中外科学技术发展比较研究

21世纪是科学技术飞速发展的世纪，论述了世界科学技术近年来的发展趋势，分析和对比了中外科学技术应用研究与发展情况，指出了实施科教兴国战略是加快我国科学技术发展的一条根本出路。     

Effect of bisphosphonates on the stimulation of macrophages by alumina ceramic particles: A comparison with ultra-high-molecular-weight polyethylene

Wear particle-induced osteolysis and loosening is a critical process that limits the longevity of total hip arthroplasty. Despite their potential value in the management of aseptic loosening, little is known about the cellular response to bisphosphonates (BPs) in the presence of particulate debris. In the present study, we compared the effect of pamidronate and clodronate, two structurally different bisphosphonates, on the induction of TNF-α release by alumina ceramic (Al₂O₃) and ultra-high-molecular-weight-polyethylene (UHMWPE) particles. We also looked, by Trypan blue exclusion, at the viability of J774 mouse macrophages incubated with Al₂O₃ and UHMWPE particles in combination with pamidronate or clodronate. Results showed that pamidronate and clodronate can inhibit UHMWPE particle-induced TNF-α release while they had no effect on Al₂O₃-stimulated TNF-α release. The co-incubation of pamidronate or clodronate and Al₂O₃ had no effect on the induction by Al₂O₃ of poly(ADP-ribose)polymerase (PARP) proteolysis and DNA fragmentation. On the other hand, UHMWPE particles had no effect on these apoptotic markers. However, the co-incubation of pamidronate or clodronate with UHMWPE particles led to the appearance of these markers of apoptosis. Al₂O₃ and UHMWPE particles had no effect on macrophage cell death or the number of macrophages at the end of experiments. Co-incubation of UHMWPE particles with pamidronate and clodronate led to a significant increase in cell death. Interestingly, the number of macrophages co-incubated with particles and pamidronate or clodronate significantly decreased. In conclusion, our results suggest that the effect of BPs on particle-stimulated macrophages is, at least in part, particle composition dependent.     

A Sustainable Funding and Financing Strategy for Urban Infrastructure Renewal in China

In a relatively short time, many of China’s cities have become major industrial, shipping, and financial hubs. To support this unprecedented growth and economic development, China has invested enormous sums to provide transportation, power, communications, sanitation, and other basic infrastructures. Although much of this investment has been in newer urban districts, old districts within existing cities still add value to the economy and are often repositories of China’s considerable cultural heritage. Maintaining compatibility between the old and the new is always challenging but the renewal of older infrastructure systems often lags behind due to a shortage of capital and difficulties in raising sufficient revenue to support replacement and upgrading of basic systems. This paper will examine the range of funding and financing options that are in use throughout the world to see what mix of public and private approaches might be most suitable for Chinese cities to adopt as part of a funding and financing strategy that will support enduring and sustainable renewal and redevelopment of older urban districts.     

Computer study of tweed as a precursor to a martensitic transformation of a Bcc lattice

Using molecular dynamics computer simulations we have studied a bcc crystal with an interatomic potential having a second derivative which passes through zero near second neighbor distances. This causes an inherent tetragonal instability which manifests itself as random dynamic tetragonal distortions at high temperature (“dynamic tweed”), quasi-static and somewhat spatially correlated tetragonal distortions at intermediate temperatures (“static tweed”), and an apparent martensitic transformation to a close-packed structure at low temperatures. The effect of simple defects (vacancies and interstitials) on the development and spatial localization of the pretransformation structure (tweed) and the subsequent martensitic transformation will also be discussed. This paper is based on a presentation made in the symposium “Pretransformation Behavior Related to Displacive Transformation in Alloys” presented at the 1986 annual AIME meeting in New Orleans, March 2–6, 1986, under the auspices of the ASM-MSD Structures Committee.     

预倾角对液晶响应时间的影响

从理论上分析了预倾角对液晶动力学的影响,推导出一系列可用于描述预倾角非0条件下的液晶响应分析公式。使用垂直取向的液晶盒能够通过实验验证理论分析的正确性,这一发现将预倾角与液晶响应时间定量的联系在一起。对预倾角和液晶响应时间的关系的研究,将加深我们对液晶动力学过程的理解,从而有助于优化液晶的响应时间。从理论上分析了预倾角对液晶动力学的影响,推导出一系列可用于描述预倾角非0条件下的液晶响应分析公式。使用垂直取向的液晶盒能够通过实验验证理论分析的正确性,这一发现将预倾角与液晶响应时间定量的联系在一起。对预倾角和液晶响应时间的关系的研究,将加深我们对液晶动力学过程的理解,从而有助于优化液晶的响应时间。     

国外典型的VSAT用户网络

ＶＳＡＴ是８０年代中期迅速发展起来的新型卫星通信技术，具有投资少、见效快、周期短、应用广泛等特点。本文着重介绍国外一些典型的ＶＳＡＴ用户网络的情况。