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Traffic

Distribution by Scientific Domains
Engineering44%
Life Sciences16%
Information Science and Computing12%
Medical Sciences7%
Humanities and Social Sciences6%
Business, Economics, Finance and Accounting3%
Mathematics and Statistics3%
Earth and Environmental Science2%
2 Other Domains7%
Distribution within Engineering
Communication Technology63%
General & Introductory Civil Engineering & Construction9%
9 Other Subdomains28%

Kinds of Traffic

  • air traffic
  • data traffic
  • internet traffic
    		•
  • membrane traffic
  • multimedia traffic
  • network traffic
    		•
  • real-time traffic
  • road traffic
  • vehicular traffic
    		•

    Terms modified by Traffic

  • traffic accident
  • traffic assignment
  • traffic assignment problem
  • traffic characteristic
  • traffic condition
  • traffic congestion
    		•
  • traffic control
  • traffic data
  • traffic distribution
  • traffic engineering
  • traffic flow
  • traffic flow model
    		•
  • traffic intensity
  • traffic light
  • traffic load
  • traffic management
  • traffic model
  • traffic parameter
    		•
  • traffic pattern
  • traffic profile
  • traffic safety
  • traffic volume

    • Selected Abstracts

    Novel DLC model for QoS enhancement of bursty VBR traffic in wireless ATM networks

    EUROPEAN TRANSACTIONS ON TELECOMMUNICATIONS, Issue 8 2008
    Hosam El-Ocla
    Several data-link control (DLC) protocol procedures have been proposed in order to provide reliable data transmission over powerless radio links. However, many quality of service (QoS) issues still need to be achieved such as balance between cell transfer delay (CTD) and cell loss rate (CLR), absence of cell delay variation (CDV) and network traffic utilisation. The main problem with wireless ATM is how to overcome the unreliability of the wireless link in order to maintain QoS requirements especially for variable bit rate (VBR) application. Here, we propose a model that provides QoS support for ATM virtual connections (VC) and solves the unreliability problem of the wireless ATM through an efficient DLC protocol for bursty VBR traffic. This model mainly concerns with enhancing QoS to gain error-free wireless transmission and regulating VBR Traffic. Copyright © 2008 John Wiley & Sons, Ltd. [source]

    Magnetic quantification of urban pollution sources in atmospheric particulate matter

    GEOPHYSICAL JOURNAL INTERNATIONAL, Issue 2 2004
    S. Spassov
    SUMMARY A new method is presented for fast quantification of urban pollution sources in atmospheric particulate matter (PM). The remanent magnetization of PM samples collected in Switzerland at sites with different exposures to pollution sources is analysed. The coercivity distribution of each sample is calculated from detailed demagnetization curves of anhysteretic remanent magnetization (ARM) and is modelled using a linear combination of appropriate functions which represent the contribution of different sources of magnetic minerals to the total magnetization. Two magnetic components, C1 and C2, are identified in all samples. The low-coercivity component C1 predominates in less polluted sites, whereas the concentration of the higher-coercivity component C2 is large in urban areas. The same sites were monitored independently by Hüglin using detailed chemical analysis and a quantitative source attribution of the PM. His results are compared with the magnetic component analysis. The absolute and relative magnetic contributions of component C2 correlate very well with absolute and relative mass contributions of exhaust emissions, respectively. Traffic is the most important PM pollution source in Switzerland: it includes exhaust emissions and abrasion products released by vehicle brakes. Component C2 and traffic-related PM sources correlate well, which is encouraging for the implementation of non-destructive magnetic methods as an economic alternative to chemical analysis when mapping urban dust pollution. [source]

    A New Light-Path Setup Scheme for Dynamic Traffic in Ring-based Optical Networks

    IEEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING, Issue 5 2009
    Yusuke Sato Non-Member
    Abstract A simple and fast ring management token (RMT) wavelength reservation method for dynamic traffic in multi-ring wavelength-routed networks is proposed. The RMT is an agent that can control and manage the used wavelength in the network efficiently. We show that the proposed scheme achieves a high performance in terms of setup delay and loss probability. Copyright © 2009 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [source]

    Traffic flow continuum modeling by hypersingular boundary integral equations

    INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 1 2010
    Luis M. Romero
    Abstract The quantity of data necessary in order to study traffic in dense urban areas through a traffic network, and the large volume of information that is provided as a result, causes managerial difficulties for the said model. A study of this kind is expensive and complex, with many sources of error connected to each step carried out. A simplification like the continuous medium is a reasonable approximation and, for certain dimensions of the actual problem, may be an alternative to be kept in mind. The hypotheses of the continuous model introduce errors comparable to those associated with geometric inaccuracies in the transport network, with the grouping of hundreds of streets in one same type of link and therefore having the same functional characteristics, with the centralization of all journey departure points and destinations in discrete centroids and with the uncertainty produced by a huge origin/destination matrix that is quickly phased out, etc. In the course of this work, a new model for characterizing traffic in dense network cities as a continuous medium, the diffusion,advection model, is put forward. The model is approached by means of the boundary element method, which has the fundamental characteristic of only requiring the contour of the problem to be discretized, thereby reducing the complexity and need for information into one order versus other more widespread methods, such as finite differences and the finite element method. On the other hand, the boundary elements method tends to give a more complex mathematical formulation. In order to validate the proposed technique, three examples in their fullest form are resolved with a known analytic solution. Copyright © 2009 John Wiley & Sons, Ltd. [source]

    Neural bandwidth allocation function (NBAF) control scheme at WiMAX MAC layer interface

    INTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 9 2007
    Mario Marchese
    Abstract The paper proposes a bandwidth allocation scheme to be applied at the interface between upper layers (IP, in this paper) and Medium Access Control (MAC) layer over IEEE 802.16 protocol stack. The aim is to optimally tune the resource allocation to match objective QoS (Quality of Service) requirements. Traffic flows characterized by different performance requirements at the IP layer are conveyed to the IEEE 802.16 MAC layer. This process leads to the need for providing the necessary bandwidth at the MAC layer so that the traffic flow can receive the requested QoS. The proposed control algorithm is based on real measures processed by a neural network and it is studied within the framework of optimal bandwidth allocation and Call Admission Control in the presence of statistically heterogeneous flows. Specific implementation details are provided to match the application of the control algorithm by using the existing features of 802.16 request,grant protocol acting at MAC layer. The performance evaluation reported in the paper shows the quick reaction of the bandwidth allocation scheme to traffic variations and the advantage provided in the number of accepted calls. Copyright © 2006 John Wiley & Sons, Ltd. [source]

    Adaptive protocols for optical LANs with bursty and correlated traffic

    INTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 2-3 2002
    G. I. Papadimitriou
    Abstract Traffic in gigabit LANs is highly bursty. Furthermore, the destinations of packets transmitted by the same station are highly correlated. An adaptive protocol for WDM passive star networks, which is capable of operating efficiently under bursty and correlated traffic, is introduced. According to the proposed protocol, the stations which are granted permission to transmit at each time slot are selected by taking into account the network feedback information. Although the traffic parameters are unknown and time-variable, the bandwidth of each wavelength is allocated to the stations according to their needs. In this way, the number of idle slots is reduced, resulting in a significant improvement in the network throughput. Copyright © 2001 John Wiley & Sons, Ltd. [source]

    Structural Disparities of Urban Traffic in Southern California: Implications for Vehicle-Related Air Pollution Exposure in Minority and High-Poverty Neighborhoods

    JOURNAL OF URBAN AFFAIRS, Issue 5 2004
    Douglas Houston
    Emerging atmospheric science and epidemiological research indicates hazardous vehicle-related pollutants (e.g., diesel exhaust) are highly concentrated near major roadways, and the prevalence of respiratory ailments and mortality are heightened in these high-traffic corridors. This article builds on recent findings that low-income and minority children in California disproportionately reside in high-traffic areas by demonstrating how the urban structure provides a critical framework for evaluating the causes, characteristics, and magnitude of traffic, particularly for disadvantaged neighborhoods. We find minority and high-poverty neighborhoods bear over two times the level of traffic density compared to the rest of the Southern California region, which may associate them with a higher risk of exposure to vehicle-related pollutants. Furthermore, these areas have older and more multifamily housing, which is associated with higher rates of indoor exposure to outdoor pollutants, including intrusion of motor vehicle exhaust. We discuss the implications of these patterns on future planning and policy strategies for mitigating the serious health consequences of exposure to vehicle-related air pollutants. [source]

    Border Effects in Passenger Air Traffic

    KYKLOS INTERNATIONAL REVIEW OF SOCIAL SCIENCES, Issue 4 2004
    Henning Klodt
    SUMMARY The empirical literature on border effects suggests that national borders substantially reduce the level of economic transactions. This paper adds another piece of evidence to the significance of border effects by applying a new data set which is completely independent of the data sets of previous studies. Our data refer to domestic and international passenger departures from German airports. The econometric results indicate that the German border reduces passenger air traffic by a factor of four to five. This magnitude is in line with the results of previous studies for trade and investment flows. ZUSAMMENFASSUNG Die empirische Literatur zum Einfluss von Grenzen hat gezeigt, dass nationale Grenzen den Umfang von ökonomischen Transaktionen beträchtlich reduzieren. Dieser Beitrag präsentiert einen weiteren Beleg für die Relevanz von Grenzen, indem ein neuer Datensatz ausgewertet wird, der vollständig unabhängig von den in früheren Studien verwendeten Datensätzen ist. Unsere Daten beziehen sich auf die Passagierzahlen bei nationalen und internationalen Abflügen von deutschen Flughäfen. Den Schätzergebnissen zufolge reduziert die deutsche Grenze das Passagieraufkommen im Flugverkehr um den Faktor vier bis fünf. Diese Größenordnung steht in Einklang mit den Grenzeffekten, wie sie in anderen Studien für Handels- und Investitionsströme gemessen worden sind. RÉSUMÉ La littérature empirique sur les effets des frontières suggère que le niveau des transactions économiques est fortement réduit par les frontières nationales. Cet article propose de contribuer à ce débat en utilisant une nouvelle base de données qui se différencie substantiellement de celles utilisées jusqu'à présent. Nous utilisons des données sur le nombre de passagers au départ d'aéroports allemands vers des destinations nationales et internationales. Les résultats économétriques démontrent que l'existence des frontières allemandes réduit le trafic de passagers aériens par un facteur de quatre à cinq. Cet ordre de grandeur est comparable aux études antérieures concernant le commerce et les flux d'investissement. [source]

    Using Multinomial Mixture Models to Cluster Internet Traffic

    AUSTRALIAN & NEW ZEALAND JOURNAL OF STATISTICS, Issue 2 2004
    Murray Jorgensen
    Summary The paper considers the clustering of two large sets of Internet traffic data consisting of information measured from headers of transmission control protocol packets collected on a busy arc of a university network connecting with the Internet. Packets are grouped into 'flows' thought to correspond to particular movements of information between one computer and another. The clustering is based on representing the flows as each sampled from one of a finite number of multinomial distributions and seeks to identify clusters of flows containing similar packet-length distributions. The clustering uses the EM algorithm, and the data-analytic and computational details are given. [source]

    The Coolie Trade, the Traffic in Chinese Labourers to Latin America 1847,1874 , By Arnold J. Meagher

    AUSTRALIAN ECONOMIC HISTORY REVIEW, Issue 1 2010
    Kent G. Deng
    No abstract is available for this article. [source]

    Cross-border ,Traffic': Stories of dangerous victims, pure whores and HIV/AIDS in the experiences of mainland female sex workers in Hong Kong

    ASIA PACIFIC VIEWPOINT, Issue 1 2005
    Kevin D. Ming
    Abstract:,In recent years, dramatically increasing numbers of mainland Chinese women have entered Hong Kong to engage in sexual labour. Public discourses on the threat of HIV/AIDS increasingly locate these women's bodies as sites of danger, colluding with pre-existing imaginations of mainland rural women as ignorant, desperate and deceptive in representing these women's penetration of Hong Kong's border as a primary means of infection of the Hong Kong body. Drawing on state, media and popular representations, and the narratives of female sex workers themselves, this paper examines the interwoven bio-medical, gendered, sexual and cross-border relationships that intersect in the experiences of mainland Chinese sex workers in Hong Kong. I argue that while images of disease and danger have been used to regulate these women's bodies, mainland female sex workers challenge these images by drawing on other popular stereotypes of mainland women as pure, feminine and traditional. Although images of the related but still ,other' figure of the mainland Chinese woman are powerful mechanisms for the regulation of these women's bodies, mainland female sex workers skilfully use inherent tensions in those images in resisting that control and in struggling to achieve their own personal and economic goals. [source]

    Bi-level Programming Formulation and Heuristic Solution Approach for Dynamic Traffic Signal Optimization

    COMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 5 2006
    Dazhi Sun
    Conventional methods of signal timing optimization assume given traffic flow pattern, whereas traffic assignment is performed with the assumption of fixed signal timing. This study develops a bi-level programming formulation and heuristic solution approach (HSA) for dynamic traffic signal optimization in networks with time-dependent demand and stochastic route choice. In the bi-level programming model, the upper level problem represents the decision-making behavior (signal control) of the system manager, while the user travel behavior is represented at the lower level. The HSA consists of a Genetic Algorithm (GA) and a Cell Transmission Simulation (CTS) based Incremental Logit Assignment (ILA) procedure. GA is used to seek the upper level signal control variables. ILA is developed to find user optimal flow pattern at the lower level, and CTS is implemented to propagate traffic and collect real-time traffic information. The performance of the HSA is investigated in numerical applications in a sample network. These applications compare the efficiency and quality of the global optima achieved by Elitist GA and Micro GA. Furthermore, the impact of different frequencies of updating information and different population sizes of GA on system performance is analyzed. [source]

    A Linear Model for the Continuous Network Design Problem

    COMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 5 2006
    S. Travis Waller
    A linear programming formulation is introduced based on a dynamic traffic assignment (DTA) model that propagates traffic according to the cell transmission model. The introduced approach is limited to continuous link improvements and does not provide for new link additions. The main contribution of the article is to provide an analytical formulation for network design that accounts for DTA conditions that can be used for further analysis and extensions. The model is tested on a single destination example network, resembling a freeway corridor, for various congestion levels, loading patterns and budget sizes, to demonstrate the simplicity and effectiveness of the approach. [source]

    Dynamic Optimal Traffic Assignment and Signal Time Optimization Using Genetic Algorithms

    COMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 4 2004
    H. R. Varia
    A simulation-based approach is employed for the case of multiple-origin-multiple-destination traffic flows. The artificial intelligence technique of genetic algorithms (GAs) is used to minimize the overall travel cost in the network with fixed signal timings and optimization of signal timings. The proposed method is applied to the example network and results are discussed. It is concluded that GAs allow the relaxation of many of the assumptions that may be needed to solve the problem analytically by traditional methods. [source]

    Roughness Characterization through 3D Textured Image Analysis: Contribution to the Study of Road Wear Level

    COMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 2 2004
    M. Khoudeir
    The microtexture is defined as surface irregularities whose height ranges from 0.001 mm to 0.5 mm and whose width is less than 0.5 mm (Alvarez and Mprel, 1994). The deterioration due to the road traffic, especially polishing effect, involves a change in the microtexture. So, we suggest a method to characterize, through image analysis, wear level or microroughness of road surfaces. We propose then, on one hand a photometric model for road surface, and, on the other hand, a geometrical model for road surface profile. These two models allow us to develop roughness criteria based on the study of the statistical properties of: the distribution of the gray levels in the image, the distribution of the absolute value of its gradient, the form of its autocorrelation function, and the distribution of its curvature map. Experiments have been done with images of laboratory-made road specimens at different wear levels. The obtained results are similar to those obtained by a direct method using road profiles. [source]

    Case,Based Reasoning for Assessing Intelligent Transportation Systems Benefits

    COMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 3 2003
    Adel Sadek
    Existing transportation planning modeling tools have critical limitations with respect to assessing the benefits of intelligent transportation systems (ITS) deployment. In this article, we present a novel framework for developing modeling tools for quantifying ITS deployments benefits. This approach is based on using case,based reasoning (CBR), an artificial intelligence paradigm, to capture and organize the insights gained from running a dynamic traffic assignment (DTA) model. To demonstrate the feasibility of the approach, the study develops a prototype system for evaluating the benefits of diverting traffic away from incident locations using variable message signs. A real,world network from the Hartford area in Connecticut is used in developing the system. The performance of the prototype is evaluated by comparing its predictions to those obtained using a detailed DTA model. The prototype system is shown to yield solutions comparable to those obtained from the DTA model, thus demonstrating the feasibility of the approach. [source]

    Managing Transportation Infrastructure for Sustainable Development

    COMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 3 2002
    Edward O. Akinyemi
    Major requirements for operationalization of the concept of sustainable development in urban transportation infrastructure operations management are presented. In addition, it is shown that the current approach to management is incompatible with the requirements for sustainable urban development. Consequently, the conceptual framework of a desirable approach is proposed. The philosophy of this approach is that the basic mission of infrastructure operations management is to obtain and maintain the maximum levels of people and goods mobility possible within the resources and environmental capacities in an area. A mathematical model is presented for obtaining the desirable levels and characteristics of traffic on each segment of an urban transportation network. In addition, three illustrative applications of the implemented model are presented. [source]

    Feature Extraction for Traffic Incident Detection Using Wavelet Transform and Linear Discriminant Analysis

    COMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 4 2000
    A. Samant
    To eliminate false alarms, an effective traffic incident detection algorithm must be able to extract incident-related features from the traffic patterns. A robust feature-extraction algorithm also helps reduce the dimension of the input space for a neural network model without any significant loss of related traffic information, resulting in a substantial reduction in the network size, the effect of random traffic fluctuations, the number of required training samples, and the computational resources required to train the neural network. This article presents an effective traffic feature-extraction model using discrete wavelet transform (DWT) and linear discriminant analysis (LDA). The DWT is first applied to raw traffic data, and the finest resolution coefficients representing the random fluctuations of traffic are discarded. Next, LDA is employed to the filtered signal for further feature extraction and reducing the dimensionality of the problem. The results of LDA are used as input to a neural network model for traffic incident detection. [source]

    An architecture for exploiting multi-core processors to parallelize network intrusion prevention

    CONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 10 2009
    Robin Sommer
    Abstract It is becoming increasingly difficult to implement effective systems for preventing network attacks, due to the combination of the rising sophistication of attacks requiring more complex analyses to detect; the relentless growth in the volume of network traffic that we must analyze; and, critically, the failure in recent years for uniprocessor performance to sustain the exponential gains that for so many years CPUs have enjoyed. For commodity hardware, tomorrow's performance gains will instead come from multi-core architectures in which a whole set of CPUs executes concurrently. Taking advantage of the full power of multi-core processors for network intrusion prevention requires an in-depth approach. In this work we frame an architecture customized for parallel execution of network attack analysis. At the lowest layer of the architecture is an ,Active Network Interface', a custom device based on an inexpensive FPGA platform. The analysis itself is structured as an event-based system, which allows us to find many opportunities for concurrent execution, since events introduce a natural asynchrony into the analysis while still maintaining good cache locality. A preliminary evaluation demonstrates the potential of this architecture. Copyright © 2009 John Wiley & Sons, Ltd. [source]

    On the effectiveness of runtime techniques to reduce memory sharing overheads in distributed Java implementations

    CONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 13 2008
    Marcelo Lobosco
    Abstract Distributed Java virtual machine (dJVM) systems enable concurrent Java applications to transparently run on clusters of commodity computers. This is achieved by supporting Java's shared-memory model over multiple JVMs distributed across the cluster's computer nodes. In this work, we describe and evaluate selective dynamic diffing and lazy home allocation, two new runtime techniques that enable dJVMs to efficiently support memory sharing across the cluster. Specifically, the two proposed techniques can contribute to reduce the overheads due to message traffic, extra memory space, and high latency of remote memory accesses that such dJVM systems require for implementing their memory-coherence protocol either in isolation or in combination. In order to evaluate the performance-related benefits of dynamic diffing and lazy home allocation, we implemented both techniques in Cooperative JVM (CoJVM), a basic dJVM system we developed in previous work. In subsequent work, we carried out performance comparisons between the basic CoJVM and modified CoJVM versions for five representative concurrent Java applications (matrix multiply, LU, Radix, fast Fourier transform, and SOR) using our proposed techniques. Our experimental results showed that dynamic diffing and lazy home allocation significantly reduced memory sharing overheads. The reduction resulted in considerable gains in CoJVM system's performance, ranging from 9% up to 20%, in four out of the five applications, with resulting speedups varying from 6.5 up to 8.1 for an 8-node cluster of computers. Copyright © 2007 John Wiley & Sons, Ltd. [source]

    Distributed end-host multicast algorithms for the Knowledge Grid

    CONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 15 2007
    Wanqing Tu
    Abstract The Knowledge Grid built on top of the peer-to-peer (P2P) network has been studied to implement scalable, available and sematic-based querying. In order to improve the efficiency and scalability of querying, this paper studies the problem of multicasting queries in the Knowledge Grid. An m -dimensional irregular mesh is a popular overlay topology of P2P networks. We present a set of novel distributed algorithms on top of an m -dimensional irregular mesh overlay for the short delay and low network resource consumption end-host multicast services. Our end-host multicast fully utilizes the advantages of an m -dimensional mesh to construct a two-layer architecture. Compared to previous approaches, the novelty and contribution here are: (1) cluster formation that partitions the group members into clusters in the lower layer where cluster consists of a small number of members; (2) cluster core selection that searches a core with the minimum sum of overlay hops to all other cluster members for each cluster; (3) weighted shortest path tree construction that guarantees the minimum number of shortest paths to be occupied by the multicast traffic; (4) distributed multicast routing that directs the multicast messages to be efficiently distributed along the two-layer multicast architecture in parallel, without a global control; the routing scheme enables the packets to be transmitted to the remote end hosts within short delays through some common shortest paths; and (5) multicast path maintenance that restores the normal communication once the membership alteration appears. Simulation results show that our end-host multicast can distributively achieve a shorter delay and lower network resource consumption multicast services as compared with some well-known end-host multicast systems. Copyright © 2006 John Wiley & Sons, Ltd. [source]

    Towards a more realistic comparative analysis of multicomputer networks

    CONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 13 2004
    H. Sarbazi-Azad
    Abstract Several studies have examined the relative performance merits of the torus and hypercube taking into account the channel bandwidth constraints imposed by implementation technology. While the torus has been shown to outperform the hypercube under the constant wiring density constraint, the opposite conclusion has been reached when the constant pin-out constraint is considered. However, these studies have assumed a pure uniform traffic pattern and deterministic routing. The ,uniform traffic' assumption is not always justifiable in practice as there are many real-world parallel applications that exhibit non-uniform traffic patterns, which can create unbalanced traffic such as hotspots in the network. This paper re-examines the performance merits of the torus and hypercube in the presence of hotspot traffic. The comparative analysis is based on fully adaptive routing as this has been gaining popularity in recent practical multicomputers. Moreover, it uses a new cost model that takes into account the implementation cost of the network and its routers. The results reveal that for moderate and large system sizes, lower dimensional k -ary n -cubes (e.g. 2D torus) always outperform their higher dimensional counterparts even under the pin-out constraint. Copyright © 2004 John Wiley & Sons, Ltd. [source]

    Regulation of glucose transporter 4 traffic by energy deprivation from mitochondrial compromise

    ACTA PHYSIOLOGICA, Issue 1 2009
    A. Klip
    Abstract Skeletal muscle is the major store and consumer of fatty acids and glucose. Glucose enters muscle through glucose transporter 4 (GLUT4). Upon insufficient oxygen availability or energy compromise, aerobic metabolism of glucose and fatty aids cannot proceed, and muscle cells rely on anaerobic metabolism of glucose to restore cellular energy status. An increase in glucose uptake into muscle is a key response to stimuli requiring rapid energy supply. This chapter analyses the mechanisms of the adaptive regulation of glucose transport that rescue muscle cells from mitochondrial uncoupling. Under these conditions, the initial drop in ATP recovers rapidly, through a compensatory increase in glucose uptake. This adaptive response involves AMPK activation by the initial ATP drop, which elevates cell surface GLUT4 and glucose uptake. The gain in surface GLUT4 involves different signals and routes of intracellular traffic compared with those engaged by insulin. The hormone increases GLUT4 exocytosis through phosphatidylinositol 3-kinase and Akt, whereas energy stress retards GLUT4 endocytosis through AMPK and calcium inputs. Given that energy stress is a component of muscle contraction, and that contraction activates AMPK and raises cytosolic calcium, we hypothesize that the increase in glucose uptake during contraction may also involve a reduction in GLUT4 endocytosis. [source]

    Human peripheral blood B-cell compartments: A crossroad in B-cell traffic,

    CYTOMETRY, Issue S1 2010
    M. Perez-Andres
    Abstract A relatively high number of different subsets of B-cells are generated through the differentiation of early B-cell precursors into mature B-lymphocytes in the bone marrow (BM) and antigen-triggered maturation of germinal center B-cells into memory B-lymphocytes and plasmablasts in lymphoid tissues. These B-cell subpopulations, which are produced in the BM and lymphoid tissues, recirculate through peripheral blood (PB), into different tissues including mucosa and the BM, where long-living plasma cells produce antibodies. These circulating PB B-cells can be classified according to their maturation stage into i) immature/transitional, ii) naïve, and iii) memory B-lymphocytes, and iv) plasmablasts/plasma cells. Additionally, unique subsets of memory B-lymphocytes and plasmablasts/plasma cells can be identified based on their differential expression of unique Ig-heavy chain isotypes (e.g.: IgM, IgD, IgG, IgA). In the present paper, we review recent data reported in the literature about the distribution, immunophenotypic and functional characteristics of these cell subpopulations, as well as their distribution in PB according to age and seasonal changes. Additional information is also provided in this regard based on the study of a population-based cohort of 600 healthy adults aged from 20 to 80 years, recruited in the Salamanca area in western Spain. Detailed knowledge of the distribution and traffic of B-cell subsets through PB mirrors the immune status of an individual subject and it may also contribute to a better understanding of B-cell disorders related to B-cell biology and homeostasis, such as monoclonal B-cell lymphocytosis (MBL). © 2010 International Clinical Cytometry Society [source]

    Glutamylated tubulin: Diversity of expression and distribution of isoforms

    CYTOSKELETON, Issue 1 2003
    Marie-Louise Kann
    Abstract Glutamylation of , and , tubulin isotypes is a major posttranslational modification giving rise to diversified isoforms occurring mainly in neurotubules, centrioles, and axonemes. Monoglutamylated tubulin isoforms can be differentially recognized by two mAbs, B3 and GT335, which both recognize either polyglutamylated isoforms. In the present study, immunoelectron microscopy and immunofluorescence analyses were performed with these two mAbs to determine the expression and distribution of glutamylated tubulin isoforms in selected biological models whose tubulin isotypes are characterized. In mouse spermatozoa, microtubules of the flagellum contain polyglutamylated isoforms except in the tip where only monoglutamylated isoforms are detected. In spermatids, only a subset of manchette microtubules contain monoglutamylated tubulin isoforms. Cytoplasmic microtubules of Sertoli cells are monoglutamylated. Mitotic and meiotic spindles of germ cells are monoglutamylated whereas the HeLa cell mitotic spindle is polyglutamylated. Three models of axonemes are demonstrated as a function of the degree and extent of tubulin glutamylation. In lung ciliated cells, axonemes are uniformly polyglutamylated. In sea urchin sperm and Chlamydomonas, flagellar microtubules are polyglutamylated in their proximal part and monoglutamylated in their distal part. In Paramecium, cilia are bi- or monoglutamylated only at their base. In all cells, centrioles or basal bodies are polyglutamylated. These new data emphasize the importance of glutamylation in all types of microtubules and strengthen the hypothesis of its role in the regulation of the intracellular traffic and flagellar motility. Cell Motil. Cytoskeleton 55:14,25, 2003. © 2003 Wiley-Liss, Inc. [source]

    Disaster management and mitigation: the telecommunications infrastructure

    DISASTERS, Issue 1 2009
    Frédéric Patricelli
    Among the most typical consequences of disasters is the near or complete collapse of terrestrial telecommunications infrastructures (especially the distribution network,the ,last mile') and their concomitant unavailability to the rescuers and the higher echelons of mitigation teams. Even when such damage does not take place, the communications overload/congestion resulting from significantly elevated traffic generated by affected residents can be highly disturbing. The paper proposes innovative remedies to the telecommunications difficulties in disaster struck regions. The offered solutions are network-centric operations-cap able, and can be employed in management of disasters of any magnitude (local to national or international). Their implementation provide ground rescue teams (such as law enforcement, firemen, healthcare personnel, civilian authorities) with tactical connectivity among themselves, and, through the Next Generation Network backbone, ensure the essential bidirectional free flow of information and distribution of Actionable Knowledge among ground units, command/control centres, and civilian and military agencies participating in the rescue effort. [source]

    Do cities export biodiversity?

    DIVERSITY AND DISTRIBUTIONS, Issue 1 2008
    Traffic as dispersal vector across urban, rural gradients
    ABSTRACT Urban areas are among the land use types with the highes richness in plant species. A main feature of urban floras is the high proportion of non-native species with often divergent distribution patterns along urban,rural gradients. Urban impacts on plant species richness are usually associated with increasing human activity along rural-to-urban gradients. As an important stimulus of urban plant diversity, human-mediated seed dispersal may drive the process of increasing the similarity between urban and rural floras by moving species across urban,rural gradients. We used long motorway tunnels as sampling sites for propagules that are released by vehicles to test for the impact of traffic on seed dispersal along an urban,rural gradient. Opposite lanes of the tunnels are separated by solid walls, allowing us to differentiate seed deposition associated with traffic into vs. out of the city. Both the magnitude of seed deposition and the species richness in seed samples from two motorway tunnels were higher in lanes leading out of the city, indicating an ,export' of urban biodiversity by traffic. As proportions of seeds of non-native species were also higher in the outbound lanes, traffic may foster invasion processes starting from cities to the surrounding landscapes. Indicator species analysis revealed that only a few species were confined to samples from lanes leading into the city, while mostly species of urban habitats were significantly associated with samples from the outbound lanes. The findings demonstrate that dispersal by traffic reflects different seed sources that are associated with different traffic directions, and traffic may thus exchange propagules along the urban,rural gradient. [source]

    A review of drug prevention system development in Romania and its impact on youth drug consumption trends, 1995,2005

    DRUG AND ALCOHOL REVIEW, Issue 4 2009
    CSABA L. DÉGI
    Abstract Issues. A tremendous growth occurred in the reported drug use and abuse in Romania from 1995 to 1999. Lack of concern by government and little policy attention contributed to the surprising delay of drug policy and drug prevention system development. General public stigmatize drug users and drug consumption is considered a matter of personal fault and responsibility. There is some but not sufficient research and evaluation on drug use, abuse problem. Approach. Drug use, abuse and prevention are discussed from research-based, user-focused and prevention system development perspectives. Prevalence and trends of drug use, abuse in the past decade (1995,2005) are summarized. Prevention issues are discussed based on research data from adolescents, parents and teachers. The Romanian primary drug prevention system has been evaluated based on our experiences in drug use prevention activities carried out in schools and recreational environments. Key Findings. Public and scientific perspectives on drug consumption in Romania, between 1995 and 1999, were dominated by an idealistic, non-realistic perception. Since 1995, drug use among adolescents increased almost four times in less than 4 years. The first law against drug traffic and consumption was issued only in 2000. Now primary drug prevention strategies are in action, but in general they are lacking standard evaluation procedures. Implications/Conclusion. Conclusions are drafted for new perspectives in prevention activities. More long-term, user-focused, demand-centred prevention activities should be carried out in more and more diversified settings and evaluation should be thoroughly considered.[Dégi CL. A review of drug prevention system development in Romania and its impact on youth drug consumption trends, 1995,2005. Drug Alcohol Rev 2009;28:419,425] [source]

    The worldwide airline network and the dispersal of exotic species: 2007,2010

    ECOGRAPHY, Issue 1 2009
    Andrew J. Tatem
    International air travel has played a significant role in driving recent increases in the rates of biological invasion and spread of infectious diseases. By providing high speed, busy transport links between spatially distant, but climatically similar regions of the world, the worldwide airline network (WAN) increases the risks of deliberate or accidental movements and establishment of climatically sensitive exotic organisms. With traffic levels continuing to rise and climates changing regionally, these risks will vary, both seasonally and year-by-year. Here, detailed estimates of air traffic trends and climate changes for the period 2007-2010 are used to examine the likely directions and magnitudes of changes in climatically sensitive organism invasion risk across the WAN. Analysis of over 144 million flights from 2007-2010 shows that by 2010, the WAN is likely to change little overall in terms of connecting regions with similar climates, but anticipated increases in traffic and local variations in climatic changes should increase the risks of exotic species movement on the WAN and establishment in new areas. These overall shifts mask spatially and temporally heterogenous changes across the WAN, where, for example, traffic increases and climatic convergence by July 2010 between parts of China and northern Europe and North America raise the likelihood of exotic species invasions, whereas anticipated climatic shifts may actually reduce invasion risks into much of eastern Europe. [source]

    Research and recreational disturbance of Wedge-tailed Shearwater burrows on Rottnest Island, Western Australia: Managing human traffic in burrowing seabird colonies

    ECOLOGICAL MANAGEMENT & RESTORATION, Issue 1 2009
    Article first published online: 21 APR 200
    First page of article [source]