THE OPTIMAL HARVESTING OF A PREDATOR-PREY SYSTEM WITH STAGE-STRUCTURE

In this paper,we establish the exploitation of continuous harvest of preda- tor and prey with stage-structures.We investigate the properties of harvesting multispecies systems.With some special methods,we obtain boundedness and global attractiveness of all the nonnegative equilibria for proportional harvest. Finally,we solve the problem of optimal harvest policy using Pontragin's ma- ximal principle.     

Preparation of copper aluminum borate whiskers via flux method

Single‐crystal and uniform copper aluminum borate whiskers have been synthesized by heating a mixture of boric acid, copper sulfate and aluminum sulfate with potassium sulfate as flux at 870 °C for 4 h. The synthesized whiskers exhibit a well‐crystallized, one‐dimensional structure with diameters ranging from 100 nm to 5 μm, lengths from 5 to 100 μm. Heating temperature and flux addition affect the aspect ratio and morphology of the copper aluminum borate whiskers. A possible growth mechanism of the whiskers is proposed. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

8-METHOXYPSORALEN DNA INTERSTRAND CROSS-LINKING OF THE RIBOSOMAL RNA GENES IN Tetrahymena thermophila. DISTRIBUTION, REPAIR AND EFFECT ON rRNA SYNTHESIS

Abstract— The distribution and repair of 8-methoxypsoralen-DNA interstrand cross-links in the ribosomal RNA gencs (rDNA) in Tetrahymena thermophila have been studied in vivo by Southern blot analysis. It is found that the cross-links at a density of ≤ 1/2 × 10⁴ base pairs (bp) are distributed equally between three domains (terminal spacer, transcribed region and central spacer) as defined by restriction enzyme analysis ( Bam HI and Cla I). It is furthermore shown that a dosage resulting in approximately one cross-link per rDNA molecule (21 kbp, two genes) is suficient to block KNA synthesis. Finally, it is shown that the cross-links in the rDNA molecules are repaired at equal rate in all three domains within 24 h and that RNA synthesis is partly restored during this repair period. The majority of the cells also go through one to two cell divisions in this period but do not survive.     

乙烯在Ru( )表面价带电子特性研究

在200K以下乙烯（C2H4）可以在Ru（1010^-）表面上以分子状态稳定吸附,200K以上乙烯发生了脱氢分解反应生成乙炔（C2H2）。乙烯分解生成乙炔后,σCC和σCH 分子轨道能级向高结合 能方向分别移动了0.5和1.1eV。偏振角分辨紫外光电子谱（ARUPS）结果表明：在Ru(10106-)表面上,乙烯和脱氢反应后生成的乙炔分子在C－C键轴都不平行 于表面,而是沿表面<0001>晶向倾斜。     

气相色谱-飞行时间质谱法测定食用植物油中197种农药残留

建立了气相色谱-飞行时间质谱(GC-TOF-MS)同时测定食用植物油中197种农药残留的方法。样品经乙腈超声提取,冷冻除脂,C18和PSA吸附剂共同净化;目标物经HP-5MS UI毛细管柱(30 m×0.25 mm×0.25 μm)分离,电子轰击源电离,全扫描模式采集质谱信息;MassHunter软件对数据进行定性与定量分析,设置精确质量数偏差为±5×10^-5,保留时间偏差为±0.1 min。实验考察了基质效应情况和方法学性能。结果表明,大多数农药表现出基质增强效应,需采用基质标准工作溶液进行定量。在优化的条件下,174种农药定量限可以达到0.01 mg/kg,占全部被测农药的88%,另外23种农药的定量限为0.025~0.1 mg/kg。除联苯的线性范围为2~100 μg/L外,其余农药的线性范围均为定量限~200 μg/L,相关系数(R²)均大于0.99。在3个添加水平(0.1、0.25和0.5 mg/kg)下,有156种农药的回收率为70%~120%,占全部被测农药的79%,有185种农药的相对标准偏差<10%,占全部被测农药的94%。应用该方法对23份市售植物油样品进行了检测,结果在12个样品中检出13种农药。该方法操作简便,一次进样即可实现近200种农药的同时检测,且检测结果的准确度和灵敏度良好,适用于食用植物油中197种农药残留的快速检测。     

链型抽样方案综述(Ⅰ)

本文讨论了链型抽样方案（ｎ,ｉ）及其操作特性函数,并介绍了选取方案的方法。为制定链型抽样方案的检验标准及在实际中使用链型抽样方案提供理论依据     

K/Ru(10(1-)0)表面上的CO-4a1轨道对称性确定

用同步辐射角分辨偏振紫外光电子谱对K/Ru(10(1-)0)面上吸附的CO分子轨道的对称性测量发现:结合能在11.2eV的CO-4a1(4σ)分子轨道对s偏振光(在沿<1(2-)10>的入射面)是禁戒的.结果表明由于K的强烈影响,CO的分子轨道重新排列(sp2杂化).依据选择定则和分子轨道的对称性说明,sp2再杂化的CO分子吸附的桥位取向是<1(2-)10>晶向.     

Optical phonon modes and transmissivity in BaWO4 single crystal

Barium tungstate (BaWO₄) single crystal has been grown using Czochralski technique. It belongs to the scheelite structure, forming the space group I 4₁/a at room temperature and the primitive cell contains two molecular units. The polarized Raman spectra were recorded by a micro‐Raman spectrophotometer system in the backscattering geometry. All the observed Raman modes were assigned. The Raman mode at 924 cm^–1, which belongs to the totally symmetrical A_g optical modes, has the strongest intensity and its linewidth is 4.6 cm^–1. The infrared active lattice vibrations have been studied, eight optical modes were observed and assigned. The ultraviolet absorption edge is at 256 nm and the optical transparency range is up to 2500 nm at room temperature. The energy gap E_g of this crystal was obtained from the optical transmission spectra. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

气相色谱-质谱联用同时分析新型细菌多糖中的单糖和糖醛酸

对纯化的新型细菌多糖进行酸水解,用乙硫醇-三氟乙酸和醋酐-吡啶体系先后对酸水解物进行衍生,与之前报道不同的是糖醛酸得到有效衍生化。以木糖为内标,采用气相色谱-质谱联用(GC-MS)定量分析该多糖酸水解物中单糖和糖醛酸衍生物发现,该多糖的糖链由岩藻糖、葡萄糖、葡萄糖醛酸和半乳糖组成,其相对物质的量比为1.50:1.0:0.79:2.06;中性糖比例与糖醇乙酸酯化分析岩藻糖、葡萄糖和半乳糖的相对物质的量比(1.76:1.0:1.98)接近;糖醛酸咔唑法与该方法分析葡萄糖醛酸的含量分别为16.19%和14.85%。以上结果表明所建立的衍生化方法及GC-MS同时定量分析多糖酸水解物中单糖和糖醛酸的方法可行。此外还对葡萄糖醛酸的质谱裂解机理进行了阐述。     

CSNS靶站谱仪T0信号扇出设备研制

中国散裂中子源(Chinese Spallation Neutron Source, CSNS)靶站谱仪T0信号的高准确性和高可靠性是CSNS高效运行的重要条件之一。基于CPLD(Complex Programmable Logic Device)和PMC(Peripheral Mezzanine Card)子母板组合,设计了满足分布式架构的T0信号扇出设备,自主研制了24 V电平触发的中子斩波器专用触发信号接收插件;在1.6 GeV质子束首次打靶前,对T0信号延迟及信号调理做了优化。T0信号扇出设备接口信号灵活多变,具有较强的可维护性和可扩展性,已投入使用近三年,系统稳定可靠,为今后二期谱仪更高需求的T0信号扇出设备的研发积累了宝贵的建设经验。