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"Cheng, Yuanfang"
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Promoting Singlet/triplet Exciton Transformation in Organic Optoelectronic Molecules: Role of Excited State Transition Configuration
Exciton transformation, a non-radiative process in changing the spin multiplicity of an exciton usually between singlet and triplet forms, has received much attention recently due to its crucial effects in manipulating optoelectronic properties for various applications. However, current understanding of exciton transformation mechanism does not extend far beyond a thermal equilibrium of two states with different multiplicity and it is a significant challenge to probe what exactly control the transformation between the highly active excited states. Here, based on the recent developments of three types of purely organic molecules capable of efficient spin-flipping, we perform
ab initio
structure/energy optimization and similarity/overlap extent analysis to theoretically explore the critical factors in controlling the transformation process of the excited states. The results suggest that the states having close energy levels and similar exciton characteristics with same transition configurations and high heteroatom participation are prone to facilitating exciton transformation. A basic guideline towards the molecular design of purely organic materials with facile exciton transformation ability is also proposed. Our discovery highlights systematically the critical importance of vertical transition configuration of excited states in promoting the singlet/triplet exciton transformation, making a key step forward in excited state tuning of purely organic optoelectronic materials.
Journal Article
Eight high-quality genomes reveal pan-genome architecture and ecotype differentiation of Brassica napus
Rapeseed (
Brassica napus
) is the second most important oilseed crop in the world but the genetic diversity underlying its massive phenotypic variations remains largely unexplored. Here, we report the sequencing, de novo assembly and annotation of eight
B. napus
accessions. Using pan-genome comparative analysis, millions of small variations and 77.2–149.6 megabase presence and absence variations (PAVs) were identified. More than 9.4% of the genes contained large-effect mutations or structural variations. PAV-based genome-wide association study (PAV-GWAS) directly identified causal structural variations for silique length, seed weight and flowering time in a nested association mapping population with ZS11 (reference line) as the donor, which were not detected by single-nucleotide polymorphisms-based GWAS (SNP-GWAS), demonstrating that PAV-GWAS was complementary to SNP-GWAS in identifying associations to traits. Further analysis showed that PAVs in three
FLOWERING LOCUS C
genes were closely related to flowering time and ecotype differentiation. This study provides resources to support a better understanding of the genome architecture and acceleration of the genetic improvement of
B. napus
.
The assembly of eight high-quality rapeseed genomes allows identification of presence and absence variations (PAVs) and small variations. PAV-based genome-wide association analysis uncovered causal variations for agronomic traits and ecotype differentiation.
Journal Article
Soil consolidation acoustic experiment and pore pressure prediction model establishment—taking the Yingqiong Basin as an example
To establish a pore pressure prediction model suitable for the Yingqiong Basin in the South China Sea. A new laboratory test method was designed to simulate the core consolidation process, and an acoustic experiment for soil consolidation was carried out to analyze various parameters and establish an abnormal pore pressure prediction model suitable for the target block. First, the cause of abnormally high pressure in the Yingqiong Basin is analyzed and identified, and a simulation experiment of stratum loading and unloading is performed. The soil consolidation, experimental equipment and experimental plan are designed. Several sets of experiments were carried out, the changes in various parameters during the experiment were analyzed and summarized, the pore pressure prediction model suitable for this area was standardized and established, and application verification and evaluation were carried out in some wells in this area. The results show that the prediction model is accurate and applicable, and the pore pressure can be predicted by the soil consolidation experiment method that the prediction accuracy is slightly better than the traditional prediction model. In this study, a feasible soil consolidation acoustic experiment method can be used to establish a rock mechanics experiment and a pore pressure prediction model without strict core rock. The experiments have proved the feasibility of this method and obtained two prediction models, including loading mechanism and unloading mechanism prediction models.
Journal Article
Machine learning enhanced formation pressure prediction using integrated well logging and mud logging
The difficulty of accurately predicting abnormally high-pressure formation pressure is one of the critical challenges in the field of petroleum engineering. Due to the low accuracy of formation pressure prediction and the narrow drilling safety density window, accidents such as leakage and blowout occur frequently. To address this issue, improving the accuracy of pore pressure predictions is essential. The well logging and mud logging data were combined to analyze the correlation between various parameters. Analysis using the Spearman correlation coefficient revealed that pore pressure exhibits varying correlation relationships with different parameters. Pore pressure is closely related to factors such as depth, weight of hanging, and mud weight. Pore pressure has a medium to high correlation with the rate of penetration, weight on bit, torque, slurry pump pressure, acoustic time difference, density, and volume of clay. Pore pressure has a medium to low correlation with the rotation per minute. Based on machine learning algorithms and a large amount of known data, a machine learning formation pressure model with integrated well logging and mud logging data (IWM) was established. The prediction results of traditional models and IWM models were compared using neighboring wells as the prediction targets. The results indicate that the backpropagation neural network model based on a genetic algorithm and IWM (IWM-GABP) achieves the highest prediction accuracy, with an average prediction accuracy greater than 96%. When predicting formation pressure, it is advisable to use the back propagation neural network model based on IWM or the IWM-GABP model, rather than the radial basis function neural network model based on IWM. The IWM model significantly reduces the prediction error of formation pore pressure, achieving an average improvement of 8.32% enhancement in prediction accuracy compared to traditional data models. The research method effectively improves the accuracy of formation pressure prediction and provides support for efficient on-site development.
Journal Article
Preliminary Insight into Ice Melting, Surface Subsidence, and Wellhead Instability during Oil and Gas Extraction in Permafrost Region
Oil and gas production in permafrost can effectively alleviate energy tensions. However, ice melting around wellbores and the accompanying wellhead instability affect the efficiency and safety of oil and gas development in permafrost. Moreover, the potential oil and gas leakage will damage the environment and the ecology of permafrost. Unfortunately, ice melting, formation subsidence, and wellhead behavior during this process have rarely been investigated in previous studies. In the present work, mechanical properties of permafrost were first experimentally investigated, which provided the basic parameter for subsequent numerical simulation. It was found that the ultimate strength gradually increased with the decreasing temperature, as well as the increasing confining pressure. Meanwhile, although the elastic modulus increased with decreasing temperature, it was less affected by confining pressure. Unlike other parameters, the Poisson’s ratio was hardly affected by temperature and confining pressure. Moreover, both the internal friction angle and the cohesion increased with decreasing temperature, but the influence degree varied within different temperature ranges. Then, ice melting, formation subsidence, and the instability behavior of the wellhead caused by the disturbance of the development operation were numerically explored. The investigation results show that the ice melting range in the reservoir section reached 8.06 m, which is much wider than that in other well sections. Moreover, failure of the cement–permafrost interface, caused by ice melting, resulted in a wellhead sinking of up to 1.350 m. Finally, the insulation effect of the vacuum-insulated casing showed that the temperature drop of the designed vacuum-insulated casing was much lower than that of the ordinary casing. When the fluid temperature within the wellbore was 70 °C, the temperature drop of the designed vacuum-insulated casing was 3.54 °C lower than that of the ordinary casing. This study provides support for maintaining wellhead stability during oil and gas extraction in permafrost for avoiding some environmental disasters (such as oil and gas leakage).
Journal Article
Mechanism and performance evaluation of a dual-crystal synergistic plugging system for high-temperature reservoir conformance control
Addressing steam channeling and water invasion in multi-cycle thermal recovery is now a critical challenge in heavy oil development. The study developed a high-temperature plugging system based on dual-crystal synergistic effects. The plugging agent, composed of calcium chloride, sodium sulfate, sodium carbonate, polymers, and dispersants, precipitates CaSO
4
and CaCO
3
crystals upon injection into the formation, synergistically sealing high-permeability channels. Experiments demonstrated that the agent effectively crystallizes within a temperature range of 60–200 °C. Displacement tests revealed well plugging performance under high-temperature conditions, with a core plugging rate of 99.3% at 150 °C and a permeability of 3195.6 mD, a breakthrough pressure gradient of 10.07 MPa/m, and a plugging strength of 4.70 MPa/m. The agent achieved effective plugging across a permeability range of 500–3000 mD. High-temperature stability experiments indicated that crystal consolidation slightly improved with aging time, confirming its long-term plugging capability. Further studies showed that the agent adapts well to high-salinity formation water, as increased salinity shortened crystallization time without significantly affecting plugging performance. Chemical compatibility tests revealed that small-molecule viscosity reducers had no notable impact on the agent’s performance, while polymers extended crystallization time at low temperatures, slightly reducing injectability. Therefore, the dual-crystal synergistic plugging agent demonstrates broad applicability. The study provides technical support for water control and production stabilization in the middle and late stages of heavy oil thermal recovery, highlighting the agent’s advantages of high-temperature resistance, strong plugging strength, wide permeability adaptability, and chemical compatibility.
Graphical abstract
Journal Article
Dietary Nucleotides Supplementation Improves the Intestinal Development and Immune Function of Neonates with Intra-Uterine Growth Restriction in a Pig Model
The current study aimed to determine whether dietary nucleotides supplementation could improve growth performance, intestinal development and immune function of intra-uterine growth restricted (IUGR) neonate using pig as animal model. A total of 14 pairs of normal birth weight (NBW) and IUGR piglets (7 days old) were randomly assigned to receive a milk-based control diet (CON diet) or diet supplemented with nucleotides (NT diet) for a period of 21 days. Blood samples, intestinal tissues and digesta were collected at necropsy and analyzed for morphology, digestive enzyme activities, microbial populations, peripheral immune cells, expression of intestinal innate immunity and barrier-related genes and proteins. Compared with NBW piglets, IUGR piglets had significantly lower average daily dry matter intake and body weight gain (P<0.05). Moreover, IUGR markedly decreased the villous height and villi: crypt ratio in duodenum (P<0.05), as well as the maltase activity in jejunum (P<0.05). In addition, IUGR significantly decreased the serum concentrations of IgA, IL-1βand IL-10 (P<0.05), as well as the percentage of peripheral lymphocytes (P<0.05). Meanwhile, the down-regulation of innate immunity-related genes such as TOLLIP (P<0.05), TLR-9 (P = 0.08) and TLR-2 (P = 0.07) was observed in the ileum of IUGR relative to NBW piglets. Regardless of birth weight, however, feeding NT diet markedly decreased (P<0.05) feed conversion ratio, increased the villous height in duodenum (P<0.05), activities of lactase and maltase in jejunum (P<0.05), count of peripheral leukocytes (P<0.05), serum concentrations of IgA and IL-1β as well as gene expressions of TLR-9, TLR-4 and TOLLIP in ileum (P<0.05). In addition, expressions of tight junction proteins (Claudin-1 and ZO-1) in ileum were markedly increased by feeding NT diet relative to CON diet (P<0.05). These results indicated that IUGR impaired growth performance, intestinal and immune function, but dietary nucleotides supplementation improved nutrients utilization, intestinal function and immunity.
Journal Article
Permeability Change Caused by Stress Damage of Gas Shale
Stress damage of shale during the uniaxial loading process will cause the change of permeability. The study of stress sensitivity of shale has focused on the influence of confining pressure on shale permeability and the change of shale permeability during the loading process of axial stress is lacking. The permeability of gas shale during loading process was tested. The results show that shale damage macroscopically reflects the process of axial micro-cracks generation and expansion, and the axial micro-cracks will cause permeability change during the loading process. There is a good corresponding relationship between damage development and micro-crack expansion during the process of shale loading. The damage factor will increase in the linear elastic stage and enlarge rapidly after entering the stage of unstable micro-crack expansion, and the permeability of shale increases with the increasing of shale damage. The research results provide a reliable test basis for further analysis of the borehole instability and hydraulic fracture mechanisms in shale gas reservoirs.
Journal Article