Showing papers by "National University of Cuyo published in 1982"
TL;DR: In this paper, the theory of superconductive networks put forward by de Gennes and Alexander can be formulated in terms of two generalized Kirchhoff laws: the current law is generalized to the complex parts of the quantum-mechanical current and the voltage law to the flux linkage.
Abstract: The theory of superconductive networks put forward by de Gennes and Alexander can be formulated in terms of two generalized Kirchhoff laws The current law is generalized to the complex parts of the quantum-mechanical current and the voltage law to the flux linkage These laws are applied to a (SQUID), a boleadora, and a balanced Wheatstone bridge The normal-superconducting phase boundaries are obtained in the limit that the thickness of the wires is neglected
45 citations
TL;DR: Arterial tissue contains an enzyme with physicochemical characteristics quite similar to those of kallikreins of glandular origin, and by using antibodies that specifically inhibit kinins, the biological action was completely abolished.
Abstract: 1. The present study was undertaken to examine whether there is a kallikrein-like enzyme in vascular tissue. Isolated saline-perfused rat mesenteric arteries were used and arterial homogenate was incubated with heat-treated dog plasma and citrate/phosphate buffer (pH 8.5) in the presence of peptidase inhibitors for 60 min. 2. The kallikrein-like enzyme showed optimum activity in the range pH 7.0-9.0. The rate at which it releases kinin is similar to the release of kinin by kallikrein and trypsin. The release is unaffected by incubation of the enzyme with trypsin-inhibitors, but completely inhibited by aprotinin. 3. The kinin released by arterial homogenate resembles bradykinin in its chemical and pharmacological properties, and by using antibodies that specifically inhibit kinins, the biological action was completely abolished. 4. These results indicate that arterial tissue contains an enzyme with physicochemical characteristics quite similar to those of kallikreins of glandular origin.
26 citations
TL;DR: In this paper, the de Gennes-Alexander theory of superconductive networks is used to study the upper critical fields of two-dimensional square lattices built from equally spaced infinite wires joined by transverse strands.
Abstract: The de Gennes-Alexander theory of superconductive networks is used to study the upper critical fields of two-dimensional square lattices built from $N$ equally spaced infinite wires joined by transverse strands. Phase diagrams and current-flow patterns for representative cases are shown. A critical value is found of the magnetic flux per square below which the current flow resembles the Meissner state, and above which an ordered array of vortices appears, in general incommensurate with the underlying lattice. The critical flux decreases for increasing $N$.
24 citations
TL;DR: The two-scalar-potentials method for anisotropic materials is formulated and a computer program and the solution of an example problem are presented and the use of infinite multipolar elements is discussed.
Abstract: The two-scalar potentials idea has been used with success for the computation of static magnetic fields in the presence of nonlinear isotropic magnetic materials by the finite element method. In this communication we formulate the two-scalar-potentials method for anisotropic materials and present a computer program and the solution of an example problem. The use of infinite multipolar elements is also discussed. Several advanced methods and ideas are employed by the program: scalar potentials, rather than vector potentials, giving only one unknown quantity; the finite element method, in which the solution is approximated by a continuous function; the Galerkin method to solve the differential equations; accurate infinite elements, which avoid the introduction of an artificial boundary for unbounded problems; automatic mesh generation, which means that the user can construct a large mesh and represent a complicated geometry with little effort; automatic elimination of nodes outside the iron, which restricts the iterations to the nonlinear anisotropic region with economy of computer time; use of sparse matrix technology, which represents a further economy in computer time when assembling the linear equations and solving them by either Gauss elimination or iterative techniques such as the conjugated gradient method, etc. The combination of these techniques is very convenient.
23 citations
TL;DR: In this article, the electrical resistivity, superconducting critical temperature and thermal conductivity of amorphous metals Zr70Cu30 and La70cu30 were measured.
20 citations
TL;DR: In this paper, it was shown that the hexagonal and the original 3R martensite have the same formation free energy, which implies that the two structures cannot be described by their difference in stacking fault density (compared to a face centered lattice), and an energy difference which is proportional to it.
20 citations
TL;DR: The anomalous contraction that cerium undergoes when it is the A component in AB 2 Laves phase compounds was used to estimate its metallic radius when it was joined to a given B component as mentioned in this paper.
Abstract: The anomalous contraction that cerium undergoes when it is the A component in AB 2 Laves phase compounds is used to estimate its metallic radius when it is joined to a given B component. In each case, isostructural compounds of trivalent (rare earths) and tetravalent (zirconium, hafnium and thorium) A elements with the same B element are taken as the reference system. The trivalent metallic radius ( r 3 = 1.846 A ) of cerium proposed by Gschneidner and Smoluchowski was confirmed, but a tetravalent metallic radius ( r 4 = 1.688 A ) of cerium which exceeds their value by 1% was obtained. The presence of A-B contacts is related to the intermediate valency behaviour, and the valency calculated for each compound is compared with other physical properties. A distinction between localized conduction band hybridization and interconfigurational fluctuation is proposed.
15 citations
TL;DR: The results clearly show that sex differences occur in both experienced and control groups of rats and rats reared on lemon scented bedding from birth to weaning acquire a permanent preference for nesting in the Lemon scented chamber.
15 citations
TL;DR: Novel findings in the toad testis are reported using freeze‐fracture techniques and the fact that they are present in amphibia might indicate that they represent a widespread pattern.
Abstract: The present work reports novel findings in the toad testis using freeze-fracture techniques. Tight and gap junctions are observed in the nonfenestrated endothelial cells. Numerous gap junctions are present between interstitial cells. Sertoli-Sertoli junctional specializations in the toad are similar to those described in mammals although they appear to be less elaborate. The appearance of nuclear pores, in the seminiferous epithelium, ranges from a uniformly and apparently random distribution in Sertoli cells to large aggregations of closely spaced pores separated by free areas in the nuclear envelope of spermatocytes. Inasmuch as these features have also been described in mammals, the fact that they are present in amphibia might indicate that they represent a widespread pattern.
Concomitantly with increasing chromatin condensation, nuclear pores diminish in round spermatids and seem to disappear in the more mature germ cells. The en face freeze-fracture views of annulate lamellae in the postnuclear cytoplasm and membranous features of the acrosome formation, flagellum, and undulating membrane of elongating spermatids are also described.
10 citations
TL;DR: It appears that both sexes contribute to the ‘glueing’ mechanism during mating, and new hypotheses to explain the adhesion between the sexes are proposed, viz., that the shift to terrestrial habils and subterranean laying in Breviceps have secondarily resulted in male si2e diminution.
Abstract: During mating male and female Breviceps become ‘glued’ together. The distribution of multicellular dermal glands varies between the sexes. The mate has a large number of holocrine glands on the ventrum, while the female has similar glands on the dorsum of the back. II thus appears that both sexes contribute to the ‘glueing’ mechanism. New hypotheses to explain the adhesion between the sexes are proposed, viz., that the shift to terrestrial habils and subterranean laying in Breviceps have secondarily resulted in male si2e diminution. In other microhylids which adhere during aquatic oviposition, yet demonstrate a terrestrial morphology and habits, bouyancy is suggested to be of primary functional value.
8 citations
TL;DR: In this paper, the electrostatic energy of a charge immersed in the screened Coulomb potential of the total charge distribution of the metal was selected as the most appropriate parameter for correlating different cerium environments.
Abstract: By means of a semiempirical analysis the electrostatic energy Eψ of a charge immersed in the screened Coulomb potential of the total charge distribution of the metal was selected as the most appropriate parameter for correlating different cerium environments. The choice was made by determining the smallest dispersion in plots of various physicochemical parameters versus the rate of depression α of the superconducting transition temperature Tc of thorium-based alloys containing cerium impurities. The magnetic moment of cerium, which depends on the environment, was found to have the greatest effect on the depression of Tc. Eψ was found to be proportional to α − 1 2 . The analysis was extended to some ABj compounds (A ≡ elements of groups II–V including cerium and thorium; Bj ≡ N, Sn3, Tl3, Rh3, Co2, Ir2, B6 and Be13). An empirical relationship between Eψ and the volume contraction ΔV V due to the formation of the compound was found. The cerium valence for any CeBj compound is deduced from the Eψ(Ce) value compatible with the curve of ΔV V versusEψ(A), taking into account the fact that the valence and atomic radius of cerium are related.
TL;DR: The results suggest that the mechanisms regulating tubulin depolymerization in vivo are different from those taking place in vitro, and are similar to that occurring by incubation at 20 degrees C.
Abstract: The tubulin of both brain and testis of the toad Bufo arenarum was partially depolymerized when the animals were maintained on ice for 90 minutes or 17 hours. Recovery of the animals at room temperature restored the normal degree of polymerization in both organs. Normalization of the polymerization degree also occurred in organs separated from cooled animals and incubated in vitro for 90 minutes at 20°C. When the organs were cooled in vitro, only testicular tubulin underwent depolymerization, and in a degree similar to that occurring by incubation at 20°C. The results suggest that the mechanisms regulating tubulin depolymerization in vivo are different from those taking place in vitro.
TL;DR: In this paper, a set of non-linear equations is given which solve the stationary Schrodinger equation in terms of a known subproblem, and an iterative solution of the equations yields the degenerate version of Rayleigh-Schrodinger perturbation theory.
TL;DR: In this article, a variational approach was proposed to turn a gauge problem into a global-symmetric equivalent model, and the use in the latter of a mean field method with an effective dimensionality was shown to give agreement with the low and high-temperature expansions.
Abstract: A previously described variational approach turns a gauge problem into a global-symmetric equivalent model. The use in the latter of a mean-field method with an effective dimensionality is shown to give agreement with the low- and high-temperature expansions. We apply this method to the $Z(2)$ gauge and matter field model in any dimension finding in particular that it quantitatively improves the results for the (2+1)-dimensional case.
TL;DR: It is suggested that ADH is released after copulation and that such a release is maintained for at lest 60 min, while oxytocin of the neurointermediate lobe is retained for at least 60 min.
Abstract: The plasma antidiuretic activity and the content of antidiuretic hormone (ADH) and oxytocin of the neurointermediate lobe were determined in male rats under normal conditions and after copulation. The plasma samples from control rats assayed directly in the water-loaded ethanol-anaesthetized rat had no detectable antidiuretic activity. The same negative result was observed in plasma obtained from male rats during courtship. However, plasma obtained from male rats at different time intervals after copulation had an antidiuretic activity which was maximal one h after ejaculation. When the ADH was extracted from pools of plasma samples, the circulating level of the hormone in control rats was also measured. The plasma antidiuretic activity after copulation was abolished after thioglycolate treatment which inactivates the neurohypophysial hormones. These findings suggest that ADH is released after copulation and that such a release is maintained for at least 60 min.
TL;DR: In this paper, a non-magnetic singlet ground state for the Pr 3+ ions due to crystal field splitting is discussed in terms of a nonsmooth ground state.
TL;DR: In this article, an exactly solvable Hamiltonian was proposed to describe intermediate valence systems fluctuating between two magnetic configurations, consisting of a set of localized, highly correlated states hybridized through a conduction band.
TL;DR: In this paper, the authors measured the energy distributions of Ne autoionization electrons produced in collisions of 0.5-3 keV Ne + ions with Al surfaces and found a strong broadening and a weak energy shift of the lines with increasing projectile energy.