bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characteristics of TLE‐producing lightning in a coastal thunderstorm
Authors: Chang Shu‐Chun , Hsu Rue‐Ron , Huang Sung‐Ming , Su Han‐Tzong , Kuo Cheng‐Ling , Chou Jung‐Kung , Lee Li‐Jou , Wu Yeng‐Jung , Chen Alfred B. 
Published: November 2014

AbstractObserving from southern Taiwan on 2 August 2010, a thunderstorm near Luzon Island, Philippines, about 500 km away was found to produce 72 transient luminous events (TLEs). Besides optical images, ULF and VLF sferics of lightning from this thunderstorm were also recorded. This work examines the characteristics of TLE‐producing lightning through studying their ULF and VLF sferics. The attenuation of ULF and VLF sferics in the Earth cavity is obtained through analyzing the sferics associated with Imager of Sprite and Upper Atmospheric Lightning elves that occurred within ~1500 km of Taiwan. Amplitudes of the ULF and the VLF sferics are found to vary as D−0.871 and D−1.207, respectively, where D is the source distance from the sferic stations. After normalizing the sferics from the 2 August 2010 storm to 500 km distance, the ratio of the peak ULF and the VLF magnetic fields is found to be distinct for different TLE‐producing lightning. The ratio for the halo‐producing lightning is nearly 3 times that of the elve‐producing lightning, but it is comparable to that of the halo‐sprite‐producing lightning, although the ULF strength for the halo‐sprite lightning is significantly larger than that for the halo lightning. Therefore, it is possible to distinguish between the TLE‐types using the ULF to VLF peak ratio or the strength of ULF/VLF band emissions of the parent lightning. Comparison of numerically simulated and the observed lightning radiation fields indicates that the best fit discharge time of the elve lightning is about 100 µs, while that for the halo‐producing lightning is between 200 and 500 µs.
Comparative investigation of the energetic ion spectra comprising the magnetospheric ring currents of the solar system
Authors: Mauk B. H. 
Published: November 2014

AbstractInvestigated here are factors that control the intensities and shapes of energetic ion spectra that make up the ring current populations of the strongly magnetized planets of the solar system, specifically those of Earth, Jupiter, Saturn, Uranus, and Neptune. Following a previous and similar comparative investigation of radiation belt electrons, we here turn our attention to ions. Specifically, we examine the possible role of the differential ion Kennel‐Petschek limit, as moderated by Electromagnetic Ion Cyclotron (EMIC) waves, as a standard for comparing the most intense ion spectra within the strongly magnetized planetary magnetospheres. In carrying out this investigation, the substantial complexities engendered by the very different ion composition distributions of these diverse magnetospheres must be addressed, given that the dispersion properties of the EMIC waves are strongly determined by the ion composition of the plasmas within which the waves propagate. Chosen for comparison are the ion spectra within these systems that are the most intense observed, specifically at 100 keV and 1 MeV. We find that Earth and Jupiter are unique in having their most intense ion spectra likely limited and sculpted by the Kennel‐Petschek process. The ion spectra of Saturn, Uranus, and Neptune reside far below their respective limits and are likely limited by interactions with gas and dust (Saturn) and by the absence of robust ion acceleration processes (Uranus and Neptune). Suggestions are provided for further testing the efficacy of the differential Kennel‐Petschek limit for ions using the Van Allen Probes.
The spatial and temporal structure of twin peaks and midday bite out in foF2 (with associated height changes) in the Australian and South Pacific low midlatitude ionosphere
Authors: Lynn Kenneth J. W. , Gardiner‐Garden Robert S. , Heitmann Andrew 
Published: November 2014

AbstractMorning and afternoon peaks in daytime critical frequency foF2 defining a midday bite out were found to occur regularly across northern Australia during April 2008. This behavior was sufficiently repetitive to appear in the monthly median values of foF2. The twin peak and bite out phenomenon was observable across the entire longitudinal range of ionosondes which were accessible for this study, from Niue in mid‐Pacific to Learmonth on the western side of Australia. The high geographic density of ionosondes operating in Australia enabled the limited latitudinal range of occurrence to be established, the phenomenon ceasing to be present in the southern half of Australia or at equatorial latitudes. While strongest in 2008, the foF2 bite out and associated variation in hmF2, the peak height of the ionosphere, continued to be seen in monthly April medians from sunspot minimum (2007–2008) to the current low sunspot maximum (2011–2013) while diminishing in magnitude. This phenomenon was also present around the September equinox, though not of such magnitude or consistency as during the April equinox. The morning and afternoon peaks in foF2 occurred during periods of falling virtual and true height and were associated with the maximum compression of the ionosphere at this time as measured by the subpeak equivalent parabolic layer thickness ym. Meridional winds in the F2 layer are suggested as a driver of the twin peak enhancements in foF2, which may possibly be related to a simultaneous occurrence of strong tidal influences as seen to be present in descending sporadic E.
Extended lunar precursor regions: Electron‐wave interaction
Authors: Harada Y. , Halekas J. S. , Poppe A. R. , Kurita S. , McFadden J. P. 
Published: November 2014

AbstractWe present Acceleration, Reconnection, Turbulence and Electrodynamics of the Moon's Interaction with the Sun (ARTEMIS) observations of electron‐wave interactions which extend to quite large distances upstream from the Moon. We first study electron velocity distributions and wave spectra on an event basis. In both the solar wind and terrestrial plasma sheet, we observe strong whistler wave activity on the magnetic field lines connected to the dayside lunar surface. These whistlers are most likely driven by the anisotropy of upward electrons caused by surface absorption. The whistler growth rates computed from the measured electron distributions successfully reproduced the spectral characteristics of the observed ∼100 Hz narrowband oscillations and those reaching lower frequencies. Meanwhile, the incoming solar wind strahl beam is occasionally isotropized near the Moon, and broadband electrostatic waves are observed simultaneously, suggesting streaming instabilities between the incoming and outgoing beams. Based on the case study, we statistically survey the spatial variations of the characteristic quantities of the upstream electron‐wave interactions. Both the electron anisotropy and electromagnetic wave intensity decay with increasing field line distances but remain higher than the ambient level at 6 lunar radii (∼10,000 km) or more. The strahl electron isotropization and electrostatic waves are found mainly at lower altitudes below 1 lunar radius. The electron anisotropy and whistler intensity exhibit clear anticorrelation with crustal magnetic fields, indicating that the magnetic anomalies suppress the whistler wave growth. The ARTEMIS observations convincingly illustrate that the lunar influence on electrons reaches out to 6 lunar radii or more upstream from the Moon.
Solar heating of the Arctic Ocean in the context of ice‐albedo feedback
Authors: Pinker Rachel T. , Niu Xiaolei , Ma Yingtao 
Published: November 2014

AbstractTo study the relationship of solar heat input into the Arctic open water and the variations of sea ice extent, improved satellite‐based estimates of shortwave radiative (SWR) fluxes and most recent observations of ice extent are used. The SWR flux estimates are based on observations from the Moderate Resolution Imaging Spectroradiometer (MODIS) and from the Advanced Very High Resolution Radiometer (AVHRR) for the period of 1984–2009. Ice extent information at 25 km resolution comes from Nimbus‐7 SMMR and DMSP SSM/I Passive Microwave Data as generated with the NASA Team algorithm developed by the Oceans and Ice Branch, Laboratory for Hydrospheric Processes, NASA Goddard Space Flight Center. The trends of the solar heat input into the ocean and the open water fraction for 1984–2009 are found to be positive: 0.3%/yr and 0.8%/yr, respectively, at a 99% confidence level. There is an obvious transition region separating the 26 years into two periods: one with moderate change: 1984–2002, and the other with an abrupt growth in both solar heat input and open water fraction: 2003–2009. The impact of the observed changes on the reduction of winter ice growth in 2007 is estimated to be about 44 cm, and a delay in fall freezeup as about 10–36 days.
Unsteady stress partitioning and momentum transfer in the wave bottom boundary layer over movable rippled beds
Authors: Rodríguez‐Abudo S. , Foster D. L. 
Published: November 2014

AbstractObservations of the nearbed velocity field over a rippled sediment bed under asymmetric wave forcing conditions were collected using a submersible particle image velocimetry (PIV) system. To examine the role of bed form‐induced dynamics in the total momentum transfer, a double‐averaging technique was implemented on the two‐dimensional time‐dependent velocity field by means of the full momentum equation. This approach allows for direct determination of the bed form‐induced stresses, i.e., stresses that arise due to the presence of bed forms, which are zero in flat bed conditions. This analysis suggests that bed form‐induced stresses are closely related to the presence of coherent motions and may be partitioned from the turbulent stresses. Inferences of stress provided by a bed load transport model suggest that total momentum transfer obtained from the double‐averaging technique is capable of reproducing bed form mobilization. Comparisons between the total momentum transfer and stress estimates obtained from local velocity profiles show significant variability across the ripple and suggest that an array of sensors is necessary to reproduce bed form evolution. The imbalance of momentum obtained by resolving the different terms constituting the near‐bed momentum balance (i.e., acceleration deficit, stress gradient, and bed form‐induced skin friction) provides an estimate of the bed form‐induced pressure that is consistent with flow separation. This analysis reveals three regions in the flow: the free‐stream, where all terms are relatively balanced; the near‐bed, where momentum imbalance is significant during flow weakening; and below ripple crests, where bed form‐induced pressure is the leading order mechanism.
SST patterns and dynamics of the southern Senegal‐Gambia upwelling center
Authors: Ndoye S. , Capet X. , Estrade P. , Sow B. , Dagorne D. , Lazar A. , Gaye A. , Brehmer P. 
Published: November 2014

AbstractThe southern end of the Canary current system comprises of an original upwelling center that has so far received little attention, the Southern Senegal‐Gambia Upwelling Center (SSUC). We investigate its dynamical functioning by taking advantage of favorable conditions in terms of limited cloud coverage. Analyses and careful examinations of over 1500 satellite images of sea surface temperature scenes contextualized with respect to wind conditions confirm the regularity and stability of the SSUC dynamical functioning (as manifested by the recurrence and persistence of particular SST patterns). The analyses also reveal subtle aspects of its upwelling structure: shelf break cooling of surface waters consistent with internal tide breaking/mixing; complex interplay between local upwelling and the Mauritanian current off the Cape Verde headland; complexity of the inner‐shelf/mid shelf frontal transition. The amplitude of the diurnal cycle suggests that large uncertainties exist in the SSUC heat budget. The studies limitations underscore the need for continuous in situ measurement in the SSUC, particularly of winds.
The location of Airy‐0, the Mars prime meridian reference, from stereo photogrammetric processing of THEMIS IR imaging and digital elevation data
Authors: Duxbury T. C. , Christensen P. , Smith D. E. , Neumann G. A. , Kirk R. L. , Caplinger M. A. , Albee A. A. , Seregina N. V. , Neukum G. , Archinal B. A. 
Published: November 2014

AbstractThe small crater Airy‐0 was selected from Mariner 9 images to be the reference for the Mars prime meridian. Initial analyses in the year 2000 tied Viking Orbiter and Mars Orbiter Camera images of Airy‐0 to the evolving Mars Orbiter Laser Altimeter global digital terrain model to update the location of Airy‐0. Based upon this tie and radiometric tracking of landers/rovers from Earth, new expressions for the Mars spin axis direction, spin rate, and prime meridian epoch value were produced to define the orientation of the Martian surface in inertial space over time. Since the Mars Global Surveyor mission and Mars Orbiter Laser Altimeter global digital terrain model were completed some time ago, a more exhaustive study has been performed to determine the accuracy of the Airy‐0 location and orientation of Mars at the standard epoch. Thermal Emission Imaging System (THEMIS) IR image cubes of the Airy and Gale crater regions were tied to the global terrain grid using precision stereo photogrammetric image processing techniques. The Airy‐0 location was determined to be about 0.001° east of its predicted location using the currently defined International Astronomical Union (IAU) prime meridian location. Information on this new location and how it was derived will be provided to the NASA Mars Exploration Program Geodesy and Cartography Working Group for their assessment. This NASA group will make a recommendation to the IAU Working Group on Cartographic Coordinates and Rotational Elements to update the expression for the Mars spin axis direction, spin rate, and prime meridian location.
Impact of changes in the formulation of cloud‐related processes on model biases and climate feedbacks
Authors: Lacagnina Carlo , Selten Frank , Siebesma A. Pier 
Published: November 2014

AbstractTo test the impact of modeling uncertainties and biases on the simulation of cloud feedbacks, several configurations of the EC‐Earth climate model are built altering physical parameterizations. An overview of the various radiative feedbacks diagnosed from the reference EC‐Earth configuration is documented for the first time. The cloud feedback is positive and small. While the total feedback parameter is almost insensitive to model configuration, the cloud feedback, in particular its shortwave (SW) component, can vary considerably depending on the model settings. The lateral mass exchange rate of penetrative convection and the conversion rate from condensed water to precipitation are leading uncertain parameters affecting the radiative feedbacks diagnosed. Consistent with other studies, we find a strong correlation between low‐cloud model fidelity and low‐cloud response under global warming. It is shown that this relationship holds only for stratocumulus regimes and is contributed by low‐cloud cover, rather than low‐cloud optical thickness. Model configurations simulating higher stratocumulus cover, which is closer to the observations, exhibit a stronger positive SW cloud feedback. This feedback is likely underestimated in the reference EC‐Earth configuration, over the eastern basins of the tropical oceans. In addition, connections between simulated high‐cloud top altitude in present‐day climate and longwave cloud feedback are discussed.
Climate and climate sensitivity to changing CO2 on an idealized land planet
Authors: Becker Tobias , Stevens Bjorn 
Published: November 2014

AbstractThe comprehensive general circulation model ECHAM6 is used in a radiative‐convective equilibrium configuration. It is coupled to a perfectly conducting slab. To understand the local impact of thermodynamic surface properties on the land‐ocean warming contrast, the surface latent heat flux and surface heat capacity are reduced stepwise, aiming for a land‐like climate. Both ocean‐like and land‐like RCE simulation reproduce the tropical atmosphere over ocean and land in a satisfactory manner and lead to reasonable land‐ocean warming ratios. A small surface heat capacity induces a high diurnal surface temperature range which triggers precipitation during the day and decouples the free troposphere from the diurnal mean temperature. With increasing evaporation resistance, the net atmospheric cooling rate decreases because cloud base height rises, causing a reduction of precipitation. Climate sensitivity depends more on changes in evaporation resistance than on changes in surface heat capacity. A feedback analysis with the partial radiation perturbation method shows that amplified warming over idealized land can be associated with disproportional changes in the lapse rate versus the water vapor feedback. Cloud feedbacks, convective aggregation, and changes in global mean surface temperature confuse the picture.
Pituitary adenylate cyclase activating polypeptide and migraine
Authors: Zagami Alessandro S. , Edvinsson Lars , Goadsby Peter J. 
Published: November 2014

AbstractPituitary adenylate cyclase activating peptide (PACAP) is found in human trigeminocervical complex and can trigger migraine. PACAP levels were measured using a sensitive radioimmunoassay. Stimulation of the superior sagittal sinus (SSS) in cat elevated PACAP levels in cranial blood. Patients with moderate or severe migraine headache had elevated PACAP in the external jugular vein during headache (n = 15), that was reduced 1 h after treatment with sumatriptan 6 mg (n = 11), and further reduced interictally (n = 9). The data suggest PACAP, or its receptors, are a promising target for migraine therapeutics.
Dental fast track: Prenatal enamel growth, incisor eruption, and weaning in human infants
Authors: Mahoney Patrick 
Published: November 2014

ABSTRACTCorrelation between the timing of permanent first molar eruption and weaning age in extant primates has provided a way to infer a life history event in fossil species, but recent debate has questioned whether the same link is present in human infants. Deciduous incisors erupt at an age when breast milk can be supplemented with additional foods (mixed feeding), and weaning is typically complete before permanent first molars erupt. Here, I use histological methods to calculate the prenatal rate by which enamel increases in thickness and height on human deciduous incisors, canines, and molars (n = 125). Growth trajectories for each tooth type are related to the trimesters and assessed against the eruption sequence and final crown height. Analyses show that central incisors initiate early in the second trimester with significantly faster secretion rates relative to canines and second molars, which initiate closer to birth. Even though initial extension rates were correlated with crown height and scaled with positive allometry within each tooth class, the relatively short incisors still increased in height at a significantly faster rate than the taller canines and molars. The incisor prenatal “fast track” produces a greater proportion of the crown before birth than all other tooth types. This growth mechanism likely facilitates early incisor eruption at a time when the mixed feeding of infants can be initiated as part of the weaning process. Findings provide a basis from which to explore new links between developmental trends along the tooth row and mixed feeding age in other primates. Am J Phys Anthropol 156:407–421, 2015. © 2014 Wiley Periodicals, Inc.
Argentophile Wechselwirkungen
Authors: Schmidbaur Hubert , Schier Annette 
Published: November 2014

AbstractZwischen 1990 und 2000 wuchs in der Goldchemie das Interesse an aurophilen Wechselwirkungen, nachdem man festgestellt hatte, dass diese eine Vielzahl struktureller und anderer physikalischer Eigenschaften von Gold(I)‐Verbindungen nennenswert beeinflussen. Die Aufmerksamkeit, die man diesem kontraintuitiven inter‐ und intramolekularen Typ von Bindung zwischen Metallzentren mit scheinbar abgeschlossener Elektronenschale entgegenbrachte, hat sich schnell auch auf die Chemie des Silbers ausgeweitet. Hunderte von Untersuchungen widmeten sich seither dem Phänomen der Argentophilie. Dieser Aufsatz gibt einen Überblick über diese Entwicklung mit Hauptaugenmerk auf molekularen Systemen mit zwei oder mehr in engem Kontakt stehenden Silber(I)‐Zentren, was zu spezifischen strukturellen sowie zu einer Vielzahl neuartiger physikalischer Eigenschaften führt. Diese schließen vor allem stark veränderte Ligand→Metall‐Ladungstransferprozesse ein, aber auch eine überdimensionale thermische Kontraktion auf der einen und eine beispiellose negative lineare Kompressibilität von Kristallparametern auf der anderen Seite.
Enzymatic Halogenation of Tryptophan on a Gram Scale
Authors: Frese Marcel , Sewald Norbert 
Published: November 2014

AbstractHalogenated arenes are important building blocks in medicinal and agrochemistry. Chemical electrophilic aromatic halogenation requires molecular halogen, whereas FAD‐dependent halogenases form halogenated arenes with high regioselectivity while only halide salts and O2 are required. This reaction proceeds at room temperature in aqueous media. However, enzymatic halogenation is considered inefficient, mainly because halogenases are not stable. Thus, the preparative application remained elusive. We were able to show that the long‐term stability and, hence, the preparative efficiency of the tryptophan‐7‐halogenase RebH can be significantly improved by immobilization together with the other enzymes required for cofactor regeneration. We established a facile scalable method suitable for the halogenation of tryptophan and its derivatives on a gram scale using a solid, multifunctional, and recyclable biocatalyst; this immobilization strategy might also be applicable for other FAD‐dependent halogenases.
Reinforcement of graphene nanoplatelets on plasticized poly(lactic acid) nanocomposites: Mechanical, thermal, morphology, and antibacterial properties
Authors: Chieng Buong Woei , Ibrahim Nor Azowa , Yunus Wan Md Zin Wan , Hussein Mohd Zobir , Then Yoon Yee , Loo Yuet Ying 
Published: November 2014

ABSTRACTPlasticized poly(lactic acid) (PLA)‐based nanocomposites filled with graphene nanoplatelets (xGnP) and containing poly(ethylene glycol) (PEG) and epoxidized palm oil (EPO) with ratio 2 : 1 (2P : 1E) as hybrid plasticizer were prepared by melt blending method. The key objective is to take advantage of plasticization to increase the material ductility while preserving valuable stiffness, strength, and toughness via addition of xGnP. The tensile modulus of PLA/2P : 1E/0.1 wt % xGnP was substantially improved (30%) with strength and elasticity maintained, as compared to plasticized PLA. TGA analysis revealed that the xGnP was capable of acting as barrier to reduce thermal diffusion across the plasticized PLA matrix, and thus enhanced thermal stability of the plasticized PLA. Incorporation of xGnP also enhanced antimicrobial activity of nanocomposites toward Escherichia coli, Salmonella typhimurium, Staphylococcus aureus, and Listeria monocytogenes. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41652.