13,165 research outputs found
A Statistical Model to Explain the Mendel--Fisher Controversy
In 1866 Gregor Mendel published a seminal paper containing the foundations of
modern genetics. In 1936 Ronald Fisher published a statistical analysis of
Mendel's data concluding that "the data of most, if not all, of the experiments
have been falsified so as to agree closely with Mendel's expectations." The
accusation gave rise to a controversy which has reached the present time. There
are reasonable grounds to assume that a certain unconscious bias was
systematically introduced in Mendel's experimentation. Based on this
assumption, a probability model that fits Mendel's data and does not offend
Fisher's analysis is given. This reconciliation model may well be the end of
the Mendel--Fisher controversy.Comment: Published in at http://dx.doi.org/10.1214/10-STS342 the Statistical
Science (http://www.imstat.org/sts/) by the Institute of Mathematical
Statistics (http://www.imstat.org
Optimal diffusion in ecological dynamics with Allee effect in a metapopulation
How diffusion impacts on ecological dynamics under the Allee effect and
spatial constraints? That is the question we address. Employing a microscopic
minimal model in a metapopulation (without imposing nonlinear birth and death
rates) we evince --- both numerically and analitically --- the emergence of an
optimal diffusion that maximises the survival probability. Even though, at
first such result seems counter-intuitive, it has empirical support from recent
experiments with engineered bacteria. Moreover, we show that this optimal
diffusion disappears for loose spatial constraints.Comment: 16 pages; 6 figure
Lorentz invariance for mixed neutrinos
We show that a proper field theoretical treatment of mixed (Dirac) neutrinos
leads to non-trivial dispersion relations for the flavor states. We analyze
such a situation in the framework of the non-linear relativity schemes recently
proposed by Magueijo and Smolin. We finally examine the experimental
implications of our theoretical proposals by considering the spectrum and the
end-point of beta decay in tritium.Comment: 8 pages, 4 figures. Presented at 2nd International Workshop DICE2004:
From Decoherence and Emergent Classicality to Emergent Quantum Mechanics,
Castello di Piombino, Tuscany, Italy, 1-4 Sep 200
Spinwave damping in the two-dimensional ferromagnetic XY model
The effect of damping of spinwaves in a two-dimensional classical
ferromagnetic XY model is considered. The damping rate is
calculated using the leading diagrams due to the quartic-order deviations from
the harmonic spin Hamiltonian. The resulting four-dimensional integrals are
evaluated by extending the techniques developed by Gilat and others for
spectral density types of integrals. is included into the memory
function formalism due to Reiter and Solander, and Menezes, to determine the
dynamic structure function . For the infinite sized system, the
memory function approach is found to give non-divergent spinwave peaks, and a
smooth nonzero background intensity (``plateau'' or distributed intensity) for
the whole range of frequencies below the spinwave peak. The background
amplitude relative to the spinwave peak rises with temperature, and eventually
becomes higher than the spinwave peak, where it appears as a central peak. For
finite-sized systems, there are multiple sequences of weak peaks on both sides
of the spinwave peaks whose number and positions depend on the system size and
wavevector in integer units of . These dynamical finite size effects
are explained in the memory function analysis as due to either spinwave
difference processes below the spinwave peak or sum processes above the
spinwave peak. These features are also found in classical Monte Carlo --
Spin-Dynamics simulations.Comment: 20 two-column page
New housing supply: what do we know and how can we learn more?
This paper reviews the literature on new housing supply. The paper starts by summarizing the results of the empirical studies on housing supply, showing that overall these studies reject the hypothesis of a perfectly elastic housing supply and reveal that housing supply is negatively related with financial costs, inflation and sales delay while showing inconclusive results with respect to the construction costs. In addition, we review a recent branch of the literature on housing supply that uses strategic interaction models. There is evidence that the housing market is not well described by the perfect competition model. Thus, a deeper understanding of housing supply can be achieved by considering theoretical models that take into account the strategic interaction between land developers and by using data where the unit of analysis is the land developer.Housing supply; price elasticity of supply, strategic interaction.
Global and regional source attribution of Shiga toxin-producing Escherichia coli infections using analysis of outbreak surveillance data
Shiga toxin-producing Escherichia coli (STEC) infections pose a substantial health and economic burden worldwide. To target interventions to prevent foodborne infections, it is important to determine the types of foods leading to illness. Our objective was to determine the food sources of STEC globally and for the six World Health Organization regions. We used data from STEC outbreaks that have occurred globally to estimate source attribution fractions. We categorised foods according to their ingredients and applied a probabilistic model that used information on implicated foods for source attribution. Data were received from 27 countries covering the period between 1998 and 2017 and three regions: the Americas (AMR), Europe (EUR) and Western-Pacific (WPR). Results showed that the top foods varied across regions. The most important sources in AMR were beef (40%; 95% Uncertainty Interval 39-41%) and produce (35%; 95% UI 34-36%). In EUR, the ranking was similar though with less marked differences between sources (beef 31%; 95% UI 28-34% and produce 30%; 95% UI 27-33%). In contrast, the most common source of STEC in WPR was produce (43%; 95% UI 36-46%), followed by dairy (27%; 95% UI 27-27%). Possible explanations for regional variability include differences in food consumption and preparation, frequency of STEC contamination, the potential of regionally predominant STEC strains to cause severe illness and differences in outbreak investigation and reporting. Despite data gaps, these results provide important information to inform the development of strategies for lowering the global burden of STEC infections
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