Changes In Chemical Structure Research Articles

The interaction between sludge and microplastics during thermal hydrolysis of sludge

In municipal wastewater treatment plants (WWTPs), large number of microplastics (MPs) accumulated in wastewater migrated into sludge. Thermal hydrolysis of sludge (THS) was one of the most promising processes for promoting changes in molecular structure of MPs. The physicochemical properties and degradative pathways of polyethylene (PE) and polyethylene terephthalate (PET) in THS under different temperatures were studied in this paper. It was found that there was a mutual promotion relationship between sludge degradation and MPs aging. The presence of PE and PET MPs not only increased organics and nitrogen concentrations of sludge filtrate, but also enhanced the transformation of organics like proteins. Sludge accelerated the aging of PE and PET MPs. The friability of PE and PET MPs was increased with more surface fragmentation and breakage under the temperature of 120 ℃−180 ℃. Moreover, PE and PET MPs occurred thermal oxidation and reduction reactions with significant chemical structure changes at 160 °C and 140 °C, respectively. Pristine PE and PET had multiple carbon and oxygen active sites. During THS reaction, not only PE and PET reacted hydrolysis/decomposition to produce short-chain hydroxyl-terminated compounds, but also hydrothermal shear broke the polymer molecules and formed carboxyl-terminated and olefin-terminated low-carbon chains. This study provided some promising sign for in situ microplastic removal during sludge treatments.

Smart molecular probes with controllable photophysical property for smart medicine

AbstractPrecision medicine calls for advanced theranostics that integrate controllable diagnostic and therapeutic capabilities into one platform for disease treatment in the early stage. Phototheranostics such as fluorescence imaging (FLI), photoacoustic imaging (PAI), photodynamic therapy (PDT), and photothermal therapy (PTT) have attracted considerable attention in recent years, which mainly employ different excited‐state energy dissipation pathways of a chromophore. According to the Jablonski diagram, FLI is related to the radiative process, PAI and PTT are derived from the nonradiative thermal deactivation, and PDT originates from the triplet state energy, in which these processes are usually competitive. Therefore, it is critically important to precisely tune the photophysical energy transformation processes to realize certain diagnosis and treatment properties in optimal state for boosting biomedical applications. Currently, there are mainly two strategies including chemical structure and aggregate behavior changes that relate to the regulation of excited state energy dissipation. In this review, we will discuss the recent advances of smart molecular probes that the photophysical properties can be regulated by external triggers and their applications in biomedical fields. We will summarize the development of activatable phototheranostic molecular probes in response to stimuli such as reactive oxygen species, pH, light, hypoxia, enzyme and gas. The assembly and disassembly of molecular aggregates that greatly affect the photophysical energy transformation processes will also be highlighted. This review aims to provide valuable insights into the development of more accurate diagnostic and therapeutic systems, thereby advancing the emerging field of smart medicine.

Extrusion can ameliorate negative effects of molecular structures of brewer's spent grain on energy contents and amino acid digestibility in growing pigs.

The objectives of this study were to investigate the effects of extrusion on the chemical compositions, surface structure, and molecular structure of brewer's spent grain (BSG), as well as to determine the digestible energy (DE), metabolizable energy (ME), apparent total tract digestibility (ATTD) of nutrients and energy, and amino acid (AA) digestibility of extruded BSG when fed to growing pigs. Firstly, we determined the changes in chemical compositions and molecular structure of both non-extruded and extruded BSG. In Exp. 1, eighteen growing pigs were fed three different diets including one corn-soybean meal basal diet and two experimental diets containing 20% BSG with or without extrusion. Feces and urine were collected to determine the ATTD of nutrients and energy, DE, and ME of extruded or non-extruded BSG. In Exp. 2, eighteen growing pigs were fed three different diets including 30% BSG with or without extrusion, and an N-free diet. Ileal digesta was collected through the slaughter method to determine the apparent ileal digestibility (AID) and standardized ileal digestibility (SID) of AA of extruded or non-extruded BSG. The results showed that extrusion reduced the neutral detergent fiber, hemicellulose and cellulose contents in BSG, and increased the Arg, Asp, Glu, Ser, Tyr, total indispensable AA and total AA contents of BSG, altered the surface structure of BSG, increased the peak absorbance in amide I and amide II height, amide II and amide (I+II) area, α-helix height, decreased β-sheet height, and weakened band intensities in cellulosic compounds (CELC) area, structural carbohydrates (SCHO) area, carbohydrates area (CHO) peak 2 and 3 height, the area ratio of CELC: CHO and CELC: SCHO. Moreover, DE and ME values and ATTD of energy, dry matter, crude protein, acid detergent fiber, neutral detergent fiber, cellulose and hemicellulose increased (P < 0.05) when pigs were fed extruded BSG diets. The AID and SID of Arg, His, Lys, Val and Gly increased, whereas the AID and SID of Ile and Leu decreased when pigs were fed extrusion diets (P < 0.05). Our study found that the ATTD of nutrients and AA digestibility in pigs were positively correlated with the molecular structure of proteins, and negatively correlated with the molecular structure of carbohydrates (P < 0.05). These findings suggested that extrusion had the potential to improve the nutrient digestibility of BSG by altering its chemical compositions, surface structure, and molecular structure.

Use of optical absorption and scattering properties to monitor the change of chemical characteristics, particle structure and viscoelasticity during apple puree processing

This work explored the optical absorption (μa) and reduced scattering (μs') properties at 400–1050 nm (Vis-NIR) and 900–1650 nm (SWIR) of apple puree at different heating times to evaluate their changes in composition and structure. The optical absorption and scattering coefficients of μa and μs' decreased with increasing heating time. The specific μs' coefficients at 432 nm, 455 nm, 1183 nm and 1304 nm were related to particle structural changes. The partial least squares regression (PLSR) models based on μs' coefficients in the combined Vis-NIR and SWIR regions provided satisfactory estimations of puree particle area (Rp2 = 0.90) and particle perimeter (Rp2 = 0.85), whereas the μs' coefficients in the Vis-NIR region predicted puree viscosity (Rp2 = 0.83), elasticity modulus (Rp2 = 0.81) and viscous modulus (Rp2 = 0.78). Consequently, optical properties can be a potential tool to determine structural and rheological changes of apple puree.

Metabolic RNA labeling in non-engineered cells following spontaneous uptake of fluorescent nucleoside phosphate analogues.

RNA and its building blocks play central roles in biology and have become increasingly important as therapeutic agents and targets. Hence, probing and understanding their dynamics in cells is important. Fluorescence microscopy offers live-cell spatiotemporal monitoring but requires labels. We present two fluorescent adenine analogue nucleoside phosphates which show spontaneous uptake and accumulation in cultured human cells, likely via nucleoside transporters, and show their potential utilization as cellular RNA labels. Upon uptake, one nucleotide analogue, 2CNqAXP, localizes to the cytosol and the nucleus. We show that it could then be incorporated into de novo synthesized cellular RNA, i.e.it was possible to achieve metabolic fluorescence RNA labeling without using genetic engineering to enhance incorporation, uptake-promoting strategies, or post-labeling through bio-orthogonal chemistries. By contrast, another nucleotide analogue, pAXP, only accumulated outside of the nucleus and was rapidly excreted. Consequently, this analogue did not incorporate into RNA. This difference in subcellular accumulation and retention results from a minor change in nucleobase chemical structure. This demonstrates the importance of careful design of nucleoside-based drugs, e.g. antivirals to direct their subcellular localization, and shows the potential of fine-tuning fluorescent base analogue structures to enhance the understanding of the function of such drugs.

Combined effects of organic solvent and ultrasonic pretreatments on cellulose fiber extraction from hemp

Extracting pure cellulose fibers from hemp bast for potential textile industry applications requires the removal of non-cellulosic gummy materials. However, traditional degumming methods are largely limited because of the long procedure time, high energy consumption, heavy environmental pollution and insufficient efficiency. Organic solvents have been proved to be an innovative method for lignocellulose extraction. Herein, ethylene glycol solvent combined ultrasonic pretreatment was explored to degum hemp fibers without any further treatment. The purified hemp fibers were systematically characterized using analytical test techniques. Results revealed that the combined degumming could effectively remove non-cellulosic components without damaging the cellulose, and reducing the reaction temperature by 10 ℃ for reaction process. Comparing to the traditional method, the fibers by ultrasonic pretreatment-ethylene glycol process had superior average yield of 68.32 %, higher thermal stability (maximum degradation temperature reached 395 ℃), higher breaking tenacity of 6.13 cN/dtex, higher crystallinity of 78 % and the cellulose content of over 91 %. Moreover, the degumming time and chemical usage were reduced to 40 % and 51.8 %, respectively. Besides, the changes of fibers chemical structure were further investigated and verified by FTIR, EDS, and 13C NMR analysis. Featured with less chemical and energy consumption, eco-friendly and short time-consuming, this treatment has a broad application scope for hemp cellulose fiber extraction.

Photoacoustic Spectroscopy of Titanium Dioxide, Niobium Pentoxide, Titanium:Niobium, and Ruthenium-Modified Oxides Synthesized Using Sol-Gel Methodology.

The aim of this work was the development and morphological/chemical, spectroscopic, and structural characterization of titanium dioxide, niobium pentoxide, and titanium:niobium (Ti:Nb) oxides, as well as materials modified with ruthenium (Ru) with the purpose of providing improvement in photoactivation capacity with visible sunlight radiation. The new materials synthesized using the sol-gel methodology were characterized using the following techniques: scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), photoacoustic spectroscopy (PAS), and X-ray diffraction (XRD). The SEM-EDS analyses showed the high purity of the bases, and the modified samples showed the adsorption of ruthenium on the surface with the crystals' formation and visible agglomerates for higher calcination temperature. The nondestructive characterization of PAS in the ultraviolet visible region suggested that increasing calcination temperature promoted changes in chemical structures and an apparent decrease in gap energy. The separation of superimposed absorption bands referring to charge transfers from the ligand to the metal and the nanodomains of the transition metals suggested the possible absorption centers present at the absorption threshold of the analyzed oxides. Through the XRD analysis, the formation of stable phases such as T-Nb16.8O42, o-Nb12O29, and rutile was observed at a lower temperature level, suggesting pore induction and an increase in surface area for the oxides studied, at a calcination temperature below that expected by the related literature. In addition, the synthesis with a higher temperature level altered the previously existing morphologies of the Ti:Nb, base and modified with Ru, forming the new mixed crystallographic phases Ti2Nb10O29 and TiNb2O7, respectively. As several semiconductor oxide applications aim to reduce costs with photoexcitation under visible light, the modified Ti:Ru oxide calcined at a temperature of 800 °C and synthesized according to the sol-gel methodology used in this work is suggested as the optimum preparation point. This study presented the formation of a stable crystallographic phase (rutile), a significant decrease in gap energy (2.01 eV), and a visible absorption threshold (620 nm).

Effect of Thickener Type on Change the Tribological and Rheological Characteristics of Vegetable Lubricants.

This paper presents the results of a study on the effect of the dispersed phase on the lubricating and rheological properties of selected lubricant compositions. A vegetable oil base (rapeseed oil) was used to prepare vegetable lubricants, which were then thickened with lithium stearate, calcium stearate, aluminum stearate, amorphous silica, and montmorillonite. Based on the results of the tribological tests of selected lubricating compositions, it was found that calcium stearate and montmorillonite have the most beneficial effect on the anti-wear properties of the tested lubricating greases, while silica thickeners (amorphous silica and montmorillonite) provide the effective anti-wear protection in compared to the lubricants produced on lithium and aluminum stearate. The lowest structural viscosity was found for grease thickened with montmorillonite. Much higher values of this parameter were observed for composition, where aluminum stearate was the dispersed phase, while the highest value of structural viscosity was observed for composition, where aerosol-amorphous silica was the thickener. The composition thickened with amorphous silica had the highest yield point value, while the composition in which montmorillonite was the dispersed phase had the lowest value. Dynamic viscosity decreases with temperature, which is characteristic of lubricants. No significant differences in dynamic viscosity were found for the lubricating compositions tested at temperatures above 50 [°C]. The most favorable rheological properties were observed for composition, which was produced using calcium stearate, as it allows the lowest dynamic viscosity at -20 [°C]. Lubricants produced with lithium stearate or aluminum stearate were characterized by higher viscosity at low temperatures. For grease, in which the lithium stearate was used as a thickener, the value of the elasticity index determines the weak viscoelastic properties of tested grease and a greater tendency to change structure under the influence of applied forces. For vegetable grease thickened with aluminum stearate, more than 15 times lower values of the MSD function were observed, and the calculated elasticity index value proves the stronger viscoelastic properties of the aluminum stearate grease in relation to grease thickened with the lithium stearate. The elasticity index value for grease thickened with amorphous silica was lower than for greases thickened with lithium and aluminum stearate, indicating its stronger viscoelastic properties in relation to these two greases. For grease composition prepared on the vegetable oil base and thickened with montmorillonite. The value of the elasticity index was lower than most of the tested grease compositions, without the composition, in which the calcium stearate was used as a thickener. Such results testify to moderately strong viscoelastic properties, which leads to the conclusion that the produced lubricant was a stable substance on changes in chemical structure under the influence of variable conditions prevailing during work in tribological joints.

In-Situ Liquid-Electrochemical X-Ray and Electron Microscopy for Multi-Modal Energy Materials Characterization

In-situ liquid cell electron and x-ray microscopy have enabled dynamic studies of electrochemical reactions in energy materials and revealed relationships between the performance, structure, and chemical composition of these material systems. Such fundamental relationships are critical to improving the performance of batteries, catalysts, and other energy materials. Growing research interest in energy materials systems has accelerated the development of in-situ liquid-electrochemical microscopy techniques into mature and robust characterization workflows using novel and versatile scientific hardware.Multiple characterization techniques or in-situ processing steps are often required to fully understand the mechanisms governing the behavior of energy materials for all relevant length scales and environmental conditions. A multi-modal workflow combining in-situ liquid-electrochemical transmission electron, X-ray synchrotron and scanning electron microscopy methods is presented. The breadth of research applications is discussed, including the study of chemical dynamics and structural changes to micron-scale LixFePO4 battery particles during lithium-ion insertion/extraction, electrocatalytic behavior of β-Co(OH)2 platelet particles, and electrochemical oxidation of copper nanoparticles under reductive electrolytic conditions. New insights into these materials systems provided by these experiments will directly inform the development of predictive models for material performance and guide improvement of material design and synthesis.New scientific hardware and method development has been critical to in-situ nano-scale liquid cell microscopy and spectroscopy of electrochemical systems. Therefore, best-practice hardware and method design and development for these in-situ liquid-electrochemical microscopy experiments are also discussed. The connections between potentiostat, holder, and on-chip leads must be carefully considered with respect to different ground potentials, and the incorporation of real bulk-scale reference electrodes in this hardware has yielded quantitatively higher fidelity data with less degradation from further electrochemical cycling. Heating the sample or illuminating with light during in-situ electrochemical data collection has begun to further expand the range of environmental conditions that can be incorporated into experiments.

Measuring Erosion of Biodegradable Polymers in Brimonidine Drug Delivery Implants by Quantitative Proton NMR Spectroscopy (q-HNMR)

Erosion of biodegradable polymeric excipients, such as polylactic acid (PLA) and polylactic-co-glycolic acid (PLGA), is generally characterized by microbalance for the remaining mass of PLA and/or PLGA and Gel Permeation Chromatography (GPC) for molecular weight (MW) decrease. For polymer erosion studies of intravitreal sustained release brimonidine implants, however, both microbalance and GPC present several challenges. Mass loss measurement by microbalance does not have specificity for excipient polymers and drug substances. Accuracy of the remaining mass by weighing could also be low due to sample mass loss through retrieval-drying steps, especially at later drug release (DR) time points. When measuring the decrease of polymer MW by GPC, trace amounts of polymeric degradants (oligomers and/or monomers) trapped inside the implants during DR tests may not be measurable due to sensitivity limitations of the GPC detector and column MW range. Previous efforts to measure remained PLGA weight of dexamethasone micro-implants using qNMR with external calibration have been performed, however, these measurements do not account for chemical structure changes (i.e. LA to GA ratio changes from time zero) of PLGA implants during drug release tests. Here, a qNMR method with an internal standard was developed to monitor the following changes in micro-implants during drug release tests: 1. The remaining overall PLA/PLGA mass. 2. The remaining lactic acid (LA), glycolic acid (GA) unit and PLGA's lauryl ester end group percentages. 3. The trace content of PLA/PLGA oligomers as degradants retained in the implants. Unlike microbalance analysis, qNMR has both specificity for drug substance, excipient polymer, and accuracy due to minimal implant loss during sample preparation. Compared to the overall PLA/PLGA remaining mass generally monitored in erosion studies, the percentage of remaining LA, GA, and the ester end group provide more information about the microstructure change (such as hydrophobicity) of PLA/PLGA. Additionally, the qNMR method can complement GPC methods by measuring the change of remaining PLA and PLGA oligomer concentrations in brimonidine implants, with tenfold less sample and no MW cutoff. The qNMR method can be used as a sensitive tool for both polymer excipient characterization and kinetics studies of brimonidine implant erosion.

Evaluation of the Effect of Mineral Oil Exposure on Changes in the Structure and Mechanical Properties of Polymer Parts Produced by Additive Manufacturing Techniques.

The paper describes the type of changes in the structure and mechanical properties of 3D printed shapes under the influence of mineral oil. The effects of a room (23 °C) and elevated temperature (70 °C) on 3D prints manufactured by the FDM method and stored in oil for 15, 30, and 60 days on the change of properties and structure were investigated. The samples were produced from ABS (poly(acrylonitrile-co-butadiene-co-styrene)), ASA (poly(acrylonitrile-co-styrene-co-acrylate), PLA (poly(lactic acid)), and HIPS (high-impact polystyrene). Tests related to the strength of the materials, such as the static tensile test and Charpy impact test, were carried out. The structure was evaluated using a scanning electron microscope, and changes in chemical structure were determined by conducting FTIR (Fourier transform infrared spectroscopy) and TGA (thermogravimetric analysis) tests. The analysis of the results provided important information about the impact of mineral oil on specific materials. This is critical for designing and manufacturing components that can withstand mineral oil exposure in real-world environments. The materials underwent varying changes. Strength increased for PLA by about 28%, remained unchanged for ABS and HIPS during exposure for 30 days, and decreased for ASA with extended exposure up to 14%.

Molecular structure and evolution mechanism of shale kerogen: Insights from thermal simulation and spectroscopic analysis

During thermal evolution, the kerogen in shale formation undergoes significant chemical, structural and compositional changes, continuously influencing the shale storage capacity, hydrocarbon generation potential, and gas occurrence state. This study systematically examines the chemical structural changes during the thermal evolution of Longmaxi shale kerogen using hydrothermal laboratory experiments from 420 to 850 °C. Additionally, a range of characterization techniques, including Fourier Transform Infrared (FTIR) spectroscopy, Raman spectroscopy, High-Resolution Transmission Electron Microscopy (HRTEM), X-ray Diffraction (XRD), and Solid-state 13C Nuclear Magnetic Resonance (13C NMR), were employed to systematically investigate the kerogen structure and its evolution patterns. Results indicate that Longmaxi Formation kerogen comprises a large molecular carbon framework with aromatic structures, long-chain aliphatic components, and oxygen-containing functional groups. As thermal maturity reaches 2.6 %, the alignment of aromatic fringes gradually increased, with over 60 % aligning in the main direction. Throughout thermal evolution (1.9–3.2 %), fringes in the 5–10 Å range within aromatic structures peak at over 20.45 %, with fringes over 50 Å rapidly increasing from 3 % to over 15 %. Early in the thermal evolution, the long-chain aliphatic component of the kerogen decreases rapidly and part of the structure forms small aromatic rings through aromatisation. The mature to over-mature stage can be divided into three phases: 1) 1.7–2.4 % (loss of oxygen-containing functional groups), 2) 2.4–3.5 % (formation of larger aromatic structures via condensation reactions), 3) over 3.5 % (continued aggregation of aromatic rings, resulting in an increase in the length of aromatic fringes). At a macroscopic level, this induces changes in kerogen pore structure and carbonization features. This study thus provides new insights into the thermal evolution of shale kerogen, which in turn improve understanding of shale reservoirs for hydrocarbon exploitation.

Composite Copolymer Beads Incorporating Red Mud for Water Amendment by Adsorption—Oxidation Processes

We face significant environmental pollution problems due to various industries, such as the aluminum industry, which generates large amounts of red mud (RM) waste, or agriculture, in which case the use of pesticides creates huge water pollution problems. In this context, the present study offers a better perspective to originally solve both environmental issues. Thus, the main target of the study referred to using RM waste as a filler for preparing composite copolymer beads. Thereafter, this can achieve significant removal of water pollutants due to their adsorption/oxidation characteristics. As evidenced by the changes in chemical structure and composition, thermal stability, morphology, and porosity, RM was homogenously incorporated in poly(acrylonitrile-co-acrylic acid) beads prepared by wet phase inversion. The final assessment for the removal of pesticides by adsorption and oxidation processes was proven successful. In this regard, 2,4-dichlorophenoxyacetic acid was chosen as a model pollutant, for which an adsorption capacity of 16.08 mg/g composite beads was achieved.

Composite flat-sheet membrane adsorbent of Li2TiO3-Ethylene-co-vinyl alcohol (LTO-EVAL) for lithium extraction

Composite bead adsorbents have been prevalent for the extraction of Li+ from brines. However, adsorbent beads generally demonstrate declining adsorption capacity and require extended equilibrium time when used repeatedly in absorption/desorption cycles. To overcome this challenge, a novel composite flat-sheet membrane adsorbent based on ethylene-co-vinyl alcohol (EVAL) and Li2TiO3 (LTO) is reported herein for highly efficient Li+ extraction from a geothermal brine. At an optimal LTO loading and membrane thickness, the resulting LTO-EVAL membrane was characterized by a large open macrovoid structure for fast ion transport, a fast adsorption rate that reached equilibrium in 0.5 h, and a high capacity of 96 % of that of the powder. The new membrane adsorbent showed adsorption behavior consistent with the Langmuir model and pseudo-second-order kinetic model. For a geothermal brine with a low lithium concentration, the LTO-EVAL membrane showed stable performance in 13 rapid adsorption/desorption cycles, with adsorption capacity at an average adsorption capacity of 7.3 mg/g and a 70 % adsorption efficiency. The average dissolution rate of Ti4+ was below 0.6 % in each cycle. The structure of the adsorbent material showed no discernable changes in chemical structure as confirmed by XRD and SEM results. With the improved extraction efficiency, the reusable membrane adsorbents would be economically viable in the long run and could potentially serve as the next generation of scalable Li+ adsorption material for brines. Further utilization of membrane adsorbent would lead to new design of adsorption modules and systems with reduced footprint. We need to further optimize the stability of the membrane adsorbents so that loss of Li2TiO3 remain at low level to reduce the lost for lithium extraction from the geothermal brine.

Structural evolution and reaction kinetics of lignin-carbohydrate complex oxidized by chlorine dioxide

Lignin-carbohydrate complexes (LCC) present a significant barrier to pulp purification, and their oxidation mechanisms remain unclear. In this study, chlorine dioxide (ClO2), a common oxidant in the paper industry, was used to treat LCCs from various plant sources. The chemical composition, structural changes, and reaction kinetics of LCC were analyzed. After ClO2 oxidation, the LC bonds connected to syringyl (S)-type lignin structural unit and FA/pCA structures in LCC were effectively degraded, whereas those connected to guaiacyl (G) and p-hydroxyphenyl propane (H)-type units remained stable. Kinetic studies revealed that under conventional oxidation conditions, the degradation rates of LCCs from bagasse, bamboo, and eucalyptus were 0.40, 1.12, and 1.75, respectively, with consumption amounts of 6.23 mg, 10.92 mg, and 15.48 mg. The differences in the degree of LCC oxidative degradation were determined by the composition of lignin structural units. The findings provide theoretical support for the action mechanism of ClO2 on LCCs during the pulp purification process, and offer important guidance for optimizing the pulp purification process.

Phase Transition Control in Molecular Solids via Complementarity of Hydrogen-Bond Strength.

Phase transitions in molecular solids involve synergistic changes in chemical and electronic structures, leading to diversification in physical and chemical properties. Despite the pivotal role of hydrogen bonds (H-bonds) in many phase-transition materials, it is rare and challenging to chemically regulate the dynamics and to elucidate the structure-property relationship. Here, four high-spin CoII compounds were isolated and systematically investigated by modifying the ligand terminal groups (X=S, Se) and substituents (Y=Cl, Br). S-Cl and Se-Br undergo a reversible structural phase transition near room temperature, triggering the rotation of 15-crown-5 guests and the swing between syn- and anti-conformation of NCX- ligands, accompanied by switchable magnetism. Conversely, S-Br and Se-Cl retain stability in ordered and disordered phases, respectively. H-bonds geometric analysis and ab initio calculations reveal that the electronegativity of X and Y affects the strength of NY-ap-H⋅⋅⋅X interactions. Entropy-driven structural phase transitions occur when the H-bond strength is appropriate; otherwise, the phase stays unchanged if it is too strong or weak. This work highlights a phase transition driven by H-bond strength complementarity - pairing strong acceptor with weak donor and vice versa, which offers a straightforward and effective approach for designing phase-transition molecular solids from a chemical perspective.

Glucomannan is a promising isoniazid's enhancer that inducing macrophage phagocytosis.

Isoniazid (INH) is a frontline antituberculosis agent effective against Mycobacterium tuberculosis (Mtb), but the increasing challenge of avoiding multidrug-resistant tuberculosis, including INH resistance, necessitates innovative approaches. This study focused on enhancing macrophage phagocytosis to overcome INH resistance. Glucomannan, an immunomodulatory polysaccharide, emerged as a potential macrophage activator. Our objective was to characterize the glucomannan-INH mixture and assess its impact on INH efficacy and macrophage activity. Detailed examination of the glucomannan from Amorphophallus muelleri (0.05%-0.2%) was performed in several methods. INH sensitivity tests were carried out with the Mtb strain H37RV on Löwenstein-Jensen medium. Murine macrophage (RAW264.7) viability and activity were evaluated through MTT and latex bead phagocytosis assays. Ultraviolet-wavelength spectrophotometry was used to analyze chemical structure changes. Glucomannan (0.05%-0.2%) significantly enhanced murine macrophage viability and activity. When glucomannan was combined with INH, the IC50 value was greater compared to INH only. Phagocytosis assays revealed heightened macrophage activity in the presence of 0.05% and 0.1% glucomannan. Importantly, glucomannan did not compromise INH efficacy or alter its chemical structure. This study underscores the potential of glucomannan, particularly with a lower molecular weight, as a promising enhancer of INH, boosting macrophage phagocytosis against INH-resistant Mtb. These findings challenge the assumptions about the impact of glucomannan on drug absorption and prompt potential reevaluation. While specific receptors for glucomannan in macrophage phagocytosis require further exploration, the complement receptors are proposed to be potential mediators.

On application of molecular dynamics simulation for studying the effect of temperature and heating rate on HTL of biomass

Abstract Hydrothermal liquefaction (HTL) of biomass has garnered increasing attention as a promising pathway for converting solid biomass to liquid biofuels and valuable chemical products. HTL involves processing of biomass in water at high-temperature and high-pressure conditions. The heating rate during this process plays a critical role in determining the yield and composition of the liquefied products. To probe the impact of heating rate, we develop a detailed atomistic model biomass by using cellulose as model compound and place it in a simulated HTL reactor. Our Reactive molecular dynamics simulations are capable of capturing the dynamic chemical reactions and structural changes during HTL. The effect of reaction temperature and heating rates on reaction pathways, product distributions, and reaction kinetics is rigorously analyzed. Our findings reveal that the reaction temperature and heating rate significantly influences the extent of cellulose degradation and the composition of bio-oil product.

NMR Analysis of Thermally‐Oxidized Hydroxyl‐Terminated Polybutadiene (HTPB)

AbstractNuclear magnetic resonance spectroscopy was employed to monitor the change in chemical structures, olefin units (cis, trans and vinyl) and hydroxyl value on stabilized Hydroxyl‐terminated polybutadiene (HTPB) under accelerated ageing condition. Thermal ageing of HTPB was carried out at 65 °C for 10‐weeks and periodically withdrawn sample for NMR analysis. 1H and 13C NMR spectroscopy provided detailed structural information for all HTPB samples, including the quantification of olefin units and the determination of hydroxyl value. The analysis revealed a decrease in signal intensity, particularly for the olefin near or at the molecular end, suggesting that they were oxidized before those in the middle position within the chain. The quantitative assessment of olefin units indicates a slight decrease of 2 % in 1,2‐vinyl unit after 10‐weeks of ageing. The NMR spectra did not show any detectable signals corresponding to epoxides, peroxides or alcohols in any HTPB samples. However, a slight increase in the OH value was observed after 8 and 10 weeks of ageing, suggesting the possible incorporation of new hydroxyl groups due to thermal‐oxidation. The antioxidants used to stabilize HTPB exhibited limited effectiveness in preventing degradation reactions, even after 4 weeks of ageing at 65 °C.

Change in Chemical Structure of ZnDTP-Derived Tribofilm Formed from Low-Viscosity Engine Oil by Addition of PMA-Series Polar Compounds

Change in Chemical Structure of ZnDTP-Derived Tribofilm Formed from Low-Viscosity Engine Oil by Addition of PMA-Series Polar Compounds