碳酸二苯酯中微量杂质的高效液相色谱分析

碳酸二苯酯和双酚A产生酯交换和缩聚反应,制得聚碳酸酯.聚碳酸酯耐压、透明性好,在机械制造、电子电器、军事及照明工业.安全与医疗器械等许多方面有着广泛的用途,是一种性能优良的工程塑料.聚碳酸酯的色泽与许多因素有关.由于原料碳酸二苯酯在制造过程中,一些沸点与之相近的杂质极易残留在产品里.要想得到高质量的聚碳酸酯,必须使其每一种杂质含量控制在100μg/g以下.至今未见报道同时检测碳酸二苯酯中3种微量杂质的分析方法.因此,本文结合单位工艺研究建立了一种用液相色谱进行分析的方法.     

252Cf冷裂变瞬发γ射线

用四参量关联实验技术研究了²⁵²Cf冷裂变瞬发γ射线发射性质. 孪生屏栅电离室收集极和栅极信号分别用于确定碎片的动能和发射角. 圆柱形电离室轴线上的NaI(T1)晶体用于符合记录裂变瞬发γ射线.结果表明,不仅冷裂变瞬发γ射线角分布系数约为正常二分裂变值的两倍,而且冷裂变轻碎片发射的γ射线数目几乎是重碎片发射数目的三倍.对后一实验事实目前尚未有满意的理论解释.     

Stability of Inverse Problems for Ultrahyperbolic Equations

In this paper, the authors consider inverse problems of determining a coefficient or a source term in an ultrahyperbolic equation by some lateral boundary data. The authors prove Hlder estimates which are global and local and the key tool is Carleman estimate.     

Rapid isocratic HPLC investigation of radiochemical purity for <Superscript>90</Superscript>Y-DOTATATE

DOTA-conjugated peptides, such as [DOTA⁰, Tyr³]ocreotide (DOTATOC) and [DOTA⁰, Tyr³]octreotate (DOTATATE) can be labeled with radionuclides such as ⁹⁰Y, ¹⁷⁷Lu and ¹¹¹In at high specific activities. These radiolabelled somatostatin analogues are used for peptide receptor radionuclide therapy (PRRT). Currently, radio-high performance liquid chromatography (radio-HPLC) and radio-thin layer chromatography (radio-TLC) are the methods of choice for the analysis of the labeled compounds. In literature, radiochemical purity of the radiolabelled DOTATATE was investigated using gradient reversed-phase radio-HPLC. However, these studies indicate long retention time of the radiolabelled compound of 14.52 min. In our study, a new simple and rapid reversed-phase isocratic system enables the radiochemical purity of the radiolabelled DOTATATE within a few minutes.     

p53 overexpression represses androgen-mediated induction of NKX3.1 in a prostate cancer cell line

Prostate cancer is a disease involving complicated multiple-gene alterations. Both NKX3.1 and p53 are related to prostate cancer and play crucial roles in prostate cancer progression. However, little is known about the relationships and interactions between p53 and NKX3.1 in prostate cancer. We found that NKX3.1 expression is down-regulated by over-expression of wild type (wt) p53 in prostate cancer LNCaP cells. NKX3.1 is down-regulated at both the mRNA and protein levels by p53 over- expression due to either transient transfection of exogenous p53 or induction of endogenous p53. p53 over-expression represses androgen-induced transactivation of NKX3.1 by inhibiting the promoter of the androgen acceptor (AR) gene and by blocking AR-DNA binding activity. In addition, transfection with the p21 expression vector (pPSA-p21) showed that p21 does not reduce NKX3.1 expression, indicating that NKX3.1 expression is not the result of nonspecific effects of cell growth arrest. Our results provide biochemical and cellular biologic evidence that NKX3.1 is down-regulated by p53 over-expression in prostate cancer cells.     

High-resolution discrete absorption spectrum of alpha-methallyl free radical in the vapor phase

The alpha-methallyl free radical is formed in the flash photolysis of 3-methylbut-1-ene, and cis-pent-2-ene in the vapor phase, and then subsequent reactions have been investigated by kinetic spectroscopy and gas-liquid chromatography. The photolysis flash was of short duration and it was possible to follow the kinetics of the radicals' decay, which occurred predominantly by bimolecular recombination. The measured rate constant for the alpha-methallyl recombination was (3.5+/-0.3) x 10(10) mol(-1) ls(-1) at 295+/-2K. The absolute extinction coefficients of the alpha-methallyl radical are calculated from the optical densities of the absorption bands. Detailed analysis of related absorption bands and lifetime measurements in the original alpha-methallyl high-resolution discrete absorption spectrum image were also carried out by image processing techniques.     

Controlling morphology and particle size of hollow poly(styrene-divinylbenzene) microspheres fabricated by template-based method

Hollow poly(styrene–divinylbenzene) (P(S-DVB)) microspheres were fabricated via template-based method including synthesis of silica particles by sol-gel method, preparation of silica/P(S-DVB) particles by dispersion polymerization and chemical etching of silica cores by NaOH solution. TEM, FTIR and TG analyses confirmed that the hollow P(S-DVB) microspheres were successfully obtained. The morphology of hollow P(S-DVB) microspheres could be controlled by adjusting the amounts of DVB, AIBN and VTES, and the round-ball-like hollow P(S-DVB) microspheres were fabricated when the amount of DVB, AIBN and VTES was 30.0?wt%, 5.0?wt% and 30.0?vol% respectively. Both the size of silica particles and amount of monomers were regarded as the two key factors to control the particle size of the round-ball-like hollow P(S-DVB) microspheres.     

Comparative study of the water oxidizing reactions and the millisecond delayed chlorophyll fluorescence in photosystem II at different pH

Water splitting activity, the multiline EPR signal associated with S(2)-state of the CaMn(4)-cluster and the fast and slow phases of the induction curve of the millisecond delayed chlorophyll fluorescence from photosystem II (PSII) in the pH range of 4.5-8.5 were studied in the thylakoid membranes and purified PSII particles. It has been found that O(2) evolution and the multiline EPR signal were inhibited at acidic (pK approximately 5.3) and alkaline (pK approximately 8.1) pH values, and were maximal at pH 6.0-7.0. Our results indicate that the loss of O(2) evolution and the S(2)-state multiline EPR signal associated with the decrease of the millisecond delayed chlorophyll fluorescence only in alkaline region (pH 7.0-8.5). Possible correlations of the millisecond delayed chlorophyll fluorescence components with the donor side reactions in PSII are discussed.     

Behaviour of Prompt Gamma-Ray Emission in ColdFission of 252Cf

The behaviour of prompt γ-ray emission in the cold fission of ²⁵²Cf was investigated experimentally using a four-parameter correlation technique. A twin gridded ionization chamber was employed to detect the fission signals and to determine the fragment emission angles, and a φ10cm×10cm NaI(T1) detector was used to record the γ-ray energies. The result shows that the angular distribution coefficient of γ-rays emitted in cold fission is twice as large as that in the normal fission.The fact that in the cold fission the number of γ-rays emitted from the light fragments is approximately three times as large as that from the heavy ones can not be explained satisfactorily so far.     

Hybridization-triggered isothermal signal amplification coupled with MutS for label-free and sensitive fluorescent assay of SNPs

Combining the specific recognization of MutS protein for mismatched DNA sequences with the target-driven molecular switch that acts as both the template and primer of the polymerization reaction, a new label-free and sensitive fluorescent assay strategy for specific single-stranded DNA sequences or SNPs is proposed.