The southeastern Chinese Loess Plateau is the terminal deposition area of dusts transported by the East Asian winter monsoon and the frontal area penetrated by the East Asian summer monsoon,and thus a climate sensitiv...The southeastern Chinese Loess Plateau is the terminal deposition area of dusts transported by the East Asian winter monsoon and the frontal area penetrated by the East Asian summer monsoon,and thus a climate sensitive region.This paper reports a rock magnetic study of a Quaternary loess-paleosol section in such a region.We tried to reconstruct the paleoclimate evolution history in the region during 1.95–0.40 Ma with magnetic parameters.The results show a general up-section decreasing trend of the ratio of HIRM/(SIRM–IRM100 mT),indicating a long-term decreasing trend of hematite coercivities in the deposits,which can be mainly related to the cooling and aridification trend of the environment in interglacial depositional area and glacial dust source region.The ratio,lf/ARM,widely used to reflect the variations of magnetic mineral grain size,manifests a long-term increasing trend of the magnetic mineral grain size and tends to indicate an overall weakening trend of the East Asian summer monsoon that controlled the pedogenic intensity.Although the regional multi-segmented paleoclimatic records revealed by several magnetic parameters in our study,the long-term Asian cooling and aridification trend inferred here is of global correlation significance.展开更多
Magnetic nanoparticles （Fe304） were prepared by chemical precipitation method using Fe^2＋ and Fe^3＋ salts with sodium hydroxide in the nitrogen atmosphere. Fe3O4 nanoparticles were coated with human serum albumin...Magnetic nanoparticles （Fe304） were prepared by chemical precipitation method using Fe^2＋ and Fe^3＋ salts with sodium hydroxide in the nitrogen atmosphere. Fe3O4 nanoparticles were coated with human serum albumin（HSA） for magnetic resonance imaging as contrast agent. Characteristics of magnetic particles coated or uncoated were carried out using scanning electron microscopy and X-ray diffraction. Zeta potentials, package effects and distributions of colloid particles were measured to confirm the attachment of HSA on magnetic particles. Effects of Fe3O4 nanoparticles coated with HSA on magnetic resonance imaging were investigated with rats. The experimental results show that the adsorption of HSA on magnetic particles is very favorable to dispersing of magnetic Fe3O4 particles, while the sizes of Fe3O4 particles coated are related to the molar ratio of Fe3O4 to HSA. The diameters of the majority of particles coated are less than 100 nm. Fe3O4 nanoparticle coated with HSA has a good biocompatibility and low toxicity. This new contrast agent has some effects on the nuclear magnetic resonance imaging of liver and the lowest dosage is 20μmol/kg for the demands of diagnosis.展开更多
基金supported by the National Basic Research Program of China(2010CB833405)the National Natural Science Foundation of China(41102115 and 40930106)
文摘The southeastern Chinese Loess Plateau is the terminal deposition area of dusts transported by the East Asian winter monsoon and the frontal area penetrated by the East Asian summer monsoon,and thus a climate sensitive region.This paper reports a rock magnetic study of a Quaternary loess-paleosol section in such a region.We tried to reconstruct the paleoclimate evolution history in the region during 1.95–0.40 Ma with magnetic parameters.The results show a general up-section decreasing trend of the ratio of HIRM/(SIRM–IRM100 mT),indicating a long-term decreasing trend of hematite coercivities in the deposits,which can be mainly related to the cooling and aridification trend of the environment in interglacial depositional area and glacial dust source region.The ratio,lf/ARM,widely used to reflect the variations of magnetic mineral grain size,manifests a long-term increasing trend of the magnetic mineral grain size and tends to indicate an overall weakening trend of the East Asian summer monsoon that controlled the pedogenic intensity.Although the regional multi-segmented paleoclimatic records revealed by several magnetic parameters in our study,the long-term Asian cooling and aridification trend inferred here is of global correlation significance.
文摘Magnetic nanoparticles （Fe304） were prepared by chemical precipitation method using Fe^2＋ and Fe^3＋ salts with sodium hydroxide in the nitrogen atmosphere. Fe3O4 nanoparticles were coated with human serum albumin（HSA） for magnetic resonance imaging as contrast agent. Characteristics of magnetic particles coated or uncoated were carried out using scanning electron microscopy and X-ray diffraction. Zeta potentials, package effects and distributions of colloid particles were measured to confirm the attachment of HSA on magnetic particles. Effects of Fe3O4 nanoparticles coated with HSA on magnetic resonance imaging were investigated with rats. The experimental results show that the adsorption of HSA on magnetic particles is very favorable to dispersing of magnetic Fe3O4 particles, while the sizes of Fe3O4 particles coated are related to the molar ratio of Fe3O4 to HSA. The diameters of the majority of particles coated are less than 100 nm. Fe3O4 nanoparticle coated with HSA has a good biocompatibility and low toxicity. This new contrast agent has some effects on the nuclear magnetic resonance imaging of liver and the lowest dosage is 20μmol/kg for the demands of diagnosis.
