Sample records for DISPERSIONES (dispersions)
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1

Dispersiones acuosas de poliuretano bloqueado: una alternativa como agente curtiente/ Aqueous dispersions of blocked polyurethane: an alternative as tanning agents

Mata-Mata, José Luis; Mendoza Olivares, Diana; Alvarado Castro, Diego Ismael; Amézquita López, Fernando de Jesús
2008-06-01

Resumen en español Se sintetizaron y se evaluaron como agentes curtientes de pieles vacunas dos tipos de agentes de reticulación base poliuretano bloqueado. Se presentan los resultados de la síntesis de dispersiones acuosas de poliuretano bloqueado (DPU’s), basadas en prepolímeros a partir de la reacción de los diisocianatos alifáticos H12MDI (4,4’ metilenbis-ciclohexilisocianato) y HDI (hexametilendiisocianato) con polioles base poliéter óxido de etileno de peso molecular 1 y 2 KD (mas) a, en una relación molar isocianato/oxhidrilo (NCO/OH) de 4:1 y 6:1 a 100 °C por 2 y 4 horas. En una segunda reacción, los grupos isocianato (NCO) libres del prepolímero se bloquearon con una solución acuosa de NaHSO3 ó Na2S2O5 al 40%p/p. Los prepolímeros se caracterizaron mediante espectroscopia IR y RMN de ¹H. El tanto por ciento de isocianato libre en el prepolímero, así como el bloqueo de dichos grupos, se determinaron por espectroscopía IR. La evaluación de la capacidad curtiente de las DPU’s se determinó de acuerdo a la estabilidad térmica de la piel (temperatura de desnaturalización), mediante Calorimetría Diferencial de Barrido (DSC) y a la determinación del índice de reticulación de las DPU’s con la colágena de la piel mediante un ensayo con ninhidrina. Resumen en inglés Two types of crosslinking agents blocked polyurethanes were synthesized and evaluated as tanning agents of bovine skins. The results of the synthesis of aqueous dispersions of blocked polyurethane (DPU’s) are presented. They were based on prepolymers from the reaction of the aliphatic diisocyanates H12MDI 4,4’-methylenebis(cyclohexyl isocyanate) and HDI (hexamethylene diisocyanate) with HO-polyols such as polyethylene oxide of molecular weight 1 and 2 kDa. The molar NCO (mas) /OH ratio was fixed in 4:1 or 6:1, at 100 °C and 2 or 4 hours for the reaction time. In a second reaction, the prepolymer containing terminal NCO groups were blocked by reaction with an aqueous NaHSO3 or Na2S2O5 solution to 40% w/w. The obtained prepolymers were characterized by IR and ¹H NMR. The % of free isocyanate (NCO) in the prepolymer as well as the blockade of these groups were determined by IR. The evaluation of the tanning capacity of the DPU’s was determined according to the thermal stability of the skin (thermal denaturalization), through the differential scanning calorimetry analysis (DSC). The index of crosslinking of the DPU’s with the collagen of the skin was determined with the nynhidrin essay.

Scientific Electronic Library Online (Spanish)

2

Síntesis y caracterización de adhesivos reposicionables de poliuretano dispersos en agua, obtenidos a partir de aceite de castor maleinizado/ Synthesis and characterization of pressure-sensitive adhesives of waterborne polyurethane from maleinizated castor oil

Mazo, Paula; López, Lysa; Restrepo, David; Rios, Luis
2010-06-01

Resumen en español El presente trabajo se centró en la producción de dispersiones acuosas de poliuretano empleando el método de emulsificación por inversión de fases. Para la síntesis fueron empleados dos polioles: uno comercial tipo poliéster y el otro es aceite de castor maleinizado (MACO); dos diisocianatos, uno aromático Toluen diisocianato (TDI) y otro alifático Hexametilen diisocianato (HDI), siendo poco comunes para esta aplicación. Como emulsificante interno se empleó ác (mas) ido cítrico el cual es muy económico y de fácil adquisición. Como factores se evaluaron la cantidad de ácido cítrico y la relación molar de grupos isocianato a hidroxilos (NCO/OH), generando un diseño de experimentos factorial 3² y minimizando el contenido de sólidos sedimentados. Mediante la metodología de superficie de respuesta, se obtuvo una ecuación polinomial cuadrática por un análisis de regresión múltiple. Los poliuretanos formados fueron evaluados en cuanto a sus propiedades adhesivas y mecánicas (pegajosidad tack, pegajosidad en cinta loop tack, cohesión hold, pelado peel), lo que permitió clasificar el adhesivo como reposicionable, para emplearlo en etiquetas. Resumen en inglés This work focused on the production of aqueous dispersions of polyurethane using the emulsification method by phase inversion. For the synthesis two polyols were employed, viz. a commercial polyester and Maleinizated Castor Oil (MACO), with two diisocyanates: one aromatic, toluene diisocyanate (TDI) and another aliphatic, hexamethylene diisocyanate (HDI), which are not common for this application. Citric acid was used as internal emulsifier which is inexpensive and readil (mas) y available. The parameters were the amount of citric acid and the mole ratio of isocyanate groups to hydroxyl (NCO/OH), generating a 3² factorial design, with minimization of the sedimented solids. The surface methodology was used to obtain a quadratic polynomial equation by multiple regression analysis. Polyurethanes synthesized were evaluated for their mechanical and adhesive properties (tack, loop tack, hold, peel). These measurements allowed classifying the polyurethanes synthesized as repositionable adhesives, for use in labels.

Scientific Electronic Library Online (Spanish)

3

Efecto de la dureza del endospermo del maíz sobre las propiedades de hidratación y cocción.

Gonzalez, R.J; Torres, R; De Greef, D; Bonaldo, A; Robutti, J; Borrás, F
2005-12-01

Resumen en español El conocimiento acerca de la asociación entre las propiedades de cocción y la dureza del endospermo del maíz puede ayudar tanto a los nutricionistas como a los procesadores a seleccionar las materias primas para elaborar productos a base de maíz, particularmente aquellos que se consumen en forma de dispersiones cocidas. Se seleccionaron siete cultivares de maíz con distinta dureza, la que fue evaluada utilizando diferentes métodos. Los granos fueron descascarados, d (mas) esgerminados y reducidos a harinas para determinar la composición, el poder de hinchamiento (PH), la solubilidad y la respuesta amilográfica. Los resultados mostraron que las diferencias en dureza de endospermo (directamente relacionada con el contenido de proteína de la harina), puede explicar las diferencias observadas tanto en el poder de hinchamiento como en los valores de consistencia amilográfica. Los cultivares de endospermo más duro muestran los menores valores de PH a alta temperatura y también los menores valores de consistencia amilográfica (viscosidad). Por el contrario los endospermos más blandos presentan los mayores valores de PH y de consistencia amilográfica. Estas diferencias son atribuidas a la restricción al hinchamiento de los gránulos del almidón que provoca la estructura de la matriz proteica. Las medida de dureza del endospermo y las de PH a 95 °C pueden ser muy útiles para seleccionar cultivares que serán utilizados para lograr alimentos tales como atoles, polenta, etc. Resumen en inglés Knowledge of the association between cooking properties and endosperm hardness may help nutritionist and processors to select raw materials for preparing maize based food products, particularly those eaten as cooked dispersions. Seven commercial maize cultivars differing in hardness were selected to evaluate endosperm hardness on the kernels and some characteristics such as composition and hydration and cooking properties on the grits obtained from those maizes. Results s (mas) how that the differences in endosperm hardness (directly related to grits protein content) can explain the differences in swelling and amylographic consistencies values. Cultivars with the hardest endosperm show the lowest values at high temperature. They also show the lowest amylographic consistencies. On the other hand softer endosperms present the highest swelling power and the highest amylographic consistencies. These differences are attributed to the restriction for starch swelling caused by the protein matrix. Endosperm hardness measurements and swelling power at 95 ºC, can be useful to select cultivars that are going to be used to prepare maize based foods like atoles, polenta, etc.

Scientific Electronic Library Online (Spanish)

4

Effects of the thermal treatments on dispersion, reducibility and activity of Ni/Al2O3 and Ni-Sn/Al2O3 catalysts

Arteaga, Geomar; García, María; Khair, Yesenia; Choren, Eduardo; Sánchez, Jorge
2002-04-01

Resumen en español Se estudiaron los efectos de la calcinación y la oxicloración sobre la actividad de los catalizadores de Ni/Al2O3 y Ni-Sn/Al2O3 para la deshidrogenación de ciclohexano. Se prepararon cuatro catalizadores libres de Cl: dos monometálicos con 1.0 y 5.0% Ni por impregnación y dos bimetálicos con 1.0% Ni-0.5% Sn y 5.0% Ni-2.5% Sn, ambos con una relación atómica Sn/Ni = 0.25, por impregnación secuencial. La calcinación en aire y la oxicloración en aire + CHCl3 se efe (mas) ctuaron a 500°C por 1 h. Los catalizadores se caracterizaron mediante la reducción a temperatura programada (TPR), quimisorción de CO a 22°C y titulación con O2 a 400°C. La reacción se realizó en un reactor de flujo a 300°C. Todos los catalizadores presentaron dispersiones de Ni muy bajas. Los tratamientos, particularmente la oxicloración, causaron una fuerte disminución en la dispersión y variaciones en el grado de reducción. Estos efectos fueron dependientes del contenido de Ni y de la presencia de Sn. Los perfiles de TPR sugieren la formación de agregados bimetálicos en el catalizador 5.0Ni-2.5Sn calcinado u oxiclorado. Este catalizador mostró una actividad baja, la cual fue independiente del tratamiento. Para los catalizadores restantes, la oxicloración produjo catalizadores más activos que la calcinación. Efectos electrónicos del Sn sobre Ni explican la menor actividad de los agregados bimetálicos. Resumen en inglés Effects of the calcination and oxychlorination on cyclohexane dehydrogenation activity of Ni/Al2O3 and Ni-SnAl2O3 catalysts were studied. Four Cl-free catalysts were prepared, two monometallic catalysts with 1.0 and 5.0% Ni by impregnation, and two bimetallic catalysts with 1.0%Ni-0.5%Sn and 5.0%Ni-2.5%Sn by step impregnation, both with Sn/Ni atomic ratio = 0.25. Calcination (in air) and oxychlorination (in air + CHCl3) treatments were carried out at 500°C for 1 h. The c (mas) atalysts were characterized by temperature-programmed reduction (TPR), CO chemisorption at 22°C and oxygen titration at 400°C. The reaction was performed using a flow reactor at 300°C. All the catalysts presented very low Ni dispersions. The thermal treatments, particularly the oxychlorination, caused a decrease in the dispersion and variations in the degree of reduction. These effects were dependent on the Ni content and the presence of Sn. The TPR profiles suggest the formation of bimetallic particles of Ni and Sn in the 5.0Ni-2.5Sn catalyst subjected to calcination or oxychlorination. This catalyst showed a low activity, which was independent of the treatment. For the remaining catalysts, the oxychlorination produced more active catalysts than the calcination. Electronic effects of Sn on Ni explain the lower activity of bimetallic ensembles.

Scientific Electronic Library Online (Spanish)

5

X-ray scattering applied to the analysis of carbon nanotubes, polymers and nanocomposites

García-Gutiérrez, Mari Cruz; Nogales Ruiz, Aurora; Hernández, Jaime J.; Rueda, Daniel R.; Ezquerra Sanz, Tiberio A.
2007-01-01

Digital.CSIC (Spain)

6

Wind as a Long-distance Dispersal Vehicle in the Southern Hemisphere

Muñoz, Jesús; Felicísimo, Ángel M.; Cabezas, Francisco; Burgaz, Ana Rosa; Martínez, Isabel
2004-05-21

Digital.CSIC (Spain)

7

Water-dispersible polyaniline/nanotube composites

Jimenez, Pablo; Benito, Ana M; Castell, Pere; Sainz, Raquel; Martinez, M. Teresa; In het Panhuis, Marc; Maser, Wolfgang K
2009-06-07

Digital.CSIC (Spain)

8

Uso alternativo de liposomas mixtos en la dispersión de colorantes antraquinónicos y su vehiculización en la tintura de lana

Maza, Alfons de la; Manich, Albert M.; Parra Juez, José Luis; Coderch Negra, M. Luisa
1996-01-01

Digital.CSIC (Spain)

9

Treatment of Cu-bearing liquid effluents by non-dispersive solvent extraction with strip dispersion membrane technology

Alguacil, Francisco José; Alonso Gámez, Manuel; López Gómez, Félix Antonio; Padilla, I.; López Delgado, Aurora
2009-11-01

Digital.CSIC (Spain)

10

Tracing the impact of the Andean uplift on Neotropical plant evolution

Antonelli, Alexandre; Nylander, Johan A. A.; Perssona, Claes; Sanmartín, Isabel
2009-05-26

Digital.CSIC (Spain)

11

The provision of quality in a bilateral search market

Ponsatí, Clara; Sákovics, József
2002-08-02

Digital.CSIC (Spain)

12

Tape casting of Y-TZP with low binder content

Gurauskis, J.; Baudín, C.; Sánchez-Herencia, A.J.
2007-01-01

Digital.CSIC (Spain)

14

Spontaneous formation of vesicles and dispersed cubic and hexagonal particles in amino acid-based catanionic surfactant systems

Rosa, Mónica; Infante, Maria Rosa; Miguel, Maria da Graça; Lindman, Björn

9 pages, 10 figures, 1 table.-- PMID: 16768481 [PubMed].-- Printed version published Jun 20, 2006. | Mixed catanionic surfactant systems based on amino acids were investigated with respect to the formation of liquid crystal dispersions and the stability of the dispersions. The surfactants used were ...

DRIVER (Spanish)

16

Spatial distribution of annual grass weed populations in winter cereals

Gonzalez-Andujar, Jose Luis; Saavedra, Milagros
2003-05-01

Digital.CSIC (Spain)

17

Sorption of alkyl benzyl dimethyl ammonium compounds by activated sludge

García, María Teresa; Campos, Encarna; Sánchez-Leal, Joaquim; Comelles, Francesc
2006-06-01

Digital.CSIC (Spain)

19

Sensitivity of Hawking radiation to superluminal dispersion relations

Barceló, Carlos; Garay, Luis Javier; Jannes, Gil
2009-01-22

Digital.CSIC (Spain)

20

Seedling recruitment in a semi-arid steppe: The role of microsite and post-dispersal seed predation

González Barberá, Gonzalo; Navarro-Cano, J. A.; Castillo Sánchez, Victor Manuel
2006-01-01

Digital.CSIC (Spain)

21

Seed dispersal by common ravens Corvus corax among island habitats (Canarian Archipelago)

Nogales, Manuel; Hernández, Elizabeth C.; Valdés, Francisco
1999-01-01

Digital.CSIC (Spain)

22

Seed Dispersal Anachronisms: Rethinking the Fruits Extinct Megafauna Ate

Guimarães, Paulo R.; Galetti, Mauro; Jordano, Pedro
2008-03-05

Digital.CSIC (Spain)

23

Secondary seed dispersal systems, frugivorous lizards and predatory birds in insular volcanic badlands

Nogales, Manuel; Pérez Padilla, David; Nieves, Concepción; Illera, Juan Carlos; Traveset, Anna
2007-09-27

Digital.CSIC (Spain)

24

Reproductive biology of the Iberian species of Potentilla L. (Rosaceae)

Guillén, Antonio; Rico, Enrique; Castroviejo, Santiago
2005-06-30

Digital.CSIC (Spain)

26

Realización de patrones de Dispersion del Modo por Polarización (PMD)

Corredera Guillén, Pedro; Rodríguez Barrios, Alberto
2007-07-01

Digital.CSIC (Spain)

27

Quantitative study of piping processes in badland areas of the Ebro Basin, NE Spain

Gutiérrez, M.; Sancho, C.; Benito, Gerardo; Sirvent, J.; Desir, G.
1995-09-19

Digital.CSIC (Spain)

28

Pseudovivipary, a new form of asexual reproduction in the seagrass Posidonia oceanica

Ballesteros, Enric; Cebrián, Emma; García-Rubies, Antoni; Alcoverro, Teresa; Romero Sánchez, Javier; Font, Xavier
2005-05-01

Digital.CSIC (Spain)

29

Procedimiento para la dispersión de nanopartículas en seco y la obtención de estructuras jerárquicas y recubrimientos

Fernández Lozano, José Francisco; Lorite, Israel; Rubio Marcos, Fernando; Romero Fanego, Juan José; García García-Tuñón, Miguel Ángel; Quesada, Adrián; Martín-González, Marisol S.; Costa Krämer, José Luis
2010-01-25

Digital.CSIC (Spain)

32

Predicting Spatial Patterns of Plant Recruitment Using Animal-Displacement Kernels

Santamaría, Luis; Rodríguez-Pérez, Javier; Rodríguez Larrinaga, Asier; Pias, Beatriz
2007-10-10

Digital.CSIC (Spain)

33

Potential distribution of forest species in dehesas of Extremadura (Spain).

Felicísimo, Ángel M.; Gómez, A.; Muñoz, Jesús
2004-01-01

Digital.CSIC (Spain)

34

Plant dispersal by teal (Anas crecca) in the Camargue: duck guts are more important than their feet

Brochet, A. L.; Guillemain, M.; Fritz, H.; Gauthier-Clerc, M.; Green, Andy J.
2010-06-01

Digital.CSIC (Spain)

35

Photonic crystals with anomalous dispersion: Unconventional propagating modes in the photonic band gap

Hermann, D.; Diem, M.; Mingaleev, S.F.; García-Martín, Antonio; Woelfle, P.; Busch, K.
2008-01-11

Digital.CSIC (Spain)

38

Passive Treatment of Acid Mine Drainage with High Metal Concentrations Using Dispersed Alkaline Substrate

Rötting, Tobias S.; Thomas, Robert C.; Ayora, Carlos; Carrera, Jesús
2008-08-01

Digital.CSIC (Spain)

39

Ocean Surface Winds Drive Dynamics of Transoceanic Aerial Movements

Felicísimo, Ángel M.; Muñoz, Jesús; González-Solís, Jacob
2008-08-13

Digital.CSIC (Spain)

41

Nanofibrilar Polyaniline: Direct Route to Carbon Nanotube Water Dispersions of High Concentration

Jimenez, Pablo; Maser, Wolfgang K; Castell, Pere; Martinez, M Teresa; Benito, Ana M

Water dispersible nanofibrilar polyaniline (NF-PANI) provides a novel and direct route towards carbon nanotube water dispersions of high concentration. Carrying out the chemical synthesis of NF-PANI in the presence of carbon nanotubes (CNTs) results in an entirely nanostructured nanofibrilar polyani...

DRIVER (Spanish)

42

Nanofibrilar Polyaniline: Direct Route to Carbon Nanotube Water Dispersions of High Concentration

Jimenez, Pablo; Maser, Wolfgang K; Castell, Pere; Martinez, M. Teresa; Benito, Ana M
2009-03-19

Digital.CSIC (Spain)

44

Method for the dry dispersion of nanoparticles and the production of hierarchical structures and coatings

Fernández Lozano, José Francisco; Lorite, Israel; Rubio Marcos, Fernando; Romero Fanego, Juan José; García García-Tuñón, Miguel Ángel; Quesada, Adrián; Martín-González, Marisol S.; Costa Krämer, José Luis
2010-01-28

Digital.CSIC (Spain)

45

Method and apparatus for correcting ultrasound images by means of phase analysis

Fritsch Yusta, Carlos; Parrilla Romero, Montserat; Camacho Sosa Días, Jorge
2010-02-18

Digital.CSIC (Spain)

46

Mapas de dispersión cromática en fibras ópticas monomodo

González Herráez, Miguel; Corredera Guillén, Pedro; Hernanz, María Luisa; Thévenaz, Luc; Méndez, José Antonio; Martín López, Sonia
2003-10-31

Digital.CSIC (Spain)

47

Magnons and BFKL

Gómez, César; Gunnesson, Johan; Hernández, Rafael
2008-07-22

Digital.CSIC (Spain)

49

Liposomes of phosphatidylcholine: a biological natural surfactant as a dispersing agent.

Martí Gelabert, Meritxell; Coderch Negra, M. Luisa; Maza, Alfons de la; Parra Juez, José Luis
2007-07-17

Digital.CSIC (Spain)

50

Liposomed disperse dyes

Martí Gelabert, Meritxell; Coderch Negra, M. Luisa; Parra Juez, José Luis; Maza, Alfons de la
2010-12-16

Digital.CSIC (Spain)

51

Lamb waves generation in plates using glued piezoceramics

Gómez Ullate Ricón, Yago; Montero de Espinosa Freijo, Francisco; Saletes, I.
2006-05-01

Digital.CSIC (Spain)

53

La dispersión de semillas del tasaigo

Pérez Padilla, David; Nieves, Concepción; Illera, Juan Carlos; Nogales, Manuel
2007-05-01

Digital.CSIC (Spain)

55

Innovación tecnológica en la tintura de la lana con colorantes dispersos azoicos vía liposomas

Maza, Alfons de la; Parra Juez, José Luis; Manich, Albert M.; Coderch Negra, M. Luisa
1995-07-01

Digital.CSIC (Spain)

56

Influence of dispersion conditions of two pharmaceutical grade clays on their interaction with some tetracyclines.

Aguzzi, C.; Viseras, C.; Cerezo, P.; Rossi, S.; Ferrari, F.; López-Galindo, A.; Caramella, C.
2005-09-01

Digital.CSIC (Spain)

59

Improved processing of polyaniline-carbon nanotube nanocomposites via water dispersions

Jiménez, Pablo; Maser, Wolfgang K.; Martínez, M. Teresa; Benito, Ana M.

In this work we show a nanostructured composite between polyaniline (PANI) and multi-wall carbon nanotubes[1] (MWNTs) that can be dispersed in aqueous solutions in high concentrations, which allows different kinds of processing[2]. The content of MWNTs in these composites can be as high as 50% wt. w...

DRIVER (Spanish)

60

Improved processing of polyaniline-carbon nanotube nanocomposites via water dispersions

Jimenez, Pablo; Maser, Wolfgang K; Martinez, M. Teresa; Benito, Ana M
2009-03-09

Digital.CSIC (Spain)

63

Geographic variations in seed dispersal by ants: are plant and seed traits decisive?

Boulay, Raphaël; Coll Toledano, Josep; Manzaneda, Antonio J.; Cerdá, Xim
2007-03-01

Digital.CSIC (Spain)

65

Geographic patterns in fruit colour diversity: do leaves constrain the colour of fleshy fruits?

Burns, Kevin C.; Cazetta, Eliana; Galetti, Mauro; Valido, Alfredo; Schaefer, H. Martin
2008-11-26

Digital.CSIC (Spain)

66

Generation and Dispersion of Airborne Microorganisms from Composting Facilities

Sánchez-Monedero, Miguel Ángel; Stentiford, E. I.
2003-05-01

Digital.CSIC (Spain)

67

Formation of Dispersive Hybrid Bands at an Organic-Metal Interface

González-Lakunza, N.; Fernández-Torrente, I.; Franke, K. J.; Lorente, N.; Arnau, Andrés; Pascual, J. I.
2008-04-17

Digital.CSIC (Spain)

68

Fluorescent, water dispersible polyaniline and its composites with carbon nanotube

Jimenez, Pablo; Maser, Wolfgang K; Martinez, M. Teresa; Benito, Ana M.

POSTER CONTRIBUTION Nº: P3-21 | A new kind of fluorescent nanofibrillar polyaniline (NF-PANI) derivative is synthesized, characterised and composites with multi-walled carbon nanotubes (MWNTs) prepared. With the introduction of a small amount of a synthesized carbazole derivative (fig 1.) in the oxi...

DRIVER (Spanish)

69

Fluorescent, water dispersible polyaniline and its composites with carbon nanotube

Jimenez, Pablo; Maser, Wolfgang K; Martinez, M. Teresa; Benito, Ana M
2009-06-07

Digital.CSIC (Spain)

71

Experimental Study on the Role of Chromatic Dispersion in Continuous-Wave Supercontinuum Generation

Abrardi, Laura; Martín-López, Sonia; Carrasco-Sanz, Ana; Rodríguez-Barrios, Félix; Corredera, Pedro; Hernanz, Mª Luisa; González-Herráez, Miguel
2009-02-15

Digital.CSIC (Spain)

72

Estudio preliminar del impacto socioeconómico sobre los puntajes de una batería multidimensional de aptitudes en niños preescolares/ A preliminary study on the socioeconomic impact on the scores of a set of multidimensional aptitude tests in pre-school children

Merino Soto, César; Muñoz Valera, Paola
2007-12-01

Resumen en español El presente estudio explora las relaciones entre nivel socioeconómico, género y tipo de centro educativo preescolar y el desempeño cognitivo de niños preescolares (N = 323) de Lima (Perú), con una prueba multidimensional de aptitudes. Con la aplicación de la técnica multivariada de análisis de perfiles se hallaron diferencias estadísticamente significativas y de moderada magnitud del efecto en los puntajes cognitivos, debidas a la ubicación del centro educativo; (mas) no se detectaron diferencias que se atribuyan al género y al tipo de centro. Se trabajó en base a tres hipótesis: La primera es la hipótesis de igualdad de niveles, en la que se examinan las diferencias que en promedio existen entre los dos grupos. La segunda es la hipótesis de igualdad de la dispersión, que examina si las variables de respuesta (puntajes en las subescalas) tienen la misma respuesta en promedio. Y la tercera, la hipótesis de paralelismo, que prueba si el patrón de elevaciones en el perfil es similar entre los dos grupos. Los resultados fueron evaluados con respecto a la consistencia interna y a la definición del nivel socioeconómico (ubicación geográfica). Se discuten las diferencias halladas en el aspecto socioeconómico y relacionándolas con la bibliografía sobre el tema y la utilidad de la batería multidimensional de aptitudes para niños preescolares. Es importante destacar que el estudio reporta información normativa acerca del desempeño de los niños preescolares, en lo que respecta al género y ubicación de los centros educativos y su carácter correlacional y la magnitud del efecto de los resultados. Resumen en inglés The present study explores the relationship between socioeconomic level, gender and type of pre-school education center, and cognitive development in 323 pre-schoolers in Lima (Perú), using a multidimensional aptitude test. By applying the multivariate technique, we found statistical significant differences and medium size effects on the cognitive scores due to the educational center location, whereas gender and type of educational center differences were not found. The (mas) results were considered taking into account reliability levels and also according to the definition of socioeconomic levels. The differences found are discussed based on other articles as well as on the usefulness of the multidimensional aptitude tests for pre-schoolers. The sample consisted of 323 children of 5 years old, 167 boys and 156 girls, who go to both private and public pre-schools in a district of Lima. The proportion of public pre-school students (67.2%) was double the amount of private pre-school students (32.8%). Moreover, the private pre-schools had been recently formed (4 to 5 years before) and had children from families with a medium or medium to low socioeconomic level. In order to assess general and relevant aspects of pre-school learning, we applied a pre-school diagnostic test (De la Cruz, 1991), which can be used at a pre-school level (4-5 year-olds). This test contains the following areas: Verbal concepts, Quantitative concepts and Auditive memory, Visual perceptual aptitude and Visual-motor coordination. It is a potentia test because the time varies from one student to another so as to allow every child to answer every item. Furthermore, it is also a maximum performance test because the student tries to obtain the best possible score. We contacted several educational centers (private and public) from three different districts in Lima which accepted to participate in this study. The time of application of the test varied considering: individual skills, the number of children in the collective application, the presence of a teacher's aide for the collective application, and the attitude and motivation of the students. We used MANOVA to analyze profiles, a post hoc univariate contrast, and effect size estimations such as Cohen's d. Our study was based on three hypotheses: The first hypothesis was on the equality of levels (variability between subjects) that explores the differences that exist between both groups separately. As a result, we found no correlation between test performance and gender or school location. However, when considering type of school (public or private), we did find significant differences in one scale: Auditive memory, which was higher in public schools. The second hypothesis was the equality of dispersion (within-group differences), to identify if the answer variables have the same answers on average. We found similarities regarding school conditions (public or private); but there were small differences between gender and school location. The third hypothesis was regarding parallelism, which tests whether the pattern of elevations on the profile is similar between the two groups or not. We did not find important statistical dispersions and the effect size was small. The results coincide with other studies on the correlation between gender and socioeconomic level, and cognitive development. Among some of the limitations of our study, we list the following: for example, we used the school location to determine the children's socioeconomic level. Therefore, there were also extreme scores (outliers), which could vary the central tendency estimations and the dispersion. However, they were not trimmed, since in a previous unreported analysis without these data, researchers found only minimum changes. We also had occasional difficulties in applying the tests, due to the children's disposition to participate as well as their reaction concerning the test situation, which could have added random error on the results. However, we presume their negative reactivity was reduced because of the playful manner in which the tests were presented. The results of our research shed normative information regarding the performance of preschoolers due to gender and location of their educational centers. It is important to emphasize correlations as well as effect size of the results so as not to reach erroneous conclusions.

Scientific Electronic Library Online (Spanish)

73

Estudio de Catalizadores de Rutenio para la obtención de Gas de Síntesis a partir del Reformado Seco de Metano/ A Study on Ruthenium Catalysts to Obtain SynGas by Dry Methane Reforming

Maina, Silvia C.P; de Miguel, Sergio; Scelza, Osvaldo A; Jablonski, Estanislao L
2009-01-01

Resumen en español En este trabajo se estudia el comportamiento catalítico en reformado seco de catalizadores de Ru soportados sobre alúminas con agregado de Na, K, Mg, Ca o Ba. Los soportes y catalizadores fueron caracterizados y se analizó el comportamiento catalítico en la reacción de reformado de CH4 con CO2. Los catalizadores Ru/Al2O3-Na y Ru/Al2O3-K ofrecen mayores conversiones y mejores relaciones H2/CO, asunto que está relacionado con la dispersión metálica y con la basicida (mas) d del soporte. La disminución del tiempo de reducción previa del catalizador en H2, produce una disminución de las conversiones de CO2 y CH4 para todos los catalizadores excepto para el Ru/Al2O3-Na. Este fenómeno no sería debido al efecto térmico sino al tiempo de reducción propiamente dicho Resumen en inglés This work studies the catalytic performance in dry reforming of Ru catalysts supported on γ-Al2O3 promoted with Na, K, Mg, Ca and Ba. The supports and the catalysts were characterized and tested in the reaction of CH4 reforming with CO2. Ru/Al2O3-Na and Ru/Al2O3-K catalysts showed higher conversions and better H2/CO molar ratios. This catalytic behavior would be related with the higher metallic dispersions and with the basicity of the support. When the reduction time (mas) in H2 was shortened, a decrease of the conversions for all the catalysts, except for Ru/Al2O3-Na, was observed. This phenomenon would not be due to the thermal effect but to the reduction time

Scientific Electronic Library Online (Spanish)

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77

Enhanced kinetics and free-volume universality in dense aggregating systems

Fry, D.; Sintes, Tomàs; Chakrabarti, A.; Sorensen, C. M.
2002-09-10

Digital.CSIC (Spain)

78

Endozoocoria. Interación ecológica y evolutiva.

Nogales, Manuel; Valido, Alfredo
2000-01-01

Digital.CSIC (Spain)

81

Effects of Matrix Heterogeneity on Animal Dispersal: From Individual Behavior to Metapopulation-Level Parameters

Revilla, Eloy; Wiegand, Thorsten; Palomares, Francisco; Ferreras, Pablo; Delibes Mateos, Miguel
2004-09-22

Digital.CSIC (Spain)

82

Effect of water on foaming properties of diglycerol fatty acid ester-oil systems

Shrestha, Lok Kumar; Shrestha, Rekha Goswami; Solans, Conxita; Aramaki, Kenji
2007-05-25

Digital.CSIC (Spain)

83
87

Efecto de la cobertura del suelo y de una enmienda de yeso en la infiltración del agua en riego por aspersión

Berenguer, María José; Faci González, José María; Martínez-Cob, Antonio
1994-01-01

Digital.CSIC (Spain)

89

Drifting plastic debris as a potential vector for dispersing Harmful Algal Bloom (HAB) species

Masó, Mercedes; Garcés, Esther; Pagès, Francesc; Camp, Jordi
2003-03-30

Digital.CSIC (Spain)

90

Dispersión endozoócora por ganado ovino de cuatro leguminosas herbáceas de interés forrajero

Ramos, M.ª Eugenia; Robles, Ana Belén; Ruiz Mirazo, Jabier; Cardoso, Juan Andrés; González Rebollar, José Luis
2005-06-01

Digital.CSIC (Spain)

91
95

Desarrollo de esmaltes nanoestructurados multifuncionales

Pecharromán García, Carlos; Bengochea, M. A.; Jaquotot, P.; Campillo, A.; Reinosa, J.J.; Romero Fanego, Juan José; Esteban Cubillo, Antonio; Santarén, J.; Aguilar, E.; Pina, R.; Moya Corral, José Serafín; Fernández Lozano, José Francisco
2009-04-01

Digital.CSIC (Spain)

97

Contrasting styles of the Holocene highstand sedimentation and sediment dispersal systems in the northern shelf of the Gulf of Cadiz

Lobo, F. J.; Sánchez, R.; González-Álvarez, R.; Dias, J. M. A.; Hernández-Molina, F. Javier; Fernández-Salas, L. M.; Díaz del Río, V.
2004-03-01

Digital.CSIC (Spain)

98

Composition of polymers and carbon nanotubes, method for producing same and the uses thereof

Benito, Ana M; Jiménez Manero, Pablo; Martínez Fernández de Landa, María Teresa; Maser, Wolfgang K
2009-08-20

Digital.CSIC (Spain)

99

Composición de polímeros y nanotubos de carbono, procedimiento de obtención y sus usos.

Benito, Ana M; Jiménez Manero, Pablo; Martínez Fernández de Landa, María Teresa; Maser, Wolfgang K
2010-05-31

Digital.CSIC (Spain)

100

Comportamiento coloidal de un caolín deshidratado

Ferrari Fernández, Begoña; Moreno, Rodrigo; Lange, F. F.
2000-04-01

Digital.CSIC (Spain)

102

Comparison between analytical and mineralometric methods in regional scheelite exploration

Fernandez-Turiel, J. L.; Durán Barrachina, M. E.; Querol, Xavier; López Soler, Ángel
1992-06-01

Digital.CSIC (Spain)

104

Characterization of mixing and spreading in heterogeneous media

Dentz, Marco; Sánchez Vila, Xavier; Zavala Sánchez, Gabriela Vanessa
2008-07-01

Digital.CSIC (Spain)

105

Channel plasmon-polaritons: modal shape, dispersion, and losses.

García-Vidal, Francisco J.; Moreno, Esteban
2006-11-09

Digital.CSIC (Spain)

107

Caracterización superficial de distintos materiales de construcción

Sánchez, María J.; Rubio Alonso, Juan; Elvira Lavilla, María del Rosario; Rubio Alonso, Fausto; Otero, J. Luis
2006-09-30

Digital.CSIC (Spain)

108

Are predatory birds effective secondary seed dispersers?

Nogales, Manuel; Quilis, Vicente; Medina, Félix M.; Mora, Juan L.; Trigo, Laura S.
2002-01-01

Digital.CSIC (Spain)