TiB的添加对ZnAl合金改性的微观影响

采用扫描电子显微镜、高角度环形暗场扫描透射电子显微镜和能量X射线谱,研究TiB的加入对锌铝共晶(ZA27)合金改性的微观作用。铸造一系列Zn−27Al−2Cu−0.02Mg−x(Ti+B)(x=0,0.01,0.02,0.05,0.10,0.20,质量分数,%)合金。研究结果表明,ZA27合金的硬度和强度随(Ti+B)含量的增加而提高,在(Ti+B)含量为0.05%时达到最高值。TiB改性剂可以细化初生α(Al)相晶粒,改变珊瑚状(α(Al)+η-Zn)共析组织的微观结构,这是ZA27合金力学性能提高的原因。改性后的共析组织表现出篮状和条状共析组织微观结构特点。初生α(Al)相晶粒的细化很可能与B在固−液界面上偏析引起的成分过冷有关。B和/或Ti参与共晶和共析反应,改变了共析组织的形态。

Stiffness Analysis of Spherical Parallel Mechanism U_(P+R) with 2-DOF

As one of the typical less-mobility parallel mechanisms,the spherical parallel mechanism U_(P + R) with two degrees of freedom(2-DOF)possess high order overconstraints,and the calculation of its stiffness is partly different with general parallel mechanisms owing to the bars in each branch are assumed to be arc-shaped.By means of small deformation superposition principle,the relationship between the angle displacement and line displacement of moving platform and the forces acted on the branches were derived out.Based on the results of static analysis,the relationship between the applied force,the line displacement and the angle displacement of the mechanism was set up.And then the stiffness matrix was obtained.The six principal stiffness of the mechanism and the corresponding directions were achieved by the orthogonal transformation.The numerical calculation was performed and the results showed that the principal stiffness and directions are varied with the pose-position of the mechanism,and the principal stiffness is gradually enlarged when it is far away from the origin.In addition,the torsion stiffness is much greater and the line deformation stiffness is smaller,the difference between the two parts is huge.The research content of this paper supplies the theoretical foundation for the further engineering design and application of the spherical parallel mechanism.

GENERAL DIFFERENCE SCHEMES WITH INTRINSICPARALLELISM FOR SEMILINEAR PARABOLIC SYSTEMS OFDIVERGENCE TYPE

In this paper the general finite difference schemes with intrinsic parallelism for the boundary value problem of the semilinear parabolic system of divergence type with bounded coefficients are constructed, and the existence and uniqueness of the difference solution for the general schemes are proved. And the convergence of the solutions of the difference schemes to the generalized solution of the original boundary value problem of the semilinear parabolic system is obtained. The multidimensional problems are also studied.

Rapid screening for Klinefelter syndrome with a simple high-resolution melting assay： a multicenter study

Klinefelter syndrome （KS） is the set of symptoms that result from the presence of an extra X chromosome in males. Postnatal population-based KS screening will enable timely diagnosis of this common chromosomal disease, providing the opportunity for early intervention and therapy at the time point when they are most effective and may prevent later symptoms or complications. Therefore, through this study, we introduced a simple high-resolution melting （HRM） assay for KS screening and evaluated its clinical sensitivity and specificity in three medical centers using 1373 clinical blood samples. The HRM assay utilized a single primer pair to simultaneously amplify specific regions in zinc finger protein, X-linked （ZFX） and zinc finger protein, Y-linked （ZFY）. In cases of KS, the ratios of ZFX/ZFYare altered compared to those in normal males. As a result, the specific melting profiles differ and can be differentiated during data analysis. This HRM assay displayed high analytical specificity over a wide range of template DNA amounts （5 ng-50 ng） and reproducibility, high resolution for detecting KS mosaicism, and high clinical sensitivity （100%） and specificity （98.1%）. Moreover, the HRM assay was rapid （2 h per run）, inexpensive （0.2 USD per sample）, easy to perform and automatic, and compatible with both whole blood samples and dried blood spots. Therefore, this HRM assay is an ideal postnatal population-based KS screening tool that can be used for different age groups.

Polymerase chain reaction-based assays facilitate the breeding and study of mouse models of Klinefelter syndrome

Klinefelter syndrome(KS)is one of the most frequent genetic abnormalities and the leading genetic cause of nonobstructive azoospermia.The breeding and study of KS mouse models are essential to advancing our knowledge of the underlying pathological mechanism.Karyotyping and fluorescence in situ hybridization are reliable methods for identifying chromosomal contents.However,technical issues associated with these methods can decrease the efficiency of breeding KS mouse models and limit studies that require rapid identification of target mice.To overcome these limitations,we developed three polymerase chain reaction-based assays to measure specific genetic information,including presence or absence of the sex determining region of chromosome Y(Sry),copy number of amelogenin,X-linked(Amelx),and inactive X specific transcripts(Xist)levels.Through a combined analysis of the assay results,we can infer the karyotype of target mice.We confirmed the utility of our assays with the successful generation of KS mouse models.Our assays are rapid,inexpensive,high capacity,easy to perform,and only require small sample amounts.Therefore,they facilitate the breeding and study of KS mouse models and help advance our knowledge of the pathological mechanism underlying KS.

Diagnosis of a Chinese man with 45,X/46,X,i（Y） （q10）/47,X,i（Y） （q10） ×2 mosaic Turner syndrome

Turner syndrome （TS）, characterized by the complete or partial absence of an X chromosome, is the only known viable chromosomal monosomy. It is one of the most common sex chromosome abnormalities in women, but it can also occur in men, with diverse chimeric phenotypes.