ACS Omega最新文献

Coal seams in China are characterized by low permeability, high gas pressure, and soft coal, which lead to challenging gas extraction and severe gas disasters. Hydraulic flushing is widely used in the field to enhance the permeability of coal seams. Considering this fact, studying its effect on the stress and permeability variations of loaded coal is essential for upgrading the hydraulic flushing permeability enhancement technology. In the study, large-scale physical simulation experiments on hydraulic flushing were conducted to monitor stress changes in the loaded coal. On this basis, the effect of these stress changes on the permeability was investigated. The results show that the stress falls with fluctuations during hydraulic flushing, and the magnitude of decrease declines with the increase of loading stress. After hydraulic flushing, the cross-section of the hole is an ellipse, whose minor semiaxis aligns with the direction of the lower loading stress in the cross-section. Hydraulic flushing remarkably enhances the permeability, promoting it from 0.368 to 5.112 md, a rise of nearly 1,290%. During stress loading, the permeability changes over time can be divided into three stages, i.e., the compression stage, the linear elastic stage, and the transitional stage from linear elasticity to plasticity. During stress unloading, the permeability increases continuously with the passage of time, which is indicative of remarkable pressure relief and permeability enhancement effects. The permeability of the coal body does not increase linearly with the increase in perforation water pressure but instead exhibits an optimal value. The above results provide important references for optimizing the design of permeability enhancement boreholes under different stress conditions and ensuring safe production in coal mines.

Aquaglyceroporins are channels that facilitate the flux of glycerol and water across lipid bilayers. Although structural information is available for several aquaglyceroporins, the details of how water and glycerol selectivity are maintained and how protons are excluded remain elusive. An approach to obtaining data on the hydrogen atom positions is to apply neutron macromolecular crystallography. Here, we present strategies to obtain large crystals suitable for neutron diffraction experiments by assessing a range of different methods, including new procedures for protein purification and crystallization. By applying long incubation times, macroseeding, and/or optimization of detergents, millimeter-sized crystals with different morphologies were obtained, and their diffraction quality was assessed by exposure to X-rays. The data presented here lay the foundation for continued crystallization efforts targeting aquaporins and other membrane proteins for neutron diffraction experiments.

Bis[4-(dimethylamino)pyridinium]tetraiodozincate(II), formulated as (C₇H₁₁N₂)₂ZnI₄, is a novel organic–inorganic hybrid material that is the subject of this study’s synthesis, structural evaluation and functional characterization. The material was prepared at room temperature by the slow evaporation method and crystallized having space group C2/c in the monoclinic system. The following cell parameters are a = 11.0502(3) Å, b = 13.0289(3) Å, c = 17.3038(5) Å, β = 103.896(3)°, V = 2418.35(12) ų with four formula units. The structural analysis highlights alternating inorganic layers positioned at z = 1/4 and z = 3/4, with organic cations occupying the regions at z = 0 and z = 1/2. The stability of the structure is ensured through N–H···I hydrogen bonding interactions. Furthermore, Hirshfeld surface analysis confirms that the dominant intermolecular interactions within the structure are H···H and I···H contacts, emphasizing the role of these interactions in maintaining cohesion and stability. A phase transition is detected at 369 K by thermal investigation, which is corroborated by electrical and dielectric measurements. Semicircular arcs defined by a Cole–Cole model were discovered by impedance spectroscopy recorded between 313 and 373 K in the frequency range of 40 Hz to 10 MHz. The Arrhenius type behavior is exhibited by the thermal conductivity. The title compound exhibited a relaxation phenomenon and notable protonic conduction, indicating its potential for applications in hybrid materials with advanced electrical properties.

Massive quantities of NH₃ generated after blasting in underground coal mines are believed to enhance the adsorption of O₂ by coal and accelerate the rate of coal’s spontaneous combustion oxidation. The adsorption behavior of coal for NH₃ and O₂ after blasting in underground coal mines provides critical insights into the mechanisms of coal’s spontaneous combustion. This research was conducted on Xiaolongtan lignite, examining the adsorption characteristic of NH₃/O₂ binary gas mixtures and single-component NH₃ and O₂ on lignite at 278.15–323.15 K and 0–500 kPa using Grand Canonical Monte Carlo simulations. Additionally, the kinetic properties of the lignite/NH₃ and lignite/O₂ systems were analyzed at 278.15–323.15 K using molecular dynamics simulations. The results revealed that the adsorption isotherms conformed well to the Langmuir equation. Under the specified conditions, the adsorption amount of lignite decreased with increasing temperature, and the gas adsorption amount followed the order: NH₃ > O₂. The adsorption selectivity coefficient of NH₃ and O₂ was largely unaffected by the molar ratio but decreased as the temperature increased. The integral area of the relative concentration curve confirmed that the adsorption of NH₃ and O₂ onto lignite decreased with increasing temperature, maintaining the order NH₃ > O₂. Under identical temporal conditions, the mean square displacement and diffusion coefficients of the gases increased with temperature, with O₂ exhibiting a higher diffusion coefficient than NH₃. Furthermore, the interaction energy of the lignite/NH₃ and lignite/O₂ systems decreased as the temperature increased, with NH₃ exhibiting the strongest interactions with lignite at the same temperature.

This study compares the sensing performance of glassy carbon electrodes (GCE) modified with graphene (GR), multiwalled carbon nanotubes (MWCNTs), and graphene–multiwalled carbon nanotube (GR-MWCNT) composites for the simultaneous detection of ascorbic acid (AA), dopamine (DA), and uric acid (UA). Among these electrodes, GR-MWCNT/GCE exhibited the highest sensitivity and the lowest detection limit. Using differential pulse voltammetry (DPV), AA, DA, and UA can be simultaneously detected at low potentials of −0.032, 0.206, and 0.34 V vs Ag/AgCl, with sensitivities of 0.076, 1.38, and 0.181 μA μM^–1 and detection limits (LOD) of 6.71, 0.58, and 7.30 μM, respectively. The GR-MWCNT/GCE also demonstrated good stability, reproducibility, and excellent anti-interference capability. This newly fabricated sensor was confirmed to be applicable for the simultaneous detection of AA, DA, and UA in real serum and urine samples.

The interaction of perfluoroaromatic compounds with 1-aminoadamantane followed by oxidation of the formed N-adamantylanilines with meta-chloroperoxybenzoic acid led to functionalized N-polyfluorophenyl-N-adamantylaminoxyls (mono- and diradicals) in high total yields. The molecular and crystal structures of N-adamantylanilines and the aminoxyl radicals obtained from them by oxidation have been established using single-crystal X-ray diffraction analysis. The introduction of a substituent into the polyfluorinated moiety affects the arrangement of N-adamantylanilines in the crystal structure and the formation of hydrogen bonds; in addition, short contacts of the rare N···N type are present in crystals of 4-((adamantan-1-yl)amino)-perfluorobiphenyl. In crystals of the aminoxyls, oxygen atoms make unusually short contacts with C atoms of polyfluorinated aromatic rings giving rise to ferromagnetic exchange.

This paper further simplifies the gas state equation (EOS) by introducing a thermodynamic constant, P_c^*, into the equation, a theoretical pressure that all gas converts into liquid. In the gas–liquid saturation system, linear regressions of ln P–ln x₂ from M.P. to T_c give P = P_c^*x₂. It verifies Henry’s law of gas solubility. Meanwhile, P_c^*s for most substances are found in the range of 15–16, i.e., 3.269–8.886 MPa. Hence, EOS deforms into $P=\frac{P_c^{*}RT}{{10}^{-3}{P}_c^{*}{V}_G+RT}$. Isotherm is a forced equilibrium system sustained by an outer force. Isothermal EOS is derived by differentiating heat over V_G. $P=\frac{(\beta +\gamma )P_c^{*}RT}{{10}^{-3}{P}_c^{*}{V}_G+(\beta +\gamma )RT}$, where $\gamma =-{\left[\frac{\partial \ln P}{\partial {\ln V}_G}\right]}_T$ or $\gamma =-{\left[\frac{\partial \ln x_2}{\partial {\ln V}_G}\right]}_T$. Empolying Ar as an example, EOS are demonstrated over the whole pressure range, 0–1000 MPa, including the supercritical state. Applausive results are obtained in the pressure range before the gas–liquid transition and high temperatures (1000–2000 K), respectively. The supercritical state of intermediate temperatures (160–800 K) is likely liquid-like. Hence, EOS is not fittable.

The conservation and characterization of preservation fluids are crucial for maintaining specimen integrity in natural history fluid collections. However, characterizing these fluids analytically poses significant challenges, especially as noninvasive methods are preferred to avoid opening jars and reduce the risk of compromising specimens. This proof-of-concept study investigates the feasibility of using a hand-held spatially offset Raman spectroscopy (SORS) instrument to determine the chemical composition of preservation fluids through their original glass containers. Results demonstrate that SORS can noninvasively verify the chemical identity of dominant excipients in these fluids measured through a historic glass jar. Additionally, multivariate analysis combined with SORS measurements successfully differentiated several types of typical preservation fluids prepared as mixtures of different alcohols in water, such as glycerol, ethanol, methanol, and formaldehyde. The proposed noninvasive approach was also able to differentiate between different concentration points of components in water within the same type of preservation fluid.

As a green and highly efficient coal seam penetration enhancement technology, liquid CO₂ phase change fracturing (LCPCF) technology has a great deal of promise to advance gas extraction and CO₂ geological storage. A series of investigations were conducted using low-temperature liquid N₂ adsorption (LT-N₂) adsorption, CO₂ adsorption, CT scanning, and mercury intrusion porosimetry (MIP) to elucidate further the effect of LCPCF on the coal’s pore structure. These experiments aimed to characterize coal’s internal pore structure parameters and investigate 3D pore structure changes before and after LCPCF treatment at varying fracturing displacements. The results indicate that the macropores’ (>50 nm) and mesopores’ (2–50 nm) porosity, pore volume, and pore-specific surface area (PSA) in the fractured coal showed notable enhancements in comparison to the raw coal. However, the micropores’ (<2 nm) pore structural characteristics mainly stayed unaltered. In contrast to the generally stable fractal dimension of mesopores and micropores, the macropores’ fractal dimension is exhibiting a declining trend. The connectivity porosity of coal samples Z1, Z2, and Z3 with fracturing distances of 0.5, 2.5, and 5 m increased by 160.33, 108.26, and 64.05%. On the contrary, the closed porosity of fractured coals decreased to different degrees. The shorter the fracturing distance, the more impact it has on the coal pore structure. The impact range of a single fracture hole in the LCPCF process is approximately 5 m. The results are instructive for further revealing the mechanism of LCPCF and optimizing the fracturing process parameters.

We report that self-supporting mesoporous platinum 3D nanowires with a single diamond (SD) morphology and a high specific surface area of 40.4 m² g^–1 demonstrated enhanced stability toward the oxygen reduction reaction (ORR). These were found to be superior to commercially available carbon-supported Pt nanoparticles (Pt/C). After 1000 potential cycles, there was a 21% loss in surface area for SD-Pt, as compared with a 40.3% loss for Pt/C with no reduction in their half-wave potential (measured at J = 3.0 mA cm^–2), whereas the Pt/C catalyst showed a 11.9 mV decrease. Our findings revealed that our SD-Pt thin films also exhibited excellent ORR activity, which offers significant potential for their application as high-performance cathode materials in alkaline fuel cells.