Decomposition Products Research Articles

Differences in the molecular structure of curcumin and its breakdown products affect their inhibitory effect on pepsin: Kinetic and protein spatial conformation study

Curcumin, a natural phenolic compound with various bioactivities, is easily decomposed into stability ferulic acid and vanillin molecules. Whether the functional equivalence of decomposition products can match that of curcumin is a matter worth attention. In this work, the inhibition and interaction of curcumin and its decomposition products on pepsin were studied. The inhibition by curcumin and ferulic acid belonged to competitive inhibition, the quenching types were static quenching with spontaneous process. Binding energies of curcumin, ferulic acid and vanillin were -8.33±0.14, -7.88±0.09 and -6.12±0.08 kcal/mol, respectively, through H-bonds and hydrophobic interactions. All molecules significantly changed the secondary structure of pepsin and reduced the deformation temperature about 15 °C. The results show that better inhibition on pepsin from curcumin than ferulic acid, whereas vanillin did not show inhibition. The results provided the experimental basis for curcumin as potential inhibitors of pepsin in special diets.

Synergetic enzymatic reactive crystallization of cefaclor catalyzed by PGA

In the context of the severe global carbon emission crisis, green and sustainable enzymatic reactions are garnering widespread attention in the industry. However, these processes still face numerous challenges, such as limitations imposed by reaction equilibrium, product decomposition, and inhibition. Product removal via crystallization has the potential to address these issues. More importantly, crystal product properties can be directly manipulated during enzymatic reactive crystallization (ERC), such as polymorphic purity, size, and morphology in a single batch. In the synthesis of cefaclor catalyzed by penicillin G acylase (PGA), primary and secondary hydrolysis greatly limited the efficiency of the reaction. Thus, ERC was performed to combine the advantages of green enzymatic reactions and controllable direct crystallization. Initially, a supersaturated solution of the substrate was established, and cefaclor crystals were seeded to the enzymatic reaction system at a proper time. Subsequently, operating parameters were adjusted to facilitate selective crystallization of cefaclor. It is noteworthy that both immobilized and free enzymes were examined in our research. Ultimately, cefaclor crystals with purity exceeding 99% were obtained directly. The yield of cefaclor reached as high as 88%. It is believed that this method held significant promise for the green and efficient production of high-purity cefaclor and demonstrated considerable potential for application in more similar pharmaceutical scenarios.

Effect of operating temperature on ammonia decomposition behavior and cell performance of direct ammonia solid oxide fuel cells

Direct ammonia solid oxide fuel cells (DA-SOFC) are regarded as a promising power generation technology. Nevertheless, the catalytic reaction of ammonia on the anode surface significantly affects DA-SOFC performance. This study explores the deterioration of DA-SOFC performance in the 550–700 °C and the interaction between NH3 decomposition and electrochemical reactions. The findings indicate that, at 550 °C, compared to H2, the reduction in power density of NH3 18.58% exceeds 4.56%t of NH3 d.s.g. (mixtures, 0.75H2 + 0.25N2). The anodic polarization impedance of NH3 exceeds that of H2 and NH3 d.s.g. by 51.1% and 28.9%, respectively. Cathode utilizing O2 has a dual impact on NH3 decomposition, at lower temperatures, oxidizing the anode's active site, decreasing NH3 decomposition rate, resulting in insufficient H2 supply, reducing electron transfer coefficient. Conversely, at higher temperatures, O2 promotes NH3 decomposition by boosting H2 consumption. However, more N2 is produced, increasing the concentration loss.

Innovative strategies for ammonia nitrogen removal in rare earth tailings: An advanced element recycling process using leaching, chemical precipitation and adsorption

Residual ammonium salt in closed rare earth mining sites leads to elevated levels of ammonia nitrogen in the surrounding environment. To mitigate ammonia nitrogen pollution at its source, a cost-effective and environmentally friendly recycling process was proposed. This process involves leaching residual ammonia nitrogen using a magnesium sulfate solution, followed by chemical precipitation for ammonia nitrogen removal. Additionally, nitrogen can be recovered as ammonia gas through the thermal decomposition of precipitates, allowing for further ammonia nitrogen adsorption from the leachate. The residual ammonium salts leaching rate reached 96.38 % with a 0.1 mol/L magnesium sulfate solution at a flow rate of 0.6 mL/min. The chemical precipitation method achieved a maximum nitrogen removal rate of 86.87 %, with an activation energy of 2.6 kJ/mol, indicating a relatively rapid process. At 190 °C, the ammonia nitrogen release rate of precipitates was 82.5 % after 2 h of thermal decomposition. The adsorption process was consistent with pseudo-second-order kinetics models using thermal decomposition products. Overall, the comprehensive removal rate of residual ammonium salts from the closed rare earth mining site was approximately 83.3 % in recycling process, optimizing the utilization of phosphorus, magnesium, and nitrogen and achieving efficient and environmentally friendly nitrogen removal.

 Synthesis and Characterization of Chitosan-Based Schiff Base and Cu(II) Complex from Shrimp Shells and its Application on Catalysis and Bio-sorption

In recent years, metal complexes and biopolymers have gained significant attention in environmental applications such as catalysis and heavy metal removal. Chitosan, a biopolymer derived from chitin, is well-known for its biodegradability, non-toxicity, and strong metal ion affinity, which can be further enhanced through Schiff bases to improve its catalytic and adsorption capabilities. The primary objectives of this study were to investigate whether Cu(II) complex of Chitosan Salicylaldehyde Schiff Base CSSB-Cu(II) can act as an efficient catalyst in hydrogen peroxide decomposition reaction and to find out the raw absorbent which has the highest Cadmium ion removal efficiency from among the absorbents Chitin (CT), Chitosan (CS) and Chitosan Salicylaldehyde Schiff Base (CSSB). CSSB was synthesized using the Schiff condensation reaction between the amino group of CS and the carbonyl compound of salicylaldehyde with the elimination of water molecules and it was complexed with Cu(II) ion to produce CSSB-Cu(II) complex. The catalytic effect of the CSSB-Cu(II) complex on the kinetics of the decomposition of hydrogen peroxide was investigated and compared with CSSB. CSSB-Cu(II) showed a better catalytic effect than CSSB and has a pseudo-first-order catalytic decomposition for H2 O2 . CT, CS, and CSSB were investigated as adsorbents for the Cd(II) removal to determine their cadmium removal efficiencies. This study concludes that the removal efficiency of CSSB was greater than that of CS and CT. The equilibrium data agreed more with the Langmuir model than with the Freundlich model. The IR and electronic spectral data confirm the presence of an imine bond and the existence of the complex in square planar geometry.

Experimental and molecular dynamics study on combustion characteristics of non-stick coal

To investigate the combustion characteristics of non-stick coal and the formation patterns of main combustion products and radicals, this study initially conducted a TG-DSC experiment of non-stick coal. Subsequently, non-stick coal was characterized and analyzed using XPS and 13C NMR experiments, and a molecular model with the formula C208H199O23N3S was constructed. Subsequently, the ReaxFF MD method was employed to simulate the combustion molecular dynamics of the non-stick coal periodic mixing model under varying oxygen content and temperature conditions. The analysis focused on elucidating the formation patterns of free and primary products during combustion. Experimental findings indicate that the combustion of non-stick coal progresses through stages, including water evaporation and desorption (30–145.65 °C), dynamic equilibrium (145.65–181.76 °C), oxygen weight gain (181.76–263.56 °C), thermal decomposition (263.56–379.14 °C), combustion (379.14–562.04 °C) and burnout (562.04–800 °C). The ignition temperature of non-stick coal was determined to be 379.14 °C. The simulation results indicate that an increase in temperature and oxygen content further enhances the relatively stable peak production of CO2. The peak increase of CO production is weaker than that of CO2. The rise in temperature also promotes the formation of H2O, while the increase in oxygen content initially enhances and subsequently inhibits the peak production of H2O. H radicals, O radicals, and OH radicals are primarily generated through the decomposition reactions of small molecular compounds or other free radicals. Free radical polymerization and the decomposition of small molecular compounds represent the primary pathways for the formation of CO, CO2, and H2O.

Simulation of Acetylene Formation from Methane in a Plasma Jet

This work is devoted to the numerical modeling of the reaction of methane conversion to acetylene under plasma-jet pyrolysis conditions and a comparison of the obtained results with the available experimental data. The calculations were performed within the framework of the ideal plug-flow reactor model for atmospheric pressure. The analysis of the main processes of methane decomposition and acetylene formation was carried out in cases where either hydrogen or methane was used as a plasma-forming gas. The results of calculations of the main products of methane decomposition (hydrogen and acetylene) agree quite well with the experimental data.

Decomposition Behavior of Limestone Powder in Converter Flue Gas: Effect of Fe‐Oxide Dust on Calcium Ferrite Formation

To improve the utilization level and energy conversion efficiency of converter flue gas, a novel technology is proposed for the online production of slagging and dephosphorization agent by utilizing the waste heat of converter flue gas. Herein, the effects of Fe‐oxide dust in converter flue gas on the phase composition and microstructure of decomposed product and decomposition degree are investigated by high‐temperature drop tube furnace experiment and thermogravimetric experiment to clarify the influencing mechanism of Fe‐oxide dust on limestone powder decomposition. The results show that Ca2Fe2O5 is formed during limestone decomposition in the flue gas with Fe‐oxide dust, and the increase of Fe‐oxide dust content promotes the decomposition reaction of limestone powder and formation of calcium ferrite. With the Fe‐oxide dust content increasing from 10% to 30%, the decomposition degree increases from 80.1% to 96.2% and the proportion of Ca2Fe2O5 increases from 6.35% to 35.90%. Moreover, FeO in the dust reacts with both CaCO3 and CaO completely to form calcium ferrite with the presence of external oxygen gas in converter flue gas, whereas FeO has no significant effect on the decomposition of CaCO3 in an inert atmosphere and no Ca2Fe2O5 is formed.

Investigation of the Frying Fume Composition During Deep Frying of Tempeh Using GC-MS and PTR-MS

This study employed proton transfer reaction mass spectrometry (PTR-MS) and gas chromatography–mass spectrometry (GC-MS) to identify and monitor volatile organic compounds (VOCs) in frying fumes generated during the deep frying of tempeh. The research aimed to assess the impact of frying conditions, including frying temperature, oil type, and repeated use cycles, on the formation of thermal decomposition products. A total of 78 VOCs were identified, with 42 common to both rapeseed and palm oil. An algorithm based on cosine similarity was proposed to group variables, resulting in six distinct emission clusters. The findings highlighted the prominence of saturated and unsaturated aldehydes, underscoring the role of fatty acid oxidation in shaping the frying fume composition. This study not only corroborates previous research but also provides new insights into VOC emissions during deep frying, particularly regarding the specific emission profiles of certain compound groups and the influence of frying conditions on these profiles.

Effects of nitrogen vacancy sites of oxynitride support on the catalytic activity for ammonia decomposition

Nitrogen-containing compounds such as imides and amides have been reported as efficient materials that promote ammonia decomposition over nonnoble metal catalysts. However, these compounds decompose in an air atmosphere and become inactive, which leads to difficulty in handling. Here, we focused on perovskite oxynitrides as air-stable and efficient supports for ammonia decomposition catalysts. Ni-loaded oxynitrides exhibited 2.5–18 times greater catalytic activity than did the corresponding oxide-supported Ni catalysts, even without noticeable differences in the Ni particle size and surface area of the supports. The catalytic performance of the Ni-loaded oxynitrides is well correlated with the nitrogen desorption temperature during N2 temperature-programmed desorption, which suggests that the lattice nitrogen in the oxynitride support rather than the Ni surface is the active site for ammonia decomposition. Furthermore, NH3 temperature-programmed surface reactions and density functional theory (DFT) calculations revealed that NH3 molecules are preferentially adsorbed on the nitrogen vacancy sites on the support surface rather than on the Ni surface. Thus, the ammonia decomposition reaction is facilitated by a vacancy-mediated reaction mechanism.

Fabrication of Au-decorated V2O5 based sensor for ultra trace level detection of ammonia in an environment resembling human exhaled breath

Ammonia stands out as a significant breath biomarker for kidney-related diseases. Here we present the fabrication of a gold (Au) decorated V2O5 based sensor designed for detecting ammonia at parts per billion (ppb) level. The V2O5 particles were synthesized by thermal decomposition of ammonium metavanadate (NH4VO3) instead of using tedious and expansive synthesis routes. The product of the thermal decomposition of NH4VO3 was characterized utilizing various analytical techniques. Then this product (V2O5) was used for gas sensing study as original and when decorated with gold. The V2O5 based sensor, decorated with gold (Au) for a duration of 10 s, exhibits favorable characteristics including a linear response range spanning 50–5000 ppb, heightened sensitivity, stability, and remarkable resistance to humidity within the range of 50–90 % relative humidity (RH). Remarkably, the sensor demonstrates insensitivity towards higher concentrations of possible interfering liquid vapors. The sensor exhibits response and recovery times of 36 s and 300 s, respectively, in the presence of 1000 ppb ammonia and has the potential for accurately detecting and quantifying ammonia in an environment resembling human exhaled breath. The sensing device based on this material will be a valuable tool for clinical applications.

Study of the potential energy surface of reactions in a system containing <i>i</i>-propyl and <i>n</i>-propyl radicals

The energy pathways of possible decomposition and isomerization reactions of iso-propyl (i-C3H7) and n-propyl (n-C3H7) radicals have been studied by computational methods of quantum chemistry. B3LYP, M062X, MP2, and CBS-QB3 methods are used to localize stationary points on the potential energy surface of a system containing propyl radicals. A number of intermediate compounds formed during the isomerization and decomposition of propyl radicals have been identified, and information has been obtained on their structure and thermochemical parameters. Based on the results of the research, a diagram of the energy levels of the system under consideration was constructed.

Quantitative Detection of Sulfur Hexafluoride Decomposition Product With a Gas Sensor Array

Quantitative Detection of Sulfur Hexafluoride Decomposition Product With a Gas Sensor Array

On the Nature of HOPG-Supported Pt1Ti2O7 and its Decomposition of a Nerve Agent Simulant: A Cluster Model of a Single Atom Catalyst Active Site.

Chemical weapons, including hyper lethal nerve agents, are a persistently looming threat across the modern geopolitical landscape. There is a pressing need for the design and development of improved protective materials, which can be substantially aided by the cultivation of a fundamental molecular-level understanding of candidate systems and the corresponding decomposition chemistry. The emergence of the exciting new class of single atom catalyst (SAC) materials has enhanced the prospect of subnanoscale design tailoring in the hopes of optimizing activity and selectivity for a variety of chemical applications. Here, we apply our recently developed experimental technique for modeling the active sites of such SAC materials through the preparation of surface supported size-selected single metal-atom doped metal oxide clusters. The propensity for an SAC cluster model system for Pt1/TiO2 materials, Pt1Ti2O7 supported on highly oriented pyrolytic graphite (HOPG), to adsorb and decompose nerve agent simulant dimethyl methylphosphonate (DMMP) was investigated through a combination of temperature-programmed desorption/reaction (TPD/R) and X-ray photoelectron spectroscopy (XPS). XPS measurements of the as-prepared Pt1Ti2O7 clusters supported the successful isolation of single Pt atoms in clusters monodispersed across the HOPG surface. TPD/R experiments showed that the reactivity exhibited by the Pt1Ti2O7 clusters was distinct from that of Ti2O7 clusters lacking the single Pt atom. It was found that DMMP decomposed over Pt1Ti2O7 upon heating to as low as room temperature, and higher temperature treatments evolved exclusively H2O, CO, and H2, while decomposition over Ti2O7 evolved only methanol and formaldehyde at elevated temperatures. This indicated the promotion of C-H and PO-C bond cleavage within DMMP due to the presence of single Pt atoms in the clusters. Further, the Pt1Ti2O7 clusters were found to desorb P-containing decomposition species, preventing active site poisoning; however, a change of reactivity reflecting that of Ti2O7 was observed following a single TPD/R cycle. This suggested the encapsulation of active Pt sites by titanium oxide during high temperature treatment and is thus an issue deserving of serious attention in the study of Pt1/Ti2O7 SAC materials.

Elucidating the Limit of Lithium Difluorophosphate Electrolyte Additive for High‐Voltage Li/Mn‐Rich Layered Oxide || Graphite Li Ion Batteries

Li/Mn‐rich layered oxide (LMR) cathode active materials offer remarkably high specific discharge capacity (>250 mAh g−1) from both cationic and anionic redox. The latter necessitates harsh charging conditions to high cathode potentials (>4.5 V vs Li|Li+), which is accompanied by lattice oxygen release, phase transformation, voltage fade, and transition metal (TM) dissolution. In cells with graphite anode, TM dissolution is particularly detrimental as it initiates electrode crosstalk. Lithium difluorophosphate (LiDFP) is known for its pivotal role in suppressing electrode crosstalk through TM scavenging. In LMR || graphite cells charged to an upper cutoff voltage (UCV) of 4.5 V, effective TM scavenging effects of LiDFP are observed. In contrast, for an UCV of 4.7 V, the scavenging effects are limited due to more severe TM dissolution compared an UCV of 4.5 V. Given the saturation in solubility of the TM scavenging agents, which are LiDFP decomposition products, e.g., PO43− and PO3F2−, higher concentrations of the LiDFP as “precursor” cannot enhance the amount of scavenging species, they rather start to precipitate and damage the anode.

Analysis of Energy Transfer in the Ignition System for High-Speed Combustion Engines

In order to produce reliable and reproducible ignition of lean fuel–air mixtures and highly stratified mixtures, it is necessary to ensure a high concentration of spark discharge energy and to provide a strong energy impulse for the triggering of chain processes of chemical decomposition of fuel molecules. For this reason, studies have been undertaken on the flow of electrical energy from the ignition system to the spark plug and on the formation of an electric discharge arc with a high concentration of thermal energy. The experimental results were obtained using an ignition coil energy test stand and a constant volume chamber with high-speed spark discharge recording capability. It was confirmed that increasing the charging time of the ignition coil from 0.5 ms to 5.0 ms increases the energy delivered to the coil from 9.5 mJ to 330 mJ. In the same range, the energy generated by the coil was recorded to range from 4.2 mJ to 70 mJ. The coil’s efficiency was found to decrease with increasing charging time from 45% up to 20.5%. Further energy losses were presented when the spark discharge energy was analyzed. In the paper, the results of investigations concerning electric discharge arc development have been presented, illustrated by a few exemplary photos, and discussed. The mathematical interpretation of the electrical energy flux in the ignition system resulting from the energy of the discharge arc has been conducted and illustrated by some functional independences and relationships.

Study on the Thermal Effect of Spontaneous Combustion of Coal-Based Activated Carbon By-Products Oxidized and Carbonized Powders

ABSTRACT To investigate the spontaneous combustion thermal effect of the by-products oxidized powder (OP) and carbonized powder (CP) produced during the preparation of coal-based activated carbon (CBAC). First, the changes in composition and pore structure of OP and CP compared with raw coal (RC) were measured by coal quality analysis and nitrogen adsorption experiments. The ability of OP and CP to physically adsorb oxygen was determined. Then, differential scanning calorimetry (DSC) was used to study the whole process thermal effect of the spontaneous combustion of OP and CP. Finally, the thermal effect of OP and CP during low-temperature oxidation process was further explored by the C80 micro-calorimeter, and the thermodynamic characteristics were also probed. The results show that the content of fixed carbon and carbon elements in OP and CP are significantly greater than that in RC, which makes the pore structure of both complicated. In addition, the total pore volume, average pore size, and specific surface area of OP and CP are greater than that of RC, which is more conducive to the physical adsorption of oxygen by both. No transition platform is caused by the decomposition of intermediate products on the DSC curve of CP. The characteristic temperatures of CP (except T D10) are lower than that of OP, indicating that the spontaneous combustion reaction of CP started earlier than that of OP. However, part of the combustible substance of CP was consumed in the dry distillation process, leading to the thermal release and maximum thermal release rate being smaller than that of OP. The apparent activation energy (E a) of stages H2 and H3 in the low-temperature oxidation process of OP is 75.04 and 11.42 kJ mol−1, while that of CP is 83.11 and 30.91 kJ mol−1. The threshold of CP entering stages H2 and H3 is higher than that of OP. Nevertheless, from the pre-exponential factor (A), the low-temperature oxidation process of CP is more rapid.

Modern Pollen Signatures and Vegetation Dynamics in Northwestern Himalaya, India

ABSTRACT Palynological studies have been conducted for the first time in the Renukaji Wildlife Sanctuary (RWS), a Sal-dominated region within the foothills of Northwestern (NW) Himalaya in Himachal Pradesh, India. This research enhances our understanding of the relationship between modern pollen rain and vegetation, as well as pollen representation in sediments. Furthermore, it contributes to palaeovegetation reconstruction based on paleoclimatic trends by improving our interpretation of pollen deposition patterns. The study area was delineated into three distinct zones based on biological niche characteristics: Zone 1 (Recreation Zone), Zone 2 (Buffer Zone), and Zone 3 (Core Zone). Pollen analysis conducted on 30 surface soil samples and moss cushions, collected from all three zones, reveals the dominance of dry deciduous taxa, followed by extra-terrestrial taxa and wet deciduous taxa. Land Use Land Cover (LULC) analysis performed using satellite data reveals that Shorea robusta (Sal) mixed forest covers 32% of land, followed by Pinus spp. (8%) and their associates (25%). Shorea robusta, a mixed wet deciduous taxon and high pollen producer, exhibits low pollen counts, possibly due to chemical and microbial decomposition or low pollen dispersal efficiency. This study utilises a comparative database correlating pollen data with contemporary vegetation patterns to establish a robust framework for assessing sedimentary pollen sequences. Through this approach, we aim to elucidate past vegetation dynamics and infer climate fluctuations within the NW Himalaya.

High-Resolution Terahertz Spectroscopy for MedicalDiagnostics.

The metabolomics-based approach to diagnostics and therapy monitoring is a fast-emerging trend in modern medicine. Terahertz nonstationary spectroscopy based on the induction and disintegration of freely decaying polarization in the gas mixture during the interaction of radiation with molecules at resonance frequencies is a high-sensitivity method for studying multicomponent gas mixtures, which is promising for identifying metabolites in the thermal decomposition products of biological samples. The paper presents the results of the application of high-resolution terahertz spectroscopy to the study of biological samples taken from patients with certain diseases (pathologically changed tissues of ear-nose-throat organs and similar pathologic tissues formed in other life support systems) to search for characteristic sets of metabolites characterizing the pathology. The world's first measurements of the spectra of pathologic samples of cysts, formed in different life support systems, were carried out, which made it possible to identify similar substances in tissues having the same pathology.

Molecular recognition of halogen-bond of Diiodine with an Ambidentate ligand: Fluorometry as lead strategy for analysis in solution

Chemical connectivity of halogen bond (XB) of the diiodine with an ambidentate ligand of the N1-aryl-2-(trifluoromethyl)benzo[b][1,8]naphthyridin-4(1H)-one in solution and in solid state was presented. The organic ligand was characterized by featuring four basic moieties with different hardness (N-heteroarene, ketonic oxygen, methoxy oxygen and π-arene). The study in solution was performed through a simple steady state fluorescence measurements taking advantage on the use of a donor-acceptor (D-A) fluorophore having two key characteristics (i) presence of basic groups along the d-A chain and, (ii) a fluorescence dependent on an intramolecular charge-transfer (ICT) mechanism. It allowed us to distinguish unequivocally the binding preference of the ambidentate ligand toward the diiodine from the recognition of specific dye-fluorescence responses (ICT-quenching, ICT-enhancement, etc.). Fluorometric studies allowed us to elucidate that the diiodine interacts dominantly through the borderline function (N-heteroarene) of ligand under a wide range of diiodine concentration and discretely through the harder ketonic oxygen. UV–Vis spectroscopic confirmed the binding of the diiodine through N-arene moiety, giving typical association constants of 20–40 M-1 for the tested ambidentate ligands. Additionally, the fluorometry allowed us to verify the reversibility of the XB in solution through synchronized radioactivity- and absorption-fluorescence experiments based on nuclear and chemical decomposition of the diiodine, respectively, where the total recovery of the ICT-fluorescence, which was quenched under diiodine binding, confirmed the reversibility of the XB. Further studies in solid state (Raman spectroscopy) confirmed the binding preference of the diiodine toward the borderline N-arene. Experimental evidences of XB were supported and interpreted from DFT-calculations.