Showing papers by "National University of La Plata published in 1986"
TL;DR: In this article, the authors proposed a method for electrochemical faceting of polycrystalline metal wires, which can be applied either electrochemically through conventional voltammetry in the H and O electroadsorption/electrodesorption potential range, or by scanning electron microscopy.
100 citations
TL;DR: In birds, as in mammals, the control of ACTH secretion may be exerted by neurohypophyseal peptides and a CRF-like peptide acting synergistically upon the corticomelanotropic cell.
79 citations
TL;DR: In this paper, the influence of ionic composition on the electrodissolution and passivation of iron electrodes in potassium carbonate/bicarbonate buffers is studied over the concentration range of anions compatible with the regulating capacity of the buffer, at 25°C, by using voltammetric and rotating disc electrode techniques.
72 citations
TL;DR: In this paper, the electrochemical faceting of polycrystalline (pc) gold electrodes in 1 M H2SO4 was investigated by employing wire and bead-shaped electrodes.
52 citations
51 citations
TL;DR: In this article, the IR spectra of the nitroprusside ion in Na2[Fe (CN) 5NO were obtained for thin (100) single crystal plates in the ranges 4000-430 cm-1 and 4000-550 cm- 1 for polarizations along the 1b and c -axes, respectively.
49 citations
TL;DR: The sedimentary and stratigraphic characteristics of eolian Permian deposits exposed in Mendoza, La Rioja and San Juan Provinces (west and northwest Argentina) are described in this article.
46 citations
TL;DR: In this article, a real-space observation in the nanometric range of electrochemically faceted (100)-type Pt electrodes was made using scanning tunnelling microscopy (STM) and the existence of a faceted surface consisting of flat parts surrounded by ridge-type structures.
Abstract: The surface of a number of metals such as platinum, gold, rhodium and palladium, which are of particular interest in catalytic and electrocatalytic processes, either as polycrystalline or single-crystal specimens, can be preferentially orientated by a procedure known as electrochemical faceting1–3. Here we report the first real-space observation in the nanometric range of electrochemically faceted (100)-type Pt electrodes, using scanning tunnelling microscopy (STM)4. Our findings confirm the existence of a faceted surface consisting of flat parts surrounded by ridge-type structures. At the initial stages cluster formation is observed, which subsequently develops in a preferential orientation. This constitutes direct evidence that faceting occurs through a selective electrodissolution/electrodeposition process, which probably involves a fast diffusion of metallic species either in the electrolyte or on the surface.
42 citations
TL;DR: In this paper, the electrodeposition of silver on polycrystalline platinum in 0.1 M HClO 4 at 30° C was studied using potentiostatic and potentiodynamic techniques.
41 citations
TL;DR: Overall adsorption of various symbiotic and nonsymbiotic bacterial strains to alfalfa and clover roots did not reflect the specificities of these legumes for their respective microsymbionts, R. meliloti and R. trifolii.
Abstract: Bacteria adsorbed in low numbers to alfalfa or clover root surfaces were counted after incubation of seedlings in mineral solution with very dilute inocula (less than 105 bacteria per ml) of an antibiotic-resistant strain under defined conditions. After specified washing, bacteria which remained adsorbed to roots were selectively quantitated by culturing the roots embedded in yeast extract-mannitol-antibiotic agar and counting the microcolonies along the root surface; the range was from about 1 bacterium per root (estimated as the most probable number) to 50 bacteria per cm of root length (by direct counting). This simple procedure can be used with any pair of small-rooted plant and antibiotic-resistant bacterium, requires bacterial concentrations comparable to those frequently found in soils, and yields macroscopic localization and distribution data for adsorbed bacteria over the root surface. The number of adsorbed bacteria was proportional to the size of the inoculum. One of every four Rhizobium meliloti cells adsorbed in very low numbers to alfalfa roots resulted in the formation of a nodule. Overall adsorption of various symbiotic and nonsymbiotic bacterial strains to alfalfa and clover roots did not reflect the specificities of these legumes for their respective microsymbionts, R. meliloti and R. trifolii.
36 citations
TL;DR: In this paper, the Kubelka-Munk theory was applied to determine relative concentrations of muscle pigments in packaged refrigerated beef using reflectance spectrophotometry, and the effects of storage temperatures and gaseous film permeabilities on myoglobin oxygenation and oxidation rates were analyzed in unsterile beef tissue.
Abstract: Equations derived from Kubelka-Munk theory were applied to determine relative concentrations of muscle pigments in packaged refrigerated beef using reflectance spectrophotometry. Effects of storage temperatures and gaseous film permeabilities on myoglobin oxygenation and oxidation rates were analyzed in unsterile beef tissue. Kinetic constants for metmyoglobin accumulation during aerobic storage were measured assuming a first order reaction with respect to unoxidized myoglobin; values were in the range of autoxidation rate constants reported for solutions. Myoglobin oxygenation was described as a first order reversible reaction. The influence of vacuum aging time on kinetic constants was determined considering microbial growth and losses of enzymatic activity during previous storage.
TL;DR: In this paper, Akaganeite suspended in hydrazine-containing aqueous solutions at pH 9.5-11.5 and 373 K, is transformed into magnetite through a dissolution-recrystallization mechanism.
TL;DR: In this paper, the characterization of slags from different sources by their chemical composition, glass content, rate and total heat of hydration and compressive strength development with a view to establish a relationship between some of their properties and Compressive strength is presented.
TL;DR: In this article, cyclization of benzylsulphonamides with aldehydes in strong acid media is a synthetically useful route to 3,4-dihydro-1H-2,3-benzothiazine 2,2-dioxides III.
TL;DR: The differential effects of homologous and heterologous competitors indicate that initial adsorption of R. meliloti to the root surface of its host occurs in symbiont-specific as well as nonspecific modes and suggest the existence of binding sites on roots which are highly selective for the specific microsymbiont in the presence of otherheterologous bacteria even in very unfavorable symbionT-competitor concentration ratios.
Abstract: Early (4 h) adsorption of Rhizobium meliloti L5-30 in low numbers to alfalfa roots in mineral solution was examined for competition with other bacterial strains. All tested competitor strains decreased the adsorption of L5-30 by extents which depended on the strain and its concentration. The decrease of adsorption by R. meliloti competitors (all of them infective in alfalfa) was nearly complete at saturation (97 to 99% decrease). All other heterologous rhizobia and Agrobacterium tumefaciens at saturating concentrations (106 to 107 per ml) decreased adsorption of L5-30 only partially, less than 60%. The differential effects of homologous and heterologous competitors indicate that initial adsorption of R. meliloti to the root surface of its host occurs in symbiont-specific as well as nonspecific modes and suggest the existence of binding sites on roots which are highly selective for the specific microsymbiont in the presence of other heterologous bacteria even in very unfavorable (less than 10−4) symbiont-competitor concentration ratios.
TL;DR: In this article, a low-temperature form of InVO4, belonging to the α-MnMoO4 structural type, was characterized using X-ray powder diagrams.
TL;DR: In this article, the authors studied vortex solutions in non-abelian gauge theories with spontaneous symmetry breaking and constructed string configurations with electric charge showing that they necessarily have infinite energy per unit length.
TL;DR: The electric field gradient at Zr sites has been measured by time-differential perturbed angular correlations in amorphous and crystalline Zr/sub 68/Hf/sub 2/Cu/sub 30/ alloys to support a dense random packing of atoms and discard any kind of regular atomic arrangements in the amorphously alloy.
Abstract: The electric field gradient at Zr sites has been measured by time-differential perturbed angular correlations in amorphous and crystalline ${\mathrm{Zr}}_{68}$${\mathrm{Hf}}_{2}$${\mathrm{Cu}}_{30}$ alloys. The results support a dense random packing of atoms and discard any kind of regular atomic arrangements in the amorphous alloy.
TL;DR: In this paper, the infrared and Raman spectra of Fe 2 P 2 O 7 have been recorded and discussed, and the results point to a bent bridge conformation and to a centrosymmetric space group.
TL;DR: It is suggested that estradiol in females may counteract sexual cranial development and that its inhibitory effect may be additive to the testosterone deficit evoked by malnutrition.
Abstract: Two groups of weanling rats were subjected to malnutrition, one with periodic injections of testosterone (males) and the other with estradiol (females). Two other groups (castrated males or castrated females) received normal feedings. In control animals, the relative weights (mg/gm body weight) of testes, seminal vesicles, and ovaries were greater than in malnourished rats. However, relative weights of those organs in hormone-treated, malnourished animals were greater than in those subjected to malnutrition alone and still greater than in controls. Normal sexual cranial dimorphism (SCD) was decreased 16% by male castration, 23% by malnutrition, and 83% by estradiol treatment in malnourished females. On the other hand, normal SCD was increased 20% by female castration and more than 200% by testosterone treatment in malnourished males. All monosexual comparisons corroborated the bisexual range of distances found. Testicular but not ovarian secretions seemed to influence sexual cranial dimorphism. Malnutrition delayed SCD because of a deficiency of testosterone level in stressed males. It is suggested that estradiol in females may counteract sexual cranial development and that its inhibitory effect may be additive to the testosterone deficit evoked by malnutrition.
TL;DR: A case of acquired, nonprogressive kinking of the hair, a rare abnormality, is studied by means of optical microscope and scanning electron microscopy and a standard of measure is proposed for estimation of the number of cuticular cells per diameter.
Abstract: A case of acquired, nonprogressive kinking of the hair, a rare abnormality, is studied by means of optical microscopy and scanning electron microscopy. In addition, a standard of measure is proposed for estimation of the number of cuticular cells per diameter. The criteria for confirmation of the diagnosis of this case are also described.
TL;DR: In this article, the electrochemical response of the precipitated iron hydroxide layer depends considerably on the layer thickness and precipitation conditions and was interpreted in terms of the complex structure involving an inner poorly hydrated layer and an outer porous layer.
TL;DR: In this paper, the ligand substitution kinetics of Na3 [Fe(CN)5(4-picolylamine) bridged Na6[Fe2- (CN)10(4)-picolyamine]·5H2O were reported.
Journal Article•
TL;DR: The Local Fauna Empalme Querandies (LFE) as mentioned in this paper was defined based on faunal remains Irorn sediments of Arroyo Tapalque (OlavarrIa County, Buenos Aires Province).
Abstract: This paper is part of a research prograrn that includes the faunal assemblages from Quaternary sediments. It implies the recognition of a hierarchical system of unit of mammalian stratigraphy according to the continental deposits. This system comprises the following subordinated units: Local Fauna, Land Mammal Unit and Land Mammal Age. The Local Fauna Empalme Querandies is presented in this contribution. It has been defined based on faunal remains Irorn sediments of Arroyo Tapalque (OlavarrIa County, Buenos Aires Province). These deposits were assigned to the Guerrero Member of the Lujan Forrnation. This Local Fauna corresponds to the Lujanian Land Mammal Unit (upperrnost part of the Late Pleistocene).
TL;DR: In this article, the diffusion coefficient of sulfur dioxide in potato tissue was compared to theoretical predictions in terms of molecular diffusivity, total solids content and tortuosity factor.
Abstract: Sulfur dioxide uptake by pre-peeled potatoes from dipping solutions was mathematically modeled. Diffusive mass transfer equations in porous medium were experimentally verified; residual levels of sulfur dioxide were measured in the range of industrial operating conditions. Effects of sodium bisulfite solution concentration, immersion time, size, shape, dry matter, density and velocity of the product were analyzed. Three geometric approximations to pre-peeled potato cuts were examined (spheres, cubes and parallelepipeds). The fitting of equations to experimental data determined the effective diffusion coefficient of sulfur dioxide in potato tissue, which was compared to theoretical predictions in terms of molecular diffusivity, total solids content and tortuosity factor.
TL;DR: In this paper, the infrared and Raman spectra of CCL3SCl have been thoroughly investigated and as results a complete assignment of bands and point group C1 for the molecule are proposed.
Abstract: The infrared and Raman spectra of CCL3SCl have been thoroughly investigated and as results a complete assignment of bands and point group C1 for the molecule are proposed.
TL;DR: A parallel leftward shift of the concentration-relaxation curve was detected in the K-precontracted aortic smooth muscle from hypertensive rats, and increased sensitivity seems to be related to the degree of hypertension and independent of the experimental method used to produce the high blood pressure level.
Abstract: The sensitivity of smooth muscle from aortas of spontaneously hypertensive rats (SHR), renal hypertensive rats: two kidney-one clip and one kidney-one clip (2K-1C, 1K-1C) and DOCA salt hypertensive rats to the relaxant effect of nifedipine (NIF) was studied. A parallel leftward shift of the concentration-relaxation curve was detected in the K-precontracted aortic smooth muscle from hypertensive rats. This increased sensitivity seems to be related to the degree of hypertension and independent of the experimental method used to produce the high blood pressure level. No change in sensitivity was detected either in SHR or in renal hypertensive rats when nitroglycerin was used as a vasodilator.
TL;DR: In this article, the crystal structure of polycrystalline compounds was determined from diffractometer data and refined with isotropic thermal parameters to final values ofR=0.058 and R = 0.056.
Abstract: The crystal structure of the title compound has been determined from diffractometer data and refined with isotropic thermal parameters to finalR
w
factors ofR=0.058 andR
w
=0.056. It crystallizes in the orthorhombic space groupp212121 (No. 19), witha=9.706(7),b=18.826(6), andc=25.258(6) A. The asymmetric unit contains four nitroprusside ions, eight potassium ions, and five water molecules, one of which shows disorder. The infrared spectra of the polycrystalline compound, both normal and with different degrees of deuteration at temperatures ranging from liquid nitrogen to room temperature, were obtained. The vibrational spectra present an unusual number of fundamental and first overtone NO stretching bands and a rich structure in the water bending region, in accordance with the existence of inequivalent nitroprusside ions and water molecules.
Journal Article•