bluuebunny/crossref_metadata_2025 huggingface dataset:
Maternal kidney function during pregnancy: systematic review and meta‐analysis
Authors: Lopes van Balen V. A. , van Gansewinkel T. A. G. , de Haas S. , Spaan J. J. , Ghossein‐Doha C. , van Kuijk S. M. J. , van Drongelen J. , Cornelis T. , Spaanderman M. E. A.
Published: October 2018

Objectives

To review systematically current literature on kidney function changes during pregnancy, in order to estimate the extent of adaptation over the course of both healthy physiological and complicated singleton pregnancies, and to determine healthy pregnancy reference values.

Methods

PubMed (NCBI) and EMBASE (Ovid) electronic databases were searched, from inception to July 2017, for studies on kidney function during uncomplicated and complicated pregnancies. Included studies were required to report a non‐pregnant reference value of kidney function (either in a non‐pregnant control group or as a prepregnancy or postpartum measurement) and a pregnancy measurement at a predetermined and reported gestational age. Kidney function measures assessed were glomerular filtration rate (GFR) measured by inulin clearance, GFR measured by creatinine clearance and serum creatinine level. Pooled mean differences between pregnancy measurements and reference values were calculated for predefined intervals of gestational age in uncomplicated and complicated pregnancies using a random‐effects model described by DerSimonian and Laird.

Results

Twenty‐nine studies met the inclusion criteria and were included in the analysis. As early as the first trimester, GFR was increased by up to 40–50% in physiological pregnancy when compared with non‐pregnant values. Inulin clearance in uncomplicated pregnancy was highest at 36–41 weeks, with a 55.6% (53.7; 95% CI, 44.7–62.6 mL/min) increase when compared with non‐pregnant values, and creatinine clearance was highest at 15–21 weeks' gestation, with a 37.6% (36.6; 95% CI, 26.2–46.9 mL/min) increase. Decrease in serum creatinine level in uncomplicated pregnancy was most prominent at 15–21 weeks, with a 23.2% (−0.19; 95% CI, −0.23 to −0.15 mg/dL) decrease when compared with non‐pregnant values. Eight studies reported on pregnancies complicated by a hypertensive disorder. Meta‐regression analysis showed a significant difference in all kidney function parameters when comparing uncomplicated and hypertensive complicated pregnancies.

Conclusions

In healthy pregnancy, GFR is increased as early as the first trimester, as compared with non‐pregnant values, and the kidneys continue to function at a higher rate throughout gestation. In contrast, kidney function is decreased in hypertensive pregnancy. © 2018 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of the International Society of Ultrasound in Obstetrics and Gynecology.
Stratigraphy and Sedimentology of Middle Jurassic Sequence of Chorar Island, Patan District, Kachchh Basin, Gujarat
Authors: Patel Satish J. , Darngawn Jehova L. , Joseph Jaquilin K. , Shitole Apurva D.
Published: October 2018

Chorar Island exposes ∼109 m thick middle Jurassic (Bathonian-Callovian) succession in the eastern most part of the Kachchh Basin, Patan District, Gujarat and is divided into two, Khadir and Gadhada formations. It mainly comprises of mixed siliciclastic-carbonate sediments and limestones; the shales dominate the lower part of the succession while the top of the succession is marked by ferruginous sandstone which also forms the vast, prominent peripheral zone of the Chorar dome. The field and laboratory analysis of the succession reveals nine lithofacies which includes ferruginous sandstone, cross bedded white sandstone, micritic sandstone, allochemic sandstone, sandy micrite, mudstone, sandy allochemic limestone, coralline limestone and shale. The mix siliciclastic-carbonate sediments and ferruginous facies are fossiliferous in nature and display sedimentary structures, like ripple marks, cross- and planar-lamination with biogenic sedimentary structures. Coralline limestone facies comprise of large size (>1m diameter) corals, which are diagenetically modified severely and have lost its original internal structures. The sediment characteristics and associated bioclasts indicates low to moderate wave and current energy in shoreface-offshore subsequently changing to wave dominated shoreface during the deposition of the middle Jurassic sediments of the Chorar Island.
A Preliminary Evaluation on the Prospects of Hydrocarbon Potential in the Carbonaceous Shales of Spiti and Chikkim Formations, Tethys Himalaya, India
Authors: Pandey Bindhyachal , Pathak Deo Brat , Mathur Neeraj , Jaitly Anand K. , Singh Alok K. , Singh Prakash K.
Published: October 2018

In the present investigation, an attempt has been made to explore the possibility of hydrocarbon prospects in the carbonaceous shale deposits of Spiti and Chikkim formations exposed in the Spiti valley of the Tethys Himalaya. Twenty samples, collected from successive levels of these litho-units, have been subjected to maceral analysis, Rock-Eval Pyrolysis and six samples to Fourier Transform Infra-red Spectroscopy (FTIR) and nuclear magnetic resonance (NMR) analyses. The study reveals the presence of mainly kerogen-III type of organic matter but some of the shale samples have shown a good amount of total organic carbon (TOC) to the tune of 3.19% which is sufficient to produce hydrocarbon. The results indicate the presence of methane occurring as free and fixed hydrocarbon in the shale samples. Few levels are especially rich in hydrocarbon. They have shown encouraging results with potential for generating liquid as well as lighter hydrocarbon. The data is also supported by the FTIR and NMR studies.
Morphological Dynamics of the Rivers of Brahmaputra
Authors: Sah Rajesh Kumar , Das Apurba Kumar
Published: October 2018

This study documents the sequential morphological dynamics of rivers of Brahmaputra. Landsat images for the year of 1976 and 1987-2016 (thirty consecutive years) are used in GIS environment to document the activities that have been shaping and reshaping the morphology of the rivers. The use of thirty year consecutive images facilitates an explicit assessment of morphological changes. Apparently, distributary activities, meandering activities, breaches and avulsions, and confluence migrations are the dominant geomorphic agents of morphological changes. A range of distributaries activities are readily noticed in Brahmaputra plain. The plain is densely dissected with numerous rivers and rivulets, and distributaries activities often lead to reorganization in channel network. Considering the frequency of incidence and preserved imprints of abandoned channels, majority of the rivers of Brahmaputra can be categorized as free meanders. Difference in fluvio-geomophic setups of rivers of both the banks is reflected palpably in meandering activities. The upper stretch of Brahmaputra encompassing the rivers Simen, Gai and Jiadhal is found to be the most active in terms of avulsions. High seasonal flow, large sedimentation and absence of distinct river bed in some stretches are presumably leading to these frequent avulsions. The river Simen, further, exhibited repeated confluence migration through avulsion near its confluence with Brahmaputra. The explicit picture of the morphological dynamics of rivers of Brahmaputra at basin scale presented in this work is a key aid in formulating riverine management programs which is conceivably among the most water-troubled region of the country.
Fractures Effect in Reservoir Quality of Ilam and Sarvak Formations in Hengam Oilfield Using Imaging Logs
Authors: Ebadati Naser
Published: October 2018

In this study, an attempt has been made through the data of one of exploratory wells as well as using petrophysical and FMI visual logs, the lithology, structures and failures of the field is investigated. For petro physical analysis of the area, after initial field investigation and controlling the drilled units, final approximation of the lithology of the area was made. Afterwards the raw data of well was used for the evaluation of petrophysical parameters by Geolog software. In the next step the effect of fractures on the oil production and their comparison with the initial porosity was analyzed. The results showed that the points with highest production and exploitation of the oil exists, have the greatest expansion of fractures. Comparison of the obtained results with the lithology specifications of other wells of the field shows that in zones with secondary fractures relative to the porosity the reservoir quality has been more appropriate and outputs the highest production and in comparison, the wells No.3, 4 and 5 in spite of having zones of higher porosity than the well number 2 of the lower reservoir quality.
Comparison of Varying Corticosteroid Type, Dose, and Volume for the Treatment of Pain in Small‐ and Intermediate‐Size Joint Injections: A Narrative Review
Authors: Cushman Daniel M. , Ofek Erika , Syed Raafay H. , Clements Nathan , Gardner James E. , Sams Jessica M. , Mulvey Jade L. , McCormick Zachary L.
Published: October 2018

Objective

To systematically evaluate the scientific literature examining the effect of corticosteroid type, dose, and volume of small‐ and intermediate‐size joint injections on pain and function.

Type

Narrative review.

Literature Survey

Medline (PubMed), Cochrane Central Register of Controlled Trial, and SportDiscus databases were searched.

Methodology

Inclusion criteria included prospective studies evaluating pain‐ and/or function‐related improvements following a corticosteroid injection of a small‐ or intermediate‐size joint.

Synthesis

A total of 28 articles were included, all studying patients with osteoarthritis and/or rheumatoid arthritis. Eleven studies were randomized‐controlled trials comparing corticosteroid injections to a control treatment and three were randomized trials comparing corticosteroid dose or type; the rest were prospective case series without a control. Most studies used 10 to 20 mg of methylprednisolone or triamcinolone for small joints and 20 to 40 mg for intermediate joints; wrist joints were the only joint studied that directly compared doses—20 mg was noninferior to 40 mg. Triamcinolone hexacetonide was found to be superior to methylprednisolone in the interphalangeal finger joints in a single randomized‐controlled trial; no other studies compared steroid types in any joint. No studies evaluated the effect of volume on clinical outcomes.

Conclusions

Very few studies directly examine the effect of corticosteroid type, corticosteroid dose, or injectate volume on clinical outcomes for small‐ or intermediate‐size joint arthralgia. Future studies are needed to better elucidate the most effective treatment protocols.

Level of Evidence

IV.
Wake Potential and Wake Effects on the Ionospheric Plasma Density Measurements With Sounding Rockets
Authors: Paulsson J. J. P. , Spicher A. , Clausen L. B. N. , Moen J. I. , Miloch W. J.
Published: October 2018

A new method is developed to systematically study variations in the electrostatic potential around a spinning spacecraft in flowing plasma. We argue that the main modulation of this potential is due to wake leading to different depletions in electron and ion densities. This wake potential can be calculated with the help of electric currents measured by Langmuir probes mounted on a boom system and the assumption of Boltzmann‐distributed electrons. The wake position is determined with the electric field measurements. We apply this method to data from the Investigation of Cusp Irregularities 3 ionospheric sounding rocket and find the observed wake to be larger than expected from the flow velocity and the Mach cone formation, which can be explained by the presence of booms. By using the wake potential to filter the rocket data, we show that this method is robust during highly dynamic plasma conditions and that it can be used to improve the quality of plasma density measurements and reduce the wake effects.
Crustal Magmatism and Deformation Fabrics in Northeast Japan Revealed by Ambient Noise Tomography
Authors: Chen Kai‐Xun , Gung Yuancheng , Kuo Ban‐Yuan , Huang Tzu‐Ying
Published: October 2018

Mapping both isotropic and anisotropic velocity structures of the crust provides insight into the dominant mechanisms that produce the deformation. We performed ambient noise tomography for shear velocity Vs in the Tohoku region, Japan, where plate kinematics remains simple as the Pacific plate is subducting under the Okhotsk plate. Cross‐correlation functions were retrieved from Hi‐net recordings and phase velocities of 3–16 s were measured, followed by a one‐step, wavelet‐based multiscale inversion for both Vs and its azimuthal anisotropy. The isotropic model shows that high Vs anomalies underlie the Cretaceous aged Kitakami and Abukuma Mountains from shallow crust to lower crust. Low Vs is found to track the active volcanoes with the strongest anomalies concentrated at roughly 10 km depth, which we interpret as the shallow magma reservoirs of the Quaternary magmatic system. The resolved azimuthal anisotropy exhibits a switch of anisotropy in the upper crust from island‐parallel to a random or suppressed state in 5–15 km depth interval and back to island‐parallel. The island‐parallel fast direction may map the structural fabrics of the crustal deformation, and the spatial correlation between velocity and anisotropy patterns suggests that continuous volcanic activities and magma ponding disrupt the otherwise consistent fabrics in the upper crust. Below 20 km depth, the anisotropy turns to convergence‐parallel, which may result from shearing either imposed by the return flow in the mantle wedge or frozen‐in from the last stage of extension of the continental margin that opened the Sea of Japan.
Regional Short‐Term Forecasting of Ionospheric TEC and Scintillation
Authors: Grzesiak Marcin , Cesaroni Claudio , Spogli Luca , De Franceschi Giorgiana , Romano Vincenzo
Published: October 2018

We describe a novel empirical technique for the regional, short‐term (from seconds to minutes) forecasting of both TEC (total electron content) and scintillation indices on Global Navigation Satellite System signals. To provide TEC‐forecasted values, the method exploits the continuity equation in the conservative form, while the continuity equation with source term added is used in the case of scintillation forecasting. The performance of the model is investigated, resulting to be satisfactory when applied at equatorial latitudes in Brazil and during postsunset hours, when scintillation phenomena are more likely to occur. Five days affected by strong amplitude scintillation events (S4 > 0.7) are used to test the model performance and evaluate the model accuracy. In addition, the performance of the amplitude scintillation forecasting is evaluated by leveraging on larger statistics. On the average, the forecasting accuracy, in terms of standard deviation of the distributions of the differences between forecasted and actual values, is about 5% for TEC and 15–20% for scintillation parameters.
Rejection Doesn't Have to Hurt: AGU's Manuscript Referral System
Authors: Wooden Paige
Published: October 2018

What has been the response of editors and authors to the option of transferring manuscripts from one AGU journal to another?
Congress Throws Tropical Forest Research Program a Lifeline
Authors: Popkin Gabriel
Published: October 2018

Climate researchers and ecologists laud the continuation of effort to fuse data from tropical forests with modeling.
Complexity of Marine CO2 System Highlighted by Seasonal Asymmetries
Authors: Woosley Ryan J.
Published: October 2018

The complexities of the marine carbon cycle continue to be uncovered. In this issue, Fassbender et al. (2018, https://doi.org/10.1029/2017GB005855) combined measured surface ocean partial pressure of carbon dioxide (pCO2) with model predictions of increases in dissolved inorganic carbon to explore seasonal pCO2 changes. They find that when seasonal cycles of other variables (temperature, salinity, total alkalinity, and dissolved inorganic carbon) are maintained to climatological means, seasonal amplitudes of pCO2 are affected asymmetrically. Thus, even ignoring other natural or climate change factors, the assumption that the seasonal cycle of pCO2 will be preserved may not be valid. Fassbender et al. (2018) intentionally ignore the influence of other variables such as a global warming signal in order to hone in explicitly on carbon system dynamics. The results show that when studying CO2 fluxes, especially into the future, the full seasonal cycle must be investigated, as what happens at one time of year may not translate to the rest of the year. Practically, this means that in order to fully understand the marine carbon cycle and its control over atmospheric CO2 levels, there is an urgent need for more surface pCO2 data covering more months of the year particularly in the polar oceans that are highly seasonally biased.
Submarine Deep‐Water Lava Flows at the Base of the Western Galápagos Platform
Authors: Anderson Molly , Wanless V. Dorsey , Schwartz Darin M. , McCully Emma , Fornari Daniel J. , Jones Max P. , Soule S. Adam
Published: October 2018

To investigate the initial phases of magmatism at the leading edge of the upwelling mantle plume, we mapped, photographed, and collected samples from two long, deep‐water lava flows located at the western base of the Galápagos Platform using the remotely operated vehicle Hercules. Lavas were recovered from four areas on the seafloor west of Fernandina volcano, including the western flow fronts of two deep‐water flows, heavily sedimented terrain between the two flows, and the eastern, shallower end of one flow. The sediment cover and morphologies are distinct between the western flow fronts and the eastern region based on seafloor imagery, suggesting that the long lava flows are not a single eruptive unit. Major and trace element concentrations reveal both tholeiitic and alkalic compositions and support the interpretation that multiple eruptive units comprise the deep‐water flows. Alkalic lavas have higher [La/Sm]N ratios (2.05–2.12) and total alkali contents (5.18–5.40) compared to tholeiitic lavas, which have [La/Sm]N ratios ranging from 1.64 to 1.68 and total alkali contents ranging from 3.07 to 4.08 wt%. Radiogenic isotope ratios are relatively homogeneous, suggesting a similar mantle source. We use petrologic models to assess three alternative mechanisms for the formation of the alkalic magmas: (1) high‐pressure crystallization of clinopyroxene, (2) mixing of high silica and mafic magmas, and (3) variable extents of melting of the same mantle source. Our modeling indicates that the alkalic samples form from lower extents of melting compared to the tholeiitic lavas and suggests that the deep‐water alkalic lavas are analogous to the initial, preshield building phase observed south of Hawaii and at the base of Loihi Seamount.
Saturn's Innermost Radiation Belt Throughout and Inward of the D‐Ring
Authors: Kollmann P. , Roussos E. , Kotova A. , Regoli L. , Mitchell D. G. , Carbary J. , Clark G. , Krupp N. , Paranicas C.
Published: October 2018

Cassini discovered Saturn's innermost radiation belt during the end of its mission. The belt is populated with relativistic protons, probably up to the trapping limit of ≈20 GeV. It extends from Saturn's dense atmosphere into and throughout the D‐ring. The A–C rings separate this belt entirely from the previously known radiation belts, suggesting that the innermost radiation belt is populated entirely via cosmic ray albedo neutron decay. We find that the proton pitch angle distributions are consistent with being shaped by losses to the D‐ring and the upper atmosphere rather than, for example, wave‐particle interactions. This supports that the main loss process of this new radiation belt is energy loss in neutral material, different from Saturn's other radiation belts. This property constrains the overall scale height of Saturn's exosphere to <700 km and the average D‐ring water molecule column density to being about 1 order of magnitude below the Enceladus gas torus.
Ring Shadowing Effects on Saturn's Ionosphere: Implications for Ring Opacity and Plasma Transport
Authors: Hadid L. Z. , Morooka M. W. , Wahlund J.‐E. , Moore L. , Cravens T. E. , Hedman M. M. , Edberg N. J. T. , Vigren E. , Waite J. H. , Perryman R. , Kurth W. S. , Farrell W. M. , Eriksson A. I.
Published: October 2018

We present new results obtained by the Radio and Plasma Wave Science Langmuir probe on board Cassini during the Grand Finale. The total direct current sampled by the Langmuir probe at negative bias voltage is used to study the effect of the ring shadows on the structure of the Kronian topside ionosphere. The D and C rings and the Cassini Division are confirmed to be optically thin to extreme ultraviolet solar radiation. However, different responses from the opaque A and B rings are observed. The edges of the A ring shadow are shown to match the A ring boundaries, unlike the B ring, which indicates variable responses to the B ring shadow. We show that the variable responses are due to the ionospheric plasma, more precisely to the longer chemical lifetime of H+ compared to
and
, suggesting that the plasma is transported from the sunlit region to the shadowed one in the ionosphere.
Warm Arctic, Increased Winter Sea Ice Growth?
Authors: Petty Alek A. , Holland Marika M. , Bailey David A. , Kurtz Nathan T.
Published: October 2018

We explore current variability and future projections of winter Arctic sea ice thickness and growth using data from climate models and satellite observations. Winter ice thickness in the Community Earth System Model's Large Ensemble compares well against thickness estimates from the Pan‐Arctic Ice Ocean Modeling and Assimilation System and CryoSat‐2, despite some significant regional differences—for example, a high thickness bias in Community Earth System Model's Large Ensemble in the western Arctic. Differences across the available CryoSat‐2 thickness products hinder more robust validation efforts. We assess the importance of the negative conductive feedback of sea ice growth (thinner ice grows faster) by regressing October atmosphere/ice/ocean conditions against winter ice growth. Our regressions demonstrate the importance of a strong negative conductive feedback process in our current climate, which increases winter growth for thinner initial ice, but indicate that later in the 21st century this negative feedback is overwhelmed by variations in the fall atmosphere/ocean state.
The Heat of the Flow: Thermal Equilibrium in Gravitational Mass Flows
Authors: Fischer Jan‐Thomas , Kaitna Roland , Heil Kilian , Reiweger Ingrid
Published: October 2018

Flow behavior and mobility of gravitational mass flows such as rapid‐moving landslides, ice‐rock avalanches, or snow avalanches strongly depend on the material temperature. Flow temperature dependence is particularly pronounced for materials with high homologous temperatures, such as snow or ice under natural conditions. The interplay between mechanisms driving the temperature evolution in flowing geomaterials remain largely unknown. Here we present laboratory experiments in a rotating drum, measuring the temperature evolution of steadily flowing snow at ambient temperatures below freezing. After initial heating the flow reaches thermal equilibrium. To describe the thermal energy balance, we derive an analytical model, taking into account frictional energy dissipation and heat exchange with the ambient medium. The model accurately captures the measured temperature evolution and predicts the observed thermal equilibrium, where ambient cooling compensates frictional heating. It allows to determine heat transfer coefficients and total shear stresses of the flowing material based on measured temperatures.
The Equilibrium Climate Response to Sulfur Dioxide and Carbonaceous Aerosol Emissions From East and Southeast Asia
Authors: Grandey Benjamin S. , Yeo Lik Khian , Lee Hsiang‐He , Wang Chien
Published: October 2018

We investigate the equilibrium climate response to East and Southeast Asian emissions of carbonaceous aerosols and sulfur dioxide, a precursor of sulfate aerosol. Using the Community Earth System Model with the Community Atmosphere Model version 5.3, we find that anthropogenic aerosol emissions from East and Southeast Asia exert a global mean net radiative effect of −0.49 ± 0.04 W/m2. Approximately half of this cooling effect can be attributed to anthropogenic sulfur dioxide emissions. The aerosol emissions drive widespread cooling across the Northern Hemisphere. Strong suppression of precipitation occurs over East and Southeast Asia, indicating that anthropogenic aerosol emissions may impact water resources locally. However, in contrast to previous research, we find no clear evidence of remote effects on precipitation over Australia and West Africa. We recommend further investigation of possible remote effects.
Assessing Quasi‐Periodicities in Jovian X‐Ray Emissions: Techniques and Heritage Survey
Authors: Jackman C. M. , Knigge C. , Altamirano D. , Gladstone R. , Dunn W. , Elsner R. , Kraft R. , Branduardi‐Raymont G. , Ford P.
Published: October 2018

Jupiter's auroral X‐rays are rather mysterious, with an unknown driver, and several previous reports of individual cases of quasi‐periodic emission. In this work we revisit heritage X‐ray data sets from the 1990s to 2015 and apply robust significance testing of emerging quasi‐periodicities, seeking to understand the robustness and regularity of previously reported quasi‐periodic emissions. Our analysis incorporates the use of the Rayleigh test as an alternative to Lomb‐Scargle analysis or Fast Fourier Transforms, where Rayleigh is particularly suited to a time‐tagged data set of sparse counts such as is common for jovian X‐ray data. Furthermore, the analysis techniques that we present (including Rayleigh testing and Monte Carlo simulation) can be applied to any time‐tagged data set. The code to conduct such analysis is released as supplementary information to accompany this paper. The five most significant (p value <0.01) quasi‐periods from Jupiter's northern auroral region have periods ranging from ~8.0 to 45.96 min, and the two most significant (p value <0.01) quasi‐periods from the south have periods of ~14.1 and ~34.9 min. The selection of a restrictive hot spot source region seems to be critical for detecting quasi‐periodic emission, suggesting that the site of pulsations may be spatially localized. Periods vary from one Jupiter rotation to the next in one long observation, and the north and south are shown to pulse independently in another conjugate observation. These results have important implications for understanding the driver of jovian X‐ray emission.
Multiinstrument Studies of Thermospheric Weather Above Alaska
Authors: Conde M. G. , Bristow W. A. , Hampton D. L. , Elliott J.
Published: October 2018

We describe how space weather impacts thermospheric winds above Alaska, using an array of ground and space‐based instrumentation. Forcing of the thermosphere is observed using coherent (Super Dual Auroral Radar Network) and incoherent (Poker Flat Incoherent Scatter Radar) radars to measure ion convection, plus ground and space‐based imagers to map auroral precipitation. The primary emphasis in this work is to determine the neutral thermospheric wind response at F region heights to these drivers, using an array of ground‐based all‐sky imaging Fabry‐Perot spectrometers that record Doppler spectra of optical emissions at 630‐nm wavelength, originating from a height of around 240 km. Line‐of‐sight winds are derived from Doppler shifts and, because each instrument only directly measures this one component, considerable postprocessing must be applied to infer the full three‐component vector velocity field. Several techniques for doing so are identified, and a detailed description is presented of the hybrid algorithm used here. Results show that thermospheric winds at these latitudes respond strongly to magnetospheric drivers associated with the aurora over length scales down 100 km or less, and on time scales as short as 15 min. These scales are considerably smaller than those resolved by previous observations, or those captured in semiempirical models such as the Horizontal Wind Model or global‐scale first principle models such as the Thermospheric Global Circulation Model and its relatives. Divergence and vorticity commonly occur in the observed horizontal wind fields, over regions spanning hundred of kilometers across and with magnitudes exceeding 0.5 × 10−3 s−1.
Solar Dependence of Equatorial F Region Irregularities Observed by COSMIC Radio Occultations
Authors: Yu Tao , Miyoshi Yasunobu , Xia Chunliang , Zuo Xiaomin , Yan Xiangxiang , Yang Na , Sun Yangyi , Yue Xinan , Mao Tian
Published: October 2018

With an improved method for retrieving the equatorial F region irregularities (EFIs) from radio occultation measurements, a huge amount of S4 index profiles from Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) satellites is employed to study the solar cycle variation of global EFIs during the period of 2007 to 2017. This full solar cycle data show that impacts of the solar activity on the occurrence rates and heights of EFIs are notable and complex. The occurrence rates of EFIs at higher altitude (greater than 500 km) increase with increasing the solar activity. The mean heights (
) and heights standard deviation (σh) of EFIs at higher altitudes do not show clearly the solar activity dependence. On the other hand, the occurrence rates of EFIs at entire altitudes (from 150 to 800 km) do not have clear relation with the solar activity. The
and σh of EFIs at entire altitudes increase with increasing the solar activity. Moreover, the dependence of the occurrence rates of EFIs on the solar activity are the strongest in the equinoxes, weaker in winter and weakest in summer. The electric fields and corresponding seasonal variation can account for the EFIs occurrence and height variation versus solar activities, and the EFIs at low altitudes seem to be related to the seed associated with atmospheric gravity wave.
Muon Tomography Applied to a Dense Uranium Deposit at the McArthur River Mine
Authors: Schouten Douglas , Ledru Patrick
Published: October 2018

This article reports on the first application of muon tomography (a novel method for imaging density contrasts underground using cosmic rays) for imaging dense uranium deposits within the Athabasca Basin in Canada. We present a qualitative assessment of the radiographic imaging and 3‐D density inversion of a uranium deposit using muon tomography. The muon tomography survey summarized in this article was performed at the McArthur River mine. We demonstrate the validity of muon tomographic imaging with data acquired at a depth of about 600 m underground. The statistical significance of the uranium deposit signature in the muon data was larger than 5 standard deviations, and the corresponding 3‐D density inversion compared well with drill assay data from the deposit.
Fully Dynamic Spontaneous Rupture Due to Quasi‐Static Pore Pressure and Poroelastic Effects: An Implicit Nonlinear Computational Model of Fluid‐Induced Seismic Events
Authors: Jin Lei , Zoback Mark D.
Published: October 2018

Fluid perturbations play a pivotal role in triggering earthquakes. However, the role of fluid in the coseismic rupture process remains largely unknown. To this end, we develop a 2‐D fully dynamic spontaneous rupture model for fluid‐induced earthquakes. The effect of fluid in the preseismic quasi‐static regime is modeled as either pore pressure diffusion or fully coupled poroelasticity, using our Jin and Zoback (2017, https://doi.org/10.1002/2017JB014892) computational model. The two approaches lead to radically different predictions on the time of earthquake nucleation. Correspondingly, the evolved fluid pressure or poroelastic stress on the fault, together with the spatially altered density of the fluid‐saturated hosting rock, is passed to the dynamic regime. Under the assumption of an undrained coseismic fluid‐solid system, we discretize the fully dynamic Cauchy equation of motion subjected to an exact fault contact constraint using a split‐node finite element method in space and an implicit Newmark family finite difference method in time. Within each time step, a fully implicit Newton‐Raphson scheme is implemented iteratively for linearizing the fully discrete equations. Within each Newton iteration, a physics‐based and nonstationary preconditioner is designed to accelerate the convergence of the selected generalized minimal residual method iterative linear solver. The effect of fluid is highlighted throughout the discretization and computational procedures. Finally, by conducting a numerical experiment, we illustrate that a fully coupled poroelastic model can lead to significantly different predictions on coseismic rupture behaviors and wavefields compared to a decoupled model. Our computational model can also serve as one of the earliest full‐physics modeling tool for fluid‐induced earthquakes.
Ambient Noise Monitoring of Seismic Velocity Around the Longmenshan Fault Zone From 10 Years of Continuous Observation
Authors: Liu Zhikun , Huang Jinli , He Ping , Qi Juanjuan
Published: October 2018

We present 10‐year continuous seismic velocity changes from 2007 to 2017 around the Longmenshan fault zone, where the 2008Mw7.9 Wenchuan earthquake and the 2013Mw6.6 Lushan earthquake occurred. We collected continuous waveforms recorded by 20 broadband stations covering the entire Longmenshan fault zone and used three‐component ambient noise correlation techniques to measure the velocity changes in four different period bands. Our results show that a significant drop, 0.04–0.06%, occurred in the coseismic velocity at the time of the Wenchuan earthquake, near the rupture zone for the period bands of 1–3 and 3–8 s. In addition, only one fourth of the coseismic velocity drop has been recovered 9 years after the earthquake. We also observed a subtle velocity drop, 0.0066%, delayed by ~100 days relative to the time of the mainshock in the period bands of 6–15 s. In the source region of the Lushan earthquake, we detected a weak but reliable coseismic velocity change of ~0.01% in the period band of 1–3 s. The physical mechanism of the seismic velocity change could involve the damage in the shallow subsurface layer (<3 km), the damage in the fault zone at depth (~10 km), and the postseismic slip along the deep rupture zone up to ~20 km. The uncommonly slow postseismic velocity recovery indicates the slow healing of the Longmenshan fault zone after the Wenchuan earthquake, which may be associated with the low rate of stress loading onto the fault zone.
P Wave Anisotropic Tomography of the SE Tibetan Plateau: Evidence for the Crustal and Upper‐Mantle Deformations
Authors: Huang Zhouchuan , Wang Liangshu , Xu Mingjie , Zhao Dapeng
Published: October 2018

The upper crust in the SE Tibetan Plateau is rotating around the eastern Himalayan syntax clockwise, and the western margin of the Yangtze Craton has been involved in the active tectonics. However, it is still unclear whether and how the deep crust and upper mantle respond to the plateau expansion. In this study we present a high‐resolution three‐dimensional model of P wave velocity tomography and azimuthal anisotropy in the crust and uppermost mantle beneath the SE Tibetan Plateau determined using traveltime data recorded by a dense seismic network. Widespread low‐velocity zones are revealed around a high‐velocity body in the deep crust and uppermost mantle beneath the southwest Yangtze Craton, where fast‐velocity directions of the azimuthal anisotropy are mostly parallel to the contour lines of the surface topography and the Moho depth along the plateau margin. These results indicate that gravitational potential plays an important role in the crustal and uppermost‐mantle deformations in the SE Tibetan Plateau. Meanwhile, the shallow crust may drop down to the deep crust and drive the ductile deep‐crustal material to intrude into the adjacent regions. The extruded crust is trapped in a deep‐crustal corner and obstructed by the surrounding strong blocks. The trapped crustal material may rise up, causing significant uplift and high heat flow at the surface.
Constraints on Rift Basin Structure and Border Fault Growth in the Northern Malawi Rift From 3‐D Seismic Refraction Imaging
Authors: Accardo N. J. , Shillington D. J. , Gaherty J. B. , Scholz C. A. , Nyblade A. A. , Chindandali P. R. N. , Kamihanda G. , McCartney T. , Wood D. , Wambura Ferdinand R.
Published: October 2018

We present new constraints on rift basin structure in the northern Malawi Rift from a 3‐D compressional velocity model to investigate border fault geometry, accommodation zone structure, and the role of preexisting structures underpinning this rift system. The velocity model uses observations from the first wide‐angle refraction study conducted using lake‐bottom seismometers in one of the East African great lakes. The Malawi Rift is flanked by basin‐bounding border faults and crosses several significant remnant structures, making it an ideal location to investigate the development of normal faults and their associated basins. The 3‐D velocity model reveals up to ~5 km of synrift sediments, which smoothly transition from eastward thickening against the Livingstone Fault in the North Basin to westward thickening against the Usisya Fault in the Central Basin. Greater than 4 km of sediment are imaged within the accommodation zone pointing to the early development of the border faults. We use new constraints on synrift sediment thickness to construct displacement profiles for both faults. Both faults accommodate large throws (>7 km) consistent with their significant lengths. The dimensions of these faults are close to or larger than the maximum size predicted by models of fault growth. The presence of an intermediate velocity unit with velocities of 3.75–4.5 km/s is interpreted to represent sediment deposits beneath Lake Malawi from prior rifting in the Permo‐Triassic (Karoo) and/or Cretaceous‐Paleogene. The distribution of preexisting basins implied by these sediments may help account for changes in intrabasinal faulting and border fault development between the two basins.
Spectral Reflectance of Powder Coatings on Carbonaceous Chondrite Slabs: Implications for Asteroid Regolith Observations
Authors: Kiddell C. B. , Cloutis E. A. , Dagdick B. R. , Stromberg J. M. , Applin D. M. , Mann J. P.
Published: October 2018

Carbonaceous chondrite meteorites (CCs) are among the most primitive materials in the solar system and provide important insights into solar system history and evolution. A number of planetary spacecraft missions will visit asteroids that are thought to compositionally resemble these meteorites. To better assist sample acquisition in terms of how the physical properties of CCs affect their reflectance spectra, we investigated the spectral reflectance properties of solid and powdered CCs and powder coatings on slabs of a number of CCs, including CB, CH, CK, CM, CO, CR, and CV classes. We found that decreasing grain size leads to increasing reflectance across the ~500‐ to 2,500‐nm range and steeper spectral slope, regardless of CC type. Powdered CC reflectance spectra are brighter beyond ~500 nm and redder than bare roughened slabs. For powders sprinkled on slabs, as the powder coating gets thicker, spectral slopes get redder. Optically thick fine‐grained powders are brighter beyond ~500 nm and are as red or redder than slabs covered with airfall dust (for dust thicknesses up to a few hundred microns). Diagnostic absorption features of CC minerals, particularly those in the 1,000‐nm region attributable to Fe‐bearing silicates, are ubiquitous regardless of physical properties. Reflectance spectra of terrestrially weathered (i.e., rusty) CCs are strongly modified below ~700 nm and in the 900‐ and 1,900‐nm regions by these Fe oxyhydroxides. Their effects can be mitigated through chemical treatment, but this may also affect preterrestrial ferric iron‐bearing phases. Some spectral characteristics, such as hydrous and anhydrous silicate absorption bands in CC spectra, are present regardless of physical properties (fine‐grained dust, powders, slabs, and dust on slabs). Other spectral characteristics (such as albedo and spectral slope) vary as a function of physical properties, indicating that reflectance spectroscopy could be used to ascribe spectral variations across an asteroid's surface to either physical or compositional causes. This information can, in turn, be used to inform site selection for asteroid sample return missions, where both composition and physical properties are important drivers. When searching for fine‐grained areas on an asteroid to sample, the best indication would be the brightest‐ and reddest‐sloped spectra.
Characterizing the Radiative Effect of Rain Using a Global Ensemble of Cloud Resolving Simulations
Authors: Hill P. G. , Chiu J. C. , Allan R. P. , Chern J.‐D.
Published: October 2018

The effect of rain on radiative fluxes and heating rates is a process that is neglected in most of the large scale atmospheric models used for weather forecasting or climate prediction. Yet to our knowledge, the magnitude of the resulting radiative bias remains unquantified. This study aims to quantify the rain radiative effect (RRE) at a range of temporal and spatial scales, as a step toward determining whether the radiation schemes in these models should include rain. Using off‐line radiative transfer calculations with input from an ensemble of cloud resolving model simulations, we find that rain has a negligible effect on global mean radiative fluxes (less than 0.2 W m−2). Weekly mean RREs at specific locations may be larger (less than 4 W m−2). At the finest temporal and spatial resolutions, the RRE can occasionally be much larger again (greater than 100 W m−2), but values exceeding 10 W m−2 occur in less than 0.1% of cases. Using detailed analysis of case studies we demonstrate that the magnitude and direction of the RRE depend on the rain water path, its vertical location with respect to cloud, and, for longwave radiation, the temperature at which it occurs. Large RREs generally only occur when the rain water path is large and the cloud water path is small. These cases are infrequent and intermittent. As the RREs are generally small, we conclude that this missing process is unlikely to be important for large scale atmospheric models.
PRYSM v2.0: A Proxy System Model for Lacustrine Archives
Authors: Dee Sylvia G. , Russell James M. , Morrill Carrie , Chen Zihan , Neary Ashling
Published: October 2018

Reconstructions of temperature and hydrology from lake sedimentary archives have made fundamental contributions to our understanding of past, present, and future climate and help evaluate general circulation models (GCMs). However, because paleoclimate observations are an indirect (proxy) constraint on climatic variables, confounding effects of proxy processes complicate interpretations of these archives. To circumvent these uncertainties inherent to paleoclimate data‐model comparison, proxy system models (PSMs) provide transfer functions between climate variables and the proxy. We here present a new PSM for lacustrine sedimentary archives. The model simulates lake energy and water balance, sensors including leaf wax δD and carbonate δ18O, bioturbation, and compaction of sediment to lend insight toward how these processes affect and potentially obfuscate the original climate signal. The final product integrates existing and new models to yield a comprehensive, modular, adaptable, and publicly available PSM for lake systems. Highlighting applications of the PSM, we forward model lake variables with GCM simulations of the last glacial maximum and the modern. The simulations are evaluated with a focus on sensitivity of lake surface temperature and mixing to climate forcing, using Lakes Tanganyika and Malawi as case studies. The PSM highlights the importance of mixing on interpretations of air temperature reconstructions from lake archives and demonstrates how changes in mixing depth alone may induce nonstationarity between in situ lake and air temperatures. By placing GCM output in the same reference frame as lake paleoclimate archives, we aim to improve interpretations of past changes in terrestrial temperatures and water cycling.
Depositional Evolution of the Western Amundsen Basin, Arctic Ocean: Paleoceanographic and Tectonic Implications
Authors: Castro Carlos F. , Knutz Paul C. , Hopper John R. , Funck Thomas
Published: October 2018

A new stratigraphic model and estimated sedimentation rates of the western Amundsen Basin, Arctic Ocean, are presented based on multichannel seismic reflection data, seismic refraction data, magnetic data, and integrated with the sedimentary sequence from the central Arctic Ocean, obtained during the Arctic Coring Expedition. This places new constraints on the postbreakup Cenozoic depositional history of the basin, the adjacent Lomonosov Ridge, and improves the understanding of the tectonic, climatic, and oceanographic conditions in the central Arctic region. Four distinct phases of basin development are proposed. During the Paleocene‐mid‐Oligocene, high sedimentation rates are linked to terrestrial input and increased pelagic deposition in a restricted basin. Deposition of sedimentary wedges and mass transport into marginal depocenters reflect a period of tectonic instability linked to compression associated with the Eurekan Orogeny in the Arctic. During the late Oligocene‐early Miocene, widespread passive infill associated with hemipelagic deposition reflects a phase of limited tectonism, most likely in a freshwater estuarine setting. During the middle Miocene, mounded sedimentary buildups along the Lomonosov Ridge suggest the onset of geostrophic bottom currents that likely formed in response to a deepening and widening of the Fram Strait beginning around 18 Ma. In contrast, the Plio‐Pleistocene stage is characterized by erosional features such as scarps and channels adjacent to levee accumulations, indicative of a change to a higher‐energy environment. These deposits are suggested to be partly associated with dense shelf water‐mass plumes driven by supercooling and brine formation over the northern Greenland continental shelf.
Urban Residential Surface and Subsurface Hydrology: Synergistic Effects of Low‐Impact Features at the Parcel Scale
Authors: Voter C. B. , Loheide S. P.
Published: October 2018

Accurately predicting the hydrologic effects of urbanization requires an understanding of how hydrologic processes are affected by low‐impact development practices. In this study, we explored how growing season surface runoff, deep drainage, and evapotranspiration on a residential parcel are affected by several low‐impact interventions, including three “impervious‐centric” interventions (disconnecting downspouts, disconnecting sidewalks, and adding a transverse slope to the driveway and front walk), two “pervious‐centric” interventions (decompacting soil and adding microtopography), and all possible “holistic” combinations. Results were compared to both a highly and moderately compacted baseline parcel under an average and a dry weather scenario for a temperate climate. We find that under reasonable assumptions for highly compacted soil, pervious areas are a major source of runoff and disconnecting impervious surfaces may be relatively less effective without improving soil conditions. Under both highly and moderately compacted soil conditions, combining efforts to decompact soil with impervious disconnection has a synergistic effect on reducing surface runoff and increasing deep drainage and evapotranspiration. All combinations of interventions enhance infiltration, but the partitioning of additional root zone water between deep drainage and evapotranspiration depends on the weather scenario. Importantly, when all low‐impact interventions are applied together, growing season deep drainage is higher than that from a vacant lot with no impervious surfaces. We infer that ecohydrologic interfaces between impervious and pervious areas are strong controls on urban hydrologic fluxes and that high‐resolution, process‐based models can be used to account for these interfaces and thereby improve predictions of the hydrologic effects of low‐impact interventions.