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Journal of Radioanalytical and Nuclear Chemistry
Authors:
H. López-González
,
M. Jiménez-Reyes
,
M. Solache-Ríos
, and
A. Rojas-Hernández

Abstract  

Solubility product (Lu(OH)3(s)⇆Lu3++3OH) and first hydrolysis (Lu3++H2O⇆Lu(OH)2++H+) constants were determined for an initial lutetium concentration range from 3.72·10−5 mol·dm−3 to 2.09·10−3 mol·dm−3. Measurements were made in 2 mol·dm−3 NaClO4 ionic strength, under CO2-free conditions and temperature was controlled at 303 K. Solubility diagrams (pLuaq vs. pC H) were determined by means of a radiochemical method using 177Lu. The pC H for the beginning of precipitation and solubility product constant were determined from these diagrams and both the first hydrolysis and solubility product constants were calculated by fitting the diagrams to the solubility equation. The pC H values of precipitation increases inversely to [Lu3+]initial and the values for the first hydrolysis and solubility product constants were log10 β* Lu,H = −7.92±0.07 and log10 K*sp,Lu(OH)3 = −23.37±0.14. Individual solubility values for pC H range between the beginning of precipitation and 8.5 were S Lu3+ = 3.5·10−7 mol·dm−3, S Lu(OH)2+ = 6.2·10−7 mol·dm−3, and then total solubility was 9.7·10−7 mol·dm−3.

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Abstract  

Several ornaments named tezcacuitlapilli (coccyx-mirrors) are described and chemical analyses of raw materials (slate and pigments) were carried out by neutron activation, X-ray diffraction, scanning electron microscopy and radiography. Elemental and statistical analyses revealed that three different kinds of slate were used in their manufacture. The white pigment contains gypsum while ochre, yellow and red pigments contain iron oxide. These ornaments were identified as coming from the Cave of the Sun Pyramid of Teotihuacan. An attempt was undertaken to reconstruct the contexts of their manufacture and symbolic interpretation.

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Abstract  

The behavior of uranyl ion and tervalent Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu in the solvent extraction system: M–HCl–H2O–TBP has been studied together with chromatographic elution of the first nine of these rare earth elements using DOWEX 50Wx8 resin. >99.5% of the rare earth elements, with a single exception, remained in the aqueous phase of the solvent extraction system where the initial concentration of hydrochloric acid was between 4 and 6 M. Under these conditions uranyl ions were readily extracted by TBP. The rare earth elements were quantitatively eluted from the chromatographic column using 6M hydrochloric acid solution and the uranyl ions in a 0.75M sulfuric acid solution.

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Journal of Radioanalytical and Nuclear Chemistry
Authors:
R. López-Valenzuela
,
J. López-Palacios
,
M. Jiménez-Reyes
,
G. Cataño
, and
D. Tenorio

Abstract  

Thirteen Teotihuacan-style ornaments of an incense burner were studied. Ceramic pastes, pigments and mica were analyzed by neutron activation, X-ray diffraction and scanning electron microscopy. Elemental (Sc, Cr, Fe, Co, Rb, Cs, La, Ce, Nd, Sm, Eu, Tb, Yb, Lu, Hf, Th and U) and statistical analyses of ceramic-body data showed that these pieces were made from the same raw material, which is chemically different from the fine orange ceramic of Teotihuacan. Montmorillonite and the classical components of sand were the minerals identified in the ceramic pastes. The white pigment contained calcium, titanium and aluminium, the yellow pigment was ocher, and the red pigment was a mixture of red ocher and cinnabar, the binder of the pigments being clay. Exoskeletons of diatoms and locust ootecs were found in the pigments. Mica was identified as biotite, identical with that coming from Monte Alban Oaxaca. We wish to undertake a historical reconstrution of these ornaments based on archaeometric and literature data.

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Abstract  

Five species of scleractinean corals, extracted from the Northern Havana reef, were studied by INAA and AAS. Selected specimens were sectioned in foot, center and head parts before pulverization procedure. INAA for different irradiation and decay time regimes in a reactor allowed the determination of: Na, Mg, Al, Cl, Sc, Cr, Co, Th, Lu, Eu, Ce, Hf, La and Sr. AAS was performed in a Pye Unicam Model 929 spectrometer. Cu, Mn, Ni, Zn, and Fe were detected. Ca concentration in all species was also established. Obtained Metal-Calcium ratios for Sr, Cu, Zn, Cr, Co, Fe, Mn, Ni and Sc are compared with reported values.

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Journal of Radioanalytical and Nuclear Chemistry
Authors:
O. Díaz Rizo
,
M. Manso Guevara
,
E. Herrera Peraza
,
I. Alvarez Pellón
, and
M. López Reyes

Abstract  

Using the facilities of the Triga Mark III reactor at the NNRI, Mexico and the HAV-1 multipurpose monitor, the reactor power dependency for thek 0-standardization essential neutron flux parameters as: epithermal shape factor (), thermal to epithermal ratio (f) and neutron temperature (T n ) were experimentally obtained. Evaluation of the obtained dependencies shows that it is unnecessary to analyze the possible introduction of correction factors in thek 0-INAA experimental results. A single experimental procedure to determine throughf is suggested.

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Abstract  

Obsidian samples from 13 Mexican quarries (Sierra de Pachuca and Zacualtipan, Hidalgo, Zaragoza and Oyameles, Puebla, Altotonga Veracruz and eight sites of the Zinaparo — Varal — Churintzio Hills region) have been analyzed by NAA. The concentration of 19 elements, major and trace, are reported. Excepting Altotonga Veracruz, the chemical composition of other obsidian flows was found homogenous. The region of the Varal obsidian was delimited. An excellent correlation between ytterbium and lutetium contents in obsidians was found.

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Journal of Radioanalytical and Nuclear Chemistry
Authors:
O. Díaz Rizo
,
M. Manso Guevara
,
E. Herrera Peraza
,
I. Alvarez Pellón
,
M. López Reyes
,
D. López Aldana
, and
F. Garcia Yip

Abstract  

The experimental dependence of the α,f andT n parameters, in function of the water thickness, for different irradiation channels of Triga Mark III reactor, were analyzed. An exponential law for the α(r) dependence was obtained in the neighborhood of the active zone of the reactor numerically modelated using theS n method for 69 neutrons groups, and this dependence is slower in light water reactors than in graphite reactors.

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Journal of Radioanalytical and Nuclear Chemistry
Authors:
O. Rizo
,
E. Herrera Peraza
,
M. Manso Guevara
,
I. Pellón
,
M. López Reyes
,
M. Cabrera
, and
M. Montero Cabrera

Abstract  

The main results obtained during the characterization of the Triga Mark III reactor at NNRI, Salazar, Mexico, the development of the nonconventional multimonitor HAV-1, the use of Certified Reference Material (CRM) as multimonitor fork 0-factors experimental determination, and to study the reactor power and slowing-down thickness dependencies of the reactor flux parameters and its influence ink 0-INAA are presented. The experience of thek 0-INAA group at ISCTN, in the application of this analytical technique for different purposes is resumed.

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Journal of Radioanalytical and Nuclear Chemistry
Authors:
E. Herrera Peraza
,
O. Rizo
,
M. Montero Cabrera
,
A. Hernández
,
R. Folgar
,
M. Cabrera
,
O. Aguilar
,
M. Guevara
,
I. Pellon
,
R. López Duménigo
,
G. González
, and
M. López Reyes

Abstract  

This paper explains chronologically the implementation of thek 0-standardization and other parametric methods in Cuba. Fundamental and applied results in the determination of the most important parameters are obtained, using the IBR-2 at Dubna and Triga Mark III at Mexico reactor facilities. Some modifications in the Stoughton-Halpering convention, and its comparison with the modified Westcott and Høgdahl method are presented. The application of the described methods at the CS-ISCTN low flux facility, using the big samples techniques, is presented.

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