We investigate the rotating wave approximation applied in the high-spin quantum system driven by a linearly polarized alternating magnetic field in the presence of quadrupole interactions.The conventional way to apply...We investigate the rotating wave approximation applied in the high-spin quantum system driven by a linearly polarized alternating magnetic field in the presence of quadrupole interactions.The conventional way to apply the rotating wave approximation in a driven high-spin system is to assume the dynamics being restricted in the reduced Hilbert space.However,when the driving strength is relatively strong or the driving is off resonant,the leakage from the target resonance subspace cannot be neglected for a multi-level quantum system.We propose the correct formalism to apply the rotating wave approximation in the full Hilbert space by taking this leakage into account.By estimating the operator fidelity of the time propagator,our formalism applied in the full Hilbert space unambiguously manifests great advantages over the conventional method applied in the reduced Hilbert space.展开更多
目的分析北京城区与农村老年人群的股骨近段骨密度(bone mineral density,BMD)与骨结构参数差异。方法回顾性分析2012年12月1日至2013年12月1日接受髋部定量CT(quantitative computed tomography,QCT)扫描的174名50~70岁的北京居民的相...目的分析北京城区与农村老年人群的股骨近段骨密度(bone mineral density,BMD)与骨结构参数差异。方法回顾性分析2012年12月1日至2013年12月1日接受髋部定量CT(quantitative computed tomography,QCT)扫描的174名50~70岁的北京居民的相关临床资料,根据居住地分为城区组(n=118)(男性46名、女性72名)和农村组(n=56)(男性31名、女性25名)。统计学分析由QCT测得的股骨颈体积骨密度(femoral neck volumetric bone mineral density,FN v BMD)、全髋体积骨密度(total hip volumetric bone mineral density,TH v BMD)、股骨颈面积骨密度(femoral neck areal bone mineral density,FN a BMD)、股骨大粗隆面积骨密度(trochanter areal bone mineral density,TR a BMD)、股骨粗隆间面积骨密度(intertrochanter areal bone mineral density,IT a BMD)和全髋面积骨密度(total hip areal bone mineral density,TH a BMD)等参数以及股骨近段骨强度(hip strength analysis,HSA)参数,包括股骨颈干角(neck shaft angle,NSA)、颈宽度(femur neck width,FNW)、髋轴长(hip axis length,HAL)、股骨颈横截面惯性矩(cross-sectional moment of inertia,CSMI)、股骨颈横截面面积(cross-sectional area,CSA)、曲率比率(buckling ratio,BR)、平均骨皮质厚度(averaged cortical thickness,ACT)、截面模数(section modulus,SM)等在两组人群中的差异。结果城乡男女身高比较,差异均无统计学差异(P>0.05),城区老年男性体质量(73.66±12.63)kg显著高于农村男性(67.8±9.58)kg(P<0.05);城乡男性之间的FN v BMD、TH v BMD、FN a BMD、TR a BMD、IT a BMD、TH a BMD、NSA、FNW、HAL、CSMI、CSA、BR、ACT、SM各项指标差异均无统计学意义;农村女性HAL显著高于城区女性HAL(109.41 mm vs 104.23 mm),差异有统计学意义(P<0.05);其余骨密度及骨结构参数比较,差异无统计学意义(P>0.05)。结论除老年女性HAL城乡之间存在差异外,本研究人群股骨近段QCT骨密度与骨结构参数无城乡差别。展开更多
使用疏水性石墨烯复合粉末(GCP)为碳载体,通过硼氢化钠还原制备GCP载钯颗粒催化剂(PdNPs@GCP)进行氮还原反应(NRR)研究,在-0.2 V vs.RHE电位下,氨气产率为5.2μg·h^(-1)·mg^(-1),合成氨法拉第效率在-0.1 V vs.RHE电位下高达9....使用疏水性石墨烯复合粉末(GCP)为碳载体,通过硼氢化钠还原制备GCP载钯颗粒催化剂(PdNPs@GCP)进行氮还原反应(NRR)研究,在-0.2 V vs.RHE电位下,氨气产率为5.2μg·h^(-1)·mg^(-1),合成氨法拉第效率在-0.1 V vs.RHE电位下高达9.77%。通过与纯钯相和GCP对比研究发现,催化剂NRR活性主要得益于钯颗粒与GCP的构效关系。GCP二维结构提高了电子传输效率,并提供较大的比表面积,促进NRR动力学,同时GCP的疏水表面可以一定程度地抑制析氢反应(HER)。另外,GCP表面钯颗粒有利于氮气吸附活化,为NRR提供了丰富的活性位点,而且催化剂的金属-载体作用力微调钯颗粒电子结构,优化中间产物的吸脱附,加速NRR。展开更多
基金the National Key Research and Development Program of China(Grant Nos.2017YFA0304202 and 2017YFA0205700)the National Natural Science Foundation of China(Grant Nos.11875231 and 11935012)the Fundamental Research Funds for the Central Universities(Grant No.2018FZA3005).
文摘We investigate the rotating wave approximation applied in the high-spin quantum system driven by a linearly polarized alternating magnetic field in the presence of quadrupole interactions.The conventional way to apply the rotating wave approximation in a driven high-spin system is to assume the dynamics being restricted in the reduced Hilbert space.However,when the driving strength is relatively strong or the driving is off resonant,the leakage from the target resonance subspace cannot be neglected for a multi-level quantum system.We propose the correct formalism to apply the rotating wave approximation in the full Hilbert space by taking this leakage into account.By estimating the operator fidelity of the time propagator,our formalism applied in the full Hilbert space unambiguously manifests great advantages over the conventional method applied in the reduced Hilbert space.
文摘目的分析北京城区与农村老年人群的股骨近段骨密度(bone mineral density,BMD)与骨结构参数差异。方法回顾性分析2012年12月1日至2013年12月1日接受髋部定量CT(quantitative computed tomography,QCT)扫描的174名50~70岁的北京居民的相关临床资料,根据居住地分为城区组(n=118)(男性46名、女性72名)和农村组(n=56)(男性31名、女性25名)。统计学分析由QCT测得的股骨颈体积骨密度(femoral neck volumetric bone mineral density,FN v BMD)、全髋体积骨密度(total hip volumetric bone mineral density,TH v BMD)、股骨颈面积骨密度(femoral neck areal bone mineral density,FN a BMD)、股骨大粗隆面积骨密度(trochanter areal bone mineral density,TR a BMD)、股骨粗隆间面积骨密度(intertrochanter areal bone mineral density,IT a BMD)和全髋面积骨密度(total hip areal bone mineral density,TH a BMD)等参数以及股骨近段骨强度(hip strength analysis,HSA)参数,包括股骨颈干角(neck shaft angle,NSA)、颈宽度(femur neck width,FNW)、髋轴长(hip axis length,HAL)、股骨颈横截面惯性矩(cross-sectional moment of inertia,CSMI)、股骨颈横截面面积(cross-sectional area,CSA)、曲率比率(buckling ratio,BR)、平均骨皮质厚度(averaged cortical thickness,ACT)、截面模数(section modulus,SM)等在两组人群中的差异。结果城乡男女身高比较,差异均无统计学差异(P>0.05),城区老年男性体质量(73.66±12.63)kg显著高于农村男性(67.8±9.58)kg(P<0.05);城乡男性之间的FN v BMD、TH v BMD、FN a BMD、TR a BMD、IT a BMD、TH a BMD、NSA、FNW、HAL、CSMI、CSA、BR、ACT、SM各项指标差异均无统计学意义;农村女性HAL显著高于城区女性HAL(109.41 mm vs 104.23 mm),差异有统计学意义(P<0.05);其余骨密度及骨结构参数比较,差异无统计学意义(P>0.05)。结论除老年女性HAL城乡之间存在差异外,本研究人群股骨近段QCT骨密度与骨结构参数无城乡差别。
文摘使用疏水性石墨烯复合粉末(GCP)为碳载体,通过硼氢化钠还原制备GCP载钯颗粒催化剂(PdNPs@GCP)进行氮还原反应(NRR)研究,在-0.2 V vs.RHE电位下,氨气产率为5.2μg·h^(-1)·mg^(-1),合成氨法拉第效率在-0.1 V vs.RHE电位下高达9.77%。通过与纯钯相和GCP对比研究发现,催化剂NRR活性主要得益于钯颗粒与GCP的构效关系。GCP二维结构提高了电子传输效率,并提供较大的比表面积,促进NRR动力学,同时GCP的疏水表面可以一定程度地抑制析氢反应(HER)。另外,GCP表面钯颗粒有利于氮气吸附活化,为NRR提供了丰富的活性位点,而且催化剂的金属-载体作用力微调钯颗粒电子结构,优化中间产物的吸脱附,加速NRR。
