bluuebunny/crossref_metadata_2025_split huggingface dataset:
Strong gravitational lensing by DHOST black holes
Authors: Chagoya Javier , Ortiz C , Rodríguez Benito , Roque Armando A 
Published: January 2021

Abstract
The gravitational deflection of light in the strong field limit is an important test for alternative theories of gravity. However, solutions for the metric that allow for analytic computations are not always available. We implement a hybrid analytic-numerical approximation to determine the deflection angle in static, spherically symmetric spacetimes. We apply this to a set of numerical black hole solutions within the class of modified gravity theories known as degenerate higher order scalar–tensor theories (DHOST). Comparing our results to a more time consuming full numerical integration, we find that we can accurately describe the deflection angle for light rays passing at arbitrary distances from the photon sphere with a combination of two analytic-numerical approximations. Furthermore, we find a range of parameters where our DHOST black holes predict strong lensing effects whose size is comparable with the uncertainty in the properties of the supermassive black hole in M87 reported by the event horizon telescope, showing that strong lensing is a viable alternative to put constraints on these models of modified gravity.
On the language of elementary mechanics
Authors: Young-Ziegler Ariel , Pérez Patricia E , Binder P-M 
Published: January 2021

Abstract
We performed word frequency analysis of the mechanics portion of an algebra-based introductory physics text. We identified about 400 physics and auxiliary words that constitute the core vocabulary of this subject. We present and discuss our findings especially as they inform physics instruction and communication in English, indigenous, and sign languages. This includes the Hawaiian language, our initial motivation for undertaking this work.
Oscillator strengths and integral cross-sections of the valence-shell excitations of CH3Cl studied by fast electron scattering
Authors: Li Tian-Jun , Xu Yuan-Chen , Du Xiao-Jiao , Wang Li-Han , Ma Zi-Ru , Wang Shu-Xing , Zhu Lin-Fan 
Published: January 2021

Abstract
The generalized oscillator strengths (GOSs) of the valence-shell excitations of CH3Cl have been determined at an incident electron energy of 1500 eV and an energy resolution of about 70 meV. The momentum transfer dependence behaviors of the GOSs of the valence-shell excitations have been carefully analyzed, and the A band shows a strong dipole-forbidden characteristic. By extrapolating the GOSs to the limit of a zero squared momentum transfer, the optical oscillator strengths have been obtained, which provide an independent cross-check for the previous experimental and theoretical results. The BE-scaled integral cross sections (where B is the binding energy and E is the excitation energy) of the valence-shell excitations of CH3Cl have been derived systematically from the threshold to 5000 eV with the aid of a BE-scaling method. The results provide the fundamental spectroscopic data of CH3Cl and have important applications in photochemical modeling for atmospheric physics.
Underwater imaging enhancement based on a polarization filter and histogram attenuation prior
Authors: Hu Haofeng , Qi Pengfei , Li Xiaobo , Cheng Zhenzhou , Liu Tiegen 
Published: January 2021

Abstract
Underwater images always suffer from low contrast and inaccurate colors due to scattering and absorption by particles when the target light propagates through turbid water. In this paper, we first found that a lot of intensity space is occupied by fewer pixels, called ‘tails’, on both sides of the histograms for the red, green and blue channels of the image. Based on this histogram attenuation prior and taking account of the advantage of a polarization filter we proposed an effective polarimetric recovery method to enhance the underwater image quality, which includes a specially designed histogram processing method, named ‘cut-tail histogram stretching’. This processing overcomes the limitation of traditional histogram-based methods and can further improve the restoration performance. The experimental results corresponding to underwater scenes with different turbidities and colors show that the proposed method can simultaneously enhance the image contrast and reduce the color distortion to some extent, and thus realize clear underwater vision.
Stability of electron–hole liquid in quantum wells
Authors: Vasilchenko A A 
Published: January 2021

Abstract
Density functional theory is used to calculate the energy of electron–hole liquid and the equilibrium density of electron-hole pairs in quantum wells. Nonlinear Kohn–Sham equations for electrons and holes are solved numerically. The influence of the depth and width of the quantum well, the ratio of the hole and electron masses, and the spin splitting of the hole band on the properties of electron–hole liquid is studied. The critical temperature of electron–hole liquid in quantum wells is estimated. Good agreement between the calculations and experimental results is obtained.
Half-auxetic effect and ferroelasticity in a two-dimensional monolayer TiSe
Authors: Liu Ziyuan , Pan Jinbo , Zhang Yan-Fang , Du Shixuan 
Published: January 2021

Abstract
Two-dimensional (2D) materials with both auxetic effect and ferroelasticity are rare, however, have great application potential in next generation microelectromechanical and nanoelectronic devices. Here, we report the findings of an extraordinary combination half-auxetic effect and ferroelasticity in a single p2mm-type TiSe monolayer by performing first-principles calculations. The unique half-auxetic effect, namely the material expand laterally under both uniaxial tensile strain, and compressive strain, is reported and explained by considering both the nearest and the next-nearest interactions. The ferroelasticity is stemming from the degeneracy breaking of the 3d-orbitals of Ti atoms in a distorted tetrahedron crystal field, or the so-called Jahn–Teller effect. The results provide a guideline for the future design of novel 2D multiple functional materials at the nanoscale.
Triple-temperature readout in luminescence thermometry with Cr3+-doped Mg2SiO4 operating from cryogenic to physiologically relevant temperatures
Authors: Ristić Zoran , Đorđević Vesna , Medić Mina , Kuzman Sanja , Sekulić Milica , Antić Željka , Dramićanin Miroslav D 
Published: January 2021

Abstract
Cr3+-doped Mg2SiO4 orthorhombic nanoparticles are synthesized by a combustion method. The 3d3 electron configuration of the Cr3+ ion results in the deep-red emission from optical transitions between d–d orbitals. Two overlapping emissions from the Cr3+ spin-forbidden 2Eg→ 4A2g and the spin-allowed 4T2g→ 4A2g electronic transitions are influenced by the strong crystal field in Mg2SiO4 and, thus, are suitable for ratiometric luminescence thermometry. The temperature-induced changes in Cr3+-doped Mg2SiO4 emission are tested for use in luminescence thermometry from cryogenic to physiologically relevant temperatures (10–350 K) by three approaches: (a) temperature-induced changes of emission intensity; (b) temperature-dependent luminescence lifetime; and (c) temperature-induced changes of emission band position. The second approach offers applicable thermometry at cryogenic temperatures, starting from temperatures as low as 50 K, while all three approaches offer applicable thermometry at physiologically relevant temperatures with relative sensitivities of 0.7% K−1 for emission intensity, 0.8% K−1 for lifetime and 0.85% K−1 for band position at 310 K.
Multi-Δt approach for peak-locking error correction and uncertainty quantification in PIV
Authors: Adatrao Sagar , Bertone Michele , Sciacchitano Andrea 
Published: January 2021

Abstract
A novel approach is devised for the quantification of systematic uncertainty due to peak locking in particle image velocimetry (PIV), which also leads to correction of the peak-locking errors. The approach, applicable to statistical flow properties such as time-averaged velocity and Reynolds stresses, relies on image recordings with multiple time separations Δt and a least-squares regression of the measured quantities. In presence of peak locking, the measured particle image displacement is a non-linear function of Δt due to the presence of measurement errors which vary non-linearly with the sub-pixel particle image displacement. Additionally, the measured displacement fluctuations are a combination of the actual flow fluctuations and the measurement error. When the image recordings are acquired with multiple Δt’s, a least-squares regression among the statistical results yields a correction where systematic errors due to peak locking are significantly diminished. The methodology is assessed for planar PIV measurements of the flow over a NACA0012 airfoil at 10 degrees angle of attack. Reference measurements with much larger Δt than the Δt’s of the actual measurements, such that relative peak-locking errors are negligible for the former, are used to assess the validity of the proposed approach.
A molecular dynamics study on the local mobility of cis-polyisoprene within the mixed glassy/rubbery states induced by graphene planes
Authors: Sutthibutpong Thana 
Published: January 2021

Abstract
The glass transition behavior of a simulated model consisting of cis-1,4-polyisoprene nanofilm confined within parallel graphene planes was visualized through chain mobility statistics. Firstly, simulated annealing molecular dynamics (MD) simulations were performed for a system of bulk polyisoprene and the polyisoprene nanofilm within parallel graphene planes at two different gap sizes. The glass transition temperature (T
g) and the critical density of bulk polyisoprene were then calculated. The critical density was used to compare with the local density of the confined polyisoprene segments. The mixed glassy/rubbery states were found at temperatures higher than the bulk T
g. It was also shown that bulk modulus was increased when graphene planes are present and was further increased when the gap between graphene planes became narrow, and a ‘glassy bridge’ was formed by the highly confined nanofilm with highly-ordered polymer chains. Then, local mobility of each polyisoprene chain segment was quantified through the square displacement (SD) after a 1 ns motion. Local glass transition within any region was determined by whether local SD was lower than the critical mean square displacement (MSD0) of bulk polyisoprene, which was in the ‘glassy regime.’ The analysis results showed that decreasing the temperature and reducing the gap between graphene planes increased the proportion of chain segments in the glassy regime and were in concurrence with the increased bulk modulus.
A low-T
c superconducting modification of Th4H15 synthesized under high pressure
Authors: Wang N N , Shan P F , Chen K Y , Sun J P , Yang P T , Ma X L , Wang B S , Yu X H , Zhang S , Chen G F , Cheng J-G , Dong X L , Chen X H , Zhao Z X 
Published: January 2021

Abstract
Among the metal hydrides, Th4H15 is the first reported superconductor with a relatively high T
c ≈ 8 K at ambient pressure. Here we report on the synthesis and characterization of a low-T
c superconducting modification of Th4H15, which is obtained via hydrogenating Th metal at 5 GPa and 800 °C by using the ammonia borane as the hydrogen source. Measurements of resistivity, magnetic susceptibility, and specific heat confirm that the obtained Th4H15 sample shows a bulk superconducting transition at T
c ≈ 6 K, which is about 2 K lower than that reported previously. Various characteristic superconducting parameters have been extracted for this compound and unusual lattice dynamics were evidenced from the specific-heat analysis.
Using a Josephson junction as an effective on-chip temperature sensor
Authors: Durandetto Paolo , Sosso Andrea 
Published: January 2021

Abstract
Temperature sensing and control are essential in experiments running in cryocooled systems, as with the case of liquid helium-free superconducting devices. A Josephson junction as on-chip temperature sensor operated in ac provides the highest sensitivity and minimal power loading to the cryogenic environment, thanks to the noise rejection of lock-in detection. To demonstrate the advantages of on-chip sensing, we tested it with a Josephson voltage standard array in cryocooler and compared with the conventional case of a sensor on the cold surface of the refrigerator, showing that the power dissipated within the chip may further increment the device temperature up to some tenths of kelvin. An ac Josephson junction sensor is proven to be capable of directly stabilizing the temperature of the superconductive circuit from fluctuations of dissipated power during operation. Reliability issues related to flux trapping are discussed and solutions are proposed suited to different applications. Overall, on-chip control with ac Josephson temperature sensing has the advantage of avoiding the complexities in minimization of cryogenic thermal links, virtually reducing to zero the contact resistance and keeping the operating temperature of the superconductor constant, independently of instantaneous operating power.
Second-order delay ordinary differential equations, their symmetries and application to a traffic problem
Authors: Dorodnitsyn Vladimir A , Kozlov Roman , Meleshko Sergey V , Winternitz Pavel 
Published: January 2021

Abstract
This article is the third in a series, the aim of which is to use Lie group theory to obtain exact analytic solutions of delay ordinary differential systems (DODSs). Such a system consists of two equations involving one independent variable x and one dependent variable y. As opposed to ordinary differential equations (ODEs) the variable x figures in more than one point (we consider the case of two points, x and x
−). The dependent variable y and its derivatives figure in both x and x
−. Two previous articles were devoted to first-order DODSs, here we concentrate on a large class of second-order ones. We show that within this class the symmetry algebra can be of dimension n with 0 ⩽ n ⩽ 6 for nonlinear DODSs and must be infinite-dimensional for linear or linearizable ones. The symmetry algebras can be used to obtain exact particular group invariant solutions. As a specific application we present some exact solutions of a DODS model of traffic flow.
A Tamm plasmon-porous GaN distributed Bragg reflector cavity
Authors: Pugh J R , Harbord E G H , Sarua A , Fletcher P S , Tian Y , Wang T , Cryan M J 
Published: January 2021

Abstract
This paper reports on design, measurement and optimisation of a Tamm plasmon metal-distributed Bragg reflector (DBR) cavity for use in the green part of the visible spectrum. It uses an optimised silver layer thickness and a porous DBR created using a novel electro-chemical etching technique. This device has applications in low-cost lasers, photodetectors, and photoconductive switches for the visible wavelength range.
Cadmium stannate conductive layer with high optical transmittance and tunable work function
Authors: Zhu Ziyao , Du Zhongming , Liu Xiangxin , Zhang Yufeng , Wu Qiuchen , Lin Xinlu 
Published: January 2021

Abstract
200 nm cadmium stannate (Cd2SnO4) transparent conductive layer films with a sheet resistance of 6.35 Ω/sq and resistivity of 1.27 × 10−4 Ω · cm are deposited by magnetron sputtering coupling with adjustable target bias voltage followed by 620 °C 30 min annealing. The lowest resistivity of Cd2SnO4 films reported before was 1.28 × 10−4 Ω · cm, achieved with 510 nm Cd2SnO4. The average transmission rate of 200 nm sputtering Cd2SnO4 films between 400–800 nm is 94%. The deposition rate increase target bias voltage can the and electrical performance of Cd2SnO4 films. The surface work function of Cd2SnO4 films is also tunable by target bias voltage. The Cd2SnO4 phonon spectrum and phonon density of states combined with Raman microscope shows the Cd2SnO4 films with most ideal electric properties has a identical phonon response. XPS shows the chemical component of as-deposited Cd2SnO4 films and Cd2SnO4 films after annealing with 120 V target bias voltage is Cd2.03SnO6.36 and Cd1.25SnO4.15, respectively, which is contrary to the general conclusions that interstitial cadmium atoms and oxygen vacancies are the main self-doping defects in Cd2SnO4 films.
Spectroscopy and critical quantum thermometry in the ultrastrong coupling regime
Authors: Salado-Mejía M , Román-Ancheyta R , Soto-Eguibar F , Moya-Cessa H M 
Published: January 2021

Abstract
We present an exact analytical solution of the anisotropic Hopfield model, and we use it to investigate in detail the spectral and thermometric response of two ultrastrongly coupled quantum systems. Interestingly, we show that depending on the initial state of the coupled system, the vacuum Rabi splitting manifests significant asymmetries that may be considered spectral signatures of the counterintuitive decoupling effect. Using the coupled system as a thermometer for quantum thermodynamics applications, we obtain the ultimate bounds on the estimation of temperature that remain valid in the ultrastrong coupling regime. Remarkably, if the system performs a quantum phase transition, the quantum Fisher information exhibits periodic divergences, suggesting that one can have several points of arbitrarily high thermometric precision for such a critical quantum sensor.
2D materials and their heterostructures for photocatalytic water splitting and conversion of CO2 to value chemicals and fuels
Authors: Shanker G Shiva , Biswas Abhijit , Ogale Satishchandra 
Published: January 2021

Abstract
The rapidly increasing global energy consumption utilizing conventional polluting fuels has been putting enormous stress on the health of our environment and thereby the long term sustainability of the animal and plant life on our planet. The world clearly needs to move rapidly to the alternative sources of environment-friendly, carbon-neutral, clean and renewable energy. To this end, amongst the promising strategies being pursued, one of the best approaches is to produce hydrogen energy from water by using sunlight, with unlimited available resource of both water and sunlight. Concurrently, there is also an emergent need to control CO2 emissions by reducing them to valuable fuels or chemicals using sunlight. For both these goals, it is essential to have efficient, robust and affordable photocatalysts. The early emphasis on semiconductor photocatalysts along with expensive noble-metals co-catalysts has prevented the speedy advance of this energy technology. Extensive efforts are now being expended on designing high-performance photocatalysts based on emergent functional materials endowed with a fascinating set of physical and chemical properties. Towards this end, two-dimensional (2D) materials and their heterostructures have been attracting significant attention lately as potentially viable candidates owing to their unique, and highly tunable optical and electronics functionalities, which are technically adequate for the efficient hydrogen production and conversion of CO2 to fuels. In this topical review, we address the recent progress made in the domain. We believe that by virtue of the uniquely distinct characteristics of their electronic density of states, surface states, high surface area, and diverse possibilities of innovative surface chemical engineering, the 2D materials hold a great promise for facilitating economically viable renewable/clean energy harvesting solution(s) on commercial-scale, thereby accomplishing the urgent task of ensuring the future energy security for the world.
mlr3proba: an R package for machine learning in survival analysis
Authors: Sonabend Raphael , Király Franz J. , Bender Andreas , Bischl Bernd , Lang Michel 
Published: January 2021

ABSTRACTSummaryAs machine learning has become increasingly popular over the last few decades, so too has the number of machine-learning interfaces for implementing these models. Whilst many R libraries exist for machine learning, very few offer extended support for survival analysis. This is problematic considering its importance in fields like medicine, bioinformatics, economics, engineering and more. mlr3proba provides a comprehensive machine-learning interface for survival analysis and connects with mlr3’s general model tuning and benchmarking facilities to provide a systematic infrastructure for survival modelling and evaluation.Availability and implementationmlr3proba is available under an LGPL-3 licence on CRAN and at https://github.com/mlr-org/mlr3proba, with further documentation at https://mlr3book.mlr-org.com/survival.html.
Genomic and niche divergence in an Amazonian palm species complex
Authors: Bacon Christine D , Roncal Julissa , Andermann Tobias , Barnes Christopher J , Balslev Henrik , Gutiérrez-Pinto Natalia , Morales Hernán , Núñez-Avelleneda Luis Alberto , Tunarosa Natalia , Antonelli Alexandre 
Published: January 2021

AbstractEnvironmental heterogeneity across the landscape can cause lineage divergence and speciation. The Geonoma macrostachys (Arecaceae) species complex has been proposed as a candidate case of ecological speciation in Amazonia due to evidence of habitat partitioning and pre-zygotic reproductive barriers between co-occurring morphotypes at a local scale. In this study, we provide a continent-wide perspective of the divergence patterns in G. macrostachys by integrating data from morphological traits, target sequence capture, climate, soil and reproductive biology. A morphometric analysis revealed four morphogroups, defined by traits related to leaf shape. A coalescence-based phylogenetic analysis did not recover the morphogroups as monophyletic, indicating independent evolution of leaf shape across geographical space. We demonstrate scale-dependent habitat differentiation for two of the morphogroups, in which segregation driven mostly by climate was complete at the regional scale but incomplete at the continental scale. Contrary to previous evidence of reproductive isolation in the form of different pollinators and flowering times between sympatric G. macrostachys forms in Peru and Ecuador, these were not found in Colombia, suggesting reproductive barriers have evolved multiple times across its geographical range. Taken together, our findings suggest that ecological divergence and local adaptation is driving diversification in G. macrostachys, and that hyperdiverse regions such as Amazonia are probable arenas for ecological divergence in sympatry.
Extremely rapid stone formation in cystinuria: look out for dietary supplements!
Authors: Gillion Valentine , Saussez Thibaud-Pierre , Van Nieuwenhove Sandy , Jadoul Michel 
Published: January 2021

Abstract
Cystinuria is an autosomal recessive disease characterized by recurrent nephrolithiasis. The prevention of new stones is based on diluting and alkalinizing urine, as well as a low salt and moderate protein intake. The avoidance of food rich in methionine (the precursor of cystine) is also advocated. We report the case of a young adult adherent to the preventative strategy who was stone-free and within months formed a large stone. This coincided with the recent intake of a dietary supplement containing both cystine and methionine. Patients and physicians should be aware of the potential harm of such supplements in patients with cystinuria.