cssi/SciSciGPT-SciSciNet huggingface dataset:
MagNI: A Magnetoelectrically Powered and Controlled Wireless Neurostimulating Implant

This paper presents the first wireless and programmable neural stimulator leveraging magnetoelectric (ME) effects for power and data transfer. Thanks to low tissue absorption, low misalignment sensitivity and high power transfer efficiency, the ME effect enables safe delivery of high power levels (a few milliwatts) at low resonant frequencies ( $\sim$ 250 kHz) to mm-sized implants deep inside the body (30-mm depth). The presented MagNI (Magnetoelectric Neural Implant) consists of a 1.5-mm $^2$ 180-nm CMOS chip, an in-house built 4 × 2 mm ME film, an energy storage capacitor, and on-board electrodes on a flexible polyimide substrate with a total volume of 8.2 mm $^3$ . The chip with a power consumption of 23.7 $\mu$ W includes robust system control and data recovery mechanisms under source amplitude variations (1-V variation tolerance). The system delivers fully-programmable bi-phasic current-controlled stimulation with patterns covering 0.05-to-1.5-mA amplitude, 64-to-512- $\mu$ s pulse width, and 0-to-200-Hz repetition frequency for neurostimulation.
Location Privacy in Cognitive Radios With Multi-Server Private Information Retrieval

Spectrum database-based cognitive radio networks (CRNs) have become the de facto approach for enabling unlicensed secondary users (SUs) to identify spectrum vacancies in channels owned by licensed primary users (PUs). Despite its merits, the use of spectrum databases incurs privacy concerns for both SUs and PUs. Single-server private information retrieval (PIR) has been used as the main tool to address this problem. However, such techniques incur extremely large communication and computation overheads while offering only computational privacy. Besides, some of these PIR protocols have been broken. In this paper, we show that it is possible to achieve high efficiency and (information-theoretic) privacy for both PUs and SUs in database-driven CRN with multi-server PIR. Our key observation is that, by design, database-driven CRNs comprise multiple databases that are required, by the Federal Communications Commission, to synchronize their records. To the best of our knowledge, we are the first to exploit this observation to harness multi-server PIR technology to guarantee an optimal privacy for both SUs and PUs, thanks to the unique properties of database-driven CRN. We showed, analytically and empirically with deployments on actual cloud systems, that multi-server PIR is an ideal tool to provide efficient location privacy in database-driven CRN.
Feasible generalized least squares for panel data with cross-sectional and serial correlations

This paper considers generalized least squares (GLS) estimation for linear panel data models. By estimating the large error covariance matrix consistently, the proposed feasible GLS estimator is more efficient than the ordinary least squares in the presence of heteroskedasticity, serial and cross-sectional correlations. The covariance matrix used for the feasible GLS is estimated via the banding and thresholding method. We establish the limiting distribution of the proposed estimator. A Monte Carlo study is considered. The proposed method is applied to an empirical application.
Observing trans-Planckian signatures in the cosmic microwave background

We examine the constraints cosmological observations can place on any trans-Planckian corrections to the primordial spectrum of perturbations underlying the anisotropies in the cosmic microwave background. We focus on models of trans-Planckian physics which lead to a modulated primordial spectrum. Rather than looking at a generic modulated spectrum, we base our calculations on a specific model, and they are intended as a case study for the sort of constraints one could hope to apply to a well-motivated model of trans-Planckian physics. We present results for three different approaches—a grid search in a subset of the overall parameter space, a Fisher matrix estimation of the likely error ellipses, and a Monte Carlo Markov chain fit to a simulated CMB sky. As was seen in previous analyses, the likelihood space has multiple peaks, and we show that their distribution can be reproduced via a simple semi-analytic argument. All three methods lead to broadly similar results. We vary ten cosmological parameters (including two related to the trans-Planckian terms) and show that the amplitude of the tensor perturbations is directly correlated with the detectability of any trans-Planckian modulation. We argue that this is likely to be true for any trans-Planckian modulation in the paradigm of slow roll inflation. For the specific case we consider, we conclude that if the tensor to scalar ratio r~0.15, the ratio between the inflationary Hubble scale H and the scale of new physics M has to be of the order of 0.004 if the modulation is detectable at the 2σ level. For a lower value of r, the bound on H/M becomes looser.
The chromatic splitting conjecture at n = p = 2

We show that the strongest form of Hopkins' chromatic splitting conjecture, as stated by Hovey, cannot hold at chromatic level n=2 at the prime p=2. More precisely, for V(0) the mod 2 Moore spectrum, we prove that the kth homotopy group of L_1L_{K(2)}V(0) is not zero when k is congruent to -3 modulo 8. We explain how this contradicts the decomposition of L_1L_{K(2)}S predicted by the chromatic splitting conjecture.
On Singularity Formation in a Hele-Shaw Model

We discuss a lubrication approximation model of the interface between two immiscible fluids in a Hele-Shaw cell, derived in Constantin et al. (Phys Rev E 47(6):4169–4181, 1993) and widely studied since. The model consists of a single one dimensional evolution equation for the thickness 2h = 2h(x, t) of a thin neck of fluid, $${\partial_{t} {h} + \partial_{x} (h \partial^{3}_{ x} h) = 0,}$$ for $${x \in (-1, 1)\, {\rm and}\, t \geq 0}$$ . The boundary conditions fix the neck height and the pressure jump: $${h(\pm 1, t) = 1, \quad\quad \partial^{2}_{ x} h(\pm 1, t) = P > 0.}$$ We prove that starting from smooth and positive h, as long as h(x, t) > 0, for x ∈ [−1, 1], t ∈ [0, T ], no singularity can arise in the solution up to time T. As a consequence, we prove for any P > 2 and any smooth and positive initial datum that the solution pinches off in either finite or infinite time, i.e., $${{\rm inf}_{[-1,1]\times[0,T*)}h = 0}$$ , for some $${{T}_{*} \in (0,\infty]}$$ . These facts have been long anticipated on the basis of numerical and theoretical studies.
Jet charge and machine learning

Modern machine learning techniques, such as convolutional, recurrent and recursive neural networks, have shown promise for jet substructure at the Large Hadron Collider. For example, they have demonstrated effectiveness at boosted top or W boson identification or for quark/gluon discrimination. We explore these methods for the purpose of classifying jets according to their electric charge. We find that both neural networks that incorporate distance within the jet as an input and boosted decision trees including radial distance information can provide significant improvement in jet charge extraction over current methods. Specifically, convolutional, recurrent, and recursive networks can provide the largest improvement over traditional methods, in part by effectively utilizing distance within the jet or clustering history. The advantages of using a fixed-size input representation (as with the CNN) or a small input representation (as with the RNN) suggest that both convolutional and recurrent networks will be essential to the future of modern machine learning at colliders.
Repeat SARS-CoV-2 testing models for residential college populations.

Residentialcolleges are considering re-opening under uncertain futures regarding the COVID-19 pandemic. We consider repeat SARS-CoV-2 testing models for the purpose of containing outbreaks in the residential campus community. The goal of repeat testing is to detect and isolate new infections rapidly to block transmission that would otherwise occur both on and off campus. The models allow for specification of aspects including scheduled on-campus resident screening at a given frequency, test sensitivity that can depend on the time since infection, imported infections from off campus throughout the school term, and a lag from testing until student isolation due to laboratory turnaround and student relocation delay. For early- (late-) transmission of SARS-CoV-2 by age of infection, we find that weekly screening cannot reliably contain outbreaks with reproductive numbers above 1.4 (1.6) if more than one imported exposure per 10,000 students occurs daily. Screening every three days can contain outbreaks providing the reproductive number remains below 1.75 (2.3) if transmission happens earlier (later) with time from infection, but at the cost of increased false positive rates requiring more isolation quarters for students testing positive. Testing frequently while minimizing the delay from testing until isolation for those found positive are the most controllable levers for preventing large residential college outbreaks. A web app that implements model calculations is available to facilitate exploration and consideration of a variety of scenarios.
Picky Partners: The Pairing of Component Masses in Binary Black Hole Mergers

We examine the relationship between individual black hole (BH) masses in merging binary black hole (BBH) systems. Analyzing the ten BBH detections from LIGO/Virgo's first two observing runs, we find that the masses of the component BHs comprising each binary are unlikely to be randomly drawn from the same underlying distribution. Instead, the two BHs of a given binary prefer to be of comparable mass. We show that it is $\sim 5$ times more likely that the component BHs in a given binary are always equal (to within 5\%) than that they are randomly paired. If we assume that the probability of a merger between two BHs scales with the mass ratio $q$ as $q^\beta$, so that $\beta=0$ corresponds to random pairings, we find $\beta>0$ is favored at credibility 0.987. By modeling the mass distribution, we find that the median mass ratio is $q_{50\%} = 0.91^{+0.05}_{-0.17}$ at 90\% credibility. While the pairing between BHs depends on their mass ratio, we find no evidence that it depends on the total mass of the system: it is $\sim 6$ times more likely that the pairing depends purely on the mass ratio than on the total mass. We predict that 99\% of BBHs detected by LIGO/Virgo will have mass ratios $q > 0.5$. We conclude that merging black holes do not form random pairings; instead they are selective about their partners, preferring to mate with black holes of a similar mass. The details of these selective pairings provide insight into the underlying formation channels of merging binaries.
A luminous yellow post-AGB star in the galactic globular cluster M79

We report the discovery of a luminous F-type post-asymptotic-giant-branch (PAGB) star in the Galactic globular cluster (GC) M79 (NGC 1904). At visual apparent and absolute magnitudes of and , this "yellow" PAGB star is by a small margin the visually brightest star known in any GC. It was identified using CCD observations in the uBVI photometric system, which is optimized to detect stars with large Balmer discontinuities, indicative of very low surface gravities. Follow-up observations with the SMARTS 1.3 and 1.5 m telescopes show that the star is not variable in light or radial velocity, and that its velocity is consistent with cluster membership. Near- and mid-infrared observations with 2MASS and WISE show no evidence for circumstellar dust. We argue that a sharp upper limit to the luminosity function exists for yellow PAGB stars in old populations, making them excellent candidates for Population II standard candles, which are four magnitudes brighter than RR Lyrae variables. Their luminosities are consistent with the stars being in a PAGB evolutionary phase, with core masses of . We also detected four very hot stars lying above the horizontal branch ("AGB-manque" stars); along with the PAGB star, they are the brightest objects in M79 in the near-ultraviolet. In the Appendix, we give periods and light curves for five variables in M79: three RR Lyrae stars, a Type II Cepheid, and a semiregular variable.
On construction of the smallest one-sided confidence interval for the difference of two proportions

For any class of one-sided 1 - α confidence intervals with a certain monotonicity ordering on the random confidence limit, the smallest interval, in the sense of the set inclusion for the difference of two proportions of two independent binomial random variables, is constructed based on a direct analysis of coverage probability function. A special ordering on the confidence limit is developed and the corresponding smallest confidence interval is derived. This interval is then applied to identify the minimum effective dose (MED) for binary data in dose-response studies, and a multiple test procedure that controls the familywise error rate at level α is obtained. A generalization of constructing the smallest one-sided confidence interval to other discrete sample spaces is discussed in the presence of nuisance parameters.
An Extremely Lithium-rich Bright Red Giant in the Globular Cluster M3

We have serendipitously discovered an extremely lithium-rich star on the red giant branch of the globular cluster M3 (NGC 5272). An echelle spectrum obtained with the Keck I High-Resolution Echelle Spectrograph reveals a Li I λ6707 resonance doublet of 520 mA equivalent width, and our analysis places the star among the most Li-rich giants known: log (Li) +3.0. We determine the elemental abundances of this star, IV-101, and three other cluster members of similar luminosity and color and conclude that IV-101 has abundance ratios typical of giants in M3 and M13 that have undergone significant mixing. We discuss mechanisms by which a low-mass star may be so enriched in Li, focusing on the mixing of material processed by the hydrogen-burning shell just below the convective envelope. While such enrichment could conceivably happen only rarely, it may in fact regularly occur during giant-branch evolution but be rarely detected because of rapid subsequent Li depletion.
Interpretation of twisting type N vacuum solutions with cosmological constant

We investigate a new class of twisting type N vacuum solutions with nonzero (positive) cosmological constantby studying the equations of geodesic deviations along the privileged radial timelike geodesics, generalizing J. Biycak and J. Podolsky's results on non-twisting type N solutions. It is shown that these twisting radiative spacetimes can be interpreted as exact transverse gravitational waves propagating in the de-Sitter universe, with a distinctive feature that all the wave amplitudes are proportional to � (dark energy/matter source coupling). Moreover, we demonstrate the cosmic no-hair conjecture in these spacetimes and discuss their Killing horizons.
High quality factor surface Fabry-Perot cavity of acoustic waves

Surface acoustic wave (SAW) resonators are critical components in wireless communications and many sensing applications. They have also recently emerged as a subject of study in quantum acoustics at the single phonon level. Acoustic loss reduction and mode confinement are key performance factors in SAW resonators. Here, we report the design and experimental realization of high quality factor Fabry-Perot SAW resonators formed in between the tapered phononic crystal mirrors patterned on a GaN-on-sapphire material platform. The fabricated SAW resonators are characterized by both an electrical network analyzer and an optical heterodyne vibrometer. We observed standing Rayleigh waves inside the cavity, with an intrinsic quality factor exceeding 1.3 × 104 at ambient conditions.
Entropic magmas, their homology, and related invariants of links and graphs

In the first part of the paper we show how to use the entropic property to define invariants of links and graphs that are based on the Kauffman bracket and the Tutte polynomial so that the assumption of linearity is not present in their construction. In the second part we introduce homology of entropic magmas and its counterpart for families of entropic magmas connected by a condition .a i b/ j .c i d/D .a j c/ i .b j d/.
High-contrast integral field spectrograph (HCIFS): multi-spectral wavefront control and reduced-dimensional system identification.

Any high-contrast imaging instrument in a future large space-based telescope will include an integral field spectrograph (IFS) for measuring broadband starlight residuals and characterizing the exoplanet’s atmospheric spectrum. In this paper, we report the development of a high-contrast integral field spectrograph (HCIFS) at Princeton University and demonstrate its application in multi-spectral wavefront control. Moreover, we propose and experimentally validate a new reduced-dimensional system identification algorithm for an IFS imaging system, which improves the system’s wavefront control speed, contrast and computational and data storage efficiency.
Exact solution of a two-type branching process: clone size distribution in cell division kinetics

We study a two-type branching process which provides an excellent description of experimental data on cell dynamics in skin tissue. The model involves only a single type of progenitor cell, that is it does not require support from a self-renewed population of stem cells. The progenitor cells divide and may differentiate into post-mitotic cells. We derive an exact solution for the generating function of the number of cells of different types. The generating function is then used to numerically determine the time dependent probability distribution of the numbers of the two types of cells. We also deduce large time asymptotic behaviors drawing on exact results and on a diffusion approximation.
Jet power in pre-planetary nebulae: Observations vs. theory

High velocity jets are among the most prominent features of a wide class of planetary nebulae, but their origins are not understood. Several different types of physical models have been suggested to power the jets, but there is no consensus or preferred scenario. We compare current theoretical ideas on jet formation with observations, using the best studied pre–planetary nebulae in millimeter CO, where the dynamical properties are best defined. In addition to the mass, velocity, momentum, and energy of the jets, the mass and energetics of the equatorial mass-loss that typically accompanies jet formation prove to be important diagnostics. Our integrated approach provides estimates for some key physical quantities – such as the binding energy of the envelope when the jets are launched – and allows testing of model features using correlations between parameters. Even with a relatively small sample of well-observed objects, we find that some specific scenarios for powering jets can be ruled out or rendered implausible, and others are promising at a quantitative level.
WHITE DWARFS NEAR BLACK HOLES: A NEW PARADIGM FOR TYPE I SUPERNOVAE

We present calculations indicating the possibility of a new class of Type I supernovae. In this new paradigm, relativistic terms enhance the self-gravity of a carbon-oxygen white dwarf as it passes or orbits near a black hole. This relativistic compression can cause the central density to exceed the threshold for pycnonuclear reactions so that a thermonuclear runaway ensues. We consider three possible environments: (1) white dwarfs orbiting a low-mass (~10-20 M☉) black hole, (2) white dwarfs encountering a massive [~(1-3) × 103 M☉] black hole in a dense globular cluster, and (3) white dwarfs passing a supermassive (~106-109 M☉) black hole in a dense galactic core. We estimate the rate at which such events could occur out to a redshift z ≈ 1. Event rates are estimated to be significantly less than the rate of normal Type Ia supernovae for all three classes. Nevertheless, such events may be frequent enough to warrant a search for this new class of supernova. We propose several observable signatures that might be used to identify this type of event and speculate that such an event might have produced the observed "mixed-morphology" Sgr A East supernova remnant in the Galactic core.
A model for studying double exponential growth in the two-dimensional Euler equations

We introduce a model for the two-dimensional Euler equations which is designed to study whether or not double exponential growth can be achieved for a short time at an interior point of the flow.
Fragmentation at the Earliest Phase of Massive Star Formation

We present 1.3 mm continuum and spectral line images of two massive molecular clumps P1 and P2 in the G28.34+0.06 region with the Submillimeter Array (SMA). While the two clumps contain masses of 1000 and 880 M ?, respectively, P1 has a luminosity OF <102 L ?, and a lower gas temperature and smaller line width than P2. Thus, P1 appears to be at a much earlier stage of massive star formation than P2. The high-resolution SMA observations reveal two distinctive cores in P2 with masses of 97 and 49 M ?, respectively. The 4 GHz spectral bandpass captures line emission from CO isotopologues, SO, CH3OH, and CH3CN, similar to hot molecular cores harboring massive young stars. The P1 clump, on the other hand, is resolved into five cores along the filament with masses from 22 to 64 M ? and an average projected separation of 0.19 pc. Except 12CO, no molecular line emission is detected toward the P1 cores at a 1? rms of 0.1 K. Since strong 12CO and C18O emissions are seen with the single-dish telescope at a resolution of 11'', the nondetection of these lines with the SMA indicates a depletion factor up to 103. While the spatial resolution of the SMA is better than the expected Jeans length, the masses in P1 cores are much larger than the thermal Jeans mass, indicating the importance of turbulence and/or magnetic fields in cloud fragmentation. The hierarchical structures in the P1 region provide a glimpse of the initial phase of massive star and cluster formation.
Monochromatic equilateral triangles in the unit distance graph

Let $\chi_{\Delta}(\mathbb{R}^{n})$ denote the minimum number of colors needed to color $\mathbb{R}^{n}$ so that there will not be a monochromatic equilateral triangle with side length $1$. Using the slice rank method, we reprove a result of Frankl and Rodl, and show that $\chi_{\Delta}\left(\mathbb{R}^{n}\right)$ grows exponentially with $n$. This technique substantially improves upon the best known quantitative lower bounds for $\chi_{\Delta}\left(\mathbb{R}^{n}\right)$, and we obtain \[ \chi_{\Delta}\left(\mathbb{R}^{n}\right)>(1.01446+o(1))^{n}. \]
Embedding the Pentagon

The Pentagon Model is an explicit supersymmetric extension of the Standard Model, which involves a new strongly-interacting SU(5) gauge theory at TeV-scale energies. We show that the Pentagon can be embedded into an SU(5) × SU(5) × SU(5) gauge group at the GUT scale. The doublet-triplet splitting problem, and proton decay compatible with experimental bounds, can be successfully addressed in this context. The simplest approach fails to provide masses for the lighter two generations of quarks and leptons; however, this problem can be solved by the addition of a pair of antisymmetric tensor fields and an axion.
Radio Direction Finding

Radio direction finding (DF) is a technique for estimating radiowave angle of arrival (AoA) and is based on prior knowledge of the antenna responses versus AoA. Traditional DF systems exploit rotating antennas or sampled antenna arrays for which the antenna response patterns are very carefully controlled to provide support for closed-form DF solutions or for the development of steered beams. Sources contributing to DF errors include local scattering, instrumentation, and propagation. Some more recent DF systems exploit array calibration and digital beamforming techniques to provide reliable AoA estimates while accomodating local scattering. Both of these DF system categories are designed for operation against single component plane waves. More sophisticated DF systems now exploit sampled arrays and DF processing to decompose the complex wavefields created by multiple simultaneous signal components. Keywords: direction finding (DF); angle of arrival (AoA); array manifold; superresolution; site error; DF confirmation; DF array; DF calibration
Leveraging Predictions in Smoothed Online Convex Optimization via Gradient-based Algorithms

We consider online convex optimization with time-varying stage costs and additional switching costs. Since the switching costs introduce coupling across all stages, multi-step-ahead (long-term) predictions are incorporated to improve the online performance. However, longer-term predictions tend to suffer from lower quality. Thus, a critical question is: how to reduce the impact of long-term prediction errors on the online performance? To address this question, we introduce a gradient-based online algorithm, Receding Horizon Inexact Gradient (RHIG), and analyze its performance by dynamic regrets in terms of the temporal variation of the environment and the prediction errors. RHIG only considers at most $W$-step-ahead predictions to avoid being misled by worse predictions in the longer term. The optimal choice of $W$ suggested by our regret bounds depends on the tradeoff between the variation of the environment and the prediction accuracy. Additionally, we apply RHIG to a well-established stochastic prediction error model and provide expected regret and concentration bounds under correlated prediction errors. Lastly, we numerically test the performance of RHIG on quadrotor tracking problems.
Resonant Excitation of Disk Oscillations in Two-Armed-Deformed Disks and Application to High-Frequency QPOs

In previous papers we showed that in one-armed deformed disks, p-mode and g-mode oscillations are resonantly excited by horizontal resonance, and applied it to high-frequency quasi-periodic oscillations (QPOs) observed in lowmass X-ray binaries. In that model, the observed time variation of kHz QPOs is regarded as being the result of a timedependent precession of the deformation. In this paper we consider another possible cause of the time variation of kHz QPOs. That is, we demonstrate that in two-armed deformed disks, p-mode and g-mode oscillations are excited by a vertical resonance, not by a horizontal resonance (horizontal resonance dampens them). Furthermore, we show that in the case of a vertical resonance, the frequencies of excited disk oscillations can vary with time if the vertical disk structure changes with time. A brief application of these results to the time variation of observed kHz QPOs is discussed.
Diffuse Molecular Cloud Densities from UV Measurements of CO Absorption

We use UV measurements of interstellar CO toward nearby stars to calculate the density in the diffuse molecular clouds containing the molecules responsible for the observed absorption. Chemical models and recent calculations of the excitation rate coefficients indicate that the regions in which CO is found have hydrogen predominantly in molecular form and that collisional excitation is by collisions with H_2 molecules. We carry out statistical equilibrium calculations using CO-H_2 collision rates to solve for the H_2 density in the observed sources without including effects of radiative trapping. We have assumed kinetic temperatures of 50 K and 100 K, finding this choice to make relatively little difference to the lowest transition. For the sources having T^(ex)_(10) only for which we could determine upper and lower density limits, we find 〈n(H2) 〉 = 49 cm^(–3). While we can find a consistent density range for a good fraction of the sources having either two or three values of the excitation temperature, there is a suggestion that the higher-J transitions are sampling clouds or regions within diffuse molecular cloud material that have higher densities than the material sampled by the J = 1-0 transition. The assumed kinetic temperature and derived H_2 density are anticorrelated when the J = 2-1 transition data, the J = 3-2 transition data, or both are included. For sources with either two or three values of the excitation temperature, we find average values of the midpoint of the density range that is consistent with all of the observations equal to 68 cm^(–3) for T^k = 100 K and 92 cm^(–3) for T^k = 50 K. The data for this set of sources imply that diffuse molecular clouds are characterized by an average thermal pressure between 4600 and 6800 K cm^(–3).
Debugging Tests for Model Explanations

We investigate whether post-hoc model explanations are effective for diagnosing model errors--model debugging. In response to the challenge of explaining a model's prediction, a vast array of explanation methods have been proposed. Despite increasing use, it is unclear if they are effective. To start, we categorize \textit{bugs}, based on their source, into:~\textit{data, model, and test-time} contamination bugs. For several explanation methods, we assess their ability to: detect spurious correlation artifacts (data contamination), diagnose mislabeled training examples (data contamination), differentiate between a (partially) re-initialized model and a trained one (model contamination), and detect out-of-distribution inputs (test-time contamination). We find that the methods tested are able to diagnose a spurious background bug, but not conclusively identify mislabeled training examples. In addition, a class of methods, that modify the back-propagation algorithm are invariant to the higher layer parameters of a deep network; hence, ineffective for diagnosing model contamination. We complement our analysis with a human subject study, and find that subjects fail to identify defective models using attributions, but instead rely, primarily, on model predictions. Taken together, our results provide guidance for practitioners and researchers turning to explanations as tools for model debugging.
On graphic arrangement groups

Abstract A finite simple graph Γ determines a quotient P Γ of the pure braid group, called a graphic arrangement group. We analyze homomorphisms of these groups defined by deletion of sets of vertices, using methods developed in prior joint work with R. Randell. We show that, for a K 4 -free graph Γ, a product of deletion maps is injective, embedding P Γ in a product of free groups. Then P Γ is residually free, torsion-free, residually torsion-free nilpotent, and acts properly on a CAT(0) cube complex. We also show P Γ is of homological finiteness type F m − 1 , but not F m , where m is the number of copies of K 3 in Γ, except in trivial cases. The embedding result is extended to graphs whose 4-cliques share at most one edge, giving an injection of P Γ into the product of pure braid groups corresponding to maximal cliques of Γ. We give examples showing that this map may inject in more general circumstances. We define the graphic braid group B Γ as a natural extension of P Γ by the automorphism group of Γ, and extend our homological finiteness result to these groups.
Koszul homology of codimension 3 Gorenstein ideals

AbstractIn this note, we calculate the Koszul homology of the codimension 3 Gorenstein ideals. Weﬁnd ﬁltrations for the Koszul homology in terms of modules with pure free resolutions andcompletely describe these resolutions. We also consider the Huneke–Ulrich deviation 2 ideals. Introduction. For the codimension 3 Pfaﬃan ideal of 2n × 2n Pfaﬃans of a (2n + 1) × (2n + 1) generic skew-symmetric matrix, we give an explicit description of the Koszul homology modules. By a resultof Buchsbaum–Eisenbud [BE], the general case of codimension 3 Gorenstein ideals reduces tothis case. They are ﬁltered by equivariant modules M i with self-dual pure free resolutions oflength 3 supported in the ideal of Pfaﬃans. The free resolutions of the modules M i give naturalgeneralizations of the Buchsbaum–Eisenbud complexes for codimension 3 Gorenstein ideals and areinteresting in their own right. It was known that the Koszul homology modules of codimension3 Pfaﬃan ideals are Cohen–Macaulay [Hun1, Example 2.2], but no explicit description was given.The only other example we could ﬁnd in the literature of explicit calculations of Koszul homologyis the paper of Avramov–Herzog [AH] which handles the case of codimension 2 perfect ideals. TheKoszul homology modules of codimension 3 Pfaﬃan ideals also gives examples of modules with pureﬁltrations that do not follow from the results in [EES]. Finally we calculate the Koszul homologymodules for the Huneke–Ulrich deviation 2 ideals which we were studied by Kustin [Kus].
NICMOS Observations of Low-Redshift Quasar Host Galaxies

We have obtained Near-Infrared Camera and Multi-Object Spectrometer images of 16 radio-quiet quasars observed as part of a project to investigate the "luminosity/host-mass limit." The limit results were presented in a paper by McLeod, Rieke, & Storrie-Lombardi. In this paper, we present the images themselves, along with one- and two-dimensional analyses of the host galaxy properties. We find that our model-independent one-dimensional technique is reliable for use on ground-based data at low redshifts; that many radio-quiet quasars live in de Vaucouleurs-law hosts, although some of the techniques used to determine host type are questionable; that complex structure is found in many of the hosts, but that there are some hosts that are very smooth and symmetric; and that the nuclei radiate at ~2%-20% of the Eddington rate based on the assumption that all galaxies have central black holes with a constant mass fraction of 0.6%. Despite targeting hard-to-resolve hosts, we have failed to find any that imply super-Eddington accretion rates.
Nonviolent unitarization: basic postulates to soft quantum structure of black holes

A first-principles approach to the unitarity problem for black holes is systematically explored, based on the postulates of 1) quantum mechanics 2) the ability to approximately locally divide quantum gravitational systems into subsystems 3) correspondence with quantum field theory predictions for appropriate observers and (optionally) 4) universality of new gravitational effects. Unitarity requires interactions between the internal state of a black hole and its surroundings that have not been identified in the field theory description; correspondence with field theory indicates that these are soft. A conjectured information-theoretic result for information transfer between subsystems, partly motivated by a perturbative argument, then constrains the minimum coupling size of these interactions of the quantum atmosphere of a black hole. While large couplings are potentially astronomically observable, given this conjecture one finds that the new couplings can be exponentially small in the black hole entropy, yet achieve the information transfer rate needed for unitarization, due to the large number of black hole internal states. This provides a new possible alternative to arguments for large effects near the horizon. If universality is assumed, these couplings can be described as small, soft, state-dependent fluctuations of the metric near the black hole. Open questions include that of the more fundamental basis for such an effective picture.
The action with manifest E7 type symmetry

We generalize Cremmer-Julia 1st order action of $$ \mathcal{N}=8 $$ supergravity with manifest E7(7) symmetry to cases of $$ \mathcal{N}=6 $$ with manifest SO∗(12) and $$ \mathcal{N}=5 $$ with manifest SU(1, 5) duality symmetries. These U dualities belong to groups of type E7 which do not admit a symmetric bilinear invariant for vector fields. Therefore the 2d order classical action derived from the one with manifest E7 type duality has a ghost vector field which, under appropriate boundary conditions, decouples. We show that when classical $$ \mathcal{N}\ge 5 $$ supergravitiesaredeformedbyacandidateUVdivergencetheghostfielddoesnot decouple. Therefore we argue that U duality and supersymmetry suggest an explanation of the mysterious cancellation of UV infinities at L = 4, $$ \mathcal{N}=5 $$ in d=4. The same reasoning implies that, in absence of duality and supersymmetry anomalies, which still require a better understanding, $$ \mathcal{N}\ge 5 $$ perturbative supergravities may be UV finite at higher-loops.
A mechanism of vortex generation in a supersonic flow behind a gas-plasma interface

The origin of a vortex structure generated during the shock-plasma interaction is investigated. A two-dimensional model based on the shock refraction mechanism successfully unifies the vortex generation with major co-processes typical for the interaction and thus well fits in their cause-and-consequence relationship. Numerical simulations demonstrated the possibility of an intense vortex generation with a continuous positive dynamics as the shock crosses the interface. It was shown that while the vorticity is triggered by the shock refraction on the interface, it is the gas parameter distribution that distinctively determines the parameters of the vortex evolution. The proposed model also provides an insight into interesting aspects of the refraction effects for both, the shock wave and the flow behind it (double refraction). The results are applicable to the problems of energy deposition in a hypersonic flow, a flame-shock interaction, in combustion, in astrophysics, and in the fusion research.
Nonparametric estimation of correlation functions in longitudinal and spatial data, with application to colon carcinogenesis experiments

In longitudinal and spatial studies, observations often demonstrate strong correlations that are stationary in time or distance lags, and the times or locations of these data being sampled may not be homogeneous. We propose a nonparametric estimator of the correlation function in such data, using kernel methods. We develop a pointwise asymptotic normal distribution for the proposed estimator, when the number of subjects is fixed and the number of vectors or functions within each subject goes to infinity. Based on the asymptotic theory, we propose a weighted block bootstrapping method for making inferences about the correlation function, where the weights account for the inhomogeneity of the distribution of the times or locations. The method is applied to a data set from a colon carcinogenesis study, in which colonic crypts were sampled from a piece of colon segment from each of the 12 rats in the experiment and the expression level of p27, an important cell cycle protein, was then measured for each cell within the sampled crypts. A simulation study is also provided to illustrate the numerical performance of the proposed method.
Anisotropic nano-scale resolution in 3D Bragg coherent diffraction imaging

We demonstrate that the resolution of three-dimensional (3D) real-space images obtained from Bragg coherent x-ray diffraction measurements is direction dependent. We propose and demonstrate the effectiveness of a metric to determine the spatial resolution of images that accounts for the directional dependence. The measured direction dependent resolution of ∼4–9 nm is higher than the best previously obtained 3D measurements. Finally, we quantify the relationship between the resolution of recovered real-space images and dosage and discuss its implications in the light of next generation synchrotrons.
A cartesian presentation of weak n–categories

We propose a notion of weak (n+k,n)–category, which we call (n+k,n)–Θ–spaces. The (n+k,n)–Θ–spaces are precisely the fibrant objects of a certain model category structure on the category of presheaves of simplicial sets on Joyal’s category Θn. This notion is a generalization of that of complete Segal spaces (which are precisely the (∞,1)–Θ–spaces). Our main result is that the above model category is cartesian.
On deterministic conditions for subspace clustering under missing data

In this paper we present deterministic analysis of sufficient conditions for sparse subspace clustering under missing data, when data is assumed to come from a Union of Subspaces (UoS) model. In this context we consider two cases, namely Case I when all the points are sampled at the same co-ordinates, and Case II when points are sampled at different locations. We show that results for Case I directly follow from several existing results in the literature, while results for Case II are not as straightforward and we provide a set of dual conditions under which, perfect clustering holds true. We provide extensive set of simulation results for clustering as well as completion of data under missing entries, under the UoS model. Our experimental results indicate that in contrast to the full data case, accurate clustering does not imply accurate subspace identification and completion, indicating the natural order of relative hardness of these problems.
On arc index and maximal Thurston-Bennequin number

We discuss the relation between arc index, maximal Thurston–Bennequin number, and Khovanov homology for knots. As a consequence, we calculate the arc index and maximal Thurston–Bennequin number for all knots with at most 11 crossings. For some of these knots, the calculation requires a consideration of cables which also allows us to compute the maximal self-linking number for all knots with at most 11 crossings.
Kinetics of diffusion-controlled annihilation with sparse initial conditions

We study diffusion-controlled single-species annihilation with sparse initial conditions. In this random process, particles undergo Brownian motion, and when two particles meet, both disappear. We focus on sparse initial conditions where particles occupy a subspace of dimension δ that is embedded in a larger space of dimension d. We find that the co-dimension Δ = d − δ governs the behavior. All particles disappear when the co-dimension is sufficiently small, Δ ≤ 2; otherwise, a finite fraction of particles indefinitely survive. We establish the asymptotic behavior of the probability S(t) that a test particle survives until time t. When the subspace is a line, δ = 1, we find inverse logarithmic decay, , in three dimensions, and a modified power-law decay, , in two dimensions. In general, the survival probability decays algebraically when Δ < 2, and there is an inverse logarithmic decay at the critical co-dimension Δ = 2.
Low-Magnitude Seismicity With a Downhole Distributed Acoustic Sensing Array—Examples From the FORGE Geothermal Experiment

We show the capabilities of a downhole Distributed Acoustic Sensing (DAS) array in detecting, locating and characterizing low-magnitude earthquakes occurring in the vicinity of the Frontier Observatory for Research in Geothermal Energy (FORGE) site in Utah. 10.5 days of continuous data were acquired in a monitoring well at the FORGE geothermal site during the initial stimulation of an Enhanced Geothermal System in April-May 2019. Earthquake activity beneath Mineral Mountains, Utah also occurred within 10 km of the FORGE monitoring well. During the experiment, four events from those areas were cataloged by the University of Utah Seismograph Stations. Our processing of DAS data, including template matching, finds 82 earthquakes during that period, of which 16 are visible on the regional network. The magnitude of completeness obtained by DAS processing is better by at least M=0.5 than the dense surface array around the FORGE site. While a single vertical DAS array is limited in terms of event location due to its azimuthal ambiguity, multiple DAS wells or a combination of a downhole array with surface stations or near-surface horizontal DAS could jointly resolve locations. All detected events probably originated from the two active source areas and can be clustered into several distinct families.
Admixture Analysis Using Genotyping-by-Sequencing Reveals Genetic Relatedness and Parental Lineage Distribution in Highbush Blueberry Genotypes and Cross Derivatives

Blueberries (Vaccinium section Cyanococcus) are perennial shrubs widely cultivated for their edible fruits. In this study, we performed admixture and genetic relatedness analysis of northern highbush (NHB, primarily V. corymbosum) and southern highbush (SHB, V. corymbosum introgressed with V. darrowii, V. virgatum, or V. tenellum) blueberry genotypes, and progenies of the BNJ16-5 cross (V. corymbosum × V. darrowii). Using genotyping-by-sequencing (GBS), we generated more than 334 million reads (75 bp). The GBS reads were aligned to the V. corymbosum cv. Draper v1.0 reference genome sequence, and ~2.8 million reads were successfully mapped. From the alignments, we identified 2,244,039 single-nucleotide polymorphisms, which were used for principal component, haplotype, and admixture analysis. Principal component analysis revealed three main groups: (1) NHB cultivars, (2) SHB cultivars, and (3) BNJ16-5 progenies. The overall fixation index (FST) and nucleotide diversity for NHB and SHB cultivars indicated wide genetic differentiation, and haplotype analysis revealed that SHB cultivars are more genetically diverse than NHB cultivars. The admixture analysis identified a mixture of various lineages of parental genomic introgression. This study demonstrated the effectiveness of GBS-derived single-nucleotide polymorphism markers in genetic and admixture analyses to reveal genetic relatedness and to examine parental lineages in blueberry, which may be useful for future breeding plans.
Stacked generalizations in imbalanced fraud data sets using resampling methods

Predicting fraud is challenging due to inherent issues in the fraud data structure, since the crimes are committed through trickery or deceit with an ever-present moving target of changing modus op...
SQuARE: Semantics-based Question Answering and Reasoning Engine.

Understanding the meaning of a text is a fundamental challenge of natural language understanding (NLU) and from its early days, it has received significant attention through question answering (QA) tasks. We introduce a general semantics-based framework for natural language QA and also describe the SQuARE system, an application of this framework. The framework is based on the denotational semantics approach widely used in programming language research. In our framework, valuation function maps syntax tree of the text to its commonsense meaning represented using basic knowledge primitives (the semantic algebra) coded using answer set programming (ASP). We illustrate an application of this framework by using VerbNet primitives as our semantic algebra and a novel algorithm based on partial tree matching that generates an answer set program that represents the knowledge in the text. A question posed against that text is converted into an ASP query using the same framework and executed using the s(CASP) goal-directed ASP system. Our approach is based purely on (commonsense) reasoning. SQuARE achieves 100% accuracy on all the five datasets of bAbI QA tasks that we have tested. The significance of our work is that, unlike other machine learning based approaches, ours is based on "understanding" the text and does not require any training. SQuARE can also generate an explanation for an answer while maintaining high accuracy.
Impact of Guided Inquiry with Simulations on Knowledge of Electricity and Wave Phenomena

The impact of inquiry-based instruction on the improvement of content knowledge of electricity and wave properties in two studies was the subject of this investigation. Groups of pre-college and undergraduate students performed a series of tasks designed to determine the effectiveness of exploratory/investigative approaches to the study of wave properties in fostering content retention and conceptual change, as well as in comparison with traditionally performed experimental activities. The results show that a guided inquiry-based method using simulations significantly improves content performance on electricity and wave motion, although not in optics; in particular, it helps students to visualize charge exchanges and electric neutrality, the shape of electric fields, types of waves and their characteristics, and the effects of the transmitting medium on the speed of a wave. Additionally, its exploratory nature is superior to the confirmatory laboratory experience, both in content retention and in facilitating the incorporation of perceptual features that help learners deal with documented challenging properties of waves.