bluuebunny/crossref_metadata_2025_split huggingface dataset:
Global sampling to assess the value of diverse observations in conditioning a real‐world groundwater flow and transport model
Authors: Delsman Joost R. , Winters Pieter , Vandenbohede Alexander , Oude Essink Gualbert H. P. , Lebbe Luc 
Published: February 2016

AbstractThe use of additional types of observational data has often been suggested to alleviate the ill‐posedness inherent to parameter estimation of groundwater models and constrain model uncertainty. Disinformation in observational data caused by errors in either the observations or the chosen model structure may, however, confound the value of adding observational data in model conditioning. This paper uses the global generalized likelihood uncertainty estimation methodology to investigate the value of different observational data types (heads, fluxes, salinity, and temperature) in conditioning a groundwater flow and transport model of an extensively monitored field site in the Netherlands. We compared model conditioning using the real observations to a synthetic model experiment, to demonstrate the possible influence of disinformation in observational data in model conditioning. Results showed that the value of different conditioning targets was less evident when conditioning to real measurements than in a measurement error‐only synthetic model experiment. While in the synthetic experiment, all conditioning targets clearly improved model outcomes, minor improvements or even worsening of model outcomes was observed for the real measurements. This result was caused by errors in both the model structure and the observations, resulting in disinformation in the observational data. The observed impact of disinformation in the observational data reiterates the necessity of thorough data validation and the need for accounting for both model structural and observational errors in model conditioning. It further suggests caution when translating results of synthetic modeling examples to real‐world applications. Still, applying diverse conditioning data types was found to be essential to constrain uncertainty, especially in the transport of solutes in the model.
Importance of titanohematite in detrital remanent magnetizations of strata spanning the Cretaceous‐Paleogene boundary, Hell Creek region, Montana
Authors: Sprain Courtney J. , Feinberg Joshua M. , Renne Paul R. , Jackson Mike 
Published: February 2016

AbstractIntermediate composition titanohematite, Fe2‐yTiyO3 with 0.5 ≤ y ≤ 0.7, is seldom the focus of paleomagnetic study and is commonly believed to be rare in nature. While largely overlooked in magnetostratigraphic studies, intermediate titanohematite has been identified as the dominant ferrimagnetic mineral in an array of Late Mesozoic and early Cenozoic Laramide clastic deposits throughout the central United States. Intermediate titanohematite is ferrimagnetic and has similar magnetic properties to titanomagnetite, except its unique self‐reversing property. Due to these similarities, and with detrital remanent magnetizations masking its self‐reversing nature, intermediate titanohematite is often misidentified in sedimentary deposits. Past studies relied upon nonmagnetic techniques including X‐ray diffraction and electron microprobe analysis. While these techniques can identify the presence of intermediate titanohematite, they fail to test whether the mineral is the primary recorder. To facilitate the identification of intermediate titanohematite in sedimentary deposits, we characterize this mineral using low‐temperature magnetometry and high‐temperature susceptibility experiments, and present a new identification technique based on titanohematite's self‐reversing property, for sediments that span the Cretaceous‐Paleogene boundary (Hell Creek region, Montana). Results from the self‐reversal test indicate that the majority of remanence is held by minerals that become magnetized parallel to an applied field, but that intermediate, self‐reversing titanohematite (y = 0.53–0.63) is an important ancillary carrier of remanence. While earlier literature suggests that intermediate titanohematite is rare in nature, reanalysis using specialized rock magnetic techniques may reveal that it is more abundant in the rock record, particularly within depositional basins adjacent to calc‐alkaline volcanics, than previously thought.
Reconnection events in Saturn's magnetotail: Dependence of plasmoid occurrence on planetary period oscillation phase
Authors: Jackman C. M. , Provan G. , Cowley S. W. H. 
Published: February 2016

AbstractDuring its exploration of Saturn's magnetotail the Cassini magnetometer has detected many in situ examples of magnetic reconnection, in the form of plasmoids, traveling compression regions (TCRs), and dipolarizations. Meanwhile, many magnetospheric phenomena have been shown to be organized with particular regularity by planetary period oscillation systems driven separately from the Northern and Southern Hemispheres of the planet. Here we examine the relationship between the occurrence of plasmoids and TCRs and the magnetic phases of the northern and southern systems. We find a striking degree of organization of the events by both northern and southern phases, with events linked preferentially to intervals in which the magnetospheric plasma and field lines are displaced outward from the planet and the current sheet thinned, both effects being likely to favor the occurrence of reconnection and plasmoid‐related mass loss. Little evidence is found for significant visibility effects associated with north‐south motions of the plasma sheet.
Sources, fate, and pathways of Leeuwin Current water in the Indian Ocean and Great Australian Bight: A Lagrangian study in an eddy‐resolving ocean model
Authors: Yit Sen Bull Christopher , van Sebille Erik 
Published: February 2016

AbstractThe Leeuwin Current is the dominant circulation feature in the eastern Indian Ocean, transporting tropical and subtropical water southward. While it is known that the Leeuwin Current draws its water from a multitude of sources, existing Indian Ocean circulation schematics have never quantified the fluxes of tropical and subtropical source water flowing into the Leeuwin Current. This paper uses virtual Lagrangian particles to quantify the transport of these sources along the Leeuwin Current's mean pathway. Here the pathways and exchange of Leeuwin Current source waters across six coastally bound sectors on the south‐west Australian coast are analyzed. This constitutes the first quantitative assessment of Leeuwin Current pathways within an offline, 50 year integration time, eddy‐resolving global ocean model simulation. Along the Leeuwin Current's pathway, we find a mean poleward transport of 3.7 Sv in which the tropical sources account for 60–78% of the transport. While the net transport is small, we see large transports flowing in and out of all the offshore boundaries of the Leeuwin Current sectors. Along the Leeuwin Current's pathway, we find that water from the Indonesian Throughflow contributes 50–66% of the seasonal signal. By applying conditions on the routes particles take entering the Leeuwin Current, we find particles are more likely to travel offshore north of 30°S, while south of 30°S, particles are more likely to continue downstream. We find a 0.2 Sv pathway of water from the Leeuwin Current's source regions, flowing through the entire Leeuwin Current pathway into the Great Australian Bight.
Influences of El Niño Modoki event 1994/1995 on aerosol concentrations over southern China
Authors: Feng Juan , Li Jianping , Zhu Jianlei , Liao Hong 
Published: February 2016

AbstractThe potential influence of El Niño Modoki event 1994/1995 on tropospheric aerosol concentrations was investigated for southern China using the GEOS‐Chem model with meteorological data collected from 1986 to 2006. The results suggest that aerosol concentrations increase during mature phases of El Niño Modoki event 1994/1995 (boreal winter) and decrease during decay phases (boreal spring, summer, and autumn). Aerosol concentrations anomalies were found to be due to circulation changes associated with El Niño Modoki, whereby both the horizontal and vertical transport of aerosol mass fluxes determined the pattern of aerosol concentrations associated with the event. In contrast, the role of wet deposition appeared to be limited. Furthermore, these results suggest that the amplitude of anomalous aerosol concentrations associated with El Niño Modoki event 1994/1995 have the potential to reach approximately 30% of the climatological mean, indicating that El Niño Modoki plays an important role in influencing aerosol concentrations over southern China.
Analysis of the seasonal ozone budget and the impact of the summer monsoon on the northeastern Qinghai‐Tibetan Plateau
Authors: Zhu Bin , Hou Xuewei , Kang Hanqing 
Published: February 2016

AbstractSeasonal variations in ozone (O3) and the impact of the East Asian summer monsoon at Mount Waliguan (WLG) in the northeastern Qinghai‐Tibetan Plateau (TP) and in the surrounding regions were analyzed for 1997–2007 using a global chemical transport model coupled with O3 tagging simulations. The model‐simulated O3 and its precursors agreed well with observed values. An O3 budget analysis combined with O3 tagging results implied that photochemistry over the TP and long‐range transport of O3 from East Asia, Europe, and Africa were responsible for the surface O3 summer maximum at WLG. In June, the contribution of O3 from the TP was 11.8 ppbv, and the total contribution of O3 transport from eastern China, Japan, Korean Peninsula, Europe, and Africa was 22.7 ppbv. At 400 mb, the O3 exports from the stratosphere, Europe, Africa, and the Americas seemed to be the main sources of O3 at WLG. The contributions to surface O3 from deep convection process and lightning‐induced photochemistry at WLG were both low in summer and are unlikely to be the key processes or contributors for the O3 peak. At several mountain sites in southeast East Asia, the increasing summer monsoon index was related to a decreasing trend for O3 from spring onward at Mount Tai and Mount Huang. At Mount Hua and WLG, regional O3 accumulated over the monsoon's northernmost marginal zone under the influence of the East Asian summer monsoon and TP thermal circulation; this is most likely a key reason for the O3 summer maxima.
Temporal and spatial patterns of remotely sensed litterfall in tropical and subtropical forests of Taiwan
Authors: Wang Hsueh‐Ching , Lin Kuo‐Chuan , Huang Cho‐ying 
Published: February 2016

AbstractLitterfall is important for returning nutrients and carbon to the forest floor, and microbes decompose the litterfall to release CO2 into the atmosphere. Litterfall is a pivotal component in the forest biogeochemical cycle, which is sensitive to climate variability and plant physiology. In this study, we combined field litterfall estimates and time series (2001–2011) climate (the Moderate Resolution Imaging Spectroradiometer (MODIS) land surface temperature (LST) and Tropical Rainfall Measuring Mission (TRMM) precipitations) and green vegetation (MODIS photosynthetically active vegetation cover (PV)) variables to estimate regional annual litterfall in tropical/subtropical forests in Taiwan. We found that time series MODIS LST‐ and PV‐derived metrics, the annual accumulated MODIS LST, and coefficient of variation of PV, respectively, but not the TRMM precipitation variables were salient factors for the estimation (r2 = 0.548 and p < 0.001). The mean (±standard deviation) annual litterfall was 5.1 ± 1.2 Mg ha−1 yr−1 during the observation period. The temporal dynamics of the litterfall revealed that typhoons and consecutive drought events might affect the litterfall temporal variation. Overall, the annual litterfall decreased along the elevation gradient, which may reflect a change in the vegetation type. The northeast and northwest facing slopes yielded the highest amount of annual litterfall (≥5.9 Mg ha−1 yr−1), which was in contrast with the southern aspect (5.1 Mg ha−1 yr−1). This variation may be associated with the dryness of the microclimate influenced by solar radiation. This study demonstrates the feasibility of utilizing time series MODIS LST and PV data to predict large‐scale field litterfall, which may facilitate large‐scale monitoring of biogeochemical cycles in forest ecosystems.
Assimilative model for ionospheric dynamics employing delay, Doppler, and direction of arrival measurements from multiple HF channels
Authors: Fridman Sergey V. , Nickisch L. J. , Hausman Mark , Zunich George 
Published: February 2016

AbstractWe describe the development of new HF data assimilation capabilities for our ionospheric inversion algorithm called GPSII (GPS Ionospheric Inversion). Previously existing capabilities of this algorithm included assimilation of GPS total electron content data as well as assimilation of backscatter ionograms. In the present effort we concentrated on developing assimilation tools for data related to HF propagation channels. Measurements of propagation delay, angle of arrival, and the ionosphere‐induced Doppler from any number of known propagation links can now be utilized by GPSII. The resulting ionospheric model is consistent with all assimilated measurements. This means that ray tracing simulations of the assimilated propagation links are guaranteed to be in agreement with measured data within the errors of measurement. The key theoretical element for assimilating HF data is the raypath response operator (RPRO) which describes response of raypath parameters to infinitesimal variations of electron density in the ionosphere. We construct the RPRO out of the fundamental solution of linearized ray tracing equations for a dynamic magnetoactive plasma. We demonstrate performance and internal consistency of the algorithm using propagation delay data from multiple oblique ionograms (courtesy of Defence Science and Technology Organisation, Australia) as well as with time series of near‐vertical incidence sky wave data (courtesy of the Intelligence Advanced Research Projects Activity HFGeo Program Government team). In all cases GPSII produces electron density distributions which are smooth in space and in time. We simulate the assimilated propagation links by performing ray tracing through GPSII‐produced ionosphere and observe that simulated data are indeed in agreement with assimilated measurements.
Thermal effects of groundwater flow through subarctic fens: A case study based on field observations and numerical modeling
Authors: Sjöberg Ylva , Coon Ethan , K. Sannel A. Britta , Pannetier Romain , Harp Dylan , Frampton Andrew , Painter Scott L. , Lyon Steve W. 
Published: February 2016

AbstractModeling and observation of ground temperature dynamics are the main tools for understanding current permafrost thermal regimes and projecting future thaw. Until recently, most studies on permafrost have focused on vertical ground heat fluxes. Groundwater can transport heat in both lateral and vertical directions but its influence on ground temperatures at local scales in permafrost environments is not well understood. In this study we combine field observations from a subarctic fen in the sporadic permafrost zone with numerical simulations of coupled water and thermal fluxes. At the Tavvavuoma study site in northern Sweden, ground temperature profiles and groundwater levels were observed in boreholes. These observations were used to set up one‐ and two‐dimensional simulations down to 2 m depth across a gradient of permafrost conditions within and surrounding the fen. Two‐dimensional scenarios representing the fen under various hydraulic gradients were developed to quantify the influence of groundwater flow on ground temperature. Our observations suggest that lateral groundwater flow significantly affects ground temperatures. This is corroborated by modeling results that show seasonal ground ice melts 1 month earlier when a lateral groundwater flux is present. Further, although the thermal regime may be dominated by vertically conducted heat fluxes during most of the year, isolated high groundwater flow rate events such as the spring freshet are potentially important for ground temperatures. As sporadic permafrost environments often contain substantial portions of unfrozen ground with active groundwater flow paths, knowledge of this heat transport mechanism is important for understanding permafrost dynamics in these environments.
River stage influences on uranium transport in a hydrologically dynamic groundwater‐surface water transition zone
Authors: Zachara John M. , Chen Xingyuan , Murray Chris , Hammond Glenn 
Published: February 2016

AbstractA well‐field within a uranium (U) plume in the groundwater‐surface water transition zone was monitored for a 3 year period for water table elevation and dissolved solutes. The plume discharges to the Columbia River, which displays a dramatic spring stage surge resulting from snowmelt. Groundwater exhibits a low hydrologic gradient and chemical differences with river water. River water intrudes the site in spring. Specific aims were to assess the impacts of river intrusion on dissolved uranium (Uaq), specific conductance (SpC), and other solutes, and to discriminate between transport, geochemical, and source term heterogeneity effects. Time series trends for Uaq and SpC were complex and displayed large temporal and well‐to‐well variability as a result of water table elevation fluctuations, river water intrusion, and changes in groundwater flow directions. The wells were clustered into subsets exhibiting common behaviors resulting from the intrusion dynamics of river water and the location of source terms. Hot‐spots in Uaq varied in location with increasing water table elevation through the combined effects of advection and source term location. Heuristic reactive transport modeling with PFLOTRAN demonstrated that mobilized Uaq was transported between wells and source terms in complex trajectories, and was diluted as river water entered and exited the groundwater system. While Uaq time‐series concentration trends varied significantly from year‐to‐year as a result of climate‐caused differences in the spring hydrograph, common and partly predictable response patterns were observed that were driven by water table elevation, and the extent and duration of river water intrusion.
Protonated Phosphazenes: Structures and Hydrogen‐Bonding Organocatalysts for Carbonyl Bond Activation
Authors: Jardel Damien , Davies Clotilde , Peruch Frédéric , Massip Stéphane , Bibal Brigitte 
Published: February 2016

AbstractThe synthesis and application of protonated phosphazeniums as hydrogen‐bond donor groups was demonstrated in the solid state and in solution. In particular, their catalytic activity was shown in the activation of the carbonyl group within cyclic esters, using a benchmark reaction, that is, in the ring‐opening polymerization of lactide and valerolactone, in the presence of a basic co‐catalyst. The reactions proceed differently depending on monomers and/or phosphazenium salts. The impact of catalysts and reactants steric hindrance upon the outcome of the reaction is then highlighted and discussed.magnified image
Disentangling the associations between parental BMI and offspring body composition using the four‐component model
Authors: Devakumar Delan , Grijalva‐Eternod Carlos , Cortina‐Borja Mario , Williams Jane , Fewtrell Mary , Wells Jonathan 
Published: February 2016

ABSTRACTObjectivesThis study sets out to investigate the intergenerational associations between the body mass index (BMI) of parents and the body composition of their offspring.MethodsThe cross‐sectional data were analyzed for 511 parent–offspring trios from London and south‐east England. The offspring were aged 5–21 years. Parental BMI was obtained by recall and offspring fat mass and lean mass were obtained using the four‐component model. Multivariable regression analysis, with multiple imputation for missing paternal values was used. Sensitivity analyses for levels of non‐paternity were conducted.ResultsA positive association was seen between parental BMI and offspring BMI, fat mass index (FMI), and lean mass index (LMI). The mother's BMI was positively associated with the BMI, FMI, and LMI z‐scores of both daughters and sons and of a similar magnitude for both sexes. The father's BMI showed similar associations to the mother's BMI, with his son's BMI, FMI, and LMI z‐scores, but no association with his daughter. Sensitivity tests for non‐paternity showed that maternal coefficients remained greater than paternal coefficients throughout but there was no statistical difference at greater levels of non‐paternity.ConclusionsWe found variable associations between parental BMI and offspring body composition. Associations were generally stronger for maternal than paternal BMI, and paternal associations appeared to differ between sons and daughters. In this cohort, the mother's BMI was statistically significantly associated with her child's body composition but the father's BMI was only associated with the body composition of his sons. Am. J. Hum. Biol. 28:524–533, 2016. © 2016 The Authors American Journal of Human Biology Published by Wiley Periodicals, Inc.
Phonon‐polariton entrapment in homogenous surface phonon cavities
Authors: Yudistira Didit , Boes Andreas , Dumas Benjamin , Rezk Amgad R. , Yousefi Morteza , Djafari‐Rouhani Bahram , Yeo Leslie Y. , Mitchell Arnan 
Published: February 2016

Surface phonon cavities that are homogenous in both mechanical and dielectric properties are reported. The cavities are formed by the placement of a defect of a single domain within periodic domain inversion of single crystal piezoelectric lithium niobate that exhibits surface phononic bandgap through the phonon‐polariton coupling. Surface cavity resonances are observed within the bandgap, which manifest in entrapment of phonon‐polariton within the defect. In addition to demonstrating that the observed resonances are non‐radiative and decoupled to bulk radiation, which is critical for high Q cavities, it is also shown the possibility to tune the surface cavity resonance spectra simply by varying the defect width. Such an ability to excite surface cavity resonance that is non‐radiative with simultaneous localization of the electric field together with the advantage of a cavity that is physically formed from a completely monolithic and uniform material offers unique opportunities for widespread applications for example in actuation, detection, and phonon lasing that can be fully integrated with other physical systems such as quantum acoustics, photonics, and microfluidics.image
Validating Eaton's Hypothesis: Cubane as a Benzene Bioisostere
Authors: Chalmers Benjamin A. , Xing Hui , Houston Sevan , Clark Charlotte , Ghassabian Sussan , Kuo Andy , Cao Benjamin , Reitsma Andrea , Murray Cody‐Ellen P. , Stok Jeanette E. , Boyle Glen M. , Pierce Carly J. , Littler Stuart W. , Winkler David A. , Bernhardt Paul V. , Pasay Cielo , De Voss James J. , McCarthy James , Parsons Peter G. , Walter Gimme H. , Smith Maree T. , Cooper Helen M. , Nilsson Susan K. , Tsanaktsidis John , Savage G. Paul , Williams Craig M. 
Published: February 2016

AbstractPharmaceutical and agrochemical discovery programs are under considerable pressure to meet increasing global demand and thus require constant innovation. Classical hydrocarbon scaffolds have long assisted in bringing new molecules to the market place, but an obvious omission is that of the Platonic solid cubane. Eaton, however, suggested that this molecule has the potential to act as a benzene bioisostere. Herein, we report the validation of Eaton's hypothesis with cubane derivatives of five molecules that are used clinically or as agrochemicals. Two cubane analogues showed increased bioactivity compared to their benzene counterparts whereas two further analogues displayed equal bioactivity, and the fifth one demonstrated only partial efficacy. Ramifications from this study are best realized by reflecting on the number of bioactive molecules that contain a benzene ring. Substitution with the cubane scaffold where possible could revitalize these systems, and thus expedite much needed lead candidate identification.