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Optimization of culture conditions for enhanced carotenoid production by
No full textParacoccus haeundaensis SAB E11 is a carotenoid producer that enhances the adaptive response of Schizosaccharomyces pombe ARC039 to oxidative stress. This study aimed to determine the optimal carbon and nitrogen sources and most suitable fermentation conditions for carotenoid production by P. haeundaensis SAB E11. The basic medium, seawater complete (SWC), was modified with various carbon sources (glycerol, glucose, sucrose, lactose, and starch) and nitrogen sources (beef extract, tryptone, ammonium sulfate, and ammonium chloride), and the temperature, pH, and salinity were adjusted. Treatments were assessed using analysis of variance (ANOVA), and significant variance was identified using Duncan's multiple range test. Optimal fermentation conditions for dry cell weight and total carotenoid were achieved using glycerol and beef extract as carbon and nitrogen sources at a salinity of 22.5%, a temperature of 27°C, and a pH of 7, resulting in dry cell weight and total carotenoid concentrations of 3.96±0.25 g/L and 44.65±2.22 μg/L, respectively. Under these conditions, the dry cell weight and total carotenoid content increased by 1.33-fold and 1.43-fold, respectively. The optimal conditions for carotenoid production by Paracoccus haeundaensis SAB E11 serve as a foundational reference for applications in food and pharmaceutical industries
Sobriété expérimentale en action : l’exemple de la microfluidique
No full textLes bilans effectués dans de nombreux laboratoires de physique montrent que les activités expérimentales contribuent fortement aux émissions de gaz à effet de serre, notamment via les achats. Si des initiatives émergent pour réduire leur volume (réparation, prêt), une réflexion autour des pratiques expérimentales est moins souvent entreprise. Nous illustrons et discutons ici, à partir de l’exemple de la recherche en microfluidique, une démarche de réduction d’impact intégrant l’ensemble des activités, le cout environnemental des consommables et des équipements utilisés, et reposant sur une coconstruction des solutions
Modelling the total solar eclipse in 2024 with COCONUT
No full textContext. Coronal modelling is crucial for a better understanding of solar physics and heliophysics. Accurate plasma conditions at the outer boundary of a solar corona lead to more precise space weather predictions. Because the Sun is so very bright and we lack white-light (WL) observations of the solar atmosphere and low corona (1–1.5 R⊙), total solar eclipses have become a standard approach for validating the coronal models. We validate the coronal model COCONUT by predicting the coronal configuration during the total solar eclipse on April 8, 2024.
Aims. We aim to predict the accurate configuration of the solar corona during the total solar eclipse on April 8, 2024. Additionally, we compare the predictive capabilities in the steady and dynamic driving of the boundary conditions in COCONUT. We used a full 3D magnetohydrodynamics (MHD) model to reconstruct the solar corona from the solar surface to 30 R⊙.
Methods. We started by predicting the upcoming total solar eclipse on March 21. The predictions were conducted in three different regimes: quasi-steady driving of the inner boundary conditions (BCs) with a daily cadence, and dynamic driving of the inner BCs with daily and hourly cadences. The results from all the simulations were compared to the total solar eclipse images. Additionally, the synthetic WL images were generated from the Solar Terrestrial Relations Observatory Ahead (STEREO-A) field of view and compared to COR2 observed images. The normalised polarised brightness was compared in the COR2 and synthetic WL images.
Results. The predicted solar corona does not vary significantly in the first half of the prediction window because the observations of the magnetic field are not yet accurately updated on the solar surface corresponding to April 8. The magnetic field changes more significantly as the eclipse date approaches. The dynamic simulations yielded better results than the quasi-steady predictions. Driving the simulations at a higher cadence did not significantly improve the results because the magnetic field maps are highly processed. The west limb was better reconstructed in the simulations than the east limb.
Conclusions. We predicted the total solar eclipse coronal configuration 18 days before the total solar eclipse. We conclude that the dynamic simulations produced more accurate predictions. The availability of comprehensive observations is crucial because the emergence of the active region on the east limb made it difficult to accurately predict the east-limb coronal configuration because the input of the magnetic field data was incorrect. More detailed input BCs are necessary for reconstructing smaller-scale structures in the corona
Impact of connected vehicles on the traffic efficiency and PM emissions of mixed traffic flows
No full textAs the rapid development of connected vehicles (CVs), it is inevitable that human-driven vehicles (HVs) and CVs run on a same road in the near future. Besides the traffic efficiency, the sustainable development in society cares more and more about particulate matter (PM) emissions very recently. In this work, mixed traffic flows with both CVs and HVs on a two-lane expressway are proposed and effects of CVs penetration rate on the traffic flow and the PM emission are the focus. The numerical simulation results show that the traffic flow is effectively improved as the proportion of CVs increases. But there are two stages of PM emissions. When the density is lower, the greater the proportion of CVs, the lower the PM emissions. When the density is higher, the situation reverses. Furthermore, traffic flows on two lanes are not the same and the symmetry is terribly broken when the penetration of CVs is high. As for the forward observable interval of CVs, it can limit PM emissions and increase traffic flow. Thus a high traffic efficiency and a low PM emission asks for a high CVs penetration but an appropriate observable interval
The ALMA survey to Resolve exoKuiper belt Substructures (ARKS)
No full textContext. The outer regions of planetary systems host dusty debris discs analogous to the Kuiper belt (exoKuiper belts), which provide crucial constraints on planet formation and evolution processes. ALMA dust observations have revealed a great diversity in terms of radii, widths, and scale heights. At the same time, ALMA has also shown that some belts contain CO gas, whose origin and implications are still highly uncertain. Most of this progress, however, has been limited by low angular resolution observations that hinder our ability to test existing models and theories.
Aims. High-resolution observations of these belts are crucial for understanding the detailed distribution of solids and for constraining the gas distribution and kinematics.
Methods. We conducted the first ALMA large programme dedicated to debris discs: the ALMA survey to Resolve exoKuiper belt Substructures (ARKS). We selected the 24 most promising belts to best address our main objectives: analysing the detailed radial and vertical structure, and characterising the gas content. The data were reduced and corrected to account for several systematic effects, and then imaged. Using parametric and non-parametric models, we constrained the radial and vertical distribution of dust, as well as the presence of asymmetries. For a subset of six belts with CO gas, we constrained the gas distribution and kinematics. To interpret these observations, we used a wide range of dynamical models.
Results. The first results of ARKS are presented as a series of ten papers. We discovered that up to 33% of our sample exhibits substructures in the form of multiple dusty rings that may have been inherited from their protoplanetary discs. For highly inclined belts, we found that non-Gaussian vertical distributions are common and could be indicative of multiple dynamical populations. Half of the derived scale heights are small enough to be consistent with self-stirring in low-mass belts (Mbelt ≤ MNeptune). We also found that 10 of the 24 belts present asymmetries in the form of density enhancements, eccentricities, or warps. We find that the CO gas is radially broader than the dust, but this could be an effect of optical depth. At least one system shows non-Keplerian kinematics due to strong pressure gradients, which may have triggered a vortex that trapped dust in an arc. Finally, we find evidence that the micron-sized grains may be affected by gas drag in gas-rich systems, pushing the small grains to wider orbits than the large grains.
Conclusions. ARKS has revealed a great diversity of radial and vertical structures in exoKuiper belts that may arise when they are formed in protoplanetary discs or subsequently via interactions with planets and/or gas. We encourage the community to explore the reduced data and data products that we have made public through a dedicated website
Effect of conduit friction and presence of charged species on rise of xylem sap
No full textWe study water uptake in plants by modelling the xylem as a narrow capillary tube through which sap rises under transpiration pull. We modify the classical Bosanquet equation, incorporating the effect of friction f, arising from xylem wall protrusions, while including corrections to the surface tension due to the presence of ions in the sap and due to local curvature via the Tolman correction. We also take into consideration an externally imposed transpiration flux. We identify a dimensionless tuning parameter, , that is a relative measure of capillary to hydrostatic forces that, along with f, affects system behaviour. In the absence of transpiration, transitions between oscillatory and non-oscillatory behavior of the sap column depends on , while its rate of rise depends on f. We find that the addition of transpiration to the xylem capillary system, by considering diffusion and evaporation at the leaves, causes the system to instead stabilize around a nonlinear center, also crucially increasing the maximal height to which the water rises. We obtain scaling power-laws for the time required for the sap to reach to reach its maximum height, and the characteristic time scale for oscillations in the column to decay to its fixed point, as functions, respectively, of f and of . We investigate the competitive effects of transpiration pull and presence of corrugation in the conduits. Our approach integrates capillary flow physics with dynamical systems theory to uncover new insights and get a more comprehensive and novel understanding of the problem of water transport in plants
White light interferometry analysis for measuring thin film thickness down to a few nanometers
No full textWe present a practical white-light interferometric method, supported by an open-source Python library optifik for automated spectrum-to-thickness deduction, enabling foam film measurements down to a few nanometers. We describe three typical spectral scenarii encountered in this method: spectra exhibiting numerous interference fringes, spectra with a moderate number of peaks, and spectra with only a few identifiable features, providing illustrative examples for each case. We also discuss the main limitations of the technique, including spectral range constraints, the necessity of knowing the refractive index, and the influence of spectral resolution and signal quality. Finally, we demonstrate the application of the method in a time-resolved study of a TTAB (tetradecyltrimethylammonium bromide) foam film undergoing elongation and thinning. This method can be adapted to measure any thin non-opaque layer
Effect of anisotropy on the overall fluctuation instability of the interface morphology of deep cellular crystal
No full textIn this paper, we constructed a mathematical model of deep cellular crystal growth under anisotropic surface tension and anisotropic interface kinetics during directional solidification. Using the multivariate expansion method and the matched asymptotic expansion method, the dispersion relation of the rate of change of the perturbation amplitude at the deep cellular crystal interface and the quantization condition of the interface morphology are deduced, analyzed the stability of the growth of deep cellular crystal under the influence of anisotropic surface tension and anisotropic interface kinetics in the directional solidification, and revealed the influence of anisotropic parameters on the size of the unstable region. The results show that in the directional solidification considering anisotropic surface tension and anisotropic interface kinetics, there are two overall instability mechanisms for the morphology of deep cellular crystal growth interfaces: global oscillatory (GTW) instability and low-frequency (LF) instability. The stability analysis shows that the anisotropic surface tension and anisotropic interface kinetics have a significant effect on the global oscillatory instability mechanism in the low-order approximation. As the anisotropy parameter increases, the stable region of global oscillatory instability gradually expands. Relatively, the influence of the anisotropic interface kinetics parameter on the overall fluctuation instability of the interface morphology is more remarkable than the anisotropic surface tension parameter
Development of an actively cooled radio-frequency test bench for the ITER ICRF windows
No full textRadio-Frequency (RF) windows (or feedthroughs) are under development for the ITER Ion Cyclotron Range of Frequencies (ICRF) system (40-55 MHz). To test these first of a kind RF window units, an actively cooled radio-frequency coaxial resonator was designed and is currently under construction at CEA/IRFM. This testbed is specified to reach 50 kV peak maximum voltage or 2.5 kA peak maximum current at the middle of the test articles in continuous-wave operation (3600 s RF pulses with a ¼ duty cycle). The operating frequency of the resonator is set to 55 MHz. The conditions of the tests are 0.6 MPa (absolute, dry air) at one side of the RF windows, vacuum (10-4 Pa) environment at the other side of the front window and 0.3 MPa (absolute, dry air) at the rear window. These conditions are representative of the current ITER ICRF environment: the vacuum side simulates the torus vacuum inside the tokamak, and the pressurized side mimics the gas conditions within the transmission lines connecting the RF generators to the antenna. Since it is not possible to maximise both voltage and current at a given position of a resonator, two resonator configurations are foreseen, for each of the front and rear windows (hence 4 different configurations). Each of the front and rear windows will be tested at maximum voltage and maximum current. The test bench was designed to be modular, allowing the positioning of either the rear of the front windows for voltage or current RF test, hence leading to cost reduction. This paper is a description of the RF design, the mechanical design, and a rough description of the ongoing manufacturing phase
Overview of ICRF plasma production and heating in gas mixtures in stellarators
No full textThe study of plasma production and heating in the ion cyclotron range of frequencies (ICRF) has a long history in fusion research. The ICRF discharges have been studied in stellarators, tokamaks and mirror devices, mainly. The possibility of efficient additional plasma heating using ICRF is one of the main aims of the studies. Plasma production using ICRF discharges is also studied, but to a lesser extent. For the purpose of wall conditioning in both pure gases and their mixtures has been used with lower RF power level. In support of the ICRF experiments for plasma production at Wendelstein 7-X, studies on the development of an ICRF start-up scenario were initiated on the Uragan-2M (U-2M) stellarator. Experiments with a controlled minority of hydrogen in helium atmosphere showed a significant increase in the resulting plasma density compared with pure helium and pure hydrogen. Then, the ICRF plasma production was demonstrated on the LHD with the scenario based on U-2M experiment. Successful experiments at U-2M and LHD showed that the ICRF start-up scenario can be scaled up to large stellarator devices, producing plasma with favorable parameters from scratch using ICRF only