bluuebunny/crossref_metadata_2025_split huggingface dataset:
Where is mineral ballast important for surface export of particulate organic carbon in the ocean?
Authors: Le Moigne Frédéric A. C. , Pabortsava Katsiaryna , Marcinko Charlotte L. J. , Martin Patrick , Sanders Richard J. 
Published: October 2014

AbstractCorrelations between particulate organic carbon (POC) and mineral fluxes in the deep ocean have inspired the inclusion of “ballast effect” parameterizations in carbon cycle models. A recent study demonstrated regional variability in the effect of ballast minerals on the flux of POC in the deep ocean. We have undertaken a similar analysis of shallow export data from the Arctic, Atlantic, and Southern Oceans. Mineral ballasting is of greatest importance in the high‐latitude North Atlantic, where 60% of the POC flux is associated with ballast minerals. This fraction drops to around 40% in the Southern Ocean. The remainder of the export flux is not associated with minerals, and this unballasted fraction thus often dominates the export flux. The proportion of mineral‐associated POC flux often scales with regional variation in export efficiency (the proportion of primary production that is exported). However, local discrepancies suggest that regional differences in ecology also impact the magnitude of surface export. We propose that POC export will not respond equally across all high‐latitude regions to possible future changes in ballast availability.
Sudden impulse observations in the dayside magnetosphere by THEMIS
Authors: Samsonov A. A. , Sibeck D. G. , Walsh B. M. , Zolotova N. V. 
Published: October 2014

AbstractWe present a study of the magnetospheric response to interplanetary shocks. We show eight events with simultaneous observations of sudden impulses in the dayside magnetosphere and interplanetary shocks in the solar wind. The spacecraft measurements in the equatorial plane, even those very close to the Earth, can be interpreted in terms of the vortices predicted by previous studies employing global MHD models. In fact, these vortices are velocity oscillations with the properties of Alfvén waves. The amplitude and frequency of the oscillations depend on radial distance from the Earth. The amplitude of the velocity perturbations decreases with increase of the density and magnetic field magnitude, but the velocity amplitude shows no dependence on magnitude of the solar wind dynamic pressure change attending the interplanetary shocks. The oscillations are observed both in the outer magnetosphere and the plasmasphere, but they become less sinusoidal near the plasmapause, i.e., in the region with a large‐density gradient. The amplitude of the magnetic field enhancement in the sudden impulses also depends on the radial distance. The MHD simulations successfully predict the amplitudes of magnetic field increase and the first cycles of the velocity oscillations in these events.
Intensity asymmetries in the dusk sector of the poleward auroral oval due to IMF Bx
Authors: Reistad J. P. , Østgaard N. , Laundal K. M. , Haaland S. , Tenfjord P. , Snekvik K. , Oksavik K. , Milan S. E. 
Published: October 2014

AbstractIn the exploration of global‐scale features of the Earth's aurora, little attention has been given to the radial component of the Interplanetary Magnetic Field (IMF). This study investigates the global auroral response in both hemispheres when the IMF is southward and lies in the xz plane. We present a statistical study of the average auroral response in the 12–24 magnetic local time (MLT) sector to an x component in the IMF. Maps of auroral intensity in both hemispheres for two IMF Bx dominated conditions (± IMF Bx) are shown during periods of negative IMF Bz, small IMF By, and local winter. This is obtained by using global imaging from the Wideband Imaging Camera on the IMAGE satellite. The analysis indicates a significant asymmetry between the two IMF Bx dominated conditions in both hemispheres. In the Northern Hemisphere the aurora is brighter in the 15–19 MLT region during negative IMF Bx. In the Southern Hemisphere the aurora is brighter in the 16–20 MLT sector during positive IMF Bx. We interpret the results in the context of a more efficient solar wind dynamo in one hemisphere. Both the intensity asymmetry and its location are consistent with this idea. This has earlier been suggested from case studies of simultaneous observations of the aurora in both hemispheres, but hitherto never been observed to have a general impact on global auroral brightness in both hemispheres from a statistical study. The observed asymmetries between the two IMF Bx cases are not large; however, the difference is significant with a 95% confidence level. As the solar wind conditions examined in the study are rather common (37% of the time) the accumulative effect of this small influence may be important for the total energy budget.
Evidence for the braking of flow bursts as they propagate toward the Earth
Authors: Hamrin M. , Pitkänen T. , Norqvist P. , Karlsson T. , Nilsson H. , André M. , Buchert S. , Vaivads A. , Marghitu O. , Klecker B. , Kistler L. M. , Dandouras I. 
Published: October 2014

AbstractIn this article we use energy conversion arguments to investigate the possible braking of flow bursts as they propagate toward the Earth. By using E·J data (E and J are the electric field and the current density) observed by Cluster in the magnetotail plasma sheet, we find indications of a plasma deceleration in the region −20 RE < X < − 15 RE. Our results suggest a braking mechanism where compressed magnetic flux tubes in so‐called dipolarization fronts (DFs) can decelerate incoming flow bursts. Our results also show that energy conversion arguments can be used for studying flow braking and that the position of the flow velocity peak with respect to the DF can be used as a single‐spacecraft proxy when determining energy conversion properties. Such a single‐spacecraft proxy is invaluable whenever multispacecraft data are not available. In a superposed epoch study, we find that a flow burst with the velocity peak behind the DF is likely to decelerate and transfer energy from the particles to the fields. For flow bursts with the peak flow at or ahead of the DF we see no indications of braking, but instead we find an energy transfer from the fields to the particles. From our results we obtain an estimate of the magnitude of the deceleration of the flow bursts, and we find that it is consistent with previous investigations.
Observations in the E region ionosphere of kappa distribution functions associated with precipitating auroral electrons and discrete aurorae
Authors: Kaeppler S. R. , Nicolls M. J. , Strømme A. , Kletzing C. A. , Bounds S. R. 
Published: October 2014

AbstractPrecipitating auroral electrons can produce discrete auroral arcs that contain signatures of the magnetospheric auroral source region. Differential number flux observations over two discrete aurorae were obtained by the Auroral Currents and Electrodynamics Structure sounding rocket mission, which successfully launched in 2009. These observations were made at E region altitudes of approximately 130 km. A model of precipitating auroral electrons as described by Evans (1974) was fit to the electron differential number flux obtained by the payloads, and parameters from the model were used to infer properties of the auroral source region. It is shown that the field‐aligned precipitating electrons were better fit by a kappa distribution function versus a Maxwellian distribution function for the equatorward side of the first, quasi‐stable, auroral arc crossing. The latter half of the first auroral arc crossing and second auroral crossing show that the precipitating electrons were better fit by a Maxwellian distribution function, which provides additional observational confirmation of previous studies. The low‐energy electron population determined by the Evans (1974) model was within a factor of 2 of the observed differential number flux. The source region parameters determined from fitting the model to the data were compared with relevant studies from sounding rockets and satellites. Our observations are consistent with the results of Kletzing et al. (2003) that the plasma sheet electrons mapping to auroral zone invariant latitudes are characterized by kappa distribution functions.
The case for a common spectrum of particles accelerated in the heliosphere: Observations and theory
Authors: Fisk L. A. , Gloeckler G. 
Published: October 2014

AbstractIn the last decade a significant discovery has been made in the heliosphere: the spectrum of particles accelerated in both the inner heliosphere and in the heliosheath is the same: a power law in particle speed with a spectral index of −5, when the spectrum is expressed as a distribution function; or equivalently, a differential intensity spectrum that is a power law in energy with a spectral index of −1.5. In the inner heliosphere this common spectrum occurs at quite low energies and is most evident in instruments designed to measure suprathermal particles. In the heliosheath, the common spectrum is observed over the full energy range of the Voyager energetic particle instruments, up to energies of ~100 MeV. The remarkable discovery of a common spectrum is compounded by the realization that no traditional acceleration mechanism, i.e., diffusive shock acceleration or stochastic acceleration, can account for the common spectrum. There is thus an opportunity to once again demonstrate the relevance of heliospheric physics by developing a new acceleration mechanism that yields the common spectrum, with the expectation that such a new acceleration mechanism will find broader applications in astrophysics. In this paper, the observations of the common spectrum in the heliosphere are summarized, with emphasis on those that best reveal the conditions in which the acceleration must operate. Then, building on earlier work, a complete derivation is presented of an acceleration mechanism, a pump acceleration mechanism, that yields the common spectrum, and the various subtleties associated with this derivation are discussed.
Excitation of nightside magnetosonic waves observed by Van Allen Probes
Authors: Zhou Qinghua , Xiao Fuliang , Yang Chang , Liu Si , Kletzing C. A. , Kurth W. S. , Hospodarsky G. B. , Spence H. E. , Reeves G. D. , Funsten H. O. , Blake J. B. , Baker D. N. , Wygant J. R. 
Published: October 2014

AbstractDuring the recovery phase of the geomagnetic storm on 30–31 March 2013, Van Allen Probe A detected enhanced magnetosonic (MS) waves in a broad range of L = 1.8–4.7 and magnetic local time (MLT) = 17–22 h, with a frequency range ∼10–100 Hz. In the meanwhile, distinct proton ring distributions with peaks at energies of ∼10 keV, were also observed in L = 3.2–4.6 and L = 5.0–5.6. Using a subtracted bi‐Maxwellian distribution to model the observed proton ring distribution, we perform three‐dimensional ray tracing to investigate the instability, propagation, and spatial distribution of MS waves. Numerical results show that nightside MS waves are produced by proton ring distribution and grow rapidly from the source location L = 5.6 to the location L = 5.0 but remain nearly stable at locations L < 5.0. Moreover, waves launched toward lower L shells with different initial azimuthal angles propagate across different MLT regions with divergent paths at first, then gradually turn back toward higher L shells and propagate across different MLT regions with convergent paths. The current results further reveal that MS waves are generated by a ring distribution of ∼10 keV proton and proton ring in one region can contribute to the MS wave power in another region.
Empirical assessment of theory for bankfull characteristics of alluvial channels
Authors: Trampush S. M. , Huzurbazar S. , McElroy B. 
Published: October 2014

AbstractWe compiled a data set of 541 bankfull measurements of alluvial rivers (see supporting information) and used Bayesian linear regression to examine empirical and theoretical support for the hypothesis that alluvial channels adjust to a predictable condition of basal shear stress as a function of sediment transport mode. An empirical closure based on channel slope, bankfull channel depth, and median grain size is proposed and results in the scaling of bankfull Shields stress with the inverse square root of particle Reynolds number. The empirical relationship is sufficient for purposes of quantifying paleohydraulic conditions in ancient alluvial channels. However, it is not currently appropriate for application to alluvial channels on extraterrestrial bodies because it depends on constant‐valued, Earth‐based coefficients.
Pore‐scale study of dissolution‐induced changes in hydrologic properties of rocks with binary minerals
Authors: Chen Li , Kang Qinjun , Viswanathan Hari S. , Tao Wen‐Quan 
Published: October 2014

AbstractA pore‐scale numerical model for reactive transport processes based on the Lattice Boltzmann method is used to study the dissolution‐induced changes in hydrologic properties of a fractured medium and a porous medium. The solid phase of both media consists of two minerals, and a structure reconstruction method called quartet structure generation set is employed to generate the distributions of both minerals. Emphasis is put on the effects of undissolved minerals on the changes of permeability and porosity under different Peclet and Damkohler numbers. The simulation results show porous layers formed by the undissolved mineral remain behind the dissolution reaction front. Due to the large flow resistance in these porous layers, the permeability increases very slowly or even remains at a small value although the porosity increases by a large amount. Besides, due to the heterogeneous characteristic of the dissolution, the chemical, mechanical and hydraulic apertures are very different from each other. Further, simulations in complex porous structures demonstrate that the existence of the porous layers of the nonreactive mineral suppresses the wormholing phenomena observed in the dissolution of mono‐mineralic rocks.
Ecogeomorphic feedbacks and flood loss of riparian tree seedlings in meandering channel experiments
Authors: Kui Li , Stella John C. , Lightbody Anne , Wilcox Andrew C. 
Published: October 2014

AbstractDuring floods, fluvial forces interact with riparian plants to influence evolution of river morphology and floodplain plant community development. Understanding of these interactions, however, is constrained by insufficient precision and control of drivers in field settings, and insufficient realism in laboratory studies. We completed a novel set of flume experiments using woody seedlings planted on a sandbar within an outdoor meandering stream channel. We quantified effects on local sedimentation and seedling loss to scour and burial across realistic ranges of woody plant morphologies (Populus versus Tamarix species), densities (240 plants m−2 versus 24 m−2), and sediment supply (equilibrium versus deficit). Sedimentation was higher within Tamarix patches than Populus patches, reflecting Tamarix's greater crown frontal area and lower maximum crown density. Plant dislodgement occurred rarely (1% of plants) and was induced in plants with shorter roots. Complete burial was most frequent for small Tamarix that occurred at high densities. Burial risk decreased 3% for Populus and 13% for Tamarix for every centimeter increment in stem height, and was very low for plants >50 cm tall. These results suggest that Tamarix are proportionally more vulnerable than Populus when small (<20 cm tall), but that larger plants of both species are resistant to both burial and scour. Thus, plant morphological traits and development windows must be considered in addition to physical drivers when designing process‐based restoration efforts on regulated rivers such as flow releases to benefit native tree species.
Weniger ist mehr: Neue Messkonzepte in der Chemie durch Compressed Sensing
Authors: Holland Daniel J. , Gladden Lynn F. 
Published: October 2014

AbstractDie Mathematik hat einen tiefgreifenden Einfluss auf die Wissenschaft, und sie gibt den Wissenschaftlern einzigartige Instrumente an die Hand, um die Welt um uns herum zu erklären. Mit dem Anbruch des digitalen Zeitalters gewann auch die Bedeutung der Informationstheorie enorm an Bedeutung. Insbesondere führten Entwicklungen der letzten zwanzig Jahre im Datensampling und der Funktionsrekonstruktion zum Konzept des Compressed Sensing. Was zunächst nach einer abstrakten Idee klang, hat heute einen maßgeblichen Einfluss auf die Wissenschaft, z. B. in der klinischen Medizin, wo das Compressed Sensing die hochauflösende Bildgebung von Patienten ermöglicht, sowie in der 3D‐Elektronentomographie von Katalysator‐Nanopartikeln und der mehrdimensionalen NMR‐Spektroskopie von Proteinen. Der Kurzaufsatz fasst diese Anwendungen zusammen und wirft einen Blick in die Zukunft des Compressed Sensing in der physikalischen, biologischen und medizinischen Metrologie.
Spot the Difference: Engineered and Natural Nanoparticles in the Environment—Release, Behavior, and Fate
Authors: Wagner Stephan , Gondikas Andreas , Neubauer Elisabeth , Hofmann Thilo , von der Kammer Frank 
Published: October 2014

AbstractThe production and use of nanoparticles leads to the emission of manufactured or engineered nanoparticles into the environment. Those particles undergo many possible reactions and interactions in the environment they are exposed to. These reactions and the resulting behavior and fate of nanoparticles in the environment have been studied for decades through naturally occurring nanoparticulate (1–100 nm) and colloidal (1–1000 nm) substances. The knowledge gained from these investigations is nowhere near sufficiently complete to create a detailed model of the behavior and fate of engineered nanoparticles in the environment, but is a valuable starting point for the risk assessment of these novel materials. It is the aim of this Review to critically compare naturally observed processes with those found for engineered systems to identify the “nanospecific” properties of manufactured particles and describe critical knowledge gaps relevant for the risk assessment of manufactured nanomaterials in the environment.
Asymmetric Disulfonimide‐Catalyzed Synthesis of δ‐Amino‐β‐Ketoester Derivatives by Vinylogous Mukaiyama–Mannich Reactions
Authors: Wang Qinggang , van Gemmeren Manuel , List Benjamin 
Published: October 2014

AbstractAn organocatalytic asymmetric synthesis of δ‐amino‐β‐ketoester derivatives has been developed. A chiral disulfonimide (DSI) serves as a highly efficient precatalyst for a vinylogous Mukaiyama–Mannich reaction of readily available dioxinone‐derived silyloxydienes with N‐Boc‐protected imines, delivering products in excellent yields and enantioselectivities. The synthetic utility of this reaction is illustrated in various transformations, including a new CC bond‐forming reaction, which provide useful enantioenriched building blocks. The methodology is applied in a formal synthesis of (−)‐lasubin.
The design and performance of a vane mixer based on extensional flow for polymer blends
Authors: Xiaochun Yin , Zhongwei Yu , Zengwenbing  , Guangjian He , Zhitao Yang , Baiping Xu 
Published: October 2014

ABSTRACTA new laboratory‐scale mixing device called the “Vane Mixer” was designed, built, and tested. The vane mixer consists of three vane plasticizing and conveying unit. In comparison with the existing laboratory mixers, material flow in this vane mixer is characterized by a high contribution from extensional flow. As the mixer has mixing chamber of very simple geometry, the cleaning is very easy and the material lost is very small. The influences of mixing time and rotor speed on dispersed phase size were characterized and discussed. Morphology data on model immiscible polystyrene/high density polyethylene (PS/HDPE) blend have proved the high distributive and dispersive mixing efficiency. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41551.
Degradation kinetics ofPVCplasticized with different plasticizers under isothermal conditions
Authors: Tüzüm Demir Ayşe Pınar , Ulutan Sevgi 
Published: October 2014

ABSTRACTThe aim of the present work is to elucidate the degradation kinetics of polyvinyl chloride (PVC) plasticized with some phthalate and nonphthalate plasticizers. A PVC thermomat instrument was utilized to maintain the isothermal degradation conditions at 140 and 160°C, and to suppress the oxidative degradation by means of nitrogen flow. The conductivity measurements were performed to follow hydrogen chloride (HCl) gas which is released upon PVC degradation and trapped in water. Dehydrochlorination of plasticized PVC films occurred with activation energies of about 23–160 and 26–117 kJ mol−1and the isokinetic temperatures, at which the dehydrochlorination rate constants of all p‐PVC films would have the same value, were found to be 171 and 128°C for initial and linear regions of dehydrochlorination curve, respectively. Plasticizer incorporation contributes to the stability of the films particularly after the consumption of stabilizer due to the dehydrochlorination. Influence of temperature rise by 20°C on the degradation rate constant is the lowest for DINCH having p‐PVC films as 0.36 and 0.42% increment at the initial region and linear region, respectively. On the other hand, DOTP reveals greater stability than the others do since the compensation ratio of the PVC film having DOTP is greater than the other films. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci.2015,132, 41579.
Enhanced photochromism of heteropolyacid/polyvinylpyrolidone composite film by TiO2 doping
Authors: Lu Cong , Sun Yan , Liu Jialu , Wang Xiansheng , Liu Su‐Ling , Feng Wei 
Published: October 2014

ABSTRACTNovel composite film was synthesized by TiO2 doping into phosphomolybdic acid (PMoA)/polyvinylpyrrolidone (PVP) system. The influence of TiO2 doping on its microstructure and photochromic properties was investigated via atomic force microscopy, transmission electron microscope, Fourier transform infrared spectroscopy (FT‐IR), ultraviolet–visible spectra, and X‐ray photoelectron spectroscopy (XPS). After TiO2 doping, the surface of TiO2/PMoA/PVP composite film changed to rough from smooth, and the particle size significantly increased. The FT‐IR results verified that the basic structure of PMoA and PVP were not destroyed in the composite films. The non‐bonded interaction between the acid and polymer was strengthened by TiO2 doping. Irradiated with UV light, composite films changed from colorless to blue. The TiO2/PMoA/PVP composite film exhibited a strong photochromic effect and faster bleaching reaction than that of PMoA/PVP film. XPS results indicated that the amount of PMoA in photo‐reductive reaction was increased after TiO2 doping, which resulted in the photochromic efficiencies enhanced. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41583.