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Search Results: 1 - 10 of 41433 matches for " Ramírez-Ortiz "
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Método para monitorear el rendimiento y contenido de metil-ésteres en el biodiesel usando la espectroscopia vibracional IR Método para monitorear el rendimiento y contenido de metil-ésteres en el biodiesel usando la espectroscopia vibracional IR
Jorge Medina-Valtierra,Gabriela Camarillo Martínez,Jorge Ramírez-Ortiz
Acta Universitaria , 2012,
Abstract: Trans-esterification main product from corn oil were synthesized and characterised by infrared spectroscopy technique, detecting methyl-esters and normal paraffins, compounds present in diesel and confirming that biodiesel from fresh and cocking oil was obtained. In this work, the difference for infrared peaks intensities at 2 925 cm-1 and 1 170 cm-1, that correspond to vibrations of –CH3 y C=O groups in biodiesel, was related with product yield and other proprieties through a regression model that fit behaviour of several factors. Important information is generated from this mathematical model combining handling factors and using differences between two infrared typical peaks in order to predict inherent proprieties, reducing thus time and costs. El producto principal de la trans-esterificación de aceite comestible fue caracterizado por medio de la espectroscopia del infrarrojo confirmando la presencia de metil-esteres en los mismos, así como la presencia notable de alcanos posiblemente presentes en el diesel, lo que indica que se trata de biodiesel obtenido a partir de aceite comestible. En este trabajo se considera la diferencia en intensidad de los picos en el espectro del infrarrojo en las posiciones 2 925 cm-1 y 1 170 cm-1, que corresponden a las vibraciones de los grupos –CH3 y C=O presentes en el biodiesel, diferencia que se relaciona con el rendimiento del producto y con otras propiedades a través de un modelo matemático que prediga el comportamiento de la variabilidad de diferentes factores. Se puede obtener información a partir del modelo matemático generado con la relación de intensidades de picos característicos y confirmarse con pruebas experimentales. Esto para emplear el modelo matemático para pronosticar diferentes propiedades inherentes sin necesidad de llevar a cabo la experimentación, disminuyendo tiempo y costos.
Obtención de biodiesel con aceite de maíz usado en frituras y metacaolinita como catalizador Obtención de biodiesel con aceite de maíz usado en frituras y metacaolinita como catalizador
Jorge Ramírez-Ortiz,Jorge Medina-Valtierra,José Merced Martínez Rosales
Acta Universitaria , 2012,
Abstract: Biodiesel production with used frying corn oil by transesterification reaction, with methanol, using a commercial kaolinite thermally-activated solid acid catalyst was investigated. The surface area, the average pore diameter and volume of pore of metakaolinite were 10 m2/g, 13.0 nm and 30 mm3/g, respectively. The optimal conditions for the transesterification reaction were determinate to be oil/methanol, in a molar ratio 1:31, temperature 160 oC, manometer pressure of 1.65 MPa and catalyst concentration of 3 % (w/w). The yield of fatty acid methyl esters (biodiesel) was 92.4 % after 2 h of reaction. This method of preparation of biodiesel can be a positive alternative for utilizing used frying corn oil for feedstock of biodiesel combined with the cited inexpensive, “green” catalyst. Se investigó la producción de biodiesel usando un reactor intermitente, se utilizó la metacaolinita como un catalizador sólido ácido que presentó una alta actividad para la pro-ducción de biodiesel a partir de aceite de maíz usado en freidora. El área superficial de la metacaolinita, diámetro de poro y volumen de poro fueron 10 m2/g, 13.0 nm y 30 mm3/g, respectivamente. Las condiciones óptimas para la reacción de transesterificación fueron: una relación molar aceite/metanol 1:31, temperatura de 160 oC, presión manométrica de 1.65 MPa y una cantidad de catalizador de 3 (% peso). El rendimiento de ésteres metílicos de ácidos grasos (biodiesel) fue de 92.4 % para 2 h de reacción. Este método de preparación de biodiesel puede ser una buena alternativa para la utilización de aceite de maíz usado en freidora como una fuente muy barata para la producción de biodiesel combinado con un catalizador barato y además amigable con el medio ambiente.
The effects of social networks on tobacco use among high-school adolescents in Mexico
Ramírez-Ortiz,Guadalupe; Caballero-Hoyos,Ramiro; Ramírez-López,Guadalupe; Valente,Thomas W;
Salud Pública de México , 2012, DOI: 10.1590/S0036-36342012000400014
Abstract: objective: to identify the effect of centrality in social network positions on tobacco-use among high-school adolescents in tonala, jalisco, mexico. materials and methods: longitudinal sociometric social network data were collected among 486 high-school adolescents in 2003 and 399 in 2004. the survey included: social network components, smoking and sociodemographic characteristics. social network measures of centrality were calculated and multivariate logistic regression was used. results: ever used tobacco (or= 44.98), marginalized-low stratum (or= 2.16) and in-degree (or=1.10) predicted tobacco use. out-degree (or= 0 .89) and out-in-degree (or= 0.90) protected against tobacco use. conclusion: nominating more friends rather than receiving such nominations was protective for tobacco use. popular students, those receiving many nominations, were at higher risk for tobacco use. involvement of leaders with capacity to influence might be an efficient strategy for dissemination of preventive messages.
Gene expression profiling of intestinal regeneration in the sea cucumber
Pablo A Ortiz-Pineda, Francisco Ramírez-Gómez, Judit Pérez-Ortiz, Sebastián González-Díaz, Francisco Santiago-De Jesús, Josue Hernández-Pasos, Cristina Del Valle-Avila, Carmencita Rojas-Cartagena, Edna C Suárez-Castillo, Karen Tossas, Ana T Méndez-Merced, José L Roig-López, Humberto Ortiz-Zuazaga, José E García-Arrarás
BMC Genomics , 2009, DOI: 10.1186/1471-2164-10-262
Abstract: For the last decade, our laboratory has been using the sea cucumber Holothuria glaberrima to dissect the cellular and molecular events that allow for such amazing regenerative processes. We have already established an EST database obtained from cDNA libraries of normal and regenerating intestine at two different regeneration stages. This database now has over 7000 sequences.In the present work we used a custom-made microchip from Agilent with 60-mer probes for these ESTs, to determine the gene expression profile during intestinal regeneration. Here we compared the expression profile of animals at three different intestinal regeneration stages (3-, 7- and 14-days post evisceration) against the profile from normal (uneviscerated) intestines. The number of differentially expressed probes ranged from 70% at p < 0.05 to 39% at p < 0.001. Clustering analyses show specific profiles of expression for early (first week) and late (second week) regeneration stages. We used semiquantitative reverse transcriptase polymerase chain reaction (RT-PCR) to validate the expression profile of fifteen microarray detected differentially expressed genes which resulted in over 86% concordance between both techniques. Most of the differentially expressed ESTs showed no clear similarity to sequences in the databases and might represent novel genes associated with regeneration. However, other ESTs were similar to genes known to be involved in regeneration-related processes, wound healing, cell proliferation, differentiation, morphological plasticity, cell survival, stress response, immune challenge, and neoplastic transformation. Among those that have been validated, cytoskeletal genes, such as actins, and developmental genes, such as Wnt and Hox genes, show interesting expression profiles during regeneration.Our findings set the base for future studies into the molecular basis of intestinal regeneration. Moreover, it advances the use of echinoderms in regenerative biology, animals that becaus
Diversidad de ara?as (Arachnida: Araneae) asociadas con viviendas de la ciudad de México (Zona Metropolitana)
Durán-Barrón, César Gabriel;Francke, Oscar F.;Pérez-Ortiz, Tila Ma.;
Revista mexicana de biodiversidad , 2009,
Abstract: urban ecology is a relatively new area of research, with urban ecosystems being defined as environments dominated by humans. insects and arachnids are 2 groups that successfully exploit the habitats offered by human habitations. we analyzed the occurrence and densities of spiders found in houses in méxico city. we used material collected between 1985 and 2003. we recorded 1 196 spiders from 109 houses. the list includes 25 families, 52 genera and 63 species of synanthropic spiders. indices of ocupation, density and seasonality, as well as rank analyses were used to make the following classification of synanthropism: accidental (density index 0-0.9), occasional (1-2.9), frequent (3.0-9.9) and common (10 or more). the synanthropic spider faunas of 5 new world countries are compared.
Diversidad de ara as (Arachnida: Araneae) asociadas con viviendas de la ciudad de México (Zona Metropolitana) Spider diversity (Arachnida: Araneae) associated with houses in México city (Metropolitan area)
César Gabriel Durán-Barrón,Oscar F. Francke,Tila Ma. Pérez-Ortiz
Revista mexicana de biodiversidad , 2009,
Abstract: La ecología urbana es un área de investigación relativamente reciente. Los ecosistemas urbanos son aquellos definidos como ambientes dominados por el hombre. Con el proceso de urbanización, insectos y arácnidos silvestres aprovechan los nuevos microhábitats que las viviendas humanas ofrecen. Se revisaron ara as recolectadas dentro de 109 viviendas durante los a os de 1985 a 1986, 1996 a 2001 y 2002 a 2003. Se cuantificaron 1 196 organismos , los cuales se determinaron hasta especie. Se obtuvo una lista de 25 familias, 52 géneros y 63 especies de ara as sinantrópicas. Se utilizaron 3 índices (ocupación, densidad y estacionalidad) y un análisis de intervalos para sustentar la siguiente clasificación: accidentales (índice de densidad de 0-0.9), ocasionales (1-2.9), frecuentes (3.0-9.9) y comunes (10 en adelante). Se comparan las faunas de ara as sinantrópicas de 5 países del Nuevo Mundo. Urban ecology is a relatively new area of research, with urban ecosystems being defined as environments dominated by humans. Insects and arachnids are 2 groups that successfully exploit the habitats offered by human habitations. We analyzed the occurrence and densities of spiders found in houses in México City. We used material collected between 1985 and 2003. We recorded 1 196 spiders from 109 houses. The list includes 25 families, 52 genera and 63 species of synanthropic spiders. Indices of ocupation, density and seasonality, as well as rank analyses were used to make the following classification of synanthropism: accidental (density index 0-0.9), occasional (1-2.9), frequent (3.0-9.9) and common (10 or more). The synanthropic spider faunas of 5 New World countries are compared.
La actividad Alfa frontal en insomnes primarios con dificultad para iniciar el sue?o
Figueredo-Rodríguez, Pedro;del Río-Portilla, Yolanda;Sánchez-Romero, Jorge Iván;Pérez-Ortiz, Alfonso;Corsi-Cabrera, María;
Salud mental , 2009,
Abstract: difficulty in sleep initiation, with or without objective signs, is one of the most frequent complaints in primary insomniacs. the electroencephalographic (eeg) activity characteristic of waking (beta and alpha oscillations) is gradually replaced by the eeg signs of sleep (sleep spindles and theta/delta waves) during the sleep onset period (sop) in normal subjects. the decrease in fast oscillations occurs at the first signs of stage 1, whereas theta and delta increase occurs later, indicating that waking promoting mechanisms are turned off before sleep-promoting mechanisms are fully started. it could be therefore hypothesized that difficulty in sleep initiation in insomniacs might be due to either a hyperactivation of waking promoting systems, a weakness of sleep promoting mechanisms or an imbalance between them. quantitative eeg analysis has revealed higher beta during wakefulness, as well as during sleep and lower slow (delta) activity in insomniacs. the presence of alpha activity during cognitive information processing, especially of slow alpha activity in relation to attention, as well as in some pathologies associated to sleep disturbances, has suggested that alpha activity during sleep is a sign of activation; however, alpha activity during sleep has been less studied in insomniacs. only broad bands have been considered in all of the aforementioned studies, and in almost all of them the analyses were restricted to central regions. it is therefore important to study the entire frequency spectrum of eeg activity in insomniacs. sleep initiation does not occur simultaneously over the entire cortex but starts as a local process which gradually invades the rest of the cortex, in which the frontal lobes play a crucial role. frontal and parietal regions are part of an important network involved in attention and conduction of thought. thus, quantitative analysis of narrow eeg bands and their distribution in the cerebral cortex may contribute to a better understanding o
(Z)-Ethyl 3-(2,6-diisopropylanilino)but-2-enoate
Manuel Amézquita-Valencia,Simón Hernández-Ortega,G. Alejandra Suárez-Ortiz,Armando Cabrera
Acta Crystallographica Section E , 2010, DOI: 10.1107/s1600536810003260
Abstract: The title compound, C18H27NO2, crystallizes as the enamine form with Z geometry. The β-enaminoester fragment forms a dihedral angle of 87.5 (1)° with the isopropylphenyl frame. The structure exhibits an intramolecular N—H...O hydrogen bond. In addition, in the crystal, molecules are linked by a centrosymmetric intermolecular N—H...O hydrogen bond.
(Z)-Ethyl 3-(2,4,6-trimethylanilino)but-2-enoate
Manuel Amézquita-Valencia,Simón Hernández-Ortega,G. Alejandra Suárez-Ortiz,Rubén Alfredo Toscano
Acta Crystallographica Section E , 2009, DOI: 10.1107/s160053680903949x
Abstract: The title compound, C15H21NO2, was obtained by the reaction of acetoacetate with 2,4,6-trimethylaniline using Mexican bentonitic clay as a catalyst. It crystallizes in the enamine form. The β-enamino ester residue is almost perpendicular to the aromatic ring [dihedral angle = 88.10 (6)°]. The molecular conformation is stabilized by a strong intramolecular N—H...O hydrogen bond. In addition, the N—H group forms a weak intermolecular N—H...O hydrogen bond linking the molecules into centrosymmetric dimers.
La actividad Alfa frontal en insomnes primarios con dificultad para iniciar el sue o
Pedro Figueredo-Rodríguez,Yolanda del Río-Portilla,Jorge Iván Sánchez-Romero,Alfonso Pérez-Ortiz
Salud mental , 2009,
Abstract: La dificultad para conciliar el sue o es uno de los síntomas más frecuentes del insomnio primario. La apreciación subjetiva de un periodo prolongado de latencia al sue o, aun en presencia de signos de sue o, puede deberse a la coexistencia de los mecanismos promotores de la vigilia y del sue o, y la lucha por el predominio de uno de ellos. La red de atención ejecutiva, conformada por las áreas de asociación frontales y parietales, cumple un papel de particular importancia en el control endógeno de la atención y en la regulación del alertamiento por parte de la corteza. Las frecuencias del EEG en el rango de actividad alfa lenta (7 y 8 Hz) participan en los procesos cognoscitivos activos de la vigilia, especialmente en la atención y la memoria, y son indicadoras del control corticofugo, o top-down, de estos procesos. Sin embargo, el análisis cuantitativo del EEG durante el proceso de conciliación del sue o en los insomnes se ha centrado fundamentalmente en la actividad delta, theta y beta, y únicamente en las regiones centrales (C3 y C4), de tal forma que el análisis de banda estrecha del EEG y su distribución en toda la corteza podría contribuir a una mejor comprensión de los mecanismos neurales comprometidos en la etiología del insomnio primario. El objetivo principal de esta investigación es, por lo tanto, analizar el espectro de frecuencias con resolución de 1 Hz en todas las derivaciones del Sistema Internacional 10-20 en insomnes primarios crónicos durante el periodo inicial del sue o (PIS) y comparar a estos últimos con un grupo control. Con el fin de aislar las características del EEG de los insomnes de causas circunstanciales, se analizará la primera noche de PSG igualando en ambos grupos el efecto activador que ejerce el medio circundante sobre el Sistema Nervioso Central, el estado psicológico y la arquitectura del sue o...
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