Miracle-dz/UniFAR-FTUs huggingface dataset:
Interplay between ferroelectricity and metallicity in BaTiO3†

We explore the interplay between ferroelectricity and metallicity, which are generally considered to be contra-indicated properties, in the prototypical ferroelectric barium titanate, BaTiO3. Using first-principles density functional theory, we calculate the effects of electron and hole doping, first by introducing a hypothetical background charge, and second through the introduction of explicit impurities (La, Nb and V for electron doping, and K, Al and Sc for hole doping). We find that, apart from a surprising increase in polarization at small hole concentrations, both charge-carrier types decrease the tendency towards ferroelectricity, with the strength of the polarization suppression, which is different for electrons and holes, determined by the detailed structure of the conduction and valence bands. Doping with impurity atoms increases the complexity and allows us to identify three factors that influence the ferroelectricity: structural effects arising largely from the size of the impurity ion, electronic effects from the introduction of charge carriers, and changes in unit-cell volume and shape. A competing balance between these contributions can result in an increase or decrease in ferroelectricity with doping.
Calculus and Digital Natives in Rendezvous: wxMaxima Impact

This article covers how a computer algebra system (CAS) wxMaxima can be explored for teaching single-variable and multivariable calculus to Korean digital natives. We present several examples where wxMaxima can handle calculus problems easily, not straightforwardly but still successfully with some human intervention, and unsuccessfully. By soliciting qualitative feedback on students’ experience in exploiting the CAS, we gathered a mixed reaction. Although some students commented positively, the majority seemed to be resistant to embracing a new technological tool.
Fourier transform infrared spectroscopy study of acid birnessites before and after Pb2+ adsorption

Abstract To provide fundamental knowledge for studying the relative content of vacant sites and exploring the mechanism of interaction between Pb2+ and birnessite, Fourier transform infrared spectroscopy (FTIR) of birnessites with different Mn average oxidation states (AOS) before and after Pb2+ adsorption were investigated. The number of absorption bands of FTIR spectra was determined by using the second derivatives of the original spectra. The band at 899-920 cm-1 was assigned to the bending vibration of -OH located at vacancies. The bands at 1059-1070, 1115-1124 and 1165-1171 cm-1 could be attributed to the vibrations of Mn(III)-OH in MnO6 layers, and the intensities of these bands increased with decreasing Mn AOS. The bands at 990 and 1023-1027 cm-1 were ascribed to the vibrations of Mn(III)-OH in the interlayers. Mn(III) in MnO6 layers partially migrated to interlayers during Pb2+ adsorption, which led to an increased intensity of the band at 990 cm-1. The band at 564-567cm-1 was assigned to the vibration of Mn-O located at vacancies. This band could split by coupling of vibrations due to Pb2+ and/or Mn2+ adsorbed at vacant sites. The large distance between the band at 610-626 cm-1 and that at 638-659 cm-1 might reflect small Mn(III) ions located in Mn(III)-rich rows.
Emergence of traveling waves and their stability in a free boundary model of cell motility

We introduce a two-dimensional Hele-Shaw type free boundary model for motility of eukaryotic cells on substrates. The key ingredients of this model are the Darcy law for overdamped motion of the cytoskeleton gel (active gel) coupled with advection-diffusion equation for myosin density leading to elliptic-parabolic Keller-Segel system. This system is supplemented with Hele-Shaw type boundary conditions: Young-Laplace equation for pressure and continuity of velocities. We first show that radially symmetric stationary solutions become unstable and bifurcate to traveling wave solutions at a critical value of the total myosin mass. Next we perform linear stability analysis of these traveling wave solutions and identify the type of bifurcation (subor supercritical). Our study sheds light on the mathematics underlying instability/stability transitions in this model. Specifically, we show that these transitions occur via generalized eigenvectors of the linearized operator.
Ion acceleration to 100 keV by the ExB wave mechanism in collision-less shocks

It is shown that ions can be accelerated to about 100 keV in the direction perpendicular to the magnetic field by the ExB mechanism of electrostatic waves. The acceleration occurs in discrete steps of duration being a small fraction of the gyroperiod and can explain observations of ion energization to 10 keV at quasi-perpendicular shocks and to hundreds keV at quasi-parallel shocks. A general expression is provided for the maximum energy of ions accelerated in shocks of arbitrary configuration. The waves involved in the acceleration are related to three cross-field current-driven instabilities: the lower hybrid drift (LHD) instability induced by the density gradients in shocks and shocklets, followed by the modified two-stream (MTS) and electron cyclotron drift (ECD) instabilities, induced by the ExB drift of electrons in the strong LHD wave electric field. The ExB wave mechanism accelerates heavy ions to energies proportional to the atomic mass number, which is consistent with satellite observations upstream of the bow shock and also with observations of post-shocks in supernovae remnants. The results are compared with other acceleration mechanisms traditionally discussed in the literature.
TRS: Transferability Reduced Ensemble via Encouraging Gradient Diversity and Model Smoothness

Adversarial Transferability is an intriguing property of adversarial examples – a perturbation that is crafted against one model is also effective against another model, which may arise from a different model family or training process. To better protect ML systems against such adversarial attacks, several questions are raised: what are the sufﬁcient conditions for adversarial transferability? Is it possible to bound such transferability? Is there a way to reduce the transferability in order to improve the robustness of an ensemble ML model? To answer these questions, in this work we aim to ﬁrst theoretically analyze and outline checkable sufﬁcient conditions for transferability between models; then propose a practical algorithm to reduce transferability between base models within an ensemble to improve its robustness. Our theoretical analysis, as the ﬁrst work, shows that only the orthogonality between gradients of different models is not enough to ensure low adversarial transferability; in the meantime, the model smoothness is an important factor to impact the transferability together with gradient orthogonality. In particular, we provide a lower bound of adversarial transferability based on model gradient similarity, as well as an upper bound for low risk classiﬁers based on gradient orthogonality and model smoothness. We demonstrate that under the condition of gradient orthogonality, smoother classiﬁers will guarantee lower adversarial transferability. Finally, inspired by our theoretical analysis, we propose an effective T ransferability R educed S mooth-ensemble (TRS) training strategy to train a robust ensemble with low transferability by enforcing model smoothness and gradient orthogonality between base models. We conduct extensive experiments on TRS and compare with 6 state-of-the-art ensemble baselines against 8 whitebox attacks on different datasets, showing that the proposed TRS outperforms all baselines signiﬁcantly. We believe our analysis on adversarial transferability will not only provide further understanding on predictions of ML models, but also inspire future research towards developing robust ML models taking these adversarial transferability properties into account.
Log-Domain Decoding of Quantum LDPC Codes Over Binary Finite Fields

A quantum stabilizer code over <inline-formula><tex-math notation="LaTeX">$\operatorname{GF}(q)$</tex-math></inline-formula> corresponds to a classical additive code over <inline-formula><tex-math notation="LaTeX">$\operatorname{GF}(q^2)$</tex-math></inline-formula> that is self-orthogonal with respect to a symplectic inner product. We study the decoding of quantum low-density parity-check (LDPC) codes over binary finite fields <inline-formula><tex-math notation="LaTeX">$\operatorname{GF}(q=2^l)$</tex-math></inline-formula> by the sum-product algorithm, also known as belief propagation (BP). Conventionally, a message in a nonbinary BP for quantum codes over <inline-formula><tex-math notation="LaTeX">$\operatorname{GF}(2^l)$</tex-math></inline-formula> represents a probability vector over <inline-formula><tex-math notation="LaTeX">$\operatorname{GF}(2^{2l})$</tex-math></inline-formula>, inducing high decoding complexity. In this article, we explore the property of the symplectic inner product and show that scalar messages suffice for BP decoding of nonbinary quantum codes, rather than vector messages necessary for the conventional BP. Consequently, we propose a BP decoding algorithm for quantum codes over <inline-formula><tex-math notation="LaTeX">${\operatorname{GF}(2^l)}$</tex-math></inline-formula> by passing scalar messages so that it has low computation complexity. The algorithm is specified in log domain by using log-likelihood ratios of the channel statistics to have a low implementation cost. Moreover, techniques such as message normalization or offset can be naturally applied in this algorithm to mitigate the effects of short cycles to improve the BP performance. This is important for nonbinary quantum codes since they may have more short cycles compared to binary quantum codes. Several computer simulations are provided to demonstrate these advantages. The scalar-based strategy can also be used to improve the BP decoding of classical linear codes over <inline-formula><tex-math notation="LaTeX">$\operatorname{GF}(2^l)$</tex-math></inline-formula> with many short cycles.
Biodegradable ionic liquids Part II. Effect of the anion and toxicology

Although ionic liquids are generally referred to in a 'green' context, little is known about their degradation in the environment. Part I of this series focused on the biodegradability of the commonly used dialkylimidazolium ionic liquids and the effect of the imidazolium cation on biodegradability. We now report the influence of the anion on biodegradability. Preliminary investigations into the toxicology of ionic liquids are also described.
Vertex connectivity in poly-logarithmic max-flows

The vertex connectivity of an m-edge n-vertex undirected graph is the smallest number of vertices whose removal disconnects the graph, or leaves only a singleton vertex. In this paper, we give a reduction from the vertex connectivity problem to a set of maxflow instances. Using this reduction, we can solve vertex connectivity in (mα) time for any α ≥ 1, if there is a mα-time maxflow algorithm. Using the current best maxflow algorithm that runs in m4/3+o(1) time (Kathuria, Liu and Sidford, FOCS 2020), this yields a m4/3+o(1)-time vertex connectivity algorithm. This is the first improvement in the running time of the vertex connectivity problem in over 20 years, the previous best being an Õ(mn)-time algorithm due to Henzinger, Rao, and Gabow (FOCS 1996). Indeed, no algorithm with an o(mn) running time was known before our work, even if we assume an (m)-time maxflow algorithm. Our new technique is robust enough to also improve the best Õ(mn)-time bound for directed vertex connectivity to mn1−1/12+o(1) time
LoFTR: Detector-Free Local Feature Matching with Transformers

We present a novel method for local image feature matching. Instead of performing image feature detection, description, and matching sequentially, we propose to first establish pixel-wise dense matches at a coarse level and later refine the good matches at a fine level. In contrast to dense methods that use a cost volume to search correspondences, we use self and cross attention layers in Transformer to obtain feature descriptors that are conditioned on both images. The global receptive field provided by Transformer enables our method to produce dense matches in low-texture areas, where feature detectors usually struggle to produce repeatable interest points. The experiments on indoor and outdoor datasets show that LoFTR outperforms state-of-the-art methods by a large margin. LoFTR also ranks first on two public benchmarks of visual localization among the published methods. Code is available at our project page: https://zju3dv.github. io/loftr/.
Multicomponent Fokas–Lenells equations on Hermitian symmetric spaces

Multi-component integrable generalizations of the Fokas–Lenells equation, associated with each irreducible Hermitian symmetric space are formulated. Description of the underlying structures associated to the integrability, such as the Lax representation and the bi-Hamiltonian formulation of the equations is provided. Two reductions are considered as well, one of which leads to a nonlocal integrable model. Examples with Hermitian symmetric spaces of all classical series of types A.III, BD.I, C.I and D.III are presented in details, as well as possibilities for further reductions in a general form.
Stochastic Modeling of an Infectious Disease, Part III-B: Analysis of the Time-Nonhomogeneous BDI Process and Simulation Experiments of both BD and BDI Processes

In Section 1, we revisit the partial differential equation (PDE) for the probability generating function (PGF) of the time-nonhomogeneous BDI (birth-and-death-with-immigration) process and derive a closed form solution. To the best of our knowledge, this is a new mathematical result. We state this result as Proposition 1. We state as Corollary 1 that the negative binomial distribution of the time-homogeneous BDI process discussed in Part I [2] extends to the general time-nonhomogeneous case, provided that the ratio of the immigration rate ν(t) to the birth rate λ(t) is a constant. In section 1.2, we take up the heuristic approach discussed by Bartlett and Bailey (1964), and carry it out to completion by arriving at the solution obtained above,. In Section 2, we present the results of our extensive simulation experiments of the timenonhomogeneous BD process that was analyzed in Part III-A [3] and confirm our analytic results. In Section 3, we undertake similar simulation experiments for the BDI process that is analyzed in Section 1. As we discuss in Section 4, our stochastic model now seems more promising and powerful than has been heretofore expected. In Appendix B, a closed form solution for the M(t)/M(t)/∞ queue is obtained, as a special case of this BDI process model.
Schrödinger-Newton-Hooke system in higher dimensions: Stationary states

The Schrödinger equation with a harmonic potential coupled to the Poisson equation, called the Schrödinger–Newton–Hooke (SNH) system, has been considered in a variety of physical contexts, ranging from quantum mechanics to general relativity. Our work is directly motivated by the fact that the SNH system describes the nonrelativistic limit of the Einstein-massive-scalar system with negative cosmological constant. With this paper we begin the investigations aiming at understanding solutions of the SNH system in the energy supercritical spatial dimensions d ≥ 7, where we expect to observe interesting short wavelength behaviours due to the confinement of waves by the trapping potential. Here we study stationary solutions and prove existence of one-parameter families of nonlinear ground and excited states. The frequency of the ground state as the function of the central density is shown to exhibit different qualitative behaviours in dimensions 7 ≤ d ≤ 15 and d ≥ 16, which is expected to affect the stability properties of the ground states in these dimensions. Our results bear many similarities to the analogous problem that has been studied for the GrossPitaevskii equation.
Upper-tail large deviation principle for the ASEP

We consider the asymmetric simple exclusion process (ASEP) on $\mathbb{Z}$ started from step initial data and obtain the exact Lyapunov exponents for $H_0(t)$, the integrated current of ASEP. As a corollary, we derive an explicit formula for the upper-tail large deviation rate function for $-H_0(t)$. Our result matches with the rate function for the integrated current of the totally asymmetric simple exclusion process (TASEP) obtained in [Johansson 00](arXiv:math/9903134).
Convolutional Dynamic Alignment Networks for Interpretable Classifications

We introduce a new family of neural network models called Convolutional Dynamic Alignment Networks 1 (CoDA-Nets), which are performant classifiers with a high degree of inherent interpretability. Their core building blocks are Dynamic Alignment Units (DAUs), which linearly transform their input with weight vectors that dynamically align with task-relevant patterns. As a result, CoDA-Nets model the classification prediction through a series of input-dependent linear transformations, allowing for linear decomposition of the output into individual input contributions. Given the alignment of the DAUs, the resulting contribution maps align with discriminative input patterns. These model-inherent decompositions are of high visual quality and outperform existing attribution methods under quantitative metrics. Further, CoDA-Nets constitute performant classifiers, achieving on par results to ResNet and VGG models on e.g. CIFAR-10 and TinyImagenet.
Long-Lasting Orientation of Symmetric-Top Molecules Excited by Two-Color Femtosecond Pulses

Impulsive orientation of symmetric-top molecules excited by two-color femtosecond pulses is considered. In addition to the well-known transient orientation appearing immediately after the pulse and then reemerging periodically due to quantum revivals, we report the phenomenon of field-free long-lasting orientation. Long-lasting means that the time averaged orientation remains non-zero until destroyed by other physical effects, e.g., intermolecular collisions. The effect is caused by the combined action of the field-polarizability and field-hyperpolarizability interactions. The dependence of degree of long-lasting orientation on temperature and pulse parameters is considered. The effect can be measured by means of second (or higher-order) harmonic generation, and may be used to control the deflection of molecules traveling through inhomogeneous electrostatic fields.
Deep Learning assessment of galaxy morphology in S-PLUS Data Release 1

The morphological diversity of galaxies is a relevant probe of galaxy evolution and cosmological structure formation, but the classification of galaxies in large sky surveys is becoming a significant challenge. We use data from the Stripe-82 area observed by the Southern Photometric Local Universe Survey (S-PLUS) in 12 optical bands, and present a catalogue of the morphologies of galaxies brighter than r = 17 mag determined both using a novel multiband morphometric fitting technique and Convolutional Neural Networks (CNNs) for computer vision. Using the CNNs, we find that, compared to our baseline results with three bands, the performance increases when using 5 broad and 3 narrow bands, but is poorer when using the full 12 band S-PLUS image set. However, the best result is still achieved with just three optical bands when using pre-trained network weights from an ImageNet data set. These results demonstrate the importance of using prior knowledge about neural network weights based on training in unrelated, extensive data sets, when available. Our catalogue contains 3274 galaxies in Stripe-82 that are not present in Galaxy Zoo 1 (GZ1), and we also provide our classifications for 4686 galaxies that were considered ambiguous in GZ1. Finally, we present a prospect of a novel way to take advantage of 12 band information for morphological classification using morphometric features, and we release a model that has been pre-trained on several bands that could be adapted for classifications using data from other surveys. The morphological catalogues are publicly available.
Full-Duplex mmWave Massive MIMO Systems: A Joint Hybrid Precoding/Combining and Self-Interference Cancellation Design

Millimeter-wave (mmWave) massive multiple-input multiple-output (MIMO) systems have been considered as one of the primary candidates for the fifth generation (5G) and beyond 5G wireless communication networks to satisfy the ever-increasing capacity demands. Full-duplex technology can further enhance the advantages of mmWave massive MIMO systems. However, the strong self-interference (SI) is the major limiting factor in the full-duplex technology. Hence, this paper proposes a novel angular-based joint hybrid precoding/combining (AB-JHPC) technique for the full-duplex mmWave massive-MIMO systems. Our primary goals are listed as: (i) improving the self-interference cancellation (SIC), (ii) increasing the intended signal power, (iii) decreasing the channel estimation overhead, (iv) designing the massive MIMO systems with a low number of RF chains. First, the RF-stage of AB-JHPC is developed via slow time-varying angle-of-departure (AoD) and angle-of-arrival (AoA) information. A joint transmit/receive RF beamformer design is proposed for covering (excluding) the AoD/AoA support of intended (SI) channel. Second, the BB-stage of AB-JHPC is constructed via the reduced-size effective intended channel. After using the well-known singular value decomposition (SVD) approach at the BB-stage, we also propose a new semi-blind minimum mean square error (S-MMSE) technique to further suppress the residual SI power by using AoD/AoA parameters. Thus, the instantaneous SI channel knowledge is not needed in the proposed AB-JHPC technique. Finally, we consider a transfer block architecture to minimize the number of RF chains. The numerical results demonstrate that the SI signal is remarkably canceled via the proposed AB-JHPC technique. It is shown that AB-JHPC achieves 85.7 dB SIC and the total amount of SIC almost linearly increases via antenna isolation techniques. We observe that the proposed full-duplex mmWave massive MIMO systems double the achievable rate capacity compared to its half-duplex counterpart as the antenna array size increases and the transmit/receive antenna isolation improves. Moreover, the proposed S-MMSE algorithm provides considerably high capacity than the conventional SVD approach.
Polycyclic Aromatic Hydrocarbons in Superficial Sediments of the Negro River in the Amazon Region of Brazil

Polycyclic aromatic hydrocarbons (PAHs) were identified and quantified in samples of superficial sediments of the Negro River, in the Amazon region of Brazil, through analyses performed by GC/MS. Total PAH concentration that includes parent and alkylated PAHs ranged from 6.5 to 5348 ng g-1 of dry weight. The ∑16 PAHs prioritized in environmental studies by the U.S. Environmental Protection Agency (USEPA) ranged from 5.6 to 1187 ng g-1. The most contaminated places were those where muddy sediments were found, with the highest concentrations of organic matter, carbon and total nitrogen. The priority PAHs with high molecular weight represented 70% of the total abundance and showed that the main source of contamination of the sediments was pyrogenic. However, petrogenic PAHs coming from oil and derivatives input is also an important contamination source to be considered.