某铜矿山巷道内气溶胶浓度与粒径分布的测量和分析

目的 定性了解矿山巷道内气溶胶的浓度和粒径分布特性。方法 在巷道内的不同区间,分别用凝结核颗粒计数器和个人气溶胶测量仪巡测气溶胶的粒子数和质量浓度,并通过质量浓度的分级测量定性评价微米级气溶胶的粒径分布;在调度室内外,用金属丝网筛扩散法测量亚微米级气溶胶的粒径分布。结果 巷道内可吸入颗粒物(PM10)的平均质量浓度为0.42 mg/m³,其量值大小因工作断面而异,且受人工活动影响变化较大;巷道内粒径大于1.0 μm的颗粒物广泛存在,而粒子直径小于5 nm的气溶胶基本上未被检出。结论 矿山巷道内气溶胶特性因工作断面、人工活动和通风条件的不同而变化明显,在开展内照射剂量评价时应考虑粒径大于1.0 μm放射性气溶胶粒子的剂量贡献。     

天然放射性气溶胶的粒径分布及其测量方法

天然放射性气溶胶粒径分布的变化会引起氡及其子体所致肺剂量的较大涨落。由于我国对其报道甚少，在肺剂量估算中均引用ＵＮＳＣＥＡＲ的推荐值。为验证这种引用的合理性和建立气溶胶粒径分布的测量方法，开展本项研究。方法采用金属丝网筛（１６５目）扩散法测量天然空气经不同数目网筛扩散前后的放射性浓度比（衰减比）来绘制衰减曲线，然后用池边模式计算出粒径分布曲线。衰减比、粒径分布的计算和曲线的绘制均采用计算机。结果室内外天然放射性气溶胶粒径呈几何正态分布，分布的峰值的平均值分别为（０．２０±０．０９）μｍ和（０．２７±０．１１）μｍ。粒径分布和氡浓度、气压、气温、湿度等未发现相关关系。结论本研究结果与ＵＮＳＣＥＡＲ报告书（１９８８）的推荐值相比，室内值相同，室外值略高，与Ｊａｃｏｂｉ的研究相近。由此可得出结论，福州地区引用ＵＮＳＣＥＡＲ报告书的推荐值来估算氡及其子体所致肺剂量是合适的。此结论能否推广到其他地区，还需作进一步的研究。     

Relationship of Diet to Small and Large Adenomas of the Sigmoid Colon

The relation of dietary factors to the risk of adenomas of the sigmoid colon was examined in men receiving a retirement health examination at the Self-Defense Forces Fukuoka Hospital between October 1986 and 1990. A total of 187 adenoma cases and 1557 controls with normal colonoscopy were identified in the series. Cases were further classified into small-adenoma (<5 mm, n=78) and large-adenoma (≥5 mm, n=67) groups. The consumptions of selected foods and beverages were ascertained before colonoscopy by means of a self-administered questionnaire. After adjustment for smoking, alcohol use, rank and body mass index, low rice consumption and high meat intake were independently associated with an increased risk of large adenomas. The risk of small adenomas was not related to either rice consumption or meat intake. Adjusted odds ratios of large adenomas for the low, intermediate and high consumption levels of rice were estimated to be 1.0 (referent), 0.83 and 0.43, respectively (trend P = 0.08), and the corresponding figures for meat consumption were 1.0 (referent), 1.58 and 2.38, respectively (trend P =0.02). The findings suggest that low rice consumption and high meat intake may promote the growth of colon adenomas, thereby increasing the risk of colon cancer.     

盛夏时节成都市区空气飘尘浓度及分散度测试分析

利用光散射法对盛夏时节成都市区空气中的风尘浓度及分散度进行了测试，并就风尘的粒径分布及分散度的统计模式、气象参数时飘尘浓度的影响，以及飘尘浓度和分散度的日变化进行了分析。结果表明：成都市区空气中飘尘的大多数粒径分布的统计模式为Ｊｕｎｇｅ分布，峰值浓度出现在中午１２：００前后，相对湿度对空气中飘尘浓度影响显著，降雨对风尘有明显的清除作用。测试结果对评价城市环境卫生条件和分析人类活动对环境的干扰情况有参考价值。     

A morphological transition in the pleomorphic bacterium Ramlibacter tataouinensis TTB310

We provide microscopic evidence that motile rod-shaped forms of Ramlibacter tataouinensis TTB310 are formed from dividing cyst-like cells. Careful estimation of the size of the two morphotypes was conducted using optical and transmission electron microscopy (TEM). The cyst-like cell was shown to be a sphere with a diameter Dc=850 nm. The rod-shaped form was a round-ended cylinder with length Lr=2.91 microm and diameter Dr=239 nm. The membrane area of the two morphotypes was the same. However, the formation of rods from cysts involved loss of two-thirds of the cell volume. TEM showed that, prior to division and transition into rods, cysts contained condensed cytoplasmic material. These results suggest that the morphological transition occurs by pure reshaping of cells.     

How sensitive is hand transport to illusory context effects?

A recent report that hand transport was sensitive to a size-contrast illusion (SCI) implied that the distinction between visual processing for perception versus action might only affect visual information obtained late during reaching. In this study, the presence of a perceptual SCI did not affect reaction time, movement time, or movement amplitude. However, both perception and action became sensitive to the SCI with memory-based responses. It is concluded that the distinction between visual processing for perception versus action does extend to hand transport. Immediate action is entirely based on veridical visuo-motor representations, whereas even slightly delayed actions begin to reflect distorted perceptual representations.     

Variable abundance of a mitochondrial DNA fragment in cultured tobacco cells

Summary The relative abundance of a cloned 4.5 kilobase (kb) pair mitochondrial DNA sequence in two suspension cultures of tobacco (Nicotiana tabacum cv Turkish samsun and Nicotiana tabacum NT-1) has been examined. This sequence is 70-fold reduced in NT-1 relative to Turkish samsun; the reduction is correlated with an increase in supercoiled mitochondrial DNA. This sequence does not hybridize with mitochondrial DNA from watermelon, maize, or Saccharomyces cerevisiae, nor with several cloned mitochondrial genes and is thus probably not a gene. It may represent most of the plant mitochondria) genome thought to be non-essential for mitochondrial function. The sequence complexity of supercoiled mitochondrial DNA from NT-1 cells is about one-third that found for the entire mitochondrial genome and does not include the cytochrome oxidase subunit II gene.     

Optimum support properties for protein separations by high-performance size exclusion chromatography

Optimum chromatographic properties of high performance size exclusion chromatography (HPSEC) of proteins, such as resolution, molecular weight accuracy and recovery, are obtained on packings and columns with tailor-made physical and chemical structures, employed at properly adjusted eluent compositions and operation conditions. SEC-theory suggests that a broad molecular weight fractionation range and high linearity of the log-linear calibration plot can be achieved by the use of two packings (10- and 80-nm pore size, characterized by a pore-size distribution (psd) equal to or less than 1 decade and by equal internal column porosity (p)), rather than a single 30- to 50-nm pore-size packing with a wide psd. Favourably high-phase ratios of (p)/(o)/ 1.0 for HPSEC columns were accomplished with a minimum interstitial column porosity (o) and a high value for the internal column porosity (p) (the specific pore volume, nu(p), multiplied by the packing density, varrho(p).) Ligands such as diol, N-acetoxyamino and oligomeric ether with a propyl- or propoxy-spacer bonded to the silica at the highest density appear to provide high mass recovery and bioactivity as well as chemical stability. Such packings, available in 3-5 mum particle size ranges of narrow distribution, packed into columns 6 mm i.d. and 500 mm in length, offer the best compromise with respect to resolution, speed and pressure drop. More careful studies are required to explain the effects of protein conformational changes and interconversions during elution on HPSEC columns.     

Molecular weights of poly(butyl cyanoacrylate) nanoparticles determined by mass spectrometry and size exclusion chromatography

Matrix-assisted laser desorption ionisation time-of-flight mass spectrometry (MALDI-TOF MS) and size exclusion chromatography (SEC) were employed to elucidate the chemical composition, mean number average molecular weight (M_n), mean weight average molecular weight (M_w), and polydispersity (PD) of poly(butyl cyanoacrylate) (PBCA) manufactured by emulsion polymerisation. Both methods gave similar results for M_n, but substantial differences were observed for M_w and PD, with MALDI producing consistently lower values which could not be improved by off-line coupling of SEC and MALDI. MALDI gave a more detailed view on the chemical composition of the cyanoacrylate and revealed the presence of two additional polymer series with different end groups besides the expected PBCA series, which showed different retention in SEC. Their formation is explained by the secession/addition of formaldehyde from/to the regular polymer via (reverse) Knoevenagel reaction. In additional experiments, the influence of different pH on PBCA-NP during polymerisation was examined by comparison of polymerisation yield and particle diameter to their chemical composition as revealed by the MALDI spectra. The most uniform nanoparticles, with the highest polymerisation yield, narrowest particle size, and mass distribution were produced at pH 1.