bluuebunny/crossref_metadata_2025 huggingface dataset:
ERP evidence on how gaze convergence affects social attention
Authors: Wang Nanbo , Xu Shan , Zhang Shen , Luo Yiqi , Geng Haiyan
Published: May 2019

How people process gaze cues from multiple others is an important topic but rarely studied. Our study investigated this question using an adapted gaze cueing paradigm to examine the cueing effect of multiple gazes and its neural correlates. We manipulated gaze directions from two human avatars to be either convergent, created by the two avatars simultaneously averting their gazes to the same direction, or non-convergent, when only one of the two avatars shifted its gaze. Our results showed faster reaction times and larger target-congruency effects following convergent gazes shared by the avatars, compared with the non-convergent gaze condition. These findings complement previous research to demonstrate that observing shared gazes from as few as two persons is sufficient to enhance gaze cueing. Additionally, ERP analyses revealed that (1) convergent gazes evoked both left and right hemisphere N170, while non-convergent gazes evoked N170 mainly in the hemisphere contralateral to the cueing face; (2) effects of target congruency on target-locked N1 and P3 were modulated by gaze convergence. These findings shed light on temporal features of the processing of multi-gaze cues.
Phosphatidylcholine synthesis through cholinephosphate cytidylyltransferase is dispensable in Leishmania major
Authors: Moitra Samrat , Pawlowic Mattie C. , Hsu Fong-fu , Zhang Kai
Published: May 2019

Phosphatidylcholine (PC) is a major cell membrane constituent and precursor of important second messengers. In Leishmania parasites, PC synthesis can occur via the choline branch of the Kennedy pathway, the N-methylation of phosphatidylethanolamine (PE), or the remodeling of exogenous phospholipids. To investigate the role of de novo PC synthesis in Leishmania major, we focused on the cholinephosphate cytidylyltransferase (CPCT) which catalyzes the formation of CDP-choline, a key intermediate in the choline branch of the Kennedy pathway. Without CPCT, L. major parasites cannot incorporate choline into PC, yet the CPCT-null mutants contain similar levels of PC and PE as wild type parasites. Loss of CPCT does not affect the growth of parasites in complete medium or their virulence in mice. These results suggest that other mechanisms of PC synthesis can compensate the loss of CPCT. Importantly, CPCT-null parasites exhibited severe growth defects when ethanolamine and exogenous lipids became limited or when they were co-cultured with certain bacteria that are known to be members of sandfly midgut microbiota. These findings suggest that Leishmania employ multiple PC synthesis pathways to utilize a diverse pool of nutrients, which may be crucial for their survival and development in the sandfly.
Mechanism study of photo-induced gold nanoparticles formation by Shewanella oneidensis MR-1
Authors: Huang Bo Chuan , Yi Ying-Chen , Chang Jo-Shu , Ng I-Son
Published: May 2019

Shewanella oneidensisMR-1, a bioelectricity generating bacterium, is broadly used in bioremediation, microbial fuel cell and dissimilatory reduction and recovery of precious metals. Herein, we report for the first time that photo induction as a trigger to stimulate gold nanoparticles (Au@NPs) formation by MR-1, with wavelength and light intensity as two key variables. Results indicated that sigmoidal model is the best fit for Au@NPs formation at various wavelengths (with R2 > 0.97). Light intensity in terms of photosynthetic photon flux density (PPFD) critically influences the rate constant in the low-light intensity region (PPFD < 20), while wavelength controls the maximum rate constant in the high-light region (PPFD > 20). By deletion of Mtr pathway genes in MR-1, we proposed the mechanism for light induced Au@NP formation is the excitation effect of light on certain active groups and extracellular polymeric substances (EPS) on the cell surface. Also, the release of electrons from proteins and co-enzyme complexes enhance electron generation. To the best of our knowledge, this is the first-attempt to explore the effect of photo-induction on Au@NPs production by MR-1, which provides an alternative cost-effective and eco-friendly process in green chemical industry.
Corpse management of the invasive Argentine ant inhibits growth of pathogenic fungi
Authors: Kesäniemi Jenni , Koskimäki Janne J. , Jurvansuu Jaana
Published: May 2019

A dead conspecific poses a potential pathogen risk for social animals. We have discovered that Argentine ants (Linepithema humile) prevent spread of pathogenic fungi from corpses by depositing the dead to combined toilet and refuse areas and applying pygidial gland secretion on them. The presence of a corpse in a nest increases this secretion behaviour. We identified three fungi growing on Argentine ant corpses. Growth of the Argentine ant pathogen Aspergillus nomius and the plant pathogen Fusarium solani on corpses was inhibited as long as the ants were constantly attending them as the ant anal secretion only delayed germination of their spores. In contrast, the effect of the ant anal secretion on the human pathogen Aspergillus fumigatus was much stronger: it prevented spore germination and, accordingly, the fungus no longer grew on the treated corpses. The Argentine ants are one of the world’s worst invasive alien species as they cause ecological and economical damage in their new habitats. Our discovery points at a novel method to limit Argentine ant colonies through their natural fungal pathogens.
Extracellular vesicle microRNA quantification from plasma using an integrated microfluidic device
Authors: Ramshani Zeinab , Zhang Chenguang , Richards Katherine , Chen Lulu , Xu Geyang , Stiles Bangyan L. , Hill Reginald , Senapati Satyajyoti , Go David B. , Chang Hsueh-Chia
Published: May 2019

Extracellular vesicles (EV) containing microRNAs (miRNAs) have tremendous potential as biomarkers for the early detection of disease. Here, we present a simple and rapid PCR-free integrated microfluidics platform capable of absolute quantification (<10% uncertainty) of both free-floating miRNAs and EV-miRNAs in plasma with 1 pM detection sensitivity. The assay time is only 30 minutes as opposed to 13 h and requires only ~20 μL of sample as oppose to 1 mL for conventional RT-qPCR techniques. The platform integrates a surface acoustic wave (SAW) EV lysing microfluidic chip with a concentration and sensing microfluidic chip incorporating an electrokinetic membrane sensor that is based on non-equilibrium ionic currents. Unlike conventional RT-qPCR methods, this technology does not require EV extraction, RNA purification, reverse transcription, or amplification. This platform can be easily extended for other RNA and DNA targets of interest, thus providing a viable screening tool for early disease diagnosis, prognosis, and monitoring of therapeutic response.
Identifying the murine mammary cell target of metformin exposure
Authors: Shehata Mona , Kim Hyeyeon , Vellanki Ravi , Waterhouse Paul D. , Mahendralingam Mathepan , Casey Alison E. , Koritzinsky Marianne , Khokha Rama
Published: May 2019

The heterogeneity of breast cancer makes current therapies challenging. Metformin, the anti-diabetic drug, has shown promising anti-cancer activities in epidemiological studies and breast cancer models. Yet, how metformin alters the normal adult breast tissue remains elusive. We demonstrate metformin intake at a clinically relevant dose impacts the hormone receptor positive (HR+) luminal cells in the normal murine mammary gland. Metformin decreases total cell number, progenitor capacity and specifically reduces DNA damage in normal HR+ luminal cells, decreases oxygen consumption rate and increases cell cycle length of luminal cells. HR+ luminal cells demonstrate the lowest levels of mitochondrial respiration and capacity to handle oxidative stress compared to the other fractions, suggesting their intrinsic susceptibility to long-term metformin exposure. Uncovering HR+ luminal cells in the normal mammary gland as the major cell target of metformin exposure could identify patients that would most benefit from repurposing this anti-diabetic drug for cancer prevention/therapy purposes.
Substrate geometry modulates self-assembly and collection of plasma polymerized nanoparticles
Authors: Santos Miguel , Reeves Bryce , Michael Praveesuda , Tan Richard , Wise Steven G. , Bilek Marcela M. M.
Published: May 2019

Plasma polymerized nanoparticles (PPN) formed in plasma reactors have been considered undesirable in technological applications. More recently however, PPN were proposed as a new class of multifunctional nanocarriers for drug delivery. Therefore, synthesis of PPN requires cost-effective collection strategies that maximize yield and improve reproducibility. This work shows that the collection of PPN in dusty plasmas is modulated by modifying the geometry of substrates from planar to well-shaped collectors. The electric field profile around the wells acts as an electrostatic lens, concentrating nanoparticles and significantly bolstering process yield. The aggregation of PPN is governed by a balance between plasma expansion throughout the wells, inter-particle repulsion, particle size and density. PPN are readily dispersed in aqueous solution yielding monodisperse populations. The use of a disposable well-shape collector provides a cost-effective nanoparticle collection approach that can be adopted in a wide range of plasma polymerization configurations without the need for reactor re-design.
New horizon in C1 chemistry: breaking the selectivity limitation in transformation of syngas and hydrogenation of CO2into hydrocarbon chemicals and fuels
Authors: Zhou Wei , Cheng Kang , Kang Jincan , Zhou Cheng , Subramanian Vijayanand , Zhang Qinghong , Wang Ye
Published: May 2019

Recent advances in bifunctional catalysis for conversion of syngas and hydrogenation of CO2into chemicals and fuels have been highlighted.
Kinase network dysregulation in a human induced pluripotent stem cell model of DISC1 schizophrenia
Authors: Bentea Eduard , Depasquale Erica A. K. , O’Donovan Sinead M. , Sullivan Courtney R. , Simmons Micah , Meador-Woodruff James H. , Zhou Ying , Xu Chongchong , Bai Bing , Peng Junmin , Song Hongjun , Ming Guo-li , Meller Jarek , Wen Zhexing , McCullumsmith Robert E.
Published: May 2019

iPSCs from a schizophrenia patient harboring a mutation in the DISC1 gene show large scale abnormalities in serine/threonine kinase activity.
Single, double, and triple intercluster bonds: analyses of M2Au36(SR)24(M = Au, Pd, Pt) as 14-, 12- and 10-ve superatomic molecules
Authors: Muñoz-Castro Alvaro
Published: May 2019

Single, double, and triple-bonds can be found in fused superatomic clusters.
Assessing the formation of cobalt carbide and its catalytic performance under realistic reaction conditions and tuning product selectivity in a cobalt-based FTS reaction
Authors: Lin Qiang , Liu Bing , Jiang Feng , Fang Xuejin , Xu Yuebing , Liu Xiaohao
Published: May 2019

The formation of cobalt carbide (Co2C) and its catalytic behavior were systematically investigated using realistic reaction conditions.
Patterning Cu nanostructures tailored for CO2 reduction to electrooxidizable fuels and oxygen reduction in alkaline media
Authors: Michalak Magdalena , Roguska Agata , Nogala Wojciech , Opallo Marcin
Published: May 2019

Bare (non-capped) copper nanocatalysts were obtained from a polycrystalline metallic source.
Functionalization of biodegradable PLA nonwoven fabrics as super-wetting membranes for simultaneous efficient dye and oil/water separation
Authors: Chen Yashi , Li Qing , Chen Xinhong , Xu Xi
Published: May 2019

Although the construction process of dual functional materials for dye and oil/water separation has been developed rapidly, the postprocess of the used separation materials themselves is still a problem owing to their non-degradation in the natural environment.
Aerobic oxidation of C4–C6 α,ω-diols to the diacids in base-free medium over zirconia-supported (bi)metallic catalysts
Authors: Mounguengui-Diallo Modibo , Sadier Achraf , Da Silva Perez Denilson , Nikitine Clémence , Puchot Laura , Habibi Youssef , Pinel Catherine , Perret Noémie , Besson Michèle
Published: May 2019

Aerobic oxidation of (C4–C6) α,ω-diols in water produces the corresponding α,ω-diacids in high 83–96% yields over a Au–Pt/ZrO2 catalyst.
Preparation of a magnetically recyclable visible-light-driven photocatalyst based on phthalocyanine and its visible light catalytic degradation of methyl orange and p-nitrophenol
Authors: Ma Xiaolong , Luo Ming , Yan Liqiang , Tang Ningli , Li Jianping
Published: May 2019

A magnetically recyclable visible-light-driven photocatalyst based on metallophthalocyanine for bidirectional degradation of methyl orange and p-nitrophenol was prepared.
pH-Modulated memristive behavior based on an edible garlic-constructed bio-electronic device
Authors: Mao Shuangsuo , Sun Bai , Yu Tian , Mao Weiwei , Zhu Shouhui , Ni Yuxiang , Wang Hongyan , Zhao Yong , Chen Yuanzheng
Published: May 2019

A new type of memristive memory device with an edible garlic-constructed Ag/garlic/fluorine-doped SnO2(FTO) structure for analog neuromorphic sensor applications was designed.
The crucial role of end group planarity for fused-ring electron acceptors in organic solar cells
Authors: Rech Jeromy J. , Bauer Nicole , Dirkes David , Kaplan Joseph , Peng Zhengxing , Zhang Huotian , Ye Long , Liu Shubin , Gao Feng , Ade Harald , You Wei
Published: May 2019

Planar acceptor moieties in FREAs are necessary, as expanding the π–π stacking by only 1 Å disrupts the packing and decreases performance.
Metal- and phosphine-free electrophilic vicinal chloro-alkylthiolation and trifluoromethylthiolation of indoles using sodium sulfinate in the presence of triphosgene
Authors: He Xiu-ling , Majumder Swarup , Wu Jiang , Jin Chen-di , Guo Sheng-rong , Guo Zhi-ping , Yang Minghua
Published: May 2019

Efficient chloro-alkylthiolation and trifluoromethylthiolation of indole derivatives were developed.
Variable temperature solid-state NMR spectral and relaxation analyses of the impregnation of polyethylene glycol (PEG) into coniferous wood
Authors: Nishida Masakazu , Tanaka Tomoko , Miki Tsunehisa , Shigematsu Ichinori , Kanayama Kozo
Published: May 2019

To investigate the behaviours of polyethylene glycol (PEG) and its interaction with biomass constituents in coniferous wood (Japanese cypress), variable temperature solid-state NMR spectra and relaxation times were measured from 20–80 °C.
Glassy dynamics predicted by mutual role of free and activation volumes
Authors: Kipnusu Wycliffe K. , Elsayed Mohamed , Iacob Ciprian , Pawlus Sebastian , Krause-Rehberg Reinhard , Paluch Marian
Published: May 2019

Broadband Dielectric Spectroscopy (BDS) at elevated pressures and Positron Annihilation Lifetime Spectroscopy (PALS) are employed to elucidate the importance of the ratio of activation and free volumes during vitrification.
A sustainable approach to hierarchically porous carbons from tannic acid and their utilization in supercapacitive energy storage systems
Authors: Díez Noel , Ferrero Guillermo A. , Sevilla Marta , Fuertes Antonio B.
Published: May 2019

We synthesized hierarchically porous carbons with a high surface area using a salt template-assisted chemical activation approach using tannic acid as the precursor. When tested as electrode active materials for supercapacitors, they exhibit a high capacitance in aqueous and organic electrolytes at high current rates.
Recent advances in transition metal-based electrocatalysts for alkaline hydrogen evolution
Authors: Chen Zhijie , Duan Xiaoguang , Wei Wei , Wang Shaobin , Ni Bing-Jie
Published: May 2019

Transition metal-based electrocatalysts for alkaline hydrogen evolution reaction.
In situ formed ultrafine NbTi nanocrystals from a NbTiC solid-solution MXene for hydrogen storage in MgH2
Authors: Wang Zeyi , Zhang Xuelian , Ren Zhuanghe , Liu Yong , Hu Jianjiang , Li Haiwen , Gao Mingxia , Pan Hongge , Liu Yongfeng
Published: May 2019

In situ formed NbTi nanocrystals from a NbTiC solid-solution MXene offer highly stable catalytic activity for hydrogen storage in MgH2.
One-step vulcanization of Cd(OH)Cl nanorods to synthesize CdS/ZnS/PdS nanotubes for highly efficient photocatalytic hydrogen evolution
Authors: Sun Guotai , Mao Siman , Ma Dandan , Zou Yajun , Lv Yixuan , Li Zhihui , He Chi , Cheng Yonghong , Shi Jian-Wen
Published: May 2019

In this work, a novel strategy, one-step vulcanization of Cd(OH)Cl nanorods in the presence of ZnCl2 and Na2PdCl4, is successfully developed to synthesize CdS/ZnS/PdS nanotubes (NTs) for the first time.
Design of wide-bandgap polymers with deeper ionization potential enables efficient ternary non-fullerene polymer solar cells with 13% efficiency
Authors: Liu Delong , Zhang Ying , Zhan Lingling , Lau Tsz-Ki , Yin Hang , Fong Patrick W. K. , So Shu Kong , Zhang Shaoqing , Lu Xinhui , Hou Jianhui , Chen Hongzheng , Wong Wai-Yeung , Li Gang
Published: May 2019

Two regioisomeric wide-bandgap polymers with different nitrogen topologies along the conjugated backbone were developed and applied in non-fullerene polymer solar cells.
Assessing the Breastfeeding Dyad: A Guide for Speech-Language Pathologists
Authors: Mahurin-Smith Jamie , Genna Catherine Watson
Published: May 2019

Purpose

More than 80% of U.S. mothers initiate breastfeeding; for many of them, direct breastfeeding is an important goal. Speech-language pathologists (SLPs) who assess infants with feeding concerns, however, are generally much more familiar with assessing bottle-feeding. The purpose of this tutorial is to assist SLPs in building on their existing assessment skills in order to provide effective, evidence-based options for mothers who wish to breastfeed their infants.

Conclusion

SLPs can assist families in meeting their breastfeeding goals through effective assessment of breastfeeding dyads.
Temporal changes of the flare activity of Proxima Centauri
Authors: Pavlenko Ya. V. , Suárez Mascareño A. , Zapatero Osorio M. R. , Rebolo R. , Lodieu N. , Béjar V. J. S. , González Hernández J. I. , Mohorian M.
Published: May 2019

Context. We study temporal variations of the emission lines of Hα, Hɛ, H and K CaII, D1 and D2 NaI, He4026, and He5876 in the HARPS spectra of Proxima Centauri across an extended time of 13.2 yr, from May 27, 2004 to September 30, 2017.

Aims. We analyse the common behaviour and differences in the intensities and profiles of different emission lines in flare and quiet modes of Proxima activity.

Methods. We compare the pseudo-equivalent widths (pEW) and profiles of the emission lines in the HARPS high-resolution (R ~ 115 000) spectra observed at the same epochs.

Results. All emission lines show variability with a timescale of at least 10 min. The strength of all lines except He4026 correlate with Hα. During strong flares the “red asymmetry” appears in the Hα emission line indicating the infall of hot condensed matter into the chromosphere with velocities greater than 100 km s−1 disturbing chromospheric layers. As a result, the strength of the CaII lines anti-correlates with Hα during strong flares. The HeI lines at 4026 and 5876 Å appear in the strong flares. The cores of D1 and D2 NaI lines are also seen in emission. During the minimum activity of Proxima Centauri, CaII lines and Hɛ almost disappear while the blue part of the NaI emission lines is affected by the absorption in the extending and condensing flows.

Conclusions. We see different behaviour of emission lines formed in the flare regions and chromosphere. Chromosphere layers of Proxima Cen are likely heated by the flare events; these layers are cooled in the “non-flare” mode. The self-absorption structures in cores of our emission lines vary with time due to the presence of a complicated system of inward and outward matter flows in the absorbing layers.
Circulating FGF21 Levels in Human Health and Metabolic Disease
Authors: Keuper Michaela , Häring Hans-Ulrich , Staiger Harald
Published: May 2019

Human fibroblast growth factor 21 (FGF21) is primarily produced and secreted by the liver as a hepatokine. This hormone circulates to its target tissues (e. g., brain, adipose tissue), which requires two components, one of the preferred FGF receptor isoforms (FGFR1c and FGFR3c) and the co-factor beta-Klotho (KLB) to trigger downstream signaling pathways. Although targeting FGF21 signaling in humans by analogues and receptor agonists results in beneficial effects, e. g., improvements in plasma lipids and decreased body weight, it failed to recapitulate the improvements in glucose handling shown for many mouse models. FGF21’s role and metabolic effects in mice and its therapeutic potential have extensively been reviewed elsewhere. In this review we focus on circulating FGF21 levels in humans and their associations with disease and clinical parameters, focusing primarily on obesity and obesity-associated diseases such as type-2 diabetes. We provide a comprehensive overview on human circulating FGF21 levels under normal physiology and metabolic disease. We discuss the emerging field of inactivating FGF21 in human blood by fibroblast activation protein (FAP) and its potential clinical implications.
Catalyst-Controlled Regio- and Stereoselective Bromolactonization with Chiral Bifunctional Sulfides
Authors: Tsuchihashi Ayano , Shirakawa Seiji
Published: May 2019

Highly regioselective 5-exo bromolactonizations of stilbene-type carboxylic acids bearing electron-withdrawing substituents are achieved for the first time via the use of chiral bifunctional sulfide catalysts possessing a urea moiety. The chiral phthalide products are obtained in moderate to good enantioselectivities as the result of 5-exo cyclizations.
Visible-Light-Driven Organic Photochemical Reactions in the Absence of External Photocatalysts
Authors: Wei Yi , Zhou Quan-Quan , Tan Fen , Lu Liang-Qiu , Xiao Wen-Jing
Published: May 2019

Visible-light-driven organic photochemical reactions have attracted substantial attention from the synthetic community. Typically, catalytic quantities of photosensitizers, such as transition metal complexes, organic dyes, or inorganic semiconductors, are necessary to absorb visible light and trigger subsequent organic transformations. Recently, in contrast to these photocatalytic processes, a variety of photocatalyst-free organic photochemical transformations have been exploited for the efficient formation of carbon–carbon and carbon–heteroatom bonds. In addition to not requiring additional photocatalysts, they employ low-energy visible light irradiation, have mild reaction conditions, and enable broad substrate diversity and functional group tolerance. This review will focus on a summary of representative work in this field in terms of different photoexcitation modes.

1 Introduction

2 Visible Light Photoexcitation of a Single Substrate

3 Visible Light Photoexcitation of Reaction Intermediates

4 Visible Light Photoexcitation of EDA Complexes between Substrates

5 Visible Light Photoexcitation of EDA Complexes between Substrates and Reaction Intermediates

6 Visible Light Photoexcitation of Products

7 Conclusion and Outlook
An investigation of the parameter space for a family of dissipative mappings
Authors: de Oliveira Juliano A. , Montero Leonardo T. , da Costa Diogo R. , Méndez-Bermúdez J. A. , Medrano-T Rene O. , Leonel Edson D.
Published: May 2019

The parameter plane investigation for a family of two-dimensional, nonlinear, and area contracting map is made. Several dynamical features in the system such as tangent, period-doubling, pitchfork, and cusp bifurcations were found and discussed together with cascades of period-adding, period-doubling, and the Feigeinbaum scenario. The presence of spring and saddle-area structures allow us to conclude that cubic homoclinic tangencies are present in the system. A set of complex sets such as streets with the same periodicity and the period-adding of spring-areas are observed in the parameter space of the mapping.
Variational selection of features for molecular kinetics
Authors: Scherer Martin K. , Husic Brooke E. , Hoffmann Moritz , Paul Fabian , Wu Hao , Noé Frank
Published: May 2019

The modeling of atomistic biomolecular simulations using kinetic models such as Markov state models (MSMs) has had many notable algorithmic advances in recent years. The variational principle has opened the door for a nearly fully automated toolkit for selecting models that predict the long time-scale kinetics from molecular dynamics simulations. However, one yet-unoptimized step of the pipeline involves choosing the features, or collective variables, from which the model should be constructed. In order to build intuitive models, these collective variables are often sought to be interpretable and familiar features, such as torsional angles or contact distances in a protein structure. However, previous approaches for evaluating the chosen features rely on constructing a full MSM, which in turn requires additional hyperparameters to be chosen, and hence leads to a computationally expensive framework. Here, we present a method to optimize the feature choice directly, without requiring the construction of the final kinetic model. We demonstrate our rigorous preprocessing algorithm on a canonical set of 12 fast-folding protein simulations and show that our procedure leads to more efficient model selection.
Multilevel reflectance switching of ultrathin phase-change films
Authors: Vermeulen P. A. , Yimam D. T. , Loi M. A. , Kooi B. J.
Published: May 2019

Several design techniques for engineering the visible optical and near-infrared response of a thin film are explored. These designs require optically active and absorbing materials and should be easily grown on a large scale. Switchable chalcogenide phase-change material heterostructures with three active layers are grown here using pulsed laser deposition. Both Fabry–Perot and strong interference principles are explored to tune the reflectance. Robust multilevel switching is demonstrated for both principles using dynamic ellipsometry, and measured reflectance profiles agree well with simulations. We find, however, that switching the bottom layer of a three-layer device does not yield a significant change in reflectance, indicating a maximum in accessible levels. The pulsed laser deposition films grown show promise for optical display applications, with three shown reflectance levels.
Limit cycles created by piecewise linear centers
Authors: Llibre Jaume , Zhang Xiang
Published: May 2019

In the last few years, the interest for studying the piecewise linear differential systems has increased strongly, mainly due to their applications to many physical phenomena. In the study of these differential systems, the limit cycles play a main role. Up to now, the major part of papers which study the limit cycles of the piecewise linear differential systems consider only two pieces. Here, we consider piecewise linear differential systems with three pieces. In this paper, we study the limit cycles of the discontinuous piecewise linear differential systems in the plane R2 formed by three arbitrary linear centers separated by the set Σ={(x,y)∈R2:y=0{or}x=0{and}y≥0}. We prove that such discontinuous piecewise linear differential systems can have 1, 2, or 3 limit cycles, with 3 the maximum number of limit cycles that such systems can have. Moreover, the limit cycles are nested and must intersect Σ in three or four points. The limit cycles having three intersection points with Σ can reach the maximum number 3. The limit cycles having four intersection points with Σ are at most 1, and if it exists, the systems could simultaneously have 1 or 2 limit cycles intersecting Σ in three points.
Prediction of quantum anomalous Hall effect and giant magnetic anisotropy in graphene with adsorbed Ir-based dimers
Authors: Zhang Kai-Cheng , Li Yong-Feng , Liu Yong , Zhu Yan
Published: May 2019

In order to explore the quantum anomalous Hall effect in two-dimensional materials, it is crucial to find membrane systems with a robust out-of-plane magnetization. By adsorbing certain transition metal dimers onto graphene, a robust Chern insulator with giant magnetic anisotropy can be realized in this Dirac electronic material. We have investigated the structural, magnetic, and topological properties of graphene with adsorbed Ir-based dimers by density-functional calculations as well as the tight-binding model. Our results reveal that two adsorption systems, Ir-Fe@G and Ir2@BG, possess a giant magnetic anisotropy of 31.5 and 130.1 meV, respectively, as well as nontrivial topological bandgaps of 30.4 and 11.2 meV at the Fermi level. Integer anomalous Hall conductivities of ±2e2/h emerge as the chemical potential scans through the bandgaps. The adsorption dimers are perpendicular to the graphene layer and robust against thermal fluctuation. Both the magnetic anisotropy and the topological bandgaps can be effectively modulated by the electric field, which makes them feasible in the application of quantum devices.
Giant reversible stress-induced change of resistivity in Ni-Mn-In-Co alloys
Authors: Konoplyuk Sergiy , Kokorin Volodymyr , Mashirov Alexey , Dilmieva Elvina , Dalinger Andrei
Published: May 2019

Ni43Mn37.8In12.2Co7 and Ni43Mn37.65In12.35Co7 polycrystalline alloys were tested mechanically in uniaxial compression in order to determine the stress–strain response and accompanying changes of electrical resistivity. Compression of the specimen by 9% at room temperature resulted in a 250% increase of resistivity followed by almost full recovery to its predeformation level upon heating to 400 K. Microstructural observations revealed that giant reversible changes of electrical resistivity occurred due to stress-induced martensitic transformation and shape recovery of plastically deformed grains induced by heating.
Fractional repetitive control of nanopositioning stages for tracking high-frequency periodic inputs with nonsynchronized sampling
Authors: Li Linlin , Gu Guoying , Zhu LiMin
Published: May 2019

The repetitive control (RC) has been employed for high-speed tracking control of nanopositioning stages due to its abilities of precisely tracking periodic trajectories and rejecting periodic disturbances. However, in digital implementation, the sampling frequency should be integer multiple of the tracking frequency of the desired periodic trajectory. Otherwise, the rounding error would result in a significant degradation of the tracking performance, especially for the case of high input frequencies. To mitigate this rounding effect, the fractional repetitive control (FRC) technique is introduced to control the nanopositioning stage so as to precisely track high-frequency periodic inputs without imposing constraints on the sampling frequency of the digital control system. The complete procedure of controller design and implementation is presented. The techniques to deal with the problems of non-minimum phase system and fractional delay points number are described in detail. The proposed FRC is plugged into the proportional-integral control, and implemented on a custom-built piezo-actuated nanopositioning stage. Validation experiments are conducted, and the results show that the tracking errors caused by the rounding effect in the traditional RC approach are almost completely eliminated, when tracking sinusoidal waveforms with frequencies from 1000 Hz to 1587.3 Hz under the sampling frequency of 50 kHz, where the fractional parts being rounded vary from 0 to 0.5.
Spike chimera states and firing regularities in neuronal hypernetworks
Authors: Bera Bidesh K. , Rakshit Sarbendu , Ghosh Dibakar , Kurths Jürgen
Published: May 2019

A complex spatiotemporal pattern with coexisting coherent and incoherent domains in a network of identically coupled oscillators is known as a chimera state. Here, we report the emergence and existence of a novel type of nonstationary chimera pattern in a network of identically coupled Hindmarsh–Rose neuronal oscillators in the presence of synaptic couplings. The development of brain function is mainly dependent on the interneuronal communications via bidirectional electrical gap junctions and unidirectional chemical synapses. In our study, we first consider a network of nonlocally coupled neurons where the interactions occur through chemical synapses. We uncover a new type of spatiotemporal pattern, which we call “spike chimera” induced by the desynchronized spikes of the coupled neurons with the coherent quiescent state. Thereafter, imperfect traveling chimera states emerge in a neuronal hypernetwork (which is characterized by the simultaneous presence of electrical and chemical synapses). Using suitable characterizations, such as local order parameter, strength of incoherence, and velocity profile, the existence of several dynamical states together with chimera states is identified in a wide range of parameter space. We also investigate the robustness of these nonstationary chimera states together with incoherent, coherent, and resting states with respect to initial conditions by using the basin stability measurement. Finally, we extend our study for the effect of firing regularity in the observed states. Interestingly, we find that the coherent motion of the neuronal network promotes the entire system to regular firing.
Indium incorporation in homoepitaxial β-Ga2O3 thin films grown by metal organic vapor phase epitaxy
Authors: Bin Anooz S. , Popp A. , Grüneberg R. , Wouters C. , Schewski R. , Schmidbauer M. , Albrecht M. , Fiedler A. , Ramsteiner M. , Klimm D. , Irmscher K. , Galazka Z. , Wagner G.
Published: May 2019

Homoepitaxial β-(In,Ga)2O3 thin films were grown on (100) β-Ga2O3 substrates by metal organic vapor phase epitaxy using triethylgallium (TEGa) and triethylindium (TEIn). Deposition temperatures from 650 to 825 °C and pressures from 5 to 20 mbar have been explored. The growth rate decreased linearly with increasing deposition temperature and decreased exponentially with increasing pressure. The resulting films were characterized by atomic force microscopy (AFM), high resolution x-ray diffraction (HR-XRD), and transmission electron microscopy (TEM). As the flow rate of TEIn varied from 0 to 0.13 μmol/min during the growth, AFM showed the surface roughness of about 1 nm, while HR-XRD measurements revealed an increase of the vertical lattice spacing. The maximum atomic concentration of indium incorporated in monoclinic β-(In,Ga)2O3 is about 3.5% and shifts the optical absorption edge to lower energy by ∼0.18 eV. Further increase of the indium flow rate leads to an increase of the surface roughness and a decrease in the vertical lattice spacing due to the formation of a separate cubic In2O3 phase that was confirmed by HR-TEM images. X-ray reciprocal space maps showed that the β-(In,Ga)2O3 thin films were grown coherently on β-Ga2O3.
Fabrication of polymeric lenses using magnetic liquid molds
Authors: Falahati Mojtaba , Zhou Wenchen , Yi Allen , Li Lei
Published: May 2019

Traditional molding and casting processes in optical manufacturing require sophisticated and expensive molds and molding equipment. In this work, magnetic liquid droplets were used as soft and deformable molds. The magnetic drop within an immiscible polymeric resin forms a conical shape at the interface due to the equilibrium of magnetostatic force and surface tension, which results in a plano–concave lens after curing. An apparatus was assembled to control the amplitude and gradient of the magnetic field. A Shack-Hartmann sensor was employed to measure the focal length of the formed polydimethylsiloxane lenses. The effects of magnetic field intensity, gradient of the magnetic field, and magnetic susceptibility were investigated. This technique is low cost, rapid, and straightforward and can be used for forming lenses with different sizes and shapes.
Multiple aging mechanisms in ferroelectric deuterated potassium dihydrogen phosphate
Authors: Fields Gregory A. , Cieszynski Samuel F. , Zhao Bo , Tadesse Kidan A. , Sheikh Mohammed A. , Colla Eugene V. , Weissman M. B.
Published: May 2019

The anomalously large dielectric aging in ferroelectric partially deuterated potassium dihydrogen phosphate is found to have multiple distinct mechanisms. Two components cause a decrease in dielectric response over a limited range of fields around the aging field. Substantial aging occurs on time scales of ∼1000 s after a field change, as expected for a hydrogen/deuterium diffusion mechanism. A slower component can give an almost complete loss of domain-wall dielectric response at the aging field after weeks of aging. There is also a particularly unusual aging in which the dielectric response increases with time after rapid cooling.
Probing polaritons in the mid- to far-infrared
Authors: Folland T. G. , Nordin L. , Wasserman D. , Caldwell J. D.
Published: May 2019

The long free-space wavelengths associated with the mid- to far-infrared spectral range impose significant limitations on the form factor of associated optic and electro-optic components. Specifically, current commercial optical sources, waveguides, optical components (lenses and waveplates), and detector elements are larger than the corresponding diffraction limit, resulting in reduced image resolution and bulky optical systems, with deleterious effects for a number of imaging and sensing applications of interest to commercial, medical, and defense related arenas. The field of nanophotonics, where the ultimate objective is to confine and manipulate light at deeply subwavelength, nanometer length scales, offers significant opportunities to overcome these limitations. The demonstration of nanoscale optics in the infrared can be achieved by leveraging polaritons, quasiparticles comprised of oscillating charges within a material coupled to electromagnetic excitations. However, the predominant polaritonic materials and the characterization techniques and methods implemented for measuring these quasiparticles in the mid- to far-IR require a different approach with respect to similar efforts in the ultraviolet, visible, and near-IR. The purpose of this tutorial is to offer an overview of the basic materials, tools, and techniques for exciting, manipulating, and probing polaritons in the mid- to far-infrared wavelength range, providing a general guide to subwavelength and nanoscale optics for those entering this exciting and burgeoning research field.
Magnetic localization and control of helical robots for clearing superficial blood clots
Authors: Khalil Islam S. M. , Adel Alaa , Mahdy Dalia , Micheal Mina M. , Mansour Mohanad , Hamdi Nabila , Misra Sarthak
Published: May 2019

This work presents an approach for the localization and control of helical robots during removal of superficial blood clots inside in vitro and ex vivo models. The position of the helical robot is estimated using an array of Hall-effect sensors and precalculated magnetic field map of two synchronized rotating dipole fields. The estimated position is used to implement closed-loop motion control of the helical robot using the rotating dipole fields. We validate the localization accuracy by visual feedback and feature tracking inside the in vitro model. The experimental results show that the magnetic localization of a helical robot with diameter of 1 mm can achieve a mean absolute position error of 2.35 ± 0.4 mm (n = 20). The simultaneous localization and motion control of the helical robot enables propulsion toward a blood clot and clearing at an average removal rate of 0.67 ± 0.47 mm3/min. This method is used to localize the helical robot inside a rabbit aorta (ex vivo model), and the localization accuracy is validated using ultrasound feedback with a mean absolute position error of 2.6 mm.
Demonstration of waferscale voltage amplifier and electrostatic quadrupole focusing array for compact linear accelerators
Authors: Vinayakumar K. B. , Ardanuc S. , Ji Q. , Persaud A. , Seidl P. , Schenkel T. , Lal A.
Published: May 2019

Compact linear accelerators, with beam energies in the kiloelectron volt to megaelectron volt range, have applications in medicine, neutron/X-ray generation, surface modifications, etc. The size, weight, and power of existing accelerators preclude them from mass availability in portable formats. This paper presents a specific implementation of an ion accelerator architecture based on planar wafers with accelerating and focusing sections. Our low cost approach allows the control of the final ion beam energy with potential applications, for example, for accelerator-based ion implantation. In this paper, we demonstrate two important waferscale modules required to build a linear particle accelerator; these include (1) on-wafer voltage amplification for beam acceleration using Inductor-Capacitor (LC) resonators and (2) waferscale electrostatic quadrupole arrays (ESQA) to refocus the ion beams during transport. On-board LC resonators were developed using Printed Circuit Board fabrication processes to implement an LC element resonant at ∼16.6 MHz with a quality factor of 25. An energy gain of ∼250 eV was observed using a two wafer acceleration unit with an argon ion beam with 6.5 keV initial energy. A 3 × 3 ESQA was fabricated on a glass wafer with metal electrodes formed by depositing copper metal around the beam apertures. The ESQA was used to focus and defocus an argon ion beam, demonstrating a field gradient of ∼500 V over a gap of ∼250 μm.
Soliton ratchet induced by random transitions among symmetric sine-Gordon potentials
Authors: Casado-Pascual Jesús , Sánchez-Rey Bernardo , Quintero Niurka R.
Published: May 2019

The generation of net soliton motion induced by random transitions among N symmetric phase-shifted sine-Gordon potentials is investigated, in the absence of any external force and without any thermal noise. The phase shifts of the potentials and the damping coefficients depend on a stationary Markov process. Necessary conditions for the existence of transport are obtained by an exhaustive study of the symmetries of the stochastic system and of the soliton velocity. It is shown that transport is generated by unequal transfer rates among the phase-shifted potentials or by unequal friction coefficients or by a properly devised combination of potentials (N>2). Net motion and inversions of the currents, predicted by the symmetry analysis, are observed in simulations as well as in the solutions of a collective coordinate theory. A model with high efficient soliton motion is designed by using multistate phase-shifted potentials and by breaking the symmetries with unequal transfer rates.
Strong nonlinear optical response from ZnO by coupled and lattice-matched nanoantennas
Authors: Protte Maximilian , Weber Nils , Golla Christian , Zentgraf Thomas , Meier Cedrik
Published: May 2019

We show the effective generation of second harmonic generated light in thin zinc oxide (ZnO) films by using double-resonant plasmonic nanoantennas. The designed structure consists of three gold rods with two localized surface plasmon resonances at ω and 2ω. Two of the nanoantennas are designed to be resonant for the fundamental frequency ω in order to provide a strong localization of light. The third antenna lies in between the two fundamental antennas separated by a small gap (≈30nm). Due to a strong overlap between the second harmonic resonance at 2ω and the fundamental resonance, the overall far-field radiation is significantly increased. Second harmonic generation spectroscopy measurements show an enhancement by a factor of nine compared to the emission from single dipole rods. Additionally, by optimizing the lattice constant for the nanoantenna arrays, the overall second harmonic response from the ZnO was significantly increased by a factor as large as 70, which is a great improvement for comparable plasmonic nanoantennas on thin zinc oxide.
Precise control of hydrogen response of semicontinuous palladium film using piezoelectric resonance method
Authors: Nakamura N. , Ueno T. , Ogi H.
Published: May 2019

During deposition of metallic material on a substrate, a semicontinuous film composed of isolated and connected clusters is formed transiently at a few nanometers thickness. The surface electrical conductivity at this moment is governed by the tunneling conduction, and slight subsequent evolution of the film morphology changes the conductivity markedly because of the island connection. When the semicontinuous palladium film is exposed to hydrogen, its morphology changes because of absorption of hydrogen, changing the surface conductivity drastically. This phenomenon is applicable for hydrogen sensing. However, it has been significantly difficult to fabricate an optimum semicontinuous structure because it appears in a very short time during deposition. In the present study, we precisely control the palladium film morphology using the piezoelectric resonance method. In this method, an electric field is excited around the substrate surface using the resonant vibration of the piezoelectric material. The electric field generates the electrical current in the deposited material, and the vibrational energy of the piezoelectric material is spent on it. Because the energy loss depends on the electrical conductivity (morphology) of the deposited material, by measuring the change in the attenuation of the resonant vibration, evolution of the morphology is detectable. Using this method, palladium films with several morphologies were fabricated, and the conductivity change in hydrogen was evaluated. The change ratio of the conductivity significantly depended on the morphology, and the conductive sensitivity to the hydrogen detection with the optimum structure was larger than that reported in the previous study by a factor of 12.
Ultralong spin lifetimes in one-dimensional semiconductor nanowires
Authors: Dirnberger Florian , Kammermeier Michael , König Jan , Forsch Moritz , Faria Junior Paulo E. , Campos Tiago , Fabian Jaroslav , Schliemann John , Schüller Christian , Korn Tobias , Wenk Paul , Bougeard Dominique
Published: May 2019

We experimentally demonstrate ultralong spin lifetimes of electrons in the one-dimensional (1D) quantum limit of semiconductor nanowires. Optical probing of single wires of different diameters reveals an increase in the spin relaxation time by orders of magnitude as the electrons become increasingly confined until only a single 1D sub-band is populated after thermalization. We find the observed spin lifetimes of more than 200 ns to result from the robustness of 1D electrons against major spin relaxation mechanisms, highlighting the promising potential of these wires for long-range transport of coherent spin information.
On the importance of onset times and multiple-wavelength analysis of photoluminescence decays
Authors: Kůsová K. , Popelář T.
Published: May 2019

The characterization of photoluminescence (PL) decay is a very basic optical measurement. In this article, we propose a straightforward yet effective procedure to analyze PL decays measured at multiple wavelengths at once, using a time-gated CCD or a streak camera. In our procedure, we make sure to include the onset edge of the PL decay, because its omission can significantly reduce the quality of the analysis and propose a way to accurately determine this parameter.
Computational study of electron paramagnetic resonance parameters for Mg and Zn impurities in
β
-Ga2O3
Authors: Skachkov Dmitry , Lambrecht Walter R. L.
Published: May 2019

A computational study of electron paramagnetic resonance (EPR) g-tensors and hyperfine tensors in Mg- and Zn-doped β-Ga2O3 is presented. While Mg has been found previously to prefer the octahedral site, we find here that Zn prefers the tetrahedral substitutional site. The EPR signatures are found to be distinct for the two sites. Good agreement with experiment is found for the g-tensor and the hyperfine interaction for MgGa2, and predictions are made for the Zn case.