Modelling of isoprene distribution and cycling in the ocean

Isoprene (C5H8) is the most widely emitted biogenic volatile organic carbon (BVOC). It is produced in the biosphere both on land and in the ocean, and in the atmosphere it acts as a precursor of secondary organic aerosols. Isoprene has an eminently biological origin in phytoplankton; but its agents, production and recycling mechanisms, including photochemistry, are very poorly known. There still are large discrepancies in the estimations of global oceanic emission of isoprene (0.1 - 11.6 Tg C yr-1). Despite lower marine emissions than terrestrial ones, they play a key role in cloud formation and brightness in remote regions of the oceans. Due to the unfeasibility of getting synoptic measurements of isoprene emissions over the global ocean, they need to be calculated with numerical models that use variables that can be measured using remote sensing data from satellites or generated through ecosystem models. To achieve the capacity to predict the distribution and emission of isoprene in the surface ocean in time and space, in this thesis computational tools for the statistical treatment of data and for the diagnosis/prognosis were used. Thus, different approaches to predict and study isoprene in surface waters, including statistical modeling, biogeochemical-ecological modeling, and remote sensing retrieval were tested. Regarding the SO, isoprene concentration levels are driven by phytoplankton abundance over environmental or physical descriptors. Simple statistical models based on chlorophyll-a were developed showing different slopes and intercepts above and below a sea surface temperature threshold of 3.4ºC. The strong relationship between isoprene and photoprotective pigments brought new evidence to the potential role of marine isoprene as a photoprotective response in phytoplankton. Isoprene concentration levels were retrieved for SO waters using remote sensing algorithm based on chlorophyll-a and sea surface temperature products from MODIS-Aqua. The highest values of isoprene concentration and emissions peak in summer season, in coastal areas of Antarctica, in blooming areas close to islands, and around latitudes of 40ºS. The results suggested a total emission value of 0.063 Tg C yr-1, which supports the range of previous bottom-up estimates. We estimated new values of isoprene production and degradation rates from Lagrangian experiments during the PEGASO cruise. These rates together with others previously published in the literature and estimated in laboratory conditions, were implemented on the ROMS-BEC model, a regional ecological model for the SO which includes 3 Phytoplankton Functional Groups (PFT's): diatoms, coccolitophores and a group of small mixed phytoplankton. Diatoms dominated the isoprene production in SO waters and a value of total emission of isoprene of 0.071 Tg C yr-1 was calculated, agreeing with the values from remote sensing retrieval of isoprene concentration and bottom-up estimates. As to the global ocean, isoprene production rates were implemented in DARWNIN model, which includes 35 PFT's that are grouped in 6 groups: diatoms, coccolitophores, mixotrophic dinoflagellates, prokaryotes, diazotrophs, and pico-eukaryotes. According to the model outputs, diatoms were the most important PFT in terms of isoprene production at the global scale, being specially relevant in surface waters of the SO. Finally, the turnover of isoprene in the surface ocean was studied from incubation experiments performed in different oceanic regions. Production of isoprene normalized to chlorophyll-a levels increased with temperature until 23ºC, and drastically decreased in warmer waters. Biological degradation rate constants were dependent on chlorophyll-a concentration and were generally similar or faster than ventilation rate constants, and much faster than vertical mixing. Overall, the results suggest that isoprene cycling in the surface ocean is faster than previously thought, with turnover times in the range 1-16 days.El isopreno (C5H8) es el carbono orgánico volátil biogénico (BVOC) más ampliamente emitido. Se produce en la biosfera tanto en tierra como en el océano, y en la atmósfera actúa como precursor de aerosoles orgánicos secundarios. El isopreno tiene un origen eminentemente biológico en el fitoplancton; pero sus agentes, mecanismos de producción y reciclado, incluida la fotoquímica, son muy poco conocidos. Todavía hay grandes discrepancias en las estimaciones de la emisión oceánica global de isopreno (0.1 - 11.6 Tg C año-1). A pesar de que las emisiones marinas son más bajas que las terrestres, juegan un papel clave en la formación y brillo de las nubes en regiones remotas de los océanos. Debido a la inviabilidad de obtener mediciones sinópticas de las emisiones de isopreno sobre el océano global, deben calcularse con modelos numéricos que utilicen variables que se puedan medir utilizando datos de detección remota de satélites o generados a través de modelos de ecosistemas. Para poder predecir la distribución y emisión de isopreno en el océano superficial en el tiempo y el espacio, en esta tesis se utilizaron herramientas computacionales para el tratamiento estadístico de datos y para el diagnóstico/pronóstico. Por lo tanto, se probaron diferentes enfoques para predecir y estudiar el isopreno en aguas superficiales, incluidos el modelado estadístico, el modelado biogeoquímico-ecológico y la detección remota. Con respecto al Océano Antártico (OA), los niveles de concentración de isopreno son controlados por la abundancia de fitoplancton sobre los descriptores ambientales o físicos. Se desarrollaron modelos estadísticos simples basados en clorofila-a que muestran diferentes pendientes e intersecciones por encima y por debajo de un umbral de temperatura de la superficie del mar de 3.4ºC. La fuerte relación entre el isopreno y los pigmentos fotoprotectores aportó nuevas pruebas del papel potencial del isopreno marino como respuesta fotoprotectora en el fitoplancton. Los niveles de concentración de isopreno se calcularon para aguas OA utilizando un nuevo algoritmo de detección remota basado en productos de clorofila-a y temperatura de la superficie del mar de MODIS-Aqua. Los valores de concentración de isopreno y emisiones alcanzan su punto máximo en la temporada de verano, en las zonas costeras de la Antártida, en las zonas productivas cercanas a las islas y alrededor de los 40ºS. Los resultados sugirieron un valor de emisión total de 0.063 Tg C año-1, que respalda el rango de estimaciones anteriores del tipo "bottom-up". Estimamos nuevos valores de producción de isopreno y tasas de degradación a partir de experimentos lagrangianos durante la campaña PEGASO. Estas tasas, se implementaron en el modelo ROMS-BEC, un modelo ecológico regional para el OA. Las diatomeas dominaron la producción de isopreno en aguas OA y se calculó un valor de emisión total de isopreno de 0.071 Tg C año-1, que se encuentra en el rango de los valores estimados mediante detección remota de la concentración de isopreno. En cuanto al océano global, las tasas de producción de isopreno se implementaron en el modelo DARWN, que incluye 35 PFT que se agrupan en 6 grupos. Según los resultados, las diatomeas fueron el PFT más importante en términos de producción de isopreno a escala mundialFinalmente, se estudió el recambio de isopreno en la superficie del océano a partir de experimentos de incubación realizados en diferentes regiones oceánicas. La producción de isopreno normalizado a clorofila-a aumentó con la temperatura hasta 23ºC y dismunye drásticamente en aguas más cálidas. Las constantes de la tasa de degradación biológica dependían de la concentración de clorofila-a y generalmente eran similares o más rápidas que las constantes de la tasa de ventilación, y mucho más rápidas que la mezcla vertical. Los resultados sugieren que el reciclado del isopreno en la superficie del océan

Modelling of isoprene distribution and cycling in the ocean

Isoprene (C5H8) is the most widely emitted biogenic volatile organic carbon (BVOC). It is produced in the biosphere both on land and in the ocean, and in the atmosphere it acts as a precursor of secondary organic aerosols. Isoprene has an eminently biological origin in phytoplankton; but its agents, production and recycling mechanisms, including photochemistry, are very poorly known. There still are large discrepancies in the estimations of global oceanic emission of isoprene (0.1 - 11.6 Tg C yr-1). Despite lower marine emissions than terrestrial ones, they play a key role in cloud formation and brightness in remote regions of the oceans. Due to the unfeasibility of getting synoptic measurements of isoprene emissions over the global ocean, they need to be calculated with numerical models that use variables that can be measured using remote sensing data from satellites or generated through ecosystem models. To achieve the capacity to predict the distribution and emission of isoprene in the surface ocean in time and space, in this thesis computational tools for the statistical treatment of data and for the diagnosis/prognosis were used. Thus, different approaches to predict and study isoprene in surface waters, including statistical modeling, biogeochemical-ecological modeling, and remote sensing retrieval were tested. Regarding the SO, isoprene concentration levels are driven by phytoplankton abundance over environmental or physical descriptors. Simple statistical models based on chlorophyll-a were developed showing different slopes and intercepts above and below a sea surface temperature threshold of 3.4ºC. The strong relationship between isoprene and photoprotective pigments brought new evidence to the potential role of marine isoprene as a photoprotective response in phytoplankton. Isoprene concentration levels were retrieved for SO waters using remote sensing algorithm based on chlorophyll-a and sea surface temperature products from MODIS-Aqua. The highest values of isoprene concentration and emissions peak in summer season, in coastal areas of Antarctica, in blooming areas close to islands, and around latitudes of 40ºS. The results suggested a total emission value of 0.063 Tg C yr-1, which supports the range of previous bottom-up estimates. We estimated new values of isoprene production and degradation rates from Lagrangian experiments during the PEGASO cruise. These rates together with others previously published in the literature and estimated in laboratory conditions, were implemented on the ROMS-BEC model, a regional ecological model for the SO which includes 3 Phytoplankton Functional Groups (PFT's): diatoms, coccolitophores and a group of small mixed phytoplankton. Diatoms dominated the isoprene production in SO waters and a value of total emission of isoprene of 0.071 Tg C yr-1 was calculated, agreeing with the values from remote sensing retrieval of isoprene concentration and bottom-up estimates. As to the global ocean, isoprene production rates were implemented in DARWNIN model, which includes 35 PFT's that are grouped in 6 groups: diatoms, coccolitophores, mixotrophic dinoflagellates, prokaryotes, diazotrophs, and pico-eukaryotes. According to the model outputs, diatoms were the most important PFT in terms of isoprene production at the global scale, being specially relevant in surface waters of the SO. Finally, the turnover of isoprene in the surface ocean was studied from incubation experiments performed in different oceanic regions. Production of isoprene normalized to chlorophyll-a levels increased with temperature until 23ºC, and drastically decreased in warmer waters. Biological degradation rate constants were dependent on chlorophyll-a concentration and were generally similar or faster than ventilation rate constants, and much faster than vertical mixing. Overall, the results suggest that isoprene cycling in the surface ocean is faster than previously thought, with turnover times in the range 1-16 days.El isopreno (C5H8) es el carbono orgánico volátil biogénico (BVOC) más ampliamente emitido. Se produce en la biosfera tanto en tierra como en el océano, y en la atmósfera actúa como precursor de aerosoles orgánicos secundarios. El isopreno tiene un origen eminentemente biológico en el fitoplancton; pero sus agentes, mecanismos de producción y reciclado, incluida la fotoquímica, son muy poco conocidos. Todavía hay grandes discrepancias en las estimaciones de la emisión oceánica global de isopreno (0.1 - 11.6 Tg C año-1). A pesar de que las emisiones marinas son más bajas que las terrestres, juegan un papel clave en la formación y brillo de las nubes en regiones remotas de los océanos. Debido a la inviabilidad de obtener mediciones sinópticas de las emisiones de isopreno sobre el océano global, deben calcularse con modelos numéricos que utilicen variables que se puedan medir utilizando datos de detección remota de satélites o generados a través de modelos de ecosistemas. Para poder predecir la distribución y emisión de isopreno en el océano superficial en el tiempo y el espacio, en esta tesis se utilizaron herramientas computacionales para el tratamiento estadístico de datos y para el diagnóstico/pronóstico. Por lo tanto, se probaron diferentes enfoques para predecir y estudiar el isopreno en aguas superficiales, incluidos el modelado estadístico, el modelado biogeoquímico-ecológico y la detección remota. Con respecto al Océano Antártico (OA), los niveles de concentración de isopreno son controlados por la abundancia de fitoplancton sobre los descriptores ambientales o físicos. Se desarrollaron modelos estadísticos simples basados en clorofila-a que muestran diferentes pendientes e intersecciones por encima y por debajo de un umbral de temperatura de la superficie del mar de 3.4ºC. La fuerte relación entre el isopreno y los pigmentos fotoprotectores aportó nuevas pruebas del papel potencial del isopreno marino como respuesta fotoprotectora en el fitoplancton. Los niveles de concentración de isopreno se calcularon para aguas OA utilizando un nuevo algoritmo de detección remota basado en productos de clorofila-a y temperatura de la superficie del mar de MODIS-Aqua. Los valores de concentración de isopreno y emisiones alcanzan su punto máximo en la temporada de verano, en las zonas costeras de la Antártida, en las zonas productivas cercanas a las islas y alrededor de los 40ºS. Los resultados sugirieron un valor de emisión total de 0.063 Tg C año-1, que respalda el rango de estimaciones anteriores del tipo "bottom-up". Estimamos nuevos valores de producción de isopreno y tasas de degradación a partir de experimentos lagrangianos durante la campaña PEGASO. Estas tasas, se implementaron en el modelo ROMS-BEC, un modelo ecológico regional para el OA. Las diatomeas dominaron la producción de isopreno en aguas OA y se calculó un valor de emisión total de isopreno de 0.071 Tg C año-1, que se encuentra en el rango de los valores estimados mediante detección remota de la concentración de isopreno. En cuanto al océano global, las tasas de producción de isopreno se implementaron en el modelo DARWN, que incluye 35 PFT que se agrupan en 6 grupos. Según los resultados, las diatomeas fueron el PFT más importante en términos de producción de isopreno a escala mundialFinalmente, se estudió el recambio de isopreno en la superficie del océano a partir de experimentos de incubación realizados en diferentes regiones oceánicas. La producción de isopreno normalizado a clorofila-a aumentó con la temperatura hasta 23ºC y dismunye drásticamente en aguas más cálidas. Las constantes de la tasa de degradación biológica dependían de la concentración de clorofila-a y generalmente eran similares o más rápidas que las constantes de la tasa de ventilación, y mucho más rápidas que la mezcla vertical. Los resultados sugieren que el reciclado del isopreno en la superficie del océan

Substantial loss of isoprene in the surface ocean due to chemical and biological consumption

Isoprene contributes to the formation of ozone and secondary organic aerosol in the atmosphere, and thus influences cloud albedo and climate. Isoprene is ubiquitous in the surface open ocean where it is produced by phytoplankton, however emissions from the global ocean are poorly constrained, in part due to a lack of knowledge of oceanic sink or degradation terms. Here, we present analyses of ship-based seawater incubation experiments with samples from the Mediterranean, Atlantic, tropical Pacific and circum-Antarctic and Subantarctic oceans to determine chemical and biological isoprene consumption in the surface ocean. We find the total isoprene loss to be comprised of a constant chemical loss rate of 0.05¿±¿0.01 d-1 and a biological consumption rate that varied between 0 and 0.59 d-1 (median 0.03 d-1) and was correlated with chlorophyll-a concentration. We suggest that isoprene consumption rates in the surface ocean are of similar magnitude or greater than ventilation rates to the atmosphere, especially in chlorophyll-a rich waters.Postprint (published version

Analytical, experimental, and Monte Carlo system response matrix for pinhole SPECT reconstruction

Purpose: To assess the performance of two approaches to the system response matrix (SRM) calculation in pinhole single photon emission computed tomography (SPECT) reconstruction. Methods: Evaluation was performed using experimental data from a low magnification pinhole SPECT system that consisted of a rotating flat detector with a monolithic scintillator crystal. The SRM was computed following two approaches, which were based on Monte Carlo simulations (MC-SRM) and analytical techniques in combination with an experimental characterization (AE-SRM). The spatial response of the system, obtained by using the two approaches, was compared with experimental data. The effect of the MC-SRM and AE-SRM approaches on the reconstructed image was assessed in terms of image contrast, signal-to-noise ratio, image quality, and spatial resolution. To this end, acquisitions were carried out using a hot cylinder phantom (consisting of five fillable rods with diameters of 5, 4, 3, 2, and 1 mm and a uniform cylindrical chamber) and a custom-made Derenzo phantom, with center-to-center distances between adjacent rods of 1.5, 2.0, and 3.0 mm. Results: Good agreement was found for the spatial response of the system between measured data and results derived from MC-SRM and AE-SRM. Only minor differences for point sources at distances smaller than the radius of rotation and large incidence angles were found. Assessment of the effect on the reconstructed image showed a similar contrast for both approaches, with values higher than 0.9 for rod diameters greater than 1 mm and higher than 0.8 for rod diameter of 1 mm. The comparison in terms of image quality showed that all rods in the different sections of a custom-made Derenzo phantom could be distinguished. The spatial resolution (FWHM) was 0.7 mm at iteration 100 using both approaches. The SNR was lower for reconstructed images using MC-SRM than for those reconstructed using AE-SRM, indicating that AE-SRM deals better with the projection noise than MC-SRM. Conclusions: The authors' findings show that both approaches provide good solutions to the problem of calculating the SRM in pinhole SPECT reconstruction. The AE-SRM was faster to create and handle the projection noise better than MC-SRM. Nevertheless, the AE-SRM required a tedious experimental characterization of the intrinsic detector response. Creation of the MC-SRM required longer computation time and handled the projection noise worse than the AE-SRM.Nevertheless, the MC-SRM inherently incorporates extensive modeling of the system and therefore experimental characterization was not required

Analytical, experimental, and Monte Carlo system response matrix for pinhole SPECT reconstruction

PURPOSE: To assess the performance of two approaches to the system response matrix (SRM) calculation in pinhole single photon emission computed tomography (SPECT) reconstruction. METHODS: Evaluation was performed using experimental data from a low magnification pinhole SPECT system that consisted of a rotating flat detector with a monolithic scintillator crystal. The SRM was computed following two approaches, which were based on Monte Carlo simulations (MC-SRM) and analytical techniques in combination with an experimental characterization (AE-SRM). The spatial response of the system, obtained by using the two approaches, was compared with experimental data. The effect of the MC-SRM and AE-SRM approaches on the reconstructed image was assessed in terms of image contrast, signal-to-noise ratio, image quality, and spatial resolution. To this end, acquisitions were carried out using a hot cylinder phantom (consisting of five fillable rods with diameters of 5, 4, 3, 2, and 1 mm and a uniform cylindrical chamber) and a custom-made Derenzo phantom, with center-to-center distances between adjacent rods of 1.5, 2.0, and 3.0 mm. RESULTS: Good agreement was found for the spatial response of the system between measured data and results derived from MC-SRM and AE-SRM. Only minor differences for point sources at distances smaller than the radius of rotation and large incidence angles were found. Assessment of the effect on the reconstructed image showed a similar contrast for both approaches, with values higher than 0.9 for rod diameters greater than 1 mm and higher than 0.8 for rod diameter of 1 mm. The comparison in terms of image quality showed that all rods in the different sections of a custom-made Derenzo phantom could be distinguished. The spatial resolution (FWHM) was 0.7 mm at iteration 100 using both approaches. The SNR was lower for reconstructed images using MC-SRM than for those reconstructed using AE-SRM, indicating that AE-SRM deals better with the projection noise than MC-SRM. CONCLUSIONS: The authors' findings show that both approaches provide good solutions to the problem of calculating the SRM in pinhole SPECT reconstruction. The AE-SRM was faster to create and handle the projection noise better than MC-SRM. Nevertheless, the AE-SRM required a tedious experimental characterization of the intrinsic detector response. Creation of the MC-SRM required longer computation time and handled the projection noise worse than the AE-SRM.Nevertheless, the MC-SRM inherently incorporates extensive modeling of the system and therefore experimental characterization was not required

Hole selective contacts based on transition metal oxides for c-Ge thermophotovoltaic devices

© 2022 Elsevier. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/Thermophotovoltaics has become a very attractive solution for heat-to-electricity conversion due to its excellent conversion efficiencies. However, further research is needed to reduce the device cost which is typically based on III-V semiconductors. To tackle this limitation, crystalline germanium (c-Ge) has been proposed as an excellent substrate for low-cost devices. One of the key advances behind high system efficiencies is the excellent reflectance of the out-of-band photons at the rear surface of the photovoltaic device. These photons with lower energy than the absorber bandgap are reflected back to the thermal emitter reducing its thermal losses. In this work, we explore the performance of hole selective contacts based on evaporated transition metal oxides (MoOx, VOx, WOx) to be introduced at the rear surface of c-Ge devices. Regarding electrical properties, we characterize the selectivity of the contact by measuring effective surface recombination velocity (Seff) and contact resistivity (¿C). Best results are obtained with MoOx contacted by Ag/ITO with Seff = 588 cm/s and ¿C = 55.6 mO cm2 which can be improved by using gold as a metal contact leading to Seff = 156 cm/s and ¿C = 60.9 mO cm2. Regarding out-of-band reflectance, it is better for the case of Ag/ITO/MoOx contact with 87.5% compared to 78.9% for Au/MoOx when a 1473 K black body spectrum is used. Device simulations show potential system efficiencies in the range of 18–19% which are comparable to the best reported efficiencies using c-Ge thermophotovoltaic devices.This work has been supported by the Spanish government under projects PID2019-109215RB-C41 (SCALED), PID2020-116719RB-C41 (MATER ONE) and PID2020-115719RB-C21 (GETPV) funded by MCIN/ AEI/10.13039/501100011033. The authors would like to thank the master student Oscar Llados ´ and Guillem Ayats for their help in processing the samples, Dr. Alejandro Datas from Instituto de Energía Solar (IES) in Madrid for providing the c-Ge wafers and fruitful discussions.Peer ReviewedPostprint (published version

Optical Flow in a Smart Sensor Based on Hybrid Analog-Digital Architecture

The purpose of this study is to develop a motion sensor (delivering optical flow estimations) using a platform that includes the sensor itself, focal plane processing resources, and co-processing resources on a general purpose embedded processor. All this is implemented on a single device as a SoC (System-on-a-Chip). Optical flow is the 2-D projection into the camera plane of the 3-D motion information presented at the world scenario. This motion representation is widespread well-known and applied in the science community to solve a wide variety of problems. Most applications based on motion estimation require work in real-time; hence, this restriction must be taken into account. In this paper, we show an efficient approach to estimate the motion velocity vectors with an architecture based on a focal plane processor combined on-chip with a 32 bits NIOS II processor. Our approach relies on the simplification of the original optical flow model and its efficient implementation in a platform that combines an analog (focal-plane) and digital (NIOS II) processor. The system is fully functional and is organized in different stages where the early processing (focal plane) stage is mainly focus to pre-process the input image stream to reduce the computational cost in the post-processing (NIOS II) stage. We present the employed co-design techniques and analyze this novel architecture. We evaluate the system’s performance and accuracy with respect to the different proposed approaches described in the literature. We also discuss the advantages of the proposed approach as well as the degree of efficiency which can be obtained from the focal plane processing capabilities of the system. The final outcome is a low cost smart sensor for optical flow computation with real-time performance and reduced power consumption that can be used for very diverse application domains

Evaluación del efecto de la magnetoterapia, la electroterapia y los ejercicios del suelo pélvico como tratamiento rehabilitador en la incontinencia urinaria.

La incontinencia urinaria tiene elevada prevalencia, preferentemente en mujeres, afectando la vida personal y social de los enfermos. Evaluamos el impacto del tratamiento rehabilitador del suelo pélvico sobre síntomas y signos de incontinencia en 28 pacientes, 25 mujeres y 3 hombres con edades promedio de 53.9 y 66.6 años En las mujeres predominó la incontinencia asociada a otras patologías del suelo pélvico, seguida por la mixta y en los hombres la secundaria a prostatectomía. Evaluamos la incontinencia al inicio y evolutivamente mediante historia clínica, necesidad de uso de colectores, prueba decompresa y diario miccional. Aplicamosmagnetoterapia en región pélvica, electroterapia estimuladora de musculatura perineal y ejercicios para fortalecimiento muscular pélvico sola o combinada. Once pacientes abandonaron el tratamiento, 53% curaron, 29% tuvieron mejoría notable y 18% mantienen el tratamiento. Concluimos que la rehabilitación del suelo pélvico constituye una terapia útil y definitiva para curar o mejorar la incontinencia urinaria.  Palabras clave: Incontinencia urinaria, Tratamiento rehabilitador

Utilización de las Redes sociales en el aprendizaje colaborativo y transversal de la Farmacovigilancia Veterinaria

Sección Deptal. de Farmacología y Toxicología (Veterinaria)Fac. de VeterinariaFALSEsubmitte