Showing papers by "University of the Algarve published in 1992"

Photosynthetic capacity of leaves of Eucalyptus globulus (Labill.) growing in the field with different nutrient and water supplies.

Abstract: The effects of water and nutrient availability on photosynthetic capacity of juvenile and adult leaves of Eucalyptus globulus Labill. seedlings were evaluated by measuring oxygen evolution at light and CO(2) saturation. Seedlings supplied with near optimal amounts of water and nutrients had higher growth rates than non-irrigated, unfertilized control seedlings, but photosynthetic capacity was similar in both treatments. Differences in foliar nitrogen concentrations between the two treatments were minor, which largely explains why the growth response to near optimal nutrition was not associated with an increase in photosynthetic capacity per unit leaf area. Nevertheless, the photosynthetic capacity of juvenile leaves decreased from distal to proximal positions in the mid-crown and was positively correlated with leaf nitrogen concentration expressed on a leaf surface area basis. During the dry season, non-irrigated, unfertilized seedlings fixed carbon at lower rates than irrigated seedlings supplied with near optimal nutrition because of stomatal closure even though photosynthetic capacity was unaffected by water deficits. In both treatments, there were differences between the photosynthetic capacity of adult and juvenile leaves that were largely explained by the low specific leaf area of adult leaves.

Immunocytochemistry of somatotrophs, gonadotrophs, prolactin and adrenocorticotropin cells in larval sea bream (Sparus auratus) pituitaries.

Abstract: The chronological appearance of endocrine cells in the pituitary of sea-bream (Sparus auratus) larvae was studied using antisera against salmon prolactin, trout growth hormone, salmon gonadotropin and N-terminal human adrenocorticotropin. The larval pituitary (1–12 days after hatching) was oval in shape and was composed of a dense mass of cells with few neurohypophysial fibres. By 60 days after hatching it began to resemble the adult and was divisible into a distinct rostral pars distalis containing prolactin and adrenocorticotropin cells; a proximal pars distalis containing somatotrophs and gonadotrophs and a pars intermedia. Cells immunoreactive with antisera against growth hormone were observed immediately after hatching (2 days post-fertilization). Weakly staining prolactin cells were observed 2 days later in the region corresponding to the rostral pars distalis. Cells immunoreactive with anti-gonadotropin and anti-adrenocorticotropin sera were observed in the pituitary 6 and 8 days after hatching, respectively. All the cell-types studied were immunoreactive from the time they were first identified until the final samples 90 days after hatching.

A Methodology for Obtaining Information On the Age Structure and Growth Rates of the Norway Lobster, Nephrops Nor Vegicus (L.) (Decapoda, Nephropoidea)

Abstract: [Ce travail decrit une methodologie qui peut etre utilisee pour evaluer la structure d'âge d'une population de langoustines, l'espece etudiee etant Nephrops norvegicus (Linne, 1758). La croissance de la langoustine est consideree comme le resultat de deux facteurs differents, l'accroissement a la mue et la periode d'intermue. Ces deux aspects de la croissance sont modeles separement, et tous deux sont consideres en fonction de la longueur de la carapace. Des estimations sont requises pour les parametres des modeles et pour la variabilite des variables dependantes. Le modele exprimant la periode d'intermue comme une fonction de la longueur de carapace a ete considere comme exponentiel, suivant Kurata (1962) et l'information applicable a Nephrops. L'accroissement a la mue a ete presume etre une fonction lineaire de la longueur de carapace, suivant Hiatt (1948). Ces presomptions ont ete appuyees par plusieurs etudes sur Nephrops norvegicus en captivite (Thomas, 1965; Hillis, 1971; Figueiredo, 1975, 1989; Charuau, 1977; Sarda, 1983, 1985). Des simulations de la croissance ont ete faites pour 100 individus. Les donnees fournissent des informations sur les taux de croissance et sur les longueurs moyennes attendues suivant l'âge. Si on le desire, une courbe de croissance peut etre etablie d'apres ces donnees, comme suggere par Caddy (1987). Un travail de cette nature peut aussi etre utilise comme guide dans l'analyse des frequences de longueurs de Nephrops et dans la construction de clefs âge-longueur., Ce travail decrit une methodologie qui peut etre utilisee pour evaluer la structure d'âge d'une population de langoustines, l'espece etudiee etant Nephrops norvegicus (Linne, 1758). La croissance de la langoustine est consideree comme le resultat de deux facteurs differents, l'accroissement a la mue et la periode d'intermue. Ces deux aspects de la croissance sont modeles separement, et tous deux sont consideres en fonction de la longueur de la carapace. Des estimations sont requises pour les parametres des modeles et pour la variabilite des variables dependantes. Le modele exprimant la periode d'intermue comme une fonction de la longueur de carapace a ete considere comme exponentiel, suivant Kurata (1962) et l'information applicable a Nephrops. L'accroissement a la mue a ete presume etre une fonction lineaire de la longueur de carapace, suivant Hiatt (1948). Ces presomptions ont ete appuyees par plusieurs etudes sur Nephrops norvegicus en captivite (Thomas, 1965; Hillis, 1971; Figueiredo, 1975, 1989; Charuau, 1977; Sarda, 1983, 1985). Des simulations de la croissance ont ete faites pour 100 individus. Les donnees fournissent des informations sur les taux de croissance et sur les longueurs moyennes attendues suivant l'âge. Si on le desire, une courbe de croissance peut etre etablie d'apres ces donnees, comme suggere par Caddy (1987). Un travail de cette nature peut aussi etre utilise comme guide dans l'analyse des frequences de longueurs de Nephrops et dans la construction de clefs âge-longueur.]

Basis-Set algorithm for a generalized linear complementarity problem

Abstract: In this paper, the authors develop a new direct method for the solution of a BLCP, that is, a linear complementarity problem (LCP) with upper bounds, when its matrix is a symmetric or an unsymmetricP-matrix. The convergence of the algorithm is established by extending Murty's principal pivoting method to an LCP which is equivalent to the BLCP. Computational experience with large-scale BLCPs shows that the basic-set method can solve efficiently large-scale BLCPs with a symmetric or an unsymmetricP-matrix.

Reconstructing the metric of space-time from Chern-Simons gravity with point sources

Abstract: We show that a metric theory of gravity in three dimensions arises naturally from Poincare Chern-Simons gravity, as a theory of the representation space of the Poincare group. In addition, we obtain exact solutions of the constraints of the Chern-Simons theory with an arbitrary number of isolated point sources in relative motion, and show show the space-time metric is reconstructed.

Cell suspension cultures ofOnonis natrix L. subspeciesramosissima: Establishment and culture conditions

Abstract: Explants from petioles, folioles or hypocotyls ofOnonis natrix have been used for calli initiation. Hypocotyls inoculated on MS medium supplemented with 2% sucrose and 0.5 mg.1−1 2,4-D / 1 mg.1−1 Kin showed to be the best primary explant. Cell suspension cultures were established in MS basal medium supplemented with 2% sucrose, 0.5 mg.1−1 NAA or 2,4-D and 1 mg.1−1 Kin. Different subculturing periods, inoculum density, hormonal supplementation and sucrose concentration were assayed in order to obtain the best culture growth conditions. The optimal conditions were achieved with cultures initiated with 40 g.1−1 of initial inoculum, growing in MS basal medium supplemented with 4% sucrose, 0.5 mg.1−1 NAA and 1 mg.1−1 Kin subcultured every twelve days. Under these experimental conditions, the cultures showed a doubling time of 36.3 hours.