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Modest Variations (modest + variation)
Selected AbstractsThermal acclimation of photosynthesis: a comparison of boreal and temperate tree species along a latitudinal transectPLANT CELL & ENVIRONMENT, Issue 6 2010DYLAN N. DILLAWAY ABSTRACT Common gardens were established along a ,900 km latitudinal transect to examine factors limiting geographical distributions of boreal and temperate tree species in eastern North America. Boreal representatives were trembling aspen (Populus tremuloides Michx.) and paper birch (Betula papyrifera Marsh.), while temperate species were eastern cottonwood (Populus deltoides Bartr ex. Marsh var. deltoides) and sweetgum (Liquidambar styraciflua L.). The species were compared with respect to adjustments of leaf photosynthetic metabolism along the transect, with emphasis on temperature sensitivities of the maximum rate of ribulose bisphosphate (RuBP) carboxylation (EV) and regeneration (EJ). During leaf development, the average air temperature (Tgrowth) differed between the coolest and warmest gardens by 12 °C. Evidence of photosynthetic thermal acclimation (metabolic shifts compensating for differences in Tgrowth) was generally lacking in all species. Namely, neither EV nor EJ was positively related to Tgrowth. Correspondingly, the optimum temperature (Topt) of ambient photosynthesis (Asat) did not vary significantly with Tgrowth. Modest variation in Topt was explained by the combination of EV plus the slope and curvature of the parabolic temperature response of mesophyll conductance (gm). All in all, species differed little in photosynthetic responses to climate. Furthermore, the adaptive importance of photosynthetic thermal acclimation was overshadowed by gm's influence on Asat's temperature response. [source] Synthesis, Characterization, and Protonation Reactions of Ar-BIAN and Ar-BICAT Diimine Platinum Diphenyl ComplexesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 9 2010Jerome Parmene Abstract PtII diphenyl complexes (N,N)PtPh2 [N,N = diimines Ar,N=C(An)C=N,Ar with Ar = substituted aryl groups] have been prepared and characterized by 1H, 13C, and 195Pt NMR spectroscopy. The 195Pt NMR spectroscopic data establish the electronic influence exerted by substituents at the backbone of the diimine ligand system to the metal center. When compared to diimines Ar,N=CMe,CMe=N,Ar, the electron-withdrawing ability of the Ar-BIAN ligand and the electron-donating ability of the O,O-heterocyclic Ar-BICAT systems are demonstrated. Trends in 195Pt NMR chemical shifts suggest that electronic tuning of the metal center is better achieved through variations of the diimine backbone substituents rather than variation of the substituents at the N-Aryl groups. Protonation of (N,N)PtPh2 in dichloromethane/acetonitrile at ,78 °C furnishes the corresponding PtIV hydrides (N,N)PtPh2H(NCMe)+. The PtIV hydrides liberate benzene with the formation of (N,N)PtPh(NCMe)+ when the temperature is raised. A second protonation and rapid benzene elimination produces the dicationic PtII species (N,N)Pt(NCMe)22+ at approximately 50 °C. Protonation of (N,N)PtPh2 in the absence of acetonitrile results in the clean formation of (N,N)PtPh(,2 -C6H6)+ at temperatures that depend on the steric hindrance provided by the alkyl substituents at the diimine N-aryl groups. These findings support the notion that the metal is the kinetically preferred site of protonation. The results qualitatively agree with a recent mechanistic study of protonation-induced reactions of (diimine)PtPh2 complexes that bear simple methyl substituents at the diimine backbone. Several compounds have been crystallographically characterized. All complexes have the expected square planar environment at the metal. Modest variations in the metric parameters suggest that the Ar-BICAT system has a weaker trans influence than the Ar-BIAN and Ar-DAB systems. [source] Does Trade Credit Substitute Bank Credit?ECONOMIC NOTES, Issue 1 2005Evidence from Firm-level Data The paper examines micro data on Italian manufacturing firms' inventory behaviour to test the Meltzer (1960) hypothesis according to which firms substitute bank credit with trade credit (TC) during money tightening. We find that inventory investment of Italian manufacturing firms is constrained by their availability of TC and that this effect more than doubles during monetary restrictions. As for the magnitude of the substitution effect, however, we find that it is not sizeable. This is in line with the micro theories of TC and the evidence on actual firm practices, according to which credit terms display modest variations over time. [source] Water Framework Directive: ecological classification of Danish lakesJOURNAL OF APPLIED ECOLOGY, Issue 4 2005MARTIN SØNDERGAARD Summary 1The European Water Framework Directive (WFD) requires that all European waterbodies are assigned to one of five ecological classes, based primarily on biological indicators, and that minimum good ecological quality is obtained by 2015. However, the directive provides only general guidance regarding indicator definitions and determination of boundaries between classes. 2We used chemical and biological data from 709 Danish lakes to investigate whether and how lake types respond differently to eutrophication. In the absence of well-defined reference conditions, lakes were grouped according to alkalinity and water depth, and the responses to eutrophication were ordered along a total phosphorus (TP) gradient to test the applicability of pre-defined boundaries. 3As a preliminary classification we suggest a TP-based classification into high, good, moderate, bad and poor ecological quality using 0,25, 25,50, 50,100, 100,200 and > 200 µg P L,1 boundaries for shallow lakes, and 0,12·5, 12·5,25, 25,50, 50,100 and > 100 µg P L,1 boundaries for deep lakes. Within each TP category, median values are used to define preliminary boundaries for the biological indicators. 4Most indicators responded strongly to increasing TP, but there were only minor differences between low and high alkalinity lakes and modest variations between deep and shallow lakes. The variability of indicators within a given TP range was, however, high, and for most indicators there was a considerable overlap between adjacent TP categories. Cyanophyte biomass, submerged macrophyte coverage, fish numbers and chlorophyll a were among the ,best' indicators, but their ability to separate different TP classes varied with TP. 5When using multiple indicators the risk that one or more indicators will indicate different ecological classes is high because of a high variability of all indicators within a specific TP class, and the ,one out , all out' principle in relation to indicators does not seem feasible. Alternatively a certain compliance level or a ,mean value' of the indicators can be used to define ecological classes. A precise ecological quality ratio (EQR) using values between 0 and 1 can be calculated based on the extent to which the total number of indicators meets the boundary conditions, as demonstrated from three Danish lakes. 6Synthesis and applications. The analysis of Danish lakes has identified a number of useful indicators for lake quality and has suggested a method for calculating an ecological quality ratio. However, it also demonstrates that the implementation of the Water Framework Directive faces several challenges: gradual rather than stepwise changes for all indicators, large variability of indicators within lake classes, and problems using the one out , all out principle for lake classification. [source] An Organizational Echelon Analysis of the Determinants of Red Tape in Public OrganizationsPUBLIC ADMINISTRATION REVIEW, Issue 6 2008Richard M. Walker This article adopts an organizational echelon approach to the study of red tape in public organizations and argues that the nature and extent of red tape will vary at different levels of the organizational hierarchy. These propositions are tested with a multiple-informant survey using a lagged model. The empirical results across the three organizational echelons sampled indicate modest variations in the levels of perceived red tape and major variations in its determinants. Results from the more senior managers uphold prior research findings and hypotheses on the determinants of red tape. This is not surprising because earlier studies typically sampled senior executives. Yet the lower down the organizational hierarchy one travels, the more red tape officials perceive and the more multifaceted the findings on determinants become. The authors conclude that prior empirical work is likely to have underestimated the extent of red tape in public organizations, and oversimplified its determinants. The implications for theory and practice are discussed. [source] | |||||||||||||