bluuebunny/crossref_metadata_2025 huggingface dataset:
Large‐Scale Rotational Motion Within the Main Central Thrust Zone in the Darjeeling‐Sikkim Himalaya, India
Authors: Roberts A. G. , Weinberg R. F. , Hunter N. J. R. , Ganade C. E.
Published: November 2020

Much of the shortening associated with the India‐Eurasia collision has been accommodated by orogen‐spanning shear zones within the fold‐and‐thrust belt that forms the Himalayan orogen. The kinematics on these shear zones and how they accommodated large‐scale displacements remain poorly understood. In general, rock flow has been described as orogen perpendicular towards the south. Here, structural mapping and microstructural analysis are applied to demonstrate that the Darjeeling‐Sikkim section of the Main Central Thrust Zone (MCTZ) records an anticlockwise rotation of the resolved stresses within the orogenic wedge, changing from south to north over the period between 20 and at least 9 Ma. The transport direction during thrusting varies systematically defining broad arcs at the scale of 50 to 100 km, rotating by up to 140° from SE‐ or S‐vergence in the north, to SW‐vergence in the south. This rotation is independent of the ~60‐km‐wide dome in the footwall of the MCTZ, exposed as a broad half‐window. Rotation may have been a response to rheological heterogeneities within the orogeny forming large‐scale flow impediments.
Understanding the 3D Formation of a Wide Rift: The Central South China Sea Rift System
Authors: Cameselle Alejandra L. , Ranero César R. , Barckhausen Udo
Published: November 2020

Rifted margins result from continental lithosphere extension, breakup, and transition to seafloor spreading by modes typically described by end‐member conceptual models. However, current geophysical data challenge these archetypes showing a more complex spectrum of rifting styles. Here, we integrate geophysical and geological observations to constrain the time and space evolution of the central South China Sea (SCS) rift system. We provide new insights into the continental extension mechanisms and continent‐ocean transition (COT) formation from a seismic transect parallel to the extensional direction of the central SCS rift system. We present 850‐km‐wide region of continental crust where distributed extensional deformation formed a pattern of lithospheric boudinage defined by seven 100‐ to 200‐km‐long structural segments. Each segment is formed by an 18‐ to 24‐km‐thick crust sector laterally thinning into an interboudin neck with ≤10‐km ultrathin crust (ß factors ~3.3–6.5). Drill and stratigraphic information support that extension continued at all six interboudin necks in the central SCS until ~23 Ma, when breakup by seafloor spreading propagation reached one of them. We propose that the seven segments evolved as discrete subsystems from early rifting to breakup. Structurally equivalent ultrathin crust grabens occur NE and SW of both SCS conjugate margins, supporting a 3D wide rift mode of deformation across the SCS rift system. The six ultrathin crust contemporaneous necks and the abrupt nature and location of the COT support that the breakup was not controlled by further continental lithospheric thinning but rather was determined by the seafloor spreading propagation toward the SW.
A Geologically Based Indoor‐Radon Potential Map of Kentucky
Authors: Haneberg William C. , Wiggins Amanda , Curl Douglas C. , Greb Stephen F. , Andrews William M. , Rademacher Kathy , Rayens Mary Kay , Hahn Ellen J.
Published: November 2020

We combined 71,930 short‐term (median duration 4 days) home radon test results with 1:24,000‐scale bedrock geologic map coverage of Kentucky to produce a statewide geologically based indoor‐radon potential map. The test results were positively skewed with a mean of 266 Bq/m3, median of 122 Bq/m3, and 75th percentile of 289 Bq/m3. We identified 106 formations with ≥10 test results. Analysis of results from 20 predominantly monolithologic formations showed indoor‐radon concentrations to be positively skewed on a formation‐by‐formation basis, with a proportional relationship between sample means and standard deviations. Limestone (median 170 Bq/m3) and dolostone (median 130 Bq/m3) tended to have higher indoor‐radon concentrations than siltstones and sandstones (median 67 Bq/m3) or unlithified surficial deposits (median 63 Bq/m3). Individual shales had median values ranging from 67 to 189 Bq/m3; the median value for all shale values was 85 Bq/m3. Percentages of values falling above the U.S. Environmental Protection Agency (EPA) action level of 148 Bq/m3 were sandstone and siltstone: 24%, unlithified clastic: 21%, dolostone: 46%, limestone: 55%, and shale: 34%. Mississippian limestones, Ordovician limestones, and Devonian black shales had the highest indoor‐radon potential values in Kentucky. Indoor‐radon test mean values for the selected formations were also weakly, but statistically significantly, correlated with mean aeroradiometric uranium concentrations. To produce a map useful to nonspecialists, we classified each of the 106 formations into five radon‐geologic classes on the basis of their 75th percentile radon concentrations. The statewide map is freely available through an interactive internet map service.
Decadal Variability in Salinity of the Indian Ocean Subtropical Underwater During the Argo Period
Authors: Nie Xunwei , Wei Zexun , Li Ying
Published: November 2020

Salinity of the Indian Ocean Subtropical Underwater (IOSTUW) showed robust decadal variability during the Argo period, with a freshening trend between 2005 and 2013 and a salinification trend between 2014 and 2019. The salinity variability of the IOSTUW originated from both the sea surface salinity maximum region in the subtropical South Indian Ocean and the southeastern tropical Indian Ocean. The mixed layer salinity variabilities in these two regions are dominated by horizontal advection, which is mainly influenced by anomalous local surface currents and salinity anomalies from the western tropical Pacific and Maritime Continent. Both of these two factors have a close relationship with the El Niño‐Southern Oscillation (ENSO) signal. As a result, the mixed layer salinity in those two regions changed dramatically during the strong and long‐lasting ENSO events and thus led to the decadal variability in salinity of the IOSTUW.
Convective Invigoration Traced to Warm‐Rain Microphysics
Authors: Chua Xin Rong , Ming Yi
Published: November 2020

Aerosols are postulated to alter moist convection by increasing cloud droplet number concentration (Nd). Cloud‐resolving model simulations of radiative‐convective equilibrium show that higher Nd leads to stronger convective mass flux, seemingly in line with a hypothesis that links the convective invigoration to delayed rain formation allowing more cloud liquid condensate to be frozen. Yet, the invigoration is also present in an alternative model configuration with warm‐rain microphysics only, suggesting that ice microphysics is not central to the phenomenon. The key dynamical mechanism lies in the different vertical distributions of the increases in water vapor condensation and in cloud liquid reevaporation, causing a dipole pattern favoring convection. This is further supported by a pair of mechanism‐denial experiments in which an imposed weakening of cloud liquid reevaporation tends to mute invigoration.
Dielectric Properties of Lunar Subsurface Materials
Authors: Dong Zehua , Fang Guangyou , Zhao Di , Zhou Bin , Gao Yunze , Ji Yicai
Published: November 2020

The dielectric permittivity is one of the most significant properties of lunar material. For the past decades, researchers have assumed or used an indirect density versus depth relation to constrain the subsurface permittivity on the Moon. On 3 January 2019, Chang'E‐4 (CE‐4) rover‐borne lunar penetrating radar (LPR) successfully landed on the Von Kármán crater on the Moon's farside. CE‐4 LPR is the first surface radar on the Moon's farside for exploring regolith thickness and geological structure. Numerous parabolic‐shaped diffractions (PSD), which indicate subsurface objects, are identified in LPR data. We estimate the permittivity of the first ~50 m at the landing region using these PSDs based on a hyperbolic fitting method. A best‐fit permittivity/density versus depth relation is obtained, and this relation could be used at different areas on the Moon.
An 18‐Year Climatology of Directional Stratospheric Gravity Wave Momentum Flux From 3‐D Satellite Observations
Authors: Hindley N. P. , Wright C. J. , Hoffmann L. , Moffat‐Griffin T. , Mitchell N. J.
Published: November 2020

Atmospheric gravity waves (GWs) are key drivers of the atmospheric circulation, but their representation in general circulation models (GCMs) is challenging, leading to significant biases in middle atmospheric circulations. Unresolved GW momentum transport in GCMs must be parameterized, but global directional GW observations are needed to constrain this. Here we present an 18‐year climatology of directional stratospheric GW momentum flux (GWMF) from global AIRS/Aqua 3‐D satellite observations during 2002 to 2019. Striking hemispheric asymmetries are found at high latitudes, including dramatic reductions and reversals of GWMF during sudden stratospheric warmings. During Southern Hemisphere winter, a lateral convergence of GWMF toward 60°S is found that has no Northern Hemisphere counterpart. In the tropics, we find that zonal GWMF in AIRS measurements is strongly modulated by the semiannual oscillation (SAO) but not the quasi‐biennial oscillation (QBO). Our results provide guidance for future GW parameterizations needed to resolve long‐standing biases in GCMs.
Detection of Coccolithophore Blooms With BioGeoChemical‐Argo Floats
Authors: Terrats L. , Claustre H. , Cornec M. , Mangin A. , Neukermans G.
Published: November 2020

Coccolithophores (calcifying phytoplankton) form extensive blooms in temperate and subpolar oceans as evidenced from ocean‐color satellites. This study examines the potential to detect coccolithophore blooms with BioGeoChemical‐Argo (BGC‐Argo) floats, autonomous ocean profilers equipped with bio‐optical and physicochemical sensors. We first matched float data to ocean‐color satellite data of calcite concentration to select floats that sampled coccolithophore blooms. We identified two floats in the Southern Ocean, which measured the particulate beam attenuation coefficient (cp) in addition to two core BGC‐Argo variables, Chlorophyll‐a concentration ([Chl‐a]) and the particle backscattering coefficient (bbp). We show that coccolithophore blooms can be identified from floats by distinctively high values of (1) the bbp/cp ratio, a proxy for the refractive index of suspended particles, and (2) the bbp/[Chl‐a] ratio, measurable by any BGC‐Argo float. The latter thus paves the way to global investigations of environmental control of coccolithophore blooms and their role in carbon export.
Fault‐Zone Damage Promotes Pulse‐Like Rupture and Back‐Propagating Fronts via Quasi‐Static Effects
Authors: Idini B. , Ampuero J.‐P.
Published: November 2020

Damage zones are ubiquitous components of faults that may affect earthquake rupture. Simulations show that pulse‐like rupture can be induced by the dynamic effect of waves reflected by sharp fault zone boundaries. Here we show that pulses can appear in a highly damaged fault zone even in the absence of reflected waves. We use quasi‐static scaling arguments and quasi‐dynamic earthquake cycle simulations to show that a crack turns into a pulse after the rupture has grown larger than the fault zone thickness. Accompanying the pulses, we find complex rupture patterns involving back‐propagating fronts that emerge from the primary rupture front. Our model provides a mechanism for back‐propagating fronts recently observed during large earthquakes. Moreover, we find that slow‐slip simulations in a highly compliant fault zone also produce back‐propagating fronts, suggesting a new mechanism for the rapid tremor reversals observed in Cascadia and Japan.
Energetic Proton Acceleration Associated With Io's Footprint Tail
Authors: Clark G. , Mauk B. H. , Kollmann P. , Szalay J. R. , Sulaiman A. H. , Gershman D. J. , Saur J. , Janser S. , Garcia‐Sage K. , Greathouse T. , Paranicas C. , Allegrini F. , Bagenal F. , Bolton S. J. , Connerney J. E. P. , Ebert R. W. , Hospodarsky G. , Haggerty D. , Hue V. , Imai M. , Kotsiaros S. , McComas D. J. , Rymer A. , Westlake J.
Published: November 2020

Observations of energetic charged particles associated with Io's footprint (IFP) tail, and likely within or very near the Main Alfvén Wing, during Juno's 12th perijove (PJ) crossing show evidence of intense proton acceleration by wave‐particle heating. Measurements made by Juno/JEDI reveal proton characteristics that include pitch angle distributions concentrated along the upward loss cone, broad energy distributions that span ~50 keV to 1 MeV, highly structured temporal/spatial variations in the particle intensities, and energy fluxes as high as ~100 mW/m2. Simultaneous measurements of the plasma waves and magnetic field suggest the presence of ion cyclotron waves and transverse Alfvénic fluctuations. We interpret the proton observations as upgoing conics likely accelerated via resonant interactions with ion cyclotron waves. These observations represent the first measurements of ion conics associated with moon‐magnetosphere interactions, suggesting energetic ion acceleration plays a more important role in the IFP tail region than previously considered.
First Detection of Kilometer‐Scale Density Irregularities in the Martian Ionosphere
Authors: Fowler C. M. , Bonnell J. W. , Xu S. , Benna M. , Elrod M. , McFadden J. , Mitchell D. L. , Espley J. , Andersson L. , Ergun R. E. , Lillis R. , Jakosky B.
Published: November 2020

Plasma instabilities have been studied for many decades in the terrestrial ionosphere via remote and in‐situ measurement techniques. The study of these kilometer‐scale instabilities has provided crucial insight into coupling between the neutral atmosphere and ionosphere. A special high‐time cadence observation mode developed for the Mars Atmosphere and Volatile EvolutioN (MAVEN) mission has demonstrated for the first time that kilometer‐scale density fluctuations exist at Mars. Density and associated magnetic fluctuations are observed to occur both in and out of phase with each other, suggesting that multiple instability mechanisms are active, similar to Earth. The unique solar wind interaction with Mars and its localized crustal magnetic fields appears to play an important role in the formation of these irregularity events, which form preferentially during meridionally pointing magnetic field within the ionosphere. This is in contrast to Earth where the strong dipole magnetic field dominates in the terrestrial ionosphere.
Aseismic Deformation During the 2014 Mw 5.2 Karonga Earthquake, Malawi, From Satellite Interferometry and Earthquake Source Mechanisms
Authors: Zheng Whyjay , Oliva Sarah Jaye , Ebinger Cynthia , Pritchard Matthew E.
Published: November 2020

Aseismic deformation has been suggested as a mechanism to release the accumulated strain in rifts. However, the fraction and the spatial distribution of the aseismic strain are poorly constrained during amagmatic episodes. Using Sentinel‐1 interferograms, we identify the surface deformation associated with the 2014 Mw5.2 Karonga earthquake, Malawi, and perform inversions for fault geometry. We also analyze aftershocks and find a variety of source mechanisms within short timescales. A significant discrepancy in the earthquake depth determined by geodesy (3–6 km) and seismology (11–13 km) exists, although both methods indicate Mw5.2. We propose that the surface deformation is caused by aseismic slip from a shallow depth. This vertical partitioning from seismic to aseismic strain is accommodated by intersecting dilatational faults in the shallow upper crust and sedimentary basin, highlighting the importance of considering aseismic deformation in active tectonics and time‐averaged strain patterns, even in rifts with little volcanism.
Revealing the Dynamical Transition of Anisotropy Behind the HOST by Koopman Analysis
Authors: Li Licheng , Zuo Hongchao , Chen Bolong , Guo Yang , Ma Mengmeng , Dong Longxiang
Published: November 2020

The hockey‐stick transition (HOST), which is depicted by the “local and global shear” assumption, about the turbulence kinetic energy with the averaged flow intensity is noticed widely. However, the intrinsic mechanism of averaged flow influences turbulence kinetic energy via shear and buoyancy is missing. In this research, we deploy the Koopman operator to expose invariant subspaces of the Ri series to identify the quasiperiodic coherent structures from the single tower observation. Analysis of turbulence fluxes and anisotropy demonstrates the mechanism, that is, horizontal kinetic energy coupled with vertical downward flux, whereby anisotropy evolution is changed. Examining the anisotropy invariants changing with kinetic energy reveals a dynamical transition that determines the threshold of HOST. Moreover, the mechanism about how the shear and vertical momentum influences the transition point of HOST is at first given by a group of a quadratic relationship when the anisotropy crossed over the transition point.
Multipoint Conjugate Observations of Dayside ULF Waves During an Extended Period of Radial IMF
Authors: Shi X. , Hartinger M. D. , Baker J. B. H. , Ruohoniemi J. M. , Lin D. , Xu Z. , Coyle S. , Kunduri B. S. R. , Kilcommons L. M. , Willer A.
Published: November 2020

Long‐lasting Pc5 ultralow frequency (ULF) waves spanning the dayside and extending from L ∼ 5.5 into the polar cap region were observed by conjugate ground magnetometers. Observations from MMS satellites in the magnetosphere and magnetometers on the ground confirmed that the ULF waves on closed field lines were due to fundamental toroidal standing Alfvén waves. Monochromatic waves at lower latitudes tended to maximize their power away from noon in both the morning and afternoon sectors, while more broadband waves at higher latitudes tended to have a wave power maximum near noon. The wave power distribution and MMS satellite observations during the magnetopause crossing indicate surface waves on a Kelvin‐Helmholtz (KH) unstable magnetopause coupled with standing Alfvén waves. The more turbulent ion foreshock during an extended period of radial interplanetary magnetic field (IMF) likely plays an important role in providing seed perturbations for the growth of the KH waves. These results indicate that the Pc5 waves observed on closed field lines and on the open field lines of the polar cap were from the same source.
Evaluation and Projection of Surface Wind Speed Over China Based on CMIP6 GCMs
Authors: Wu Jie , Shi Ying , Xu Ying
Published: November 2020

Surface wind speed has great impacts on the economy, environment, and society around the world. Based on 24 global climate models (GCMs) from Coupled Model Intercomparison Project Phase 6 (CMIP6), this paper assesses the historical surface wind speed over China, and quantifies the advancements of CMIP6 over CMIP5. In addition, future changes of surface wind speed under the Shared Socioeconomic Pathway scenarios of 1‐2.6, 2‐4.5, and 5‐8.5 (SSP1‐2.6, SSP2‐4.5, and SSP5‐8.5) are also provided, by using 18 out of the 24 models with all three scenarios. Results show that multimodel ensemble mean of CMIP6 can well capture the spatial distributions of the annual, summer, and winter surface wind speed and generally performs better than both the median of the individual CMIP6 GCMs and multimodel ensemble mean of CMIP5 in monthly, seasonal, and annual wind climatology. However, CMIP6 GCMs fail to reproduce the observed decreasing trends, in terms of magnitude and/or sign. Meanwhile, the annual cycle of the surface wind speed simulated by CMIP6 GCMs falsely demonstrates the maximum in winter instead of spring. In the context of global warming, surface wind speed is projected to decrease in most parts of China in the middle and late 21st century under the three scenarios. Moreover, the trends of wind speed averaged over China will decrease significantly in both annual and winter under all three scenarios, but it will increase significantly in summer under SSP5‐8.5.
Long‐Term Trends in Acid Precipitation and Watershed Elemental Export From an Alpine Catchment of the Colorado Rocky Mountains, USA
Authors: Crawford John T. , Hinckley Eve‐Lyn S. , Neff Jason C.
Published: November 2020

Acid deposition associated with precipitation is an ecological problem that has affected watersheds in industrialized parts of North America and Europe, but remote landscapes, such as the Colorado Rocky Mountains, have also been impacted. The deposition of strong acids, including nitric and sulfuric acids, has decreased substantially over the past 30 years at Niwot Ridge, a high‐alpine watershed of Colorado. The pH of precipitation has followed these declines and has increased to ~5.5. Meanwhile, NH4+, another important constituent of acid/base balance, and a fertilizing nutrient, has more than doubled in precipitation between 1984 and 2017. A statistical model of long‐term water chemistry concentrations and loads revealed a variety of trends in watershed export of acids and bases, some of which were unexpected, and remain unexplained. For example, despite declining sulfate deposition, sulfate export has increased. On the other hand, watershed nitrate export has remained constant despite decreases in atmospheric deposition, while watershed NH4+ export has increased, albeit minimally, relative to total nitrogen export. Watershed pH and alkalinity appear to have stabilized in response to decreased acid precipitation, which may be explained by geochemical processes, such as carbonate weathering. Overall, in this high‐alpine watershed, atmospheric deposition is trending toward preindustrial conditions, and there is a need to conduct targeted, process‐based studies to determine the mechanisms underlying these trends. The unexpected watershed responses that we identify here require a new framework for understanding acid precipitation recovery.
Changes of Light Components and Impacts on Interannual Variations of Photosynthesis in China Over 2000–2017 by Using a Two‐Leaf Light Use Efficiency Model
Authors: Yan H. , Wang S. Q. , Wang J. B. , Shugart H. H.
Published: November 2020

Diffuse radiation produces a higher light use efficiency (LUE) than does direct radiation. However, light components and their impacts on interannual variations of photosynthesis in China have not been intensively studied. We estimated gross primary production (GPP) from a two‐leaf LUE model that incorporates a diffuse radiation effect and compared it with a big‐leaf LUE model that ignores the diffuse radiation impact. The results show that a dimming occurred in China—the estimated annual photosynthetically active radiation (PAR) declined by −1.79 MJ m−2 yr−1. However, the diffuse fraction and diffuse PAR increased over this interval. Both GPP models simulated an increasing trend of GPP in China from 2000 to 2017. The big‐leaf GPP model underestimated the increasing trend of GPP from the two‐leaf GPP model by 6.4%. The diffuse fraction change during the dimming exerted an embedded positive impact relative to the big‐leaf GPP trend in China.

To evaluate the impact of total PAR versus its components on GPP, annual anomaly percentage (Ap) of GPP shows that the big‐leaf GPP model had a positive correlation between Ap of GPP and PAR across China. Considering the diffuse radiation impact, Ap of two‐leaf GPP was negatively correlated with PAR in southern China, which had a higher leaf area index (2.02) and a greater diffuse fraction (0.63). Strong diffuse radiation effects in southern China produced GPP anomalies in opposition to the direction of the PAR changes. These findings highlight the distinctive impact of light components on interannual variations of plant photosynthesis.
Global Patterns and Climate Controls of Terrestrial Ecosystem Light Use Efficiency
Authors: Tang Shuchang , Wang Xuhui , He Mingzhu , Huang Ling , Zhang Yuan , Yang Hui , Piao Shilong
Published: November 2020

Light use efficiency (LUE) is a critical parameter, on which we rely to quantify the vegetation's capability to harvest solar energy and thus the photosynthesis carbon uptake. However, our understanding on its magnitude, global pattern, and climatic drivers remains uncertain. In this study, we investigated global mean annual LUE during 1980–2013 based on state‐of‐the‐art estimates from scaled‐up eddy covariance measurements (data‐driven models) and 10 process‐based models used in Global Carbon Project. We found comparable global LUE estimates from data‐driven models (0.90 ± 0.25 g C MJ−1) and process‐based models (0.73 ± 0.22 g C MJ−1), with individual model estimates ranging from 0.49 to 0.98 g C MJ−1. While both types of models agreed on highest LUE over the tropical evergreen forests, discrepancies remained over middle and high latitudes of the Northern Hemisphere, which probably resulted from different response of LUE to climatic factors. Spatial analyses revealed that LUE variations were more driven by temperature and precipitation than by solar radiation. While the response of LUE to precipitation was almost always positive globally, the response of LUE to temperature was only positive in part of the nontropical regions. Process‐based models showed that precipitation strongly regulated the response of LUE to temperature, which shifted from negative to positive when mean annual precipitation was larger than 1,000 mm yr−1. Our results provide converging global LUE estimates and highlight the need to take fully account of interactive effects of climatic factors in regulating LUE and thus the response of photosynthesis to climate change.
Fate of Dissolved Organic Carbon in Antarctic Surface Environments During Summer
Authors: Samui Gautami , Antony Runa , Thamban Meloth
Published: November 2020

While the role of supraglacial environments such as the cryoconite holes and surface snow in cycling of carbon and nutrients has gained momentum in the last decade, little has been done to assess how interactions with sunlight and microbes control the dissolved organic matter cycling in these environments. In this study, the cryoconite holes, which are subjected to different light conditions, were monitored in the coastal Antarctica during the summer in order to determine how the geochemistry of these environments varied through the melt season. Additionally, mesocosm experiments were conducted to understand the impact of photochemical and microbial activities on dissolved organic carbon (DOC) and ionic constituents in the snow and cryoconite holes. In situ measurements of primary and bacterial production carried out in the surface snow and cryoconite holes showed that the primary production rates were higher than the bacterial production rates. Both photochemical and microbial processes resulted in changing the concentration of DOC, carboxylate, and nitrate ions in these environments. Sunlight‐induced production of biologically labile compounds, such as acetate and formate, and photochemical degradation of oxalate were also observed. Microbial activity had the opposite effect, resulting in an increase in oxalate and decrease in acetate and formate concentrations. Consequences of these combined processes would determine the fate of DOC and associated nutrients in the Antarctic supraglacial environments and potentially influence the local productivity within these systems.
Initiation of the Western Pacific Warm Pool at the Middle Miocene Climate Transition?
Authors: Sosdian S. M. , Lear C. H.
Published: November 2020

Across the middle Miocene, Earth's climate underwent a major cooling and expansion of the Antarctic ice sheet. However, the associated response and development of the tropical climate system is not fully understood, in part because this is influenced by both global climate and also low‐latitude tectonic gateways and paleoceanography. Here we use combined δ18O and Mg/Ca of planktic foraminifera to reconstruct the thermal history and changes in hydrology from the Indo‐Pacific region from 16.5 to 11.5 Ma. During the warmth of the early middle Miocene, our records indicate a dynamic ocean‐atmosphere system in the Indo‐Pacific region, with episodes of saltier and warmer tropical surface waters associated with high pCO2 and retreat of the Antarctic ice sheet. We show that across the Middle Miocene Climate Transition (MMCT) surface ocean temperatures in the Indo‐Pacific cooled by ~2°C, synchronous with the advance of the Antarctic ice sheet. The associated cooling in the Southern Ocean appears to have started earlier and was stronger. Further, we show that western Pacific Ocean warmed and eastern tropical Indian Ocean freshened following the MMCT, likely caused by the constriction of the Indonesian Seaway and reduced connectivity between the Pacific and Indian Oceans following Antarctic glaciation. The MMCT therefore represented a key phase in the evolution of the West Pacific Warm Pool and associated tropical climate dynamics.
The Role of Tectonic Plate Thickness and Mantle Conductance in Determining Regional Vulnerability to Extreme Space Weather Events: Possible Enhancement of Magnetic Source Fields by Secondary Induction in the Asthenosphere
Authors: Simpson Fiona , Bahr Karsten
Published: November 2020

During magnetic storms, solar‐magnetosphere‐ionosphere‐Earth interactions give rise to geomagnetically induced currents (GICs) in man‐made technological conductors such as power grids, gas pipelines, and railway networks with potentially damaging outcomes. Generally, electrically conductive regions of the Earth are assumed to be less at risk to GICs than resistive ones, since induced electric fields associated with GICs are linearly related to given magnetic source fields via Earth's impedance. Here, we show that magnetic source fields associated with storms can be enhanced by secondary electromagnetic (EM) induction in Earth's electrically conductive asthenosphere and that this previously neglected effect can give rise to larger electric fields close to the lithosphere‐asthenosphere boundary in regions where the conductance of the asthenosphere is higher. Our analysis of data from the 30 October 2003 “Halloween” and 8 September 2017 storms shows that the magnitudes of electric fields from both storms are affected by lithospheric plate thickness and asthenosphere conductance (conductivity‐thickness product) and that they are 5 times larger in southern Sweden (>5 V/km for the 30 October 2003 “Halloween” storm) than in central Scotland. Our results provide insight into why Sweden experienced a storm‐related power outage in 2003, whereas Scotland did not.
Real‐Time Imaging Reveals Distinct Pore‐Scale Dynamics During Transient and Equilibrium Subsurface Multiphase Flow
Authors: Spurin Catherine , Bultreys Tom , Rücker Maja , Garfi Gaetano , Schlepütz Christian M. , Novak Vladimir , Berg Steffen , Blunt Martin J. , Krevor Samuel
Published: November 2020

Many subsurface fluid flows, including the storage of CO2 underground or the production of oil, are transient processes incorporating multiple fluid phases. The fluids are not in equilibrium meaning macroscopic properties such as fluid saturation and pressure vary in space and time. However, these flows are traditionally modeled with equilibrium (or steady‐state) flow properties, under the assumption that the pore‐scale fluid dynamics are equivalent. In this work, we used fast synchrotron X‐ray tomography with 1 s time resolution to image the pore‐scale fluid dynamics as the macroscopic flow transitioned to steady state. For nitrogen or decane, and brine injected simultaneously into a porous rock, we observed distinct pore‐scale fluid dynamics during transient flow. Transient flow was found to be characterized by intermittent fluid occupancy, whereby flow pathways through the pore space were constantly rearranging. The intermittent fluid occupancy was largest and most frequent when a fluid initially invaded the rock. But as the fluids established an equilibrium the dynamics decreased to either static interfaces between the fluids or small‐scale intermittent flow pathways, depending on the capillary number and viscosity ratio. If the fluids were perturbed after an equilibrium was established, by changing the flow rate, the transition to a new equilibrium was quicker than the initial transition. Our observations suggest that transient flows require separate modeling parameters. The time scales required to achieve equilibrium suggest that several meters of an invading plume front will have flow properties controlled by transient pore‐scale fluid dynamics.
Impact of Sub‐core‐scale Heterogeneity on Meter‐Scale Flow and Brine Displacement in Drainage by CO2
Authors: Moreno Z. , Rabinovich A.
Published: November 2020

Studies of CO2‐brine two‐phase flow are predominantly carried out on core samples or reservoir‐scale domains. In this work we investigate intermediate‐scale flow considering a cubic rock with 1 m3 volume incorporating sub‐core (mm)‐scale heterogeneity. First, a coreflooding experiment is analyzed to estimate subcore permeability spatial distribution and the results are used as input into the meter‐scale model without any upscaling required. High‐resolution numerical simulations are conducted to model CO2 injection into a brine saturated rock. We find significant differences between the meter‐scale rock simulation and core experiment saturation distributions resulting from highly influential boundary effects on the core scale and pronounced gravity impact on the meter scale. A detailed analysis of flow and brine trapping in rock simulations is presented considering different flow models and permeability structures. It is shown that gravity and capillary heterogeneity have substantial impact on the saturation in the deeper regions, which exhibit sufficiently low capillary pressure, and these regions also show increased trapping of brine. Two trapping mechanisms are discussed: Type I which is a result of entry pressure considerations and Type II, which occurs due to lack of CO2 connectivity. The two types of trapping are found to be correlated to the permeability structure. A formula is presented relating between trapping and permeability statistical parameters, that is, variance of log‐permeability and correlation length scale, as well as to the Bond number characterizing the ratio between gravity and capillary effects.
Correction: Early-life stress induces EAAC1 expression reduction and attention-deficit and depressive behaviors in adolescent rats
Authors: Kim Han-Byeol , Yoo Ji-Young , Yoo Seung-Yeon , Suh Sang Won , Lee Seoul , Park Ji Hye , Lee Jun-Ho , Baik Tai-Kyoung , Kim Hye-Sun , Woo Ran-Sook
Published: November 2020

An amendment to this paper has been published and can be accessed via a link at the top of the paper.
Periodontitis-level butyrate-induced ferroptosis in periodontal ligament fibroblasts by activation of ferritinophagy
Authors: Zhao Yunhe , Li Jiao , Guo Wei , Li Houxuan , Lei Lang
Published: November 2020

Loss of periodontal ligament fibroblasts (PDLFs) is one critical issue for regenerating lost periodontal tissues. A wide variety of regulated cell death pathways, such as apoptosis, pyroptosis, and necroptosis have been proposed in the periodontitis development. The aim of the present study was to explore whether long-term periodontitis-level butyrate may trigger ferroptosis, a newly characterized iron-dependent regulated cell death in PDLFs. Here, we showed that long-term treatment of butyrate, an important short-chain fatty acid in the periodontal pocket, induces the cargo receptor nuclear receptor coactivator 4 (NCOA4)-mediated ferritinophagy and ferroptosis in PDLFs. Butyrate-induced iron accumulation, reactive oxygen species (ROS) generation, glutathione depletion and lipid peroxidation in PDLFs, and the butyrate-induced ferroptosis can be blocked by the lipid peroxide scavenger ferrostatin-1. The NCOA4-mediated ferritinophagy is dependent on p38/hypoxia inducible factor-1α (HIF-1α) pathway activation as well as Bromodomain-containing protein (BRD) 4 and cyclin-dependent kinase 9 (CDK9) coordination. These lines of evidence provide a new mechanistic insight into the mechanism of loss of PDLFs during periodontitis development, showing that periodontitis-level butyrate disrupted iron homeostasis by activation of NCOA4-mediated ferritinophagy, leading to ferroptosis in PDLFs.
Observation of nanoscale opto-mechanical molecular damping as the origin of spectroscopic contrast in photo induced force microscopy
Authors: Almajhadi Mohammad A. , Uddin Syed Mohammad Ashab , Wickramasinghe H. Kumar
Published: November 2020

Infrared photoinduced force microscopy (IR-PiFM) is a scanning probe spectroscopic technique that maps sample morphology and chemical properties on the nanometer (nm)-scale. Fabricated samples with nm periodicity such as self-assembly of block copolymer films can be chemically characterized by IR-PiFM with relative ease. Despite the success of IR-PiFM, the origin of spectroscopic contrast remains unclear, preventing the scientific community from conducting quantitative measurements. Here we experimentally investigate the contrast mechanism of IR-PiFM for recording vibrational resonances. We show that the measured spectroscopic information of a sample is directly related to the energy lost in the oscillating cantilever, which is a direct consequence of a molecule excited at its vibrational optical resonance—coined as opto-mechanical damping. The quality factor of the cantilever and the local sample polarizability can be mathematically correlated, enabling quantitative analysis. The basic theory for dissipative tip-sample interactions is introduced to model the observed opto-mechanical damping.
DNA-assembled superconducting 3D nanoscale architectures
Authors: Shani Lior , Michelson Aaron N. , Minevich Brian , Fleger Yafit , Stern Michael , Shaulov Avner , Yeshurun Yosef , Gang Oleg
Published: November 2020

Studies of nanoscale superconducting structures have revealed various physical phenomena and led to the development of a wide range of applications. Most of these studies concentrated on one- and two-dimensional structures due to the lack of approaches for creation of fully engineered three-dimensional (3D) nanostructures. Here, we present a ‘bottom-up’ method to create 3D superconducting nanostructures with prescribed multiscale organization using DNA-based self-assembly methods. We assemble 3D DNA superlattices from octahedral DNA frames with incorporated nanoparticles, through connecting frames at their vertices, which result in cubic superlattices with a 48 nm unit cell. The superconductive superlattice is formed by converting a DNA superlattice first into highly-structured 3D silica scaffold, to turn it from a soft and liquid-environment dependent macromolecular construction into a solid structure, following by its coating with superconducting niobium (Nb). Through low-temperature electrical characterization we demonstrate that this process creates 3D arrays of Josephson junctions. This approach may be utilized in development of a variety of applications such as 3D Superconducting Quantum interference Devices (SQUIDs) for measurement of the magnetic field vector, highly sensitive Superconducting Quantum Interference Filters (SQIFs), and parametric amplifiers for quantum information systems.
A tunable LIC1-adaptor interaction modulates dynein activity in a cargo-specific manner
Authors: Lee In-Gyun , Cason Sydney E. , Alqassim Saif S. , Holzbaur Erika L. F. , Dominguez Roberto
Published: November 2020

Cytoplasmic dynein-1 (dynein) is the motor responsible for most retrograde transport of cargoes along microtubules in eukaryotic cells, including organelles, mRNA and viruses. Cargo selectivity and activation of processive motility depend on a group of so-called “activating adaptors” that link dynein to its general cofactor, dynactin, and cargoes. The mechanism by which these adaptors regulate dynein transport is poorly understood. Here, based on crystal structures, quantitative binding studies, and in vitro motility assays, we show that BICD2, CRACR2a, and HOOK3, representing three subfamilies of unrelated adaptors, interact with the same amphipathic helix of the dynein light intermediate chain-1 (LIC1). While the hydrophobic character of the interaction is conserved, the three adaptor subfamilies use different folds (coiled-coil, EF-hand, HOOK domain) and different surface contacts to bind the LIC1 helix with affinities ranging from 1.5 to 15.0 μM. We propose that a tunable LIC1-adaptor interaction modulates dynein’s motility in a cargo-specific manner.
Estimation of global tropical cyclone wind speed probabilities using the STORM dataset
Authors: Bloemendaal Nadia , de Moel Hans , Muis Sanne , Haigh Ivan D. , Aerts Jeroen C. J. H.
Published: November 2020

Tropical cyclones (TC) are one of the deadliest and costliest natural disasters. To mitigate the impact of such disasters, it is essential to know extreme exceedance probabilities, also known as return periods, of TC hazards. In this paper, we demonstrate the use of the STORM dataset, containing synthetic TCs equivalent of 10,000 years under present-day climate conditions, for the calculation of TC wind speed return periods. The temporal length of the STORM dataset allows us to empirically calculate return periods up to 10,000 years without fitting an extreme value distribution. We show that fitting a distribution typically results in higher wind speeds compared to their empirically derived counterparts, especially for return periods exceeding 100-yr. By applying a parametric wind model to the TC tracks, we derive return periods at 10 km resolution in TC-prone regions. The return periods are validated against observations and previous studies, and show a good agreement. The accompanying global-scale wind speed return period dataset is publicly available and can be used for high-resolution TC risk assessments.
3D micro-organisation printing of mammalian cells to generate biological tissues
Authors: Jeffries Gavin D. M. , Xu Shijun , Lobovkina Tatsiana , Kirejev Vladimir , Tusseau Florian , Gyllensten Christoffer , Singh Avadhesh Kumar , Karila Paul , Moll Lydia , Orwar Owe
Published: November 2020

Significant strides have been made in the development of in vitro systems for disease modelling. However, the requirement of microenvironment control has placed limitations on the generation of relevant models. Herein, we present a biological tissue printing approach that employs open-volume microfluidics to position individual cells in complex 2D and 3D patterns, as well as in single cell arrays. The variety of bioprinted cell types employed, including skin epithelial (HaCaT), skin cancer (A431), liver cancer (Hep G2), and fibroblast (3T3-J2) cells, all of which exhibited excellent viability and survivability, allowing printed structures to rapidly develop into confluent tissues. To demonstrate a simple 2D oncology model, A431 and HaCaT cells were printed and grown into tissues. Furthermore, a basic skin model was established to probe drug response. 3D tissue formation was demonstrated by co-printing Hep G2 and 3T3-J2 cells onto an established fibroblast layer, the functionality of which was probed by measuring albumin production, and was found to be higher in comparison to both 2D and monoculture approaches. Bioprinting of primary cells was tested using acutely isolated primary rat dorsal root ganglia neurons, which survived and established processes. The presented technique offers a novel open-volume microfluidics approach to bioprint cells for the generation of biological tissues.
Transcriptome analysis of xa5-mediated resistance to bacterial leaf streak in rice (Oryza sativa L.)
Authors: Xie Xiaofang , Chen Zhiwei , Zhang Binghui , Guan Huazhong , Zheng Yan , Lan Tao , Zhang Jing , Qin Mingyue , Wu Weiren
Published: November 2020

Bacterial leaf steak (BLS) caused by Xanthomonas oryzae pv. oryzicola (Xoc) is a devastating disease in rice production. The resistance to BLS in rice is a quantitatively inherited trait, of which the molecular mechanism is still unclear. It has been proved that xa5, a recessive bacterial blast resistance gene, is the most possible candidate gene of the QTL qBlsr5a for BLS resistance. To study the molecular mechanism of xa5 function in BLS resistance, we created transgenic lines with RNAi of Xa5 (LOC_Os05g01710) and used RNA-seq to analyze the transcriptomes of a Xa5-RNAi line and the wild-type line at 9 h after inoculation with Xoc, with the mock inoculation as control. We found that Xa5-RNAi could (1) increase the resistance to BLS as expected from xa5; (2) alter (mainly up-regulate) the expression of hundreds of genes, most of which were related to disease resistance; and (3) greatly enhance the response of thousands of genes to Xoc infection, especially of the genes involved in cell death pathways. The results suggest that xa5 is the cause of BLS-resistance of QTL qBlsr5a and it displays BLS resistance effect probably mainly because of the enhanced response of the cell death-related genes to Xoc infection.
From bridges to cycles in spectroscopic networks
Authors: Árendás P. , Furtenbacher T. , Császár A. G.
Published: November 2020

Spectroscopic networks provide a particularly useful representation of observed rovibronic transitions of molecules, as well as of related quantum states, whereby the states form a set of vertices connected by the measured transitions forming a set of edges. Among their several uses, SNs offer a practical framework to assess data in line-by-line spectroscopic databases. They can be utilized to help detect flawed transition entries. Methods which achieve this validation work for transitions taking part in at least one cycle in a measured spectroscopic network but they do not work for bridges. The concept of two-edge-connectivity of graph theory, introduced here to high-resolution spectroscopy, offers an elegant approach that facilitates putting the maximum number of bridges, if not all, into at least one cycle. An algorithmic solution is shown how to augment an existing spectroscopic network with a minimum number of new spectroscopic measurements selected according to well-defined guidelines. In relation to this, two metrics are introduced, ranking measurements based on their utility toward achieving the goal of two-edge-connectivity. Utility of the new concepts are demonstrated on spectroscopic data of $$^{14} {\text {NH}}_3$$

14

NH
3

.
Detection of stratospheric gravity waves induced by the total solar eclipse of July 2, 2019
Authors: Colligan Thomas , Fowler Jennifer , Godfrey Jaxen , Spangrude Carl
Published: November 2020

Atmospheric gravity waves generated by an eclipse were first proposed in 1970. Despite numerous efforts since, there has been no definitive evidence for eclipse generated gravity waves in the lower to middle atmosphere. Measuring wave characteristics produced by a definite forcing event such as an eclipse provides crucial knowledge for developing more accurate physical descriptions of gravity waves. These waves are fundamental to the transport of energy and momentum throughout the atmosphere and their parameterization or simulation in numerical models provides increased accuracy to forecasts. Here, we present the findings from a radiosonde field campaign carried out during the total solar eclipse of July 2, 2019 aimed at detecting eclipse-driven gravity waves in the stratosphere. This eclipse was the source of three stratospheric gravity waves. The first wave (eclipse wave #1) was detected 156 min after totality and the other two waves were detected 53 and 62 min after totality (eclipse waves #2 and #3 respectively) using balloon-borne radiosondes. Our results demonstrate both the importance of field campaign design and the limitations of currently accepted balloon-borne analysis techniques for the detection of stratospheric gravity waves.