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Showing papers by "National Autonomous University of Mexico published in 1978"


Journal ArticleDOI
01 Oct 1978-Gene
TL;DR: In vitro recombinant DNA techniques were used to construct two new cloning vehicles, pBR324 and pBR235, which permit the molecular cloning and easy selection of EcoRI, BamHI, HindIII, PstI, HincII, SalI, (XamI), Smal, ( XmaI), BglII and DpnII restriction generated DNA molecules.

708 citations


Journal ArticleDOI
TL;DR: In this article, the Lagrangian density for interacting electromagnetic, gravitational, torsion, and complex scalar fields is presented, as well as the resulting field equations, which imply the existence of both electric and magnetic currents due to the interaction of the electromagnetic and Torsion fields.
Abstract: A formalism is given which makes it possible for a modified form of local gauge invariance and minimal coupling to be compatible with torsion. One consequence is a restriction on the possible form of torsion in that it must be determined by the gradient of a scalar function. Furthermore, a dynamical theory is obtained for this scalar and hence allows propagation of torsion in vacuum. The Lagrangian density for interacting electromagnetic, gravitational, torsion, and complex scalar fields is presented, as well as the resulting field equations. The formalism implies the existence of both electric and magnetic currents due to the interaction of the electromagnetic and torsion fields.

109 citations


Journal ArticleDOI

89 citations


Journal ArticleDOI
TL;DR: In this article, the steady-state response of a bilinear hysteretic structure supported on the surface of a viscoelastic half-space is analyzed, and simplified approximate formulas are obtained for the fundamental resonant frequency of the system and for the effective critical damping ratio.
Abstract: An analysis is made of the steady-state response of a bilinear hysteretic structure supported on the surface of a viscoelastic half-space. The method of equivalent linearization is used to solve the equations of motion, and simplified approximate formulas are obtained for the fundamental resonant frequency of the system and for an effective critical damping ratio. Numerical results indicate that for non-linear hysteretic structures compliance of the soil foundation may lead to larger displacements than would occur if the base were rigid. This behaviour differs from that generally observed for linear systems, for which the effect of soil-structure interaction is to reduce the rigid-base response.

79 citations


Journal ArticleDOI
TL;DR: It is explained how complete connectivity conditions can be used to replace boundary integral equations in many situations, and it is shown that completeness is satisfied not only in steady-state problems such as potential, reduced wave equation and static and quasi-static elasticity, but also in time-dependent problemssuch as heat and wave equations and dynamical elasticity.
Abstract: In previous papers Herrera developed a theory of connectivity that is applicable to the problem of connecting solutions defined in different regions, which occurs when solving partial differential equations and many problems of mechanics. In this paper we explain how complete connectivity conditions can be used to replace boundary integral equations in many situations. We show that completeness is satisfied not only in steady-state problems such as potential, reduced wave equation and static and quasi-static elasticity, but also in time-dependent problems such as heat and wave equations and dynamical elasticity. A method to obtain bases of connectivity conditions, which are independent of the regions considered, is also presented.

77 citations


Journal ArticleDOI
TL;DR: It is concluded that glutamate is a better precursor than glutamine of the GABA pool spontaneously released, whereas the reverse is true for the pool releasable by K(+)-depolarization.

76 citations


Journal ArticleDOI
TL;DR: The point version of the MENGER's theorem was proved in this paper, which states that the maximum number of disjoint paths joining two non-adjacent points is equal to the minimum number of points whose deletion destroys all paths joining u and v.
Abstract: Let u and v be non-adjacent points in a connected graph G . A classical result known to all graph theorists is that called MENGER's theorem . The point version of this result says that the maximum number of point-disjoint paths joining u and v is equal to the minimum number of points whose deletion destroys all paths joining u and v . The theorem may be proved purely in the language of graphs (probably the best known proof is indirect, and is due to DiRAC [3] while a more neglected, but direct, proof may be found in ORE [7]) . One may also prove the theorem by appealing to flow theory (e.g . BERGE [1], p. 167) . In many real-world situations which can be modeled by graphs certain paths joining two non-adjacent points may well exist, but may prove essentially useless because they are too long . Such considerations led the authors to study the following two parameters . Let n be any positive integer and let u and v be any two non-adjacent points in a graph G . Denote by A„(u, v) the maximum number of point-disjoint paths joining u and v whose length (i .e ., number of lines) does not exceed n. Analogously, let V„(u, v) be the minimum number of points in G the deletion of which destroys all paths joining u and v which do not exceed n in length., A special case would obtain when n = p = I V(G)I, and we have by Monger's theorem, the equality A„(u, v) = V,,(u, v) .

71 citations


Journal ArticleDOI
TL;DR: In this paper, a discussion of the formulations of the time and energy uncertainty principle given by Mandelstam, Tamm, Wigner, and the one proposed recently by the present authors, based on the concept of the equivalent width, is presented.

69 citations


Journal ArticleDOI
TL;DR: In this article, the authors study the classical canonical transformations to action and angle variables for the repulsive and attractive oscillator and the free particle and find the ambiguity group for the three problems mentioned, which connects points in one phase space that are mapped on a single point in the other.

67 citations


Journal ArticleDOI
TL;DR: The criteria for selecting the coronal incision for the brow-lift are discussed and the surgical techniques are described in detail.

61 citations


01 Jan 1978
TL;DR: For example, in this paper, the authors report that lagunas costeras of Guerrero present a ciclo de fisiologia ambiental with tres periodos ecologicos anuales: Periodo 1 (normal, salinidades entre 15 and 34‰), agosto a noviembre, las lagunás se encuentran en contacto con el mar a traves de una boca en la barrera arenosa existiendo un intercambio biologico, fisico and
Abstract: 1. Las lagunas costeras de Guerrero presentan un ciclo de fisiologia ambiental con tres periodos ecologicos anuales: Periodo 1 (normal, salinidades entre 15 y 34‰), agosto a noviembre, las lagunas se encuentran en contacto con el mar a traves de una boca en la barrera arenosa existiendo un intercambio biologico, fisico y quimico. Periodo 2 (hipersalino, salinidades mayores de 35‰ noviembre a mayo, las lagunas se encuentran aisladas del mar y la evaporacion excede a los aportes de aguas dulces; minimo volumen de agua en las lagunas, Periodo 3 (hipo salino, salinidades menores de 15‰ mayo a agosto, las lagunas se encuentran aisladas del mar y los aportes de aguas dulces exceden a la tasa de evaporacion; maximo volumen de agua en las lagunas. 2. La vegetacion de las lagunas se compone de los siguientes elementos: a) palmar, b) lignetum pernnifolio de manglar, c) semiacuatica, y d) acuatica. Los principales productores primarios son los manglares y fitoplancton. 3. Segun estudios de otros autores la biomasa fitoplanctonica es alta comparada con otros ecosistemas lagunares de Mexico. 4. Los grupos del zooplancton mas comunes han sido copepodos, quetognatos, larvas de gastropodos, larvas de bivalvos, larvas de cirripedios, larvas de poliquetos, larvas de decapodos, y algunas larvas y huevecillos de peces. Estudios de otros autores discuten la diversidad especifica y abundancia del zooplancton en las lagunas de Guerrero. 5. La macrofauna bentonica tiene representantes de Porifera, Cnidaria, Annelida, Mollusca (bivalos y gastropodos) en fondos blandos y duros, Arthropoda (Scalpellidae, Balanidae, Penaeidae, Palaemonidae, Callianasidae, Diogenidae, Coenobitidae, Portunidae, Xanthidae, Pinnotheridae, Grapsidae, Gecarcinidae, Ocypodidae, Isopoda y Tanaidacea) distribuidos en: a) facie de playa, b) facie de manglar, c) facie bentonico pelagico, y d) facie bentonico de fondos arenosos y fangosos. En general el bentos esta pobremente repre

Journal ArticleDOI
TL;DR: In this paper, the primary production, oxygen consumption of substrate, and biomass of invertebrates and fish in a Mexican coastal lagoon were measured and concluded that net production in the water column of 2.45 g C m −2 day −1 was sufficient to cover the metabolic requirements of the infauna in the wet season, and that production by macrophytes e.g. Ruppia maritima covered the increased input necessary for the epifauna, and for deposition in the substrate.

Journal ArticleDOI
TL;DR: The finding that [35S]taurine release was not stimulated by K+-depolarization in any of the regions studied, under experimental conditions identical to those resulting in an enhancement of [3H]GABA and [14C]glycine release, argues against a neurotransmitter role of this amino acid in brain and spinal cord.

Journal ArticleDOI
TL;DR: In this article, the second-order differential equations of motion of spinning test particles (tops) were derived from a variational principle in a given gravitational background defined by a Riemannian metric and a torsion tensor.
Abstract: The (second-order differential) equations of motion of spinning test particles (tops) are derived from a variational principle in a given gravitational background defined by a Riemannian metric and a torsion tensor. The mass and (magnitude of) the spin of the top are conserved. There exists a Regge trajectory linking the mass and the spin of the top. Constants of the motion associated with Killing vectors of the metric along which the Lie derivative of the torsion tensor vanish are found.

Journal ArticleDOI
TL;DR: The effect of depolarizing potassium concentration on the release of [14C]glycine, [3H]GABA, and [35S]taurine was investigated in the whole chick retina and in a synaptosomal fraction prepared from the chick retina.
Abstract: The effect of depolarizing potassium concentration on the release of [14C]glycine, [3H]GABA, and [35S]taurine was investigated in the whole chick retina and in a synaptosomal fraction prepared from the chick retina. In the whole retina, increasing potassium concentration above 40 mM resulted in an increased release of the three amino acids. The release of glycine was the most stimulated and that of taurine, the least. The potassium-evoked release of glycine and GABA was calcium dependent. In the synaptosomal fraction, 68.5 mM potassium significantly stimulated the efflux of GABA and glycine by a calcium-dependent mechanism. The release of taurine from this fraction was unaffected by high potassium.

Journal ArticleDOI
TL;DR: In this paper, the two-point correlation function for complex spectra described by the Gaussian Orthogonal Ensemble (GOE) is calculated, and its essential simplicity displayed, by an elementary procedure which derives from orthogonal invariance and the dominance of intrinsic binary correlations.

Journal ArticleDOI
TL;DR: It is suggested that adenosine ameliorated the ethanol-induced fatty liver through an increased utilization of reducing equivalents by the mitochondria and an interdependence of these effects is proposed and discussed.

Journal ArticleDOI
TL;DR: The theoretical justification of the model potential method is studied in some detail in this article, and the correct equations within the framework of Roothaan's open-shell scheme are derived and the approximations necessary to get a workable method are discussed.
Abstract: The theoretical justification of the model potential method is studied in some detail. The correct equations within the framework of Roothaan's open-shell scheme are derived and the approximations necessary to get a workable method are discussed. Analysis of the local part of the model potential suggests a new analytical form for it. The new expression is theoretically more consistent than the original one, and it can be determined in a more straightforward way. A basis set approximation, which is particularly suitable for approximate evaluation of two-electron integrals when only valence orbitals are involved, is discussed and tested with encouraging results. The ideas are tested on the Fe and I atoms.

Journal ArticleDOI
TL;DR: Data indicate that in exponentially growing N. crassa, the nitrogen source regulates glutamine synthetase by adjusting specific mRNA levels, and cultures grown on glutamate as the sole nitrogen source had higher mRNA activities than did those grown on glutamine.
Abstract: Neurospora crassa glutamine synthetase mRNA was measured by its capacity to direct the synthesis of the specific protein in a cell-free system derived from rabbit reticulocytes. N. crassa cultures grown on glutamate as the sole nitrogen source had higher mRNA activities than did those grown on glutamine. The differences were about 10-fold when polysomal RNA was used for translation and about 5-fold when either total cellular RNA or polyadenylic acid-enriched cellular RNA was used. These data indicate that in exponentially growing N. crassa, the nitrogen source regulates glutamine synthetase by adjusting specific mRNA levels.

Journal ArticleDOI
TL;DR: Ethidium bromide, besides, can stimulate the uptake of Mn2+ and14C-glycine and could be a good weapon to magnify and study some of the characteristics of ion transport systems in yeast.
Abstract: Ethidium bromide and other cationic dyes have been found to inhibit movalent cation uptake. This dye also produces in a K+-free medium an efflux of K+ which could be of the electrogenic type.

Journal ArticleDOI
TL;DR: Results reveal that in both simple and complex learned behaviors overtraining induces protection againts performance decrements.

Journal ArticleDOI
TL;DR: In this paper, configuration-interaction calculations for the lowest states of neutral lithium have been carried out with a basis of $10s8p8d6f3g2h1i$ Slater-type orbitals.
Abstract: Configuration-interaction calculations for the lowest $^{4}S$, $^{4}P^{o}$, $^{4}P$, $^{4}D^{o}$, $^{4}D$, $^{4}F^{o}$, and $^{4}F$ states of neutral lithium have been carried out with a basis of $10s8p8d6f3g2h1i$ Slater-type orbitals. The nonrelativistic-energy upper bounds converge to within 4-45 ${\mathrm{cm}}^{\ensuremath{-}1}$ of the expected nonrelativistic energies. An explanation is given for the fact that transitions from $^{4}F$ states have not been observed in beam-foil experiments. Some aspects involved in the assessment of the reliability of calculated oscillator strengths are discussed, and the calculated mean lifetimes for electric dipole decay are compared with experiment.

Journal ArticleDOI
TL;DR: Observations indicate that H (or D) bonding between the solvent and the protein as well as the strength of the hydrophobic interactions within the enzyme as determined by the solvent are of central importance in determining the overall activity of F 1 and the stability of the enzyme to denaturing conditions.

Journal ArticleDOI
TL;DR: Several experiments were carried out to confirm the allelopathic potential ofAmbrosia cumanensis H.B.K. (Compositae) in a tropical zone of Mexico and the aqueous extracts of leaves and roots inhibited growth of several species used in bioassays.
Abstract: Several experiments were carried out to confirm the allelopathic potential ofAmbrosia cumanensis H.B.K. (Compositae) in a tropical zone of Mexico. The aqueous extracts of leaves and roots inhibited growth of several species used in bioassays. The wash-water of the leaves inhibited some species and stimulated others. The aqueous solutions of soil, in reference to those collected in July, were significant in their general inhibitory action. Decomposition of leaves and roots, in pots where several species were growing, was highly inhibitory to some of the seedlings; microorganisms have a major role in this process.

Journal ArticleDOI
TL;DR: Results of biotests carried out with several sesquiterpene lactones produced by Ambrosia cumanensis showed different effects on the germination and growth of several species of the secondary vegetation of a tropical zone of Mexico.
Abstract: Results of biotests carried out with several sesquiterpene lactones produced byAmbrosia cumanensis are presented These compounds showed different effects on the germination and growth of several species of the secondary vegetation of a tropical zone of Mexico


Journal ArticleDOI
TL;DR: In this paper, a complete list of separable coordinate systems for nonorthogonal coordinate systems with special emphasis on non-orthogonal coordinates is presented and applications to general relativity theory are indicated.
Abstract: We present a complete list of all separable coordinate systems for the equations\(\sum\limits_{i,j = 1}^4 {g^{ - 1/2} \partial _i (g^{1/2} g^{ij} \partial _j \Phi )} = E\Phi\) and\(\sum\limits_{i,j = 1}^4 {g^{ij} \partial _i W\partial _j W} = E\) with special emphasis on nonorthogonal coordinates. Applications to general relativity theory are indicated.

Journal ArticleDOI
TL;DR: In this paper, the connection between stochastic electrodynamics and the quantum theory of matter is further explored, and the Fokker-Planck-like equation of SED can be recast into the form of a Schrodinger equation with radiative corrections, when the system is close to a state of equilibrium.
Abstract: The connection between stochastic electrodynamics (SED) and the quantum theory of matter is further explored. The main result is that the Fokker-Planck-like equation of SED can be recast into the form of a Schrodinger equation with radiative corrections, when the system is close to a state of equilibrium. The phase-space distribution can be written as Wigner's pseudo-distribution plus corrections due to the nonlinearity of the external force and to radiative effects. The radiative corrections predicted by the theory, namely the Lamb shift and the decay of excited atomic states, coincide with those predicted by QED. Moreover, the theory offers a clear physical interpretation of these phenomena as due to the coupling of the electric dipole of the system with the zero-point radiation field and to radiation reaction, respectively.


Journal ArticleDOI
TL;DR: Data were interpreted as demonstrating that this inherited type of gynecomastia represents the mildest expression of the androgen resistance syndromes and, therefore, belongs to the type 1 form of familial incomplete male pseudohermaphroditism.
Abstract: Four postpubertal 46 XY male patients with an inherited form of bilateral gynecomastia were studied to delineate the nature of the disease. Normal serum FSH and moderately elevated serum LH with concomitantly increased circulating levels of testosterone (T) and estradiol (E2) were found persistently in all cases in blood samples drawn at frequent intervals. LRH pituitary stimulation resulted in an exaggerated LH response and a normal FSH response. Chronic administration of T-cyclopentylate failed to decrease serum LH levels. The peripheral conversion rate of androstenedione to estrone was within normal limits. All patients had low ejaculate volumes with relatively normal spermatozoa counts. Testicular biopsies revealed normal Leydig cells and complete spermatogenesis. Urological examination disclosed that the prostate gland was extremely small. The breast tissue demonstrated the presence of tubular structures as well as the specific binding of [3H]T and [3H]dihydrotestosterone (DHT), which was inhibited by nonlabeled T, DHT, E2, and progesterone, but not by cortisol. The pedigree suggested a recessive X-linked inherited trait. A patient with a nonfamilial form of gynecomastia served as a control in all studies. These data were interpreted as demonstrating that this inherited type of gynecomastia represents the mildest expression of the androgen resistance syndromes and, therefore, belongs to the type 1 form of familial incomplete male pseudohermaphroditism.