bluuebunny/crossref_metadata_2025 huggingface dataset:
A high performance all solid state lithium sulfur battery with lithium thiophosphate solid electrolyte
Authors: Bonnick Patrick , Niitani Keita , Nose Masafumi , Suto Koji , Arthur Timothy S. , Muldoon John
Published: August 2019

Polysulfide dissolution plagues the lithium–sulfur battery. The ideal solution to polysulfide dissolution is solid electrolyte.
Morphology of small molecular donor/polymer acceptor blends in organic solar cells: effect of the π–π stacking capability of the small molecular donors
Authors: Zhang Zijian , Ding Zicheng , Miao Junhui , Xin Jingming , Ma Wei , Dou Chuandong , Liu Jun , Wang Lixiang
Published: August 2019

A small molecular donor with strong π–π stacking overaggregates into discontinuous large domains, while a small molecular donor with weak π–π stacking remains amorphous in the as-cast film and crystallizes into nano-sized domains during thermal annealing.
The synthesis of branched-chain fatty acids is limited by enzymatic decarboxylation of ethyl- and methylmalonyl-CoA
Authors: Dewulf Joseph P. , Gerin Isabelle , Rider Mark H. , Veiga-da-Cunha Maria , Van Schaftingen Emile , Bommer Guido T.
Published: August 2019

Most fatty acids (FAs) are straight chains and are synthesized by fatty acid synthase (FASN) using acetyl-CoA and malonyl-CoA units. Yet, FASN is known to be promiscuous as it may use methylmalonyl-CoA instead of malonyl-CoA and thereby introduce methyl-branches. We have recently found that the cytosolic enzyme ECHDC1 degrades ethylmalonyl-CoA and methylmalonyl-CoA, which presumably result from promiscuous reactions catalyzed by acetyl-CoA carboxylase on butyryl- and propionyl-CoA. Here, we tested the hypothesis that ECHDC1 is a metabolite repair enzyme that serves to prevent the formation of methyl- or ethyl-branched FAs by FASN. Using the purified enzyme, we found that FASN can incorporate not only methylmalonyl-CoA but also ethylmalonyl-CoA, producing methyl- or ethyl-branched FAs. Using a combination of gas-chromatography and liquid chromatography coupled to mass spectrometry, we observed that inactivation of ECHDC1 in adipocytes led to an increase in several methyl-branched FAs (present in different lipid classes), while its overexpression reduced them below wild-type levels. In contrast, the formation of ethyl-branched FAs was observed almost exclusively in ECHDC1 knockout cells, indicating that ECHDC1 and the low activity of FASN toward ethylmalonyl-CoA efficiently prevent their formation. We conclude that ECHDC1 performs a typical metabolite repair function by destroying methyl- and ethylmalonyl-CoA. This reduces the formation of methyl-branched FAs and prevents the formation of ethyl-branched FAs by FASN. The identification of ECHDC1 as a key modulator of the abundance of methyl-branched FAs opens the way to investigate their function.
Performance analysis of moving ship target signal integration and detection in geosynchronous synthetic aperture radar
Authors: Zhang Ying , Dong Xichao , Xiong Wei , Hu Cheng
Published: August 2019

Geosynchronous synthetic aperture radar (GEO SAR) has the characteristics of wide coverage and short revisit time, which makes GEO SAR moving target indication more valuable than other platforms. This article analyses the influence of moving target on ‘Stop‐and‐Go’ error in GEO SAR, and then the accurate slant range model of moving target is constructed. The signal‐to‐noise ratio of the raw data echoes for moving ship target is very low because of the high satellite orbit altitude, so it cannot be detected by constant false alarm detection. Based on the accurate slant range model of moving target in GEO SAR, three kinds of integration methods are reconstructed, including moving target detection, Radon transform and generalised Radon Fourier transform (GRFT). The performance of these methods is compared through numerical simulation. GRFT can provide the best detection performance in a reasonable integration time.
The effects of the temperature on the mechanical properties of natural yarns
Authors: Ben Smail Y. , El Moumen A. , Lmai F. , Imad A.
Published: August 2019

The jute fiber is one of the strongest lignocellulosic fibers with different applications such as fabrics, ropes as well as engineered composites for automobile parts. In this study, the jute yarns were exposed to different temperatures of the thermal cycles (22°C, 40°C, 80°C, 105°C and 150°C). The mechanical tests were conducted using the 3R Syntax machine and the experimental results depended on different temperatures of thermal cycles were recorded. The mechanical properties of jute yarns decrease with the increase of temperature of the thermal cycles.
A three dimensional meshfree-simulation of the selective laser sintering process with constant thermal coefficients applied to nylon 12 powders
Authors: Yaagoubi H. , Abouchadi H.
Published: August 2019

3D printing is an intersting process in the context of creating original objects. Selective laser sintering printers use a laser to fuse polyamide particles together with specific resin and heat. The difference in temperature between the different areas in the process causes the appearance of deformations, the objective of this work is the modeling of the thermal SLS phenomenona, by following the evolution of the temperature as a function of time.This model is based on the resolution of the heat conduction equation coupling with convection and radiation conditions with a distribution heat source and constant thermal coefficients by the meshless method based on radial basis function , the result of this study,will be presented and compared with other works.
Analytische Charakterisierung und Vergleich medizinisch genutzter Echinacea-haltiger Zubereitungen
Authors: Classen Birgit , Pferschy-Wenzig Eva-Maria , Geske Thomas , Ardjomand-Wölkart Karin , Bauer Rudolf
Published: August 2019

Die drei Sonnenhutarten Echinacea angustifolia, E. pallida und E. purpurea werden als Ausgangsmaterial für die Produktion phytotherapeutischer und homöopathischer Zubereitungen genutzt, welche als unspezifische Immunstimulanzien Einsatz finden. Dabei sind vermutlich sowohl nieder- als auch hochmolekulare Inhaltsstoffe an der Wirkung beteiligt. Aus den verschiedenen Pflanzen und Pflanzenteilen entstehen durch Anwendung unterschiedlicher Herstellungsmethoden aufgrund der Vorgaben der Arzneibücher Zubereitungen, die erhebliche Unterschiede in ihrer stofflichen Zusammensetzung erwarten lassen. In den vorliegenden Untersuchungen wurden daher verschiedene Echinacea-haltige Zubereitungen hinsichtlich des Vorkommens von Kaffeesäurederivaten, Alkamiden, Polysacchariden und Proteoglykanen analytisch charakterisiert und verglichen.Erwartungsgemäß zeigte sich, dass sich homöopathische Urtinkturen bzw. alkoholische Extrakte sowohl hinsichtlich der hochmolekularen Inhaltsstoffe (Polysaccharide, Proteoglykane) als auch bei den polaren und lipophilen niedermolekularen Inhaltsstoffen von Echinacea-purpurea-Presssaftzubereitungen deutlich unterscheiden und sie daher nicht als äquivalent angesehen werden können. Auch zwischen den homöopathischen Urtinkturen der einzelnen Arten existieren Unterschiede und selbst innerhalb der Echinacea-purpurea-Presssaftzubereitungen konnten, je nach Herstellungsart, verschiedene Inhaltsstoffmuster detektiert werden. Bei der Bewertung von Wirksamkeit und Unbedenklichkeit von Echinacea-Zubereitungen sollten diese Unterschiede in Zukunft mehr berücksichtigt werden.
3D Printed Model Used as Preoperative Tool for Treating Acromioclavicular Joint Dislocation with Pre-Contoured Clavicle Hook Plate: Technical Note
Authors: Wu Xuhua , Wang Gang , Rong Ke , Xia Qingquan , Gan Minfeng , Wen Gen , Yin Xiaofan , Yang Huilin
Published: August 2019

Objective To introduce a new technique using real-size 3D-printed acromioclavicular joint models as preoperative tools for treating acromioclavicular (AC) joint dislocation.

Methods Both the injured AC joint and the mirrored normal side AC joint are 3D printed into real-size models. A proper hook plate is selected and pre-bended to fit the normal side AC joint. The bended plate is then used to perform a reduction operation on a real-size injured AC joint model and the result is compared with the mirrored normal AC joint model to see if the reduction is accurate.

Results It is easy to select and bend a clavicle hook plate to achieve an accurate reduction with the help of a 3D printing technique.

Conclusion With this technique, surgeons can achieve an accurate reduction of the injured AC joint with a clavicle hook plate which might be helpful to reduce the risk of complications.
Clinical Significance of Electroencephalography in Children with Specific Learning Disorders
Authors: Aksoy Erhan , Öztoprak Ülkühan , Sabancı Murat , Çetinkaya Miray , Genç-Sel Çiğdem , Kayılıoğlu Hülya , Aksoy Ayşe , Yüksel Deniz
Published: August 2019

A specific learning disorder (SLD) is a neurodevelopmental disorder in which academic skills, such as reading, writing, and mathematics ability, are below the expected range. This study was conducted to determine the relationship between spike-wave index and SLD in children. We recruited 110 child psychiatry outpatients (38 girls, 72 boys) with SLDs for this study between January 2015 and March 2018. The mean ± standard deviation patient age was 9.17 ± 1.87 years. Electroencephalography (EEG) findings were abnormal in 20.9% of children. We found that children with expressive language delay and who were born prematurely had a significantly higher risk of spike-wave index. Attention deficit/hyperactivity disorder was present in 55.5% of children with SLD. This comorbidity was significantly higher in children with a history of prenatal smoking exposure or premature birth. The EEG findings were particularly important in cases of SLD in children who were born prematurely and had expressive language delay. The spike-wave index is a potential marker of SLD and can be easily and noninvasively detected by EEG.
Postpartum Psychiatric Admissions in the United States
Authors: Wen Timothy , Fein Arielle W. , Wright Jason D. , Mack William J. , Attenello Frank J. , D'Alton Mary E. , Friedman Alexander M.
Published: August 2019

Objective This study aimed to assess risk for postpartum psychiatric admissions in the United States.

Study Design This study used the 2010 to 2014 Nationwide Readmissions Database to identify psychiatric admissions during the first 60 days after delivery hospitalization. Timing of admission after delivery discharge was determined. We fit multivariable log-linear regression models to assess the impact of psychiatric comorbidity on admission risk, adjusting for patient, obstetrical, and hospital factors.

Results Of 15.7 million deliveries from 2010 to 2014, 11,497 women (0.07%) were readmitted for a primary psychiatric diagnosis within 60 days postpartum. Psychiatric admissions occurred relatively consistently across 10-day periods after delivery hospitalization discharge. Psychiatric diagnoses were present among 5% of women at delivery but 40% of women who were readmitted postpartum for a psychiatric indication. In the adjusted model, women with psychiatric diagnoses at delivery hospitalization were 9.7 times more likely to be readmitted compared with those without psychiatric comorbidity. Women at highest risk for psychiatric admission were those with Medicare and Medicaid, in lower income quartiles, and of younger age.

Conclusion While a large proportion of psychiatric admissions occurred among a relatively small proportion of at-risk women, admissions occurred over a broad temporal period relative to other indications for postpartum admission.
Green Hospital Lichtenfels: Das grüne Vorbild
Authors: Kucera Martin
Published: August 2019

Das Helmut-G.-Walther-Klinikum Lichtenfels ist das erste Krankenhaus in Bayern, das umfassend nach umweltfreundlichen Gesichtspunkten gebaut wurde. Durch den konsequenten Einsatz regenerativer Energien ist ein Klinikgebäude mit landesweitem Vorbildcharakter entstanden, das auch seinen Mitarbeitern und Patienten mehr zu bieten hat als konventionelle Gesundheitsbauten.
Healing Architecture: Wenn Architekten Ärzten helfen
Authors: Kohrs Jens
Published: August 2019

Wie die Architektur eines Krankenhauses die Genesung von Patienten unterstützen kann, beschäftigt auch deutsche Klinikplaner zunehmend. Im Interview erklärt die Münchner Architektin Prof. Christine Nickl-Weller, was genau hinter dem Konzept der Healing Architecture steckt.
Field reconstruction from proton radiography of intense laser driven magnetic reconnection
Authors: Palmer C. A. J. , Campbell P. T. , Ma Y. , Antonelli L. , Bott A. F. A. , Gregori G. , Halliday J. , Katzir Y. , Kordell P. , Krushelnick K. , Lebedev S. V. , Montgomery E. , Notley M. , Carroll D. C. , Ridgers C. P. , Schekochihin A. A. , Streeter M. J. V. , Thomas A. G. R. , Tubman E. R. , Woolsey N. , Willingale L.
Published: August 2019

Magnetic reconnection is a process that contributes significantly to plasma dynamics and energy transfer in a wide range of plasma and magnetic field regimes, including inertial confinement fusion experiments, stellar coronae, and compact, highly magnetized objects like neutron stars. Laboratory experiments in different regimes can help refine, expand, and test the applicability of theoretical models to describe reconnection. Laser-plasma experiments exploring magnetic reconnection at a moderate intensity (IL ∼ 1014 W cm−2) have been performed previously, where the Biermann battery effect self-generates magnetic fields and the field dynamics studied using proton radiography. At high laser intensities (ILλL2>1018 Wcm−2μm2), relativistic surface currents and the time-varying electric sheath fields generate the azimuthal magnetic fields. Numerical modeling of these intensities has shown the conditions that within the magnetic field region can reach the threshold where the magnetic energy can exceed the rest mass energy such that σcold = B2/(μ0nemec2) > 1 [A. E. Raymond et al., Phys. Rev. E 98, 043207 (2018)]. Presented here is the analysis of the proton radiography of a high-intensity (∼1018 W cm−2) laser driven magnetic reconnection geometry. The path integrated magnetic fields are recovered using a “field-reconstruction algorithm” to quantify the field strengths, geometry, and evolution.
Influence of lanthanum substitution on microstructure and impedance behavior of barium strontium titanate glass-ceramics
Authors: Zhao Zhangyuan , Song Xiaozhen , Zhang Tianyuan , Hu Kangjia , Liang Xuewei , Li Shenhou , Zhang Yong , Baturin Ivan , Shur Vladimir
Published: August 2019

Barium strontium titanate glass-ceramics with different La2O3 contents (0, 0.5, 1.0, and 1.5 mol. %) were prepared by the melt-quenching technique. The phase developments, microstructures, and impedance behavior of these glass-ceramics have been investigated as a function of La2O3 content. By the X-ray diffraction study, a gradual change with increasing La2O3 content was observed. X-ray photoelectron spectroscopy indicated that the oxygen vacancy concentration decreases with the increase of La2O3 content. Lanthanum substitution resulted in an initial increase and then a decrease in the value of dielectric constant. From impedance spectroscopy, there are two electrical responses occurring: a low frequency response, which is related to the crystal-glass interface, and a high frequency response corresponding to the crystal phase. The low frequency peak shifts to lower frequencies and the high frequency peak shifts to higher frequencies with increasing lanthanum content. Both the temperature sensitivity of impedance and the value of ac conductivity decrease with the increase of La2O3 content.
Experimental determination of the electro-acoustic properties of thin film AlScN using surface acoustic wave resonators
Authors: Kurz Nicolas , Ding Anli , Urban Daniel F. , Lu Yuan , Kirste Lutz , Feil Niclas M. , Žukauskaitė Agnė , Ambacher Oliver
Published: August 2019

In this work, all electroacoustic material parameters, i.e., the elastic, piezoelectric, and dielectric coefficients, as well as the mass density, were determined experimentally for wurtzite aluminum scandium nitride (Al1−xScxN) for a wide range of Sc concentrations of up to x = 0.32 from the same material source for the first time. Additionally, the mass density and piezoelectric coefficient were determined even up to x=0.42. Two sets of 1 μm-thick AlScN(0001) thin films were deposited on Si(001) using reactive pulsed-DC magnetron cosputtering. One set of thin films was used to determine the a- and c- lattice parameters and the effective relative dielectric coefficient ε33,f, using X-ray diffraction and capacitive measurements, respectively. Lattice parameters were then used to extract average internal parameter u, bond length, and bond angle, as well as mass density, as a function of Sc concentration. Density functional theory calculations were performed to provide the equilibrium lattice parameters a, c, and u, as well as the bond angle and the bond lengths for wurtzite-AlN and layered hexagonal-ScN. The second set of films was used to fabricate surface acoustic wave (SAW) resonators with wavelengths λ from 2 up to 24 μm. The SAW dispersion in conjunction with finite element modeling fitting was used to extract the elastic stiffness as well as the piezoelectric coefficients. The overall evolution of the material parameters and the change of the crystal structure as a function of Sc concentration is discussed in order to provide a possible explanation of the observed behavior.
An electronic temperature definition for the reactive electronic species: Conciliating practical approaches in conceptual chemical reactivity theory with a rigorous ensemble formulation
Authors: Franco-Pérez Marco
Published: August 2019

By working under the framework of the Helmholtz potential as a functional of the equilibrium density matrix, in this contribution, we provide theoretical evidence about a particular thermodynamic situation, where electronic species display their highest susceptibility to exchange electrons to or from surroundings. This situation is denominated as the electronic temperature condition. Neutral chemical species display their lowest possible hardness value at the electronic temperature condition, and remarkably, under this circumstance, the exchange of any amount of electronic charge will necessarily be translated into a net increase in the corresponding chemical hardness. Chemical response functions defined as partial derivatives of the Helmholtz potential with respect to the (average) number of electrons and evaluated at the electronic temperature condition provide comparable results than those obtained from the coarse quadratic approximation to the exact dependence of the electronic energy vs the number of electrons, including composite quantities as the electrophilicity index. In this context, we show that the exact Helmholtz potential dependence with respect to the number of electrons can accurately be approximated by “temperature dependent” polynomial fits (up to fourth order), evaluated at the electronic temperature condition.
Defect dependence of electronic transport of multiwall carbon nanotube buckypaper filled with iron-based nanowires
Authors: Shi Lin , Boi Filippo S. , Xiang Gang , Sameera Ivaturi , Bhatia Ravi , Zhang Xi
Published: August 2019

We report the structure and magnetotransport properties of buckypaper films comprising multiwall carbon nanotubes with a Bernal-like concentric shell structure and mixed Russian doll and jellyroll structure filled along the capillary core with micrometer-long ferromagnetic Fe-based nanowires. Our results show a not previously reported dependence of the magnetoconductance (MC) on the concentration of carbon nanotube (CNT) defects, which can be tuned experimentally by modifying the quantity of dichlorobenzene precursor and interpreted by a weak localization mechanism. Surprisingly, no MC contribution arising from the encapsulated ferromagnetic nanocrystals could be probed, despite the high filling ratio (above 39%) of the CNTs. Such an unusual result suggests that the presence of highly resistive Fe/C interfacial regions prevents the interaction between transport electrons and encapsulated ferromagnetic crystals. Our results may have important implications in electronics and data storage systems where separate engineering of conductance by defects and ferromagnetism by filled crystals could result in multifunctional applications.
Significance of isostructural distortion and strong magnetoelastic coupling in the weak ferromagnet YFe0.9Cr0.1O3
Authors: Raut Subhajit , Kar Biman , Velaga Srihari , Poswal Himanshu K. , Panigrahi S.
Published: August 2019

We report the appearance of weak ferromagnetism above the long-range canted antiferromagnetic order TN = 553 K at which the Fe-Cr interactions become dominant in YFe0.9Cr0.1O3. The weak ferromagnetic order above TN appears due to the increasing magnetic interactions in Fe-sublattices resulting in a canted antiferromagnetic transition at TFe-Fe = 620 K. Electrical hysteresis loop studies and Positive-Up Negative-Down protocol measurements reveal spontaneous but weak ferroelectricity in the system. Dielectric measurements as a function of temperature and frequency reveal a relaxorlike dielectric anomaly within a temperature interval of 400–500 K and anomalous signatures at and temperatures above TN. Synchrotron x-ray diffraction studies over a broad temperature range, 298–873 K, illustrate a significant magnetoelastic coupling at TN and around TFe-Fe. Isostructural distortions are further revealed over the temperature range of 400–500 K from the x-ray diffraction studies. Analyses of the diffraction patterns reveal the delicate interplay between the in-plane and out-of-plane exchange interactions over TN and in isostructural distortion regions. We strongly argue that the ferroelectricity in YFe0.9Cr0.1O3 results from the magnetostriction and Dzyaloshinskii-Moriya interaction manifested through a significant magnetoelastic coupling at TN and TFe-Fe.
Transient overshoot and storage of charge carriers on ligands in quantum dot LEDs
Authors: Blauth Christian , Mulvaney Paul , Hirai Tadahiko
Published: August 2019

Quantum dot light emitting diodes (QLEDs) emitting at 410 nm were studied by time-resolved electroluminescence measurements. A transient overshoot after voltage turn-off was seen, which is attributed to the accumulation and storage of charge carriers at the ligand-quantum dot interface. Shorter ligands showed a faster rise time and prevented the formation of an overshoot, whereas longer ligands caused the storage of charges, responded slower, and showed an overshoot. When the external voltage was switched off, the electric field between the injected and stored electrons and holes led to the occurrence of the overshoot. Applying a dual voltage pulse avoided this overshoot and instead a delayed luminescence was observed. As the accumulated charges were immobile and trapped in shallow states, a reverse pulse was applied to fully deplete the emissive layer. Because the transient overshoot disappeared after the device had been turned on, this can be used as a measure of the degradation of QLEDs. The ligands constitute a major obstacle for an efficient and long lasting blue/purple quantum dot emitter.
Calculation of coherences in Förster and modified Redfield theories of excitation energy transfer
Authors: Trushechkin Anton
Published: August 2019

Förster and modified Redfield theories play one of the central roles in the description of excitation energy transfer in molecular systems. However, in the present state, these theories describe only the dynamics of populations of local electronic excitations or delocalized exciton eigenstates, respectively, i.e., the diagonal elements of the density matrix in the corresponding representation. They do not give prescription for propagating the off-diagonal elements of the density matrix (coherences). This is commonly accepted as a limitation of these theories. Here, we derive formulas for the dynamics of the coherences in the framework of Förster and modified Redfield theories and, thus, remove this limitation. For the dimer case, these formulas provide excellent correspondence with numerically exact calculations according to the hierarchical equations of motion.
Influence of pressure assisted sintering and reaction sintering on microstructure and thermoelectric properties of bi-doped and undoped calcium cobaltite
Authors: Bresch Sophie , Mieller Bjoern , Schoenauer-Kamin Daniela , Moos Ralf , Giovanelli Fabien , Rabe Torsten
Published: August 2019

Calcium cobaltite (Ca3Co4O9) is considered as one of the most promising thermoelectric p-type oxides for energy harvesting applications at temperatures above 500 °C. It is challenging to sinter this material as its stability is limited to 920 °C. To facilitate a practicable and scalable production of Ca3Co4O9 for multilayer generators, a systematic study of the influence of powder calcination, Bi doping, reaction sintering, and pressure-assisted sintering (PAS) on microstructure and thermoelectric properties is presented. Batches of doped, undoped, calcined, and not calcined powders were prepared, tape-cast, and sintered with and without uniaxial pressure at 900 °C. The resulting phase compositions, microstructures, and thermoelectric properties were analyzed. It is shown that the beneficial effect of Bi doping observed on pressureless sintered samples cannot be transferred to PAS. Liquid phase formation induces distortions and abnormal grain growth. Although the Seebeck coefficient is increased to 139 μV/K by Bi doping, the power factor is low due to poor electrical conductivity. The best results were achieved by PAS of calcined powder. The dense and textured microstructure exhibits a high power factor of 326 μW/m K2 at 800 °C but adversely high thermal conductivity in the relevant direction. The figure of merit is higher than 0.08 at 700 °C.
Impact of the Lewis number on finger flame acceleration at the early stage of burning in channels and tubes
Authors: Alkhabbaz Mohammed , Abidakun Olatunde , Valiev Damir , Akkerman V’yacheslav
Published: August 2019

For premixed combustion in channels and tubes with one end open, when a flame is ignited at the centerline at the closed end of the pipe and it propagates toward the open one, significant flame acceleration occurs at an early stage of the combustion process due to formation of a finger-shaped flame front. This scenario is tagged “finger flame acceleration” (FFA), involving an initially hemispherical flame kernel, which subsequently acquires a finger shape with increasing surface area of the flame front. Previous analytical and computational studies of FFA employed a conventional assumption of equidiffusivity when the thermal-to-mass-diffusivity ratio (the Lewis number) is unity (Le = 1). However, combustion is oftentimes nonequidiffusive (Le ≠ 1) in practice such that there has been a need to identify the role of Le in FFA. This demand is addressed in the present work. Specifically, the dynamics and morphology of the Le ≠ 1 flames in two-dimensional (2D) channels and cylindrical tubes are scrutinized by means of the computational simulations of the fully compressible reacting flow equations, and the role of Le is identified. Specifically, the Le > 1 flames accelerate slower as compared with the equidiffusive ones. In contrast, the Le < 1 flames acquire stronger distortion of the front, experience the diffusional-thermal combustion instability, and thereby accelerate much faster than the Le = 1 flames. In addition, combustion in a cylindrical configuration shows stronger FFA than that under the same burning conditions in a 2D planar geometry.
Strain-tunable electronic structure, optical response, and high electron mobility of Bi2O2Se crystals
Authors: Huang Xiaoyu , Niu Chun-Yao , Zhang Jinping , Wang Aihua , Jia Yu , Song Yuling
Published: August 2019

Newly fabricated semiconductor Bi2O2Se films exhibit excellent electron transport and optical properties, with potential application in optoelectronics. In this work, using first-principle calculations combined with the modified Becke-Johnson exchange potential, we have systematically investigated the electronic, transport, and optical properties of bulk Bi2O2Se. Our calculations have shown that external strain can effectively tune the bulk Bi2O2Se electronic bandgap and optical response and that, in particular, the appropriate strain can lead to a transition from an indirect to a direct bandgap. In addition, we found that electron mobility increased with Bi2O2Se crystal thickness and that the computed bulk Bi2O2Se acoustic-phonon-limited electron mobility could reach ∼940 and 535 cm2 V−1 s−1 in the a(b) and c directions at 300 K—which was much higher than that (∼50 cm2 V−1 s−1) achieved by the monolayer. There was a clear anisotropy of the electron mobility in bulk Bi2O2Se, which could be attributed to the synergistic effect between the elastic modulus anisotropy and the deformation potential. Our results not only have given new insight into the high carrier mobility of different thickness Bi2O2Se films (monolayer to bulk) but have also revealed the importance of the electron-transport direction to device performance. Together with the high carrier mobility, strain-tunable electronic structure, and optical response, Bi2O2Se films with different thicknesses have been shown to be very attractive for application to optoelectronic and electronic devices.
Multifunctional anti-ambipolar p-n junction based on MoTe2/MoS2 heterostructure
Authors: Hu Ruixue , Wu Enxiu , Xie Yuan , Liu Jing
Published: August 2019

The discovery of atomically thin two-dimensional materials enables building numerous van der Waals heterostructures with original and promising properties for potential electronic and optoelectronic applications. Among them, the antiambipolar characteristic is one of the most appealing ones, which refers to the inverse “V” shape of the transfer curve of the heterojunction. As a result, it is expected to implement various important logic functions, such as double-frequency and multivalue. In this work, we modulated an ambipolar MoTe2/MoS2 heterojunction to show prominent antiambipolar behavior by simply annealing the device at elevated temperature. The on-off ratio and on-state current of the antiambipolar characteristic can be tuned as large as 106 and approximately microamperes, respectively, by optimizing the annealing temperature. Furthermore, we preliminarily demonstrated a self-powered photodetector and a ternary inverter based on this device. The photodetector showed a short-current circuit and an open-circuit voltage of 0.4 μA and 7.5 mV, respectively, at incident light intensity of 2.54 mW/cm2, and gate tunable photocurrent ranging from 0 to 380 pA under zero source-drain bias. The ternary inverter can output three distinct values varying on the order of subvolt as the input voltage (gate bias) ranges from −60 V to 60 V.
Synergy effect of intraband transition and impact-Auger in optical hot-carrier solar cells
Authors: Takeda Yasuhiko
Published: August 2019

An optical hot-carrier solar cell (opt-HC-SC) is a variant of hot-carrier solar cells (HC-SCs). Hot luminescence in a specific narrow energy range is enhanced and extracted from the absorber through an optical energy-selective contact (opt-ESC) and illuminates a neighboring photovoltaic cell of a conventional type. Thus, this concept eliminates the requisites for carrier transport to achieve high conversion efficiency. In the present study, I clarified the issues for high efficiency using an improved detailed-balance model and determined the solutions. The serious issue is that the enhancement effect of the opt-ESC on the hot luminescence is considerably lower in practice than the optimal value, and this necessitates a high carrier density in the absorber for sufficient photon extraction and results in significant energy loss originating from carrier thermalization. When impact ionization occurs immediately, the average carrier energy lowers, the carrier density can decrease, and hence the thermalization energy loss significantly reduces. This, in turn, enables absorption of sub-bandgap photons arising from the intraband transition to improve the efficiency. Consequently, the synergy effect of both the aforementioned phenomena notably improves the efficiency to 53.6% under the practical upper limit of the enhancement effect, the carrier thermalization time of 1 ns, and 1000-times concentrated solar illumination, from 45.1% for no intraband transition or impact-Auger. By contrast, the individual effects are marginal. This is a unique feature of opt-HC-SCs and is not found in HC-SCs (carrier extraction). The present finding serves as a guide to material design to realize highly efficient opt-HC-SCs.
Enhanced stability of guanidinium-based organic-inorganic hybrid lead triiodides in resistance switching
Authors: Kim Younghoon , Bae Changdeuck , Jung Hyun Suk , Shin Hyunjung
Published: August 2019

We describe guanidinium-based organic-inorganic hybrid lead triiodides (GAPbI3) as an active layer in resistive switching structures and compare the switching results to those of the conventional compound, MAPbI3. Both the GAPbI3- and MAPbI3-based ReRAM devices showed bistable switching characteristics with a low operating voltage (<0.25 V) and high on/off ratio (∼106). Remarkably, we found that the GAPbI3-based devices exhibited prolonged switching behaviors for over 40 days under ambient conditions (MAPbI3, only 4 days). The GAPbI3 devices lasted for a larger number of cycles (>1900) in an endurance test and exhibited a longer data storage time (>3 × 104 s) in a retention test. Our results suggest that GAPbI3 has stronger hydrogen bonding in the lattice and thus the potential for application in memory devices.
Mechanical properties of ultra-hard nanocrystalline cubic boron nitride
Authors: Solozhenko Vladimir L. , Bushlya Volodymyr , Zhou Jinming
Published: August 2019

Nanostructure and mechanical properties of bulk nanocristalline cubic boron nitride have been studied by transmission electron microscopy and micro- and nanoindentation. The obtained data on hardness, elastic properties, and fracture toughness clearly indicate that nano-cubic (F4¯3m) boron nitride belongs to a family of advanced ultrahard materials.
Nonvolatile reversible capacitance changes through filament formation in a floating-gate metal-oxide-semiconductor capacitor with Ag/CeOx/Pt/HfOx/n-Si structure
Authors: Kim Minju , Beom Keonwon , Lee Hyerin , Kang Chi Jung , Yoon Tae-Sik
Published: August 2019

Nonvolatile and reversible capacitance changes are demonstrated in a floating-gate metal-oxide-semiconductor (FG-MOS) capacitor with a Ag-control-gate/CeOx-control-oxide/Pt-floating-gate/HfOx-tunneling-oxide/n-Si structure. Different from the conventional floating-gate MOS field-effect-transistor (MOSFET) operating with a threshold voltage shift by electrical charging in the floating-gate (charge storage node), the proposed device operates with the change of gate oxide capacitance as one of the parameters determining the electrical properties of MOSFET. Applying positive voltage to the Ag control-gate forms a conducting filament in the Ag/CeOx/Pt stack and consequently increases the gate oxide capacitance. The accumulation capacitance increases from the capacitance of serial capacitors consisting of Ag/CeOx/Pt and Pt/HfOx/n-Si before the filament formation to that of a single capacitor of Pt/HfOx/n-Si after the filament formation. The capacitance is reversibly decreased to the initial value by rupturing the filament upon applying negative voltage. The change of capacitance is stable over time with the retention >90% for 12 h of measured time. These noncharge-storage-based nonvolatile and reversible changes in the gate oxide capacitance through the filament formation would modulate the MOSFET properties with the advantages of better uniformity, superior immunity to the radiation, and less cross talk between adjacent devices for the application to nonvolatile memory and programmable logic devices.
Observation of increased nanostructure cone growth on Cr due to grazing-incidence Ta seed atom deposition in a He plasma
Authors: Hollmann E. M. , Nishijima D. , Patino M. I. , Chrobak C. , Doerner R. P. , Nagata D. , Tokitani M.
Published: August 2019

Nanostructure cone growth on chromium during helium plasma exposure in the PISCES-A linear plasma device is found to increase with the deposition of heavy tantalum atoms. Tantalum is found to be especially effective at increasing cone growth if the tantalum is incident on the surface at a grazing angle (∼5° or less). Tantalum atoms at grazing incidence are observed to be dominantly deposited at the cone tips, consistent with reduced sputtering of the cone tips and increased cone growth. Monte-Carlo simulations are found to be qualitatively consistent with the experimental observation that grazing-incidence heavy atom deposition on a lighter substrate will tend to increase cone growth.
Temperature-dependence of X-ray excited luminescence of
β
-Ga2O3 single crystals
Authors: Tang Huili , He Nuotian , Zhu Zhichao , Gu Mu , Liu Bo , Xu Jun , Xu Mengxuan , Chen Liang , Liu Jinliang , Ouyang Xiaoping
Published: August 2019

We investigated the temperature-dependence of X-ray excited luminescence of β-Ga2O3 single crystals. The recombination of free-electrons with self-trapped holes (STHs) responsible for the ultraviolet luminescence (UVL) band was observed. For the as-grown sample with a high electron concentration, the Auger recombination becomes important, which accelerates the decay dynamics and reduces the ultraviolet luminescence band. The ultraviolet luminescence band is controlled by temperature quenching due to the migration of self-trapped holes to VGa3− centers. Annealing in an oxygen environment can increase the VGa3− concentration, which contributes to the blue-green luminescence band when VGa3− captures a self-trapped hole forming a VGa2− center at rising temperature.
Dramatic impact of pressure and annealing temperature on the properties of sputtered ferroelectric HZO layers
Authors: Bouaziz Jordan , Rojo Romeo Pedro , Baboux Nicolas , Negrea Raluca , Pintilie Lucian , Vilquin Bertrand
Published: August 2019

The crystallization of ferroelectric (Hf,Zr)O2 thin films is achieved by playing on the deposition pressure during reactive magnetron sputtering from a Hf/Zr metallic target. Postdeposition annealing was tried at different temperatures in order to optimize the quality of the samples. Structural characterizations are performed by transmission electron microscopy (TEM) and electrical characterizations are carried out. TEM analyses reveal that the samples deposited at a low working pressure show no orthorhombic phase, and thus are not ferroelectric, whereas the samples deposited at higher working pressure show the orthorhombic ferroelectric phase. The maximum remnant polarization is 6 µC/cm2 and is obtained for the sample annealed at 600 °C. The maximum cycles to breakdown is higher than 2 × 1010 cycles and is reached for the sample annealed at 400 °C. These results are discussed in the matter of phase transition and oxygen vacancies redistribution.
Observation and control of the anomalous Aharonov-Bohm oscillation in enhanced-mode topological insulator nanowire field-effect transistors
Authors: Zhu Hao , Richter Curt A. , Yu Sheng , Ye Huixian , Zeng Min , Li Qiliang
Published: August 2019

Aharonov-Bohm (AB) oscillation is a quantum mechanical phenomenon which reveals the coupling of electromagnetic potentials with the electron wave function, affecting the phase of the wave function. Such a quantum interference effect can be demonstrated through the magnetotransport measurement focusing on low-dimensional electronic states. Here, we report the experimental observation of anomalous AB oscillation in an enhanced-mode topological insulator Bi2Se3 nanowire field-effect transistor (FET) under strong surface disorder, which is different from the reported AB oscillation in topological insulator nanostructures. The surrounding gate of the nanowire FET gives rise to tunability of the chemical potential and introduces strong disorder on the surface states, leading to primary oscillation with an anomalous h/e period. Furthermore, the oscillation exhibits a significant dependence on the gate voltage which has been preliminary explained with the quantization of the surface conduction channel. The experimental demonstration can be very attractive for further exploration of quantum phase interference through electrical approaches, enabling applications in future information and electromagnetic sensing technology.
Rheological signatures of aging in hard sphere colloidal glasses
Authors: Jacob Alan R. , Moghimi Esmaeel , Petekidis George
Published: August 2019

Colloidal glasses are out-of-equilibrium in nature. When such materials are quenched from a shear-melted state into a quiescent one, their structure freezes due to entropic caging of the constituents. However, thermal fluctuations allow slow structural evolution, a process known as aging, in favor of minimizing free energy. Here, we examine the rheological signatures of aging, in a model system of nearly hard sphere colloidal glass. Subtle changes in the linear viscoelastic properties are detected with the age of the colloidal glass where viscous modulus shows a decrease with aging whereas the elastic modulus remains unaffected. This is associated with the slowing-down of long-time out-of-cage dynamics as the glass ages. On the contrary, nonlinear rheological measurements such as start-up shear flow, stress relaxation, and creep experiments show a strong dependence on sample age. Moreover, creep and stress relaxation experiments show ample evidence of avalanche type processes that occur during aging of colloidal glasses. Finally, comparison of creep and start-up shear flow measurements indicate that the latter is more energy efficient in inducing flow in colloidal glasses irrespective of aging dynamics.
Multi-particle collision dynamics for a coarse-grained model of soft colloids
Authors: Ruiz-Franco José , Jaramillo-Cano Diego , Camargo Manuel , Likos Christos N. , Zaccarelli Emanuela
Published: August 2019

The growing interest in the dynamical properties of colloidal suspensions, both in equilibrium and under an external drive such as shear or pressure flow, requires the development of accurate methods to correctly include hydrodynamic effects due to the suspension in a solvent. In the present work, we generalize Multiparticle Collision Dynamics (MPCD) to be able to deal with soft, polymeric colloids. Our methods build on the knowledge of the monomer density profile that can be obtained from monomer-resolved simulations without hydrodynamics or from theoretical arguments. We hereby propose two different approaches. The first one simply extends the MPCD method by including in the simulations effective monomers with a given density profile, thus neglecting monomer-monomer interactions. The second one considers the macromolecule as a single penetrable soft colloid (PSC), which is permeated by an inhomogeneous distribution of solvent particles. By defining an appropriate set of rules to control the collision events between the solvent and the soft colloid, both linear and angular momenta are exchanged. We apply these methods to the case of linear chains and star polymers for varying monomer lengths and arm number, respectively, and compare the results for the dynamical properties with those obtained within monomer-resolved simulations. We find that the effective monomer method works well for linear chains, while the PSC method provides very good results for stars. These methods pave the way to extend MPCD treatments to complex macromolecular objects such as microgels or dendrimers and to work with soft colloids at finite concentrations.
Full quantum calculation of the rovibrational states and intensities for a symmetric top-linear molecule dimer: Hamiltonian, basis set, and matrix elements
Authors: Zhang Xiao-Long , Ma Yong-Tao , Zhai Yu , Li Hui
Published: August 2019

The rovibrational energy levels and intensities of the CH3F–H2 dimer have been obtained using our recent global intermolecular potential energy surface [X.-L. Zhang et al., J. Chem. Phys. 148, 124302 (2018)]. The Hamiltonian, basis set, and matrix elements are derived and given for a symmetric top-linear molecule complex. This approach to the generation of energy levels and wavefunctions can readily be utilized for studying the rovibrational spectra of other van der Waals complexes composed of a symmetric top molecule and a linear molecule, and may readily be extended to other complexes of nonlinear molecules and linear molecules. To confirm our method, the rovibrational levels of the H2O–H2 dimer have been computed and shown to be in good agreement with experiment and with previous theoretical results. The rovibrational Schrödinger equation has been solved using a Lanczos algorithm together with an uncoupled product basis set. As expected, dimers containing ortho-H2 are more strongly bound than dimers containing para-H2. Energies and wavefunctions of the discrete rovibrational levels of CH3F–paraH2 complexes obtained from the direct vibrationally averaged 5-dimensional potentials are in good agreement with the results of the reduced 3-dimensional adiabatic-hindered-rotor (AHR) approximation. Accurate calculations of the transition line strengths for the orthoCH3F–paraH2 complex are also carried out, and are consistent with results obtained using the AHR approximation. The microwave spectrum associated with the orthoCH3F–orthoH2 dimer has been predicted for the first time.
Specific features of Nd3+ Kramers doublets’ splitting in an antiferromagnetic crystal NdFe3(BO3)4 in an external magnetic field
Authors: Gnatchenko S. L. , Kachur I. S. , Kurnosov V. S. , Piryatinskaya V. G. , Malakhovskii A. V. , Gudim I. A.
Published: August 2019

The optical absorption spectra of an easy-plane NdFe3(BO3)4 antiferromagnet are measured in the region of the 4I9/2 → 2H11/2 transition of the of Nd3+ ion. The study is performed in the 2–35 К temperature range, in external magnetic fields of up to 65 kOe directed both along the С3 axis and the basal plane of the crystal. The splitting values of the Nd3+ excited states in the exchange field of the Fe3+ subsystem and the g-factors of the 2H11/2 multiplet states are determined. The nontrivial dependences of the splitting of some Nd3+ states in a magnetic field indicate that these states have anisotropic Fe–Nd exchange interaction.
Spontaneous solid-solid interface melting driven by concentration gradient
Authors: Zhu Yiying , Wang Hao , Li Mo
Published: August 2019

The contact of heterogeneous materials with different atomic structures and concentrations becomes omnipresent in modern materials. The differences across the interface introduce various gradients that could alter thermodynamic and kinetic behaviors of the materials. Here, we report a spontaneous melting of the interface formed by a crystalline metal and an amorphous solid at the temperature below their respective equilibrium melting temperatures. The transformation can even become continuous with disappearance of all known features of the first-order melting transition. We show that the change in the nature of melting in the interface region is caused by random disordering induced by interdiffusing atomic elements or impurities in the crystalline phase and the presence of a strong concentration gradient constrained by the sample geometry.