Papers by Guillermo González
Icarus, 2002
We explore the likelihood that early remains of Earth, Mars, and Venus have been preserved on the... more We explore the likelihood that early remains of Earth, Mars, and Venus have been preserved on the Moon in high enough concentrations to motivate a search mission. During the Late Heavy Bombardment, the inner planets experienced frequent large impacts. Material ejected by these impacts near the escape velocity would have had the potential to land and be preserved on the surface of the Moon. Such ejecta could yield information on the geochemical and biological state of early Earth, Mars, and Venus. To determine whether the Moon has preserved enough ejecta to justify a search mission, we calculate the amount of terran material incident on the Moon over its history by considering the distribution of ejecta launched from the Earth by large impacts. In addition, we make analogous estimates for Mars and Venus. We find, for a well-mixed regolith, that the median surface abundance of terran material is roughly 7 ppm, corresponding to a mass of approximately 20,000 kg of terran material over a 10×10-square-km area. Over the same area, the amount of material transferred from Venus is 1–30 kg and material from Mars as much as 180 kg. Given that the amount of terran material is substantial, we estimate the fraction of this material surviving impact with intact geochemical and biological tracers.
Behavioral Ecology and Sociobiology, 2001
Female preference for mates with elaborated ornaments has often been explained on the basis that ... more Female preference for mates with elaborated ornaments has often been explained on the basis that exaggerated secondary sexual traits might reflect individual quality and females might gather direct and indirect benefits in mating with such males. Sexual signals must however also entail costs to be reliable indicators of male quality. Androgens have been suggested as a physiological link between sexual signals and individual quality for several reasons, including their immunosuppressive effect. In this study, we tested two hypotheses linked to the hormonal basis of sexual signal expression. First, we investigated whether testosterone is correlated with the size of the black feather bib on the throat of male house sparrows (Passer domesticus) – a trait involved in intra- and inter-sexual selection. Second, we tested whether testosterone affects the seasonal exposure of the trait. Observational work conducted in 1998 showed that the testosterone level was positively correlated with badge size both in spring and in the subsequent fall, after molt. In 1999, we experimentally reduced spring testosterone levels using silastic implants filled with cyproterone acetate, an antiandrogen. Male house sparrows implanted with cyproterone acetate showed reduced exposure of the badge, because the white tips of the black feathers of the badge wore off later than in control males implanted with empty silastic tubes. This result suggests that testosterone can be causally involved in the expression of a secondary sexual trait in house sparrows, at least in terms of its seasonal exposure.
Oecologia, 2001
Nestling birds produced later in the season are hypothesized to be of poor quality with a low pro... more Nestling birds produced later in the season are hypothesized to be of poor quality with a low probability of survival and recruitment. In a Spanish population of house martins (Delichon urbica), we first compared reproductive success, immune responses and morphological traits between the first and the second broods. Second, we investigated the effects of an ectoparasite treatment and breeding date on the recapture rate the following year. Due probably to a reverse situation in weather conditions during the experiment, with more rain during rearing of the first brood, nestlings reared during the second brood were in better condition and had stronger immune responses compared with nestlings from the first brood. Contrary to other findings on house martins, we found a similar recapture rate for chicks reared during the first and the second brood. Furthermore, ectoparasitic house martin bugs had no significant effect on the recapture rate. Recaptured birds had similar morphology but higher immunoglobulin levels when nestlings compared with non-recaptured birds. This result implies that a measure of immune function is a better predictor of survival than body condition per se.
Journal of Animal Ecology, 1999
We tested the condition-dependent hypothesis of sexual advertisement in house sparrows (Passer do... more We tested the condition-dependent hypothesis of sexual advertisement in house sparrows (Passer domesticus). Male house sparrows have a bib of black feathers which serves as both a badge of social status and as a cue for female choice. We manipulated environmental conditions during the premoult period of juvenile house sparrows kept in outdoor aviaries. Birds were assigned to two treatments differing in the amount of dietary proteins, which are known to aect the expression of immune response in birds. We tested whether birds in the protein-rich group had better immune responses and developed larger bibs than birds reared on a protein-poor diet. We also checked whether immune response was a predictor of survival and parasite resistance. 2. Individuals with higher cellular immune response at capture had greater probability to survive during the 3 months of the experiment, and they had a higher probability to recover from infection with Haemoproteus sp. (a blood parasite). Conversely, birds with high immunoglobulin concentrations at capture had a higher probability of mortality. 3. Birds on the protein-rich diet had a higher cellular immune response compared to birds in the protein-poor treatment. Humoral immune response showed the opposite pattern, being higher for birds in the protein-poor treatment. We did not ®nd any eect of food quality on the development of the badge, assessed as the size of the trait and its colour properties. 4. In conclusion, our results support the view that immune defences are important for survival and parasite resistance in natural populations, and that they might be costly to produce. On the other hand, we did not ®nd support for the conditiondependent hypothesis of sexual advertisement, suggesting that the badge may not be a costly trait to produce. However, badge size could re¯ect other aspects of condition. The kind of pigments involved in colour signals may be the key factor determining the production costs of such traits.
American Naturalist, 2003
fected by the workload required to feed the brood. Overall, this study stresses the magnitude of ... more fected by the workload required to feed the brood. Overall, this study stresses the magnitude of costs associated with mounting immune responses and the ecological and evolutionary consequences for natural populations.
Behavioral Ecology and Sociobiology, 1999
The immunocompetence handicap hypothesis postulates that secondary sexual traits are honest signa... more The immunocompetence handicap hypothesis postulates that secondary sexual traits are honest signals of male quality because steroid hormones (such as corticosteroids and sex steroids), which are supposed to favor the development of secondary sexual traits, may also have immunosuppressive effects. Certain secondary sexual traits are not only used as mate choice signals but also play a role as badges of status. In the house sparrow (Passer domesticus), males have a bib of black feathers which is used both as a signal of social status in male-male interactions and by females when choosing a mate. We investigated the relationships between bib size and cellular immune response in male house sparrows during and outside the reproductive season. Males with large badges were found to have lower levels of immunocompetence, as assessed using a T-cell-mediated immunity assay, during the reproductive season, as predicted by the immunocompetence handicap hypothesis. Conversely, in November, the correlation between badge size and cellular immune response was positive, possibly reflecting the better access to trophic resources of large-badged dominant males in winter flocks.
Journal of Neurosurgery, 1975
The authors describe investigations in cats to delineate a vasodilator system to the face, which ... more The authors describe investigations in cats to delineate a vasodilator system to the face, which they undertook after a previous study showed that radiofrequency coagulation of the trigeminal ganglion produced a pronounced flush in the skin of the corresponding division. Results demonstrate a vasodilator system emerging from the brain stem with the facial nerve which, by way of the greater superficial petrosal nerve, reaches the trigeminal ganglion. There the fibers are distributed to each of the divisions of the fifth nerve; in addition, a moderate number of vasodilator fibers also appear to leave the brain stem directly with the trigeminal nerve. Vasodilator effects were elicited by stereotaxic stimulation of the facial and trigeminal nuclei in the brain stem. There is, therefore, a dual vasomotor control of the facial cutaneous vascular bed; the classical sympathetic vasoconstrictor system of the face is complemented by a vasodilator system capable of producing changes of equal but opposite amplitude in vessel caliber.
Soft-sensors assist in solving the problem created by the unavailability of a sensor by providing... more Soft-sensors assist in solving the problem created by the unavailability of a sensor by providing a software backup for it, thus allowing a reduction of losses in plant performance. Similarly, the use of a soft sensor to estimate a plant variable for which no sensor is installed can improve plant performance. The core of a soft-sensor is a partial plant model allowing the generation of a estimated measurement to replace missing measurements. Coupled with the model is a problem of signal estimation, interpolation and prediction. Modes considered here are black box models and gray models which include phenomenological knowledge. Also, comparisons are made concerning the requirements for soft-sensor models and for models used in model based control. An approach to an integrated view of the various soft-sensor modeling methods is attempted. Other aspects considered include use for interpolation and prediction of measurements having a sampling rate which is too low; performance of a control loop; performance of the soft-sensor indication in the period following the removal of the actual sensor, as plant characteristics change; complementary considerations for ensuring the availability of soft-sensors in industrial environments; and problems related to the use of soft-sensors in automatic control loops. A review made of a sample of the technical literature on applications as well as of research and development in this field, is commented in the text and summarized in a table
La intervención del Parlamento se justifica en razón de la competencia inicial que se le concede ... more La intervención del Parlamento se justifica en razón de la competencia inicial que se le concede para aprobar, enmendar o rechazar los presupuestos generales del Estado. Es lógico que al organismo que se otorga el poder de decisión sobre el presupuesto es además al que deben darse la facultad de control de la autorización concedida. 1 Esta facultas de control, es una facultas hipotética que ofrece muy pocas posibilidades de control efectivo, ya que el examen que realiza es a posteriori de las cuentas ya aprobadas por los órganos competentes se justifica más por un respeto a la legalidad que por una efectividad en el funcionamiento de ese control.
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Papers by Guillermo González