Home About us Contact
|
Home About us Contact | ||
|
|
||
Remaining Challenges (remaining + challenge)
Selected AbstractsDual-Gate Organic Field-Effect Transistors as Potentiometric Sensors in Aqueous SolutionADVANCED FUNCTIONAL MATERIALS, Issue 6 2010Mark-Jan Spijkman Abstract Buried electrodes and protection of the semiconductor with a thin passivation layer are used to yield dual-gate organic transducers. The process technology is scaled up to 150-mm wafers. The transducers are potentiometric sensors where the detection relies on measuring a shift in the threshold voltage caused by changes in the electrochemical potential at the second gate dielectric. Analytes can only be detected within the Debye screening length. The mechanism is assessed by pH measurements. The threshold voltage shift depends on pH as ,Vth,=,(Ctop/Cbottom),×,58,mV per pH unit, indicating that the sensitivity can be enhanced with respect to conventional ion-sensitive field-effect transistors (ISFETs) by adjusting the ratio of the top and bottom gate capacitances. Remaining challenges and opportunities are discussed. [source] EVOLUTION AND STABILITY OF THE G-MATRIX ON A LANDSCAPE WITH A MOVING OPTIMUMEVOLUTION, Issue 8 2004Adam G. Jones Abstract In quantitative genetics, the genetic architecture of traits, described in terms of variances and covariances, plays a major role in determining the trajectory of evolutionary change. Hence, the genetic variance-covariance matrix (G-matrix) is a critical component of modern quantitative genetics theory. Considerable debate has surrounded the issue of G-matrix constancy because unstable G-matrices provide major difficulties for evolutionary inference. Empirical studies and analytical theory have not resolved the debate. Here we present the results of stochastic models of G-matrix evolution in a population responding to an adaptive landscape with an optimum that moves at a constant rate. This study builds on the previous results of stochastic simulations of G-matrix stability under stabilizing selection arising from a stationary optimum. The addition of a moving optimum leads to several important new insights. First, evolution along genetic lines of least resistance increases stability of the orientation of the G-matrix relative to stabilizing selection alone. Evolution across genetic lines of least resistance decreases G-matrix stability. Second, evolution in response to a continuously changing optimum can produce persistent maladaptation for a correlated trait, even if its optimum does not change. Third, the retrospective analysis of selection performs very well when the mean G-matrix (,) is known with certainty, indicating that covariance between G and the directional selection gradient (3 is usually small enough in magnitude that it introduces only a small bias in estimates of the net selection gradient. Our results also show, however, that the contemporary ,-matrix only serves as a rough guide to ,. The most promising approach for the estimation of G is probably through comparative phylogenetic analysis. Overall, our results show that directional selection actually can increase stability of the G-matrix and that retrospective analysis of selection is inherently feasible. One ?riajor remaining challenge is to gain a sufficient understanding of the G-matrix to allow the confident estimation of ,. [source] Solar-Energy Production and Energy-Efficient Lighting: Photovoltaic Devices and White-Light-Emitting Diodes Using Poly(2,7-fluorene), Poly(2,7-carbazole), and Poly(2,7-dibenzosilole) DerivativesADVANCED MATERIALS, Issue 8 2010Serge Beaupré Abstract World energy needs grow each year. To address global warming and climate changes the search for renewable energy sources with limited greenhouse gas emissions and the development of energy-efficient lighting devices are underway. This Review reports recent progress made in the synthesis and characterization of conjugated polymers based on bridged phenylenes, namely, poly(2,7-fluorene)s, poly(2,7-carbazole)s, and poly(2,7-dibenzosilole)s, for applications in solar cells and white-light-emitting diodes. The main strategies and remaining challenges in the development of reliable and low-cost renewable sources of energy and energy-saving lighting devices are discussed. [source] Canadian Policy on Human Trafficking: A Four-year Analysis1INTERNATIONAL MIGRATION, Issue 4 2005Jacqueline Oxman-Martinez ABSTRACT This article introduces readers to Canadian Government policy and practice surrounding human trafficking since the adoption of the United Nations (UN) Protocol on Trafficking in 2000. After offering an overview of the UN Protocol, the article reviews and critically analyses Canada's efforts in the three key areas of the Protocol: prevention of human trafficking, protection of trafficking victims, and the prosecution of traffickers. Since the beginning of our research, progress has been made in Canadian policy responses. The Government began by developing and implementing its tools for the prosecution of traffickers, thereby responding to most of the prosecution recommendations of the UN Protocol. Different government agencies are also coordinating their efforts to implement prevention projects, both in source countries and at home, including awareness-raising campaigns, education campaigns, and policy development collaborations. However, the more structural elements of prevention have yet to be adequately addressed. Finally, without shifting their basic border control framework, Canadian government agencies are in the process of improving the protection of trafficking victims who are intercepted in law enforcement operations or who come forward for help. These protection measures would be strengthened further if migrants' rights were explicitly protected by law, something that has failed to occur given recent prioritization of crime and security. The formal protection of victims, as implemented to some degree in several European and American policies, is introduced for comparison. The article concludes with the remaining challenges that face Canadian policy makers, particularly in terms of shifting away from current focus on crime and security to the protection and promotion of the human rights of trafficking victims. LA POLITIQUE CANADIENNE EN MATIÈRE DE TRAITE DES ÊTRES HUMAINS : UNE ANALYSE SUR QUATRE ANS Cet article présente au lecteur la politique et la pratique du gouvernement canadien en matière de traite des êtres humains depuis l'adoption, en 2000, du Protocole additionnel à la Convention des Nations unies contre la criminalité transnationale organisée visant à prévenir, réprimer et punir la traite des personnes, en particulier des femmes et des enfants. Après avoir présenté le Protocole dans son ensemble, l'article examine et analyse de façon critique l'action du Canada dans trois domaines essentiels du Protocole : la prévention de la traite, la protection des victimes et la punition des trafiquants. Depuis le début de notre recherche, le Canada a fait un pas en avant dans les mesures politiques adoptées. Le gouvernement a commencé par élaborer et mettre en oeuvre des mécanismes pour punir les trafiquants, donnant de ce fait suite à la plupart des recommandations du protocole des Nations unies en la matière. Par ailleurs, différents organes de l'État coordonnent leurs efforts pour mettre en place des projets de prévention, tant dans les pays d'origine que sur le territoire canadien, avec des campagnes de sensibilisation et d'éducation, et des collaborations en matière d'élaboration des politiques. Il reste néanmoins à trouver une solution adéquate aux aspects les plus structurels de la prévention. Enfin, sans s'éloigner du cadre fondamental du contrôle des frontières, les services gouvernementaux canadiens améliorent actuellement la protection des victimes de la traite interceptées lors d'opérations de police ou qui viennent demander de l'aide. Ces mesures de protection seraient davantage renforcées si les droits des migrants étaient explicitement inscrits dans la loi, ce qui n'est pas le cas en raison de la priorité accordée à la répression de la criminalité et à la sécurité. La protection formelle des victimes, telle que mise en oeuvre jusqu'à un certain point par des mesures appliquées en Europe et aux États-Unis, est présentée à titre de comparaison. Les conclusions de cet article exposent les défis auxquels restent confrontés les décideurs canadiens, à savoir moins insister sur la répression de la criminalité et la sécurité pour s'occuper davantage de la protection et de la promotion des droits fondamentaux des victimes de la traite. POLÍTICA CANADIENSE RELATIVA A LA TRATA DE PERSONAS: UN ANÁLISIS CUADRIENAL Este artículo presenta las políticas y prácticas del Gobierno canadiense en torno a la trata de personas desde la adopción, en 2000, del Protocolo de las Naciones Unidas relativo a la trata de personas. Tras hacer un repaso del Protocolo de las Naciones Unidas, este artículo examina y analiza críticamente los empeños del Canadá en tres esferas clave del Protocolo: prevención de la trata de personas, protección de las víctimas de la trata, y enjuiciamiento de los traficantes. Desde que se iniciara este estudio se han observado progresos en las respuestas políticas canadienses. El Gobierno comenzó desarrollando y llevando a la práctica sus instrumentos para la sanción y enjuiciamiento de los traficantes, respondiendo así a la mayoría de las recomendaciones de enjuiciamiento que contiene el Protocolo de las Naciones Unidas. Varias instituciones gubernamentales también coordinan sus esfuerzos con miras a la puesta en práctica de proyectos de prevención, tanto en los países de origen como en el Canadá, incluyendo campañas de concienciación, campañas educativas y colaboraciones con miras al desarrollo de políticas. Sin embargo, aún quedan por encarar los elementos más estructurales de la prevención. Finalmente, sin salir del marco básico de control de fronteras, las instituciones gubernamentales canadienses están tratando de mejorar la protección de las víctimas de la trata interceptadas en operaciones de aplicación de la ley o que se presentan a las autoridades con miras a solicitar ayuda. Si se aspira a proteger explícitamente por ley los derechos de los migrantes, habrá que reforzar las medidas de protección, algo que no figura entre las prioridades establecidas recientemente con relación al ámbito delictivo y de seguridad. Con fines comparativos, se presenta la protección oficial que brindan a las víctimas las políticas europeas y americanas. Este artículo concluye con los desafíos que tienen ante sí los formuladores de políticas canadienses, particularmente en cuanto al cambio del centro de atención actual en materia de actividades delictivas y de seguridad hacia la protección y promoción de los derechos humanos de las víctimas de la trata. [source] Recent advances in controlled/living radical polymerization in emulsion and dispersionJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 21 2008Jung Kwon Oh Abstract Effective ways to conduct controlled/living radical polymerization (CRP) in emulsion systems are necessary for commercial latex production without significant modification of current industrial facilities. Conducting CRP in emulsion media is more complicated and more challenging than its application in homogeneous bulk. These challenges come from the intrinsic kinetics of emulsion polymerization. They include mass transport, slow chain growth mechanism, and exit of short radicals from polymeric particles. This review describes the recent developments of CRP in heterogeneous dispersion, including miniemulsion, microemulsion, dispersion, and especially emulsion. Various approaches for conducting emulsion CRP are detailed, including controlled seeded emulsion polymerization, nanoprecipitation, use of short oligomers as macroinitiators for in situ block copolymerization, and RAFT-mediated self-assembly. In addition many remaining challenges of the current methods barring wide spread industrial application of emulsion CRP are also suggested. © Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6983,7001, 2008 [source] Recent advances in the synthesis of well-defined glycopolymersJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 11 2007Sebastian G. Spain Abstract Glycopolymers are receiving increasing interest due to their application in areas, such as glycomics, medicine, biotechnology, sensors, and separation science. Consequently, new methods for their synthesis are constantly being developed, with an increasing emphasis on the preparation of well-defined polymers and on the production of complex macromolecular architectures such as stars. This review covers recent developments in the synthesis of glycopolymers, with a particular emphasis on (i) the use of controlled radical polymerization to prepare well-defined glycopolymers from unprotected monomers and (ii) postpolymerization modification strategies using reactive polymer precursors (including "click" reactions). Recent work on the production of glycosylated polypeptides, which are under investigation as mimics of naturally occurring glycoproteins, is also included. The authors offer some suggestions as to future developments and remaining challenges in this topical area of polymer chemistry. © 2007 Wiley Periodicals, Inc. J Polym Sci PartA: Polym Chem45: 2059,2072, 2007 [source] Identifying English Language Learners with Learning Disabilities: Key Challenges and Possible ApproachesLEARNING DISABILITIES RESEARCH & PRACTICE, Issue 1 2005Richard K. Wagner The need for effective approaches for identifying English language learners with learning disabilities is great and growing. Meeting this need is complicated by recent developments in the field of learning disabilities that are unrelated to the English language learning status, and by limitations in existing knowledge specific to the identification of English language learners with learning disabilities. We review recent developments in the field of learning disabilities concerning the need for earlier identification, the need for a more appropriate conceptualization of learning disability, and the need for more effective assessments and treatments. We discuss challenges to assessment and identification of English language learners with learning disabilities, provide examples of two approaches to meeting these challenges, and describe some remaining challenges. [source] Hepatic tissue engineering for adjunct and temporary liver support: Critical technologiesLIVER TRANSPLANTATION, Issue 11 2004Christina Chan The severe donor liver shortage, high cost, and complexity of orthotopic liver transplantation have prompted the search for alternative treatment strategies for end-stage liver disease, which would require less donor material, be cheaper, and less invasive. Hepatic tissue engineering encompasses several approaches to develop adjunct internal liver support methods, such as hepatocyte transplantation and implantable hepatocyte-based devices, as well as temporary extracorporeal liver support techniques, such as bioartificial liver assist devices. Many tissue engineered liver support systems have passed the "proof of principle" test in preclinical and clinical studies; however, they have not yet been found sufficiently reliably effective for routine clinical use. In this review we describe, from an engineering perspective, the progress and remaining challenges that must be resolved in order to develop the next generation of implantable and extracorporeal devices for adjunct or temporary liver assist. (Liver Transpl 2004;10:1331,1342.) [source] Extra pair paternity in birds: a review of interspecific variation and adaptive functionMOLECULAR ECOLOGY, Issue 11 2002Simon C. Griffith Abstract The application of molecular genetic techniques has revolutionized our view of avian mating systems. Contrary to prior expectations, birds are only very rarely sexually monogamous, with ,extra-pair offspring' found in approximately 90% of species. Even among socially monogamous species, over 11% of offspring are, on average, the result of extra-pair paternity (EPP). Based on over 150 molecular genetic studies of EPP in birds, we review two topical areas: (i) ecological explanations for interspecific variation in the rate of EPP; and (ii) evidence bearing on the adaptive function of EPP. We highlight the remaining challenges of understanding the relative roles of genes and ecology in determining variation between taxa in the rate of extra paternity, and testing for differences between extra-pair offspring and those sired within-pair. [source] Thin film solar modules: the low cost, high throughput and versatile alternative to Si wafersPROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 5 2006S. Hegedus Abstract Thin film solar cells (TFSC) have passed adolescence and are ready to make a substantial contribution to the world's electricity generation. They can have advantages over c-Si solar modules in ease of large area, lower cost manufacturing and in several types of applications. Factors which limit TFSC module performance relative to champion cell performance are discussed along with the importance of increased throughput and yield. The consensus of several studies is that all TFSC can achieve costs below 1,$/W if manufactured at sufficiently large scale >100,MW using parallel lines of cloned equipment with high material utilization and spray-on encapsulants. There is significant new commercial interest in TFSC from small investors and large corporations, validating the thin film approach. Unique characteristics are discussed which give TFSC an advantage over c-Si in two specific markets: small rural solar home systems and building integrated photovoltaic installations. TFSC have outperformed c-Si in annual energy production (kWhrs/kW), have demonstrated outdoor durability comparable to c-Si and are being used in MW scale installations worldwide. The merits of the thin film approach cannot be judged on the basis of efficiency alone but must also account for module performance and potential for low cost. TFSC advocates should promote their unique virtues compared to c-Si: lower cost, higher kWhr/kW output, higher battery charging current, attractive visual appearance, flexible substrates, long-term stability comparable to c-Si, and multiple pathways for deposition with room for innovation and evolutionary improvement. There is a huge market for TFSC even at today's efficiency if costs can be reduced. A brief window of opportunity exists for TFSC over the next few years due the Si shortage. The demonstrated capabilities and advantages of TFSC must be proclaimed more persistently to funding decision-makers and customers without minimizing the remaining challenges. Copyright © 2006 John Wiley & Sons, Ltd. [source] Recent developments in adeno-associated virus vector technologyTHE JOURNAL OF GENE MEDICINE, Issue 7 2008Hildegard Büning Abstract Adeno-associated virus (AAV), a single-stranded DNA parvovirus, is emerging as one of the leading gene therapy vectors owing to its nonpathogenicity and low immunogenicity, stability and the potential to integrate site-specifically without known side-effects. A portfolio of recombinant AAV vector types has been developed with the aim of optimizing efficiency, specificity and thereby also the safety of in vitro and in vivo gene transfer. More and more information is now becoming available about the mechanism of AAV/host cell interaction improving the efficacy of recombinant AAV vector (rAAV) mediated gene delivery. This review summarizes the current knowledge of the infectious biology of AAV, provides an overview of the latest developments in the field of AAV vector technology and discusses remaining challenges. Copyright © 2008 John Wiley & Sons, Ltd. [source] CT30 PERCUTANEOUS VALVE ACCOMPLISHMENTS AND CHALLENGESANZ JOURNAL OF SURGERY, Issue 2007A. Campbell At the end of the 20th century several inventors had suggested methods for catheter based implantation of cardiac valves. In September of 2000 Professor Philipp Bonhoeffer made transcatheter valve delivery a reality with the implantation of a stent mounted biological valve in the pulmonary position. Dr. Alain Cribier followed in 2002 with the first successful transcatheter implantation of a valve into the more challenging aortic position. Cardiac surgeons and industry seemed to show little interest in percutaneous valve delivery until January of 2004 when Edwards Life Science invested over $125 million in acquiring PVT, the company building the valves implanted by Dr. Cribier and Medtronic revealed the company's support for Dr. Bonhoeffer's efforts. A number of challenges have been identified and significant progress has been made in addressing some of these challenges. This presentation will describe the challenges associated with pulmonic and aortic transcatheter valve delivery. The progress that has been made in overcoming these challenges as well as the efforts being made to overcome the remaining challenges will be discussed. [source] | ||||||||||||||||