bluuebunny/crossref_metadata_2025 huggingface dataset:
Gerard Manley Hopkins : quelle théologie lit-on dans son œuvre ?
Authors: Jossua Jean-Pierre
Published: April 2014

Le poète jésuite Gerard Hopkins a produit une œuvre remarquable révélée après sa mort. La théologie qui y est explicite est celle de son temps : la providence, l’expiation, l’apologie de la souffrance, etc. Mais une étude de sa poétique, très originale et réfléchie, permet de discerner d’autres orientations qui sont du plus grand intérêt.
Véhicule électrique et gestion de son autonomie : une approche prospective ancrée dans l'expérience vécue
Authors: Nguyen Claudine , Cahour Béatrice
Published: April 2014

Le développement du Véhicule Electrique (VE) pose la question de l’impact possible de ce dernier sur l’activité de conduite en raison de son autonomie limitée. Cette recherche prospective explore les comportements et expériences vécues des utilisateurs de véhicule thermique et de VE relatifs aux modes de gestion de l’autonomie. Dans une première phase, quatre styles de gestion de l’autonomie ont été identifiés suite à des entretiens avec des conducteurs de véhicules thermiques et quantifiés à l’aide d’un questionnaire. Ces styles dépendent de la relation affective au risque de panne, qui motive généralement le comportement de recharge, plus ou moins anticipateur ou réactif. D’autres facteurs contextuels qui peuvent intervenir sont précisés. Dans une seconde phase, à partir de deux semaines de prêts de VE, nous avons pu observer le transfert de ces styles de gestion de l’autonomie du véhicule thermique au VE, ce qui indique qu’ils peuvent être utilisés afin de prédire les conduites des futurs utilisateurs. La difficulté de préciser l’évolution de l’autonomie du VE peut générer des inquiétudes et la conception de nouveaux instruments et services permettra de réduire l’incertitude ; la perception et l’interprétation différenciée des instruments ont ainsi été analysées. Une troisième phase, s’appuyant sur l’expérience vécue de nos conducteurs et la confrontation à deux prototypes, a permis de stimuler la créativité des participants et de leur faire exprimer des attentes en termes de services et outils à développer dans le futur. L’articulation de méthodologies variées, en s’appuyant sur l’expérience vécue, fournit des pistes prospectives afin de garantir le développement et la conception d’instruments et services innovants qui participeront à la sécurité et au confort émotionnel des conducteurs des futurs VE.
E-learning and Benchmarking Platform for Parallel and Distributed Computing
Authors: Gusev Marjan , Ristov Sasko , Velkoski Goran , Ivanovska Bisera
Published: April 2014

Emerging technologies and increased computing resources challenge the universities to establish learning environments, where the students will learn to efficiently utilize multicore or multi-chip multiprocessors. In this paper, we present a new pilot project with the following goals: (1) as an e-Learning platform for the course on Parallel and Distributed Computing, and (2) as a benchmarking plat-form to measure the algorithm performance indicators such as speed, speedup and efficiency of the parallel implementation.
ICTs in Kindergarten
Authors: Drigas Athanasios , Kokkalia Georgia
Published: April 2014

Recent development in the role of kindergarten in children's progress includes the use of Information and Communication Technologies (ICTs). ICT nowadays is recognized as a tool that can foster the knowledge and the experiences for this crucial age and the support of specific areas in kindergarten according to the educational perspective is thought significant. In this paper we present a brief overview of the most representative studies of the last decade (2003-2013) which concentrates on the skills that are examined in kindergarten (early literacy ,early mathematics, cognitive, social-emotional, motor, creativity) and are supported by ICTs. The effectiveness of ICT in special education and gifted children in the regular kindergarten is examined. The attitudes of kindergarten teachers towards ICTs are presented.
The Application of KINECT Motion Sensing Technology in Game-Oriented Study
Authors: Yang Hui Yu , Zhang Hao , Xu Wei , Zhang Ping Jian , Xu Liang Ming
Published: April 2014

The learning environment based on the KINECT Motion Sensing technology is able to fully mobilize the learners' multi-sensory organs, closely combine study with sports and enhance human-computer interactions, which can be conducive to the learners' health, greatly increase the relishes of learning and promote effective learning in the game, and finally compensate for the shortage of human-computer interactions in the traditional mouse and keyboard mode. The article elaborates on the KINECT Motion Sensing Technology and its educational applications status by analyzing its effective supports for game-oriented studying environment, based on which the article establishes a game-oriented learning environment. Eventually the article reveals an applicable case of game-oriented teaching and learning as a reference for related researches.
Assessing Effects of Variation in Global Climate Data Sets on Spatial Predictions from Climate Envelope Models
Authors: Watling James I. , Fletcher Robert J. , Speroterra Carolina , Bucklin David N. , Brandt Laura A. , Romañach Stephanie S. , Pearlstine Leonard G. , Escribano Yesenia , Mazzotti Frank J.
Published: April 2014

Climate change poses new challenges for natural resource managers. Predictive modeling of species–environment relationships using climate envelope models can enhance our understanding of climate change effects on biodiversity, assist in assessment of invasion risk by exotic organisms, and inform life-history understanding of individual species. While increasing interest has focused on the role of uncertainty in future conditions on model predictions, models also may be sensitive to the initial conditions on which they are trained. Although climate envelope models are usually trained using data on contemporary climate, we lack systematic comparisons of model performance and predictions across alternative climate data sets available for model training. Here, we seek to fill that gap by comparing variability in predictions between two contemporary climate data sets to variability in spatial predictions among three alternative projections of future climate. Overall, correlations between monthly temperature and precipitation variables were very high for both contemporary and future data. Model performance varied across algorithms, but not between two alternative contemporary climate data sets. Spatial predictions varied more among alternative general-circulation models describing future climate conditions than between contemporary climate data sets. However, we did find that climate envelope models with low Cohen's kappa scores made more discrepant spatial predictions between climate data sets for the contemporary period than did models with high Cohen's kappa scores. We suggest conservation planners evaluate multiple performance metrics and be aware of the importance of differences in initial conditions for spatial predictions from climate envelope models.
Implementation of UML Schema in Relational Databases
Authors: Nagni Maurizio , Ventouras Spiros
Published: April 2014

Numerous disciplines require information concerning phenomena implicitly or explicitly associated with a location relative to the Earth. Disciplines using Geographic Information (GI) in particular are those within the earth and physical sciences, and increasingly those within social science and medical fields. Therefore geographic datasets are increasingly being shared, exchanged and frequently re-purposed for uses beyond their original intended use. Being part of the ISO 19100 Geographic Information Standard series, the ISO 19136 called Geography Markup Language (GML), defines the rules a data model described using the Unified Modeling Language (UML) has to follow in order to generate from it an XSD schema. However, if GML is essential for exchange data among different organization, it may not be the best option for persisting or searching operations. On the other side, the Relational Database Model (RDBM) has been heavily optimized over the decades to store and search data. This paper does not address “How to store an GML complaint document in an RDBM” but “How to realize an RDBM from an ISO 19100 complaint UML data model” and within this context, it describes the experience and the lessons learnt. The conclusions show how the information contained in such UML is able to produce not only representations as GML schema, but also RDBM or RDF without passing by any intermediary step.
A Game-Based Approach to Support Social Presence and Awareness in Distributed Project-Based Learning
Authors: Marklund Björn Berg , Backlund Per , Dahlin Carl-Johan , Engström Henrik , Wilhelmsson Ulf
Published: April 2014

An important factor for success in project-based learning (PBL) is that the involved project groups establish an atmosphere of social interaction in their working environment. In PBL-scenarios situated in distributed environments, most of a group's work-processes are mediated through the use of production-focused tools that are unconcerned with the important informal and social aspects of a project. On the other hand, there are plenty of tools and platforms that focus on doing the opposite and mainly support informal bonding (e.g., Facebook), but these types of environments can be obtrusive and contain distractions that can be detrimental to a group's productivity and are thus often excluded from working environments. The aim of this paper is to examine how a game-based multi-user environment (MUVE) can be designed to support project-based learning by bridging the gap between productivity-focused and social software. To explore this, the authors developed a game-based MUVE which was evaluated in a PBL-scenario. The result of the study revealed several crucial design elements that are needed to make such a MUVE work effectively, and that the acceptance towards game-based MUVEs is high, even with a rudimentary execution.
Studying the User Experience of a Tablet Based Math Game
Authors: Kiili Kristian , Ketamo Harri , Koivisto Antti , Finn Enda
Published: April 2014

This paper presents the first findings from Math Elements user experience (UX) studies. Math Elements is a game that makes the whole Finnish maths K-2 curriculum (kindergarten and primary school grades 1 and 2) available for players all over the world. The game is based on teachable agent approach, which means that in the game players can teach math skills to their game characters. Research focused on evaluating the implementation of the game, exploring players' opinions about the game, and studying how the game fits to classroom usage. The participants were Finnish (N = 111) and Irish (N = 42) primary school pupils. In both cases interviews, game log data and observation methods were used to evaluate the UX. The Finnish study was conducted in two phases. First, one first grade class (N = 23) participated in a focus group study in which they played the Math Elements game in small groups and finally eight of the pupils participated in an eye tracking study. Second, the class introduced the game in their school and after that all first and second graders of the school played the game daily during a three weeks period. The Irish case study was different from Finnish study and the results are not directly comparable. The Irish pupils (fourth and fifth graders) played the game for 50 minutes as a part of their regular schoolwork. In general, Math Elements was experienced as an engaging learning game in all studied age groups and it was found to fit well into classroom usage in certain contexts. The paper presents the details of the conducted UX studies and discusses the meaning of UX in educational games.
Open Source Software Adaptation in Africa
Authors: Bakar Abubakar Diwani , Sultan Abu Bakar Md. , Zulzalil Hazura , Din Jamilah
Published: April 2014

The African continent has long benefited from adopting OSS in its private and public organizations that have changed their way of development, the use and how to acquire proprietary software. This frequency of adaptation does not appear to be in balance with the contribution to the OSS community. Using views from experienced software practitioners working in different organizations across two African countries it has been observed that neglected infrastructure, a wide availability of proprietary software and misconceptions of a clear meaning of Open Source Software across Africa have been an obstacle towards the participation in the OSS technology in the global network.
The Gold Standard for Assessing Creativity
Authors: Baer John , McKool Sharon S.
Published: April 2014

The most widely used creativity assessments are divergent thinking tests, but these and other popular creativity measures have been shown to have little validity. The Consensual Assessment Technique is a powerful tool used by creativity researchers in which panels of expert judges are asked to rate the creativity of creative products such as stories, collages, poems, and other artifacts. The Consensual Assessment Technique is based on the idea that the best measure of the creativity of a work of art, a theory, a research proposal, or any other artifact is the combined assessment of experts in that field. Unlike other measures of creativity, the Consensual Assessment Technique is not based on any particular theory of creativity, which means that its validity (which has been well established empirically) is not dependent upon the validity of any particular theory of creativity. The Consensual Assessment Technique has been deemed the “gold standard” in creativity research and can be very useful in creativity assessment in higher education.
Integrated Security Process Improvement Framework for Systems and Services
Authors: Ramachandran Muthu
Published: April 2014

Security of systems and services has been dominant research area in recent years as today's cloud services, big data and networked systems, especially when they provide wireless application access where personal and confidential data to be transmitted across the networked systems. Numerous tools and technologies are available to ensure system's security; however, external threats to computer systems and applications residents thereon, are also becoming more and more sophisticated and on the increase. Therefore, the key aim of this research is to integrate security engineering techniques and process with systems development life-cycle and process improvement frameworks. This paper presents a framework that consists of two components: 1) a security assessment model to looks at the existing security infrastructure of an organisation to determine its security maturity level; and 2) a security improvement maturity model to suggest an improvement mechanism for the organisation to progress from one maturity level to the next higher level. The intention is to provide a scheme to improve the organisation's Systems and network security with the aim that it becomes more efficient and effective than before.
A Study of Replicators and Hypercycles by Hofstadter's Typogenetics
Authors: Kvasnička V. , Pospíchal J.
Published: April 2014

A Typogenetics is a formal system designed to study origins of life from a “primordial soup” of DNA molecules, enzymes and other building materials. It was introduced by Hofstadter (1979) in his seminal book Dialogues with Gödel, Escher, Bach: An Eternal Golden Braid. Autoreplicating molecules and systems of mutually replicating and catalyzing molecules (autoreplicators and hypercycles) are modeled in the present paper in a form composed of two strands of symbols. These strands are vehicle of two fold information: The first one corresponds to information that is transferred by strands. The second type of information specifies a process of strand replication. The used replicating molecules - strands are created by an approach closely related to evolutionary algorithms. While a small hypercycle of two molecules mutually supporting their reproduction can be created without extreme difficulties, it is nearly impossible to create a hypercycle involving more than 4 autoreplicators at once. This paper demonstrates that larger hypercycles can be created by an optimization and inclusion of new molecules into a smaller hypercycle. Such a sequential construction of hypercycles can substantially reduce the combinatorial complexity in comparison with a simultaneous optimization of single components of a large hypercycle.
Broadband Developments in the United States Subsequent to the Federal Communications Commission's 2010 National Broadband Plan
Authors: Meisel John B. , Navin John C. , Sullivan Timothy S.
Published: April 2014

The United States Federal Communications Commission delivered to Congress a national broadband plan in 2010. The purpose of this article is to analyze key economic arguments involving the development of the broadband plan addressing open network and competition issues, to make recommendations to the Commission in its formulation of federal policy as to positions that make the most economic sense, and to indicate recent economic and legal developments in broadband markets since publication of the broadband plan. One critical issue prior to the development of the broadband plan and subsequent to its publication is the competitiveness of the Internet Service Provider market. There is emerging evidence that, at least with respect to very high-speed broadband markets, a cable monopoly may be looming. The authors continue to predict with confidence that technological innovations are likely to make many opposing legal arguments obsolete in the near future.
Examining the Evidence to Guide Practice: Challenging Practice Habits
Authors: Makic Mary Beth Flynn , Rauen Carol , Watson Robin , Poteet Ann Will
Published: April 2014

Nurses are the largest segment of the nation’s health care workforce, which makes nurses vital to the translation of evidence-based practice as a practice norm. Critical care nurses are in a position to critically appraise and apply best evidence in daily practice to improve patients’ outcomes. It is important for critical care nurses to continually evaluate their current practice to ensure that they are applying the current best evidence rather than practicing on the basis of tradition. This article is based on a presentation at the 2013 National Teaching Institute of the American Association of Critical-Care Nurses. Four practice interventions that are within the realm of nursing are critiqued on the basis of current best evidence: (1) turning critically ill patients, (2) sleep promotion in the intensive care unit, (3) feeding tube management in infants and children, and (4) prevention of venothromboembolism…again. The related beliefs, current evidence, and implications for practice associated with each topic are described.
CTLA-4 Is Expressed by Activated Mouse NK Cells and Inhibits NK Cell IFN-γ Production in Response to Mature Dendritic Cells
Authors: Stojanovic Ana , Fiegler Nathalie , Brunner-Weinzierl Monika , Cerwenka Adelheid
Published: April 2014

NK cells express an array of activating and inhibitory receptors that determine NK cell responses upon triggering by cognate ligands. Although activating NK cell receptors recognize mainly ligands expressed by stressed, virus-infected, or transformed cells, most inhibitory receptors engage MHC class I, preventing NK cell activation in response to healthy cells. In this study, we provide insight into the regulation and function of additional receptors involved in mouse NK cell responses: CTLA-4 and CD28. CTLA-4 and CD28 engage the same ligands, B7-1 and B7-2, which are primarily expressed by APCs, such as dendritic cells. Our data demonstrate that activation of mouse NK cells with IL-2 induces the expression of CTLA-4 and upregulates CD28. CTLA-4 expression in IL-2–expanded NK cells was further up- or downregulated by IL-12 or TGF-β, respectively. Using gene-deficient NK cells, we show that CD28 induces, and CTLA-4 inhibits, IFN-γ release by NK cells upon engagement by the recombinant ligand, B7-1, or upon coculture with mature dendritic cells. Notably, we show that mouse NK cells infiltrating solid tumors express CD28 and CTLA-4 and respond to stimulation with recombinant B7-1, suggesting that the NK cell responses mediated by the CD28/CTLA-4:B7-1/B7-2 system could be of importance during malignant disease. Accordingly, our study might have implications for immunotherapy of cancer based on blocking anti–CTLA-4 mAbs.
High Molecular Weight Kininogen Binds Phosphatidylserine and Opsonizes Urokinase Plasminogen Activator Receptor–Mediated Efferocytosis
Authors: Yang Aizhen , Dai Jihong , Xie Zhanli , Colman Robert W. , Wu Qingyu , Birge Raymond B. , Wu Yi
Published: April 2014

Phagocytosis of apoptotic cells (efferocytosis) is essential for regulation of immune responses and tissue homeostasis and is mediated by phagocytic receptors. In this study, we found that urokinase plasminogen activator receptor (uPAR) plays an important role in internalization of apoptotic cells and also characterized the underlying mechanisms. In a flow cytometry–based phagocytic assay, uPAR-deficient macrophages displayed significant defect in internalization but not tethering of apoptotic cells. When uPAR-deficient mice were challenged with apoptotic cells, they exhibited pronounced splenomegaly resulting from accumulation of abundant apoptotic cells in spleen. Overexpression of uPAR in HEK-293 cells enhanced efferocytosis, which was inhibited by Annexin V and phosphatidylserine (PS) liposome, suggesting that uPAR-mediated efferocytosis is dependent on PS. In serum lacking high m.w. kininogen (HK), a uPAR ligand, uPAR-mediated efferocytosis was significantly attenuated, which was rescued by replenishment of HK. As detected by flow cytometry, HK selectively bound to apoptotic cells, but not viable cells. In purified systems, HK was specifically associated with PS liposome. HK binding to apoptotic cells induced its rapid cleavage to the two-chain form of HK (HKa) and bradykinin. Both the H chain and L chain of HKa were associated with PS liposome and apoptotic cells. HKa has higher binding affinity than HK to uPAR. Overexpression of Rac1/N17 cDNA inhibited uPAR-mediated efferocytosis. HK plus PS liposome stimulated a complex formation of CrkII with p130Cas and Dock-180 and Rac1 activation in uPAR-293 cells, but not in control HEK-293 cells. Thus, uPAR mediates efferocytosis through HK interaction with PS on apoptotic cells and activation of the Rac1 pathway.
Genetic Structure Inferred from Mitochondrial 12S Ribosomal RNA Sequence of Oncomelania quadrasi, the Intermediate Snail Host of Schistosoma japonicum in the Philippines
Authors: Saijuntha Weerachai , Jarilla Blanca , Leonardo Alvin K. , Sunico Louie S. , Leonardo Lydia R. , Andrews Ross H. , Sithithaworn Paiboon , Petney Trevor N. , Kirinoki Masashi , Kato-Hayashi Naoko , Kikuchi Mihoko , Chigusa Yuichi , Agatsuma Takeshi
Published: April 2014

Species and subspecies of the Oncomelania hupensis species complex are recognized as intermediate hosts of Schistosoma japonicum. Of these species and subspecies, O. quadrasi is distributed throughout the Philippines. This study used 12S ribosomal RNA sequences to explore the genetic structure of O. quadrasi populations in the Philippines. Three subspecies, O. h. hupensis, O. h. formosana, and O. h. chiui of this group were also examined. The phylogenetic tree and haplotypes network showed that O. quadrasi separated from the subspecies. Ten O. quadrasi haplotypes (Oq1–Oq10) clustered in relation to their geographic origin. Genetic differentiation (FST) and estimated gene flow (Nm) among populations showed significant differences, ranging from 0.556–1.000 to 0.00–0.74, respectively. Genetic differences among groups (FCT = 0.466), populations within a group (FSC = 0.727), and populations (FST = 0.854) were observed. These results indicate that the O. quadrasi populations in the Philippines have a substructure associated with their geographic origin.
Effects of environmental factors on dimethylated sulfur compounds and their potential role in the antioxidant system of the coral holobiont
Authors: Deschaseaux E. S. M. , Jones G. B. , Deseo M. A. , Shepherd K. M. , Kiene R. P. , Swan H. B. , Harrison P. L. , Eyre B. D.
Published: April 2014

Biogenic dimethylsulfide (DMS) and its main precursors, dimethylsulfoniopropionate (DMSP) and dimethylsulfoxide (DMSO), are potential scavengers of reactive oxygen species in marine algae, and these dimethylated sulfur compounds (DSC) could take part in the algal antioxidant system. In this study, a link between the DSC production and the antioxidant capacity (AOC) of Acropora aspera reef coral was investigated under a range of environmental factors (temperature, light, salinity, and air exposure) that can lead to oxidative stress in the coral holobiont. Enhanced DMS(P)(O) production occurred under experimental conditions, indicating that DSC are potential biomarkers of stress level in coral tissue. Differences in concentrations and partitioning as a response to different treatments suggest that DSC production and turnover undergo different biochemical pathways depending on the type and severity of environmental stress. Osmotic pressure and light depletion led to an up‐regulation of the coral AOC that was correlated with a significant increase in DMSO : DSC ratio. These results, combined with a positive correlation between the AOC and DMSO concentrations under these two treatments, suggest that the DMSP‐based antioxidant system is involved in the overall antioxidant regulation of the coral holobiont. Enhanced DMS production coupled with an increased DMS : DSC ratio under increased temperature indicated that thermal stress triggers DMS formation in coral tissue. Considering the role that DMS can have in both climate regulation and the DMSP‐based antioxidant system, our findings highlight the need to further examine the fate of DSC in coral reef environments under scenarios of increasing sea surface temperatures.
Horizontal divergence of typhoon-generated gravity waves in the upper troposphere and lower stratosphere (UTLS) and its influence on typhoon evolution
Authors: Kim S. H. , Chun H.-Y. , Jang W.
Published: April 2014

Abstract. The characteristics of horizontal divergence induced by typhoon-generated gravity waves (HDTGWs) and the influence of HDTGW on typhoon evolution are investigated based on the simulation results of Typhoon Saomai (2006) using the Weather Research and Forecasting (WRF) model. The power spectral density of HDTGW shows dominant powers at horizontal wavelengths of 20–30 km and at periods of less than 1 h. This is associated with gravity waves generated by vigorous convective clouds in an inner core region of the typhoon. However, the domain-averaged HDTGW in the upper troposphere and lower stratosphere had a spectral peak at 24 h, which is well correlated with the minimum sea-level pressure of the typhoon, especially during a rapidly developing period. The 24 h period of the averaged HDTGW stems from the inertia–gravity waves generated by the convective clouds in the spiral rainbands, and showed no clear association with the thermal tides or the diurnal variation of precipitation.
Simulation of GOES-R ABI aerosol radiances using WRF-CMAQ: a case study approach
Authors: Christopher S. A.
Published: April 2014

Abstract. In anticipation of the upcoming GOES-R launch we simulate visible and near-infrared reflectances of the Advanced Baseline Imager (ABI) for cases of high aerosol loading containing regional haze and smoke over the eastern United States. The simulations are performed using the Weather Research and Forecasting (WRF), Sparse Matrix Operator Kernel Emissions (SMOKE), and Community Multiscale Air Quality (CMAQ) models. Geostationary, satellite-derived, biomass-burning emissions are also included as an input to CMAQ. Using the CMAQ aerosol concentrations and Mie calculations, radiance is computed from the discrete ordinate atmospheric radiative transfer model. We present detailed methods for deriving aerosol extinction from WRF and CMAQ outputs. Our results show that the model simulations create a realistic set of reflectances in various aerosol scenarios. The simulated reflectances provide distinct spectral features of aerosols which are then compared to data from the Moderate Resolution Imaging Spectroradiometer (MODIS). We also present a simple technique to synthesize green band reflectance (which will not be available on the ABI), using the model-simulated blue and red band reflectance. This study is an example of the use of air quality modeling in improving products and techniques for Earth-observing missions.
Displacement-based error metrics for morphodynamic models
Authors: Bosboom J. , Reniers A. J. H. M.
Published: April 2014

Abstract. The accuracy of morphological predictions is generally measured by an overall point-wise metric, such as the mean-squared difference between pairs of predicted and observed bed levels. Unfortunately, point-wise accuracy metrics tend to favour featureless predictions over predictions whose features are (slightly) misplaced. From the perspective of a coastal morphologist, this may lead to wrong decisions as to which of two predictions is better. In order to overcome this inherent limitation of point-wise metrics, we propose a new diagnostic tool for 2-D morphological predictions, which explicitly takes (dis)agreement in spatial patterns into account. Our approach is to formulate errors based on a smooth displacement field between predictions and observations that minimizes the point-wise error. We illustrate the advantages of this approach using a variety of morphological fields, generated with Delft3D, for an idealized case of a tidal inlet developing from an initially very schematized geometry. The quantification of model performance by the new diagnostic tool is found to better reflect the qualitative judgement of experts than traditional point-wise metrics do.
Fine sediment dynamics in the Río de la Plata
Authors: Fossati M. , Cayocca F. , Piedra-Cueva I.
Published: April 2014

Abstract. This paper investigates the main characteristics of the fine sediments dynamics in a very complex and extensive inner shelf area located in South America, the Río de la Plata. The results derive from a 5 yr international research program that allowed intensive data acquisition throughout the area, as well as the development of the first numerical model investigating sediment dynamics at a regional scale in the area. The model is based on the MARS3D suite: it computes the regional tide- and wind-induced circulation, as well as sediment mixtures dynamics (erosion, advection and deposition of several sedimentary variables). Erosion due to wave action is taken into account thanks to the use of SWAN. The hydrodynamic and wave models were calibrated against several measurements in different zones of the Río de la Plata. Turbidity data (time series and vertical profiles) were then used in order to calibrate the sediment dynamics model. The model is shown to accurately reproduce the sediment concentration variability during both fair and stormy weather conditions in the intermediate and in the outer Río de la Plata. The paper also shows that the suspended sediment dynamics in the Río de la Plata is mainly driven by water/bottom exchanges.
Repeated erosion of cohesive sediments with biofilms
Authors: Valentine K. , Mariotti G. , Fagherazzi S.
Published: April 2014

Abstract. This study aims to explore the interplay between biofilms and erodability of cohesive sediments. Erosion experiments were run in four laboratory annular flumes with natural sediments. After each erosion the sediment was allowed to settle, mimicking intermittent physical processes like tidal currents and waves. The time between consecutive erosion events ranged from 1 to 12 days. Turbidity of the water column caused by sediment resuspension was used to determine the erodability of the sediments with respect to small and moderate shear stresses. Erodability was also compared on the basis of the presence of benthic biofilms, which were quantified using a Pulse-Amplitude Modulation (PAM) Underwater Fluorometer. We found that frequent erosion lead to the establishment of a weak biofilm, which reduced sediment erosion at small shear stresses (around 0.1 Pa). If prolonged periods without erosion were present, the biofilm fully established, resulting in lower erosion at moderate shear stresses (around 0.4 Pa). We conclude that an unstructured extracellular polymeric substances (EPS) matrix always affect sediment erodability at low shear stresses, while only a fully developed biofilm mat can reduce sediment erodability at moderate shear stresses.
The AquaVIT-1 intercomparison of atmospheric water vapor measurement techniques
Authors: Fahey D. W. , Gao R.-S. , Möhler O. , Saathoff H. , Schiller C. , Ebert V. , Krämer M. , Peter T. , Amarouche N. , Avallone L. M. , Bauer R. , Bozóki Z. , Christensen L. E. , Davis S. M. , Durry G. , Dyroff C. , Herman R. L. , Hunsmann S. , Khaykin S. M. , Mackrodt P. , Meyer J. , Smith J. B. , Spelten N. , Troy R. F. , Vömel H. , Wagner S. , Wienhold F. G.
Published: April 2014

Abstract. The AquaVIT-1 Intercomparison of Atmospheric Water Vapor Measurement Techniques was conducted at the aerosol and cloud simulation chamber AIDA at the Karlsruhe Institute of Technology, Germany, in October 2007. The overall objective was to intercompare state-of-the-art and prototype atmospheric hygrometers with each other and with independent humidity standards under controlled conditions. This activity was conducted as a blind intercomparison with coordination by selected referees. The effort was motivated by persistent discrepancies found in atmospheric measurements involving multiple instruments operating on research aircraft and balloon platforms, particularly in the upper troposphere and lower stratosphere where water vapor reaches its lowest atmospheric values (less than 10 ppm). With the AIDA chamber volume of 84 m3, multiple instruments analyzed air with a common water vapor mixing ratio, either by extracting air into instrument flow systems, locating instruments inside the chamber, or sampling the chamber volume optically. The intercomparison was successfully conducted over 10 days during which pressure, temperature, and mixing ratio were systematically varied (50 to 500 hPa, 185 to 243 K, and 0.3 to 152 ppm). In the absence of an accepted reference instrument, the reference value was taken to be the ensemble mean of a core subset of the measurements. For these core instruments, the agreement between 10 and 150 ppm of water vapor is considered good with variation about the reference value of about ±10% (±1σ). In the region of most interest between 1 and 10 ppm, the core subset agreement is fair with variation about the reference value of ±20% (±1σ). The upper limit of precision was also derived for each instrument from the reported data. These results indicate that the core instruments, in general, have intrinsic skill to determine unknown water vapor mixing ratios with an accuracy of at least ±20%. The implication for atmospheric measurements is that the substantially larger differences observed during in-flight intercomparisons stem from other factors associated with the moving platforms or the non-laboratory environment. The success of AquaVIT-1 provides a template for future intercomparison efforts with water vapor or other species that are focused on improving the analytical quality of atmospheric measurements on moving platforms.
Comparison between CARIBIC aerosol samples analysed by accelerator-based methods and optical particle counter measurements
Authors: Martinsson B. G. , Friberg J. , Andersson S. M. , Weigelt A. , Hermann M. , Assmann D. , Voigtländer J. , Brenninkmeijer C. A. M. , van Velthoven P. J. F. , Zahn A.
Published: April 2014

Abstract. Inter-comparison of results from two kinds of aerosol systems in the CARIBIC (Civil Aircraft for the Regular Investigation of the atmosphere Based on an Instrument Container) passenger aircraft based observatory, operating during intercontinental flights at 9–12 km altitude, is presented. Aerosol from the lowermost stratosphere (LMS), the extra-tropical upper troposphere (UT) and the tropical mid troposphere (MT) were investigated. Aerosol particle volume concentration measured with an optical particle counter (OPC) is compared with analytical results of the sum of masses of all major and several minor constituents from aerosol samples collected with an impactor. Analyses were undertaken with accelerator-based methods particle-induced X-ray emission (PIXE) and particle elastic scattering analysis (PESA). Data from 48 flights during one year are used, leading to a total of 106 individual comparisons. The ratios of the particle volume from the OPC and the total mass from the analyses were in 84% within a relatively narrow interval. Data points outside this interval are connected with inlet-related effects in clouds, large variability in aerosol composition, particle size distribution effects and some cases of non-ideal sampling. Overall, the comparison of these two CARIBIC measurements based on vastly different methods show good agreement, implying that the chemical and size information can be combined in studies of the MT/UT/LMS aerosol.
The influence of temperature calibration on the OC-EC results from a dual optics thermal carbon analyzer
Authors: Pavlovic J. , Kinsey J. S. , Hays M. D.
Published: April 2014

Abstract. Thermal-optical analysis (TOA) is a widely used technique that fractionates carbonaceous aerosol particles into organic and elemental carbon (OC and EC), or carbonate. Thermal sub-fractions of evolved OC and EC are also used for source identification and apportionment; thus, oven temperature accuracy during TOA analysis is essential. Evidence now indicates that the "actual" sample (filter) temperature and the temperature measured by the built-in oven thermocouple (or set-point temperature) can differ by as much as 50 °C. This difference can affect the OC-EC split point selection and consequently the OC and EC fraction and sub-fraction concentrations being reported, depending on the sample composition and in-use TOA method and instrument. The present study systematically investigates the influence of an oven temperature calibration procedure for TOA. A dual-optical carbon analyzer that simultaneously measures transmission and reflectance (TOT and TOR) is used, functioning under the conditions of both the NIOSH 5040 and IMPROVE protocols. Application of the oven calibration procedure to our dual optics instrument significantly changed NIOSH 5040 carbon fractions (OC and EC) and the IMPROVE OC fraction. In addition, the well-known OC-EC split difference between NIOSH and IMPROVE methods is even further perturbed following the instrument calibration. Further study is needed to determine if the wide-spread application of this oven temperature calibration procedure will indeed improve accuracy and our ability to compare among carbonaceous aerosol studies that use TOA.
Spatial scale-dependent land–atmospheric methane exchanges in the northern high latitudes from 1993 to 2004
Authors: Zhu X. , Zhuang Q. , Lu X. , Song L.
Published: April 2014

Abstract. Effects of various spatial scales of water table dynamics on land–atmospheric methane (CH4) exchanges have not yet been assessed for large regions. Here we used a coupled hydrology–biogeochemistry model to quantify daily CH4 exchanges over the pan-Arctic from 1993 to 2004 at two spatial scales of 100 km and 5 km. The effects of sub-grid spatial variability of the water table depth (WTD) on CH4 emissions were examined with a TOPMODEL-based parameterization scheme for the northern high latitudes. We found that both WTD and CH4 emissions are better simulated at a 5 km spatial resolution. By considering the spatial heterogeneity of WTD, net regional CH4 emissions at a 5 km resolution are 38.1–55.4 Tg CH4 yr−1 from 1993 to 2004, which are on average 42% larger than those simulated at a 100 km resolution using a grid-cell-mean WTD scheme. The difference in annual CH4 emissions is attributed to the increased emitting area and enhanced flux density with finer resolution for WTD. Further, the inclusion of sub-grid WTD spatial heterogeneity also influences the inter-annual variability of CH4 emissions. Soil temperature plays an important role in the 100 km estimates, while the 5 km estimates are mainly influenced by WTD. This study suggests that previous macro-scale biogeochemical models using a grid-cell-mean WTD scheme might have underestimated the regional CH4 emissions. The spatial scale-dependent effects of WTD should be considered in future quantification of regional CH4 emissions.
Holocene changes in African vegetation: tradeoff between climate and water availability
Authors: Hély C. , Lézine A.-M. , contributors APD
Published: April 2014

Abstract. Although past climate change is well documented in West Africa through instrumental records, modeling activities, and paleo-data, little is known about regional-scale ecosystem vulnerability and long-term impacts of climate on plant distribution and biodiversity. Here we use paleohydrological and paleobotanical data to discuss the relation between available surface water, monsoon rainfall and vegetation distribution in West Africa during the Holocene. The individual patterns of plant migration or community shifts in latitude are explained by differences among tolerance limits of species to rainfall amount and seasonality. Using the probability density function methodology, we show here that the widespread development of lakes, wetlands and rivers at the time of the "Green Sahara" played an additional role in forming a network of topographically defined water availability, allowing for tropical plants to migrate north from 15 to 24° N (reached ca. 9 cal ka BP). The analysis of the spatio–temporal changes in biodiversity, through both pollen occurrence and richness, shows that the core of the tropical rainbelt associated with the Intertropical Convergence Zone was centered at 15–20° N during the early Holocene wet period, with comparatively drier/more seasonal climate conditions south of 15° N.
10Be in late deglacial climate simulated by ECHAM5-HAM – Part 2: Isolating the solar signal from 10Be deposition
Authors: Heikkilä U. , Shi X. , Phipps S. J. , Smith A. M.
Published: April 2014

Abstract. This study investigates the effect of deglacial climate on the deposition of the solar proxy 10Be globally, and at two specific locations, the GRIP site at Summit, Central Greenland, and the Law Dome site in coastal Antarctica. The deglacial climate is represented by three 30 year time slice simulations of 10 000 BP (years before present = 1950 CE), 11 000 and 12 000 BP, compared with a preindustrial control simulation. The model used is the ECHAM5-HAM atmospheric aerosol–climate model, driven with sea-surface temperatures and sea ice cover simulated using the CSIRO Mk3L coupled climate system model. The focus is on isolating the 10Be production signal, driven by solar variability, from the weather- or climate-driven noise in the 10Be deposition flux during different stages of climate. The production signal varies at lower frequencies, dominated by the 11 year solar cycle within the 30 year timescale of these experiments. The climatic noise is of higher frequencies than 11 years during the 30 year period studied. We first apply empirical orthogonal function (EOF) analysis to global 10Be deposition on the annual scale and find that the first principal component, consisting of the spatial pattern of mean 10Be deposition and the temporally varying solar signal, explains 64% of the variability. The following principal components are closely related to those of precipitation. Then, we apply ensemble empirical decomposition (EEMD) analysis to the time series of 10Be deposition at GRIP and at Law Dome, which is an effective method for adaptively decomposing the time series into different frequency components. The low-frequency components and the long-term trend represent production and have reduced noise compared to the entire frequency spectrum of the deposition. The high-frequency components represent climate-driven noise related to the seasonal cycle of e.g. precipitation and are closely connected to high frequencies of precipitation. These results firstly show that the 10Be atmospheric production signal is preserved in the deposition flux to surface even during climates very different from today's both in global data and at two specific locations. Secondly, noise can be effectively reduced from 10Be deposition data by simply applying the EOF analysis in the case of a reasonably large number of available data sets, or by decomposing the individual data sets to filter out high-frequency fluctuations.
Linking mineralisation process and sedimentary product in terrestrial carbonates using a solution thermodynamic approach
Authors: Rogerson M. , Pedley H. M. , Kelham A. , Wadhawan J. D
Published: April 2014

Abstract. Determining the processes which generate terrestrial carbonate deposits (tufas, travertines and to a lesser extent associated chemical sediments such as calcretes and speleothems) is a long-standing problem. Precipitation of mineral products from solution reflects a complex combination of biological, equilibrium and kinetic processes, and the different morphologies of carbonate sediment produced by different processes have yet to be clearly demarked. Building on the groundbreaking work of previous authors, we propose that the underlying control on the processes leading to the deposition of these products can be most parsimoniously understood from the thermodynamic properties of their source solutions. Here, we report initial observations of the differences in product generated from spring and lake systems spanning a range of temperature–supersaturation space. We find that at high supersaturation, biological influences are masked by high rates of physico-chemical precipitation, and sedimentary products from these settings infrequently exhibit classic "biomediated" fabrics such as clotted micrite. Likewise, at high temperature (>40 °C) exclusion of vascular plants and complex/diverse biofilms can significantly inhibit the magnitude of biomediated precipitation, again impeding the likelihood of encountering the "bio-type" fabrics. Conversely, despite the clear division in product between extensive tufa facies associations and less spatially extensive deposits such as oncoid beds, no clear division can be identified between these systems in temperature–supersaturation space. We reiterate the conclusion of previous authors, which demonstrate that this division cannot be made on the basis of physico-chemical characteristics of the solution alone. We further provide a new case study of this division from two adjacent systems in the UK, where tufa-like deposition continuous on a metre scale is happening at a site with lower supersaturation than other sites exhibiting only discontinuous (oncoidal) deposition. However, a strong microbiological division is demonstrated between these sites on the basis of suspended bacterial cell distribution, which reach a prominent maximum where tufa-like deposits are forming. We conclude that at high supersaturation, the thermodynamic properties of solutions provide a highly satisfactory means of linking process and product, raising the opportunity of identifying water characteristics from sedimentological/petrological characteristics of ancient deposits. At low supersaturation, we recommend that future research focuses on geomicrobiological processes rather than the more traditional, inorganic solution chemistry approach dominant in the past.