bluuebunny/crossref_metadata_2025 huggingface dataset:
Lignin provides mechanical support to herbaceous peony (Paeonia lactiflora Pall.) stems
Authors: Zhao Daqiu , Luan Yuting , Xia Xing , Shi Wenbo , Tang Yuhan , Tao Jun
Published: December 2020

Stem bending caused by mechanical failure is a major constraint for high-quality herbaceous peony (Paeonia lactiflora Pall.) cut flowers, but little is known about the underlying factors. In this study, two P. lactiflora cultivars, Xixia Yingxue (bending) and Hong Feng (upright), were used to investigate differences in stem bending. The results showed that the stem mechanical strength of Hong Feng was significantly higher than that of Xixia Yingxue, and the thickening of the secondary cell wall and the number of thickened secondary cell wall layers in Hong Feng were significantly higher than those in Xixia Yingxue. Moreover, compared with Xixia Yingxue, Hong Feng showed greater lignification of the cell wall and lignin deposition in the cell walls of the sclerenchyma, vascular bundle sheath and duct. All three types of lignin monomers were detected. The S-lignin, G-lignin, and total lignin contents and the activities of several lignin biosynthesis-related enzymes were higher in Hong Feng than in the other cultivar, and the S-lignin content was closely correlated with stem mechanical strength. In addition, 113,974 full-length isoforms with an average read length of 2106 bp were obtained from the full-length transcriptome of P. lactiflora stems, and differential expression analysis was performed based on the comparative transcriptomes of these two cultivars. Ten lignin biosynthesis-related genes, including 26 members that were closely associated with lignin content, were identified, and multiple upregulated and downregulated transcription factors were found to positively or negatively regulate lignin biosynthesis. Consequently, lignin was shown to provide mechanical support to P. lactiflora stems, providing useful information for understanding the formation of P. lactiflora stem strength.
Resource prioritization and balancing for the quantum internet
Authors: Gyongyosi Laszlo , Imre Sandor
Published: December 2020

The quantum Internet enables networking based on the fundamentals of quantum mechanics. Here, methods and procedures of resource prioritization and resource balancing are defined for the quantum Internet. We define a model for resource consumption optimization in quantum repeaters, and a strongly-entangled network structure for resource balancing. We study the resource-balancing efficiency of the strongly-entangled structure. We prove that a strongly-entangled quantum network is two times more efficient in a resource balancing problem than a full-mesh network of the traditional Internet.
An accurate and sensitive effervescence-assisted liquid phase microextraction method for the determination of cobalt after a Schiff base complexation by slotted quartz tube-flame atomic absorption spectrophotometry in urine samples
Authors: Borahan Tülay , Zaman Buse Tuğba , Arıca Polat Büşra Sümeyye , Bakırdere Emine Gülhan , Bakırdere Sezgin
Published: December 2020

In this study, an accurate analytical method development for cobalt determination in urine samples was described.
Incorporation of H2O and CO2 into a BN-embedded 3aH-3a1H-acephenanthrylene derivative
Authors: Guo Rui , Jiang Jingxing , Ke Zhuofeng , Tung Chen-Ho , Kong Lingbing
Published: December 2020

A zwitterionic fused BN-heterocyclic compound displays FLP chemical behavior for small molecule activation.
Interconversion between square-planar palladium(ii) and octahedral palladium(iv) centres in a sulfur-bridged trinuclear structure
Authors: Kouno Masahiro , Kuwamura Naoto , Konno Takumi
Published: December 2020

Coordination of six thiolato groups from two RhIII metalloligands stabilizes an octahedral PdIV centre, which is interconvertible with a square-planar PdII centre retaining the RhPdRh trinuclear structure.
A theoretical study on the signal transduction process of bacterial photoreceptor PpSB1 based on the Markov state model
Authors: Zhao Yajie , Zhang Yue , Sun Minzhang , Zheng Qingchuan
Published: December 2020

Light–oxygen–voltage (LOV) domains are blue light sensors and play an important role in signal transduction in many organisms.
The mechanism of the selective binding ability between opiate metabolites and acyclic cucurbit[4]uril: an MD/DFT study
Authors: Xiao Song , Jin Long-Yi , Wang Jian-Ping , Sun Guang-Yan
Published: December 2020

Subtle changes in molecular structure often lead to significant differences in host–guest interactions, which result in different host–guest recognition capabilities and dynamics behaviours in complex formation.
Utilization of a Pt(ii) di-yne chromophore incorporating a 2,2′-bipyridine-5,5′-diyl spacer as a chelate to synthesize a green and red emitting d–f–d heterotrinuclear complex
Authors: Al-Busaidi Idris Juma , Ilmi Rashid , Dutra José D. L. , Oliveira Willyan F. , Haque Ashanul , Al Rasbi Nawal K. , Marken Frank , Raithby Paul R. , Khan Muhammad S.
Published: December 2020

The heteronuclear trimetallic d–f–d complex [Eu(btfa)3{(Ph)(Et3P)2Pt–CC–R–CC–Pt(Et3P)2(Ph)}] has been synthesized and characterized spectroscopically. The complex displays both red and green emissions in solution.
A–π–A, D–π–D and D–π–A blue emitting fluorophores based on dispiro[fluorene-9,6′-indeno[1,2-b]fluorene-12′,9′′-fluorene]
Authors: Thirion Damien , Romain Maxime , Rault-Berthelot Joëlle , Poriel Cyril
Published: December 2020

We report a series of blue fluorophores based on the dispiro[fluorene-9,6′-indeno[1,2-b]fluorene-12′,9′′-fluorene] (DSF-IF) scaffold.
Understanding the Joule-heating behaviours of electrically-heatable carbon-nanotube aerogels
Authors: Xia Dong , Li Heng , Huang Peng
Published: December 2020

Electrically-heatable carbon-nanotube aerogels under Joule-heating using the side–side arrangement and the top–bottom arrangement displaying significantly different heating behaviours.
Ligand influence versus electronic configuration of d-metal ion in determining the fate of NIR emission from LnIII ions: a case study with CuII, NiII and ZnII complexes
Authors: Verma Abhineet , Hossain S. K. Saddam , Sunkari Sailaja S. , Reibenspies Joseph , Saha Satyen
Published: December 2020

Based on fifteen lanthanide complexes, where Cu, Ni and Zn ions with a Schiff-base ligand act as an antenna, it is demonstrated that electronic configuration of the d-block metal ion is very crucial for obtaining emission in NIR region.
A novel fluorescent probe with high photostability for imaging distribution of RNA in living cells and tissues
Authors: Wang Zhaomin , Liu Yong , Wang Weishan , Zhao Chang , Lin Weiying
Published: December 2020

Herein, we have firstly developed a novel fluorescent probe based on 2,2′-bithiophene for imaging distribution of RNA in living cells and tissues.
Enhancing plasmonic hot-carrier generation by strong coupling of multiple resonant modes
Authors: Wong Yat Lam , Jia Huaping , Jian Aoqun , Lei Dangyuan , El Abed Abdel I. , Zhang Xuming
Published: December 2020

Plasmonic hot-carrier generation can be harnessed by the strong coupling of the cavity mode, the LSPR mode, and the gap surface plasmon polariton.
Stereoselective total syntheses of (−)-hygrophorone A12, 4-O-acetyl-hygrophorone A12 and (+)-hygrophorone B12
Authors: Das Sayani , Dalal Anu , Gholap Shivajirao L.
Published: December 2020

Total syntheses of anti-fungal cyclopentenones (−)-hygrophorone A12, 4-O-acetyl-hygrophorone A12 and (+)-hygrophorone B12 were achieved in high overall yields from d-(−)-tartaric acid.
Active mixtures in a narrow channel: motility diversity changes cluster sizes
Authors: de Castro Pablo , Diles Saulo , Soto Rodrigo , Sollich Peter
Published: December 2020

We predict that the average size of the persistence-induced clusters formed by run-and-tumble bacteria in narrow channels increases when tumbling rates are more diverse. The effect may be strong for E. coli and present throughout active matter.
Sheath losses correction factor for cross‐bonded cable systems with unknown minor section lengths: Analytical expressions
Authors: Noufal Sameh M. , Anders George J.
Published: December 2020

The IEC Standard 60287‐1‐1 contains the formulae for the calculation of the sheath and armour loss factors of a three‐phase cable circuit where sheath circulating current losses are computed for single‐, multiple‐ or cross‐bonded systems. For cross‐bonded systems, the standard gives a formula allowing calculation of the circulating current losses when the lengths of the minor sections are known. When the lengths of the minor sections are not known, the standard suggests using a correction factor of 0.004, which multiplies the circulating current loss factor computed for a multi‐point bonded system. Previous studies by the authors have shown that this assumption may lead to a significant error in the evaluation of the sheath loss factor for some combinations of the minor section lengths. This paper provides analytical formulae for the correction factor in the cross‐bonded system with unknown section lengths with the aim of improving the accuracy of the IEC 60287‐1‐1. Several numerical examples illustrate the applicability and accuracy of the proposed approach.
Optimal planning and utilisation of existing infrastructure with electric vehicle charging stations
Authors: Moupuri Satish Kumar Reddy , K Selvajyothi
Published: December 2020

In order to address the increased demand for utility with the adoption of electrification in the transport sector, infrastructure development plays an important role. This research helps in planning the optimum utilisation of the existing infrastructure. The planning of electric vehicle (EV) infrastructure is analysed by considering various loads such as (1) static (2) dynamic and (3) heuristic on balanced radial distribution system (BRDS). The introduction of electric vehicle charging station (EVCS) into BRDS increases the total losses. The optimised reconfiguration helps in reducing the losses and ensures increased reliability of the system. The major objective of this process is to minimise both the real power loss and the reliability index energy not supplied of the radial distribution system (RDS) with the placement of charging stations. The planning is accomplished with a single‐step process in which the optimum location of the EVCS along with reconfiguration of BRDS is done using the multiple objective particle swarm optimisation (MOPSO). The performance of the BRDS with the proposed method is elaborated under three scenarios with three internal cases. The proposed methodology is validated through simulation for a three feeder IEEE 16 bus BRDS considering various load scenarios using MATLAB.
Analysis on segmentation and biomarker‐based approaches for liver cancer detection: A survey
Authors: Gunasekhar P. , Vijayalakshmi S.
Published: December 2020

Liver cancer is the major reason for death in this entire world. Manual detection of cancer tissue is found time consuming and difficult. Therefore, the development of an automatic detection approach with high accuracy for liver cancer is considered as the main aim of this work. The image processing approach can use the CAD for the classification of liver cancer in order to assist the physician in the decision‐making process. An automated approach to effective classification of the liver tumour using effective features is conveyed in terms of the CAD system. Traditionally, radiologists delineate the liver and liver lesion on a slice‐by‐slice basis, which is time consuming and susceptible to inter‐ and intra‐rater variations. Automatic methods for the segmentation of liver and liver tumours are, thus, highly demanded in clinical practice. A systematic review is being carried out to detect reported liver cancer from 2013 to 2020. Finally, a more precise technical direction is provided for all researchers in this review. Research gaps for earlier detection and its potential future aspects are also discussed.
Unsupervised change detection method in SAR images based on deep belief network using an improved fuzzy C‐means clustering algorithm
Authors: Attioui Sanae , Najah Said
Published: December 2020

Deep learning methods have recently displayed ground‐breaking results for synthetic aperture radar image change detection problem. However, they still face the challenges of intrinsic noise and the difficulty of acquiring labeled data. To sort out these issues, we aim to develop a change detection approach specifically designed for analyzing synthetic aperture radar images based on Deep Belief Network as the deep architecture which includes unsupervised feature learning and supervised network fine‐tuning. The deep neural networks can reach the final change maps directly from the two original images. A pre‐classification based on Morphological Reconstruction and Membership Filtering is employed in order to minimize the effect of noise. Appropriate diversity samples are provided by a virtual sample generation method in order to mitigate overfitting raised by limited synthetic aperture radar data. Visual and quantitative analysis as well as comparisons with advanced algorithms show that our algorithm not only achieves better results but also requires less implementation time.
DNR-Protokoll auf Intensivstationen
Authors: von Pruski Nikolei , Büscher Andreas
Published: December 2020

Die zunehmende Übertherapie von Patienten am Lebensende wird kritisch diskutiert. Besonders im Bereich der intensivmedizinischen Versorgung werden schätzungsweise bis zu 50 Prozent aller Patienten mit teilweise aussichtslosen Behandlungen übertherapiert. Um dieser Problematik entgegenzuwirken, wurde im Christlichen Krankenhaus Quakenbrück ein DNR-Protokoll für die Intensiveinheit implementiert, das eine strukturierte Dokumentationsmöglichkeit zur Therapiebegrenzung bietet. Die dabei gewonnenen Erfahrungen werden in zwei Beiträgen in der intensiv dargestellt. In diesem ersten Teil geht es um eine Handlungsempfehlung zur modellhaften Implementierung des DNR-Protokolls in Anlehnung an das Phasenmodell des Deutschen Netzwerks für Qualitätsentwicklung in der Pflege.
Straightforward Functionalization of Sulfur-Containing Peptides via 5- and 6-endo-dig Cyclization Reactions
Authors: Arsenyan Pavel , Lapcinska Sindija
Published: December 2020

We present a simple and convenient method for the generation of sulfenyl electrophiles from peptides containing S–S or S–H bonds by employing N-chlorosuccinimide. The corresponding sulfenyl electrophiles are further utilized in 5- and 6-endo-dig cyclization reactions yielding indolizinium salts, indoles, benzo[b]furans, polyaromatic hydrocarbons (PAHs) and isocoumarins, as well as quinolinones bearing a glutathione moiety. PAH derivatives can be used as selective fluorescent dyes for the visualization of lipid droplets in living cells.
Photo-Controlled Adhesives Based on Photoinduced Solid-to-Liquid Transition of an Azobenzene Compound
Authors: Niu Bing , Chen Mingsen , Zhao Xiaolei , Liu Yuanli , Wu Si
Published: December 2020

The development of photo-controlled adhesives can overcome the problems associated with daily lives and industrial applications. Adhesion is a multidiscipline field of engineering, physics, and chemistry. The solid-to-liquid transformation of light-controlled adhesives can be used for direct bonding onto diverse surfaces. Here, a photoresponsive azobenzene compound is developed for photo-controlled adhesion. The azobenzene compound 4, 4'-hexyl diacrylate-3-methylazobenzene (M1) exhibits photoinduced solid-to-liquid transition due to trans–cis photoisomerization. The prepolymer coating based on the azobenzene compound M1 is prepared on an adhesive surface. After UV irradiation, the solid coating was quickly transformed into liquid for adhesion. This photo-controlled adhesive has strong adhesion to different surfaces.
Dynamics of hierarchical weighted networks of van der Pol oscillators
Authors: Monsivais-Velazquez Daniel , Bhattacharya Kunal , Barrio Rafael A. , Maini Philip K. , Kaski Kimmo K.
Published: December 2020

We investigate the dynamics of regular fractal-like networks of hierarchically coupled van der Pol oscillators. The hierarchy is imposed in terms of the coupling strengths or link weights. We study the low frequency modes, as well as frequency and phase synchronization, in the network by a process of repeated coarse-graining of oscillator units. At any given stage of this process, we sum over the signals from the oscillator units of a clique to obtain a new oscillating unit. The frequencies and the phases for the coarse-grained oscillators are found to progressively synchronize with the number of coarse-graining steps. Furthermore, the characteristic frequency is found to decrease and finally stabilize to a value that can be tuned via the parameters of the system. We compare our numerical results with those of an approximate analytic solution and find good qualitative agreement. Our study on this idealized model shows how oscillations with a precise frequency can be obtained in systems with heterogeneous couplings. It also demonstrates the effect of imposing a hierarchy in terms of link weights instead of one that is solely topological, where the connectivity between oscillators would be the determining factor, as is usually the case.
Hamiltonian multiform description of an integrable hierarchy
Authors: Caudrelier Vincent , Stoppato Matteo
Published: December 2020

Motivated by the notion of Lagrangian multiforms, which provide a Lagrangian formulation of integrability, and by the results of the authors on the role of covariant Hamiltonian formalism for integrable field theories, we propose the notion of Hamiltonian multiforms for integrable 1 + 1-dimensional field theories. They provide the Hamiltonian counterpart of Lagrangian multiforms and encapsulate in a single object an arbitrary number of flows within an integrable hierarchy. For a given hierarchy, taking a Lagrangian multiform as the starting point, we provide a systematic construction of a Hamiltonian multiform based on a generalization of techniques of covariant Hamiltonian field theory. This also produces two other important objects: a symplectic multiform and the related multi-time Poisson bracket. They reduce to a multisymplectic form and the related covariant Poisson bracket if we restrict our attention to a single flow in the hierarchy. Our framework offers an alternative approach to define and derive conservation laws for a hierarchy. We illustrate our results on three examples: the potential Korteweg–de Vries hierarchy, the sine-Gordon hierarchy (in light-cone coordinates), and the Ablowitz–Kaup–Newell–Segur hierarchy.
Fluid modeling of stimulated Raman scattering accounting for trapped particles benchmarked against fully kinetic simulations
Authors: Tran G. , Loiseau P. , Fusaro A. , Héron A. , Hüller S. , Maëder L. , Masson-Laborde P.-E. , Penninckx D. , Riazuelo G.
Published: December 2020

A new fluid model describing backward stimulated Raman scattering (SRS) is presented based on parametric three-wave coupling in multidimensional geometry. It takes into account kinetic effects in the description of the plasma wave via a nonlinear frequency shift due to trapped electrons. This model is valid in the regime of hot and weakly inhomogeneous plasmas under conditions relevant for inertial confinement fusion with the plasma parameter kLλDe⩾ 0.25 (where kL stands for the plasma wave number and λDe for the Debye length). Benchmarks of the model have been performed against the Maxwell-particle-in-cell (PIC) code Emi2D in order to calibrate the adjustable parameters controlling the nonlinear frequency shift. Two major configurations have been tested, one in a homogeneous plasma, with the onset of laser pump depletion, and the other in an inhomogeneous plasma, producing auto-resonant growth. Good agreement between fluid and PIC simulations has been found for both configurations, in particular, for the growth of SRS, and further on in time for the average backscatter level. This model is a promising tool to be implemented in multi-dimensional laser-plasma interaction packages coupled to hydrodynamics codes in order to compute SRS in mm-size volumes, usually inaccessible with PIC codes.
Improvement in step resolution and response time of ultrasonic motor by using a piezoelectric resonant shunting circuit as damping control
Authors: Guo Mingsen , Pan Song , Chen Lei , Li Huafeng , Ye Junfeng , Ji Hongli , Hu Junhui
Published: December 2020

Ultrasonic motors can be driven by burst voltage to obtain micro-stepping motion, and the corresponding step size depends on the load and cycle number of the applied ac driving voltage in one burst. The rotor of the motor achieves a step motion through a process of startup-acceleration–deceleration-stop. To obtain a large torque (or thrust force) and quick startup, a large vibration amplitude of a stator and a high growth rate are desired; thus, a large mechanical quality factor and a high electromechanical coupling factor are required. However, the stator vibration decays for a long time before it stops because of low mechanical energy loss; meanwhile, the rotor moves a big step. Hence, there is contradiction between thrust force and resolution/response time. This paper presents a new drive method to improve the step resolution and response time while keeping the torque by damping control. By simply adding a switch and a shunting damp circuit and connecting the shunting circuit to ultrasonic motors at the end of a drive burst signal, the stator vibration attenuates more rapidly and the step size is reduced. First, the damping effect of the piezoelectric system with a passive resonant shunting circuit (a resistor and an inductor connected in series) on the free stator of a bar-type rotary traveling wave ultrasonic motor has been tested. Next, a drive circuit comprising electronic switches and the shunting circuit is designed and utilized for measuring the performance of the motor. Experimental results have well proven the proposed method.
Collision of expanding plasma clouds: Mixing, flow morphology, and instabilities
Authors: Sotnikov V. I. , Hamilton A. , Malkov M. A.
Published: December 2020

The collision of two expanding plasma flows is investigated with an emphasis on the mixing flow. The study adheres to laboratory experiments where two Ohmically exploding parallel wires launch hot plasma coronas toward each other. The interpenetration and mixing of the coronas is followed by the collision and mixing of the slowly moving phases of the melted wires. In a recent publication [M. A. Malkov and V. I. Sotnikov, Phys. Plasmas 25(10), 102108 (2018)], a stationary flow that emerges from interpenetrating coronas and plasma microinstabilities in the mixing region had been studied analytically. In this present work, using two-dimensional numerical simulations, we investigate the time evolution of the flow, compare its patterns resulting from collisions of the rarefied coronas and dense wire material, and examine the macroscopic stability of the flow. The stability of the mixing layer with respect to the so-called thin-shell instability is specifically addressed.
High breakdown voltage in La0.7Sr0.3MnO3/LaAlO3/SrTiO3 heterostructures
Authors: Zeeshan Hafiz M. , Butt Mehwish K. , Wang Shuanhu , Rafiq Mubashar , Jin Kexin
Published: December 2020

The junction diode as a high-voltage rectifier has a great impact within the electronic industry because of its applications. It has been synthesized accommodating two dimensional materials, [Sahatiya et al., 2D Mater. 4(2), 025053 (2017)]. Si-based p-n junctions and Si-based heterostructures in combination with complex oxides [Zhao et al., Appl. Phys. Lett. 93(25), 252110 (2008)]. In this Letter, we have synthesized the p–i–n junction using complex oxides La0.7Sr0.3MnO3 (LSMO), LaAlO3 (LAO), and SrTiO3 (STO), which exhibits the rectifying behavior as Si-based heterostructures in combination with complex oxides. In addition, the light-induced weak localization effect is observed in the LSMO film. This research will further assist in the growth of the electronic industry of STO-based heterostructures.
First principles study of thermoelectric properties of
β
-gallium oxide
Authors: Kumar Avinash , Singisetti Uttam
Published: December 2020

The thermoelectric effects in bulk β-gallium oxide crystals are investigated in this work using the ab initio calculated electron-phonon interactions and semi-classical Boltzmann transport theory. We have taken all major scattering mechanisms into account, namely, polar and non-polar optical phonon, acoustic phonon, and ionized impurity scattering. To accurately account for the polar phonon scattering rate, we take into account the dynamic screening at higher electron densities. An iterative solution of the Boltzmann transport equation is used in order to account for the inelastic and anisotropic nature of polar optical phonon scattering. The thermoelectric transport coefficients, Seebeck coefficient, Peltier coefficient, and electronic thermal conductivity, are calculated for a wide range of temperatures and doping densities. The calculated Seebeck coefficient is compared with the experimentally measured value and found to be in good agreement considering the mobility of the samples. The value of the Seebeck coefficient at 300 K is found to be −341 μV K−1, which is high compared to that of the other commonly studied semiconductors. The larger Seebeck coefficient is due to the higher density of states arising from comparatively high electron effective mass.
On star-convex volumes in 2-D hydrodynamical flows and their relevance for coherent transport
Authors: Lünsmann Benedict J. , Kantz Holger
Published: December 2020

Oceanic surface flows are dominated by finite-time mesoscale structures that separate two-dimensional flows into volumes of qualitatively different dynamical behavior. Among these, the transport boundaries around eddies are of particular interest since the enclosed volumes show a notable stability with respect to filamentation while being transported over significant distances with consequences for a multitude of different oceanic phenomena. In this paper, we present a novel method to analyze coherent transport in oceanic flows. The presented approach is purely based on convexity and aims to uncover maximal persistently star-convex (MPSC) volumes, volumes that remain star-convex with respect to a chosen reference point during a predefined time window. Since these volumes do not generate filaments, they constitute a sub-class of finite-time coherent volumes. The new perspective yields definitions for filaments, which enables the study of MPSC volume formation and dissipation. We discuss the underlying theory and present an algorithm, the material star-convex structure search, that yields comprehensible and intuitive results. In addition, we apply our method to different velocity fields and illustrate the usefulness of the method for interdisciplinary research by studying the generation of filaments in a real-world example.
Experimental and theoretical study of energy transfer in a chromophore triad: What makes modeling dynamics successful?
Authors: Freixas Victor M. , Nelson Tammie , Ondarse-Alvarez Dianelys , Nijjar Parmeet , Mikhailovsky Alexander , Zhou Cheng , Fernandez-Alberti Sebastian , Bazan Guillermo C. , Tretiak Sergei
Published: December 2020

Simulation of electronic dynamics in realistically large molecular systems is a demanding task that has not yet achieved the same level of quantitative prediction already realized for its static counterpart. This is particularly true for processes occurring beyond the Born–Oppenheimer regime. Non-adiabatic molecular dynamics (NAMD) simulations suffer from two convoluted sources of error: numerical algorithms for dynamics and electronic structure calculations. While the former has gained increasing attention, particularly addressing the validity of ad hoc methodologies, the effect of the latter remains relatively unexplored. Indeed, the required accuracy for electronic structure calculations to reach quantitative agreement with experiment in dynamics may be even more strict than that required for static simulations. Here, we address this issue by modeling the electronic energy transfer in a donor–acceptor–donor (D–A–D) molecular light harvesting system using fewest switches surface hopping NAMD simulations. In the studied system, time-resolved experimental measurements deliver complete information on spectra and energy transfer rates. Subsequent modeling shows that the calculated electronic transition energies are “sufficiently good” to reproduce experimental spectra but produce over an order of magnitude error in simulated dynamical rates. We further perform simulations using artificially shifted energy gaps to investigate the complex relationship between transition energies and modeled dynamics to understand factors affecting non-radiative relaxation and energy transfer rates.
Theory of quasi-simple dispersive shock waves and number of solitons evolved from a nonlinear pulse
Authors: Kamchatnov A. M.
Published: December 2020

The theory of motion of edges of dispersive shock waves generated after wave breaking of simple waves is developed. It is shown that this motion obeys Hamiltonian mechanics complemented by a Hopf-like equation for evolution of the background flow, which interacts with the edge wave packets or the edge solitons. A conjecture about the existence of a certain symmetry between equations for the small-amplitude and soliton edges is formulated. In the case of localized simple-wave pulses propagating through a quiescent medium, this theory provided a new approach to derivation of an asymptotic formula for the number of solitons eventually produced from such a pulse.
The role of structural disorder on luminescence of Eu-doped Na0.5Bi0.5TiO3
Authors: Dunce M. , Krieke G. , Birks E. , Bikse L. , Antonova M. , Sarakovskis A.
Published: December 2020

A detailed analysis of photoluminescence of Eu-doped Na0.5Bi0.5TiO3 (NBT) is performed using it as a tool for describing the local structure of NBT. The obtained results reveal the low symmetry of the Eu3+ local environment in NBT, as indicated by the observed maximal number of sublevels of the 5D0→7F1 and the 5D0→7F2 luminescence transitions, clearly observed at low temperatures. Approximation of the luminescence spectra by Gaussian peaks provides valuable information about the shift of the involved levels upon change of the excitation wavelength. Variation in the strength of the crystal field in Eu-doped NBT is evaluated. Temperature dependence of the luminescence above room temperature is analyzed for the poled and the unpoled states of the material. The results obtained for Eu-doped NBT are compared with the results for Er-doped NBT reported previously.
MOCVD growth of high purity Ga2O3 epitaxial films using trimethylgallium precursor
Authors: Seryogin George , Alema Fikadu , Valente Nicholas , Fu Houqiang , Steinbrunner Erich , Neal Adam T. , Mou Shin , Fine Aaron , Osinsky Andrei
Published: December 2020

We report on the growth of β-Ga2O3 thin films using trimethylgallium (TMGa) as a source for gallium and pure O2 for oxidation. The growth rate of the films was found to linearly increase with the increase in the molar flow rate of TMGa and reach as high as ∼6 μm/h at a flow rate of 580 μmol/min. High purity, lightly Si-doped homoepitaxial β-Ga2O3 films with a good surface morphology, a record low temperature electron mobility exceeding 23 000 cm2/V s at 32 K, and an acceptor concentration of 2 × 1013 cm−3 were realized, showing an excellent purity film. Films with room temperature (RT) electron mobilities ranging from 71 cm2/V s to 138 cm2/V s with the corresponding free carrier densities between ∼1.1 × 1019 cm−3 and ∼1.5 × 1016 were demonstrated. For layers with the doping concentration in the range of high-1017 and low-1018 cm−3, the RT electron mobility values were consistently more than 100 cm2/V s, suggesting that TMGa is suitable to grow channel layers for lateral devices, such as field effect transistors. The results demonstrate excellent purity of the films produced and confirm the suitability of the TMGa precursor for the growth of device quality β-Ga2O3 films at a fast growth rate, meeting the demands for commercializing Ga2O3-based high voltage power devices by metalorganic chemical vapor deposition.
Current transient response and role of the internal resistance in HfOx-based memristors
Authors: Gonzalez M. B. , Maestro-Izquierdo M. , Jiménez-Molinos F. , Roldán J. B. , Campabadal F.
Published: December 2020

Filamentary-type valence change memristors based on HfO2 are currently being explored as potential candidates to emulate the synaptic functionality of biological inspired neuromorphic circuits due to their ability to tune their resistance state (synaptic weight) needed to optimize their learning mechanisms. In this paper, the resistive switching dynamics associated with the electric field and temperature-assisted oxygen vacancy/ion migration, generation, and recombination processes is investigated in-depth through current transient experiments. Special attention is given to the influence of the intrinsic series resistance and applied voltage on the switching speed and on the abrupt or gradual resistance modulation capability, providing a deeper insight into the key parameters that have a crucial influence in the SET and RESET transitions and can strongly impact the programming energy consumption of redox-based HfO2-memristors.
Modeling non-Markovian data using Markov state and Langevin models
Authors: Lickert Benjamin , Stock Gerhard
Published: December 2020

Markov processes provide a popular approach to construct low-dimensional dynamical models of a complex biomolecular system. By partitioning the conformational space into metastable states, protein dynamics can be approximated in terms of memory-less jumps between these states, resulting in a Markov state model (MSM). Alternatively, suitable low-dimensional collective variables may be identified to construct a data-driven Langevin equation (dLE). In both cases, the underlying Markovian approximation requires a propagation time step (or lag time) δt that is longer than the memory time τM of the system. On the other hand, δt needs to be chosen short enough to resolve the system timescale τS of interest. If these conditions are in conflict (i.e., τM > τS), one may opt for a short time step δt = τS and try to account for the residual non-Markovianity of the data by optimizing the transition matrix or the Langevin fields such that the resulting model best reproduces the observables of interest. In this work, rescaling the friction tensor of the dLE based on short-time information in order to obtain the correct long-time behavior of the system is suggested. Adopting various model problems of increasing complexity, including a double-well system, the dissociation of solvated sodium chloride, and the functional dynamics of T4 lysozyme, the virtues and shortcomings of the rescaled dLE are discussed and compared to the corresponding MSMs.
Post-growth modulation doping by ion implantation
Authors: Chiu P.-Y. , Lidsky D. , Chuang Y. , Su Y.-H. , Li J.-Y. , Harris C. T. , Lu T. M.
Published: December 2020

Modulation doping is a commonly adopted technique to create two-dimensional (2D) electrons or holes in semiconductor heterostructures. One constraint, however, is that the intentional dopants required for modulation doping are controlled and incorporated during the growth of heterostructures. Using undoped strained germanium quantum wells as the model material system, we show, in this work, that modulation doping can be achieved post-growth of heterostructures by ion implantation and dopant-activation anneals. The carrier density is controlled ex situ by varying the ion fluence and implant energy, and an empirical calibration curve is obtained. While the mobility of the resulting 2D holes is lower than that in undoped heterostructure field-effect transistors built using the same material, the achievable carrier density is significantly higher. Potential applications of this modulation-doping technique are discussed.
Eyring equation and fluctuation–dissipation far away from equilibrium
Authors: Santamaría-Holek I. , Pérez-Madrid A.
Published: December 2020

Understanding and managing the influence that either external forces or non-equilibrated environments may have on chemical processes is essential for the current and future development of theoretical chemistry. One of the central questions to solve is how to generalize the transition state theory in order to make it applicable in far from equilibrium situations. In this sense, here we propose a way to generalize Eyring’s equation based on the definition of an effective thermal energy (temperature) emerging from the coupling of both fast and slow dynamic variables analyzed within the generalized Langevin dynamics scheme. This coupling makes the energy distribution of the fast degrees of freedom not equilibrate because they have been enslaved to the dynamics of the corresponding slow degrees. However, the introduction of the effective thermal energy enables us to restore an effective adiabatic separation of timescales leading to a renormalization of the generalized fluctuation–dissipation theorem. Hence, this procedure opens the possibility to deal with systems far away from equilibrium. A significant consequence of our results is that Eyring’s equation is generalized to treat systems under the influence of strong external forces.
Tailored coupled cluster theory in varying correlation regimes
Authors: Mörchen Maximilian , Freitag Leon , Reiher Markus
Published: December 2020

The tailored coupled cluster (TCC) approach is a promising ansatz that preserves the simplicity of single-reference coupled cluster theory while incorporating a multi-reference wave function through amplitudes obtained from a preceding multi-configurational calculation. Here, we present a detailed analysis of the TCC wave function based on model systems, which require an accurate description of both static and dynamic correlation. We investigate the reliability of the TCC approach with respect to the exact wave function. In addition to the error in the electronic energy and standard coupled cluster diagnostics, we exploit the overlap of TCC and full configuration interaction wave functions as a quality measure. We critically review issues, such as the required size of the active space, size-consistency, symmetry breaking in the wave function, and the dependence of TCC on the reference wave function. We observe that possible errors caused by symmetry breaking can be mitigated by employing the determinant with the largest weight in the active space as reference for the TCC calculation. We find the TCC model to be promising in calculations with active orbital spaces which include all orbitals with a large single-orbital entropy, even if the active spaces become very large and then may require modern active-space approaches that are not restricted to comparatively small numbers of orbitals. Furthermore, utilizing large active spaces can improve on the TCC wave function approximation and reduce the size-consistency error because the presence of highly excited determinants affects the accuracy of the coefficients of low-excited determinants in the active space.
Detection of charge states of an InAs nanowire triple quantum dot with an integrated nanowire charge sensor
Authors: Li Weijie , Mu Jingwei , Huang Shaoyun , Pan Dong , Zhao Jianhua , Xu H. Q.
Published: December 2020

A linear triple quantum dot (TQD) integrated with a quantum dot (QD) charge sensor is realized. The TQD and the charge sensor are built from two adjacent InAs nanowires by the fine finger gate technique. The charge state configurations of the nanowire TQD are studied by measurements of the direct transport signals of the TQD and by detection of the charge state transitions in the TQD via the nanowire QD sensor. Excellent agreement in the charge stability diagrams of the TQD obtained by the direct transport measurements and by the charge-state transition detection measurements is achieved. It is shown that the charge stability diagrams are featured by three groups of charge state transition lines of different slopes, corresponding to the changes in the electron occupation numbers of the three individual QDs in the TQD. It is also shown that the integrated nanowire QD sensor is highly sensitive and can detect the charge state transitions in the cases where the direct transport signals of the TQD are too weak to be measurable. Tuning to a regime, where all three QDs in the TQD are close to being on resonance with the Fermi level of the source and drain reservoirs and co-existence of triple and quadruple points becomes possible, has also been demonstrated with the help of the charge sensor in the region where the direct transport signals of the TQD are hardly visible.
THz-range Faraday rotation in the Weyl semimetal candidate Co2TiGe
Authors: Bhandia Rishi , Cheng Bing , Brown-Heft Tobias L. , Chatterjee Shouvik , Palmstrøm Christopher J. , Armitage N. P.
Published: December 2020

The Co2 family of ferromagnetic Heusler alloys has attracted interest due to their fully spin-polarized nature, making them ideal for applications in spintronic devices. More recently, the existence of room temperature time-reversal-breaking Weyl nodes near the Fermi level was predicted and confirmed in these systems. As a result of the presence of these Weyl nodes, these systems possess a non-zero momentum space Berry curvature that can dramatically influence transport properties such as the anomalous Hall effect. One of these candidate compounds is Co2TiGe. Recently, high-quality molecular beam epitaxy-grown thin films of Co2TiGe have become available. In this work, we present a THz-range measurement of MBE-grown Co2TiGe films. We measure the THz-range Faraday rotation, which can be understood as a measure of the anomalous Hall effect. We supplement this work with electronic band-structure calculations showing that the principal contribution to the anomalous Hall effect in this material stems from the Berry curvature of the material. Our work shows that this class of Heusler materials shows promise for Weyl semimetal based spintronics.
Accurate MP2-based force fields predict hydration free energies for simple alkanes and alcohols in good agreement with experiments
Authors: Rogers T. Ryan , Wang Feng
Published: December 2020

Force fields for four small molecules, methane, ethane, methanol, and ethanol, were created by force matching MP2 gradients computed with triple-zeta-quality basis sets using the Adaptive Force Matching method. Without fitting to any experimental properties, the force fields created were able to predict hydration free energies, enthalpies of hydration, and diffusion constants in excellent agreements with experiments. The root mean square error for the predicted hydration free energies is within 1 kJ/mol of experimental measurements of Ben-Naim et al. [J. Chem. Phys. 81(4), 2016–2027 (1984)]. The good prediction of hydration free energies is particularly noteworthy, as it is an important fundamental property. Similar hydration free energies of ethane relative to methane and of ethanol relative to methanol are attributed to a near cancellation of cavitation penalty and favorable contributions from dispersion and Coulombic interactions as a result of the additional methyl group.
Polarization switching in thin doped HfO2 ferroelectric layers
Authors: Materano Monica , Lomenzo Patrick D. , Mulaosmanovic Halid , Hoffmann Michael , Toriumi Akira , Mikolajick Thomas , Schroeder Uwe
Published: December 2020

The deployment of ferroelectrics in device concepts such as Ferroelectric Random Access Memory and Ferroelectric Field Effect Transistors requires a good understanding of the polarization switching mechanisms. While several reports already exist involving classical perovskite ferroelectrics, only recently has the switching dynamics in HfO2-based layers started to be addressed. In this work, the Kolmogorov–Avrami–Ishibashi (KAI), the Nucleation Limited Switching (NLS), the Landau–Khalatnikov (LK), and the Inhomogeneous Field Mechanism (IFM) models for polarization switching are surveyed and evaluated with the existing body of literature. Data concerning NLS and IFM are compared to experiments undertaken in this study. After excluding the KAI model because of considerations dealing with film morphology and domain wall energy, we conclude that the NLS, the LK, and the IFM models do not necessarily mutually exclude each other, but rather give a diverse perspective on the switching phenomenon based on thermodynamic, kinetic, statistic, microscopic, and/or macroscopic points of view.
Gruneisen parameters of bead-spring chains: MD simulation and theory
Authors: Stevenson Craig S. , Curro John G. , McCoy John D.
Published: December 2020

Molecular Dynamics (MD) simulations were carried out in a microcanonical ensemble to compute the Gruneisen parameter (denoted as γ) of a liquid of bead-spring chains having 10 beads/chain. γ was studied over a wide range of temperatures below and above the glass transition temperature. We found that the Gruneisen parameter varied in the range of 2.1–3.1 and was significantly higher than typically observed experimentally in real polymers. In the glass, a theory was developed for γ using a cell model in which the beads are harmonically bound to their respective cell centers. The resulting Gruneisen parameter is predicted to increase slightly with temperature. Above the glass transition temperature, we employed the generalized Flory dimer equation-of-state and the polymer reference interaction model theory to calculate γ. In these calculations, we found that γ decreased with temperature in the liquid. The theoretical predictions for γ were found to be in good qualitative agreement with our MD simulations, without any adjustable parameters, both above and below Tg. In experiments on real polymers, γ undergoes a sharp discontinuity at the glass transition. By contrast, in our MD simulations, γ varies smoothly over a broad transition region.
PACAP is a pathogen-inducible resident antimicrobial neuropeptide affording rapid and contextual molecular host defense of the brain
Authors: Lee Ernest Y. , Chan Liana C. , Wang Huiyuan , Lieng Juelline , Hung Mandy , Srinivasan Yashes , Wang Jennifer , Waschek James A. , Ferguson Andrew L. , Lee Kuo-Fen , Yount Nannette Y. , Yeaman Michael R. , Wong Gerard C. L.
Published: December 2020

Significance

Neuropeptides of the central nervous system regulate neurodevelopment, metabolism, emotion, and stress responses. However, despite previously established recognition of antimicrobial activity in vitro, their precise role(s) in host defense of the brain and other contexts in vivo have been poorly understood. Here, we discovered that the neuropeptide PACAP is an evolutionarily conserved antimicrobial peptide induced in the brain in response to bacterial and fungal infection. Tissue-specific PACAP induction coincided with minimal immune cell infiltration or neuroinflammation. These findings support an emerging paradigm wherein coevolution of the immune and nervous systems is linked through ancient, multifunctional peptides having neurological and immunomodulatory functions that protect the brain. We predict that PACAP is a prototypical example of a general class of endogenous, infection-inducible host-defense neuropeptides and serves as a model template to design next-generation antiinfectives with neurohomeostatic and immunomodulatory capabilities.