cssi/SciSciGPT-SciSciNet huggingface dataset:
Learning Visual-Semantic Embeddings for Reporting Abnormal Findings on Chest X-rays

Automatic medical image report generation has drawn growing attention due to its potential to alleviate radiologists’ workload. Existing work on report generation often trains encoder-decoder networks to generate complete reports. However, such models are affected by data bias (e.g. label imbalance) and face common issues inherent in text generation models (e.g. repetition). In this work, we focus on reporting abnormal findings on radiology images; instead of training on complete radiology reports, we propose a method to identify abnormal findings from the reports in addition to grouping them with unsupervised clustering and minimal rules. We formulate the task as cross-modal retrieval and propose Conditional Visual-Semantic Embeddings to align images and fine-grained abnormal findings in a joint embedding space. We demonstrate that our method is able to retrieve abnormal findings and outperforms existing generation models on both clinical correctness and text generation metrics.
A Wide-Field Camera and Fully Remote Operations at the Wyoming Infrared Observatory

Upgrades at the 2.3 meter Wyoming Infrared Observatory telescope have provided the capability for fully remote operations by a single operator from the University of Wyoming campus. A line-of-sight 300 Megabit s−1 11 GHz radio link provides high-speed internet for data transfer and remote operations that include several realtime video feeds. Uninterruptable power is ensured by a 10 kVA battery supply for critical systems and a 55 kW autostart diesel generator capable of running the entire observatory for up to a week. The construction of a new four-element prime-focus corrector with fused-silica elements allows imaging over a 40' field of view with a new 40962 UV-sensitive prime-focus camera and filter wheel. A new telescope control system facilitates the remote operations model and provides 20'' rms pointing over the usable sky. Taken together, these improvements pave the way for a new generation of sky surveys supporting space-based missions and flexible-cadence observations advancing emerging astrophysical priorities such as planet detection, quasar variability, and long-term time-domain campaigns.
A Dataset and an Approach for Identity Resolution of 38 Million Author IDs extracted from 2B Git Commits

The data collected from open source projects provide means to model large software ecosystems, but often suffer from data quality issues, specifically, multiple author identification strings in code commits might actually be associated with one developer. While many methods have been proposed for addressing this problem, they are either heuristics requiring manual tweaking, or require too much calculation time to do pairwise comparisons for 38M author IDs in, for example, the World of Code collection. In this paper, we propose a method that finds all author IDs belonging to a single developer in this entire dataset, and share the list of all author IDs that were found to have aliases. To do this, we first create blocks of potentially connected author IDs and then use a machine learning model to predict which of these potentially related IDs belong to the same developer. We processed around 38 million author IDs and found around 14.8 million IDs to have an alias, which belong to 5.4 million different developers, with the median number of aliases being 2 per developer. This dataset can be used to create more accurate models of developer behaviour at the entire OSS ecosystem level and can be used to provide a service to rapidly resolve new author IDs.
Quasiclassical Lian-Zuckerman Homotopy Algebras, Courant Algebroids and Gauge Theory

We define a quasiclassical limit of the Lian-Zuckerman homotopy BV algebra (quasiclassical LZ algebra) on the subcomplex, corresponding to “light modes”, i.e. the elements of zero conformal weight, of the semi-infinite (BRST) cohomology complex of the Virasoro algebra associated with vertex operator algebra (VOA) with a formal parameter. We also construct a certain deformation of the BRST differential parametrized by a constant two-component tensor, such that it leads to the deformation of the A∞-subalgebra of the quasiclassical LZ algebra. Altogether this gives a functor the category of VOA with a formal parameter to the category of A∞-algebras. The associated generalized Maurer-Cartan equation gives the analogue of the Yang-Mills equation for a wide class of VOAs. Applying this construction to an example of VOA generated by β - γ systems, we find a remarkable relation between the Courant algebroid and the homotopy algebra of the Yang-Mills theory.
Does the Milky Way Obey Spiral Galaxy Scaling Relations

It is crucial to understand how the Milky Way (MW), the galaxy we can study in the most intimate detail, fits in among other galaxies. Key considerations include the Tully–Fisher relation (TFR)—i.e., the tight correlation between luminosity (L) and rotational velocity (V rot)—and the three-dimensional luminosity–velocity–radius (LVR) scaling relation. Several past studies have characterized the MW as a 1–1.5σ outlier to the TFR. This study re-examines such comparisons using new estimates of MW properties that are robust to many of the systematic uncertainties that have been a problem in the past and are based on assumptions consistent with those used for other spiral galaxies. Comparing to scaling relations derived from modern extragalactic data, we find that our Galaxy's properties are in excellent agreement with TFRs defined using any Sloan Digital Sky Survey-filter absolute magnitude, stellar mass, or baryonic mass as the L proxy. We next utilize disk scale length (R d) measurements to extend this investigation to the LVR relation. Here we find that our Galaxy lies farther from the relation than ~90% of other spiral galaxies, yielding ~9.5σ evidence that it is unusually compact for its L and V rot (based on MW errors alone), a result that holds for all of the L proxies considered. The expected R d for the MW from the LVR relation is ~5 kpc, nearly twice as large as the observed value, with error estimates placing the two in tension at the ~1.4σ level. The compact scale length of the Galactic disk could be related to other ways in which the MW has been found to be anomalous.
MINIMAL ELECTROWEAK SYMMETRY BREAKING MODEL IN EXTRA DIMENSIONS

We show that if the Standard Model gauge fields and fermions propagate in extra dimenions, a composite Higgs field with the correct quantum number can arise naturally as a bound state due to the strong gauge interactions in higher dimensions. The top quark mass and the Higgs mass can be predicted from the infrared fixed points of the renormalization group equations. The top quark mass is in good agreement with the experimental value, and the Higgs boson mass is predicted to be ~ 200GeV. There may be some other light bound states which could be observed at upcoming collider experiments.
An optimal resource allocation with frequency reuse in cellular networks

In this paper, we introduce a novel approach for optimal resource allocation with frequency reuse for users with elastic and inelastic traffic in cellular networks. In our model, we represent users' applications running on different user equipments (UE)s by logarithmic and sigmoidal-like utility functions. We applied utility proportional fairness allocation policy, i.e. the resources are allocated among users with fairness in utility percentage of the application running on each mobile station. Our objective is to allocate the cellular system resources to mobile users optimally from a multi-cell network. In our model, a minimum quality-of-service (QoS) is guaranteed to every user subscribing for the mobile service with priority given to users with real-time applications. We prove that the novel resource allocation optimization problem with frequency reuse is convex and therefore the optimal solution is tractable. We present a distributed algorithm to allocate the resources optimally from Mobility Management Entity (MME) to evolved NodeBs' (eNodeB)s sectors. Finally, we present the simulation results for the performance of our rate allocation algorithm.
Thin discs, thick discs and transition zones

Accretion onto a compact object must occur through a disc when the material has some initial angular momentum. Thin discs and the thicker low radiative efficiency accretion flows (LRAFs) are solutions to this problem that have been widely studied and applied. This is an introduction to these accretion flows within the context of X-ray binaries and cataclysmic variables.
Overview of the Tevatron collider complex: goals, operations and performance

For more than two decades the Tevatron proton-antiproton collider was the centerpiece of the world's high energy physics program. The collider was arguably one of the most complex research instruments ever to reach the operation stage and is widely recognized for numerous physics discoveries and for many technological breakthroughs. In this article we outline the historical background that led to the construction of the Tevatron Collider, the strategy applied to evolution of performance goals over the Tevatron's operational history, and briefly describe operations of each accelerator in the chain and achieved performance.
A Strong Pockels Effect in Integrated Photonic Circuits

We enable a new class of electro-optic components based on a strong Pockels effect (>900 pm/V) in photonic integrated circuits. Integration concepts and examples of high-speed electro-optic modulators and ultra-low power tuning elements are discussed.
Ultra-light Dark Matter Is Incompatible with the Milky Way’s Dwarf Satellites

The density profiles of dwarf galaxies are a highly varied set. If the dark matter is an ultra-light particle such as axions, then simulations predict a distinctive and unique profile. If the axion mass is large enough to fit the ultra-faint dwarf (UFD) satellites($m\gtrapprox 10^{-21}$ eV), then the models do not fit the density profile of Fornax and Sculptor and are ruled out by more than $3-\sigma$ confidence. If the axion mass is in the mass range that can fit mass profiles of Fornax and Sculptor dwarf spheroidals, then its extended profile implies enormous masses ($\approx10^{11}-10^{12}M_{\odot}$) for the UFDs. These large masses for the UFDS are ruled out by more than $3-\sigma$ confidence by dynamical friction arguments. The tension would increase further considering star formation histories and stellar masses of the UFDs. Unless future ultra-light dark matter (ULDM) simulations with baryonic feedback show a significant change in the density structure of the halos, the current data is incompatible with the ULDM scenario. Relaxing the slope constraint from classical dwarf galaxies would lead to excluding ULDM with mass less than $6\times10^{-22}$ eV.
Electromagnetic Signatures of Neutron Star Mergers in the Advanced LIGO Era

The mergers of binaries containing neutron stars and stellar-mass black holes are among the most promising sources for direct detection in gravitational waves by the interferometers Advanced LIGO and Virgo over the next few years. The concurrent detection of electromagnetic emission from these events would greatly enhance the scientific return of these discoveries. We review the state of the art in modeling the electromagnetic signal of neutron star binary mergers across different phases of the merger and multiple wavelengths. We focus on those observables that provide the most sensitive diagnostics of the merger physics and the contribution to the synthesis of rapid neutron capture (r-process) elements in the Galaxy. We also outline expected future developments on the observational and theoretical sides of this rapidly evolving field.
A Jørgensen–Thurston theorem for homomorphisms

We provide a description of the structure of the set of homomorphisms from a finitely generated group to any torsion-free (3‐dimensional) Kleinian group with uniformly bounded finite covolume. This is analogous to the Jorgensen‐Thurston Theorem in hyperbolic geometry. 57M07; 57M50, 20F65
Multi-modal Predictive Models of Diabetes Progression

With the increasing availability of wearable devices, continuous monitoring of individuals' physiological and behavioral patterns has become significantly more accessible. Access to these continuous patterns about individuals' statuses offers an unprecedented opportunity for studying complex diseases and health conditions such as type 2 diabetes (T2D). T2D is a widely common chronic disease that its roots and progression patterns are not fully understood. Predicting the progression of T2D can inform timely and more effective interventions to prevent or manage the disease. In this study, we have used a dataset related to 63 patients with T2D that includes the data from two different types of wearable devices worn by the patients: continuous glucose monitoring (CGM) devices and activity trackers (ActiGraphs). Using this dataset, we created a model for predicting the levels of four major biomarkers related to T2D after a one-year period. We developed a wide and deep neural network and used the data from the demographic information, lab tests, and wearable sensors to create the model. The deep part of our method was developed based on the long short-term memory (LSTM) structure to process the time-series dataset collected by the wearables. In predicting the patterns of the four biomarkers, we have obtained a root mean square error of ±1.67% for HBA1c, ±6.22 mg/dl for HDL cholesterol, ±10.46 mg/dl for LDL cholesterol, and ±18.38 mg/dl for Triglyceride. Compared to existing models for studying T2D, our model offers a more comprehensive tool for combining a large variety of factors that contribute to the disease.
Impact of domain anisotropy on the inverse cascade in geostrophic turbulent convection

The effect of domain anisotropy on the inverse cascade occurring within the geostrophic turbulence regime of rapidly rotating Rayleigh–Benard convection is investigated. In periodic domains with square cross-section in the horizontal, a domain-filling dipole state is present. For rectangular periodic domains, a Kolmogorov-like flow parallel to the short side and consisting of a periodic array of alternating unidirectional jets with embedded vortices is observed, together with an underlying weak meandering transverse jet. Similar transitions occurring in weakly dissipative two-dimensional flows driven by externally imposed small-amplitude noise and in classical hydrostatic geostrophic turbulence are a consequence of inviscid conservation of energy and potential enstrophy, and can be understood using statistical mechanics considerations. Rotating Rayleigh–Benard convection represents an important three-dimensional system with only one inviscid invariant which nonetheless exhibits large-scale structures driven by intrinsically generated fluctuations.
Dynamic Load Balancing for Compressible Multiphase Turbulence

CMT-nek is a new scientific application for performing high fidelity predictive simulations of particle laden explosively dispersed turbulent flows. CMT-nek involves detailed simulations, is compute intensive and is targeted to be deployed on exascale platforms. The moving particles are the main source of load imbalance as the application is executed on parallel processors. In a demonstration problem, all the particles are initially in a closed container until a detonation occurs and the particles move apart. If all processors get an equal share of the fluid domain, then only some of the processors get sections of the domain that are initially laden with particles, leading to disparate load on the processors. In order to eliminate load imbalance in different processors and to speedup the makespan, we present different load balancing algorithms for CMT-nek on large scale multicore platforms consisting of hundred of thousands of cores. The detailed process of the load balancing algorithms are presented. The performance of the different load balancing algorithms are compared and the associated overheads are analyzed. Evaluations on the application with and without load balancing are conducted and these show that with load balancing, simulation time becomes faster by a factor of up to 9.97.
Estimating causal moderation effects with randomized treatments and non‐randomized moderators

Researchers are often interested in analyzing conditional treatment effects. One variant of this is "causal moderation," which implies that intervention upon a third (moderator) variable would alter the treatment effect. This study considers the conditions under which causal moderation can be identified and presents a generalized framework for estimating causal moderation effects given randomized treatments and non-randomized moderators. As part of the estimation process, it allows researchers to implement their preferred method of covariate adjustment, including parametric and non-parametric methods, or alternative identification strategies of their choosing. In addition, it provides a set-up whereby sensitivity analysis designed for the average-treatment-effect context can be extended to the moderation context. To illustrate the methods, the study presents two applications: one dealing with the effect of using the term "welfare" to describe public assistance in the United States, and one dealing with the effect of asylum seekers' religion on European attitudes toward asylum seekers.
3C 48: Stellar Populations and the Kinematics of Stars and Gas in the Host Galaxy*

We present deep Keck LRIS spectroscopy of the host galaxy of 3C 48. Our observations at various slit positions sample the different luminous components near the quasar, including the apparent tidal tail to the northwest and several strong emission line regions. By fitting Bruzual & Charlot population synthesis models to our spectra, we obtain ages for the most recent major episodes of star formation in various parts of the host galaxy covered by our slits. There is vigorous current star formation in regions just northeast and southeast of the quasar and post-starburst regions with ages up to ~108 yr in other parts of the host galaxy, but most of the northwest tidal tail shows no sign of significant recent star formation. We use these model fits, together with the kinematics of the stars and gas, to outline a plausible evolutionary history for the host galaxy, its recent starburst activity, the triggering of the quasar, and the interaction of the radio jet with the ambient gas. There is strong evidence that the 3C 48 host is an ongoing merger, and that it is probably near the peak of its starburst activity. Nevertheless, the quasar itself seems to suffer little extinction, perhaps because we are viewing it along a particularly favorable line of sight.
Physics of Non-Gaussian Fields and the Cosmological Genus Statistic

We report a technique to calculate the impact of distinct physical processes inducing non-Gaussianity on the cosmological density field. A natural decomposition of the cosmic genus statistic into an orthogonal polynomial sequence allows complete expression of the scale-dependent evolution of the topology of large-scale structure, in which effects including galaxy bias, nonlinear gravitational evolution, and primordial non-Gaussianity may be delineated. The relationship of this decomposition to previous methods for analyzing the genus statistic is briefly considered and the following applications are made: (1) the expression of certain systematics affecting topological measurements, (2) the quantification of broad deformations from Gaussianity that appear in the genus statistic as measured in the Horizon Run simulation, and (3) the study of the evolution of the genus curve for simulations with primordial non-Gaussianity. These advances improve the treatment of flux-limited galaxy catalogs for use with this measurement and further the use of the genus statistic as a tool for exploring non-Gaussianity.
Cryo-electron microscopy structures of pyrene-labeled ADP-Pi- and ADP-actin filaments

Since the fluorescent reagent N-(1-pyrene)iodoacetamide was first used to label skeletal muscle actin in 1981, the pyrene-labeled actin has become the most widely employed tool to measure the kinetics of actin polymerization and the interaction between actin and actin-binding proteins. Here we report high-resolution cryo-electron microscopy structures of actin filaments with N-1-pyrene conjugated to cysteine 374 and either ADP (3.2 A) or ADP-phosphate (3.0 A) in the active site. Polymerization buries pyrene in a hydrophobic cavity between subunits along the long-pitch helix with only minor differences in conformation compared with native actin filaments. These structures explain how polymerization increases the fluorescence 20-fold, how myosin and cofilin binding to filaments reduces the fluorescence, and how profilin binding to actin monomers increases the fluorescence. For almost forty years, N-(1-pyrene) iodoacetamide has been used to label actin at C374, but the mechanisms of the fluorescence changes are still unknown due to the lack of structural information. Here authors provide cryo-EM structures of actin filaments with N-1-pyrene conjugated to cysteine 374 and either ADP or ADP-phosphate in the active site.
The Evolution of Viscous Inclined Disks in Axisymmetric and Triaxial Galaxies

We have used a set of equations developed by Pringle to follow the evolution of a viscous twisted disk in a galaxy-like potential that is stationary or tumbling relative to inertial space. In an axisymmetric potential, the disk settles to the equatorial plane at a rate largely determined by the coefficient ν2, associated with shear perpendicular to the local disk plane. If the disk is initially close to the galaxy equator, then the rate at which the inclination decays is well described by the analytic formula of Steiman-Cameron & Durisen; in a highly inclined disk, "breaking waves" of curvature steepen as they propagate through the disk, rendering the numerical treatment untrustworthy. In a triaxial potential that is stationary in inertial space, settling is faster than in an oblate or prolate galaxy, since the disk twists simultaneously about two perpendicular axes. If the figure of the potential tumbles about one of its principal axes, the viscous disk can settle into a warped state in which gas at each radius follows a stable tilted orbit, which precesses in such a way as to remain stationary relative to the underlying galaxy.
Regularity underlies erratic population abundances in marine ecosystems

The abundance of a species' population in an ecosystem is rarely stationary, often exhibiting large fluctuations over time. Using historical data on marine species, we show that the year-to-year fluctuations of population growth rate obey a well-defined double-exponential (Laplace) distribution. This striking regularity allows us to devise a stochastic model despite seemingly irregular variations in population abundances. The model identifies the effect of reduced growth at low population density as a key factor missed in current approaches of population variability analysis and without which extinction risks are severely underestimated. The model also allows us to separate the effect of demographic stochasticity and show that single-species growth rates are dominantly determined by stochasticity common to all species. This dominance—and the implications it has for interspecies correlations, including co-extinctions—emphasizes the need for ecosystem-level management approaches to reduce the extinction risk of the individual species themselves.
Open-Source Synthesizable Analog Blocks for High-Speed Link Designs: 20-GS/s 5b ENOB Analog-to-Digital Converter and 5-GHz Phase Interpolator

Using digital standard cells and digital place-and-route (PnR) tools, we created a 20 GS/s, 8-bit analog-to-digital converter (ADC) for use in high-speed serial link applications with an ENOB of 5.6, a DNL of 0.96 LSB, and an INL of 2.39 LSB, which dissipated 175 mW in 0.102 mm2 in a 16nm technology. The design is entirely described by HDL so that it can be ported to other processes with minimal effort and shared as open source.
LIMITS ON ALPHA PARTICLE TEMPERATURE ANISOTROPY AND DIFFERENTIAL FLOW FROM KINETIC INSTABILITIES: SOLAR WIND OBSERVATIONS

Previous studies have shown that the observed temperature anisotropies of protons and alpha particles in the solar wind are constrained by theoretical thresholds for pressure and anisotropy driven instabilities such as the Alfven/ion-cyclotron (A/IC) and fast-magnetosonic/whistler (FM/W) instabilities. In this Letter, we use a long period of in situ measurements provided by the Wind spacecraft's Faraday cups to investigate the combined constraint on the alpha proton differential flow velocity and the alpha particle temperature anisotropy due to A/IC and FM/W instabilities. We show that the majority of the data are constrained to lie within the region of parameter space in which A/IC and FM/W waves are either stable or have extremely low growth rates. In the minority of observed cases in which the growth rate of the A/IC (FM/W) instability is comparatively large, we find relatively higher values of T ⊥α/T ⊥p (T ∥α/T ∥p ) when the alpha proton differential flow velocity is small, where T ⊥α and T ⊥p (T ∥α and T ∥p ) are the perpendicular (parallel) temperatures of alpha particles and protons. We conjecture that this observed feature might arise from preferential alpha particle heating which can drive the alpha particles beyond the instability thresholds.
Role of intrinsic motivation in user interface design to enhance worker performance in Amazon MTurk

Biologists and scientists have been tackling the problem of marine life monitoring and fish stock estimation for many years now. Efforts are now directed to move towards non-intrusive methods, by utilizing specially designed underwater robots to collect images of the marine population. Training machine learning algorithms on the images collected, we can now estimate the population. This in turn helps to impose regulations to control overfishing. To train these models, however, we need annotated images. Annotation of large sets of images collected over a decade is quite challenging. Hence, we resort to Amazon Mechanical Turk (MTurk), a crowdsourcing platform, for the image annotation task. Although it is fast to get work done in MTurk, the work obtained is often of poor quality. This work aims to understand the human factors in designing Human Intelligence Tasks (HITs), from the perspective of the Self-Determination Theory. Applying elements from the theory, we design an HIT to increase the competence and motivation of the workers. Within our experimental framework, we find that the new interface significantly improves the accuracy of worker performance.
Effect of Ion-Neutral Collisions in Simulations of Emerging Active Regions

We present results of 2.5D numerical simulations of the emergence of sub-surface magnetic flux into the solar atmosphere, with emerging flux regions ranging from 1018 to 1021 Mx, representing both ephemeral and active regions. We include the presence of neutral hydrogen in the governing equations, improve upon previous models by including the ionization in the equation of state, and use a more realistic convection zone model. We find that ionization and recombination of plasma during the rise of a convection zone flux tube reduces the rise speed of the tube's axis. The presence of neutral hydrogen allows the effective flow of mass across field lines, by the addition of a Pedersen resistivity to the generalized Ohm's law, which dissipates current perpendicular to the magnetic field. This causes an increase of up to 10% in the amount of magnetic in-plane flux supplied to the corona and a reduction of up to 89% in the amount of sub-surface plasma brought up into the corona. However, it also reduces the amount of free magnetic energy supplied to the corona, and thus does not positively affect the likelihood of creating unstable coronal structures.
Interstellar Polarization in M31

The wavelength dependence of interstellar polarization due to dust in M31 has been observed along four sight lines. Only one sight line had been measured previously. The globular clusters, S78, S150, S233, and Baade 327 were used as point sources to probe the interstellar dust in M31. The Serkowski law produces good fits for all the sight lines, although the relationship between K and λmax may be different from that found in the Galaxy. The results of this study imply that the slope K/λmax may be significantly larger in M31. The Serkowski curves are significantly narrower than those of the same λmax in the Galaxy and may require extreme modifications to the size distributions of silicate particles. The fits for the four sight lines reveal values of λmax ranging from 4800 to 5500 A. These are consistent with average values of λmax measured in the Galaxy and the Magellanic Clouds. The range measured for M31 corresponds to RV values of 2.7–3.1. The range in RV seen in the Galaxy is 2.5–5.5 implying, for this small sample, that the average size of interstellar grains in M31 is typically smaller than that seen for Galactic grains if the nature of the grains is the same. Also, the polarization efficiency for these sight lines is large, although some bias is expected since sight lines known to have significant interstellar polarization were selected for the sample.
Effective string tension and renormalizability: string theory in a noncommutative space

We show that the one loop amplitudes of open and closed string theory in a constant background two-form tensor field are characterized by an effective string tension larger than the fundamental string tension, and by the appearance of antisymmetric and symmetric noncommutativity parameters. We derive the form of the phase functions normalizing planar and nonplanar tachyon scattering amplitudes in this background, verifying the decoupling of the closed string sector in the regime of infinite momentum transfer. We show that the functional dependence of the phase functions on the antisymmetric star product of external momenta permits interpretation as a finite wavefunction renormalization of vertex operators in the open string sector. Using world-sheet duality we clarify the regimes of finite and zero momentum transfer between boundaries, demonstrating the existence of poles in the nonplanar amplitude when the momentum transfer equals the mass of an on-shell closed string state. Neither noncommutativity parameter has any impact on the renormalizability of open and closed string theory in the wilsonian sense. We comment on the relationship to noncommutative scalar field theory and the UV-IR correspondence.
Parallel chip-firing on the complete graph: Devil's staircase and Poincaré rotation number

We study how parallel chip-firing on the complete graph K n changes behavior as we vary the total number of chips. Surprisingly, the activity of the system, defined as the average number of firings per time step, does not increase smoothly in the number of chips; instead it remains constant over long intervals, punctuated by sudden jumps. In the large n limit we find a ‘devil’s staircase’ dependence of activity on the number of chips. The proof proceeds by reducing the chip-firing dynamics to iteration of a self-map of the circle S 1 , in such a way that the activity of the chip-firing state equals the Poincare rotation number of the circle map. The stairs of the devil’s staircase correspond to periodic chip-firing states of small period.
Generalized Number Theoretic Spin Chain-Connections to Dynamical Systems and Expectation Values

We generalize the number theoretic spin chain, a one-dimensional statistical model based on the Farey fractions, by introducing a parameter \(x \geqslant 0\). This allows us to write recursion relations in the length of the chain. These relations are closely related to the Lewis three-term equation, which is useful in the study of the Selberg ζ-function. We then make use of these relations and spin orientation transformations. We find a simple connection with the transfer operator of a model of intermittency in dynamical systems. In addition, we are able to calculate certain spin expectation values explicitly in terms of the free energy or correlation length. Some of these expectation values appear to be directly connected with the mechanism of the phase transition
Pressure Hessian and viscous contributions to velocity gradient statistics based on Gaussian random fields

Understanding the non-local pressure contributions and viscous effects on the small-scale statistics remains one of the central challenges in the study of homogeneous isotropic turbulence. Here we address this issue by studying the impact of the pressure Hessian as well as viscous diffusion on the statistics of the velocity gradient tensor in the framework of an exact statistical evolution equation. This evolution equation shares similarities with earlier phenomenological models for the Lagrangian velocity gradient tensor evolution, yet constitutes the starting point for a systematic study of the unclosed pressure Hessian and viscous diffusion terms. Based on the assumption of incompressible Gaussian velocity fields, closed expressions are obtained as the results of an evaluation of the characteristic functionals. The benefits and shortcomings of this Gaussian closure are discussed, and a generalization is proposed based on results from direct numerical simulations. This enhanced Gaussian closure yields, for example, insights on how the pressure Hessian prevents the finite-time singularity induced by the local self-amplification and how its interaction with viscous effects leads to the characteristic strain skewness phenomenon.
Physically informed artificial neural networks for atomistic modeling of materials.

Large-scale atomistic computer simulations of materials heavily rely on interatomic potentials predicting the energy and Newtonian forces on atoms. Traditional interatomic potentials are based on physical intuition but contain few adjustable parameters and are usually not accurate. The emerging machine-learning (ML) potentials achieve highly accurate interpolation within a large DFT database but, being purely mathematical constructions, suffer from poor transferability to unknown structures. We propose a new approach that can drastically improve the transferability of ML potentials by informing them of the physical nature of interatomic bonding. This is achieved by combining a rather general physics-based model (analytical bond-order potential) with a neural-network regression. This approach, called the physically informed neural network (PINN) potential, is demonstrated by developing a general-purpose PINN potential for Al. We suggest that the development of physics-based ML potentials is the most effective way forward in the field of atomistic simulations. Traditional machine learning potentials suffer from poor transferability to unknown structures. Here the authors present an approach to improve the transferability of machine-learning potentials by including information on the physical nature of interatomic bonding.
Structure on Interplanetary Shock Fronts: Type II Radio Burst Source Regions

We present in situ observations of the source regions of interplanetary (IP) type II radio bursts, using data from the Wind spacecraft during the period 1996-2002. We show the results of this survey, as well as in-depth analysis of several individual events. Each event analyzed in detail is associated with an interplanetary coronal mass ejection (ICME) and an IP shock driven by the ICME. Immediately prior to the arrival of each shock, electron beams along the interplanetary magnetic field (IMF) and associated Langmuir waves are detected, implying magnetic connection to a quasi-perpendicular shock front acceleration site. These observations are analogous to those made in the terrestrial foreshock region, indicating that a similar foreshock region exists on IP shock fronts. The analogy suggests that the electron acceleration process is a fast Fermi process, and this suggestion is borne out by loss cone features in the electron distribution functions. The presence of a foreshock region requires nonplanar structure on the shock front. Using Wind burst mode data, the foreshock electrons are analyzed to estimate the dimensions of the curved region. We present the first measurement of the lateral, shock-parallel scale size of IP foreshock regions. The presence of these regions on IP shock fronts can explain the fine structure often seen in the spectra of type II bursts.
Discrete flux and velocity fields of probability and their global maps in reaction systems.

Stochasticity plays important roles in reaction systems. Vector fields of probability flux and velocity characterize time-varying and steady-state properties of these systems, including high probability paths, barriers, checkpoints among different stable regions, as well as mechanisms of dynamic switching among them. However, conventional fluxes on continuous space are ill-defined and are problematic when at the boundaries of the state space or when copy numbers are small. By re-defining the derivative and divergence operators based on the discrete nature of reactions, we introduce new formulations of discrete fluxes. Our flux model fully accounts for the discreetness of both the state space and the jump processes of reactions. The reactional discrete flux satisfies the continuity equation and describes the behavior of the system evolving along directions of reactions. The species discrete flux directly describes the dynamic behavior in the state space of the reactants such as the transfer of probability mass. With the relationship between these two fluxes specified, we show how to construct time-evolving and steady-state global flow-maps of probability flux and velocity in the directions of every species at every microstate and how they are related to the outflow and inflow of probability fluxes when tracing out reaction trajectories. We also describe how to impose proper conditions enabling exact quantification of flux and velocity in the boundary regions, without the difficulty of enforcing artificial reflecting conditions. We illustrate the computation of probability flux and velocity using three model systems, namely, the birth-death process, the bistable Schlogl model, and the oscillating Schnakenberg model.
Surface segregation and the Al problem in GaAs quantum wells

Low-defect two-dimensional electron systems (2DESs) are essential for studies of fragile many-body interactions that only emerge in nearly-ideal systems. As a result, numerous efforts have been made to improve the quality of modulation-doped ${\mathrm{Al}}_{x}{\mathrm{Ga}}_{1\ensuremath{-}x}\mathrm{As}$/GaAs quantum wells (QWs), with an emphasis on purifying the source material of the QW itself or achieving better vacuum in the deposition chamber. However, this approach overlooks another crucial component that comprises such QWs, the ${\mathrm{Al}}_{x}{\mathrm{Ga}}_{1\ensuremath{-}x}\mathrm{As}$ barrier. Here we show that having a clean Al source and hence a clean barrier is instrumental to obtain a high-quality GaAs 2DES in a QW. We observe that the mobility of the 2DES in GaAs QWs declines as the thickness or Al content of the ${\mathrm{Al}}_{x}{\mathrm{Ga}}_{1\ensuremath{-}x}\mathrm{As}$ barrier beneath the QW is increased, which we attribute to the surface segregation of oxygen atoms that originate from the Al source. This conjecture is supported by the improved mobility in the GaAs QWs as the Al cell is cleaned out by baking.
Exotic quantum statistics and thermodynamics from a number-conserving theory of Majorana fermions

We propose a closed form for the statistical distribution of non-interacting Majorana fermions at low temperature. Majorana particles often appear in the contemporary many-body literature in the Kitaev, Fu-Kane, or Sachdev-Ye-Kitaev models, where the Majorana condition of self-conjugacy immediately results in nonconserved particle number, non-trivial braiding statistics, and the absence of a noninteracting limit. We deviate from this description and instead consider a gas of noninteracting, spin-1/2 Majorana fermions that obey the spin-statistics theorem via imposing a condensed matter analog of momentum conservation. This allows us to build a quantum statistical theory of the Majorana system in the low temperature, low density limit without the need to account for strong fluctuations in the particle number. A combinatorial analysis leads to a configurational entropy which deviates from the fermionic result with an increasing number of available microstates. A number-conserving Majorana distribution function is derived which shows signatures of a sharply-defined Fermi surface at finite temperatures. Such a distribution is then re-derived from a microscopic model in the form of a modified Kitaev chain with a bosonic pair interaction. The thermodynamics of this free Majorana system is found to be nearly identical to that of a free Fermi gas, except now distinguished by a two-fold ground state degeneracy and, subsequently, a residual entropy at zero temperature. Despite clear differences with the anyonic or Sachdev-Ye-Kitaev models, we nevertheless find surprising agreement between our theory and experimental signatures of Majorana excitations in several materials. Experimental realization of our exactly solvable model is also discussed in the realm of astrophysical and high-energy phenomena.
Measuring Star Formation Histories, Distances, and Metallicities with Pixel Color-Magnitude Diagrams. II. Applications to Nearby Elliptical Galaxies

We present spatially-resolved measurements of star formation histories (SFHs), metallicities, and distances in three nearby elliptical galaxies and the bulge of M31 derived using the pixel color-magnitude diagram (pCMD) technique. We compute pCMDs from archival $\textit{HST}$ photometry of M87, M49, NGC 3377 and M31, and fit the data using the new code $\texttt{PCMDPy}$. We measure distances to each system that are accurate to $\sim 10\%$. The recovered non-parametric SFHs place reasonable ($\pm 1$ dex) constraints on the recent (< 2 Gyr) star formation in M31 and NGC 3377, both of which show evidence of inside-out growth. The SFHs in M87 and M49 are constrained only at the oldest ages. The pCMD technique is a promising new avenue for studying the evolutionary history of the nearby universe, and is highly complementary to existing stellar population modeling techniques.
Predictive liability models and visualizations of high dimensional retail employee data

Employee theft and dishonesty is a major contributor to loss in the retail industry. Retailers have reported the need for more automated analytic tools to assess the liability of their employees. In this work, we train and optimize several machine learning models for regression prediction and analysis on this data, which will help retailers identify and manage risky employees. Since the data we use is very high dimensional, we use feature selection techniques to identify the most contributing factors to an employee's assessed risk. We also use dimension reduction and data embedding techniques to present this dataset in a easy to interpret format.
Nonaffine deformation under compression and decompression of a flow-stabilized solid

Understanding the particle-scale transition from elastic deformation to plastic flow is central to making predictions about the bulk material properties and response of disordered materials. To address this issue, we perform experiments on flow-stabilized solids composed of micron-scale spheres within a microfluidic channel, in a regime where particle inertia is negligible. Each solid heap exists within a stress field imposed by the flow, and we track the positions of particles in response to single impulses of fluid-driven compression or decompression. We find that the resulting deformation field is well-decomposed into an affine field, with a constant strain profile throughout the solid, and a non-affine field. The magnitude of this non-affine response decays with the distance from the free surface in the long-time limit, suggesting that the distance from jamming plays a significant role in controlling the length scale of plastic flow. Finally, we observe that compressive pulses create more rearrangements than decompressive pulses, an effect that we quantify using the statistic for non-affine motion. Unexpectedly, the time scale for the compression response is shorter than for decompression at the same strain (but unequal pressure), providing insight into the coupling between deformation and cage-breaking.
Neutrinos, supernovae, and the origin of the heavy elements

Stars of $\sim~8$-$100\,M_\odot$ end their lives as core-collapse supernovae (SNe).In the process they emit a powerful burst of neutrinos, produce a variety of elements, and leave behindeither a neutron star or a black hole. The wide mass range for SN progenitors results in diverseneutrino signals, explosion energies, and nucleosynthesis products. A major mechanism to producenuclei heavier than iron is rapid neutron capture, or the $r$ process. This process may be connectedto SNe in several ways. A brief review is presented on current understanding of neutrino emission,explosion, and nucleosynthesis of SNe.
Studying Two Dimensional Systems With the Density Matrix Renormalization Group

The density matrix renormalization group (DMRG) is one of the most powerful numerical methods for studying two-dimensional quantum lattice systems, despite a perception that it is only suitable for one dimension. Reviewing past applications of DMRG in 2D demonstrates its success in treating a wide variety of problems, although it remains underutilized in this context. We present techniques for performing cutting-edge 2D DMRG studies including methods for ensuring convergence, extrapolating finite-size data, and extracting gaps and excited states. Finally, we consider a selection of recently developed 2D tensor network methods and compare the performance of one of these to 2D DMRG.
Frontier Fields: High-redshift Predictions and Early Results

The Frontier Fields program is obtaining deep Hubble and Spitzer Space Telescope images of new "blank" fields and nearby fields gravitationally lensed by massive galaxy clusters. The Hubble images of the lensed fields are revealing nJy sources (AB mag > 31), the faintest galaxies yet observed. The full program will transform our understanding of galaxy evolution in the first 600 million years (z > 9). Previous programs have yielded a dozen or so z > 9 candidates, including perhaps fewer than expected in the Ultra Deep Field and more than expected in shallower Hubble images. In this paper, we present high-redshift (z > 6) number count predictions for the Frontier Fields and candidates in three of the first Hubble images. We show the full Frontier Fields program may yield up to ~70 z > 9 candidates (~6 per field). We base this estimate on an extrapolation of luminosity functions observed between 4 9. We defer quantitative analysis of the z > 9 deficit (including detection completeness estimates) to future work including additional data. At these redshifts, cosmic variance (field-to-field variation) is expected to be significant (greater than ±50%) and include clustering of early galaxies formed in overdensities. The full Frontier Fields program will significantly mitigate this uncertainty by observing six independent sightlines each with a lensing cluster and nearby blank field.
Exotic iterated Dehn twists

Let M D T L be the cotangent bundle of a closed connected oriented n–manifold L with its standard symplectic structure !M D d M . This is a Liouville manifold, modeled at infinity on the positive part of the symplectization of the contact sphere bundle @1M D S L. Let Symp.M / be the group of symplectic automorphisms which are of contact type at infinity, or equivalently such that M M is closed and has compact support. Fix some point q 2L. Write F D T q L M for the cotangent fiber at that point, and K D S q LD @1F @1M for the corresponding sphere fiber. Let