bluuebunny/crossref_metadata_2025 huggingface dataset:
Spatial and Temporal Ionospheric Monitoring Using Broadband Sferic Measurements
Authors: McCormick J. C. , Cohen M. B. , Gross N. C. , Said R. K.
Published: March 2018

The D region of the ionosphere (60–90 km altitude) is highly variable on timescales from fractions of a second to many hours, and on spatial scales up to many hundreds of kilometers. Very low frequency (VLF) and low‐frequency (LF) (3–30 kHz and 30–300 kHz) radio waves are guided to global distances by reflections from the ground and the D region. Therefore, information about its current state is encoded in received VLF/LF signals. VLF transmitters have been used in the past for D region studies, with ionospheric disturbances manifesting as perturbations in amplitude and/or phase. The return stroke of lightning is an impulsive VLF radiator, but unlike VLF transmitters, lightning events are distributed broadly in space allowing for much greater spatial coverage of the D region compared to VLF transmitter‐based remote sensing in addition to the broadband spectral advantage over the narrowband transmitters. The challenge is that individual lightning‐generated waveforms, or “sferics,” vary due to the lightning current parameters and uncertainty in the time/location information, in addition to D region ionospheric variability. These factors make it difficult to utilize the VLF/LF emissions from lightning in a straightforward manner. We describe a technique to recover the time domain and amplitude/phase spectra for both Bϕ and Br with high fidelity and consider the utility of our technique with ambient and varied ionospheric conditions. We demonstrate a technique to simulate sferics and infer a parameterized ionosphere with the Wait and Spies parameters (h
and β) offering all of the tools needed for a global measurement.
A Statistical Study of Spatial Variation of Relativistic Electron Precipitation Energy Spectra With Polar Operational Environmental Satellites
Authors: Shekhar S. , Millan R. M. , Hudson M. K.
Published: March 2018

The mechanisms that drive relativistic electron precipitation (REP) from the radiation belts can be better understood with a better knowledge of the particle energies involved. National Oceanic and Atmospheric Administration Polar Operational Environmental Satellites, being a network of multiple satellites, can provide multiple point spectral data over a long time period, including the Van Allen Probe's era. The number of energy channels is limited, but the particle detectors on Polar Operational Environmental Satellites have a narrow field of view allowing an investigation of bounce loss cone particles. We use the ratio of count rates in the E3 (>300 keV) and the P6 (>700 keV) channels as a parameter to define spectral hardness. Using this parameter, the spatial variation of spectral hardness of REP events was investigated. It was found that very soft events were mostly found in the dusk‐midnight‐early morning magnetic local time sectors and L∼ 5–7 while the hardest events were located in the postnoon sector peaking at L∼ 4–5. The hardest events peaked at lower L shells, and less than 20% were coincident with low‐energy (30–80 keV) proton precipitation. Further, around 70% of nightside REP coincident with proton precipitation was associated with stretched magnetic field lines indicating that curvature scattering may have been an important driver. Around 62% of nightside REP coincident with proton precipitation associated with relaxed magnetic field lines, suggesting a mechanism other than magnetic field curvature scattering, was highly energetic.
Deformation of the Pacific/North America Plate Boundary at Queen Charlotte Fault: The Possible Role of Rheology
Authors: ten Brink U. S. , Miller N. C. , Andrews B. D. , Brothers D. S. , Haeussler P. J.
Published: March 2018

The Pacific/North America (PA/NA) plate boundary between Vancouver Island and Alaska is similar to the PA/NA boundary in California in its kinematic history and the rate and azimuth of current relative motion, yet their deformation styles are distinct. The California plate boundary shows a broad zone of parallel strike slip and thrust faults and folds, whereas the 49‐mm/yr PA/NA relative plate motion in Canada and Alaska is centered on a single, narrow, continuous ~900‐km‐long fault, the Queen Charlotte Fault (QCF). Using gravity analysis, we propose that this plate boundary is centered on the continent/ocean boundary (COB), an unusual location for continental transform faults because plate boundaries typically localize within the continental lithosphere, which is weaker. Because the COB is a boundary between materials of contrasting elastic properties, once a fault is established there, it will probably remain stable. We propose that deformation progressively shifted to the COB in the wake of Yakutat terrane's northward motion along the margin. Minor convergence across the plate boundary is probably accommodated by fault reactivation on Pacific crust and by an eastward dipping QCF. Underthrusting of Pacific slab under Haida Gwaii occurs at convergence angles >14°–15° and may have been responsible for the emergence of the archipelago. The calculated slab entry dip (5°–8°) suggests that the slab probably does not extend into the asthenosphere. The PA/NA plate boundary at the QCF can serve as a structurally simple site to investigate the impact of rheology and composition on crustal deformation and the initiation of slab underthrusting.
An Integrated Study of the Eolian Dust in Pelagic Sediments From the North Pacific Ocean Based on Environmental Magnetism, Transmission Electron Microscopy, and Diffuse Reflectance Spectroscopy
Authors: Zhang Qiang , Liu Qingsong , Li Jinhua , Sun Youbin
Published: March 2018

Eolian dust is a major terrigenous component in North Pacific Ocean pelagic sediments and is an important recorder of Asian terrestrial environmental evolution and Northern Hemisphere atmospheric circulation. In order to extract and quantify wind‐borne mineral signals and develop a reliable eolian dust proxy for pelagic sediments, we investigated sediments from Ocean Drilling Program Hole 885A, North Pacific Ocean, by integrating results from environmental magnetism, transmission electron microscopy, and diffuse reflectance spectroscopy (DRS). Our results indicate that ferrimagnetic and antiferromagnetic minerals coexist in the sediments. The former includes biogenic magnetite, nano‐sized single domain (titano) magnetite inclusions embedded in silicate hosts, submicron vortex state magnetite, and ultrafine superparamagnetic maghemite. The latter includes hematite and goethite. Our results indicate that magnetic properties can be used to determine an overall trend of increased eolian dust inputs, with additional significant influence from biogenic and volcanogenic components. In contrast, a newly proposed parameter RelHm+Gt (combined hematite and goethite concentration) obtained from DRS measurements extracts precisely the eolian signal and precludes other components. Our DRS results indicate that hematite/goethite and siliceous fractions deposited at Hole 885A were jointly delivered to the North Pacific Ocean from Asian dust sources. Therefore, we suggest that RelHm+Gt is a reliable eolian dust proxy for pelagic sediments in this region.
Along‐Trench Structural Variations of the Subducting Juan de Fuca Plate From Multichannel Seismic Reflection Imaging
Authors: Han Shuoshuo , Carbotte Suzanne M. , Canales Juan Pablo , Nedimović Mladen R. , Carton Hélène
Published: March 2018

To characterize the along‐strike structural variations of the Juan de Fuca (JdF) Plate as it enters the Cascadia subduction zone, we present prestack time migrated multichannel seismic reflection images of the JdF Plate along a 400‐km‐long trench‐parallel transect extending from 44.3°N to 47.8°N. Beneath the 1.8–3.0‐km‐thick sediment cover, our data reveal basement topographic anomalies associated with a 1.2‐km‐high seamount and in the vicinity of propagator wakes (390–540‐m relief). Weak Moho reflections are imaged beneath the propagator wakes and coincide with reduced Vp in the lower crust and/or uppermost mantle. The inferred locations of propagator wakes in the downgoing plate collocate with some of the boundaries of episodic tremor and slip events. We propose that the structural and hydration heterogeneities associated with these features could lead to anomalous plate interface properties and contribute to episodic tremor and slip segmentation. Intracrustal reflections with apparent dips (20°–30°) consistent with subduction bending normal faults change near 45.8°N, from northward dipping reflections confined to the middle crust in the north to antithetic reflections through the crust in the south, coinciding with a Vp reduction in the lower crust. These observations indicate more extensive faulting deformation and associated hydration of the JdF Plate south of 45.8°N, which likely results from variations of slab dip and resistance to subduction across 46°N. Basement offsets and abrupt depth/amplitude changes in Moho reflections are imaged beneath the four major WNW trending strike‐slip faults that cross the Cascadia deformation front, providing strong evidence of a lower plate origin for these faults.
A Critical Appraisal of the “Day” Diagram
Authors: Roberts Andrew P. , Tauxe Lisa , Heslop David , Zhao Xiang , Jiang Zhaoxia
Published: March 2018

The “Day” diagram (Day et al., 1977,https://doi.org/10.1016/0031-9201(77)90108-X) is used widely to make inferences about the domain state of magnetic mineral assemblages. Based on theoretical and empirical arguments, the Day diagram is demarcated into stable “single domain” (SD), “pseudo single domain” (“PSD”), and “multidomain” (MD) zones. It is straightforward to make the necessary measurements for a sample and to plot results within the “domain state” framework based on the boundaries defined by Day et al. (1977,https://doi.org/10.1016/0031-9201(77)90108-X). We discuss 10 issues that limit Day diagram interpretation, including (1) magnetic mineralogy, (2) the associated magnetocrystalline anisotropy type, (3) mineral stoichiometry, (4) stress state, (5) surface oxidation, (6) magnetostatic interactions, (7) particle shape, (8) thermal relaxation, (9) magnetic particle mixtures, and (10) definitional/measurement issues. In most studies, these variables are unknowns and cannot be controlled for, so that hysteresis parameters for single bulk samples are nonunique and any data point in a Day diagram could result from infinite combinations of relevant variables. From this critical appraisal, we argue that the Day diagram is fundamentally ambiguous for domain state diagnosis. Widespread use of the Day diagram has also contributed significantly to prevalent but questionable views, including underrecognition of the importance of stable SD particles in the geological record and reinforcement of the unhelpful PSD concept and of its geological importance. Adoption of approaches that enable correct domain state diagnosis should be an urgent priority for component‐specific understanding of magnetic mineral assemblages and for quantitative rock magnetic interpretation.
Investigating the Mechanisms Associated With the Evolutions of Twin Extratropical Cyclones Over the Northwest Pacific Ocean in Mid‐January 2011
Authors: Fu Shen‐Ming , Sun Jian‐Hua , Li Wan‐Li , Zhang Yuan‐Chun
Published: March 2018

Twin extratropical cyclones that appeared over the northwest Pacific Ocean in mid‐January 2011 experienced significantly different transitions: the northern cyclone dissipated rapidly, whereas the southern cyclone developed into an extreme example of an explosive (i.e., rapidly deepening) extratropical cyclone. This event was reasonably reproduced by the fifth‐generation Mesoscale Model, and its associated mechanisms were investigated using piecewise potential vorticity inversion and the Zwack‐Okossi vorticity budget. Main results are as follows. (i) The extratropical cyclone‐included twin cyclone event showed a Fujiwhara effect, during which the two cyclones orbited cyclonically about a midpoint, approached each other, and finally merged. The twin cyclone interactions enhanced the northern cyclone, but weakened the southern cyclone, by inducing warm advection and cold advection, respectively. (ii) Although upper level tropopause folding contributed the most to deepening of the twin cyclones, significant differences in their deepening rates were due predominantly to the contrast between lower level temperature advection and precipitation‐related latent heating. (iii) Stronger upper tropospheric positive absolute‐vorticity advection and warm advection associated with an upper level jet, and larger latent heating, made geostrophic vorticity of the southern cyclone increase more rapidly than that of the northern cyclone. (iv) Explosive deepening of the southern cyclone showed insensitive responses to its relative configuration with the upper level jet, whereas its rotation enhancement was faster when the cyclone was embedded within the upper level jet. (v) The upper level forcing had a greater influence on the large‐scale flow associated with the twin cyclones, whereas the middle‐level and lower level forcings were more dominant close to the cyclone core regions.
Investigation of a Generalized Nonlinear Form of the Complementary Principle for Evaporation Estimation
Authors: Liu Xiaomang , Liu Changming , Brutsaert Wilfried
Published: March 2018

A generalized nonlinear form of the complementary principle for evaporation estimation was tested against evaporation measurements from seven flux stations in China representing different climatic conditions and ecosystem types. The method was implemented using routine meteorological data and pan evaporation measurements. The results indicate that the generalized nonlinear form with its regular boundary conditions can accurately estimate daily evaporation; its performance was somewhat better when the atmospheric evaporative demand was determined from the Penman equation than from pan evaporation. In addition, two formulations of the generalized nonlinear form, namely, a basic formulation and a more flexible quartic formulation, were compared. The comparisons indicate that the quartic formulation is not necessary and may only be needed possibly to accommodate unusual situations. The results should further advance and facilitate the application of the generalized nonlinear form to estimate daily evaporation; since only routine meteorological data are required as input, the method should be useful to generate long time series and their trends, wherever such data are available.
Effects of Different Stratospheric SO2 Injection Altitudes on Stratospheric Chemistry and Dynamics
Authors: Tilmes Simone , Richter Jadwiga H. , Mills Michael J. , Kravitz Ben , MacMartin Douglas G. , Garcia Rolando R. , Kinnison Douglas E. , Lamarque Jean‐Francois , Tribbia Joseph , Vitt Francis
Published: March 2018

Strategically applied geoengineering is proposed to reduce some of the known side effects of stratospheric aerosol modifications. Specific climate goals could be reached depending on design choices of stratospheric sulfur injections by latitude, altitude, and magnitude. Here we explore in detail the stratospheric chemical and dynamical responses to injections at different altitudes using a fully coupled Earth System Model. Two different scenarios are explored that produce approximately the same global cooling of 2°C over the period 2042–2049, a high‐altitude injection case using 24 Tg SO2/year at 30 hPa (≈25‐km altitude) and a low‐altitude injection case using 32 Tg SO2/year injections at 70 hPa (between 19‐ and 20‐km altitude), with annual injections divided equally between 15°N and 15°S. Both cases result in a warming of the lower tropical stratosphere up to 10 and 15°C for the high‐ and low‐altitude injection case and in substantial increases of stratospheric water vapor of up to 2 and 4 ppm, respectively, compared to no geoengineering conditions. Polar column ozone in the Northern Hemisphere is reduced by up to 18% in March for the high‐altitude injection case and up to 8% for the low‐altitude injection case. However, for winter middle and high northern latitudes, low‐altitude injections result in greater column ozone values than without geoengineering. These changes are mostly driven by dynamics and advection. Antarctic column ozone in 2042–2049 does not recover from present‐day (2002–2009) values for both cases.
Effects of Landcover, Soil Property, and Temperature on Covariations of DOC and CDOM in Inland Waters
Authors: Li Jiwei , Yu Qian , Tian Yong Q. , Boutt David F.
Published: March 2018

Significant uncertainty exists in the estimation of dissolved organic carbon (DOC) concentration via remote sensing from colored dissolved organic matter (CDOM) absorption in inland waters pointing to a need for more process‐based understanding of the relationship between CDOM and DOC. In this study, we examine the factors affecting the covariations of DOC and CDOM using controlled experiments combined with field measurements at subbasin scale that have varying environmental and biological conditions. Our analysis reveals that the DOC:CDOM ratio is mainly related to landcover types. Higher DOC:CDOM linear regression slopes observed in evergreen leaf litter leachate suggest that CDOM comprises a smaller fraction of the DOC pool in evergreen sites in comparison to agricultural and deciduous leaf litter leachates. Given the same DOC concentrations, the range of CDOM levels from deciduous forest plant varied 3 times greater than that from other plant types. Results indicate that soil narrows the slope differences in the linear regressions of DOC from CDOM for all plant types (by 19% of evergreen, 18% of agriculture, and 77% of deciduous). Raising soil temperature by 5°C could double the range of DOC concentration and CDOM absorption for all scenarios. We present a mathematical model to estimate DOC concentration in freshwater environment via CDOM variations with reference to land cover and soil effects. The model was able to explain 95% of field measurements of multiple years in four subbasins. This improved understanding is critical for the remote sensing of DOC directly via observations of CDOM.
The Effects of Turbulence and Carbon Amendments on Nitrate Uptake and Microbial Gene Abundances in Stream Sediment
Authors: Tomasek Abigail A. , Barman Tusha D. , Wang Ping , Kozarek Jessica L. , Staley Christopher , Sadowsky Michael J. , Hondzo Miki
Published: March 2018

Understanding the mechanisms governing nitrate uptake in aquatic ecosystems is paramount in mitigating the impact of increased anthropogenic nitrogen loading on water quality. An experimental laboratory flume with agricultural sediment and carbon‐amended sediment was used to evaluate the effect of turbulent fluid flow above rough sediment on oxygen uptake, nitrate uptake, and sediment bacterial gene abundances. The transport of dissolved oxygen to the sediment scaled with the friction velocity and sediment roughness height. Results demonstrated that nitrate uptake was mediated by turbulence levels, as quantified by friction velocity, above the sediment‐water interface. Facilitated nitrate uptake for amended and unamended sediment occurred under midrange of friction velocities from 0.75 to 1.2 cm/s, which corresponds to Reynolds numbers from 2,010 to 5,200. High turbulence levels in the water column above the sediment with friction velocities larger than 1.40 cm/s or Reynolds numbers larger than 5,500, as well as low turbulence with friction velocities less than 0.65 cm/s or Reynolds numbers less than 1,400, were determined to minimize nitrate uptake by the sediment. Carbon‐amended sediment had approximately 100 times greater nitrate uptake fluxes compared to field‐collected unamended sediment. For unamended sediment experiments, gene abundances significantly increased over the course of the experiments for midrange friction velocities; increases were not observed in the low and high friction velocities. Gene abundances did not significantly increase in any experiments for carbon‐amended sediment. Maintaining optimal turbulence levels could facilitate sustained nitrate uptake and reduce nitrogen loading to higher‐order streams in aquatic ecosystems.
Regional 3‐D Modeling of Ground Electromagnetic Field Due To Realistic Geomagnetic Disturbances
Authors: Ivannikova Elena , Kruglyakov Mikhail , Kuvshinov Alexey , Rastätter Lutz , Pulkkinen Antti
Published: March 2018

During extreme space weather events the fluctuating geomagnetic field induces an electric field in the conducting Earth. This geoelectric field in turn generates currents in ground‐based technological systems, affecting their operation. Thus, calculation of the geoelectric field is a key step in predicting, assessing, and, potentially, forecasting the space weather impact on critical infrastructure. We present an approach and a tool for the first fully coupled regional three‐dimensional (3‐D) forward modeling of the electromagnetic field from far geospace down to the surface of the Earth. Applying the developed tool to the British Isles, we perform a 3‐D study in order to explore in detail the so‐called coastal effect (i.e., the anomalous behavior of the geoelectric field near the coasts) and to understand the limitations of the thin‐sheet model widely used for estimating this effect. For this purpose we compare the results of 3‐D and thin‐sheet modelings for plane wave source of excitation and different periods of variations. We conclude that for the British Isles the thin sheet is a reasonable approximation for periods longer than a few minutes. However, for shorter periods 3‐D modeling is essential. Another inference from the results of 3‐D modeling for plane wave and realistic sources is that for the British Isles the geoelectric field is distorted by the coastal effect practically everywhere on land. Finally, we compare modeled and observed geomagnetic fields at four observatories in the region during the first day of the Halloween storm in 2003 and discuss the results of this comparison.
Uncertainty Quantification of Medium‐Term Heat Storage From Short‐Term Geophysical Experiments Using Bayesian Evidential Learning
Authors: Hermans Thomas , Nguyen Frédéric , Klepikova Maria , Dassargues Alain , Caers Jef
Published: March 2018

In theory, aquifer thermal energy storage (ATES) systems can recover in winter the heat stored in the aquifer during summer to increase the energy efficiency of the system. In practice, the energy efficiency is often lower than expected from simulations due to spatial heterogeneity of hydraulic properties or non‐favorable hydrogeological conditions. A proper design of ATES systems should therefore consider the uncertainty of the prediction related to those parameters. We use a novel framework called Bayesian Evidential Learning (BEL) to estimate the heat storage capacity of an alluvial aquifer using a heat tracing experiment. BEL is based on two main stages: pre‐ and postfield data acquisition. Before data acquisition, Monte Carlo simulations and global sensitivity analysis are used to assess the information content of the data to reduce the uncertainty of the prediction. After data acquisition, prior falsification and machine learning based on the same Monte Carlo are used to directly assess uncertainty on key prediction variables from observations. The result is a full quantification of the posterior distribution of the prediction conditioned to observed data, without any explicit full model inversion. We demonstrate the methodology in field conditions and validate the framework using independent measurements.
Nightside Detection of a Large‐Scale Thermospheric Wave Generated by a Solar Eclipse
Authors: Harding B. J. , Drob D. P. , Buriti R. A. , Makela J. J.
Published: March 2018

The generation of a large‐scale wave in the upper atmosphere caused by a solar eclipse was first predicted in the 1970s, but the experimental evidence remains sparse and comprises mostly indirect observations. This study presents observations of the wind component of a large‐scale thermospheric wave generated by the 21 August 2017 total solar eclipse. In contrast with previous studies, the observations are made on the nightside, after the eclipse ended. A ground‐based interferometer located in northeastern Brazil is used to monitor the Doppler shift of the 630.0‐nm airglow emission, providing direct measurements of the wind and temperature in the thermosphere, where eclipse effects are expected to be the largest. A disturbance is seen in the zonal and meridional wind which is at or above the 90% significance level based on the measured 30‐day variability. These observations are compared with a first principles numerical model calculation from the Thermosphere‐Ionosphere‐Mesosphere‐Electrodynamics General Circulation Model, which predicted the propagation of a large‐scale wave well into the nightside. The modeled disturbance matches well the difference between the wind measurements and the 30‐day median, though the measured perturbation (∼60 m/s) is larger than the prediction (38 m/s) for the meridional wind. No clear evidence for the wave is seen in the temperature data, however.
Type‐Dependent Responses of Ice Cloud Properties to Aerosols From Satellite Retrievals
Authors: Zhao Bin , Gu Yu , Liou Kuo‐Nan , Wang Yuan , Liu Xiaohong , Huang Lei , Jiang Jonathan H. , Su Hui
Published: March 2018

Aerosol‐cloud interactions represent one of the largest uncertainties in external forcings on our climate system. Compared with liquid clouds, the observational evidence for the aerosol impact on ice clouds is much more limited and shows conflicting results, partly because the distinct features of different ice cloud and aerosol types were seldom considered. Using 9‐year satellite retrievals, we find that, for convection‐generated (anvil) ice clouds, cloud optical thickness, cloud thickness, and cloud fraction increase with small‐to‐moderate aerosol loadings (<0.3 aerosol optical depth) and decrease with further aerosol increase. For in situ formed ice clouds, however, these cloud properties increase monotonically and more sharply with aerosol loadings. An increase in loading of smoke aerosols generally reduces cloud optical thickness of convection‐generated ice clouds, while the reverse is true for dust and anthropogenic pollution aerosols. These relationships between different cloud/aerosol types provide valuable constraints on the modeling assessment of aerosol‐ice cloud radiative forcing.
Investigating Source Contributions of Size‐Aggregated Aerosols Collected in Southern Ocean and Baring Head, New Zealand Using Sulfur Isotopes
Authors: Li Jianghanyang , Michalski Greg , Davy Perry , Harvey Mike , Katzman Tanya , Wilkins Benjamin
Published: March 2018

Marine sulfate aerosols in the Southern Ocean are critical to the global radiation balance, yet the sources of sulfate and their seasonal variations are unclear. We separately sampled marine and ambient aerosols at Baring Head, New Zealand for 1 year using two collectors and evaluated the sources of sulfate in coarse (1–10 μm) and fine (0.05–1 μm) aerosols using sulfur isotopes (δ34S). In both collectors, sea‐salt sulfate (SO42−SS) mainly existed in coarse aerosols and nonsea‐salt sulfate (SO42−NSS) dominated the sulfate in fine aerosols, although some summer SO42−NSS appeared in coarse particles due to aerosol coagulation. SO42−NSS in the marine aerosols was mainly (88–100%) from marine biogenic dimethylsulfide (DMS) emission, while the SO42−NSS in the ambient aerosols was a combination of DMS (73–79%) and SO2 emissions from shipping activities (~21–27%). The seasonal variations of SO42−NSS concentrations inferred from the δ34S values in both collectors were mainly controlled by the DMS flux.
Correlation Between Fracture Network Properties and Stress Variability in Geological Media
Authors: Lei Qinghua , Gao Ke
Published: March 2018

We quantitatively investigate the stress variability in fractured geological media under tectonic stresses. The fracture systems studied include synthetic fracture networks following power law length scaling and natural fracture patterns based on outcrop mapping. The stress field is derived from a finite‐discrete element model, and its variability is analyzed using a set of mathematical formulations that honor the tensorial nature of stress data. We show that local stress perturbation, quantified by the Euclidean distance of a local stress tensor to the mean stress tensor, has a positive, linear correlation with local fracture intensity, defined as the total fracture length per unit area within a local sampling window. We also evaluate the stress dispersion of the entire stress field using the effective variance, that is, a scalar‐valued measure of the overall stress variability. The results show that a well‐connected fracture system under a critically stressed state exhibits strong local and global stress variabilities.
53–43 Ma Deformation of Eastern Tibet Revealed by Three Stages of Tectonic Rotation in the Gongjue Basin
Authors: Zhang Yang , Huang Wentao , Huang Baochun , van Hinsbergen Douwe J. J. , Yang Tao , Dupont-Nivet Guillaume , Guo Zhaojie
Published: March 2018

The Gongjue basin from the eastern Qiangtang terrane is located in the transition region where the regional structural lineation curves from east‐west‐oriented in Tibet to north‐south‐oriented in Yunnan. In this study, we sampled the red beds in the basin from the lower Gongjue to upper Ranmugou formations for the first time covering the entire stratigraphic profile. The stratigraphic ages are bracketed within 53–43 Ma by new detrital zircon U‐Pb ages constraining the maximum deposition age to 52.5 ± 1.5 Ma. Rock magnetic and petrographic studies indicate that detrital magnetite and hematite are the magnetic carriers. Positive reversals and fold tests demonstrate that the characteristic remanent magnetization has a primary origin. The Gongjue and Ranmugou formations yield mean characteristic remanent magnetization directions of Ds/Is = 31.0°/21.3° and Ds/Is = 15.9°/22.0°, respectively. The magnetic inclination of these characteristic remanent magnetizations is significantly shallowed compared to the expected inclination for the locality. However, the elongation/inclination correction method does not provide a meaningful correction, likely because of syn‐depositional rotation. Rotations relative to the Eurasian apparent polar wander path occurred in three stages: Stage I, 33.3 ± 3.4° clockwise rotation during the deposition of the Gongjue and lower Ranmugou formations; Stage II, 26.9 ± 3.7° counterclockwise rotation during deposition of the lower and middle Ranmugou formation; and Stage III, 17.7 ± 3.3° clockwise rotation after 43 Ma. The complex rotation history recorded in the basin is possibly linked to sinistral shear along the Qiangtang block during India indentation into Asia and the early stage of the extrusion of the northwestern Indochina blocks away from eastern Tibet.
Heterogeneous N2O5 Uptake During Winter: Aircraft Measurements During the 2015 WINTER Campaign and Critical Evaluation of Current Parameterizations
Authors: McDuffie Erin E. , Fibiger Dorothy L. , Dubé William P. , Lopez‐Hilfiker Felipe , Lee Ben H. , Thornton Joel A. , Shah Viral , Jaeglé Lyatt , Guo Hongyu , Weber Rodney J. , Michael Reeves J. , Weinheimer Andrew J. , Schroder Jason C. , Campuzano‐Jost Pedro , Jimenez Jose L. , Dibb Jack E. , Veres Patrick , Ebben Carly , Sparks Tamara L. , Wooldridge Paul J. , Cohen Ronald C. , Hornbrook Rebecca S. , Apel Eric C. , Campos Teresa , Hall Samuel R. , Ullmann Kirk , Brown Steven S.
Published: March 2018

Nocturnal dinitrogen pentoxide (N2O5) heterogeneous chemistry impacts regional air quality and the distribution and lifetime of tropospheric oxidants. Formed from the oxidation of nitrogen oxides, N2O5 is heterogeneously lost to aerosol with a highly variable reaction probability, γ(N2O5), dependent on aerosol composition and ambient conditions. Reaction products include soluble nitrate (HNO3 or NO3−) and nitryl chloride (ClNO2). We report the first‐ever derivations of γ(N2O5) from ambient wintertime aircraft measurements in the critically important nocturnal residual boundary layer. Box modeling of the 2015 Wintertime INvestigation of Transport, Emissions, and Reactivity (WINTER) campaign over the eastern United States derived 2,876 individual γ(N2O5) values with a median value of 0.0143 and range of 2 × 10−5 to 0.1751. WINTER γ(N2O5) values exhibited the strongest correlation with aerosol water content, but weak correlations with other variables, such as aerosol nitrate and organics, suggesting a complex, nonlinear dependence on multiple factors, or an additional dependence on a nonobserved factor. This factor may be related to aerosol phase, morphology (i.e., core shell), or mixing state, none of which are commonly measured during aircraft field studies. Despite general agreement with previous laboratory observations, comparison of WINTER data with 14 literature parameterizations (used to predict γ(N2O5) in chemical transport models) confirms that none of the current methods reproduce the full range of γ(N2O5) values. Nine reproduce the WINTER median within a factor of 2. Presented here is the first field‐based, empirical parameterization of γ(N2O5), fit to WINTER data, based on the functional form of previous parameterizations.
Kinetic contribution to extracellular Na+/K+ selectivity in the Na+/K+ pump
Authors: Vleeskens Elizabeth , Clarke Ronald J.
Published: March 2018

The sodium potassium pump (Na+,K+‐ATPase) shows a high selectivity for K+ over Na+ binding from the extracellular medium. To understand the K+ selectivity in the presence of a high concentration of competing Na+ ions requires consideration of more than just ion binding affinities. Here, equilibrium‐based calculations of the extracellular occupation of the Na+,K+‐ATPase transport sites by Na+ and K+ are compared to fluxes through Na+ and K+ transport pathways. The results show that, under physiological conditions, there is a 332‐fold selectivity for pumping of K+ from the extracellular medium into the cytoplasm relative to Na+, whereas equilibrium calculations alone predict only a 7.5‐fold selectivity for K+. Thus, kinetic effects make a major contribution to the determination of extracellular K+ selectivity.
Bioinformatic screening for key miRNAs and genes associated with myocardial infarction
Authors: Wu Ke , Zhao Qiang , Li Zhengmei , Li Nannan , Xiao Qiang , Li Xiuchang , Zhao Quanming
Published: March 2018

Despite significant advances in understanding of the causes of and treatment of myocardial infarction (MI) in recent years, morbidity and mortality is still high. The aim of this study was to identify miRNAand genes potentially associated with MI.mRNAand miRNAexpression datasets were downloaded from the Gene Expression Omnibus database (http://www.ncbi.nlm.nih.gov/geo/). Interactions between miRNAand the expression and function of target genes were analyzed, and a protein–protein interaction network was constructed. The diagnostic value of identified miRNAand genes was assessed. Quantitative RT‐PCR was applied to validate the results of the bioinformatics analysis. MiR‐27a, miR‐31*, miR‐1291, miR‐139‐5p, miR‐204, miR‐375, and target genes includingCX3CR1,HSPA6,andTPM3had potential diagnostic value. The genesTFEB,IRS2,GRB2,FASLG,LIMS1,CX3CR1,HSPA6,TPM3,LAT2,CEBPD,AQP9,andMAPKAPK2were associated with recovery from MI. In conclusion, the identified miRNAand genes might be associated with the pathology of MI.
Tuning Electrical and Thermal Transport in AlGaN/GaN Heterostructures via Buffer Layer Engineering
Authors: Yalamarthy Ananth Saran , So Hongyun , Muñoz Rojo Miguel , Suria Ateeq J. , Xu Xiaoqing , Pop Eric , Senesky Debbie G.
Published: March 2018

Progress in wide bandgap, III–V material systems based on gallium nitride (GaN) has enabled the realization of high‐power and high‐frequency electronics. Since the highly conductive, 2D electron gas (2DEG) at the aluminum gallium nitride (AlGaN)/GaN interface is based on built‐in polarization fields and is confined to nanoscale thicknesses, its charge carriers exhibit much higher mobilities compared to their doped counterparts. This study shows that such 2DEGs also offer the unique ability to manipulate electrical transport separately from thermal transport, through the examination of fully suspended AlGaN/GaN diaphragms of varied GaN buffer layer thickness. Notably, ≈100 nm thin GaN layers can considerably impede heat flow without electrical transport degradation. These achieve 4× improvement in the thermoelectric figure of merit (zT) over externally doped GaN, with state‐of‐the‐art power factors of 4–7 mW m‐1 K‐2. The remarkable tuning behavior and thermoelectric enhancement, elucidated here for the first time in a polarization‐based heterostructure, are achieved because electrons are at the heterostructured interface, while phonons are within the material system. These results highlight the potential for using 2DEGs in III–V materials for on‐chip thermal sensing and energy harvesting.
Development of Graphene Oxide/Polyaniline Inks for High Performance Flexible Microsupercapacitors via Extrusion Printing
Authors: Liu Yuqing , Zhang Binbin , Xu Qun , Hou Yuyang , Seyedin Shayan , Qin Si , Wallace Gordon G. , Beirne Stephen , Razal Joselito M. , Chen Jun
Published: March 2018

Extrusion printing of interdigitated electrodes for flexible microsupercapacitors (fMSCs) offers an attractive route to the fabrication of flexible devices where cost, scalability, and processability of ink formulations are critical. In this work, highly concentrated, viscous, and water‐dispersible inks are developed based on graphene oxide (GO)/polyaniline (PANi) composite for extrusion printing. The optimized GO/PANi‐based all‐solid‐state symmetric fMSCs obtained by extrusion printing interdigitated microelectrodes can deliver outstanding areal capacitance of 153.6 mF cm−2 and volumetric capacitance of 19.2 F cm−3 at 5 mV s−1. It is shown that by fabricating asymmetric fMSCs using the GO/PANi as positive electrode and a graphene‐based negative electrode, the voltage window can be widened from 0.8 to 1.2 V and improvements can be achieved in energy density (from 3.36 to 4.83 mWh cm−3), power density (from 9.82 to 25.3 W cm−3), and cycling stability (from 75% to 100% capacitance retention over 5000 cycles) compared with the symmetric counterpart. The simple ink preparation and facile device fabrication protocols reported here make the scalable fabrication of extrusion printed fMSCs a promising technology.
Quasi‐Stable Electroless Ni–P Deposition: A Pivotal Strategy to Create Flexible Li–S Pouch Batteries with Bench Mark Cycle Stability and Specific Capacity
Authors: Gou Jian , Zhang Hongzhang , Yang Xiaofei , Chen Yuqing , Yu Ying , Li Xianfeng , Zhang Huamin
Published: March 2018

Development of flexible Li–S batteries brings along the flourishing prospective for energy‐hungry wearable devices. However, it is still seriously restricted due to lack of facile methods to solve its inherent problems and flexible device‐related current collection issues. Herein, quasi‐stable electroless deposition method is firstly proposed to solve these problems by fabricating 3D tunable Ni–P networks in the C/S free‐standing electrode. The ultrathin Ni–P layers which are highly conductive and strongly adhesive with electrode substrates improve the electronic conductivity by two orders of magnitude and rise initial specific capacity from 1200 to 1600 mAh g−1. The harmful shuttle effect of polysulfide is also effectively alleviated due to the chemical adsorption and physical sieving properties of the 3D networks. The flexible pouch Li–S batteries assembled with commercially applicable structure also show high flexibility and as high as 1420 mAh g−1 output capacity at 0.1C in cycling test. This method can definitely be extended to other flexible devices such as Li‐ion batteries, Li–O2 batteries, and supercapacitors.
Self‐Limited Epitaxial Growth of Ultrathin Nonlayered CdS Flakes for High‐Performance Photodetectors
Authors: Jin Bao , Huang Pu , Zhang Qi , Zhou Xing , Zhang Xiuwen , Li Liang , Su Jianwei , Li Huiqiao , Zhai Tianyou
Published: March 2018

2D nonlayered materials that possess appealing properties are entering the researchers' vision. However, direct access to the 2D level of these materials is still a great challenge due to the instrinsic isotropic chemical bond. This work presents the initially self‐limited epitaxial growth of ultrathin nonlayered CdS flakes (as thin as 6 nm) on mica substrate with a large domain size (>40 µm) by employing In2S3 as the passivation agent. Besides, the thickness and sizes of the products could be tunable by the addition level of In2S3 amount. The growth mechanism is evidenced via experiments and theoretical calculations, which is attributed to the surface distortion effect of In–S motif and the preference of local environments for In on the CdS (0001) surface. The photodetector designed on CdS flake demonstrates a high photoswitching ratio (up to 103), a high detectivity (D* ≈ 2.71 × 109 Jones), and fast photoresponse speed (τR = 14 ms, τD = 8 ms). The as‐proposed self‐limited epitaxial growth method opens a new avenue to synthetize 2D nonlayered materials and will promote their further applications in novel optoelectronic devices.
Microwave Combustion for Rapidly Synthesizing Pore‐Size‐Controllable Porous Graphene
Authors: Wan Jun , Huang Liang , Wu Jiabin , Xiong Liukang , Hu Zhimi , Yu Huimin , Li Tianqi , Zhou Jun
Published: March 2018

Porous graphene has been widely applied in energy storage, electrocatalysis, photoelectron devices, etc. However, the producing process for porous graphene usually needs long time and is a tedious step. In this work, porous graphene is prepared with controllable pore size by using active metal nanoparticles to catalytically oxidize carbon under microwave combustion process within tens of seconds. The ion exchange membrane based on porous graphene with ≈5 nm pore diameter exhibits a great performance for salinity gradient power generation application with a power density output of ≈1.15 W m−2. This work highlights a new strategy for the design and synthesis of pore‐size‐controllable porous graphene and provides new opportunities for 2D porous nanomaterials.
Remarkable Acid Stability of Polypyrrole‐MoS4: A Highly Selective and Efficient Scavenger of Heavy Metals Over a Wide pH Range
Authors: Xie Linxia , Yu Zihuan , Islam Saiful M. , Shi Keren , Cheng Yahan , Yuan Mengwei , Zhao Jing , Sun Genban , Li Huifeng , Ma Shulan , Kanatzidis Mercouri G.
Published: March 2018

The new material polypyrrole/MoS42−(MoS4‐Ppy), prepared by ion‐exchange of NO3‐ of NO3‐Ppy with MoS42−, displays high acid stability and excellent uptake for heavy metal ions such as Hg2+, Ag+, Cu2+, and Pb2+. The different maximum adsorption capacities (qm) for Cu2+, Pb2+, Hg2+, and Ag+ depend on the various binding modes arising from the different thiophilicity of these metal ions. The removals of Ag+ and Pb2+ reach >99.6% within 5 min, and for highly toxic Hg2+, >98% removal achieves at 1 min. At strong acid limit, the exceptional qm(Ag+) of 725 mg g−1 places the MoS4‐Ppy at the top of materials for such removal. Uptake kinetics of Ag+, Hg2+, and Pb2+ is extremely fast: >99.9% removal rates at wide pH range (0.5–6) within 1–5 min. Also, at strongly acidic conditions (pH ≈ 1), for highly toxic Hg2+, <2 ppb concentration can be achieved, accepted as safe limit. The MoS4‐Ppy demonstrates an outstanding ability to separate low‐concentrated Ag+ from high concentrated Cu2+ especially under strong acidic conditions (pH ≈ 1), showing a large separation factor SFAg/Cu (KdAg/KdCu) of 105 (>100). MoS4‐Ppy is a superior and novel sorbent material for water remediation applications as well as precious metals recovery.
Substitutional Carbon‐Modified Anatase TiO2 Decahedral Plates Directly Derived from Titanium Oxalate Crystals via Topotactic Transition
Authors: Niu Ping , Wu Tingting , Wen Lei , Tan Jun , Yang Yongqiang , Zheng Shijian , Liang Yan , Li Feng , Irvine John T. S. , Liu Gang , Ma Xiuliang , Cheng Hui‐Ming
Published: March 2018

Changing the composition and/or structure of some metal oxides at the atomic level can significantly improve their performance in different applications. Although many strategies have been developed, the introduction of heteroatoms, particularly anions to the internal part of metal oxide particles, is still not adequate. Here, an effective strategy is demonstrated for directly preparing polycrystalline decahedral plates of substitutional carbon‐doped anatase TiO2 from titanium (IV) oxalate by a thermally induced topotactic transition in an inert atmosphere. Because of the carbon concentration gradient introduced in side of the plates, the carbon‐doped TiO2 (TiO2–xCx) shows an increased visible light absorption and a two orders of magnitude higher electrical conductivity than pure TiO2. Consequently, it can be used as a photocatalyst and an active material for lithium storage and shows much superior activity in generating hydroxyl radicals under visible light and greatly increased electrical‐specific capacity at high charge–discharge rates. The strategy developed could also be applicable to the atomic‐scale modification of other metal oxides.
Kirigami‐Inspired Nanoconfined Polymer Conducting Nanosheets with 2000% Stretchability
Authors: Guan Ying‐Shi , Zhang Zhuolei , Tang Yichao , Yin Jie , Ren Shenqiang
Published: March 2018

Stretchable conductors are essential components of wearable electronics. However, such materials typically sacrifice their electronic conductivity to achieve mechanical stretchability and elasticity. Here, the nanoconfinement and air/water interfacial assembly is explored to grow freestanding mechanical endurance conducting polymer nanosheets that can be stretched up to 2000% with simultaneously high electrical conductivity, inspired by kirigami. Such stretchable conductors show remarkable electronic and mechanical reversibility and reproducibility under more than 1000 cycle durability tests with 2000% deformability, which can be accurately predicted using finite element modeling. The conductivity of nanoconfined freestanding conductor nanosheets increases by three orders of magnitude from 2.2 × 10−3 to 4.002 S cm−1 is shown, due to the charge‐transfer complex formation between polymer chain and halogen, while the electrical conductance of the stretchable kirigami nanosheets can be maintained over the entire strain regime. The nanoconfined polymer nanosheets can also act as a sensor capable of sensing the pressure with high durability and real‐time monitoring.
Stimuli‐Driven Control of the Helical Axis of Self‐Organized Soft Helical Superstructures
Authors: Bisoyi Hari Krishna , Bunning Timothy J. , Li Quan
Published: March 2018

Supramolecular and macromolecular functional helical superstructures are ubiquitous in nature and display an impressive catalog of intriguing and elegant properties and performances. In materials science, self‐organized soft helical superstructures, i.e., cholesteric liquid crystals (CLCs), serve as model systems toward the understanding of morphology‐ and orientation‐dependent properties of supramolecular dynamic helical architectures and their potential for technological applications. Moreover, most of the fascinating device applications of CLCs are primarily determined by different orientations of the helical axis. Here, the control of the helical axis orientation of CLCs and its dynamic switching in two and three dimensions using different external stimuli are summarized. Electric‐field‐, magnetic‐field‐, and light‐irradiation‐driven orientation control and reorientation of the helical axis of CLCs are described and highlighted. Different techniques and strategies developed to achieve a uniform lying helix structure are explored. Helical axis control in recently developed heliconical cholesteric systems is examined. The control of the helical axis orientation in spherical geometries such as microdroplets and microshells fabricated from these enticing photonic fluids is also explored. Future challenges and opportunities in this exciting area involving anisotropic chiral liquids are then discussed.