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Search Results: 1 - 10 of 6906 matches for " ángeles-Chávez "
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Degradación de la tenacidad al impacto durante el envejecimiento acelerado de soldadura en acero microaleado
Vargas-Arista, B.,Hallen, J. M.,Albiter, A.,ángeles-Chávez, C.
Revista de Metalurgia , 2008,
Abstract: The effect of accelerated aging on the toughness and fracture of the longitudinal weld metal of an API5L-X52 linepipe steel was evaluated by Charpy V-notch impact test, fracture analysis and transmission electron microscopy. Aging was performed at 250 °C for 100 to 1000 h. The impact results indicated a significant reduction in the fracture energy and impact toughness as a function of aging time, which were achieved by the scanning electron microscope fractographs that showed a decrease in the vol fraction of microvoids by Charpy ductile failure with the aging time, which favored the brittle fracture by transgranular cleavage. The minimum vol fraction of microvoids was reached at 500 h due to the peak-aged. The microstructural analysis indicated the precipitation of transgranular iron nanocarbides in the aged specimens, which was related to the deterioration of toughness and change in the ductile to brittle behavior. Se evaluó, mediante el ensayo de impacto Charpy, fractografía y microscopia electrónica de transmisión el efecto del envejecimiento acelerado sobre la tenacidad y fractura de la soldadura en tubería de acero API5L-X52. El envejecimiento se realizó a 250 °C por 1.000 h, con control cada 100 h. Los resultados de impacto indicaron una disminución en la energía de fractura y tenacidad al impacto en función del tiempo del envejecimiento, los cuales se evidenciaron mediante fractografía, por la reducción en la fracción volumétrica de microhuecos por fractura dúctil con el tiempo, favoreciendo la fractura frágil por clivaje transgranular. Sin embargo, a 500 h, se observó la fracción volumétrica mínima debido al pico del envejecimiento. El análisis microestructural evidenció la precipitación de nanocarburos de hierro transgranulares en las muestras envejecidas, la cual se relaciono con la pérdida de tenacidad y cambio en el comportamiento dúctil a frágil, confirmado por fractografía.
Contamination Potential of an Urban Mine Tailings Deposit in Central Mexico—A Preliminary Estimation  [PDF]
Liliana Lizárraga-Mendiola, Diana Elizabeth ángeles-Chávez, Alberto Blanco-Pi?ón, Màrius Ramírez-Cardona, Francisco Javier Olguín-Coca, María del Refugio González-Sandoval
International Journal of Geosciences (IJG) , 2014, DOI: 10.4236/ijg.2014.53030
Abstract:

This study consisted of a geochemical analysis of the Dos Carlos tailings’ deposit located in the Mining District of Pachuca-Real del Monte in the state of Hidalgo, Central Mexico. The goal of the study was to determine the potential effects of this deposit on the environment and health of the population of the metropolitan area of Pachuca. Sampling was conducted from the top to the base of two raised sections at opposite ends of the deposit, and macroscopic features (profiles A and B) of these deposits were evaluated. Subsequently, mineralogical analyses of the collected samples were performed using X-ray diffraction and physico-chemical analysis of the leachates. The results were compared with the maximum permissible limits established by different national and international standards for drinking water and hazardous waste. In addition, geochemical modeling was conducted using PHREEQC to calculate the distribution of aqueous species, ionic activities and saturation indices.(For more information, please refer to the PDF.)

Glomalina y secuestro de Carbono en tepetates cultivados
Báez-Pérez, Aurelio;González-Chávez, M. C. ángeles;Etchevers-Barra, Jorge D.;Prat, Christian;Hidalgo-Moreno, Claudia;
Agrociencia , 2010,
Abstract: the tepetates are hardened volcanic tuffs that outcrop on the surface due to erosive processes; some of them can be ameliorated for agriculture and thus sequester carbon (c). this element accumulates in fragile aggregates that are formed as part of their developing physical structure after being cultivated, but the mechanism by which it is sequestered in the mineral fraction in these volcanic substrates is unknown. it is assumed that the biological activity contributes to the stabilization of the organic c (cos), specifically that of the arbuscular mycorrhizal fungi (amf). it has been postulated that glomalin (a glycoprotein produced by the amf) influences both processes. to contribute to the comprehension of this phenomenon, the present study was made with the following objectives: 1) to evaluate the accumulation of cos, glomalin and glomalin carbon (gc) in cultivated tepetates; 2) to measure the contribution of c made by the glomalin to the cos; and 3) to evaluate the tendency of accumulation of gc with years of cultivation. based on interviews with producers of the texcoco river basin, 83 plots were selected with 10 to 20 years of cultivation, and 10 classes of agronomic management were defined (i to x). as reference four phaesozem soils of the region were used, grouped in two classes of management. another 21 plots of tepetate had from 4 to over 100 years of cultivation. tepetate samples were collected (0-20 cm) and cos, glomalin and gc were determined. the relationship between cos and the latter variables was close (r>0.91). the agronomic management had significant influence (p<0.05) on the accumulation of cos, glomalin and gc. as function of the maximum concentration of cos observed, it was calculated that the tepetates ameliorated for agricultural production after two decades of cultivation, with an agronomic management with constant incorporation of organic residues, have capacity for storing approximately 90 t ha-1 of c in the first 20 cm of depth, with a c
Actualización de la terapéutica del papilomavirus humano: Terapia convencional
Hernández Menéndez,Maité; Ríos Hernández,María de los ángeles; Aguilar Vela de Oro,Orlando; Torres Chávez,Andrés;
Revista Cubana de Medicina , 2004,
Abstract: it has been proved that the human papilloma virus is infecting a great number of persons in the world. it is associated with benign, premalignant and malignant lesions of different localizations. approximately 120 types of hpv infecting the human being (a group of them is closely associated with the appearance and development of cancer) are known. even though there are various treatments to eliminate the different lesions caused by this virus, a consensus on therapeutics has not been reached. this is the first paper of a series of 3 publications. conventional treatments used to fight hpv, such as the physical elimination of the lesions, the use of citotoxic agents, etc., were approached. in the second part, the antivirals and the most used immunomodulatory substances to treat this virus were summarized. in the third and last part, the prophylactic vaccines, as well as the promising therapeutic vaccines, were dealt with.
Actualización de la terapéutica del papilomavirus humano: Terapia convencional Updating of the human papillomavirus therapeutics. Conventional therapy
Maité Hernández Menéndez,María de los ángeles Ríos Hernández,Orlando Aguilar Vela de Oro,Andrés Torres Chávez
Revista Cubana de Medicina , 2004,
Abstract: Se ha comprobado que el virus del papiloma humano está infectando a gran número de personas al nivel mundial, está asociado a lesiones benignas, premalignas y malignas de diferentes localizaciones. Se conocen alrededor de 120 tipos de HPV que infectan al ser humano (un grupo de ellos está estrechamente asociado a la aparición y desarrollo del cáncer). Aunque existen diversos tratamientos encaminados a eliminar las diferentes lesiones causadas por este virus aún no se ha llegado a un consenso en la terapéutica. Este es el primer trabajo de una serie de 3 publicaciones y se abordaron los tratamientos convencionales empleados para combatir el HPV: la eliminación física de las lesiones, el empleo de agentes citotóxicos, etc. En la segunda parte se resumieron los antivirales y las sustancias inmunomoduladoras más empleadas para tratar este virus. En la tercera y última parte, las vacunas, tanto las del tipo profilácticas como las prometedoras vacunas terapéuticas. It has been proved that the human papilloma virus is infecting a great number of persons in the world. It is associated with benign, premalignant and malignant lesions of different localizations. Approximately 120 types of HPV infecting the human being (a group of them is closely associated with the appearance and development of cancer) are known. Even though there are various treatments to eliminate the different lesions caused by this virus, a consensus on therapeutics has not been reached. This is the first paper of a series of 3 publications. Conventional treatments used to fight HPV, such as the physical elimination of the lesions, the use of citotoxic agents, etc., were approached. In the second part, the antivirals and the most used immunomodulatory substances to treat this virus were summarized. In the third and last part, the prophylactic vaccines, as well as the promising therapeutic vaccines, were dealt with.
Predicting Ecosystem Response to Perturbation from Thermodynamic Criteria  [PDF]
V. Alonso Chávez, K Michaelian
Journal of Modern Physics (JMP) , 2011, DOI: 10.4236/jmp.2011.226073
Abstract: The response of ecosystems to perturbations is considered from a thermodynamic perspective by acknowl-edging that, as for all macroscopic systems and processes, the dynamics and stability of ecosystems is sub-ject to definite thermodynamic law. For open ecosystems, exchanging energy, work, and mass with the en-vironment, the thermodynamic criteria come from non-equilibrium or irreversible thermodynamics. For ecosystems during periods in which the boundary conditions may be considered as being constant, it is shown that criteria from irreversible thermodynamic theory are sufficient to permit a quantitative prediction of ecosystem response to perturbation. This framework is shown to provide a new perspective on the popula-tion dynamics of real ecosystems.
INVESTIGACIONES ARQUEOLóGICAS DE ALTA MONTA?A EN EL SUR DEL PERú
Chávez Chávez,José Antonio;
Chungará (Arica) , 2001, DOI: 10.4067/S0717-73562001000200014
Abstract: we started our research in high mountains in southern perú by 1980 together with dr. johan reinhard. we have concurrently performed fieldwork and have gathered literature relevant to our research. then, we have a lot of information about the inca santuaries in high mountains. our research is mainly about ampato, pichu pichu, calcha, sara sara, hualca hualca, huarancante, misti, coropuna and other volcanoes. so far, we have recovered and are keeping eight human bodies from: ampato volcano (4 bodies), pichu pichu ( 3 bodies), and sara sara (1 body). as a result, of our research we now have a better understanding and conceptual framework about human sacrifices and offerings that were carried out by inca as worship to the mountains (apus). our research work confirms many data written in early chronicles of spaniards. sanctuaries that were investigated by us in pichu pichu and ampato, confirmed that inca performed their offerings on those mountains trying to appease the apus after the volcanic eruptions in misti (about 1440 ad _ 1450 a.d. ), and sabancaya volcanoes (about 1466 a.d.). our preliminary results obtained after hard multidisciplinary team work open new avenues for research since the variety of materials collected is enormous. material available for research includes: dna, pollen, microorganisms, chemicals, cat scan views etc
INVESTIGACIONES ARQUEOLóGICAS DE ALTA MONTA A EN EL SUR DEL PERú
José Antonio Chávez Chávez
Chungará (Arica) - Revista de Antropología Chilena , 2001,
Abstract: Las investigaciones arqueológicas en Alta Monta a, en el Sur del Perú las iniciamos hacia el a o de 1980 junto al Dr. Johan Reinhard, continuando desde entonces en forma ininterrumpida en la investigación bibliográfica y de campo, logrando con ello obtener una amplia información acerca de los Santuarios de los Incas en Alta Monta a, referidos a los volcanes de Ampato, Pichu Pichu, Sara Sara, Hualca Hualca, Huarancante, Misti, Coropuna, Calcha y otros. En la actualidad, se han logrado poner en salvaguarda ocho cuerpos de los volcanes de Ampato (4 cuerpos), del Pichu Pichu (3), del Sara Sara (1). Producto de estas investigaciones, tenemos una mejor conceptualización y conocimiento acerca de las ofrendas y sacrificios humanos realizados por los Incas a las Monta as (Apus). Una parte de los relatos ofrecidos por los cronistas, se ven confirmados por nuestros trabajos. Los santuarios investigados en el Pichu Pichu y Ampato confirman que los Incas han realizado sus ofrendas en dichas monta as a raíz de las erupciones volcánicas del Misti (aproximadamente hacia el a o 1440-1450), y del Sabancaya (aproximadamente en el a o 1466) . Los resultados preliminares obtenidos en la investigación multidisciplinaria abren nuevos canales entre ellas mismas, lo que se convierte en una riqueza de información invalorable: DNA, polen, microorganismos, químicos, Cat Scan etc We started our research in high mountains in Southern Perú by 1980 together with Dr. Johan Reinhard. We have concurrently performed fieldwork and have gathered literature relevant to our research. Then, we have a lot of information about the Inca Santuaries in high mountains. Our Research is mainly about Ampato, Pichu Pichu, Calcha, Sara Sara, Hualca Hualca, Huarancante, Misti, coropuna and other volcanoes. So far, we have recovered and are keeping eight human bodies from: Ampato volcano (4 bodies), Pichu Pichu ( 3 bodies), and Sara Sara (1 body). As a result, of our research we now have a better understanding and conceptual framework about human sacrifices and offerings that were carried out by Inca as worship to the mountains (Apus). Our research work confirms many data written in early chronicles of Spaniards. Sanctuaries that were investigated by us in Pichu Pichu and Ampato, confirmed that Inca performed their offerings on those mountains trying to appease the Apus after the volcanic eruptions in Misti (about 1440 AD _ 1450 A.D. ), and Sabancaya volcanoes (about 1466 A.D.). Our preliminary results obtained after hard multidisciplinary team work open new avenues for research since the variety of materi
Evaluación de la actividad de extractos marinos sobre Plasmodium falciparum in vitro y aspártico proteasas
Mendiola Martínez,Judith; Guerra Borrego,Yazle; Valdés Iglesias,Olga; Miguel Morales,Maydelín; Hernández Zanuy,Ayda; Fernández-Calienes Valdés,Aymé; Rojas Rivero,Lázara; Chávez Planes,María de los ángeles;
Revista Cubana de Medicina Tropical , 2008,
Abstract: background: the search for new drugs or therapeutic alternatives for malaria treatment is a high priority in the struggle against this disease. at present, several studies are focused on the evaluation of aspartic protease inhibitors present in the digestive vacuole of plasmodium falciparum, which are part of the enzymes involved in hemoglobin degradation. the few reports in literature on the purification of aspartic proteases inhibitors from marine organisms suggest that they are a practically unexplored source of this type of molecules. methods: marine invertebrate species phallusia nigra, bugula sp., lyssodendoryx isodictyalis, ascidia sydneiensis, microscosmus goanus, holothuria mexicana, lytechinus variegatus y echinaster sp.were detected in puerto esperanza area, pinar del rio province, on april 2006 and then ethanol extracts were prepared. in vitro antimalarial evaluation of these extracts against plasmodium falciparum, with descriptive efficacy values being comparable with those used worldwide. the results were associated to the findings of aspartic protease model-like pepsin enzymatic action inhibition tests and to the chemical profile of secondary metabolites in these extracts. results: good reproducibility of antimalarial action of p. nigra, m. goanus y l. isodictyalis extracts was found, being the average inhibitory concentrations lower than 50 μg/ml. m. goanus extract showed a possible pepsin inhibitor. the chemical profile for ascidians corresponded to the main compounds reported in pyuridae y ascidiidae families. the antimalarial activity as well as the pepsin inhibitory activity might be attributed to some of the detected secondary metabolites. conclusions: the breaking-up of these extracts is recommended in order to isolate the chemical compounds involved in the studied biological activities.
Nanocarriers for transdermal drug delivery
Escobar-Chávez JJ, Díaz-Torres R, Rodríguez-Cruz IM, Domínguez-Delgado CL, Sampere Morales R, ángeles-Anguiano E, Melgoza-Contreras LM
Research and Reports in Transdermal Drug Delivery , 2012, DOI: http://dx.doi.org/10.2147/RRTD.S32621
Abstract: nocarriers for transdermal drug delivery Review (1527) Total Article Views Authors: Escobar-Chávez JJ, Díaz-Torres R, Rodríguez-Cruz IM, Domínguez-Delgado CL, Sampere Morales R, ángeles-Anguiano E, Melgoza-Contreras LM Video abstract presented by Jose Juan Escobar-Chavez Views: 135 Published Date November 2012 Volume 2012:1 Pages 3 - 17 DOI: http://dx.doi.org/10.2147/RRTD.S32621 Received: 30 July 2012 Accepted: 08 October 2012 Published: 13 November 2012 José Juan Escobar-Chávez,1 Roberto Díaz-Torres,2 Isabel Marlen Rodríguez-Cruz,3 Clara Luisa Domínguez-Delgado,4 Rafael Sampere Morales,5 Enrique ángeles-Anguiano,6 Luz María Melgoza-Contreras7 1Sistemas Transdérmicos y Materiales Nanoestructurados, 2Toxicología y Genética, Universidad Nacional Autónoma de México, Cuautitlán Izcalli, México; 3Unidad de Ense anza e Investigación, Hospital Regional de Alta Especialidad de Zumpango, Zumpango, México; 4Departamento de Ingeniería y Tecnología, 5Departamento de Ciencias Químicas, 6Laboratorio de Química Medicinal, Universidad Nacional Autónoma de México, Cuautitlán Izcalli, México; 7Departamento de Sistemas Biológicos, Universidad Autónoma Metropolitana-Xochimilco, México City, México Abstract: Transdermal drug delivery offers an attractive alternative to the conventional drug-delivery methods of oral administration and injection. Apart from the convenience and noninvasiveness, the skin also provides a “reservoir” that sustains delivery over a period of days. It offers multiple sites to avoid local irritation and toxicity, yet it can also offer the option of concentrating drugs at local areas to avoid undesirable systemic effects. However, at present, the clinical use of transdermal delivery is limited by the fact that very few drugs can be delivered transdermally at a viable rate. This difficulty is because the stratum corneum of skin acts as an efficient barrier that limits penetration of drugs through the skin, and few noninvasive methods are known to significantly enhance the penetration of this barrier. In order to increase the range of drugs available for transdermal delivery, the use of nanocarriers has emerged as an interesting and valuable alternative for delivering lipophilic and hydrophilic drugs throughout the stratum corneum with the possibility of having a local or systemic effect for the treatment of many different diseases. These nanocarriers (nanoparticles, ethosomes, dendrimers, liposomes, etc) can be made of a lot of different materials, and they are very different in structure and chemical nature. They are too small to be detected by the immune system, and furthermore they can deliver the drug in the target organ using lower drug doses in order to reduce side effects.
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