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Showing papers by "National University of Comahue published in 1994"


Journal ArticleDOI
TL;DR: The structure of the wing and pectoral girdle of Neuquenornis indicates that it was an active flyer, an aptitude also inferred for the El Brete enantiornithines from the Upper Cretaceous Lecho Formation of northwestern Argentina.
Abstract: A new genus and species of Late Cretaceous (Coniancian–Santonian) birds, Neuquenornis volans, is described. This new taxon is known from a fairly complete, articulated specimen from the Rio Colorado Formation of northwestern Patagonia. Synapomorphies of the humerus, radius, ulna, coracoid, femur, tibiotarsus, tarsometatarsus, and thoracic vertebrae, support its allocation to the Enantiornithes. The tarsometatarsal structure of Neuquenornis refers it to the Late Cretaceous family Avisauridae. The structure of the wing and pectoral girdle of Neuquenornis indicates that it was an active flyer, an aptitude also inferred for the El Brete enantiornithines from the Upper Cretaceous Lecho Formation of northwestern Argentina. The pedal structure of Neuquenornis and Soroavisaurus from El Brete, indicates that avisaurids were capable of perching in trees.

135 citations


Journal ArticleDOI
TL;DR: In this article, three plots were established in natural forests in the Parque Nacional Nahuel Huapi (Argentina). Each tree was labelled and surveyed for visual symptoms and maps of each plot were constructed.

31 citations


Journal ArticleDOI
TL;DR: A comparative study of parathion susceptibility on early embryonic and larval stages of the Argentinian toad is dealt with.
Abstract: Received: 31 March 1993/Accepted: 24 October 1993 Parathion (O,O-diethyl O-p-nitrophenyl phosphorothioate) is a widely used agricultural insecticide highly toxic to mammals; however, very little is known about the detoxication capacity in some natural enemies of insects such as amphibians (Harriet al 1979; Llamas et al. 1985; Caballero de Castro et al 1991; Gauna et al. 1991). The biota may be stressed by discharges of pesticides, and it is therefore essential to know its potential effect on non-target organisms before irreversible change occurs. Some monitoring techniques use amphibian larvae as an useful indicator for aquatic contamination (Dumpert and Zeitz 1984; Beiswenger 1988; Williams et al. 1989). An ideal insecticide should be efficacious against pest species, but relatively safe for non-target organisms. To develop selective insecticides it is important to understand the differences and similarities of the defense systems between insects and the beneficial fauna such as predators and parasitoids. Thus, this report deals with a comparative study of parathion susceptibility on early embryonic and larval stages of the Argentinian toad

22 citations


Journal ArticleDOI
30 Jun 1994-Bosque
TL;DR: N. desantisi was found, for the first time, as a new species in the lower valley of Rio Chubut, Argentina, in 1980/81 and showed an extensive and fast spread in this country (3.000 km in 9-10 years).
Abstract: N. desantisi was found, for the first time, as a new species in the lower valley of Rio Chubut, Argentina, in 1980/ 81. It showed an extensive and fast spread in this country (3.000 km in 9-10 years). It was detected in Santiago de Chile in 1983/84. It causes intensive defoliations and loss of trees in Salix sp., and it also damages Populus sp., very important trees in Patagonia. Consequently it was decided to study its bioecology in Rio Negro and Neuquen. The results indicate that, at present, it is found in the whole basin of the rio Negro. The following aspects are described: date of beginning the oviposition, date of starting in diapause, oviposition and morphology of egg, larvae, pupae and imago. It has 4-5 generations/year, and these are overlapped. Three new parasitoids were found which were classified by De Santis: Pteromalidae sp., Isdromas gigantii sp. nov. (Ichneumonidae) and Cirrospilus gracielae sp. nov. (Eulophidae). The following species are mentioned as new hosts: Salix alba, S. elegantissima, S. matsudana and Populus alba.

16 citations


Journal ArticleDOI
TL;DR: It is concluded that neoplastic cells from NMU induced tumors express H2 histamine membrane receptors which are coupled to a transductional pathway different from cAMP production, which may be involved in the regulation of tumor growth.

9 citations


Journal ArticleDOI
TL;DR: In this article, the appropriate combination of identification methods and input signal excitation is given in order to get a minimal measurement time in electrochemical impednace spectroscopy, and the necessary tools to design the experiment using commercially available equipment or by programming multipurpose digital equipment.

9 citations


Journal ArticleDOI
TL;DR: Non-equatorial free-ranging cervids exhibit a seasonal reproductive strategy which is synchronous with the yearly growth pattern of plants, and Behavioral and physiological adaptations in cervids result in lipid deposition in autumn and lipid mobilization in winter.
Abstract: Nichtaquatoriale freilebende Cerviden besitzen eine saisonale Reproduktionsstrategie, die dem jahrlichen Pflanzenwachstum angepast ist. Es bestehen Verhaltensweisen und physiologische Adaptionen, die zur Fettdeponierung im Herbst und zum Fettabbau im Winter fuhren. Diese Fettdeponierung bestimmt zum grosten Teil das Korpergewicht der weiblichen Stucke. Unter allen nichtaquatorialen Cerviden besteht eine starke Korrelation zwischen Korpergewicht, Ovulationsrate und Zeitpunkt des Ostrus, die aber bei Anwendung von Fettmasse statt Korpergewicht noch besser ausfallt. Die Tatsache, das Ernahrung durch Beeinflussung der Fettmasse und daher des Korpergewichtes der hauptsachliche Modulator der Reproduktion ist, ist gut dokumentiert. Hingegen wird in der Literatur ausschlieslich das Korpergewicht als ausschlaggebender Faktor betrachtet. Anhand von Erkenntnissen in der Humanmedizin schlage ich eine Hypothese vor, die einen biochemischen Mechanismus beschreibt. Fettgewebe sind metabolisch sehr aktiv und aromatisierten u. a. Androgen zu Estrogen. Der Zeitpunkt der Ovulation wird indirekt durch die Blutkonzentration von Estrogen bestimmt, indem es die fur die Ovulation benotigte Welle der Hormone LH und FSH auslost. Es ist deshalb moglich, das die Blutkonzentration von endogenem Estrogen durch Fettmetabolismus so erhoht wird, bis Ovulation erfolgt. Der Beitrag von Estrogen durch Fettmetabolismus ist etwa 30% in premenopausalen und 100% in post-menopausalen Frauen. Die Fettmasse ist naturlich proportional zum Beitrag von Estrogen. Um in Cerviden hohe Reproduktionsraten zu erzielen, ist es eine Voraussetzung, das die weibliche Population mit einer entsprechenden Futterqualitat und Habitatsstruktur versehen werden, so das optimale Fettreserven wahrend des Spatsommers und Herbstes angelegt werden konnen.

7 citations


Journal ArticleDOI
TL;DR: The dynamics of planktonic rotifer in Laguna Ezquerra (Rio Negro, Argentina) was studied from October 1988 to March 1989, in relation to food resources and cladoceran populations and total rotifer density differed markedly.
Abstract: The dynamics of planktonic rotifer in Laguna Ezquerra (Rio Negro, Argentina) was studied from October 1988 to March 1989, in relation to food resources and cladoceran populations. During the spring and summer period, total rotifer density differed markedly. In spring rotifer populations remained at low density and an inverse relationship with cladoceran biomass was found. In contrast, in summer, the rotifer densities increased greatly and a positive relationship with cladoceran biomass was observed. Food resources decreased during mid January and this seemed to give rotifers a competitive advantage over cladocerans. Bosmina longirostris and Ceriodaphnia dubia were both present during the spring, but only Bosmina prevailed in summer. The composition of cladoceran assemblages together with food resources seem to be an important factor in rotifer dynamics.

7 citations


Journal ArticleDOI
TL;DR: In this article, the surface tension of dimethylsulfoxide (1) + thiophene (2) was determined over the whole composition range at 298.15 K. The densities have been determined with a vibrating tube densimeter and the surface tensions by the differential capillary rise technique.
Abstract: Densities and surface tensions of dimethylsulfoxide (1) + thiophene (2) were determined over the whole composition range at 298.15 K. The densities have been determined with a vibrating tube densimeter and the surface tensions by the differential capillary rise technique. Negative excess surface tensions were observed. From the different equations existing in the literature for estimation of surface tensions of mixtures we have used the equations due to Rice and Teja [1] and Winterfeld, Scriven and Davis [2]. The Rice and Teja's Equation gives better results.

6 citations


Journal Article
TL;DR: The records of Oncorhynchus mykiss, Galaxias platei, Patagonia hatcheri and Percichtys trucha extend the number of known hosts for D. chilensis and add new localities, thus extending the distributions of the mollusc.
Abstract: The presence of glochidia of Diplodon chilensis Haas 1931 (Mollusca, Pelecypoda) has been reported in gills of wild freshwater fish in the Argentinian Patagonia. Death occurrences due to glochidiasis have not been observed either in wild fish or in cultured fish. The records of Oncorhynchus mykiss, Galaxias platei, Patagonia hatcheri and Percichtys trucha extend the number of known hosts for D. chilensis and add new localities, thus extending the distributions of the mollusc.

5 citations


Journal ArticleDOI
TL;DR: The preliminary world list of threatened conifer taxa by Farjon et al. (1993) summarizes the knowledge on the conservation status of many valuable tree species, and it is suggested that the following species be included in that list.
Abstract: The preliminary world list of threatened conifer taxa by Farjon et al. (1993) summarizes the knowledge on the conservation status of many valuable tree species. Some of the species are found only in the Southern Hemisphere and for many of them little is known beyond their scientific name. This is particularly true for the conifer taxa of temperate forests of southern South America for which the list was incomplete. Before describing these species, let me give some general background on these forests that cover both eastern and western slopes of the southern Andes. South of 35°S approximately, there is found one of the steepest precipitation gradients of the world, ranging from over 5000 mm on the western to 200 mm on the eastern slopes of the Andes (De Fina, 1972). This leads to a dramatic shift in vegetation composition, from temperate rainforest in Chile to xeric steppe in northern Patagonia (Argentina). This temperate forest is dominated by tree species of the genus Nothofagus (southern beech) and several conifer species which in general have restricted geographical ranges. Conifers in southern South America belong to three different families: Araucariaceae, Cupressaceae, and Podocarpaceae. Given the absence of most of the species of the latter family in the threatened conifer world list, I suggest the following species be included in that list:

Journal ArticleDOI
TL;DR: In this article, a generalized model for a two-dimensional situation is presented which permits a better representation of the phenomena that occur in a test involving crack growth and large displacements, and the use of a twodimensional factor, that corrects the measured displacements by converting them into ones that would be measured under a one-dimensional hypothesis, is proposed.
Abstract: — Several experimental techniques used in fracture toughness tests are based on the “Plastic hinge” model that permits different fracture mechanics parameters to be determined. This model is only valid under the following conditions: small displacements, small stable crack growth, and small distances between knife edges and the apparent centre of rotation. A generalized model for a two-dimensional situation is presented which permits a better representation of the phenomena that occur in a test involving crack growth and large displacements. The use of a two-dimensional factor, that corrects the measured displacements by converting them into ones that would be measured under a one-dimensional hypothesis, is proposed. In this way the same methodology used for CTOD determination, may again be used.

Journal ArticleDOI
TL;DR: As a result of a study of coprophilous pyrenomycetes s.

Journal ArticleDOI
TL;DR: The acanthocephalan Pomphorhynchus patagonicus was found in 3 species of fish in the Alicura Reservoir (Patagonia, Argentina) and no mature eggs were found in O. mykiss; this, together with the parasite's low growth rate, underlines the hypothesis that this species is not a suitable host for P. patagonica.
Abstract: The acanthocephalan Pomphorhynchus patagonicus was found in 3 species of fish in the Alicura Reservoir (Patagonia, Argentina). These included Oncorhynchus mykiss, Patagonina hatcheri, and Percichthys trucha. Prevalence, intensity, size of the parasites, and percentage of gravid females were analyzed. The relatively low prevalence and intensity were probably due to the low consumption of the intermediate host, Hyalella patagonica. The highest values of intensity, length, and percentage of gravid females were found in Percichthys trucha. This species is considered to be the preferred host of P. patagonicus in the reservoir. No mature eggs were found in O. mykiss; this, together with the parasite's low growth rate, underlines the hypothesis that this species is not a suitable host for P. patagonicus.

01 Jan 1994
TL;DR: In the region of Neuquen, la population of paysans chiliens trouverent une solution a ces problemes a travers l'emigration as mentioned in this paper, a region proche de leur terre d'origine and permettant une communication relativement aisee avec elle, pourvu des terres fiscales en abondances and ou l'implantation de l'appareil etatique.
Abstract: Devant l'impossibilite d'acceder a la terre, soumis a diverse formes d'exploitation et incapables d'articuler des ripostes politiques a cette situation, les paysans chiliens trouverent une solution a ces problemes a travers l'emigration. Le territoire de Neuquen, proche de leur terre d'origine et permettant une communication relativement aisee avec elle, pourvu des terres fiscales en abondances et ou l'implantation de l'appareil etatique etait faible, fut percu comme un lieu attractif pour recreer une vie rurale, et des miliers de paysans chiliens s'y installerent. Cette region fut « chilenisee » du point de vue de la production et de la circulation materielle et symbolique. Cette situation provoqua l'apparition d'une serie de prejuges de la part de ceux qui se sentirent leser dans leurs interets par la presence chilienne ou par les partisants de la « patrie ». Ces memes « patriotes » emirent un discours sur l'« argentinisation » de la population patagonique a travers une serie de strategies, parmi lesquelles s'est distinguer l'education, comme methode de soumission de l'« autre » en un « moi patriote »