Varistor ceramics are typical electronic ceramics, which are widely used in circuits of overvoltage protection, high voltage stabilization and high energy surge absorption. TiO<sub>2</sub> varistor ceramic...Varistor ceramics are typical electronic ceramics, which are widely used in circuits of overvoltage protection, high voltage stabilization and high energy surge absorption. TiO<sub>2</sub> varistor ceramics has the advantages of low varistor voltage and good dielectric properties, but their low nonlinearity limited the application. The influence of annealing on the varistor properties of TiO<sub>2</sub>-Nb<sub>2</sub>O<sub>5</sub>-SrCO<sub>3</sub> ceramics was investigated in this paper. TiO<sub>2</sub>-Nb<sub>2</sub>O<sub>5</sub>-SrCO<sub>3</sub> varistor ceramics were prepared by the traditional method of ball grinding-forming-sintering and they were annealed in oxygen and nitrogen, respectively. The nonlinear coefficient <em>α</em> and the breakdown voltage <em>E</em><sub>B</sub> of the samples were tested using the varistor dc parameter meter. The microstructure of samples was analyzed by XRD, SEM, STEM-EDAX and SAEDP. The results show that during annealing, Sr<sup>2+</sup> ions with a larger radius obtain the kinetic energy and are segregated to grain boundaries, which increases the acceptor density of the grain boundaries and improves <em>α</em>. Annealing in an oxygen atmosphere, the enrichment of oxygen at grain boundaries is also helpful to increase the density of acceptor states and the height of the potential barrier, so as to further increase <em>α</em>. Meanwhile, annealing makes crystalline grains grow properly, which results in even grain size, reduces the porosity and increases the density of grains. So <em>E</em><sub>B</sub> tends to reduce. As the doping concentration of Nb<sub>2</sub>O<sub>5</sub> and SrCO<sub>3</sub> is 0.15 mol%, respectively, and sintering temperature is 1300<span style="white-space:normal;">°</span>C, TiO<sub>2</sub>-Nb<sub>2</sub>O<sub>5</sub>-SrCO<sub>3</sub> varistor ceramics annealed in oxygen for 3 h at 750<span style="white-space:normal;">°</span>C achieved the highest nonlinear coefficient <em>α</em> = 8.9 and the lowest breakdown voltage <em>E</em><sub>B展开更多
目的比较早期内镜逆行胰胆管造影术(ERCP)±内镜下十二指肠乳头括约肌切开术(EST)和保守治疗应用于急性重症胆源性胰腺炎(ASBP)的有效性及安全性。方法在Pubmed、Web of Science、Embase、Cochrane Library、中国知网数据库、万方...目的比较早期内镜逆行胰胆管造影术(ERCP)±内镜下十二指肠乳头括约肌切开术(EST)和保守治疗应用于急性重症胆源性胰腺炎(ASBP)的有效性及安全性。方法在Pubmed、Web of Science、Embase、Cochrane Library、中国知网数据库、万方数据库和维普数据库中检索有关比较早期内镜干预和保守方法治疗ASBP的随机对照研究(RCT),并使用RevMan 5.3软件分析数据。结果纳入10篇RCT,共806例患者。Meta分析结果显示,与保守治疗相比,早期内镜干预能降低ASBP总并发症发生率(OR=0.58,95%CI:0.41~0.82,P=0.002)、系统并发症发生率(O^R=0.46,95%CI:0.32~0.67,P=0.000)和胆管炎发生率(OR=0.11,95%CI:0.03~0.42,P=0.001);缩短患者腹痛持续时间(MD=-6.09,95%CI:-7.47~-4.70,P=0.000)和住院时间(MD=-10.15,95%CI:-13.20~-7.09,P=0.000);但两组患者在死亡率、多器官功能障碍综合征(MODS)发生率、呼吸衰竭发生率、局部并发症发生率、假性囊肿发生率和胰腺脓肿/坏死发生率等方面比较,差异均无统计学意义(P>0.05)。结论早期内镜干预治疗ASBP是安全可行的,且具有降低并发症发生率、缓解腹痛及缩短住院时间等优势,有望成为治疗ASBP的首选方法。展开更多
目的:观察小针刀综合治疗对膝关节炎患者疼痛及生存质量的影响,并从生物力学平衡和炎性反应因子两个方面探析小针刀的机制。方法:随机选取2014年1月至2015年10月,于我院针灸科、骨科门诊部和住院部就诊的膝关节炎患者60例,以就诊先后顺...目的:观察小针刀综合治疗对膝关节炎患者疼痛及生存质量的影响,并从生物力学平衡和炎性反应因子两个方面探析小针刀的机制。方法:随机选取2014年1月至2015年10月,于我院针灸科、骨科门诊部和住院部就诊的膝关节炎患者60例,以就诊先后顺序编号,单盲随机数字表法分为针刀组和对照组,每组各30例。对照组采用西药玻璃酸钠注射液注入膝关节腔内治疗,针刀组基于对照组基础上,采用小针刀治疗。用疼痛视觉模拟评分(Visual Simulation Score,VAS)评价小针刀对膝关节炎患者疼痛的影响,以生存质量量表-36(Items Short Form Health Survey Scale-36,SF-36)评估患者治疗后的生存质量。通过测量股骨角、胫骨角、股胫角、LT/LP值(髌韧带的长度(LT)与髌骨最大对角线长度(LP)的比值)和LT/HI值(髌韧带的长度(LT)与胫骨切迹高度(HI)的比值),分析小针刀治疗后对膝关节生物力学平衡的影响,同时结合检测膝关节腔积液中肿瘤坏死因子-α(Tumor Necrosis Factor-alpha,TNF-α)的表达情况,协同探讨小针刀治疗膝关节炎的机制。结果:针刀组治疗后VAS评分低于治疗前(t=-9.063,P=0.001<0.05);与对照组相比,针刀组评分较低(t=-7.811,P=0.003<0.05)。治疗后,针刀组SF-36量表中8个维度评分均明显提高,与治疗前和对照组治疗后比较,差异均有统计学意义(P<0.01)。2组治疗前后股骨角、胫骨角和股胫角测量结果比较,差异无统计学意义(P>0.05)。针刀组治疗后LT/LP值和LT/HI值均较治疗前有所改善,差异有统计学意义(P<0.05);对照组治疗前后均未见明显改变(P>0.05)。与对照组(52.42±4.37)pg/mL相比,治疗后针刀组TNF-α表达(34.25±3.83)pg/mL较低(t=-2.54,P=0.01<0.05)。治疗后针刀组TNF-α表达(34.25±3.83)pg/mL较治疗前(101.35±6.44)pg/mL低(t=3.14,P=0.000<0.05)。结论:小针刀综合治疗膝关节炎,松解粘连和消除挛缩,恢复膝关节生物力学平衡和降低炎性反应,减轻�展开更多
Valley Nernst effect is a newly proposed and experimentally confirmed effect,which could be used to design novel thermoelectric devices.We study the valley Nernst effect in(M+N)-layer twisted multilayer graphene syste...Valley Nernst effect is a newly proposed and experimentally confirmed effect,which could be used to design novel thermoelectric devices.We study the valley Nernst effect in(M+N)-layer twisted multilayer graphene systems by a simple low-energy effective model.It is found that the total valley Nernst coefficient(VNC)is three orders of magnitude larger than that in monolayer group-Ⅵdichalcogenides.The total VNC increases with the increase of layer numbers.It is shown that the total VNC exhibits a structure with three peaks as a function of the Fermi energy.We identify that the central peak is always negative stemming from the flat band.Two shoulder peaks are positively induced by the conduction and valence bands,respectively.These predicted features can be tested experimentally.The present work would shed more light on valley caloritronics.展开更多
目的分析家庭喂养方式与2~6岁儿童营养不足的关系,为指导科学喂养儿童提供支持,并为儿童营养不足的干预提供参考。方法采用多阶段抽样方法,于2021年选取安徽省合肥市幼儿园在园儿童3655例为研究对象,并对其家长进行问卷调查,问卷内容包...目的分析家庭喂养方式与2~6岁儿童营养不足的关系,为指导科学喂养儿童提供支持,并为儿童营养不足的干预提供参考。方法采用多阶段抽样方法,于2021年选取安徽省合肥市幼儿园在园儿童3655例为研究对象,并对其家长进行问卷调查,问卷内容包括儿童和家长的一般情况及儿童喂养问卷。该问卷用于评估家长在儿童喂养方面的行为和信念,重点调查涉及父母喂养方式的3个维度,即限制进食、逼迫进食和监督进食,共12个条目。通过建立多因素logistic回归模型分析家庭喂养方式与儿童营养不足的关系。结果安徽省合肥市2021年秋季幼儿园在园2~6岁儿童营养不足检出率为3.09%。家长采用监督的喂养方式看护的儿童营养不足检出率低于家长采用非监督的喂养方式(χ^(2)=6.672,P=0.010);家长采用逼迫的喂养方式看护的儿童营养不足检出率高于家长采用非逼迫的喂养方式(χ^(2)=14.008,P<0.001);家长是否采用限制的喂养方式照护下的儿童营养不足检出率比较差异无统计学意义(χ^(2)=0.001,P=0.974)。调整性别、出生体重、父亲体质指数(body mass index,BMI)、母亲BMI、父亲文化水平等混杂因素,家长采用监督的喂养方式是儿童营养不足的保护因素[OR(95%CI)=0.633(0.430~0.932),P=0.020];家长采用逼迫的喂养方式是儿童营养不足的危险因素[OR(95%CI)=2.104(1.328~3.335),P=0.002]。结论家庭喂养方式与2~6岁儿童营养不足发生情况有关,应提倡家长采用科学合理的喂养方式,尽最大可能降低儿童营养不足发生的风险。展开更多
Based on the hierarchical equations of motion(HEOM)calculation,we theoretically investigate the corresponding control of a triangular triple-quantum-dots(TTQD)ring which is connected to two reservoirs.We initially dem...Based on the hierarchical equations of motion(HEOM)calculation,we theoretically investigate the corresponding control of a triangular triple-quantum-dots(TTQD)ring which is connected to two reservoirs.We initially demonstrate by adding bias voltage and further adjusting the coupling strength between quantum dots,the chiral current induced by bias will go through a transformation of clockwise to counterclockwise direction and an unprecedented effective Hall angle will be triggered.The transformation is very rapid,with a corresponding characteristic time of 80-200 ps.In addition,by adding a magnetic flux to compensate for the chiral current in the original system,we elucidate the relationship between the applied magnetic flux and the Berry phase,which can realize direct measurement of the chiral current and reveal the magnetoelectric coupling relationship.展开更多
The famous strongly binary Goldbach’s conjecture asserts that every even number 2n ≥ 8 can always be expressible as a sum of two distinct odd prime numbers. We use a new approach to dealing with this conjecture. Spe...The famous strongly binary Goldbach’s conjecture asserts that every even number 2n ≥ 8 can always be expressible as a sum of two distinct odd prime numbers. We use a new approach to dealing with this conjecture. Specifically, we apply the element order prime graphs of alternating groups of degrees 2n and 2n −1 to characterize this conjecture, and present its six group-theoretic versions;and further prove that this conjecture is true for p +1 and p −1 whenever p ≥ 11 is a prime number.展开更多
文摘Varistor ceramics are typical electronic ceramics, which are widely used in circuits of overvoltage protection, high voltage stabilization and high energy surge absorption. TiO<sub>2</sub> varistor ceramics has the advantages of low varistor voltage and good dielectric properties, but their low nonlinearity limited the application. The influence of annealing on the varistor properties of TiO<sub>2</sub>-Nb<sub>2</sub>O<sub>5</sub>-SrCO<sub>3</sub> ceramics was investigated in this paper. TiO<sub>2</sub>-Nb<sub>2</sub>O<sub>5</sub>-SrCO<sub>3</sub> varistor ceramics were prepared by the traditional method of ball grinding-forming-sintering and they were annealed in oxygen and nitrogen, respectively. The nonlinear coefficient <em>α</em> and the breakdown voltage <em>E</em><sub>B</sub> of the samples were tested using the varistor dc parameter meter. The microstructure of samples was analyzed by XRD, SEM, STEM-EDAX and SAEDP. The results show that during annealing, Sr<sup>2+</sup> ions with a larger radius obtain the kinetic energy and are segregated to grain boundaries, which increases the acceptor density of the grain boundaries and improves <em>α</em>. Annealing in an oxygen atmosphere, the enrichment of oxygen at grain boundaries is also helpful to increase the density of acceptor states and the height of the potential barrier, so as to further increase <em>α</em>. Meanwhile, annealing makes crystalline grains grow properly, which results in even grain size, reduces the porosity and increases the density of grains. So <em>E</em><sub>B</sub> tends to reduce. As the doping concentration of Nb<sub>2</sub>O<sub>5</sub> and SrCO<sub>3</sub> is 0.15 mol%, respectively, and sintering temperature is 1300<span style="white-space:normal;">°</span>C, TiO<sub>2</sub>-Nb<sub>2</sub>O<sub>5</sub>-SrCO<sub>3</sub> varistor ceramics annealed in oxygen for 3 h at 750<span style="white-space:normal;">°</span>C achieved the highest nonlinear coefficient <em>α</em> = 8.9 and the lowest breakdown voltage <em>E</em><sub>B
文摘目的比较早期内镜逆行胰胆管造影术(ERCP)±内镜下十二指肠乳头括约肌切开术(EST)和保守治疗应用于急性重症胆源性胰腺炎(ASBP)的有效性及安全性。方法在Pubmed、Web of Science、Embase、Cochrane Library、中国知网数据库、万方数据库和维普数据库中检索有关比较早期内镜干预和保守方法治疗ASBP的随机对照研究(RCT),并使用RevMan 5.3软件分析数据。结果纳入10篇RCT,共806例患者。Meta分析结果显示,与保守治疗相比,早期内镜干预能降低ASBP总并发症发生率(OR=0.58,95%CI:0.41~0.82,P=0.002)、系统并发症发生率(O^R=0.46,95%CI:0.32~0.67,P=0.000)和胆管炎发生率(OR=0.11,95%CI:0.03~0.42,P=0.001);缩短患者腹痛持续时间(MD=-6.09,95%CI:-7.47~-4.70,P=0.000)和住院时间(MD=-10.15,95%CI:-13.20~-7.09,P=0.000);但两组患者在死亡率、多器官功能障碍综合征(MODS)发生率、呼吸衰竭发生率、局部并发症发生率、假性囊肿发生率和胰腺脓肿/坏死发生率等方面比较,差异均无统计学意义(P>0.05)。结论早期内镜干预治疗ASBP是安全可行的,且具有降低并发症发生率、缓解腹痛及缩短住院时间等优势,有望成为治疗ASBP的首选方法。
文摘目的:观察小针刀综合治疗对膝关节炎患者疼痛及生存质量的影响,并从生物力学平衡和炎性反应因子两个方面探析小针刀的机制。方法:随机选取2014年1月至2015年10月,于我院针灸科、骨科门诊部和住院部就诊的膝关节炎患者60例,以就诊先后顺序编号,单盲随机数字表法分为针刀组和对照组,每组各30例。对照组采用西药玻璃酸钠注射液注入膝关节腔内治疗,针刀组基于对照组基础上,采用小针刀治疗。用疼痛视觉模拟评分(Visual Simulation Score,VAS)评价小针刀对膝关节炎患者疼痛的影响,以生存质量量表-36(Items Short Form Health Survey Scale-36,SF-36)评估患者治疗后的生存质量。通过测量股骨角、胫骨角、股胫角、LT/LP值(髌韧带的长度(LT)与髌骨最大对角线长度(LP)的比值)和LT/HI值(髌韧带的长度(LT)与胫骨切迹高度(HI)的比值),分析小针刀治疗后对膝关节生物力学平衡的影响,同时结合检测膝关节腔积液中肿瘤坏死因子-α(Tumor Necrosis Factor-alpha,TNF-α)的表达情况,协同探讨小针刀治疗膝关节炎的机制。结果:针刀组治疗后VAS评分低于治疗前(t=-9.063,P=0.001<0.05);与对照组相比,针刀组评分较低(t=-7.811,P=0.003<0.05)。治疗后,针刀组SF-36量表中8个维度评分均明显提高,与治疗前和对照组治疗后比较,差异均有统计学意义(P<0.01)。2组治疗前后股骨角、胫骨角和股胫角测量结果比较,差异无统计学意义(P>0.05)。针刀组治疗后LT/LP值和LT/HI值均较治疗前有所改善,差异有统计学意义(P<0.05);对照组治疗前后均未见明显改变(P>0.05)。与对照组(52.42±4.37)pg/mL相比,治疗后针刀组TNF-α表达(34.25±3.83)pg/mL较低(t=-2.54,P=0.01<0.05)。治疗后针刀组TNF-α表达(34.25±3.83)pg/mL较治疗前(101.35±6.44)pg/mL低(t=3.14,P=0.000<0.05)。结论:小针刀综合治疗膝关节炎,松解粘连和消除挛缩,恢复膝关节生物力学平衡和降低炎性反应,减轻�
基金Project supported in part by the National Key R&D Program of China(Grant No.2018YFA0305800)the National Natural Science Foundation of China(Grant Nos.11974348 and 11834014)+2 种基金supported by the Strategic Priority Research Program of Chinese Academy of Sciences(Grant Nos.XDB28000000 and XDB33000000)supported in part by the Training Program of Major Research plan of the National Natural Science Foundation of China(Grant No.92165105)CAS Project for Young Scientists in Basic Research(Grant No.YSBR-057)。
文摘Valley Nernst effect is a newly proposed and experimentally confirmed effect,which could be used to design novel thermoelectric devices.We study the valley Nernst effect in(M+N)-layer twisted multilayer graphene systems by a simple low-energy effective model.It is found that the total valley Nernst coefficient(VNC)is three orders of magnitude larger than that in monolayer group-Ⅵdichalcogenides.The total VNC increases with the increase of layer numbers.It is shown that the total VNC exhibits a structure with three peaks as a function of the Fermi energy.We identify that the central peak is always negative stemming from the flat band.Two shoulder peaks are positively induced by the conduction and valence bands,respectively.These predicted features can be tested experimentally.The present work would shed more light on valley caloritronics.
文摘目的分析家庭喂养方式与2~6岁儿童营养不足的关系,为指导科学喂养儿童提供支持,并为儿童营养不足的干预提供参考。方法采用多阶段抽样方法,于2021年选取安徽省合肥市幼儿园在园儿童3655例为研究对象,并对其家长进行问卷调查,问卷内容包括儿童和家长的一般情况及儿童喂养问卷。该问卷用于评估家长在儿童喂养方面的行为和信念,重点调查涉及父母喂养方式的3个维度,即限制进食、逼迫进食和监督进食,共12个条目。通过建立多因素logistic回归模型分析家庭喂养方式与儿童营养不足的关系。结果安徽省合肥市2021年秋季幼儿园在园2~6岁儿童营养不足检出率为3.09%。家长采用监督的喂养方式看护的儿童营养不足检出率低于家长采用非监督的喂养方式(χ^(2)=6.672,P=0.010);家长采用逼迫的喂养方式看护的儿童营养不足检出率高于家长采用非逼迫的喂养方式(χ^(2)=14.008,P<0.001);家长是否采用限制的喂养方式照护下的儿童营养不足检出率比较差异无统计学意义(χ^(2)=0.001,P=0.974)。调整性别、出生体重、父亲体质指数(body mass index,BMI)、母亲BMI、父亲文化水平等混杂因素,家长采用监督的喂养方式是儿童营养不足的保护因素[OR(95%CI)=0.633(0.430~0.932),P=0.020];家长采用逼迫的喂养方式是儿童营养不足的危险因素[OR(95%CI)=2.104(1.328~3.335),P=0.002]。结论家庭喂养方式与2~6岁儿童营养不足发生情况有关,应提倡家长采用科学合理的喂养方式,尽最大可能降低儿童营养不足发生的风险。
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11774418,11374363,11674317,11974348,11834014,and 21373191)the Strategic Priority Research Program of CAS(Grant Nos.XDB28000000 and XDB33000000)the Training Program of Major Research Plan of NSFC(Grant No.92165105)。
文摘Based on the hierarchical equations of motion(HEOM)calculation,we theoretically investigate the corresponding control of a triangular triple-quantum-dots(TTQD)ring which is connected to two reservoirs.We initially demonstrate by adding bias voltage and further adjusting the coupling strength between quantum dots,the chiral current induced by bias will go through a transformation of clockwise to counterclockwise direction and an unprecedented effective Hall angle will be triggered.The transformation is very rapid,with a corresponding characteristic time of 80-200 ps.In addition,by adding a magnetic flux to compensate for the chiral current in the original system,we elucidate the relationship between the applied magnetic flux and the Berry phase,which can realize direct measurement of the chiral current and reveal the magnetoelectric coupling relationship.
文摘The famous strongly binary Goldbach’s conjecture asserts that every even number 2n ≥ 8 can always be expressible as a sum of two distinct odd prime numbers. We use a new approach to dealing with this conjecture. Specifically, we apply the element order prime graphs of alternating groups of degrees 2n and 2n −1 to characterize this conjecture, and present its six group-theoretic versions;and further prove that this conjecture is true for p +1 and p −1 whenever p ≥ 11 is a prime number.
