Changes In Molecular Structure Research Articles

Renal Calcium and Magnesium Handling During Pregnancy: Modeling and Analysis.

Pregnancy is associated with elevated demand of most nutrients, with many trace elements and minerals critical for the development of fetus. In particular, calcium (Ca2+) and magnesium (Mg2+) are essential for cellular function, and their deficiency can lead to impaired fetal growth. A key contributor to the homeostasis of these ions is the kidney, which in a pregnant rat undergoes major changes in morphology, hemodynamics, and molecular structure. The goal of this study is to unravel the functional implications of these pregnancy-induced changes in renal handling of Ca2+ and Mg2+, two cations that are essential in a healthy pregnancy. We developed computational models of electrolyte and water transport along the nephrons of a rat in mid and late pregnancy. Model simulations reveal a substantial increase in the reabsorption of Mg2+ along the proximal tubules and thick ascending limbs. In contrast, the reabsorption of Ca2+ is increased in the proximal tubules but decreased in the thick ascending limbs, due to the lower transepithelial concentration gradient of Ca2+ along the latter. Despite the enhanced transport capacity, the marked increase in glomerular filtration rate results in elevated urinary excretions of Ca2+ and Mg2+ in pregnancy. Furthermore, we conducted simulations of hypocalcemia and hypomagnesemia. We found that hypocalcemia lowers Ca2+ excretion substantially more than Mg2+ excretion, especially in virgin rats. Conversely, hypomagnesemia reduces the excretion of Mg2+ and Ca2+ to more similar degrees. These differences can be explained by the greater sensitivity of the calcium-sensing receptor (CaSR) to Ca2+ compared to Mg2+.

Effects of pH-varying thermal modification on sewage sludge: A focus on releasing nitrogen- and phosphorus-containing substances

Sewage sludge is promising for the recovery and utilisation of nutrient components, but its complex nature hinders the release of these components. The combination of pH and thermal modifications shows promise for the release of nutrient components from sludge. However, comprehensive studies on the full spectrum of pH levels and corresponding mechanisms of pH-varying thermal modification are lacking. In this study, the main nutrient components, physicochemical properties, molecular structure, and noncovalent interactions of sludge were comprehensively investigated through pH-varying thermal modification (within a pH range of 2.0 to 12.0 under the same thermal condition). The experimental results showed that the release of main organics, particularly nitrogen (N)-containing organics, was well-fitted, with a tick-like function (R2: 0.74–0.96). The thermal protons exhibited a notable accumulative mutagenic effect on the N-containing organics release, while the thermal hydroxyl ions had a more direct effect, as revealed by the changes in multivalent metals and molecular structures with the protonation–deprotonation of carboxyl groups. The driving force for the release of N-containing organics was identified as the fluctuation of electrostatic interactions at the solid–liquid interface of the sludge. However, the release of phosphorus (P)-containing substances exhibited a contrasting response to that of N-containing substances with varying pH, likely because the reaction sites of thermal protons and thermal hydroxyl ions for P-containing substances were different. Moreover, high concentrations of thermal protons and hydroxyl ions collapsed the Lifshitz–van der Waals interactions of sludge, resulting in a decrease in viscoelasticity and binding strength. These propositions were further confirmed through statistical analyses of the main indicators of the main nutrient components, physicochemical properties, and noncovalent interactions of sludge. These findings can provide a basis for optimising characteristic-specific methods to recovery nutrient components (N/P) from sludge.

Quantitative analysis of molecular interactions in κ-carrageenan-Isovanillin biocomposite for biodegradable packaging and pharmaceutical applications using NMR, TOF-SIMS, and XPS approach

This study explores the molecular interactions and structural changes in κ-carrageenan crosslinked with isovanillin to create a biocomposite material suitable for hard capsule and bio-degradable packaging applications. Proton Nuclear Magnetic Resonance (1H NMR) spectroscopy revealed chemical changes in the conjugate molecule, indicating improved electronegativity due to intermolecular hydrogen bonding between κ-carrageenan and isovanillin. Time-of-flight Secondary Ion Mass Spectrometry (ToF-SIMS) analysis revealed enhanced ion intensity due to intermolecular interactions, particularly between sulphate and hydrogen ions. X-ray Photoelectron Spectroscopy (XPS) study demonstrated that κ-carrageenan and isovanillin form stronger hydrogen bonds, with a shift in binding energy indicating higher electronegativity. These findings shed light on the molecular mechanisms that underpin the formation of the biocomposite material, as well as its potential for use in hard capsule and biodegradable packaging materials, addressing the need for sustainable alternatives in the pharmaceutical and packaging industries while also contributing to environmental conservation.

Artificial Muscles Based on Coiled Conductive Polymer Yarns

AbstractLightweight artificial muscles with large strain and large stress output have great application prospects in robotics, rehabilitation, prosthetic, and exoskeletons. Despite the excellent performance of carbon nanotube‐based artificial muscles in recent years, their widespread use is hindered by the high manufacturing costs associated with carbon nanotubes. In this paper, the study introduces a novel approach by developing artificial muscles based on pure conductive polymer coiled yarns. This achievement is facilitated by the successful fabrication of high‐strength conductive polymer microfibers. Furthermore, the study elucidates the molecular structural changes occurring during electrochemical processes that induce a substantial radial volume expansion in the microfibers. The resultant anisotropic volume change is magnified by the coiled yarn, yielding a remarkable contractile strain exceeding 11% at a high stress of 5 MPa, equivalent to lifting loads more than 4000 times their own masses, all achieved with a low input voltage of 1 V. Additionally, these conductive polymer‐based artificial muscles exhibit hydration‐induced contraction up to 33%, with swift recovery through electrical heating, leveraging their intrinsic high conductivity. This breakthrough positions high‐performance conductive polymer microfibers as a promising cost‐effective alternative to carbon nanotubes, establishing them at the forefront of lightweight artificial muscles.

Multifunctional montmorillonite/polyhydroxy butyrate composites using surfactant structure modulation strategy for packaging applications

AbstractThe biodegradable materials for the packaging sector have attracted much attention as they can effectively reduce the reliance on fossil fuel products. The introduction of two‐dimensional layered fillers is readily available for packaging materials to minimize costs while enhancing performance. However, few studies have investigated the molecular structure changes of OMMT to further modulate the comprehensive performance of polyhydroxy butyrate (PHB) materials. To fill this gap, we innovatively modified the surfactant's structure to regulate the embedding and dispersion of montmorillonite (OMMT) and interfacial bonding with the substrate, thus further examining the material's antibacterial and degrading properties and discussing mechanisms for the first time. The prepared C18M7@PHB materials present enhanced tensile strength (180%) and high thermal stability, excellent antimicrobial properties compared to the unmodified one. Both the water vapor and oxygen permeabilities of composites have decreased by 87% and 55%, respectively. Moreover, it is found that the composites exhibit various degradation cycles mainly depending on active agent chain length. This work lays a solid foundation for multifunctional packaging materials based on fillers with two‐dimensional layered structures.Highlights Determining the ideal film's bulk ratio and active agent structure. Optimizing the film's excellent tensile strength and antimicrobial properties. Significantly blocking the infiltration of water vapor and oxygen. Identifying the film's filler's degradation behavior and barrier mechanism.

Capturing interference variations of atomic motion in vibrational modes by non-resonant Raman images

Non-resonant Raman imaging associated with vibrational modes provides an optical means to structure and function characterisation for a single molecule, where the interference between atomic motions in a vibrational mode plays an important role. Taking the [18]annulene as a proof-of-the-concept molecule, we present here a comprehensive study on the dependence of non-resonant Raman images on interference variations involving the phase and amplitude of atomic displacements in vibrational modes. Calculations demonstrate that constructive and destructive phase interferences contribute to the characteristic merging and repulsion of Raman patterns, respectively, which should be attributed to the same/opposite signs of Raman polarisability. In addition, the imaging characteristic by constructive and destructive interferences become more significant with the increase of plasmonic size. Moreover, Raman images are highly sensitive to the subtle variations of interference induced by molecular symmetry and element substitution, highlighting the importance of amplitude variations of interference in modes for Raman images to monitor molecular structure changes. Our findings propose the capability of Raman images toward capturing interference variations in modes, serving as good references for Raman imaging to characterise various molecules and their corresponding structure changes by analysing interference effects in vibrational modes.

Mechanical insights into jawbone characteristics under chronic kidney disease: A comprehensive nanoindentation approach

The mechanical properties of the jawbone play a critical role in determining the successful integration of dental prostheses. Chronic kidney disease (CKD) has been identified to abnormally accelerate bone turnover rates. However, the impact of CKD on the mechanical characteristics of the jawbone has not been extensively studied. This study sought to evaluate the time-dependent viscoelastic behaviors of rat jawbones, particularly in the scenarios both with and without CKD. We hypothesized that CKD might compromise the bone's innate toughening mechanisms, potentially owing to the time-dependent viscoelasticity of the bone matrix proteins. The maxillary and mandibular bones of Wistar rats were subjected to nanoindentation and Raman micro-spectroscopy. Load-hold-displacement curves from the cortical regions were obtained via nanoindentation and were mathematically characterized using a suitable viscoelastic constitutive model. Raman micro-spectroscopy was employed to identify nuanced vibrational changes in local molecular structures induced by CKD. The time course of indenter penetration onto cortical bones during the holding stage (creep behavior) can be mathematically represented by a series arrangement of the Kelvin–Voigt bodies. This configuration dictates the overall viscoelastic response observed during nanoindentation tests. The CKD model exhibited a reduced extent of viscoelastic contributions, especially during the initial ramp loading phase in both the maxillary and mandibular cortical bones. The generalized Kelvin–Voigt model comprises 2 K–Voigt elements that signify an immediate short retardation time (τ1) and a subsequent prolonged retardation time (τ2), respectively. Notably, the mandibular CKD model led to an increase in the delayed τ2 alongside an increase in non-enzymatic collagen cross-linking. These suggest that, over time, CKD diminishes the bone's capability for supplementary energy absorption and dimensional recovery, thus heightening their susceptibility to fractures.

Elucidating the Changes in Molecular Structure at the Buried Interface of RTV Silicone Elastomers during Curing.

Silicone elastomers are widely used in many industrial applications, including coatings, adhesives, and sealants. Room-temperature vulcanized (RTV) silicone, a major subcategory of silicone elastomers, undergoes molecular structural transformations during condensation curing, which affect their mechanical, thermal, and chemical properties. The role of reactive hydroxyl (-OH) groups in the curing reaction of RTV silicone is crucial but not well understood, particularly when multiple sources of hydroxyl groups are present in a formulated product. This work aims to elucidate the interfacial molecular structural changes and origins of interfacial reactive hydroxyl groups in RTV silicone during curing, focusing on the methoxy groups at interfaces and their relationship to adhesion. Sum frequency generation (SFG) vibrational spectroscopy is an in situ nondestructive technique used in this study to investigate the interfacial molecular structure of select RTV formulations at the buried interface at different levels of cure. The primary sources of hydroxyl groups required for interfacial reactions in the initial curing stage are found to be those on the substrate surface rather than those from the ingress of ambient moisture. The silylation treatment of silica substrates eliminates interfacial hydroxyl groups, which greatly impact the silicone interfacial behavior and properties (e.g., adhesion). This study establishes the correlation between interfacial molecular structural changes in RTV silicones and their effect on adhesion strength. It also highlights the power of SFG spectroscopy as a unique tool for studying chemical and structural changes at RTV silicone/substrate interface in situ and in real time during curing. This work provides valuable insights into the interfacial chemistry of RTV silicone and its implications for material performance and application development, aiding in the development of improved silicone adhesives.

Evolution of kerogen structure during the carbonization stage

Currently, certain unconventional gas is mainly extracted from high-maturity shale reservoirs, but limited attention has been given to the evolution of kerogen structure subsequent to the overmature, gas generative stage, corresponding to metagenesis and is termed the carbonization stage. In this study, we performed heating treatment on overmature kerogen samples to obtain samples in the carbonization stage and then conducted Raman, thermogravimetric-mass spectrometric analysis (TG-MS), X ray diffraction (XRD), and high resolution transmission electron microscope (HRTEM) experiments on these samples to investigate the changes in kerogen structure. Low pressure N2 and CO2 adsorption experiments also were performed to investigate the changes in pore structure. The results show that as the heat treatment temperature is raised to 1000 °C, the ID/IG ratio (D band intensity to G band intensity) experiences an increase, reaching 1.12. Additionally, the full width at half maximum (FWHM) of 002 peak consistently remains above 3.8°. This suggests that these samples were matured to an early meta-anthracite (meta-kerogen) stage, which is significantly distant from the graphite stage. During this particular stage, the most obvious changes in molecular structure are the enlargement of aromatic clusters and the decrease in hydrogen atoms, and thus, H2 rather than methane is produced, as revealed by the results of TC-MS experiment. Following an initial increase, the pore volume and surface area of kerogen samples decrease gradually, reaching their maximum values at 700 °C. Kerogen subjected to a heating temperature of 1000 °C exhibits a greater pore volume in comparison to the initial overmature kerogen. Thus, this observation provides evidence that shale kerogen in carbonization stage, which is typically lying at significant depths, holds promise as a viable reservoir for shale gas extraction.

Influence of structural properties on the suspension performance of ultra-high temperature stabilizers

One of the key challenges preventing the exploration and development of ultra-deep oil and gas deposits is the settlement instability of cement slurry at extremely high temperatures. In the previous work, an ultra-high temperature suspension stabilizer was created to enhance the cement slurry's high temperature settlement stability. This work investigates its mechanism from the standpoint of structural characteristics based on the prior research. Thermal stability tests and calculations of the pyrolysis activation energy were used to examine the structural features of the suspension stabilizer. The viscosity-temperature relationship, the microstructure of the suspension stabilizer solution, the molecular structure change of the suspension stabilizer in the solution environment, and the interaction energy with water molecules were all studied in conjunction with contemporary material testing techniques and molecular dynamics simulation calculations. The findings indicate that: 1) The bulk structure of the suspension stabilizer has a pyrolysis temperature of 330 °C, which indicates a degree of heat resistance; 2) In a solution environment, the viscosity of the solution is a critical factor in determining the stability of the cement slurry's sedimentation, which is dependent on the integrity of the amide group in the suspension stabilizer. The cyclic functional group's ortho action prevents the amide monomer from hydrolyzing in the ultra-high temperature suspension stabilizer. The cement slurry has good sedimentation stability because the hydrogen link between the retained amide group and the water molecule has not entirely broken down, and the solution still has some viscosity.

Effect of SBS/SBR/component molecular compatibility on anti-aging properties for asphalt binder

To explain the effect of SBS/SBR/component molecular compatibility on anti-aging properties for asphalt binder, the micro-aging behavior of SBS/SBR composite modified asphalt binder was studied by molecular simulation, scanning electron microscopy (SEM) and infrared spectroscopy (IR). First, the micro-models of SBS molecule, SBR molecule and component molecule (asphaltene, resin, saturation, aromatic) were established, and the molecule number was determined by component test. Additionally, the characteristics of micro-model were analyzed, and the change characteristics of molecular compatibility for unaged asphalt binder and aged asphalt binder were obtained. Lastly, the rationality of molecular compatibility simulation results of SBS/SBR/component was demonstrated by SEM and IR tests, respectively. The results show that there is a close relationship between SBS/SBR/component molecular compatibility and asphalt binder anti-aging performance. The change of molecular space structure leads to the increase of asphalt binders density and the decrease of intermolecular distance. The study revealed the anti-aging properties of asphalt binder from the aspect of SBS/SBR/component molecular compatibility, which provided a theoretical foundation for the improvement of its aging resistance.

Changes in molecular conformation and electronic structure of DNA under 12C ions based on first-principles calculations

Fundamental studies on the interaction between ionizing radiation and deoxyribonucleic acid (DNA) can contribute to understanding the biological effects of radiation protection and radiotherapy. The transitional process from ionized and excited DNA to DNA lesions, such as strand breaks and base lesions, remains uncertain. In this study, we focused in particular on the direct effects of radiation on DNA and calculated the number of ionizations induced within 10 base pairs of DNA using the Particle and Heavy Ion Transport code System, a general-purpose Monte Carlo code for radiation transport. The electronic structure of the ionized DNA is subsequently calculated using the first-principles calculation software OpenMX. Through these calculations, we successfully identified the redox site of DNA and quantitatively evaluated the amount of molecular bond cleavage. The scientific findings of this study will elucidate the cleavage mechanism of DNA in the high-density radiation field realized by ion beam irradiation by determining the redox sites.

Solid-state effect on the luminescence mechanism of thermally activated delayed fluorescence with aggregation induced emission: A theoretical perspective

An investigation of high-performance organic green thermally activated delayed fluorescence (TADF) material, PyB-DPAC, with aggregation-induced luminescence (AIE) characteristics was theoretically conducted by the first principle calculations method in this work. The polarizable continuum mode (PCM) and the combination of quantum mechanics and molecular mechanics (QM/MM) method were employed to consider the liquid-phase and solid-phase environments, respectively. Results show that TADF mechanism of the molecule is mainly due to the occurrence of efficient intersystem crossing (ISC) and reverse intersystem crossing (RISC) processes between S1 and T2, which benefits from the small energy gap, large SOC and the limited changes of molecular geometry structures in solid-phase environment. The increase of radiative transition rate (Kr) and significant decrease of non-radiative transition rate (Knr) is responsible for the AIE property. Our calculations reasonably explained the experimental results and showed that PyB-DPAC is an excellent TADF material with AIE characteristics, this may help to better understand the influence of solid-state effect and the luminescence mechanism of AIE-TADF molecules.

Cold atmospheric plasma modified polycaprolactone solution prior to electrospinning: A novel approach for improving quercetin-loaded nanofiber drug delivery systems

In this study, we present a novel approach for enhancing the performance of Quercetin-loaded nanofiber drug delivery systems through the modification of Polycaprolactone (PCL) solution using Cold Atmospheric Plasma (CAP) prior to electrospinning. CAP treatment was applied to PCL solutions for varying durations, namely, 0.5, 1, and 3 min. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) collectively demonstrate that CAP application and QU loading induce morphological changes in nanofibers, facilitating the creation of drug delivery systems with modified fiber diameters, devoid of bead formation. CAP treatment duration correlates with varying fiber diameters, with the longest treatment (3 min) producing the largest fibers (1324 ± 387 nm). Concurrently, the incorporation of quercetin (QU) into the PCL nanofibers resulted in reduced fiber diameter. These observations emphasize the pivotal role of CAP modification in tailoring nanofiber size and morphology. Notably, minimal peak shifts indicate no significant molecular structure changes in PCL nanofibers compared to PCL solutions, assuring the absence of unwanted chemical modifications or degradation during electrospinning. Furthermore, specific QU peaks are undetectable in Fourier-transform infrared (FTIR) spectra, suggesting dispersed or amorphous QU molecules within the nanofibers. Additionally, X-ray diffraction (XRD) results demonstrate that CAP treatment does not alter the crystalline structure of the PCL nanofiber drug delivery system. Crystalline planes of PCL remain unchanged, affirming stability under CAP treatment conditions. Water contact angles indicate that CAP treatment affects nanofiber hydrophobicity, with shorter CAP treatment times rendering more hydrophilic surfaces. Cumulative QU release percentages vary, with PCL/CAP-0.5-QU exhibiting the highest release at 56 ± 2.2 %, surpassing unmodified PCL/QU. Moreover, cell viability remains comparable or slightly increased when QU is incorporated into CAP-treated PCL nanofibers, suggesting potential mitigation of cytotoxic effects induced by CAP treatment. The combination of QU and CAP treatment enhances cancer cell viability reduction, QU release from nanofibers, and drug loading efficiency in a synergistic manner.

Engineering and Life Cycle Assessment (LCA) of Sustainable Zeolite-Based Geopolymer Incorporating Blast Furnace Slag

This study aims to investigate the preparation of zeolite-based geopolymer composites incorporating blast furnace slag at various temperatures and varying amounts of blast furnace slag as potential sustainable building and construction materials. The primary objectives were to use mining waste streams for geopolymer production and assess the mechanical behavior of these hybrid geopolymers, along with performing a life cycle assessment (LCA) to compare their environmental impact with conventional concrete. It was observed that the hybrid geopolymers attained a maximum mechanical strength of 40 MPa. Remarkably, substituting just 20% of the material with blast furnace slag resulted in a 92% improvement in compressive strength. To assess environmental impacts, a cradle-to-gate LCA was performed on different geopolymer mix designs, focusing particularly on the global warming potential (GWP). The results indicated that geopolymer concrete generated a maximum of 240 kg CO2-e/m3, which was 40% lower than the emissions from ordinary cement, highlighting the environmental advantages of geopolymer materials. Further, X-ray diffraction was used to determine the mineral composition of both raw and developed composites. Solid-state nuclear magnetic resonance (NMR) was applied to study the molecular structure changes upon incorporating blast furnace slag. The initial setting time and shrinkage of the geopolymers were also investigated. Morphological characteristics were analyzed by scanning electron microscopy (SEM). Thermal analyses confirmed the stability of the geopolymers up to 800 °C. Geopolymer composites with high thermal stability can be used in construction materials that require fire resistance. This study not only enhances the understanding of geopolymer composite properties but also confirms the substantial environmental advantages of utilizing geopolymerization in sustainable construction.

Study of the molecular structure of proteins in fermented Maize-Soybean meal-based rations based on FTIR spectroscopy

This research investigates the dynamic alterations that occur in protein molecular structure during the fermentation process of feed. Fourier transform infrared spectroscopy (FTIR), coupled with deconvolution, second derivative and curve-fitting methodologies, was employed to comparatively analyse the protein molecular structures in fermented feed. At the 48-h fermentation mark, the α-helix and β-sheet contents reached their peaks, while the random coil and β-turn contents were at their lowest. Simultaneously, the β-sheet/α-helix ratio was minimized. FTIR spectroscopy emerged as a comprehensive tool, revealing the nuanced changes in molecular structure throughout the fermentation process of corn-soybean meal feed. When integrated with spectral quantitative analysis, it provides a novel perspective for evaluating the nutritional value of fermented feed.

Cryoprotective effect of curdlan on frozen wheat gluten: With respect to physicochemical properties and molecular structure

Curdlan alleviates the quality deterioration of frozen dough during storage by a mechanism related to retarded migration of moisture. However, the strengthening effect of curdlan on the gluten structure needs to be proved. Therefore, the effect of curdlan on physicochemical properties and molecular structure changes of frozen wheat gluten was investigated. Frozen storage resulted in decreased water-holding capacity and viscoelasticity properties, as well as increase in oil-holding capacity and surface hydrophobicity. However, curdlan significantly inhibited the rheological and physicochemical properties changes of gluten. Scanning electron microscope results showed that the structure of gluten with curdlan had relatively smoother and less damaged surface during frozen storage. Curdlan alleviated the depolymerization of gluten macropolymers (GMP) by restraining the breakage of S–S bonds, with GMP depolymerization degree of 20% after 90 days of storage, significantly lower than that of the control (38%). Curdlan restrained the transition of α-helix to β-turn and antiparallel β-sheet, and suppressed the protein unfolding and chromophores exposure. Curdlan interacted with gluten prominently by hydrogen bonds, followed by hydrophobic interactions, thus strengthening the gluten structure. Alleviation of dough quality loss during frozen storage by curdlan could be related to its strengthening gluten structure.

Interaction of Polycarboxylate-Based Water-Reducing Admixture Molecular Structure with Fly Ash Substituted Cementitious Systems: Marsh-Funnel and Mini-Slump Performance

Polycarboxylate ether-based high-range water-reducing admixtures (PCE) play a crucial role in enhancing the workability of fly ash-substituted cementitious systems. Alterations to the chemical structures of both the main and side chains can particularly enhance the electrostatic repulsion and steric hindrance effects of PCEs. As a consequence, this results in improved performance within cementitious systems containing fly ash substitutions. This study investigated the compatibility of the altered molecular structure of polycarboxylate ether (PCE) with cementitious systems containing fly ash substitutions. To achieve this, five polymers were synthesized, varying the side chain length, molecular weight, main chain length, and main chain lengths of PCEs while maintaining other properties constant. Cement pastes were then prepared using the synthesized PCEs with fly ash replacements at three different rates. Marsh-funnel flow time and mini-slump values were measured in the prepared mixtures. The study revealed that in mixtures without fly ash, PCEs with a long main chain (40k) and short side chain length (1000 g/mole) exhibited the lowest Marsh-funnel flow and mini-slump performance among PCEs with diverse molecular structures. For the other PCEs in these mixtures, the change in molecular structure did not significantly affect their performance. However, as the fly ash replacement rate increased, PCE having a medium main chain (21k) and side chain (2400 g/mole) length outperformed other PCEs in terms of Marsh-funnel flow and mini-slump performance.

Study on the inhibitory effect of inhibitor based on the coal molecular structure analysis: A case study of Zhundong coal, Xinjiang, China

The aim of this work is to use the changes in coal molecular structure to study the effect and mechanism of inhibitors, and to provide a reference for better preventing and controlling coal spontaneous combustion. In this study, Xinjiang Zhundong coal was used to construct the macromolecular structure. The changes in the molecular structure of the coal under different inhibitor concentrations and temperature conditions were analyzed by Fourier infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis. ChemDraw and Materials Studio were used to construct a coal molecular structure model with an inhibitor concentration of 20 % at 50 ℃. Results showed that the molecular formula of the ZD2–1 is C222H123O39N. The coal molecule contained a higher number of aliphatic hydrocarbon branches and a lower degree of aromatic ring condensation. When heated to 300 ℃, the proportion of adsorbed oxygen in raw coal decreased obviously, while the reduction of adsorbed oxygen was inhibited under inhibitor conditions. The change of functional groups of coal samples was obvious under 20 % inhibitor concentration, and the dosage was less than that of 30 % inhibitor concentration, revealing the optimal inhibitory effect on coal samples of Zhundong with this concentration.

Pure Hydrolysis of Polyamides: A Comparative Study

Polyamides (PAs) undergo local environmental degradation, leading to a decline in their mechanical properties over time. PAs can experience various forms of degradation, such as thermal degradation, oxidation, hydrothermal oxidation, UV oxidation, and hydrolysis. In order to better comprehend the degradation process of PAs, it is crucial to understand each of these degradation mechanisms individually. While this review focuses on hydrolysis, the data from degrading similar PAs under pure thermal oxidation and/or hydrothermal oxidation are also collected to grasp more perspective. This review analyzes the available characterization data and evaluates the changes in molecular weight, crystallinity, chemical structure, and mechanical properties of PAs that have aged in oxygen-free water at high temperatures. The molecular weight and mechanical strength decrease as the crystallinity ratio rises over aging time. This development is occurring at a slower rate than degradation in pure thermal oxidation. By combining the data for the changes in mechanical properties with the ones for molecular weight and crystallinity, the point of embrittlement can be not only predicted, but also modeled. This prediction is also shown to be dependent on the fibers, additives, types of PA, pH, and more.