bluuebunny/crossref_metadata_2025_split huggingface dataset:
High-speed shear-driven dynamos. Part 1. Asymptotic analysis
Authors: Deguchi Kengo 
Published: April 2019

Rational large Reynolds number matched asymptotic expansions of three-dimensional nonlinear magneto-hydrodynamic (MHD) states are the concern of this contribution. The nonlinear MHD states, assumed to be predominantly driven by a unidirectional shear, can be sustained without any linear instability of the base flow and hence are responsible for subcritical transition to turbulence. Two classes of nonlinear MHD states are found. The first class of nonlinear states emerged out of a nice combination of the purely hydrodynamic vortex/wave interaction theory by Hall & Smith (J. Fluid Mech., vol. 227, 1991, pp. 641–666) and the resonant absorption theories on Alfvén waves, developed in the solar physics community (e.g. Sakurai et al. Solar Phys., vol. 133, 1991, pp. 227–245; Goossens et al. Solar Phys., vol. 157, 1995, pp. 75–102). Similar to the hydrodynamic theory, the mechanism of the MHD states can be explained by the successive interaction of the roll, streak and wave fields, which are now defined both for the hydrodynamic and magnetic fields. The derivation of this ‘vortex/Alfvén wave interaction’ state is rather straightforward as the scalings for both of the hydrodynamic and magnetic fields are identical. It turns out that the leading-order magnetic field of the asymptotic states appears only when a small external magnetic field is present. However, it does not mean that purely shear-driven dynamos are not possible. In fact, the second class of ‘self-sustained shear-driven dynamo theory’ shows a magnetic generation that is slightly smaller in size in the absence of any external field. Despite its small size, the magnetic field causes the novel feedback mechanism in the velocity field through resonant absorption, wherein the magnetic wave becomes more strongly amplified than the hydrodynamic counterpart.
Patterns and drivers of genetic diversity and structure in the biological control parasitoidHabrobracon hebetorin Niger
Authors: Garba M. , Loiseau A. , Tatard C. , Benoit L. , Gauthier N. 
Published: April 2019

AbstractWhen a promising natural enemy of a key pest exists locally, it is a common practice in biological control (BC) to rear and release it for supplementary control in the targeted agroecosystem even though significant knowledge gaps concerning pre/post release may still exist. Incorporating genetic information into BC research fills some of these gaps.Habrobracon hebetor, a parasitoid of many economically important moths that infest stored and field crops worldwide is commonly used, particularly against the millet head miner (MHM), a key pest of millet in Sahelian countries. To advance our knowledge on howH. hebetorthat occurs naturally in open-field cropping systems and grain stores as well as being mass-produced and released for MHM control, performs in millet agroecosystems in Niger we evaluated its population genetics using two mitochondrial and 21 microsatellite markers. The field samples were genetically more diverse and displayed heterozygote excess. Very few field samples had faced significant recent demographic bottlenecks. The mating system (i.e. nonrandom mating with complementary sex determination) of this species may be the major driver of these findings rather than bottlenecks caused by the small number of individuals released and the scarcity of hosts during the longlasting dry season in Niger.H. hebetorpopulation structure was represented by several small patches and genetically distinct individuals. Gene flow occurred at local and regional scales through human-mediated and natural short-distance dispersal. These findings highlight the importance of the mating system in the genetic diversity and structure ofH. hebetorpopulations, and contribute to our understanding of its reported efficacy against MHM in pearl millet fields.
The effect of caloric restriction on working memory in healthy non-obese adults
Authors: Leclerc Emilie , Trevizol Alisson Paulino , Grigolon Ruth B. , Subramaniapillai Mehala , McIntyre Roger S. , Brietzke Elisa , Mansur Rodrigo B. 
Published: April 2019

Objective.We aim to evaluate the effect of caloric restriction (CR) in cognition by comparing performance in neuropsychological tests for working memory between a group of non-obese healthy subjects doing CR for 2 years with another consuming ad libitum diet (AL).Methods.This study was part of a larger multicenter trial called CALERIE that consisted of a randomized clinical trial with parallel-group comparing 2 years of 25% CR and AL in 220 volunteers with a BMI between 22 and 28 kg/m2, across 3 sites. The cognitive tests used were the Cambridge Neuropsychological Tests Automated Battery (CANTAB) for Spatial Working Memory (SWM) including the total number of errors (SWMTE) and strategy (SWMS). Included as possible moderators were sleep quality, mood states, perceived stress, and energy expenditure. Analyses were performed at baseline and months 12 and 24.Results.After adjustments, there was a significantly greater improvement in working memory assessed by the SWM for CR individuals, compared to AL. At month 24, it was related mostly to lower protein intake, compared to other macronutrients. Changes in SWM were moderated by changes in sleep quality, physical activity, and energy expenditure.Conclusion.On the long term, CR in healthy individuals seems to have a slightly positive effect on working memory. The study of brain CR targets opens new possibilities to prevent and treat cognitive deficits.
Left rostrolateral prefrontal cortex lesions reduce suicidal ideation in penetrating traumatic brain injury
Authors: Pardini Matteo , Grafman Jordan , Raymont Vanessa , Amore Mario , Serafini Gianluca , Koenigs Michael , Krueger Frank 
Published: April 2019

Objectives.The objective of this study is to evaluate the relationship between suicidal ideation (SI), structural brain damage, and cognitive deficits in patients with penetrating traumatic brain injury (pTBI).Methods.Vietnam War veterans (n= 142) with pTBI to the prefrontal cortex (PFC) underwent combination of neuropsychological and psychiatric examinations and non-contrast CT brain scan. Patients were divided into SI positive (SI+) and SI negative (SI−) groups according to the SI item of the Beck Depression Inventory.Results.Lesions to the left rostrolateral PFC (rlPFC) were associated with alower riskof SI independent of depression and global functioning. Left rlPFC lesion also reduced abstract reasoning skills, which mediated the lesion effects on suicide ideation.Conclusions.The left rlPFC plays a crucial role in SI independently of depression and global functioning.
Portable X‐Ray Fluorescence Spectroscopy as a Tool for Cyclostratigraphy
Authors: Saker‐Clark Matthew , Kemp David B. , Coe Angela L. 
Published: April 2019

AbstractCyclostratigraphic studies are used to create relative and high‐resolution time scales for sedimentary successions based on identification of regular cycles in climate proxy data. This method typically requires the construction of long, high‐resolution data sets. In this study, we have demonstrated the efficacy of portable X‐ray fluorescence spectroscopy (pXRF) as a nondestructive method of generating compositional data for cyclostratigraphy. The rapidity (100 samples per day) and low cost of pXRF measurements provide advantages over relatively time‐consuming and costly elemental and stable isotopic measurements that are commonly used for cyclostratigraphy. The nondestructive nature of pXRF also allows other geochemical analyses on the same samples. We present an optimized protocol for pXRF elemental concentration measurement in powdered rocks. The efficacy of this protocol for cyclostratigraphy is demonstrated through analysis of 360 Toarcian mudrock samples from North Yorkshire, UK, that were previously shown to exhibit astronomical forcing of [CaCO3], [S], and δ13Corg. Our study is the first to statistically compare the cyclostratigraphic results of pXRF analysis with more established combustion analysis. There are strong linear correlations of pXRF [Ca] with dry combustion elemental analyzer [CaCO3] (r2 = 0.7616) and of pXRF [S] and [Fe] with dry combustion elemental analyzer [S] (r2 = 0.9632 and r2 = 0.9274, respectively). Spectral and cross‐spectral analyses demonstrate that cyclicity previously recognized in [S], significant above the 99.99% confidence level, is present above the 99.92% and 99.99% confidence levels in pXRF [S] and [Fe] data, respectively. Cyclicity present in [CaCO3] data above the 99.96% confidence level is also present in pXRF [Ca] above the 98.12% confidence level.
Seasonal Variations of Low‐Latitude Migrating and Nonmigrating Diurnal and Semidiurnal Tides in TIMED‐SABER Temperature and Their Relationship With Source Variations
Authors: Sridharan S. 
Published: April 2019

AbstractSeasonal and source variations of migrating and nonmigrating tides are studied using Thermosphere‐Ionosphere‐Mesosphere Energetics and Dynamics‐Sounding of the Atmosphere using Broadband Emission Radiometry temperature data at 10°N (5–15°N) for the year 2009. The migrating DW1 shows equinoctial maximum and summer minimum at low latitudes. It shows equinoctial asymmetry with larger amplitudes during spring equinox than fall equinox. The migrating semidiurnal tidal amplitude (SW2) shows larger amplitudes (~20 K) during March–October at 30–60°S. Its seasonal variation resembles stratospheric (10 hPa) ozone variations at southern midlatitudes. During the sudden stratospheric warming of 2009, the SW1 shows larger amplitudes over the equator and it is generated due to nonlinear interaction between SW2 and planetary wave of zonal wave number 1. The eastward nonmigrating DE4 and DE3 tides enhance in summer. The DE3 and DE4 appear to be generated due to latent heat release in the troposphere, as their amplitudes in the National Center for Environmental Prediction (NCEP)'s Precipitable water vapor (proxy for latent heat release) enhance at similar times as in mesosphere. The DW2 and DW0 tides are likely to be generated due to nonlinear interaction between DW1 and planetary wave of zonal wave number 1. The SW3 enhancement during the early winter (November‐December) may be due to nonlinear interaction between DW1 and the large‐amplitude DW2. The nonlinear interactions of DW1 with planetary wave and nonmigrating tides explain the summer minimum and equinoctial asymmetry of DW1.
Episodic Reef Growth in the Northern South China Sea linked to Warm Climate During the Past 7,000 Years: Potential for Future Coral Refugia
Authors: Yan Shuang , Zhao Jian‐xin , Lau A. .Y. Annie , Roff George , Leonard Nicole D. , Clark Tara R. , Nguyen Ai D. , Feng Yue‐xing , Wei Gangjian , Deng Wenfeng , Chen Xuefei 
Published: April 2019

AbstractHigh‐precision uranium‐thorium (U‐Th) dating of dead branching corals from Luhuitou reef, Sanya, northern South China Sea indicates that the reef framework grew episodically over the past 7,000 years. Episodes of coral reef growth (“switch‐on” phases) occurred in response to regional warming during the mid‐Holocene Climate Optimum, Medieval Warm Period, and Current Warm Period, when the East Asian summer monsoon was strong and the East Asian winter monsoon was weak. In contrast, episodes when reef growth dramatically slowed or ceased (“switch‐off” phases) occurred during comparatively cold periods (e.g., Dark Age Cold Period and Little Ice Age) and are linked to abrupt weakening of the East Asian summer monsoon and concurrent strengthening of the East Asian winter monsoon. In the context of global warming, the northern South China Sea may become an important refugium for coral reef growth of up to 2 °C above present, but only if local anthropogenic pressures are reduced.
An Evaluation of the Ocean and Sea Ice Climate of E3SM Using MPAS and Interannual CORE‐II Forcing
Authors: Petersen Mark R. , Asay‐Davis Xylar S. , Berres Anne S. , Chen Qingshan , Feige Nils , Hoffman Matthew J. , Jacobsen Douglas W. , Jones Philip W. , Maltrud Mathew E. , Price Stephen F. , Ringler Todd D. , Streletz Gregory J. , Turner Adrian K. , Van Roekel Luke P. , Veneziani Milena , Wolfe Jonathan D. , Wolfram Phillip J. , Woodring Jonathan L. 
Published: April 2019

AbstractThe Energy Exascale Earth System Model (E3SM) is a new coupled Earth system model sponsored by the U.S Department of Energy. Here we present E3SM global simulations using active ocean and sea ice that are driven by the Coordinated Ocean‐ice Reference Experiments II (CORE‐II) interannual atmospheric forcing data set. The E3SM ocean and sea ice components are MPAS‐Ocean and MPAS‐Seaice, which use the Model for Prediction Across Scales (MPAS) framework and run on unstructured horizontal meshes. For this study, grid cells vary from 30 to 60 km for the low‐resolution mesh and 6 to 18 km at high resolution. The vertical grid is a structured z‐star coordinate and uses 60 and 80 layers for low and high resolution, respectively. The lower‐resolution simulation was run for five CORE cycles (310 years) with little drift in sea surface temperature (SST) or heat content. The meridional heat transport (MHT) is within observational range, while the meridional overturning circulation at 26.5°N is low compared to observations. The largest temperature biases occur in the Labrador Sea and western boundary currents (WBCs), and the mixed layer is deeper than observations at northern high latitudes in the winter months. In the Antarctic, maximum mixed layer depths (MLD) compare well with observations, but the spatial MLD pattern is shifted relative to observations. Sea ice extent, volume, and concentration agree well with observations. At high resolution, the sea surface height compares well with satellite observations in mean and variability.
Fractionation Behavior of Chromium Isotopes during the Sorption of Cr (VI) on Kaolin and its Implications for Using Black Shales as a Paleoredox Archive
Authors: Frank Anja B. , Klaebe Robert M. , Frei Robert 
Published: April 2019

AbstractChromium stable isotope variations in marine black shales are increasingly used to constrain redox changes though time. However, how well black shale δ53Cr values represent ambient seawater δ53Cr values is difficult to assess as black shales contain both detrital and authigenic mineral phases, of which only authigenic phases are expected to mirror seawater, while detrital silicate phases are expected to show igneous δ53Cr values. In order to correct for detrital contamination, it is thus imperative to know whether detrital minerals are in fact characterized by igneous δ53Cr values. To investigate this further, three sets of Cr (VI) batch sorption experiments were conducted, reacting kaolin with (1) with a synthetic Cr (VI) solution, (2) with Cr (VI) doped river water, and (3) with Cr (VI) doped seawater. Further, sequential leaches were applied to reacted kaolin to evaluate how well sorbed Cr (VI) can be leached. The experiments revealed that Cr (VI) readily sorbs on kaolin, changing its Cr concentration and isotopic composition. In river water, kaolin sorbed up to 36 μg of Cr (VI) per gram of kaolin and recorded a negative offset in bulk δ53Cr of up to 0.26‰ relative to unreacted kaolin, while no sorption was observed in seawater. Our leaching experiments revealed that already a weak acid leach (0.5M HCl) readily mobilizes some of the sorbed Cr from kaolin, which when applied to black shales will likely contaminate leachates designed to release authigenic Cr. This has major implications for the application of Cr stable isotopes in black shales as marine paleoredox archives.
On the Long Lasting “C‐Type” Structures in the Sodium Lidargram: The Lifetime of Kelvin‐Helmholtz Billows in the Mesosphere and Lower Thermosphere Region
Authors: Mondal S. , Sarkhel S. , Agarwal Jay , Chakrabarty D. , Sekar R. , Yuan Tao , Cai Xuguang , Liu Alan Z. , Nozawa Satonori , Saito Norihito , Kawahara Takuya D. , Mlynczak Martin G. , Russell James M. 
Published: April 2019

AbstractIn order to understand the characteristics of long‐lasting “C‐type” structure in the Sodium (Na) lidargram, six cases from different observational locations have been analyzed. The Na lidargram, collected from low‐, middle‐, and high‐latitude sites, show long lifetime of the C‐type structures which is believed to be the manifestation of Kelvin‐Helmholtz (KH) billows in the Mesosphere and Lower Thermosphere (MLT) region. In order to explore the characteristics of the long‐lasting C‐type structures, the altitude profile of square of Brunt‐Väisälä frequency in the MLT region has been derived using the temperature profile collected from the Na lidar instruments and the SABER instrument onboard TIMED satellite. It is found to be positive in the C‐type structure region for all the six cases which indicates that the regions are convectively stable. Simultaneous wind measurements, which allowed us to calculate the Richardson numbers and Reynolds numbers for three cases, suggest that the regions where the C‐type structure appeared were dynamically stable and nonturbulent. This paper brings out a hypothesis wherein the low temperature can increase the magnitude of the Prandtl number and convectively stable atmospheric region can cause the magnitude of Reynolds number to decrease. As a consequence, the remnant of previously generated KH billows in nearly “frozen‐in” condition can be advected through this conducive region to a different location by the background wind where they can sustain for a long time without much deformation. These long‐lived KH billows in the MLT region will eventually manifest the long‐lasting C‐type structures in the Na lidargram.
Vertical SiC taper with a small angle fabricated by slope transfer method
Authors: Xin Yu , Pandraud Gregory , French Paddy J. 
Published: April 2019

In this Letter, a slope transfer method to fabricate vertical waveguide couplers is proposed. This method utilises wet etched Si as a mask, and takes advantage of dry etching selectivity between Si and SiC, to successfully transfer the profile from the Si master into SiC. By adopting this method, a <2° slope is achieved. Such a taper can bring the coupling efficiency in SiC waveguides to 80% (around 1 dB loss) or better from around 10% (10 dB loss) without taper. It further increases the alignment tolerance at the same time, which ensures the successful development of a plug‐and‐play solution for optical sensing. This is the first reported taper made in SiC.
Variographic analysis to evaluate the coverage area of a wireless system at 5.8 GHz band in a region of oil fields
Authors: Fialho B.R. , Andrade H.D. , Fontgalland G. , Paiva J.L.S. , Queiroz I.S. 
Published: April 2019

The advancement of embedded technologies has led to increasing demand for bandwidth in telecommunications solutions, this increased the researches related to the architecture of wireless networks and applied electromagnetism. In view of this, the digital transceiver radios need an adequate received signal strength indicator to enable the traffic of information by the radio propagation channel and to provide quality in the data network for the users to exercise the operational activities. The objective of this Letter is to perform the exploratory and variographic analysis of the data collected in the oil fields. Hence, evaluate the behaviour of the surface power distribution received from a wireless system in the frequency range of 5.8 GHz located in the well‐automation region called Canto do Amaro, Brazil, where there are frequent communications failures for mobile stations. With the data measured in the measurement campaigns, variogram models were constructed and compared for the construction of interpolation matrices and contour maps, with these results the precision criteria of the kriging methods employed in the study region were established.
Data‐dependent reduced‐dimension STAP
Authors: Zhang Wei , Han Minghua , He Zishu , Li Huiyong 
Published: April 2019

Space‐time adaptive processing (STAP) is supposed to be a key technique for detection of slow‐moving targets in airborne radar applications. To overcome the difficulties of obtaining lots of independent and identical distributed secondary data samples, many sub‐optimal STAP algorithms are proposed such as reduced‐dimension STAP, reduced‐rank STAP, or the sparse‐recovery‐based STAP. In this study, based on the observation that the STAP filter weight is sparse, a novel clutter‐dependent reduced‐dimension STAP is proposed. In the proposed approach, the sparse feature of the weight vector in the angular–Doppler domain is utilised to design the reduced‐dimension transform matrix. Simulation results show that the output signal‐to‐interference‐plus‐noise ratio loss is just 3 dB with only one secondary data sample in the extremely heterogeneous clutter environments.
Lumped parameter model of the novel L‐C‐T used in the PSFB ZVS converter
Authors: Jiashen Tian , Yiming Zhang , Junxia Gao 
Published: April 2019

A novel inductor‐capacitor‐transformer (L‐C‐T) has been proposed to integrate the passive components into an integrated magnetic component. The phase‐shift full‐bridge (PSFB) zero‐voltage switching (ZVS) converter with a novel L‐C‐T has high‐power density performance, which is used in electromagnetic exploration. The structure of the novel L‐C‐T is very complicated, and the lumped parameter of the L‐C‐T is very difficult to determine. Based on the dual method of the magnetic circuit, the electromagnetic energy method and the six‐lumped capacitance method, a lumped parameter model suitable for the novel L‐C‐T is proposed. Moreover, the experiments and finite element analysis (FEA) are used to verify the accuracy of the lumped parameter model, and a 40 kW prototype of the PSFB ZVS converter with a novel L‐C‐T is designed and tested.
Densification behaviour and microstructure of spark plasma sintered alumina–mullite nanocomposite
Authors: Sedaghat Ahangari Hossein Zadeh Ali , Taheri‐Nassaj Ehsan 
Published: April 2019

Spark plasma sintering (SPS) is a consolidation technique that combines high heating and cooling rates with a uniaxial applied pressure which results in short processing time. SPS is successful in producing ceramics with novel microstructures, which are often reported to be made at temperatures lower than ones used in conventional densification techniques. In this work, the densification and microstructure development sequences of the alumina–15 vol% mullite composite during the SPS and the conventional process were compared. Through SPS technique, the fully dense 0.5 µm grain sized alumina composite (99.5% T.D.) was obtained at 1600°C and its microstructure exhibited nanocrystalline in submicron‐sized grains. The nanocrystalline grains were arranged in ground‐shaped clusters. Vickers hardness and fracture toughness values for spark plasma sintered composite were calculated as 2098 ± 66 kgf/mm2 and 3.61 ± 0.06 MPa m1/2, respectively.
Synthesis of hollow CuO/ZnO/Al2O3 composite microspheres for catalysing carbon dioxide hydrogenation
Authors: Tian Hai‐feng , Yu Lei , Ding Jian , Zha Fei , Tang Xiao‐hua , Chang Yue 
Published: April 2019

Homogeneous hollow CuO–ZnO–Al2O3 microspheres, which were synthesised, used carbonaceous saccharide as a template by the hydrothermal treatment at 180°C. The hollow microspheres structure of composite metal oxides was characterised by the methods of X‐ray powder diffraction, thermogravimetric analysis, scanning electron microscopy, transmission electron microscopy and N2 adsorption–desorption isothermal. In the evaluation of the hydrogenation of carbon dioxide, the synthesised hollow CuO/ZnO/Al2O3 composite microspheres exhibited higher selectivity and yield of methanol than CuO/ZnO/Al2O3 prepared by a co‐precipitation method. An optimum yield of methanol of 15.3% with the 24.7% CO2 per pass conversion was obtained under the reaction conditions of pressure at 3.0 MPa, space velocity at 1800 ml gcat −1 h−1, the volume ratio of CO2/H2 at 1:3 and temperature at 262°C.