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Dynamic Environment (dynamic + environment)
Selected AbstractsSoft Decision with Soft Target for Car-like Mobile Vehicle in Dynamic EnvironmentIEEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING, Issue 4 2009Yougen Chen Non-member Abstract Online flexible operation of a car-like mobile vehicle with non-holonomic constraints in dynamic environment is still a very challenging problem because the surrounding situations are not qualified in static, knowledge is only partial and the execution is often associated with uncertainty. The difficulty lies in the setting of appropriate moving sub-targets in real-time to obtain a collision-free and low-cost path. In this paper, we present a new approach for the autonomous motion control of mobile vehicle in a narrow area with static and dynamic obstacles. It is based on the selection of sub-target points of vehicle's movement called ,soft target' which is a target set defined as all possible and reachable via-points in a navigation space. The soft target is acquired by online learning based on the final target and environment information. Each element of it has its membership value in [0, 1] denoting its evaluation degree. With the acquired soft target, soft decision is made like human's decision process by predictive fuzzy control (PFC) to achieve final target safely and economically. The simulation results show the effectiveness and flexibility of the proposed vehicle motion control method. © 2009 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [source] Optimal Velocity Planning of Wheeled Mobile Robots on Specific Paths in Static and Dynamic EnvironmentsJOURNAL OF FIELD ROBOTICS (FORMERLY JOURNAL OF ROBOTIC SYSTEMS), Issue 12 2003María Prado This paper deals with optimal temporal-planning of wheeled mobile robots (WMRs) when navigating on predefined spatial paths. A method is proposed to generate a time-optimal velocity profile for any spatial path in static environments or when mobile obstacles are present. The method generates a feasible trajectory to be tracked by fully exploiting velocity, acceleration and deceleration boundaries of the WMR, and by ensuring the continuity of the velocity and acceleration functions. As an additional benefit for the tracking process the jerk is also bounded. The algorithm is not time consuming, since it mostly uses closed mathematical expressions, nonetheless iteration strategies are presented to solve specific situations. However, such situations are not expected to occur when the spatial paths are planned as smooth curves. The success of the algorithm was tested by experimental and simulation results on the WMR "RAM." © 2003 Wiley Periodicals, Inc. [source] Integrating Decentralized Strategy Making and Strategic Planning Processes in Dynamic EnvironmentsJOURNAL OF MANAGEMENT STUDIES, Issue 8 2004Torben Juul Andersen abstract Decentralized post-bureaucratic organizations are deemed to display superior performance in dynamic environments, but recent evidence indicates that centralized integrative cross-functional processes may be equally critical. Accordingly, this paper hypothesizes that organizational performance can be ascribed to the simultaneous emphasis on decentralized strategy making and strategic planning processes. This is investigated in a study of 185 manufacturing organizations operating in diverse industries spanning food processing and computer products. The study shows that both decentralized decision structure and planning activities are associated with higher performance in dynamic environments. These findings confirm that effective organizations engage in more complex strategy formation processes that complement the decentralized post-bureaucratic form with formal mechanisms of rational analyses and operational integration. The paper highlights a need to extend our understanding of the duality between decentralization and planning. [source] Efficient resource discovery in self-organized unstructured peer-to-peer networksCONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 2 2009Lu Liu Abstract In unstructured peer-to-peer (P2P) networks, two autonomous peer nodes can be connected if users in those nodes are interested in each other's data. Owing to the similarity between P2P networks and social networks, where peer nodes can be regarded as people and connections can be regarded as relationships, social strategies are useful for improving the performance of resource discovery by self-organizing autonomous peers on unstructured P2P networks. In this paper, we present an efficient social-like peer-to-peer (ESLP) method for resource discovery by mimicking different human behaviours in social networks. ESLP has been simulated in a dynamic environment with a growing number of peer nodes. From the simulation results and analysis, ESLP achieved better performance than current methods. Copyright © 2008 John Wiley & Sons, Ltd. [source] Perplexing Pax: From puzzle to paradigmDEVELOPMENTAL DYNAMICS, Issue 10 2008Judith A. Blake Abstract Pax transcription factors are critical for the development of the central nervous system (CNS) where they have a biphasic role, initially dictating CNS regionalization, while later orchestrating differentiation of specific cell subtypes. While a plethora of expression, misexpression, and mutation studies lend support for this argument and clarify the importance of Pax genes in CNS development, less well understood, and more perplexing, is the continued Pax expression in the adult CNS. In this article we explore the mechanism of action of Pax genes in general, and while being cognizant of existing developmental data, we also draw evidence from (1) adult progenitor cells involved in regeneration and tissue maintenance, (2) specific expression patterns in fully differentiated adult cells, and (3) analysis of direct target genes functioning downstream of Pax proteins. From this, we present a more encompassing theory that Pax genes are key regulators of a cell's measured response to a dynamic environment. Developmental Dynamics 237:2791,2803, 2008. © 2008 Wiley-Liss, Inc. [source] Channels, wetlands and islands in the Okavango Delta, Botswana, and their relation to hydrological and sedimentological processesEARTH SURFACE PROCESSES AND LANDFORMS, Issue 1 2004T. Gumbricht Abstract The Okavango wetland in northern Botswana is one of the world's largest inland deltas. The delta is a dynamic environment with shifting channel routes, causing growth and decay of ,anking wetlands, and giving birth to islands. Primary island nuclei are formed by ,uvial processes and bioengineering, and subsequently grow into secondary larger islands of irregular shape by clastic and chemical sedimentation, and later by coalescence. This article presents classi,cations and quantitative estimations of channels, wetlands and islands of the Okavango Delta. Islands were classi,ed dependent on composition, pattern of composition, shape and juxtaposition. 90 per cent of all islands in the entire wetland were identi,ed, with a classi,cation accuracy of 60 to 85 per cent. Smaller islands of the nucleus types dominate the upper parts of the delta, whereas larger secondary islands are more common in the distal part, a re,ection of the age of the islands. Islands in the entry valley of the delta, the Panhandle, are larger in the top end , the primary region of recent clastic sedimentation. The overall size distribution of islands in the delta, however, shows no clumps, indicating that island growth is a uniform process over time and space. The total area ,ooded at least every decade is approximately 14 000 km2, of which 9000 km2 is classi,ed as actual wetland. Channel meandering decreases from the Panhandle to the distal part of the delta, with the abandoned Thaoge channel as an exception. Occurrence of ,uvially formed islands in the distal delta indicates that the water ,ow and area of inundation must once have been much larger. Copyright © 2004 John Wiley & Sons, Ltd. [source] Financial Innovation and the Transactions Demand for CashECONOMETRICA, Issue 2 2009Fernando Alvarez We document cash management patterns for households that are at odds with the predictions of deterministic inventory models that abstract from precautionary motives. We extend the Baumol,Tobin cash inventory model to a dynamic environment that allows for the possibility of withdrawing cash at random times at a low cost. This modification introduces a precautionary motive for holding cash and naturally captures developments in withdrawal technology, such as the increasing diffusion of bank branches and ATM terminals. We characterize the solution of the model, which qualitatively reproduces several empirical patterns. We estimate the structural parameters using micro data and show that quantitatively the model captures important economic patterns. The estimates are used to quantify the expenditure and interest rate elasticity of money demand, the impact of financial innovation on money demand, the welfare cost of inflation, and the benefit of ATM ownership. [source] Behavior selection of mobile robot based on integration of multimodal informationELECTRICAL ENGINEERING IN JAPAN, Issue 2 2007Bin Chen Abstract Recently, biologically inspired robots have been developed to acquire the capacity for directing visual attention to salient stimulus generated from the audiovisual environment. For the purpose of realizing this behavior, a general method is to calculate saliency maps to represent how much the external information attracts the robot's visual attention, where the audiovisual information and robot's motion status should be involved. In this paper, we represent a visual attention model where three modalities,audio information, visual information, and robot's motor status,are considered, because previous research has not considered all of them. First, we introduce a 2D density map, on which the value denotes how much the robot pays attention to each spatial location. Then we model the attention density using a Bayesian network where the robot's motion statuses are involved. Next, the information from both audio and visual modalities is integrated with the attention density map in integrate-fire neurons. The robot can direct its attention to the locations where the integrate-fire neurons are fired. Finally, the visual attention model is applied to make the robot select the visual information from the environment, and react to the content selected. Experimental results show that it is possible for robots to acquire the visual information related to their behaviors by using the attention model considering motion statuses. The robot can select its behaviors to adapt to the dynamic environment as well as to switch to another task according to the recognition results of visual attention. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 158(2): 39,48, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20335 [source] Agent-based ontology mapping and integration towards interoperabilityEXPERT SYSTEMS, Issue 3 2008Li Li Abstract: Interoperability is an important issue in ontology research. In this paper, a novel agent-based framework for managing ontologies in a dynamic environment is developed. The framework has several key characteristics such as flexibility and extensibility that differentiate this research from others. Based on the proposed framework, ontology mapping and integration are investigated. It is believed that inter-ontology processes like ontology mapping with logical semantics are foundations of ontology-based applications. Accordingly, several types of semantic relations are proposed and corresponding mapping mechanisms are developed. Based on mapping results, ontology integration is developed to provide abstract views for participating organizations in the presence of a variety of ontologies. A prototype is built to demonstrate the design and functionalities and is applied to beer ontologies. The prototype shows that the framework is not only flexible but also practical. All agents derived from the framework exhibit their behaviours as expected. [source] Effects of cooperative and competitive incentives on agility, quality, and speed in an experimental settingHUMAN FACTORS AND ERGONOMICS IN MANUFACTURING & SERVICE INDUSTRIES, Issue 4 2004Charlene A. Yauch Inter- and intraorganizational cooperation have been identified as essential characteristics of agile manufacturing. For this research, agility was compared using two experimental treatments: cooperative versus competitive. Student teams performed a task and were confronted with random changes to simulate a dynamic environment. Although differences were not statistically significant, the results show that cooperative incentives do not result in greater agility. Speed also decreased with cooperative incentives but quality improved. The experiment provides a preliminary understanding of how competition, cooperation, and agility interrelate and suggest that intra-organizational cooperation may not be the best means of achieving manufacturing agility. © 2004 Wiley Periodicals, Inc. Hum Factors Man 14: 403,413, 2004. [source] Soft Decision with Soft Target for Car-like Mobile Vehicle in Dynamic EnvironmentIEEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING, Issue 4 2009Yougen Chen Non-member Abstract Online flexible operation of a car-like mobile vehicle with non-holonomic constraints in dynamic environment is still a very challenging problem because the surrounding situations are not qualified in static, knowledge is only partial and the execution is often associated with uncertainty. The difficulty lies in the setting of appropriate moving sub-targets in real-time to obtain a collision-free and low-cost path. In this paper, we present a new approach for the autonomous motion control of mobile vehicle in a narrow area with static and dynamic obstacles. It is based on the selection of sub-target points of vehicle's movement called ,soft target' which is a target set defined as all possible and reachable via-points in a navigation space. The soft target is acquired by online learning based on the final target and environment information. Each element of it has its membership value in [0, 1] denoting its evaluation degree. With the acquired soft target, soft decision is made like human's decision process by predictive fuzzy control (PFC) to achieve final target safely and economically. The simulation results show the effectiveness and flexibility of the proposed vehicle motion control method. © 2009 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [source] Adaptive secure multicast in wireless networksINTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 9 2009Yiliang Han Abstract Secure multicast is one of the majority services in the near future. The frameworks for IP multicast cannot be directly applied in wireless networks. To address the natural issues of wireless multicast and enhance the efficiency, an adaptive secure multicast framework based on a new primitive called multi-recipient generalized signcryption and a multi-recipient generalized signcryption scheme based on the gap Diffie,Hellman problem (MGSC-GDH) are proposed. The key technologies to construct a high-performance adaptive scheme including identification function, randomness reusing are investigated. The framework provides separate or joint encryption and signature functions according to users' identities and requirements transparently, and has the ability to aggregate multiple unicast besides the common multicast service. Therefore, overheads are reduced sharply for multiple functions which are provided with a single primitive. By the precise reduction, the gap-bridge between the security of a base scheme and the corresponding multi-recipient generalized signcryption scheme is built, which is a direct measure to quantify the security. Analysis shows that MGSC-GDH is a semantic secure multi-recipient generalized signcryption scheme and more efficient than other similar schemes in computational and communicational aspects. It is suitable for dynamic environment for rekeying is avoided when membership changes. Copyright © 2009 John Wiley & Sons, Ltd. [source] Using temporal correlation for fault localization in dynamically changing networksINTERNATIONAL JOURNAL OF NETWORK MANAGEMENT, Issue 4 2008Maitreya Natu A mobile ad hoc network creates a dynamic environment where node mobility can cause periodic changes in routes. Most existing fault localization algorithms assume availability of a complete and/or deterministic dependency model. Such assumptions cannot be made in the dynamically changing networks. This paper is aimed at developing a fault diagnosis architecture and algorithm to address the issue of dynamically changing dependencies in networks. We propose an architecture to capture the changes in dependencies and introduce a temporal correlation algorithm to perform fault diagnosis with the dynamically changing dependency information. We present an experimental evaluation of our work through simulation results using Qualnet. Copyright © 2007 John Wiley & Sons, Ltd. [source] The problem of postoperative pain: Issues for future researchINTERNATIONAL JOURNAL OF NURSING PRACTICE, Issue 6 2004Mari Botti RN DipNsg BA PGDCAP PhD MRCNA Uncontrolled postoperative pain continues despite abundant research in the area. The purposes of the paper are to review how past research influences our understanding of pain in the postsurgery context and to argue for a methodological shift towards naturalistic inquiry. Such a shift incorporates the complexities of pain assessment and management in the clinical practice environment. Decisions regarding pain are often examined outside of the contextual concerns of clinical practice. Research approaches have involved analyses of nurse and patient-related factors associated with pain. These approaches do not account for complex interactions that occur between nurses, patients and the dynamic environment in which these interactions take place. The failure of research to address the context of pain decisions has several implications. It limits our understanding of why pain continues despite ongoing research and it does not enable evaluation of clinical strategies to improve pain decision-making and pain outcomes for patients. [source] Learning scheduling control knowledge through reinforcementsINTERNATIONAL TRANSACTIONS IN OPERATIONAL RESEARCH, Issue 2 2000K. Miyashita Abstract This paper introduces a method of learning search control knowledge in schedule optimization problems through application of reinforcement learning. Reinforcement learning is an effective approach for the problem faced by the agent that learns its behavior through trial-and-error interactions with a dynamic environment. Nevertheless, reinforcement learning has a difficulty of slow convergence when applied to the problems with a large state space. The paper discusses the case-based function approximation technique, which makes reinforcement learning applicable to the large scale problems such as a job-shop scheduling problem. To show effectiveness of the approach, reinforcement learning is applied to acquire search control knowledge in repair-based schedule optimization process. Preliminary experiment results show that repair-action selection made by learned search control knowledge succeeded in improving scheduling quality efficiently. [source] The importance of information flows temporal attributes for the efficient scheduling of dynamic demand responsive transport servicesJOURNAL OF ADVANCED TRANSPORTATION, Issue 1 2006Marco Diana The operation of a demand responsive transport service usually involves the management of dynamic requests. The underlying algorithms are mainly adaptations of procedures carefully designed to solve static versions of the problem, in which all the requests are known in advance. However there is no guarantee that the effectiveness of an algorithm stays unchanged when it is manipulated to work in a dynamic environment. On the other hand, the way the input is revealed to the algorithm has a decisive role on the schedule quality. We analyze three characteristics of the information flow (percentage of real-time requests, interval between call-in and requested pickup time and length of the computational cycle time), assessing their influence on the effectiveness of the scheduling process. [source] Who will win Wimbledon?JOURNAL OF BEHAVIORAL DECISION MAKING, Issue 4 2006The recognition heuristic in predicting sports events Abstract Goldstein and Gigerenzer (2002) described the recognition heuristic as a fast, frugal, and effective decision strategy. However, most studies concerning the recognition heuristic have been conducted in static domains, that is, in domains where it could plausibly be argued that relevant variables stay relatively constant. Yet the question is whether the heuristic would also work in dynamic environments where the quality of the actors rises and falls, such as in sports. We tested performance of the recognition heuristic in a dynamic environment and used it to predict the outcomes of tennis matches in Wimbledon 2003. Recognition data of amateur tennis players and laypeople was used to build recognition rankings. These rankings correlated with official rankings and led to at least as good predictions. Simulations of individual choices showed high recognition validities of both amateurs (0.73) and laypeople (0.67). In a second study the recognition heuristic correctly predicted 90% of actual individual choices. Overall, the recognition heuristic may be effectively generalized to dynamic environments. Copyright © 2006 John Wiley & Sons, Ltd. [source] Understanding leadership skills of hospice executivesJOURNAL OF LEADERSHIP STUDIES, Issue 3 2008Paul Longenecker The healthcare industry is a rapidly changing environment requiring leaders to possess a high level of leadership skills. Leaders in the hospice industry have experienced the same level of change, but over the brief span of 25 years. With the aging of hospice executives and the dynamic environment of the hospice industry, the need for strong leadership is more important than ever. This research study reports on the perceived leadership skills of hospice executives and is a replication of an earlier study (Longenecker, 2006). All study participants were executives of organizations that participated in clinical and operational benchmarking activities at the national level. The study evaluated leadership skills using transformational leadership theory as the conceptual model by which leadership skills were measured. The results of the study identified that the participants perceived they displayed an ideal use of skills based on transformational leadership theory. [source] Community family medicine teachers' perceptions of their teaching roleMEDICAL EDUCATION, Issue 3 2001Karen V Mann Objectives Our study explored community preceptors' perceptions of their teaching role, to better understand effective ambulatory and community-based teaching. Methods Bandura's social cognitive theory and Schön's notion of reflective practice guided conceptual development of an interview exploring preceptors' views of their role, teaching goals, teaching techniques, student assessment practices, factors affecting teaching and learning, and balance of patient and student needs. Preceptors reflected also on a significant personal teaching experience. A total of 17 highly student-rated preceptors participated. A trained interviewer conducted each interview; all were transcribed and subjected to content analysis. Results Preceptors (male, 14; female, 3) described learner-centred approaches, setting goals jointly with the student. Demonstration, guided practice, observation and feedback were integral to the experience. Preceptors saw student comfort in the environment as key to effective learning; they attempted to maximize students' learning and breadth of experience. They wanted students to understand content, ,know-how' and ,being a family physician'. Patients remained the primary responsibility, but learners' needs were viewed as compatible with that responsibility. Many preceptors perceived a professional responsibility as ,role models'. Conclusions Preceptors recognized the dynamic environment in which they taught students, and they described strategies which demonstrated how they adapted their teaching to meet the needs of the learner in that environment. These teachers combined learner-centred approaches with sound educational practices, broad learning experiences, attention to student learning and concern for development of professional expertise and judgement. These findings may assist faculty development in family medicine, and other disciplines, in providing effective ambulatory care teaching. [source] An extensible modeling framework for dynamic reassignment and rerouting in cooperative airborne operationsNAVAL RESEARCH LOGISTICS: AN INTERNATIONAL JOURNAL, Issue 7 2010Chase C. Murray Abstract Unmanned aerial vehicles (UAVs), increasingly vital to the success of military operations, operate in a complex and dynamic environment, sometimes in concert with manned aircraft. We present an extensible modeling framework for the solution to the dynamic resource management (DRM) problem, where airborne resources must be reassigned to time-sensitive tasks in response to changes in battlespace conditions. The DRM problem is characterized by diverse tasks with time windows, heterogeneous resources with fuel- and payload-capacity limitations, and multiple competing objectives. We propose an integer linear programing formulation for this problem, where mathematical feasibility is guaranteed. Although motivated by airborne military operations, the proposed general modeling framework is applicable to a wide array of settings, such as disaster relief operations. Additionally, land- or water-based operations may be modeled within this framework, as well as any combination of manned and unmanned vehicles. © 2010 Wiley Periodicals, Inc. Naval Research Logistics, 2010 [source] An asymptotically optimal greedy heuristic for the multiperiod single-sourcing problem: The cyclic caseNAVAL RESEARCH LOGISTICS: AN INTERNATIONAL JOURNAL, Issue 5 2003H. Edwin Romeijn The dynamics of the environment in which supply chains evolve requires that companies frequently redesign their logistics distribution networks. In this paper we address a multiperiod single-sourcing problem that can be used as a strategic tool for evaluating the costs of logistics network designs in a dynamic environment. The distribution networks that we consider consist of a set of production and storage facilities, and a set of customers who do not hold inventories. The facilities face production capacities, and each customer's demand needs to be delivered by a single facility in each period. We deal with the assignment of customers to facilities, as well as the location, timing, and size of inventories. In addition, to mitigate start and end-of-study effects, we view the planning period as a typical future one, which will repeat itself. This leads to a cyclic model, in which starting and ending inventories are equal. Based on an assignment formulation of the problem, we propose a greedy heuristic, and prove that this greedy heuristic is asymptotically feasible and optimal in a probabilistic sense. We illustrate the behavior of the greedy heuristic, as well as some improvements where the greedy heuristic is used as the starting point of a local interchange procedure, on a set of randomly generated test problems. © 2003 Wiley Periodicals, Inc. Naval Research Logistics 50: 412,437, 2003 [source] Using feed process as a means of performance improvement in a dynamic environmentPERFORMANCE IMPROVEMENT, Issue 8 2010John R. Turner The literature on performance improvement provides limited information for using feedback loops as part of the performance improvement process. Information regarding feedforward loops, as applied to performance improvement efforts, remains scarce. This article focuses on applying strategic feedback and feedforward loops for the purpose of performance improvement in a dynamic environment. Introducing strategic feedback and feedforward loops, at the process and subprocess levels, performance improvement could be obtained while operating in a dynamic environment. [source] Permafrost in a dynamic environmentPERMAFROST AND PERIGLACIAL PROCESSES, Issue 2 2003Douglas L. Kane No abstract is available for this article. [source] Modeling volatile isoprenoid emissions , a story with split endsPLANT BIOLOGY, Issue 1 2008R. Grote Abstract Accurate prediction of plant-generated volatile isoprenoid fluxes is necessary for reliable estimation of atmospheric ozone and aerosol formation potentials. In recent years, significant progress has been made in understanding the environmental and physiological controls on isoprenoid emission and in scaling these emissions to canopy and landscape levels. We summarize recent developments and compare different approaches for simulating volatile isoprenoid emission and scaling up to whole forest canopies with complex architecture. We show that the current developments in modeling volatile isoprenoid emissions are "split-ended" with simultaneous but separated efforts in fine-tuning the empirical emission algorithms and in constructing process-based models. In modeling volatile isoprenoid emissions, simplified leaf-level emission algorithms (Guenther algorithms) are highly successful, particularly after scaling these models up to whole regions, where the influences of different ecosystem types, ontogenetic stages, and variations in environmental conditions on emission rates and dynamics partly cancel out. However, recent experimental evidence indicates important environmental effects yet unconsidered and emphasize, the importance of a highly dynamic plant acclimation in space and time. This suggests that current parameterizations are unlikely to hold in a globally changing and dynamic environment. Therefore, long-term predictions using empirical algorithms are not necessarily reliable. We show that process-based models have large potential to capture the influence of changing environmental conditions, in particular if the leaf models are linked with physiologically based whole-plant models. This combination is also promising in considering the possible feedback impacts of emissions on plant physiological status such as mitigation of thermal and oxidative stresses by volatile isoprenoids. It might be further worth while to incorporate main features of these approaches in regional empirically-based emission estimations thereby merging the "split ends". [source] Welfare Measures when Agents can Learn: A Unifying Theory,THE ECONOMIC JOURNAL, Issue 540 2009Jinhua Zhao We extend Graham's (1981) welfare analysis under uncertainty to a dynamic environment where the agent can delay and obtain information. The dynamic willingness to pay locus unifies the concepts of option price, dynamic WTP, commitment costs and quasi-option value. Option price (dynamic WTP) corresponds to the ex ante WTP when the agent ignores (recognises) the learning opportunity. The commitment cost, or the difference between option price and dynamic WTP, equals the annualised and monetised quasi-option value. State contingent contracts have added value by allowing trading among agents with heterogeneous access to future information and delay opportunities. [source] Fecal bacterial diversity of human-habituated wild chimpanzees (Pan troglodytes schweinfurthii) at Mahale Mountains National Park, Western TanzaniaAMERICAN JOURNAL OF PRIMATOLOGY, Issue 7 2010Brian A. Szekely Abstract Although the intestinal flora of chimpanzees has not been studied, insight into this dynamic environment can be obtained through studies on their feces. We analyzed fecal samples from human-habituated, wild chimpanzees at Mahale Mountains National Park, Tanzania, and compared microbial community profiles to determine if members of the same social group were similar. Between July and December 2007, we collected fresh fecal samples from 12 individuals: four juveniles, four adolescents, and four adults, including three parent,offspring pairs. Each sample was analyzed using Terminal-Restriction Fragment Length Polymorphism of amplified 16S rRNA genes. Twelve different profiles were generated, having between 1 and 15 Terminal-Restriction Fragments (T-RFs). Overall, a total of 23 different T-RFs were produced. Putative assignments of T-RFs corresponded to the phyla Firmicutes (Clostridia, Bacilli, and Lactobacilli), Bacteroidetes, Tenericutes (Mollicutes Class), Actinobacteria, and Proteobacteria, as well as to uncultured or unidentified organisms. Firmicutes and Bacteroidetes phyla and Mollicutes Class were the most commonly assigned in 11, 8, and 8 of the samples, respectively, with this being the first report of Mollicutes in wild chimpanzees. Principal Components Analysis (PCA) revealed clustering of nine samples, and 80.5% of the diversity was accounted for by three samples. Morisita indices of community similarity ranged between 0.00 and 0.89, with dissimiliarity (<0.5) between most samples when compared two at a time. Our findings suggest that, although phylotypes are common among individuals, profiles among members of the same social group are host-specific. We conclude that factors other than social group, such as kinship and age, may influence fecal bacterial profiles of wild chimpanzees, and recommend that additional studies be conducted. Am. J. Primatol. 72:566,574, 2010. © 2010 Wiley-Liss, Inc. [source] Population and species boundaries in the South American subterranean rodent Ctenomys in a dynamic environmentBIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 2 2010PATRICIA MIROL Subterranean rodents of the genus Ctenomys are an interesting system to assess the effects of habitat instability on the genetic structure of populations. The perrensi group is a complex of three species (C. roigi, C. perrensi and C. dorbignyi) and several forms of uncertain taxonomic status, distributed in the vicinity of the Iberá wetland in Argentina. Because of limited availability of suitable dry habitat, Ctenomys populations are distributed patchily around a vast mosaic of marshes, swamps and lagoons and become connected or isolated over time, depending particularly on the precipitation regime. Genetic variation at 16 microsatellite loci in 169 individuals collected in the area revealed eight clusters of populations which are thought to be evolutionary units, but which do not fit previous species limits. We interpret this lack of congruence between taxonomy and genetic structure as the result of a dynamic population structure. Where populations become connected, hybridization is possible. Where populations become isolated, rapid genetic divergence may occur. In the perrensi group, it appears that both of these factors disrupt the association between different genetic and morphological characters. The study of multiple characters is crucial to the understanding of the recent evolutionary history for dynamic systems such as this. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100, 368,383. [source] Developing Expert Medical Teams: Toward an Evidence-based ApproachACADEMIC EMERGENCY MEDICINE, Issue 11 2008Rosemarie Fernandez MD Abstract Current health care literature cites communication breakdown and teamwork failures as primary threats to patient safety. The unique, dynamic environment of the emergency department (ED) and the complexity of patient care necessitate the development of strong interdisciplinary team skills among emergency personnel. As part of the 2008 Academic Emergency Medicine Consensus Conference on "The Science of Simulation in Healthcare," our workshop group identified key theory and evidence-based recommendations for the design and implementation of team training programs. The authors then conducted an extensive review of the team training literature within the domains of organizational psychology, aviation, military, management, and health care. This review, in combination with the workshop session, formed the basis for recommendations and need for further research in six key areas: 1) developing and refining core competencies for emergency medicine (EM) teams; 2) leadership training for emergency physicians (EPs); 3) conducting comprehensive needs analyses at the organizational, personnel, and task levels; 4) development of training platforms to maximize knowledge transfer; 5) debriefing and provision of feedback; and 6) proper implementation of simulation technology. The authors believe that these six areas should form an EM team training research platform to advance the EM literature, while leveraging the unique team structures present in EM to expand team training theory and research. [source] Trust-based robust scheduling and runtime adaptation of scientific workflowCONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 16 2009Mingzhong Wang Abstract Robustness and reliability with respect to the successful completion of a schedule are crucial requirements for scheduling in scientific workflow management systems because service providers are becoming autonomous. We introduce a model to incorporate trust, which indicates the probability that a service agent will comply with its commitments to improve the predictability and stability of the schedule. To deal with exceptions during the execution of a schedule, we adapt and evolve the schedule at runtime by interleaving the processes of evaluating, scheduling, executing and monitoring in the life cycle of the workflow management. Experiments show that schedules maximizing participants' trust are more likely to survive and succeed in open and dynamic environments. The results also prove that the proposed approach of workflow evaluation can find the most robust execution flow efficiently, thus avoiding the need of scheduling every possible execution path in the workflow definition. Copyright © 2009 John Wiley & Sons, Ltd. [source] Reliability in grid computing systems,CONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 8 2009Christopher Dabrowski Abstract In recent years, grid technology has emerged as an important tool for solving compute-intensive problems within the scientific community and in industry. To further the development and adoption of this technology, researchers and practitioners from different disciplines have collaborated to produce standard specifications for implementing large-scale, interoperable grid systems. The focus of this activity has been the Open Grid Forum, but other standards development organizations have also produced specifications that are used in grid systems. To date, these specifications have provided the basis for a growing number of operational grid systems used in scientific and industrial applications. However, if the growth of grid technology is to continue, it will be important that grid systems also provide high reliability. In particular, it will be critical to ensure that grid systems are reliable as they continue to grow in scale, exhibit greater dynamism, and become more heterogeneous in composition. Ensuring grid system reliability in turn requires that the specifications used to build these systems fully support reliable grid services. This study surveys work on grid reliability that has been done in recent years and reviews progress made toward achieving these goals. The survey identifies important issues and problems that researchers are working to overcome in order to develop reliability methods for large-scale, heterogeneous, dynamic environments. The survey also illuminates reliability issues relating to standard specifications used in grid systems, identifying existing specifications that may need to be evolved and areas where new specifications are needed to better support the reliability. Published in 2009 by John Wiley & Sons, Ltd. [source] | ||||||||||||||||||||||||||||