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Search Results: 1 - 10 of 546122 matches for " M.;Vargas-Pérez "
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Análisis espacial de la ocurrencia de incendios forestales en el estado de Durango
ávila-Flores, D. Y.;Pompa-García, M.;Vargas-Pérez, E.;
Revista Chapingo. Serie ciencias forestales y del ambiente , 2010, DOI: 10.5154/r.rchscfa.2009.08.028
Abstract: an exploratory analysis was carried out of the spatial distribution pattern of forest fires for the state of durango, having as a hypothesis that the fires have a nonrandom spatial pattern. weekly fire reports from conafor (national forestry commission) for a five-year period were analyzed using moran's coefficient. a graphical analysis was developed with the scatterplot diagram and local indicator of spatial association. the results show a high spatial correlation between areas with fire history, where moran's statistic captures 98.3% of the global structure of longitudinal and altitudinal association.
Modification of tRNALysUUU by Elongator Is Essential for Efficient Translation of Stress mRNAs
Jorge Fernández-Vázquez equal contributor,Itzel Vargas-Pérez equal contributor,Miriam Sansó,Karin Buhne,Mercè Carmona,Esther Paulo,Damien Hermand,Miguel Rodríguez-Gabriel,José Ayté,Sebastian Leidel,Elena Hidalgo
PLOS Genetics , 2013, DOI: 10.1371/journal.pgen.1003647
Abstract: The Elongator complex, including the histone acetyl transferase Sin3/Elp3, was isolated as an RNA polymerase II-interacting complex, and cells deficient in Elongator subunits display transcriptional defects. However, it has also been shown that Elongator mediates the modification of some tRNAs, modulating translation efficiency. We show here that the fission yeast Sin3/Elp3 is important for oxidative stress survival. The stress transcriptional program, governed by the Sty1-Atf1-Pcr1 pathway, is affected in mutant cells, but not severely. On the contrary, cells lacking Sin3/Elp3 cannot modify the uridine wobble nucleoside of certain tRNAs, and other tRNA modifying activities such as Ctu1-Ctu2 are also essential for normal tolerance to H2O2. In particular, a plasmid over-expressing the tRNALysUUU complements the stress-related phenotypes of Sin3/Elp3 mutant cells. We have determined that the main H2O2-dependent genes, including those coding for the transcription factors Atf1 and Pcr1, are highly expressed mRNAs containing a biased number of lysine-coding codons AAA versus AAG. Thus, their mRNAs are poorly translated after stress in cells lacking Sin3/Elp3 or Ctu2, whereas a mutated atf1 transcript with AAA-to-AAG lysine codons is efficiently translated in all strain backgrounds. Our study demonstrates that the lack of a functional Elongator complex results in stress phenotypes due to its contribution to tRNA modification and subsequent translation inefficiency of certain stress-induced, highly expressed mRNAs. These results suggest that the transcriptional defects of these strain backgrounds may be a secondary consequence of the deficient expression of a transcription factor, Atf1-Pcr1, and other components of the transcriptional machinery.
Portadores pediátricos asintomáticos de Enterobacteriaceae con resistencia a la ciprofloxacina
Herrera,M. L.; Vargas,A.; Pérez,C.; Moya,T.;
Revista Médica del Hospital Nacional de Ni?os Dr. Carlos Sáenz Herrera , 2004,
Abstract: se estudiaron 100 ni?os costarricenses sanos, por la presencia en su material fecal de integrantes de la familia enterobacteriaceae con resistencia a la ciprofloxacina. en 145 cepas estudiadas, se encontraron 6 cepas ciprofloxacino resistentes (4,13%), 5 correspondientes a escherichia coli y una cepa de proteus mirabilis, todas con cmi entre 8 y 32 ug/ml. no se encontró ningún factor de riesgo que ayudara a explicar como se adquirió la resistencia a la ciprofloxacina y tampoco se pudo determinar ninguna asociación con sexo, edad, o procedencia con dicha resistencia
Espumado por microondas de mezclas de silicato de sodio-ortofosfato cálcico dibásico
Vargas, G.,Pérez, J. C.,Méndez, J.,Méndez, M.
Boletín de la Sociedad Espa?ola de Cerámica y Vidrio , 2002,
Abstract: The effect of microwave application on the thermal behaviour, volume change, size and pore size distribution as well as chemical reactions and dissolution of sodium silicate/dibasic calcium phosphate ceramic (DCF) samples have been analysed. Ceramics foams with porosities between 71 and 79 wt% and pore sizes ranging from 10 to 200 microns have been obtained. After 90 seconds the temperature of samples reach about 130 °C with a weight loss of 23 wt%. Differences in the proportion of DCF in the initial mixture originate changes in volume and different chemical compounds in the final obtained foams. Additions of 10, 20 and 30 wt% of DCF originates volume increases of 350, 300 and 250 % respectively. In foam samples with 30 wt% of DCF, heated by microwave during 90 sec., the amount of the new compound β-NaCaPO4 was about 42.9 wt%. The other component of this sample, 57.1 wt%, was DCF. Dissolution tests were made, using one gram of sample, in 100 ml of distilled water. The dissolution of 10 wt% DCF foamed samples, after 20 days into water, were 900 ppm/gr of Na and 2.7 ppm/gr of Ca. In samples with 30 wt% of DCF the dissolution were 470 ppm/gr and 5 ppm/gr for Na and Ca respectively. La acción de la energía de las microondas, genera porosidad interna en un material cerámico húmedo. En el presente trabajo, se analiza el efecto del tiempo de aplicación de las microondas sobre el comportamiento térmico, cambio de volumen, tama o y distribución de poros, reacciones químicas y disolución de probetas cerámicas de silicato de sodio / ortofosfato cálcico dibásico (FCD). Para caracterizar las espumas cerámicas, se utilizó, análisis de imágenes, microscopía electrónica de barrido, difracción de rayos X y picnometría de helio. Se obtuvieron espumas cerámicas con una porosidad de 71 a 79 % y un rango de tama o de poro de 10 a 200 μm. Después de 90 segundos, las probetas alcanzaron una temperatura de aproximadamente 130°C y una pérdida de peso de 23% con respecto al peso total de la muestra. Se observaron cambios de volumen y de los compuestos químicos en las muestras espumadas cuando se varió la proporción del FCD en la mezcla. Para contenidos de 10, 20 y 30% en peso de FCD, el incremento de volumen se redujo a 350, 300 y 250% respectivamente. En muestras con 30% de FCD calentadas por microondas durante 90 segundos la cantidad de un nuevo compuesto en la espuma, constituido por β-NaCaPO4, fue del orden de 42.9%. En esa misma muestra, el 57.1 % restante fue FCD. Considerando pruebas de disolución de un gramo de muestra en 100 ml de agua destilada, la disolución obtenida
Effect of Aerobic Exercise on Protein Expression in Muscle of Obese Mexican Adolescents: A Proteomic and Bioinformatic Analysis  [PDF]
Maciste H. Macías-Cervantes, Juan M. Guzmán-Flores, Katya Vargas-Ortiz, Francisco J. Díaz-Cisneros, Joel Ramírez-Emiliano, Victoriano Pérez-Vázquez
Natural Science (NS) , 2014, DOI: 10.4236/ns.2014.69063
Abstract:

The beneficial effects of exercise have been recognized for many years yet the molecular mechanisms by which exercise show benefits on health are still elusive. A combination of experimental and bioinformatics approaches can be an invaluable tool to increase the cellular understanding of the molecular mechanisms that underlie the aerobic exercise in obese adolescents. Muscle skeletal proteins were separated by 2D-PAGE and changes in protein expression were revealed by ImageMaster 2D Platinum analysis software. Proteins with expression changes after aerobic exercise were identified by comparison with 2D maps from SWISS-2DPAGE and interactions of proteins were analyzed with STRING and DAVID databases. After aerobic exercise, all participants decreased glucose, insulin, total cholesterol, body mass index and waist circumference. Proteomic differential analysis revealed 10 overexpressed proteins after aerobic training, which correspond to carbonic anhydrase III, beta enolase, creatine kinase, ATP synthase beta subunit, aldolase A, glyceraldehyde-3-phosphate dehydrogenase, triosephosphate isomerase, pyruvate kinase, lactate dehydrogenase and adenylate kinase. Exercise increased glycolysis and oxidative phosphorylation pathways, which is likely to be regulated by ubiquitin c protein. In conclusion, our analysis suggested that obese adolescents show changes in their body mass index, waist circumference and serum glucose after aerobic exercise through improved protein expression patterns that aid, especially, glucose metabolism and increase the oxidative phosphorylation. The most likely explanation for the observed pattern is that ubiquitin c protein keeps the glycolytic enzymes bound within skeletal muscle, obtaining a non-degradative role in cell signaling.

Funcionamiento y balance energético en agroecosistemas diversos
Valdés,N; Pérez,D; Márquez,M; Angarica,Lidia; Vargas,Dania;
Cultivos Tropicales , 2009,
Abstract: results from this research work deal with some studies on energy working performed in 20 farms from la palma municipality, pinar del rio. the following indicators were evaluated: energy production, protein production, amount of persons that can be fed by the farm considering energy and protein requirements, as well as input energy/output energy unit ratio. data and calculations were recorded by means of energía software. thus, it was concluded that energy balance in those farms is mainly affected by external inputs supplied for animal production purposes. such inputs correspond to food concentrates used for pig breeding in most cases, whereas inputs applied to crops are not significant factors, since they are used in tiny proportions.
Educación a distancia: Perspectiva de los alumnos acerca de los recursos educativos
Peretó,Nora; Ghiotti,Mónica; Pérez,Beatriz; Goría,Carla; Vargas,Silvia;
Ciencia, docencia y tecnolog?-a , 2010,
Abstract: we conducted a study aimed to learn about the students' preferences on mediums and materials used at an e-learnin programme with credits for the bachelor of science in nursing (bsn) at the universidad nacional de rosario (rosario city, argentina), as part of a research project intended to analyze and evaluate the educational methods by means of an anonymous and voluntary survey used to qualify the different educational resources through open and closed questions. this paper presents the results of the qualitative study focused on the answers to the open questions.
Optical effects by high energy electrons in additively colored KCl and KBr crystals
R. Aceves,R. Pérez-Salas,T.M. Piters,C. Vargas-Aburto
Revista mexicana de física , 2008,
Abstract: Radiation effects of high energy electrons on pure and additively colored (AC) KCl and KBr crystals have been studied by optical absorption in the 200-800 nm range at RT. Besides the main F-center related absorption band at 553 nm, the F+ 2 (670 nm) and F2 (740 nm) bands (R1 and R2 centers in old notation) ascribed to F centers aggregates in additively colored KCl are clearly observed. After electron irradiation with energy of 1.0 MeV and doses of 100 kGy or 3.5 MeV and 180 kGy, the F+ 2 and F2 bands are strongly diminished, the intensity of the F bands is increased and its peak lightly shifted to low energy at 558 nm. In KBr, the related absorption band maximum for the pure and AC samples after irradiation shows the same peak position as the F-center absorption. For AC KBr the intensity of this peak versus accumulative doses shows a maximum around 300 kGy but in pure KBr the peak continuously increases. In contrast, KCl does not show such dependence on accumulative doses. For both samples, the electron irradiation induce at least two bands in the 210-300 nm (UV bands) range that has been related with hole centers (V bands). The results have been analyzed in terms of surface close F centers and alkali and halogen ions desorption processes.
Flat Bands in Slightly Twisted Bilayer Graphene
E. Suárez Morell,J. D. Correa,P. Vargas,M. Pacheco,Z. Barticevic
Physics , 2010, DOI: 10.1103/PhysRevB.82.121407
Abstract: The bands of graphite are extremely sensitive to topological defects which modify the electronic structure. In this paper we found non-dispersive flat bands no farther than 10 meV of the Fermi energy in slightly twisted bilayer graphene as a signature of a transition from a parabolic dispersion of bilayer graphene to the characteristic linear dispersion of graphene. This transition occurs for relative rotation angles of layers around $1.5^o$ and is related to a process of layer decoupling. We have performed ab-initio calculations to develop a tight binding model with an interaction Hamiltonian between layers that includes the $\pi$ orbitals of all atoms and takes into account interactions up to third nearest-neighbors within a layer.
Mold flux characterization for thin slab casting of steel
Cruz-Ramírez, A.,Vargas-Ramírez, M.,Hernández-Pérez, M. A.,Palacios-Beas, E.
Revista de Metalurgia , 2012,
Abstract: The mineralogical constitution and the melting-solidification behavior of two commercial fluxes for thin slab casting of steel were determined. The characterization of the commercial fluxes as received show the presence of wollastonite (CaO. SiO2), a sodium carbonate (Na2CO3), calcite (CaCO3), fluorite (CaF2) and carbon as the main components by X ray powder diffraction (XRD) and microscopic techniques. When fluxes were heated to 1573 K and further solidification, there was almost a whole transformation from the original compounds to cuspidine (3CaO - 2SiO2 - CaF2) and nepheline (Na2O - Al2O3 - 2SiO2) phases. The thermal gravimetrical analysis showed an important weight reduction in both fluxes due to the thermal decompositions of calcite and sodium carbonate. The characterization reveals that fluxes are produced by an agglomeration process. Se determinó la composición mineralógica y el comportamiento de fusión-solidificación de dos fundentes comerciales para la colada de planchón delgado de acero. La caracterización de los fundentes comerciales por difracción de rayos X (XRD) y técnicas de microscopía muestra la presencia de wollastonita (CaO - SiO2), un carbonato de sodio (Na2CO3), calcita (CaCO3), fluorita (CaF2) y carbono como los principales componentes. Cuando los fundentes se calentaron a 1.573 K y después de la solidificación, hubo una transformación casi total de los compuestos originales a las fases cuspidina (3CaO - 2SiO2 - CaF2) y nefelina (Na2O - Al2O3 - 2SiO2). El análisis termogravimétrico muestra una importante reducción de peso en los fundentes debido a la descomposición térmica de la calcita y el carbonato de sodio. La caracterización indica que los fundentes son producidos por un proceso de aglomeración.
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