick and sharp transients in low permeability rocks is unveiled, i.e. the non-linear Burgers solitons. We therefore propose that the actual transport process in porous rocks for large signals is not the linear diffusion, but could be governed by solitons. A test of an eventual presence of solitons in a rock is here proposed, and then applied to Pierre Shale, Bearpaw Shale, Boom Clay and Oznam-Mugu silt and clay. A quick analysis showing the presence of solitons for nuclear waste disposal and salty water intrusions is also analyzed. Finally, in a kind of "theoretical experiment" we show that solitons could also be present in Jordan and St. Peter sandstones, thus suggesting the occurrence of osmosis in these rocks.
Enhancing entanglement, local and non-local information of accelerated two-qubit and two- qutrit systems via weak-reverse measurements
Creators: name: Metwally, Nasser
Publisher: name: arXiv
Year: 2016
Subjects: subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: The possibility of recovering and protecting the entanglement of accelerated 2-qubit and 2-qutrit systems is discussed using weak-reverse measurements. The accelerated partial entangled states are more responsive to be protected than the accelerated maximum entangled states. The accelerated coded local information in qutrit system is more robust than that encoded in a 2-qubit system, and it can be conserved even for larger values of accelerations. Meanwhile, the non-accelerated information in qubit system is not affected by the local operation compared with that depicted on qutrit system. For larger values of accelerations, the weak-reverse measurements can improve the coherent information at the expanse of the accelerated information.
title: Fachbewusst im Sprachunterricht: Deutsch-Förderung an Themen des UF GW unter Berücksichtigung unterschiedlicher Sprachniveaus
Creators: name: Stritzl, Michael
Year: 2023

description: Migration ist eines der bedeutendsten Themen des 21. Jahrhunderts. Bildungseinrichtungen in Österreich sind nicht nur für die Ausbildung von Kindern und Jugendlichen mit Deutsch als Erstsprache verantwortlich, sondern haben auch die Aufgabe, Lernende mit Deutsch als Zweitsprache bestmöglich zu unterstützen. In den letzten Jahrzehnten haben sich im deutschsprachigen Raum zahlreiche Forschungsbemühungen der sprachlichen Förderung von Schüler*innen mit einer anderen Erstsprache als Deutsch gewidmet. Unter dem Stichwort „Sprachsensibler Fachunterricht“ wurden zahlreiche Unterrichtsvorschläge unterbreitet. Weniger stark thematisiert wurde hingegen der „Fachsensible Sprachunterricht“, der sich mit der Frage nach der Beschäftigung mit fachlichen Inhalten im Rahmen des Sprachförderunterrichts auseinandersetzt. An dieser Stelle möchte die vorliegende Arbeit ansetzen. Sie beschäftigt sich damit, wie Deutsch-Förderung an Themen von GW unter Berücksichtigung unterschiedlicher Sprachniveaus gelingen kann. Dazu wird eine vierstündige Unterrichtsreihe für drei DaZ-Lernende zum Thema „Bildungswege und Arbeitswelten“ entworfen, die sowohl sprachliche als auch fachliche Lernziele berücksichtigt. Zudem sollen vier Qualitätskriterien der Durchgängigen Sprachbildung miteinbezogen werden. Anhand von Gedächtnisprotokollen wird überprüft, ob die vorab festgelegten Ziele erreicht werden konnten. Die Ergebnisse zeigen, dass die Berücksichtigung fachlicher Inhalte im Sprachförderunterricht nicht nur möglich, sondern auch sinnvoll ist.
Engaging Participants in Online Interviews: Lessons Learned from Implementing a Participatory Visual Approach in Two Explorative Health Information Behavior Studies
Creators: name: Dewitz, Leyla
Publisher: name: Zenodo
Year: 2023
Subjects: Health Information Behavior
Information Behavior
Participatory research
Qualitative methods

description: Supplementary material for the following article: Dewitz, L. (accepted for publication). Engaging Participants in Online Interviews: Lessons Learned from Implementing a Participatory Visual Approach in Two Explorative Health Information Behavior Studies. In Proceedings of the 86th Annual Meeting of the Association for Information Science & Technology, Okt 27-31, 2023, London, United Kingdom.

 The appendices I – III include the following supplementary materials:

 Appendix I
 Table 1. Study design, methodological needs, and implementation of visual participatory elements within the presented studies. Appendix II
 Figure 1. Miro board 1 with (from left to right) blank post-its, app collection, smartphone/tablet for gathering the apps used, trash can for the apps implemented but not used. Figure 2. In Miro board 2 participants were encouraged to specify or classify feelings associated with the specific apps used by having them allocate those apps into categories (from left to right: "makes me feel good", "makes me feel partly good/not good", "makes me feel bad").

 Figure 3. In Miro board 3 participants were encouraged to share information needs (questions) and information sources / channels that they have used in the past or use in present. Figure 4. Miro board 4 aimed to map participants’ personal health information infrastructures with potential sources to choose from (in gray) and blank cards (post-its) to add sources used (left). The red rings (left) helped to mark the main sources and arrows (not shown here) to visualize relationships between sources/actors. Figure 5. Miro board 5 was used for assessing the scientificity of different health information sources by assigning colored buttons (“scientific”, “not scientific,” or “partly scientific”) to stimulate discussion about scientificity of health information resources and criteria for the subjective assessment of scientificity. APPENDIX III
 Figure 6. Example of the personal health information infrastructure of participant P05 (study I). Figure 7. Example of the personal health information infrastructure of participant P17 (study II).
Core motifs predict dynamic attractors in combinatorial threshold-linear networks
Creators: name: Parmelee, Caitlyn
name: Moore, Samantha
name: Morrison, Katherine
name: Curto, Carina
Publisher: name: arXiv
Year: 2021
Subjects: subject: Neurons and Cognition (q-bio.NC)
subject: FOS: Biological sciences

description: Combinatorial threshold-linear networks (CTLNs) are a special class of inhibition-dominated TLNs defined from directed graphs. Like more general TLNs, they display a wide variety of nonlinear dynamics including multistability, limit cycles, quasiperiodic attractors, and chaos. In prior work, we have developed a detailed mathematical theory relating stable and unstable fixed points of CTLNs to graph-theoretic properties of the underlying network. Here we find that a special type of fixed points, corresponding to core motifs, are predictive of both static and dynamic attractors. Moreover, the attractors can be found by choosing initial conditions that are small perturbations of these fixed points. This motivates us to hypothesize that dynamic attractors of a network correspond to unstable fixed points supported on core motifs. We tested this hypothesis on a large family of directed graphs of size $n=5$, and found remarkable agreement. Furthermore, we discovered that core motifs with similar embeddings give rise to nearly identical attractors. This allowed us to classify attractors based on structurally-defined graph families. Our results suggest that graphical properties of the connectivity can be used to predict a network's complex repertoire of nonlinear dynamics.
description: 39 pages (18 pages main text, 21 pages supplementary information), 25 figures, and 6 tables
Quantification of Probe-Sample Electrostatic Forces with Dynamic Atomic Force Microscopy
Creators: name: Balke, Nina
name: Jesse, Stephen
name: Carmichael, Ben
name: Okatan, M. Baris
name: Kravchenko, Ivan I.
name: Kalinin, Sergei V.
name: Tselev, Alexander
Publisher: name: arXiv
Year: 2016
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: FOS: Physical sciences

description: Atomic Force Microscopy (AFM) methods utilizing resonant mechanical vibrations of cantilevers in contact with a sample surface have shown sensitivities as high as few picometers for detecting surface displacements. Such a high sensitivity is harnessed in several AFM imaging modes. Here, we demonstrate a cantilever-resonance-based method to quantify electrostatic forces on a probe arising in the presence of a surface potential or when a bias voltage is applied to the AFM probe. We find that the electrostatic forces acting on the probe tip apex can strongly dominate cantilever response in electromechanical measurements and produce signals equivalent to few pm of surface displacement. In combination with modeling, the measurements of the force were used to determine the strength of the electrical field at the probe tip apex in contact with a sample. We find an evidence that the electric field strength in the junctions is limited by about 0.5 V/nm. This field can be sufficiently strong to significantly influence material states and kinetic processes through charge injection, Maxwell stress, shifts of phase equilibria, and reduction of energy barriers for activated processes. Besides, the results provide a baseline for accounting for the effects of local electrostatic forces in electromechanical AFM measurements as well as offer additional means to probe ionic mobility and field-induced phenomena in solids.
description: Corrected misprints in units of Table 1
Design and Model Predictive Control of Mars Coaxial Quadrotor
Creators: name: Patel, Akash
name: Banerjee, Avijit
name: Lindqvist, Bjorn
name: Kanellakis, Christoforos
name: Nikolakopoulos, George
Publisher: name: arXiv
Year: 2021
Subjects: subject: Robotics (cs.RO)
subject: FOS: Computer and information sciences
subject: I.2.9

description: Mars has been a prime candidate for planetary exploration of the solar system because of the science discoveries that support chances of future habitation on this planet. Martian caves and lava tubes like terrains, which consists of uneven ground, poor visibility and confined space, makes it impossible for wheel based rovers to navigate through these areas. In order to address these limitations and advance the exploration capability in a Martian terrain, this article presents the design and control of a novel coaxial quadrotor Micro Aerial Vehicle (MAV). As it will be presented, the key contributions on the design and control architecture of the proposed Mars coaxial quadrotor, are introducing an alternative and more enhanced, from a control point of view concept, when compared in terms of autonomy to Ingenuity. Based on the presented design, the article will introduce the mathematical modelling and automatic control framework of the vehicle that will consist of a linearised model of a co-axial quadrotor and a corresponding Model Predictive Controller (MPC) for the trajectory tracking. Among the many models, proposed for the aerial flight on Mars, a reliable control architecture lacks in the related state of the art. The MPC based closed loop responses of the proposed MAV will be verified in different conditions during the flight with additional disturbances, induced to replicate a real flight scenario. In order to further validate the proposed control architecture and prove the efficacy of the suggested design, the introduced Mars coaxial quadrotor and the MPC scheme will be compared to a PID-type controller, similar to the Ingenuity helicopter's control architecture for the position and the heading.
Next generation 3D pharmacophore modeling
Creators: name: Šribar, Dora
name: Noonan, Theresa
name: Deng, Lihua
name: Nguyen, Trung Ngoc
name: Pach, Szymon
name: Machalz, David
name: Bermudez, Marcel
name: Wolber, Gerhard
name: Schaller, David
Publisher: name: Freie Universität Berlin
Year: 2020
Subjects: subject: 3D pharmacophores
subject: artifical intelligence
subject: machine learning
subject: virtual screening
subject: web services
subject: 600 Technik, Medizin, angewandte Wissenschaften::610 Medizin und Gesundheit::615 Pharmakologie, Therapeutik

description: 3D pharmacophore models are three‐dimensional ensembles of chemically defined interactions of a ligand in its bioactive conformation. They represent an elegant way to decipher chemically encoded ligand information and have therefore become a valuable tool in drug design. In this review, we provide an overview on the basic concept of this method and summarize key studies for applying 3D pharmacophore models in virtual screening and mechanistic studies for protein functionality. Moreover, we discuss recent developments in the field. The combination of 3D pharmacophore models with molecular dynamics simulations could be a quantum leap forward since these approaches consider macromolecule–ligand interactions as dynamic and therefore show a physiologically relevant interaction pattern. Other trends include the efficient usage of 3D pharmacophore information in machine learning and artificial intelligence applications or freely accessible web servers for 3D pharmacophore modeling. The recent developments show that 3D pharmacophore modeling is a vibrant field with various applications in drug discovery and beyond.
The detection and X-ray view of the changing look AGN HE 1136-2304
Creators: name: Parker, M. L.
name: Komossa, S.
name: Kollatschny, W.
name: Walton, D. J.
name: Schartel, N.
name: Santos-Lleo, M.
name: Harrison, F. A.
name: Fabian, A. C.
name: Zetzl, M.
name: Grupe, D.
name: Rodriguez-Pascual, P. M.
name: Vasudevan, R. V.
Publisher: name: arXiv
Year: 2016
Subjects: subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: FOS: Physical sciences

description: We report the detection of high-amplitude X-ray flaring of the AGN HE 1136-2304, which is accompanied by a strong increase in the flux of the broad Balmer lines, changing its Seyfert type from almost type 2 in 1993 down to 1.5 in 2014. HE 1136-2304 was detected by the XMM-Newton slew survey at >10 times the flux it had in the ROSAT all-sky survey, and confirmed with Swift follow-up after increasing in X-ray flux by a factor of 30. Optical spectroscopy with SALT shows that the AGN has changed from a Seyfert 1.95 to a Seyfert 1.5 galaxy, with greatly increased broad line emission and an increase in blue continuum AGN flux by a factor of > 4. The X-ray spectra from XMM-Newton and NuSTAR reveal moderate intrinsic absorption and a high energy cutoff at 100 keV. We consider several different physical scenarios for a flare, such as changes in obscuring material, tidal disruption events, and an increase in the accretion rate. We find that the most likely cause of the increased flux is an increase in the accretion rate, although it could also be due to a change in obscuration.
description: 10 pages, 10 figures. Accepted for publication in MNRAS
Regulating Ruminative Web-browsing Based on the Counterbalance Modeling Approach
Creators: name: Morita, Junya
name: Pitakchokchai, Thanakit
name: Raj, Giri Basanta
name: Yamamoto, Yusuke
name: Yuhashi, Hiroyasu
name: Koguchi, Teppei
Publisher: name: arXiv
Year: 2021
Subjects: subject: Human-Computer Interaction (cs.HC)
subject: Artificial Intelligence (cs.AI)
subject: FOS: Computer and information sciences

description: Even though the web environment facilitates daily life, emotional problems caused by its incompatibility with human cognition are becoming increasingly serious. To alleviate negative emotions during web use, we developed a browser extension that presents memorized product images to users, in the form of web advertisements. This system utilizes the cognitive architecture Adaptive Control of Thought-Rational (ACT-R) as a model of memory and emotion. A heart rate sensor modulates the ACT-R model parameters: The emotional states of the model are synchronized or counterbalanced with the physiological state of the user. An experiment demonstrates that the counterbalance model suppresses negative ruminative web browsing. The authors claim that this approach is advantageous in terms of explainability.
Optical Spectroscopic Observations of Gamma-ray Blazar Candidates. V. TNG, KPNO, and OAN Observations of Blazar Candidates of Uncertain Type in the Northern Hemisphere
Creators: name: Crespo, N. Álvarez
name: Masetti, N.
name: Ricci, F.
name: Landoni, M.
name: Patiño-Álvarez, V.
name: Massaro, F.
name: D'Abrusco, R.
name: Paggi, A.
name: Chavushyan, V.
name: Jiménez-Bailón, E.
name: Torrealba, J.
name: Latronico, L.
name: La Franca, F.
name: Smith, Howard A.
name: Tosti, G.
Publisher: name: arXiv
Year: 2016
Subjects: subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: FOS: Physical sciences

description: The extragalactic $γ$-ray sky is dominated by emission from blazars, a peculiar class of active galactic nuclei (AGNs). Many of the $γ$-ray sources included in Fermi -Large Area Telescope Third Source catalog (3FGL) are classified as a blazar candidate of uncertain type (BCU) because there is no optical spectra available in the literature to confirm their nature. In 2013 we started a spectroscopic campaign to look for the optical counterparts of the BCUs and of the Unidentified $γ$-ray Sources. The main goal of our investigation is to confirm the blazar nature of these sources having peculiar properties as compact radio emission and/or selected on the basis of their infrared (IR) colors. Whenever possible we also determine their redshifts. Here we present the results of the observations carried out in the Northern hemisphere in 2013 and 2014 at Telescopio Nazionale Galilleo (TNG), Kitt Peak National Observatory (KPNO) and Observatorio Astronómico Nacional (OAN) in San Pedro Mártir. In this paper we describe the optical spectra of 25 sources. We confirmed that all the 15 BCUs observed in our campaign and included in our sample are blazars and we estimated the redshift for 3 of them. In addition, we present the spectra for 3 sources classified as BL Lacs in the literature but with no optical spectra available to date. We found that one of them is a quasar (QSO) at a redshift $z$ = 0.208 and the other 2 are BL Lacs. Moreover, we also present 7 new spectra for known blazars listed in the Roma-BZCAT having an uncertain redshift or being classified as BL Lac candidates. We found that one of them, 5BZB J0724+2621 is a `changing look' blazar. According to the spectrum available in the literature it was classified as a BL Lac but in our observation we clearly detected a broad emission line that lead to classify this source as a QSO at $z$=1.17.
description: 21 pages, 26 figures, 3 tables, pre-proof version, published on the Astronomical Journal. arXiv admin note: text overlap with arXiv:1503.04202
Cable-driven parallel mechanisms for minimally invasive robotic surgery
Creators: name: Oude Vrielink, Timo Joric Corman
Publisher: name: Imperial College London
Year: 2019

description: Minimally invasive surgery (MIS) has revolutionised surgery by providing faster recovery times, less post-operative complications, improved cosmesis and reduced pain for the patient. Surgical robotics are used to further decrease the invasiveness of procedures, by using yet smaller and fewer incisions or using natural orifices as entry point. However, many robotic systems still suffer from technical challenges such as sufficient instrument dexterity and payloads, leading to limited adoption in clinical practice. Cable-driven parallel mechanisms (CDPMs) have unique properties, which can be used to overcome existing challenges in surgical robotics. These beneficial properties include high end-effector payloads, efficient force transmission and a large configurable instrument workspace. However, the use of CDPMs in MIS is largely unexplored. This research presents the first structured exploration of CDPMs for MIS and demonstrates the potential of this type of mechanism through the development of multiple prototypes: the ESD CYCLOPS, CDAQS, SIMPLE, neuroCYCLOPS and microCYCLOPS. One key challenge for MIS is the access method used to introduce CDPMs into the body. Three different access methods are presented by the prototypes. By focusing on the minimally invasive access method in which CDPMs are introduced into the body, the thesis provides a framework, which can be used by researchers, engineers and clinicians to identify future opportunities of CDPMs in MIS. Additionally, through user studies and pre-clinical studies, these prototypes demonstrate that this type of mechanism has several key advantages for surgical applications in which haptic feedback, safe automation or a high payload are required. These advantages, combined with the different access methods, demonstrate that CDPMs can have a key role in the advancement of MIS technology.
Sub-wavelength photonics from solution-processing
Creators: name: Yuan, Hua-Kang
Publisher: name: Imperial College London
Year: 2019

description: Light is pervasive: it transmits information at celeritas lucis, interfaces with everyday electronics and offers a source of renewable energy. The optics and photonics which manage light should satisfy its growing prevalence. One organic polymer and Titanium hybrid is synthesised simply in two steps and is processable as a liquid at room temperature at low capital intensity. It exhibits a tunable refractive index with a large range of 1.5 to 2.0. Light management applications are explored, focusing on two forms of light propagation: free radiation and guided waves. All devices are fabricated from solution-processable materials. The behaviour of light is manipulated by periodic modulations of refractive index. Two directions of periodicity are investigated: parallel and perpendicular to light propagation. Thin-film multilayers form dielectric mirrors with parallel periodicity. The radiation of selected wavelengths are suppressed whilst others are enhanced. These are used to modify emission properties of a photoluminescent dye; a method towards improving efficiencies in optoelectronic devices without chemical alterations. Perpendicular periodicity is provided by thin-film diffraction gratings, enabling coupling between guided and freely radiating light; a key function of solar concentrators and wearable augmented-reality displays. An experimental system is developed to measure coupled light transmissions. To facilitate the design and assessment of these devices, Transfer Matrix Method (TMM) and Finite-Element Method (FEM) models are used. Refractive indices of thin-films are extracted by fitting transmittance and reflectance spectra to TMM. For dielectric mirrors, a phase reconstruction algorithm is extended to account for incoherent substrates. In doing so, information on band-gap positioning is extracted. Meanwhile, diffraction spectra are modelled using the Fraunhofer expression and modified by TMM to include thin-film interferences. This is utilised to fit grating dimensions, which support FEM calculations to identify guided transmissions. A variety of devices are fabricated from solution and characterised using the models developed.
Mechanical characterisation of biological materials using Brillouin microscopy
Creators: name: Wu, Pei-Jung
Publisher: name: Imperial College London
Year: 2019

description: Biomechanics studies how biomaterials deform subjected to external loads. Most techniques used in biomechanics require direct contact or lack of subcellular resolution. By contrast, Brillouin microscopy is a contactless and label-free technique used to characterise mechanical properties of cells and tissues. Despite Brillouin microscopy measuring longitudinal modulus M , an empirical power law has been widely used to interpret Brillouin measurements as stiffness. In this thesis, we focused on the interpretation and relevance between the Brillouin microscopy measurements and quasi-static mechanical properties using hydrogels and cells. To investigate how Brillouin measurements relate to the mechanical properties of biological materials, we use hydrogels that approximate the mechanics of biphasic hydrated materials. By varying water content ε and Young’s modulus E in hydrogels, we found Brillouin measurements reflect changes in ε and the relationship between M and E arises due to their mutual dependence on ε. We further used binary mixture theory and polymer theory to explain the underlying physics. However, cells are neither passive nor homogeneous, we discussed the assumptions required to relate M and E to contextualise measurements made. We varied the osmotically active water content ε^* of cells by controlling the external osmotic stress whilst measuring M and E. We found both M and E depends on ε^* in a manner that can be explained by binary mixture theory and the ideal gas law. However, the correlation between M and E does not always exist when comparing different cellular components. Furthermore, we also assessed the potential of using Brillouin microscopy as an early diagnostic tool to detect the structural changes of ECM degradation in osteoarthritis (OA). To mimic OA, porcine cartilage was digested by enzyme and our results show that Brillouin microscopy can detect the structure change in OA and hence Brillouin microscopy could develop to a minimally-invasive arthroscope.
CC-Cert: A Probabilistic Approach to Certify General Robustness of Neural Networks
Creators: name: Pautov, Mikhail
name: Tursynbek, Nurislam
name: Munkhoeva, Marina
name: Muravev, Nikita
name: Petiushko, Aleksandr
name: Oseledets, Ivan
Publisher: name: arXiv
Year: 2021
Subjects: subject: Machine Learning (cs.LG)
subject: Artificial Intelligence (cs.AI)
subject: FOS: Computer and information sciences

description: In safety-critical machine learning applications, it is crucial to defend models against adversarial attacks -- small modifications of the input that change the predictions. Besides rigorously studied $\ell_p$-bounded additive perturbations, recently proposed semantic perturbations (e.g. rotation, translation) raise a serious concern on deploying ML systems in real-world. Therefore, it is important to provide provable guarantees for deep learning models against semantically meaningful input transformations. In this paper, we propose a new universal probabilistic certification approach based on Chernoff-Cramer bounds that can be used in general attack settings. We estimate the probability of a model to fail if the attack is sampled from a certain distribution. Our theoretical findings are supported by experimental results on different datasets.
description: In Proceedings of AAAI-22, the Thirty-Sixth AAAI Conference on Artificial Intelligence
Resurgence of the dressing phase for ${\rm AdS}_5\times {\rm S}^5$
Creators: name: Arutyunov, Gleb
name: Dorigoni, Daniele
name: Savin, Sergei
Publisher: name: arXiv
Year: 2016
Subjects: subject: High Energy Physics - Theory (hep-th)
subject: Mathematical Physics (math-ph)
subject: FOS: Physical sciences

description: We discuss the resummation of the strong coupling asymptotic expansion of the dressing phase of the ${\rm AdS}_5\times {\rm S}^5$ superstring. The dressing phase proposed by Beisert, Eden and Staudacher can be recovered from a modified Borel-Ecalle resummation of this asymptotic expansion only by completing it with new, non-perturbative and exponentially suppressed terms that can be organized into different sectors labelled by an instanton-like number. We compute the contribution to the dressing phase coming from the sum over all the instanton sectors and show that it satisfies the homogeneous crossing symmetry equation. We comment on the semiclassical origin of the non-perturbative terms from the world-sheet theory point of view even though their precise explanation remains still quite mysterious.
description: 53 pages, 5 figures
Testing of Plant Fiber Composites: The Potential of Acoustic Emission Methods
Creators: name: Liew, Chin Kian
Publisher: name: Singapore Institute of Technology
Year: 2023
Subjects: Composite and hybrid materials
Mechanical engineering not elsewhere classified

description: This paper presents a series of acoustic emission (AE) tests and preliminary mechanical analysis of plant fiber composites (PFCs) tensile loaded to failure. The aim of these tests was to identify the potential of AE in evaluating the mechanical properties of the PFCs from the detection of different damage modes. Unidirectional long fibers and randomly oriented fiber mats embedded in thermoplastic polyamide or thermoset epoxy resin were considered. It was found that the onset of damage can be clearly detected in the AE response for the PFC specimens, which would otherwise be missed in the mechanical test data. This provides some form of early indication regarding the interfacial properties of the composite system as the acoustic events were the result of several damage modes originating from the fiber-matrix interface.
Metabolic phenotyping of acute and chronic liver disease characterised by 1H NMR spectroscopy and UPLC-MS analysis
Creators: name: Zia, Rabiya
Publisher: name: Imperial College London
Year: 2018

description: Liver disease is a major cause of premature mortality, the incidence of which continues to rise steadily in the UK. Cirrhosis is the most common form, with a significant risk to patients who can deteriorate from acute decompensation (AD) to acute-on-chronic liver failure (ACLF). Mechanisms of cell death and immune dysfunction drive disease pathogenesis and have been linked to metabolic perturbations associated with the progression of cirrhosis to ACLF and short-term mortality. In this thesis, metabolic phenotypes of plasma and serum from patients with AD, ACLF and acute liver failure (ALF) were characterised using both 1H NMR spectroscopy and ultra-performance liquid chromatography – mass spectrometry (UPLC-MS). Untargeted 1H NMR spectroscopy and targeted UPLC-MS analysis of amino compounds, confirmed perturbations of metabolic pathways related to energy metabolism and the urea cycle, which were common to ALF, AD and ACLF. In addition, targeted UPLC-MS analysis of amino compounds identified unique metabolic perturbations for ACLF and ALF, which included increased concentrations of alanine, asparagine, glutamine, glycine, histidine, lysine, proline, threonine and tyrosine in ALF together with a reduced concentration of serine in ACLF. Furthermore, the quantitative amino compound data also indicated a greater metabolic perturbation in ALF compared to ACLF. Untargeted UPLC-MS lipid profiling also identified metabolic perturbations that were both common and discriminant for ACLF, AD and ALF. Lipids including lysophosphatidylcholines (LysoPCs), sphingomyelins (SMs) and triglycerides (TGs) were depleted in these groups relative to healthy controls (HCs), whilst lysophosphatidic acids (LPA) were elevated and phosphatidylcholines (PC) were both elevated and depleted. Furthermore, lipid profiles generated from AD and ACLF patients were superior to standard clinical scores including CLIF- SOFA and MELD for predicting 30-day mortality based on AUROC analysis, with SM and LysoPC depletion associated with 30-day mortality in AD and ACLF patients. In conclusion, this thesis identifies discriminant metabolic phenotypes of ACLF vs ALF and AD vs ACLF for the first time. In addition, metabolic changes associated with mortality risk are also identified, which highlights the potential for metabolic phenotyping to drive personalised predictive models of outcome in the clinical setting.
Assessing Human Error Against a Benchmark of Perfection
Creators: name: Anderson, Ashton
name: Kleinberg, Jon
name: Mullainathan, Sendhil
Publisher: name: arXiv
Year: 2016
Subjects: subject: Artificial Intelligence (cs.AI)
subject: Computer Science and Game Theory (cs.GT)
subject: Social and Information Networks (cs.SI)
subject: FOS: Computer and information sciences

description: An increasing number of domains are providing us with detailed trace data on human decisions in settings where we can evaluate the quality of these decisions via an algorithm. Motivated by this development, an emerging line of work has begun to consider whether we can characterize and predict the kinds of decisions where people are likely to make errors. To investigate what a general framework for human error prediction might look like, we focus on a model system with a rich history in the behavioral sciences: the decisions made by chess players as they select moves in a game. We carry out our analysis at a large scale, employing datasets with several million recorded games, and using chess tablebases to acquire a form of ground truth for a subset of chess positions that have been completely solved by computers but remain challenging even for the best players in the world. We organize our analysis around three categories of features that we argue are present in most settings where the analysis of human error is applicable: the skill of the decision-maker, the time available to make the decision, and the inherent difficulty of the decision. We identify rich structure in all three of these categories of features, and find strong evidence that in our domain, features describing the inherent difficulty of an instance are significantly more powerful than features based on skill or time.
description: KDD 2016; 10 pages
Learning Attacker's Bounded Rationality Model in Security Games
Creators: name: Żychowski, Adam
name: Mańdziuk, Jacek
Publisher: name: arXiv
Year: 2021
Subjects: subject: Computer Science and Game Theory (cs.GT)
subject: Neural and Evolutionary Computing (cs.NE)
subject: FOS: Computer and information sciences

description: The paper proposes a novel neuroevolutionary method (NESG) for calculating leader's payoff in Stackelberg Security Games. The heart of NESG is strategy evaluation neural network (SENN). SENN is able to effectively evaluate leader's strategies against an opponent who may potentially not behave in a perfectly rational way due to certain cognitive biases or limitations. SENN is trained on historical data and does not require any direct prior knowledge regarding the follower's target preferences, payoff distribution or bounded rationality model. NESG was tested on a set of 90 benchmark games inspired by real-world cybersecurity scenario known as deep packet inspections. Experimental results show an advantage of applying NESG over the existing state-of-the-art methods when playing against not perfectly rational opponents. The method provides high quality solutions with superior computation time scalability. Due to generic and knowledge-free construction of NESG, the method may be applied to various real-life security scenarios.
Statistical properties of a free-electron laser revealed by the Hanbury Brown and Twiss interferometry
Creators: name: Gorobtsov, O. Yu.
name: Mercurio, G.
name: Brenner, G.
name: Lorenz, U.
name: Gerasimova, N.
name: Kurta, R. P.
name: Hieke, F.
name: Skopintsev, P.
name: Zaluzhnyy, I.
name: Lazarev, S.
name: Dzhigaev, D.
name: Rose, M.
name: Singer, A.
name: Wurth, W.
name: Vartanyants, I. A.
Publisher: name: arXiv
Year: 2016
Subjects: subject: Optics (physics.optics)
subject: FOS: Physical sciences

description: We present a comprehensive experimental analysis of statistical properties of the self-amplified spontaneous emission (SASE) free-electron laser (FEL) FLASH at DESY in Hamburg by means of Hanbury Brown and Twiss (HBT) interferometry. The experiments were performed at the FEL wavelengths of 5.5 nm, 13.4 nm, and 20.8 nm. We determined the 2-nd order intensity correlation function for all wavelengths and different operation conditions of FLASH. In all experiments a high degree of spatial coherence (above 50%) was obtained. Our analysis performed in spatial and spectral domains provided us with the independent measurements of an average pulse duration of the FEL that were below 60 fs. To explain complicated behaviour of the 2-nd order intensity correlation function we developed advanced theoretical model that includes the presence of multiple beams and external positional jitter of the FEL pulses. By this analysis we determined that in most experiments several beams were present in radiating field and in one of the experiments external positional jitter was about 25% of the beam size. We envision that methods developed in our study will be used widely for analysis and diagnostics of the FEL radiation.
description: 29 pages, 14 figures, 3 tables
Automatic generation of high-throughput systolic tree-based solvers for modern FPGAs
Creators: name: Tavakkoli, Aryan
Publisher: name: Imperial College London
Year: 2019

description: Tree-based models are a class of numerical methods widely used in financial option pricing, which have a computational complexity that is quadratic with respect to the solution accuracy. Previous research has employed reconfigurable computing with small degrees of parallelism to provide faster hardware solutions compared with general-purpose processing software designs. However, due to the nature of their vector hardware architectures, they cannot scale their compute resources efficiently, leaving them with pricing latency figures which are quadratic with respect to the problem size, and hence to the solution accuracy. Also, their solutions are not productive as they require hardware engineering effort, and can only solve one type of tree problems, known as the standard American option. This thesis presents a novel methodology in the form of a high-level design framework which can capture any common tree-based problem, and automatically generates high-throughput field-programmable gate array (FPGA) solvers based on proposed scalable hardware architectures. The thesis has made three main contributions. First, systolic architectures were proposed for solving binomial and trinomial trees, which due to their custom systolic data-movement mechanisms, can scale their compute resources efficiently to provide linear latency scaling for medium-size trees and improved quadratic latency scaling for large trees. Using the proposed systolic architectures, throughput speed-ups of up to 5.6X and 12X were achieved for modern FPGAs, compared to previous vector designs, for medium and large trees, respectively. Second, a productive high-level design framework was proposed, that can capture any common binomial and trinomial tree problem, and a methodology was suggested to generate high-throughput systolic solvers with custom data precision, where the methodology requires no hardware design effort from the end user. Third, a fully-automated tool-chain methodology was proposed that, compared to previous tree-based solvers, improves user productivity by removing the manual engineering effort of applying the design framework to option pricing problems. Using the productive design framework, high-throughput systolic FPGA solvers have been automatically generated from simple end-user C descriptions for several tree problems, such as American, Bermudan, and barrier options.
Audio-to-Image Cross-Modal Generation
Creators: name: Żelaszczyk, Maciej
name: Mańdziuk, Jacek
Publisher: name: arXiv
Year: 2021
Subjects: subject: Multimedia (cs.MM)
subject: Machine Learning (cs.LG)
subject: Sound (cs.SD)
subject: Audio and Speech Processing (eess.AS)
subject: FOS: Computer and information sciences
subject: FOS: Electrical engineering, electronic engineering, information engineering

description: Cross-modal representation learning allows to integrate information from different modalities into one representation. At the same time, research on generative models tends to focus on the visual domain with less emphasis on other domains, such as audio or text, potentially missing the benefits of shared representations. Studies successfully linking more than one modality in the generative setting are rare. In this context, we verify the possibility to train variational autoencoders (VAEs) to reconstruct image archetypes from audio data. Specifically, we consider VAEs in an adversarial training framework in order to ensure more variability in the generated data and find that there is a trade-off between the consistency and diversity of the generated images - this trade-off can be governed by scaling the reconstruction loss up or down, respectively. Our results further suggest that even in the case when the generated images are relatively inconsistent (diverse), features that are critical for proper image classification are preserved.
Incidence of WISE-Selected Obscured AGNs in Major Mergers and Interactions from the SDSS
Creators: name: Weston, Madalyn E.
name: McIntosh, Daniel H.
name: Brodwin, Mark
name: Mann, Justin
name: Cooper, Andrew
name: McConnell, Adam
name: Nielsen, Jennifer L.
Publisher: name: arXiv
Year: 2016
Subjects: subject: Astrophysics of Galaxies (astro-ph.GA)
subject: FOS: Physical sciences

description: We use the Wide-field Infrared Survey Explorer (WISE) and the Sloan Digital Sky Survey (SDSS) to confirm a connection between dust-obscured active galactic nuclei (AGNs) and galaxy merging. Using a new, volume-limited (z <= 0.08) catalog of visually-selected major mergers and galaxy-galaxy interactions from the SDSS, with stellar masses above 2x10^10 Msun, we find that major mergers (interactions) are 5-17 (3-5) times more likely to have red [3.4]-[4.6] colors associated with dust-obscured or `dusty' AGNs, compared to non-merging galaxies with similar masses. Using published fiber spectral diagnostics, we map the [3.4]-[4.6] versus [4.6]-[12] colors of different emission-line galaxies and find one-quarter of Seyferts have colors indicative of a dusty AGN. We find that AGNs are five times more likely to be obscured when hosted by a merging galaxy, half of AGNs hosted by a merger are dusty, and we find no enhanced frequency of optical AGNs in merging over non-merging galaxies. We conclude that undetected AGNs missed at shorter wavelengths are at the heart of the ongoing AGN-merger connection debate. The vast majority of mergers hosting dusty AGNs are star-forming and located at the centers of Mhalo<10^13 Msun groups. Assuming plausibly short duration dusty-AGN phases, we speculate that a large fraction of gas-rich mergers experience a brief obscured AGN phase, in agreement with the strong connection between central star formation and black hole growth seen in merger simulations.
description: 25 pages, 18 figures, submitted second revision to MNRAS 09/12/2016
Exploring gut microbiome – host interactions in the extremes of health and disease
Creators: name: Penney, Nicholas
Publisher: name: Imperial College London
Year: 2018

description: Introduction: Multi ‘omics analyses, including metabonomic and metagenomic profiling techniques, have enabled new insights into systems biology over the past decade. Using two extremes of a continuum between health and disease – elite athletes and obese patients undergoing bariatric surgery – the work in this thesis aims to apply metabolic phenotyping to further understand the impact of exercise, diet and obesity on human metabolism. Furthermore, through combinatorial analysis of metabonomic and gut microbiome data sets, host – gut microbiome co-metabolism and its influence on health is explored in these two extreme populations. Methods: Biofluids were collected from three cohorts: i) elite athletes and age and sex matched controls, ii) healthy individuals before and after a high protein diet, exercise regime or both, and iii) obese subjects pre and post bariatric surgery. Multiple analytical platforms were utilised for metabolic profiling including 1H-NMR spectroscopy, UPLC-MS and GC-MS. Gut microbiome analysis was performed using next generation metagenomic sequencing. After pre-processing the metabonomic and metagenomic data; univariate, unsupervised and supervised multivariate analyses were performed as well as gut microbiome-metabolite association studies. Results: Distinct metabolic and microbial phenotypes existed between both athletes and controls and between obese patients before and after bariatric surgery. Discriminatory metabolites higher in athletes include metabolites associated with muscle turnover, vitamins and recovery supplements, a high protein diet and those derived from gut microbes. Interestingly, increased bacterial diversity seen in athletes correlated with a specific subset of metabolites. Similarly, bariatric surgery resulted in large changes to circulating metabolites. A number of these metabolites were linked to changes in the gut microbiome, including bile acids, short-chain fatty acids and amino acids. Conclusion: This thesis extends existing knowledge of the gut microbiome’s influence on human health through small molecule signalling. Mechanistic studies are now needed to establish causal links between gut microbes, changes to circulating metabolites and disease status.
On the sighting of unicorns: a variational approach to computing invariant sets in dynamical systems
Creators: name: Junge, Oliver
name: Kevrekidis, Ioannis G.
Publisher: name: arXiv
Year: 2016
Subjects: subject: Dynamical Systems (math.DS)
subject: Chaotic Dynamics (nlin.CD)
subject: FOS: Mathematics
subject: FOS: Physical sciences

description: We propose to compute approximations to general invariant sets in dynamical systems by minimizing the distance between an appropriately selected finite set of points and its image under the dynamics. We demonstrate, through computational experiments that this approach can successfully converge to approximations of (maximal) invariant sets of arbitrary topology, dimension and stability as, e.g., saddle type invariant sets with complicated dynamics. We further propose to extend this approach by adding a Lennard-Jones type potential term to the objective function which yields more evenly distributed approximating finite point sets and perform corresponding numerical experiments.