bluuebunny/crossref_metadata_2025 huggingface dataset:
Metastatic Phaeochromocytoma: Spinning Towards More Promising Treatment Options
Authors: Nölting Svenja , Grossman Ashley , Pacak Karel
Published: September 2018

Phaeochromocytomas (PCC) and paragangliomas (PGL) are rare tumours arising from the chromaffin cells of the adrenal medulla (PCC) or the paraganglia located outside the adrenal gland (PGL). However, their incidence is likely to be underestimated; around 10% of all PCC/PGL are metastatic, with higher metastatic potential of PGLs compared to PCCs. If benign, surgery is the treatment of choice, but if metastatic, therapy is challenging. Here we review the currently existing therapy options for metastatic PCCs/PGLs including conventional chemotherapy (the original Averbuch scheme, but updated), radiopharmaceutical treatments (131I-MIBG, 90Y- and 177Lu-DOTATATE) and novel targeted therapies (anti-angiogenic tyrosine kinase inhibitors and mTORC1 inhibitors), emphasising future therapeutic approaches (HIF-2α and PARP inhibitors, temozolomide alone, metronomic temozolomide, somatostatin analogues) based on the oncogenic signalling pathways related to three different clusters comprising more than 20 well-characterised PCC/PGL susceptibility genes. We suggest that targeted combination therapies including repurposed agents may offer more effective future options worthy of exploration.
Total Synthesis and Cytotoxic Activity of 6,8-Dimethoxy-1,3-dimethylisoquinoline Isolated from Ancistrocladus tectorius: A 6π-Azaelectrocyclization Approach
Authors: Kaufman Teodoro , Bracca Andrea , Cortés Iván , Borini Etichetti Carla , Girardini Javier
Published: September 2018

A facile and convenient approach toward the total synthesis of 1,3-dimethyl-6,8-dimethoxyisoquinoline from phloroacetophenone is reported. The sequence entailed the selective 2,4-di-O-methylation and further triflation of the resulting phenolic product. This was followed by a Stille-type allylation, an allyl-to-propenyl isomerization, and the methoximation of the carbonyl moiety. A final microwave-assisted 6π-azaelectrocyclization completed the sequence. Functionalized derivatives on C-1 were also prepared. The heterocycles exhibited cytotoxic activity.
Pro-Angiogenic Effects of Latent Heparanase and Thrombin Receptor-Mediated Pathways—Do They Share a Common Ground in Melanoma Cells?
Authors: Hoß Sebastian , Grundmann Manuel , Benkel Tobias , Gockel Lukas , Schwarz Svenja , Kostenis Evi , Schlesinger Martin , Ilan Neta , Vlodavsky Israel , Bendas Gerd
Published: September 2018

Heparanase (HPSE) is an endo-β-D-glucuronidase that cleaves heparan sulphate (HS) chains of proteoglycans (HSPGs). Besides a remodelling of the extracellular matrix, HPSE increases the bioavailability of pro-angiogenic mediators, such as HS-associated vascular endothelial growth factor (VEGF), thereby contributing to metastatic niche formation. Notably, HPSE also induces release of VEGF from tumour cells independent of its enzymatic activity, but the underlying molecular mechanisms remain unresolved. We found that exogenous addition of latent HPSE stimulates VEGF release from human MV3 melanoma cells. The same effect was noted upon direct stimulation of thrombin receptor (protease-activated receptor 1 [PAR-1]) by Thrombin Receptor Activator Peptide 6 (TRAP-6). The matricellular ligand cysteine-rich 61 protein (Cyr61) was identified as pathway component since Cyr61 knockdown in MV3 cells abolished the VEGF release by TRAP-6 and HPSE. Since both TRAP-6 and HPSE mediated an up-regulation of phosphorylated focal adhesion kinase, which could be blocked by antagonizing PAR-1, we postulated a crosstalk between latent HPSE and PAR-1 in promoting pro-angiogenic pathways. To test this hypothesis at a molecular level, we applied dynamic mass redistribution (DMR) technique measuring intracellular mass relocation as consequence of direct receptor activation. Indeed, latent HPSE evoked a concentration-dependent DMR signal in MV3 cells as TRAP-6 did. Both could be modulated by targeting G-protein receptor signalling in general or by the PAR-1 inhibitor RWJ 56110. Using cells devoid of cell surface HS synthesis, we could confirm HPSE effects on PAR-1, independent of HSPG involvement. These data indicate, for the first time, a crosstalk between latent HPSE, thrombin receptor activation and G-protein signalling in general.
Analysis of the Performance of 11 Formulae for Fetal Weight Estimation in Preterm Fetuses with Abnormal Doppler Velocimetry – A Retrospective Multicenter Study
Authors: de Lima Alessandra Martins Heringer , de Carvalho Paulo Roberto Nassar , Junior Saint Clair Gomes , Carioca Ana Carolina Costa , Lopes José Maria de Andrade
Published: September 2018

Objective To assess 11 formulae commonly used to estimate fetal weight in a population of premature fetuses who had abnormal Doppler velocimetry due to early-onset placental insufficiency. The performance of each formula was evaluated in subgroups of fetuses with expected growth and intrauterine growth restriction.

Methods Data were collected from fetuses and mothers who delivered at three Brazilian hospitals between November 2002 and December 2013. We used the following formulae: Campbell; Hadlock I, II, III, IV and V; Shepard; Warsof; Weiner I and II; and Woo III.

Results We analyzed 194 fetuses. Of these, 116 (59.8%) were considered appropriate for gestational age (AGA), and 103 (53.1%) were male. The amniotic fluid volume was reduced in 87 (44.8%) fetuses, and the umbilical artery Doppler revealed absence or inversion of diastolic flow in 122 (62.9%) cases, and the analysis of the ductus venosus revealed abnormal flow in 60 (34.8%) fetuses. The Hadlock formulae using three or four fetal biometric parameters had low absolute percentage error in the estimated fetal weight among preterm fetuses with abnormal Doppler studies who were born within 5 days of the ultrasound evaluation. The results were not influenced by the clinical and ultrasound parameters often found in early-onset placental insufficiency.

Conclusion In this study, the formulae with the best performance for fetal weight estimation in the analyzed population were Hadlock I and IV, which use four and three fetal biometric parameters respectively to estimate the weight of preterm fetuses with abnormal Doppler studies.
Venous Thrombosis Risk after Arthroscopy of the Knee: Derivation and Validation of the L-TRiP(ascopy) Score
Authors: Nemeth Banne , van Adrichem Raymond , van Hylckama Vlieg Astrid , Baglin Trevor , Rosendaal Frits , Nelissen Rob , le Cessie Saskia , Cannegieter Suzanne
Published: September 2018

Patients at high risk for venous thrombosis (VT) following knee arthroscopy could potentially benefit from thromboprophylaxis. We explored the predictive values of environmental, genetic risk factors and levels of coagulation markers to integrate these into a prediction model. Using a population-based case–control study into the aetiology of VT, we developed a Complete (all variables), Screening (easy to use in clinical practice) and Clinical (only environmental risk factors) model. The Clinical model was transformed into the Leiden-Thrombosis Risk Prediction (arthroscopy) score [L-TRiP(ascopy) score]. Model validation was performed both internally and externally in another case–control study. A total of 4,943 cases and 6,294 controls were maintained in the analyses, 107 cases and 26 controls had undergone knee arthroscopy. Twelve predictor variables (8 environmental, 3 haemorheological and 1 genetic) were selected from 52 candidates and incorporated into the Complete model (area under the curve [AUC] of 0.81, 95% confidence interval [CI], 0.76–0.86). The Screening model (9 predictors: environmental factors plus factor VIII activity) reached an AUC of 0.76 (95% CI, 0.64–0.88) and the Clinical (and corresponding L-TRiP(ascopy)) model an AUC of 0.72 (95% CI, 0.60–0.83). In the internal and external validation, the Complete model reached an AUC of 0.78 (95% CI, 0.52–0.98) and 0.75 (95% CI, 0.42–1.00), respectively, while the other models performed slightly less well.
Trends in drug prescription of young psychiatrists and trainees
Authors: Gerber S. , Andlauer O. , Marques J. G. , Mendonca L. , Dumitrescu I. , Roventa C. , Lydall G. , Guloksuz S. , Dobrzynska E. , De Vriendt N. , Mufic A. , Van Zanten J. , Riese F. , Favre G. , Nazaralieva A. , Bendix M. , Nwachukwu I. , Soriano S. , Nawka A. , Jauhar S. ,   EFPT Research Group
Published: September 2018

A Pan-European group of psychiatric trainees conducted a semi-structured web-based survey of factors influencing decision-making in relation to antipsychotic, antidepressant and mood stabilizer prescribing. The acceptance of such a survey is in itself a positive result. In the current climate of evidence based medicine and guidelines, preliminary results from this survey suggest that, when asked regarding treatment choice for themselves, psychiatry trainees preferred second-generation atypical antipsychotic medication, based on perceived efficacy. The results for mood stabilisers were less striking. The relevance of this survey, in the context of recent evidence, may relate to trainees’ perceptions as opposed to evidence base.
Dynamically enhanced low-coherence interferometry
Authors: Mitsui Takahisa , Aoki Kenichiro
Published: September 2018

In the investigations of inhomogeneous media, availability of methods to study the interior of the material without affecting it is valuable. Optical coherence tomography provides such a functionality by providing depth resolved images of semi-transparent objects non-invasively. This is especially useful in medicine and is used not only in research but also in clinical practice. Optical coherence tomography characterizes each cross section by its reflectance. The basic physics principle underlying optical coherence tomography is low-coherence interferometry, which is combined with lateral scanning to produce cross sections. It is clearly desirable to obtain more detailed information regarding each cross section, if available. We have developed a system which measures the fluctuation spectra at all depths in low-coherence interferometry. By providing more information for each cross section, this can in principle be effective in tissue characterization and pathological diagnosis. The system uses the time dependence of the low-coherence interferometry data to obtain the fluctuation spectrum at each depth. Additionally, noise reduction is applied to obtain the spectra without unwanted noise, such as shot-noise, which can swamp the signal. The measurement system is applied to samples with no external stimuli, and depth resolved thermal fluctuation spectra of the samples are obtained. These spectra are compared with their corresponding theoretical expectations and are found to agree. The measurement system requires dualizing the detectors in the low-coherence interferometer but otherwise requires little additional equipment. The measurements were performed in ten to a hundred seconds.
Modulational and three wave decay instabilities in degenerate electron-ion dense plasmas
Authors: Rozina Ch. , Ali S. , Shah H. A. , Jamil M.
Published: September 2018

A formalism for nonlinear interaction of degenerate upper-hybrid waves (DUHWs) with degenerate ion-cyclotron waves (DICWs) and degenerate Alfven waves (DAWs) is revisited to account for quantum corrections owing to quantum Bohm potential, quantum exchange-correlations, and quantum statistical pressure. For this purpose, different nonlinear dispersion relations are derived with quantum settings. By using the phasor matching techniques, the growth rates of three wave decay and modulational instabilities are analyzed by identifying the nonlinear coupling of high-frequency DUHWs with low-frequency DICWs and DAWs. Numerically, it is revealed that parametric three wave decay and modulational instabilities are significantly influenced by the impact of Fermi pressure and exchange-correlation in a degenerate magnetoplasma. The present results are important to understand the dispersive properties of nonlinear waves and their mutual couplings at quantum scales in degenerate environments like white dwarfs, neutron stars, and magnetars.
Ratcheting droplet pairs
Authors: Galeano-Rios C. A. , Couchman M. M. P. , Caldairou P. , Bush J. W. M.
Published: September 2018

Millimetric droplets may be levitated on the surface of a vibrating fluid bath. Eddi et al. [Europhys. Lett. 82, 44001 (2008)] demonstrated that when a pair of levitating drops of unequal size are placed nearby, they interact through their common wavefield in such a way as to self-propel through a ratcheting mechanism. We present the results of an integrated experimental and theoretical investigation of such ratcheting pairs. Particular attention is given to characterizing the dependence of the ratcheting behavior on the droplet sizes and vibrational acceleration. Our experiments demonstrate that the quantized inter-drop distances of a ratcheting pair depend on the vibrational acceleration, and that as this acceleration is increased progressively, the direction of the ratcheting motion may reverse up to four times. Our simulations highlight the critical role of both the vertical bouncing dynamics of the individual drops and the traveling wave fronts generated during impact on the ratcheting motion, allowing us to rationalize the majority of our experimental findings.
Suppression of higher diffraction orders in the extreme ultraviolet range by a reflective quasi-random square nano-pillar array
Authors: Wei Lai , Chen Yong , Wang Shaoyi , Fan Quanping , Zhang Qiangqiang , Qian Feng , Shen Zhenxiang , Zhang Zhong , Hua Yilei , Zhu Xiaoli , Xie Changqing , Wang Zhanshan , Cao Leifeng
Published: September 2018

Higher diffraction orders of a grating introduce so-called harmonics contamination that leads to ambiguity in the spectral data. They are also present in “monochromatic” output beams processed by grating monochromators at synchrotron radiation facilities, making calibration results of optical elements and detectors imprecise. The paper describes a new design of a reflective quasi-random square nano-pillar array grating to reduce the amount of data of the grating relief pattern that is 10 cm in size and suppresses higher diffraction orders in the extreme ultraviolet range. In addition, a laboratory-scale grating monochromator equipped with the grating has been developed to test its spectroscopy characteristics at grazing incidence. The results illustrate that it can suppress higher diffraction orders and maintain the spectral resolving power as an ordinary grating at grazing incidence. The grating has great potential in harmonics suppression in the field of synchrotron radiation, spectral diagnostics of plasma, and astrophysics.
Development of a backlit-multi-pinhole radiography source
Authors: VanDervort Robert , Trantham Matthew , Klein Sallee , Sorce Chuck , Keiter Paul A. , Drake R. Paul
Published: September 2018

Backlit-pinhole radiography uses a pinhole placed between an x-ray source and a sample. The backlit-multi-pinhole design uses two pinholes on the same substrate, which are separated by a wall, to create two radiographic images projected along similar axes. The wall, a 100-μm thick titanium foil, prevents x-rays generated near one pinhole from exiting the other pinhole. First results indicate that the multi-pinhole target can create two independent radiographs along similar axes. The images are recorded 2 ns apart. Details of our multi-pinhole design and our first results are discussed.
Photoluminescence quantum yields for atomically thin-layered ReS2: Identification of indirect-bandgap semiconductors
Authors: Mohamed Nur Baizura , Shinokita Keisuke , Wang Xiaofan , Lim Hong En , Tan Dezhi , Miyauchi Yuhei , Matsuda Kazunari
Published: September 2018

Rhenium dichalcogenides have attracted considerable attention as new members of group VII layered semiconductor transition-metal dichalcogenides (TMDs) with respect to fundamental physics and potential applications. In this study, room-temperature photoluminescence (PL) spectra, as well as PL quantum yields (QYs) of thin-layer rhenium disulfide (ReS2), were evaluated. Low PL QYs of ∼10–4 were determined from a monolayer thickness to seven layers (1–7L) of ReS2 regardless of the layer number. These low PL QYs strongly suggest that the ReS2 is an indirect-bandgap semiconductor from a monolayer limit to the bulk, which is in contrast to those observed for group VI TMDs (MX2: M = Mo and W; X = S and Se). Our experimental findings will provide valuable information for the electronic and optical device applications in atomically thin-layered ReS2.
Experimental study on the discharge ignition in a capillary discharge based pulsed plasma thruster
Authors: Cheng Le , Wang Yanan , Ding Weidong , Ge Chongjian , Yan Jiaqi , Li Yue , Li Zhichuang , Sun Anbang
Published: September 2018

Low power capillary discharge based pulsed plasma thrusters (CDPPTs) are electrothermally dominated thrusters and they have aroused renewed interest in the investigation and enhancement of the basic performance for the application of micro/nano satellites recently. Research on the ignition mechanism of a CDPPT has been conducted to provide insight into the optimization of the structure design and promotion of the lifetime performance. It has been found that the electrical parameters, the geometry parameters, and the cumulative effect of discharge jointly determine the discharge ignition characteristics. A single ignition process is divided into the breakdown of igniter and the development of the main discharge, while the results show that the jitter of the ignition delay time is mainly introduced from the former. Shorter ignition delay time and lower jitter can be obtained with a higher ignition energy and main charging voltage or a shorter and narrower cavity, which is positively correlated to the electric field distribution along the propellant surface. Moreover, with long duration experiments, it reveals that the surface deposits and morphology of propellant and igniter are the dominant factors that cause the dispersity of the ignition effect and main discharge characteristics.
Structural and electrical characterization of polycrystalline NbO2 thin film vertical devices grown on TiN-coated SiO2/Si substrates
Authors: Joshi Toyanath , Borisov Pavel , Lederman David
Published: September 2018

We report on the electrical properties of polycrystalline NbO2 thin film vertical devices grown on TiN coated SiO2/Si substrates using pulsed laser deposition. First, we analyzed the thickness and contact size dependences of threshold switching of NbO2 films grown in 10 mTorr Ar/O2 mixed growth pressure, where 25.1%/74.9% of NbO2/Nb2O5 surface composition content was estimated by ex-situ x-ray photoelectron spectroscopy. Then the threshold switching and self-sustained current oscillatory behavior of films with different NbO2/Nb2O5 composition ratios was measured and analyzed. The current-voltage measurement revealed that the leakage current property in the insulating state was dominated by the trap-charge assisted Poole-Frankel conduction mechanism. All films showed threshold switching behavior in agreement with the previously proposed Joule heating mechanism. The second film was grown in lower (1 mTorr) growth pressure, which resulted in a higher (34.2%/65.8%) NbO2/Nb2O5 film surface composition. The film grown in higher growth pressure demonstrated lower off-state leakage current, faster switching, and self-sustained oscillations with higher frequency than the film grown in lower growth pressure.
The neutron camera upgrade for MAST Upgrade
Authors: Cecconello M. , Sperduti A. , Fitzgerald I. , Conroy S. , Holm S. J. , Weiszflog M.
Published: September 2018

The Neutron Camera Upgrade (NCU) is a neutron flux monitor consisting of six lines of sight (LoSs) under installation on Mega Ampere Spherical Tokamak (MAST) Upgrade. The NCU is expected to contribute to the study of the confinement of fast ions and on the efficiency of non-inductive current drive in the presence of on-axis and off-axis neutral beam injection by measuring the neutron emissivity profile along the equatorial plane. This paper discusses the NCU main design criteria, the engineering and interfacing issues, and the solutions adopted. In addition, the results from the characterization and performance studies of the neutron detectors using standard γ-rays sources and a 252Cf source are discussed. The proposed design has a time resolution of 1 ms with a statistical uncertainty of less than 10% for all MAST Upgrade scenarios with a spatial resolution of 10 cm: higher spatial resolution is possible by moving the LoSs in-between plasma discharges. The energy resolution of the neutron detector is better than 10% for a light output of 0.8 MeVee, and the measured pulse shape discrimination is satisfactory.
Calibration and cross-laboratory implementation of scintillating screens for electron bunch charge determination
Authors: Kurz Thomas , Couperus Jurjen Pieter , Krämer Jakob Matthias , Ding Hao , Kuschel Stephan , Köhler Alexander , Zarini Omid , Hollatz Dominik , Schinkel David , D’Arcy Richard , Schwinkendorf Jan-Patrick , Osterhoff Jens , Irman Arie , Schramm Ulrich , Karsch Stefan
Published: September 2018

We revise the calibration of scintillating screens commonly used to detect relativistic electron beams with low average current, e.g., from laser-plasma accelerators, based on new and expanded measurements that include higher charge density and different types of screens than previous work [Buck et al., Rev. Sci. Instrum. 81, 033301 (2010)]. Electron peak charge densities up to 10 nC/mm2 were provided by focused picosecond-long electron beams delivered by the Electron Linac for beams with high Brilliance and low Emittance (ELBE) at the Helmholtz-Zentrum Dresden-Rossendorf. At low charge densities, a linear scintillation response was found, followed by the onset of saturation in the range of nC/mm2. The absolute calibration factor (photons/sr/pC) in this linear regime was measured to be almost a factor of 2 lower than that reported by Buck et al. retrospectively implying a higher charge in the charge measurements performed with the former calibration. A good agreement was found with the results provided by Glinec et al. [Rev. Sci. Instrum. 77, 103301 (2006)]. Furthermore long-term irradiation tests with an integrated dose of approximately 50 nC/mm2 indicate a significant decrease of the scintillation efficiency over time. Finally, in order to enable the transfer of the absolute calibration between laboratories, a new constant reference light source has been developed.
Novel welding machine based on small PMSG wind turbine
Authors: Boussiala Boubakr , Nezli Lazhari , Mahmoudi Mohand Oulhadj , Deboucha Abdelhakim
Published: September 2018

This paper investigates a small wind turbine based on a permanent magnet synchronous generator (PMSG) to replace the used diesel generator in welding machines at remote sites. The proposed welding machine is designed using a variable-speed PMSG wind turbine to achieve an optimal performance. The problem of fluctuation in wind energy is solved by adding a storage battery and a maximum power point tracking (MPPT) stage. A controllable direct current power supply based on the full-bridge inverter topology is adopted for the welding side. The control strategies of MPPT, pitch angle blade, and arc welding current are also discussed. Matlab/Simulink is utilized to simulate the proposed system. Simulation results show that the proposed welding machine can provide a stable and robust welding current under varying wind and arc load conditions. Simulation results demonstrate the feasibility and efficiency of the proposed welding machine.
Plasma surface modification of P(VDF-TrFE): Influence of surface chemistry and structure on electronic charge injection
Authors: Vecchio Michael A. , Meddeb Amira Barhoumi , Lanagan Michael T. , Ounaies Zoubeida , Shallenberger Jeffrey R.
Published: September 2018

Reactive ion plasma treatments have been used to alter the high field electrical properties of organic dielectrics via a grafting process of chemical species within the plasma to the surface of the dielectric. This study determines the effect of a CF4/O2 plasma based processing procedure on polyvinylidene fluoride trifluoroethylene [P(VDF-TrFE)] on low and high field electrical performance. Plasma treatment in conjunction with a thermal annealing procedure is analyzed in the following ways: X-ray Photoelectron Spectroscopy to determine the changes in surface chemistry of films post plasma treatment, optical profilometry to measure evolution in surface topology, water contact angle to track surface polarity as a function of plasma treatment time, and current-voltage measurements at low and high-fields to capture the electrical behavior of the films. The results indicate that plasma treatment causes the chemical modification of P(VDF-TrFE) surface through the addition of carbonyl (C=O) groups, as well as oxygen and fluorine based moieties (CF-O, C-O) which are dependent on processing condition. Contact angle with water shows an increase as a function of plasma treatment time from ∼84° to 111° in plasma treated films, indicating decreased surface polarity after plasma treatment. Finally, plasma treatment decreases film resistivity by one order of magnitude, from 8.0 × 1011 Ω m in untreated control samples to 0.8 × 1011 Ω m, as well as resulted in enhanced Schottky emission caused by decreased Schottky barrier height. Modeling I(V) data using both a surface limited (Schottky) and bulk limited (Poole-Frenkel) approaches suggest that conduction in P(VDF-TrFE) thin films results from Schottky emission and is dependent on the chemical environment of the metal/dielectric contact. This study ultimately demonstrates the ability to alter the electrical properties by plasma surface treatment and also the importance of surface chemistry in organic dielectrics to control conduction through the material for high energy and power applications.
Variation in the linear stability property of resistive ballooning mode including the parametric dependence of its growth rate in L-mode edge
Authors: Kim J. Y. , Han H. S.
Published: September 2018

Motivated by some unexpected features, like the stabilization of the density gradient driven RBM (resistive ballooning mode) by temperature gradient or the smooth transition from the RBM to the ion temperature gradient mode, observed in a recent numerical work [J. Y. Kim et al., Phys. Plasmas 24, 042503 (2017)], an additional study is presented on the linear stability of the RBM in L-mode edge-like plasmas. From an approximate analysis of the RBM dispersion relation in the local fluid limit, it is first shown that the above behaviors can be explained as due to the substantial change of the RBM linear stability, which occurs when the effects by the coupling to drift wave branch or the finite electron thermal conduction are fully considered through the generalized Ohm's law. Corresponding to this significant change in the linear stability property, a check is also presented on the parametric dependence of the RBM growth rate. It is shown that there can be also a large variation in this dependence, with the modified one apparently having a better agreement with the observed L-H threshold power scaling when we assume such a scaling is mainly determined from the RBM growth rate property.
A study of the emergence of flux rope from the solar convection zone into the atmosphere by using a novel numerical method
Authors: Yang Yun , Feng Xue-Shang , Jiang Chao-Wei , Manchester Ward B.
Published: September 2018

In this paper, we successfully use our newly developed numerical method to study the process of the emergence of magnetic flux rope from the solar convection zone into the atmosphere with a stratified hydro-static equilibrium as the initial ambient state. Our simulation has obtained some key characteristics revealed by observation or other researchers' simulations. To achieve the process from emergence until eruption requires a numerical scheme with low numerical diffusion. Otherwise, the emergence process will be suppressed by diffusion of magnetic flux during the long emergence period caused by the great gradient for density and pressure in the ambient state. The results demonstrate that our code can simulate the emergence process very well, which allows us to explore flux emergence mechanisms.
Mechanisms governing metal vacancy formation in BaTiO3 and SrTiO3
Authors: Baker Jonathon N. , Bowes Preston C. , Harris Joshua S. , Irving Douglas L.
Published: September 2018

Barium titanate (BTO) and strontium titanate (STO) are often treated as close analogues, and models of defect behavior are freely transferred from one material to the other with only minor modifications. On the other hand, it is often reported that B-site vacancies (vB) are the dominant metal vacancy in BTO, while A-site vacancies (vA) dominate in STO. This difference precludes the use of analogous defect models for BTO and STO, begging the question: how similar are the defect chemistries of the two materials? Here, we address this question with density functional theory calculations using a state-of-the-art hybrid exchange correlation functional, which more accurately describes the electronic structure and charge localization than traditional functionals. We find that vA is the dominant metal vacancy in STO but that different combinations of vA, vB, and vB-vO complexes are present in BTO depending on processing and doping. Mechanistically, this occurs for two reasons: thermodynamic differences in the accessible processing conditions of the two materials and energy differences in the bonds broken when forming the vacancies. These differences can also lead to widely differing responses when impurity dopants are intentionally added. Therefore, the response of metal vacancy behavior in BTO and STO to the inclusion of niobium and iron, two typical dopants in these systems, is examined and compared.
Porous metamaterials for deep sub-wavelength ultrasonic imaging
Authors: Amireddy Kiran Kumar , Balasubramaniam Krishnan , Rajagopal Prabhu
Published: September 2018

This paper reports the application of a porous medium as an aperiodic metamaterial lens for ultrasonic imaging in the context of nondestructive evaluation and non-invasive diagnostics. Experimental results are presented, demonstrating a deep sub-wavelength imaging down to 1/36th of the operating wavelength, which is the highest resolution demonstrated worldwide using bulk ultrasound. The improvement in the resolution is shown to be linked to aperiodicity overcoming the Wood anomaly, which sets limits on wave transmission by holey structured lenses.
Branched InAs nanowire growth by droplet confinement
Authors: Tornberg Marcus , Dick Kimberly A. , Lehmann Sebastian
Published: September 2018

Anisotropy in crystal growth of III-V semiconductor nanowires can be enhanced by the assistance of a liquid particle. During the past decades, selected scientific works have reported a controlled change in the nanowire growth direction by manipulation of the assisting droplet. Although these results are interesting from an engineering point of view, a detailed understanding of the process is necessary in order to rationally design complex nanostructures. In this letter, we utilize our understanding of the growth-assisting droplet to control the morphology and direction of gold-assisted wurtzite-phase InAs nanowires, using controlled droplet displacement followed by resumed growth. By confining the droplet to the nanowire sidewall using zincblende inclusions as barriers, epitaxial growth of horizontal branches from existing nanowires is demonstrated. This is done by tailoring droplet wetting of the nanowire and using identical conditions for the nanowire “stem” and branch growth. This work demonstrates the importance of the droplet dynamics and wetting stability, along with the benefits of crystallographic control, for understanding the growth along different directions. Controlled branched growth is one way to achieve designed nanowire networks.
Investigation on volt-ampere characteristic of secondary arc burning in atmospheric air
Authors: Sun Qiuqin , Liu Hao , Xiao Zhibin , Chen She , Wang Feng , Zhong Lipeng
Published: September 2018

The secondary arc, as a common phenomenon in a high voltage power transmission system, is an essence of an electric arc. It not only damages the electrical power equipment but also threatens the safety of the power system. A series of experiments on the secondary arc have been conducted in this work. The volt-ampere curves are measured, the motion trajectories are captured, and the centroid of the secondary arc body is calculated by means of image processing. The experimental results indicate that the secondary arc length can reach several meters, and its volt-ampere curve is completely different from that of short-gap arcs and others operated in some special dielectrics such as vacuum. The evolution of the secondary arc can be generally divided into two stages. In the early stage, the arc column performs a vertical motion and has an upward trend due to thermal buoyancy. Basically, the volt-ampere curve has a shape of a regular hysteresis loop. The impacts of the frequent short-circuit behavior of the arc column on the volt-ampere curve and arcing time are investigated. At the later stage, the secondary arc temperature drops and the zero-off behavior becomes obvious. The volt-ampere curve is inevitably affected. The zero-off duration is obtained, and the key factors are discussed. The dynamics of charged particles in the zero-off interval are analyzed. Furthermore, under the effect of strong wind, it has been found that the secondary arc current is occasionally forced to zero and preceded by the voltage. The mechanism for such a phenomenon is first elucidated from the perspective of energy balance. The results lay a theoretical basis for secondary arc physics.
Using fluorescence detected two-dimensional spectroscopy to investigate initial exciton delocalization between coupled chromophores
Authors: Schröter Marco , Pullerits Tõnu , Kühn Oliver
Published: September 2018

Förster theory describes electronic exciton energy migration in molecular assemblies as an incoherent hopping process between donor and acceptor molecules. The rate is expressed in terms of the overlap integral between donor fluorescence and acceptor absorption spectra. Typical time scales for systems like photosynthetic antennae are on the order of a few picoseconds. Prior to transfer, it is assumed that the initially excited donor molecule has equilibrated with respect to the local environment. However, upon excitation and during the equilibration phase, the state of the system needs to be described by the full density matrix, including coherences between donor and acceptor states. While being intuitively clear, addressing this regime experimentally has been a challenge until the recently reported advances in fluorescence detected two-dimensional spectroscopy. Here, we demonstrate using fourth order perturbation theory the conditions for the presence of donor-acceptor coherence induced cross-peaks at zero waiting time between the first and the second pair of pulses. The approach is illustrated for a heterodimer model which facilitates an analytical solution.
Dissipative solitons in electron oscillators with a saturable absorber
Authors: Ginzburg N. S. , Kocharovskaya E. R. , Vilkov M. N. , Sergeev A. S. , Fil'chenkov S. E.
Published: September 2018

We analyze the mechanisms of passive mode locking and ultrashort pulse generation in microwave electron oscillators with a bleaching absorber in the feedback loop. It is shown that in the group synchronism regime, where the translational velocity of particles coincides with the group velocity of an electromagnetic wave, the formation of pulses obeys the equations known in the theory of a dissipative soliton which is widely used for the description of the femtosecond pulse formation in laser physics. At the same time, in electron oscillators, for the formation of pulses with the maximum amplitude, beneficial conditions in which the translational velocity of the particles is different from the group velocity of the wave and the generated soliton moving along the electron beam consecutively (cumulatively) extracts energy from various electron fractions are required. In this case, the soliton can be generated in both hard and soft excitation modes. It is shown that nonlinear absorption can be provided in the additional unit installed in the feedback loop, in which an independent electron beam interacts with the radiation under the Kompfner dip conditions.
Multilacunarity as a spatial multiscale multi-mass morphometric of change in the meso-architecture of plant parenchyma tissue
Authors: Valous N. A. , Xiong W. , Halama N. , Zörnig I. , Cantre D. , Wang Z. , Nicolai B. , Verboven P. , Rojas Moraleda R.
Published: September 2018

The lacunarity index (monolacunarity) averages the behavior of variable size structures in a binary image. The generalized lacunarity concept (multilacunarity) on the basis of generalized distribution moments is an appealing model that can account for differences in the mass content at different scales. The model was tested previously on natural images [J. Vernon-Carter et al., Physica A 388, 4305 (2009)]. Here, the computational aspects of multilacunarity are validated using synthetic binary images that consist of random maps, spatial stochastic patterns, patterns with circular or polygonal elements, and a plane fractal. Furthermore, monolacunarity and detrended fluctuation analysis were employed to quantify the mesostructural changes in the intercellular air spaces of frozen-thawed parenchymatous tissue of pome fruit [N. A. Valous et al., J. Appl. Phys. 115, 064901 (2014)]. Here, the aim is to further examine the coherence of the multilacunarity model for quantifying the mesostructural changes in the intercellular air spaces of parenchymatous tissue of pome and stone fruit, acquired with X-ray microcomputed tomography, after storage and ripening, respectively. The multilacunarity morphometric is a multiscale multi-mass fingerprint of spatial pattern composition, assisting the exploration of the effects of metabolic and physiological activity on the pore space of plant parenchyma tissue.
Antireflection coated semiconductor laser amplifier for Bose-Einstein condensation experiments
Authors: Pandey Saurabh , Mas Hector , Drougakis Giannis , Mavrakis Kostas G. , Mylonakis Mikis , Vasilakis Georgios , Bolpasi Vasiliki , von Klitzing Wolf
Published: September 2018

We present a slave laser highly suitable for the preparation and detection of 87Rb Bose-Einstein condensates (BEC). A highly anti-reflection coated laser diode serves as an optical amplifier, which requires neither active temperature stabilization nor dedicated equipment monitoring the spectral purity of the amplified light. The laser power can be controlled with a precision of 10 μW in 70 mW with relative fluctuations down to 2 × 10−4. Due to its simplicity and reliability, this slave laser will be a useful tool for laboratory, mobile, or even space-based cold-atom experiments. By the way of demonstration this slave laser was used as the sole 780 nm light-source in the production of 3 × 104 BECs in a hybrid magnetic/dipole trap.
Steady flows in deformed elastic sphere subject to rotational oscillations
Authors: Kozlov V. G. , Subbotin S. V. , Sabirov R. R.
Published: September 2018

Steady flow in a cavity with an elastic wall performing rotational oscillations is studied experimentally. The cavity of the initially spherical shape is deformed by placing it between two boundaries, free for tangential displacement. Thus, in the course of rotational oscillations, the shape of the elastic cavity in the laboratory frame remains unchanged. This formulation is aimed at modeling the flows in a drop located in an oscillatory shear flow. In the absence of deformation, steady flow has the form of two axisymmetric toroidal vortices and is observed in a wide range of the dimensionless frequency of oscillations. Deformation leads to a violation of the symmetry of the toroidal flow and the generation of steady flows in the area of deformation in the form of two pairs of jointly rotating vortices. The resulting flow is a superposition of toroidal vortices near the poles and longitudinal vortices in the area of deformation. The velocity of averaged motion in the vortices is proportional to the frequency and the square of the amplitude of the oscillations. As the dimensionless frequency decreases, the flow structure in the deformation area gradually transforms. In the low-frequency region, it takes the form of two pairs of vortices in which the direction of motion is opposite to the case of high dimensionless frequencies. It is shown that deformation of the cavity leads to a qualitative change in the steady flows in the low dimensionless frequencies region. The intensity of the flow is an order of magnitude higher than in the undeformed sphere.
Vortices in oscillating droplets
Authors: Larter Raima
Published: September 2018

Complex three-dimensional flow patterns are observed in a cavity with a flexible wall subject to rotational oscillations. The flow is visualized using laser light and tiny light scattering particles.
New model describing defects in similar oxides provides insight into the stabilization of vacancies
Authors: DeJarnette Drew
Published: September 2018

A computational framework could offer higher quality oxides for electronic components through a better understanding of different underlying defect behaviors of materials typically treated as similar.
Phevamine A, a small molecule that suppresses plant immune responses
Authors: O’Neill Erinn M. , Mucyn Tatiana S. , Patteson Jon B. , Finkel Omri M. , Chung Eui-Hwan , Baccile Joshua A. , Massolo Elisabetta , Schroeder Frank C. , Dangl Jeffery L. , Li Bo
Published: September 2018

Significance

Bacterial pathogens cause plant diseases that threaten the global food supply. To control diseases, it is important to understand how pathogenic bacteria evade plant defense and promote infection. We identify from the phytopathogen
Pseudomonas syringae
a small-molecule virulence factor—phevamine A. Both the chemical structure and mode of action of phevamine A are different from known bacterial phytotoxins. Phevamine A promotes bacterial growth by suppressing plant immune responses, including both early (the generation of reactive oxygen species) and late (the deposition of cell wall reinforcing callose in leaves and leaf cell death) markers. This work uncovers a widely distributed, small-molecule virulence factor and shows the power of a multidisciplinary approach to identify small molecules important for plant infection.
Magnetically Separable and Reusable Fe3O4/ZnO/Nanographene Platelets Photocatalyst for the Removal of Dye
Authors: Taufik Ardiansyah , Susanto Iqriah K. , Saleh Rosari
Published: September 2018

In this study, we report the sol-gel synthesis of nanocomposite Fe3O4/ZnO with nanographene platelets (NGP)and characterized by suitable techniques, including field emission scanning electron microscope (FESEM), X-ray diffraction (XRD), energy dispersive X-ray analysis (EDX), UV-visible diffuse reflectance spectroscopy and vibrating sample magnetometer. The as-synthesized Fe3O4/ZnO/NGP nanocomposites materials were used for photocatalyst under UV as well as visible light irradiation to remove methylene blue as a model of organic polutan. The XRD spectra reveal peaks that can be attributed to cubic spinel Fe3O4, hexagonal wurtzite ZnO and nanographene platelets structure. The FESEM images show Fe3O4/ZnO uniformly decorating NGP sheets. EDX analysis signifies the formation of Fe3O4/ZnO/NGP. The photocatalytic activity was found to be ZnO loading dependent. Higher ZnO loading lead to higher rate of photocatalytic activity under UV light irradiation, while the opposite trend observed under visible light irradiation. The addition of NGP effectively enhanced the photocatalytic performance of Fe3O4/ZnO nanocomposites. Separation of Fe3O4/ZnO/NGP nanocomposites from the solution could be achieved by applying an external magnetic field, demonstrating the magnetic properties of the nanocomposites.
Decomposition of organic pollutant in waste water using magnetic catalyst nanocomposite
Authors: Tju H , Taufik A , Fauzian M , Saleh R
Published: September 2018

In this study, magnetic recyclable catalyst Fe3O4/CuO/ZnO/nanographene platelets (Fe3O4/CuO/ZnO/NGP) and Fe3O4/CuO/TiO2/nanographene platelets (Fe3O4/CuO/TiO2/NGP) composites were synthesized by simple hydrothermal method. Methylene blue was used as a model of textile dye to evaluate their catalytic activities. A range of analytical techniques including X-ray diffraction, energy-dispersive X-ray spectroscopy and vibrating sample magnetometer were employed to reveal the crystal structure, composition and property of the nanocomposites. The catalytic performance was evaluated by degradation of methylene blue in aqueous solution under UV light and ultrasonic irradiation simultaneously. X-ray diffraction results revealed that cubic spinel Fe3O4, monoclinic CuO, hexagonal wurtzite ZnO and graphene platelets exist in Fe3O4/CuO/ZnO/NGP, while in Fe3O4/CuO/TiO2/NGP nanocomposites instead of hexagonal wurtzite ZnO, anatase TiO2 is observed. These results confirmed that the nanocomposites were the desired materials. In addition, all samples exhibited ferromagnetic behavior at room temperature and could be rapidly separated from aqueous solution for repeated use under external magnetic field. From the degradation of methylene blue, it is found that the as-prepared nanocomposites exhibited excellent catalytic activity compared with nanocomposite synthesized without nanographene platelets. The nanocomposites still retain the 100% of the initial activity after it has been used four times repeatedly.
Assessment of existing steel bridges: codes and standard
Authors: Siviero Erica , Pavan Roberto
Published: September 2018

The assessment of existing structures adopting a specific code or standard is a technical procedure that is provided only in some nation. The possibility of harmonizing these type of procedure is needed in Europe, together with a completely new plan of infrastructural renewal. In this study new insight on this theme are provided, together with some code proposal for the new Eurocode era. Many existing bridges all over the world were not designed for the high service loads and the increased number of load cycles that they are exposed to today. Some bridges will have to be either strengthened or replaced in the next decades. Advancing their age, bridges could be subjected to a large variety of not designed actions or could also be not accurately maintained, leading to a particular state in which they need particular care and attention, in order to remain in service. Moreover, existing structures were not exempted from serious failures and engineers had regularly to suffer setbacks. These setbacks contributed in many cases, however, to research and advancements in better understanding structural behaviour and developing new theories (Kuhn et al. 2010). In these cases, the assessment procedures are needed.