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Composition Changes (composition + change)
Kinds of Composition Changes Selected AbstractsLipid Changes of Freeze-Dried Spinach by Various Kinds of OxidationJOURNAL OF FOOD SCIENCE, Issue 8 2000J. Lee ABSTRACTM : Lipid changes in freeze-dried spinach by various oxidations were studied by using thin-layer chromatography and gas chromatography. There were no characteristic changes in lipids by the oxidation except decrease in esterified sterols in NL and phosphatidic acid and phosphatidylcholine in PL. Stability of the freeze-dried spinach lipid to the oxidation was higher when it was in the form of total lipid than when separated into NL, GL, or PL. Autoxidation and enzyme-catalyzed oxidation resulted in the highest fatty-acid composition change in NL. However, photooxidation showed the biggest change in PL and GL. C16 fatty acids tended to be more stable than C18 fatty acids to the oxidation. [source] A method for calculating effective bulk composition modification due to crystal fractionation in garnet-bearing schist: implications for isopleth thermobarometryJOURNAL OF METAMORPHIC GEOLOGY, Issue 6 2004T. P. Evans Abstract Quantitative P,T path determination in metamorphic rocks is commonly based on the variation in composition of growth-zoned garnet. However, some component of growth zoning in garnet is necessarily the result of an effective bulk composition change within the rock that has been generated by crystal fractionation of components into the core of garnet. Therefore, any quantitative calculation of the P,T regime of garnet growth should be completed using an accurate assessment of the composition of the chemical system from which garnet is growing. Consequently, a method for calculating the extent of crystal fractionation that provides a means of estimating the composition of the unfractionated rock at any stage during garnet growth is developed. The method presented here applies a Rayleigh fractionation model based on measured Mn content of garnet to generate composition v. modal proportion curves for garnet, and uses those curves to estimate the vectors of crystal fractionation. The technique is tested by calculating the precision of the equilibrium between three garnet compositional variables within the chemical system determined to be appropriate for each of a series of microprobe analyses from garnet. Application of the fractionation calculations in conjunction with the P,T estimates based on intersecting compositional isopleths provides a means of calculating P,T conditions of garnet growth that is based on individual point-analyses on a garnet grain. Such spatially precise and easily obtainable P,T data allow for detailed parallel studies of the microstructural, the P,T, and the chemical evolution of metamorphosed pelites. This method provides a means of studying the dynamics of orogenic systems at a resolution that was previously unattainable. [source] Ants accelerate succession from mountain grassland towards spruce forestJOURNAL OF VEGETATION SCIENCE, Issue 4 2009Blanka Vlasáková Abstract Question: What is the role of mound-building ants (Lasius flavus) in successional changes of a grassland ecosystem towards a spruce forest? Location: Slovenské Rudohorie Mountains, Slovakia; ca. 950 m a.s.l. near the Obrubovanec point (1020 m a.s.l.; 48°41,N, 19°39,E). Methods: Both chronosequence data along a successional gradient and temporal data from long-term permanent plots were collected on ants, spruce establishment, and vegetation structure, together with additional data on spruce growth. Results: There are more spruce seedlings on ant mounds (4.72 m,2) than in the surrounding vegetation (0.81 m,2). Spruce seedlings grow faster on these mounds compared to surrounding areas. The first colonization wave of seedlings was rapid and probably occurred when grazing prevailed over mowing. Ant colony presence, mound volume, and plant species composition change along the successional gradient. Mounds become bigger when partly shaded but shrink in closed forest, when ant colonies disappear. Shade-tolerant acidophylic species replace grassland plants both on the mounds and in surrounding areas. Conclusions: The massive occurrence of Lasius flavus anthills contributes to a runaway feedback process that accelerates succession towards forest. The effect of ants as ecosystem engineers is scale-dependent: although they stabilize the system at the scale of an individual mound, they may destabilize the whole grassland system over a longer time scale if combined with changes in mowing regime. [source] Nomenclature of magnetic, incommensurate, composition-changed morphotropic, polytype, transient-structural and quasicrystalline phases undergoing phase transitions.ACTA CRYSTALLOGRAPHICA SECTION A, Issue 5 2001A general nomenclature applicable to the phases that form in any sequence of transitions in the solid state has been recommended by an IUCr Working Group [Acta Cryst. (1998). A54, 1028,1033]. The six-field notation of the first Report, hereafter I, was applied to the case of structural phase transitions, i.e. to transformations resulting from temperature and/or pressure changes between two crystalline (strictly periodic) phases involving modifications to the atomic arrangement. Extensive examples that illustrate the recommendations were provided. This second Report considers, within the framework of a similar six-field notation, the more complex nomenclature of transitions involving magnetic phases, incommensurate phases and transitions that occur as a function of composition change. Extension of the nomenclature to the case of phases with less clearly established relevance to standard schemes of transition in equilibrium systems, namely polytype phases, radiation-induced and other transient phases, quasicrystalline phases and their transitions is recommended more tentatively. A uniform notation for the translational periodicity, propagation vector or wavevector for magnetic and/or incommensurate substances is specified. The notation adopted for incommensurate phases, relying partly on the existence of an average structure, is also consistent with that for commensurate phases in a sequence. The sixth field of the nomenclature is used to emphasize the special features of polytypes and transient phases. As in I, illustrative examples are provided for each category of phase sequence. [source] How do management and restoration needs of mountain grasslands depend on moisture regime?APPLIED VEGETATION SCIENCE, Issue 3 2009Experimental study from north-western Slovakia (Western Carpathians) Abstract Question: How does species composition change in traditionally managed meadows after mowing has ceased, and in abandoned meadows after re-introduction of mowing? Are there differences in the dynamics of dry and moderately wet meadows? Location: Zázrivá-Ple,ivá (19°11,N, 49°16,E), north-western Slovakia, western Carpathians. Methods: Pairs of experimental plots (mown and unmown) were established to replicate each combination of dry/wet and traditionally managed/abandoned meadows. Changes in species composition were studied over 5 years. The data on changes in species composition was analysed by constrained and unconstrained ordinations, and visualized using Principal Response Curves. Results: Species composition of newly abandoned wet grasslands was changing towards the corresponding long-abandoned plots even in the first year of abandonment. Similarly, newly established restoration mowing in abandoned dry grasslands rapidly shifted the stand species composition towards that of traditionally managed ones. Nevertheless, 4 year after reintroduction of mowing, the species composition of the restored plots was still far from the target composition. The effect of mowing in abandoned wet grasslands and abandonment in dry grasslands was much less pronounced and slower. Conclusions: Moisture regime is a very important factor determining the management needs of various grassland types. Wet grasslands are much more sensitive to abandonment, with a rapid degradation rate and limited possibilities for restoration, which can be extremely slow. Even in the dry grasslands, that quickly responded to restoration mowing, restoration is a long-term process. [source] Hurricane Disturbance Alters Secondary Forest Recovery in Puerto RicoBIOTROPICA, Issue 2 2010Dan F.B. Flynn ABSTRACT Land-use history and large-scale disturbances interact to shape secondary forest structure and composition. How introduced species respond to disturbances such as hurricanes in post-agriculture forest recovery is of particular interest. To examine the effects of hurricane disturbance and previous land use on forest dynamics and composition, we revisited 37 secondary forest stands in former cattle pastures across Puerto Rico representing a range of exposure to the winds of Hurricane Georges in 1998. Stands ranged from 21 to>80 yr since agricultural abandonment and were measured 9 yr posthurricane. Stem density decreased as stands aged, while basal area and species richness tended to increase. Hurricane disturbance exerted contrasting effects on stand structure, contingent on stand age. In older stands, the basal area of large trees fell, shifting to a stand structure characteristic of younger stands, while the basal area of large trees tended to rise in younger stands with increasing hurricane disturbance. These results demonstrate that large-scale natural disturbances can alter the successional trajectory of secondary forest stands recovering from human land use, but stand age, precipitation and soil series were better predictors of changes in stand structure across all study sites. Species composition changed substantially between census intervals, but neither age nor hurricane disturbance consistently predicted species composition change. However, exposure to hurricane winds tended to decrease the abundance of the introduced tree Spathodea campanulata, particularly in smaller size classes. In all sites the abundance of the introduced tree Syzygium jambos showed a declining trend, again most strongly in smaller size classes, suggesting natural thinning through succession. Abstract in Spanish is available at http://www.blackwell-synergy.com/loi/btp [source] Spatiotemporal changes of beetle communities across a tree diversity gradientDIVERSITY AND DISTRIBUTIONS, Issue 4 2009Stephanie Sobek Abstract Aim, Plant and arthropod diversity are often related, but data on the role of mature tree diversity on canopy insect communities are fragmentary. We compare species richness of canopy beetles across a tree diversity gradient ranging from mono-dominant beech to mixed stands within a deciduous forest, and analyse community composition changes across space and time. Location, Germany's largest exclusively deciduous forest, the Hainich National Park (Thuringia). Methods, We used flight interception traps to assess the beetle fauna of various tree species, and applied additive partitioning to examine spatiotemporal patterns of diversity. Results, Species richness of beetle communities increased across the tree diversity gradient from 99 to 181 species per forest stand. Intra- and interspecific spatial turnover among trees contributed more than temporal turnover among months to the total ,-beetle diversity of the sampled stands. However, due to parallel increases in the number of habitat generalists and the number of species in each feeding guild (herbivores, predators and fungivores), no proportional changes in community composition could be observed. If only beech trees were analysed across the gradient, patterns were similar but temporal (monthly) species turnover was higher compared to spatial turnover among trees and not related to tree diversity. Main conclusions, The changes in species richness and community composition across the gradient can be explained by habitat heterogeneity, which increased with the mix of tree species. We conclude that understanding temporal and spatial species turnover is the key to understanding biodiversity patterns. Mono-dominant beech stands are insufficient to conserve fully the regional species richness of the remaining semi-natural deciduous forest habitats in Central Europe, and analysing beech alone would have resulted in the misleading conclusion that temporal (monthly) turnover contributes more to beetle diversity than spatial turnover among different tree species or tree individuals. [source] On the measurement of growth with applications to the modelling and analysis of plant growthFUNCTIONAL ECOLOGY, Issue 2 2000Roderick M. L. Abstract 1.,In this paper, a theoretical framework for the analysis of growth is described. Growth is equated with change in volume (V) and the growth rate is given by the equation; dV/dt = (dm/dt)(1/,) , (d,/dt)(m/,2) where m is the mass and , the density. The volume is inclusive of internal air spaces. 2.,The second term of the growth equation (see above) can be ignored if density is constant over time. Data for humans (and presumably other large animals) show that while composition changes over time, the density is approximately constant at about that of water. In that case, the growth rate can be estimated from measures of the rate of change of mass. However, the density of plants is variable (c. 0·4,1·2 g cm,3) and measures of mass and density are necessary to analyse plant growth. 3.,To use the theory as the basis of plant growth models, it is necessary to develop simple methods for estimating the surface area of roots, stems and leaves assuming that the mass and volume are known. A literature review found that the surface area to volume ratios of leaves and roots generally increase with the mass concentration of water. Theoretical arguments are used to predict that in woody stems, the situation should be reversed such that the surface area to volume ratio increases with the mass concentration of dry matter. Those relationships should be very useful in the development of plant growth models. 4.,Measures of plant dry mass and estimates of the rate of change in dry mass are shown to be very difficult to interpret because of differences in the mass concentration of dry matter between individuals and over time. 5.,It is concluded that measures of mass and density will be necessary before plant growth analysis can achieve its full potential. A framework for extending the theory to include the forces necessary for growth to occur is described. [source] A model for pore-fluid-sensitive rock behavior using a weathering state parameterINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 16 2008R. J. Hickman Abstract Chalk and other porous rocks are known to behave differently when saturated with different pore fluids. The behavior of these rocks varies with different pore fluids and additional deformation occurs when the pore fluid composition changes. In this article, we review the evidence that behavior in porous rocks is pore-fluid-dependent, present a constitutive model for pore-fluid-dependent porous rocks, and present a compilation of previously published data to develop quantitative relationships between various pore fluids and mechanical behavior. The model proposed here is based on a state parameter approach for weathering and has similarities to models previously proposed for weathering-sensitive rocks in that the values for parameters that characterize material behavior vary as a function of weathering. Comparisons with published experimental data indicate that the model is capable of reproducing observed behavior of chalk under a variety of loading conditions and changes in pore fluid composition. Copyright © 2008 John Wiley & Sons, Ltd. [source] PARAFASCA: ASCA combined with PARAFAC for the analysis of metabolic fingerprinting dataJOURNAL OF CHEMOMETRICS, Issue 2 2008Jeroen J. Jansen Abstract Novel post-genomics experiments such as metabolomics provide datasets that are highly multivariate and often reflect an underlying experimental design, developed with a specific experimental question in mind. ANOVA-simultaneous component analysis (ASCA) can be used for the analysis of multivariate data obtained from an experimental design instead of the widely used principal component analysis (PCA). This increases the interpretability of the model in terms of the experimental question. Aside from the levels of individual factors, variation that can be described by the experimental design may also depend on levels of multiple (crossed) factors simultaneously, e.g. the interactions. ASCA describes each contribution with a PCA model, but a contribution depending on crossed factors may be described more parsimoniously by multiway models like parallel factor analysis (PARAFAC). The combination of PARAFAC and ASCA, named PARAFASCA, provides a view on the data that is both parsimonious and focused on the experimental question. The novel method is used to analyze a dataset in which the effect of two doses of hydrazine on the urinary chemical composition of rats is investigated by time-resolved metabolic fingerprinting with nuclear magnetic resonance (NMR) spectroscopy. This experiment has been conducted to monitor the dose-specific urine composition changes in time upon hydrazine administration. Comparison of the PCA, the ASCA and the PARAFASCA models shows that ASCA and PARAFASCA describe the data more dedicated to the experimental question than PCA, but that PARAFASCA is more parsimonious than ASCA, and separates the variation underlying different effects better. Copyright © 2008 John Wiley & Sons, Ltd. [source] Chemical Differences Are Observed in Children's Versus Adults' Latent Fingerprints as a Function of Time,JOURNAL OF FORENSIC SCIENCES, Issue 2 2010Kimone M. Antoine B.S. Abstract:, The identification of aged latent fingerprints is often difficult, especially for those of children. To understand this phenomenon, the chemical composition of children's versus adults' latent fingerprints was examined over time using Fourier transform infrared microscopy. Hierarchical cluster analysis revealed that children's and adults' prints were distinguishable for up to 4 weeks after deposition, based on differences in sebum composition. Specifically, adults had a higher lipid content than children, but both decreased over time, attributable to the volatility of free fatty acids. The aliphatic CH3, aliphatic CH2, and carbonyl ester compositions changed differently in adults versus children over time, consistent with higher cholesterol and cholesteryl esters in children's prints and wax esters and glycerides in adults' prints. Thus, fingerprint composition changes with time differently in children versus adults, making it a sensitive metric to estimate the age of an individual, especially when the age of the print is known. [source] Deformation-enhanced metamorphic reactions and the rheology of high-pressure shear zones, Western Gneiss Region, NorwayJOURNAL OF METAMORPHIC GEOLOGY, Issue 1 2006M. P. TERRY Abstract Microstructural and petrological analysis of samples with increasing strain in high-pressure (HP) shear zones from the Haram garnet corona gabbro give insights into the deformation mechanisms of minerals, rheological properties of the shear zone and the role of deformation in enhancing metamorphic reactions. Scanning electron microscopy with electron backscattering diffraction (SEM,EBSD), compositional mapping and petrographic analysis were used to evaluate the nature of deformation in both reactants and products associated with eclogitization. Plagioclase with a shape-preferred orientation that occurs in the interior part of layers in the mylonitic sample deformed by intracrystalline glide on the (0 0 1)[1 0 0] slip system. In omphacite, crystallographic preferred orientations indicate slip on (1 0 0)[0 0 1] and (1 1 0)[0 0 1] during deformation. Fine-grained garnet deformed by diffusion creep and grain-boundary sliding. Ilmenite deformed by dislocation glide on the basal and, at higher strains, prism planes in the a direction. Relationships among the minerals present and petrological analysis indicate that deformation and metamorphism in the shear zones began at 500,650 °C and 0.5,1.4 GPa and continued during prograde metamorphism to ultra-high-pressure (UHP) conditions. Both products and reactants show evidence of syn- and post-kinematic growth indicating that prograde reactions continued after strain was partitioned away. The restriction of post-kinematic growth to narrow regions at the interface of garnet and plagioclase and preservation of earlier syn-kinematic microstructures in older parts layers that were involved in reactions during deformation show that diffusion distances were significantly shortened when strain was partitioned away, demonstrating that deformation played an important role in enhancing metamorphic reactions. Two important consequences of deformation observed in these shear zones are: (i) the homogenization of chemical composition gradients occurred by mixing and grain-boundary migration and (ii) composition changes in zoned metamorphic garnet by lengthening diffusion distances. The application of experimental flow laws to the main phases present in nearly monomineralic layers yield upper limits for stresses of 100,150 MPa and lower limits for strain rates of 10,12 to 10,13 s,1 as deformation conditions for the shear zones in the Haram gabbro that were produced during subduction of the Baltica craton and resulted in the production of HP and UHP metamorphic rocks. [source] Modeling hydrogen spillover in dual-bed catalytic reactorsAICHE JOURNAL, Issue 4 2004John C. Weigle Abstract A semiquantitative model was developed to describe hydrogen spillover in dual-bed catalytic reactors. In previous studies it has been conclusively demonstrated that hydrogen can diffuse macroscopic distances and activate catalytic sites. The test reaction in those studies was the isomerization of 1-butene to 2-butene. The model is derived based on the fundamental principles of transport phenomena and reaction kinetics. Because many of the required values in the model are unknown, it cannot be solved quantitatively. Thus, a parametric analysis was conducted. The model successfully predicts trends observed experimentally. Specifically, the activity increases nonlinearly as the bed composition changes, the selectivity was low for all dual-bed reactors, and the selectivity was high for well-mixed catalyst beds. © 2004 American Institute of Chemical Engineers AIChE J, 50: 821,828, 2004 [source] Terpolymerization monitoring with ATR-FTIR spectroscopyJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 11 2001Hong Hua Abstract Butyl acrylate, methyl methacrylate, and vinyl acetate solution and emulsion terpolymerizations were conducted. Attenuated total relflection-Fourier transform infrared spectroscopy equipped with conduit and diamond-composite sensor technology was used to monitor solution terpolymerizations off-line and emulsion terpolymerizations in-line. Monomer conversion and terpolymer composition changes as a function of time were calculated by monitoring the peak height of characteristic absorbances of each monomer. Results obtained from the ReactIRÔ 1000 reaction-analysis system agreed well with those determined by traditional gravimetry and 1H NMR spectroscopy. For the solution terpolymerizations, improved models developed previously to incorporate solvent effects on solution polymerizations of butyl acrylate and vinyl acetate monomers were applied to predict monomer conversion, copolymer composition, and molecular weight averages. Comparisons between experimental data and model predictions are presented. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1860,1876, 2001 [source] Ageing of calcium silicate cements for endodontic use in simulated body fluids: a micro-Raman studyJOURNAL OF RAMAN SPECTROSCOPY, Issue 12 2009Paola Taddei Abstract To evaluate bioactivity properties, a calcium silicate experimental cement (wTC) and a phosphate-doped wTC cement (wTC-TCP) were aged for different times (1,180 days) at 37 °C in two simulated body fluids, i.e. Dulbecco's phosphate buffered saline (DPBS) and Hank's balanced salt solution (HBSS). The cements were analyzed by micro-Raman spectroscopy to investigate the presence of calcium phosphate deposits and the composition changes as a function of the storage time (hydration of anhydrite/gypsum and formation of ettringite; hydration of belite/alite and formation of hydrated silicates). After 1 day of ageing in DPBS, the two cements already showed a different behavior: only the surface of wTC-TCP cement showed the band at 965 cm,1, suggesting the formation of a detectably thick calcium phosphate deposit. The trend of the I965/I990 Raman intensity ratio indicated the formation of a meanly thicker apatite deposit on the wTC-TCP cement until 90 days. After 60 days of ageing in DPBS, the thickness of the apatite deposit on wTC and wTC-TCP was about 200 and 500 µm, respectively, whereas at 180 days, the two cements did not appear significantly different (thickness of about 900 µm). The bioactivity of both cements in HBSS was less pronounced than in DPBS, according to the lower phosphate concentration of HBSS; at the same time, higher amounts of calcite were found on the surface of both cements. The wTC-TCP cement showed a higher bioactivity in this medium also; after 180 days, the thickness of the apatite deposit on wTC and wTC-TCP was < 50 µm and about 100 µm, respectively. Copyright © 2009 John Wiley & Sons, Ltd. [source] Natural avalanche disturbance shapes plant diversity and species composition in subalpine forest beltJOURNAL OF VEGETATION SCIENCE, Issue 5 2007Christian Rixen Abstract Background: Disturbances by avalanches have created unique habitats for animals and plants in subalpine ecosystems worldwide, but at the same time avalanches can pose a major threat to humans. Thus, avalanches are suppressed by means of avalanche barriers to protect settlements and infrastructures in populated areas of the European Alps. As a consequence, the disturbance regime in avalanche tracks has fundamentally changed. Methods: In the present study we address ecological consequences of avalanche suppression on plant diversity. We analysed plant diversity and species composition in recent and old avalanche tracks with and without avalanche suppression and in undisturbed adjacent forests at high and low elevations. Results: The number of species was higher in both active and inactive avalanche tracks as compared to undisturbed subalpine forest. The species composition indicated a wider range of ecological niches in active than in inactive avalanche tracks. The vegetation from active tracks showed lower indicator values for temperature and nitrogen availability. The proportion of alpine species was lower in formerly active tracks. Conclusions: The conditions that exist in active avalanche tracks increase plant diversity in relation to undisturbed forest. In the few decades following avalanche suppression, species composition changes in tracks from which avalanches have been excluded. Continued suppression of avalanche disturbance may lead to a decline in plant and habitat diversity. Avalanche disturbance can exert an important influence on the biodiversity of subalpine forests and provide important habitats. Anthropogenic changes in the natural regime of avalanche disturbance are likely to contribute significantly to future landscape changes in subalpine forests. [source] The Nutrition Transition: An Overview of World Patterns of ChangeNUTRITION REVIEWS, Issue 2004Barry M. Popkin Ph.D. This paper examines the speed of change in diet, activity, and obesity in the developing world, and notes potential exacerbating biological relationships that contribute to differences in the rates of change. The focus is on lower- and middle-income countries of Asia, Africa, the Middle East, and Latin America. These dietary, physical activity, and body composition changes are occurring at great speed and at earlier stages of these countries' economic and social development. There are some unique issues that relate to body composition and potential genetic factors that are also explored, including potential differences in body mass index (BMI),disease relationships and added risks posed by high levels of poor fetal and infant growth patterns. In addition there is an important dynamic occurring,the shift in the burden of poor diets, inactivity and obesity from the rich to the poor. The developing world needs to give far greater emphasis to addressing the prevention of the adverse health consequences of this shift to the nutrition transition stage of the degenerative diseases [source] Growth patterns in children with sickle cell anemia during pubertyPEDIATRIC BLOOD & CANCER, Issue 4 2009Melissa Rhodes MD Abstract Background Previous studies of children with homozygous sickle cell anemia (SCA) show impaired growth and maturation. The correlation of this suboptimal growth with metabolic and hematological factors during puberty is poorly understood. Procedure We studied a group of pre-adolescent children with SCA (19 males, 14 females) and healthy controls (16 males, 15 females) matched for race, sex, body size, and pubertal development. Height, weight, body mass index (BMI), and body composition changes were longitudinally assessed over a 2-year period and compared between the groups and with Z scores based on US growth charts. These changes were correlated with hemoglobin (Hgb) concentration and with energy expenditure (EE) measured using indirect whole-room calorimetry. Results Children with SCA progressed through puberty slower than control children. While, after 2 years, pubertal males with SCA were shorter, their annual increases in weight were not different from controls. The mean fat free mass (FFM) increments were significantly less in males and females with SCA than in control children. In males with SCA, growth in height declined over time and was significantly slower than in matched controls (P,<,0.05). Conclusion Growth delays were present during puberty in children with SCA. Decreased growth velocity in children with SCA was independently associated with decreased Hgb concentration and increased total EE. Pediatr Blood Cancer 2009;53:635,641. © 2009 Wiley-Liss, Inc. [source] A Richer Understanding of Australia's Productivity Performance in the 1990s: Improved Estimates Based Upon Firm-Level Panel Data,THE ECONOMIC RECORD, Issue 265 2008ROBERT BREUNIG Australian industry is characterised by differences across firms, entry of new firms and exit of unsuccessful firms. These facts highlight the inappropriateness of measuring productivity using aggregate production functions based upon representative firms. In this study, we model heterogeneous firms which change over time. We model the interrelationship between productivity shocks, input choices and decisions to cease production. Firm-level data provides production function estimates for 25 two-digit Australian industries. A new aggregation method for industry-level data allows us to separate productivity changes from output composition changes. Our study sheds new light on the Australian productivity performance. [source] Rate of succession in restored wetlands and the role of site contextAPPLIED VEGETATION SCIENCE, Issue 3 2010Jeffrey W. Matthews Abstract Question: Are changes in plant species composition, functional group composition and rates of species turnover consistent among early successional wetlands, and what is the role of landscape context in determining the rate of succession? Location: Twenty-four restored wetlands in Illinois, USA. Methods: We use 4 years of vegetation sampling data from each site to describe successional trends and rates of species turnover in wetlands. We quantify: (1) the rate at which composition changes from early-successional to late-successional species and functional groups, as indicated by site movement in ordination space over time, and (2) the rate of change in the colonization and local extinction of individual species. We correlate the pace of succession to site area, isolation and surrounding land cover. Results: Some commonalities in successional trends were evident among sites. Annual species were replaced by clonal perennials, and colonization rates declined over time. However, differences among sites outweighed site age in determining species composition, and the pace of succession was influenced by a site's landscape setting. Rates of species turnover were higher in smaller wetlands. In addition, wetlands in agricultural landscapes underwent succession more rapidly, as indicated by a rapid increase in dominance by late-successional plants. Conclusions: Although the outcome of plant community succession in restored wetlands was somewhat predictable, species composition and the pace of succession varied among sites. The ability of restoration practitioners to accelerate succession through active manipulation may be contingent upon landscape context. [source] Measurement of total body composition changes of common carp by computer tomographyAQUACULTURE RESEARCH, Issue 12 2003Csaba Hancz Abstract The crude fat and protein content of the total body was estimated by X-ray computer tomography (CT) and determined by chemical analyses during a feeding experiment with sexually matured common carp. Between 21 and 35 serial scans were taken of altogether 41 fish and samples from the homogenized body were prepared for chemical analyses. Experimental fish with an average body weight of 1453 g originated from a commercial stock of mirror carp. Two feeding regimes (carp feed and carp feed+ad libitum maize) were applied for 57 days and followed by a fasting period of 27 days. Both feeding regimes significantly increased the crude fat content of the whole body that did not decrease during fasting in spite of high water temperature (22°C). No significant changes were observed in crude protein content. The variables used for producing the prediction equations were taken from the density values of the Hounsfield scale, on a range between ,90 and +160, by summing the frequencies within each interval of 10 values. Whole body fat content could be estimated with R2=0.89,0.91 accuracy with the principal component analysis using data of all (seven) body regions and only dorsal fin region respectively. Adequate linear regression model could not be calculated by the same procedure for crude protein. Three-dimensional ,volumetric' estimation of fat tissue was also carried out on the basis of fat index showing high correlation with measured fat content. The changes of body composition of individual fish can be followed by sequential CT scanning. [source] DEMOGRAPHIC DEMAND SYSTEMS WITH APPLICATION TO EQUIVALENCE SCALES ESTIMATION AND INEQUALITY ANALYSIS: THE AUSTRALIAN EVIDENCEAUSTRALIAN ECONOMIC PAPERS, Issue 3 2010PAUL BLACKLOW This paper proposes and applies an alternative demographic procedure for extending a demand system to allow for the effect of household size and composition changes, along with price changes, on expenditure allocation. The demographic procedure is applied to two recent demand functional forms to obtain their estimable demographic extensions. The estimation on pooled time series of Australian Household Expenditure Surveys yields sensible and robust estimates of the equivalence scale, and of its variation with relative prices. Further evidence on the usefulness of this procedure is provided by using it to evaluate the nature and magnitude of the inequality bias of relative price changes in Australia over a period from the late 1980s to the early part of the new millennium. [source] Origin and Accumulation of Natural Gases in the Upper Paleozoic Strata of the Ordos Basin in Central ChinaACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 1 2009Yangming ZHU Abstract: The natural gases in the Upper Paleozoic strata of the Ordos basin are characterized by relatively heavy C isotope of gaseous alkanes with ,13C1 and ,13C2 values ranging mainly from ,35, to ,30, and ,27, to ,22,, respectively, high ,13C excursions (round 10) between ethane and methane and predominant methane in hydrocarbon gases with most C1/(C1 -C5) ratios in excess of 0.95, suggesting an origin of coal-derived gas. The gases exhibit different carbon isotopic profiles for C1 -C4 alkanes with those of the natural gases found in the Lower Paleozoic of this basin, and believed to be originated from Carboniferous-Permian coal measures. The occurrence of regionally pervasive gas accumulation is distinct in the gently southward-dipping Shanbei slope of the central basin. It is noted that molecular and isotopic composition changes of the gases in various gas reservoirs are associated with the thermal maturities of gas source rocks. The abundances and ,13C values of methane generally decline northwards and from the basin center to its margins, and the effects of hydrocarbon migration on compositional modification seem insignificant. However, C isotopes of autogenetic calcites in the vertical and lateral section of reservoirs show a regular variation, and are as a whole depleted upwards and towards basin margins. Combination with gas maturity gradient, the analysis could be considered to be a useful tool for gas migration. [source] Partial growth hormone deficiency in adults; should we be looking for it?CLINICAL ENDOCRINOLOGY, Issue 4 2010Stephen M. Shalet Summary Quantitatively, GH secretion exists as a continuum in states ranging from good health through to hypopituitarism. Currently, GH replacement is considered only for adults designated as being severely GH deficient (GHD). In clinical practice the gold standard, on which the biochemical diagnosis of severe GHD is based, centres on the presence of two or more additional anterior pituitary hormone deficits. Cohorts of adults with partial GHD (Growth Hormone Insufficiency [GHI]) have been reported with adverse body composition changes, dyslipidaemia, insulin resistance, altered cardiac performance and increased carotid intima-media thickness. The diagnosis of GHI in an individual patient, however, is extremely difficult because such patients rarely exhibit additional anterior pituitary hormone deficits, and the levels of GH-dependent proteins, including IGF-I, are normal in the majority. Currently, GH replacement therapy should only be considered in a patient characterized as GHI by dynamic GH testing in whom there is a plausible cause for hypopituitarism and in whom the IGF-I level is pathologically low. [source] | |||||||||||||||||||||||||