Browsing by Author "Fernández, R"

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    Acute ventilatory and circulatory reactions evoked by nicotine
    (2002) Fernández, R; Larraín, C; Zapata, P
    Either excitatory or inhibitory cardio-respiratory responses induced by nicotine have been reported. We evaluated the joint and separate contributions of peripheral arterial chemoreceptors and pulmonary vagal afferences to nicotine-induced cardio-respiratory responses in 11 pentobarbitone-anaesthetized cats. Nicotine, given i.v. in doses of from 1 to 200 mug/kg, evoked dose-dependent transient increases in tidal volume (VT) and arterial blood pressure (BP), but the highest doses evoked brief apnoea, immediately followed by intense hyperventilation, as well as discrete early hypotension followed by late hypertension. Bilateral section of the aortic and carotid nerves abolished all hyperventilatory responses to nicotine, giving way to apnoea followed by few cycles of reduced VT and profound hypotension followed by slight hypertension in response to intermediate doses (50-100 mug/kg). Subsequent bilateral vagotomy (BV) suppressed apnoeic and hypotensive responses. In other cats initially subjected to BV, only increases in VT and BP were observed in response to nicotine, effects which were no longer observed after additional carotid and aortic deafferentation. These data suggest that excitatory effects of nicotine on respiration and BP are reflexes evoked by stimulation of peripheral arterial chemoreceptors, while inhibitory effects are also reflex responses but evoked from stimulation of pulmonary vagal afferences. (C) 2002 Elsevier Science B. V. All rights reserved.
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    Photo-ethnography and Political Engagement: Studying performative subversions of public space
    (2020) Hermansen Ulibarri, Pablo Ignacio; Fernández, R
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    Proper motion and kinematics of the ansae in NGC 7009
    (2004) Fernández, R; Monteiro, H; Schwarz, HE
    We have measured the proper motion (PM) and kinematics of the ansae in NGC 7009 using high-dispersion echelle spectra and archive narrowband Hubble Space Telescope images. Assuming that the ansae are moving at equal and opposite velocities from the central star, we obtain a system radial velocity of -53 +/- 2 km s(-1), the eastern ansa approaching and the western ansa receding at v(r) = 5.3 +/- 1 km s(-1) with respect to this value. The PM of the eastern ansa is 28 +/- 8 mas yr(-1), which, with our weighted distance to NGC 7009 of 0.86 +/- 0.34 kpc, gives V-exp = 114 +/- 32 km s-(1). The electron temperature and density in both ansae were determined to be T-e similar to 9000 +/- 400 K and n(e) similar to 2300 +/- 400 cm(-3). The dynamic age of the ansae is similar to910 +/- 260 yr, and the implied PM of the central star is mu(CS) = 1 +/- 0.5 mas yr(-1). This is in qualitative but not quantitative agreement with previous work.
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    Rotochemical heating in millisecond pulsars
    (2005) Fernández, R; Reisenegger, A
    Rotochemical heating originates in a departure from beta equilibrium due to spin-down compression in a rotating neutron star. The main consequence is that the star eventually arrives at a quasi-equilibrium state in which the thermal photon luminosity depends only on the current value of the spin-down power, which is directly measurable. Only in millisecond pulsars does the spin-down power remain high long enough for this state to be reached with a substantial luminosity. We report an extensive study of the effect of this heating mechanism on the thermal evolution of millisecond pulsars, developing a general formalism in the slow-rotation approximation of general relativity that takes the spatial structure of the star fully into account, and using a sample of realistic equations of state to solve the nonsuperfluid case numerically. We show that nearly all observed millisecond pulsars are very likely to be in the quasi-equilibrium state. Our predicted quasi-equilibrium temperatures for PSR J0437-4715 are only 20% lower than inferred from observations. Accounting for superfluidity should increase the predicted value.