In this work,we revisit the adaptive L1 time-stepping scheme for solving the time-fractional Allen-Cahn equation in the Caputo’s form.The L1 implicit scheme is shown to preserve a variational energy dissipation law o...In this work,we revisit the adaptive L1 time-stepping scheme for solving the time-fractional Allen-Cahn equation in the Caputo’s form.The L1 implicit scheme is shown to preserve a variational energy dissipation law on arbitrary nonuniform time meshes by using the recent discrete analysis tools,i.e.,the discrete orthogonal convolution kernels and discrete complementary convolution kernels.Then the discrete embedding techniques and the fractional Gronwall inequality are applied to establish an L^(2)norm error estimate on nonuniform time meshes.An adaptive time-stepping strategy according to the dynamical feature of the system is presented to capture the multi-scale behaviors and to improve the computational performance.展开更多
We investigate the decay rates of the planar viscous rarefaction wave of the initial-boundary value problem to scalar conservation law with degenerate viscosity in several dimensions on the half-line space, where the ...We investigate the decay rates of the planar viscous rarefaction wave of the initial-boundary value problem to scalar conservation law with degenerate viscosity in several dimensions on the half-line space, where the corresponding one-dimensional problem admits the rarefaction wave as an asymptotic state. The analysis is based on the standard L2-energy method and L1-estimate.展开更多
目的探讨腹膜透析患者血清CHI3L1、FABP4、容量超负荷及蛋白质能量消耗的相关性。方法本研究纳入160例临床状况稳定、在北京大学第三医院腹膜透析中心规律随访的腹膜透析患者。通过ELISA方法测定血清CHI3L1及FABP4浓度。根据多频生物电...目的探讨腹膜透析患者血清CHI3L1、FABP4、容量超负荷及蛋白质能量消耗的相关性。方法本研究纳入160例临床状况稳定、在北京大学第三医院腹膜透析中心规律随访的腹膜透析患者。通过ELISA方法测定血清CHI3L1及FABP4浓度。根据多频生物电阻抗原理测定患者体成分,以水负荷(overdydration,OH)值来评估腹膜透析患者的容量负荷状态,OH值≥2L为容量超负荷,OH值<2L为容量正常。纳入分析的生化指标包括血清白蛋白、尿毒氮、血肌酐、三酰甘油、总胆固醇、低密度脂蛋白胆固醇、高密度脂蛋白胆固醇等。根据蛋白质能量消耗(protein energy wasting,PEW)诊断标准,将入组腹膜透析患者分为蛋白质能量消耗组(PEW组)和非蛋白质能量消耗组(非PEW组)。结果腹膜透析患者血清CHI3L1和FABP4水平呈正相关(r=0.273,P=0.001)。血清CHI3L1水平与容量超负荷呈负相关(r=-0.191,P=0.020),与肌肉重量呈负相关(r=-0.443,P=0.000)。血清FABP4水平与容量超负荷呈负相关(r=-0.172,P=0.040),与肌肉重量呈负相关(r=-0.188,P=0.025)。与容量正常组相比,容量超负荷组的血清CHI3L1水平更低(289.6±117.9ng/ml比335.3±119.3ng/ml,t=2.349,P=0.020),FABP4水平也更低[152.0(131.6,194.6)ng/ml比170.0(132.0,374.9)ng/ml,z=-2.051,P=0.040]。容量超负荷患者的PEW发生率更高(61.7%比42.3%,χ~2=5.756,P=0.013),但是PEW组和非PEW组的CHI3L1、FABP4水平无显著性差异。Logistic回归分析提示PEW的独立危险因素是容量负荷(OR=2.744,95%CI 1.190~6.327,P=0.018)、血清白蛋白(OR=0.837,95%CI 0.734~0.955,P=0.008)和肌肉重量(OR=0.936,95%CI0.891~0.982,P=0.007)。结论腹膜透析患者的血清CHI3L1、FABP4水平显著升高,首次发现两者呈正相关且均与容量超负荷呈负相关,并与肌肉量负相关;PEW发生的独立危险因素是低白蛋白血症、低肌肉量及容量超负荷,而与CHI3L1、FABP4水平无关。展开更多
Metallic alloys with high strength and large ductility are required for extreme structural applications.However,the achievement of ultrahigh strength often results in a substantially decreased ductility.Here,we report...Metallic alloys with high strength and large ductility are required for extreme structural applications.However,the achievement of ultrahigh strength often results in a substantially decreased ductility.Here,we report a strategy to achieve the strength-ductility synergy by tailoring the alloy composition to control the local stacking fault energy(SFE)of the face-centered-cubic(fcc)matrix in an L1_(2)-strengthened superlattice alloy.As a proof of concept,based on the thermodynamic calculations,we developed a non-equiatomic CoCrNi_(2)(Al_(0.2)Nb_(0.2))alloy using phase separation to create a near-equiatomic low SFE disordered CoCrNi medium-entropy alloy matrix with in situ formed high-content coherent Ni_(3)(Al,Nb)-type ordered nanoprecipitates(∼12 nm).The alloy achieves a high tensile strength up to 1.6 GPa and a uniform ductility of 33%.The low SFE of the fcc matrix promotes the formation of nanotwins and parallel microbands during plastic deformation which could remarkably enhance the strain hardening capacity.This work provides a strategy for developing ultrahigh-strength alloys with large uniform ductility.展开更多
Super-fine L1_(0)-Fe Pt nanoparticles(NPs)with high ordering degree were successfully prepared by a modified two-step sintering method,which includes low-temperature pre-sintering,and the high magnetic field(HMF)assis...Super-fine L1_(0)-Fe Pt nanoparticles(NPs)with high ordering degree were successfully prepared by a modified two-step sintering method,which includes low-temperature pre-sintering,and the high magnetic field(HMF)assisted post-sintering processes.The particle size of the L1_(0)-FePt NPs was obviously refined by lowering the sintering temperature.By applying the HMF during the post-sintering process,the fine size characteristics of L1_(0)-Fe Pt NPs were retained,and the ordering degree was significantly improved.The L1_(0)-Fe Pt NPs with sizes of about 4.5 nm,ordering degree of 0.940,and coercivity of 22.01 k Oe were obtained by this two-step sintering under a magnetic field of 12 T.The mechanism investigation of HMF enhancing the ordering degree indicates that the HMF enhances lattice distortion and magnetization energy(Zeeman energy).The enhanced lattice distortions cause high stress existing in the lattice,which can effectively promote the disordered-order transition.When the magnetic field reaches to 3 T,the Zeeman energy of the NPs is higher than the thermal disturbing energy of the NPs,and the magnetization effect is stronger.Therefore,the HMF(higher than 3 T)can obviously improve the disorder-order transition by lowering the energy barrier and accelerating the orderly diffusions of atoms.The HMF is a promising assistant to synthesize the L1_(0)-phase NPs with both of high ordering degree and super-fine size.展开更多
PU.1和KLF7基因在多个组织中的表达具有相关性。在前脂肪细胞分化过程中,两个转录因子都可以通过抑制PPARγ的表达而抑制脂肪形成。然而两者是否存在蛋白水平相互作用还不清楚。为了验证PU.1和KLF7在前脂肪细胞中的关系,该研究构建了重...PU.1和KLF7基因在多个组织中的表达具有相关性。在前脂肪细胞分化过程中,两个转录因子都可以通过抑制PPARγ的表达而抑制脂肪形成。然而两者是否存在蛋白水平相互作用还不清楚。为了验证PU.1和KLF7在前脂肪细胞中的关系,该研究构建了重组表达载体pECFP-N1-PU.1和pEYFP-N1-KLF7,并瞬时转染到3T3-L1前脂肪细胞系中。利用激光共聚焦显微镜,观察到PU.1和KLF7蛋白共定位于3T3-L1细胞核中。荧光共振能量转移(fluorescence resonance energy transfer,FRET)实验分析显示,PU.1和KLF7之间有明显的能量共振转移。实验结果证实,PU.1和KLF7之间存在直接的相互作用关系,为脂肪生成的调控机制研究提供新思路。展开更多
基金The authors would like to thank Dr.Bingquan Ji for his help on numerical computations.H.-L.Liao is supported by the National Natural Science Foundation of China(Grant 12071216)J.Wang is supported by the Hunan Provincial Innovation Foundation for Postgraduate(Grant XDCX2020B078).
文摘In this work,we revisit the adaptive L1 time-stepping scheme for solving the time-fractional Allen-Cahn equation in the Caputo’s form.The L1 implicit scheme is shown to preserve a variational energy dissipation law on arbitrary nonuniform time meshes by using the recent discrete analysis tools,i.e.,the discrete orthogonal convolution kernels and discrete complementary convolution kernels.Then the discrete embedding techniques and the fractional Gronwall inequality are applied to establish an L^(2)norm error estimate on nonuniform time meshes.An adaptive time-stepping strategy according to the dynamical feature of the system is presented to capture the multi-scale behaviors and to improve the computational performance.
基金supported by the NSF of China (10625105,10431060)the Program for New Centary Excellent Talents in University (NCEF-04-0745)
文摘We investigate the decay rates of the planar viscous rarefaction wave of the initial-boundary value problem to scalar conservation law with degenerate viscosity in several dimensions on the half-line space, where the corresponding one-dimensional problem admits the rarefaction wave as an asymptotic state. The analysis is based on the standard L2-energy method and L1-estimate.
文摘目的探讨腹膜透析患者血清CHI3L1、FABP4、容量超负荷及蛋白质能量消耗的相关性。方法本研究纳入160例临床状况稳定、在北京大学第三医院腹膜透析中心规律随访的腹膜透析患者。通过ELISA方法测定血清CHI3L1及FABP4浓度。根据多频生物电阻抗原理测定患者体成分,以水负荷(overdydration,OH)值来评估腹膜透析患者的容量负荷状态,OH值≥2L为容量超负荷,OH值<2L为容量正常。纳入分析的生化指标包括血清白蛋白、尿毒氮、血肌酐、三酰甘油、总胆固醇、低密度脂蛋白胆固醇、高密度脂蛋白胆固醇等。根据蛋白质能量消耗(protein energy wasting,PEW)诊断标准,将入组腹膜透析患者分为蛋白质能量消耗组(PEW组)和非蛋白质能量消耗组(非PEW组)。结果腹膜透析患者血清CHI3L1和FABP4水平呈正相关(r=0.273,P=0.001)。血清CHI3L1水平与容量超负荷呈负相关(r=-0.191,P=0.020),与肌肉重量呈负相关(r=-0.443,P=0.000)。血清FABP4水平与容量超负荷呈负相关(r=-0.172,P=0.040),与肌肉重量呈负相关(r=-0.188,P=0.025)。与容量正常组相比,容量超负荷组的血清CHI3L1水平更低(289.6±117.9ng/ml比335.3±119.3ng/ml,t=2.349,P=0.020),FABP4水平也更低[152.0(131.6,194.6)ng/ml比170.0(132.0,374.9)ng/ml,z=-2.051,P=0.040]。容量超负荷患者的PEW发生率更高(61.7%比42.3%,χ~2=5.756,P=0.013),但是PEW组和非PEW组的CHI3L1、FABP4水平无显著性差异。Logistic回归分析提示PEW的独立危险因素是容量负荷(OR=2.744,95%CI 1.190~6.327,P=0.018)、血清白蛋白(OR=0.837,95%CI 0.734~0.955,P=0.008)和肌肉重量(OR=0.936,95%CI0.891~0.982,P=0.007)。结论腹膜透析患者的血清CHI3L1、FABP4水平显著升高,首次发现两者呈正相关且均与容量超负荷呈负相关,并与肌肉量负相关;PEW发生的独立危险因素是低白蛋白血症、低肌肉量及容量超负荷,而与CHI3L1、FABP4水平无关。
基金The authors also thank the Microscope and Imaging Center at Southern University of Science and Technology,China.This work was financially supported by the National Natural Science Foundation of China(52122102)Guangdong Innovative&Entrepreneurial Research Team Program(2016ZT06C279)APT research was conducted at the Inter-University 3D APT Unit of City University of Hong Kong(CityU),which is supported by the CityU grant(9360161).
文摘Metallic alloys with high strength and large ductility are required for extreme structural applications.However,the achievement of ultrahigh strength often results in a substantially decreased ductility.Here,we report a strategy to achieve the strength-ductility synergy by tailoring the alloy composition to control the local stacking fault energy(SFE)of the face-centered-cubic(fcc)matrix in an L1_(2)-strengthened superlattice alloy.As a proof of concept,based on the thermodynamic calculations,we developed a non-equiatomic CoCrNi_(2)(Al_(0.2)Nb_(0.2))alloy using phase separation to create a near-equiatomic low SFE disordered CoCrNi medium-entropy alloy matrix with in situ formed high-content coherent Ni_(3)(Al,Nb)-type ordered nanoprecipitates(∼12 nm).The alloy achieves a high tensile strength up to 1.6 GPa and a uniform ductility of 33%.The low SFE of the fcc matrix promotes the formation of nanotwins and parallel microbands during plastic deformation which could remarkably enhance the strain hardening capacity.This work provides a strategy for developing ultrahigh-strength alloys with large uniform ductility.
基金financially supported by the National Natural Science Foundation of China(Grant nos.51871045,52071070,and 51690161)the Fundamental Research Funds for the Central Universities(Grant no.N2017003)the Doctoral Start-up Foundation of Liaoning Province(Grant no.2019-BS-116)。
文摘Super-fine L1_(0)-Fe Pt nanoparticles(NPs)with high ordering degree were successfully prepared by a modified two-step sintering method,which includes low-temperature pre-sintering,and the high magnetic field(HMF)assisted post-sintering processes.The particle size of the L1_(0)-FePt NPs was obviously refined by lowering the sintering temperature.By applying the HMF during the post-sintering process,the fine size characteristics of L1_(0)-Fe Pt NPs were retained,and the ordering degree was significantly improved.The L1_(0)-Fe Pt NPs with sizes of about 4.5 nm,ordering degree of 0.940,and coercivity of 22.01 k Oe were obtained by this two-step sintering under a magnetic field of 12 T.The mechanism investigation of HMF enhancing the ordering degree indicates that the HMF enhances lattice distortion and magnetization energy(Zeeman energy).The enhanced lattice distortions cause high stress existing in the lattice,which can effectively promote the disordered-order transition.When the magnetic field reaches to 3 T,the Zeeman energy of the NPs is higher than the thermal disturbing energy of the NPs,and the magnetization effect is stronger.Therefore,the HMF(higher than 3 T)can obviously improve the disorder-order transition by lowering the energy barrier and accelerating the orderly diffusions of atoms.The HMF is a promising assistant to synthesize the L1_(0)-phase NPs with both of high ordering degree and super-fine size.
文摘PU.1和KLF7基因在多个组织中的表达具有相关性。在前脂肪细胞分化过程中,两个转录因子都可以通过抑制PPARγ的表达而抑制脂肪形成。然而两者是否存在蛋白水平相互作用还不清楚。为了验证PU.1和KLF7在前脂肪细胞中的关系,该研究构建了重组表达载体pECFP-N1-PU.1和pEYFP-N1-KLF7,并瞬时转染到3T3-L1前脂肪细胞系中。利用激光共聚焦显微镜,观察到PU.1和KLF7蛋白共定位于3T3-L1细胞核中。荧光共振能量转移(fluorescence resonance energy transfer,FRET)实验分析显示,PU.1和KLF7之间有明显的能量共振转移。实验结果证实,PU.1和KLF7之间存在直接的相互作用关系,为脂肪生成的调控机制研究提供新思路。
