25 research outputs found
Design of artificial genetic regulatory networks with multiple delayed adaptive responses
Genetic regulatory networks with adaptive responses are widely studied in
biology. Usually, models consisting only of a few nodes have been considered.
They present one input receptor for activation and one output node where the
adaptive response is computed. In this work, we design genetic regulatory
networks with many receptors and many output nodes able to produce delayed
adaptive responses. This design is performed by using an evolutionary algorithm
of mutations and selections that minimizes an error function defined by the
adaptive response in signal shapes. We present several examples of network
constructions with a predefined required set of adaptive delayed responses. We
show that an output node can have different kinds of responses as a function of
the activated receptor. Additionally, complex network structures are presented
since processing nodes can be involved in several input-output pathways
Autonomous Learning by Simple Dynamical Systems with Delayed Feedbacks
A general scheme for construction of dynamical systems able to learn
generation of the desired kinds of dynamics through adjustment of their
internal structure is proposed. The scheme involves intrinsic time-delayed
feedback to steer the dynamics towards the target performance. As an example, a
system of coupled phase oscillators, which can by changing the weights of
connections between its elements evolve to a dynamical state with the
prescribed (low or high) synchronization level, is considered and investigated
A simple electronic device to experiment with the Hopf bifurcation
We present a simple low-cost electronic circuit that is able to show two different dynamical regimens with oscillations of voltages and with constant values of them. This device is designed as a negative feedback three-node network, inspired in the genetic repressilator. The circuit's behavior is modeled by a system of differential equations which is studied in several different ways by applying the dynamical system formalism, making numerical simulations and constructing and measuring it experimentally. We find that the most important characteristics of the Hopf bifurcation can be found and controlled. Particularly, a resistor value plays the role of the bifurcation parameter, which can be easily varied experimentally. As a result, this system can be employed to introduce many aspects of a research in a real physical system, and it enables us to study one of the most important kinds of bifurcation.Fil: Rim, Daniela Noemí. Universidad Nacional de Cuyo. Facultad de Ciencias Exactas y Naturales; ArgentinaFil: Cremades, Pablo Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Cuyo. Facultad de Ciencias Exactas y Naturales; ArgentinaFil: Kaluza, Pablo Federico. Universidad Nacional de Cuyo. Facultad de Ciencias Exactas y Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin
The complex network of global cargo ship movements
Transportation networks play a crucial role in human mobility, the exchange
of goods, and the spread of invasive species. With 90% of world trade carried
by sea, the global network of merchant ships provides one of the most important
modes of transportation. Here we use information about the itineraries of
16,363 cargo ships during the year 2007 to construct a network of links between
ports. We show that the network has several features which set it apart from
other transportation networks. In particular, most ships can be classified in
three categories: bulk dry carriers, container ships and oil tankers. These
three categories do not only differ in the ships' physical characteristics, but
also in their mobility patterns and networks. Container ships follow regularly
repeating paths whereas bulk dry carriers and oil tankers move less predictably
between ports. The network of all ship movements possesses a heavy-tailed
distribution for the connectivity of ports and for the loads transported on the
links with systematic differences between ship types. The data analyzed in this
paper improve current assumptions based on gravity models of ship movements, an
important step towards understanding patterns of global trade and bioinvasion.Comment: 7 figures Accepted for publication by Journal of the Royal Society
Interface (2010) For supplementary information, see
http://www.icbm.de/~blasius/publications.htm
Epidemics in partially overlapped multiplex networks
Many real networks exhibit a layered structure in which links in each layer
reflect the function of nodes on different environments. These multiple types
of links are usually represented by a multiplex network in which each layer has
a different topology. In real-world networks, however, not all nodes are
present on every layer. To generate a more realistic scenario, we use a
generalized multiplex network and assume that only a fraction of the nodes
are shared by the layers. We develop a theoretical framework for a branching
process to describe the spread of an epidemic on these partially overlapped
multiplex networks. This allows us to obtain the fraction of infected
individuals as a function of the effective probability that the disease will be
transmitted . We also theoretically determine the dependence of the epidemic
threshold on the fraction of shared nodes in a system composed of two
layers. We find that in the limit of the threshold is dominated by
the layer with the smaller isolated threshold. Although a system of two
completely isolated networks is nearly indistinguishable from a system of two
networks that share just a few nodes, we find that the presence of these few
shared nodes causes the epidemic threshold of the isolated network with the
lower propagating capacity to change discontinuously and to acquire the
threshold of the other network.Comment: 13 pages, 4 figure
Primer mamífero Mesozoico de Chile: el registro más austral de un gondwanaterio del Cretácico tardío
Se describe a Magallanodon baikashkenke gen. et. sp. nov., un nuevo mamífero gondwanaterio del Cretácico tardío de la Región de Magallanes, en el sur de Chile (Valle del Río de Las Chinas, Estancia Cerro Guido, norte de Puerto Natales, Provincia de Última Esperanza). Las capas portadoras se ubican entre los niveles del Campaniano tardío-Maastrichtiano temprano de la Formación Dorotea (Cuenca de Magallanes/Austral). Los nuevos restos constituyen el registro más austral de un mamífero gondwanaterio del Mesozoico, como así también el primer mamífero Mesozoico conocido para Chile. El nuevo taxón es comparable en tamaño a las formas hipsodontes Gondwanatherium (Cretácico tardío) y Sudamerica (Paleoceno temprano), pero con molares notoriamente braquidontes soportados por cuatro a cinco raíces. Como en otros gondwanaterios, posee al menos un incisivo superior rodentiforme en la serie superior. Se diagnostica y describe brevemente el nuevo taxón, considerado tentativamente como un ferugliotérido (Ferugliotheriidae). De confirmarse esta asignación, este nuevo taxón representaría el miembro de mayor tamaño para la familia. El patrón oclusal de los molariformes, con el desgaste, se semeja también al de otros gondwanaterios, en particular al de los ferugliotéridos y al del sudamerícido Gondwanatherium, agregando en consecuencia más evidencias en favor de la proximidad filogenética entre ambas familias. Se llevó a cabo un análisis de la microestructura del esmalte del incisivo superior de Magallanodon; como resultado, se encontraron varias similitudes importantes con el patrón existente en Gondwanatherium (Sudamericidae). Se discute la significación de Magallanodon en la adquisición, entre los gondwanaterios, de un patrón molariforme caracterizado por la presencia de lofos transversos. Finalmente, se discute la significación del nuevo hallazgo en el contexto de las biotas australes, incluyendo aquellas de Patagonia y Antártica.We describe Magallanodon baikashkenke gen. et. sp. nov., a new gondwanatherian mammal from the Late Cretaceous of the Magallanes Region in southern Chile (Río de Las Chinas Valley, Estancia Cerro Guido, north of Puerto Natales city, Última Esperanza Province). The mammal-bearing layer is placed within the Late Campanian-Early Maastrichtian levels of the Dorotea Formation (Magallanes/ Austral Basin). The new remains constitute the southernmost record of a Mesozoic gondwanatherian mammal, as well as the first Mesozoic mammal from Chile. This taxon is comparable in size to the hypsodont-toothed Gondwanatherium (Late Cretaceous) and Sudamerica (Early Paleocene) but with noticeably brachyodont molariforms supported by four to five roots. As in other gondwanatherians, it has at least one hypertrophied, rodent-like incisor in the upper jaw. The new taxon is here diagnosed and described, and is regarded as a possible ferugliotheriid (?Ferugliotheriidae). If confirmed, it would represent the largest known taxon for this family. Its molariform occlusal crown pattern, after wear, resembles that of other gondwanatherians, particularly ferugliotheriids and that of the sudamericid Gondwanatherium. This adds new evidence on the phylogenetic proximity of ferugliotheriid and sudamericid gondwanatherians. An analysis of the enamel microstructure of the upper incisor of Magallanodon was performed demonstrating several crucial similarities with the pattern shown by Gondwanatherium (Sudamericidae). We discuss the significance of Magallanodon for understanding the acquisition, within gondwanatherians, of a lophed molariform pattern. Finally, we discuss the significance of the new finding in the context of southern biotas, including those of Patagonia and Antarctica.Fil: Goin, Francisco Javier. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Paleontología Vertebrados; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; ArgentinaFil: Martinelli, Agustín Guillermo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; ArgentinaFil: Soto Acuña, Sergio. Universidad de Santiago de Chile. Facultad de Ciencias; ChileFil: Vieytes, Emma Carolina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Zoología de Vertebrados; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; ArgentinaFil: Manriquez, Leslie. Universidad de Vale do Rio dos Sinos; BrasilFil: Fernandez, Roy A.. Universidad de Santiago de Chile. Facultad de Ciencias; ChileFil: Pino, Juan Pablo. Instituto Antártico Chileno; ChileFil: Trevisan Cristine. Instituto Antártico Chileno; ChileFil: Kaluza, Jonatan Ezequiel. Universidad de Santiago de Chile. Facultad de Ciencias; Chile. Fundación de Historia Natural Félix de Azara; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Reguero, Marcelo Alfredo. Museo Nacional de Historia Natural de Santiago; Chile. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; ArgentinaFil: Leppe, Marcelo. Instituto Antártico Chileno; ChileFil: Ortiz, Hector. Universidad de Santiago de Chile. Facultad de Ciencias; ChileFil: Rubilar Rogers, David. Museo Nacional de Historia Natural de Santiago; ChileFil: Vargas, Alexander. Universidad de Santiago de Chile. Facultad de Ciencias; Chil
Cosmology, Oscillating Physics and Oscilllating Biology
According to recent reports there is an excess correlation and an apparent
regularity in the galaxy one-dimensional polar distribution with a
characteristic scale of 128 Mpc. This aparent spatial periodicity can
be naturally explained by a time oscillation of the gravitational constant .
On the other hand, periodic growth features of bivalve and coral fossiles
appear to show a periodic component in the time dependence of the number of
days per year. In this letter we show that a time oscillating gravitational
constant with similar period and amplitude can explain such a feature.Comment: 9 pages. latex using revtex. This revised version is supposed to be
free of e-mail nois
Relict duck-billed dinosaurs survived into the last age of the dinosaurs in subantarctic Chile
In the dusk of the Mesozoic, advanced duck-billed dinosaurs (Hadrosauridae) were so successful that they likely outcompeted other herbivores, contributing to declines in dinosaur diversity. From Laurasia, hadrosaurids dispersed widely, colonizing Africa, South America, and, allegedly, Antarctica. Here, we present the first species of a duck-billed dinosaur from a subantarctic region, Gonkoken nanoi, of early Maastrichtian age in Magallanes, Chile. Unlike duckbills further north in Patagonia, Gonkoken descends from North American forms diverging shortly before the origin of Hadrosauridae. However, at the time, non-hadrosaurids in North America had become replaced by hadrosaurids. We propose that the ancestors of Gonkoken arrived earlier in South America and reached further south, into regions where hadrosaurids never arrived: All alleged subantarctic and Antarctic remains of hadrosaurids could belong to non-hadrosaurid duckbills like Gonkoken. Dinosaur faunas of the world underwent qualitatively different changes before the Cretaceous-Paleogene asteroid impact, which should be considered when discussing their possible vulnerability