bluuebunny/crossref_metadata_2025 huggingface dataset:
The less significant role of large-scale environment than optical AGN in nearby, isolated elliptical galaxies
Authors: Lacerna I. , Argudo-Fernández M. , Duarte Puertas S.
Published: October 2018

Context. The formation and evolution of elliptical galaxies in low-density environments are less understood than classical elliptical galaxies in high-density environments. Isolated galaxies are defined as galaxies without massive neighbors within scales of galaxy groups. The effect of the environment at several Mpc scales on their properties has been barely explored. We study the role of the large-scale environment in 573 isolated elliptical galaxies out toz= 0.08.

Aims. We aim to explore whether the large-scale environment affects some of the physical properties of the isolated galaxies studied in this work.

Methods. We used three environmental estimators of the large-scale structure within a projected radius of 5 Mpc around isolated galaxies: the tidal strength parameter, projected densityηk,LSS, and distance to the fifth nearest neighbor galaxy. We studied isolated galaxies regarding stellar mass, integrated opticalg−icolor, specific star formation rate (sSFR), and emission lines.

Results. We find 80% of galaxies at lower densities correspond to “red and dead” elliptical galaxies. Blue and red galaxies do not tend to be located in different environments according toηk,LSS. Almost all the isolated ellipticals in the densest large-scale environments are red or quenched, of which a third are low-mass galaxies. The percentage of isolated elliptical galaxies located in the active galactic nucleus (AGN) region of the BPT diagram is 64%. We identified 33 blue, star-forming (SF) isolated ellipticals using both color and sSFR. Half of these are SF nuclei in the BPT diagram, which amounts to 5% of the galaxies in this diagram.

Conclusions. The large-scale environment does not play the primary role in determining the color or sSFR of isolated elliptical galaxies. The large-scale environment seems to be negligible from a stellar mass scale around 1010.6M⊙, probably because of the dominant presence of AGN at higher masses. For lower masses, the processes of cooling and infall of gas from large scales are very inefficient in ellipticals. Active galactic nuclei might also be an essential ingredient to keep most of the low-mass isolated elliptical galaxies quenched.
Intrauterine Fetal Growth Delay During Late Pregnancy After Maternal Gastric Bypass Surgery
Authors: Feichtinger Michael , Falcone Veronica , Schoenleitner Theresa , Stopp Tina , Husslein Peter Wolf , Eppel Wolfgang , Chalubinski Kinga M. , Göbl Christian S.
Published: October 2018

Purpose To investigate intrauterine fetal growth development and birth anthropometry of fetuses conceived after maternal gastric bypass surgery.

Materials and Methods Longitudinal cohort study describing longitudinal growth estimated by ultrasound on 43 singleton pregnancies after gastric bypass compared to 43 BMI-matched controls.

Results In fetuses after maternal gastric bypass surgery, growth percentiles decreased markedly from the beginning of the second trimester until the end of the third trimester (decrease of 3.1 fetal abdomen circumference percentiles (95 %CI 0.9–5.3, p = 0.007) per four gestational weeks). While in the second trimester, fetal anthropometric measures did not differ between the groups, the mean abdomen circumference percentiles appeared significantly smaller during the third trimester in offspring of mothers after gastric bypass (mean difference 25.1 percentiles, p < 0.001). Similar tendencies have been observed in estimated fetal weight resulting in significantly more SGA offspring at delivery in the gastric bypass group. In children born after maternal gastric bypass surgery, weight percentiles (32.12th vs. 55.86th percentile, p < 0.001) as well as placental weight (525.2 g vs. 635.7 g, p < 0.001) were significantly reduced compared to controls.

Conclusion In fetuses conceived after maternal gastric bypass, intrauterine fetal growth distinctively declined in the second and third trimester, most prominently observed in fetal abdomen circumferences. Birth weight and placental weight at birth was significantly lower compared to BMI-matched controls, possibly due to altered maternal metabolic factors and comparable to mothers experiencing chronic hunger episodes.
Efficacy and safety of radiofrequency ablation of Barrett’s esophagus in the absence of reimbursement: a multicenter prospective Belgian registry
Authors: Vliebergh Joke , Deprez Pierre , de Looze Danny , Ferrante Marc , Orlent Hans , Macken Elisabeth , Christiaens Paul , Mana Fazia , De Hertogh Gert , Willekens Hilde , Bisschops Raf
Published: October 2018

Background Radiofrequency ablation (RFA), combined with endoscopic resection, can be used as a primary treatment for low grade dysplasia, high grade dysplasia, and early esophageal adenocarcinoma (EAC) in Barrett’s esophagus (BE). The aim of the Belgian RFA registry is to capture the real-life outcome of endoscopic therapy for BE with RFA and to assess efficacy and safety outside study protocols, in the absence of reimbursement.

Patients and methods Between February 2008 and January 2017, data from 7 different expert centers were prospectively collected in the registry. Efficacy outcomes included complete remission of intestinal metaplasia (CR-IM), complete remission of dysplasia (CR-D), and durability of remission. Safety outcomes included immediate and late adverse events.

Results 684 RFA procedures in 342 different patients were registered. Of these, 295 patients were included in the efficacy analysis, with CR-IM achieved in 88 % and CR-D in 93 %, in per-protocol analysis; corresponding rates in intention-to-treat analysis were 82 % and 87 %, respectively. Sustained remission was seen in 65 % with a median (interquartile range) follow-up of 25 (12 – 47) months. No risk factors for recurrent disease were identified. Immediate complications occurred in 4 % of all procedures and 6 % of all patients, whereas late complications occurred in 9 % of all procedures and in 20 % of all patients.

Conclusions Data from the Belgian registry confirm that RFA in combination with endoscopic resection is an efficient treatment for BE with dysplasia or early EAC. In the absence of reimbursement, more rescue treatments are used, not compromising outcome. Since there is recurrent disease after CR-IM in 35 %, surveillance endoscopy remains necessary.
PPARα and γ Activation Effects of New Nor-triterpenoidal Saponins from the Aerial Parts of Anabasis articulata
Authors: Salah El Dine Riham , Abdallah Hossam , Kandil Zeinab , Zaki Ahmed , Khan Shabana , Khan Ikhlas
Published: October 2018

Anabasis articulata, traditionally used to treat diabetes, is rich in saponin content. This study was performed to investigate the agonistic effect of its saponins on peroxisome proliferator-activated receptor-α and peroxisome proliferator-activated receptor-γ in human hepatoma (HepG2) cells to explore the possibility of the involvement of these nuclear receptors in the mechanism of the antidiabetic effect of the plant. Chemical investigation of the n-butanol fraction resulted in the isolation of three new and one known 30-noroleanane triterpenoid saponins. The structures of the new compounds were elucidated as 3β-hydroxy,23-aldehyde-30-norolean-12,20(29)-dien-28-oic acid-28-O-β-D-glucopyranosyl ester (1), 3β-O-D-galactopyranosyl-23-aldehyde-30-norolean-12,20(29)-dien-28-oic acid-28-O-β-D-glucopyranosyl ester (2), and 3β-O-D-xylopyranosyl-30-norolean-12,20(29)-dien-28-oic acid 28-O-β-D-glucopyranosyl ester (3), while the known 30-nortriterpenoidal saponin was identified as boussingoside E (4). Although, the isolated saponins (1 – 4) did not show > 1.5-fold activation of peroxisome proliferator-activated receptor-γ, but two of them (1 and 3) activated peroxisome proliferator-activated receptor-α to the higher extents of 2.25- and 1.86-fold, respectively. These results suggest that the reported antidiabetic action of the isolated saponins may not solely involve the activation of peroxisome proliferator-activated receptor-γ. However, the agonistic activity of the n-butanol fraction of A. articulata (1.71-fold induction) and two of its saponins (1 and 3) towards peroxisome proliferator-activated receptor-α may be beneficial in the cardiovascular condition that is closely associated with diabetes and other metabolic disorders.
Aryne-Mediated Arylation of Hantzsch Esters: Access to Highly Substituted Aryl-dihydropyridines, Aryl-tetrahydropyridines and Spiro[benzocyclobutene-1,1′-(3′,4′-dihydropyridines)]
Authors: Jones Christopher , Sun Weitao , Trinchera Piera , Kurdi Nada , Palomas David , Crespo-Otero Rachel , Afshinjavid Saeed , Javid Farideh
Published: October 2018

This is a full account of our studies into the generation of highly functionalised 2-aryl-1,2-dihydropyridines and 2-methylene-3-aryl-1,2,3,4-tetrahydropyridines via intermolecular aryne ene reactions of Hantzsch esters. Furthermore, exposure to excess aryne revealed unusual 3′-aryl-spiro[benzocyclobutene-1,1′-(3′,4′-dihydropyridines)]. Mechanistic insights are provided by deuterium-labelling studies and DFT calculations, whilst preliminary cytotoxicity investigations reveal that the spirocycles are selective against colon carcinomas over ovarian cancer cell lines and that all the compounds have high selectivity indices with regards to non-cancer cells.
Harvesting New Chiral Phosphotriesters by Phosphorylation of BINOL and Parent Bis-phenols
Authors: Argouarch G. , Lalli C. , Ndimba A. , Roisnel T.
Published: October 2018

A systematic study on the phosphorylation of BINOL and other bis-phenols with chlorophosphates is described. An intriguing reactivity has been observed that is attributable to the hydroxyl group acidity and to the leaving group nucleofuge character within the phosphorylating agent used. By playing on these two parameters, new chiral monophosphotriesters, symmetrical homo-BINOL bisphosphates, and unsymmetrical non-homo-BINOL derivatives incorporating a non-chiral side unit, were synthesized selectively and in good yields.
Surgical Management Patterns of Sinonasal Malignancy: A Population-Based Study
Authors: Husain Qasim , Joshi Rohan R. , Cracchiolo Jennifer R. , Roman Benjamin R. , Ganly Ian , Tabar Viviane , Cohen Marc A.
Published: October 2018

Objectives Determining surgical trends and outcomes for sinonasal tumors is challenging given their low incidence and heterogeneous pathology. This study utilized the National Cancer Database (NCDB) to identify trends and outcomes associated with surgical management of sinonasal tumors.

Design Retrospective database analysis.

Setting National Cancer Database.

Participants Patients with sinonasal malignancies identified from the NCDB between 2010 and 2015.

Main Outcome Measures The primary outcome was the choice of surgical therapy used for sinonasal tumor resection: endoscopic versus open approach. Each was cohort analyzed with respect to various demographic and clinicopathologic factors. A treatment effect model was used to identify potential differences between surgical approaches. Survival was evaluated using Kaplan–Meier analysis.

Results A total of 10,193 patients with sinonasal malignancies were identified in the NCDB database; of these, 2,292 had a documented subsite, histology, and definitive surgical treatment with documented surgical approach and were included in the analysis. About 71.9% of patients had an open approach and 28.1% a purely endoscopic procedures. Tumor histology, treatment facility type, margin status, and length of stay were all variables that were associated with significant differences between the open and endoscopic cohort. Five-year survival rates for the open and endoscopic cohorts were not significantly different (59.6 and 60.8%, respectively).

Conclusions Assessment of the NCDB revealed that 28% patients with sinonasal malignancy were selected for endoscopic surgery. These patients had comparable oncologic outcomes to open resection.
Direct evidence for the coexistence of nanoscale high-conduction and low-conduction phases in VO2 films
Authors: Feng Jiajun , Yang Cheng , Zhang Aihua , Li Qiang , Fan Zhen , Qin Minghui , Zeng Min , Gao Xingsen , Lin Yuan , Zhou Guofu , Lu Xubing , Liu J.-M.
Published: October 2018

A systematic investigation of the nanoscale conduction behavior of vanadium dioxide (VO2) films deposited on aluminum oxide (Al2O3) substrates, using conductive atomic force microscopy, is presented. Aside from the macroscale resistance-temperature characteristics, which show a steep insulator-metal transition at the transition point Tm ∼ 68 °C, our experiments demonstrate a coexistence of nanoscale high-conduction and low-conduction phases over a broad temperature window (50 K range) across the Tm. In addition, the area (volume) fraction of the high-conduction phase increases with increasing temperature across the transition point. The current-voltage data obtained on a nanoscale indicate that the high-conduction phase is not a good metal. When the temperature increased across the Tm, the probed charge transport behavior of the high-conduction phase is found to change from a mechanism dominated by space-charge limited current to a mechanism dominated by Schottky emission.
State transition identification in multivariate time series (STIMTS) applied to rotational jump trajectories from single molecules
Authors: Bauer Marius , Li Chen , Müllen Klaus , Basché Thomas , Hinze Gerald
Published: October 2018

Time resolved data from single molecule experiments often suffer from contamination with noise due to a low signal level. Identifying a proper model to describe the data thus requires an approach with sufficient model parameters without misinterpreting the noise as relevant data. Here, we report on a generalized data evaluation process to extract states with piecewise constant signal level from simultaneously recorded multivariate data, typical for multichannel single molecule experiments. The method employs the minimum description length principle to avoid overfitting the data by using an objective function, which is based on a tradeoff between fitting accuracy and model complexity. We validate our method with synthetic data from Monte Carlo simulations modeling fluorescence resonance energy transfer and rotational jumps, respectively. The method is applied to quantify rotational jump dynamics of single terrylene diimide (TDI) molecules deposited on a solid substrate. Depending on the substitution pattern of the TDI molecules and the chosen substrate materials, we find significant differences in time scale and geometry of molecular reorientation. From an additional application of our state transition identification in multivariate time series approach, a significant correlation between shifts of emission spectra and the occurrence of rotational jumps was found.
Upconversion luminescence from magnetron-sputtered Er3+-doped TiO2 films: Influence of deposition- and annealing temperatures and correlation to decay times
Authors: Lakhotiya Harish , Christiansen Jeppe , Hansen John Lundsgaard , Balling Peter , Julsgaard Brian
Published: October 2018

The optical properties of radio-frequency magnetron sputtered TiO2 thin films doped with Er3+ are strongly influenced by the deposition and post-annealing temperatures. This has an impact on the applications of the material for upconversion, i.e., the merging of two low-energy photons to one photon of higher energy. Maximum upconversion luminescence (UCL) yield is obtained using a deposition temperature of 350 °C without post-annealing. Motivated by the possibilities that become available by sequential depositions (several layers), the effect of post-annealing is systematically investigated. In general, post-annealing treatments reduce the UCL; however, for the lowest deposition temperatures, post-annealing has a positive impact on the UCL provided that the samples are not exposed to ambient air prior to the annealing step. These observations are further analyzed using time-resolved photoluminescence spectroscopy for determining the characteristic decay times of the Er3+ energy levels in the different samples. It is found that the UCL yield scales to a good approximation linearly with the product of the decay times of the two lowest-lying Er3+ excited energy levels (4I11/2 and 4I13/2). The combined data provide strong evidence that the reduction in UCL is due to the opening of non-radiative decay channels from the Er3+ excited levels. Structural measurements show no change of the amorphous samples upon annealing, so these decay channels are most likely related to energy transfer between Er3+ and defect states in the TiO2 bandgap. The non-radiative decay could possibly be related to the loss of hydrogen termination of dangling bonds or related to the oxygen vacancies in TiO2.
Coherence-imaging spectroscopy for 2D distribution of ion temperature and flow velocity in a laboratory magnetosphere
Authors: Nakamura K. , Nishiura M. , Takahashi N. , Yoshida Z. , Kenmochi N. , Sugata T. , Katsura S. , Howard J.
Published: October 2018

A coherence-imaging spectroscopy (CIS) technique was developed to investigate plasma confinement in a dipole system that imitates a planetary magnetosphere. Optical interference generated using birefringent crystals enables two-dimensional Doppler spectroscopy to measure ion temperatures and flow velocities in plasmas. CIS covers the entire dynamics of the pole areas as well as of the core and edge areas on a dipole confinement device. The two-dimensional visualization of these quantities in the magnetospheric-plasma device RT-1 was demonstrated using CIS.
A Monte Carlo study of the electrical double layer of a shape-asymmetric electrolyte around a spherical colloid
Authors: Hernández-Martínez Luis Fernando , Chávez-Navarro Moisés Alfonso , González-Tovar Enrique , Chávez-Páez Martín
Published: October 2018

In this paper, we present a Monte Carlo simulation study on the structure of the electrical double layer around a spherical colloid surrounded by a binary electrolyte composed of spherical and non-spherical ions. Results are provided for the radial distribution functions between the colloid and ions, the orientation correlations between the colloid and non-spherical particles, and the integrated charge. Work is reported mainly for non-spherical particles modeled as spherocylinders, although a particular comparison is made between spherocylindrical particles and dimers. For the conditions investigated here, spherocylinders and dimers produce essentially the same structural information. Additionally, it is shown that spherocylinders mostly orient tangentially to the colloid at its surface; this preferred orientation disappears for larger distances. We also evidence that, near the colloid, the integrated charge attenuates monotonically when the macroparticle is highly charged, whereas for intermediate and low charged states of the colloid, the integrated charge can display charge reversal, overcharging, or both, with magnitudes that are sensitive to the salt concentration and to the localization of charge inside the spherocylinders.
Noise-sustained patterns in a model of volume-coupled neural tissue
Authors: Verisokin A. Yu. , Verveyko D. V. , Kuryshovav E. A. , Postnov D. E.
Published: October 2018

Computational neuroscience operates on models based on several important paradigms. Among them is the assumption that coupling in neural ensembles is provided by chemical or electrical synapses. This assumption works well under normal conditions. However, there is a growing body of data that show the importance of other communication pathways caused by bi-directional transport of substances between the cells and the intercellular space. This type of interaction is called “volume transmission” and has not been rarely addressed in the model studies. The volume transmission pathway naturally appears in multidimensional quantitative models of cellular processes, but is not sufficiently represented at the level of lumped and computationally effective neural models. In this paper, we propose a simple model that allows one to study the features of volume transmission coupling at various spatial scales and taking into account various inhomogeneities. This model is obtained by the extension of the well-known FitzHugh–Nagumo system by the addition of the nonlinear terms and equations to describe, at a qualitative level, the release of potassium into the intercellular space, its diffusion, and the reverse effect on the neurons. The study of model dynamics in various spatial configurations has revealed a number of characteristic spatio-temporal types of behavior that include self-organizing bursting and phase-locked firing patterns, different scenarios of excitation spreading, noise-sustained target patterns, and long-living slow moving wave segments.
Alternative edge illumination set-up for single-shot X-ray phase contrast imaging
Authors: Zhang Cui , Pan Xiaodong , Shang Hongjie , Li Gongping
Published: October 2018

Edge illumination (EI) is a promising X-ray phase contrast imaging (XPCI) technique and is expected to translate XPCI into practical applications with laboratory X-ray sources. However, traditional double-mask EI setup requires two acquisitions for extracting phase and absorption information. Although the latest single-mask EI setup allows phase retrieval with single-shot, it requires a nearly ideal detector point spread function (PSF). In this paper, an alternative EI setup is proposed, which remains double-mask but requires only a single-shot. It can implement single-shot XPCI and relax the detector requirements. Numerical calculations are carried out to compare the characteristics of the double- and single-mask EI setup and the proposed setup. The performance of this setup with different illumination conditions is evaluated theoretically. The results suggest that the proposed setup is less affected by the detector PSF compared to the single-mask EI setup and therefore has higher contrast and contrast-to-noise ratio. Phase retrieval can be implemented by this setup with a single-shot, which helps to simplify the operations and eliminate the potential errors in the double-mask EI setup. A narrow illumination width contributes to the contrast but adversely affects the radiation utilization efficiency, and some appropriate trade-offs should be selected according to the practical applications and experimental conditions. On the basis of this setup, the extraction of the quantitative phase and absorption information was also conducted by numerical calculation.
Ultra low frequency Barkhausen noise versus domain structure and reversal magnetization in sintered (NdDy)(FeCo)B magnets
Authors: Kunitsyna E. , Koplak O. , Kucheryaev V. , Valeev R. , Korolev D. , Piskorskii V. , Morgunov R.
Published: October 2018

The continuous and jumpwise components of the magnetic relaxation were analyzed in the (NdDy)(FeCo)B sintered magnets in the stationary magnetic field close to the coercive field. The jumpwise magnetic relaxation of the extremely low frequency (∼0.01–0.1 Hz) and a large average amplitude (∼0.2%) of the saturation magnetization were revealed. The 2%–3% Sm doping ions increase the continuous relaxation up to 2 times and decrease the magnetization probability and average jump size down to 1.5 times. The spectral power of the magnetization jumps corresponds to the white noise appearing due to the uncorrelated individual magnetization reversal of the ∼103 independent grains. The continuous relaxation is due to the domain wall motion. Magnetic force microscopy allows us to distinguish the domain walls shift and the reversal of the grains to estimate the energy and width of the domain walls. First order reversal curve analysis revealed the contribution of the 2-14-1 phase and isolated 1-4-1 phase inclusions and the effect of Sm doping on the distribution of the switching and interaction fields of these phases.
Tutorial: High-speed low-power neuromorphic systems based on magnetic Josephson junctions
Authors: Schneider Michael L. , Donnelly Christine A. , Russek Stephen E.
Published: October 2018

Josephson junctions and single flux quantum (SFQ) circuits form a natural neuromorphic technology with SFQ pulses and superconducting transmission lines simulating action potentials and axons. Josephson junctions consist of superconducting electrodes with nanoscale barriers that modulate the coupling of the complex superconducting order parameter across the junction. When the order parameter undergoes a 2π phase jump, the junction emits a voltage pulse with an integrated amplitude of a flux quantum ϕ0 = h/(2e) = 2.068 × 10−15 V s. The coupling across a junction can be controlled and modulated by incorporating the nanoscale magnetic structure in the barrier. The magnetic state of embedded nanoclusters can be changed by applying small current or field pulses, enabling both unsupervised and supervised learning. The advantage of this magnetic/superconducting technology is that it combines natural spiking behavior and plasticity in a single nanoscale device and is orders of magnitude faster and lower energy than other technologies. Maximum operating frequencies are above 100 GHz, while spiking and training energies are ∼10−20 J and 10−18 J, respectively. This technology can operate close to the thermal limit, which at 4 K is considerably lower energy than in a human brain. The transition from deterministic to stochastic behavior can be studied with small temperature modifications. Here, we present a tutorial on the spiking behavior of Josephson junctions; the use of the nanoscale magnetic structure to modulate the coupling across the junction; the design and operation of magnetic Josephson junctions, device models, and simulation of magnetic Josephson junction neuromorphic circuits; and potential neuromorphic architectures based on hybrid superconducting/magnetic technology.
Investigation of wide-range refractive index sensor based on asymmetric metal-cladding dielectric waveguide structure
Authors: Wang Xiangxian , Wu Xiaoxiong , Chen Yizhen , Bai Xuelin , Pang Zhiyuan , Yang Hua , Qi Yunping , Wen Xiaolei
Published: October 2018

A refractive index (RI) sensor based on an asymmetric metal-cladding dielectric waveguide structure, in which an analyte is used as the guiding layer, is proposed in this report. The angular scanning attenuated total reflection spectra of the sensor and optical field distributions under waveguide mode resonance conditions were simulated, which confirmed that multiple waveguide modes can be used for sensing, and that different waveguide modes exist in different analyte RI ranges. The curves of both waveguide mode resonance angles and the sensitivity as a function of the analyte RI demonstrated that a wide sensing range can be achieved by combining waveguide modes of different orders. The proposed sensor could be applied to numerous fields, such as biological and chemical detection.
Diffusion of Rb in polycrystalline Cu(In,Ga)Se2 layers and effect of Rb on solar cell parameters of Cu(In,Ga)Se2 thin-film solar cells
Authors: Wuerz R. , Hempel W. , Jackson P.
Published: October 2018

The diffusion of the heavy alkali element rubidium (Rb) in Cu(In,Ga)Se2 (CIGS) layers was investigated over a temperature range from 148 °C to 311 °C by outdiffusion from a rubidium fluoride layer. The diffusion profiles were measured by secondary ion mass spectrometry. By using CIGS layers with different grain sizes, diffusion along grain boundaries could be distinguished from diffusion into the grain interior. Rb was found to diffuse from the CIGS surface along grain boundaries but also within the grain bulk. Based on these data, the slower diffusion coefficient in the volume can be described by the Arrhenius equation DV (Rb) = 3.8·10−8 exp(−0.44 eV/kBT) cm2 s−1 and the fast diffusion along the grain boundaries by DGB (Rb) = 5.7·10−9 exp(−0.29 eV/kBT) cm2 s−1. Further, the effect of Na on Rb diffusion was investigated by comparing Rb diffusion into a Na-containing CIGS layer in contrast to Rb diffusion into an alkali-free CIGS layer. This comparison revealed some aspects of the ion exchange mechanism. Finally, the effect of Rb on the solar cell parameters of CIGS thin-film solar cells was investigated. Rb was found to enhance the open-circuit voltage, the fill factor, and charge carrier density in a similar manner as observed for potassium and sodium.
Highly longitudinally polarized coherent anti-Stokes Raman scattering microscopy with improved spatial resolution
Authors: Lin Jian , Wei Shishen , Zhuang Songlin
Published: October 2018

We proposed a method to enhance the longitudinally polarized component and improve the spatial resolution of radially polarized coherent anti-Stokes Raman scattering (CARS) microscopy by phase modulation. A specially designed phase pattern is applied onto the pump beam to suppress the radially polarized field component at the focal region. With this modulation, the calculated intensity ratio between the longitudinally and radially polarized CARS field is increased from 2.57 to 14.7, and the simulation of CARS imaging on a 120 nm polystyrene bead shows more than 3-fold spatial resolution improvement for both forward and backward detection. It is expected that this method could also be applied to other nonlinear optical imaging modalities for enhancing the longitudinally polarized component.
Tailored dielectric and magnetic properties of composite electroceramics with ferroelectric and ferrimagnetic components
Authors: Geyer Richard G. , Asadi-Zeydabadi Masoud
Published: October 2018

High-frequency coaxial waveguide measurements are used to evaluate composition- and frequency-dependent complex permittivities and permeabilities of polycrystalline ferroelectric and ferrimagnetic ceramics. Material dielectric and magnetic property measurements were performed on ferroelectric barium titanate (BaTiO3) and ferrimagnetic yttrium iron garnet (YIG), with the upper measurement frequency bound below gyromagnetic resonance of YIG. These polycrystalline materials were chosen because of their widespread use in voltage- and magnetic field-tunable devices. Wideband frequency material measurements were used to predict dielectric and magnetic properties of various two-phase composite media incorporating BaTiO3 and YIG. Two effective medium theories were used: an asymmetric, modified Maxwell-Garnett type and a symmetric Bruggeman model. The Bruggeman effective medium model is extended to include three-phases. The three-phase Bruggeman predictive model is employed when controlled porosity is introduced into the composite and when two component phases are combined with polytetrafluoroethylene.
Modification of turbulent wake characteristics by two small control cylinders at a subcritical Reynolds number
Authors: Yan T. , Wang R. , Bao Y. , Zhou D. , Zhu H. B. , Ping H. , Han Z. L. , Ng B. F.
Published: October 2018

In this paper, the flow around a main circular cylinder with two small control cylinders is numerically investigated at a subcritical Reynolds number of 3900. Two small control cylinders with diameter ratio of d/D = 0.04 (d and D are the diameters of the control cylinders and the main cylinder, respectively) are symmetrically placed inside the separated shear layers emanating from the main cylinder. The computation is performed with highly resolved direct numerical simulations employing a high-order spectral/hp element method. For validation purposes, the results of the flow over a single cylinder are presented at first, and the current simulation is in good agreement with the existing experiments and large eddy simulations. For the main cylinder with the two control cylinders, the dynamics of shear layers is found to be modified strongly owing to the disturbance from the small control cylinders. As a consequence, the recirculation length is decreased by 89% as compared to that of a single cylinder. The presence of the small control cylinders further leads to a significant increase in the fluctuating lift and the mean drag exerting on the main cylinder. Furthermore, the statistical analysis and turbulent wake visualization imply that the turbulent intensity is amplified in the near wake region and becomes weaker further downstream. This study then suggests that the small control cylinders located in the near wake region of the main cylinder may work differently in the turbulent wake against that in the laminar wake.
Spectroscopic studies of the effects of mechanochemical synthesis on BaTiO3 nanocolloids prepared using high-energy ball-milling
Authors: Idehenre I. U. , Barnakov Y. A. , Basun S. A. , Evans D. R.
Published: October 2018

BaTiO3 ferroelectric nanoparticles have provided benefits to numerous liquid crystal applications, while the chemistry of these nanocolloids was not fully understood. In this paper, infrared absorption spectra reveal that ferroelectric BaTiO3 nanocolloids are more than BaTiO3 nanoparticles in heptane with an oleic acid surfactant as previously believed. It is shown that ball-milling plays a bigger role than just a top-down approach for creating nanoparticles; it also is a means of mechanochemical synthesis. This paper demonstrates that mechanochemical synthesis is responsible for converting a large amount of the oleic acid to a metal carboxylate compound. This suggests that one cannot treat the oleic acid as a mere surfactant when considering new methods/recipes to improve fabrication processes for creating highly ferroelectric nanoparticles or when exploring the various effects that the organic additives may have on liquid crystal systems.
Electric field effect on the photoionization cross section of a single dopant in a strained AlAs/GaAs spherical core/shell quantum dot
Authors: M’zerd S. , El Haouari M. , Aghoutane M. , El-Yadri M. , Feddi E. , Dujardin F. , Zorkani I. , Jorio A. , Sadoqi M. , Long G.
Published: October 2018

This paper reports a recent study on the polarizability and the photoionization cross section (PCS) of a hydrogenic impurity confined in a spherical AlAs/GaAs core/shell quantum dot under external electric field and hydrostatic pressure. In the framework of effective mass theory, a variational approach is used to determine the polarizability, binding energy, and the PCS of a single donor in a spherical core/shell quantum dot. Our numerical calculations reveal that all these fundamental parameters are deeply dependent on the core and shell radii. The study of the localization of the impurity inside the core/shell indicates that the Stark shift is more important when the impurity is positioned at the center of the core/shell and becomes less important when the donor moves toward the boundaries of the shell layer. In addition, a rapid decrease of the intensity of electric polarizability under hydrostatic pressure is observed. In order to understand the optical responses during the photoionization of the donor dopant, we investigated the PCS under hydrostatic pressure, electric field, ionized donor position, and core/shell sizes.
High fidelity field stop collection for polarization-entangled photon pair sources
Authors: Lohrmann Alexander , Villar Aitor , Stolk Arian , Ling Alexander
Published: October 2018

We present an experimental demonstration of a bright and high fidelity polarization entangled photon pair source. The source is constructed using two critically phase matched β-Barium Borate crystals with parallel optical axes, and photon pairs are collected after filtering with a circular field stop. Near-unity fidelities are obtained with detected pair rates exceeding 100 000 pairs/s mW, approaching the brightness of practical quasi-phase matched entangled photon sources. We find that the brightness scales linearly with the crystal length. We present models supporting the experimental data and propose strategies for further improvement. The source design is a promising candidate for emerging quantum applications outside of laboratory environments.
Investigating core-excited states of nitrosyl chloride (ClNO) and their break-up dynamics following Auger decay
Authors: Salén Peter , Schio Luca , Richter Robert , Alagia Michele , Stranges Stefano , Zhaunerchyk Vitali
Published: October 2018

The fragmentation of ClNO upon resonant core-electron excitation to the LUMO and LUMO+1 orbitals at the N and O K-edges is investigated. The produced fragment ions were detected in coincidence with a position sensitive ion time-of-flight detector which enables deduction of the angular distribution of the ions. This facilitates a comparison between the two resonances and the two K-edges with respect to fragmentation time, transition dipole moment orientation, fragment yield of single-ion and ion-pair channels, and fragmentation mechanisms. We observe significant correlations between the core-excited site and the location of the bonds that are broken, as well as the dissociation time. Moreover, we observe preferential cleavage of specific bonds upon excitation to the LUMO and LUMO+1 states which can be attributed to their orbital character.
Evaluation of an energy consistent entrainment model for volumetrically forced jets using large eddy simulations
Authors: Pant Chandra Shekhar , Bhattacharya Amitabh
Published: October 2018

We examine an existing energy-consistent approach for modeling entrainment rate coefficient, α, in the context of a volumetrically forced jet. The steady buoyancy forcing, with a Gaussian radial profile, is externally imposed within a prescribed height range. Large Eddy Simulations (LESs) of the forced jet are performed to generate the relevant flow statistics. We vary the forcing Richardson number RiFZ (ranging from 0 to 2.12) and the ratio of the forcing region to the jet width, λFZ (ranging from 0.33 to 1), over a set of 11 cases. We also construct a Gaussian one-dimensional model for evolving the forced jet, based on mixing length model. LES statistics shows that the mixing length constant, Cmix, can reduce significantly in the presence of volumetric forcing. Large differences exist between the results from LESs and 1-D model if a constant value of Cmix is used in the model. Using the value of Cmix obtained from LESs, the error between the 1-D model and LESs is reduced, especially for cases with λFZ = 1. For low values of λFZ, the velocity profile of the jet in the forcing zone departs from a Gaussian shape. The 1-D model is nevertheless able to successfully predict the qualitative trends for α, jet width, and centerline velocity and yields a good estimate for the buoyancy flux. The LES statistics also show reasonably good agreement between the exact closure for α and its measured value.
SKIFFS: Superconducting Kinetic Inductance Field-Frequency Sensors for sensitive magnetometry in moderate background magnetic fields
Authors: Asfaw A. T. , Kleinbaum E. I. , Hazard T. M. , Gyenis A. , Houck A. A. , Lyon S. A.
Published: October 2018

We describe sensitive magnetometry using lumped-element resonators fabricated from a superconducting thin film of NbTiN. Taking advantage of the large kinetic inductance of the superconductor, we demonstrate a continuous resonance frequency shift of 27 MHz for a change in the magnetic field of 1.8 μT within a perpendicular background field of 60 mT. By using phase-sensitive readout of microwaves transmitted through the sensors, we measure phase shifts in real time with a sensitivity of 1°/nT. We present measurements of the noise spectral density of the sensors and find that their field sensitivity is at least within one to two orders of magnitude of superconducting quantum interference devices operating with zero background field. Our superconducting kinetic inductance field-frequency sensors enable real-time magnetometry in the presence of moderate perpendicular background fields up to at least 0.2 T. Applications for our sensors include the stabilization of magnetic fields in long coherence electron spin resonance measurements and quantum computation.
Direct numerical simulation of turbulent flow above zigzag riblets
Authors: Okabayashi Kie , Hirai Kenshi , Takeuchi Shintaro , Kajishima Takeo
Published: October 2018

We investigate the drag-reducing performance of a zigzag riblet inspired by the “Miura fold” and its influence on the streamwise vortices above a wall-bounded turbulent flow through direct numerical simulations of channel flows. The employed channel wall geometries are a flat plate, straight riblet, and zigzag riblet. The drag-reducing performance of various zigzag riblets with adjusted configuration parameters is superior or at least comparable to that of the straight riblet. We assume an analogy between the drag reduction mechanisms of spatially periodic forcing and the zigzag riblet, because both methods induce similar sinusoidal velocity profiles. To investigate the characteristics of the zigzag riblets, we apply a conditional sampling technique to the near-wall streamwise vortices that is also applied to the wall-bounded flow under spatially periodic forcing. The flow toward the wall of the rotating motion of a vortex becomes relatively small, as the main flow levitates at the tips of the zigzag riblet. Thus, the ejection increases and the sweep decreases. In the phase where the direction of the induced spanwise velocity coincides with the vortical motion, the latter is weakened because the vortex tilts in the spanwise direction at the phase; then, vortex stretching is suppressed. The zigzag riblet can reduce the drag via a mechanism analogous to active control, such as periodic oscillation. However, the effect of the upward flow is dominant above the zigzag riblet, and the analogous mechanisms are less remarkable. The considered zigzag riblet has potential application as a kind of active feedback control.
Pressure drop for adiabatic air-water flow through a time-varying constriction
Authors: Van Hirtum A. , Bouvet A. , Pelorson X.
Published: October 2018

The pressure drop for air-water flow within a vertical rigid channel containing a severe time-varying constriction is studied for different forcing frequencies fc ∈ {1, 6, 10} Hz after water (0 up to 5 ml) is injected upstream. The pressure drop at the minimum aperture is observed experimentally and can be modeled with a quasi-steady one-dimensional approach and viscous mixing during the closing and opening phase. It is found that the flow can be regarded as gas dominated during the closing phase. During the opening phase, mixing enhances as fc > 1 Hz, which emphasizes the contribution of water and water droplets to the viscous mixture. Eventually, for fc = 10 Hz and greater water volumes (≥3 ml), mixing is further increased so that the flow becomes homogeneous and turbulent during the opening phase. Assessed conditions are relevant to flow through the human glottis.
How to measure the thickness of a lubrication film in a pancake bubble with a single snapshot?
Authors: Atasi O. , Haut B. , Dehaeck S. , Dewandre A. , Legendre D. , Scheid B.
Published: October 2018

In the in-line bright-field image of a pancake-like bubble, a ring-shaped zone of maximum intensity is visible, called the glare ring. It is due to multiple interactions of light with the bubble interface. In this study, we develop a method to measure the thickness of the lubrication film around a pancake-like bubble translating inside a microchannel, based on the location of this glare ring. By means of ray tracing, a correlation is proposed to relate the film thickness to the location of the glare ring with respect to the bubble edge and to the ratio of refractive indices of the inner and outer phases. This makes the method also applicable to inviscid pancake drops. Additionally, for static bubbles, the method can be used to measure the depth of a microchannel. For moving bubbles, provided the speed of the bubble is also measured, the method can be used to measure surface tension or viscosity. Finally, the method can also be extended to viscous drops, provided the shape function of the interface is adapted.
Observation of charge density waves in free-standing 1T-TaSe2 monolayers by transmission electron microscopy
Authors: Börner P. C. , Kinyanjui M. K. , Björkman T. , Lehnert T. , Krasheninnikov A. V. , Kaiser U.
Published: October 2018

While bulk 1T-TaSe2 is characterized by a commensurate charge density wave (CCDW) state below 473 K, the stability of the CCDW state in a 1T-TaSe2 monolayer, although theoretically predicted, has not been experimentally confirmed so far. As charge density waves and periodic lattice distortions (PLDs) always come together, we evaluate the PLD in a 1T-TaSe2 monolayer from low-voltage aberration-corrected high-resolution transmission electron microscopy experiments. To prevent fast degradation of 1T-TaSe2 during exposure to the electron-beam, a 1T-TaSe2/graphene heterostructure was prepared. We also perform the image simulations based on atom coordinates obtained using density functional theory calculations. From the agreement between the experimental and simulated images, we confirm the stability of the CCDW/PLD in a monolayer 1T-TaSe2/graphene heterostructure at room temperature in the form of a 13×13 superstructure. At the same time, we find that in comparison to multi-layer structures, the superstructure is less pronounced.
Samarium cation (Sm+) reactions with H2, D2, and HD: SmH+ bond energy and mechanistic insights from guided ion beam and theoretical studies
Authors: Demireva Maria , Armentrout P. B.
Published: October 2018

Guided ion beam tandem mass spectrometry is used to study the reaction of the lanthanide samarium cation (Sm+) with H2 and its isotopologues (HD and D2) as a function of collision energy. Modeling the resulting energy dependent product ion cross sections from these endothermic reactions yields 2.03 ± 0.06 eV (two standard deviations) for the 0 K bond dissociation energy of SmH+. Quantum chemical calculations are performed to determine stabilities of the ground and low-energy states of SmH+ for comparison with the experimentally measured thermochemistry. The calculations generally overestimate the SmH+ bond energy, but a better agreement between experiment and theory is achieved after correcting for spin-orbit energy contributions, with coupled-cluster with single, double and perturbative triple excitations/complete basis set [CCSD(T)/CBS] results reproducing the experiment well. In the HD reaction, the SmH+ product is observed to be favored over the SmD+ by about a factor of three, indicating that the reaction proceeds via a direct mechanism with short-lived intermediates. This is consistent with quantum chemical calculations of relaxed potential energy surface scans of SmH2+, which show that there is no strongly bound dihydride intermediate. The reactivity and hydride bond energy of Sm+, which has a valence electron configuration typical of most lanthanides, are compared with previous results for the lanthanide cations La+, Gd+, and Lu+, which exhibit configurations more closely related to the group 3 metal cations, Sc+ and Y+. Periodic trends across the lanthanide series and insights into the role of the electronic configurations on hydride bond strength and reactivity with H2 are discussed.