bluuebunny/crossref_metadata_2025_split huggingface dataset:
Contrasting electron acceleration processes during two substorms
Authors: Liang Haoming , Ashour‐Abdalla Maha , Richard Robert , Schriver David , El‐Alaoui Mostafa , Walker Raymond J. 
Published: June 2014

AbstractAlthough energetic particle injections during substorms have been observed near geosynchronous orbit since the late 1960s, how the injected particles are accelerated during a substorm is still not fully understood. Studies show that injections are associated with earthward propagating dipolarization fronts and suggest that particle acceleration can occur due to a combination of betatron acceleration during earthward convection and acceleration in the vicinity of magnetotail reconnection sites. Since observed energetic particle distributions vary from substorm to substorm, it is important to study acceleration mechanisms as a function of different substorm magnetotail configurations. In this paper, we discuss electron acceleration for two substorm events featuring different magnetotail configurations and particle acceleration processes. The study utilizes in situ observations, global MHD simulations, and large‐scale‐kinetic (LSK) simulations. The two substorms in question occurred on 15 February 2008 and 15 August 2001. The 15 February 2008 event was observed by the THEMIS spacecraft at xGSE ~ −10 RE, while the 15 August 2001 event was observed by Cluster spacecraft at xGSE ~ −20 RE. Earthward propagating dipolarization fronts are found in both the observations and the MHD simulations, which are driven by the solar wind conditions that existed during those events. The two simulations show that very different magnetotail configurations are formed for each event, with contrasting flows, magnetic reconnection configuration, and plasma sheet structure. We find that for the 15 February 2008 event reconnection is localized with a narrow region of high‐speed flow. During this event, the electron velocity distribution functions f(v) are found to be anisotropic with f(v⊥) > f(v||), where || and ⊥ correspond to parallel and perpendicular to magnetic field. In contrast, for the 15 August 2001 event, there is a wide neutral line extending across the tail with low‐speed flows. For this event, the distribution functions are anisotropic with f(v||) > f(v⊥), the opposite sense as the 15 February 2008 event. We are able to relate these differences to the different magnetotail configurations seen during each event. These differences lead to contrasting occurrence rates of nonadiabatic acceleration. The differences between the magnetotail configurations during these two substorms may result from differences in the location of dayside reconnection. On 15 August 2001 the reconnection occurs on the flanks of the magnetopause, while on 15 February 2008 the reconnection occurs nearer the subsolar point.
A novel method for estimating the onset of thermal stratification in lakes from surface water measurements
Authors: Woolway R. Iestyn , Maberly Stephen C. , Jones Ian D. , Feuchtmayr Heidrun 
Published: June 2014

AbstractHigh‐frequency surface water temperature measurements were analyzed for 17 annual data series from seven lakes to assess whether the onset of thermal stratification can be determined from time series of surface water temperature measurements alone. Current methods for estimating the start of thermal stratification require depth‐resolved temperature measurements, whereas many existing high‐frequency measurements are often limited only to the lake surface. In this study, we show that the magnitude of the diel surface water temperature range can be used to estimate the onset of thermal stratification. We assess the accuracy of using the diel range as an estimate of the onset of thermal stratification by applying two methods based on the calculation of (1) the absolute difference in the diel surface temperature range and (2) the magnitude of the diel range from wavelet analysis. Our study shows that the onset of thermal stratification can be accurately estimated by wavelet analysis with a root mean square error of 2.1 days and by the observed diel temperature range method with a root mean square error of 11.8 days. This approach enables existing, and future, high‐resolution surface water data sets to be used to estimate the onset of lake stratification. Furthermore, the continuously increasing observational powers of satellites may eventually result in surface water temperature being measured at a sufficiently high temporal resolution at the spatial scales of small lakes to allow the onset of thermal stratification to be estimated remotely.
Dating terrestrial impact structures: U‐Pb depth profiles and (U‐Th)/He ages of zircon
Authors: Wielicki Matthew M. , Harrison T. Mark , Stockli Daniel 
Published: June 2014

AbstractWe investigate the presence of epitaxial overgrowth rims and “reset” zircon, complete loss of radiogenic lead (Pb*), from terrestrial impactites to constrain the occurrence of such phenomenon in impact environments and their possible use in dating impact events. We also explore (U‐Th)/He dating of zircon to evaluate this geochronometer in accurately identifying impact ages, particularly when no dateable melt sheet exists. Our results show that (U‐Th)/He ages of zircon from the brecciated, and presumably shocked target, can accurately date an impact event and provides another tool to determine impact ages when no melt sheet exists, an alternative to problematic interpretations of commonly used apparent 40Ar/39Ar plateau ages. No evidence of epitaxial overgrowth rims and/or reset zircon was observed, suggesting that zircons within shocked impactites have remarkably slow Pb diffusion and possibly explaining the relatively few reset grains reported in terrestrial impactites.
On the performance of the IRI‐2012 and NeQuick2 models during the increasing phase of the unusual 24th solar cycle in the Brazilian equatorial and low‐latitude sectors
Authors: Venkatesh K. , Fagundes P. R. , Seemala Gopi K. , de Jesus R. , de Abreu A. J. , Pillat V. G. 
Published: June 2014

AbstractIt is known that the equatorial and low‐latitude ionosphere is characterized with typical dynamical phenomena namely, the equatorial ionization anomaly (EIA). Accurate modeling of the characteristic variations of the EIA is more important to arrive at the correct estimation of range delays required for the communication and navigation applications. The total electron content (TEC) data from a chain of Global Positioning System (GPS) receivers at seven identified locations from equator to the anomaly crest and beyond along 315°E geographic longitude in the Brazilian sector are considered. The performances of the latest available IRI‐2012 and NeQuick2 models have been investigated during 2010–2013 in the increasing phase of the 24th solar cycle. A comparative study on the morphological variations of the GPS measured and modeled TEC revealed that the performances of the models are improved during low solar activity periods compared to that during the increased solar activity years. The strength and the locations of the EIA crest are nearly well represented by both the models during the low solar activity while the models underestimate the peak TEC at the EIA during the increased solar activity conditions. The deviations between the GPS‐measured and model‐derived TEC are more during equinoctial and summer months at and around the anomaly crest locations. Significant differences have also been observed in between the TEC values derived from both the models. The causes for the discrepancies in the modeled TEC values are discussed based on the model‐derived and ionosonde‐measured vertical electron density profiles variations.
Ocean variability contributing to basal melt rate near the ice front of Ross Ice Shelf, Antarctica
Authors: Arzeno Isabella B. , Beardsley Robert C. , Limeburner Richard , Owens Breck , Padman Laurie , Springer Scott R. , Stewart Craig L. , Williams Michael J. M. 
Published: June 2014

AbstractBasal melting of ice shelves is an important, but poorly understood, cause of Antarctic ice sheet mass loss and freshwater production. We use data from two moorings deployed through Ross Ice Shelf, ∼6 and ∼16 km south of the ice front east of Ross Island, and numerical models to show how the basal melting rate near the ice front depends on sub‐ice‐shelf ocean variability. The moorings measured water velocity, conductivity, and temperature for ∼2 months starting in late November 2010. About half of the current velocity variance was due to tides, predominantly diurnal components, with the remainder due to subtidal oscillations with periods of a few days. Subtidal variability was dominated by barotropic currents that were large until mid‐December and significantly reduced afterward. Subtidal currents were correlated between moorings but uncorrelated with local winds, suggesting the presence of waves or eddies that may be associated with the abrupt change in water column thickness and strong hydrographic gradients at the ice front. Estimated melt rate was ∼1.2 ± 0.5 m a−1 at each site during the deployment period, consistent with measured trends in ice surface elevation from GPS time series. The models predicted similar annual‐averaged melt rates with a strong annual cycle related to seasonal provision of warm water to the ice base. These results show that accurately modeling the high spatial and temporal ocean variability close to the ice‐shelf front is critical to predicting time‐dependent and mean values of meltwater production and ice‐shelf thinning.
Spatial relationship between the mental foramen and mandibular developing teeth in modern humans, chimpanzees, and hamadryas baboons
Authors: Fukase Hitoshi 
Published: June 2014

ABSTRACTThe mental foramen (MF) of adult human mandibles is characterized by its high position and posterosuperior opening orientation, compared with that of nonhuman primates. In this study, to examine when and how such interspecies variations in MF position/orientation are manifested in the context of dental development, positional relationships between the MF and nearby forming teeth (dc, dm1, C, P3) were assessed using CT‐scanned growth‐series mandibles of the following three species with various MF positions and anterior dental sizes: modern humans, chimpanzees, and hamadryas baboons. Results showed that modern humans have more antero‐superiorly located MF and dc than the two nonhuman samples during growth, whereas the MF and dm1 of hamadryas baboons are the most inferiorly positioned. Considering that the mandibular canal generally reaches the dc/dm1 position during infancy, the species differences in MF position can be attributed largely to the positions where the anterior deciduous teeth first appear. Specifically, the distinctive dental position of modern humans should stem eventually from the comparatively small anterior dental size. Furthermore, human MF position shifted slightly upwards with alveolar development, unlike in the nonhuman samples, accompanied by strong curvature and vertical elongation of the anterior mandibular canal. Meanwhile, the human MF shifted from a forward to a lateral/backward orientation in association with human‐specific growth‐related alveolar recession. The findings of this study, thus, collectively indicate that taxonomic variations in adult MF position/orientation can be interpreted partly by the positions of the surrounding developing teeth. Am J Phys Anthropol 154:594–603, 2014. © 2014 Wiley Periodicals, Inc.
Secular trend of dental development in Dutch children
Authors: Vucic Strahinja , de Vries Esther , Eilers Paul H.C. , Willemsen Sten P. , Kuijpers Mette A.R. , Prahl‐Andersen Birte , Jaddoe Vincent W.V. , Hofman Albert , Wolvius Eppo B. , Ongkosuwito Edwin M. 
Published: June 2014

ABSTRACTMany studies have established dental age standards for different populations; however, very few studies have investigated whether dental development is stable over time on a population level. Therefore, the aim of this study was to analyze changes in dental maturity in Dutch children born between 1961 and 2004. We used 2,655 dental panoramic radiographs of 2‐ to 16‐year‐old Dutch children from studies performed in three major cities in the Netherlands. Based on a trend in children born between 1961 and 1994, we predicted that a child of a certain age and gender born in 1963 achieved the same dental maturity on average, 1.5 years later than a child of the same age born 40 years later. After adjusting for the birth year of a child in the analysis, the regression coefficient of the city variable was reduced by 56.6% and it remained statistically significant. The observed trend from 1961 to 1994 was extrapolated to 9‐ to 10‐year‐old children born in 2002–2004, and validation with the other samples of children with the same characteristics showed that 95.9%–96.8% of the children had dental maturity within the 95% of the predicted range. Dental maturity score was significantly and positively associated with the year of birth, gender, and age in Dutch children, indicating a trend in earlier dental development during the observation period, 1961–2004. These findings highlight the necessity of taking the year of birth into account when assessing dental development within a population with a wider time span. Am J Phys Anthropol 155:91–98, 2014. © 2014 Wiley Periodicals, Inc.
Pyrrolysin‐Synthase (PylD) katalysiert die Bildung von Pyrrolin‐ und Tetrahydropyridinringen in Aminosäuren
Authors: Quitterer Felix , Beck Philipp , Bacher Adelbert , Groll Michael 
Published: June 2014

AbstractDie Dehydrogenase PylD katalysiert den letzten Schritt der Pyrrolysin‐Biosynthese, indem sie das Isopeptid L‐Lysin‐Nε‐3R‐Methyl‐D‐ornithin zur zweiundzwanzigsten proteinogenen Aminosäure umsetzt. Hier zeigen wir, wie PylD für die oxidative Umwandlung verschiedener Isopeptide zu neuen Aminosäuren genutzt werden kann. Die Kombination von chemischer Synthese, Enzymkinetik und Röntgenkristallographie ermöglicht eine genaue Beschreibung der Reaktionsfolge für PylD zur Synthese von Pyrrolin‐ und Tetrahydropyridinringen als Bestandteile von Pyrrolysin‐Analoga.
Predicting the Relative Solubilities of Racemic and Enantiopure Crystals by Density‐Functional Theory
Authors: Otero‐de‐la‐Roza Alberto , Cao Blessing Huynh , Price Ivy K. , Hein Jason E. , Johnson Erin R. 
Published: June 2014

AbstractIsolation of chiral molecules as pure enantiomers remains a fundamental challenge in chemical research. Enantioselective enrichment through preferential crystallization is an efficient method to achieve enantiopure compounds, but its applicability depends on the relative stability of the enantiopure and racemic crystal forms. Using a simple thermodynamic model and first‐principles density‐functional calculations, it is possible to predict the difference in solubility between the enantiopure and racemic solid phases. This approach uses dispersion‐corrected density functionals and is capable of accurately predicting the solution‐phase entantiomeric excess to within about 10 % of experimental measurements on average. The accuracy of the exchange‐hole dipole moment (XDM) model of dispersion enables the viability of the proposed method.
EDTA and pH‐sensitive crosslinking polymerization of acrylic acid, 2‐acrylamidoglycolic acid, and 2‐acrylamide‐2‐methyl‐1‐propanesulfonic acid
Authors: Kim Byungsoo , Hong Daesun , Chang Wenji V. 
Published: June 2014

ABSTRACTNetwork formation was monitored by shear storage modulus (G′) during free radical crosslinking polymerization to investigate the effects of pH and ethylenediaminetetraacetic acid (EDTA; a complex agent). Three types of acrylic monomers, acrylic acid (AAc), 2‐acrylamidoglycolic acid (AmGc), and 2‐acrylamido‐2‐methyl propanesulfonic acid (AmPS), were polymerized in the presence of a crosslinking agent. The ratio of crosslinking agent (methylene bis‐acrylamide; MBAAm) to monomer was varied as: 0.583 × 10−3, 1.169 × 10−3, 1.753 × 10−3, and 2.338 × 10−3. G′ of the hydrogel in crosslinking polymerizations of AAc and AmPS was effectively increased by addition of EDTA, which was not the case for the crosslinking polymerization of AmGc. The order of magnitude of G′ differed based on the acidity of monomer. The maximum values of G′ in crosslinking polymerizations of AAc, AmGc, and AmPS were ∼20,000 Pa, 6000 Pa, and 400 Pa, respectively. G′ varied linearly with the molecular weight between crosslinks (Mwc). pH and EDTA‐complex affected the rate of intramolecular propagation during crosslinking polymerization. Our results indicated that G′ was primarily affected by the following factors in the order: (1) acidity of monomer, (2) Mwc, and (3) physical interactions induced by pH and EDTA. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 41026.
Electrospun polyvinyl alcohol/waterborne polyurethane composite nanofibers involving cellulose nanofibers
Authors: Dai Lei , Long Zhu , Ren Xue‐hong , Deng Hai‐bo , He Hong , Liu Wen 
Published: June 2014

ABSTRACTTEMPO‐oxidized cellulose nanofibers (TOCNs) were used as nanofillers in this work. Composite nanofibers of polyvinyl alcohol (PVA)/waterborne polyurethane (WPU) reinforced with TOCNs were produced by electrospinning. The reinforcing capability of TOCNs was investigated by tensile tests. Scanning electron microscopy (SEM), X‐ray diffraction, and thermogravimetry analyses were also carried out in order to characterize the appearance, crystallinity, and reinforcing effect of the cellulose nanofibers. SEM results showed that PVA/WPU/TOCNs composite nanofibers presented a highly homogeneous dispersion of TOCNs. The reinforced composites had about 44% increase in their mechanical properties with addition of only 5 wt % of TOCNs while about 42% decrease in elongation at break. The TOCNs reinforced composite nanofibers were more thermally stable than pure PVA/WPU nanofibers. The development of crystalline structure in the composite fibers was observed by XRD. Since PVA, WPU, and TOCNs are hydrophilic, non‐toxic, and biocompatible, and therefore, these nanocomposite nanofibers could be used for tissue scaffolding, filtration materials, and medical industries as wound dressing materials. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 41051.
Incorporating work zone configuration factors into speed‐flow and capacity models
Authors: Weng Jinxian , Meng Qiang 
Published: June 2014

SummaryThis study aims to develop work zone speed‐flow and capacity models, which incorporate work zone configuration factors including the number of work zones, geometrical alignment, work zone speed limit, and work zone length. On the basis of the traffic data from six work zone sites with various work zone configurations, two nonlinear traffic speed and flow models including work zone configuration factors are developed for the uncongested and congested traffic conditions, respectively. A work zone capacity model is proposed on the basis of the two models. The three models can further be used to examine the effects of work zone configuration factors on the speed‐flow relationship and capacity at work zones. Results show that traffic speed, traffic flow, and work zone capacity increase with the posted speed limit. Traffic speed under uncongested conditions decreases with the geometric alignment, the number of work zones, work zone length, and heavy vehicle percentage. Under congested conditions, the increase of the number of work zones is found to exhibit a larger negative impact on the traffic flow than the increase of geometric alignment. The number of work zones is also found to have the largest negative impacts on work zone capacity, followed by the geometric alignment. Short work zone length exhibits a relatively minor contribution to increasing work zone capacity. Copyright © 2014 John Wiley & Sons, Ltd.
Zum Einfluss von Atrien auf die Gebäudeenergieeffizienz – eine Fallanalyse mit Betriebsoptimierung eines Atriumgebäudes
Authors: Zargari Mani 
Published: June 2014

AbstractDer Einfluss von Atrien auf die Energieeffizienz und den thermischen Komfort eines Gebäudes kann sehr unterschiedlich ausfallen. Entscheidend hierfür sind die konstruktiven Randbedingungen und das Energiekonzept eines Atriumgebäudes. Anhand der erfolgreichen Umsetzung von Optimierungsmaßnahmen am Hauptgebäude der LBS Nord Hannover Kronsberg mit einem begleitenden messtechnischen Monitoring wird demonstriert, wie sich unterschiedliche Energiekonzepte auf die Energieeffizienz und den thermischen Komfort des Gesamtgebäudes auswirken. Die Belüftung der zwischen den Gebäuderiegeln liegenden verglasten Grünhöfe wird so angepasst, dass die jeweils geltenden Konditionierungsanforderungen des Kerngebäudes unterstützt werden. Durch eine verbesserte Integration der Grünhöfe in das Belüftungskonzept der Kerngebäude werden die Lüftungswärmeverluste und der Energieaufwand für die mechanische Belüftung verringert. Im Beobachtungszeitraum ist daher eine signifikante Reduzierung des Energieverbrauchs für Wärme, Kälte und Strom zu verzeichnen. Darüber hinaus hat sich das sommerliche Raumklima in den Grünhöfen und den Büros deutlich verbessert. Zudem wird aufgezeigt, wie diese Maßnahmen unter Berücksichtigung der thermischen Anforderungen der winterlichen Vegetationsruhe der Bepflanzung umgesetzt werden können.The effect of atria to the energy efficiency of buildings – a case study with the re‐commissioning of an atria building. The influence of an atrium on the energy efficiency and the thermal comfort of a building can be different. Decisive are construction boundaries and the energy design of the building. On the basis of an successful optimization of the headquarter building of LBS Nord in Hannover Kronsberg with an accompanying measurement based monitoring it can be shown, what kind of impact different energy concepts of the integrated atria have on the energy efficiency and thermal comfort of the whole building. The ventilation of the unconditioned atrium in the analyzed building has been adapted to the heating and cooling requirements of the core building in a way that these demands are actively supported. Due to this improved integration of the atrium in the whole building the ventilation heat loss and the electric power consumption for the air handling systems are lowered. In the observation period the energy demand of the building for heating, cooling and lighting had been reduced. The thermal comfort in the atria and the adjacent offices during the summer period has been improved. Additionally it has been shown how the changes in the energy concept can be achieved by considering the thermal requirements of the winter dormancy of the plants inside the atria.