Nuclear Magnetic Resonance Scanning Research Articles

Symmetric Refunctionalization of Diaminodinitropyrazine with Hydrazine and Aminotetrazole: Strategy for Enhancing Detonation Performance and Safety in Energetic Materials.

Two novel nitrogen-rich green energetic compounds were synthesized for the first time from readily available and cost-effective pyrazine starting materials. All newly synthesized molecules were comprehensively characterized, including infrared spectroscopy, nuclear magnetic resonance, elemental analysis, mass spectrometry, and thermogravimetric analysis-differential scanning calorimetry. All compounds have additionally been validated by single-crystal X-ray diffraction analysis. The physicochemical properties of compounds 2, 4, and 5 were thoroughly investigated. Notably, all compounds exhibit remarkable performance, such as a high density (>1.84 g cm-3), excellent detonation properties (VOD > 8582 m s-1, and DP > 31.3 GPa), outstanding thermostability (>205 °C), and high insensitivity (IS > 35 J, and FS = 360 N). These attributes are quite comparable to those of secondary benchmark explosives such as TATB, RDX, LLM-105, and FOX-7. This tuned performance evidences that the incorporation of hydrazine, nitro, and aminotetrazole into the pyrazine framework fosters robust nonbonded interactions, ultimately enhancing thermal stability and reducing sensitivity. The findings of this study not only signify that compounds 2 and 5 have excellent detonation properties and stability but also prove that the strategy of replacing amino groups with hydrazine and aminotetrazole is a practical means of developing new insensitive energetic materials.

Hybrid Dendrimer Network based on Silsesquioxane and glycidyl methacrylate for Enhanced Adsorption of Iodine and Dyes in Environmental Remediation.

A novelhybrid network was synthesized in two steps: the first step involved the attachment of glycidyl methacrylate (GMA)to octa(aminophenyl) silsesquioxane (OAPS) through a ring-opening reaction, forming a hybrid dendrimer structure, and the second stepinvolved the cross-linking of hybrid dendrimer using an azobisisobutyronitrile initiator to create the final hybrid network of OAPS-GMA. The synthesized hybrid material was comprehensively characterized using fourier transform infrared Spectroscopy (FTIR), nuclear magnetic resonance ((1H,13C, and 29Si NMR) spectroscopy, thermogravimetric Analysis (TGA), and scanning electron microscopy (SEM). The BET surface area was found to be 25.44 m²/g, and significant 2.341 cm³/g of total pore volume was observed. The TGA analysis shows that the material is highly stable up to 450 oC. The synthesized network demonstrated remarkable adsorption capacities for iodine and dyes. It exhibited an iodine adsorption capacity of 3.4g/g from vapors and 874mg/g from solution. Additionally, it showed significant adsorption capacities for Rhodamine B and Congo red, with values of 762mg/g and 517mg/g, respectively. This study not only provides a novel method for preparing GMA-functionalized silsesquioxane-based porous hybrid polymers but also contributes to advancing solutions for environmental pollution issues.

Porosity and pore structure evolution during the weathering of black shale

Pore type and pore structure evolves systematically across continuous black shale weathering profile. However, the extend and process of pore structure change is still an enigma. In this study, we try to unveil the pore structure evolution during weathering process through studying Cambrian Hetang shales in southern China. Fourteen shale samples, from protolith zone (PZ), fractured and weathered shale zone (FWZ), and saprolite zone (SZ), were collected to elucidate how porosity and pore structure develop during black shale weathering under subtropical condition. Through low pressure argon (Ar) gas adsorption (LP-ArGA), high pressure mercury intrusion (HPMI), nuclear magnetic resonance(NMR) and field emission scanning electron microscope (FESEM) observation, the results reveal significant differences in physical properties and pore structures among the PZ, FWZ, and SZ samples. Specifically, compared to PZ, FWZ and SZ samples are characterized by higher clay mineral content, lower organic matter (OM), and the absence of carbonates and pyrite. Total porosity, determined through HPMI and NMR, exhibits a gradual increase from PZ (6.70 % and 6.41 %) to FWZ (20.47 % and 13.45 %) and SZ (23.22 % and 12.48 %). Ar adsorption isotherms indicate a change in pore type from predominantly ink-bottle and slit-shaped in the PZ to mainly slit-shaped in FWZ and SZ. Integrated analysis of LP-ArGA, HPMI, NMR and SEM observation suggests a substantial decrease in the contribution of micropores to total pore volume (PV) and a concurrent increase in larger pores (meso-macropores) with the increase of weathering intensity. This results in smoother surfaces of micro-transition pores but rougher surfaces of macropores. Changes in mineralogy composition during weathering play a crucial role in influencing pore structure of shales and further accelerating the release and migration of toxic elements in black shale. Our study provides the essential theoretical foundation for the remediation of soil and water environmental pollution caused by black shale weathering.

Synergistic modification of hot-melt extrusion and nobiletin on the multi-scale structures, interactions, thermal properties, and in vitro digestibility of rice starch.

Rice starch has high digestibility due to its large carbohydrate content. Synergistic modification of hot-melt extrusion (HME) and additives such as flavonoids, hydrocolloids, proteins, lipids, and other additives has the tendency to retard the rate of starch hydrolysis. Hence, the current investigation aimed to study the combined effect of the HME-assisted addition of nobiletin (NOB, 0, 2, 4, and 6%) on the multi-scale structures, interactions, thermal, and digestibility characteristics of rice starch. The study employed density functional theory calculations and an infrared second derivative of an Fourier-transform infrared (FTIR) spectrometer to analyze the interactions between NOB and starch. The physicochemical properties of the starch extrudates were characterized by FTIR, 13C nuclear magnetic resonance, X-ray diffraction, and differential scanning calorimetry, while the digestibility was evaluated using an in vitro digestion model. HME was found to disrupt the crystalline structure, helix structure, short-ordered structure, and thermal properties of starch. The interaction between NOB and starch involved hydrophobic interactions and hydrogen bonds, effectively preventing the molecular chains of starch from interacting with each other and disrupting their double helix structure. The addition of NOB led to the formation of a highly single-helical V-type crystalline structure, along with the formation of ordered structural domains. Consequently, the combined treatment significantly enhanced the ordered structure and thermal stability of starch, thus effectively leading to an increase in resistant starch and slowly digestion starch. The study underscores that synergistic modification of HME and NOB holds promise for enhancing both the nutritional value and functional properties of rice starch. These findings offer valuable insights for developing high-quality rice starch products with broader applications.

Enzyme-catalyzed transesterification of galactomannan extracted from mesquite seed (Prosopis velutina) with vinyl carboxylate esters

Galactomannans (GM) are hemicellulosic polysaccharides composed of D-mannopyranose chains linked by β (1 → 4) glycosidic linkages with branches of D-galactopyranose linked by α (1 → 6) linkages. This polysaccharide is recognized for its hydrophilic character, as it is rich in hydroxyl groups (-OH). This chemical characteristic, combined with the absence of ionic charges, enables structural modifications such as transesterification of the fatty acid chains (FA), which provides a strategy for obtaining amphiphilic structures. The enzyme-catalyzed syntheses were carried out in DMSO with GM decanoate (GMD) and GM palmitate (GMP) at different molar ratios (0.5 and 1.0) and the resulting structures were evaluated with infrared spectroscopy (FTIR), solid-state nuclear magnetic resonance (CP/MAS 13C NMR) and differential scanning calorimetry (DSC). The FTIR spectrum confirmed the transesterification of GM with the appearance of a CO band (1730-1750 cm−1). These results were confirmed by the signals observed at 177 and 30 ppm in the CP/MAS 13C NMR spectrum, which corresponded to the CO groups of the esters and the terminal –CH3 groups of the FA chains, respectively. Finally, DSC showed glass transition temperatures (Tg) in the range 43–51 °C, while the melting temperatures (Tm) of the GM esters (59 °C) were not affected by different degrees of esterification (DE) for GMD (0.37 and 0.71) and GMP (0.47 and 0.57).

Spectroscopic analysis, quantum computational, and molecular docking investigations on the crystalline salt of 4-phenyl sulfanyl butanoic acid and piperazine with enhanced cytotoxic activity

In this investigation, the target crystalline salt was synthesized by combining 4-phenyl sulfanyl butanoic acid (PSBA) and piperazine (PZ). The process encompassed experimental methodologies, such as Powder X-ray Diffraction (PXRD),Single Crystal X-ray Diffraction (SCXRD), Nuclear Magnetic Resonance (NMR), Infrared Spectroscopy (IR),Thermogravimetric Analysis and Differential Scanning Colorimetry (TGA-DSC), as well as theoretical analyses of the synthesized compound.The crystalline salt was successfully synthesized via the solvent evaporation method at room temperature.PZ-PSBA has an orthorhombic crystal system with space group Pbca and unit cell parameters a = 7.4357(10)Å, b = 9.4853(12)Å, c = 34.299(5), and α=β=γ=90°. We employed the B3LYP functional with 6–311++G (d, p) as a basis set to geometrically optimize the molecular structure using Density Functional Theory (DFT).The synthesized material inhibits the human colon cancer cell line HT-29, the human lung adenocarcinoma cell line A549, and the human gastric cancer cell line MKN45, with substantial biological effects that have been demonstrated to be effective. According to in vitro and in sillico anticancer studies, PZ-PSBA has better activity against the human cervical cancer cell line (HeLa) and in bioinformatics analysis. PZ-PSBA suppressed pathogenic strains better than its parent chemical and can thus be suggested for the treatment of bacterial infections.

TENOFOVIR DISOPROXIL FUMARATE RELEASE FROM GLUTARALDEHYDE CROSS-LINKED CHITOSAN/Β-CYCLODEXTRIN HYDROGEL

In this study, chitosan was produced from crayfish Astacus leptodactylus, and then it was used to synthesize chitosan-graft-β-cyclodextrin (CS-g-β-CD) hydrogel. The produced chitosan (CS) and the sythesized CS-g-β-CD hydrogel were characterized using a Fourier Transform Infrared Spectroscopy (FTIR), Proton Nuclear Magnetic Resonance Spectroscopy (1H-NMR), X-ray Diffraction (XRD), and Scanning Electron Microscopy (SEM). Tenofovir disoproxil fumarate (TDF) was used as a model to investigate the antiviral drug release properties of the CS-g-β-CD hydrogel. The synthesized hydrogel had an almost homogeneous pore structure and a high swelling capacity which increases depending on the amount of β-Cyclodextrin (β-CD). The drug-loaded CS-g-β-CD hydrogels was examined by XRD and 1H-NMR, and SEM analyses. Seventy-three percent of the TDF loaded on the synthesized hydrogels was released into phosphate-buffered saline (PBS) solution at 37 ºC. The drug release behavior of all prepared CS-g-β-CD hydrogels fitted the Korsmeyer-Peppas model. The addition of β-CD into the gel improved the swelling ability and TDF release of the CS-g-β-CD hydrogel system.

Experiment of dynamic seepage of tight/shale oil under matrix fracture coupling

A physical simulation method with a combination of dynamic displacement and imbibition was established by integrating nuclear magnetic resonance (NMR) and CT scanning. The microscopic production mechanism of tight/shale oil in pore throat by dynamic imbibition and the influencing factors on the development effect of dynamic imbibition were analyzed. The dynamic seepage process of fracking–soaking–backflow–production integration was simulated, which reveals the dynamic production characteristics at different development stages and their contribution to enhancing oil recovery (EOR). The seepage of tight/shale reservoirs can be divided into three stages: strong displacement and weak imbibition as oil produced rapidly by displacement from macropores and fractures, weak displacement and strong imbibition as oil produced slowly by reverse imbibition from small pores, and weak displacement and weak imbibition at dynamic equilibrium. The greater displacement pressure results in the higher displacement recovery and the lower imbibition recovery. However, if the displacement pressure is too high, the injected water is easy to break through the front and reduce the recovery degree. The higher the permeability, the greater the imbibition and displacement recovery, the shorter the time of imbibition balance, and the higher the final recovery. The fractures can effectively increase the imbibition contact area between matrix and water, reduce the oil-water seepage resistance, promote the oil-water displacement between matrix and fracture, and improve the oil displacement rate and recovery of the matrix. The soaking after fracturing is beneficial to the imbibition replacement and energy storage of the fluid; also, the effective use of the carrying of the backflow fluid and the displacement in the mining stage is the key to enhancing oil recovery.

Novel insights into the amorphous feature of granulated blast furnace slag-supplemented magnesium potassium phosphate cement and its effect on bulk properties

This paper reports the effects of MgO:PO4 (3, 9, and 15) ratio and granulated blast furnace slag dosage (0 wt%, 40 wt%, and 80 wt%) on the phase formation, microstructure, and bulk properties of magnesium potassium phosphate cement (MKPC). Results show that the supplementary of slag and the increment in MgO:PO4 inhibit the formation of K-struvite via X-ray diffraction. While the detections of 29Si magic-angle spinning nuclear magnetic resonance spectroscopy and scanning electron microscope-energy dispersion spectrum further unveil the dissolution of slag and the formation of Q4 amorphous structure in slag supplemented MKPCs. Although the Q4 structure increases the interplanar spacing of K-struvite even leads to its amorphization in MKPCs with high MgO:PO4 (>9), the optimum coexisting of K-struvite and Q4 structure minimizes the porosity and maximizes the compressive strength of MKPCs with MgO:PO4=3 and 40 wt% slag. These results are crucial to developing optimal mixture formulations of MKPC with superior mechanical performance and lower costs associated with their production.

Study of a high salt tolerant amphiphilic polymer and its salt thickening mechanism

Polymer flooding is the most reliable method for the petroleum industry to further enhance oil recovery from the developed oil field and to keep the total oil production. For the reservoirs with high salinity, traditional polymer fluids, for example partially hydrolyzed polyacrylamide (HPAM), are failed to improve oil recovery rate due to the molecular agglomeration caused by compression-diffusion electric double layer. By optimizing the copolymerization of cyclic structure monomer n-vinylpyrrolidone (NVP) and long-chain hydrophobic monomer cetyl dimethyl allyl ammonium chloride (C16DMAAC), a high salt tolerant amphiphilic polymer P(AM/NVP/C16DMAAC), abbreviated as PANC, is synthesized. The optimal polymerization conditions were determined depending on the apparent viscosity measured by the rheometer. The microstructure of the polymer was evaluated using Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy and scanning electron microscopy. The viscosity of 2000 mg/L PANC increased to 42.7 mPa·s at the salinity of 11.6 × 104 mg/L and temperature of 40 °C, while the viscosity of HPAM was only 7.3 mPa·s under the same condition. The viscosity of PANC was 479 % higher than that of HPAM, indicating the remarkable salt tolerant property of PANC. The viscosity of PANC increased from 12 mPa·s to 42.7 mPa·s when the salinity increased from 1 × 104 mg/L to 11.6 × 104 mg/L. By comparing the salt resistance of polymer PANC and polymer P(AM/AA/C16), abbreviated as AP-C16, indicating that NVP enhanced the rigidity of the PANC molecular chain, and hindered the shrinkage and curling of the molecular chain after salt addition. The inclusion effect of β-cyclodextrin on the hydrophobic groups of PANC indicated that PANC increased viscosity through the hydrophobic association of C16DMAAC. Furthermore, PANC showed a salt thickening ability due to the synergy effect of C16DMAAC and NVP. As such, the salt tolerant amphiphilic polymer PANC offers a novel polymer flooding material for oil displacement, especially under a high-salinity condition.

Microstructure and chloride transport of aeolian sand concrete under long-term natural immersion

Abstract River sand was consumed in large quantities, and alternatives to river sand were urgently needed. There are a large number of natural resources of aeolian sand in western China. Aeolian sand was prepared into aeolian sand concrete (ASC). It can greatly reduce the consumption of river sand and inhibit the process of desertification to protect the environment. ASC is a new type of concrete material prepared by using aeolian sand as fine aggregate. To clarify the chloride ion transport behaviour in the ASC under long-term natural immersion, the aeolian sand was 100% substituted for the river sand to prepare the full ASC with three water–binder ratios. The ASC was naturally immersed in 3 and 6% NaCl solutions for a long time, and nuclear magnetic resonance and microscopic scanning electron microscopy techniques were used. The change rule of chloride ion content at different depths of the ASC was studied, and its microstructure characteristics under different erosion times were analysed. The results showed that the free chloride ion concentration at different depths of the ASC increased with increasing water–binder ratio, immersion time, and chloride concentration. After soaking in the salt solution, the hydration products in the ASC reacted with chloride ions to form Friedel salt, which filled the internal pores and microcracks of the ASC, improved its interface transition zone structure, and increased the compactness of the test piece. The porosity of the three groups of ASC with different water–binder ratios decreased by 0.95, 1.03, and 1.15% after soaking in 6% salt solution for 12 m. To study the diffusion law of chloride ions in ASC, combined with influencing factors such as temperature, humidity, D value, deterioration effect and chloride ion combination, Fick’s second law was modified, and a chloride ion diffusion model of ASC with high accuracy was established, with a fitting correlation number above 0.93, which provided a reference for the research and application of ASC in saline areas.

Cooling Damage Characterization and Chemical-Enhanced Oil Recovery in Low-Permeable and High-Waxy Oil Reservoirs

The well productivity of high-waxy reservoirs is highly influenced by temperature changes. A decrease in temperature can cause the precipitation of wax from the crude oil, leading to a decrease in the formation’s drainage capacity and a drop in oil production. In this study, the wax precipitation of crude oil is characterized by rheological properties tests and differential scanning calorimetry (DSC) thermal analysis. The wax damage characteristics of cores and the relative permeability curves at different temperatures were investigated through coreflood experiments. Furthermore, nanoemulsion is selected as a chemical agent for injection fluid. The nuclear magnetic resonance (NMR) scanning technique is used to investigate the effects of oil recovery enhancement at different pores by increasing temperature and adding nanoemulsion. By comparing the changes in T2 spectra and the distribution pattern of residual oil before and after liquid injection, the results have shown that both increasing temperature and adding nanoemulsion have a significant effect on oil recovery. The improvement of micropores is less pronounced compared to macropores. The produced oil mainly comes from the large pores. When the temperature is lower than the crude oil dewaxing point temperature, there is a serious dewaxing plugging phenomenon in the pores. Additionally, by observing the pattern of residual oil distribution at the end of the NMR online drive, it is hereby classified into wax deposition retention type, weak water washing retention type, and immobilized type, each with its own distinct characteristics. Wettability alteration and interfacial tension reduction can help to improve the drainage capacity of high-wax oil reservoirs, which is the main mechanism of nanoemulsion for enhanced oil recovery. These findings are highly valuable for enhancing the comprehension of the impact of highly waxed crude oils on drainage capacity and the ultimate oil recovery rate, particularly in relation to wax precipitation deposition.

Connectivity assessment in hierarchical zeolites by correlating nuclear magnetic resonance, electron microscopy/tomography and adsorption scanning

Hierarchical zeolites presenting different pore domains have the potential to reduce problems associated with low diffusion in zeolites, thus holding great promise in a wide range of application fields. Nevertheless, efficient transfer between the different porous networks is required for the mesopores (2–50 nm) and macropores (>50 nm) to be effective in promoting the transit of molecules towards the micropores (<2 nm). In this work, the connectivity between the various pore domains in a class of hierarchical zeolites – denominated as nanoparticle aggregates – is investigated through 2D exchange spectroscopy (EXSY) 1H nuclear magnetic resonance (NMR) using paraxylene as a probe molecule. This approach allows to track whether the probe molecule visits distinct pore environments over time, providing unique insight into pore connectivity. The analysis of scanning curves through N2 adsorption/desorption cycles completes the characterization of pore connectivity. Furthermore, electron microscopy and tomography are used as visual techniques to confirm the arrangement of the mesoporous and macroporous networks generated by the nanoparticle aggregates.

Synthesis and Characterization of Polyester Derived from Glycerol and Its Application as an Adhesive on Different Adherents

With the increase in the supply of glycerol and its economic devaluation, it is important to develop strategies that add value to this substance. Among the various alternatives, one application is its use as a precursor in the synthesis of new polyesters. Therefore, this work describes the condensation reaction of glycerol with valeric acid, obtaining functionalized glycerol, which was used in the polycondensation reaction with terephthalic acid. The samples were characterized by infrared spectroscopy, thermogravimetric analysis, hydrogen nuclear magnetic resonance and differential scanning calorimetry. Spectroscopic analyses confirmed the conversion of the reagents into esters and polyesters. The polyesters showed superior thermal stability than the individual components, a glass transition temperature of -3.8 °C and adhesive properties on glass, wood, paper and rigid polyvinyl chloride substrates. The adhesive capabilities of the samples were compared with those of commercial adhesives already established in the Brazilian market. Samples of polyesters synthesized through the reaction between functionalized glycerol and terephthalic acid showed adhesive behavior in the range of mechanical resistance observed in commercial adhesives, with an elastic modulus ranging from 60.9 ± 36.0 MPa to 162.1 ± 102.4 kPa, depending on the type of adhesive substrate, behaving either as an elastic and/or thermoplastic adhesive.

A Diruthenium Metallodrug as a Potent Inhibitor of Amyloid-β Aggregation: Synergism of Mechanisms of Action.

The physical and chemical properties of paddlewheel diruthenium compounds are highly dependent on the nature of the ligands surrounding the bimetallic core. Herein, we compare the ability of two diruthenium compounds, [Ru2Cl(D-p-FPhF)(O2CCH3)3]·H2O (1) (D-p-FPhF- = N,N'-bis(4-fluorophenyl)formamidinate) and K3[Ru2(O2CO)4]·3H2O (2), to act as inhibitors of amyloid aggregation of the Aβ1-42 peptide and its peculiar fragments, Aβ1-16 and Aβ21-40. A wide range of biophysical techniques has been used to determine the inhibition capacity against aggregation and the possible mechanism of action of these compounds (Thioflavin T fluorescence and autofluorescence assays, UV-vis absorption spectroscopy, circular dichroism, nuclear magnetic resonance, mass spectrometry, and electron scanning microscopy). Data show that the most effective inhibitory effect is shown for compound 1. This compound inhibits fiber formation and completely abolishes the cytotoxicity of Aβ1-42. The antiaggregatory capacity of this complex can be explained by a binding mechanism of the dimetallic units to the peptide chain along with π-π interactions between the formamidinate ligand and the aromatic side chains. The results suggest the potential use of paddlewheel diruthenium complexes as neurodrugs and confirm the importance of the steric and charge effects on the properties of diruthenium compounds.

Levofloxacin-Fatty Acid Systems: Dual Enhancement Through Deep Eutectic Formation and Solubilization for Pharmaceutical Potential and Antibacterial Activity.

Fatty acids, including medium-chain saturated and polyunsaturated fatty acids, are known for their broad health benefits, including antimicrobial activity. Through their green properties, deep eutectic systems have been heralded as having the potential to be at the forefront of pharmaceutical applications. In this work, capric acid and geranic acid, two examples of medium-chain saturated and polyunsaturated fatty acids, were employed to enhance the pharmaceutical properties and the antibacterial activity of levofloxacin. To this end, levofloxacin formulations with either capric or geranic acid were prepared and characterized using appropriate techniques. Levofloxacin was utilized to create innovative deep eutectic systems in conjunction with capric acid at three different molar ratios: 1:9, 2:8 and 3:7. This was confirmed through a rigorous analysis involving nuclear magnetic resonance, infrared spectroscopy and differential scanning calorimetry. Furthermore, it is noteworthy that geranic acid demonstrated an impressive threefold improvement in levofloxacin's solubility compared to its solubility in aqueous solutions. The antibacterial activity of the novel combinations of levofloxacin with either fatty acid was evaluated using a checkerboard titration assay. Gratifyingly, both formulations exhibited synergistic effects against a panel of levofloxacin-sensitive and resistant Gram-negative bacteria. In conclusion, the observed superior antibacterial activity of levofloxacin illuminates the potential use of fatty acid-based formulations and deep eutectic systems as green and innovative strategies to combat the global antimicrobial resistance problem.

Influence of nanosized magnesia on the hydration of borehole-sealing cements prepared using different methods

Gas drainage is an effective technology for gas control in coal mines. A high borehole-sealing quality is the fundamental precondition for efficient gas drainage. The expansibilities of cement pastes used in borehole-sealing processes are critical for the borehole-sealing effect. Nanosized magnesia expansive agents are used to improve the expansibilities of cement pastes and improve the borehole-sealing effect. Nuclear magnetic resonance spectrometry and scanning electron microscopy were adopted to study the effects of nanosized magnesia on the hydration of borehole-sealing cements used with different preparation methods. The results showed that an increase in the mass fraction of the nanosized magnesia promoted cement hydration, and the mass fraction was positively correlated with the promotion effect. The use of different preparation methods did not change the water-phase distribution in the cement. When using the wet-mixing preparation method, nanosized magnesia promoted the induction, acceleration, and deceleration periods of hydration; when using the dry-mixing preparation method, the nanosized magnesia promoted the induction period of cement hydration, and the promotion effect was less obvious than that seen when using the wet-mixing method. When using the wet-mixing preparation method, the nanosized magnesia was uniformly dispersed, thus enlarging the surface area of the reaction, which provided more nucleation sites for the hydration products of the cement and therefore accelerated the hydration reaction. When using the dry-mixing preparation method, the nanosized magnesia powders were dispersed nonuniformly and aggregated. Under these conditions, only a few nanosized magnesia particles on the surfaces of the aggregated clusters took part in hydration, so only a small number of nucleation sites were provided for the hydration products of cement. This led to inconsistent hydration of cement pastes prepared using the dry-mixing method. The surface porosity of the cement prepared with the wet-mixing preparation method first decreased and then increased with increases in the mass fraction of the nanosized magnesia. The cement surface exhibited compact hydration products and few pores, and the surface was relatively smooth. In comparison, the surface porosity of the cement prepared using the dry-mixing method fluctuated with increasing mass fraction of the nanosized magnesia, resulting in a rough cement surface and microfractures on some surfaces. The two preparation methods both reduced the surface porosity of the cement. The wet-mixing preparation was more effective and consistent in improving the compactness of the cement than the dry-mixing preparation. These results provide important guidance on the addition of nanosized magnesia in borehole-sealing engineering and the selection of cement preparation methods, and they also lay a solid foundation for realizing safe and efficient gas drainage.

Experimental Study of the Dynamic Characteristics and Microscopic Mechanism of Lightweight Soil Modified with Expanded Polystyrene and Sisal Fibre

With the increasing demand and use of highways, railways and tunnels in China, the phenomena of foundation settlement, uneven deformation and ground cracking caused by the cyclic loading by traffic are becoming increasingly significant. There is now an emphasis on research to prevent or decrease these phenomena by mixing new materials into the soil body. In this study, cyclic loading tests were conducted on lightweight soils modified with expanded polystyrene (EPS) and sisal. A GDS true/dynamic triaxial apparatus was used to study the dynamic elastic modulus and damping ratio of clays with different dosages of EPS and sisal fibre. The modified soil samples were tested, and then, they underwent micro-scale analysis. The results showed that, with the continuous increase in EPS doping and dynamic stress, the trend of the growth of the dynamic strain of the specimens increased. At the same time, with the increase in the dynamic strain, the dynamic elastic modulus decreased, and the trend increased with increasing doping of the soil with EPS particles. A comparison of the improvement effect coefficient of the soil samples showed that the most suitable EPS doping volume was 5%. Different dosages of sisal fibre were added to the most suitable EPS-modified lightweight soil, and the dynamic elastic modulus first increased and then decreased with increasing sisal dosage. In addition, the damping ratio first increased and then decreased. The best dynamic performance of the soil was obtained when the dosage of sisal was 1.2%. Nuclear magnetic resonance and electron microscope scanning tests verified that, when the sisal doping was 1.2%, the soil particles had the largest compactness, the best interparticle bonding and the best improvement effect.

Proof-of-Concept in Developing a 45% Drug Loaded Amorphous Nanoparticle Formulation

Amorphous solid dispersion (ASD) is an enabling approach utilized to deliver poorly soluble compounds. ASDs can spontaneously generate drug-rich amorphous nanoparticles upon dissolution, which can act as a reservoir for maintaining supersaturation during oral absorption. But, conventional ASDs are often limited in drug loadings to < 20 %. For indications where the dose is high, this can translate into a significant pill burden. The aim of this research was to develop a high drug loading (DL) amorphous nanoparticle (ANP) formulation that can release the drug-rich nanoparticles into solution upon contact with aqueous environment. Nanoparticles were directly engineered using solvent/anti-solvent precipitation. The obtained nanoparticle suspension was then concentrated followed by solidification to a re-dispersible amorphous dosage form using spray drying or lyophilization. The impact of process variables was studied using dynamic light scattering (DLS), scanning electron microscopy (SEM), high performance liquid chromatography (HPLC), nuclear magnetic resonance (NMR) and differential scanning calorimetry (DSC). It was observed that spray drying led to a non-re-dispersible formulation. Sucrose and trehalose containing lyocakes resulted in re-dispersible formulations. The trehalose containing lyocakes, in a dog study, gave comparable performance to the reference tablet in the fasted state but lower area under the curve (AUC) in fed state.

Synthesis, Characterization, Thermal Stability, and Kinetic Degradation of Cellulose p‐Halide Benzoates in an Ionic Liquid 1‐Butyl‐3‐methylimidazolium Chloride

AbstractCellulose p‐halide benzoates (C‐p‐HB) were synthesized by reacting microcrystalline cellulose (MCC) with p‐halide benzoyl chloride (p‐HBCl) namely; the p‐Iodobenzoyl chloride (p‐IBCl), p‐Bromobenzyl chloride (p‐BBCl), and p‐Nitrobenzoyl chloride( p‐NBCl) in ionic liquid 1‐butyl‐3‐methylimidazolium chloride [Bmim](Cl) at 60 °C for 2 h in the presence of 4‐dimethylaminopyridine (DMAP) as a base. The synthetic products were characterized through infrared spectrometry (FT‐IR), nuclear magnetic resonance (NMR) spectroscopy, XRD, and scanning electron microscopy (SEM). Then, the effects of p‐halide benzoate groups on the thermal degradation of C‐p‐HB esters with DS≈1 were investigated using thermogravimetric analysis under an inert atmosphere from room temperature to 600 °C at a heating rate of 5 °C/min. The DSC analysis was used to determine the glass temperature and heat of the reaction of C‐p‐HB esters. The results indicated that the C‐p‐HB was successfully synthesized in [Bmim](Cl) with a DS≈1. The kinetic parameters were determined by the Coats‐Redfern (CR) method. The corresponding kinetic parameters of the main degradation stages were also determined. The thermal stability of MCC was remarkably decreased through esterification with p‐HBCl. The Criado method was used to determine the most probable degradation functions. Thus, reaction orders F2 and F3 were most probably the functions that describe the degradation of C‐p‐HB.