当今CAPP的发展动态(英文)

计算机辅助工艺设计（ＣＡＰＰ）的概念已提出多年并已在工业界得到应用。然而,由于其自身的复杂性和灵活性,许多瓶颈问题尚未得到解决,影响了ＣＡＰＰ的进一步推广。基于大量的论文检索和阅读分析。揭示了当今有关此研究领域的一些最新方向和动态,以期望对将来的ＣＡＰＰ发展作出贡献。     

支持产品可制造性设计的渐进式CAPP系统研究

分析了并行设计模式下ＣＡＰＰ技术的新特点和目前研究工作中存在的问题。在此基础上，提出了基于原型的渐进式工艺设计新方法，详细地讨论了它的关键性技术和实施策略，总结了这一方法的突出特点。     

不同封装的扩展电阻温度传感器瞬态热响应模型

研究了扩展电阻温度传感器的封装效应。对扩展电阻传感器封装热阻的测量和瞬态热响应 理论和实验研究。理论结果和实验结果吻合。实验和理论结果表明，管壳的几何形状比封装材料传感器瞬态响应时间的影响更重要。对于要求高灵敏度和快速响应的传感器封装，小型和球型的封装方式总是被推荐。的     

SiO_xN_y和SiO_2膜中的高场电子陷阱的温度依赖性和产生机理

研究了温度从１００～４２３Ｋ范围内在薄氮氧化硅膜和薄二氧化硅膜中的高场电子陷阱的温度依赖性。我们发现；在研究的温度范围内，当温度降低时，薄氮氧化硅膜中的有效高场电子陷饼表面浓度增加，相反，在薄二氧化硅膜中的有效高场电子陷阱表面浓度减少；对于二氧化硅膜，有效的高场电子陷阶能级集中在一个非常窄的能量范围，它的产生率是１．２８３×１０１１／ｃｍ２，激活能是０．１９２ｅＶ。根据实验结果，提出了一个在二氧化硅中的高场电子陷阱的产生模型。     

Mutant alpha subunits of Gi2 inhibit cyclic AMP accumulation

One or more of three Gi proteins, Gi1-3, mediates hormonal inhibition of adenylyl cyclase. Whether this inhibition is mediated by the alpha or by the beta gamma subunits of Gi proteins is unclear. Mutations inhibiting the intrinsic GTPase activity of another G protein, the stimulatory regulator of adenylyl cyclase (Gs), constitutively activate it by replacing either of two conserved amino acids in its alpha subunit (alpha s). These mutations create the gsp oncogene which is found in human pituitary and thyroid tumours. In a second group of human endocrine tumours, somatic mutations in the alpha subunit of Gi2 replace a residue cognate to one of those affected by gsp mutations. This implies that the mutations convert the alpha i2 gene into a dominantly acting oncogene, called gip2, and that the mutant alpha i2 subunits are constitutively active. We have therefore assessed cyclic AMP accumulation in cultured cells which stably or transiently express exogenous wild-type alpha i2 complementary DNA or either of two mutant alpha i2 cDNAs. The results show that putatively oncogenic mutations in alpha i2 constitutively activate the protein's ability to inhibit cAMP accumulation.     

带有两个确定时滞的捕食——被捕食系统的全局渐近稳定性

本文对于带有两个确定时滞的捕食——被捕食系统进行了讨论,得到了使它的正平衡点全局渐近稳定的充分条件。     

Inhibition of pluripotential embryonic stem cell differentiation by purified polypeptides

Murine embryonic stem (ES) cells are pluripotent cell lines established directly from the early embryo which can contribute differentiated progeny to all adult tissues, including the germ-cell lineage, after re-incorporation into the normal embryo. They provide both a cellular vector for the generation of transgenic animals and a useful system for the identification of polypeptide factors controlling differentiation processes in early development. In particular, medium conditioned by Buffalo rat liver cells contains a polypeptide factor, ES cell differentiation inhibitory activity (DIA), which specifically suppresses the spontaneous differentiation of ES cells in vitro, thereby permitting their growth as homogeneous stem cell populations in the absence of heterologous feeder cells. ES cell pluripotentiality, including the ability to give rise to functional gametes, is preserved after prolonged culture in Buffalo rat liver media as a source of DIA. Here, we report that purified DIA is related in structure and function to the recently identified hematopoietic regulatory factors human interleukin for DA cells and leukaemia inhibitory factor. DIA and human interleukin DA/leukaemia inhibitory factor have thus been identified as related multifunctional regulatory factors with distinct biological activities in both early embryonic and hematopoietic stem cell systems.     

Spontaneous mutation rates to new length alleles at tandem-repetitive hypervariable loci in human DNA

Tandem-repetitive minisatellite regions in vertebrate DNA frequently show substantial allelic variation in the number of repeat units. This variation is thought to arise through processes such as unequal crossover or replication slippage. We show here that the spontaneous mutation rate to new length alleles at extremely variable human minisatellites is sufficiently high to be directly measurable in human pedigrees. The mutation rate at different loci increases with variability in accord with the neutral mutation/random drift hypothesis, and rises to 5% per gamete for the most unstable human minisatellite isolated. Mutations are sporadic, occur with similar frequencies in sperm and oocytes, and can involve the gain or loss of substantial numbers of repeat units, consistent with length changes arising primarily by unequal exchange at meiosis. Germline instability must therefore be taken into account when using hypervariable loci as genetic markers, particularly in pedigree analysis and parenthood testing.     

Engineered polycaprolactone – magnesium hybrid biodegradable porous scaffold for bone tissue engineering

In this paper, we describe the fabrication of a new biodegradable porous scaffold composed of polycaprolactone(PCL) and magnesium(Mg)micro-particles. The compressive modulus of PCL porous scaffold was increased to at least 150% by incorporating 29% Mg particles with the porosity of 74% using Micro-CT analysis. Surprisingly, the compressive modulus of this scaffold was further increased to at least 236% when the silane-coupled Mg particles were added. In terms of cell viability, the scaffold modified with Mg particles significantly convinced the attachment and growth of osteoblasts as compared with the pure PCL scaffold. In addition, the hybrid scaffold was able to attract the formation of apatite layer over its surface after 7 days of immersion in normal culture medium, whereas it was not observed on the pure PCL scaffold. This in vitro result indicated the enhanced bioactivity of the modified scaffold. Moreover, enhanced bone forming ability was also observed in the rat model after 3 months of implantation. Though bony in-growth was found in all the implanted scaffolds. High volume of new bone formation could be found in the Mg/PCL hybrid scaffolds when compared to the pure PCL scaffold. Both pure PCL and Mg/PCL hybrid scaffolds were degraded after 3 months. However, no tissue inflammation was observed. In conclusion, these promising results suggested that the incorporation of Mg micro-particles into PCL porous scaffold could significantly enhance its mechanical and biological properties. This modified porous bio-scaffold may potentially apply in the surgical management of large bone defect fixation.