cometadata/datacite-rtg-text-other-reclassification-records huggingface dataset:
Characterization and use of laser-based lysis for cell analysis on-chip
Creators: name: Allbritton, N. L
name: Quinto-Su, P. A
name: Bachman, M.
name: Sims, C. E
name: Lai, H.-H.
name: Li, G.P
name: Venugopalan, V.
Publisher: name: The University of North Carolina at Chapel Hill University Libraries
Year: 2008

description: We demonstrate the use of a pulsed laser microbeam for cell lysis followed by electrophoretic separation of cellular analytes in a microfluidic device. The influence of pulse energy and laser focal point within the microchannel on the threshold for plasma formation was measured. The thickness of the poly(dimethylsiloxane) (PDMS) layer through which the beam travelled was a critical determinant of the threshold energy. An effective optical path length, Leff, for the laser beam can be used to predict the threshold for optical breakdown at different microchannel locations. A key benefit of laser-based cell lysis is the very limited zone (less than 5 μm) of lysis. A second asset is the rapid cell lysis times (approx. microseconds). These features enable two analytes, fluorescein and Oregon Green, from a cell to be electrophoretically separated in the channel in which cell lysis occurred. The resolution and efficiency of the separation of the cellular analytes are similar to those of standards demonstrating the feasibility of using a pulsed laser microbeam in single-cell analysis.
Probing the MQN01 Cosmic Structure: Unveiling a Dense Population of AGN through Chandra Observations
Creators: name: Travascio, Andrea
name: Cantalupo, Sebastiano
name: Tozzi, Paolo
Publisher: name: Zenodo
Year: 2023
Subjects: multiple QSOs in Cosmic Web

description: Understanding the processes of galaxy formation and evolution requires a comprehensive exploration of the Cosmic Web, its filamentary structures, and their connection with Active Galactic Nuclei.
 I will present the analyses of 600 ks of Chandra X-ray observations of MQN01, the largest (4x4 cMpc^2) contiguous cosmic web structure discovered so far in Ly-alpha emission at z=3.2. MQN01 was identified through extensive mosaic MUSE observations, offering a unique opportunity to investigate the intricate relationship between galaxies/AGN and the large cosmic structure. Our primary objective, utilizing Chandra observations, is to perform a comprehensive census of the AGN population within MQN01 and compare their properties with those of the cosmic web, shedding light on potential connections.
Theoretical analysis of the astrophysical S-factor for the alpha+d -->6Li + gamma capture reaction in the two body model
Creators: name: Tursunov, E. M.
name: Turakulov, S. A.
name: Descouvemont, P.
Publisher: name: arXiv
Year: 2014
Subjects: subject: Nuclear Theory (nucl-th)
subject: FOS: Physical sciences

description: Theoretical estimations for the astrophysical S-factor and the d(alpha,gamma)6Li reaction rates are obtained on the base of the two-body model with the alpha-d potential of a simple Gaussian form, which describes correctly the phase-shifts in the S-, P-, and D-waves, the binding energy and the asymptotic normalization constant in the final S-state. Wave functions of the bound and continuum states are calculated by using the Numerov algorithm of a high accuracy. A good convergence of the results for the E1- and E2- components of the transition is shown when increasing the upper limit of effective integrals up to 40 fm. The obtained results for the S-factor and reaction rates in the temperature interval 10E+6 K < T < 10E+10 K are in a good agreement with the results of Ref. A.M. Mukhamedzhanov, et.al., Phys. Rev., C 83, 055805 (2011), where the authors used the known asymptotical form of wave function at low energies and a complicated potential at higher energies.
description: 15 pages, 7 figs, 1 table
Light-Matter interactions in Hofstadter lattice with the next-nearest neighbor couplings
Creators: name: Li, Jia-Qi
name: Gao, Zhao-Min
name: Liu, Wen-Xiao
name: Wang, Xin
Publisher: name: arXiv
Year: 2023
Subjects: subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: The light-mater interactions for an emitter coupling to the bulk region of a Hofstadter lattice has recently investigated by De Bernardis \textit{et al.} [D. De Bernardis, Z.-P. Cian, I. Carusotto, M. Hafezi, and P. Rabl, \href{https://link.aps.org/doi/10.1103/PhysRevLett.126.103603}{Phys. Rev. Lett. 126, 103603 (2021)}]. We propose the light-mater interactions in an extended Hofstadter lattice with the next-nearest neighbor (NNN) couplings. Compared with the standard Hofstadter lattice, the NNN couplings break the mirror symmetry and the energy bands are not flat, i.e., dispersive with nonzero group velocity. In contrast to the study by De Bernardis \textit{et al.}, when a two-level emitter interacts with the bulk region of extended Hofstadter lattice, the emitter is no longer tapped by the coherent oscillations with the flat band, and can radiate photons unidirectional. The chiral mechanism stems from the broken parity symmetry. Both the radiation rate and the chirality periodically change with the emitter's coupling position. All of those particular features can be realized on the photonic lattice platform and may find potential application in chiral quantum information processing.
description: 10 pages and 5 figures
Higgs boson induced reheating and ultraviolet frozen-in dark matter
Creators: name: Ahmed, Aqeel
name: Grzadkowski, Bohdan
name: Socha, Anna
Publisher: name: arXiv
Year: 2022
Subjects: subject: High Energy Physics - Phenomenology (hep-ph)
subject: FOS: Physical sciences

description: A reheating phase in the early universe is an essential part of all inflationary models during which not only the Standard Model (SM) quanta are produced but it can also shed light on the production of dark matter. In this work, we explore a class of reheating models where the reheating is induced by a cubic interaction of the inflaton $ϕ$ to the SM Higgs boson ${\textbf h}$ of the form $g_{hϕ} M_{\rm Pl} ϕ|{\textbf h}|^2$ adopting the $α$-attractor T-model of inflation. Assuming inflaton as a background field such interaction implies a $ϕ$-dependent mass term of the Higgs boson and a non-trivial phase-space suppression of the reheating efficiency. As a consequence, the reheating is prolonged and the maximal temperature of the SM thermal bath is reduced. In particular, due to oscillations of the inflaton field the $ϕ$-dependent Higgs boson mass results in periodic transitions between phases of broken and unbroken electroweak gauge symmetry. The consequences of these rapid phase transitions have been studied in detail. A purely gravitational reheating mechanism in the presence of the inflaton background, i.e., for $g_{hϕ}=0$, has also been investigated. It turned out that even though it may account for the total production of SM radiation in the absence of $g_{hϕ}$, its contribution to the reheating is subdominant for the range of $g_{hϕ}$ considered in this work. As a dark matter candidate, a massive Abelian vector boson, $X_μ$, has been considered. Various production mechanisms of $X_μ$ have been discussed including (i) purely gravitational production from the inflaton background, (ii) gravitational freeze-in from the SM quanta, (iii) inflaton decay through a dim-5 effective operator, and (iv) Higgs portal freeze-in and Higgs decay through a dim-6 effective operator. Parameters that properly describe the observed relic abundance have been determined.
description: v2: 38 pages, 16 figures and 3 tables; added a subsection on tachyonic resonant production of Higgs boson; matches published version in JHEP
An Empirical Method for Improving the Quality of RXTE PCA Spectra
Creators: name: Garcia, Javier
name: McClintock, Jeffrey E.
name: Steiner, James F.
name: Remillard, Ronald A.
name: Grinberg, Victoria
Publisher: name: arXiv
Year: 2014
Subjects: subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: Instrumentation and Methods for Astrophysics (astro-ph.IM)
subject: FOS: Physical sciences

description: We fitted all of the several hundred {\it RXTE} PCA spectra of the Crab individually to a simple power-law model; the total number of counts in the composite spectrum is $>10^9$. We then used the spectrum of residuals to derive a calibration tool, called {\tt pcacorr}, that we apply to large samples of spectra for GX~339--4, H1743--322, and XTE J1550--564. Application of the tool improved the quality of all the fits, and the improvement is dramatic for spectra with $\gtrsim10^7$ counts. The Crab residual spectrum is somewhat different for each of the five PCA detectors, but it was relatively stable over the course of the mission. We recommend that {\tt pcacorr} be routinely applied to spectra with $\gtrsim10^6$ counts and that one include a systematic error of 0.1\%, rather than the 0.5--1\% value that has customarily been used. We expect that application of the tool will result in an increase in sensitivity of the PCA to faint spectral features by up to an order of magnitude.
description: 11 pages, 16 figures. Accepted in ApJ
Magnetic levitation by rotation
Creators: name: Hermansen, Joachim Marco
name: Durhuus, Frederik Laust
name: Frandsen, Cathrine
name: Beleggia, Marco
name: Bahl, Christian R. H.
name: Bjørk, Rasmus
Publisher: name: arXiv
Year: 2023
Subjects: subject: Applied Physics (physics.app-ph)
subject: Soft Condensed Matter (cond-mat.soft)
subject: FOS: Physical sciences

description: A permanent magnet can be levitated simply by placing it in the vicinity of another permanent magnet that rotates in the order of 200 Hz. This surprising effect can be easily reproduced in the lab with off-the-shelf components. Here we investigate this novel type of magnetic levitation experimentally and clarify the underlying physics. Using a 19 mm diameter spherical NdFeB magnet as rotor magnet, we capture the detailed motion of levitating, spherical NdFeB magnets, denoted floater magnets. We find that as levitation occurs, the floater magnet frequency-locks with the rotor magnet, and, noticeably, that the magnetization of the floater is oriented close to the axis of rotation and towards the like pole of the rotor magnet. This is in contrast to what might be expected by the laws of magnetostatics as the floater is observed to align its magnetization essentially perpendicular to the magnetic field of the rotor. Moreover, we find that the size of the floater has a clear influence on the levitation: the smaller the floater, the higher the rotor speed necessary to achieve levitation, and the further away the levitation point shifts. We verify that magnetostatic interactions between the rotating magnets are responsible for creating the equilibrium position of the floater. Hence, this type of magnetic levitation does not rely on gravity as a balancing force to achieve an equilibrium position. Based on theoretical arguments and a numerical model, we show that a constant, vertical field and eddy-current enhanced damping is sufficient to produce levitation from rest. This enables a gyroscopically stabilised counter-intuitive steady-state moment orientation, and the resulting magnetostatically stable, mid-air equilibrium point. The numerical model display the same trends with respect to rotation speed and the floater magnet size as seen in the experiments.
description: 15 pages, 6 figures, 10 videos + 8 pages supplementary material. Videos available at https://youtube.com/playlist?list=PLOfbFSFa_WoK4PgYQXhuNucS_WcIxXDET
On the binomial sums of Horadam sequence
Creators: name: Yilmaz, Nazmiye
name: Taskara, Necati
Publisher: name: arXiv
Year: 2014
Subjects: subject: Combinatorics (math.CO)
subject: FOS: Mathematics

description: The main purpose of this paper is to establish some new properties of Horadam numbers in terms of binomial sums. By that, we can obtain these special numbers in a new and direct way. Moreover, some connections between Horadam and generalized Lucas numbers are revealed to get a more strong result.
Model reduction for constrained mechanical systems via spectral submanifolds
Creators: name: Li, Mingwu
name: Jain, Shobhit
name: Haller, George
Publisher: name: arXiv
Year: 2022
Subjects: subject: Dynamical Systems (math.DS)
subject: FOS: Mathematics

description: Dynamical systems are often subject to algebraic constraints in conjunction to their governing ordinary differential equations. In particular, multibody systems are commonly subject to configuration constraints that define kinematic compatibility between the motion of different bodies. A full-scale numerical simulation of such constrained problems is challenging, making reduced-order models (ROMs) of paramount importance. In this work, we show how to use spectral submanifolds (SSMs) to construct rigorous ROMs for mechanical systems with configuration constraints. These SSM-based ROMs enable the direct extraction of backbone curves and forced response curves, and facilitate efficient bifurcation analysis. We demonstrate the effectiveness of this SSM-based reduction procedure on several examples of varying complexity, including nonlinear finite-element models of multi-body systems. We also provide an open-source implementation of the proposed method that also contains all details of our numerical examples.
A Design Space for Surfacing Content Recommendations in Visual Analytic Platforms
Creators: name: Zhou, Zhilan
name: Wang, Wenyuan
name: Guo, Mengtian
name: Wang, Yue
name: Gotz, David
Publisher: name: arXiv
Year: 2022
Subjects: subject: Human-Computer Interaction (cs.HC)
subject: FOS: Computer and information sciences

description: Recommendation algorithms have been leveraged in various ways within visualization systems to assist users as they perform of a range of information tasks. One common focus for these techniques has been the recommendation of content, rather than visual form, as a means to assist users in the identification of information that is relevant to their task context. A wide variety of techniques have been proposed to address this general problem, with a range of design choices in how these solutions surface relevant information to users. This paper reviews the state-of-the-art in how visualization systems surface recommended content to users during users' visual analysis; introduces a four-dimensional design space for visual content recommendation based on a characterization of prior work; and discusses key observations regarding common patterns and future research opportunities.
description: Accepted to VIS2022
Sulla modellazione meccanica di giunzioni adesive tra elementi tubolari di materiale composito fibrorinforzato
Creators: name: Orefice, Agostina
Publisher: name: Universita degli studi di Salerno
Year: 2018
Subjects: subject: ICAR/08 SCIENZA DELLE COSTRUZIONI
subject: FRP
subject: Connessioni adesive
subject: Tubi

description: 2016 - 2017
description: Traditional materials (steel, concrete, timber and masonry) still dominate the building industry. However new materials are constantly being explored by engineers and scientists due to their numerous advantages offered. With the acronym FRP (Fibre Reinforced Polymers) we indicate a family of composite materials obtained by coupling a polymeric matrix and fibres. More specifically, high strength fibres (glass, carbon, aramid or ultra-thin steel wires) provide strength and stiffness while the resin (polyester, vinylester or epoxy) protects the fibres and guarantees the stress transfer between them. As a result, enhanced final properties are obtained with respect to those exhibited by the individual constituents. Nowadays composite materials are widely used for the strengthening and repair of civil structures. This is due to their advantages such as light-weight, good mechanical properties and corrosion-resistance. Composite materials are also appropriate for applications where the aesthetic preservation of the original structure is required (buildings of historic or artistic interest) or where traditional strengthening techniques cannot be effectively employed. Composite materials are available in several geometries types ranging from laminates with regular surfaces to bi-directional fabrics that are easily adaptable to the shape of the member being strengthened. The evolution and the study of these materials has also encouraged their use not only as structural reinforcements, but also as main structural elements made of pultruded profiles... [edited by Author]
Impact of release dynamics of laser-irradiated polymer micropallets on the viability of selected adherent cells
Creators: name: Ras, M.
name: Small, D. W.
name: Allbritton, N. L.
name: Ma, H.
name: Sims, C. E.
name: Venugopalan, V.
name: Wang, Y.
name: Mismar, W.
Publisher: name: The University of North Carolina at Chapel Hill University Libraries
Year: 2012

description: We use time-resolved interferometry, fluorescence assays and computational fluid dynamics (CFD) simulations to examine the viability of confluent adherent cell monolayers to selection via laser microbeam release of photoresist polymer micropallets. We demonstrate the importance of laser microbeam pulse energy and focal volume position relative to the glass–pallet interface in governing the threshold energies for pallet release as well as the pallet release dynamics. Measurements using time-resolved interferometry show that increases in laser pulse energy result in increasing pallet release velocities that can approach 10 m s−1 through aqueous media. CFD simulations reveal that the pallet motion results in cellular exposure to transient hydrodynamic shear stress amplitudes that can exceed 100 kPa on microsecond timescales, and which produces reduced cell viability. Moreover, CFD simulation results show that the maximum shear stress on the pallet surface varies spatially, with the largest shear stresses occurring on the pallet periphery. Cell viability of confluent cell monolayers on the pallet surface confirms that the use of larger pulse energies results in increased rates of necrosis for those cells situated away from the pallet centre, while cells situated at the pallet centre remain viable. Nevertheless, experiments that examine the viability of these cell monolayers following pallet release show that proper choices for laser microbeam pulse energy and focal volume position lead to the routine achievement of cell viability in excess of 90 per cent. These laser microbeam parameters result in maximum pallet release velocities below 6 m s−1 and cellular exposure of transient hydrodynamic shear stresses below 20 kPa. Collectively, these results provide a mechanistic understanding that relates pallet release dynamics and associated transient shear stresses with subsequent cellular viability. This provides a quantitative, mechanistic basis for determining optimal operating conditions for laser microbeam-based pallet release systems for the isolation and selection of adherent cells.
An array of microresonators as a Photonic Extreme Learning Machine
Creators: name: Biasi, Stefano
name: Franchi, Riccardo
name: Cerini, Lorenzo
name: Pavesi, Lorenzo
Publisher: name: arXiv
Year: 2023
Subjects: subject: Emerging Technologies (cs.ET)
subject: Optics (physics.optics)
subject: FOS: Computer and information sciences
subject: FOS: Physical sciences

description: Machine learning technologies have found fertile ground in optics due to its promising features based on speed and parallelism. Feed-forward neural networks are one of the most widely used machine learning algorithms due to their simplicity and universal approximation capability. However, the typical training procedure, where all weights are optimized, can be time and energy consuming. An alternative approach is the Extreme Learning Machine, a feed-forward neural network in which only the output weights are trained, while the internal connections are random. Here we present an experimental implementation of a photonic extreme learning machine (PELM) in an integrated silicon chip. The PELM is based on the processing of the image of the scattered light by an array of 18 gratings coupled to microresonators. Light propagation in the microresonator array is a linear process while light detection by the video camera is a nonlinear process. Training is done offline by analyzing the recorded scattered light image with a linear classifier. We provide a proof-of-concept demonstration of the PELM by solving both binary and analog tasks, and show how the performance depends on the number of microresonators used in the readout procedure.
description: 12 pages and 6 figures
Equilibrium Temperature for Black Holes with Nonextensive Entropy
Creators: name: Çimdiker, Ilim
name: Dabrowski, Mariusz P.
name: Gohar, Hussain
Publisher: name: arXiv
Year: 2022
Subjects: subject: General Relativity and Quantum Cosmology (gr-qc)
subject: FOS: Physical sciences

description: Hawking temperature has been widely utilised in the literature as the temperature that corresponds to various nonextensive entropies. In this study, we analyze the compatibility of the Hawking temperature with the nonextensive entropies. We demonstrate that, for every nonextensive entropy, one may define an effective temperature (which we call equilibrium temperature) by utilizing the equilibrium condition, and that there is always an additive equilibrium entropy associated with this effective temperature. Except for Bekenstein entropy, we show that Hawking temperature is thermodynamically inconsistent with other nonextensive entropies. We focus on the equilibrium requirement for the Tsallis-Cirto black hole entropy and demonstrate that the Bekenstein-Hawking entropy is the related equilibrium entropy, and the Hawking temperature is the associated equilibrium temperature for the Tsallis-Cirto black hole entropy.
description: 19 pages, some sections merged, accepted for publication in Eur. Phys. J. C
Thermalization of anisotropic quark-gluon plasma produced by decays of color flux tubes
Creators: name: Florkowski, Wojciech
name: Ryblewski, Radoslaw
Publisher: name: arXiv
Year: 2014
Subjects: subject: High Energy Physics - Phenomenology (hep-ph)
subject: Nuclear Theory (nucl-th)
subject: FOS: Physical sciences

description: Kinetic equations are used to study thermalization of the anisotropic quark-gluon plasma produced by decays of color flux tubes possibly created at the very early stages of relativistic heavy-ion collisions. The decay rates of the initial color tubes are given by the Schwinger formula, while the collision terms are taken in the relaxation-time approximation. By connecting the relaxation time with viscosity we analyze production and thermalization processes in the plasma characterized by different values of the ratio of the shear viscosity to entropy density.
description: Talk presented by WF at Quark Matter 2014
Misalignment and mode mismatch error signals for higher-order Hermite-Gauss modes from two sensing schemes
Creators: name: Tao, Liu
name: Green, Anna C.
name: Fulda, Paul
Publisher: name: arXiv
Year: 2023
Subjects: subject: Instrumentation and Methods for Astrophysics (astro-ph.IM)
subject: Instrumentation and Detectors (physics.ins-det)
subject: Optics (physics.optics)
subject: FOS: Physical sciences

description: The locking of lasers to optical cavities is ubiquitously required in the field of precision interferometry such as Advanced LIGO to yield optimal sensitivity. Using higher-order Hermite-Gauss (HG) modes for the main interferometer beam has been a topic of recent study, due to their potential for reducing thermal noise of the test masses. It has been shown however that higher-order HG modes are more susceptible to coupling losses into optical cavities: the misalignment and mode mismatch induced power losses scale as $2n+1$ and $n^{2}+n+1$ respectively with $n$ being the mode index. In this paper we calculate analytically for the first time the alignment and mode mismatch sensing signals for arbitrary higher-order HG modes with both the traditional sensing schemes (using Gouy phase telescopes and quadrant photodetectors) and the more recently proposed radio-frequency jitter-based sensing schemes (using only single element photodiodes). We show that the sensing signals and also the signal-to-shot noise ratios for higher-order HG modes are larger than for the fundamental mode. In particular, the alignment and mode mismatch sensing signals in the traditional sensing schemes scale approximately as $\sqrt{n}$ and $n$ respectively, whereas in the jitter-based sensing schemes they scale exactly as $2n+1$ and $n^{2}+n+1$, respectively, which exactly matches the decrease in their respective tolerances. This potentially mitigates the downside of higher-order HG modes for their suffering from excessive misalignment and mode-mismatch induced power losses.
description: 11 pages 6 figures
Memory, Identity and the Supranational History Museum: Building the House of European History
Creators: name: Remes, Anastasia
Publisher: name: Universita' degli Studi di Salerno
Year: 2017

description: This paper examines the House of European History (HEH), a museum opening its doors in Brussels early 2017. It was initiated by the European Parliament to stimulate the emergence of European identity, just like national historical museums were founded all over Europe in the 19th century to develop national identity and thus contribute to national consolidation. Still today, history is seen as the malleable raw material out of which contemporary identity can be constructed. Yet, the Academic Project Team (APT), which developed the permanent exhibition, chose to replace the concept of identity with memory, stressing its potential to offer a more differentiated historical narrative. Analyzing the museological, political and historiographical aspects of the museum, I discuss whether the HEH can become the place for conflicting views and debate that the APT aspires it to be, or whether it will end up disseminating a new master narrative for the EU.
Continuum effective Hamiltonian for graphene bilayers for an arbitrary smooth lattice deformation from microscopic theories
Creators: name: Vafek, Oskar
name: Kang, Jian
Publisher: name: arXiv
Year: 2022
Subjects: subject: Strongly Correlated Electrons (cond-mat.str-el)
subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: FOS: Physical sciences

description: We provide a systematic real space derivation of the continuum Hamiltonian for a graphene bilayer starting from a microscopic lattice theory, allowing for an arbitrary inhomogeneous smooth lattice deformation, including a twist. Two different microscopic models are analyzed: first, a Slater-Koster like model and second, ab-initio derived model. We envision that our effective Hamiltonian can be used in conjunction with an experimentally determined atomic lattice deformation in twisted bilayer graphene in a specific device to predict and compare the electronic spectra with scanning tunneling spectroscopy measurements. As a byproduct, our approach provides electron-phonon couplings in the continuum Hamiltonian from microscopic models for any bilayer stacking. In the companion paper we analyze in detail the continuum models for relaxed atomic configurations of magic angle twisted bilayer graphene.
description: 9 pages, 1 figure, typos are corrected
Non-random biodiversity loss underlies predictable increases in viral disease prevalence
Creators: name: Borer, E. T.
name: Jolles, A.
name: Mitchell, C. E.
name: Power, A. G.
name: Lacroix, C.
name: Seabloom, E. W.
Publisher: name: The University of North Carolina at Chapel Hill University Libraries
Year: 2013

description: Disease dilution (reduced disease prevalence with increasing biodiversity) has been described for many different pathogens. Although the mechanisms causing this phenomenon remain unclear, the disassembly of communities to predictable subsets of species, which can be caused by changing climate, land use or invasive species, underlies one important hypothesis. In this case, infection prevalence could reflect the competence of the remaining hosts. To test this hypothesis, we measured local host species abundance and prevalence of four generalist aphid-vectored pathogens (barley and cereal yellow dwarf viruses) in a ubiquitous annual grass host at 10 sites spanning 2000 km along the North American West Coast. In laboratory and field trials, we measured viral infection as well as aphid fecundity and feeding preference on several host species. Virus prevalence increased as local host richness declined. Community disassembly was non-random: ubiquitous hosts dominating species-poor assemblages were among the most competent for vector production and virus transmission. This suggests that non-random biodiversity loss led to increased virus prevalence. Because diversity loss is occurring globally in response to anthropogenic changes, such work can inform medical, agricultural and veterinary disease research by providing insights into the dynamics of pathogens nested within a complex web of environmental forces.
Pseudo-magnetic fields, particle-hole asymmetry, and microscopic effective continuum Hamitonians of twisted bilayer graphene
Creators: name: Kang, Jian
name: Vafek, Oskar
Publisher: name: arXiv
Year: 2022
Subjects: subject: Strongly Correlated Electrons (cond-mat.str-el)
subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: FOS: Physical sciences

description: Using the method developed in the companion paper, we construct the effective continuum theories for two different microscopic tight binding models of the twisted bilayer graphene at the twist angle of $1.05^\circ$, one Slater-Koster based and the other ab-initio Wannier based. The energy spectra obtained from the continuum theory -- either for rigid twist or including lattice relaxation -- are found to be in nearly perfect agreement with the spectra from the tight binding models when the gradient expansion is carried out to second order, demonstrating the validity of the method. We also analyze the properties of the Bloch states of the resulting narrow bands, finding non-negligible particle-hole symmetry breaking near the $Γ$ point in our continuum theory constructed for the ab-initio based microscopic model due to a term in the continuum theory that was previously overlooked. This reveals the difference with all existing continuum models where the particle-hole symmetry of the narrow band Hilbert space is nearly perfect.
description: 20 pages, 13 figures, and 18 pages appendix. Typos are corrected
Ordering Dynamics of the Random Field Long-range Ising Model in One Dimension
Creators: name: Agrawal, Ramgopal
name: Corberi, Federico
name: Lippiello, Eugenio
name: Puri, Sanjay
Publisher: name: arXiv
Year: 2023
Subjects: subject: Statistical Mechanics (cond-mat.stat-mech)
subject: FOS: Physical sciences

description: We investigate the influence of long-range (LR) interactions on the phase ordering dynamics of the one-dimensional random field Ising model (RFIM). Unlike the usual RFIM, a spin interacts with all other spins through a ferromagnetic coupling that decays as $r^{-(1+σ)}$, where $r$ is the distance between two spins. In the absence of LR interactions, the size of coarsening domains $R(t)$ exhibits a crossover from pure system behavior $R(t) \sim t^{1/2}$ to an asymptotic regime characterized by logarithmic growth: $R(t) \sim (\ln t)^2$. The LR interactions affect the pre-asymptotic regime, which now exhibits ballistic growth $R(t) \sim t$, followed by $σ$-dependent growth $R(t) \sim t^{1/(1+σ)}$. Additionally, the LR interactions also affect the asymptotic logarithmic growth, which becomes $R(t) \sim (\ln t)^{α(σ)}$ with $α(σ) < 2$. Thus, LR interactions lead to faster growth than for the nearest-neighbor system at short times. Unexpectedly, this driving force causes a slowing-down of the dynamics ($α< 2$) in the asymptotic logarithmic regime. This is explained in terms of a non-trivial competition between the pinning force caused by the random field and the driving force introduced by LR interactions. We also study the spatial correlation function and the autocorrelation function of the magnetization field. The former exhibits superuniversality for all $σ$, i.e., a scaling function that is independent of the disorder strength. The same holds for the autocorrelation function when $σ<1$, whereas a signature of the violation of superuniversality is seen for $σ>1$.
description: 27 pages, 12 figures
Structure-preserving finite volume arbitrary Lagrangian-Eulerian WENO schemes for the shallow water equations
Creators: name: Zhang, Jiahui
name: Xia, Yinhua
name: Xu, Yan
Publisher: name: arXiv
Year: 2022
Subjects: subject: Numerical Analysis (math.NA)
subject: FOS: Mathematics

description: This paper develops the structure-preserving finite volume weighted essentially non-oscillatory (WENO) hybrid schemes for the shallow water equations under the arbitrary Lagrangian-Eulerian (ALE) framework, dubbed as ALE-WENO schemes. The WENO hybrid reconstruction is adopted on moving meshes, which distinguishes the smooth, non-smooth, and transition stencils by a simple smoothness detector. To maintain the positivity preserving and the well-balanced properties of the ALE-WENO schemes, we adapt the positivity preserving limiter and the well-balanced approaches on static meshes to moving meshes. The rigorous theoretical analysis and numerical examples demonstrate the high order accuracy and positivity-preserving property of the schemes under the ALE framework. For the well-balanced schemes, it is successful in the unique exact equilibrium preservation and capturing small perturbations of the hydrostatic state well without numerical oscillations near the discontinuity. Moreover, our ALE-WENO hybrid schemes have an advantage over the simulations on static meshes due to the higher resolution interface tracking of the fluid motion.
description: 43 pages, 50 figures
Tuning bulk and surface conduction in topological Kondo insulator SmB6
Creators: name: Syers, Paul
name: Kim, Dohun
name: Fuhrer, Michael S.
name: Paglione, Johnpierre
Publisher: name: arXiv
Year: 2014
Subjects: subject: Strongly Correlated Electrons (cond-mat.str-el)
subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: Materials Science (cond-mat.mtrl-sci)
subject: FOS: Physical sciences

description: Bulk and surface state contributions to the electrical resistance of single-crystal samples of the topological Kondo insulator compound SmB6 are investigated as a function of crystal thickness and surface charge density, the latter tuned by ionic liquid gating with electrodes patterned in a Corbino disk geometry on a single surface. By separately tuning bulk and surface conduction channels, we show conclusive evidence for a model with an insulating bulk and metallic surface states, with a crossover temperature that depends solely on the relative contributions of each conduction channel. The surface conductance, on the order of 100 e^2/h and electron-like, exhibits a field-effect mobility of 133 cm^2/V/s and a large carrier density of ~2x10^{14}/cm^2, in good agreement with recent photoemission results. With the ability to gate-modulate surface conduction by more than 25%, this approach provides promise for both fundamental and applied studies of gate-tuned devices structured on bulk crystal samples.
description: 5 pages, 3 figures
Improved List Decoding for Polar-Coded Probabilistic Shaping
Creators: name: Runge, Constantin
name: Wiegart, Thomas
name: Lentner, Diego
Publisher: name: arXiv
Year: 2023
Subjects: subject: Information Theory (cs.IT)
subject: FOS: Computer and information sciences

description: A modified successive cancellation list (SCL) decoder is proposed for polar-coded probabilistic shaping. The decoder exploits the deterministic encoding rule for shaping bits to rule out candidate code words that the encoder would not generate. This provides error detection and decreases error rates compared to standard SCL decoding while at the same time reducing the length of the outer cyclic redundancy check code.
description: 5 pages, 3 figures; as presented at ISTC 2023
Three-dimensional flow and lift characteristics of a hovering ruby-throated hummingbird
Creators: name: Song, J.
name: Luo, H.
name: Hedrick, T. L.
Publisher: name: The University of North Carolina at Chapel Hill University Libraries
Year: 2014

description: A three-dimensional computational fluid dynamics simulation is performed for a ruby-throated hummingbird (Archilochus colubris) in hovering flight. Realistic wing kinematics are adopted in the numerical model by reconstructing the wing motion from high-speed imaging data of the bird. Lift history and the three-dimensional flow pattern around the wing in full stroke cycles are captured in the simulation. Significant asymmetry is observed for lift production within a stroke cycle. In particular, the downstroke generates about 2.5 times as much vertical force as the upstroke, a result that confirms the estimate based on the measurement of the circulation in a previous experimental study. Associated with lift production is the similar power imbalance between the two half strokes. Further analysis shows that in addition to the angle of attack, wing velocity and surface area, drag-based force and wing–wake interaction also contribute significantly to the lift asymmetry. Though the wing–wake interaction could be beneficial for lift enhancement, the isolated stroke simulation shows that this benefit is buried by other opposing effects, e.g. presence of downwash. The leading-edge vortex is stable during the downstroke but may shed during the upstroke. Finally, the full-body simulation result shows that the effects of wing–wing interaction and wing–body interaction are small.
Multiplex networks in metropolitan areas: generic features and local effects
Creators: name: Dobson, Simon
name: Strano, Emanuele
name: Barthelemy, Marc
name: Shai, Saray
Publisher: name: The University of North Carolina at Chapel Hill University Libraries
Year: 2015

description: Most large cities are spanned by more than one transportation system. These different modes of transport have usually been studied separately: it is however important to understand the impact on urban systems of coupling different modes and we report in this paper an empirical analysis of the coupling between the street network and the subway for the two large metropolitan areas of London and New York. We observe a similar behaviour for network quantities related to quickest paths suggesting the existence of generic mechanisms operating beyond the local peculiarities of the specific cities studied. An analysis of the betweenness centrality distribution shows that the introduction of underground networks operate as a decentralizing force creating congestion in places located at the end of underground lines. Also, we find that increasing the speed of subways is not always beneficial and may lead to unwanted uneven spatial distributions of accessibility. In fact, for London—but not for New York—there is an optimal subway speed in terms of global congestion. These results show that it is crucial to consider the full, multimodal, multilayer network aspects of transportation systems in order to understand the behaviour of cities and to avoid possible negative side-effects of urban planning decisions.
The use of propensity scores to assess the generalizability of results from randomized trials
Creators: name: Bradshaw, Catherine P.
name: Cole, Stephen R.
name: Leaf, Philip J.
name: Stuart, Elizabeth A.
Publisher: name: The University of North Carolina at Chapel Hill University Libraries
Year: 2001

description: Randomized trials remain the most accepted design for estimating the effects of interventions, but they do not necessarily answer a question of primary interest: Will the program be effective in a target population in which it may be implemented? In other words, are the results generalizable? There has been very little statistical research on how to assess the generalizability, or “external validity,” of randomized trials. We propose the use of propensity-score-based metrics to quantify the similarity of the participants in a randomized trial and a target population. In this setting the propensity score model predicts participation in the randomized trial, given a set of covariates. The resulting propensity scores are used first to quantify the difference between the trial participants and the target population, and then to match, subclassify, or weight the control group outcomes to the population, assessing how well the propensity score-adjusted outcomes track the outcomes actually observed in the population. These metrics can serve as a first step in assessing the generalizability of results from randomized trials to target populations. This paper lays out these ideas, discusses the assumptions underlying the approach, and illustrates the metrics using data on the evaluation of a schoolwide prevention program called Positive Behavioral Interventions and Supports.
Quantum Hair During Gravitational Collapse
Creators: name: Calmet, Xavier
name: Casadio, Roberto
name: Hsu, Stephen D. H.
name: Kuipers, Folkert
Publisher: name: arXiv
Year: 2023
Subjects: subject: High Energy Physics - Theory (hep-th)
subject: General Relativity and Quantum Cosmology (gr-qc)
subject: FOS: Physical sciences

description: We consider quantum gravitational corrections to the Oppenheimer-Snyder metric describing time-dependent dust ball collapse. The interior metric also describes Friedmann-Lemaitre-Robertson-Walker cosmology and our results are interpreted in that context. The exterior corrections are an example of quantum hair, and are shown to persist throughout the collapse. Our results show the quantum hair survives throughout the horizon formation and that the internal state of the resulting black hole is accessible to outside observers.
description: 13 pages
Testing Gravity Theories Using Stars
Creators: name: Sakstein, Jeremy
name: Jain, Bhuvnesh
name: Vikram, Vinu
Publisher: name: arXiv
Year: 2014
Subjects: subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: General Relativity and Quantum Cosmology (gr-qc)
subject: High Energy Physics - Phenomenology (hep-ph)
subject: High Energy Physics - Theory (hep-th)
subject: FOS: Physical sciences

description: Modified theories of gravity have received a renewed interest due to their ability to account for the cosmic acceleration. In order to satisfy the solar system tests of gravity, these theories need to include a screening mechanism that hides the modifications on small scales. One popular and well-studied theory is chameleon gravity. Our own galaxy is necessarily screened, but less dense dwarf galaxies may be unscreened and their constituent stars can exhibit novel features. In particular, unscreened stars are brighter, hotter and more ephemeral than screened stars in our own galaxy. They also pulsate with a shorter period. In this essay, we exploit these new features to constrain chameleon gravity to levels three orders of magnitude lower the previous measurements. These constraints are currently the strongest in the literature.
description: This essay received an honourable mention by the Gravity Research Foundation's Awards for Essays 2014 under the title "Detecting Modified Gravity in the Stars". This version has been expanded to contain a brief discussion of the prospects for testing gravity using a binary system
Nonlinearities in Black Hole Ringdowns
Creators: name: Mitman, Keefe
name: Lagos, Macarena
name: Stein, Leo C.
name: Ma, Sizheng
name: Hui, Lam
name: Chen, Yanbei
name: Deppe, Nils
name: Hébert, François
name: Kidder, Lawrence E.
name: Moxon, Jordan
name: Scheel, Mark A.
name: Teukolsky, Saul A.
name: Throwe, William
name: Vu, Nils L.
Publisher: name: arXiv
Year: 2022
Subjects: subject: General Relativity and Quantum Cosmology (gr-qc)
subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: High Energy Physics - Theory (hep-th)
subject: FOS: Physical sciences

description: The gravitational wave strain emitted by a perturbed black hole (BH) ringing down is typically modeled analytically using first-order BH perturbation theory. In this Letter we show that second-order effects are necessary for modeling ringdowns from BH merger simulations. Focusing on the strain's $(\ell,m)=(4,4)$ angular harmonic, we show the presence of a quadratic effect across a range of binary BH mass ratios that agrees with theoretical expectations. We find that the quadratic $(4,4)$ mode's amplitude exhibits quadratic scaling with the fundamental $(2,2)$ mode -- its parent mode. The nonlinear mode's amplitude is comparable to or even larger than that of the linear $(4,4)$ mode. Therefore, correctly modeling the ringdown of higher harmonics -- improving mode mismatches by up to 2 orders of magnitude -- requires the inclusion of nonlinear effects.
description: 6+2 pages, 4 figures, 1 table. Matches PRL version
Multitask quantum thermal machines and cooperative effects
Creators: name: Lu, Jincheng
name: Wang, Zi
name: Wang, Rongqian
name: Peng, Jiebin
name: Wang, Chen
name: Jiang, Jian-Hua
Publisher: name: arXiv
Year: 2022
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: FOS: Physical sciences

description: Including phonon-assisted inelastic process in thermoelectric devices is able to enhance the performance of nonequilibrium work extraction. In this work, we demonstrate that inelastic phonon-thermoelectric devices have a fertile functionality diagram, where particle current and phononic heat currents are coupled and fueled by chemical potential difference. Such devices can simultaneously perform multiple tasks, e.g., heat engines, refrigerators, and heat pumps. Guided by the entropy production, we mainly study the efficiencies and coefficients of performance of multitask quantum thermal machines, where the roles of the inelastic scattering process and multiple biases in multiterminal setups are emphasized. Specifically, in a three-terminal double-quantum-dot setup with a tunable gate, we show that it efficiently performs two useful tasks due to the phonon-assisted inelastic process. Moreover, the cooperation between the longitudinal and transverse thermoelectric effects in the three-terminal thermoelectric systems leads to markedly improved performance of the thermal machines. While for the four-terminal four-quantum-dot thermoelectric setup, we find that additional thermodynamic affinity furnishes the system with both enriched functionality and enhanced efficiency. Our work provides insights into optimizing phonon-thermoelectric devices.
description: 14 pages, 7 figures
Joint generalized estimating equations for multivariate longitudinal binary outcomes with missing data: an application to acquired immune deficiency syndrome data
Creators: name: Sinha, Debajyoti
name: Parzen, Michael
name: Fitzmaurice, Garrett M.
name: Ibrahim, Joseph G.
name: Lipsitz, Stuart R.
name: Lipshultz, Steven
Publisher: name: The University of North Carolina at Chapel Hill University Libraries
Year: 2009

description: In a large, prospective longitudinal study designed to monitor cardiac abnormalities in children born to HIV-infected women, instead of a single outcome variable, there are multiple binary outcomes (e.g., abnormal heart rate, abnormal blood pressure, abnormal heart wall thickness) considered as joint measures of heart function over time. In the presence of missing responses at some time points, longitudinal marginal models for these multiple outcomes can be estimated using generalized estimating equations (GEE) (Liang and Zeger, 1986), and consistent estimates can be obtained under the assumption of a missing completely at random (MCAR) mechanism. When the missing data mechanism is missing at random (MAR), that is the probability of missing a particular outcome at a time-point depends on observed values of that outcome and the remaining outcomes at other time points, we propose joint estimation of the marginal models using a single modified GEE based on an EM-type algorithm. The proposed method is motivated by the longitudinal study of cardiac abnormalities in children born to HIV-infected women and analyses of these data are presented to illustrate the application of the method. Further, in an asymptotic study of bias, we show that under an MAR mechanism in which missingness depends on all observed outcome variables, our joint estimation via the modified GEE produces almost unbiased estimates, provided the correlation model has been correctly specified, whereas estimates from standard GEE can lead to substantial bias.