混合矩阵为病态情况下的盲信号提取快速算法

在盲信号提取技术中,当混合矩阵是病态情况（混合矩阵奇异或欠定）时,根据混合矩阵秩的性质,提出了在该情况下的盲信号可提取性判据,并给出了一种可提取信号的快速提取算法。该算法中只使用了待提取信号与其他观测量之间的四阶累积量,而不需要计算各个观测量之间的四阶累积量,因此大大减少了算法的复杂度。先提取信号的误差没有对后提取的信号产生累积,因此提高了提取信号的精确度。该算法简单。仿真结果表明该算法有效,并且有很好的性能。     

Monoclonal antibodies against troponin I for the detection of rendered muscle tissues in animal feedstuffs

Regulatory controls to prevent the spread of BSE have prohibited the use of certain animal proteins in feed in several countries. Accurate analytical methods for detecting prohibited material in feedstuffs are needed to ensure compliance with the new regulations. Six IgG class monoclonal antibodies (MAbs) against troponin I (TnI), a thermostable marker protein, have been developed for the detection and differentiation of rendered muscle tissue in animal feed. MAbs 1F9, 2G3 and 7F7 reacted to TnI of all species, including mammalian, poultry and fish, while MAbs 7A12 and 8A12 recognized only mammalian TnI (porcine, bovine, ovine, equine, and deer). MAb 2A8 was able to differentiate TnI of ruminant origin (bovine, ovine and deer) from other species. Three indirect enzyme-linked immunosorbent assays (ELISAs) employing these MAbs were developed for the determination of animal muscle, mammalian muscle or ruminant muscle in animal feeds.     

冷轧多晶纯镍中晶界对显微硬度和微观组织结构的影响

纯度为99．9％的多晶镍（晶粒尺寸为0．5～2mm），被轧制到55％形变量，用测试显微硬度的手段研究选定晶粒内部的形变不均匀性．用扫描电镜（SEM）上的背散射电子衬度成像分析晶粒内不同位置的微观组织的变化。结果表明，与轧制方向成较大角度的晶界的影响导致晶粒内形变的不均匀性，造成微观组织及形变储能的不同，宏观上表现为显微硬度的不同。     

A test of Rasmussen's risk management framework in the food safety domain: BSE in the UK

In 1986, bovine spongiform encephalopathy (BSE) was identified in the UK. Millions of BSE-infected cows were slaughtered and over 150 people contracted variant Creutzfeldt–Jakob disease, an inevitably fatal human form of BSE. Tragic incidents such as this provide valuable opportunities to understand and improve the safety of complex socio-technical systems. By studying accidents, knowledge can be gained that can improve system safety. The purpose of this article is to test the usefulness of Rasmussen's risk management framework for explaining how and why accidents occur in the food production domain. This was accomplished by using the framework to retrospectively investigate how and why BSE was transmitted through the human and animal food supply in the UK from 1986 to 1996. More specifically, an AcciMap and Conflict Map were constructed to represent contributing factors of the epidemic according to the structure of Rasmussen's framework. These factors were used to test the seven predictions made by the framework. All seven predictions were supported by the evidence, indicating that Rasmussen's risk management framework shows promise as a theoretically driven explanation of how and why accidents happen in complex socio-technical systems, particularly in the food production domain.     

Detection and survival of prion agents in aquatic environments

Environmental contamination is considered a potential mechanism of transmission of prion diseases. Sheep scrapie and cervid chronic wasting diseases (CWD) epizootics are thought to be maintained by natural horizontal transmission through the environment. Here, we describe a method for the detection of prion proteins (PrPres) in aquatic environments. The procedure is based on a glycine buffer-mediated extraction, sonication, and an ultracentrifugation step. The detection limit of the method was estimated to be over 5-10 microg of infected tissue. In order to determine the inactivation of these agents, we spiked infected brain tissue in urban sewage, seawater and a buffered solution (final concentrations of 0.1-0.2% brain in matrix), and studied the decay of BSE- and scrapie-associated PrPres over time (up to 265 days). Densitometric data from Western blots were plotted in logarithmic scale against time. Reduction of PrPres titer in sewage was quantified in one logarithm after 13.5 days for BSE, 27.9 days for mouse-passaged scrapie and 32.6 days for sheep scrapie. In the buffered solution, a logarithm of BSE-associated PrPres also disappeared earlier than that of scrapie (113.9 and 214.3 days, respectively). By means of the covariance analysis, these differences in the inactivation patterns were shown to be statistically significant. According to the data, prions may be stable for extended periods of time in buffered solutions like PBS, but would show limited survival in aquatic environmental matrices.     

Backscattered electron imaging of titanium dioxide in frozen hydrated preparations

Backscattered electron (BSE) imaging was used to study ultrafine TiO₂ crystals distribution in a test cream. The cream was fast frozen, cryofractured and observed uncoated at low temperature. The BSE detector was a microchannel plate. The results demonstrate that up-to-date photoprotective preparations can be investigated by this technique.