bluuebunny/crossref_metadata_2025 huggingface dataset:
Microstructural characterization of a double pulse resistance spot welded 1200 MPa TBF steel
Authors: Stadler Manfred , Gruber Martin , Schnitzer Ronald , Hofer Christina
Published: December 2019

In the automotive industry resistance, spot welding is the dominant technology in sheet metal joining of advanced high strength steels (AHSS). In order to improve the mechanical performance of AHSS welds, in-process tempering via a second pulse is a possible approach. In this work, two different double pulse welding schemes were applied to a 1200 MPa transformation-induced plasticity (TRIP)-aided bainitic ferrite (TBF) steel. The different microstructures in the welds were characterized via light optical and scanning electron microscopy. Additionally, hardness mappings with several hundred indents were performed. It is shown that the second pulse, following a low first pulse which is high enough to produce a weld nugget that fulfills the quality criterion of a minimum spot weld diameter of 4*√t, leads to partial reaustenitization and consequently to a ferritic/martensitic microstructure after final quenching. Hardness mappings revealed that this inner FZ is harder than the surrounding FZ consisting of tempered martensite. In contrast, if the highest current without splashing is chosen for the first pulse, the same second pulse does not reaustenitize the FZ but only temper the martensite.
Hydrothermal synthesis of spherical carbon nanoparticles (CNPs) for supercapacitor electrodes uses
Authors: Sedira Sofiane , Mendaci Bilel
Published: December 2019

In this paper, hydrothermal method was used to provide stable colloidal suspension of spherical carbon nanoparticles (CNPs) with good uniformity of size and shape. XRD analyses showed the formation of crystalline structure of carbon material. CNPs Raman spectrum indicates the high quality with a low content of structural defects and high graphitic degree. The formation of CNPs is confirmed by an absorption peak at 264 nm. XPS technique showed well a significant decrease of oxygen-containing functional groups, indicating a low degree of graphite oxidation. The active surface area of CNPs was measured by BET technique. TEM images show that CNPs are nearly spherical in shape and the diameters varying between 50 and 120 nm. The CV behaviors showed that CNPs exhibit the higher specific capacitance values, and is greatly improved over that of previously reported carbon nanomaterials.
SCR-Filter Model Order Reduction (1): Development and Validation of the Base “High-Fidelity” Model
Authors: Olowojebutu Seun , Steffen Thomas , Bush Phillip
Published: December 2019

Catalysed diesel particulate filters (c-DPF) have been described as multifunctional reactor systems. Integration of selective catalytic reduction (SCR) functionality in the DPF enhances filter performance to achieve nitrous oxides (NOx) treatment along with particulate matter (PM) collection. The physical and chemical aspects of the integrated SCR-filter make modelling difficult. The goal of this work is to develop a low-complexity model of the SCR-filter system with good fidelity. The first part of our work—presented in this paper—lays out the structure of the SCR-filter model and highlights a new approach to implement faster than real-time solution to the “full-order” or “high-complexity” model. The validated model was applied to evaluate the impact of diffusion on deNOx functionality of the SCR-filter system in a simulated characterisation exercise for the SCR-filter unit. We found that internal (pore) diffusion (effective diffusivity coefficient) and external channel to wall diffusion (mass transfer coefficient) orthogonal to the channel direction are significant for accurate characterisation of the deNOx performance of the SCR-coated filter system. System modelling can be used to select the geometric properties of the monolith (length and density of the SCR-coated filter system) and micro-properties of the washcoat (catalyst loading and zoning) to optimise the influence of diffusion on the system performance. The main contribution of this paper is the presentation of a different approach to implementing the solution to the cDPF model and in enough detail so that it can be easily replicated.
The incidence of early post-operative hypoxemia and its contributing factors among patients underwent operation under anesthesia at University of Gondar comprehensive and specialized referral hospital, Gondar, North West Ethiopia, 2018. A prospective observational study
Authors: Melesse Debas Yaregal , Denu Zewditu Abdissa , Kassahun Habtamu Getinet , Agegnehu Abatneh Feleke
Published: December 2019

ABSTRACT

Background:

Hypoxemia is defined as low level of oxygen in the blood. The early postoperative period is a critical time for developing hypoxemia. It is well known that the physiological response of the patient is not reversed immediately after anesthesia and surgery. Supplemental oxygen should be considered in patients who had operation under anesthesia at the potential time of post-operative period.

Objective:

The objective of this study was to determine the incidence of early post-operative hypoxemia and its contributing factors among operated patients under anesthesia during transportation to recovery rooms and at recovery rooms.

Methods:

A prospective observational study design was conducted to determine the incidence of early post-operative hypoxemia and to identify the contributing factors among operated patients who had undergone with anesthesia from March 1 to April 10, 2018. Data were checked on daily basis. Data were entered to Epi Info and analyzed by statistical package for social sciences (SPSS) version 20 software. Descriptive statistics were used to summarize patient's sociodemographic data. Bivariate and multivariate binary logistic regressions were conducted to see the existence of the association between dependent and independent variables.

Results:

424 operated patients were included. The overall incidence of early post-operative hypoxemia among the study subjects (424) was 113 (26.7%). The risk factors of early post-operative hypoxemia were preoperative oxygen saturation <95%, general anesthesia, heart disease, subcostal incision, surgical duration ≥120 min, muscular strength score 0 and hepato-biliary-pancreas surgeries.

Conclusion:

The incidence of early postoperative hypoxemia was high and risk factors of early post-operative hypoxemia were preoperative oxygen saturation<95%, general anesthesia, heart disease, subcostal incision, surgical duration >120 min, muscular strength score 0 and hepato-biliary-pancreas surgeries. Therefore, oxygen administration should be commenced to all risky patients for hypoxemia during early post-operative period.

Highlights:
Inhomogeneous phase-type distributions and heavy tails
Authors: Albrecher Hansjörg , Bladt Mogens
Published: December 2019

We extend the construction principle of phase-type (PH) distributions to allow for inhomogeneous transition rates and show that this naturally leads to direct probabilistic descriptions of certain transformations of PH distributions. In particular, the resulting matrix distributions enable the carrying over of fitting properties of PH distributions to distributions with heavy tails, providing a general modelling framework for heavy-tail phenomena. We also illustrate the versatility and parsimony of the proposed approach in modelling a real-world heavy-tailed fire insurance dataset.
How strong can the Parrondo effect be?
Authors: Ethier S. N. , Lee Jiyeon
Published: December 2019

Parrondo’s coin-tossing games were introduced as a toy model of the flashing Brownian ratchet in statistical physics but have emerged as a paradigm for a much broader phenomenon that occurs if there is a reversal in direction in some system parameter when two similar dynamics are combined. Our focus here, however, is on the original Parrondo games, usually labeledAandB. We show that if the parameters of the games are allowed to be arbitrary, subject to a fairness constraint, and if the two (fair) gamesAandBare played in an arbitrary periodic sequence, then the rate of profit can not only be positive (the so-called Parrondo effect), but can also be arbitrarily close to 1 (i.e. 100%).
A Risk Assessment of Ships Groundings in Rivers: The Case of Parana River
Authors: Karahalios Hristos
Published: December 2019

A ship's grounding appears to be a significant threat to the safety of its crew, marine environment and the local ports economy. The risk of such incidents is higher in rivers since weather conditions can significantly alter the depths of channels from those shown on navigation charts. By means of a fuzzy analytic hierarchy process, a new methodology is proposed, capable of evaluating the hazards of a ship's grounding in a river. The proposed method contributes to safe navigation in rivers. Navigators are able to assess grounding risk in a river passage based on local information of past incidents. The proposed methodology is used to evaluate commercial risks from groundings in the Parana River. A case study was carried out using data from 118 cases, as provided by local agencies for the period 2008–2017.
Coutinho's Method for the Altitude
Authors: Canas António Costa , Marabujo Magda Ramires , Sousa Teresa
Published: December 2019

In the first aerial crossing of the South Atlantic, by Gago Coutinho and Sacadura Cabral in 1922, several methods of astronomical maritime navigation were used with adaptions to aerial navigation. In order to apply these methods, the navigator needed to know the approximate altitude of the aircraft so that its position could be determined. The instrument available at that time, the altimeter, did not give reliable values for altitude. Therefore, Coutinho had to devise a method that enabled the navigator to determine the altitude quickly and efficiently. The method Coutinho devised is based on a mathematical and geometrical procedure. In this paper, we study in detail Coutinho's method to determine altitude, with diagrams to aid understanding of the deductions and calculations. We also present a real example of how this method would be used during the flight.
Dynamics of the contents and distribution of ABA, auxins and aquaporins in developing caryopses of an ABA-deficient barley mutant and its parental cultivar
Authors: Seldimirova Oksana A. , Kudoyarova Guzel R. , Katsuhara Maki , Galin Ilshat R. , Zaitsev Denis Yu. , Kruglova Natalia N. , Veselov Dmitry S. , Veselov Stanislav Yu.
Published: December 2019

Dynamics of abscisic acid (ABA) and indole-3-acetic acid (IAA) contents were followed in developing barley caryopses of the ABA-deficient mutant AZ34 and its parental cultivar Steptoe. Distribution of these hormones and HvPIP2 aquaporins (AQPs) was studied with the help of immunohistochemical methods in the roots and coleorhiza of developing embryos. In Steptoe, maturation of the caryopsis was accompanied by vast accumulation of ABA, while this hormone accumulated more slowly in the caryopsis of AZ34 and its content was lower than in Steptoe. Accumulation of ABA was accompanied by a decline in IAA level in the developing caryopsis, the process being delayed in AZ34 in accordance with the slower accumulation of ABA. ABA accumulated to high levels in the coleorhiza cells of Steptoe, while the effect was absent in AZ34. The high level of ABA was likely to be important for maintaining the barrier function of the coleorhiza, preventing germination of seminal roots and enabling seed dormancy, while the absence of ABA accumulation in coleorhiza of AZ34 may be responsible for the initiation of root germination inside the caryopsis. The abundance of HvPIP2 AQPs in the seminal roots was higher at the beginning of maturation of Steptoe caryopsis and declined afterwards, while the levels of APQs increased later in AZ34 in accordance with the delay in ABA accumulation. These results suggest the importance of ABA accumulation in coleorhiza for preventing precocious growth of seminal roots, and suggest regulation of IAA and aquaporin levels by this hormone during maturation of embryos.
Neuropsychological Trajectories Associated with Adolescent Alcohol and Cannabis Use: A Prospective 14-Year Study
Authors: Infante M. Alejandra , Nguyen-Louie Tam T. , Worley Matthew , Courtney Kelly E. , Coronado Clarisa , Jacobus Joanna
Published: December 2019

Objectives:

Alcohol and cannabis remain the substances most widely used by adolescents. Better understanding of the dynamic relationship between trajectories of substance use in relation to neuropsychological functioning is needed. The aim of this study was to examine the different impacts of within- and between-person changes in alcohol and cannabis use on neuropsychological functioning over multiple time points.

Methods:

Hierarchical linear modeling examined the effects of alcohol and cannabis use on neuropsychological functioning over the course of 14 years in a sample of 175 adolescents (aged 12–15 years at baseline).

Results:

Time-specific fluctuations in alcohol use (within-person effect) predicted worse performance across time on the Wechsler Abbreviated Scale of Intelligence Block Design subtest (B = −.05, SE = .02, p = .01). Greater mean levels of percent days of cannabis use across time (between-person effect) were associated with an increased contrast score between Delis–Kaplan Executive Function System Color Word Inhibition and Color Naming conditions (B = .52, SE = .14, p < .0001) and poorer performance over time on Block Design (B = −.08, SE = .04, p = .03). Neither alcohol and/nor cannabis use over time was associated with performance in the verbal memory and processing speed domains.

Conclusions:

Greater cumulative cannabis use over adolescence may be linked to poorer inhibitory control and visuospatial functioning performance, whereas more proximal increases in alcohol consumption during adolescence may drive alcohol-related performance decrements in visuospatial functioning. Results from this prospective study add to the growing body of literature on the impact of alcohol and cannabis use on cognition from adolescent to young adulthood.
Je älter der Bergwanderer, umso schwerer die Verletzung – eine retrospektive Analyse der Bergwanderunfälle aus den Schweizer Alpen in den Jahren 2009–2018
Authors: Gasser Benedikt
Published: December 2019

Zusammenfassung. Bergwandern stellt eine häufige Aktivität von Betagten dar. Inwiefern jedoch dadurch besondere Risiken entstehen, ist weitgehend unbeantwortet. Insgesamt wurden 10 185 Bergnotfälle beim Wandern im Zeitraum von 2009 bis 2018 anhand des Registers des Schweizer Alpen-Clubs analysiert, was es erlaubte, Regressionen zwischen dem Alter der Verunglückten und dem NACA-Score zu berechnen. Trotz methodischer Limitationen kann aufgezeigt werden, dass ältere Bergwanderer höhere NACA-Werte aufweisen als jüngere bzw. im höheren Alter die Bergnotfälle gravierender waren. Die tendenziell schwereren Bergnotfälle bei älteren Bergwanderern können auf verschiedene Ursachen zurückgeführt werden. Insbesondere die bedeutendste Klasse der Stürze ist zu erwähnen, da vermutlich bedingt durch die altersverursachte Abnahme der posturalen Stabilität schwerere Ereignisse resultieren und oft aus einem simplen Stolpersturz ein Absturz wird.
Testing the Radiation Pattern of Meteor Radio Afterglow
Authors: Varghese S. S. , Obenberger K. S. , Taylor G. B. , Dowell J.
Published: December 2019

Radio emission from meteors or meteor radio afterglows (MRAs) was first detected using the all‐sky imaging capabilities of the first station of the Long Wavelength Array (LWA1). In this work, we use the recently commissioned LWA Sevilleta (LWA‐SV) station along with the LWA1 to carry out coordinated observations. The combined all‐sky observations with LWA1 and LWA‐SV have coobserved 32 MRAs and 21 transmitter reflections from meteors (meteor scatter events), which are believed to be specular reflections from overdense trails. The flux density of the events observed by each station was measured from the all‐sky images. Triangulating the angular direction of events from each station gave the physical location and the distance of the event to each station. The luminosity of the events in each station was calculated using the flux distance relation for an isotropic source. The luminosity distribution for MRAs and meteor scatter events observed by each station shows a clear distinction between these two types of events as the ratio of luminosities is closer to unity for MRAs than the meteor scatter events. Furthermore, we find that MRAs follow an isotropic radiation pattern. This suggests, either a complete incoherent emission mechanism or an incoherent addition of coherently emitting small regions within the meteor trail.
Collapse of Reacted Fracture Surface Decreases Permeability and Frictional Strength
Authors: Spokas K. , Fang Y. , Fitts J. P. , Peters C. A. , Elsworth D.
Published: December 2019

Geochemical and geomechanical perturbations of the subsurface caused by the injection of fluids present risks of leakage and seismicity. This study investigated how acidic fluid flow affects hydraulic and frictional properties of fractures using experiments with 3.8‐cm‐long specimens of Eagle Ford shale, a laminated shale with carbonate‐rich strata. In low‐pressure flow cells, one set of samples was exposed to acidic brine and another set was exposed to neutral brine. X‐ray computed tomography and energy‐dispersive X‐ray spectroscopy revealed that samples exposed to acidic brine were calcite‐depleted and had developed a porous altered layer, while the other set showed no evidence of alteration. After reaction, samples were compressed and sheared in a triaxial cell that supplied normal stress and differential pore pressure at prescribed sliding velocities, independently measuring friction and permeability. During the initial compression, the porous altered layer collapsed into fine particles that filled the fracture. This effectively impeded flow and sealed the fracture, resulting in fracture permeability to decrease 1 to 2 orders of magnitude relative to the unaltered fractures. This is a favorable outcome in subsurface applications where the goal is to reduce leakage risks. However, during shear the reacted fracture had lower frictional strength because the fine‐grained particles in the collapsed layer prevented the formation of interlocking microasperities. Therefore, coupled geochemical and geomechanical processes that could favorably seal fractures could also increase the likelihood of induced seismicity. These findings have important implications for geological carbon sequestration, pressurized fluid energy storage, geothermal energy, and other subsurface technologies.
Adakite‐Like Potassic Magmatism and Crust‐Mantle Interaction in a Postcollisional Setting: An Experimental Study of Melting Beneath the Tibetan Plateau
Authors: Wang Xiong , Zhang Junfeng , Rushmer Tracy , Adam John , Turner Simon , Xu Wangchun
Published: December 2019

Adakite‐like potassic rocks are widespread in postcollisional settings where they provide potential insights into deep crustal processes that include partial melting, lower crustal flow and thickening, plateau uplift, and the creation of porphyry metal deposits. Although substantial progress has been made in characterizing the geochemical and geophysical features of postcollisional adakite‐like potassic rocks, their petrogenesis remains controversial. Here we report direct experimental evidence for the origins of these rocks with partial melting experiments on (1) garnet amphibolite and (2) the same garnet amphibolite mixed with 20 wt. % of a primitive Tibetan shoshonite. The experiments were conducted at 1.5–2.0 GPa and 800–1,000 °C. The partial melts of garnet amphibolite have typical adakitic signatures and are calc‐alkalic but lack the enrichment in potassium and other strongly incompatible elements (Rb, Ba, Th, U) that are characteristic of Tibetan adakite‐like rocks. In contrast, all characteristic features of the natural adakite‐like rocks are convincingly reproduced by the hybrid experiments. This includes negative inflections for Nb, Ta, and Ti on mantle‐normalized plots which are inherited from source materials rather than the effects of rutile in melting residues. The input of mantle‐derived shoshonitic mafic melts to a crustal source can be argued to provide not only the high concentrations of incompatible elements characteristic of adakite‐like potassic magmas but also the heat necessary for crustal melting. Our experimental results demonstrate that, in the case of the Tibetan Plateau at least, the production of adakite‐like potassic rocks in postcollisional settings can be best explained by such a model.
Weeks‐Long and Years‐Long Slow Slip and Tectonic Tremor Episodes on the South Central Alaska Megathrust
Authors: Rousset Baptiste , Fu Yuning , Bartlow Noel , Bürgmann Roland
Published: December 2019

We jointly investigate aseismic slip transients and tremor activity in south central Alaska. Near the eastern downdip edge of the Mw 9.2 1964 Prince Williams earthquake rupture, kinematic modeling of the Mw=7.6 2009–2013 slow slip event suggests cumulative transient slip of up to 55 cm. During this 5‐year transient event, tectonic tremors were co‐located with the inferred aseismic slip zone and occurred in weeks‐long bursts of events. A short‐term transient deformation event is observed in the GPS time series spanning a tremor burst in September 2010. The time‐dependent slip modeling of this Mw=6.9 subevent shows that it migrated along strike with tremor at speeds of ∼8 km/day and with slip rates of ∼3 mm/day. It released 9% of the 5‐year transient event total moment in 1.4% of its duration. The decomposition of GPS time series relative to tremor times during the whole 5‐year transient event shows that GPS site velocities were on average three to six times higher during tremor bursts than in between, suggesting that slip pulses are generally associated with tremor bursts. This inference is strengthened by the decomposition of the GPS time series after the 5‐years‐long deformation event, during which the plate interface is being loaded in between the short‐duration events and slips at times of tremor bursts. The 5‐years‐long transient deformation event could either represent a cluster of short‐term events or be the sum of short‐term ETS events and a smooth long‐term slip event located updip.
An Experimental Investigation of Acceleration‐Skewed Oscillatory Flow Over Vortex Ripples
Authors: Yuan Jing , Wang Dongxu
Published: December 2019

A full‐scale experimental study of acceleration‐skewed oscillatory flow over vortex ripples, which is an approximation of wave‐driven flow over a rippled seabed, was conducted in an oscillatory water tunnel. Three acceleration‐skewed‐flow tests and a reference sinusoidal‐flow tests were involved in this study. In each test, two‐dimensional vortex ripples were generated from a coarse‐sand movable bed, and the flow field was measured with a particle image velocimetry. The dominant feature of phase‐averaged flow is the generation of onshore (offshore) coherent vortices during the onshore (offshore) half‐cycle. The acceleration skewness expedites the offshore‐onshore flow reversal and therefore speeds up the ejection of offshore vortex, while the opposite occurs for the onshore vortex. The ripple‐averaged flow is similar to the acceleration‐skewed turbulent oscillatory flow over a flat bed in terms of leading Fourier harmonics, boundary layer thickness, and cycle‐averaged flow, suggesting a possible analogy between the two. From the aspect of flow turbulence, acceleration skewness elongates the offshore accelerating quarter, so the turbulence embedded in the offshore vortex can be better developed. This, together with a quick ejection process, allows the offshore vortex to carry a significant amount of residual turbulence to the onshore‐side ripple flank, which may even enhance the production of turbulence within the onshore half‐cycle. Some results on pressure field and form drag are also presented in this paper.
Coastal Ocean Response and Its Feedback to Typhoon Hato (2017) Over the South China Sea: A Numerical Study
Authors: Zhang Ze , Wang Yuqing , Zhang Weimin , Xu Jing
Published: December 2019

The coastal ocean response and feedback to Typhoon Hato (2017) were studied based on high‐resolution numerical simulations using both a coupled and an uncoupled cloud‐resolving model. As a category 3 landfalling typhoon that moved west‐northwestward across the northern South China Sea, Hato (2017) rapidly intensified prior to its landfall and induced significant impacts on the coastal water column, causing warm and cold patches in sea surface temperature (SST) over the continental shelf to the right of the track. This feature was well captured in an air‐sea coupled model experiment. The coastal SST warming was found to be related to a two‐layer oceanic circulation across the continental shelf forced by the onshore surface wind stress to the right of the storm track. The associated onshore surface currents imposed a warm temperature advection and downwelling, leading to the SST warming in the inner sea shelf, as diagnosed from an ocean temperature budget analysis. A sensitivity experiment, in which the typhoon vortex was removed from the initial conditions, further confirmed that it was the strong onshore wind stress to the right of the storm track that forced the onshore surface currents and the SST warming in the inner sea shelf. Results from an atmosphere‐only model experiment with the typhoon‐forced coastal warm SST anomalies removed demonstrate that the typhoon‐induced coastal warm SST anomalies contributed partly to the rapid intensification of Typhoon Hato prior to its landfall over South China and also slowed down the weakening of Hato at and shortly after its landfall.
Identifying Source Regions and the Distribution of Cross‐Tropopause Convective Outflow Over North America During the Warm Season
Authors: Clapp C.E. , Smith J.B. , Bedka K.M. , Anderson J.G.
Published: December 2019

We analyzed the interaction between the North American monsoon anticyclone (NAMA) and summertime cross‐tropopause convective outflow by applying a trajectory analysis to a climatology of convective overshooting tops (OTs) identified in GOES satellite images, which covers the domain from 29°S to 68°N and from 205 to 1.25°W for the time period of May through September 2013. With this analysis we identified seasonally, geographically, and altitude‐dependent variability in NAMA strength and in cross‐tropopause convection that control their interaction. We find that the NAMA has the strongest impact on the circulation of convectively influenced air masses in August. Over the entire time period examined the intertropical convergence zone contributes the majority of OTs with a larger fraction of total OTs at 370 K (on average 70%) than at 400 K (on average 52%). During August at 370 K, the convectively influenced air masses within the NAMA circulation, as determined by the trajectory analysis, are primarily sourced from the intertropical convergence zone (monthly average of 66.1%), while at 400 K the Sierra Madres and the Central United States combined constitute the dominant source region (monthly average of 44.1%, compared to 36.6% of the combined Intertropical Convergence Zone regions). When evaluating the impact of cross‐tropopause convection on the composition and chemistry of the upper troposphere and lower stratosphere, the effects of the NAMA on both the distribution of convective outflow and the residence time of convectively influenced air masses within the NAMA region must be considered.
A Big Root Approximation of Site‐Scale Vegetation Water Uptake
Authors: Bouda Martin
Published: December 2019

Land surface model (LSM) predictions of soil moisture and transpiration under water‐limited conditions suffer from biases due to a lack of mechanistic process description of vegetation water uptake. Here, I derive a “big root” approach from the porous pipe equation for root water uptake and compare its predictions of soil moistures during the 2010 summer drought at the Wind River Crane site to two previously used Ohm's law analog plant hydraulic models. Due to a fuller representation of pressure gradients and flows within a complex root system architecture, the new formulation achieves somewhat improved fit and significantly lower bias compared to the Ohm's law analog models. A key advantage of the improved physical representation is the increased robustness of fits and predictions, making it less liable to overfitting. This new mechanistic model advances our understanding of vegetation water limitation at site scale with potential to improve LSM predictions of soil moisture, temperature and surface heat, water, and carbon fluxes.
Improving Neutral Density Predictions Using Exospheric Temperatures Calculated on a Geodesic, Polyhedral Grid
Authors: Weimer D. R. , Mehta P. M. , Tobiska W. K. , Doornbos E. , Mlynczak M. G. , Drob D. P. , Emmert J. T.
Published: December 2019

A new model of exospheric temperatures has been developed, with the objective of predicting global values with greater spatial and temporal accuracy. From these temperatures, the neutral densities in the thermosphere can be calculated, through use of the Naval Research Laboratory Mass Spectrometer and Incoherent Scatter radar Extended (NRLMSISE‐00) model. The exospheric temperature model is derived from measurements of the neutral densities on several satellites. These data were sorted into triangular cells on a geodesic grid, based on location. Prediction equations are derived for each grid cell using least error fits. Several versions of the model equations have been tested, using parameters such as the date, time, solar radiation, and nitric oxide emissions, as measured with the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument on the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) satellite. Accuracy is improved with the addition of the total Poynting flux flowing into the polar regions, from an empirical model that uses the solar wind velocity and interplanetary magnetic field. Given such inputs, the model can produce global maps of the exospheric temperature. These maps show variations in the polar regions that are strongly modulated by the time of day, due to the daily rotation of the magnetic poles. For convenience the new model is referred to with the acronym EXTEMPLAR (EXospheric TEMperatures on a PoLyhedrAl gRid). Neutral densities computed from the EXTEMPLAR‐NRLMSISE‐00 models combined are found to produce very good results when compared with measured values.
Perspectives on Continental Rifting Processes From Spatiotemporal Patterns of Faulting and Magmatism in the Rio Grande Rift, USA
Authors: Abbey Alyssa L. , Niemi Nathan A.
Published: December 2019

Analysis of spatiotemporal patterns of faulting and magmatism in the Rio Grande rift (RGR) in New Mexico and Colorado, USA, yields insights into continental rift processes, extension accommodation mechanisms, and rift evolution models. We combine new apatite (U‐Th‐Sm)/He and zircon (U‐Th)/He thermochronometric data with previously published thermochronometric data to assess the timing of fault initiation, magnitudes of fault exhumation, and growth and linkage patterns of rift faults. Thermal history modeling of these data reveals contemporaneous rift initiation at ca. 25 Ma in both the northern and southern RGR with continued fault initiation, growth, and linkage progressing from ca. 25 to ca. 15 Ma. The central RGR, however, shows no evidence of Cenozoic fault‐related exhumation as observed with thermochronometry and instead reveals extension accommodated through Late Cenozoic magmatic injection. Furthermore, faulting in the northern and southern RGR occurs along an approximately north‐south strike, whereas magmatism in the central RGR occurs along the northeast to southwest trending Jemez lineament. Differences in deformation orientation and rift accommodation along strike appear to be related to crustal and lithospheric properties, suggesting that rift structure and geometry are at least partly controlled by inherited lithospheric‐scale architecture. We propose an evolutionary model for the RGR that involves initiation of fault‐accommodated extension by oblique strain followed by block rotation of the Colorado Plateau, where extension in the RGR is accommodated by faulting (southern and northern RGR) and magmatism (central RGR). This study highlights different processes related to initiation, geometry, extension accommodation, and overall development of continental rifts.
Bankfull Transport Capacity and the Threshold of Motion in Coarse‐Grained Rivers
Authors: Phillips C. B. , Jerolmack D. J.
Published: December 2019

The threshold stress for bed sediment transport exerts a primary control on the geometry and stability of coarse‐grained rivers (diameter ≥ 5 mm). Understanding how riverbed mobility couples to channel form is a key mechanistic link for predicting river response to external perturbations such as land use practices and changing climate. Unfortunately, determination of a representative threshold stress is notoriously difficult in the field. Empirical studies have observed that the critical dimensionless shear (Shields) stress (τ*c) is correlated with channel slope, a property that is substantially easier to estimate. Mechanistic models have been developed to explain the observed correlation; however, limited field data preclude the widespread application of these models. For practical reasons, the empirical regressions between slope and τ*c are utilized as predictive models. Through a large compilation of field data, we demonstrate that there are two significant problems with using the empirical regressions: (1) they are based on a partial sampling of the observed parameter space of coarse‐grained rivers, and (2) they do not capture the covariation between the bankfull Shields stress (τ*bf) and τ*c. These regressions provide spurious predictions for the bankfull transport capacity (τ*bf/τ*c) of gravel‐bed rivers. When site‐specific empirical measurements of τ*c are made, coarse‐grained rivers exhibit a remarkably constant transport capacity that is in close agreement with equilibrium channel theory (τ*bf = 1.2τ*c). From these data we advocate that, in the absence of measurements, τ*c can be reasonably estimated from the τ*bf using equilibrium channel theory.
How Important is Denitrification in Riparian Zones? Combining End‐Member Mixing and Isotope Modeling to Quantify Nitrate Removal from Riparian Groundwater
Authors: Lutz Stefanie R. , Trauth Nico , Musolff Andreas , Van Breukelen Boris M. , Knöller Kay , Fleckenstein Jan H.
Published: December 2019

Riparian zones are important buffer zones for streams as they are hotspots of nitrate transformation and removal in agricultural catchments. However, mixing of water from different sources and various transformation processes can complicate the quantification of nitrate turnover in riparian zones. In this study, we analyzed nitrate concentration and isotope data in riparian groundwater along a 2‐km stream section in central Germany. We developed a mathematical model combining end‐member mixing and isotope modeling to account for mixing of river water and groundwater and quantify nitrate transformation in riparian groundwater. This enabled us to explicitly determine the extent of denitrification (as process leading to permanent nitrate removal from riparian groundwater) and transient nitrate removal by additional processes associated with negligible isotope fractionation (e.g., plant uptake and microbial assimilation) and to perform an extensive uncertainty analysis. Based on the nitrogen isotope data of nitrate, the simulations suggest a mean removal of up to 28% by additional processes and only about 9% by denitrification. Nitrate removal from riparian groundwater by additional processes exceeded denitrification particularly in winter and at larger distance from the river, underlining the role of the river as organic carbon source. This highlights that nitrate consumption by additional processes predominates at the field site, implying that a substantial fraction of agricultural nitrogen input is not permanently removed but rather retained in the riparian zone. Overall, our model represents a useful tool to better compare nitrogen retention to permanent nitrogen removal in riparian zones at various temporal and spatial scales.
Sensing Area‐Average Snow Water Equivalent with Cosmic‐Ray Neutrons: The Influence of Fractional Snow Cover
Authors: Schattan P. , Köhli M. , Schrön M. , Baroni G. , Oswald S. E.
Published: December 2019

Cosmic‐ray neutron sensing (CRNS) is a promising non‐invasive technique to estimate snow water equivalent (SWE) over large areas. In contrast to preliminary studies focusing on shallow snow conditions (SWE
130 mm), more recently the method was shown experimentally to be sensitive also to deeper snowpacks providing the basis for its use at mountain experimental sites. However, hysteretic neutron response has been observed for complex snow cover including patchy snow‐free areas. In the present study we aimed to understand and support the experimental findings using a comprehensive neutron modeling approach. Several simulations have been set up in order to disentangle the effect on the signal of different land surface characteristics and to reproduce multiple observations during periods of snow melt and accumulation. To represent the actual land surface heterogeneity and the complex snow cover, the model used data from terrestrial laser scanning. The results show that the model was able to accurately reproduce the CRNS signal and particularly the hysteresis effect during accumulation and melting periods. Moreover, the sensor footprint was found to be anisotropic and affected by the spatial distribution of liquid water and snow as well as by the topography of the nearby mountains. Under fully snow‐covered conditions the CRNS is able to accurately estimate SWE without prior knowledge about snow density profiles or other spatial anomalies. These results provide new insights into the characteristics of the detected neutron signal in complex terrain and support the use of CRNS for long‐term snow monitoring in high elevated mountain environments.
Satellite‐Based Assessment of Land Surface Energy Partitioning–Soil Moisture Relationships and Effects of Confounding Variables
Authors: Feldman Andrew F. , Short Gianotti Daniel J. , Trigo Isabel F. , Salvucci Guido D. , Entekhabi Dara
Published: December 2019

Land surface energetic partitioning between latent, sensible, and ground heat fluxes determines climate and influences the terrestrial segment of land‐atmosphere coupling. Soil moisture, among other variables, has a direct influence on this partitioning. Dry surfaces characterize a water‐limited regime where evapotranspiration and soil moisture are coupled. This coupling is subdued for wet surfaces, or an energy‐limited regime. This framework is commonly evaluated using the evaporative fraction–‐soil moisture relationship. However, this relationship is explicitly or implicitly prescribed in land surface models. These impositions, in turn, confound model‐based evaluations of energetic partitioning‐–soil moisture relationships. In this study, we use satellite‐based observations of surface temperature diurnal amplitude (directly related to available energy partitioning) and soil moisture, free of model impositions, to estimate characteristics of surface energetic partitioning–‐soil moisture relationships during 10–‐20‐day surface drying periods across Africa. We specifically estimate the spatial patterns of water‐limited energy flux sensitivity to soil moisture (m) and the soil moisture threshold separating water and energy‐limited regimes (θ*). We also assess how time evolution of other factors (e.g., solar radiation, vapor pressure deficit, surface albedo, and wind speed) can confound the energetic partitioning–‐soil moisture relationship. We find higher m in drier regions and interestingly similar spatial θ* distributions across biomes. Vapor pressure deficit and insolation increases during drying tend to increase m. Only vapor pressure deficit increases in the Sahelian grasslands systematically decrease θ*. Ultimately, soil and atmospheric moisture availability together play the largest role in land surface energy partitioning with minimal consistent influences of time evolution of other forcings.
Examining Observed Rainfall, Soil Moisture, and River Network Variabilities on Peak Flow Scaling of Rainfall‐Runoff Events with Implications on Regionalization of Peak Flow Quantiles
Authors: Perez Gabriel , Mantilla Ricardo , Krajewski Witold F. , Quintero Felipe
Published: December 2019

The scaling of peak flows associated with a probability of exceedance (Qp) or a specific rainfall‐runoff event (QR) with respect to drainage area (A) is known as flood scaling and it has been widely used in peak flow regionalization. The attenuation and aggregation processes within the hillslopes and river network in a rainfall‐runoff event, provide a framework to test the scaling of QR. Although scaling of Qp has been reported in empirical studies, its physical interpretation is compromised, since Qp at each site could come from different rainfall‐runoff events. To address this problem, the authors explored the effect of actual variabilities of rainfall and soil moisture fields, and the effect of the river network structure, in the scaling of peak flows of 85 rainfall‐runoff events and peak flow quantiles that were observed in the Iowa River Basin at 43 streamflow gauges. The authors established empirical evidence that addresses two questions: (1) What does control the performance of the scaling of observed QR? (2) What is the interplay between sampling errors and the selection of explanatory variables in the construction of regional regression models for QR and Qp? For the first question, the authors found that the slope magnitude in the scaling of the rainfall intensity fields with respect to A controls the scaling' performance of QR. Regarding the second question, the authors demonstrate that the inclusion of river network descriptors should improve the regional equations to estimate peak flow quantiles unless stream gauging sampling errors affect the analysis.
Microbial community and geochemical analyses of trans-trench sediments for understanding the roles of hadal environments
Authors: Hiraoka Satoshi , Hirai Miho , Matsui Yohei , Makabe Akiko , Minegishi Hiroaki , Tsuda Miwako , Juliarni  , Rastelli Eugenio , Danovaro Roberto , Corinaldesi Cinzia , Kitahashi Tomo , Tasumi Eiji , Nishizawa Manabu , Takai Ken , Nomaki Hidetaka , Nunoura Takuro
Published: December 2019

Hadal trench bottom (>6000 m below sea level) sediments harbor higher microbial cell abundance compared with adjacent abyssal plain sediments. This is supported by the accumulation of sedimentary organic matter (OM), facilitated by trench topography. However, the distribution of benthic microbes in different trench systems has not been well explored yet. Here, we carried out small subunit ribosomal RNA gene tag sequencing for 92 sediment subsamples of seven abyssal and seven hadal sediment cores collected from three trench regions in the northwest Pacific Ocean: the Japan, Izu-Ogasawara, and Mariana Trenches. Tag-sequencing analyses showed specific distribution patterns of several phyla associated with oxygen and nitrate. The community structure was distinct between abyssal and hadal sediments, following geographic locations and factors represented by sediment depth. Co-occurrence network revealed six potential prokaryotic consortia that covaried across regions. Our results further support that the OM cycle is driven by hadal currents and/or rapid burial shapes microbial community structures at trench bottom sites, in addition to vertical deposition from the surface ocean. Ourtrans-trench analysis highlights intra- and inter-trench distributions of microbial assemblages and geochemistry in surface seafloor sediments, providing novel insights into ultradeep-sea microbial ecology, one of the last frontiers on our planet.
The enemy from within: a prophage of Roseburia intestinalis systematically turns lytic in the mouse gut, driving bacterial adaptation by CRISPR spacer acquisition
Authors: Cornuault Jeffrey K , Moncaut Elisabeth , Loux Valentin , Mathieu Aurélie , Sokol Harry , Petit Marie-Agnès , De Paepe Marianne
Published: December 2019

Despite an overall temporal stability in time of the human gut microbiota at the phylum level, strong variations in species abundance have been observed. We are far from a clear understanding of what promotes or disrupts the stability of microbiome communities. Environmental factors, like food or antibiotic use, modify the gut microbiota composition, but their overall impacts remain relatively low. Phages, the viruses that infect bacteria, might constitute important factors explaining temporal variations in species abundance. Gut bacteria harbour numerous prophages, or dormant viruses, which can evolve to become ultravirulent phage mutants, potentially leading to important bacterial death. Whether such phenomenon occurs in the mammal’s microbiota has been largely unexplored. Here we studied temperate phage–bacteria coevolution in gnotoxenic mice colonised with Roseburia intestinalis, a dominant symbiont of the human gut microbiota, and Escherichia coli, a sub-dominant member of the same microbiota. We show that R. intestinalis L1-82 harbours two active prophages, Jekyll and Shimadzu. We observed the systematic evolution in mice of ultravirulent Shimadzu phage mutants, which led to a collapse of R. intestinalis population. In a second step, phage infection drove the fast counter-evolution of host phage resistance mainly through phage-derived spacer acquisition in a clustered regularly interspaced short palindromic repeats array. Alternatively, phage resistance was conferred by a prophage originating from an ultravirulent phage with a restored ability to lysogenize. Our results demonstrate that prophages are a potential source of ultravirulent phages that can successfully infect most of the susceptible bacteria. This suggests that prophages can play important roles in the short-term temporal variations observed in the composition of the gut microbiota.
Long-term nutrient inputs shift soil microbial functional profiles of phosphorus cycling in diverse agroecosystems
Authors: Dai Zhongmin , Liu Guofei , Chen Huaihai , Chen Chengrong , Wang Jingkuan , Ai Shaoying , Wei Dan , Li Daming , Ma Bin , Tang Caixian , Brookes Philip C , Xu Jianming
Published: December 2019

Microorganisms play an important role in soil phosphorus (P) cycling and regulation of P availability in agroecosystems. However, the responses of the functional and ecological traits of P-transformation microorganisms to long-term nutrient inputs are largely unknown. This study used metagenomics to investigate changes in the relative abundance of microbial P-transformation genes at four long-term experimental sites that received various inputs of N and P nutrients (up to 39 years). Long-term P input increased microbial P immobilization by decreasing the relative abundance of the P-starvation response gene (phoR) and increasing that of the low-affinity inorganic phosphate transporter gene (pit). This contrasts with previous findings that low-P conditions facilitate P immobilization in culturable microorganisms in short-term studies. In comparison, long-term nitrogen (N) input significantly decreased soil pH, and consequently decreased the relative abundances of total microbial P-solubilizing genes and the abundances of Actinobacteria, Gammaproteobacteria, and Alphaproteobacteria containing genes coding for alkaline phosphatase, and weakened the connection of relevant key genes. This challenges the concept that microbial P-solubilization capacity is mainly regulated by N:P stoichiometry. It is concluded that long-term N inputs decreased microbial P-solubilizing and mineralizing capacity while P inputs favored microbial immobilization via altering the microbial functional profiles, providing a novel insight into the regulation of P cycling in sustainable agroecosystems from a microbial perspective.