bluuebunny/crossref_metadata_2025 huggingface dataset:
Four Tools for Critical Inquiry in History, Social Studies, and Civic Education
Authors: Bermudez Angela
Published: June 2015

The promotion of critical thinking is an important but elusive goal in history, social studies, and civic education. Teachers often struggle to translate general definitions of critical thinking into specific pedagogical tools to plan learning activities and to observe and interpret student work in these subjects. They also struggle to distinguish between “teaching critical content” and “teaching students to think critically.” In this paper, I draw upon scholarship on critical thinking, history education, moral education, and critical pedagogy to propose four tools for critical inquiry in the social domain: Problem-posing, Reflective skepticism, Multi-perspectivity and Systemic thinking. I describe how each tool works, discussing how they integrate the epistemic purpose of fostering good understanding with the social purpose of cultivating thoughtful, responsible, pluralist and non-violent citizens.
Enseñanza de “temas controversiales” en el curso de historia, desde la perspectiva de los estudiantes chilenos
Authors: Toledo Jofré María Isabel , Kolstrein Abraham Magendzo , Gutiérrez Gianella Virna , Segura Ricardo Iglesias , López-Facal Ramón
Published: June 2015

This article analyzes students’ statements regarding the teaching of “controversial issues” during the first cycle of secondary school. The survey covered 1,210 Chilean students in a random, stratified, non-probabilistic sample. Descriptive statistics were used and a typology of teachers was defined. The most controversial issues correspond to human rights violations. There is no correlation between the level of controversy of a topic and its teaching. The teachers present different interpretations and develop innovative activities, strategies, teaching procedures and evaluations. Students play an active role, value dialogue, ask for their teacher’s’ opinion, and want to construct their own interpretations about history. However, in order for a pedagogical transformation to occur, empowering and transformative practices must be deployed.
Lys63-linked ubiquitin chain adopts multiple conformational states for specific target recognition
Authors: Liu Zhu , Gong Zhou , Jiang Wen-Xue , Yang Ju , Zhu Wen-Kai , Guo Da-Chuan , Zhang Wei-Ping , Liu Mai-Li , Tang Chun
Published: June 2015

A polyubiquitin comprises multiple covalently linked ubiquitins and recognizes myriad targets. Free or bound to ligands, polyubiquitins are found in different arrangements of ubiquitin subunits. To understand the structural basis for polyubiquitin quaternary plasticity and to explore the target recognition mechanism, we characterize the conformational space of Lys63-linked diubiquitin (K63-Ub2). Refining against inter-subunit paramagnetic NMR data, we show that free K63-Ub2 exists as a dynamic ensemble comprising multiple closed and open quaternary states. The quaternary dynamics enables K63-Ub2 to be specifically recognized in a variety of signaling pathways. When binding to a target protein, one of the preexisting quaternary states is selected and stabilized. A point mutation that shifts the equilibrium between the different states modulates the binding affinities towards K63-Ub2 ligands. This conformational selection mechanism at the quaternary level may be used by polyubiquitins of different lengths and linkages for target recognition.
Transgenic shRNA pigs reduce susceptibility to foot and mouth disease virus infection
Authors: Hu Shengwei , Qiao Jun , Fu Qiang , Chen Chuangfu , Ni Wei , Wujiafu Sai , Ma Shiwei , Zhang Hui , Sheng Jingliang , Wang Pengyan , Wang Dawei , Huang Jiong , Cao Lijuan , Ouyang Hongsheng
Published: June 2015

Foot-and-mouth disease virus (FMDV) is an economically devastating viral disease leading to a substantial loss to the swine industry worldwide. A novel alternative strategy is to develop pigs that are genetically resistant to infection. Here, we produce transgenic (TG) pigs that constitutively expressed FMDV-specific short interfering RNA (siRNA) derived from small hairpin RNA (shRNA). In vitro challenge of TG fibroblasts showed the shRNA suppressed viral growth. TG and non-TG pigs were challenged by intramuscular injection with 100 LD50 of FMDV. High fever, severe clinical signs of foot-and-mouth disease and typical histopathological changes were observed in all of the non-TG pigs but in none of the high-siRNA pigs. Our results show that TG shRNA can provide a viable tool for producing animals with enhanced resistance to FMDV.
Analysis of null sets (zero catch) made by the Mexican tuna purse seine fleet (2000–2013)
Authors: Dreyfus-León Michel J , Mejía-Trejo Adán , Villaseñor-Derbez Juan Carlos
Published: June 2015

The world tuna fishing fleet is dominated by purse seine boats. Purse seine sets are sometimes unsuccessful in capturing fish; these unsuccessful attempts are known as null sets. Null sets have been widely documented and the numbers indicate that they happen in large proportions. In Mexico, the tuna fishery represents the second most important fishery by volume and value. The frequency of occurrence of null sets during the period 2000–2013 was analyzed to identify the regions, periods, and oceanographic conditions (e.g., ENSO) related to them. Null sets on free-swimming fish schools and between June and July had a higher relative representation. The region with highest relative occurrence was the mouth of the Gulf of California (between August and October). A positive correlation was observed between the occurrence of null sets on free-swimming fish schools and the Multivariate El Niño Index. The maximum values of occurrence of null sets were related to those months in which the water column structure presented changes. Comprehension of this phenomenon (null sets) and its relation to natural events is of importance for the fishery, as there could be repercussions for the economy and management of the resource.
Fecundity of Sebastes mentella and Sebastes norvegicus in the Irminger Sea and Icelandic waters
Authors: Saborido-Rey Fran , Domínguez-Petit Rosario , Garabana Dolores , Sigurðsson Þhorstein
Published: June 2015

Fecundity of redfish Sebastes mentella and Sebastes norvegicus in the Irminger Sea and Icelandic waters was analyzed in relation to several maternal features and oocyte developmental stages. The mean potential fecundity in S. norvegicus was estimated to be 123,300 oocytes and relative fecundity averaged 116 oocytes g–1. Mean potential fecundity in S. mentella was 50,013 oocytes and relative fecundity was 64 oocytes g–1. Strong fecundity down-regulation (50% on average) was observed during oocyte development estimated from September to November, when oocytes reached the advanced stage of vitellogenesis. This result implies that fecundity can only be comparable between individuals presenting the same stage of oocyte development. However, the development rates differed between species and between stocks, and therefore the same stage is reached at a different time of the year. Fecundity varied significantly with female weight and length, while condition had little influence on fecundity variation.
A web-based survey of the motivations and challenges faced by emerging researchers in the chiropractic profession
Authors: de Luca Katie , Tuchin Peter , Bonello Rod
Published: June 2015

Objective

To investigate the motivations, challenges and perceptions of the educational environment of emerging researchers in chiropractic.

Methods

A descriptive web-based survey of higher-degree chiropractic research students was performed between October and November 2013. The survey consisted of open and closed questions and the Dundee Ready Education Environment Measure.

Results

Twenty-two students currently enrolled in a higher-degree research program participated. Students were most commonly enrolled in a doctor of philosophy program at a part-time rate. Motivations of research were desire to improve the clinical care aspects of chiropractic for the public and belief that chiropractic research is lacking. The greatest challenges were the negative attitudes towards chiropractic, finding enough time to do everything required, and feelings of isolation. The higher-degree research educational environment was perceived to be more positive than negative, with the stimulating nature of research a positive feature. A negative feature of the educational environment was poor undergraduate preparation for higher-degree research.

Conclusion

This study is the first study to describe higher-degree chiropractic research students. Primary motivations included building research, while challenges included not only negative attitudes toward the chiropractic profession but also negative attitudes toward researchers from within the profession. The higher-degree research educational environment was perceived to be positive. By acknowledging the issues that surround emerging researchers in chiropractic, the profession is better placed to foster academics and build research capacity.
A new look at ocean carbon remineralization for estimating deepwater sequestration
Authors: Guidi Lionel , Legendre Louis , Reygondeau Gabriel , Uitz Julia , Stemmann Lars , Henson Stephanie A.
Published: June 2015

The “biological carbon pump” causes carbon sequestration in deep waters by downward transfer of organic matter, mostly as particles. This mechanism depends to a great extent on the uptake of CO2 by marine plankton in surface waters and subsequent sinking of particulate organic carbon (POC) through the water column. Most of the sinking POC is remineralized during its downward transit, and modest changes in remineralization have substantial feedback on atmospheric CO2 concentrations, but little is known about global variability in remineralization. Here we assess this variability based on modern underwater particle imaging combined with field POC flux data and discuss the potential sources of variations. We show a significant relationship between remineralization and the size structure of the phytoplankton assemblage. We obtain the first regionalized estimates of remineralization in biogeochemical provinces, where these estimates range between −50 and +100% of the commonly used globally uniform remineralization value. We apply the regionalized values to satellite‐derived estimates of upper ocean POC export to calculate regionalized and ocean‐wide deep carbon fluxes and sequestration. The resulting value of global organic carbon sequestration at 2000 m is 0.33 Pg C yr−1, and 0.72 Pg C yr−1 at the depth of the top of the permanent pycnocline, which is up to 3 times higher than the value resulting from the commonly used approach based on uniform remineralization and constant sequestration depth. These results stress that variable remineralization and sequestration depth should be used to model ocean carbon sequestration and feedback on the atmosphere.
First‐order control of syntectonic sedimentation on crustal‐scale structure of mountain belts
Authors: Erdős Zoltán , Huismans Ritske S. , van der Beek Peter
Published: June 2015

The first‐order characteristics of collisional mountain belts and the potential feedback with surface processes are predicted by critical taper theory. While the feedback between erosion and mountain belt structure has been fairly extensively studied, less attention has been given to the potential role of synorogenic deposition. For thin‐skinned fold‐and‐thrust belts, recent studies indicate a strong control of syntectonic deposition on structure, as sedimentation tends to stabilize the thin‐skinned wedge. However, the factors controlling basement deformation below fold‐and‐thrust belts, as evident, for example, in the Zagros Mountains or in the Swiss Alps, remain largely unknown. Previous work has suggested that such variations in orogenic structure may be explained by the thermotectonic “age” of the deforming lithosphere and hence its rheology. Here we demonstrate that sediment loading of the foreland basin area provides an additional control and may explain the variable basement involvement in orogenic belts. When examining the role of sedimentation, we identify two end‐members: (1) sediment‐starved orogenic systems with thick‐skinned basement deformation in an axial orogenic core and thin‐skinned deformation in the bordering forelands and (2) sediment‐loaded orogens with thick packages of synorogenic deposits, derived from the axial basement zone, deposited on the surrounding foreland fold‐and‐thrust belts, and characterized by basement deformation below the foreland. Using high‐resolution thermomechanical models, we demonstrate a strong feedback between deposition and crustal‐scale thick‐skinned deformation. Our results show that the loading effects of syntectonic sediments lead to long crustal‐scale thrust sheets beneath the orogenic foreland and explain the contrasting characteristics of sediment‐starved and sediment‐loaded orogens, showing for the first time how both thin‐ and thick‐skinned crustal deformations are linked to sediment deposition in these orogenic systems. We show that the observed model behavior is consistent with observations from a number of natural orogenic systems.
Three‐dimensional distribution of a major desert dust outbreak over East Asia in March 2008 derived from IASI satellite observations
Authors: Cuesta Juan , Eremenko Maxim , Flamant Cyrille , Dufour Gaëlle , Laurent Benoît , Bergametti Gilles , Höpfner Michael , Orphal Johannes , Zhou Daniel
Published: June 2015

We describe the daily evolution of the three‐dimensional (3D) structure of a major dust outbreak initiated by an extratropical cyclone over East Asia in early March 2008, using new aerosol retrievals derived from satellite observations of IASI (Infrared Atmospheric Sounding Interferometer). A novel auto‐adaptive Tikhonov‐Phillips‐type approach called AEROIASI is used to retrieve vertical profiles of dust extinction coefficient at 10 µm for most cloud‐free IASI pixels, both over land and ocean. The dust vertical distribution derived from AEROIASI is shown to agree remarkably well with along‐track transects of CALIOP spaceborne lidar vertical profiles (mean biases less than 110 m, correlation of 0.95, and precision of 260 m for mean altitudes of the dust layers). AEROIASI allows the daily characterization of the 3D transport pathways across East Asia of two dust plumes originating from the Gobi and North Chinese deserts. From AEROIASI retrievals, we provide evidence that (i) both dust plumes are transported over the Beijing region and the Yellow Sea as elevated layers above a shallow boundary layer, (ii) as they progress eastward, the dust layers are lifted up by the ascending motions near the core of the extratropical cyclone, and (iii) when being transported over the warm waters of the Japan Sea, turbulent mixing in the deep marine boundary layer leads to high dust concentrations down to the surface. AEROIASI observations and model simulations also show that the progression of the dust plumes across East Asia is tightly related to the advancing cold front of the extratropical cyclone.
Evaluation of cloud‐resolving model simulations of midlatitude cirrus with ARM and A‐train observations
Authors: Muhlbauer A. , Ackerman T. P. , Lawson R. P. , Xie S. , Zhang Y.
Published: June 2015

Cirrus clouds are ubiquitous in the upper troposphere and still constitute one of the largest uncertainties in climate predictions. This paper evaluates cloud‐resolving model (CRM) and cloud system‐resolving model (CSRM) simulations of a midlatitude cirrus case with comprehensive observations collected under the auspices of the Atmospheric Radiation Measurements (ARM) program and with spaceborne observations from the National Aeronautics and Space Administration A‐train satellites. The CRM simulations are driven with periodic boundary conditions and ARM forcing data, whereas the CSRM simulations are driven by the ERA‐Interim product. Vertical profiles of temperature, relative humidity, and wind speeds are reasonably well simulated by the CSRM and CRM, but there are remaining biases in the temperature, wind speeds, and relative humidity, which can be mitigated through nudging the model simulations toward the observed radiosonde profiles. Simulated vertical velocities are underestimated in all simulations except in the CRM simulations with grid spacings of 500 m or finer, which suggests that turbulent vertical air motions in cirrus clouds need to be parameterized in general circulation models and in CSRM simulations with horizontal grid spacings on the order of 1 km. The simulated ice water content and ice number concentrations agree with the observations in the CSRM but are underestimated in the CRM simulations. The underestimation of ice number concentrations is consistent with the overestimation of radar reflectivity in the CRM simulations and suggests that the model produces too many large ice particles especially toward the cloud base. Simulated cloud profiles are rather insensitive to perturbations in the initial conditions or the dimensionality of the model domain, but the treatment of the forcing data has a considerable effect on the outcome of the model simulations. Despite considerable progress in observations and microphysical parameterizations, simulating the microphysical, macrophysical, and radiative properties of cirrus remains challenging. Comparing model simulations with observations from multiple instruments and observational platforms is important for revealing model deficiencies and for providing rigorous benchmarks. However, there still is considerable need for reducing observational uncertainties and providing better observations especially for relative humidity and for the size distribution and chemical composition of aerosols in the upper troposphere.
Spectrally Enhanced Cloud Objects—A generalized framework for automated detection of volcanic ash and dust clouds using passive satellite measurements: 2. Cloud object analysis and global application
Authors: Pavolonis Michael J. , Sieglaff Justin , Cintineo John
Published: June 2015

A new approach for quantitatively detecting volcanic ash and dust from satellite has been developed. The Spectrally Enhanced Cloud Objects (SECO) algorithm utilizes a combination of radiative transfer theory, a statistical model, and image processing techniques to identify volcanic ash and dust clouds in satellite imagery with a very low false alarm rate. This fully automated technique is globally applicable (day and night) and can be adapted to a wide range of low Earth orbit and geostationary satellite sensors or even combinations of satellite sensors. The SECO algorithm consists of four primary components: conversion of satellite measurements into robust spectral metrics, application of a Bayesian method to estimate the probability that a given satellite pixel contains volcanic ash and/or dust, construction of cloud objects, and the selection of cloud objects deemed to have the physical attributes consistent with volcanic ash and/or dust clouds. The first two components of the SECO algorithm were described in Part 1 of this study. The final two components are described in this paper. In addition, case studies and a global analysis are utilized to illustrate the benefits of the SECO approach relative to the traditional “split window” ash/dust detection technique. The SECO algorithm can form the basis for more advanced applications such as volcanic cloud alerting and data assimilation.
Incorporating an advanced aerosol activation parameterization into WRF‐CAM5: Model evaluation and parameterization intercomparison
Authors: Zhang Yang , Zhang Xin , Wang Kai , He Jian , Leung L. Ruby , Fan Jiwen , Nenes Athanasios
Published: June 2015

Aerosol activation into cloud droplets is an important process that governs aerosol indirect effects. The advanced treatment of aerosol activation by Fountoukis and Nenes (2005) and its recent updates, collectively called the FN series, have been incorporated into a newly developed regional coupled climate‐air quality model based on the Weather Research and Forecasting model with the physics package of the Community Atmosphere Model version 5 (WRF‐CAM5) to simulate aerosol‐cloud interactions in both resolved and convective clouds. The model is applied to East Asia for two full years of 2005 and 2010. A comprehensive model evaluation is performed for model predictions of meteorological, radiative, and cloud variables, chemical concentrations, and column mass abundances against satellite data and surface observations from air quality monitoring sites across East Asia. The model performs overall well for major meteorological variables including near‐surface temperature, specific humidity, wind speed, precipitation, cloud fraction, precipitable water, downward shortwave and longwave radiation, and column mass abundances of CO, SO2, NO2, HCHO, and O3 in terms of both magnitudes and spatial distributions. Larger biases exist in the predictions of surface concentrations of CO and NOx at all sites and SO2, O3, PM2.5, and PM10 concentrations at some sites, aerosol optical depth, cloud condensation nuclei over ocean, cloud droplet number concentration (CDNC), cloud liquid and ice water path, and cloud optical thickness. Compared with the default Abdul‐Razzack Ghan (2000) parameterization, simulations with the FN series produce ~107–113% higher CDNC, with half of the difference attributable to the higher aerosol activation fraction by the FN series and the remaining half due to feedbacks in subsequent cloud microphysical processes. With the higher CDNC, the FN series are more skillful in simulating cloud water path, cloud optical thickness, downward shortwave radiation, shortwave cloud forcing, and precipitation. The model evaluation identifies several areas of improvements including emissions and their vertical allocation as well as model formulations such as aerosol formation, cloud droplet nucleation, and ice nucleation.
Construction and destruction of Mont Pelée volcano: Volumes and rates constrained from a geomorphological model of evolution
Authors: Germa Aurelie , Lahitte Pierre , Quidelleur Xavier
Published: June 2015

This study presents long‐term volumes and construction rates for the Mont Conil‐Mont Pelée volcano and rate estimates at which volcanic activity creates relief. An algorithm, ShapeVolc, is used to numerically model topographic surfaces. Volcano morphology is analyzed using current digital elevation model in combination with mapped geology to produce 10 paleotopographies at the end of four constructional stages and three destructional events. Volumes of each constructional stage were estimated at about 35.2 km3, 26.2 km3, 8.3 km3, and 2.5 km3 for a total cumulative erupted volume of 72.2 km3. We estimate that Mont Pelée accounted for about 10% of the Lesser Antilles arc production in the last 100 kyr. The volcano has been built at an average rate of 0.13 km3/kyr during the last 550 kyr. During that time, construction rates varied by a factor of 15, from 0.04 km3/kyr in early stages up to 0.52 km3/kyr after the second flank collapse. Volumes displaced by each flank collapse were estimated at 14.7 km3, 8.8 km3, and 3.5 km3, thus about 37% of the total constructed volume. Integrated over the volcano's lifetime, the rate at which flank collapses removed material off the island is 0.15 km3/kyr. In contrast, long‐term erosion rates outside collapsed areas are estimated at about 0.05 ± 0.7 km3/kyr, or ~11 km3 of material removed. This latter rate is not negligible, which strengthens the importance of taking into account recurrent small erosional events on the geomorphological evolution of a volcanic island in a tropical context.
Palynological evidence for late Quaternary climate and marine primary productivity changes along the California margin
Authors: Pospelova Vera , Price Andrea M. , Pedersen Thomas F.
Published: June 2015

A high‐resolution sedimentary record of dinoflagellate cysts from Ocean Drilling Program Hole 1017E (off Point Conception, California margin) reflects how marine primary productivity has changed in response to major shifts in climate and ocean circulation along the California margin over the past 42 kyr. Throughout the studied sequence, dinoflagellate cyst assemblages are dominated by upwelling‐related taxa, signifying the continued presence of coastal upwelling on the margin during the late Quaternary. The cyst record suggests that marine primary productivity was enhanced during the Holocene and Bølling, and to a lesser extent, during the late glacial and most Dansgaard‐Oeschger events, while an apparent reduction in primary productivity can be seen during the Younger Dryas. The best analogue technique, based on a modern dinoflagellate cyst assemblage database from the northeast Pacific, was used for quantitative reconstruction of past sea surface conditions. It points to dynamic changes in annual marine primary productivity (~235–331 g C m−2 yr−1) and sea surface temperature (~10.1–12.6°C in winter; ~13.1–14.3°C in summer), while sea surface salinity appears to be confined to a narrower range (~32.9–33.4 in summer). Our results also indicate noticeable climate variability during the Holocene in this region.
New insights into landslide processes around volcanic islands from Remotely Operated Vehicle (ROV) observations offshore Montserrat
Authors: Watt S. F. L. , Jutzeler M. , Talling P. J. , Carey S. N. , Sparks R. S. J. , Tucker M. , Stinton A. J. , Fisher J. K. , Wall‐Palmer D. , Hühnerbach V. , Moreton S. G.
Published: June 2015

Submarine landslide deposits have been mapped around many volcanic islands, but interpretations of their structure, composition, and emplacement are hindered by the challenges of investigating deposits directly. Here we report on detailed observations of four landslide deposits around Montserrat collected by Remotely Operated Vehicles, integrating direct imagery and sampling with sediment core and geophysical data. These complementary approaches enable a more comprehensive view of large‐scale mass‐wasting processes around island‐arc volcanoes than has been achievable previously. The most recent landslide occurred at 11.5–14 ka (Deposit 1; 1.7 km3) and formed a radially spreading hummocky deposit that is morphologically similar to many subaerial debris‐avalanche deposits. Hummocks comprise angular lava and hydrothermally altered fragments, implying a deep‐seated, central subaerial collapse, inferred to have removed a major proportion of lavas from an eruptive period that now has little representation in the subaerial volcanic record. A larger landslide (Deposit 2; 10 km3) occurred at ∼130 ka and transported intact fragments of the volcanic edifice, up to 900 m across and over 100 m high. These fragments were rafted within the landslide, and are best exposed near the margins of the deposit. The largest block preserves a primary stratigraphy of subaerial volcanic breccias, of which the lower parts are encased in hemipelagic mud eroded from the seafloor. Landslide deposits south of Montserrat (Deposits 3 and 5) indicate the wide variety of debris‐avalanche source lithologies around volcanic islands. Deposit 5 originated on the shallow submerged shelf, rather than the terrestrial volcanic edifice, and is dominated by carbonate debris.
Crustal‐scale degassing due to magma system destabilization and magma‐gas decoupling at Soufrière Hills Volcano, Montserrat
Authors: Christopher T. E. , Blundy J. , Cashman K. , Cole P. , Edmonds M. , Smith P. J. , Sparks R. S. J. , Stinton A.
Published: June 2015

Activity since 1995 at Soufrière Hills Volcano (SHV), Montserrat has alternated between andesite lava extrusion and quiescence, which are well correlated with seismicity and ground deformation cycles. Large variations in SO2 flux do not correlate with these alternations, but high and low HCl/SO2 characterize lava dome extrusion and quiescent periods respectively. Since lava extrusion ceased (February 2010) steady SO2 emissions have continued at an average rate of 374 tonnes/day (± 140 t/d), and incandescent fumaroles (temperatures up to 610oC) on the dome have not changed position or cooled. Occasional short bursts (over several hours) of higher (∼ 10x) SO2 flux have been accompanied by swarms of volcano‐tectonic earthquakes. Strain data from these bursts indicate activation of the magma system to depths up to 10 km. SO2 emissions since 1995 greatly exceed the amounts that could be derived from 1.1 km3 of erupted andesite, and indicating extensive partitioning of sulfur into a vapour phase, as well as efficient decoupling and outgassing of sulfur‐rich gases from the magma. These observations are consistent with a vertically extensive, crustal magmatic mush beneath SHV. Three states of the magmatic system are postulated to control degassing. During dormant periods (103 to 104 years) magmatic vapour and melts separate as layers from the mush and decouple from each other. In periods of unrest (years) without eruption, melt and fluid layers become unstable, ascend and can amalgamate. Major destabilization of the mush system leads to eruption, characterized by magma mixing and release of volatiles with different ages, compositions and sources.
Assessment of future changes in water availability and aridity
Authors: Greve P. , Seneviratne S. I.
Published: June 2015

Substantial changes in the hydrological cycle are projected for the 21st century, but these projections are subject to major uncertainties. In this context, the “dry gets drier, wet gets wetter” (DDWW) paradigm is often used as a simplifying summary. However, recent studies cast doubt on the validity of the paradigm and also on applying the widely used P − E (precipitation − evapotranspiration) metric over global land surfaces. Here we show in a comprehensive CMIP5‐based assessment that projected changes in mean annual P − E are generally not significant, except for high‐latitude regions showing wetting conditions until the end of the 21st century. Significant increases in aridity do occur in many subtropical and also adjacent humid regions. However, combining both metrics still shows that approximately 70% of all land area will not experience significant changes. Based on these findings, we conclude that the DDWW paradigm is generally not confirmed for projected changes in most land areas.
Coordinated lightning, balloon‐borne electric field, and radar observations of triggered lightning flashes in North Florida
Authors: MacGorman D. R. , Biggerstaff M. I. , Waugh S. , Pilkey J. T. , Uman M. A. , Jordan D. M. , Ngin T. , Gamerota W. R. , Carrie G. , Hyland P.
Published: June 2015

This study examines coordinated storm and triggered lightning observations made in July–August 2013 at the International Center for Lightning Research and Testing to determine why triggered flashes in Florida typically transition from an upward vertical channel entering the cloud to horizontal structure near the storm's melting level. Data from a balloon‐borne electric field meter, a mobile 5 cm wavelength radar, and a small‐baseline VHF Lightning Mapping Array acquired during a period in which three flashes were triggered on 1 August confirmed the hypothesis that the transition to horizontal lightning structure just above the melting level occurred in a layer of negative charge. This experiment was the first to provide vertical profiles of the electric field in Florida storms, from which their vertical charge distribution could be inferred. Three dissipating storms observed on different days all had negative charge near the melting level, but a growing mature storm had positive charge there.
Microscopic structural change in a liquid Fe‐C alloy of ~5 GPa
Authors: Shibazaki Yuki , Kono Yoshio , Fei Yingwei
Published: June 2015

The structure of a liquid Fe‐3.5 wt % C alloy is examined for up to 7.2 GPa via multiangle energy‐dispersive X‐ray diffraction using a Paris‐Edinburgh type large‐volume press. X‐ray diffraction data show clear changes in the pressure‐dependent peak positions of structure factor and reduced pair distribution function at 5 GPa. These results suggest that the liquid Fe‐3.5 wt % C alloys change structurally at approximately 5 GPa. This finding serves as a microscopic explanation for the alloy's previously observed density change at the same pressure. The pressure dependencies of the nearest and second neighbor distances of the liquid Fe‐3.5 wt % C alloy are similar to those of liquid Fe which exhibits a structural change near the bcc‐fcc‐liquid triple point (5.2 GPa and 1991 K). Similarities between Fe‐3.5 wt % C and Fe suggest that a density change also occurs in liquid Fe and that this structural change extends to other Fe‐light element alloys.
The existence of radial anisotropy in Earth's upper inner core revealed from seismic normal mode observations
Authors: Lythgoe Karen H. , Deuss Arwen
Published: June 2015

As we strive to understand the most remote region of our planet, one critical area of investigation is the uppermost inner core since its structure is related to solidification of outer core material at the inner core boundary (ICB). Previous seismic studies have used body waves to show that the top ∼100 km of the inner core is isotropic. However, radial anisotropy cannot be uniquely determined by body wave observations. Alternatively, normal mode center frequencies are sensitive to spherically symmetric Earth structure, therefore may provide a constraint on the existence of radial anisotropy in the inner core. Here we show that normal mode center frequency measurements are compatible with 2–5% radial anisotropy in the top ∼100 km of the inner core with a fast direction radially outward and a slow direction along the ICB. Given the uncertainties in the mineral physics and processes that produce anisotropy, the observed radial anisotropy may be reconciled with predictions based on either solidification processes or from texturing due to anisotropic growth.
Warm‐air advection, air mass transformation and fog causes rapid ice melt
Authors: Tjernström Michael , Shupe Matthew D. , Brooks Ian M. , Persson P. Ola G. , Prytherch John , Salisbury Dominic J. , Sedlar Joseph , Achtert Peggy , Brooks Barbara J. , Johnston Paul E. , Sotiropoulou Georgia , Wolfe Dan
Published: June 2015

Direct observations during intense warm‐air advection over the East Siberian Sea reveal a period of rapid sea‐ice melt. A semistationary, high‐pressure system north of the Bering Strait forced northward advection of warm, moist air from the continent. Air‐mass transformation over melting sea ice formed a strong, surface‐based temperature inversion in which dense fog formed. This induced a positive net longwave radiation at the surface while reducing net solar radiation only marginally; the inversion also resulted in downward turbulent heat flux. The sum of these processes enhanced the surface energy flux by an average of ~15 W m−2 for a week. Satellite images before and after the episode show sea‐ice concentrations decreasing from > 90% to ~50% over a large area affected by the air‐mass transformation. We argue that this rapid melt was triggered by the increased heat flux from the atmosphere due to the warm‐air advection.
Optical emissions associated with energetic electrons produced by stepping leaders in cloud‐to‐ground lightning discharges
Authors: Xu Wei , Celestin Sebastien , Pasko Victor P.
Published: June 2015

Both natural cloud‐to‐ground and rocket‐triggered lightning flashes have been found to be associated with intense and brief bursts of X‐ray emissions. Using a full energy Monte Carlo model combined with an optical emission model, we quantify the optical emissions induced by the strong acceleration of thermal runaway electrons in the highly inhomogeneous electric field produced by stepping lightning leaders. The results demonstrate that this acceleration process is accompanied with not only high‐energy X‐ray emissions but also detectable levels of optical emissions. The fluorescence beam exhibits a conical shape and appears to be larger than the streamer zone associated with the lightning leader. Moreover, we emphasize that the size of the fluorescence beam largely depends on the electrical properties of the associated lightning leader and the intensity ratio between emissions from the second positive band system of N2 and the first negative band system of N
reflects the intrinsic difference in the energetics of electrons involved. Therefore, corresponding measurements compared to modeling results can provide useful information for understanding of the stepping mechanism of lightning leaders and associated X‐ray production processes.
Bottom water export from the western Ross Sea, 2007 through 2010
Authors: Gordon Arnold L. , Huber Bruce A. , Busecke Julius
Published: June 2015

Bottom water export from the Ross Sea, February 2007 to January 2011, exhibits seasonal and interannual variability. Temperature minima coupled to salinity maxima in late austral summer, into the fall, indicate input from High‐Salinity Shelf Water (HSSW). Secondary temperature minima lacking the high‐salinity trait, characteristic of Low‐Salinity Shelf Water (LSSW), appear in the spring. Warmer bottom water similar to modified Circumpolar Deep Water (mCDW) is observed in winter and in early summer. The LSSW and mCDW may be drawn from the Drygalski Basin, as the HSSW pool retreats poleward from the shelf break in response to increased winter polar easterlies allowing these less dense overlying waters to spill into the deep ocean within the benthic layer. Bottom salinity decreased from 2007 to 2011 by 0.007 year−1 significantly higher than regional decadal trends, which we propose is a result of HSSW retreat induced by strengthening polar easterlies.
An electrical conductivity model for fractal porous media
Authors: Wei Wei , Cai Jianchao , Hu Xiangyun , Han Qi
Published: June 2015

Archie's equation is an empirical electrical conductivity‐porosity model that has been used to predict the formation factor of porous rock for more than 70 years. However, the physical interpretation of its parameters, e.g., the cementation exponent m, remains questionable. In this study, a theoretical electrical conductivity equation is derived based on the fractal characteristics of porous media. The proposed model is expressed in terms of the tortuosity fractal dimension (DT), the pore fractal dimension (Df), the electrical conductivity of the pore liquid, and the porosity. The empirical parameter m is then determined from physically based parameters, such as DT and Df. Furthermore, a distinct interrelationship between DT and Df is obtained. We find a reasonably good match between the predicted formation factor by our model and experimental data.
Hydrogen self‐diffusivity in single crystal ringwoodite: Implications for water content and distribution in the mantle transition zone
Authors: Sun Wei , Yoshino Takashi , Sakamoto Naoya , Yurimoto Hisayoshi
Published: June 2015

Hydrogen lattice diffusion in Fe‐bearing ringwoodite was investigated through hydrogen and deuterium interdiffusing in a pair of synthesized single crystals at various temperatures (1000–1300 K) at 21 GPa. Diffusion profiles were investigated by secondary ion mass spectrometer to determine the hydrogen self‐diffusivity in ringwoodite. Temperature dependences of hydrogen diffusion in ringwoodite were determined to be DH = 10− 7.29(±0.46) exp[−101(±10)kJ mol− 1/RT] m2/s in ringwoodite at 21 GPa. The proton conductivities of ringwoodite estimated from the present diffusion coefficients are similar to those of Yoshino et al. [2008] at the transition zone condition at low water content (<1000 ppm by weight (ppmw)) but lower at higher water content range (>1000 ppmw). If the proton‐vacancy mechanism is assumed to be a main controlling mechanism, contribution of water to the electrical conductivity of ringwoodite is insignificant due to large contribution of hopping conduction at the transition zone condition, and global average water concentration in the lower part of transition zone is less than 1000 ppmw.
Detections of lunar exospheric ions by the LADEE neutral mass spectrometer
Authors: Halekas J. S. , Benna M. , Mahaffy P. R. , Elphic R. C. , Poppe A. R. , Delory G. T.
Published: June 2015

The Lunar Atmosphere and Dust Environment Explorer (LADEE) Neutral Mass Spectrometer (NMS), operating in ion mode, provides sensitive detections of ions from the lunar exosphere. By analyzing ion‐mode data from the entire mission, utilizing Acceleration, Reconnection, Turbulence, and Electrodynamics of the Moon's Interaction with the Sun (ARTEMIS) plasma and magnetic field measurements to organize NMS data and eliminate background sources, we identify highly significant detections of lunar ions at mass per charge of 2, 4, 12, 20, 28, 39, and 40, moderately significant detections at 14 and 23, and weak detections at 24, 25, and 36. Unlike many previous observations of Moon‐derived ions, an outward pointing viewing geometry ensures that these ions originate from the exosphere, rather than directly from the surface. For species with known neutral distributions, inferred ion production rates appear consistent with expectations for both magnitude and spatial distribution, assuming photoionization as the predominant source mechanism. Unexpected signals at mass per charge 12 and 28 suggest the presence of a significant exospheric population of carbon‐bearing molecules.
A 20 year decline in solar photospheric magnetic fields: Inner‐heliospheric signatures and possible implications
Authors: Janardhan P. , Bisoi Susanta Kumar , Ananthakrishnan S. , Tokumaru M. , Fujiki K. , Jose L. , Sridharan R.
Published: June 2015

We report observations of a steady 20 year decline of solar photospheric fields at latitudes ≥45° starting from ∼1995. This prolonged and continuing decline, combined with the fact that cycle 24 is already past its peak, implies that magnetic fields are likely to continue to decline until ∼2020, the expected minimum of the ongoing solar cycle 24. In addition, interplanetary scintillation observations of the inner heliosphere for the period 1983–2013 and in the distance range 0.2–0.8 AU have also shown a similar and steady decline in solar wind microturbulence levels, in sync with the declining photospheric fields. Using the correlation between the polar field and heliospheric magnetic field (HMF) at solar minimum, we have estimated the value of the HMF in 2020 to be 3.9 (±0.6) nT and a floor value of the HMF of ∼3.2 (±0.4) nT. Given this floor value for the HMF, our analysis suggests that the estimated peak sunspot number for solar cycle 25 is likely to be 62 (±12).
Atmospheric discharges and particle fluxes
Authors: Chilingarian A. , Chilingaryan S. , Reymers A.
Published: June 2015

Fluxes of the electrons, gamma rays, and neutrons observed by particle detectors located on the Earth's surface during thunderstorms originate so‐called Thunderstorm Ground Enhancements (TGEs). The relativistic runaway electron avalanches giving rise to TGEs originate in the thundercloud's lower dipole between the main negatively charged region in the middle of the thundercloud and transient lower positively charged region. Acceleration of electrons in the upper dipole between main negative and main positive charge regions leads to initiation of the terrestrial gamma flashes (TGFs) intensive researched during the last two decades by orbiting gamma ray observatories. TGFs are exceptionally intense, submillisecond bursts of electromagnetic radiation directed to the open space from the thunderstorm atmosphere. Unlike visible lightning, TGF beams do not create a hot plasma channel and optical flash; hence, in the literature they got name “dark lightning.” We investigate the TGEs development in 1 min and 1 s time series of particle detector count rates. Synchronized time series of the near‐surface electric field and lightning occurrences allows interconnecting two atmospheric phenomena. Registration of the Extensive Air Showers allows approaching problems of relation of the lightning occurrences and particle fluxes.
Studies of the ionospheric turbulence excited by the fourth gyroharmonic at HAARP
Authors: Najmi A. , Milikh G. , Yampolski Y. M. , Koloskov A. V. , Sopin A. A. , Zalizovski A. , Bernhardt P. , Briczinski S. , Siefring C. , Chiang K. , Morton Y. , Taylor S. , Mahmoudian A. , Bristow W. , Ruohoniemi M. , Papadopoulos K.
Published: June 2015

A study is presented of artificial ionospheric turbulence (AIT) induced by HF heating at High Frequency Active Auroral Research Program (HAARP) using frequencies close to the fourth electron gyroharmonic, in a broad range of radiated powers and using a number of different diagnostics. The diagnostics include GPS scintillations, ground‐based stimulated electromagnetic emission (SEE), the HAARP ionosonde, Kodiak radar, and signals received at the Ukrainian Antarctic Station (UAS). The latter allowed analysis of waves scattered by the AIT into the ionospheric waveguide along Earth's terminator, 15.6 mm from the HAARP facility. For the first time, the amplitudes of two prominent SEE features, the downshifted maximum and broad upshifted maximum, were observed to saturate at ~50% of the maximum HAARP effective radiated power. Nonlinear effects in slant total electron content, SEE, and signals received at UAS at different transmitted frequencies and intensities of the pump wave were observed. The correlations between the data from different detectors demonstrate that the scattered waves reach UAS by the waveguide along the Earth's terminator, and that they were injected into the waveguide by scattering off of artificial striations produced by AIT above HAARP, rather than via direct injection from sidelobe radiation.
Classifying onset durations of early VLF events: Scattered field analysis and new insights
Authors: Kotovsky D. A. , Moore R. C.
Published: June 2015

The physical processes responsible for a variety of early VLF scattering events have not yet been satisfactorily identified. Properly categorizing the early VLF event type is imperative to understand the causative physical processes involved. In this paper, the onset durations of 26 exceptionally high signal‐to‐noise ratio early VLF scattering events are analyzed, using scattered fields to classify events. New observations of events that exhibit “slow” amplitude changes, but “fast” scattered field changes are presented, which call into question previous analyses of early/slow events. We separately identify and analyze three early VLF events that definitively exhibit slow scattered field behavior. Additionally, we identify a significant number of events which have onset durations between the current definitions of fast and slow. Four events are observed which unambiguously exhibit a rapid initial rotation of the scattered field phasor during the first few seconds of the recovery stage. Possible physical mechanisms are discussed.