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Recent Experiments (recent + experiment)
Selected AbstractsInfluence of the Wall Characteristics on the Development of MARFE in TokamaksCONTRIBUTIONS TO PLASMA PHYSICS, Issue 7-9 2006O. Marchuk Abstract Multifaceted asymmetric radiation from the edge (MARFE) normally develops in fusion devices close to the density limit. MARFE is considered a result of thermal instabilities excited under critical conditions through different mechanisms: impurity radiation, recycling of neutral particles, anomalous transport of charged particles and energy. Recent experiments on tokamaks TEXTOR and JET show that plasma-wall interaction, leading to release of recycling neutrals and impurities, plays a very important role for the formation of MARFE. In the present contribution we develop further the MARFE models based on the instability of particle recycling on the tokamak wall by including a simple description for the release of recycling neutrals from the wall surface into the plasma. This development takes into account the time delay between the out flow of charged particles from the plasma and in flux of neutrals. The linear stability analysis shows that this does not change the critical plasma density for the MARFE formation but modifies significantly the growth rate of unstable perturbations developing when the density exceeds the threshold. These findings are confirmed in a non-linear consideration by solving the equations for the particle, momentum and energy transfer in the plasma coupled with the wall particle balance equations. This is done in a one-dimensional approximation by taking into account the variation of the main plasma parameters in the poloidal direction and making averaging in the radial direction over the plasma edge width of the penetration depth of neutrals. The intrinsic poloidal asymmetry of the system, defining the MARFE localization, is introduced by the Shafranov shift of magnetic flux surfaces. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Quantum-Chemical Characterization of the Origin of Dipole Formation at Molecular Organic/Organic InterfacesADVANCED FUNCTIONAL MATERIALS, Issue 4 2009Igor Avilov Abstract Recent experiments have reported a vacuum level shift at the interface between organic materials due to the formation of an interface dipole layer. On the basis of quantum-chemical calculations, this paper sheds light on the factors contributing to the formation of an interface dipole between an electron donor and an electron acceptor, considering as model system a complex made of tetrathiafulvalene (TTF) as a donor and tetracyanoquinodimethane (TCNQ) as an acceptor. The results indicate that the interface dipole is governed both by charge-transfer and polarization effects and allow for disentangling of their respective contributions. Two regimes of charge transfer can be distinguished depending on the strength of the electronic coupling: a fractional charge transfer occurs in the strong coupling regime while only integer charges are transferred when the coupling is weak. The polarization contribution can be significant, even in the presence of a pronounced charge transfer between the donor and acceptor molecules. The values of ionization potential and electron affinity of the donor and acceptor molecules may experience shifts as large as several tenths of an eV at the interface with respect to the isolated compounds. [source] Increased hepatotoxicity of tumor necrosis factor,related apoptosis-inducing ligand in diseased human liver,HEPATOLOGY, Issue 5 2007Xandra Volkmann Tumor necrosis factor,related apoptosis-inducing ligand (TRAIL) induces apoptosis in tumor cells but not in most normal cells and has therefore been proposed as a promising antitumor agent. Recent experiments suggested that isolated primary human hepatocytes but not monkey liver cells are susceptible to certain TRAIL agonists, raising concerns about the use of TRAIL in cancer treatment. Whether TRAIL indeed exerts hepatotoxicity in vivo and how this is influenced by chemotherapeutic drugs or liver disease are completely unknown. Employing different forms of recombinant TRAIL, we found that the cytokine can induce proapoptotic caspase activity in isolated human hepatocytes. However in marked contrast, these different TRAIL preparations induced little or no cytotoxicity when incubated with tissue explants of fresh healthy liver, an experimental model that may more faithfully mimic the in vivo situation. In healthy liver, TRAIL induced apoptosis only when combined with histone deacetylase inhibitors. Strikingly, however, TRAIL alone triggered massive apoptosis accompanied by caspase activation in tissue explants from patients with liver steatosis or hepatitis C viral infection. This enhanced sensitivity of diseased liver was associated with an increased expression of TRAIL receptors and up-regulation of proapoptotic Bcl-2 proteins. Conclusion: These results suggest that clinical trials should be performed with great caution when TRAIL is combined with chemotherapy or administered to patients with inflammatory liver diseases. (HEPATOLOGY 2007.) [source] Microstructure development in concentrated suspensions in a spinning ball rheometer,INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 3 2006Anne M. Grillet Abstract The spinning ball rheometer has been proposed as a method to measure the microstructure effect on the bulk rheological properties of concentrated suspensions. Recent experiments have shown that the measured extra torque on the spinning ball decreases as the radius of the spinning ball becomes comparable to the size of the suspended particle. We have performed a series of three-dimensional boundary element calculations of the rheometer geometry to probe the microstructure effects that contribute to that apparent slip. We present a series of quasi-static results based on random initial configurations as well as fully three-dimensional transient calculations, both of which are compared to the available experimental data. For the two cases, the apparent viscosity decreased as the size of the spinning ball decreased relative to the suspended particle. Comparison of the quasi-static and transient simulations indicates that the microstructure development is critical even at short times. In the transient calculations, the viscosity was observed to increase substantially relative to the torque based on the random initial configuration. Published in 2005 by John Wiley & Sons, Ltd. [source] Three-photon microscopy shows that somatic release can be a quantitatively significant component of serotonergic neurotransmission in the mammalian brainJOURNAL OF NEUROSCIENCE RESEARCH, Issue 15 2008S.K. Kaushalya Abstract Recent experiments on monoaminergic neurons have shown that neurotransmission can originate from somatic release. However, little is known about the quantity of monoamine available to be released through this extrasynaptic pathway or about the intracellular dynamics that mediate such release. Using three-photon microscopy, we directly imaged serotonin autofluorescence and investigated the total serotonin content, release competence, and release kinetics of somatic serotonergic vesicles in the dorsal raphe neurons of the rat. We found that the somata of primary cultured neurons contain a large number of serotonin-filled vesicles arranged in a perinuclear fashion. A similar distribution is also observed in fresh tissue slice preparations obtained from the rat dorsal raphe. We estimate that the soma of a cultured neuron on an average contains about 9 fmoles of serotonin in about 450 vesicles (or vesicle clusters) of ,370 nm average diameter. A substantial fraction (>30%) of this serotonin is released with a time scale of several minutes by K+ -induced depolarization or by para-chloroamphetamine treatment. The amount of releasable serotonin stored in the somatic vesicles is comparable to the total serotonin content of all the synaptic vesicles in a raphe neuron, indicating that somatic release can potentially play a major role in serotonergic neurotransmission in the mammalian brain. © 2008 Wiley-Liss, Inc. [source] Biodiversity effects on ecosystem functioning: emerging issues and their experimental test in aquatic environmentsOIKOS, Issue 3 2004Paul S. Giller Recent experiments, mainly in terrestrial environments, have provided evidence of the functional importance of biodiversity to ecosystem processes and properties. Compared to terrestrial systems, aquatic ecosystems are characterised by greater propagule and material exchange, often steeper physical and chemical gradients, more rapid biological processes and, in marine systems, higher metazoan phylogenetic diversity. These characteristics limit the potential to transfer conclusions derived from terrestrial experiments to aquatic ecosystems whilst at the same time provide opportunities for testing the general validity of hypotheses about effects of biodiversity on ecosystem functioning. Here, we focus on a number of unique features of aquatic experimental systems, propose an expansion to the scope of diversity facets to be considered when assessing the functional consequences of changes in biodiversity and outline a hierarchical classification scheme of ecosystem functions and their corresponding response variables. We then briefly highlight some recent controversial and newly emerging issues relating to biodiversity-ecosystem functioning relationships. Based on lessons learnt from previous experimental and theoretical work, we finally present four novel experimental designs to address largely unresolved questions about biodiversity-ecosystem functioning relationships. These include (1) investigating the effects of non-random species loss through the manipulation of the order and magnitude of such loss using dilution experiments; (2) combining factorial manipulation of diversity in interconnected habitat patches to test the additivity of ecosystem functioning between habitats; (3) disentangling the impact of local processes from the effect of ecosystem openness via factorial manipulation of the rate of recruitment and biodiversity within patches and within an available propagule pool; and (4) addressing how non-random species extinction following sequential exposure to different stressors may affect ecosystem functioning. Implementing these kinds of experimental designs in a variety of systems will, we believe, shift the focus of investigations from a species richness-centred approach to a broader consideration of the multifarious aspects of biodiversity that may well be critical to understanding effects of biodiversity changes on overall ecosystem functioning and to identifying some of the potential underlying mechanisms involved. [source] Ion dispersion near parallel wire grids in orthogonal acceleration time-of-flight mass spectrometry: predicting the effect of the approach angle on resolutionRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 6 2002Mark Lewin Ions experience small deflections in the vicinity of grids in accelerators and ion mirrors in time-of-flight (TOF) mass spectrometers. Recent experiments with an orthogonal acceleration (oa) TOF instrument have verified that the effect can significantly degrade resolution when ions approach grids at an angle deviating from 90,°. The phenomenon becomes significant only when ions have components of velocity at right angles to the wires of the grids. A model is presented in this study to predict this phenomenon for parallel wire grids. The fractional energy spread of ions (calculated in the static TOF-spectrometer frame of reference) scales directly with the approach angle of ions to the grid (as measured from normal approach). The energy spread also scales with the range of angles that is a consequence of the focusing effect in each gap between the wires of the grid. The equations imply that closely spaced parallel wire grids are best for deployment in oa-TOF systems where non-zero approach angles are unavoidable. Such grids are relatively impractical to manufacture and support but rectangular repeat cell grids with relatively few wires at right angles to the source axis are shown experimentally to introduce minimal energy spread. When these grids are rotated by 90,°, the resolution measured in a Q-TOF spectrometer is degraded in approximate agreement with the parallel wire model. A practical implication of this work is that grid transmissions in oa-TOF systems may be significantly increased without loss of resolution. Improvements of ,200% (V-mode) and ,400% (W-mode) in ion transmission were obtained in this study without compromising resolution. This was achieved with ,73% transmission grids and greater potential improvements in transmission are being realised since this study with ,89% transmission grids having similar geometry. Copyright © 2002 John Wiley & Sons, Ltd. [source] Developmental and adult expression of semaphorin 2a in the cricket Gryllus bimaculatus,THE JOURNAL OF COMPARATIVE NEUROLOGY, Issue 1 2007Kristen R. Maynard Abstract Developmental guidance cues act to direct growth cones to their correct targets in the nervous system. Recent experiments also demonstrate that developmental cues are expressed in the adult mammalian nervous system, although their function in the brain is not yet clear. The semaphorin gene family has been implicated in the growth of dendrites and axons in a number of different species. While the expression of semaphorin and its influence on tibial pioneer neurons in the developing limb bud have been well characterized in the grasshopper, the expression of semaphorin 2a (sema2a) has not been explored in the adult insect. In this study we used polymerase chain reaction (PCR) with degenerate and gene-specific primers to clone part of the secreted form of sema2a from Gryllus bimaculatus. Using in situ hybridization and immunohistochemistry, we confirmed that sema2a mRNA and protein expression patterns in the embryonic cricket were similar to that seen in the grasshopper. We also showed that tibial neuron development in crickets was comparable to that described in grasshopper. An examination of both developing and adult cricket brains showed that sema2a mRNA and protein were expressed in the Kenyon cells in mushroom bodies, an area involved in learning and memory. Sema2a expression was most obvious near the apex of the mushroom body in a region surrounding the neurogenic tip, which produces neurons throughout the life of the cricket. We discuss the role of neurogenesis in learning and memory and the potential involvement of semaphorin in this process. J. Comp. Neurol. 503:169,181, 2007. © 2007 Wiley-Liss, Inc. [source] Human Herpesvirus-8 (HHV-8)-Associated Primary Effusion Lymphoma in two Renal Transplant Recipients Receiving RapamycinAMERICAN JOURNAL OF TRANSPLANTATION, Issue 3 2008E. Boulanger The Akt/mammalian target of rapamycin (mTOR) signaling cascade has been demonstrated to be constitutively activated in several malignancies, including Kaposi sarcoma (KS) and human herpesvirus-8 (HHV-8)-associated primary effusion lymphoma (PEL). In organ transplant recipients, therapeutic change from cyclosporin to the mTOR inhibitor rapamycin can lead to regression of KS lesions. Recent experiments using PEL cell lines and murine xenograft PEL models suggested that rapamycin could inhibit the growth of PEL cells. In the present report, we describe the cases of two HIV-1-negative males of African origin who underwent renal transplantation and developed PEL while receiving rapamycin as immunosuppressive treatment. Both patients were retrospectively found to be HHV-8 seropositive before renal transplantation. The present case report suggests that rapamycin may not protect HHV-8-infected renal transplant recipients from occurrence of PEL or progression of pre-existing PEL. [source] Oxidized/misfolded superoxide dismutase-1: the cause of all amyotrophic lateral sclerosis?ANNALS OF NEUROLOGY, Issue 6 2007Edor Kabashi PhD The identification in 1993 of superoxide dismutase-1 (SOD1) mutations as the cause of 10 to 20% of familial amyotrophic lateral sclerosis cases, which represents 1 to 2% of all amyotrophic lateral sclerosis (ALS) cases, prompted a substantial amount of research into the mechanisms of SOD1-mediated toxicity. Recent experiments have demonstrated that oxidation of wild-type SOD1 leads to its misfolding, causing it to gain many of the same toxic properties as mutant SOD1. In vitro studies of oxidized/misfolded SOD1 and in vivo studies of misfolded SOD1 have indicated that these protein species are selectively toxic to motor neurons, suggesting that oxidized/misfolded SOD1 could lead to ALS even in individuals who do not carry an SOD1 mutation. It has also been reported that glial cells secrete oxidized/misfolded mutant SOD1 to the extracellular environment, where it can trigger the selective death of motor neurons, offering a possible explanation for the noncell autonomous nature of mutant SOD1 toxicity and the rapid progression of disease once the first symptoms develop. Therefore, considering that sporadic (SALS) and familial ALS (FALS) cases are clinically indistinguishable, the toxic properties of mutated SOD1 are similar to that of oxidized/misfolded wild-type SOD1 (wtSOD1), and secreted/extracellular misfolded SOD1 is selectively toxic to motor neurons, we propose that oxidized/misfolded SOD1 is the cause of most forms of classic ALS and should be a prime target for the design of ALS treatments. Ann Neurol 2007 [source] Developmental genetics and early hominid craniodental evolutionBIOESSAYS, Issue 6 2001Melanie A. McCollum Although features of the dentition figure prominently in discussions of early hominid phylogeny, remarkably little is known of the developmental basis of the variations in occlusal morphology and dental proportions that are observed among taxa. Recent experiments on tooth development in mice have identified some of the genes involved in dental patterning and the control of tooth specification. These findings provide valuable new insight into dental evolution and underscore the strong developmental links that exist among the teeth and the jaws and cranium. The latter has important implications for cladistic studies that traditionally consider features of the skull independently from the dentition. BioEssays 23:481,493, 2001. © 2001 John Wiley & Sons, Inc. [source] 2451: What's new in neuroprotectionACTA OPHTHALMOLOGICA, Issue 2010L WHEELER Purpose Vision loss is a an important patient concern in glaucoma and retinal diseases. This talk will update recent findings with alpha-2 agonists and NMDA antagonists in light of recent clinical experience in neuroprotection. Alpha-2 agonists have been shown to be neuroprotective in many animal models by mechanisms thought to enhance neuronal survival. The physiological role of alpha-2 receptors is still an emerging area of research in the retina and optic nerve. Methods Recent experiments suggest that alpha-2 agonists can improve retinal performance in laboratory animals. The new methods to demonstrate this will be presented. How is this different than neuroprotection? Or is it? Results A number of ideas are being pursued to explain the observation of improved retinal performance: increased axonal transport in rats; changes in down stream receptor signalling, etc. Conclusion Understanding the mechanism(s)of action for how alpha-2 agonists affect neuroportection and retinal performance may lead to new medical therapies and the role of these receptors in the physiology and function of the eye. Commercial interest [source] The role of genotypic diversity in determining grassland community structure under constant environmental conditionsJOURNAL OF ECOLOGY, Issue 5 2007RAJ WHITLOCK Summary 1A recent experiment varied the genetic diversity of model grassland communities under standardized soil and management conditions and at constant initial species diversity. After 5 years' growth, genetically diverse communities retained more species diversity and became more similar in species composition than genetically impoverished communities. 2Here we present the results of further investigation within this experimental system. We proposed that two mechanisms , the first invoking genetically determined and constant differences in plant phenotypes and the second invoking genotype,environment interactions , could each underpin these results. This mechanistic framework was used as a tool to interpret our findings. 3We used inter-simple sequence repeat (ISSR) DNA markers to confirm which of the individuals of six study species initially included in the model communities were unique genotypes. We then used the molecular markers to assess the survival and abundance of each genotype at the end of the 5-year experimental period. 4The DNA marker data were used to create, for the first time, a genotype abundance hierarchy describing the structure of a community at the level of genotypes. This abundance hierarchy revealed wide variation in the abundance of genotypes within species, and large overlaps in the performance of the genotypes of different species. 5Each genotype achieved a consistent level of abundance within genetically diverse communities, which differed from that attained by other genotypes of the same species. The abundance hierarchy of genotypes within species also showed consistency across communities differing in their initial level of genetic diversity, such that species abundance in genetically impoverished communities could be predicted, in part, by genotypic identity. 6Three species (including two canopy-dominants) experienced shifts in their community-level genotype abundance hierarchies that were consistent with an increased influence of genotype,environment interactions in genetically impoverished communities. 7Our results indicate that under relatively constant environmental conditions the species abundance structure of plant communities can in part be predicted from the genotypic composition of their component populations. Genotype,environment interactions also appear to shape the structure of communities under such conditions, although further experiments are needed to clarify the magnitude and mechanism of these effects. [source] "BACK THE BID": THE 2012 SUMMER OLYMPICS AND THE GOVERNANCE OF LONDONJOURNAL OF URBAN AFFAIRS, Issue 3 2007PETER NEWMAN ABSTRACT:,The Olympic Park being developed in east London for the 2012 Games is one large urban renewal project among many in the city. The impact of the Games on urban development may be of less significance than the impact on city politics. Bidding for and delivering the Games has contributed to a reassessment of the recent experiment with mayoral government. The article examines these changing representations of the structures of London government that are now seen as a success. Much of the literature on Olympic cities is highly critical of the impact of the games, but the (current) substantial support for London 2012 also needs to be explained. We examine how London has created opportunities for support, and moments and spaces for celebration when political leaders and Londoners can come together around particular representations of themselves and the city. [source] Dynamical T-matrix theory for high-density excitons in coupled quantum wellsPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 10 2006R. Zimmermann Abstract Excitons in coupled quantum wells open the possibility to reach high densities close to equilibrium. In a recent experiment employing a lateral trap potential, a blue shift and a broadening of the exciton emission line has been seen [D. W. Snoke et al., Solid State Commun. 134, 37 (2005)]. The standard Hartree,Fock treatment can explain the blue shift but fails to give a finite broadening. Starting from the (spin-dependent) many-exciton Hamiltonian with direct and exchange potential, we present a dynamical T-matrix calculation for the single-exciton Green's function which is directly related to the frequency- and angle-resolved photoluminescence. The calculated spectrum is blue shifted and broadened due to exciton,exciton scattering. At high excitation, both the spectrum and the angular emission are getting narrow. This is a direct manifestation for off-diagonal long range order and a precursor of condensation. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Physics with dense positroniumPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 10 2007David B. Cassidy Abstract Our recent experiment on Ps-Ps spin exchange quenching represents the first time that two Ps atoms have been observed interacting with each other. The implication is that experimentation on various systems containing more than one Ps atom is now possible, including the Ps2 molecule, the Ps Bose-Einstein condensate, the Ps atom laser and the annihilation gamma ray laser. Here we describe various aspects of such research, including the development of new techniques, work currently underway and some possible future experiments. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Strategy Similarity and Coordination,THE ECONOMIC JOURNAL, Issue 497 2004Rajiv Sarin In the payoff assessment model of choice (Sarin and Vahid, 1999), only the assessment of the chosen strategy is updated. We extend that model to allow the agent to also update the assessments of strategies that the agent thinks are similar to the chosen strategy. We use this model to explain observed behaviour in a recent experiment. Statistical tests cannot distinguish between the payoff distributions generated by the model and the observed payoff distributions in almost every period. [source] Consumer Control of Salt Marshes Driven by Human DisturbanceCONSERVATION BIOLOGY, Issue 3 2008MARK D. BERTNESS control de consumidor; impactos humanos; conservación de pantano de sal; cascadas de trophic Abstract:,Salt marsh ecosystems are widely considered to be controlled exclusively by bottom,up forces, but there is mounting evidence that human disturbances are triggering consumer control in western Atlantic salt marshes, often with catastrophic consequences. In other marine ecosystems, human disturbances routinely dampen (e.g., coral reefs, sea grass beds) and strengthen (e.g., kelps) consumer control, but current marsh theory predicts little potential interaction between humans and marsh consumers. Thus, human modification of top,down control in salt marshes was not anticipated and was even discounted in current marsh theory, despite loud warnings about the potential for cascading human impacts from work in other marine ecosystems. In spite of recent experiments that have challenged established marsh dogma and demonstrated consumer-driven die-off of salt marsh ecosystems, government agencies and nongovernmental organizations continue to manage marsh die-offs under the old theoretical framework and only consider bottom,up forces as causal agents. This intellectual dependency of many coastal ecologists and managers on system-specific theory (i.e., marsh bottom,up theory) has the potential to have grave repercussions for coastal ecosystem management and conservation in the face of increasing human threats. We stress that marine vascular plant communities (salt marshes, sea grass beds, mangroves) are likely more vulnerable to runaway grazing and consumer-driven collapse than is currently recognized by theory, particularly in low-diversity ecosystems like Atlantic salt marshes. Resumen:,Se ha considerado extensamente que los ecosistemas de marismas son controlados exclusivamente por dinámicas abajo-arriba, pero se ha acumulado evidencia de que las perturbaciones humanas están provocando el control por consumidores en marismas del Atlántico occidental, a menudo con consecuencias catastróficas. En otros ecosistemas marinos, las perturbaciones humanas rutinariamente disminuyen (e.g., arrecifes de coral, pastos marinos) y refuerzan (e.g., varec) el control por consumidores, pero la teoría de marismas actual predice una leve interacción potencial entre humanos y consumidores en las marismas. Por lo tanto, las modificaciones humanas al control arriba-abajo en las marismas no estaba anticipada y aun era descontada en la teoría de marismas actual, a pesar de advertencias sobre el potencial de impactos humanos en cascada en trabajos en otros ecosistemas marinos. No obstante los experimentos recientes que han desafiado el dogma de marismas establecido y que han demostrado la desaparición gradual de marismas conducida por consumidores, las agencias gubernamentales y las organizaciones no gubernamentales continúan manejando la disminución de marismas en el marco de la teoría vieja y sólo consideran como agentes causales a factores abajo-arriba. Esta dependencia intelectual en la teoría sistema-específico (i.e., teoría de marismas abajo-arriba) de muchos ecólogos y manejadores costeros tiene el potencial de tener repercusiones graves para el manejo y conservación de ecosistemas costeros frente a las crecientes amenazas humanas. Enfatizamos que las comunidades plantas vasculares marinas (marismas, pastos marinos, manglares) son potencialmente más vulnerables al pastoreo descontrolado y al colapso conducido por consumidores que lo que reconoce la teoría actualmente, particularmente en ecosistemas con baja diversidad como las marismas del Atlántico. [source] Mapping Common Futures: Customary Communities, NGOs and the State in Indonesia's Reform EraDEVELOPMENT AND CHANGE, Issue 1 2005Carol Warren The post-Suharto ,Reform Era' has witnessed explosive revitalization movements among Indonesia's indigenous minorities or ,customary'(adat) communities attempting to redress the disempowerment they suffered under the former regime. This study considers the current resurgence of customary claims to land and resources in Bali, where the state-sponsored investment boom of the 1990s had severe social and environmental impacts. It focuses on recent experiments with participatory community mapping, aimed at reframing the relationship between state and local institutions in planning and decision-making processes. Closely tied to the mapping and planning strategy have been efforts to strengthen local institutions and to confront the problems of land alienation and community control of resources. The diversity of responses to this new intervention reflects both the vitality and limitations of local adat communities, as well as the contributions and constraints of non-governmental organizations that increasingly mediate their relationships to state and global arenas. This ethnographic study explores participants' experiences of the community mapping programme and suggests its potential for developing ,critical localism' through long-term, process-oriented engagements between communities, governments, NGOs, and academic researchers. [source] Beyond early development: Xenopus as an emerging model for the study of regenerative mechanismsDEVELOPMENTAL DYNAMICS, Issue 6 2009Caroline W. Beck Abstract While Xenopus is a well-known model system for early vertebrate development, in recent years, it has also emerged as a leading model for regeneration research. As an anuran amphibian, Xenopus laevis can regenerate the larval tail and limb by means of the formation of a proliferating blastema, the lens of the eye by transdifferentiation of nearby tissues, and also exhibits a partial regeneration of the postmetamorphic froglet forelimb. With the availability of inducible transgenic techniques for Xenopus, recent experiments are beginning to address the functional role of genes in the process of regeneration. The use of soluble inhibitors has also been very successful in this model. Using the more traditional advantages of Xenopus, others are providing important lineage data on the origin of the cells that make up the tissues of the regenerate. Finally, transcriptome analyses of regenerating tissues seek to identify the genes and cellular processes that enable successful regeneration. Developmental Dynamics 238:1226,1248, 2009. © 2009 Wiley-Liss, Inc. [source] Geographic Scale and Grass-Roots Internationalism: The Liverpool Dock Dispute, 1995,1998,ECONOMIC GEOGRAPHY, Issue 3 2000Noel Castree Abstract: In the context of ongoing debates over the effects of "globalization" on organized labor and, specifically, recent experiments in labor internationalism, this paper examines the geography of the Liverpool dock dispute, 1995,98. The dispute has rarely been subject to a serious analysis of its causes and trajectory. This is surprising since it was not only the most protracted industrial dispute in recent British history but also the hub of a relatively novel form of transnational labor organizing: namely, a form of grass-roots internationalism organized largely outside the formal apparatuses of national and international unionism. In the paper I focus on the nature and dynamics of this "grass-roots internationalism" with a view to making two claims that have a wider thematic and theoretical relevance to the study of labor geographies. First, contrary to an emerging new orthodoxy in labor geography (and labor studies more generally), the Liverpool case in fact suggests that the necessity for labor to "up-scale" solidarity and struggle in the 1990s is much overstated. Second, the Liverpool case suggests that international labor organizing is only efficacious when considered in relation to two scales of struggle often thought increasingly irrelevant or ineffectual in a globalizing world: the local and the national. Thus, while those few analysts who have cited the Liverpool dispute, basing their assessments on secondhand knowledge, have held the dockers up as exemplars of a new form of labor internationalism, in this paper I suggest the need for a more complex and contingent appreciation of the multiscalar dynamics of labor struggles. In short, we have not yet reached the stage, even in a globalizing world, where labor's "spatial fixes" must be preeminently supranational. [source] Wilson's Storm Petrels Oceanites oceanicus Recognise the Olfactory Signature of Their MateETHOLOGY, Issue 12 2007Pierre Jouventin Chemical signals in birds have rarely been considered as recognition cues. Nevertheless, recent experiments showed that several petrel species are able to recognize their nest by smell, and in at least one species even their mate. But the use of smell may be different across the petrel species and olfactory nest recognition appears to be dependent on species' breeding biology. To increase our knowledge of individual olfactory recognition in petrels and the relationships between breeding biology and use of smell, we tested Wilson's storm petrels Oceanites oceanicus in Antarctica. In previous experiments, these birds failed to home if rendered anosmic, but the method employed to obtain anosmia (potentially stressing birds) and the fact that they breed in 24-h daylight suggest that they might use visual, rather than olfactory, cues to recognize their nest. Our birds were tested in T-maze experiments where nest odours or partner odours were presented. Wilson's storm petrels preferred odours of their own nest and mate. Results on olfactory nest recognition confirm and complete previous results, viz. anosmic Wilson's storm petrels do not home. Storm petrels olfactory mate recognition suggests that this ability may be widespread in burrowing petrels and implements olfactory nest recognition. [source] Thyroid hormones determine developmental mode in sand dollars (Echinodermata: Echinoidea)EVOLUTION AND DEVELOPMENT, Issue 6 2004Andreas Heyland Summary Evolutionary transitions in larval nutritional mode have occurred on numerous occasions independently in many marine invertebrate phyla. Although the evolutionary transition from feeding to nonfeeding development has received considerable attention through both experimental and theoretical studies, mechanisms underlying the change in life history remain poorly understood. Facultative feeding larvae (larvae that can feed but will complete metamorphosis without food) presumably represent an intermediate developmental mode between obligate feeding and nonfeeding. Here we show that an obligatorily feeding larva can be transformed into a facultative feeding larva when exposed to the thyroid hormone thyroxine. We report that larvae of the subtropical sand dollar Leodia sexiesperforata (Echinodermata: Echinoidea) completed metamorphosis without exogenous food when treated with thyroxine, whereas the starved controls (no thyroxine added) did not. Leodia sexiesperforata juveniles from the thyroxine treatment were viable after metamorphosis but were significantly smaller and contained less energy than sibling juveniles reared with exogenous food. In a second starvation experiment, using an L. sexiesperforata female whose eggs were substantially larger than in the first experiment (202±5 vs. 187±5 ,m), a small percentage of starved L. sexiesperforata larvae completed metamorphosis in the absence of food. Still, thyroxine-treated larvae in this experiment completed metamorphosis faster and in much higher numbers than in the starved controls. Furthermore, starved larvae of the sand dollar Mellita tenuis, which developed from much smaller eggs (100±2 ,m), did not complete metamorphosis either with or without excess thyroxine. Based on these data, and from recent experiments with other echinoids, we hypothesize that thyroxine plays a major role in echinoderm metamorphosis and the evolution of life history transitions in this group. We discuss our results in the context of current life history models for marine invertebrates, emphasizing the role of egg size, juvenile size, and endogenous hormone production for the evolution of nonfeeding larval development. [source] Retinoid signaling and cardiac anteroposterior segmentationGENESIS: THE JOURNAL OF GENETICS AND DEVELOPMENT, Issue 3 2001José Xavier-Neto Abstract Summary: Establishment of anterior,posterior polarity is one of the earliest decisions in cardiogenesis. Specification of anterior (outflow) and posterior (inflow) structures ensures proper connections between venous system and inflow tract and between arterial tree and outflow tract. The last few years have witnessed remarkable progress in our understanding of cardiac anteroposterior patterning. Molecular cloning and subsequent studies on RALDH2, the key embryonic retinaldehyde dehydrogenase in retinoic acid (RA) synthesis, provided the missing link between teratogenic studies on RA deficiency and excess and normal chamber morphogenesis. We discuss work establishing the foundations of our current understanding of the mechanisms of cardiac anteroposterior segmentation, the reasons why early evidence pointing to the role of RA in anteroposterior segmentation was overlooked, and the key experiments unraveling the role of RA in cardiac anteroposterior segmentation. We have also integrated recent experiments in a model of cardiac anteroposterior patterning in which RALDH2 expression determines anteroposterior boundaries in the heart field. genesis 31:97,104, 2001. © 2001 Wiley-Liss, Inc. [source] Threshold Voltage Shifts in Organic Thin-Film Transistors Due to Self-Assembled Monolayers at the Dielectric SurfaceADVANCED FUNCTIONAL MATERIALS, Issue 6 2009Stefan K. Possanner Abstract Recently, it has been shown by several groups that the electrical characteristics of organic thin-film transistors (OTFTs) can be significantly influenced by depositing self-assembled monolayers (SAMs) at the organic semiconductor/dielectric interface. In this work, the effect of such SAMs on the transfer characteristics and especially on the threshold voltage of OTFTs is investigated by means of two-dimensional drift-diffusion simulations. The impact of the SAM is modeled either by a permanent space charge layer that can result from chemical reactions with the active material, or by a dipole layer representing an array of ordered dipolar molecules. It is demonstrated that, in both model cases, the presence of the SAM significantly changes the transfer characteristics. In particular, it gives rise to a modified, effective gate voltage Veff that results in a rigid shift of the threshold voltage, ,Vth, relative to a SAM-free OTFT. The achievable amount of threshold voltage shift, however, strongly depends on the actual role of the SAM. While for the investigated device dimensions, an organic SAM acting as a dipole layer can realistically shift the threshold voltage only by a few volts, the changes in the threshold voltage can be more than an order of magnitude larger when the SAM leads to charges at the interface. Based on the analysis of the different cases, a route to experimentally discriminate between SAM-induced space charges and interface dipoles is proposed. The developed model allows for qualitative description of the behavior of organic transistors containing reactive interfacial layers; when incorporating rechargeable carrier trap states and a carrier density-dependent mobility, even a quantitative agreement between theory and recent experiments can be achieved. [source] Experiments in Environmental Economics and Some Close RelativesJOURNAL OF ECONOMIC SURVEYS, Issue 3 2006Bodo Sturm Abstract., It is not only the great number of papers written on environment economics that make it worth dealing with this special branch of experimental research, but the environmental problem in all its facets seems to serve as a catalyst for identifying some methodological problems of the experimental method. For this reason, we will not only try to give an overview of recent experiments in environmental economics but also add some thoughts on the methodological implications of this work. We identify three direct connecting factors for the experimental method and environmental economics. First, social dilemmas are, in many cases, at the core of environmental problems. Experiments are able to test theoretical hypotheses for individual behavior in such social dilemma situations. The second connecting factor comes from the field of applied experimental work and can be characterized as the testbedding of institutional arrangements for the solution of environmental problems. The last direct application of experimental methods to environmental economics concerns the individual evaluation of environmental resources. [source] Debugging Decomposition Data,Comparative Taphonomic Studies and the Influence of Insects and Carcass Size on Decomposition RateJOURNAL OF FORENSIC SCIENCES, Issue 1 2010Tal Simmons Ph.D. Abstract:, Comparison of data from a variety of environments and ambient temperatures has previously been difficult as few studies used standardized measures of time/temperature and decomposition. In this paper, data from previous studies and recent experiments are compared using simple conversions. These conversions allow comparison across multiple environments and experiments for the first time. Plotting decomposition score against logADD allows the exponential progression of decomposition to be expressed as a simple linear equation. Data comparison from many environments and temperatures shows no difference in decomposition progression when measured using Accumulated Degree Days. The major effector of change in rate was insect presence, regardless of depositional environment, species, or season. Body size is significant when carcasses are accessed by insects; when insects are excluded, while bodies are indoors, submerged, or buried, then decomposition progresses at the same rate regardless of body size. [source] Cerebral ischemia/stroke and small ubiquitin-like modifier (SUMO) conjugation , a new target for therapeutic intervention?JOURNAL OF NEUROCHEMISTRY, Issue 3 2008Wei Yang Abstract Transient cerebral ischemia/stroke activates various post-translational protein modifications such as phosphorylation and ubiquitin conjugation that are believed to play a major role in the pathological process triggered by an interruption of blood supply and culminating in cell death. A new system of post-translational protein modification has been identified, termed as small ubiquitin-like modifier (SUMO) conjugation. Like ubiquitin, SUMO is conjugated to the lysine residue of target proteins in a complex process. This review summarizes observations from recent experiments focusing on the effect of cerebral ischemia on SUMO conjugation. Transient global and focal cerebral ischemia both induced a rapid, dramatic and long-lasting rise in levels of SUMO2/3 conjugation. After transient focal cerebral ischemia, SUMO conjugation was particularly prominent in neurons located at the border of the ischemic territory where SUMO-conjugated proteins translocated to the nucleus. Many SUMO conjugation target proteins are transcription factors and sumoylation has been shown to have a major impact on the activity, stability, and cellular localization of target proteins. The rise in levels of SUMO-conjugated proteins is therefore likely to have a major effect on the fate of post-ischemic neurons. The sumoylation process could provide an exciting new target for therapeutic intervention. [source] The C-terminal C1 cassette of the N -methyl- d -aspartate receptor 1 subunit contains a bi-partite nuclear localization sequenceJOURNAL OF NEUROCHEMISTRY, Issue 6 2002K. D. Holmes Abstract The N -methyl- d -aspartate receptor (NMDAR) is a multimeric transmembrane protein composed of at least two subunits. One subunit, NR1, is derived from a single gene and can be subdivided into three regions: the N-terminal extracellular domain, the transmembrane regions, and the C-terminal intracellular domain. The N-terminal domain is responsible for Mg2+ metal ion binding and channel activity, while the transmembrane domains are important for ion channel formation. The intracellular C-terminal domain is involved in regulating receptor activity and subcellular localization. Our recent experiments indicated that the intracellular C-terminal domain, when expressed independently, localizes almost exclusively in the nucleus. An examination of the amino acid sequence reveals the presence of a putative nuclear localization sequence (NLS) in the C1 cassette of the NR1 intracellular C-terminus. Using an expression vector designed to test whether a putative NLS sequence is a valid, functional NLS, we have demonstrated that a bi-partite NLS does in fact exist within the NR1-1 C-terminus. Computer algorithms identified a putative helix,loop,helix motif that spanned the C0C1 cassettes of the C-terminus. These data suggest that the NR1 subunit may represent another member of a family of transmembrane proteins that undergo intramembrane proteolysis, releasing a cytosolic peptide that is actively translocated to the nucleus leading to alterations in gene regulation. [source] Theoretical Consequences of Fluctuating Versus Constant Liganding of Oestrogen Receptor-, in NeuronesJOURNAL OF NEUROENDOCRINOLOGY, Issue 6 2010D. W. Pfaff A theory is put forward that emphasises differences in neuronal responses to fluctuations in steroid hormone levels compared to constant hormone levels. We propose that neuronal functions that regulate gonadotrophin release from the anterior pituitary tend to be more sensitive to rapid increases in the levels of oestrogens than they are to constant oestrogen levels. By contrast, neurones that control certain behavioral functions are affected just as well by constant oestrogen levels as by positively accelerating levels of oestrogen. In addition to providing examples of data from recent experiments that examine actions of the long-term effects of oestrogen on mouse behaviour, we illustrate the behavioural effects of microinjections of adeno-associated viral vectors of small interfering RNA directed against the mRNA for oestrogen receptor-, (ER,). This manipulation provides for a long-term loss of ER, function in a neuranatomically specific manner. The theoretical distinction between temporal features of oestrogen sensitivity of neuroendocrine versus behavioural function is not absolute, but is intended to stimulate new experimentation that examines temporal features of oestrogen administration. [source] | |||||||||||||||||||||||||||||||||||||||||||