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Main Challenges (main + challenge)
Selected AbstractsA comparative study of awareness methods for peer-to-peer distributed virtual environmentsCOMPUTER ANIMATION AND VIRTUAL WORLDS (PREV: JNL OF VISUALISATION & COMPUTER ANIMATION), Issue 5 2008S. Rueda Abstract The increasing popularity of multi-player online games is leading to the widespread use of large-scale Distributed Virtual Environments (DVEs) nowadays. In these systems, peer-to-peer (P2P) architectures have been proposed as an efficient and scalable solution for supporting massively multi-player applications. However, the main challenge for P2P architectures consists of providing each avatar with updated information about which other avatars are its neighbors. This problem is known as the awareness problem. In this paper, we propose a comparative study of the performance provided by those awareness methods that are supposed to fully solve the awareness problem. This study is performed using well-known performance metrics in distributed systems. Moreover, while the evaluations shown in the literature are performed by executing P2P simulations on a single (sequential) computer, this paper evaluates the performance of the considered methods on actually distributed systems. The evaluation results show that only a single method actually provides full awareness to avatars. This method also provides the best performance results. Copyright © 2008 John Wiley & Sons, Ltd. [source] Atypical antipsychotics and anorexia nervosa: A reviewEUROPEAN EATING DISORDERS REVIEW, Issue 1 2010Rebecca F. McKnight Abstract Background There is currently mixed opinion regarding the value of using atypical antipsychotics to treat anorexia nervosa (AN). Aims To evaluate the literature on the use of atypical antipsychotics in AN. Method A review of all studies and clinical guidelines published before September 2009 involving use of an atypical antipsychotic in patients with AN. Analysis is by narrative synthesis. Results Forty-three publications or study protocols were found, including four randomized-controlled trials, five open-label trials and 26 case reports. The most studied drugs were olanzapine, quetiapine and risperidone. Atypical antipsychotics appear safe and there is some evidence of positive effects on depression, anxiety and core eating disordered psychopathology in patients with anorexia nervosa. Currently there is insufficient evidence to confirm atypical antipsychotics enhance weight gain in this setting. Conclusions Further high quality evidence is needed in this area in order to provide practical guidance to clinicians. However, the main challenge is to persuade adequate numbers of AN patients to participate in research trials. Copyright © 2010 John Wiley & Sons, Ltd and Eating Disorders Association. [source] Solving nursing shortages: a common priorityJOURNAL OF CLINICAL NURSING, Issue 24 2008James Buchan Aims and objectives., This paper provides a context for this special edition. It highlights the scale of the challenge of nursing shortages, but also makes the point that there is a policy agenda that provides workable solutions. Results., An overview of nurse:population ratios in different countries and regions of the world, highlighting considerable variations, with Africa and South East Asia having the lowest average ratios. The paper argues that the ,shortage' of nurses is not necessarily a shortage of individuals with nursing qualifications, it is a shortage of nurses willing to work in the present conditions. The causes of shortages are multi-faceted, and there is no single global measure of their extent and nature, there is growing evidence of the impact of relatively low staffing levels on health care delivery and outcomes. The main causes of nursing shortages are highlighted: inadequate workforce planning and allocation mechanisms, resource constrained undersupply of new staff, poor recruitment, retention and ,return' policies, and ineffective use of available nursing resources through inappropriate skill mix and utilisation, poor incentive structures and inadequate career support. Conclusions., What now faces policy makers in Japan, Europe and other developed countries is a policy agenda with a core of common themes. First, themes related to addressing supply side issues: getting, keeping and keeping in touch with relatively scarce nurses. Second, themes related to dealing with demand side challenges. The paper concludes that the main challenge for policy makers is to develop a co-ordinated package of policies that provide a long term and sustainable solution. Relevance to clinical practice., This paper highlights the impact that nursing shortages has on clinical practice and in health service delivery. It outlines scope for addressing shortage problems and therefore for providing a more positive staffing environment in which clinical practice can be delivered. [source] Gelatin microspheres crosslinked with genipin for local delivery of growth factorsJOURNAL OF TISSUE ENGINEERING AND REGENERATIVE MEDICINE, Issue 7 2010Luis Solorio Abstract A main challenge in tissue engineering and regenerative medicine is achieving local and efficient growth factor release to guide cell function. Gelatin is a denatured form of collagen that cells can bind to and degrade through enzymatic action. In this study, gelatin microspheres were used to release bone morphogenetic protein 2 (BMP2). Spherical microparticles with diameters in the range of 2,6 µm were created by an emulsification process and were stabilized by crosslinking with the small molecule genipin. The degree of crosslinking was varied by controlling the incubation time in genipin solution. Loading rate studies, using soy bean trypsin inhibitor as a model protein, showed rapid protein uptake over the first 24 h, followed by a levelling off and then a further increase after approximately 3 days, as the microspheres swelled. Growth factor release studies using microspheres crosslinked to 20%, 50% and 80% of saturation and then loaded with BMP2 showed that higher degrees of crosslinking resulted in higher loading efficiency and slower protein release. After 24 h, the concentration profiles produced by all microsphere formulations were steady and approximately equal. Microspheres incubated with adult human mesenchymal stem cells accumulated preferentially on the cell surface, and degraded over time in culture. BMP2-loaded microspheres caused a three- to eight-fold increase in expression of the bone sialoprotein gene after 14 days in culture, with more crosslinked beads producing a greater effect. These results demonstrate that genipin-crosslinked gelatin microspheres can be used to deliver growth factors locally to cells in order to direct their function. Copyright © 2010 John Wiley & Sons, Ltd. [source] Desert water harvesting from takyr surfaces: assessing the potential of traditional and experimental technologies in the KarakumLAND DEGRADATION AND DEVELOPMENT, Issue 1 2007L. Fleskens Abstract From historical times the traditionally nomadic people in desert environments of Turkmenistan have applied a range of innovative technologies to secure water supply for consumptive and productive purposes. These technologies make use of takyrs, flat or slightly sloping dense clay surfaces which act as natural catchment areas. In recent history, these technologies have been neglected, in part due to a booming water supply through irrigation development, and takyr surfaces have suffered various degradation processes. However, the limited scope for further extension of irrigation systems presents a challenge to reconsider these traditional technologies. In this paper, results of cost-benefit analysis are presented by which an assessment is made of the potential of both traditional and experimental takyr use technologies. It is shown that they bear considerable potential for the future at relatively low investment cost, that they may help limit degradation processes and provide for a sustainable development pathway for the inhabitants of the desert. A main challenge in order to benefit from this potential is to find an appropriate management structure for maintenance and resource use of these water-harvesting technologies. Copyright © 2006 John Wiley & Sons, Ltd. [source] Nanostructured Materials for Skeletal RepairMACROMOLECULAR SYMPOSIA, Issue 1 2010Joerg Brandt Abstract The treatment of bone and cartilage defects with bioengineered constructs of artificial scaffolds and autogenous cells became the main challenge of contemporary regenerative medicine. Early defect repair may prevent secondary injury. Recent studies could prove that bone and cartilage cells are sensitive to microscale and nanoscale patterns of surface topography and chemical structure. Nanostructured materials provide an environment for tissue regeneration mimicking the physiological range of extracellular matrix. The article reviews several studies substantiating the superiority of nanostructured materials for bone and cartilage repair along with own results on cell attachment. [source] Analytic practice: Convergences and divergences,THE INTERNATIONAL JOURNAL OF PSYCHOANALYSIS, Issue 2 2010Cláudio Laks Eizirik The author discusses current convergences and divergences concerning analytic practice. After presenting a clinical vignette that can be understood differently according to different theoretical approaches, he discusses Wallerstein's proposal of a common ground in psychoanalysis and suggests that the present state of the art indicates that psychoanalysis is a pluralistic discipline, with different ways of training and practising it, and that the main challenge is to improve our ability to listen to and to learn from different approaches. [source] Power cut in the countertransferenceTHE JOURNAL OF ANALYTICAL PSYCHOLOGY, Issue 4 2010Alessandra Cavalli Abstract:, This paper is an attempt to describe and understand a certain type of defence that I shall call a ,power cut' because of its crippling and anti-relational nature. I will take extracts from a baby observation to show how this type of defence can be adopted from the beginning of life, followed by vignettes from my work with a young child and an adult patient which addresses the particular kind of difficulty the analyst has to face with patients who resort to such a defence. I am arguing that while defending from another, the patient is able to destabilize not only the connection between himself and this other, the analyst, but also that between the analyst and the analyst's internal world. I understand this as the violent re-enactment of the patient's uncontained and split off primitive experience. I see recovery from ,power cuts' as the main challenge for the analyst who is helping the patient to recover from an early failure in containment which has led to defective splitting. Only when the unthinkable experience of ,power cut' can become an experience that can be lived through and converted into a deintegrate, may integration be achieved. Translations of Abstract Cet article est une tentative de décrire et de comprendre un certain type de défenses que je nommerai « courts-circuits», du fait de leur nature invalidante et anti-relationnelle. Je présenterai des extraits d'une observation de nourrisson pour montrer comment ce type de défenses peut être adopté dès le début de la vie. Je poursuivrai par des vignettes de mon travail avec un jeune enfant et un patient adulte révélatrices du type de difficultés auxquelles est confronté l'analyste avec des patients relevant de ce type de défenses. Je montre que, tandis qu'il se défend d'un autre, l'individu est capable de déstabiliser non seulement le lien qui le relie à cet autre, l'analyste en l'occurrence, mais également le lien de l'analyste avec son propre monde interne. Je comprends cela comme une violente remise en acte de l'expérience primaire de clivage et d'absence de contenant. J'envisage la guérison des « courts-circuits» comme le défi majeur de l'analyste qui aide le patient à réparer la faille précoce du contenant primaire génératrice du clivage. Ce n'est que lorsque l'expérience impensable du « court-circuit » est devenue une expérience vivable pour le patient, que celle-ci peut se transformer en un dé-intégrat et ouvrir la voie à l'intégration. Dieser Text ist ein Versuch, einen bestimmten Abwehrtypus zu beschreiben und zu verstehen, den ich wegen seiner lähmenden und antibeziehungshaften Natur ,Stromsperre' nennen werde. Ich werde Auszüge aus einer Babybeobachtung heranziehen um zu zeigen, wie dieser Abwehrmodus vom Beginn des Lebens an aufgebaut werden kann. Es folgen Vignetten aus meiner Arbeit mit einem Kleinkind und einem erwachsenen Patienten die sich auf die bestimmte Art von Schwierigkeiten beziehen, die dem Analytiker bei Patienten begegnen, die sich in solcherart Abwehr flüchten. Ich zeige auf, daß, während er sich vor dem anderen schützt, der Patient nicht nur in die Lage gerät, die Verbindung zwischen ihm selbst und diesem anderen, dem Analytiker, zu destabilisieren, sondern auch jene zwischen dem Analytiker und des Analytikers innerer Welt. Ich verstehe dies als die gewaltsame Reinszenierung einer nicht eingebundenen und abgespaltenen primitiven Erfahrung des Patienten. Ich sehe die Behebung von ,Stromsperren' als Hauptherausforderung für den Analytiker an, der dem Patienten hilft, von einem frühen Versagen des Gehaltenwerdens zu genesen, daß zur Spaltung geführt hat. Nur wenn die undenkbare Erfahrung ,Stromsperre' zu einer Erfahrung werden kann, die durchlebt und in ein Nichtintegriertes überführt werden kann, mag Integration erreicht werden. Questo lavoro è un tentativo di descrivere e comprendere un certo tipo di difesa che chiamerò,corto circuito' per via della sua natura mutilante e antirelazionale. Presenterò estratti dall'osservazione del neonato per mostrare come questo tipo di difesa può essere adottata fin dagli inizi della vita seguiti da vignette del mio lavoro con un bambino e con un paziente adulto che indicano il particolare tipo di difficoltà che l'analista deve affrontare con pazienti che si aggrappano a tale difesa. Sostengo che mentre si difende dall'altro il paziente è capace di destabilizzare non solo le connessioni tra se stesso e questo altro, ma anche tra l'analista e il mondo interno dell'analista. Intendo con ciò il violento ripresentarsi della esperienza primaria del paziente non contenuta e scissa. Considero il riprendersi dalla ,corto circuito' come la sfida principale petr l'analista che sta aiutando il paziente a guarire dal precoce fallimento del contenimento che ha portato alla scissione. L'integrazione può essere raggiunta solo quando l'esperienza impensabile della ,corto circuito' può diventare una esperienza che si può attraversare e convertire in una reintegrazione. Este trabajo es una intento por de describir y comprender un cierto tipo de defensa que llamaré un ,corte de energía' a causa de su efecto paralizador y su naturaleza anti-relacional. Tomaré extractos de una observación de un bebé para mostrar cómo este tipo de defensa puede surgir al principio de la vida, seguido por viñetas de mi trabajo con un niño y un paciente adulto para explorar el tipo de dificultad que el analista tiene que encarar con pacientes que recurren a tal defensa. Discuto que al defenderse del otro, el paciente puede desestabilizar no sólo la conexión con él mismo y este otro, el analista, sino también entre el analista y el mundo interno del analista. Entiendo esto como la reconstrucción violenta sin contención y disociadora de la experiencia primitiva del paciente. ,Considero a ,estos cortes de energía' como el principal desafío para el analista que ayuda al paciente a recuperarse de un fracaso temprano en la contención que lo ha llevado a la disociación. Sólo cuando la experiencia inconcebible de ,corte de energía' pueda ser revivida y convertida en una desintegración, se puede lograr la integración. [source] Synthesis: Sharing Ecological Knowledge,The Way ForwardBIOTROPICA, Issue 5 2009Julia Born ABSTRACT Knowledge sharing between scientists and nonscientist stakeholders is necessary to implement research findings in an appropriate and effective manner within the context of the environment and conservation sectors. Yet scientific ecological knowledge is rarely shared and transferred effectively. This special section has addressed a number of opportunities and barriers to the improvement of scientific communication and knowledge transfer with respect to environmental management in tropical settings. A main challenge is seen in creating a research ,impact-metric' system, which is fundamental to foster knowledge sharing with institutional research incentives. Partnering with local institutions and research centers as well as participatory research methods will promote effective knowledge exchange. Research relevance and impact will be improved by matching interdisciplinary research with local capacity building and support through research activities. We conclude that training the next generation of tropical biologists through more effective knowledge sharing will be crucial to the long term success of scientifically based environmental management in tropical regions. [source] GraphDice: A System for Exploring Multivariate Social NetworksCOMPUTER GRAPHICS FORUM, Issue 3 2010A. Bezerianos Abstract Social networks collected by historians or sociologists typically have a large number of actors and edge attributes. Applying social network analysis (SNA) algorithms to these networks produces additional attributes such as degree, centrality, and clustering coefficients. Understanding the effects of this plethora of attributes is one of the main challenges of multivariate SNA. We present the design of GraphDice, a multivariate network visualization system for exploring the attribute space of edges and actors. GraphDice builds upon the ScatterDice system for its main multidimensional navigation paradigm, and extends it with novel mechanisms to support network exploration in general and SNA tasks in particular. Novel mechanisms include visualization of attributes of interval type and projection of numerical edge attributes to node attributes. We show how these extensions to the original ScatterDice system allow to support complex visual analysis tasks on networks with hundreds of actors and up to 30 attributes, while providing a simple and consistent interface for interacting with network data. [source] Broad Beam Ion Sources for Electrostatic Space Propulsion and Surface Modification Processes: From Roots to Present ApplicationsCONTRIBUTIONS TO PLASMA PHYSICS, Issue 7 2007H. Neumann Abstract Ion thrusters or broad beam ion sources are widely used in electrostatic space propulsion and in high-end surface modification processes. A short historical review of the roots of electric space propulsion is given. In the following, we introduce the electrostatic ion thrusters and broad beam ion sources based on different plasma excitation principles and describe the similarities as well as the differences briefly. Furthermore, an overview on source plasma and ion beam characterisation methods is presented. Apart from that, a beam profile modelling strategy with the help of numerical trajectory codes as basis for a special grid system design is outlined. This modelling represents the basis for the adaptation of a grid system for required technological demands. Examples of model validation demonstrate their reliability. One of the main challenges in improvement of ion beam technologies is the customisation of the ion beam properties, e.g. the ion current density profile for specific demands. Methods of an ex-situ and in-situ beam profile control will be demonstrated. Examples for the use of ion beam technologies in space and on earth , the RIT-10 rescue mission of ESA's satellite Artemis, the RIT-22 for BepiColombo mission and the deposition of multilayer stacks for EUVL (Extreme Ultra Violet Lithography) mask blank application are provided in order to illustrate the potential of plasma-based ion beam sources. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Privatisation and outsourcing in wartime: the humanitarian challengesDISASTERS, Issue 4 2006Gilles Carbonnier Abstract The tendency today to privatise many activities hitherto considered the exclusive preserve of the state has given rise to sharp debate. The specific nature of humanitarian emergencies elucidates in particularly stark contrast some of the main challenges connected to the privatisation and outsourcing of essential public services, such as the provision of drinking water and health care. Privatising the realms of defence and security, which are at the very core of state prerogative, raises several legal and humanitarian concerns. This article focuses on the roles and responsibilities of the various parties involved in armed conflicts, especially those of private companies engaged in security, intelligence and interrogation work, and in the provision of water supply and health services. It highlights the need for humanitarian and development actors to grasp better the potential risks and opportunities related to privatisation and outsourcing with a view to supplying effective protection and assistance to communities affected by war. [source] Tailoring Cell Behavior on Polymers by the Incorporation of Titanium Doped Phosphate Glass Filler,ADVANCED ENGINEERING MATERIALS, Issue 7 2010Wojciech Chrzanowski Abstract Understanding tissue response to materials, to enable modulation and guided tissue regeneration is one of the main challenges in biomaterials science. Nowadays polymers, glasses, and metals dominate as biomaterials. Often native properties of those materials are not sufficient and there is a need to combine them, so as to modify and adjust their properties to the application. The primary aim of this study was to improve cell response to polymer (PLDL) using phosphate glass as filler (titanium doped phosphate glass). As a control ,-tricalcium phosphate (TCP) filler was used. Various concentrations of the filler were used (10,40 vol%). Wetting behavior, , -potentials, mechanical and thermal properties, and human cells response to the materials were evaluated. Results showed that with increase in glass filler loading wettability improved, , -potentials dropped, and increase in stiffness of materials was observed. Importantly cell culture experiments showed more developed and well spread cells on the samples with glass content up to 20 vol%. Cells responded much more positively to the glass filled samples than to TCP filled. However, expression of osteocalcin and osteopontin, proteins that indicate formation of the mineralized structures was positive for all the samples including pure PLDL. It was concluded that due to improved wetting behavior, lower , -potentials, and specific chemistry of the glass filler it was possible to alter cells response, improve bioactivity of the polymer, and vary mechanical properties. [source] Influence of Filler Composition on the Microstructure and Mechanical Properties of Steel,Aluminum Joints Produced by Metal Arc Joining,ADVANCED ENGINEERING MATERIALS, Issue 5 2009Leonardo Agudo Jácome Chemical joining of aluminum to steel parts is one of the main challenges in the automotive industry to achieve sound economical solutions for required automobile weight reduction. The cold metal transfer (CMT) is a fusion welding process developed to meet that challenge. It is shown in this paper how the choice of proper filler materials can yield appropriate mechanical performance of specially designed dissimilar CMT butt joints by improving the seam characteristics and weld bead properties. [source] Modelling night-time ecosystem respiration by a constrained source optimization methodGLOBAL CHANGE BIOLOGY, Issue 2 2002Chun-Ta Lai Abstract One of the main challenges to quantifying ecosystem carbon budgets is properly quantifying the magnitude of night-time ecosystem respiration. Inverse Lagrangian dispersion analysis provides a promising approach to addressing such a problem when measured mean CO2 concentration profiles and nocturnal velocity statistics are available. An inverse method, termed ,Constrained Source Optimization' or CSO, which couples a localized near-field theory (LNF) of turbulent dispersion to respiratory sources, is developed to estimate seasonal and annual components of ecosystem respiration. A key advantage to the proposed method is that the effects of variable leaf area density on flow statistics are explicitly resolved via higher-order closure principles. In CSO, the source distribution was computed after optimizing key physiological parameters to recover the measured mean concentration profile in a least-square fashion. The proposed method was field-tested using 1 year of 30-min mean CO2 concentration and CO2 flux measurements collected within a 17-year-old (in 1999) even-aged loblolly pine (Pinus taeda L.) stand in central North Carolina. Eddy-covariance flux measurements conditioned on large friction velocity, leaf-level porometry and forest-floor respiration chamber measurements were used to assess the performance of the CSO model. The CSO approach produced reasonable estimates of ecosystem respiration, which permits estimation of ecosystem gross primary production when combined with daytime net ecosystem exchange (NEE) measurements. We employed the CSO approach in modelling annual respiration of above-ground plant components (c. 214 g C m,2 year,1) and forest floor (c. 989 g C m,2 year,1) for estimating gross primary production (c. 1800 g C m,2 year,1) with a NEE of c. 605 g C m,2 year,1 for this pine forest ecosystem. We conclude that the CSO approach can utilise routine CO2 concentration profile measurements to corroborate forest carbon balance estimates from eddy-covariance NEE and chamber-based component flux measurements. [source] University Efficiency: Complementariness versus Trade-off between Teaching, Research and Administrative ActivitiesHIGHER EDUCATION QUARTERLY, Issue 4 2010Ricardo Sellers-Rubio University managers should be aware of the importance that efficiency has for their own universities, orientating their actions towards research and teaching excellence. This study estimates teaching and research efficiency of the different departments of a university and tests the complementariness versus trade-off between them. The results obtained show high levels of efficiency for the departments analysed, which is important for budget allocation, as one of the main challenges faced by a university is the allocation of budgets to different departments. The results also support the trade-off between teaching efficiency and research activity, the complementariness between teaching efficiency and research efficiency, between research efficiency and time deducted from teaching, as well as the complementariness between research efficiency and administration activity. [source] 1D Conducting Polymer Nanostructures: One-Dimensional Conducting Polymer Nanostructures: Bulk Synthesis and Applications (Adv. Mater.ADVANCED MATERIALS, Issue 14-15 200915/2009) One-dimensional conducting polymer nanostructures hold great promise for many technological applications and can be chemically synthesized in bulk quantities using either template or template-free strategies. Richard Kaner and co-workers highlight on page 1487 recent research activities in this field and present their perspectives on the main challenges and future research directions for this new class of nanomaterials. [source] One-Dimensional Conducting Polymer Nanostructures: Bulk Synthesis and ApplicationsADVANCED MATERIALS, Issue 14-15 2009Henry D. Tran Abstract This Progress Report provides a brief overview of current research activities in the field of one-dimensional (1D) conducting polymer nanostructures. The synthesis, properties, and applications of these materials are outlined with a strong emphasis on recent literature examples. Chemical methods that can produce 1D nanostructures in bulk quantities are discussed in the context of two different strategies: 1) procedures that rely on a nanoscale template or additive not inherent to the polymer and 2) those that do not. The different sub-classifications of these two strategies are delineated and the virtues and vices of each area are discussed. Following this discussion is an outline of the properties and applications of 1D conducting polymer nanostructures. This section focuses on applications in which nanostructured conducting polymers are clearly advantageous over their conventional counterparts. We conclude with our perspective on the main challenges and future research directions for this new class of nanomaterials. This Progress Report is not intended as a comprehensive review of the field, but rather a summary of select contributions that we feel will provide the reader with a strong basis for further investigation into this fast emerging field. [source] A peer-to-peer IPTV service architecture for the IP multimedia subsystemINTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 6-7 2010A. Bikfalvi Abstract During these last years the Internet Protocol Television (IPTV) service and the different peer-to-peer (P2P) technologies have generated an increasing interest for the developers and the research community that find in them the solution to deal with the scalability problem of media streaming and reducing costs at the same time. However, despite of the benefits obtained in Internet-based applications and the growing deployment of commercial IPTV systems, there has been a little effort in combining them both. With the advent of the next-generation-network platforms such as the IP Multimedia Subsystem (IMS), which advocates for an open and inter-operable service infrastructure, P2P emerges as a possible solution in situations where the traditional streaming mechanisms are not possible or not economically feasible. In this paper, we propose an IPTV service architecture for the IMS that combines a centralized control layer and a distributed, P2P-like, media layer that relies on the IMS devices or peers located in the customers' premises to act as streaming forwarding nodes. We extend the existing IMS IPTV standardization work that has already been done in 3GPP and ETSI TISPAN in order to require a minimum number of architectural changes. The objective is to obtain a system with a similar performance to the one in currently deployed systems and with the flexibility of P2P. One of the main challenges is to achieve comparable response times to user actions such as changing and tuning into channels, as well as providing a fast recovery mechanism when streaming nodes leave. To accomplish this we introduce the idea of foster peers as peers having inactive multimedia sessions and reserved resources. These peers are on stand-by until their functionality is required and at that moment, they are able to accept downstream peers at short notice for events requiring urgent treatment like channel changing and recovery. Copyright © 2009 John Wiley & Sons, Ltd. [source] Integration of mobility and intrusion detection for wireless ad hoc networksINTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 6 2007Bo Sun Abstract One of the main challenges in building intrusion detection systems (IDSs) for mobile ad hoc networks (MANETs) is to integrate mobility impacts and to adjust the behaviour of IDSs correspondingly. In this paper, we first introduce two different approaches, a Markov chain-based approach and a Hotelling's T2 test based approach, to construct local IDSs for MANETs. We then demonstrate that nodes' moving speed, a commonly used parameter in tuning IDS performances, is not an effective metric to tune IDS performances under different mobility models. To solve this problem, we further propose an adaptive scheme, in which suitable normal profiles and corresponding proper thresholds can be selected adaptively by each local IDS through periodically measuring its local link change rate, a proposed unified performance metric. We study the proposed adaptive mechanism at different mobility levels, using different mobility models such as random waypoint model, random drunken model, and obstacle mobility model. Simulation results show that our proposed adaptive scheme is less dependent on the underlying mobility models and can further reduce false positive ratio. Copyright © 2006 John Wiley & Sons, Ltd. [source] Congestion control for multimedia applications in the wireless internetINTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 7 2004Veselin Rakocevic Abstract This paper provides a parallel review of two important issues for the next-generation multimedia networking. Firstly, the emerging multimedia applications require a fresh approach to congestion control in the Internet. Currently, congestion control is performed by TCP; it is optimised for data traffic flows, which are inherently elastic. Audio and video traffic do not find the sudden rate fluctuations imposed by the TCP multiplicative-decrease control algorithm optimal. The second important issue is the mobility support for multimedia applications. Wireless networks are characterized by a substantial packet loss due to the imperfection of the radio medium. This increased packet loss disturbs the foundation of TCP's loss-based congestion control. This paper contributes to the ongoing discussion about the Internet congestion control by providing a parallel analysis of these two issues. The paper describes the main challenges, design guidelines, and existing proposals for the Internet congestion control, optimised for the multimedia traffic in the wireless network environment. Copyright © 2004 John Wiley & Sons, Ltd. [source] Conducting rehabilitation groups for people suffering from chronic painINTERNATIONAL JOURNAL OF NURSING PRACTICE, Issue 3 2010Elin Dysvik RN PhD Dysvik E, Stephens P. International Journal of Nursing Practice 2010; 16: 233,240 Conducting rehabilitation groups for people suffering from chronic pain The aim of this study was to offer guidelines for counsellors who work with rehabilitation groups of patients with chronic pain. The sample involved nine counsellors engaged in a multidisciplinary pain management programme. Two focus group interviews were conducted. Data were analysed using qualitative content analysis. These indicate that main challenges facing counsellors were related to maintaining constructive group processes and being mentally prepared. The counsellors reported that knowledge concerning self-awareness, theoretical frameworks and counselling techniques was important. Personal learning included: group leadership, teamwork, grasping the inside story and obtaining supervision. The results show how important it is to have trained counsellors that are well prepared to prevent and deal with challenging group processes. Counsellors need to understand the concept of pain and be acquainted with cognitive behavioural framework and group processes. The results indicate that counsellors perceive regular supervision as supportive and is likely to promote good team functioning. [source] The minimized dead-end elimination criterion and its application to protein redesign in a hybrid scoring and search algorithm for computing partition functions over molecular ensemblesJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 10 2008Ivelin Georgiev Abstract One of the main challenges for protein redesign is the efficient evaluation of a combinatorial number of candidate structures. The modeling of protein flexibility, typically by using a rotamer library of commonly-observed low-energy side-chain conformations, further increases the complexity of the redesign problem. A dominant algorithm for protein redesign is dead-end elimination (DEE), which prunes the majority of candidate conformations by eliminating rigid rotamers that provably are not part of the global minimum energy conformation (GMEC). The identified GMEC consists of rigid rotamers (i.e., rotamers that have not been energy-minimized) and is thus referred to as the rigid-GMEC. As a postprocessing step, the conformations that survive DEE may be energy-minimized. When energy minimization is performed after pruning with DEE, the combined protein design process becomes heuristic, and is no longer provably accurate: a conformation that is pruned using rigid-rotamer energies may subsequently minimize to a lower energy than the rigid-GMEC. That is, the rigid-GMEC and the conformation with the lowest energy among all energy-minimized conformations (the minimized-GMEC) are likely to be different. While the traditional DEE algorithm succeeds in not pruning rotamers that are part of the rigid-GMEC, it makes no guarantees regarding the identification of the minimized-GMEC. In this paper we derive a novel, provable, and efficient DEE-like algorithm, called minimized-DEE (MinDEE), that guarantees that rotamers belonging to the minimized-GMEC will not be pruned, while still pruning a combinatorial number of conformations. We show that MinDEE is useful not only in identifying the minimized-GMEC, but also as a filter in an ensemble-based scoring and search algorithm for protein redesign that exploits energy-minimized conformations. We compare our results both to our previous computational predictions of protein designs and to biological activity assays of predicted protein mutants. Our provable and efficient minimized-DEE algorithm is applicable in protein redesign, protein-ligand binding prediction, and computer-aided drug design. © 2008 Wiley Periodicals, Inc. J Comput Chem, 2008 [source] Societal Safety: Concept, Borders and DilemmasJOURNAL OF CONTINGENCIES AND CRISIS MANAGEMENT, Issue 2 2007Odd Einar Olsen In most industrialized countries, the end of the Cold War marked a change in focus from preparedness for war to an increasing focus on civil society's own vulnerability and safety. To meet new threats and changing risks, there is also a need for new analytical concepts. Societal safety is a concept developed in Norway during the last decade. It could be defined as: ,The society's ability to maintain critical social functions, to protect the life and health of the citizens and to meet the citizens' basic requirements in a variety of stress situations'. It aims to be a systematic approach for understanding, mitigating and responding to social problems such as extraordinary stresses and losses, interferences in complex and mutual dependent systems, or lack of trust in vital social institutions. Future threats to society are not limited to specific sectors or areas, but stem from complex interactions amongst economic, technological, social and cultural factors. Thus, the main challenges to improve societal safety will be the ability to coordinate, organize and assign clear roles to different actors at the international, national and local levels. Societal safety has interfaces with other safety-related areas such as national security, sustainable development, human security and incident management (handling of isolated accidents, common illness and ordinary criminal acts). Societal safety is, however, a sensitive political issue containing dilemmas and value choices that are hardly possible to perceive or solve as pure scientific problems. [source] Emulsion-Based Delivery Systems for Lipophilic Bioactive ComponentsJOURNAL OF FOOD SCIENCE, Issue 8 2007D.J. McClements ABSTRACT:, There is a pressing need for edible delivery systems to encapsulate, protect, and release bioactive lipids within the food, medical, and pharmaceutical industries. The fact that these delivery systems must be edible puts constraints on the type of ingredients and processing operations that can be used to create them. Emulsion technology is particularly suited for the design and fabrication of delivery systems for encapsulating bioactive lipids. This review provides a brief overview of the major bioactive lipids that need to be delivered within the food industry (for example, ,-3 fatty acids, carotenoids, and phytosterols), highlighting the main challenges to their current incorporation into foods. We then provide an overview of a number of emulsion-based technologies that could be used as edible delivery systems by the food and other industries, including conventional emulsions, multiple emulsions, multilayer emulsions, solid lipid particles, and filled hydrogel particles. Each of these delivery systems could be produced from food-grade (GRAS) ingredients (for example, lipids, proteins, polysaccharides, surfactants, and minerals) using simple processing operations (for example, mixing, homogenizing, and thermal processing). For each type of delivery system, we describe its structure, preparation, advantages, limitations, and potential applications. This knowledge can be used to facilitate the selection of the most appropriate emulsion-based delivery system for specific applications. [source] Social distance in Bosnia-Herzegovina and the North Caucasus region of Russia: Inter and intra-ethnic attitudes and identities,NATIONS AND NATIONALISM, Issue 2 2009KRISTIN M. BAKKE ABSTRACT. This article examines attitudinal differences and similarities among ethnic groups in conflict-affected societies. Conventional wisdom tells us that societies that have experienced violent struggles in which individuals of different ethnic groups have (been) mobilized against each other are likely to become polarized along ethnic lines. Indeed, both policy-makers and scholars often assume that such divisions are some of the main challenges that must be overcome to restore peace after war. We comparatively examine this conventional wisdom by mapping dimensions of social distance among 4,000 survey respondents in Bosnia-Herzegovina and the North Caucasus region of Russia. The surveys were carried out in December 2005. Using multidimensional scaling methods, we do not find patterns of clear attitudinal cleavages among members of different ethnic groups in Bosnia-Herzegovina. Nor do we find patterns of clear ethnic division in the North Caucasus, although our social distance matrices reveal a difference between Russians and ethnic minority groups. [source] Sustainable consumption and production: Trends, challenges and options for the Asia-Pacific regionNATURAL RESOURCES FORUM, Issue 1 2010Wei Zhao Abstract This paper highlights current trends in consumption and production patterns in Asian developing countries and emerging economies. It describes the main challenges and opportunities for Asian countries making the transition towards sustainable consumption and production patterns. The main challenge for Asian economies is to address the unsustainable consumption patterns of urban consumers, which entails a policy shift from the current focus on pollution and inefficient industrial production. In view of future consumption trends and the global convergence of consumption patterns, the characteristics of the emerging ,global consumer class' are examined, with particular focus on urban ecological footprints and carbon emissions. Furthermore, the difference between urban and rural consumption is discussed, together with opportunities for low-carbon urban development in the megacities of Asian developing countries. To conclude, the paper presents an overview of current policy measures taken in Asian countries to green economic development and realise sustainable consumption and production patterns. [source] Simulation and implementation of a porous silicon reflector for epitaxial silicon solar cellsPROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 5 2008Filip Duerinckx Abstract One of the main challenges in the ongoing development of thin film crystalline silicon solar cells on a supporting silicon substrate is the implementation of a long-wavelength reflector at the interface between the epitaxial layer and the substrate. IMEC has developed such a reflector based on electrochemical anodization of silicon to create a multi-layer porous silicon stack with alternating high and low porosity layers. This innovation results in a 1,2% absolute increase in efficiency for screenprinted epitaxial cells with a record of 13·8%. To reach a better understanding of the reflector and to aid in its continued optimization, several extensive optical simulations have been performed using an in-house-developed optical software programme. This software is written as a Microsoft Excel workbook to make use of its user-friendliness and modular structure. It can handle up to 15 individual dielectric layers and is used to determine the influence of the number and the sequence of the layers on the internal reflection. A sensitivity analysis is also presented. A study of the angle at which the light strikes the reflector shows separate regions in the physical working of the reflector which include a region where the Bragg effect is dominant as well as a region where total internal reflection plays the largest role. The existence of these regions is proved using reflection measurements. Based on these findings, an estimate is made for the achievable current gain with an ideal reflector and the potential of epitaxial silicon solar cells is determined. Copyright © 2008 John Wiley & Sons, Ltd. [source] Serum biomarker profiling by solid-phase extraction with particle-embedded micro tips and matrix-assisted laser desorption/ionization mass spectrometry,RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 7 2008Arti Navare One of the main challenges in high-throughput serum profiling by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) is the development of proteome fractionation approaches that allow the acquisition of reproducible profiles with a maximum number of spectral features and minimum interferences from biological matrices. This study evaluates a new class of solid-phase extraction (SPE) pipette tips embedded with different chromatographic media for fractionation of model protein digests and serum samples. The materials embedded include strong anion exchange (SAX), weak cation exchange (WCX), C18, C8, C4, immobilized metal affinity chromatography (IMAC) and zirconium dioxide particles. Simple and rapid serum proteome profiling protocols based on these SPE micro tips are described and tested using a variety of MALDI matrices. We show that different types of particle-embedded SPE micro tips provide complementary information in terms of the spectral features detected for , -casein digests and control human serum samples. The effect of different sample pretreatments, such as serum dilution and ultrafiltration using molecular weight cut-off membranes, and the reproducibility observed for replicate experiments, are also evaluated. The results demonstrate the usefulness of these simple SPE tips combined with offline MALDI-TOF MS for obtaining information-rich serum profiles, resulting in a robust, versatile and reproducible open-source platform for serum biomarker discovery. Copyright © 2008 John Wiley & Sons, Ltd. [source] Optimal Synthesis of Protein Purification ProcessesBIOTECHNOLOGY PROGRESS, Issue 4 2001Elsa Vásquez-Alvarez There has been an increasing interest in the development of systematic methods for the synthesis of purification steps for biotechnological products, which are often the most difficult and costly stages in a biochemical process. Chromatographic processes are extensively used in the purification of multicomponent biotechnological systems. One of the main challenges in the synthesis of purification processes is the appropriate selection and sequencing of chromatographic steps that are capable of producing the desired product at an acceptable cost and quality. This paper describes mathematical models and solution strategies based on mixed integer linear programming (MILP) for the synthesis of multistep purification processes. First, an optimization model is proposed that uses physicochemical data on a protein mixture, which contains the desired product, to select a sequence of operations with the minimum number of steps from a set of candidate chromatographic techniques that must achieve a specified purity level. Since several sequences that have the minimum number of steps may satisfy the purity level, it is possible to obtain the one that maximizes final purity. Then, a second model that may use the total number of steps obtained in the first model generates a solution with the maximum purity of the product. Whenever the sequence does not affect the final purity or more generally does not impact the objective function, alternative models that are of smaller size are developed for the optimal selection of steps. The models are tested in several examples, containing up to 13 contaminants and a set of 22 candidate high-resolution steps, generating sequences of six operations, and are compared to the current synthesis approaches. [source] | |||||||||||||||||||||||||||||||||||||