1,776 research outputs found
Particulate barium tracing of significant mesopelagic carbon remineralisation in the North Atlantic
The remineralisation of sinking particles by prokaryotic heterotrophic activity is important for controlling oceanic carbon sequestration. Here, we report mesopelagic particulate organic carbon (POC) remineralisation fluxes in the North Atlantic along the GEOTRACES-GA01 section (GEOVIDE cruise; May-June 2014) using the particulate biogenic barium (excess barium; Baxs/ proxy. Important mesopelagic (100-1000 m) Baxs differences were observed along the transect depending on the intensity of past blooms, the phytoplankton community structure, and the physical forcing, including downwelling. The subpolar province was characterized by the highest mesopelagic Baxs content (up to 727 pmol L-1/, which was attributed to an intense bloom averaging 6 mg chl a m-3 between January and June 2014 and by an intense 1500m deep convection in the central Labrador Sea during the winter preceding the sampling. This downwelling could have promoted a deepening of the prokaryotic heterotrophic activity, increasing the Baxs content. In comparison, the temperate province, characterized by the lowest Baxs content (391 pmol L-1/, was sampled during the bloom period and phytoplankton appear to be dominated by small and calcifying species, such as coccolithophorids. The Baxs content, related to oxygen consumption, was converted into a remineralisation flux using an updated relationship, proposed for the first time in the North Atlantic. The estimated fluxes were of the same order of magnitude as other fluxes obtained using independent methods (moored sediment traps, incubations) in the North Atlantic. Interestingly, in the subpolar and subtropical provinces, mesopelagic POC remineralisation fluxes (up to 13 and 4.6 mmol Cm-2 d-1, respectively) were equalling and occasionally even exceeding upper-ocean POC export fluxes, deduced using the 234Th method. These results highlight the important impact of the mesopelagic remineralisation on the biological carbon pump of the studied area with a near-zero, deep (> 1000 m) carbon sequestration efficiency in spring 2014
The Allure of Technology: How France and California Promoted Electric Vehicles to Reduce Urban Air Pollution
All advanced industrialized societies face the problem of air pollution produced by motor vehicles. In spite of striking improvements in internal combustion engine technology, air pollution in most urban areas is still measured at levels determined to be harmful to human health. Throughout the 1990s and beyond, California and France both chose to improve air quality by means of technological innovation, adopting legislation that promoted clean vehicles, prominently among them, electric vehicles (EVs). In California, policymakers chose a technology-forcing approach, setting ambitious goals (e.g., zero emission vehicles), establishing strict deadlines and issuing penalties for non-compliance. The policy process in California called for substantial participation from the public, the media, the academic community and the interest groups affected by the regulation. The automobile and oil industries bitterly contested the regulation, in public and in the courts. In contrast, in France the policy process was non-adversarial, with minimal public participation and negligible debate in academic circles. We argue that California's stringent regulation spurred the development of innovative hybrid and fuel cell vehicles more effectively than the French approach. However, in spite of the differences, both California and France have been unable to put a substantial number of EVs on the road. Our comparison offers some broad lessons about how policy developments within a culture influence both the development of technology and the impact of humans on the environment.Environmental policy, Electric vehicles, Air pollution, Technology policy, Sustainable transport
Opportunities and Limits for MayoralâPublic Employee Union Collaborations: The Case of the de Blasio Administration in New York City, 2013â2017
This dissertation sheds light on how the relations between public employeesâ unions and the de Blasio administration shape the design and implementation of local policies in areas of particular concern to public workers. It asks how public sector labor-management relations and public sector employee unionsâ political influence affect this mayoral administrationâs efforts at policy innovation and administrative practice. In particular, how, if at all, do public employee unions shape the administrationâs decisions about the balance between providing public services directly versus contracting them out to nongovernmental organizations? How do these relations affect the direction of institutional reform? This project does not attempt to develop a general model of the political influence of public sector labor unions, but it does identify the potential for and limits to their policy entrepreneurship in an environment that should be unusually supportive. A close examination of three major New York City unions reveals that while these public employeesâ unions differ greatly from each other and take varying approaches toward influencing policymaking, they are all constrained by their internal dilemmas and interunion fragmentation, which limit their impact on administrative decision-making. At the same time, the Mayorâs attitude toward the cityâs workforce is a significant factor in how much access and power unions have over policy formation
The Biogeochemical Cycling of Particulate Trace Metals off the Southwest African and Peruvian Shelves
Marine particles in the ocean play an important role in the marine biogeochemical cycling of trace metals (TMs), yet our understanding of the marine biogeochemical cycling of TMs remains incomplete. Additionally, particulate TM (pTM) datasets from key dynamic regions of the global ocean, such as continental shelves, upwelling sites, and oxygen minimum zones (OMZs), are lacking, impeding progress toward fully understanding the processes which impact pTM cycling and distributions. This work studies the biogeochemical cycling of particulate iron (Fe), manganese (Mn), cobalt (Co), aluminum (Al), copper (Cu), nickel (Ni), zinc (Zn), cadmium (Cd), lead (Pb), titanium (Ti), vanadium (V), and phosphorus (P) on the SW African and Peruvian shelves, employing a chemical leach to marine particles collected on two separate research expeditions. The distributions and biogeochemical cycling of biogeochemical tracers, molybdenum (Mo), barium (Ba), chromium (Cr), tungsten (W), thorium (Th), and uranium (U) are explored only on the SW African shelf. Transects from these sites traversed through contrasting biogeochemical regimes with diverse particle sources, including the Benguela and Humboldt upwelling regions, OMZs, and the Congo River plume, offering unique gradients under which pTM cycling can be studied. Differentiating between labile and refractory pTM fractions, provided a more accurate assessment of the biogeochemical behavior and fate of pTMs within the different marine environments. Elemental ratios and particle type proxies were also utilized to determine redox and scavenging processes, and biological uptake of TMs in the water column. This approach allowed for the characterization of the principal carrier phases of pTMs in the water column, which is a critical step toward constraining the mechanisms that control their fate and interactions with dissolved phases in the water column
Effets de la composition forestiÚre initiale et du temps depuis le dernier feu sur la dynamique des combustibles et du comportement du feu dans la pessiÚre à mousse de la ceinture d'argile du Québec
TrĂšs peu d'Ă©tudes concernant la dynamique des combustibles dans la forĂȘt borĂ©ale existent, et encore moins dans les peuplements Ă fort potentiel de paludification comme dans la pessiĂšre Ă mousse de la ceinture d'argile de l'est du Canada. L'objectif gĂ©nĂ©ral de ce mĂ©moire est donc d'Ă©tudier les interactions entre le TDF, les compositions initiales et plusieurs caractĂ©ristiques des combustibles, et de vĂ©rifier leurs effets potentiels sur le comportement des feux. Plus prĂ©cisĂ©ment, le chapitre 1 vise Ă comprendre comment s'accumulent et/ou s'arrangent les diffĂ©rentes catĂ©gories de combustibles selon le TDF et la composition initiale. De son cĂŽtĂ©, le chapitre 2 concerne l'analyse du comportement des feux potentiels reliĂ©s Ă ces combustibles avec deux logiciels de prĂ©vision des incendies forestiers (FBP - Fire Behavior Prediction et BehavePlus 5.0). Pour atteindre ces objectifs, nous avons inventoriĂ© les caractĂ©ristiques des combustibles dans 61 sites ĂągĂ©s de 11 Ă 356 ans et catĂ©gorisĂ©s dans 4 compositions initiales diffĂ©rentes Ă©tant dominĂ©es en dĂ©but de succession par : 1) le peuplier faux-tremble (PTR), 2) le pin gris (PBA), 3) l'Ă©pinette issue d'un feu sĂ©vĂšre (PMA-S) et issue d'un feu non sĂ©vĂšre (PMA-N). Dans le premier chapitre, il est dĂ©montrĂ© que la composition initiale a un effet important sur les caractĂ©ristiques des combustibles, alors que le TDF en a que trĂšs peu. Les plus grandes diffĂ©rences sont observĂ©es entre les chronosĂ©quences de PTR et de PMA-N. En effet, contrairement Ă la composition initiale de PTR, celle de PMA-N tend Ă avoir une charge de matiĂšre morte au sol moindre, tout en ayant une meilleure continuitĂ© entre les diffĂ©rentes strates de combustibles. Nous montrons aussi, qu'Ă l'inverse de certains autres biomes forestiers, il y a peu d'accumulation de combustibles avec le TDF. Dans le deuxiĂšme chapitre, les rĂ©sultats se rapportant au comportement du feu associĂ©s avec les valeurs de combustibles sont diffĂ©rents selon le modĂšle de comportement du feu utilisĂ©. Ătonnamment, dans les deux modĂšles, la composition initiale de PMA-N possĂšde la plus grande vitesse de propagation. Dans FBP, l'intensitĂ© y Ă©tait mĂȘme maximale. De plus, les diffĂ©rences significatives au niveau de la charge en combustible entre les compositions initiales de PTR et des autres compositions initiales se sont traduites en comportements trĂšs diffĂ©rents dans les deux modĂšles. Nos conclusions sont donc que la paludification a un effet indirect sur la dynamique des combustibles en pessiĂšre Ă mousse. Cet effet s'opĂšre lors de la transformation de la composition des forĂȘts avec le TDF, qui elle, a un effet direct sur plusieurs caractĂ©ristiques des combustibles. NĂ©anmoins, nous soulignons le fait que les rĂ©sultats portant sur le comportement du feu proviennent d'outils de prĂ©vision qui ne sont pas adaptĂ©s Ă la pessiĂšre Ă mousse en ceinture d'argile et qu'il serait important de les amĂ©liorer en implantant un nouveau module de prĂ©vision de la combustion lente au sol et/ou un nouveau type de combustible incorporant les modifications en structure des peuplements paludifiĂ©s pour le FBP.\ud
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Evaluation of a proton pencil bean algorithm for dose calculations in heterogenous media
Purpose: To develop an improved nuclear halo dose model of a pencil beam algorithm (PBA) for dose calculation of proton beams in heterogeneous media. Methods: The proton PBA consisted of a central axis term and an off axis term. The central axis term was determined from a central axis depth dose profile of a Monte Carlo simulated proton beam in water and was scaled by a mass stopping power ratio to account for other materials. The off axis term was determined from Fermi-Eyges scattering theory with material-dependent scattering powers to calculate the lateral spread of the proton beam in heterogeneous media. The nuclear halo dose, which was caused by large angle and non-elastic scattering events, was modeled using two terms: a Gaussian distribution and a Cauchy-Lorentz distribution. Depth-dependent widths and amplitudes of each distribution were determined by fitting a simulated 1-mm x 1-mm pencil beam in water. The PBA was evaluated in approximately 30 test phantoms containing bone and/or air heterogeneities at 4 energies and for 2 field sizes. Agreement between PBA and Monte Carlo simulations of the test conditions was quantified by computing the percentage of points within 2 percent dose difference or 1 mm distance to agreement. Results: With the improved nuclear halo model, PBA calculations showed better than of 97% of dose points within 2% or 1 mm of MC distributions for all geometries examined. For phantoms containing laterally infinite heterogeneities, agreement between PBA and MC distributions was 100% at 2% or 1mm. For phantoms containing laterally finite heterogeneities, agreement was at least 97%. The points failing were due to the central axis approximation of the PBA in regions not influenced by the nuclear halo model. Conclusions: The nuclear halo model developed in this work improves the agreement of the PBA with MC simulations in heterogeneous phantoms, particularly in low-dose regions that can be important for scanned-beam proton therapy
INTELLIGENTE TRANSPORT SYSTEMEN ITS EN VERKEERSVEILIGHEID
This report discusses Intelligent Transport Systems (ITS). This generic term is used for a broad range of information-, control- and electronic technology that can be integrated in the road infrastructure and the vehicles themselves, saving lives, time and money bymonitoring and managing traffic flows, reducing conges-tion, avoiding accidents, etc.
Because this report was written in the scope of the Policy Research Centre Mobility & Public Works, track Traffic Safety, it focuses on ITS systems from the traffic safety point of view.
Within the whole range of ITS systems, two categories can be distinguished: autonomous and cooperative systems. Autonomous systems are all forms of ITS which operate by itself, and do not depend on the cooperation with other vehicles or supporting
infrastructure. Example applications are blind spot detection using radar, electronic stability control, dynamic traffic management using variable road signs, emergency call, etc. Cooperative systems are ITS systems based on communication and cooperation, both between vehicles as between vehicles and infrastructure. Example applications are alerting vehicles approaching a traffic jam, exchanging data regarding hazardous road conditions, extended electronic brake light, etc. In some cases, autonomous systems can evolve to autonomous cooperative systems. ISA (Intelligent Speed Adaptation) is an
example of this: the dynamic aspect as well as communication with infrastructure (eg Traffic lights, Variable Message Sign (VMS)...) can provide additional road safety. This is the clear link between the two parts of this report.
The many ITS applications are an indicator of the high expectations from the government, the academic world and the industry regarding the possibilities made possible by both categories of ITS systems. Therefore, the comprehensive discussion of both of them is the core of this report.
The first part of the report covering the autonomous systems treats two aspects:
1. Overview of European projects related to mobility and in particular to road safety
2. Overview for guidelines for the evaluation of ITS projects.
Out of the wide range of diverse (autonomous) ITS applications a selection is made; this selection is focused on E Safety Forum and PreVENT. Especially the PreVent research project is interesting because ITS-applications have led to a number of concrete demonstration vehicles that showed - in protected and
unprotected surroundings- that these ITS-applications are already technically useful or could be developed into useful products.
The component âguidelines for the evaluation of ITS projectsâ outlines that the government has to have specific evaluation tools if the government has the ambition of using ITS-applications for road safety.
Two projects -guidelines for the evaluation of ITS projects- are examined; a third evaluation method is only mentioned because this description shows that a specific targeting of the government can be desirable :
1. TRACE describes the guidelines for the evaluation of ITS projects which are useful for the evaluation of specific ITS-applications.
2. FITS contains Finnish guidelines for the evaluation of ITS project; FIS is an adaptation of methods used for evaluation of transport projects.
3. The third evaluation method for the evaluation of ITS projects is developed in an ongoing European research project, eImpact. eImpact is important because, a specific consultation of stake holders shows that the social importance of some techniques is underestimated. These preliminary results show that an appropriate guiding role for the government could be important.
In the second part of this document the cooperative systems are discussed in depth.
These systems enable a large number of applications with an important social relevance, both on the level of the environment, mobility and traffic safety. Cooperative systems make it possible to warn drivers in time to avoid collisions (e.g. when approaching the tail of a traffic jam, or when a ghost driver is detected). Hazardous road conditions can be automatically communicated to other drivers (e.g. after the detection of black ice or an oil trail by the ESP). Navigation systems can receive detailed real-time up-dates about the current traffic situation and can take this into account when calculating their routes.
When a traffic distortion occurs, traffic centers can immediately take action and can actively influence the way that the traffic will be diverted. Drivers can be notified well in advance about approaching emergency vehicles, and can be directed to yield way in a uniform manner. This is just a small selection from the large number of applications that are made possible because of cooperative ITS systems, but it is very obvious that these
systems can make a significant positive contribution to traffic safety. In literature it is estimated that the decrease of accidents with injuries of fatalities will be between 20% and 50% .
It is not suprising that ITS systems receive a lot of attention for the moment. On an international level, a number of standards are being established regarding this topic. The International Telecommunications Uniont (ITU), Institute for Electrical and Electronics Engineers (IEEE), International Organization for Standardization (ISO), Association of Radio Industries and Business (ARIB) and European committee for standardization (CEN) are currently defining standards that describe different aspects of ITS systems. One of the names that is mostly mentioned in literature is the ISO TC204/WG16 Communications Architecture for Land Mobile environment (CALM) standard. It describes a framework that enables transparent (both for the application and the user) continuous communication through different communication media.
Besides the innumerable standardization activities, there is a great number of active research projects. On European level, the most important are the i2010 Intelligent Car Initiative, the eSafety Forum, and the COMeSafety, the CVIS, the SAFESPOT, the
COOPERS and the SEVECOM project. The i2010 Intelligent Car Initiative is an European initiative with the goal to halve the number of traffic casualties by 2010. The eSafety Forum is an initiative of the European Commission, industry and other stakeholders and targets the acceleration of development and deployment of safety-related ITS systems.
The COMeSafety project supports the eSafety Forum on the field of vehicle-to-vehicle and vehicle-to-infrastructure communication. In the CVIS project, attention is given to both technical and non-technical issues, with the main goal to develop the first free and
open reference implementation of the CALM architecture. The SAFEST project investigates which data is important for safety applications, and with which algorithmsthis data can be extracted from vehicles and infrastructure. The COOPERS project mainly
targets communication between vehicles and dedicated roadside infrastructure. Finally, the SEVECOM project researches security and privacy issues. Besides the European projects, research is also conducted in the United States of America (CICAS and VII
projects) and in Japan (AHSRA, VICS, Smartway, internetITS).
Besides standardization bodies and governmental organizations, also the industry has a considerable interest in ITS systems. In the scope of their ITS activities, a number of companies are united in national and international organizations. On an international level, the best known names are the Car 2 Car Communication Consortium, and Ertico.
The C2C CC unites the large European car manufacturers, and focuses on the development of an open standard for vehicle-to-vehicle and vehicle-to-infrastructure communications based on the already well established IEEE 802.11 WLAN standard.
Ertico is an European multi-sector, public/private partnership with the intended purpose of the development and introduction of ITS systems. On a national level, FlandersDrive and The Telematics Cluster / ITS Belgium are the best known organizations.
Despite the worldwide activities regarding (cooperative) ITS systems, there still is no consensus about the wireless technology to be used in such systems. This can be put down to the fact that a large number of suitable technologies exist or are under
development. Each technology has its specific advantages and disadvantages, but no single technology is the ideal solution for every ITS application. However, the different candidates can be classified in three distinct categories. The first group contains solutions for Dedicated Short Range Communication (DSRC), such as the WAVE technology. The second group is made up of several cellular communication networks providing coverage over wide areas. Examples are GPRS (data communication using the GSM network), UMTS (faster then GPRS), WiMAX (even faster then UMTS) and MBWA (similar to WiMAX). The third group consists of digital data broadcast technologies such as RDS (via the current FM radio transmissions, slow), DAB and DMB (via current digital radio transmissions, quicker) and DVB-H (via future digital television transmissions for mobiledevices, quickest).
The previous makes it clear that ITS systems are a hot topic right now, and they receive a lot of attention from the academic world, the standardization bodies and the industry.
Therefore, it seems like that it is just a matter of time before ITS systems will find their way into the daily live. Due to the large number of suitable technologies for the implementation of cooperative ITS systems, it is very hard to define which role the
government has to play in these developments, and which are the next steps to take.
These issues were addressed in reports produced by the i2010 Intelligent Car Initiative and the CVIS project. Their state of the art overview revealed that until now, no country has successfully deployed a fully operational ITS system yet. Seven EU countries are the furthest and are already in the deployment phase: Sweden, Germany, the Netherlands, the United Kingdom, Finland, Spain and France. These countries are trailed by eight countries which are in the promotion phase: Denmark, Greece, Italy, Austria, Belgium,Norway, the Czech Republic and Poland. Finally, the last ten countries find themselves in the start-up phase: Estonia, Lithuania, Latvia, Slovenia, Slovakia, Hungary, Portugal,
Switzerland, Ireland and Luxembourg.
These European reports produced by the i2010 Intelligent Car Initiative and the CVIS project have defined a few policy recommendations which are very relevant for the Belgian and Flemish government. The most important recommendations for the Flemish government are:
âą Support awareness: research revealed that civilians consider ITS applications useful, but they are not really willing to pay for this technology. Therefore, it is important to convince the general public of the usefulness and the importance of ITS systems.
âą Fill the gaps: Belgium is situated in the promotion phase. This means that it should focus at identifying the missing stakeholders, and coordinating national and regional ITS activities. Here it is important that the research activities are coordinated in a national and international context to allow transfer of knowledge from one study to the next, as well as the results to be comparable.
âą Develop a vision: in the scope of ITS systems policies have to be defined regarding a large number of issues. For instance there is the question if ITS users should be educated, meaning that the use of ITS systems should be the subject of the drivers license exam. How will the regulations be for the technical inspection
of vehicles equipped with ITS technology? Will ITS systems be deployed on a voluntary base, or will they e.g. be obliged in every new car? Will the services be offered by private companies, by the public authorities, or by a combination of them? Which technology will be used to implement ITS systems? These are just a few of the many questions where the government will have to develop a point of view for.
âą Policy coordination: ITS systems are a policy subject on an international, national and regional level. It is very important that these policy organizations can collaborate in a coordinated manner.
âą Iterative approach to policy development: developing policies for this complex matter is not a simple task. This asks for an iterative approach, where policy decisions are continuously refined and adjusted
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