Julio Santiago
Universidad Nacional Mayor de San Marcos, Organic Chemistry, Faculty Member
- Doctor en química con experiencia en Cristales líquidos, materiales fotoconductores, catálisis fotoquímica, fotosensi... moreDoctor en química con experiencia en Cristales líquidos, materiales fotoconductores, catálisis fotoquímica, fotosensibilizadores y terapia fotodinámica. Responsable de proyectos en Biomateriales que incluyen extractos de productos naturales o nanopartículas metálicas, con actividad biológica, especialmente para el tratamiento de tuberculosis, úlceras (leishmania cutánea), quemaduras, y lesiones a la piel en general. Igualmente ejecuto proyectos multidisciplinarios sobre la terapia fotodinamica del cancer y Tratamiento de efluentes industrialesedit
A morphological and microscopic study of the paste from Nasca pottery has been performed. A stereo microscope (x20) and a digital camera were used to study the morphology of the paste while a transmission electron microscope and electron... more
A morphological and microscopic study of the paste from Nasca pottery has been performed. A stereo microscope (x20) and a digital camera were used to study the morphology of the paste while a transmission electron microscope and electron diffraction were used for the study of the microcrystal presents in the paste. The main component of the paste were determined and also some insight about the quality of the paste preparation and calcinations.
Research Interests: Mechanical Engineering, Chemical Engineering, Materials Science, Glass, Scanning Electron Microscopy, and 15 morePyrolysis, Heat Treatment, Powder technology, Atomic Force Microscopy, Surface Roughness, Photocatalysis, Porosity, Thin Film, Grain size, Methylene Blue, Anatase, Surface Area, Thermal Treatment, Roughness, and Spray Pyrolysis
Universidad Nacional Mayor de San Marcos, Organismo Internacional de Energia Atomica, Instituto Peruano de Energia Nuclear.
Research Interests: Archaeology, Mössbauer Spectroscopy, Archaeometry, Transmission Electron Microscopy, Archeometry, and 12 moreNasca culture, Nasca, Quito, X ray diffraction, Optically Stimulated Luminescence, Nuclear Analytical techniques, Nazca, Ceramic Analysis Archaeology, Microscopía electrónica de transmisión (MET), Ceramica Nasca, Termoluminiscencia, and Difracción De Rayos X
RESUMEN Se ha aplicado diversas dosis (0-20 kGy) de radiación gamma a muestras de harina de maca (Lepidium meyenii walp) amarilla, blanca y morada para descontaminarlas. La dosis de radiación gamma necesaria para eliminar los aerobios... more
RESUMEN Se ha aplicado diversas dosis (0-20 kGy) de radiación gamma a muestras de harina de maca (Lepidium meyenii walp) amarilla, blanca y morada para descontaminarlas. La dosis de radiación gamma necesaria para eliminar los aerobios mesófilos fue 12-15 kGy mientras que para eliminar hongos fue necesario 1-8 kGy, dependiendo del tipo de ecotipo. Se determinó la actividad antioxidante de las muestras irradiadas por el método de neutralización del radical DPPH. Los valores de IC50 de las muestras estudiadas indican que la radiación gamma no modifica sustancialmente la actividad antioxidante de los extractos acuosos de maca amarilla, blanca y morada. En cambio, la actividad antioxidante de los extractos hidroalcohólicos de maca amarilla irradiada disminuye notoriamente, mas no así la de los otros ecotipos. Palabras clave: Maca, radiación gamma, descontaminación, actividad antioxidante. ABSTRACT Various doses (0-20 kGy) of gamma radiation have been applied to samples of maca (Lepidium ...
Se han obtenido hidrogeles de quitosano con alcohol polivinílico (PVA) utilizando radiación gamma. Se presenta un análisis preliminar del tipo de interacción entre las cadenas de quitosano y del PVA en estos hidrogeles. El quitosano en... more
Se han obtenido hidrogeles de quitosano con alcohol polivinílico (PVA) utilizando radiación gamma. Se presenta un análisis preliminar del tipo de interacción entre las cadenas de quitosano y del PVA en estos hidrogeles. El quitosano en solución disminuye rápidamente su peso molecular por efecto de la radiación gamma, mientras que el PVA en solución acuosa forma hidrogeles luego de ser irradiadas a dosis mayores a 5 kGy. Sin embargo, las mezclas de quitosano y PVA forman hidrogeles en los cuales estos polímeros no se degradan significativamente, y forman hidrogeles estables. Presentamos evidencias que sugieren que las cadenas de PVA y quitosano están entrecruzadas covalentemente. Esto se explica en términos de reactividad de los radicales formados por radiación gamma.
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The present work studies the improvement of the physical properties wood-polymer composites obtained by means of infiltration in vacuum of styrene-polyester, methyl methacrylate, and their mixtures. The polymerization was done by gamma... more
The present work studies the improvement of the physical properties wood-polymer composites obtained by means of infiltration in vacuum of styrene-polyester, methyl methacrylate, and their mixtures. The polymerization was done by gamma radiation and microwaves. Capirona, Oje Blanco and Cumala woods, were used in this study. The polymerization by microwaves depends on the working power. High power produces bubbles, deformation and fractures of the obtained polymer. The minimum dose to provoke the polymerization by gamma radiation is 14 kGy. The wood-polymer composites show low water absorption in comparison with the non-treated wood.
The antioxidant activity, total polyphenol content and antimicrobial activity of different extracts from dragon's blood, Croton lechleri, powder have been evaluated. The fractions obtained with ethanol, methanol, water-alcohol... more
The antioxidant activity, total polyphenol content and antimicrobial activity of different extracts from dragon's blood, Croton lechleri, powder have been evaluated. The fractions obtained with ethanol, methanol, water-alcohol solution and ethyl acetate treatment have different characteristics. The ethanol fraction has the highest antioxidant activity, while the original latex has the highest content of total polyphenols. However, the water-alcohol solution has higher antimicrobial activity against S. aureus.
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Various doses (0-20 kGy) of gamma radiation have been applied to samples of maca (Lepidium meyenii walp) flour, yellow, white and purple ecotypes, to decontaminate them. The gamma radiation dose required to eliminate the aerobic... more
Various doses (0-20 kGy) of gamma radiation have been applied to samples of maca (Lepidium meyenii walp) flour, yellow, white and purple ecotypes, to decontaminate them. The gamma radiation dose required to eliminate the aerobic mesophiles was 12-15 kGy while it was necessary to applied 1-8 kGy to kill fungi, depending on the ecotype of Maca. We have determined the antioxidant activity of the irradiated samples by the method of neutralization of DPPH radical. IC50 values of the studied samples indicate that gamma radiation does not substantially alter the antioxidant activity of aqueous extracts of maca yellow, white and purple. In contrast, the antioxidant activity of hydroalcoholic extracts of irradiated maca yellow decrease sharply, but not the other ecotypes.
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TiO2-doped polyvinyl alcohol films (PVA) have been prepared from a suspension of TiO2 nanoparticles in PVA 10% water solution. The suspension was stabilized by ultrasound
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Chitosan-polyvinyl(alcohol) films containing dragon’s blood (Croton lechleri) hydro alcoholic, alcoholic and aqueous extract have been prepared and their antimicrobial properties against S. aureus, E. coli and P. aeruginosa have been... more
Chitosan-polyvinyl(alcohol) films containing dragon’s blood (Croton lechleri) hydro alcoholic, alcoholic and aqueous extract have been prepared and their antimicrobial properties against S. aureus, E. coli and P. aeruginosa have been evaluated. These films as well as the latex exhibit activity against S. aureus only and have potential application as wound healing material.
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The preparation of an oligomeric complex obtained from the reaction of 1,1'-bis(octadecyl)-2,2'-benzimidazole and CoCl2 is reportad. This oligomero has been characterized by UV-visible spectroscopy, FT-IR and 1 H-RMN. The... more
The preparation of an oligomeric complex obtained from the reaction of 1,1'-bis(octadecyl)-2,2'-benzimidazole and CoCl2 is reportad. This oligomero has been characterized by UV-visible spectroscopy, FT-IR and 1 H-RMN. The elemental analysis does not throw a defined relation between cobalt and the ligand. The oligomeric complex undergoes decomposition when heating according to ose analysis.
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Hydrogels of poly(vinyl alcohol) (PVA) – poly(vinyl pyrrolidone) (PVP) has been obtained using gamma radiation, 10-30 kGy. The PVP films exhibit a greater swelling degree than those of PVA, 1600 and 350% respectively. In contrast the PVA... more
Hydrogels of poly(vinyl alcohol) (PVA) – poly(vinyl pyrrolidone) (PVP) has been obtained using gamma radiation, 10-30 kGy. The PVP films exhibit a greater swelling degree than those of PVA, 1600 and 350% respectively. In contrast the PVA films are those that arrive at their point of saturation faster than those from PVP, being those of PVA-PVP those that present a quite slow swelling. Transparent hydrogels with good adhesiveness and good mechanical properties were obtained. These properties show that these films have a good potential to be used as polymeric matrix in skin disordered treatment.
The intracellular localization of a lipophilic alkyl long-chain tetraphenylporphyrin in electrocytes, Psammobatis extenta (Rajidae) is described. In contrast to the usual case, this porphyrin derivative was localized in electromotor... more
The intracellular localization of a lipophilic alkyl long-chain tetraphenylporphyrin in electrocytes, Psammobatis extenta (Rajidae) is described. In contrast to the usual case, this porphyrin derivative was localized in electromotor nerves and in nuclei chromatin of electrocytes. Both structures exhibited intense fluorescence. However, the mitochondria were slightly fluorescent. These data are discussed in relation to electrocyte death in a weak electric fish. Additionally, the electron probe X-ray microanalysis suggest the activation of the chloride and cationic channels.
Third World Academy of Science (TWAS) por el financiamiento parcial de este trabajo que cubre un aspecto del proyecto de investigacion: “Leishmanicidal effects of Croton lechlery extract desorbed from a biopolymer”.
Instituto Peruano de Energia Nuclear - Organismo Internacional de Energia Atomica (OIEA) Proyecto: CRP PER13058.
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... de electrocitos tratados con 1 en: a) xiieno-EtOH-buffer imidazol yb) CHCI3 (x1C0) 2.3 Cambios morfológicos de los electrocitos La Figura 3a muestra una micrografia SEM de la cara no inervada ... 1-18. [17]EM Schwiebert, L. Cid-Soto,... more
... de electrocitos tratados con 1 en: a) xiieno-EtOH-buffer imidazol yb) CHCI3 (x1C0) 2.3 Cambios morfológicos de los electrocitos La Figura 3a muestra una micrografia SEM de la cara no inervada ... 1-18. [17]EM Schwiebert, L. Cid-Soto, D. Stafford, M. Carter, С Blaisdell, P.Zeitlin ...
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The antimicrobial activity of ethanolic extracts of propolis, Apis mellifera, and of chitosanpolyvinyl alcohol films immersed in those solutions against S. aureus, E. aeruginosa coli and P. aeruginosa have been studied. The ethanolic... more
The antimicrobial activity of ethanolic extracts of propolis, Apis mellifera, and of chitosanpolyvinyl alcohol films immersed in those solutions against S. aureus, E. aeruginosa coli and P. aeruginosa have been studied. The ethanolic extract of propolis exhibits antimicrobial activity against S. aureus ATCC 25923, even after dilution in a 10 % hydroalcoholic solution. However, films of chitosan-PVA immersed in the same hydroalcoholic solution of propolis have no antimicrobial activity against the same microorganism. None of the studied samples exhibited activity against E. coli and P. aeruginosa.
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One hundred and twenty-seven Nazca pottery and ten imitations were analysed by thermoluminescence, neutron activation analysis, X ray fluorescence, transmission electron microscopy, X ray diffraction and Mӧssbauer spectroscopy, to obtain... more
One hundred and twenty-seven Nazca pottery and ten imitations were analysed by thermoluminescence, neutron activation analysis, X ray fluorescence, transmission electron microscopy, X ray diffraction and Mӧssbauer spectroscopy, to obtain analytical differences that allow differentiating them quickly. Additionally, 20 pieces of the Wari culture found in the city of Cahuachi were analysed. The multielementary composition of the Nazca ceramics obtained by AAN allows, owing to a multivariate analysis, differentiation of the samples according to their geographic origin but a chronological classification could not be obtained. This indicates that the Nazca pottery of each city was always prepared with the same raw material. However, samples from the museum of the UNMSM could not be classified, since these samples were collected in all Nazca regions. The brown, orange and yellow pigments of Nazca pottery contain different amounts of manganese and iron oxides. The same elements were found in modern ceramics, but additionally lead and zinc were detected in the yellow colour of modern ceramics. The presence of illita in the paste of all the analysed samples indicates that the firing temperature of Nazca pottery did not exceed 800°C. Also, the fact that the quadrupole splitting in the Mӧssbauer spectra as a function of temperature stays more or less constant until 700°C and soon falls quickly indicates that the firing temperature was approximately 700°C. This was corroborated with the same analysis on samples from modern ceramics heated to approximate temperatures of 700°C and 900°C.
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In methanolic solutions, disproportionation of the TCNQ anion radical to neutral TCNQ0 and the dianion TCNQ2− followed by aerobic oxidation of TCNQ2− results in the formation of methyl-4-dicyanomethylene benzoate anion (MDCB−). This anion... more
In methanolic solutions, disproportionation of the TCNQ anion radical to neutral TCNQ0 and the dianion TCNQ2− followed by aerobic oxidation of TCNQ2− results in the formation of methyl-4-dicyanomethylene benzoate anion (MDCB−). This anion coordinates to the manganese(III) atom of 5,10,15,20-tetraphenylporphinatomanganese(III) leading to the complex whose X-ray crystal structure is reported. The crystal had the monoclinic space group P21/n with unit cell dimensions a=13.327(3), b=20.236(6), c=16.914(5) Å and β=92.26(2)°. An important driving force behind the crystal packing is ahydrogen bonding interaction between non-identical ligands of adjacent molecules.
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2-pentadecylbenzimidazole (I) and 1,1'-bis(octadecyl)-2,2'-bibenzimidazole (II) have been synthesized and characterized by 1H-RMN, 13C-RMN, FT-IR, UV-Visible spectroscopy and elemental analysis. Their mesomorphic properties have... more
2-pentadecylbenzimidazole (I) and 1,1'-bis(octadecyl)-2,2'-bibenzimidazole (II) have been synthesized and characterized by 1H-RMN, 13C-RMN, FT-IR, UV-Visible spectroscopy and elemental analysis. Their mesomorphic properties have studied by differential scanning calorimetry and optical microscopy with polarized light. I exhibit an enantiotropic smectic C phase between 93 and 102 °C, whereas II exhibit a monotropic cholesteric one between 52 and 29 °C. The appearance of this phase is unusual considering that the molecule is not quiral. I and II represent the first benzimidazole-based liquid crystals.
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The intracellular localization of a tetraphenylporphyrin bearing four long lipophilic alkyl chains in electrocytes from Psammobatis extenta(Rajidae) is described. In contrast to what is usually the case, this porphyrin derivative is... more
The intracellular localization of a tetraphenylporphyrin bearing four long lipophilic alkyl chains in electrocytes from Psammobatis extenta(Rajidae) is described. In contrast to what is usually the case, this porphyrin derivative is localized in the electromotor nerves and the nuclear chromatin of the electrocytes. Both structures exhibited intense fluorescence, whereas, the mitochondria were only slightly fluorescent. These data are discussed in relation to electrocyte death in a weakly electric fish. Additionally, electron probe X-ray microanalysis suggests a migration of chloride and cationic ions, which might be implicated in chloride and cationic channel activation in the electrocyte.
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Abstract We have introduced a silicon metal in 5, 10, 15, 20-tetrakis (4-n-dodecylphenyl) porphyrin core to have the complexes possessing two axial ligands (C12TPPSi (X) 2, X˭ OH (1) or OCH3 (2)) in terms of highly conducting liquid... more
Abstract We have introduced a silicon metal in 5, 10, 15, 20-tetrakis (4-n-dodecylphenyl) porphyrin core to have the complexes possessing two axial ligands (C12TPPSi (X) 2, X˭ OH (1) or OCH3 (2)) in terms of highly conducting liquid crystalline materials. The ...
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ABSTRACT The mesomorphic phase transition behavior of a series of long-chain metallotetraphenylporphyrin complexes (C12TPPM, M: Co, Ni, Cu, Zn, Pd, Pt, V=O, Al(OH), Mo=O(OH) and Si(OH)2) were compared to reveal that the intermolecular... more
ABSTRACT The mesomorphic phase transition behavior of a series of long-chain metallotetraphenylporphyrin complexes (C12TPPM, M: Co, Ni, Cu, Zn, Pd, Pt, V=O, Al(OH), Mo=O(OH) and Si(OH)2) were compared to reveal that the intermolecular interaction by the axial group significantly affects the columnar arrangement. Furthermore, it was indicated that the more rigid columnar backbone with a capability of free rotation of disc-shaped molecules leads to the formation of hexagonal and tetragonal arrays of columns.
A new metallomesogen, the dihydroxo [5, 10, 15, 20-tetrakis (4-n-dodecylphenyl) porphinato] silicon (IV) complex, C12TPPSi (OH) 2, was synthesized and its mesomorphism was investigated in terms of the axial hydrogen bond interaction in... more
A new metallomesogen, the dihydroxo [5, 10, 15, 20-tetrakis (4-n-dodecylphenyl) porphinato] silicon (IV) complex, C12TPPSi (OH) 2, was synthesized and its mesomorphism was investigated in terms of the axial hydrogen bond interaction in the stacked columnar ...
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ABSTRACT Ureas react thermally with Ru3(CO)12 to give trinuclear complexes of the type (μ2-H)Ru3(CO)9(μ3-η2-R1NCONHR2) (1: R1 = R2 = H, 2: R1 = R2 = Me, 3: R1 = H, R2 = Ph, cis-4: R1 = H, R2 = cis-CHCHMe, trans-4: R1 = H, R2 =... more
ABSTRACT Ureas react thermally with Ru3(CO)12 to give trinuclear complexes of the type (μ2-H)Ru3(CO)9(μ3-η2-R1NCONHR2) (1: R1 = R2 = H, 2: R1 = R2 = Me, 3: R1 = H, R2 = Ph, cis-4: R1 = H, R2 = cis-CHCHMe, trans-4: R1 = H, R2 = trans-CHCHMe). In the reaction of allylurea, the allylic double bond is displaced; the resulting complexes cis-4 and trans-4 contain a methylvinylurea ligand. The X-ray analysis of cis-4 shows the coordination of the urea moiety as a tripodal handle perpendicular to a nearly isosceles metal triangle.ZusammenfassungHarnstoffe reagieren thermisch mit Ru3(CO)12 zu dreikernigen Komplexen des Typs (μ2-H)Ru3(CO)9(μ3-η2-R1NCONHR2) (1: R1 = R2 = H, 2: R1 = R2 = Me, 3: R1 = H, R2 = Ph, cis-4: R1 = H, R2 = cis-CHCHMe, trans-4: R1 = H, R2 = trans-CH CHMe). Bei der Reaktion mit Allylharnstoff wird die allylische Doppelbindung verschoben; die resultierenden Komplexe cis-4 und trans-4 enthalten einen Methylvinylharnstoffliganden. Die Röntgenstrukturanalyse von cis-4 zeigt die Koordination der Harnstoff-Einheit als dreibeinigen Henkel senkrecht auf einem fast gleichschenkeligen Metalldreieck.
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Intense research activity has been devoted to metallomesog-ens.' The search for original structures possessing unique properties has been the main motivation for these studies. However, little attention has been focussed on... more
Intense research activity has been devoted to metallomesog-ens.' The search for original structures possessing unique properties has been the main motivation for these studies. However, little attention has been focussed on metallocene-containing liquid crystals. The few known ...
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The title compounds have been synthesized and their liquid-crystal properties investigated. The reported ferrocene derivatives exhibited enantiotropic nematic and/or smectic A phases associated with broad anisotropic domains. The... more
The title compounds have been synthesized and their liquid-crystal properties investigated. The reported ferrocene derivatives exhibited enantiotropic nematic and/or smectic A phases associated with broad anisotropic domains. The molecular arrangement within the smectic ...
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... J. Am. Chem. Soc., 99 (1977), p. 3647. [20] LR Melby, RJ Harder, WR Hertler, W. Mahler, REBenson and WE Mochel. J. Am. Chem. Soc., 84 (1962), p. 3374. ... J. Am. Chem. Soc., 98 (1976), p. 250. [23] WR Hertler, HD Hartzler, DS Acker... more
... J. Am. Chem. Soc., 99 (1977), p. 3647. [20] LR Melby, RJ Harder, WR Hertler, W. Mahler, REBenson and WE Mochel. J. Am. Chem. Soc., 84 (1962), p. 3374. ... J. Am. Chem. Soc., 98 (1976), p. 250. [23] WR Hertler, HD Hartzler, DS Acker and RE Benson. J. Am. Chem. ...
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Abstract The thermal properties of two ferrocene derivatives, substituted by either one or two cholesteryloxycarbonyl units, were investigated. While the monosubstituted ferrocene derivative 1 was found to be non-mesomorphic, the... more
Abstract The thermal properties of two ferrocene derivatives, substituted by either one or two cholesteryloxycarbonyl units, were investigated. While the monosubstituted ferrocene derivative 1 was found to be non-mesomorphic, the disubstituted ferrocene derivative 2 ...
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The two series I and II of 1,1′ -disubstituted ferrocenes which differ by the direction of the ester function included in the rigid organic part were synthesized and their liquid crystal properties examined. These latter were found to be... more
The two series I and II of 1,1′ -disubstituted ferrocenes which differ by the direction of the ester function included in the rigid organic part were synthesized and their liquid crystal properties examined. These latter were found to be strongly dependent on the orientation of the ...
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ABSTRACT The first phthalocyaninatooxotitanium discotic liquid crystal has been synthesized for a novel photoconductive liquid crystal. The thermal behaviour of 2,3,9,10,16,17,23,24 octakis(octadecylthio)phthalocyaninatooxotitanium(TV)... more
ABSTRACT The first phthalocyaninatooxotitanium discotic liquid crystal has been synthesized for a novel photoconductive liquid crystal. The thermal behaviour of 2,3,9,10,16,17,23,24 octakis(octadecylthio)phthalocyaninatooxotitanium(TV) was investigated by polarised light microscopy and differential scanning calorimetry (DSC) and X-ray diffraction, to reveal that it exhibits two hexagonal columnar mesophases.
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Se ha estudiado un conjunto de fragmentos de cerámica de la cultura Nasca (Ica - Perú) mediante diferentes técnicas analíticas para obtener información sobre la tecnología utilizada en su preparación. Por medio de Espectroscopía Mössbauer... more
Se ha estudiado un conjunto de fragmentos de cerámica de la cultura Nasca (Ica - Perú) mediante diferentes técnicas analíticas para obtener información sobre la tecnología utilizada en su preparación. Por medio de Espectroscopía Mössbauer hemos obtenido datos que evidenciarían que la temperatura de cocción de los cerámicos estuvo entre 700 oC y 900 oC. La aplicación de Difracción de Electrones selectivamente, sobre minerales en granulometría muy fina, determinó la presencia de Illita en todas las muestras, lo que sugiere que éstas no superaron los 800 oC durante la cocción. La presencia de otros minerales en la composición de estos fragmentos se realizó por Difracción de Rayos X. Debido a que los fragmentos estudiados provienen del Museo de Arqueología y Antropología de la Universidad Nacional Mayor de San Marcos y no de excavaciones, se aplicó Termoluminiscencia y Luminiscencia Ópticamente Estimulada para verificar la autenticidad de las piezas.