cometadata/datacite-rtg-text-other-reclassification-records huggingface dataset:
BMS Field Theories and Weyl Anomaly
Creators: name: Bagchi, Arjun
name: Dutta, Sudipta
name: Kolekar, Kedar S.
name: Sharma, Punit
Publisher: name: arXiv
Year: 2021
Subjects: subject: High Energy Physics - Theory (hep-th)
subject: FOS: Physical sciences

description: Two dimensional field theories with Bondi-Metzner-Sachs symmetry have been proposed as duals to asymptotically flat spacetimes in three dimensions. These field theories are naturally defined on null surfaces and hence are conformal cousins of Carrollian theories, where the speed of light goes to zero. In this paper, we initiate an investigation of anomalies in these field theories. Specifically, we focus on the BMS equivalent of Weyl invariance and its breakdown in these field theories and derive an expression for Weyl anomaly. Considering the transformation of partition functions under this symmetry, we derive a Carrollian Liouville action different from ones obtained in the literature earlier.
description: 35 pages
title: Eine umfassende adaptive Middleware für gemischt-kritische cyber-physische Netzwerke
Creators: name: Feist, Melanie
Publisher: name: Gesellschaft für Informatik e.V.
Year: 2024

description: Das rasante Wachstum von Cyber-Physical Systems (CPS) hat zu einer starken Erhöhung der Systemkomplexität geführt, maßgeblich bedingt durch die steigende Anzahl von Wechselwirkungen und Interdependenz von heterogenen Komponenten (physikalischen Prozessen, Sensorik, Aktorik, Kommunikationsnetzen und Rechenressourcen). Ein Netzwerk von kooperierenden CPS - ein sogenanntes Cyber-Physical Network (CPN) - macht die Situation noch komplexer, da Informationen zwischen den CPS im Netzwerk ausgetauscht und Aktionen koordiniert und eingesetzt werden müssen. Durch den Einsatz solcher CPNs in sicherheitskritischen Bereichen wie Verkehr
und Gesundheitswesen gibt es zusätzlich oft Anwendungen mit unterschiedlicher Kritikalität, welche berücksichtigt werden muss. Diese Dissertation stellt die umfassende adaptive Middleware Chameleon Middleware vor, welche eine efﬁziente, ﬂexible und zuverlässige Verwaltung von gemischt-kritischen CPNs ermöglicht.
Universal scaling in the branching of the Tree of Life
Creators: name: Herrada, E. Alejandro
name: Tessone, Claudio J.
name: Klemm, Konstantin
name: Eguiluz, Victor M.
name: Hernandez-Garcia, Emilio
name: Duarte, Carlos M.
Publisher: name: arXiv
Year: 2008
Subjects: subject: Populations and Evolution (q-bio.PE)
subject: Quantitative Methods (q-bio.QM)
subject: FOS: Biological sciences

description: Understanding the patterns and processes of diversification of life in the planet is a key challenge of science. The Tree of Life represents such diversification processes through the evolutionary relationships among the different taxa, and can be extended down to intra-specific relationships. Here we examine the topological properties of a large set of interspecific and intraspecific phylogenies and show that the branching patterns follow allometric rules conserved across the different levels in the Tree of Life, all significantly departing from those expected from the standard null models. The finding of non-random universal patterns of phylogenetic differentiation suggests that similar evolutionary forces drive diversification across the broad range of scales, from macro-evolutionary to micro-evolutionary processes, shaping the diversity of life on the planet.
description: 6 pages + 19 of Supporting Information
Mesoporous core-shell silica nanoparticles with anti-fouling properties for ovarian cancer therapy
Creators: name: Sanchez-Salcedo, Sandra
name: Vallet-Regi, Maria
name: Shanin, Sophia Allaf
name: Glackin, Carlotta A.
name: Zink, Jeffrey I.
Publisher: name: arXiv
Year: 2021
Subjects: subject: Tissues and Organs (q-bio.TO)
subject: FOS: Biological sciences

description: Mesoporous silica nanoparticles (MSNPs) have many potential applications in biomedical fields. However, when MSNPs are exposed to plasma, protein adsorption leads to opsonization and decreases blood circulation time. A new multifunctional nanodevice based on polyethylenimine (PEI) coated core-shell Fe3O4@SiO2 MSNPs with a zwitterionic 2-methacryloyloxyethyl phosphorylcholine (MPC) surface was designed to minimize unspecific protein adhesion. Particle size measurements demonstrated an excellent non-fouling capacity in solutions containing Bovine Serum Albumin (BSA) and Fetal Bovine Serum (FBS) plasma proteins. The system was used in this study to co-deliver two different cargos: siRNA and daunorubicin. Anti-TWIST siRNA plays critical role in modulating knockdown of TWIST and sensitizing cells to chemotherapeutics such as daunorubicin for ovarian cancer therapy. The drug was released in response to externally controlled oscillating magnetic fields (OMF). siRNA (siGFP) silenced expression of green fluorescence protein (GFP) in Ovcar8 cancer cells, demonstrating the incorporation of core shell MSNPs into cells and siGFP delivery. The synergistic effect of the co-release of anti-TWIST-siRNA loaded in the PEI and daunorubicin loaded in NPs pores c aused increased cytotoxicity in Ovcar8 of up to 50% from both zwitteronic and non-zwitteronic NPs. The system is the first example of silencing by anti-TWITS-siRNA /daunorubicin co-delivered using zwitterionic core-shell nanoparticles with low-fouling adsorption. This engineered multifunctional approach may provide therapeutic potential for the treatment of currently incurable ovarian cancer.
description: 43 pages, 8 figures
First operation of Transition-Edge Sensors in space with the Micro-X sounding rocket
Creators: name: Adams, J. S.
name: Baker, R.
name: Bandler, S. R.
name: Bastidon, N.
name: Danowski, M. E.
name: Doriese, W. B.
name: Eckart, M. E.
name: Figueroa-Feliciano, E.
name: Fuhrman, J.
name: Goldfinger, D. C.
name: Heine, S. N. T.
name: Hilton, G. C.
name: Hubbard, A. J. F.
name: Jardin, D.
name: Kelley, R. L.
name: Kilbourne, C. A.
name: Manzagol-Harwood, R. E.
name: McCammon, D.
name: Okajima, T.
name: Porter, F. S.
name: Reintsema, C. D.
name: Serlemitsos, P.
name: Smith, S. J.
name: Wikus, P.
Publisher: name: arXiv
Year: 2021
Subjects: subject: Instrumentation and Methods for Astrophysics (astro-ph.IM)
subject: High Energy Physics - Experiment (hep-ex)
subject: Instrumentation and Detectors (physics.ins-det)
subject: FOS: Physical sciences

description: With its first flight in 2018, Micro-X became the first program to fly Transition-Edge Sensors and their SQUID readouts in space. The science goal was a high-resolution, spatially resolved X-ray spectrum of the Cassiopeia A Supernova Remnant. While a rocket pointing error led to no time on target, the data was used to demonstrate the flight performance of the instrument. The detectors observed X-rays from the on-board calibration source, but a susceptibility to external magnetic fields limited their livetime. Accounting for this, no change was observed in detector response between ground operation and flight operation. This paper provides an overview of the first flight performance and focuses on the upgrades made in preparation for reflight. The largest changes have been upgrading the SQUIDs to mitigate magnetic susceptibility, synchronizing the clocks on the digital electronics to minimize beat frequencies, and replacing the mounts between the cryostat and the rocket skin to improve mechanical integrity. As the first flight performance was consistent with performance on the ground, reaching the instrument goals in the laboratory is considered a strong predictor of future flight performance.
title: Entwurfsautomatisierungs-Tools und Software für Quantencomputing
Creators: name: Burgholzer, Lukas
Publisher: name: Gesellschaft für Informatik e.V.
Year: 2024

description: Quantencomputing hat das Potenzial viele Bereiche des 21. Jahrhunderts zu revolutionie-
ren. Trotz stetiger Verbesserungen zugrundeliegender Technologien ist die beste Hardware aber nur
so gut wie die verfügbare Software, um entsprechende Anwendungen zu realisieren—eine Lektion
aus den letzten fünfzig Jahren Forschung zur Entwicklung klassischer Schaltungen und Systeme. So
können wir heute dank der Methoden für die elektronische Entwurfsautomatisierung (EDA) klassi-
sche Systeme mit einer immensen Anzahl von Transistoren erstellen, die wir oft als selbstverständ-
lich sehen. Im Vergleich dazu lassen bisher vorhandene Softwarelösungen zum Entwurf und der
Optimierung von Quantenschaltungen diese jahrzehntelange Forschung meist ungenutzt. In dieser
Dissertation wird dieses latente Potenzial durch die Entwicklung von Entwurfsautomatisierungsme-
thoden und -software für Quantencomputing nutzbar gemacht. Die vorgestellten Lösungen zeigen
signifikante Verbesserungen in Bezug auf Effizienz, Skalierbarkeit und Zuverlässigkeit. Weiter ver-
anschaulichen sie die enormen Vorteile der Nutzung vorhandenen Wissens und Know-hows im klas-
sischen Schaltungs- und Systementwurf. Alle im Rahmen dieser Arbeit entwickelten Tools und Soft-
warelösungen werden als Open-Source-Pakete zur Verfügung gestellt, die bereits über 690000 mal
heruntergeladen wurden. Die Arbeit trägt somit erheblich zum Fortschritt des Standes der Technik
im Bereich des Quantencomputing bei und zeigt die Bedeutung von Entwurfsautomatisierungsme-
thoden für zukünftige Fortschritte.
Scalable Learning With a Structural Recurrent Neural Network for Short-Term Traffic Prediction
Creators: name: Kim, Youngjoo
name: Wang, Peng
name: Mihaylova, Lyudmila
Publisher: name: arXiv
Year: 2021
Subjects: subject: Machine Learning (cs.LG)
subject: FOS: Computer and information sciences

description: This paper presents a scalable deep learning approach for short-term traffic prediction based on historical traffic data in a vehicular road network. Capturing the spatio-temporal relationship of the big data often requires a significant amount of computational burden or an ad-hoc design aiming for a specific type of road network. To tackle the problem, we combine a road network graph with recurrent neural networks (RNNs) to construct a structural RNN (SRNN). The SRNN employs a spatio-temporal graph to infer the interaction between adjacent road segments as well as the temporal dynamics of the time series data. The model is scalable thanks to two key aspects. First, the proposed SRNN architecture is built by using the semantic similarity of the spatio-temporal dynamic interactions of all segments. Second, we design the architecture to deal with fixed-length tensors regardless of the graph topology. With the real traffic speed data measured in the city of Santander, we demonstrate the proposed SRNN outperforms the image-based approaches using the capsule network (CapsNet) by 14.1% and the convolutional neural network (CNN) by 5.87%, respectively, in terms of root mean squared error (RMSE). Moreover, we show that the proposed model is scalable. The SRNN model trained with data of a road network is able to predict traffic speed of different road networks, with the fixed number of parameters to train.
description: 9 pages, 6 figures
Kinetics of lead concentrate oxidation in a stagnant gas reactor
Creators: name: Salomon De Friedberg, Adam Maciej
Publisher: name: University of British Columbia
Year: 2010

description: The behaviour of lead concentrate particles oxidizing in a stagnant gas reactor has been examined and a mathematical model which predicts the kinetics of galena particles developed. The effects of oxygen concentration, particle size, furnace temperature and concentrate composition were studied. The results showed that the concentrates all exhibited sharply defined ignition points. The ignition points were found to be strongly dependent on oxygen concentration. Reductions in ignition temperature of up to 100 K were observed when the concentrates were reacted in pure oxygen rather than in air. Iron composition was found to have a similar effect on ignition temperature. The modelling results predict short reaction times for ignited particles (less than 100 milliseconds). Particles which ignited in air attained predicted temperatures in excess of 2600 K. In oxygen, particle temperatures were calculated to be greater than 2800 K. Good agreement was found between experimental results and model predictions.
Strong Conformity and Assembly Bias: Towards a Physical Understanding of the Galaxy-Halo Connection in SDSS Clusters
Creators: name: Zu, Ying
name: Song, Yunjia
name: Shao, Zhiwei
name: Chen, Xiaokai
name: Zheng, Yun
name: Gao, Hongyu
name: Yu, Yu
name: Shan, Huanyuan
name: Jing, Yipeng
Publisher: name: arXiv
Year: 2021
Subjects: subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: Astrophysics of Galaxies (astro-ph.GA)
subject: FOS: Physical sciences

description: Understanding the physical connection between cluster galaxies and massive haloes is key to mitigating systematic uncertainties in next-generation cluster cosmology. We develop a novel method to infer the level of conformity between the stellar mass of the brightest central galaxies~(BCGs) $M_*^{BCG}$ and the satellite richness $λ$, defined as their correlation coefficient $ρ_{cc}$ at fixed halo mass, using the abundance and weak lensing of SDSS clusters as functions of $M_*^{BCG}$ and $λ$. We detect a halo mass-dependent conformity as $ρ_{cc}{=}0.60{+}0.08\ln(M_h/3{\times}10^{14}M_{\odot}/h)$. The strong conformity successfully resolves the "halo mass equality" conundrum discovered in Zu et al. 2021 -- when split by $M_*^{BCG}$ at fixed $λ$, the low and high-$M_*^{BCG}$ clusters have the same average halo mass despite having a $0.34$ dex discrepancy in average $M_*^{BCG}$. On top of the best-fitting conformity model, we develop a cluster assembly bias~(AB) prescription calibrated against the CosmicGrowth simulation, and build a conformity+AB model for the cluster weak lensing measurements. Our model predicts that with a ${\sim}20\%$ lower halo concentration $c$, the low-$M_*^{BCG}$ clusters are ${\sim}10\%$ more biased than the high-$M_*^{BCG}$ systems, in excellent agreement with the observations. We also show that the observed conformity and assembly bias are unlikely due to projection effects. Finally, we build a toy model to argue that while the early-time BCG-halo co-evolution drives the $M_*^{BCG}$-$c$ correlation, the late-time dry merger-induced BCG growth naturally produces the $M_*^{BCG}$-$λ$ conformity despite the well-known anti-correlation between $λ$ and $c$. Our method paves the path towards simultaneously constraining cosmology and cluster formation with future cluster surveys.
description: Final MN accepted version (w/ Fig 6 replaced)
Search for Cosmological time dilation from Gamma-Ray Bursts -- A 2021 status update
Creators: name: Singh, Amitesh
name: Desai, Shantanu
Publisher: name: arXiv
Year: 2021
Subjects: subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: FOS: Physical sciences

description: We carry out a search for signatures of cosmological time dilation in the light curves of Gamma Ray Bursts (GRBs), detected by the Neil Gehrels Swift Observatory. For this purpose, we calculate two different durations ($T_{50}$ and $T_{90}$) for a sample of 247 GRBs in the fixed rest frame energy interval of 140-350 keV, similar to Zhang et al. We then carry out a power law-based regression analysis between the durations and redshifts. This search is done using both the unbinned as well as the binned data, where both the weighted mean and the geometric mean was used. For each analysis, we also calculate the intrinsic scatter to determine the tightness of the relation. We find that weighted mean-based binned data for long GRBs and the geometric mean-based binned data is consistent with the cosmological time dilation signature, whereas the analyses using unbinned durations show a very large scatter. We also make our analysis codes and the procedure for obtaining the light curves and estimation of $T_{50}$/$T_{90}$ publicly available.
description: 27 pages, 18 figures. Accepted for publication in JCAP
Fano resonance and incoherent interlayer excitons in molecular van der Waals heterostructures
Creators: name: Lien-Medrano, Carlos R.
name: Bonafé, Franco P.
name: Yam, Chi Yung
name: Palma, Carlos-Andres
name: Sánchez, Cristián G.
name: Frauenheim, Thomas
Publisher: name: arXiv
Year: 2021
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: Chemical Physics (physics.chem-ph)
subject: FOS: Physical sciences

description: Complex van der Waals heterostructures from layered molecular stacks are promising optoelectronic materials offering means to efficient, modular charge separation and collection layers. The effect of stacking in the electrodynamics of such hybrid organic-inorganic two-dimensional materials remains largely unexplored, whereby molecular scale engineering could lead to advanced optical phenomena. For instance, tunable Fano engineering could make possible on-demand transparent conducting layers or photoactive elements, and passive cooling. We employ an adapted Gersten-Nitzan model and real time time-dependent density functional tight-binding to study the optoelectronics of self-assembled monolayers on graphene nanoribbons. We find Fano resonances that cause electromagnetic induced opacity and transparency, and reveal an additional incoherent process leading to interlayer exciton formation with a characteristic charge transfer rate. These results showcase hybrid van der Waals heterostructures as paradigmatic 2D optoelectronic stacks, featuring tunable Fano optics and unconventional charge transfer channels.
description: Published in Nano Letters
Fermiology of two-dimensional titanium carbide and nitride MXenes
Creators: name: Bagheri, Mohammad
name: Ibragimova, Rina
name: Komsa, Hannu-Pekka
Publisher: name: arXiv
Year: 2021
Subjects: subject: Materials Science (cond-mat.mtrl-sci)
subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: FOS: Physical sciences

description: MXenes are a family two-dimensional transition metal carbide and nitride materials, which often exhibit very good metallic conductivity and are thus of great interest for applications in, e.g., flexible electronics, electrocatalysis, and electromagnetic interference shielding. However, surprisingly little is known about the fermiology of MXenes, i.e, the shape and size of their Fermi-surfaces, and its effect on the material properties. One reason for this may be that MXene surfaces are almost always covered by a mixture of functional groups, and studying Fermi-surfaces of disordered systems is cumbersome. Here, we study fermiology of four common Ti-based MXenes as a function of the surface functional group composition. We first calculate the effective band structures of systems with explicit mixed surfaces and observe gradual evolution in the filling of the Ti-d band and resulting shift of Fermi-level. We then demonstrate that these band structures can be closely approximated by using pseudohydrogenated surfaces, and also compare favorably to the experimental angle-resolved photoemission spectroscopy results. By modifying the pseudohydrogen charge we then proceed to plot Fermi-surfaces for all systems and extract their properties, such as the Fermi-surface area and average Fermi-velocity. These are in turn used to evaluate the electrical conductivity with the relaxation time fitted to experimentally measured conductivities.
description: 7 pages, 5 figures
Pseudo-magnetic catalysis of the time-reversal symmetry breaking in graphene
Creators: name: Herbut, Igor F.
Publisher: name: arXiv
Year: 2008
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: Strongly Correlated Electrons (cond-mat.str-el)
subject: High Energy Physics - Theory (hep-th)
subject: FOS: Physical sciences

description: Finite flux of the (time-reversal-symmetric) pseudo-magnetic field, which represents the effect of wrinkling of the graphene sheet for example, is shown to be a catalyst for spontaneous breaking of the time-reversal symmetry of Dirac fermions in two dimensions. Possible experimental consequences of this effect for graphene are discussed.
description: 4 revtex pages; improved presentation, updated references
Finite-Time Thermodynamics of Fluctuations in Microscopic Heat Engines
Creators: name: Watanabe, Gentaro
name: Minami, Yuki
Publisher: name: arXiv
Year: 2021
Subjects: subject: Statistical Mechanics (cond-mat.stat-mech)
subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: Fluctuations of thermodynamic quantities become non-negligible and play an important role when the system size is small. We develop finite-time thermodynamics of fluctuations in microscopic heat engines whose environmental temperature and mechanical parameter are driven periodically in time. Within the slow-driving regime, this formalism universally holds in a coarse-grained time scale whose resolution is much longer than the correlation time of the fluctuations, and is shown to be consistent with the relation analogous to the fluctuation-dissipation relation. Employing a geometric argument, a scenario to simultaneously minimize both the average and fluctuation of the dissipation in the Carnot cycle is identified. For this simultaneous optimization, the existence of a zero eigenvalue of the singular metric for the scale invariant equilibrium state is found to be essential. Furthermore, we demonstrate that our optimized protocol can improve the dissipation and its fluctuation over the current experiment.
description: 7 + 6 pages, 1 figure, accepted for publication as a Letter in Phys. Rev. Research
Local effective dynamics of quantum systems: A generalized approach to work and heat
Creators: name: Weimer, Hendrik
name: Henrich, Markus J.
name: Rempp, Florian
name: Schröder, Heiko
name: Mahler, Günter
Publisher: name: arXiv
Year: 2007
Subjects: subject: Quantum Physics (quant-ph)
subject: Statistical Mechanics (cond-mat.stat-mech)
subject: FOS: Physical sciences

description: By computing the local energy expectation values with respect to some local measurement basis we show that for any quantum system there are two fundamentally different contributions: changes in energy that do not alter the local von Neumann entropy and changes that do. We identify the former as work and the latter as heat. Since our derivation makes no assumptions on the system Hamiltonian or its state, the result is valid even for states arbitrarily far from equilibrium. Examples are discussed ranging from the classical limit to purely quantum mechanical scenarios, i.e. where the Hamiltonian and the density operator do not commute.
description: 5 pages, 1 figure, published version
title: Effiziente und skalierbare Simulationen aktiver Hydrodynamik in drei Dimensionen
Creators: name: Singh, Abhinav
Publisher: name: Gesellschaft für Informatik e.V.
Year: 2024

description: Aktive Materie kann sich aus eigenem Antrieb bewegen und verformen. Dies beschreibt
insbesondere lebende Materie, wie biologische Zellen, Muskelgewebe oder Vogelschwärme. Die
Erforschung des Verhaltens aktiver Materie wird aber dadurch erschwert, dass die Komplexität ihrer
mathematischen Beschreibung hohe Anforderungen an Rechenleistung und numerische Algorithmen
stellt. Wir präsentieren Algorithmen und Software zur effizienten Lösung der komplexen partiellen
Differentialgleichungen aktiver Materie. Dies basiert auf einem C++ Ausdrucksystem für wissen-
schaftliches Rechnen, welches Experimente mit verschiedenen numerischen Verfahren in komplexen
Geometrien erlaubt. Die Implementierung in der OpenFPM-Software für paralleles Hochleistungs-
rechnen gewährleistet Performanz und Skalierbarkeit. Algorithmisch präsentieren wir einen gitterlosen
numerischen Löser, der direkt auf adaptiven Punktwolken rechnet, was die Handhabung komplexer
Geometrien und gekrümmter Oberflächen vereinfacht. In der Anwendung hat unsere Lösung bereits
zur Entdeckung neuer physikalischer Phänomene aktiver Materie geführt. Dies zeigt die Bedeutung
von Fortschritten in der Informatik für die interdisziplinäre Erforschung lebender Materie.
Scaling Relation between Sunyaev-Zel'dovich Effect and X-ray Luminosity and Scale-Free Evolution of Cosmic Baryon Field
Creators: name: Yuan, Qiang
name: Wan, Hao-Yi
name: Zhang, Tong-Jie
name: Liu, Ji-Ren
name: Feng, Long-Long
name: Fang, Li-Zhi
Publisher: name: arXiv
Year: 2008
Subjects: subject: Astrophysics (astro-ph)
subject: FOS: Physical sciences

description: It has been revealed recently that, in the scale free range, i.e. from the scale of the onset of nonlinear evolution to the scale of dissipation, the velocity and mass density fields of cosmic baryon fluid are extremely well described by the self-similar log-Poisson hierarchy. As a consequence of this evolution, the relations among various physical quantities of cosmic baryon fluid should be scale invariant, if the physical quantities are measured in cells on scales larger than the dissipation scale, regardless the baryon fluid is in virialized dark halo, or in pre-virialized state. We examine this property with the relation between the Compton parameter of the thermal Sunyaev-Zel'dovich effect, $y(r)$, and X-ray luminosity, $L_{\rm x}(r)$, where $r$ being the scale of regions in which $y$ and $L_{\rm x}$ are measured. According to the self-similar hierarchical scenario of nonlinear evolution, one should expect that 1.) in the $y(r)$-$L_x(r)$ relation, $y(r)=10^{A(r)}[L_{\rm x}(r)]^{α(r)}$, the coefficients $A(r)$ and $α(r)$ are scale-invariant; 2.) The relation $y(r)=10^{A(r)}[L_{\rm x}(r)]^{α(r)}$ given by cells containing collapsed objects is also available for cells without collapsed objects, only if $r$ is larger than the dissipation scale. These two predictions are well established with a scale decomposition analysis of observed data, and a comparison of observed $y(r)$-$L_x(r)$ relation with hydrodynamic simulation samples. The implication of this result on the characteristic scales of non-gravitational heating is also addressed.
description: 21 pages, 8 figures and 3 tables. Accepted for publication in New Astronomy
Properties of ultra fine grain [beta]-CuAlNi strain memory alloys
Creators: name: Mukunthan, Kannappar
Publisher: name: University of British Columbia
Year: 2010

description: A method has been developed to produce grain sizes as low as 5µm in β-CuAlNi alloys and the effect of grain size on mechanical and strain-memory properties was studied. The thermomechanical treatment procedure involved two. sequential warm working and recrystallization steps at 600° C and 800° C respectively on eutectoid alloys. Three different eutectoid alloys, two with Ms temperature of around 0°C and one with Ms = 220° C were used for the present studies. Even at fine grain sizes, the specimens produced were of single β- phase type without any second phases. Two-stage characteristic stress-strain curves were obtained for most of the specimens in both the strain memory and pseudoelastic states. It was found that the ultimate tensile strength and strain to failure increased with decreasing grain size according to a Hall-Petch relationship down to a grain size of 5µm with the exception of one alloy. Fracture strengths of 1,200 MPa and fracture strains of 10% could be obtained. It was found that the major recovery mode, whether pseudoelastic or strain memory, did not have any significant effect on the total recovery obtained. Recovery properties were not affected significantly by decreasing grain size. Approximately 86% recovery could be obtained for an initial applied strain of 5% at a grain size of around 10µm. Grain refinement increased the fatigue life considerably, possibly due to high ultimate fracture strength and ductile fracture mode. Fatigue life of 275,000 cycles could be obtained for an applied stress of 330 MPa and a steady state strain of 0.6%. Most of the fractures are due to intergranular-type brittle fracture. At fine grain sizes, transgranular-type brittle fracture and microvoid coalescence-type ductile fracture dominated the fracture mode. Oxygen segregation at grain boundaries is the possible explanation for the different mechanical properties shown by different alloys in the present work by being a major factor in causing intergranular-type fracture.
Open and anisotropic soft regions in a model polymer glass
Creators: name: Massa, Carlo Andrea
name: Puosi, Francesco
name: Tripodo, Antonio
name: Leporini, Dino
Publisher: name: arXiv
Year: 2021
Subjects: subject: Soft Condensed Matter (cond-mat.soft)
subject: Disordered Systems and Neural Networks (cond-mat.dis-nn)
subject: FOS: Physical sciences

description: The vibrational dynamics of a model polymer glass is studied by Molecular Dynamics simulations. The focus is on the "soft" monomers with high participation to the lower-frequency vibrational modes contributing to the thermodynamic anomalies of glasses. To better evidence their role, the threshold to qualify monomers as soft is made severe, allowing for the use of systems with limited size. A marked tendency of soft monomers to form quasi-local clusters involving up to 15 monomers is evidenced. Each chain contributes to a cluster up to about three monomers and a single cluster involves monomer belonging to about 2-3 chains. Clusters with monomers belonging to a single chain are rare. The open and tenuous character of the clusters is revealed by their fractal dimension $d_f < 2$. The inertia tensor of the soft clusters evidences their strong anisotropy in shape and remarkable linear correlation of the two largest eigenvalues. Owing to the limited size of the system, finite-size effects, as well as dependence of the results on the adopted polymer length, cannot be ruled out.
Midlatitude Cirrus Clouds and Multiple Tropopauses from a 2002-2006 Climatology over the SIRTA Observatory
Creators: name: Noel, Vincent
name: Haeffelin, Martial
Publisher: name: arXiv
Year: 2007
Subjects: subject: Atmospheric and Oceanic Physics (physics.ao-ph)
subject: FOS: Physical sciences

description: This study present a comparison of lidar observations of midlatitude cirrus clouds over the SIRTA observatory between 2002 and 2006 with multiple tropopauses (MT) retrieved from radiosounding temperature profiles. The temporal variability of MT properties (frequency, thickness) are discussed. Results show a marked annual cycle, with MT frequency reaching its lowest point in May (~18% occurrence of MT) and slowly rising to more than 40% in DJF. The average thickness of the MT also follows an annual cycle, going from less than 1 km in spring to 1.5 km in late autumn. Comparison with lidar observations show that cirrus clouds show a preference for being located close below the 1st tropopause. When the cloud top is above the 1st tropopause (7% of observations), in 20% of cases the cloud base is above it as well, resulting in a cirrus cloud "sandwiched" between the two tropopauses. Compared to the general distribution of cirrus, cross-tropopause cirrus show a higher frequency of large optical depths, while inter-tropopause cirrus show almost exclusively low optical depths (Tau < 0.03 in 90% of cases) typical of subvisible clouds. Results suggest the occurrence of inter-tropopause cirrus clouds is correlated with the frequency of multiple tropopauses.
Time Dilation in Type Ia Supernova Spectra at High Redshift
Creators: name: Blondin, S.
name: Davis, T. M.
name: Krisciunas, K.
name: Schmidt, B. P.
name: Sollerman, J.
name: Wood-Vasey, W. M.
name: Becker, A. C.
name: Challis, P.
name: Clocchiatti, A.
name: Damke, G.
name: Filippenko, A. V.
name: Foley, R. J.
name: Garnavich, P. M.
name: Jha, S. W.
name: Kirshner, R. P.
name: Leibundgut, B.
name: Li, W.
name: Matheson, T.
name: Miknaitis, G.
name: Narayan, G.
name: Pignata, G.
name: Rest, A.
name: Riess, A. G.
name: Silverman, J. M.
name: Smith, R. C.
name: Spyromilio, J.
name: Stritzinger, M.
name: Stubbs, C. W.
name: Suntzeff, N. B.
name: Tonry, J. L.
name: Tucker, B. E.
name: Zenteno, A.
Publisher: name: arXiv
Year: 2008
Subjects: subject: Astrophysics (astro-ph)
subject: FOS: Physical sciences

description: We present multiepoch spectra of 13 high-redshift Type Ia supernovae (SNe Ia) drawn from the literature, the ESSENCE and SNLS projects, and our own separate dedicated program on the ESO Very Large Telescope. We use the Supernova Identification (SNID) code of Blondin & Tonry to determine the spectral ages in the supernova rest frame. Comparison with the observed elapsed time yields an apparent aging rate consistent with the 1/(1+z) factor (where z is the redshift) expected in a homogeneous, isotropic, expanding universe. These measurements thus confirm the expansion hypothesis, while unambiguously excluding models that predict no time dilation, such as Zwicky's "tired light" hypothesis. We also test for power-law dependencies of the aging rate on redshift. The best-fit exponent for these models is consistent with the expected 1/(1+z) factor.
description: 14 pages (emulateapj), 10 figures; accepted for publication in ApJ. Version with full-resolution figures available at http://www.cfa.harvard.edu/~sblondin/publications/timedilation/
Margin-Aware Intra-Class Novelty Identification for Medical Images
Creators: name: Guo, Xiaoyuan
name: Gichoya, Judy Wawira
name: Purkayastha, Saptarshi
name: Banerjee, Imon
Publisher: name: arXiv
Year: 2021
Subjects: subject: Computer Vision and Pattern Recognition (cs.CV)
subject: FOS: Computer and information sciences

description: Traditional anomaly detection methods focus on detecting inter-class variations while medical image novelty identification is inherently an intra-class detection problem. For example, a machine learning model trained with normal chest X-ray and common lung abnormalities, is expected to discover and flag idiopathic pulmonary fibrosis which a rare lung disease and unseen by the model during training. The nuances from intra-class variations and lack of relevant training data in medical image analysis pose great challenges for existing anomaly detection methods. To tackle the challenges, we propose a hybrid model - Transformation-based Embedding learning for Novelty Detection (TEND) which without any out-of-distribution training data, performs novelty identification by combining both autoencoder-based and classifier-based method. With a pre-trained autoencoder as image feature extractor, TEND learns to discriminate the feature embeddings of in-distribution data from the transformed counterparts as fake out-of-distribution inputs. To enhance the separation, a distance objective is optimized to enforce a margin between the two classes. Extensive experimental results on both natural image datasets and medical image datasets are presented and our method out-performs state-of-the-art approaches.
description: 35 pages, 8 figures
Materials Design using Correlated Oxides: Optical Properties of Vanadium Dioxide
Creators: name: Tomczak, Jan M.
name: Biermann, Silke
Publisher: name: arXiv
Year: 2008
Subjects: subject: Strongly Correlated Electrons (cond-mat.str-el)
subject: Materials Science (cond-mat.mtrl-sci)
subject: FOS: Physical sciences

description: Materials with strong electronic Coulomb interactions play an increasing role in modern materials applications. "Thermochromic" systems, which exhibit thermally induced changes in their optical response, provide a particularly interesting case. The optical switching associated with the metal-insulator transition of vanadium dioxide (VO2), for example, has been proposed for use in "intelligent" windows, which selectively filter radiative heat in hot weather conditions. In this work, we develop the theoretical tools for describing such a behavior. Using a novel scheme for the calculation of the optical conductivity of correlated materials, we obtain quantitative agreement with experiments for both phases of VO2. On the example of an optimized energy-saving window setup, we further demonstrate that theoretical materials design has now come into reach, even for the particularly challenging class of correlated electron systems.
description: 4+x pages, 2 figures
Three-dimensional solitons and vortices in dipolar Bose-Einstein condensates
Creators: name: Zaliznyak, Yu. A.
name: Yakimenko, A. I.
Publisher: name: arXiv
Year: 2007
Subjects: subject: Pattern Formation and Solitons (nlin.PS)
subject: FOS: Physical sciences

description: Three-dimensional solitary and vortex structures in Bose-Einstein condensates are studied in the framework of Gross-Pitaevskii model including the simultaneous action of local cubic-quintic nonlinearity and nonlocal dipole-dipole interactions. Nonlocal interactions are shown to change significantly the formation threshold and the numbers of atoms confined into the coherent structures. An appearance of robust high-order ($m=2$) three-dimensional vortices is revealed.
description: 5 pages, 6 figures
Turn towards the crowd
Creators: name: Dauchot, Olivier
Publisher: name: arXiv
Year: 2021
Subjects: subject: Soft Condensed Matter (cond-mat.soft)
subject: FOS: Physical sciences

description: A type of polar self-propelled particle generates a torque that makes it naturally drawn to higher-density areas. The collective behaviour this induces in assemblies of particles constitutes a new form of phase separation in active fluids.
description: 3 pages, 1 figure
Spectroscopy of Strong-Pulse Superradiance in a Bose-Einstein condensate
Creators: name: Bar-Gill, Nir
name: Rowen, Eitan E.
name: Davidson, Nir
Publisher: name: arXiv
Year: 2007
Subjects: subject: Other Condensed Matter (cond-mat.other)
subject: FOS: Physical sciences

description: We study experimentally superradiance in a Bose-Einstein condensate using a two-frequency pump beam. By controlling the frequency difference between the beam components, we measure the spectrum of the backward (energy-mismatched) superradiant atomic modes. In addition, we show that the populations of these modes display coherent time-dynamics. These results are compared to a semi-classical model based on coupled Schroedinger-Maxwell equations.
Stellar dynamical evidence against a cold disc origin for stars in the Galactic Centre
Creators: name: Cuadra, Jorge
name: Armitage, Philip J.
name: Alexander, Richard D.
Publisher: name: arXiv
Year: 2008
Subjects: subject: Astrophysics (astro-ph)
subject: FOS: Physical sciences

description: Observations of massive stars within the central parsec of the Galaxy show that, while most stars orbit within a well-defined disc, a significant fraction have large eccentricities and / or inclinations with respect to the disc plane. Here, we investigate whether this dynamically hot component could have arisen via scattering from an initially cold disc -- the expected initial condition if the stars formed from the fragmentation of an accretion disc. Using N-body methods, we evolve a variety of flat, cold, stellar systems, and study the effects of initial disc eccentricity, primordial binaries, very massive stars and intermediate mass black holes. We find, consistent with previous results, that a circular disc does not become eccentric enough unless there is a significant population of undetected 100--1000 Msun objects. However, since fragmentation of an eccentric disc can readily yield eccentric stellar orbits, the strongest constraints come from inclinations. We show that_none_ of our initial conditions yield the observed large inclinations, regardless of the initial disc eccentricity or the presence of massive objects. These results imply that the orbits of the young massive stars in the Galactic Centre are largely primordial, and that the stars are unlikely to have formed as a dynamically cold disc.
description: 5 pages, 6 colour figures. MNRAS Letters in press. (v2: very minor changes)
Sensitivity study of \emph{r}-process abundances to nuclear masses
Creators: name: Jiang, Xiao-Fei
name: Wu, Xin-Hui
name: Zhao, Peng-Wei
Publisher: name: arXiv
Year: 2021
Subjects: subject: Nuclear Theory (nucl-th)
subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: FOS: Physical sciences

description: The impact of nuclear mass uncertainties on the \emph{r}-process abundances has been systematically studied with the classical \emph{r}-process model by varying the mass of every individual nucleus in the range of $\pm0.1$ to $\pm3.0\ \mathrm{MeV}$ based on six different mass models. A new quantitative relation between the uncertainties of \emph{r}-process abundances and those of the nuclear masses is extracted, i.e., a mass uncertainty of $\pm0.5\ \mathrm{MeV}$ would lead to an abundance uncertainty of a factor around 2.5. It is found that this conclusion holds true for various mass models.
description: 13 pages, 4 figures
Abundant stable gauge field hair for black holes in anti-de Sitter space
Creators: name: Baxter, J. E.
name: Helbling, Marc
name: Winstanley, Elizabeth
Publisher: name: arXiv
Year: 2007
Subjects: subject: General Relativity and Quantum Cosmology (gr-qc)
subject: High Energy Physics - Theory (hep-th)
subject: FOS: Physical sciences

description: We present new hairy black hole solutions of su(N) Einstein-Yang-Mills theory (EYM) in asymptotically anti-de Sitter (adS) space. These black holes are described by N+1 independent parameters, and have N-1 independent gauge field degrees of freedom. Solutions in which all gauge field functions have no zeros exist for all N, and for sufficiently large (and negative) cosmological constant. At least some of these solutions are shown to be stable under classical, linear, spherically symmetric perturbations. Therefore there is no upper bound on the amount of stable gauge field hair with which a black hole in adS can be endowed.
description: 4 pages, 3 figures, new introduction, additional minor changes, published in Physical Review Letters
Generative and Contrastive Self-Supervised Learning for Graph Anomaly Detection
Creators: name: Zheng, Yu
name: Jin, Ming
name: Liu, Yixin
name: Chi, Lianhua
name: Phan, Khoa T.
name: Chen, Yi-Ping Phoebe
Publisher: name: arXiv
Year: 2021
Subjects: subject: Machine Learning (cs.LG)
subject: FOS: Computer and information sciences

description: Anomaly detection from graph data has drawn much attention due to its practical significance in many critical applications including cybersecurity, finance, and social networks. Existing data mining and machine learning methods are either shallow methods that could not effectively capture the complex interdependency of graph data or graph autoencoder methods that could not fully exploit the contextual information as supervision signals for effective anomaly detection. To overcome these challenges, in this paper, we propose a novel method, Self-Supervised Learning for Graph Anomaly Detection (SL-GAD). Our method constructs different contextual subgraphs (views) based on a target node and employs two modules, generative attribute regression and multi-view contrastive learning for anomaly detection. While the generative attribute regression module allows us to capture the anomalies in the attribute space, the multi-view contrastive learning module can exploit richer structure information from multiple subgraphs, thus abling to capture the anomalies in the structure space, mixing of structure, and attribute information. We conduct extensive experiments on six benchmark datasets and the results demonstrate that our method outperforms state-of-the-art methods by a large margin.
description: 14 pages, 5 figures, 4 tables. Published in IEEE Transactions on Knowledge and Data Engineering (TKDE)
The thermal regime during electron beam hearth remelting
Creators: name: Tripp, David William
Publisher: name: University of British Columbia
Year: 2010

description: Electron beam hearth remelting is extensively used in refining of superalloys, titanium alloys and the recycling of these materials. The removal of impurities and exhogenous particles during the hearth melting operation depends primarily on the time at temperature relationship developed within a pool of molten metal. In the past hearth melters have acted largely on empirical evidence to specify such parameters as melt rates, power levels and skull sizes. This work describes a mathematical model which could be used to predict certain parameters (such as pool volume or alloy element evaporation rates) when given skull geometry, power input and melt rate. A three dimensional steady state heat transfer model of both the skull and water cooled copper mould during electron beam hearth remelting has been developed. The model has been used to investigate the effects of surface temperature, liquid motion, power input, skull geometry, presence of the hearth mould and melt rate on parameters such as pool volume during skull melting. In general the choice of any combination of operating parameters depends on a balance between the refining capacity of the process (i.e. liquid volume) and the loss of alloy elements by evaporation. In the case of melting pure materials (e.g. CP titanium) the balance is between refining capacity and efficient energy use. It was found that forced convection is significantly more effective in increasing the volume of the liquid pool than any other single parameter. Increasing the power input to the skull, increasing the skull width and removing the water cooled copper mould from around the skull also increase the pool volume. The evaporation rates of alloy elements within the skull were most effected by changes in the power distribution and the degree of liquid motion.
title: Emergenz und Resilienz in lernenden Multiagentensystemen
Creators: name: Phan, Thomy
Publisher: name: Gesellschaft für Informatik e.V.
Year: 2024

description: Durch die rasante Entstehung diverser künstlich intelligenter Systeme entwickelt sich unsere Welt zu einem technologisch intelligenten Ökosystem, das aus mehreren lernenden und interagierenden Agenten besteht, welche autonom Entscheidungen treffen und sich zur Laufzeit anpassen können.

Üblicherweise wird ein kooperatives Verhalten mithilfe von maschinellen Lernmethoden
angestrebt, um die effiziente Nutzung von geteilten Ressourcen und die koordinierte Lösung von gemeinsamen Aufgaben zu ermöglichen. Allerdings funktionieren aktuelle Lernmethoden nur mit einer begrenzten Anzahl von Agenten. Zudem bieten sie keine ausreichende Robustheit, was zu Ausfällen oder Katastrophen durch sporadische Veränderungen führen kann. Diese Arbeit untersucht die Emergenz und Resilienz von kooperativen Verhalten in lernenden Multiagentensystemen, um skalierbare und robuste Lernmethoden zu entwickeln, welche ein wichtiges Fundament für ein sicheres und künstlich intelligentes Ökosystems bilden. Dabei untersuchen wir die emergente Kooperation in sozialen Dilemmas mittels bilateraler Anreize, nutzen emergente Strukturen für die Verbesserung der Skalierbarkeit und betrachten Resilienz für das Training und Testen ausfallsicherer Systeme.
Temperature Controlled Open Quantum System Dynamics using Time-dependent Variational Method
Creators: name: Jakučionis, Mantas
name: Abramavičius, Darius
Publisher: name: arXiv
Year: 2021
Subjects: subject: Quantum Physics (quant-ph)
subject: Chemical Physics (physics.chem-ph)
subject: FOS: Physical sciences

description: Dirac-Frenkel variational method with Davydov D2 trial wavefunction is extended by introducing a thermalization algorithm and applied to simulate dynamics of a general open quantum system. The algorithm allows to control temperature variations of a harmonic finite size bath, when in contact with the quantum system. Thermalization of the bath vibrational modes is realised via stochastic scatterings, implemented as a discrete-time Bernoulli process with Poisson statistics. It controls bath temperature by steering vibrational modes' evolution towards their canonical thermal equilibrium. Numerical analysis of the exciton relaxation dynamics in a small molecular cluster reveals that thermalization additionally provides significant calculation speed up due to reduced number of vibrational modes needed to obtain the convergence.