顶空气相色谱法测定聚苯乙烯食品包装材料中挥发组分

以顶空气相色谱法直接测定聚苯乙烯食品包装材料固体试样中的苯，甲本、对二甲苯和苯乙烯，最小检出量为１０－１０＾１０ｇ，回收率为９７．６％－１０２．５％。该法基体干扰小、操作简便。     

Routine cytogenetic prenatal diagnosis using dynamic banding (RBG-GBG): A highly reproducible method for amniocytes,fetal cord blood,and chorionic villus investigations

Dynamic banding (RBG-GBG) using pulse 5-bromodeoxyuridine (5-BrdU) incorporation during part of the last S-phase before harvesting has been used in prenatal investigations. This method has already been routinely applied in 1344 cytogenetic investigations. GBG and RBG bandings produced almost identical patterns to classical G- and R-banding methods except for heterochromatic portions and some euchromatic segments. Nevertheless, these discordances may be somewhat helpful for cytogenetic diagnosis (i.e., X numerical abnormalities). The results showed particularly good contrast and staining; 5-BrdU incorporation did not prevent additional staining. Likewise, previous RBG or GBG disclosure allowed further chromosomal identification with C-banding or nucleolar organizer staining. Simplicity and reproducibility were very helpful in cases with a low mitotic index. 5-BrdU had no significant effect on in-vitro damage because only 0.31 per cent of cells were affected; so, we believe that dynamic banding should be used more extensively in cytogenetic investigations. Moreover, the staining and contrast qualities were very suitable for automatic methods of analysis now in use: i.e., metaphase finding and computer-assisted karyogram creation.     

Metal prices and the business cycle

Metal price fluctuations have recently been of interest not only because of their cyclical volatility but also of their interaction with business cycles. A related issue is whether metal prices move together sufficiently to collectively reflect macroeconomic influences. Correlation or the tendency for prices to move together has been termed “comovement”, where the commonality in prices reflects the tendency of commodity markets to respond to common business cycle and trend factors. Metal prices are known to respond to macroeconomic influences and the latter might well explain the common factor which causes them to move together. Our goal is to provide an estimate of the common factor in metal prices and to relate this factor to important macroeconomic influences. The prices we study are for aluminum, copper, tin, lead and zinc; the macroeconomic variables include industrial production, consumer prices, interest rates, stock prices, and exchange rates. Our results confirm that the common factor in metal prices can be related to such macroeconomic influences.     

Long-term perspectives on world metal use—a system-dynamics model

In this paper, a system dynamics model is described, which simulates long-term trends in the production and consumption of metals (i.e. iron/steel and an aggregate of metals of medium abundance) in relation to impacts such as ore-grade decline, capital and energy requirements and waste flows. This metal model can be of assistance in exploring the issue of sustainability of metal resource use. Application of the model to historical trends shows it to be fairly capable of reproducing the long-term trends in the 1900–1990 period, among others on the basis of two intensity of use curves applied to 13 world regions. For future trends, a set of perspective-based long-term scenarios has been constructed that represent the major paradigms in resource use. These scenarios highlight some of the uncertain factors in the relation between economic growth, metal resource exploitation and use, and energy and environmental consequences. They also indicate that apparently similar metal flows in society may be the result of quite different and sometimes contrary assumptions on metal demand, production patterns and resource base characteristics. Such analyses contribute to a more open and transparent discussion on the issue at hand by adding quantitative explications to qualitative views.     

Studies on Biodegradation of Nicotine by Arthrobacter sp. Strain HF-2

A nicotine-degrading bacterium, strain HF-2, was isolated from tobacco waste-contaminated soil and identified as a member of Arthrobacter sp. based on morphology, physiological tests, 16S rDNA sequence and phylogenetic characteristics. At thermal denaturation test indicated that the G + C mol% of strain HF-1 was 63.5. The relationship between the growth of the isolate and the nicotine degradation suggested that strain HF-2 could utilize nicotine as sole sources of carbon, nitrogen and energy. Blue pigment was observed during the nicotine degradation by strain HF-2. The isolate grew well at 20 to 33°C, initial pH 6.5 to 8.0 and 0.5 to 2.0 g L^?1 of nicotine concentration in the nicotine inorganic salt media. The maximum growth and nicotine degradation occurred at 30°C, initial pH 7.0 and 0.7 g·L^?1 of nicotine concentration in media under natural incubation condition. Strain HF-2 could degrade 100% of nicotine under the optimized incubation conditions for 43 h. The concentrations of nicotine were monitored by high performance liquid chromatography. This study demonstrates Arthrobacter sp. strain HF-2 had a great ability to degrade nicotine, and it may be available for the application to the bioremediation of environments contaminated by tobacco waste.     

Dynamic material flow analysis of zinc resources in China

Zinc is one of the most widely applied nonferrous metals in China. Study on the applications and recurrent situation of zinc resources is of great strategic importance for the sustainable development of China's economy. In this paper, a dynamic material flow analysis (MFA) method has been adopted to analyze quantificationally zinc resources in China, as well as to analyze and predict the quantity of zinc product scrap and their recycling situation. The weighted average method was applied to calculate average lifetimes of six major zinc products in China. The average lifetimes of battery, zinc oxide, zinc die-casting alloys, zinc material products, galvanized zinc and brass are 0.17, 5.3, 11.1, 12, 21 and 30 years, respectively. Assuming the lifetime of zinc product group obeys the Weibull distribution and the consumption of zinc products varies linearly with time, the future consumption and scrap generation of zinc products will increase continuously. It is expected that they would increase from 49% to 76% during 2004–2020, respectively. Assuming the recycling rate remains unchanged with time, the zinc old scrap index, both the theoretical and actual values, would continue increasing in China. The values are expected to reach 0.402 and 0.076 by 2020, respectively. Therefore, the regeneration resource of depreciated zinc is actually insufficient in China. According to the scenario analysis, the actual value of old scrap indexes is positively correlated with the recycling rate of zinc products. Because galvanized products are the largest consumption area of zinc products in China, the influence of their recycling rate on old scrap index is obviously larger than other zinc products. Through the analysis, this paper suggests that the increase of the recycling rate of zinc products could not only improve to a certain degree China's relative shortage of zinc resources, but greatly relive the supply pressure of zinc in the world.     

公路隧道内危险物质泄漏扩散的研究

针对隧道内装有危险物质 (乙炔 )的载重车在行驶过程中发生小孔泄漏导致乙炔扩散的情况 ,建立了物理数学模型。即采用有限体积法和Simple算法 ,求解雷诺时均的Navier Stokes方程和k ε湍流模型。分析了车辆行使过程中危险物质释放前后隧道内的流场和两种释放方式下 (水平释放、垂直释放 )乙炔的浓度分布 ;针对不同的泄漏方式 ,考虑了后面跟随车辆及隧道顶部通风对乙炔扩散过程的影响 ;得出了有意义的结果 ,为进一步了解实际情况下危险气体扩散行为 ,并加以控制和减少事故提供了理论依据。     

大型游艺机——过山车的安全性分析

研究基于虚拟样机技术的过山车的安全性问题,旨在解决传统设计的弊端,有效降低设计成本,提高过山车的安全性能。在ADAMS软件中建立过山车的虚拟样机模型。研究轨道圆环直径、车厢重量、制动力对过山车安全性能的影响,获得以上各参数的合理范围,使车厢连接副受力状况与加速度得到改善,制动力精确性得到提高。为探索运动类特种设备———过山车的安全保障技术提供了新途径。     

The biodegradation of lactic acid-based poly(ester-urethanes)

The biodegradability of lactic acid based poly(ester-urethanes) was studied using the headspace test method, which was performed at several elevated temperatures. The poly(ester-urethanes) were prepared using a straight two-step lactic acid polymerization process. The lactic acid is first condensation polymerized to a low molecular weight hydroxyl-terminated telechelic prepolymer and then the molecular weight is increased with a chain extender such as diisocyanate. In the biodegradation studies the effect of different stereostructures (different amounts of D-units in the polymer chain), the length of ester units, and the effect of crosslinking on the biodegradation rate were studied. The results indicate that poly(ester-urethanes) do not biodegrade at 25‡C, but at elevated temperatures they biodegrade well. The different stereostructures and crosslinking have a strong influence on the biodegradation rate. The length of ester units in the polymer chain also affects the biodegradation rate, but much less than crosslinking and stereostructure.     

被控对象动力特性对人操作者手控跟踪效率的影响

人操作者的手动控制能力在人机环境系统的工效研究中具有广泛的应用价值。本文研究了人操作者的手动控制能力，以跟踪时间、跟踪误差和失误率为评价指标；分析不同被控对象动力学特性对人操作者在两自由度跟踪能力的影响。