1,605 research outputs found
Supply-driven evolution: mutation bias and trait-fitness distributions can drive macro-evolutionary dynamics
Many well-documented macro-evolutionary phenomena still challenge current evolutionary theory. Examples include long-term evolutionary trends, major transitions in evolution, conservation of certain biological features such as hox genes, and the episodic creation of new taxa. Here, we present a framework that may explain these phenomena. We do so by introducing a probabilistic relationship between trait value and reproductive fitness. This integration allows mutation bias to become a robust driver of long-term evolutionary trends against environmental bias, in a way that is consistent with all current evolutionary theories. In cases where mutation bias is strong, such as when detrimental mutations are more common than beneficial mutations, a regime called “supply-driven” evolution can arise. This regime can explain the irreversible persistence of higher structural hierarchies, which happens in the major transitions in evolution. We further generalize this result in the long-term dynamics of phenotype spaces. We show how mutations that open new phenotype spaces can become frozen in time. At the same time, new possibilities may be observed as a burst in the creation of new taxa
PERSYST, a model for ex ante assessment of cropping systems performances. Adaptation to organic farming in the Ile-de-France region
PERSYST is a web software for ex ante assessment of crop yield that takes explicitely into account the cropping system (i.e. crop rotation and crop management) perspective. Environmental and economic indicators are calculated at crop rotation scale to complete the previous yield assessment. In 2012, a research program enabled the model adaptation to organic systems, taking into account weed management and organic inputs supply. This program also allowed to parameterize the web software in the Ile-de-France region for 8 soil types and 18crops. Parameterization has been validated for the most common situations. Validation remains to be done for less common ones. When completed, validation will make it possible to test the software in promising situations of use, such as supporting organic farmers analyzing their current cropping systems, or supporting farmers thinking about converting their farms to organic farming
Experimental demonstration of Aharonov-Casher interference in a Josephson junction circuit
A neutral quantum particle with magnetic moment encircling a static electric
charge acquires a quantum mechanical phase (Aharonov-Casher effect). In
superconducting electronics the neutral particle becomes a fluxon that moves
around superconducting islands connected by Josephson junctions. The full
understanding of this effect in systems of many junctions is crucial for the
design of novel quantum circuits. Here we present measurements and quantitative
analysis of fluxon interference patterns in a six Josephson junction chain. In
this multi-junction circuit the fluxon can encircle any combination of charges
on five superconducting islands, resulting in a complex pattern. We compare the
experimental results with predictions of a simplified model that treats fluxons
as independent excitations and with the results of the full diagonalization of
the quantum problem. Our results demonstrate the accuracy of the fluxon
interference description and the quantum coherence of these arrays
Domino D3.1 - Architecture definition
This deliverable presents the concept of operation of Domino. It includes a description of the systems, subsystems and processes that will be taken into account in the model, as well as the general scope of the model. For each of the mechanisms suggested to be modelled in the project, the deliverable provides a set of possible operational concepts and uptake/scope to be deployed
Phase-charge duality in Josephson junction circuits: Role of inertia and effect of microwave irradiation
We investigate the physics of coherent quantum phase slips in two distinct
circuits containing small Josephson junctions: (i) a single junction embedded
in an inductive environment and (ii) a long chain of junctions. Starting from
the standard Josephson Hamiltonian, the single junction circuit can be analyzed
using quasi-classical methods; we formulate the conditions under which the
resulting quasi-charge dynamics is exactly dual to the usual phase dynamics
associated with Josephson tunneling. For the chain we use the fact that its
collective behavior can be characterized by one variable: the number of
quantum phase slips present on it. We conclude that the dynamics of the
conjugate quasi-charge is again exactly dual to the standard phase dynamics of
a single Josephson junction. In both cases we elucidate the role of the
inductance, essential to obtain exact duality. These conclusions have profound
consequences for the behavior of single junctions and chains under microwave
irradiation. Since both systems are governed by a model exactly dual to the
standard resistively and capacitively shunted junction model, we expect the
appearance of current-Shapiro steps. We numerically calculate the corresponding
current-voltage characteristics in a wide range of parameters. Our results are
of interest in view of a metrological current standard
Predictors of shared book reading at home with preschoolers: Are there differences between Roma and non-Roma low-income families?
Previous research highlights several benefits of shared book reading (SBR) for child development, but less studies exist about its predictors (Yarosz & Barnett, 2001). Literature on home SBR in Portugal is scarce (Araújo & Costa, 2015; Peixoto et al., 2008), and studies on its predictors in families at socioeconomic risk or Roma families in this context are, respectively, reduced (Gamelas et al., 2003) or inexistent. This study aimed to investigate the predictors of the frequency of SBR in two ethnically diverse groups of families. Specifically, we studied the associations between child and family (mother) characteristics, parental aspirations, and parental involvement in preschool events and frequency of home SBR. Two hundred and six caregivers of Portuguese Roma ( n = 101) and non-Roma ( n = 105) low-income preschoolers (109 boys; M age = 5, SD age = 0.94) living in the Metropolitan areas of Lisbon and Oporto, Portugal, completed a survey, in face-to-face meetings. A multiple regression model, using AMOS (v. 25), showed that mothers’ educational level, educational aspirations for their child, and involvement in informal (but not formal) events in preschool were positively associated with frequency of SBR. Ethnicity did not moderate these associations. The overall similar pattern results for Roma and non-Roma low income families is an important finding, suggesting that these families may experience similar challenges in engaging in SBR with their preschool children and, therefore, may benefit from interventions with similar features.info:eu-repo/semantics/acceptedVersio
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