Showing papers by "National University of La Plata published in 1985"
TL;DR: In this paper, the characteristics of hydrous zirconia gels obtained by hydrolysis of highly acidic ZrOCl2 · 8H2O solutions at ∼100‡C are described.
Abstract: The characteristics of hydrous zirconia gels obtained by hydrolysis of highly acidic ZrOCl2 · 8H2O solutions at ∼100‡C are described. Under adequate conditions, monodisperse spherical hydrous zirconia is obtained. The role of sulphate and chloride ions is described. The gel has a large water content, indicating only modest crosslinking. Crystallization upon heating takes place with the formation of both monoclinic and tetragonal zirconia polymorphs; X-ray line widening studies do not indicate a particle size-crystal structure correlation. On the basis of this observation and using Stranki's rule, the crystallization sequence upon heating is rationalized. Surface properties of hydrous zirconia are discussed on the basis of electrophoretic measurements, and compared with those of baddeleyte. The site binding model is not very adequate to describe these systems, and the existence of a very thin gel-like region at the baddeleyte-water interface is postulated.
103 citations
TL;DR: In this paper, the kinetics of starch gelatinization in potatoes were determined by a dynamic DSC method and the results were verified by an isothermal method, assuming a semi-cooperative process where the gelatinization of the amorphous regions of the granule acts as a reaction "promoter" of the crystalline zones.
Abstract: The kinetics of starch gelatinization in potatoes was determined by a dynamic DSC method. The results were verified by an isothermal method. Experiments were carried out on small portions of potato tissue, thus assuring that the gelatinization conditions obtained were representative of the sum of the processes occurring on thermal treatment of potatoes. The rate constants were calculated and two activation energies were found for different temperature ranges. At temperatures below 67.5°C gelatinization was not complete, even for long reaction times. A reaction mechanism is proposed, assuming a semi-cooperative process where the gelatinization of the amorphous regions of the granule acts as a reaction “promoter” of the crystalline zones.
73 citations
TL;DR: In this article, the estimation of regression parameters after summarizing the data by a covariance matrix of the concatenated vector of explanatory variables and response variable is discussed, and the resulting regression estimator is compared to a few previously proposed robust regression estimators.
Abstract: This paper discusses the estimation of regression parameters after summarizing the data by a covariance matrix of the concatenated vector of explanatory variables and response variable. A robust estimate of the covariance matrix leads to a robust regression estimator. An M-estimator at the covariance estimation step is studied in the paper, and the resulting regression estimator is compared to a few previously proposed robust regression estimators.
36 citations
TL;DR: In this paper, a stroboscopic map of symmetric self-oscillators driven by pulses of alternating sign is constructed, for the regime of strong relaxation, by means of the so-called phase transition curve.
Abstract: The stroboscopic map of symmetric self-oscillators driven by pulses of alternating sign is constructed, for the regime of strong relaxation, by means of the so-called phase-transition curve. An ordering for the symmetries of the phase-locked orbits is found which is conjectured to be universal. Both results are illustrated by an exactly solvable example of such a system. When the approximation fails, unusual period doubling from symmetric orbits and strange attractors of two-dimensional structure are encountered.
29 citations
TL;DR: In this paper, the i.r. and Raman spectra of the phases of InVO 4 and TlVO 4 were analyzed with the aid of a site symmetry analysis and by comparison with the results obtained for other orthovanadates.
24 citations
TL;DR: In guinea-pig infected with foot-and-mouth disease virus, Langerhans cells in the foot pads increase in number and show viral antigens 24 hours post-inoculation, preceding appearance of virus in epithelial cells and vesiculation.
Abstract: In guinea-pig infected with foot-and-mouth disease virus (FMDV), Langerhans cells in the foot pads increase in number and show viral antigens 24 hours post-inoculation, preceding appearance of virus in epithelial cells and vesiculation. This observation suggests that Langerhans cells may be engaged in virus transport from the blood to the non vascularized epidermis.
24 citations
TL;DR: It is concluded that 1400 hr, as contrast to 0200 hr, is an optimal time for hepatectomy if one wants to obtain the highest mitotic index first peak during regeneration in a normal phase position.
Abstract: Standardized (light from 0600 to 1800) C3HS mice, hepatectomized at different circadian stages, were killed at 1400 (the peak time of mitotic activity in intact mice). The higher values of mitotic index were those of mice operated at 1400, 48 hr before. The curve of mitotic activity of the regenerating liver of mice operated at 1400 and that of mice operated at 0200 (an opposite time in the circadian stage) are, both, grossly in phase with the curves of mitotic index in young and adult mice liver. The amplitude of the first peak of mitotic activity in mice operated at 0200 was dramatically lower than that of animals operated at 1400. The same applies to hepatocytes as well as to the sinusoid litoral population of cells. It is concluded that 1400 hr, as contrast to 0200 hr, is an optimal time for hepatectomy if one wants to obtain the highest mitotic index first peak during regeneration in a normal phase position (the position of the mitotic index peak in the liver of normal young and adult mice).
21 citations
TL;DR: Immature embryos of 4 flint, 3 floury-a and 1 dent inbred and 6 hybrid genotypes of Zea mays L. were cultured on three different 2,4-D-containing nutrient media producing an opaque, white to pale yellow, soft, friable and organogenic callus.
18 citations
TL;DR: Variations of DNA synthesis (DNAS) and mitotic indices along a circadian time span are described in the hepatocyte and sinusoid litoral cell populations of adult intact male mouse liver.
Abstract: Variations of DNA synthesis (DNAS) and mitotic indices along a circadian time span are described in the hepatocyte and sinusoid litoral cell populations of adult intact male mouse liver. Standardized (light from 0600 to 1800) mice were killed in groups of six to nine animals, every 2-4 hr along a circadian time span. Hepatocytes show significant peaks in the synthesis of DNA and the mitotic activity at 0200 and 1400, respectively. These results correspond to those previously described by us in young immature liver, regenerating liver and hepatomas. The phase differences between these peaks and the differences between their absolute values are discussed. Also considered are the practical consequences of our findings for experimental design. The curve of DNA synthesis of sinusoid litoral cells show a peak at 0200. The mitotic index show a bimodal waveform with peaks at 0800 and 2000. The existence of four different cell populations composing the so called sinusoid litoral cells and also the migration into a...
18 citations
TL;DR: The growth of nine strains of four different species ofRhizobium was studied with media containing malt sprouts extract (MSE), in place of yeast extract (YE), as source of nitrogen and growth factors, and the results obtained in batch cultures indicated that all the strains grew well in MSE medium.
Abstract: The growth of nine strains of four different species ofRhizobium (R. leguminosarum, R. meliloti, R. phaseoli andR. japonicum) was studied with media containing malt sprouts extract (MSE), in place of yeast extract (YE), as source of nitrogen and growth factors. The results obtained in batch cultures indicated that all the strains grew well in MSE medium. In the case of fast-growing strains the biomass increased with increase in the concentration of MSE in the medium, but with the slow-growing strains, likeR. japonicum, growth was inhibited completely by using a concentration of MSE (containing 3.75% w/v of solids) of 40% v/v. With all the strains the concentration of cells attained was greater than 5×109 cells/ml, which clearly indicates that MSE is a suitable component of media, and one which can be used instead of YE. The results of continuous culture experiments showed that a high productivity of cells (15.3×108 cells/ml/h) could be obtained using MSE medium.
18 citations
TL;DR: In this paper, Li, Na, K, Rb, Cs and Ag were all introduced into the aluminosilicate framework of leached spodumene and each cationized phase was studied by infrared and X-ray techniques.
TL;DR: In this article, the total energy and pressure-volume relations for Si, Ge, and \ensuremath{\alpha}-Sn within the local density functional formalism, with use of first-principles nonlocal pseudopotentials.
Abstract: The total-energy and pressure-volume relations are calculated nonrelativistically for Si, Ge, and \ensuremath{\alpha}-Sn within the local-density-functional formalism, with use of first-principles nonlocal pseudopotentials. Ground-state static structural properties (total energy, lattice constant, and bulk modulus and its pressure derivative) are obtained and are in good agreement with experimental values. A prediction of these for \ensuremath{\alpha}-Sn from pressure determinations has not yet been reported. Its bulk modulus from both total-energy and pressure calculations is much smaller than that determined by experimental measurement. This confirms a recent theoretical prediction from other authors casting doubts on the experimental value. An assessment has been made on the advantages and disadvantages of pressure calculations over total-energy calculations and on the influence on the results of the size of all cutoff parameters and perturbative schemes used.
TL;DR: The hyperfine quadrupole interaction of HfF4.3H2O at Hf sites is investigated from 14 to 820 K in this article, and no transitions have been found.
Abstract: The hyperfine quadrupole interaction of HfF4.3H2O at Hf sites is investigated from 14 to 820 K. No transitions have been found. After the complete dehydration of this compound at 393 K, chemical reactions take place which give rise to hafnium oxifluorides and metastable forms of hafnium oxide. Heating treatments at increasing temperatures make HfO2 turn into its monoclinic phase.
01 Jan 1985
TL;DR: In this paper, the infrared spectra of polycrystalline compound of the title, both normal and with different degrees of deuteration, at temperatures ranging between ca. 80 K and room temperature, were obtained.
TL;DR: Although seed tubers of the December planting were physiologically significantly younger than those obtained from the November planting in two of the three seasons studied, no reliable effect upon tuber yield was found.
Abstract: The effect of two planting dates upon the physiological age of seed tubers, measured by their incubation period, and their yielding potential was studied during a three-year period with two medium-early and one medium-late cultivar. Although seed tubers of the December planting were physiologically significantly younger than those obtained from the November planting in two of the three seasons studied, no reliable effect upon tuber yield was found. Reasons for this lack of relation are discussed. The accumulated day-degrees above 17°C (daily mean temperature) during the bulking period of the seed crop modified the incubation period of the tubers clearly.
TL;DR: The results suggest that dolichols may play a role in biological membranes, besides the well-known glycosyl carrier function in the biosynthesis of glycoproteins, and that K+ was significantly increased above the phase transition temperature.
TL;DR: In this article, the preparation of VO(PO 2 H 2 ) 2 ·H 2 O was possible by direct reduction of V 2 O 5 with hypophosphorous acid or by interaction of VOSO 4 and H 3 PO 2 solutions, and subsequent crystallization.
TL;DR: The results would suggest that activation of phospholipases, particularly A2, is involved in the mechanism by which glucose stimulates insulin release, which increases the intracellular concentration of arachidonic acid, prostaglandins and probablyospholipid degradation products, that could act as messengers for the stimulus-secretion coupling of insulin.
01 Jan 1985
TL;DR: Several pro-opiomelanocortin (POMC) peptides were detected by means of three heterologous RIA systems: alpha-MSH, ACTH and beta-endorphin, and parallelism among extracts displacement curves ranged from 26% to 95% of those of the standard curves for the different systems employed.
TL;DR: In this paper, a detailed study of the pressure dependence of the energy gaps has been made, for prototype semiconductor Si. It is shown that although the correct gaps for semiconductors cannot be obtained within local density functional, their pressure variation is still well accounted for.
TL;DR: Bosonization rules for fermion currents in QCD 2 are constructed using a very simple approach within the path-integral framework, based on the existence of a gauge condition in which fermions can be decoupled.
TL;DR: In this article, the hyperfine interactions at In and Sn sites of In2O3∶Sn (ITO) were measured through time-differential perturbed angular correlations and Mossbauer spectroscopy, respectively.
Abstract: The hyperfine interactions at In and Sn sites of In2O3∶Sn (ITO) were measured through time-differential perturbed angular correlations and Mossbauer spectroscopy, respectively. Polycrystalline samples prepared by co-precipitation with nominal 0.025, 1 and 5 at.% Sn were studied. They all showed the cubic bixbyite structure characteristic of In2O3 after annealings at 200 °C. The quadrupole interaction at In sites appears nearly independent of Sn concentration being the main result of the presence of Sn in the lattice, the gradual disappearence of the dynamic perturbation caused by after-effects. The Mossbauer data demonstrate that Sn ions are in a 4+ state with ΔQ=0.606 mm/s andδ=0.226 mm/s relative to SnO3Ca at room temperature.
TL;DR: It is suggested that raised CIC detected by the 125I-C1q method may reflect a progressive state in ALL and that quantitation of these immune complexes may provide an adequate biochemical marker for prognosis.
Abstract: A total of 122 sera from acute lymphoblastic leukemia (ALL) patients were analyzed for circulating immune complexes (CIC) by two methods: the 125I-C1q binding assay and the polyethylene glycol precipitation test (PEG). The results were correlated with induction, remission and relapse stages of the disease. Using the first method the levels of CIC in induction were 15.18±9.15, with 19/29 positive cases (65.50%), P<0.001 compared with controls. In the remission phase the levels were 9.02±5.62, 11/45 (24.49%) nonsignificant P value, and in relapse they were 16.14±11.17 28/48 (58.33%) P<0.001. The PEG precipitation test results were: 0.33±0.10, 8/22 (36.36%); 0.24±0.11, 10/48 (20.83%) and 0.28±0.10, 6/28 (21.42%), respectively. Thus the values of CIC as measured by PEG in the three clinical of phases ALL did not differ significantly from controls. This contrasts with results obtained by the radioiodinated C1q binding assay, where the incidence of positive values was significantly higher in induction and in relapse and lower in the remission phase. These observations were extended in sequential vertical studies performed in a group of patients. These results suggest that raised CIC detected by the 125I-C1q method may reflect a progressive state in ALL and that quantitation of these immune complexes may provide an adequate biochemical marker for prognosis.
01 Jan 1985
TL;DR: The gas chromatographic retention behavior of nineteen halogenated hydrocarbons and of seven saturated polycyclic aromatic compounds (PAHs) was measured at four temperatures from 55 to 65°C in tri-n-octylphosphine oxide (TOPO) and at 60 °C in squalane (SQ), and the equilibrium constants were calculated by reference to the inert solvent SQ as discussed by the authors.
Abstract: The gas chromatographic retention behavior of nineteen halogenated hydrocarbons and of seven saturated hydrocarbons was measured at four temperatures from 55 to 65°C in tri-n-octylphosphine oxide (TOPO) and at 60°C in squalane (SQ). Thermodynamic functions of solution in TOPO were computed from these data. Strongly negative deviations from the ideal behavior were interpreted in terms of halogenated hydrocarbon+TOPO association, and the equilibrium constants were calculated by reference to the inert solvent SQ. The larger equilibrium constants correspond to solutes with a definite proton donor capability. The substitution of Cl for Br, however, produces an increase in the association constants suggesting the existence of other interaction mechanisms. Complexing of halogenated hydrocarbons with TOPO is markedly greater than with ethers, thioethers or tertiary amines.
Journal Article•
TL;DR: In this paper, a new series of tellurium containing mixed oxides of composition K3MIIITe3O12 (M = Al, Ga, Cr, Fe) has been described They crystallize in a superstructure-lattice of the PbTiO3 type.
Abstract: Es wird eine neue Reihe tellurhaltiger Mischoxide der Zusammensetzung K3MIIITe3O12 (mit M = Al, Ga, Cr, Fe) beschrieben, welche in einer Uberstruktur des PbTiO3-Typs kristallisieren Die kristallographischen Daten der tetragonalen Elementarzellen wurden aus Pulverdiagrammen ermittelt Die IR-Spektren dieser Phasen sowie auch das 57Fe-Mosbauer-Spektrum von K3FeTe3O12 wurden aufgenommen und analysiert
Preparation and Properties of a New Series of Tellurium Containing Perovskites of the Type K3MIIITe3O12
A new series of tellurium containing mixed oxides of composition K3MIIITe3O12 (M = Al, Ga, Cr, Fe) has been described They crystallize in a superstructure-lattice of the PbTiO3 type The crystallographic data of the tetragonal unit cells have been determined from powder diffractograms The ir spectra of these phases as well as the 57Fe-Mossbauer-spectrum of K3FeTe3O12 were recorded and discussed
TL;DR: Apple pomace, a solid waste from processing industries, was used as the raw material for production of a protein enriched pro-duct, which is adequate for cattle feed-ing and proves the technical feasibility of the process.
Abstract: Apple pomace, a solid waste from ap-ple processing industries, was used as the raw ma-terial for production of a protein enriched pro-duct. The experiments were conducted on a small scale in Erlenmeyer flasks or 4-1 fermentors in batch and fed-batch processes usingSaccharo-mycopsis lipolytica and Trichoderma reesei in sin-gle and mixed cultures. The results obtained indi-cate the technical feasibility of the process for ob-taining products containing 13% to 15% protein, on dry basis, which is adequate for cattle feed-ing.