Energy and Infrared Radiation Characteristics of the Sandstone Damage Evolution Process

The mechanical characteristics and mechanisms of rock failure involve complex rock mass mechanics problems involving parameters such as energy concentration, storage, dissipation, and release. Therefore, it is important to select appropriate monitoring technologies to carry out relevant research. Fortunately, infrared thermal imaging monitoring technology has obvious advantages in the experimental study of rock failure processes and energy dissipation and release characteristics under load damage. Therefore, it is necessary to establish the theoretical relationship between the strain energy and infrared radiation information of sandstone and to reveal its fracture energy dissipation and disaster mechanism. In this study, an MTS electro-hydraulic servo press was used to carry out uniaxial loading experiments on sandstone. The characteristics of dissipated energy, elastic energy, and infrared radiation during the damage process of sandstone were studied using infrared thermal imaging technology. The results show that (1) the transition of sandstone loading from one stable state to another occurs in the form of an abrupt change. This sudden change is characterized by the simultaneous occurrence of elastic energy release, dissipative energy surging, and infrared radiation count (IRC) surging, and it has the characteristics of a short duration and large amplitude variation. (2) With the increase in the elastic energy variation, the surge in the IRC of sandstone samples presents three different development stages, namely fluctuation (stage Ⅰ), steady rise (stage Ⅱ), and rapid rise (stage Ⅲ). (3) The more obvious the surge in the IRC, the greater the degree of local damage of the sandstone and the greater the range of the corresponding elastic energy change (or dissipation energy change). (4) A method of sandstone microcrack location and propagation pattern recognition based on infrared thermal imaging technology is proposed. This method can dynamically generate the distribution nephograph of tension-shear microcracks of the bearing rock and accurately evaluate the real-time process of rock damage evolution. Finally, this study can provide a theoretical basis for rock stability, safety monitoring, and early warning.

Incidence, Risk Factors, and Management of Postoperative Hematoma Following Anterior Cervical Decompression and Fusion for Degenerative Cervical Diseases

OBJECTIVE

Studies discussed few risk factors for specific patients, such as duration of disease; or surgical factors, such as duration and time of surgery; or C3 or C7 involvement, which could have led to the formation of hematomas (HTs). To investigate the incidence, risk factors especially the factors mentioned above, and management of postoperative HTs following anterior cervical decompression and fusion (ACF) for degenerative cervical diseases.

METHODS

Medical records of 1,150 patients who underwent ACF for degenerative cervical diseases at our hospital between 2013 and 2019 were identified and reviewed. Patients were categorized into the HT group (HT group) or normal group (no-HT group). Demographic, surgical and radiographic data were recorded prospectively to identify risk factors for HT.

RESULTS

Postoperative HT was identified in 11 patients, with an incidence rate of 1.0% (11 of 1,150). HT occurred within 24 hours postoperatively in 5 patients (45.5%), while it occurred at an average of 4 days postoperatively in 6 patients (54.5%). Eight patients (72.7%) underwent HT evacuation; all patients were successfully treated and discharged. Smoking history (odds ratio [OR], 5.193; 95% confidence interval [CI], 1.058-25.493; p = 0.042), preoperative thrombin time (TT) value (OR, 1.643; 95% CI, 1.104-2.446; p = 0.014) and antiplatelet therapy (OR, 15.070; 95% CI, 2.663-85.274; p = 0.002) were independent risk factors for HT. Patients with postoperative HT had longer days of first-degree/intensive nursing (p < 0.001) and greater hospitalization costs (p = 0.038).

CONCLUSION

Smoking history, preoperative TT value and antiplatelet therapy were independent risk factors for postoperative HT following ACF. High-risk patients should be closely monitored through the perioperative period. Postoperative HT in ACF was associated with longer days of first-degree/intensive nursing and more hospitalization costs.

Quantitative Prediction of Charge Mobilities and Theoretical Insight into the Regulation of Site-Specific Trifluoromethylethynyl Substitution to Electronic and Charge Transport Properties of 9,10-Anthraquinone

Herein, we systematically studied the electronic and conducting properties of 9,10-anthraquinone (AQ) and its derivatives and discussed the substitute-site effects on their organic field-effect transistor (OFET) properties in detail. Our calculation results show the influence of different substitute sites on the ionization potential (IP), electronic affinity (EA), reorganization energy (λ), electronic couplings (V), and anisotropic mobility (μ) of semiconducting materials, which mainly originates from the variations of the frontier molecular orbital charge distributions, the steric hindrance, and the conjugate degree. Combining quantum-chemical calculations with charge transfer theory, we simulated the intermolecular hopping rate in the organic crystals of AQ derivatives and predicted the fluctuation range of three-dimensional (3D) anisotropic charge carrier mobility for the first time. Our calculation results well reproduced the experimental observations and provided evidence for the determination of the optimal OFET conduction plane and channel direction relative to the crystal axis.

Rational Design of Carbon-Based Porous Aerogels with Nitrogen Defects and Dedicated Interfacial Structures toward Highly Efficient CO2 Greenhouse Gas Capture and Separation

CO₂ capture from flowing flue gases through adsorption technology is essential to reduce the emission of CO₂ to the atmosphere. The rational design of highly efficient carbon-based absorbents with interfacial structures containing interconnected porous structures and abundant adsorption sites might be one of the promising strategies. Here, we report the synthesis of nitrogen-doped carbon aerogels (NCAs) via prepolymerized phenol-melamine-formaldehyde organic aerogels (PMF) by controlling the addition amount of ZnCl₂ and the precursor M/P ratio. It has been revealed that NCAs with a higher specific surface area and interconnected porous structures contain a large amount of pyridinic nitrogen and pyrrolic nitrogen. These would act as the intrinsic adsorption sites for highly effective CO₂ capture and further improve the CO₂/N₂ separation efficiencies. Among the prepared samples, NCA-1-2 with a high micropore surface area and high nitrogen content exhibits a high CO₂ adsorption capacity (4.30 mmol g^-1 at 0 °C and 1 bar) and CO₂/N₂ selectivity (36.5 at 25 °C, IAST). Under typical flue gas conditions (25 °C and 1.01 bar), equilibrium gas adsorption analysis and dynamic breakthrough measurement associated with a high adsorption capacity of 2.65 mmol g^-1 at 25 °C and 1.01 bar and 0.81 mmol g^-1 at 25 °C and 0.15 bar. This rationally designed N-doped carbon aerogel with specific interfacial structures and high CO₂ adsorption capacity, high selectivity, and adsorption performance remained pretty stable after multiple uses.

Catalytic Effect of Alkali Metals on the Gasification Dissolution Reaction and Deep Reaction Behavior of Metallurgical Cokes

In this paper, the deep reaction behaviors of tamping and top-charging cokes with different K₂CO₃ and Na₂CO₃ contents were investigated and the evolution of the functional group structure and the carbon structure of coke with the extension of the deep reaction was clarified. The results showed that the deep reaction gasification of coke steadily increased with the K₂CO₃ and Na₂CO₃ content. However, the catalytic effect of different contents of K₂CO₃ seemed to be stronger than that of different contents of Na₂CO₃. Meanwhile, the catalytic effect of alkali metals on the gasification reaction of tamping coke was more significant. The gasification dissolution of coke gradually decreased from the outside to the inside of the particle with the extension of the deep reaction, while the catalytic effect of K₂CO₃ and Na₂CO₃ seemed to be more dramatic on surface of the coke particle. In contrast, the gasification dissolution reaction on the surface of tamping coke was more severe; consequently, the surface pore area of tamping coke was much higher than that of top-charging coke. According to the variations in the functional group structure of cokes, aromatic hydrocarbon gradually became the dominant functional group in the coke structure with the extension of the deep reaction. The above variation led to a gradual decrease in the reactivity of coke, though the decomposition reactions of oxygen-containing functional groups in coke were promoted to some extent by the addition of K₂CO₃. With the extension of the deep reaction of coke, amorphous carbon was gradually transformed into sequential carbon.

Amine-Modified Chitosan Flocculant Synthesized via Single-Mode Microwave Method for Laundry Wastewater Treatment

In this study, an effective and environmentally friendly polyaminated cross-linked chitosan (M-PACTS) flocculant was successfully synthesized via circular focus single-mode microwave synthesizer irradiation. Epichlorohydrin and tetraethylenepentamine were used as the cross-linking agent and active cationic reagent, respectively. The same formation was used to prepare cationic lightly cross-linked chitosan (C-PACTS) via the conventional heating method. The flocculant was characterized using Fourier transform infrared spectroscopy, X-ray diffraction analysis, and scanning electron microscopy. The flocculation capability of C-PACTS and M-PACTS was compared using laundry wastewater as a model pollutant. The pH, PACTS dosage, temperature, stirring rate, stirring time, and setting time were systematically investigated. The experimental results showed that circular focus single-mode microwave synthesizer irradiation was a more efficient method to modify chitosan. M-PACTS exhibited a higher capacity for turbidity and chemical oxygen demand (COD_Cr) removal. Under optimal conditions, the removal rate values of M-PACTS were up to 96% (turbidity) and 78% (COD_Cr). The proposed PACTS is suitable for treatment of polluted wastewater in an eco-friendly manner without causing secondary pollution.

Effect of Sn on the CO Catalytic Activity and Water Resistance of Cu-Mn Catalyst

In view of the problem that excessive CO in underground coal mine space can easily lead to a large number of casualties, Cu-Mn-Sn water-resistant eliminators with different Sn contents were prepared by a co-precipitation method. The activity of the eliminators was analyzed by using an independently developed activity testing platform, N₂ adsorption and desorption, XRD, SEM, XPS, and FTIR to characterize the activity factors and water resistance. The results showed that Cu-Mn-Sn-20 with 20% Sn content had the highest activity, which was 3.23 times that of Cu-Mn. The main reason for the increased activity is that Cu-Mn-Sn-20 doped with 20% Sn provides a larger specific surface area and more active sites and reduces the pore size, so that the crystallization degree of Cu_1.4Mn_1.5O₄ is lower. The doping of 20% Sn reduces the absorption of lattice water and coordination water and improves the water resistance of Cu-Mn-Sn-type eliminators. The Cu-Mn-Sn-20 water-resistant eliminator is used to quickly eliminate CO in underground coal mines, which is of great significance for the rescue workers in underground coal mines after disasters.

Effects of Fine MgO-Bearing Flux on the Strength of Sinter before and after Low-Temperature Reduction

Decreasing the MgO content can improve most of the metallurgical properties of sinter, but the low-temperature reduction disintegration index (RDI) property will be worse. In order to improve the RDI property of sinter under certain MgO contents, the effects of fine MgO-bearing flux on the strength of sintered samples before and after reduction in three systems (Fe₂O₃-MgO, Fe₂O₃-MgO-CaO, and Fe₂O₃-MgO-CaO-SiO₂) were investigated in the present work. The experimental results show that (1) in the three systems, the percentage of fine light calcined magnesite (LCM) increases from 0 to 100%, and the compression strength of the samples before reduction increases from 0.140 to 0.187 MPa, from 0.115 to 0.175 MPa, and from 0.121 to 0.164 MPa, respectively. The compression strength of the samples after reduction increases from 0.062 to 0.151 MPa, from 0.100 to 0.156 MPa, and from 0.099 to 0.151 MPa, respectively. (2) The fundamental reason is that the fine powders can increase the specific surface area and the surface energy of the interface. It is beneficial to promoting the mineralization of MgO-bearing flux. More formation of MgO·Fe₂O₃ may increase the strength of samples before reduction. Less transformation from Fe₂O₃ to Fe₃O₄ may increase the strength of samples after reduction. The microstructures of samples are more compact and uniform. Therefore, fine LCM can improve the strength of sinter before and after reduction. The outcomes of the present work can improve the sintering quality by using the fine MgO-bearing flux in the sintering process.

2D Strategy for the Construction of an Enzyme-Activated NIR Fluorophore Suitable for the Visual Sensing and Profiling of Homologous Nitroreductases from Various Bacterial Species

Nitroreductases (NTRs) mediate the reduction of nitroaromatic compounds to the corresponding nitrite, hydroxylamine, or amino derivatives. The activity of NTRs in bacteria facilitates the metabolic activation and antibacterial activity of 5-nitroimidazoles. Therefore, NTR activity correlates with the drug susceptibility and resistance of pathogenic bacteria. As such, it is important to develop a rapid and visual assay for the real-time sensing of bacterial NTRs for the evaluation and development of antibiotics. Herein, an activatable near-infrared fluorescent probe (HC-NO2) derived from a hemicyanine fluorophore was designed and developed based on two evaluation factors, including the calculated partition coefficient (Clog P) and fluorescence wavelength. Using HC-NO2 as the special substrate of NTRs, NTR activity can be assayed efficiently, and then, bacteria can be imaged based on the detection of NTRs. More importantly, a sensitive in-gel assay using HC-NO2 has been developed to selectively identify NTRs and sensitively determine NTR activity. Using the in-gel assay, NTRs from various bacterial species have been profiled visually from the "fluorescence fingerprints", which facilitates the rapid identification of NTRs from bacterial lysates. Thus, various homologous NTRs were identified from three metronidazole-susceptible bacterial species as well as seven unsusceptible species, which were confirmed by the whole-genome sequence. As such, the evaluation of NTRs from different bacterial species should help improve the rational usage of 5-nitroimidazole drugs as antibiotics.

Influence of Temperature and CO2 on High-Temperature Behavior and Microstructure of Metallurgical Coke

Metallurgical coke is an important raw material for blast furnaces. Specifically, temperature and CO₂ significantly affect its metallurgical behavior. In this study, the influence of temperature and CO₂ on the high-temperature behavior of three metallurgical coke samples, used in blast furnaces of different volumes, was investigated. The carbon structure and pore structure of the coke samples were analyzed. The results indicated that as the temperature increased from 1100 to 1500 °C, the weight loss ratio increased 10-fold and the drum strength decreased to approximately 80% in Ar. Under a CO₂ atmosphere, as the temperature increased from 1100 to 1300 °C, the reactivity index increased from 20 to 70%, and the strength after reaction exhibited the lowest value of 40% at 1250 °C. When the temperature increased from 1100 to 1500 °C, the stacking height of the layer structure Lc of the coke samples increased to ∼5.5 nm. Under the influence of CO₂ and temperature, the Lc of the coke samples increased to approximately 4 nm between 1100 and 1300 °C. Furthermore, CO₂ slightly affected the carbon structure. The changes in pores under the influence of CO₂ and temperature were greater than those under the influence of temperature between 1100 and 1300 °C. Typically, the strength of coke is high when the pore number, roundness, and porosity are low. The strength and microstructure parameters of the coke samples were correlated via multiple regression. The results of the multiple regression showed that the carbon structure and pore number had the highest impact on coke strength, followed by roundness and porosity.