Digital light processing(DLP)is a crucial additive manufacturing(AM)technique for producing high-precision ceramic com-ponents.This study aims to optimize the formulation of Si_(3)N_(4)slurry to enhance both its perfo...Digital light processing(DLP)is a crucial additive manufacturing(AM)technique for producing high-precision ceramic com-ponents.This study aims to optimize the formulation of Si_(3)N_(4)slurry to enhance both its performance and manufacturability in the DLP process,and investigate key factors such as particle size distribution,photopolymer resin monomer ratios,and dispersant types to im-prove the slurry’s rheological properties.Through these optimizations,a photosensitive Si_(3)N_(4)slurry with 50vol%solid content was de-veloped,exhibiting excellent stability,and low viscosity(2.48 Pa·s at a shear rate of 12.8 s^(-1)).The effects of gas-pressure sintering on the material’s phase composition,microstructure,and mechanical properties were further explored,revealing that this technique significantly increases the flexural strength of the green sample from(109±10.24)to(618±42.15)MPa.The sintered ceramics exhibited high hard-ness((16.59±0.05)GPa)and improved fracture toughness((4.45±0.03)MPa·m^(1/2)).Crack trajectory analysis revealed that crack deflec-tion,crack bridging,and the pull-out of rod-likeβ-Si_(3)N_(4)grains,are the main toughening mechanisms,which could effectively mitigate crack propagation.Among these mechanisms,crack deflection and bridging were particularly influential,significantly enhancing the frac-ture toughness of the Si_(3)N_(4)matrix.Overall,this research highlights how monomer formulation and gas-pressure sintering strengthen the performance of Si_(3)N_(4)slurry in the DLP three-dimensional printing technique.This work is expected to provide new insights for fabricat-ing complex Si_(3)N_(4)ceramic components with superior mechanical properties.展开更多
Osteoarthritis （OA） is the most common degenerative joint disease and a major cause of pain and disability in adult individuals. The etiology of OA includes joint injury, obesity, aging, and heredity. However, the d...Osteoarthritis （OA） is the most common degenerative joint disease and a major cause of pain and disability in adult individuals. The etiology of OA includes joint injury, obesity, aging, and heredity. However, the detailed molecular mechanisms of OA initiation and progression remain poorly understood and, currently, there are no interventions available to restore degraded cartilage or decelerate disease progression. The diathrodial joint is a complicated organ and its function is to bear weight, perform physical activity and exhibit a joint-specific range of motion during movement. During OA development, the entire joint organ is affected, including articular cartilage, subchondral bone, synovial tissue and meniscus. A full understanding of the pathological mechanism of OA development relies on the discovery of the interplaying mechanisms among different OA symptoms, including articular cartilage degradation, osteophyte formation, subchondral sclerosis and synovial hyperplasia, and the signaling pathway（s） controlling these pathological processes.展开更多
AIM: To elucidate the mechanisms of mesenteric vasodilation in portal hypertension (PHT), with a focus on endothelin signaling. METHODS: PHT was induced in rats by common bile duct ligation (CBDL). Portal pressure (PP...AIM: To elucidate the mechanisms of mesenteric vasodilation in portal hypertension (PHT), with a focus on endothelin signaling. METHODS: PHT was induced in rats by common bile duct ligation (CBDL). Portal pressure (PP) was measured directly via catheters placed in the portal vein tract. The level of endothelin-1 (ET-1) in the mesenteric circulation was determined by radioimmunoassay, and the expression of the endothelin A receptor (ETAR) and endothelin B receptor (ETBR) was assessed by immunofluorescence and Western blot. Additionally, expression of G protein coupled kinase-2 (GRK2) and β-arrestin 2, which influence endothelin receptor sensitivity, were also studied by Western blot. RESULTS: PP of CBDL rats increased significantly (11.89 ± 1.38 mmHg vs 16.34 ± 1.63 mmHg). ET-1 expression decreased in the mesenteric circulation 2 and 4 wk after CBDL. ET-1 levels in the systemic circulation of CBDL rats were increased at 2 wk and decreased at 4 wk. There was no change in ETAR expression in response to CBDL; however, increased expression of ETBR in the endothelial cells of mesenteric arterioles and capillaries was observed. In sham-operated rats, ETBR was mainly expressed in the CD31+ endothelial cells of the arterioles. With development of PHT, in addition to the endothelial cells, ETBR expression was noticeably detectable in the SMA+ smooth muscle cells of arterioles and in the CD31+ capillaries. Following CBDL, increased expression of GRK2 was also found in mesenteric tissue, though there was no change in the level of β-arrestin 2. CONCLUSION: Decreased levels of ET-1 and increased ETBR expression in the mesenteric circulation following CBDL in rats may underlie mesenteric vasodilation in individuals with PHT. Mechanistically, increased GRK2 expression may lead to desensitization of ETAR, as well as other vasoconstrictors, promoting this vasodilatory effect.展开更多
Objectives:To examine the relationship between cardiovascular disease risk factors and frailty in a sample of older Chinese adults.Methods:A total of 458 community-dwelling older adults(>65 years)in Lanzhou,Gansu P...Objectives:To examine the relationship between cardiovascular disease risk factors and frailty in a sample of older Chinese adults.Methods:A total of 458 community-dwelling older adults(>65 years)in Lanzhou,Gansu Province of China participated in a cross-sectional survey.Their status was evaluated in terms of frailty phenotype(unintentional weight loss,exhaustion,low activity levels,slowness and weakness).Participants were categorized as not frail,prefrail or frail.Cardiovascular disease risk factors that were assessed included:blood pressure,body mass index,waist circumference,blood glucose,total cholesterol,triglycerides,lowdensity lipoproteins and high-density lipoproteins.Results:Individuals with obesity had an increased risk of prefrailty(OR:2.26;95%CI:1.05,4.84).Hypertension was inversely associated with frailtyamong the participants(OR:0.31;95%CI:0.11,0.87)after adjusting for covariates.Conclusions:The findings suggest that much more attention should be paid to weight control of the elderly in the community for preventing them from transition to prefrailty or frailty.Active prevention and control of cardiovascular diseases among the community-dwelling elder are still of great importance.展开更多
The design synthesis is the key issue in the mechanical conceptual design to generate the design candidates that meet the design requirements.This paper devotes to propose a novel and computable synthesis approach of ...The design synthesis is the key issue in the mechanical conceptual design to generate the design candidates that meet the design requirements.This paper devotes to propose a novel and computable synthesis approach of mechanisms based on graph theory and polynomial operation.The graph framework of the synthesis approach is built firstly,and it involves:(1)the kinematic function units extracted from mechanisms;(2)the kinematic link graph that transforms the synthesis problem from mechanical domain into graph domain;(3)two graph representations,i.e.,walk representation and path representation,of design candidates;(4)a weighted matrix theorem that transforms the synthesis process into polynomial operation.Then,the formulas and algorithm to the polynomial operation are presented.Based on them,the computational flowchart to the synthesis approach is summarized.A design example is used to validate and illustrate the synthesis approach in detail.The proposed synthesis approach is not only supportive to enumerate the design candidates to the conceptual design of a mechanical system exhaustively and automatically,but also helpful to make that enumeration process computable.展开更多
Folate-containing dextran ligand （FA-Dextran-DTPA） was synthesized by the incorporation of diethylenetriamine- pentaacetic acid （DTPA） and folate （FA） as a tumor-targeting group into dextran as a polymer carrier...Folate-containing dextran ligand （FA-Dextran-DTPA） was synthesized by the incorporation of diethylenetriamine- pentaacetic acid （DTPA） and folate （FA） as a tumor-targeting group into dextran as a polymer carrier. This ligand was further reacted with gadolinium chloride to make a dextran gadolinium complex FA-Dextran-DTPA-Gd. The ligand and its gadolinium complex were characterized by 1H-NMR, FTIR, UV-Vis, average particle sizes and zeta potential, as well. In vitro properties including relaxivity, cytotoxicity assay, cellular uptake assay, and magnetic resonance imaging （MRI） were also evaluated. Compared with Gd-DTPA, FA-Dextran-DTPA-Gd possessed obviously higher relaxation effectiveness and lower cytotoxicity to HeLa cells. FA-Dextran-DTPA-Gd had a high affinity to the H460 and MDA-MB-231 tumor cells and can be taken up selectively by these tumor cells. Moreover, FA-Dextran-DTPA-Gd showed enhanced signal intensities （SI） of MRI and enhanced the contrast of MR images of tumor cells. These results indicated that FA-Dextran-DTPA-Gd showed the potential as a tumor-targeting contrast agent in MRI.展开更多
目的观察多模态磁共振成像(MRI)和计算机体层摄影(CT)检查对超时间窗或发病时间不明急性缺血性脑卒中(AIS)患者总体疗效及预后的影响。方法回顾性分析80例超时间窗或发病时间不明AIS患者的临床资料。比较行多模态MRI检查(MRI组)与行多模...目的观察多模态磁共振成像(MRI)和计算机体层摄影(CT)检查对超时间窗或发病时间不明急性缺血性脑卒中(AIS)患者总体疗效及预后的影响。方法回顾性分析80例超时间窗或发病时间不明AIS患者的临床资料。比较行多模态MRI检查(MRI组)与行多模态CT检查(CT组)的一般临床资料、检查时效性与治疗效果。对比分析MRI组与CT组中接受血管内治疗(EVT)的患者;再灌注治疗病例(再灌注治疗组)与内科常规治疗病例(内科常规治疗组)的预后情况。结果MRI组检查时间较CT组长(P<0.001)。但两组疗效及两组中接受EVT治疗的患者疗效差异均无统计学意义(P>0.05)。MRI组磁敏感成像(SWI)发现14例存在磁敏感血管征(包括5例双层磁敏感血管征),提示心源性血栓,23例存在微出血灶,CT组在血栓特征及微出血检测方面未发现具有诊断意义的相应征象(P<0.001)。再灌注治疗组患者的预后(90 d mRS评分)优于内科常规治疗组(P<0.05)。结论多模态MRI评估超时间窗或发病时间不明AIS临床结局与多模态CT相当,但其可提供更全面的影像学证据。展开更多
基金supported in part by the National Natural Science Foundation of China.(Nos.62461160259,92360307 and 92267103).
文摘Digital light processing(DLP)is a crucial additive manufacturing(AM)technique for producing high-precision ceramic com-ponents.This study aims to optimize the formulation of Si_(3)N_(4)slurry to enhance both its performance and manufacturability in the DLP process,and investigate key factors such as particle size distribution,photopolymer resin monomer ratios,and dispersant types to im-prove the slurry’s rheological properties.Through these optimizations,a photosensitive Si_(3)N_(4)slurry with 50vol%solid content was de-veloped,exhibiting excellent stability,and low viscosity(2.48 Pa·s at a shear rate of 12.8 s^(-1)).The effects of gas-pressure sintering on the material’s phase composition,microstructure,and mechanical properties were further explored,revealing that this technique significantly increases the flexural strength of the green sample from(109±10.24)to(618±42.15)MPa.The sintered ceramics exhibited high hard-ness((16.59±0.05)GPa)and improved fracture toughness((4.45±0.03)MPa·m^(1/2)).Crack trajectory analysis revealed that crack deflec-tion,crack bridging,and the pull-out of rod-likeβ-Si_(3)N_(4)grains,are the main toughening mechanisms,which could effectively mitigate crack propagation.Among these mechanisms,crack deflection and bridging were particularly influential,significantly enhancing the frac-ture toughness of the Si_(3)N_(4)matrix.Overall,this research highlights how monomer formulation and gas-pressure sintering strengthen the performance of Si_(3)N_(4)slurry in the DLP three-dimensional printing technique.This work is expected to provide new insights for fabricat-ing complex Si_(3)N_(4)ceramic components with superior mechanical properties.
基金supported by NIH grants AR055915 and AR054465 to DC
文摘Osteoarthritis （OA） is the most common degenerative joint disease and a major cause of pain and disability in adult individuals. The etiology of OA includes joint injury, obesity, aging, and heredity. However, the detailed molecular mechanisms of OA initiation and progression remain poorly understood and, currently, there are no interventions available to restore degraded cartilage or decelerate disease progression. The diathrodial joint is a complicated organ and its function is to bear weight, perform physical activity and exhibit a joint-specific range of motion during movement. During OA development, the entire joint organ is affected, including articular cartilage, subchondral bone, synovial tissue and meniscus. A full understanding of the pathological mechanism of OA development relies on the discovery of the interplaying mechanisms among different OA symptoms, including articular cartilage degradation, osteophyte formation, subchondral sclerosis and synovial hyperplasia, and the signaling pathway（s） controlling these pathological processes.
基金Supported by Grant from National Key New Drug Creation Project of China, No. 2009ZX09102
文摘AIM: To elucidate the mechanisms of mesenteric vasodilation in portal hypertension (PHT), with a focus on endothelin signaling. METHODS: PHT was induced in rats by common bile duct ligation (CBDL). Portal pressure (PP) was measured directly via catheters placed in the portal vein tract. The level of endothelin-1 (ET-1) in the mesenteric circulation was determined by radioimmunoassay, and the expression of the endothelin A receptor (ETAR) and endothelin B receptor (ETBR) was assessed by immunofluorescence and Western blot. Additionally, expression of G protein coupled kinase-2 (GRK2) and β-arrestin 2, which influence endothelin receptor sensitivity, were also studied by Western blot. RESULTS: PP of CBDL rats increased significantly (11.89 ± 1.38 mmHg vs 16.34 ± 1.63 mmHg). ET-1 expression decreased in the mesenteric circulation 2 and 4 wk after CBDL. ET-1 levels in the systemic circulation of CBDL rats were increased at 2 wk and decreased at 4 wk. There was no change in ETAR expression in response to CBDL; however, increased expression of ETBR in the endothelial cells of mesenteric arterioles and capillaries was observed. In sham-operated rats, ETBR was mainly expressed in the CD31+ endothelial cells of the arterioles. With development of PHT, in addition to the endothelial cells, ETBR expression was noticeably detectable in the SMA+ smooth muscle cells of arterioles and in the CD31+ capillaries. Following CBDL, increased expression of GRK2 was also found in mesenteric tissue, though there was no change in the level of β-arrestin 2. CONCLUSION: Decreased levels of ET-1 and increased ETBR expression in the mesenteric circulation following CBDL in rats may underlie mesenteric vasodilation in individuals with PHT. Mechanistically, increased GRK2 expression may lead to desensitization of ETAR, as well as other vasoconstrictors, promoting this vasodilatory effect.
基金supported by the National Natural Science Foundation of China[grant number 71804064].
文摘Objectives:To examine the relationship between cardiovascular disease risk factors and frailty in a sample of older Chinese adults.Methods:A total of 458 community-dwelling older adults(>65 years)in Lanzhou,Gansu Province of China participated in a cross-sectional survey.Their status was evaluated in terms of frailty phenotype(unintentional weight loss,exhaustion,low activity levels,slowness and weakness).Participants were categorized as not frail,prefrail or frail.Cardiovascular disease risk factors that were assessed included:blood pressure,body mass index,waist circumference,blood glucose,total cholesterol,triglycerides,lowdensity lipoproteins and high-density lipoproteins.Results:Individuals with obesity had an increased risk of prefrailty(OR:2.26;95%CI:1.05,4.84).Hypertension was inversely associated with frailtyamong the participants(OR:0.31;95%CI:0.11,0.87)after adjusting for covariates.Conclusions:The findings suggest that much more attention should be paid to weight control of the elderly in the community for preventing them from transition to prefrailty or frailty.Active prevention and control of cardiovascular diseases among the community-dwelling elder are still of great importance.
基金Supported by State Key Program of National Natural Science Foundation of China(Grant No.51535009)111 Project of China(Grant No.B13044).
文摘The design synthesis is the key issue in the mechanical conceptual design to generate the design candidates that meet the design requirements.This paper devotes to propose a novel and computable synthesis approach of mechanisms based on graph theory and polynomial operation.The graph framework of the synthesis approach is built firstly,and it involves:(1)the kinematic function units extracted from mechanisms;(2)the kinematic link graph that transforms the synthesis problem from mechanical domain into graph domain;(3)two graph representations,i.e.,walk representation and path representation,of design candidates;(4)a weighted matrix theorem that transforms the synthesis process into polynomial operation.Then,the formulas and algorithm to the polynomial operation are presented.Based on them,the computational flowchart to the synthesis approach is summarized.A design example is used to validate and illustrate the synthesis approach in detail.The proposed synthesis approach is not only supportive to enumerate the design candidates to the conceptual design of a mechanical system exhaustively and automatically,but also helpful to make that enumeration process computable.
基金financially supported by the National Natural Science Foundation of China(Nos.51173140 and 51373128)Wuhan Scientific and Technological Project(No.2013010501010131)+1 种基金Wuhan Science and Technology Innovation Team of Hi-tech Industrial Project,Hubei Province(No.2015070504020217)Innovation Fund for Post-graduate Education(Nos.CX2014058 and CX2013083),Wuhan Institute of Technology,China
文摘Folate-containing dextran ligand （FA-Dextran-DTPA） was synthesized by the incorporation of diethylenetriamine- pentaacetic acid （DTPA） and folate （FA） as a tumor-targeting group into dextran as a polymer carrier. This ligand was further reacted with gadolinium chloride to make a dextran gadolinium complex FA-Dextran-DTPA-Gd. The ligand and its gadolinium complex were characterized by 1H-NMR, FTIR, UV-Vis, average particle sizes and zeta potential, as well. In vitro properties including relaxivity, cytotoxicity assay, cellular uptake assay, and magnetic resonance imaging （MRI） were also evaluated. Compared with Gd-DTPA, FA-Dextran-DTPA-Gd possessed obviously higher relaxation effectiveness and lower cytotoxicity to HeLa cells. FA-Dextran-DTPA-Gd had a high affinity to the H460 and MDA-MB-231 tumor cells and can be taken up selectively by these tumor cells. Moreover, FA-Dextran-DTPA-Gd showed enhanced signal intensities （SI） of MRI and enhanced the contrast of MR images of tumor cells. These results indicated that FA-Dextran-DTPA-Gd showed the potential as a tumor-targeting contrast agent in MRI.
文摘目的观察多模态磁共振成像(MRI)和计算机体层摄影(CT)检查对超时间窗或发病时间不明急性缺血性脑卒中(AIS)患者总体疗效及预后的影响。方法回顾性分析80例超时间窗或发病时间不明AIS患者的临床资料。比较行多模态MRI检查(MRI组)与行多模态CT检查(CT组)的一般临床资料、检查时效性与治疗效果。对比分析MRI组与CT组中接受血管内治疗(EVT)的患者;再灌注治疗病例(再灌注治疗组)与内科常规治疗病例(内科常规治疗组)的预后情况。结果MRI组检查时间较CT组长(P<0.001)。但两组疗效及两组中接受EVT治疗的患者疗效差异均无统计学意义(P>0.05)。MRI组磁敏感成像(SWI)发现14例存在磁敏感血管征(包括5例双层磁敏感血管征),提示心源性血栓,23例存在微出血灶,CT组在血栓特征及微出血检测方面未发现具有诊断意义的相应征象(P<0.001)。再灌注治疗组患者的预后(90 d mRS评分)优于内科常规治疗组(P<0.05)。结论多模态MRI评估超时间窗或发病时间不明AIS临床结局与多模态CT相当,但其可提供更全面的影像学证据。
