Cambios en la vegetación producidos por los hormigueros de Lasius flavus en pastos supraforestales del pirineo occidental

7 páginasPara averiguar los cambios en la vegetación debidos a la presencia de montículos de tierra producidos por la hormiga Lasius flavus, se llevaron a cabo muestreos dentro y fuera de hormigueros seleccionados al azar. Diez pares de muestras se tomaron en cada una de las comunidades de pasto Bromion erecti y Nardion strictae en el Pirineo occidental. Se determinó la cobertura de especies, y el N total, pH y temperatura del suelo. En general las especies que colonizan los hormigueros no son diferentes de las que se encuentran en su entorno, pero cambia su abundancia. Thymus praecox, Cerastium arvense y Calluna vulgaris fueron las únicas especies significativamente más abundantes en los hormigueros que en el pasto contiguo. En general aumentan las especies termófilas y disminuyen las calcífugas (p.e. Nardus stricta), al presentar los hormigueros una mayor alcalinidad. El número de especies es menor en los hormigueros que fuera de ellos, pero estos contribuyen a aumentar la heterogeneidad ambiental general de la comunidad.Peer reviewe

Effects of low pH on synthesis and release of catecholamines in the cat carotid body in vitro

Producción CientíficaThe rates of dopamine and noradrenaline synthesis in the cat carotid body (c.b.) are 5.9 _+ 0.58 pmol/c.b./2 h and 0.3 + 0.02 pmol/c.b./2 h, respectively. The synthesis is doubled when the organs are incubated at pH 7. Similarly, low pH induces a release of dopamine from the c.b. which is proportional to increased activity in the carotid sinus nerve

Synthesis and Release of Catecholamines by the Cat Carotid Body in Vitro: Effects of Hypoxic Stimulation

Producción CientíficaThe role of catecholamines (CAs) in cat carotid body chemoreception has been controversial. On the basis of pharmacological experiments, it would appear that endogenous dopamine (DA) may act either as an inhibitory or excitatory transmitter. Neurochemical studies on the effects of natural stimulation on the release of carotid body CAs in the cat have also been inconclusive. In the present study, we have characterized the synthesis and release of CAs in the in vitro cat carotid body preparation in response to different levels of hypoxic stimulation and have correlated these measures with the chemosensory activity of the carotid sinus nerve. The synthesis of [3H]DA and [3H]norepinephrine was linear for at least 4 h in carotid bodies incubated with their natural precursor [~H]tyrosine. Synthesis of both [3H]CAs plateaued when the [3H]tyrosine concentration in the media reached 40 uM, which is a concentration similar to that found in cat plasma. Exposure of the animals to an atmosphere of 10% 02 in N~ for 3 h prior to removal and incubation of the carotid bodies with [3H]tyrosine resulted in an approximately 100% increase in the rate of [3H]DA synthesis but no change in [3H]norepinephrine synthesis. This selective increase in [3H]DA synthesis was not detected when [3H]dihydroxyphenylalanine was used as precursor. Carotid bodies first incubated with [3H]tyrosine and later superfused with solutions equilibrated with different gas mixtures (0 100% 0 2 in N2) exhibited an increase in [3H]DA release and carotid sinus nerve discharge which were inversely related to the oxygen concentration. This relationship was strongest for the weaker stimuli (between 50% and 20% O 2 in N2), where both nerve activity and [3H]DA release increased almost in parallel. With lower oxygen concentrations (10% O 2 and 0% 02 equilibrated solutions), the increase in the release of [3H]DA was proportionally greater than the increase in carotid sinus nerve discharge. Our results demonstrate that hypoxic stimulation increases both the rate of synthesis and release of DA in the cat carotid body. Although the precise role of DA in this chemoreceptor organ is presently unknown, our findings suggest that this biogenic amine plays a direct role in generating or controlling the electrical activity in the carotid sinus nerve. INTRODUCTION The mammalian carotid body is an arterial chemoreceptor organ activated by low paO2, low pH and high p~CO2 (ref. 21). Structurally, the receptor complex is formed by clusters of two types of cells, the type I and type II cells; the clusters lie within a supporting connective tissue matrix containing a dense capillary net24, 41. Sensory fibers of the carotid sinus nerve (CSN) penetrate these cell clusters to end in synaptic apposition with type I cells, which are considered to be preneural (receptor) elements. Two perennial issues pertaining to arterial chemoreception, concern first, whether the type 1 cells are in fac

Pure spin current manipulation in antiferromagnetically exchange coupled heterostructures

We present a model to describe the spin currents generated by ferromagnet/spacer/ferromagnet exchange coupled trilayer systems and heavy metal layers with strong spin-orbit coupling. By exploiting the magnitude of the exchange coupling (oscillatory RKKY-like coupling) and the spin-flop transition in the magnetization process, it has been possible to produce spin currents polarized in arbitrary directions. The spin-flop transition of the trilayer system originates pure spin currents whose polarization vector depends on the exchange field and the magnetization equilibrium angles. We also discuss a protocol to control the polarization sign of the pure spin current injected into the metallic layer by changing the initial conditions of magnetization of the ferromagnetic layers previously to the spin pumping and inverse spin Hall effect experiments. The small differences in the ferromagnetic layers lead to a change in the magnetization vector rotation that permits the control of the sign of the induced voltage components due to the inverse spin Hall effect. Our results can lead to important advances in hybrid spintronic devices with new functionalities, particularly, the ability to control microscopic parameters such as the polarization direction and the sign of the pure spin current through the variation of macroscopic parameters, such as the external magnetic field or the thickness of the spacer in antiferromagnetic exchange coupled systems.Fil: Avilés Félix, L.. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; ArgentinaFil: Butera, Alejandro Ricardo. Comision Nacional de Energía Atómica. Gerencia de Área Investigaciones y Aplicaciones no Nucleares. Gerencia de Física (Centro Atómico Bariloche). División Resonancias Magnéticas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; ArgentinaFil: González Chávez, D. E.. Centro Brasileiro de Pesquisas Físicas; BrasilFil: Sommer, R. L.. Centro Brasileiro de Pesquisas Físicas; BrasilFil: Gomez, Javier Enrique. Comision Nacional de Energía Atómica. Gerencia de Área Investigaciones y Aplicaciones no Nucleares. Gerencia de Física (Centro Atómico Bariloche). División Resonancias Magnéticas; Argentin

Comportamiento en fluencia de un material compuesto de matriz metálica Al6061-15 vol % SiCw pulvimetalúrgico

Se ha realizado un estudio de las propiedades en fluencia del material compuesto pulvimetalúrgico Al6061-15 vol % SiCw. Su comportamiento se ha comparado con el de la aleación Al6061 pulvimetalúrgica y la aleación Al6061 de colada. El comportamiento del material pulvimetalúrgico sin reforzar mejora respecto al del material de colada. Al mismo tiempo, el del material compuesto mejora respecto al comportamiento del material pulvimetalúrgico sin reforzar. Se consideran dos factores microestructurales como los principales responsables de la mejora de las propiedades en fluencia de este material compuesto. Por un lado, las partículas de Al2O3 de tamaño nanométrico y, por otro, las partículas de fibra corta cerámicas de SiC de tamaño micrométrico. Aunque ambos tipos de partículas dan lugar a un efecto de refuerzo similar, los mecanismos intrínsecos asociados a la presencia de estas partículas tienen una naturaleza diferente debido a la diferencia en la escala microestructural.Peer reviewe

Andamios porosos (apatita/colágeno) de origen marino para aplicaciones biomédicas

1 póster presentado en las III Xornadas de Investigación BioIntegraSaúde 2015, Vigo 16 xuño 2015.-- E. López-Senra ... et al.FP7/REGPOT-2012-2013.1 (nº 316265, BIOCAPS); UE-INTERREG 2011-1/164 MARMED; Ministerio de Ciencia e Innovación (Project MAT2010-18281)Peer reviewe

Neutrinos and the matter-antimatter asymmetry in the Universe

The discovery of neutrino oscillations provides a solid evidence for nonzero neutrino masses and leptonic mixing. The fact that neutrino masses are so tiny constitutes a puzzling problem in particle physics. From the theoretical viewpoint, the smallness of neutrino masses can be elegantly explained through the seesaw mechanism. Another challenging issue for particle physics and cosmology is the explanation of the matter-antimatter asymmetry observed in Nature. Among the viable mechanisms, leptogenesis is a simple and well-motivated framework. In this talk we briefly review these aspects, making emphasis on the possibility of linking neutrino physics to the cosmological baryon asymmetry originated from leptogenesis.Comment: 8 pages, 1 table, 1 figure; Based on talk given at the Symposium STARS2011, 1 - 4 May 2011, Havana, Cuba; to be published in the Proceeding

Dispositivo y procedimiento útil para el control de un automóvil, con ayuda de GPS y comunicaciones inalámbricas, que permite efectuar adelantamientos

Dispositivo y procedimiento útil para el control de un automóvil, con ayuda de GPS y comunicaciones inalámbricas, que permite efectuar adelantamientos. El dispositivo y procedimiento permite el control automático para realizar mediante un computador maniobras de adelantamiento en carretera, manejando los tres actuadores principales del vehículo, acelerador, freno y dirección sin intervención humana, basándose en información sensorial proveniente de sistemas GNSS, redes de comunicaciones inalámbricas Wi.Fi y la información de navegación del propio vehículo. La computación de control del sistema esta basada en algoritmos de lógica borrosa desarrollados por los autores.Peer reviewedConsejo Superior de Investigaciones Científicas (España)A1 Solicitud de patentes con informe sobre el estado de la técnic