Unstable Products Research Articles

Egg Yolk, a Multifunctional Emulsifier: New Insights on Factors Influencing and Mechanistic Pathways in Egg Yolk Emulsification

Egg yolk is a highly effective natural emulsifier used in various food products. Its emulsifying properties are influenced by food product chemical conditions, and processing methods. Nevertheless, to effectively utilize egg yolk in food products, a more comprehensive understanding of these factors is crucial. This review discusses recent developments regarding how factors like pH, ionic strength, thermal treatments, enzymatic treatments, and novel non-thermal treatments affect egg yolk emulsifying properties. It also explores the underlying mechanisms involved in egg yolk emulsification. Food products involve different ingredients leading to varying pH values and ionic strength, which affect egg yolk protein adsorption and emulsion stability. Processing steps like thermal treatment can damage egg yolk proteins, reducing their emulsifying capabilities and leading to unstable products. Incorporating sugar, salt, and amino acids can enhance egg yolk’s resistance to heat and preserve its ability to form stable emulsions. As an alternative to thermal treatment, non-thermal techniques such as high-pressure processing and high-intensity ultrasound can be employed to preserve egg yolk. Furthermore, forming egg yolk–polysaccharide complexes can enhance egg yolk emulsifying properties. These advancements have facilitated the creation of egg yolk-based products such as high internal phase Pickering emulsions (HIPEs), low-fat mayonnaise, and egg yolk gels. A comprehensive understanding of the emulsifying mechanisms and factors involved in egg yolk will be instrumental in improving food quality and creating novel egg yolk-based products.

An easy and sensitive assay for acetohydroxyacid synthases based on the simultaneous detection of substrates and products in a single step.

Acetohydroxyacid synthase (AHAS, EC 2.2.1.6) catalyzes the first step in the synthesis of the branched-chain amino acids valine, leucine, and isoleucine, pathways being present in plants and microorganisms, but not in animals. Thus, AHAS is an important target for numerous herbicides and, more recently, for the development of antimicrobial agents. The need to develop new and optimized herbicides and pharmaceuticals requires a detailed understanding of the biochemistry of AHAS. AHAS transfers an activated two-carbon moiety derived from pyruvate to either pyruvate or 2-oxobutyrate as acceptor substrates, forming 2-acetolactate or 2-acetohydroxy-2-butyrate, respectively. Various methods have been described in the literature to biochemically characterize AHAS with respect to substrate preferences, substrate specificity, or kinetic parameters. However, the simultaneous detection and quantification of substrates and unstable products of the AHAS-catalyzed reaction have always been a challenge. Using AHAS isoform II from Escherichia coli, we have developed a sensitive assay for AHAS-catalyzed reactions that uses derivatization with ethyl chloroformate to stabilize and volatilize all reactants in the aqueous solution and detect them by gas chromatography coupled to flame ionization detection or mass spectrometry. This assay allows us to characterize the product formation in reactions in single and dual substrate reactions and the substrate specificity of AHAS, and to reinterpret previous biochemical observations. This assay is not limited to the AHAS-catalyzed reactions, but should be applicable to studies of many metabolic pathways.

Opportunities and Challenges in the Synthesis of Noble Metal Nanoparticles via the Chemical Route in Microreactor Systems.

The process of noble metal nanoparticle synthesis is complex and consists of at least two steps: slow nucleation and fast autocatalytic growth. The kinetics of these two processes depends on the reductant "power" and the addition of stabilizers, as well as other factors (e.g., temperature, pH, ionic strength). Knowing these parameters, it is possible to synthesize materials with appropriate physicochemical properties, which can be simply adjusted by the type of the used metal, particle morphology and surface property. This, in turn, affects the possibility of their applications in various areas of life, including medicine, catalysis, engineering, fuel cells, etc. However, in some cases, the standard route, i.e., the chemical reduction of a metal precursor carried out in the batch reactor, is not sufficient due to problems with temperature control, properties of reagents, unstable or dangerous intermediates and products, etc. Therefore, in this review, we focused on an alternative approach to their chemical synthesis provided by microreactor systems. The use of microreactors for the synthesis of noble metal nanomaterials (e.g., Ag, Au, Pt, Pd), obtained by chemical reduction, is analyzed, taking into account investigations carried out in recent years. A particular emphasis is placed on the processes in which the use of microreactors removed the limitations associated with synthesis in a batch reactor. Moreover, the opportunities and challenges related to the synthesis of noble nanomaterials in the microreactor system are underlined. This review discusses the advantages as well as the problems of nanoparticle synthesis in microreactors.

Structure-Based Computational Scanning of Chemical Modification Sites in Biologics.

To address the challenges of short half-life, immunogenicity, and nonspecific distribution, chemical modifications of peptide and protein-based drugs have emerged as a versatile strategy for improving their therapeutic efficacy. One such modification involves the derivatization of peptides and proteins with fatty acids, which can protract their half-life, modify their biodistribution, and potentially enable targeted delivery to specific tissues or disease sites of interest. However, the present strategies for the synthesis of such synthetically modified biologics require numerous rounds of experimental testing and often yield unstable, inactive, or heterogeneous products. To address the inefficiencies in designing modified biologics, we developed a hybrid computational workflow that integrates RosettaMatch from the Rosetta suite of protein modeling tools with molecular dynamics (MD) simulations. This approach not only reduces the number of amino acid positions that need to be experimentally tested by targeting only the most promising candidates for modification but also expedites the design of chemically modified biologics with the desired properties, ensuring a rapid and cost-effective development cycle. Although we demonstrate the utility of our method on a peptide therapeutic, GLP-1, with different fatty acid derivatizations, this straightforward approach has the potential to streamline the design process of a diverse range of chemically modified therapeutics, enabling tailored enhancements to their pharmacokinetic properties.

Increased Productivity of Regional Potential-based MSMEs through Partnership Development

The current existing condition in Labuhanbatu Regency, where the number and performance of SMEs are not yet competitive enough, especially in the digital market which currently holds significant influence in the buying and selling process of SME products. There is a need for further training related to digital transformation, considering that technology now plays a crucial role in SME development. This research aims to examine the average productivity index of SMEs in Labuhanbatu, the region's potential, and partnership strategies in Labuhanbatu Regency. The study employs average index analysis using a perception measurement scale of 1-7 on 81 SMEs in Labuhanbatu and 8 local government organizations, as well as a SWOT analysis. Based on the Strengths, Weaknesses, Opportunities, and Threats analysis, SMEs in Labuhanbatu have strengths such as optimized production, adequate local potential, support programs for SMEs, and fairly good SME skills. Weaknesses include limited production support equipment and inadequate marketing networks. Opportunities for SMEs include the growth of SME industries, supportive skills training programs, improved communication, ease of licensing processes, and non-burdensome taxes for businesses. Meanwhile, threats include unstable product prices, inadequate financial support from local government, and insufficient marketing awareness efforts by the local government.

Design of wireless transmission system for intelligent agricultural greenhouse data acquisition based on modbus communication protocol

Abstract Traditional agricultural greenhouses rely too much on manual labor and have a poor ability to adjust the key factors that affect crop growth, such as temperature, humidity, and illumination, resulting in low production efficiency and unstable product quality. Based on the MODBUS communication protocol, a set of intelligent agricultural greenhouse data acquisition wireless transmission systems is designed in this paper. Intelligent instruments, sensors, wireless transmission equipment, and smart control equipment (PLC) have been introduced in agricultural greenhouses. These sensors and instruments automatically collect data and wirelessly transmit it to the intelligent control system in the control room, which is located a few kilometers away. The intelligent control system processes the data and generates various control instructions which are then transmitted to the executive mechanism in agricultural greenhouses for implementation. We complete automatic adjustment of temperature, humidity, illuminance, and other parameters and operations. The intelligent, large-scale, and unmanned agricultural greenhouses are realized. It greatly improves the production efficiency and product quality of crops.

Reactivity-Tunable Fluorescent Platform for Selective and Biocompatible Modification of Cysteine or Lysine.

Chemoselective modification of specific residues within a given protein poses a significant challenge, as the microenvironment of amino acid residues in proteins is variable. Developing a universal molecular platform with tunable chemical warheads can provide powerful tools for precisely labeling specific amino acids in proteins. Cysteine and lysine are hot targets for chemoselective modification, but current cysteine/lysine-selective warheads face challenges due to cross-reactivity and unstable reaction products. In this study, a versatile fluorescent platform is developed for highly selective modification of cysteine/lysine under biocompatible conditions. Chloro- or phenoxy-substituted NBSe derivatives effectively labeled cysteine residues in the cellular proteome with high specificity. This finding also led to the development of phenoxy-NBSe phototheragnostic for the diagnosis and activatable photodynamic therapy of GSH-overexpressed cancer cells. Conversely, alkoxy-NBSe derivatives are engineered to selectively react with lysine residues in the cellular environment, exhibiting excellent anti-interfering ability against thiols. Leveraging a proximity-driven approach, alkoxy-NBSe probes are successfully designed to demonstrate their utility in bioimaging of lysine deacetylase activity. This study also achieves integrating a small photosensitizer into lysine residues of proteins in a regioselective manner, achieving photoablation of cancer cells activated by overexpressed proteins.

Frictional Stability of Laumontite Under Hydrothermal Conditions and Implications for Injection‐Induced Seismicity in the Gonghe Geothermal Reservoir, Northwest China

AbstractLaumontite is a common and potentially frictionally unstable hydrothermal alteration product present in deep faults of the Gonghe EGS reservoir. We characterize the friction‐stability characteristics of synthetic laumontite gouge under in situ reservoir conditions. The pure laumontite gouge is frictionally strong (μ = 0.73–0.98) and the quartz/laumontite mixture (1:1) is generally less strong (μ = 0.73–0.78) under experimental conditions (Pc = 95 MPa, T = 90–250°C, Pf = 0–90 MPa). The shear velocity was stepped between 6.1, 0.61, then 0.061 μm/s for our experiments. For both gouges, the friction coefficient is independent of temperature and increases with elevated pore pressures. The pure gouge and mixture are strongly velocity‐weakening over a broad range in temperatures (∼90–220°C) and excess pore pressures (0–90 MPa) relevant to the Gonghe stimulation. Microearthquakes (MEQs) observed during stimulation are confined to within the broad depth range of inferred frictional instability—although fluid overpressures are also limited to this region. The observation that laumontite mixtures are frictionally unstable over a broad range of pressures and especially temperatures representative of EGS reservoirs and insensitive to the presence of the coexisting mineral phase (quartz) suggests its presence is a strong indicator of potential seismic hazard.

Logistic regression in approximation of the results of gas chromatographic analysis of thermally unstable compounds

Regularities and peculiarities of gas chromatographic analysis of thermally unstable compounds were considered on the example of mixture of the reaction products of isopropylbenzene (cumene) free-radical chlorination. The principal constituent in this mixture is (1-chloro-1-methylethyl)benzene, which has the lowest thermal stability, and is partially converted to a-methylstyrene, the only product of its thermal destruction at the chromatograph injector temperatures up to 300 °С. Nevertheless, the results of the study confirms that the gas chromatographic analysis of chloroalkylarenes is possible without their decomposition with the injector temperatures up to 200 °С, even if the analytes contain chlorine atoms at the tertiary carbon atoms and in the “benzylic” positions relative to the aromatic fragment. Similar control of thermal stability of analytes can be recommended for other samples contained potentially unstable constituents. It is shown that thermal decomposition of thermally unstable constituents of samples cannot be revealed from the results of gas chromatographic analysis with capillary columns using variations of their absolute peak areas. Such task can be solved only by using relative peak areas calculated in respect to thermally stable compounds. The dependencies of relative peak areas of unstable constituents vs. temperature (descending), as well as those of their decomposition products (ascending) are characterized by presence of two limits. Low temperature limits correspond to the real content of unstable constituents or their decomposition products is the samples, while the upper limits – to the composition of such samples at their hypothetically complete destruction. Such dependencies can be approximated by logistic regression equation if sampling into capillary columns is carried out at relatively high split ratios (approx. not less than 10 : 1). At lower split ratios the temperature dependencies of peak areas of unstable constituents and products of their transformation are strongly distorted by so-called sample’s composition discrimination effects that make impossible data approximation using logistic regression.

Research on Hema Fresh Agricultural Products E-commerce Operation Strategy

With the development of the economy, people's living standards continue to improve, and the requirements for food quality and food safety are also constantly increasing. More and more fresh agricultural products e-commerce companies have appeared on the market. Hema Fresh has achieved great success in the Shanghai area. A great success. After Hema Fresh successfully operated in Shanghai, it has been launched in Beijing, Hangzhou, Guangzhou and other cities one after another, providing convenience to consumers. However, Hema Fresh also encountered some problems during its development. This article first analyzes the problems encountered by Hema Fresh in the development process, mainly including: unstable product quality, low logistics and distribution efficiency, single platform partners, etc.; secondly, it uses SWOT analysis method to analyze Hema Fresh’s operation process The existing strengths, weaknesses, opportunities, and threats were analyzed; finally, based on the actual situation of Hema Fresh, a series of suggestions and countermeasures were put forward to improve its operational capabilities.

Optimization effect of propylene oxide (PO) on evaporation, combustion, and pollutant emissions of high-energy–density JP-10 fuel

JP-10 is a high-energy–density fuel that is widely used in aerospace propulsion systems due to its wide range of synthetic raw materials and low production costs. However, it faces challenges related to difficult ignition, low combustion efficiency and high pollutant emissions. To address this, blending JP-10 with propylene oxide (PO), a highly volatile substance, provides a practical solution. This study investigates the propagation and evolution characteristics of JP-10/PO binary fuel in large horizontal pipelines. The results demonstrate a synergistic enhancement effect achieved by the JP-10/PO hybrid fuel. PO, with its lower boiling point, quickly evaporates from the mixed droplets, creating a continuous primary flame. As the droplet temperature increases, JP-10, known for its high combustion heat, starts to evaporate, actively participating in the explosion process and forming a secondary flame that spreads in two directions. The combustion of the JP-10/PO mixed droplets involves both physical and chemical processes, including droplet evaporation and gaseous combustion. A binary droplet evaporation model is developed to quantitatively assess the impact of PO fuel ratio on spray evaporation. Additionally, the study examines steam explosion parameters and reaction product characteristics under different PO fuel ratios. It is observed that the evaporation of JP-10/PO mixed droplets occurs in three stages: transient heating, binary equilibrium evaporation, and single component equilibrium evaporation. Increasing the PO fuel ratio leads to a higher temperature rise rate of the droplets and an increased evaporation reaction rate constant. Moreover, the ignition delay time of JP-10/PO gas-phase mixture fuel decreases, while the adiabatic flame temperature gradually reduces. Furthermore, higher PO fuel ratios help reduce the emissions of unstable products in both mixed fuels due to the inherent oxygen content of PO molecules. The current research results can provide scientific references for the improvement of high-energy density fuels and the development of new propellants.

The Physicochemical Properties and Melting Behavior of Ice Cream Fortified with Multimineral Preparation from Red Algae.

Ice cream is a popular frozen food consumed worldwide throughout the year. However, as a thermally unstable product, it requires proper cold chain management. Thermal fluctuations alter the physicochemical properties of ice cream and reduce its quality. This study was conducted to evaluate the physicochemical and sensory properties of ice cream containing different amounts (0.5; 0.8; 1.0%) of a multimineral preparation from Atlantic red algae. The effect of thermal shock on the quality of ice cream after preparation and 90 days of frozen storage was studied. The addition of a multimineral component slightly increased the freezing and glass transition temperatures of the ice cream. The overrun of the ice cream ranged from 48.55 to 52.78% and decreased with the frozen storage time, but the samples with 0.8 and 1.0% mineral content had the most stable overrun in terms of storage time and thermal fluctuations. Ice cream stored for both 7 and 90 days showed a similar melting behavior, although a shift in the melting curves was observed after long frozen storage. The samples exposed to the thermal treatment had lower melting rates by 39.2-59.9% and 55.2-65.4% for 7-day and 90-day stored ice cream, respectively. The hardness parameters of the ice cream did not change significantly under the conditions applied, so the fragility of the ice cream and its fluffiness did not seem to be affected. The organoleptic evaluation showed that ice cream with a mineral content of 0.8% was the most acceptable in terms of taste, texture, and overall acceptability. The applied mineral and sucrose content ratios did not alter the main physicochemical and organoleptic parameters, but significantly affected the nutrient density of the ice cream.

Enhancement of telomerase extension via quadruple nucleic acid recycling to develop a novel colorimetric biosensing method for kanamycin assay

BackgroundColorimetric biosensors have important value for antibiotic residue testing. However, many previous methods were constructed based on the optical density change of certain unstable single-colored products with poor discrimination for visual measurements. Moreover, their low extinction coefficients usually result in low sensitivity of biosensors. In addition, many conventional signal amplification strategies often involve sophisticated nanomaterial preparation, inconvenient multi-step assay manipulation and limited signal amplification ability. Therefore, the development of new colorimetric biosensing strategies with excellent visual discrimination, high sensitivity and convenient manipulation is highly desirable. ResultsWe designed a target recycling accelerated cascade DNA walking amplification mechanism to trigger a telomerase extension-related enzymatic reaction, and developed a novel colorimetric biosensing strategy for kanamycin (Kana) assay. The target recycling was induced by an exonuclease III-assisted aptamer recognition reaction, which could also trigger the successive DNA walking at the streptavidin (SA)- and magnetic bead (MB)-based tracks. This not only caused the quantitative exposure of the telomeric substrate primers on MB surfaces but also released another strand to accelerate the SA-based DNA walking. By using the telomerase extension product to link numerous alkaline phosphatases and induce the plasmonic property change of gold nanobipyramids (Au NBPs), a colorimetric signal output strategy was constructed. This method could be applied for the high-resolution visual screening of Kana, and it also showed a very low detection limit of 17.6 fg mL−1 for assaying Kana over a wide, five-order-magnitude linear range. SignificanceThe quadruple nucleic acid recycling-enhanced telomerase extension resulted in the ultrahigh sensitivity of the method and also excluded the sophisticated manipulations involved in conventional biosensing strategies. The multiple enzyme catalysis-induced plasmonic property change of Au NBPs realized the stable and multicolor visual signal transduction. Together with its low cost, simple operation, high selectivity, excellent repeatability, and reliable performances, this method exhibits great potential for use in practical applications.

Alternative Options for Ebullated Bed Vacuum Residue Hydrocracker Naphtha Utilization

The vacuum residue hydrocracker naphtha (VRHN) is a chemically unstable product that during storage changes its colour and forms sediments after two weeks. It cannot be directly exported from the refinery without improving its chemical stability. In this research, the hydrotreatment of H-Oil naphtha with straight run naphtha in a commercial hydrotreater, its co-processing with fluid catalytic cracking (FCC) gasoline in a commercial Prime-G+ post-treater, and its co-processing with vacuum gas oil (VGO) in a commercial FCC unit were discussed. The hydrotreatment improves the chemical stability of H-Oil naphtha and reduces its sulphur content to 3 ppm. The Prime-G+ co-hydrotreating increases the H-Oil naphtha blending research octane number (RON) by 6 points and motor octane number (MON) by 9 points. The FCC co-cracking with VGO enhances the blending RON by 11.5 points and blending MON by 17.6 points. H-Oil naphtha conversion to gaseous products (C1–C4 hydrocarbons) in the commercial FCC unit was found to be 50%. The use of ZSM 5 containing catalyst additive during processing H-Oil naphtha showed to lead to FCC gasoline blending octane enhancement by 2 points. This enabled an increment of low octane number naphtha in the commodity premium near zero sulphur automotive gasoline by 2.4 vol.% and substantial improvement of refinery margin. The processing of H-Oil naphtha in the FCC unit leads also to energy saving as a result of an equivalent lift steam substitution in the FCC riser.

Optimal cyclic scheduling of ethylene plants in backup furnace mode with separation capacity constraints

Ethylene plants (EPs) are a critical output source of ethylene. The cyclic scheduling optimization is crucial to increase the profitability of an EP. The EP comprises the ethylene cracking furnace system (ECFS), quenching, compression, separation sections, etc., which culminates in a large-scale optimization problem. In addition, the performance-decaying and semi-continuous characteristics of the ECFS inevitably lead to fluctuations in product throughput, resulting in an unstable production process and product quality decline. To address this issue, we propose a mixed-integer quadratic programming (MIQP) model for the cyclic scheduling of the EP in backup furnace mode with separation capacity constraints. This novel model can reduce fluctuations in product throughput by running a backup furnace when one furnace is shut down for decoking. Besides, the separation capacity constraints ensure that high-quality products can be separated from the cracked gas downstream. Moreover, the reformulated normalized multiparametric disaggregation technique (RNMDT), which relies on convex envelopes, is employed to relax the proposed MIQP model into a mixed-integer linear programming (MILP) model by partitioning the domain of the variables in the quadratic terms. Subsequently, an optimization framework based on the RNMDT is established to enhance the solution efficiency of the original problem. Finally, a case study from the real world reveals the effectiveness of the proposed method, which can provide instructive optimal cyclic scheduling for the EP.

Effect of Al Content on the Long-Term Corrosion Behavior of Arc-Sprayed ZnAl Alloy Coatings

The corrosion of steel structures in aggressive marine environments is a vital issue that induces significant degradation of their performance and lifespan. Herein, three arc-sprayed ZnAl coatings with varied Al contents of 0 wt.%, 15 wt.%, and 50 wt.% were deposited onto a hull steel substrate. The effect of Al content on the long-term corrosion protection performance of ZnAl coatings left in a chloride-containing solution for 840 h was systematically investigated. The evolutions of open-circuit potential, polarization curves, and electrochemical impedance spectroscopy of different ZnAl coatings during the long-term immersion test were examined. The morphologies and phase constitutions of the corrosion products were characterized. The results indicated that the corrosion rate of ZnAl coatings decreased as the Al content increased, and the ZnAl50 coating exhibited the most superior long-term corrosion protection performance. Moreover, for the three ZnAl coatings with an Al contents varying from 0 to 50%, their corrosion rate increased with immersion time in the initial 360 h due to the formation of the unstable and porous corrosion product ZnO; after 360 h immersion, their corrosion rate decreased with the prolonging of immersion time. This was revealed to be related to the formation of different corrosion products. ZnO and stable Al2O3 were the main corrosion products for the pure Zn coating and ZnAl15 coating, respectively. Al2O3 and powerful layered double hydroxide Zn6Al2(OH)16CO3·4H2O were found to be the dominant corrosion products of the ZnAl50 coating, which was responsible for its remarkable long-term corrosion protection performance.

Unraveling the Antioxidant Activity of 2R,3R-dihydroquercetin.

It has been reported that in an oxidative environment, the flavonoid 2R,3R-dihydroquercetin (2R,3R-DHQ) oxidizes into a product that rearranges to form quercetin. As quercetin is a very potent antioxidant, much better than 2R,3R-DHQ, this would be an intriguing form of targeting the antioxidant quercetin. The aim of the present study is to further elaborate on this targeting. We can confirm the previous observation that 2R,3R-DHQ is oxidized by horseradish peroxidase (HRP), with H2O2 as the oxidant. However, HPLC analysis revealed that no quercetin was formed, but instead an unstable oxidation product. The inclusion of glutathione (GSH) during the oxidation process resulted in the formation of a 2R,3R-DHQ-GSH adduct, as was identified using HPLC with IT-TOF/MS detection. GSH adducts appeared on the B-ring of the 2R,3R-DHQ quinone, indicating that during oxidation, the B-ring is oxidized from a catechol to form a quinone group. Ascorbate could reduce the quinone back to 2R,3R-DHQ. No 2S,3R-DHQ was detected after the reduction by ascorbate, indicating that a possible epimerization of 2R,3R-DHQ quinone to 2S,3R-DHQ quinone does not occur. The fact that no epimerization of the oxidized product of 2R,3R-DHQ is observed, and that GSH adducts the oxidized product of 2R,3R-DHQ on the B-ring, led us to conclude that the redox-modulating activity of 2R,3R-DHQ quinone resides in its B-ring. This could be confirmed by chemical calculation. Apparently, the administration of 2R,3R-DHQ in an oxidative environment does not result in 'biotargeting' quercetin.

Study on photodissociation and photoconversion characteristics of CS2 in O2/O3 environment using real-time conversion products obtained by UV-DOAS

Carbon disulfide (CS2) is extremely susceptible to decomposition by ultraviolet radiation, and its decomposition products affect the concentration of trace gases in the atmosphere, which disrupts the balance of atmospheric chemistry. It is essential to elucidate the photochemical reaction characteristics of CS2 for more in-depth study of the complex chemical and physical changes in the atmosphere. Therefore, this paper firstly provides a clear visualization of the evolution process of CS2 and conversion products by UV differential optical absorption spectroscopy combined with multi-wavelength least squares method, and then the photodissociation and photoconversion characteristics of CS2 under trace-oxygen, additional-oxygen and additional-ozone conditions are explained. The results show that the generation of SO2 from CS2 is about 100 ppm when only trace-oxygen is present, and the main channels of the reaction are CS2+hv→CS+S and CS+4O→SO2+CO2. The SO2 concentration increased from 138 ppm to 150 ppm as the oxygen concentration increased with the main reaction channels CS2+6O→2SO2+CO2 and CS+4O→SO2+CO2. However, in the additional-ozone environment, the main reaction channels CS2+2O3→2SO2+CO2 and CS+4/3O3→SO2+CO2 gradually dominate as the ozone concentration increases, at which point the SO2 concentration decreases from 140 ppm to 125 ppm. The results indicate that in the photochemical reaction of CS2, the unstable products O atoms and CS directly affect the photochemical reaction rate and the concentration of SO2. This study not only enables real-time monitoring of the evolution process and conversion products of CS2, but also lays the foundation for future studies on the conversion properties of CS2 in photochemical reactions.

Multi-Zone Integrated Iterative-Decoupling Control of Temperature Field of Large-Scale Vertical Quenching Furnaces Based on ESRNN

Temperature uniformity within a large vertical quenching furnace is the key factor to determine the properties of aluminum workpieces. The existing temperature control method for quenching furnaces cannot overcome the influence of multi-zone coupling issues, which lead to unstable product performance and a lack of key performance. Based on a workpiece temperature field model, a spatial-temporal dimensional extrapolation method is proposed to realize fast and accurate solving of the temperature model. In view of the over-burning and under-burning problems during the temperature rising period, a self-incentive nonparametric adaptive iterative control algorithm is presented, which realizes consistent temperature rising of multiple heating zones. Aiming at the strong coupling problem of the multi-zone heating manner during the temperature holding period, the decoupling problem of multiple control loops is converted into a multi-loop integrated control optimization problem. An eigenvector self-update recurrent neural network (ESRNN) is constructed to determine the Jacobian information and tune the control parameters of each loop controller in real time, thereby realizing the integrated intelligent decoupling control of multiple heating loops. Simulation and industrial results verify the superiority of the proposed method, which can realize high-precision and high-uniformity control of a large-scale temperature field and effectively improve the quality and performance of aluminum alloy workpieces.

A biosynthetic aspartate N-hydroxylase performs successive oxidations by holding intermediates at a site away from the catalytic center

Nitrosuccinate is a biosynthetic building block in many microbial pathways. The metabolite is produced by dedicated L-aspartate hydroxylases that use NADPH and molecular oxygen as co-substrates. Here, we investigate the mechanism underlying the unusual ability of these enzymes to perform successive rounds of oxidative modifications. The crystal structure of Streptomyces sp. V2 L-aspartate N-hydroxylase outlines a characteristic helical domain wedged between two dinucleotide-binding domains. Together with NADPH and FAD, a cluster of conserved arginine residues forms the catalytic core at the domain interface. Aspartate is found to bind in an entry chamber that is close to but not in direct contact with the flavin. It is recognized by an extensive H-bond network that explains the enzyme's strict substrate-selectivity. A mutant designed to create steric and electrostatic hindrance to substrate binding disables hydroxylation without perturbing the NADPH oxidase side-activity. Critically, the distance between the FAD and the substrate is far too long to afford N-hydroxylation by the C4a-hydroperoxyflavin intermediate whose formation is confirmed by our work. We conclude that the enzyme functions through a catch-and-release mechanism. L-aspartate slides into the catalytic center only when the hydroxylating apparatus is formed. It is then re-captured by the entry chamber where it waits for the next round of hydroxylation. By iterating these steps, the enzyme minimizes the leakage of incompletely oxygenated products and ensures that the reaction carries on until nitrosuccinate is formed. This unstable product can then be engaged by a successive biosynthetic enzyme or undergoes spontaneous decarboxylation to produce 3-nitropropionate, a mycotoxin.