Disminuir el impacto ambiental derivado del uso de combustibles fósiles necesita el desarrollo de fuentes de energía renovables, y la producción sostenible de combustibles líquidos. Los éteres de ...oximetileno (OMEs), son compuestos oxigenados que han surgido como una potencial alternativa para sustituir el combustible Diesel. El uso de estos éteres en los motores disminuye la formación de hollín y óxidos de nitrógeno (NOx) durante la combustión. Dentro de esta familia de compuestos, el 1,1-dimetoximetano (OME1) tiene especial interés, no solo por su uso como solvente industrial o como intermediario químico, sino, también porque puede ser usado como materia prima para la producción de OMEs de cadena larga. La síntesis directa de OME1 involucra la oxidación selectiva de metanol sobre catalizadores bifuncionales, los cuales han sido objeto de estudio durante las últimas décadas. Este trabajo resume las principales características de los distintos sistemas catalíticos desarrollados, los cuales juegan un papel fundamental para la producción comercial del 1,1-dimetoximetano.
Multi-walled carbon nanotube growth by catalytic decomposition of methane over Ni–Al2O3 catalyst has been carried out using a riser simulator (mini-fluidized bed batch) reactor. The catalyst was ...prepared by incipient wetness impregnation and characterized by nitrogen adsorption, powder X-ray diffraction, Raman spectroscopy and temperature programmed reduction (TPR). The multi-walled carbon nanotubes (MWCNTs) formed were characterized by transmission electron microscopy and Raman spectroscopy. The observed degree of MWCNT graphitization increased with temperature and time leading to better quality MWCNTs. Measured methane conversion against time data was used to find the reaction order for methane decomposition. A first order rate with respect to methane was obtained. The calculated activation energy for methane decomposition on Ni–Al2O3 catalyst was 37.1±3.5kJ/mol.
► MWCNT growth was conducted in a riser simulator by methane decomposition. ► First order decomposition of methane during MWCNT growth. ► Deactivation of the Ni–Al2O3 catalyst was minimal during carbon nanotube growth. ► Activation energy for methane decomposition on the catalyst was 37.1±3.5kJ/mol.
Síndrome polen-alimento. Revisión con un toque O'Farrill-Romanillos, Patricia Maria; Bermúdez-Marquez, José Efraín; Maldonado-Domínguez, Edwin Daniel ...
Revista alergia Mexico (Tecamachalco, Pueblo, Mexico : 1993),
2022, Volume:
69, Issue:
Supl1
Journal Article
Peer reviewed
Open access
El síndrome polen-alimento (SPA) se caracteriza por la sensibilización alérgica a proteínas de pólenes de pastos, malezas y árboles, que producen una reacción de hipersensibilidad de tipo I, asociada ...a la ingesta de alimentos derivados de plantas, usualmente en forma cruda. Las familias de proteínas que más frecuentemente están asociadas son las profilinas, las PR-10 y las ns LTP; sin embargo, se ha documentado otras, como las taumatinas, isoflavonas reductasas y las B1,2 gluconasas. El síndrome prototipo es el abedul-frutas-vegetales, y de ellos el más común es el abedul-manzana, debido a que más de 70 % de los pacientes sensibilizados al abedul presentan síntomas asociados a la ingesta de alimentos derivados de plantas. Los síntomas están restringidos a la cavidad oral; sin embargo, algunos pacientes pueden presentar síntomas sistémicos, incluso anafilaxia, por lo que es importante identificar el tipo de proteína implicada, ya que de eso depende el tipo de reacción que puede presentar el paciente. Pese a todo, se considera una entidad que puede estar subdiagnosticada debido a su valoración y tratamiento complejos, debido a que el procedimiento en la mayor parte de los casos es dieta de eliminación, ya que aún no está disponible el tratamiento con inmunoterapia. El objetivo de esta revisión es describir la fisiopatología, así como los síndromes polen-alimento más comunes.
Aplicaciones del ozono en la agricultura cubana González Ramírez, José Efraín; Bataller Venta, Mayra Olga; Veliz Lorenzo, Eliet ...
Anales de la Academia de Ciencias de Cuba,
09/2022, Volume:
12, Issue:
3
Journal Article
Peer reviewed
Open access
RESUMEN Introducción. Importantes pérdidas agrícolas se han asociado a la mala calidad fitosanitaria de las semillas empleadas y al deterioro de los productos durante la poscosecha. La escasez del ...agua para el riego ha limitado los programas de desarrollo agrícola. El empleo del ozono podría constituir en una alternativa ambientalmente amigable y económicamente factible en el tratamiento de productos para el consumo humano y la recuperación de aguas residuales domésticas. Métodos. Se diseñaron y probaron los reactores para la aplicación segura y eficiente del ozono según los objetivos específicos. Se evaluaron dosis de ozono, tanto en atmósferas como en disolución acuosa y los tiempos necesarios para cada uno de los casos en estudio. Resultados. Se establecieron metodologías para el tratamiento de semillas de especies vegetales, así como explantes de ñame y malanga para la desinfección, el saneamiento y la potenciación de su capacidad de germinación. También para la desinfección de frascos y locales biotecnológicos. Se estandarizó un procedimiento para la recuperación de aguas residuales domésticas. Se establecieron metodologías para el beneficio poscosecha de tomate y frutabomba. Conclusiones. La aplicación de ozono ha redundado en metodologías económicamente factibles pues ha permitido acortar los tiempos empleados en los procesos, aumentar la calidad de los productos tratados y reducir los costos de almacenamiento. Además, ha resultado amigable con el medio ambiente al sustituir el empleo de químicos causantes de una mayor carga contaminante.
AIMS: Morphological, biochemical and genotypic characterization of a halophilic bacterium isolated from hypersaline ponds located at Las Coloradas (Río Lagartos, Yucatán, Mexico). Characterization of ...polymer produced by this strain was also performed. METHODS AND RESULTS: Twenty strains were isolated from water samples of salt ponds and selected based on both morphological features and their PHA storage capacity, which were determined by SEM and staining methods with Nile red and Nile blue, respectively; strains were also analysed by the fluorescence imaging technique. Among them, JCCOL25.8 strain showed the highest production of PHA's reason why phenotypic and genotypic characterization was performed; this strain was identified as Halomonas nitroreducens. Polymer produced by this strain was characterized by FTIR, DSC, GPC and EDX spectroscopy. Results indicated that the biosynthesized polymer was polyhydroxybutyrate (PHB) which had a melting peak at 170°C and a crystallinity percentage of about 36%. CONCLUSIONS: Based on phenotypic and genotypic aspects, JCCOL25.8 strain was identified as H. nitroreducens and it was capable to accumulate PHB. SIGNIFICANCE AND IMPACT OF THE STUDY: To our knowledge, there is only one study published on the biosynthesis of PHA's by H. nitroreducens strains, although the characterization of the obtained polymer was not reported.
Single-wall carbon nanotubes (SWNT) are considered one of the building blocks for nanoscale science and nanotechnology. Extensive research work is now focused on the large-scale manufacture of these ...materials since there is not yet an established method that provides large quantities of SWNT of well-determined and reproducible characteristics. A clear understanding of the formation mechanism of SWNT is therefore a key issue for the development of further advances in this topic. This study is focused on the understanding of the processes that occur on the catalyst surface during the synthesis of SWNT nanotubes by CO disproportionation over a bimetallic Co Mo catalyst. A series of analytical techniques have been employed to fully characterize the structure and chemical state of the catalyst. The state of Co and Mo has been investigated using laser Raman spectroscopy, extended X-ray absorption fine structure spectroscopy, X-ray absorption near-edge spectroscopy, ultraviolet-visible diffuse reflectance spectroscopy, Hz temperature-programmed reduction, X-ray photoelectron spectroscopy, and diffuse reflectance Fourier transform infrared spectroscopy of adsorbed NO; after two sequential pretreatments and after the production of SWNT under pure CO. In a similar way, the SWNT materials have been characterized using laser Raman spectroscopy, transmission electron microscopy, optical absorption spectroscopy and fluorescence. The information obtained during the catalyst characterization revealed an intrinsic dependence between the selectivity of the catalysts toward SWNT and the stabilization of Co species in a nonmetallic state, which in turn results from an interaction with Mo in the form of a surface Co molybdate-like structure. To examine the validity of this hypothesis different catalyst formulations and reaction conditions have been used. These series of tests included the doping of the Co Mo catalyst with sodium, the substitution of molybdenum by tungsten in the original catalyst formulation, the variation on reaction temperature as well as the introduction of hydrogen in the gas feedstock. All these modifications were carried out in order to modify the growth conditions in which the SWNT are formed. The results are consistent with the proposed hypothesis and have opened the possibility of tailoring the properties of the SWNT obtained.
25 a 29 de septiembre de 2017 Facultad de Ciencias y Educación Proyecto Curricular de Licenciatura en Física Universidad Distrital Francisco José de Caldas
species are known for their mycoparasitic activity against phytopathogenic fungi that cause significant economic losses in agriculture. During mycoparasitism,
spp. recognize molecules produced by the ...host fungus and release secondary metabolites and hydrolytic enzymes to kill and degrade the host's cell wall. Here, we explored the participation of the
RNAi machinery in the interaction with six phytopathogenic fungi of economic importance. We determined that both Argonaute-3 and Dicer-2 play an essential role during mycoparasitism. Using an RNA-Seq approach, we identified that perception, detox, and cell wall degradation depend on the
-RNAi when interacting with
AG2
and
AG5. Furthermore, we constructed a gene co-expression network that provides evidence of two gene modules regulated by RNAi, which play crucial roles in essential processes during mycoparasitism. In addition, based on small RNA-seq, we conclude that siRNAs regulate amino acid and carbon metabolism and communication during the
-host interaction. Interestingly, our data suggest that siRNAs might regulate allorecognition (
) and transport genes in a cross-species manner. Thus, these results reveal a fine-tuned regulation in
dependent on siRNAs that is essential during the biocontrol of phytopathogenic fungi, showing a greater complexity of this process than previously established.IMPORTANCEThere is an increasing need for plant disease control without chemical pesticides to avoid environmental pollution and resistance, and the health risks associated with the application of pesticides are increasing. Employing
species in agriculture to control fungal diseases is an alternative plant protection strategy that overcomes these issues without utilizing chemical fungicides. Therefore, understanding the biocontrol mechanisms used by
species to antagonize other fungi is critical. Although there has been extensive research about the mechanisms involved in the mycoparasitic capability of
species, there are still unsolved questions related to how
regulates recognition, attack, and defense mechanisms during interaction with a fungal host. In this work, we report that the Argonaute and Dicer components of the RNAi machinery and the small RNAs they process are essential for gene regulation during mycoparasitism by
.
Objectives
Propolis has been used in folk medicine in different regions of the world including Latin America. Propolis is a resinous mixture of substances collected by honey bees from several ...botanical sources, and its composition contains a rich chemical variety, depending on the geographical area and plant sources. Our aim was to compare the modulatory effect of propolis samples from three different countries of Latin America (Brazil, Cuba and Mexico) on pro‐ and anti‐inflammatory cytokine production (tumor necrosis factor (TNF)‐α and interleukin (IL)‐10, respectively) by human monocytes.
Methods
Cells were incubated with propolis for 18 h at 37°C. Cell viability was assessed by 3‐(4,5‐dimethyl‐thiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide method, and cytokine production was determined by ELISA.
Key findings
All samples did not affect monocyte viability. Brazilian propolis stimulated both TNF‐α and IL‐10 production by monocytes. Cuban propolis stimulated TNF‐α and inhibited IL‐10 production, while Mexican sample exerted the opposite effect, inhibiting TNF‐α and stimulating IL‐10 production. The major compounds found in Brazilian, Cuban and Mexican propolis samples were artepillin C, isoflavonoids and pinocembrin, respectively.
Conclusion
Brazilian, Cuban and Mexican propolis contained different components that may exert pro‐ and anti‐inflammatory activity depending on concentration, what may provide a novel approach to the development of immunomodulatory drugs containing propolis.
PDF
