275 research outputs found
Thermodynamic parameters of bonds in glassy materials from viscosity-temperature relationships
Doremus's model of viscosity assumes that viscous flow in amorphous materials is mediated by broken bonds (configurons). The resulting equation contains four coefficients, which are directly related to the entropies and enthalpies of formation and motion of the configurons. Thus by fitting this viscosity equation to experimental viscosity data these enthalpy and entropy terms can be obtained. The non-linear nature of the equation obtained means that the fitting process is non-trivial. A genetic algorithm based approach has been developed to fit the equation to experimental viscosity data for a number of glassy materials, including SiO2, GeO2, B2O3, anorthite, diopside, xNa2Oâ(1-x)SiO2, xPbOâ(1-x)SiO2, soda-lime-silica glasses, salol, and α-phenyl-o-cresol. Excellent fits of the equation to the viscosity data were obtained over the entire temperature range. The fitting parameters were used to quantitatively determine the enthalpies and entropies of formation and motion of configurons in the analysed systems and the activation energies for flow at high and low temperatures as well as fragility ratios using the Doremus criterion for fragility. A direct anti-correlation between fragility ratio and configuron percolation threshold, which determines the glass transition temperature in the analysed materials, was found
A mosaic of induced and non-induced branches promotes variation in leaf traits, predation and insect herbivore assemblages in canopy trees
A remembrance of things (best) forgotten: The 'allegorical past' and the feminist imagination
This is the author's PDF version of an article published in Feminist theology© 2012. The definitive version is available at http://fth.sagepub.com/This article discusses the US TV series Mad Men, which is set in an advertising agency in 1960s New York, in relation to two key elements which seem significant for a consideration of the current state of feminism in church and academy, both of which centre around what it means to remember or (not) to forget
A mosaic of induced and non-induced branches promotes variation in leaf traits, predation and insect herbivore assemblages in canopy trees
Forest canopies are complex and highly diverse environments. Their diversity is
affected by pronounced gradients in abiotic and biotic conditions, including variation
in leaf chemistry. We hypothesised that branch-localised
defence induction
and vertical stratification in mature oaks constitute sources of chemical variation
that extend across trophic levels. To test this, we combined manipulation of plant
defences, predation monitoring, food-choice
trials with herbivores and sampling of
herbivore assemblages. Both induction and vertical stratification affected branch
chemistry, but the effect of induction was stronger. Induction increased predation
in the canopy and reduced herbivory in bioassays. The effects of increased predation
affected herbivore assemblages by decreasing their abundance, and indirectly,
their richness. In turn, we show that there are multiple factors contributing to
variation across canopies. Branch-localised
induction, variation between tree individuals
and predation may be the ones with particularly strong effects on diverse
assemblages of insects in temperate forests
Prediction of Emerging Technologies Based on Analysis of the U.S. Patent Citation Network
The network of patents connected by citations is an evolving graph, which
provides a representation of the innovation process. A patent citing another
implies that the cited patent reflects a piece of previously existing knowledge
that the citing patent builds upon. A methodology presented here (i) identifies
actual clusters of patents: i.e. technological branches, and (ii) gives
predictions about the temporal changes of the structure of the clusters. A
predictor, called the {citation vector}, is defined for characterizing
technological development to show how a patent cited by other patents belongs
to various industrial fields. The clustering technique adopted is able to
detect the new emerging recombinations, and predicts emerging new technology
clusters. The predictive ability of our new method is illustrated on the
example of USPTO subcategory 11, Agriculture, Food, Textiles. A cluster of
patents is determined based on citation data up to 1991, which shows
significant overlap of the class 442 formed at the beginning of 1997. These new
tools of predictive analytics could support policy decision making processes in
science and technology, and help formulate recommendations for action
Produtividade da soja cultivada sobre diferentes coberturas de solo, e diferentes adubaçÔes.
O objetivo deste trabalho foi avaliar a interferĂȘncia de diferentes coberturas de solo nas caracterĂsticas agronĂŽmicas e na produtividade da cultura da soja, e mensurar a necessidade da adubação quĂmica da cultura da soja quando esta for cultivada sob diferentes coberturas.FertBio 2010
Insect herbivory and herbivores of Ficus species along a rain forest elevational gradient in Papua New Guinea
Classic research on elevational gradients in plantâherbivore interactions holds that insect herbivore pressure is stronger under warmer climates of low elevations. However, recent work has questioned this paradigm, arguing that it oversimplifies the ecological complexity in which plantâinsect herbivore interactions are embedded. Knowledge of antagonistic networks of plants and herbivores is however crucial for understanding the mechanisms that govern ecosystem functioning. We examined herbivore damage and insect herbivores of eight species of genus Ficus (105 saplings) and plant constitutive defensive traits of two of these species, along a rain forest elevational gradient of Mt. Wilhelm (200â2,700 m a.s.l.), in tropical Papua New Guinea. We report overall herbivore damage 2.4% of leaf area, ranging from 0.03% in Ficus endochaete at 1,700 m a.s.l. to 6.1% in F. hombroniana at 700 m a.s.l. Herbivore damage and herbivore abundances varied significantly with elevation, as well as among the tree species, and between the wet and dry season. Communityâwide herbivore damage followed a humpâshaped pattern with the peak between 700 and 1,200 m a.s.l. and this pattern corresponded with abundance of herbivores. For two tree species surveyed in detail, we observed decreasing and humpâshaped patterns in herbivory, in general matching the trends found in the set of plant defenses measured here. Our results imply that vegetation growing at midâelevations of the elevational gradient, that is at the climatically most favorable elevations where water is abundant, and temperatures still relatively warm, suffers the maximum amount of herbivorous damage which changes seasonally, reflecting the water availability
Assessing the Long Term Impact of Phosphorus Fertilization on Phosphorus Loadings Using AnnAGNPS
High phosphorus (P) loss from agricultural fields has been an environmental concern because of potential water quality problems in streams and lakes. To better understand the process of P loss and evaluate the effects of different phosphorus fertilization rates on phosphorus losses, the USDA Annualized AGricultural Non-Point Source (AnnAGNPS) pollutant loading model was applied to the Ohio Upper Auglaize watershed, located in the southern portion of the Maumee River Basin. In this study, the AnnAGNPS model was calibrated using USGS monitored data; and then the effects of different phosphorus fertilization rates on phosphorus loadings were assessed. It was found that P loadings increase as fertilization rate increases, and long term higher P application would lead to much higher P loadings to the watershed outlet. The P loadings to the watershed outlet have a dramatic change after some time with higher P application rate. This dramatic change of P loading to the watershed outlet indicates that a âcritical pointâ may exist in the soil at which soil P loss to water changes dramatically. Simulations with different initial soil P contents showed that the higher the initial soil P content is, the less time it takes to reach the âcritical pointâ where P loadings to the watershed outlet increases dramatically. More research needs to be done to understand the processes involved in the transfer of P between the various stable, active and labile states in the soil to ensure that the model simulations are accurate. This finding may be useful in setting up future P application and management guidelines
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