Detachment Conditions Research Articles

Experimental research on the TCV tokamak

Abstract Tokamak à configuration variable (TCV), recently celebrating 30 years of near-continual operation, continues in its missions to advance outstanding key physics and operational scenario issues for ITER and the design of future power plants such as DEMO. The main machine heating systems and operational changes are first described. Then follow five sections: plasma scenarios. ITER Base-Line (IBL) discharges, triangularity studies together with X3 heating and N2 seeding. Edge localised mode suppression, with a high radiation region near the X-point is reported with N2 injection with and without divertor baffles in a snowflake configuration. Negative triangularity (NT) discharges attained record, albeit transient, β N ∼ 3 with lower turbulence, higher low-Z impurity transport, vertical stability and density limits and core transport better than the IBL. Positive triangularity L-Mode linear and saturated ohmic confinement confinement saturation, often-correlated with intrinsic toroidal rotation reversals, was probed for D, H and He working gases. H-mode confinement and pedestal studies were extended to low collisionality with electron cyclotron heating obtaining steady state electron iternal transport barrier with neutral beam heating (NBH), and NBH driven H-mode configurations with off-axis co-electron cyclotron current drive. Fast particle physics. The physics of disruptions, runaway electrons and fast ions (FIs) was developed using near-full current conversion at disruption with recombination thresholds characterised for impurity species (Ne, Ar, Kr). Different flushing gases (D2, H2) and pathways to trigger a benign disruption were explored. The 55 kV NBH II generated a rich Alfvénic spectrum modulating the FI fas ion loss detector signal. NT configurations showed less toroidal Alfvén excitation activity preferentially affecting higher FI pitch angles. Scrape-off layer and edge physics. gas puff imaging systems characterised turbulent plasma ejection for several advanced divertor configurations, including NT. Combined diagnostic array divertor state analysis in detachment conditions was compared to modelling revealing an importance for molecular processes. Divertor physics. Internal gas baffles diversified to include shorter/longer structures on the high and/or low field side to probe compressive efficiency. Divertor studies concentrated upon mitigating target power, facilitating detachment and increasing the radiated power fraction employing alternative divertor geometries, optimised X-point radiator regimes and long-legged configurations. Smaller-than-expected improvements with total flux expansion were better modelled when including parallel flows. Peak outer target heat flux reduction was achieved (>50%) for high flux-expansion geometries, maintaining core performance (H 98 > 1). A reduction in target heat loads and facilitated detachment access at lower core densities is reported. Real-time control. TCV’s real-time control upgrades employed MIMO gas injector control of stable, robust, partial detachment and plasma β feedback control avoiding neoclassical tearing modes with plasma confinement changes. Machine-learning enhancements include trajectory tracking disruption proximity and avoidance as well as a first-of-its-kind reinforcement learning-based controller for the plasma equilibrium trained entirely on a free-boundary simulator. Finally, a short description of TCV’s immediate future plans will be given.

Detachment of inclined spheroidal particles from flat substrates

The detachment of fine particles attached to a solid substrate or rock surface significantly affects colloidal transport in porous media. The work is devoted to quantifying the detachment conditions for inclined oblate spheroids subjected to creeping viscous flow. A numerical and a laboratory study were conducted to systematically evaluate the impact of the orientation (pitch) angle towards the hydrodynamic moment, adhesive DLVO force, contact area, and critical detachment velocity. The methodology developed to produce stretched latex polystyrene particles reduces the geometric uncertainty of nonspherical fines. The geometry of the produced oblate spheroids is fully determined by the semi-major and semi-minor axes. For inclined attached particles, an explicit formula has been derived for the detaching velocity, where the detaching drag torque exceeds the attaching adhesion torque. The probabilistic distribution of the model parameters for the detachment velocity of the inclined particles attached to the plane substrate provides upscaling for fines detachment from the particle to porous media scale.

The loss of crude oil droplets by filter feeders and the role of surfactants

Various methods of oil spill remediation exist, e.g., floating booms, controlled burning and the release of chemical surfactants. These surfactants facilitate the breakup of the slick into micron-sized droplets. Here, we studied the impact such a surfactant has on the size distribution of oil droplets in the water column and in the gut of the filter feeder Daphnia magna. We also studied the effect of surfactants on detachment conditions of chemically and mechanically dispersed oil (respectively MDO and CDO) droplets from capture fibers. Our results show that including solubilized dioctyl sulfosuccinate sodium salt in the mixing of the emulsion produces smaller droplets and a narrower size distribution in the water. In the gut, the size of ingested droplets does not change whether the oil is mixed mechanically or chemically. Also, surfactant coated droplets detach at a lower velocity than mechanically dispersed droplet because of their lower oil/water interfacial tension.

Visualization of Cellular Membranes in 2D and 3D Conditions Using a New Fluorescent Dithienothiophene S,S-Dioxide Derivative.

Cellular membranes play a key role in cell communication with the extracellular environment and neighboring cells. Any changes, including their composition, packing, physicochemical properties and formation of membrane protrusions may affect cells feature. Despite its great importance, tracking membrane changes in living cells is still a challenge. For investigation of processes related to tissue regeneration and cancer metastasis, such as the induction of epithelial-mesenchymal transition, increased cell motility, and blebbing, the possibility to conduct prolonged observation of membrane changes is beneficial, albeit difficult. A particular challenge is conducting this type of research under detachment conditions. In the current manuscript, a new dithienothiophene S,S-dioxide (DTTDO) derivative is presented as an effective dye for staining the membranes of living cells. The synthetic procedures, physicochemical properties, and biological activity of the new compound are presented herein. In addition to the labeling of the membranes in a monolayer culture, its usefulness for visualization of membranes under detachment conditions is also demonstrated. Obtained data have proven that a new DTTDO derivative may be used to stain membranes in various types of experimental procedures, from traditional 2D cell cultures to unanchored conditions. Moreover, due to the specific optical properties, the background signal is reduced and, thus, observation may be performed without washing.

Recent Progress in Some Issues of Divertor Physics under Detachment Conditions

Recent Progress in Some Issues of Divertor Physics under Detachment Conditions

Linked microstructural and geochemical evolution of mylonitic quartzite during exhumation of a core complex

A novel method for combining microstructural analysis and Ti-in-quartz measurements is used to characterize interactions between quartz deformation and Ti equilibration during progressive deformation and cooling in a mylonitic shear zone. Mylonitic quartzite from the Wildhorse detachment, the major bounding structure of the Pioneer metamorphic core complex (Idaho, USA), contains a continuum of microstructures: minimally deformed relict grains, quartz ribbons, and a matrix dominated by subgrain rotation recrystallization. EBSD and semi-quantitative Ti mapping via EPMA and cathodoluminescence imaging are used to correlate quartz microstructure and Ti concentration [Ti]. The Ti-in-quartz thermobarometer is used to estimate P-T conditions during and prior to mylonitization. Relict and ribbon quartz preserve high [Ti] (∼60 ppm) indicative of temperatures >650 °C, whereas recrystallized quartz contains low [Ti] (<5 ppm), reflecting equilibration to temperatures <450 °C. The high-T record may reflect either relict conditions prior to detachment deformation or conditions that prevailed in the early stages of strain localization in the detachment, whereas the low-T record likely reflects the final stages of ductile deformation. The preservation of multiple microstructures with distinct [Ti] facilitates construction of a multi-phase history of linked ductile deformation and Ti equilibration during cooling.

An approach to implement a heat flux limit in a model for fusion relevant plasmas

An approach to implement a heat flux limit (HFL) in a plasma model is proposed. The HFL arises if the mean free path length of the heat carrying electrons, λh, significantly exceeds the characteristic length of the temperature variation, LT. For λh≫LT, the heat flux becomes nearly independent of the temperature gradient, in contrast to the case of λh≪LT where it is gradient dependent. As a result, by going from λh≪LT to λh≫LT, the order of the heat balance equation changes and the method proposed allows a reliable integration of this equation in these limits, as well as for λh∼LT. By solving a set of one-dimensional fluid equations for particle, momentum, and heat balance numerically, the importance of the HFL for fusion relevant conditions is demonstrated for plasma parameter profiles at the edge of the heliotron Large Helical Device and detachment conditions in helium plasmas of the linear device NAGDIS-II.

Modeling snowflake divertors in MAST-U Tokamak

In a snowflake (SF) divertor, two magnetic field nulls are placed close to each other, creating four strike points (SPs) compared to two in a standard X-point divertor. In preparation for MAST-U experiments, magnetic configurations with the standard and SF divertors with various locations and separation distances of the nulls were modeled using the two-dimensional multi-fluid code UEDGE with a full plasma transport model featuring charge-state-resolved sputtered carbon impurities. The complex interplay of the plasma transport and magnetic configurations was comprehensively studied using a simple model for the theoretically predicted fast plasma mixing driven by the ‘churning’ mode instability in the two-null SF region. The modeling results show that (1) all SF-plus configurations and SF-minus configuration with closely located nulls produce the same plasma parameters and heat fluxes at the same SPs; (2) SF divertors approach the outer and inner SP detachment conditions at lower upstream density w.r.t. the standard divertor; (3) heat flux profiles at primary SPs are substantially broadened and peak values are reduced in SF configurations w.r.t. SN divertors; this broadening becomes more pronounced with the fast plasma mixing increase.

Dynamic Study of Load Detachment in Supercritical Carbon Dioxide Brayton Cycle

The supercritical carbon dioxide Brayton cycle has become the choice of a wide range of users because of its higher efficiency and smaller turbine size, and is often used in space vehicles, sodium cooled fast reactors, Marine power equipment and other energy storage and power generation applications. However, in the process of use, the detachment of the load is a common problem, if not well handled often cause the system to crash. In this paper, based on the software Simulink in MATLAB, the moment of inertia of turbine and generator is regarded as fixed value, the key parameter differential equations of Brayton cycle are derived, and the dynamic recompression and intercooling Brayton cycle models are established. The response parameters of the system after load disconnection and different time tie-back are studied. The responses of key parameters of the system after load detachment were obtained. It was found that the recompression model had higher stability under load detachment and tie-back conditions than the intercooling model, and the length of parameter variation after load detachment was linear. The earlier the tie-back was, the faster the system could restore stability.

Cell-cell and cell-substratum contacts in the regulation of MAPK and Akt signalling: Importance in therapy, biopharmacy and bioproduction

The use of cultured cells as a tool for research, precision medicine, biopharmacy, and biomanufacturing is constantly increasing. In parallel, the role of cell-cell and cell-substratum contacts in cell functioning is increasingly validated. Adhesion signalling plays a key role here. The activity of cell fate-regulating signalling molecules is an important factor in determining cell behaviour, as well as their response to treatment, depending on cell phenotypic status and location in the body. Three cellular state models (adherent, single cells in suspension, and aggregated cells) were compared for cell signalling, including focal adhesion (FAK), mitogen-activated (MAPK), as well as Akt protein kinases, and transcription factor cJun, by using lung adenocarcinoma A549, muscle-derived stem Myo, as well as primary lung cancer cell lines. Survival of both A549 and Myo cells was dependent on kinases Akt and ERK in detached conditions. Intercellular contacts in aggregates promoted activation of Akt and ERK, and cell survival. Loss of contacts with the substrate increased phosphorylation of MAP kinases JNK and p38, while decreased Akt phosphorylation by processes involving FAK. Unexpectedly, detachment increased phosphorylation of antiapoptotic kinase ERK in A549, while in Myo stem cells ERK phosphorylation was downregulated. JNK target transcription factor cJun protein level was markedly diminished by contacts between cells possibly involving mechanism of proteasomal degradation. Furthermore, studies revealed the opposite dependence of molecules of the same signalling pathway – phospho-cJun and phospho-JNK – on cell culture density. Differences in ERK activation under detachment conditions indicate that targeting of prosurvival kinases during anoikis should be different in different cells. Moreover, the outcome of JNK activation in cells may depend on the amount of cJun, which is determined by cell-cell contacts.

Impact of shape on particle detachment in linear shear flows

Transport and detachment of colloidal particles with irregular shapes occur in geology, environmental, and water-resource engineering. We investigated the effect of shape and aspect ratio on the detachment of non-spherical microparticles attached to a plane substrate, in Couette linear shear flow, under favourable conditions. The detachment conditions were determined by the mechanical equilibrium of drag, lift, gravity and adhesion forces acting on the particle. Drag and lift were evaluated using Computational Fluid Dynamics (CFD), introducing the shape-dependent corrections into traditional formulae for spherical particles. The adhesive particle–surface force is determined by the Surface Element Integration (SEI) method, which also corrects the classical DLVO expression. The forces exerted on spheroids and cylinders can significantly differ from spheres and their detachment exhibit non-monotonic dependencies with aspect ratio. Direct visualisation experiments were performed by piecewise-constant change of flow velocity and the observed detachment were in good agreement with the mechanical-equilibrium based predictions.

Denitrification Modeling using Natural Organic Solid Substrates as Carbon Sources

En los últimos años, se han estudiado Sustratos Sólidos Orgánicos Naturales (SSON) como fuentes de carbono económicas y seguras, para su uso en la desnitrificación del agua. Aunque los resultados de desnitrificación con SSON han sido satisfactorios, aún es limitada la información de los procesos que intervienen en la interfaz SSON-biopelícula. Con el objetivo de comprender dichos procesos, desarrollamos un modelo matemático unidimensional de desnitrificación en contragradiente, con el cual evaluamos: el comportamiento de la biopelícula adherida al SSON y su efecto en la liberación del carbono; transporte y consumo de carbono, transporte y consumo de nitrato. Para tal fin, se usó Saccharum Spontaneum L. como SSON de referencia, de la cual se tienen parámetros biocinéticos y de hidrólisis generados en estudios previos de desnitrificación. En este artículo se presentan los resultados de la modelación matemática de desnitrificación, con SSON como fuentes de carbono, lo cual se simuló con el programa AQUASIM. Los supuestos y simplificaciones definidas permitieron predecir teóricamente la desnitrificación en reactores batch y completamente mezclado con flujo. Las mejores simulaciones del estudio se obtuvieron en condiciones con desprendimiento de biopelícula, donde la desnitrificación fue superior al 80%. Los parámetros más significativos de esta modelación matemática fueron el rendimiento neto de bacterias (Yh) y la hidrólisis (kh). Estos hallazgos demuestran la importancia de plantear modelos conceptuales y matemáticos de desnitrificación usando SSON. Este estudio sería una primera aproximación de un modelo matemático de desnitrificación en contragradiente, usando a los SSON como fuente de carbono y portador de biopelícula.

Modeling snowflake divertors in MAST-U tokamak using UEDGE code

In a snowflake (SF) divertor, two magnetic field nulls are placed close to each other creating four strike points (SPs) cf. two in a standard single-null (SN) divertor. In preparation to MAST-U experiments, magnetic configurations with SN and SF divertors located symmetrically at the top and at the bottom of the tokamak were modeled using a two-dimensional multi-fluid code UEDGE with a full plasma transport model featuring charge-state-resolved sputtered carbon impurities. SF configurations with various relative locations of the nulls and small null separation were considered. The complex interplay of the plasma transport and magnetic configurations was comprehensively studied using a simple model for the theoretically predicted fast plasma mixing (the “churning” mode) in the two-null SF region. The modeling results show that: 1) SF-plus and SF-minus configurations with closely located nulls produce same plasma parameters and heat fluxes at same SPs; 2) SF divertors approach the outer and inner SP detachment conditions at lower upstream density w.r.t. SN divertor; 3) heat flux profiles at primary SPs are substantially broadened and peak values are reduced in SF configurations w.r.t. SN divertor; this effect becomes more pronounced with the fast plasma mixing increase; 4) with the SF mixing, secondary SPs receive up to 10% (each) of the heat flux to the primary outer SP.

Total Bilirubin Predicts Severe Progression of Diabetic Retinopathy and the Possible Causal Mechanism.

Early detection and treatment are key to delaying the progression of diabetic retinopathy (DR), avoiding loss of vision, and reducing the burden of advanced disease. Our study is aimed at determining if total bilirubin has a predictive value for DR progression and exploring the potential mechanism involved in this pathogenesis. A total of 540 patients with nonproliferative diabetic retinopathy (NPDR) were enrolled between July 2014 and September 2016 and assigned into a progression group (N = 67) or a stable group (N = 473) based on the occurrence of diabetic macular edema (DME), vitreous hemorrhage, retinal detachment, or other conditions that may cause severe loss of vision following a telephonic interview in August 2019. After further communication, 108 patients consented to an outpatient consultation between September and November 2019. Our findings suggest the following: (1) TBIL were significant independent predictors of DR progression (HR: 0.70, 95% CI: 0.54–0.89, p = 0.006). (2) Examination of outpatients indicated that compared to stable group patients, progression group patients had more components of urobilinogen and LPS but a lower concentration of TBIL. The relationship between bilirubin and severe DR was statistically significant after adjusting for sex, age, diabetes duration, type of diabetes, FPG, and HbA1c (OR: 0.70, 95% CI: 0.912–0.986, p = 0.016). The addition of serum LPS and/or urobilinogen attenuated this association. This study concludes that total bilirubin predicts an increased risk of severe DR progression. Decreasing bilirubin might be attributed to the increased levels of LPS and urobilinogen, which may indicate that the change of bilirubin levels is secondary to intestinal flora disorder and/or intestinal barrier destruction. Further prospective investigations are necessary to explore the causal associations for flora disorder, intestinal barrier destruction, and DR.

On the low-temperature plasma discharge in methane/air diffusion flames

Interest in methane has grown recently because of its encouraging characteristics. However, methane comes with serious concerns regarding stability and flammability limitations. Some methods have been proposed to improve the ignition characteristics of methane in diffusion flame burners such as electrical fields, dielectric barrier discharge, and low-temperature plasma. In this study, an innovative single-element coaxial shear injector coupled with a high-voltage nanosecond pulse generator has been used to study the effects of low-temperature plasma (LTP) discharge on methane/air inverse diffusion flame at different plasma and flow conditions. The stability analysis focuses on the detachment conditions of the flame and how RNP discharge can delay this phenomenon, explaining the presence of an optimal operating point with the least applied energy. Comparing the lean blow-off limits for the cases with and without plasma discharge, it is shown that low-temperature plasma discharge enhances the flammability of the diffusion flame. The effect of LTP discharge on laminar flames is also discussed using chemiluminescence photography. It shows that the shape of the diffusion flame becomes more similar to premixed flame with more air entrainment and stability. Resultantly, it is shown that RNP discharge can improve the flame stability and ignition characteristics.

Bone marrow mesenchymal stem cells enhance autophagy and help protect cells under hypoxic and retinal detachment conditions.

Our study aimed to evaluate the protective role and mechanisms of bone marrow mesenchymal stem cells (BMSCs) in hypoxic photoreceptors and experimental retinal detachment. The cellular morphology, viability, apoptosis and autophagy of hypoxic 661w cells and cells cocultured with BMSCs were analysed. In retinal detachment model, BMSCs were intraocularly transplanted, and then, the retinal morphology, outer nuclear layer (ONL) thickness and rhodopsin expression were studied as well as apoptosis and autophagy of the retinal cells. The hypoxia‐induced apoptosis of 661w cells obviously increased together with autophagy levels increasing and peaking at 8 hours after hypoxia. Upon coculturing with BMSCs, hypoxic 661w cells had a better morphology and fewer apoptosis. After autophagy was inhibited, the apoptotic 661w cells under the hypoxia increased, and the cell viability was reduced, even in the presence of transplanted BMSCs. In retina‐detached eyes transplanted with BMSCs, the retinal ONL thickness was closer to that of the normal retina. After transplantation, apoptosis decreased significantly and retinal autophagy was activated in the BMSC‐treated retinas. Increased autophagy in the early stage could facilitate the survival of 661w cells under hypoxic stress. Coculturing with BMSCs protects 661w cells from hypoxic damage, possibly due to autophagy activation. In retinal detachment models, BMSC transplantation can significantly reduce photoreceptor cell death and preserve retinal structure. The capacity of BMSCs to reduce retinal cell apoptosis and to initiate autophagy shortly after transplantation may facilitate the survival of retinal cells in the low‐oxygen and nutrition‐restricted milieu after retinal detachment.

Differential detachment of intact and viable cells of different sizes using laser-induced microbubbles.

Single cell isolation is a prerequisite for the analysis of rare or small cell subtypes. Here, we selectively detach single cells in a heterogeneous population comprised of different morphological subtypes whose sizes vary in body and extension. Such a cellular environment is first accommodated for by a photomechanical method in which pulsed laser irradiation produces microbubbles from a polymer substrate, thus pushing out and detaching cultured cells in an intact, viable, and spatially tailored way. While this has previously only bene used at a very low cell density with lack of quantitative characterization, we determine optimal detachment conditions for different cell sizes in terms of an optical fluence and the number of laser pulses. Importantly, our approach is employed to isolate cancer cells with inherent size variation and elucidate cellular heterogeneity in drug sensitivity: i.e., higher resistance for larger cell size. For cells detached by laser-induced microbubbles, morphology, proliferation, and viability are compared with those of conventional trypsin-treated cells detached without any spatial selectivity. These results support the suitability of our photomechanical method for biochemical screen and secondary analysis of cells with unusual responses.

Mobilization of Attached Clustered Colloids in Porous Media

AbstractThe models for colloidal mobilization in porous media are often based on Derjaguin‐Landau‐Verwey‐Overbeek interaction energy profiles. Despite abundant evidence on mobilization of particle clusters, the models to date have been limited to single colloid‐surface Derjaguin‐Landau‐Verwey‐Overbeek calculations. We show through visualization tests, qualitative and quantitative modeling, and data evaluation, that the widely accepted single colloid‐single surface isolation does not always adequately describe colloid behavior. The experiments were performed with kaolinite and latex particles mobilized from sand grains and glass beads in a transparent visualization cell. The particles were mobilized under increasing velocity and pH and decreasing salinity. The detachment conditions were determined by a torque balance of electrostatic, drag, lifting, and gravity forces, combined with a theory of a contact area between a single soft particle and a plane surface. The tests show that the calculations based on the mechanical equilibrium of a single particle on a plane surface significantly underestimate the critical detachment velocity. A better prediction is obtained using a cluster approximation. High‐resolution images taken during mobilization tests show 2‐12 particle clusters on media surface and in its proximity. The mechanical‐equilibrium calculations show that the attaching torque for clusters with assumed size and cylindrical shape is significantly higher than that for single particles. The critical detachment velocity of clusters, derived from the mechanical‐equilibrium force and torque balances, is higher than for single particles and provides a better fit to the experimental data. Our study suggests that a cluster approximation can accurately predict the mobilization of colloids in porous media.

Jorunnamycin A from Xestospongia sp. Suppresses Epithelial to Mesenchymal Transition and Sensitizes Anoikis in Human Lung Cancer Cells.

Metastasis is a key driving force behind the high mortality rate associated with lung cancer. Herein, we report the first study revealing the antimetastasis activity of jorunnamycin A, a bistetrahydroisoquinolinequinone isolated from a Thai blue sponge Xestospongia sp. evidenced by its inhibition of epithelial to mesenchymal transition (EMT), sensitization of anoikis, and suppression of anchorage-independent survival in human lung cancer cells. Treatment with jorunnamycin A (0.05-0.5 μM) altered the expression of p53 and Bcl-2 family proteins, particularly causing the down-regulation of antiapoptosis Bcl-2 and Mcl-1 proteins. Under detachment conditions for 12 h, jorunnamycin A-treated cells exhibited diminution of pro-survival proteins p-Akt and p-Erk as well as the survival-promoting factor caveolin-1. Corresponding with the inhibition on the Akt and Erk pathway as well as activation of p53, there was an increase in the epithelial marker E-cadherin and a remarkable decrease of EMT markers and associated proteins including vimentin, snail, and claudin-1. As the loss of anchorage dependence is an important barrier to metastasis, the observed inhibitory effects of jorunnamycin A on the coordinating networks of EMT and anchorage-independent growth emphasize the potential development of jorunnamycin A as an effective agent against lung cancer metastasis.

Adhesion and debonding in a model of elastic string

We study the problem of adhesion and debonding of an elastic body interacting with a rigid substrate through a layer made of soft breakable adhesive material. The general problem is formulated in the multidimensional vectorial case, while a detailed analysis is carried for the one dimensional case leading to the study of a 1D semilinear wave equation. The initial boundary value problem is affected by the presence of a source term characterizing the interaction of the string withe the adhesive layer. This discontinuous force jumps to zero when a critical value of the displacement is reached. We obtain conditions for the initial boundary value problem ensuring the regularity of the solutions and the attachment–detachment conditions. Finally, we focus on a numerical investigation of the problem by considering regularizations of the source term and different initial conditions.