bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ionospheric response to the 2009 sudden stratospheric warming over the equatorial, low, and middle latitudes in the South American sector
Authors: Fagundes P. R. , Goncharenko L. P. , de Abreu A. J. , Venkatesh K. , Pezzopane M. , de Jesus R. , Gende M. , Coster A. J. , Pillat V. G. 
Published: August 2015

AbstractThe present study investigates the ionospheric total electron content (TEC) and F‐layer response in the Southern Hemisphere equatorial, low, and middle latitudes due to major sudden stratospheric warming (SSW) event, which took place during January–February 2009 in the Northern Hemisphere. In this study, using 17 ground‐based dual frequency GPS stations and two ionosonde stations spanning latitudes from 2.8°N to 53.8°S, longitudes from 36.7°W to 67.8°W over the South American sector, it is observed that the ionosphere was significantly disturbed by the SSW event from the equator to the midlatitudes. During day of year 26 and 27 at 14:00 UT, the TEC was two times larger than that observed during average quiet days. The vertical TEC at all 17 GPS and two ionosonde stations shows significant deviations lasting for several days after the SSW temperature peak. Using one GPS station located at Rio Grande (53.8°S, 67.8°W, midlatitude South America sector), it is reported for the first time that the midlatitude in the Southern Hemisphere was disturbed by the SSW event in the Northern Hemisphere.
Interplanetary shocks and the resulting geomagnetically induced currents at the equator
Authors: Carter B. A. , Yizengaw E. , Pradipta R. , Halford A. J. , Norman R. , Zhang K. 
Published: August 2015

AbstractGeomagnetically induced currents (GICs) caused by interplanetary shocks represent a serious space weather threat to modern technological infrastructure. The arrival of interplanetary shocks drives magnetosphere and ionosphere current systems, which then induce electric currents at ground level. The impact of these currents at high latitudes has been extensively researched, but the magnetic equator has been largely overlooked. In this paper, we investigate the potential effects of interplanetary shocks on the equatorial region and demonstrate that their magnetic signature is amplified by the equatorial electrojet. This local amplification substantially increases the region's susceptibility to GICs. Importantly, this result applies to both geomagnetic storms and quiet periods and thus represents a paradigm shift in our understanding of adverse space weather impacts on technological infrastructure.
Recent decrease in DOC concentrations in Arctic lakes of southwest Greenland
Authors: Saros Jasmine E. , Osburn Christopher L. , Northington Robert M. , Birkel Sean D. , Auger Jeffrey D. , Stedmon Colin A. , Anderson Nicholas John 
Published: August 2015

AbstractA key indicator of changes in the terrestrial carbon cycle is shifting dissolved organic carbon (DOC) concentrations in surface waters. Arctic permafrost holds twice as much C as the atmosphere, thus recent warming and changes in atmospheric deposition to the region raise the need for a better understanding of how DOC is changing in arctic surface waters. In Kangerlussuaq, Greenland, lakewater DOC concentrations declined by 14 to 55% (absolute changes of 1 to 24 mg L−1) between 2003 and 2013, without significant changes in quality. Lakewater sulfate concentrations, but not chloride or conductivity, increased. These results suggest that similar to processes that have occurred at northern midlatitudes, increases in soil ionic strength as a result of sulfate enrichment may be linked to declining surface water DOC concentrations. Such enrichment may be occurring with enhanced non‐sea‐salt sulfate deposition. Our results reveal that rapid changes are occurring in the carbon cycle of this region of southwest Greenland.
The low‐degree shape of Mercury
Authors: Perry Mark E. , Neumann Gregory A. , Phillips Roger J. , Barnouin Olivier S. , Ernst Carolyn M. , Kahan Daniel S. , Solomon Sean C. , Zuber Maria T. , Smith David E. , Hauck Steven A. , Peale Stanton J. , Margot Jean‐Luc , Mazarico Erwan , Johnson Catherine L. , Gaskell Robert W. , Roberts James H. , McNutt Ralph L. , Oberst Juergen 
Published: August 2015

AbstractThe shape of Mercury, particularly when combined with its geoid, provides clues to the planet's internal structure, thermal evolution, and rotational history. Elevation measurements of the northern hemisphere acquired by the Mercury Laser Altimeter on the MErcury Surface, Space ENvironment, GEochemistry, and Ranging spacecraft, combined with 378 occultations of radio signals from the spacecraft in the planet's southern hemisphere, reveal the low‐degree shape of Mercury. Mercury's mean radius is 2439.36 ± 0.02 km, and there is a 0.14 km offset between the planet's centers of mass and figure. Mercury is oblate, with a polar radius 1.65 km less than the mean equatorial radius. The difference between the semimajor and semiminor equatorial axes is 1.25 km, with the long axis oriented 15° west of Mercury's dynamically defined principal axis. Mercury's geoid is also oblate and elongated, but it deviates from a sphere by a factor of 10 less than Mercury's shape, implying compensation of elevation variations on a global scale.
Response of Atlantic overturning to future warming in a coupled atmosphere‐ocean‐ice sheet model
Authors: Gierz Paul , Lohmann Gerrit , Wei Wei 
Published: August 2015

AbstractClimate change can influence sea surface conditions and the melting rates of ice sheets; resulting in decreased deep water formation rates and ultimately affecting the strength of the Atlantic Meridional Overturning Circulation (AMOC). As such, a detailed study of the interactive role of dynamic ice sheets on the AMOC and therefore on global climate is required. We utilize a climate model in combination with a dynamic ice sheet model to investigate changes to the AMOC and North Atlantic climate in response to Intergovernmental Panel on Climate Change scenarios for RCP4.5 and RCP6. It is demonstrated that the inclusion of an ice sheet component results in a drastic freshening of the North Atlantic by up to 2 practical salinity units, enhancing high‐latitude haloclines and weakening the AMOC by up to 2 sverdrup (106 m3/s). Incorporating a bidirectionally coupled dynamic ice sheet results in relatively reduced warming over Europe due to the associated decrease in heat transport.
Topside ionospheric response to solar EUV variability
Authors: Anderson Phillip C. , Hawkins Jessica M. 
Published: August 2015

AbstractWe present an analysis of 23 years of thermal plasma measurements in the topside ionosphere from the Defense Meteorological Satellite Program (DMSP) spacecraft. The H+/O+ ratio and density vary dramatically with the solar cycle; cross‐correlation coefficients between E10.7 and the daily averaged densities are greater than 0.85. The ionospheric parameters also vary dramatically with season, particularly at latitudes away from the equator where the solar zenith angle varies greatly with season. There are also 27 day solar rotation periodicities in the density, associated with periodicities in the directly measured solar EUV flux. Empirical orthogonal function analysis captures over 95% of the variation in the density in the first two principal components. The first principal component (PC1) is clearly associated with the solar EUV while the second principal component (PC2) is clearly associated with the solar zenith angle variation. The magnitude of the variation of the response of the topside ionosphere to solar EUV variability is shown to be closely related to the ionospheric composition. This is interpreted as the result of the effect of composition on the scale height in the topside ionosphere and the “pivot effect” in which the variation in density near the F2 peak is amplified by a factor of e at an altitude a scale height above the F2 peak. When the topside ionosphere is H+ dominated during solar minimum, DMSP may be much less than a scale height above the F2 peak while during solar maximum, when it is O+ dominated, DMSP may be several scale heights above the F2 peak.
Two‐mode ionospheric response and Rayleigh wave group velocity distribution reckoned from GPS measurement following Mw 7.8 Nepal earthquake on 25 April 2015
Authors: Reddy C. D. , Seemala Gopi K. 
Published: August 2015

AbstractThe coseismic‐induced ionospheric total electron content (TEC) perturbations were analyzed following the Mw 7.8 Nepal earthquake (28.147°N, 84.708°E; depth ~15 km) that occurred on 25 April 2015 at 06:11:26 UTC. The ionospheric response is due to both the modes, i.e., shock acoustic waves (slow mode) and Rayleigh wave induced (fast mode). The continuous Global Positioning System (GPS) data at about 60 sites from various GPS networks have been used in the present study. All the sites within epicentral distance of ~2400 km and 70°–170° azimuth recorded the Rayleigh wave‐induced TEC response, while the sites within ~400–2200 km in the same azimuth recorded the response from both the modes. The maximum coseismic‐induced peak‐to‐peak TEC amplitude is ~1.2 total electron content unit, 1 TECU = 1016 el m−2. From Hodochron plot, the apparent Rayleigh wave velocity has been determined as ~2400 m/s on the average and the acoustic wave velocity as 1180 m/s, both these waves being discernible beyond ~1200 km of epicentral distance as also evident from Hodochron plot and wavelet spectrographs. We reckoned the Rayleigh wave group velocities using ionospheric response at selected radial pairs of stations and validated. The ionospheric response distribution seen mainly depending on the epicentral distance, satellite geometry, directivity of radiation pattern, and the upper crustal heterogeneity. This study highlights the characteristics of ionospheric response consequent to the 2015 Nepal earthquake.
Estimation of interplanetary electric field conditions for historical geomagnetic storms
Authors: Kumar Sandeep , Veenadhari B. , Tulasi Ram S. , Selvakumaran R. , Mukherjee Shyamoli , Singh Rajesh , Kadam B. D. 
Published: August 2015

AbstractGround magnetic measurements provide a unique database in understanding space weather. The continuous geomagnetic records from Colaba‐Alibag observatories in India contain historically longest and continuous observations from 1847 to present date. Some of the super intense geomagnetic storms that occurred prior to 1900 have been revisited and investigated in order to understand the probable interplanetary conditions associated with intense storms. Following Burton et al. (1975), an empirical relationship is derived for estimation of interplanetary electric field (IEFy) from the variations of Dst index and ΔH at Colaba‐Alibag observatories. The estimated IEFy values using Dst and ΔHABG variations agree well with the observed IEFy, calculated using Advanced Composition Explorer (ACE) satellite observations for intense geomagnetic storms in solar cycle 23. This study will provide the uniqueness of each event and provide important insights into possible interplanetary conditions for intense geomagnetic storms and probable frequency of their occurrence.
No clear evidence for localized tidal periodicities in earthquakes in the central Japan region
Authors: Wang W. , Shearer P. M. 
Published: August 2015

AbstractWe search for possible localized tidal triggering in earthquake occurrence near Japan by testing for tidal periodicities in seismicity within a variety of space/time bins. We examine 74,610 earthquakes of M ≥ 3 in the Japan Meteorological Agency catalog from January 2000 to April 2013. Because we use many earthquakes for which accurate focal mechanisms are not available, we do not compute tidal stresses on individual fault planes but instead assume that the mechanisms are likely to be similar enough among nearby events that tidal triggering will promote earthquake occurrence at specific tidal phases. After dividing the data into cells at a range of spatial (0.2°, 0.5°, and 1.0°) and temporal dimensions (100, 200, and 400 days), we apply Schuster's test for nonrandom event occurrence with respect to both the semidiurnal and semimonthly tidal phases. Because the resulting p values will be biased by temporal clustering caused by aftershocks, we apply a declustering method that retains only one event per tidal cycle per phase increment. Our results show a wide range of p values for the localized earthquake bins, but the number of bins with very small p values (e.g., p < 0.05) is no more than might be expected due to random chance, and there is no correlation of low p value bins with the time of the 2010 M 9.0 Tohoku‐Oki earthquake.
Characteristics and potential sources of atmospheric mercury at a subtropical near‐coastal site in East China
Authors: Yu Ben , Wang Xun , Lin Che‐Jen , Fu Xuewu , Zhang Hui , Shang Lihai , Feng Xinbin 
Published: August 2015

AbstractTo evaluate the impact of regional mercury (Hg) emissions and understand possible source regions of atmospheric Hg in Eastern China, 2 year observation for speciated atmospheric Hg was conducted at the Dameishan Atmospheric Observatory, a mountain site near the east coast of China. The observed concentration of total gaseous Hg (TGM) was 3.3 ± 1.4 ng m−3. During the sampling period, gaseous oxidized Hg and particulate bound Hg were 6.7 ± 4.3 pg m−3 and 180 ± 110 pg m−3 in winter and 5.9 ± 3.4 pg m−3 and 130 ± 100 pg m−3 in spring, respectively. The relatively high mean concentration of TGM was mainly caused by regional anthropogenic emissions and occasional long‐range transport from domestic source regions. Seasonal variation in the TGM concentration was observed with lower values in the wet monsoon season (from May to September) and higher values in the dry monsoon season (from October to April). Backward trajectories and potential source contribution function analysis suggested that anthropogenic Hg emission from coal combustion in the Yangtze River Delta region was the most likely cause for the elevated TGM concentrations. Relatively clean air originating from the East China Sea was the most possible cause for the observed low TGM concentrations. Positive correlation between TGM concentration and air quality index suggests that emissions that influenced regional air quality contributed to the elevated TGM concentrations.
Macroscopic cloud properties in the WRF NWP model: An assessment using sky camera and ceilometer data
Authors: Arbizu‐Barrena Clara , Pozo‐Vázquez David , Ruiz‐Arias José A. , Tovar‐Pescador Joaquín 
Published: August 2015

AbstractThe ability of six microphysical parameterizations included in the Weather Research and Forecasting (WRF) numerical weather prediction (NWP) model to represent various macroscopic cloud characteristics at multiple spatial and temporal resolutions is investigated. In particular, the model prediction skills of cloud occurrence, cloud base height, and cloud cover are assessed. When it is possible, the results are provided separately for low‐, middle‐, and high‐level clouds. The microphysical parameterizations assessed are WRF single‐moment six‐class, Thompson, Milbrandt‐Yau, Morrison, Stony Brook University, and National Severe Storms Laboratory double moment. The evaluated macroscopic cloud properties are determined based on the model cloud fractions. Two cloud fraction approaches, namely, a binary cloud fraction and a continuous cloud fraction, are investigated. Model cloud cover is determined by overlapping the vertically distributed cloud fractions following three different strategies. The evaluation is conducted based on observations gathered with a ceilometer and a sky camera located in Jaén (southern Spain). The results prove that the reliability of the WRF model mostly depends on the considered cloud parameter, cloud level, and spatiotemporal resolution. In our test bed, it is found that WRF model tends to (i) overpredict the occurrence of high‐level clouds irrespectively of the spatial resolution, (ii) underestimate the cloud base height, and (iii) overestimate the cloud cover. Overall, the best cloud estimates are found for finer spatial resolutions (1.3 and 4 km with slight differences between them) and coarser temporal resolutions. The roles of the parameterization choice of the microphysics scheme and the cloud overlapping strategy are, in general, less relevant.
Geometry and kinematics of the Grant Range brittle detachment system, eastern Nevada, U.S.A.: An end‐member style of upper crustal extension
Authors: Long Sean P. , Walker Jerome P. 
Published: August 2015

AbstractDocumenting the range of styles of normal faulting is fundamental to understanding crustal extension. Here geologic mapping, field relationships, and deformed and restored cross sections illustrate the geometry and kinematic development of a system of west‐vergent detachment faults in the Grant Range in eastern Nevada. Faults exhibit brecciation and stratigraphic cutoff angles of 5–15° at all structural levels and deform a 10 km thick section of Paleozoic and Paleogene rocks. The fault system is folded across an anticlinal culmination, which grew during extension, as indicated by progressively increasing interlimb angles and incision in the axial zone. The eastern limb consists of an imbricate stack of faults that were emplaced from bottom to top. In the western limb, several faults exhibit apparent thrust relationships. The oldest faults are cut by a ~29 Ma dike, and the highest preserved fault cuts ~32 Ma volcanic rocks that restore to paleodepths of ~1 km. Retrodeformation of folding and minimal structural relief and angularity across a Paleogene unconformity indicate the faults were active at 5–15° angles. Retrodeformation of offset indicates ≥49 km (98%) extension. We propose a model of stationary, sustained isostatic uplift and incision at the culmination axis (a “fixed hinge”), with updip excision producing bottom‐to‐top growth of the imbricate stack and downdip excision producing apparent thrust relationships. The fault system exhibits similarities to core complex detachment systems, though it is confined to upper crustal levels, and there are no preserved high‐angle or listric normal faults, indicating a unique extension style dominated by low‐angle excision.
Total Synthesis of (+)‐Petromyroxol, a Marine Natural Product
Authors: Gahalawat Suraksha , Garg Yuvraj , Pandey Satyendra Kumar 
Published: August 2015

AbstractAn efficient total synthesis of (+)‐petromyroxol, a marine natural product, is described. The synthesis utilizes the Sharpless asymmetric dihydroxylation (AD), intramolecular SN2 cyclization and stereoselective Grignard reaction as key steps.
Organocatalytic Enantioselective Cascade Aza‐Michael/Michael Addition Sequence for Asymmetric Synthesis of Chiral Spiro[pyrrolidine‐3,3′‐oxindole]s
Authors: Zhao Bo‐Liang , Du Da‐Ming 
Published: August 2015

AbstractThe spiro[pyrrolidine‐3,3′‐oxindole] scaffold is common to a range of bioactive compounds; however, the asymmetric synthesis of this scaffold is complicated due to the presence of multiple chiral centers. An organocatalytic asymmetric cascade aza‐Michael/Michael addition between tosylaminomethyl enones or enoates and 3‐ylideneoxindoles catalyzed by a chiral squaramide that afforded complex and flexible spiro[pyrrolidine‐3,3’‐oxindole]s has been developed. Single‐step construction of molecules with three contiguous stereocenters including one quaternary center in excellent yields with highly diastereo‐ and enantioselectivity are rare and should be useful in medicinal chemistry and diversity oriented synthesis of this intriguing class of compounds.
The association between septal deviation and the presence of a maxillary accessory ostium
Authors: Ozel Halil Erdem , Ozdogan Fatih , Esen Erkan , Genc Meliha Gulden , Genc Selahattin , Selcuk Adin 
Published: August 2015

BackgroundThe etiology and the effects of the maxillary accessory ostium (MAO) are not well understood. The aim of this study is to investigate the association between septal deviation (SD) and the presence of an MAO.MethodsParanasal computed tomography (CT) scans of 1104 adult patients were studied retrospectively. Patients with chronic sinusitis, acute sinusitis, nasal polyposis, allergic rhinitis, paranasal sinus tumors, septal perforation, and unilateral or bilateral maxillary sinus hypoplasia/aplasia, as well as patients who had previously had nasal surgery or a history of nasal trauma, were not included in the study. Eight‐hundred and seven patients were found to meet the criteria and were included in the study. CT scans were examined to note the presence of SD and MAO and the side of both diseases.ResultsA total of 807 patients were evaluated. SD and MAO were detected in 572 (70.9%) and 299 (37.1%) patients, respectively. A statistically significant relationship was found between the presence of SD and MAO, regardless of side of the disease (p = 0.002). The side of MAO showed a significant correlation with the direction of SD (p < 0.001).ConclusionOur results revealed a link between SD and MAO. This relationship was correlated with the side of occurrence of the disease.
Electrocatalytic Hydrogen Production by an Aluminum(III) Complex: Ligand‐Based Proton and Electron Transfer
Authors: Thompson Emily J. , Berben Louise A. 
Published: August 2015

AbstractEnvironmentally sustainable hydrogen‐evolving electrocatalysts are key in a renewable fuel economy, and ligand‐based proton and electron transfer could circumvent the need for precious metal ions in electrocatalytic H2 production. Herein, we show that electrocatalytic generation of H2 by a redox‐active ligand complex of Al3+ occurs at −1.16 V vs. SCE (500 mV overpotential).
Dual Catalysis for the Redox Annulation of Nitroalkynes with Indoles: Enantioselective Construction of Indolin‐3‐ones Bearing Quaternary Stereocenters
Authors: Liu Ren‐Rong , Ye Shi‐Chun , Lu Chuan‐Jun , Zhuang Gui‐Lin , Gao Jian‐Rong , Jia Yi‐Xia 
Published: August 2015

AbstractThe enantioselective redox annulation of nitroalkynes with indoles is enabled by gold/chiral phosphoric acid dual catalysis. A range of indolin‐3‐one derivatives bearing quaternary stereocenters at the C2 position were afforded in good yields and excellent enantioselectivities (up to 96 % ee) from readily available starting materials.
Rote pyrotechnische Leuchtsätze – ohne Chlor!
Authors: Sabatini Jesse J. , Koch Ernst‐Christian , Poret Jay C. , Moretti Jared D. , Harbol Seth M. 
Published: August 2015

AbstractDieser Beitrag behandelt die Entwicklung eines roten, chlorfreien pyrotechnischen Leuchtsatzes hoher Lichtstärke und Farbsättigung. Sätze auf der Grundlage von Mg/Sr(NO3)2/Epon‐Binder werden durch Zusatz von 5‐Amino‐1H‐tetrazol oder Hexamethylentetramin desoxidiert, wodurch die Bildung von rot‐orange emittierendem SrO(g) unterdrückt und die Entstehung des einzigen roten Emitters SrOH gefördert wird. Die neuen Sätze haben hohe Zündtemperaturen. Durch die vollständige Vermeidung von Chlor kann jegliches Risiko der Bildung von PBCs, PCDDs und PCDFs ausgeschlossen werden. Diese Entdeckung hat daher große Bedeutung für die militärische und zivile Pyrotechnik und wird auch den Feuerwerkssektor nachhaltig beeinflussen.
The Methylsulfonyloxyl Radical, CH3SO3
Authors: Zhu Bifeng , Zeng Xiaoqing , Beckers Helmut , Francisco Joseph S. , Willner Helge 
Published: August 2015

AbstractThe methylsulfonyloxyl radical, CH3SO3, one of the key intermediates in the atmospheric oxidation of dimethyl sulfide (DMS), was generated by flash pyrolysis of CH3SO2OOSO2CH3 and subsequently isolated in solid noble‐gas matrices. The radical has been characterized by UV/Vis and IR spectroscopy and its tautomerization to CH2SO3H observed upon irradiation with light of λ≥360 nm.