1,721,196 research outputs found
A microscopic model of evolution of recombination
No full textWe study the evolution of recombination using a microscopic model developed within the frame of the theory of quantitative traits. Two components of fitness are considered: a static one that describes adaptation to environmental factors not related to the population itself, and a dynamic one that accounts for interactions between organisms, e.g. competition. We focus on the dynamics of colonization of an empty niche. As competition is a function of the population, selection pressure rapidly changes in time. The simulations show that both in the case of flat and steep static fitness landscapes, recombination provides a high velocity of movement in the phenotypic space thus allowing recombinants to colonize the highest fitness regions earlier than non-recombinants that are often driven to extinction. The stabilizing effects of competition and assortativity are also discussed. Finally, the analysis of phase diagrams shows that competition is the key factor for the evolution of recombination, while assortativity plays a significant role only in small populations. © 2004 Published by Elsevier B.V
Alone no more: pain in premature children
No full textIt is only recently that newborns have been recognised to feel pain. To avoid the drawbacks of common analgesics, alternative analgesic methods (e.g. sucking and/or oral sugar) have been proposed. We showed that these methods are of little effect without the relaxing, distracting, comforting presence of a person at the cribside who talks to and massages the baby. This is a further demonstration that newborns, including premature babies, look for a reassuring presence when experiencing pain. This is surprising as premature babies are relatively unreactive, often completely isolated in an incubator and considered incapable of social behavior. To the attentive observer, however, they reveal an unsuspected emotional world. Not only do they feel pain, but they are also capable of suffering, distress, anxiety and fear. This needs to be considered in neonatal analgesic treatment, even for extremely premature children. It is mandatory for caregivers to be a reassuring presence during painful procedures: premature babies are exacting patients. They not only feel pain, they even suffer; they request not only drugs, but a human presence nearby
Modeling Social Groups, Policies and Cognitive Behavior in COVID-19 Epidemic Phases. Basic Scenarios
Full text linkThe covid19 pandemic is distinct from Spanish flu of 1918 from many aspects among which the contrast between the overabundance of worldwide exchange of information (infomedia) and the actual scarce knowledge of the pathogen and the infection mechanism. Another important distinction is that the epidemics threaten society components, social groups, communities and jobs in very different ways and different death tolls. With this in mind, we start with simple models of pandemics and we drive the reader to more complex models that take into accounts social compartments and communities. The discrete-state models are built by adding elements, first in a mean-field approximation, then adding age classes and differential contact rates, and finally inserting the social group dimension. The novel element we insert is the effect of restrictions in contacts and travels, filtered by the risk perception, according with the growth of the number of infected or recovered people. Assimilating risk perception with cognitive behavior, we obtain several coarse-grain scenarios, that can be used for instance to calibrate the level of restrictions so not to exceed the capacity of the health system, and to speed the post-emergency recovery
A self-organized method for computing the epidemic threshold in computer networks
No full textIn many cases, tainted information in a computer network can spread in a way similar to an epidemics in the human world. On the other had, information processing paths are often redundant, so a single infection occurrence can be easily "reabsorbed". Randomly checking the information with a central server is equivalent to lowering the infection probability but with a certain cost (for instance processing time), so it is important to quickly evaluate the epidemic threshold for each node. We present a method for getting such information without resorting to repeated simulations. As for human epidemics, the local information about the infection level (risk perception) can be an important factor, and we show that our method can be applied to this case, too. Finally, when the process to be monitored is more complex and includes "disruptive interference", one has to use actual simulations, which however can be carried out "in parallel" for many possible infection probabilities
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
11- to 15-Year-old children of women who danced during their pregnancy
No full textAIM:
To determine whether high levels of maternal physical activity (dancing during pregnancy), influenced the offspring.
MATERIALS AND METHODS:
Sixty-four women (32 of whom had continued to dance for at least 2 months after the beginning of pregnancy) filled in a questionnaire to assess the health and behavior of their offspring, now 11-15 years of age.
RESULTS:
More children born from women who had continued to dance during pregnancy needed to be rocked to sleep during their first year (p < 0.05). More children in the study group played musical instruments (p < 0.05). There were no significant differences between the groups regarding other parameters.
CONCLUSIONS:
The greater need to be rocked to fall asleep and the attitude to play musical instruments recorded in the children of dancers may be related to prenatal maternal movement. But they may also be due to other causes as discussed
- …
