bluuebunny/crossref_metadata_2025 huggingface dataset:
Analytical solution for interdiffusion in multicomponent systems and its application in high entropy alloys
Authors: Kulkarni Kaustubh N.
Published: January 2021

In the present work, an analytical solution is derived for the diffusion equation as applicable to a multicomponent diffusion couple with a constant set of interdiffusion coefficients. The multicomponent diffusion equation was first decoupled using similarity transformation of the interdiffusivity matrix. The decoupled equation was then solved for the boundary conditions pertaining to an infinite diffusion couple, in general, containing n diffusing components by using Laplace transform. It is shown that the analytical solution derived here deduces to the forms specifically applicable to binary and ternary systems available in the literature. The analytical solutions were then applied to reproduce the concentration profiles developed in experimental diffusion couples prepared with quaternary Fe–Ni–Co–Cr and quinary Fe–Ni–Co–Cr–Mn alloys. The determination of the sets of 9 quaternary and 16 quinary interdiffusion coefficients in the said couple was done experimentally using Kirladly’s approach and was independent of the closed form solutions derived here. The constant sets of quaternary and quinary interdiffusion coefficients determined at approximately equi-molar compositions in the two systems were used in the present work to reproduce the concentration profiles in these couples, having reasonably large differences in the terminal alloy concentrations. It was found that the concentration profiles calculated using the solutions developed here agree very well with the experimental profiles developed in all three quaternary and all four quinary couples. The excellent agreement between the experimental and theoretical profiles not only validates the closed form solution developed here but also highlights the constancy of interdiffusivities over reasonably large composition ranges in such systems. This is significant as it enables the use of analytical solutions of the diffusion equation for modeling various processes in such concentrated multicomponent alloys.
A numerical study on flapping dynamics of a flexible two-layered plate in a uniform flow
Authors: Saravanakumar Aditya Karthik , Supradeepan K. , Gurugubelli P. S.
Published: January 2021

Over the past few decades, energy generation from piezoelectric patches mounted on a flexible flat plate exhibiting flapping motion has gained attention. Piezoelectric patches are generally multilayered consisting of piezoelectric, substrate, and electrode layers placed on top of each other. Although the flapping dynamics of single-layered structures have been extensively studied, understanding the flapping dynamics of multilayered structures is minimal. We propose a quasi-monolithic formulation with exact interface tracking to simulate the fluid–multilayered structure interactions. The proposed formulation is validated by considering a simple two-layered plate-like structure with identical material properties against a single-layered plate. We then use this formulation to perform parametric simulations by providing different material properties to each layer of the plate to understand the effect of differences in the material properties on the flapping dynamics. The simulations are performed by selecting different values of Young’s modulus and density for each of the layers such that the average structure-to-fluid mass ratio m*avg=0.1 and the average non-dimensional bending stiffness KBavg=0.0005 remain constant for a Reynolds number Re = 1000. First, the effects of difference in elasticity between the two layers on the flapping amplitude, frequency, forces, and vortex shedding patterns are investigated. Following this, the effect of differences in elastic properties on the onset of flapping is investigated for a case with Re = 1000, m*avg=0.1, and KBavg=0.0008, for which a single-layered plate does not undergo self-sustained flapping. Two distinct response regimes are observed depending on the difference in elastic properties between the two layers: (I) fixed-point stable and (II) periodic limit cycle oscillations. Finally, we look into the effects of structural density differences on the flapping dynamics of a two-layered plate.
Two-dimensional van der Waals electrical contact to monolayer MoSi2N4
Authors: Cao Liemao , Zhou Guanghui , Wang Qianqian , Ang L. K. , Ang Yee Sin
Published: January 2021

A two-dimensional (2D) MoSi2N4 monolayer is an emerging class of air-stable 2D semiconductors possessing exceptional electrical and mechanical properties. Despite intensive recent research effort devoted to uncover the material properties of MoSi2N4, the physics of electrical contacts to MoSi2N4 remains largely unexplored thus far. In this work, we study van der Waals heterostructures composed of MoSi2N4 contacted by graphene and NbS2 monolayers using first-principles density functional theory calculations. We show that the MoSi2N4/NbS2 contact exhibits an ultralow Schottky barrier height (SBH), which is beneficial for nanoelectronics applications. For the MoSi2N4/graphene contact, the SBH can be modulated via the interlayer distance or via external electric fields, thus opening up an opportunity for reconfigurable and tunable nanoelectronic devices. Our findings provide insights into the physics of 2D electrical contacts to MoSi2N4 and shall offer a critical first step toward the design of high-performance electrical contacts to MoSi2N4-based 2D nanodevices.
Transition characteristics and electron kinetics in microhollow cathode discharges
Authors: Fu Yangyang , Zheng Bocong , Zhang Peng , Fan Qi Hua , Verboncoeur John P.
Published: January 2021

We demonstrate the transition characteristics and electron kinetics of microdischarges in a microgap with a cathode having microstructures using two-dimensional particle-in-cell/Monte Carlo collision (2d3v) simulations. It is found that the microdischarge is inside the hollow cavity at lower pressures, forming microhollow cathode discharges (MHCDs), while the dominant discharge moves outside the cavity at higher pressures, locating above the cathode rectangular protrusion tip. The spatial distributions of the microdischarge parameters (e.g., electric potential and electron density) are presented by capturing the transition characteristics. The electron kinetics of the microdischarges are examined based on the moment analysis of the electron Boltzmann equation. The collisional and non-collisional components of the electron power absorption are decomposed, which were seldomly investigated for microdischarges previously. The results provide fundamental insights into MHCD formation with a structured electrode at varying pressure conditions, which could be beneficial for the design and fabrication of microplasma devices in practical applications.
Alpha particle channeling in ITER
Authors: White Roscoe , Romanelli Francesco , Cianfrani Francesco , Valeo Ernest
Published: January 2021

Alpha particle channeling, the attempt to extract energy from high-energy fusion alpha particles using a combination of high- and low-frequency waves introduced in the plasma with antennae, is studied using a guiding center code. We examine the effect of the combination of cooling caused by a cyclotron mode, particle diffusion due to Alfvén modes introduced for ash removal, the inclusion of microturbulent diffusion, and the slowing down of the alpha particles on electrons. Induced cooling is achieved with a cyclotron resonance, producing additional losses of particles above 3.5 MeV in an amount about equal to the prompt loss. The removal of the low-energy cooled particles by additional modes or by microturbulent diffusion is the hardest challenge for alpha channeling. The cooled alpha particles remain deep in the plasma center, so for this removal, the method used must be capable of providing transport from the plasma center to the edge without also causing losses of high-energy particles.
On the happiness of ferroelectric surfaces and its role in water dissociation: The example of bismuth ferrite
Authors: Efe Ipek , Spaldin Nicola A. , Gattinoni Chiara
Published: January 2021

We investigate, using density functional theory, how the interaction between the ferroelectric polarization and the chemical structure of the (001) surfaces of bismuth ferrite influences the surface properties and reactivity of this material. A precise understanding of the surface behavior of ferroelectrics is necessary for their use in surface science applications such as catalysis as well as for their incorporation in microelectronic devices. Using the (001) surface of bismuth ferrite as a model system, we show that the most energetically favored surface geometries are combinations of surface termination and polarization direction that lead to uncharged stable surfaces. On the unfavorable charged surfaces, we explore the compensation mechanisms of surface charges provided by the introduction of point defects and adsorbates, such as water. Finally, we propose that the special surface properties of bismuth ferrite (001) could be used to produce an effective water splitting cycle through cyclic polarization switching.
Density-related properties from self-interaction corrected density functional theory calculations
Authors: Withanage Kushantha P. K. , Bhattarai Puskar , Peralta Juan E. , Zope Rajendra R. , Baruah Tunna , Perdew John P. , Jackson Koblar A.
Published: January 2021

The Perdew–Zunger self-interaction correction (PZ-SIC) removes unphysical electron self-interaction from calculations employing standard density functional approximations. Doing so improves many computed properties, bringing them into better agreement with experimental observations or with results from high-level quantum chemistry calculations. However, while PZ-SIC generally corrects in the right direction relative to the corresponding reference values, in many cases, it over-corrects. For this reason, scaled-down versions of PZ-SIC have been proposed and investigated. These approaches have mostly employed exterior scaling in which SIC correction terms are scaled in the same way at every point in space. Recently, a new local, or interior, scaling SIC method was proposed on non-empirical grounds to restore a property of the exact, but unknown, density functional that is broken in PZ-SIC. In this approach, the scaling at each point depends on the character of the charge density at that point. However, the local scaling can be done in various ways while still restoring the behavior of the exact functional. In this work, we compare and contrast the performance of various interior scaling approaches for addressing over-corrections of calculated molecular dipole moments and atomic polarizabilities and properties that reflect the nature of the electronic charge density.
Rich phase transitions in strongly confined polymer–nanoparticle mixtures: Nematic ordering, crystallization, and liquid–liquid phase separation
Authors: Roy Supriya , Chen Yeng-Long
Published: January 2021

We investigate the rich phase behavior of strongly confined semi-flexible (SFC) polymer–nanoparticle (NP) systems using the graphics processing unit accelerated Langevin dynamics simulation. Hard nanoparticles (HNP) that repel each other and ideal nanoparticles (INP) that do not interact with the same species are used as model additives to a strongly confined semiflexible polymer fluid. Both types of NPs exclude the monomer beads in the same way, but they have qualitatively different effects on the SFC isotropic–nematic (I–N) transition. For the total volume fraction ϕtot < 0.16, adding a low volume fraction of HNPs (ϕp) disrupts the long range nematic order of the polymers, whereas adding HNPs in a moderately packed system (0.16 < ϕtot < 0.32) facilitates polymer alignment due to the restricted polymer orientational degree of freedom. For dense packing (ϕtot > 0.32), polymers and NPs separate into layers along the slit height and the NPs form crystalline microdomains. In contrast, INP additives always promote inter-polymer alignment for low to moderate monomer volume fractions (ϕm). Furthermore, we found that INPs form a droplet-like fluid domain in dense nematic polymer systems.
Theoretical method for near-field Raman spectroscopy with multipolar Hamiltonian and real-time-TDDFT: Application to on- and off-resonance tip-enhanced Raman spectroscopy
Authors: Takenaka Masato , Taketsugu Tetsuya , Iwasa Takeshi
Published: January 2021

Tip-enhanced Raman spectroscopy in combination with scanning tunneling microscopy could produce ultrahigh-resolution Raman spectra and images for single-molecule vibrations. Furthermore, a recent experimental study successfully decoupled the interaction between the molecule and the substrate/tip to investigate the intrinsic properties of molecules and their near-field interactions by Raman spectroscopy. In such a circumstance, more explicit treatments of the near field and molecular interactions beyond the dipole approximation would be desirable. Here, we propose a theoretical method based on the multipolar Hamiltonian that considers full spatial distribution of the electric field under the framework of real-time time-dependent density functional theory. This approach allows us to treat the on- and off-resonance Raman phenomena on the same footing. For demonstration, a model for the on- and off-resonance tip-enhanced Raman process in benzene was constructed. The obtained Raman spectra are well understood by considering both the spatial structure of the near field and the molecular vibration in the off-resonance condition. For the on-resonance condition, the Raman spectra are governed by the transition moment, in addition to the selection rule of off-resonance Raman. Interestingly, on-resonance Raman can be activated even when the near field forbids the π–π* transition at equilibrium geometry due to vibronic couplings originating from structural distortions.
Influence of oxygen on trap-limited diffusion of hydrogen in proton-irradiated n-type silicon for power devices
Authors: Kiyoi Akira , Kawabata Naoyuki , Nakamura Katsumi , Fujiwara Yasufumi
Published: January 2021

The growing demand for power devices has led to the use of magnetic field-applied Czochralski (m:Cz) wafers owing to the limited production capacity and available diameters of the traditionally used floating zone (FZ) wafers. Consequently, the influence of oxygen impurities in the wafers on the electrical properties of devices, regardless of the growth method, needs to be investigated to achieve a stable fabrication process for power devices. Using the proton irradiation doping process and spreading resistance profiling technique, we evaluated the effective diffusion coefficient (Deff) related to trap-limited diffusion of hydrogen and the effects of impurities on diffusivity. We irradiated n-type silicon wafers, which have different carbon, oxygen, and phosphorus concentrations, with 2 MeV protons and annealed them at 300–400 °C. By analyzing the width of the n-type region, where hydrogen-related shallow donors (HDs) are induced, we estimated Deff to be five to six orders of magnitude lower than the intrinsic diffusion coefficient, indicating that hydrogen motion is highly trap-limited. Deff was significantly dependent on the oxygen concentration, and the activation energy of hydrogen diffusion varied from 0.57 ± 0.15 eV (pure epitaxial wafer) to 2.19 ± 0.15 eV (m:Cz wafer). This trend suggests that oxygen-related defects preferentially trap the mobile hydrogen released from thermally dissociated HDs. This study also reveals that the diffusion coefficients of different materials when annealed at 400 °C are comparable. This information is essential to realize the cost-effective production of power devices because we can treat m:Cz and FZ wafers equivalently during the doping process.
Direct numerical simulations of turbulent non-premixed flames: Assessment of turbulence within swirling flows
Authors: Xiao Hualin , Luo Kun , Jin Tai , Wang Haiou , Xing Jiangkuan , Fan Jianren
Published: January 2021

Direct numerical simulations of non-premixed swirling fuel-rich/fuel-lean flames within a high-pressure model gas turbine combustor are conducted to investigate the flow and flame structures, as well as the transport mechanisms of both turbulent kinetic energy (TKE) and enstrophy. The effects of non-premixed flames upon these characteristics are also analyzed through comparison with the corresponding non-reacting swirling flows. We demonstrate that the turbulence state in the swirling flows behaves axisymmetrically overall in the current cylindrical laboratory-type combustor and is more likely to be cigar shaped in the presence of combustion. The analysis of TKE budgets within non-reacting swirling flows indicates that TKE is predominantly produced by mean shear in the shear layers and redistributed by transport effects from the inner shear layer (ISL) to the internal-recirculation zone; however, these transport effects are suppressed by combustion in fuel-lean non-premixed flames. Although the total pressure effects consume TKE with a similar magnitude in all cases, the essential cause is different. The influence of combustion upon TKE budgets is more significant for fuel-lean flames than for fuel-rich flames as a result of the stronger burning intensity in the ISL of the former. Analysis of enstrophy dynamics shows that dilatation and baroclinic torque play relatively noticeable roles in swirling non-premixed flames, unlike their negligible effects in high-intensity homogeneous isotropic turbulence. The augmentation of baroclinic torque caused by non-premixed swirling combustion mainly arises from the remarkable decrease in density and enhancement of preferential alignment between the vorticity and baroclinic torque vectors.
Epitaxial stabilization of (111)-oriented frustrated quantum pyrochlore thin films
Authors: Wen Fangdi , Wu Tsung-Chi , Liu Xiaoran , Terilli Michael , Kareev Mikhail , Chakhalian Jak
Published: January 2021

Frustrated rare-earth pyrochlore titanates, Yb2Ti2O7 and Tb2Ti2O7, have been proposed as promising candidates to realize quantum spin ice (QSI). Multiple exotic quantum phases, including Coulombic ferromagnet, quantum valence bond solid, and quadrupolar ordering, have been predicted to emerge in the QSI state upon the application of a (111)-oriented external magnetic field. Here, we report on the successful layer-by-layer growth of thin films of the frustrated quantum pyrochlores, R2Ti2O7 (R=Er, Yb, and Tb), along the (111) direction. We confirm their high crystallinity and proper chemical composition by a combination of methods, including in situ RHEED, x-ray diffraction, reciprocal space mapping, and x-ray photoelectron spectroscopy. The availability of large area (111)-oriented QSI structures with planar geometry offers a new complementary to the bulk platform to explore the strain and the magnetic field-dependent properties in the quasi-2D limit.
The importance of singly charged oxygen vacancies for electrical conduction in monoclinic HfO2
Authors: Mueller Michael P. , Gunkel Felix , Hoffmann-Eifert Susanne , De Souza Roger A.
Published: January 2021

The point-defect structure of monoclinic HfO2 (m-HfO2) was studied by means of equilibrium electrical conductance measurements as a function of temperature 1050≤T/K≤1200 and oxygen partial pressure −20≤log(pO2/bar)≤−2. The total conductivity σ displayed similar behavior at each temperature examined. In oxidizing conditions (pO2≥10−7bar), the total conductivity increased with increasing oxygen partial pressure and was assigned to hole conduction. Around 10−10 bar, a region of almost constant conductivity was found; this is ascribed to ionic conduction by means of doubly charged oxygen vacancies. In reducing conditions (pO2≤10−16bar), the total conductivity surprisingly decreased with decreasing oxygen partial pressure. Defect-chemical modeling indicates that this behavior is consistent with the conversion of mobile doubly charged oxygen vacancies into less mobile singly charged vacancies by electron trapping. Point-defect concentrations at the oxygen partial pressures relevant to resistive switching devices are predicted and discussed.
Multi-particle collision dynamics with a non-ideal equation of state. I
Authors: Zantop Arne W. , Stark Holger
Published: January 2021

The method of multi-particle collision dynamics (MPCD) and its different implementations are commonly used in the field of soft matter physics to simulate fluid flow at the micron scale. Typically, the coarse-grained fluid particles are described by the equation of state of an ideal gas, and the fluid is rather compressible. This is in contrast to conventional fluids, which are incompressible for velocities much below the speed of sound, and can cause inhomogeneities in density. We propose an algorithm for MPCD with a modified collision rule that results in a non-ideal equation of state and a significantly decreased compressibility. It allows simulations at less computational costs compared to conventional MPCD algorithms. We derive analytic expressions for the equation of state and the corresponding compressibility as well as shear viscosity. They show overall very good agreement with simulations, where we determine the pressure by simulating a quiet bulk fluid and the shear viscosity by simulating a linear shear flow and a Poiseuille flow.
Physics guided machine learning using simplified theories
Authors: Pawar Suraj , San Omer , Aksoylu Burak , Rasheed Adil , Kvamsdal Trond
Published: January 2021

Recent applications of machine learning, in particular deep learning, motivate the need to address the generalizability of the statistical inference approaches in physical sciences. In this Letter, we introduce a modular physics guided machine learning framework to improve the accuracy of such data-driven predictive engines. The chief idea in our approach is to augment the knowledge of the simplified theories with the underlying learning process. To emphasize their physical importance, our architecture consists of adding certain features at intermediate layers rather than in the input layer. To demonstrate our approach, we select a canonical airfoil aerodynamic problem with the enhancement of the potential flow theory. We include the features obtained by a panel method that can be computed efficiently for an unseen configuration in our training procedure. By addressing the generalizability concerns, our results suggest that the proposed feature enhancement approach can be effectively used in many scientific machine learning applications, especially for the systems where we can use a theoretical, empirical, or simplified model to guide the learning module.
Simultaneous three-axis torque measurements of micromagnetism
Authors: Fast K. R. , Thibault J. A. , Sauer V. T. K. , Dunsmore M. G. , Kav A. , Losby J. E. , Diao Z. , Luber E. J. , Belov M. , Freeman M. R.
Published: January 2021

Measurements of magnetic torque are most commonly preformed about a single axis or component of torque. Such measurements are very useful for hysteresis measurements of thin film structures in particular, where high shape anisotropy yields a near-proportionality of in-plane magnetic moment and the magnetic torque along the perpendicular in-plane axis. A technique to measure the full magnetic torque vector (three orthogonal torque components) on micro- and nano-scale magnetic materials is introduced. The method is demonstrated using a modified, single-paddle silicon-on-insulator resonant torque sensor. The mechanical compliances to all three orthogonal torque components are maximized by clamping the sensor at a single point. Mechanically-resonant AC torques are driven by an RF field containing a frequency component for each fundamental torsional mode of the device, and the resulting displacements read out through optical position-sensitive detection. Measurements are compared against micromagnetic simulations of mechanical torque to augment the interpretation of the signals. As an application example, simultaneous observations of hysteresis in the net magnetization along with the field-dependent in-plane anisotropy is highly beneficial for studies of exchange bias.
Key traits for ruminant livestock across diverse production systems in the context of climate change: perspectives from a global platform of research farms
Authors: Rivero M. Jordana , Lopez-Villalobos Nicolas , Evans Alex , Berndt Alexandre , Cartmill Andrew , Neal Andrew L. , McLaren Ann , Farruggia Anne , Mignolet Catherine , Chadwick Dave , Styles David , McCracken Davy , Busch Dennis , Martin Graeme B. , Fleming Hannah , Sheridan Helen , Gibbons James , Merbold Lutz , Eisler Mark , Lambe Nicola , Rovira Pablo , Harris Paul , Murphy Paul , Vercoe Philip E. , Williams Prysor , Machado Rui , Takahashi Taro , Puech Thomas , Boland Tommy , Ayala Walter , Lee Michael R. F.
Published: January 2021

Ruminant livestock are raised under diverse cultural and environmental production systems around the globe. Ruminant livestock can play a critical role in food security by supplying high-quality, nutrient-dense food with little or no competition for arable land while simultaneously improving soil health through vital returns of organic matter. However, in the context of climate change and limited land resources, the role of ruminant-based systems is uncertain because of their reputed low efficiency of feed conversion (kilogram of feed required per kilogram of product) and the production of methane as a by-product of enteric fermentation. A growing human population will demand more animal protein, which will put greater pressure on the Earth’s planetary boundaries and contribute further to climate change. Therefore, livestock production globally faces the dual challenges of mitigating emissions and adapting to a changing climate. This requires research-led animal and plant breeding and feeding strategies to optimise ruminant systems. This study collated information from a global network of research farms reflecting a variety of ruminant production systems in diverse regions of the globe. Using this information, key changes in the genetic and nutritional approaches relevant to each system were drawn that, if implemented, would help shape more sustainable future ruminant livestock systems.
In vitro production of small ruminant embryos: latest improvements and further research
Authors: Souza-Fabjan Joanna M. G. , Batista Ribrio I. T. P. , Correia Lucas F. L. , Paramio Maria Teresa , Fonseca Jeferson F. , Freitas Vicente J. F. , Mermillod Pascal
Published: January 2021

This review presents the latest advances in and main obstacles to the application of invitro embryo production (IVEP) systems in small ruminants. This biotechnology is an extremely important tool for genetic improvement for livestock and is essential for the establishment of other biotechnologies, such as cloning and transgenesis. At present, the IVEP market is almost non-existent for small ruminants, in contrast with the trends observed in cattle. This is probably related to the lower added value of small ruminants, lower commercial demand and fewer qualified professionals interested in this area. Moreover, there are fewer research groups working on small ruminant IVEP than those working with cattle and pigs. The heterogeneity of oocytes collected from growing follicles in live females or from ovaries collected from abattoirs remains a challenge for IVEP dissemination in goats and sheep. Of note, although the logistics of oocyte collection from live small ruminant females are more complex than in the bovine, in general the IVEP outcomes, in terms of blastocyst production, are similar. We anticipate that after appropriate training and repeatable results, the commercial demand for small ruminant invitro-produced embryos may increase.
Embryonic diapause in mammals and dormancy in embryonic stem cells with the European roe deer as experimental model
Authors: van der Weijden Vera A. , Rüegg Anna B. , Bernal-Ulloa Sandra M. , Ulbrich Susanne E.
Published: January 2021

In species displaying embryonic diapause, the developmental pace of the embryo is either temporarily and reversibly halted or largely reduced. Only limited knowledge on its regulation and the inhibition of cell proliferation extending pluripotency is available. In contrast with embryos from other diapausing species that reversibly halt during diapause, embryos of the roe deer Capreolus capreolus slowly proliferate over a period of 4–5 months to reach a diameter of approximately 4mm before elongation. The diapausing roe deer embryos present an interesting model species for research on preimplantation developmental progression. Based on our and other research, we summarise the available knowledge and indicate that the use of embryonic stem cells (ESCs) would help to increase our understanding of embryonic diapause. We report on known molecular mechanisms regulating embryonic diapause, as well as cellular dormancy of pluripotent cells. Further, we address the promising application of ESCs to study embryonic diapause, and highlight the current knowledge on the cellular microenvironment regulating embryonic diapause and cellular dormancy.
39 Concentration of obestatin in different stages of ovarian activity in cattle
Authors: Torres-Simental J. F. , Romo-Garcia S. , Munguia-Ramirez A. L. , Luna-Nevarez P.
Published: January 2021

The objective of the present study was to measure serum levels of obestatin by ELISA with the purpose of establishing parameters and being able to use it as an endocrine marker for the selection of reproductive characteristics of milk and beef cattle. In test 1, 15 Creole cows with genetic tendencies of Charolais, Angus, Brangus, and Gelbvieh were sampled in diestrus and 15 in proestrus, determining their structures with an Aloka Prosound ultrasound with a 7.5-MHz linear transducer. In test 2, 16 Holstein cows were sampled in 2 different ovarian stages, diestrus and proestrus. The standardized technique was a bovine obestatin 96-well ELISA kit from My Biosource Inc. The data were analysed by measuring central tendency and linear regression, where the average levels of obestatin were related to the corpus luteum size and size and number of follicles in milk and beef cattle. We found average levels of 556.99 and 453.35 pg for beef and dairy cattle, respectively (P<0.05). We also found a significant difference (P<0.05) in obestatin concentrations depending on the size of the follicles (751.74, 615.33, and 357.39 pg for follicles of 15, 10, and 5mm, respectively). We found a significant difference in concentration of obestatin (644.53, 550.69, and 455.88 pg; P<0.05) for corpus luteum sizes of >20mm, 10–20mm, and <10mm, respectively. In dairy cattle, obestatin levels were also evaluated at different stages of the cycle, and we found concentrations of 414.79 pg in diestrus and 530.48 pg in proestrus (P<0.05). We conclude that obestatin concentration is positively associated with a greater number and size of follicles as well as with larger corpus luteum because its effect on cell proliferation interacting positively with high levels of progesterone in the blood. We found higher concentrations in beef cattle than in dairy cattle.
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.
Permissive selection followed by affinity-based proliferation of GC light zone B cells dictates cell fate and ensures clonal breadth
Authors: Nakagawa Rinako , Toboso-Navasa Amparo , Schips Marta , Young George , Bhaw-Rosun Leena , Llorian-Sopena Miriam , Chakravarty Probir , Sesay Abdul Karim , Kassiotis George , Meyer-Hermann Michael , Calado Dinis Pedro
Published: January 2021

Significance

Light zone (LZ) B cells are selected in germinal centers (GCs) in a cMyc-dependent manner, before dark zone (DZ) migration. Antigen affinity of B cells is enhanced during GC responses, and some differentiate into plasmablasts or memory B cells (MBCs). Currently, GC selection is presumed as a competitive affinity-dependent process. This cannot explain retention of GC B cells with varied affinities. We identified cMyc
+
LZ B cell subpopulations enriched with either higher-affinity plasmablast precursors or lower-affinity MBC precursors and future DZ entrants, which diverged soon after permissive selection. Future DZ entrants’ affinity was enhanced through preferential proliferation of higher-affinity cells, and lower-affinity cells were retained in GCs. These findings elucidate mechanistically how GC selection ensures clonal diversity for broad protection.
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

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

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

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

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

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

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

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

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

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

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

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

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

Silicene, 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.