bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Impact of Nonequilibrium Flow on the Structure of Turbulence Over River Dunes
Authors: Unsworth C. A. , Parsons D. R. , Hardy R. J. , Reesink A. J. H. , Best J. L. , Ashworth P. J. , Keevil G. M. 
Published: August 2018

AbstractMost past experimental investigations of flow over river dunes have focused on conditions that match semiempirical flow‐depth scaling laws, yet such equilibrium conditions are of limited value because they rarely occur in natural channels. This paper quantifies the structure of mean and turbulent flow over fixed 2‐D laboratory dunes across a range of nonequilibrium conditions within the dune flow regime. The flow field was quantified using 2‐D particle imaging velocimetry for 12 conditions, including flows that are too deep, too shallow, too fast, or too slow for the size of the fixed dunes. The results demonstrate major departures in the patterns of the mean flow and structure of turbulence when compared to dunes formed under equilibrium flow conditions. The length of flow reattachment scales linearly with the ratio of mean depth‐averaged streamwise velocity to shear velocity at the dune crest (
), which provides a new predictive measure for flow reattachment length. Depth‐averaged vertical velocities at the dune crest (
) show a parabolic relationship with
, peaking at
~0.60 m/s, which matches the relationship of dune aspect ratio with transport stage present in mobile bed conditions. The spatial location of the turbulent wake was found to vary with flow depth and velocity, with lower
and greater flow depths causing the wake to rise toward the free surface. Deeper flows are likely to show less flow convergence over the crests of dunes due to reduced interaction of turbulence with the free surface, resulting in a reduction of transport stage.
Beyond Regime: A Stochastic Model of Floods, Bank Erosion, and Channel Migration
Authors: Davidson S. L. , Eaton B. C. 
Published: August 2018

AbstractEquilibrium or regime models based on a single formative (channel‐forming) discharge have been instrumental in developing a quantitative understanding of river channel dynamics. However, alternative paradigms can be used to ask fundamentally different questions about river channel behavior. In this paper, we present the Stochastic Channel Simulator (STOCHASIM), a simple biogeomorphic model that models the interplay between erosion and vegetation encroachment through changes in channel geometry. Results for a range of flood distributions are compared to predictions from a similar model based upon a traditional regime approach. Flood variability strongly influences the mean channel geometry and channel stability; the regime model and the stochastic model predict the same channel width when flow variability is low but diverge as flow variability increases. The return period of the formative flow required to match the geometry generated by a traditional regime approach increases systematically, from about 2 years for flow regimes in humid regions to nearly 8 years for more variable flow regimes, like those typical of arid regions. While the traditional regime approach provides a reasonable simplification for streams with little variability in the flood distribution, stochastic modeling may provide more realistic estimates of channel size as flood variability increases (e.g., in arid streams or small watersheds). The success of STOCHASIM in replicating realistic patterns of erosion, as well as the historical contingency often observed in natural streams, suggests that adopting a stochastic dynamics paradigm could advance geomorphology, just as it has done in hydrology, ecology, and other natural sciences.
Changes in Deep Water Oxygenation of the South China Sea Since the Last Glacial Period
Authors: Li Gang , Rashid Harunur , Zhong Lifeng , Xu Xing , Yan Wen , Chen Zhong 
Published: August 2018

AbstractThe Pacific meridional overturning circulation is thought to have a significant influence on global climate. However, the extent to which intermediate and deep circulations have changed in the Pacific Ocean since the Last Glacial Maximum (LGM) is not well known. At present, the South China Sea Deep Water (SCSDW) is fed by the upper Pacific Deep Water. Here we present new benthic foraminiferal δ13C and redox‐sensitive elemental data from a sediment core retrieved from the southern deep SCS to reconstruct the oxygenation history of the SCSDW since the LGM. Oxygenation records from the deep SCS and intermediate and deep waters in the Pacific Ocean demonstrate that the SCSDW deeper than 1,600 m has been sourced by the Pacific Deep Water since the LGM. Our data suggest that the well‐ventilated North Pacific Intermediate Water would not have influenced the SCSDW during cold stadials of the last deglacial period.
Large‐Scale Atmospheric Control on Non‐Gaussian Tails of Midlatitude Temperature Distributions
Authors: Linz Marianna , Chen Gang , Hu Zeyuan 
Published: August 2018

AbstractObserved surface temperature distributions are non‐Gaussian, which has important implications for the likelihood of extreme events in a changing climate. We use a two‐dimensional advection‐diffusion model of temperature stirred by stochastically generated Rossby waves with a sustained background temperature gradient to explore non‐Gaussian temperature distributions. We examine how these distributions change with changes to thermal relaxation and eddy stirring. Weakening the background temperature gradient leads to decreased variance but no changes in other moments, while the eddy properties affect both the variance and skewness. A poleward movement of eddy stirring latitude leads to reduced skewness for most latitudes, implying a shift toward longer negative tails in temperature distributions, all else being equal. In contrast, the dependence of temperature skewness on eddy speed is a nuanced, nonlinear relationship.
On the Sensitivity of the Relationship Between Hadley Circulation Asymmetry and ENSO in CMIP5 Models
Authors: Guo Yi‐Peng , Tan Zhe‐Min 
Published: August 2018

AbstractRecent study shows that the asymmetric component (AC) of Hadley circulation variability during late winter and early spring can be explained by the combined effect between background sea surface temperature (SST) and the SST anomalies associated with El Niño–Southern Oscillation (ENSO). But the sensitivity of AC‐ENSO relationship to background SST and ENSO properties is still unknown. Using 17 climate models from the Coupled Model Intercomparison Project phase 5, we investigated the sensitivity of the AC‐ENSO relationship to the background SST and three ENSO properties. Most of the Coupled Model Intercomparison Project phase 5 models capture the spatial structure of the AC and reproduce the AC‐ENSO relationship, but the AC‐ENSO relationship has large intermodel spread. The AC‐ENSO relationship is mostly sensitive to ENSO zonal extent. ENSO amplitude can also influence the AC‐ENSO relationship by affecting the zonal extent. However, ENSO meridional extent and background SST—above a certain threshold—have little influence on the AC‐ENSO relationship.
GaAs Spectrometer for Planetary Electron Spectroscopy
Authors: Lioliou G. , Butera S. , Zhao S. , Whitaker M. D. C. , Barnett A. M. 
Published: August 2018

AbstractWork toward producing a radiation‐hard and high temperature tolerant direct detection electron spectrometer is reported. The motivation is to develop a low‐mass, low‐volume, low‐power, multimission capable instrument for future space science missions. The resultant prototype electron spectrometer employed a GaAs p+‐i‐n+ mesa photodiode (10 μm i layer thickness; 200 μm diameter) and a custom‐made charge‐sensitive preamplifier. The GaAs detector was initially electrically characterized as a function of temperature. The detector‐preamplifier assembly was then investigated for its utility in electron spectroscopy across the temperature range 100 to 20 °C using a laboratory 63Ni radioisotope β− particle source (end point energy = 66 keV). Monte Carlo simulations using the computer program CASINO were conducted and showed that the spectrometer had a quantum detection efficiency which increased with increasing electron energy up to 70 keV; a quantum detection efficiency of 73% was calculated. The accumulated 63Ni β− particle spectra together with CASINO simulations of the detected spectra showed that the GaAs based spectrometer could be used for counting electrons and measuring the energy deposited per electron in the detector's active region (i layer). The development of a GaAs electron spectrometer of this type may find use in future space missions to environments of intense radiation (such as at the surface of Europa for investigation of electron‐driven radiolysis of ice) and high temperature (such as at Mercury, and comets passing close to the Sun).
Mesoscale Plasma Convection Perturbations in the High‐Latitude Ionosphere
Authors: Chen Yun‐Ju , Heelis Roderick A. 
Published: August 2018

AbstractAn investigation of flow perturbations with spatial scale sizes between 100 and 500 km in the high‐latitude ionosphere is presented. These localized flow perturbations are deviations from the large‐scale background convection, expected to give us new insights into the magnetosphere‐ionosphere coupling process. Ion drift measurements from the Defense Meteorological Satellite Program F17 are utilized to identify these mesoscale flow perturbations. Our intent is to discover the properties of these perturbations in terms of perturbation flow speeds, location, scale size, and occurrence frequency as well as their dependence on the interplanetary magnetic field (IMF) and underlying large‐scale convection pattern. Observation suggests that flow perturbation locations strongly depend on the IMF orientation as does the occurrence frequency of the flow perturbations. For southward IMF, more flow perturbations occur in regions of sunward background flow than in regions of antisunward background flow. For flow perturbations with speeds over 300 m/s, an asymmetry in the preferred direction and scale size is seen for those embedded in sunward and antisunward background flows. Significantly less asymmetry is present for flow perturbations with speeds between 100 and 300 m/s. The flow perturbations exceeding 300 m/s are most likely closed locally with lower magnitude return flows or with adjacent flows across the convection reversal boundary and representing additional sources of frictional heating and momentum transfer to the thermosphere. The perturbation flow speed is almost independent of the scale size and underlying convection speed, but the largest speeds are preferentially seen at scale sizes between 200 and 300 km.
Fluid‐Assisted Deformation and Strain Localization in the Cooling Mantle Wedge of a Young Subduction Zone (Semail Ophiolite)
Authors: Prigent C. , Guillot S. , Agard P. , Ildefonse B. 
Published: August 2018

AbstractThis study reports on feedback mechanisms between fluid migration, ductile deformation, and strain localization processes in an incipiently forming mantle wedge: the basal banded unit of the Semail ophiolite. These peridotites were located right above the plate interface during intraoceanic subduction infancy that ultimately led to ophiolite obduction. During this stage, they were affected by coeval ductile deformation, forming (proto)mylonites at ~900–800 °C to ultramylonites at ~700 °C, and interaction with subduction fluids. From the petrological and microstructural study of these hydrated peridotites and their protolith (preserved lenses of porphyroclastic tectonites), we show that peridotite interaction with hydrous fluids triggered dissolution/precipitation processes. Dissolution of coarser grains and precipitation of new and smaller ones (mainly pyroxenes, spinel, and amphibole) resulted in a drastic grain size reduction, phase mixing and a switch from olivine dislocation to grain size sensitive creep in (proto)mylonites. Data also evidence a feedback process of fluid focusing in actively deforming shear zones. This rapid switch in olivine deformation mechanism, driven by subduction fluid‐peridotite interaction, triggered an intense weakening of the peridotites at ~900–800 °C and a transition from a mechanically decoupled to coupled plate interface (as witnessed by the detachment and underplating of a high‐temperature metamorphic sole to the base of the ophiolite). It also explains the intense strain localization (<1‐km‐thick shear zone) along this ductile portion of the plate interface. Considering that similar mechanisms take place in mature subduction zones, they may explain plate interface coupling at subarc depths in worldwide subduction zones.
O+Escape During the Extreme Space Weather Event of 4–10 September 2017
Authors: Schillings Audrey , Nilsson Hans , Slapak Rikard , Wintoft Peter , Yamauchi Masatoshi , Wik Magnus , Dandouras Iannis , Carr Chris M. 
Published: August 2018

AbstractWe have investigated the consequences of extreme space weather on ion outflow from the polar ionosphere by analyzing the solar storm that occurred early September 2017, causing a severe geomagnetic storm. Several X‐flares and coronal mass ejections were observed between 4 and 10 September. The first shock—likely associated with a coronal mass ejection—hit the Earth late on 6 September, produced a storm sudden commencement, and began the initial phase of the storm. It was followed by a second shock, approximately 24 hr later, that initiated the main phase and simultaneously the Dst index dropped to Dst = −142 nT and Kp index reached Kp = 8. Using COmposition DIstribution Function data on board Cluster satellite 4, we estimated the ionospheric O+outflow before and after the second shock. We found an enhancement in the polar cap by a factor of 3 for an unusually high ionospheric O+outflow (mapped to an ionospheric reference altitude) of 1013 m−2 s−1. We suggest that this high ionospheric O+outflow is due to a preheating of the ionosphere by the multiple X‐flares. Finally, we briefly discuss the space weather consequences on the magnetosphere as a whole and the enhanced O+outflow in connection with enhanced satellite drag.
Perturbed Input Ensemble Modeling With the Space Weather Modeling Framework
Authors: Morley S. K. , Welling D. T. , Woodroffe J. R. 
Published: August 2018

AbstractTo assess the effect of uncertainties in solar wind driving on the predictions from the operational configuration of the Space Weather Modeling Framework, we have developed a nonparametric method for generating multiple possible realizations of the solar wind just upstream of the bow shock, based on observations near the first Lagrangian point. We have applied this method to the solar wind inputs at the upstream boundary of Space Weather Modeling Framework and have simulated the geomagnetic storm of 5 April 2010. We ran a 40‐member ensemble for this event and have used this ensemble to quantify the uncertainty in the predicted Sym‐H index and ground magnetic disturbances due to the uncertainty in the upstream boundary conditions. Both the ensemble mean and the unperturbed simulation tend to underpredict the magnitude of Sym‐H in the quiet interval before the storm and overpredict in the storm itself, consistent with previous work. The ensemble mean is a more accurate predictor of Sym‐H, improving the mean absolute error by nearly 2 nT for this interval and displaying a smaller bias. We also examine the uncertainty in predicted maxima in ground magnetic disturbances. The confidence intervals are typically narrow during periods where the predicted dBH/dt is low. The confidence intervals are often much wider where the median prediction is for enhanced dBH/dt. The ensemble also allows us to identify intervals of activity that cannot be explained by uncertainty in the solar wind driver, driving further model improvements. This work demonstrates the feasibility and importance of ensemble modeling for space weather applications.
Exploring Controls on Rainfall‐Runoff Events: 2. Regional Patterns and Spatial Controls of Event Characteristics in Germany
Authors: Tarasova L. , Basso S. , Poncelet C. , Merz R. 
Published: August 2018

AbstractThis study unveils regional patterns of rainfall‐runoff event characteristics in Germany and identifies their spatial controls. Characteristics describing mean value, variability, and seasonality of event runoff coefficient, time scale, rise time, and of the occurrence of multiple‐peak events are derived for a set of 196,073 rainfall‐runoff events observed in 401 mesoscale German catchments. Multiobjective performances of various variable selection methods are used to identify hydrologically relevant variables from a comprehensive set of 115 descriptors of climate, topography, geomorphology, soil, land use, hydrogeology, and geology for every catchment. Results show that although event characteristics have relatively clear regional patterns due to the dominance of climatic controls at regional scale, subsurface properties (i.e., catchment storage) play a considerable role for the prediction of event runoff response. Compared to other tested variable selection methods, the application of a backward elimination procedure allows for the most accurate prediction of spatial patterns and regionalized values of event characteristics identifying soil depth, hydraulic permeability and frequency, size, and seasonality of wet spells as hydrologically relevant catchment descriptors. Climatic and hydrogeological descriptors outperform other generic groups of catchment descriptors. The hydrological interpretation of the emergent regional pattern of event characteristics, their variability, and seasonality provides insight on archetypical catchment behaviors and their controls.
Neurofilament light interaction with GluN1 modulates neurotransmission and schizophrenia-associated behaviors
Authors: Yuan Aidong , Veeranna  , Sershen Henry , Basavarajappa Balapal S. , Smiley John F. , Hashim Audrey , Bleiwas Cynthia , Berg Martin , Guifoyle David N. , Subbanna Shivakumar , Darji Sandipkumar , Kumar Asok , Rao Mala V. , Wilson Donald A. , Julien Jean-Pierre , Javitt Daniel C. , Nixon Ralph A. 
Published: August 2018

AbstractNeurofilament (NFL) proteins have recently been found to play unique roles in synapses. NFL is known to interact with the GluN1 subunit of N-methyl-d-aspartic acid (NMDAR) and be reduced in schizophrenia though functional consequences are unknown. Here we investigated whether the interaction of NFL with GluN1 modulates synaptic transmission and schizophrenia-associated behaviors. The interaction of NFL with GluN1 was assessed by means of molecular, pharmacological, electrophysiological, magnetic resonance spectroscopy (MRS), and schizophrenia-associated behavior analyses. NFL deficits cause an NMDAR hypofunction phenotype including abnormal hippocampal function, as seen in schizophrenia. NFL−/− deletion in mice reduces dendritic spines and GluN1 protein levels, elevates ubiquitin-dependent turnover of GluN1 and hippocampal glutamate measured by MRS, and depresses hippocampal long-term potentiation. NMDAR-related behaviors are also impaired, including pup retrieval, spatial and social memory, prepulse inhibition, night-time activity, and response to NMDAR antagonist, whereas motor deficits are minimal. Importantly, partially lowering NFL in NFL+/− mice to levels seen regionally in schizophrenia, induced similar but milder NMDAR-related synaptic and behavioral deficits. Our findings support an emerging view that central nervous system neurofilament subunits including NFL in the present report, serve distinctive, critical roles in synapses relevant to neuropsychiatric diseases.
A study paradigm integrating prospective epidemiologic cohorts and electronic health records to identify disease biomarkers
Authors: Mosley Jonathan D. , Feng QiPing , Wells Quinn S. , Van Driest Sara L. , Shaffer Christian M. , Edwards Todd L. , Bastarache Lisa , Wei Wei-Qi , Davis Lea K. , McCarty Catherine A. , Thompson Will , Chute Christopher G. , Jarvik Gail P. , Gordon Adam S. , Palmer Melody R. , Crosslin David R. , Larson Eric B. , Carrell David S. , Kullo Iftikhar J. , Pacheco Jennifer A. , Peissig Peggy L. , Brilliant Murray H. , Linneman James G. , Namjou Bahram , Williams Marc S. , Ritchie Marylyn D. , Borthwick Kenneth M. , Verma Shefali S. , Karnes Jason H. , Weiss Scott T. , Wang Thomas J. , Stein C. Michael , Denny Josh C. , Roden Dan M. 
Published: August 2018

AbstractDefining the full spectrum of human disease associated with a biomarker is necessary to advance the biomarker into clinical practice. We hypothesize that associating biomarker measurements with electronic health record (EHR) populations based on shared genetic architectures would establish the clinical epidemiology of the biomarker. We use Bayesian sparse linear mixed modeling to calculate SNP weightings for 53 biomarkers from the Atherosclerosis Risk in Communities study. We use the SNP weightings to computed predicted biomarker values in an EHR population and test associations with 1139 diagnoses. Here we report 116 associations meeting a Bonferroni level of significance. A false discovery rate (FDR)-based significance threshold reveals more known and undescribed associations across a broad range of biomarkers, including biometric measures, plasma proteins and metabolites, functional assays, and behaviors. We confirm an inverse association between LDL-cholesterol level and septicemia risk in an independent epidemiological cohort. This approach efficiently discovers biomarker-disease associations.
Interferon priming is essential for human CD34+ cell-derived plasmacytoid dendritic cell maturation and function
Authors: Laustsen A. , Bak R. O. , Krapp C. , Kjær L. , Egedahl J. H. , Petersen C. C. , Pillai S. , Tang H. Q. , Uldbjerg N. , Porteus M. , Roan N. R. , Nyegaard M. , Denton P. W. , Jakobsen M. R. 
Published: August 2018

AbstractPlasmacytoid dendritic cells (pDC) are essential for immune competence. Here we show that pDC precursor differentiated from human CD34+ hematopoietic stem and progenitor cells (HSPC) has low surface expression of pDC markers, and has limited induction of type I interferon (IFN) and IL-6 upon TLR7 and TLR9 agonists treatment; by contrast, cGAS or RIG-I agonists-mediated activation is not altered. Importantly, after priming with type I and II IFN, these precursor pDCs attain a phenotype and functional activity similar to that of peripheral blood-derived pDCs. Data from CRISPR/Cas9-mediated genome editing of HSPCs further show that HSPC-pDCs with genetic modifications can be obtained, and that expression of the IFN-α receptor is essential for the optimal function, but dispensable for the differentiation, of HSPC-pDC percursor. Our results thus demonstrate the biological effects of IFNs for regulating pDC function, and provide the means of generating of gene-modified human pDCs.