bluuebunny/crossref_metadata_2025 huggingface dataset:
Live Virtual Technologies to Support Extended Events in Online Communities of Practice
Authors: Tomadaki Eleftheria , Scott Peter J. , Quick Kevin A.
Published: May 2010

Online communities of practice often require support for collaboration over extended periods of time, in what are effectively very long meetings. While there are a wide range of support systems for ‘foreground’ interactions, such as phone calls and video meetings, and a similar range of tools for ‘background’ interactions, such as email and instant messaging, there is a lack in tools that exclusively cater for extended events without switching to different platforms. The current study presents qualitative and quantitative data from a naturalistic insight into the use of two online synchronous communication tools, FM for videoconference and Hexagon for ambient awareness, to support an extended event in a working online community. A complex mix of planned and opportunistic interactions require a new set of working synchronous tools, managing the trade-off between awareness and disruption. Switching between foreground and background ‘meeting activity’ remains a very big challenge.
Individual Learning and Emotional Characteristics in Web-based Communities of Practice
Authors: Tsianos Nikos , Lekkas Zacharias , Germanakos Panagiotis , Mourlas Constantinos
Published: May 2010

The knowledge management paradigm of communities of practice can be efficiently realized in Web-based environments, especially if one considers the extended social networks that have proliferated within the Internet. In terms of increasing performance through the exchange of knowledge and shared learning, individual characteristics, such as learners’ preferences that relate to group working, may be of high importance. These preferences have been summarized in cognitive and learning styles typologies, as well as emotional characteristics which define implications that could serve as personalization guidelines for designing collaborative learning environments. This chapter discusses the theoretical assumptions of two distinct families of learning style models, cognitive personality and information processing styles (according to Curry’s onion model), and the role of affection and emotion, in order to explore the possibilities of personalization at the group level of CoP.
An Organizational Knowledge Circulation Management System for Universities
Authors: Ninomiya Toshie , Anma Fumihiko , Okamoto Toshio
Published: May 2010

In this chapter, the concept of an organizational knowledge circulation management system of e-learning is presented. The authors have developed a mentoring system module and a learning design repository based on technological and pedagogical aspects, and evaluated the system in two case studies. They also describe important functions and evaluation aspects of new information technology system of e-learning.
The Role of Learner in an Online Community of Inquiry
Authors: Cleveland-Innes Martha , Garrison Randy
Published: May 2010

Students experiencing an online educational community for the first time experience adjustment in the role of learner. Findings from a study of adjustment to online learning from the instructor’s point of view validate five main areas of adjustment identified in previous research: technology, instructor role, modes of interaction, self-identity and course design. Using a confirmatory research model, instructors from two open and distance institutions were interviewed. Data confirmed that instructors also perceive adjustment in the five areas of online experience identified by students. In addition, student adjustment in these five areas can be understood in light of core dimensions of learner role requirements in an online community of inquiry (Garrison, Anderson, and Archer, 2000). Instructor comments provide understanding of the experience of online learners, including the challenges, interventions and resolutions that present themselves as unique incidents. Recommendations for the support and facilitation of adjustment are made. Funding for this research was received from the Athabasca University Mission Critical Research Fund.
Preview
Authors: Yu Songmei , Atluri Vijayalakshmi , Adam Nabil
Published: May 2010

One of the major challenges facing a data warehouse is to improve the query response time while keeping the maintenance cost to a minimum. Recent solutions to tackle this problem suggest to selectively materialize certain views and compute the remaining views on-the-fly, so that the cost is optimized. Unfortunately, in the case of a spatial data warehouse, both the view materialization cost and the onthe- fly computation cost are often extremely high. This is due to the fact that spatial data are larger in size and spatial operations are more complex than the traditional relational operations. In this chapter, the authors propose a new notion, called preview, for which both the materialization and on-the-fly costs are significantly smaller than those of the traditional views. Essentially, to achieve these cost savings, a preview pre-processes the non-spatial part of the query, and maintains pointers to the spatial data. In addition, it exploits the hierarchical relationships among the different views by maintaining a universal composite lattice, and mapping each view onto it. The authors present a cost model to optimally decompose a spatial query into three components, the preview part, the materialized view part and the on-the-fly computation part, so that the total cost is minimized. They demonstrate the cost savings with realistic query scenarios, and implement their method to show the optimal cost savings.
Decisional Annotations
Authors: Cabanac Guillaume , Chevalier Max , Ravat Franck , Teste Olivier
Published: May 2010

This chapter deals with an annotation-based decisional system. The decisional system the authors present is based on multidimensional databases, which are composed of facts and dimensions. The expertise of decision-makers is modeled, shared and stored through annotations. These annotations allow decision-makers to carry on active analysis and to collaborate with other decision-makers on a common analysis.
Built-In Indicators to Support Business Intelligence in OLAP Databases
Authors: Cubillé Jérôme , Derquenne Christian , Goutier Sabine , Guisnel Françoise , Klajnmic Henri , Cariou Véronique
Published: May 2010

This chapter is in the scope of static and dynamic discovery-driven explorations of a data cube. It presents different methods to facilitate the whole process of data exploration. Each kind of analysis (static or dynamic) is developed for either a count measure or a quantitative measure. Both are based on the calculation, on the fly, of specific statistical built-in indicators. Firstly, a global methodology is proposed to help a dynamic discovery-driven exploration. It aims at identifying the most relevant dimensions to expand. A built-in rank on dimensions is restituted interactively, at each step of the process. Secondly, to help a static discovery-driven exploration, generalized statistical criteria are detailed to detect and highlight interesting cells within a cube slice. The cell’s degree of interest is determined by the calculation of either test-value or Chi-Square contribution. Their display is done by a color-coding system. A proof of concept implementation on the ORACLE 10g system is described at the end of the chapter.
Deploying Data Warehouses in Grids with Efficiency and Availability
Authors: de Carvalho Costa Rogério Luís , Furtado Pedro
Published: May 2010

Many global organizations are generating huge volumes of data, which are stored in highly distributed databases. These databases can be put together through a Grid infrastructure in order to form a large virtual data warehouse, which is physically distributed but can be transparently queried by Grid participants. But in Grids the system environment is heterogeneous and resource availability may vary over time, which may lead to performance degradation and data unavailability. In this chapter, the authors present Grid-NPDW which uses specialized data placement and job scheduling strategies in order to construct a Grid-based data warehouse with high performance and availability.
MUSTER
Authors: Coulin Chad , Zowghi Didar , Sahraoui Abd-El-Kader
Published: May 2010

In this chapter they present a collaborative and situational tool called MUSTER, that has been specifically designed and developed for requirements elicitation workshops, and which utilizes, extends, and demonstrates a successful application of intelligent technologies for Computer Aided Software Engineering and Computer Aided Method Engineering. The primary objective of this tool is to improve the effectiveness and efficiency of the requirements elicitation process for software systems development, whilst addressing some of the common issues often encountered in practice through the integration of intelligent technologies. The tool also offers an example of how a group support system, coupled with artificial intelligence, can be applied to very practical activities and situations within the software development process.
Impact of Design Changes on Contractors’ Cash Flow
Authors: Zainudeen MN , Kumari GRSP , Seneviratne TKKS
Published: May 2010

Several factors affect the cash flow profile of contractors. Among these design changes play a vital role. This research explores the impact of design changes on contractors' cash flow. Twenty completed building projects were selected for the analysis. It was found that design changes have a significant contribution amounting to 50% of the total cost overruns. Most of the cost overruns took place during 75% to 100% stages of the projects. Further, the results show that the impact of design changes to the contractors' cash flow was significant for M3 grade contractors than M1 and M2. When design changes occur, contractors have to search for additional interim finance than planned, often at a higher cost, which reduces their profit margin. Therefore, contractors need to consider the requirement for additional finance that may become a necessity during the execution of a project and incorporate necessary provisions when preparing a cash flow forecast. DOI: 10.4038/besl.v8i1.1905 Built-Environment Sri Lanka Vol.8(1) 2008 2-10
Key challenges to the incorporation of climatic design knowledge in contemporary tropical architecture
Authors: Emmanuel R
Published: May 2010

DOI: 10.4038/besl.v8i2.1908Built-Environment Sri Lanka Vol.8(2) 2008 23
Qualitative risk analysis framework for office developments
Authors: Zainudeen Nisa , Jeyamathan Jeyarajah
Published: May 2010

Property investment always carry significant amount of risks and uncertainties. Risk management is not much trendy practice within property developers in Sri Lanka. Risk analysis is important to realize the impact of risks and how it affects financial aspects of the developer if occurred. This research facilitates the developers to identify what are the potential risks that could occur during development and post development stages of office developments. This will further assist them in order to make decisions on alternative solutions and/or to reserve necessary funds so as to cope with risks in an effective manner by providing prior knowledge of potential risks. Identification of probable risk factors has been accomplished via semi structured interviews reinforced by findings of the literature survey. Identified risk factors in development and post development stages of office developments have been qualitatively analyzed applying a risk matrix considering the overall impact of risks in terms of significance and probability. The analysis reveals that the overall impact of risk is not very high in both office property development and management. Furthermore the risks during post development stage are lesser than at development stage. It was further revealed that most of the risks could be reduced or eliminated by means of proper planning, executing and regular monitoring in terms of consequence and/or likelihood of occurrence of risk factors. DOI: 10.4038/besl.v8i2.1910 Built-Environment Sri Lanka Vol.8(2) 2008 32-40
Managing knowledge as quantity surveyors: An exploratory case study in Sri Lanka
Authors: Senaratne S , Sabesan S
Published: May 2010

Being one of the key professionals in the construction industry who is the expert in construction cost management, quantity surveyor has a necessity to manage its knowledge to continuously learn and improve. Quantity surveyor has the responsibility to address cost, financial and contractual issues of the construction process, which is highly influenced by environmental parameters, which are very sensitive to changes and unique for every project. These key drivers have made them to relate and narrate new conditions with existing knowledge and past experience. Quantity surveyors can accomplish this expertise by learning from the past and sharing knowledge within the profession. Thus, the study which is reported in this paper is aimed at exploring issues related to quantity surveyors in Sri Lanka when managing their knowledge in order to learn and improve as professionals. Case studies were used to investigate this research problem. The case studies specifically explored key challenges faced by Quantity Surveyors and their knowledge transfer and sharing processes. These were compiled into a framework to represent the managing knowledge process of Sri Lankan Quantity Surveyors. The findings further revealed even though the Sri Lankan Quantity Surveyors are performing well in their duties with their current level of knowledge, due to very tight work schedules and comparatively low recognition to other construction professionals, there are less opportunities for them to acquire new knowledge and develop tacit knowledge base. Thus, the findings offers implications to construction industry and other professionals, too, as to improve wider knowledge dissemination mechanisms within the industry and more specific implications include for managerial level quantity surveyors to open up discussions with government departments and make them aware of quantity surveying and make it recognised in the country. Further, junior quantity surveyors should not just consider profit maximisation but also continuous professional development by acquiring and utilising new knowledge in their day-to-day work, so that the profession will develop as a whole. DOI: 10.4038/besl.v8i2.1911 Built-Environment Sri Lanka Vol.8(2) 2008 41-47
Carbamylation-Dependent Activation of T Cells: A Novel Mechanism in the Pathogenesis of Autoimmune Arthritis
Authors: Mydel Piotr , Wang Zeneng , Brisslert Mikael , Hellvard Annelie , Dahlberg Leif E. , Hazen Stanley L. , Bokarewa Maria
Published: May 2010

The posttranslational modification of proteins has the potential to generate neoepitopes that may subsequently trigger immune responses. The carbamylation of lysine residues to form homocitrulline may be a key mechanism triggering inflammatory responses. We evaluated the role of carbamylation in triggering immune responses and report a new role for this process in the induction of arthritis. Immunization of mice with homocitrulline-containing peptides induced chemotaxis, T cell activation, and Ab production. The mice also developed erosive arthritis following intra-articular injection of peptides derived from homocitrulline and citrulline. Adoptive transfer of T and B cells from homocitrulline-immunized mice into normal recipients induced arthritis, whereas systemic injection of homocitrulline-specific Abs or intra-articular injection of homocitrulline-Ab/citrulline-peptide mixture did not. Thus, the T cell response to homocitrulline-derived peptides, as well as the subsequent production of anti-homocitrulline Abs, is critical for the induction of autoimmune reactions against citrulline-derived peptides and provides a novel mechanism for the pathogenesis of arthritis.
General Preservers of Quasi-Commutativity
Authors: Dolinar Gregor , Kuzma Bojan
Published: May 2010

LetMnbe the algebra of alln×nmatrices over ℂ. We say thatA,B∈Mnquasi-commute if there exists a nonzero 𝛏 ∈ ℂ such thatAB= 𝛏BA. In the paper we classify bijective not necessarily linear maps φ:Mn→Mnwhich preserve quasi-commutativity in both directions.
The Brascamp–Lieb Polyhedron
Authors: Valdimarsson Stefán Ingi
Published: May 2010

A set of necessary and sufficient conditions for the Brascamp–Lieb inequality to hold has recently been found by Bennett, Carbery, Christ, and Tao. We present an analysis of these conditions. This analysis allows us to give a concise description of the set where the inequality holds in the case where each of the linear maps involved has co-rank 1. This complements the result of Barthe concerning the case where the linear maps all have rank 1. Pushing our analysis further, we describe the case where the maps have either rank 1 or rank 2.

A separate but related problem is to give a list of the finite number of conditions necessary and sufficient for the Brascamp–Lieb inequality to hold. We present an algorithm which generates such a list.
Transport timescales and tracer properties in the extratropical UTLS
Authors: Hoor P. , Wernli H. , Hegglin M. I.
Published: May 2010

Abstract. A comprehensive evaluation of seasonal backward trajectories initialized in the Northern Hemisphere lowermost stratosphere (LMS) has been performed to investigate the origin of air parcels and the main mechanisms determining characteristic structures in H2O and CO within the LMS. In particular we explain the fundamental role of the transit time since last tropopause crossing (tTST) for the chemical structure of the LMS as well as the feature of the extra-tropical tropopause transition layer (ExTL) as identified from CO profiles. The distribution of H2O in the background LMS above Θ=320 K and 340 K in northern winter and summer, respectively, is found to be governed mainly by the saturation mixing ratio, which in turn is determined by the Lagrangian Cold Point (LCP) encountered by each trajectory. Most of the backward trajectories from this region in the LMS experienced their LCP in the tropics and sub-tropics. The transit time since crossing the tropopause from the troposphere to the stratosphere (tTST) is independent of the H2O value of the air parcel. TST often occurs 20 days after trajectories have encountered their LCP. CO, on the other hand, depends strongly on tTST due to its finite lifetime. The ExTL as identified from CO measurements is then explained as a layer of air just above the tropopause, which on average encountered TST fairly recently.
Results from a new linear O3 scheme with embedded heterogeneous chemistry compared with the parent full-chemistry 3-D CTM
Authors: Monge-Sanz B. M. , Chipperfield M. P. , Cariolle D. , Feng W.
Published: May 2010

Abstract. A detailed full-chemistry 3-D chemistry and transport model (CTM) is used to evaluate the current stratospheric O3 parameterisation in the European Centre for Medium-Range Weather Forecasts (ECMWF) model and to obtain an alternative version of the ozone scheme implicitly including heterogeneous chemistry. The approach avoids the inaccurate treatment currently given to heterogeneous ozone chemistry in the ECMWF model, as well as the uncertainties of a cold-tracer. The new O3 scheme (COPCAT) is evaluated within the same CTM used to calculate it. It is the first time such a comparison has been possible, providing direct information on the validity of the linear parameterisation approach for stratospheric ozone. Simulated total column and O3 profiles are compared against Total Ozone Mapping Spectrometer (TOMS) and Halogen Occultation Experiment (HALOE) observations. COPCAT successfully simulates polar loss and reproduces a realistic Antarctic O3 hole. The new scheme is comparable to the full-chemistry in many regions for multiannual runs. The parameterisation produces less ozone over the tropics around 10 hPa, compared to full-chemistry and observations, however, this problem can be ameliorated by choosing a different ozone climatology for the scheme. The new scheme is compared to the current ECMWF scheme in the same CTM runs. The Antarctic O3 hole with the current ECMWF scheme is weaker and disappears earlier than with the new COPCAT scheme. Differences between the current ECMWF scheme and COPCAT are difficult to explain due to the different approach used for heterogeneous chemistry and differences in the photochemical models used to calculate the scheme coefficients. Results with the new COPCAT scheme presented here show that heterogeneous and homogeneous ozone chemistry can be included in a consistent way in a linear ozone parameterisation, without any additional tunable parameters, providing a parameterisation scheme in much better agreement with the current knowledge of stratospheric O3 chemistry than previous approaches.
Interplanetary shock transmitted into the Earth's magnetosheath: Cluster and Double Star observations
Authors: Pallocchia G. , Samsonov A. A. , Bavassano Cattaneo M. B. , Marcucci M. F. , Rème H. , Carr C. M. , Cao J. B.
Published: May 2010

Abstract. On day 7 May 2005, the plasma instruments on board Double Star TC1 and Cluster SC3 spacecraft register inside the magnetosheath, at 19:15:12 and 19:16:20 UT, respectively, a strong pressure pulse due to the impact of an interplanetary shock wave (IS) on the terrestrial bow shock. The analysis of this event provides clear and quantitative evidences confirming and strengthening some results given by past simulations and observational studies. In fact, here we show that the transmitted shock is slowed down with respect to the incident IS (in the Earth's reference frame) and that, besides the transmitted shock, the IS – bow shock interaction generates a second discontinuity. Moreover, supported also by a special set three-dimensional magnetohydrodynamic simulation, we discuss, as further effects of the interaction of the IS with the magnetosphere, other two interesting aspects of the present event, that is: the TC1 double crossing of the bow shock (observed few minutes after the impact of the IS) and the presence, only in the SC3 data, of a third discontinuity produced inside the magnetosheath.
Stratigraphic analysis of lake level fluctuations in Lake Ohrid: an integration of high resolution hydro-acoustic data and sediment cores
Authors: Lindhorst K. , Vogel H. , Krastel S. , Wagner B. , Hilgers A. , Zander A. , Schwenk T. , Wessels M. , Daut G.
Published: May 2010

Abstract. Ancient Lake Ohrid is a steep sided, oligotrophic, karst lake of likely Pliocene age and often referred to as a hotspot of endemic biodiversity. This study aims on tracing significant lake level fluctuations at Lake Ohrid using high-resolution acoustic data in combination with lithological, geochemical, and chronological information from two sediment cores recovered from sub-aquatic terrace levels at ca. 32 and 55 m. According to our data, significant lake level fluctuations with prominent lowstands of ca. 60 and 35 m below the present water level occurred during MIS 6 and MIS 5, respectively. The effect of these lowstands on biodiversity in most coastal parts of the lake is negligible, due to only small changes in lake surface area, coastline, and habitat. In contrast, biodiversity in shallower areas was more severely affected due to disconnection of today sub-lacustrine springs from the main water body. Multichannel seismic data from deeper parts of the lake clearly imaged several clinoform structures stacked on top of each other. These stacked clinoforms indicate significantly lower lake levels prior to MIS 6 and a stepwise rise of water level with intermittent stillstands since its existence as water filled body, which might have caused enhanced expansion of endemic species within Lake Ohrid.
Do periodic consolidations of Pacific countercurrents trigger global cooling by equatorially symmetric La Niña?
Authors: Duke J. H.
Published: May 2010

Abstract. A sporadic phenomenon of internal tide resonance (ITR) in the western equatorial Pacific thermocline is shown to precede 11 of 12 major upturns in the Niño 3.4 index between 1992 and 2008. Observed ITR has up to 9 °C semidiurnal temperature excursions indicating thermocline heave, but is invisible in time resolution longer than one day. It is independent of westerly wind bursts (WWB). A hypothesis is advanced that (1) ITR dissipates vorticity, leading to Pacific countercurrent consolidation (PCC) by reducing the vortex stretching term in Sverdrup balance. The consequence of lost vorticity survives ephemeral ITR events; (2) The specific surface area of countercurrents is reduced by PCC, which reduces frictional opposition to zonal gradient pressure, which triggers eastward advection at El Niño onset; (3) PCC also accelerates transfer of potential energy to the "pycnostad" below the Equatorial Undercurrent. This shoals the equatorial thermocline, leading to a distinct mode of equatorially symmetric La Niña (ESLN) characterized by a winter monsoon cell above a "cold eye" that is separated from the South American continent, as in 1998; (4) Precessional southward intertropical convergence zone migration (ITCZ) is an alternate PCC trigger, but its effect is modulated by obliquity; and (5) ESLN causes global cooling in all timescales by (a) reduced Hadley cell water vapor production when its rising branch is above the cold eye, (b) equatorward shift in southern circumpolar westerlies due to Hadley cell constriction, (c) possible CO2 sequestration by increased EUC iron fertilized export production on the equator, and (d) possible adjacent cloud seeding by biogenic dimethyl sulphide. Surprising coincidences of WWB with perigean eclipses suggest a parallel atmospheric tide influence. Proposed PCC-ESLN forcing operates in multiple timescales, beginning where the annual cycle of strong equinoctial tides coincides with the minimum perigee cycle. This forcing corresponds with El Niño Southern Oscillation (ENSO) events in 1997, 2002, and 2006. Next, extreme central eclipses that perturb perigee-sysygy intervals also correspond with extreme ENSO events, notably in 1877, 1888, and 1982, and a 586 year cycle in the frequency of these eclipses corresponds with known stadial events in the past 4 thousand years. Contrast in the 586 year cycle increases with Earth eccentricity because it is the result of shorter synodic months at aphelion. Longer timescale forcing is by orbital control of the east-central Pacific ITCZ position, yielding a 10 thousand year fast ice sheet melt interval between March and September perihelion. But default ESLN is only interrupted when perihelion in March coincides with rising obliquity. A change in the phase relation between obliquity and precession from 1:2 to 3:5 or 2:5 may therefore explain skipped obliquity cycles after the mid-Pleistocene transition. A secular improvement in eclipse commensurability that parallels Cenozoic cooling is noted.
Climatic and ecological future of the Amazon: likelihood and causes of change
Authors: Cook B. , Zeng N. , Yoon J.-H.
Published: May 2010

Abstract. Some recent climate modeling results suggested a possible dieback of the Amazon rainforest under future climate change, a prediction that raised considerable interest as well as controversy. To determine the likelihood and causes of such changes, we analyzed the output of 15 models from the Intergovernmental Panel on Climate Change Fourth Assessment Report (IPCC/AR4) and a dynamic vegetation model VEGAS driven by these climate output. Our results suggest that the core of the Amazon rainforest should remain largely stable as rainfall is projected to increase in nearly all models. However, the periphery, notably the southern edge of the Amazon and further south in central Brazil, are in danger of drying out, driven by two main processes. Firstly, a decline in precipitation of 22% in the southern Amazon's dry season (May–September) reduces soil moisture, despite an increase in precipitation during the wet season, due to nonlinear responses in hydrology and ecosystem dynamics. Two dynamical mechanisms may explain the lower dry season rainfall: (1) a general subtropical drying under global warming when the dry season southern Amazon is under the control of the subtropical high pressure; (2) a stronger north-south tropical Atlantic sea surface temperature gradient, and to lesser degree a warmer eastern equatorial Pacific. Secondly, evaporation demand will increase due to the general warming, further reducing soil moisture. In terms of ecosystem response, higher maintenance cost and reduced productivity under warming may also have additional adverse impact. The drying corresponds to a lengthening of the dry season by 11 days. As a consequence, the median of the models projects a reduction of 20% in vegetation carbon stock in the southern Amazon, central Brazil, and parts of the Andean Mountains. Further, VEGAS predicts enhancement of fire risk by 10–15%. The increase in fire is primarily due to the reduction in soil moisture, and the decrease in dry season rainfall, which is when fire danger reaches its peak. Because the southern Amazon is also under intense human influence as a result of deforestation and land use, added pressure to the region's ecosystems from climate change may subject the region to profound changes in the 21st century.
Kristian Birkeland's pioneering investigations of geomagnetic disturbances
Authors: Egeland A. , Burke W. J.
Published: May 2010

Abstract. More than 100 years ago Kristian Birkeland (1967–1917) addressed questions that had vexed scientists for centuries. Why do auroras appear overhead while the Earth's magnetic field is disturbed? Are magnetic storms on Earth related to disturbances on the Sun? To answer these questions Birkeland devised terrella simulations, led coordinated campaigns in the Arctic wilderness, and then interpreted his results in the light of Maxwell's synthesis of laws governing electricity and magnetism. After analyzing thousands of magnetograms, he divided disturbances into 3 categories: 1. Polar elementary storms are auroral-latitude disturbances now called substorms. 2. Equatorial perturbations correspond to initial and main phases of magnetic storms. 3. Cyclo-median perturbations reflect enhanced solar-quiet currents on the dayside. He published the first two-cell pattern of electric currents in Earth's upper atmosphere, nearly 30 years before the ionosphere was identified as a separate entity. Birkeland's most enduring contribution toward understanding geomagnetic disturbances flowed from his recognition that field-aligned currents must connect the upper atmosphere with generators in distant space. The existence of field-aligned currents was vigorously debated among scientists for more than 50 years. Birkeland's conjecture profoundly affects present-day understanding of auroral phenomena and global electrodynamics. In 1896, four years after Lord Kelvin rejected suggestions that matter passes between the Sun and Earth, and two years before the electron was discovered, Birkeland proposed current carriers are "electric corpuscles from the Sun" and "the auroras are formed by corpuscular rays drawn in from space, and coming from the Sun". It can be reasonably argued that the year 1896 marks the founding of space plasma physics. Many of Birkeland's insights were rooted in observations made during his terrella experiments, the first attempts to simulate cosmic phenomena within a laboratory. Birkeland's ideas were often misinterpreted or dismissed, but were verified when technology advances allowed instrumented spacecraft to fly in space above the ionosphere.
FEM and ANN combined approach for predicting pressure source parameters at Etna volcano
Authors: Di Stefano A. , Currenti G. , Del Negro C. , Fortuna L. , Nunnari G.
Published: May 2010

Abstract. A hybrid approach for forward and inverse geophysical modeling, based on Artificial Neural Networks (ANN) and Finite Element Method (FEM), is proposed in order to properly identify the parameters of volcanic pressure sources from geophysical observations at ground surface. The neural network is trained and tested with a set of patterns obtained by the solutions of numerical models based on FEM. The geophysical changes caused by magmatic pressure sources were computed developing a 3-D FEM model with the aim to include the effects of topography and medium heterogeneities at Etna volcano. ANNs are used to interpolate the complex non linear relation between geophysical observations and source parameters both for forward and inverse modeling. The results show that the combination of neural networks and FEM is a powerful tool for a straightforward and accurate estimation of source parameters in volcanic regions.
A gain modification form for Kalman filtering under state inequality constraints
Authors: Sircoulomb V. , Hoblos G. , Chafouk H.
Published: May 2010

This paper presents a method for dealing with Kalman filtering under particular classes of nonlinear state model and state inequality constraints. This method is based on a modification of the optimal Kalman gain in order to enforce the state constraints if necessary. The proposed method is applied to a nonlinear hydraulic system in order to highlight the efficiency of this method. Copyright © 2010 John Wiley & Sons, Ltd.
Boosting the Non Linear Optical Response of Carbon Nanotube Saturable Absorbers for Broadband Mode‐Locking of Bulk Lasers
Authors: Cho W. B. , Yim J. H. , Choi S. Y. , Lee S. , Schmidt A. , Steinmeyer G. , Griebner U. , Petrov V. , Yeom D.‐I. , Kim K. , Rotermund F.
Published: May 2010

Single‐walled carbon‐nanotube absorbers are experimentally demonstrated for laser mode‐locking. A saturable absorber device is used to mode‐lock three different bulk solid‐state lasers in a 500 nm‐wide wavelength interval. The devices exhibit a low saturation fluence of <10 µJ cm−2, low scattering losses, and an exceptionally rapid relaxation, with time constants reaching <100 fs. The latter two properties are explained by a decreased curling tendency and increased tube‐to‐tube interactions of the nanotubes, respectively. These properties are the result of an optimized manufacturing procedure in combination with the use of a starting material with a higher microscopic order. The decreased scattering enables universal use of these devices in bulk solid‐state lasers, which tend to be highly sensitive against non‐saturable device losses as caused by scattering. The favorable saturable absorption properties are experimentally verified by mode‐locking the three lasers, which all exhibit near transform‐limited performance with about 100 fs pulse duration. The complete and unconditional absence of Q‐switching side bands verifies the small saturation fluence of these devices.
Neuromotor effects of short‐term and long‐term exposures to trichloroethylene in workers
Authors: Murata Katsuyuki , Inoue Osamu , Akutsu Masanori , Iwata Toyoto
Published: May 2010

Background

Health effects of long‐term exposure to organic solvents at low levels are a major concern in industrialized countries. To assess the neuromotor impact of trichloroethylene objectively, static postural sway and hand tremor parameters, along with urinary trichloroethanol (TCOH) and trichloroacetic acid (TCAA) levels, were investigated in 57 workers without obvious neurological disorders and 60 control subjects.

Methods

The workers had been occupationally exposed to trichloroethylene for 0.1–37 years. The cumulative exposure index (CEI) was calculated from their occupational history and total trichloro‐compounds (TCOH + TCAA).

Results

Median levels in the workers were 1.7 mg/L for TCOH and 2.5 mg/L for TCAA, and the maximum ambient trichloroethylene concentration was estimated to be <22 ppm from the previously reported equation using TCOH + TCAA. Sway parameters with eyes open and tremor intensity in dominant hand were significantly larger in the exposed workers than in the control subjects when adjusting for possible confounders. A significant dose–effect association was seen between two sway parameters and urinary TCOH level in the workers. Tremor intensities in non‐dominant hand differed significantly among three groups of the workers divided according to the CEI.

Conclusions

These findings suggest that trichloroethylene exposure, even at low levels of less than the short‐term exposure limit by the ACGIH, can affect the neuromotor function of workers. The postural instability appears to result from recent exposure, and the increased tremor may occur due to short‐term and long‐term exposures. Hereafter, such objective measures, along with subjective symptoms, should be carefully used for the occupational exposure limit setting. Am. J. Ind. Med. 53:915–921, 2010. © 2010 Wiley‐Liss, Inc.
New evidence on the health hazards and control of metalworking fluids since completion of the OSHA advisory committee report
Authors: Mirer Franklin E.
Published: May 2010

Background

Metalworking fluids (MWF) are used in the manufacture of engines, transmissions, chassis parts and other products. In 2003, OSHA denied a union petition to promulgate a standard for MWF. The 3rd Circuit Court of Appeals rejected a union lawsuit to compel OSHA to regulate MWF. OSHA relied exclusively on the 1999 Metal Working Fluids Standards Advisory Committee report, therefore, only evidence available before 1999 was quoted supporting the denial. This review was conducted to identify studies published since 1998.

Methods

Electronic reference sources were queried for the terms for metalworking fluids, machining fluids, cutting fluids, cutting oils, coolants, machining, and machinist. All items returned were reviewed for relevance to MWF regulation.

Results

The review noted 227 reports in the peer reviewed literature directly relevant to regulation of MWF exposures. Of these, 26 addressed cancer; 58 respiratory effects; 32 skin effects or absorption; 45 microbial contaminants; and 76 exposure measurements and controls. Three major studies identified excess cancer including lung, liver, pancreatic, laryngeal, and leukemia associated with MWF exposures. Reports strengthened associations of asthma and hypersensitivity pneumonitis with recent exposure to MWF.

Conclusions

Material new evidence demonstrates significant risks to material impairment of health at prevailing exposure levels and feasibility of lower exposure limits. Am. J. Ind. Med. 53:792–801, 2010. © 2010 Wiley‐Liss, Inc.
Solution polymerization of N‐vinylcaprolactam in 1,4‐dioxane. Kinetic dependence on temperature, monomer, and initiator concentrations
Authors: Medeiros Simone F. , Barboza Jayne C. S. , Ré Maria I. , Giudici Reinaldo , Santos Amilton M.
Published: May 2010

The kinetics of the solution free radical polymerization of N‐vinylcaprolactam, in 1,4‐dioxane and under various polymerization conditions was studied. Azobisisobutyronitrile and 3‐mercaptopropionic acid were used as initiator and as chain transfer agent (CTA), respectively. The influence of monomer and initiator concentrations and polymerization temperature on the rate of polymerizations (Rp) was investigated. In general, high conversions were obtained. The order with respect to initiator was consistent with the classical kinetic rate equation, while the order with respect to the monomer was greater than unity. The overall activation energy of 53.6 kJ mol−1 was obtained in the temperature range 60–80 °C. The decreasing of the absolute molecular weights when increasing the CTA concentration was confirmed by GPC/SEC/LALS analyses. It was confirmed by UV‐visible analyses the effect of molecular weights on the lower critical solution temperature of the polymers. It was also verified that the addition of the CTA influenced the kinetic of the polymerizations. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Effects of glycerol content and film thickness on the properties of vital wheat gluten films cast at pH 4 and 11
Authors: Cho S.‐W. , Gällstedt M. , Hedenqvist M. S.
Published: May 2010

This study deals with the optical properties and plasticizer migration properties of vital wheat gluten (WG) films cast at pH 4 and 11. The films contained initially 8, 16, and 25 wt % glycerol and were aged at 23°C and 50% relative humidity for at least 17 weeks on a paper support to simulate a situation where a paper packaging is laminated with an oxygen barrier film of WG. The films, having target thicknesses of 50 and 250 μm, were characterized visually and with ultraviolet/visible and infrared spectroscopy; the mass loss was measured by gravimetry or by a glycerol‐specific gas chromatography method. The thin films produced at pH 4 were, in general, more heterogeneous than those produced at pH 11. The thin pH 4 films consisted of transparent regions surrounding beige glycerol‐rich regions, the former probably rich in gliadin and the latter rich in glutenin. This, together with less Maillard browning, meant that the thin pH 4 films, in contrast to the more homogeneous (beige) thin pH 11 films, showed good contact clarity. The variations in glycerol content did not significantly change the optical properties of the films. All the films showed a significant loss of glycerol to the paper support but, after almost 9 months, the thick pH 11 film containing initially 25 wt % glycerol was still very flexible and, despite a better contact to the paper, had a higher residual glycerol content than the pH 4 film, which was also more brittle. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Preparation and characterization of graphene/poly(vinyl alcohol) nanocomposites
Authors: Jiang Lei , Shen Xiao‐Ping , Wu Ji‐Li , Shen Ke‐Cheng
Published: May 2010

Graphene (GE)‐based nanocomposites are emerging as a new class of materials that hold promise for many applications. In this article, we present a general approach for the preparation of GE/poly(vinyl alcohol) (PVA) nanocomposites. The basic strategy involved the preparation of graphite oxide from graphite, complete exfoliation of graphite oxide into graphene oxide sheets, followed by reduction to GE nanosheets, and finally, the preparation of the GE/PVA nanocomposites by a simple solution‐mixing method. The synthesized products were characterized by X‐ray diffraction, field emission scanning electron microscopy, Fourier transform infrared spectroscopy, thermogravimetry, and differential scanning calorimetry analysis. The GE nanosheets were well dispersed in the PVA matrix, and the restacking of the GE sheets was effectively prevented. Because of the strong interfacial interaction between PVA and GE, which mainly resulted from the hydrogen‐bond interaction, together with the improvement in the PVA crystallinity, the mechanical properties and thermal stability of the nanocomposites were obviously improved. The tensile strength was increased from 23 MPa for PVA to 49.5 MPa for the nanocomposite with a 3.25 wt % GE loading. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Influence of environmental conditioning on the shear behavior of poly(phenylene sulfide)/glass fiber composites
Authors: Costa A. P. , Botelho E. C. , Pardini L. C.
Published: May 2010

Advanced thermoplastic composites are an alternative because of their ease of processing and storage. Poly(phenylene sulfide) (PPS) stands out among these materials because of its structural characteristics; for instance, it provides size, shape, and thermal stability, low moisture absorption, excellent chemical resistance, and good mechanical properties, including flexure, strength, and shear properties, compared to thermoset composites. Thus, the objective of this study was to evaluate the influence of environmental conditioning on the shear strength behavior of PPS/glass fiber composites. For this reason, first, some samples were treated to UV‐light exposure in a chamber. Other samples were immersed in seawater and hygrothermal baths simultaneously. They were tested with the interlaminar shear strength (ILSS) and Iosipescu shear test methods. The shear values obtained for the treated samples were compared against the dry sample values. For all samples tested with the ILSS and Iosipescu methods, the results indicate that the PPS/glass fiber composites presented a decrease in shear strength after they were submitted to hygrothermal and seawater solution conditioning. The moisture absorption was not uniform throughout the material, and wet conditioning induced strong matrix plasticization, which reduced the shear strength values of the laminates. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Effect of weight ratio of thermoplastic and thermosetting boron‐containing phenolic resin on mechanical, bonding, and ablative properties of thermal insulating composites
Authors: Gao Guoxin , Zhang Zhicheng , Li Xuefei , Meng Qingjie , Zheng Yuansuo , Jin Zhihao
Published: May 2010

To improve the tensile strength, the bond strength, and the ablation resistant properties as well as the elongation at break of the short aramid fibers reinforced EPDM‐based thermal insulation composites, two kinds of boron‐containing phenolic resin, thermoplastic (TPBPR) and thermosetting (TSBPR), were added into the composites with a series of weight ratio of TPBPR and TSBPR, such as 0 : 20, 5 : 15, 10 : 10, 15 : 5, and 20 : 0. The effects of TPBPR and TSBPR weight ratio on the mechanical, bonding, and ablative properties of the composites were investigated systematically, respectively. The results showed that the crosslink density, the tensile strength, the bond strength, and the ablation resistant abilities of the composites decrease continuously with the increasing weight ratio, which confirms that the mechanical reinforcement and the ablation resistant abilities of TSBPR are higher than that of TPBPR. However, the elongation increases sharply with TPBPR and TSBPR weight ratio increasing. Therefore, the optimal weight ratio of TPBPR and TSBPR should be 10 : 10 to obtain the very thermal insulation composites with the excellent comprehensive properties. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Pressure dependence of the CO2/propylene oxide copolymerization catalyzed by zinc glutarate
Authors: Jintang Duan , Jiajun Wang , Lianfang Feng , Long Wang , Xueping Gu
Published: May 2010

The pressure dependence of the CO2/propylene oxide copolymerization catalyzed by zinc glutarate was studied in this article. The effects of pressure on the product composition, yield, backbone structure of poly(propylene carbonate) (PPC), molecular weight and its distribution, and thermal stability were systematically investigated. Low pressure favored formation of byproducts (cyclic carbonate and polyether), whereas PPC still covered the majority of the product under 0.5 MPa. The copolymerization rate increased with pressure increasing under low pressures. Higher pressure led to a decline in the polymer yield because of catalyst/epoxide dilution. On the other hand, the carbonate linkage fraction decreased slightly with the drop of pressure, from 99% at 5.2 MPa to 96% at 0.5 MPa. All the PPCs synthesized under different pressures exhibited high molecular weights and broad distributions. However, the polymer prepared under 0.5 MPa possessed a relatively lower thermal stability than others. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010