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Showing papers by "University of Buenos Aires published in 1985"


Journal ArticleDOI
TL;DR: In this article, the authors extend earlier work by its authors on formal aspects of the processes of contracting a theory to eliminate a proposition and revising it to introduce a new proposition.
Abstract: This paper extends earlier work by its authors on formal aspects of the processes of contracting a theory to eliminate a proposition and revising a theory to introduce a proposition. In the course of the earlier work, Gardenfors developed general postulates of a more or less equational nature for such processes, whilst Alchourron and Makinson studied the particular case of contraction functions that are maximal, in the sense of yielding a maximal subset of the theory (or alternatively, of one of its axiomatic bases), that fails to imply the proposition being eliminated. In the present paper, the authors study a broader class, including contraction functions that may be less than maximal. Specifically, they investigate “partial meet contraction functions”, which are defined to yield the intersection of some nonempty family of maximal subsets of the theory that fail to imply the proposition being eliminated. Basic properties of these functions are established: it is shown in particular that they satisfy the Gardenfors postulates, and moreover that they are sufficiently general to provide a representation theorem for those postulates. Some special classes of partial meet contraction functions, notably those that are “relational” and “transitively relational”, are studied in detail, and their connections with certain “supplementary postulates” of Gardenfors investigated, with a further representation theorem established.

2,855 citations


Journal ArticleDOI
TL;DR: A notion of “safe contraction” of a set of propositions is defined, it is shown that it satisfies the Gärdenfors postulates for contraction and thus can be represented as a partial meet contraction, and its properties are studied both in general and under various natural constraints.
Abstract: This paper is concerned with formal aspects of the logic of theory change, and in particular with the process of shrinking or contracting a theory to eliminate a proposition. It continues work in the area by the authors and Peter Gardenfors. The paper defines a notion of “safe contraction” of a set of propositions, shows that it satisfies the Gardenfors postulates for contraction and thus can be represented as a partial meet contraction, and studies its properties both in general and under various natural constraints.

245 citations


Journal ArticleDOI
TL;DR: The results are in good agreement with current ideas on the mechanism of aerobic glucose fermentation by trypanosomatids, and suggest that, under the experimental conditions used, both T. cruzi and C. fasciculata used glucose perferentially over amino acids for growth.

193 citations


Journal ArticleDOI
TL;DR: Sister-chromatid exchanges (SCE) and chromosomal aberrations were studied in a population of floriculturists occupationally exposed to organophosphorus, carbamate and organochlorine pesticides and were not correlated with intoxication symptomatology.

111 citations


Journal ArticleDOI
TL;DR: Seven aristololactam alkaloids were isolated from Aristolochia argentina and five are reported for the first time.

86 citations


Journal ArticleDOI
TL;DR: It is suggested that the susceptibility of the nasal environment to hormonal and neural influences may account for the differences in perceived pungency between males and females.

64 citations


Journal ArticleDOI
08 Feb 1985-Science
TL;DR: The results support the threshold concept of the systemic toxicity of metals, and gamma-glutamyl transpeptidase is a useful and sensitive marker for preclinical effects of toxic metals.
Abstract: Phenylmercury absorbed through the skin from contaminated diapers affected urinary excretion in infants in Buenos Aires. The effects were reversible and quantitatively related to the concentration of urinary mercury. Excretion of gamma-glutamyl transpeptidase, an enzyme in the brush borders of renal tubular cells, increased in a dose-dependent manner when mercury excretion exceeded a "threshold" value. Urine volume also increased but at a higher threshold with respect to mercury. The results support the threshold concept of the systemic toxicity of metals. gamma-Glutamyl transpeptidase is a useful and sensitive marker for preclinical effects of toxic metals.

57 citations


Journal ArticleDOI
TL;DR: The liver of tumor-bearing animals is subjected, during the early phase after tumor implantation, to an oxidative stress with increased steady-state levels of peroxyl radicals, which are essentially responsible for the increased photoemission observed in vivo.

49 citations


Journal ArticleDOI
TL;DR: Clinically, papillary adenoma of the nipple typically occurred in a female patient as an erosion, ulceration, or mass that was sometimes accompanied by serous or bloody discharge from the nipple and was frequently misdiagnosed as Paget's disease.
Abstract: Fifteen cases of papillary adenoma (florid papillomatosis, erosive adenomatosis) of the nipple were compared with forty examples of syringadenoma papilliferum, twenty-four of hidradenoma papilliferum, and one hundred of breast carcinoma metastatic to skin. Clinically, papillary adenoma of the nipple typically occurred in a female patient as an erosion, ulceration, or mass that was sometimes accompanied by serous or bloody discharge from the nipple and was frequently misdiagnosed as Paget's disease. Histologically, there was usually a papillary and adenomatous growth in the corium that connected with the surface and showed a lining of apocrine type secretory epithelium, a sometimes plasmacytic stroma, and horn cysts in the upper corium. Papillary adenoma of the nipple is often histologically misinterpreted as syringadenoma papilliferum, hidradenoma papilliferum, or low-grade adenocarcinoma, but it has received almost no attention in the dermatology literature.

49 citations


Journal ArticleDOI
TL;DR: In this article, a simple exponential model relating the number of rhizome sprouts m−2 to accumulated thermal units, calculated as the sum of the daily mean air temperatures above 15°C, provided a good estimate of cumulative shoot emergence populations (r2= 0·93) over all sampling dates between June and January.
Abstract: Summary The dynamics of Sorghum helpense (L.) Pers. rhizome sprout emergence was followed in three different crop systems. A simple exponential model relating the number of rhizome sprouts m−2 to accumulated thermal units, calculated as the sum of the daily mean air temperatures above 15°C, provided a good estimate of cumulative shoot emergence populations (r2= 0·93) over all sampling dates between June and January. A good description of the dynamics of shoot emergence in an independent experiment was obtained from the model. The possible influence of the crop structure and soil water supply in relation to the model fitness is discussed. Rasuma Prediction de l'emission de pousses par les rhizomes de Sorghum halepense (L.) Pers. en fonction de la temperature atmospherique La dynamique de l'emission de pousses par les rhizomes de Sorghum halepense (L.) Pers. a eteetudiee dans trois systemes de culture differents. Un simple modele exponentiel qui relie le nombre de pousses m−2 aux unites thermiques accumulees, c'est-a-dire le total des temperatures atmosphŕiques quotidiennes moyennes qui depassaient 15°C, a fourni une evaluation assez juste des peuplements globaux de pousses (r2= 0,93) sur toutes les dates d'echantillonnage entre les mois de juin et janvier. Dans une experimentation autonome, le modele a fourni une bonne description de la dynamique d'emergence des pousses. La discussion porte sur les possibilites d'influence de la structure de la culture et de l'hydrographie du sol par rapport au modele. Zusammenfassung Prognose der Austriebsdynamik von Sorghum halepense (L.) Pers. in Beziehung zur Lufttemperatur In drei Kulturen wurde die Dynamik des Austreibens der Rhizome von Sorghum halepense (L.) Pers. untersucht. Ein einfaches Exponentialmodel, basierend auf der Beziehung zwischen der Anzahl Austriebe pro m2 und den kumulierten Temperatureinheiten (berechnet als Summe der taglichen Temperaturmittelwerte uber 15°C) ergab eine gute Schatzung der kumulierten Austriebsdichten bei allen Auswertungsdaten zwischen Juni und Januar. In einem unabhangigen Versuch wurde eine gute Uebereinstimmung der Dynamik der Triebentwiuklung mit dem Modell festgestellt. Ein moglicher Einfluss von Bodenstruktur und verfugbarem Bodenwasser in Bezug auf die Zuverlassigkeit des Modells wird diskutiert.

46 citations


Journal ArticleDOI
TL;DR: The 30 MJ superconducting magnetic energy storage (SMES) system was installed in the Bonneville Power Administration (BPA) Tacoma Substation in 1982-83 as mentioned in this paper.
Abstract: The 30 MJ superconducting magnetic energy storage (SMES) system was installed in the Bonneville Power Administration (BPA) Tacoma Substation in 1982-83. Operation of the unit since that time has been for over 1200 hours. Specific tests to explore the SMES system's thermal and electrical characteristics and the control functions were conducted. The coil heat load with current modulation was determined. A converter with two 6-pulse bridges interfaces the superconducting coil to the power bus. Equal bridge voltage amplitude and constant reactive power modes of operation of the system were run with computer control of the SCR bridge firing angles. Coil energy dump tests were performed. Electrical grid system response to SMES modulation was observed, and full power SMES modulation was undertaken.


Journal ArticleDOI
01 Sep 1985-Chest
TL;DR: The discovery in this case of an estrogen receptor represents important evidence for establishing an association between tuberous sclerosis and lymphangiomyomatosis.

Journal ArticleDOI
TL;DR: Oral and maxillofacial surgeons should be aware of this unusual presentation of myxoma of the jaws so that a misdiagnosis of malignant bone tumor is not made.

Journal ArticleDOI
TL;DR: In the light of present data, dogs must be considered as the major donors of parasites to vector bugs and thus, principal contributors to transmission in this region of Argentina.
Abstract: Trypanosoma cruzi prevalence rates of human, dog and cat populations from 47 households of 3 rural localities of the phytogeographical Chaquena area of Argentina were determined both by serological and xenodiagnostic procedures Human prevalence rates were uniform and ranged from 496 to 587% Overall prevalence rate in dogs (750%) was significantly higher than in humans (510%) The overall proportion of parasitemic individuals assessed by xenodiagnosis was significantly higher in either dog (642%) or cat (636%) populations than among humans (125%) Although both the average number of resident as well as infected individuals per household was higher for people than for dogs (65 vs 33, and 34 vs 24, respectively), the reverse was recorded when parasitemic individuals were considered (10 vs 21) Results are discussed in relation to dog between dogs and people, and dogs and bugs In the light of present data, dogs must be considered as the major donors of parasites to vector bugs and thus, principal contributors to transmission in this region of Argentina

Journal ArticleDOI
TL;DR: In this paper, the number of reinforcement trials and reinforcement pairings per session were equated across two factorial group sets and all groups were trained for a fixed total number of acquisition trials (192).

Journal ArticleDOI
TL;DR: It is suggested that fertilization is not strictly species-specific, at least among the species the authors studied, but that there are some factors that reduce the efficiency of interspecific fertilization.
Abstract: Cross fertilization was tested between oocytes of Calomys callidus and spermatozoa from C. callidus, C. musculinus and C. laucha by both in vivo and in vitro insemination. After in vivo and in vitro insemination, respectively, percentages of oocytes fertilized were 68.8 and 46.6 (C. callidus X C. callidus), 20.3 and 12.7 (C. callidus X C. musculinus), 26.7 and 4.3 (C. callidus X C. laucha). Thus, the percentages obtained after in vitro insemination were always lower than those obtained with in vivo insemination. It was found that 23.9% and 44.4% of two-cell hybrid embryos were present in oviducts 30 hr after in vivo insemination of C. callidus females with C. musculinus or C. laucha spermatozoa, respectively. At a later stage (56 hr postinsemination), development did not progress further, and abnormal embryos were found both at 30 and 56 hr postinsemination, suggesting some kind of cleavage arrest or degeneration of the embryos. We suggest that fertilization is not strictly species-specific, at least among the species we studied, but that there are some factors that reduce the efficiency of interspecific fertilization.

Journal ArticleDOI
TL;DR: In this paper, the 13C resonances of the hydrate, keto and enol forms of oxaloacetic acid in aqueous solutions at low pH, at pH 4.3 and at pH 7.3 were assigned on the basis of the J(CH) values and the chemical shifts of reference compounds.
Abstract: The 13C resonances of the hydrate, keto and enol forms of oxaloacetic acid in aqueous solutions at low pH, at pH 4.3 and at pH 7.3 were assigned on the basis of the J(CH) values and the chemical shifts of reference compounds. At low pH the hydrate form predominated, while only small amounts of the keto and enol forms were detected. At pH 4.3 and 7.3 the keto form was the major form. In anhydrous dimethyl sulphoxide solution only the keto and enol forms were detected, whereas on addition of water the hydrate form became predominant. On prolonged recording of the spectra at the probe temperature (30°C) citroylformic acid was formed either at low pH or at pH 7–12, whereas only traces of pyruvic acid were detected. The aldol condensation product of oxalacetic acid was detected when the spectra were recorded at 7°C before its decarboxylation to citroylformic acid. In the spectra recorded at pH 3–7 pyruvic acid and its aldol condensation product, 4-hydroxy-4-methyl-2-ketoglutaric acid, were detected together with citroylformic acid. A complete assignment of the 13C resonances of these derivatives was made.

Journal ArticleDOI
TL;DR: Kinetoplast DNA from Trypanosoma cruzi epimastigotes pretreated with the trypanocidal drugs nifurtimox or benznidazole showed an increased number of strand-breaks, as revealed by trapping of alkali-denatured kDNA by nitrocellulose filters and electrophoresis in an alkaline 2% agarose gel.

Journal ArticleDOI
TL;DR: In this paper, the authors consider the problem of defining a reduced number of new variables or indicators which summarize the information contained in the set of original variables, and generalize the method of principal components by allowing for nonlinear relationships between the new indicators and the original variables.
Abstract: Suppose that several variables are defined for each element of a population. Here we consider the problem of defining a reduced number of new variables or indicators which summarize the information contained in the set of original variables. One way of dealing with this problem is through the method of principal components. This method, in its original version (Hotelling, 1933), consists of finding the linear combinations of the original variables with maximum variances. Rao (1964) and Darroch (1965) showed that the principal components may be interpreted in terms of recovering the information contained in the original variables through linear functions. In this paper we generalize the method of principal components by allowing for nonlinear relationships between the new indicators and the original variables. Henry and Lazarsfeld (1968, Chap. 8) and McDonald (1962, 1967) have also considered models where the relationship between factors and variables is nonlinear. The models considered in these works assume the structural hypothesis that the errors are independent of the factors, and may therefore be considered models of factor analysis. The present approach, on the contrary, is "data analytic", and there is no necessity to assume any a priori structure. Another approach to nonlinear components was suggested by Gnanadesikan (1977). However, this latter approach is useful primarily for adjusting hypersurfaces (surfaces of maximum dimension) to a set of data, while we are here concerned with adjusting curves (surfaces of dimension 1), or surfaces of small dimension.

Journal ArticleDOI
TL;DR: The levels of free porphyrins was low and the level of Heme-S, measured using protoporphyrin as substrate, was twice as high in symbiote-containing than in aposymbiotic C. deanei.

Journal ArticleDOI
TL;DR: Investigation of several mechanisms for the cytotoxic action of tingenone pointed to the interaction with DNA as the most likely factor involved.
Abstract: Tingenone and horminone, two natural quinonoid substances, inhibited the in vitro growth of Trypanosoma cruzi, 30 microM drug concentration producing total inhibition of growth. Tingenone inhibited total uptake and incorporation of [3H]thymidine, [3H]uridine, L-[3H]leucine into parasite macromolecules. Other quinonoids assayed were either less effective (abruquinone A) or even quite inactive (visminone B and ferruginin B). Investigation of several mechanisms for the cytotoxic action of tingenone pointed to the interaction with DNA as the most likely factor involved. Tingenone also inhibited the growth of Crithidia fasciculata, but the drug was significantly less active on this organism than on T. cruzi.


Journal ArticleDOI
TL;DR: Multifocal damage of the testis was induced in 70% of the rats injected with an antiserum against a non-collagenous fraction (D-STBM) obtained from a preparation enriched in basement membranes of seminiferous tubules.


Journal ArticleDOI
TL;DR: In this article, a rapida exposition sobre arqueologia regional que voy a dar en estas paginas and de acuerdo con lo que me solicita Patty Jo Watson, con motivo del cincuentenario de American Antiquity, is the producto of un tanto personal, el testimonio bastante directo de alguien que vivio en esta zona durante ese medio siglo practicando la arqueology de campaiia mas o menos permanentemente and dentro
Abstract: 1. En disciplinas cientificas jovenes medio siglo de existencia es un largo lapso. En la primera etapa de la vida de un ser humano, este mismo periodo de tiempo es el mas importante de toda la existencia, ya que incluye los anos de mayores posibilidades creadoras y las mas profundas vivencias existenciales. Una historia de los ultimos cincuenta anos de la arqueologia del Noroeste Argentino, deberia ser, como en la historia de cualquier ciencia, un relato cronologico, analitico y valorativo de sus avances tecnicos, de los diferentes marcos teoricos y categorias utilizadas dentro del panorama cambiante de la sociedad que le dio origen. Ninguna ciencia puede desgajarse del contexto sociopolitico, economico e ideologico en que se desarrolla y transcurre su historia. Asi, la arqueologia andina de los ultimos cincuenta anos, si bien manteniendo cierta unidad general de desarrollo, muestra bastantes diferencias en cada uno de los paises y es bastante distinta del desarrollo historico de la arqueologia de otras naciones como Mexico o Estados Unidos. Entender, y mas aun explicar esa historia requiere el conocimiento historico integral, socio-economico y cultural de los paises respectivos, su desarrollo y la cosmovision de sus pueblos. Pero por otro lado, tampoco puede tomarse la historia de cada pais aisladamente. Hay un contexto universal, dentro del cual, y en mayor o menor grado, todas las naciones inscriben su propio acontecer individual. La rapida exposition sobre arqueologia regional que voy a dar en estas paginas y de acuerdo con lo que me solicita Patty Jo Watson, con motivo del cincuentenario de American Antiquity, es el producto de un punto de vista un tanto personal, el testimonio bastante directo de alguien que vivio en esta zona durante ese medio siglo practicando la arqueologia de campaiia mas o menos permanentemente y dentro de lo que las circunstancias se lo permitieron. Es muy probable que este testimonio sea un tanto partial, ya que nuestra perspectiva surge de la experiencia habida en una region periferica del gran centra nuclear andino. De cualquier manera la historia es mas objetiva y valedera cuanto mas testimonios se acumulan. Desde un punto de vista general los que hemos envejecido a lo largo de estos ultimos cincuenta anos, hemos sido testigos de la mas grande revolution tecnologica creada por la humanidad desde el descubrimiento del fuego. Esta revolution no solo ha cambiado a nuestra sociedad sino que ha incidido en todas las disciplinas cientificas, arqueologia incluida. En este lapso de cincuenta anos los medios de comunicacion han adquirido el mas extraordinario desarrollo. De la modesta radio de galena primero y de grandes tubos auriculares con tableros de comando con medio metro de Haves despues, hemos llegado a los modernos aparatos de transitores, compactos, de alcance universal. La television pone ante nuestros ojos sucesos acaecidos en las antipodas, al mismo tiempo que nos adocena hasta la idiocia. En transporte ha habido una revolution paralela. De los modestos aviones provistos de motor a explosion y helice (palas) se ha llegado a los aviones de propulsion (jets) capaces de velocidades inauditas con el consiguiente acortamiento de distancias. En el comienzo de la etapa considerada era muy dificil pensar desde Buenos Aires

Journal ArticleDOI
TL;DR: In this article, a new high-spin level scheme, comprising several rotational bands, was presented, and the positive-parity ΔI = 2 ground state band was possibly the first example of a hitherto unreported scheme called double decoupling associated with a proton and neutron both occupying Ω = 1 2 orbits of decoupled parameters larger than unity.

Journal ArticleDOI
TL;DR: The results suggest that ethanol increases prolactin secretion because it decreases the release of dopamine by the hypothalamus, probably because it antagonizes the inhibitory action of opioids on dopaminergic neurons.
Abstract: We investigated the effect of naloxone on the concentration of dopamine in the hypothalamus and on the concentration of prolactin in serum and anterior pituitary of male rats acutely treated with ethanol. Acute ethanol administration increased serum prolactin levels and hypothalamic dopamine concentration. Pituitary prolactin was not modified by this treatment. Naloxone administered 15 min before the animals were sacrificed decreased serum prolactin levels and hypothalamic dopamine concentration in ethanol-treated rats. These results suggest that ethanol increases prolactin secretion because it decreases the release of dopamine by the hypothalamus. Naloxone decreases prolactin release probably because it antagonizes the inhibitory action of opioids on dopaminergic neurons.

Journal ArticleDOI
TL;DR: Estradiol-17 beta acting in vitro inhibited [3H]imipramine binding in control membranes of striatum, hippocampus and hypothalamus, but not in the same regions from ovariectomized rats.

Journal ArticleDOI
TL;DR: The effect of the intraperitoneal administration of ethanol on [3H]GABA binding and glutamic acid decarboxylase in cerebellum and hypothalamus was investigated and changes in GABA binding may be involved in some of the neuropharmacological effects of ethanol.