bluuebunny/crossref_metadata_2025 huggingface dataset:
Evolution of microstructure, texture and inhibitor of medium temperature grain-oriented silicon steel
Authors: Fan Li-Feng , Zhao Xing-Yuan , Xiao Li-Jun , Huang Jiao , Zhang Yuan Xiang
Published: September 2020

The medium temperature reheating and two-stage cold rolling process were adopted to produce industrialized Grain-oriented silicon steel. Results showed there were three sections (surface layer, transition layer and central layer) along the thickness direction on hot rolled sheets. Surface layer was occupied by complete recrystallization grains with average grain size 42.81 µm, while the central layer mainly consisted of fibrous microstructure. The Goss texture appeared only on surface layer with content 3.44%∼3.65%. After the first cold rolling with 72% reduction and decarburization annealing, the primary recrystallization occurred and average grains size reached 19.0 µm, simultaneously accompanied with texture rotated to λ, γ fiber texture and Goss texture dropped to 2.89%. Adopting the second cold rolling with 58% reduction, the cold rolled sheet consisted of deformed fiber microstructure and the texture maintained γ fiber texture with a peak at {111} <112>. The precipitates in hot rolled sheets comprised Cu2S and few AlN, and the average particle size was ∼14 nm. The inhibitors in the decarburization annealing sheet were mainly AlN, Cu2S, MnS and their composite precipitation, which were spherical or massive with the average particle size ∼21 nm. The single Goss oriented grains with average grain size 9.41 mm were obtained after high temperature annealing, and the intensity reached 873.30. The final magnetic properties were: B8 = 1.865 T and P1.7/50 = 1.124 W/kg, which met the requirement of 27Q120.
Les effets de l’intégration de la simulation sur l’apprentissage des gestes procéduraux de base et de l’examen physique en stage hospitalier dans le cursus pré-gradué des études médicales d’une faculté de médecine en Algérie
Authors: Mohammed Mokhtar Riad , Maizia Abdelkader , Seddiki Mohamed Mhamed Salaheddine , Mokhtari Lakhdar
Published: September 2020

Contexte et problématique : Pour apporter une valeur pédagogique significative, la simulation doit idéalement être intégrée dans un curriculum, articulée aux autres dispositifs et non simplement ajoutée. Dans le cadre du cursus pré-gradué de la Faculté de médecine de Mostaganem (Algérie), nous avons associé au stage hospitalier, en début de cycle clinique, un programme pédagogique de simulation ayant comme objectifs principaux l’apprentissage des examens physiques et des gestes procéduraux de base, à destination d’un public novice. Objectif : Comparer les effets sur l’apprentissage des examens physiques et gestes procéduraux de base d’un stage hospitalier avec programme de simulation par rapport à l’immersion hospitalière seule. Méthodes : Une promotion de 115 étudiants de troisième année de médecine en immersion hospitalière a été randomisée en deux groupes croisés, qui ont suivi, respectivement, le programme des gestes procéduraux avec simulation et le programme des examens physiques sans simulation, ou réciproquement. Une évaluation des apprentissages a été réalisée par examen clinique objectif structuré (ECOS) pour les acquisitions pratiques et par un test de connaissances avec questions à choix multiple pour les acquisitions théoriques. L’ensemble des scores obtenus ont été comparés par un test non paramétrique de Wilcoxon. Résultats : Les scores du groupe bénéficiant d’apprentissage par simulation avec immersion hospitalière ont été significativement supérieurs au groupe témoin, et ce aussi bien pour les acquisitions pratiques que pour les connaissances théoriques. Conclusion : Dans les conditions de l’étude, un dispositif pédagogique recourant à la simulation en articulation avec un compagnonnage classique pendant les stages d’externat s’est révélé être une approche pédagogique efficace pour l’amélioration de l’acquisition et la maîtrise des « examens physiques » et « gestes procéduraux » de base aux étudiants en début de cycle clinique.
Alkoholintoxikation bei Kindern und Jugendlichen –
Untersuchung 287 stationärer Fälle Schwere und Besonderheiten
bei Kindern unter 14 Jahren
Authors: Lozada Cesar Armando Quinones , Bartels Marco Baz , Kieslich Matthias
Published: September 2020

Hintergrund Trotz eines erfreulichen Rückgangs der aufgrund
einer akuten Alkoholintoxikation stationär behandelten
Minderjährigen, stellt der Alkoholkonsum bei Kindern und
Jugendlichen weiterhin eine problematische und besorgniserregende
Angelegenheit dar. Verstärkt wird diese Problematik aufgrund einer
vermutlich ausgeprägteren Symptomatik bei Kindern und Jugendlichen
in Rahmen einer Alkoholintoxikation als Erwachsenen.

Methoden Es wurden insgesamt 287 Fällen von Kindern und
Jugendlichen unter 18 Jahren, die aufgrund einer akuten Alkoholintoxikation
zwischen Januar 2002 und Dezember 2015 stationär in der Kinderklinik
des Universitätsklinikums Frankfurt behandelt wurden, analysiert. Es
erfolgte eine Alterseinteilung in Anlehnung an das Jugendschutzgesetz.

Ergebnisse Die Mehrheit (82/126) der Patienten mit einer
mittleren und schweren Bewusstseinsstörung waren Kinder und
Jugendliche unter 16 Jahre, trotz vergleichbarer, durchschnittlicher
Blutalkoholkonzentration (BAK). Eine präklinische
notärztliche Untersuchung fand bei jüngeren Patienten
deutlich häufiger als bei den älteren (>16 Jahre:
5,8%;<16 Jahre: 13,5% und<14 Jahre:
27,3%) statt. 7,3% der Minderjährigen mussten auf
der Intensivstation behandelt werden, zwei Drittel davon waren
jünger als 16 Jahre. Der Anteil der auf der Intensivstation
behandelten Kinder unter 14 Jahre lag sogar bei 13,6%. Bei 5
Patienten war eine maschinelle Beatmung notwendig, 4 davon waren
jünger als 16 Jahre und 2 davon sogar unter 14 Jahre.

Schlussfolgerungen Minderjährige und speziell Kinder unter 14
Jahre stellen eine besondere Risikogruppe aufgrund einer bedrohlichen
Symptomatik und der Notwendigkeit einer intensiveren medizinischen
Versorgung bei einer Alkoholintoxikation dar. Die konsequente Umsetzung des
Jugendschutzgesetzes, sowie die Entwicklung weitere und Fortführung
der bereits bestehenden Präventionsprogramme, wie das HaLT-Programm,
stellen die wichtigsten Handlungsmaßnahmen für die Zukunft
dar.
Diskriminationstraining
Authors: Mehrholz Jan , Thomas Simone , Elsner Bernhard
Published: September 2020

Für ein motorisches Training in der neurologischen Rehabilitation existiert seit vielen Jahren nunmehr eine große Anzahl an Übungsprotokollen und Studien. Dem sensorischen Üben, also dem Training der Wahrnehmung, wird im Vergleich dazu wissenschaftlich deutlich weniger Beachtung geschenkt. Der Artikel betrachtet in Studien untersuchte Übungsprotokolle zur Behandlung sensorischer Defizite wie die Diskrimination der Stereognosie.
COVID-19 in Children and Adolescents with Endocrine Conditions
Authors: Kostopoulou Eirini , Güemes Maria , Shah Pratik
Published: September 2020

The rapid spread of coronavirus disease (COVID-19) worldwide justifies global effort to combat the disease but also the need to review effective preventive strategies and medical management for potentially high-risk populations during the pandemic. Data regarding the COVID-19 manifestations in adults with underlying endocrine conditions, especially diabetes mellitus, are increasingly emerging. Albeit children and adolescents are considered to be affected in a milder manner, paucity of information regarding COVID-19 in children who suffer from endocrinopathies is available. The present review comprehensively collects recommendations issued by various health organizations and endocrine associations for the management of pediatric endocrine conditions during the pandemic. Adhering to the specific “sick day management rules” and undelayed seeking for medical advice are only needed in most of the cases, as the vast majority of children with endocrine disorders do not represent a high-risk population for contamination or severe presentation of COVID-19. Psychological implications in these children and adolescents are also considered.
Ultrasound-guided Dry Needling in Jumper’s Knee: A Case Report
Authors: Cuñado-González Álvaro , Ríos-León Marta
Published: September 2020

Background Jumper’s knee is a highly prevalent tendon condition in volleyball players population. Research on clinical effects of tendon dry needling in jumper’s knee is scarce. Therefore, the aim of this study was to present clinical effects of ultrasound-guided dry needling of quadricipital tendon in a patient with jumper’s knee.

Methods A 23-years-old volleyball player, who experienced pain in quadricipital tendon for 5 months, was presented and treated by ultrasound-guided dry needling of quadricipital tendon with one session. Slightly limited knee flexion range of motion, high scores in Visual Analogue Scale (VAS) at rest and during Single-Leg decline Squat test (SLDS) related to high pain intensity, low scores in Victorian Institute of Sport Assessment (VISA-P) scale and Lower Extremity Functional Scale (LEFS) were found. Further examination revealed sensitization of the quadricipital tendon (low pressure pain threshold).

Results We found important improvements in VISA-P, LEFS and VAS. Besides, pressure pain threshold and knee flexion during SLDS also showed improvements. Results which were obtained were better in all the variables studied and these recoveries were stable for 6 months.

Conclusions Our findings showed improvements in pain and function in medium term and could provide preliminary evidence of beneficial effects of quadricipital tendon dry needling in patients with jumper’s knee. Future studies are needed to clarify our results and compare dry needling with conservative treatments.
Endoscopic ultrasound-guided gallbladder drainage as a rescue therapy for unresectable malignant biliary obstruction: a multicenter experience
Authors: Issa Danny , Irani Shayan , Law Ryan , Shah Shawn , Bhalla Sean , Mahadev Srihari , Hajifathalian Kaveh , Sampath Kartik , Mukewar Saurabh , Carr-Locke David L. , Khashab Mouen A. , Sharaiha Reem Z.
Published: September 2020

Background Endoscopic retrograde cholangiopancreatography (ERCP) is often unsuccessful in patients with duodenal stenosis or malignant ampullary infiltration. While endoscopic ultrasound-guided biliary drainage (EUS-BD) has been proposed as an alternative, EUS-guided gallbladder drainage (EUS-GBD) is an attractive option when both approaches fail. We aimed to assess the effectiveness and safety of EUS-GBD as rescue therapy for malignant distal bile duct obstruction.

Methods A multicenter retrospective study was performed on patients with unresectable malignant distal bile duct obstruction who underwent EUS-GBD between 2014 and 2019 after unsuccessful ERCP and EUS-BD. Clinical success was defined as a decrease in serum bilirubin of > 50 % within 2 weeks.

Results 28 patients were included, with a lumen-apposing metal stent used in 26 (93 %) and a self-expandable metal stent in two (7 %). The technical success rate was 100 %. The clinical success rate was 93 %, with an improvement in bilirubin (7.3 [SD 5.4] pre-procedure vs. 2.8 [SD 1.1] post-procedure; P = 0.001). Delayed adverse events included food impaction of the stent (n = 3), with a further two patients developing cholecystitis and bleeding.

Conclusion This study demonstrates the feasibility of gallbladder drainage to relieve malignant distal bile duct obstruction in patients with failed ERCP and EUS-BD.
A Practical Approach for the Transamidation of N,N-Dimethyl Amides with Primary Amines Promoted by Sodium tert-Butoxide under Solvent-Free Conditions
Authors: Cheng Hua , Chen Cheng , Zhang Rui , Zhang Jun-Chao , Zhang Wei-Yi , He Yu-Qing , Gu Yu-Cheng
Published: September 2020

A practical sodium tert-butoxide (NaOtBu)-mediated protocol is disclosed for the transamidation of various N,N-dimethyl amides with primary amines to afford the corresponding amides in moderate to good yields at room temperature under solvent-free conditions. This protocol features a facile work-up procedure and good functional group compatibility, especially for N,N-dimethyl amides with long-chain alkyl groups and heteroatom-containing amines. Notably, a few representative gram-scale reactions proceed smoothly to furnish the desired amides in high yields, which demonstrates the potential of this process for further practical applications. Several control experiments are carried out and a plausible mechanism is provided.
Catalytic C–H Arylation of Tetrathiafulvalenes for the Synthesis of Functional Materials
Authors: Yorimitsu Hideki , Yoshimura Aya , Misaki Yohji
Published: September 2020

Sulfur-containing functional π-conjugated cores play key roles in materials science, mostly due to their unique electrochemical and photophysical properties. Among these, the excellent electron donor tetrathiafulvalene (TTF) has occupied a central position since the emergence of organic electronics. Peripheral C–H modification of this highly useful sulfur-containing motif has resulted in the efficient creation of new molecules that expand the applications of TTFs. This Short Review begins with the development of the palladium-catalyzed direct C–H arylation of TTF. Subsequently, it summarizes the applications of this efficient C–H transformation for the straightforward synthesis of useful TTF derivatives that are employed in a variety of research fields, demonstrating that the development of a new reaction can have a significant impact on chemical science.

1 Introduction

2 Development of the Palladium-Catalyzed Direct C–H Arylation of TTF

3 Synthesis of TTF-Based Tetrabenzoic Acid and Tetrapyridine for MOFs

4 Synthesis of TTF-Based Tetrabenzaldehyde and Tetraaniline for COFs

5 Tetraarylation of TTFAQ

6 Synthesis of Multistage-Redox TTF Derivatives

7 Miscellaneous Examples

8 Conclusions
Management and Nutrition of Neonates during the COVID-19 Pandemic: A Review of the Existing Guidelines and Recommendations
Authors: Genoni Giulia , Conio Alessandra , Binotti Marco , Manzoni Paolo , Castagno Matteo , Rabbone Ivana , Monzani Alice
Published: September 2020

Objective We aimed at reviewing the currently available guidelines and scientific recommendations regarding the neonatal in-hospital management and feeding in the light of the coronavirus disease 2019 (COVID-19) pandemic.

Study Design We systematically searched the guideline databases, Medline, Embase, and nationale/international neonatal societies websites as of June 19, 2020, for guidelines on neonatal management and feeding during the COVID-19 pandemic, at the same time assessing the methodological quality using the Appraisal of Guidelines for Research and Evaluation II tool.

Results Eleven guidelines were included. The Chinese and American recommendations suggest separation of the mother and her neonate, whereas in French, Italian, UK, Canadian, and World Health Organization consensus documents the rooming-in is suggested, with Centers for Disease Control and Prevention guidelines suggesting to decide on a case-by-case basis. All the guidelines recommend breastfeeding or feeding with expressed maternal milk; the only exception is the Chinese recommendations, these last suggesting to avoid breastfeeding.

Conclusion This review may provide a useful tool for clinicians and organizers, highlighting differences and similarities of the existing guidelines on the management and feeding strategies in the light of the COVID-19 pandemic.

Key Points
Transcervical (SP) and Transhiatal DaVinci Robotic Esophagectomy: A Cadaveric Study
Authors: van der Sluis Pieter , Egberts Jan-Hendrik , Stein Hubert , Sallum Rubens , van Hillegersberg Richard , Grimminger Peter P.
Published: September 2020

Background This is a preclinical cadaveric study to investigate the feasibility of a fully robotic McKeown esophagectomy in simultaneous rendezvous technique using the DaVinci X for transhiatal dissection and the DaVinci single port (SP) for transcervical dissection.

Methods Two transcervical esophagectomies with the DaVinci SP surgical system were performed as training procedures. In the third transcervical cadaveric procedure, the DaVinci SP was installed for the transcervical approach and the DaVinci X surgical system for the abdominal transhiatal phase. Primary outcomes were operating time and lymphadenectomy.

Results The mobilization of the esophagus was successfully completed in 118 minutes by using the DaVinci SP for the transcervical phase and the DaVinci X for the transhiatal abdominal phase simultaneously. In total 18 lymph nodes were dissected in the thorax; 3 were located paratracheal right, 3 paratracheal left, 4 subcarinal, 4 para-aortic, 2 paraesophageal upper mediastinal, and 2 paraesophageal middle mediastinal.

Conclusion This preclinical study demonstrated that a fully robotic McKeown esophagectomy in simultaneous rendezvous technique using the DaVinci X for transhiatal dissection and the DaVinci SP for transcervical dissection was feasible with adequate lymphadenectomy in a cadaver model. Future research will elucidate the indications for the use of the fully robotic transhiatal and transcervical esophagectomy.
First-principles study on crystal structures and superconductivity of molybdenum hydrides under high pressure
Authors: Liao Zhiguang , Liu Changdong , Zhang Yue , Guo Yongliang , Ke Xuezhi
Published: September 2020

Hydrogen-rich compounds are promising candidates for high temperature superconductors [Duan et al., Natl. Sci. Rev. 4, 121 (2017); Bi et al., arXiv:1806.00163 (2018); Pickard et al., Ann. Rev. Condens. Matter Phys. 11, 57 (2020); Flores-Livas et al., Phys. Rep. 856, 1 (2020)]. Combining first-principles calculation and the swarm intelligence-based structure search method, we investigated structures and superconductivity of molybdenum hydrides under high pressures. Four new phases have been predicted, namely, I4/m−MoH4, I4/mmm−MoH4, C2/m−MoH6, and Immm−MoH6. The superconducting critical temperature of Immm−MoH6 under 300 GPa was predicted to be 80 K, which is the highest value among hydrides of group six elements in the periodic table. Intriguingly, the phase transition from I4/mmm−MoH4 to I4/m−MoH4 at 280 GPa is driven by the imaginary optical modes and the soft optical modes significantly enhance the superconducting critical temperature.
Vortex-field acoustic levitation in tubes
Authors: Hong Z. Y. , Yin J. F. , Zhang B. W. , Yan N.
Published: September 2020

Vortex-field acoustic levitation (VAL) is a versatile acoustic levitation method that allows simultaneous rotation and movement of the levitated object. However, the levitation capability of VAL in air was previously limited to the levitation of objects with a density equal to or less than that of water. Here, we generate first-order acoustic vortices using an annular array of sources and investigate the characteristics of VAL within a cylindrical tube. It is shown that the number of potential minima on the vortex axis and the levitation capability of VAL can be enhanced by careful choice of the geometry of the array and the tube. As an example, a stainless steel sphere (density about 7.9 g/cm3) and a copper sphere (density about 8.7 g/cm3) have been successfully levitated.
Low field transport calculation of 2-dimensional electron gas in β-(AlxGa1−x)2O3/Ga2O3 heterostructures
Authors: Kumar Avinash , Ghosh Krishnendu , Singisetti Uttam
Published: September 2020

β -Gallium oxide (β-Ga2O3) is an emerging wide bandgap semiconductor with potential applications in power and RF electronic systems. Previous theoretical calculation on a two-dimensional electron gas (2DEG) in β-(AlxGa1−x)2O3/Ga2O3 heterostructures, taking only polar optical and remote impurity scattering into account, shows improved mobility compared to bulk β-Ga2O3. However, the experimental results in 2DEGs have not achieved the predicted mobility values. In this work, we perform more comprehensive calculations to study the low field 2DEG transport properties in the β-(AlxGa1−x)2O3/Ga2O3 heterostructures. A self-consistent Poisson–Schrödinger simulation of a heterostructure is used to obtain the sub-band energies and the wavefunctions in the quantum well. The phonon dispersion is calculated based on the ab initio methods under the density functional theory and density functional perturbation theory frameworks. The different scatterings that are included in the calculation are due to phonons (polar and non-polar), remote impurities, the alloy disorder, and interface roughness. We include a full dynamic screening of polar optical phonons. We report the temperature dependent low-field electron mobility as a function of 2DEG density. The overall mobility is found to be increasing with electron density with an exception at low density where the antiscreening of LO phonons reduces mobility. The effect of spacer thickness, aluminum fraction, and roughness parameters on mobility is shown to be critically important. The effect of the confinement direction on 2DEG mobility is found to be small and comparable to bulk. A comparison of calculated mobility values with experimentally reported data shows a good agreement.
Low interface state densities at Al2O3/GaN interfaces formed on vicinal polar and non-polar surfaces
Authors: Ando Yuto , Nagamatsu Kentaro , Deki Manato , Taoka Noriyuki , Tanaka Atsushi , Nitta Shugo , Honda Yoshio , Nakamura Tohru , Amano Hiroshi
Published: September 2020

Ni/Al2O3/GaN structures with vicinal GaN surfaces from the c- or m-plane were formed. Then, electrical interface properties of the structures were systematically investigated. It was found that interface state density (Dit) at the Al2O3/GaN interface for the c-plane is higher than that for the m-plane, and post-metallization annealing is quite effective to reduce Dit for both c- and m-planes. As a result, the low Dit value of ∼ 3 × 1010 eV−1 cm−2 was demonstrated for both planes.
Geometrical nonlinearity of circular plates and membranes: An alternative method
Authors: Cattiaux D. , Kumar S. , Zhou X. , Fefferman A. , Collin E.
Published: September 2020

We apply the well-established theoretical method developed for geometrical nonlinearities of micro-/nano-mechanical clamped beams to circular drums. The calculation is performed under the same hypotheses, the extra difficulty being to analytically describe the (coordinate-dependent) additional stress generated in the structure by the motion. Specifically, the model applies to non-axisymmetric mode shapes. An analytic expression is produced for the Duffing (hardening) nonlinear coefficient, which requires only the knowledge of the mode shape functions to be evaluated. This formulation is simple to handle and does not rely on complex numerical methods. Moreover, no hypotheses are made on the drive scheme and the nature of the in-plane stress: it is not required to be of an electrostatic origin. We confront our predictions with both typical experimental devices and relevant theoretical results from the literature. Generalization of the presented method to Duffing-type mode-coupling should be a straightforward extension of this work. We believe that the presented modeling will contribute to the development of nonlinear physics implemented in 2D micro-/nano-mechanical structures.
Cloaking using anisotropic multilayer circular cylinder
Authors: Batool Sidra , Nisar Mehwish , Mangini Fabio , Frezza Fabrizio
Published: September 2020

In this article, we study a homogenization model for cloaking applications. In the given model, we consider an isotropic inner layer, which is coated with a multilayer anisotropic circular cylinder. We describe the electrostatic response of a polarly radially anisotropic (PRA) multilayer circular cylinder. It consists of different components of permittivity in radial and tangential directions for each layer. We have shown the mathematical derivation of the polarizability and effective permittivity of a PRA multilayer circular cylinder. Moreover, we demonstrate the cloaking behavior using a PRA multilayer circular cylinder. Meanwhile, we test our formation with advanced computational approaches. During our numerical test, we have investigated the numerical results of the polarizability of a PRA multilayer circular cylinder. We employ an inner cloak surrounded by a multilayer anisotropic circular cylinder. However, for an ideal cloak, the contrast between the permittivity parameters approaches infinity.
Terahertz emission from submicron solid targets irradiated by ultraintense femtosecond laser pulses
Authors: Déchard J. , Davoine X. , Gremillet L. , Bergé L.
Published: September 2020

Using high-resolution, two-dimensional particle-in-cell simulations, we investigate numerically the mechanisms of terahertz (THz) emissions in sub-micrometer-thick carbon solid foils driven by ultraintense (∼1020 W cm−2), ultrashort (30 fs) laser pulses at normal incidence. The considered range of target thicknesses extends down to the relativistic transparency regime that is known to optimize ion acceleration by femtosecond laser pulses. By disentangling the fields emitted by longitudinal and transverse currents, our analysis reveals that, within the first picosecond after the interaction, THz emission occurs in bursts as a result of coherent transition radiation by the recirculating hot electrons and antenna-type emission by the shielding electron currents traveling along the fast-expanding target surfaces.
Observation of carrier lifetime distribution in 4H-SiC thick epilayers using microscopic time-resolved free carrier absorption system
Authors: Nagaya K. , Hirayama T. , Tawara T. , Murata K. , Tsuchida H. , Miyasaka A. , Kojima K. , Kato T. , Okumura H. , Kato M.
Published: September 2020

The carrier lifetime is an important parameter for high voltage SiC bipolar devices because its distribution in drift layers affects the device performance. Observation techniques for carrier lifetime, along with the development of carrier lifetime control processes, are important to control carrier lifetime distribution. In this study, we developed a microscopic time-resolved free carrier absorption system that has a variable spot size of excitation light and two different probe light wavelengths (405 and 637 nm). By selecting a relatively small spot size of excitation light and the probe light of shorter wavelength (405 nm), the distribution of carrier lifetime was observed with a high spatial resolution of ∼3 μm. Additionally, by using a relatively large spot size of excitation light and the probe light that leads to stronger free carrier absorption (637 nm), an accurate measurement of carrier lifetime was obtained. The developed system enables the design and development of bipolar SiC devices with carrier lifetime distribution control.
Recent advancements in the study of intrinsic magnetic topological insulators and magnetic Weyl semimetals
Authors: Ning Wei , Mao Zhiqiang
Published: September 2020

The studies of topological insulators (TI) and topological semimetals have been at frontiers of condensed matter physics and material science. Both classes of materials are characterized by robust surface states created by the topology of the bulk band structures and exhibit exotic transport properties. When magnetism is present in topological materials and breaks the time-reversal symmetry, more exotic quantum phenomena can be generated, e.g., quantum anomalous Hall effect (QAHE), axion insulator, and large intrinsic AHE. In this research update, we briefly summarize the recent research progress in magnetic topological materials, including intrinsic magnetic TI and magnetic Weyl semimetals.
Correlation between excitons recombination dynamics and internal quantum efficiency of AlGaN-based UV-A multiple quantum wells
Authors: Murotani Hideaki , Miyoshi Hiroyuki , Takeda Ryohei , Nakao Hiroki , Ajmal Khan M. , Maeda Noritoshi , Jo Masafumi , Hirayama Hideki , Yamada Yoichi
Published: September 2020

The correlation between the recombination dynamics of excitons and the internal quantum efficiency (IQE) of AlGaN-based UV-A multiple quantum wells (MQWs) was studied via photoluminescence (PL) and time-resolved PL (TRPL) spectroscopy. The probability ratio of the capture of excitons by nonradiative recombination centers (NRCs) and the radiative recombination of excitons was evaluated individually via two different experimental analyses. The IQE was evaluated via temperature- and excitation power density-dependent PL measurements and its dependence on excitation density was analyzed using a rate equation model based on the radiative and nonradiative recombination of excitons. Moreover, the radiative and nonradiative recombination lifetimes were evaluated via temperature-dependent TRPL measurements; furthermore, they were analyzed as functions of temperature and excitation energy density. The probability ratios obtained from the two individual analyses were in agreement. This quantitative agreement indicated that the analysis based on the radiative and nonradiative recombination processes of excitons, which included the process of filling NRCs, was valid for AlGaN-based UV-A MQWs.
Narrow-band and tunable intense terahertz pulses for mode-selective coherent phonon excitation
Authors: Vicario C. , Trisorio A. , Allenspach S. , Rüegg C. , Giorgianni F.
Published: September 2020

We generate frequency-tunable narrow-band intense fields in the terahertz (THz) range by optical rectification of a temporally modulated near-infrared laser pumping a nonlinear organic crystal. Carrier-frequency tunability between 0.5 and 6.5 THz is achieved by changing the modulation period of the laser pump. This tunable narrow-band THz source allows the selective coherent excitation of adjacent vibrational modes, which are demonstrated for two phonons with a frequency offset of 0.8 THz in single-crystal SrCu2(BO3)2. Our compact and scalable source enables an effective approach for the advanced manipulation of low-energy collective modes in condensed matter and has the potential to reveal the coupling of specific lattice vibrations with other degrees of freedom.
Thermodynamic susceptibility as a measure of cooperative behavior in social dilemmas
Authors: Benjamin Colin , Dash Aditya
Published: September 2020

The emergence of cooperation in the thermodynamic limit of social dilemmas is an emerging field of research. While numerical approaches (using replicator dynamics) are dime a dozen, analytical approaches are rare. A particularly useful analytical approach is to utilize a mapping between the spin-1/2 Ising model in 1D and the social dilemma game and calculate the magnetization, which is the net difference between the fraction of cooperators and defectors in a social dilemma. In this paper, we look at the susceptibility, which probes the net change in the fraction of players adopting a certain strategy, for both classical and quantum social dilemmas. The reason being, in statistical mechanics problems, the thermodynamic susceptibility as compared to magnetization is a more sensitive probe for microscopic behavior, e.g., observing small changes in a population adopting a certain strategy. In this paper, we find the thermodynamic susceptibility for reward, sucker’s payoff, and temptation in classical Prisoner’s Dilemma to be positive, implying that the turnover from defect to cooperate is greater than vice versa, although the Nash equilibrium for the two-player game is to defect. In the classical hawk–dove game, the thermodynamic susceptibility for resource suggests that the number of players switching to hawk from dove strategy is dominant. Entanglement in Quantum Prisoner’s Dilemma has a non-trivial role in determining the behavior of thermodynamic susceptibility. At maximal entanglement, we find that sucker’s payoff and temptation increase the number of players switching to defect. In the zero-temperature limit, we find that there are two second-order phase transitions in the game, marked by a divergence in the susceptibility. This behavior is similar to that seen in type-II superconductors wherein also two second-order phase transitions are seen.
Time-jerk optimal deployment trajectory planning of deployable parabolic cylindrical antenna
Authors: Zhou Jinhua , Lin Fei , Guo Yunyun , Chen Meng
Published: September 2020

A time-jerk optimal deployment trajectory planning method of a large cable-strut deployable parabolic cylindrical antenna is proposed. First, in order to decouple the complex multi-loop mechanisms, the multi-loop basic mechanism of the deployable support structure is split into three single-loop linkages, and the geometric constraint model is established based on the Denavit–Hartenberg method. Then, the kinematic model with jerk characteristics of the basic mechanism is obtained by differentiation. By considering the basic mechanism into a motion element, the kinematic model of the deployable support structure is also established based on matrix coding and motion synthesis theory. Second, by using cubic splines and considering the comprehensive optimal performance of deployment time and system jerk, an antenna deployment trajectory optimization model is established. At last, for obtaining a high precision and stable optimal solution rapidly, the non-dominated sorting genetic algorithm-II is improved by introducing the expected solution preserving strategy. The experimental results show that the proposed approach is able to effectively solve real-parameter multi-objective problems and has better performance on convergence, diversity, and the degree of controlling self-adaptation. The optimal trajectory is efficient and has a smooth kinematic performance.
Tunneling matrix element and tunneling pathways of protein electron transfer calculated with a fragment molecular orbital method
Authors: Kitoh-Nishioka Hirotaka , Shigeta Yasuteru , Ando Koji
Published: September 2020

Practical ways to calculate the tunneling matrix elements and analyze the tunneling pathways for protein electron-transfer (ET) reactions with a fragment molecular orbital (FMO) method are presented. The straightforward use of minimal basis sets only for the atoms involved in the covalent bond detachment in FMO can properly describe the ETs through the protein main-chains with the cost-effective two-body corrections (FMO2) without losing the quality of double-zeta basis sets. The current FMO codes have been interfaced with density functional theory, polarizable continuum model, and model core potentials, with which the FMO-based protein ET calculations can consider the effects of electron correlation, solvation, and transition-metal redox centers. The reasonable performance of the FMO-based ET calculations is demonstrated for three different sets of protein-ET model molecules: (1) hole transfer between two tryptophans covalently bridged by a polyalanine linker in the ideal α-helix and β-strand conformations, (2) ET between two plastoquinones covalently bridged by a polyalanine linker in the ideal α-helix and β-strand conformations, and (3) hole transfer between ruthenium (Ru) and copper (Cu) complexes covalently bridged by a stretch of a polyglycine linker as a model for Ru-modified derivatives of azurin.
A brush-coating approach to achieve anisotropic optical film via field-induced stretching of carbon nanotube clusters in a reactive mesogen
Authors: Lim Young Jin , Manda Ramesh , Cho Kyung Jun , Kim Tae Hyung , Tie Weiwei , Torres Jorge , Yun Minhee , Lee Seung Hee
Published: September 2020

We present a novel brush coating method for fabricating a coatable polarizer that utilizes a mixture of functionalized single-walled carbon nanotubes (h-SWCNTs) grafted with carboxyl and hydroxyl groups and a reactive mesogen (RM), which possess a long-range orientational ordering of their rod-shaped molecules with photo-sensitive functional groups. The h-SWCNTs are shortened to a length of around 150 nm by an acid sonochemical oxidation process and then dispersed in an RM solution. The brush-coated thin layer initially consists of h-SWCNT clusters, but applying an in-plane electric field induces large-scale stretching of these along the field direction, after which the layer is photo-polymerized by ultraviolet irradiation to form a film embedding the stretched nanotubes. The uniaxially aligned carbon nanotubes (CNTs) produce a broadband absorption spectrum that enables the film to exhibit an optical anisotropic property that absorbs incident light from the ultraviolet to the visible spectrum selectively depending on the polarization direction, thus acting as a coatable CNT polarizer. The dispersibility and elongation of h-SWCNT clusters induced by applying the electric field, as well as the anisotropic light-absorption properties of the h-SWCNT film, are investigated.
Reciprocal microswimmers in a viscoelastic fluid
Authors: Yasuda Kento , Kuroda Mizuki , Komura Shigeyuki
Published: September 2020

We suggest several reciprocal swimming mechanisms that lead to locomotion only in viscoelastic fluids. In the first situation, we consider a three-sphere microswimmer with a difference in oscillation amplitudes for the two arms. In the second situation, we consider a three-sphere microswimmer in which one of the frequencies of the arm motion is twice as large as the other one. In the third situation, we consider a two-sphere microswimmer with a difference in size for the two spheres. In all these three cases, the average velocity is proportional to the imaginary part of the complex shear viscosity of a surrounding viscoelastic medium. We show that it is essential for a micromachine to break its structural symmetry in order to swim in a viscoelastic fluid by performing reciprocal body motions.
Connection between liquid and non-crystalline solid phases in water
Authors: Martelli Fausto , Leoni Fabio , Sciortino Francesco , Russo John
Published: September 2020

The origin of water anomalies hides in an experimentally inaccessible region of the phase diagram known as no-man’s land, bounded at low temperature by the domain of stability of amorphous glasses, and at high temperature by the homogeneous nucleation line, below which liquid water loses its metastability. The existence of at least two different forms of glass on one side, i.e., the low-density amorphous (LDA) and the high-density amorphous (HDA) ices, and of one anomalous liquid on the other side, points to a hidden connection between these states, whose understanding has the potential to uncover what happens in no-man’s land and shed light on the complex nature of water’s behavior. Here, we develop a Neural Network scheme capable of discerning local structures beyond tetrahedrality. Applied over a wide region of the water’s phase diagram, we show that the local structures that characterize both LDA and HDA amorphous phases are indeed embedded in the supercooled liquid phase. Remarkably, the rapid increase in the LDA-like population with supercooling occurs in the same temperature and pressure region where thermodynamic fluctuations are maximized, linking these structures with water’s anomalies. At the same time, the population of HDA-like environments rapidly increases with pressure, becoming the majority component at high density. Our results show that both LDA and HDA are genuine glasses, and provide a microscopic connection between the non-equilibrium and equilibrium phase diagrams of water.
Helical magnetic structure and exchange bias across the compensation temperature of Gd/Co multilayers
Authors: Basha M. A. , Prajapat C. L. , Bhatt Harsh , Kumar Yogesh , Gupta M. , Kinane C. J. , Cooper J. F. K. , Caruana A. , Gonal M. R. , Langridge S. , Basu S. , Singh Surendra
Published: September 2020

Antiferromagnetic coupling between rare-earth (RE) and transition metals (TM) gives rise to various magnetic ground states in RE/TM heterostructures. Interface structure and morphology tend to play important roles in defining the magnetic properties of heterostructures of these materials. Using spin-dependent polarized neutron reflectivity (PNR), we found a distinct magnetic structure for RE/TM (Gd/Co) multilayers having different interface morphologies. Two Gd/Co multilayers, each consisting of eight bilayers of Gd and Co, were grown at different argon pressures to accomplish variation in the interface morphology. The Gd/Co multilayer, which is grown at a lower argon pressure, exhibits lower intermixing/interdiffusion at the interfaces and shows asymmetric magnetic hysteresis loops below the compensation temperature (Tcomp ∼ 140 K) and antisymmetric magnetoresistance at Tcomp. The other multilayer, grown at two different argon pressures for the top and bottom four bilayers, shows a double hysteresis loop with an exchange-bias-like shift to the field axis at temperatures above Tcomp (∼150 K). From PNR measurements across Tcomp, these behaviors were attributed to interface dependent magnetic helical structures. The PNR results indicate the formation of a twisted helical magnetic structure with planar 2π domain walls and the evolution of magnetic inhomogeneities below Tcomp. The interface dependent twisted helical magnetic structures and the development of highly correlated magnetic inhomogeneities may find applications in all-spin-based technologies.
Photooxidation of water with heptazine-based molecular photocatalysts: Insights from spectroscopy and computational chemistry
Authors: Domcke Wolfgang , Sobolewski Andrzej L. , Schlenker Cody W.
Published: September 2020

We present a conspectus of recent joint spectroscopic and computational studies that provided novel insight into the photochemistry of hydrogen-bonded complexes of the heptazine (Hz) chromophore with hydroxylic substrate molecules (water and phenol). It was found that a functionalized derivative of Hz, tri-anisole-heptazine (TAHz), can photooxidize water and phenol in a homogeneous photochemical reaction. This allows the exploration of the basic mechanisms of the proton-coupled electron-transfer (PCET) process involved in the water photooxidation reaction in well-defined complexes of chemically tunable molecular chromophores with chemically tunable substrate molecules. The unique properties of the excited electronic states of the Hz molecule and derivatives thereof are highlighted. The potential energy landscape relevant for the PCET reaction has been characterized by judicious computational studies. These data provided the basis for the demonstration of rational laser control of PCET reactions in TAHz–phenol complexes by pump–push–probe spectroscopy, which sheds light on the branching mechanisms occurring by the interaction of nonreactive locally excited states of the chromophore with reactive intermolecular charge-transfer states. Extrapolating from these results, we propose a general scenario that unravels the complex photoinduced water-splitting reaction into simple sequential light-driven one-electron redox reactions followed by simple dark radical–radical recombination reactions.
Band alignment at
β
-Ga2O3/III-N (III = Al, Ga) interfaces through hybrid functional calculations
Authors: Lyu Sai , Pasquarello Alfredo
Published: September 2020

The band alignment and the chemical bonding at the β-Ga2O3/AlN and β-Ga2O3/GaN interfaces are studied through hybrid functional calculations. We construct realistic slab models with III–O (III = Al, Ga) bonds dominating the chemical bonding at both interfaces. The epitaxial relationships between β-Ga2O3 and wurtzite AlN and GaN determined from experiments are adopted in our slab models. These models satisfy electron counting rules, and all the dangling bonds are saturated at the interfaces. β-Ga2O3 is found to form type II heterojunctions with both wurtzite AlN and GaN. For the interfaces with AlN and GaN substrates, the calculated valence band offsets are 0.74 and 0.90 eV, respectively. These are in good agreement with the experimental values. The obtained band alignments are useful for designing optical and electronic devices based on β-Ga2O3 and group III nitrides.
A new simple algorithm for space charge limited emission
Authors: Stoltz P. H. , Luginsland J. W. , Chap A. , Smithe D. N. , Cary J. R.
Published: September 2020

Many high power electronic devices operate in a regime where the current they draw is limited by the self-fields of the particles. This space charge limited current poses particular challenges for numerical modeling where common techniques like over-emission or Gauss' Law are computationally inefficient or produce nonphysical effects. In this paper, we show an algorithm using the value of the electric field in front of the surface instead of attempting to zero the field at the surface, making the algorithm particularly well suited to both electromagnetic and parallel implementations of the particle-in-cell algorithm. We show how the algorithm is self-consistent within the framework of finite difference (for both electrostatics and electromagnetics). We show several 1D and 2D benchmarks against both theory and previous computational results. Finally, we show the application in 3D to high power microwave generation in a 13 GHz magnetically insulated line oscillator.
A soft chemistry approach to the synthesis of single crystalline and highly pure (NH4)CoF3 for optical and magnetic investigations
Authors: Siebeneichler Stefanie , Dorn Katharina V. , Smetana Volodymyr , Valldor Martin , Mudring Anja-Verena
Published: September 2020

A new ionothermal synthesis utilizing 1-alkyl-pyridinium hexafluorophosphates [CxPy][PF6] (x = 2, 4, 6) led to the formation of highly crystalline single-phase ammonium cobalt trifluoride, (NH4)CoF3. Although ammonium transition-metal fluorides have been extensively studied with respect to their structural and magnetic properties, multiple aspects remain unclear. For that reason, the obtained (NH4)CoF3 has been investigated over a broad temperature range by means of single-crystal and powder x-ray diffraction as well as magnetization and specific heat measurements. In addition, energy-dispersive x-ray and vibrational spectroscopy as well as thermal analysis measurements were undertaken. (NH4)CoF3 crystallizes in the cubic perovskite structure and undergoes a structural distortion to a tetragonal phase at 127.7 K, which also is observable in the magnetic susceptibility measurements, which has not been observed before. A second magnetic phase transition occurring at 116.9 K is of second-order character. The bifurcation of the susceptibility curves indicates a canted antiferromagnetic ordering. At 2.5 K, susceptibility measurements point to a third phase change for (NH4)CoF3.
Recharging and rejuvenation of decontaminated N95 masks
Authors: Hossain Emroj , Bhadra Satyanu , Jain Harsh , Das Soumen , Bhattacharya Arnab , Ghosh Shankar , Levine Dov
Published: September 2020

N95 respirators comprise a critical part of the personal protective equipment used by frontline health-care workers and are typically meant for one-time usage. However, the recent COVID-19 pandemic has resulted in a serious shortage of these masks leading to a worldwide effort to develop decontamination and re-use procedures. A major factor contributing to the filtration efficiency of N95 masks is the presence of an intermediate layer of charged polypropylene electret fibers that trap particles through electrostatic or electrophoretic effects. This charge can degrade when the mask is used. Moreover, simple decontamination procedures (e.g., use of alcohol) can degrade any remaining charge from the polypropylene, thus severely impacting the filtration efficiency post-decontamination. In this report, we summarize our results on the development of a simple laboratory setup allowing measurement of charge and filtration efficiency in N95 masks. In particular, we propose and show that it is possible to recharge the masks post-decontamination and recover filtration efficiency.