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Dietary fiber (DF) is an important active polysaccharide in Hericium erinaceus. Obesity can lead to a wide range of diseases. In this work, we investigated the in vitro lipid-lowering effect of soluble dietary fiber (SDF) from H. erinaceus, aiming to provide a basis for the subsequent development of lipid-lowering products. Ultrasound-assisted enzymatic extraction (UAEE) of SDF from H. erinaceus was performed. The optimal extraction parameters determined via single-factor experiments and response surface methodology (RSM) were as follows: Lywallzyme concentration, 1.0%; complex protease concentration, 1.2%; ultrasonication time, 35 min; and ultrasonication power, 150 W. In vitro lipid-lowering experiments revealed that the adsorption amount of cholesterol micelles by H. erinaceus SDF was 11.91 mg/g. The binding amount and binding rate of sodium taurocholate were 3.73 mg/g and 42.47%, respectively, and those of sodium glycocholate were 3.43 mg/g and 39.12%, respectively. The pancreatic lipase inhibition rate reached 52.11%, and the type of inhibition was competitive. Therefore, H. erinaceus SDF has good in vitro lipid-lowering ability.

Ectomycorrhizal fungi employ different strategies for mycelial growth and host colonization under varying nutrient conditions. However, key genes associated with mycorrhizal interaction should be influenced solely by the inoculation treatment and not by nutrient variations. To utilize subtle nutrient differences and rapidly screen for key genes related to the interaction between Suillus luteus and Pinus massoniana, we performed an inoculation experiment using culture bottles containing high- and low-nutrient media. Interestingly, S. luteus LS88 promoted the growth of P. massoniana seedlings without mature ectomycorrhiza, and the impact of LS88 inoculation on P. massoniana roots was greater than that of nutrient changes. In this study, the resequenced genome of the LS88 strain was utilized for transcriptome analysis of the strain. The analysis indicated that a unique gene encoding glutathione S-transferase (GST) in LS88 is likely involved in colonizing P. massoniana roots. In this study, the GST gene expression was independent of nutrient levels. It was probably induced by P. massoniana and could be used as a marker for S. luteus colonization degree.

Suillus luteus is an edible ectomycorrhizal fungus (EMF). The S. luteus strain LS88 secretes many phytohormones, including salicylic acid (SA) and indole-3-carboxylic acid (ICA). LS88 was inoculated to the tree Pinus massoniana and treated with the amino acid fertilizer GGR6. Plant growth parameters, plant enzyme activities, chlorophyll contents, and element contents were analyzed. Our results show that GGR6 may help the development of S. luteus-P. massoniana ectomycorrhiza. Moreover, LS88 and GGR6 synergistically affect P. massoniana growth and element uptake. Phytohormone detection on the roots of LS88-inoculated P. massoniana seedlings showed that LS88 could significantly increase the ICA content within a week. The SA content in the roots in the inoculated group seedlings increased slightly, but the salicylic acid 2-O-β-glucoside (SAG) content decreased. Therefore, we speculate GGR6 may enhance the growth-promoting effect of EMF on plants, and LS88 affects P. massoniana growth through secreting phytohormones.

The cyclic loading generated by injection and production operations in underground gas storage facilities can lead to fatigue damage to cement sheaths and compromise the integrity of wellbores. To investigate the influence of cyclic loading on the fatigue damage of well cement, uniaxial and triaxial loading tests were conducted at different temperatures, with maximum cyclic loading intensity ranging from 60% to 90% of the ultimate strength. Test results indicate that the compressive strength and elastic modulus of well cement subjected to monotonic loading under high-temperature and high-pressure (HTHP) testing conditions were 14–21% lower than those obtained under ambient testing conditions. The stress–strain curve exhibits stress–strain hysteresis loops during cyclic loading tests, and the plastic deformation capacity is enhanced at HTHP conditions. Notably, a higher intensity of cyclic loading results in more significant plastic strain in oil-well cement, leading to the conversion of more input energy into dissipative energy. Furthermore, the secant modulus of well cement decreased with cycle number, which is especially significant under ambient test conditions with high loading intensity. Within 20 cycles of cyclic loading tests, only the sample tested at a loading intensity of 90% ultimate strength under an ambient environment failed. For samples that remained intact after 20 cycles of cyclic loading, the compressive strength and stress–strain behavior were similar to those obtained before cyclic loading. Only a slight decrease in the elastic modulus is observed in samples cycled with high loading intensity. Overall, oil-well cement has a longer fatigue life when subjected to HTHP testing conditions compared to that tested under ambient conditions. The fatigue life of well cement increases significantly with a decrease in loading intensity and can be predicted based on the plastic strain evolution rate.

In order to obtain insights into the mechanical responses of well cementing materials under various service conditions and provide more precise guidance for well cementing design, the mechanical behavior of a silica-enriched well cement system was investigated at various temperatures, pressures and drying conditions. Prior to mechanical testing, ultrasonic strength tests and a series of microscopic tests were conducted to verify that the silica-cement system cured at 150 °C/20.7 MPa exhibited stable properties with limited risk of strength retrogression. Triaxial tests conducted at ambient temperature (25 °C) demonstrate that the well cement exhibited an increase of peak strength and plasticity with increasing confining pressure, particularly under dry conditions. Additionally, brittle to ductile transition is more readily achieved for dried samples. However, the simultaneous application of both high temperature and high confining pressure (150 °C/30 MPa) resulted in reduced yield stress of the well cement, possibly because the weakening effect of high temperature overpowers the strengthening effect of high confining pressure. The peak strength and yield stress of the well cement increased significantly with the reduction of water content. The plasticity of the well cement increased upon the removal of evaporable water, but decreased with the removal of nonevaporable C–S–H bound water.

Understanding the synthesis process of Portland cement's various mineral phases and the phase interactions during hydration is highly critical for the design and optimization of cement-based materials. In this work, by using an optimized solid-state reaction method, three pure clinker phases (alite, belite and ferrite) and two polyphase phases (alite-belite and alite-ferrite-belite) of Portland cement were synthesized. The optimized method is featured with high-quality product yield, short burning time without regrinding or reburning. The factors that influence synthesis results, such as crystallinity/purity of the synthesized pure phases, were discussed based on X-ray powder diffraction (XRD) tests along with Rietveld refinement analysis with an external standard. The hydration behavior of the synthesized phases in monophase, polyphase as well as mixture states was investigated via isothermal calorimetry along with thermogravimetry and XRD. The results indicate that alite and belite have relatively little interactions during hydration, while the hydration rate of ferrite can be strongly inhibited in the presence of alite both in mixture and polyphase states.

A comprehensive experimental investigation of Portland cement hydration kinetics in a wide temperature range from 35 °C to 150 °C with pressure up to 50 MPa was performed by heat of hydration, chemical shrinkage and ultrasonic measurements. Increasing curing temperature was found to have a stronger acceleration effect during the main hydration period while increasing curing pressure had a stronger acceleration effect during the pre-induction period of cement hydration. By comparing chemical shrinkage test results with other methods of estimating cement degree of hydration, such as quantitative X-ray diffraction, non-evaporable water content measured by thermogravimetric analysis, as well as heat of hydration, it was observed that total chemical shrinkage of cement at complete hydration decreased with curing temperature from 35 °C to 75 °C and then stayed stable between 75 °C and 150 °C. Similarly, the P-wave velocity of cement (which is an indicator of physical and mechanical properties) as a function of hydration degree decreased with increasing curing temperature in the range between 35 °C to 75 °C, then remained relatively stable between 75 °C and 130 °C. The reduction of gel water content in C–S–H from 35 °C to 75 °C is believed to be the primary cause of these observed phenomena.

In order to investigate the problem of long-term strength retrogression in oil well cement systems exposed to high pressure and high temperature (HPHT) curing conditions, various influencing factors, including cement sources, particle sizes of silica flour, and additions of silica fume, alumina, colloidal iron oxide and nano-graphene, were investigated. To simulate the environment of cementing geothermal wells and deep wells, cement slurries were directly cured at 50 MPa and 200 °C. Mineral compositions (as determined by X-ray diffraction Rietveld refinement), water permeability, compressive strength and Young's modulus were used to evaluate the qualities of the set cement. Short-term curing (2–30 d) test results indicated that the adoption of 6 μm ultrafine crystalline silica played the most important role in stabilizing the mechanical properties of oil well cement systems, while the addition of silica fume had a detrimental effect on strength stability. Long-term curing (2–180 d) test results indicated that nano-graphene could stabilize the Young’s modulus of oil well cement systems. However, none of the admixtures studied here can completely prevent the strength retrogression phenomenon due to their inability to stop the conversion of amorphous to crystalline phases.

Nanomaterials have great potential to influence the properties of cement-based materials due to their small particle size and large specific surface area. The influences of Nano-SiO2 (NS), gamma-nano-Al2O3 (GNA), alpha-nano-Al2O3 (ANA), and nano-TiO2 (NT) on the rheology and hydration kinetics of class G cement at 30 °C were investigated in this study. The nanomaterials were added in dry powder form at dosages of 1, 2, 3, 5, and 7% by weight of cement (bwoc), and their dispersion was accomplished using polycarboxylate superplasticizer (PCE) at a dosage of 1.6% bwoc. PCE provides a uniform dispersion of nanoparticles in the cement matrix, enhancing the efficiency of nanomaterials. The w/c ratio varied between 0.718 and 0.78 to form a constant-density slurry of 1.65 g/cm3. Our test results showed that NS and GNA caused significant increases in the rheology of the cement slurry, with this effect increasing with dosage, while ANA and NT tended to reduce the rheology of the slurry. Compared to a well-suspended and well-dispersed cement slurry generated by the use of PCE and diutan gum, all nanomaterials can accelerate early hydration by reducing the induction time, with GNA having the strongest influence, while NS was the only nanomaterial that further increased the long-term hydration heat release at 7 days. The stronger effect of NS and GNA on the cement slurry properties can be attributed to their higher chemical reactivity. The dosage effect on total hydration extent was relatively strong for ANA, NT, and NS from 3% to 5% but weak for GNA in the range from 3% to 7%.

In order to clarify on the driving force of cement long-term strength retrogression, a comprehensive quantitative X-ray diffraction (XRD) analysis were conducted on silica-enriched (60%–80% by weight of cement) cement samples set and cured under the condition of 200°C and 50 MPa with a maximum duration of 180 days. The phase content evolution with time was determined by three different methods on the average of three specimens: the external standard method; the partial or no known crystal structure (PONKCS) method; and the hybrid method. Although the specific phase content estimated by different methods varied slightly, the overall trend of change of all phases were similar. The phase transformation in set cement at high temperature condition is dependent on the slurry composition. In silica-deficient system, tobermorite and amorphous C-S-H were transformed to xonotlite; while in silica-sufficient system, tobermorite and amorphous C-S-H were transformed to gyrolite. These phase transformations involve gradual structural changes of cement hydration products, which may be the driving force of long-term strength retrogression. However, such structural changes can only be detected by XRD once the transformation is complete.

Modeling the hydration kinetics of oil well cement as a function of temperature is critical for offshore cementing projects related to natural gas hydrates. During this study, the heat release of oil well cement hydration in the temperature range between 5 and 30°C was monitored by isothermal calorimetry. The influence of the source of cement, water-to-cement (w/c) ratio, and CaCl2 on hydration kinetics was evaluated in great detail. Results indicated the temperature effect on cement hydration kinetics can be modeled by a scale factor derived from the apparent activation energy (Ea) of the cement reaction. Ea showed moderate dependence on the cement source and relatively little dependence on the w/c ratio and CaCl2 addition. By combining with previous experimental data, a function correlating Ea and temperature in a wide temperature range (5–87°C) was obtained.

The influences of curing pressure on the physical and mechanical property development of oil well cement during long-term curing were studied. Five silica-enriched cement slurries designed without and with reinforcement materials (latex fiber and nano-graphene) were autoclaved at 200 °C under two different pressures. The low pressure (50 MPa) curing was conducted for 2, 60, 90 and 180 days; the high pressure (150 MPa) curing was conducted for 2 and 360 days. The physical and mechanical properties of set cement were characterized by compressive strength, Young’s modulus, and water/gas permeability; the mineral composition and microstructure were determined by X-ray diffraction, mercury intrusion porosimetry, thermogravimetry and scanning electron microscope. Test results showed that high pressure (150 MPa) curing led to a more compact microstructure, which reduced the rate of strength retrogression in the long term. Samples with reinforcement materials, especially the latex fiber, showed higher compressive strength, Young’s modulus and lower permeability during long-term curing at both pressures.

Annular pressure has been recognized as one of the most challenging problems in the petroleum industry, posing a series of threats to wellbore integrity. Annular pressure caused by thermal expansion during the cement hydration process is rarely studied by researchers. In light of the hydration heat generation process, a kinetics model for cement hydration under different curing temperatures is demonstrated in this paper. Considering interactions between temperature and cement hydration, a transient temperature prediction model during well cementing is built. On the basis of these assumptions, the prediction model of annular pressure is established, considering the change in cement temperature and the change in annulus volume. Using the models illustrated in this paper, a series of numerical simulations are performed. The changing roles of transient cement hydration degree and temperature in wellbores are analyzed thoroughly. The annular pressure during well cementing shows a rapid increase and then a decrease, which is similar to that of the temperature. In addition, a sensitive analysis of annular pressure is conducted. The analysis shows that the annular pressure increases with the geothermal gradient, the cement hydration heat, and the wellbore diameter. Suggestions and conclusions can provide safety guidance for the management of annular pressure during well cementing.