8Li次级束的产生

在北京串列加速器次级束流线上通过2 H(7Li,8Li) 1H逆运动学反应产生了用于核天体物理研究的8Li次级束。准直后的次级束纯度达到 80 %以上 ,对于 44MeV的7Li强度约为 3 0s- 1·pnA- 1,可以用来进行逆几何转移反应的实验测量。     

Microbiological safety of kinema, a fermented soya bean food

Kinema is a fermented soya bean food of Nepal and the hilly regions of North-eastern States of India. Generally, the fermentation is dominated by Bacillus spp. that often cause alkalinity and desirable stickiness in the product. The present study was undertaken in a limited number of commercial (market) kinema samples to test for the presence of foodborne pathogens and their properties. Bacillus cereus was present in numbers exceeding 10⁴ cfu/g product in five of the tested 15 market samples. Enterobacteriaceae and coliform bacteria exceeded 10⁵ cfu/g in 10 of the 15 samples. Escherichia coli exceeding 10⁵ cfu/g was found in two samples. Staphylococcus aureus was not detected in any of the tested samples. Of 31 isolated typical and atypical strains of B. cereus, 18 representative strains were tested qualitatively for the ability to produce diarrhoeal type enterotoxin (BCET) using an Oxoid BCET-RPLA test kit. Overall, BCET was formed by 12 strains in BHIG (brain heart infusion broth +1% glucose), by seven strains on sterilized cooked rice, and by five strains on sterilized cooked soya beans. Semi-quantitative tests on BCET revealed that levels exceeding 256 ng/g soya beans, produced by single pure culture inoculation with the isolated B. cereus strains, were reduced to ≤ 8 ng/g by frying kinema in oil, a common procedure when making kinema curry. It was also shown in a mixed pure culture experiment that a kinema strain B. Subtilis DK-W1, is able to suppress growth and BCET formation by a selected toxin producing strain (BC7-5) of B. cereus. It is concluded that the traditional way of making kinema and its culinary use in curries is safe. However, for novel applications of kinema, safety precautions are advisable.     

热成型机曲柄肘杆开合模机构的设计及仿真

在充分分析热成型工艺对开合模机构性能要求的基础上。设计了一种新型的曲柄肘杆开合模机构,并采用矢量法建立了数学模型;在MATLAB软件中编程求解,对机构进行仿真分析。得到了其运动学及动力学参数,并验证了曲柄肘杆开合模机构设计的合理性。     

Changes in Soya Bean Lipid Profiles during Kinema Production

The influence of processing on soya bean lipids during kinema production was studied. The crude lipid (CL), free fatty acid (FFA) and phytosterol contents of raw beans were 121 g, 6·9 g and 0·8 g kg⁻¹ dry matter, respectively. After soaking and cooking the moisture content of beans increased significantly from 121 to 749 g kg⁻¹, whilst the lipid contents were unchanged. During a 2 day fermentation at 37°C, the lipid contents increased significantly as indicated by capillary column gas chromatography (GC) analysis of petroleum ether extracts of lyophilised samples of unfermented and fermented beans. The fatty acids, palmitic (C16:0), stearic (C18:0), oleic (C18:1), linoleic (C18:2), linolenic (C18:3) and arachidic (C20:0) acids were identified. The major fatty acid present in all samples was the essential fatty acid, linoleic acid. All of the aforementioned fatty acids (except arachidic) were liberated during fermentation by microbial lipases, yielding approximately the same proportion of fatty acids found in unfermented beans. The unsaponifiable soya bean lipids identified by GC were campesterol, stigmasterol and β-sitosterol (ratio 1·2:1:3·4). Levels of these increased during fermentation by 50–61%, but remained in approximately the same proportions.     

B-group vitamin and mineral contents of soybeans during kinema production

Concentrations of several B-group vitamins, determined by high-performance liquid chromatography (HPLC), and minerals, determined by inductively coupled plasma atomic emission spectroscopy (ICP-AES), in soybeans during different kinema production stages were compared. After soaking soybeans in water, thiamine (B₁) content decreased, whereas riboflavin (B₂) content remained unchanged. Cooking had no influence on the B₁ content, but it enhanced the level of B₂ and niacin (B₃). Incubation of beans at 37°C for 48 h, when mixed with Bacillus subtilis, caused an increase in concentration of both B₁ and B₂. Vitamin B₁ levels decreased when either Enterococcus faecium accompanied B subtilis or the temperature was elevated for 18 h fermentation. Traditionally prepared kinema contained 8 mg B₁, 12 mg B₂, 45 mg B₃, 683 mg Ca, 4 mg Cu, 18 mg Fe, 494 mg Mg, 10 mg Mn, 1257 mg P, 2077 mg K, 13 mg Zn and <0·5 mg of Cd, Cr, Pb, Ni and Na per kg dry matter. While the vitamin B₁ content was significantly (P<0·05) higher, the contents of vitamins B₂ and B₃ were significantly (P<0·05) lower in raw soybeans than those in kinema. Mineral concentrations were 3·1–8·3 times higher in raw soybeans than in kinema. © 1998 Society of Chemical Industry.