bluuebunny/crossref_metadata_2025 huggingface dataset:
Detection of codeine and fentanyl in saliva, blood plasma and whole blood in 5-minutes using a SERS flow-separation strip
Authors: Shende Chetan , Brouillette Carl , Farquharson Stuart
Published: August 2019

A rudimentary flow strip, based on SERS, was developed and used to measure drugs, such as fentanyl, in saliva, plasma, and blood. Fully developed, the strip could be used with hand-held Raman spectrometers as a simple, point-of-care drug analyzer.
A supramolecular approach of modified polyoxometalate polymerization and visualization of a single polymer chain
Authors: Guan Weiming , Wang Gengxin , Ding Jingbo , Li Bao , Wu Lixin
Published: August 2019

Photo-polymerization based on pre-assembly of anthracene-grafted polyoxometalate through host–guest inclusion of cyclodextrins is realized and a single polymer chain is visualized.
Two polyoxovanadate-based metal–organic polyhedra with undiscovered “near-miss Johnson solid” geometry
Authors: Gong Yaru , Tao Yanli , Xu Na , Sun Chunyi , Wang Xinlong , Su Zhongmin
Published: August 2019

Two new polyoxovanadate-based metal–organic polyhedra were synthesized based on double polyoxovanadate-based molecular building blocks with a “near-miss Johnson solids” geometry.
Influence of the drying configuration on the patterning of ellipsoids – concentric rings and concentric cracks
Authors: Mondal Ranajit , Basavaraj Madivala G.
Published: August 2019

The configuration in which colloidal dispersions are dried i.e. sessile and sphere-on-plate, is shown to dictate the morphology of the final deposition patterns and colloidal particle self-assembly.
An N-heterocyclic carbene-functionalised covalent organic framework with atomically dispersed palladium for coupling reactions under mild conditions
Authors: Yang Junjuan , Wu Yuanyuan , Wu Xiaowei , Liu Wenjing , Wang Yaofang , Wang Junwen
Published: August 2019

We report a heterogeneous catalyst based on N-heterocyclic carbene-functionalized covalent organic framework, which shows high activity in the C–C cross coupling reaction at room temperature in pure/ethanol aqueous solvent even with multiple reuse.
Developing degraders: principles and perspectives on design and chemical space
Authors: Maple Hannah J. , Clayden Nat , Baron Anne , Stacey Callum , Felix Robert
Published: August 2019

Degraders (e.g. PROTACs, SNIPERs, degronimers etc.) are a new modality offering increasing potential both as tools for basic research and therapeutic development.
Synthesis and crystal structures of a copper(ii) dinuclear complex and zinc(ii) coordination polymers as materials for efficient oxidative desulfurization of dibenzothiophene
Authors: Tella Adedibu C. , Oladipo Adetola C. , Adimula Vincent O. , Ameen Olanrewaju A. , Bourne Susan A. , Ogunlaja Adeniyi S.
Published: August 2019

Dinuclear copper(ii) complex [Cu2(BAc)4(QX)2], and 2D zinc(ii) coordination polymer, [Zn(TDPA)2(TMPy)2]n, presented high oxidation and adsorption thermodynamics for dibenzothiophene sulfoxide (DBTO).
Magnetic MCM-41 nanoparticles as a support for the immobilization of a palladium organometallic catalyst and its application in C–C coupling reactions
Authors: Tahmasbi Bahman , Ghorbani-Choghamarani Arash
Published: August 2019

An organometallic catalyst of palladium has been immobilized on magnetic MCM-41 nanoparticles and used for C–C coupling reactions. The products were obtained in high yields and good TOF values which were indicate the high efficiency of this catalyst.
3-Hydroxy-3-((3-methyl-4-nitroisoxazol-5-yl)methyl)indolin-2-one as a versatile intermediate for retro-Henry and Friedel–Crafts alkylation reactions in aqueous medium
Authors: Nagaraju Sakkani , Sathish Kota , Paplal Banoth , Satyanarayana Neeli , Kashinath Dhurke
Published: August 2019

The first example of a retro-Henry type reaction is reported using 3-hydroxy-3-((3-methyl-4-nitroisoxazol-5-yl)methyl)indolin-2-ones which are prepared via catalyst-free Henry reaction of 3,5-dimethyl-4-nitroisoxazole and isatin.
A bifunctional electrode engineered by sulfur vacancies for efficient electrocatalysis
Authors: Wang Fan , Li Kai , Li Jingjing , Wolf Lawrence M. , Liu Kai , Zhang Hongjie
Published: August 2019

Proper defect consumption may inhibit aggregation and maintain active sites over a long period of time.
Rapid solvo-microwave annealing for optimizing ordered nanostructures and crystallization of regioregular polythiophene-based block copolymers
Authors: Han Junghun , Kim Jin-Seong , Shin Jae Man , Yun Hongseok , Kim Youngkwon , Park Hyeonjung , Kim Bumjoon J.
Published: August 2019

Solvo-microwave annealing is an effective method for producing thin films of polythiophene-based block copolymers with ordered structures and high crystallinity in a very short processing time (∼3 min).
NiFePd/UiO-66 nanocomposites as highly efficient catalysts to accelerate hydrogen evolution from hydrous hydrazine
Authors: Song Xue , Yang Pan , Wang Jingchuan , Zhao Xiaochong , Zhou Yuanlin , Li Yintao , Yang Lijun
Published: August 2019

NiFe nano-catalysts modified by the dopant of Pd were reducted on UiO-66 by NaBH4, which have been used as a low cost and high efficient catalyst with outstanding activity and durability for hydrogen generation from the decomposition of hydrazine hydrate.
Core–shell-type ZIF-8@ZIF-67@POM hybrids as efficient electrocatalysts for the oxygen evolution reaction
Authors: Wang Yan , Wang Yuyin , Zhang Li , Liu Chun-Sen , Pang Huan
Published: August 2019

ZIF-8@ZIF-67@POM hybrids were synthesized using a simple coprecipitation method, and they exhibit remarkable performance in OER, with the synergistic effect between POM and ZIF species, their regular architecture and their high surface area.
Ruthenium(ii)-catalyzed chemoselective deacylative annulation of 1,3-diones with sulfoxonium ylides via C–C bond activation
Authors: Wen Si , Lv Weiwei , Ba Dan , Liu Jing , Cheng Guolin
Published: August 2019

Highly chemoselective Ru(ii)-catalyzed deacylative annulation of 1,3-diones with sulfoxonium ylides was achieved to afford (hetero)aryl substituted furans.
Distance to the nearby dwarf galaxy [TT2009] 25 in the NGC 891 group using the tip of the red giant branch
Authors: Müller Oliver , Ibata Rodrigo , Rejkuba Marina , Posti Lorenzo
Published: August 2019

Dwarf galaxies are key objects for small-scale cosmological tests like the abundance problems or the planes-of-satellites problem. A crucial task is therefore to get accurate information for as many nearby dwarf galaxies as possible. Using extremely deep, ground-based V and i-band Subaru Suprime Cam photometry with a completeness of i = 27 mag, we measure the distance of the dwarf galaxy [TT2009] 25 using the tip of the red giant branch as a standard candle. This dwarf resides in the field around the Milky Way-analog NGC 891. Using a Bayesian approach, we measure a distance of 10.28−1.73+1.17 Mpc, which is consistent with the distance of NGC 891, and thus confirm it as a member of NGC 891. The dwarf galaxy follows the scaling relations defined by the Local Group dwarfs. We do not find an extended stellar halo around [TT2009] 25. In the small field of view of 100 kpc covered by the survey, only one bright dwarf galaxy and the giant stream are apparent. This is comparable to the Milky Way, where one bright dwarf resides in the same volume, as well as the Sagittarius stream – excluding satellites which are farther away but would be projected in the line-of-sight. It is thus imperative to survey for additional dwarf galaxies in a larger area around NGC 891 to test the abundance of dwarf galaxies and compare this to the number of satellites around the Milky Way.
Assessment of a set of rapeseed (Brassica napus L.) varieties under waterlogging stress at different plant growth stages
Authors: Nabloussi Abdelghani , Bahri Hakima , Lakbir Mariame , Moukane Hajar , Kajji Abdellah , El Fechtali Mohamed
Published: August 2019

Rapeseed (Brassica napus L.) crop has a high yield potential in Morocco, particularly in the Gharb region. However, this area is subjected to relatively frequent water floods usually accompanied with soil waterlogging, which is harmful for the crop. This study aimed to assess the behavior and productivity of four Moroccan varieties under waterlogging stress conditions at four plant growth stages, against the control (absence of waterlogging). A field trial was carried out at the INRA experiment station of Allal Tazi during 2013/2014, and a pot experiment was conducted under shelter at the National School of Agriculture of Meknes during 2014/2015. The results obtained show that waterlogging stress significantly affected most of the studied parameters for all varieties and that germination and post-emergence seedling stages were the most sensitive to waterlogging stress conditions. Particularly, seed yield was drastically reduced for all varieties, and the reduction rate ranged from 19% for “INRA-CZH3” to 73% for “Narjisse” when waterlogging happened under rosette and young seedling stages, respectively. Overall, the variety “INRA-CZH3” presented the best agronomic performance and was the most tolerant to waterlogging occurring at different plant growth stages. Therefore, we recommend cultivation of this variety in the Gharb area. Its tolerance to such stress conditions is certainly attributed to its developed root system, its high seedling vigor and its large collar diameter. The two latter traits presented a high correlation with seed yield components and, thus, we recommend their use as selection criteria to breed for waterlogging rapeseed tolerance.
Prevention and Therapy of Preterm Birth. Guideline of the DGGG, OEGGG and SGGG (S2k Level, AWMF Registry Number 015/025, February 2019) – Part 1 with Recommendations on the Epidemiology, Etiology, Prediction, Primary and Secondary Prevention of Preterm Birth
Authors: Berger Richard , Abele Harald , Bahlmann Franz , Bedei Ivonne , Doubek Klaus , Felderhoff-Müser Ursula , Fluhr Herbert , Garnier Yves , Grylka-Baeschlin Susanne , Helmer Hanns , Herting Egbert , Hoopmann Markus , Hösli Irene , Hoyme Udo , Jendreizeck Alexandra , Krentel Harald , Kuon Ruben , Lütje Wolf , Mader Silke , Maul Holger , Mendling Werner , Mitschdörfer Barbara , Nicin Tatjana , Nothacker Monika , Olbertz Dirk , Rath Werner , Roll Claudia , Schlembach Dietmar , Schleußner Ekkehard , Schütz Florian , Seifert-Klauss Vanadin , Steppat Susanne , Surbek Daniel
Published: August 2019

Aims This is an official guideline of the German Society for Gynecology and Obstetrics (DGGG), the Austrian Society for Gynecology and Obstetrics (ÖGGG) and the Swiss Society for Gynecology and Obstetrics (SGGG). The aim of this guideline is to improve the prediction, prevention and management of preterm birth based on evidence obtained from recent scientific literature, the experience of the members of the guideline commission and the views of self-help groups.

Methods Based on the international literature, the members of the participating medical societies and organizations developed Recommendations and Statements. These were adopted following a formal process (structured consensus conference with neutral moderation, voting was done in writing using the Delphi method to achieve consensus).

Recommendations Part I of this short version of the guideline lists Statements and Recommendations on the epidemiology, etiology, prediction and primary and secondary prevention of preterm birth.
Metal-Catalyzed Site-Selective Monoacylation of Diols in Aqueous Media
Authors: Li Yuyang , Kluger Ronald
Published: August 2019

Site-selective reactions of water-soluble biomolecules are being developed to produce efficient conversions in water and water­/solvent mixtures. This review focuses on the use of designs based on bis-bidentate chelation of large metal ions by diols to be acylated by a co-chelated water-stable reagent. Topics discussed include: 1. The preparation and properties of water-stable acyl phosphate monoesters and their reactions with diol-chelated metal ions. 2. Site-selective monoaminoacylation of 3′-terminal diols of RNA and their applications in protein engineering. 3. Site-selective monoacylation of sugars with acyl phosphate monoesters associated with metal ions, including lanthanum and lead. The combination of metal ion, 1,2-diol, and acyl phosphate monoester produces site-selective reactions in aqueous media­ that can produce a general approach to site-selective mono-(amino)acylation in RNA and carbohydrates.

1 Introduction

2 Synthetic Aminoacylation of tRNA

3 Activated Amino Acids in Water

4 Metal Ions and Their Effects on the Reactivity of Acyl Phosphate
Monoesters

5 The Challenge of Site-Selective Acylation of Carbohydrates in
Water

6 Conclusions and Prospects
Design Considerations and Assays for Hemocompatibility of FDA-Approved Nanoparticles
Authors: Saha Amit K. , Zhen Min-Yi S. , Erogbogbo Folarin , Ramasubramanian Anand K.
Published: August 2019

Nanoparticles have numerous biomedical applications including, but not limited to, targeted drug delivery, diagnostic imaging, sensors, and implants for a wide range of diseases including cancer, diabetes, heart disease, and tuberculosis. Although the mode of delivery of the nanoparticles depends on the application and the disease, the nanoparticles are often in immediate contact with the systemic circulation either because of intravenous administration or their ability to enter the bloodstream with relative ease or their longer survival time in circulation. Once in circulation, the nanoparticles may elicit unintended hemostatic and inflammatory responses, and hence the design of nanoparticles for therapeutic applications should take broad hemocompatibility concerns into consideration. In this review, we present the principles underlying the structural and functional design of various classes of nanoparticles that are currently approved by the US Food and Drug Administration, categorize these particles based on their interactions with cardiovascular tissues and ensuing adverse events, and also describe various in vitro assays that may be used evaluate their hemocompatibility.
[3+2]-Cycloaddition of α-Diazocarbonyl Compounds with Arenediazonium Salts Catalyzed by Silver Nitrate Delivers 2,5-Disubstituted Tetrazoles
Authors: Chuprun Sergey , Dar’in Dmitry , Kantin Grigory , Krasavin Mikhail
Published: August 2019

[3+2]-Cycloaddition of arenediazonium salts with diazo compounds (earlier exemplified only for trimethylsilyldiazomethane and 2,2,2-trifluorodiazoethane) has been developed to include a wide range of readily available α-diazocarbonyl compounds. The resulting 2-aryl-5-acyl-2H-tetrazoles are of high value in medicinal chemistry.
Ein halbes Jahr PPUG: Kein Durchbruch für die Pflege, aber Hoffnung
Authors: Heeser Alexandra
Published: August 2019

Die Pflegepersonaluntergrenzen, kurz PPUG, gelten seit über einem halben Jahr in vier Bereichen – seit 1. April müssen Kliniken bei Nichteinhaltung gemäß PPUG-Sanktions-Vereinbarung womöglich Sanktionen wie Vergütungsabschläge oder Verringerung der Fallzahlen hinnehmen, wenn sie im monatlichen Schnitt unter der Quote liegen. Was haben die PPUG bislang gebracht außer erhöhtem Bürokratieaufwand?
Theoretical validation of photovoltaic thermal (PVT) module with a copper base for thermal and electrical performance
Authors: Fatima Hoor , Tiwari G. N.
Published: August 2019

In this paper, a mathematical model based on energy balance equations of the copper base photovoltaic thermal (PVT) water heating system has been developed. An analytical expression for storage water, outlet water from the PVT collector, and solar cell temperatures has been derived as a function of climatic and design parameters. The developed thermal model has been validated for experimental work carried out for the climatic condition of Chennai, India. Furthermore, the instantaneous thermal energy efficiency is known as a characteristic equation, from which temperature-dependent electrical efficiency and overall thermal and exergy efficiencies have been derived. A fair agreement has been observed between the experimental and theoretical storage water temperatures with a glazing presenting correlation coefficient (r) of 0.999 and a mean square error (e) of 7.48%. It has also been observed that the maximum overall thermal and exergy efficiencies obtained are 33.75% and 14.71%, respectively.
Eradicating abrupt collapse on single network with dependency groups
Authors: Xie Jiarong , Yuan Youyou , Fan Zhengping , Wang Jiahai , Wu Jiajing , Hu Yanqing
Published: August 2019

The dependency among nodes has significant effects on the cascading failures of complex networks. Although the prevention of cascading failures on multilayered networks in which the failures of nodes in one layer affect the functioning of nodes in other layers has been widely investigated, the prevention of catastrophic cascade has rarely been addressed to single-layer networks where nodes are grouped and nodes within the same group are dependent on each other. For such networks, we find that it is already enough to prevent abrupt catastrophic collapses by randomly reinforcing a constant density of nodes. More importantly, we give the analytical solutions to the proportion of needed reinforced nodes for three typical networks, i.e., dependent Erdős-Rényi (ER), random regular (RR), and scale-free (SF) networks. Interestingly, the density of reinforced nodes is a constant 0.1756, which holds true for ER networks with group size 2 regardless of average degree, RR, and SF networks with a large average degree. Also, we find the elegant expression of the density with any group size. In addition, we find a hybrid phase transition behavior, which is present in RR and SF networks while absent in ER networks. Our findings might shed some new light on designing more resilient infrastructure networks.
Limiting behavior of non-autonomous stochastic reaction-diffusion equations on unbounded thin domains
Authors: Shi Lin , Li Xiliang
Published: August 2019

This article is concerned with the limiting behavior of dynamics of a class of nonautonomous stochastic partial differential equations driven by multiplicative white noise on unbounded thin domains. We first prove the existence of tempered pullback random attractors for the equations defined on (n + 1)-dimensional unbounded thin domains. Then, we show the upper semicontinuity of these attractors when the (n + 1)-dimensional unbounded thin domains collapse onto the n-dimensional space Rn. Here, the tail estimates are utilized to deal with the noncompactness of Sobolev embeddings on unbounded domains.
Interaction of cylindrical converging shocks with an equilateral triangular SF6 cylinder
Authors: Zheng Chun , Zhang Huanhao , Chen Zhihua , Wu Wei-Tao , Sha Sha
Published: August 2019

Based on the compressible large eddy simulation method, combined with the hybrid scheme of the weighted essentially nonoscillatory scheme and the tuned central difference scheme, the interaction of the cylindrical converging shock wave with an equilateral triangle SF6 cylinder is numerically simulated in this work. The numerical results clearly show the evolution of the interface induced by the Richtmyer-Meshkov instability due to the interaction of the converging shock and the interface, which are in good agreement with previous experimental results. However, the numerical results reveal clearly the evolution and characteristics of the shock wave structures, and find that there are five times of shock focusing during the interaction process of shock waves with the interfaces. The characteristics of the mean flow, the width and growth rate of the mixing-layer, the circulation evolution, and history of the mixing ratio have also been quantitatively analyzed and it was found that the secondary reflected shock can lead to rapid mixing. Meanwhile, a dynamic mode decomposition method is applied to extract the coherent structures for discovering the mechanism of turbulent mixing.
A review of compressed-air energy storage
Authors: Yu Qihui , Wang Qiancheng , Tan Xin , Fang Guihua , Meng Jianguo
Published: August 2019

Due to the high variability of weather-dependent renewable energy resources, electrical energy storage systems have received much attention. In this field, one of the most promising technologies is compressed-air energy storage (CAES). In this article, the concept and classification of CAES are reviewed, and the cycle efficiency and effective energy are analyzed in detail to enhance the current understanding of CAES. Furthermore, the importance of the real-gas properties of air is discussed. Related research on adiabatic CAES and isothermal CAES is also presented.
Evolution of high frequency waves in shoaling and breaking wave spectra
Authors: Ardani Samira , Kaihatu James M.
Published: August 2019

Mathematical derivation and numerical verification of a wave transformation model in the frequency domain are discussed. The model is a fully dispersive nonlinear wave model and is derived based on the boundary value problem. Transforming the problem in the frequency domain and using multiple scale analysis in space and perturbation theory, the model is expanded up to second order in wave steepness. This fully dispersive nonlinear wave model is a set of evolution equations which explicitly contains quadratic near-resonant interactions. The comparison between the presented model, the existing fully dispersive model, and a nearshore model with different sets of laboratory and field data shows that the presented model provides significant improvements particularly at higher frequency.
Sensitive measurement of phase shift of an AC magnetic field by quantum sensing with multiple-pulse decoupling sequences
Authors: Ishikawa Toyofumi , Yoshizawa Akio , Mawatari Yasunori , Kashiwaya Satoshi , Watanabe Hideyuki
Published: August 2019

Magnetometry utilizing a spin qubit in a solid state possesses high sensitivity. In particular, a magnetic sensor with a high spatial resolution can be achieved with the electron-spin states of a nitrogen-vacancy (NV) center in the diamond. In this study, we demonstrated that NV quantum sensing based on multiple-pulse decoupling sequences can sensitively measure not only the amplitude but also the phase shift of an alternating-current (AC) magnetic field. In the AC magnetometry based on decoupling sequences, the maximum phase accumulation of the NV spin due to an AC-field can be generally obtained when the π-pulse period in the sequences matches the half time period of the field and the relative phase difference between the sequences and the field is zero. By contrast, the NV quantum sensor acquires no phase accumulation if the relative phase difference is π/2. Thus, this phase-accumulation condition does not have any advantage for the magnetometry. However, we revealed that the nonphase-accumulation condition is available for detecting a very small phase shift of an AC-field from its initial phase. Measurements of the real part and the imaginary part of AC impedance require the amplitude and the phase information of an AC-field, and thus, this finding is expected to provide a guide for realizing sensitive measurement of AC impedance in the micrometer and nanometer scales.
Effects of microstructure and growth conditions on quantum emitters in gallium nitride
Authors: Nguyen Minh , Zhu Tongtong , Kianinia Mehran , Massabuau Fabien , Aharonovich Igor , Toth Milos , Oliver Rachel , Bradac Carlo
Published: August 2019

Single-photon emitters in gallium nitride (GaN) are gaining interest as attractive quantum systems due to the well-established techniques for growth and nanofabrication of the host material, as well as its remarkable chemical stability and optoelectronic properties. We investigate the nature of such single-photon emitters in GaN with a systematic analysis of various samples produced under different growth conditions. We explore the effect that intrinsic structural defects (dislocations and stacking faults), doping, and crystal orientation in GaN have on the formation of quantum emitters. We investigate the relationship between the position of the emitters—determined via spectroscopy and photoluminescence measurements—and the location of threading dislocations—characterized both via atomic force microscopy and cathodoluminescence. We find that quantum emitters do not correlate with stacking faults or dislocations; instead, they are more likely to originate from point defects or impurities whose density is modulated by the local extended defect density.
Design of broadband impedance-matching Bessel lens with acoustic metamaterials
Authors: Zhao Yue , Dong Hui Yuan , Zhao Songwei , Min Suwei , Cheng Jie , Li Bin , Chi Fengfeng , Liu Shengli
Published: August 2019

In this paper, a gradient-index lens is designed to implement an acoustic Bessel beam. Here, the wave from the point source is reshaped to the Bessel beam with the energy concentrated near the axial direction and almost no divergence. The two-dimensional distribution of the gradient refractive index is obtained based on the analysis of the impedance matching theory. The interface reflection is reduced significantly due to the impedance matching with air. The effect of the acoustic Bessel lens is found to work in a broadband with the use of the subwavelength unit cell and the finite-element simulations. Our results may provide the potential applications for medical ultrasound imaging and signal detection.
1D Schrödinger operators with Coulomb-like potentials
Authors: Golovaty Yuriy
Published: August 2019

We study the convergence of 1D Schrödinger operators Hε with the potentials which are regularizations of a class of pseudopotentials having, in particular, the form αδ′(x) + βδ(x) + γ/|x| or αδ′(x) + βδ(x) + γ/x. The limit behavior of Hε in the norm resolvent topology, as ε → 0, essentially depends on a way of regularization of the Coulomb potential and the existence of zero-energy resonances for δ′-like potential. All possible limits are described in terms of point interactions at the origin. As a consequence of the convergence results, different kinds of L∞(R)-approximations to the even and odd Coulomb potentials, both penetrable and impenetrable in the limit, are constructed.
Electrochromic properties of Li4Ti5O12: From visible to infrared spectrum
Authors: Li Meng , Gould Tim , Su Zhong , Li Shunning , Pan Feng , Zhang Shanqing
Published: August 2019

Recently, Li4Ti5O12 (LTO) has been experimentally proven as a promising broadband electrochromic material for applications like smart windows, thermal management, and infrared camouflage. However, a detailed understanding of the fundamental mechanism of these phenomena is still lacking, especially how and why the optical spectrum changes with lithiation. We fill this knowledge gap by performing a detailed analysis of LTO's optical properties during charging/discharging via a robust study of the density functional theory (DFT). Our study suggests that the absorption of infrared light is highly sensitive to intercalation of Li in the LTO lattice, in contrast to that of visible wavelengths. This unique characteristic of LTO offers an effective mechanism in controlling infrared radiation intensity with minimal attenuation on the transmission of visible light. Furthermore, the DFT study also reveals that the electrochemical intercalation of Li introduces donor states which will gradually expand and move to deeper levels in the forbidden band. This electronic structure change leads to better conductivity and lower transmittance, which is in line with the experimental observation in the literature.
Electrically pumped semiconductor laser with low spatial coherence and directional emission
Authors: Kim Kyungduk , Bittner Stefan , Zeng Yongquan , Liew Seng Fatt , Wang Qijie , Cao Hui
Published: August 2019

We design and fabricate an on-chip laser source that produces a directional beam with low spatial coherence. The lasing modes are based on the axial orbit in a stable cavity and have good directionality. To reduce the spatial coherence of emission, the number of transverse lasing modes is maximized by fine-tuning the cavity geometry. In a cavity with the size of hundreds of micrometers, 1000 transverse modes lase simultaneously and independently, reducing the speckle contrast to 0.03. Decoherence is reached in a few nanoseconds as a result of frequency detuning of lasing modes. Such rapid decoherence will facilitate applications in ultrafast speckle-free full-field imaging.
Performance evaluation of twin piezoelectric wind energy harvesters under mutual interference
Authors: Hu Gang , Wang Junlei , Su Zhen , Li Guoping , Peng Huayi , Kwok K. C. S.
Published: August 2019

This study evaluated the performance of twin adjacent galloping-based piezoelectric wind energy harvesters based on mutual interference. The relative position between the twin harvesters is crucial to their energy generation efficiency. A series of wind tunnel tests were conducted to test energy generation of the two harvesters in tandem or staggered arrangements. The optimal relative position, a streamwise center to center spacing of 1.2B (B is the width of the harvester's square prism) and a transverse center to center spacing of 1.0B, was identified. The total output power of the two harvesters placed in the optimal relative position is up to 2.2 times that of two isolated harvesters. The output power is also much larger than that of the harvesters in tandem arrangements that have been widely tested in previous studies. Therefore, it is recommended to position two adjacent harvesters in optimal relative position(s) to deliver an optimal power output.
Flow structure around and heat transfer from cylinders modified from square to circular
Authors: Zafar Farhan , Alam Md. Mahbub
Published: August 2019

This work aims at numerically investigating the influence of corner modification on the flow structure around and heat transfer from a square cylinder at a Reynolds number Re = 150 based on the cylinder width d and freestream velocity. The sharp corners of the square cylinder are rounded with r/d = 0 (square), 0.125, 0.25, 0.375, and 0.5 (circular), where r is the radius of the corner. The rounded corners have a profound effect on the flow structure from the perspective of flow separation, vortex strength, separation bubble, and wake bubble each playing a role in heat transfer from different surfaces of the cylinder. The boundary layer having a higher friction coefficient on the front and side surfaces leads to a higher local heat transfer. A shorter wake bubble renders a higher heat transfer from the rear surface. The increase in r/d from 0 to 0.5 leads to a 33% enhancement in the heat transfer from the cylinder. The enhancement largely results from a shrink in the wake bubble and an increase in vortex strength. The minimum time-mean drag and fluctuating forces are achieved at r/d = 0.25 and 0.125, respectively. The effect of r/d in various Reynolds averaged quantities is discussed.
Reduced thermal dependence of the sensitivity of a planar Hall sensor
Authors: Mahfoud Mohamed , Tran Quang-Hung , Wane Sidina , Ngo Duc-The , Belarbi El Habib , Boukra AbdelAziz , Kim Mijin , Elzwawy Amir , Kim CheolGi , Reiss Guenter , Dieny Bernard , Bousseksou Azzedine , Terki Ferial
Published: August 2019

The ability to stabilize the sensitivity of a magnetoresistance sensor in unstable thermal environments is a key parameter in many high precision measurements. Here, we propose a method to stabilize the sensitivity of a highly sensitive and low noise magnetic sensor based on a planar Hall Effect crossed junction. The stability is achieved by controlling the interplay between Zeeman energy, exchange bias energy, and anisotropy energy as a function of the temperature of the sensor stack comprising a trilayer structure NiFe/Cu/IrMn (10/0.12/10 nm). The high thermal stability of the sensor sensitivity of 4.5 ± 0.15 × 10−3 V/A/T/K is achieved when the external magnetic field is set around ±2 ± 0.04 mT and the applied current is fixed at 20 mA in the temperature range of 110 K–360 K. This method improves the magnetic sensor detection by about an order of magnitude, enabling its deployment in various research fields, particularly to study magnetic properties of small quantities of magnetic materials toward the detection of single magnetic objects, which was impossible before.
The effect of the fear factor on the dynamics of a predator-prey model incorporating the prey refuge
Authors: Wang Jing , Cai Yongli , Fu Shengmao , Wang Weiming
Published: August 2019

In this paper, we investigate the dynamics of an improved Leslie-Gower predator–prey model which is characterized by the reduction of the prey growth rate due to fear of the predator (i.e., antipredator behavior). The value of this study lies in two aspects: mathematically, (i) it provides the existence and the stability of the positive equilibrium; (ii) it gives the existence of the Hopf bifurcation and limit cycle; and (iii) it shows the mechanisms of the fear factor and the prey refuge on the level of the positive equilibrium. Biologically, we find that the influence of the fear factor is complex: (i) increasing the level of fear can cause the level of the population density to decrease and the prey to become extinct; (ii) the effect of the cost of fear on the stability of the positive equilibrium is rich and complex: it can either destabilize the stability and benefit the emergency of the periodic behavior or stabilize the system by excluding the existence of periodic solutions; (iii) with a fixed level of fear, the prey refuge is beneficial to the coexistence of the prey and the predator, and with the increase of the level of the prey refuge, the positive equilibrium may change from stable spiral sink to unstable spiral source to stable spiral sink. These results may enrich the dynamics of the predator–prey systems.
Extended correlations in the critical superheated solid
Authors: Olguín-Arias Vivianne , Davis Sergio , Gutiérrez Gonzalo
Published: August 2019

Metastable states in first-order phase transitions reveal interesting behavior about a wide range of systems in statistical mechanics, including spin systems, cellular automata, and condensed matter systems. These metastable states are often observed in a microcanonical setting, where they manifest long-range correlations due to collective effects. In this work, we show the existence of long-range potential energy correlations between atoms in a microcanonical superheated Lennard-Jones crystal prior to homogeneous melting. Our results suggest that the cooperative motion made possible by the presence of vacancy-interstitial pairs above the melting temperature induces effective long-range interatomic forces even beyond the fourth neighboring layer.
Low-latency adiabatic superconductor logic using delay-line clocking
Authors: Takeuchi Naoki , Nozoe Mai , He Yuxing , Yoshikawa Nobuyuki
Published: August 2019

Adiabatic quantum-flux-parametron (AQFP) logic is an energy-efficient superconductor logic family. The switching energy of an AQFP gate can be arbitrarily reduced via adiabatic switching. However, AQFP logic has somewhat long latency due to the multiphase clocking scheme, in which each logic operation requires a quarter clock cycle. The latency in AQFP logic should be improved in order to design complex digital circuits such as microprocessors. In the present paper, we propose a low-latency clocking scheme for AQFP logic, which we call delay-line clocking. In delay-line clocking, the latency for each logic operation is determined by the propagation delay of the excitation current, which can be much shorter than a quarter clock cycle. Our numerical simulation shows that AQFP gates can operate with a latency of only a few picoseconds. We fabricated an AQFP circuit adopting delay-line clocking using the 10 kA/cm2 Nb high-speed standard process provided by the National Institute of Advanced Industrial Science and Technology. The circuit was demonstrated at 4 GHz with a latency of 10 ps per gate. The above results indicate that delay-line clocking can significantly reduce the latency in AQFP logic.
Governing factors of supports of ammonia synthesis in an electric field found using density functional theory
Authors: Murakami Kota , Tanaka Yuta , Hayashi Sasuga , Sakai Ryuya , Hisai Yudai , Mizutani Yuta , Ishikawa Atsushi , Higo Takuma , Ogo Shuhei , Seo Jeong Gil , Tsuneki Hideaki , Nakai Hiromi , Sekine Yasushi
Published: August 2019

Efficient ammonia synthesis at low temperatures is anticipated for establishing a hydrogen carrier system. We reported earlier that application of an electric field on the Cs/Ru/SrZrO3 catalyst enhanced catalytic ammonia synthesis activity. It is now clear that N2 dissociation is activated by hopping protons in the electric field. Efficient ammonia synthesis proceeds by an “associative mechanism” in which N2 dissociates via an N2H intermediate, even at low temperatures. The governing factor of ammonia synthesis activity in an electric field for active metals differed from that in the conventional mechanism. Also, N2H formation energy played an important role. The effects of dopants (Al, Y, Ba, and Ca) on this mechanism were investigated using activity tests and density functional theory calculations to gain insights into the support role in the electric field. Ba and Ca addition showed positive effects on N2H formation energy, leading to high ammonia synthesis activity. The coexistence of proton-donating and electron-donating abilities is necessary for efficient N2H formation at the Ru–support interface.
Modeling and optimizing the delay propagation in Chinese aviation networks
Authors: Qin Shuo , Mou Jianhong , Chen Saran , Lu Xin
Published: August 2019

We define metrics to quantify the level of overall delay and propose an agent-based data-driven model with four factors, including aircraft rotation, flight connectivity, scheduling process, and disturbance, to build a simulator for reproducing the delay propagation in aviation networks. We then measure the impact on the propagation by the delay at each airport and analyze the relevance to its temporal characteristics. When delay occurs, airline schedule planning may become infeasible, and rescheduling of flights is usually required to maintain the function of the system, so we then develop an improved genetic algorithm (GA) to reschedule flights and to relax the root delay. Results indicate that priority-based strategy rather than First-Come-First-Serve can achieve minimum overall delay when congestion occurs, and aircraft rotation is the most important internal factor contributing to delay propagation. Furthermore, the reschedule generated by the improved GA can decrease delay propagation more significantly compared to the agent-based model.
Oscillating grid turbulence in shear-thinning polymer solutions
Authors: Lacassagne T. , Simoëns S. , EL Hajem M. , Lyon A. , Champagne J.-Y.
Published: August 2019

Oscillating grid apparatuses are well known and convenient tools for the fundamental study of turbulence and its interaction with other phenomena since they allow to generate turbulence supposedly homogeneous, isotropic, and free of mean shear. They could, in particular, be used to study turbulence and mass transfer near the interface between non-Newtonian liquids and a gas, as already done in air-water situations. Although frequently used in water and Newtonian fluids, oscillating grid turbulence (OGT) generation has yet been rarely applied and never characterized in non-Newtonian media. The present work consists of a first experimental characterization of the flow properties of shear-thinning polymer (Xanthan Gum, XG) solutions stirred by an oscillating grid. Various polymer concentrations are tested for a single grid stirring condition. The dilute and semidilute entanglement concentration regimes are considered. Liquid phase velocities are measured by Particle Image Velocimetry. The existing mean flow established in the tank is described and characterized, as well as turbulence properties (intensity, decay rate, length scales, isotropy, etc.). OGT in dilute polymer solutions induces an enhanced mean flow compared to water, a similar decay behavior with yet different decay rates, and enhanced turbulence large scales and anisotropy. In the semidilute regime of XG, turbulence and mean flows are essentially damped by viscosity. The evolution of mean flow and turbulence indicators leads to the definition of several polymer concentration subregimes, within the dilute one. Critical concentrations around 20 ppm and 50 ppm are found, comparable to drag reduction characteristic concentrations.
Pulse interfacial defrosting
Authors: Chavan S. , Foulkes T. , Gurumukhi Y. , Boyina K. , Rabbi K. F. , Miljkovic N.
Published: August 2019

Frost formation and ice accretion are major problems for a plethora of industries. Common defrosting and deicing techniques utilize energy-intensive mechanical actuation to dislodge ice/frost or heating methods to melt ice/frost from surfaces. Here, we develop an ultraefficient method to defrost/deice surfaces by spatially and temporally localizing thermal energy at the substrate-ice/frost interface. To remove ice/frost efficiently, it is beneficial only to melt the interfacial layer adhering the ice/frost to the solid surface by using a localized “pulse” of heat, allowing gravity or gas shear in conjunction with the ultrathin lubricating melt water layer to remove the ice/frost. To probe the physics of pulse defrosting, we first developed a transient numerical heat transfer model. Experimental validation of the model was achieved via pulse (≈100 ms) joule heating of indium tin oxide on glass samples. Utilizing transient heat fluxes ranging from 10 to 100 W/cm2, spontaneous melting of the interfacial ice/frost layer was achieved, leading to rapid ice removal. We employed our validated model to outline design guidelines for pulse defrosting applications, showing <1% of the energy and <0.01% of the defrosting time needed when compared to conventional thermal-based defrosting methods.
Negative differential resistance and multilevel resistive switching in BaSrTiO3 films
Authors: He Jing , Zhu Jie , Ma Changcheng , Lu Jingjing , Hu Zuoqi
Published: August 2019

Epitaxial BaxSr1−xTiO3 (BST) films are grown on SrTiO3:Nb (NSTO) substrates by hydrothermal means. A Pt/BST/NSTO device exhibits typical rectification characteristics under relatively low voltage and forming-free bipolar resistive switching under relatively high voltage, with the resistance ratio between the high and low resistance states exceeding four orders of magnitude. Furthermore, negative differential resistance arises during the reset process, and multilevel resistive switching is achieved under various reset voltages. These behaviors in the Pt/BST/NSTO device are likely due to trapping/detrapping of electrons by oxygen vacancies at the Pt/BST interface.
Direct femtosecond-laser writing of optical-range nanoscale metagratings/metacouplers on diamond surfaces
Authors: Kudryashov S. I. , Levchenko A. O. , Danilov P. A. , Smirnov N. A. , Rudenko A. A. , Melnik N. N. , Busleev N. I. , Ionin A. A.
Published: August 2019

A natural diamond surface was nanopatterned in a subablative scanning mode by multiple tightly focused 515-nm, 300-fs laser pulses, resulting in regular surface metagratings (nanoripples) with a subwavelength period of Λ ∼ 100 nm, an almost undistorted crystalline structure, free from sp2-carbon, oriented perpendicular to the laser polarization, and stackable both along and normal to their stripes. In the visible-near-IR ranges (400–800 nm), these metagratings demonstrate the pronounced resonant antireflective effect in the wavelength range near ∼4Λ, while the overall specular reflectance/transmittance is considerably diminished with respect to both the simulation results and the reference diamond surface, indicating strong (∼50%) coupling/scattering of light inside the crystal. Our modeling indicates the laser wavelength-dependent plasmon-based tunability of metagrating periods, implying the corresponding tunability of their spectral response.
Particularities of shocks generated by underwater electrical explosions of a single wire and wire arrays
Authors: Rososhek A. , Efimov S. , Virozub A. , Maler D. , Krasik Ya. E.
Published: August 2019

The results of experimental and numerical research of shockwaves generated by the underwater electrical explosion of a single wire and a planar wire array are reported. Experiments were conducted using a microsecond time scale pulse power generator delivering a <210 kA current with a <1 μs rise time. Streak and fast framing cameras were used to study the time- and space-resolved evolution of the shocks. The results show that (a) an aperiodic discharge constitutes the most efficient method of generating a shockwave; (b) in the case of a planar wire array, an almost simultaneous explosion can be obtained when the individual wire diameter is <100 μm (current density >2 × 107 A/cm2); (c) the planar shock velocity can be accelerated using the combustion properties of the Al wires efficiently, and (d) the shock velocity can be enhanced using a metal reflector placed below the array.
Attenuation limit of silica-based hollow-core fiber at mid-IR wavelengths
Authors: Yu Fei , Song Peng , Wu Dakun , Birks Tim , Bird David , Knight Jonathan
Published: August 2019

We study the mid-infrared attenuation of antiresonant hollow-core fiber made of fused silica glass. The role of absorptive losses increases with wavelength but can be minimized by reducing the overlap of the trapped light with the silica. We show that this overlap is least at the lowest-order antiresonance condition, corresponding to the thinnest core wall, and for higher resonances scales with the core wall thickness. A record-low minimum attenuation of 18 dB/km measured in our fiber at 3.1 µm wavelength is not limited by silica absorption. We measured 40 dB/km attenuation at 4 µm wavelength, where the attenuation of bulk silica is 860 dB/m. We show that this corresponds to a modal overlap of 2.81 × 10−5 which is in good agreement with simulations, suggesting that at this wavelength, attenuation is limited by silica absorption. This enables us to predict the achievable attenuation at longer wavelengths as well. Extrinsic losses due to gaseous molecular absorption may make demonstration of such losses difficult in some spectral bands. In contrast to shorter wavelengths, where leakage loss is the primary attenuation mechanism, introducing additional elements into the cladding design is unlikely to reduce the attenuation further, and further loss reduction would require a larger core size.
Instability of a smooth shear layer through wave interactions
Authors: Carpenter J. R. , Guha A.
Published: August 2019

Wave interaction theory can be used as a tool to understand and predict instability in a variety of homogeneous and stratified shear flows. It is, however, most often limited to piecewise-linear profiles of the shear layer background velocity, in which stable vorticity wave modes can be easily identified and their interaction quantified. This approach to understanding shear flow instability is extended herein to smooth shear layer profiles. We describe a method, by which the stable vorticity wave modes can be identified, and show that their interaction results in an excellent description of the stability properties of the smooth shear layer, thus demonstrating the presence of the wave interaction mechanism in smooth shear flows.