bluuebunny/crossref_metadata_2025_split huggingface dataset:
Jet collimation in NGC 315 and other nearby AGN
Authors: Boccardi B. , Perucho M. , Casadio C. , Grandi P. , Macconi D. , Torresi E. , Pellegrini S. , Krichbaum T. P. , Kadler M. , Giovannini G. , Karamanavis V. , Ricci L. , Madika E. , Bach U. , Ros E. , Giroletti M. , Zensus J. A. 
Published: January 2021

Aims. The collimation of relativistic jets in galaxies is a poorly understood process. Detailed radio studies of the jet collimation region have been performed so far in a few individual objects, providing important constraints for jet formation models. However, the extent of the collimation zone as well as the nature of the external medium possibly confining the jet are still debated.
Methods. In this article, we present a multifrequency and multiscale analysis of the radio galaxy NGC 315, including the use of mm-VLBI data up to 86 GHz, aimed at revealing the evolution of the jet collimation profile. We then consider results from the literature to compare the jet expansion profile in a sample of 27 low-redshift sources, mainly comprising radio galaxies and BL Lacs, which were classified based on the accretion properties as low-excitation (LEG) and high-excitation (HEG) galaxies.
Results. We propose that the jet collimation in NGC 315 is completed on sub-parsec scales. A transition from a parabolic to conical jet shape is detected at zt = 0.58 ± 0.28 parsecs or ∼5 × 103 Schwarzschild radii (RS) from the central engine, a distance which is much smaller than the Bondi radius, rB ∼ 92 pc, estimated based on X-ray data. The jet in this and in a few other LEG in our sample may be initially confined by a thick disk extending out to ∼103 − 104RS. A comparison between the mass-scaled jet expansion profiles of all sources indicates that jets in HEG are surrounded by thicker disk-launched sheaths and collimate on larger scales with respect to jets in LEG. These results suggest that disk winds play an important role in the jet collimation mechanism, particularly in high-luminosity sources. The impact of winds on the origin of the FRI and FRII dichotomy in radio galaxies is also discussed.
The Interplanetary and Magnetospheric causes of Geomagnetically Induced Currents (GICs) > 10 A in the Mäntsälä Finland Pipeline: 1999 through 2019
Authors: Tsurutani Bruce T. , Hajra Rajkumar 
Published: January 2021

The interplanetary and magnetospheric phenomena time-coincident with intense geomagnetically induced current (GIC) > 10 A and > 30 A events during 21 years (1999 through 2019) at the Mäntsälä, Finland (57.9° magnetic latitude) gas pipeline have been studied. Although forward shocks and substorms are predominant causes of intense GICs, some newly discovered geoeffective interplanetary features are: solar wind plasma parcel (PP) impingements, possible interplanetary magnetic field (IMF) northward (Bn) and southward (Bs) turnings, and reverse shocks. The PPs are possibly the loop and filament portions of coronal mass ejections (CMEs).
From a study of > 30 A GIC events, it is found that supersubstorm (SSS: SML < −2500 nT) and intense substorm (−2500 nT < SML < −2000 nT) auroral electrojet intensifications are the most frequent (76%) cause of all of these GIC events. These events occur most often (76%) in superstorm (SYM-H ≤ −250 nT) main phases, but they can occur in other storm phases and lesser intensity storms as well. After substorms, PPs were the most frequent causes of Mäntsälä GIC > 30 A events. Forward shocks were the third most frequent cause of the > 30 A events. Shock-related GICs were observed to occur at all local times.
The two “Halloween” superstorms of 29–30 and 30–31 October 2003 produced by far the greatest number of GICs in the interval of study (9 > 30 A GICs and 168 > 10 A GICs). In the first Halloween superstorm, a shock-triggered SSS (SML < −3548 nT) caused 33, 57, 51 and 52 A GICs. The 57 A GIC was the most intense event of the superstorm and of this study. It is possible that this SSS is a new form of substorm. Equally intense magnetic storms were also studied but their related GICs were far less numerous and less intense.
Multinational energy utilities in the energy transition: A configurational study of the drivers of FDI in renewables
Authors: Patala Samuli , Juntunen Jouni K. , Lundan Sarianna , Ritvala Tiina 
Published: January 2021

AbstractThe global energy system has a long way to go to meet international climate goals, and significant investment in renewable energy is required to accelerate the energy transition (IRENA, 2016, 2019). We examine how firm- and country-specific conditions in the electric utility sector impact foreign direct investment (FDI) in renewables. Using a unique dataset of 289 greenfield investments by 17 multinational energy utilities, we employ a fuzzy set qualitative comparative analysis (fsQCA) that yields five causal configurations leading to FDI in renewables and four configurations leading to investment in non-renewables. Our results indicate that private MNEs are at the forefront of investment in renewables, and while state-owned MNEs (SOMNEs) do invest in them, they tend to follow strategies that are less risky compared to private MNEs and more responsive to host-country incentives. Our analysis suggests that for private MNEs, international experience is strongly associated with investment in renewables, while for SOMNEs it is associated with investment in non-renewables. Further, we also identify instances where MNEs contribute simultaneously to a ‘race to the top’ and a ‘race to the bottom’ by investing in both renewables and non-renewables in different markets, thereby reducing the pace of the energy transition.
Phylogenomic fingerprinting of tempo and functions of horizontal gene transfer within ochrophytes
Authors: Dorrell Richard G. , Villain Adrien , Perez-Lamarque Benoît , Audren de Kerdrel Guillemette , McCallum Giselle , Watson Andrew K. , Ait-Mohamed Ouardia , Alberti Adriana , Corre Erwann , Frischkorn Kyle R. , Pierella Karlusich Juan J. , Pelletier Eric , Morlon Hélène , Bowler Chris , Blanc Guillaume 
Published: January 2021

Significance
The ochrophytes are an ancient and important group of eukaryotic algae, including diatoms, the most important photosynthesisers in the modern ocean, and a wide range of other species. Throughout their history, ochrophytes have exchanged genes with bacteria and eukaryotes through horizontal gene transfer (HGT), diversifying their cell biology. Here, we profile thousands of phylogenetic trees, showing that HGTs from bacteria contribute particularly to the recent evolution of diatoms, occurring more frequently than HGTs from eukaryotes and, potentially, more frequently in diatoms than other ochrophytes. Using experimental and computational techniques, we show that bacterial HGTs predominantly impact the diatom secreted proteome, which may contribute to the striking evolutionary success of diatoms.
Investigation of circular geodesics in a rotating charged black hole in the presence of perfect fluid dark matter
Authors: Das Anish , Saha Ashis , Gangopadhyay Sunandan 
Published: January 2021

Abstract
In this work we have obtained a charged black hole solution in the presence of perfect fluid dark matter (PFDM) and discuss its energy conditions. The metric corresponding to the rotating avatar of this black hole solution is obtained by incorporating the Newman–Janis algorithm. We then compute two types of circular geodesics, namely, the null geodesics and time-like geodesics for this rotating spacetime geometry. For the case of time-like geodesics, we consider both neutral as well as charged massive particles. The effective potentials of the corresponding circular geodesics has also been studied. We then present our results by graphically representing the collective effects of the black hole parameters, namely, the charge of the black hole (Q), spin parameter (a) and the PFDM parameter (α) on the energy (E), angular momentum (L) and effective potential (V
eff) of the concerned particle. Finally, we discuss the Penrose process in order to study the negative energy particles having possible existence within the ergosphere, and which in turn leads to the energy gain of the emitted particle.
Galaxy number counts at second order: an independent approach
Authors: Fuentes Jorge L , Hidalgo Juan Carlos , Malik Karim A 
Published: January 2021

Abstract
Next generation surveys will be capable of determining cosmological parameters beyond percent level. To match this precision, theoretical descriptions should look beyond the linear perturbations to approximate the observables in large scale structure. A quantity of interest is the Number density of galaxies detected by our instruments. This has been focus of interest recently, and several efforts have been made to explain relativistic effects theoretically, thereby testing the full theory. However, the results at nonlinear level from previous works are in disagreement. We present a new and independent approach to computing the relativistic galaxy number counts to second order in cosmological perturbation theory. We derive analytical expressions for the full second order relativistic observed redshift, for the angular diameter distance and for the volume spanned by a survey. Finally, we compare our results with previous works which compute the general distance-redshift relation, finding that our result is in agreement at linear order.
Ball bouncing down rounded edge stairs: chaotic but tricky
Authors: L Tóth Ábel , Tél Tamás 
Published: January 2021

Abstract
The aim of this study is to investigate the bouncing dynamics of a small elastic ball on a staircase consisting of rounded edge steps, as an example of a dissipative gravitational billiard, and to determine if its dynamics is chaotic. We derive a nonlinear recursion for the coordinates of the collisions, completed with numerical simulations, which indicate that the bouncing dynamics is chaotic, as also follows from elementary considerations regarding the Lyapunov exponent. It is, however, surprising that instead of permanent chaos, only the transient form is present. The main reason behind this is that a collision with the rounded edge of the step enhances the horizontal velocity leading to larger and larger jumps. Not even the introduction of a tangential coefficient of restitution (COR) on the curvature can hinder the flying away of some trajectories. There is also a chance for remaining trapped on a single step in the form of sliding, representing another possibility for escape. Therefore, chaoticity holds for long trajectories before any kind of escape takes place. We also show that an impact-velocity-dependent COR converts the dynamics to permanently chaotic with an underlying fractal attractor. Only elementary mathematics is required for the analytic calculations used, and we offer a set of problems to solve, as well as a user-friendly demo software on our website: https://theorphys.elte.hu/fiztan/stairs to facilitate experimentation and further understanding of this complex phenomenon.
K-shell ionization cross section of Ti and Cu atoms by 1 and 2 GeV electrons
Authors: Nazhmudinov R M , Shchagin A V , Trofymenko S V , Kishin I A , Kubankin A S , Potylitsyn A P , Gogolev A S , Filatov N A , Kube G , Potylitsina-Kube N A , Stanitzki M , Novokshonov A 
Published: January 2021

Abstract
The K-shell ionization cross sections of titanium and copper atoms were determined by analyzing the spectra of characteristic X-ray radiation generated by an electron beam with energies of 1 and 2 GeV in metal foils. New data obtained for these energies demonstrate the influence of the density effect on the ionization cross sections values. The results were compared with previous experimental data and calculations based on pure theoretical and semi-empirical models.
A review on the low external quantum efficiency and the remedies for GaN-based micro-LEDs
Authors: Hang Sheng , Chuang Chia-Ming , Zhang Yonghui , Chu Chunshuang , Tian Kangkai , Zheng Quan , Wu Tingzhu , Liu Zhaojun , Zhang Zi-Hui , Li Qing , Kuo Hao-Chung 
Published: January 2021

Abstract
GaN-based micro-size light-emitting diode (μLED) have emerged as a promising light sources for a wide range of applications in displays, visible light communication etc. In parallel with the two key technological bottlenecks: full-color scheme and mass transfer technique that need overcoming, it is known that the low external quantum efficiency (EQE) is also another challenge for μLEDs from the perspective of manufacturing technology and device physics. The low EQE for GaN based μLEDs is opposite to the common belief for GaN-based LEDs, such that GaN based LEDs are featured with high quantum efficiency, mechanically robust and energy saving. Therefore, in this work, we have reviewed the origin for the low EQE for μLEDs. More importantly, we have also reported the underlying devices physics and proposed optimization strategies to boost the EQE for μLEDs. Our work is targeted to provide a guideline for the community to develop high-performance GaN-based μLEDs.
Analytical model for the spatiotemporal permittivity of uncured-composite devices in an AC electric field
Authors: Shen Zikui , Wang Xilin , Xin Zhenyu , Zhang Tianfeng , Xu Chi , Jia Zhidong 
Published: January 2021

Abstract
Electric-field grading by dielectric permittivity gradient devices is an effective way of enhancing the insulation performance. In situ electric-field-driven assembly is an advanced method for the fabrication of insulating devices with adaptive permittivity gradients; however, there is no theoretical guidance for its use in design. We develop an analytical model for the spatiotemporal permittivity of an uncured-composite device in an AC electric field and investigate the coupling effects between the in situ assisted electric field and rod-like filler self-assembly in three devices: a pin-flat insulator, a basin insulator, and a silicone-gel-insulated gate bipolar transistor. Our model is based on optical images and dielectric permittivity monitoring, thus avoiding complicated electrodynamic calculations. The electric-field uniformity follows a U-shaped curve with assisted-voltage application time. We also find a combination of experimental parameters that constitutes an optimal tradeoff between internal and surface electric-field uniformities. This work establishes a theoretical design framework to optimize the performance (e.g. flashover voltage and breakdown strength) of a composite device.
Negative electron affinity of adamantane on Cu(111)
Authors: Li Jieru , Niesner Daniel , Fauster Thomas 
Published: January 2021

Abstract
Photoelectron spectroscopy is used to show that thick adamantane films on Cu(111) have a negative electron affinity of −0.3 ± 0.1 eV. The ionization potential is obtained as 8.55 ± 0.15 eV resulting in a band gap of 8.9 ± 0.1 eV. For films of about 1.4 monolayer thickness the electron affinity is close to zero and the valence bands are shifted toward the Fermi energy due to charge transfer from Cu 3d bands.
Bosonic Hofstadter butterflies in synthetic antiferromagnetic patterns
Authors: Krivosenko Yury S , Iorsh Ivan V , Shelykh Ivan A 
Published: January 2021

Abstract
The emergence of Hofstadter butterflies for bosons in synthetic-gauge-field antiferromagnetic (AFM) patterns is theoretically studied. We report on a specific tight-binding model of artificial AFM structures incorporating both nearest and next-to-nearest neighbour tunnelings and allowing for the formation of the fractal spectra even with the vanishing gauge field flux through the lattice. The model is applied to square and honeycomb lattices. Possible experimental realization is suggested for the lattices of microring resonators connected by waveguides. Finally, the structure of the butterflies is analyzed for different points in the magnetic Brillouin zone for both the ferromagnetic and AFM patterns.
Interference effect in the electronic transport of a topological insulator quantum dot
Authors: Zhang Shu-feng , Gong Wei-jiang 
Published: January 2021

Abstract
Edge and bulk energy levels can coexist in a quantum dot (QD) made of a topological insulator. Interference effect will occur between bulk and edge levels and also between degenerate edge levels. It can be observed in the transport behavior. For the former, it acts as Fano interference with edge and bulk levels contributing continuous and resonant transport channels, respectively. Generally speaking, Fano interference can be realized in a two-armed junction with a single QD or a one-armed junction with at least two QDs. But here it is realized in a one-armed junction with a single QD. As for the interference between degenerate edge levels, it leads to a spin and space dependent scattering process. Spin of an incident electron will either be conserved or rotate about an axis for transmitting into different leads. It is determined by the local spin polarization of edge levels and the accumulated phase in transport paths in the QD. It may be used in the design of a spin field-effect transistor.
Distribution of RKKY coupling value in 1D crystal with disorder. Specific heat in XY model
Authors: Krainov I V , Baryshnikov K A 
Published: January 2021

Abstract
The presence of disorder in one-dimensional crystals leads to the localization of all charge carriers and the calculation of the indirect exchange interaction (Ruderman–Kittel–Kasuya–Yosida (RKKY) interaction) cannot be performed perturbatively on disorder. In two and three-dimensional systems it makes sense to calculate the magnitude of RKKY interaction perturbatively treating nearly free carriers scattering on the random potential, and this approach results in a rather high magnitude of the exchange interaction due to interference effects similar to weak localization. We show that in one-dimensional systems the indirect exchange interaction should be described as a random value with heavy-tail distribution function, which is calculated in this work, on scales of carriers localization length. We also demonstrate that heavy tails and the absence of a characteristic value of RKKY interaction magnitude leads to a significant change in observables for these systems. We calculate a specific heat for the one-dimensional XY model taking into account the effect of disorder and assuming that typical distance between impurities exceeds the localization length. In contrast to an ideal system, where specific heat temperature dependence has a peak at a certain temperature proportional to exchange constant describing characteristic energy scale, disorder eliminates the peak as soon as there is no characteristic excitation energy in this case anymore.
Orbital competition of Mn3+ and V3+ ions in Mn1+x
V2-x
O4
Authors: Jiao J L , Zhang H P , Huang Q , Wang W , Sinclair R , Wang G , Ren Q , Lin G T , Huq A , Zhou H D , Li M Z , Ma J 
Published: January 2021

Abstract
The structural and magnetic properties of Mn1+x
V2-x
O4 (0 < x ⩽ 1) have been investigated by the heat capacity, magnetization, x-ray diffraction and neutron diffraction measurements, and a phase diagram of temperature versus composition was built up. For x ⩽ 0.3, a cubic-to-tetragonal (c > a) phase transition was observed. For x > 0.3, the system maintained the tetragonal lattice. Although the collinear and noncollinear magnetic transitions of V3+ ions were obtained in all compositions, the canting angles between the V3+ ions decreased with Mn3+-doping, and the ordering of the Mn3+ ions was only observed as x > 0.4. In order to study the dynamics of the ground state, the first principles simulation was applied to analyze not only the orbital effects of Mn2+, Mn3+, and V3+ ions, but also the related exchange energies.
Electron microscopy in semiconductor inspection
Authors: Nakamae Koji 
Published: January 2021

Abstract
Currently, semiconductor devices are manufactured in a technology node of several nanometers. Electron microscopy is mainly used in semiconductor inspection in manufacturing stages since accelerated electrons have wavelengths of nanometers or less, and a high spatial resolution can be expected. Among various electron microscopes since the scanning electron microscope (SEM) can observe the sample as it is without processing the sample, the SEM-based inspection instrument is mainly used at each stage of manufacturing the semiconductor device. The paper presents a review of SEM-based electron microscopy in semiconductor inspection. First, an overview of electron microscopy is described to understand the electron-sample interaction, the characteristics of electrons emitted from an irradiated specimen, charging, noise, and so on. Next, application areas such as mask inspection are introduced. Finally, future challenges are discussed.
Silicene growth on Ag(110) and Ag(111) substrates reconsidered in light of Si–Ag reactivity
Authors: Colonna S , Flammini R , Ronci F 
Published: January 2021

AbstractSilicene, the 2D silicon allotrope analogue of graphene, was theoretically predicted in 1994 as a metastable buckled honeycomb silicon monolayer. Similarly to its carbon counterpart it was predicted to present an electronic structure hosting Dirac cones. In the last decade a great deal of work has been done to synthesize silicene and exploit its properties. In this paper we will review our research group activity in the field, dealing in particular with silicon-substrate interaction upon silicon deposition, and discuss the still debated silicene formation starting from the chemistry of silicon unsaturated compounds.
Template-free method for the synthesis of high-pore-volume γ-Al2O3 nanofibers in a membrane dispersion microreactor
Authors: Li Fei , Wan Lisha , Wang Yuqi , Wang Yujun 
Published: January 2021

Abstract
Mesoporous γ-Al2O3 nanofibers with high pore volume and uniform pore size distributions were successfully synthesized via a template-free method in a membrane dispersion microreactor followed by calcination. The effects of crystal temperature, pH values, continuous phase concentration and washing solvent on the γ-Al2O3 nanofibers were carefully studied. The results showed that the as-obtained γ-Al2O3 nanofibers showed a length of 40–60 nm and a width of 3.2–3.4 nm, which were attributed to the high microscopic mixing rate in the membrane dispersion microreactor. Moreover, the precursors of γ-Al2O3 nanofibers treated with deionized water and mixed deionized water/alcohol solution had high pore volumes, reaching to 1.60 ml g−1 and 2.00 ml g−1, respectively. Furthermore, the adsorption performance of γ-Al2O3 nanofibers with high pore volumes was also investigated. These fibers showed an excellent adsorption capacity of 1323.68 mg g−1 for the removal of Congo red from aqueous solution, thereby indicating their potential for applications in adsorption and other related areas.
Colorimetric and turn-on fluorescence determination of mercury (II) by using carbon dots and gold nanoparticles
Authors: Lu Changfang , Ding Hao , Wang Yutong , Xiong Chaoying , Wang Xianxiang 
Published: January 2021

Abstract
A colorimetric and turn-on fluorometric assay with high sensitivity and selectivity is described for the optical detection of mercury (II) ions (Hg2+), based on carbon dots with –SH (SN-CDs) and gold nanoparticles (AuNPs). On addition of Hg2+, the color of the system (SN-CDs/AuNPs) changes from red to blue. A new absorption peak appears at 700 nm, and its absorbance increases with the concentration of Hg2+, while at 530 nm, the absorbance of AuNPs decreases. Taking the ratio of absorbance at 700 and 530 nm as a signal, a colorimetric method with linear detection range of 0.5–4.0 μM was established for the determination of Hg2+. Meanwhile, citrate ions on the surface of AuNPs can reduce Hg2+ to Hg0, and through the strong affinity of Hg0 and gold, gold–mercury alloys were formed to occupy the surface of AuNPs, so that the SN-CDs were re-free and the fluorescence of SN-CDs was restored. Consequently, a fluorometric method was founded in the linear detection range from 0.5 to 15.0 μM of mercury (II). This dual-mode (colorimetric and turn-on fluorometric) method was applied successfully for determination of Hg2+ in real water samples.