Escuela de Química

URI permanente para esta comunidadhttp://10.0.96.45:4000/handle/11056/14435

Misión Contribuir con el desarrollo integral de la sociedad costarricense en un marco de solidaridad y armonía con la naturaleza, por medio de su quehacer en investigación, extensión, docencia y producción, lo que permite la generación de conocimiento, la vinculación externa y la formación y actualización de profesionales en Enseñanza de la Química, Química y sus aplicaciones. Visión Es la Escuela de Química con liderazgo por su excelencia académica, innovación, y vocación de servicio en las áreas de Enseñanza de la Química, Química y sus aplicaciones. Goza de prestigio, a partir de una oferta académica (investigación, docencia, extensión y producción) actualizada, flexible y que responde a las necesidades emergentes del desarrollo nacional e internacional.

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Mostrando 1 - 20 de 114

A methane sink in the Central American high elevation páramo: Topographic, soil moisture and vegetation effects
(Elsevier B.V., 2020-03-15) Chai, Leanne L.; Hernández Ramirez, Guillermo; Hik, David S; Barrio, Isabel C.; Frost, Carol M.; Chinchilla Soto, Isabel Cristina; Esquivel-Hernández, Germain
Methane (CH4) is a strong greenhouse gas with a global warming potential 23 times larger than that of carbon dioxide. Characterizing ecosystems as either sources or sinks for methane and their magnitudes informs on biosphere contributions to the global CH4 budget and to warming of the atmosphere. We quantified methane fluxes for the first time in a neotropical alpine páramo (Valle de Los Conejos, Chirripó Massif, Costa Rica) and examined the relationships of these fluxes with topography, soil moisture and vegetation, during the transition from dry to rainy season. Using closed chambers and laser spectroscopy, we measured soil CH4 and CO2 fluxes across a field site encompassing: a grassy plain as well as a plain, a gentle slope and a plateau dominated by a dwarf bamboo (Chusquea subtessellata Hitchcock). We found that the páramo landscape acts as a sink for CH4 [−53.1 ± 29.6 (mean ± SE) µg C m−2 hr−1]. Of the four field areas, the grassy plain was on average the strongest CH4 sink, likely because this soil profile had no drainage restrictions and was well aerated. By contrast, in the slope and plateau, a heavily-consolidated subsurface layer was shown to perch water, increasing surface soil moisture and limiting CH4 uptake. Conversely, in certain parts of the plain, where Chusquea grew vigorously in discrete, tall patches, we found intense CH4 uptake beneath these patches. Within the Chusquea plain, these hot spots of CH4 uptake localized under the tall Chusquea had double the uptake rates than outside these patches, with even greater uptake than the average in the grassy plain. Our results show that CH4 uptake in the páramo is driven by moisture interacting with impeding soil layers, vegetation and topography.
A preliminary isotope-based evapotranspiration partitioningapproach for tropical Costa Rica
(John Wiley and Sons Ltd, 2021-07) Iraheta, Alberto; Birkel, Christian; Benegas, Laura; Ríos, Ney; Sánchez-Murillo, Ricardo; Beyer, Matthias
Spatially and seasonally distributed information on transpiration (T) fluxes is limited in the tropics. Here, we applied a coupled isotope mass balance model to separate water fluxes of T and evapotranspiration (ET) from precipitation (P). The mean annual T was estimated at a resolution of 100 m for Costa Rica (51,100 km2) and a partitioning of monthly T and evaporation (E) for the 2370-km2 San Carlos catchment. The dominant flux in the forest ecosystems was T with a mean annual T of 1086 mm that ranged from 700 mm in Tropical Montane Very Humid Forest to 1400 mm in Subtropical and Tropical Low Montane Rainforests. We estimated an average 85% of ET was T, which is concurrent with expectations for forested tropical regions, but varied according to model parameterization and data sources. A model comparison exercise showed a range of mean annual T estimates from 988 to 1465 mm and a range of T/P from 0.35 to 0.5 with temperature and relative humidity exhibiting the highest impact on the model results. Across Costa Rica, we estimated an average loss of precipitation by T of 38% (1085 mm), whereas interception (I) constitutes 10% (230 mm) and direct evaporation (E) only 7% (192 mm). Similarly, the results at the catchment scale indicated that monthly T contributes 76% (85-mm monthly average) to total ET and E corresponds to 24% (24-mm monthly average). The T rates exhibited an opposite seasonality to rainfall with highest T over the drier months from December to April with a peak in March (101–144 mm) and the minimum T in September (53–71 mm). Around 17% (79–130 mm) of precipitation over the catchment area is lost to T, both E (10–35 mm) and I (15–38 mm) correspond to 5%. Despite the inherent uncertainties of the data assumptions and simplifications, including data interpolation errors, the coupled isotope mass balance model showed in comparison to other global products reasonable water partitioning for different ecosystems in Costa Rica and the San Carlos catchment area. These results can help to evaluate the impact of land cover conversion on the hydrological cycle in Costa Rica, and the simple isotope-based model could be transferred to different biomes of the tropics.
Adaptación del método de descarga de arco voltaico para la síntesis de nanotubos de carbono de pared simple
(Universidad Nacional (Costa Rica), 2009-11) Ramírez Amador, Sergio Alberto; Vega Baudrit, José
Los nanotubos de carbono fueron descubiertos por el físico japonés Sumio lijima en 1991. Sus propiedades físicas y químicas catalogadas como extraordinarias, siguen demostrando gran potencial en multitud de campos. Los nanotubos de carbono son tubos diminutos, basados únicamente en átomos de carbono. Poseen un diámetro de apenas unos pocos nanómetros, sin embargo, su longitud puede ser de hasta un milímetro, (dispone de una relación longitud: diámetro hasta ahora sin precedentes). Están formados a partir de una o varias láminas de grafeno enrolladas sobre sí mismas en forma cilíndrica. Algunos nanotubos están cerrados por media esfera de fulereno y no están cerrados. Existen nanotubos monocapa (NTCPS, un sólo tubo) y multicapa (varios tubos concéntricos). Los nanotubos de una sola capa se llaman nanotubos de carbono de pared simple (Single-Wall Nanotube, SWNT, inglés) y los de varias capas, nanotubos de carbono de multipared, NTCPM, (Multi-Walled Nanotubes, MWNT, en inglés). Debido a la forma en que los átomos de carbono se enlazan en las estructuras de los nanotubos, éstos son muy fuertes. Incluso más fuertes que los diamantes, que poseen también una estructura tridimensional basada principalmente de átomos de carbono. Estos nanotubos son las fibras más fuertes conocidas, un sólo nanotubo perfecto es cerca de 10 a 100 veces más fuerte que el acero por unidad de peso. La investigación sobre nanotubos de carbono es interesante por sus múltiples aplicaciones y posibilidades, pero a la vez compleja por la variedad de sus propiedades electrónicas, térmicas y estructurales que cambian según el diámetro, la longitud, la forma de enrollar y otros. Los nanotubos de carbono, además de ser muy resistentes, poseen propiedades eléctricas interesantes, pues pueden comportarse como conductores o semiconductores de electricidad según el acomodamiento de sus átomos. En el presente proyecto, se buscó la optimización de la metodología encontrada en la literatura para la síntesis de nanotubos de carbono de pared simple por descarga de arco voltaico. Para alcanzar esta optimización, se sintetizaron distintas muestras de NTCPS bajo la modificación de las variables del proceso. Las variables estudiadas fueron la corriente eléctrica de la fuente de poder, presión y tipo de gas. Las sintetizadas fueron caracterizadas por análisis termogravimétrico (TGA), microscopia de fuerza atómica (AFM), microscopia de transmisión electrónica (TEM), microscopia de barrido electrónico (SEM) y por análisis de infrarrojo con transformada de Fourier (FTIR). El fin fue el de corroborar la existencia de NTCPS y su grado de pureza.
Addition of nanosilicas with different silanol content to thermoplastic polyurethane adhesives
(Elsevier, 2005-08-15) Jose-Roberto, Vega-Baudrit; Navarro Bañón, Virtudes; Vásquez, Patricia; Martín Martínez, José Miguel
Three nanosilicas with different silanol contents were prepared by treatment of hydrophilic fumed silica with dimethyldichlorosilane. This treatment reduced the silanol content and produced the particle agglomeration of the nanosilicas. Thermoplastic polyurethane (TPU) adhesives containing nanosilicas were prepared and characterized by FTIR spectroscopy, differential scanning calorimetry (DSC), plate-plate rheology, dynamic mechanical thermal analysis (DMTA), transmission electron microscopy (TEM) and stress-strain testing. Adhesive strength was obtained from T-peel tests of PVC/polyurethane adhesive joints. The addition of hydrophilic nanosilicas favoured the degree of phase separation between the hard (i.e. isocyanate+chain extender) and soft (i.e. polyol) segments in the TPUs; the higher the silanol content on the surface of silica, the higher the degree of phase separation, and the crystallinity of the polyurethane (due to the soft segments) was also increased. Hydrogen bonds between the ester carbonyl groups in the TPU and the silanol groups on the silica surface were created and more favoured by increasing the silanol content. The tensile strength increased and the elongation at break of the polyurethane decreased by increasing the silanol content of the nanosilica. Addition of nanosilica increased the immediate adhesion of the polyurethane adhesives to PVC, irrespective of the silanol content on the nanosilica. The higher the mechanical and the rheological properties of the polyurethanes containing nanosilicas with different silanol content, the higher the final adhesive strength. © 2005 Elsevier Ltd. All rights reserved.
An approach to rheological and electrokinetic behaviour of lipidic vesicles covered with chitosan biopolymer
(Elsevier, 2008) Madrigal-Carballo, Sergio; Seyler, D.; Manconi, M.; Mura, S.; Vila, A.; Molina, F.
The rheological and electrokinetic properties of soybean lecithin vesicles prepared from concentrated soy lecithin dispersions (250 g/L) obtained by slow swelling under shear conditions and mixed with chitosan biopolymer solutions were studied. The rheological behaviour of lecithin-chitosan vesicles was determined by shear stress against shear rate measurements, as well as by the variation on the hysteresis loop area. The results were compared with the rheopectic behaviour of soy lecithin dispersions without chitosan. An important change on the rheological properties of the complex dispersion was observed, depicting in a thixotropic behaviour with a plastic character in the presence of chitosan. This observation indicates that chitosan promotes the transition of planar sheets into closed structures, such as vesicles. The influence on the rheological and the electrokinetic behaviours of several electrolytes, such as NaCl, CaCl2 and AlCl3 with concentrations ranging between 10-5 and 10-2 mol/L were also studied. In all of the cases, an estimation of the diameters of the closed structures was obtained. © 2007 Elsevier B.V. All rights reserved.
Análisis de la producción de metano entérico generado vía fermentación ruminal In vitro
(Universidad Nacional (Costa Rica), 2020) Martínez Arroyo, Mariela; Esquivel Hernández, Germain
La generación de CH4 entérico de origen bovino es una problemática que afecta el balance radiativo del planeta, ya que, el potencial de calentamiento global del CH4, debido a la absorción de radiación infrarroja, es 28 veces mayor al del CO2. La concentración de este gas en la atmósfera es favorecida por la fermentación de las pasturas que realizan los animales rumiantes de los sistemas ganaderos y significa una pérdida de la energía asimilable por la alimentación de hasta un 12 %, lo cual implica problemas en su desarrollo, así como una disminución en la calidad de los productos que se obtienen de este. En este estudio se analizaron seis especies de pastos tropicales (kikuyo, ratana, mombaza, toledo, diamantes y estrella africana) para evaluar su emisión de CH4, vía digestión ruminal in vitro. Para ello, se muestrearon las especies en cuatro edades de rebrote: 14, 28, 42 y 56 días, entre abril y mayo del 2018. Las muestras recolectadas se incubaron para una fermentación en frascos provistos de un sensor de presión, el cual registró las variaciones en la presión total del sistema, producto de la generación de gases de la fermentación de cada pasto. La fermentación se llevó a cabo a 39 °C, a un pH de 7,01 y por 24 h, las cuales se determinaron que eran las condiciones óptimas para el análisis. Se obtuvo que el pasto que generó la mayor cantidad de CH4 fue el estrella africana, con un promedio de concentración de 0,360 g/kg, mientras que la especie que emitió menos gas fue el kikuyo, con un promedio de concentración de 0,095 g/kg. Estos pastos tuvieron promedios de generación significativamente distintos (p < 0,05) a las especies restantes. Las emisiones de las otras pasturas estuvieron entre 0,178 g/kg y 0,250 g/kg. La emisión de CH4 del pasto mombaza a los 14 días de edad fue significativamente distinta (p < 0,001) a la generación del gas en las demás edades de rebrote de esta especie, para el grupo 1 (14 días de rebrote) fue en promedio de 0,43 g/kg, mientras que la del grupo 2 (28, 42 y 56 días) fue de 0,182 g/kg. Se identificó una correlación (método de Spearman) significativa (p < 0,05) entre la emisión de CH4 del pasto mombaza a los 28, 42 y 56 días de rebrote, con la fibra detergente neutro (FDN), la proteína y la edad. Además, se modeló la emisión de CH4 de estas edades (28, 42 y 56 días), donde la variable predictiva fue la proteína y el R2 de 0,81. Se concluyó que el factor más determinante en la generación de CH4 fue la composición química del tipo de pasto, la cual no necesariamente va en detrimento con la edad, ya que hay otros elementos asociados como la acumulación de carbohidratos solubles que influyen en la digestión ruminal. Sin embargo, para escoger el mejor forraje para el pastoreo, deben considerarse componentes adicionales a la generación de metano, tales como la productividad por unidad de área, meteorología y el tipo de suelo, así como la calidad nutricional.
Analysis of a drinking water disinfection system: an input for improving supply management in a rural aqueduct in Costa Rica
(2024-06-05) Salas-Gónzalez, Edwin; Sánchez-Gutiérrez, Rolando; Fonseca Sanchez, Alicia; Alfaro-Chinchilla, Carolina; Esquivel-Hernández, Germain; Rodríguez Rodríguez, Jorengeth Abad; Rodríguez Corrales, José
Analysis of energy transfer and ternary non-covalent filler/matrix/UV stabilizer interactions in carbon nanofiber and oxidized carbon nanofiber filled poly(methyl methacrylate) composites
(Elsevier, 2011-10-27) Gunes, I. Sedat; Pérez Bolívar, César; Jiménez, Guillermo A.; Çelikbıçak, Ömür; Li, Fengyu; Anzenbacher, Jr., Pavel; Wesdemiotis, Chrys; Jana, Sadhan
Ternary non-covalent interactions between carbon nanofibers (CNFs), oxidized carbon nanofibers (ox- CNFs), poly(methyl methacrylate) (PMMA) chains, and benzotriazole-containing UV stabilizers were analyzed using Fourier-transform infra red spectroscopy (FTIR), time-resolved fluorescence emission spectroscopy, and fluorescence lifetime imaging microscopy. The results indicated that PMMA chains form hydrogen bonds both with ox-CNF fibers and the UV stabilizer molecules. It was also determined that UV stabilizers strongly interact with CNF particles via p-p interactions. The extent of p-p and hydrogen bonding interactions was determined to be lower between ox-CNF particles and UV stabilizers due to less perfect graphitic structure of the former. The morphology of the composites indicated that the hydrogen bonds between PMMA chains and ox-CNF particles resulted in highly improved state of filler dispersion in ox-CNF/PMMA composites.
Analysis of non-covalent interactions between the nanoparticulate fillers and the matrix polymer as applied to shape memory performance
(The Royal Society of Chemistry, 2010) Sedat Gunes, I; Perez Bolivar, Cesar; Cao, Feina; Jimenez, Guillermo A.; Anzenbacher, Pavel; Sadhan, Jana
Non-covalent interactions between filler particles and polyurethanes were investigated using fluorescence emission spectroscopy. The results were used in the analysis of shape memory (SM) performance of polyurethanes. Composites of shape memory polyurethane (SMPU) and carbon nanofiber (CNF), oxidized carbon nanofiber (ox-CNF), organoclay, silicon carbide, and carbon black were prepared from diphenylmethane diisocyanate, 1,4-butanediol, and poly(caprolactone)diol. It was revealed by fluorescence emission spectroscopy that primarily the urethane groups located in the hard segments of SMPU interacted with the polar functional groups on filler particles. A close correlation between the extent of non-covalent filler-matrix interactions, soft segment crystallinity, and SM properties of polyurethane composites was discussed. It was observed that weak non-covalent interactions of polymer chains with CNF and SiC particles caused significant reductions in soft segment crystallinity of SMPU and hence the shape memory properties of the composites. © The Royal Society of Chemistry 2010.
Announcing the call for the Issue Focus on the 2nd Costa Rican Biophysics Symposium—virtual meeting, March 2021
(Springer (Alemania), 2021) Solis-Ocampo, Chrisopher; Chaves Barboza, Gustavo; Rodríguez-Corrales, José
This Commentary is a call for submissions for the upcoming Issue Focus that will highlight some of the scientific topics discussed during the 2nd Costa Rica Biophysics Symposium.
Anthrone and oxanthrone C,O-diglycosides from Picramnia teapensis
(Elsevier, 2000) Rodríguez Gamboa, Tatiana; Victor, Sandra R.; Fernandes, Joao B.; Rodrigues Fo, Edson; Da Silva, M. Fatima das G.F.; Vieira, Paulo C.; Pagnocca, Fernado C.; Hebling, Maria Jose A.; Castro C., Oscar
Two C,O-diglycosylated compounds, the anthrone picramnioside F, and the oxanthrone mayoside C, were isolated from the stem bark of Picramnia teapensis, along with the previously reported anthraquinones, 1-O-b-d- and 8-O-b-d-glucopyranosyl emodin. The compounds were separated by recycling-HPLC, and their structures were determined on the basis of spectroscopic analysis. CD measurements were used to establish the absolute con®guration of the anthrone and oxanthrone. The antifungal activity of 1- O-b-d- and 8-O-b-d-glucopyranosyl emodin against Leucoagaricus gongilophorus was shown to be similar to that of the lignan sesamin. # 2000 Elsevier Science Ltd. All rights reserved.
Antimicrobial activities of Marcgraviaceae species and isolation of a naphthoquinone from Marcgravia nervosa (Marcgraviaceae)
(NRC Research Press, 2015) Carballo Arce, Ana Francis; Chieu Anh, Kim Ta; do Nascimento Rocha, Marco Eduardo; Rui, Liu; Harmsen, Irene; Mogg, Christopher; Otárola-Rojas, Marco; Garcia, Mario; Sánchez Vindas, Pablo; Poveda, Luis; Rajagopal Subramaniam; Smith, Myron; Coelho Kaplan, Maria Auxiliadora; Figueiredo, Maria Raquel; Durst, Tony; Arnason, John
The Marcgraviaceae is a neotropical plant family of lianas and shrubs distributed throughout Central and South America, mainly in evergreen and semi-evergreen tropical forests. In this study, extracts of 12 Marcgraviaceae species were assessed for inhibition of bacterial quorum sensing (QS) in Chromobacterium violaceum, bacterial biofilm formation in Pseudomonas aeruginosa PA14, and fungal growth in Saccharomyces cerevisiae. Six species showed promising inhibitory activities in at least one of the three bioassays (Marcgravia nervosa Triana & Planch., Marcgravia polyantha Delp., Marcgravia schippii Standl., Marcgraviastrum subsessile (Benth.) Bedell, Schwartzia brasiliensis (Choisy) Bedell ex Gir-Cañas, and Schwartzia costaricensis (Gilg.) Bedell). Analyses of the crude extract of the leaves of Marcgravia nervosa using HPLC–APCI–MS showed the presence of five pentacyclic triterpenes: ursolic acid (2), betulinic acid (3), α–amyrin (4), β–amyrin (5), lupeol (6). Bioassay-guided fractionation of this plant resulted in the isolation and identification of 2-methoxy-1,4-naphthoquinone (1) as the active principle with a minimum inhibitory concentration (MIC) of 85–100 μmol·L−1 against Saccharomyces cerevisiae BY4741 (haploid) and BY4743 (diploid).
Arsenate removal by chitosan iron oxyhydroxide beads: Preparation, characterization, and adsorption studies
(Desalination Publications, 2021) González Rodríguez, José Ricardo; Rojas Carrillo, Oscar; Romero-Esquivel, Luis G.
This study compared arsenic removal from drinking water by two different adsorbents: iron-im-pregnated chitosan beads (Fe-ICB) and iron-doped chitosan beads (Fe-dCB). Scanning electron microscopy, X-ray diffraction (XRD), Fourier transform infrared, and Raman spectroscopy were applied to characterize the materials produced. The As(V) adsorption capacity of both types of materials was evaluated by batch tests, followed by a column test using the most promising material. The XRD and the Raman spectroscopy confirmed the presence of 2-line ferrihydrite in the produced Fe-dCB, and no specific iron oxy-hydroxide was identified in the Fe-ICB. Both types of materials followed either the Langmuir or the Freundlich isotherm adsorption models. The Fe-dCB were more efficient in removing As(V) than the Fe-ICB. The actual maximum capacity of the produced Fe-dCB ranged from 0.27 to 0.61 mg/g under the conditions tested (concentration: 1 mg/L; pH: 7.0; 100 rpm). The Fe-dCB with the better adsorption capacity at low concentrations (<0.1 mg/L) were used in a column test using an As(V) influent concentration of 0.060 mg/L. The Fe-dCB produced close to 91,000 BVs, meeting the standard for drinking water (0.01 mg/L). Therefore, the material exhibits promising adsorbent properties for filtration applications with low arsenic concentrations.
Arthropod biodiversity loss and the transformation of a tropical agro-ecosystem
(Chapman & Hall, 1997) Perfecto, Ivette; Vandermeer, John; Hanson, Paul; Cartin, Víctor
The coffee (coffea arabica) agro-ecosystem in the Central Valley of Costa Rica was formerly characterized by a high vegetational diversity. This complex system has been undergoing a major transformation to capital-intensive monocultural plantations where all shade trees are eliminated. In this study we examined the pattern of arthropod biodiversity loss associated with this transformation. Canopy arthropods were sampled in three coffee farms: a traditional plantation with many species of shade trees, a moderately shaded plantation with only Erythrina poeppigeana and coffee, and a coffee monoculture. An insecticidal fogging technique was used to sample both canopy and coffee arthropods. Data are presented on three major taxonomic groups: Coleoptera, non-formicid Hymenoptera, and Formicidae. Data demonstrate that the transformation of the coffee agro-ecosystem results in a significant loss of biological diversity of both canopy arthropods as well as arthropods living in coffee bushes. Percentage of species overlap was very small for all comparisons. Furthermore, species' richness on a per tree basis was found to be within the same order of magnitude as that reported for trees in tropical forests. If results presented here are generalizable, this means that conservation efforts to preserve biological diversity should also include traditional agro-ecosystems as conservation units.
Bacterial Genome Editing with CRISPR-Cas9: Taking Clostridium beijerinckii as an Example
(Springer (Alemania), 2018) Zhang, Zhong-Tian; Jiménez-Bonilla, Pablo; Seo, Seung-Oh; Lu, Ting; Jin, Yong-Su; Blaschek, Hans P.; Wang, Yi
Abstract. CRISPR-Cas9 has been explored as a transformative genome engineering tool for many eukaryotic organisms. However, its utilization in bacteria remains limited and ineffective. This chapter, taking Clostridium beijerinckii as an example, describes the use of Streptococcus pyogenes CRISPR-Cas9 system guided by the single chimeric guide RNA (gRNA) for diverse genome-editing purposes, including chromosomal gene deletion, integration, single nucleotide modification, as well as “clean” mutant selection. The general principle is to use CRISPR-Cas9 as an efficient selection tool for the edited mutant (whose CRISPR-Cas9 target site has been disrupted through a homologous recombination event and thus can survive selection) against? the wild type background cells. This protocol is broadly applicable to other microorganisms for genome-editing purposes.
Biofabrication of Gold Nanotriangles Using Liposomes as a Dual Functional Reductant and Stabilizer
(American Chemical Society, 2021-03-23) Soto, Jackeline; Conejo-Valverde, Paolo; Sáenz-Arce, Giovanni; Dou, Hongjing; Rojas Carrillo, Oscar
Negatively charged liposomes accomplished both functions as a reducing and stabilizing agent in the synthesis of gold nanotriangles (GNTs). Liposomes are based on a mixture of phospholipids phosphatidylcholine/phosphoglycerol, and they were used as a template phase to perform the GNTs. The method was evaluated under different conditions such as temperature, reaction time, phosphoglycerol chain length, and precursor concentration. Isotropic and anisotropic gold nanoparticles are formed simultaneously during the synthesis. Therefore, by combining centrifugation and depletion flocculation strategies, the sample was concentrated in terms of GNTs from 15% crude to 80% by using sodium dodecyl sulfate (SDS). As a result, a green colored dispersion was obtained containing highly purified, well-defined, negatively charged GNTs, where the edge length of most particles is centered in the range of 60-80 nm with an average thickness of 7.8 ± 0.1 nm. By this purification process, it was possible to highly increase the yield in terms of GNTs. Other surfactants [cetyltrimethylammonium chloride (CTAC), hexadecyltrimethylammonium bromide (CTAB), Tween 20, and dodecyldimethylammonium bromide] were evaluated during the purification stage, and both CTAB and CTAC show similar results to those obtained by using SDS. These GNTs are potential candidates for future applications in molecular imaging, photothermal therapy, drug delivery, biosensing, and photodynamic therapy.
Biogardens as constructed wetlands in tropical climate: A case study in the Central Pacific Coast of Costa Rica
(Elsevier, 2019-03-25) Pérez-Salazar, Roy; Mora Aparicio, Carmen; Alfaro-Chinchilla, Carolina; Sasa Marín, Jihad; Scholz, Carola; Rodríguez-Corrales, José
In Costa Rica, <10% of wastewater is treated before its discharge. This generates a significant impact on the environment, public health, and tourism industry, which is one of the country's main economic activities. Biogardens, subsurface flow artificial wetlands, are alternative systems for the treatment of wastewater. The present study evaluated the removal of organic matter and nutrients in a biogarden located at a hotel in the Central Pacific Coast of Costa Rica between 2012 and 2017. Pretreatment involved septic tanks and grease traps for sewage and gray water, respectively. The biogarden, which is composed of seven wetlands with an average area of 12 m2 and a depth of 0.7 m, contains river cobble as support material, gravel as bed, and Cyperus papyrus and Heliconia sp. plants. Removal of the biochemical oxygen demand (BOD), the chemical oxygen demand (COD), and the total suspended solids (TSS) on average were 80%, 66%, and 72%, respectively, thus producing an effluent in compliance with current national legislation. Furthermore, the biogarden did not emit noxious odors or display an excessive presence of mosquitoes. The results showed consistent and efficient removal of organic matter and nutrients from the wastewater throughout different seasons and pollutant loads, verifying that such systems can be used in decentralized locations (e.g., tourist areas) in tropical climates.
Bioprocess Development of an Extremophilic Methanotroph and Microalgae Coculture for the Production of a Novel Proteinaceous Biofeed
(University of Canterbur, 2022) Cartín Caballero, Carlos Manuel; Carere, Carlos
Biorefinery by the hand of the nanotechnology: biodegradable polymers from industrial biomass waste
(ACCEFYN & NanoCiTec (Colombia), 2016) Jose-Roberto, Vega-Baudrit; Hernandez-Miranda, Michael; González-Paz, Rodolfo; Corrales, Yendry
Abstract. Biorefineries contribute to solve energy, water and environmental problems due to the used of thousands of tons of agricultural biomass residues for production of high value materials, that from a social point of view could help developing countries to improve their economy. The technological and scientific advances in sciences as nanotechnology have increased the understanding of material properties; helping to find new applications. Examples of materials extracted from Costa Rica biomass waste are presented.
Calidad química, física y microbiológica del agua superficial en la microcuenca del río Poás
(Universidad Nacional (Costa Rica), 2023) Jiménez Jiménez, Marianela; Sánchez Gutiérrez, Rolando
Resumen. La microcuenca del río Poás exhibe algunas alteraciones en la calidad del agua superficial, por lo tanto, se optó por evaluar la calidad del recurso hídrico en la microcuenca mediante la aplicación de indicadores e índices de calidad del agua con el propósito de identificar los sitios de atención prioritaria y determinar el grado de afectación del recurso hídrico. Se estudiaron 9 sitios distribuidos de manera representativa en la microcuenca durante el período comprendido entre junio 2021 y enero del 2022, en el cual, se realizó una caracterización química, física y microbiológica del agua superficial. Los parámetros seleccionados son los que se contemplan en el Índice Holandés, en el Índice Fundación Nacional de Saneamiento y otros parámetros tales como las propiedades ópticas de la materia orgánica fluorescente. Se incluye el análisis del índice de fluorescencia, el índice de humificación y el índice de contribución biológica reciente, índices no contemplados en la normativa nacional de la calidad del agua superficial. El análisis estadístico inferencial evidencia que existen variaciones espaciales de la calidad del agua con respecto al sitio de muestreo y zona de la microcuenca. Los resultados revelan que los sitios de estudio ubicadas en la zona media y baja de la microcuenca presentaron niveles de contaminación mayores que la zona alta. Los sitios localizados en la zona baja del río Poás, en la zona media del río Prendas y en la parte baja del río Itiquis, se catalogaron como sitios de atención prioritaria, por consiguiente, se propone la creación de una red de monitoreo en la microcuenca del río Poás que incluyan los sitios enlistados. El monitoreo de los ríos contribuye a la generación de bases de resultados de calidad del agua que ayudan a los actores sociales a ejecutar acciones de remediación, mitigación o acciones que mejores la calidad del recurso hídrico. Además, se propone un plan de muestreo semestral, con propósito de recolectar datos durante la época lluviosa y la seca, mientras que el plan de análisis debe incluir los parámetros contemplados en el índice Holandés para la valoración de la calidad química y física del agua superficial, el parámetro microbiológico E. coli, nitrato, fósforo y algunos otros indicadores tales como las propiedades ópticas de la materia orgánica disuelta fluorescente. El estudio revela la importancia de utilizar parámetros físicos, químicos y microbiológicos complementarios para la clasificación inicial o reclasificación y el monitoreo de los cuerpos de agua superficial, debido a que los parámetros establecidos en la normativa nacional como indispensables para determinar la calidad del agua proporcionan información deficiente para la toma de decisiones sobre la gestión del recurso hídrico.

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