bluuebunny/crossref_metadata_2025_split huggingface dataset:
Signatures of Lithospheric Flexure and Elevated Heat Flow in Stereo Topography at Coronae on Venus
Authors: O'Rourke Joseph G. , Smrekar Suzanne E. 
Published: January 2018

AbstractSignatures of lithospheric flexure were previously identified at a dozen or more large coronae on Venus. Thin plate models fit to topographic profiles return elastic parameters, allowing derivation of mechanical thickness and surface heat flows given an assumed yield strength envelope. However, the low resolution of altimetry data from the NASA Magellan mission has hindered studying the vast majority of coronae, particularly those less than a few hundred kilometers in diameter. Here we search for flexural signatures around 99 coronae over ∼20% of the surface in Magellan altimetry data and stereo‐derived topography that was recently assembled from synthetic aperture radar images. We derive elastic thicknesses of ∼2 to 30 km (mostly ∼5 to 15 km) with Cartesian and axisymmetric models at 19 coronae. We discuss the implications of low values that were also noted in earlier gravity studies. Most mechanical thicknesses are estimated as <19 km, corresponding to thermal gradients >24 K km−1. Implied surface heat flows >95 mW m−2—twice the global average in many thermal evolution models—imply that coronae are major contributors to the total heat budget or Venus is cooling faster than expected. Binomial statistics show that “Type 2” coronae with incomplete fracture annuli are significantly less likely to host flexural signatures than “Type 1” coronae with largely complete annuli. Stress calculations predict extensional faulting where nearly all profiles intersect concentric fractures. We failed to identify systematic variations in flexural parameters based on type, geologic setting, or morphologic class. Obtaining quality, high‐resolution topography from a planetwide survey is vital to verifying our conclusions.
Comparison of Big‐Leaf, Two‐Big‐Leaf, and Two‐Leaf Upscaling Schemes for Evapotranspiration Estimation Using Coupled Carbon‐Water Modeling
Authors: Luo Xiangzhong , Chen Jing M. , Liu Jane , Black T. Andrew , Croft Holly , Staebler Ralf , He Liming , Arain M. Altaf , Chen Bin , Mo Gang , Gonsamo Alemu , McCaughey Harry 
Published: January 2018

AbstractEvapotranspiration (ET) is commonly estimated using the Penman‐Monteith equation, which assumes that the plant canopy is a big leaf (BL) and the water flux from vegetation is regulated by canopy stomatal conductance (Gs). However, BL has been found to be unsuitable for terrestrial biosphere models built on the carbon‐water coupling principle because it fails to capture daily variations of gross primary productivity (GPP). A two‐big‐leaf scheme (TBL) and a two‐leaf scheme (TL) that stratify a canopy into sunlit and shaded leaves have been developed to address this issue. However, there is a lack of comparison of these upscaling schemes for ET estimation, especially on the difference between TBL and TL. We find that TL shows strong performance (r2 = 0.71, root‐mean‐square error = 0.05 mm/h) in estimating ET at nine eddy covariance towers in Canada. BL simulates lower annual ET and GPP than TL and TBL. The biases of estimated ET and GPP increase with leaf area index (LAI) in BL and TBL, and the biases of TL show no trends with LAI. BL miscalculates the portions of light‐saturated and light‐unsaturated leaves in the canopy, incurring negative biases in its flux estimation. TBL and TL showed improved yet different GPP and ET estimations. This difference is attributed to the lower Gs and intercellular CO2 concentration simulated in TBL compared to their counterparts in TL. We suggest to use TL for ET modeling to avoid the uncertainty propagated from the artificial upscaling of leaf‐level processes to the canopy scale in BL and TBL.
Geological and Chemical Factors that Impacted the Biological Utilization of Cobalt in the Archean Eon
Authors: Moore Eli K. , Hao Jihua , Prabhu Anirudh , Zhong Hao , Jelen Ben I. , Meyer Mike , Hazen Robert M. , Falkowski Paul G. 
Published: January 2018

AbstractThe geosphere and biosphere coevolved and influenced Earth's biological and mineralogical diversity. Changing redox conditions influenced the availability of different transition metals, which are essential components in the active sites of oxidoreductases, proteins that catalyze electron transfer reactions across the tree of life. Despite its relatively low abundance in the environment, cobalt (Co) is a unique metal in biology due to its importance to a wide range of organisms as the metal center of vitamin B12 (aka cobalamin, Cbl). Cbl is vital to multiple methyltransferase enzymes involved in energetically favorable metabolic pathways. It is unclear how Co availability is linked to mineral evolution and weathering processes. Here we examine important biological functions of Co, as well as chemical and geological factors that may have influenced the utilization of Co early in the evolution of life. Only 66 natural minerals are known to contain Co as an essential element. However, Co is incorporated as a minor element in abundant rock‐forming minerals, potentially representing a reliable source of Co as a trace element in marine systems due to weathering processes. We developed a mineral weathering model that indicates that dissolved Co was potentially more bioavailable in the Archean ocean under low S conditions than it is today. Mineral weathering, redox chemistry, Co complexation with nitrogen‐containing organics, and hydrothermal environments were crucial in the incorporation of Co in primitive metabolic pathways. These chemical and geological characteristics of Co can inform the biological utilization of other trace metals in early forms of life.
MODIS‐Based Estimates of Global Terrestrial Ecosystem Respiration
Authors: Ai Jinlong , Jia Gensuo , Epstein Howard E. , Wang Hesong , Zhang Anzhi , Hu Yonghong 
Published: January 2018

AbstractTerrestrial ecosystem respiration (Reco) represents a large carbon source from land to atmosphere and is highly spatiotemporally heterogeneous across scales. Upscaling of field‐measured respiration data using remote sensing information is urgently needed for understanding regional and global patterns of ecosystem respiration. Using Moderate Resolution Imaging Spectroradiometer (MODIS) data with resolutions of 1 km and 8 days and flux measurements from 171 sites (total of 812 site years) across the world from 2000 to 2014, we developed a semiempirical, yet physiologically based, remote sensing model, which can simulate Reco observed across most biomes with a small margin of error (R2 = 0.55, root‐mean‐square error = 1.67 gCm−2d−1, efficiency = 0.46, and mean bias error = 0.18 gCm−2d−1). The reference respiration at the annual mean nighttime land surface temperature (LST) can be well represented by MODIS enhanced vegetation index and LST. A comprehensive comparison of six respiration‐temperature (R‐T) models shows that the more physiologically based R‐T model (extended Arrhenius model) may be most suitable for estimating the respiration rate at higher latitudes. Integrating an effect of vegetation change on Reco in different biomes effectively improves estimates of Reco in almost all of the biomes.
An Environmentally Forced Tropical Cyclone Hazard Model
Authors: Lee Chia‐Ying , Tippett Michael K. , Sobel Adam H. , Camargo Suzana J. 
Published: January 2018

AbstractA new statistical‐dynamical model is developed for estimating the long‐term hazard of rare, high impact tropical cyclones events globally. There are three components representing the complete storm lifetime: an environmental index‐based genesis model, a beta‐advection track model, and an autoregressive intensity model. All three components depend upon the local environmental conditions, including potential intensity, relative sea surface temperature, 850 and 250 hPa steering flow, deep‐layer mean vertical shear, 850 hPa vorticity, and midlevel relative humidity. The hazard model, using 400 realizations of a 32 year period (approximately 3,000 storms per realization), captures many aspects of tropical cyclone statistics, such as genesis and track density distribution. Of particular note, it simulates the observed number of rapidly intensifying storms, a challenging issue in tropical cyclone modeling and prediction. Using the return period curve of landfall intensity as a measure of local tropical cyclone hazard, the model reasonably simulates the hazard in the western north Pacific (coastal regions of the Philippines, China, Taiwan, and Japan) and the Caribbean islands. In other regions, the observed return period curve can be captured after a local landfall frequency adjustment that forces the total number of landfalls to be the same as that observed while allowing the model to freely simulate the distribution of intensities at landfall.
Evidence for 1.5 km of Uplift of the Central Anatolian Plateau's Southern Margin in the Last 450 kyr and Implications for Its Multiphased Uplift History
Authors: Öğretmen Nazik , Cipollari Paola , Frezza Virgilio , Faranda Costanza , Karanika Konstantina , Gliozzi Elsa , Radeff Giuditta , Cosentino Domenico 
Published: January 2018

AbstractAt the southern margin of the Central Anatolian Plateau (CAP), marine deposits that overlie the Central Tauride units at up to 2 km of elevation were used to constrain the onset of uplift to the middle‐late Miocene. This study demonstrates that much younger marine deposits cap the southern margin. We recognize the Last Common Occurrence ofNeogloboquadrinaspp. (sin) (0.61 Ma) andPseudoemiliania lacunosa(0.467 Ma), which points to an early middle Pleistocene age. The benthic fauna indicates an epibathyal marine environment (400 to 500 m paleodepth), with an associated paleocoastline now at ~1,500 to 1,600 m above sea level. Our new results imply uplift rates of up to 3.21–3.42 mm/yr for the CAP southern margin since the deposition of the young marine units. In the area, the evaluation of late Pleistocene and Holocene uplift rates of ~1 mm/yr points to a post early middle Pleistocene short‐lived period of rapid uplift of the CAP southern margin, which can correlate the short‐lived surface uplift signal in numerical models of slab breakoff. Overall, this work demonstrates that the majority of the modern topography at the CAP southern margin (1,500 to 1,600 m) was only recently acquired, pointing to the absence of a significant orographic barrier along the southern plateau margin prior to 500 ka. The multiphased uplift recognized at the CAP southern margin by previous authors, as well as the fast uplift rate documented in this work, can be linked to lithosphere delamination and subsequent slab breakoff during the Arabian‐Anatolian continental collision.
Minimized Capillary End Effect During CO2 Displacement in 2‐D Micromodel by Manipulating Capillary Pressure at the Outlet Boundary in Lattice Boltzmann Method
Authors: Kang Dong Hun , Yun Tae Sup 
Published: January 2018

AbstractWe propose a new outflow boundary condition to minimize the capillary end effect for a pore‐scale
displacement simulation. The Rothman‐Keller lattice Boltzmann method with multi‐relaxation time is implemented to manipulate a nonflat wall and inflow‐outflow boundaries with physically acceptable fluid properties in 2‐D microfluidic chip domain. Introducing a mean capillary pressure acting at
‐water interface to the nonwetting fluid at the outlet effectively prevents
injection pressure from suddenly dropping upon
breakthrough such that the continuous
invasion and the increase of
saturation are allowed. This phenomenon becomes most pronounced at capillary number of logCa = −5.5, while capillary fingering and massive displacement of
prevail at low and high capillary numbers, respectively. Simulations with different domain length in homogeneous and heterogeneous domains reveal that capillary pressure and
saturation near the inlet are reproducible compared with those with a proposed boundary condition. The residual
saturation uniquely follows the increasing tendency with increasing capillary number, corroborated by experimental evidences. The determination of the mean capillary pressure and its sensitivity are also discussed. The proposed boundary condition is commonly applicable to other pore‐scale simulations to accurately capture the spatial distribution of nonwetting fluid and corresponding displacement ratio.
Modeling of Future Changes in Seasonal Snowpack and Impacts on Summer Low Flows in Alpine Catchments
Authors: Jenicek Michal , Seibert Jan , Staudinger Maria 
Published: January 2018

AbstractIt is expected that an increasing proportion of the precipitation will fall as rain in alpine catchments in the future. Consequently, snow storage is expected to decrease, which, together with changes in snowmelt rates and timing, might cause reductions in spring and summer low flows. The objectives of this study were (1) to simulate the effect of changing snow storage on low flows during the warm seasons and (2) to relate drought sensitivity to the simulated snow storage changes at different elevations. The Swiss Climate Change Scenarios 2011 data set was used to derive future changes in air temperature and precipitation. A typical bucket‐type catchment model, HBV‐light, was applied to 14 mountain catchments in Switzerland to simulate streamflow and snow in the reference period and three future periods. The largest relative decrease in annual maximum SWE was simulated for elevations below 2,200 m a.s.l. (60–75% for the period 2070–2099) and the snowmelt season shifted by up to 4 weeks earlier. The relative decrease in spring and summer minimum runoff that was caused by the relative decrease in maximum SWE (i.e., elasticity), reached 40–90% in most of catchments for the reference period and decreased for the future periods. This decreasing elasticity indicated that the effect of snow on summer low flows is reduced in the future. The fraction of snowmelt runoff in summer decreased by more than 50% at the highest elevations and almost disappeared at the lowest elevations. This might have large implications on water availability during the summer.
Uncertainty Quantification and Global Sensitivity Analysis of Subsurface Flow Parameters to Gravimetric Variations During Pumping Tests in Unconfined Aquifers
Authors: Maina Fadji Zaouna , Guadagnini Alberto 
Published: January 2018

AbstractWe study the contribution of typically uncertain subsurface flow parameters to gravity changes that can be recorded during pumping tests in unconfined aquifers. We do so in the framework of a Global Sensitivity Analysis and quantify the effects of uncertainty of such parameters on the first four statistical moments of the probability distribution of gravimetric variations induced by the operation of the well. System parameters are grouped into two main categories, respectively, governing groundwater flow in the unsaturated and saturated portions of the domain. We ground our work on the three‐dimensional analytical model proposed by Mishra and Neuman (2011), which fully takes into account the richness of the physical process taking place across the unsaturated and saturated zones and storage effects in a finite radius pumping well. The relative influence of model parameter uncertainties on drawdown, moisture content, and gravity changes are quantified through (a) the Sobol' indices, derived from a classical decomposition of variance and (b) recently developed indices quantifying the relative contribution of each uncertain model parameter to the (ensemble) mean, skewness, and kurtosis of the model output. Our results document (i) the importance of the effects of the parameters governing the unsaturated flow dynamics on the mean and variance of local drawdown and gravity changes; (ii) the marked sensitivity (as expressed in terms of the statistical moments analyzed) of gravity changes to the employed water retention curve model parameter, specific yield, and storage, and (iii) the influential role of hydraulic conductivity of the unsaturated and saturated zones to the skewness and kurtosis of gravimetric variation distributions. The observed temporal dynamics of the strength of the relative contribution of system parameters to gravimetric variations suggest that gravity data have a clear potential to provide useful information for estimating the key hydraulic parameters of the system.
Regional Variability of Nitrate Fluxes in the Unsaturated Zone and Groundwater, Wisconsin, USA
Authors: Green Christopher T. , Liao Lixia , Nolan Bernard T. , Juckem Paul F. , Shope Christopher L. , Tesoriero Anthony J. , Jurgens Bryant C. 
Published: January 2018

AbstractProcess‐based modeling of regional
fluxes to groundwater is critical for understanding and managing water quality, but the complexity of
reactive transport processes makes implementation a challenge. This study introduces a regional vertical flux method (VFM) for efficient estimation of reactive transport of
in the vadose zone and groundwater. The regional VFM was applied to 443 well samples in central‐eastern Wisconsin. Chemical measurements included O2,
, N2 from denitrification, and atmospheric tracers of groundwater age including carbon‐14, chlorofluorocarbons, tritium, and tritiogenic helium. VFM results were consistent with observed chemistry, and calibrated parameters were in‐line with estimates from previous studies. Results indicated that (1) unsaturated zone travel times were a substantial portion of the transit time to wells and streams, (2) since 1945 fractions of applied N leached to groundwater have increased for manure‐N, possibly due to increased injection of liquid manure, and decreased for fertilizer‐N, and (3) under current practices and conditions, approximately 60% of the shallow aquifer will eventually be affected by downward migration of
, with denitrification protecting the remaining 40%. Recharge variability strongly affected the unsaturated zone lag times and the eventual depth of the
front. Principal components regression demonstrated that VFM parameters and predictions were significantly correlated with hydrogeochemical landscape features. The diverse and sometimes conflicting aspects of N management (e.g., limiting N volatilization versus limiting N losses to groundwater) warrant continued development of large‐scale holistic strategies to manage water quality and quantity.
Prediction of the peak seismic response of asymmetric buildings under bidirectional horizontal ground motion using equivalentSDOFmodel
Authors: Fujii Kenji 
Published: January 2018

AbstractThe applicability of a simplified procedure, namely mode‐adaptive bidirectional pushover analysis (MABPA), to the prediction of the non‐linear peak response of a multistory asymmetric building subjected to bidirectional excitation is discussed. The first part of the paper summarizes the formulation of 2 independent equivalent single‐degree‐of‐freedom models representing the first and second modal responses. The relationship between the critical assumptions ofMABPAand the torsional index defined based on mode shape is then discussed. In the latter part of the paper, non‐linear time‐history analyses of 4‐story torsionally stiff (TS) or torsionally flexible asymmetric buildings are described, and the results are compared with the predictions. The results show thatMABPApredicts the peak response displacement of only theTSasymmetric buildings satisfactorily. Therefore,MABPAshould be considered applicable only toTSbuildings. The applicability ofMABPAto a given asymmetric building may be evaluated by using the torsional indices of the first 3 modes.
Is seizure frequency variance a predictable quantity?
Authors: Goldenholz Daniel M. , Goldenholz Shira R. , Moss Robert , French Jacqueline , Lowenstein Daniel , Kuzniecky Ruben , Haut Sheryl , Cristofaro Sabrina , Detyniecki Kamil , Hixson John , Karoly Philippa , Cook Mark , Strashny Alex , Theodore William H. 
Published: January 2018

AbstractBackgroundThere is currently no formal method for predicting the range expected in an individual's seizure counts. Having access to such a prediction would be of benefit for developing more efficient clinical trials, but also for improving clinical care in the outpatient setting.MethodsUsing three independently collected patient diary datasets, we explored the predictability of seizure frequency. Three independent seizure diary databases were explored: SeizureTracker (n = 3016), Human Epilepsy Project (n = 93), and NeuroVista (n = 15). First, the relationship between mean and standard deviation in seizure frequency was assessed. Using that relationship, a prediction for the range of possible seizure frequencies was compared with a traditional prediction scheme commonly used in clinical trials. A validation dataset was obtained from a separate data export of SeizureTracker to further verify the predictions.ResultsA consistent mathematical relationship was observed across datasets. The logarithm of the average seizure count was linearly related to the logarithm of the standard deviation with a high correlation (R2 > 0.83). The three datasets showed high predictive accuracy for this log–log relationship of 94%, compared with a predictive accuracy of 77% for a traditional prediction scheme. The independent validation set showed that the log–log predicted 94% of the correct ranges while the RR50 predicted 77%.ConclusionReliably predicting seizure frequency variability is straightforward based on knowledge of mean seizure frequency, across several datasets. With further study, this may help to increase the power of RCTs, and guide clinical practice.