bluuebunny/crossref_metadata_2025 huggingface dataset:
Radar Observations of Flows Leading to Longitudinal Expansion of Substorm Onset Over Alaska
Authors: Lyons Larry R. , Liu Jiang , Nishimura Yukitoshi , Wang Chih‐Ping , Reimer Ashton S. , Bristow William A. , Hampton Don L. , Shi Xueling , Varney Roger H. , Donovan Eric F.
Published: February 2021

Longitudinal expansion of brightening of the substorm onset arc likely represents longitudinal expansion of the substorm onset instability. We used Poker Flat radar campaign auroral observations to identify seven substorm onsets seen east or west of the radar that expanded into the radar field‐of‐view. The radar observations were used to show flows relative to the expanding onset aurora. Flow enhancements were found equatorward (poleward) of the westward (eastward) longitudinal expansion of the onset arc brightening that agree with plasma sheet bubble modeling. This lends significant additional supporting evidence that an incoming reduced entropy flow channel leads to onset. As a flow channel enters the auroral oval (plasma sheet) from the polar cap (magnetotail lobes) and starts to move equatorward (earthward in the plasma sheet) as a bubble, it simultaneously expands azimuthally due to the combination of electric drift along dawnward tilted equipotentials and westward magnetic drift of more energetic ions. As the azimuthally expanding bubble reaches near the equatorward boundary of the electron auroral oval, it leads to the onset instability indicated by the auroral beading and associated flows if conditions are appropriate. The instability grows in the initial onset region, as it simultaneously extends longitudinally with the continued azimuthal expansion of the bubble within the plasma sheet. Additionally, after onset, the auroral bulge expands poleward and can lead to a westward traveling surge. We observe strong flows heading toward the front of the surge that appear to bring low entropy plasma, perhaps from the polar cap, into the surge.
Thermospheric Impact on the Magnetosphere Through Ionospheric Outflow
Authors: Pham K. H. , Lotko W. , Varney R. H. , Zhang B. , Liu J.
Published: February 2021

We have taken a key step in evaluating the importance of ionospheric outflows relative to electrodynamic coupling in the thermosphere’s impact on geospace dynamics. We isolated the thermosphere’s material influence and suppressed electrodynamic feedback in whole geospace simulations by imposing a time‐constant ionospheric conductance in the ionospheric Ohm’s law in a coupled model that combines the multifluid Lyon‐Fedder‐Mobarry magnetosphere model with the Thermosphere Ionosphere Electrodynamic General Circulation Model and the Ionosphere Polar Wind Model that includes both polar wind and transversely accelerated ion species. Numerical experiments were conducted for different thermospheric states parameterized by F10.7 for interplanetary driving representative of the stream interaction region that swept past Earth on March 27, 2003. We demonstrate that thermosphere through its regulation of ionospheric outflows influences magnetosphere‐ionosphere (MI) convection and the ion composition, symmetries, x‐line perimeter and magnetic merging of the magnetosphere. Feedback to the ionosphere‐thermosphere from evolving MI convection, and Alfvénic Poynting fluxes and soft (∼few 100 eV) electron precipitation originating in the magnetosphere, in turn, modify the evolving O+ outflow properties. The simulation results identify a variety of observed magnetospheric features that are attributable directly to the thermosphere’s material influence: Asymmetries in O+ outflow fluxes and velocities in the pre/postnoon low‐altitude magnetosphere, dawn/duskside lobes and pre/postmidnight plasmasheet; O+ distribution of the plasmasheet; magnetic x‐line location and reconnection rate along it. O+ outflows during solar maximum conditions (high F10.7) tend to counteract the plasmasheet’s pre/postmidnight asymmetries caused by the night‐to‐day gradient in ionospheric Hall conductance.
Spatiotemporal Variations of Quiet Time Equatorial Ionosphere Longitudinal Structure Under Low Solar Activity
Authors: Hou Weijun , Xu Buyun , Wang Hongxia , Li Yihong , Li Xihai , Liu Daizhi
Published: February 2021

The low‐latitude longitudinally periodic density structure with three or four peaks at a fixed local time is well known. Both harmonic analysis of observations and numerical simulations have been extensively performed to ascribe the periodic structures to different atmospheric tides. But to date, no research has been done to explain how the two structures transform between seasons. Besides, other different wave structures have also been reported. To clarify these uncertainties, the COSMIC electron density data during 2006–2019 are used to further examine the spatiotemporal variations of the longitudinal structure. The results show that a wavenumber‐4 structure is clearly distinguishable during equinoxes and the four peaks are basically the same size, but in two solstices, a wavenumber‐3 structure is finally observed and the three peaks vary greatly in size. The wavenumber‐4 is well established before noon while the stable wavenumber‐3 form cannot be reached until after noon. Due to the blurred boundary caused by plasma transportation, the density distribution can be characterized by other wave structures before reaching its stable form during solstices. Subdividing the data, we find that from vernal (autumn) equinox to June (December) solstice, the peak in American sector gradually merges with its west (east) side peak into a super‐large one, its east (west) side peak weakens into a small one, and the peak in Southeast Asian sector gradually shrinks (expands). We speculate that the transition from wavenumber‐4 to wavenumber‐3 is due to the modulation of transequatorial winds and magnetic declination.
Evolution of Microstructural Properties in Sheared Iron‐Rich Olivine
Authors: Qi Chao , Zhao Yong‐Hong , Zimmerman Mark E. , Kim Daeyeong , Kohlstedt David L.
Published: February 2021

Iron‐rich olivine is mechanically weaker than olivine of mantle composition, ca. Fo90, and thus is more amenable to study under a wide range of laboratory conditions. To investigate the effects of iron content on deformation‐produced crystallographic preferred orientation (CPO) and grain size, we analyzed the microstructures of olivine samples with compositions of Fo70, Fo50, and Fo0 that were deformed in torsion under either anhydrous or hydrous conditions at 300 MPa. Electron backscatter diffraction (EBSD) observations reveal a transition in CPO from D‐type fabric, induced by dislocation glide on both the (010)[100] and the (001)[100] slip systems, at low strains, to A‐type fabric, caused by dislocation glide on the (010)[100] slip system, at high strains for all of our samples, independent of iron content and hydrous/anhydrous conditions. A similar evolution of fabric with increasing strain is also reported to occur for Fo90. Radial seismic anisotropy increases with increasing strain, reaching a maximum value of ∼1.15 at a shear strain of ∼3.5 for each sample, demonstrating that the seismic anisotropy of naturally deformed olivine‐rich rocks can be well approximated by that of iron‐rich olivine. Based on EBSD observations, we derived a piezometer for which recrystallized grain size decreases inversely with stress to the ∼1.2 power. Also, recrystallized grain size increases with increasing iron content. Our experimental results contribute to understanding the microstructural evolution in the mantle of not only Earth but also Mars, where the iron content in olivine is higher.
Ground Deformation After a Caldera Collapse: Contributions of Magma Inflow and Viscoelastic Response to the 2015–2018 Deformation Field Around Bárðarbunga, Iceland
Authors: Li Siqi , Sigmundsson Freysteinn , Drouin Vincent , Parks Michelle M. , Ófeigsson Benedikt G. , Jónsdóttir Kristín , Grapenthin Ronni , Geirsson Halldór , Hooper Andrew , Hreinsdóttir Sigrún
Published: February 2021

Improvement of our understanding of the role of ground deformation due to viscoelastic relaxation following eruptions is important, as the generated signals can resemble renewed magma inflow. We study post‐eruptive unrest at the subglacial Bárðarbunga volcano, Iceland, after a caldera collapse and major magma drainage in 2014–2015. Elevated seismicity began about 6 months after the eruption ended, including nine Mlw > 4.5 earthquakes. Global Navigation Satellite System and Sentinel‐1 Interferometric Synthetic Aperture Radar geodesy are applied to evaluate post‐eruptive ground deformation from 2015 to 2018. Horizontal velocities locally exceed 10 cm/year and rapidly decay with distance away from the caldera. We explore two end‐member models and their combination to explain the post‐eruptive deformation field: 1) viscoelastic relaxation caused by the co‐eruptive caldera collapse and magma withdrawal, and 2) renewed magma inflow. We find parameter combinations for each model that explain the observed ground deformation. The purely viscoelastic relaxation model, consisting of a half‐space composed of a 7‐km thick elastic layer on top of a viscoelastic layer with a viscosity of 3.0 × 1018 Pa s reproduces broadly the observations. A simple magma inflow model consisting of a single point source with an inflow rate of 1 × 107 m3/year at 0.7 km depth broadly fits the observations, but may be unrealistic. A more elaborate model of magma inflow into a 10‐km deep sill combined with slip on the caldera ring fault explains the observations well. Our results suggest that the co‐eruptive deformation field is likely influenced by viscoelastic relaxation, renewed magma inflow, or a combination of both processes.
Overlapped Postseismic Deformation Caused by Afterslip and Viscoelastic Relaxation Following the 2015 Mw 7.8 Gorkha (Nepal) Earthquake
Authors: Diao Faqi , Wang Rongjiang , Xiong Xiong , Liu Chengli
Published: February 2021

Studying transient postseismic deformation is one of the key approaches to probe fault kinematics and rheological behavior of rocks surrounding tectonic faults. Previous studies have shown that transient postseismic deformation is dominantly induced by afterslip and postseismic viscoelastic relaxation. However, effects of these two mechanisms are generally overlapped in space and time, making the analysis of the observations challenging. Here, we investigate the overlapping effects of afterslip and viscoelastic relaxation following the 2015 Gorkha earthquake based on the first 4‐years’ Global Positioning System observations and finite element models. Separated mechanisms either fail to explain the observations or lead to unreasonable model parameters. A combined model that incorporates stress‐driven afterslip and viscoelastic relaxation can overcome the limitations of separated mechanisms. Our results indicate that only short‐term (<1 year) postseismic deformation in near‐to middle‐fields is caused mainly by afterslip, whereas that in far‐field or long‐term are dominated by the viscoelastic relaxation effect. The stress‐driven afterslip is mainly confined to a narrow zone adjacent to the coseismic rupture asperities, in contrast to the widespread deep afterslip as suggested by previous studies. The total seismic moment released by the afterslip is ∼5% of that released by the Mw 7.8 main shock. The optimal viscosity of the lower crust beneath the south Tibet is estimated to be 2.5 × 1018 Pa∙s, which is at least one order lower than that beneath Indian plate, suggesting a significant lateral variation across the Himalayan fault. Validations by using independent InSAR observations further confirm the reliability of the combined model.
Genesis of Intermediate and Silicic Arc Magmas Constrained by Nb/Ta Fractionation
Authors: Chen Wei , Zhang Guoliang , Ruan Mengfei , Wang Shuai , Xiong Xiaolin
Published: February 2021

Resolving the geochemical discrepancies in Nb/Ta between the bulk continental crust and its parental mantle melts can provide insights into the processes by which basaltic magmas differentiated into the felsic crust. Deep‐seated garnet pyroxenite cumulates (i.e., arclogite) have high Nb/Ta values due to the presence of high Nb/Ta‐rutile. For this reason, rutile‐bearing arclogites having Nb‐rich composition were proposed to complement the low Nb/Ta nature of the continental crust and evolved arc magmas, that is to say, continental arc magma evolution dominantly occurred in the stability field of garnet. However, this suggestion is challenged by the incomplete understanding of the role of rutile in the Nb/Ta fractionation during arc magma evolution due to insufficient partitioning data at low temperatures (T ≤ 1,000°C). Here, we determined Nb and Ta partitioning ratios in rutile‐felsic melt systems at 2.0 GPa, 850–1,000°C and ∼4–20 wt.% H2O. Our results confirm that equilibrium crystallization of rutile with respect to Nb and Ta will not impart lower Nb/Ta values to any derivative liquids, whereas diffusive fractionation of Nb/Ta in siliceous melts during the growth of rutile can reduce Nb/Ta ratios in melts. However, a positive correlation between Nb/Ta and Dy/Yb for mature continental arc magmas, incipient continental arc magmas, island arc magmas, and global arc magmas indicates that amphibole rather than rutile‐bearing arclogite was responsible for causing low Nb/Ta ratios of many evolved intermediate rocks. Accordingly, the chemical differentiation from primary basaltic to average andesitic compositions of the continental crust mainly occurred in the stability field of amphibole.
Cross Validation of Stress Drop Estimates and Interpretations for the 2011 Prague, OK, Earthquake Sequence Using Multiple Methods
Authors: Pennington Colin N. , Chen Xiaowei , Abercrombie Rachel E. , Wu Qimin
Published: February 2021

We compare source parameter estimates for earthquakes in the 2011 Prague Mw 5.7, Oklahoma, sequence to investigate random uncertainty and systematic bias, and resolve reliable relative variations in stress drop. Source parameters provide insight into the earthquake rupture processes but large variations between studies occur. The Prague earthquake sequence is a prime example of this, with different studies reaching contrasting interpretations of the effects of injection on source parameters. We examine the Prague earthquake sequence using a single coherent catalog for all the events detected by the Oklahoma Geological Survey (OGS) and McMahon et al. (2017). We use three principal approaches to estimate stress drop in order to understand the biases of each: a spectral decomposition method based on stacking, individual event spectral modeling, and a spectral ratio method based on highly correlated events. We also compare our results with previous studies for the Prague sequences aftershocks, as well as past results for the Mw 4.8 foreshock and Mw 4.8 aftershock and Mw 5.7 mainshock. The absolute values of stress drop vary significantly between methods, but the relative patterns remain consistent, except when low quality or low bandwidth data are included. The consistent relative patterns reveal that the stress drops of aftershocks are dependent on the fault orientation and the proximity of the events to the mainshocks slip. These results indicate that fault structure as well as past events play an important role in stress drop patterns.
What Controls Effective Elastic Thickness of the Lithosphere in the Pacific Ocean?
Authors: Lu Zhezhe , Audet Pascal , Li Chun‐Feng , Zhu Shuang , Wu Zhaocai
Published: February 2021

The effective elastic thickness () of the lithosphere is a proxy for mechanical strength and can be used to constrain lithospheric rheology and understand how surface deformation relates to deep Earth processes. Here, we map variations over the Pacific Ocean from the inversion of the admittance between free‐air gravity anomaly and bathymetry data calculated using a continuous wavelet transform, taking both surface and subsurface loads into account. The Pacific lithosphere show ranging between 0 and 80 km with a mean of 13.5 km and a standard deviation of 12.3 km. We find that is generally poorly correlated with plate loading age, crustal age, heat flow and Curie point depth, except for relatively young (<60 Ma) and warm lithospheres. Most oceanic plateaus and seamounts show km, with the lowest values (<5 km) around active spreading centers. The highest estimates (>30 km) are found along subduction zones and around the Hawaiian‐Emperor Seamount Chain (HESC). Taken together, these results support a temperature control on for small loads and warm lithosphere through steady‐state creep processes, but strain hardening operating at large plastic strain and low temperature could explain high associated with large‐amplitude and long‐wavelength loads (subduction zones and the HESC) and should be incorporated in yield strength models of oceanic .
The Route to Spring Phytoplankton Blooms Simulated by a Lagrangian Plankton Model
Authors: Noh Kyung Min , Noh Yign , Brereton Ashley , Kug Jong‐Seong
Published: February 2021

A Lagrangian plankton model (LPM) is developed, in which the motion of a large number of Lagrangian particles, representing a parcel of plankton, is calculated under the turbulence field simulated by large‐eddy simulation. A spring phytoplankton bloom is realized using the LPM, and the mechanism for its 1 generation is investigated. The criterion based on these results is proposed as , where δ

E
(= u
∗/f) is the scale for the Ekman boundary layer, δ

S
(= ) is the scale for the depth of a seasonal thermocline, u
∗ is the wind stress, Q
0 is the surface buoyancy flux, f is the Coriolis parameter, and C
1 and C
2 are constants. The critical depth hypothesis can be applied for the onset of a spring bloom, when , using the mixing layer depth instead of the mixed layer depth, as z

c 
> C
2
δ

S
, but the critical turbulence hypothesis can be applied, as z

c 
> C
1
δ

E
, when . A spring bloom is more likely to occur at higher latitudes, even if the atmospheric forcing is the same. The diurnal variation of Q
0 tends to increase the strength of the spring bloom at small u
∗. Furthermore, various statistics of Lagrangian particles, such as the mixing length of plankton, the residence time of plankton within the euphotic zone, and the growth of plankton clarify the movement and growth of plankton cells.
Drought and Salinization Stress Induced by Stand Development Alters Mineral Element Cycling in a Larch Plantation
Authors: Deng Meifeng , Li Ping , Wang Zhenhua , Guo Lulu , Wu Yuntao , Huang Junsheng , Wang Xuhui , Liu Lingli
Published: February 2021

Grassland afforestation promotes carbon sequestration at the expense of consuming water resources. With the development of forest plantations, the increase in aboveground biomass could aggravate the limitations of soil moisture and nutrients, and thus alter understory succession. However, it is unclear how these changes influence the mineral element cycle in plant‐soil systems. We conducted a four‐year experiment in young, middle‐aged, and mature stands in a larch plantation and investigated how stand development affects macronutrient (K, Ca, and Mg) and micronutrient (Na, Fe, and Zn) concentrations in soils and leaves of larch and understory plants. Our results showed that as stand age increased, soil moisture and soil pH decreased. The reduced soil moisture directly led to an increase in soil total sodium (Na) and potassium (K) concentrations. There was no significant difference in mineral element concentrations in the larch leaves among the three stands. However, the understory vegetation in the mature stands had higher foliar K concentration but lower foliar Na concentration than in the young stands. Furthermore, plant calcium (Ca) concentration was positively correlated with plant K:Na ratio. The stoichiometric coupling between leaf [Ca] and K:Na ratio became tighter with increased stand age, which could improve the tolerance of plants to drought and soil salinization. Our findings suggested that water limitation and soil salinization caused by grassland afforestation intensified with increased stand age. To adapt to these stresses, understory vegetation often shifts to species with high K but low Na leaf concentrations.
Understanding the Bioaccumulation of Mercury in Rice Plants at the Wanshan Mercury Mine, China: Using Stable Mercury Isotopes
Authors: Chang Chuanyu , Yin Runsheng , Huang Fang , Sun Guangyi , Mao Kang , Lei Da , Zhang Hua
Published: February 2021

Rice can accumulate a substantial amount of mercury (Hg). At the Wanshan Mercury Mine (WMM), the bioaccumulation of Hg by rice was complicated by historical large‐scale mining and active artisanal smelting activities. This study investigated the concentration and isotopic composition of Hg in rice roots, leaves and paddy soil collected from abandoned Hg mining sites and active artisanal smelting sites at the WMM. At all sites, correlations between δ202Hg and 1/THg were observed in soil, suggesting a mixing of Hg from waste calcine and unroasted Hg ore. Significantly positive correlations were also observed in THg concentrations between roots and soil (r2 = 0.84, p < 0.01) and between leaves and total gaseous mercury (r2 = 0.87, p < 0.01), reflecting that roots and leaves receive Hg mainly from soil and atmosphere, respectively. Large differences of −0.87 ± 0.57‰ and −1.85 ± 0.57‰ in δ202Hg between the root and soil were observed at abandoned Hg mining sites and active artisanal smelting sites, respectively, suggesting that roots preferentially accumulate lighter Hg isotopes from the soil. Offsets of 0.05‰ and 0.27‰ in Δ199Hg between rice roots and leaves, with higher Δ199Hg values in roots than leaves, were observed at abandoned Hg mining sites and active artisanal smelting sites, respectively. The Hg‐mass‐independent fractionation signal is believed to be caused by Hg(II) photoreduction in paddy water; however, the extent of photoreduction is variable among rice paddies. Overall, this study suggests that Hg isotopes can be a useful tool to understand the sources and bioaccumulation of Hg in rice paddies.
In Situ Estimates of Net Primary Production in the Western North Atlantic With Argo Profiling Floats
Authors: Yang Bo , Fox James , Behrenfeld Michael J. , Boss Emmanuel S. , Haëntjens Nils , Halsey Kimberly H. , Emerson Steven R. , Doney Scott C.
Published: February 2021

The 14C incubation method for net primary production (NPP) has limited spatial/temporal resolution, while satellite approaches cannot provide direct information at depth. With chlorophyll‐a and backscatter measurements from BGC‐Argo floats, we quantified year‐round NPP in the western North Atlantic Ocean using both the Carbon‐based Productivity Model (CbPM) and Photoacclimation Productivity Model (PPM). Comparison with NPP profiles from 14C incubation measurements showed advantages and limitations of both models. CbPM reproduced the magnitude of NPP in most cases. However, in the summer the CbPM‐based NPP had a large peak in the subsurface, which was an artifact from the subsurface chlorophyll maximum caused by photoacclimation. PPM avoided the artifacts from photoacclimation, but the magnitude of PPM‐derived NPP was smaller than the 14C result. Different NPP distribution patterns along a North‐South transect in the Western North Atlantic Ocean were observed, including higher winter NPP/lower summer NPP in the south, timing differences in NPP seasonal phenology, and different NPP depth distribution patterns in the summer months. Using a 6‐months record of concurrent oxygen and bio‐optical measurements from two Argo floats, we also demonstrated the ability of Argo floats to obtain estimates of the net community production to NPP ratio, ranging from 0.3 in July to −1.0 in December 2016. Our results highlight the utility of float bio‐optical profiles and indicate that environmental conditions (e.g., light availability, nutrient supply) are major factors controlling the seasonality and spatial (horizontal and vertical) distributions of NPP in the western North Atlantic Ocean.
Spatiotemporal Change of Marsh Vegetation and Its Response to Climate Change in China From 2000 to 2019
Authors: Shen Xiangjin , Liu Binhui , Jiang Ming , Wang Yanji , Wang Lei , Zhang Jiaqi , Lu Xianguo
Published: February 2021

China has the third largest area of marshes in the world. Understanding the change of marsh, vegetation and its response to climate change in China is important for the protection of wetland ecosystem. Based on the climate and normalized difference vegetation index (NDVI) data, we investigated the spatiotemporal variation in vegetation and its response to climate change for different types of marshes in China. The results indicated that growing season NDVI increased significantly (0.02/decade, P < 0.01) over the whole marshes of China from 2000 to 2019. The increased precipitation and minimum temperature during the growing season could promote the growth of marsh vegetation over China. This study found for the first time that the increase of temperature during the day and at night had asymmetric effects on vegetation growth in marshes of China, and the positive effect of night warming was more significant. Spatially, increasing growing season precipitation was beneficial to the vegetation growth of herbaceous marshes, marsh meadows, inland salt marshes, and seasonal saltwater marshes in eastern Inner Mongolia. Increased growing season minimum temperature could greatly promote the vegetation growth of marsh meadows, herbaceous marshes, inland salt marshes, forest swamp, and bush swamp in cold and high‐altitude regions of Northern Northeast China and the Tibet Plateau. In the context of global climate change, more attention should be paid to the different responses of vegetation to climate change for different marsh types, especially when we use the model to simulate the impact of climate change on vegetation in different marsh regions of China.
Representation of Plant Hydraulics in the Noah‐MP Land Surface Model: Model Development and Multiscale Evaluation
Authors: Li Lingcheng , Yang Zong‐Liang , Matheny Ashley M. , Zheng Hui , Swenson Sean C. , Lawrence David M. , Barlage Michael , Yan Binyan , McDowell Nate G. , Leung L. Ruby
Published: February 2021

Plants are expected to face increasing water stress under future climate change. Most land surface models, including Noah‐MP, employ an idealized “big‐leaf” concept to regulate water and carbon fluxes in response to soil moisture stress through empirical soil hydraulics schemes (SHSs). However, such schemes have been shown to cause significant uncertainties in carbon and water simulations. In this paper, we present a novel plant hydraulics scheme (PHS) for Noah‐MP (hereafter, Noah‐MP‐PHS), which employs a big‐tree rather than big‐leaf concept, wherein the whole‐plant hydraulic strategy is considered, including root‐level soil water acquisition, stem‐level hydraulic conductance and capacitance, and leaf‐level anisohydricity and hydraulic capacitance. Evaluated against plot‐level observations from a mature, mixed hardwood forest at the University of Michigan Biological Station and compared with the default Noah‐MP, Noah‐MP‐PHS better represents plant water stress and improves water and carbon simulations, especially during periods of dry soil conditions. Noah‐MP‐PHS also improves the asymmetrical diel simulation of gross primary production under low soil moisture conditions. Noah‐MP‐PHS is able to reproduce different patterns of transpiration, stem water storage and root water uptake during a 2‐week dry‐down period for two species with contrasting plant hydraulic behaviors, i.e., the “cavitation risk‐averse” red maple and the “cavitation risk‐prone” red oak. Sensitivity experiments with plant hydraulic capacitance show that the stem water storage enables nocturnal plant water recharge, affects plant water use efficiency, and provides an important buffer to relieve xylem hydraulic stress during dry soil conditions.
Overlooked Implication of Sediment Transport at Low Flow: Migrating Ripples Modulate Streambed Phototrophic and Heterotrophic Microbial Activity
Authors: Scheidweiler David , Mendoza‐Lera Clara , Mutz Michael , Risse‐Buhl Ute
Published: February 2021

Sandy streambeds are mobile even at low flow velocities at which sediments can be transported as bedload, more specifically as migrating ripples. Small variations in discharge can result in transitions between sediment transport and no‐transport. Despite being inherent processes of streams and rivers, the effect of sediment transport and transport regime transition on the phototrophic and heterotrophic activity of streambed microbial communities remains unclear. We performed a microcosm experiment mimicking sediment transport as migrating ripples (i.e., migrating) and no sediment transport (i.e., stationary), and their transition to observe the response of the phototrophic and heterotrophic microbial community. Both net community production and community respiration were respectively 77% and 40% suppressed in migrating sediments compared to stationary sediments. In migrating sediments, a combination of mechanical stress, light limitation, and limited habitable area likely hampered microbial metabolism. Stationary conditions facilitated an active community of phototrophs, mainly diatoms, as indicated by high net community production, high rates of dissolved organic carbon release and silicon retention. After transitioning migrating to stationary and vice versa, differences were maintained regardless of the change in mechanical stress and associated stressors, most likely as a result of the interaction between their antecedent transport conditions and developmental stage that shaped the microbial community. Our results indicate that sediment transported as migrating ripples at low flow velocity can strongly modulate streambed metabolism, and discharge oscillations resulting in sediment transport transitions will result in a mosaic of microbial activity and biomass that will emerge at larger scales determining reach‐scale metabolism.
Comparison of Surface Water‐Groundwater Exchange Fluxes Derived From Hydraulic and Geochemical Methods and a Regional Groundwater Model
Authors: Bouchez Camille , Cook Peter G. , Partington Daniel , Simmons Craig T.
Published: February 2021

Intercomparison of surface water‐groundwater (SW‐GW) exchange fluxes at the regional scale is rarely undertaken, mainly because estimates are method and scale‐dependent and usually associated with large errors. In the present study, we compare SW‐GW exchange fluxes calculated from a multitracer mass balance in the river, an application of Darcy's law using near‐river piezometers and a surface‐subsurface flow model calibrated at the catchment scale. SW‐GW exchange fluxes are estimated for 7 km long reaches along the 140 km long Campaspe River, a tributary of the Murray River, Australia. Differences are found in the directions and magnitudes of the exchange fluxes estimated by the different methods. The application of Darcy's law in near‐river piezometers seems the most appropriate method to infer SW‐GW flow directions and temporal variability. The tracer mass balance is limited to gaining reaches but gives quantitative estimates of the fluxes. While numerical models should overcome deficiencies associated with some of the intrinsic assumptions of the two field‐methods, the regional‐scale calibration is subject to high uncertainties in the simulated heads near the river, resulting in uncertainty of SW‐GW exchange fluxes. In particular, we show that loosely quantified river abstractions and irrigation patterns directly impact the simulated SW‐GW fluxes. In gaining reaches, additional river chemistry data improved model calibration and SW‐GW flux estimates. While numerical models are crucial for water management, their reliability to estimate SW‐GW fluxes can be limited by their complexity and lacking data availability. Therefore, we recommend comparing numerical model results with easily implemented field‐based methods.
Author Correction: Edgetic perturbation signatures represent known and novel cancer biomarkers
Authors: Kataka Evans , Zaucha Jan , Frishman Goar , Ruepp Andreas , Frishman Dmitrij
Published: February 2021

An amendment to this paper has been published and can be accessed via a link at the top of the paper.
Author Correction: Corticostriatal functional connectivity of bothersome tinnitus in single-sided deafness
Authors: Henderson-Sabes Jennifer , Shang Yingying , Perez Philip L. , Chang Jolie L. , Pross Seth E. , Findlay Anne M. , Mizuiri Danielle , Hinkley Leighton B. , Nagarajan Srikantan S. , Cheung Steven W.
Published: February 2021

An amendment to this paper has been published and can be accessed via a link at the top of the paper.
Elimination of macrophage-entrapped antibiotic-resistant bacteria by a targeted metal–organic framework-based nanoplatform
Authors: Liu Xuemeng , Deng Qingqing , Zhang Lu , Sang Yanjuan , Dong Kai , Ren Jinsong , Qu Xiaogang
Published: February 2021

A novel metal-organic framework-based nanoplatform was designed for eliminating intracellular antibiotic-resistant bacteria. With the merits of targeting and internalizing ability, the agent could kill stealthy bacteria efficiently under irradiation.
A unique photoswitch: intrinsic photothermal heating induced reversible proton conductivity of a HKUST-1 membrane
Authors: Wang Shilin , Li Peipei , Fan Shuaikang , Fang Zhou , Wang Xiaobin , Li Zhuoyi , Peng Xinsheng
Published: February 2021

Excellent photoswitchable proton conduction of a HKUST-1 membrane was achieved based on its efficient intrinsic photothermal effect without photoactive additives.
Puerarin improves hepatic glucose and lipid homeostasis in vitro and in vivo by regulating the AMPK pathway
Authors: Xu Dong-Xue , Guo Xiao-Xuan , Zeng Zhu , Wang Yong , Qiu Jing
Published: February 2021

Identification of potential therapeutic effects of puerarin for the prevention of hepatic insulin resistance and steatosis in vivo and in vitro.
A new pH/NIR responsive theranostic agent for magnetic resonance imaging guided synergistic therapy
Authors: Du Yechao , Wang Daguang , Wang Shuo , Li Wei , Suo Jian
Published: February 2021

A new nanotheraontic agent for magnetic resonance imaging (MRI) guided combined photothermal therapy (PTT) and chemotherapy has been reported.
Dual active sites fabricated through atomic layer deposition of TiO2 on MoS2 nanosheet arrays for highly efficient electroreduction of CO2 to ethanol
Authors: Qi Feixuanyu , Liu Kang , Ma De-Kun , Cai Fangfang , Liu Min , Xu Quanlong , Chen Wei , Qi Chenze , Yang Dongpeng , Huang Shaoming
Published: February 2021

Ultrathin TiO2/MoS2 nanosheet arrays containing dual active sites could achieve efficient CO2 reduction reaction toward ethanol. A new regulatory mechanism of the CO coupling reaction was proposed based on experimental results and DFT calculations.
Multicharge β-cyclodextrin supramolecular assembly for ATP capture and drug release
Authors: Chen Changhui , Chen Yong , Dai Xianyin , Li Jingjing , Jia Shanshan , Wang Shuaipeng , Liu Yu
Published: February 2021

A hyaluronidase-responsive polysaccharide supramolecular assembly for targeted drug release and capturing ATP, with enhanced efficacy of anticancer drugs on cancer chemotherapy.
Triiron clusters derived from dinuclear complexes related to the active site of [Fe–Fe] hydrogenases: steric effect of the dithiolate bridge on redox properties, a DFT analysis
Authors: Hobballah Ahmad , Arrigoni Federica , Elleouet Catherine , Greco Claudio , Laurans Maxime , Pétillon François Y. , Schollhammer Philippe
Published: February 2021

CV and DFT calculations reveal that electrochemical behaviours of triiron clusters [Fe3(CO)5(κ2-dppe)(μ-pdtR2)(μ-pdt)] depend on the nature of the dithiolate bridge.
Binary non-fullerene-based polymer solar cells with a 430 nm thick active layer showing 15.39% efficiency and 73.38% fill factor
Authors: Pan Feilong , Luo Mei , Liu Xuncheng , Jiang Haiying , Wang Zhen , Yuan Dong , Wang Qian , Qing Lechi , Zhang Zesheng , Zhang Lianjie , Zou Yingping , Chen Junwu
Published: February 2021

High hole mobility polymer and Y-series non-fullerene acceptor boost efficiency and fill factor of thick-film polymer solar cells.
Carrier phase correction for GNSS space‐time array processing based on frequency jerk detection
Authors: Xie Yuchen , Chen Yuwei , Chen Feiqiang , Wang Feixue
Published: February 2021

The signals of Global Navigation Satellite System (GNSS) are so vulnerable that can be easily jammed by intentional or unintentional interferences. One of the effective ways to protect GNSS signals from jamming is to use the Space‐Time Array Processing (STAP) technology. However, undesired carrier phase bias would be induced to the signals because of the STAP, which significantly influences the precision of positioning. Many algorithms have been proposed to deal with this carrier phase bias, but most of them need the directional information of signals or the pre‐test of antennas. In this paper, a carrier phase correction algorithm without the need of prior information is proposed. Alarmed by the jerk of carrier frequency, the algorithm can detect the change of jamming and calculate the induced carrier phase bias. Then it can correct this bias from the signal and alleviate its influence. The simulation results show that the algorithm can limit the bias from more than 60° to less than 10°, which verifies that the proposed algorithm is effective in the low dynamic receiver.
Instantaneous active and reactive load signature applied in non‐intrusive load monitoring systems
Authors: Brito Ricardo , Wong Man‐Chung , Zhang Hong Cai , Da Costa Junior Miguel Gomes , Lam Chi‐Seng , Wong Chi‐Kong
Published: February 2021

The performance of non‐intrusive load monitoring (NILM) systems heavily depends on the uniqueness of the load signature extracted from the electrical appliances. Different load signatures have been proposed. Recently, in particular, v–i trajectory feature extraction is attracting more and more attention due to its unique characteristics. Herein, instantaneous p–q load signature (IpqLS) feature extraction is first proposed and applied in NILM, which shows that conventional methods cannot distinguish load signatures under some situations. Applying IpqLS with several machine learning algorithms is not only extracting unique features compared to the overlapping problems of P–Q and v–i trajectory but also improving load classification accuracy. Simulations and experimental results verified the effectiveness of the proposed method.
Bar-like galaxies in IllustrisTNG
Authors: Łokas Ewa L.
Published: February 2021

We study a sample of bar-like galaxies in the Illustris TNG100 simulation, in which almost the whole stellar component is in the form of a prolate spheroid. The sample is different from the late-type barred galaxies studied before. In addition to the requirement of a high enough stellar mass and resolution, the 277 galaxies were selected based on the single condition of a low enough ratio of the intermediate to long axis of the stellar component. We followed the mass and shape evolution of the galaxies as well as their interactions with other objects and divided them into three classes based on the origin of the bar and the subsequent history. In galaxies of class A (comprising 28% of the sample), the bar was induced by an interaction with a larger object, most often a cluster or group central galaxy, and the galaxies were heavily stripped of dark matter and gas. In classes B and C (27% and 45% of the sample, respectively) the bars were induced by a merger or a passing satellite, or they were formed by disk instability. Class B galaxies were then partially stripped of mass, while those of class C evolved without strong interactions, thus retaining their dark matter and gas in the outskirts. We illustrate the properties of the different classes with three representative examples of individual galaxies. In spite of the different evolutionary histories, the bars are remarkably similar in strength, length, and formation times. The gas fraction in the baryonic component within two stellar half-mass radii at the time of bar formation is always below 0.4 and usually very low, which confirms in the cosmological context the validity of this threshold, which has previously been identified in controlled simulations. Observational counterparts of these objects can be found among early-type fast rotators, S0 galaxies, or red spirals with bars.
Rotational spectroscopy of isotopic cyclopropenone, c-H2C3O, and determination of its equilibrium structure
Authors: Müller Holger S. P. , Brahmi M. Ananya , Guillemin Jean-Claude , Lewen Frank , Schlemmer Stephan
Published: February 2021

Context. Cyclopropenone was first detected in the cold and less dense envelope of the giant molecular cloud Sagittarius B2(N). It was found later in several cold dark clouds and it may be possible to detect its minor isotopic species in these environments. In addition, the main species may well be identified in warmer environments.

Aims. We aim to extend existing line lists of isotopologs of c-H2C3O from the microwave to the millimeter region and create one for the singly deuterated isotopolog to facilitate their detections in space. Furthermore, we aim to extend the line list of the main isotopic species to the submillimeter region and to evaluate an equilibrium structure of the molecule.

Methods. We employed a cyclopropenone sample in natural isotopic composition to investigate the rotational spectra of the main and 18O-containing isotopologs as well as the two isotopomers containing one 13C atom. Spectral recordings of the singly and doubly deuterated isotopic species were obtained using a cyclopropenone sample highly enriched in deuterium. We recorded rotational transitions in the 70−126 and 160−245 GHz regions for all isotopologs and also in the 342−505 GHz range for the main species. Quantum-chemical calculations were carried out to evaluate initial spectroscopic parameters and the differences between ground-state and equilibrium rotational parameters in order to derive semi-empirical equilibrium structural parameters.

Results. We determined new or improved spectroscopic parameters for six isotopologs and structural parameters according to different structure models.

Conclusions. The spectroscopic parameters are accurate enough to identify minor isotopic species at centimeter and millimeter wavelengths while those of the main species are deemed to be reliable up to 1 THz. Our structural parameters differ from earlier ones. The deviations are attributed to misassignments in the earlier spectrum of one isotopic species.
A cautionary tale in fitting galaxy rotation curves with Bayesian techniques
Authors: Li Pengfei , Lelli Federico , McGaugh Stacy , Schombert James , Chae Kyu-Hyun
Published: February 2021

The application of Bayesian techniques to astronomical data is generally non-trivial because the fitting parameters can be strongly degenerated and the formal uncertainties are themselves uncertain. An example is provided by the contradictory claims over the presence or absence of a universal acceleration scale (g†) in galaxies based on Bayesian fits to rotation curves. To illustrate this we present an analysis in which the Newtonian gravitational constant GN is allowed to vary from galaxy to galaxy when fitting rotation curves from the SPARC database, in analogy to g† in the recently debated Bayesian analyses. When imposing flat priors on GN, we obtain a wide distribution of GN which, taken at face value, would rule out GN as a universal constant with high statistical confidence. However, imposing an empirically motivated log-normal prior returns a virtually constant GN with no sacrifice in fit quality. This implies that the inference of a variable GN (or g†) is the result of the combined effect of parameter degeneracies and unavoidable uncertainties in the error model. When these effects are taken into account, the SPARC data are consistent with a constant GN (and constant g†).
Mechatronics design and testing of a cable-driven upper limb rehabilitation exoskeleton with variable stiffness
Authors: Li Zhongyi , Li Wang , Chen Wei-Hai , Zhang Jianbin , Wang Jianhua , Fang Zaojun , Yang Guilin
Published: February 2021

In this paper, we present a cable-driven exoskeleton with variable stiffness for upper limb rehabilitation. Adjustable stiffness of the cable-driven exoskeleton is achieved by attaching a novel variable stiffness module (VSM) to each driving cable. The module is able to vary stiffness in a large range through changing cable tension. In this paper, a stiffness model is developed for a cable-driven exoskeleton to reveal the stiffness performance of the exoskeleton with the influence of VSMs. Based on the stiffness model, a controller with stiffness-oriented strategy is proposed to vary the stiffness of the exoskeleton. Experiments on a prototype of a cable-driven exoskeleton are conducted to validate the controller.
Birational geometry of singular Fano double spaces of index two
Authors: Pukhlikov A. V.
Published: February 2021

We describe the birational geometry of Fano double spaces

of index 2 and dimension

with at most quadratic singularities of rank

, satisfying certain additional conditions of general position: we prove that these varieties have no structures of a rationally connected fibre space over a base of dimension

, that every birational map

onto the total space of a Mori fibre space

induces an isomorphism

of the blow-up

of

along

, where

is a linear subspace of codimension 2, and that every birational map of

onto a Fano variety

with

-factorial terminal singularities and Picard number 1 is an isomorphism. We give an explicit lower estimate, quadratic in

, for the codimension of the set of varieties

that have worse singularities or do not satisfy the conditions of general position. The proof makes use of the method of maximal singularities and the improved

-inequality for the self-intersection of a mobile linear system.

Bibliography: 20 titles.
Taqi Erāni, Bizhan Jazani, and a Marxian Framework for the Critique of Religion in Twentieth Century Iranian Political Thought
Authors: Saffari Siavash
Published: February 2021

This article examines the development of a Marxian frame for the critique of religion in twentieth century Iranian political thought by Taqi Erāni and Bizhan Jazani. It argues that, following Marx, Erāni and Jazani understand religion to be a superstructural relic from an earlier stage of human development which will gradually and inevitably withdraw from collective human life as a consequence of the material dialectics of history. It further shows that Erāni and Jazani consider religion to be instrumental in sustaining relations of oppression, and they view with skepticism attempts to reform religion or to use religious faith as an instrument for mass mobilization in revolutionary struggles.