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Ensemble
Kinds of Ensemble Terms modified by Ensemble Selected AbstractsGIS-based niche models identify environmental correlates sustaining a contact zone between three species of European vipersDIVERSITY AND DISTRIBUTIONS, Issue 3 2008F. Martínez-Freiría ABSTRACT The current range of European vipers is mostly parapatric but local-scale allopatric distribution is common and few cases of sympatry are known. In the High Course of Ebro River, northern Spain, there is a contact zone between Vipera aspis, V. latastei, and V. seoanei. Sympatry was detected between aspis and latastei and also specimens with intermediate morphological traits. Presence-data at a local scale (1 × 1 km) and ecological niche-based models manipulated in a GIS were used to (1) identify how environmental factors correlate with the distribution of the three vipers and with the location of the sympatry area, and (2) identify potential areas for viper occurrence and sympatry. Ensemble for casting with 10 Maximum Entropy models identified a mixture of topographical (altitude, slope), climatic (precipitation, evapotranspiration, and minimum and maximum temperature), and habitat factors (land cover) as predictors for viper occurrence. Similar predicted probabilities according to the variation of some environmental factors (indicating probable sympatry) were observed only for aspis-latastei and aspis-seoanei. In fact, areas of probable occurrence of vipers were generally allopatric but probable sympatry between vipers was identified for aspis-latastei in 76 UTM 1 × 1 km squares, for aspis-seoanei in 23 squares, and latastei-seoanei in two squares. Environmental factors correlate with the location of this contact zone by shaping the species range: some enhance spatial exclusion and constrain distribution to spatially non-overlapping ranges, while others allow contact between species. The distribution in the contact zone apparently results from the balance between the pressures exerted by the different environmental factors and in the sympatry area probably by interspecific competition. Further ecological and genetical data are needed to evaluate the dynamics of the probable hybrid zone. GIS and niche-modelling tools proved to be powerful tools to identify environmental factors sustaining the location of contact zones. [source] ,Aus so prosaischen Dingen wie Kartoffeln, Straßen, Traktoren werden poetische Dinge!': Brecht, Sinn und Form, and Strittmatter's KatzgrabenGERMAN LIFE AND LETTERS, Issue 1 2003Matthew Philpotts This article takes as its starting,point an essay written by Bertolt Brecht in praise of the GDR playwright Erwin Strittmatter and his Socialist Realist drama, Katzgraben, which was staged by the Berliner Ensemble in May 1953. Published in the late summer of 1953 in Sinn und Form, this rather neglected essay is of significance because Brecht adopts in it a highly orthodox GDR position at a time when he was otherwise making dissenting interventions in GDR cultural politics. Publication of the essay, at a time when political pressure on Brecht had eased, is evidence that his interest in Strittmatter's play was not merely a short,term tactical manoeuvre to placate the SED regime. Rather, it was part of a consistent belief in the necessity of demonstrating what Brecht perceived to be the genuine achievements of the GDR. The events of 17 June, and the fascist mindset which Brecht saw underlying them, only served to reinforce this necessity in his mind. Brecht's pre,occupation with Katzgraben has a broader significance in highlighting the tendency in Brecht criticism to over,privilege tactical explanations for his behaviour in the GDR and in demonstrating that his cultural,political dissent was vitiated all the time by consistent ideological assent. [source] Fluorescent proteins for single-molecule fluorescence applicationsJOURNAL OF BIOPHOTONICS, Issue 1 2008Britta Seefeldt Abstract We present single-molecule fluorescence data of fluorescent proteins GFP, YFP, DsRed, and mCherry, a new derivative of DsRed. Ensemble and single-molecule fluorescence experiments proved mCherry as an ideally suited fluorophore for single-molecule applications, demonstrated by high photostability and rare fluorescence-intensity fluctuations. Although mCherry exhibits the lowest fluorescence quantum yield among the fluorescent proteins investigated, its superior photophysical characteristics suggest mCherry as an ideal alternative in single-molecule fluorescence experiments. Due to its spectral characteristics and short fluorescence lifetime of 1.46 ns, mCherry complements other existing fluorescent proteins and is recommended for tracking and localization of target molecules with high accuracy, fluorescence resonance energy transfer (FRET), fluorescence lifetime imaging microscopy (FLIM), or multicolor applications. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Ensemble and single particle photophysical properties (two-photon excitation, anisotropy, FRET, lifetime, spectral conversion) of commercial quantum dots in solution and in live cellsMICROSCOPY RESEARCH AND TECHNIQUE, Issue 4-5 2004H.E. Grecco Abstract In this work, we characterized streptavidin-conjugated quantum dots (QDs) manufactured by Quantum Dot Corporation. We present data on: (1) two-photon excitation; (2) fluorescence lifetimes; (3) ensemble and single QD emission anisotropy; (4) QDs as donors for Förster resonance energy transfer (FRET); and (5) spectral conversion of QDs exposed to high-intensity illumination. We also demonstrate the utility of QDs for (1) imaging the binding and uptake of biotinylated transferrin on living cells, and (2) resolving by fluorescence lifetime imaging microscopy (FLIM) signals originating from QDs from those of spatially and spectrally overlapping visible fluorescent proteins (VFPs). Microsc. Res. Tech. 65:169,179, 2004. © 2005 Wiley-Liss, Inc. [source] Représentations , observations sur Le tour du monde en quatre-vingts joursORBIS LITERARUM, Issue 3 2008Hans Färnlöf Dans Le tour du monde en quatre-vingts jours (1873) sont développés trois types de représentations. Par la représentation générique, Verne inscrit sa variation « moderne » du roman d'aventures (Bakhtine) en modifiant l'enjeu de l'intrigue traditionnelle; par la représentation mimétique, il crée une dialectique efficace entre la didactique et le romanesque; par la représentation diégétique, il attribue différentes fonctions narratives à ses personnages principaux (Fogg et Passepartout). Ensemble, ces représentations témoignent d'une poétique conséquente et élaborée chez Verne, qui situe habilement son projet d'écriture et par rapport à l'héritage littéraire et par rapport à l'esthétique contemporaine. De ce fait, Verne occupe une place notable dans le champ littéraire de la deuxième moitié du XIXe siècle. Par conséquent, il conviendrait, dans le discours théorique et historique littéraires, de ne plus considérer systématiquement Verne comme simple « auteur populaire », mais de lui accorder la place qui correspond à sa juste valeur d'écrivain. [source] Amide-to-Ester Substitution Allows Fine-Tuning of the Cyclopeptide Conformational Ensemble,ANGEWANDTE CHEMIE, Issue 15 2010Tommaso Cupido Ohne die dreidimensionale Gesamtstruktur zu beeinflussen, hat eine Substitution von Amid- gegen Esterfunktionen im Molekülgerüst deutliche Auswirkungen auf das Konformationsgleichgewicht des RGD-Cyclopeptids Cilengitid und seiner Derivate (siehe Bild; RGD=Arg-Gly-Asp). Die geeignete Substitution stabilisiert die Rezeptor-komplementären Konformationen und verbessert die biologische Aktivität dieses Integrin-Antagonisten. [source] Spektroskopie an einzelnen MolekülenCHEMIE IN UNSERER ZEIT (CHIUZ), Issue 3 2008Article first published online: 2 JUN 200 Erst das Verständnis, dass Materie aus Elementen zusammengesetzt ist, durch deren Umordnung sie transformiert werden kann, erst die Vorstellung von Atomen und Molekülen ermöglichte die Entwicklung der modernen Chemie und die Beschreibung einer Vielzahl chemischer und biochemischer Vorgänge in der Natur. Es ist erstaunlich, dass chemische Reaktionen seit langem auf der Basis einzelner Moleküle erdacht, niedergeschrieben und modelliert werden, obwohl die Anzahl der Moleküle, die an einer Reaktion im Labormaßstab beteiligt sind, um ca. 23 Größenordnungen darüber liegt. Die Entwicklung der optischen Einzelmolekülspektroskopie erlaubt erstmals die direkte Beobachtung molekularer Prozesse und den Vergleich mit dem Ensemble. [source] ChemInform Abstract: Synthesis, Photophysical and Electrochemical Properties of a D-,-A Ensemble Derived from Porphyrazine and Tetrathiafulvalene.CHEMINFORM, Issue 46 2009Ruibin Hou Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] The Study of Protein Folding and Dynamics by Determination of Intramolecular Distance Distributions and Their Fluctuations Using Ensemble and Single-Molecule FRET Measurements,CHEMPHYSCHEM, Issue 5 2005Elisha Haas Prof. Abstract The folding and dynamics of globular proteins is a multidimensional problem. The structures of the heterogeneous population of refolding protein molecules are characterized by multiple distances and time constants. Deciphering the mechanism of folding depends on studies of the processes rather than the folded structures alone. Spectroscopy is indispensable for these sorts of studies. Herein, it is shown that the determination of intramolecular distance distributions by ensemble and single-molecule FRET experiments enable the exploration of partially folded states of refolding protein molecules. [source] On the Effective Liapunov Exponent with Increasing Stochasticity for TokamapCONTRIBUTIONS TO PLASMA PHYSICS, Issue 4 2004A. Maluckov Abstract The effective Liapunov exponent statistical description of tokamap with increasing stochasticity is numerically developed. As the 2D Hamiltonian mapping, tokamap is characterized by the two Liapunov exponents lx = ,l, , 0, and 2D Liapunov exponent L = 0. The time development of the effective Liapunov exponent Lxe, the number of trajectories with lx > 0, Np, and the statistics of the non-negative Liapunov exponents are numerically considered following the test ensemble of N = 10000 trajectories. The sticking to regular structures in the phase space of tokamap, which is associated with the non-positive Liapunov exponent lx, clearly effects its statistics. Thus, the behavior of the effective Liapunov exponent Lxe may be taken as one of the qualitative measures of the degree of stochasticity for the observed mapping. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Phosphorylation of tropomyosin extends cooperative binding of myosin beyond a single regulatory unitCYTOSKELETON, Issue 1 2009Vijay S. Rao Abstract Tropomyosin (Tm) is one of the major phosphoproteins comprising the thin filament of muscle. However, the specific role of Tm phosphorylation in modulating the mechanics of actomyosin interaction has not been determined. Here we show that Tm phosphorylation is necessary for long-range cooperative activation of myosin binding. We used a novel optical trapping assay to measure the isometric stall force of an ensemble of myosin molecules moving actin filaments reconstituted with either natively phosphorylated or dephosphorylated Tm. The data show that the thin filament is cooperatively activated by myosin across regulatory units when Tm is phosphorylated. When Tm is dephosphorylated, this "long-range" cooperative activation is lost and the filament behaves identically to bare actin filaments. However, these effects are not due to dissociation of dephosphorylated Tm from the reconstituted thin filament. The data suggest that end-to-end interactions of adjacent Tm molecules are strengthened when Tm is phosphorylated, and that phosphorylation is thus essential for long range cooperative activation along the thin filament. Cell Motil. Cytoskeleton 2008. © 2008 Wiley-Liss, Inc. [source] Ecological boundary detection using Carlin,Chib Bayesian model selectionDIVERSITY AND DISTRIBUTIONS, Issue 6 2005Ralph Mac Nally ABSTRACT Sharp ecological transitions in space (ecotones, edges, boundaries) often are where ecologically important events occur, such as elevated or reduced biodiversity or altered ecological functions (e.g. changes in productivity, pollination rates or parasitism loads, nesting success). While human observers often identify these transitions by using intuitive or gestalt assignments (e.g. the boundary between a remnant woodland patch and the surrounding farm paddock seems obvious), it is clearly desirable to make statistical assessments based on measurements. These assessments often are straightforward to make if the data are univariate, but identifying boundaries or transitions using compositional or multivariate data sets is more difficult. There is a need for an intermediate step in which pairwise similarities between points or temporal samples are computed. Here, I describe an approach that treats points along a transect as alternative hypotheses (models) about the location of the boundary. Carlin and Chib (1995) introduced a Bayesian technique for comparing non-hierarchical models, which I adapted to compute the probabilities of each boundary location (i.e. a model) relative to the ensemble of models constituting the set of possible points of the boundary along the transect. Several artificial data sets and two field data sets (on vegetation and soils and on cave-dwelling invertebrates and microclimates) are used to illustrate the approach. The method can be extended to cases in with several boundaries along a gradient, such as where there is an ecotone of non-zero thickness. [source] Simplified inelastic seismic analysis of base-isolated structures using the N2 methodEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 9 2010Vojko Kilar Abstract In the paper a simplified nonlinear method has been applied to the analysis of base-isolated structures. In the first part, a three-linear idealization of the capacity curve is proposed. The initial stiffness is defined based on the first yielding point in the superstructure, whereas the secondary slope depends on the failure mechanism of the superstructure. A consequence is a much more pronounced secondary slope, which does not correspond to the presumptions used in the originally proposed N2 method. A parametric nonlinear dynamic study of single degree of freedom systems with different hardening slopes and damping has been performed for an ensemble of seven EC8 spectrum-compatible artificial accelerograms. It was concluded that, in the long-period range, the equal displacement rule could be assumed also for the proposed systems with non-zero post-yield stiffness. In the second part, the proposed idealization was used for the analysis of isolated RC frame buildings that were isolated with different (lead) rubber-bearing isolation systems. The stiffness of the isolators was selected for three different protection levels and for three different ground motion intensities, which have resulted in elastic as well as moderately and fully damaged superstructure performance levels. Three different lateral load distributions were investigated. It was observed that a triangular distribution, with an additional force at the base, works best in the majority of practical cases. It was concluded that the N2 method can, in general, provide a reasonably accurate prediction of the actual top displacement, as well as of the expected damage to the superstructure. Copyright © 2009 John Wiley & Sons, Ltd. [source] Design of passive systems for control of inelastic structuresEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 6 2009Gian Paolo Cimellaro Abstract A design strategy for control of buildings experiencing inelastic deformations during seismic response is formulated. The strategy is using weakened, and/or softened, elements in a structural system while adding passive energy dissipation devices (e.g. viscous fluid devices, etc.) in order to control simultaneously accelerations and deformations response during seismic events. A design methodology is developed to determine the locations and the magnitude of weakening and/or softening of structural elements and the added damping while insuring structural stability. A two-stage design procedure is suggested: (i) first using a nonlinear active control algorithm, to determine the new structural parameters while insuring stability, then (ii) determine the properties of equivalent structural parameters of passive system, which can be implemented by removing or weakening some structural elements, or connections, and by addition of energy dissipation systems. Passive dampers and weakened elements are designed using an optimization algorithm to obtain a response as close as possible to an actively controlled system. A case study of a five-story building subjected to El Centro ground motion, as well as to an ensemble of simulated ground motions, is presented to illustrate the procedure. The results show that following the design strategy, a control of both peak inter-story drifts and total accelerations can be obtained. Copyright © 2008 John Wiley & Sons, Ltd. [source] Estimation of seismic drift and ductility demands in planar regular X-braced steel framesEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 15 2007Theodore L. Karavasilis Abstract This paper summarizes the results of an extensive study on the inelastic seismic response of X-braced steel buildings. More than 100 regular multi-storey tension-compression X-braced steel frames are subjected to an ensemble of 30 ordinary (i.e. without near fault effects) ground motions. The records are scaled to different intensities in order to drive the structures to different levels of inelastic deformation. The statistical analysis of the created response databank indicates that the number of stories, period of vibration, brace slenderness ratio and column stiffness strongly influence the amplitude and heightwise distribution of inelastic deformation. Nonlinear regression analysis is employed in order to derive simple formulae which reflect the aforementioned influences and offer a direct estimation of drift and ductility demands. The uncertainty of this estimation due to the record-to-record variability is discussed in detail. More specifically, given the strength (or behaviour) reduction factor, the proposed formulae provide reliable estimates of the maximum roof displacement, the maximum interstorey drift ratio and the maximum cyclic ductility of the diagonals along the height of the structure. The strength reduction factor refers to the point of the first buckling of the diagonals in the building and thus, pushover analysis and estimation of the overstrength factor are not required. This design-oriented feature enables both the rapid seismic assessment of existing structures and the direct deformation-controlled seismic design of new ones. A comparison of the proposed method with the procedures adopted in current seismic design codes reveals the accuracy and efficiency of the former. Copyright © 2007 John Wiley & Sons, Ltd. [source] Evaluation of residual drift demands in regular multi-storey frames for performance-based seismic assessmentEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 13 2006Jorge Ruiz-García Abstract This paper summarizes results of a comprehensive analytical study aimed at evaluating the amplitude and heightwise distribution of residual drift demands in multi-storey moment-resisting frames after earthquake excitation. For that purpose, a family of 12 one-bay two-dimensional generic frame models was subjected to an ensemble of 40 ground motions scaled to different intensities. In this investigation, an inelastic ground motion intensity measure was employed to scale each record, which allowed reducing the record-to-record variability in the estimation of residual drift demands. The results were statistically processed in order to evaluate the influence of ground motion intensity, number of stories, period of vibration, frame mechanism, system overstrength, and hysteretic behaviour on central tendency of residual drift demands. In addition, a special emphasis was given to evaluate the uncertainty in the estimation of residual drift demands. Results of incremental dynamic analyses indicate that the amplitude and heightwise distribution of residual drift demands strongly depends on the frame mechanism, the heightwise system structural overstrength and the component hysteretic behaviour. An important conclusion for performance-based assessment is that the evaluation of residual drift demands involves significantly larger levels of uncertainty (i.e. record-to-record variability) than that of maximum drift demands, which suggests that this variability and corresponding uncertainty should be explicitly taken into account when estimating residual drift demands during performance-based seismic assessment of frame buildings. Copyright © 2006 John Wiley & Sons, Ltd. [source] Residual displacement ratios for assessment of existing structuresEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 3 2006Jorge Ruiz-García Abstract Results of an analytical study aimed at evaluating residual displacement ratios, Cr, which allow the estimation of residual displacement demands from maximum elastic displacement demands is presented. Residual displacement ratios were computed using response time-history analyses of single-degree-of-freedom systems having 6 levels of relative lateral strength when subjected to an ensemble of 240 earthquake ground motions recorded in stations placed on firm sites. The results were statistically organized to evaluate the influence of the following parameters: period of vibration, level of relative lateral strength, site conditions, earthquake magnitude, and distance to the source. In addition, the influence of post-yield stiffness ratio in bilinear systems and of the unloading stiffness in stiffness-degrading systems was also investigated. A special emphasis is given to the uncertainty of these ratios. From this study, it is concluded that mean residual displacement ratios are more sensitive to changes in local site conditions, earthquake magnitude, distance to the source range and hysteretic behaviour than mean inelastic displacement ratios. In particular, residual displacement ratios exhibit large levels of record-to-record variability and, therefore, this dispersion should be taken into account when estimating residual displacements. A simplified expression is presented to estimate mean residual displacements ratios for elastoplastic systems during the evaluation of existing structures built on firm soil sites. Copyright © 2005 John Wiley & Sons, Ltd. [source] Optimal design of supplemental viscous dampers for irregular shear-frames in the presence of yieldingEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 8 2005Oren Lavan Abstract A methodology for the optimal design of supplemental viscous dampers for regular as well as irregular yielding shear-frames is presented. It addresses the problem of minimizing the added damping subject to a constraint on an energy-based global damage index (GDI) for an ensemble of realistic ground motion records. The applicability of the methodology for irregular structures is achieved by choosing an appropriate GDI. For a particular choice of the parameters comprising the GDI, a design for the elastic behavior of the frame or equal damage for all stories is achieved. The use of a gradient-based optimization algorithm for the solution of the optimization problem is enabled by first deriving an expression for the gradient of the constraint. The optimization process is started for one ,active' ground motion record which is efficiently selected from the given ensemble. If the resulting optimal design fails to satisfy the constraints for other records from the original ensemble, additional ground motions (loading conditions) are added one by one to the ,active' set until the optimum is reached. Two examples for the optimal designs of supplemental dampers are given: a 2-story shear frame with varying strength distribution and a 10-story shear frame. The 2-story shear frame is designed for one given ground motion whereas the 10-story frame is designed for an ensemble of twenty ground motions. Copyright © 2005 John Wiley & Sons, Ltd. [source] Statistical performance analysis of seismic-excited structures with active interaction controlEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 7 2003Yunfeng Zhang Abstract This paper presents a statistical performance analysis of a semi-active structural control system for suppressing the vibration response of building structures during strong seismic events. The proposed semi-active mass damper device consists of a high-frequency mass damper with large stiffness, and an actively controlled interaction element that connects the mass damper to the structure. Through actively modulating the operating states of the interaction elements according to pre-specified control logic, vibrational energy in the structure is dissipated in the mass damper device and the vibration of the structure is thus suppressed. The control logic, categorized under active interaction control, is defined directly in physical space by minimizing the inter-storey drift of the structure to the maximum extent. This semi-active structural control approach has been shown to be effective in reducing the vibration response of building structures due to specific earthquake ground motions. To further evaluate the control performance, a Monte Carlo simulation of the seismic response of a three-storey steel-framed building model equipped with the proposed semi-active mass damper device is performed based on a large ensemble of artificially generated earthquake ground motions. A procedure for generating code-compatible artificial earthquake accelerograms is also briefly described. The results obtained clearly demonstrate the effectiveness of the proposed semi-active mass damper device in controlling vibrations of building structures during large earthquakes. Copyright © 2003 John Wiley & Sons, Ltd. [source] Inelastic deformation response of SDOF systems subjected to earthquakesEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 3 2002Rafael Riddell Abstract Performance-based seismic design requires reliable methods to predict earthquake demands on structures, and particularly inelastic deformations, to ensure that specific damage-based criteria are met. Several methods based on the response of equivalent linear single-degree-of-freedom (SDOF) systems have been proposed to estimate the response of multi-degree-of-freedom structures. These methods do not offer advantages over the traditional Veletsos,Newmark,Hall (VNH) procedure, indeed, they have been shown to be inaccurate. In this study, the VNH method is revised, considering the inelastic response of elastoplastic, bilinear, and stiffness-degrading systems with 5% damping subjected to two sets of earthquake ground motions. One is an ensemble of 51 earthquake records in the Circumpacific Belt, and the other is a group of 44 records in California. A statistical analysis of the response data provides factors for constructing VNH inelastic spectra. Such factors show that the ,equal-displacement' and ,equal-energy' rules to relate elastic and inelastic responses are unconservative for high ductilities in the acceleration- and velocity-sensitive regions of the spectrum. It is also shown that, on average, the effect of the type of force,deformation relationship of non-linear systems is not significant, and responses can be conservatively predicted using the simple elastoplastic model. Copyright © 2001 John Wiley & Sons, Ltd. [source] Hysteretic energy spectrum and damage controlEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 12 2001Rafael Riddell Abstract The inelastic response of single-degree-of-freedom (SDOF) systems subjected to earthquake motions is studied and a method to derive hysteretic energy dissipation spectra is proposed. The amount of energy dissipated through inelastic deformation combined with other response parameters allow the estimation of the required deformation capacity to avoid collapse for a given design earthquake. In the first part of the study, a detailed analysis of correlation between energy and ground motion intensity indices is carried out to identify the indices to be used as scaling parameters and base line of the energy dissipation spectrum. The response of elastoplastic, bilinear, and stiffness degrading systems with 5 per cent damping, subjected to a world-wide ensemble of 52 earthquake records is considered. The statistical analysis of the response data provides the factors for constructing the energy dissipation spectrum as well as the Newmark,Hall inelastic spectra. The combination of these spectra allows the estimation of the ultimate deformation capacity required to survive the design earthquake, capacity that can also be presented in spectral form as an example shows. Copyright © 2001 John Wiley & Sons, Ltd. [source] Assessing ecosystem threats from global and regional change: hierarchical modeling of risk to sagebrush ecosystems from climate change, land use and invasive species in Nevada, USAECOGRAPHY, Issue 1 2010Bethany A. Bradley Global change poses significant challenges for ecosystem conservation. At regional scales, climate change may lead to extensive shifts in species distributions and widespread extirpations or extinctions. At landscape scales, land use and invasive species disrupt ecosystem function and reduce species richness. However, a lack of spatially explicit models of risk to ecosystems makes it difficult for science to inform conservation planning and land management. Here, I model risk to sagebrush (Artemisia spp.) ecosystems in the state of Nevada, USA from climate change, land use/land cover change, and species invasion. Risk from climate change is based on an ensemble of 10 atmosphere-ocean general circulation model (AOGCM) projections applied to two bioclimatic envelope models (Mahalanobis distance and Maxent). Risk from land use is based on the distribution of roads, agriculture, and powerlines, and on the spatial relationships between land use and probability of cheatgrass Bromus tectorum invasion in Nevada. Risk from land cover change is based on probability and extent of pinyon-juniper (Pinus monophylla; Juniperus spp.) woodland expansion. Climate change is most likely to negatively impact sagebrush ecosystems at the edges of its current range, particularly in southern Nevada, southern Utah, and eastern Washington. Risk from land use and woodland expansion is pervasive throughout Nevada, while cheatgrass invasion is most problematic in the northern part of the state. Cumulatively, these changes pose major challenges for conservation of sagebrush and sagebrush obligate species. This type of comprehensive assessment of ecosystem risk provides managers with spatially explicit tools important for conservation planning. [source] Sulfonated molecules that bind a partially structured species of ,2 -microglobulin also influence refolding and fibrillogenesisELECTROPHORESIS, Issue 7 2008Chiara Carazzone Abstract Human ,2 -microglobulin (,2 -m) is a small amyloidogenic protein responsible for dialysis-related amyloidosis, which represents a severe complication of long-term hemodialysis. A therapeutic approach for this amyloidosis could be based on the stabilization of ,2 -m through the binding to a small molecule, to possibly inhibit protein misfolding and amyloid fibril formation. The search of a strong ligand of this protein is extremely challenging: by using CE in affinity and refolding experiments we study the effect that previously selected sulfonated molecules have on the equilibrium between the native form and an ensemble of conformers populating the slow phase of ,2 -m folding. These data are correlated with the effect that the same molecules exert on in vitro fibrillogenesis experiments. [source] An idealised model of turbulent dispersion: two rectangular pulse initial conditionENVIRONMETRICS, Issue 5 2009Nils Mole Abstract An idealised model of turbulent dispersion was introduced by Zimmerman and Chatwin in 1995 and it was further developed by Mole and Yeun in 2007, for the case of an initial concentration field consisting of one rectangular pulse. Here we extend this model to the case of two initial pulses in order to investigate the effect of varying concentration. We present analytical and numerical results for the dependence of the variance, skewness, kurtosis and probability density function of concentration on time and on the pulse locations and concentrations. For moderately large concentration difference between the pulses, one pulse dominates and the behaviour is close to that for the one pulse case. This suggests that a model incorporating distributions of pulse separations and concentrations can be constructed by averaging over an ensemble of one pulse cases. The distributions used would be those appropriate to the ,strands' of highest concentration. Copyright © 2008 John Wiley & Sons, Ltd. [source] A Competitive European Agriculture Designed for the Citizens , Romania's Perspective Une agriculture européenne compétitive au service des citoyens : La perspective de la Roumanie Eine an die Bedürfnisse der Bürger angepasste, wettbewerbsfähige Europäische Landwirtschaft , die Perspektive RumäniensEUROCHOICES, Issue 3 2008Dacian Ciolo Summary A Competitive European Agriculture Designed for the Citizens , Romania's Perspective In the coming months and years the European Union has to make fundamental choices for the future of agriculture, food, landscape and quality of life within its whole territory. These choices have now to be made for 27 Member States, which together give a new configuration to the Community. Poland and Romania together now represent nearly half of the total active population involved in EU agriculture. European agriculture has to be multifunctional, competitive not only for the market but also for citizens, as an economic activity that uses and manages renewable resources of public interest. Higher competitiveness inevitably leads to restructuring and modernisation of the agro-food sector in the New Member States. This must be achieved gradually to avoid a negative social impact, through a rural development policy supporting job creation outside agriculture. Romanian agriculture employs about 30 per cent of the country's active population and half of the country's population live in rural areas. Romania, therefore, aims to preserve a substantial CAP budget to promote investment in agriculture and quality of life in rural areas. It is in the interest of the whole EU to ensure not just proper use of the productive potential of Romanian agriculture but also economic development of the Romanian countryside. Au cours des prochains mois et des prochaines années, l'Union européenne doit faire des choix fondamentaux quant à l'avenir de l'agriculture, de l'alimentation et de la qualité de vie sur l'ensemble de son territoire. Ces choix relèvent actuellement de 27 état membres qui, ensemble, donnent à la communauté une nouvelle configuration. Actuellement, la Pologne et la Roumanie représentent à elles deux pratiquement la moitié de la population agricole de l'Union européenne. L'agriculture européenne doit être multifonctionnelle et compétitive, pas seulement pour les marchés mais aussi pour les citoyens, en tant qu'activitééconomique qui utilise et gère des ressources renouvelables d'intérêt public. La hausse de la compétitivité entraînera inévitablement une restructuration et une modernisation du secteur agro-alimentaire dans les nouveaux états membres. Ce processus doit être progressif pour éviter des conséquences sociales négatives, et il doit s'accompagner d'une politique de développement rural pour promouvoir la création d'emplois hors du secteur agricole. L'agriculture roumaine emploie environ 30 pour cent de la population active nationale et la moitié de la population du pays vit dans des zones rurales. La Roumanie compte donc utiliser une grande partie du budget de la PAC pour la promotion des investissements dans le secteur agricole et l'amélioration de la qualité de vie dans les zones rurales. Il est dans l'intérêt de l'ensemble de l'Union européenne de s'assurer non seulement que le potentiel productif agricole de la Roumanie est correctement utilisé mais également que la campagne roumaine se développe économiquement. In den kommenden Monaten und Jahren wird die Europäische Union grundlegende Entscheidungen im Hinblick auf Landwirtschaft, Lebensmittel, Landschaftsbild und Lebensqualität zu treffen haben, die sich auf ihr gesamtes Gebiet auswirken werden. Diese Entscheidungen betreffen nun alle 27 Mitgliedsstaaten, die der Gemeinschaft ein neues Gesicht verleihen. Mittlerweile stellen Polen und Rumänien zusammen etwa die Hälfte der aktiv in der Landwirtschaft der EU beschäftigten Bevölkerung. Die europäische Landwirtschaft muss multifunktional und nicht nur mit Blick auf den Markt wettbewerbsfähig sein, sondern auch mit Blick auf ihre Bürger, als ein Wirtschaftszweig, der erneuerbare Ressourcen verwendet und verwaltet, für die ein öffentliches Interesse besteht. Eine höhere Wettbewerbsfähigkeit führt unweigerlich zur Umstrukturierung und Modernisierung des Agro-Food-Sektors in den neuen Mitgliedsstaaten. Zur Vermeidung negativer Auswirkungen auf die Gesellschaft muss dies schrittweise durch eine Politik zur Entwicklung des ländlichen Raums erfolgen, die Arbeitsplätze außerhalb der Landwirtschaft fördert. In Rumänien sind 30 Prozent der Erwerbstätigen in der Landwirtschaft tätig, und die Hälfte der Bevölkerung lebt im ländlichen Raum. Daher ist Rumänien daran gelegen, weiterhin einen hinreichend großen Haushalt für die GAP zu erhalten, um Investitionen in die Landwirtschaft und die Lebensqualität im ländlichen Raum zu fördern. Es ist im Interesse aller EU-Länder, nicht nur die Ausschöpfung des produktiven Potenzials der rumänischen Landwirtschaft, sondern ebenfalls die wirtschaftliche Entwicklung des ländlichen Raums in Rumänien sicherzustellen. [source] Chemoselective Reagents for Covalent Capture and Display of Glycans in Microarrays,EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 3 2010Emiliano Cló Abstract Glycobiology has made very significant progress in the past decades. However, further progress will significantly depend on the establishment of novel methods for miniaturized, high-throughput analysis of glycan,protein interactions. Robust solid-phase chemical tools and new, chemoselective reagents for biologically meaningful display of surface-immobilized glycans are likely to play a key role. Here we present four new bifunctional linkers that allow highly chemoselective capture of unprotected glycans in solution to form glycan-linker conjugates for direct construction of glycan microarrays (glycochips). The bifunctional linkers carry O -linked aminooxy moieties, some with N -substituents at one end and an amino group at the other. In addition, they contain a substituted benzene ring for UV traceability and improved purification of glycan-linker conjugates. NMR spectroscopic studies in solution proved that N -substituted aminooxy linkers provided model glycan-linker conjugates with the ,-glucopyranoside configuration, i.e. the ring-closed form required for biological recognition. Then an ensemble of glycan-linker conjugates were assembled from mannobiose, lactose, and N -acetyl-lactosamine and used for covalent printing of glycan microarrays. The stability of oximes were studied both in solution and on-chip. In solution, two of the linkers provided glycan-linker conjugates with a remarkable stability at pH 4 or higher, on-chip this relative stability was upheld. Two of the linkers, with different properties, are recommended for the glycobiology toolbox for the construction of glycan microarrays from unprotected glycans. [source] Multicolor Tunable Emission from Organogels Containing Tetraphenylethene, Perylenediimide, and Spiropyran DerivativesADVANCED FUNCTIONAL MATERIALS, Issue 19 2010Qun Chen Abstract A dendron-substituted tetraphenylethene low molecular weight gelator (LMWG)compound, LMWG1, is designed and investigated. Gelation-induced fluorescence enhancement is observed for the gel based on LMWG1 and its fluorescence can be reversibly tuned by varying the temperature of the ensemble. The photoinduced energy-transfer can occur between LMWG1 and PI2 (perylene diimide) in the gel phase, but it cannot occur in the corresponding solution. The emission color of the gel of LMWG1 and PI2 can be tuned from cyan, yellow, to red by varying the concentration of PI2. By taking advantage of the photochromic transformation of spiropyran, the emission color of the organogels based on LMWG1 and SP3 can be switched by alternating UV and visible-light irradiations. The emission color can also be tuned by varying the irradiation time. In this way, organogels based on LMWG1 with multiemission color can be achieved in the presence of SP3 after light irradiations. [source] Engineering Nanoparticle Cluster Arrays for Bacterial Biosensing: The Role of the Building Block in Multiscale SERS SubstratesADVANCED FUNCTIONAL MATERIALS, Issue 16 2010Linglu Yang Abstract Noble metal nanoparticle cluster arrays (NCAs) are a novel class of engineered substrates for surface enhanced Raman spectroscopy (SERS), in which the noble metal nanoparticles interact on multiple length scales to create a multiscale E-field cascade enhancement. In this work the role of the building block for the NCA performance is quantified. Periodic NCAs with constant cluster diameter (D = 200 nm) but variable nanoparticle diameter (d) and intercluster separation (,) were assembled on glass and their optical response and SERS enhancement were systematically characterized as a function of D, ,, and d. An increase of d from 40 to 80 nm and simultaneous decrease of , from 200 to 50 nm led to an improvement of the ensemble averaged SERS enhancement factor by a factor of up to ,8. The coefficient of variation (cv) of the enhancement factors (G) is significantly lower for the d = 80 nm NCAs than for the d = 40 nm and d = 60 nm NCAs. Optimized (D = 200 nm, , = 50 nm, d = 80 nm) NCAs show the overall highest signal reproducibility of all investigated NCAs and random nanoparticle substrates and achieve effective single cell detection sensitivity. [source] Response of native and denatured hen lysozyme to high pressure studied by 15N/1H NMR spectroscopyFEBS JOURNAL, Issue 6 2001Yuji O. Kamatari High-pressure 15N/1H NMR techniques were used to characterize the conformational fluctuations of hen lysozyme, in its native state and when denatured in 8 m urea, over the pressure range 30,2000 bar. Most 1H and 15N signals of native lysozyme show reversible shifts to low field with increasing pressure, the average pressure shifts being 0.069 ± 0.101 p.p.m. (1H) and 0.51 ± 0.36 p.p.m. (15N). The shifts indicate that the hydrogen bonds formed to carbonyl groups or water molecules by the backbone amides are, on average, shortened by ,,0.02 Å as a result of pressure. In native lysozyme, six residues in the , domain or at the ,/, domain interface have anomalously large nonlinear 15N and 1H chemical-shift changes. All these residues lie close to water-containing cavities, suggesting that there are conformational changes involving these cavities, or the water molecules within them, at high pressure. The pressure-induced 1H and 15N shifts for lysozyme denatured in 8 m urea are much more uniform than those for native lysozyme, with average backbone amide shifts of 0.081 ± 0.029 p.p.m. (1H) and 0.57 ± 0.14 p.p.m. (15N). The results show that overall there are no significant variations in the local conformational properties of denatured lysozyme with pressure, although larger shifts in the vicinity of a persistent hydrophobic cluster indicate that interactions in this part of the sequence may rearrange. NMR diffusion measurements demonstrate that the effective hydrodynamic radius of denatured lysozyme, and hence the global properties of the denatured ensemble, do not change detectably at high pressure. [source] New phases of thermal SYM and LST from Kaluza-Klein black holesFORTSCHRITTE DER PHYSIK/PROGRESS OF PHYSICS, Issue 7-8 2005T. Harmark Abstract We review the recently found map that takes any static and neutral Kaluza-Klein black hole, i.e. any static and neutral black hole on Minkowski-space times a circle ,d × S1, and maps it to a corresponding solution for a non- and near-extremal brane on a circle. This gives a precise connection between phases of Kaluza-Klein black holes and the thermodynamic behavior of the non-gravitational theories dual to near-extremal branes on a circle. In particular, for the thermodynamics of strongly-coupled supersymmetric Yang-Mills theories on a circle we predict the existence of a new non-uniform phase and find new information about the localized phase. We also find evidence for the existence of a new stable phase of (2,0) Little String Theory in the canonical ensemble for temperatures above its Hagedorn temperature. [source] | |||||||||||||||||||||||||||||||||||||