大鼠脑视前区性双形核突触组成的雌雄差别

本文用透射电镜,观察了雌雄大鼠脑视前区性双形核中突触的组成。结果表明,雌雄大鼠在突触组成上有明显的性差异:1.突触总数和占总数绝大比例的轴-树(干)突触数,雄性皆大于雌性2倍。2.轴-棘突触数,雌性高于雄性4.6倍。3.含有清亮小泡和混合小泡的棘突触以及Gray Ⅰ型和 Gray Ⅱ型棘突触数,雌性都高于雄性,但雄性的 Gray Ⅱ/Gray Ⅰ比值高于雌性2.4倍。4.含有清亮小泡的干突触数,雄性高于雌性,但含有混合小泡的干突触数,雌雄间无明显差异。5.Gray Ⅰ型干突触数,雌雄间无明显差异,但 Gray Ⅱ型干突触数,雄性大于雌性2.7倍。

大鼠脑视前区性双形核细胞构筑的雌雄差别

本研究用尼氏染色和快速 Golgi 法在光镜下观察了雌雄大鼠脑视前区性双形核的细胞构筑。结果表明;1.核团体积雄性大于雌性3.1倍。2.核团内神经元密度无明显性差异,但与核团外细胞密度比较有显著差别。3.神经元组成上的百分比有明显的性差别,雄性大神经元多于雌性,雌性的中、小神经元多于雄性。4.树突树分布方向有明显性差别,雄性树突树多向背外侧、腹外侧和内侧方向分布;而雌性多向背侧和腹内侧方向分布。5.树突树平均总长度,雄性大于雌性,雌雄树突树在 X 轴上的分布范围有显著差别,但在 Y 轴上无明显差异。6.树突棘的密度,雌性高于雄性2.1倍。

Effect of annealing temperature on microstructure and mechanical properties of cold-rolled commercially pure titanium sheets

The strength of traditional commercially pure titanium(CP-Ti) alloys often fails to meet the demand of structural materials. In order to enhance their mechanical properties, the cold-rolled CP-Ti alloys were annealed at different temperatures, and the recrystallization behavior and texture evolution were investigated. It was found that the bimodal microstructure(equiaxed and elongated grains) was formed after partial recrystallization, and the corresponding sample exhibited an excellent combination of ultimate tensile strength(702 MPa) and total elongation(36.4%). The recrystallization nucleation of CP-Ti sheets occurred preferentially in the high strain and the high-angle grain boundaries(HAGBs) regions. Meanwhile, the internal misorientations of the deformed heterogeneous grains increased and transformed into HAGBs, which further promoted the recrystallization nucleation. The main recrystallization texture was basal TD-split texture transformed from cold-rolled basal RD-split texture, and the oriented nucleation played a dominated role during recrystallization.

Effect of duplex aging on microstructure and mechanical properties of near-βtitanium alloy processed by isothermal multidirectional forging

The effects of sub-transus(α+β)annealing treatment(ST),followed by single aging(SA)or duplex aging(DA)on the microstructural evolution and mechanical properties of near-βTi-4Al-1Sn-2Zr-5Mo-8V-2.5Cr(mass fraction,%)alloy were investigated using optical microscopy,scanning electron microscopy,and transmission electron microscopy.The results show that the finer secondaryαphase precipitates in the alloy after DA than SA(e.g.,149 nm for SA and 69 nm for DA,both after ST at 720℃).The main reason is that the pre-aging step(300℃)in the DA process leads to the formation of intermediateωphase nanoparticles,which assist in the nucleation of the acicular secondaryαphase precipitates.In addition,the strength of the alloy after DA is higher than that of SA at the specific ST temperature.A good combination is achieved in the alloy subjected to ST at 750℃,followed by DA(UTS:1450 MPa,EL:3.87%),which is due to the precipitation of nanoscale secondaryαphase by DA.In conclusion,DA is a feasible process for this new near-βtitanium alloy.

Tailored microstructures and strengthening mechanisms in an additively manufactured dualphase high-entropy alloy via selective laser melting

Dual-phase high-entropy alloys(DP-HEAs)with excellent strength-ductility combinations have attracted scientific interests.In the present study,the microstructures of AlCrCuFeNi3.0DP-HEA fabricated via selective laser melting(SLM)are rationally adjusted and controlled.The mechanisms engendering the hierarchical microstructures are revealed.It is found that the AlCrCuFeNi3.0fabricated by SLM at the scanning speed of 400 mm s-1falls into the eutectic coupled zone,and increasing the scanning speed will make this composition deviate away from the eutectic coupled zone due to the increased cooling rate.The enrichment of Cr and Fe solutes with large growth restriction values ahead of the solid/liquid interface can develop a constitutional supercooling zone,thus facilitating the heterogeneous nucleation and nearequiaxed grain formation.The synergy of the near-eutectic DP nano-structures and near-equiaxed grains instead of columnar ones effectively suppresses cracking for the as-built DP-HEA.During the tensile deformation,the intergranular back stress hardening similar to the grain-boundary strengthening is discovered.Meanwhile,the near-eutectic microstructures comprised of soft face-centered cubic and hard ordered bodycentered cubic(B2)DP nano-structures lead to plastic strain incompatibility within grains,thus producing the intragranular back stress.The Cr-rich nano-precipitates inside the B2 phase are found to be sheared by dislocation gliding and can complement the back stress.Additionally,multiple strengthening mechanisms are physically evaluated,and the back stress strengthening contributes obviously to the high performances of the as-built DP-HEA.