With the development of virtual reality (VR) technology, more and more industries are beginning to integrate with VR technology. In response to the problem of not being able to directly render the lighting effect of C...With the development of virtual reality (VR) technology, more and more industries are beginning to integrate with VR technology. In response to the problem of not being able to directly render the lighting effect of Caideng in digital Caideng scenes, this article analyzes the lighting model. It combines it with the lighting effect of Caideng scenes to design an optimized lighting model algorithm that fuses the bidirectional transmission distribution function (BTDF) model. This algorithm can efficiently render the lighting effect of Caideng models in a virtual environment. And using image optimization processing methods, the immersive experience effect on the VR is enhanced. Finally, a Caideng roaming interactive system was designed based on this method. The results show that the frame rate of the system is stable during operation, maintained above 60 fps, and has a good immersive experience.展开更多
Understanding the structural origin of the competition between oxygen 2p and transition-metal 3d orbitals in oxygen-redox(OR)layered oxides is eminently desirable for exploring reversible and high-energy-density Li/Na...Understanding the structural origin of the competition between oxygen 2p and transition-metal 3d orbitals in oxygen-redox(OR)layered oxides is eminently desirable for exploring reversible and high-energy-density Li/Na-ion cathodes.Here,we reveal the correlation between cationic ordering transition and OR degradation in ribbon-ordered P3-Na_(0.6)Li_(0.2)Mn_(0.8)O_(2) via in situ structural analysis.Comparing two different voltage windows,the OR capacity can be improved approximately twofold when suppressing the in-plane cationic ordering transition.We find that the intralayer cationic migration is promoted by electrochemical reduction from Mn^(4+)to Jahn–Teller Mn^(3+)and the concomitant NaO_(6) stacking transformation from triangular prisms to octahedra,resulting in the loss of ribbon ordering and electrochemical decay.First-principles calculations reveal that Mn^(4+)/Mn^(3+)charge ordering and alignment of the degenerate eg orbital induce lattice-level collective Jahn–Teller distortion,which favors intralayer Mn-ion migration and thereby accelerates OR degradation.These findings unravel the relationship between in-plane cationic ordering and OR reversibility and highlight the importance of superstructure protection for the rational design of reversible OR-active layered oxide cathodes.展开更多
Phase transitions involving oxygen ion extraction within the framework of the crystallographic relevance have been widely exploited for sake of superconductivity,ferromagnetism,and ion conductivity in perovskiterelate...Phase transitions involving oxygen ion extraction within the framework of the crystallographic relevance have been widely exploited for sake of superconductivity,ferromagnetism,and ion conductivity in perovskiterelated oxides.However,atomic-scale pathways of phase transitions and ion extraction threshold are inadequately understood.Here we investigate the atomic structure evolution of LaCoO_(3) films upon oxygen extraction and subsequent Co migration,focusing on the key role of epitaxial strain.The brownmillerite to Ruddlesden-Popper phase transitions are discovered to stabilize at distinct crystal orientations in compressive-and tensile-strained cobaltites,which could be attributed to in-plane and out-of-plane Ruddlesden-Popper stacking faults,respectively.A two-stage process from exterior to interior phase transition is evidenced in compressive-strained LaCoO_(2.5),while a single-step nucleation process leaving bottom layer unchanged in tensile-strained situation.Strain analyses reveal that the former process is initiated by an expansion in Co layer at boundary,whereas the latter one is associated with an edge dislocation combined with antiphase boundary.These findings provide a chemomechanical perspective on the structure regulation of perovskite oxides and enrich insights into strain-dependent phase diagram in epitaxial oxides films.展开更多
Fast-charging lithium-ion batteries are highly required,especially in reducing the mileage anxiety of the widespread electric vehicles.One of the biggest bottlenecks lies in the sluggish kinetics of the Li^(+)intercal...Fast-charging lithium-ion batteries are highly required,especially in reducing the mileage anxiety of the widespread electric vehicles.One of the biggest bottlenecks lies in the sluggish kinetics of the Li^(+)intercalation into the graphite anode;slow intercalation will lead to lithium metal plating,severe side reactions,and safety concerns.The premise to solve these problems is to fully understand the reaction pathways and rate-determining steps of graphite during fast Li^(+)intercalation.Herein,we compare the Li^(+)diffusion through the graphite particle,interface,and electrode,uncover the structure of the lithiated graphite at high current densities,and correlate them with the reaction kinetics and electrochemical performances.It is found that the rate-determining steps are highly dependent on the particle size,interphase property,and electrode configuration.Insufficient Li^(+)diffusion leads to high polarization,incomplete intercalation,and the coexistence of several staging structures.Interfacial Li^(+)diffusion and electrode transportation are the main rate-determining steps if the particle size is less than 10μm.The former is highly dependent on the electrolyte chemistry and can be enhanced by constructing a fluorinated interphase.Our findings enrich the understanding of the graphite structural evolution during rapid Li^(+)intercalation,decipher the bottleneck for the sluggish reaction kinetics,and provide strategic guidelines to boost the fast-charging performance of graphite anode.展开更多
Intercalation provides to the host materials a means for controlled variation of many physical/chemical properties and dominates the reactions in metal‐ion batteries.Of particular interest is the graphite intercalati...Intercalation provides to the host materials a means for controlled variation of many physical/chemical properties and dominates the reactions in metal‐ion batteries.Of particular interest is the graphite intercalation compounds with intriguing staging structures,which however are still unclear,especially in their nanostructure and dynamic transition mechanism.Herein,the nature of the staging structure and evolution of the lithium(Li)‐intercalated graphite was revealed by cryogenic‐transmission electron microscopy and other methods at the nanoscale.The intercalated Li‐ions distribute unevenly,generating local stress and dislocations in the graphitic structure.Each staging compound is found macroscopically ordered but microscopically inhomogeneous,exhibiting a localized‐domains structural model.Our findings uncover the correlation between the long‐range ordered structure and short‐range domains,refresh the insights on the staging structure and transition of Li‐intercalated/deintercalated graphite,and provide effective ways to enhance the reaction kinetic in rechargeable batteries by defect engineering.展开更多
Gas hydrates have been found in the western continental margin of South China Sea,which are revealed by widespread bottom simulating reflectors(BSRs)imaged from a three-dimensional(3D)seismic volume near the Guangle c...Gas hydrates have been found in the western continental margin of South China Sea,which are revealed by widespread bottom simulating reflectors(BSRs)imaged from a three-dimensional(3D)seismic volume near the Guangle carbonate platform in the western South China Sea.Fluid-escape structures(faults and gas chimneys)are originated below BSR were distinguished.A comprehensive model in three-level structure was proposed to depict the gas hydrate accumulation in the study area.In Level 1,regional major faults and gas chimneys provide the first pathways of upward migration of gas near basement.In Level 2,pervasive polygonal faults in carbonate layer promote the migration of gas.In Level 3,gases sourced from near-basement accumulate within shallow sediment layers and form gas hydrate above the unit with faults once appropriate temperature and pressure occur.The gas hydrates in the study area are mainly in microbial origin,and their accumulation occurs only when fluid-escape structures align in all the three levels.The proposed model of the gas hydrate accumulation in western SCS margin provides new insights for further studies in this poorly studied area.展开更多
Hetero-element doping is a promising strategy to improve the cycling stability of nickel-rich cobalt-free cathodes for the next-generation high energy-density Li ion batteries.To make doping effective,it is important ...Hetero-element doping is a promising strategy to improve the cycling stability of nickel-rich cobalt-free cathodes for the next-generation high energy-density Li ion batteries.To make doping effective,it is important to understand the mechanism of how the dopants regulate the electronic band,lattice parameter adjusting,or hetero-phase formation to achieve high stability.In this study,we investigate LiNi_(0.9)Mn_(0.1)O_(2)cathodes doped with IVB grouping elements via multiple characterization techniques.By utilizing in situ XRD and TEM methods,we found that the stronger Ti-O bond effectively improves the cathode stability via a dual protection mechanism.Specifically,the bulk lattice of cathode is wellpreserved during cycling as a result of the suppressed H_(2)-H_(3)phase transition,while a in situ formed Ti-rich surface layer can prevent continuous surface degradation.As a result,the 5%Ti doped LiNi_(0.9)Mn_(0.1)O_(2)cathode exhibits a high capacity retention of 96%after 100 cycles.Whereas,despite IVB group elements Zr and Hf have stronger bonding energy with oxygen,their larger ionic radii actually impede their diffusion into the cathode,thereby they can not improve the cycling stability.Our findings uncover the functional origin of doped elements with their dynamic modification on cathode structure,providing mechanistic insights into the design of nickel-rich cobalt-free cathodes.展开更多
The Yuhuang hydrothermal field(YHF)is located between the Indomed and Gallieni fracture zones near the top of the off-axis slope on the south rift wall of Segment 29 on the ultraslow Southwest Indian Ridge(SWIR).Previ...The Yuhuang hydrothermal field(YHF)is located between the Indomed and Gallieni fracture zones near the top of the off-axis slope on the south rift wall of Segment 29 on the ultraslow Southwest Indian Ridge(SWIR).Previous studies have shown that sulfides in the YHF formed during different mineralization episodes and the YHF has the greatest potential for the formation of large-scale seafloor massive sulfide deposits.However,the sulfide chronology and hydrothermal activity of the YHF remain poorly constrained.In this study,mineralogical analyses and 230Th/U dating were performed.Hydrothermal activity may start about(35.9±2.3)ka from the southwest part of the YHF and may cease about(708±81)a ago from the northeast part of the YHF.The 74 nonzero chronological data from hydrothermal sulfide samples provide the first quantitative characterization of the spatial and temporal history along the SWIR.Hydrothermal activity in the SWIR has been relatively active over the past20 ka.In contrast,between 40 ka and 100 ka,hydrothermal activity was relatively infrequently and short in duration.The maximum activity occurred at 15–11 ka,9–7 ka,6–0.2 ka.There was a slight positive correlation between the maximal age and estimated surface area or estimated tonnage.The minimum mass accumulation rate of YHF is about 278 t/a,which is higher than most HFs related to ultramafic systems.The ultraslow spreading SWIR has the greatest potential to form large-scale seafloor massive sulfides(SMS)deposits.The results of this study provide new insights into the metallogenic mechanism of hydrothermal sulfides along ultraslow-spreading ridges.展开更多
Ovarian cancer(OC)is one of the most common and recurring malignancies in gynecology.Patients with relapsed OC always develop"cascade drug resistance"(CDR)under repeated chemotherapy,leading to subsequent fa...Ovarian cancer(OC)is one of the most common and recurring malignancies in gynecology.Patients with relapsed OC always develop"cascade drug resistance"(CDR)under repeated chemotherapy,leading to subsequent failure of chemotherapy.To overcome this challenge,amphiphiles(P1)carrying a nitric oxide(NO)donor(Isosorbide 5-mononitrate,ISMN)and high-density disulfide are synthesized for encapsulatingmitochondria-targeted tetravalent platinum prodrug(TPt)to construct a nanocomposite(INP@TPt).Mechanism studies indicated that INP@TPt significantly inhibited drug-resistant cells by increasing cellular uptake and mitochondrial accumulation of platinum,depleting glutathione,and preventing apoptosis escape through generating highly toxic peroxynitrite anion(ONOO−).To better replicate the microenvironmental and histological characteristics of the drug resistant primary tumor,an OC patient-derived tumor xenograft(PDXOC)model in BALB/c nude mice was established.INP@TPt showed the best therapeutic effects in the PDXOC model.The corresponding tumor tissues contained high ONOO−levels,which were attributed to the simultaneous release of O_(2)^(·−)and NO in tumor tissues.Taken together,INP@TPtbased systematic strategy showed considerable potential and satisfactory biocompatibility in overcoming platinum CDR,providing practical applications for ovarian therapy.展开更多
Pancreatic cancer is associated with high mortality and is one of the most aggressive of malignancies,but studies have not fully evaluated its molecular subtypes,prognosis and response to immunotherapy of different su...Pancreatic cancer is associated with high mortality and is one of the most aggressive of malignancies,but studies have not fully evaluated its molecular subtypes,prognosis and response to immunotherapy of different subtypes.The purpose of this study was to explore the molecular subtypes and the key genes associated with the prognosis of pancreas cancer patients and study the clinical phenotype,prognosis and response to immunotherapy using single-cell seq data and bulk RNA seq data,and data retrieved from GEO and TCGA databases.Methods:Single-cell seq data and bioinformatics methods were used in this study.Pancreatic cancer data were retrieved from GEO and TCGA databases,the molecular subtypes of pancreatic cancer were determined using the six cGAS-STING related pathways,and the clinical phenotype,mutation,immunological characteristics and pathways related to pancreatic cancer were evaluated.Results:Pancreatic cancer was classified into 3 molecular subtypes,and survival analysis revealed that patients in Cluster3(C3)had the worst prognosis,whereas Cluster1(C1)had the best prognosis.The clinical phenotype and gene mutation were statistically different among the three molecular subtypes.Analysis of immunotherapy response revealed that most immune checkpoint genes were differentially expressed in the three subtypes.A lower risk of immune escape was observed in Cluster1(C1),indicating higher sensitivity to immunotherapeutic drugs and subjects in this Cluster are more likely to benefit from immunotherapy.The pathways related to pancreatic cancer were differentially enriched among the three subtypes.Five genes,namely SFRP1,GIPR,EMP1,COL17A and CXCL11 were selected to construct a prognostic signature.Conclusions:Single-cell seq data were to classify pancreatic cancer into three molecular subtypes based on differences in clinical phenotype,mutation,immune characteristics and differentially enriched pathways.Five prognosis-related genes were identified for prediction of survival of pancreatic cancer patients and to evaluate the efficacy of immunotherapy in various subtypes.展开更多
Objective: To evaluate the feasibility and safety of total mesopancreas excision (TMpE) in the treatment of pancreatic head cancer. Methods: The clinical and pathological data of 120 patients with pancreatic head ...Objective: To evaluate the feasibility and safety of total mesopancreas excision (TMpE) in the treatment of pancreatic head cancer. Methods: The clinical and pathological data of 120 patients with pancreatic head cancer who had undergone TMpE in our center from May 2010 to January 2014 were retrospectively analyzed. Results: The mean operative time was (275.0±50.2) min and the average intra-operative blood loss was (390.0±160.5) mL. Post-operative complications were reported in 45 patients, while no peri-operative death was noted. The specimen margins were measured in three dimensions, and 86 patients (71.6%) achieved R0 resection. Conclusions: TMpE is safe and feasible for pancreatic head cancer and is particularly helpful to increase the R0 resection rate.展开更多
This case reports an application of conventional duodenoscope in a post pancreaticoduodenectomy patient with the help of retrieval balloon assisted enterography.The 56-year-old woman had pancreaticoduodenectomy with C...This case reports an application of conventional duodenoscope in a post pancreaticoduodenectomy patient with the help of retrieval balloon assisted enterography.The 56-year-old woman had pancreaticoduodenectomy with Child reconstruction 9 mo ago because of pancreatic adenocarcinoma and now there are recurrent enlarged lymph nodes in the anastomotic stoma of hepaticojejunostomy.Considering the patient's late-stage cancer,a plastic stent was then successfully placed there to drainage.The main challenge in this case was the extremely long afferent loop and blind cannulation through the anastomotic stoma of hepaticojejunostomy.Retrieval balloon assisted enterography is very helpful for duodenoscope going through the reconstructed intestinal tract and for the cannulation.After two weeks,the patient remained free of painful symptoms and free of fever.Liver function improved well.Four months after the placement of stent,the patient died of cachexia without jaundice,fever and abdominal pain according to her daughter's statement.展开更多
BACKGROUND: Developing a model of focal cortical dysplasia in microgyrus and observing the ultrastructure of focal tissue is of important significance for analyzing the pathology of cortical developmental disorder an...BACKGROUND: Developing a model of focal cortical dysplasia in microgyrus and observing the ultrastructure of focal tissue is of important significance for analyzing the pathology of cortical developmental disorder and the factors of structural changes. OBJECTIVE: This study was to observe the pathological characteristics of focal tissue around the microgyrus of rats with cortical developmental disorder using an electron microscope, so as to analyze the causes associated with cerebral cortical developmental disorder. DESIGN: A randomized controlled animal experiment. SETTING: The First Affiliated Hospital of Chongqing Medical University. MATERIALS: This study was carried out in the Chongqing Key Laboratory of Neurology, Room for Electron Microscope of Chongqing Medical University, and Laboratory Animal Center, Research Institute of Surgery, Daping Hospital, Third Military Medical University of Chinese PLA between January 2004 and August 2006. Eighteen healthy newborn male Wistar rats, weighing 3.0 - 6.0 g, provided by the Laboratory Animal Center, Daping Hospital, Third Military Medical University of Chinese PLA, were involved in this study. The protocol was carried out in accordance with animal ethics guidelines for the use and care of animals. Probes (Chongqing Wire & Cable Factory, China) were made of copper core wire with diameter of 1mm. METHODS: The rats were randomly divided into 3 groups with 6 in each: normal control group, liquid nitrogen injured group and sham-operation group. (1)In the liquid nitrogen injured group, a blunt probe frozen by liquid nitrogen was placed on fronto-parietal crinial bone of rats for 8 s. A 3 - 5 cm of microgyrus was induced in the unilateral cerebral sensory cortical area. In the sham-operation group, probe was placed at the room temperature. In the normal control group, rats were untouched. (2) The conscious state and electrical activity of brain of rats in each group were observed. (3) 2 - 3 mm thickness of hippocampal tissue with coronary section was taken for observing its ultrastructure under a transmission electron microscope. MAIN OUTCOME MEASURES: (1) The ultrastructure of hippocampal tissue. (2)The conscious state and electrical activity of brain of rats. RESULTS: Eighteen rats were enrolled in the final analysis. (1) Observation of hippocampal ultrastructure: Electromicroscopic pathological findings showed that for each rat of the liquid nitrogen injured group, mitochondrium in the pyramidal neuron around the microgyrus was swelled, endoplasmic reticulum was expanded, glial cells were swelled, water gathered around the blood capillary, partial medullary sheath was degenerated, neuropilem was normal and no obviously abnormal synapse was found. (2) Changes in conscious state of rats: Rats in the normal control group and sham-operation group had no convulsive seizure, but those in the liquid nitrogen injured group had occasionally. Most of them showed increased activities, excitation and restlessness, scratching and frequent " watching face-like activities". (3)Electrical activity of brain of rats: Electroencephalogram recording of liquid nitrogen injured group showed that small wave amplitude of rhythm took the main part. No typical sharp wave, V wave, sharp and slow wave, V and slow waves were discharged. CONCLUSION: Liquid nitrogen can lead to cerebral cortical developmental disorder. Pathological changes of ultrastructure of focal tissue around the microgyrus can provide pathological basis for epilepsy associated with focal cortical developmental disorder.展开更多
Collapse is a common geomorphic process in karst areas,especially on the Yunnan-Guizhou Plateau,which has a tectonic background of integral uplift.The frequent occurrence of collapse processes in karst underground cav...Collapse is a common geomorphic process in karst areas,especially on the Yunnan-Guizhou Plateau,which has a tectonic background of integral uplift.The frequent occurrence of collapse processes in karst underground caves and canyons indicates that collapses play an important role in the formation of canyons.Through an analysis of the morphology of a semicircular cliff in the Huajiang Grand Canyon and an investigation of sediments at the bottom of the cliff,a large-scale collapse event was found to have occurred.U-series dating of secondary calcium carbonate cement in the collapse breccias indicates that collapse processes occurred approximately 200 ka.According to the geomorphological evolution of the Huajiang Grand Canyon,the following geomorphic evolutionary process is proposed:underground river-cave hall-collapse of a tiankeng-tiankeng degradation-canyon formation.These findings also show that the dating of collapsed breccia cement can be effectively used to determine the development times of karst canyons and the formation ages of tiankengs.展开更多
Oxygen vacancies play a crucial role in determining the catalytic properties of Ce-based catalysts,especially in oxidation reactions.The design of catalytic activity requires keen insight into oxygen vacancy formation...Oxygen vacancies play a crucial role in determining the catalytic properties of Ce-based catalysts,especially in oxidation reactions.The design of catalytic activity requires keen insight into oxygen vacancy formation mechanisms.In this work,we investigate the origin of oxygen vacancies in CeO_(2)from the perspective of electron density via high-energy synchrotron powder x-ray diffraction.Multipole refinement results indicate that there is no obvious hybridization between bonded Ce and O atoms in CeO_(2).Subsequent quantitative topological analysis of the experimental total electron density reveals the closed-shell interaction behavior of the Ce-O bond.The results of first-principles calculation indicate that the oxygen vacancy formation energy of CeO_(2)is the lowest among three commonly used redox catalysts.These findings indicate the relatively weak bond strength of the Ce-O bond,which induces a low oxygen vacancy formation energy for CeO_(2)and thus promotes CeO_(2)as a superior catalyst for oxidation reactions.This work provides a new direction for design of functional metal oxides with high oxygen vacancy concentrations.展开更多
Electron density plays an important role in determining the properties of functional materials.Revealing the electron density distribution experimentally in real space can help to tune the properties of materials.Spin...Electron density plays an important role in determining the properties of functional materials.Revealing the electron density distribution experimentally in real space can help to tune the properties of materials.Spinel Li Mn2 O4 is one of the most promising cathode candidates because of its high voltage,low cost,and non-toxicity,but suffers severe capacity fading during electrochemical cycling due to the Mn dissolution.Real-space measurement of electron distribution of Li Mn2 O4 experimentally can provide direct evaluation on the strength of Mn–O bond and give an explanation of the structure stability.Here,through high energy synchrotron powder x-ray diffraction(SPXRD),accurate electron density distribution in spinel Li Mn2 O4 has been investigated based on the multipole model.The electron accumulation between Mn and O atoms in deformation density map indicates the shared interaction of Mn–O bond.The quantitative topological analysis at bond critical points shows that the Mn–O bond is relatively weak covalent interaction due to the oxygen loss.These findings suggest that oxygen stoichiometry is the key factor for preventing the Mn dissolution and capacity fading.展开更多
The lack of adequate and modern transport infrastructures makes the cost of transport in Africa higher than the rest of the world. Most of the transport infrastructures that exist were constructed during the colonial ...The lack of adequate and modern transport infrastructures makes the cost of transport in Africa higher than the rest of the world. Most of the transport infrastructures that exist were constructed during the colonial era which makes inter-regional connectivity difficult. The African Union in collaboration with other organization has committed to bridge the transport gap in Africa but still, face some challenges. This paper discusses the main issues that contribute for the weak nature of transportation in Sub-Saharan Africa with regards to the main transport modes and seeks to establish the possibility of sustainable intermodal transport through the integration of the different transport modes. Some policy reforms and other bilateral agreements such as deregulating the transport markets in West and Central Africa have been suggested to facilitate the development of an effective and efficient transport network in the Sub-Saharan African region.展开更多
The method used to estimate the form factor of low-speed vessel will cause a large error when estimating the form factor of high-speed catamaran because of the interference effects. A method based on computational flu...The method used to estimate the form factor of low-speed vessel will cause a large error when estimating the form factor of high-speed catamaran because of the interference effects. A method based on computational fluid dynamics( CFD) method is proposed to estimate the form factor of high-speed catamaran with asymmetrical hulls. This paper focused on a 2000-toners catamaran with asymmetrical hulls to compare the difference between normal method and CFD method. The resistance of this catamaran is calculated by the CFD method,and it was compared to the model test data to verify the validity of this method. The form factors calculated by CFD method are very different from the results calculated by Prohaska method in high speed area.Thus,the method used to estimate the form factor of low-speed vessel is not applicative for high-speed catamaran. It is more accurate and efficient when using the CFD method to estimate the form factor of high-speed catamaran with asymmetrical hulls.展开更多
文摘With the development of virtual reality (VR) technology, more and more industries are beginning to integrate with VR technology. In response to the problem of not being able to directly render the lighting effect of Caideng in digital Caideng scenes, this article analyzes the lighting model. It combines it with the lighting effect of Caideng scenes to design an optimized lighting model algorithm that fuses the bidirectional transmission distribution function (BTDF) model. This algorithm can efficiently render the lighting effect of Caideng models in a virtual environment. And using image optimization processing methods, the immersive experience effect on the VR is enhanced. Finally, a Caideng roaming interactive system was designed based on this method. The results show that the frame rate of the system is stable during operation, maintained above 60 fps, and has a good immersive experience.
基金This work was supported by the National Natural Science Foundation of China(No.22273065 and No.21673158)Science&Technology Commission of Shanghai Municipality(14DZ2261100).
基金funding supports from the National Key R&D Program of China(Grant Nos.2022YFB2404400 and 2019YFA0308500)Beijing Natural Science Foundation(Z190010)National Natural Science Foundation of China(Grant Nos.51991344,52025025,52072400,and 52002394)。
文摘Understanding the structural origin of the competition between oxygen 2p and transition-metal 3d orbitals in oxygen-redox(OR)layered oxides is eminently desirable for exploring reversible and high-energy-density Li/Na-ion cathodes.Here,we reveal the correlation between cationic ordering transition and OR degradation in ribbon-ordered P3-Na_(0.6)Li_(0.2)Mn_(0.8)O_(2) via in situ structural analysis.Comparing two different voltage windows,the OR capacity can be improved approximately twofold when suppressing the in-plane cationic ordering transition.We find that the intralayer cationic migration is promoted by electrochemical reduction from Mn^(4+)to Jahn–Teller Mn^(3+)and the concomitant NaO_(6) stacking transformation from triangular prisms to octahedra,resulting in the loss of ribbon ordering and electrochemical decay.First-principles calculations reveal that Mn^(4+)/Mn^(3+)charge ordering and alignment of the degenerate eg orbital induce lattice-level collective Jahn–Teller distortion,which favors intralayer Mn-ion migration and thereby accelerates OR degradation.These findings unravel the relationship between in-plane cationic ordering and OR reversibility and highlight the importance of superstructure protection for the rational design of reversible OR-active layered oxide cathodes.
基金supported by the National Natural Science Foundation of China(Grant Nos.52322212,52072400,52025025,and 52250402)。
文摘Phase transitions involving oxygen ion extraction within the framework of the crystallographic relevance have been widely exploited for sake of superconductivity,ferromagnetism,and ion conductivity in perovskiterelated oxides.However,atomic-scale pathways of phase transitions and ion extraction threshold are inadequately understood.Here we investigate the atomic structure evolution of LaCoO_(3) films upon oxygen extraction and subsequent Co migration,focusing on the key role of epitaxial strain.The brownmillerite to Ruddlesden-Popper phase transitions are discovered to stabilize at distinct crystal orientations in compressive-and tensile-strained cobaltites,which could be attributed to in-plane and out-of-plane Ruddlesden-Popper stacking faults,respectively.A two-stage process from exterior to interior phase transition is evidenced in compressive-strained LaCoO_(2.5),while a single-step nucleation process leaving bottom layer unchanged in tensile-strained situation.Strain analyses reveal that the former process is initiated by an expansion in Co layer at boundary,whereas the latter one is associated with an edge dislocation combined with antiphase boundary.These findings provide a chemomechanical perspective on the structure regulation of perovskite oxides and enrich insights into strain-dependent phase diagram in epitaxial oxides films.
基金supported by the National Natural Science Foundation of China(NSFC No.52172257 and 22005334)the Natural Science Foundation of Beijing(Grant No.Z200013)the National Key Research and Development Program of China(Grant No.2022YFB2502200).
文摘Fast-charging lithium-ion batteries are highly required,especially in reducing the mileage anxiety of the widespread electric vehicles.One of the biggest bottlenecks lies in the sluggish kinetics of the Li^(+)intercalation into the graphite anode;slow intercalation will lead to lithium metal plating,severe side reactions,and safety concerns.The premise to solve these problems is to fully understand the reaction pathways and rate-determining steps of graphite during fast Li^(+)intercalation.Herein,we compare the Li^(+)diffusion through the graphite particle,interface,and electrode,uncover the structure of the lithiated graphite at high current densities,and correlate them with the reaction kinetics and electrochemical performances.It is found that the rate-determining steps are highly dependent on the particle size,interphase property,and electrode configuration.Insufficient Li^(+)diffusion leads to high polarization,incomplete intercalation,and the coexistence of several staging structures.Interfacial Li^(+)diffusion and electrode transportation are the main rate-determining steps if the particle size is less than 10μm.The former is highly dependent on the electrolyte chemistry and can be enhanced by constructing a fluorinated interphase.Our findings enrich the understanding of the graphite structural evolution during rapid Li^(+)intercalation,decipher the bottleneck for the sluggish reaction kinetics,and provide strategic guidelines to boost the fast-charging performance of graphite anode.
基金support from the National Natural Science Foundation of China(NSFC nos.52172257,22005334,21773301 and 52022106)the Natural Science Foundation of Beijing(grant no.Z200013).
文摘Intercalation provides to the host materials a means for controlled variation of many physical/chemical properties and dominates the reactions in metal‐ion batteries.Of particular interest is the graphite intercalation compounds with intriguing staging structures,which however are still unclear,especially in their nanostructure and dynamic transition mechanism.Herein,the nature of the staging structure and evolution of the lithium(Li)‐intercalated graphite was revealed by cryogenic‐transmission electron microscopy and other methods at the nanoscale.The intercalated Li‐ions distribute unevenly,generating local stress and dislocations in the graphitic structure.Each staging compound is found macroscopically ordered but microscopically inhomogeneous,exhibiting a localized‐domains structural model.Our findings uncover the correlation between the long‐range ordered structure and short‐range domains,refresh the insights on the staging structure and transition of Li‐intercalated/deintercalated graphite,and provide effective ways to enhance the reaction kinetic in rechargeable batteries by defect engineering.
基金Supported by the China Academy of Petroleum Exploration and Development(Nos.2019B-4909,2021DJ2401)Dr.Wei LI is specially funded by the CAS Pioneer Hundred Talents Program(No.Y8SL011001)。
文摘Gas hydrates have been found in the western continental margin of South China Sea,which are revealed by widespread bottom simulating reflectors(BSRs)imaged from a three-dimensional(3D)seismic volume near the Guangle carbonate platform in the western South China Sea.Fluid-escape structures(faults and gas chimneys)are originated below BSR were distinguished.A comprehensive model in three-level structure was proposed to depict the gas hydrate accumulation in the study area.In Level 1,regional major faults and gas chimneys provide the first pathways of upward migration of gas near basement.In Level 2,pervasive polygonal faults in carbonate layer promote the migration of gas.In Level 3,gases sourced from near-basement accumulate within shallow sediment layers and form gas hydrate above the unit with faults once appropriate temperature and pressure occur.The gas hydrates in the study area are mainly in microbial origin,and their accumulation occurs only when fluid-escape structures align in all the three levels.The proposed model of the gas hydrate accumulation in western SCS margin provides new insights for further studies in this poorly studied area.
基金the funding support from the National Key Research and Development Program of China(2020YFB2007400)the National Natural Science Foundation of China(22209202,22075317)the Strategic Priority Research Program(B)(XDB33030200)of Chinese Academy of Sciences。
文摘Hetero-element doping is a promising strategy to improve the cycling stability of nickel-rich cobalt-free cathodes for the next-generation high energy-density Li ion batteries.To make doping effective,it is important to understand the mechanism of how the dopants regulate the electronic band,lattice parameter adjusting,or hetero-phase formation to achieve high stability.In this study,we investigate LiNi_(0.9)Mn_(0.1)O_(2)cathodes doped with IVB grouping elements via multiple characterization techniques.By utilizing in situ XRD and TEM methods,we found that the stronger Ti-O bond effectively improves the cathode stability via a dual protection mechanism.Specifically,the bulk lattice of cathode is wellpreserved during cycling as a result of the suppressed H_(2)-H_(3)phase transition,while a in situ formed Ti-rich surface layer can prevent continuous surface degradation.As a result,the 5%Ti doped LiNi_(0.9)Mn_(0.1)O_(2)cathode exhibits a high capacity retention of 96%after 100 cycles.Whereas,despite IVB group elements Zr and Hf have stronger bonding energy with oxygen,their larger ionic radii actually impede their diffusion into the cathode,thereby they can not improve the cycling stability.Our findings uncover the functional origin of doped elements with their dynamic modification on cathode structure,providing mechanistic insights into the design of nickel-rich cobalt-free cathodes.
基金The National Key R&D Program of China under contract No.2022YFE0140200the National Natural Science Foundation of China under contract Nos 42127807 and 42006074+1 种基金the China Ocean Mineral Resources R&D Association Project under contract Nos DY135-S1-1-02 and DY135-S1-1-01the Macao Science and Technology Development Fund under contract No.FDCT-002/2018/A1。
文摘The Yuhuang hydrothermal field(YHF)is located between the Indomed and Gallieni fracture zones near the top of the off-axis slope on the south rift wall of Segment 29 on the ultraslow Southwest Indian Ridge(SWIR).Previous studies have shown that sulfides in the YHF formed during different mineralization episodes and the YHF has the greatest potential for the formation of large-scale seafloor massive sulfide deposits.However,the sulfide chronology and hydrothermal activity of the YHF remain poorly constrained.In this study,mineralogical analyses and 230Th/U dating were performed.Hydrothermal activity may start about(35.9±2.3)ka from the southwest part of the YHF and may cease about(708±81)a ago from the northeast part of the YHF.The 74 nonzero chronological data from hydrothermal sulfide samples provide the first quantitative characterization of the spatial and temporal history along the SWIR.Hydrothermal activity in the SWIR has been relatively active over the past20 ka.In contrast,between 40 ka and 100 ka,hydrothermal activity was relatively infrequently and short in duration.The maximum activity occurred at 15–11 ka,9–7 ka,6–0.2 ka.There was a slight positive correlation between the maximal age and estimated surface area or estimated tonnage.The minimum mass accumulation rate of YHF is about 278 t/a,which is higher than most HFs related to ultramafic systems.The ultraslow spreading SWIR has the greatest potential to form large-scale seafloor massive sulfides(SMS)deposits.The results of this study provide new insights into the metallogenic mechanism of hydrothermal sulfides along ultraslow-spreading ridges.
基金supported by the Guangdong Basic and Applied Basic Research Foundation of China(No.2021A1515011050)President Foundation of The Third Affiliated Hospital of SouthernMedical University[grant number YM202202].
文摘Ovarian cancer(OC)is one of the most common and recurring malignancies in gynecology.Patients with relapsed OC always develop"cascade drug resistance"(CDR)under repeated chemotherapy,leading to subsequent failure of chemotherapy.To overcome this challenge,amphiphiles(P1)carrying a nitric oxide(NO)donor(Isosorbide 5-mononitrate,ISMN)and high-density disulfide are synthesized for encapsulatingmitochondria-targeted tetravalent platinum prodrug(TPt)to construct a nanocomposite(INP@TPt).Mechanism studies indicated that INP@TPt significantly inhibited drug-resistant cells by increasing cellular uptake and mitochondrial accumulation of platinum,depleting glutathione,and preventing apoptosis escape through generating highly toxic peroxynitrite anion(ONOO−).To better replicate the microenvironmental and histological characteristics of the drug resistant primary tumor,an OC patient-derived tumor xenograft(PDXOC)model in BALB/c nude mice was established.INP@TPt showed the best therapeutic effects in the PDXOC model.The corresponding tumor tissues contained high ONOO−levels,which were attributed to the simultaneous release of O_(2)^(·−)and NO in tumor tissues.Taken together,INP@TPtbased systematic strategy showed considerable potential and satisfactory biocompatibility in overcoming platinum CDR,providing practical applications for ovarian therapy.
文摘Pancreatic cancer is associated with high mortality and is one of the most aggressive of malignancies,but studies have not fully evaluated its molecular subtypes,prognosis and response to immunotherapy of different subtypes.The purpose of this study was to explore the molecular subtypes and the key genes associated with the prognosis of pancreas cancer patients and study the clinical phenotype,prognosis and response to immunotherapy using single-cell seq data and bulk RNA seq data,and data retrieved from GEO and TCGA databases.Methods:Single-cell seq data and bioinformatics methods were used in this study.Pancreatic cancer data were retrieved from GEO and TCGA databases,the molecular subtypes of pancreatic cancer were determined using the six cGAS-STING related pathways,and the clinical phenotype,mutation,immunological characteristics and pathways related to pancreatic cancer were evaluated.Results:Pancreatic cancer was classified into 3 molecular subtypes,and survival analysis revealed that patients in Cluster3(C3)had the worst prognosis,whereas Cluster1(C1)had the best prognosis.The clinical phenotype and gene mutation were statistically different among the three molecular subtypes.Analysis of immunotherapy response revealed that most immune checkpoint genes were differentially expressed in the three subtypes.A lower risk of immune escape was observed in Cluster1(C1),indicating higher sensitivity to immunotherapeutic drugs and subjects in this Cluster are more likely to benefit from immunotherapy.The pathways related to pancreatic cancer were differentially enriched among the three subtypes.Five genes,namely SFRP1,GIPR,EMP1,COL17A and CXCL11 were selected to construct a prognostic signature.Conclusions:Single-cell seq data were to classify pancreatic cancer into three molecular subtypes based on differences in clinical phenotype,mutation,immune characteristics and differentially enriched pathways.Five prognosis-related genes were identified for prediction of survival of pancreatic cancer patients and to evaluate the efficacy of immunotherapy in various subtypes.
基金Supported by Shanghai municipal hospital burgeoning and leading edge technology projects No.SHDC12014109
文摘Objective: To evaluate the feasibility and safety of total mesopancreas excision (TMpE) in the treatment of pancreatic head cancer. Methods: The clinical and pathological data of 120 patients with pancreatic head cancer who had undergone TMpE in our center from May 2010 to January 2014 were retrospectively analyzed. Results: The mean operative time was (275.0±50.2) min and the average intra-operative blood loss was (390.0±160.5) mL. Post-operative complications were reported in 45 patients, while no peri-operative death was noted. The specimen margins were measured in three dimensions, and 86 patients (71.6%) achieved R0 resection. Conclusions: TMpE is safe and feasible for pancreatic head cancer and is particularly helpful to increase the R0 resection rate.
文摘This case reports an application of conventional duodenoscope in a post pancreaticoduodenectomy patient with the help of retrieval balloon assisted enterography.The 56-year-old woman had pancreaticoduodenectomy with Child reconstruction 9 mo ago because of pancreatic adenocarcinoma and now there are recurrent enlarged lymph nodes in the anastomotic stoma of hepaticojejunostomy.Considering the patient's late-stage cancer,a plastic stent was then successfully placed there to drainage.The main challenge in this case was the extremely long afferent loop and blind cannulation through the anastomotic stoma of hepaticojejunostomy.Retrieval balloon assisted enterography is very helpful for duodenoscope going through the reconstructed intestinal tract and for the cannulation.After two weeks,the patient remained free of painful symptoms and free of fever.Liver function improved well.Four months after the placement of stent,the patient died of cachexia without jaundice,fever and abdominal pain according to her daughter's statement.
基金the National Natural Science Foundation of China, No. 30570636a Grant from Applied Basic Research of Committee of Education of Chongqing, No.2001-12-29Medical Science and Technology Foundation of Chongqing City, No. 01-1-013
文摘BACKGROUND: Developing a model of focal cortical dysplasia in microgyrus and observing the ultrastructure of focal tissue is of important significance for analyzing the pathology of cortical developmental disorder and the factors of structural changes. OBJECTIVE: This study was to observe the pathological characteristics of focal tissue around the microgyrus of rats with cortical developmental disorder using an electron microscope, so as to analyze the causes associated with cerebral cortical developmental disorder. DESIGN: A randomized controlled animal experiment. SETTING: The First Affiliated Hospital of Chongqing Medical University. MATERIALS: This study was carried out in the Chongqing Key Laboratory of Neurology, Room for Electron Microscope of Chongqing Medical University, and Laboratory Animal Center, Research Institute of Surgery, Daping Hospital, Third Military Medical University of Chinese PLA between January 2004 and August 2006. Eighteen healthy newborn male Wistar rats, weighing 3.0 - 6.0 g, provided by the Laboratory Animal Center, Daping Hospital, Third Military Medical University of Chinese PLA, were involved in this study. The protocol was carried out in accordance with animal ethics guidelines for the use and care of animals. Probes (Chongqing Wire & Cable Factory, China) were made of copper core wire with diameter of 1mm. METHODS: The rats were randomly divided into 3 groups with 6 in each: normal control group, liquid nitrogen injured group and sham-operation group. (1)In the liquid nitrogen injured group, a blunt probe frozen by liquid nitrogen was placed on fronto-parietal crinial bone of rats for 8 s. A 3 - 5 cm of microgyrus was induced in the unilateral cerebral sensory cortical area. In the sham-operation group, probe was placed at the room temperature. In the normal control group, rats were untouched. (2) The conscious state and electrical activity of brain of rats in each group were observed. (3) 2 - 3 mm thickness of hippocampal tissue with coronary section was taken for observing its ultrastructure under a transmission electron microscope. MAIN OUTCOME MEASURES: (1) The ultrastructure of hippocampal tissue. (2)The conscious state and electrical activity of brain of rats. RESULTS: Eighteen rats were enrolled in the final analysis. (1) Observation of hippocampal ultrastructure: Electromicroscopic pathological findings showed that for each rat of the liquid nitrogen injured group, mitochondrium in the pyramidal neuron around the microgyrus was swelled, endoplasmic reticulum was expanded, glial cells were swelled, water gathered around the blood capillary, partial medullary sheath was degenerated, neuropilem was normal and no obviously abnormal synapse was found. (2) Changes in conscious state of rats: Rats in the normal control group and sham-operation group had no convulsive seizure, but those in the liquid nitrogen injured group had occasionally. Most of them showed increased activities, excitation and restlessness, scratching and frequent " watching face-like activities". (3)Electrical activity of brain of rats: Electroencephalogram recording of liquid nitrogen injured group showed that small wave amplitude of rhythm took the main part. No typical sharp wave, V wave, sharp and slow wave, V and slow waves were discharged. CONCLUSION: Liquid nitrogen can lead to cerebral cortical developmental disorder. Pathological changes of ultrastructure of focal tissue around the microgyrus can provide pathological basis for epilepsy associated with focal cortical developmental disorder.
基金funded by the National Natural Science Foundation of China(Grant Nos:42061001,41501006)The Science and Technology Foundation of Guizhou Province(Grant Nos:Qianke Jichu-ZK[2021]190)Natural science research funding project of Guizhou Provincial Department of Education(Grant No.:Qian Jiao KY[2021]036).
文摘Collapse is a common geomorphic process in karst areas,especially on the Yunnan-Guizhou Plateau,which has a tectonic background of integral uplift.The frequent occurrence of collapse processes in karst underground caves and canyons indicates that collapses play an important role in the formation of canyons.Through an analysis of the morphology of a semicircular cliff in the Huajiang Grand Canyon and an investigation of sediments at the bottom of the cliff,a large-scale collapse event was found to have occurred.U-series dating of secondary calcium carbonate cement in the collapse breccias indicates that collapse processes occurred approximately 200 ka.According to the geomorphological evolution of the Huajiang Grand Canyon,the following geomorphic evolutionary process is proposed:underground river-cave hall-collapse of a tiankeng-tiankeng degradation-canyon formation.These findings also show that the dating of collapsed breccia cement can be effectively used to determine the development times of karst canyons and the formation ages of tiankengs.
基金supported by the Beijing Natural Science Foundation(Grant No.Z190010)the National Key R&D Program of China(Grant No.2019YFA0308500)+2 种基金the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDB07030200)the Key Research Projects of Frontier Science of Chinese Academy of Sciences(Grant No.QYZDB-SSW-JSC035)the National Natural Science Foundation of China(Grant Nos.51421002,51672307,51991344,and 52025025)。
文摘Oxygen vacancies play a crucial role in determining the catalytic properties of Ce-based catalysts,especially in oxidation reactions.The design of catalytic activity requires keen insight into oxygen vacancy formation mechanisms.In this work,we investigate the origin of oxygen vacancies in CeO_(2)from the perspective of electron density via high-energy synchrotron powder x-ray diffraction.Multipole refinement results indicate that there is no obvious hybridization between bonded Ce and O atoms in CeO_(2).Subsequent quantitative topological analysis of the experimental total electron density reveals the closed-shell interaction behavior of the Ce-O bond.The results of first-principles calculation indicate that the oxygen vacancy formation energy of CeO_(2)is the lowest among three commonly used redox catalysts.These findings indicate the relatively weak bond strength of the Ce-O bond,which induces a low oxygen vacancy formation energy for CeO_(2)and thus promotes CeO_(2)as a superior catalyst for oxidation reactions.This work provides a new direction for design of functional metal oxides with high oxygen vacancy concentrations.
基金Beijing Natural Science Foundation,China(Grant No.Z190010)the National Key Research and Development Program of China(Grant No.2019YFA0308500)+2 种基金the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDB07030200)Key Research Projects of Frontier Science of Chinese Academy of Sciences(Grant No.QYZDB-SSW-JSC035)the National Natural Science Foundation of China(Grant Nos.51421002,51672307,51991344,52025025,and 52072400).
文摘Electron density plays an important role in determining the properties of functional materials.Revealing the electron density distribution experimentally in real space can help to tune the properties of materials.Spinel Li Mn2 O4 is one of the most promising cathode candidates because of its high voltage,low cost,and non-toxicity,but suffers severe capacity fading during electrochemical cycling due to the Mn dissolution.Real-space measurement of electron distribution of Li Mn2 O4 experimentally can provide direct evaluation on the strength of Mn–O bond and give an explanation of the structure stability.Here,through high energy synchrotron powder x-ray diffraction(SPXRD),accurate electron density distribution in spinel Li Mn2 O4 has been investigated based on the multipole model.The electron accumulation between Mn and O atoms in deformation density map indicates the shared interaction of Mn–O bond.The quantitative topological analysis at bond critical points shows that the Mn–O bond is relatively weak covalent interaction due to the oxygen loss.These findings suggest that oxygen stoichiometry is the key factor for preventing the Mn dissolution and capacity fading.
文摘The lack of adequate and modern transport infrastructures makes the cost of transport in Africa higher than the rest of the world. Most of the transport infrastructures that exist were constructed during the colonial era which makes inter-regional connectivity difficult. The African Union in collaboration with other organization has committed to bridge the transport gap in Africa but still, face some challenges. This paper discusses the main issues that contribute for the weak nature of transportation in Sub-Saharan Africa with regards to the main transport modes and seeks to establish the possibility of sustainable intermodal transport through the integration of the different transport modes. Some policy reforms and other bilateral agreements such as deregulating the transport markets in West and Central Africa have been suggested to facilitate the development of an effective and efficient transport network in the Sub-Saharan African region.
基金Sponsored by the National Basic Research Program of China(Grant No.2013CB036103)the Self Research Project of State Key Laboratory of Ocean Engineering:Piercing Pentamaran Advanced Research and Conceptual Design(Grant No.GKZD010056-1)
文摘The method used to estimate the form factor of low-speed vessel will cause a large error when estimating the form factor of high-speed catamaran because of the interference effects. A method based on computational fluid dynamics( CFD) method is proposed to estimate the form factor of high-speed catamaran with asymmetrical hulls. This paper focused on a 2000-toners catamaran with asymmetrical hulls to compare the difference between normal method and CFD method. The resistance of this catamaran is calculated by the CFD method,and it was compared to the model test data to verify the validity of this method. The form factors calculated by CFD method are very different from the results calculated by Prohaska method in high speed area.Thus,the method used to estimate the form factor of low-speed vessel is not applicative for high-speed catamaran. It is more accurate and efficient when using the CFD method to estimate the form factor of high-speed catamaran with asymmetrical hulls.