Due to their unique properties and appealing applications,low dimensional sp^(3)carbon nanostructures have attracted increasing attention recently.Based on the beam theory and atomistic studies,this work carries out a...Due to their unique properties and appealing applications,low dimensional sp^(3)carbon nanostructures have attracted increasing attention recently.Based on the beam theory and atomistic studies,this work carries out a comprehensive investigation on the vibrational properties of the ultrathin carbon nanothreads(NTH).Size effect is observed in transverse free vibrations of NTHs.To quantify such effects,the modified couple stress theory(MCST)is utilized to modify the Timoshenko beam theory.According to the first four order frequencies of NTHs from atomistic simulations,the critical length scale parameter of MCST is calibrated as 0.1 nm.It is shown that MCST has minor effect on the first four order modal shapes,except for the clamped boundary.MCST makes the modal shapes at the clamped boundary closer to those observed in atomistic simulations.This study suggests that to some extent the MCST-based Timoshenko beam theory can well describe the transverse vibration characteristics of the ultrafine NTHs,which are helpful for designing and fabricating the NTH-based nanoscale mechanical resonators.展开更多
Human dental pulp stem cell transplantation has been shown to be an effective therapeutic strategy for spinal cord injury.However,whether the human dental pulp stem cell secretome can contribute to functional recovery...Human dental pulp stem cell transplantation has been shown to be an effective therapeutic strategy for spinal cord injury.However,whether the human dental pulp stem cell secretome can contribute to functional recovery after spinal cord injury remains unclear.In the present study,we established a rat model of spinal cord injury based on impact injury from a dropped weight and then intraperitoneally injected the rats with conditioned medium from human dental pulp stem cells.We found that the conditioned medium effectively promoted the recovery of sensory and motor functions in rats with spinal cord injury,decreased expression of the microglial pyroptosis markers NLRP3,GSDMD,caspase-1,and interleukin-1β,promoted axonal and myelin regeneration,and inhibited the formation of glial scars.In addition,in a lipopolysaccharide-induced BV2 microglia model,conditioned medium from human dental pulp stem cells protected cells from pyroptosis by inhibiting the NLRP3/caspase-1/interleukin-1βpathway.These results indicate that conditioned medium from human dental pulp stem cells can reduce microglial pyroptosis by inhibiting the NLRP3/caspase-1/interleukin-1βpathway,thereby promoting the recovery of neurological function after spinal cord injury.Therefore,conditioned medium from human dental pulp stem cells may become an alternative therapy for spinal cord injury.展开更多
microRNAs(miRNAs)是一类小RNA分子,在植物和动物的基因表达调控中发挥着重要作用,miRNAs不参与蛋白质的直接合成,而是转录后基因表达的重要调控因子。它们不仅在身体发育中起着关键作用,也是细胞周期、凋亡和分化的关键调节因子。成熟m...microRNAs(miRNAs)是一类小RNA分子,在植物和动物的基因表达调控中发挥着重要作用,miRNAs不参与蛋白质的直接合成,而是转录后基因表达的重要调控因子。它们不仅在身体发育中起着关键作用,也是细胞周期、凋亡和分化的关键调节因子。成熟miRNAs的产生需要几个关键步骤。首先,在细胞核中经由RNA polymerase II(PolII)转录完成聚腺苷酸化和封顶产生primary mi RNAs(Pri-miRNAs)。Pri-miRNAs通过Drosha/DGCR8复合物进一步加工合成hairpin precursor mi RNAs(pre-miRNAs)。Pre-miRNAs通过输出蛋白5(XPO5)输出到细胞质中,并被Dicer切割,在这一过程进行末端环的切割后形成成熟的miRNAs。miRNAs以互补序列结合靶mRNA,发挥调控作用。研究表明,超过30%的蛋白质编码基因受miRNAs调控。miRNAs的失调和功能障碍与人类疾病有关,miRNAs的异常表达被认为是癌症发生的重要过程。本文就microRNAs在妇科肿瘤发生发展中的研究现状进行综述。展开更多
目的探讨体质量指数(BMI)与腔隙性脑梗死患者预后的关系。方法纳入中国脑卒中管理质量评估登记研究(China Quality Evaluation of Stroke Care and Treatment)数据库中TOAST分型为腔隙性脑梗死的患者3410例,其中低体质量组(BMI<18.5k...目的探讨体质量指数(BMI)与腔隙性脑梗死患者预后的关系。方法纳入中国脑卒中管理质量评估登记研究(China Quality Evaluation of Stroke Care and Treatment)数据库中TOAST分型为腔隙性脑梗死的患者3410例,其中低体质量组(BMI<18.5kg/m^2)182例、正常体质量组(BMI 18.5~23.9kg/m^2)1639例、超重组(BMI24.0~27.9kg/m^2)1212例和肥胖组(BMI≥28.0kg/m^2)377例。终点事件包括12个月时全因死亡、死亡或严重残疾、感染并发症和脑卒中复发。结果与正常体质量组比较,低体质量组12个月时累计全因死亡率升高(19.1%vs 6.7%,P<0.01),超重组和肥胖组变化无显著差异(6.0%和3.8%vs 6.7%,P>0.05)。多因素分析显示,以正常体质量组为参照,低体质量组12个月累计全因死亡(HR=1.91,95%CI:1.22~2.98,P=0.004)、12个月时死亡或严重残疾(OR=1.50,95%CI:1.05~2.14,P=0.026)及感染并发症(OR=1.92,95%CI:1.21~3.06,P=0.006)的风险更高,脑卒中复发风险无显著差异;超重组和肥胖组患者发生上述终点事件的风险无显著差异。结论腔隙性脑梗死患者中,低体质量伴随脑卒中预后不良风险升高,但脑卒中复发的风险无显著改变。展开更多
In this work,we have searched for quasi-periodic oscillations(QPOs)in the 15 GHz light curve of the FSRQ PKS J0805-0111 monitored by the Owens Valley Radio Observatory(OVRO)40 m telescope during the period from 2008 J...In this work,we have searched for quasi-periodic oscillations(QPOs)in the 15 GHz light curve of the FSRQ PKS J0805-0111 monitored by the Owens Valley Radio Observatory(OVRO)40 m telescope during the period from 2008 January 9 to 2019 May 9,using the weighted wavelet Z-transform(WWZ)and the Lomb-Scargle Periodogram(LSP)techniques.This is the first time to search for a periodic radio signal in the FSRQ PKS J0805-0111 by these two methods.Both methods consistently reveal a repeating signal with a periodicity of 3.38±0.8 yr(>99.7%confidence level).In order to determine the significance of the periods,the false alarm probability method was applied,and a large number of Monte Carlo simulations were performed.As possible explanations,we discuss a number of scenarios including the thermal instability of thin disks scenario,the spiral jet scenario and the binary supermassive black hole scenario.We expect that the binary black hole scenario,where the QPO is caused by the precession of binary black holes,is the most likely explanation.FSRQ PKS J0805-0111 thus could be a good binary black hole candidate.In the binary black hole scenario,the distance between the primary black hole and the secondary black hole is about 1.71×10^(16) cm.展开更多
Small mammals have been proposed playing an important role in the energy flow and regeneration of forest ecosystems. We compared species richness, diversity (H’) of small mammal communities and abundance of six domin...Small mammals have been proposed playing an important role in the energy flow and regeneration of forest ecosystems. We compared species richness, diversity (H’) of small mammal communities and abundance of six dominant species of small mammals in disturbed and protected forests (four age classes: 6 - 10, 11 - 15, 16 - 20 and 31 - 40 years old) in China. We also investigated the structural variables (such as species richness, cover rate and abundance of shrubs and grasses) in the bottom layer, which considered to be important for small mammals and might be altered by human disturbance. The relationships between small mammals and these structural variables were examined to determine the potential effects of human disturbance on the small mammals in the restored forests. Our results indicated that the structure and composition of the vegetation in the bottom layer were simplified by human disturbance, while the abundance and cover rate of grasses were significantly increased. Although no significant differences were observed in species richness of small mammals between the protected and disturbed forests at the same age, the diversity index of small mammals in the protected forests was always significantly higher than in the disturbed forests. Regression showed that the species richness and diversity of small mammals increased with the species richness of shrubs, and was negatively correlated to the cover rate of grasses in the bottom layer. Human disturbance increased the total abundance of small mammals, and the increased cover rate of grasses in the bottom layer was beneficial to the abundance of small mammals. Obvious succession of small mammal communities occurred as the protected forest aged. In the protected forests, small ground-dwelling mammals (A. chevrieri, E. miletus and M. pahari) were the dominant species in the younger forests. Other mammals (T. belangeri, D. pernyi and C. erythraeus) gradually became the dominant species as the protected forests aged. However, in the disturbed forests, the smaller ground-dwelling mammals (T. belangeri, D. pernyi and C. erythraeus) were always the dominant species at all ages of the disturbed forests. Regression indicated that the cover rate of grasses in the bottom layer was beneficial to the three smaller body size and ground-dwelling small mammal species, while the shrubs were beneficial to the three bigger body size mammal species.展开更多
基金the National Natural Science Foundation of China(Grant No.12102176)the China Postdoctoral Science Foundation(Grant No.2022M711617)+1 种基金the Natural Science Foundation of Jiangsu Province of China(Grant No.BK20210274)Partially supported by the High Performance Computing Platform of Nanjing University of Aeronautics and Astronautics。
文摘Due to their unique properties and appealing applications,low dimensional sp^(3)carbon nanostructures have attracted increasing attention recently.Based on the beam theory and atomistic studies,this work carries out a comprehensive investigation on the vibrational properties of the ultrathin carbon nanothreads(NTH).Size effect is observed in transverse free vibrations of NTHs.To quantify such effects,the modified couple stress theory(MCST)is utilized to modify the Timoshenko beam theory.According to the first four order frequencies of NTHs from atomistic simulations,the critical length scale parameter of MCST is calibrated as 0.1 nm.It is shown that MCST has minor effect on the first four order modal shapes,except for the clamped boundary.MCST makes the modal shapes at the clamped boundary closer to those observed in atomistic simulations.This study suggests that to some extent the MCST-based Timoshenko beam theory can well describe the transverse vibration characteristics of the ultrafine NTHs,which are helpful for designing and fabricating the NTH-based nanoscale mechanical resonators.
基金supported by the Research Foundation of Technology Committee of Tongzhou District,No.KJ2019CX001(to SX).
文摘Human dental pulp stem cell transplantation has been shown to be an effective therapeutic strategy for spinal cord injury.However,whether the human dental pulp stem cell secretome can contribute to functional recovery after spinal cord injury remains unclear.In the present study,we established a rat model of spinal cord injury based on impact injury from a dropped weight and then intraperitoneally injected the rats with conditioned medium from human dental pulp stem cells.We found that the conditioned medium effectively promoted the recovery of sensory and motor functions in rats with spinal cord injury,decreased expression of the microglial pyroptosis markers NLRP3,GSDMD,caspase-1,and interleukin-1β,promoted axonal and myelin regeneration,and inhibited the formation of glial scars.In addition,in a lipopolysaccharide-induced BV2 microglia model,conditioned medium from human dental pulp stem cells protected cells from pyroptosis by inhibiting the NLRP3/caspase-1/interleukin-1βpathway.These results indicate that conditioned medium from human dental pulp stem cells can reduce microglial pyroptosis by inhibiting the NLRP3/caspase-1/interleukin-1βpathway,thereby promoting the recovery of neurological function after spinal cord injury.Therefore,conditioned medium from human dental pulp stem cells may become an alternative therapy for spinal cord injury.
文摘microRNAs(miRNAs)是一类小RNA分子,在植物和动物的基因表达调控中发挥着重要作用,miRNAs不参与蛋白质的直接合成,而是转录后基因表达的重要调控因子。它们不仅在身体发育中起着关键作用,也是细胞周期、凋亡和分化的关键调节因子。成熟miRNAs的产生需要几个关键步骤。首先,在细胞核中经由RNA polymerase II(PolII)转录完成聚腺苷酸化和封顶产生primary mi RNAs(Pri-miRNAs)。Pri-miRNAs通过Drosha/DGCR8复合物进一步加工合成hairpin precursor mi RNAs(pre-miRNAs)。Pre-miRNAs通过输出蛋白5(XPO5)输出到细胞质中,并被Dicer切割,在这一过程进行末端环的切割后形成成熟的miRNAs。miRNAs以互补序列结合靶mRNA,发挥调控作用。研究表明,超过30%的蛋白质编码基因受miRNAs调控。miRNAs的失调和功能障碍与人类疾病有关,miRNAs的异常表达被认为是癌症发生的重要过程。本文就microRNAs在妇科肿瘤发生发展中的研究现状进行综述。
文摘目的探讨体质量指数(BMI)与腔隙性脑梗死患者预后的关系。方法纳入中国脑卒中管理质量评估登记研究(China Quality Evaluation of Stroke Care and Treatment)数据库中TOAST分型为腔隙性脑梗死的患者3410例,其中低体质量组(BMI<18.5kg/m^2)182例、正常体质量组(BMI 18.5~23.9kg/m^2)1639例、超重组(BMI24.0~27.9kg/m^2)1212例和肥胖组(BMI≥28.0kg/m^2)377例。终点事件包括12个月时全因死亡、死亡或严重残疾、感染并发症和脑卒中复发。结果与正常体质量组比较,低体质量组12个月时累计全因死亡率升高(19.1%vs 6.7%,P<0.01),超重组和肥胖组变化无显著差异(6.0%和3.8%vs 6.7%,P>0.05)。多因素分析显示,以正常体质量组为参照,低体质量组12个月累计全因死亡(HR=1.91,95%CI:1.22~2.98,P=0.004)、12个月时死亡或严重残疾(OR=1.50,95%CI:1.05~2.14,P=0.026)及感染并发症(OR=1.92,95%CI:1.21~3.06,P=0.006)的风险更高,脑卒中复发风险无显著差异;超重组和肥胖组患者发生上述终点事件的风险无显著差异。结论腔隙性脑梗死患者中,低体质量伴随脑卒中预后不良风险升高,但脑卒中复发的风险无显著改变。
基金supported by the National Natural Science Foundation of China(Grant No.11663009)the High-Energy Astrophysics Science and Technology Innovation Team of Yunnan Higher School+1 种基金the OVRO40-m monitoring program(Fan&Wu 2018)which is supported in part by NASA grants NNX08AW31GNNX11A043G and NNX14AQ89G,and NSF grants AST-0808050 and AST-1109911。
文摘In this work,we have searched for quasi-periodic oscillations(QPOs)in the 15 GHz light curve of the FSRQ PKS J0805-0111 monitored by the Owens Valley Radio Observatory(OVRO)40 m telescope during the period from 2008 January 9 to 2019 May 9,using the weighted wavelet Z-transform(WWZ)and the Lomb-Scargle Periodogram(LSP)techniques.This is the first time to search for a periodic radio signal in the FSRQ PKS J0805-0111 by these two methods.Both methods consistently reveal a repeating signal with a periodicity of 3.38±0.8 yr(>99.7%confidence level).In order to determine the significance of the periods,the false alarm probability method was applied,and a large number of Monte Carlo simulations were performed.As possible explanations,we discuss a number of scenarios including the thermal instability of thin disks scenario,the spiral jet scenario and the binary supermassive black hole scenario.We expect that the binary black hole scenario,where the QPO is caused by the precession of binary black holes,is the most likely explanation.FSRQ PKS J0805-0111 thus could be a good binary black hole candidate.In the binary black hole scenario,the distance between the primary black hole and the secondary black hole is about 1.71×10^(16) cm.
文摘Small mammals have been proposed playing an important role in the energy flow and regeneration of forest ecosystems. We compared species richness, diversity (H’) of small mammal communities and abundance of six dominant species of small mammals in disturbed and protected forests (four age classes: 6 - 10, 11 - 15, 16 - 20 and 31 - 40 years old) in China. We also investigated the structural variables (such as species richness, cover rate and abundance of shrubs and grasses) in the bottom layer, which considered to be important for small mammals and might be altered by human disturbance. The relationships between small mammals and these structural variables were examined to determine the potential effects of human disturbance on the small mammals in the restored forests. Our results indicated that the structure and composition of the vegetation in the bottom layer were simplified by human disturbance, while the abundance and cover rate of grasses were significantly increased. Although no significant differences were observed in species richness of small mammals between the protected and disturbed forests at the same age, the diversity index of small mammals in the protected forests was always significantly higher than in the disturbed forests. Regression showed that the species richness and diversity of small mammals increased with the species richness of shrubs, and was negatively correlated to the cover rate of grasses in the bottom layer. Human disturbance increased the total abundance of small mammals, and the increased cover rate of grasses in the bottom layer was beneficial to the abundance of small mammals. Obvious succession of small mammal communities occurred as the protected forest aged. In the protected forests, small ground-dwelling mammals (A. chevrieri, E. miletus and M. pahari) were the dominant species in the younger forests. Other mammals (T. belangeri, D. pernyi and C. erythraeus) gradually became the dominant species as the protected forests aged. However, in the disturbed forests, the smaller ground-dwelling mammals (T. belangeri, D. pernyi and C. erythraeus) were always the dominant species at all ages of the disturbed forests. Regression indicated that the cover rate of grasses in the bottom layer was beneficial to the three smaller body size and ground-dwelling small mammal species, while the shrubs were beneficial to the three bigger body size mammal species.
