Showing papers by "National University of Cuyo published in 1979"

Electron emission from clean metal surfaces induced by low-energy light ions

Abstract: We have measured the electron emission yields of clean Li, Al, Cr, Cu, Ag, and Au surfaces under bombardment with ${\mathrm{H}}^{+}$, ${\mathrm{H}}_{2}^{+}$, ${\mathrm{D}}^{+}$, ${\mathrm{D}}_{2}^{+}$, and ${\mathrm{He}}^{+}$ ions in the energy range 2-50 keV. The clean surfaces were produced by in-situ evaporation of high-purity metals under ultrahigh-vacuum conditions. It is found that the ${Z}_{2}$ dependence of the yields for hydrogen and helium projectiles are very similar, that the yields for ${\mathrm{H}}^{+}$ and ${\mathrm{D}}^{+}$ show the same energy dependence as that of the electronic stopping powers, that molecular ions give lower yields per atom than atomic ions, and that isotope effects are negligible in our energy range. It is proposed that kinetic-electron emission under low-energy-light-ion bombardment results mainly from the escape of excited electrons produced by direct binary collisions between the projectile and the valence electrons of the target.

Effects of a histamine synthesis inhibitor and antihistamines on the sexual behavior of female rats.

Abstract: Intraventricular administration of α-hydrazinohistidine, a histamine synthesis inhibitor, at different doses and times before testing produced a significant decrease of lordotic responses and sexual receptivity in ovariectomized estrogen plus progesterone-primed female rats. The H1-antihistamines pyrilamine and chlorfeniramine and the H2-antihistamine metiamide, injected in the lateral ventricle, significantly decreased the lordosis quotient but did not modify receptivity; antihistamine-injected rats showed no soliciting behavior. Exploratory activity was decreased by both α-hydrazinohistidine and metiamide but not by the H1-antihistamines. It is concluded that treatments which either deplete histamine or block their receptors can alter female copulatory responsiveness. The mechanism of this antihistamine effect appears to be unrelated to that of other side effects, such as motor impairment, sedation, or local anesthesia.

Intermediate valence: Phase diagram and Kondo behaviour in a simple model

Abstract: We have studied an infinitely narrow band version of the Anderson Hamiltonian. Including a Coulomb repulsion between localized and band states in the mean field approximation, we have been able to describe metal-insulator phase transitions and different properties characteristic of intermediate valence in both phases. These include: non-integer occupation, specific heat, saturating static magnetic succeptibility and dynamical properties such as Mossbauer spectra and spin flip neutron spectra. We discuss for what range of values of the parameters some results can be reproduced by a narrow band version of the Kondo Hamiltonian.

A Simple Method to Detect Complement Receptors using Baker's Yeast: YC Rosettes

Abstract: A technique is described to identify complement-receptor-bearing cells, using serum-treated baker's yeast as a ligand. The method consists of incubation of heat-killed baker's yeasts with fresh AB normal serum, freezing, thawing, and washing of the particles, followed by mixing with the cells. Serum is required to coat the yeasts for the rosette formation. Experiments designed to establish the serum factors responsible for the attachment of the particles to cells show that heat inactivation, chelating agents, or anti-C3 treatment prevent rosette formation. This is taken as evidence that yeasts (Y) are coated with complement (C) to compose the reagent for the YC rosette technique. The application of this technique to twenty-five normal individuals demonstrated that a mean of 11.6 per 100 lymphocytes (+/- 4.3) form rosettes; absolute number: 275 (+/- 160) rosette-forming lymphocytes per mm3. Either AB or autologous fresh serum can be used to coat the yeasts. A combined technique for YC plus E rosettes can be performed allowing the identification and enumeration of four populations of lymphocytes: (a) those having receptors for sheep erythrocytes, (b) complement-receptor-bearing lymphocytes, (c) those having both receptors (D lymphocytes), and (d) non-rosette-forming non-phagocytic cells.

Release of prolactin and LH and histamine-containing cells in brain.

Abstract: The effects of histamine released from mast cells by the compound 48/80, a degranulating agent, on plasma prolactin and LH levels, were examined in rats. Compound 48/80 given systemically (s.c.) at a dose of 2 mg/100 g b.w. significantly increased at 15 and 60 min after injection, both prolactin and LH release in ovariectomized, steroid-primed rats. Prolactin but not LH was also augmented in the plasma of male rats following s.c. administration of compound 48/80.