Homogeneous System Research Articles

Coupled homogeneous/heterogeneous Fenton-like system to enhance the synchronized decontamination of aqueous tetracycline and Salmonella typhi

Aqueous chemical and biological co-contaminants containing heavy metals, antibiotics and antibiotic resistant bacteria (ARB) are harmful for the ecological environment. An innovative degradation-inactivation mechanism and a coupled homogeneous and heterogeneous Fenton-like system were proposed herein to synchronously decontaminate aqueous tetracycline (TC) and TC-resistant Salmonella typhi (TRST). Results showed that the homogeneous Cu(II)/PMS system, wherein, trace Cu(II) and TC co-existed to form cupric complexes that activated PMS, effectively caused TC degradation and TRST inactivation by Cu(III) oxidation. However, the inactivation efficiency was only ∼ 47 % in mono Cu(II)/PMS system because of the generation of limited radicals from the conversion of Cu(III). After the addition of Fe/N/S-doped biochar (Fe/N/S-BC) to Cu(Ⅱ)-TC-TRST ternary contaminants, the heterogeneous Fe/N/S-BC/PMS system superposed on the effect of homogeneous Cu(II)/PMS system by generating abundant reactive oxygen species (ROS) and promoting TC degradation and TRST inactivation. Despite the competition of Cu(II) and TC, the coupled homogeneous/heterogeneous Fenton-like system enhanced the inactivation of TRST increasing to ≥98 %. Both radical (•OH, •O2–etc) and nonradical (Cu(III) and 1O2) pathways participated in the synchronized decontamination of TC and TRST and its antibiotic resistant genes (ARGs) in Cu(II)-TC-TRST ternary contaminants.

Mittag-Leffler stability analysis of a class of homogeneous fractional systems

Mittag-Leffler stability analysis of a class of homogeneous fractional systems

Carbon nitride with water soluble ability: Enhanced oxygen species interphase mass transfer for homogenous photocatalytic water purification

Heterogeneous catalysis has been considered a promising way for waste purification, however the catalytic performances of the heterogeneous-based systems are still unsatisfactory, mainly due to the limited active sites exposure and sluggish reactants mass transfer. In this study, we propose a conceptual carbonitride-based quasi-homogeneous catalytic system, exhibiting remarkable photocatalytic activity toward organic pollutants degradation and pathogenic bacteria inactivation. We verify that downsizing carbonitride into nanodot level and modifying the material with hydrophilic groups can endow it with water soluble ability, forming a quasi-homogeneous catalytic system to maximize the active sites exposure and minimize the reactants mass transfer resistance for high-efficient water purification. As a result, the as-established quasi-homogeneous photocatalytic system exhibits abundant surface-active sites and reactants mass transfer efficiencies that allows remarkable O2 reduction for ROS generation. In addition, the treated water containing the functionalized carbonitride is found capable of driving the fast flocculate of suspended substance, which helps to build a well water decontamination and suspended substance removal water purification nexus for practical applications. The work demonstrated here sheds new light in designing high-efficient homogeneous catalytic system for energy and environmental related applications.

Effect of Interfacial Action on the Generation and Transformation of Reactive Oxygen Species in Tripolyphosphate-Enhanced Heterogeneous Fe3O4/O2 Systems.

It has been reported that tripolyphosphate (TPP) can enhance the oxygenation of natural Fe(II)-containing minerals to produce reactive oxygen species (ROS). However, the molecular structure of the TPP-Fe(II) mineral surface complex and the role of this complex in the generation and transformation of ROS have not been fully characterized. In the present study, a heterogeneous magnetite (Fe3O4)/O2/TPP system was developed for the degradation of p-nitrophenol (PNP). The results showed that the addition of TPP significantly accelerated the removal of PNP in the Fe3O4/O2 system and extended the range of effective pH to neutral. Experiments combined with density functional theory calculations revealed that the activation of O2 mainly occurs on the surface of Fe3O4 induced by a structural Fe(II)-TPP complex, where the generated O2•- (intermediate active species) can be rapidly converted into H2O2, and then the •OH generated by the Fenton reaction is released into the solution. This increases the concentration of •OH produced and the efficiency of •OH produced relative to Fe(II) consumed, compared with the homogeneous system. Furthermore, the binding of TPP to the surface of Fe3O4 led to stretching and even cleavage of the Fe-O bonds. Consequently, more Fe(II)/(III) atoms are exposed to the solvation environment and are available for the binding of active O2 and O2•-. This study demonstrates how common iron minerals and O2 in the natural environment can be combined to yield a green remediation technology.

On the Relative Stability of Linear Time Invariant Systems

In this paper, state space representation based approach to relative stability of Linear Time Invariant (LTI) systems is discussed. Specifically, given a bound on the output, relative Bounded Input-Bounded Output (BIBO) stability of LTI systems is discussed. The bound on dominant pole is first determined using input-output description of LTI system. Using state space representation of homogeneous (no external input) LTI system, the components of state vector are upper bound. The results are applied to Continuous Time Markov Chains (i.e. homogeneous stochastic linear systems). Finally, using state space representation of arbitrary (with external input) Linear Time Invariant systems, the location of dominant pole is bounded. Using the upper bound, the location of line (parallel to imaginary-axis jω and to the left of it) is utilized for determining relative stability.

Production Systems with Parallel Heterogeneous Servers of Limited Capacity: Accurate Modeling and Performance Analysis

Heterogeneous systems of limited capacity have general applications in manufacturing, but also in logistic or service systems due to the differences in server or workstation performance or work assignment; this is in close relationship with system flexibility, where saturation and blocking are ordinary situations of systems with high demand and limited capacity, and thus, accurate loss quantification is essential for performance evaluation. Multi-class systems of limited capacity have been studied much less than parallel homogeneous systems (Erlang models). In this context, accurate models for parallel heterogeneous ordered-entry systems were developed: without any prior queue, i.e., M/Mi/c/c, and with a k-capacity queue, i.e., M/Mi/c/c + k. These new matrix models gave an exact state formulation, and their accuracy was verified using discrete event simulation and comparison with literature results. Also, the effect of the queue capacity was studied in relationship to the pattern of service rates. Next, the heterogeneous recirculating system model was also developed with good approximation results. Finally, the proposed models were applied to evaluate systems with non-exponential service times using a new hybrid methodology by combining the Markovian model and the Monte Carlo method (MCM) for normal or lognormal service times, which also yielded useful good approximations to the simulated system.

Modelling functionalized drug release for a spherical capsule

Advances in material design have led to the rapid development of novel materials with increasing complexity and functions in bioengineering. In particular, functionally graded materials (FGMs) offer important advantages in various fields of application. In this work, we consider a heterogeneous reaction-diffusion model for an FGM spherical drug release system that generalizes the multi-layer configuration to arbitrary spatially-variable coefficients. Our model proposes a possible form for the drug diffusivity and reaction rate functions exhibiting fixed average material properties and a drug release profile that can be continuously varied between the limiting cases of a homogeneous system (constant coefficients) and two-layer system (stepwise coefficients). A semi-analytical solution is then used to solve the model, which provides closed-form expressions for the drug concentration and drug release profiles in terms of generalized Fourier series. Our results show how the release rate of the proposed FGM drug release system can be controlled and continuously varied between a fast (homogeneous) and slow (two-layer) release while maintaining the same averaged values for the diffusivity and reaction rate.

Recent advances in N-formylation reaction for the chemical recycling of carbon dioxide

The homogeneous and heterogeneous catalyst systems applied in N-formylation reaction of amines and CO2 reaction from both homogeneous and heterogeneous systems are summarized.

Some types of homogeneous systems of difference equations of dimension four

The suggested study’s main objective is to create a new meaning for the word “homogeneous system.” With m being a positive integer, this phrase describes a P-self-semi-homogenous system of difference equations on the order of magnitude m. Furthermore, we introduced theorems for scenarios where P equals one and those where it takes any number. Every situation has a value of m, of which some are greater than one and some are equal to one. We provide examples to support each of these values.

Polymerized ionic liquid Co-catalysts driving photocatalytic CO2 transformation.

Photocatalytic production of CO from CO2 has the potential for safe and atom-economic production of feedstock chemicals via in situ carbonylation chemistry. We developed novel ionic liquid-based polymeric materials through radical copolymerisation of 1-butyl-3-vinylimidazolium chloride and photocatalytically active Re- and Ru-complexes that serve as the CO2 reduction catalyst and photosensitiser, respectively. The crosslinked polymeric framework allows for the facile immobilisation of molecular organometallic complexes for use as heterogenised catalysts; moreover, the involved imidazolium core units co-catalyze the reduction of CO2 via covalent interaction. The ratio of sensitiser and catalyst was analysed by laser ablation inductively coupled plasma mass spectroscopy (LA-ICP-MS) and set in relation to results from photocatalytic experiments. Ultimately, the heterogenous polymeric framework showed high selectivity for CO formation on photocatalytic CO2 reduction with improved stability to the corresponding homogenous system.

Illumination homogenization of highly coherent light source based on phase modulation

When using a fly’s eye lens system to homogenize highly coherent light sources, the interference effect between the sub-beams can cause a periodic speckle distribution of illumination intensity, thereby disrupting illumination uniformity. It has been shown that using a rotating optical phase-shift plate behind the fly’s eye lens can eliminate interference patterns, but it only demonstrates engineering realizations. And the theoretical analysis and technical guidance on the phase modulation method and statistical averaging method for fly’s eye lens homogenization systems are still lacking. In this work, a simulation model of fly’s eye random phase modulation homogenization system is developed and studied in detail. Each sub-beam of the fly’s eye lens is randomly phase-modulated to break the coherence condition, and the illumination intensity of multiple independent modulations is accumulated to eliminate the interference pattern. The more times the intensity is accumulated, the better the homogenization is. Meanwhile, studied in this paper are the influence of the diffraction effect on homogenization, and the influence of the sub-lens size and focal length on the homogenization, which result in the diffracting-type system and the imaging-type system respectively. For an imaging type system, it is necessary to ensure that the first fly’s eye lens is in the front focal plane of the second fly’s eye lens. By optimizing the parameters of the fly’s eye lens and using an imaging-type system with <i>p</i> = 1.8 mm and <i>f</i><sub>A</sub> = 9 mm, a Gaussian beam with the non-uniformity of 117% is homogenized into a flat-topped beam with the non-uniformity of 1.2% in a square illumination area of 100 mm<sup>2</sup>. This fly’s eye lens random phase modulation homogenization system has a simple structure, low energy loss, and good illumination uniformity, and can be used in systems that require high coherent laser input and high resolution. This technology can be used in the field of deep-ultraviolet mask defect detection.

Hydrophobic diamine-functionalized ionic liquid for effective transformation of CO2: a bridge to achieve separation and recycling processes in homogeneous systems

The ionic liquid [MAMIm][PF6] promotes the reaction of CO2 and halohydrins under mild conditions with a high yield of cyclic carbonates, and can be readily recycled by simple washing.

Preparation of ceramifiable and ablatively resistant epoxy resins by microphase structure modulation of silicones

The development of ceramic-polymer composites is a focal point in the research of thermal protection systems, and the control of microstructure is crucial for fabricating high-performance resins. In order to investigate the effect of the silicon phase structure on the properties of epoxy resins and preparate the ablation-resistant ceramifiable resins, the homogeneous and “sea-island” phases of epoxy resins with different amounts of silicones were prepared by ring-opening and grafting reactions. The reaction mechanism and the microphase structure of silicone were verified by SEM and TEM. It was found that the homogeneous silicone-epoxy resins exhibited exceptional ablation resistance, with mass and linear ablation rates of 0.0646 g/s and 0.0073 mm/s, which were 78.61 % and 98.36 % lower than those of epoxy resins, and exceeded most of the resin-based ablation-resistant materials reported in the literatures. The homogeneous silicone further slows down the pyrolysis rate of the epoxy resin and inhibits the release of pyrolysis products. During the carbonization and ceramization, the carbothermal reduction reaction between silicon and carbon occurs sufficiently in the homogeneous system, which enhanced the content of SiC ceramics in the carbon layer. Eventually, a dense char layer with low porosity and a highly graphitized structure constructed in situ on the ablative surface, which greatly improves the ablative resistance. Furthermore, its exceptional mechanical properties render it capable of substituting conventional resin-based thermal protection materials, thereby meeting the stringent demands of challenging environments.

Developing homogeneous first row early transition metal catalysts for the oxygen reduction reaction.

The oxygen reduction reaction (ORR) remains an important fixture in biological and synthetic systems for energy conversion and chemical functionalization. Late transition metals continue to dominate in the development of new catalyst systems, inspired by well-characterized metallocofactors and prior successes. By comparison, metals to the left of Fe on the periodic table are relatively understudied for the ORR. This Frontier article summarizes advancements related to the use of Mn, Cr, and V in homogeneous catalyst systems for the ORR and discusses the implications of these results for the development of catalyst systems from these metals and those earlier in the transition metal series.

Oriented Rotatability Exponents of Solutions to Homogeneous Autonomous Linear Differential Systems

Oriented Rotatability Exponents of Solutions to Homogeneous Autonomous Linear Differential Systems

Unlocking the valorization potential of Rooibos tea waste-derived activated carbon in the adsorptive removal of remazol brilliant blue R dye

In this work, we report the use of spent rooibos tea leaves to fabricate activated carbon and use it to adsorptively remove the toxic Remazol Brilliant Blue R (RBBR) from the aqueous solution. The resulting activated carbon (SRTLAC) was characterized by Brunauer-Emmett-Teller N2 adsorption/desorption for surface area analysis, scanning electron microscopy, thermogravimetric analysis, Fourier transform infrared spectroscopy, Raman spectroscopy, and X-ray diffraction for morphological, functional group and crystallinity analyses. A Taguchi design approach was employed to determine the optimal conditions for the RBBR adsorption onto SRTLAC. Among the process variables studied, the sorbent dosage, initial concentration, and pH predominantly affected the removal capacity. The maximum removal of 246.5 mg/g was attained at the highest initial RBBR concentration of 120 mg/L, solution pH of 2, sorbent dosage of 20 mg, and agitation time of 110 min. The analysis of variance results showed that RBBR initial concentration contributed the most significant percentage (95.33 %) towards the removal uptake, highlighting its considerable impact. The adsorption data collected at various concentrations (20 – 120 mg/L) were modelled using three non-linear regression isotherms and kinetic models. The Langmuir isotherm model provided the optimal fit for adsorption, suggesting a monolayer and homogenous sorption system with a maximum capacity of 491.38 mg/g. Meanwhile, the pseudo-2nd order kinetic models accurately elucidated the sorption mechanism. The RBBR species interacted with the SRTLAC functional groups via hydrogen bonding, dipole-dipole interactions, and ion-dipole forces. Therefore, SRTLAC presents a powerful tool for ridding the environment of RBBR dye pollution.

Light switching for product selectivity control in photocatalysis.

Artificial switchable catalysis is a new, rapidly expanding field that offers great potential advantages for both homogeneous and heterogeneous catalytic systems. Light irradiation is widely accepted as the best stimulus to artificial switchable chemical systems. In recent years, tremendous progress has been made in the synthesis and application of photo-switchable catalysts that can control when and where bond formation and dissociation take place in reactant molecules. Photo-switchable catalysis is a niche area in current catalysis, on which systematic analysis and reviews are still lacking in the scientific literature, yet it offers many intriguing and versatile applications, particularly in organic synthesis. This review aims to highlight the recent advances in photo-switchable catalyst systems that can result in two different chemical product outcomes and thus achieve a degree of control over organic synthetic reactions. Furthermore, this review evaluates different approaches that have been employed to achieve dynamic control over both the catalytic function and the selectivity of several different types of synthesis reactions, along with the remaining challenges and potential opportunities. Owing to the great diversity of the types of reactions and conditions adopted, a quantitative comparison of efficiencies between considered systems is not the focus of this review, instead the review showcases how insights from successful adopted strategies can help better harness and channel the power of photoswitchability in this new and promising area of catalysis research.

Liquid-phase hydrogenation of carbon monoxide to methanol using a recyclable manganese-based catalytic system

A simple and recyclable homogeneous catalytic system for the hydrogenation of carbon monoxide to methanol was established.

Multi-groups

In the present paper we define homogeneous algebraic systems. Particular cases of these systems are semigroup (monoid, group) systems. These algebraic systems were studied by J. Loday, A. Zhuchok, T. Pirashvili, and N. Koreshkov. Quandle systems were introduced and studied by V. Bardakov, D. Fedoseev, and V. Turaev. We construct some group systems on the set of square matrices over a field k. Also, we define rack systems on the set V x G , where V is a vector space of dimension n over k and G is a subgroup of GLn(k). Finally, we find the connection between skew braces and dimonoids.

Controlling product selectivity during dioxygen reduction with Mn complexes using pendent proton donor relays and added base.

The catalytic reduction of dioxygen (O2) is important in biological energy conversion and alternative energy applications. In comparison to Fe- and Co-based systems, examples of catalytic O2 reduction by homogeneous Mn-based systems is relatively sparse. Motivated by this lack of knowledge, two Mn-based catalysts for the oxygen reduction reaction (ORR) containing a bipyridine-based non-porphyrinic ligand framework have been developed to evaluate how pendent proton donor relays alter activity and selectivity for the ORR, where Mn(p-tbudhbpy)Cl (1) was used as a control complex and Mn(nPrdhbpy)Cl (2) contains a pendent -OMe group in the secondary coordination sphere. Using an ammonium-based proton source, N,N'-diisopropylethylammonium hexafluorophosphate, we analyzed catalytic activity for the ORR: 1 was found to be 64% selective for H2O2 and 2 is quantitative for H2O2, with O2 binding to the reduced Mn(ii) center being the rate-determining step. Upon addition of the conjugate base, N,N'-diisopropylethylamine, the observed catalytic selectivity of both 1 and 2 shifted to H2O as the primary product. Interestingly, while the shift in selectivity suggests a change in mechanism for both 1 and 2, the catalytic activity of 2 is substantially enhanced in the presence of base and the rate-determining step becomes the bimetallic cleavage of the O-O bond in a Mn-hydroperoxo species. These data suggest that the introduction of pendent relay moieties can improve selectivity for H2O2 at the expense of diminished reaction rates from strong hydrogen bonding interactions. Further, although catalytic rate enhancements are observed with a change in product selectivity when base is added to buffer proton activity, the pendent relays stabilize dimer intermediates, limiting the maximum rate.