Higher-order Reactions Research Articles

Characteristics of unsteady thermo-bioconvection chemical reactive stagnation point flow of trihybrid nanofluid around rotating sphere with Oxytactic Microorganisms

The present study is to highlight the significance of viscous dissipation, Joule heating and magnetic field on the stagnation point Darcy-Forchheimer flow of THNF (trihybrid nanofluid) around a spinning sphere containing Oxytactic and gyrotactic microorganisms. The analysis also includes the effects of heat generation and higher-order chemical reaction. A trihybrid nanofluid consisting of water (H2O) as the base fluid and TiO2,Cu and Fe3O4 nanoparticles is used. The Hamilton–Crosser model of trihybrid nanofluid is used in this work to compare their respective performance. This model is applicable to the optimization and design of sophisticated cooling systems where effective heat transfer is necessary, like electronic cooling, nuclear reactors, and high-performance heat exchangers. This model is used in biomedical engineering to comprehend drug delivery systems where exact control over reactions and fluid dynamics is required. Oxytactic microorganisms are important because they help break down contaminants in environmental engineering and wastewater treatment procedures. The fundamental system of the PDEs (partial differential equations) and the pertinent BCs (boundary conditions) have been transformed for computation using a few appropriate transformations. The numerical estimations for the appropriate system of differential equations are derived by employing the shooting approach (Bvp4c). Extensive studies are conducted to examine the effects of pertinent limitations on the rates of heat transfer, mass transfer, density of Oxytactic and gyrotactic microorganisms for both hybrid and trihybrid nanofluid. Among the various findings of this investigation is the observation that a higher Oxytactic and gyrotactic microorganisms Schmidt numbers result in a slower trihybrid nanofluid and hybrid nanofluid Oxytactic and gyrotactic microorganism's distributions. By increasing the value of Peclet number up to 7% the values of local density gyrotactic microorganisms enhance up to 9% .

Periodic wave solutions for a generalized reaction–convection–diffusion equation of high-order

In this paper, we investigate the uniqueness of periodic wave solutions for a generalized reaction–convection–diffusion equation with arbitrarily high-order reaction term or convection term. The main technique is to prove the monotonicity of the ratio of two Abelian integrals by a new criterion and Descartes’ rule of signs. A positive answer to a conjecture stated in Wei and Chen (2023) is given and some numeric simulations are carried out to illustrate the obtained theoretical results.

Physical limits to acceleration of enzymatic reactions inside phase-separated compartments.

We present a theoretical analysis of phase-separated compartments to facilitate enzymatic chemical reactions. While phase separation can facilitate reactions by increasing local concentration, it can also hinder the mobility of reactants. In particular, we find that the attractive interactions that concentrate reactants within the dense phase can inhibit reactions by lowering the mobility of the reactants. This mobility loss severely limits the potential to enhance reaction rates. Phase separation provides greater benefit in situations where multiple sequential reactions occur and/or high order reactions, provided the enzymes are unsaturated, transport to the condensate is not limiting, and the reactants are mobile. We show that mobility can be maintained if recruitment to the condensed phase is driven by multiple attractive moieties that can bind and release independently. However, the spacers necessary to ensure independence between stickers are prone to entangle with the dense phase scaffold. We find an optimal sticker affinity that balances the need for rapid binding/unbinding kinetics and minimal entanglement. Reaction rates can be accelerated by shrinking the size of the dense phase with a corresponding increase in the number of stickers. Our results showcase the potential capabilities of phase-separated compartments to act as biochemical reaction crucibles within living cells.

Multiscale Anion-Hybrid in Atomic Ni Sites for High-Rate Water Electrolysis: Insights into the Charge Accumulation Mechanism.

Single-atom catalysts, characterized by transition metal-(N/O)4 units on nanocarbon (M-(N/O)4-C), have emerged as efficient performers in water electrolysis. However, there are few guiding principles for accurately controlling the ligand fields of single atoms to further stimulate the catalyst activities. Herein, using the Ni-(N/O)4-C unit as a model, we develop a further modification of the P anion on the outer shells to modulate the morphology of the ligand. The catalyst thus prepared possesses high activity and excellent long-term durability, surpassing commercial Pt/C, RuO2, and currently reported single-atom catalysts. Notably, mechanistic studies demonstrated that the pseudocapacitive feature of multiscale anion-hybrid nanocarbon is considerable at accumulating enough positive charge [Q], contributing to the high oxygen evolution reaction (OER) order (β) through the rate formula. DFT calculations also indicate that the catalytic activity is decided by the suitable barrier energy of the intermediates due to charge accumulation. This work reveals the activity origin of single atoms on multihybrid nanocarbon, providing a clear experiential formula for designing the electronic configuration of single-atom catalysts to boost electrocatalytic performance.

Brownian motion and thermophoresis effects on radiative polar fluid flow with higher-order chemical reaction along a vertical porous plate

The unsteady simulation of hydromagnetic radiative polar fluid, including thermophoresis, Brownian motion, and higher-order chemical reactions across a perpendicular permeable plate with heat radiation, is performed numerically. The nonlinear PDEs are solved by the explicit finite difference technique and studio developer FORTRAN. The stability and convergence of the present model and a comparison are done to obtain accuracy. The effects of various parameters such as Brownian motion, thermophoresis, radiative heat transfer, and higher-order chemical reactions on the velocity, temperature, and concentration fields are investigated. It is found that the parameters have a significant influence on velocity and temperature profiles, angular velocity, concentration, shear stress, angular momentum density, and Nusselt and Sherwood numbers. In addition, the local share stress rises with the chemical reaction, Eckert number, and thermophoresis, whereas it decreases with the magnetic field and porous medium. In addition, the Nu (local) intensifies with higher order chemical reactions and porous mediums, whereas it falls with Eckert number, Brownian effects, micro-rotation, and thermophoresis. The concentration profile decreases with higher radiation, and the Lewis number whereas it augments with higher radiation. With an Eckert number and thermophoresis, the temperature and velocity increase. Additionally, the higher order of chemical reaction and Brownian motion augment the Sherwood number, whereas the chemical reaction, magnetic field, and porous medium reduce it. Moreover, the study may help to understand the dynamics of flow and heat transfer for the design and optimization of various engineering applications such as heat exchangers, pollutant dispersion models, energy systems, biomedical, and so on.

Irreversibility analysis of radiative Williamson nanofluid flow with higher order chemical reaction and quadratic drag force over an extended surface: Non-similar computations

This study aims to present non-similar solutions for the radiative Williamson nanofluid flow with a quadratic drag force effect over a horizontally extended surface. The sheet is extended along the X-axis, and the magnetic field is applied along the Y-axis, perpendicular to the flow. The Buongiorno nanofluid model is employed to incorporate the random dispersion and thermal characteristics of the nanofluid. The innovation in the proposed model lies in its consideration of the effects of viscous and ohmic dissipation, Robin boundary conditions, and higher-order chemical reactions. The governing equations for the flow are scaled down to the second level using an appropriate transformation combined with a non-similarity technique and computationally assessed using the MATLAB bvp4c algorithm. The significant influences of the dimensionless parameters on the velocity, thermal, and solutal fields are depicted graphically. The findings reveal that the fluid velocity diminishes with increasing Weissenberg and Hartmann numbers. The solutal field experiences a reduction with variations in the chemical reaction parameter, while it rises with an increase in the higher-order chemical reaction parameter. The wall heat transfer rate is augmented with higher Eckert and thermal Biot numbers. The mass transfer rate rises with higher values of the chemical reaction parameter, Schmidt number, and solutal Biot number. A comparison of the results from this study with previous research demonstrates strong agreement, affirming the validity of the proposed model. For the value of the Williamson parameter [Formula: see text], the percentage error of the present analysis with established studies is 0% and 0.096770%.

Scientific Deep Machine Learning Concepts for the Prediction of Concentration Profiles and Chemical Reaction Kinetics: Consideration of Reaction Conditions.

Emerging concepts from scientific deep machine learning such as physics-informed neural networks (PINNs) enable a data-driven approach for the study of complex kinetic problems. We present an extended framework that combines the advantages of PINNs with the detailed consideration of experimental parameter variations for the simulation and prediction of chemical reaction kinetics. The approach is based on truncated Taylor series expansions for the underlying fundamental equations, whereby the external variations can be interpreted as perturbations of the kinetic parameters. Accordingly, our method allows for an efficient consideration of experimental parameter settings and their influence on the concentration profiles and reaction kinetics. A particular advantage of our approach, in addition to the consideration of univariate and multivariate parameter variations, is the robust model-based exploration of the parameter space to determine optimal reaction conditions in combination with advanced reaction insights. The benefits of this concept are demonstrated for higher-order chemical reactions including catalytic and oscillatory systems in combination with small amounts of training data. All predicted values show a high level of accuracy, demonstrating the broad applicability and flexibility of our approach.

(Invited) Plasma-Enhanced Deposition Mechanism of Hydrogenated Amorphous Carbon Analyzed By Combining Reactive Species Measurement and Machine Learning

Hydrogenated amorphous carbon (a-C:H) thin films synthesized by plasma-enhanced chemical vapor deposition (PECVD)are widely used in various fields of science and technology. For example, they are essential as etching hard masks for the production of 3D-NAND flash memory, because of their high selectivity to Si-based materials and chemical stability. With the demand for higher aspect ratio etching, there is a strong need to improve etching resistance and reduce residual stress of a-C:H masks. They are also widely used in the field of tribology as an important coating for improving friction resistance and slidability. Analyzing the plasma process in which synergistic effects among reactive species and higher-order reactions contribute is generally difficult. Therefore, similar to other process technologies, machine learning-based condition optimization approaches have been actively investigated in recent years. However, machine learning models are generally black boxes, and it is difficult to understand their mechanism of action. Also, the versatility of the learning model is low between different devices. On the other hand, reactive species measurement is effective for understanding the reaction mechanism of the plasma process, but the synergy of multiple reactive species is still extremely complicated. In this study, the contribution of radical species to the etching resistance of a-C:H thin films were quantitatively analyzed using machine learning.The deposition of a-C:H by PECVD using H2/C3H6/CH4 plasma and etching with O2 plasma were alternately repeated at 120 conditions. The radicals generated during the film deposition were measured by a quadrupole mass spectrometer (QMS), and film thickness change during the etching was measured by spectroscopic ellipsometry (SE). A random forest model was learned to predict the etching rate from the mass spectra, and the contribution of each radical to the etching rate was quantitatively evaluated by SHapley additive exPlanation (SHAP).The distribution of SHAP values for the 10 most influential radicals is shown in Figure 1. The positive and negative SHAP values represent the correlation between QMS intensity and SHAP value. The radicals with high hydrogen ratios such as CH~CH4, C2H5, C4H9, C5H9, and C5H11 contributed to the increase of etching rate, while the radicals with low hydrogen ratios such as C3H3 and C5H5 contributed to the decrease of etching rate. The deposition of radicals with low hydrogen ratios and multiple bonds, and the effect of hydrogen extraction in the film are considered to have increased the density of a-C:H and reduced the etching rate. It was found that the control of C/H ratio of radicals as film precursors is important to improve etching resistance. Comparisons with different data set range or other contribution degrees such as LIME enable us to understand the mechanism of action of local active species. By using the contribution analysis methods, it is possible to quantitatively analyze the synergistic effect of reactive species in the process plasma. Figure 1

Bioconvection analysis of EMHD and dissipative Williamson nanofluid over a three dimensional Riga plate with Joule heating effect

ABSTRACT The current study investigates the weakly hydromagnetic and bioconvection nanofluid flow of Williamson fluid, which conveys gyrotactic microorganisms, over a three-dimensional Riga surface. The primary objective is to stabilize biological, mechanical, and thermal systems through the introduction of exponentially decaying rheology in both the momentum and energy equations, known as the electro-magneto-hydrodynamic actuator (EMHD). As such, the working fluid is assumed to be dissipative, with significant consideration given to the magnetic Reynolds number and a higher-order reaction rate. To simplify the phenomenon of suspended nanoparticles’ bioconvection, an appropriate similarity transformation is applied, converting the system of partial differential equations (PDEs) into systems of ordinary differential equations (ODEs). To analyze the governing flow parameters, the numerical approach, Galerkin Weighted Residual Method (GWRM), is employed. The results are presented through tables and graphs, providing valuable insights. The findings of the study highlight that Hartmann number improves the weak movement of the Williamson fluid, thermophoresis number positively affects all flow distributions. Moreover, the temperature field is influenced by Brownian motion, leading to inflation, while the concentration field experiences a decrease due to a lower number of fluid particles available for reaction. Furthermore, higher buoyancy forces indicate significant fluid movement, resulting in a reduction in the Williamson fluid chemical reaction rate.

Study of radiative heat and mass intensification with magnetic field for Casson and Williamson nanofluid flow model over a porous stretching sheet with higher-order chemical reaction: application of solar energy

Study of radiative heat and mass intensification with magnetic field for Casson and Williamson nanofluid flow model over a porous stretching sheet with higher-order chemical reaction: application of solar energy

Cross-Diffusion and Higher-Order Chemical Reaction Effects on Hydromagnetic Copper–Water Nanofluid Flow Over a Rotating Cone in a Porous Medium

Spin coating of engineering components with advanced functional nanomaterials which respond to magnetic fields is growing. Motivated by exploring the fluid dynamics of such processes, a mathematical model is developed for chemically reactive Cu–H2O magnetohydrodynamic (MHD) nanofluid swirl coating flow on a revolving vertical electrically insulated cone adjacent to a porous medium under a radial static magnetic field. Heat and mass transfer is included and Dufour and Soret cross-diffusion effects are also incorporated in the model. Thermal and solutal buoyancy forces are additionally included. To simulate chemical reaction of the diffusing species encountered in manufacturing processes, a higher-order chemical reaction formulation is also featured. Via suitable scaling transformations, the governing nonlinear coupled partial differential conservation equations and associated boundary conditions are reformulated as a nonlinear ordinary differential boundary value problem. MATLAB-based shooting quadrature with a Runge–Kutta method is deployed to solve the emerging system. Concentration, temperature and velocity variations for various nondimensional flow parameters have been visualized and analyzed. In addition, key wall characteristics, i.e., radial and circumferential skin friction, Nusselt number and Sherwood number, have also been computed. Validation with earlier studies is also included. The simulations indicate that when compared to a lower-order chemical reaction, a higher-order chemical reaction allows a greater rate of heat and mass transfer at the cone surface. Increasing Dufour (diffuso-thermal) and Soret numbers generally reduces radial and circumferential skin friction and also Nusselt number, whereas it elevates the Sherwood number. Both skin friction components are also suppressed with increasing Richardson number. Strong deceleration in the tangential and circumferential velocity components is induced with greater magnetic field.

Divergent access to 5,6,7-perifused cycles

Nitrogen-containing heterocycles are the key components in many pharmaceuticals and functional materials. In this study, we report a transition metal-catalyzed high-order reaction sequence for synthesizing a structurally unique N-center 5,6,7-perifused cycle (NCPC). The key characteristics include the formation of a seven-membered ring by the 8π electrocyclization of various alkenes and aromatic heterocycles as π-components, in which metal carbene species are generated that further induce the cleavage of the α-C-H or -C-C bond. Specifically, the latter can react with various nucleophilic reagents containing -O, -S, -N, and -C. The stereo-controlled late-stage modification of some complicated pharmaceuticals indicates the versatility of this protocol.

Conditionally integrable PDEs, non-classical symmetries and applications

Some multi-dimensional nonlinear partial differential equations reduce to a linear equation in fewer dimensions after imposing one additional constraint. A large class of useful conditionally integrable reaction–diffusion equations follows from a single non-classical symmetry reduction, yielding an infinite-dimensional but incomplete solution space. This solution device extends further to other nonlinear equations such as higher-order reaction–diffusion, fractional-order diffusion and diffusion–convection. Applications are shown for population dynamics with or without weak Allee effects, speed-limited hyperbolic diffusion, material phase field dynamics, soil–water–plant dynamics and calcium transport on the curved surface of an oocyte. Beyond non-classical symmetry analysis, examples of other conditionally integrable equations are given; nonlinear diffusion in 1 + 2 dimensions and the Madelung–Burgers quantum fluid in 1 + 3 dimensions.

Aspects of active-passive controls of nanoparticles of chemically reactive and radiative nanofluid flow past a frequently moving thin needle with thermal and velocity slip: A numerical framework

This communication unfolds the flow features and distribution of mass, heat of a steady MHD nanofluidic stream over an axially moved thin needle with passive and active controls of tiny particles. A linear sort of heat radiation with magnetic influence and a higher-order chemical reaction are addressed in this study. The investigation has been enriched by the consideration of thermophoretic forces with the Brownian movement of fluid. The statement of the problem is formed on the basis of Buongiorno’s model, which introduced the existence of thermal & velocity slips. A suitable set of conversions was utilized to transfigure the foremost equations into nondimensional ordinary ones. Due to the extreme nonlinearity of this problem, we avoid the analytical scheme of solution. Hence, we have implemented the RK4 procedure in shooting approach through the algebra software MAPLE 2017, to solve it in a numerical manner. Numerous graphical diagrams and tables are buildups to discuss our attained impacts. Also, it is ensured the validation of these results with the study which was published earlier. Investigation depicts that the order of chemical reaction intensifies fluid density for active control, while the reverse is recorded in the passive strategy. Velocity slip amplifies the drag friction but reduces the transportation of heat. In the active control system, advanced chemical reaction offers more transmission of heat, but the opposite happens in another control.

Heat source and Joule heating effects on convective MHD stagnation point flow of Casson nanofluid through a porous medium with chemical reaction

This investigation explores the convective MHD stagnation point flow of Casson nanofluid over a stretching sheet in a porous medium with higher-order chemical reactions and multiple slips. The examination of heat transmission is carried out in the presence of radiation, Joule heating, viscous dissipation, and heat source. The system of governing equations was simplified by using appropriate transformations. The transformed equations are tackled numerically by a Runge-Kutta-based shooting technique with the bvp5c MATLAB package. The graphical and numerical results for different parametric values are discussed and presented through figures and tables. It is observed that an increase in the magnetic field, porosity, and Casson fluid parameter reduces the velocity whereas the opposite trend is seen in the case of the thermal Grashof number and the solutal Grashof number. Increasing values of radiation and Joule heating parameters, and the Eckert number, lead to an increase in the temperature. The chemical reaction, suction, and solutal slip were found to reduce the concentration. The friction factor was reduced due to the higher values of the thermal Grashof number, solutal Grashof number, and the velocity ratio parameter. Also, an increase in the Brownian motion and thermal slip parameters decreases the heat transfer rate. The computational results of the Nusselt number have been validated with published results in the literature and found good agreement. The results obtained in this investigation have applications to biomedical, engineering, and industrial sectors such as food processing, polymer manufacturing, glass, and fiber production, improving oil recovery, and material processing.

Straightforward synthesis of quinoxaline-furan bis-heterocyclic structures via a multicomponent reaction

An efficient and straightforward synthetic strategy based on the higher-order multicomponent reactions (MCRs) is established for the synthesis of quinoxaline-furan bis-heterocyclic structures. The process includes a one-pot, pseudo-five component reaction of 3,4-diaminobenzoic acid, a 1,2-dicarbonyl compound, a dialkyl acetylenedicarboxylate, and two equivalents of an isocyanide as the readily available precursors. The noticeable features of the method are pot and atom economy, seven new bond formations, operational simplicity, high yields, and applicability on the gram-scale. Indolo[2,3-b]quinoxaline-furan tris-heterocycles were also synthesized using isatin derivatives via consecutive reactions.

Generation and Analysis of Tritium-Substituted Methane

An unavoidable category of molecular species in large-scale tritium applications, such as nuclear fusion, are tritium-substituted hydrocarbons, which form by radiochemical reactions in the presence of (circulating) tritium and carbon (mainly from the steel of vessels and tubing). Tritium-substituted methane species, CQ4 (with Q = H,D,T), are often the precursor for higher-order reaction chains, and thus are of particular interest. Here we describe the controlled production of CQ4 carried out in the CAPER facility of the Tritium Laboratory Karlsruhe, exploiting catalytic reactions and species enrichment via the CAPER integral permeator. CQ4 was generated in substantial quantities (>1000 cm3 at ~850 mbar, with CQ4content of up to ~20%). The samples were analyzed using laser Raman and mass spectrometry to determine the relative isotopologue composition and to trace the generation of tritiated chain hydrocarbons.

Two first-order phase transitions in hybrid compact stars: Higher-order multiplet stars, reaction modes, and intermediate conversion speeds

We study compact stars with hybrid equations of state consisting of a nuclear outer region and two nested quark phases, each separated from the lower density phase by a strong first-order phase transition. The stability of these models is determined by calculating their radial oscillation modes with different conversion rates between adjacent phases and hence junction conditions for the modes at the phase separation interface between them. In the case when the timescale of transition is faster than the period of oscillations, we recover the traditional stability criterion implying that $\ensuremath{\partial}M/\ensuremath{\partial}{\ensuremath{\rho}}_{c}>0$ on the stable branch(es), where $M$ is the mass and ${\ensuremath{\rho}}_{c}$ is the central density. In the opposite limit of slow conversion, we find stable stellar multiplets beyond triplets consisting of stars that are stable by the usual criterion plus slow-conversion (denoted by $s$) hybrid stars with $\ensuremath{\partial}M/\ensuremath{\partial}{\ensuremath{\rho}}_{c}<0$ that are stabilized due to an alternative junction condition on the fluid displacement field at the interface reflecting the slow rate of conversion. We also study the properties of the reaction mode, the radial mode that only exists for stars with rapid (abbreviated by $r$) phase transitions, in stars with either two rapid phase transitions or alternating rapid and slow phase transitions for the first time. The implications of alternative junction conditions are also examined, with these conditions generally being found to provide stability properties similar to those for a slow conversion rate.

CBT‐Cys click reaction for optical bioimaging in vivo

AbstractDerived from the D‐luciferin regeneration pathway in firefly body, the click condensation reaction between 2‐cyanobenzothiazole (CBT) and D‐cysteine (Cys) (CBT‐Cys click reaction) possesses unique advantages, including superior biocompatibility, high second order reaction rate, and metal‐free mild conditions, emerging as a powerful bioorthogonal tool for a variety of chemical biological applications. Moreover, owing to its programmable controllability (e.g., pH, reduction, or enzyme), CBT‐Cys click reaction is exploited to fabricate stimuli‐activatable imaging probes with self‐assembling behaviors in physiological context. At stimuli‐rich pathological lesions of interest, these probes undergo CBT‐Cys click reaction to form cyclic dimers/oligomers or linear polymers, and further self‐assemble into nanostructures. The in situ formed nanostructures promote the selective accumulation and retention of imaging agent cargos at pathological lesions, thus enabling precise and enhanced in vivo imaging of diseases (especially tumors). To address the significance and recent breakthroughs of smart CBT‐Cys probes for enhanced optical imaging of tumors/other diseases, we herein propose this mini‐review, in which advances (particularly in recent 5 years) and potential challenges (or chances) in this field are emphasized.

Magnetic SWCNT–Ag/H2O nanofluid flow over cone with volumetric heat generation

The theme of this model is to examine the characteristics of heat and mass transfer flow through cone along with volumetric heat generation, variable viscosity, magnetic field and higher-order chemical reaction utilizing SWCNT–Ag/H2O hybrid nanofluid. The transformed partial differential equations are solved by shooting scheme. The numerical outcomes of physical quantities are revealed by graphs and tables. The local Nusselt number and Sherwood number are displayed with the support of bar diagram. The study depicted that an increase in temperature-dependent viscosity parameter for a particular magnetic field induced an increase in the local Nusselt number and Sherwood number. Furthermore, there was a rise in the data of internal heat generation, temperature outlines of hybrid nanofluid escalated while concentration profiles of working fluid depreciated.