bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ducted electromagnetic waves in the Martian ionosphere detected by the Mars Advanced Radar for Subsurface and Ionosphere Sounding radar
Authors: Zhang Zhenfei , Orosei Roberto , Huang Qian , Zhang Jie 
Published: July 2016

AbstractIn the data of the Mars Advanced Radar for Subsurface and Ionosphere Sounding on board the European Space Agency (ESA) mission Mars Express (MEX), a distinctive type of signals (called the “epsilon signature”), which is similar to that previously detected during radio sounding of the terrestrial F region ionosphere, is found. The signature is interpreted to originate from multiple reflections of electromagnetic waves propagating along sounder pulse‐created, crustal magnetic field‐aligned plasma bubbles (waveguides). The signatures have a low (below 0.5%) occurrence rate and apparent cutoff frequencies 3–5 times higher than the theoretical one for an ordinary mode wave. These properties are explained by the influence of the perpendicular ionospheric plasma density gradient and the sounder pulse frequency on the formation of waveguides.
The impact of SST biases on projections of anthropogenic climate change: A greater role for atmosphere‐only models?
Authors: He Jie , Soden Brian J. 
Published: July 2016

AbstractThere is large uncertainty in the model simulation of regional climate change from anthropogenic forcing. Recent studies have tried to link such uncertainty to intermodel differences in the pattern of sea surface temperature (SST) change. On the other hand, coupled climate models also contain systematic biases in their climatology, largely due to drift in SSTs. To the extent that the projected changes depend on the mean state, biases in the present‐day climatology also contribute to the intermodel spread in climate change projections. By comparing atmospheric general circulation model (AGCM) simulations using the climatological SSTs from different coupled models, we show that biases in the climatological SST generally have a larger impact on regional projections over land than do intermodel differences in the pattern of SST change. These results advocate for a greater application of AGCM simulations with observed SSTs or flux‐adjusted coupled models to improve regional projections of anthropogenic climate change.
Chromophoric signatures of microbial by‐products in the dark ocean
Authors: Catalá Teresa S. , Reche Isabel , Ramón Cintia L. , López‐Sanz Àngel , Álvarez Marta , Calvo Eva , Álvarez‐Salgado Xosé A. 
Published: July 2016

AbstractDetailed examination of the absorption spectra from dark ocean samples allowed us to identify and deconvolve two distinct chromophores centered at 302 nm (UV) and 415 nm (visible) from the exponential decay curve characteristic of humic substances. The UV chromophore was ubiquitous in intermediate and deep waters, and it has been proposed as the secondary absorption peak of nitrate. The visible chromophore was prominent at the central and intermediate water masses of the North Pacific, and it has been proposed as cytochrome c. Subtraction of the modeled absorption spectra of the two chromophores from the measured absorption spectrum of the samples leads to a spectral slope overestimation by 13.3 ± 6.0% for S275–295 and 14.8 ± 10.6% for S350–400. To only consider the chromophoric fraction of DOM, the absorption spectra of nitrate should be subtracted in samples with a [NO3−]:a302 ratio > 70 µM m.
Can atomic oxygen production explain the ionospheric annual asymmetry?
Authors: Lei Jiuhou , Wang Wenbin , Burns Alan G. , Luan Xiaoli , Dou Xiankang 
Published: July 2016

AbstractThe causes of the ionospheric annual asymmetry, which refers to a larger averaged electron density at geomagnetic conjugate latitudes in December than in June, remain an unresolved problem that still generates considerable interest. The ionospheric annual asymmetry in the peak electron density of the F2 layer (NmF2) is typically 20–40%, which cannot be explained by the 7% annual asymmetry in photoionization caused by the shorter Sun‐Earth distance in December. Mikhailov and Perrone (2011, 2015) suggested that the annual asymmetry in atomic oxygen production due to O2 dissociation is sufficient to explain the ionospheric annual asymmetry at middle latitudes. In our study, a series of the Global Mean Model (GMM) simulations have been conducted to test this hypothesis. Although O2 dissociation and eddy diffusion processes are included in the GMM, the simulated annual asymmetry of NmF2 is only 13%. Furthermore, the annual asymmetry increase in neutral composition in our GMM simulations can only explain about one fifth of the ionospheric annual asymmetry. Therefore, the atomic oxygen production mechanism is unlikely to be a major contributor to the ionospheric annual asymmetry.
New perspectives on equatorial electrojet tidal characteristics derived from the Swarm constellation
Authors: Zhou Yun‐Liang , Lühr Hermann , Alken Patrick , Xiong Chao 
Published: July 2016

AbstractUsing 2 years of magnetic field measurements from the Swarm constellation, we present a detailed study of the equatorial electrojet (EEJ) and its longitudinal gradient (ΔEEJ). This study represents for the first time the tidal characteristics derived from the longitudinal gradient of EEJ. Our analysis mainly focuses on the months around August (133 days centered on 15 August, day of year: 161–293) of 2014 and 2015 when the longitudinal wave number 4 (WN4) pattern is known to be most prominent. The EEJ intensity, derived from the average of the Swarm A and C current estimates, peaks around 11:30 LT and exhibits a clear WN4 pattern. These features are compatible with earlier CHAMP observations. The ΔEEJ, which can be considered as a high‐pass filtered result of EEJ, although having much smaller values than the EEJ, exhibits clearly the local time gradient of the EEJ diurnal variation. This kind of high‐pass filtering makes the tidal signatures in ΔEEJ more prominent. The crests of longitudinal WN4 patterns in ΔEEJ have locations different from those of EEJ. Prominent tidal components in ΔEEJ during August months are DE3, DW5, SW3, SW4, SW6, SPW1, SPW2, and SPW4. For a given wave number pattern the westward propagating components are more amplified in ΔEEJ than the eastward ones, which explains their numerous appearance. Using spectral analysis, we can confirm that the observed amplitude ratios of different tidal components between ΔEEJ and EEJ are as expected. Also, the phase differences between ΔEEJ and EEJ fit reasonably the theoretical values. The preferred amplification of westward propagating tides in ΔEEJ allows for a more detailed investigation of these components, which are assumed to be closer related to local electrodynamics processes.
Galactic cosmic ray variations in the inner heliosphere from solar distances less than 0.5 AU: Measurements from the MESSENGER Neutron Spectrometer
Authors: Lawrence David J. , Peplowski Patrick N. , Feldman William C. , Schwadron Nathan A. , Spence Harlan E. 
Published: July 2016

AbstractThe Neutron Spectrometer (NS) on board NASA's MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft is sensitive to galactic cosmic ray (GCR) protons greater than 125 MeV. During the MESSENGER orbital mission of Mercury, which lasted from March 2011 to April 2015, the NS made continual measurements of GCR variations, which represent the first long‐term GCR measurements for solar distances less than 0.5 AU. These relative GCR variations are compared to GCR variations measured by the Cosmic Ray Telescope for Environmental Radiation (CRaTER) on the Lunar Reconnaissance Orbiter. The two data sets are highly correlated, with correlation coefficients ranging from 0.91 to 0.98 for time integrations ranging from 1 to 25 days. The MESSENGER NS and CRaTER measurements of GCR variations are used to investigate the GCR radial gradient within the inner solar system. We find that the GCR radial gradient is less than 10% per AU, which is consistent with GCR radial gradients measured for solar distances greater than 1 AU.
Insights into shallow magmatic processes at Kīlauea Volcano, Hawaiʻi, from a multiyear continuous gravity time series
Authors: Poland Michael P. , Carbone Daniele 
Published: July 2016

AbstractContinuous gravity data collected near the summit eruptive vent at Kīlauea Volcano, Hawaiʻi, during 2011–2015 show a strong correlation with summit‐area surface deformation and the level of the lava lake within the vent over periods of days to weeks, suggesting that changes in gravity reflect variations in volcanic activity. Joint analysis of gravity and lava level time series data indicates that over the entire time period studied, the average density of the lava within the upper tens to hundreds of meters of the summit eruptive vent remained low—approximately 1000–1500 kg/m3. The ratio of gravity change (adjusted for Earth tides and instrumental drift) to lava level change measured over 15 day windows rose gradually over the course of 2011–2015, probably reflecting either (1) a small increase in the density of lava within the eruptive vent or (2) an increase in the volume of lava within the vent due to gradual vent enlargement. Superimposed on the overall time series were transient spikes of mass change associated with inflation and deflation of Kīlauea's summit and coincident changes in lava level. The unexpectedly strong mass variations during these episodes suggest magma flux to and from the shallow magmatic system without commensurate deformation, perhaps indicating magma accumulation within, and withdrawal from, void space—a process that might not otherwise be apparent from lava level and deformation data alone. Continuous gravity data thus provide unique insights into magmatic processes, arguing for continued application of the method at other frequently active volcanoes.
Transient deformation in the Asal‐Ghoubbet Rift (Djibouti) since the 1978 diking event: Is deformation controlled by magma supply rates?
Authors: Smittarello D. , Grandin R. , De Chabalier J.‐B. , Doubre C. , Deprez A. , Masson F. , Socquet A. , Saad I. A. 
Published: July 2016

AbstractThe Asal‐Ghoubbet Rift (AG Rift) in Djibouti lies in the subaerial continuation of the Aden ridge system, thereby constituting a unique location to study rifting processes and mechanisms involved in continental breakup and oceanic spreading. Continually upgraded and expanded geodetic technology has been used to record the 1978 Asal rifting event and postdiking deformation. In light of recent results obtained for the Manda Hararo‐Dabbahu rifting event (2005–2010), we propose that the horizontal and vertical geodetic data can be modeled with a double source, involving a dike‐like inflation component aligned along the rift axis and a spherical pressure source located at midsegment below the Fieale caldera. By revisiting the codiking data, we propose that the reservoir below Fieale could have fed, at least partially, the 1978 injection and the contemporaneous Ardoukôba eruption and potentially induced local subsidence due to magma draining out of the central reservoir. As an alternative to previously proposed viscoelastic relaxation models, we reinterpret postdiking observations using a purely elastic rheology. We determine the relative contribution of a midsegment reservoir inflation and a dike‐like opening component, together with their respective time evolutions. Our results suggest that interactions between steadily accumulating tectonic strain and temporal variations in melt supply to the shallow magma plumbing system below the AG Rift may entirely explain the geodetic observations and that viscoelastic deformation processes played a minor role in the 30 years following the 1978 rifting event.
Tidal deformation of Ganymede: Sensitivity of Love numbers on the interior structure
Authors: Kamata Shunichi , Kimura Jun , Matsumoto Koji , Nimmo Francis , Kuramoto Kiyoshi , Namiki Noriyuki 
Published: July 2016

AbstractTidal deformation of icy satellites provides crucial information on their subsurface structures. In this study, we investigate the parameter dependence of the tidal displacement and potential Love numbers (i.e., h2 and k2, respectively) of Ganymede. Our results indicate that Love numbers for Ganymede models without a subsurface ocean are not necessarily smaller than those with a subsurface ocean. The phase lag, however, depends primarily on the presence/absence of a subsurface ocean. Thus, the determination of the phase lag would be of importance to infer whether Ganymede possesses a subsurface ocean or not based only on geodetic measurements. Our results also indicate that the major control on Love numbers is the thickness of the ice shell if Ganymede possesses a subsurface ocean. This result, however, does not necessarily indicate that measurement of either of h2 or k2 alone is sufficient to estimate the shell thickness; while a thin shell leads to large h2 and k2 independent of parameters, a thick shell does not necessarily lead to small h2 and k2. We found that to reduce the uncertainty in the shell thickness, constraining k2 in addition to h2 is necessary, highlighting the importance of collaborative analyses of topography and gravity field data.
Sustainable polyacetals from erythritol and bioaromatics
Authors: Rostagno Mayra , Price Erik J. , Pemba Alexander G. , Ghiriviga Ion , Abboud Khalil A. , Miller Stephen A. 
Published: July 2016

ABSTRACTThe polymerization of biorenewable molecules to polymers with hydrolyzable main‐chain functionality is one approach to identifying sustainable replacements for common, environmentally unsound packaging plastics. Bioaromatic polyacetals were synthesized via acid‐catalyzed acetal formation from dialdehydes and tetraols. Ethylene linked dialdehyde monomers VV and SS were constructed from bioaromatics vanillin and syringaldehyde, respectively. Tetraol monomers included biogenic erythritol (E), along with pentaerythritol (P), and ditrimethylolpropane (D). Four copolymer series were prepared with varying tetraol content: E/P‐VV; E/D‐VV; E/P‐SS; and E/D‐SS. Number average molecular weights (Mn) ranged from 1,400 to 27,100 Da. Generally, the copolymerization yields were inversely proportional to the feed fraction of erythritol (E), implying that tetraols P and D react more readily. The materials were typically amorphous and exhibited glass transition temperatures (Tg) ranging from 57 to 159 °C, suitably mimicking the Tg values of several commodity plastics. The syringaldehyde‐based copolymers exhibited a higher Tg range (71–159 °C) than the vanillin‐based copolymers (57–110 °C). Accelerated degradation studies in aqueous HCl (3 M, 6 M, concentrated) over 24 h showed that degradation (Mn decrease) was proportional to the acid concentration. A one‐year degradation study of E50/D50‐SS (from 50% feed of erythritol) in seawater, deionized water, tap water, or pH 5 buffer showed no Mn decrease; but in pH 1 buffer, the decrease was 40% (18,800 to 11,200). © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 44089.
Extrusion foaming behavior of a polypropylene/nanoclay microcellular foam
Authors: Wang Mingyi , Xie Linsheng , Qian Bo , Ma Yulu , Zhou Nanqiao 
Published: July 2016

ABSTRACTWith maleic anhydride grafted polypropylene (PP‐g‐MAH) as a compatibilizer, composites of block‐copolymerized polypropylene (B‐PP)/nanoclay were prepared. The effects of the PP‐g‐MAH and nanoclay content on the crystallization and rheological properties of B‐PP were investigated. The microcellular foaming behavior of the B‐PP/nanoclay composite material was studied with a single‐screw extruder foaming system with supercritical (SC) carbon dioxide (CO2) as the foaming agent. The experimental results show that the addition of nanoclay and PP‐g‐MAH decreased the melt strength and complex viscosity of B‐PP. When 3 wt % SC CO2 was injected as the foaming agent for the extrusion foaming process, the introduction of nanoclay and PP‐g‐MAH significantly increased the expansion ratio of the obtained foamed samples as compared with that of the pure B‐PP matrix, lowered the die pressure, and increased the cell population density of the foamed samples to some extent. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 44094.
Montmorillonite as support for peroxide in the melt grafting of maleic anhydride onto polypropylene
Authors: Muñoz Pablo Andres Riveros , Bettini Sílvia Helena Prado 
Published: July 2016

ABSTRACTGrafting of maleic anhydride onto polypropylene was performed in a Haake torque rheometer, in the presence of organically modified montmorillonite, MMT (used as support for the peroxide), according to a 23 factorial design, where the maleic anhydride concentration (CMA), peroxide concentration (Cper) and reaction time (tr) were varied. For comparison, the reaction in the absence of MMT was also conducted. Polypropylene degradation was assessed by parallel plate rheometry and size exclusion chromatography (SEC) and percentage of reacted maleic anhydride (%MAg) was obtained by titration and FTIR spectroscopy. The results showed differences in both systems, conventional and in the presence of MMT. The structure of polypropylene grafted with maleic anhydride, PP‐g‐MA, indicates longer branches are formed in the presence of MMT compared to in its absence, demonstrated by FTIR analysis. As in conventional reaction systems, an increase in Cper caused an increase in %MAg and a reduction in molar mass. The variable CMA showed to be not significant in the grafting reaction in the presence of MMT, even at high DCP levels, at a 5% significance level. On the other hand, increase in CMA resulted in significant increase in viscosity. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 44134.
Temporal regularity of intrinsic cerebral activity in patients with chronic primary insomnia: a brain entropy study using resting‐state fMRI
Authors: Zhou Fuqing , Huang Suhua , Gao Lei , Zhuang Ying , Ding Shan , Gong Honghan 
Published: July 2016

AbstractIntroductionSeveral neuroimaging studies have suggested that patients with chronic primary insomnia (CPI) exhibit anatomical and functional alterations of the brain, but the temporal regularity in spontaneous neuronal activity remains unknown. Here, brain entropy (BEN), a data‐driven method used to measure the signal regularity of a time series, was applied for the first time to investigate changes in the entire brain at the voxel level.MethodsResting‐state functional MRI data were used to investigate insomnia‐related BEN alterations and the resting‐state functional connectivity (rsFC) pattern in seed regions with altered BEN in 29 patients with identified and untreated CPI and 29 matched healthy controls. Subsequently, within the CPI group, correlation analysis was conducted to evaluate the relationship between the clinical variables and the BEN and rsFC of the abnormal regions.ResultsChronic primary insomnia patients showed significant increase in BEN in the central part of the default‐mode network (DMN), the anterior regions of the task‐positive network (TPN), the hippocampus (Hipp), and basal ganglia (BG), and decreases in BEN in the right postcentral gyrus (PoCG) and right temporal–occipital junction (TOJ). We also demonstrated that three altered resting‐state functional connectivity (rsFC) patterns were associated with abnormal BEN regions in CPI patients. Correlation analysis identified an association between the altered rsFC and clinical variables, such as the Pittsburgh Sleep Quality Index (PSQI), in CPI patients.ConclusionsTogether, these findings suggest that abnormal BEN‐related intrinsic functional plasticity in CPI patients corresponds to poor sleep quality during chronic insomnia. Alterations in both BEN and its affected connectivity may improve our understanding of treatment‐naïve CPI patients and promote the future development of new therapeutic strategies.
Impurities in Nitrile Solvents Commonly Used for Electrochemistry, and their Effects on Voltammetric Data
Authors: Tessensohn Malcolm E. , Ng Shu Jun , Chan Kwok Kiong , Gan Sher Li , Sims Natalie F. , Koh Yu Rong , Webster Richard D. 
Published: July 2016

AbstractVoltammetry experiments were performed on 1,4‐benzoquinone and 1,4‐phenylenediamine in acetonitrile, propionitrile (from five commercial suppliers: Acros Organics, Aldrich, Alfa Aesar, Fluka, and Merck), and butyronitrile, to which different electrochemical responses were collected across the three nitrile solvents and within the five commercial brands of propionitrile, owing to the reduced (1,4‐benzoquinone) or oxidized (1,4‐phenylenediamine) compounds reacting with impurities in the solvents. Of the three solvents, propionitrile suffered from the most impurities, which adversely affected the electrochemical results. Distillation of the propionitrile over phosphorus pentoxide or passing it through a flash column containing silica gel was partially effective in removing some of the impurities and resulted in the recovery of the familiar oxidation behavior of 1,4‐phenylenediamine. The reduction behavior of 1,4‐benzoquinone could be improved if propionitrile was purified by passing it through a column of basic activated alumina, thus a combination of distillation and flash chromatography is necessary to adequately purify propionitrile for reductive and oxidative voltammetry experiments. Purge and trap‐gas chromatography–mass spectrometry analyses positively identified 2‐methyl‐2‐pentenal among the impurities, but it was discovered to only have a mild effect on the voltammetric behavior of the quinone and not exert any influence on the electrochemical response of the phenylenediamine. The results of this study lead to the possibility of using the voltammetry of quinones and phenylenediamines as a sensitive method for determining the purity of organic solvents.
Electrocatalytic Oxidation of Alcohols, Tripropylamine, and DNA with Ligand‐Free Gold Nanoclusters on Nitrided Carbon
Authors: Yao Huiqin , Liu Ben , Mosa Islam M. , Bist Itti , He Jie , Rusling James F. 
Published: July 2016

AbstractElectrocatalytic properties of ligand‐free gold nanoclusters (AuNCs, <2 nm) grown on nitrided carbon supports (denoted as AuNCs@N‐C) were evaluated for the oxidation of representative organic molecules including alcohols, an amine, and deoxyguanosine in oligonucleotides. AuNCs@N‐C catalysts were incorporated into films of architecture {PDDA/AuNCs@N‐C}n by using layer‐by‐layer assembly with oppositely charged poly(diallyldimethylammonium) (PDDA) on pyrolytic graphite (PG) electrodes. Cyclic voltammetry and electrochemical impedance spectroscopy (EIS) were used to survey the electrocatalytic properties of these AuNCs@N‐C films. Ligand‐free AuNCs in these films demonstrated excellent electrocatalytic oxidation activity with maximum peak currents and the lowest potentials for oxidizing ethanol, propanol, and tripropylamine (TprA) compared to controls with Au‐surface capping agents or to larger sized Au nanocrystals on the nitrided carbon supports. EIS kinetic studies showed that ligand‐free AuNCs films have the smallest charge‐transfer resistance, largest electrochemically active surface area, and largest apparent standard rate constants, as compared to the control films for all compounds examined. DNA films on AuNCs@N‐C were oxidized at deoxyguanosine moieties with good catalytic activity that depended on charge transport within the films.