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Partitioning
Kinds of Partitioning Terms modified by Partitioning Selected AbstractsMULTILEVEL SELECTION AND THE PARTITIONING OF COVARIANCE: A COMPARISON OF THREE APPROACHESEVOLUTION, Issue 3 2004Samir Okasha Abstract Where the evolution of a trait is affected by selection at more than one hierarchical level, it is often useful to compare the magnitude of selection at each level by asking how much of the total evolutionary change is attributable to each level of selection. Three statistical partitioning techniques, each designed to answer this question, are compared, in relation to a simple multilevel selection model in which a trait's evolution is affected by both individual and group selection. None of the three techniques is wholly satisfactory: one implies that group selection can operate even if individual fitness is determined by individual phenotype alone, whereas the other two imply that group selection can operate even if there is no variance in group fitness. This has significant implications both for our understanding of what the term "multilevel selection" means and for the traditional concept of group selection. [source] EFFECT OF SALTS AND POLYETHYLENE GLYCOLS ON THE PARTITIONING AND RECOVERY OF TRYPSIN FROM HYBRID CATFISH VISCERA IN AQUEOUS TWO-PHASE SYSTEMSJOURNAL OF FOOD BIOCHEMISTRY, Issue 4 2010SAPPASITH KLOMKLAO ABSTRACT The partitioning behavior of trypsin from hybrid catfish viscera in aqueous two-phase systems (ATPS) was studied. Factors such as polyethylene glycol (PEG) molecular mass and concentration, as well as types and concentration of salts, affected protein separation. Trypsin partitioned mainly in the top PEG-rich phase. ATPS formed by PEG of molecular weight 4,000 (20%, w/w) and NaH2PO4 (20%, w/w) showed the best capability for trypsin purification from hybrid catfish viscera. Under such conditions, the highest specific activity (30.05 units/µg protein) and purification (27.3-fold), were obtained. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis revealed that the enzyme after ATPS separation was near homogeneity and based on the activity staining, the band intensity of enzyme in ATPS fraction increased, indicating the greater specific activity of the viscera extract. The partitioned enzyme displayed optimal activity at pH 9.0 and 50C, respectively. The enzyme was stable up to 40C and within the pH range of 8,12. The enzyme exhibited a progressive decrease in activity with increasing NaCl concentration. PRACTICAL APPLICATIONS This paper describes the separation and recovery of trypsin from hybrid catfish viscera in ATPS and its properties. ATPS provides an efficient and attractive method for partitioning and recovery of trypsin from hybrid catfish viscera. Trypsins from various sources catalyze the hydrolysis of peptide bonds on the carboxyl sides of arginine and lysine. Therefore, it is expected that like other trypsins, trypsin after ATPS separation from hybrid catfish viscera could be useful in the biomedical, food and beverage industries. [source] HIGH YIELD PURIFICATION OF DEXTRANSUCRASE FROM LEUCONOSTOC MESENTEROIDES NRRL B-512F BY PHASE PARTITIONINGJOURNAL OF FOOD BIOCHEMISTRY, Issue 1 2006MANISHA NIGAM ABSTRACT The extracellular dextransucrase (sucrose: 1,6-,-D-glucan 6-,-D-glucosyltransferase EC 2.4.1.5) from Leuconostoc mesenteroides NRRL B-512F was purified by phase partitioning using poly(ethylene) glycol (PEG) and dextran generated by dextransucrase. Three steps of repeated phase partitioning by PEG 6000 and PEG 400 showed that the purification of dextransucrase by PEG 6000 was much greater than that obtained by PEG 400. Both the specific activity of 42.1 U/mg and the overall yield of 84% of dextransucrase activity obtained after the third step of phase partitioning by PEG 6000 were significantly higher than that of 23.8 U/mg and 46% overall yield, respectively, by PEG 400 or of that previously reported. The successive three steps, two-phase partitioning with a final concentration of 5% PEG 6000, reproducibly yielded a homogeneous preparation of dextransucrase. [source] Motorcycle Graphs: Canonical Quad Mesh PartitioningCOMPUTER GRAPHICS FORUM, Issue 5 2008David Eppstein Abstract We describe algorithms for canonically partitioning semi-regular quadrilateral meshes into structured submeshes, using an adaptation of the geometric motorcycle graph of Eppstein and Erickson to quad meshes. Our partitions may be used to efficiently find isomorphisms between quad meshes. In addition, they may be used as a highly compressed representation of the original mesh. These partitions can be constructed in sublinear time from a list of the extraordinary vertices in a mesh. We also study the problem of further reducing the number of submeshes in our partitions,we prove that optimizing this number is NP-hard, but it can be efficiently approximated. [source] Employee Stock Option Fair-Value Estimates: Do Managerial Discretion and Incentives Explain Accuracy?,CONTEMPORARY ACCOUNTING RESEARCH, Issue 4 2006Leslie Hodder Abstract We examine the determinants of managers' use of discretion over employee stock option (ESO) valuation-model inputs that determine ESO fair values. We also explore the consequences of such discretion. Firms exercise considerable discretion over all model inputs, and this discretion results in material differences in ESO fair-value estimates. Contrary to conventional wisdom, we find that a large proportion of firms exercise value-increasing discretion. Importantly, we find that using discretion improves predictive accuracy for about half of our sample firms. Moreover, we find that both opportunistic and informational managerial incentives together explain the accuracy of firms' ESO fair-value estimates. Partitioning on the direction of discretion improves our understanding of managerial incentives. Our analysis confirms that financial statement readers can use mandated contextual disclosures to construct powerful ex ante predictions of ex post accuracy. [source] Partitioning, bioavailability, and toxicity of the pyrethroid insecticide cypermethrin in sedimentsENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 1 2002Steve J. Maund Abstract The partitioning, bioavailability, and toxicity of cypermethrin in water,sediment systems was investigated. Cypermethrin adsorbed extensively and rapidly, with an overall mean organic carbon (OC) adsorption partition coefficient (Koc) of 350,000, and approximately 99% adsorption occurred within 24 h. Bioavailability was measured via body burdens of Daphnia magna and Chironomus tentans. Mean biota,sediment accumulation factors (BSAFs), that is, the concentration in the organism as a proportion of the concentration in the sediment, decreased with increasing OC content. The BSAF values were 0.31, 0.14, and 0.08 for D. magna and 0.63, 0.19, and 0.08 for C. tentans, in 1, 3, and 13% OC sediments, respectively. The 10-d median lethal sediment concentrations (LC50s) of cypermethrin were 3.6, 18, and 32 mg/kg for Hyalella azteca and 13, 67, and 62 mg/kg for C. tentans in 1, 3, and 13% OC sediments, respectively. Predictions of aqueous concentrations at the LC50 in sediments (based on Koc) compared well to each other and to effect concentrations from studies in water alone, suggesting that equilibrium partitioning theory could be used reasonably to predict and normalize the toxicity of cypermethrin across sediments of differing OC content. [source] Partitioning of copper at concentrations below the marine water quality criteria,ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 5 2001Anthony J. Paulson Abstract Partitioning of Cu between the aqueous and particulate phases and among their components was examined in six ambient Puget Sound, Washington State, USA, samples (6,10 nM Cu). Most of the particulate Cu (4,12% of the total Cu) was associated with particulate organic matter, and resulted in distribution coefficients (Kd) ranging between 104,55 and 105,1. For the dissolved phase, the portion of Cu extracted by C18 -packed cartridges averaged 44% (+ 11%). Radioactive 64Cu was added to these samples to total stable Cu concentrations (17,33 nM). After 24 h of equilibration, the portion of 64Cu associated with the particulate matter in five of the six samples (Kd between 1047 and 1053) was an average of 70% higher than that of natural Cu in the ambient samples. In contrast, only 19 ± 7% of the 64Cu was extracted by C18 -packed cartridges. The partitioning of natural Cu and 64Cu onto particles was not significantly different when the equilibria were based on dissolved Cu passing through the C18 cartridges. Further research is warranted on utilizing the hydrophilic component of the dissolved phase as a parameter on which water quality criteria are based. [source] Laser Flash Photolysis of Disulfonyldiazomethanes: Partitioning between Hetero-Wolff Rearrangement and Intramolecular Carbene Oxidation by a Sulfonyl GroupEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 11 2003Götz Bucher Abstract Laser flash photolysis of bis(phenylsulfonyl)diazomethane (1a) and ditosyldiazomethane (1b) leads to the formation of sulfonylsulfenes 8a/8b (,max = 310 nm). Non-first-order kinetics and non-linear Stern,Volmer behavior suggest the formation of another transient species also absorbing at , = 310 nm. Based on the results of DFT calculations, these species are tentatively identified as dithiocarbonate S,S,S, -trioxides 12a/b, which are formed from the oxathiirene S -oxides 9a/b. The latter compounds bear the characteristics of masked carbenes (, estimated as 700 ps) and are quenched by methanol and cyclooctene. Singlet disulfonylcarbenes 2a/b are not predicted to be minima, since all attempts at optimizing the geometry of 2a led to 9a instead. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source] Partitioning of metals (Cd, Co, Cu, Ni, Pb, Zn) in soils: concepts, methodologies, prediction and applications , a reviewEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 4 2009F. Degryse Summary Prediction of the fate of metals in soil requires knowledge of their solid,liquid partitioning. This paper reviews analytical methods and models for measuring or predicting the solid,liquid partitioning of metals in aerobic soils, and collates experimental data. The partitioning is often expressed with an empirical distribution coefficient or Kd, which gives the ratio of the concentration in the solid phase to that in the solution phase. The Kd value of a metal reflects the net effect of various reactions in the solid and liquid phases and varies by orders of magnitude among soils. The Kd value can be derived from the solid,liquid distribution of added metal or that of the soil-borne metal. Only part of the solid-phase metal is rapidly exchangeable with the solution phase. Various methods have been developed to quantify this ,labile' phase, and Kd values based on this phase often correlate better with soil properties than Kd values based on total concentration, and are more appropriate to express metal ion buffering in solute transport models. The in situ soil solution is the preferred solution phase for Kd determinations. Alternatively, water or dilute-salt extracts can be used, but these may underestimate in situ concentrations of dissolved metals because of dilution of metal-complexing ligands such as dissolved organic matter. Multi-surface models and empirical models have been proposed to predict metal partitioning from soil properties. Though soil pH is the most important soil property determining the retention of the free metal ion, Kd values based on total dissolved metal in solution may show little pH dependence for metal ions that have strong affinity for dissolved organic matter. The Kd coefficient is used as an equilibrium constant in risk assessment models. However, slow dissociation of metal complexes in solution and slow exchange of metals between labile and non-labile pools in the solid phase may invalidate this equilibrium assumption. [source] The canopy conductance of a boreal aspen forest, Prince Albert National Park, CanadaHYDROLOGICAL PROCESSES, Issue 9 2004P. D. Blanken Abstract Annual fluxes of canopy-level heat, water vapour and carbon dioxide were measured using eddy covariance both above the aspen overstory (Populus tremuloides Michx.) and hazelnut understory (Corylus cornuta Marsh.) of a boreal aspen forest (53·629 °N 106·200 °W). Partitioning of the fluxes between overstory and understory components allowed the calculation of canopy conductance to water vapour for both species. On a seasonal basis, the canopy conductance of the aspen accounted for 70% of the surface conductance, with the latter a strong function of the forest's leaf area index. On a half-hour basis, the canopy conductance of both species decreased non-linearly as the leaf-surface saturation deficits increased, and was best parameterized and showed similar sensitivities to a modified form of the Ball,Berry,Woodrow index, where relative humidity was replaced with the reciprocal of the saturation deficit. The negative feedback between the forest evaporation and the saturation deficit in the convective boundary layer varied from weak when the forest was at full leaf to strong when the forest was developing or loosing leaves. The coupling between the air at the leaf surface and the convective boundary layer also varied seasonally, with coupling decreasing with increasing leaf area. Compared with coniferous boreal forests, the seasonal changes in leaf area had a unique impact on vegetation,atmosphere interactions. Copyright © 2004 John Wiley & Sons, Ltd. [source] Metallic Glasses: Nanoscale Solute Partitioning in Bulk Metallic Glasses (Adv. Mater.ADVANCED MATERIALS, Issue 3 20093/2009) Devitrification of bulk metallic glass leads to novel microstructures with high-density nanoscale crystalline precipitates evenly distributed in a glassy matrix. Xun-Li Wang and co-workers report on p. 305 that significant chemical segregation is revealed in unprecedented detail by atom-probe tomography. This level of detail is crucial for understanding the interference peaks observed in small-angle X-ray and neutron scattering experiments. [source] Nanoscale Solute Partitioning in Bulk Metallic Glasses,ADVANCED MATERIALS, Issue 3 2009Ling Yang Devitrification of bulk metallic glass leads to a novel microstructure, with high-density nanoscale crystalline precipitates evenly distributed in a glassy matrix. Significant chemical segregation is revealed at unprecedented detail by atom-probe tomography. This level of detail is crucial for understanding the interference peaks observed in small-angle X-ray and neutron scattering experiments, an unsolved mistery for over a decade. [source] Effects of Interactions of Moisture Regime and Nutrient Addition on Nodulation and Carbon Partitioning in Two Cultivars of Bean (Phaseolus vulgaris L.)JOURNAL OF AGRONOMY AND CROP SCIENCE, Issue 4 2001T. Boutraa Major limitations of bean (Phaseolus vulgaris L.) production in arid and semiarid regions are lack of moisture and low soil fertility. An experiment was conducted to determine the effects of soil moisture and N : P : K (20 : 10 : 10) fertilizer on root and shoot growth of two cultivars of bean: cv. Carioca, an indeterminate Brazilian landrace, and cv. Prince, a determinate cultivar grown in Europe. Carioca appears generally stress-tolerant while Prince is intolerant. Seedlings were grown in pots of non-sterile soil at 30, 60 or 90 % field capacity (FC), and given 0, 0.1 or 1 g (kg soil),1 of compound fertilizer. The soil contained a population of effective Rhizobium. Growth of both cultivars was greatest in the high moisture and high nutrient treatments. Root fractions were highest at low nutrient supply; the effect of water was not significant. Leaf fraction decreased as root fraction increased. Numbers of nodules were highest at high and intermediate moisture when no fertilizer was applied. Numbers were lowest at 30 % FC and at the highest fertilizer rate. Masses of nodules and fractions followed the same pattern. Decreasing water regime reduced the relative growth rate (RGR) of Prince, while Carioca maintained high RGR at unfavourable conditions of water and nutrients. Net assimilation rates (NAR) were unaffected by nutrient addition, and reduced by low moisture regime. Water use efficiencies (WUEs) were reduced by water stress but increased by nutrient deficiency. The water utilization for dry matter production was optimal at 60 % FC. Einflüsse der Interaktionen von Bodendenfeuchte und Düngung auf die Knöllchenbildung und Kohlenstoff verteilung bei zwei Bohnenkultivaren (Phaseolus vulgaris L.) Der begrenzende Hauptfaktor der Bohnenproduktion in ariden und semiariden Regionen sind der Feuchtigkeitsmangel und die Bodenfruchbarkeit. Es wurde ein Experiment durchgeführt, um die Wirkungen des Bodenwassers und von N : P : K (20 : 10 : 10) Dünger auf das Wurzel- und Sproßwachstum an zwei Kultivaren von Bohnen (Phaseolus vulgaris L. cv. Carioca, eine brasilianischen, indeterminierte Landsorte und cv. Prince, eine determinierter in Europa angebauter Kultivar) zu untersuchen. Carioca erscheint grundsätzlich streßtoleranter im Vergleich zu Prince. Die Sämlinge wurden in Gefäßen mit nichtsterilisiertem Boden unter Feldkapazitäten von 30,60 oder 90 % mit 0, 0,1 oder 1 g eines Volldüngers angezogen. Der Boden enthielt eine Population von wirksamem Rhizobium. Das stärkste Wachstum wurde bei beiden Kultivaren unter dem Einfluß des höchsten Feuchtigkeitsgehaltes und der höchsten Düngermenge gefunden. Der Wurzelanteil war bei der geringen Düngermenge am niedrigsten. Der Einfluß der Bodenfeuchtigkeit war nicht signifikant. Der Blattanteil nahm mit zunehmendem Wurzelanteil ab. Die Anzahl der Knötchen war bei hoher und mittlerer Bodenfeuchte und ohne Düngeranwendung am höchsten. Die Anzahl war am geringsten bei 30 % FC und der höchsten Düngermenge. Die Knötchenmasse und ihr Anteil reagierte entsprechend. Abnehmende Bodenfeuchte reduzierte die relative Wachtumsrate (RGR) von Prince, während Carioca einen hohen RGR auch bei ungünstigen Bedingungen bezüglich Wasser und Düngung behielt. Die Nettoassimilationsraten wurden durch die Düngung nicht beeinflußt; sie gingen bei geringer Bodenfeuchte zurück. Die Wassernutzungseffiziens (WUE) wurde bei Wasserstreß reduziert, nahm aber bei Düngermangel zu. Die Wassernutzung für die Trockenmasseproduktion war bei 60 % Feldkapazität am höchsten. [source] Partitioning of chicken egg white proteins in polyelectrolyte/salt aqueous two-phase systems composed of polyethyleneoxide,maleic acid copolymer and potassium phosphateJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 4 2002Toshio Kajiuchi Abstract Aqueous two-phase systems were formed from solutions of a polyelectrolyte, polyethyleneoxide,maleic acid copolymer, and potassium phosphate. The properties of such aqueous two-phase systems were highly dependent on pH. This was reflected in the partition behavior of three chicken egg white proteins: lysozyme, conalbumin and ovalbumin. Separability of these three proteins was improved by the use of the polyelectrolyte, in comparison with when uncharged polyethylene glycol (poly(1,2-dihydroxyethane)) was used as a phase-forming polymer. © 2002 Society of Chemical Industry [source] Partitioning of the plasma membrane Ca2+ -ATPase into lipid rafts in primary neurons: effects of cholesterol depletionJOURNAL OF NEUROCHEMISTRY, Issue 2 2007Lei Jiang Abstract Spatial and temporal alterations in intracellular calcium [Ca2+]i play a pivotal role in a wide array of neuronal functions. Disruption in Ca2+ homeostasis has been implicated in the decline in neuronal function in brain aging and in neurodegenerative disorders. The plasma membrane Ca2+ -ATPase (PMCA) is a high affinity Ca2+ transporter that plays a crucial role in the termination of [Ca2+]i signals and in the maintenance of low [Ca2+]i essential for signaling. Recent evidence indicates that PMCA is uniquely sensitive to its lipid environment and is stimulated by lipids with ordered acyl chains. Here we show that both PMCA and its activator calmodulin (CaM) are partitioned into liquid-ordered, cholesterol-rich plasma membrane microdomains or ,lipid rafts' in primary cultured neurons. Association of PMCA with rafts was demonstrated in preparations isolated by sucrose density gradient centrifugation and in intact neurons by confocal microscopy. Total raft-associated PMCA activity was much higher than the PMCA activity excluded from these microdomains. Depletion of cellular cholesterol dramatically inhibited the activity of the raft-associated PMCA with no effect on the activity of the non-raft pool. We propose that association of PMCA with rafts represents a novel mechanism for its regulation and, consequently, of Ca2+ signaling in the central nervous system. [source] Genetic structure of the European polecat (Mustela putorius) and its implication for conservation strategiesJOURNAL OF ZOOLOGY, Issue 1 2006C. Pertoldi Abstract During the last century, the European polecat Mustela putorius populations in most of Europe declined and survived in fragmented patches, because of habitat alterations and direct persecution. To assess the genetic consequences of the demographic decline and to describe the spatial pattern of genetic diversity, 250 polecats sampled at seven localities from five European countries , Poland, Denmark (southern Denmark and northern Denmark), Spain, Belgium (eastern and western) and the Netherlands , were screened by means of nine microsatellite loci. Genetic diversity estimated by mean expected heterozygosity (HE) and allelic richness (AR) were moderately high within populations [range: 0.50 (northern Denmark) ,HE,0.64 (Poland) and 1.33,AR,7.80] as compared with other carnivores and mustelids. Bottleneck tests suggested that polecat populations in southern Denmark and Poland have declined recently and populations from northern Denmark and the Netherlands have expanded recently, whereas the remaining populations did not show any sign of demographic change. Recent demographic changes could suggest that some of the populations are still not in equilibrium, which could partly explain the relatively high genetic variability observed in polecat populations despite the drastic decline in population size observed in several European countries. A significant heterozygote deficiency [FIS=0.19; 0.01,95% confidence interval (CI),0.32] suggests substructuring within the total European sample. Partitioning of the genetic variation among sampling locations (FST=0.14; 0.06,95% CI,0.23) and pairwise FST between localities (range: 0.01,FST,0.37) without any correlation with the geographic distances between localities were found, suggesting a recent divergence and a restriction of gene flow between populations and the action of genetic drift. An assignment test showed that the Polish and the northern Danish populations were the most unique, whereas the other populations were partially admixed. Factorial component analysis tests indicate a subdivision of the total sample into two distinct groups: one including the samples from Poland and the two Danish localities and the second group comprising the remaining localities investigated. The observed pattern of genetic differentiation is suggested to be due to two main routes of recolonization after the last glacial period. To compare the results obtained with microsatellite data, the most variable region of the mitochondrial DNA (d-loop) was sequenced and different phylogenetic reconstructions and genetic diversity analyses based on nucleotide (,) and haplotype diversity (h) measures within populations were performed using a subsample of populations. The lack of well-defined geographical structure, as well as the reduced level of mitochondrial DNA variability (,: 0.00274±0.00038; h: 0.876±0.028) that was found, has been previously reported in several studies on different carnivores and supports the hypothesis of post-glacial recolonization from southern or eastern refugees of Europe as suggested by the microsatellite data. Implications for conservation strategies of the polecat at the European level are discussed. [source] Partitioning of metabolizable energy intake in sucking altricial and precocial rodent pupsJOURNAL OF ZOOLOGY, Issue 4 2006M. Kam Abstract We partitioned the metabolizable energy intake (MEI) into energy for maintenance (MEm) and for growth (MEg) in sucking precocial and altricial rodent pups. Each of the two components includes energy loss due to the heat increment of feeding. MEm of precocial pups expressed as average daily energy costs or as a proportion of MEI was greater than in altricial pups of similar size and, therefore, less energy was available for growth. Consequently, the overall energy cost (via total MEI) per unit postnatal growth of precocial pups was greater than for altricial pups of similar size. We used the proportion of calculated MEm to that predicted by body mass as an index of precociality in rodent pups. The proportion of MEg to MEI in precocial pups was lower than in altricial pups and was inversely related to the index of precociality. [source] Influence of Solute Charge and Hydrophobicity on Partitioning and Diffusion in a Genetically Engineered Silk-Elastin-Like Protein Polymer HydrogelMACROMOLECULAR BIOSCIENCE, Issue 10 2010Adam A. Dinerman Abstract The influence of solute hydrophobicity and charge on partitioning and diffusion in physically crosslinked networks of a genetically engineered SELP polymer was investigated. A series of fluorescent dyes were used to assess the impact of solute charge and hydrophobicity on release behavior. The mechanism of solute release from the SELP hydrogel appeared to vary as a function of dye hydrophobicity. The extent of FITC attachment to amine-terminated G4 dendrimers influenced SELP hydrogel partitioning more than dendrimer diffusion properties. Results suggest the possibility of controlling solute release from SELP hydrogels by modifying the hydrophobicity and surface charge of drugs and drug/polymer conjugates as well as the possibility of "designing-in" solute-specific interactions. [source] Designing herbicide formulation characteristics to maximize efficacy and minimize rice injury in paddy environmentsPEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 6 2001Steven A Cryer Abstract Mathematical descriptors, coupled with experimental observations, are used to quantify differential uptake of an experimental herbicide in Japonica and Indica rice (Oryza sativa, non-target) and barnyardgrass (Echinochloa crus-galli, target). Partitioning, degradation, plant uptake and metabolism are described using mass-balance conservation equations in the form of kinetic approximations. Estimated environmental concentrations, governed by the pesticide formulation, are described using superimposed analytical solutions for the one-dimensional diffusion equation in spherical coordinates and by a finite difference representation of the two-dimensional diffusion equation in Cartesian coordinates. Formulation attributes from granules include active ingredient release rates, particle sizes, pesticide loading, and granule spacing. The diffusion model for pesticide transport is coupled with the compartment model to follow the fate and transport of a pesticide from its initial application location to various environmental matrices of interest. Formulation effects, partitioning and degradation in the various environmental matrices, differential plant uptake and metabolism, and dose-response information for plants are accounted for. This novel model provides a mechanism for selecting formulation delivery systems that optimize specific attributes (such as weed control or the therapeutic index) for risk-assessment procedures. In this report we describe how this methodology was used to explore the factors affecting herbicide efficacy and to define an optimal release rate for a granule formulation. © 2001 Society of Chemical Industry [source] Effects of Drought on the Competitive Interference of an Early Successional Species (Rubus fruticosus) on Fagus sylvatica L. Seedlings: 15N Uptake and Partitioning, Responses of Amino Acids and other N CompoundsPLANT BIOLOGY, Issue 3 2002M. N. Fotelli Abstract: We assessed the role of water availability as a factor regulating the ability of beech seedlings to cope with competitive interference for nitrogen resources by an early successional species (Rubus fruticosus). A glasshouse experiment was performed with two levels of interference (beech with and without R. fruticosus) and three levels of irrigation (high, intermediate, none). 15N uptake and partitioning of both species, and composition of N pools in leaves, roots and phloem of beech, were determined. Under all irrigation regimes, 15N uptake by beech seedlings decreased when grown together with R. fruticosus. R. fruticosus had higher 15N uptake rates than beech, under all water supply levels. When irrigation was reduced, a substantial decrease in 15N uptake of beech seedlings and a concurrent increase in 15N uptake by R. fruticosus were observed. Interference by R. fruticosus and low irrigation also affected the 15N partitioning in beech seedlings and resulted in reduced allocation of 15N to the roots. The combination of competitive interference and lack of irrigation led to an increase in soluble non-protein N in roots and leaves of beech, due to protein degradation. This response was attributed to an increase in levels of amino acids serving as osmoprotectants under these conditions. The concentration of proline in leaves of beech was negatively correlated to shoot water potential. A competition-induced reduction of total N in leaves of beech under high and intermediate irrigation was found. These results illustrate (1) the advantage of R. fruticosus in terms of N uptake when compared to young beech, particularly under inadequate water supply, and (2) the changes in N composition of beech seedlings in order to cope with reduced soil water and interference by R. fruticosus. [source] The interplay between experiment and theory in charge-density analysisACTA CRYSTALLOGRAPHICA SECTION A, Issue 5 2004Philip Coppens The comparison of theory and experiment remains a cornerstone of scientific inquiry. Various levels of such comparison applicable to charge-density analysis are discussed, including static and dynamic electron densities, topological properties, d -orbital occupancies and electrostatic moments. The advantages and drawbacks of the pseudoatom multipole are discussed, as are the experimentally constrained wavefunctions introduced by Jayatilaka and co-workers, which combine energy minimization with the requirement to provide a reasonable fit to the X-ray structure factors. The transferability of atomic densities can be exploited through construction of a pseudoatom databank, which may be based on analysis of ab initio molecular electron densities, and can be used to evaluate a host of physical properties. Partitioning of theoretical energies with the Morokuma,Ziegler energy decomposition scheme allows direct comparison with electrostatic interaction energies obtained from electron densities represented by the pseudoatom formalism. Compared with the Buckingham expression for the interaction between non-overlapping densities, the agreement with theory is much improved when a newly developed hybrid EP/MM (exact potential/multipole model) method is employed. [source] Interfirm Innovation under Uncertainty: Empirical Evidence for Strategic Knowledge Partitioning,THE JOURNAL OF PRODUCT INNOVATION MANAGEMENT, Issue 5 2008Jaegul Lee This paper analyzes how uncertainty and life-cycle effects condition the knowledge boundary between assemblers and suppliers in interfirm product development. Patents associated with automotive emission control technologies for both assemblers and suppliers are categorized as architectural or component innovations, and technology-forcing regulations imposed by the government on the auto industry from 1970 to 1998 are used to define periods of high and low uncertainty. Results confirm that suppliers dominate component innovation whereas assemblers lead on architectural innovation. More importantly, when facing uncertainty firms adjust their knowledge boundary by increasing the knowledge overlap with their supply-chain collaborators. Suppliers clearly expand their knowledge base relatively more into architectural knowledge during such periods. But assemblers' greater emphasis on component innovation in periods of greater uncertainty is only true as a relative deviation from an overall trend toward increasing component innovation over time. This trend results from an observed life-cycle effect, whereby architectural innovation dominates before the emergence of a dominant design, with component innovation taking the lead afterward. Thus, for assemblers life-cycle effects may dominate over task uncertainty in determining relative effort in component versus architectural innovation. This work extends research on strategic interfirm knowledge partitioning as well as on the information-processing view of product development. First, it provides a large-scale empirical justification for the claim that firms' knowledge boundaries need to extend beyond their task boundaries. Further, it implies that overlaps in knowledge domains between an assembler and suppliers are particularly important for projects involving new technologies. Second, it offers a dynamic view of knowledge partitioning, showing how architectural knowledge prevails in the early phase of the product life cycle whereas component knowledge dominates the later stages. Yet the importance of life-cycle effects versus task uncertainty in conditioning knowledge boundaries is different for assemblers and suppliers, with the former dominating for assemblers and the latter more influential for suppliers. Finally, it supports the idea that architectural and component knowledge are critical elements in the alignment of cognitive frameworks between assemblers and suppliers and thus are key for information-exchange effectiveness and resolution of task uncertainties in interfirm innovation. [source] Multistep Phase-Switch Synthesis by Using Liquid,Liquid Partitioning of Boronic Acids: Productive Tags with an Expanded Repertoire of Compatible Reactions,ANGEWANDTE CHEMIE, Issue 16 2010Sam Mothana Eine Phasentransfersynthese mit der Boronsäuregruppe als Phasenmarker wurde entwickelt. Der Marker koordiniert an Sorbit und erleichtert bei hohem pH-Wert den Stofftransfer von einem organischen Lösungsmittel in die Wasserphase. Die Methode ermöglicht die gezielte Produktsynthese und macht die Aufreinigung durch Kieselgelchromatographie überflüssig. [source] Partitioning of temporal activity among desert lizards in relation to prey availability and temperatureAUSTRAL ECOLOGY, Issue 1 2010CHRISTOPHER E. GORDON Abstract Partitioning of activity time within ecological communities potentially reduces interspecific competition and increases the number of species that can coexist. We investigated temporal activity in a highly diverse lizard assemblage in the Simpson Desert, central Australia, to determine the degree of partitioning that occurs. Three periods were defined, daytime (sunrise to sunset), early night (sunset to midnight) and late night (midnight to sunrise), and live captures of lizards were tallied for each period during two sampling months (September and November 2007). We also quantified the activity times of potential invertebrate prey and measured ambient temperatures during the different time periods to investigate any associations between these factors and lizard activity. Some 77% of captures of 13 lizard species were made by day, with Ctenotus pantherinus, Egernia inornata (Scincidae) and Nephrurus levis (Gekkonidae) the only species showing extended nocturnal activity. Activity of both species of skink was recorded at temperatures 4°C lower than those for agamid and varanid lizards early in the night, and at temperatures as low as 18,20°C. Surface-active invertebrates differed in composition between time periods and were less abundant during the late night period in the drier of the two sample months (September), but were distributed equally over time in the other month. Termites were active in subterranean galleries at night in September and mostly by day in November, but available at all times on surface/subsurface baits. We conclude that activity is distributed unevenly within this lizard assemblage, with partitioning facilitated by the ready availability of invertebrate prey and by lizards having relatively broad temperature tolerances that, in some cases, permit opportunistic exploitation of resources beyond usual times of activity. [source] Characteristics of protein partitioning in an aqueous micellar-gel systemBIOTECHNOLOGY & BIOENGINEERING, Issue 2 2006L.J.P. van den Broeke Abstract Partitioning of proteins has been studied experimentally in a system combining a gel-bead phase and a nonionic micellar phase. The micellar phase consists of cylindrically shaped micelles, which are completely excluded from the gel-bead phase. Partitioning of single-component protein solutions (myoglobin, ovalbumin, and BSA) is determined by excluded-volume interactions in the micellar phase, and as a result the proteins prefer the gel-bead phase to the micellar phase. The protein concentration inside the gel beads increases with an increase in volume fraction of the micelles and increases with an increase in the size of the proteins. The protein partition coefficients obtained for a binary mixture of myoglobin and bovine serum albumin (BSA) show the same protein concentration dependence as the single-component protein partition coefficients. © 2005 Wiley Periodicals, Inc. [source] Partitioning and Characterization of Tyrosine-Tagged Green Fluorescent Proteins in Aqueous Two-Phase SystemsBIOTECHNOLOGY PROGRESS, Issue 3 2004Sara Fexby The green fluorescent protein GFPuv has been genetically engineered to investigate the influence of N-terminal tyrosine extensions in aqueous two-phase systems. Fusions in the N-terminus affected the protein expression, and tags containing three tyrosines and prolines influenced the expression favorably. This effect is probably due to changes in mRNA stability, because the amounts of corresponding mRNAs correlated with the amounts of GFPuv proteins. The partitioning was investigated in two different aqueous two-phase systems, a two-polymer system composed of EO30PO70/dextran and a PEG/salt system with potassium phosphate. Partitioning in the PEG/salt system generally was more favorable than in the EO30PO70/dextran system. Tags with three tyrosines resulted in higher partitioning toward the EO30PO70- and PEG-rich phases, respectively. The effect of adding proline residues to the tag was also investigated, and the partitioning effect of the tag was enhanced when prolines were included in the tags with three tyrosines. The best tyrosine tag, Y3P2, increased the partition coefficient 5 times in the PEG/salt system. Thermoseparation of the EO30PO70 phase allowed recovery of 83% Y3P2-GFPuv protein in a water phase. [source] Macroaffinity Ligand-Facilitated Three-Phase Partitioning (MLFTPP) of ,-Amylases Using a Modified AlginateBIOTECHNOLOGY PROGRESS, Issue 2 2003Kalyani Mondal The crude extracts of ,-amylases when mixed with alginate, tert -butyl alcohol, and ammonium sulfate resulted in an interfacial precipitate containing polymer-bound amylase. The precipitate was dissolved in 1 M maltose to recover ,-amylase activity. The recovery of ,-amylases were 74%, 77%, and 92% in the case of Bacillus amyloliquefaciens, wheat germ, and porcine pancreas, respectively. All purified preparations showed a single band on SDS-PAGE. [source] Resource Partitioning in Sympatric Cynopterus bats in Lowland Tropical Rain Forest, ThailandBIOTROPICA, Issue 2 2007Sara Bumrungsri ABSTRACT Diet and habitat use of the closely related and size-overlapping sympatric Cynopterus brachyotis and C. sphinx were established in lowland dry evergreen forest, Thailand, between March 1998 and March 2000. Feces from netted bats were analyzed, and the recapture rate determined. Although both species share a set of food plants, and fruits from early successional forest contribute about half of their diet, C. brachyotis, the smaller of the two species, ate a significantly greater proportion of fruits from early successional forest than C. sphinx. The latter ate a significantly greater proportion of fruit species in larger size classes. More C. brachyotis were captured in early successional forest in almost every month, while C. sphinx is more common in old-growth forest. However, the capture rate of C. sphinx increased in early successional forest in the mid-dry season when its preferred fruits become available. The recapture rate of C. brachyotis in early successional forest was significantly higher than that of C. sphinx, and the reverse situation was observed in old-growth forest. Male C. sphinx had a significantly higher recapture rate in early successional forest than females. Fruit size and habitat use are the major determinants of resource partitioning between these size-overlapping congeners. [source] Measuring Model Flexibility With Parameter Space Partitioning: An Introduction and Application ExampleCOGNITIVE SCIENCE - A MULTIDISCIPLINARY JOURNAL, Issue 8 2008Mark A. Pitt Abstract A primary criterion on which models of cognition are evaluated is their ability to fit empirical data. To understand the reason why a model yields a good or poor fit, it is necessary to determine the data-fitting potential (i.e., flexibility) of the model. In the first part of this article, methods for comparing models and studying their flexibility are reviewed, with a focus on parameter space partitioning (PSP), a general-purpose method for analyzing and comparing all classes of cognitive models. PSP is then demonstrated in the second part of the article in which two connectionist models of speech perception (TRACE and ARTphone) are compared to learn how design differences affect model flexibility. [source] BqR-Tree: A Data Structure for Flights and Walkthroughs in Urban Scenes with Mobile ElementsCOMPUTER GRAPHICS FORUM, Issue 6 2010J.L. Pina I.3.6 [Computer Graphics]: Graphics data structures and data types Abstract BqR-Tree, the data structure presented in this paper is an improved R-Tree data structure based on a quadtree spatial partitioning which improves the rendering speed of the usual R-trees when view-culling is implemented, especially in urban scenes. The city is split by means of a spatial quadtree partition and the block is adopted as the basic urban unit. One advantage of blocks is that they can be easily identified in any urban environment, regardless of the origins and structure of the input data. The aim of the structure is to accelerate the visualization of complex scenes containing not only static but dynamic elements. The usefulness of the structure has been tested with low structured data, which makes its application appropriate to almost all city data. The results of the tests show that when using the BqR-Tree structure to perform walkthroughs and flights, rendering times vastly improve in comparison to the data structures which have yielded best results to date, with average improvements of around 30%. [source] | ||||||||||||||||||||||||||||||||||||||||||||||||||||