Artículos (Física Aplicada II)

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129I in sediment cores from the Celtic Sea by AMS through a microwave digestion process
(Elsevier, 2022) Lérida Toro, Victoria; Abascal Ruíz, Unai; Villa Alfageme, María; Klar, Jessica K.; Hicks, Natalie; López Gutiérrez, José María; Universidad de Sevilla. Departamento de Física Aplicada II; Universidad de Sevilla. Departamento de Física Aplicada I
Radiochemical methods before measurement are indispensable to determine Iodine-129 by Accelerator Mass Spectrometry (AMS) in environmental samples. In particular, in sediments, iodine is associated with both inorganic and organic matter, and it presents in several chemical forms. Therefore, the radiochemical procedure must be designed to extract all the different iodine species from the matrix, whilst being as robust and time effective as possible. In this work, different microwave digestion methods, together with the processing of the iodine species to be measured by AMS, were tested and their performances are presented here. Two sediment cores, one with muddy sediment (core A) and one with permeable sandy sediment (core I), collected in the Celtic Sea, were used and the results were evaluated to determine an optimized iodine extraction. The method consisted of a microwave digestion with concentrated nitric acid followed by a double liquid–liquid extraction and the final precipitation of silver iodide (AgI), required to measure iodine by AMS. Back extraction of iodine in a reducing solution during purification was carried out with hydrazine (NH2-NH2). Subsequent additional steps were added to optimize all iodine species extraction. First, hydrochloric hydroxylamine (NH2OH⋅HCl) and so dium bisulfite (Na2S2O5) were used to homogenize all iodine species before extraction through a redox process. Second, sodium hypochlorite (NaOCl) was added to remove any final organic matter after digestion. The final method incorporated sodium hydroxide (NaOH) combined with NaOCl to facilitate reduction of iodine in so lution and enhance the NaOCl effect. The different methods were validated against an internal standard and the last method was chosen, as it showed the most reproducible and accurate results. As practical application, Iodine129 concentration from both cores were compared, showing concentrations between 0.19 × 1012 at/kg and 7.16 × 1012 at/kg for core A and between 0.28 × 1012 at/kg and 2.40 × 1012 at/kg for core I. Despite the 129I diffusion detected in the deeper layers, depth profiles accurately reproduced Sellafield discharges, which is the nuclear fuel reprocessing plant closest to the cores.
Comparison and validation of methods for the determination of 90Sr by Cerenkov counting in biological and sediment samples, including green chemistry metrics
(Springer, 2019) Rivera Silva, Jorge; Hurtado Bermúdez, Santiago José; Villa Alfageme, María; Manjón Collado, Guillermo; Universidad de Sevilla. Departamento de Física Aplicada II
In this work, a comparative study of two popular radiochemical procedures for 90Sr determination in biological and sediment samples via Cerenkov counting was performed. Comparative tests were carried out with a Liquid Scintillation Counter (LSC) and several key factors related to green analytical chemistry were considered. Chemical yields, time of analysis, cost per sample, hazardous reagents used (H-factor), wastes generated (E-factor) and energy consumed (Q-factor) were calculated. The separation methods are based on two contrasted extraction mechanisms: chromatographic extraction (using Sr resin, a crown-ether diluted in octanol) and liquid–liquid solvent extraction (using HDEHP, an organophosphorus compound), where the chromatographic extraction method was optimized. The developed analytical procedure based on HDEHP was cheaper and faster than the analytical procedure based on Sr resin, according to the green chemistry. On the other hand, the Sr resin method provided a minimum detectable activity (MDA) of 1.1 Bq kg−1, lower than 1.5 Bq kg−1 corresponding to HDEHP method, due to the higher capacity of sample that can be loaded into the resin. The accuracy and reproducibility of both methods was confrmed in the analysis of certifed reference materials provided by the International Atomic Energy Agency (IAEA)
Correlation of phytoplankton satellite observations and 210Po radiological doses in molluscs
(Elsevier, 2021) Hurtado Bermúdez, Santiago José; Expósito Gálvez, Juan Carlos; Villa Alfageme, María; Universidad de Sevilla. Departamento de Física Aplicada II
Po is strongly accumulated by marine organisms, thus the contribution of 210Po from sea-food is crucial to evaluate population radiological doses by food ingestion. Consequently, 210Po constitutes the primary source of natural radiation to radiological doses in humans through the consumption of food and contributes significantly to the total radiation dose. Most of the national regulations on radiological doses include coastal measurements of 210Po, for this reason fast, robust techniques to evaluate 210Po concentrations and doses in molluscs are required. Data of salinity, temperature, suspended particulate matter (SPM), chlorophyll-a, and phytoplankton concentration in the Gibraltar Strait coast, in the confluence of the Mediterranean Sean and the Atlantic Ocean, during the period of May 2014–June 2015 were analyzed together with 210Po, 40K, 210Pb and 234Th activity concentration in different types of bivalve mollusks in the same time-period. The physicochemical parameters were evaluated using the Copernicus Marine Environment Monitoring Service (CMEMS) products based on satellite observations. This tool provides biogeochemical data of the ocean on a global and regional scale. A multivariate statistical analysis, including contrasted natural radioactivity contents, allowed the discrimination of bivalve mollusks from Atlantic and Mediterranean coasts. A cluster analysis determined which physicochemical parameters influence the radioisotopes concentrations in molluscs. A highly significant negative correlation 210Po concentration in molluscs and phytoplankton concentration suggested that phytoplankton concentration in the water column is a determinant factor to regulate 210Po concentration in those animals. In this work it is presented a first approach to use this relationship to estimate radiological doses by mollusks ingestion from phytoplankton concentrations. These results introduce a useful tool to calculate the radiological doses in seafood from chlorophyll satellite image (e.g. using CMEMS tools).
Distribution of 1 236U in the U.S. GEOTRACES Eastern Pacific Zonal Transect and its use as a 2 water mass tracer
(Elsevier, 2019) Villa Alfageme, María; Chamizo Calvo, Elena; Kenna, Timothy C.; López Lora, Mercedes; Casacuberta, Nuria; Chang, Clara H.; Masqué, Pere; Christi, Marcus; Universidad de Sevilla. Departamento de Física Aplicada II; Universidad de Sevilla. Departamento de Física Aplicada I
We report dissolved concentrations of the long-lived radioisotope 236U measured in the water column along the 2013 US GEOTRACES Eastern Pacific Zonal Transect (GP16). This transect followed a 10–15°S line from Manta, Ecuador, to Papeete, Haiti, French Polynesia, crossing the southern East Pacific Rise, intercepting one of the largest hydrothermal plumes as well as a productivity gradient, which includes the upwelling zone and associated low oxygen waters offshore from Peru and the oligotrophic sub-tropical gyre. Accelerator Mass Spectrometry was used to measure dissolved seawater 236U concentrations as low as 1 × 103 atom kg−1, which are among the lowest levels reported to date. Differences in upper water column 236U distributions from east to west are a result of variable contributions from different surface and intermediate waters encountered along the transect. The distribution of 236U, both in depth and geographically, provides complementary information to that obtained from Δ14C and helium isotopes, demonstrating that 236U concentrations are diagnostic in the identification of and contributions from the different deep and bottom water masses encountered along the EPZT (Jenkins et al., 2017). For example, we observe minimum 236U concentrations along the EPZT between 2000 and 3000 m that are consistent with contributions attributed to Pacific Deep Water. We also observe increases in 236U below 3000 m at the eastern and western termini of the EPZT. This is consistent with contributions associated with Antarctic Bottom Water and Lower Circumpolar Deep Water. Our results indicate that 236U may be used in conjunction with Δ14C and 3He isotopes as an additional tool with which to identify and resolve contributions from different water masses in the Pacific Ocean.
Inefficient transfer of diatoms through the subpolar Southern Ocean twilight zone
(Springer Nature, 2024) Williams, Jimmy R.; Giering, Sarah; Baker, Christopher A.; Pabortsava, Katsiaryna; Briggs, ‪Nathan; East, Holly; Espinola, Benoit; Blackbird, Sabena; Le Moigne, Frédéric; Villa Alfageme, María; Poulton, Alex J.; Carvalho, Filipa; Pebody, Corinne; Saw, Kevin; Moore, C. Mark; Henson, Stephanie A.; Sanders, Richard; Martin, Adrian P.; Universidad de Sevilla. Departamento de Física Aplicada II
The Southern Ocean, a region highly vulnerable to climate change, plays a vital role in regulating global nutrient cycles and atmospheric CO2 via the biological carbon pump. Diatoms, photosynthetically active plankton with dense opal skeletons, are key to this process as their exoskeletons are thought to enhance the transfer of particulate organic carbon to depth, positioning them as major vectors of carbon storage. Yet conficting observations obscure the mechanistic link between diatoms, opal and particulate organic carbon fuxes, especially in the twilight zone where greatest fux losses occur. Here we present direct springtime fux measurements from diferent sectors of the subpolar Southern Ocean, demonstrating that across large areas of the subpolar twilight zone, carbon is efciently transferred to depth, albeit not by diatoms. Rather, opal is retained near the surface ocean, indicating that processes such as diatom buoyancy regulation and grazer repackaging can negate ballast efects of diatoms’ skeletons. Our results highlight that the presence of diatoms in surface waters of the Southern Ocean’s largest biome does not guarantee their importance as vectors for efcient carbon transfer through the subpolar twilight zone. Climate change-driven shifts in phytoplankton community composition may afect biologically sequestered carbon pools less than currently predicted.
Seasonal variations of sinking velocities in Austral diatom blooms: lessons learned from COMICS
(Elsevier, 2024) Villa Alfageme, María; Briggs, ‪Nathan; Ceballos Romero, Elena; Soto Borrero, Feliciano Carlos de; Manno, Clara; Giering, Sarah; Universidad de Sevilla. Departamento de Física Aplicada II
The sinking velocity (SV) of organic particles is a critical driver of carbon transport to the deep sea. Accurate determination of marine particle SV and their influencing factors is therefore a key to better understanding of biological carbon storage in the ocean. We used two different approaches to estimate average SVs of particles during a Southern Ocean spring bloom (North of South Georgia): optical backscatter sensors on gliders (“large”, >50 μm diameter), and radioactive pairs ( 234Th–238U and 210Po-210Pb). Our results were complemented with time-of flight estimations of bulk SVs from deep sediment traps deployed at 1950 m. Bulk SVs increased consistently with depth from 15 ± 1 m d− 1 at 10 m to 50 ± 10 m d− 1 at the depth of export (Zp = 95 m) and from 96 ± 35 m d− 1 at 150 m to 119 ± m d− 1 at 450 m. Only the fastest particles, mainly comprised by faecal pellets (FPs) and diatom aggregates, survived remineralization and dominated carbon fluxes at deep depth. The SV variability at the base of the Euphotic Zone was studied in relation to the stage of the bloom by analysing three different moments of the spring diatom bloom in the region during the years 2012, 2013 and 2017. The export efficiency (ExpEff), defined as the ratio POC flux exported below the Euphotic Zone to the satellite derived surface NPP, was also evaluated. It was found from the temporal series that ExpEff and SV vary throughout the diatom bloom as the community structure progresses. A good correlation between both variables was observed (ExpEff = (0.023 ± 0.006) SV, r = 0.82, p = 0.04). Showing that the variability in how efficiently the carbon flux is exported out of the Euphotic Zone can be explained by the SV at which the particles sink. Further investigations are required to analyse if this is a specific model of the functioning of the BCP during the diatom bloom in North South Georgia or if it can be extrapolated to other scenarios.
Sequestration efficiency in the iron-limited North Atlantic: implications for iron supply mode to fertilized blooms
(American Geophysical Union, 2014) Le Moigne, Frederic; Moore, C. Mark; Sanders, Richard; Villa Alfageme, María; Steigenberger, Sebastian; Achterberg, Eric P.; Universidad de Sevilla. Departamento de Física Aplicada II
Estimates of the amount of carbon sequestered in the ocean interior per unit iron (Fe) supplied, as quantified by the sequestration efficiency (Ceffx), vary widely. Such variability in Ceffx has frequently been attributed to estimate uncertainty rather than intrinsic variability. Here we derive new estimates of Ceffx for the subpolar North Atlantic, where Fe stressed conditions have recently been demonstrated. Derived values of Ceffx from across the region, including areas subject to atypical external Fe fertilization events during the year of sample collection (2010), ranged from 17 to 19 kmol C (mol Fe 1). Comparing these estimates with values from other systems, considered in the context of variable bloom durations in the different oceanographic settings, we suggest that apparent variability in Ceffx may be related to the mode of Fe delivery.
Polypropylene as an absorbent layer for acoustic ceilings: Sound absorption and life cycle assessment
(Elsevier, 2024-11-01) Galindo del Pozo, Miguel; Alberdi Causse, Enedina; Sánchez Burgos, Marco Antonio; Nieves Pavón, Francisco José; Flores-Colen, Inês; Universidad de Sevilla. Departamento de Física Aplicada II; Universidad de Sevilla. Departamento de Construcciones Arquitectónicas I (ETSA); Ministerio de Ciencia e Innovación (MICIN). España; Agencia Estatal de Investigación. España; Fundação para a Ciência e a Tecnologia. Portugal; Universidad de Sevilla. TEP130: Arquitectura, Patrimonio y Sostenibilidad: Acústica, Iluminación, Óptica y Energía; Universidad de Sevilla. TEP205: Análisis y Evaluación de Sistemas Constructivos y Estructurales en la Arquitectura
The substantial volume of polypropylene fabric waste generated because of its use in protective elements in hospital environments calls for the exploration of environmentally friendly solutions. This study characterises the acoustic absorption coefficient of surgical mask waste (polypropylene) to be used as absorbent layers in acoustic ceilings. Additionally, a life cycle assessment (LCA) has been carried out. Although values of absorption coefficients for polypropylene have been published, none include life cycle studies. This research is in keeping with the principles of circular economy, contributing to waste reduction while also exploring innovative applications for recycled materials. The starting point of this study is the replacement of the most common material layer on the market, mineral wool, with a polypropylene layer that has the same or better acoustic performance based on single number absorption indexes and ratings following international standards for the calculation of sound absorption coefficients and life cycles. Various waste processing methods and different densities and thicknesses have been evaluated. The results show that recycled polypropylene material exhibits suitable behaviour as an acoustic absorbent layer, particularly in acoustic ceilings. The LCA considered transport, shredding, washing, disinfection, and drying and confirms the eco-efficiency of this absorbent layer.
A benchmark for Monte Carlo simulation in gamma-ray spectrometry
(Elsevier, 2019-12) Lépy, M. C.; Thiam, C.; Anagnostakis, M.; Galea, R.; Gurau, D.; Hurtado Bermúdez, Santiago José; Karfopoulos, K.; Liang, J.; Liu, H.; Luca, A.; Mitsios, I.; Potiriadis, C.; Savva, M. I.; Thanh, T. T.; Thomas, V.; Townson, R. W.; Vasilopoulou, T.; Zhang, M.; Universidad de Sevilla. Departamento de Física Aplicada II; Universidad de Sevilla. RNM138: Física Nuclear Aplicada
Monte Carlo (MC) simulation is widely used in gamma-ray spectrometry, however, its implementation is not always easy and can provide erroneous results. The present action provides a benchmark for several MC software for selected cases. The examples are based on simple geometries, two types of germanium detectors and four kinds of sources, to mimic eight typical measurement conditions. The action outputs (input files and efficiency calculation results, including practical recommendations for new users) are made available on a dedicated webpage.
Consistency test of coincidence-summing calculation methods for extended sources
(Elsevier, 2020-01) Sima, O.; De Vismes Ott, A.; Dias, M. S.; Dryak, P.; Ferreux, L.; Gurau, D.; Hurtado Bermúdez, Santiago José; Jodlowski, P.; Karfopoulos, K.; Koskinas, M. F.; Laubenstein, M.; Lee, Y. K.; Lépy, M. C.; Luca, A.; Menezes, M. O.; Moreira, D. S.; Nikolič, J.; Peyres, V.; Saganowski, P.; Savva, M. I.; Semmler, R.; Solc, J.; Thanh, T. T.; Tyminska, K.; Tyminski, Z.; Vidmar, T.; Vukanac, I.; Yucel, H.; Universidad de Sevilla. Departamento de Física Aplicada II; Universidad de Sevilla. RNM138: Física Nuclear Aplicada
An internal consistency test of the calculation of coincidence-summing correction factors FC for volume sources is presented. The test is based on exact equations relating the values of FC calculated for three ideal measurement configurations. The test is applied to a number of 33 sets of FC values sent by 21 teams. Most sets passed the test, but not the results obtained using the quasi-point source approximation; in the latter case the test qualitatively indicated the magnitude of the bias of FC.
Optimization of a new liquid scintillation spectrometer for the measurement of environmental levels of 3H in water samples
(Elsevier, 2024-07) García León, José Luis; García León, Manuel; Manjón Collado, Guillermo; Rivera Silva, Jorge; Universidad de Sevilla. Departamento de Física Aplicada II; Universidad de Sevilla. Departamento de Física Atómica, Molecular y Nuclear; Consejo de Seguridad Nuclear; Universidad de Sevilla. RNM138: Física Nuclear Aplicada
The activity concentration of 3H in water samples collected from places unaffected by nuclear activities or for human consumption can be very low. In these cases, determination procedures must achieve a Minimum Detectable Activity (MDA) low enough to ensure that 3H is accurately determined. In this paper, we present a method that uses a new Liquid Scintillation Spectrometer (LSC in what follows): the Quantulus GCT 6220. Furthermore, a new liquid scintillation cocktail, the ProSafe LT+, has been tested for 3H measurement, showing to be a good option for the determination of low levels of this radionuclide. The MDAs achieved are low enough to enable the measurement of very low levels of 3H in recent environmental water. The results obtained using a Quantulus GCT 6220 and Prosafe LT + are compared to those obtained with a Quantulus 1220 and Prosafe HC + as liquid scintillation cocktail.
Transfer of 129I to freshwater fish species within Fukushima and Chernobyl exclusion zones
(Elsevier, 2023) Teien, Hans Christian; Wada, Toshihiro; Kashparov, Valery; López Gutiérrez, José María; García-Tenorio García-Balmaseda, Rafael; Hinton, Thomas G.; Salbu, Brit; Universidad de Sevilla. Departamento de Física Aplicada II
Unique data is reported on the transfer of 129I iodine from freshwaters to fish as well as the internal distribution within fish from the Fukushima and Chernobyl exclusion zones (ChEZ). Samples of water, sediments and fish were collected in the contaminated ponds Inkyozaka and Suzuuchi, and in the less contaminated Abukuma river in Fukushima, as well as in the contaminated Glubokoye lake and in the less contaminated Starukha lake in ChEZ. In water, 129I was mainly present as low molecular mass (LMM) and negatively charged species, while a minor fraction was associated with colloidal fraction, most probably organic material in water. The sedimentwater 129I apparent distribution coefficients, Kd, ranged from 225 to 329 L/kg, equal that of stable iodine, but did not correlate with 129I/127I ratio or 129I/137Cs ratio as the environmental distribution of radioactive iodine was different from that of stable iodine and radioactive cesium. Concentration ratios (CR) of 129I in muscle of freshwater fish ranged from 85 to 544 across waterbodies with limited water exchange, similar in Fukushima and Chernobyl, but varied with respect to fish species. Thus, this is the first results on the transfer of 129I to freshwater fish, showing that the CR for freshwater fish is higher than CR reported for marine fish. Concentrations of 129I in fish muscle were, however, lower than in the intestinal content, indicating the influence of more contaminated dietary ingredients probably of terrestrial origin based due to δ13C signal on as well as of biodilution. The present results highlighted also that the radiation dose in fish was highly inhomogeneously distributed. Based on the present 129I/127I atomic ratio of 10− 5 in the most contaminated fish in the ponds in Fukushima and Glubokoye lake in Chernobyl, however, a radiation dose of 10 μSv/y would not pose any harm to the fish population.
Impact of vegetable oil type on the rheological and tribological behavior of Montmorillonite-based oleogels
(MDPI, 2022-08-13) Martín Alfonso, Manuel Antonio; Rubio Valle, José Fernando; Hinestroza, Juan P.; Martín Alfonso, José Enrique; Universidad de Sevilla. Departamento de Física Aplicada II; European Commission (EC). Fondo Europeo de Desarrollo Regional (FEDER); Junta de Andalucía
We formulated and characterized oleogels based on montmorillonite clay and vegetable oils that could serve as eco-friendly semi-solid lubricants. In particular, we studied the influence of the physical-chemical properties of olive, castor, soybean, linseed, and sunflower oils on the rheological, chemical, thermal, and tribological properties of the semi-solid lubricants. We prepared the oleogels via the highly intensive mixing of vegetable oils with clay at a concentration of 30 wt.%. The oleogels exhibited shear-thinning, thixotropy, structural recovery, and gel-like behavior commonly related to that of a three-dimensional network. The results were corroborated via XRD measurements showing the presence of intercalated nanoclay structures well-dispersed in the vegetable oil. Empirical correlations between the content of saturated (SFAs), unsaturated (UFAs), mono-unsaturated (MUFAs) and poly-unsaturated (PUFAs) fatty acids and the plateau modulus of the aerogels were found. From these experimental results, we can conclude that the fatty acid profile of the vegetable oils exerts an important influence on the rheological and tribological properties of resulting clay and vegetable oil oleogels.
Exploring cellulose triacetate nanofibers as sustainable structuring agent for castor oil: formulation design and rheological insights
(MDPI, 2024-03-25) Martín Alfonso, Manuel Antonio; Rubio Valle, José Fernando; Estrada Villegas, Gethzemani Mayeli; Sánchez Domínguez, Margarita; Martín Alfonso, José Enrique; Universidad de Sevilla. Departamento de Física Aplicada II; European Commission (EC). Fondo Europeo de Desarrollo Regional (FEDER); Universidad de Huelva; Junta de Andalucía
Developing gelled environmentally friendly dispersions in oil media is a hot topic for many applications. This study aimed to investigate the production of electrospun cellulose triacetate (CTA) nanofibers and to explore their potential application as a thickening agent for castor oil. The key factors in the electrospinning process, including the intrinsic properties of CTA solutions in methylene chloride (DCM)/ethanol (EtOH), such us the shear viscosity, surface tension, and electrical conductivity, were systematically studied. The impact of the CTA fiber concentration and the ratio of DCM/EtOH on the rheological properties of the gel-like dispersions in castor oil was then investigated. It was found that dispersions with a non-Newtonian response and above a critical concentration (5 wt.%), corresponding to approximately 2–2.5 times the entanglement concentration, are required to produce defect-free nanofibers. The average fiber diameter increased with CTA concentration. Further, the morphology and texture of the electrospun nanofibers are influenced by the ratio of solvents used. The rheological properties of dispersions are strongly influenced by the concentration and surface properties of nanofibers, such as their smooth or porous textures, which allow their modulation. Compared to other commonly used thickeners, such as synthetic polymers and metal soaps, CTA electrospun nanofibers have a much higher oil structuring capacity. This work illustrated the potential of using CTA nanofibers as the foundation for fabricating gel-like dispersions in oil media, and thus exerting hierarchical control of rheological properties through the use of a nanoscale fabrication technique.
Experimental post-selection loophole-free time-bin and energy-time nonlocality with integrated photonics
(Optica Publishing Group, 2024-04-20) Santagiustina, Francesco B.L.; Agnesi, Costantino; Alarcón Cuevas, Álvaro; Cabello Quintero, Adán; Xavier, Guilherme B.; Villoresi, Paolo; Vallone, Giuseppe; Universidad de Sevilla. Departamento de Física Aplicada II; Linköpings Universitet; Ministerio de Ciencia, Innovación y Universidades (MICINN). España; Agencia Estatal de Investigación. España; Ministero dell’Istruzione, dell’Università e della Ricerca; Wallenberg Center for Quantum Technology
Time-bin (TB) and energy-time (ET) entanglements are crucial resources for long-distance quantum information processing. However, their standard implementations suffer from the so-called post-selection loophole that allows for classical simulation and thus prevents quantum advantage. The post-selection loophole has been addressed in proof-of-principle experiments. An open problem though is to close it in real-life applications based on integrated technologies. This is especially important since, so far, all integrated sources of TB and ET entanglements suffer from the post-selection loophole. Here, we report post-selection loophole-free certification of TB or ET entanglement in integrated technologies, by implementing in a silicon nitride chip the “hug” scheme [Phys. Rev. Lett. 102, 040401 (2009) [CrossRef] ] and certifying genuine TB entanglement through the violation of a Bell inequality.
Spectrometric Performance of SiC Radiation Detectors at High Temperature
(Elsevier, 2024) Jiménez Ramos, María del Carmen; García Osuna, Adrián; Rodríguez Ramos, Mauricio; Viezzer, Eleonora; Pellegrini, G.; Godignon, P.; Rafí, J. M.; Rius, G.; García López, Francisco Javier; Universidad de Sevilla. Departamento de Física Atómica, Molecular y Nuclear; Universidad de Sevilla. Departamento de Física Aplicada II; Ministerio de Ciencia, Innovación y Universidades (MICINN). España; Junta de Andalucía; Ministerio de Ciencia e Innovación (MICIN). España
In this work, we have investigated the performance of a 4H–SiC radiation sensor in the temperature range from 25 °C to 450 °C to explore its compatibility as detector of fast ion losses in plasma diagnostic of future nuclear fusion reactors. To simulate the escape of fusion-born alpha particles in D-T (deuterium-tritium) fusion plasmas, spectroscopic measurements were carried out in a vacuum chamber by irradiating the detector with a 3.5 MeV alpha beam from a Tandem accelerator. The detector was found to have an energy resolution ≤2% over the entire temperature range analyzed. Relevantly, the excellent spectrometric capabilities of the device have allowed us to calculate from experimental data, with unprecedented accuracy, the average energy required to create a single electron-hole pair in 4H–SiC as a function of temperature.
Oleo-dispersions of electrospun cellulose acetate butyrate nanostructures: toward renewable semisolid lubricants
(Wiley, 2024) Martín Alfonso, Manuel Antonio; Rubio Valle, José Fernando; Martín Alfonso, José Enrique; Franco Gómez, José María; Universidad de Sevilla. Departamento de Física Aplicada II; Ministerio de Ciencia e Innovación (MICIN). España; European Commission (EC). Fondo Europeo de Desarrollo Regional (FEDER); Junta de Andalucía
In this work, the electrospinnability of cellulose acetate butyrate (CAb)solutions, and the ability of the resulting micro- and nano-architectures tostructure castor oil are studied aiming to develop eco-friendly lubricatinggreases. Particles, beaded-fibers, defect-free fibers, and porousnanostructures are successfully prepared by dissolving CAb inN,N-dimethylacetamide/acetone (DMAc:Ac, 1:2 w/w) and methylenechloride/acetone (DM:Ac, 1:1 w/w) solvent mixtures at differentconcentrations (2.5–15 wt.%). The formation of bead-free nanofibers isfavored at concentration above 10 wt.%, when solutions achieve relaxationtimes of≈50 ms and shear-thinning in extensional and shear flow tests,respectively. Non-porous and porous CAb nanostructures are successfullyused as castor oil thickeners at concentrations of 3–5 wt.%, leading a widevariety of rheological responses which mimic those of traditional semisolidlubricants. The surface properties of the nanofibers have a significant impacton the wear and friction performance in metal–metal contact, which has beenassociated with the oil release ability of the generated 3D network.Oleo-dispersions prepared with smooth fibers show tribological performancecomparable to, or even better than, commercial lithium greases. Overall, thisstudy reveals the potential of CAb electrospun nanostructures for thedevelopment of next-generation renewable semisolid lubricant formulations.
Application of phosphogypsum and organic amendment for bioremediation of degraded soil in Tunisia oasis targeting circular economy
(MDPI, 2023-03-08) Gabsi, Hajer; Tallou, Anas; Aziz, Faissal; Boukchina, Rachid; Karbout, Nissaf; Andreu Cáceres, Luis; García-Tenorio García-Balmaseda, Rafael; Boudabbous, Khaoula; Moussa, Mohamed; Universidad de Sevilla. Departamento de Física Aplicada II; Universidad de Sevilla. Departamento de Agronomía; Universidad de Sevilla. AGR188: Agronomía
This study was conducted at the Institute of Arid Regions of Gabes in Tunisia. Three plots were left as controls and received no input, three plots were amended with cattle manure with a dose equivalent to 37.5 t/ha, and nine plots were amended with phosphogypsum in three doses (12.5 t/ha, 25 t/ha, and 50 t/ha), with three repetitions for each dose. A pot test to determine the germination index and radioactivity analysis was carried out in the laboratory. The results showed that organic manure amendments and phosphogypsum improved the germination rate of the different crops (jute mallow, turnip, and oat) compared with the control. At the same time, the 50 t/ha dose had the highest germination rate. An increase in yield of all crops during the whole duration of the experiment was observed for the soil amended by phosphogypsum. The best yield was recorded when the highest dose of phosphogypsum was applied. The cadmium level in plants of the two applied amendments was variable but still below the toxicity threshold (7 ppm). The values recorded following the analysis of the phosphogypsum radioactivity showed that the mean value of Ra-226 equals 214.45 Bq/kg, which is below the limit announced by the EPA (Environmental Protection Agency). The radioactivity results from the control soil samples showed the presence of natural radioactivity. Samples of phosphogypsum-amended soil and plants grown in these soils have radioactivity values that are still lower than those announced by the EPA. The novelty aspect of this study is the application of phosphogypsum in different crops during two consecutive years in degraded-soil areas of Tunisia, in addition to the study of different aspects of phosphogypsum reuse in agriculture as a promising strategy for a sustainable environment.
Pruebas nucleares atmosféricas (1945-1980) y diseminación de radiactividad artificial en el medioambiente
(Consejo de Seguridad Nuclear, 2023-06) García-Tenorio García-Balmaseda, Rafael; Universidad de Sevilla. Departamento de Física Aplicada II; Universidad de Sevilla. RNM138: Física Nuclear Aplicada
La Segunda Guerra Mundial finalizó prácticamente con el lanzamiento de dos bombas nucleares a las ciudades japonesas de Hiroshima y Nagasaki. Inmediatamente después comenzó una enorme escalada en la realización de pruebas nucleares atmosféricas por las grandes potencias, cada vez de mayor energía, con la consecuente liberación de radiactividad al medio ambiente, con el fin de liderar la denominada carrera armamentística nuclear. El número de pruebas y la energía liberada en ellas llegó a ser tan elevado que las principales potencias mundiales acordaron en 1962 una moratoria que impidiera este tipo de pruebas. Estados Unidos, la antigua Unión Soviética y Gran Bretaña cumplieron esa moratoria mientras que países como Francia y China siguieron realizando pruebas nucleares atmosféricas hasta los 80, aunque con una liberación de energía muy inferior a las alcanzadas a en los 50 y principios de los 60 por EE.UU. y la U.R.S.S.
Machine learning techniques for the ab initio Bravais lattice determination
(Wiley, 2023-02) Silva Ramírez, Esther Lydia; Cumbrera Conde, Inmaculada; Cano Crespo, Rafael; Cumbrera Hernández, Francisco Luis; Universidad de Sevilla. Departamento de Física Aplicada II; Universidad de Sevilla. Departamento de Física de la Materia Condensada; Universidad de Sevilla. FQM393: Propiedades Mecánicas, Procesado y Modelización de Cerámicas Avanzadas
Machine learning-based algorithms have been widely applied recently in different areas due to its ability to solve problems in all fields. In this research, machine learning techniques classifying the Bravais lattices from a conventional X-ray diffraction diagram have been applied. Indexing algorithms are an essential tool of the preliminary protocol for the structural determination problem in crystallography. The task of reverting the obtained information in reciprocal lattice to direct space is a complex issue. As an alternative way to afford this problem, different machine learning algorithms have been applied and a comparison between them has been conducted. The obtained accuracy was 95.9% using 10-fold cross-validation (while the best result obtained so far has been 84%). A model based on Bragg positions was our unique predictor, allowing us to obtain the set of the interplanar lattice distances. Our model was successfully checked with a complex example. In addition, our procedure incorporates the following advantages: robustness versus imprecision in data acquisition and reduction of the amount of necessary input data. This is the first time so far that such classification has been carried out in true ab initio condition.

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