Showing papers by "University of Los Andes published in 1986"
TL;DR: In this article, the electrical and thermal properties of CuInSe2 single crystals have been reviewed and in some cases, taking into account recently reported experimental values for the transport parameters, earlier results have been reexamined.
185 citations
TL;DR: In this article, a simple and rapid method is proposed for the determination of copper, zinc and iron in whole blood, where the injected sample is mineralized in the flow system on passage through a microwve oven and the metals are determined by atomic absorption spectrometry.
95 citations
TL;DR: In this article, the authors consider the Volterra-lotka equations for two competing species in which the right-hand sides are periodic in time and show that conditions recently given by K. Gopalsamy imply the existence of a periodic solution with positive components, also imply the uniqueness and asymptotic stability of the solution.
Abstract: We consider the Volterra-Lotka equations for two competing species in which the right-hand sides are periodic in time. Using topological degree, we show that conditions recently given by K. Gopalsamy, which imply the existence of a periodic solution with positive components, also imply the uniqueness and asymptotic stability of the solution. We also give optimal upper and lower bounds for the components of the solution.
94 citations
TL;DR: In this article, the stability of the emulsion is estimated from a dual criterion, i.e., from both oil and water phases settling, and the two criteria overlap and swap their respective meaning (coalescence vs clearing) in the three phase zone.
84 citations
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TL;DR: In this paper, the authors argue that the identification of distributive shares with sector or marginal factor productivity in value terms and, after deflating these values by prices, with physical productivity as well may lead to mistaken policies designed to foster or accelerate growth.
77 citations
TL;DR: In this paper, the first-order action for self-dual linearized massive gravity in D = 3 is given, and two master actions relevant for this spin-2 case are given, explaining the equivalence between the selfdual formulation and the topological massive one.
64 citations
TL;DR: In this paper, the authors present a map of emulsion inversion with nonionic surfactant systems, which is essentially similar to the general forxnulation-WOR phenomenology.
Abstract: The bidimensional Temperature-WOR map of emulsion inversion with nonionic surfactant systems is essentially similar to the general forxnulation-WOR phenomenology. This suggests that the temperature may be included in the deviation from optimum formulation for three-phase behavior, as well as emulsion inversion phenomena. At low ethylene oxide content, low surfactant concentration,and relatively high oil alkane carbon numbers, some distorsion
53 citations
TL;DR: In this article, a single crystal grown from stoichiometric melts was studied by differential thermal analysis, X-ray diffraction, optical absorption and photoluminescence measurements.
52 citations
TL;DR: A hypothetical functional relationship between the feeding area of the lateral hypothalamus and the medullary and pontine taste areas was assessed in rats and electrical stimulation of the hypothalamus had the same inhibitory or excitatory effect on a given gustatory neuron as the sapid stimulation ofThe tongue did.
50 citations
TL;DR: In this paper, the binding energy of the exciton and ionization energy of acceptors and donors were determined to be 18, 54, and 26 (ifmmode\pm/pm\else\textpm\fi{}0.01 eV, respectively.
Abstract: In this work we report on an optical absorption study near the band gap of n-type ${\mathrm{CuInSe}}_{2}$ at 7 K. From the analysis of the results the energy gap is found to be 1.02\ifmmode\pm\else\textpm\fi{}0.01 eV. The binding energy of the exciton and the ionization energy of acceptors and donors are determined to be 18, 54, and 26 (\ifmmode\pm\else\textpm\fi{}5) meV, respectively. It is suggested that ${\mathrm{In}}_{\mathrm{Cu}}$ antisite donors and ${V}_{\mathrm{Cu}}$ acceptors are the predominant active intrinsic defects in ``In-rich'' ${\mathrm{CuInSe}}_{2}$.
48 citations
TL;DR: When normal adult rats were allowed to choose among different ambient temperatures in a thermocline they selected temperatures about 224 degrees out of phase with their own intracranial temperature circadian oscillations, difficult to reconcile with the idea that circadian body temperature rhythm is due to a cyclical shift in the set point temperature.
TL;DR: In this article, lead is extracted from urine with ammonium pyrrolidien dithiocrbamate into methyl isobutyl ketone, and 20 μl of the extract is injected into a water carrier stream in a flow-injection/atomic absorption system.
TL;DR: The dependence of the bandgap in CuInSe 2 on temperature is explained by a model which takes into account the contribution of all the vibrational modes in the electron-phonon interaction as mentioned in this paper.
TL;DR: Use of radioactive molybdenum demonstrates that the tetrathionate reductase of Salmonella typhimurium is a molydenum containing enzyme and it is proposed that this enzyme shares with other molyBdo-proteins, such as nitrate reduct enzyme, a common moly bdenumcontaining cofactor the defect of which leads to the loss of the t Petrathionates reductases activities.
TL;DR: In this article, the cathodic reduction of styrene in acetonitrile and tetra-n-butylammonium tetrafluoroborate is discussed and a well defined voltammetric wave was obtained at Ep = −2.8 V and its study reveals irreversible electron transfer as the first step in the electrochemical reaction.
Journal Article•
TL;DR: In this paper, a parthenogenetische Zyklus is beschrieben und sexuelle Weibchen with prokutikulaerer Sklerotisierung vorgestellt, ueber das Auftreten von Maennchen und die Bildung von "Primitivephippien" with Wintereiern berichtet.
Abstract: Die vorliegende Studie ueber Cyclestheria hislopi (Baird, 1859) weist die Art fuer Kolumbien nach und traegt zur Kenntnis ihrer Naturgeschichte bei, wobei der Schwerpunkt auf die Lebenszyklen gelegt wird. Es wird der parthenogenetische Zyklus beschrieben und es werden sexuelle Weibchen mit prokutikulaerer Sklerotisierung vorgestellt sowie ueber das Auftreten von Maennchen und die Bildung von "Primitivephippien" mit Wintereiern berichtet. Es wird ausserdem ein unvollstaendiger Seitenzyklus erwaehnt mit Weibchen und Maennchen, die Hypoderrnissklerotisierung aufweisen. Die Weibchen dieses Zyklus koennen mit der Bildung schlupffaehiger parthenogenetischer Eier beginnen, gehen dann aber zur Bildung von Dauereiern ueber.
01 Jan 1986
TL;DR: In this article, the locus of inversion is plotted on a formulation-water/oil ratio (WOR) bidimensional diagram, which is divided into six regions with different emulsion characteristics.
Abstract: Provided that the system contains a reasonable amount of surfactant, the emulsion type essentially depends upon two factors: (1) the water/oil ratio (WOR), and (2) the physico-chemical formulation. The latter may involve such variables as surfactant type or HLB, oil nature (EACN), alcohol type and concentration, temperature, or any combination of these; it may be represented by a single generalized variable, i.e., the deviation from optimum formulation for three phase behavior. The locus of inversion is plotted on a formulation-WOR bidimensional diagram. Such a diagram shows that there exist two different inversion regimes. The first occurs for medium internal phase ratio systems, and is associated with optimum formulation. This kind of inversion is linked with a minimum in both emulsion stability and viscosity. The second kind occurs at high internal phase ratio and off-optimum formulation, and consists of two branches. In this second case of inversion, the stability exhibits a sudden change, while the viscosity passes through a maximum. The bidimensional formulation-WOR diagram is divided into six regions with different emulsion characteristics. Typical properties for each region and transition through boundaries are discussed.
TL;DR: In this article, the authors studied the behavior of ground-dwelling ground-squirrels and the evolution of sociality, including the limits of ground squirrel nepotism.
Abstract: MCLEAN, I. G., AND A. J. TOWNS. 1981. Differences in weight changes and the annual cycle of male and female Arctic ground squirrels. Arctic, 34: 249-254. MICHENER, G. R. 1979. Spatial relationships and social organization of adult Richardson's ground squirrels. Canadian J. Zool., 57:125-139. ? 1983. Kin identification, matriarchies, and the evolution of sociality in ground-dwelling sciurids. Pp. 528-572, in Recent advances in the study of mammalian behavior (J. F. Eisenberg and D. F. Kleiman, eds.). Spec. Publ., Amer. Soc. Mamm., 7:1-753. ? 1984. Age, sex, and species differences in the annual cycles of ground-dwelling sciurids: implications for sociality. Pp. 81-107, in Biology of ground-dwelling squirrels: annual cycles, behavioral ecology, and sociality (J. 0. Murie and G. R. Michener, eds.). University of Nebraska Press, Lincoln, 459 pp. MURIE, J. O., AND M. A. HARRIS. 1978. Territoriality and dominance in male Columbian ground squirrels (Spermophilus columbianus). Canadian J. Zool., 56:2402-2412. OWINGS, D. H., M. BORCHERT, AND R. VIRGINIA. 1977. The behaviour of California ground squirrels. Anim. Behav., 25:221-230. SHERMAN, P. W. 1980. The limits of ground squirrel nepotism. Pp. 504-544, in Sociobiology: beyond nature/nuture? (G. W. Barlow, and J. Silverberg, eds.). Westview Press, Boulder, Colorado, 627 pp. . 1981. Reproductive competition and infanticide in Belding's ground squirrels and other organisms. Pp. 311-331, in Natural selection and social behavior: recent research and new theory (R. D. Alexander and D. W. Tinkle, eds.). Chiron Press, New York, 532 pp. SILVERMAN, D. L. 1981. The behavioral ecology of the thirteen-lined ground squirrel (Spermophilus tridecemlineatus). Unpubl. M.S. thesis, Univ. Michigan, Ann Arbor, 45 pp. STORER, T. I., F. C. EVANS, AND R. G. PALMER. 1944. Some rodent populations in the Sierra Nevada of California. Ecol. Monogr., 14:165-192. STROUD, D. C. 1983. Seasonal activity, demography, dispersal, and a population simulation model of the California ground squirrel, Spermophilus beecheyi. Unpubl. Ph.D. dissert., Univ. California, Davis, 149 pp. TOMICH, P. Q. 1962. The annual cycle of the California ground squirrel, Citellus beecheyi. Univ. California Publ. Zool., 65:213-282.
TL;DR: The observations of other workers, as well as the results described here, indicate that certain strains of T. rangeli under certain conditions may well cause pathological alterations in mammals.
Abstract: Male mice (NMRI strain) of 3 and 5 g were inoculated i. p. with 8 x 106 and 9 x 104 metatrypomastigotes/g harvested from a 12-day-old LIT culture of Trypanosoma rangeli of the "Dog-82" strain. At regular intervals after inoculation, the animals were sacrificed and portions of heart, liver, spleen, lung, thigh, kidney, stomach, intestine, brain, sternum, and vertebral column were embedded in paraffin, sectioned, and stained with haematoxylin-eosin and Giemsa colophonium. Pathology was encountered in the first five tissues cited above. The subcutaneous, periosteal, interstitial, and peribronchial connective tissues, and later the muscle cells of the heart, were heavily parasitized by amastigotes and trypomastigotes. The possible reasons for the decrease in tissue parasitosis at the same time that the parasitemia is reaching its peak, and for the low level of inflammation in the parasitized tissues, are discussed. The observations of other workers, as well as the results described here, indicate that certain strains of T. rangeli under certain conditions may well cause pathological alterations in mammals.
Journal Article•
TL;DR: The results indicate that T. rangeli requires an adequate maintenance system, so that under experimental condition the biological characteristics, normally expressed under natural conditions, are conserved.
Abstract: Two laboratory maintenance systems of Trypanosoma rangeli were compared. The maintenance by weekly subinoculations in Tobie's culture medium and the intrafemoral inoculation of Rhodnius prolixus with cultured flagellates, resulted in loss of infectivity of the metacyclic salivarian trypomastigotes for mice, ten months after maintenance in culture. With the system of cyclical passes through culture- Rhodnius -mouse- culture- Rhodnius , the infectivity of the metacyclic trypomastigotes for mice, was maintained during the three years of the experiment. The number and porcentage of metaeyclic trypomastigotes formed in the salivary glands of R. prolixus , previously inoculated intrafemorally or intracoelomically with culture forms of T. rangeli , did not show correlation with the inoculated dose, however the inoculated quantity demostrated a direct relation with the mortality rate of the insects. The results indicate that T. rangeli requires an adequate maintenance system, so that under experimental condition the biological characteristics, normally expressed under natural conditions, are conserved.
TL;DR: In this paper, the photoconductivity spectrum of AgInTe 2 has been studied at 300 and 77 K in the range from 0.65 to 1.1 μ and the corresponding results are analyzed in terms of p-d hybridization model.
TL;DR: The Schrodinger equation for distinguishable particles is derived from classical mechanics with the additional assumption that the charged particles are subject to a flickering motion independent of external forces and, therefore, constant in time.
Abstract: The Schrodinger equation forN distinguishable particles is derived from classical mechanics with the additional assumption that the charged particles are subject to a flickering motion independent of external forces and, therefore, constant in time. We neglect the radiative corrections due, in classical terms, to the background, stochastic electromagnetic fleld generated by all the other particles of the Universe and constituting what is called ≪ zero-point fleld ≫ of quantum electrodynamics.
TL;DR: In this paper, a Stokes-Planck-like ether theory was proposed to explain the deviations of starlight when refracting through a prism and then through air, for different stars.
Abstract: Classical ether theories and special relativity predict different results for the experiment of Arago. This consists in observing deviations of starlight, when refracting through a prism and then through air. Apparently, Arago's experiment indicates a nonnull result since he observed, for different stars, different deviation differences. If these differences are due to experimental errors, only special relativity is confirmed; if they represent a real effect, its magnitude is such that it can be predicted only by a Stokes-Planck-like ether theory, while it rules out the other ether theories and special relativity.
TL;DR: In this paper, an anionic-nonionic surfactant mixture was used to maintain the optimum formulation over a certain range of temperature, but no auto-acceleration was observed.
Abstract: Polymerization was carried out with surfactant-styrene-brine systems which were formulated for the attainement of ultra-low interfacial tension and three-phase behavior. An anionic-nonionic surfactant mixture was used to maintain the optimum formulation over a certain range of temperature. Dispersion polymerization experiments were carried out with the initiator either in water (persulfate) or in styrene (AIBN). The polymerization systems exhibited both rate of polymerization and molecular weight dependence on the amount of added initiator, but no autoacceleration was observed.
TL;DR: In this article, the absorption spectra of as-grown and copper-annealed n-CuInSe 2 samples were obtained at room temperature, and a shift of the bandgap to higher energy was observed for the annealed sample compared with its value in the as grown sample.
01 Jan 1986
TL;DR: In this paper, a potential vs state variable graph exhibits one or several minima, which correspond to actual or possible stable states of the system, depending upon the value of the control variables.
Abstract: Catastrophe theory provides a tool to analyse the structural stability of natural phenomena involving sudden changes such as phase transition or emulsion inversion* An appropriate potential (such as Gibbs free energy) is defined as a function of a state variable, which describes an intrinsic or structural property of the system, and several control variables, which stand for the familiar composition and formulation variables (surfactant concentration, water/oil ratio, salinity, Alkane Carbon Number, etc)* Depending upon the value of the control variables, the potential vs state variable graph exhibits one or several minima, which correspond to actual or possible stable states of the system.
Journal Article•
TL;DR: In der vorliegenden Studie werden taxonomische Merkmale von fuenf kolumbianischen Arten der Gattung Chlamydotheca Saussure, 1858 beschrieben.
Abstract: In der vorliegenden Studie werden taxonomische Merkmale von fuenf kolumbianischen Arten der Gattung Chlamydotheca Saussure, 1858 beschrieben. Vier davon sind neue Arten.
Journal Article•
TL;DR: In der vorliegenden Studie werden zwei neue kolumbianische Arten der Gattung Strandesia Stuhlmann, 1888 vorgestellt as discussed by the authors.
Abstract: In der vorliegenden Studie werden zwei neue kolumbianische Arten der Gattung Strandesia Stuhlmann, 1888 vorgestellt. Die beiden Formen werden wegen morphologischer Uebereinstimmungen zusammen mit Strandesia variabilis Roessler, 1986 und Strandesia centrura Klie, 1940 in eine taxonomische Einheit gestellt, die nach Strandesia variabilis Roessler, 1986 benannt wird, einer Art, die in der vorhergehenden Studie beschrieben wurde (Roessler, 1986).