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Search Results: 1 - 10 of 48814 matches for " Eduardo González-Zamora "
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Sulphated Zirconia as an Eco-Friendly Catalyst in Acylal Preparation under Solvent-Free Conditions, Acylal Deprotection Assisted by Microwaves, and the Synthesis of Anhydro-Dimers of o-Hydroxybenzaldehydes
Laura Nadxieli Palacios-Grijalva,Deysi Y. Cruz-González,Leticia Lomas-Romero,Eduardo González-Zamora,Gerardo Ulibarri,Guillermo E. Negrón-Silva
Molecules , 2009, DOI: 10.3390/molecules14104065
Abstract: A solvent-free approach is described for the regioselective synthesis of acylals (1,1-diacetates) in shorter reaction times and higher yields, compared to conventional methodology using solvents. In the protection reaction of the o-hydroxybenzaldehyde the formation of acetyl compounds and anhydro-dimers was observed. The deprotection reaction involves microwave (MW) exposure of diluted reactants in the presence of solid sulphated zirconia (SZ) catalyst that can be easily recovered and reused. The sulphated zirconia was recycled several times without any loss of activity.
Microwave-Enhanced Sulphated Zirconia and SZ/MCM-41 Catalyzed Regioselective Synthesis of β-Amino Alcohols Under Solvent-Free Conditions
Guillermo Negrón-Silva,C. Xochitl Hernández-Reyes,Deyanira Angeles-Beltrán,Leticia Lomas-Romero,Eduardo González-Zamora
Molecules , 2008, DOI: 10.3390/molecules13040977
Abstract: A solvent-free approach for the regioselective synthesis of β-amino alcohols inshorter reaction times and higher yields, compared to conventional heating is described. Itinvolves microwave (MW) exposure of undiluted reactants in the presence of sulphatedzirconia (SZ) or sulphated zirconia over MCM-41 (SZM) as catalyst. Both acid materialscan be easily recovered and reused.
Sulfated Zirconia-Catalyzed Synthesis of 3,4-Dihydropyrimidin-2(1H)-ones (DHPMs) Under Solventless Conditions: Competitive Multicomponent Biginelli vs. Hantzsch Reactions
Deyanira Angeles-Beltrán,Leticia Lomas-Romero,Victor H. Lara-Corona,Eduardo González-Zamora,Guillermo Negrón-Silva
Molecules , 2006, DOI: 10.3390/11100731
Abstract: The catalytic ability of ZrO2/SO42- to promote solventless three-componentcondensation reactions of a diversity of aromatic aldehydes, urea or thoiurea and ethylacetoacetate was studied. Products resulting from Hantzsch and/or Biginelli multi-component reactions are obtained in the presence of solid acid catalysts using the samereactants but different temperature conditions. The sulfated zirconia catalyst can berecovered and recycled in subsequent reactions with a gradual decrease of activity.
Comparative Study of Regioselective Synthesis of β-Aminoalcohols under Solventless Conditions Catalyzed by Sulfated Zirconia and SZ/MCM-41
Guillermo Negrón-Silva,C. Xochitl Hernández-Reyes,Deyanira Angeles-Beltrán,Leticia Lomas-Romero,Eduardo González-Zamora,Juan Méndez-Vivar
Molecules , 2007, DOI: 10.3390/12112515
Abstract: Sulfated zirconia and SZ/MCM-41 were used as catalysts for the synthesis of β-aminoalcohols via epoxide aminolysis. Sulfated zirconia was prepared by sol-gel andSZ/MCM-41 was obtained by impregnation. Solid catalysts were characterized by XRD,SEM-EDS, UV-Vis, FT-IR pyridine desorption and Nitrogen physisorption. Both acidmaterials were useful as catalysts, even when they were recycled several times. The β-aminoalcohols were characterized by FT-IR, 1H- and 13C-NMR and GC-MS.
Synthesis of Azanucleosides through Regioselective Ring-Opening of Epoxides Catalyzed by Sulphated Zirconia under Microwave and Solvent-Free Conditions
Celia Xochitl Hernández-Reyes,Deyanira Angeles-Beltrán,Leticia Lomas-Romero,Eduardo González-Zamora,Rubén Gavi?o,Jorge Cárdenas,José Antonio Morales-Serna,Guillermo E. Negrón-Silva
Molecules , 2012, DOI: 10.3390/molecules17033359
Abstract: New azanucleosides were obtained using sulphated zirconia (ZS) as catalyst in the nucleophilic oxirane ring opening reaction of 1-allyl-3-(oxiran-2-ylmethyl) pyrimidine-2,4(1H,3H)-dione and 1-allyl-5-methyl-3-(oxiran-2-ylmethyl)-pyrimidine-2,4(1H,3H)-dione, with (S)-prolinol. The new templates were obtained with good yields following a route which exploits the reactivity of epoxides in the presence of sulphated zirconia as catalyst. The key step was carried out using microwave and solvent-free conditions and proceeds with high selectivity.
Synthesis of New Pentacyclo[5.4.0.02,6.03,10.05,9]undecane-8,11-dione (PCU) Cyanosilylated Derivatives Using Sulphated Zirconia and Hydrotalcite as Catalysts in Microwave-Assisted Reactions under Solvent Free Conditions
Nahí Adriana Guerra-Navarro,Laura Nadxieli Palacios-Grijalva,Deyanira Angeles-Beltrán,Guillermo E. Negrón-Silva,Leticia Lomas-Romero,Eduardo González-Zamora,Rubén Gavi?o-Ramírez,Juan Navarrete-Bola?os
Molecules , 2011, DOI: 10.3390/molecules16086561
Abstract: A comparison was made of the effectiveness of the functionalization reactions of pentacyclo[5.4.0.02,6.03,10.05,9]undecane-8,11-dione (PCU) using sulphated zirconia in protection-deprotection reactions and Mg/Al hydrotalcite in a cyanosilylation reaction, under classical thermal conditions and imposing microwave radiation; improved yields and reaction times were considered.
Xenobiotic-Metabolizing Enzymes in Skeletal Muscle of Children and Adolescents  [PDF]
Dora Molina-Ortiz, José Francisco González-Zamora, Rafael Camacho-Carranza, Ocarol Lopez-Acosta, Oscar Colin-Martinez, Adriana Miriam Domínguez-Ramírez, Araceli Vences-Mejía
Pharmacology & Pharmacy (PP) , 2013, DOI: 10.4236/pp.2013.42032
Abstract:

Cytochrome P450 (CYP) enzymes metabolize endogenous compounds such as steroid hormones, fatty acids, and xenobiotics, including drugs and carcinogens. The skeletal muscle is highly exposed to circulating xenobiotics; nevertheless the knowledge on the expression of these enzymes not only in adult skeletal muscle but also in younger individuals has been very little. Therefore, the aim of the present study was to investigate the expression of CYP enzymes in healthy skeletal muscles of children and adolescents. This was investigated in a total of 18 biopsies taken from the quadriceps skeletal muscle of younger patients: 9 boys and 9 girls (≤18 years) by using specific antibodies in immunoblots and by RT-PCR mRNA analysis. The mRNA transcripts for CYP1B1 and CYP2E1 were consistently detected in all samples, but in the immunoblot only was identified CYP1B1 protein in four samples. Regarding CYP1A1, CYP3A4 and CYP3A5 enzymes in skeletal muscle, there were found in some samples in both techniques, although with significant inter-individual variations. Finally CYP2W1 only was detected in one sample belonging to the youngest patient. These data show that a range of CYP enzymes are expressed in the skeletal muscle of children and adolescents, suggesting that the metabolism of several xenobiotic chemicals to which humans are exposed takes place in muscle cells. Moreover, since the potential participation of muscles is a fact in pharmacokinetics of many therapeutic drugs, expression of CYPs in skeletal muscle may play an important role in drug-dependent toxicity.

The northern naked-tailed armadillo in the Lacandona rainforest, Mexico: new records and potential threats Armadillo de cola desnuda en la selva lacandona, México: nuevos registros y amenazas potenciales
Arturo González-Zamora,Víctor Arroyo-Rodríguez,Ana María González-Di Pierro,Rafael Lombera
Revista mexicana de biodiversidad , 2012,
Abstract: We review historic occurrences in Mexico of one of the least known Xenarthra of Mesoamerica - the northern naked-tailed armadillo (Cabassous centralis Miller, 1899). We document 6 new records in the Lacandona rainforest, southern Mexico, and through interviews with local people, we assess potential threats for this species in the region. In addition to being locally rare, our results show that hunting and death by road-kill may be major threats to this species in the region. Se revisaron los registros históricos en México de uno de los xenartros menos conocidos de Mesoamérica - el armadillo de cola desnuda (Cabassous centralis Miller, 1899). Se documentan 6 nuevos registros en la selva lacandona, sur de México. A través de entrevistas con pobladores locales, se evaluaron las amenazas potenciales para esta especie en la región. Además de ser localmente rara, nuestros resultados muestran que la cacería y las muertes por atropellamiento pueden ser las principales amenazas para esta especie en la región.
Sleeping Sites and Latrines of Spider Monkeys in Continuous and Fragmented Rainforests: Implications for Seed Dispersal and Forest Regeneration
Arturo González-Zamora, Víctor Arroyo-Rodríguez, Ken Oyama, Victoria Sork, Colin A. Chapman, Kathryn E. Stoner
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0046852
Abstract: Spider monkeys (Ateles geoffroyi) use sites composed of one or more trees for sleeping (sleeping sites and sleeping trees, respectively). Beneath these sites/trees they deposit copious amounts of dung in latrines. This behavior results in a clumped deposition pattern of seeds and nutrients that directly impacts the regeneration of tropical forests. Therefore, information on the density and spatial distribution of sleeping sites and latrines, and the characteristics (i.e., composition and structure) of sleeping trees are needed to improve our understanding of the ecological significance of spider monkeys in influencing forest composition. Moreover, since primate populations are increasingly forced to inhabit fragmented landscapes, it is important to assess if these characteristics differ between continuous and fragmented forests. We assessed this novel information from eight independent spider monkey communities in the Lacandona rainforest, Mexico: four continuous forest sites and four forest fragments. Both the density of sleeping sites and latrines did not differ between forest conditions. Latrines were uniformly distributed across sleeping sites, but the spatial distribution of sleeping sites within the areas was highly variable, being particularly clumped in forest fragments. In fact, the average inter-latrine distances were almost double in continuous forest than in fragments. Latrines were located beneath only a few tree species, and these trees were larger in diameter in continuous than fragmented forests. Because latrines may represent hotspots of seedling recruitment, our results have important ecological and conservation implications. The variation in the spatial distribution of sleeping sites across the forest indicates that spider monkeys likely create a complex seed deposition pattern in space and time. However, the use of a very few tree species for sleeping could contribute to the establishment of specific vegetation associations typical of the southeastern Mexican rainforest, such as Terminalia-Dialium, and Brosimum-Dialium.
Por qué los alumnos no asisten a clase y no se presentan a los exámenes? . Datos y reflexiones sobre absentismo y abandono universitario
Macarena Sacristán-Díaz,Pedro Garrido-Vega,Ma del Mar González-Zamora,Rafaela Alfalla-Luque
WPOM : Working Papers on Operations Management , 2012, DOI: 10.4995/wpom.v3i2.1103
Abstract: El absentismo y el abandono del alumnado son problemas generalizados en la Universidad espa ola que plantean dudas sobre el propio modelo universitario. El objetivo del presente trabajo es aportar algunos datos y reflexiones desde nuestra experiencia docente. Para ello, analizamos la magnitud del problema y sus posibles causas a través de investigaciones previas, y mostramos a continuación los resultados obtenidos en relación con una asignatura táctico-operativa de Dirección de Operaciones. La metodología de investigación incluye, por un lado, una encuesta on-line a los alumnos de dicha asignatura en el curso 09/10 sobre los motivos por los que no asistían regularmente a clase. Por otro, un experimento de campo realizado en tres cursos académicos consecutivos con diferentes sistemas de evaluación (06/07 a 08/09), durante los que se recabaron datos sobre la tasa de presentados a examen. Los resultados muestran que las principales causas del absentismo están relacionadas con la disponibilidad del material de las clases y con la propia actitud del alumnado y que los controles periódicos después de cada tema contribuyen a aumentar el número de presentados a examen.
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