Homogeneous System Research Articles

Conversion of Penta‐Acetyl‐Xylitol to 3‐Acetoxymethylene‐Tetrahydrofuran by a Combined Hetero‐/Homogeneous Tandem Catalyst System

A tandem catalyst system comprised of trifluoromethanesulfonic (triflic acid, HOTf) or Hafnium tetratriflate (Hf(OTf)4) and Ru/C in glacial acetic acid (HOAc) as the solvent at 200 °C and ~ 7 MPa hydrogen pressure in a batch reactor converts penta‐acetyl‐xylitol ((2R,3R,4S)‐Pentane‐1,2,3,4,5‐penta‐acetoxy‐pentane) or unprotected xylitol to 3‐acetoxymethylene‐tetrahydrofuran (3‐AMT) in up to 15 % yield at full conversion. A comparative analysis by SEM‐EDS and XPS of the fresh commercial Ru/C catalyst vs catalyst reused and recovered after 5 cycles shows increasing aggregation of ruthenium to larger particles with a concomitant decrease in yield of 3‐AMT to 8‐9 % for cycles 4 and 5. 3‐AMT or its hydrolysis product 3‐hydroxymethyl‐tetrahydrofuran (3‐HMT) are valuable synthons for the preparation of agrochemicals, pharmaceuticals and specialty polyurethanes and polyesters.

PH Dependence of Dihydroxyacetone Oxidation by Electrocatalytic Viologen Self-Assembled Monolayers on Gold Electrodes.

Carbohydrate fuel cells garner much research interest as the world's focus shifts from fossil fuels to renewable energy. Many catalyst options are available for carbohydrate fuel cell development, including enzymes and microbes, various metal-based catalysts, and natural or synthetic mediators. Research challenges include low power output, system fouling and poisoning, inefficient electron release, and complex mechanisms, with multiple pathways leading to low product selectivity. Here, we further investigate a novel approach to catalyze carbohydrate oxidation using Au electrodes with viologen self-assembled monolayers (SAMs). SAM-mediated fuel cells have the potential to address the challenges of other catalyst systems by protecting the electrode surface and controlling the local concentration and structure to increase current generation. The effects of increasing pH on dihydroxyacetone (DHA) oxidation by three viologen SAMs on Au electrodes are presented. Current and power generated during DHA oxidation at varying pH were measured and compared to those of bare Au performance. Two of the SAMs produced more current and power than bare Au at elevated pH. The SAM system produced more current and peak power per molecule than both dilute and concentrated homogeneous viologen systems in the same cell setup. These results demonstrate the benefits and limitations of electrodes modified with redox-active groups for the production of electricity from simple sugars and other carbohydrate sources. These results are encouraging for the development of new strategies for electrical power generation from renewable resources.

Pairing phase favored by magnetic frustration.

The interplay between magnetic frustration and pairing is investigated by adopting a BCS-like pairing mechanism on the frustrated $J_1-J_2$ Ising model on the square lattice. The ground-state and thermal phase transitions of the model are analyzed using a fermionic formulation within a cluster mean-field method. In this approach, the lattice system is divided into identical clusters, where the intracluster dynamic is exactly solved, and the intercluster interactions are replaced by self-consistent mean fields. We introduce a framework with two pairing couplings: an intracluster local coupling, $g$, which controls the electron pairing and its mobility within the clusters, and an intercluster coupling, $g'$, which adjusts the pairing mechanism between clusters. Tuning $g'/g$ allows evaluating how the pairing phase evolves from a weak pairing coupling between clusters (clustered system) to a strong one ($g' \rightarrow g$, homogeneous system). In the range $0 \le g'/g \le 1$, we find that a gradual increase in $g'/g$ favors the pairing phase and induces a change in criticality. In particular, our results reveal the presence of tricriticality for a certain range of $g'/g$. In addition, an increase in competing magnetic interactions weakens the magnetic orders, causing the pairing phase to occur at lower strengths of pairing interactions, especially when $g' = g$. Therefore, our findings support that magnetic frustration favors the pairing phase, contributing to the onset of a superconducting state.

Modelling of filtered drag force for clustered particle-laden flows based on interface-resolved simulation data

Interface-resolved direct numerical simulations (DNS) of clustered settling suspensions in a periodic domain are performed to study the filtered drag force for clustered particle-laden flows. Our results show that, for the homogeneous system, the filtered drag is independent of the filter size, whereas for the clustered particle-laden flows, the averaged drag becomes smaller than the homogeneous drag at the filter size above 4 particle diameters. The drag reduction saturates at the filter size being comparable to the cluster size in the horizontal direction in our simulations. A new correlation is proposed to account for the mesoscale effect on the filtered drag force by using drift velocity and variance of the solid volume fraction, based on the modification of existing subgrid drag models for the inhomogeneous system. The existing models for the drift velocity and the variance of the solid volume fraction are assessed using our DNS data. A new model for the drift velocity and the variance of the solid volume fraction is proposed, based on the combination and modification of the previous models. All mesoscale models considered can predict well the filtered drag with comparable accuracy, and are superior to the homogeneous drag model for the clustered system. Our models with the same parameter values obtained from the large-scale system can also predict well the filtered drag for smaller computational domain sizes.

Methanol-assisted NO oxidation under an oxygen atmosphere for efficient denitration: Experiments and ReaxFF-MD simulations

The development of selective catalytic reduction technologies for controlling nitrogen oxide (NOx) emissions in flue gas is hampered by high equipment and catalyst costs. In this study, a catalyst-free and efficient denitration process using methanol and oxygen as reactants was developed. Various gas atmospheres with differing concentrations were investigated to remove NO without catalysts. The addition of methanol significantly enhanced NO removal efficiency, reaching 94.6 % at 550 °C, with 55.1 % of NO converted to NO2, which can be absorbed by downstream alkali solutions. Reactive force field molecular dynamics (ReaxFF-MD) simulations were employed to analyze the atomic level NO oxidation mechanism in the CH3OH/NO/O2/H2O homogeneous reaction system. The simulation revealed the generation pathway of three key oxidizing intermediates (OH, HO2, and H2O2) and their roles in NO oxidation. This study offers critical insights into developing a cost-effective denitration process, highlighting the potential for improved NOx emission control.

A New Perspective on the Homogeneous Coordinate System for Calculating Interatomic Distances and Their Derivatives in Terms of Internal Coordinates (Adv. Theory Simul. 11/2024)

A New Perspective on the Homogeneous Coordinate System for Calculating Interatomic Distances and Their Derivatives in Terms of Internal Coordinates (Adv. Theory Simul. 11/2024)

The role of mobile-immobile sorbents on flow and colloid-facilitated contaminant transport through porous media: Two-dimensional modeling

A mathematical model based on conceptual equilibrium has been devised to study the role of mobile-immobile sorbents on colloid-facilitated contaminant transport through a two-dimensional, saturated, and homogeneous groundwater system with transient flow conditions. The primary drawback of the kinetic model arises from its inability to handle the large number of parameters involved in multi-dimensional regions at bigger scales when several transport processes and transient flow conditions are included. In order to prevent model complexity, the current study is the first attempt to investigate the equilibrium approach with transient flow conditions in a two-dimensional domain. Conventionally, colloids enhance the contaminant transport by adsorbing contaminants through multiple sorption reactions. However, it was noticed that even in the presence of colloids (Cc=100mg/l), BTCs get attenuated due to an increase in k3, which indicates a stronger affinity of pollutants with the static solid matrix. Therefore, the present study suggests that the mere existence of colloids may not guarantee enhanced contaminant movement. A contaminant plume with 50 mg/l of colloids travels 2 m ahead of the contaminant without colloids, and this distance increases to 4.7 m for 100 mg/l colloids. Therefore, colloids can either be favorable in the case of contaminated aquifer rehabilitation or adverse in the event of groundwater contamination spread.

Eutectic Strategy for the Solvent-Free Synthesis of Hydrophobic Cellulosic Cross-Linked Networks with Broad Multifunctional Applications.

Cellulose-based functional materials play a crucial role in sustainable social development. However, during the material synthesis process, there is typically significant reliance on various solvent systems for macroscopic- or molecular-scale functionalization modifications. In this study, an innovative hydrophobic eutectic solvent (HES) was developed using ethyl cellulose (EC) and thymol (Thy) without any external solvents. Utilizing this homogeneous system, it is convenient to chemically modify the components without any catalyst. Furthermore, a hydrophobic cellulosic cross-linked network (HCCN) can be successfully prepared through in situ photopolymerization. The HCCN film exhibits high transparency, excellent mechanical properties, chemical stability, and durability. The EC/Thy prepolymer system also demonstrates favorable processability for the preparation of various polymeric materials. Additionally, the applicability of other biomasses and derivatives based on the eutectic strategy has been verified. The methodology proposed in this study offers novel insights into the green and solvent-free preparation of biomass functional materials.

Water-promoted oxidative coupling of aromatics with subnanometer palladium clusters confined in zeolites

A fundamental understanding of the active sites in working catalysts can guide the rational design of new catalysts with improved performances. In this work, we have followed the evolution of homogeneous and heterogeneous Pd catalysts under the reaction conditions for aerobic oxidative coupling of toluene for the production of 4,4′-bitolyl. We have found that subnanometer Pd clusters made with a few Pd atoms are the working active sites in both homogeneous and heterogeneous catalytic systems. Moreover, water can promote the activity of Pd clusters by nearly one-order magnitude for oxidative coupling reaction by facilitating the activation of O2. These new insights lead to the preparation of a catalyst made with Pd clusters supported on a two-dimensional zeolite, which expands the scope of the oxidative coupling of aromatics to larger substrates.

Interweavable Metalloporphyrin‐based Fibers for Indirect Electrocatalysis

The applications of indirect electrocatalysis toward potential industrial processes are drastically limited by the utilization or processing forms of electrocatalysts. The remaining challenges of electrocatalysts like the recycling in homogeneous systems or pulverization in heterogeneous systems call for advanced processing forms to meet the desired requirements. Here, we report a series of metalloporphyrin‐based polymer fibers (M‐PF, M = Ni, Cu and Zn) through a rigid‐flexible polymerization strategy based on rigid metalloporphyrin and flexible thiourea units that can be applied as heterogenous redox‐mediators in indirect electrocatalysis. These functional fibers with high strength and flexibility exhibit interweavable and designable functions that can be processed into different fiber‐forms like knotted, two‐spiral, three‐ply, five‐ply fibers or even interweaved networks. Interestingly, they can be readily applied in S‐S bond cleaving/cyclization reaction or extended oxidative self‐coupling reaction of thiols with high efficiency. Remarkably, it enables the scale‐up production (1.25 g in a batch‐experiment) under laboratory conditions.

Interweavable Metalloporphyrin-based Fibers for Indirect Electrocatalysis.

The applications of indirect electrocatalysis toward potential industrial processes are drastically limited by the utilization or processing forms of electrocatalysts. The remaining challenges of electrocatalysts like the recycling in homogeneous systems or pulverization in heterogeneous systems call for advanced processing forms to meet the desired requirements. Here, we report a series of metalloporphyrin-based polymer fibers (M-PF, M = Ni, Cu and Zn) through a rigid-flexible polymerization strategy based on rigid metalloporphyrin and flexible thiourea units that can be applied as heterogenous redox-mediators in indirect electrocatalysis. These functional fibers with high strength and flexibility exhibit interweavable and designable functions that can be processed into different fiber-forms like knotted, two-spiral, three-ply, five-ply fibers or even interweaved networks. Interestingly, they can be readily applied in S-S bond cleaving/cyclization reaction or extended oxidative self-coupling reaction of thiols with high efficiency. Remarkably, it enables the scale-up production (1.25 g in a batch-experiment) under laboratory conditions.

Homogeneous Catalysts of RedOx Processes Based on Heteropolyacid Solutions. VI: Developing a Process for Low-Temperature Oxidation of CO with Oxygen

Research on the development of a homogeneous process for low-temperature oxidation of carbon monoxide in the presence of a “platinum group metal + vanadium-containing heteropolyacid (HPA)” catalytic system has been presented. The optimal reaction conditions, ensuring the maximum rate of CO oxidation to CO2, have been determined; for this reaction the kinetic features have been established, and its mechanism has been proposed. It has been shown that homogeneous systems based on PdII complex exhibit high activity and productivity, but have low stability and operate only at pH below 1,5. The stability of the catalyst can be increased by simultaneous introduction of σ- and π-donor ligands into the system; however, it is more effective to use the PtIV complex in the presence of catalytic amounts of palladium salt at a ratio of 100/1. The transition from HPA solutions with a low content of vanadium atoms (H7PMo8V4O40) to solutions of modified compositions (H10P3Mo18V7O84) ensures an increase in the activity and productivity of the system, with the kinetics of CO oxidation being maintained. The combined homogeneous catalyst PtIV + PdII + H10P3Mo18V7O84 remains stable during multi-cycle use without reducing activity, operates without an induction period and can be used at pH range of 1,7–2,0, which simplifies the process equipment.

Corrolato(oxo)antimony(V) Dimer with Hydrogen-Bond Donor Groups in Secondary Coordination Sphere as a Catalyst for Hydrogen Evolution Reaction.

The focus is on developing alternative molecular catalysts using main-group elements and implementing strategic improvements for sustainable hydrogen production. For this purpose, a FB corrole with a (2-(2-((4-methylphenyl)sulfonamido)ethoxy)phenyl) group inserted into the meso position (C-10) of the corrole, along with its high-valent (corrolato)(oxo)antimony(V) dimer, was synthesized. In the crystal structure analysis of the FB corrole and the (corrolato)(oxo)antimony(V) dimer complex, it was noted that the sulfonamido group in the ligand periphery sits atop the corrole ring. The electrochemical hydrogen evolution reaction (HER) of the (corrolato)(oxo)antimony(V) dimer was studied and compared with a previously reported (corrolato)(oxo)antimony(V) complex, which lacks hydrogen-bond donor groups in the secondary coordination sphere. The newly designed molecules, featuring hydrogen-bond donor groups in the secondary coordination sphere, demonstrated clear superiority in the electrochemical HER. Controlled potential electrolysis was employed to evaluate the charge accumulation associated with hydrogen generation in a homogeneous three-electrode system in the presence of 50 mM TFA. The produced hydrogen exhibits a Faradaic efficiency of approximately 80.96%, a turnover frequency (TOF) of 0.44 h-1, and a production rate of 52.83 μL h-1, highlighting the effective catalytic activity of the (corrolato)(oxo)antimony(V) dimer in hydrogen evolution.

Collective behavior of active filaments with homogeneous and heterogeneous stiffness.

The collective dynamics of active biopolymers is crucial for many processes in life, such as cellular motility, intracellular transport, and division. Recent experiments revealed fascinating self-organized patterns of diverse active filaments, while an explicit parameter control strategy remains an open problem. Moreover, theoretical studies so far mostly dealt with active chains with uniform stiffness, which are inadequate in describing the more complicated class of polymers with varying stiffness along the backbone. Here, using Langevin dynamics simulations, we investigate the collective behavior of active chains with homogeneous and heterogeneous stiffness in a comparative manner. We map a detailed non-equilibrium phase diagram in activity and stiffness parameter space. A wide range of phase states, including melt, cluster, spiral, polar, and vortex, are demonstrated. The appropriate parameter combination for large-scale polar and vortex formation is identified. In addition, we find that stiffness heterogeneity can substantially modulate the phase behaviors of the system. It has an evident destructive effect on the long-ranged polar structure but benefits the stability of the vortex pattern. Intriguingly, we unravel a novel polar-vortex transition in both homogeneous and heterogeneous systems, which is closely related to the local alignment mechanism. Overall, we achieve new insights into how the interplay among activity, stiffness, and heterogeneity affects the collective dynamics of active filament systems.

Wave Speeds for a Time-Periodic Bistable Three-Species Lattice Competition System

In this paper, we consider propagation direction (which can be used to predict which species will occupy the habitat or win the competition eventually) of a bistable wave for a three-species time-periodic lattice competition system with bistable nonlinearity, aiming to address an open problem. As a first step, by transforming the competition system to a cooperative one, we study the asymptotic behavior for the bistable wave profile and then prove the uniqueness of the bistable wave speed. Secondly, we utilize comparison principle and build up two couples of upper and lower solutions to judge the sign of the bistable wave speed which partially provides the answer to the open problem. As an application, we reduce the time-periodic system to a space–time homogeneous system, we obtain the corresponding criteria and carry out numerical simulations to illustrate the availability of our results. Moreover, an interesting phenomenon we have found is that the two weak competitors can wipe out the strong competitor under some circumstances.

Multifunctional property of N,N-bis (carboxymethyl) glutamic acid modified biomass material: adsorption and degradation removals of cationic dyes in wastewater

As a common type of pollutants in industrial wastewater, cationic dyes have attracted great attentions. Using biodegradable N,N-di (carboxymethyl) glutamic acid (GLDA) as ligand and corn stalk (CS) as matrix, a novel and green biomass modified material GLDA-CS was successfully prepared. The multifunctional property of GLDA-CS for removing methylene blue (MB), malachite green (MG) and alkaline red 46 (R-46) from wastewater was evaluated. The dyes were removed by the electrostatic adsorption based on the cationic adsorption properties of GLDA-CS. The removal rates of MB, MG and R-46 can quickly reach 90.4%, 96.8% and 94.8% in short time. especially for MG and R-46 even only 20 min. The adsorption capacities of the dyes still remain more than 86.5% of the initial values after 5 cycles. In a heterogeneous system, the dyes were removed by Fenton-like degradation based on the metal chelating property of GLDA-CS. 100% degradation rates of the dyes can be achieved in 35 min under the acidic region. Even if at pH 7, degradation rates are 44.1%, 47.1% and 56.6% higher than those under the conventional homogeneous system, and the degradation rate remained at 83.7% after 5 cycles. Regardless of the adsorption or degradation, GLDA-CS shows strong anti-anion interference ability. The potential mechanisms of adsorption and degradation for the dyes by GLDA-CS were deduced by quantization calculation. It is concluded that the adsorption removal of the dyes by GLDA-CS follows MG > R-46 > MB, and mainly depends on the electrostatic interaction between -COOH in GLDA-CS and -N- in the dye molecules. Based on the degradation mechanism of Fenton-like reaction, the possible active sites of the dyes attacked by free radicals and their possible degradation intermediates were predicted by the calculations of Fukui function.

Enzymatic reaction and competitive prereduction enable label-free and separation-free inductively coupled plasma mass spectrometry detection of leukemia cells

The enzyme terminal deoxynucleotidyl transferase (TdT) exhibits significant activity in various leukemia cells, including human acute lymphoblastic leukemia cells (CCRF). It demonstrates substantial potential as a diagnostic biomarker for acute lymphoblastic leukemia (ALL). Herein, a highly sensitive method for the homogeneous quantification of TdT and CCRF cells, without the need for labeling or separation, was established based on inductively coupled plasma mass spectrometry (ICP-MS). The simple sensor relied on the TdT-induced polymerization process, lengthening the DNA strand and producing large amounts of the by-product phosphates of pyrophosphate (PPi). The PPi formed complexes with Cu²⁺, altering its morphology in homogeneous systems. The remaining Cu²⁺ competed with Hg²⁺ in consuming ascorbic acid (AA) through the pre-reduction of Hg²⁺, affecting the ICP-MS signal of Hg²⁺. Under optimal conditions, this approach exhibited excellent specificity and ultrahigh sensitivity, with limits of detection (LODs) as low as 0.05 U/L for TdT and 5 cells/mL for CCRF cells, respectively. The proposed method offers significant advantages, including high sensitivity and precision, operation at room temperature without the involvement of proteases, and the ability to accurately quantify in complex biological matrices. Consequently, the proposed method shows great promise as a valuable tool for TdT-related biological research and leukemia diagnosis.

Методика перетворення кодових послідовностей у відповідності до системи координат модуляційного диска

An analysis of current approaches used in the design of optical recording systems for modulation disks has been conducted. By adapting mathematical models, software algo-rithms were developed to transform code sequences represented in polar, homogeneous, and parametric coordinate systems, and the unique characteristics of each approach in de-veloping a universal method for ensuring accurate and efficient modulation pattern trans-formation were established. It was noted that the polar coordinate system is the most suit-able for practical applications in code sequence transformations. Its ability to effectively represent circular and symmetrical structures, as well as the convenient representation of objects with radial symmetry, provides advantages in the creation of modulation disks. As a result of the study, effective software solutions for automating data processing in the formation of modulation patterns were identified. The implementation of the developed software algorithms for the presented approach involves adapting the code sequence to the current metric within the design of an optical system based on modulation disks. The pre-sented methodology ensures the ability to transform code sequences regardless of the cho-sen coordinate system, which significantly enhances its flexibility and versatility for prac-tical applications.

A Versatile Method to Create Antibody/Split‐Enzyme Complexes and Its Application to a Rapid, Homogeneous, and Universal Electrochemical Immunosensing System

AbstractIn this study, a versatile method is developed to create an antibody/split‐enzyme complex for use in electrochemical immunosensors. SpyCatchers are genetically fused at each terminus of flavin adenine dinucleotide‐dependent glucose dehydrogenase (FAD‐GDH) and a protease recognition sequence is inserted into a loop region to prepare a soluble protein and the split GDH. SpyTag‐fused single‐chain variable fragments (scFvs) are employed, which leads to the simple preparation of antibody‐split enzyme complexes (split AECs). The addition of pentameric C‐reactive protein (CRP), as a representative multimeric protein, restored the GDH activity of the split AECs, as the two split AEC fragments formed active GDH when in close proximity. CRP in human serum is electrochemically detected within 5 min without any washing steps with a clinically relevant CRP detection range (0.03–1 mg dL−1). The detection system is expanded to detect hemoglobin, SARS‐CoV‐2 spike protein, and inactivated SARS‐CoV‐2 by exchanging the scFvs. These results show that the convenient preparation method of the split GDH and the split AEC by the insertion of the protease recognition sequence and the use of SpyCatcher/SpyTag can realize a rapid, homogeneous, and universal electrochemical detection system that can be integrated into a commercially available electrochemical glucose sensor.

Existence and Uniqueness of Homogeneous Linear Equation Solutions in Supertropical Algebra

This research investigates the existence and uniqueness of solutions to homogeneous linear equations in supertropical algebra. We analyze the structure of supertropical matrices to identify the conditions in which nontrivial solutions exist for the system of equations A⊗𝒙 ⊨ 𝜀, where A is a matrix over a supertropical semiring and x is a vector. By applying determinant-based criteria, we demonstrate how tropical and supertropical values influence the solution space. The research applies theorems that determine the presence of trivial and nontrivial solutions and uses examples to illustrate practical methods for solving homogeneous matrix systems. This highlights the distinct characteristics of supertropical algebra compared to classical linear algebra. Our findings provide a deeper insight into solution behaviors in supertropical systems, paving the way for further research in tropical mathematics.