bluuebunny/crossref_metadata_2025 huggingface dataset:
Place de l’accompagnement et du contrôle dans les dispositifs de formation en alternance
Authors: GREMION Christophe
Published: March 2018

Les dispositifs de formation en alternance d’enseignants proposent fréquemment un accompagnement réflexif pour soutenir l’apprentissage et favoriser la professionnalisation. Cette fonction est le plus souvent assumée par des formateurs de l’institution et/ou des formateurs de terrain qui se retrouvent ainsi à enseigner des contenus, certifier certaines compétences et accompagner des étudiants dans l’analyse ou l’exercice de leurs pratiques.

Ces différents rôles que doivent jouer les formateurs peuvent créer des champs de tensions. En effet, si les assumer en parallèle semble possible du point de vue de l’ingénierie et de l’activité des formateurs, que vivent les personnes en formation dans de tels dispositifs ? C’est le point d’entrée de cette étude de cas, une situation difficile d’accompagnement que nous questionnons par une analyse stratégique et systémique (Crozier & Friedberg, 1977). Cette recherche met en évidence des axes de réflexion pouvant être utiles aux concepteurs de tels dispositifs de même qu’aux acteurs impliqués dans ceux-ci : quels sont les buts visés par le dispositif lui-même, les fonctions et objets de l’évaluation, la répartition des différents rôles de l’évaluation entre les acteurs et le mode d’attribution des accompagnateurs ?
Evaluation, norme et accompagnement : effets d’un dispositif de développement de l’analyse réflexive des professeurs stagiaires en enseignement
Authors: VACHER Yann
Published: March 2018

L’accompagnement, dans la pluralité de ses déclinaisons, apparaît comme une alternative ou un complément aux modèles traditionnels de formation. Dans ces modèles, la place de l’évaluation certificative et de la norme à atteindre est historiquement définie. Qu’en est-il dans le processus d’accompagnement ? A travers l’étude des effets d’un dispositif d’accompagnement par de développement de la pratique réflexive des enseignants en formation initiale, nous tenterons de répondre à cette question. Afin d’étayer les réponses proposées, les déplacements du rapport à la norme et à l’évaluation qui sont mis en lumière, sont mis en perspective avec les stratégies de conception de ce dispositif d’analyse de pratiques professionnelles. La sécurisation de l’activité des participants ou encore les processus de mise à distance affective et cognitive d’avec la pratique professionnelle constituent quelques-uns des éléments à l’origine de ces déplacements et qui sont présentés dans ce texte. Le cadre théorique, le contexte de la recherche, la présentation des résultats et leur interprétation constituent le coeur de cet article.
Marine Fishes Expert Network: findings and recommendations from the Circumpolar Biodiversity Monitoring Program’s State of the Arctic Marine Biodiversity Report
Authors: Hedges Kevin J , MacPhee Shannon , Þór Valtýsson Hreiðar , Johannesen Edda , Mecklenburg Catherine W
Published: March 2018

Pelagic and benthic fish species are important in Arctic marine ecosystems because they transfer energy to predators such as seabirds, marine mammals, as well as people. The CBMP Marine Fishes Expert Network aggregated and reviewed data on the population status and trends of three marine fish Focal Ecosystem Components (FECs) across eight Arctic Marine Areas. Fishes are affected by environmental conditions such as temperature, sea ice availability and salinity, and are constrained by prey availability and predator pressure, which can be influenced by climate change. The three marine fish FECs discussed here are indicative of different changes that are occurring in the Arctic and demonstrate the varied responses observed among species. The presentation will summarize current level of monitoring across the Arctic, the status and trends of FECs, drivers of observed trends, and knowledge and monitoring gaps.
Resilience of small intestinal beneficial bacteria to the toxicity of soybean oil fatty acids
Authors: Di Rienzi Sara C , Jacobson Juliet , Kennedy Elizabeth A , Bell Mary E , Shi Qiaojuan , Waters Jillian L , Lawrence Peter , Brenna J Thomas , Britton Robert A , Walter Jens , Ley Ruth E
Published: March 2018

Over the past century, soybean oil (SBO) consumption in the United States increased dramatically. The main SBO fatty acid, linoleic acid (18:2), inhibits in vitro the growth of lactobacilli, beneficial members of the small intestinal microbiota. Human-associated lactobacilli have declined in prevalence in Western microbiomes, but how dietary changes may have impacted their ecology is unclear. Here, we compared the in vitro and in vivo effects of 18:2 on Lactobacillus reuteri and L. johnsonii. Directed evolution in vitro in both species led to strong 18:2 resistance with mutations in genes for lipid biosynthesis, acid stress, and the cell membrane or wall. Small-intestinal Lactobacillus populations in mice were unaffected by chronic and acute 18:2 exposure, yet harbored both 18:2- sensitive and resistant strains. This work shows that extant small intestinal lactobacilli are protected from toxic dietary components via the gut environment as well as their own capacity to evolve resistance.
Occurrence of long-term depression in the cerebellar flocculus during adaptation of optokinetic response
Authors: Inoshita Takuma , Hirano Tomoo
Published: March 2018

Long-term depression (LTD) at parallel fiber (PF) to Purkinje cell (PC) synapses has been considered as a main cellular mechanism for motor learning. However, the necessity of LTD for motor learning was challenged by demonstration of normal motor learning in the LTD-defective animals. Here, we addressed possible involvement of LTD in motor learning by examining whether LTD occurs during motor learning in the wild-type mice. As a model of motor learning, adaptation of optokinetic response (OKR) was used. OKR is a type of reflex eye movement to suppress blur of visual image during animal motion. OKR shows adaptive change during continuous optokinetic stimulation, which is regulated by the cerebellar flocculus. After OKR adaptation, amplitudes of quantal excitatory postsynaptic currents at PF-PC synapses were decreased, and induction of LTD was suppressed in the flocculus. These results suggest that LTD occurs at PF-PC synapses during OKR adaptation.
How early-career researchers are shaping eLife
Authors: Patterson Mark , Schekman Randy
Published: March 2018

Journals can benefit from listening to graduate students, postdocs and newly-independent group leaders.
Special Issue: Complexity, Routines, and Reflexivity in Professional Work
Authors: Smeby Jens-Christian
Published: March 2018

Vol 8, No 1 (2018)
Genome rearrangements and phylogeny reconstruction in Yersinia pestis
Authors: Bochkareva Olga O. , Dranenko Natalia O. , Ocheredko Elena S. , Kanevsky German M. , Lozinsky Yaroslav N. , Khalaycheva Vera A. , Artamonova Irena I. , Gelfand Mikhail S.
Published: March 2018

Genome rearrangements have played an important role in the evolution of Yersinia pestis from its progenitor Yersinia pseudotuberculosis. Traditional phylogenetic trees for Y. pestis based on sequence comparison have short internal branches and low bootstrap supports as only a small number of nucleotide substitutions have occurred. On the other hand, even a small number of genome rearrangements may resolve topological ambiguities in a phylogenetic tree. We reconstructed phylogenetic trees based on genome rearrangements using several popular approaches such as Maximum likelihood for Gene Order and the Bayesian model of genome rearrangements by inversions. We also reconciled phylogenetic trees for each of the three CRISPR loci to obtain an integrated scenario of the CRISPR cassette evolution. Analysis of contradictions between the obtained evolutionary trees yielded numerous parallel inversions and gain/loss events. Our data indicate that an integrated analysis of sequence-based and inversion-based trees enhances the resolution of phylogenetic reconstruction. In contrast, reconstructions of strain relationships based on solely CRISPR loci may not be reliable, as the history is obscured by large deletions, obliterating the order of spacer gains. Similarly, numerous parallel gene losses preclude reconstruction of phylogeny based on gene content.
Oxygen Saturation Surrounding Deep Water Formation Events in the Labrador Sea From Argo‐O2 Data
Authors: Wolf Mitchell K. , Hamme Roberta C. , Gilbert Denis , Yashayaev Igor , Thierry Virginie
Published: March 2018

Deep water formation supplies oxygen‐rich water to the deep sea, spreading throughout the ocean by means of the global thermohaline circulation. Models suggest that dissolved gases in newly formed deep water do not come to equilibrium with the atmosphere. However, direct measurements during wintertime convection are scarce, and the controls over the extent of these disequilibria are poorly quantified. Here we show that, when convection reached deeper than 800 m, oxygen in the Labrador Sea was consistently undersaturated at −6.1% to −7.6% at the end of convection. Deeper convection resulted in greater undersaturation, while convection ending later in the year resulted in values closer to equilibrium, from which we produce a predictive relationship. We use dissolved oxygen data from six profiling Argo floats in the Labrador Sea between 2003 and 2016, allowing direct observations of wintertime convection. Three of the six optode oxygen sensors displayed substantial average in situ drift of −3.03 μmol O2 kg−1 yr−1 (−0.94% O2 yr−1), which we corrected to stable deepwater oxygen values from repeat ship surveys. Observations of low oxygen intrusions during restratification and a simple mixing calculation demonstrate that lateral processes act to lower the oxygen inventory of the central Labrador Sea. This suggests that the Labrador Sea is a net sink for atmospheric oxygen, but uncertainties in parameterizing gas exchange limit our ability to quantify the net uptake. Our results constrain the oxygen concentration of newly formed Labrador Sea Water and allow more precise estimates of oxygen utilization and nutrient regeneration in this water mass.
Relations Between vz and Bx Components in Solar Wind and their Effect on Substorm Onset
Authors: Kubyshkina Marina , Semenov Vladimir , Erkaev Nikolay , Gordeev Evgeny , Dubyagin Stepan , Ganushkina Natalia , Shukhtina Maria
Published: March 2018

We analyze two substorm onset lists, produced by different methods, and show that the (Bx·vz) product of the solar wind (SW) velocity and interplanetary magnetic field (IMF) components for two thirds of all substorm onsets has the same sign as IMF Bz. The explanation we suggest is the efficient displacement of the magnetospheric plasma sheet due to IMF Bx and SW flow vz, which both force the plasma sheet moving in one direction if the sign of (Bx·vz) correlates with the sign Bz. The displacement of the current sheet, in its turn, increases the asymmetry of the magnetotail and can alter the threshold of substorm instabilities. We study the SW and IMF data for the 15‐year period (which comprises two substorm lists periods and the whole solar cycle) and reveal the similar asymmetry in the SW, so that the sign of (Bx·vz) coincides with the sign of IMF Bz during about two thirds of all the time. This disproportion can be explained if we admit that about 66% of IMF Bz component is transported to the Earth's orbit by the Alfvén waves with antisunward velocities.
Global Changes in Drought Conditions Under Different Levels of Warming
Authors: Naumann G. , Alfieri L. , Wyser K. , Mentaschi L. , Betts R. A. , Carrao H. , Spinoni J. , Vogt J. , Feyen L.
Published: March 2018

Higher evaporative demands and more frequent and persistent dry spells associated with rising temperatures suggest that drought conditions could worsen in many regions of the world. In this study, we assess how drought conditions may develop across the globe for 1.5, 2, and 3°C warming compared to preindustrial temperatures. Results show that two thirds of global population will experience a progressive increase in drought conditions with warming. For drying areas, drought durations are projected to rise at rapidly increasing rates with warming, averaged globally from 2.0 month/°C below 1.5°C to 4.2 month/°C when approaching 3°C. Drought magnitudes could double for 30% of global landmass under stringent mitigation. If contemporary warming rates continue, water supply‐demand deficits could become fivefold in size for most of Africa, Australia, southern Europe, southern and central states of the United States, Central America, the Caribbean, north‐west China, and parts of Southern America. In approximately 20% of the global land surface, drought magnitude will halve with warming of 1.5°C and higher levels, mainly most land areas north of latitude 55°N, but also parts of South America and Eastern and South‐eastern Asia. A progressive and significant increase in frequency of droughts is projected with warming in the Mediterranean basin, most of Africa, West and Southern Asia, Central America, and Oceania, where droughts are projected to happen 5 to 10 times more frequent even under ambitious mitigation targets and current 100‐year events could occur every two to five years under 3°C of warming.
Monitoring and Modeling the Rapid Evolution of Earth's Newest Volcanic Island: Hunga Tonga Hunga Ha'apai (Tonga) Using High Spatial Resolution Satellite Observations
Authors: Garvin J. B. , Slayback D. A. , Ferrini V. , Frawley J. , Giguere C. , Asrar G. R. , Andersen K.
Published: March 2018

We have monitored a newly erupted volcanic island in the Kingdom of Tonga, unofficially known as Hunga Tonga Hunga Ha'apai, by means of relatively frequent high spatial resolution (~50 cm) satellite observations. The new ~1.8 km2 island formed as a tuff cone over the course of a month‐long hydromagmatic eruption in early 2015 in the Tonga‐Kermadec volcanic arc. Such ash‐dominated eruptions usually produce fragile subaerial landscapes that wash away rapidly due to marine erosion, as occurred nearby in 2009. Our measured rates of erosion are ~0.00256 km3/year from derived digital topographic models. Preliminary measurements of the topographic expression of the primary tuff cone over ~30 months suggest a lifetime of ~19 years (and potentially up to 42 years). The ability to measure details of a young island's landscape evolution using satellite remote sensing has not previously been possible at these spatial and temporal resolutions.
Determining Individual Particle Magnetizations in Assemblages of Micrograins
Authors: de Groot Lennart V. , Fabian Karl , Béguin Annemarieke , Reith Pim , Barnhoorn Auke , Hilgenkamp Hans
Published: March 2018

Obtaining reliable information from even the most challenging paleomagnetic recorders, such as the oldest igneous rocks and meteorites, is paramount to open new windows into Earth's history. Currently, such information is acquired by simultaneously sensing millions of particles in small samples or single crystals using superconducting quantum interference device magnetometers. The obtained rock‐magnetic signal is a statistical ensemble of grains potentially differing in reliability as paleomagnetic recorder due to variations in physical dimensions, chemistry, and magnetic behavior. Here we go beyond bulk magnetic measurements and combine computed tomography and scanning magnetometry to uniquely invert for the magnetic moments of individual grains. This enables us to select and consider contributions of subsets of grains as a function of particle‐specific selection criteria and avoid contributions that arise from particles that are altered or contain unreliable magnetic carriers. This new, nondestructive, method unlocks information from complex paleomagnetic recorders that until now goes obscured.
Ice Core Records of West Greenland Melt and Climate Forcing
Authors: Graeter K. A. , Osterberg E. C. , Ferris D. G. , Hawley R. L. , Marshall H. P. , Lewis G. , Meehan T. , McCarthy F. , Overly T. , Birkel S. D.
Published: March 2018

Remote sensing observations and climate models indicate that the Greenland Ice Sheet (GrIS) has been losing mass since the late 1990s, mostly due to enhanced surface melting from rising summer temperatures. However, in situ observational records of GrIS melt rates over recent decades are rare. Here we develop a record of frozen meltwater in the west GrIS percolation zone preserved in seven firn cores. Quantifying ice layer distribution as a melt feature percentage (MFP), we find significant increases in MFP in the southernmost five cores over the past 50 years to unprecedented modern levels (since 1550 CE). Annual to decadal changes in summer temperatures and MFP are closely tied to changes in Greenland summer blocking activity and North Atlantic sea surface temperatures since 1870. However, summer warming of ~1.2°C since 1870–1900, in addition to warming attributable to recent sea surface temperature and blocking variability, is a critical driver of high modern MFP levels.
Remote Drying in the North Atlantic as a Common Response to Precessional Changes and CO2 Increase Over Land
Authors: Kelly Patrick , Kravitz Ben , Lu Jian , Leung L. Ruby
Published: March 2018

Here we demonstrate that changes of the North Atlantic subtropical high and its regional rainfall pattern during mid‐Holocene precessional changes and idealized 4xCO2 increase can both be understood as a remote response to increased land heating near North Africa. Despite different sources and patterns of radiative forcing (increase in CO2 concentration versus changes in orbital parameters), we find that the pattern of energy, circulation, and rainfall responses in the Northern Hemisphere summer subtropics are remarkably similar in the two forcing scenarios because both are dominated by the same land‐sea heating contrast in response to the forcing. An increase in energy input over arid land drives a westward displacement of the coupled North Atlantic subtropical high‐monsoon circulation, consistent with increased precipitation in the Afro‐Asia region and decreased precipitation in the America‐Atlantic region. This study underscores the importance of land heating in dictating remote drying through zonal shifts of the subtropical circulation.
The Cross‐Polar Cap Saturation in GUMICS‐4 During High Solar Wind Driving
Authors: Lakka A. , Pulkkinen T. I. , Dimmock A. P. , Myllys M. , Honkonen I. , Palmroth M.
Published: March 2018

It is well known that the Earth's ionospheric cross‐polar cap potential (CPCP) saturates as a response to the solar wind (SW) driver especially when the level of driving is high and the interplanetary magnetic field is oriented southward. Moreover, previous studies have shown that the upstream Alfvén Mach number may be an important factor in the saturation effect. While the CPCP is often viewed as a measure of the SW‐magnetosphere‐ionosphere coupling, the processes associated with the nonlinearity of the coupling remain an open issue. We use fourth edition of the Grand Unified Magnetosphere‐Ionosphere Coupling Simulation (GUMICS‐4) and artificial SW data to mimic weak and strong driving in order to study the CPCP response to a wide range of interplanetary magnetic field magnitudes (3.5–30 nT) and upstream Alfvén Mach number values (1.2–22). The results provide the first overview of the CPCP saturation in GUMICS‐4 and show that the onset of saturation is strongly dependent on the upstream Alfvén Mach number and the physical processes responsible for the saturation effect might take place both in the Earth's magnetosheath and in the upstream SW.
Surface Drifter Observations From the Arctic Ocean's Beaufort Sea: Evidence for Submesoscale Dynamics
Authors: Mensa J. A. , Timmermans M.‐L. , Kozlov I. E. , Williams W. J. , Özgökmen T. M.
Published: March 2018

Position and velocity data are analyzed from a release of surface ocean drifters in the Arctic Ocean's Beaufort Sea in ice‐free conditions. Position information is returned at sufficiently high frequency to allow for the investigation of surface‐ocean flows ranging from around 0.5 km in lateral scale (submesoscale, SM, flows) to flows that are tens of kilometers in horizontal extent. Lagrangian statistics from the drifter release are analyzed in conjunction with Eulerian (ship‐based) measurements of surface ocean temperature and salinity. Results show dynamics that are largely consistent with flows at similar scales in the midlatitude oceans. Horizontal wavenumber k spectra of density in the surface ocean scale as
, consistent with energetic SM flows. Lagrangian drifters indicate local dispersion in the surface ocean layer at horizontal scales smaller than 10 km, which confirms the presence of active submesoscale dynamics. Features at these scales give rise to lateral diffusivities (in the range 1–103 m2 s−1) of similar range to values inferred in the midlatitudes. Velocity structure functions present an energy‐cascade inertial range at submesoscales with indication of a transition to a forward energy cascade at scales smaller than 1 km confirming the transition to 3‐D turbulence. The active SM flow‐field drives enhanced lateral and vertical fluxes in the Arctic Ocean mixed layer, which has first‐order implications to the transport of heat, sea‐ice floes, nutrients, and contaminants.
Modeling Impacts of Urbanization and Urban Heat Island Mitigation on Boundary Layer Meteorology and Air Quality in Beijing Under Different Weather Conditions
Authors: Chen Lei , Zhang Meigen , Zhu Jia , Wang Yongwei , Skorokhod Andrei
Published: March 2018

Beijing has experienced a rapid urbanization in the last few decades and has been suffering from serious air pollution during recent years. The Weather Research and Forecasting‐Chem model is used to quantify the effects of urbanization on regional climate and air quality and those of urban heat island (UHI) mitigation strategy on urban air quality in Beijing, with a special focus on the impacts under different weather conditions (heat waves in summer and polluted days in winter). The modification of rural land use into urban impervious surface significantly increases 2‐m temperature (T2) and planetary boundary layer height but decreases 2‐m relative humidity (RH2) and 10‐m wind speed (WS10) in urban Beijing, which further leads to the increases in surface‐layer O3 concentrations of 9.5 ppbv in summer and 1.8 ppbv in winter and the decreases in PM2.5 concentrations of 16.6 μg m−3 in summer and 26.2 μg m−3 in winter. Compared with normal days (clean days), the UHI intensity is enhanced by 11.1% during heat waves in summer (by 16.7% during polluted days in winter). Although increasing urban albedo is an effective mitigation strategy to decrease UHI intensity, it worsens the urban air quality. When the urban albedo increases from 0.2 to 0.85, the daily average PM2.5 concentrations are increased by 10.2 (6.1) μg m−3 in summer (in winter), and the daily maximum O3 concentrations are increased by 12.8 ppbv under heat waves in summer.
Extreme Climate Effects on Dissolved Organic Carbon Concentrations During Snowmelt
Authors: Tiwari Tejshree , Sponseller Ryan A. , Laudon Hjalmar
Published: March 2018

Extreme weather and climate events are predicted to increase in frequency and severity in the near future, which could have detrimental consequences for water quality in northern latitudes. Key processes that regulate the production and transport of solutes, like dissolved organic carbon (DOC), from soils to streams can be potentially altered by episodes of extreme temperature and/or precipitation. Here we use an intensively studied research catchment in northern Sweden with 23 years of data to ask how extreme antecedent climate events influence DOC concentration during snowmelt. Specifically, we used a combination of principal components analysis, cluster analysis, and multivariate partial least square analysis to show that almost every year provides some combination of extreme conditions in terms of intensity, duration, or frequency of temperature and/or rainfall. However, in terms of DOC responses to these events, variations in peak concentrations were most closely related to cold winter conditions, winter precipitation (snow), and temperature during the previous autumn. Specifically, years with most severe frost and icing during winter, but low winter precipitation, previous summer precipitation, and warmer autumns, showed the highest peaks in concentrations. In contrast, the lowest peak DOC concentrations were observed during spring snowmelt following high summer precipitation, colder autumns, and high winter precipitation. While this research highlights the importance of winter climate for influencing the DOC concentration during the spring, it also points to the potential importance of lag effects from preceding seasons on responses observed during the snowmelt season.
Propagation Directions of High‐Frequency Waves in the Ionosphere
Authors: James H. Gordon
Published: March 2018

The direction of propagation of electromagnetic waves in the ionosphere from ground‐based transmitters can be measured in the ionosphere by crossed dipoles in a single cold‐plasma mode. In the Enhanced Polar Output Probe (e‐POP), 6‐m dipoles on the Radio Receiver Instrument connect to a high input impedance and act therefore as voltage probes from which the electric field of incoming waves can be simply computed. When combined with cold‐magnetoplasma electric‐field theory, the relationship of voltages on the two orthogonal dipoles is used to deduce the direction of arrival of an incoming wave in three dimensions. The technique is illustrated by application to e‐POP/Radio Receiver Instrument observations of 6.2‐MHz waves transmitted by the European Incoherent Scatter HF facility in Tromsø, Norway.
Seismic Reflection Profiles and Subsurface Geology of the Area Interested by the 2016–2017 Earthquake Sequence (Central Italy)
Authors: Porreca M. , Minelli G. , Ercoli M. , Brobia A. , Mancinelli P. , Cruciani F. , Giorgetti C. , Carboni F. , Mirabella F. , Cavinato G. , Cannata A. , Pauselli C. , Barchi M. R.
Published: March 2018

Starting from 24 August 2016, a long seismic sequence, including nine Mw > 5.0 earthquakes, struck a wide area of the Central Italy. A large amount of geological, geodetic, and seismological data envisages a complex system of NNW‐SSE trending, seismogenic normal faults. These active tectonic structures are well known at the surface and consistent with previous seismotectonic studies. In order to improve the comprehension of the seismotectonic framework of this seismic sequence, we provide a novel reconstruction of the subsurface geology of the area close to the Norcia Mw 6.5 mainshock (30 October 2016), based on previously unpublished seismic reflection profiles and available geological data. All the data have been synthesized along a 47 km long, WSW‐ENE trending geological cross section, interpreted down to a depth of 12 km. Comparing the subsurface geological model with the available seismological data, we find that the majority of seismicity is confined within the sedimentary sequence and does not penetrate the underlying basement. The basement has been constrained at depths of 8 to 11 km and coincides with the cutoff of the seismicity. We have also traced the trajectories of the seismogenic normal faults activated during this seismic sequence, reconciling the high‐angle (dip>65°) normal faults exposed at the surface, with their angle (dip < 50°) at hypocentral depths. The results of this study may be useful for better understanding the rheological properties of the seismogenic rock volume, as well as the coseismic deformations of the topographic surface observed by geodetic techniques and field mapping.
Permeability Estimation Directly From Logging‐While‐Drilling Induced Polarization Data
Authors: Fiandaca G. , Maurya P. K. , Balbarini N. , Hördt A. , Christiansen A. V. , Foged N. , Bjerg P. L. , Auken E.
Published: March 2018

In this study, we present the prediction of permeability from time domain spectral induced polarization (IP) data, measured in boreholes on undisturbed formations using the El‐log logging‐while‐drilling technique. We collected El‐log data and hydraulic properties on unconsolidated Quaternary and Miocene deposits in boreholes at three locations at a field site in Denmark, characterized by different electrical water conductivity and chemistry. The high vertical resolution of the El‐log technique matches the lithological variability at the site, minimizing ambiguity in the interpretation originating from resolution issues. The permeability values were computed from IP data using a laboratory‐derived empirical relationship presented in a recent study for saturated unconsolidated sediments, without any further calibration. A very good correlation, within 1 order of magnitude, was found between the IP‐derived permeability estimates and those derived using grain size analyses and slug tests, with similar depth trends and permeability contrasts. Furthermore, the effect of water conductivity on the IP‐derived permeability estimations was found negligible in comparison to the permeability uncertainties estimated from the inversion and the laboratory‐derived empirical relationship.
The Morphology of the Solar Wind Magnetic Field Draping on the Dayside of Mars and Its Variability
Authors: Fang Xiaohua , Ma Yingjuan , Luhmann Janet , Dong Yaxue , Brain David , Hurley Dana , Dong Chuanfei , Lee Christina O. , Jakosky Bruce
Published: March 2018

The magnetic field draping pattern in the magnetosheath of Mars is of interest for what it tells us about both the solar wind interaction with the Mars obstacle and the use of the field measured there as a proxy for the upstream interplanetary magnetic field (IMF) clock angle. We apply a time‐dependent, global magnetohydrodynamic model toward quantifying the spatial and temporal variations of the magnetic field draping direction on the Martian dayside above 500‐km altitude. The magnetic field and plasma are self‐consistently solved over one Mars rotation period, with the dynamics of the field morphology considered as the result of the rotation of the crustal field orientation. Our results show how the magnetic field direction on the plane perpendicular to the solar wind flow direction gradually departs from the IMF as the solar wind penetrates toward the obstacle and into the tail region. This clock angle departure occurs mainly inside the magnetic pileup region and tailward of the terminator plane, exhibiting significant dawn‐dusk and north‐south asymmetries. Inside the dayside sheath region, the field direction has the greatest departure from the IMF‐perpendicular component direction downstream of the quasi‐parallel bow shock, which for the nominal Parker spiral is over the dawn quadrant. Thus, the best region to obtain an IMF clock angle proxy is within the dayside magnetosheath at sufficiently high altitudes, particularly over subsolar and dusk sectors. Our results illustrate that the crustal field has only a mild influence on the magnetic field draping direction within the magnetosheath region.
Earth's Correlation Wavefield: Late Coda Correlation
Authors: Phạm Thanh‐Son , Tkalčić Hrvoje , Sambridge Malcolm , Kennett Brian L. N.
Published: March 2018

Cross correlation of seismograms provides new information on the Earth both through the exploitation of ambient noise and specific components of earthquake records. Here we cross‐correlate recordings of large earthquakes on a planetary scale and identify a range of hitherto unobserved seismic phases in Earth's correlation wavefield. We show that both arrivals with the timing expected for the regular seismic wavefield and previously unexplained phases are produced by interference between seismic paths having the same ray parameter but with only a subset of propagation legs in common. This insight explains the origin and generation mechanism of the features of Earth's correlation wavefield and opens up new ways of addressing issues in global seismology. Strong similarity between observed and synthesized correlation wavefields indicates that the Earth's radial structure is remarkably well constrained in the intermediate period range.
Detection of Artificially Generated Seismic Signals Using Balloon‐Borne Infrasound Sensors
Authors: Krishnamoorthy Siddharth , Komjathy Attila , Pauken Michael T. , Cutts James A. , Garcia Raphael F. , Mimoun David , Cadu Alexandre , Sournac Anthony , Jackson Jennifer M. , Lai Voon Hui , Bowman Daniel C.
Published: March 2018

We conducted an experiment in Pahrump, Nevada, in June 2017, where artificial seismic signals were created using a seismic hammer, and the possibility of detecting them from their acoustic signature was examined. In this work, we analyze the pressure signals recorded by highly sensitive barometers deployed on the ground and on tethers suspended from balloons. Our signal processing results show that wind noise experienced by a barometer on a free‐flying balloon is lower compared to one on a moored balloon. This has never been experimentally demonstrated in the lower troposphere. While seismoacoustic signals were not recorded on the hot air balloon platform owing to operational challenges, we demonstrate the detection of seismoacoustic signals on our moored balloon platform. Our results have important implications for performing seismology in harsh surface environments such as Venus through atmospheric remote sensing.
Joint Elastic‐Electrical Properties of Artificial Porous Sandstone With Aligned Fractures
Authors: Han Tongcheng
Published: March 2018

Seismic and electromagnetic surveys are among the most important geophysical applications to understand the subsurface Earth. Joint interpretation of the independent but complementary exploration data can provide geophysical parameters needed to better assess the rocks. However, cross‐property relationship between the elastic and electrical properties of fractured porous rocks, the key to the successful joint interpretation of seismic and electromagnetic data in anisotropic formations, is poorly understood. Here we use dedicated laboratory experiments and theoretical modeling to show how elastic velocity and electrical conductivity are linked in porous sandstone with aligned fractures and how the joint properties are affected by the fractures. The P and SH wave velocities are found to be approximately linearly correlated with electrical conductivity when measured in varying directions, and the linear trends are determined by the geometry and amount of the fractures in the rocks. The results provide a pathway to successful joint interpretation in fractured rocks.
Global Distribution and Spectral Properties of Low‐Reflectance Material on Mercury
Authors: Klima Rachel L. , Denevi Brett W. , Ernst Carolyn M. , Murchie Scott L. , Peplowski Patrick N.
Published: March 2018

We examine the global distribution and spectral properties of low‐reflectance material (LRM) across Mercury to estimate the relative carbon abundance of prominent exposures and to test hypotheses for the origin of carbon in LRM. Our mapping demonstrates that LRM is consistently excavated from depth and that the spectral curvature attributed to carbon becomes more subdued as these surface deposits age. We find that the 600‐nm band depth in LRM deposits is related to carbon content and can be used to estimate carbon enrichment. LRM deposits excavated by basins and large craters may be enriched with as much as 4 wt% carbon over the local mean. Regional deposits, associated with the most heavily cratered terrains, are enriched by an average of ~2.5 wt% carbon. The association of LRM with excavation from depth shows that the carbon in LRM is native to the planet, rather than deposited over time by impacts.
Crustal Deformation across the Jericho Valley Section of the Dead Sea Fault as Resolved by Detailed Field and Geodetic Observations
Authors: Hamiel Yariv , Piatibratova Oksana , Mizrahi Yaakov , Nahmias Yoav , Sagy Amir
Published: March 2018

Detailed field and geodetic observations of crustal deformation across the Jericho Fault section of the Dead Sea Fault are presented. New field observations reveal several slip episodes that rupture the surface, consist with strike slip and extensional deformation along a fault zone width of about 200 m. Using dense Global Positioning System measurements, we obtain the velocities of new stations across the fault. We find that this section is locked for strike‐slip motion with a locking depth of 16.6 ± 7.8 km and a slip rate of 4.8 ± 0.7 mm/year. The Global Positioning System measurements also indicate asymmetrical extension at shallow depths of the Jericho Fault section, between 0.3 and 3 km. Finally, our results suggest the vast majority of the sinistral slip along the Dead Sea Fault in southern Jorden Valley is accommodated by the Jericho Fault section.
Lightning Mapping With an Array of Fast Antennas
Authors: Wu Ting , Wang Daohong , Takagi Nobuyuki
Published: March 2018

Fast Antenna Lightning Mapping Array (FALMA), a low‐frequency lightning mapping system comprising an array of fast antennas, was developed and established in Gifu, Japan, during the summer of 2017. Location results of two hybrid flashes and a cloud‐to‐ground flash comprising 11 return strokes (RSs) are described in detail in this paper. Results show that concurrent branches of stepped leaders can be readily resolved, and K changes and dart leaders with speeds up to 2.4 × 107 m/s are also well imaged. These results demonstrate that FALMA can reconstruct three‐dimensional structures of lightning flashes with great details. Location accuracy of FALMA is estimated by comparing the located striking points of successive RSs in cloud‐to‐ground flashes. Results show that distances between successive RSs are mainly below 25 m, indicating exceptionally high location accuracy of FALMA.
The Role of Transformation‐Induced Plasticity in the Development of Advanced High Strength Steels
Authors: Liu Li , He Binbin , Huang Mingxin
Published: March 2018

Lightweight structural components made of advanced high‐strength steels (AHSSs) in the automotive industry can substantially reduce greenhouse gas emissions. The 3rd‐generation AHSSs, which consist of medium Mn steel, quenching and partitioning (Q&P) steel, and carbide‐free bainitic (CFB) steel, is the current research focus of the steel community. In particular, the retained austenite grains are the intrinsic components of the 3rd‐generation AHSSs. These retained austenite grains can demonstrate a transformation‐induced plasticity (TRIP) effect by transforming into martensite during mechanical loading, improving the strain‐hardening behavior of AHSSs. Consequently, intensive research has been carried out over the past 30 years to understand the role of the TRIP effect on the development of AHSSs. Therefore, this review article is aimed to provide a state‐of‐the‐art summary of recent progress on AHSSs with the TRIP effect. Specifically, the processing, the relationship between microstructure and mechanical properties, and the potential industrial applications of TRIP‐enabled AHSSs will be addressed in this review. More importantly, the mechanical stability of the retained austenite grains, which determines the overall performance of the TRIP effect in AHSSs, will be discussed by considering several governing factors.
High‐Performance n‐ and p‐Type Field‐Effect Transistors Based on Hybridly Surface‐Passivated Colloidal PbS Nanosheets
Authors: Ramin Moayed Mohammad Mehdi , Bielewicz Thomas , Noei Heshmat , Stierle Andreas , Klinke Christian
Published: March 2018

Colloidally synthesized nanomaterials are among the promising candidates for future electronic devices due to their simplicity and the inexpensiveness of their production. Specifically, colloidal nanosheets are of great interest since they are conveniently producible through the colloidal approach while having the advantages of two‐dimensionality. In order to employ these materials, according transistor behavior should be adjustable and of high performance. It is shown that the transistor performance of colloidal lead sulfide nanosheets is tunable by altering the surface passivation, the contact metal, or by exposing them to air. It is found that adding halide ions to the synthesis leads to an improvement of the conductivity, the field‐effect mobility, and the on/off ratio of these transistors by passivating their surface defects. Superior n‐type behavior with a field‐effect mobility of 248 cm2 V−1 s−1 and an on/off ratio of 4 × 106 is achieved. The conductivity of these stripes can be changed from n‐type to p‐type by altering the contact metal and by adding oxygen to the working environment. As a possible solution for the post‐Moore era, realizing new high‐quality semiconductors such as colloidal materials is crucial. In this respect, the results can provide new insights which helps to accelerate their optimization for potential applications.
Cavitation Mediated 3D Microstructured Architectures from Nanocarbon
Authors: Zhang Zishuai , Ye Siyu , Gbureck Uwe , Barralet Jake E. , Merle Géraldine
Published: March 2018

Here, the formation of high surface area microscale assemblies of nanocarbon through phosphate and ultrasound cavitation treatment is reported. Despite high conductivity and large surface area, potential health and safety concerns limit the use of nanocarbon and add challenges to handling. Previously, it is shown that phosphate ultrasonic bonding is ineffective for organic materials but in this study, it is found that by a preliminary oxidizing treatment, several carbons can be readily assembled from xerogels. Assembling nanocarbon into microparticles can usually require a binder or surfactants, which can reduce surface area or conductivity and generate a low microsphere yield. Carbon nanotube microspheres are nitrogen‐doped and flower‐like nanostructured Pt deposited on their surface, and finally showcased as efficient cathode electrocatalysts for the oxygen reduction reaction (half‐wave potential 0.78 V vs reversible hydrogen electrode) and methanol oxidation (417 mA mg−1). In particular, no significant degradation of the catalysts is detected after 12 000 cycles (26.6 h). These results indicate the potential of this multimaterial assembly method and open a new way to improve handling of nanoscale materials.
Role of Localized States in Photoluminescence Dynamics of High Optical Gain CsPbBr3 Nanocrystals
Authors: Dey Amrita , Rathod Pravin , Kabra Dinesh
Published: March 2018

Temperature‐dependent time‐resolved photoluminescence (TRPL) spectroscopy of high optical gain CsPbBr3 nanocrystals (NCs) films along with temperature‐dependent steady‐state absorption and photoluminescence (PL) spectra is studied. A red shift in the optical band edge and the corresponding PL peak is observed by lowering the temperature from room temperature, analogous to hybrid perovskite semiconductors. However, the faster PL decay of CsPbBr3 NCs film at a low temperature as compared to room temperature is in contrast with many other traditional colloidal quantum dots. The TRPL spectroscopy as a function of temperature suggests the presence of a red‐shifted (≈75 ± 15 meV) defect‐induced emission peak at longer times. Temperature‐dependent PL intensity study shows an Arrhenius type of character with two activation energies: ≈77 ± 18 and ≈12 ± 3 meV. A qualitative model is developed where interaction between the excitonic level and these observed localized states as a function of temperature can qualitatively explain the contrasting PL decay mechanism of CsPbBr3 NCs film. To ensure the quality of in‐house synthesized CsPbBr3 NCs with a mixture of oleylamine and octylamine ligands, the amplified spontaneous emission from CsPbBr3 NCs film as a planar waveguide medium is studied, which shows state‐of‐art optical gain coefficient of ≈51cm−1 and a loss coefficient of ≈15cm−1 at room temperature.
Catalytic Asymmetric Synthesis of All Possible Stereoisomers of 2,3,4,6‐Tetradeoxy‐4‐Aminohexopyranosides
Authors: Zhu Zhongpeng , Glazier Daniel A. , Yang Daoshan , Tang Weiping
Published: March 2018

We recently developed a divergent strategy for the synthesis of all eight possible 2,3,6‐trideoxyhexopyranosides with three stereogenic centers. However, the diastereoselectivity for one of the three stereogenic centers was low and it was not controlled by catalysts. In this update, we described a systematic method for the first catalytic asymmetric synthesis of all eight possible 2,3,6‐trideoxyhexopyranosides and all eight possible 2,3,4,6‐tetradeoxy‐4‐aminohexopyranosides. The products derived from this strategy include the glycone of natural products grecocycline A, spinosyn A, and ossamycin. All three stereogenic centers in each product was controlled by a pair of chiral catalysts. The key to the success is the application of our recently developed dynamic kinetic stereodivergent acylation of Achmatowicz rearrangement products and chiral catalyst‐directed reduction. Simple dimethylation of the 2,3,4,6‐tetradeoxy‐4‐amino sugars afforded derivatives of naturally occurring β‐D‐forosaminide and β‐L‐ossaminide.

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Painful Terminal Neuroma Prevention by Capping PRGD/PDLLA Conduit in Rat Sciatic Nerves
Authors: Yi Jiling , Jiang Nan , Li Binbin , Yan Qiongjiao , Qiu Tong , Swaminatha Iyer Killugudi , Yin Yixia , Dai Honglian , Yetisen Ali K. , Li Shipu
Published: March 2018

Neuroma formation after amputation as a long‐term deficiency leads to spontaneous neuropathic pain that reduces quality of life of patients. To prevent neuroma formation, capping techniques are implemented as effective treatments. However, an ideal, biocompatible material covering the nerves is an unmet clinical need. In this study, biocompatible characteristics presented by the poly(D,L‐lactic acid)/arginylglycylaspartic acid (RGD peptide) modification of poly{(lactic acid)‐co‐ [(glycolic acid)‐alt‐(L‐lysine)]} (PRGD/PDLLA) are evaluated as a nerve conduit. After being capped on the rat sciatic nerve stump in vivo, rodent behaviors and tissue structures are compared via autotomy scoring and histological analyses. The PRGD/PDLLA capped group gains lower autotomy score and improves the recovery, where inflammatory infiltrations and excessive collagen deposition are defeated. Transmission electron microscopy images of the regeneration of myelin sheath in both groups show that abnormal myelination is only present in the uncapped rats. Changes in related genes (MPZ, MBP, MAG, and Krox20) are monitored quantitative real‐time polymerase chain reaction (qRT‐PCR) for mechanism investigation. The PRGD/PDLLA capping conduits not only act as physical barriers to inhibit the invasion of inflammatory infiltration in the scar tissue but also provide a suitable microenvironment for promoting nerve repairing and avoiding neuroma formation during nerve recovery.
From Checkerboard‐Like Sand Barriers to 3D Cu@CNF Composite Current Collectors for High‐Performance Batteries
Authors: Luo Jian , Yuan Wei , Huang Shimin , Zhao Bote , Chen Yu , Liu Meilin , Tang Yong
Published: March 2018

While the architecture, surface morphology, and electrical conductivity of current collectors may significantly affect the performance of electrochemical cells, many challenges still remain in design and cost‐effective fabrication of highly efficient current collectors for a new generation of energy storage and conversion devices. Here the findings in design and fabrication of a 3D checkerboard‐like Cu@CNF composite current collector for lithium‐ion batteries are reported. The surface of the current collector is modified with patterned grooves and amorphous carbon nanofibers, imitating the checkerboard‐like sand barriers in desert regions. Due to a combined effect of the grooves and the carbon nanofibers, a battery based on this current collector retains a reversible capacity of 410.1 mAh g−1 (beyond the theoretical capacity of carbonaceous materials of 372 mAh g−1) with good capacity retention (greater than 84.9% of the initial capacity after 50 cycles), resulting in 66.2% and 42.6% improvement in reversible capacity and capacity retention, respectively, compared to the batteries using traditional Cu current collectors. Based on the excellent electrochemical performance, this composite current collector is believed to be an attractive alternative to the traditional commercially used current collectors for the anode of high‐power energy storage systems.