Miracle-dz/UniFAR-FTUs huggingface dataset:
Learning 4DVAR inversion directly from observations

Variational data assimilation and deep learning share many algorithmic aspects in common. While the former focuses on system state estimation, the latter provides great inductive biases to learn complex relationships. We here design a hybrid architecture learning the assimilation task directly from partial and noisy observations, using the mechanistic constraint of the 4DVAR algorithm. Finally, we show in an experiment that the proposed method was able to learn the desired inversion with interesting regularizing properties and that it also has computational interests.
Variable selection for nonlinear Cox regression model via deep learning

Variable selection problem for the nonlinear Cox regression model is considered. In survival analysis, one main objective is to identify the covariates that are associated with the risk of experiencing the event of interest. The Cox proportional hazard model is being used extensively in survival analysis in studying the relationship between survival times and covariates, where the model assumes that the covariate has a log-linear effect on the hazard function. However, this linearity assumption may not be satisfied in practice. In order to extract a representative subset of features, various variable selection approaches have been proposed for survival data under the linear Cox model. However, there exists little literature on variable selection for the nonlinear Cox model. To break this gap, we extend the recently developed deep learning-based variable selection model LassoNet to survival data. Simulations are provided to demonstrate the validity and effectiveness of the proposed method. Finally, we apply the proposed methodology to analyze a real data set on diffuse large B-cell lymphoma.
Time-resolved Polarimetry of the Superluminous SN 2015bn with the Nordic Optical Telescope

We present imaging polarimetry of the superluminous supernova SN 2015bn, obtained over nine epochs between −20 and +46 days with the Nordic Optical Telescope. This was a nearby, slowly evolving Type I superluminous supernova that has been studied extensively and for which two epochs of spectropolarimetry are also available. Based on field stars, we determine the interstellar polarization in the Galaxy to be negligible. The polarization of SN 2015bn shows a statistically significant increase during the last epochs, confirming previous findings. Our well-sampled imaging polarimetry series allows us to determine that this increase (from ∼0.54% to ≳1.10%) coincides in time with rapid changes that took place in the optical spectrum. We conclude that the supernova underwent a “phase transition” at around +20 days, when the photospheric emission shifted from an outer layer, dominated by natal C and O, to a more aspherical inner core, dominated by freshly nucleosynthesized material. This two-layered model might account for the characteristic appearance and properties of Type I superluminous supernovae.
Compton-thick AGNs in the NuSTAR Era. III. A Systematic Study of the Torus Covering Factor

We present the analysis of a sample of 35 candidate Compton-thick active galactic nuclei (AGNs) selected in the nearby universe (average redshift ) with the Swift-BAT 100-month survey. All sources have available NuSTAR data, thus allowing us to constrain with unprecedented quality important spectral parameters such as the obscuring torus line-of-sight column density (NH,z), the average torus column density (NH,tor), and the torus covering factor (fc). We compare the best-fit results obtained with the widely used MYTorus (Murphy & Yaqoob ) model with those of the recently published borus02 model (Baloković et al. ) used in the same geometrical configuration of MYTorus (i.e., with fc = 0.5). We find a remarkable agreement between the two, although with increasing dispersion in NH,z moving toward higher column densities. We then use borus02 to measure fc. High-fc sources have, on average, smaller offset between NH,z and NH,tor than low-fc ones. Therefore, low fc values can be linked to a “patchy torus” scenario, where the AGN is seen through an overdense region in the torus, while high-fc objects are more likely to be obscured by a more uniform gas distribution. Finally, we find potential evidence of an inverse trend between fc and the AGN 2–10 keV luminosity, i.e., sources with higher fc values have on average lower luminosities.
Characteristics of a Zn0.7Mg0.3O∕ZnO heterostructure field-effect transistor grown on sapphire substrate by molecular-beam epitaxy

Characterization of a Zn0.7Mg0. 3O∕ZnO heterostructure field-effect transistor (HFET) is reported. The HFET was based on a Zn0.7Mg0. 3O∕ZnO∕Zn0.7Mg0. 3O single quantum well (SQW) grown on an a-plane sapphire substrate by molecular-beam epitaxy, and was fabricated by a conventional photolithography technique combined with dry etching. Room-temperature characteristic of the HFET was a n-channel depletion type with a transconductance of 0.70mS∕mm and a field-effect mobility of 140cm2∕Vs, in good agreement with the electron Hall mobility in SQW of 130cm2∕Vs. The on∕off ratio at VDS=3V was ∼800, which was limited by an insufficiently suppressed leakage current through the bottom Zn0.7Mg0. 3O barrier.
Effects of impurities in random sequential adsorption on a one-dimensional substrate

We have solved the kinetics of random sequential adsorption of linear k-mers on a one-dimensional disordered substrate for the random sequential adsorption initial condition and for the random initial condition. The jamming limits \ensuremath{\theta}(\ensuremath{\infty},k\ensuremath{'},k) at a fixed length of linear k-mers have a minimum point at a particular density of the linear k\ensuremath{'}-mer impurity for both cases. The coverage of the surface and the jamming limits are compared to the results for Monte Carlo simulation. The Monte Carlo results for the jamming limits are in good agreement with the analytical results. The continuum limits are derived from the analytical results on lattice substrates.
Plasmonic performance of AuxAgyCu1−x−y alloys from many-body perturbation theory

We present a detailed appraisal of the optical and plasmonic properties of ordered alloys of the form AuxAgyCu1-x-y, as predicted by means of first-principles many-body perturbation theory augmented by a semi-empirical Drude–Lorentz model. In benchmark simulations on elemental Au, Ag, and Cu, we find that the random-phase approximation (RPA) fails to accurately describe inter-band transitions when it is built upon semi-local approximate Kohn–Sham density-functional theory band-structures. We show that non-local electronic exchange-correlation interactions sufficient to correct this, particularly for the fully-filled, relatively narrow d-bands which contribute strongly throughout the low-energy spectral range (0–6 eV), may be modeled very expediently using band-stretching operators that imitate the effect of a perturbative self-energy correction incorporating quasiparticle (QP) mass renormalization. We thereby establish a convenient work-flow for carrying out approximated spectroscopic calculations on alloys and, in particular here, we have considered alloy concentrations down to 12.5% in , including all possible crystallographic orderings of face-centred cubic type. We develop a pragmatic procedure for calculating the Drude plasmon frequency from first principles, including self-energy effects, as well as a semi-empirical scheme for interpolating the plasmon inverse lifetimes between stoichiometries. A distinctive M-shaped profile is observed in both quantities for binary alloys, in qualitative agreement with previous experimental findings. A range of optical and plasmonic figures of merit are discussed, and plotted for ordered at three representative solid-state laser wavelengths. On this basis, we predict that certain compositions may offer improved performance over elemental Au for particular application types. We predict that while the loss functions for both bulk and surface plasmons are typically diminished in strength through binary alloying, certain stoichiometric ratios may exhibit higher-quality (longer-lived) localized surface-plasmons and surface-plasmon polaritons, at technologically-relevant wavelengths, than those in elemental Au.
Feature Analysis for Machine Learning-based IoT Intrusion Detection

Internet of Things (IoT) networks have become an increasingly attractive target of cyberattacks. Powerful Machine Learning (ML) models have recently been adopted to implement network intrusion detection systems to protect IoT networks. For the successful training of such ML models, selecting the right data features is crucial, maximising the detection accuracy and computational efficiency. This paper comprehensively analyses feature sets' importance and predictive power for detecting network attacks. Three feature selection algorithms: chi-square, information gain and correlation, have been utilised to identify and rank data features. The attributes are fed into two ML classifiers: deep feed-forward and random forest, to measure their attack detection performance. The experimental evaluation considered three datasets: UNSW-NB15, CSE-CIC-IDS2018, and ToN-IoT in their proprietary flow format. In addition, the respective variants in NetFlow format were also considered, i.e., NF-UNSW-NB15, NF-CSE-CIC-IDS2018, and NF-ToN-IoT. The experimental evaluation explored the marginal benefit of adding individual features. Our results show that the accuracy initially increases rapidly with adding features but converges quickly to the maximum. This demonstrates a significant potential to reduce the computational and storage cost of intrusion detection systems while maintaining near-optimal detection accuracy. This has particular relevance in IoT systems, with typically limited computational and storage resources.
High‐frequency asymptotic analysis of a dissipative transmission problem resulting in generalized impedance boundary conditions

The present work investigates boundary conditions that modelize the penetration of a time-harmonic wave into a dissipative obstacle. The exact model is given through a transmission problem that couples the propagations into an absorbing domain and an exterior domain. The conditions arise from an asymptotic analysis of the interior solution whose propagation is studied by using pseudodifferential technics classically involved for the construction of radiation boundary conditions. Herein, first and second-order conditions are analyzed and some numerical experiments illustrate their validity domain.
Strain and Band-Gap Engineering in 
Ge
-
Sn
 Alloys via 
P
 Doping

Ge with a quasi-direct band gap can be realized by strain engineering, alloying with Sn, or ultrahigh n-type doping. In this work, we use all three approaches together to fabricate direct-band-gap Ge-Sn alloys. The heavily doped n-type Ge-Sn is realized with CMOS-compatible nonequilibrium material processing. P is used to form highly doped n-type Ge-Sn layers and to modify the lattice parameter of P-doped Ge-Sn alloys. The strain engineering in heavily-P-doped Ge-Sn films is confirmed by x-ray diffraction and micro Raman spectroscopy. The change of the band gap in P-doped Ge-Sn alloy as a function of P concentration is theoretically predicted by density functional theory and experimentally verified by near-infrared spectroscopic ellipsometry. According to the shift of the absorption edge, it is shown that for an electron concentration greater than 1x10^20 cm-3 the band-gap renormalization is partially compensated by the Burstein-Moss effect. These results indicate that Ge-based materials have high potential for use in near-infrared optoelectronic devices, fully compatible with CMOS technology.
Influence of picosecond laser irradiation on nickel-based superalloy surface microstructure

The investigation presented in this paper was carried out on the nickel-based superalloy, Nimonic 263, a material widely used at elevated temperatures and pressures. The samples were exposed to a Nd3+:YAG pulsed laser, at a wavelength of 1064 nm and a pulse duration of 170 ps, and the estimated threshold damage was 2 mJ. Different pulse energies and numbers of pulses were applied in air and helium-enriched atmospheres. Spots obtained by the laser interaction with the material were observed by optical and scanning electron microscopes and analyzed by energy-dispersive spectroscopy. Vickers microhardness tests were performed. In this paper, the changes that had occurred at the sample surface microstructure as a result of laser–material interaction are discussed with the aim of contributing to the determination of optimal laser parameters in the laser surface treatment process.
Dissipative phonon-Fock-state production in strong nonlinear optomechanics

We put forward a deterministic dissipative protocol to prepare phonon Fock states in nonlinear quantum optomechanical devices. The system is composed of a mechanical mode interacting with an optical field via radiation pressure, whereas the light mode is laser-driven in the resolved blue-sideband regime. To keep our results tractable, we have switched to an interaction picture in a displaced basis, where the effective Hamiltonian exhibits the selective photon-phonon interaction explicitly. After proper parameter adjustment and similarly to cavity-cooling schemes, the quantum evolution allows steering the mechanical degree of freedom to the desired Fock state by directing the optical excitations dynamically towards the target phonon state. The numerical results, including decoherence on both the mechanical and the optical degrees of freedom, show to be quite robust in the good- and bad-cavity regimes with fidelities exceeding $95\%$. Lastly, characterization of the achieved nonclassicality, as well as the limitations and feasibility of our protocol under experimental parameters, are also analyzed.
Region-based super-resolution using adaptive diffusion regularization

In conventional super-resolution algorithms, a single scheme is usually adopted and applied for a whole image, regardless of region characteristics. Since an image consists of various regions having different characteristics, these algorithms may not provide equally good performance for all regions. To alleviate this fundamental drawback of the conventional approach, we propose a region-based super-resolution algorithm. In the algorithm, an image is first analyzed and segmented into smooth, intermediate, and edge regions. According to the region type, a different diffusion-based regularization term and different reconstruction parameters are then used. For regularization in edge regions in particular, we adopt directional smoothing based on adaptive anisotropic diffusion, rather than omni-directional smoothing, to restore the continuity and sharpness of edges and simultaneously reduce undesired noise. The reconstruction parameters are independently managed, depending on the region type, to maximize the visual quality of the whole image. Experimental results show that the proposed method improves the objective quality as well as the subjective visual quality of reconstructed high-resolution images.
A Study of the Strong Gravity Region of the Black Hole in GS 1354–645

It is thought that the spacetime metric around astrophysical black holes is well described by the Kerr solution of Einstein’s gravity. However, robust observational evidence of the Kerr nature of these objects is still lacking. Here we fit the X-ray spectrum of the stellar-mass black hole in GS 1354–645 with a disk reflection model beyond Einstein’s gravity in order test the Kerr black hole hypothesis. We consider the Johannsen metric with the deformation parameters α13 and α22. The Kerr metric is recovered for . For α22 = 0, our measurements of the black hole spin and of the deformation parameter α13 are and −0.34 < α13 < 0.16, respectively. For α13 = 0, we find a* > 0.975 and −0.09 < α22 < 0.42. All the reported uncertainties are at 99% of confidence level for two relevant parameters.
A Genetic Algorithm-based Exploration of Three Filament Models: A Case for the Magnetic Support of the G11.11–0.12 Infrared-dark Cloud

The G11.11-0.12 infrared-dark cloud has a filamentary appearance, both in extinction against the diffuse infrared emission of the Galactic plane and in emission at 850 μm. We use a novel computational technique based on an advanced genetic algorithm to explore thoroughly three different models of self-gravitating, pressure-truncated filaments and to constrain their parameters. Specifically, the models tested are the nonmagnetic Ostriker model, a generalized version of the magnetic Stodólkiewicz model, and the magnetic Fiege & Pudritz model. Previous results showed that G11.11-0.12 has a much steeper ~r-4 radial density profile than other filaments, where the density varies approximately as r-2, and that this steep density profile is consistent with the Ostriker model. We present a more complete analysis that shows that the radial structure of G11.11-0.12 is consistent with regimes of each of these models. All of the magnetic models that agree with the data are threaded by a dominant poloidal magnetic field, and most have dynamically significant fields. Thus, G11.11-0.12 is an excellent candidate for radial support by a magnetic field that is predominantly poloidal. We predict the polarization patterns expected for both magnetic models and show that the two magnetic models produce different polarization patterns that should be distinguished by observations.
Final-state effects in the 3 d photoelectron spectrum of Fe 3 O 4 and comparison with Fe x O

Photoelectron-spin-polarization measurements with photon energies up to 11 eV on ${\mathrm{Fe}}_{3}$${\mathrm{O}}_{4}$ and energy distribution curves in the photon energy range $5lh\ensuremath{\nu}l90$ eV on magnetite ${\mathrm{Fe}}_{3}$${\mathrm{O}}_{4}$ and wustite (FeO) are interpreted in terms of the atomic theory of the single-ion-in-a-crystal-field model. The combination of the two different experiments yields the shapes and positions of the filled oxygen $2p$ bands and the $3{d}^{n\ensuremath{-}1}$ final states of Fe ions with a reliability previously not attained. The $3{d}^{n\ensuremath{-}1}$-multiplet structure of ${\mathrm{Fe}}_{3}$${\mathrm{O}}_{4}$ can be explained with the following set of parameters: $10Dq=1.75$ eV and the Racah parameter $B=645$ ${\mathrm{cm}}^{\ensuremath{-}1}$ for ${\mathrm{Fe}}^{3+}$ left behind in $B$ lattice sites; $10Dq=1.55$ eV for ${\mathrm{Fe}}^{4+}$ in $A$ sites. The difference in threshold for photoionization of ${\mathrm{Fe}}^{2+}$ and ${\mathrm{Fe}}^{3+}$ in $B$ sites is 1.0 eV. The oxygen $2p$ emission is found to be centered at 7.3 eV below the Fermi level with a full width of 3 eV at half-maximum. The $3d$-multiplet structure of ${\mathrm{Fe}}_{x}\mathrm{O}$ can be explained with $10Dq=1.7\ifmmode\pm\else\textpm\fi{}0.1$ eV and $B=800$ ${\mathrm{cm}}^{\ensuremath{-}1}$.
Quantum entanglement as an interpretation of bosonic character in composite two-particle systems

We consider a composite particle formed by two fermions or two bosons. We discover that composite behavior is deeply related to the quantum entanglement between the constituent particles. By analyzing the properties of creation and annihilation operators, we show that bosonic character emerges if the constituent particles become strongly entangled. Such a connection is demonstrated explicitly in a class of two-particle wave functions.
New Observations of Extra-Disk Molecular Gas in Interacting Galaxy Systems, Including a Two-Component System in Stephan’s Quintet

We present new CO (1–0) observations of 11 extragalactic tails and bridges in nine interacting galaxy systems, almost doubling the number of such features with sensitive CO measurements. Eight of these 11 features were undetected in CO to very low CO/H I limits, with the most extreme case being the NGC 7714/5 bridge. This bridge contains luminous H II regions and has a very high H I column density (1.6 × 1021 cm-2 in the 55″ CO beam), yet was undetected in CO to rms T = 2.4 mK. The H I column density is higher than standard H2 and CO self-shielding limits for solar-metallicity gas, suggesting that the gas in this bridge is metal-poor and has an enhanced N/ICO ratio compared with the Galactic value. Only one of the 11 features in our sample was unambiguously detected in CO, a luminous H I–rich star formation region near an optical tail in the compact group Stephan's Quintet. We detect CO at two widely separated velocities in this feature, at ∼6000 and ∼6700 km s-1. Both of these components have H I and Hα counterparts. These velocities correspond to those of galaxies in the group, suggesting that this gas is material that has been removed from two galaxies in the group. The CO/H I/Hα ratios for both components are similar to global values for spiral galaxies.
Scaling laws in the distribution of galaxies

Past surveys have revealed that the large-scale distribution of galaxies in the universe is far from random: it is highly structured over a vast range of scales. Surveys being currently undertaken and being planned for the next decades will provide a wealth of information about this structure. The ultimate goal must be not only to describe galaxy clustering as it is now, but also to explain how this arose as a consequence of evolutionary processes acting on the initial conditions that we see in the cosmic microwave background anisotropy data. In order to achieve this we need to build mathematically quantifiable descriptions of cosmic structure. Identifying where scaling laws apply and the nature of those scaling laws is an important part of understanding which physical mechanisms have been responsible for the organization of clusters of galaxies, superclusters, and the voids between them. Finding where these scaling laws are broken is equally important since this indicates the transition to different underlying physics. In describing scaling laws it is helpful to make analogies with fractals, mathematical constructs that can possess a wide variety of scaling properties. We must beware, however, of saying that the universe is a fractal on some range of scales: it merely exhibits a specific kind of fractal-like behavior on those scales. The richness of fractal scaling behavior is an important supplement to the usual battery of statistical descriptors. This article reviews the history of how we have learned about the structure of the universe and presents the data and methodologies that are relevant to an understanding of any scaling properties that structure may have. The ultimate goal is to have a complete understanding of how that structure emerged. We are getting close!
AGN-driven Convection in Galaxy-Cluster Plasmas

This paper describes how active galactic nuclei can heat galaxy-cluster plasmas by driving convection in the intracluster medium. A model is proposed in which a central supermassive black hole accretes intracluster plasma at the Bondi rate ṀBondi and powers a radio source. The central radio source produces cosmic rays, which mix into the thermal plasma. The cosmic-ray luminosity Lcr is ∝ṀBondic2. The cosmic-ray pressure gradient drives convection, which causes plasma heating. It is assumed that plasma heating balances radiative cooling. The plasma heating rate is self-regulating because ṀBondi is a decreasing function of the specific entropy near the cluster center s0; if heating exceeds cooling, then s0 increases, ṀBondi and Lcr decrease, and the convective heating rate is reduced. This paper focuses on the role of intracluster magnetic fields, which affect convection by causing heat and cosmic rays to diffuse primarily along magnetic field lines. A new stability criterion is derived for convection in a thermal-plasma/cosmic-ray fluid, and equations for the average fluid properties in a convective cluster are obtained with the use of a nonlocal two-fluid mixing-length theory. Numerical solutions of the model equations compare reasonably well with observations without requiring fine-tuning of the model parameters.