Reaction Rate Research Articles

Atomic Electrostatic Potential as a Descriptor of Aminolysis of Phenyl and Thiophenyl Acetates and Hydrolysis of Acetanilides

Abstract: Hydrolysis of acetanilides and aminolysis of phenyl and thiophenyl acetates are related reactions since these are processes of nucleophilic substitution on the carbonyl carbon. Current views of chemical reactivity based on the DFT theory rely upon reactivity indices that are descriptors of both the reaction center and the molecule as a whole, and have not been applied to the given processes before. One of such descriptors is an atomic electrostatic potential. The given parameter was calculated by the DFT theory M06/6-311+G (non-specific solvation, MeCN, SMD, and full optimization) for the structures of substituted phenyl acetates XPhO-C(O)Me, acetanilides XPhNHC(O)Me, thiophenyl acetates ZPhSC(=O)Me, and benzyl amines XPhСH2NH2 (X, Z substituents). It has been found that all relationships between the atomic electrostatic potential, the charge on the reaction center in the Hirshfeld scheme, and logK are symbatic. Consequently, in all of the cases, the rate is determined by the nucleophilic attack on the reaction center, with the activity/selectivity relationship being observed. The fact that the reaction rate is limited by the nucleophilic attack of the reagent is not inconsistent with the views of the reaction being concerted, since it is known that such reactions may be quite concerted though not quite synchronous.

Exceptional stability of spinel Ni–MgAl2O4 catalyst with ordered mesoporous structure for dry reforming of methane

The dry reforming of methane reaction holds significant importance for the comprehensive utilization of CO2 and CH4, contributing to carbon neutrality. However, due to the high reaction temperatures, catalyst deactivation due to carbon deposition and sintering remains a challenge. In this study, a one-pot method was employed to improve the solvent evaporation self-assembly process for the preparation of Ni–MgAl2O4 catalysts. The impact of calcination temperature (600 °C, 800 °C, and 1000 °C) on the ordered mesoporous structure of the catalyst was investigated. Catalysts without an ordered mesoporous structure, such as Ni–MgAl2O4-1000, suffered deactivation due to carbon deposition caused by the large size of Ni grains, while Ni–MgAl2O4-600 deactivated due to sintering caused by the lack of confinement effect of the support on Ni. Conversely, Ni–MgAl2O4 catalysts with an ordered mesoporous structure exhibited confinement effects on Ni metal, resulting in excellent resistance to carbon deposition and sintering. Further investigation into the effect of different loading methods of Ni on methane dry reforming was conducted. A comparison was made between Ni–MgAl2O4 (800 °C) prepared by the one-pot method and Ni/MgAl2O4 (800 °C) prepared by the impregnation method. It was observed that Ni–MgAl2O4 catalysts, with Ni incorporated into the support, exhibited strong interaction between Ni and the support. During a 500-h long-term reaction, both CO2 and CH4 conversion rates remained at 90% for Ni–MgAl2O4 catalysts, with less carbon deposition and slower grain growth rate, demonstrating excellent reaction activity and stability. In contrast, the performance of Ni/MgAl2O4 catalysts gradually declined after 260 h. Ni–MgAl2O4 catalysts with ordered mesopores and strong interaction between Ni and the support displayed superior resistance to carbon deposition and sintering.

Fluidized bed reactor for 4-chlorophenol photodegradation via solar and visible radiation using ZnO/g-C3N4/carbon xerogel as a photocatalyst

This study investigates the feasibility of employing a fluidized bed reactor for the degradation of 4-chlorophenol (4CP), considering multiple operational parameters (type of radiation, fresh inlet flow rate and recycle flow rate). The selection of the ZnO/g-C3N4/carbon xerogel as photocatalyst, a choice motivated by the improved charge transfer and increased catalyst activity under visible radiation provided by the presence of carbon xerogel and g-C3N4, was previously determined through tests conducted in a jacketed batch reactor under visible radiation, in which the ternary material efficiency was compared to their constituting counterpart materials. The semiconductors constituting the unary, binary, and ternary materials were chosen based on considerations of availability, sustainability, and abundance in nature. The use of the proposed fluidized bed reactor brings advantages in scalability, distribution of irradiated light and overall costs when compared to commonly used batch reactors, whereas the investigation of the flow parameters involved in such process is of great importance to understand and optimize the efficiency of the pollutant degradation process. Regarding the ternary photocatalyst, X-ray diffractometry (XRD) revealed the presence of zinc oxide's hexagonal crystalline structure. Moreover, additional characterization using Raman spectroscopy, Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy-dispersive spectroscopy (EDS) confirmed the presence not only of ZnO but also of carbon xerogel and g-C3N4 in the composite. From the photodegradation experiments, it was determined that the optimal fresh inlet flow rate to achieve the best degradation, as well as the recycle flow rate for this purpose, were 0.07 and 25 L h−1, respectively. Mathematical simulations described that the model that best fits the system's behavior considers the specific reaction rate as dependent on the concentration of the catalyst in the medium.

Heavy Atom Quantum Mechanical Tunneling in Total Synthesis.

Contributions from quantum mechanical tunneling to the rates of several radical coupling reactions between carbon sp2 centers used as key steps in natural product total syntheses were computed using density functional theory. Contributions ranging from ∼15-52% from tunneling were predicted at room temperature, thereby indicating that tunneling plays an important role in the rates of these reactions and should perhaps be considered when designing complex synthetic schemes.

Evolution Kinetics of Stabilizing Pickering Emulsion by Brush-Modified Janus Particles: DPD Simulation and Experimental Insights.

In the present study, we report the evolution of stabilizing Pickering emulsions using brush-modified Janus particles (JPs), utilizing the dissipative particle dynamics (DPD) simulation technique. Our results are subsequently corroborated with experimental findings. Each JP has one-half of the hydrophobic surface, with the other half embedded with hydrophilic polymer brushes grown via atom transfer radical polymerization (ATRP). Our generic simulation model analyzes the chemical kinetics of polymer brush growth on one-half of the initiator-embedded microparticle (MP) surface, resulting in the formation of JP. This involves evaluating monomer conversion and reaction rates. Our results exhibit a substantial influence of the number of JPs, grafted brush density, and brush length on oil-in-water emulsion stability. We studied the evolution kinetics and stability of emulsion formation by analyzing the growth of average domain size and corresponding scaling functions up to a late time limit. This study aims to clarify the connection between the size, quantity, and functionality of JPs and the stability of Pickering emulsions.

Skeletal Kinetics Reduction for Astrophysical Reaction Networks

A novel methodology is developed to extract accurate skeletal reaction models for nuclear combustion. Local sensitivities of isotope mass fractions with respect to reaction rates are modeled based on the forced optimally time-dependent (f-OTD) scheme. These sensitivities are then analyzed temporally to generate skeletal models. The methodology is demonstrated by conducting skeletal reduction of constant density and temperature burning of carbon and oxygen relevant to Type Ia supernovae (SNe Ia). The 495-isotopes Torch model is chosen as the detailed reaction network. A map of maximum production of 56Ni in SNe Ia is produced for different temperatures, densities, and proton-to-neutron ratios. The f-OTD simulations and the sensitivity analyses are then performed with initial conditions from this map. A series of skeletal models are derived and their performances are assessed by comparison against currently existing skeletal models. Previous models have been constructed intuitively by assuming the dominance of α-chain reactions. The comparison of the newly generated skeletal models against previous models is based on the predicted energy release and 44Ti and 56Ni abundances by each model. The consequences of y e ≠ 0.5 in the initial composition are also explored where y e is the electron fraction. The simulated results show that 56Ni production decreases by decreasing y e as expected, and that the 43Sc is a key isotope in proton and neutron channels toward 56Ni production. It is shown that an f-OTD skeletal model with 150 isotopes can accurately predict the 56Ni abundance in SNe Ia for y e ≲ 0.5 initial conditions.

High-Entropy Alloy Electrocatalysts Bidirectionally Promote Lithium Polysulfide Conversions for Long-Cycle-Life Lithium-Sulfur Batteries.

High-entropy alloys (HEAs) have attracted considerable attention, owing to their exceptional characteristics and high configurational entropy. Recent findings demonstrated that incorporating HEAs into sulfur cathodes can alleviate the shuttling effect of lithium polysulfides (LiPSs) and accelerate their redox reactions. Herein, we synthesized nano Pt0.25Cu0.25Fe0.15Co0.15Ni0.2 HEAs on hollow carbons (HCs; denoted as HEA/HC) by a facile pyrolysis strategy. The HEA/HC nanostructures were further integrated into hypha carbon nanobelts (HCNBs). The solid-solution phase formed by the uniform mixture of the five metal elements, i.e., Pt0.25Cu0.25Fe0.15Co0.15Ni0.2 HEAs, gave rise to a strong interaction between neighboring atoms in different metals, resulting in their adsorption energy transformation across a wide, multipeak, and nearly continuous spectrum. Meanwhile, the HEAs exhibited numerous active sites on their surface, which is beneficial to catalyzing the cascade conversion of LiPSs. Combining density functional theory (DFT) calculations with detailed experimental investigations, the prepared HEAs bidirectionally catalyze the cascade reactions of LiPSs and boost their conversion reaction rates. S/HEA@HC/HCNB cathodes achieved a low 0.034% decay rate for 2000 cycles at 1.0 C. Notably, the S/HEA@HC/HCNB cathode delivered a high initial areal capacity of 10.2 mAh cm-2 with a sulfur loading of 9 mg cm-2 at 0.1 C. The assembled pouch cell exhibited a capacity of 1077.9 mAh g-1 at the first discharge at 0.1 C. The capacity declined to 71.3% after 43 cycles at 0.1 C. In this work, we propose to utilize HEAs as catalysts not only to improve the cycling stability of lithium-sulfur batteries, but also to promote HEAs in energy storage applications.

Strong coupling-induced frequency shifts of highly detuned photonic modes in multimode cavities.

Strong coupling between light and molecules is a fascinating topic exploring the implications of the hybridization of photonic and molecular states. For example, many recent experiments have explored the possibility that strong coupling of photonic and vibrational modes might modify chemical reaction rates. In these experiments, reactants are introduced into a planar cavity, and the vibrational mode of a chemical bond strongly couples to one of the many photonic modes supported by the cavity. Some experiments quantify reaction rates by tracking the spectral shift of higher-order cavity modes that are highly detuned from the vibrational mode of the reactant. Here, we show that the spectral position of these cavity modes, even though they are highly detuned, can still be influenced by strong coupling. We highlight the need to consider this strong coupling-induced frequency shift of cavity modes if one is to avoid underestimating cavity-induced reaction rate changes. We anticipate that our work will assist in the re-analysis of several high-profile results and has implications for the design of future strong coupling experiments.

Vinylidene rearrangements of internal borylalkynes via 1,2-boryl migration.

Vinylidene rearrangement of alkynes is a well-established and powerful method for alkyne transformations, while use of borylalkynes has remained largely unexplored. This paper describes vinylidene rearrangements of internal borylalkynes using a cationic ruthenium complex. This rearrangement is applicable to alkynes with both tri-(B(pin), B(dan)) and tetracoordinate (B(mida)) boryl groups, and the reaction rate is dramatically affected by the Lewis acidity of the boryl group. Mechanistic study revealed that the rearrangement proceeds via 1,2-boryl migration regardless of the coordination number of the boron center. The migration mode was elucidated by theoretical calculations to indicate that the migration of the tricoordinate boryl groups is an electrophilic process in contrast to the previous vinylidene rearrangements of internal alkynes with two carbon substituents.

Reaction Rate and Stereoselectivity Enhancement in Glycosidations with O-Glycosyl Trihaloacetimidate Donors due to Catalysis by a Lewis Acid-Nitrile Cooperative Effect.

Activation of O-glycosyl trihaloacetimidate glycosyl donors with AuCl3 as a catalyst and pivalonitrile (tBuCN) as a ligand led to excellent glycosidation results in terms of yield and anomeric selectivity. In this way, various β-d-gluco- and β-d-galactopyranosides were obtained conveniently and efficiently. Experimental studies and density functional theory (DFT) calculations, in order to elucidate the reaction course, support formation of the tBuCN-AuCl2-OR(H)+ AuCl4- complex as a decisive intermediate in the glycosidation event. Proton transfer from this acceptor complex to the imidate nitrogen leads to donor activation. In this way, guided by the C-2 configuration of the glycosyl donor, the alignment of the acceptor complex enforces the stereoselective β-glycoside formation in an intramolecular fashion, thus promoting also a fast reaction course. The high stereocontrol of this novel 'Lewis acid-nitrile cooperative effect' is independent of the glycosyl donor anomeric configuration and without the support of neighboring group or remote group participation. The power of the methodology is shown by a successful glycoalkaloid solamargine synthesis.

Cannabidiol impairs sperm quality and function in adult mice

BackgroundConsidering the growing therapeutic use of cannabidiol as well as the presence of cannabinoid receptors in sperm and its possible genotoxic activity, the effect of cannabidiol on sperm quality and function was examined.MethodsThirty male NMRI mice were randomly divided into three groups: control (no injection), sham (intraperitoneal (IP) injection of DMSO daily for 34 days), and cannabidiol (IP injection of cannabidiol 30 mg/ml daily for 34 days). Following 35 days after the last injection, sperm parameters, chromatin integrity (CMA3 staining), acrosome reaction (FITC-PNA method), fertility-related genes (IZUMO1, PLCζ), and blastulation rate of the embryos obtained from the oocytes fertilized with the mentioned sperms was investigated.ResultsCount, motility, and morphology of sperm were not significantly affected by cannabidiol. CMA3+ sperms (protamine deficiency) were significantly higher in the cannabidiol group compared to the control group (P = 0.03). The acrosomal reaction and fertility-related genes (IZUMO1, PLCζ) in the cannabidiol group did not differ significantly compared to the control group. Also, there was no significant difference between the cannabidiol group and the control group in the two-cell and the eight-cell stages but the rate of blastocyst formation was significantly lower in the cannabidiol group compared to other groups (P < 0.0001).ConclusionsOur results showed that cannabidiol leads to negative effects on the male reproductive system through an effect on sperm chromatin and the rate of reaching the blastocyst stage of the embryo.Graphical

In Situ Generated CO Enables High-Current CO2 Reduction to Methanol in a Molecular Catalyst Layer.

Molecular catalysts such as cobalt phthalocyanine (CoPc) exhibit remarkable electrochemical activity in methanol production from CO2 or CO, but fast conversion with a high current density is still yet to be realized. While adopting flow cells with gas diffusion electrodes is a common approach to enhanced reaction rates, the current scientific and engineering knowledge primarily centers on metal particle-based catalysts like Cu. This focus overlooks the emerging heterogenized molecular catalysts with distinct physical and chemical properties. In this work, we observe that the partial current density of CO reduction to methanol catalyzed by tetraamine-substituted CoPc (CoPc-NH2) supported on carbon nanotubes (CNTs) remains below 30 mA cm-2, even with systematic optimization of structural and operational parameters of the flow cell. A comparative analysis with a Cu metal catalyst reveals that the porous and electrolyte-philic nature of CoPc-NH2/CNT leaves a large fraction of active sites deprived of CO under reaction conditions. To address this microenvironmental challenge, we directly use CO2 as the reactant, leveraging its faster diffusion rate in water compared to CO. Effective CO2 reduction generates CO in situ to feed the catalytic sites, achieving an unprecedently high partial current density for methanol of 129 mA cm-2. This research underscores the necessity for new insights and approaches in the development of molecular catalyst-based electrodes.

New Potential Energy Surface for the H + Cl2 Reaction and Quantum Dynamics Studies.

The reaction of H + Cl2 → HCl + Cl plays a crucial role in various fields. However, no previous study has investigated this reaction using accurate quantum mechanical methods. In this paper, we construct a global potential energy surface (PES) using the neural network method with more than 20,000 ab initio energies obtained by the MRCI-F12+Q method with the aug-cc-pV5Z basis and extrapolated to the complete basis set limit. The spin-orbit coupling of the Cl atom has been considered in the PES. With this new PES, product state-resolved quantum dynamics calculations for the H + Cl2 (v0 = 0, j0 = 0-2) → HCl + Cl reaction was carried out. Numerical results show that the initial rotational excitation of the Cl2 has negligible effects on the reactivity. Product state-resolved integral cross sections (ICS) and rate constants reveal that the HCl is most favorably produced in its v' = 2 vibrational state. The calculated product vibrational state-resolved and total reaction rate constants suggest that the new global PES is accurate enough, as compared with the available experimental measurements.

Solar-matched S-scheme ZnO/g-C3N4 for visible light-driven paracetamol degradation

In pursuit of an efficient visible light driven photocatalyst for paracetamol degradation in wastewater, we have fabricated the ZnO/g-C3N4 S-Scheme photocatalysts and explored the optimal percentage to form a composite of graphitic carbon nitride (g-C3N4) with zinc oxide (ZnO) for enhanced performance. Our study aimed to address the urgent need for a catalyst capable of environmentally friendly degradation of paracetamol, a common pharmaceutical pollutant, using visible light conditions. Here, we tailored the band gap of a photocatalyst to match solar radiation as a transformative advancement in environmental catalysis. Notably, the optimized composite, containing 10 wt.% g-C3N4 with ZnO, demonstrated outstanding paracetamol degradation efficiency of 95% within a mere 60-min exposure to visible light. This marked enhancement represented a 2.24-fold increase in the reaction rate compared to lower wt. percentage composites (3 wt.% g-C3N4) and pristine g-C3N4. The exceptional photocatalytic activity of the optimized composite can be attributed to the band gap narrowing that closely matched the maximum solar radiation spectrum. This, coupled with efficient charge transfer mechanisms through S-scheme heterojunction formation and an abundance of active sites due to increased surface area and reduced particle size, contributed to the remarkable performance. Trapping experiments identified hydroxyl radicals as the primary reactive species responsible for paracetamol photoreduction. Furthermore, the synthesized ZnO/g-C3N4 composite exhibited exceptional photostability and reusability, underscoring its practical applicability. Thus, this research marks a significant stride towards the development of an effective and sustainable visible light photocatalyst for the removal of pharmaceutical contaminants from aquatic environments.

Development of an Elementary Reaction-Based Kinetic Model to Predict the Aqueous-Phase Fate of Organic Compounds Induced by Reactive Free Radicals.

ConspectusAqueous-phase free radicals such as reactive oxygen, halogen, and nitrogen species play important roles in the fate of organic compounds in the aqueous-phase advanced water treatment processes and natural aquatic environments under sunlight irradiation. Predicting the fate of organic compounds in aqueous-phase advanced water treatment processes and natural aquatic environments necessitates understanding the kinetics and reaction mechanisms of initial reactions of free radicals with structurally diverse organic compounds and other reactions. Researchers developed conventional predictive models based on experimentally measured transformation products and determined reaction rate constants by fitting with the time-dependent concentration profiles of species due to difficulties in their measurements of unstable intermediates. However, the empirical treatment of lumped reaction mechanisms had a model prediction limitation with respect to the specific parent compound's fate. We use ab initio and density functional theory quantum chemical computations, numerical solutions of ordinary differential equations, and validation of the outcomes of the model with experiments. Sensitivity analysis of reaction rate constants and concentration profiles enables us to identify an important elementary reaction in formating the transformation product. Such predictive elementary reaction-based kinetics models can be used to screen organic compounds in water and predict their potentially toxic transformation products for a specific experimental investigation.Over the past decade, we determined linear free energy relationships (LFERs) that bridge the kinetic and thermochemical properties of reactive oxygen species such as hydroxyl radicals (HO•), peroxyl radicals (ROO•), and singlet oxygen (1O2); reactive halogen species such as chlorine radicals (Cl•) and bromine radicals (Br•); reactive nitrogen species (NO2•); and carbonate radicals (CO3•-). We used literature-reported experimental rate constants as kinetic information. We considered the theoretically calculated aqueous-phase free energy of activation or reaction to be a kinetic or a thermochemical property, and obtained via validated ab initio or density functional theory-based quantum chemical computations using explicit and implicit solvation models. We determined rate-determining reaction mechanisms involved in reactions by observing robust LFERs. The general accuracy of LFERs to predict aqueous-phase rate constants was within a difference of a factor of 2-5 from experimental values.We developed elementary reaction-based kinetic models and predicted the fate of acetone induced by HO• in an advanced water treatment process and methionine by photochemically produced reactive intermediates in sunlit fresh waters. We provided mechanistic insight into peroxyl radical reaction mechanisms and critical roles in the degradation of acetone and the formation of transformation products. We highlighted different roles of triplet excited states of two surrogate CDOMs, 1O2, and HO•, in methionine degradation. Predicted transformation products were compared to those obtained via benchtop experiments to validate our elementary reaction-based kinetic models. Predicting the reactivities of reactive halogen and nitrogen species implicates our understanding of the formation of potentially toxic halogen- and nitrogen-containing transformation products during water treatment processes and in natural aquatic environments.

FRECKLL: Full and Reduced Exoplanet Chemical Kinetics DistiLLed

We introduce a new Python 1D chemical kinetic code, Full and Reduced Exoplanet Chemical Kinetics distiLLed (FRECKLL), to evolve large chemical networks efficiently. FRECKLL employs “distillation” in computing the reaction rates, which minimizes the error bounds to the minimum allowed by double precision values (ϵ ≤ 10−15). Compared to summation of rates with traditional algorithms like pairwise summation, distillation provides a tenfold reduction in solver time for both full and reduced networks. Both the full and reduced Venot2020 networks are packaged in FRECKLL as well as a TauREx 3.1 plug-in for usage in forward modeling and retrievals of exoplanet atmospheres. We present TauREx retrievals performed on a simulated HD 189733b JWST spectra using the full and reduced Venot2020 chemical networks and demonstrate the viability of total disequilibrium chemistry retrievals and the ability for JWST to detect disequilibrium processes.

A Kinetic and Mechanistic Study of Ir (III)-Catalyzed Oxidation of Methionine by HCF (III) in an Aqueous Alkaline Medium

Introduction: The kinetic study of Ir (III) chloride-catalyzed oxidation of methionine by hexacyanoferrate (abbreviated as HCF) III ions in aqueous alkaline medium was performed spectrophotometrically at constant ionic strength of 0.5 moldm-3 and temperature of 35±0.10C. Method: The progress of the reaction was found to be first-order rate dependence kinetics with respect to [HCF (III)], [OH-], and [IrCl3]. The rate of reaction was found to decrease with an increased concentration of methionine. The ionic strength of the reaction mixture showed a positive salt effect on the reaction rate. Different activation parameters were also evaluated by studying the reaction at four different temperatures. The stoichiometry of the reaction showed Methionine: HCF (III) = 1:4. Result: The oxidation product of the reaction was found to be methionine sulphone, which was identified by an organic solvent method and IR Spectroscopy. Further, a suitable mechanism was proposed to explain all the experimental results. Conclusion: It is assumed that the reaction proceeded through complex formation between substrate (abbreviated) and iridium trichloride. A rate law was derived, which verified the results. CH3-S-(CH2)2-CH (NH2)-COO- + 4HCF (III) Ir (III), H2O CH3-SO2-(CH2)2-CH- (NH2)-COO- + 4HCF (II) result: 1.Methionine sulphone was found to be the main product of oxidation was identified using an organic solvent method and IR Spectroscopy. A suitable mechanism has been proposed to explain all the experimental results. It is assumed that reaction proceeds through complex formation between substrate (abbreviated) and iridium trichloride. A rate law has been derived which verifies the results. CH3 –S-(CH2)2-CH (NH2) – COO- + 4HCF (III) □(→┴(Ir(III),H2O) ) CH3-SO2-(CH2)2-CH (NH2)-COO- + 4HCF (II) 2. Degradation kinetic is anticipated to follow the first order kinetics at lower concentration. 3. The catalytic system can be recycled and reused without loss of activity. 4. The anticipated easy recovery of catalyst from the reaction mixture shows another positive signigficance.

Ultrasonication-assisted synthesis of transition metal carbide of MXene: an efficient and promising material for photocatalytic organic dyes degradation of rhodamine B and methylene blue in wastewater.

Water pollutants of non-biodegradable toxic aromatic dye including Methylene blue (MB) and Rhodamine (RhB) are extremely carcinogenic thiazines used in various industries such asleather industry, paper industry, and the dyeing industry. The presence of dyes in wastewater causes severe threats to human health that are responsible for various harmful chronic or acute diseases and also shows an adverse impact on the environment as it reduces transparency and is harmful to water microorganisms. To overcome severe issues, many traditional techniques have been used to remove toxic pollutants, but thesemethods are insufficient to remove chemically stable dyes that remain in the treated wastewater. However, the photocatalytic degradation process is an efficient approach to degrade the dye up to the maximum extent with improved efficiency. Therefore, in this work, a new class of two-dimensional (2D) transition metal carbide of Titanium Carbide (Ti3C2Tx) MXene material was used for the organic dyes degradation such as MB and RhB using a photocatalytic process. A layered structure of hexagonal lattice symmetry of Ti3C2Tx MXene was successfully synthesized from the Titanium Aluminum Carbide ofTi3AlC2 bulk phase using an exfoliation process. Further, the XRD spectrum confirms the transformation of bulk MAX phase having (002) plane at 9.2° to Ti3C2Tx MXene of (002) plane at 8.88° confirms the successful removal of Al layer from MAX phase. A smooth, transparent, thin sheet-like morphology of Ti3C2Txnanosheet sizewere found to be in the range of 70 to 150nm evaluated fromTEM images. Also,no holes or damages in the thin sheets were foundafter the treatment with strong hydrofluoric acid confirms the formationTi3C2Tx layered sheets. The synthesized Ti3C2Tx MXene possesses excellent photocatalytic activity for the degradation of dyes MB, RhB, and mixtures of MB and RhB dyes. MB dye degraded with a degradation percentage efficiency of 99.32% in 30min, while RhB dye was degraded upto98.9% in 30min. Also, experiments were conducted for degradation ofmixture of MB and RhB dyes by UV light, and the degradationpercentage efficiency were found to be 98.9% and 99.75% for mixture of MB and RhB dyein 45min, respectively. Moreover, reaction rate constant (k) was determined for each dye of MB, RhB, and mixtures of MB and RhB and was found to be 0.0215min-1 and 0.0058min-1, and for mixtures, it was 0.0020min-1 and 0.009min-1, respectively.

Comparative observation of the effectiveness and safety of remimazolam besylate versus dexmedetomidine in gastrointestinal surgery in obese patients

BACKGROUND Surgery for obese patients carries a higher risk of anesthesia complications compared with surgery for nonobese patients. Thus, a safe and effective anesthesia strategy is necessary to improve the medical experience of such patients and ensure their safety. AIM To compared the effectiveness and safety of remimazolam besylate versus dexmedetomidine (DEX) in gastrointestinal surgery in obese patients. METHODS The study cohort included 60 obese patients undergoing gastrointestinal surgery between July 2021 and April 2023, comprising 30 patients who received DEX intervention (control group) and 30 patients who received remimazolam besylate intervention (research group). Heart rate (HR), respiratory rate (RR), mean arterial pressure (MAP), blood oxygen saturation (SpO2), safety (nausea and vomiting, bradycardia, hypotension, and apnea), anesthesia and examination indices [induction time, anesthesia recovery time, and postanesthesia care unit (PACU) discharge time], sedation effect (Ramsay Sedation Scale), and postoperative pain visual analog scale were comparatively analyzed before anesthesia (T0), during anesthesia (T1), and after anesthesia (T2). RESULTS At T1, the research group showed significantly smaller changes in HR, RR, MAP, and SpO2 than the control group, with a significantly lower adverse reaction rate and shorter induction, anesthesia recovery, and PACU discharge times. Additionally, the intra- and postoperative Ramsay Sedation Scale scores were statistically higher in the research group than in the control group. CONCLUSION Remimazolam besylate was significantly more effective than DEX in gastrointestinal surgery in obese patients and had a higher safety profile and value in clinical promotion.

VOF based model of numerical simulation for single aluminum droplet evaporation and combustion

ABSTRACT This study investigates the combustion of a single aluminum droplet in a high-temperature convective setting, focusing on the interplay between the environment and droplet evaporation combustion. Using the VOF numerical method, a two-dimensional multiphase flow combustion model for micron-sized aluminum droplets is developed. Experimental validation compares predicted droplet diameter with experimental data. The combustion behavior of aluminum droplets in high-temperature convective environments is analyzed, emphasizing gas-phase combustion during stable stages. Parametric variations in flow velocity and oxygen concentration reveal the formation of vortices around the droplet, influencing aluminum vapor accumulation and evaporation rates. Combustion primarily occurs at the droplet’s windward side, with reaction rates decreasing downstream. Increasing gas velocity from 1.5 m/s to 3 m/s thins the aluminum vapor concentration boundary layer, boosting combustion rates by 35%. Elevating oxygen concentration from 20% to 50% brings the flame closer to the droplet, accelerating combustion rates by 2.7 times, suggesting oxygen concentration’s role in reaction acceleration and combustion duration reduction. This research offers insights for simulating aluminum droplets in propellant applications.