Kinetic Mode Research Articles

Impurity effects on kinetic ballooning instability in high q regions of tokamak plasmas

Abstract The impurity effects on kinetic ballooning modes (KBMs) in high q regions of tokamak plasmas are numerically investigated, using a full gyrokinetic description for main and impurity ions. The findings indicate that the critical plasma pressure ratio β c for KBM is significantly lower (higher) than the first (second) stable threshold β MHD predicted by MHD theory. The KBM exhibits stronger extended instabilities for low q , while the instability region of KBM becomes significantly narrow for high q , resulting in a more concentrated instability window (localized in narrow medium- β region). In addition, the contributions from electromagnetic effect and Shafranov shift are identified in detail, i.e. the electromagnetic destabilizing effect is suppressed by the Shafranov shift, and strong stabilizing effect of Shafranov shift for high β e or α on KBM is pronounced. The impurity ions with negative gradient ratio L e z have stabilizing (destabilizing) effects on KBMs for high (low) q . Such distinct behaviors are demonstrated to be associated with the used parameters close to the second and first unstable α region, i.e. the instability reduces and enhances with the increase of α , respectively. Significantly, the presence of impurities, regardless of the peaking directions of their density profiles, serves to stabilize KBMs and reduce the window of extended instability for high q region, which is in significant contrast with the results for low q region. Furthermore, high concentration, steep negative gradient ratio L ez , and high mass numbers of impurity ions as well as large temperature gradient η i and η e contribute to the stabilization of KBMs and improvement of confinement in high q regions of tokamaks. The region of stabilizing effect of magnetic shear on KBM, is found not belonging to the conventional magnetic shear region, but shows strong sensitivity to q value.

Finite-β turbulence in Wendelstein 7-X enhanced by sub-threshold kinetic ballooning modes

Abstract Magnetic fluctuations affecting turbulence and transport, which are manifest at finite normalized plasma pressure beta, pose a significant challenge to magnetic confinement fusion devices aiming to achieve high performance. Such regimes are not yet comprehensively understood in stellarator geometry. This work presents simulations of electromagnetic instabilities and high-beta turbulence in the Wendelstein 7-X (W7-X) stellarator, showing how ion-temperature-gradient-driven (ITG) turbulence is enhanced by unconventional kinetic ballooning modes well below the ideal MHD threshold. These sub-threshold KBMs (stKBMs) become strongly excited in the turbulent state and enable higher fluxes via zonal-flow erosion. The threshold of stKBM impact on turbulent fluxes is heavily dependent on the pressure gradient, evidenced here by the enhanced destabilization and fluxes resulting from the inclusion of an electron temperature gradient. Understanding and controlling these stKBMs will be paramount for W7-X and potentially other stellarators to achieve optimal performance.

Blue Phase-Polymer-Templated Ferroelectric Nematic Liquid Crystal.

Ferroelectric nematic liquid crystals (NFLCs) are promising electronic materials owing to their giant permittivity, polarization, and nonlinear optical coefficients. Although it is difficult to polymer-stabilize the NFLC orientation state due to their low affinity to polymers, in this study, we have succeeded in stabilizing the orientation into a blue phase (BP) three-dimensional structure by using BP polymer networks. This BP polymer-templated NFLC retains their ferroelectric properties and stabilizes with macroscopically canceled polarization due to the BP structure. The large polarization and dielectric constant of the NFLCs resulted in a large electro-optical Kerr effect. In addition, Curie point was observed in the BP polymer-templated NFLC, indicating the existence of multiple kinetic modes in the NFLCs themselves. This breakthrough expands the range of applications for both BPs and NFLCs.

Implementation of magnetic compressional effects at arbitrary wavelength in the global version of GENE

The global tokamak code GENE has been extended including the effect of magnetic compression caused by B1,|| turbulent fluctuations of the magnetic field parallel to the equilibrium one. This paper outlines the basic structure of the algorithm, valid at arbitrary wavelengths of the gyrokinetic fluctuations, with emphasis on the numerical construction of the so-called “gyrodisk-integral” operators necessary for the model. The numerical implementation is successfully verified against radially local simulations, recovering excellent agreement. Global tokamak simulations are presented as well. The upgrade enables studying a large variety of new physical scenarios at high plasma-β, such as kinetic ballooning modes, MHD-like modes or the interaction of B1,|| with fast particle modes, reducing the gap between gyrokinetic models and physically realistic systems.

Verification of the kinetic electron role in the microinstabilities in a negative triangularity model equilibrium

Effect of kinetic electrons on negative triangularity plasmas has been investigated and compared against the corresponding positive triangularity plasmas, using the global gyrokinetic code X-point Gyrokinetic Code with scale-separated delta-f option without Coulomb collisions. Our model magnetic equilibria have strong positive and negative triangularities and weak magnetic shear. However, unusually large ρi/a and low density plasmas are chosen to maximize the nonlocal effect to investigate the finite ρi effect and to be clearly away from kinetic ballooning modes. Similar conclusions to previous flux tube and global simulations have been obtained in this highly nonlocal model plasma: it is essential to include kinetic electrons in the micro-instability study of negative triangularity plasmas. Most physics findings agree with existing reports, with some disagreement. We offer a new “effective trapping fraction” concept that can add to the explanation of the growth rate difference between NT and PT plasmas, pointing to the significant variation in trapped particle fractions that have turning points in the mode growth regions.

Investigation on Swelling of Agar-Based Antibacterial Hydrogels for Hard-to-Heal Wound Dressings.

Despite a wide range of available wound treatments, hard-to-heal wounds still pose a challenge. Hydrogels are often used as dressings for these wounds, because they sustain moisture in the wound environment, supporting the natural healing process. However, it is still not fully understood how physicochemical properties of hydrogel matrix affect the drug release process. Thus, detailed swelling kinetics examination coupled with modeling is needed together with studies on drug release. In this regard, several hydrogels based on plant-derived agar and modified with amikacin sulfate were investigated. The main properties of hydrogels were examined focusing on detailed swelling kinetics. Drug release was studied as microbiological activity against E. coli and S. Epidermidis strains. The obtained hydrogels were characterized by high swelling, reaching values in range from 465-1300 %, fitting the second order kinetics mode and exhibiting the quasi-Fickian diffusion properties. Furthermore, there was no correlation found between swelling properties and antibacterial activity against tested strains. The results confirmed that presented hydrogel materials have desirable properties for application as dressings for hard-to-heal wounds. The suggested compositions are a promising base for modification with other active substances (e. g., regenerative, anti-inflammatory) and studying the broader correlation between swelling and drug release.

Synthesis of a novel bio-based curing agent and the curing behavior of the corresponding epoxy asphalt system

Traditional epoxy asphalt is made from petroleum resources. However, petroleum-based materials may cause environmental pollution and are not renewable. In this study, a bio-based curing agent MYM was synthesized from Maleic anhydride and Myrcene. The cured epoxy EP/MYM with the weight ratio of 1:1 were prepared. When preparing the modified asphalt, carboxyl-terminated liquid nitrile butadiene rubber (CTBN) was incorporated into the EP/MYM system to obtain the EP/MYM/CTBN modified asphalt system (referred to EMC epoxy asphalt). Firstly, the chemical structure of MYM was characterized using Fourier transform infrared spectroscopy (FTIR). Secondly, the mechanical properties and thermal stability of the cured EP/MYM were investigated by tensile test and thermogravimetric analysis (TG). Thirdly, the novel EMC epoxy asphalt was prepared and its composition was optimized. The curing behavior of the EMC epoxy asphalt was investigated by differential scanning calorimetry (DSC). And the time-temperature-transition diagrams (TTT diagrams) were plotted to determine the optimal curing process. Then the surface micro-morphology of EMC epoxy asphalt was investigated by atomic force microscopy (AFM). Finally, the high-temperature viscoelastic properties of EMC epoxy asphalt were investigated using dynamic shear rheology (DSR) tests. The results showed that EP/MYM has better mechanical strength and more excellent flexibility than those of EP/MTHPA and EP/MHHPA. The weight ratio of EP:MYM:CTBN was 10:8:1.5, and the optimal amount of diluent was 8 % of the total weight of the modifier. The semi-empirical kinetic modes of curing reaction were used to plot the TTT diagram of EMC epoxy asphalt, thus determining its curing technique as 120℃/2 h+160℃/3 h. The cured EMC epoxy asphalt showed uniform alternation of light and dark areas in the AFM images, indicating good compatibility and stability. The high-temperature deformation resistance of EMC epoxy asphalt was significantly improved compared to the base asphalt. The novel epoxy asphalt system prepared in this research provides a new route for the development of echo-friendly epoxy asphalt.

HS-AFM single-molecule structural biology uncovers basis of transporter wanderlust kinetics.

The Pyrococcus horikoshii amino acid transporter GltPh revealed, like other channels and transporters, activity mode switching, previously termed wanderlust kinetics. Unfortunately, to date, the basis of these activity fluctuations is not understood, probably due to a lack of experimental tools that directly access the structural features of transporters related to their instantaneous activity. Here, we take advantage of high-speed atomic force microscopy, unique in providing simultaneous structural and temporal resolution, to uncover the basis of kinetic mode switching in proteins. We developed membrane extension membrane protein reconstitution that allows the analysis of isolated molecules. Together with localization atomic force microscopy, principal component analysis and hidden Markov modeling, we could associate structural states to a functional timeline, allowing six structures to be solved from a single molecule, and an inward-facing state, IFSopen-1, to be determined as a kinetic dead-end in the conformational landscape. The approaches presented on GltPh are generally applicable and open possibilities for time-resolved dynamic single-molecule structural biology.

On the importance of parallel magnetic-field fluctuations for electromagnetic instabilities in STEP

This paper discusses the importance of parallel perturbations of the magnetic-field in gyrokinetic simulations of electromagnetic instabilities and turbulence at mid-radius in the burning plasma phase of the conceptual high-β, reactor-scale, tight-aspect-ratio tokamak STEP. Previous studies have revealed the presence of unstable hybrid kinetic ballooning modes (hKBMs) and subdominant microtearing modes at binormal scales approaching the ion Larmor radius. In this STEP plasma it was found that the hKBM requires the inclusion of parallel magnetic-field perturbations to be linearly unstable. Here, the extent to which the inclusion of fluctuations in the parallel magnetic-field can be relaxed is explored through gyrokinetic simulations. In particular, the frequently used MHD approximation (dropping δB∥ and setting the ∇B drift frequency equal to the curvature drift frequency) is discussed and simulations explore whether this approximation is useful for modelling STEP plasmas. It is shown that the MHD approximation can reproduce some of the linear properties of the full STEP gyrokinetic system, but is too stable at low ky and nonlinear simulations using the MHD approximation result in very different transport states. It is demonstrated that the MHD approximation is challenged by the high β′ values in STEP, and that the approximation improves considerably at lower β′ . Furthermore, it is shown that the sensitivity of STEP to δB∥ fluctuations is primarily because the plasma sits close to marginality and it is shown that in slightly more strongly driven conditions the hKBM is unstable without δB∥. Crucially, it is demonstrated that the state of large transport typically predicted by local electromagnetic gyrokinetic simulations of STEP plasmas is not solely due to δB∥ physics.

Role of electrostatic perturbation on kinetic resistive wall mode with application to spherical tokamak

A more complete non-perturbative magnetohydrodynamic (MHD)-kinetic hybrid formulation is developed by including the perturbed electrostatic potential δφ in the particle Lagrangian. The fluid-like counter-parts of the hybrid equations, in the Chew-Goldberger-Low high-frequency limit, are also derived and utilized to test the new toroidal implementation in the MARS-K code. Application of the updated non-perturbative hybrid model for a high-β spherical tokamak plasma in MAST finds that the perturbed electrostatic potential generally plays a minor role in the n = 1 (n is the toroidal mode number) resistive wall mode instability. The effect of δφ is largely destabilizing, with the growth rate of the instability increased by several (up to 20) percent as compared to the case without including δφ. A similar relative change is also obtained for the kinetic-induced resonant field amplification effect at high-β in the MAST plasma considered. The updated capability of the MARS-K code allows quantitative exploration of drift kinetic effects on various MHD instabilities and the antenna-driven plasma response where the electrostatic perturbation, coupled to magnetic perturbations, may play important roles.

Effect of preparation conditions of nanocrystalline Pd/MgO catalysts on their performance in selective hydrogenation of acetylene

In the present work, an alkoxide sol-gel method was applied to prepare Pd/MgO catalysts. The sol-gel procedure was followed by supercritical drying (aerogels) or conventional drying (xerogels) in a furnace. These materials were compared with the impregnated samples. The Pd loading was 1 wt% in all the cases. The as-prepared catalysts were characterized by a set of physicochemical methods. Both the type of the Pd precursor and the preparation route were found to affect the porous structure of the materials as well as the dispersion of the palladium particles and their localization over the MgO support. Both the xerogel and incipient wetness impregnation methods lead to a narrower pore size distribution in comparison to the aerogel technique. The most dispersed particles with an average size of ∼ 2.0–2.2 nm were observed for the samples prepared by xerogel and impregnation methods. In the case of aerogel-prepared samples, metallic palladium particles possess bimodal distribution with average diameters of 4.3 and 8.4 nm. The best catalytic performance in acetylene hydrogenation to ethylene (50 % acetylene conversion at 37 °C with selectivity ∼60 %) was observed for the Pd/MgO catalyst prepared via the aerogel route using [Pd(NH3)4](NO3)2. Compared to other samples, this material is characterized by relatively weak metal-support interactions and the availability of active sites for reactants, which ensures the kinetic mode of the hydrogenation reaction (Ea = 74.9 kJ/mol).

Stochastic Assessment of Dissolution at Fluid‐Mineral Interfaces

AbstractChemical weathering associated with dissolution/precipitation at interfaces between minerals and flowing fluids is key for the evolution of geologic systems, including groundwater contamination and storage capacity. Relying on Atomic Force Microscopy (AFM) yields reaction rates at nanoscale resolutions. Challenges limiting our ability to quantify heterogeneity associated with these processes include establishing reliable platforms allowing AFM imaging of real‐time and in situ absolute material fluxes across mineral surfaces under continuous flow conditions to complement typically acquired surface topography images. We provide an experimental workflow and heterogeneous absolute rates at the nanoscale across the surface of a calcite crystal under dissolution. These high‐quality experimental observations are then interpreted through a stochastic approach. The latter is geared to embed diverse kinetic modes driving the degree of spatial heterogeneity of the reaction and corresponding to different mechanistic processes documented across the crystal surface.

Progress of open systems at Budker Institute of Nuclear Physics

This paper is based on a report at the 2nd International Fusion Plasma Conference & 13th International Conference on Open Magnetic Systems for Plasma Confinement (iFPC & OS 2023), August 21–25, 2023, Busan, Korea and provides a brief overview of the status of work at the Budker Institute on the study of hot plasma confinement in open-type magnetic traps with a linear axisymmetric configuration. The main attention is paid to key problems: magnetohydrodynamics (MHD) stability in regimes with extremely high relative pressure, longitudinal electronic thermal conductivity, stability with respect to the development of kinetic modes and transverse transport. This paper provides an overview of the methods we are developing to address these problems, the experimental and theoretical results achieved and plans for future development. The last section of the article provides brief information about the preliminary design of the gas-dynamic multiple-mirror trap device, the development of which has been completed.

Kinetics of zinc leaching from intermediate feedstocks

The aim of the work was to study the leaching kinetics of zinc from the compound CaO. ZnO, formed during the sintering of dust from electric arc furnaces with limestone, as well as to identify the mechanisms by means which such chemical interactions occur. The object of the study was the dust sinter of electric arc furnaces with limestone obtained at the Chelyabinsk Zinc Plant. It was found that zinc is contained in sinter in the form of readily soluble CaO. ZnO. The elemental composition of the initial dusts and sinter was determined by the spectral atomic emission method using inductively coupled plasma on a Spectroblue optical emission device and spark spectrometry. The phase composition of the materials was studied on a Bruker D8 Advance X-ray diffractometer. The initial sinter was milled to apowder state having a particle size of ~0.04 mm and with a yield of ~97% of the composition, %: 11.9 Zn; 28.5 Ca; 16.6 Fe; 0.38 Mg; 0.14 Pb; 0.05 Cl. Experiments on the leaching of Zn with NaOH solution were carried out at the following parameters: the initial concentration of zinc in the pulp was 0.202 g-ion/dm3 ; alkali concentration – 5‒9 mol/dm3 NaOH; L:S = 9:1; pulp mixing rate – 10‒20 rad. c-1; temperature – 333‒363 K; duration – 0.5–2.5 hours. It has been shown that zinc from sinter passes into solution as sodium tetrahydroxozincate Na2[Zn(OH)4], while calcium remains in the cake, mainly as insoluble Ca(OH)2, which reacts with carbon dioxide to form insoluble calcium carbonate CaCO3. The process of dissolving zinc from the sinter corresponds to the external diffusion mode of mutual transfer of the initial reagents and reaction products through the surface layer of the liquid at the interface of the “liquid–solid” phases with an activation energy value equal to 12.44 kJ/mol. Thus, with the studied parameters of zinc leaching with NaOH solution, the process proceeds in an external diffusion mode. The results are of interest when identifying conditions corresponding to the intradiffusion and kinetic modes of zinc leaching.

On electromagnetic turbulence and transport in STEP

In this work, we present first-of-their-kind nonlinear local gyrokinetic (GK) simulations of electromagnetic turbulence at mid-radius in the burning plasma phase of the conceptual high-β, reactor-scale, tight-aspect-ratio tokamak Spherical Tokamak for Energy Production (STEP). A prior linear analysis in Kennedy et al (2023 Nucl. Fusion 63 126061) reveals the presence of unstable hybrid kinetic ballooning modes (KBMs), where inclusion of the compressional magnetic field fluctuation, δB∥ , is crucial, and subdominant microtearing modes (MTMs) are found at binormal scales approaching the ion-Larmor radius. Local nonlinear GK simulations on the selected surface in the central core region suggest that hybrid KBMs can drive large turbulent transport, and that there is negligible turbulent transport from subdominant MTMs when hybrid KBMs are artificially suppressed (through the omission of δB∥ ). Nonlinear simulations that include perpendicular equilibrium flow shear can saturate at lower fluxes that are more consistent with the available sources in STEP. This analysis suggests that hybrid KBMs could play an important role in setting the turbulent transport in STEP, and possible mechanisms to mitigate turbulent transport are discussed. Increasing the safety factor or the pressure gradient strongly reduces turbulent transport from hybrid KBMs in the cases considered here. Challenges of simulating electromagnetic turbulence in this high-β regime are highlighted. In particular the observation of radially extended turbulent structures in the absence of equilibrium flow shear motivates future advanced global GK simulations that include δB∥ .

Abstract 1210: High-throughput time-resolved single-cell analysis of T-cell activation

Abstract How immune cells respond to stimuli is fundamental in developing adoptive cell therapies, vaccines, and other immunotherapies. T cells dynamically undergo activation, exhaustion, expansion, phenotype switching, and cell killing. Flow cytometry is the gold standard method for characterizing these at high throughput, typically by comparing T cell populations before and at different timepoints after treatment. This approach is limited to population-level analyses and overlooks any heterogeneity of individual T cell responses over time, which may contribute to variability in response. Here, we describe the development of a novel flow cytometry-based method (Time-lapse flowTM) to characterize immune cell responses over time at the single cell level. To measure the same cells repeatedly on a flow cytometer, we employed a new optical barcoding technology called laser particles (LPs) that provide individual cells with a unique spectral signature that can be tracked over the course of multiple measurements. Using a custom flow cytometer with fluorescence and LP detection, we performed a multi-day assay to capture how T cell marker expression changes over time after CD3/CD28 activation. Specifically, we used releasable antibodies to quantify PD1, CD69 and CD25 at each time-point and correlated these expression kinetics with cell function at the end of the assay by measuring cytokine secretion (IFNg, IL2, TNFa) after PMA/ionomycin stimulation. We found significant cellular heterogeneity in kinetic profiles of PD1, CD69 and CD25 expression, with different dominant ‘kinetic modes’ present for each marker. For example, while a large proportion of PD1 expression was transient (positive on day 1, but not on days 2 and 3), nearly all cells that express CD69 on day 1 retained their expression on day 2. We also found that T cells with late expression of PD1 had significantly more cytokine secretion compared to cells that were initially positive for PD1. These results were replicated with at least 3 replicate samples for multiple donors. Differences in kinetic phenotypes were not explained by conventional phenotyping with CD4, CD8, CD45RA and CCR7. To date, immune cell phenotyping with flow cytometry involves classifying cell types through their marker expression profiles at a single time-point. Here, we introduce a novel approach for acquiring time-resolved single-cell data with a flow cytometer and applied it to study T cell activation. We found novel kinetic phenotypes of T cells defined by their marker expression over time, which also correlated to their functional potential (cytokine secretion). These kinetic phenotypes could not be identified with conventional flow cytometry. Our approach could have significant implications for immunotherapy development, particularly in identifying the most suitable cell populations to use, understanding mechanisms of exhaustion and persistence, and elucidating the basis of donor variability. Citation Format: Sheldon J. Kwok, Sarah Forward, Emane Rose Assita, Trevor Brown, Marissa Fahlberg, Pratip Chattopadhyay. High-throughput time-resolved single-cell analysis of T-cell activation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1210.

Abstract 1666: A novel sox-based continuous and homogeneous assay for the discovery of inhibitors of inactive and active AKT

Abstract Introduction: The activity of protein kinases plays a critical role in the aberrant activation of oncogenic signaling pathways which can drive tumorigenesis and malignant transformation in cancer. AKT has been shown to be both upregulated and mutated in cancer cells allowing it to serve as a driver of cancer cell growth and progression. Inhibition of AKT activation and activity are both attractive targets for effective cancer drug discovery. Experimental Procedures: We developed continuous, homogeneous assays for unactive AKTs. A peptide substrate, modified with a sulfonamido-oxine fluorophore (Sox), utilizes chelation-enhanced fluorescence to enable a real-time readout of AKT-driven phosphorylation. First, a subset of 30,000 Sox-containing sequences were evaluated for AKT substrate candidates, selecting for assay robustness and specificity. A physiologically relevant peptide substrate was identified and used to develop a kinetic assay to monitor AKT1 activation and activity. Unactive AKT1 was incubated with DOPS/DOPC and PIP3, which mimics the plasma membrane, allowing the PH domain of AKT to bind, leading to a conformational change that enables full activation of AKT by PDK1 and MK2. Upon assay initiation, active AKT phosphorylates the sensor peptide, and the resulting signal is read in kinetic mode using a fluorescence intensity readout. First derivative plots for each progress curve were generated; the slope of the linear regions of each plot, representing acceleration towards a steady-state, were used to determine relative rates of activation for each AKT. Results: We developed a novel assay for AKT activation and substrate phosphorylation utilizing AQT0076, DOPS/DOPC, PIP3, PDK1, and MK2. With a mix of classical AKT inhibitors and allosteric inhibitors that rely on an inactive “PH-in” conformation, we demonstrated inhibition and quantified inhibitor potency of both active “PH-out” AKT activity and inactive “PH-in” AKT activation via dose-response measurements of steady-state rate and rate acceleration, respectively. Conclusions: A robust, homogeneous assay was developed to simultaneously monitor AKT activation and substrate phosphorylation kinetically over time. Through a continuous assay, we captured both steady-state rates and rate acceleration as a function of inhibitor concentration, allowing for accurate quantitation of both classes of AKT inhibitors in a single experimental format. With some inhibitors, we observed potencies that matched reported literature values, while with others we observed marked differences that may reflect a more physiological context that could translate through to higher efficacy in the clinic. This novel assay format provides a new tool that can be used in drug discovery to generate more effective next generation inhibitors of both AKT activation and subsequent substrate phosphorylation to prevent cancer cell growth and progression. Citation Format: Susan Cornell-Kennon, Daniel Urul, Matthew Hakar, Hayley McMahon, Khanh Huynh, Earl May, Erik Schaefer. A novel sox-based continuous and homogeneous assay for the discovery of inhibitors of inactive and active AKT [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1666.

Novel Thiazolidine‐2,4‐Dione Derivatives as Potential VEGFR‐2 Inhibitors: Synthesis, Biological Testing, and in Silico Studies

AbstractIn this work novel 2,4‐dioxothiazolidine‐derived compounds targeting VEGFR‐2 were designed and synthesized. Such compounds were evaluated for their anti‐proliferative and VEGFR‐2 inhibitory abilities. Compound 17 specifically demonstrated the strongest anti‐proliferative activity against the HCT‐116 cell line, with an IC50 value of 10.09 μM. Additionally, compounds 15, 18, and 19 revealed good anti‐proliferative effects with IC50 values of 12.46, 16.87, and 12.35 μM, respectively. Compound 17 demonstrated potent anti‐VEGFR‐2 efficacy, with an IC50 value of 0.068 μM, which was comparable to sorafenib (IC50 value of 0.058 μM). Compound 17 induced apoptosis in HCT‐116 cancer cells and caused G0‐G1 phase cell cycle arrest. Furthermore, it upregulated BAX levels (5.1‐fold) and downregulated Bcl‐2 levels (4.2‐fold), indicating its pro‐apoptotic effects. Compound 17 also increased caspase‐8 and caspase‐9 levels by 3.3‐fold and 4.7‐fold, respectively, compared to the control. The computational studies provided insights into the kinetic, structural properties, and binding mode of the VEGFR‐2‐17 complex. The DFT calculations elucidated compound 17′s structural and electronic properties, while computational ADMET and toxicity tests suggested acceptable degrees of drug‐likeness potential for the synthesized compounds. Our findings suggest that compound 17 holds promise as a potent apoptotic VEGFR‐2 inhibitor and may guide future efforts in developing new anticancer drugs.

Fine-tuning covalent organic frameworks for structure-activity correlation via adsorption and catalytic studies

In applications utilizing Covalent Organic Frameworks (COFs) for adsorption, the interplay between crystallinity (vis-à-vis surface area) and active sites still remains ambiguous. To address this, the present study introduces three isoreticular COFs—COP-N18 (covalent organic polymer with short-range order), COF-N18 (COF having long-range order), and COF-N27 (semicrystalline COF with pyridyl heteroatoms)—to explore this duality. Through systematic variations in structural order, pore volume, and pore-wall nitrogen content, we aim to establish a structure–activity relationship (SAR) for these COFs via adsorption and catalysis, using CO2 and I2 as probes. Our investigation highlights the positive influence of crystallinity, surface area, and pore volume in adsorption as well as catalysis. However, the presence of heteroatoms manifests complex behavior in CO2 adsorption and CO2 cycloaddition reactions with epoxides. COF-N18 and COF-N27 showed comparable CO2 uptake capacities at different temperatures (273, 293, and 313 K) and ∼1 bar pressure. Additionally, CO2 cycloaddition reactions were performed with substrates possessing different polarities (epichlorohydrin, 1,2-epoxydodecane) to elucidate the role of COF surface polarity. Further investigation into iodine adsorption was performed to understand the impact of COF structural features on the modes of adsorption and adsorption kinetics. Improvements in COF-crystallinity results in faster average iodine uptake rate at 80% (K80% = 1.79 g/h) by COF-N18. Whereas, heteroatom doping slows down iodine adsorption kinetics (0.35 g/h) by prolonging the adsorption process up to 72 h. Overall, this study advances our understanding of COFs as adsorbents and catalysts, providing key insights into their SAR while emphasizing structural fine-tuning as a key factor for impactful environmental applications.

KINETICS OF CATHODIC HYDROGEN EVOLUTION ON MOLYBDENUM DISILICIDE IN ACID SULPHATE MEDIA

The kinetics and mechanism of hydrogen evolution on the MoSi2 electrode in x M H2SO4 + (0.5 - x) M Na2SO4 (x = 0.50; 0.35; 0.20) solutions have been studied. The cathodic polarization curves of MoSi2 in the studied solutions are characterized by Tafel region with a slope of (-0.070)±0.002 V. The reaction order of the cathodic process with respect to hydrogen ions at the potentials of Tafel region is ~1.0; the derivative of the electrode potential with a change in electrolyte acidity is ~0.072 V. The impedance spectra of the MoSi2 electrode in the studied potential range have the shape of a semicircle located in the capacitive half-plane, with the centre in the region of positive values of the imaginary impedance component; in the region of the highest frequencies, a short straight section is recorded on the impedance plots, indicating the presence of pores in the surface layer of the electrode. To describe the hydrogen evolution reaction on MoSi2, we used an equivalent electrical circuit, the Faraday impedance of which consists of series-connected charge transfer resistance (R1) and a parallel R2C2Zd-chain responsible for the adsorption of atomic hydrogen on the surface and its diffusion into the depth of the electrode material. The equivalent circuit also includes the solution resistance (Rs) and the double layer capacitance impedance, which is modeled by the constant phase element CPE1. It is shown that the hydrogen evolution reaction on molybdenum disilicide in a sulphuric acid electrolyte proceeds along the discharge - recombination route with a quasi-equilibrium discharge stage when the Temkin logarithmic isotherm for adsorbed atomic hydrogen is fulfilled. The hydrogen evolution reaction is complicated by hydrogen absorption proceeding in the mode of solid-phase diffusion kinetics.