bluuebunny/crossref_metadata_2025_split huggingface dataset:
Slow Long‐Term Exhumation of the West Central Andean Plate Boundary, Chile
Authors: Avdievitch Nikita N. , Ehlers Todd A. , Glotzbach Christoph 
Published: July 2018

AbstractWe present a regional analysis of new low‐temperature thermochronometer ages from the Central Andean fore arc to provide insights into the exhumation history of the western Andean margin. To derive exhumation rates over 10 million‐year timescales, 38 new apatite and zircon (U‐Th)/He ages were analyzed along six ~500‐km long near‐equal‐elevation, coast parallel, transects in the Coastal Cordillera (CC) and higher‐elevation Precordillera (PC) of the northern Chilean Andes between latitudes 18.5°S and 22.5°S. These transects were augmented with age‐elevation profiles where possible. Results are synthesized with previously published thermochronometric data, corroborating a previously observed trenchward increase in cooling ages in Peru and northern Chile. One‐dimensional thermal‐kinematic modeling of all available multichronometer equal‐elevation samples reveals mean exhumation rates of <0.2 km/Myr since ~50 Ma in the PC and ~100 Ma in the CC. Regression of pseudovertical age‐elevation transects in the CC yields comparable rates of ~0.05 to ~0.12 km/Myr between ~40 and 80 Ma. Differences between the long‐term mean 1‐D rates and shorter‐term age‐elevation‐derived rates indicate low variability in the exhumation history. Modeling results suggest similar background exhumation rates in the CC and PC; younger ages in the PC are largely a function of increased heat flow and consequently an elevated geothermal gradient near the arc. Slow exhumation rates are suggestive of semiarid conditions across the region since at least the Eocene and deformation and development of the Andean fore arc around this time.
An Increase of the Indonesian Throughflow by Internal Tidal Mixing in a High‐Resolution Quasi‐Global Ocean Simulation
Authors: Sasaki H. , Kida S. , Furue R. , Nonaka M. , Masumoto Y. 
Published: July 2018

AbstractThe impact of internal tidal mixing on the volume transport of the Indonesian Throughflow (ITF) is examined by a comparison of high‐resolution quasi‐global ocean simulations with and without a tidal mixing scheme. The ITF transport is found to be increased in the presence of tidal mixing. This is because tidal mixing decreases the density within and below the lower thermocline and increases the buoyancy of the water column. As a result, the surface pressure and the sea surface height (SSH) are raised. The magnitude of the SSH increase is larger for the tropical Pacific Ocean than for the other basins, possibly because many islands exist in the tropical Pacific and tidal mixing is effective around their shallow and rough topographies. Since SSH increases more in the tropical Pacific than in the Indian Ocean, the pressure difference between the two basins is enhanced and thus the ITF transport is strengthened.
Evaluation of Reconstructions of Snow/Ice Melt in Greenland by Regional Atmospheric Climate Models Using Laser Altimetry Data
Authors: Sutterley Tyler C. , Velicogna Isabella , Fettweis Xavier , Rignot Eric , Noël Brice , van den Broeke Michiel 
Published: July 2018

AbstractThe surface mass balance of the Greenland ice sheet critically depends on the intensity of ice melt/snowmelt in its ablation zone, but in situ data have been too limited to quantify the error of regional climate models. Here we use 23 years of NASA satellite and airborne laser altimetry from the Airborne Topographic Mapper; Land, Vegetation, and Ice Sensor; and Ice, Cloud, and land Elevation Satellite to generate time series of elevation change to compare with surface mass balance products from the Regional Atmospheric Climate Model and from the Modèle Atmosphérique Régional. For 1994–2016, the results agree at the 15–26% level, with the largest discrepancy in North Greenland. During the cold summer of 2015, the root‐mean‐square discrepancy is 40% in the north, 30% in the southwest, and 18–25% at low elevation. The difference drops to 23% in the southwest and 14% at low elevation during the 2016 warm summer.
Buoyant Asthenosphere Beneath Cascadia Influences Megathrust Segmentation
Authors: Bodmer Miles , Toomey Douglas R. , Hooft Emilie E. E. , Schmandt Brandon 
Published: July 2018

AbstractGreat megathrust earthquakes (magnitude 8+) do not typically rupture an entire convergent margin but rather are limited to one or more along‐strike segments. A fundamental question of subduction zone dynamics and hazard assessment is what physical properties or dynamic processes govern megathrust segmentation. Here we use onshore‐offshore teleseismic delay time data to tomographically image the upper mantle seismic structure of the Cascadia subduction zone. Our results reveal along‐strike segmentation in the oceanic asthenosphere beneath the subducting plate with pronounced low‐velocity anomalies below regions of increased plate locking and greater occurrence of episodic tremor and slip. We attribute the anomalous asthenospheric velocities to independent mantle upwellings associated with hot spot‐derived material in northern Cascadia and fragmentation processes at a diffuse plate boundary in southern Cascadia. Based on these relations, we hypothesize that subslab buoyancy modulates the plate coupling force at the thrust interface, thereby contributing to the localization of subduction zone segmentation.
The Formation of Clay‐Enriched Horizons by Lessivage
Authors: Calabrese Salvatore , Richter Daniel D. , Porporato Amilcare 
Published: July 2018

AbstractSoils with argillic horizons comprise more than 25% of the Earth's surface. Although their origin is still debated, lessivage is often invoked to explain them, but the long timescales involved hinder its direct experimental verification. We present a parsimonious model of clay transport, formulated for long timescales over which lessivage is modeled stochastically, complemented by detailed field observations. This probabilistic description allows us to predict the clay profile, the depth of the Bt horizon from the surface, and the mean clay residence time. The results are tested with field measurements at different locations in the Calhoun Critical Zone Observatory. Dimensional analysis unveils two dimensionless parameters governing lessivage dynamics, leading to a classification based on erosion rates and lessivage characteristics. We identify static and eluviated regimes, in which erosion or eluviation prevails, and an illuviated regime, in which the balance between lessivage and erosion brings about the formation of a Bt horizon.
Microburst Scale Size Derived From Multiple Bounces of a Microburst Simultaneously Observed With the FIREBIRD‐II CubeSats
Authors: Shumko Mykhaylo , Sample John , Johnson Arlo , Blake Bern , Crew Alex , Spence Harlan , Klumpar David , Agapitov Oleksiy , Handley Matthew 
Published: July 2018

AbstractWe present the observation of a spatially large microburst with multiple bounces made simultaneously by the Focused Investigation of Relativistic Electron Bursts: Intensity, Range, and Dynamics II (FIREBIRD‐II) CubeSats on 2 February 2015. This is the first observation of a microburst with a subsequent decay made by two coorbiting but spatially separated spacecraft. From these unique measurements, we place estimates on the lower bounds of the spatial scales as well as quantify the electron bounce periods. The microburst's lower bound latitudinal scale size was 29 ± 1 km and the longitudinal scale size was 51 ± 1 km in low Earth orbit. We mapped these scale sizes to the magnetic equator and found that the radial and azimuthal scale sizes were at least 500 ± 10 km and 530 ± 10 km, respectively. These lower bound equatorial scale sizes are similar to whistler mode chorus wave source scale sizes, which supports the hypothesis that microbursts are a product of electron scattering by chorus waves. Lastly, we estimated the bounce periods for 200‐ to 800‐keV electrons and found good agreement with four common magnetic field models.
Impacts of 1.5 and 2.0 °C Warming on Pan‐Arctic River Discharge Into the Hudson Bay Complex Through 2070
Authors: MacDonald Matthew K. , Stadnyk Tricia A. , Déry Stephen J. , Braun Marco , Gustafsson David , Isberg Kristina , Arheimer Berit 
Published: July 2018

AbstractDischarge projections into the Hudson Bay Complex to 2070 are investigated for global mean temperature warming levels of 1.5 and 2.0 °C. Median precipitation increases from 1986–2005, ranging from 2% during summer to 19% during winter, are projected to increase discharge in all seasons except summer. The rise in discharge is greatest furthest north, into Foxe Basin, Ungava Bay, and Hudson Strait, exceeding 10% above historical annual means. A 2.0 °C warming results in higher discharge than 1.5 °C warming owing to greater precipitation (e.g., 6.5% greater spring discharge increase); however, summer discharge for 2.0 °C warming is lower due to enhanced evaporation and lower precipitation increase from historical (4.0% lower summer discharge increase). Extreme daily high flows are projected to be greater than historical, more so for 2.0 °C warming than 1.5 °C warming, and this is greatest in the eastern and northern regions. These projections suggest continued increasing river discharge into pan‐Arctic coastal oceans.
The Role of the Parallel Electric Field in Electron‐Scale Dissipation at Reconnecting Currents in the Magnetosheath
Authors: Wilder F. D. , Ergun R. E. , Burch J. L. , Ahmadi N. , Eriksson S. , Phan T. D. , Goodrich K. A. , Shuster J. , Rager A. C. , Torbert R. B. , Giles B. L. , Strangeway R. J. , Plaschke F. , Magnes W. , Lindqvist P. A. , Khotyaintsev Y. V. 
Published: July 2018

AbstractWe report observations from the Magnetospheric Multiscale satellites of reconnecting current sheets in the magnetosheath over a range of out‐of‐plane “guide” magnetic field strengths. The currents exhibit nonideal energy conversion in the electron frame of reference, and the events are within the ion diffusion region within close proximity (a few electron skin depths) to the electron diffusion region. The study focuses on energy conversion on the electron scale only. At low guide field (antiparallel reconnection), electric fields and currents perpendicular to the magnetic field dominate the energy conversion. Additionally, electron distributions exhibit significant nongyrotropy. As the guide field increases, the electric field parallel to the background magnetic field becomes increasingly strong, and the electron nongyrotropy becomes less apparent. We find that even with a guide field less than half the reconnecting field, the parallel electric field and currents dominate the dissipation. This suggests that parallel electric fields are more important to energy conversion in reconnection than previously thought and that at high guide field, the physics governing magnetic reconnection are significantly different from antiparallel reconnection.
A Numerical Study of Tropical Cyclone‐Induced Sediment Dynamics on the Australian North West Shelf
Authors: Dufois François , Lowe Ryan J. , Rayson Matthew D. , Branson Paul M. 
Published: July 2018

AbstractOwing to their strong forcing of the ocean surface, tropical cyclones strongly modify the hydrodynamics of Australia's North West Shelf (one of the world's tropical cyclone hot spots), which in turn plays a dominant role in its sediment dynamics. Previous modeling studies have focused on describing the short‐term sediment dynamics during individual tropical cyclones but have lacked validation of the responses using field observations. As a consequence, the long‐term cumulative impact of the tropical cyclones on the residual sediment transport pathways at the shelf scale remains unclear. In this study we apply a sediment transport model over the North West Shelf, validate its performance using an extensive field data set, and implement a 14‐year‐long model simulation to assess the sediment fluxes. The model results confirm the overwhelming role tropical cyclones play on sediment transport processes over most of the shelf, despite each cyclone only influencing a small portion of the shelf at a particular time. Overall, we identified 19 tropical cyclone events over the 14‐year period, which, despite accounting for less than 5% of time, were found to drive the majority of both the suspended sediment alongshore and seaward cross‐shore transport. The results revealed significant interannual variability of the tropical cyclone‐induced sediment dynamics with greater suspended transport during the three consecutive Ningaloo Niño years (2011–2013) where sea surface temperatures off northwestern Australia were anomalously warm with elevated tropical cyclone activity.
Roles of Cloud Microphysics on Cloud Responses to Sea Surface Temperatures in Radiative‐Convective Equilibrium Experiments Using a High‐Resolution Global Nonhydrostatic Model
Authors: Ohno Tomoki , Satoh Masaki 
Published: July 2018

AbstractThe high‐cloud amount responses to sea surface temperature (SST) changes were investigated based on simulations with radiative‐convective equilibrium configuration using a high‐resolution nonhydrostatic icosahedral atmospheric model. The radiative‐convective equilibrium was calculated using a nonrotating sphere with Earth radius and a 14‐km horizontal mesh with uniform SSTs of 300 and 304 K. Two types of cloud microphysics schemes (single‐ and double‐moment bulk schemes) and two types of vertical layer configurations (38 and 78 layers) were tested. The radiatively driven circulation weakens with increasing SST in all simulation pairs due to the increase in the static stability, as suggested in previous studies. In contrast, the high‐cloud amount increases in three simulation pairs and decreases in one pair. These indicate that the weakening of radiatively driven circulation with increasing SST does not always accompany the high‐cloud amount decrease. We determined that the tropopause layer was wet (dry) in simulations that showed positive (negative) high‐cloud cover responses. The radiatively driven upward moisture transport just below the wet tropopause layer increases with increasing SST in the simulation pairs with positive high‐cloud amount responses, and this causes the supply of ice condensate to the lower layer through the sedimentation process, while this feedback was not observed in the simulation pair with the negative response. These indicate that the high‐cloud cover response depends on the occurrence of the feedback and there is a feedback threshold among the variety of simulations. And furthermore, these speculate that whether the feedback mechanism is effective or not has the large impact on high‐cloud responses in the real atmosphere.
Large ice loss variability at Nioghalvfjerdsfjorden Glacier, Northeast-Greenland
Authors: Mayer Christoph , Schaffer Janin , Hattermann Tore , Floricioiu Dana , Krieger Lukas , Dodd Paul A. , Kanzow Torsten , Licciulli Carlo , Schannwell Clemens 
Published: July 2018

AbstractNioghalvfjerdsfjorden is a major outlet glacier in Northeast-Greenland. Although earlier studies showed that the floating part near the grounding line thinned by 30% between 1999 and 2014, the temporal ice loss evolution, its relation to external forcing and the implications for the grounded ice sheet remain largely unclear. By combining observations of surface features, ice thickness and bedrock data, we find that the ice shelf mass balance has been out of equilibrium since 2001, with large variations of the thinning rates on annual/multiannual time scales. Changes in ice flux and surface ablation are too small to produce this variability. An increased ocean heat flux is the most plausible cause of the observed thinning. For sustained environmental conditions, the ice shelf will lose large parts of its area within a few decades and ice modeling shows a significant, but locally restricted thinning upstream of the grounding line in response.
A radical S-adenosyl-L-methionine enzyme and a methyltransferase catalyze cyclopropane formation in natural product biosynthesis
Authors: Jin Wen-Bing , Wu Sheng , Jian Xiao-Hong , Yuan Hua , Tang Gong-Li 
Published: July 2018

AbstractCyclopropanation of unactivated olefinic bonds via addition of a reactive one-carbon species is well developed in synthetic chemistry, whereas natural cyclopropane biosynthesis employing this strategy is very limited. Here, we identify a two-component cyclopropanase system, composed of a HemN-like radical S-adenosyl-l-methionine (SAM) enzyme C10P and a methyltransferase C10Q, catalyzes chemically challenging cyclopropanation in the antitumor antibiotic CC-1065 biosynthesis. C10P uses its [4Fe-4S] cluster for reductive cleavage of the first SAM to yield a highly reactive 5′-deoxyadenosyl radical, which abstracts a hydrogen from the second SAM to produce a SAM methylene radical that adds to an sp2-hybridized carbon of substrate to form a SAM-substrate adduct. C10Q converts this adduct to CC-1065 via an intramolecular SN2 cyclization mechanism with elimination of S-adenosylhomocysteine. This cyclopropanation strategy not only expands the enzymatic reactions catalyzed by the radical SAM enzymes and methyltransferases, but also sheds light on previously unnoticed aspects of the versatile SAM-based biochemistry.
Involvement of leptin signaling in the development of cannabinoid CB2 receptor-dependent mirror image pain
Authors: Nozaki Chihiro , Nent Elisa , Bilkei-Gorzo Andras , Zimmer Andreas 
Published: July 2018

AbstractNeuropathic pain typically appears in a region innervated by an injured or diseased nerve and, in some instances, also on the contralateral side. This so-called mirror image pain is often observed in mice lacking CB2 receptors after sciatic nerve injury, but the underlying mechanisms for this phenotype largely remain unclear. Here we focused on peripheral leptin signaling, which modulates neuropathic pain development and interacts with the endocannabinoid system. Leptin production is induced at the site of nerve injury in CB2-deficient mice (CB2-KO) mice and wild type controls (WT). However, induction of leptin receptor expression was only observed in the injured nerve of CB2-KO mice. This was paralleled by a stimulation of the leptin receptor-downstream STAT3 signaling and an infiltration of F4/80-positive macrophages. Interestingly, an upregulation of leptin receptor expression STAT3 activity and macrophage infiltration was also observed on the non-injured nerve of CB2-KO mice thus reflecting the mirror image pain in CB2-KO animals. Importantly, perineurally-administered leptin-neutralizing antibodies reduced mechanical hyperalgesia, blocked mirror image pain and inhibited the recruitment of F4/80-positive macrophages. These results identify peripheral leptin signaling as an important modulator of CB2 signaling in neuropathic pain.
Detection and Discrimination of Bacterial Colonies with Mueller Matrix Imaging
Authors: Badieyan Saeedesadat , Dilmaghani-Marand Arezou , Hajipour Mohammad Javad , Ameri Ali , Razzaghi Mohammad Reza , Rafii-Tabar Hashem , Mahmoudi Morteza , Sasanpour Pezhman 
Published: July 2018

AbstractThe polarization imaging technique is a powerful approach to probe microstructural and optical information of biological structures (e.g., tissue samples). Here, we have studied the polarization properties of different bacterial colonies in order to evaluate the possibility of bacterial detection and discrimination. In this regard, we have taken the backscattering Mueller matrix images of four different bacteria colonies (i.e., Escherichia coli,Lactobacillus rhamnosus,Rhodococcus erythropolis, andStaphylococcus aureus). Although the images have the potential to distinguish qualitatively different bacterial colonies, we explored more accurate and quantitative parameters criteria for discrimination of bacterial samples; more specifically, we have exploited the Mueller matrix polar decomposition (MMPD),frequency distribution histogram (FDH), and central moment analysis method. The outcomes demonstrated a superior capacity of Mueller matrix imaging, MMPD, and FDH in bacterial colonies identification and discrimination. This approach might pave the way for a reliable, efficient, and cheap way of identification of infectious diseases.
Association of Decreased Handgrip Strength with Reduced Cortical Thickness in Japanese Female Patients with Type 2 Diabetes Mellitus
Authors: Nakamura Miyuki , Inaba Masaaki , Yamada Shinsuke , Ozaki Etsuko , Maruo Saori , Okuno Senji , Imanishi Yasuo , Kuriyama Nagato , Watanabe Yoshiyuki , Emoto Masanori , Motoyama Koka 
Published: July 2018

AbstractLD-100, a quantitative ultrasonic device, allows us to measure cortical thickness (CoTh). Patients with type 2 diabetes mellitus (T2DM) show high prevalence of sarcopenia. This study aimed to clarify the association of handgrip strength (HGS) with cortical porosis, a major risk for fracture of DM. CoTh and trabecular bone mineral density (TrBMD) at the 5.5% distal radius were assessed in T2DM female patients (n = 122) and non-DM female controls (n = 704) by LD-100. T2DM patients aged older 40 years showed significantly lower HGS and CoTh, but not TrBMD, than non-DM counterparts. Although HGS was significantly and positively correlated with CoTh and TrBMD in T2DM patients, multivariate analysis revealed HGS as an independent factor positively associated with CoTh, but not TrBMD, in T2DM patients, suggesting the preferential association of HGS with cortical, but not trabecular, bone component in T2DM female patients. In conclusion, the present study demonstrated an early decline of HGS in T2DM female patients as compared with non-DM healthy controls after the age of 40 years, which is independently associated with thinner CoTh, but not TrBMD in T2DM patients, and thus suggested that reduced muscle strength associated with DM might be a major factor for cortical porosis development in DM patients.
Generation of hydroxyl radicals from reactions between a dimethoxyhydroquinone and iron oxide nanoparticles
Authors: Lyngsie Gry , Krumina Lelde , Tunlid Anders , Persson Per 
Published: July 2018

AbstractThe hydroxyl radical (·OH) is a powerful oxidant that is produced in a wide range of environments via the Fenton reaction (Fe2+  + H2O2 → Fe3+  + ·OH + OH-). The reactants are formed from the reduction of Fe3+ and O2, which may be promoted by organic reductants, such as hydroquinones. The aim of this study was to investigate the extent of ·OH formation in reactions between 2,6-dimethoxyhydroquinone (2,6-DMHQ) and iron oxide nanoparticles. We further compared the reactivities of ferrihydrite and goethite and investigated the effects of the O2 concentration and pH on the generation of ·OH. The main finding was that the reactions between 2,6-DMHQ and iron oxide nanoparticles generated substantial amounts of ·OH under certain conditions via parallel reductive dissolution and catalytic oxidation reactions. The presence of O2 was essential for the catalytic oxidation of 2,6-DMHQ and the generation of H2O2. Moreover, the higher reduction potential of ferrihydrite relative to that of goethite made the former species more susceptible to reductive dissolution, which favored the production of ·OH. The results highlighted the effects of surface charge and ligand competition on the 2,6-DMHQ oxidation processes and showed that the co-adsorption of anions can promote the generation of ·OH.