Under the influence of air humidity,dust,aerosols,etc.,in real scenes,haze presents an uneven state.In this way,the image quality and contrast will decrease.In this case,It is difficult to detect the target in the ima...Under the influence of air humidity,dust,aerosols,etc.,in real scenes,haze presents an uneven state.In this way,the image quality and contrast will decrease.In this case,It is difficult to detect the target in the image by the universal detection network.Thus,a dual subnet based on multi-task collaborative training(DSMCT)is proposed in this paper.Firstly,in the training phase,the Gated Context Aggregation Network(GCANet)is used as the supervisory network of YOLOX to promote the extraction of clean information in foggy scenes.In the test phase,only the YOLOX branch needs to be activated to ensure the detection speed of the model.Secondly,the deformable convolution module is used to improve GCANet to enhance the model’s ability to capture details of non-homogeneous fog.Finally,the Coordinate Attention mechanism is introduced into the Vision Transformer and the backbone network of YOLOX is redesigned.In this way,the feature extraction ability of the network for deep-level information can be enhanced.The experimental results on artificial fog data set FOG_VOC and real fog data set RTTS show that the map value of DSMCT reached 86.56%and 62.39%,respectively,which was 2.27%and 4.41%higher than the current most advanced detection model.The DSMCT network has high practicality and effectiveness for target detection in real foggy scenes.展开更多
When the geological environment of rock masses is disturbed,numerous non-persisting open joints can appear within it.It is crucial to investigate the effect of open joints on the mechanical properties of rock mass.How...When the geological environment of rock masses is disturbed,numerous non-persisting open joints can appear within it.It is crucial to investigate the effect of open joints on the mechanical properties of rock mass.However,it has been challenging to generate realistic open joints in traditional experimental tests and numerical simulations.This paper presents a novel solution to solve the problem.By utilizing the stochastic distribution of joints and an enhanced-fractal interpolation system(IFS)method,rough curves with any orientation can be generated.The Douglas-Peucker algorithm is then applied to simplify these curves by removing unnecessary points while preserving their fundamental shape.Subsequently,open joints are created by connecting points that move to both sides of rough curves based on the aperture distribution.Mesh modeling is performed to construct the final mesh model.Finally,the RB-DEM method is applied to transform the mesh model into a discrete element model containing geometric information about these open joints.Furthermore,this study explores the impacts of rough open joint orientation,aperture,and number on rock fracture mechanics.This method provides a realistic and effective approach for modeling and simulating these non-persisting open joints.展开更多
Eucalyptus nitens(E.nitens)has been much used for producing paper but also shows promise for structural applications.In this study,static compressive tests were undertaken to examine its suitability to be used in an i...Eucalyptus nitens(E.nitens)has been much used for producing paper but also shows promise for structural applications.In this study,static compressive tests were undertaken to examine its suitability to be used in an innovative composite column.The composite column was comprised of a rectangular steel tube with E.nitens timber infill.The nonlinear compressive behaviour of the composite column filled with E.nitens wood for both dry and wet conditions was examined.The same tests on rectangular steel tubes and bare dry and wet E.nitens samples were also undertaken as a comparison.For samples with different conditions,the ultimate capacity was evaluated and the effect of each condition on the compressive behaviour of the composite column was clarified.The steel tubes showed greater ductile behaviour,and more ductility was found in the wet samples.The steel tubes with E.nitens timber infill samples exhibited a greater linear elastic range connected with higher maximum loads,while the bare timber samples could support only lower maximum loads.The results from this research were promising for the use of rectangular steel tubes with E.nitens timber infill in structural applications.展开更多
BACKGROUND: Angelica sinensis is a widely used herb in Chinese traditional medicine. It has been shown to improve hypoxia in embryonic rats and reduce nestin expression in neural stem cells, resulting in proliferation...BACKGROUND: Angelica sinensis is a widely used herb in Chinese traditional medicine. It has been shown to improve hypoxia in embryonic rats and reduce nestin expression in neural stem cells, resulting in proliferation of neural stem cells. OBJECTIVE: To study the protective effect of Angelica on neural stem cell proliferation in neonatal rats after intrauterine hypoxia. DESIGN, TIME AND SETTING: The randomized, controlled, experiment was performed at the Department of Histology and Embryology, Luzhou Medical College, China from July 2007 to January 2008. MATERIALS: Because gestational days 14-15 are a key stage in rat nervous system development, 21 healthy, pregnant Sprague Dawley rats (14 days after conception) were used for this study. Nestin monoclonal primary antibody was obtained from Chemicon, USA. Angelica parenteral solution (250 g/L) was obtained from Pharmaceutical Preparation Section, Second Affiliated Hospital of Wuhan University, China. METHODS: Rats were randomly divided into a control group (n = 5), a hypoxia group (n = 8), and an Angelica group (n = 8). Saline (8 mL/kg) was injected into the caudal vein of rats in the hypoxia group once a day for seven consecutive days. Intrauterine hypotonic hypoxia was induced using 13% O2 for two hours per day on three consecutive days. Rats in the Angelica group received injections of Angelica parenteral solution (250 g/L); all other protocols were the same as the hypoxia group. The control group procedures were identical to the hypoxia group, but under normal, non-hypoxic conditions. After birth, brain tissues were immediately obtained from neonatal rats and prepared for nestin immunohistochemistry. MAIN OUTCOME MEASURES: Nestin-positive cells in hippocampal CA3 area of neonatal rats in each group were quantified using image analysis to detect signal absorbance. RESULTS: The number of nestin-positive cells increased in the hippocampal CA3 area of neonatal rats in the hypoxia group. The number of nestin-positive cells was less in the Angelica group than in the hypoxia group. Integral absorbance of nestin-positive cells in the hippocampal CA3 area of neonatal rats was significantly higher in the hypoxia group, compared with the control group (P < 0.05). The integral absorbance of nestin positive cells was lower in the Angelica group, compared with the hypoxia group (P < 0.05). CONCLUSION: Intrauterine hypoxia, induced for 2 hours daily for three consecutive days, with an oxygen concentration of 13%, stimulated the proliferation of neural stem cells. Angelica injection has a protective effect on neural stem cells from neonatal rats following intrauterine hypoxia by decreasing proliferation of neural stem cells.展开更多
OBJECTIVE To examine the ultrastructure of gastric cancer cel s by the electron microscope,in order to assess the relationship between neuroendocrine differentiation and post-operative survival time. METHODS NSE,Syn a...OBJECTIVE To examine the ultrastructure of gastric cancer cel s by the electron microscope,in order to assess the relationship between neuroendocrine differentiation and post-operative survival time. METHODS NSE,Syn and CgA immunohistochemical labeling was conducted in 168 cases with a common-type of gastric cancer.Electron microscopy was performed in 80 cases with positive immunohistochemical labeling. These cases were fol owed-up for over 5 years and the post-operative survival data analyzed. RESULTS Neuroendocrine granules were found by electron microscopy in 39 cases.The rate of neuroendocrine differentiation found was 23% (39/168),using routine diagnostic criteria and electron microscopy(REM). The post-operative survival time of gastric cancer patients with neuroendocrine differentiation was significantly shorter(P=0.0032)compared to those without neuroendocrine differentiation. CONCLUSION It is of significant clinical importance to determine if the neuroendocrine cells are differentiated in gastric cancers.The gastric cancer patients with neuroendocrine differentiation have a shorter post-operative survival time and a poorer prognosis.Electron microscopy is a reliable method of providing a diagnosis.展开更多
We investigate a high sensitive chiral molecule detector based on Goos–Hanchen shift(S) in Kretschmann configuration involving chiral tri(diethylene glycol monobutyl) citrates(TDBCs). Fresnel equations and the statio...We investigate a high sensitive chiral molecule detector based on Goos–Hanchen shift(S) in Kretschmann configuration involving chiral tri(diethylene glycol monobutyl) citrates(TDBCs). Fresnel equations and the stationary phase method are employed to calculate S. Due to the interaction between surface plasmon polaritons and chiral TDBCs, S with chiral TDBCs are amplified at near the resonant wavelengths of chiral TDBCs. Our calculation results show that although the difference between the resonant wavelengths of left and right TDBCs is 4.5 nm, the positions of the largest S for the structures with left TDBCs and right TDBCs do not overlap. S reaches 400 times(or 200 times) the incident wavelength around the resonant wavelength of left TDBCs(or right TDBCs). The difference of S with chiral TDBCs(?S) can reach400 times or 200 times the incident wavelength in certain conditions, which can be directly observed in experiments. Left TDBCs and right TDBCs are easily distinguished. There is an optimal thickness of the metal film to realize the largest difference of S between Kretschmann configurations with left TDBCs and right TDBCs. Furthermore, we discuss the oscillator strength f, which is mainly determined by TDBC concentration. We find that our proposed detector is quite sensitive with f. By changing f from 0.008 to 0.014 with the step of 0.002, the change of ?S is no less than five times the incident wavelength(2.9 μm). Our proposed structure is very sensitive to the chirality and the concentration of TDBCs and has potential applications in distinguishing the chirality detector.展开更多
Gas hydrate(GH) dissociates owing to thermal injection or pressure reduction from the well in gas/oil or GH exploitation. GH dissociation leads to, for example, decreases in soil strength, engineering failures such as...Gas hydrate(GH) dissociates owing to thermal injection or pressure reduction from the well in gas/oil or GH exploitation. GH dissociation leads to, for example, decreases in soil strength, engineering failures such as wellbore instabilities, and marine landslides. The FLAC3 D software was used to analyze the deformation of the soil stratum and vertical wells with GH dissociation. The effects of Young's modulus, internal friction angle, cohesion of the GH layer after dissociation, and the thickness of the GH layer on the deformation of soils were studied. It is shown that the maximum displacement in the whole soil stratum occurs at the interface between the GH layer and the overlayer. The deformation of the soil stratum and wells increases with decreases in the modulus, internal friction angle, and cohesion after GH dissociation. The increase in thickness of the GH layer enlarges the deformation of the soil stratum and wells with GH dissociation. The hydrostatic pressure increases the settlement of the soil stratum, while constraining horizontal displacement. The interaction between two wells becomes significant when the affected zone around each well exceeds half the length of the GH dissociation zone.展开更多
The dilemma for the synthesis of covalent organic frameworks(COFs)is crystallinity and stability.Herein,we present the synthesis of a single-crystalline amide-linked COF,and demonstrate its excellent chemical as well ...The dilemma for the synthesis of covalent organic frameworks(COFs)is crystallinity and stability.Herein,we present the synthesis of a single-crystalline amide-linked COF,and demonstrate its excellent chemical as well as thermal stabilities.This study will inspire the synthesis of a wide spectrum of highly crystalline and stable COFs,promote their structure-property investigations and boost their applications in selective gas adsorption,storage and separation.展开更多
Dynamic surface patterns(DSPs)have attracted significant interest in anti-counterfeiting,enabling information to be stored,encrypted and decrypted in response to external stimuli.However,creating dynamic surface patte...Dynamic surface patterns(DSPs)have attracted significant interest in anti-counterfeiting,enabling information to be stored,encrypted and decrypted in response to external stimuli.However,creating dynamic surface patterns,capable of controlling wrinkling time and independently modulating different information in both wrinkled and fluorescent states,remains a tremendous challenge.These limit DSPs to further enhance tamper-proofing capacity and extend the information storage density.Here,a rationally designed patterning strategy based on controllable elastic modulus was demonstrated to fabricate self-erasable dynamic surface patterns(S-DSPs)that increase information storage density.These novel S-DSPs strategically integrated amino co-oligomers(ACOs)with the 9-anthracenemethanol(9-AM)as skin layers,designing a bilayer multi-encoding system which could carry several different types of information with wrinkled and fluorescent patterns.The ACOs with relatively low molecular weight can endow the elastic modulus of skin layers with a wide range of regulation.As a result,the difference between the compressive strain and the critical wrinkle strain in the bilayer system would be precisely modulated by photo-dimerization to form quick-response(minimum<1 min)and self-erasable(3 min–8 days)wrinkled patterns for S-DSPs.Meanwhile,the fluorescence pattern could be independently erased and reprogrammed without affecting the change in the wrinkle pattern under modulus-controlled conditions.Moreover,controllable self-erasure in S-DSPs significantly develops tamper-proof capabilities in a supply chain.This original strategy could provide a new approach to the tamper-proof,high-density,and multi-encoded information storage in the product security or inkless printing.展开更多
Ancient dolomite reservoirs play an increasingly important role in deep oil and gas exploration.The mechanism of formation and preservation of dolomite reservoirs is complex,which is always the key issue.With the disc...Ancient dolomite reservoirs play an increasingly important role in deep oil and gas exploration.The mechanism of formation and preservation of dolomite reservoirs is complex,which is always the key issue.With the discovery of deep oil and gas in the Ediacaran dolomites of the world,the upper Ediacaran Qigebrak Formation in the Tabei area has begun to attract attention,but its reservoir space difference and formation mechanism have yet to be clarified.Based on ultra-deep drilling cores and field outcrops in the Tabei area,the lithofacies,reservoir space,and formation mechanism are systematically analyzed by macro to micro,and qualitative to quantitative petrology:(1)The types of dolomite can be divided into five major categories,including microbial dolomite,granular dolomite,residual granular dolomite,crystalline dolomite and karst breccias.(2)The main types of reservoir space are microbial-framework pores,microbial-mold pores,and non-fabric selective dissolution pores.Spongiomicrobialite,karst breccias,and fine-grained dolomite are the dominant reservoir rock types.(3)High-frequency sedimentary cycles and meteoric dissolution are the key factors of reservoir formation.Two sets of large-scale reservoirs are present:the first set is mainly controlled by the supergene karst of the Keping movement,and the second set is mainly controlled by high-frequency sedimentary cycles in the penecontemporaneous period.The reservoirs formed at the shallow burial stage and were preserved until the deep burial stage.(4)The quality of a deep reservoir depends on the geological events that affect the processes of pore reduction and increase.Cementation,compaction and pressure solution are the main destructive diagenetic processes;however,the reservoir space can still be effectively preserved under the influence of constructive diagenetic processes,such as meteoric dissolution and early dolomitization.This research has important theoretical and practical significance for revealing the formation mechanism of upper Ediacaran deep dolomite reservoirs in the Tarim Basin.展开更多
Congenital heart disease(CHD)is one of the most common causes of neonatal mortality.The worldwide morbidity of CHD is 9.410%o,while the proportion of CHD patients who are reported to carry mutations in coding regions ...Congenital heart disease(CHD)is one of the most common causes of neonatal mortality.The worldwide morbidity of CHD is 9.410%o,while the proportion of CHD patients who are reported to carry mutations in coding regions is<50%.Enhancers play an important role in the spatio-temporal expression of target genes,and a lot of related variations are associated with CHD.There are conserved and nonconserved enhancers.展开更多
Silver nanocubes enriched with {100} facets have been extensively used for surface-enhanced Raman scattering. Herein, we report a new water-phase synthesis method for weU-defined Ag nanocubes with tunable sizes via a ...Silver nanocubes enriched with {100} facets have been extensively used for surface-enhanced Raman scattering. Herein, we report a new water-phase synthesis method for weU-defined Ag nanocubes with tunable sizes via a two-step procedure at room temperature. First, irregularly shaped Ag nanoparticles （INPs） were prepared by reducing silver ammonia solution using ethylal. Second, the agglomerated INPs were selectively etched with HNO3 and C1- to yield {100} facet-rich mesoporous Ag nanocubes. The mechanism of Ag-nanocube formation and growth was investigated in detail by elucidating the involved chemical reactions and physical changes at each step during the synthesis. The addition of C1- anions was responsible for facilitating Ag nanoparticle growth by removing surface-adsorbed Ag＋ species, thereby eliminating inter-particle repulsive forces. This agglomeration was found crucial for the subsequent selective oxidation of Ag nanoparticles because the protective agent used, polyvinylpyrrolidone （PVP）, was the most effective one for adsorption on the surfaces of Ag nanoparticles of size greater than approximately 50 nm. Importantly mesopores were found inside the Ag nanocubes; this can be attributed to the unavoidable imperfect packing during the agglomeration of INPs. The newly prepared Ag nanocubes were further used to enhance the Raman signal of rhodamine 6G, which is capable of reducing the detection limitation to 10-16 mol·L-1.展开更多
A three-dimensional thermal analysis of GaN HEMTs on diamond substrate is investigated using the finite element method. The diamond substrate thickness, area and shape, transition layer thickness and thermal conductiv...A three-dimensional thermal analysis of GaN HEMTs on diamond substrate is investigated using the finite element method. The diamond substrate thickness, area and shape, transition layer thickness and thermal conductivity of the transition layer are considered and treated appropriately in the numerical simulation. The temperature distribution and heat spreading paths are investigated under different conditions and the results indicate that the existence of the transition layer causes an increase in the channel temperature and the thickness, area and shape of the diamond substrate have certain impacts on the channel temperature too. Channel temperature reduces with increasing diamond substrate thickness and area but with a decreasing trend, which can be explained by the saturation effects of the diamond substrate. The shape of diamond substrate also affects the temperature performance of GaN HEMTs, therefore, to achieve a favorable heat dissipation effect with the settled diamond substrate area, the shape should contain as many isothermal curves as possible when the isothermal gradient is constant. The study of the thermal properties of GaN on diamond substrate is useful for the prediction of heating of high power GaN HEMTs devices and optimal designs of an efficient heat spreader for GaN HEMTs.展开更多
Superoxide dismutase(SOD) is an important antioxidant enzyme in the body. SOD has special physiological activity and is the primary substance for scavenging free radicals in living organisms.However, the expensive and...Superoxide dismutase(SOD) is an important antioxidant enzyme in the body. SOD has special physiological activity and is the primary substance for scavenging free radicals in living organisms.However, the expensive and complex extraction processes, low SOD yield, as well as difficult to store at room temperature have seriously hindered its application pace. Herein, the enzyme mimetic function of Mn-doped ZnS quantum dots(QDs) was discovered. The improved Marklund and McCord method both showed that Mn-doped ZnS QDs possess intrinsic SOD-like activity. The effects of temperature and pH on the mimetic enzyme activity of Mn-doped ZnS QDs have been investigated compared with SOD enzymes.The low cost and easy to synthesize white Mn-doped ZnS QDs with good biocompatibility are expected to be used as a new type of SOD nanozymes in the biology-relevant fields.展开更多
As a metallic orthopedic implant,316L stainless steel(316L SS)is used extensively for its good resistance to corrosion and mechanical properties.However,it takes a long time to achieve osseointegration between 316L SS...As a metallic orthopedic implant,316L stainless steel(316L SS)is used extensively for its good resistance to corrosion and mechanical properties.However,it takes a long time to achieve osseointegration between 316L SS and adjacent tissues due to its bio-inert characteristic.Hence,the aim is to improve the bio-adaption of 316L SS.A good approach is to add elements to materials to improve their osteogenic capabilities by the appropriate release of ions.Hence copper-containing 316L stainless steel(316L-Cu SS)was investigated in this work,where Cu is an essential trace element that can stimulates osteogenesis.It was found that 316L-Cu SS was bio-safe and did not affect the proliferation of co-cultured osteoblasts in comparison with 316L SS.It increased cell apoptosis on day 1 but inhibited it on day 3,which cooperates with new bone formation processes.Osteoblasts extend themselves more quickly and in a better manner on the surface of 316L-Cu SS,wheneven more pseudopodia are present.Furthermore,the gene expression of alkaline phosphatase,collagen I and runt-related transcription factor 2(Runx2)in osteoblasts cultured with 316L-Cu SS was significantly enhanced.Runx2 protein expression increased,and osteogenesis was stimulated by 316L-Cu SS via an Akt cell signaling pathway.In conclusion,316L-Cu SS stimulates osteogenesis through activation of the Akt cell signaling pathway and the upregulation of Runx2.Thus,316L-Cu SS is a promising material that may be used in surgical implants to stimulate osteogenesis.展开更多
The spectral purity of fiber lasers has become a critical issue in both optical sensing and communication fields.As a result of ultra-narrow intrinsic linewidth, stimulated thermal Rayleigh scattering(STRS) has presen...The spectral purity of fiber lasers has become a critical issue in both optical sensing and communication fields.As a result of ultra-narrow intrinsic linewidth, stimulated thermal Rayleigh scattering(STRS) has presented special potential to compress the linewidth of fiber lasers. To suppress stimulated Brillouin scattering(SBS), the most dominant disturbance for STRS in optical fibers, a semi-quantitative estimation has been established to illuminate the mechanism of suppressing SBS in a periodic tapered fiber, and it agrees with experimental results. Finally, a linewidth compression device based on STRS is integrated into a single-longitudinal-mode ring-cavity fiber laser with secondary cavities, and its linewidth is verified to be 200 Hz through a self-heterodyne detecting and Voigt fitting method.展开更多
Film plays a key role in the sustainable development of our society.Freestanding thin films of two-dimensional covalent organic frameworks(coFs)have been produced by interface,spin coating,microwave-assisted synthesis...Film plays a key role in the sustainable development of our society.Freestanding thin films of two-dimensional covalent organic frameworks(coFs)have been produced by interface,spin coating,microwave-assisted synthesis,and screen printing methods and are applied in nanofitration,molecular separation,photochemical sensing,anion transport,heat conduction,and proton conduction.On the other hand,the synthesis of their three-dimensional(3D)analogues and subsequent integration in devices remains challenging.Herein,self-supporting thin films of a three-dimensionai COF with tunable thickness was created by a stearic acid mediated synthesis methodology on water surface at room temperature in air.The film could be transferred onto arbitrary substrate,and when supported on indium tin oxide glass,it exhibited irreversible electrochromism.The optical feature made it act as a one-time anti-counterfeiting label in an electrochemical device.This work will inspire the synthesis of thin films of 3D COFs as well as other 3D materials,and boost their property and application exploration.展开更多
White-light emitting(WLE) polymers have attracted continuous attention for their promising applications in solid-state lighting,flexible display and related fields. However, achieving dual-emission and pure white-ligh...White-light emitting(WLE) polymers have attracted continuous attention for their promising applications in solid-state lighting,flexible display and related fields. However, achieving dual-emission and pure white-light emission in a single-component polymer is still challenging. In this study, a brominated single-component polymer Br OD-TFB was designed and synthesized,which shows dual-emission and white light emission properties in solution and room-temperature phosphorescence(RTP) in thin films. The dual-emission properties can be tuned by concentration, solvent polarity, and excitation energy. Spectral analyses and theoretical calculations reveal that the origin of the high-energy emission band(HEB) is intramolecular charge transfer(ICT)along the polymer chain, whilst the low-energy emission band(LEB) originates from the excited-state related to the intra-chain and inter-chain C–Br···π interactions as demonstrated by the single-crystal structure of the model compound. Appropriate control of the formation and the destruction of the halogen-assisted interactions can initiate white-light emission in the singlecomponent polymer. More interestingly, by dispersing Br OD-TFB(0.1 wt%) in a non-emissive, colorless and transparent polymer, the characteristics of this white-light emission can be fully demonstrated while exhibiting unexpected RTP properties,with photoluminescence quantum efficiency(Φ_(PL)) of up to 23% and CIE coordinates of(0.32, 0.32).展开更多
基金This work was jointly supported by the Special Fund for Transformation and Upgrade of Jiangsu Industry and Information Industry-Key Core Technologies(Equipment)Key Industrialization Projects in 2022(No.CMHI-2022-RDG-004):“Key Technology Research for Development of Intelligent Wind Power Operation and Maintenance Mothership in Deep Sea”.
文摘Under the influence of air humidity,dust,aerosols,etc.,in real scenes,haze presents an uneven state.In this way,the image quality and contrast will decrease.In this case,It is difficult to detect the target in the image by the universal detection network.Thus,a dual subnet based on multi-task collaborative training(DSMCT)is proposed in this paper.Firstly,in the training phase,the Gated Context Aggregation Network(GCANet)is used as the supervisory network of YOLOX to promote the extraction of clean information in foggy scenes.In the test phase,only the YOLOX branch needs to be activated to ensure the detection speed of the model.Secondly,the deformable convolution module is used to improve GCANet to enhance the model’s ability to capture details of non-homogeneous fog.Finally,the Coordinate Attention mechanism is introduced into the Vision Transformer and the backbone network of YOLOX is redesigned.In this way,the feature extraction ability of the network for deep-level information can be enhanced.The experimental results on artificial fog data set FOG_VOC and real fog data set RTTS show that the map value of DSMCT reached 86.56%and 62.39%,respectively,which was 2.27%and 4.41%higher than the current most advanced detection model.The DSMCT network has high practicality and effectiveness for target detection in real foggy scenes.
基金supported by the National Key R&D Program of China (2018YFC0407004)the Fundamental Research Funds for the Central Universities (Nos.B200201059,2021FZZX001-14)the National Natural Science Foundation of China (Grant No.51709089)and 111 Project.
文摘When the geological environment of rock masses is disturbed,numerous non-persisting open joints can appear within it.It is crucial to investigate the effect of open joints on the mechanical properties of rock mass.However,it has been challenging to generate realistic open joints in traditional experimental tests and numerical simulations.This paper presents a novel solution to solve the problem.By utilizing the stochastic distribution of joints and an enhanced-fractal interpolation system(IFS)method,rough curves with any orientation can be generated.The Douglas-Peucker algorithm is then applied to simplify these curves by removing unnecessary points while preserving their fundamental shape.Subsequently,open joints are created by connecting points that move to both sides of rough curves based on the aperture distribution.Mesh modeling is performed to construct the final mesh model.Finally,the RB-DEM method is applied to transform the mesh model into a discrete element model containing geometric information about these open joints.Furthermore,this study explores the impacts of rough open joint orientation,aperture,and number on rock fracture mechanics.This method provides a realistic and effective approach for modeling and simulating these non-persisting open joints.
文摘Eucalyptus nitens(E.nitens)has been much used for producing paper but also shows promise for structural applications.In this study,static compressive tests were undertaken to examine its suitability to be used in an innovative composite column.The composite column was comprised of a rectangular steel tube with E.nitens timber infill.The nonlinear compressive behaviour of the composite column filled with E.nitens wood for both dry and wet conditions was examined.The same tests on rectangular steel tubes and bare dry and wet E.nitens samples were also undertaken as a comparison.For samples with different conditions,the ultimate capacity was evaluated and the effect of each condition on the compressive behaviour of the composite column was clarified.The steel tubes showed greater ductile behaviour,and more ductility was found in the wet samples.The steel tubes with E.nitens timber infill samples exhibited a greater linear elastic range connected with higher maximum loads,while the bare timber samples could support only lower maximum loads.The results from this research were promising for the use of rectangular steel tubes with E.nitens timber infill in structural applications.
基金the founda-tion of Sichuan Provincial Department of Science and Technology, No. 05JY029-103-1the foundation of Sichuan Provincial Health Department, No. 060052
文摘BACKGROUND: Angelica sinensis is a widely used herb in Chinese traditional medicine. It has been shown to improve hypoxia in embryonic rats and reduce nestin expression in neural stem cells, resulting in proliferation of neural stem cells. OBJECTIVE: To study the protective effect of Angelica on neural stem cell proliferation in neonatal rats after intrauterine hypoxia. DESIGN, TIME AND SETTING: The randomized, controlled, experiment was performed at the Department of Histology and Embryology, Luzhou Medical College, China from July 2007 to January 2008. MATERIALS: Because gestational days 14-15 are a key stage in rat nervous system development, 21 healthy, pregnant Sprague Dawley rats (14 days after conception) were used for this study. Nestin monoclonal primary antibody was obtained from Chemicon, USA. Angelica parenteral solution (250 g/L) was obtained from Pharmaceutical Preparation Section, Second Affiliated Hospital of Wuhan University, China. METHODS: Rats were randomly divided into a control group (n = 5), a hypoxia group (n = 8), and an Angelica group (n = 8). Saline (8 mL/kg) was injected into the caudal vein of rats in the hypoxia group once a day for seven consecutive days. Intrauterine hypotonic hypoxia was induced using 13% O2 for two hours per day on three consecutive days. Rats in the Angelica group received injections of Angelica parenteral solution (250 g/L); all other protocols were the same as the hypoxia group. The control group procedures were identical to the hypoxia group, but under normal, non-hypoxic conditions. After birth, brain tissues were immediately obtained from neonatal rats and prepared for nestin immunohistochemistry. MAIN OUTCOME MEASURES: Nestin-positive cells in hippocampal CA3 area of neonatal rats in each group were quantified using image analysis to detect signal absorbance. RESULTS: The number of nestin-positive cells increased in the hippocampal CA3 area of neonatal rats in the hypoxia group. The number of nestin-positive cells was less in the Angelica group than in the hypoxia group. Integral absorbance of nestin-positive cells in the hippocampal CA3 area of neonatal rats was significantly higher in the hypoxia group, compared with the control group (P < 0.05). The integral absorbance of nestin positive cells was lower in the Angelica group, compared with the hypoxia group (P < 0.05). CONCLUSION: Intrauterine hypoxia, induced for 2 hours daily for three consecutive days, with an oxygen concentration of 13%, stimulated the proliferation of neural stem cells. Angelica injection has a protective effect on neural stem cells from neonatal rats following intrauterine hypoxia by decreasing proliferation of neural stem cells.
基金This work was supported by a grant from theSocial Development and Scientific Programof the Nantong Municipal Government,Ji-angsu Province,China(No.S30062).
文摘OBJECTIVE To examine the ultrastructure of gastric cancer cel s by the electron microscope,in order to assess the relationship between neuroendocrine differentiation and post-operative survival time. METHODS NSE,Syn and CgA immunohistochemical labeling was conducted in 168 cases with a common-type of gastric cancer.Electron microscopy was performed in 80 cases with positive immunohistochemical labeling. These cases were fol owed-up for over 5 years and the post-operative survival data analyzed. RESULTS Neuroendocrine granules were found by electron microscopy in 39 cases.The rate of neuroendocrine differentiation found was 23% (39/168),using routine diagnostic criteria and electron microscopy(REM). The post-operative survival time of gastric cancer patients with neuroendocrine differentiation was significantly shorter(P=0.0032)compared to those without neuroendocrine differentiation. CONCLUSION It is of significant clinical importance to determine if the neuroendocrine cells are differentiated in gastric cancers.The gastric cancer patients with neuroendocrine differentiation have a shorter post-operative survival time and a poorer prognosis.Electron microscopy is a reliable method of providing a diagnosis.
基金supported by Science and Technology Nova Plan of Beijing City,China (Grant No. Z201100006820122)Fundamental Research Funds for the Central Universities,China。
文摘We investigate a high sensitive chiral molecule detector based on Goos–Hanchen shift(S) in Kretschmann configuration involving chiral tri(diethylene glycol monobutyl) citrates(TDBCs). Fresnel equations and the stationary phase method are employed to calculate S. Due to the interaction between surface plasmon polaritons and chiral TDBCs, S with chiral TDBCs are amplified at near the resonant wavelengths of chiral TDBCs. Our calculation results show that although the difference between the resonant wavelengths of left and right TDBCs is 4.5 nm, the positions of the largest S for the structures with left TDBCs and right TDBCs do not overlap. S reaches 400 times(or 200 times) the incident wavelength around the resonant wavelength of left TDBCs(or right TDBCs). The difference of S with chiral TDBCs(?S) can reach400 times or 200 times the incident wavelength in certain conditions, which can be directly observed in experiments. Left TDBCs and right TDBCs are easily distinguished. There is an optimal thickness of the metal film to realize the largest difference of S between Kretschmann configurations with left TDBCs and right TDBCs. Furthermore, we discuss the oscillator strength f, which is mainly determined by TDBC concentration. We find that our proposed detector is quite sensitive with f. By changing f from 0.008 to 0.014 with the step of 0.002, the change of ?S is no less than five times the incident wavelength(2.9 μm). Our proposed structure is very sensitive to the chirality and the concentration of TDBCs and has potential applications in distinguishing the chirality detector.
基金supported by the National Natural Science Foundation of China (Grants 11272314, 51239010, 41376078)a joint project of the Chinese National Petroleum Corporation and the Chinese Academy of Sciences (Grant 2015A-4813)a project of the China Geological Survey (Grant GZH201100311)
文摘Gas hydrate(GH) dissociates owing to thermal injection or pressure reduction from the well in gas/oil or GH exploitation. GH dissociation leads to, for example, decreases in soil strength, engineering failures such as wellbore instabilities, and marine landslides. The FLAC3 D software was used to analyze the deformation of the soil stratum and vertical wells with GH dissociation. The effects of Young's modulus, internal friction angle, cohesion of the GH layer after dissociation, and the thickness of the GH layer on the deformation of soils were studied. It is shown that the maximum displacement in the whole soil stratum occurs at the interface between the GH layer and the overlayer. The deformation of the soil stratum and wells increases with decreases in the modulus, internal friction angle, and cohesion after GH dissociation. The increase in thickness of the GH layer enlarges the deformation of the soil stratum and wells with GH dissociation. The hydrostatic pressure increases the settlement of the soil stratum, while constraining horizontal displacement. The interaction between two wells becomes significant when the affected zone around each well exceeds half the length of the GH dissociation zone.
基金We thank financial support from National Natural Science Foundation of China(52061135103 and 52173296)Structure characterizations were supported by Instrumental Analysis and Research Center of Sun Yat-sen University.
文摘The dilemma for the synthesis of covalent organic frameworks(COFs)is crystallinity and stability.Herein,we present the synthesis of a single-crystalline amide-linked COF,and demonstrate its excellent chemical as well as thermal stabilities.This study will inspire the synthesis of a wide spectrum of highly crystalline and stable COFs,promote their structure-property investigations and boost their applications in selective gas adsorption,storage and separation.
基金This work was supported by the National Natural Science Foundations of China(Nos.51903058,51873042,and 51833011)Key Laboratory for Polymeric Composite and Functional Materials of Ministry of Education(No.PCFM-2922A02)Guangzhou Basic and Applied Basic Research Foundation(No.202201010382).
文摘Dynamic surface patterns(DSPs)have attracted significant interest in anti-counterfeiting,enabling information to be stored,encrypted and decrypted in response to external stimuli.However,creating dynamic surface patterns,capable of controlling wrinkling time and independently modulating different information in both wrinkled and fluorescent states,remains a tremendous challenge.These limit DSPs to further enhance tamper-proofing capacity and extend the information storage density.Here,a rationally designed patterning strategy based on controllable elastic modulus was demonstrated to fabricate self-erasable dynamic surface patterns(S-DSPs)that increase information storage density.These novel S-DSPs strategically integrated amino co-oligomers(ACOs)with the 9-anthracenemethanol(9-AM)as skin layers,designing a bilayer multi-encoding system which could carry several different types of information with wrinkled and fluorescent patterns.The ACOs with relatively low molecular weight can endow the elastic modulus of skin layers with a wide range of regulation.As a result,the difference between the compressive strain and the critical wrinkle strain in the bilayer system would be precisely modulated by photo-dimerization to form quick-response(minimum<1 min)and self-erasable(3 min–8 days)wrinkled patterns for S-DSPs.Meanwhile,the fluorescence pattern could be independently erased and reprogrammed without affecting the change in the wrinkle pattern under modulus-controlled conditions.Moreover,controllable self-erasure in S-DSPs significantly develops tamper-proof capabilities in a supply chain.This original strategy could provide a new approach to the tamper-proof,high-density,and multi-encoded information storage in the product security or inkless printing.
基金supported by the National Natural Science Foundation of China(Grant Nos.41821002,41902131)the Program of the Major Science and Technology Program(Grant No.ZD2019-183-002)。
文摘Ancient dolomite reservoirs play an increasingly important role in deep oil and gas exploration.The mechanism of formation and preservation of dolomite reservoirs is complex,which is always the key issue.With the discovery of deep oil and gas in the Ediacaran dolomites of the world,the upper Ediacaran Qigebrak Formation in the Tabei area has begun to attract attention,but its reservoir space difference and formation mechanism have yet to be clarified.Based on ultra-deep drilling cores and field outcrops in the Tabei area,the lithofacies,reservoir space,and formation mechanism are systematically analyzed by macro to micro,and qualitative to quantitative petrology:(1)The types of dolomite can be divided into five major categories,including microbial dolomite,granular dolomite,residual granular dolomite,crystalline dolomite and karst breccias.(2)The main types of reservoir space are microbial-framework pores,microbial-mold pores,and non-fabric selective dissolution pores.Spongiomicrobialite,karst breccias,and fine-grained dolomite are the dominant reservoir rock types.(3)High-frequency sedimentary cycles and meteoric dissolution are the key factors of reservoir formation.Two sets of large-scale reservoirs are present:the first set is mainly controlled by the supergene karst of the Keping movement,and the second set is mainly controlled by high-frequency sedimentary cycles in the penecontemporaneous period.The reservoirs formed at the shallow burial stage and were preserved until the deep burial stage.(4)The quality of a deep reservoir depends on the geological events that affect the processes of pore reduction and increase.Cementation,compaction and pressure solution are the main destructive diagenetic processes;however,the reservoir space can still be effectively preserved under the influence of constructive diagenetic processes,such as meteoric dissolution and early dolomitization.This research has important theoretical and practical significance for revealing the formation mechanism of upper Ediacaran deep dolomite reservoirs in the Tarim Basin.
基金This work was supported by The Natural Science Foundation of Shanghai(China)(No.21ZR1410100)The National Natural Science Foundation of China(No.81873481,81771632,81470442,81741081 and 81170147)+2 种基金The National Key Research and Development Program of China(No.2016YFC1000500)National Basic Research Program of China(973 Program)(No.2013CB945401)The Shanghai Key Laboratory of Birth Defects(China)(No.13DZ2260600).
文摘Congenital heart disease(CHD)is one of the most common causes of neonatal mortality.The worldwide morbidity of CHD is 9.410%o,while the proportion of CHD patients who are reported to carry mutations in coding regions is<50%.Enhancers play an important role in the spatio-temporal expression of target genes,and a lot of related variations are associated with CHD.There are conserved and nonconserved enhancers.
文摘Silver nanocubes enriched with {100} facets have been extensively used for surface-enhanced Raman scattering. Herein, we report a new water-phase synthesis method for weU-defined Ag nanocubes with tunable sizes via a two-step procedure at room temperature. First, irregularly shaped Ag nanoparticles （INPs） were prepared by reducing silver ammonia solution using ethylal. Second, the agglomerated INPs were selectively etched with HNO3 and C1- to yield {100} facet-rich mesoporous Ag nanocubes. The mechanism of Ag-nanocube formation and growth was investigated in detail by elucidating the involved chemical reactions and physical changes at each step during the synthesis. The addition of C1- anions was responsible for facilitating Ag nanoparticle growth by removing surface-adsorbed Ag＋ species, thereby eliminating inter-particle repulsive forces. This agglomeration was found crucial for the subsequent selective oxidation of Ag nanoparticles because the protective agent used, polyvinylpyrrolidone （PVP）, was the most effective one for adsorption on the surfaces of Ag nanoparticles of size greater than approximately 50 nm. Importantly mesopores were found inside the Ag nanocubes; this can be attributed to the unavoidable imperfect packing during the agglomeration of INPs. The newly prepared Ag nanocubes were further used to enhance the Raman signal of rhodamine 6G, which is capable of reducing the detection limitation to 10-16 mol·L-1.
基金Project supported by the National Natural Science Foundation of China(Nos.60876042,61176018,61627812)
文摘A three-dimensional thermal analysis of GaN HEMTs on diamond substrate is investigated using the finite element method. The diamond substrate thickness, area and shape, transition layer thickness and thermal conductivity of the transition layer are considered and treated appropriately in the numerical simulation. The temperature distribution and heat spreading paths are investigated under different conditions and the results indicate that the existence of the transition layer causes an increase in the channel temperature and the thickness, area and shape of the diamond substrate have certain impacts on the channel temperature too. Channel temperature reduces with increasing diamond substrate thickness and area but with a decreasing trend, which can be explained by the saturation effects of the diamond substrate. The shape of diamond substrate also affects the temperature performance of GaN HEMTs, therefore, to achieve a favorable heat dissipation effect with the settled diamond substrate area, the shape should contain as many isothermal curves as possible when the isothermal gradient is constant. The study of the thermal properties of GaN on diamond substrate is useful for the prediction of heating of high power GaN HEMTs devices and optimal designs of an efficient heat spreader for GaN HEMTs.
基金the National Natural Science Foundation of China(Nos.61571426,61671435,81630053)Beijing Natural Science Foundation(No.4161003)for financial support
文摘Superoxide dismutase(SOD) is an important antioxidant enzyme in the body. SOD has special physiological activity and is the primary substance for scavenging free radicals in living organisms.However, the expensive and complex extraction processes, low SOD yield, as well as difficult to store at room temperature have seriously hindered its application pace. Herein, the enzyme mimetic function of Mn-doped ZnS quantum dots(QDs) was discovered. The improved Marklund and McCord method both showed that Mn-doped ZnS QDs possess intrinsic SOD-like activity. The effects of temperature and pH on the mimetic enzyme activity of Mn-doped ZnS QDs have been investigated compared with SOD enzymes.The low cost and easy to synthesize white Mn-doped ZnS QDs with good biocompatibility are expected to be used as a new type of SOD nanozymes in the biology-relevant fields.
基金financially supported by the National Key Research and Development Program of China (No. 2018YFC1106600)the National Natural Science Foundation (Nos.81571778 and 51631009)the Science and Technology Plan of Shenyang (Nos.17-230-9-42 and 18-014-4-28)
文摘As a metallic orthopedic implant,316L stainless steel(316L SS)is used extensively for its good resistance to corrosion and mechanical properties.However,it takes a long time to achieve osseointegration between 316L SS and adjacent tissues due to its bio-inert characteristic.Hence,the aim is to improve the bio-adaption of 316L SS.A good approach is to add elements to materials to improve their osteogenic capabilities by the appropriate release of ions.Hence copper-containing 316L stainless steel(316L-Cu SS)was investigated in this work,where Cu is an essential trace element that can stimulates osteogenesis.It was found that 316L-Cu SS was bio-safe and did not affect the proliferation of co-cultured osteoblasts in comparison with 316L SS.It increased cell apoptosis on day 1 but inhibited it on day 3,which cooperates with new bone formation processes.Osteoblasts extend themselves more quickly and in a better manner on the surface of 316L-Cu SS,wheneven more pseudopodia are present.Furthermore,the gene expression of alkaline phosphatase,collagen I and runt-related transcription factor 2(Runx2)in osteoblasts cultured with 316L-Cu SS was significantly enhanced.Runx2 protein expression increased,and osteogenesis was stimulated by 316L-Cu SS via an Akt cell signaling pathway.In conclusion,316L-Cu SS stimulates osteogenesis through activation of the Akt cell signaling pathway and the upregulation of Runx2.Thus,316L-Cu SS is a promising material that may be used in surgical implants to stimulate osteogenesis.
基金National Natural Science Foundation of China(NSFC)(51575140,61377084)Science Fund for Distinguished Young Scholars of Harbin(RC2016JQ006007)
文摘The spectral purity of fiber lasers has become a critical issue in both optical sensing and communication fields.As a result of ultra-narrow intrinsic linewidth, stimulated thermal Rayleigh scattering(STRS) has presented special potential to compress the linewidth of fiber lasers. To suppress stimulated Brillouin scattering(SBS), the most dominant disturbance for STRS in optical fibers, a semi-quantitative estimation has been established to illuminate the mechanism of suppressing SBS in a periodic tapered fiber, and it agrees with experimental results. Finally, a linewidth compression device based on STRS is integrated into a single-longitudinal-mode ring-cavity fiber laser with secondary cavities, and its linewidth is verified to be 200 Hz through a self-heterodyne detecting and Voigt fitting method.
基金This work was supported by the National Natural Science Foundation of China(52061135103,52173296,and 51833011)the Natural Science Foundation of Guangdong Province(China)(2018A030313458)。
文摘Film plays a key role in the sustainable development of our society.Freestanding thin films of two-dimensional covalent organic frameworks(coFs)have been produced by interface,spin coating,microwave-assisted synthesis,and screen printing methods and are applied in nanofitration,molecular separation,photochemical sensing,anion transport,heat conduction,and proton conduction.On the other hand,the synthesis of their three-dimensional(3D)analogues and subsequent integration in devices remains challenging.Herein,self-supporting thin films of a three-dimensionai COF with tunable thickness was created by a stearic acid mediated synthesis methodology on water surface at room temperature in air.The film could be transferred onto arbitrary substrate,and when supported on indium tin oxide glass,it exhibited irreversible electrochromism.The optical feature made it act as a one-time anti-counterfeiting label in an electrochemical device.This work will inspire the synthesis of thin films of 3D COFs as well as other 3D materials,and boost their property and application exploration.
基金supported by the National Natural Science Foundation of China(51873239,51373204,U20A20255)the Science and Technology Project of Guangdong Province(2015B090915003,2019B040401002,2020B010182001)+2 种基金National Basic Research Program of China(2014CB643605)the Leading Scientific,Technical and Innovation Talents of Guangdong Special Support Program(2016TX03C295)the Natural Science Foundation of Guangdong Province(2114050001078)。
文摘White-light emitting(WLE) polymers have attracted continuous attention for their promising applications in solid-state lighting,flexible display and related fields. However, achieving dual-emission and pure white-light emission in a single-component polymer is still challenging. In this study, a brominated single-component polymer Br OD-TFB was designed and synthesized,which shows dual-emission and white light emission properties in solution and room-temperature phosphorescence(RTP) in thin films. The dual-emission properties can be tuned by concentration, solvent polarity, and excitation energy. Spectral analyses and theoretical calculations reveal that the origin of the high-energy emission band(HEB) is intramolecular charge transfer(ICT)along the polymer chain, whilst the low-energy emission band(LEB) originates from the excited-state related to the intra-chain and inter-chain C–Br···π interactions as demonstrated by the single-crystal structure of the model compound. Appropriate control of the formation and the destruction of the halogen-assisted interactions can initiate white-light emission in the singlecomponent polymer. More interestingly, by dispersing Br OD-TFB(0.1 wt%) in a non-emissive, colorless and transparent polymer, the characteristics of this white-light emission can be fully demonstrated while exhibiting unexpected RTP properties,with photoluminescence quantum efficiency(Φ_(PL)) of up to 23% and CIE coordinates of(0.32, 0.32).
