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Subjects: Biology >> Botany >> Applied botany

为研究金花茶组植物花色与细胞内重要环境因子的关系，以花色不同的8个金花茶组物种的9个居群为试材，测定了其花瓣的颜色、总黄酮含量、含水量、细胞pH, 7种金属离子浓度。结果表明，所测金花茶组植物的花色平均值明度L为80.82、色相a‘为一2.88、色相b‘为53.97、彩度C为54.10、色相角h为93.19，故金花茶花色为明度较亮的黄色，其中色相b‘为描述黄色的主要指标，据此可将所测植物分为金黄、黄、浅黄3类。花瓣总黄酮含量为20.17%，花瓣含水量为88.14%，物种间均达到差异显著，且均与花色呈弱相关，对黄色呈现影响较小。花瓣细胞偏弱酸性，pH平均值为6.19，不同物种间差异显著，细胞pH与花色呈显著正相关，即中偏弱酸性细胞环境有利于金花茶花瓣黄色的呈现。金属离子浓度中，K+含量最高(12.61 mg "g-1)，依次为Cat+(3.91 mg "g-1), Mgt+(1.28 mg "g-1), A13+(0.98mg·g-1), Na+(0.17 mg·g-1), Fe3+(0.07 mg·g-1) } Cu2+含量最低(0.0038 mg·g-')} 7种金属离子在所测植物间均存在显著差异，其中A13+, Fe3+和Cat+}IJ对金花茶黄色花色的形成具有不同程度的干扰作用，随着这3种金属离子浓度升高，黄度降低，花色变淡，因此较低浓度的A13+, Fe3+, Ca2+可能更有利于金花茶黄色花的呈现。 |

submitted time
2018-12-19
From cooperative journals:《广西植物》
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Subjects: Biology >> Bioengineering

间充质干细胞(mesenchymal stem cells, MSCs) 具有很强的自我复制能力和多向分化潜能，是近年来热门研究的种子细胞。MSCs的生长微环境可以影响调控干细胞的生长、分化，力学刺激是MSCs分化的影响因素之一。细胞外基质硬度、机械应力（剪切力、静压力、牵张力）、微重力等因素对MSCs的分化作用是当前研究的热点。本文从细胞外基质硬度、机械应力以及机械应力作用于三维支架培养对MSCs分化的影响等方面进行综述。 |

submitted time
2018-05-23
From cooperative journals:《中国生物工程杂志》
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Subjects: Physics >> Condensed Matter: Electronic Structure, Electrical, Magnetic, and Optical Properties

Cubic helimagnet FeGe has emerged as a class of skyrmion materials near room temperature that may impact future information technology. Experimentally identifying the detailed properties of skyrmion materials enables their practical application acceleratedly. Here we study the magnetic entropy change (MEC) of single crystalline FeGe in its precursor region and clarify its close relation to the critical exponents of a second-order phase transition in this area. The maximum MEC is found to be 2.86 J/kg.K for 7.0 T magnetic field change smaller than that of common magnetocaloric materials indicating the multiplicity and complexity of the magnetic structure phases in the precursor region. This result also implies that the competition among the multimagnetic phases can partly counteract the magnetic field driven force and establishes a stable balance. Based on the obtained MEC and the critical exponents, the exact Curie temperature of single crystalline FeGe under zero magnetic field is confirmed to be 279.1 K, higher than previously reported 278.2 K. This finding pave the way for reconstruction of FeGe phase diagram in the precursor region. |

Subjects: Physics >> Condensed Matter: Electronic Structure, Electrical, Magnetic, and Optical Properties

The magnetic entropy change [ΔSM(T;H)] around the phase transition temperature TC is investigated by the scaling method for Fe0:5Co0:5Si, which exhibits a skyrmion phase below TC. The parameters of ΔSM(T;H) exhibit field dependent behaviors. The ΔSM(T;H) curves under high field can be well scaled into a single universal curve independent of external field and temperature. However, ΔSM(T;H) curves under low field become divergent just below TC, which indicates a characteristic of first-order transition. The scaling investigation of ΔSM(T;H) curves indicates that the phase transition in Fe0:5Co0:5Si is of a weak first-order type in low field region, while it is driven into a second-order one under high field. This weak first-order phase transition in low field region resembles that in typical skyrmion system MnSi which is caused by the critical fluctuation. The result suggests that critical fluctuation plays an important role in the phase transition and formation of skyrmion state. |

Subjects: Physics >> Condensed Matter: Electronic Structure, Electrical, Magnetic, and Optical Properties

The magnetism of the single crystal Cr1=3NbS2, which exhibits chiral soliton lattice (CSL) state, is investigated. The magnetization displays strong magnetic anisotropy when the field is applied perpendicularly and parallel to the c-axis in low field region (H < HS, HS is the saturation field). The critical exponents of Cr1=3NbS2 are obtained as β = 0.370(4), γ = 1.380(2), and δ = 4.853(6), which are close to the theoretical prediction of three-dimensional Heisenberg model. Based on the scaling equation and the critical exponents, the H T phase diagram in the vicinity of the phase transition is constructed, where two critical points are determined. One is a tricrtical point which locates at the intersection between the CSL, forced ferromagnetic (FFM), and paramagnetic (PM) states. The other one is a critical point situated at the boundaries between CSL, helimagnetic (HM), and PM states. |

Subjects: Physics >> Condensed Matter: Electronic Structure, Electrical, Magnetic, and Optical Properties

Critical phenomenon of the noncentrosymmetric Cr11Ge19, which exhibits an itinerant ferromagnetic ground state, is investigated by scaling of the magnetic entropy change [ΔSM(T;H)]. It is found that parameters #14;FWHM (the full width at half maximum), ΔSmax M (the maximum of the magnetic entropy change), and RCP (the relative cooling power) of ΔSM(T) are governed by the power law of critical exponents. With the critical exponents, ΔSM(T;H) curves are scaled into a universal curve independent of temperature and field, which suggests that the magnetic transition is of a second order type. The universal collapse of ΔSM(T;H) indicates that the critical behavior of Cr11Ge19 can be well described by the scaling laws for the critical phenomenon. Moreover, the ΔSM follows the power law of Hn with n(T;H) = dlnjΔSMj=dln(H). The temperature dependence of n values reach minimum at #24; 71.5 K. Based on the magnetic specific change ΔCp(T;H), the actual magnetic transition temperature is strictly determined as TC = 71:3 #6; 0:2 K for the single crystal Cr11Ge19. |

Localization induced by pressure in pyrochlore Bi2Ir2O7

张蕾Subjects: Physics >> Condensed Matter: Electronic Structure, Electrical, Magnetic, and Optical Properties

In this work, the resistivity and magnetization of Bi2Ir2O7 are investigated under hydrostatic pressure. At ambient pressure, the resistivity of Bi2Ir2O7 exhibits a metallic behavior with the decrease of temperature. When the pressure is applied, a metal-insulator phase transition at low temperature is induced under a pressure of #24; 0.48 GPa. The metal-insulator phase transition temperature (TMI ) increases linearly with pressure as dTMI/dP = 3.4 #6;0.3 K/GPa. The temperature dependence of resistivity [#26;(T)] in the pressure-induced insulating phase exhibits a thermal activation behavior (#26; = #26;0eΔE=kBT ), where the thermal activation energy (ΔE) increases monotonously with the pressure. Meanwhile, the magnetization is enhanced by the pressure, which indicates an enhancement of magnetic ordering. The results suggest that localization occurs due to the magnetic ordering induced by the pressure, which confirms the magneto-electronic coupling in Bi2Ir2O7 |

Subjects: Physics >> Condensed Matter: Electronic Structure, Electrical, Magnetic, and Optical Properties

The iso-spinel structural systems CuIr2S4 and MgTi2O4 exhibit phase transitions of the similar nature at #24; 230 K and #24; 260 K respectively, which are explained as an orbitally-induced Peierls phase transition. However, in this work, we uncover that applied pressure has opposite pressure effects on the phase transitions in CuIr2S4 and MgTi2O4. As pressure increases, the phase transition temperature (TMI ) for CuIr2S4 increases while that for MgTi2O4 decreases. In addition, the phase transition intensity becomes weaker for CuIr2S4 but gets stronger for MgTi2O4 under pressure. Our results indicate that the applied pressure suppresses the metallic phase in CuIr2S4, while enhances that in MgTi2O4. Combining the experimental observations with first-principle electronic structure calculations, we suggest that the opposite pressure effects in CuIr2S4 and MgTi2O4 originate from the different orbital ordering configurations (dxy, dyz/dxz) caused by different lattice distortions in these two systems. Our findings directly indicate that the interplay between the orbital and lattice degrees of freedom plays an important role in the orbitally-induced Peierls phase transition. |

Critical phenomenon of the near room temperature skyrmion material FeGe

张蕾Subjects: Physics >> Condensed Matter: Electronic Structure, Electrical, Magnetic, and Optical Properties

The cubic B20 compound FeGe, which exhibits a near room temperature skyrmion phase, is one of the most promising candidate of the next generation spintronic devices. In this work, the critical behavior of the cubic FeGe is investigated by means of bulk dc-magnetization. We obtain the critical exponents (#12; = 0:336#6;0:004, = 1:352#6;0:003, and #14; = 5:267#6;0:001), where the self-consistency and reliability are verified by the Widom scaling law and scaling equations. The magnetic exchange distance is found to decay as J(r) #25; r4:9, which is close to the theoretical prediction of 3DHeisenberg model (r5). The critical behavior of FeGe indicates a short-range magnetic interaction. Meanwhile, the critical exponents also imply an anisotropic magnetic coupling in this system. |

Spin-dimensionality change induced by Co-doping in the chiral magnet Fe1xCoxSi

张蕾Subjects: Physics >> Condensed Matter: Electronic Structure, Electrical, Magnetic, and Optical Properties

Dimensionality is one of the most important parameters in determination of the physical properties. Therefore, tuning of effective dimensionality is of significant importance for modulating the functionality of materials. In this work, we find that the spin-dimensionality can be changed by the Co-doing in Fe1xCoxSi system. Investigation of the critical behavior shows that critical exponents for x = 0.3 agree with the three-dimensional (3D) Heisenberg model with fd : n = 3 : 3g (d is the spatial-dimensionality, and n is the spin-dimensionality). With the increase of Co-content, the critical exponents for x = 0.5 fulfill the 3D-XY model with fd : n = 3 : 2g, while those for x = 0.6 approach the 3D-Ising model with fd : n = 3 : 1g. These results indicate the lowering of the spin-dimensionality with the increase of Co-content in Fe1xCoxSi. We suggest that the modulation of the spin-dimensionality in Fe1xCoxSi should be resulted from the enhancement of the anisotropic magnetic interaction induced by the doping of Co. |