bluuebunny/crossref_metadata_2025 huggingface dataset:
Unique Luminescence of Hexagonal Dominant Colloidal Copper Indium Sulphide Quantum Dots in Dispersed Solutions
Authors: Shin Samuel Jaeho , Koo Ja-Jung , Lee Jin-Kyu , Chung Taek Dong
Published: December 2019

Luminescent hexagonal dominant copper indium sulphide (h-dominant CIS) quantum dots (QDs) by precursor-injection of mixed metal-dialkyldithiocarbamate precursors. Owing to the different reactivity of the precursors, this method allowed the CIS QDs to grow while retaining the crystallinity of the hexagonal nucleus. The photoluminescence (PL) spectra exhibited dual emission (600–700 nm red emission and 700–800 nm NIR emission) resulting from the combined contributions of the hexagonal (wurtzite) h-CIS and tetragonal (chalcopyrite) t-CIS QDs, i.e. the NIR and red emissions were due to the h-CIS QDs and coexisting t-CIS QDs (weight ratio of h-CIS/t-CIS ~ 10), respectively. The PL intensities of the h-CIS as well as t-CIS QDs were enhanced by post-synthetic heat treatment; the t-CIS QDs were particularly sensitive to the heat treatment. By separating h-CIS and t-CIS successfully, it was demonstrated that this phenomenon was not affected by size and composition but by the donor-acceptor pair states and defect concentration originating from their crystal structure. The h-dominant CIS QDs in this work provide a new technique to control the optical property of Cu-In-S ternary NCs.
Transferred monolayer MoS2 onto GaN for heterostructure photoanode: Toward stable and efficient photoelectrochemical water splitting
Authors: Hassan Mostafa Afifi , Kim Min-Woo , Johar Muhammad Ali , Waseem Aadil , Kwon Min-Ki , Ryu Sang-Wan
Published: December 2019

Solar-driven photoelectrochemical water splitting (PEC-WS) using semiconductor photoelectrodes is considered a promising solution for sustainable, renewable, clean, safe and alternative energy sources such as hydrogen. Here, we report the synthesis and characterization of a novel heterostructure MoS2/GaN to be used as a photoanode for PEC-WS. The heterostructure was synthesized by metal-organic chemical vapor deposition of single crystalline GaN onto a c-plane sapphire substrate, followed by the deposition of a visible light responding MoS2 monolayer (Eg = 1.9 eV) formed by a Mo-sulfurization technique. Our experimental results reveal that MoS2/GaN photoanode achieved efficient light harvesting with photocurrent density of 5.2 mA cm−2 at 0 V vs Ag/AgCl, which is 2.6 times higher than pristine GaN. Interestingly, MoS2/GaN exhibited a significantly enhanced applied-bias-photon-to-current conversion efficiency of 0.91%, whereas reference GaN yielded an efficiency of 0.32%. The superior PEC performance of the MoS2/GaN photoelectrode is mainly related to the enhanced light absorption due to excellent photocatalytic behavior of MoS2, which reduces charge transfer resistance between the semiconductor and electrolyte interface, and the improvement of charge separation and transport. This result gives a new perspective on the importance of MoS2 as a cocatalyst coated onto GaN to synthesize photoelectrodes for efficient solar energy conversion devices.
Development of hypoallergenic variants of the major horse allergen Equ c 1 for immunotherapy by rational structure based engineering
Authors: Haka Jaana , Niemi Merja H. , Mattila Pekka , Jänis Janne , Takkinen Kristiina , Rouvinen Juha
Published: December 2019

The use of recombinant allergens is a promising approach in allergen-specific immunotherapy (AIT). Considerable limitation, however, has been the ability of recombinant allergens to activate effector cells leading to allergic reactions. Recombinant hypoallergens with preserved protein folding and capacity to induce protective IgG antibodies binding effectively to the native allergen upon sensitization would be beneficial for safer AIT. In this study, hypoallergen variants of the major horse allergen Equ c 1 were designed by introducing one point mutation on the putative IgE epitope region and two mutations on the monomer-monomer interface of Equ c 1 dimer. The recombinant Equ c 1 wild type and the variants were produced and purified to homogeneity, characterized by size-exclusion ultra-high performance liquid chromatography and ultra-high resolution mass spectrometry. The IgE-binding profiles were analyzed by a competitive immunoassay and the biological activity by a histamine release assay using sera from horse allergic individuals. Two Equ c 1 variants, Triple 2 (V47K + V110E + F112K) and Triple 3 (E21Y + V110E + F112K) showed lower allergen-specific IgE-binding capacity and decreased capability to release histamine from basophils in vitro when using sera from six allergic individuals. Triple 3 showed higher reduction than Triple 2 in IgE-binding (5.5 fold) and in histamine release (15.7 fold) compared to wild type Equ c 1. Mutations designed on the putative IgE epitope region and monomer-monomer interface of Equ c 1 resulted in decreased dimerization, a lower IgE-binding capacity and a reduced triggering of an allergic response in vitro.
Mandibular advancement impairs swallowing ability more than head extension but less than mouth opening in the supine position
Authors: Hanamoto Hiroshi , Togawa Eriko , Maegawa Hiroharu , Yokoe Chizuko , Inoue Mika , Oyamaguchi Aiko , Kudo Chiho , Niwa Hitoshi
Published: December 2019

Mandibular advancement in the supine position may influence swallowing during dental treatment under intravenous sedation. This study investigated the influence of mandibular advancement in the supine position on swallowing ability, compared with head extension and mouth opening. The water swallowing test was performed in 13 healthy, awake, supine, adult subjects under four head and mandibular positions. An electromyogram of the suprahyoid muscles was recorded; the duration and peak amplitude were examined. A greater volume of water remained in the mouth during mouth opening and mandibular advancement relative to the neutral position; the volume in the mandibular advancement position was larger and smaller than that in the head extension position and during mouth opening, respectively. The duration of the electromyogram in the head extension position was longer than that in the mandibular advancement position, without differences in the amplitude. Thus, swallowing ability in the supine position was more impaired with mandibular advancement, relative to neutral and head extension positions, but less than that observed with mouth opening. Although unconfirmed by electromyogram, our findings suggest that head extension might improve airway patency by reducing the impairment of swallowing ability compared with mandibular advancement.
Mesolimbic dopamine D2 receptors and neural representations of subjective value
Authors: Castrellon Jaime J. , Young Jacob S. , Dang Linh C. , Cowan Ronald L. , Zald David H. , Samanez-Larkin Gregory R.
Published: December 2019

The process by which the value of delayed rewards is discounted varies from person to person. It has been suggested that these individual differences in subjective valuation of delayed rewards are supported by mesolimbic dopamine D2-like receptors (D2Rs) in the ventral striatum. However, no study to date has documented an association between direct measures of dopamine receptors and neural representations of subjective value in humans. Here, we examined whether individual differences in D2R availability were related to neural subjective value signals during decision making. Human participants completed a monetary delay discounting task during an fMRI scan and on a separate visit completed a PET scan with the high affinity D2R tracer [18 F]fallypride. Region-of-interest analyses revealed that D2R availability in the ventral striatum was positively correlated with subjective value-related activity in the ventromedial prefrontal cortex and midbrain but not with choice behavior. Whole-brain analyses revealed a positive correlation between ventral striatum D2R availability and subjective value-related activity in the left inferior frontal gyrus and superior insula. These findings identify a link between a direct measure of mesolimbic dopamine function and subjective value representation in humans and suggest a mechanism by which individuals vary in neural representation of discounted subjective value.
Experimental colitis reduces microglial cell activation in the mouse brain without affecting microglial cell numbers
Authors: Sroor Hoda M. , Hassan Ahmed M. , Zenz Geraldine , Valadez-Cosmes Paulina , Farzi Aitak , Holzer Peter , El-Sharif Amany , Gomaa Fatma Al-Zahraa M. , Kargl Julia , Reichmann Florian
Published: December 2019

Inflammatory bowel disease (IBD) patients frequently suffer from anxiety disorders and depression, indicating that altered gut-brain axis signalling during gastrointestinal inflammation is a risk factor for psychiatric disease. Microglia, immune cells of the brain, is thought to be involved in a number of mental disorders, but their role in IBD is largely unknown. In the current work, we investigated whether colitis induced by dextran sulphate sodium (DSS), a murine model of IBD, alters microglial phenotypes in the brain. We found that colitis caused a reduction of Iba-1 and CD68 immunoreactivity, microglial activation markers, in specific brain regions of the limbic system such as the medial prefrontal cortex (mPFC), while other areas remained unaffected. Flow cytometry showed an increase of monocyte-derived macrophages during colitis and gene expression analysis in the mPFC showed pronounced changes of microglial markers including cluster of differentiation 86 (CD86), tumour necrosis factor-α, nitric oxide synthase 2, CD206 and chitinase-like protein 3 consistent with both M1 and M2 activation. Taken together, these findings suggest that experimental colitis-induced inflammation is propagated to the brain altering microglial function.
Role of GDF15 in active lifestyle induced metabolic adaptations and acute exercise response in mice
Authors: Gil Carla Igual , Ost Mario , Kasch Juliane , Schumann Sara , Heider Sarah , Klaus Susanne
Published: December 2019

Physical activity is an important contributor to muscle adaptation and metabolic health. Growth differentiation factor 15 (GDF15) is established as cellular and nutritional stress-induced cytokine but its physiological role in response to active lifestyle or acute exercise is unknown. Here, we investigated the metabolic phenotype and circulating GDF15 levels in lean and obese male C57Bl/6J mice with long-term voluntary wheel running (VWR) intervention. Additionally, treadmill running capacity and exercise-induced muscle gene expression was examined in GDF15-ablated mice. Active lifestyle mimic via VWR improved treadmill running performance and, in obese mice, also metabolic phenotype. The post-exercise induction of skeletal muscle transcriptional stress markers was reduced by VWR. Skeletal muscle GDF15 gene expression was very low and only transiently increased post-exercise in sedentary but not in active mice. Plasma GDF15 levels were only marginally affected by chronic or acute exercise. In obese mice, VWR reduced GDF15 gene expression in different tissues but did not reverse elevated plasma GDF15. Genetic ablation of GDF15 had no effect on exercise performance but augmented the post exercise expression of transcriptional exercise stress markers (Atf3, Atf6, and Xbp1s) in skeletal muscle. We conclude that skeletal muscle does not contribute to circulating GDF15 in mice, but muscle GDF15 might play a protective role in the exercise stress response.
Recent advances in fast-scan cyclic voltammetry
Authors: Puthongkham Pumidech , Venton B. Jill
Published: December 2019

We reviewed recent advances and future challenges in fast-scan cyclic voltammetry for real-time detection of neurotransmitters.
Single atomic Au induced dramatic promotion of the photocatalytic activity of TiO2 hollow microspheres
Authors: Hu Zhao , Yang Chao , Lv Kangle , Li Xiaofang , Li Qin , Fan Jiajie
Published: December 2019

Surface oxygen vacancies (Ov) are used to stabilize single atomic Au on the surfaces of TiO2 hollow microspheres (TiO2-HMSs), sharply improving their photoreactivity towards acetone oxidation.
Engineering the energy gap of black phosphorene quantum dots by surface modification for efficient chemiluminescence
Authors: Liu Houjing , Su Yingying , Sun Tong , Deng Dongyan , Lv Yi
Published: December 2019

In this work, NH2-functionalized BPQDs (N-BPQDs) were purposely synthesized with small the energy gap for efficient chemiluminescence (CL) with the assistance of persulfate (K2S2O8).
A stable dual-emitting dye@LMOF luminescence probe for the rapid and visible detection of organophosphorous pesticides in aqueous media
Authors: Zhang Jie , Zhou Wendi , Zhai Lijun , Niu Xiaoyan , Hu Tuoping
Published: December 2019

The composite RhB@LMOF 1 was synthesized and exhibited sensitive and selective recognition ability for the detection of organophosphorous (OPs) pesticides in aqueous media.
Effects of different exchanging ions on the band structure and photocatalytic activity of defect pyrochlore oxide: a case study on KNbTeO6
Authors: Waehayee Anurak , Watthaisong Panuwat , Wannapaiboon Suttipong , Chanlek Narong , Nakajima Hideki , Wittayakun Jatuporn , Suthirakun Suwit , Siritanon Theeranun
Published: December 2019

The effects of different exchanging ions including Ag, Cu, and Sn on enhancing the photocatalytic activity of KNbTeO6are investigated by means of experiments and calculations.
Promotion effect of cerium doping on iron–titanium composite oxide catalysts for selective catalytic reduction of NOx with NH3
Authors: Zhang Wenshuo , Shi Xiaoyan , Shan Yulong , Liu Jingjing , Xu Guangyan , Du Jinpeng , Yan Zidi , Yu Yunbo , He Hong
Published: December 2019

Doping with a suitable amount of Ce enhances the SCR performance of FeTi catalysts.
A coaxial three-layer (Ni, Fe)OxHy/Ni/Cu mesh electrode: excellent oxygen evolution reaction activity for water electrolysis
Authors: Zhao Jizuo , Wu Weibing , Jia Xiangyu , Zhao Zhenlu , Hu Xun
Published: December 2019

The structure of the coaxial three-layer Cu/Ni/(Ni,Fe)OxHy and the OER polarization curves of (Ni,Fe)OxHy grown on different substrates with iR-correction.
Alkyl pyridinium iodocyanocuprate(i) chains (RPy)2[Cu2I3(CN)]: insight into structural, electronic and spectroscopic properties
Authors: Wells Taylor C. , Streep Michaela E. , Martucci Abigail L. , Nicholas Aaron D. , Pike Robert D.
Published: December 2019

Reaction of RPyI, CuI, and CuCN produces anionic iodocyanocuprate(i) chains, (RPy)2[Cu2I3CN] which exhibit charge transfer that is influenced by the hydrogen bonding between the cation and the triiodide groups.
Citrus flavonoids suppress IL-5 and ROS through distinct pathways in PMA/ionomycin-induced EL-4 cells
Authors: Yang Wei-Ling , Chen Sheng-Yi , Ho Cheng-Ying , Yen Gow-Chin
Published: December 2019

Proposed mechanisms for the protective effect of citrus flavonoids (hesperidin and gardenin A) on PMA/ionomycin-induced Th2 response.
Oligo(ethylene glycol) as side chains of conjugated polymers for optoelectronic applications
Authors: Meng Bin , Liu Jun , Wang Lixiang
Published: December 2019

Except hydrophobic alkyl side chains, hydrophilic oligo(ethylene glycol) (OEG) has also been used as side chains of conjugated polymers and endow the resulting polymers with interesting properties and excellent opto-electronic device performance.
Transition metal-free catalytic reduction of primary amides using an abnormal NHC based potassium complex: integrating nucleophilicity with Lewis acidic activation
Authors: Bhunia Mrinal , Sahoo Sumeet Ranjan , Das Arpan , Ahmed Jasimuddin , P. Sreejyothi , Mandal Swadhin K.
Published: December 2019

An abnormal N-heterocyclic carbene (aNHC) based potassium complex was used as a transition metal-free catalyst for reduction of primary amides to corresponding primary amines under ambient conditions.
Mirror, mirror on the outflow cavity wall
Authors: Fedriani R. , Caratti o Garatti A. , Koutoulaki M. , Garcia-Lopez R. , Natta A. , Cesaroni R. , Oudmaijer R. , Coffey D. , Ray T. , Stecklum B.
Published: December 2019

Aims. The inner regions of high-mass protostars are often invisible in the near-infrared, obscured by thick envelopes and discs. We aim to investigate the inner gaseous disc of IRAS 11101-5829 through scattered light from the outflow cavity walls.

Methods. We observed the immediate environment of the high-mass young stellar object IRAS 11101-5829 and the closest knots of its jet, HH135-136, with the integral field unit VLT/SINFONI. We also retrieved archival data from the high-resolution long-slit spectrograph VLT/X-shooter. We analysed imaging and spectroscopic observations to discern the nature of the near-infrared CO emission.

Results. We detect the first three bandheads of the υ = 2−0 CO vibrational emission for the first time in this object. It is coincident with continuum and Brγ emission and extends up to ~10 000 au to the north-east and ~10 000 au to the south-west. The line profiles have been modelled as a Keplerian rotating disc assuming a single ring in local thermodynamic equilibrium. The model output gives a temperature of ~3000 K, a CO column density of ~1 × 1022 cm−2, and a projected Keplerian velocity vK sin idisc ~ 25 km s−1, which is consistent with previous modelling in other high-mass protostars. In particular, the low value of vK sin idisc suggests that the disc is observed almost face-on, whereas the well-constrained geometry of the jet imposes that the disc must be close to edge-on. This apparent discrepancy is interpreted as the CO seen reflected in the mirror of the outflow cavity wall.

Conclusions. From both jet geometry and disc modelling, we conclude that all the CO emission is seen through reflection by the cavity walls and not directly. This result implies that in the case of highly embedded objects, as for many high-mass protostars, line profile modelling alone might be deceptive and the observed emission could affect the derived physical and geometrical properties; in particular the inclination of the system can be incorrectly interpreted.
Small-Molecule Donor/Polymer Acceptor Type Organic Solar Cells: Effect of Terminal Groups of Small-Molecule Donors
Authors: Miao Junhui , Meng Bin , Liu Jun , Wang Lixiang
Published: December 2019

Small-molecule donor/polymer acceptor type (MD/PA-type) organic solar cells (OSCs) have the great advantage of superior thermal stability. However, very few small molecular donors can match polymer acceptors, leading to low power conversion efficiency (PCE) of MD/PA-type OSCs. In this work, we studied the effect of terminal groups of small molecular donors on the optoelectronic properties and OSC device performance of MD/PA-type OSCs. We select a benzodithiophene unit bearing carbazolyl substituents as the core, terthiophene as the bridging unit, and electron-withdrawing methyl 2-cyanoacetate, 3-ethylrhodanine, and 2H-indene-1,3-dione as the terminal groups to develop three small-molecule donors. With the increase of the electron-withdrawing capability of the terminal groups, the small molecular donors exhibit redshifted absorption spectra and downshifted LUMO levels. Among the three small-molecule donors, the one with 3-ethylrhodanine terminal group exhibits the best photovoltaic performance with the PCE of 8.0% in MD/PA-type OSCs. This work provides important guidelines for the design of small-molecule donors for MD/PA-type OSC applications.
Numerical study on the effect of blade surface deterioration by erosion on the performance of a large wind turbine
Authors: Im Heejeon , Kim Bumsuk
Published: December 2019

As the demand for the development of onshore wind farms in areas with low wind speeds and large offshore wind farms increases, the size of the wind turbine and its rotor has also increased rapidly. An increase in the rotor diameter implies an increase in the relative wind velocity (with respect to each cross section in the radial direction of the blade) near the tip region of the blade. This in return accelerates the surface damage caused by the erosion of the leading edge, thereby increasing the frequency of maintenance and lowering competitiveness in the cost of energy. In this study, computational fluid dynamics (CFD) analysis was performed to analyze the correlation between the leading-edge erosion damage and output performance of the blade. CFD simulations were performed using a tip airfoil (NACA 64_618) and a full-scale wind turbine (NREL 5 MW) based on the state of erosion of discarded blades considering approximately 12 years of maintenance-free operation. The irregular erosion at the airfoil leading edge results in premature stall phenomena and reduces the aerodynamic efficiency. Thus, the accurate analysis of the flow separation point and flow change is necessary. Therefore, three-dimensional transient CFD analysis was performed to consider the complex flow generated on the blade surface. The erosion at the leading edge reduced the airfoil lift by up to 23% and drag by 100%, reducing the aerodynamic efficiency, which in effect reduced annual energy production by up to 4%.
High-pressure microwave plasma oxidation of 4H-SiC with low interface trap density
Authors: Liu Xinyu , Hao Jilong , You Nannan , Bai Yun , Wang Shengkai
Published: December 2019

Microwave plasma oxidation under a relatively high pressure (6 kPa) region is developed to rapidly grow a high-quality SiO2 layer on 4H-SiC, based on a thermodynamic analysis of SiC oxidation. By optimizing the plasma power, an atomically flat interface is achieved, and the interface trap density is lower than that of standard 1300 °C thermal-oxidized and 1350 °C NO-annealed samples measured by various methods under multiple temperature conditions. Moreover, the oxide breakdown field is higher than 9.3 MV/cm, which is comparable to that of a sample produced by high-temperature thermal oxidation. Particularly, the results of electron energy loss spectroscopy show that the transition layer between 4H-SiC and SiO2 is lower than 2 nm, indicating that microwave plasma oxidation can greatly suppress the formation of interface defects. The results strongly demonstrate the effectiveness of high-pressure plasma oxidation for SiC.
Influence of parallel shearing flow on the switch-off effect of magnetic reconnection
Authors: Liu Yang , Huang Junfeng , Zhu Tengfei , Chen Jinzhu , Xia Tianjie
Published: December 2019

Parallel shearing flows significantly affect the structure of the magnetic reconnection layer and generate new shock structures such as intermediate shock (IS) and time-dependent IS. The strength of shock waves (such as slow shock) can be changed and result in the switch-off of magnetic reconnection under certain conditions. In this study, we perform numerical simulations of one-dimensional resistive magnetohydrodynamic equations by using the total variation diminishing algorithm to investigate the influence of parallel shear flow on the switch-off effect of magnetic reconnection on both asymmetric and symmetric magnetic reconnection layers. Numerical results show that there exists a critical shear velocity Vzc that equals VA in symmetrical antiparallel magnetic reconnection, where VA denotes the inflow Alfvén velocity. For symmetric component magnetic reconnection, Vzc drops with the increase in guide magnetic field strength, which also equals the component of inflow Alfvén velocity along the z-axis. In regard to asymmetric magnetic reconnection, the critical shear velocity, Vzc, that leads to the switch-off of magnetic reconnection, ranging between the z-axis components of inflow Alfvén velocity in the magentosheath and in the magnetosphere. A new parameter associated with the Alfvén velocity on both sides is proposed; for both antiparallel reconnection and component reconnection, this new parameter equals the critical shear velocities.
On the role of four-wave mixing effect in the interactions between nonlinear modes of coupled generalized nonlinear Schrödinger equation
Authors: Vishnu Priya N. , Senthilvelan M. , Rangarajan Govindan
Published: December 2019

In this paper, we investigate the effect of four-wave mixing in the interactions among nonlinear waves such as solitons, breathers, and rogue waves of a coupled generalized nonlinear Schrödinger equation. We explore several interesting results including superposition of breather pulses, increment in the number of breather pulses and in amplitudes of breathers, and rogue waves. By strengthening the four-wave mixing parameter, we observe different transformations that occur between different localized structures. For instance, we visualize a transformation from bright soliton to breather form, bright and dark rogue wave to four-petaled rogue wave structures, four-petaled rogue wave to other rogue wave forms, and so on. Another important observation that we report here is that the interaction of a bright soliton with a rogue wave in the presence of the four-wave mixing effect provides interaction between a dark oscillatory soliton and a rogue wave.
Successive orbital ordering transitions in FeV2O4 from first-principles calculation
Authors: Xie Wei , Xing Xianran , Cao Zhanmin
Published: December 2019

The interactions among spin, orbital, and lattice are essential to reveal the complicated phase transitions in FeV2O4, a spinel with spin and orbital degrees of freedom both at Fe and V sites. By employing first-principle calculations, we investigate these interactions to propose the orbital ordering of Fe2+ and V3+ ions. At the Fe sites, orbital states transform from dz2 to dx2−z2, to dx2−y2, and to dy2−z2 accompanying structural phase transitions. At the V sites, one electron occupies the dxy, dxz, dxy, and dyz orbitals. The second electron occupies the dxz±dyz, dxy±dyz, dxz±dyz, and dxy±dxz orbitals, which alternate in the corresponding ab, ac, ab, and bc planes along the c, b, c, and a axes, respectively. The effect of spin-orbital coupling on the orbital ordering of Fe2+ and V3+ ions is not significant. The orbital orderings are driven by the combination of the Jahn-Teller distortions and the electron correlation effect.
Simulating nanocrystal-based solar cells: A lead sulfide case study
Authors: Lin Weyde M. M. , Yazdani Nuri , Yarema Olesya , Volk Sebastian , Yarema Maksym , Kirchartz Thomas , Wood Vanessa
Published: December 2019

Nanocrystal-based solar cells are promising candidates for next generation photovoltaic applications; however, the most recent improvements to the device chemistry and architecture have been mostly trial-and-error based advancements. Due to complex interdependencies among parameters, determining factors that limit overall solar cell efficiency are not trivial. Furthermore, many of the underlying chemical and physical parameters of nanocrystal-based solar cells have only recently been understood and quantified. Here, we show that this new understanding of interfaces, transport, and origin of trap states in nanocrystal-based semiconductors can be integrated into simulation tools, based on 1D drift-diffusion models. Using input parameters measured in independent experiments, we find excellent agreement between experimentally measured and simulated PbS nanocrystal solar cell behavior without having to fit any parameters. We then use this simulation to understand the impact of interfaces, charge carrier mobility, and trap-assisted recombination on nanocrystal performance. We find that careful engineering of the interface between the nanocrystals and the current collector is crucial for an optimal open-circuit voltage. We also show that in the regime of trap-state densities found in PbS nanocrystal solar cells (∼1017 cm−3), device performance exhibits strong dependence on the trap state density, explaining the sensitivity of power conversion efficiency to small changes in nanocrystal synthesis and nanocrystal thin-film deposition that has been reported in the literature. Based on these findings, we propose a systematic approach to nanocrystal solar cell optimization. Our method for incorporating parameters into simulations presented and validated here can be adopted to speed up the understanding and development of all types of nanocrystal-based solar cells.
Impact of capillary drops of complex fluids on a solid surface
Authors: Oishi C. M. , Thompson R. L. , Martins F. P.
Published: December 2019

The drop impact on a solid surface is studied in the context of complex fluids that exhibit viscoplastic, viscoelastic, and thixotropic behavior. The effects of rheology and surface tension are investigated for a range of corresponding dimensionless numbers associated with each phenomenon. Two usual quantities are employed to understand the drop dynamics, namely, the maximum spreading diameter and the time the drop remains in contact with the solid. Another result is the drop shape evolution, captured by displaying selected instants. The first part of the work is dedicated to examine the influence of capillary effects for more real fluids, in the present case, solutions of Carbopol, kaolin, and bentonite whose mechanical properties are taken from experimental measurements reported in the literature. In the second part, we conduct parametric studies varying the dimensionless numbers that govern the problem. We have shown that the influence of surface tension in yield stress materials is less significant and can be negligible when real parameters are input in the model. On the other hand, Newtonian and viscoelastic fluids are more susceptible to surface tension effects. This quantity tends to decrease maximum spreading diameter and decrease contact time due to its resistance in the spreading stage. While inertia, elasticity, and plastic effects favor the drop to spread and to increase its contact time with the solid substrate, a more thixotropic behavior leads to the opposite trend.
Dual-structure microwave-assisted magnetic recording using only a spin torque oscillator
Authors: Greaves Simon John , Saito Waka
Published: December 2019

The selective switching of dual-structure magnetic dots under the influence of the stray field from a spin torque oscillator was investigated. A configuration was found which allowed selective switching of either structure when subject to ac magnetic fields oscillating at 9 GHz and 20 GHz. No other external magnetic fields were needed to switch the magnetisation of the structures.
Comparative study of hybrid-PM variable-flux machines with different series PM configurations
Authors: Liu Faliang , Cheng Luming , Wang Mingqiao , Qiao Guangyuan , Zheng Ping , Yang Hui
Published: December 2019

Aiming at extending the operating speed range and increasing the machine efficiency, three series-configuration hybrid-permanent-magnet variable-flux machines (HPM-VFMs) with both low and high coercive-force magnets are proposed. The magnetization characteristics of the machine with different dimensions of the high coercive-force (HCF) magnet are investigated. Then, in order to improve the contribution rate of the HCF magnet, two improved topologies are presented. The electromagnetic characteristics of the two proposed machines, including back electromotive force (EMF), maximum torque characteristics, magnetization state (MS) variation range and magnetic field distribution, are comprehensively analyzed and compared. The influence of different types of windings on the performance of the machine is also investigated. Finally, the torque-speed curves of the machine under different MSs are given by finite element method (FEM). The results show that the HPM-VFM can operate over a wide-speed range with high efficiency.
Micromagnetic study of soft magnetic nanowires
Authors: Ahmadi F. , Donahue M. J. , Sozer Y. , Tsukerman I.
Published: December 2019

In this paper, micromagnetic analysis of an array of long magnetic nanowires (NWs) embedded in a nonmagnetic matrix is performed. It is found that for NWs with diameters on the order of a hundred nanometers, the anisotropy and exchange energies are negligible, so the total free energy is a sum of the Zeeman and magnetostatic energies. The minimum magnetostatic energy corresponds to the maximum Zeeman energy, whereby half of the NWs are magnetized parallel to the external field, while the rest of the NWs are magnetized antiparallel to the external fields. The study shows a vortex behavior of the magnetic moments in the magnetization reversal process. Additionally, the hysteresis loop area of the nanocomposite is inversely proportional to the NW diameter in the range from 20 to 200 nm. The results pave the way for designing of NW-based devices such as optimized magnetic sensors for biomedical applications with a trade-off between miniaturization and energy loss.
Magnetically modulated orbit for human motion energy harvesting
Authors: Zhao Lin-Chuan , Zou Hong-Xiang , Gao Qiu-Hua , Yan Ge , Liu Feng-Rui , Tan Ting , Wei Ke-Xiang , Zhang Wen-Ming
Published: December 2019

Human energy harvesting for powering wearable or portable electronics has been extensively studied. We propose an electromagnetic energy harvester with a magnetic orbit (EMH-MO) for low-frequency and irregular human motion energy harvesting. A circular uniform low potential orbit is designed using the reasonable arrangement of multiple magnetic fields. Driven by irregular excitations, the moving magnet is magnetically modulated to move more regularly along the noncontact magnetic orbit, which is conducive to electromechanical energy conversion. A theoretical model is established to characterize the proposed energy harvester. Both simulations and experiments indicate that EMH-MO can work effectively under ultralow frequency (<5 Hz) weak excitation. The peak-peak open-circuit voltage is 4.3 V, and the average power is 0.33 mW under a reciprocating motion of 10 Hz and 20 mm. Besides, the EMH-MO can effectively harvest energy from walking, jogging, and running of people with different physical characteristics (chunky males, tall males, and petite females).
Low-damping ferromagnetic resonance in electron-beam patterned, high-Q vanadium tetracyanoethylene magnon cavities
Authors: Franson Andrew , Zhu Na , Kurfman Seth , Chilcote Michael , Candido Denis R. , Buchanan Kristen S. , Flatté Michael E. , Tang Hong X. , Johnston-Halperin Ezekiel
Published: December 2019

Integrating patterned, low-loss magnetic materials into microwave devices and circuits presents many challenges due to the specific conditions that are required to grow ferrite materials, driving the need for flip-chip and other indirect fabrication techniques. The low-loss (α = (3.98 ± 0.22) × 10−5), room-temperature ferrimagnetic coordination compound vanadium tetracyanoethylene (V[TCNE]x) is a promising new material for these applications that is potentially compatible with semiconductor processing. Here, we present the deposition, patterning, and characterization of V[TCNE]x thin films with lateral dimensions ranging from 1 μm to several millimeters. We employ electron-beam lithography and liftoff using an aluminum encapsulated poly(methyl methacrylate), poly(methyl methacrylate-methacrylic acid) copolymer bilayer [PMMA/P(MMA-MAA)] on sapphire and silicon. This process can be trivially extended to other common semiconductor substrates. Films patterned via this method maintain low-loss characteristics down to 25 μm with only a factor of 2 increase down to 5 μm. A rich structure of thickness and radially confined spin-wave modes reveals the quality of the patterned films. Further fitting, simulation, and analytic analysis provide an exchange stiffness, Aex = (2.2 ± 0.5) × 10−10erg/cm, as well as insights into the mode character and surface-spin pinning. Below a micron, the deposition is nonconformal, which leads to interesting and potentially useful changes in morphology. This work establishes the versatility of V[TCNE]x for applications requiring highly coherent magnetic excitations ranging from microwave communication to quantum information.
Understanding the effects of radiative preheat and self-emission from shock heating on equation of state measurement at 100s of Mbar using spherically converging shock waves in a NIF hohlraum
Authors: Nilsen Joseph , Kritcher Andrea L. , Martin Madison E. , Tipton Robert E. , Whitley Heather D. , Swift Damian C. , Döppner Tilo , Bachmann Benjamin L. , Lazicki Amy E. , Kostinski Natalie B. , Maddox Brian R. , Collins Gilbert W. , Glenzer Siegfried H. , Falcone Roger W.
Published: December 2019

Over the last six years many experiments have been done at the National Ignition Facility to measure the Hugoniot of materials, such as CH plastic at extreme pressures, up to 800 Mbar. The “Gbar” design employs a strong spherically converging shock launched through a solid ball of material using a hohlraum radiation drive. The shock front conditions are characterized using x-ray radiography. In this paper we examine the role of radiation in heating the unshocked material in front of the shock to understand the impact it has on equation of state measurements and how it drives the measured data off the theoretical Hugoniot curve. In particular, the two main sources of radiation heating are the preheating of the unshocked material by the high-energy kilo-electron-volt x-rays in the hohlraum and the heating of the material in front of the shock, as the shocked material becomes hot enough to radiate significantly. Using our model, we estimate that preheating can reach 4 eV in unshocked material, and that radiation heating can begin to drive data off the Hugoniot significantly, as pressures reach above 400 Mb.
Phase transition induced spectral tuning of dual luminescent crystalline zinc-phthalocyanine thin films and OLEDs
Authors: Hammer S. , Ferschke T. , Eyb G. v. , Pflaum J.
Published: December 2019

We analyze the impact of the first order structural phase transition between the α- and β-phases in crystalline zinc-phthalocyanine thin films on their luminescent behavior. Upon optical excitation, two intensity maxima governing the dual fluorescence can be attributed to thin film excimer emission of the α-phase at 930 nm and bulk Frenkel exciton emission of the corresponding β-phase at 780 nm. Comprehensive temperature and time dependent studies on the structural phase transition reveal a controllable shift of spectral weight between these two maxima. Applying this approach to thin film devices, we demonstrate the preparation of dual luminescent organic light emitting diodes with tunable emission characteristics in the near infrared, which are of interest as electro-optical units in future hybrid photonic devices.
Direct observation of mobility of thin polymer layers via asymmetric interdiffusion using neutron reflectivity measurements
Authors: Ooe Megumi , Miyata Kairi , Yoshioka Jun , Fukao Koji , Nemoto Fumiya , Yamada Norifumi L.
Published: December 2019

In this study, we investigated the diffusion dynamics at the interface between deuterated poly(methyl methacrylate) (d-PMMA) and protonated poly(methyl methacrylate) (h-PMMA) in two-layered thin films of d- and h-PMMA layers via neutron reflectivity (NR) measurements during isothermal annealing above the glass transition temperature Tg. When Tg of d-PMMA was higher than that of h-PMMA, the d-PMMA layer thickness increased with increasing annealing time ta and, simultaneously, the h-PMMA layer thickness decreased. However, the opposite ta dependence of the layer thicknesses was observed, if the Tg of d-PMMA was decreased by the increase in the fraction of the low-molecular weight d-PMMA: With increasing ta, the d-PMMA layer thickness decreased and the h-PMMA layer thickness increased when Tg of d-PMMA was lower than that of h-PMMA. This change in the ta dependence of the layer thickness was related to the change in the mobility of the d-PMMA layer accompanied by the change in the Tg value of d-PMMA. With the decrease in the d-PMMA layer thickness from 49 nm to 13 nm, when the h-PMMA layer thickness was maintained, the ta dependence of the layer thickness changed and the mobility of the d-PMMA layer dramatically increased. These results suggest that the mobility of thin polymer films can be determined by the observation of interfacial dynamics via NR measurements.
High-voltage vertical Ga2O3 power rectifiers operational at high temperatures up to 600 K
Authors: Wang Boyan , Xiao Ming , Yan Xiaodong , Wong Hiu Yung , Ma Jiahui , Sasaki Kohei , Wang Han , Zhang Yuhao
Published: December 2019

This work presents the temperature-dependent forward conduction and reverse blocking characteristics of a high-voltage vertical Ga2O3 power rectifier from 300 K to 600 K. Vertical β-Ga2O3 Schottky barrier diodes (SBDs) were fabricated with a bevel-field-plated edge termination, where a beveled sidewall was implemented in both the mesa and the field plate oxide. The Schottky barrier height was found to increase from 1.2 eV to 1.3 eV as the temperature increases from 300 K to 600 K, indicating the existence of barrier height inhomogeneity. The net donor concentration in the drift region shows little dependence on the temperature. The reverse leakage current up to 500 V was found to be limited by both the thermionic-field electron injection at the Schottky contact and the electron hopping via the defect states in the depletion region. At 300–500 K, the leakage is first limited by the electron injection at low voltages and then by the hopping in depleted Ga2O3 at high voltages. At temperatures above 500 K, the thermionic field emission limits the device leakage over the entire voltage range up to 500 V. Compared to the state-of-the-art SiC and GaN SBDs when blocking a similar voltage, our vertical Ga2O3 SBDs are capable of operating at significantly higher temperatures and show a smaller leakage current increase with temperature. This shows the great potential of Ga2O3 SBDs for high-temperature and high-voltage power applications.
Deep donors and acceptors in β-Ga2O3 crystals: Determination of the Fe2+/3+ level by a noncontact method
Authors: Lenyk C. A. , Gustafson T. D. , Halliburton L. E. , Giles N. C.
Published: December 2019

Electron paramagnetic resonance (EPR), infrared absorption, and thermoluminescence (TL) are used to determine the Fe2+/3+ level in Fe-doped β-Ga2O3 crystals. With these noncontact spectroscopy methods, a value of 0.84 ± 0.05 eV below the conduction band is obtained for this level. Our results clearly establish that the E2 level observed in deep level transient spectroscopy (DLTS) experiments is due to the thermal release of electrons from Fe2+ ions. The crystals used in this investigation were grown by the Czochralski method and contained large concentrations of Fe acceptors and Ir donors, and trace amounts of Cr donors. Exposing a crystal at room temperature to 325, 375, or 405 nm laser light converts neutral Fe3+ acceptors to their singly ionized Fe2+ charge state and, at the same time, converts a similar number of neutral Ir3+ donors to the Ir4+ charge state. The Fe3+ EPR spectrum slowly recovers after the light is removed, as electrons are thermally released from Fe2+ ions to the conduction band. Most of these released electrons recombine nonradiatively with holes at the deep Ir4+ donors. Using a general-order kinetics model, the analysis of isothermal recovery curves for the Fe3+ EPR signal taken between 296 and 310 K gives the activation energy for the decay of the photoinduced Fe2+ ions. A TL peak, with emitted light having wavelengths longer than 500 nm, occurs near 349 K when a few of the electrons released from Fe2+ ions recombine radiatively with holes at Ir4+ and Cr4+ donors. Photoluminescence and EPR verify the presence of Cr3+ ions.
Positive effects of a Schottky-type diode on unidirectional resistive switching devices
Authors: Lee Dong Kyu , Kim Gun Hwan , Sohn Hyunchul , Yang Min Kyu
Published: December 2019

In this research, 1-diode (1D), 1-resistor (1R), and 1D1R stacked devices were separately fabricated using a 400 nm diameter hole substrate. It was observed that, in 1D1R, there was a fivefold increase in endurance and 52% improvement in the resistance distribution characteristics compared to those of 1R. It could be surmised that the stacked diode not only plays the role of a selection device to minimize the interference in the crossbar array type resistive switching device but also acts as an external load resistor to suppress the unexpected current overflow during resistance transition. These experimental results demonstrated that the optimized diode shows significant promise as a unidirectional resistive switching device for memory-related applications.
Vibronic structure and predissociation dynamics of 2-methoxythiophenol (S1): The effect of intramolecular hydrogen bonding on nonadiabatic dynamics
Authors: Lim Jean Sun , You Hyun Sik , Kim So-Yeon , Kim Junggil , Park Young Choon , Kim Sang Kyu
Published: December 2019

Vibronic spectroscopy and the S–H bond predissociation dynamics of 2-methoxythiophenol (2-MTP) in the S1 (ππ*) state have been investigated for the first time. Resonant two-photon ionization and slow-electron velocity map imaging (SEVI) spectroscopies have revealed that the S1–S0 transition of 2-MTP is accompanied with the planar to the pseudoplanar structural change along the out-of-plane ring distortion and the tilt of the methoxy moiety. The S1 vibronic bands up to their internal energy of ∼1000 cm−1 are assigned from the SEVI spectra taken via various S1 vibronic intermediate states with the aid of ab initio calculations. Intriguingly, Fermi resonances have been identified for some vibronic bands. The S–H bond breakage of 2-MTP occurs via tunneling through an adiabatic barrier under the S1/S2 conical intersection seam, and it is followed by the bifurcation into either the adiabatic or nonadiabatic channel at the S0/S2 conical intersection where the diabatic S2 state (πσ*) is unbound with respect to the S–H bond elongation coordinate, giving the excited (Ã) or ground (X̃) state of the 2-methoxythiophenoxy radical, respectively. Surprisingly, the nonadiabatic transition probability at the S0/S2 conical intersection, estimated from the velocity map ion images of the nascent D fragment from 2-MTP-d1 (2-CH3O–C6H4SD) at the S1 zero-point energy level, is found to be exceptionally high to give the X̃/Ã product branching ratio of 2.03 ± 0.20, which is much higher than the value of ∼0.8 estimated for the bare thiophenol at the S1 origin. It even increases to 2.33 ± 0.17 at the ν452 mode (101 cm−1) before it rapidly decays to 0.69 ± 0.05 at the S1 internal energy of about 2200 cm−1. This suggests that the strong intramolecular hydrogen bonding of S⋯D⋯OCH3 in 2-MTP at least in the low S1 internal energy region should play a significant role in localizing the reactive flux onto the conical intersection seam. The minimum energy pathway calculations (second-order coupled-cluster resolution of the identity or time-dependent-density functional theory) of the adiabatic S1 state suggest that the intimate dynamic interplay between the S–H bond cleavage and intramolecular hydrogen bonding could be crucial in the nonadiabatic surface hopping dynamics taking place at the conical intersection.
Another view of the maximum principle for infinite-horizon optimal control problems in economics
Authors: Aseev S. M. , Veliov V. M.
Published: December 2019

The authors present their recently developed complete version of the Pontryagin maximum principle for a class of infinite-horizon optimal control problems arising in economics. The main distinguishing feature of the result is that the adjoint variable is explicitly specified by a formula analogous to the Cauchy formula for solutions of linear differential systems. In certain situations this formula implies the ‘standard’ transversality conditions at infinity. Moreover, it can serve as an alternative to them. Examples demonstrate the advantages of the proposed version of the maximum principle. In particular, its applications are considered to Halkin’s example, to Ramsey’s optimal economic growth model, and to a basic model for optimal extraction of a non-renewable resource. Also presented is an economic interpretation of the characterization obtained for the adjoint variable.

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