bluuebunny/crossref_metadata_2025 huggingface dataset:
Malaria in Guinean Rural Areas: Prevalence, Management, and Ethnotherapeutic Investigations in Dionfo, Sub-Prefecture of Labe
Authors: Baldé Aliou Mamadou , Balde Alpha Oumar , Bah Bilo , Barry Halimatou , Traore Saidou , Bah Fatoumata , Balde Mamadou Aliou , Camara Aissata , Traore Mohamed Sahar , Balde Elhadj Saidou , Sylla Ibrahima Kalil , Diallo Sadou
Published: July 2021

As part of a validation program of antimalarial traditional recipes, an ethnotherapeutic approach was applied in Dionfo, a meso-endemic Guinean rural area where conventional health facilities are insufficient. A prevalence investigation indicated a malarial burden of 4.26%. Ethnomedical and ethnobotanical surveys led to a collection of 63 plant species used against malaria from which Terminalia albida (Combretaceae) was one of the most cited. Ethnotherapeutic evaluation of a remedy based on T. albida was applied to 9 voluntary patients suffering from uncomplicated malaria. Treatment of 7 to 14 days led to an improvement of clinical symptoms and a complete parasite clearance achievement of 8/9 patients without side effects. In addition to antiplasmodial activity in vitro and in vivo previously described, this study indicates an efficacy to support the antimalarial traditional use of T. albida, which could constitute a first-aid treatment
when access to other medicines is delayed in the Dionfo community. Ethnotherapeutical investigation could be a valuable approach to guide subsequent investigations on traditional remedies.
Auswirkungen des Lockdowns im Frühjahr 2020 während der COVID-19-Pandemie auf das Ess- und Sportverhalten – Ergebnisse einer Onlinebefragung
Authors: Koopmann Anne , Müller Astrid , Lemenager Tagrid , Hillemacher Thomas , Kiefer Falk , Georgiadou Ekaterini
Published: July 2021

Einleitung Die Ausgangseinschränkungen und Kontaktverbote während der COVID-19-Pandemie haben mit dem Wegfall vieler beruflicher und privater Verpflichtungen und Strukturen massive Auswirkungen auf den Alltag der Allgemeinbevölkerung. Gleichzeitig verstärken sich für viele Menschen die Sorgen vor allem bezüglich ihrer finanziellen und beruflichen Zukunft. Eine vermehrte Nahrungsaufnahme stellt in dieser Situation eine mögliche Bewältigungsstrategie im Umgang mit den als unangenehm erlebten Gefühlen dar. Gleichzeitig fallen wegen der Ausgangs- und Kontaktbeschränkungen viele Möglichkeiten zur sportlichen Betätigung weg. Dies birgt die Gefahr einer Zunahme der kardiovaskulären Risikofaktoren in der Allgemeinbevölkerung und insbesondere für die Entstehung von Adipositas sowie Diabetes mellitus Typ 2. In dieser Studie untersuchten wir daher die Veränderungen des Ess- und Sportverhaltens in der Allgemeinbevölkerung in Deutschland während des Lockdowns im Frühjahr 2020.

Material und Methodik An der Onlinebefragung zu Veränderungen des Ess- und Sportverhaltens während des Lockdowns im Frühjahr 2020 konnten Frauen und Männer zwischen 18 und 80 Jahren aus der Allgemeinbevölkerung teilnehmen. Die Umfrage war online verfügbar zwischen dem 8. April und dem 11. Mai 2020.

Ergebnisse Von 3259 Teilnehmern gaben 40,3 % an, während des Lockdowns mehr als vor dessen Beginn gegessen zu haben, 38,3 % berichteten, während des Lockdowns weniger Sport gemacht zu haben als in der Zeit davor. Bei einer kombinierten Betrachtung der Verhaltensänderungen zeigten 58,5 % der Teilnehmer mindestens eine Verhaltensänderung, die dauerhaft potenziell negative gesundheitliche Folgen für sie haben könnte und die Entwicklung eines Diabetes mellitus Typ 2 fördert. Mit 18,5 % aller Studienteilnehmer gab die größte Gruppe an, weniger Sport gemacht und gleichzeitig mehr gegessen zu haben während des Lockdowns.

Schlussfolgerungen Diese Ergebnisse weisen darauf hin, dass es sowohl in der ambulanten als auch in der stationären Patientenversorgung in den nächsten Monaten wichtig sein wird, die Patienten auf die Gesundheitsrisiken, die sich durch eine Reduktion von sportlicher Aktivität und eine vermehrte Nahrungsaufnahme ergeben, hinzuweisen und ihr Ess- und Sportverhalten sowie die Veränderung des Körpergewichts zu beobachten, um eine Zunahme des Risikos für Diabetes mellitus Typ 2 in der Allgemeinbevölkerung zu verhindern.
Ag(I)/CAAA-Amidphos Complex Catalyzed Asymmetric 1,3-Dipolar Cycloaddition of Acrylates for the Formal Synthesis of (+)-Ibophyllidine
Authors: Gong Chuliang , Zhang Chen , Zhou Guiyin , Chen Yao , Wang Haifei , Zheng Xiaojun , Hou Qinglin , Zhou Qingxia
Published: July 2021

In this work, we introduced a multifunctional Ag(I)/CAAA-amidphos complex catalyzed asymmetric 1,3-dipolar cycloaddition of acrylates with α-imino esters, affording a series of 2,4,5-trisubstituted endo-pyrrolidines in good yields (up to 97%) with high enantioselectivities (up to 98% ee). Meanwhile, the catalytic system was also applied in the three-component one-pot reaction of α-imino esters formed in situ under the action of N,N′-diisopropylcarbodiimide. In addition, the gram-scale reaction was realized for the formal synthesis of (+)-ibophyllidine in eight steps.
Facilitating Genetics Aware Clinical Decision Support: Putting the eMERGE Infrastructure into Practice
Authors: Taylor Casey Overby , Rasmussen Luke V. , Rasmussen-Torvik Laura J. , Prows Cynthia A. , Dorr David A. , Samal Lipika , Aronson Samuel
Published: July 2021

This editorial provides context for a series of published case reports in ACI Open by summarizing activities and outputs of joint electronic health record integration and pharmacogenomics workgroups in the NIH-funded electronic Medical Records and Genomics (eMERGE) Network. A case report is a useful tool to describe the range of capabilities that an IT infrastructure or a particular technology must support. The activities we describe have informed infrastructure requirements used during eMERGE phase III, provided a venue to share experiences and ask questions among other eMERGE sites, summarized potential hazards that might be encountered for specific clinical decision support (CDS) implementation scenarios, and provided a simple framework that captured progress toward implementing CDS at eMERGE sites in a consistent format.
Nitrofurantoin Susceptibility Pattern in Gram-Negative Urinary Isolates: In Need of Increased Vigilance
Authors: Gautam Garima , Gogoi Sanjib , Saxena Sonal , Kaur Ravinder , Dhakad Megh Singh
Published: July 2021

Nitrofurantoin is the first-line drug in the treatment of uncomplicated urinary tract infections (UTIs) and its use has increased exponentially in recent years.

Objectives This study aims to determine the susceptibility pattern of nitrofurantoin in gram-negative urinary isolates and to evaluate their bacteriological and epidemiological profile along with co-existing resistance to other important urinary antimicrobials.

Material and Methods This was a retrospective study conducted in a tertiary care hospital in New Delhi in which 500 gram-negative bacterial urinary isolates were evaluated. Records of antimicrobial susceptibility were reviewed from July to September 2019. Antimicrobial susceptibility was performed using the Kirby–Bauer disk diffusion method on Mueller Hinton agar and interpreted using CLSI 2019. Test for extended spectrum β-lactamase (ESBL) producers was done using double disk approximation test.

Statistical Analysis Data analysis was performed using the SPSS windows version 25.0 software.

Results Out of total 500 isolates, 20.17% (94) isolates were resistant (R) to nitrofurantoin and 9.01% (42) were found to be intermediate (I). Highest resistance was seen in Klebsiella sp. (44.61%) and Escherichia coli (8.12%). About 28.82% of the I/R isolates were of the pediatrics age group and most of the isolates belonged to females (64.69%). High resistance was also seen against ampicillin (92.30%), cefazolin (88.46%), ceftazidime (73.0%), and fluoroquinolones (65.38%). Carbapenemase co-resistance was seen in 57.15% isolates whereas ESBL production was seen in 30.76% of E. coli and 12.06% of Klebsiella sp.

Conclusion Increase in multidrug resistance uropathogens along with a near absence of novel oral antibiotics has led to increased consumption of nitrofurantoin since its resistance has increased.
Non-enzymatic glucose sensor based on porous foam Au/MXene nanocomposites
Authors: Bi Cheng , Song Shu-xiang , Li Hai-sheng , Peng Hui-ling , Li Quan-fu
Published: July 2021

A novel electrochemical non-enzymatic glucose sensor based on three-dimensional Au/MXene nanocomposites was developed. MXenes were prepared using the mild etched method, and the porous foam of Au nanoparticles was combined with the MXene by means of in situ synthesis. By controlling the mass of MXene in the synthesis process, porous foam with Au nanoparticles was obtained. The three-dimensional foam structure of nanoparticles was confirmed by scanning electron microscopy. Cyclic voltammetry and electrochemical impedance spectroscopy were used to study the electrochemical performance of the Au/MXene nanocomposites. The Au/MXene nanocomposites acted as a fast redox probe for non-enzymatic glucose oxidation and showed good performance, including a high sensitivity of 22.45 µA · (mmol/L)−1 ·cm−1 and a wide linear range of 1 — 12 mmol/L. Studies have shown that MXene as a catalyst-supported material is beneficial to enhance the conductivity of electrons and increase the loading rate of the catalyst materials. The foam structure with Au nanoparticles can provide a larger surface area, increase the contact area with the molecule in the catalytic reaction, and enhance the electrochemical reaction signal. In summary, this study shows that Au/MXene nanoparticles have the potential to be used in non-enzymatic glucose sensors.
Ultrafast spectroscopic study on non-adiabatic UV protection mechanism of hemicyanines
Authors: Zhang Ming-shui , Chu Ya , Wu Zibo , Guo Yu-rong , Shi Ya-nan , Wang Chao , Wang Meng-qi , Zhong Ying-qian , Zhang Hao-yue , Wang Ya-nan , Wang Jun , Zhao Guang-jiu
Published: July 2021

In this work, we firstly elucidated the ultra-violet light protection dynamics mechanism of the typical hemicyanines, i.e. Hemicy and DHemicy, by combining the theoretical calculation method and the transient absorption spectra. It is theoretically and experimentally demonstrated that both Hemicy and DHemicy have strong absorption in UVC (200−280 nm), UVB (280−300 nm), and UVA (320−400 nm) regions. More-over, after absorbing energy, Hemicy and DHemicy can jump into the excited states. Subsequently, Hemicy and DHemicy relax to S0 states from S1 states rapidly by the non-adiabatic transition at the conical intersection point between the potential energy curves of S1 and S0 states, and are accompanied by the trans-cis photoisomerism. The transient absorption spectra show that trans-cis photoisomerization occur within a few picoseconds. Thus, the ultraviolet energy absorbed by Hemicy and DHemicy could be relaxed ultrafastly by the non-adiabatic trans-cis photoisomerization processes.
Improving photoelectrochemical water oxidation activity of BiFeO3 photoanode via surface passivation
Authors: Yu Qian , Yang Minji , Luo Xin , Fan Zeyu , Wu Qianbao , Zeng Qiugui , Li Yanbo
Published: July 2021

Bismuth iron oxide (BiFeO3) has attracted widespread attention in the field of photoelectrochemistry due to its special ferroelectric properties. However, its high charge recombination from defects and sluggish water oxidation kinetics limit the potential application. Herein, oxygen vacancies are first introduced in BiFeO3 thin films by Ar annealing to improve the bulk charge transfer efficiency. Subsequently, a p-type conductive poly(3, 4-ethylenedioxythiophene) (PEDOT) is employed to suppress the surface-defect-related recombination of photogenerated carriers and to form a p–n junction to increase the charge extraction efficiency. As a result, the photocurrent density of the optimized NiCoFe-Bi/PEDOT/BiFeO3 photoanode reaches 0.17 mA cm−2 at 1.23 V vs reversible hydrogen electrode (RHE) under simulated 1 sun irradiation for water oxidation, which is enhanced by six times compared with that of the photoanode without PEDOT modification. The photocurrent density is further improved to 0.23 mA cm−2 at 1.23 V vs RHE through polarization of the ferroelectric material. This study strongly suggests that surface passivation is an effective way to improve the activity of the BiFeO3 photoanode for solar water splitting.
Defect-free interface between amorphous (Al2O3)1−x(SiO2)x and GaN(0001) revealed by first-principles simulated annealing technique
Authors: Chokawa Kenta , Shiraishi Kenji , Oshiyama Atsushi
Published: July 2021

We report first-principles molecular dynamics (MD) simulations that unveil the interface structures of amorphous mixed oxide (Al2O3)1−x(SiO2)x and GaN polar surfaces. The MD allows us to perform the melt and quench (simulated annealing) simulations to forge distinct amorphous samples. We find that the dangling bonds are completely absent at all the obtained interfaces. This annihilation is due to the diffusion of appropriate species, O for (Al2O3)1−x(SiO2)x/GaN(0001) and Al and Si for (Al2O3)1−x(SiO2)x/GaN(0001¯), from the amorphous to the interface and the subsequent formation of strong bonds with both ionicity and covalency at the interface. This absence of the dangling bond indicates the superiority of (Al2O3)1−x(SiO2)x films to Al2O3 or SiO2 as a gate oxide for the GaN–metal–oxide–semiconductor field effect transistor.
Strong exciton−photon coupling with colloidal quantum dots in a tunable microcavity
Authors: Dovzhenko Dmitriy , Lednev Maksim , Mochalov Konstantin , Vaskan Ivan , Samokhvalov Pavel , Rakovich Yury , Nabiev Igor
Published: July 2021

Polariton emission from optical cavities integrated with various luminophores has been extensively studied recently due to the wide variety of possible applications in photonics, particularly promising in terms of the fabrication of low-threshold sources of coherent emission. Tunable microcavities allow extensive investigation of the photophysical properties of matter placed inside the cavity by deterministically changing the coupling strength and controllable switching from weak to strong and ultra-strong coupling regimes. Here, we demonstrate room-temperature strong coupling of exciton transitions in CdSe/ZnS/CdS/ZnS colloidal quantum dots with the optical modes of a tunable low-mode-volume microcavity. Strong coupling is evidenced by a large Rabi splitting of the photoluminescence spectra depending on the detuning of the microcavity. A coupling strength of 154 meV has been achieved. High quantum yields, excellent photostability, and scalability of fabrication of quantum dots (QDs) pave the way to practical applications of coupled systems based on colloidal QDs in photonics, optoelectronics, and sensing.
Coupling of lattice dynamics and configurational disorder in metal deficient Al1−δB2 from first-principles
Authors: Johansson Erik , Eriksson Fredrik , Ektarawong Annop , Rosen Johanna , Alling Björn
Published: July 2021

We investigate the role metal vacancies play in the phase stability and properties of Al1−δB2 using first-principles calculations, alloy theory simulations, phonon calculations, and experimental in situ x-ray diffraction measurements of thermal expansion. The relevant concentrations and configurations of metal vacancies are analyzed using cluster expansion and special quasirandom structure methods combined with vibrational free energy calculations within the quasiharmonic approximation for ordered and disordered phases. We find that electronic structure effects stabilize Al1−δB2 in a narrow composition range of 0.073≤δ≤0.096 depending only weakly on temperature while they destabilize ideal stoichiometric AlB2. This composition corresponds to the narrow range 0.311≤x≤0.317 in the formulation of AlxB1−x, which can explain the appearance of this phase as a line compound with the ideal AlB2 stoichiometry in most phase diagrams. The ordered structures of vacancies found at low temperature are destabilized and disordered already at a low temperature of ∼200 K. Our experiments observe linear thermal expansion coefficients αa=4.8×10−6 K−1 and αc=10.85×10−6 K−1 at room temperature. Only thermal expansion calculations of disordered phases compare well with these measurements, and, in particular, stoichiometric vacancy-free AlB2 shows dramatic overestimations of the experimental thermal expansion. These results highlight the importance of disordered Al vacancies on both stability and vibrational properties of Al1−δB2.
Research on self-organizing evolution mechanism of clean energy value co-creation system in China
Authors: Liu Jicheng , Yin Yu
Published: July 2021

Clean energy has become one of the more broadly acceptable options for the future transformation of existing energy systems. The energy transformation also requires comprehensive preparatory actions. Organizing a multi-chain clean energy value chain into a complex clean energy network system is likely to be critical to the successful utilization of clean energy in the future. This article proposes a novel concept for a clean energy value co-creation system covering the entire clean energy value chain with division on power generation, energy storage, and end utilization sections. This article mainly analyzes the self-organizing evolution mechanism and value co-creation of the clean energy value co-creation system (CEVCS), which is therefore critical to the further development of the renewable energy industry. First, this article analyzes the connotation and basic structure of CEVCS and introduces the self-organizing characteristics of CEVCS. Second, the self-organizing evolution mechanism of CEVCS is discussed, which is analyzed from four aspects: evolutionary power, evolutionary path, evolutionary form, and evolutionary process. Third, this paper analyzes the information cooperative evolution process of CEVCS, defines the value order parameter, and studies how the constituent elements of CEVCS realize value creation through a synergy mechanism based on the theory of synergy. Then the dissipative structure model and information resource collaborative model of CEVCS are presented. Finally, the conclusions are given in the end. The proposed CEVCS concept would support the effective operation of the clean energy value chain within municipalities by establishing virtual energy cooperatives aimed at meeting energy needs and supporting community development.
Mechanical reliability of self-similar serpentine interconnect for fracture-free stretchable electronic devices
Authors: Qaiser Nadeem , Damdam Asrar Nabil , Khan Sherjeel Munsif , Elatab Nazek , Hussain Muhammad Mustafa
Published: July 2021

Currently, silicon (Si)-based island–interconnect structures are emerging in next-generation stretchable electronic devices such as flexible medical implants, soft robotics, and wearables. Various geometrical designs are being used as interconnects for promising stretchable electronic systems. Among them, self-similar serpentine interconnects (SS-interconnects) are widely used due to their high areal efficiency and stretchability. However, to date, pertinent devices choose random parameters of SS-interconnects since the detailed design guidelines are still elusive. Additionally, no study has revealed how the lateral size or width affects the stretchability during in-plane and out-of-plane stretching. Here, we show how the mechanics could help get the optimized Si-based SS-interconnect without losing its areal efficiency. Our numerical and experimental results show that thin interconnects attain 70%–80% higher stretchability than thicker counterparts. The numerical and experimental results match well. Numerical results indicate the areas prone to break earlier, followed by experimental validation. We devise how induced stress could predict the fracture conditions for any given size and shape of an interconnect. Our results demonstrate that the larger width plays a crucial role in out-of-plane stretching or rotation, i.e., the stress values are 60% higher for the larger width of SS-interconnect during rotation (up to 90°). Our calculations reveal the fracture-free zone for SS-interconnects, showing the figure-of-merit. We demonstrate the detailed guidelines that could help choose the right parameters for fracture-free SS-interconnects for required stretchability, devising the next-generation stretchable and wearable electronic devices.
Stealth black hole perturbations in kinetic gravity braiding
Authors: Bernardo Reginald Christian , Vega Ian
Published: July 2021

We study stealth black hole perturbations in shift symmetric kinetic gravity braiding and obtain its analogous Regge–Wheeler and Zerilli master equations for the odd and even parity sectors. We show that the nontrivial hair of static and spherically symmetric stealth black holes contributes only an additional source term to the even parity master equation. Furthermore, we derive exact solutions to the monopolar and dipolar perturbations and show that they are generally pathological non-gauge modes or else reduce to the pure-gauge low-order multipoles of general relativity.
Probing the bright exciton state in twisted bilayer graphene via resonant Raman scattering
Authors: DeCapua Matthew C. , Wu Yueh-Chun , Taniguchi Takashi , Watanabe Kenji , Yan Jun
Published: July 2021

The band structure of bilayer graphene is tunable by introducing a relative twist angle between the two layers, unlocking exotic phases, such as superconductors and Mott insulators, and providing a fertile ground for new physics. At intermediate twist angles around 10°, highly degenerate electronic transitions hybridize to form excitonic states, a quite unusual phenomenon in a metallic system. We probe the bright exciton mode using resonant Raman scattering measurements to track the evolution of the intensity of the graphene Raman G peak, corresponding to the E2g phonon. By cryogenically cooling the sample, we are able to resolve both the incoming and outgoing resonances in the G peak intensity evolution as a function of excitation energy, a prominent manifestation of the bright exciton serving as the intermediate state in the Raman process. For a sample with twist angle 8.6°, we report a weakly temperature dependent resonance broadening γ ≈ 0.07 eV. In the limit of small inhomogeneous broadening, the observed γ places a lower bound for the bright exciton scattering lifetime at 10 fs in the presence of charges and excitons excited by the light pulse for the Raman measurement, limited by the rapid exciton–exciton and exciton–charge scattering in graphene.
The quantum confinement effect on the spectrum of near-field thermal radiation by quantum dots
Authors: Zare Saman , Edalatpour Sheila
Published: July 2021

The quantum confinement effect on the spectrum of near-field thermal radiation by periodic and random arrays of quantum dots (QDs) is investigated. The local density of states (LDOS) thermally emitted by QD arrays made of three lead chalcogenides, namely, lead sulfide, lead selenide, and lead telluride, is computed at a near-field distance from the arrays. The dielectric function of the QDs is extracted from their absorption spectra by utilizing an optimization technique. The thermal discrete dipole approximation is used for computing the LDOS. It is shown that the peak wavenumber of near-field LDOS emitted by periodic arrays of lead chalcogenide QDs can be significantly modulated (up to 4490 cm−1) by varying the size of the dots. The LDOS is proportional to the imaginary part of the QDs' polarizability, which peaks at the bandgap energy of the QDs. The bandgap energy of the QDs (and thus the LDOS peak) is significantly affected by the quantum confinement effect, which is size dependent. While the magnitude of thermal radiation by random arrays of QDs can be different from the periodic arrays with the same filling factor by up to ±26%, the LDOS spectrum and peak location are the same for both periodic and random arrays. The peak wavenumber of near-field radiative heat transfer between the QD arrays is also strongly affected by quantum confinement in the QDs, and thus, it can be tuned by changing the size of the QDs.
Effect of time interval between pulses on the synthetic sound generated by repetitive nanosecond pulse discharge
Authors: Li Handong , Li Yutai , Wang Xinxin , Zou Xiaobing , Wang Haixu , Luo Haiyun
Published: July 2021

The time interval between pulses is the key parameter of sound synthesis generated by repetitive nanosecond pulse discharge. In this paper, the experimental studies on repetitive nanosecond pulse discharges at different intervals using a pin–pin electrode were carried out and the time-domain sound waveforms were obtained using a capacitor microphone. The experiment results show that a single pulse discharge with a FWHM (full width at half maxima) of 6 ns can produce a pulse sound with a much wider FWHM of 16 μs because of thermal inertia. Based on this measured waveform of the sound pressure and the burst modulation method, the time interval between the repetitive pulses for a better synthesis of 100 Hz sound was theoretically determined to be shorter than 15 μs. However, it was experimentally found that this theoretically determined time interval is too short for the gas to recover its insulating ability from the previous pulse discharge. The energy deposited into the discharge and the sound pressure generated by the following pulses are greatly reduced. The experimental synthetic sound is considerably lower than the theoretical one.
Embedded gas sensing setup for air samples analysis
Authors: Kwiatkowski Andrzej , Drozdowska Katarzyna , Smulko Janusz
Published: July 2021

This paper describes a measurement setup (eNose) designed to analyze air samples containing various volatile organic compounds (VOCs). The setup utilizes a set of resistive gas sensors of divergent gas selectivity and sensitivity. Some of the applied sensors are commercially available and were proposed recently to reduce their consumed energy. The sensors detect various VOCs at sensitivities determined by metal oxide sensors’ technology and operating conditions. The setup can utilize prototype gas sensors, made of resistive layers of different compositions, as well. Their properties can be modulated by selecting operating temperature or using UV light irradiation. The unit is controlled by an embedded system M5Stack Core2 ESP32 IoT. We used this development kit to program the measurement procedure and data recording fastly. The setup utilizes an aluminum gas chamber of a volume of 220 ml, a set of electrical valves to introduce there an air sample with the help of an electrical micropump. The handling of the setup was simplified to a selection of a few operations by touch screen only without a necessity of extra training. The recorded data are saved in a memory card for further processing. The evolved setup can be upgraded to apply more advanced data processing by utilizing WiFi or Bluetooth connection. The control program was prepared using the Arduino IDE software environment and can be further advanced with ease. The applied materials and the established measurement procedure can use various air samples, including exhaled breath samples for patients’ screening check-ups. We applied the same time of 10 min for response and recovery, acceptable for practical use.
In-plane anisotropic electronic properties in layered α′-In2Se3
Authors: Liu Zhun , Wu Jing , Li Jingbo
Published: July 2021

In2Se3 polymorphs have been extensively studied because of their diverse physical properties such as piezoelectricity, photoelectricity, and ferroelectricity, thereby showing plentiful promising applications in integrated electronic devices. These diverse properties are strongly dependent on or affected by their atomic bonding arrangement in the crystal phases. Combining lattice symmetry and local atomic perturbation, we demonstrate a novel layered α′-In2Se3 phase by using the first-principles calculations, which is reconstructed from the inverted tetrahedral bonding configuration by the in-plane displacive middle layer Se atom. The optimized structure of monolayer α′-In2Se3 has triple degenerated atomic configurations with different Se atom orientations. We noted that these degenerated atomic configurations exhibit a moderate switching barrier (about 61 meV/f.u.) between them. To further explore this atom-oriented anisotropic property in α′-In2Se3, the electronic properties were studied with an orthorhombic unit cell. The comparative results for the orthogonal Se atom orientations suggest that the nonbonding orbital coupling of the displacive Se atoms induces large in-plane anisotropic optical absorption and electrical transport properties. This study of the layered α′-In2Se3 phase can extend the realm of switchable anisotropic optoelectronic applications in future electronic devices.
Finite-temperature full random-phase approximation of bandgap narrowing in quasi-neutral regions: Theory including nonparabolicity and application to silicon and InGaAs
Authors: Schenk A.
Published: July 2021

The bandgap narrowing (BGN) in quasi-neutral regions of semiconductors is calculated in a finite-temperature full random-phase approximation formalism based on a simple isotropic dispersion model including band nonparabolicity. The total quasi-particle shift (QPS) is determined by the exchange-correlation self-energy of the free carriers and the correlation energy of the interaction between carriers and ionized dopants. At cryogenic temperatures, the latter part results in giant shifts of the minority band edge in n-type semiconductors with a large ratio of valence to conduction band density of states, as often present in III–V materials. However, at room temperature, the BGN does not exceed common values. The reason for this behavior is explained analytically. Whereas the exchange-correlation energy of free carriers is known to be insensitive to band structure details, the nonparabolicity of the conduction band (CB) has a strong effect on the ionic QPS of the minority carriers in n-type III–V materials. It strongly reduces the BGN at cryogenic temperatures compared to the case of a parabolic CB. This is demonstrated numerically and also analytically for n-type InGaAs. The BGN in n-type silicon becomes independent of temperature at high concentrations, but in p-type silicon, a weak temperature dependence re-emerges above the Mott density, which also can be attributed to the ionic QPS of the minority electrons. The calculated BGN for quasi-neutral regions in silicon is in good agreement with earlier photoluminescence and more recent photo-conductance measurements.
Electrical tuning of the spin–orbit interaction in nanowire by transparent ZnO gate grown by atomic layer deposition
Authors: Takase Keiko , Tateno Kouta , Sasaki Satoshi
Published: July 2021

We develop an InAs nanowire gate-all-around field-effect transistor using a transparent conductive zinc oxide (ZnO) gate electrode, which is in situ atomic layer deposited after growth of a gate insulator of Al2O3. We perform magneto-transport measurements and find a crossover from the weak localization effect to the weak antilocalization effect with an increasing gate voltage, which demonstrates that the Rashba spin–orbit coupling is tuned by the gate electrode. The efficiency of the gate tuning of the spin–orbit interaction is higher than those obtained for a two-dimensional electron gas, and as high as that for a gate-all-around nanowire metal-oxide-semiconductor field-effect transistor that was previously reported. The spin–orbit interaction is discussed in line with not only a conventionally used one-dimensional model but also with a recently proposed model that considers effects of microscopic band structures of materials.
Temperature-dependent periodicity halving of the in-plane angular magnetoresistance in La0.67Sr0.33MnO3 thin films on LaAlO3
Authors: Burema A. A. , Banerjee T.
Published: July 2021

Strain-engineering is used as a tool to alter electronic and magnetic properties like anisotropy energy. This study reports the different angle-dependent magnetoresistance properties of the strain-engineered La0.67Sr0.33MnO3 (LSMO) thin films, grown on LaAlO3, compared to their bulk analogs. Upon increasing temperature, a symmetry change from fourfold [cos(4θ)] to twofold [cos(2θ)] is observed in the angle-dependent resistance measurements. This systematic study with increasing temperature allows us to define three distinct temperature-dependent phases. The fourfold symmetric signal originates from magnetocrystalline anisotropy, whereas the twofold symmetric signal is believed to be the conventional anisotropic magnetoresistance. Our observations show that strain-engineering creates the possibility to manipulate the anisotropy, which, for example, can ultimately lead to observations of noncollinear quasi-particles like skyrmions in single layer thin films of LSMO.
DSMC study of hypersonic rarefied flow using the Cercignani–Lampis–Lord model and a molecular-dynamics-based scattering database
Authors: Liu Wenbin , Zhang Jinbai , Jiang Yazhong , Chen Laiwen , Lee Chun-Hian
Published: July 2021

This study proposes a scattering database method to model gas–solid interaction based on a database of distributions of scattering velocity obtained by a molecular dynamics simulation. The proposed method is used as the boundary condition in the direct simulation Monte Carlo method to simulate hypersonic flow over a rounded wedge at different Knudsen numbers (Kn). The effects of different wall models [e.g., the scattering database method and the Cercignani–Lampis–Lord (CLL) model] on the flow simulation were compared and analyzed. When Kn ≥ 1, the results based on the CLL model are evidently different from those of the scattering database model, where this difference increases with the degree of rarefication of flow. The mechanism of this discrepancy is such that when the flow is rarefied, a large number of freestream molecules from the far-field directly collide with the wall. In particular, near the stagnation point, the tangential reflection kinetic energy of freestream molecules is amplified due to the conversion of their normal incident kinetic energy. The scattering feature of this conversion is challenging to reproduce based on the theoretical framework of the CLL model. Still, a specific local parameter can describe the ratio of this conversion. Therefore, compared with the traditional wall model, the scattering database method can show more detailed scattering features and, hence, could be a promising tool for the study of gas–solid interaction in hypersonic rarefied flow.
Super-reaction: The collective enhancement of a reaction rate by molecular polaritons in the presence of energy fluctuations
Authors: Thanh Phuc Nguyen
Published: July 2021

Recent experiments have demonstrated that molecular polaritons, hybrid states of light and matter formed by the strong coupling between molecular electronic or vibrational excitations and an optical cavity, can substantially modify the physical and chemical properties of molecular systems. Here, we show that by exploiting the collective character of molecular polaritons in conjunction with the effect of polaron decoupling, i.e., the suppression of environmental influence on the polariton, a super-reaction can be realized, involving a collective enhancement of charge or excitation-energy transfer reaction rate in a system of donors all coupled to a common acceptor. This effect is analogous to the phenomenon of super-radiation. Since the polariton is a superposition state of excitations of all the molecules coupled to the cavity, it is vulnerable to the effect of decoherence caused by energy fluctuations in molecular systems. Consequently, in the absence of a strong light–matter interaction, the reaction rate decreases significantly as the number of molecules increases, even if the system starts from the polariton state. By turning on the light–matter interaction, the dynamic behavior of the system changes dramatically, and the reaction rate increases with the number of molecules, as expected for a super-reaction. The underlying mechanism is shown to be the protection of quantum coherence between different donors as the light–matter interaction becomes stronger.
Energy feedthrough and microstructure evolution during direct laser peening of aluminum in femtosecond and picosecond regimes
Authors: Nakhoul A. , Rudenko A. , Sedao X. , Peillon N. , Colombier J. P. , Maurice C. , Blanc G. , Borbély A. , Faure N. , Kermouche G.
Published: July 2021

Ultrafast laser was recently used to modify the surface integrity and peen the surface region of aluminum based alloy 2024-T351 without a sacrificial layer prior to the process. We show that controllable laser parameters such as fluence and pulse duration have a significant influence on peening qualities, such as the compressive residual stress, hardness, and surface roughness of peened parts. The residual stress profile was analyzed by x-ray diffraction. By controlling the laser fluence and pulse duration, it was possible to obtain 200 MPa of compressive residual stresses close to the surface and 100 MPa of compressive residual stresses at 50 μm depth. Moreover, micro-hardness was increased from 2.1 to 2.5 GPa in the near-surface region. In addition, the dislocation densities were evaluated from high-resolution x-ray diffraction peaks. The increase of the dislocation density indicates that plastic deformation occurred, which generated compressive residual stresses and hardness enhancement. Plastic deformation is considered to be created by an ultrafast laser-induced pressure wave. The correlation between laser parameters and modified surface properties is interpreted by the complex interplay between laser excitation, material relaxation, and pressure waves. A pulse duration in the picosecond range and a relatively low fluence is possibly the optimal condition for a best peening quality with small surface roughness, which could potentially be used to reduce surface cracking and associated failures of additively manufactured parts.
Highly coupled and low frequency vibrational energy harvester using lithium niobate on silicon
Authors: Clementi Giacomo , Ouhabaz Merieme , Margueron Samuel , Suarez Miguel Angel , Bassignot Florent , Gauthier-Manuel Ludovic , Belharet Djaffar , Dulmet Bernard , Bartasyte Ausrine
Published: July 2021

LiNbO3 has been little studied for the piezoelectric energy harvesting applications. Although it is a cheap piezoelectric material without lead and toxic elements, it beneficiates of technological maturity in single crystal fabrication for optical and acoustic applications. In this Letter, we propose to investigate a (YXlt)/128°/90° LiNbO3 cut as it offers a transverse piezoelectric coupling of k23 = 0.49, which is comparable to that of commonly used PZT ceramics. A flexible beam of 65 mm length and a tip mass made of a LiNbO3 thick film bonded on silicon were studied under 0.1 g sinusoidal acceleration. The beam presented an open-circuit resonance frequency of 105.9 Hz and a displacement up to 1.5 mm. In the frame of a single degree of freedom lumped model with a rectifying bridge, the electromechanical coupling of the device (km2), the figure of merit km2Q, and the normalized average power density were compared to both Pb-based and Pb-free current devices. The generated power density by our device was 965 μW/cm2/g2, which is among the highest reported values compared to both Pb- and Pb-free vibrational harvesting devices.
Increasing the efficiency and maneuverability of one-hinge swimmer
Authors: Choudhary Priyanka , Babu Sujin B.
Published: July 2021

Understanding the dynamics of micro-organisms will help in developing artificial swimmers for applications like drug delivery. In the present study, a two-dimensional one-hinge swimmer resembling a scallop in Newtonian fluid is explored. To model the one-hinge swimmer, we use bead-spring model and the fluid is simulated using multi-particle collision dynamics with Anderson thermostat. We consider a non-uniform distribution of the bending rigidity along the arms of the swimmer, where we reduce the bending rigidity progressively from the hinge to the end of the arms. The non-uniform arms show higher swimming speed for the same average bending rigidity, thereby enhancing the efficiency of the swimmer. It was observed that the bending rigidity variation along the arm of the swimmer following a geometric sequence was more efficient than linear or quadratic for the same average bending rigidity. We also study the maneuverability of the one-hinge swimmer having asymmetrical bending rigidity for the arms, thereby the swimmer undergoes curved path. We find that depending upon the stiffness of the arm, the swimmer undergoes clockwise or anticlockwise rotation. We also find that the angular and transnational velocities of the swimmer are maximum at approximately the same sperm number ∼1.8. The angular velocity of the swimmer scaled linearly with the amplitude of actuation as predicted by resistive force theory. Finally, we show that in the case of a two-dimensional one-hinge swimmer angular velocity, curvature and the direction of rotation can be controlled by just changing the relative bending rigidity of the arms.
Rotation of dust particles in an inhomogeneous weak magnetic field in a DC glow discharge
Authors: Abdirakhmanov A. R. , Bastykova N. Kh. , Kodanova S. K. , Ramazanov T. S.
Published: July 2021

We report an explanation for the opposite direction of the rotation of the charged dust particles above and below the Helmholtz coil in an inhomogeneous weak magnetic field in the direct current glow discharge. Experiments with monodispersed melamine-formaldehyde particles were performed in an argon plasma in an inhomogeneous weak magnetic field (with the induction values 4, 12, and 18 mT). The linear and angular velocities of rotational motion of the clusters of dust particles formed in regions with an inhomogeneous weak magnetic field above and below the Helmholtz coil were analyzed. The peculiarity is that the directions of rotation in these areas are opposite, whereas there is no rotational motion in the region of a uniform magnetic field. To explain these observations, the theoretical model that takes into account the magnetic field inhomogeneity and provides good agreement with experimental data is presented.
Growth of PtSe2 few-layer films on NbN superconducting substrate
Authors: Sojková Michaela , Hrdá Jana , Volkov Serhii , Vegso Karol , Shaji Ashin , Vojteková Tatiana , Slušná Lenka Pribusová , Gál Norbert , Dobročka Edmund , Siffalovic Peter , Roch Tomáš , Gregor Maroš , Hulman Martin
Published: July 2021

Few-layer films of transition metal dichalcogenides have emerged as promising candidates for applications in electronics. Within this group of 2D materials, platinum diselenide (PtSe2) was predicted to be a compound with one of the highest charge carrier mobility. Recently, the successful integration of group III–V nitride semiconductors with NbNx-based superconductors was reported with a semiconductor transistor grown directly on a crystalline superconductor. This opens up the possibility of combining the macroscopic quantum effects of superconductors with the electronic, photonic, and piezoelectric properties of the semiconducting material. Here, we report on the fabrication of a few-layer PtSe2 film on top of an NbN substrate layer by selenization of pre-deposited 3 nm thick Pt layers. We found the selenization parameters preserving the chemical and structural integrity of both the PtSe2 and NbN films. The PtSe2 film alignment can be tuned by varying the nitrogen flow rate through the reaction chamber. The superconducting critical temperature of NbN is only slightly reduced in the optimized samples compared to pristine NbN. The carrier mobility in PtSe2 layers determined from Hall measurements is below 1 cm2/V s.
Two typical collective behaviors of the heavy ions expanding in cold plasma with ambient magnetic field
Authors: Peng Guo-Liang , Zhang Jun-Jie , Chen Jian-Nan , Du Tai-Jiao , Xie Hai-Yan
Published: July 2021

We have numerically studied the evolution of heavy ions that expand in a cold background plasma at a large scale. Two typical collective behaviors of the heavy ions are identified with the conditions where only the traversing heavy ions' initial total mass is different. Our work has demonstrated that a difference in the initial total mass of the moving heavy ions is able to induce completely different collective behaviors of the plasma. The simulation is performed via the hybrid model in which the ions and electrons are treated as classical particles and mass-less fluids, respectively. Due to the imbalance of the electric and magnetic force on the heavy ions, these particles will evolve into different collective patterns eventually. These patterns manifest a rather different stopping behavior of the moving ions and an opposite drifting direction of the electron fluid at the rim of the expanding plasma. Further numerical and analytical calculations show that the imbalance depends not only on the number densities of the plasma ions but also on the spatial variations of the magnetic fields. Our work reveals that the collective behavior of the heavy ions is highly non-linear, and the non-linearity is able to induce different phenomena in the evolution of the system at a large scale.
Metastructures with double-spiral resonators for low-frequency flexural wave attenuation
Authors: Chen Jung-San , Chen Tzung-Yu , Chang Yu-Chi
Published: July 2021

This study introduces a novel framework for local resonant systems to low bandgap frequencies without greatly increasing spatial penalties in grid structures. The proposed double-spiral resonator (DSR) consists of a pair of spiral spring-like structures and a rigid plate acting as the “mass” of the oscillating system, which can serve as an effective mechanical filter. A rapid and accurate calculation based on the stiffness matrix method is proposed to precisely predict the fundamental resonant frequency of the resonator. Periodic installation of these resonators in a grid-like beam structure can lead to the formation of a new type of metastructure that possesses negative effective properties. Investigations on the bandgap characteristics of the proposed metastructure are conducted using the finite element method. It is found that a low-frequency resonant-type bandgap is present in such a structure. Changing the thickness of the central mass or the number of parasitic beam segments enables the manipulation of the bandgap location. The validity of the analytical results is evaluated via comparison with the finite element results and experimental measurements. By using multiple resonators with similar resonance frequencies, the attenuation bandwidth can be effectively broadened. The physics behind wave attenuation can be realized by introducing a negative effective mass density. The results demonstrate that the proposed structure exhibiting unique dynamic characteristics can successfully attenuate undesired structural vibrations at low frequencies. It may be concluded that this DSR can be used as an alternative to current vibration filtering systems.