Showing papers by "National University of Cuyo published in 1994"
TL;DR: In this article, it was shown that random walks in which the set of visited points is a fractal emerge from a maximun entropy formalism applied to the generalized entropies introduced by Tsallis [J. Stat. Phys. 52, 479 (1988), upon suitable constraints.
Abstract: It is shown that random walks in which the set of visited points is a fractal emerge from a maximun entropy formalism applied to the generalized entropies introduced by Tsallis [J. Stat. Phys. 52, 479 (1988)], upon suitable constraints. This connection between fractals and Tsallis entropies suggests that the generalized statistical mechanics derived from the latter could provide a natural frame for studying fractally structured systems.
152 citations
TL;DR: It is concluded that endosomes can fuse by two mechanisms, one that has an absolute requirement for calcium and is probably mediated by annexins, and another that does not require calcium.
114 citations
TL;DR: The increased resistance of neonatally stressed rats to the estrous cycle effects of chronic aleatory stress in adulthood supports the speculation that neonatal manipulation can increase resistance of rats to stress-induced reactions throughout life.
29 citations
TL;DR: The binding was saturable, with a Kd in the nanomolar range, was inhibited with phosphorylated derivates of fructose, and did not depend on Ca2+, showing that it is different from the mannose 6-P-recognizing system existing in other tissues for this and other acid hydrolases.
Abstract: Summary
The binding of N-acetyl-β-D-glucosaminidase from rat epidldymal fluid to the surf-ace of spermatozoa from the cauda epididymis was measured in the presence of sugars, its phosphorylated derivatives, or after treatment of the cells or the enzyme with agents that alter the integrity of proteins or carbohydrates. The binding was saturable, with a K, in the nanomolar range, was inhibited with phosphorylated derivates of fructose, and did not depend on Ca2+ showing that it is different from the mannose 6-P-recognizing system existing in other tissues for this and other acid hydrolases. Treatment of the cells with sodium periodate or trypsin inhibited the binding, showing that a glycoprotein of the plasmalemma is involved in the affinity site. Fructose or phosphorylated derivates were not detected in the proteins of the epididymal fluid with HPLC. However, with the method used, the presence of these compounds cannot be ruled out, if among the proteins of the fluid there are only a small number of acid hydrolases containing this sugar.
23 citations
TL;DR: Results presented here show that rosettes begin to appear following the sites of DE secretion and permit us to postulate that DE is involved in rosette formation and constitutes another example of gamete‐epididymal interaction.
Abstract: Recently, a new head-to-head sperm association was described in the rat during epididymal transit. This association was called a rosette and a filamentous and PAS-positive material was also described joining the sperm heads. The beginning of rosette formation in the epididymis and the linking material between heads have remained unclear. Epididymides of adult rats were fixed by vascular perfusion and thin sections of the principal regions were studied by transmission electron microscopy (TEM). The first evidence of rosette formation was observed in the distal corpus. Rosettes were isolated from the distal corpus and processed for immunogold and immunofluorescence microscopy to detect an epididymal glycoprotein called DE. This glycoprotein is secreted by the corpus epididymis and appears to be involved in sperm maturation. Colloidal gold marks and fluorescence were observed in the linking material between the sperm heads. The results presented here show that rosettes begin to appear following the sites of DE secretion and permit us to postulate that DE is involved in rosette formation and constitutes another example of gamete-epididymal interaction.
23 citations
TL;DR: By mapping these reactions into processes that preserve the particle number, an approximate solution is found, which, as compared with numerical simulations for the square lattice, turns out to be exact for short and long times.
Abstract: We present a method to obtain the concentration decay for coagulation, A+A\ensuremath{\rightarrow}A (\ensuremath{\epsilon}=1), and annihilation, A+A\ensuremath{\rightarrow}0 (\ensuremath{\epsilon}=2), of diffusing particles, on two-dimensional lattices. By mapping these reactions into processes that preserve the particle number, we find an approximate solution, which, as compared with numerical simulations for the square lattice, turns out to be exact for short and long times. The particle number along the whole course of the reaction is obtained in a closed form, and can be written as a function of only the mean number of distinct sites visited by a single particle. For a homogeneous initial particle distribution the particle number behaves at long times as N(t)\ensuremath{\sim}\ensuremath{\epsilon}N(0)(8aDt${)}^{\mathrm{\ensuremath{-}}1}$ln(8bDt), where D is the diffusivity and a and b depend on the lattice type. On the other hand, for a strongly inhomogeneous (fractal) initial distribution, the particle number decays at long times as N(t)\ensuremath{\sim}\ensuremath{\epsilon}N(0)(8aDt${)}^{\mathrm{\ensuremath{-}}\ensuremath{\gamma}/2}$ln(8bDt), where \ensuremath{\gamma} is the fractal dimension of the initial particle distribution (02).
16 citations
TL;DR: The chirality transitions induced by gravitational fields on Dirac particles are studied within the framework of field theory in curved spaces, and an upper bound for the corresponding amplitude is estimated.
Abstract: The chirality transitions induced by gravitational fields on Dirac particles are studied within the framework of field theory in curved spaces. To have these transitions both a non-null mass for the particle and an angular momentum for the source of the gravitational field are necessary. The results of this analysis are applied to some simple examples, and an upper bound for the corresponding amplitude is estimated.
15 citations
TL;DR: In this paper, training effects on the characteristics of the transformation when using pseudoelastic compressive cycling are studied from σ-e curves and calorimetric measurements, and several characteristics produced by tensile cycling and observed in thermally induced martensitic transformations also appear in this case.
Abstract: Training effects on the characteristics of the transformation when using pseudoelastic compressive cycling are studied from σ-e curves and calorimetric measurements. Several characteristics produced by tensile cycling and observed in thermally induced martensitic transformations also appear in this case. For a fixed number of training cycles, the efficiency of the two-way shape memory effect (TWSME) obtained after compressive tests is higher than that measured when tensile experiments are done. In a certain range, the efficiency of the resulting TWSME after compressive training increases with the magnitude of the applied stress. Values of the stress (threshold stress) which trained samples with an induced TWSME are able to overcome when going to martensite are presented for two sets of samples. These opposing stresses are related to different degrees of the TWSME inhibition. These values increase with the number of compressive cycles and show a saturation behavior.
15 citations
TL;DR: The vascular kallikrein-kinin system may help counteract the elevation of vascular resistance in the earliest stages of DOCA-salt hypertension, and suggest that mineralocorticoids increase vascular kAllikre in and that established hypertension lowers both arterial kallkrein and kallIKrein released by the vasculature, whereas venous kall Kikrein is under a different regulatory control.
Abstract: We determined the status of vascular kallikrein in rats with severe hypertension caused by treatment with deoxycorticosterone acetate (DOCA) and drinking of 1% NaCl for 6 weeks. We assayed active and total kininogenase (kallikrein) activity in the perfusate and in arterial and venous tissue. DOCA-salt rats had higher systolic blood pressure at 6 weeks (214 +/- 5 mm Hg) than rats drinking tap water (135 +/- 4 mm Hg) or saline (145 +/- 8 mm Hg). Kininogenase in the perfusate (nanograms bradykinin per minute per kilogram body weight) increased significantly at 2 weeks, from 5.8 +/- 2.1 to 8.9 +/- 1.4 for active kallikrein and from 28.7 +/- 0.4 to 48.7 +/- 2.9 for total kallikrein. Total kallikrein returned to control values at 4 weeks, whereas it was significantly reduced at 6 weeks (20.9 +/- 0.7). Active kallikrein was significantly depressed at 4 and 6 weeks (1.08 +/- 0.1 and 0.85 +/- 0.1, respectively [P < .05]). Active kallikrein in arterial tissue (picograms bradykinin per milligram per minute) showed a small but significant increase at 2 weeks, from 156 +/- 7 to 201 +/- 10 (P < .05), finally decreasing significantly by 6 weeks to 64 +/- 3; however, total kallikrein showed a significant decrease only at 6 weeks, from 844 +/- 17 to 427 +/- 27. Both active and total kallikrein in the veins were higher than control values at 2 weeks, changing from 437 +/- 7 to 541 +/- 19 and from 1619 +/- 17 to 2062 +/- 86, respectively. Venous kallikrein remained elevated until the end of the experiment.(ABSTRACT TRUNCATED AT 250 WORDS)
12 citations
TL;DR: Results are interpreted as local actions of PRL on hippocampal neuron affecting expression of behaviours of rats depending on the stressful conditions of the environment.
Abstract: The probable behavioural effects of rat prolactin (rPRL) locally applied into the ventral hippocampus (HPC) were studied in cycling female rats. Three experiments were performed examining the behavioural responses of rats subjected to three different situations: (i) Exploratory activity in an enriched holeboard (ii) exploratory activity under conflicting situation and (iii) escape behaviours in a forced swimming test. Behavioural parameters studied were: underground and object-directed exploration and locomotion (Experiment 1); latency time and exploration behaviours (Experiment 2); swimming time and escape behaviours (Experiment 3). In Experiment 1 results showed that rPRL decreased the underground exploration and also locomotion but increased the object-directed exploration and had no effect on non-ambulatory activity. In Experiment 2 results showed that treatment of rPRL increased the latency time but did not modify the exploratory activity. In Experiment 3 results showed that rPRL augmented the swimming time and one of two parameters (frequency of immersions intents) of the escape behaviour. Results are interpreted as local actions of PRL on hippocampal neuron affecting expression of behaviours of rats depending on the stressful conditions of the environment.
9 citations
TL;DR: In this paper, factorization properties of scattering amplitudes are used to study the discrete state structure of superconformal matter coupled to 2D supergravity theory, and the fitting of these states into SU(2) multiplets is briefly discussed.
Abstract: Factorization properties of scattering amplitudes are used to study the discrete state structure of superconformal matter coupled to 2D supergravity theory. Vertex operators are explicitly constructed and possible gauge transformations analyzed. The fitting of these states into SU(2) multiplets is briefly discussed. The algebra generated by both Neveu–Schwarz and Ramond states is considered in the limit of null cosmological constant.
TL;DR: In this article, the magnetic resonance properties of a three-sublattice-coupled paramagnetic-weak-ferromagnetic system are derived in the molecular-field approximation.
Abstract: The magnetic-resonance modes for a three-sublattice-coupled paramagnetic--weak-ferromagnetic system are derived in the molecular-field approximation. The model is proposed to describe the microwave-absorption experiments in the Gd cuprates below the ordering temperature of the Cu magnetic moments. Two of the sublattices are associated with the Cu moments and the third describes the ${\mathrm{Gd}}^{3+}$ paramagnetic lattice. An isotropic antiferromagnetic interaction is considered to couple the Cu moments with an antisymmetric exchange being responsible for the weak ferromagnetism. Two separate components are considered for the magnetic anisotropy of the Cu moments: a strong out-of-plane term (coincident with the ${\mathrm{CuO}}_{2}$ planes), and a smaller in-plane anisotropy. The Cu and Gd magnetic moments are assumed to interact through an isotropic ferromagnetic exchange interaction. Static and dynamic corrections to the paramagnetic and weak-ferromagnetic modes are described. The former are due to internal fields originated in the Cu-Gd interaction. The dynamic corrections are important for some orientations of the applied magnetic field for which the modes become degenerate. Anticrossing and strong mode mixing is observed in this case. The predictions of the model are compared with the available experimental data. It is shown that both static and dynamic corrections are needed in order to account for the anisotropy of the observed microwave absorptions. A consistent description of the complex magnetic resonance behavior of the Gd cuprates is obtained within the proposed model.
Journal Article•
TL;DR: The multiple percutaneous drainage of the cysts was useful in this case to reduce the endocraneal hypertension and to achieve a neurological improvement.
Abstract: A case of hydatid cerebral disease with multiple cysts is reported with the purpose of presenting this unusual form of hydatid neurological involvement and to discuss some aspects of the pathogenesis and treatment. In this patient, the liver hydatid cyst surgery two years prior to the development of multiple pulmonary and cerebral cysts suggests a vascular invasion of oncoesphere during the hepatic surgery with hematological dissemination to the lungs and brain. The multiplicity and deep localization of the cerebral cysts prevented the performance of a definitive surgical resection. The multiple percutaneous drainage of the cysts was useful in this case to reduce the endocraneal hypertension and to achieve a neurological improvement. Albendazole has proved of benefit as a chemo-therapeutic agent in these cases and Magnetic Resonance Imaging has proven useful for surgical planning.
Journal Article•
TL;DR: Pasquali as mentioned in this paper preguntaba por la comunicabilidad de un proceso, pensada en relacion con el retorno, con el modo de lograr la incorporacion del receptor and marcaba una diferencia no es lo mismo hablar de informacion que de comunicacion corresponde a practicas unidireccionales, a mensajes en una sola via, en cambio alude the posibilidad del retorno.
Abstract: La reflexion sobre los medios de comunicacion en America Latina comenzo en la decada de los 60, mas concretamente en el 64, con la publicacion de diferentes libros de comunicacion y cultura de masas, esta reflexion se hace desde las escuelas y facultades de comunicacion. En efecto Pasquali se preguntaba por la comunicabilidad de un proceso, pensada en relacion con el retorno, con el modo de lograr la incorporacion del receptor y marcaba una diferencia no es lo mismo hablar de informacion que de comunicacion las primera corresponde a practicas unidireccionales, a los mensajes en una sola via, la segunda, en cambio alude la posibilidad del retorno, del intercambio entre seres. En sintesis la T.V era destaca desde dos frentes el de la lectura y el de los mensajes y la monopolizacion de la informacion y de la programacion. Todo periodo de descalificacion de los medios, de la identificacion de los mismos con una maquina universal para cerrarnos la conciencia, de reduccion de toda oferta de mensajes a la trivializacion, de denuncia a los monopolios y en definitiva, de terror ante el espectaculo y junto al ello el crecimiento permanente del numero de televidentes, de los tiempos de programacion de los recursos del lenguaje audiovisual, de las tecnicas de lectura de los modos de percibir y destacar de los perceptores.
TL;DR: In this article, it was shown that the characteristics of the MAMMA signal at any field orientation (H, θ) can be described in terms of a reduced field h = H ( cos 2 θ + γ 2 sin 2 ) 1 2, where γ is the anisotropy parameter.
Abstract: Magnetically modulated microwave absorption (MAMMA) measurements have been performed on a superconducting Sm2−xCexCuO4−δ single crystal by sweeping the temperature at constant magnetic fields applied in different orientations. The result of each measurement is a well-defined peak, whose onset determines, in a mean field approximation, the superconducting transition. We have found that the characteristics of the MAMMA signal at any field orientation (H, θ) can be described in terms of a reduced field h = H ( cos 2 θ + γ 2 sin 2 θ) 1 2 , where γ is the anisotropy parameter. The scaling of the experimental data has allowed us to determine γ ≈ 75.
TL;DR: In this article, the WF transition in Gd 2 CuO 4 has been accurately determined from dc magnetization measurements, which follows the characteristic law of classical ferromagnets, h = t ( γ + β ), with (γ + β ) = 1.8(2).
Abstract: Gd 2 CuO 4 developes, at T N , a long range AF order with a weak ferromagnetic (WF) component. This component is allowed by in-plane distortions of the tetragonal T' structure and persists above T N , induced by the magnetic field, in a large temperature interval. From dc magnetization measurements, we have accurately determined the WF transition, which follows the characteristic law of classical ferromagnets, h = t ( γ + β ), with ( γ + β ) = 1.8(2). The WF component persists in Gd 1.85 Ce 0.15 CuO +δ , even after a reduction procedure, although the Ce 4+ doping lowers T N . A set of Gd 2−x Sr x CuO 4−δ samples, prepared via a sol-gel method at a maximum temperature of 900°C, showed an expanded unit cell without distortions, the absence of a WF component and strongly modified magnetic properties of the Gd sublattice.
01 Jan 1994
02 Apr 1994-Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms
TL;DR: In this paper, the authors show how incorrect angular normalization can lead to the appearance of a misleading "infolded" structure in the electron transfer to the continuum (ETC) peak.
Abstract: Calibration of the angular efficiency of the equipment with isotropic Auger lines has usually been employed for the experimental study of energy and angular distributions of electrons ejected in atomic collisions. However, the electron-projectile interaction gives rise to a pronounced enhancement of the electronic intensity in the forward direction. Therefore, if the angular calibration is carried out with an Auger line which was assumed to be isotropic, the cross section will be underestimated at small angles. We show how this incorrect angular normalization can lead to the appearance of a misleading “infolded” structure in the electron transfer to the continuum (ETC) peak.