708 research outputs found
Importance of space and competition in optimizing genetic control strategies.
Advances in the genetic modification of organisms are creating new opportunities for the control of insect pests of both agriculture and public health significance. The timing and sex specificity of lethal transgene activation can be tailored to enhance the pest population control efficiency of mass-released, genetically modified insects. We developed mathematical models to determine the optimal timing and sex specificity of lethal transgene activation for the control of different types of pest population. We show that optimal release strategies are not only sensitive to the parameters governing growth of the population but also can be drastically affected by the inclusion of insect stage structuring, competition, and space. We emphasize the necessity of including these additional levels of complexity in future theoretical assessments as they are likely important considerations for designing transgenic organisms as well as their application in genetic control
Ignorance can be evolutionarily beneficial
Information is increasingly being viewed as a resource used by organisms to
increase their fitness. Indeed, it has been formally shown that there is a
sensible way to assign a reproductive value to information and it is
non-negative. However, all of this work assumed that information collection is
cost-free. Here, we account for such a cost and provide conditions for when the
reproductive value of information will be negative. In these instances,
counter-intuitively, it is in the interest of the organism to remain ignorant.
We link our results to empirical studies where Bayesian behaviour appears to
break down in complex environments and provide an alternative explanation of
lowered arousal thresholds in the evolution of sleep.Comment: 5 pages, submitte
Parasite Replication and the Evolutionary Epidemiology of Parasite Virulence
Parasite virulence evolution is shaped by both within-host and population-level processes yet the link between these differing scales of infection is often neglected. Population structure and heterogeneity in both parasites and hosts will affect how hosts are exploited by pathogens and the intensity of infection. Here, it is shown how the degree of relatedness among parasites together with epidemiological parameters such as pathogen yield and longevity influence the evolution of virulence. Furthermore, the role of kin competition and the degree of cheating within highly structured parasite populations also influences parasite fitness and infectivity patterns. Understanding how the effects of within-host processes scale up to affect the epidemiology has importance for understanding host-pathogen interactions
Road User Charging ā Pricing Structures.
This project considers the extent to which the public could cope with complex price or tariff structures such as those that might be considered in the context of a national congestion pricing scheme. The key elements of the brief were:
ā¢ to review existing studies of road pricing schemes to assess what information and evidence already exists on the key issues;
ā¢ to identify what can be learned about pricing structures from other transport modes and other industries and in particular what issues and conclusions might be transferable;
ā¢ to improve the general understanding of the relationship between information and peopleās ability to respond; and
ā¢ to recommend what further research would be most valuable to fill evidence gaps and enable conclusions to be drawn about an effective structure
Autistic spectrum disorder in prehistory
Individuals with 'extraordinary' or 'different' minds have been suggested to be central to invention and the spread of new ideas in prehistory, shaping modern human behaviour and conferring an evolutionary advantage at population level. In this article the potential for neuropsychiatric conditions such as autistic spectrum disorders to provide this difference is explored, and the ability of the archaeological record to provide evidence of human behaviour is discussed. Specific reference is made to recent advances in the genetics of these conditions, which suggest that neuro psychiatric disorders represent a non-advantageous, pathological extreme of the human mind and are likely a by-product rather than a cause of human cognitive evolution
The Weiss conjecture on admissibility of observation operators for contraction semigroups
We prove the conjecture of George Weiss for contraction semigroups on Hilbert spaces, giving a characterization of infinite-time admissible observation functionals for a contraction semigroup, namely that such a functional C is infinite-time admissible if and only if there is an M > 0 such that parallel to IC(sI - A)(-1)parallel to less than or equal to M/root Re s for all s in the open right half-plane. Here A denotes the infinitesimal generator of the semigroup. The result provides a simultaneous generalization of several celebrated results from the theory of Hardy spaces involving Carleson measures and Hankel operators
Loschmidt echo and fidelity decay near an exceptional point
Non-Hermitian classical and open quantum systems near an exceptional point
(EP) are known to undergo strong deviations in their dynamical behavior under
small perturbations or slow cycling of parameters as compared to Hermitian
systems. Such a strong sensitivity is at the heart of many interesting
phenomena and applications, such as the asymmetric breakdown of the adiabatic
theorem, enhanced sensing, non-Hermitian dynamical quantum phase transitions
and photonic catastrophe. Like for Hermitian systems, the sensitivity to
perturbations on the dynamical evolution can be captured by Loschmidt echo and
fidelity after imperfect time reversal or quench dynamics. Here we disclose a
rather counterintuitive phenomenon in certain non-Hermitian systems near an EP,
namely the deceleration (rather than acceleration) of the fidelity decay and
improved Loschmidt echo as compared to their Hermitian counterparts, despite
large (non-perturbative) deformation of the energy spectrum introduced by the
perturbations. This behavior is illustrated by considering the fidelity decay
and Loschmidt echo for the single-particle hopping dynamics on a tight-binding
lattice under an imaginary gauge field.Comment: 11 pages, 6 figures, to appear in Annalen der Physi
What Do Management Earnings Forecasts Convey About the Macroeconomy?
We decompose quantitative management earnings forecasts into macroeconomic and firm-specific components to determine the extent to which voluntary disclosure provided by management has macroeconomic information content. We provide evidence that the forecasts of bellwether firms, which are defined as firms in which macroeconomic news explains the greatest amount of variation in the forecasts, provide timely information to the market about the macroeconomy when bundled with earnings announcements. Further, we show that bellwether firms provide timely information about both industry-specific events and broader economic events. Finally, we document that the macroeconomic news in individual forecasts is more pronounced for bad news and point forecasts
- ā¦