Artículos científicos

URI permanente para esta colecciónhttp://10.0.96.45:4000/handle/11056/14610

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A combined experimental and theoretical study of gas sorption on nanoporous silver triazolato metal-organic frameworks
(2014-01-01) Yang, Guang; Santana, Juan A; Rivera Ramos, Milton E.; García - Ricard, Omar; Saavedra-Arias, José; Ishikawa, Yasuyuki; Hernandez-Maldonado, Arturo; Raptis, Raphael G.
A new silver-triazolate metal-organic framework (MOF), {Ag 3[Ag5(μ3-3,5-tBu 2tz)6](BF4)2}n (2), has been prepared and structurally characterized. The CO2 sorption properties of this new MOF and previously reported isostructural analog {Ag 3[Ag5(μ3-3,5-Ph2tz) 6](NO3)2}n (1), were determined experimentally and probed theoretically by a density functional (DF) method. The structures of 1 and 2 are based on flexible Ag5tz 6-structural building units (SBUs), which allow the expansion/contraction of the structure, depending on either the steric requirements of the pendant groups - tBu, or Ph - of the SBUs, or the pressure of the gaseous sorbate. Both silver-triazolate MOFs sorb CO 2 preferentially to N2, O2, CH4 and H2. DF calculations show CO2 to be bound by van der Waals forces to the organic moieties of the porous framework. This work shows that van der Waals interactions of CO2 and the aromatic and aliphatic hydrocarbons of silver-triazolate MOFs are sufficient to achieve preferential sorption of CO2.
A combined first-principles computational/experimental study on LiNi 0.66Co 0.17Mn 0.17O 2 as a potential layered cathode material
(Elsevier, 2012-08-01) Saavedra-Arias, José; Venkateswara Rao, Chitturi; Shojan, Jifi; Manivannan, Ayyakkannu; Torres, Lorraine; Ishikawa, Yasuyuki; Katiyar, Ram
First-principles calculations are used to analyze the phase stability, formation energy, and Li intercalation potential for a series of layered cathode materials. The calculations show LiNi 0.66Co 0.17Mn 0.17O 2 as a promising cathode for lithium-ion batteries. The layer-structured LiNi 0.66Co 0.17Mn 0.17O 2 is prepared via wet chemical route, followed by annealing at 1123 K and characterized using powder X-ray diffraction, scanning electron microscopy, and X-ray photoelectron spectroscopy. The characterization techniques reveal single-phase LiNi 0.66Co 0.17Mn 0.17O 2 with highly ordered structure. Galvanostatic charge-discharge curves recorded at 1C show the discharge capacity of ca. 167 mAh g -1 and good cyclic performance for 25 cycles.
A first estimation of tsunami hazard of the Pacific coast of Costa Rica from local and distant seismogenic sources
(Springer, 2021-06-04) Chacon-Barrantes, Silvia; Arozarena-Llopis, Isabel
Costa Rica has been affected by several local and distant tsunamis in the past, but the historical information is scarce and incomplete. Its Pacific coast stretches for over a thousand kilometers, and tsunami hazard has never been evaluated for its full extent. Numerical modeling of tsunami propagation and inundation is a useful tool to assess tsunami hazard, particularly in cases with limited historical information available. Here, we perform a first estimation of tsunami hazard for the Pacific coast of Costa Rica from seismogenic sources, by numerical propagation of 57 local and distant tsunamis to a depth of 20 m. The results of our study identified tsunami sources that are particularly threatening for Costa Rica and determined locations with higher tsunami hazard. For the analysis, the Pacific coast of Costa Rica was divided into segments and subsegments based on differences in continental slope morphology. Subsegments with higher tsunami heights were Southwest Nicoya Peninsula and West Osa Peninsula, and in a lesser extent North Guanacaste, North Nicoya Peninsula, and Central Pacific. Regions with long and gentle slopes and narrow continental shelf were affected by higher tsunami waves, due to more efficient tsunami energy transmission to the shelf and reduced energy loss while traveling through a narrow shelf. On the opposite, steeper continental slopes reflected most of the tsunami energy, causing smaller tsunami heights nearshore, regardless of the shelf width. Nevertheless, other effects played a major role, like curved coastlines that focused tsunami energy, wave refraction, interference, and trapped edge waves. Distant tsunamis dominated the threat, with tsunamis coming from the Tonga-Kermadec and the Colombia-Ecuador Trenches causing the greatest heights due to directivity, and arrival times of about 15 h and 75 min, respectively. Local tsunamis had short arrival times but a localized impact, mainly at the shoreline in front of the generation region but were also affected by tsunami focusing, wave refraction, and edge waves. Outer rise and Osa sources caused the lowest impact within local sources. These results provide a guide for emergency planners to prioritize coastal locations and tsunami sources for tsunami preparedness actions and warning protocols.
A new species of Halicyclops (Copepoda, Cyclopoida, Halicyclopinae) from an estuarine system of the caribbean coast of Colombia
(Universidad Nacional de Colombia, 2020-01-01) Fuentes Reinés, Juan M.; Suárez-Morales, Eduardo
Plankton samples obtained from the Ciénaga Grande de Santa Marta, an extensive estuarine system in northern Colombia, yielded adult male and female specimens of an undescribed halicyclopine cyclopid copepod of the genus Halicyclops. Cyclopid copepods are frequently found in freshwater and transitional habitats. Members of the subfamily Halicyclopinae are chiefly brackish water forms with a few freshwater species. The new species described herein is assignable to the group of species “F” of Halicyclops (sensu Pesce, 2018) with a 2333 exopodal spine formula. Currently, this group contains five species and one subspecies. Halicyclops gutierrezi sp. n. can be distinguished from its known congeners by the absence of an anal operculum, the relative length of setae of the female and male P5, the relative length of the inner setae of P4EXP3, and details of the male antennule. This is the fifth species of Halicyclopsrecorded from Colombia and the first one of Halicyclops group “F” described from the Caribbean region. With the addition of H. gutierrezi sp. n., the number of species of the genus known from the Neotropics increased to 20. A key to the species of the genus recorded in Colombia is also provided.
Abundancia, biomasa y estructura de la ictiofauna demersal en el Océano Pacífico de Centroamérica, con base en la prospección pesquera realizada a bordo del R / V Miguel Oliver
(Universidad Nacional (Costa Rica), 2020-01) BENAVIDES, ROSARIO; Campos-Calderón, Fernando; Vargas-Hernández , José Mauro
A razón de ampliar el conocimiento sobre la estructura y composición de la ictiofauna demersal en el Pacífico de Centroamérica, se realizó el estudio de muestras obtenidas en 98 puntos de arrastre efectuados con el B/O Miguel Oliver entre el 10 de noviembre y el 16 de diciembre de 2010. Con una red tipo Lofoten, se faenó por 30 minutos sobre los puntos ubicados según estratos y profundidad (máxima 1 600 m). La muestra total (17 507 ejemplares) tuvo representación de peces cartilaginosos y óseos divididos en 77 familias y 158 especies. Dicrolene filamentosa (12.27%) mostró la mayor abundancia, las biomasas más representativas del estudio fueron de Peprilus medius (35.67%) y Peprilus snyderi (12.49%) junto con Rhinoptera steindachneri (9.45%), mientras que las especies más frecuentes fueron Peristedion barbiger y Stomias atriventer (ambas con 2.71%). La costa frente a Costa Rica y Panamá mostró diversidad alta (H’:3), mientras que la equidad presentó valores uniformes. Para determinar ensamblajes con respecto a la profundidad, se utilizó un ordenamiento espacial que mostró un agrupamiento de 3 conjuntos (PERMANOVA, R = 0.54, P > 0.05) y un análisis canónico de correspondencia, el cual arrojó evidencia suficiente de que las especies fueron influenciadas en su distribución por la salinidad y la temperatura. La ictiofauna encontrada responde a eventos y condiciones ambientales particulares que revisten de gran importancia ecológica los hallazgos. Se resalta lo fundamental de los ensamblajes para evaluar cómo las poblaciones cambian como resultado de las características que exhiben las masas de agua.
Advances in tsunami preparedness at the beginning of the Ocean Decade: the Costa Rica case
(Instituto Oceanográfico da Universidade de São Paulo, 2021-04-04) Chacon-Barrantes, Silvia; Murillo Gutiérrez, Anthony; Rivera, Fabio; Aliaga Rossel, Bernardo
Following the 2004 Indian Ocean and the 2011 Tohoku earthquakes and tsunamis, there has been steady progress in tsunami science and preparedness worldwide. Currently, there are four Tsunami Warning and Mitigation Systems as Intergovernmental Coordination Groups (ICGs) coordinated by IOC/UNESCO. They include tsunami monitoring, warning, and response. They are mostly based on scientific knowledge including tsunami hazard assessments, 24/7 monitoring systems, agreed operational standard procedures (SOPs), redundant communication and community response mechanisms. Costa Rica has greatly increased its tsunami preparedness during the past six years, after the creation of SINAMOT (Sistema Nacional de Monitoreo de Tsunamis). SINAMOT works by characterizing the tsunami threat, encouraging, and supporting community preparedness, strengthening the existing tsunami warning SOPs and maintaining the sea level monitoring network. SINAMOT articulates with stakeholders and decision makers such as seismic monitoring networks, national and local government, emergency managers and committees. Four communities in Costa Rica have been recognized as Tsunami Ready by IOC/UNESCO, four more are recognized with pending guidelines and five more are working on fulfilling the requirements. Despite all the progress made, there is still plenty of work to do to have a safe and predictable ocean regarding tsunamis. Atypical tsunami sources are not yet incorporated in hazard assessments, there are many gaps in sea level monitoring, and capacity building is required in many aspects so that developing countries can be more autonomous in their tsunami preparedness and response. Our major challenges today worldwide are with staffing and funding, both to kick-off and to sustain the mentioned activities. Specifically, Costa Rica requires more physical oceanographers and geoscientists working on tsunami science and more funding to study the ocean (including sea level gauges and tsunami hazards assessment) to support the tsunami and other coastal hazard warning systems. This requires working together with communities and stakeholders to increase tsunami preparedness.
An evaluation of variables affecting the stability and performance of down-flow anaerobic fixed bed reactors treating piggery wastewater
(Taylor & Francis, 2006) Sánchez, E; Borja, R; Travieso, L; Martín, A; Colmenarejo, M; Nikolaeva, S.
The influence of the most important variables on the stability and performance of down-flow anaerobic fixed bed reactors treating piggery wastewater after primary sedimentation was evaluated at HRT in the range of 1-6 d and influent substrate concentration in the range of 2 to 12 g TCOD 1-(1). The effect of HRT was more pronounced compared to that of influent strength. An increase in the HRT increased the process stability and process performance at different influent strengths. TCOD, SCOD, BOD5, TSS, organic nitrogen (N) and Orthophosphate (P) removals increased with the HRT, independently of the initial substrate concentration (S-0). The increase in S-0 brought about an increase in the attached biomass concentration (X) at the end of the experiment. Two empirical models based on the individual effect of HRT, X and S-0 were evaluated and found to be adequate to describe the influence of these variables on the process performance. The first model took all the above-mentioned variables into consideration while the second model was simplified and based on the use of HRT as the only independent variable. The results obtained by using both models were found to be similar. This demonstrated that independently of the characteristics of the operation, the behaviour and performance of the reactors were comparable. The methane yield coefficient was found to be 0.3371 methane g(-1) TCOD removed.
Análisis de la población de condrictios (Vertebrata: Chondrichthyes) de aguas demersales y profundas del Caribe centroamericano, a partir de faenas de prospección pesquera con redes de arrastre
(Universidad Nacional (Costa Rica), 2014-12) BENAVIDES, ROSARIO; Brenes Rodríguez, Carlos L.; Márquez-Artavia, Amaru
Se describen la abundancia, riqueza, diversidad y distribución de las especies de condrictios de profundidad, capturadas en campaña de prospección pesquera del B/O Miguel Oliver en la plataforma y el talud continental de la costa Caribe de Centroamérica, entre el 3 de enero del 2011 y el 3 de febrero del 2011. Se utilizó una red tipo Lofoten para realizar arrastres de fondo de 30 minutos de duración cada uno, en 96 puntos de muestreo de los 25 transectos equidistantes. Se capturaron 28 especies, pertenecientes a 6 órdenes y 11 familias. Se describen 8 especies de rayas, 5 de quimeras y 15 de tiburones. La familia Squalidae mostró la mayor abundancia (n = 184), mayor riqueza (7 especies) y biomasa (222.6 kg, 58%), donde la especie dominante fue S. cubensis representada por un 37% en las capturas. El valor más alto del índice de diversidad de Shannon se obtuvo frente a las costas de Nicaragua (2.051). La distribución de las especies por temperatura y profundidad las ubica entre los 4 y 16ºC y entre los 20 y 1 000 m, respectivamente. Se reporta por primera vez en esta área la presencia de ocho especies: H. mirabilis, R. atlantica, D. profundorum, C. tesselatus, E. gracilispinis, E. carteri, G. springeri y H. perlo.
Análisis hidrográfico e ictiológico de las capturas realizadas con una red de trampa fija en la Laguna de Gandoca, Limón, Costa Rica
(Universidad Nacional (Costa Rica), 2010-12) BENAVIDES, ROSARIO; Brenes Rodríguez, Carlos L.
Se realizó un estudio ictiológico de las capturas obtenidas con una red de trampa fija y un registro de las propiedades hidrológicas en la Laguna de Gandoca, Limón, entre abril del 2006 y julio del 2007. Se identificaron 13 especies pertenecientes a 10 familias. El 98% de las capturas estuvo conformado por cuatro especies de valor comercial: Centropomus pectinatus (77%), Eucinostomus gula (9%), Caranx latus (7%) y Stellifer colonensis (5%). C. pectinatus (róbalo) estuvo presente en todas las capturas. Para C. pectinatus, se determinó que la relación longitud total - peso se ajustó potencialmente a través de la ecuación Pt = 0.004Lt3.1848. La talla de primera madurez de los róbalos se determinó en 30 cm de longitud total. En el ciclo anual de las propiedades termohalinas superficiales, la temperatura máxima se registró en el mes de setiembre (32°C) y la mínima durante diciembre (25.5°C). La laguna exhibe sus mayores salinidades en octubre (21), mientras que las salinidades menores ocurrieron en julio y diciembre (1). Entre setiembre y noviembre, la influencia de la onda mareal se extendió hasta media laguna con salinidades de 20, mientras que en la parte más interna no excedió a 5. Los valores más altos de contenido de oxígeno se observaron entre setiembre y noviembre, cuando el aporte de agua dulce proveniente de las escorrentías es mínimo. Finalmente, las características espacio-temporales del campo salino tienen una influencia directa en la composición y distribución de la ictiofauna que habita en la laguna.
Aplicaciones del modelo de Barbaro et al. para el cálculo de la radiación solar global por medio de estimaciones de los componentes directos y difusos, en Limón y Puntarenas, Costa Rica, para el período 1970-1972
(Universidad Nacional (Costa Rica), 1987-01-01) Wright Gilmore, Jaime
El presente trabajo utiliza un modelo atmosférico propuesto por Barbaro et al., para el cómputo de la radiación solar global a través de las estimaciones de las componentes directa y difusa, en Limón y Puntarenas, Costa Rica para el período 1970-1972. Los resultados se presentan en forma de promedios mensuales y se comparan con los valores observados proporcionados por el Instituto Meteorológico de Costa Rica. El porcentaje de error no supera el ±8,5 por ciento. No es posible verificar el cómputo de las componentes directa y difusa, debido a que en Limón y Puntarenas no se cuenta con datos de radiación solar directa ni difusa. Para verificar su confiabilidad, se recomienda aplicar el modelo a otros lugares equipados con estaciones actinométricas en Costa Rica. Esto permitirá predecir la radiación solar en lugares que carecen de datos actinométricos.
Biocomposites of Low-Density Polyethylene PlusWood Flour or Flax Straw: Biodegradation Kinetics across Three Environments
(MDPI journals, 2021-06-29) Zykova, Anna; Pantyukhov, Petr; Mastalygina, Elena; Chaverri-Ramos, Christian; Nikolaeva, Svetlana; Saavedra-Arias, José; Popov, Anatoly; Wortman, Sam; Poletto, Matheus
The purpose of this study was to assess the potential for biocomposite films to biodegrade in diverse climatic environments. Biocomposite films based on polyethylene and 30 wt.% of two lignocellulosic fillers (wood flour or flax straw) of different size fractions were prepared and studied. The developed composite films were characterized by satisfactory mechanical properties that allows the use of these materials for various applications. The biodegradability was evaluated in soil across three environments: laboratory conditions, an open field in Russia, and an open field in Costa Rica. All the samples lost weight and tensile strength during biodegradation tests, which was associated with the physicochemical degradation of both the natural filler and the polymer matrix. The spectral density of the band at 1463 cm-1 related to CH2-groups in polyethylene chains decreased in the process of soil burial, which is evidence of polymer chain breakage with formation of CH3 end groups. The degradation rate of most biocomposites after 20 months of the soil assays was greatest in Costa Rica (20.8–30.9%), followed by laboratory conditions (16.0–23.3%), and lowest in Russia (13.2–22.0%). The biocomposites with flax straw were more prone to biodegradation than those with wood flour, which can be explained by the chemical composition of fillers and the shape of filler particles. As the size fraction of filler particles increased, the biodegradation rate increased. Large particles had higher bioavailability than small spherical ones, encapsulated by a polymer. The prepared biocomposites have potential as an ecofriendly replacement for traditional polyolefins, especially in warmer climates.
Cálculo espectral de la irradiación solar directa, difusa y global en Heredia, Costa Rica
(Universidad Nacional (Costa Rica), 2008) Wright, Jaime
Un modelo espectral en condiciones de cielos claros, el cual describe el flujo de irradiación solar, es verificado experimentalmente en Heredia, Costa Rica. Se presenta una descripción del modelo comparando sus resultados con mediciones experimentales. El modelo calcula los flujos espectrales de la irradiación solar global, directa y difusa incidente en una superficie horizontal. Los datos necesarios de entrada incluyen latitud, altitud, albedo superficial como características de una localidad, así como las características atmosféricas: turbiedad, vapor de agua precipitable, el contenido total de ozono y el grueso óptico de una materia particular. Los resultados evidencian valores satisfactorios.
Cálculo y mapeo de la radiación solar directa y difusa en Costa Rica
(Universidad Nacional (Costa Rica), 2008) Wright, Jaime
El conocimiento de la radiación solar directa y difusa es de importancia fundamental en la valoración del potencial energético de Costa Rica, por lo que este trabajo está enfocado en el cálculo y en el trazado de mapas de contornos de la radiación solar directa y difusa basados en sesenta y dos estaciones radiométricas esparcidas en todo el territorio nacional. En el trazado de estos contornos se utilizaron valores experimentales y predichos de la radiación directa y difusa. Adicionalmente, se comparan la radiación solar directa y difusa durante la época seca y la época lluviosa en las seis regiones climáticas del país: Valle Central, Pacífico Norte, Pacífico Central, Pacífico Sur, Zona Norte y Vertiente del Caribe. Los niveles medios diarios observados de radiación directa oscilan entre 6.1 y 10.1 MJ/m2, con valores más altos en las secciones norte de la Vertiente del Pacífico, al oeste del Valle Central y en las cimas de las montañas más altas. Los valores más bajos coinciden con la Zona Norte y la Vertiente del Caribe. Los valores más altos de radiación difusa coinciden con la Zona Norte y el Pacífico Sur. Se observa un incremento de la radiación solar directa hasta de un 40% en los meses de la época seca.
Características hidrográficas del sistema lagunar los micos-quemada en el Caribe hondureño
(Universidad Nacional (Costa Rica), 2009-12) Brenes Rodríguez, Carlos L.; BENAVIDES, ROSARIO; Ballestero, Daniel; Ballestero Sakson, Daniel
Auspiciado por el Proyecto PREPAC (Plan Regional de Pesca y Acuicultura Continental) se realizó un levantamiento hidrográfico en 27 estaciones en el sistema lagunar Los Micos-Quemada en el litoral Caribe de Honduras. Los muestreos mensuales se extendieron de octubre del 2005 a mayo del 2006 y se determinaron la temperatura, el pH, el oxígeno disuelto, la salinidad y la turbidez. La temperatura superficial osciló entre los 24.2 y 31.8°C, con variaciones temporales extremas del orden de los 7°C. Los valores más bajos se ubican al final y principio de año (octubre-febrero). La salinidad superficial presenta un marcado ciclo estacional, con valores superiores a 12 durante los meses secos en prácticamente todo el cuerpo de agua, mientras que en la época lluviosa (octubre a febrero) están alrededor de 6. Los valores de pH encontrados para el período de estudio se ubicaron entre los 7.8 y 8.7. Los valores más altos se localizan en la zona central del sistema lagunar y los más bajos en las zonas cercanas a las orillas. Los máximos valores de turbidez se observan en febrero y diciembre. La zona con aguas más claras se localiza en la región cercana a la Barra de Miami en el lado noroeste de la laguna. El oxígeno superficial varió entre 5.0 mg/L y 7.6 mg/L durante los meses de octubre a febrero. La variación temporal del oxígeno disuelto muestra que los máximos y mínimos para todo el período de estudio se localizaron en octubre y mayo, respectivamente.
Características termohalinas de las aguas costeras del Caribe sur de Costa Rica
(Universidad Nacional (Costa Rica), 2015-12) Brenes Rodríguez, Carlos L.; BENAVIDES, ROSARIO
En agosto y noviembre del año 2012, se realizaron dos campañas hidrográficas en la zona costera del Ca ribe sur de Costa Rica, entre el Puerto de Limón y la Laguna de Gandoca. Se utilizó un CTD (perfilador de conductividad, temperatura y profundidad) en 43 estaciones para determinar la temperatura, salinidad y clorofila-a. Se encontró que las variaciones espaciales y temporales de la temperatura superficial fueron pequeñas, y los valores se ubicaron entre 28.6°C y 30°C. Asimismo, el rango de salinidades superficiales estuvo entre 33.3 y 35.2 UPS, y la distribución espacial de las concentraciones de clorofila-a en las aguas superficiales presentó un valor promedio de 0.64 mg m-3, con un valor máximo de 1.1 mg m-3 y un mínimo de 0.19 mg m-3. El campo vertical de temperatura se caracterizó por mostrar una capa de mezcla cálida (T ~ 29°C) en ambos meses de muestreo, la cual se extendió hasta los 60 m de profundidad en noviembre y menos de 10 m de profundidad en agosto. En ambos meses de muestreo a partir de la estructura vertical de las isotermas, se encontró un movimiento ciclónico (desde la superficie y hasta los 15 m de profundidad) en la región frente a Cahuita, y un movimiento anticiclónico a partir de los 20 m de profundidad en agosto, y 40 m de profundidad en noviembre. Se identificaron las masas de agua presentes en la columna de agua hasta las profundidades muestreadas: ASC, 0-80 m y ASS,> 80 m.
Characteristic atmospheric states during mid‑summer droughts over Central America and Mexico
(Springer, 2020-05-10) Holbrook, Neil; Zhao, Zijie; Oliver, Eric; Ballestero, Daniel; Vargas-Hernández , José Mauro
Annual precipitation over Central America and large areas of Mexico is typically characterised by its bimodal distribution, with a precipitation minimum in July to August that occurs between two separate maxima from May to July and August to October. Several theories have been proposed to explain this phenomenon, which is often termed the mid-summer drought (MSD), but most fail to address the diferent characteristics associated with individual MSD events. Here, a regression-based approach is used to detect and quantify the annual and climatological MSD signature over Central America and Mexico. This approach has been evaluated and shown to be robust for various datasets with diferent spatial resolutions. It was found that in the southeast of the Mexico/Central America region, MSDs start earlier and end later than elsewhere, and are thus longer in duration. However, the coast of the Gulf of Mexico, Cuba, and large areas of Central America, exhibit climatologically stronger MSDs. Changes in precipitation, brought about by the interaction between reversals of the onshore/ofshore winds and orographic forcing associated with the steep mountainous terrain, have also been shown to be signifcant factors in the timing of MSD occurrences, ofering support for a combined theory of large-scale dynamics and regional forcing. Using self-organising maps (SOMs) as an analysis tool, it was found that MSD events over the domain display strong spatial variability. The MSDs over the domain also generate distinct signatures and may be forced by particular mechanisms. We found that El Niño-Southern Oscillation (ENSO) could be a potential classifer for the SOM identifed atmospheric states, based on the correspondence of MSD occurrences with ENSO phases
Cladocera (Crustacea, Branchiopoda) of a temporary shallow pond from northern Colombia
(Universidad Nacional Mayor de San Marcos, 2019) Fuentes Reinés, Juan M.; ESLAVA ELJAIEK, PEDRO; Elmoor-Loureiro, Lourdes
Eighteen species of cladocerans are recorded from a temporary pond in northern Colombia; 12 of these records are new for La Guajira Department: Diaphanosoma brevireme Sars, 1901, D. dentatum Herbst, 1968, Sarsilotona serricauda (Sars, 1901), Moina micrura micrura Kurz, 1874, M. reticulata Daday, 1905, Grimaldina freyi Neretina and Kotov, 2017, Kurzia polyspina Hudec, 2000, Leydigia cf striata Birabén, 1939, Ovalona cf glabra (Sars, 1905), Chydorus nitidulus (Sars, 1901), Dunhevedia crassa King, 1853 and Pseudosida sp.; this latter taxon could be an yet undescribed species. The cladoceran fauna from the surveyed area is represented mostly by widespread species and commonly found in the Neotropical regions, but local morphological data are scarce in the regional literature. Brief diagnostic descriptions of the species recorded for the Colombian cladoceran fauna are provided together with illustrations of taxonomically significant appendages, morphological remarks, notes on the variability of some species, and their distribution.
Coastal currents in the Eastern Gulf of Tehuantepec from coastal altimetry
(Advances in Space Research, 2018-06-02) Salazar- Ceciliano, Juan Pablo
we study the seasonal and interannual variability of the coastal currents along the eastern shelf of the Gulf of Tehuantepec. We use sea level from coastal altimetry distributed by the Centre de Topographie des Oceans et de l’Hydrosphe`re (Toulouse, France). Local validation using tide gauge and hydrographic data indicates that this coastal product measures well the seasonal and interannual scales along this tropical coastline. Long (12 years) time series of altimetry-derived currents, 39–57 km from the coast, reveal new details of the seasonal cycle: currents flow poleward from October to February and equatorward from April to August. Spectral analysis reveals that mesoscale processes are at least as energetic as the seasonal mean. The combination of both determines to a large extent the seasonal and interannual variability of the coastal currents.
Comparative Study Of Conventional And Sbci Cardboard Solar Ovens
(Elsevier, 1992) Nandwani, Shyam S.; Fernández Gómez, Otoniel
Two folding and light solar ovens designed and constructed by Solar Box Cookers International (SBCI), Sacramento, U.S.A., have been studied experimentally. Furthermore, their performance is com pared with standard two glass solar ovens designed by one of us (S.S.N.), in the climate of Costa Rica. According to our measurements, made with and without load, taken during 30 different days, both cardboard ovens are 15-25% less efficient than the conventional oven and, secondly, the improved SBCI oven is slightly better than the previous SBCI oven.
Connecting bioloy, optics and nanomechanical properties in micro-wasps
(Springer Nature, 2020-01-29) Mora Castro, Rebeca; Hernández-Jiménez, Marcela; Sáenz-Arce, Giovanni; Porras-Peñaranda, Juan; Hanson-Snortum, Paul; Avendaño Soto, Esteban Damian
Coloration in insects provides a fruitful opportunity for interdisciplinary research involving both physics and biology, and for a better understanding of the design principles of biological structures. In this research we used nanometric and micrometric analyses to investigate the morphological and mechanical properties of the black-orange-black (BOB) color pattern in scelionid wasps, which has never been studied. The primary objective of the present investigation was to explore the structural and mechanical differences in the mesoscutum of four species: Baryconus with an orange mesosoma (i.e. BOB pattern), all black Baryconus, Scelio with an orange mesosoma (i.e. BOB pattern), and all black Scelio. The most outstanding findings include the absence of multilayer structures that generate structural color, a pigment concentrated in the upper surface of the epicuticle, and surprising differences between the four species. Three of the four species showed an accordion-like structure in the furrow (notaulus), whereas the adjacent mesoscutum was different in each species. Moreover, the normalized color component spectra for blue, green and red colors of the black mesoscutum of each genus showed the same spectral dependence while the orange color manifested small changes in the dominant wavelength, resulting in slightly different orange tones.

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