18,324 research outputs found
Theoretical and experimental studies of the nature and characteristics of space-related plasma resonance phenomena Final report, 1 Jul. 1969 - 30 Jun. 1970
Space plasma experiments involving Alouette resonances and diagnostic techniques applied to electron density and temperature and local magnetic field strength measuremen
Linking individual behaviour to community scale patterns in fungi
The fungi comprise a separate kingdom of life and epitomise the indeterminate growth form. Very little is known about the factors that influence the nature of fungal diversity and the link between individual behaviour and the structure and function of fungal communities is particularly poorly understood. Here, we present a theoretical framework that is capable of elucidating this link. An individual-based model for fungal community dynamics is introduced that has been developed from a physiologically based model for the fungal phenotype. The model is used to explore the role of individual interactions, the production of an external inhibitor field and the quality of the external environment on the structure and diversity of the resulting community. We show that traits relating to growth rate, autophagic behaviour and the production of inhibitors are key in influencing the success of a particular genotype in a community. The species richness increases with the amount of available resource. This is the first model of fungal community dynamics that introduces the concept of a biomass-based abundance distribution function that can be described by the log-normal form which typically corresponds to communities in equilibrium. The species abundance curve was stable to changes in the relative location of inocula, although the ranked abundance of the individuals was not. We present the first attempt to identify the traits that affect the form of that curve. Future studies should examine the role of environmental heterogeneity and spore dispersal
Non-demolition measurements of observables with general spectra
It has recently been established that, in a non-demolition measurement of an
observable with a finite point spectrum, the density matrix of
the system approaches an eigenstate of , i.e., it "purifies" over
the spectrum of . We extend this result to observables with
general spectra. It is shown that the spectral density of the state of the
system converges to a delta function exponentially fast, in an appropriate
sense. Furthermore, for observables with absolutely continuous spectra, we show
that the spectral density approaches a Gaussian distribution over the spectrum
of . Our methods highlight the connection between the theory of
non-demolition measurements and classical estimation theory.Comment: 22 page
Dynamic Analysis of Soil Fertility Improvement: A Bioeconomic Model for Senegal
Land Economics/Use, Downloads July 2008 - June 2009: 8,
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