Half-Saturation Constants in Functional Responses

Our aim is to provide an overview of half-saturation constants reported in literature and to explore their consistency with body size. In many ecological models, intake of nutrients by plants and consumption of food by animals is considered to be a hyperbolic function of the nutrient concentration and the food density, respectively. However, data on the concentration (or density) at which half of the maximum intake rate is reached are scarce, limiting the applicability of the computational models. The meta-analysis was conducted on literature published worldwide. Most studies focused on algae and invertebrates, whereas some included fish, birds and mammals. The half-saturation constants obtained were linked to body size using ordinary regression analysis. The observed trends were compared to those noted in reviews on other density parameters. Half-saturation constants for different clades range within one or two orders of magnitude. Although these constants are inherently variable, exploring allometric relationships across different taxa helps to improve consistent parameterization of ecological models.Comment: 6 pages, 4 figures, 1 tabl

Universality of Univariate Mixed Fractions in Divisive Meadows

Univariate fractions can be transformed to mixed fractions in the equational theory of meadows of characteristic zero.Comment: 12 page

Hedonic Regressions and the Decomposition of a House Price index into Land and Structure Components

The paper uses hedonic regression techniques in order to decompose the price of a house into land and structure components using readily available real estate sales data for a Dutch city. In order to get sensible results, it was useful to use a nonlinear regression model using data that covered multiple time periods. It also proved to be necessary to impose some restrictions on the price of structures. The resulting builder’s hedonic regression model was compared with the results for traditional logarithmic hedonic regression models.House price indexes, land and structure components, time dummy hedonic regressions, Fisher ideal indexes.

The Decomposition of a House Price index into Land and Structures Components: A Hedonic Regression Approach

The paper uses hedonic regression techniques in order to decompose the price of a house into land and structure components using readily available real estate sales data for a Dutch city. In order to get sensible results, it proved necessary to use a nonlinear regression model using data that covered multiple time periods. It also proved to be necessary to impose some monotonicity restrictions on the price of land and structures. The results of the additive model were compared with the results of a traditional logarithmic hedonic regression model.Property price indexes, hedonic regressions, repeat sales method, rolling year indexes, Fisher ideal indexes.

Discriminating Lambda-Terms Using Clocked Boehm Trees

As observed by Intrigila, there are hardly techniques available in the lambda-calculus to prove that two lambda-terms are not beta-convertible. Techniques employing the usual Boehm Trees are inadequate when we deal with terms having the same Boehm Tree (BT). This is the case in particular for fixed point combinators, as they all have the same BT. Another interesting equation, whose consideration was suggested by Scott, is BY = BYS, an equation valid in the classical model P-omega of lambda-calculus, and hence valid with respect to BT-equality but nevertheless the terms are beta-inconvertible. To prove such beta-inconvertibilities, we employ `clocked' BT's, with annotations that convey information of the tempo in which the data in the BT are produced. Boehm Trees are thus enriched with an intrinsic clock behaviour, leading to a refined discrimination method for lambda-terms. The corresponding equality is strictly intermediate between beta-convertibility and Boehm Tree equality, the equality in the model P-omega. An analogous approach pertains to Levy-Longo and Berarducci Trees. Our refined Boehm Trees find in particular an application in beta-discriminating fixed point combinators (fpc's). It turns out that Scott's equation BY = BYS is the key to unlocking a plethora of fpc's, generated by a variety of production schemes of which the simplest was found by Boehm, stating that new fpc's are obtained by postfixing the term SI, also known as Smullyan's Owl. We prove that all these newly generated fpc's are indeed new, by considering their clocked BT's. Even so, not all pairs of new fpc's can be discriminated this way. For that purpose we increase the discrimination power by a precision of the clock notion that we call `atomic clock'.Comment: arXiv admin note: substantial text overlap with arXiv:1002.257