高通量工程试验堆栅元型随堆辐照装置的研制、试验与应用

高通量工程试验堆(HFETR)内的栅元型辐照装置具有较大的灵活性和适用性。几年来,我们使用这类装置开展了一系列材料考验及同位素生产工作。本文介绍了这类装置的设计思想、应用范围、结构特点和试验结果。可供进一步开展栅元型装置研制工作参考。     

凝胶渗透色谱技术及其在食品安全检测方面的应用

凝胶渗透色谱技术是近年来发展起来的一种样品前处理技术。它根据物质的分子量大小不同达到分离目的,具有简单、分离效果好、自动化程度高、适用范围广等特点。本文综述凝胶渗透色谱技术的基本原理、优缺点。用实例介绍凝胶渗透色谱技术在食品安全检测方面的应用和存在问题。     

合理开发可再生资源的Leslie模型

首先把〔１〕提出的Ｌｅｓｌｉｅ模型推广到对可再生资源进行捕获的情形，并得到类似结果。利用所建模型成功地解决了ＣＭＣＭ９６Ａ题中的问题１。     

基于智能工程的钟表CAD系统的研究与设计

基于智能工程的思想，提出了一种并行分层结构的集成化智能ＣＡＤ系统，并在钟表ＣＡＤ中得到成功应用，同时还首次将布局理论应用到钟表机芯设计中。     

Improvement of cyclodextrin glucanotransferase as an antistaling enzyme by error-prone PCR

In an effort to improve the properties of cyclodextrin glucanotransferase (CGTase) as an antistaling enzyme, error-prone PCR was used to introduce random mutations into a CGTase cloned from alkalophilic Bacillus sp. I-5 (CGTase I-5). A mutant CGTase[3-18] with the three mutations M234T, F259I and V591A was selected by agar plate assay. Sequence alignment of various CGTases indicated that M234 and F259 are located in the vicinity of the catalytic sites of the enzyme and V591 in the starch binding domain E. The cyclization activity of CGTase[3-18] was dramatically decreased by 10-fold, while the hydrolyzing activity was increased by up to 15-fold. These mutations near subsite +1 (M234T) and at subsite +2 (F259I) are likely to alter the enzyme activity in a concerted manner, promoting hydrolysis of substrate while retarding cyclization. The addition of CGTase[3-18] reduced the retrogradation rate of bread by as much as did the commercial antistaling enzyme Novamyl during 7-day storage at 4 degrees C. No cyclodextrin (CD) was detected in bread treated with CGTase[3-18], whereas 21 mg of CD per 10 g of bread was produced in bread treated with wild-type CGTase.     

Pressure fluctuation properties in combustion of mixture of anthracite and bituminous coal in a fluidized bed

The combustion characteristics of a mixture of anthracite and bituminous coal were studied in a 0.155 m i.d. fluidized bed combustor (FBC). The properties of the pressure fluctuation for the bed such as the standard deviation, cross-correlation function, dominant frequency and the power spectral density function were obtained through statistical analysis. To interpret the combustion characteristics in the FBC with uniform or multi-sized particles of anthracitebituminous coal mixture, the properties of pressure fluctuation were determined as a function of the particle size distribution and anthracite mixing fraction. In the present work, it is known that the combustion region could be obtained from the analysis of pressure fluctuation properties, and the mixed-firing of anthracite-bituminous coal is related to the reaction models of both coals and particle size distribution. Moreover, the relation between coal size distribution and static mean pressure, and the ignition region could be obtained from the mean pressure profile.     

Inhibiting Invasion into Human Bladder Carcinoma 5637 Cells with Diallyl Trisulfide by Inhibiting Matrix Metalloproteinase Activities and Tightening Tight Junctions

Diallyl trisulfide (DATS), an organosulfur compound in garlic, possesses pronounced anti-cancer potential. However, the anti-invasive mechanism of this compound in human bladder carcinoma is not fully understood. In this study, we evaluated the anti-invasive effects of DATS on a human bladder carcinoma (5637) cell line and investigated the underlying mechanism. The results indicated that DATS suppressed migration and invasion of 5637 cells by reducing the activities and expression of matrix metalloproteinase (MMP)-2 and MMP-9 at both the protein and mRNA levels. DATS treatment up-regulated expression of tissue inhibitor of metalloproteinase (TIMP)-1 and TIMP-2 in 5637 cells. The inhibitory effects of DATS on invasiveness were associated with an increase in transepithelial electrical resistance and repression of the levels of claudin family members. Although further studies are needed, our data demonstrate that DATS exhibits anti-invasive effects in 5637 cells by down-regulating the activity of tight junctions and MMPs. DATS may have future utility in clinical applications for treating bladder cancer.     

Verifiable Hypotheses for Thymosin β4-Dependent and -Independent Angiogenic Induction of Trichinella spiralis-Triggered Nurse Cell Formation

Trichinella spiralis has been reported to induce angiogenesis for nutrient supply and waste disposal by the induction of the angiogenic molecule vascular endothelial cell growth factor (VEGF) during nurse cell formation. However, the action mechanism to induce VEGF in nurse cells by T. spiralis is not known. Hypoxia in nurse cells was suggested as a possible mechanism; however, the presence of hypoxic conditions in infected muscle or nurse cells and whether hypoxia indeed induces the expression of VEGF and subsequent angiogenesis in the infected muscle are both a matter of debate. Our recent studies have shown that thymosin β4, a potent VEGF inducing protein, is expressed in the very early stages of T. spiralis muscle infection suggesting the induction of VEGF in early stage nurse cells. Nevertheless, we now show that hypoxic conditions were not detected in any nurse cell stage but were detected only in the accumulated inflammatory cells. These studies propose that induction of angiogenesis by VEGF in T. spiralis-infected nurse cells was mediated by thymosin β4 and is unrelated to hypoxic conditions.     

Multi-physics analysis on a unimorphic piezoelectric diaphragm according to its shape and boundary conditions for the performance enhancement

A micro-viscometer for measuring viscosity change in small amount of liquid in real time has been proposed recently. The advantages of the device are the use of minimal liquid and maximized sensitivity for measuring viscosity. However, in previous research, even though the multi-physical simulation including electrical, mechanical, and acoustical phenomenon is necessary for design of micro-viscometer, only acoustical aspects have been considered. Thus, combined physical phenomena could not be reflected for an optimum design process. In this research, a multi-physical approach is developed for designing a micro-viscometer, and an optimized micro-viscometer design is proposed. The proposed method is able to capture multi-physical phenomena such as near field effect and added mass effect. It also has the advantage of flexible design of various shape and materials, leading to savings of cost and time.     

Surface modification of silicone rubber by ion beam assisted deposition (IBAD) for improved biocompatibility

We studied the preparation of antimicrobial silicone rubbers of improved interfacial strength, which could be formed with the ion beam assisted deposition (IBAD) technique for coating metallic or inorganic materials (silver (Ag), Copper (Cu), and Hydroxyapatite(HAp)/TiO₂) on the silicone surface. Those coating materials provide high product safety as well as outstanding antimicrobial activity. The deposition methodology is composed of pre‐etching with oxygen gas, vaporizing the coating materials, and post‐treatment with Ar ion. With the evaporation of the coating materials, the Ar beam was focused on the substrate to assist deposition. It was found out that the ion assisting depositions in the IBAD process give a prominent enhancement in adhesion between silicone rubbers and coatings of Ag and Cu. The HAp/TiO₂ coating layer was easily dissolved in aqueous saline solution. All deposited layers display high antimicrobial activities against Staphlococcus aureus (ATCC 6538) and Escherichia coil (ATCC 25,922), showing 99.9% reduction of bacteria, respectively. In a cytotoxicity test, the Ag and HAp/TiO₂ coated silicone shows a decrease of cytotoxicity, while the Cu coating leads to a slight increase of cytotoxicity. The result on the surface modifications of silicone rubber will be employed in further study for applications of medical or rehabilitation devices. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1095–1101, 2005