cssi/SciSciGPT-SciSciNet huggingface dataset:
High affinity binding of SARS-CoV-2 spike protein enhances ACE2 carboxypeptidase activity

The novel severe acute respiratory syndrome coronavirus (SARS-CoV-2) has emerged to a pandemic and caused global public health crisis. Human angiotensin-converting enzyme 2(ACE2) was identified as the entry receptor for SARS-CoV-2. As a carboxypeptidase, ACE2 cleaves many biological substrates besides angiotensin II to control vasodilatation and vascular permeability. Given the nanomolar high affinity between ACE2 and SARS-CoV-2 spike protein, we investigated how this interaction would affect the enzymatic activity of ACE2. Surprisingly, SARS-CoV-2 trimeric spike protein increased ACE2 proteolytic activity ∼3-10 fold against model peptide substrates, such as caspase-1 substrate and Bradykinin-analog. The enhancement in ACE2 enzymatic function was mediated by the binding of SARS-CoV-2 spike RBD domain. These results highlighted the potential for SARS-CoV-2 infection to enhance ACE2 activity, which may be relevant to the cardiovascular symptoms associated with COVID-19.
Stochastic Tools for Network Intrusion Detection

With the rapid development of Internet and the sharp increase of network crime, network security has become very important and received a lot of attention. We model security issues as stochastic systems. This allows us to find weaknesses in existing security systems and propose new solutions. Exploring the vulnerabilities of existing security tools can prevent cyber-attacks from taking advantages of the system weaknesses. We propose a hybrid network security scheme including intrusion detection systems (IDSs) and honeypots scattered throughout the network. This combines the advantages of two security technologies. A honeypot is an activity-based network security system, which could be the logical supplement of the passive detection policies used by IDSs. This integration forces us to balance security performance versus cost by scheduling device activities for the proposed system. By formulating the scheduling problem as a decentralized partially observable Markov decision process (DEC-POMDP), decisions are made in a distributed manner at each device without requiring centralized control. The partially observable Markov decision process (POMDP) is a useful choice for controlling stochastic systems. As a combination of two Markov models, POMDPs combine the strength of hidden Markov Model (HMM) (capturing dynamics that depend on unobserved states) and that of Markov decision process (MDP) (taking the decision aspect into account). Decision-making under uncertainty is used in many parts of business and science. We use here for security tools. We adopt a high-quality approximation solution for finite-space POMDPs with the average cost criterion and their extension to DEC-POMDPs. We show how this tool could be used to design a network security framework.
ANOMALOUS DIFFUSE INTERSTELLAR BANDS IN THE SPECTRUM OF HERSCHEL 36. I. OBSERVATIONS OF ROTATIONALLY EXCITED CH AND CH+ ABSORPTION AND STRONG, EXTENDED REDWARD WINGS ON SEVERAL DIBs*

Anomalously broad diffuse interstellar bands (DIBs) at 5780.5, 5797.1, 6196.0, and 6613.6 A are found in absorption along the line of sight to Herschel 36, the star illuminating the bright Hourglass region of the Hii region Messier 8. Interstellar absorption from excited CH + in the J = 1 level and from excited CH in the J = 3/2 level is also seen. To our knowledge, neither those excited molecular lines nor such strongly extended DIBs have previously been seen in absorption from interstellar gas. These unusual features appear to arise in a small region near Herschel 36 which contains most of the neutral interstellar material in the sight line. The CH + and CH in that region are radiatively excited by strong far-IR radiation from the adjacent infrared source Her 36 SE. Similarly, the broadening of the DIBs toward Herschel 36 may be due to radiative pumping of closely spaced high-J rotational levels of relatively small, polar carrier molecules. If this picture of excited rotational states for the DIB carriers is correct and applicable to most DIBs, the 2.7 K cosmic microwave background may set the minimum widths (about 0.35 A) of known DIBs, with molecular processes and/or local radiation fields producing the larger widths found for the broader DIBs. Despite the intense local UV radiation field within the cluster NGC 6530, no previously undetected DIBs stronger than 10 mA in equivalent width are found in the optical spectrum of Herschel 36, suggesting that neither dissociation nor ionization of the carriers of the known DIBs by this intense field creates new carriers with easily detectable DIB-like features. Possibly related profile anomalies for several other DIBs are noted.
Coupling dependence of jet quenching in hot strongly-coupled gauge theories

Previous top-down studies of jet stopping in strongly-coupled QCD-like plasmas with gravity duals have been in the infinite ’t Hooft coupling limit λ → ∞. They have found that, though a wide range of jet stopping distances are possible depending on initial conditions, the maximum jet stopping distance lmax scales with energy as E 1/3 at large energy. But it has always been unclear whether the large-coupling and high-energy limits commute. In this paper, we use the string α ′ expansion in AdS-CFT to study the corrections to the λ = ∞ result in powers of 1/λ. For the particular type of “jets” that we study, we find that (i) the naive expansion in 1/λ breaks down for certain initial conditions but (ii) the relative corrections to the maximum stopping distance are small when 1/λ is small. More specifically, we find that the expansion in 1/λ is well behaved for jets whose stopping distance lstop is in the range λ −1/6lmax ≪ lstop ≲ lmax, but the expansion breaks down (and the fate of λ = ∞ results is uncertain) for jets created in such a way that lstop ≪ λ −1/6lmax. The analysis requires assessing the effects of all higher-derivative corrections to the supergravity action for the gravity dual.
Cold kaons from hot fireballs

Abstract The E814 collaboration Has found a component of very low m t K + mesons with a slope parameter of T ∼ 15 MeV. We will present a scenario which explains the observed slope parameter and which allowa us to predict the expected slope parameter for kaons produced in heavier systems such as Au+Au. Implications for the restoration of chiral symmetry in relativistic heavy ion collisions are discussed.
Unitary braid representations with finite image

In this paper, we prove two loosely connected results about unitary representations of the braid group W Bn!U.d/, when n is sufficiently large and the degree d is not too large compared to n. The original motivation goes back to the work of Jones on images of Braid groups in Hecke algebra representations H.q; n/. Jones showed [10] that when q D i , the image of Bn in every irreducible factor of the Hecke algebra is finite; more explicitly, each such image is an extension of a symmetric group by a 2–group. This is in sharp contrast to the usual behavior of irreducible factors of Hecke algebra representations, in which the closure of the image of Bn contains all unimodular unitary matrices (see Freedman, Larsen and Wang [8]). Birman and Wajnryb showed [2] that when q D e i=6 , certain factors of H.q; n/ give rise to representations whose images are extensions of symplectic groups Sp.2r;F3/ by 3–groups, where n 2r (see also Goldschmidt and Jones [9]). It seems to be known by some experts, though so far as we know it has not appeared in print, that some other factors of H.e ; n/ give rise to image groups which are extensions of SU.r C 1;F2/ by 2–groups. Other (extensions of) symplectic groups appear as quotients of the braid group; Wajnryb [19] has found explicit relations exhibiting Sp.2r;Fp/ as a quotient of B2rC1 for all p . We would like to explain in some sense or at least characterize the possibilities for finite images in such representations. Such a characterization is given in Theorem 4.5.
The Faint-Galaxy Hosts of Gamma-Ray Bursts

The observed redshifts and magnitudes of the host galaxies of gamma-ray bursts (GRBs) are compared with the predictions of three basic GRB models, in which the comoving rate density of GRBs is (1) proportional to the cosmic star formation rate density, (2) proportional to the total integrated stellar density, and (3) constant. All three models make the assumption that at every epoch the probability of a GRB occurring in a galaxy is proportional to that galaxy's broadband luminosity. No assumption is made that GRBs are standard candles or even that their luminosity function is narrow. All three rate-density models are consistent with the observed GRB host galaxies to date, although model (2) is slightly disfavored relative to the others. Models (1) and (3) make very similar predictions for host galaxy magnitude and redshift distributions; these models probably will not be distinguished without measurements of host galaxy star formation rates. The fraction of host galaxies fainter than 28 mag may constrain the faint end of the galaxy luminosity function at high redshift, or, if the fraction is observed to be low, may suggest that the bursters are expelled from low-luminosity hosts. In all models, the probability of finding a z < 0.008 GRB among a sample of 11 GRBs is less than 10-4, strongly suggesting that GRB 980425, if associated with SN 1998bw, represents a distinct class of GRBs.
GAUSSIAN SPECTRAL LINE PROFILES OF ASTROPHYSICAL MASERS

Calculations are performed to demonstrate the deviations from Gaussian that occur in the spectral line profiles of a linear maser as a result of the amplification process. Near-Gaussian profiles are presented for bright, interstellar 22 GHz water masers obtained from high-resolution Very Long Baseline Array observations of W3 IRS 5. For the profiles to be so close to Gaussian, the calculations indicate that these masers must originate in quite hot gas with temperatures greater than 1200 K—a conclusion that is supportive of C-type shocks as the origin of these masers. In addition, the degree of saturation of these masers must be less than approximately one-third, from which it follows that the beaming angles are less than about 10-4 sr and the actual luminosities are modest. If spectral profiles that are as close to Gaussian as the profiles presented in this initial investigation are found to occur widely, they can be valuable diagnostics for the environments of astrophysical masers.
QCD correlation functions and instantons

Abstract QCD point-to-point correlation functions at distances .2-1 fm are very different for different channels, and they tell us a lot about inter-quark interactions. Recent studies based on experimental data, ‘instanton liquid’ approach and lattice measurements are reviewed. Agreement between all of them show that instanton-induced forces dominate the light quark physics, and new findings by Negele et al, that hadrons survive ‘cooling’ , make this statement obvious. We also argue that chiral symmetry restoration is due to breaking of the ‘instanton liquid’ into polarized ‘instanton molecules’.
Chiral flat band superconductivity from symmetry-protected three-band crossings

The author analyzes potential flat band superconductivity from the unconventional spin-1 fermionic three-band crossing points, where the critical temperature is enhanced and the Majorana fermions may arise in the chiral pairing states.
Part of Speech Tagging for Code Switched Data.

We address the problem of Part of Speech tagging (POS) in the context of linguistic code switching (CS). CS is the phenomenon where a speaker switches between two languages or variants of the same language within or across utterances, known as intra-sentential or inter-sentential CS, respectively. Processing CS data is especially challenging in intra-sentential data given state of the art monolingual NLP technology since such technology is geared toward the processing of one language at a time. In this paper we explore multiple strategies of applying state of the art POS taggers to CS data. We investigate the landscape in two CS language pairs, Spanish-English and Modern Standard Arabic-Arabic dialects. We compare the use of two POS taggers vs. a unified tagger trained on CS data. Our results show that applying a machine learning framework using two state of the art POS taggers achieves better performance compared to all other approaches that we investigate.
Confounding-Robust Policy Evaluation in Infinite-Horizon Reinforcement Learning

Off-policy evaluation of sequential decision policies from observational data is necessary in applications of batch reinforcement learning such as education and healthcare. In such settings, however, unobserved variables confound observed actions, rendering exact evaluation of new policies impossible, i.e., unidentifiable. We develop a robust approach that estimates sharp bounds on the (unidentifiable) value of a given policy in an infinite-horizon problem given data from another policy with unobserved confounding, subject to a sensitivity model. We consider stationary or baseline unobserved confounding and compute bounds by optimizing over the set of all stationary state-occupancy ratios that agree with a new partially identified estimating equation and the sensitivity model. We prove convergence to the sharp bounds as we collect more confounded data. Although checking set membership is a linear program, the support function is given by a difficult nonconvex optimization problem. We develop approximations based on nonconvex projected gradient descent and demonstrate the resulting bounds empirically.
The Anti-Diagonal Filtration: Reduced Theory and Applications

Given a knot K in S^3, Seidel and Smith described in arXiv:1002.2648v3 a graded cohomology group Kh_{symp,inv}(K), a variant of their symplectic Khovanov cohomology group. They also constructed a spectral sequence converging to the Heegaard Floer-hat homology group for the connected sum of the double branched cover and a copy of S^{2}xS^{1} (with E^1-page isomorphic to a direct summand of Kh_{symp,inv}(K)). In a previous paper (arXiv:1004.2476v5), we showed that the higher pages of this spectral sequence are knot invariants. Here we discuss a reduced version of the spectral sequence which directly computes HF-hat of the double branched cover. Under some degeneration conditions, one obtains a new absolute Maslov grading on that group. This occurs when K is a two-bridge knot, and we compute the grading in this case. We also extract some rational-valued knot invariants from this construction.
Provenance threat modeling

Provenance systems are used to capture history metadata, applications include ownership attribution and determining the quality of a particular data set. Provenance systems are also used for debugging, process improvement, understanding data proof of ownership, certification of validity, etc. The provenance of data includes information about the processes and source data that leads to the current representation. In this paper we study the security risks provenance systems might be exposed to and recommend security solutions to better protect the provenance information.
Whitney tower concordance of classical links

This paper computes Whitney tower filtrations of classical links. Whitney towers consist of iterated stages of Whitney disks and allow a tree-valued intersection theory, showing that the associated graded quotients of the filtration are finitely generated abelian groups. Twisted Whitney towers are studied and a new quadratic refinement of the intersection theory is introduced, measuring Whitney disk framing obstructions. It is shown that the filtrations are completely classified by Milnor invariants together with new higher-order Sato‐Levine and higher-order Arf invariants, which are obstructions to framing a twisted Whitney tower in the 4‐ball bounded by a link in the 3‐sphere. Applications include computation of the grope filtration and new geometric characterizations of Milnor’s link invariants. 57M25, 57M27, 57Q60; 57N10
Fixed-point free circle actions on 4-manifolds

This paper is concerned with fixed-point free S1–actions (smooth or locally linear) on orientable 4–manifolds. We show that the fundamental group plays a predominant role in the equivariant classification of such 4–manifolds. In particular, it is shown that for any finitely presented group with infinite center there are at most finitely many distinct smooth (resp. topological) 4–manifolds which support a fixed-point free smooth (resp. locally linear) S1–action and realize the given group as the fundamental group. A similar statement holds for the number of equivalence classes of fixed-point free S1–actions under some further conditions on the fundamental group. The connection between the classification of the S1–manifolds and the fundamental group is given by a certain decomposition, called a fiber-sum decomposition, of the S1–manifolds. More concretely, each fiber-sum decomposition naturally gives rise to a Z–splitting of the fundamental group. There are two technical results in this paper which play a central role in our considerations. One states that the Z–splitting is a canonical JSJ decomposition of the fundamental group in the sense of Rips and Sela. Another asserts that if the fundamental group has infinite center, then the homotopy class of principal orbits of any fixed-point free S1–action on the 4–manifold must be infinite, unless the 4–manifold is the mapping torus of a periodic diffeomorphism of some elliptic 3–manifold.
On the Deceleration and Spreading of Relativistic Jets. I. Jet Dynamics

Jet breaks in gamma-ray burst (GRB) afterglows provide a direct probe of their collimation angle. Modeling a jet break requires an understanding of the jet spreading process, whereby the jet transitions from a collimated outflow into the spherical Sedov–Taylor solution at late times. Currently, direct numerical calculations are the most accurate way to capture the deceleration and spreading process, as analytical models have previously given inaccurate descriptions of the dynamics. Here (in paper I) we present a new, semi-analytical model built empirically by performing relativistic numerical jet calculations and inferring the relationship between the Lorentz factor, opening angle, and shock radius. We then use the analytical model to calculate the Lorentz factor and jet opening angle as a function of the shock radius and compare to the numerical solutions. Our analytic model provides efficient means of computing synthetic GRB afterglow light curves and spectra, which is the focus of paper II.
Sublinear deviation between geodesics and sample paths

We give a proof of the sublinear tracking property for sample paths of random walks on various groups acting on spaces with hyperbolic-like properties. As an application, we prove sublinear tracking in Teichmuller distance for random walks on mapping class groups and on Cayley graphs of a large class of finitely generated groups.
Blocks and gaps in the asymmetric simple exclusion process: Asymptotics

In earlier work, the authors obtained formulas for the probability in the asymmetric simple exclusion process that at time t, a particle is at site x and is the beginning of a block of L consecutive particles. Here we consider asymptotics. Specifically, for the Kardar-Parisi-Zhang regime with step initial condition, we determine the conditional probability (asymptotically as t → ∞) that a particle is the beginning of an L-block, given that it is at site x at time t. Using duality between occupied and unoccupied sites, we obtain the analogous result for a gap of G unoccupied sites between the particle at x and the next one.In earlier work, the authors obtained formulas for the probability in the asymmetric simple exclusion process that at time t, a particle is at site x and is the beginning of a block of L consecutive particles. Here we consider asymptotics. Specifically, for the Kardar-Parisi-Zhang regime with step initial condition, we determine the conditional probability (asymptotically as t → ∞) that a particle is the beginning of an L-block, given that it is at site x at time t. Using duality between occupied and unoccupied sites, we obtain the analogous result for a gap of G unoccupied sites between the particle at x and the next one.
On the relationship between the non-local clustering mechanism and preferential concentration

‘Preferential concentration’ (Squires & Eaton, Phys. Fluids, vol. A3, 1991, pp. 1169–1178) refers to the clustering of inertial particles in the high strain, low-rotation regions of turbulence. The ‘centrifuge mechanism’ of Maxey (J. Fluid Mech., vol. 174, 1987, pp. 441–465) appears to explain this phenomenon. In a recent paper, Bragg & Collins (New J. Phys., vol. 16, 2014, 055013) showed that the centrifuge mechanism is dominant only in the regime , where is the Stokes number based on the Kolmogorov time scale. Outside this regime, the centrifuge mechanism gives way to a non-local, path history symmetry breaking mechanism. However, despite the change in the clustering mechanism, the instantaneous particle positions continue to correlate with high strain, low-rotation regions of the turbulence. In this paper, we analyse the exact equation governing the radial distribution function and show how the non-local clustering mechanism is influenced by, but not dependent upon, the preferential sampling of the fluid velocity gradient tensor along the particle path histories in such a way as to generate a bias for clustering in high strain regions of the turbulence. We also show how the non-local mechanism still generates clustering, but without preferential concentration, in the limit where the time scales of the fluid velocity gradient tensor measured along the inertial particle trajectories approaches zero (such as white noise flows or for particles in turbulence settling under strong gravity). Finally, we use data from a direct numerical simulation of inertial particles suspended in Navier–Stokes turbulence to validate the arguments presented in this study.
Partisan asymmetries in online political activity

We examine partisan differences in the behavior, communication patterns and social interactions of more than 18,000 politically-active Twitter users to produce evidence that points to changing levels of partisan engagement with the American online political landscape. Analysis of a network defined by the communication activity of these users in proximity to the 2010 midterm congressional elections reveals a highly segregated, well clustered, partisan community structure. Using cluster membership as a high-fidelity (87% accuracy) proxy for political affiliation, we characterize a wide range of differences in the behavior, communication and social connectivity of left- and right-leaning Twitter users. We find that in contrast to the online political dynamics of the 2008 campaign, right-leaning Twitter users exhibit greater levels of political activity, a more tightly interconnected social structure, and a communication network topology that facilitates the rapid and broad dissemination of political information.
$L^q$ bounds on restrictions of spectral clusters to submanifolds for low regularity metrics

We prove $L^q$ bounds on the restriction of spectral clusters to submanifolds in Riemannian manifolds equipped with metrics of $C^{1,\alpha}$ regularity for $0 \leq \alpha \leq 1$. Our results allow for Lipschitz regularity when $\alpha =0$, meaning they give estimates on manifolds with boundary. When $0< \alpha \leq 1$, the scalar second fundamental form for a codimension 1 submanifold can be defined, and we show improved estimates when this form is negative definite. This extends results of Burq-G\'erard-Tzvetkov and Hu to manifolds with low regularity metrics.
On the local Tamagawa number conjecture for Tate motives over tamely ramified fields

The local Tamagawa number conjecture, which was first formulated by Fontaine and Perrin-Riou, expresses the compatibility of the (global) Tamagawa number conjecture on motivic L-functions with the functional equation. The local conjecture was proven for Tate motives over finite unramified extensions K∕ℚ_p by Bloch and Kato. We use the theory of (φ,Γ)-modules and a reciprocity law due to Cherbonnier and Colmez to provide a new proof in the case of unramified extensions, and to prove the conjecture for ℚ_p(2) over certain tamely ramified extensions.
THE SDSS-HET SURVEY OF KEPLER ECLIPSING BINARIES: SPECTROSCOPIC DYNAMICAL MASSES OF THE KEPLER-16 CIRCUMBINARY PLANET HOSTS

We have used high-resolution spectroscopy to observe the Kepler-16 eclipsing binary as a double-lined system and measure precise radial velocities for both stellar components. These velocities yield a dynamical mass ratio of q = 0.2994 {+-} 0.0031. When combined with the inclination, i 90.{sup 0}3401{sup +0.0016}{sub -0.0019}, measured from the Kepler photometric data by Doyle et al. (D11), we derive dynamical masses for the Kepler-16 components of M{sub A} = 0.654 {+-} 0.017 M{sub Sun} and M{sub B} = 0.1959 {+-} 0.0031 M{sub Sun }, a precision of 2.5% and 1.5%, respectively. Our results confirm at the {approx}2% level the mass-ratio derived by D11 with their photometric-dynamical model (PDM), q = 0.2937 {+-} 0.0006. These are among the most precise spectroscopic dynamical masses ever measured for low-mass stars and provide an important direct test of the results from the PDM technique.
High-field Q-slope mitigation due to impurity profile in superconducting radio-frequency cavities

In this study, we present the recent insights into the origin of the high-field Q-slope in superconducting radio frequency cavities. Consequent hydrofluoric acid rinses are used to probe the radio frequency performance as a function of the material removal of two superconducting bulk niobium cavities prepared with low temperature nitrogen infusion. The study reveals that nitrogen infusion affects only the first few tens of nanometers below the native oxide layer. The typical high-field Q-slope behavior of electropolished cavities is indeed completely recovered after a dozen hydrofluoric acid rinses. The reappearance of the high-field Q-slope as a function of material removal was modeled by means of London's local description of screening currents in the superconductor, returning good fitting of the experimental data and suggesting that a layer of interstitial impurities with diffusion length on the order of tens of nanometers can mitigate high-field Q-slope.
Optimality Study of Existing Quantum Computing Layout Synthesis Tools

Layout synthesis, an important step in quantum computing, processes quantum circuits to satisfy device layout constraints. In this paper, we construct QUEKO benchmarks for this problem, which have known optimal depths and gate counts. We use QUEKO to evaluate the optimality of current layout synthesis tools, including Cirq from Google, Qiskit from IBM, $\mathsf {t}|\mathsf {ket}\rangle$ t | ket 〉 from Cambridge Quantum Computing, and a recent academic work. To our surprise, despite over a decade of research and development by academia and industry on compilation and synthesis for quantum circuits, we are still able to demonstrate large optimality gaps: 1.5-12x on average on a smaller device and 5-45x on average on a larger device. This suggests substantial room for improvement of the efficiency of quantum computer by better layout synthesis tools. Finally, we also prove the NP-completeness of the layout synthesis problem for quantum computing. We have made the QUEKO benchmarks open-source.
Baseline-free quantitative absorption spectroscopy based on cepstral analysis

The accuracy of quantitative absorption spectroscopy depends on correctly distinguishing molecular absorption signatures in a measured transmission spectrum from the varying intensity or ‘baseline’ of the light source. Baseline correction becomes particularly difficult when the measurement involves complex, broadly absorbing molecules or non-ideal transmission effects such as etalons. We demonstrate a technique that eliminates the need to account for the laser intensity in absorption spectroscopy by converting the measured transmission spectrum of a gas sample to a modified form of the time-domain molecular free induction decay (m-FID) using a cepstral analysis approach developed for audio signal processing. Much of the m-FID signal is temporally separated from and independent of the source intensity, and this portion can be fit directly with a model to determine sample gas properties without correcting for the light source intensity. We validate the new approach in several complex absorption spectroscopy scenarios and discuss its limitations. The technique is applicable to spectra obtained with any absorption spectrometer and provides a fast and accurate approach for analyzing complex spectra.
TRUNCATED SUM RULES AND THEIR USE IN CALCULATING FUNDAMENTAL LIMITS OF NONLINEAR SUSCEPTIBILITIES

Truncated sum rules have been used to calculate the fundamental limits of the nonlinear susceptibilities and the results have been consistent with all measured molecules. However, given that finite-state models appear to result in inconsistencies in the sum rules, it may seem unclear why the method works. In this paper, the assumptions inherent in the truncation process are discussed and arguments based on physical grounds are presented in support of using truncated sum rules in calculating fundamental limits. The clipped harmonic oscillator is used as an illustration of how the validity of truncation can be tested and several limiting cases are discussed as examples of the nuances inherent in the method.
BPS/CFT correspondence IV: sigma models and defects in gauge theory

Quantum field theory $$L_1$$ on spacetime $$X_{1}$$ can be coupled to another quantum field theory $$L_2$$ on a spacetime $$X_{2}$$ via the third quantum field theory $$L_{12}$$ living on $$X_{12} = X_{1} \cap X_{2}$$ . We explore several such constructions with two- and four-dimensional $$X_{1}, X_{2}$$ ’s and zero- and two-dimensional $$X_{12}$$ ’s, in the context of $${\mathcal {N}}=2$$ supersymmetry, non-perturbative Dyson–Schwinger equations, and BPS/CFT correspondence. The companion paper (Nekrasov, “BPS/CFT correspondence V: BPZ and KZ equations from qq-characters”, 2017. arXiv:1711.11582 [hep-th]) will show that the BPZ and KZ equations of two-dimensional conformal field theory are obeyed by the half-BPS surface defects in quiver $${\mathcal {N}}=2$$ gauge theories.
The Energetics of White-light Flares Observed by SDO /HMI and RHESSI

White-light (WL) flares have been observed and studied for more than a century since their first discovery. However, some fundamental physics behind the brilliant emission remains highly controversial. One of the important facts in addressing the flare energetics is the spatio-temporal correlation between the WL emission and the hard X-ray (HXR) radiation, presumably suggesting that energetic electrons are the energy sources. In this study, we present a statistical analysis of 25 strong flares (≥M5) observed simultaneously by the Helioseismic and Magnetic Imager (HMI), on board the Solar Dynamics Observatory ( SDO ), and the Reuven Ramaty High Energy Solar Spectroscopic Imager ( RHESSI ). Among these events, WL emission was detected by SDO/HMI in 13 flares, associated with HXR emission. To quantitatively describe the strength of WL emission, equivalent area (EA) is defined as the integrated contrast enhancement over the entire flaring area. Our results show that the EA is inversely proportional to the HXR power index, indicating that stronger WL emission tends to be associated with a larger population of high energy electrons. However, no obvious correlation is found between WL emission and flux of non-thermal electrons at 50 keV. For the other group of 13 flares without detectable WL emission, the HXR spectra are softer (larger power index) than those flares with WL emission, especially for the X-class flares in this group.
Robust Compressed Sensing using Generative Models

The goal of compressed sensing is to estimate a high dimensional vector from an underdetermined system of noisy linear equations. In analogy to classical compressed sensing, here we assume a generative model as a prior, that is, we assume the vector is represented by a deep generative model $G: \mathbb{R}^k \rightarrow \mathbb{R}^n$. Classical recovery approaches such as empirical risk minimization (ERM) are guaranteed to succeed when the measurement matrix is sub-Gaussian. However, when the measurement matrix and measurements are heavy-tailed or have outliers, recovery may fail dramatically. In this paper we propose an algorithm inspired by the Median-of-Means (MOM). Our algorithm guarantees recovery for heavy-tailed data, even in the presence of outliers. Theoretically, our results show our novel MOM-based algorithm enjoys the same sample complexity guarantees as ERM under sub-Gaussian assumptions. Our experiments validate both aspects of our claims: other algorithms are indeed fragile and fail under heavy-tailed and/or corrupted data, while our approach exhibits the predicted robustness.
Sulfate Aerosol Hazes and SO2 Gas as Constraints on Rocky Exoplanets’ Surface Liquid Water

Despite surface liquid water's importance to habitability, observationally diagnosing its presence or absence on exoplanets is still an open problem. Inspired within the Solar System by the differing sulfur cycles on Venus and Earth, we investigate thick sulfate (H2SO4-H2O) aerosol haze and high trace mixing ratios of SO2 gas as observable atmospheric features whose sustained existence is linked to the near absence of surface liquid water. We examine the fundamentals of the sulfur cycle on a rocky planet with an ocean and an atmosphere in which the dominant forms of sulfur are SO2 gas and H2SO4-H2O aerosols (as on Earth and Venus). We build a simple but robust model of the wet, oxidized sulfur cycle to determine the critical amounts of sulfur in the atmosphere-ocean system required for detectable levels of SO2 and a detectable haze layer. We demonstrate that for physically realistic ocean pH values (pH > 6) and conservative assumptions on volcanic outgassing, chemistry, and aerosol microphysics, surface liquid water reservoirs with greater than 1e-3 Earth oceans are incompatible with a sustained observable H2SO4-H2O haze layer and sustained observable levels of SO2. Thus, we propose the observational detection of a H2SO4-H2O haze layer and of SO2 gas as two new remote indicators that a planet does not host significant surface liquid water.
Approximate One-Dimensional Models for Monoenergetic Neutral Particle Transport in Ducts with Wall Migration

The problem of monoenergetic neutral particle transport in a duct, where particles travel inside the duct walls, is treated using an approximate one-dimensional model. The one-dimensional model use...
Nanofabrication by magnetic focusing of supersonic beams

We present a new method for nanoscale atom lithography. We propose the use of a supersonic atomic beam, which provides an extremely high brightness and cold source of fast atoms. The atoms are to be focused onto a substrate using a thin magnetic film, into which apertures with widths on the order of 100 nm have been etched. Focused spot sizes near or below 10 nm, with focal lengths on the order of 10 μm, are predicted. Our method can be implemented in a highly parallel manner, enabling simultaneous fabrication of 106 identical elements, and it is applicable both to precision patterning of surfaces with metastable atomic beams and to direct deposition of material.
To BERT or not to BERT: Comparing task-specific and task-agnostic semi-supervised approaches for sequence tagging

Leveraging large amounts of unlabeled data using Transformer-like architectures, like BERT, has gained popularity in recent times owing to their effectiveness in learning general representations that can then be further fine-tuned for downstream tasks to much success. However, training these models can be costly both from an economic and environmental standpoint. In this work, we investigate how to effectively use unlabeled data: by exploring the task-specific semi-supervised approach, Cross-View Training (CVT) and comparing it with task-agnostic BERT in multiple settings that include domain and task relevant English data. CVT uses a much lighter model architecture and we show that it achieves similar performance to BERT on a set of sequence tagging tasks, with lesser financial and environmental impact.
On a model of a population with variable motility

We study a reaction–diffusion equation with a nonlocal reaction term that models a population with variable motility. We establish a global supremum bound for solutions of the equation. We investigate the asymptotic (long-time and long-range) behavior of the population. We perform a certain rescaling and prove that solutions of the rescaled problem converge locally uniformly to zero in a certain region and stay positive (in some sense) in another region. These regions are determined by two viscosity solutions of a related Hamilton–Jacobi equation.
Nonlinear Modulational Instability of Dispersive PDE Models

We prove nonlinear modulational instability for both periodic and localized perturbations of periodic traveling waves for several dispersive PDEs, including the KDV type equations (for example the Whitham equation, the generalized KDV equation, the Benjamin–Ono equation), the nonlinear Schrodinger equation and the BBM equation. First, the semigroup estimates required for the nonlinear proof are obtained by using the Hamiltonian structures of the linearized PDEs. Second, for the KDV type equations the loss of derivative in the nonlinear terms is overcome in two complementary cases: (1) for smooth nonlinear terms and general dispersive operators, we construct higher order approximation solutions and then use energy type estimates; (2) for nonlinear terms of low regularity, with some additional assumptions on the dispersive operator, we use a bootstrap argument to overcome the loss of a derivative.
A prototype vector magnetic field monitoring system for a neutron electric dipole moment experiment

We present results from a first demonstration of a magnetic field monitoring system for a neutron electric dipole moment experiment. The system is designed to reconstruct the vector components of the magnetic field in the interior measurement region solely from exterior measurements.
Efficiency versus instability in plasma accelerators

Plasma wakefield acceleration is one of the main technologies being developed for future high-energy colliders. Potentially, it can create a cost-effective path to the highest possible energies for ${e}^{+}{e}^{\ensuremath{-}}$ or $\ensuremath{\gamma}\ensuremath{-}\ensuremath{\gamma}$ colliders and produce a profound effect on the developments for high-energy physics. Acceleration in a blowout regime, where all plasma electrons are swept away from the axis, is presently considered to be the primary choice for beam acceleration. In this paper, we derive a universal efficiency-instability relation, between the power efficiency and the key instability parameter of the trailing bunch for beam acceleration in the blowout regime. We also show that the suppression of instability in the trailing bunch can be achieved through Balakin-Novokhatsky-Smirnov damping by the introduction of a beam energy variation along the bunch. Unfortunately, in the high-efficiency regime, the required energy variation is quite high and is not presently compatible with collider-quality beams. We would like to stress that the development of the instability imposes a fundamental limitation on the acceleration efficiency, and it is unclear how it could be overcome for high-luminosity linear colliders. With minor modifications, the considered limitation on the power efficiency is applicable to other types of acceleration.
Dimension on discrete spaces

In this paper we develop some combinatorial models for continuous spaces. We study the approximations of continuous spaces by graphs, molecular spaces, and coordinate matrices. We define the dimension on a discrete space by means of axioms based on an obvious geometrical background. This work presents some discrete models ofn-dimensional Euclidean spaces,n-dimensional spheres, a torus, and a projective plane. It explains how to construct new discrete spaces and describes in this connection several three-dimensional closed surfaces with some topological singularities. It also analyzes the topology of (3+1)-space-time. We are also discussing the question by R. Sorkin about how to derive the system of simplicial complexes from a system of open coverings of a topological space.
Generalized north–south dynamics on the space of geodesic currents

We prove uniform north–south dynamics type results for the action of $$\varphi \in Out(F_{N})$$ on the space of projectivized geodesic currents $$\mathbb {P}Curr(S)=\mathbb {P}Curr(F_N)$$ , where $$\varphi $$ is induced by a pseudo-Anosov homeomorphism on a compact surface S with boundary such that $$\pi _{1}(S)=F_{N}$$ . As an application, we show that for a subgroup $$H\le Out(F_N)$$ , containing a fully irreducible (iwip) element, either $$H$$ contains a hyperbolic iwip or $$H$$ is contained in the image in $$Out(F_N)$$ of the mapping class group of a surface with a single boundary component.
Alice Overwatch: Online Monitoring and Data Quality Assurance Using Hlt Data

ALICE Overwatch is a project started in late 2015 to provide augmented online monitoring and data quality assurance utilizing time-stamped QA histograms produced by the ALICE High Level Trigger. The system receives the data via ZeroMQ, stores it for later review, enriches it with detector specific functionality, and visualizes it via a web application. These provided capabilities are complementary to the existing Data Quality Monitoring system. In addition to basic visualization, additional processing options are accessible to the user, including requests for data within a particular time range or reprocessing of a particular run with different processing parameters. For example, the first ten minutes of a particular run could be investigated for a transient hot trigger channel.Due to similarities between the Overwatch architecture and that which will be used for Quality Control (QC) in LHC Run 3 and beyond, Overwatch will also be utilized to develop and test various QC components during LHC Run 2. Some of the areas of QC development include a new trending and alarm framework. We report on the project᠙s design, development, and status.
A new proof of Harish-Chandra's integral formula

We present a new proof of Harish-Chandra’s formula (Harish-Chandra in Am J Math 79:87–120, 1957) $$\Pi(h_1) \Pi(h_2) \int_G e^{\langle {\mathrm{Ad}}_g h_1,h_2 \rangle} dg = \frac{ [ [ \Pi, \Pi ] ] }{|W|} \sum_{w \in W}\epsilon(w) e^{\langle w(h_1),h_2 \rangle},$$ where G is a compact, connected, semisimple Lie group, dg is normalized Haar measure, h1 and h2 lie in a Cartan subalgebra of the complexified Lie algebra, $${\Pi}$$ is the discriminant, $${\langle \cdot, \cdot \rangle}$$ is the Killing form, $${[ [ \cdot, \cdot ] ]}$$ is an inner product that extends the Killing form to polynomials, W is a Weyl group, and $${\epsilon(w)}$$ is the sign of $${w \in W}$$ . The proof in this paper follows from a relationship between heat flow on a semisimple Lie algebra and heat flow on a Cartan subalgebra, extending methods developed by Itzykson and Zuber (J Math Phys 21:411–421, 1980) for the case of an integral over the unitary group U(N). The heat-flow proof allows a systematic approach to studying the asymptotics of orbital integrals over a wide class of groups.
How does an external electrical field affect adsorption patterns of thiol and thiolate on the gold substrate

The responsive behavior of methanethiol and methylthiolate molecules on the Au(111) surface with an applied electrical potential is studied, and it is shown how the sulfur adsorption site, the S–H bond orientation and the interacting energy change with an external electric field strength. The electron charge density corresponding to an electric field minus that obtained in zero field, with zero-field optimal geometry, is calculated to explain the responsive behavior. The interacting energy for the intact methanethiol adsorption is larger than that for the dissociative one, showing that an external electric field cannot make the hydrogen dissociate from the sulfur.
JACOBI-TRUDI DETERMINANTS AND CHARACTERS OF MINIMAL AFFINIZATIONS

In their study of characters of minimal affinizations of representations of orthogonal and symplectic Lie algebras, Chari and Greenstein conjectured that certain Jacobi‐Trudi determinants satisfy an alternating sum formula. In this note, we prove their conjecture and slightly more. The proof relies on some symmetries of the ring of symmetric functions discovered by Koike and Terada. Using results of Hernandez, Mukhin and Young, and Naoi, this implies that the characters of minimal affinizations in types B, C, and D are given by a Jacobi‐Trudi determinant.
SeMA: A Design Methodology for Building Secure Android Apps

UX (user experience) designers visually capture the UX of an app via storyboards. This method is also used in Android app development to conceptualize and design apps. Recently, security has become an integral part of Android app UX because mobile apps are used to perform critical activities such as banking, communication, and health. Therefore, securing user information is imperative in mobile apps. In this context, storyboarding tools offer limited capabilities to capture and reason about the security requirements of an app. Consequently, security cannot be baked into the app at design time. Hence, vulnerabilities stemming from design flaws can often occur in apps. To address this concern, in this paper, we propose a storyboard based design methodology to enable the specification and verification of security properties of an Android app at design time.
WATER VAPOR DISTRIBUTION IN PROTOPLANETARY DISKS

Water vapor has been detected in protoplanetary disks. In this work, we model the distribution of water vapor in protoplanetary disks with a thermo-chemical code. For a set of parameterized disk models, we calculate the distribution of dust temperature and radiation field of the disk with a Monte Carlo method, and then solve the gas temperature distribution and chemical composition. The radiative transfer includes detailed treatment of scattering by atomic hydrogen and absorption by water of Lyα photons, since the Lyα line dominates the UV spectrum of accreting young stars. In a fiducial model, we find that warm water vapor with temperature around 300 K is mainly distributed in a small and well-confined region in the inner disk. The inner boundary of the warm water region is where the shielding of UV field due to dust and water itself become significant. The outer boundary is where the dust temperature drops below the water condensation temperature. A more luminous central star leads to a more extended distribution of warm water vapor, while dust growth and settling tends to reduce the amount of warm water vapor. Based on typical assumptions regarding the elemental oxygen abundance and the water chemistry, the column density of warm water vapor can be as high as 1022 cm–2. A small amount of hot water vapor with temperature higher than ~300 K exists in a more extended region in the upper atmosphere of the disk. Cold water vapor with temperature lower than 100 K is distributed over the entire disk, produced by photodesorption of the water ice.