bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Comparative Study on the Self-Assembly of Peptide TGV-9 by In Situ Atomic Force Microscopy
Authors: Li Yaping , Li Na , Wang Lei , Lu Qinhua , Ji Xiang , Zhang Feng 
Published: February 2020

AbstractPrevious studies of amyloid diseases reported that the aggregating proteins share a similar conserved peptide sequence which can form the cross-β-sheet-containing nanostructures like nanofilaments. The template-assisted self-assembly (TASA) of peptides on inorganic substrates with different hydrophilicity could be an alternative approach to shed light on the fibrillization mechanism of proteins/peptides in vivo. To figure out the effect of interfaces on amyloid aggregation, we herein employed in situ atomic force microscopy (AFM) to investigate the self-assembling of a Parkinson disease-related core peptide sequence (TGV-9) on a hydrophobic liquid–solid interface via real-time observation of the dynamic fibrillization process. The results show that TGV-9 forms one-dimensional nanostructures on the surface of highly ordered pyrolytic graphite (HOPG) with three preferred growth orientations, which are consistent with the atomic lattice of HOPG, indicating an epitaxial growth or TASA. Conversely, the nanostructures formed in bulk solution can be free-standing nanofilaments, and the fibrillization mechanism is different from that on HOPG. These results could not only deepen the understanding of the protein/peptide aggregation mechanism but also benefit for the early diagnosis and clinic treatment of related diseases.
Locally Condensed Water as a Solution for In Situ Wet Corrosion Electron Microscopy
Authors: Ahmadi Majid , Tichelaar Frans D. , Ihring Andreas , Kunze Michael , Billat Sophie , Esfahani Zahra Kolahdouz , Zandbergen Henny W. 
Published: February 2020

AbstractIn microstructural corrosion studies, knowledge on the initiation of corrosion on an nm-scale is lacking. In situ transmission electron microscope (TEM) studies can elucidate where/how the corrosion starts, provided that the proper corrosive conditions are present during the investigation. In wet corrosion studies with liquid cell nanoreactors (NRs), the liquid along the electron beam direction leads to strong scattering and therefore image blurring. Thus, a quick liquid removal or thickness control of the liquid layer is preferred. This can be done by the use of a Peltier element embedded in an NR. As a prelude to such in situ work, we demonstrate the local wetting of a TEM sample, by creating a temperature decrease of 10 ± 2°C on the membrane of an NR with planar Sb/BiSb thermoelectric materials for the Peltier element. TEM samples were prepared and loaded in an NR using a dual-beam focused ion beam scanning electron microscope. A mixture of water vapor and carrier gas was passed through a chamber, which holds the micro-electromechanical system Peltier device and resulted in quick formation of a water layer/droplets on the sample. The TEM analysis after repeated corrosion of the same sample (ex situ studies) shows the onset and progression of O2 and H2S corrosion of the AA2024-T3 alloy and cold-rolled HCT980X steel lamellae.
Linking the Atlantic and Indian Oceans: Asian textiles, Spanish silver, global capital, and the financing of the Portuguese–Brazilian slave trade (c.1760–1808)
Authors: Bohorquez J. 
Published: February 2020

AbstractThis article aims to analyse some of the multilateral flows of capital that contributed to weaving a Global South during the second half of the eighteenth century. It specifically revisits the functioning and financing of the Portuguese slave trade from a global perspective, and offers insights for assessing older frameworks that explain it, in either triangular or bilateral terms. The article argues that the Portuguese slave traffic should be liberated from the South Atlantic borders to which it has been confined. In so doing, it offers an Atlantic history in a global perspective, disclosing the connections between the Atlantic and Indian oceans. Putting the financing of the slave trade into a larger global perspective helps to more accurately explain how it actually operated in terms of the organization of trade. When the financial and institutional foundations of Asian and African trade are analysed together, it becomes evident that they were part of larger networks and capital flows, both westwards and eastwards, which were not just framed imperially or locally.
Water powers: the Second World War and the mobilization of hydroelectricity in Canada, the United States, and Germany
Authors: Cohn Julie , Evenden Matthew , Landry Marc 
Published: February 2020

AbstractComparing three of the major hydroelectric power-producing countries during the war – Canada, the United States, and Germany – this article considers the implications of expanding hydroelectricity for war production and strategy, and how wartime decisions structured the longer-term evolution of large technological systems. Despite different starting points, all three countries pursued similar strategies in attempting to mobilize hydroelectricity for the war effort. The different access to and use of hydro in these states produced a vital economic and ultimately military advantage or disadvantage. The global dimensions of hydroelectric development during the war, moreover, demonstrate that this conflict was a turning point in the history of electrification.
A benchmark for the environment: big science and ‘artificial’ geophysics in the global 1950s
Authors: Goossen Benjamin W. 
Published: February 2020

AbstractSecurity concerns during the early Cold War prompted United States strategists to solicit worldwide assistance in studying Earth’s physical environment. Comprehensive geophysical knowledge required cooperation between researchers on every part of the planet, leading practitioners to tout transnational earth science – despite direct military applications in an age of submarines and ballistic missiles – as a non-political form of peaceful universalism. This article examines the 1957–58 International Geophysical Year as a powerful fulcrum in the transfer of ideas about Earth’s global environment from Western security establishments to conservationists worldwide. For eighteen months, tens of thousands of researchers across every continent pooled resources for data collection to create a scientific benchmark for future comparisons. Illuminating Earth as dynamic and interconnected, participants robustly conceptualized humanity’s emergence as a geophysical force, capable of ‘artificially’ modifying the natural world. Studies of anthropogenic geophysics, including satellites, nuclear fallout, and climate change, conditioned the global rise of environmentalism.
A Warm Layer in the Nightside Mesosphere of Mars
Authors: Nakagawa Hiromu , Jain Sonal K. , Schneider Nicholas M. , Montmessin Franck , Yelle Roger V. , Jiang Fayu , Verdier Loic , Kuroda Takeshi , Yoshida Nao , Fujiwara Hitoshi , Imamura Takeshi , Terada Naoki , Terada Kaori , Seki Kanako , Gröller Hannes , Deighan Justin I. 
Published: February 2020

AbstractWe report a new set of stellar occultation measurements for nightside temperature profiles made by the Mars Atmosphere and Volatile EvolutioN/Imaging Ultraviolet Spectrograph that provide evidence for a recurring layer of warm air between 70 and 90 km altitudes in the nightside mesosphere of Mars during Ls = 0–180° in Martian Year 33–34. The nightside profiles reveal a recurring peak of atmospheric temperature around 80 km over the equator to the middle latitudes in the northern hemisphere. The predictions of the Mars Climate Database have a warm layer with much smaller amplitudes. The observed peak amplitudes are larger than those predicted by the model by up to 90 K. Wavenumber‐3 structures are seen in the warm layer that are potentially signatures of thermal tides or stationary planetary waves, with amplitudes two times larger than predicted.
A Preindustrial Sea‐Level Rise Hotspot Along the Atlantic Coast of North America
Authors: Gehrels W. R. , Dangendorf S. , Barlow N. L. M. , Saher M. H. , Long A. J. , Woodworth P. L. , Piecuch C. G. , Berk K. 
Published: February 2020

AbstractThe Atlantic coast of North America north of Cape Hatteras has been proposed as a “hotspot” of late 20th century sea‐level rise. Here we test, using salt‐marsh proxy sea‐level records, if this coast experienced enhanced sea‐level rise over earlier multidecadal‐centennial periods. While we find in agreement with previous studies that 20th century rates of sea‐level change were higher compared to rates during preceding centuries, rates of 18th century sea‐level rise were only slightly lower, suggesting that the “hotspot” is a reoccurring feature for at least three centuries. Proxy sea‐level records from North America (Iceland) are negatively (positively) correlated with centennial changes in the North Atlantic Oscillation. They are consistent with sea‐level “fingerprints” of Arctic ice melt, and we therefore hypothesize that sea‐level fluctuations are related to changes in Arctic land‐ice mass. Predictions of future sea‐level rise should take into account these long‐term fluctuating rates of natural sea‐level change.
Chorus Acceleration of Relativistic Electrons in Extremely Low L‐Shell During Geomagnetic Storm of August 2018
Authors: Zhang Zhenxia , Chen Lunjin , Liu Si , Xiong Ying , Li Xinqiao , Wang Yongfu , Chu Wei , Zeren Zhima , Shen Xuhui 
Published: February 2020

AbstractBased on data from the Van Allen Probes and ZH‐1 satellites, relativistic electron enhancements in extremely low L‐shell regions (reaching
) were observed during August 2018 major geomagnetic storm (minimum
nT). Contrary to what occurs in the outer belt, such an intense and deep electron penetration event is rare and more interesting. Strong whistler‐mode (chorus and hiss) waves, with amplitudes 81–126 pT, were also observed in the extremely low L‐shell simultaneously (reaching
) where the plasmapause was suppressed. The bounce‐averaged diffusion coefficient calculations support that the chorus waves can play a significantly important role in diffusing and accelerating the 1–3 MeV electrons even in such low L‐shells during storms. This is the first time that the electron acceleration induced by chorus waves in the extremely low L‐shell region is reported. This new finding will help to deeply understand the electron acceleration process in radiation belt physics.
The Relation of N‐S Auroral Streamers to Auroral Expansion
Authors: McPherron R. L. , El‐Alaoui M. , Walker R. J. , Nishimura Y. , Weygand J. M. 
Published: February 2020

AbstractWe investigate the relation of fast flows at the inner edge of the plasma sheet to the onset of auroral expansion. Recent work suggests that nearly all expansions are an instability triggered by an auroral streamer from far out in the magnetotail. We investigate an 8‐hr interval of activity on 14 March 2008 using ground magnetometer and all‐sky camera data to determine the onset times of six substorm expansions. We compare these times with Time History of Events and Macroscale Interactions during Substorms observations of plasma flow and magnetic field. We show that every expansion followed the arrival of a fast flow and dipolarization event at the inner edge of the plasma sheet. To relate the aurora to flows, we develop procedures for removing fixed lights, the moving Moon and its reflection, and contamination due to scattered moonlight. We scan movies of enhanced images for auroral streamers. Three onsets were tentatively associated with streamers. For two, the apparent source was very close to the growth phase arc mapping close to Earth. For one, an onset occurred in the recovery phase of an earlier substorm after a double oval had formed. For this one, the end of an N‐S streamer stopped about 2° north of the breakup arc. For the remaining three expansions, no streamers were associated with the onsets. Most substorms exhibit N‐S streamers in the recovery phase. These usually cannot be associated with fast flows. Either fast flows in the growth phase do not produce streamers or they make streamers that require significant image enhancement.
Subsolar Electron Temperatures in the Lower Martian Ionosphere
Authors: Peterson W.K. , Andersson L. , Ergun R. , Thiemann Ed , Pilinski Marcin , Thaller S. , Fowler C. , Mitchell D. , Benna M. , Yelle R. , Stone Shane 
Published: February 2020

AbstractMartian subsolar electron temperatures obtained below 250 km are examined using data obtained by instruments on the Mars Atmosphere Evolution Mission (MAVEN) during the three subsolar deep dip campaigns and a one‐dimensional fluid model. This analysis was done because of the uncertainty in MAVEN low electron temperature observations at low altitudes and the fact that the Level 2 temperatures reported from the MAVEN Langmuir Probe and Waves instrument are more than 400 K above the neutral temperatures at the lowest altitudes sampled (~120 km). These electron temperatures are well above those expected before MAVEN was launched. We find that an empirical normalization parameter, neutral pressure divided by local electron heating rate, organized the electron temperature data and identified a similar altitude (~160 km) and time scale (~2,000 s) for all three deep dips. We show that MAVEN data are not consistent with a plasma characterized by electrons in thermal equilibrium with the neutral population above 100 km. Because of the lack data below 120 km and the uncertainties of the data and the cross sections used in the one‐dimensional fluid model above 120 km, we cannot use MAVEN observations to prove that the electron temperature converges to the neutral temperature below 100 km. However, the uncertainty of the electron temperature altitude profile below 120 km does not impact our understanding of the role of electron temperature in determining ion escape rates because ion escape is determined by electron temperatures above 180 km.
Array‐Based Iterative Measurements of Travel Times and Their Constraints on Outermost Core Structure
Authors: Wu Wenbo , Irving Jessica C. E. 
Published: February 2020

AbstractVigorous convection in Earth's outer core led to the suggestion that it is chemically homogeneous. However, there is increasing seismic evidence for structural complexities close to the outer core's upper and lower boundaries. Both body waves and normal mode data have been used to estimate a
wave velocity,
, at the top of the outer core (the
layer), which is lower than that in the Preliminary Reference Earth Model. However, these low
models do not agree on the form of this velocity anomaly. One reason for this is the difficulty in retrieving and measuring
arrival times. To address this issue, we propose a novel approach using data from seismic arrays to iteratively measure
‐
differential travel times. This approach extracts individual
signal from mixed waveforms of the
series, allowing us to reliably measure differential travel times. We successfully use this method to measure
time delays from earthquakes in the Fiji‐Tonga and Vanuatu subduction zones.
time delays are measured by waveform cross correlation between
and
, and the cross‐correlation coefficient allows us to access measurement quality. We also apply this iterative scheme to synthetic
seismograms to investigate the 3‐D mantle structure's effects. The mantle structure corrections are not negligible for our data, and neglecting them could bias the
estimation of uppermost outer core. After mantle structure corrections, we can still see substantial time delays of
,
, and
, supporting a low
at the top of Earth's outer core.
Global‐Scale Full‐Waveform Ambient Noise Inversion
Authors: Sager Korbinian , Boehm Christian , Ermert Laura , Krischer Lion , Fichtner Andreas 
Published: February 2020

AbstractWe present the first application of full‐waveform ambient noise inversion to observed correlation functions that jointly constrains 3‐D Earth structure and heterogeneous noise sources. For this, we model and interpret ambient noise correlations as recordings of correlation wavefields, which completely eliminates the limiting assumptions of Green's function retrieval, such as equipartitioning and homogeneous random noise sources. Our method accounts for seismic wave propagation physics in 3‐D heterogeneous and attenuating media and also for the heterogeneous and nonstationary nature of the ambient noise field. Designed as a proof of concept, the study considers long periods from 100 to 300 s, thus focusing on the Earth's hum. Treating correlations as self‐consistent observables allows us to make separate measurements on the causal and acausal branches of correlation functions, without any need to choose one of them or form the average. We validate our approach by assessing the quality of the obtained models and by comparing them to previous studies. This work is a step toward the establishment of full‐waveform ambient noise inversion as a tomographic technique with the goal to go beyond ambient noise tomography based on Green's function retrieval.
Individual Particle Characteristics, Optical Properties and Evolution of an Extreme Long‐Range Transported Biomass Burning Event in the European Arctic (Ny‐Ålesund, Svalbard Islands)
Authors: Moroni B. , Ritter C. , Crocchianti S. , Markowicz K. , Mazzola M. , Becagli S. , Traversi R. , Krejci R. , Tunved P. , Cappelletti D. 
Published: February 2020

AbstractThis paper reports an exceptional biomass burning (BB) advection event from Alaska registered at Ny‐Ålesund from 10 to 17 July 2015 with particular interest on the influence of the airborne particle characteristics on the optical properties of the aerosol during the event. To this purpose we considered two DEKATI 12‐stage aerosol samples spanning the entire advection and analyzed them by scanning electron microscopy techniques. Aerosol chemical data and microphysical properties were also evaluated in order to correlate any change of individual particle characteristics with the bulk properties of the aerosol. The results of individual particle analysis depict a complex event characterized by a first phase (P1) of massive input of BB carbonaceous particles (i.e., tar balls, popcorn refractory particles, and organic particles), and by a second phase (P2) dominated by inorganic salts. The peculiar feature of this BB event is the exceptionally large grain size of the subspherical organic particles at the beginning of the event with respect to the background. At these conditions a significant increase of the scattering efficiency may occur even for a small increase of the size parameter. Results of the simulation of the complex refractive indices (n‐ik) confirm this evaluation. Aerosol evolution during the event resulted from the combination of three distinct occurrences: (a) progressive rotation of air mass circulation toward non‐BB source areas, (b) development of a thick fog layer in the planetary boundary layer, and (c) sea salt spray direct advection of local/regional provenance.
Compositions of Dust and Sea Salts in the Dome C and Dome Fuji Ice Cores From Last Glacial Maximum to Early Holocene Based on Ice‐Sublimation and Single‐Particle Measurements
Authors: Oyabu I. , Iizuka Y. , Kawamura K. , Wolff E. , Severi M. , Ohgaito R. , Abe‐Ouchi A. , Hansson M. 
Published: February 2020

AbstractWe analyzed the chemical compositions of dust and sea‐salt particles in the EPICA Dome C (EDC) ice core during 26–7 kyr BP using an ice‐sublimation technique and compared the results with existing data of the Dome Fuji (DF) ice core. Combined with ion concentration data, our data suggested similar sea‐salt fluxes in both cores and significantly lower dust flux in the EDC core. The differences in modal size and aspect ratio of dust particles between the two cores support the dominance of Patagonian source suggested by earlier works. The compositions of calcic dust showed major change at ~17 kyr BP, possibly reflecting a relative increase in dust transported via the upper troposphere. The calcium sulfate fraction was higher in the DF core than in the EDC core after ~17 kyr BP, suggesting that higher Patagonian dust contribution to the DF region. Abundant NaCl particles were found in the DF core in comparison with the EDC core from the LGM to early Holocene, possibly because of the high concentration of terrestrial dust in the DF core that reduced acid availability for sea‐salt modification. During the Holocene, the lower NaCl fraction and Cl−/Na+ ratio in the EDC core suggested that most Cl− was lost to the atmosphere from snow at Dome C, while it was preserved at Dome Fuji as NaCl and solid solution.
Suborbital Hydrological Variability Inferred From Coupled Benthic and Planktic Foraminiferal‐Based Proxies in the Southeastern Mediterranean During the Last 19 ka
Authors: Le Houedec S. , Mojtahid M. , Bicchi E. , de Lange G. J. , Hennekam R. 
Published: February 2020

AbstractWe present a high‐resolution study covering the past 19 ka from the southeastern Mediterranean Sea, based on benthic foraminiferal faunas and their stable oxygen and carbon isotopes. These data are integrated with previously published and newly acquired planktic foraminiferal data from the same sediment core in order to investigate the benthic‐planktic coupling and its response to past suborbital climate variability. On a millennial timescale, foraminiferal communities and their isotopic signatures vary following three main time periods (late glacial, sapropel S1 [~10.1–6.5 ka], and mid‐Holocene to Late Holocene). Within these intervals, we identified short‐timescale changes related to the carbon export and hydrological conditions. During the deglaciation, and except for the Younger Dryas, the coupled benthic‐planktic data indicate an overall poorly mixed water column with a low productivity. During S1 event, our data confirm the presence of a highly stratified water column, with enhanced primary productivity export to the deep sea, being associated to high Nile River activity. While the foraminiferal ecosystem is strongly driven by the combined influence of overturning circulation and the Nile River activity until the end of the African humid period, we suggest a more regional eastern Mediterranean climatic‐driven response of the foraminiferal community over the mid‐Holocene to Late Holocene. A strong multicentennial variability, probably associated to solar forcing, was found for both benthic and planktic records, and a supplementary 1,600‐year mode was found for the benthic data, suggesting a potential overturning circulation‐driven forcing for the latter.