cssi/SciSciGPT-SciSciNet huggingface dataset:
Geolocation of Multiple Noncooperative Emitters Using Received Signal Strength: Sparsity, Resolution, and Detectability

In this paper we investigate the problem of locating multiple non-cooperative radio frequency (RF) emitters using only received signal strength (RSS) data. We assume that the number of emitters is unknown and that individual emitters cannot be distinguished in the RSS data. Moreover, we assume that the environment in which the data has been collected has not been mapped or “fingerprinted” by the prior collection of RSS data. Our goal is to use knowledge of the data noise level, sensor geometry, signal attenuation model, and other variables to quantify the limiting resolution that can be obtained with this type of data, and to determine the lowest power emitters that can be detected. We use this analysis to develop an efficient algorithm for estimating the number of emitters, their locations, and their transmit powers. We approach this by formulating the recovery problem as one of sparse approximation or compressed sensing. We illustrate the reasonableness of our assumptions and conclusions with both simulated and real data.
Exciton–phonon interactions in nanocavity-integrated monolayer transition metal dichalcogenides

Cavity-integrated transition metal dichalcogenide (TMDCs) excitons have recently emerged as a promising platform to study strong light–matter interactions and related cavity quantum electrodynamics phenomena. Although this exciton-cavity system is typically modeled as coupled harmonic oscillators, to account for the rich solid-state environment, the effect of exciton–phonon interaction needs to be incorporated. We model the system by including a phenomenological deformation potential for exciton–phonon interactions and we elucidate the experimentally measured preferential coupling of the excitonic photoluminescence to the cavity modes red-detuned with respect to the exciton resonance. Furthermore, we predict and experimentally confirm the temperature dependence of this preferential coupling. By accurately capturing the exciton–phonon interaction, our model illuminates the potential of cavity-integrated TMDCs for the development of low-power classical and quantum technologies.
A Semi-Automatic Method for Efficient Detection of Stories on Social Media

Twitter has become one of the main sources of news for many people. As real-world events and emergencies unfold, Twitter is abuzz with hundreds of thousands of stories about the events. Some of these stories are harmless, while others could potentially be life-saving or sources of malicious rumors. Thus, it is critically important to be able to efficiently track stories that spread on Twitter during these events. In this paper, we present a novel semi-automatic tool that enables users to efficiently identify and track stories about real-world events on Twitter. We ran a user study with 25 participants, demonstrating that compared to more conventional methods, our tool can increase the speed and the accuracy with which users can track stories about real-world events.
Co-option of the lineage-specific LAVA retrotransposon in the gibbon genome.

Co-option of transposable elements (TEs) to become part of existing or new enhancers is an important mechanism for evolution of gene regulation. However, contributions of lineage-specific TE insertions to recent regulatory adaptations remain poorly understood. Gibbons present a suitable model to study these contributions as they have evolved a lineage-specific TE called LAVA (LINE-AluSz-VNTR-AluLIKE), which is still active in the gibbon genome. The LAVA retrotransposon is thought to have played a role in the emergence of the highly rearranged structure of the gibbon genome by disrupting transcription of cell cycle genes. In this study, we investigated whether LAVA may have also contributed to the evolution of gene regulation by adopting enhancer function. We characterized fixed and polymorphic LAVA insertions across multiple gibbons and found 96 LAVA elements overlapping enhancer chromatin states. Moreover, LAVA was enriched in multiple transcription factor binding motifs, was bound by an important transcription factor (PU.1), and was associated with higher levels of gene expression in cis. We found gibbon-specific signatures of purifying/positive selection at 27 LAVA insertions. Two of these insertions were fixed in the gibbon lineage and overlapped with enhancer chromatin states, representing putative co-opted LAVA enhancers. These putative enhancers were located within genes encoding SETD2 and RAD9A, two proteins that facilitate accurate repair of DNA double-strand breaks and prevent chromosomal rearrangement mutations. Co-option of LAVA in these genes may have influenced regulation of processes that preserve genome integrity. Our findings highlight the importance of considering lineage-specific TEs in studying evolution of gene regulatory elements.
Going by the numbers: Learning and modeling COVID-19 disease dynamics

The COrona VIrus Disease (COVID-19) pandemic caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV2) has resulted in a challenging number of infections and deaths worldwide. In order to combat the pandemic, several countries worldwide enforced mitigation measures in the forms of lockdowns, social distancing, and disinfection measures. In an effort to understand the dynamics of this disease, we propose a Long Short-Term Memory (LSTM) based model. We train our model on more than four months of cumulative COVID-19 cases and deaths. Our model can be adjusted based on the parameters in order to provide predictions as needed. We provide results at both the country and county levels. We also perform a quantitative comparison of mitigation measures in various counties in the United States based on the rate of difference of a short and long window parameter of the proposed LSTM model. The analyses provided by our model can provide valuable insights based on the trends in the rate of infections and deaths. This can also be of help for countries and counties deciding on mitigation and reopening strategies. We believe that the results obtained from the proposed method will contribute to societal benefits for a current global concern.
Directional Compliance in Obstacle-Aided Navigation for Snake Robots.

Snake robots have the potential to maneuver through tightly packed and complex environments. One challenge in enabling them to do so is the complexity in determining how to coordinate their many degrees-of-freedom to create purposeful motion. This is especially true in the types of terrains considered in this work: environments full of unmodeled features that even the best of maps would not capture, motivating us to develop closed-loop controls to react to those features. To accomplish this, this work uses proprioceptive sensing, mainly the force information measured by the snake robot's joints, to react to unmodeled terrain. We introduce a biologically-inspired strategy called directional compliance which modulates the effective stiffness of the robot so that it conforms to the terrain in some directions and resists in others. We present a dynamical system that switches between modes of locomotion to handle situations in which the robot gets wedged or stuck. This approach enables the snake robot to reliably traverse a planar peg array and an outdoor three-dimensional pile of rocks.
Obesity promotes glucocorticoid-dependent muscle atrophy in male C57BL/6J mice.

Glucocorticoids promote muscle atrophy by inducing a class of proteins called atrogenes, resulting in reductions in muscle size and strength. In this work, we evaluated whether a mouse model with pre-existing diet-induced obesity had altered glucocorticoid responsiveness. We observed that all animals treated with the synthetic glucocorticoid dexamethasone had reduced strength, but that obesity exacerbated this effect. These changes were concordant with more pronounced reductions in muscle size, particularly in Type II muscle fibers, and potentiated induction of atrogene expression in the obese mice relative to lean mice. Furthermore, we show that the reductions in lean mass do not fully account for the dexamethasone-induced insulin resistance observed in these mice. Together these data suggest that obesity potentiates glucocorticoid-induced muscle atrophy.
Resonance Raman Spectra of an O2-Binding H-NOX Domain Reveal Heme Relaxation upon Mutation

Resonance Raman and electronic absorption spectra were measured for the wild type Heme-Nitric oxide/OXygen binding domain from Thermoanaerobacter tengcongensis (Tt H-NOX WT) and three other Tt H-NOX proteins containing mutations at key conserved residues to determine the heme conformation in solution. The most dramatic changes in heme conformation occurred in the O2-bound forms, and the single Tt H-NOX P115A mutation was sufficient to generate a significant relaxation of the chromophore. Clear evidence of heme relaxation in the Tt H-NOX I5L, P115A, and I5L/P115A mutants in solution is demonstrated by the observation of reduced resonance Raman intensities for several out-of-plane low frequency modes (e.g., γ11, γ12, γ13, and γ15) in the 400-750 cm−1 region known to be sensitive to ruffling and saddling deformations, as well as increased vibrational frequencies for the core heme skeletal stretching modes, ν3, ν2, and ν10. In addition, all three mutants exhibited some degree of heme conformational heterogeneity based on several broad skeletal markers (e.g., ν10) in the high frequency region. These results are comparable to those observed by Olea et al. for Tt H-NOX P115A in crystal form, where four different heme structures were determined from a single unit cell. On the basis of the resonance Raman spectra, it is clear that the actual heme conformation for Tt H-NOX P115A in solution is considerably more relaxed than that of the WT protein, with increased flexibility within the protein pocket, allowing for rapid sampling of alternate conformations.
Conserved tryptophan mutation disrupts structure and function of immunoglobulin domain revealing unusual tyrosine fluorescence.

Immunoglobulin (Ig) domains are the most prevalent protein domain structure and share a highly conserved folding pattern; however, this structural family of proteins is also the most diverse in terms of biological roles and tissue expression. Ig domains vary significantly in amino acid sequence but share a highly conserved tryptophan in the hydrophobic core of this beta-stranded protein. Palladin is an actin binding and bundling protein that has five Ig domains and plays an important role in normal cell adhesion and motility. Mutation of the core tryptophan in one Ig domain of palladin has been identified in a pancreatic cancer cell line, suggesting a crucial role for this sole tryptophan in palladin Ig domain structure, stability, and function. We found that actin binding and bundling was not completely abolished with removal of this tryptophan despite a partially unfolded structure and significantly reduced stability of the mutant Ig domain as shown by circular dichroism investigations. In addition, this mutant palladin domain displays a tryptophan-like fluorescence attributed to an anomalous tyrosine emission at 341 nm. Our results indicate that this emission originates from a tyrosinate that may be formed in the excited ground state by proton transfer to a nearby aspartic acid residue. Furthermore, this study emphasizes the importance of tryptophan in protein structural stability and illustrates how tyrosinate emission contributions may be overlooked during the interpretation of the fluorescence properties of proteins.
A note on devising HDG+ projections on polyhedral elements

In this note, we propose a simple way of constructing HDG+ projections on polyhedral elements. The projections enable us to analyze the Lehrenfeld-Schoberl HDG (HDG+) methods in a very concise manner, and make many existing analysis techniques of standard HDG methods reusable for HDG+. The novelty here is an alternative way of constructing the projections without using $M$-decompositions as a middle step. This extends our previous results [S. Du and F.-J. Sayas, SpringerBriefs in Mathematics (2019)] (elliptic problems) and [S. Du and F.-J. Sayas, Math.~Comp.~89~(2020), 1745-1782] (elasticity) to polyhedral meshes.
On-chip optical parametric oscillation into the visible: generating red, orange, yellow, and green from a near-infrared pump

The on-chip generation of coherent, single-frequency laser light that can be tuned across the visible spectrum would help enable a variety of applications in spectroscopy, metrology, and quantum science. Recently, third-order optical parametric oscillation (OPO) in a microresonator has shown great promise as an efficient and scalable approach toward this end. However, considering visible light generation, so far only red light at 130THz of the visible spectrum, including red, orange, yellow, and green wavelengths. In particular, using an input pump laser that is scanned 5 THz in the near-infrared from 386 THz to 391 THz, the OPO output signal is tuned from the near-infrared at 395 THz to the visible at 528 THz, while the OPO output idler is tuned from the near-infrared at 378 THz to the infrared at 254 THz. The widest signal-idler separation of 274 THz is more than an octave in span and is the widest demonstrated for a nanophotonic OPO to date. More generally, our work shows how nonlinear nanophotonics can transform light from readily accessible compact near-infrared lasers to targeted visible wavelengths of interest.
Boundary Solutions of the Classical Yang--Baxter Equation

We define a new class of unitary solutions to the classical Yang--Baxter equation (CYBE). These ‘boundary solutions’ are those which lie in the closure of the space of unitary solutions of the modified classical Yang--Baxter equation (MCYBE). Using the Belavin--Drinfel'd classification of the solutions to the MCYBE, we are able to exhibit new families of solutions to the CYBE. In particular, using the Cremmer--Gervais solution to the MCYBE, we explicitly construct for all n ≥ 3 a boundary solution based on the maximal parabolic subalgebra of $${\mathfrak{s}}{\mathfrak{l}}\left( n \right)$$ obtained by deleting the first negative root. We give some evidence for a generalization of this result pertaining to other maximal parabolic subalgebras whose omitted root is relatively prime to n. We also give examples of nonboundary solutions for the classical simple Lie algebras.
Asymptotic Behavior and Stability of Mean Curvature Flow with a Conical End

Abstract If the initial hypersurface of an immortal mean curvature flow is asymptotic to a regular cone whose entropy is small, the flow will become asymptotically self-expanding. Moreover, the expander that gives rise to the limiting flow is asymptotically stable as an equilibrium solution of the normalized mean curvature flow.
SparseRT: Accelerating Unstructured Sparsity on GPUs for Deep Learning Inference

In recent years, there has been a flurry of research in deep neural network pruning and compression. Early approaches prune weights individually. However, it is difficult to take advantage of the resulting unstructured sparsity patterns on modern hardware like GPUs. As a result, pruning strategies which impose sparsity structures in the weights have become more popular. However,these structured pruning approaches typically lead to higher losses in accuracy than unstructured pruning. In this paper, we present SparseRT, a code generator that leverage unstructured sparsity toaccelerate sparse linear algebra operations in deep learning inference on GPUs. For 1x1 convolutions and fully connected layers, we demonstrate geometric mean of speedups of 3.4x over the equivalent dense computation at 90% sparsity and 5.4x at 95% sparsity when evaluated on hundreds of test cases in deep learning. For sparse 3x3 convolutions, we show speedups of over 5x on use casesin ResNet-50.
Learning Fairness-aware Relational Structures

The development of fair machine learning models that effectively avert bias and discrimination is an important problem that has garnered attention in recent years. The necessity of encoding complex relational dependencies among the features and variables for competent predictions require the development of fair, yet expressive relational models. In this work, we introduce Fair-A3SL, a fairness-aware structure learning algorithm for learning relational structures, which incorporates fairness measures while learning relational graphical model structures. Our approach is versatile in being able to encode a wide range of fairness metrics such as statistical parity difference, overestimation, equalized odds, and equal opportunity, including recently proposed relational fairness measures. While existing approaches employ the fairness measures on pre-determined model structures post prediction, Fair-A3SL directly learns the structure while optimizing for the fairness measures and hence is able to remove any structural bias in the model. We demonstrate the effectiveness of our learned model structures when compared with the state-of-the-art fairness models quantitatively and qualitatively on datasets representing three different modeling scenarios: i) a relational dataset, ii) a recidivism prediction dataset widely used in studying discrimination, and iii) a recommender systems dataset. Our results show that Fair-A3SL can learn fair, yet interpretable and expressive structures capable of making accurate predictions.
Graph-Based Intrusion Detection System for Controller Area Networks

The controller area network (CAN) is the most widely used intra-vehicular communication network in the automotive industry. Because of its simplicity in design, it lacks most of the requirements needed for a security-proven communication protocol. However, a safe and secured environment is imperative for autonomous as well as connected vehicles. Therefore CAN security is considered one of the important topics in the automotive research community. In this article, we propose a four-stage intrusion detection system that uses the chi-squared method and can detect any kind of strong and weak cyber attacks in a CAN. This work is the first-ever graph-based defense system proposed for the CAN. Our experimental results show that we have a very low 5.26% misclassification for denial of service (DoS) attack, 10% misclassification for fuzzy attack, 4.76% misclassification for replay attack, and no misclassification for spoofing attack. In addition, the proposed methodology exhibits up to 13.73% better accuracy compared to existing ID sequence-based methods.
Sensitive alignment using paralogous sequence variants improves long-read mapping and variant calling in segmental duplications.

The ability to characterize repetitive regions of the human genome is limited by the read lengths of short-read sequencing technologies. Although long-read sequencing technologies such as Pacific Biosciences (PacBio) and Oxford Nanopore Technologies can potentially overcome this limitation, long segmental duplications with high sequence identity pose challenges for long-read mapping. We describe a probabilistic method, DuploMap, designed to improve the accuracy of long-read mapping in segmental duplications. It analyzes reads mapped to segmental duplications using existing long-read aligners and leverages paralogous sequence variants (PSVs)-sequence differences between paralogous sequences-to distinguish between multiple alignment locations. On simulated datasets, DuploMap increased the percentage of correctly mapped reads with high confidence for multiple long-read aligners including Minimap2 (74.3-90.6%) and BLASR (82.9-90.7%) while maintaining high precision. Across multiple whole-genome long-read datasets, DuploMap aligned an additional 8-21% of the reads in segmental duplications with high confidence relative to Minimap2. Using DuploMap-aligned PacBio circular consensus sequencing reads, an additional 8.9 Mb of DNA sequence was mappable, variant calling achieved a higher F1 score and 14 713 additional variants supported by linked-read data were identified. Finally, we demonstrate that a significant fraction of PSVs in segmental duplications overlaps with variants and adversely impacts short-read variant calling.
Temporal and spatial dynamics in the apple flower microbiome in the presence of the phytopathogen Erwinia amylovora

Plant microbiomes have important roles in plant health and productivity. However, despite flowers being directly linked to reproductive outcomes, little is known about the microbiomes of flowers and their potential interaction with pathogen infection. Here, we investigated the temporal spatial dynamics of the apple stigma microbiome when challenged with a phytopathogen Erwinia amylovora, the causal agent of fire blight disease. We profiled the microbiome from the stigmas of individual flowers, greatly increasing the resolution at which we can characterize shifts in the composition of the microbiome. Individual flowers harbored unique microbiomes at the operational taxonomic unit level. However, taxonomic analysis of community succession showed a population gradually dominated by bacteria within the families Enterobacteriaceae and Pseudomonadaceae. Flowers inoculated with E. amylovora established large populations of the phytopathogen, with pathogen-specific gene counts of >3.0 × 107 in 90% of the flowers. Yet, only 42% of inoculated flowers later developed fire blight symptoms. This reveals that pathogen abundance on the stigma is not sufficient to predict disease outcome. Our data demonstrate that apple flowers represent an excellent model in which to characterize how plant microbiomes establish, develop, and correlate with biological processes such as disease progression in an experimentally tractable plant organ.
Managing Device Lifecycle: Reconfigurable Constrained Codes for M/T/Q/P-LC Flash Memories

Flash memory devices are winning the competition for storage density against magnetic recording devices. This outcome results from advances in physics that allow storage of more than one bit per cell, coupled with advances in signal processing that reduce the effect of physical instabilities. Constrained codes are used in storage to avoid problematic patterns, and thus prevent errors from happening. Recently, we introduced binary symmetric lexicographically-ordered constrained codes (LOCO codes) for data storage and data transmission. LOCO codes are capacity-achieving, simple, and can be easily reconfigured. This paper introduces simple constrained codes that support non-binary physical gates in multi, triple, quad, and the currently-in-development penta-level cell (M/T/Q/P-LC) Flash memories. The new codes can be easily modified if problematic patterns change with time. These codes are designed to mitigate inter-cell interference, which is a critical source of error in Flash devices. The occurrence of errors is a consequence of parasitic capacitances in and across floating-gate transistors, resulting in charge propagation from cells being programmed to the highest charge level to neighboring cells being programmed to lower levels or unprogrammed/erased. This asymmetric nature of error-prone patterns distinguishes Flash memories. The new codes are called $q$ -ary asymmetric LOCO codes (QA-LOCO codes), and the construction subsumes codes previously designed for single-level cell (SLC) Flash devices (A-LOCO codes). QA-LOCO codes work for a Flash device with any number, $q$ , of levels per cell. For $q \geq 4$ , we show that QA-LOCO codes can achieve rates greater than $0.95 \log _{2} \!q$ input bits per coded symbol. The complexity of encoding and decoding is modest, and reconfiguring a code is as easy as reprogramming an adder. Capacity-achieving rates, affordable encoding-decoding complexity, and ease of reconfigurability support the growing improvement of M/T/Q/P-LC Flash memory devices, as well as lifecycle management as the characteristics of these devices change with time, which increases their lifetime.
Rotation of a low-Reynolds-number watermill : theory and simulations

Recent experiments have demonstrated that small-scale rotary devices installed in a microfluidic channel can be driven passively by the underlying flow alone without resorting to conventionally applied magnetic or electric fields. In this work, we conduct a theoretical and numerical study on such a flow-driven ‘watermill’ at low Reynolds number, focusing on its hydrodynamic features. We model the watermill by a collection of equally spaced rigid rods. Based on the classical resistive force (RF) theory and direct numerical simulations, we compute the watermill’s instantaneous rotational velocity as a function of its rod number and the orientation. In addition, we adopt a dynamical system approach to identify the equilibrium positions of the watermill and analyse their stability. We further compare the theoretically and numerically derived rotational velocities, which agree with each other in general, while considerable discrepancy arises in certain configurations owing to the hydrodynamic interactions neglected by the RF theory. We confirm this conclusion by employing the RF-based asymptotic framework incorporating hydrodynamic interactions for a simpler watermill consisting of two or three rods and we show that accounting for hydrodynamic interactions can significantly enhance the accuracy of the theoretical predictions.
The Non-Commutative Geometry of the Complex Classes of Topological Insulators

Alain Connes’ Non-Commutative Geometry program [1] has been recently carried out [2, 3] for the entire A- and AIII-symmetry classes of topological insulators, in the regime of strong disorder where the insulating gap is completely filled with dense localized spectrum. This is a short overview of these results, whose goal is to highlight the methods of Non-Commutative Geometry involved in these studies. The exposition proceeds gradually through the cyclic cohomology, quantized calculus with Fredholm-modules, local formulas for the odd and even Chern characters and index theorems for the odd and even Chern numbers. The characterization of the A- and AIII-symmetry classes in the presence of strong disorder and magnetic fields emerges as a natural application of these tools.
New Pulsars from an Arecibo Drift Scan Search

We report the discovery of the pulsars PSR J0030+0451, PSR J0711+0931, and PSR J1313+0931 that were found in a search of 470 square degrees at 430 MHz using the 305 m Arecibo telescope. The search has an estimated sensitivity for long-period, low dispersion measure, low zenith angle, and high Galactic latitude pulsars of ~1 mJy, comparable to previous Arecibo searches. Spin and astrometric parameters for the three pulsars are presented along with polarimetry at 430 MHz. PSR J0030+0451, a nearby pulsar with a period of 4.8 ms, belongs to the less common category of isolated millisecond pulsars. We have measured significant polarization in PSR J0030+0451 over more than 50% of the period, and we use these data for a detailed discussion of the pulsar's magnetospheric geometry. Scintillation observations of PSR J0030+0451 provide an estimate of the plasma turbulence level along the line of sight through the local interstellar medium.
Why Radio Quiet Quasars are Preferred over Radio Loud Quasars Regardless of Environment and Redshift

Evidence has accumulated suggesting the clustering of radio loud quasars is greater than for radio quiet quasars. We interpret these results in a context in which the fraction of radio loud quasar formation is less than or equal to that for radio quiet quasars for all environments and redshift. Because we assume that post-merger cold gas onto large black holes produces either a radio loud or a radio quiet quasar, we show that for largest black hole masses that live in largest dark matter halos, fRLQ approaches 0.5 from below but does not exceed it, such that in rich clusters the formation of a radio loud quasar tends to be equally likely to occur as a radio quiet quasar. In dark matter halos with smaller mass, by contrast, radio quiet quasars are more likely to form and the likelihood increases inversely with dark matter halo mass. As a result, averaging over a population of radio loud and radio quiet quasars will necessarily generate lower average black hole masses for the radio quiet subgroup. Hence, despite the fact that the formation of radio quiet quasars is preferred over radio loud quasars in any environment, at any mass scale, at any luminosity, or redshift, averaging over a range of radio loud quasars will give the appearance they are preferred in cluster environments over radio quiet quasars. We show how this also accounts for the order of magnitude difference in the total number of jetted active galaxies compared to non-jetted counterparts.
Entanglement entropy in particle decay

The decay of a parent particle into two or more daughter particles results in an entangled quantum state as a consequence of conservation laws in the decay process. Recent experiments at Belle and BaBar take advantage of quantum entanglement and the correlations in the time evolution of the product particles to study CP and T violations. If one (or more) of the product particles are not observed, their degrees of freedom are traced out of the pure state density matrix resulting from the decay, leading to a mixed state density matrix and an entanglement entropy. This entropy is a measure of the loss of information present in the original quantum correlations of the entangled state. We use the Wigner-Weisskopf method to construct an approximation to this state that evolves in time in a manifestly unitary way. We then obtain the entanglement entropy from the reduced density matrix of one of the daughter particles obtained by tracing out the unobserved states, and follow its time evolution. We find that it grows over a time scale determined by the lifetime of the parent particle to a maximum, which when the width of the parent particle is narrow, describes the phase space distribution of maximally entangled Bell-like states. The method is generalized to the case in which the parent particle is described by a wave packet localized in space. Possible experimental avenues to measure the entanglement entropy in the decay of mesons at rest are discussed.
V819 Tau: A Rare Weak-lined T Tauri Star with A Weak Infrared Excess

We use Spitzer data to infer that the small infrared excess of V819 Tau, a weak-lined T Tauri star in Taurus, is real and not attributable to a 'companion' 10'' to the south. We do not confirm the mid-infrared excess in HBC 427 and V410 X-ray 3, which are also non-accreting T Tauri stars in the same region; instead, for the former object, the excess arises from a red companion 9'' to the east. A single-temperature blackbody fit to the continuum excess of V819 Tau implies a dust temperature of 143 K; however, a better fit is achieved when the weak 10 and 20 mum silicate emission features are also included. We infer a disk of sub-mum silicate grains between about 1 AU and several 100 AU with a constant surface density distribution. The mid-infrared excess of V819 Tau can be successfully modeled with dust composed mostly of small amorphous olivine grains at a temperature of 85 K, and most of the excess emission is optically thin. The disk could still be primordial, but gas-poor and therefore short-lived, or already at the debris disk stage, which would make it one of the youngest debris disk systems known.
Influence of coupling on thermal forces and dynamic friction in plasmas with multiple ion species

The recently proposed effective potential theory [Phys. Rev. Lett. 110, 235001 (2013)] is used to investigate the influence of coupling on inter-ion-species diffusion and momentum exchange in multi-component plasmas. Thermo-diffusion and the thermal force are found to diminish rapidly as strong coupling onsets. For the same coupling parameters, the dynamic friction coefficient is found to tend to unity. These results provide an impetus for addressing the role of coupling on diffusive processes in inertial confinement fusion experiments.
Collapse of axion stars

Axion stars, gravitationally bound states of low-energy axion particles, have a maximum mass allowed by gravitational stability. Weakly bound states obtaining this maximum mass have sufficiently large radii such that they are dilute, and as a result, they are well described by a leading-order expansion of the axion potential. Heavier states are susceptible to gravitational collapse. Inclusion of higher-order interactions, present in the full potential, can give qualitatively different results in the analysis of collapsing heavy states, as compared to the leading-order expansion. In this work, we find that collapsing axion stars are stabilized by repulsive interactions present in the full potential, providing evidence that such objects do not form black holes. In the last moments of collapse, the binding energy of the axion star grows rapidly, and we provide evidence that a large amount of its energy is lost through rapid emission of relativistic axions.
The Role of Carbon in Extrasolar Planetary Geodynamics and Habitability

The proportions of oxygen, carbon, and major rock-forming elements (e.g., Mg, Fe, Si) determine a planet's dominant mineralogy. Variation in a planet's mineralogy subsequently affects planetary mantle dynamics as well as any deep water or carbon cycle. Through thermodynamic models and high pressure diamond anvil cell experiments, we demonstrate that the oxidation potential of C is above that of Fe at all pressures and temperatures, indicative of 0.1-2 Earth-mass planets. This means that for a planet with (Mg+2Si+Fe+2C)/O > 1, excess C in the mantle will be in the form of diamond. We find that an increase in C, and thus diamond, concentration slows convection relative to a silicate-dominated planet, due to diamond's ~3 order of magnitude increase in both viscosity and thermal conductivity. We assert then that in the C-(Mg+2Si+Fe)-O system, there is a compositional range in which a planet can be habitable. Planets outside of this range will be dynamically sluggish or stagnant, thus having limited carbon or water cycles leading to surface conditions inhospitable to life as we know it.
THE ROLE OF INVERSE COMPTON SCATTERING IN SOLAR CORONAL HARD X-RAY AND γ-RAY SOURCES

Coronal hard X-ray (HXR) and continuum γ-ray sources associated with the impulsive phase of solar flares have been the subject of renewed interest in recent years. They have been interpreted in terms of thin-target, non-thermal bremsstrahlung emission. This interpretation has led to rather extreme physical requirements in some cases. For example, in one case, essentially all of the electrons in the source must be accelerated to non-thermal energies to account for the coronal HXR source. In other cases, the extremely hard photon spectra of the coronal continuum γ-ray emission suggest that the low-energy cutoff of the electron energy distribution lies in the MeV energy range. Here, we consider the role of inverse Compton scattering (ICS) as an alternate emission mechanism in both the ultra- and mildly relativistic regimes. It is known that relativistic electrons are produced during powerful flares; these are capable of upscattering soft photospheric photons to HXR and γ-ray energies. Previously overlooked is the fact that mildly relativistic electrons, generally produced in much greater numbers in flares of all sizes, can upscatter extreme-ultraviolet/soft X-ray photons to HXR energies. We also explore ICS on anisotropic electron distributions and show that the resulting emission can be significantly enhanced over an isotropic electron distribution for favorable viewing geometries. We briefly review results from bremsstrahlung emission and reconsider circumstances under which non-thermal bremsstrahlung or ICS would be favored. Finally, we consider a selection of coronal HXR and γ-ray events and find that in some cases the ICS is a viable alternative emission mechanism.
Derivatives of embedding functors I: the stable case

For smooth manifolds M and N, let be the homotopy fibre of the inclusion map . Consider the functor from the category of Euclidean spaces to the category of spectra, defined by the formula . In this paper, we describe the derivatives of this functor, in the sense of M. Weiss's orthogonal calculus, in the case when N is a stably parallelizable manifold (we believe that the parallelizability assumption is not essential). Our construction involves a certain space of partitions of M (or, equivalently, a space of rooted forests with leaves marked by points in M), and a certain `homotopy bundle of spectra' over this space of trees. The nth derivative is then described as the `spectrum of restricted sections' of this bundle.
Higher spin N = 8 supergravity

The product of two N = 8 supersingletons yields an infinite tower of massless states of higher spin in four dimensional anti de Sitter space. All the states with spin s ≥ 1 correspond to generators of Vasiliev's super higher spin algebra shsE(8|4) which contains the D = 4,N = 8 anti de Sitter superalgebra OSp(8|4). Gauging the higher spin algebra and introducing a matter multiplet in a quasi-adjoint representation leads to a consistent and fully nonlinear equations of motion as shown sometime ago by Vasiliev. We show the embedding of the N = 8 AdS supergravity equations of motion in the full system at the linearized level and discuss the implications for the embedding of the interacting theory. We furthermore speculate that the boundary N = 8 singleton field theory yields the dynamics of the N = 8 AdS supergravity in the bulk, including all higher spin massless fields, in an unbroken phase of M-theory.
Observational strong gravity and quantum black hole structure

Quantum considerations have led many theorists to believe that classical black hole (BH) physics is modified not just deep inside BHs but at horizon scales, or even further outward. The near-horizon regime has just begun to be observationally probed for astrophysical BHs — both by LIGO, and by the Event Horizon Telescope. This suggests exciting prospects for observational constraints on or discovery of new quantum BH structure. This paper overviews arguments for certain such structure and these prospects.
Asymptotic expansions for the conditional sojourn time distribution in the M/M/1-PS queue

We consider the M/M/1 queue with processor sharing. We study the conditional sojourn time distribution, conditioned on the customer's service requirement, in various asymptotic limits. These include large time and/or large service request, and heavy traffic, where the arrival rate is only slightly less than the service rate. The asymptotic formulas relate to, and extend, some results of Morrison (SIAM J. Appl. Math. 45:152---167, [1985]) and Flatto (Ann. Appl. Probab. 7:382---409, [1997]).
Probabilistic Polynomials and Hamming Nearest Neighbors

We show how to compute any symmetric Boolean function on n variables over any field (as well as the integers) with a probabilistic polynomial of degree O(a#x221A;n log(1/a#x03B5;))) and error at most a#x03B5;. The degree dependence on n and a#x03B5; is optimal, matching a lower bound of Razborov (1987) and Smolensky (1987) for the MAJORITY function. The proof is constructive: a low-degree polynomial can be efficiently sampled from the distribution. This polynomial construction is combined with other algebraic ideas to give the first sub quadratic time algorithm for computing a (worst-case) batch of Hamming distances in super logarithmic dimensions, exactly. To illustrate, let c(n): N -> N. Suppose we are given a database D of n vectors in {0, 1} (c(n) log n) and a collection of n query vectors Q in the same dimension. For all u in Q, we wish to compute a v in D with minimum Hamming distance from u. We solve this problem in n(2-1/O(c(n) log2 c(n))) randomized time. Hence, the problem is in "truly sub quadratic" time for O(log n) dimensions, and in sub quadratic time for d = o((log2 n)/(log log n)2). We apply the algorithm to computing pairs with maximum inner product, closest pair in l1 for vectors with bounded integer entries, and pairs with maximum Jaccard coefficients.
Substructure in Clusters Containing Wide-Angle-Tailed Radio Galaxies. I. New Redshifts

We present new redshifts and positions for 635 galaxies in nine rich clusters containing wide-angle tailed (WAT) radio galaxies. Combined with existing data, we now have a sample of 18 WAT-containing clusters with more than 10 redshifts. This sample contains a substantial portion of the WAT clusters in the VLA 20 cm survey of Abell clusters, including 75% of WAT clusters in the complete survey (z ≤ 0.09), and 20% of WAT clusters with z > 0.09. It is a representative sample, which should not contain biases other than selection by radio morphology. We graphically present the new data using histograms and sky maps. A semiautomated procedure is used to search for emission lines in the spectra in order to add and verify galaxy redshifts. We find that the average apparent fraction of emission-line galaxies is about 9% in both the clusters and the field. We investigate the magnitude completeness of our redshift surveys with CCD data for a test case, Abell 690. This case indicates that our galaxy target lists are deeper than the detection limit of a typical MX exposure, and they are 82% complete down to R = 19.0. The importance of the uniformity of the placement of fibers on targets is posited, and we evaluate this in our data sets. We find some cases of nonuniformities which may influence dynamical analyses. A second paper will use this database to look for correlations between the WAT radio morphology and the cluster's dynamical state.
Phase Separation Patterns from Directional Quenching

We study the effect of directional quenching on patterns formed in simple bistable systems such as the Allen–Cahn and the Cahn–Hilliard equation on the plane. We model directional quenching as an externally triggered change in system parameters, changing the system from monostable to bistable across a trigger line. We are then interested in patterns forming in the bistable region, in particular as the trigger progresses with small speed and increases this bistable region. We find existence and nonexistence results of single interfaces and striped patterns. For zero speed, we find stripes parallel or perpendicular to the trigger line and exclude stripes with an oblique orientation. Single interfaces are always perpendicular to the trigger line. For small positive speed, striped patterns can align perpendicularly. Other orientations are excluded in Allen–Cahn for all nonnegative speeds. Single interfaces for positive trigger speeds are excluded for Cahn–Hilliard and align perpendicularly in Allen–Cahn.
HOT JUPITER MAGNETOSPHERES

The upper atmospheres of close-in gas giant exoplanets (hot Jupiters) are subjected to intense heating and tidal forces from their parent stars. The atomic (H) and ionized (H+) hydrogen layers are sufficiently rarefied that magnetic pressure may dominate gas pressure for expected planetary magnetic field strength. We examine the structure of the magnetosphere using a 3D isothermal magnetohydrodynamic model that includes a static dead zone near the magnetic equator containing gas confined by the magnetic field, a wind zone outside the magnetic equator in which thermal pressure gradients and the magneto-centrifugal-tidal effect give rise to a transonic outflow, and a region near the poles where sufficiently strong tidal forces may suppress transonic outflow. Using dipole field geometry, we estimate the size of the dead zone to be several to tens of planetary radii for a range of parameters. Tides decrease the size of the dead zone, while allowing the gas density to increase outward where the effective gravity is outward. In the wind zone, the rapid decrease of density beyond the sonic point leads to smaller densities relative to the neighboring dead zone, which is in hydrostatic equilibrium. To understand the appropriate base conditions for the 3D isothermal model, we compute a simple 1D thermal model in which photoelectric heating from the stellar Lyman continuum is balanced by collisionally excited Lyα cooling. This 1D model exhibits a H layer with temperature T 5000-10,000 K down to a pressure P ~ 10-100 nbar. Using the 3D isothermal model, we compute maps of the H column density as well as the Lyα transmission spectra for parameters appropriate for HD 209458b. Line-integrated transit depths 5%-10% can be achieved for the above base conditions, in agreement with the results of Koskinen et al. A deep, warm H layer results in a higher mass-loss rate relative to that for a more shallow layer, roughly in proportion to the base pressure. Strong magnetic fields have the effect of increasing the transit signal while decreasing the mass loss, due to higher covering fraction and density of the dead zone. Absorption due to bulk fluid velocity is negligible at linewidths 100 km s-1 from line center. In our model, most of the transit signal arises from magnetically confined gas, some of which may be outside the L1 equipotential. Hence, the presence of gas outside the L1 equipotential does not directly imply mass loss. We verify a posteriori that particle mean free paths and ion-neutral drift are small in the region of interest in the atmosphere, and that flux freezing is a good approximation. We suggest that resonant scattering of Lyα by the magnetosphere may be observable due to the Doppler shift from the planet's orbital motion, and may provide a complementary probe of the magnetosphere. Lastly, we discuss the domain of applicability for the magnetic wind model described in this paper as well as the Roche-lobe overflow model.
Dictionary-Free MRI PERK: Parameter Estimation via Regression with Kernels

This paper introduces a fast, general method for dictionary-free parameter estimation in quantitative magnetic resonance imaging (QMRI) parameter estimation via regression with kernels (PERK). PERK first uses prior distributions and the nonlinear MR signal model to simulate many parameter-measurement pairs. Inspired by machine learning, PERK then takes these parameter-measurement pairs as labeled training points and learns from them a nonlinear regression function using kernel functions and convex optimization. PERK admits a simple implementation as per-voxel nonlinear lifting of MRI measurements followed by linear minimum mean-squared error regression. We demonstrate PERK for $ {\textit {T}_{1}}, {\textit {T}_{2}}$ estimation, a well-studied application where it is simple to compare PERK estimates against dictionary-based grid search estimates and iterative optimization estimates. Numerical simulations as well as single-slice phantom and in vivo experiments demonstrate that PERK and other tested methods produce comparable $ {\textit {T}_{1}}, {\textit {T}_{2}}$ estimates in white and gray matter, but PERK is consistently at least $140\times $ faster. This acceleration factor may increase by several orders of magnitude for full-volume QMRI estimation problems involving more latent parameters per voxel.
A regularized weighted least gradient problem for conductivity imaging

We propose and study a regularization method for recovering an approximate electrical conductivity solely from the magnitude of one interior current density field. Without some minimal knowledge of the boundary voltage potential, the problem has been recently shown to have nonunique solutions, thus recovering the exact conductivity is impossible. The method is based on solving a weighted least gradient problem in the subspace of functions of bounded variations with square integrable traces. The computational effectiveness of this method is demonstrated in numerical experiments.