bluuebunny/crossref_metadata_2025 huggingface dataset:
Continuous generation, in-line quantification and utilization of nitrosyl chloride in photonitrosation reactions
Authors: Lebl René , Cantillo David , Kappe C. Oliver
Published: January 2019

The reagent is prepared from stable, inexpensive and readily available starting materials. In-line UV/vis monitoring enables determination of the reagent's concentration after a continuous extraction and liquid–liquid separation sequence.
Formation, stability and hydrothermal waves in evaporating liquid lenses
Authors: Buffone C.
Published: January 2019

We present a fascinating experimental investigation of the formation, stability and thermal patterns of evaporating liquid lenses deposited on an evaporating or non-evaporating liquid pool.
Sodium ion removal by hydrated vanadyl phosphate for electrochemical water desalination
Authors: Lee Juhan , Srimuk Pattarachai , Zwingelstein Rose , Zornitta Rafael Linzmeyer , Choi Jaehoon , Kim Choonsoo , Presser Volker
Published: January 2019

Hydrated vanadyl phosphate is a promising electrode material for electrochemical water desalinationviareversible ion intercalation.
Cellulose nanocrystal-assembled reverse osmosis membranes with high rejection performance and excellent antifouling
Authors: Park Chan Hyung , Jeon SungKwon , Park Sang-Hee , Shin Min Gyu , Park Min Sang , Lee Sun-Young , Lee Jung-Hyun
Published: January 2019

The cellulose nanocrystal-assembled TFC membranes exhibited excellent solute (NaCl and boron) rejection and low organic fouling.
Length evolution of fused-ring electron acceptors toward optimal blend morphology in polymer solar cells incorporating asymmetric benzodithiophene-based donors
Authors: Zhu Qianqian , Liu Deyu , Lu Zhou , Gu Chunyang , Zhang Kaili , Bao Xichang , Li Qun , Yang Renqiang
Published: January 2019

Weakly aggregated donor polymers and small-sized FREAs in appropriate degree can match well with each other.
Self-stacked multilayer FeOCl supported on a cellulose-derived carbon aerogel: a new and high-performance anode material for supercapacitors
Authors: Wan Caichao , Jiao Yue , Bao Wenhui , Gao He , Wu Yiqiang , Li Jian
Published: January 2019

The findings open a new pathway to design high-energy density energy-storage systems using the FeOCl-based anode.
Solution-processable, high luminance deep-blue organic light emitting devices based on novel naphthalene bridged bis-triphenylamine derivatives
Authors: Li Yuqin , Gao Siming , Zhang Nan , Huang Xin , Tian Jinchang , Xu Feng , Sun Zhizhong , Yin Shougen , Wu Xiaoming , Chu Wenyi
Published: January 2019

The optimal device E exhibited a very high luminance of 10 407 cd m−2 and a maximum current efficiency of 7.80 cd A−1.
Bright solid-state red-emissive BODIPYs: facile synthesis and their high-contrast mechanochromic properties
Authors: Duan Chong , Zhou Yibin , Shan Guo-Gang , Chen Yuncong , Zhao Weijun , Yuan Dandan , Zeng Lintao , Huang Xiaobo , Niu Guangle
Published: January 2019

We first report several bright solid-state red-emissive BODIPYs with high fluorescence quantum yields for unusual high-contrast mechanohypsochromism.
Characterization of CD133+/CD44+human prostate cancer stem cells with ATR-FTIR spectroscopy
Authors: Güler Günnur , Guven Ummu , Oktem Gulperi
Published: January 2019

Molecular mechanisms and features of prostate cancer stem cells, which are crucial for improving target specific therapies, were elucidated with ATR-FTIR spectroscopy.
Ferritin exhibits Michaelis–Menten behavior with oxygen but not with iron during iron oxidation and core mineralization
Authors: Bou-Abdallah Fadi , Flint Nicholas , Wilkinson Tyler , Salim Samantha , Srivastava Ayush Kumar , Poli Maura , Arosio Paolo , Melman Artem
Published: January 2019

The excessively high and inconsistent literature values for Km,Fe and Km,O2 prompted us to examine the iron oxidation kinetics in ferritin, the major iron storage protein in mammals, and to determine whether a traditional Michaelis–Menten enzymatic behavior is obeyed. The kinetics of Fe(ii) oxidation and mineralization catalyzed by three different types of ferritins (recombinant human homopolymer 24H, HuHF, human heteropolymer ∼21H:3L, HL, and horse spleen heteropolymer ∼3.3H:20.7L, HosF) were therefore studied under physiologically relevant O2 concentrations, but also in the presence of excess Fe(ii) and O2 concentrations. The observed iron oxidation kinetics exhibited two distinct phases (phase I and phase II), neither of which obeyed Michaelis–Menten kinetics. While phase I was very rapid and corresponded to the oxidation of approximately 2 Fe(ii) ions per H-subunit, phase II was much slower and varied linearly with the concentration of iron(ii) cations in solution, independent of the size of the iron core. Under low oxygen concentration close to physiological, the iron uptake kinetics revealed a Michaelis–Menten behavior with Km,O2 values in the low μM range (i.e. ∼1–2 μM range). Our experimental Km,O2 values are significantly lower than typical cellular oxygen concentration, indicating that iron oxidation and mineralization in ferritin should not be affected by the oxygenation level of cells, and should proceed even under hypoxic events. A kinetic model is proposed in which the inhibition of the protein’s activity is caused by bound iron(iii) cations at the ferroxidase center, with the rate limiting step corresponding to an exchange or a displacement reaction between incoming Fe(ii) cations and bound Fe(iii) cations.
Full-visible multifunctional aluminium metasurfaces by in situ anisotropic thermoplasmonic laser printing
Authors: Zhang Yinan , Shi Liu , Hu Dejiao , Chen Shiren , Xie Shouyi , Lu Yudong , Cao Yaoyu , Zhu Zhuqing , Jin Long , Guan Bai-Ou , Rogge Sven , Li Xiangping
Published: January 2019

A new level of anisotropic plasmonic laser printing for aluminum multifunctional metasurfaces.
Catalytic asymmetric aza-Michael addition of fumaric monoacids with multifunctional thiourea/boronic acids
Authors: Michigami Kenichi , Murakami Hiroki , Nakamura Takeru , Hayama Noboru , Takemoto Yoshiji
Published: January 2019

Chiral multifunctional thiourea/boronic acid catalysts enabled the synthesis of N-hydroxyaspartate derivatives applicable for KAHA amidation through acid-β selective aza-Michael addition.
Conversation in Aphasia Across Communication Partners: Exploring Stability of Microlinguistic Measures and Communicative Success
Authors: Leaman Marion C. , Edmonds Lisa A.
Published: January 2019

Purpose

The aim of this study was to determine if people with aphasia demonstrate differences in microlinguistic skills and communicative success in unstructured, nontherapeutic conversations with a home communication partner (Home-P) as compared to a speech-language pathologist communication partner (SLP-P).

Method

Eight persons with aphasia participated in 2 unstructured, nontherapeutic 15-minute conversations, 1 each with an unfamiliar SLP-P and a Home-P. Utterance-level analysis evaluated communicative success. Two narrow measures of lexical relevance and sentence frame were used to evaluate independent clauses. Two broad lexical and morphosyntactic measures were used to evaluate elliptical and dependent clauses and to evaluate independent clauses for errors beyond lexical relevance and sentence frame (such as phonological and morphosyntactic errors). Utterances were further evaluated for presence of behaviors indicating lexical retrieval difficulty (pauses, repetitions, and false starts) and for referential cohesion.

Results

No statistical differences occurred for communicative success or for any of the microlinguistic measures between the SLP-P and Home-P conversation conditions. Four measures (2 of lexical retrieval and 1 each of communicative success and grammaticality) showed high correlations across the 2 conversation samples. Individuals showed variation of no more than 10 percentage points between the 2 conversation conditions for 46 of 56 data points. Variation greater than 10 percentage points tended to occur for the measure of referential cohesion and primarily for 1 participant.

Conclusions

Preliminary findings suggest that these microlinguistic measures and communicative success have potential for reliable comparison across Home-P and SLP-P conversations, with the possible exception of referential cohesion. However, further research is needed with a larger, more diverse sample. These findings suggest future assessment and treatment implications for clinical and research needs.

Supplemental Material

https://doi.org/10.23641/asha.7616312
Telepractice for School-Based Speech and Language Services: A Workload Management Strategy
Authors: Boisvert Michelle K. , Hall Nerissa
Published: January 2019

Purpose

This article discusses the combination of onsite and telepractice services as an effective way for professionals working in multiple schools to maximize their time and professional services in an effort to manage their workload. The combined onsite and telepractice services were used by district-wide school-based professionals to deliver direct and indirect services across various locations, thereby reducing time-consuming travel and increasing scheduling efficiency. The possible uses of telepractice as a workload management tool are discussed, as well as some challenges that the team overcame in order to successfully use this method.

Conclusions

Telepractice, in combination with onsite services, is an effective workload strategy for school-based therapists.
Wideband filtering power divider with wide rejection bandwidth and isolation
Authors: Hao Honggang , Ni Xingrui
Published: January 2019

A wideband filtering power divider (FPD) with wide rejection bandwidth and good isolation is presented, based on conventional Wilkinson structure. Parallel coupled lines and two pairs of open‐circuit stubs are used for achieving bandpass filtering response and enhancing the performance of the rejection bandwidth. Furthermore, by properly choosing two resistors between two pairs of open‐circuit stubs allows good isolation performance. Measured results indicate that the FPD operates at 2.35 GHz (f0) with a − 20 dB bandwidth of 55.3%. In the upper stopband range from 3.7 to 8.8 GHz (3.74f0), the minimum rejection is 20 dB. Within working band, the isolation between the output ports is higher than 24 dB. In addition, ultra‐wide isolation better than 20 dB from DC to 10 GHz is obtained.
Swift UVOT near-UV transit observations of WASP-121 b
Authors: Salz M. , Schneider P. C. , Fossati L. , Czesla S. , France K. , Schmitt J. H. M. M.
Published: January 2019

Close-in gas planets are subject to continuous photoevaporation that can erode their volatile envelopes. Today, ongoing mass loss has been confirmed in a few individual systems via transit observations in the ultraviolet spectral range. We demonstrate that the Ultraviolet/Optical Telescope (UVOT) onboard the Neil Gehrels Swift Observatory enables photometry to a relative accuracy of about 0.5% and present the first near-UV (200–270 nm, NUV) transit observations of WASP-121 b, a hot Jupiter with one of the highest predicted mass-loss rates. The data cover the orbital phases 0.85–1.15 with three visits. We measure a broadband NUV transit depth of 2.10 ± 0.29%. While still consistent with the optical value of 1.55%, the NUV data indicate excess absorption of 0.55% at a 1.9σ level. Such excess absorption is known from the WASP-12 system, and both of these hot Jupiters are expected to undergo mass loss at extremely high rates. With a Cloudy simulation, we show that absorption lines of Fe II in a dense extended atmosphere can cause broadband near-UV absorption at the 0.5% level. Given the numerous lines of low-ionization metals, the NUV range is a promising tracer of photoevaporation in the hottest gas planets.
Fundamental properties of the pre-main sequence eclipsing stars of MML 53 and the mass of the tertiary
Authors: Gómez Maqueo Chew Y. , Hebb L. , Stempels H. C. , Paat A. , Stassun K. G. , Faedi F. , Street R. A. , Rohn G. , Hellier C. , Anderson D. R.
Published: January 2019

We present the most comprehensive analysis to date of the Upper Centaurus Lupus eclipsing binary MML 53 (with PEB = 2.097892 d), and for the first time, confirm the bound-nature of the third star (in a P3 ∼ 9 yr orbit) by constraining its mass dynamically. Our analysis is based on new and archival spectra and time-series photometry, spanning 80% of one orbit of the outer component. From the spectroscopic analysis, we determined the temperature of the primary star to be 4880 ± 100 K. The study of the close binary incorporated treatment of spots and dilution by the tertiary in the light curves, allowing for the robust measurement of the masses of the eclipsing components within 1% (M1 = 1.0400 ± 0.0067 M⊙ and M2 = 0.8907 ± 0.0058 M⊙), their radii within 4.5% (R1 = 1.283 ± 0.043 R⊙ and R2 = 1.107 ± 0.049 R⊙), and the temperature of the secondary star (Teff, 2 = 4379 ± 100 K). From the analysis of the eclipse timings, and the change in systemic velocity of the eclipsing binary and the radial velocities of the third star, we measured the mass of the outer companion to be 0.7 M⊙ (with a 20% uncertainty). The age we derived from the evolution of the temperature ratio between the eclipsing components is fully consistent with previous, independent estimates of the age of Upper Centaurus Lupus (16 ± 2 Myr). At this age, the tightening of the MML 53 eclipsing binary has already occurred, thus supporting close-binary formation mechanisms that act early in the stars’ evolution. The eclipsing components of MML 53 roughly follow the same theoretical isochrone, but appear to be inflated in radius (by 20% for the primary and 10% for the secondary) with respect to recent evolutionary models. However, our radius measurement of the 1.04 M⊙ primary star of MML 53 is in full agreement with the independent measurement of the secondary of NP Per which has the same mass and a similar age. The eclipsing stars of MML 53 are found to be larger but not cooler than predicted by non-magnetic models, it is not clear what is the mechanism that is causing the radius inflation given that activity, spots and/or magnetic fields slowing their contraction, require the inflated stars to be cooler to remain in thermal equilibrium.
The CARMENES search for exoplanets around M dwarfs
Authors: Schöfer P. , Jeffers S. V. , Reiners A. , Shulyak D. , Fuhrmeister B. , Johnson E. N. , Zechmeister M. , Ribas I. , Quirrenbach A. , Amado P. J. , Caballero J. A. , Anglada-Escudé G. , Bauer F. F. , Béjar V. J. S. , Cortés-Contreras M. , Dreizler S. , Guenther E. W. , Kaminski A. , Kürster M. , Lafarga M. , Montes D. , Morales J. C. , Pedraz S. , Tal-Or L.
Published: January 2019

Context. The Calar Alto high-Resolution search for M dwarfs with Exo-earths with Near-infrared and optical Echelle Spectrographs (CARMENES) survey is searching for Earth-like planets orbiting M dwarfs using the radial velocity method. Studying the stellar activity of the target stars is important to avoid false planet detections and to improve our understanding of the atmospheres of late-type stars.

Aims. In this work we present measurements of activity indicators at visible and near-infrared wavelengths for 331 M dwarfs observed with CARMENES. Our aim is to identify the activity indicators that are most sensitive and easiest to measure, and the correlations among these indicators. We also wish to characterise their variability.

Methods. Using a spectral subtraction technique, we measured pseudo-equivalent widths of the He I D3, Hα, He I λ10833 Å, and Pa β lines, the Na I D doublet, and the Ca II infrared triplet, which have a chromospheric component in active M dwarfs. In addition, we measured an index of the strength of two TiO and two VO bands, which are formed in the photosphere. We also searched for periodicities in these activity indicators for all sample stars using generalised Lomb-Scargle periodograms.

Results. We find that the most slowly rotating stars of each spectral subtype have the strongest Hα absorption. Hα is correlated most strongly with He I D3, whereas Na I D and the Ca II infrared triplet are also correlated with Hα. He I λ10833 Å and Paβ show no clear correlations with the other indicators. The TiO bands show an activity effect that does not appear in the VO bands. We find that the relative variations of Hα and He I D3 are smaller for stars with higher activity levels, while this anti-correlation is weaker for Na I D and the Ca II infrared triplet, and is absent for He I λ10833 Å and Paβ. Periodic variation with the rotation period most commonly appears in the TiO bands, Hα, and in the Ca II infrared triplet.
Experimental analysis of the influence of the impinged plate by an impinging jet on the vortex dynamics using PIV
Authors: Mrach Tarek , Hamdi Jana , Abed-Meraïm Kamel , Alkheir Marwan , Assoum Hassan , Sakout Anas
Published: January 2019

In this experimental study, we are interested in the flow generated by a plane jet impacting on different plates. To analyse these flows and to compare the evolutions of the various parameters (velocities, turbulence rate, vortex structures, etc.), the PIV technique was used. For example, for a confinement ratio of 4 and a Reynolds number of 4838, a comparison is made between the deviated flows for each of the three plates considered in this study. For the smooth slotted plate, it is noted that the large structures created by the shear between the jet and the driving zone are convected and are organized differently according to the initial dynamics of the flow (Re). Indeed, depending on the configuration, these large structures are either deviated laterally in the parietal flow or pass alternately through the slot. With regard to the solid plates, Kelvin Helmholtz’s structures are always deflected, the parietal flow is more nourished but its vortex dynamics is influenced by the surface state. Indeed, for the smooth solid plate we have large swirl structures whereas for the corrugated plate, we notice the appearance of small vivid and intense vortex structures. A quantitative analysis of these phenomena is conducted in order to study and compare parietal flows.
An efficient technology of phosphorous removal from wastewater by the low-grade oolitic hematite with high phosphorous
Authors: Zhou Xuejiao , Chen Yongli , Xia Wentang , Yin Jianguo , Yuan Xiaoli
Published: January 2019

The present study aims to develop a new potentially low-cost and efficient approach to removing soluble inorganic phosphorus from acid leaching wastewater. This wastewater was of high acidity and high phosphorus content. Low-grade oolitic hematite with high phosphorus (LGOHWHP) was chosen as an economic adsorbent and was also used to adjust the acidity of the solution. The adsorption isotherms, adsorption thermodynamics, and effect of various parameters such as pH value, contact time, temperature and adsorbent dosage on the phosphorus removal from wastewater were investigated. The results showed that pH value and adsorbent dosage have a significant impact on the phosphorus removal. The phosphorus adsorption results fitted very well to Langmuir and Freundlich adsorption isotherm models, and the adsorption process was an endothermic process. At the optimum parameters pH 5.5, reaction temperature of 302 K with 20 g L−1 LGOHWHP, the phosphorus removal percentage of about 95% and the phosphorus concentration in the wastewater of about 0.27 mg L−1 are achieved after 60 min. The results indicate that the phosphorus concentration in wastewater after dephosphorization by the LGOHWHP completely meets the requirements of the national wastewater discharge standard in China. This research provides an efficient and environmentally friendly technology to remove phosphorus from wastewater.
Effect of reoxidation on inclusions in steel during calcium treatment
Authors: Li Ming , Liu Yang , Zhang Lifeng
Published: January 2019

In the current study, the effect of reoxidation on inclusions during calcium treatment was studied via adding Fe2O3into a Al-killed molten steel at 1 min after the addition of calcium. The total oxygen (T.O.) content increased from 10 to 24 ppm just after the reoxidation occurred, while it finally decreased to 14 ppm since inclusions were floated to the top of the steel and absorbed by the formed slag layer. The increased T.O. favored the decomposition of CaS, especially for the heat with high sulfur contents. The vaporization of calcium, which leads to the decrease of calcium content, is the driving force for the evolution of inclusions from CaO-CaS-(Al2O3) to CaO-Al2O3-(CaS) due to the limited degree of reoxidation. The contact angle between inclusions and the molten steel increased with the increase of Al2O3in calcium alumina, which favored the removal of inclusions. Increased sulfur content decreased the surface tension of molten steel, which led to remove less inclusions since the contact angle between inclusions and the molten steel was decreased. Thus, more inclusions were measured in heats with higher sulfur content.
Radioactivité dans l’environnement : le rôle des associations de contrôle
Authors: Boilley David
Published: January 2019

Depuis la catastrophe de Tchernobyl, l’opinion publique s’est mobilisée pour demander plus de transparence dans l’établissement de l’impact des accidents nucléaires sur les populations et l’environnement. Dans ce cadre, plusieurs associations participent au contrôle de l’exploitation des centrales nucléaires, en particulier par des mesures de radioactivité, aussi bien en France qu’à l’étranger.
Le cout de production de l’électricité nucléaire
Authors: Dessillons Anne-Sophie
Published: January 2019

Le cout de production d’un mégawatt-heure (MWh) d’électricité nucléaire est un paramètre essentiel dans l’évaluation de l’intérêt économique de la filière. La Cour des comptes a produit un rapport très détaillé qui a fait débat, et dont les éléments chiffrés permettent de se faire une idée plus claire sur les couts d’exploitation (hors recherche et développement) du nucléaire actuel et sur leur évolution dans le futur.
Nucléaires civil et militaire : des recherches liées
Authors: Bordé Jacques , Leduc Michèle
Published: January 2019

Le développement du nucléaire en France est le fruit de choix politiques qui ont établi un lien étroit entre la recherche militaire et celle sur les applications civiles. Les conséquences de ce lien sont multiples et ont conduit les physiciens à s’interroger sur leur rôle.
Lewis Acid Promoted Trapping of Chiral Aza-enolates
Authors: Lanza Francesco , Pérez Juana , Jumde Ravindra , Harutyunyan Syuzanna
Published: January 2019

We present a study on sequential conjugate addition of ­Grignard reagents to alkenyl-heteroarenes followed by trapping of the resulting enolates, yielding moderate to good diastereoselectivities. Contrary to conventional wisdom, one-pot conjugate addition/trapping using two reactive Michael acceptors in combination with Grignard reagents can proceed via conjugate addition to the least reactive Michael acceptor. This unusual chemoselectivity is triggered by the presence of a Lewis acid, reverting the usual reactivity order of Michael acceptors.
Palladium-Catalyzed Formation of Substituted Tetrahydropyrans: Mechanistic Insights and Structural Revision of Natural Products
Authors: Pilli Ronaldo , Della-Felice Franco , de Assis Francisco , Sarotti Ariel
Published: January 2019

A comprehensive study on the stereochemical outcome of palladium-catalyzed formation of 2,4,6-trisubstituted tetrahydropyrans through cyclization of the corresponding allylic acetates using both Pd(0) and Pd(II) catalysts is presented. We have found that the stereochemical outcome of this cyclization is dependent not only on the ­stereochemistry of the acyclic precursor but also on the nature of the palladium catalyst. These results were applied to the total synthesis of the putative structure of cryptoconcatone H. Experimental and computational DP4+ NMR results were used to assess the structures proposed for cryptoconcatones K and L.
Concise Synthesis of the ABC-Ring System of the Azafluoranthene, Tropoisoquinoline and Proaporphine Alkaloids: An Olefin Hydroacylation/Pomeranz–Fritsch Cyclization Approach
Authors: Vargas Didier , Larghi Enrique , Kaufman Teodoro
Published: January 2019

A straightforward approach toward a decorated cyclopenta[ij]isoquinoline embodying the ABC-ring system characteristic of the azafluoranthene (triclisine), tropoisoquinoline (pareitropone) and proaporphine (prodensiflorin B) alkaloids, is reported. The synthetic ­sequence entailed a novel 40% KF/Al2O3-mediated hydroacylation of a 2-allyl-benzaldehyde derivative, obtained in two steps from isovanillin, through O-allylation and Claisen rearrangement to assemble the AC-ring system. This was followed by an O-methylation and a reductive ­amination of the resulting indanone with aminoacetal. A modified Pomeranz–Fritsch cyclization was next implemented to install ring B, through sulfonamidation, followed by acid-promoted cyclization and ­final desulfonylation in situ.
Posterior Interosseous Neurectomy Alternative for Treating Chronic Wrist Pain
Authors: Abdelaziz Ashraf M. , Aldahshan Wael , El-Sherief Faisal Ahmed Hashem , Wahd Yaser El Sayed Hassan , Soliman Hany Abdel Gawwad
Published: January 2019

Background Wrist denervation is one of the several available options for treating chronic wrist pain; partial wrist denervation performed through a single dorsal incision by resecting the distal posterior interosseous nerve provides good outcomes.

Questions/Purposes This study evaluated the results of posterior interosseous neurectomy (PIN) in patients with chronic wrist pain secondary to scaphoid nonunion advanced collapse (SNAC) and scapholunate advanced collapse (SLAC).

Methods In total, 30 wrists obtained from 28 patients (25 males, 3 females) were assessed. The dominant hands of 25 (right-handed) patients, nondominant hands of 5, and both hands of 2 were considered. The average age at the time of surgery was 35 (range: 19–50) years, and the average follow-up duration was 18 (range: 12–30) months. Fifteen and 13 patients had wrists with SNAC and SLAC, respectively, and all of those underwent PIN performed through the dorsal approach. The pre- and postoperative range of motion, grip strength, and pain relief percentage were recorded for all the 30 wrists.

Results The average postoperative Disabilities of the Arm, Shoulder and Hand score was 30 (range: 20–80), and the difference between the pre- and postoperative scores was statistically significant. Ninety percent of the patients were satisfied with the results of PIN and reported improvement in grip strength and pain relief.

Conclusions Thus, PIN may be an effective surgical technique for wrist reconstruction.

Clinical Relevance To help patients challenge pain and maintain their wrist joint range of motion.
Optimized sleeve monopole antenna for detection of electrostatic discharge radiation of spacecraft solar array
Authors: Zhang Guozhi , Li Cunhui , Zhang Xiaoxing , Zhang Jian , Chen Ling , Liu Fan
Published: January 2019

The spacecraft operating on a geosynchronous orbit (GEO) is affected by the plasma environment and is prone to electrostatic discharges (ESD) that affect the safe operation of the spacecraft, especially solar array, radiating electromagnetic (EM) signals of a few MHz to tens of MHz. The capture of radiated EM signals helps to better study the characteristics and suppress the occurrence of ESD. In this paper, based on the frequency band characteristics of the EM wave signal radiated by ESD in space, a novel optimized compact sleeve monopole antenna is designed by using three-dimensional EM field simulation software High Frequency Structure Simulator. The length of the proposed antenna is only about 52 mm and its center frequency is 30 MHz. The frequency band of the voltage standing wave ratio (VSWR) less than 2 is 28.8-31.1 MHz and that of less than 5 is 26.8 MHz-33.2 MHz, and the bandwidth is 21.3%. The sample preparation and VSWR test by using the vector network analyzer were carried out. Finally, the sensitivity test was carried out in an EM shielding room by the piezoelectric ceramic ESD simulation experiment. The test results show that the designed antenna can receive the EM wave signal radiated by the ESD stably and can be used for spacecraft discharge detection.
A non-perturbative approach to simulate heterogeneous electron transfer dynamics: Effective mode treatment of the continuum electronic states
Authors: Xu Meng , Liu Yanying , Song Kai , Shi Qiang
Published: January 2019

We propose a non-perturbative method to simulate heterogeneous electron transfer dynamics in systems described by a Newns-Anderson type of model. The coupling between the molecule and the continuum electronic states at the metal or semiconductor surface is represented using a set of effective modes, by employing an exponential expansion of the bath correlation functions. Depending on the nature of the problems, the nuclear degrees of freedom are either treated explicitly using wave functions and density operators or as dissipative modes using the techniques from the hierarchical equations of the motion method. Numerical examples are also presented for applications in problems including (1) photo-induced charge transfer at the molecule-semiconductor interfaces, (2) heterogeneous electron transfer at the molecule-metal interface, and (3) vibrational relaxation on a metal surface.
Unexpected calcium polyhydride CaH4: A possible route to dissociation of hydrogen molecules
Authors: Wu Gang , Huang Xiaoli , Xie Hui , Li Xin , Liu Mingkun , Liang Yongfu , Huang Yanping , Duan Defang , Li Fangfei , Liu Bingbing , Cui Tian
Published: January 2019

Hydrogen-rich compounds provide an efficient route to pre-compressing hydrogen molecules and facilitating the creation of metallic hydrogen at much reduced pressure. Motivated by the long-sought theoretically proposed calcium hydrides, we have performed high-pressure experiments on the Ca–H system in a laser-heated diamond anvil cell. The unconventional compound CaH4 with I4/mmm symmetry has been discovered to be stable above 25.5 GPa. Of particular significance is the crystal structure of CaH4, which has an elongated H2 molecular unit whose intramolecular bond strength changes with pressure. Below the dissociation pressure of pure hydrogen, the elongated H2 unit is likely to dissociate into an atomic one. Our findings indicate that the presence of Ca atoms causes a very positive chemical pre-compression effect to potentially prompt the dissociation of the H2 unit.
Quantum BRST charge in gauge theories in curved space-time
Authors: Taslimi Tehrani Mojtaba
Published: January 2019

Renormalized gauge-invariant observables in gauge theories form an algebra which is obtained as the cohomology of the derivation QL,−, with QL as the renormalized interacting quantum BRST charge. For a large class of gauge theories in Lorentzian globally hyperbolic space-times, we derive an identity in renormalized perturbation theory which expresses the commutator [QL, −] in terms of a new nilpotent quantum BRST (Becchi, Rouet, Stora, Tyutin) differential and a new quantum anti-bracket which differ from their classical counterparts by certain quantum corrections. This identity enables us to prove different manifestations of gauge symmetry preservation at the quantum level in a model-independent fashion.
Design and testing of a cryogenic indentation apparatus
Authors: Wang Shunbo , Xu Hailong , Wang Yunyi , Kong Lingqi , Wang Zhaoxin , Liu Sihan , Zhang Jianhai , Zhao Hongwei
Published: January 2019

A modularized cryogenic indentation apparatus was designed and created to study the deformation mechanisms and mechanical properties of materials at low temperatures. The indentation process is actuated by piezoelectric stack and flexure hinge, and the entire mechanical module is kept inside the vacuum chamber to prevent the occurrence of ice. Numerous issues including the effects of the application of cooling module and processes to diminish the temperature effect on the indentation tip were addressed. Several influential factors during temperature indentation were discussed. Tests on calibration specimen demonstrated the feasibility of the apparatus. Monocrystalline silicon and copper were tested using the current apparatus at temperatures ranging from room temperature to 150 K to show its main functions and usability.
Tunable magneto-optical responses in a photonic crystal containing two plasma defect layers
Authors: Pourali Nima , Bahador Hamid
Published: January 2019

The magneto-optical responses of a one-dimensional photonic crystal containing two magnetized plasma defect layers with operation in the millimeter wavelength region are studied by using a 4 × 4 transfer matrix method and full wave numerical simulation. The results of this study show that not only the values of the magneto-optical effects such as Kerr and Faraday rotations are tunable by the magnetic field and plasma layer parameters but also the positions of resonant modes in the frequency region are adjustable by these parameters. Also, it is found out that the repetition numbers of middle and surrounding unit cells in the structure can be considered to be other key factors for tuning the characteristics of resonant modes and magneto-optical responses related to them.
Peculiar relaxation dynamics of propylene carbonate derivatives
Authors: Jedrzejowska Agnieszka , Hensel-Bielowka Stella , Koperwas Kajetan , Jurkiewicz Karolina , Chmiel Krzysztof , Jacquemin Johan , Kruk Danuta , Paluch Marian
Published: January 2019

The aim of this work is to analyze in detail the effect of the alkyl chain length on the dynamics of glass-forming propylene carbonate (PC) derivatives. Examined samples are low-molecular weight derivatives of the PC structure, i.e., the 4-alkyl-1,3-dioxolan-2-one series, modified by changing the alkyl substituent from methyl to hexyl. The molecular dynamics (MD) has been analyzed based on experimental data collected from differential scanning calorimetry, broadband dielectric spectroscopy (BDS), X-ray diffraction (XRD), and nuclear magnetic resonance relaxometry measurements as well as MD simulations. The dielectric results show in samples with the propyl- or longer carbon chain the presence of slow Debye-like relaxation with features similar to those found in associative materials. Both XRD and MD reveal differences in the intermolecular structure between PC and 4-butyl-1,3-dioxolan-2-one liquids. Moreover, MD shows that the probability of finding one terminal carbon atom of the side chain of BPC in the vicinity of another carbon atom of the same type is much higher than in the case of PC. It suggests that there is a preference for longer hydrocarbon chains to set themselves close to each other. Consequently, the observed slow-mode peak may be caused by movement of aggregates maintained by van der Waals interactions. Reported herein, findings provide a new insight into the molecular origin of Debye-like relaxation.
Attitude calculation method based on full-sky atmospheric polarization mode
Authors: Liu Jun , Zhao Donghua , Wang Chenguang , Yang Jiangtao , Guo Xiaoting , Tang Jun , Shen Chong
Published: January 2019

In the natural world, insects such as bees and sand ants can navigate with the aid of polarized skylight. Inspired by this, bio-inspired navigation systems based on polarized skylight have attracted considerable attention recently. As an important navigation parameter, attitude information is critical for control and navigation of a vehicle. In this paper, the structural characteristics of full-sky atmospheric polarization mode are studied to calculate the attitude of a vehicle relative to the observation point. The heading angle is obtained by subtraction between two angles. One is the angle between the solar meridian and the geographic north. The other is the angle between the solar meridian and the body coordinate system, which can be obtained from the polarization data detected by the sensor. And the solar position can also gain from the polarization data. Then based on the solar position and the coordinates of solar projection point, the zenith point can be determined. With the coordinates of the zenith point in the body and the reference coordinate system, the pitch angle and roll angle are solved. Simulation and practical experiments are conducted to validate the performance of the attitude calculation method. Experiment results with high accuracy show its feasibility and effectiveness.
Effect of thickness of metal electrode on the performance of SiNx-based resistive switching devices
Authors: Zhang Zhen Fei , Gao Hai Xia , Yang Mei , Jiang Peng Fei , Ma Xiao Hua , Yang Yin Tang
Published: January 2019

This letter studies the effect of the thickness of the top electrode on the performance of a SiNx resistive switching layer. We fabricated six devices with Ta electrodes of different thickness values (8 nm, 10 nm, 15 nm, 30 nm, 40 nm, and 50 nm) in a Ta/SiNx/Pt structure and then systematically investigated their performance. The high electrode thickness devices show stable and self-compliant bipolar resistive switching characteristics. In contrast, low electrode thickness devices display unstable RS behavior and have a high set voltage. In the low resistance state region, the Ta/SiNx/Pt devices obey Ohmic conduction, while in the high resistance state region, the conduction mechanism is Schottky emission. To explain the different RS behavior in the two device types, a nitrogen-ion-based model has been presented. According to this model, the device with a thicker top electrode has a stronger nitrogen accommodation ability, while the migration of nitrogen ions and silicon dangling bonds dominates conductive behavior.
Self-assembly in two-dimensional mixtures of Janus disks and isotropic particles
Authors: Borówko M. , Rżysko W. , Słyk E.
Published: January 2019

Using Monte Carlo simulations, we investigate the self-organization of Janus disks and small isotropic particles in two-dimensional systems. In our model, a Janus particle contains an attractive part, A, and an repulsive part, R. The isotropic particles are strongly attracted by the R-part and repelled by the A-part. The number of Janus particles is fixed, while the number of isotropic particles varies. As the concentration of isotropic particles increases, the system structure changes. We show that the size of Janus disks strongly affects the system morphology. In the case of big Janus particles, we have found a lamellar-like phase and a gel-like structure. Different structures are formed in mixtures with smaller Janus particles. At sufficiently high densities of isotropic particles, Janus particles always aggregate into small clusters that are evenly dispersed in the “sea” of isotropic particles. The energies of interactions between both species are analyzed. The mechanism of co-assembly is discussed.
Prediction of intrinsic two-dimensional non-Dirac topological insulators in triangular metal-organic frameworks
Authors: Zhang Jiayong , Zhao Bao , Ma Chunlan , Yang Zhongqin
Published: January 2019

Two-dimensional (2D) metal-organic frameworks (MOFs) with topologically nontrivial states have attracted considerable attention recently. Based on ab initio calculations, we demonstrate that Cu(C21N3H15) with a triangular lattice is an intrinsic quantum anomalous Hall insulator. The multiple p (px and py)-like molecular orbitals of the C21N3H15 molecule with C3 symmetry give rise to a degenerate energy point at the Γ point with quadratic non-Dirac band dispersions. When the spin-orbit coupling is included, the bandgap is opened around the non-Dirac Γ point and a topologically nontrivial state is achieved. Quantum spin Hall effects can also be realized in this kind of 2D triangular lattice MOF if the time-reversal symmetry is preserved, as proposed in the Ni(C21N3H15) lattice. The physical mechanism is analyzed through a k · p model built. Our results present that the 2D triangular lattice MOFs are excellent candidates for producing 2D topological insulators and might have promising applications in future microelectronics and spintronics.
The surface affinity of cations depends on both the cations and the nature of the surface
Authors: Das Sudipta , Bonn Mischa , Backus Ellen H. G.
Published: January 2019

Specific ion effects at interfaces are important for a variety of thermodynamic properties of electrolyte solutions, like surface tension and the phase behavior of surfactants. We report the relative surface affinity of Na+ and D3O+ at both the D2O-air and the sodium dodecyl sulfate (surfactant)-covered D2O surface by studying the alignment of interfacial D2O, using vibrational sum frequency generation spectroscopy. The surface propensity of ions is found to be a function of both the nature of the ion and the nature of the surface. Specifically, for the charged, surfactant-covered interface, Na+ has a higher affinity than D3O+. In contrast, D3O+ has a higher affinity than Na+ at the air-D2O interface. The relative surface affinity of cations thus depends on both details of the cation and the type of interface.
Ring-polymer molecular dynamics study on rate coefficient of the barrierless OH + CO system at low temperature
Authors: Meng Qingyong , Chen Jun
Published: January 2019

Based on the recently constructed neural-network potential energy surface [Chen et al., J. Chem. Phys. 138, 221104 (2013)], ring-polymer molecular dynamics (RPMD) calculations are performed to compute rate coefficients of the barrierless OH + CO system at T ≤ 500 K. To recover the barrierless feature, a Lindemann-Hinshelwood-type mechanism and hence a reduced rate coefficient are used to approximate the overall rate coefficient. An agreement between RPMD and experimental rate coefficients can be found. These RPMD results reproduce correctly the temperature-independence of the overall rate coefficient. Finally, potential sources of errors in the present RPMD calculations are discussed.
High quality 10.6 μm AlN grown on pyramidal patterned sapphire substrate by MOCVD
Authors: Long Hanling , Dai Jiangnan , Zhang Yi , Wang Shuai , Tan Bo , Zhang Shuang , Xu Linlin , Shan Maocheng , Feng Zhe Chuan , Kuo Hao-chung , Chen Changqing
Published: January 2019

In this letter, we demonstrate a crack and strain free AlN epilayer with a thickness of 10.6 μm grown on a pyramidal patterned sapphire substrate by metalorganic chemical vapor deposition. The full width at half maximum of the X-ray rocking curve was 165/185 arcsec for (002)/(102) planes, respectively. The total threading dislocation density was less than 3 × 108 cm−2. The dislocation evolution and the coalescence process were probed by transmission electron microscopy and scanning electron microscopy. A dual coalescence of the AlN epilayer was observed, which can effectively relax strain during the heteroepitaxy process. Owing to the approximately entire strain relaxation demonstrated by reciprocal space mapping and Raman shift, the surface morphology was crack-free and atomically smooth with a root-mean-square roughness of 0.14 nm. Temperature dependent Raman spectra showed the Raman linewidth of 4.3 cm−1 at 300 K which was comparable to that of bulk AlN; it also demonstrated good crystalline quality of the AlN epilayer.
Simulation of high-speed droplet impact against a dry/wet rigid wall for understanding the mechanism of liquid jet cleaning
Authors: Kondo Tomoki , Ando Keita
Published: January 2019

Physical cleaning techniques are of great concern to remove particulate contamination because of their low environmental impact. One of the promising candidates is based on water jets that often involve fission into droplet fragments. Particle removal is believed to be achieved by droplet-impact-induced wall shear flow. Here, we simulate a high-speed droplet impact on a dry/wet rigid wall to investigate the wall shear flow as well as water hammer after the impact. The problem is modeled by the axisymmetric compressible Navier–Stokes equations and solved by a finite volume method that can capture both shocks and material interface. As an example, we consider the impact of a spherical water droplet (200 µm in diameter) at velocity from 30 to 50 m/s against a dry/wet rigid wall. In our simulation, we can reproduce both acoustic and hydrodynamic events. In the dry wall case, the strong wall shear appears near the moving contact line at the wetted surface. On the other hand, once the wall is covered with the liquid film, the wall shear stress gets weaker as the film thickness increases—a similar trend holds for the water-hammer shock loading at the wall. According to the simulated base flow, we compute hydrodynamic force acting on small particles that are assumed to be attached at the wall, in a one-way-coupling manner. The hydrodynamic force acting on the particles is estimated under Stokes’ assumption and compared to particle adhesion of van der Waals type, enabling us to derive a simple criterion of the particle removal.
Feynman diagram description of 2D-Raman-THz spectroscopy applied to water
Authors: Sidler David , Hamm Peter
Published: January 2019

2D-Raman-THz spectroscopy of liquid water, which has been presented recently [J. Savolainen et al., Proc. Natl. Acad. Sci. U. S. A. 110, 20402 (2013)], directly probes the intermolecular degrees of freedom of the hydrogen-bond network. However, being a relatively new technique, its information content is not fully explored to date. While the spectroscopic signal can be simulated based on molecular dynamics simulation in connection with a water force field, it is difficult to relate spectroscopic signatures to the underlying microscopic features of the force field. Here, a completely different approach is taken that starts from an as simple as possible model, i.e., a single vibrational mode with electrical and mechanical anharmonicity augmented with homogeneous and inhomogeneous broadening. An intuitive Feynman diagram picture is developed for all possible pulse sequences of hybrid 2D-Raman-THz spectroscopy. It is shown that the model can explain the experimental data essentially quantitatively with a very small set of parameters, and it is tentatively concluded that the experimental signal originates from the hydrogen-bond stretching vibration around 170 cm−1. Furthermore, the echo observed in the experimental data can be quantified by fitting the model. A dominant fraction of its linewidth is attributed to quasi-inhomogeneous broadening in the slow-modulation limit with a correlation time of 370 fs, reflecting the lifetime of the hydrogen-bond networks giving rise to the absorption band.
Surface acoustic wave-based micromixing enhancement using a single interdigital transducer
Authors: Ahmed Husnain , Park Jinsoo , Destgeer Ghulam , Afzal Muhammad , Sung Hyung Jin
Published: January 2019

The realization of efficient mixing of samples inside a microfluidic channel is essential for performing numerous biological assays in miniaturized total analysis systems. The low Reynolds number flows at the microscale create laminar streams inside the microchannel, limiting flow mixing to a molecular diffusion level. In this paper, we propose a simple and efficient acoustofluidic mixing technique inside a single-layered polydimethylsiloxane (PDMS) microfluidic channel. The proposed surface acoustic wave (SAW)-based system composed of a straight interdigitated transducer (IDT) is positioned beneath the PDMS microchannel. Fluorescein dye dissolved in deionized water (sample fluid) and deionized water (sheath fluid) was introduced through the first and second inlets of the PDMS microchannel, respectively. Their flow rates were controlled such that the sample fluid with fluorescein dye was hydrodynamically focused close to the bottom of the microchannel by the sheath fluid. High-frequency (140 MHz) SAWs, generated from the IDT placed right beneath the first outlet, mixed the two fluids under the influence of strong acoustic streaming flows. The mixed samples were then collected at the two outlet ports for further analysis of the mixing efficiency. The developed acoustofluidic mixing device required an input voltage of 12 Vpp at a total flow rate of 50 μl/min to realize complete mixing. At a similar applied voltage, the throughput of the proposed device could be further increased to 200 μl/min with a mixing efficiency of >90%.