bluuebunny/crossref_metadata_2025 huggingface dataset:
Modeling of interactions between supernovae ejecta and aspherical circumstellar environments
Authors: Kurfürst P. , Krtička J.
Published: April 2019

Context. Massive stars are characterized by a significant loss of mass either via (nearly) spherically symmetric stellar winds or pre-explosion pulses, or by aspherical forms of circumstellar matter (CSM) such as bipolar lobes or outflowing circumstellar equatorial disks. Since a significant fraction of most massive stars end their lives by a core collapse, supernovae (SNe) are always located inside large circumstellar envelopes created by their progenitors.

Aims. We study the dynamics and thermal effects of collision between expanding ejecta of SNe and CSM that may be formed during, for example, a sgB[e] star phase, a luminous blue variable phase, around PopIII stars, or by various forms of accretion.

Methods. For time-dependent hydrodynamic modeling we used our own grid-based Eulerian multidimensional hydrodynamic code built with a finite volumes method. The code is based on a directionally unsplit Roe’s method that is highly efficient for calculations of shocks and physical flows with large discontinuities.

Results. We simulate a SNe explosion as a spherically symmetric blast wave. The initial geometry of the disks corresponds to a density structure of a material that orbits in Keplerian trajectories. We examine the behavior of basic hydrodynamic characteristics, i.e., the density, pressure, velocity of expansion, and temperature structure in the interaction zone under various geometrical configurations and various initial densities of CSM. We calculate the evolution of the SN–CSM system and the rate of aspherical deceleration as well as the degree of anisotropy in density, pressure, and temperature distribution.

Conclusions. Our simulations reveal significant asphericity of the expanding envelope above all in the case of dense equatorial disks. Our “low density” model however also shows significant asphericity in the case of the disk mass-loss rate Ṁcsd = 10−6 M⊙ yr−1. The models also show the zones of overdensity in the SN–disk contact region and indicate the development of Kelvin-Helmholtz instabilities within the zones of shear between the disk and the more freely expanding material outside the disk.
Extreme starlight polarization in a region with highly polarized dust emission
Authors: Panopoulou Georgia V. , Hensley Brandon S. , Skalidis Raphael , Blinov Dmitry , Tassis Konstantinos
Published: April 2019

Context. Galactic dust emission is polarized at unexpectedly high levels, as revealed by Planck.

Aims. The origin of the observed ≃20% polarization fractions can be identified by characterizing the properties of optical starlight polarization in a region with maximally polarized dust emission.

Methods. We measure the R-band linear polarization of 22 stars in a region with a submillimeter polarization fraction of ≃20%. A subset of 6 stars is also measured in the B, V, and I bands to investigate the wavelength dependence of polarization.

Results. We find that starlight is polarized at correspondingly high levels. Through multiband polarimetry we find that the high polarization fractions are unlikely to arise from unusual dust properties, such as enhanced grain alignment. Instead, a favorable magnetic field geometry is the most likely explanation, and is supported by observational probes of the magnetic field morphology. The observed starlight polarization exceeds the classical upper limit of [pV/E(B−V)]max = 9% mag−1 and is at least as high as 13% mag−1, as inferred from a joint analysis of Planck data, starlight polarization, and reddening measurements. Thus, we confirm that the intrinsic polarizing ability of dust grains at optical wavelengths has long been underestimated.
Towards the definition of a detailed transcriptomic map of berry development
Authors: Fasoli Marianna , Richter Chandra L. , Zenoni Sara , Sandri Marco , Zuccolotto Paola , Dal Santo Silvia , Pezzotti Mario , Dokoozlian Nick , Tornielli Giovanni Battista
Published: April 2019

The progress of the grapevine genomics and the development of high-throughput technologies for gene expression analysis stimulated the investigation of the physical, biochemical and physiological changes of grape berry growth and maturation at transcriptomic level. The molecular information generated in the last decade is however still fragmented since it relies upon detailed analysis of few stages and thus lacks continuity over grape development. To identify the molecular events associated with berry development at a higher temporal resolution and define a transcriptomic map, we performed RNA-seq analysis of berry samples collected every week from fruit-set to maturity in Pinot noir and Cabernet Sauvignon for three consecutive years, resulting in 219 samples. Using the most variable portion of the transcriptome, we built a preliminary transcriptomic model of berry development based on the Cabernet Sauvignon samples. The Pinot noir samples were then aligned onto this preliminary ripening map to investigate its performance in describing the development of another grape variety. A further step for testing the model was the projection of RNA-seq samples of fruit development of five red-skin Italian cultivars. For all these surveys, the transcriptomic route allowed a precise definition of the progression of berry development during both formation and ripening phases.
Development, yield potential and nutritional aspects of resistant grapevine varieties in Trentino Alto Adige
Authors: Pedò Stefano , Bottura Maurizio , Porro Duilio
Published: April 2019

The reduction of the environmental impact of agricultural activity has stimulated the evaluation of new cultivars tolerant/resistant to fungal diseases within the context of Trentino viticulture. In an alluvial soil, 15 varieties of resistant vines were planted:Aromera,Baron,Bronner,Cabernet Cantor,Cabernet Cortis,Cabernet Carbon,Cabino,Helios,Johanniter,Monarch,Muscaris,Prior,Regent,Solaris, andSouvignier gris. Since 2015 they have been evaluated for nutritional aspects, vegetative-productive balance, quantitative-qualitative parameters of musts and health status. Some cultivars (Cabernet Cortis, Cabino, Helios, and Prior) had an insufficient vegetative development, whilst other varieties presented a balanced or excessive behaviour. Regarding magnesium (Mg), some of these cultivars presented deficiencies, often confirmed by visual analysis, but not always highlighted by leaf analyses (Cabernet Cantor,Cabernet Cortis, andMonarch). For such varieties, Mg supply is recommended. Nonetheless, with the aim of new plantings, the choice of more suitable rootstock combinations should be done.Cabinoalways showed very highly susceptibility toPlasmopara viticolaattack, with an ineffective resistance.
Effects of pre-harvest techniques in the control of berry ripening in grapevine cv. Sauvignon blanc
Authors: Lucchetta Valentina , Volta Benedetta , Tononi Mattia , Zanotelli Damiano , Andreotti Carlo
Published: April 2019

Due to a variety of reasons (changing climatic conditions, higher photosynthetic efficiency of newly established vineyards, yield restriction imposed by production protocols), there is currently a tendency towards early ripening in grapevines, combined with the production of berries characterized by high sugar content. This tendency conflicts with the general market demand for wines (mostly white wines) with low alcohol level and characterised by a fresh, easy-to-drink taste. We tested two different techniques applied to the canopy (defoliation and the use of an antitranspirant product) with the aim of delaying the ripening process and improving the berry quality of the white cultivar Sauvignon blanc. The defoliation performed at veraison allowed postponement of the ripening process by about 5 days as compared to undefoliated vines, without altering the sugar/acid ratio of the berries. The antitranspirant product delayed ripening by 10 to 15 days. Brix was reduced by 1.5-2.5 degrees in the 2 considered seasons, whereas the effect on acidity was contradicting and needs further research for a full understanding of the mechanisms involved in the process.
Le spectre de Majorana
Authors: Houzet Manuel , Meyer Julia , Simon Pascal
Published: April 2019

Pour paraphraser Karl Marx, « un spectre hante la physique : le spectre d’Ettore Majorana ». Près de 80 ans après sa disparition, les travaux du physicien italien continuent d’inspirer les chercheurs. Ainsi, dans son dernier article, Majorana prédit qu’une particule élémentaire dépourvue de charge électrique pourrait être sa propre antiparticule [1], en opposition avec la théorie de Dirac, pour laquelle une particule et son antiparticule sont distinctes.

Plusieurs groupes ont récemment annoncé la découverte de quasiparticules de Majorana dans des nanostructures supraconductrices. En plus d’être leur propre antiparticule, ces quasi-particules possèdent des propriétés exotiques qui sont d’un grand intérêt pour le développement d’un ordinateur quantique topologiquement protégé.
O-Methyl Phytocannabinoids: Semi-synthesis, Analysis in Cannabis Flowerheads, and Biological Activity
Authors: Caprioglio Diego , Allegrone Gianna , Pollastro Federica , Valera Stefano , Lopatriello Annalisa , Collado Juan A. , Munoz Eduardo , Appendino Giovanni , Taglialatela-Scafati Orazio
Published: April 2019

A general protocol for the selective mono-O-methylation of resorcinyl phytocannabinoids was developed. The availability of semisynthetic monomethyl analogues of cannabigerol, cannabidiol, and cannabidivarin (1a–3a, respectively) made it possible to quantify these minor phytocannabinoids in about 40 different chemotypes of fiber hemp. No chemotype significantly accumulated mono-O-methyl cannabidiol (2b) or its lower homologue (3b), while at least three chemotypes containing consistent amounts (≥ 400 mg/kg) of O-methylcannabigerol (1b) were identified. O-Methylation of alkyl phytocannabinoids (1b–3b) does not significantly change the activity on peroxisome proliferator-activated receptors in contrast to what was reported for phenethyl analogues.
A Facile and Efﬁcient Approach for the Synthesis of 3-Aryl-4-hydroxy-1,3-thiazolidin-2-ones
Authors: Zhu Yue , Wang Qilin , Luo Haofan , Wang Zijuan , Zhang Guolin , Yu Yongping
Published: April 2019

A facile and efficient method for the synthesis of 3-aryl-4-hydroxy-1,3-thiazolidin-2-ones by the reaction of 1,4-dithiane-2,5-diol with acyl azides is reported. This reaction proceeded well at 80 °C to afford products in excellent yields for a wide range of substrates. A possible mechanism has been proposed.
Diethylaminosulfur Trifluoride (DAST)-Mediated Intramolecular Benzannulation of o-Allylchalcones: Synthesis of 3-Fluorotetralins
Authors: Chang Meng-Yang , Chen Han-Yu , Tsai Yu-Lin
Published: April 2019

A concise route for the synthesis of 3-fluorotetralines is described, including: (i) NaBH4-mediated reduction of oxygenated o-allylchalcones and (ii) sequential DAST-mediated intramolecular annulation of the resulting alkenols. A plausible mechanism is proposed and discussed. This protocol provides highly effective regio- and stereocontrolled allyl-enone cross-coupling to construct two stereocenters and one E-configured styryl group.
Exploratory Process Development of Pexidartinib through the Tandem Tsuji–Trost Reaction and Heck Coupling
Authors: Chen Dongsheng , Zhang Yi , Li Jianqi , Liu Yu
Published: April 2019

A novel synthetic route to CSF1R inhibitor pexidartinib was designed and demonstrated. Crucial to the successful synthesis is a tandem Tsuji–Trost reaction and Heck coupling in combination with palladium and silver catalysis. The final product was obtained via five steps in 49% yield with purity as high as 99.2%. The cheap and available materials and reagents and easy operations for workup and purification make this route more practical.
Evaluation of an Alternative Staining Method Using SYTO 13 to Determine Reticulated Platelets
Authors: Hille Laura , Cederqvist Marco , Hromek Julia , Stratz Christian , Trenk Dietmar , Nührenberg Thomas
Published: April 2019

Reticulated platelets reflect the rate of platelet turnover and represent the youngest circulating platelets in peripheral blood. Reticulated platelets contain residual ribonucleic acid (RNA) from megakaryocytes which is lost in a time-dependent manner and can be transcribed into proteins even in the absence of a nucleus. An increased proportion of reticulated platelets is associated with higher platelet reactivity, cardiovascular events and mortality. At present, a fully automated assay system (SYSMEX haematology analyser) is available for analysis. This method, however, is not suitable for extended laboratory investigations like subsequent cell sorting. Flow cytometry analysis after staining with thiazole orange (TO) is frequently used in such settings despite several limitations. Here, we describe a new assay for determination of reticulated platelets by flow cytometry using the nucleic acid staining dye SYTO 13 and compare it with SYSMEX and TO staining as current standards. A significant correlation between immature platelet fraction (IPF) determined by SYSMEX XE-2100 analyser and results obtained with the SYTO 13-based assay was observed (r = 0.668, p < 0.001) which was stable during a reasonable time period. In contrast, the correlation between TO staining and IPF was weaker (r = 0.478, p = 0.029) and lost after 90 minutes of staining. SYTO 13 staining of platelets enabled sorting of RNAlow and RNArich platelets which was confirmed by RNA quantification of sorted platelets. Except for fixation of platelets, sorting of these platelet sub-populations was stable under various experimental settings. In summary, determination of reticulated platelets with the new SYTO 13 assay offers distinct technical advantages enabling further laboratory processing.
Is a Chest Tube Necessary after Video-Assisted Thoracoscopic Mediastinal Tumor Resection?
Authors: Liu Yu-Wei , Chen Hao-Wei , Lee Jui-Ying , Chiang Hung-Hsing , Li Hsien-Pin , Chang Po-Chih , Chou Shah-Hwa
Published: April 2019

Background The omission of chest tubes after thoracoscopic procedures such as sympathectomy, lung biopsy, and lung resection has proven efficacious in decreasing pain and length of hospital stay in some cases. However, its safety for mediastinal diseases remains unclear. This study evaluated the feasibility and outcome of eliminating chest drains after video-assisted thoracoscopic surgery (VATS) for mediastinal tumor resection.

Methods We retrospectively investigated 70 patients receiving VATS mediastinal tumor resection in a single institution between January 2016 and November 2018. A total of 39 patients (drain group) received postoperative chest drains and 31 patients (no-drain group) did not. Group clinical outcomes and operation data were compared. A propensity score matching analysis was further performed to yield a fairer comparison.

Results Before propensity score matching, the no-drain group had a higher prevalence of cystic lesions, a shorter operative time, and less blood loss compared with the drain group (p = 0.015, p = 0.018, and p < 0.001, respectively). After matching, the group differences in these perioperative variables lost significance (p = 0.095, 0.4, and 0.2, respectively). The no-drain group had lower postoperative day 2 pain scores and shorter postoperative hospital stays than the drain group, regardless of whether they were matched (pain: p = 0.028; hospital stay < 0.001) or not (pain: p = 0.003; hospital stay < 0.001). No major adverse events occurred in either group during hospitalization or follow-up period.

Conclusion Eliminating chest drain placement after VATS mediastinal tumor resection may benefit some patients and decrease postoperative pain and hospital stay without increasing complications or compromising patient safety.
Binding of Coagulation Factor XIII Zymogen to Activated Platelet Subpopulations: Roles of Integrin αIIbβ3 and Fibrinogen
Authors: Kotova Yana N. , Podoplelova Nadezhda A. , Obydennyy Sergey I. , Kostanova Elizaveta A. , Ryabykh Alexander A. , Demyanova Aleksandra S. , Biriukova Maria I. , Rosenfeld Mark A. , Sokolov Alexey V. , Chambost Herve , Kumskova Maria A. , Ataullakhanov Fazoil I. , Alessi Marie-Christine , Panteleev Mikhail A.
Published: April 2019

Factor XIIIa (fXIIIa) is a transglutaminase that plays a crucial role in fibrin clot stabilization and regulation of fibrinolysis. It is known to bind to procoagulant platelets. In contrast, the zymogen fXIII interaction with platelets is not well characterized. We investigated the interaction of zymogen fXIII with activated platelet subpopulations. Confocal microscopy and flow cytometry using fluorescently labelled factors and antibodies. Phosphatidylserine (PS)-positive activated platelets bound 700 to 800 molecules/cell of fXIII at 100 nM, while both PS-negative activated platelets and resting platelets bound 200 to 400 molecules/cell. The binding was reversible, calcium-independent and linear within the fXIII concentration range of up to 1,000 nM. fXIII predominantly bound to the caps of procoagulant platelets and co-localized with fibrinogen. Exogenous fibrinogen promoted fXIII binding by activated PS-negative platelets; this effect was abolished by the integrin αIIbβ3 antagonist monafram. The fXIII binding was 1.5- to 3-fold decreased for platelets from four patients with grey platelet syndrome, and was variable for platelets from six patients with Glanzmann's thrombasthenia. Strong platelet stimulation, fibrinogen and αIIbβ3 play essential roles in fXIII binding, without any of them fXIII does not bind to platelets. The preferential binding in the cap-like structures might be important for increasing local fXIII concentration in platelet thrombi.
A Novel Frameshift Homozygous Mutation in DHCR7 with a Known Missense Homozygous Mutation in the PROC in a 6-Year-Old Boy: A Child with Two Rare Genetic Diseases
Authors: Gumus Evren
Published: April 2019

In the present case report, we described a 6-year-old-boy with developmental delay, mental retardation, lack of speech, skin scars, and 2 to 3 toe syndactyly from healthy consanguineous Turkish parents. The whole exome sequencing (WES) analysis of this patient showed homozygous variant c.418T > C p.(Cys140Arg) in PROC gene and novel homozygous variant c.57dupC p.(Asn20Glnfs*2) in the DHCR7 gene. This finding demonstrated that WES is of great value for the diagnosis of two separate genetic disorders in a patient with multiple dysmorphic and other clinical features. It should also be kept in mind that the coexistence of two autosomal recessive diseases could be observed in highly related consanguineous marriages. The combined evaluation of clinical and laboratory data provided extremely valuable insight into the diagnosis of this unique case.
A scalable arbitrary waveform generator for atomic physics experiments based on field-programmable gate array technology
Authors: Donnellan Sean , Hill Ian R. , Bowden William , Hobson Richard
Published: April 2019

We present a field-programmable gate array (FPGA) based control system that has been implemented to control a strontium optical lattice clock at the National Physical Laboratory, UK. Bespoke printed circuit boards have been designed and manufactured, including an 8-channel, 16-bit digital to analog converter board with a 2 μs update rate and a 4-channel direct-digital synthesis board clocked at 1 GHz. Each board includes its own FPGA with 28 digital output lines available alongside the specialized analog or radio frequency outputs. The system is scalable to a large number of control lines by stacking the individual boards in a master-slave arrangement. The timing of the digital and analog outputs is based on the FPGA clock and is thus very predictable and exhibits low jitter. A particular advantage of our hardware is its large data buffers that, when combined with a pseudoclock structure, allow complex waveforms to be created. A high reliability of the system has been demonstrated during extended atomic clock frequency comparisons.
Model reference adaptive damping control for a nanopositioning stage with load uncertainties
Authors: Ling Jie , Feng Zhao , Ming Min , Xiao Xiaohui
Published: April 2019

In this paper, a scheme of model reference adaptive integral resonant control (MRAIRC) is presented for adaptive precision motion control of a piezo-actuated nanopositioning platform. The major advantage of the proposed scheme lies in the adaptivity for dynamic changes resulting from load uncertainties. Existing standard integral resonant control (IRC) with constant controller gains is normally designed based on the identified system model under no external load. For the proposed MRAIRC, a standard IRC is first designed using an analytical approach, assuming that a second-order system model is obtained in advance. Afterwards, the designed closed-loop is utilized as a reference model for systems with model uncertainties. The adaptive laws of the controller gains are determined according to the well-known MIT rules. An offline trail-and-error operation is conducted for adaption gains’ tuning. The stability of this adaptive control system is proved through Lyapunov stability analysis. Simulation and experimental studies demonstrate that the proposed MRAIRC is superior to the standard IRC in terms of the tracking errors for commonly used raster scanning signals at 5, 10, and 20 Hz with load variations of the platform ranging from 0 to 1000 g.
Enhancement of resolution in microspherical nanoscopy by coupling of fluorescent objects to plasmonic metasurfaces
Authors: Brettin Aaron , Abolmaali Farzaneh , Blanchette Kylen F. , McGinnis Cobey L. , Nesmelov Yuri E. , Limberopoulos Nicholaos I. , Walker Dennis E. , Anisimov Igor , Urbas Augustine M. , Poffo Luiz , Maslov Alexey V. , Astratov Vasily N.
Published: April 2019

The resolution of microsphere-based nanoscopy is studied using fluorescently labeled nanospheres and F-actin protein filaments with the emission coupled to the localized surface plasmon resonances in the underlying Au nanodisk arrays. Virtual imaging is performed through high-index microspheres embedded in plastic coverslips placed in contact with the nanoscale objects. For 150 and 200 nm periods of nanoplasmonic arrays, the imaging has a solid immersion lens-limited resolution, whereas for shorter periods of 80 and 100 nm, the resolution was found to increase up to ∼λ/7, where λ is the emission wavelength. The results cannot be interpreted within a framework of a regular localized plasmonic structured illumination microscopy since the array period was significantly shorter than the wavelength and postimaging processing was not used. It is hypothesized that the observed super-resolution is based on coupling of the emission of nanoscale objects to strongly localized near-field maxima in the adjacent plasmonic metasurfaces followed by evanescent coupling to high-index microspheres.
Electrical resistivity and thermal conductivity of W and Re up to 5 GPa and 2300 K
Authors: Littleton Joshua A. H. , Secco Richard A. , Yong Wenjun , Berrada Meryem
Published: April 2019

The electrical resistivity of solid-state tungsten (W) and rhenium (Re) was experimentally measured at high pressures up to 5 GPa and temperatures up to ∼2273 K using a four-wire resistivity method. For both metals, the resistivity decreased as a function of pressure and increased as a function of temperature, in excellent agreement with 1 atm data. The Wiedemann–Franz law was used to calculate the total thermal conductivity from the resistivity. Thermal conductivity increased as a function of pressure for both metals, but decreased as a function of temperature for W and increased for Re. Values of thermal conductivity at high pressures and temperatures are consistent with most recommended previous experimental studies at 1 atm.
Solid state properties of hydroxyurea: Optical absorption measurement and DFT calculations
Authors: Silva Bruno P. , Lemes Romelia P. G. , Zanatta Geancarlo , Rodrigues dos Santos Regina Claudia , de Lima-Neto Pedro , Caetano Ewerton W. S. , Freire Valder N.
Published: April 2019

Hydroxyurea (HU) crystals were investigated using density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculations combined with experimental optical absorption spectroscopy. The crystal properties were related to those of a single hydroxyurea molecule. Their electronic structures and optical response functions were obtained. The generalized gradient and local density approximations were employed and compared by including a dispersion correction scheme for obtaining an accurate description of the geometric and electronic structures of the HU crystal. A very good agreement between the optimized structures and those determined previously by X-ray diffraction, as well as between the computed optical-electronic properties and the optical absorption measurements, was obtained. The DFT calculated bandgap was of 5.03 eV, 0.30 eV less than the estimated experimental gap of 5.33 eV, while the use of the Δ-sol scheme to correct the bandgap predicted a value of 5.47 eV. For the molecule, the gap calculated using TD-DFT was 7.30 eV. The calculated optical absorption and complex dielectric functions are shown to be anisotropic with respect to the polarization state of the incident light.
X-ray ring-focusing mirror
Authors: Mimura Hidekazu , Takeo Yoko , Motoyama Hiroto , Senba Yasunori , Kishimoto Hikaru , Ohashi Haruhiko
Published: April 2019

Mirrors used in synchrotron radiation facilities can reflect X-ray beams ideally owing to recent advancements in ultraprecise fabrication technologies. Flat mirrors can change the direction of an X-ray beam without distorting its wavefront. Elliptically figured mirrors can focus X-rays onto a spot with nanometer dimensions. The intensity distribution of a reflected X-ray beam is determined, and thus can be controlled, by the shape of the employed mirror. This study proposes, fabricates, and evaluates a ring-focusing mirror that can produce an X-ray beam with a ring-shaped intensity profile. This ring-shaped X-ray beam could be created and observed at the soft X-ray beamline BL25SU at the SPring-8 synchrotron radiation facility, Japan. The increase in the freedom of X-ray mirror shapes will lead to the development of various analytical methods and optical systems in the X-ray region.
Non-destructive evaluation of tomato based on optical scattering
Authors: Katsumata Toru , Aizawa Hiroaki , Komuro Shuji , Ito Shigeo , Matsumoto Takeshi
Published: April 2019

Equipment for the non-destructive evaluations of a tomato has been developed based on the scattering spectra, the angular distributions of the scattering intensities, and the scattering images from the specimens. The sugar concentrations of tomato can be estimated optically based on the scattering intensities using a halogen lamp, a white light-emitting diode (white LED), a yellow LED, a red LED, and near infrared LEDs (λ = 850 nm and 940 nm) as the incident lights. The scattering intensity is found to vary linearly with sugar concentrations of tomato with any wavelengths at which the scattering light can be observed. The gradient of calibration lines of the sugar concentrations against the scattering intensities varies with scattering angles, θ. Evaluations at around θ = 160° are found to be suitable because of the large gradient and good linearity with the correlation coefficient, R, close to 1.
Numerical study of the shear-thinning effect on the interaction between a normal shock wave and a cylindrical liquid column
Authors: Yang Hao , Peng Jie
Published: April 2019

Based on adaptive mesh refinement, the SIM (Sharp-Interface Method) is utilized to numerically study the interaction between a shock wave and a liquid column as well as the evolution of the flow field. The SIM consists of the LSM (Level Set Method) and the GFM (Ghost Fluid Method). The LSM tracks the gas-liquid interface, and the GFM generates the virtual domains near the interface based on the gas-liquid interface condition. The hybridized GFM has been developed by integrating the Riemann GFM and the modified GFM together, which ensures the accuracy of the interface Riemann problem in the small deformation region of the interface while ensuring that the large interface deformation can be processed correctly. By comparing with the experimental results and the numerical results in previous literature, the good agreement shows that the above algorithm can accurately simulate the interactions between shock waves and liquid columns along with achieving the evolutions of the sharp gas-liquid interfaces. Based on the algorithm above, the interactions between the shock waves and the inviscid, the Newtonian, and the shear-thinning liquid columns are simulated, respectively. The numerical results indicate that the viscous effect can cause the bending of the liquid column and large deformation in the high shearing region. However, the shear thinning effect alleviates the bending and the deformation of the liquid column in the high shear region.
Pump dependent carrier lifetimes in InAs/GaAs quantum dot photoconductive terahertz antenna structures
Authors: Gorodetsky Andrei , Bazieva Natalia , Rafailov Edik U.
Published: April 2019

In this paper, we study the behavior of photoexcited carriers in GaAs wafers containing self-assembled InAs quantum dots (QDs). These samples were designed and grown to be employed as photoconductive antennae for terahertz (THz) generation. The implanted QDs serve to shorten the overall carrier lifetime and enable pumping with lasers operating at wavelengths between 1μm and 1.3μm. Optical pump-THz probe measurements reveal carrier lifetime shortening for higher pump powers in the unbiased antennae due to increased carrier capture via Auger relaxation. This phenomenon significantly broadens the THz spectra from QD-based PCAs and explains the increased THz intensity at higher frequencies presented earlier.
ZnO/(Zn)MgO polar and nonpolar superlattices
Authors: Gorczyca I. , Skrobas K. , Christensen N. E. , Sajkowski J. , Stachowicz M. , Teisseyre H. , Kozanecki A.
Published: April 2019

The bandgaps of short period ZnO/(Zn)MgO superlattices deposited on c-, m-, and a-ZnO substrates were examined both theoretically and experimentally. Ab initio calculations showed that the bandgaps of c-oriented polar superlattices are smaller than those of nonpolar ones; however, this is mainly due to different geometric configurations, because the influence of internal electric fields existing in polar superlattices is not very significant. The calculations revealed that for 5–6 MgO monolayers in the barriers, the bandgap values become independent of the barrier thickness, which suggests that such superlattices can be treated as sets of isolated ZnO wells. In the experimental part of this work, it is demonstrated that short period ZnO/MgO and ZnO/ZnMgO superlattices can be grown successfully on differently oriented crystalline bulk ZnO substrates using molecular beam epitaxy. The bandgaps of the superlattices were determined from low temperature photoluminescence measurements. It is shown that they agree well with the theoretical results.
The effect of post-growth rapid thermal annealing on InAs/InGaAs dot-in-a-well structure monolithically grown on Si
Authors: Li W. , Chen S. , Wu J. , Li A. , Tang M. , Yang L. , Chen Y. , Seeds A. , Liu H. , Ross I.
Published: April 2019

The effect of post-growth annealing (PGA) on dot-in-well (DWELL) structures grown on Si substrates has been studied. The photoluminescence (PL) measurements showed that, compared to the DWELL structures directly grown on GaAs, the PGA process induces a distinct difference in the tuning of the emission properties. Then, transmission electron microscopy imaging of the samples revealed that PGA improved the uniformity of quantum dots (QDs) while the size of the QDs increased, in agreement with a corresponding red shift and a decrease of the full width at half maximum in the PL emission spectrum. Finally, energy-dispersive x-ray linescan provided a quantitative analysis of the composition change of DWELL grown on Si in the as-grown, 700 °C annealed, and 800 °C annealed samples. The change in the InL/GaK concentration ratio became gradual between the QDs and surrounding materials after 800 °C annealing. The analysis of the optical properties, morphology evolution, and compositional change of the QDs as a function of the annealing temperature showed good agreement.
Influence of needle impact velocity on the jetting effect of a piezoelectric needle-collision jetting dispenser
Authors: Yang Yang , Gu Shoudong , Lv Qingqing , Liu Jianfang , Yang Zhigang , Li Chunjiang , Tian Hongyu
Published: April 2019

Many scholars have conducted in-depth analysis on relevant factors that affect the accuracy of jet dispensing. However, research on the influence of needle impact velocity on jetting performance is limited. Thus, a piezoelectric needle-collision dispenser for micro-droplet jetting is designed in this study, and the influence of the needle impact velocity on jetting effect is deeply analyzed. Initially, the principle of droplet formation and injection is analyzed by Fluent simulation. Thereafter, the mathematical model of the droplet velocity in the nozzle orifice is derived, and the influence of the needle impact velocity on the jetting performance is simulated and analyzed. Results show that the needle impact velocity has an influence on the jetting effect. A prototype of the jetting dispenser is subsequently fabricated, and the needle impact velocity is tested with laser micrometer. The relationship between the needle impact velocity and droplet weight and its corresponding ejected effect are obtained through experimental research. Finally, a UV glue with viscosity of 5,000 cps can be ejected with a minimum average diameter of 272.1 μm by using a needle with a radius of 0.5 mm, a nozzle with a diameter of 50 μm, a taper angle of 90°, a supply pressure of 0.2 Mpa, and a needle impact velocity of 0.13 m/s. The variation of the droplet diameter is within ±2.5%.
Energy storage in BaBi4Ti4O15 thin films with high efficiency
Authors: Song D. P. , Yang J. , Yang B. B. , Wang Y. , Chen L.-Y. , Wang F. , Zhu X. B.
Published: April 2019

A ferroelectric film with slim polarization-electric (P-E) hysteresis loops, showing small remanent polarization (Pr) and large saturated polarization (Ps), is desired to obtain high recoverable energy density (Ure) and efficiency (η) in thin film capacitors. Here, small Pr and large Pm values are achieved in BaBi4Ti4O15 thin films through modulating film grain size. A large Ure of 44.3J/cm3 as well as a high η of 87.1% is obtained. In addition, the derived BaBi4Ti4O15 thin films show excellent energy storage performance in wide frequency range, thermal stability, and fatigue endurance. These results suggest that BaBi4Ti4O15 films can be considered as a candidate for dielectric energy storage capacitors, and the route through grain size optimization is a promising strategy to improve the capacitive performance of ferroelectric materials.
Determination of Cr density during high-current anode modes in vacuum arc
Authors: Khakpour A. , Gortschakow S. , Franke St. , Methling R. , Popov S. , Uhrlandt D.
Published: April 2019

The results of Cr density during high-current anode modes using broadband absorption spectroscopy are presented. The vapor density of atomic Cr is determined during the formation of anode spot type 1, anode spot type 2, and anode plume. Cr I resonance lines at 425.43 nm are used for the analysis. An AC current pulse with a maximum of about 7 kA and a frequency of 100 Hz is applied. By adjusting the opening time or contact opening speed, anode spot type 1 and type 2 may appear. The temporal evolution of the ground state density of Cr atoms shows about two times higher metal vapor during anode spot type 2 compared with anode spot type 1. The vapor density during an anode plume following anode spot type 2 is also determined and is compared with the same time instant in which no anode plume appears, i.e., only when anode spot type 1 appears.
Interaction of hydrogen with actinide dioxide (111) surfaces
Authors: Pegg James T. , Shields Ashley E. , Storr Mark T. , Scanlon David O. , de Leeuw Nora H.
Published: April 2019

The interaction of atomic and molecular hydrogen with actinide dioxide (AnO2, An = U, Np, Pu) (111) surfaces has been investigated by DFT+U, where noncollinear 3k antiferromagnetic behaviour and spin-orbit interactions are considered. The adsorption of atomic hydrogen forms a hydroxide group, coupled to the reduction of an actinide ion. The energy of atomic hydrogen adsorption on the UO2 (0.82 eV), NpO2 (−0.10 eV), and PuO2 (−1.25 eV) surfaces has been calculated. The dissociation of molecular hydrogen is not observed, shown to be due to kinetic rather than thermodynamic factors. As a barrier to the formation of a second hydroxyl group, an unusual charge distribution has been shown. This could be a limitation of a (1·1) unit cell method or an artefact of the systems. The recombination of hydrogen ions on the AnO2 (111) surfaces is favoured over hydroxide formation.
Control effect of micro vortex generators on leading edge of attached cavitation
Authors: Che Bangxiang , Chu Ning , Schmidt Steffen J. , Cao Linlin , Likhachev Dmitriy , Wu Dazhuan
Published: April 2019

In this study, we investigate the effects of micro vortex generators (VGs) installed close to the leading edge of a quasi-two-dimensional NACA0015 hydrofoil under cavitating and non-cavitating conditions. Our aim is to improve physical insight into interaction mechanisms of the boundary layer with the formation and stability of partial cavities. Under non-cavitating conditions, the proposed micro VGs effectively suppress laminar separation. However, under cavitating conditions, even very small micro VGs within the boundary layer promote the formation of counter-rotating cavitating vortices. In comparison with the smooth hydrofoil surface (without micro VGs), the cavitation onset is shifted toward the leading edge. Additionally, classical “fingering structures” and Tollmien–Schlichting waves are no longer present. Since the onset of the cavity does no longer appear at (or close to) the laminar separation line, a novel onset mechanism is observed experimentally. The mechanism consists of stable vortex cavitation, followed by vortex break-down into bubbly structures that are finally accumulated into an attached cavity region. By reduction in the height of the micro VGs, a delayed vortex break-down is found, leading to an increase in the length of the cavitating vortex pattern. This allows for enhanced control on the cavity dynamics, especially with respect to the penetration depth of the re-entrant jet. As a result of our investigation, we conclude that well suited micro VGs show a high potential to manipulate and control cavity dynamics.
Effect of electric field on an oscillatory film flow
Authors: Samanta Arghya
Published: April 2019

The effect of a uniform electric field on the linear stability of a viscous liquid film flow on an oscillating plane is studied. The mechanism of the long-wave instability is deciphered based on the regular perturbation method along with the Floquet theory. The analytical solution predicts that long-wave unstable region increases in the presence of the electric field. On the contrary, the growth rate of the long-wave mode decreases in the presence of the surface tension. In addition, the Orr-Sommerfeld boundary value problem (OS BVP) is formulated to explore the numerical solution in the finite wavelength regime. The Chebyshev spectral collocation method along with the Floquet theory is applied to solve the OS BVP for infinitesimal disturbances of arbitrary wavenumbers. The stability limits exhibit U-shaped form curve in various ranges of the imposed frequency at a sufficiently small wavenumber. However, the oblique stability limits emerge from the branch points detected on the U-shaped form stability limits at a finite critical wavenumber and continue monotonically with the imposed frequency. Furthermore, with the increasing value of the electric field, folds occur on the finite wavelength stability limit and result in a pair of separated unstable regions. Similarly, with the decreasing value of the surface tension, the finite wavelength stability limit demonstrates folds on it and yields a pair of separated unstable regions.
Enhanced low-frequency magnetic field sensitivity in magnetoelectric composite with amplitude modulation method
Authors: Chu Zhaoqiang , Yu Zhonghui , PourhosseiniAsl MohammadJavad , Tu Cheng , Dong Shuxiang
Published: April 2019

It is an important scientific and engineering challenge to sense a weak magnetic field HAC at extremely low-frequency (LF) below 1 Hz due to the large LF noise. In this work, we presented an amplitude modulation method (AMM) for quasi-static magnetic field detection based on a magnetoelectric (ME) sensor and a lock-in amplifier. Different from previously reported frequency conversion technology, the weak LF magnetic signal is demodulated directly from the output response of a ME sensor driven at its resonance frequency. Experimental results demonstrated that the absolute resolution with respect to a 100 mHz HAC is as low as 100 pT, indicating an enhancement by a factor of 50% in comparison with previous reports. This proposed AMM should pave another route for LF weak HAC detection.
Finite Larmor radius effects at the high confinement mode pedestal and the related force-free steady state
Authors: Lee W. W. , White R. B.
Published: April 2019

In this letter, we will first relate our previous calculations on the radial electric field at the high confinement H-mode pedestal to the actual magnetic fusion experimental measurements. We will then discuss the new pressure balance due to the E × B current, which is induced by the resulting radial electric field, and its impact on the gyrokinetic MHD equations as well as their conservation properties in the force-free steady state. The recent controversy on the H-mode physics will also be addressed.
Numerical simulations of a dust grain in a flowing magnetized plasma
Authors: Darian D. , Miloch W. J. , Mortensen M. , Miyake Y. , Usui H.
Published: April 2019

The effect of an external magnetic field on the formation of the wake in the potential distribution behind a dust grain is studied with self-consistent Particle-In-Cell numerical simulations. The collisionless plasma flow is aligned with the magnetic field. It is demonstrated that the topology of the wakefield is significantly affected by the magnetization degree of plasma and by the ion flow speed. The external magnetic field acts to reduce the potential enhancements in the wake and leads to splitting of the wake pattern across the symmetry axis. For high ion flow speeds, a strong magnetization of plasma suppresses the potential enhancements and results in a narrow negative potential line along the symmetry axis, parallel to the ion flow direction, in the wake.
Electric field control of spin polarity in spin injection into InGaAs quantum dots from a tunnel-coupled quantum well
Authors: Chen Hang , Hiura Satoshi , Takayama Junichi , Park Soyoung , Sueoka Kazuhisa , Murayama Akihiro
Published: April 2019

Electric field control of spin polarity in spin injection into InGaAs quantum dots (QDs) from a tunnel-coupled quantum well (QW) was studied. The degree of freedom of the spin state in high-density QDs will play an important role in semiconductor spintronics such as a spin-functional optical device, where it is crucial to establish spin injection and manipulation by electric fields. To solve this subject in a layered device structure, electric field effects on spin injection from a 2-dimensional QW into 0-dimensional QDs were studied. Spin-polarized electrons were photo-excited in a QW and then injected into QDs via spin-conserving tunneling. After the injection, parallel spin states to the initial spin direction in the spin reservoir of QW were observed in QDs as a result of efficient spin injection, by circularly polarized photoluminescence indicating spin states in the QDs. Moreover, reversal of spin polarity was clearly observed at QD ground states, depending on the electric fields applied along the QD-QW growth direction. The tunneling rate of an electron is different from that of a hole and largely depends on the electric field, owing to electric field induced modifications of the coupled QD-QW potential. This results in negative trions in the QDs with anti-parallel spins to the initial ones in the QW, which is evidently supported by a significant effect of p-doping. The polarization degrees of both spin polarities can be optimized by excitation-spin density, in addition to the electric field strength.
Photoluminescence studies of transparent conductive ZnO films to identify their donor species
Authors: Akazawa Housei
Published: April 2019

We studied the correlation between defect species, as probed by using photoluminescence (PL), and the transparent conductive properties of undoped ZnO films sputter-deposited on glass substrates at room temperature. The near-stoichiometric but slightly oxygen-deficient ZnO films had resistivities of 3×10−3 Ωcm and optical transmittances of 85% at visible wavelengths. The PL spectra exhibited only a band-edge emission peaking at 380 nm, suggesting that intrinsic defects were not the origin of the n-type conduction. Post annealing at 500°C in a vacuum reduced the carrier concentration by five orders of magnitude. However, the spectral features of the PL remained intact; i.e., the change was only attenuated band-edge emission. These observations can be consistently explained if we suppose that the donors are hydrogen impurities. Colored ZnO films deposited under a reducing condition had resistivities of 2−4×10−3 Ωcm, and their optical transmittances were 50−70% because of Zni atoms. Post annealing at 500°C desorbed some Zni atoms, and consequently transparency increased. The resultant PL spectra exhibited an emission at 396 nm accompanied with a deep-level emission at 400−500 nm, each corresponding to transitions from the conduction band to VZn and from Zni to the valence band. Thus, Zni was the primary donor in the Zn-rich films. Deposition under a flow of O2 gas produced resistive ZnO films. Incorporating excess oxygen atoms disordered the crystal lattice, as indicated by the broad deep-level emissions from Zni, Oi, VZn, and VO. The high resistivity was due to charge compensation between donors (Zni) and acceptors (Oi and VZn).
Acquired tolerance of the photosynthetic apparatus to photoinhibition as a result of growing Solanum lycopersicum at moderately higher temperature and light intensity
Authors: Gerganova Milena T. , Faik Aygyun K. , Velitchkova Maya Y.
Published: April 2019

The kinetics of photoinhibition in detached leaves from tomato plants (Solanium lycopersicum L. cv. M82) grown for 6 days under different combinations of optimal and moderately high temperature and optimal and high light intensity were studied. The inhibition of PSII was evaluated by changes in maximal quantum yield, the coefficient of photochemical quenching and the quantum yield of PSII. The changes of PSI activity was estimated by the redox state of P700. The involvement of different possible protective processes was checked by determination of nonphotochemical quenching and cyclic electron flow around PSI. To evaluate to what extent the photosynthetic apparatus and its response to high light treatment was affected by growth conditions, the kinetics of photoinhibition in isolated thylakoid membranes were also studied. The photochemical activities of both photosystems and changes in the energy distribution and interactions between them were evaluated by means of a Clark electrode and 77 K fluorescence analysis. The data showed an increased tolerance to photoinhibition in plants grown under a combination of moderately high temperature and light intensity, which was related to the stimulation of cyclic electron flow, PSI activity and rearrangements of pigment–protein complexes, leading to a decrease in the excitation energy delivered to PSII.