bluuebunny/crossref_metadata_2025 huggingface dataset:
Day‐ahead electric vehicle aggregator bidding strategy using stochastic programming in an uncertain reserve market
Authors: Han Bing , Lu Shaofeng , Xue Fei , Jiang Lin
Published: April 2019

Electric vehicle (EV) as dynamic energy storage systems could provide ancillary services to the grids. The aggregator could coordinate the charging/discharging of EV fleets to attend the electricity market to get profits. However, the aggregator profits are threatened by the uncertainty of the electricity market. In this study, an EV aggregator bidding strategy in the day‐ahead market (DAM) is proposed, both reserve capacity and reserve deployment are considered. The novelty of this study is that: (i) The uncertainty of the reserve developments is addressed in terms of both time and amount. (ii) Scenario‐based stochastic programming method is used to maximise the average aggregator profits based on one‐year data. The proposed method, jointly considers the reserve capacity in the DAM and the reserve deployment requirements in the real‐time market (RTM). (iii) The risk of the deployed reserve shortage is addressed by introducing a penalty factor in the model. (iv) An owner‐aggregator contract is designed, which is used to mitigate the economic inconsistency issue between the EV owners and the aggregator. Results verify the performance of the proposed strategy, that is the average aggregator profits are guaranteed by maximising reserve deployment payments and mitigating the penalties in RTM and thus the reserve deployment requirements uncertainty is well managed.
Miniaturised microstrip patch design based on highly capacitive defected ground structure with fractal boundary for X‐band microwave communications
Authors: Mishra Guru Prasad , Mangaraj Biswa Binayak
Published: April 2019

This article proposes a new class of miniaturised microstrip patch design for wireless communications at 10 GHz. Antenna miniaturisation is achieved here by loading a highly capacitive modified Minkowski fractal (type‐2) defected ground structure (MFDGS‐II) exactly beneath the center of the radiating patch. The proposed methodology involves sensitivity analysis to select best DGS configuration. The resonant frequency corresponding to the patch is reduced from 16.832 GHz to 10 GHz incorporating MFDGS‐II without any change in the physical size of the antenna. This enables a patch size reduction of as high as 68% and an overall volumetric reduction of 84% along with an improvement in bandwidth and efficiency of the antenna. A prototype of the proposed antenna is fabricated, and its performance parameters are measured. An equivalent transmission‐line model is presented to explain the theoretical background behind the shift in the resonant frequency of the antenna. Our antenna prototype with a lower patch size of 0.20λ0 × 0.15λ0, exhibits an impedance bandwidth of 270 MHz, a realised gain of 3.2 dBi with radiation efficiency of 98% centered at 10 GHz. The proposed compact antenna has the potential to meet the practical requirements for portable X‐band wireless sensor applications.
Three‐phase buck–boost PFC rectifier with common‐mode free output voltage and low semiconductor blocking voltage stress
Authors: Miniböck Johann , Mauerer Mario , Huber Jonas E. , Kolar Johann W.
Published: April 2019

Three‐phase buck–boost power‐factor correction (PFC) rectifiers are characterised by a unity power‐factor mains behaviour and/or sinusoidal input currents and are providing a wide‐output voltage range. In this study, an extension of a state‐of‐the‐art three‐phase buck–boost PFC rectifier topology is proposed. The DC output of the new topology does not suffer from a high‐frequency common‐mode voltage with respect to the (grounded) mains star point, which alleviates electromagnetic interference concerns. Also, the blocking voltage requirements of the AC‐side switches are reduced significantly (almost by a factor of two for a 400 V line‐to‐line mains and a 400 V DC output), which facilitates a broad selection of cost‐effective power semiconductors for the system's realisation. The rectifier can be controlled with a simple feedback system and the concept is especially suitable for low‐power applications. A 1 kW hardware demonstrator is employed to verify the results of theoretical considerations. The system seamlessly operates in the buck and boost regime and achieves conversion efficiencies of 95.3% and mains current total harmonic distortion figures in the range of 1–5%.
3D SAR coherent change detection for monitoring the ground under a forest canopy
Authors: Pincus Paul , Preiss Mark
Published: April 2019

A method of applying repeat‐pass synthetic aperture radar coherent change detection to forest‐covered terrain is proposed and analysed. Backscatter from the canopy can be suppressed whilst the complex reflectivity of the ground is preserved by vertically beamforming multiple across‐track image channels acquired on each pass. A multichannel coherence metric is formulated assuming a dual‐layer (surface and volume) model of the scene. The optimal volume suppression is derived and then quantified using the interferometric random‐volume‐over‐ground model for all pairs of channels. It is shown that good volume suppression is achievable with just three channels, and the resulting coherence estimation is reasonably accurate if the effective ground and volume scattering responses are of similar strength. Significant degradation occurs if knowledge of the ground height is inaccurate. Two aspects of radar design are discussed in detail: the selection of a wavelength that permits both adequate foliage penetration and high sensitivity to subtle changes in the ground clutter, and the sensitivity above noise required to measure the ground backscatter, which is typically weak at foliage‐penetrating wavelengths.
Multiple nanoparticles for improvement of thermal and dielectric properties of oil nanofluids
Authors: Mansour Diaa‐Eldin A. , Shaalan Essam M. , Ward Sayed A. , El Dein Adel Z. , Karaman Hesham S. , Ahmed Hanaa M.
Published: April 2019

To improve the performance and increase the lifetime of oil‐filled transformers, the thermal and dielectric properties of the transformer oil should be enhanced. Recently, nanotechnology was used as an effective science in the field of transformer oil development. In this study, barium titanate (BT) nanoparticles were inserted into the base transformer oil by a concentration of 0.005 g/L as an individual nanofluid sample (INFS). This insertion enhances the heat transfer coefficient by 33% but the breakdown voltage (BDV) was decreased by >10%. To overcome this problem of dielectric properties degradation, other three hybrid nanofluid samples (HNFS) were prepared using three different types of metal oxide (MO) nanoparticles; titania, alumina, and silica. These samples were prepared by adding a concentration 0.01 g/L of MO nanoparticles together with 0.005 g/L of BT nanoparticles into the oil. The thermal and dielectric properties of HNFS were measured to study the behaviour of nanoparticles hybridisation on transformer oil properties. HNFS using titania nanoparticles provided the best composition regarding either BDV or heat transfer coefficient. Dynamic light scattering (DLS) technique was used to evaluate the particle size distribution of hybrid nanoparticles and to clarify the corresponding physical mechanisms behind the obtained enhancement.
Hybrid control approach for fast switching MMCs
Authors: Schnarrenberger Mathias , Bräckle Dennis , Braun Michael
Published: April 2019

This study presents a new hybrid control approach for different control and switching frequencies for converters of the modular multi‐level converter (MMC) family. Using this concept, it is possible to achieve a higher switching frequency and output voltage update frequency than the MMC control frequency. The closed‐control loop can be calculated on a digital signal processor in floating‐point arithmetic. Only the resulting arm voltages and output voltages must be calculated with the switching frequency, e.g. on a field programmable gate array in fixed‐point arithmetic.
Comparison of conventional and cascode drive of SiC BJTs
Authors: McNeill Neville , Broadmeadow Mark A. H. , Roscoe Nina , Finney Stephen
Published: April 2019

This study compares simple conventional and cascode driver circuits for the SiC bipolar junction transistor (BJT). A low‐voltage silicon metal‐oxide‐semiconductor field‐effect transistor is used in the emitter of the BJT to realise the cascode variant. The circuits are experimentally evaluated when switching a current of 2.5 A and a voltage of 600 V in a buck converter.
Dynamic voltage stability of unbalanced distribution system with high penetration of single‐phase PV units
Authors: Islam Monirul , Mithulananthan Nadarajah , Hossain Jahangir , Shah Rakibuzzaman
Published: April 2019

Dynamic voltage instability (DVI) issues are the primary concern in low‐voltage distribution network (DN) due to growing integration of low‐inertia compressor motor loads such as air‐conditioner and refrigerator. The concern of DVI is likely to increase owing to high penetration of rooftop type single‐phase photovoltaic (PV) units in DN. On the other hand, DNs are inherently unbalanced as a result of load and line characteristics along with unbalanced PV penetration. This paper examines the impact of imbalance on the dynamic voltage stability (DVS) in DN and provides solutions to mitigate any adverse effects. Dynamic models of the single‐phase PV units are developed and utilised in the paper. The degree of unbalanced is defined first, and then its impact on the DVS is investigated. From the investigation, it is observed that degree of instability is increased with the increment of imbalance. The paper has also proposed a mitigation strategy i.e. reactive power injection by PV inverter. Case studies are conducted on modified IEEE 4 bus system which represents a low‐voltage DN. Results reveal that reactive power injection by PV inverter can improve the DVS by mitigating the impact of unbalance.
Analysis and calculation method of critical voltage of DC commutation process considering AC system single‐phase fault moments
Authors: Zhang Jingqiu , Li Yongli , Chen Xiaolong
Published: April 2019

This paper takes a close research on the impact of voltage reduction in a single phase as well as its occurring moments on commutation failures (CFs). When there is a sudden voltage reduction in a single phase, the change rule of post‐fault magnitudes and phases of commutation voltages is researched theoretically. On the basis of the change characteristic, valves that are most probable to suffer from CFs are carefully elaborated. Moreover, a method for calculating critical voltage of a single phase considering different fault moments is developed. As long as the phase voltage is lower than the critical voltage, it may result in a CF. In addition, the change regularity of critical voltage along with different fault moments and phases is given. All the analysis and theoretical calculation results are validated by simulation in PSCAD/EMTDC.
Leakage current reduction for a double‐leg boost converter by switching transition synchronisation
Authors: Zehelein Matthias , Ruthardt Johannes , Nitzsche Maximillian , Tymosch Tobias , Roth‐Stielow Jörg
Published: April 2019

With wide‐bandgap transistors, the leakage current through the parasitic transistor to heat sink capacitance is increased with the operation at higher switching transition voltage slopes. This study presents a modulation synchronisation method for a double‐leg boost converter to reduce these leakage currents. Having a similar leakage current path, the transistors turn‐on transition of one leg is synchronised on the turn‐off transition of the second leg.
Dual modular multilevel converter with shared capacitor sub‐module for MV open‐end stator winding machine drives
Authors: Diab Mohamed S. , Massoud Ahmed M. , Ahmed Shehab , Williams Barry W.
Published: April 2019

This paper proposes a new dual modular multilevel converter (MMC) topology as a medium‐voltage drive for adjustable‐speed applications incorporating open‐end stator winding machines. A novel concept of sharing one capacitor between each two adjacent‐arm sub‐modules (SMs) of MMC phase‐legs, operating with out‐of‐phase modulation, is realised through new SM arrangement. This concept allows the MMC to utilise half the number of the SM capacitors, compared to a traditional MMC topology. Additionally, the sizing requirement of the shared capacitor is diminished, which significantly reduces the volume of the drive system and its stored energy. The switching scheme of the shared capacitor between two oppositely modulated SMs eliminates the problem of capacitor wide‐voltage fluctuations, independent of the operating frequency. Further, the proposed MMC can efficiently operate at near zero frequency; therefore, a machine speed‐range from zero speed to the rated speed is possible under rated torque operating condition. The proposed MMC topology is elucidated in detail, and its effective performance is verified through simulation.
Performance of high‐power thomson coil actuator excited by a current pulse train
Authors: Vilchis‐Rodriguez Damian S. , Shuttleworth Roger , Smith Alexander C. , Barnes Mike
Published: April 2019

This paper uses FEA simulations to investigate the behaviour of a high‐speed, high‐power Thomson coil (TC) actuator suitable for HVDC protection applications, when excited by a double discharge. The influence of the resulting pulse train on the amplitude of observed armature vibration is investigated. The significance of the pulse train on the device electrical to mechanical energy conversion efficiency is assessed and compared with the efficiency obtained using the conventional single discharge approach.
Design of a three‐phase 100 A linear amplifier for power‐hardware‐in‐the‐loop machine emulation
Authors: Fischer Manuel , Malić Robert , Tröster Nathan , Ruthardt Johannes , Roth‐Stielow Jörg
Published: April 2019

Here, the setup of a three‐phase 100 A linear amplifier is proposed. This work focusses on the use of this linear amplifier as power element for machine‐emulation. In contrast to common power electronics, a linear amplifier avoids ripple content in the output current caused by switched‐mode operation.
Comparison of DC linear and non‐linear models for multi‐terminal VSC HVDC networks
Authors: Carmona‐Sanchez Jesus , Marjanovic Ognjen , Barnes Mike , Wang Wenyuan
Published: April 2019

The analysis and control design of multi‐terminal VSC‐HVDC systems requires a linearised model of these inherently non‐linear systems. This paper develops such a model, from converter to multi‐terminal system, discusses the key concepts and shows its use for some test cases. The linearised model is simulated in Matlab, and it is compared against the non‐linear model results from an established DEM PSCAD model.
Research on motor with nanocrystalline soft magnetic alloy stator cores
Authors: Nonaka Tuyoshi , Zeze Shingo , Makino Shogo , Ohto Motomichi
Published: April 2019

The authors built a prototype motor with NANOMET stator cores. NANOMET is one of the several nanocrystalline soft magnetic alloys [1]. Motor iron loss and other characteristics were compared with 35A360 (Japanese Industrial Standards), which is one of the widely used conventional electromagnetic steel sheet, and the effectiveness of the new material is shown. This study describes the method to build NANOMET stator cores, and presents the evaluation results of the prototype motor.
Low-noise femtosecond Cherenkov fiber laser, continuously tunable across the entire red-green-blue spectral range
Authors: Liu Xiaomin , Lægsgaard Jesper , Iegorov Roman , Svane Ask , Ilday F. Ömer , Tu Haohua , Boppart Stephen A. , Turchinovich Dmitry
Published: April 2019

Low-noise Cherenkov wave conversion in a tapered photonic crystal fiber turns a standard, fixed-wavelength femtosecond laser into an extremely widely-tunable source. Here we show the continuous laser tunability across the entire red-green-blue range.
Multi-mJ mid-IR light bullets in air
Authors: Shumakova Valentina , Ališauskas Skirmantas , Baltuška Andrius , Malevich Pavel , Voronin Alexander , Mitrofanov Alexander , Sidorov-Biryukov Dmitriy , Zheltikov Aleksey , Kartashov Daniil , Pugžlys Audrius
Published: April 2019

We examine mid-IR light bullets generated in ambient air. 2-optical cycle pulses confined in space are generated in filamentation regime. Few-fold solitonic self-compression is achieved for strongly chirped mid-IR pulses.
Millijoule-level sub-cycle pulses from two channels of a parallel parametric waveform synthesizer
Authors: Scheiba Fabian , Rossi Giulio Maria , Mainz Roland E. , Yang Yudong , Cirmi Giovanni , Kärtner Franz X.
Published: April 2019

We report on an optical synthesis of two compressed channels from our parametric waveform synthesizer, leading to a 0.6 mJ 3.4 fs pulse (3.2 fs transform limited) with a central wavelength of 1.8 /an, corresponding to 0.6 optical cycles.
Robust enhancement of high harmonic generation via attosecond control of ionization
Authors: Bruner Barry D. , Arusi-Parpar Talya , Krüger Michael , Pedatzur Oren , Orenstein Gal , Azoury Doron , Dudovich Nirit
Published: April 2019

We demonstrate up to two orders of magnitude enhancements in high harmonic generation efficiency via sub-cycle control and scaling of the ionization rate in a two colour laser field.
Vibrational Interferometry Enables Single-Scan Acquisition of all χ(3)Multi-Dimensional Coherent Spectra
Authors: Travis M. Autry , Moody Galan , McDonald Corry , James M. Fraser , Richard P. Mirin , Kevin L. Silverman
Published: April 2019

We demonstrate a new method for multidimensional coherent spectroscopy of nanostructures. We use a heterodyne technique implemented with a confocal microscope to record the amplitude and phase of all degenerate third-order wave-mixing processes.
A first-principles simulation method for ultra-fast nano-optics
Authors: Uemoto Mitsuharu , Yabana Kazuhiro , Sato Shunsuke A. , Hirokawa Yuta , Boku Taisuke
Published: April 2019

We develop a computational approach for ultrafast nano-optics based on first-principles time-dependent density functional theory. Solving Maxwell equations for light propagation and time-dependent Kohn-Sham equation for electron dynamics simultaneously, intense and ultrashort laser pulse interaction with a dielectric nano-structure is described taking full account of nonlinear effects. As an illustrative example, irradiation of a pulsed light on silicon nano-sphere system is presented.
Characterizing divergent spin-orbit coupling effects on ultrafast nonradiative decay in transition-metal compounds
Authors: William P. Carbery , Daniel B. Turner
Published: April 2019

Two-dimensional electronic spectroscopy reveals divergent, spin-orbit coupling mediated, electronic relaxation dynamics in iridium(IV) hexa-bromide ([IrB6]2-) and the ruthenium(II)-based DSSC dye N719.
Cooling dynamics of electrons in MAPbBr3 probed in the deep-UV
Authors: Rossi Thomas Charles , Wang Lijie , Oppermann Malte , Chen Peter , Chiang Yu-Hsien , Tsai Ming-Chang , Shih Chun-Hua , Guo Tsung-Fang , Chergui Majed
Published: April 2019

Transient absorption in the Visible and in the deep-UV is performed on MAPbBr3 thin films with 3.1 eV pump excitation. The UV probe can access higher order transitions in the material exploring different high-symmetry points of the Brillouin zone. Uncorrelated electron-hole pairs are generated within the instrument response function of 150 fs. The photobleaching at 3.3 eV shows that electron cooling happens in ~ 1 ps.
Molecular ionization enhancement by charge rearrangement at high X-ray intensity
Authors: Inhester Ludger , Hanasaki Kota , Toyota Koudai , Hao Yajiang , Vendrell Oriol , Son Sang-Kil , Santra Robin
Published: April 2019

We simulated the multi-photon multi-ionization dynamics of an iodomethane molecule, CH3I, exposed to ultraintense and ultrashort x-ray pulses. The strong ionization causes electronic charge rearrangement in the molecule that leads to an enhanced total charge.
Solvatochromic and Ligand Effects in Ultrafast Intramolecular Electron Transfer in Fe-based Molecular Photosensitizers
Authors: Kunnus Kristjan , Li Lin , Reinhard Marco , Koroidov Sergey , Kjaer Kasper S. , Ledbetter Kathryn , Hong Kiryong , Biasin Elisa , Cordones-Hahn Amy , Gaffney Kelly J.
Published: April 2019

Metal-to-ligand charge-transfer (MLCT) excited state lifetimes of [Fe(CN)4(2,2’-bipyridine)]2- and [Fe(CN)4(2,3-bis(2-pyridyl)pyrazine)]2-exhibit strong solvent and ligand dependence. We conclude that these effects can be described with Marcus-like model where changes in the MLCT energy correspond directly to the changes in the electron transfer driving force and all the other factors (e.g. reorganization energy) can be considered constant.
Konditionierende Psychose – Eine neue Form der Epilepsiepsychose? Ein Fallbericht über die bidirektionale Verknüpfung von Epilepsie und Psychose
Authors: Öhm Sascha , Kratz Torsten
Published: April 2019

Einleitung Epilepsiepsychosen bzw. Epilepsie und Psychosen stellen eine wichtige neuropsychiatrische Schnittstelle im klinischen Alltag dar. Epilepsie und Psychosen sind jedoch nicht nur durch klinische Phänomene eng miteinander verknüpft, sondern könnten sich auch bei der Entstehung gegenseitig bedingen. So gibt es Hinweise, dass epileptische Anfälle über viele Jahre chronische Psychosen induzieren können. Zur Klärung der Frage, ob Psychosen auch Epilepsie auslösen können, bedarf es weiterer Belege.

Fallbericht Wir berichten den Fall eines 28-jährigen Patienten mit einer chronischen Psychose seit der Kindheit, der im Verlauf eine Epilepsie entwickelt hat. Unter medikamentöser Behandlung remittierten Psychose und epileptische Anfälle.

Ergebnis 1.) Der vorliegende Fall könnte ein weiterer Beleg für die bidirektionale Kausalität von Epilepsie und Psychose sein. 2.) Als Sonderform einer interiktalen Psychose könnte der Begriff konditionierende Psychose die aktuelle Klassifikation ergänzen.
Synthesis of Sterically Congested Carbamates of Carbohydrates through Organic Base Catalysis
Authors: Chen Anji , Wang Dan , Samankumara Lalith P. , Wang Guijun
Published: April 2019

4,6-O-Benzylidene acetal protected α-methoxy d-glucose and d-glucosamine are useful building blocks for the syntheses of carbohydrate derivatives and functional molecular assemblies. In this research, we have developed a general method for the preparation of C-3 carbamate derivatives of densely functionalized glucose and glucosamine with isocyanates using organic bases as catalysts. Without a suitable catalyst, the C-3 hydroxy group of the glucosamine derivative could not be converted into the corresponding carbamates when treated with isocyanates. Several organic bases were screened as the catalysts for the reactions, and we discovered that 5.0 mol% of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) was an effective catalyst for the carbamoylation reaction. A library of both alkyl and aryl carbamate derivatives of the two sterically congested carbohydrates have been effectively synthesized using the current method.
Management of Life-Threatening Hemorrhage from Maxillofacial Firearm Injuries Using Foley Catheter Balloon Tamponade
Authors: Jose Anson , Arya Saurabh , Nagori Shakil Ahmed , Thukral Himanshu
Published: April 2019

The aim of this study is to evaluate the efficacy of Foley catheter in the management of hemorrhage from penetrating maxillofacial injuries in austere environment. This retrospective cohort study evaluated all penetrating head and neck trauma caused by firearm injuries reported to a military hospital at a forward aid location during 2015-2017. Foley catheter was used in the emergency management of bleeding in 11 cases. The effectiveness of this technique in controlling hemorrhage, its indication, contraindications, and complications has been explained. Out of 26 penetrating injuries received during the time period, 11 patients underwent Foley catheter balloon tamponade for the control of hemorrhage. Ten out of 11 patients responded adequately to balloon tamponade. One patient with a bullet lodged inside the neck underwent immediate surgical exploration for its removal and repair of internal jugular vein. No neurological deficits or complications were noted in any of the patients. Foley catheter balloon tamponade is very effective in managing hemorrhage from head and neck penetrating injuries. It significantly reduces the mortality by controlling bleeding from the major vessels especially in a combat environment.
Determining the orientation of the flexural modes of a thermally driven microwire cantilever
Authors: Fu Chenghua , Deng Wen , Zou Lvkuan , Zhu Wanli , Xu Feng , Wang Ning , Xue Fei
Published: April 2019

Mechanical resonators are excellent transducers for ultrasensitive detection applications. Recent advances such as vectorial force sensing and ultrahigh-resolution mass spectra rely on the identification of two flexural vibrational modes of a resonator. The orientations of the flexural modes with respect to the incident optical axis are crucial parameters for a cantilevered resonator. Previous methods have adopted complex experimental setups using quadrant photodetectors or have required simultaneous detection of two flexural modes of the cantilever. In this paper, we propose a method for determination of the orientations of the flexural vibrations of a cantilever using a microlens optical fiber interferometer that takes both the light interference and the lateral light scattering of the cantilever into account. We demonstrated the method by experimentally determining the orientation of the first three flexural vibrational modes of a thermally driven microwire. Our method can be used to characterize individual flexural modes with arbitrary orientations and thus provides a new tool for detecting vectorial forces.
Structural, electronic, and optical properties of inhomogeneous Ca1−xMgxO alloys
Authors: Almeida-Neto F. W. Q. , Santos-Castro G. , da Silva M. B. , de Sousa J. S. , Caetano E. W. S. , Lima-Neto P. , Freire V. N.
Published: April 2019

The structural, electronic, and optical properties of homogeneous and inhomogeneous Ca1−xMgxO alloys are studied with the density functional theory (DFT) under the assumption of polymorphism. Large supercells (2×2×2 and above) with different lattice symmetries and varying Mg molar fraction x were constructed, representing distinct solid phases that may coexist in micro/nanodomains of inhomogeneous alloys. We demonstrate that these polymorphs exhibit rich phenomenology like similar formation enthalpies for a given concentration x, but different electronic and optical properties. For example, Ca0.5Mg0.5O may have crystallites with four possible lattice symmetries using a 2×2×2 supercell for its description, with bandgaps varying between 3.26 eV (direct) and 4.46 eV (indirect). The DFT-simulated X-ray diffraction shows that polymorphism causes broadening and shift of the diffraction peaks. We also performed a detailed calculation of the bandgaps, optical absorption, and dielectric constants as a function of x for each polymorph, and they exhibit a structured bandgap behavior with maxima and minima in the 0.0<x<1.0 range, which is in marked contrast to Vegard’s law rule of mixtures. We also report a direct-to-indirect bandgap transition occurring between 0.072≤x≤0.1094 for the FM3¯M symmetry.
Selected transport, vibrational, and mechanical properties of low-dimensional systems under strain
Authors: Celebonovic V. , Pesic J. , Gajic R. , Vasic B. , Matkovic A.
Published: April 2019

The aim of the present paper is to discuss some recent results concerning the behavior of low-dimensional materials under strain. This concerns the electrical conductivity calculations of 1D structures under strain, within the Hubbard model, as well as ab initio investigations of phonon, electron-phonon, and superconducting properties of doped graphene and MgB2 monolayer. Two different experimental approaches to strain engineering in graphene have been considered regarding local strain engineering on monolayer flakes of graphene using atomic force microscopy and dynamic plowing lithography technique as well as the effects of mechanical straining on liquid phase exfoliated graphene and change of sheet resistance of graphene films.
Taming chaos to sample rare events: The effect of weak chaos
Authors: Leitão Jorge C. , Lopes João M. V. P. , Altmann Eduardo G.
Published: April 2019

Rare events in nonlinear dynamical systems are difficult to sample because of the sensitivity to perturbations of initial conditions and of complex landscapes in phase space. Here, we discuss strategies to control these difficulties and succeed in obtaining an efficient sampling within a Metropolis-Hastings Monte Carlo framework. After reviewing previous successes in the case of strongly chaotic systems, we discuss the case of weakly chaotic systems. We show how different types of nonhyperbolicities limit the efficiency of previously designed sampling methods, and we discuss strategies on how to account for them. We focus on paradigmatic low-dimensional chaotic systems such as the logistic map, the Pomeau-Maneville map, and area-preserving maps with mixed phase space.
Study the JSC loss of full area SHJ solar cells caused by edge recombination
Authors: Li Xingbing , Yang Lifei , Zhang Wenbin , Wang Qi
Published: April 2019

We have demonstrated that the edge recombination effect exists in full area industrial silicon heterojunction (SHJ) solar cells, which can cause significant short-circuit current density (JSC) loss. The mechanism behind this observation was studied using different SHJ cell structures. We demonstrated further that this JSC loss effect can be suppressed effectively by simply controlling the gap between the edge of the transparent conductive oxide layer and that of the cell. Using this strategy, the average JSC of our state-of-art SHJ solar cells was enhanced by 0.36 mA/cm2, resulting in an average efficiency gain of 0.28% absolute.
First-principles modeling of GaN(0001)/water interface: Effect of surface charging
Authors: Sato Masahiro , Imazeki Yuki , Fujii Katsushi , Nakano Yoshiaki , Sugiyama Masakazu
Published: April 2019

The accumulation properties of photogenerated carriers at the semiconductor surface determine the performance of photoelectrodes. However, to the best of our knowledge, there are no computational studies that methodically examine the effect of “surface charging” on photocatalytic activities. In this work, the effect of excess carriers at the semiconductor surface on the geometric and electronic structures of the semiconductor/electrolyte interface is studied systematically with the aid of first-principles calculations. We found that the number of water molecules that can be dissociated follows the “extended” electron counting rule; the dissociation limit is smaller than that predicted by the standard electron counting rule (0.375 ML) by the number of excess holes at the interface. When the geometric structure of the GaN/water interface obeys the extended electron counting rule, the Ga-originated surface states are removed from the bandgap due to the excess holes and adsorbates, and correspondingly, the Fermi level becomes free from pinning. Clearly, the excess charge has a great impact on the interface structure and most likely on the chemical reactions. This study serves as a basis for further studies on the semiconductor/electrolyte interface under working conditions.
An anisotropic four-component spin chain with integrable boundary terms
Authors: Xue Panpan , Li Guang-Liang , Cao Junpeng , Li Jiao , Hao Kun , Yang Tao , Yang Wen-Li
Published: April 2019

The anisotropic four-component spin chain with integrable off-diagonal boundary terms is studied by the nested off-diagonal Bethe ansatz method. Based on the intrinsic properties of the associated R-matrix, the recursive operator product identities of the fused transfer matrices are obtained by using the fusion. The asymptotic behaviors and the values of fused transfer matrices at certain special points are derived explicitly. The nested inhomogeneous T − Q relations of the system are constructed, and the self-consistency of these relations is demonstrated. The method and the results can be applied to study the eigenvalue problems of multicomponent integrable models with open boundaries.
Modification of ITO anodes with self-assembled monolayers for enhancing hole injection in OLEDs
Authors: An Dong , Liu Hongli , Wang Shirong , Li Xianggao
Published: April 2019

Increasing carrier injection efficiency is an important way to improve the performance of organic light-emitting diodes (OLEDs). In this work, self-assembled monolayers (SAMs) were formed on indium tin oxide (ITO) anodes with different aromatic carboxylic acids. The relationship between the molecular structure and its effect on modification was investigated. The presence of monolayers was verified by X-ray photoelectron spectroscopy. Water contact angle tests show that the surface energy of ITO has decreased after SAM modification which is beneficial to obtain a flat film of organic functional materials on ITO. In addition, the data of ultraviolet photoelectron spectroscopy reveal that the work function of SAM-ITO with different molecules modified has increased to varying degrees. Therefore, a no-hole injection layer (HIL) device whose structure is ITO/SAMs/α-naphthyphenylbiphenyldiamine (NPB) (25 nm)/tris(8-hydroxyquindino) aluminum (III) (Alq3) (60 nm)/LiF (1 nm)/Al (100 nm) was designed to explore the impact of SAMs on OLEDs. OLED performance shows SAMs of 9H-carbazole-2-carboxylic acid (CzCA) facilitating the device to obtain superior luminescence performance, with a turn-on voltage of 2.6 V and a maximum luminance of 30 418 cd·m−2. In order to study the mechanism, the highest occupied molecular orbital (HOMO) and other information of SAM molecules were calculated by Gaussian 09. According to the result, the HOMO of CzCA appears as a special “through-band,” which is beneficial to the hole transport. It is considered that when the HOMO of the SAM molecule is in a shape favorable for hole transport, hole injection will be facilitated and the performance of the OLEDs will be improved greatly.
Imaging microscopic electronic contrasts at the interface of single-layer WS2 with oxide and boron nitride substrates
Authors: Ulstrup Søren , Koch Roland J. , Schwarz Daniel , McCreary Kathleen M. , Jonker Berend T. , Singh Simranjeet , Bostwick Aaron , Rotenberg Eli , Jozwiak Chris , Katoch Jyoti
Published: April 2019

The electronic properties of devices based on two-dimensional materials are significantly influenced by interactions with the substrate and electrode materials. Here, we use photoemission electron microscopy to investigate the real- and momentum-space electronic structures of electrically contacted single-layer WS2 stacked on hBN, SiO2, and TiO2 substrates. Using work function and X-ray absorption imaging, we single-out clean microscopic regions of each interface type and collect the valence band dispersion. We infer the alignments of the electronic bandgaps and electron affinities from the measured valence band offsets of WS2 and the three substrate materials using a simple electron affinity rule and discuss the implications for vertical band structure engineering using mixed three- and two-dimensional materials.
A new class of reaction path based potential energy surfaces enabling accurate black box chemical rate constant calculations
Authors: Steffen Julien
Published: April 2019

A new method for constructing a full-dimensional potential energy surface representation in black-box fashion for an arbitrary reaction is presented. With limited knowledge of the system and with a limited number of reference-level data points, it is possible to calculate reaction rate constants with high quality. Building on our recently published application of Grimme’s quantum-mechanically derived force field (QMDFF) and its empirical valence bond extension EVB-QMDFF to rate constant calculations, an improved EVB coupling method with local corrections was developed in order to avoid spurious problems for certain systems and hence to achieve an even wider range of applicability. A given reaction path (RP) is modeled as a parametric curve via cubic spline interpolation; regions offside this path are then extrapolated with quadratic Taylor series, and regions around the transition state are corrected by introduction of direct reference interpolation; the method is named transition region corrected RP-EVB-QMDFF (TREQ). To verify the quality of TREQ, six reactions were chosen for which full-dimensional analytical potential surfaces are available in the literature. Chemical reaction rates were calculated with ring polymer molecular dynamics on the reference surfaces as well as on the TREQ surfaces resulting in excellent agreement.
Quantum system structures of quantum spaces and entanglement breaking maps
Authors: Dosi A. A.
Published: April 2019

This paper is devoted to the classification of quantum systems among the quantum spaces. In the normed case we obtain a complete solution to the problem when an operator space turns out to be an operator system. The min and max quantizations of a local order are described in terms of the min and max envelopes of the related state spaces. Finally, we characterize min-max-completely positive maps between Archimedean order unit spaces and investigate entanglement breaking maps in the general setting of quantum systems.

Bibliography: 34 titles.
Defective spermatogenesis and testosterone levels in kinase suppressor of Ras1 (KSR1)-deficient mice
Authors: Moretti Elena , Collodel Giulia , Belmonte Giuseppe , Noto Daria , Giurisato Emanuele
Published: April 2019

The aim of this study was to clarify the role of the protein kinase suppressor of Ras1 (KSR1) in spermatogenesis. Spermatogenesis in ksr1−/− mice was studied in testicular tissue and epididymal spermatozoa by light and transmission electron microscopy and by immunofluorescence using antibodies to ghrelin and 3β-hydroxysteroid dehydrogenase (3β-HSD). Blood testosterone levels were also assessed. ksr1−/− mice showed reduced epididymal sperm concentration and motility as compared with wild-type (wt) mice. Testis tissue from ksr1−/− mice revealed a prevalent spermatogenetic arrest at the spermatocyte stage; the interstitial tissue was hypertrophic and the cytoplasm of the Leydig cells was full of lipid droplets. Ghrelin signal was present in the seminiferous tubules and, particularly, in the interstitial tissue of wt mice; however, in ksr1−/− mice ghrelin expression was very weak in both the interstitial tissue and tubules. On the contrary, the signal of 3β-HSD was weak in the interstitial tissue of wt and strong in ksr1−/− mice. Testosterone levels were significantly increased in the blood of ksr1−/− mice (P<0.05) as compared with wt. The results obtained reveal the importance of the KSR scaffold proteins in the spermatogenetic process. The study of the molecular mechanisms associated with spermatogenetic defects in a mouse model is essential to understand the factors involved in human spermatogenesis.
Structural basis for ligand modulation of the CCR2 conformational landscape
Authors: Taylor Bryn C. , Lee Christopher T. , Amaro Rommie E.
Published: April 2019

CC chemokine receptor 2 (CCR2) is a part of the chemokine receptor family, an important class of therapeutic targets. These class A G-protein coupled receptors (GPCRs) are involved in mammalian signaling pathways and control cell migration toward endogenous CC chemokine ligands, named for the adjacent cysteine motif on their N terminus. Chemokine receptors and their associated ligands are involved in a wide range of diseases and thus have become important drug targets. CCR2, in particular, promotes the metastasis of cancer cells and is also implicated in autoimmunity-driven type-1 diabetes, diabetic nephropathy, multiple sclerosis, asthma, atherosclerosis, neuropathic pain, and rheumatoid arthritis. Although promising, CCR2 antagonists have been largely unsuccessful to date. Here, we investigate the effect of an orthosteric and an allosteric antagonist on CCR2 dynamics by coupling long-timescale molecular dynamics simulations with Markov-state model theory. We find that the antagonists shift CCR2 into several stable inactive conformations that are distinct from the crystal structure conformation and disrupt a continuous internal water and sodium ion pathway, preventing transitions to an active-like state. Several metastable conformations present a cryptic drug-binding pocket near the allosteric site that may be amenable to targeting with small molecules. Without antagonists, the apo dynamics reveal intermediate conformations along the activation pathway that provide insight into the basal dynamics of CCR2 and may also be useful for future drug design.
Coherent directed movement toward food modeled in
Trichoplax
, a ciliated animal lacking a nervous system
Authors: Smith Carolyn L. , Reese Thomas S. , Govezensky Tzipe , Barrio Rafael A.
Published: April 2019

Significance

Trichoplax
is a disk-shaped marine animal whose body plan and lifestyle could be similar to those of the Precambrian ancestor of many animals on earth today. It has only six cell types and no nervous system. It glides on substrates feeding on microalgae, propelled by asynchronously beating cilia. It can move in any direction, so we assume that its cilia do not have a uniform polarity and may be randomly oriented, unlike cilia in most epithelia. We show that
Trichoplax
exhibits chemotaxis and present a mathematical model to explain how directional movement could arise from collective actions of randomly oriented ciliated cells, each independently responding to a chemoattractant gradient but constrained by their attachments to other cells in the animal.
Strain-induced spontaneous Hall effect in an epitaxial thin film of a Luttinger semimetal
Authors: Ohtsuki Takumi , Tian Zhaoming , Endo Akira , Halim Mario , Katsumoto Shingo , Kohama Yoshimitsu , Kindo Koichi , Lippmaa Mikk , Nakatsuji Satoru
Published: April 2019

Significance

Weyl semimetals carry the promise of quantum electronic applications. Theoretical calculations have suggested that Luttinger semimetals recently found in iridium oxides may be a suitable group of materials where such topological phases, including Weyl semimetal state, may be found. For example, praseodymium-iridium oxide,

P
r

2

I
r

2

O

7

, is one such Luttinger semimetal that can be tuned by perturbations such as strain into a Weyl semimetal state. Despite theoretical predictions of Weyl semimetal states in

P
r

2

I
r

2

O

7

crystals, experimental proof remains elusive due to the difficulty of applying sufficient mechanical strain on single crystals. Our study provides strong experimental evidence that a Weyl semimetal state may indeed appear in strained pyrochlore iridium oxide films, opening a way to explore topological phases.
Klebsiella
and
Providencia
emerge as lone survivors following long-term starvation of oral microbiota
Authors: Baker Jonathon L. , Hendrickson Erik L. , Tang Xiaoyu , Lux Renate , He Xuesong , Edlund Anna , McLean Jeffrey S. , Shi Wenyuan
Published: April 2019

It is well-understood that many bacteria have evolved to survive catastrophic events using a variety of mechanisms, which include expression of stress-response genes, quiescence, necrotrophy, and metabolic advantages obtained through mutation. However, the dynamics of individuals leveraging these abilities to gain a competitive advantage in an ecologically complex setting remain unstudied. In this study, we observed the saliva microbiome throughout the ecological perturbation of long-term starvation, allowing only the species best equipped to access and use the limited resources to survive. During the first several days, the community underwent a death phase that resulted in a ∼50–100-fold reduction in the number of viable cells. Interestingly, after this death phase, only three species,
Klebsiella pneumoniae
,
Klebsiella oxytoca
, and
Providencia alcalifaciens
, all members of the family Enterobacteriaceae, appeared to be transcriptionally active and recoverable.
Klebsiella
are significant human pathogens, frequently resistant to multiple antibiotics, and recently, ectopic colonization of the gut by oral
Klebsiella
was documented to induce dysbiosis and inflammation. MetaOmics analyses provided several leads for further investigation regarding the ecological success of the Enterobacteriaceae. The isolates accumulated single nucleotide polymorphisms in known growth advantage in stationary phase alleles and produced natural products closely resembling antimicrobial cyclic depsipeptides. The results presented in this study suggest that pathogenic Enterobacteriaceae persist much longer than their more benign neighbors in the salivary microbiome when faced with starvation. This is particularly significant, given that hospital surfaces contaminated with oral fluids, especially sinks and drains, are well-established sources of outbreaks of drug-resistant Enterobacteriaceae.
Cytosolic Fe-superoxide dismutase safeguardsTrypanosoma cruzifrom macrophage-derived superoxide radical
Authors: Martínez Alejandra , Prolo Carolina , Estrada Damián , Rios Natalia , Alvarez María Noel , Piñeyro María Dolores , Robello Carlos , Radi Rafael , Piacenza Lucía
Published: April 2019

Significance

In Chagas disease (CD), macrophages are the first line of defense against its causative agent,Trypanosoma cruzi. Here, we show that superoxide radical (O2•−), a reactive species produced during phagocytosis, diffuses towardT. cruzi, causing toxicity. Much of O2•−permeation involves its protonation inside the acidic phagosome. To deal with host-derived oxidants,T. cruzicontains a broad antioxidant enzyme armamentarium. Herein, we generated parasites overexpressing the cytosolic superoxide dismutase (Fe-SODB) and demonstrate that this enzyme detoxifies host-derived O2•−, preventing its toxicity. These parasites were more resistant to macrophage-dependent killing than the wild type and yielded higher parasitemias and parasite burden in heart tissue of infected mice, underscoring the role of Fe-SODB as a virulence factor for CD.
Deep learning in turbulent convection networks
Authors: Fonda Enrico , Pandey Ambrish , Schumacher Jörg , Sreenivasan Katepalli R.
Published: April 2019

Significance

Turbulent convection in horizontally extended systems comprises vortices and plumes on many time and length scales. These structures interact nonlinearly to self-organize into slowly evolving turbulent superstructures, which are horizontally more extended than in height. We use a U-shaped deep-learning algorithm to generate a time-varying planar network, resulting in a drastic reduction of degrees of freedom, and use it to detect the 3D superstructures and estimate their effectiveness in transporting heat. We thus demonstrate the likely utility of deep learning for parameterizing convection in global models of atmospheric and stellar convection whenever mesoscale structures are conspicuous.
Lending practices to same-sex borrowers
Authors: Sun Hua , Gao Lei
Published: April 2019

Significance

We propose a method to infer people’s sexual orientation indirectly through gender disclosure of the borrower and coborrower in a mortgage. Furthermore, we examine lending practices toward same-sex borrowers and its spillover effects. We attempt to extend the research on race/gender discrimination by systematically investigating the potentially different lending treatment toward same-sex borrowers. The data reveal that, compared with otherwise similar different-sex applicants, same-sex applicants are 73.12% more likely to be denied, and they tend to be charged up to 0.2% higher fees/interest. Furthermore, neighborhoods’ higher same-sex population density adversely affects both same-sex and different-sex borrowers’ lending experiences. Our method might approximately measure the US homosexual population distribution up to the census tract level annually over decades.