A boron-lined proportional counter (BLPC) used in a mixed field of reactors

A boron-lined proportional counter (BLPC) with a count rate limit close to the multi-wire proportional counter was manufactured to measure the mixed field around reactors. After measurement with a standard Am-Be neutron source (activity: 100 mCi), the results show that the operating voltage of the BLPC is 800 V, the plateau length is 100 V and the slope is 13.2%/100 V. The width and rise time of the output pulse of the BLPC are 1.26 μs and 370 ns, respectively. When the BLPC works at a count rate of 1.0×10⁵ count/s, the pulse pile-up probability of the BLPC is 3.6%. A clear peak can be seen in the pulse height spectrum of the BLPC. and the performances illustrate that a BLPC working in pulse mode can serve as a source range detector of reactors.     

Probing new physics in B → J/ψπ~0 decay

We calculate the branching ratio of B → J/ψπ0 with a mixed formalism that combines the QCDimproved factorization and the perturbative QCD approaches.The result is consistent with experimental data.The quite small penguin contribution in B → J/ψπ0 decay can be calculated with this method.We suggest two methods to extract the weak phase β.One is through the dependence of the mixing induced CP asymmetry SJ/ψπ0 on the weak phase β,the other is from the relation of the total asymmetry ACP with the weak phase β.Our results show that the deviation ΔSJ/ψπ0 of the mixing induced CP asymmetry from sin（-2β） is of O（10-3） and has much less uncertainty.The above O（10-3） deviation can provide a good reference for identifying new physics.     

Probing new physics in B→J/ψπ0 decay

We calculate the branching ratio of B→J/ψπ0 with a mixed formalism that combines the QCD-improved factorization and the perturbative QCD approaches. The result is consistent with experimental data.The quite small penguin contribution in B→J/ψπ0 decay can be calculated with this method. We suggest two methods to extract the weak phase β. One is through the dependence of the mixing induced CP asymmetry SJ/ψπ0 on the weak phase β, the other is from the relation of the total asymmetry ACP with the weak phase β. Our results show that the deviation △SJ/ψπ0 of the mixing induced CP asymmetry from sin(-2β) is of O(10-3) and has much less uncertainty. The above O(10-3) deviation can provide a good reference for identifying new physics.     

Screening of acetylcholinesterase inhibitors in natural extracts by CE with electrophoretically mediated microanalysis technique

An electrophoretically mediated microanalysis (EMMA) method for screening acetylcholinesterase (AChE) inhibitors in natural extracts is described. In this method, solutions of AChE and the mixture of the substrate and the natural extract were successively injected into the capillary, and mixed electrophoretically by applying a voltage for a short time. Afterwards the voltage was reapplied to separate the product from the unreacted substrate and the natural extract. The measured peak area of the product at UV 230 nm represents the enzyme activity. Since the extract is mixed with the substrate, there is no need to separate the components before testing the inhibition. The inhibitory activity of the natural extract as a whole can be easily found if the peak area of the product is reduced. This makes the present method suitable for screening inhibitors in complex mixtures, such as natural extracts. Compared to the commonly used spectrometric method for screening of AChE inhibitors, the major advantage of the present method is the elimination of Ellman reagent, which is essential for the spectrometric method. This not only simplifies the experimental procedure but also minimizes false-positive results. Moreover, it is an obvious advantage of combining the separation power with the on-column enzyme assay for further investigating which compound(s) is/are responsible for the inhibition. The method was validated using a commercially available AChE inhibitor tacrine and a small chemical library containing four AChE inhibitors and 32 natural extracts. Inhibitors in natural extracts were identified with the present method.     

三乙醇胺对羟基亚乙基二膦酸镀铜液的影响研究

研究羟基亚乙基二膦酸(HEDPA)镀铜液中三乙醇胺(TEA)对铜还原和氧化过程的影响. 用Hull Cell测试阴极电流密度分布, 通过电位扫描、循环伏安和交流阻抗研究铜沉积的电化学行为, 通过镀液的吸光度测试和固体配合物的红外光谱分析推断配位化合物的形式. 结果表明: TEA的加入能够扩大HEDPA镀铜体系的阴极允许电流密度, 对铜电沉积有阻化作用, 促进铜阳极溶解, 并可抑制氢气的析出|随着溶液中TEA浓度增加, 在玻碳电极上发生的铜还原过程由电化学控制逐渐转变为扩散控制, 可获得结晶细小、表面平整的致密铜镀层. TEA的加入, 主要是在HEDPA镀铜体系中形成CuTEA(OH)₂配位化合物, 并吸附在电极表面而影响电化学反应.     

溶胶凝胶固定化酶流动注射化学发光法测定人体血清中的胆固醇

采用溶胶凝胶技术分别固定了胆固醇脂酶和胆固醇氧化酶,制成固定化酶柱;人体血清中胆固醇脂在胆固醇脂酶的催化作用下生成胆固醇,胆固醇在胆固醇氧化酶的催化作用下被氧化产生H2O2,将其与鲁米诺发生耦合的化学发光反应,在模拟酶血红蛋白的催化作用下产生较强的化学发光。结合流动注射技术,建立了溶胶凝胶固定化酶流动注射化学发光法测定胆固醇的新方法。实验发现,发光强度与胆固醇的浓度在一定范围内呈良好的线性关系,总胆固醇的线性范围为1.01×10-6～2.02×10-4mol/L(r=0.9975);检出限为7.5×10-7mol/L;游离胆固醇的线性范围为5.0×10-8～2.18×10-5mol/L(r=0.9991);检出限为5.0×10-9mol/L。用生化分析仪(东芝TBA-120FR)与本方法进行对照,两种方法无显著性差异。本方法已应用于临床血清样品中胆固醇的检测。     

Chiral separation and determination of the optical purity of thiamphenicol-related chiral compound by capillary zone electrophoresis with cyclodextrins as chiral selectors

Summary One classical method for quantitation of amino acids in proteins is hydrolysis of the proteins and determination of the free amino acids. Although the drastic experimental conditions necessary for complete hydrolysis always cause degradation of some of the amino acids, if mild hydrolysis conditions are used, a mixture of amino acids and oligopeptides is obtained. If these conditions are adequately tuned, the oligopeptides are almost exclusively dipeptides. For this reason we have initiated a study to find a derivatizing agent suitable for the analysis of amino acids and dipeptides by an absolute method of quantitation already tested for amino acids. FMOC-Cl was found to be a suitable derivatizing agent for this purpose.     

Quantum Theory of Two-Photon Ghost Interference

In this paper, we study two-photon ghost interference with the approach of photon quantum theory, and calculate the coincidence counts of D ₁ and D ₁ detectors. With specific attention to the two-photon interference experiment carried out by Milena D’Angelo et al. (Phys. Rev. Lett. 87:013602, 2001), and find the theoretical result is accordance with experiment data.