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Discrete
Terms modified by Discrete Selected AbstractsElectronically Linked: Wireless, Discrete, Hands-Free Communication to Improve Surgical Workflow in Mohs and Dermasurgery ClinicDERMATOLOGIC SURGERY, Issue 2 2009T. MINSUE CHEN MD First page of article [source] Discrete, Base-Free, Cationic Alkaline-Earth Complexes , Access and Catalytic Activity in the Polymerization of LactideEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 22 2010Yann Sarazin Abstract Well-defined, base free cations of zinc and the alkaline-earth metals (Mg, Ca, Sr, Ba) supported by a multidentate phenolate ligand and stabilized by perfluorinated weakly coordinating counterions are readily available by simple procedures; the solid-state structures of the magnesium and calcium derivatives were elucidated. Upon treatment with an excess of iPrOH, these complexes generate highly efficient binary catalytic systems for the immortal ring-opening polymerization of L -lactide, yielding poly(L -lactide)s with controlled architectures and molecular features. [source] Synthesis and Characterisation of [XeF5]3[Ti4F19] Containing a Discrete [Ti4F19]3, AnionEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 29-30 2009Zoran Mazej Abstract The complex [XeF5]3[Ti4F19] was prepared by reaction of XeF2, TiF4 and UV-irradiated elemental fluorine in anhydrous hydrogen fluoride as the solvent. The crystal structure of [XeF5]3[Ti4F19] consists of [XeF5]+ cations and discrete [Ti4F19]3, anions. The [XeF5] units have usual slightly distorted pseudo-octahedral symmetry. Contrary to the previously reported [Ti4F18]2, anion, where each TiF6 octahedron shares three apexes with three other octahedra, in [Ti4F19]3,, only two ,3 -[TiF6] octahedra share three apexes with three other [TiF6] units. Each of the remaining two ,2 -[TiF6] octahedra shares only two vertices with two of the above-mentioned ,3 -[TiF6] moieties. The Raman spectrum of [XeF5]3[Ti4F19] is in agreement with the presence of [XeF5]+ cations and [Ti4F19]3, anions. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Breaking Infinite CuI Carboxylate Helix Held by Cuprophilicity into Discrete Cun Fragments (n = 6, 4, 2)EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 2 2008Yulia Sevryugina Abstract A new copper(I) carboxylate complex with 3,5-bis(trifluoromethyl)benzoate ligands, [Cu(O2C(3,5-CF3)2C6H3)] (1), has been prepared in high yield and fully characterized. An X-ray diffraction study revealed a remarkable infinite double-helical chain motif held together by cuprophilic interactions ranging from 2.69 to 3.14 Ĺ. Both left- and right-handed helices are present in the unit cell of the centrosymmetric structure of 1 thus making the crystalline compound racemic. Complex 1 shows bright emission at ca. 594 nm upon UV/Vis radiation in the solid state (,ex = 350 nm). The Cu···Cu contacts in 1 are easily broken in the gas phase to afford copper clusters of ascertained nuclearity upon sublimation with various polyaromatic hydrocarbons. Several polyarenes such as fluoranthene (C16H10), pyrene (C16H10), and coronene (C24H12) were selected to cover a broad temperature range from 130 to 220 °C for the gas-phase co-deposition reactions. As a result of the successive temperature increase, cleavage of the infinite copper(I) chain into [Cun(O2C(3,5-CF3)2C6H3)n] fragments of decreasing nuclearity, n = 6, 4, and 2, has been achieved. The isolation of these units represents the first instance where various polynuclear copper(I) complexes are prepared and structurally characterized for the same carboxylate ligand.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Discrete and continuum quantum states for the Kratzer oscillatorINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 3 2002Adelio R. MatamalaArticle first published online: 2 JUL 200 Abstract Kratzer oscillator is a realistic zero-order model for describing the anharmonic ro-vibrational motion in diatomic molecules. Kratzer oscillator has an energy spectrum containing both discrete and continuum parts. Wavefunctions belonging to the continuum would be useful in the study of transitions to the continuum in molecular dissociation processes. In this article, bound and scattering wavefunctions of the Kratzer oscillator are reviewed and the bound,bound and the bound,free matrix elements are obtained. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002 [source] Discrete,continuous analysis of optimal equipment replacementINTERNATIONAL TRANSACTIONS IN OPERATIONAL RESEARCH, Issue 5 2010Yuri Yatsenko Abstract In operations research, the equipment replacement process is usually modeled in discrete time. An alternative approach is represented by continuous-time vintage capital models that explicitly involve the equipment lifetime and are described by nonlinear integral equations. The paper introduces and analyzes a model that unites both these approaches. The structure of optimal replacement, transition, and long-term dynamics, and clustering and splitting of replaced machines are discussed and illustrated with numeric examples. Equipment splitting is demonstrated when the optimal equipment lifetime increases. [source] Discrete versus In Situ -Generated Aluminum-Salen Catalysts in Enantioselective Cyanosilylation of Ketones: Role of Achiral LigandsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 5 2008Ali Alaaeddine Abstract The monometallic species {Salen}AlX (X=Me, 2a,b; X=Cl, 4a,b; O- i- Pr, 5a,b) and open bimetallic species {Salen}[AlMe2]2 (3a,b) that result from binary combinations between an aluminum precursor [trimethylaluminum, dimethylaluminum chloride, aluminum tris(isopropoxide)] and a diprotio {Salen}H2 pro-ligand 1a,b (a=1R,2R -cyclohexyl-salen; b=1R,2R -diphenylethylene-salen) have been isolated. The crystal structures of 3b, 4b and of ,-oxo species [{diphenylethylene-salen}Al]2O (6b) are reported. The discrete species 2,5a,b have been individually evaluated in the asymmetric cyanosilylation of acetophenone. It is shown that, in several cases, these discrete catalysts display dramatically different performances than the catalyst systems in situ -generated from the binary combinations. The influence of the achiral ligand X on both the enantioselectivity and activity of the cyanosilylation reaction has been investigated, resulting in the definition of a highly active and productive hexafluoro-2-propoxide-based catalyst for a variety of aryl alkyl ketones (TON up to 470, TOF up to 140,h,1 at ,20,°C for acetophenone). [source] A Discrete, Space Variation Model for Studying the Kinetics of Shape Deformation of Vesicles Coupled with Phase SeparationMACROMOLECULAR THEORY AND SIMULATIONS, Issue 5 2006Jianfeng Li Abstract Summary: The evolution dynamics of phase separation, coupled with shape deformation of vesicles is described by using dissipative dynamic equations, specifically the time-dependent Ginzburg-Landau (TDGL) equations. In order to improve the numerical stability and thus to efficiently deal with a large deformation of vesicles, a new algorithm, namely the discrete space variation model (DSVM) has been developed for the first time. The algorithm is based on the variation of the discretized free-energy functional, which is constructed in discrete membrane space, in contrast to the commonly used continuous free-energy functional. For the sake of numerical tractability, only the cylindrical vesicles (2D), with two components, are taken into consideration to illustrate the efficiency and validity of new algorithm. The simulation results, based on the DSVM algorithm have been compared with those from both linear analysis and strong segregation theory using the continuous space free-energy functional. It is found that the DSVM algorithm can correctly describe the coupling between the lateral phase-separation on the vesicle membrane and the vesicle shape deformation, both for early and late stages. A flower-like vesicle obtained by DSVM simulation. [source] Evaluation of probabilistic prediction systems for a scalar variableTHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 609 2005G. Candille Abstract A systematic study is performed of a number of scores that can be used for objective validation of probabilistic prediction of scalar variables: Rank Histograms, Discrete and Continuous Ranked Probability Scores (DRPS and CRPS, respectively). The reliability-resolution-uncertainty decomposition, defined by Murphy for the DRPS, and extended here to the CRPS, is studied in detail. The decomposition is applied to the results of the Ensemble Prediction Systems of the European Centre for Medium-range Weather Forecasts and the National Centers for Environmental Prediction. Comparison is made with the decomposition of the CRPS defined by Hersbach. The possibility of determining an accurate reliability-resolution decomposition of the RPSs is severely limited by the unavoidably (relatively) small number of available realizations of the prediction system. The Hersbach decomposition may be an appropriate compromise between the competing needs for accuracy and practical computability. Copyright © 2005 Royal Meteorological Society. [source] Light and Transmission Electron Microscopy of Immature Camelus Dromedarius OocyteANATOMIA, HISTOLOGIA, EMBRYOLOGIA, Issue 4 2004H. Nili Summary In order to provide a consistent system for laboratory production of embryos, the characteristics of immature camel oocyte must first be described. The objective of this study was to define ultrastructural features of immature camel oocyte. Ovaries were obtained from camels at a local abattoir, and then transported to the laboratory within 2 h. Camelus cumulus oocyte complexes (COCs) were aspirated from 2,6 mm follicles using a 22-gauge needle. Excellent and good quality COCs were selected and prepared for transmission electron microscopy study using a cavity slide. The fine structure of camel oocyte is morphologically similar to that of other mammalian oocytes. However, some minor differences exist between COC of camel and other mammalian species. Different size and shape of membrane-bound vesicles, lipid droplet, mitochondria and cortical granules were distributed throughout the ooplasm. Discrete or in association with endoplasmic reticulum, Golgi complexes were observed in the periphery of the oocytes. The majority of the oocytes were in the germinal vesicle stage. [source] Robust H, Non-Fragile Controller Design for Uncertain Descriptor Systems with Time-Varying Discrete and Distributed DelaysASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 3-4 2005Dong Yue This paper is concerned with the design problem of non-fragile H, controller for uncertain descriptor systems with time-varying discrete and distributed delays and controller gain variations. The designed controller is shown to be robust not only to parameter uncertainties, but also to errors in the controller coefficients. The obtained criterion to derive an efficient non-fragile H, control design is expressed as a set of nonconvex matrix inequalities, which can be solved by combining both linear matrix inequalities technique and come complementarity method. A numerical example is given to demonstrate effectiveness of the proposed methods. [source] A Versatile Birth,Death Model Applicable to Four Distinct ProblemsAUSTRALIAN & NEW ZEALAND JOURNAL OF STATISTICS, Issue 1 2004J. Gani Summary This paper revisits a simple birth,death model which arises in slightly different forms in four distinct stochastic problems. These are the barbershop queue, coupon collecting, vocabulary usage and geological dating. Discrete and continuous time Markov chains are used to characterize these problems. Somewhat different questions are posed for each particular case, and practical results are derived for each process. The paper concludes with some comments on the versatility of this applied probability model. [source] Mixtures of Varying Coefficient Models for Longitudinal Data with Discrete or Continuous Nonignorable DropoutBIOMETRICS, Issue 4 2004Joseph W. Hogan Summary The analysis of longitudinal repeated measures data is frequently complicated by missing data due to informative dropout. We describe a mixture model for joint distribution for longitudinal repeated measures, where the dropout distribution may be continuous and the dependence between response and dropout is semiparametric. Specifically, we assume that responses follow a varying coefficient random effects model conditional on dropout time, where the regression coefficients depend on dropout time through unspecified nonparametric functions that are estimated using step functions when dropout time is discrete (e.g., for panel data) and using smoothing splines when dropout time is continuous. Inference under the proposed semiparametric model is hence more robust than the parametric conditional linear model. The unconditional distribution of the repeated measures is a mixture over the dropout distribution. We show that estimation in the semiparametric varying coefficient mixture model can proceed by fitting a parametric mixed effects model and can be carried out on standard software platforms such as SAS. The model is used to analyze data from a recent AIDS clinical trial and its performance is evaluated using simulations. [source] Experience with model predictive control in the undergraduate laboratoryCOMPUTER APPLICATIONS IN ENGINEERING EDUCATION, Issue 1 2005Kenneth R. Muske Abstract A model predictive control experiment for an undergraduate senior laboratory course is outlined in this article. The process under study is a continuous stirred-tank heater and the control objective is to control the water temperature in the tank. A discrete, dynamic, physical model of this process is used in the controller. The model predictive control algorithm is a single-move, analytical controller that matches the model predicted temperature to a reference temperature trajectory at a single time in the future. A series of different control experiments using this algorithm are described and examples of each are presented. © 2005 Wiley Periodicals, Inc. Comput Appl Eng Educ 13: 40,47, 2005; Published online in Wiley InterScience (www.interscience.wiley.com); DOI 10.1002/cae.20028 [source] Fast and Scalable CPU/GPU Collision Detection for Rigid and Deformable SurfacesCOMPUTER GRAPHICS FORUM, Issue 5 2010Simon Pabst Abstract We present a new hybrid CPU/GPU collision detection technique for rigid and deformable objects based on spatial subdivision. Our approach efficiently exploits the massive computational capabilities of modern CPUs and GPUs commonly found in off-the-shelf computer systems. The algorithm is specifically tailored to be highly scalable on both the CPU and the GPU sides. We can compute discrete and continuous external and self-collisions of non-penetrating rigid and deformable objects consisting of many tens of thousands of triangles in a few milliseconds on a modern PC. Our approach is orders of magnitude faster than earlier CPU-based approaches and up to twice as fast as the most recent GPU-based techniques. [source] In-Transit Metastasis From Primary Cutaneous Squamous Cell Carcinoma in Organ Transplant Recipients and Nonimmunosuppressed Patients: Clinical Characteristics, Management, and Outcome in a Series of 21 PatientsDERMATOLOGIC SURGERY, Issue 4p2 2004John A. Carucci MD Background. In-transit metastases from cutaneous squamous cell carcinoma (SCC) may occur in organ transplant recipients and may indicate aggressive disease and poor prognosis. Objective. The objective of this study was to describe in-transit metastases from cutaneous SCC and to identify factors associated with this phenomenon in a series of 21 patients. We also attempted to evaluate outcome with respect to status as an organ transplant recipient or nonorgan transplant recipient. Methods. A multicenter case series of patients was reviewed; factors included clinical presentation, management, and outcome. Results. Twenty-one patients, 15 organ transplant recipients, and 6 nontransplant recipients with in-transit metastases were reviewed. In-transit metastases presented most commonly as discrete, dermal papules distinct from but in the vicinity of the primary tumor site. Histologic differentiation was variable. At a mean follow up of 24 months, 33% the transplant patients had no evidence of disease compared with 80% of nontransplant patients. Thirty-three percent were dead from disease and 33% were alive with nodal or distant metastases. In contrast, 80% of nonimmunosuppressed patients had no evidence of disease and none had died at mean follow-up of 24 months. Conclusion. In-transit metastasis from cutaneous SCC is a unique presentation of metastatic SCC, more commonly described in organ transplant recipients, and is associated with poor prognosis in that group. This description represents the largest experience with in-transit metastases from cutaneous SCC in the literature. [source] From segment to somite: Segmentation to epithelialization analyzed within quantitative frameworksDEVELOPMENTAL DYNAMICS, Issue 6 2007Paul M. Kulesa Abstract One of the most visually striking patterns in the early developing embryo is somite segmentation. Somites form as repeated, periodic structures in pairs along nearly the entire caudal vertebrate axis. The morphological process involves short- and long-range signals that drive cell rearrangements and cell shaping to create discrete, epithelialized segments. Key to developing novel strategies to prevent somite birth defects that involve axial bone and skeletal muscle development is understanding how the molecular choreography is coordinated across multiple spatial scales and in a repeating temporal manner. Mathematical models have emerged as useful tools to integrate spatiotemporal data and simulate model mechanisms to provide unique insights into somite pattern formation. In this short review, we present two quantitative frameworks that address the morphogenesis from segment to somite and discuss recent data of segmentation and epithelialization. Developmental Dynamics 236:1392,1402, 2007. © 2007 Wiley-Liss, Inc. [source] Dopamine and sensory tissue development in Drosophila melanogasterDEVELOPMENTAL NEUROBIOLOGY, Issue 4 2001Wendi Neckameyer Abstract Dopamine is an important signaling molecule in the nervous system; it also plays a vital role in the development of diverse non-neuronal tissues in the fruit fly Drosophila melanogaster. The current study demonstrates that males depleted of dopamine as third instar larvae (via inhibition of the biosynthetic enzyme tyrosine hydroxylase) demonstrated abnormalities in courtship behavior as adults. These defects were suggestive of abnormalities in sensory perception and/or processing. Electroretinograms (ERGs) of eyes from adults depleted of dopamine for 1 day as third instar larvae revealed diminished or absent on- and off-transients. These sensory defects were rescued by the addition of L -DOPA in conjunction with tyrosine hydroxylase inhibition during the larval stage. Depletion of dopamine in the first or second larval instar was lethal, but this was not due to a general inhibition of proliferative cells. To establish that dopamine was synthesized in tissues destined to become part of the adult sensory apparatus, transgenic lines were generated containing 1 or 4 kb of 5, upstream sequences from the Drosophila tyrosine hydroxylase gene (DTH) fused to the E. coli ,-galactosidase reporter. The DTH promoters directed expression of the reporter gene in discrete and consistent patterns within the imaginal discs, in addition to the expected expression in gonadal, brain, and cuticular tissues. The ,-galactosidase expression colocalized with tyrosine hydroxylase protein. These results are consistent with a developmental requirement for dopamine in the normal physiology of adult sensory tissues. © 2001 John Wiley & Sons, Inc. J Neurobiol 47: 280,294, 2001 [source] Differential effects of short and long duration insulinotropic agents on meal-related glucose excursionsDIABETES OBESITY & METABOLISM, Issue 2 2001C. J. De Souza SUMMARY Aim Abnormal ,-cell function, characterized as the inability of the ,-cell to mount a rapid secretory response to glucose, is a well-established pathology of type 2 diabetes mellitus. These studies were designed to demonstrate the importance of early insulin release on the control of meal-induced glucose excursions by capitalizing on the significant pharmacodynamic differences between several oral insulin secreting agents. Methods Male Sprague Dawley fitted with indwelling jugular cannulas were used to compare the pharmacodynamic profiles of nateglinide (Nateg), glipizide (Glip) and repaglinide (Repag) through frequent blood samples following the administration of these compounds via oral gavage. In similar animals which were pretrained to consume their daily food intake in two discrete 45-min meals, the effects of compound induced changes in pre-meal, meal and post-meal insulin profiles on glycaemic control were assessed through frequent blood sampling following the administration of these compounds 10 min prior to a 30-min meal. Results There were significant pharmacodynamics differences between the three oral agents tested and the time to elicit peak insulin secretory responses increased from Nateg (4 min) to Repag (10 min) to Glip (45 min). During the meal tolerance test, glibenclamide did not increase pre-meal insulin levels and glucose excursions paralleled those in the control. Conversely, the other three agents, at doses that produced hypoglycaemic responses of similar magnitude, all increased early insulin release (,AUC(-15 to 3 min) = 0.5 ± 0.01, 1.6 ± 0.4, 3.6 ± 0.0, 1.2 ± 0.1 and 1.73 ± 0.4 nmol/min, for control, Nateg at 60 and 120 mg/kg, Glip and Repag, respectively) and curbed glucose excursions during the meal at varying rates and degrees (,AUC(0,30 min) = 39 ± 6, 8 ± 7, 5 ± 7, ,,1 ± 8 and ,,3 ± 8 mmol/min for control, Nateg at 60 and 120 mg/kg, Glip and Repag, respectively). However, unlike Nateg, the longer duration of action of Repag and Glip elicited sustained post-meal relative hypoglycaemia. Conclusion These data support the impact of early and rapid insulin release in the control of prandial and post-meal glycaemia and demonstrate that a short anticipatory burst of insulin, restricted to the beginning of a meal, provides a clear metabolic advantage and prevents post-meal hypoglycaemic episodes when compared to a greater but reactive insulin exposure that follows a meal-induced increase in glucose excursion. [source] Synthesis of pattern and process in biodiversity conservation assessment: a flexible whole-landscape modelling frameworkDIVERSITY AND DISTRIBUTIONS, Issue 3 2010Simon Ferrier Abstract Aim, To describe a general modelling framework for integrating multiple pattern- and process-related factors into biodiversity conservation assessments across whole landscapes. Location, New South Wales (Australia), and world-wide. Methods, The framework allows for a rich array of alternatives to the target-based model traditionally underpinning systematic conservation planning and consists of three broad modelling components. The first component models the future state (condition) of habitat across a landscape as a function of present state, current and projected pressures acting on this state, and any proposed, or implemented, management interventions. The second component uses this spatially explicit prediction of future habitat state to model the level of persistence expected for each of a set of surrogate biodiversity entities. The third component then integrates these individual expectations to estimate the overall level of persistence expected for biodiversity as a whole. Results, Options are explored for tailoring implementation of the framework to suit planning processes varying markedly in purpose, and in availability of data, time, funding and expertise. The framework allows considerable flexibility in the nature of employed biodiversity surrogates (species-level, discrete or continuous community-level) and spatial data structures (polygonal planning units, or fine-scaled raster), the level of sophistication with which each of the three modelling components is implemented (from simple target-based assessment to complex process-based modelling approaches), and the forms of higher-level analysis supported (e.g. optimal plan development, priority mapping, interactive scenario evaluation). Main conclusions, The described framework provides a logical, and highly flexible, foundation for integrating disparate pattern- and process-related factors into conservation assessments in dynamic, multiple-use landscapes. [source] Quantifying spatial classification uncertainties of the historical Wisconsin landscape (USA)ECOGRAPHY, Issue 2 2005Janine Bolliger Landscape feature can be classified by creating categories based on aggregation of spatially explicit information. However, many landscape features appear continuous rather than discrete. The aggregation process likely involves loss of information and introduces a variety of uncertainties whose degree and extent may differ spatially. Since landscape classifications have found wide application in e.g. natural resource policies or ecological research, assessments of spatial classification uncertainties are required. We present a quantitative framework to identify the degree of landscape continuity (fuzziness) and structure (categorization) based on fuzzy classification and offer measures to quantify uncertainties originating from aggregating features into categories. Fuzzy classification is a non-hierarchical, quantitative method of assessing class definitions using degrees of association between features and class. This results in classes which are well defined and compositionally distinct, as well as classes which are less clearly defined but which, to various degrees, share characteristics with some or all classes. The spatial variation in the degree of class definition on the landscape is used to assess classification uncertainties. The two aspects of uncertainty investigated are the degree of association of a feature with the overall class definitions (membership diffusion), and the class-specific degree of association of each pixel on the landscape with each class (membership saturation). Three classification scenarios, one fuzzy and one discrete, of the historical landscape of Wisconsin (USA) were compared for spatial classification uncertainties. Membership diffusion is highest in topographically heterogeneous environments, or areas characterized by many species occupying similar ecological niches. Classification uncertainties for individual classes show that differentiated species distributions can be identified, not only distribution centers. [source] Optimal Dynamic Trading StrategiesECONOMIC NOTES, Issue 1 2004Douglas T. Breeden This article presents a straightforward technique for computing solutions to discrete, multi-period consumption/investment problems. It solves for the optimal stochastic consumption plans, as well as the optimal dynamic trading strategies that maximize utility for an individual. The technique permits general utility functions that may or may not be time-separable. It also allows general changes in the investment opportunity set and allows the user to impose upper and lower bounds on trading behaviour. Divergent borrowing and lending rates can be handled, as can stochastic labour income risks. Computed solutions verify the predictions of well-known intertemporal works by Merton, Breeden and others. J.E.L.:G13). [source] From Representation to Emergence: Complexity's challenge to the epistemology of schoolingEDUCATIONAL PHILOSOPHY AND THEORY, Issue 1 2008Deborah Osberg Abstract In modern, Western societies the purpose of schooling is to ensure that school-goers acquire knowledge of pre-existing practices, events, entities and so on. The knowledge that is learned is then tested to see if the learner has acquired a correct or adequate understanding of it. For this reason, it can be argued that schooling is organised around a representational epistemology: one which holds that knowledge is an accurate representation of something that is separate from knowledge itself. Since the object of knowledge is assumed to exist separately from the knowledge itself, this epistemology can also be considered ,spatial.' In this paper we show how ideas from complexity have challenged the ,spatial epistemology' of representation and we explore possibilities for an alternative ,temporal' understanding of knowledge in its relationship to reality. In addition to complexity, our alternative takes its inspiration from Deweyan ,transactional realism' and deconstruction. We suggest that ,knowledge' and ,reality' should not be understood as separate systems which somehow have to be brought into alignment with each other, but that they are part of the same emerging complex system which is never fully ,present' in any (discrete) moment in time. This not only introduces the notion of time into our understanding of the relationship between knowledge and reality, but also points to the importance of acknowledging the role of the ,unrepresentable' or ,incalculable'. With this understanding knowledge reaches us not as something we receive but as a response, which brings forth new worlds because it necessarily adds something (which was not present anywhere before it appeared) to what came before. This understanding of knowledge suggests that the acquisition of curricular content should not be considered an end in itself. Rather, curricular content should be used to bring forth that which is incalculable from the perspective of the present. The epistemology of emergence therefore calls for a switch in focus for curricular thinking, away from questions about presentation and representation and towards questions about engagement and response. [source] Use of poly(vinyl alcohol)-coated capillaries for separation of amino-terminated polyamidoamine dendrimersELECTROPHORESIS, Issue 3 2007Britton Carter Abstract Characterization of amino-terminated polyamidoamine dendrimers by CE suffers from a lack of resolution for higher generations and poor between-day reproducibility of retention times. Under optimal conditions of temperature, voltage, and sample amount, 0,5,generations of dendrimers could be resolved with a bare fused-silica capillary. However, reproducibility was poor due to potential interactions of the polycationic dendrimers with the uncoated quartz capillary wall. Use of a poly(vinyl alcohol)-coated capillary significantly decreased the migration times of the nanomolecules without compromising resolution. Dendrimer mixtures containing generations,0,5 are separated as discrete, nonoverlapping peaks in about 15,min. In addition, the between-day precision of retention times was dramatically improved without the need for internal standards or data normalization. Dendrimers of various generations and cores run on different days showed an RSD of retention times of less than 4%. The poly(vinyl alcohol) coating was very stable as shown by the excellent precision of migration times obtained on a capillary used for a month with more than 100,injections. Similar to PAGE, separation of polyamidoamine dendrimers on a bare fused-silica and poly(vinyl alcohol)-coated capillary showed an exponential relationship between migration times and calculated charge density of the nanomolecules. [source] Space,time modeling of 20 years of daily air temperature in the Chicago metropolitan regionENVIRONMETRICS, Issue 5 2009Hae-Kyung Im Abstract We analyze 20 years of daily minimum and maximum air temperature data in the Chicago metropolitan region and propose a parsimonious model that describes their mean function and the space,time covariance structure. The mean function contains a long-term trend, annual and semiannual harmonics, and physical covariates such as latitude, distance to the Lake Michigan, and winds, each interacted with the harmonic terms, thus allowing the effects of physical covariates to vary smoothly over time. The temporal correlation at a given location is described using an ARMA(1,2) model. The residuals (innovations) from this models are treated as independent replications of a spatial process with covariance structure in the Matérn class. The space,time covariance structure parameters are allowed to vary seasonally. Using the estimated covariance structure, we interpolate the temperature to a fine grid in the Chicago metropolitan region. This procedure borrows information from temporally and spatially adjacent data. The methods presented in this paper should be useful to approach other environmental problems where the data are discrete and regular in time but irregular in space. Copyright © 2008 John Wiley & Sons, Ltd. [source] Variance estimation for spatially balanced samples of environmental resourcesENVIRONMETRICS, Issue 6 2003Don L. Stevens Jr Abstract The spatial distribution of a natural resource is an important consideration in designing an efficient survey or monitoring program for the resource. We review a unified strategy for designing probability samples of discrete, finite resource populations, such as lakes within some geographical region; linear populations, such as a stream network in a drainage basin, and continuous, two-dimensional populations, such as forests. The strategy can be viewed as a generalization of spatial stratification. In this article, we develop a local neighborhood variance estimator based on that perspective, and examine its behavior via simulation. The simulations indicate that the local neighborhood estimator is unbiased and stable. The Horvitz,Thompson variance estimator based on assuming independent random sampling (IRS) may be two times the magnitude of the local neighborhood estimate. An example using data from a generalized random-tessellation stratified design on the Oahe Reservoir resulted in local variance estimates being 22 to 58 percent smaller than Horvitz,Thompson IRS variance estimates. Variables with stronger spatial patterns had greater reductions in variance, as expected. Copyright © 2003 John Wiley & Sons, Ltd. [source] Synthesis and Characterisation of [XeF5]3[Ti4F19] Containing a Discrete [Ti4F19]3, AnionEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 29-30 2009Zoran Mazej Abstract The complex [XeF5]3[Ti4F19] was prepared by reaction of XeF2, TiF4 and UV-irradiated elemental fluorine in anhydrous hydrogen fluoride as the solvent. The crystal structure of [XeF5]3[Ti4F19] consists of [XeF5]+ cations and discrete [Ti4F19]3, anions. The [XeF5] units have usual slightly distorted pseudo-octahedral symmetry. Contrary to the previously reported [Ti4F18]2, anion, where each TiF6 octahedron shares three apexes with three other octahedra, in [Ti4F19]3,, only two ,3 -[TiF6] octahedra share three apexes with three other [TiF6] units. Each of the remaining two ,2 -[TiF6] octahedra shares only two vertices with two of the above-mentioned ,3 -[TiF6] moieties. The Raman spectrum of [XeF5]3[Ti4F19] is in agreement with the presence of [XeF5]+ cations and [Ti4F19]3, anions. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] STATISTICAL ANALYSIS OF DIVERSIFICATION WITH SPECIES TRAITSEVOLUTION, Issue 1 2005Emmanuel Paradis Abstract Testing whether some species traits have a significant effect on diversification rates is central in the assessment of macroevolutionary theories. However, we still lack a powerful method to tackle this objective. I present a new method for the statistical analysis of diversification with species traits. The required data are observations of the traits on recent species, the phylogenetic tree of these species, and reconstructions of ancestral values of the traits. Several traits, either continuous or discrete, and in some cases their interactions, can be analyzed simultaneously. The parameters are estimated by the method of maximum likelihood. The statistical significance of the effects in a model can be tested with likelihood ratio tests. A simulation study showed that past random extinction events do not affect the Type I error rate of the tests, whereas statistical power is decreased, though some power is still kept if the effect of the simulated trait on speciation is strong. The use of the method is illustrated by the analysis of published data on primates. The analysis of these data showed that the apparent overall positive relationship between body mass and species diversity is actually an artifact due to a clade-specific effect. Within each clade the effect of body mass on speciation rate was in fact negative. The present method allows to take both effects (clade and body mass) into account simultaneously. [source] Cerebral Metabolism is Influenced by Muscle Ischaemia During Exercise in HumansEXPERIMENTAL PHYSIOLOGY, Issue 2 2003Mads K. Dalsgaard Maximal exercise reduces the cerebral metabolic ratio (O2/(glucose + 1/2lactate)) to < 4 from a resting value close to 6, and only part of this decrease is explained by the ,intent' to exercise. This study evaluated whether sensory stimulation of brain by muscle ischaemia would reduce the cerebral metabolic ratio. In 10 healthy human subjects the cerebral arterial-venous differences (a-v differences) for O2, glucose and lactate were assessed before, during and after three bouts of 10 min cycling with equal workload: (1) control exercise at light intensity, (2) exercise that elicited a high rating of perceived exertion due to a 100 mmHg thigh cuff, and (3) exercise followed by 5 min of post-exercise muscle ischaemia that increased blood pressure by , 20%. Control exercise did not significantly affect the a-v differences. However, during the recovery from exercise with thigh cuffs the cerebral metabolic ratio decreased from a resting value of 5.4 ± 0.2 to 4.0 ± 0.4 (mean ±s.e.m.. P < 0.05) as a discrete lactate efflux from the brain at rest shifted to a slight uptake. Also, following post-exercise muscle ischaemia, the cerebral metabolic ratio decreased to 4.5 ± 0.3 (P < 0.05). The results support the hypothesis that during exercise, cerebral metabolism is influenced both by the mental effort to exercise and by sensory input from skeletal muscles. [source] A metapopulation perspective for salmon and other anadromous fishFISH AND FISHERIES, Issue 4 2007Nicolas Schtickzelle Abstract Salmonids are an important component of biodiversity, culture and economy in several regions, particularly the North Pacific Rim. Given this importance, they have been intensively studied for about a century, and the pioneering scientists recognized the critical link between population structure and conservation. Spatial structure is indeed of prime importance for salmon conservation and management. At first glance, the essence of the metapopulation concept, i.e. a population of populations, widely used on other organisms like butterflies, seems to be particularly relevant to salmon, and more generally to anadromous fish. Nevertheless, the concept is rarely used, and barely tested. Here, we present a metapopulation perspective for anadromous fish, assessing in terms of processes rather than of patterns the set of necessary conditions for metapopulation dynamics to exist. Salmon, and particularly sockeye salmon in Alaska, are used as an illustrative case study. A review of life history traits indicates that the three basic conditions are likely to be fulfilled by anadromous salmon: (i) the spawning habitat is discrete and populations are spatially separated by unsuitable habitat; (ii) some asynchrony is present in the dynamics of more or less distant populations and (iii) dispersal links populations because some salmon stray from their natal population. The implications of some peculiarities of salmon life history traits, unusual in classical metapopulations, are also discussed. Deeper understanding of the population structure of anadromous fish will be advanced by future studies on specific topics: (i) criteria must be defined for the delineation of suitable habitats that are based on features of the biotope and not on the presence of fish; (ii) the collection of long-term data and the development of improved methods to determine age structure are essential for correctly estimating levels of asynchrony between populations and (iii) several key aspects of dispersal are still poorly understood and need to be examined in detail: the spatial and temporal scales of dispersal movements, the origin and destination populations instead of simple straying rates, and the relative reproductive success of immigrants and residents. [source] | |||||||||||||||||||||||||||||||||||||