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New Insights into Tyrrhenian Sea Warming and Heat Penetration through Long-Term Expendable Bathythermograph Data
Get PDFThe warming trend of the Mediterranean region is already well known, but there is still a lack of information on its seasonal/annual to multidecadal time scales and its distribution in all water masses, including deep water. New temporal and spatial evidence of this thermal variability has been presented in the Tyrrhenian Sea, thanks to twenty-year continuous monitoring by eXpendable BathyThermographs (XBTs) along a fixed route from Genoa to Palermo. The Tyrrhenian Sea is one of the deepest Mediterranean sub-basins (with a maximum depth of about 4000 m), but its interaction with neighbouring basins is controlled by topographical factors, such as the Sardinian Channel to the south and the Corsican Channel to the north. The way in which the warm signal, originating from the Levantine sub-basin, and entering from the south, affects the entire Tyrrhenian Basin spreading rapidly northwards is studied, considering its peculiarities, such as topography, surface circulation, and strong stratification, as well as its climate variability. The warming trend observed for the Tyrrhenian Sea is consistent with the trend for the Mediterranean Sea as a whole. However, the Tyrrhenian Sea shows some peculiar features: around 2014, a shift to a new equilibrium (warmer) state was detected, with mean values along the monitored route that were significantly higher than the previous period (from 1999 to 2013), especially for the subsurface level, from 100 to 450 m depth
DNS of a non-premixed CH4/O2 flame in a supercritical CO2 environment
No full text3D Direct Numerical Simulation (DNS) is performed to investigate turbulent non-premixed methane oxy-combustion in a CO2-rich environment at supercritical conditions (300 bar). The study focuses on a shear-layer configuration typical of slot burners, where the central slot carries the fuel and the oxidant mixture O2/CO2 flows on both sides of the central jet. The simulation solves the compressible Navier–Stokes equations coupled with the translated volume formulation of the Peng–Robinson cubic equation of state (VTPR-EoS), utilizing a reduced 23-species kinetic scheme derived from the ARAMCO 2.0 complete mechanism. The extremely high pressure results in turbulent scales smaller than those observed at lower pressures. Both premixed and diffusion flame zones are identified, with heat primarily released in non-premixed rich regions, leading to a CO mass fraction of up to 0.55. The flow exhibits uphill (counter-gradient) diffusion for both CO2 and H2O, primarily influenced by the interaction of binary diffusion coefficients and individual species chemical potential gradients. Values in the range of 2.52−2.62 are obtained for the fractal dimension of temperature iso-surfaces. Mixture fraction probability density functions (PDFs) are compared with the standard presumed β−PDF, revealing an underestimation of mixing. Differently from flames at atmospheric pressures, the Dufour effect in the energy diffusion flux, is not negligible. Furthermore, fugacity coefficients must be considered in the calculation of chemical species kinetic rates
Preliminary Conceptual Design of the ICRH Antenna for DTT: A Systems Engineering Approach
No full textThe Divertor Tokamak Test (DTT) facility needs a large amount of heating power to study the problem of power exhaust in reactor-relevant conditions. Among the additional heating systems, the ion cyclotron resonance heating (ICRH) is characterized by radio frequency (RF) components based on standard technology and well-assessed solutions due to the tight schedule of the DTT construction. Considering the harsh fusion operating conditions, the ICRH antenna design involves different and interacting physical fields to be managed by the systems engineering (SE) approach. Therefore, following step by step this methodology, the design started with the definition of the main requirements of the whole system. Then, the main functions have been identified with the aim to define the logical architecture of the whole antenna structure. In the end, a preliminary 3-D parametric model of the ICRH antenna with its subsystems has been developed adopting a top-down modeling approach in the CATIA V5 environment provided by Dassault Systemes. Key aspects of the 3-D model are the clear definition of the position in the available space of all subsystems and of their interfaces, and its parametrization. They allow to quickly implement the modifications required by the multiple iterations between the geometrical modeling environment and several multiphysics simulation environments to check the compliance with mechanical, electrical, thermofluid dynamics, and remote handling requirements
Activated corrosion product contamination assessments of DEMO WCLL breeding blanket primary heat transport system
Get PDFIn water-cooled fusion reactors, the assessment of the primary system contamination is essential for waste management, machine availability, occupational radiation exposure, and radiological hazard determination. The primary cooling water is not only directly activated by the intense neutron field but is a contamination vector for a significant variety of gamma emitters with short to long decay half-lives. Corrosion products can be activated in those regions under neutron flux of the primary circuit and then released in the cooling water. In the EU-DEMO fusion power plant equipped with the Water-Cooled Lithium Lead Breeding Blanket (WCLL-BB) concept, the primary coolant undergoes intense neutron fields in the first wall and the breeding zone regions of the blanket. Activated Corrosion Products (ACPs) are then formed, released into the water, transported in the cooling loop and finally deposited onto the ex -vessel surfaces of the Primary Heat Transport System (PHTS), where working personnel are susceptible to being radiologically exposed. This work addresses the complete assessment of ACPs in the WCLL-BB PHTS of EU-DEMO. The simultaneous and multi-physical processes behind the ACP formation are tackled using the OSCAR-Fusion code, a comprehensive tool developed by the CEA (France) to assess contamination in fusion nuclear reactors. The whole system is modelled with zero-dimensional nodes with assigned geometrical, thermal-hydraulics, material and chemical parameters. Activation reaction rates integrated over the whole spectrum and calculated with MCNP are given to those regions exposed to the neutron flux. Results are provided in terms of mass and activity inventories of ACPs as deposit and inner oxide layers of components (pipes, heat exchangers, pumps.), ions in solution, particles in suspension, and filters and resins trapping. Mobilizable inventories such as ions, particles and deposits are important source terms in accidental scenario evolutions, while the whole activity inventory constitutes the main long-term gamma emitting source for dose rate maps determination in the tokamak building rooms housing the main PHTS equipment
RELAP5/Mod3.3 thermal-hydraulics characterization of the steam generator mock-up during operational transients in STEAM facility in support of the design of the DEMO WCLL BoP
No full textThe Water Cooled Lithium Lead Breeding Blanket (WCLL BB) is a key candidate for the driver blanket of the European DEMO reactor, progressing toward its Conceptual phase by the end of 2027. To assess different water and lithium-lead technologies for the WCLL BB and Balance of Plant (BoP) systems, the Water-thermal-HYDRAulic (W-HYDRA) experimental platform is under development at the ENEA Brasimone Research Centre. Among the facilities constituting the new W-HYDRA multipurpose infrastructure, STEAM is going to experimentally investigate the DEMO WCLL BoP thermal-hydraulics, focusing on the Steam Generator (SG) of the Primary Heat Transfer Systems (PHTS), to qualify its performances and suitability under its unconventional operation. The paper aims at supporting the thermal-hydraulic characterization of the Steam Generator mock-up during the sudden power variations typical of a pulsed fusion reactor. The analyzed selected scenario is the operational transient dwell-pulse-dwell, which determines high thermal cycling and correspondent high thermo-mechanical stresses on the primary side components. Two control logics with their relative drawbacks have been analyzed with a RELAP5/Mod3.3 1-D model, the first regulating the primary side average temperature, the second monitoring the minimum one. The comparison of the two systems highlighted that neither approach leads to hazardous conditions for the facility. However, while the average temperature controller is characterized by reduced thermal stresses on the components, the minimum temperature controller is characterized by higher thermal gradients for the primary loop. Both methodologies will be tested in the dedicated experimental campaign, aiming at yielding insights and evaluations concerning control strategies applicable to the DEMO reactor
Modeling Fermi energy, free-carrier density, and resistivity in degenerate n-Ge
Get PDFA new expression for Fermi energy vs doping is derived using the standard model for free carriers in n-type semiconductors. The new expression is composed of the Fermi energy in non-degenerate semiconductors, a doping function for bandgap narrowing (BGN), and an adjustable energy variation. In non-degenerate semiconductors, the new expression is equivalent to the standard Boltzmann expression. Calculated curves of Fermi energy are assigned in the Fermi-Dirac expression for the donor ionization ratio, and reported data of electron density and resistivity measured in heavily doped n-Ge layers are fitted. Five reported doping functions for BGN are used. One of the BGN functions allows modeling frustrated incomplete ionization. Another allows modeling bandgap widening
The genome and population genomics of allopolyploid Coffea arabica reveal the diversification history of modern coffee cultivars
Get PDFCoffea arabica, an allotetraploid hybrid of Coffea eugenioides and Coffea canephora, is the source of approximately 60% of coffee products worldwide, and its cultivated accessions have undergone several population bottlenecks. We present chromosome-level assemblies of a di-haploid C. arabica accession and modern representatives of its diploid progenitors, C. eugenioides and C. canephora. The three species exhibit largely conserved genome structures between diploid parents and descendant subgenomes, with no obvious global subgenome dominance. We find evidence for a founding polyploidy event 350,000–610,000 years ago, followed by several pre-domestication bottlenecks, resulting in narrow genetic variation. A split between wild accessions and cultivar progenitors occurred ~30.5 thousand years ago, followed by a period of migration between the two populations. Analysis of modern varieties, including lines historically introgressed with C. canephora, highlights their breeding histories and loci that may contribute to pathogen resistance, laying the groundwork for future genomics-based breeding of C. arabica
On the effects of 30.5 GHz sinusoidal wave exposure on glioblastoma organoids
No full textIntroduction: Glioblastoma (grade IV) is the most aggressive primary brain tumor in adults, representing one of the biggest therapeutic challenges due to its highly aggressive nature. In this study, we investigated the impact of millimeter waves on tridimensional glioblastoma organoids derived directly from patient tumors. Our goal was to explore novel therapeutic possibilities in the fight against this challenging disease. Methods: The exposure setup was meticulously developed in-house, and we employed a comprehensive dosimetry approach, combining numerical and experimental methods. Biological endpoints included a global transcriptional profiling analysis to highlight possible deregulated pathways, analysis of cell morphological changes, and cell phenotypic characterization which are all important players in the control of glioblastoma progression. Results and discussion: Our results revealed a significant effect of continuous millimeter waves at 30.5 GHz on cell proliferation and apoptosis, although without affecting the differentiation status of glioblastoma cells composing the organoids. Excitingly, when applying a power level of 0.1 W (Root Mean Square), we discovered a remarkable (statistically significant) therapeutic effect when combined with the chemotherapeutic agent Temozolomide, leading to increased glioblastoma cell death. These findings present a promising interventional window for treating glioblastoma cells, harnessing the potential therapeutic benefits of 30.5 GHz CW exposure. Temperature increase during treatments was carefully monitored and simulated with a good agreement, demonstrating a negligible involvement of the temperature elevation for the observed effects. By exploring this innovative approach, we pave the way for improved future treatments of glioblastoma that has remained exceptionally challenging until now
Glycosaminoglycan dermatan sulfate supplementation decreases diet-induced obesity and metabolic dysfunction in mice
No full textGlycosaminoglycans are complex carbohydrates used as nutraceuticals for diverse applications. We studied the potential of the glycosaminoglycan dermatan sulfate (DS) to counteract the development of diet-induced obesity (DIO) using obesity-prone mice fed a high-fat diet (HFD) as a model. Oral DS supplementation protected the animals against HFD-induced increases in whole-body adiposity, visceral fat mass, adipocyte size, blood glucose levels, insulin resistance, and pro-inflammatory lipids levels in brown adipose tissue (BAT) and the liver, where it largely counteracted the HFD-induced changes in the nonpolar metabolome. Protection against DIO in the DS-supplemented mice occurred despite higher energy intake and appeared to be associated with increased energy expenditure, higher uncoupling protein 1 expression in BAT, decreased BAT “whitening,” and an enhanced channeling of fuel substrates toward skeletal muscle. This work is the first preclinical study to examine the anti-obesity activity of DS tested individually in vivo. The results support possible uses of DS as an active component in functional foods/supplements to manage obesity and associated metabolic diseases
Pre-test analysis of low power operations of STEAM, the EU-DEMO steam generator mock-up facility
No full textWhile nuclear fusion reactors hold promise, their realization faces significant complexities, not only in the construction but also in managing the auxiliary systems required for safely operating plasmas. Pulsed plasma regime, integral to reactor normal operations, determines atypical operative conditions that can cause high thermal stresses on the components and generate instabilities. R&D activities are therefore required to characterize the components behavior in the extremely severe conditions of pressure and temperatures associated with fusion, especially during sudden power transitions. ENEA, as part of the EUROfusion consortium, is planning the construction of STEAM, an experimental facility aimed at qualifying the DEMO Steam Generator during pulse-dwell-pulse transitions within the W-HYDRA platform. Dedicated experimental campaigns will reproduce the low-power phase associated with the only material activation (dwell), the full-power phase (pulse) and the corresponding power transitions. This paper focuses on the low-power phase, presenting the performed RELAP5/Mod3.3 simulations, investigating the thermal-hydraulic performances of the system at 1 %, 5 % and 10 % of the nominal power, hence in conditions considerably different from fission standard practices. The simulation results are essential for defining regulation strategies for the SG test section and ensuring the correct operation of the entire system