63 research outputs found
Statistical Analysis of Genealogical Trees for Polygamic Species
Repetitions within a given genealogical tree provides some information about
the degree of consanguineity of a population. They can be analyzed with
techniques usually employed in statistical physics when dealing with fixed
point transformations. In particular we show that the tree features strongly
depend on the fractions of males and females in the population, and also on the
offspring probability distribution. We check different possibilities, some of
them relevant to human groups, and compare them with simulations.Comment: 2 eps figs, Fig.2 changed to meet cond-mat size criteri
FenĂłmenos de crecimiento y fractura de materiales
Tesis doctoral inĂ©dita leĂda en la Universidad AutĂłnoma de Madrid, Facultad de Ciencias, Departamento de FĂsica de la Materia Condensada. Fecha de lectura: 05-12-199
Desarrollo de un estimulador eléctromecánico programable para el entrenamiento electromecánico de cultivos monocapas de células miocárdicas
Several medical studies have concluded that it is possible to regenerate cardiac tissue from stem cells. However, the survival rate of the stem cells implanted in hearts is less than 10%. A previous electromechanic conditioning of the stem cells to implant, can be effective to improve the paracrine effect, as the stem cells would be already adapted to an environment with cyclic elongation, and also, the training will promote the differentiation to an adult cardiac tissue. Therefore, in this project it has been designed and implemented an electromechanical programmable stimulator to train myocardial cell cultures.
It will be explained the solution proposed to the project, starting with the mechanical stimulator, followed by the electrical stimulator and ending with the user interface. The coordination between both stimuli and their characteristics and limitations will be detailed. The user interface based on a touch screen has been implemented and programmed thinking on simplicity for the future user in the laboratory.
Last but not least, it has been realized a budget of our project and the conclusions and the improvement proposals will be exposed.Diversos estudios mĂ©dicos han concluido que es posible regenerar tejido cardĂaco a partir de cĂ©lulas madre. A pesar de ello, la tasa de supervivencia de las cĂ©lulas madre implantadas en corazones resulta inferior al 10%. Un preacondicionamiento electromecánico de las cĂ©lulas a implantar será efectivo a la hora de aumentar el efecto paracrino, puesto que las cĂ©lulas estarĂan ya adaptadas a un entorno con estiramiento cĂclico y, adicionalmente, el entrenamiento promoverá la diferenciaciĂłn hacia tejido cardĂaco adulto. Por ello, en este proyecto se ha diseñado e implementado un estimulador electromecánico programable para entrenar cultivos de cĂ©lulas miocárdicas.
Se explicara cĂłmo se ha planteado la soluciĂłn al proyecto, empezando por el estimulador mecánico, continuando con el estimulador elĂ©ctrico y finalizando con la interfaz de usuario. Se detallará la coordinaciĂłn entre los dos estĂmulos y las caracterĂsticas y limitaciones de ambos. La interfaz de usuario basada en una pantalla táctil, se ha implementado y programado pensando en la sencillez de uso para el futuro usuario en un laboratorio.
Por último, pero no menos importante, se ha realizado un presupuesto de nuestro proyecto y se expondrán las conclusiones y propuestas de mejora.Pla Terrada, OA. (2016). Desarrollo de un estimulador eléctromecánico programable para el entrenamiento electromecánico de cultivos monocapas de células miocárdicas. http://hdl.handle.net/10251/92577TFG
A wide diversity of cortical GABAergic interneurons derives from the embryonic preoptic area
GABA-containing (GABAergic) interneurons comprise a very heterogeneous group of cells that are crucial for cortical function. Different classes of interneurons specialize in targeting specific subcellular domains of excitatory pyramidal cells or other interneurons, which provides cortical circuits with an enormous capability for information processing. As in other regions of the CNS, cortical interneuron diversity is thought to emerge from the genetic specification of different groups of progenitor cells within the subpallium. Most cortical interneurons originate from two main regions, the medial and the caudal ganglionic eminences (MGE and CGE, respectively). In addition, it has been shown that progenitors in the embryonic preoptic area (POA) also produce a small population of cortical GABAergic interneurons. Here, we show that the contribution of the POA to the complement of cortical GABAergic interneurons is larger than previously believed. Using genetic fate mapping and in utero transplantation experiments, we demonstrate that Dbx1-expressing progenitor cells in the POA give rise to a small but highly diverse cohort of cortical interneurons, with some neurochemical and electrophysiological characteristics that were previously attributed to MGE- or CGE-derived interneurons. There are, however, some features that seem to distinguish POA-derived interneurons from MGE- or CGE-derived cells, such as their preferential laminar location. These results indicate that the mechanisms controlling the specification of different classes of cortical interneurons might be more complex than previously expected. Together with earlier findings, our results also suggest that the POA generates nearly 10% of the GABAergic interneurons in the cerebral cortex of the mous
Mean Field Theory of Sandpile Avalanches: from the Intermittent to the Continuous Flow Regime
We model the dynamics of avalanches in granular assemblies in partly filled
rotating cylinders using a mean-field approach. We show that, upon varying the
cylinder angular velocity , the system undergoes a hysteresis cycle
between an intermittent and a continuous flow regimes. In the intermittent flow
regime, and approaching the transition, the avalanche duration exhibits
critical slowing down with a temporal power-law divergence. Upon adding a white
noise term, and close to the transition, the distribution of avalanche
durations is also a power-law. The hysteresis, as well as the statistics of
avalanche durations, are in good qualitative agreement with recent experiments
in partly filled rotating cylinders.Comment: 4 pages, RevTeX 3.0, postscript figures 1, 3 and 4 appended
Role of Cln1 during melanization of Cryptococcus neoformans
Cryptococcus neoformans is an opportunistic fungal pathogen that has several well-described virulence determinants. A polysaccharide capsule and the ability to produce melanin are among the most important. Melanization occurs both in vitro, in the presence of catecholamine and indole compounds, and in vivo during the infection. Despite the importance of melanin production for cryptococcal virulence, the component and mechanisms involved in its synthesis have not been fully elucidated. In this work, we describe the role of a G1/S cyclin (Cln1) in the melanization process. Cln1 has evolved specifically with proteins present only in other basidiomycetes. We found that Cln1 is required for the cell wall stability and production of melanin in C. neoformans. Absence of melanization correlated with a defect in the expression of the LAC1 gene. The relation between cell cycle elements and melanization was confirmed by the effect of drugs that cause cell cycle arrest at a specific phase, such as rapamycin. The cln1 mutant was consistently more susceptible to oxidative damage in a medium that induces melanization. Our results strongly suggest a novel and hitherto unrecognized role for C. neoformans Cln1 in the expression of virulence traits.We thank Rajendra Uphadya (Washington University School of Medicine, St. Louis, MI, USA) for providing the sequence of oligonucleotides for 18s gene used in this article. RG-R was supported by a FPI fellowship (reference BES-2009-015913) from the Spanish Ministry of Economics and Competitivity. NT-C is supported by a FPI fellowship (reference BES-2012-051837). OZ is funded by grant SAF2011-25140 and SAF2014-54336 from the Spanish Ministry for Economics and CompetitivityS
Fracture driven by a Thermal Gradient
Motivated by recent experiments by Yuse and Sano (Nature, 362, 329 (1993)),
we propose a discrete model of linear springs for studying fracture in thin and
elastically isotropic brittle films. The method enables us to draw a map of the
stresses in the material. Cracks generated by the model, imposing a moving
thermal gradient in the material, can branch or wiggle depending on the driving
parameters. The results may be used to compare with other recent theoretical
work, or to design future experiments.Comment: RevTeX file (9 pages) and 5 postscript figure
Heating and de-icing function in conductive concrete and cement paste with the hybrid addition of carbon nanotubes and graphite products
This paper aims to study the viability of conductive cement paste and conductive concrete with the hybrid addition of carbon nanotubes (CNT) and graphite powder (GP) as a self-heating material for heating, ice formation prevention and de-icing in pavements. Different heating tests, ice-preventing tests and de-icing tests were performed with cement paste and concrete specimens. Results confirm that the conductive cement composites studied, with the addition of 1% CNT + 5% GP, exhibited heating, de-icing and ice-prevention properties, when applying constant AC/DC voltages between the two end sides of each specimen, with relatively low energy consumption. The main contribution of this work is to achieve a sufficient conductivity level for the development of the heating and de-icing function using this hybrid addition in concrete, which has not been used so far, in order to be applied in real concrete structures.The authors would like to acknowledge financial support received from European Union’s Horizon 2020 Research and Innovation Programme under Grant Agreement No. 760940 and from the Generalitat Valenciana (Spain) (AICO/2019/050)
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