26,347 research outputs found
Social Effects in Science: Modelling Agents for a Better Scientific Practice
Science is a fundamental human activity and we trust its results because it
has several error-correcting mechanisms. Its is subject to experimental tests
that are replicated by independent parts. Given the huge amount of information
available, scientists have to rely on the reports of others. This makes it
possible for social effects to influence the scientific community. Here, an
Opinion Dynamics agent model is proposed to describe this situation. The
influence of Nature through experiments is described as an external field that
acts on the experimental agents. We will see that the retirement of old
scientists can be fundamental in the acceptance of a new theory. We will also
investigate the interplay between social influence and observations. This will
allow us to gain insight in the problem of when social effects can have
negligible effects in the conclusions of a scientific community and when we
should worry about them.Comment: 14 pages, 5 figure
A Rare Presentation of Invasive Tuberculosis of the Central Nervous System in an Immunocompetent Patient in a Nonendemic Country.
We herein report a rare case of a 25-year-old immunocompetent male patient with disseminated tuberculosis of central nervous system (CNS), first presenting as multiple cerebral lesions with no meningeal involvement. Subsequent diagnostic workup disclosed extensive peritoneal involvement. A broad differential diagnosis was considered, including neoplastic and infectious diseases. The diagnosis was confirmed with positive PCR result for Mycobacterium tuberculosis in the biopsied mesenteric tissue. The patient was started on tuberculostatic regimen with favorable outcome. No acquired or hereditary immunodeficiency was documented. Disseminated tuberculosis in immunocompetent individuals is extremely rare. Genetic susceptibility factors have been reported in individuals with extensive forms of the disease and a high index of suspicion is required, as observed in our case.info:eu-repo/semantics/publishedVersio
Vorton Formation
In this paper we present the first analytic model for vorton formation. We
start by deriving the microscopic string equations of motion in Witten's
superconducting model, and show that in the relevant chiral limit these
coincide with the ones obtained from the supersonic elastic models of Carter
and Peter. We then numerically study a number of solutions of these equations
of motion and thereby suggest criteria for deciding whether a given
superconducting loop configuration can form a vorton. Finally, using a recently
developed model for the evolution of currents in superconducting strings we
conjecture, by comparison with these criteria, that string networks formed at
the GUT phase transition should produce no vortons. On the other hand, a
network formed at the electroweak scale can produce vortons accounting for up
to 6% of the critical density. Some consequences of our results are discussed.Comment: 41 pages; color figures 3-6 not included, but available from authors.
To appear in Phys. Rev.
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