bluuebunny/crossref_metadata_2025 huggingface dataset:
Definitions of climate and climate change under varying external conditions
Authors: Werndl C.
Published: June 2014

Abstract. Commonly, definitions of climate are endorsed where the external conditions are held constant. This paper argues that these definitions risk being empirically void because in reality the external conditions vary. As a consequence, analogous definitions for varying external conditions are explored with help of the recently developed theory of non-autonomous dynamical systems, and the similarities and differences between the cases of constant and varying external conditions are discussed. It is argued that there are analogous definitions for varying external conditions which are preferable to the definitions where the external conditions are held constant. In this context, a novel definition is proposed (namely, climate as the distribution over time under a regime of varying external conditions), which is argued to be promising.
A strategy to overcome adverse effects of autoregressive updating of streamflow predictions
Authors: Li M. , Wang Q. J. , Bennett J. C. , Robertson D. E.
Published: June 2014

Abstract. For streamflow forecasting applications, rainfall–runoff hydrological models are often augmented with updating procedures that correct streamflow predictions based on the latest available observations of streamflow and their departures from model simulations. The most popular approach uses autoregressive (AR) models that exploit the "memory" in hydrological model simulation errors. AR models may be applied to raw errors directly or to normalised errors. In this study, we demonstrate that AR models applied in either way can sometimes cause over-correction of predictions. In using an AR model applied to raw errors, the over-correction usually occurs when streamflow is rapidly receding. In applying an AR model to normalised errors, the over-correction usually occurs when streamflow is rapidly rising. Furthermore, when parameters of a hydrological model and an AR model are estimated jointly, the AR model applied to normalised errors sometimes degrades the stand-alone performance of the base hydrological model. This is not desirable for forecasting applications, as predictions should rely as much as possible on the base hydrological model, and updating should be applied only to correct minor errors. To overcome the adverse effects of the ordinary AR models, a restricted AR model applied to normalised errors is introduced. The new model is evaluated on a number of catchments and is shown to reduce over-correction and to improve the performance of the base hydrological model considerably.
Lithosphere and upper-mantle structure of the southern Baltic Sea estimated from modelling relative sea-level data with glacial isostatic adjustment
Authors: Steffen H. , Kaufmann G. , Lampe R.
Published: June 2014

Abstract. During the last glacial maximum, a large ice sheet covered Scandinavia, which depressed the earth's surface by several 100 m. In northern central Europe, mass redistribution in the upper mantle led to the development of a peripheral bulge. It has been subsiding since the begin of deglaciation due to the viscoelastic behaviour of the mantle. We analyse relative sea-level (RSL) data of southern Sweden, Denmark, Germany, Poland and Lithuania to determine the lithospheric thickness and radial mantle viscosity structure for distinct regional RSL subsets. We load a 1-D Maxwell-viscoelastic earth model with a global ice-load history model of the last glaciation. We test two commonly used ice histories, RSES from the Australian National University and ICE-5G from the University of Toronto. Our results indicate that the lithospheric thickness varies, depending on the ice model used, between 60 and 160 km. The lowest values are found in the Oslo Graben area and the western German Baltic Sea coast. In between, thickness increases by at least 30 km tracing the Ringkøbing-Fyn High. In Poland and Lithuania, lithospheric thickness reaches up to 160 km. However, the latter values are not well constrained as the confidence regions are large. Upper-mantle viscosity is found to bracket [2–7] × 1020 Pa s when using ICE-5G. Employing RSES much higher values of 2 × 1021 Pa s are obtained for the southern Baltic Sea. Further investigations should evaluate whether this ice-model version and/or the RSL data need revision. We confirm that the lower-mantle viscosity in Fennoscandia can only be poorly resolved. The lithospheric structure inferred from RSES partly supports structural features of regional and global lithosphere models based on thermal or seismological data. While there is agreement in eastern Europe and southwest Sweden, the structure in an area from south of Norway to northern Germany shows large discrepancies for two of the tested lithosphere models. The lithospheric thickness as determined with ICE-5G does not agree with the lithosphere models. Hence, more investigations have to be undertaken to sufficiently determine structures such as the Ringkøbing-Fyn High as seen with seismics with the help of glacial isostatic adjustment modelling.
Practical analytical solutions for benchmarking of 2-D and 3-D geodynamic Stokes problems with variable viscosity
Authors: Popov I. Yu. , Lobanov I. S. , Popov S. I. , Popov A. I. , Gerya T. V.
Published: June 2014

Abstract. Geodynamic modeling is often related with challenging computations involving solution of the Stokes and continuity equations under the condition of highly variable viscosity. Based on a new analytical approach we have developed particular analytical solutions for 2-D and 3-D incompressible Stokes flows with both linearly and exponentially variable viscosity. We demonstrate how these particular solutions can be converted into 2-D and 3-D test problems suitable for benchmarking numerical codes aimed at modeling various mantle convection and lithospheric dynamics problems. The Main advantage of this new generalized approach is that a large variety of benchmark solutions can be generated, including relatively complex cases with open model boundaries, non-vertical gravity and variable gradients of the viscosity and density fields, which are not parallel to the Cartesian axes. Examples of respective 2-D and 3-D MatLab codes are provided with this paper.
Asymmetry of high-velocity lower crust on the South Atlantic rifted margins and implications for the interplay of magmatism and tectonics in continental break-up
Authors: Becker K. , Franke D. , Trumbull R. B. , Schnabel M. , Heyde I. , Schreckenberger B. , Koopmann H. , Bauer K. , Jokat W. , Krawczyk C. M.
Published: June 2014

Abstract. High-velocity lower crust (HVLC) and seaward dipping reflector sequences (SDRs) are typical features of volcanic rifted margins. However, the nature and origin of HVLC is under discussion. Here we provide a comprehensive analysis of deep crustal structures in the southern segment of the South Atlantic and an assessment of HVLC along the margins. Two new seismic refraction lines off South America fill a gap in the data coverage and together with five existing velocity models allow a detailed investigation of the lower crustal properties on both margins. An important finding is the major asymmetry in volumes of HVLC on the conjugate margins. The seismic refraction lines across the South African margin reveal four times larger cross sectional areas of HVLC than at the South American margin, a finding that is in sharp contrast to the distribution of the flood basalts in the Paraná-Etendeka Large Igneous Provinces (LIP). Also, the position of the HVLC with respect to the seaward dipping reflector sequences varies consistently along both margins. Close to the Falkland-Agulhas Fracture Zone a small body of HVLC is not accompanied by seaward dipping reflectors. In the central portion of both margins, the HVLC is below the inner seaward dipping reflector wedges while in the northern area, closer to the Rio Grande Rise/Walvis Ridge, large volumes of HVLC extend far seawards of the inner seaward dipping reflectors. This challenges the concept of a simple extrusive/intrusive relationship between seaward dipping reflector sequences and HVLC, and it provides evidence for formation of the HVLC at different times during the rifting and break-up process. We suggest that the drastically different HVLC volumes are caused by asymmetric rifting in a simple shear dominated extension.
Glacier area and length changes in Norway from repeat inventories
Authors: Winsvold S. H. , Andreassen L. M. , Kienholz C.
Published: June 2014

Abstract. In this study, we assess glacier area and length changes in mainland Norway from repeat Landsat TM/ETM+ derived inventories and digitized topographic maps. The multi-temporal glacier inventory consists of glacier outlines from within three time ranges: 1947 to 1985 (GIn50), 1988 to 1997 (GI1990), and 1999 to 2006 (GI2000). For the northernmost regions, we include an additional inventory (GI1900), based on historic maps surveyed between 1895 to 1907. Area and length changes are assessed per glacier unit, for 36 subregions, and for three main parts of Norway: southern, central and northern Norway. The results show a decrease of the glacierized area from 2994 km2 in GIn50, to 2668 km2 in GI2000 (totally 2722 glacier units), corresponding to an area reduction of −326 km2, or −11% of the initial GIn50 area. This is equivalent to an average change rate of −11 km2 a−1 over the past 30 years. The average length change for the full epoch (within GIn50 and GI2000) is −240 m, corresponding to an average length change rate of −8 m a−1. Overall, the comparison reveals both area and length reduction as a general pattern, even though some glaciers have advanced. The three northernmost glacier regions show the strongest retreat rates, whereas the central part of Norway shows the lowest change rates. Glacier area and length changes indicate that glaciers in maritime areas in southern Norway have retreated more than glaciers in the interior, and glaciers in the north have retreated more than southern glaciers. These observed spatial trends in glacier change are related to a combination of several geographical factors like glacier geometry and elevation, and other climatic aspects, such as continentality and the North Atlantic Oscillation.
White Lupin (Lupinus albus L. cv. Amiga) Increases Solubility of Minjingu Phosphate Rock, Phosphorus Balances and Maize Yields in Njoro Kenya
Authors: Lelei Joyce J. , Onwonga Richard N.
Published: June 2014

Exudation of high amounts of citrate in white lupin (Lupinus albus L. cv. Amiga) has the advantage of being effective in mobilization of a wide range of sparingly soluble P sources. To improve cultivation system of maize, a field experiment was conducted to assess effectiveness of white lupin (Lupinus albus L. cv. Amiga) in increasing solubility of minjingu phosphate rock (MPR), phosphorus balances and maize yields in Njoro sub-County, Kenya. The randomized complete block design experiment was conducted for four seasons; short (October – February) and long rain seasons (March-September) of 2010 and 2011. The treatments were; (i) fallow (F) – maize (M) rotation with triple superphosphate (TSP) applied (MTSP- F), (ii) fallow - maize rotation with MPR applied (MMPR –F), (iii) lupin (L) – maize rotation with MPR applied (MMPR- L) and (iv) maize/lupin intercrop with MPR applied (M/LMPR – F). Soil and plant P and maize grain yield were higher in M/LMPR – F (with additional lupin grain yield) and MTSP– F treatments. All treatments resulted in positive P balances at the end of two years with highest values in MTSP– F treatment and lowest in M/LMPR – F. Intercropping lupin with maize amid application of MPR is recommended for enhanced maize performance in the farming systems of resource poor farmers. Measurement of available soil nitrogen and comparison of lupin with other legumes in solubilizing MPR is recommended.

 
Vers une différenciation des trajectoires de forte croissance (FC continue vs FC discontinue)
Authors: Claveau Nathalie , Perez Muriel , Prim-Allaz Isabelle
Published: June 2014

Le focus des scientifiques et des politiques se porte assez volontiers sur les cas de forte croissance (FC) continue, les « gazelles de course » définies comme des entreprises affichant quatre années successives de forte croissance (selon la définition proposée par Birch, 1979). L’État, en soutenant ces travaux et ces trajectoires, voit là certainement un moyen de rencontrer rapidement ses propres objectifs (de puissance industrielle, d’exportation, d’emploi, etc.). Cependant, ce focus sur la FC continue ne contribue-t-il pas, d’une part, à façonner une vision erronée du développement d’une PME, vue comme « une forme organisationnelle qui doit nécessairement grossir rapidement pour devenir une ETI (Entreprise de Taille Intermédiaire) », et d’autre part, à alimenter des raisonnements simplistes tels que « les firmes qui croissent fortement en continu sont plus performantes que les autres » ? De fait, peu d’études réalisées sur le thème de la FC traitent de son aspect continu ou discontinu. Qu’en est-il exactement de la supériorité d’un processus continu sur un processus discontinu ? Un processus discontinu présente-t-il d’autres atouts  ? Les entreprises gérant une FC discontinue ont-elles les mêmes caractéristiques et capacités que ces « gazelles » ?

Afin de mieux comprendre la nature des différences entre ces deux processus de croissance, cet article propose de comparer un échantillon d’entreprises en FC continue, correspondant classiquement à la notion de gazelles, un échantillon en FC discontinue, ainsi qu’un échantillon témoin sans croissance, sur des variables démographiques (âge et taille) et des variables financières (l’accès aux ressources financières et la performance financière). Cette analyse descriptive préliminaire permet de constater que la forte croissance continue et la forte croissance discontinue ne nécessitent pas les mêmes dispositifs d’aides de la part des organismes publics et ouvre des perspectives d’approfondissement.
Perception de la responsabilité sociale des entreprises par leurs dirigeants
Authors: Ben Hassine Leïla , Ghozzi-Nékhili Chiraz
Published: June 2014

La responsabilité sociétale de l’entreprise (RSE) est aujourd’hui une réalité qui s’impose à tout type d’entreprise. Du fait du rôle dominant du dirigeant dans la prise de décision dans les petites et moyennes entreprises (PME), sa perception de la RSE constitue une source privilégiée de l’étude du concept. Partant de l’idée que la certification selon les normes internationales peut être un facteur distinctif de la perception de la RSE, nous avons mené une enquête exploratoire basée sur des études de cas multiples auprès de huit PME tunisiennes réparties en deux groupes : quatre certifiées selon les normes internationales (ISO 9001, ISO 14001, OHSAS, etc.) et quatre non certifiées. L’analyse des convergences et des divergences entre les perceptions des dirigeants de ces PME a montré une faible distinction entre les deux groupes quant à l’appropriation du concept de RSE et à l’identification des motivations et des freins à l’engagement de l’entreprise. D’autres facteurs émergents de cette étude sont liés à la conviction personnelle du dirigeant et à la culture nationale.
Le financement des PME en Tunisie
Authors: Adair Philippe , Fhima Fredj
Published: June 2014

Malgré leur importance numérique et le rôle qui leur est dévolu dans le cadre de la stratégie de promotion du secteur privé en Tunisie, les petites et moyennes entreprises (PME) ne répondent pas aux exigences des banques afin de satisfaire leur besoin de financement. L’estimation du tout premier modèle de déséquilibre appliquée à la Tunisie repose sur un panel de 1 275 PME observées entre 2001 et 2006. Il montre que la demande de crédit bancaire n’est pas déterminée par les facteurs « endogènes », tels le niveau d’activité et les ressources internes disponibles des entreprises, mais plutôt par des facteurs « exogènes », tels le coût de financement et les garanties exigées par les banques. Les exigences des banques, surtout en matière de garanties, expliquent en grande partie l’insuffisance des concours octroyés par rapport aux besoins exprimés et se traduisent par une proportion moyenne d’environ 80 % de ces entreprises qui sont - partiellement ou totalement - rationnées.
Intuition et succès entrepreneurial
Authors: Lefebvre Miruna Radu , O’Shea Noreen
Published: June 2014

Concept pluridisciplinaire en philosophie, psychologie et anthropologie, l’intuition a fait son entrée dans la littérature entrepreneuriale ces dix dernières années. Pourtant, de nombreux entrepreneurs la citaient depuis longtemps comme un élément clé de leur réussite en affaires. Quelle est la représentation sociale de l’intuition dans le champ de l’entrepreneuriat ? Quels sont ses liens avec la prise de décision et le comportement des entrepreneurs novices et consacrés ? Les représentations sociales influencent les perceptions collectives relatives à la désirabilité et la faisabilité entrepreneuriales. Les médias exercent une fonction centrale dans l’élaboration et la circulation des représentations sociales. Nous avons étudié la représentation sociale de l’intuition dans la presse française à partir d’un corpus de 700 articles de la base Lexis Nexis, entre le 5 août 2003 et le 5 août 2012. À partir d’une grille d’analyse du discours, nous avons classé et étudié ces documents afin d’identifier les éléments centraux de l’image de l’intuition dans l’espace public français – contextes d’occurrences, sources d’énonciation, impacts perçus sur l’entrepreneur et son entreprise. Nos résultats ont des implications théoriques et pratiques pour la communication de sensibilisation à la création d’entreprise, ainsi que pour l’accompagnement et l’éducation entrepreneuriale.
Mechanisms of organelle biogenesis govern stochastic fluctuations in organelle abundance
Authors: Mukherji Shankar , O'Shea Erin K
Published: June 2014

Fluctuations in organelle abundance can profoundly limit the precision of cell biological processes from secretion to metabolism. We modeled the dynamics of organelle biogenesis and predicted that organelle abundance fluctuations depend strongly on the specific mechanisms that increase or decrease the number of a given organelle. Our model exactly predicts the size of experimentally measured Golgi apparatus and vacuole abundance fluctuations, suggesting that cells tolerate the maximum level of variability generated by the Golgi and vacuole biogenesis pathways. We observe large increases in peroxisome abundance fluctuations when cells are transferred from glucose-rich to fatty acid-rich environments. These increased fluctuations are significantly diminished in mutants lacking peroxisome fission factors, leading us to infer that peroxisome biogenesis switches from de novo synthesis to primarily fission. Our work provides a general framework for exploring stochastic organelle biogenesis and using fluctuations to quantitatively unravel the biophysical pathways that control the abundance of subcellular structures.
All Purkinje cells are not created equal
Authors: Albergaria Catarina , Carey Megan R
Published: June 2014

Although the wiring of the cerebellar cortex appears to be uniform, the neurons in this region of the brain behave more differently from each other than previously thought.
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

Although 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

High‐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.
Access and Use of Data Lead to Innovative Ways to Reduce Energy Consumption, Officials Say
Authors: Showstack Randy
Published: June 2014

Aaron Woro was selling residential solar energy systems in 2006 and performing site surveys in the San Francisco Bay Area for individual rooftops that required precise measurements due to roof geometry and shade from trees. One day, while standing on the rooftop of a large home, balancing a tape measure in one hand and a shade tool in the other, he slipped and fell, crashing through tree branches and bushes that partially broke his fall.
John Orcutt Selected as Editor of New Open‐Access Journal
Authors: Finn Carol
Published: June 2014

John Orcutt will serve as the inaugural editor of AGU's newest open‐access journal, Earth and Space Science. Orcutt is a distinguished professor of geophysics at the Scripps Institution of Oceanography at the University of California, San Diego and former president and general secretary of AGU.
Polar jet stream could reveal Saturn's rotational period
Authors: Wendel JoAnna
Published: June 2014

A hexagon‐shaped atmospheric phenomenon first spotted on Saturn by Voyager 1 and Voyager 2 has intrigued scientists since the 1980s. More recently, NASA's Cassini mission has periodically observed the hexagon and its embedded strong eastward jet that rotates at 120 meters per second. Scientists believe that the persistence of the hexagon could put to rest the oft‐debated question of the length of Saturn's rotational period.
Different types of El Niño affect global temperature differently
Authors: Balcerak Ernie
Published: June 2014

The El Niño–Southern Oscillation is known to influence global surface temperatures, with El Niño conditions leading to warmer temperatures and La Niña conditions leading to colder temperatures. However, a new study by Banholzer and Donner shows that some types of El Niño do not have this effect, a finding that could explain recent decade‐scale slowdowns in global warming.
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

We 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

It 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

Basal 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.
Mechanical Properties of Reactive Air Brazed (RAB) Metal/Ceramic Joints. Part 1: Visco‐Plastic Deformation of Silver‐Based Reactive Air Brazes
Authors: Skiera Erik , Brandenberg Jörg , Li Chichi , Beck Tilmann , Singheiser Lorenz , Kuhn Bernd
Published: June 2014

Development of planar solid oxide fuel cell systems for automotive application is mostly driven by light‐weight design and durability issues. The joining technology utilized to seal ceramic and metallic stack components plays a key role. Rapid and frequent start‐up capability is required for customer satisfaction. Furthermore, operational security of the system and passenger safety precondition reliable hermeticity of the seals. Metallic joints based on reactive air brazing (RAB), utilizing silver brazes, are preferred to glass ceramics because of their potentially higher failure tolerance. Mechanical design data of full‐scale RAB joints, especially at high temperature, are scarce and for this reason up to now only estimated from literature data of bulk silver. Detailed deformation and damage mechanisms at high temperature are largely unknown, what further complicates target oriented braze development and evolution in stack design. A new testing technique (symmetric double shear testing) was proposed and successfully carried out for the characterization of full‐scale braze joints. Mechanical testing was accompanied by scanning electron microscopy examination of microstructure. High temperature deformation and damage of the joints was uncovered to be influenced by both interfaces and matrix performance. The braze matrix governs elastic‐plastic deformation, while the maximum strength is determined by the braze/joining partner interfaces. The creep properties of the joints were found to correlate to that of bulk silver.
Influence of Filler and Base Material on the Pore Development during Reactive Air Brazing
Authors: Bobzin Kirsten , Kopp Nils , Wiesner Stefanie
Published: June 2014

Innovative technologies such as solid oxide fuel cells for energy generation make high demands on materials that can often be met by embedding ceramic components into metallic structures. A promising and economic method of joining ceramic to metal or to ceramic is reactive air brazing (RAB). A disadvantage of the RAB joints is the high porosity which can lessen the strength of the joint as well as its gas tightness. Different stages of pore development in dependence of filler and base materials could be observed during the brazing process due to the vaporising of the organic binder, the melting process and a reaction between the filler metal and the base material. By adjusting the process parameters the pore formation can be decreased.
Numerical and Experimental Sensitivity Analysis for the Determination of Casting Parameter–Microstructure–Property Relations and Mechanical Properties of IN738LC in Investment Casting
Authors: Schmidt Robin , Pusch David , Voigt Matthias , Vogeler Konrad , Kulawinski Dirk , Biermann Horst , Holländer Dirk , Gampe Uwe , Tränkner Mario , Leyens Christoph
Published: June 2014

The development of manufacturing processes for high‐performance investment casting components in turbomachinery is an iterative process, which takes a lot of development time for engineers and foundry occupation. The reduction of these expensive preliminary tests is possible by combining probabilistic methods with modern simulation tools for the numerical description of the casting and solidification processes. Starting from the deterministic simulation of the casting process, the casting and solidification parameters including their production tolerances are taken into account in the probabilistic simulation. Through a multi‐dimensional statistical analysis of the numerous parameters of the casting process and the achieved virtual casting results, the correlations between the process parameters and component quality can be worked out. Furthermore, a design of experiment (DoE) was performed with real castings to confirm the influence of the main parameters on the result quantities. Mechanical and microstructural characterizations of appropriate cast specimens allow a validation of the simulation results and the formulation of casting parameter–microstructure–property relations. The mechanical properties are studied by uniaxial hot tensile tests using standard and small‐scale specimens. Furthermore, the uniaxial fatigue behavior and the life times at elevated temperatures are investigated.
Low Temperature Stabilization of Nanoscale Epitaxial Spinel Ferrite Thin Films by Atomic Layer Deposition
Authors: Coll Mariona , Montero Moreno Josep M. , Gazquez Jaume , Nielsch Kornelius , Obradors Xavier , Puig Teresa
Published: June 2014

In this work heteroepitaxial stabilization with nanoscale control of the magnetic Co2FeO4 phase at 250 °C is reported. Ultrasmooth and pure Co2FeO4 thin films (5–25 nm) with no phase segregation are obtained on perovskite SrTiO3 single crystal (100) and (110) oriented substrates by atomic layer deposition (ALD). High resolution structural and chemical analyses confirm the formation of the Co‐rich spinel metastable phase. The magneto‐crystalline anisotropy of the Co2FeO4 phase is not modified by stress anisotropy because the films are fully relaxed. Additionally, high coervice fields, 15 kOe, and high saturation of magnetization, 3.3 μB per formula unit (at 10 K), are preserved down to 10 nm. Therefore, the properties of the ALD‐Co2FeO4 films offer many possibilities for future applications in sensors, actuators, microelectronics, and spintronics. In addition, these results are promising for the use of ALD compared to the existing thin‐film deposition techniques to stabilize epitaxial multicomponent materials with nanoscale control on a wide variety of substrates for which the processing temperature is a major drawback.
Spatial relationship between the mental foramen and mandibular developing teeth in modern humans, chimpanzees, and hamadryas baboons
Authors: Fukase Hitoshi
Published: June 2014

The 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

Many 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

Die 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

Isolation 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

Network 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

TEMPO‐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.
The roles of sharing, transfer, and public funding in nanotechnology knowledge‐diffusion networks
Authors: Jiang Shan , Gao Qiang , Chen Hsinchun , Roco Mihail C.
Published: June 2014

Understanding the knowledge‐diffusion networks of patent inventors can help governments and businesses effectively use their investment to stimulate commercial science and technology development. Such inventor networks are usually large and complex. This study proposes a multidimensional network analysis framework that utilizes Exponential Random Graph Models (ERGMs) to simultaneously model knowledge‐sharing and knowledge‐transfer processes, examine their interactions, and evaluate the impacts of network structures and public funding on knowledge‐diffusion networks. Experiments are conducted on a longitudinal data set that covers 2 decades (1991–2010) of nanotechnology‐related US Patent and Trademark Office (USPTO) patents. The results show that knowledge sharing and knowledge transfer are closely interrelated. High degree centrality or boundary inventors play significant roles in the network, and National Science Foundation (NSF) public funding positively affects knowledge sharing despite its small fraction in overall funding and upstream research topics.
How is research blogged? A content analysis approach
Authors: Shema Hadas , Bar‐Ilan Judit , Thelwall Mike
Published: June 2014

Blogs that cite academic articles have emerged as a potential source of alternative impact metrics for the visibility of the blogged articles. Nevertheless, to evaluate more fully the value of blog citations, it is necessary to investigate whether research blogs focus on particular types of articles or give new perspectives on scientific discourse. Therefore, we studied the characteristics of peer‐reviewed references in blogs and the typical content of blog posts to gain insight into bloggers' motivations. The sample consisted of 391 blog posts from 2010 to 2012 in Researchblogging.org's health category. The bloggers mostly cited recent research articles or reviews from top multidisciplinary and general medical journals. Using content analysis methods, we created a general classification scheme for blog post content with 10 major topic categories, each with several subcategories. The results suggest that health research bloggers rarely self‐cite and that the vast majority of their blog posts (90%) include a general discussion of the issue covered in the article, with more than one quarter providing health‐related advice based on the article(s) covered. These factors suggest a genuine attempt to engage with a wider, nonacademic audience. Nevertheless, almost 30% of the posts included some criticism of the issues being discussed.