EFFECT OF THE RATIO Th/U ON TL DATING ACCURACY

ＥＦＦＥＣＴＯＦＴＨＥＲＡＴＩＯＴｈ／ＵＯＮＴＬＤＡＴＩＮＧＡＣＣＵＲＡＣＹ￥Ｐ．Ｌ．Ｌｅｕｎｇ（梁宝鎏）；ＭｉｃｈａｅｌＪ．Ｓｔｏｋｅｓ（ＤｅｐａｒｔｍｅｎｔｏｆＰｈｙｓｉｃｓａｎｄＭａｔｅｒｉａｌｓＳｃｉｅｎｃｅ，ＣｉｔｙＰｏｌｙｔｅｃｈｎｉｃｏ...     

用αβ谱仪测量人工αβ放射性气溶胶体积活度的试验研究

本文介绍了用αβ谱仪系统同时测量αβ谱、实现Ｒｎ／Ｔｈ子体补偿、确定超铀α核素气溶胶体积活度及人工放射性气溶胶总β体积活度的技术途径。利用ＲａＡ、ＲａＣ′ａ峰的二段时间计数可确定空气中ＲａＡ、ＲａＢ、ＲａＣ的气溶胶体积活度，相应的，也能给出ＲａＢ、ＲａＣ对总β计数的贡献。根据一般环境条件下的平衡比，用ＴｈＣ′的。计数修正Ｔｈ子体对αβ测量的影响。￣［２３９］ｐｕ或／和￣［２４１］Ａｍ人工核素的α计数，可通过两段时间分别扣除ＲａＡ、ＲａＣ′拖尾的方法确定；β计数分别扣除Ｒｎ／Ｔｈ子体β贡献即可确定。在本文规定的测量条件下，对室内天然Ｒｎ子体水平在１５Ｂｑ／ｍ￣３以下，超铀α核素气溶胶体积活度的测量下限可达到０．１Ｂｑ／ｍ￣３；即使在７５Ｂｑ／ｍ￣３环境下，人工核素总β的测量下限也可达ｌＢｑ／ｍ￣３以下。     

钍归-化在盆地γ能谱资料处理中的应用

在应用γ能谱资料寻找砂岩型铀矿的过程中，要尽可能地消除非矿化因素引起的干扰，提取与铀矿化有关的信息。介绍了钍归-化的原理及特点，采用与矿化有关的元素迁移信息的钍归-化方法，分析了二连盆地东部的γ能谱资料，揭示了该区放射性元素的分布特征、地球化学作用和后期铀元素的迁移与富集。结合其他地质资料，分析了钾剩差的变异区（正、负高值区）及铀剩差正高值区形成的原因，同时指出了经过钍归-化处理所得到的铀剩差正高值区应为氧化与还原作用过渡带的直接指示，也是该区进一步寻找砂岩型铀矿的重要标志。     

鄱阳湖湖底沉积物放射性水平

本文报道了1985年鄱阳湖湖底沉积物放射性水平的调查结果。沉积物中 U、Th、~(226)Ra、~(40)(?)和~(137)Cs 的比活度分别为64.8、67.9,58.9、676.1和3.5Bq/kg;用~(137)Cs 测龄方法作了沉积物泥芯垂直深度的年代定位,由此得知1985—1958年对应深度沉积物中 U、Th、~(226)Ra 和~(40)K 的比活度与1957—1930年对应深度沉积物比较无显著性差异;U、Th 和~(226)Ra 的浓集因予分别为5.2×10~413.9×10~4和4.8×10~4L/kg。     

未知钍—铀比的误差分析

研究了在任意Th、U含量和Th-U比覆盖整个范围(即0≤Th/U≤∝)时总α计数率对年剂量的转换因子及其误差。结果表明,当不测定Th-U比而只测量总α计数率时,最终引起的年龄误差对0≤Th/U≤∝来说为±5.1％-±8.3％,对1.1≤Th/U≤9.5来说只有±2.5％％-±4.1％。     

Non-polar nuclei in fungal microbial RNases

An application of a previously proposed method for the analysisof the non-polar structure of proteins is presented. A detailedanalysis of the composition and properties of non-polar nucleiand microclusters of fungal microbial ribonucleases has beenperformed on the basis of the 3-D structures of RNase T1 andrelated proteins. Three hydrophobic nuclei were found in thesestructures. It has been shown that all residues in non-polarnuclei have high homology ({small tilde}89%). Residues in thenuclei are practically fully buried in the interior of a molecule.Detailed analysis of non-polar nuclei properties shows thatthese nuclei determine the hydrophobic core of a protein andthe location and role of each residue in the non-polar interiorof proteins. In addition it was found that there are variableresidues not only on the surface of a protein but on the surfaceof the nuclei inside the protein and between the nuclei andthat there is a consistent region in all proteins, the hydrophobic-nuclei. An evaluation of the stability of non-polar nuclei,the conservation of their compositions and their positions inthe protein globule, allows one to assume that these three nucleiplay an important functional role in the stability and foldingof molecules of RNases and possibly can be considered as independentstructural elements of 3-D structures of these proteins.     

光纤陀螺随机误差特性ThêoH辨识

随机误差特性分析是光纤陀螺进入工程应用阶段的关键技术.针对Allan方差、总方差、Thêo1 (Theoretical variance #1)等分析方法的不足,以Thêo1为基础,通过偏差消除获得ThêoBR(Bias-removed ver?sion of Thêo1),并将其与Allan方差合成,得到光纤陀螺随机误差特性分析的ThêoH(Hybrid-ThêoBR)法.通过计算重叠Allan方差、总方差、Thêo1以及ThêoH的等效自由度,结合仿真和实测信号的随机误差特性分析实验,证明ThêoH法不仅提高了Allan方差估计的置信度,且解决了Thêo1估计有偏的问题,表明了该方法是目前能够有效辨识光纤陀螺随机误差特性的最佳方法.     

有机物中微量砷测定方法的改进

在对有机物中微量砷测定方法综合分析的基础上，选用了砷斑法￣［１］与Ａｇ－ＤＤＴＣ法￣［２］相结合的方法检测有机物中的微量砷。重点对Ａｇ－ＤＤＴＣ法的操作内容作了两处改进。实验表明，新方法检测有机物中的微量砷快速、准确。     

从60 MeV/u18O离子辐照过的钍中分离Ra

对以^212Pb,^133Ba和^224Ra比作示踪剂，（NH4）2H2EDTA为淋洗剂，用阳离子交换法从Pb、Ba中分离Ra的工艺条件做了研究。提出了一个从60MeV／u ^18O离子辐照过的ThO2靶中分离Ra的放射化学流程。实验结果表明，该流程对主要反应产物，特别是Ba的去污较好，Ra的产额可达70％以上。     

Photoreceptor Cells Constitutively Express IL-35 and Promote Ocular Immune Privilege

Interleukin-27 is constitutively secreted by microglia in the retina or brain, and upregulation of IL-27 during neuroinflammation suppresses encephalomyelitis and autoimmune uveitis. However, while IL-35 is structurally and functionally similar to IL-27, the intrinsic roles of IL-35 in CNS tissues are unknown. Thus, we generated IL-35/YFP-knock-in reporter mice (p35-KI) and demonstrated that photoreceptor neurons constitutively secrete IL-35, which might protect the retina from persistent low-grade inflammation that can impair photoreceptor functions. Furthermore, the p35-KI mouse, which is hemizygous at the il12a locus, develops more severe uveitis because of reduced IL-35 expression. Interestingly, onset and exacerbation of uveitis in p35-KI mice caused by extravasation of proinflammatory Th1/Th17 lymphocytes into the retina were preceded by a dramatic decrease of IL-35, attributable to massive death of photoreceptor cells. Thus, while inflammation-induced death of photoreceptors and loss of protective effects of IL-35 exacerbated uveitis, our data also suggest that constitutive production of IL-35 in the retina might have housekeeping functions that promote sterilization immunity in the neuroretina and maintain ocular immune privilege.