单发次皮秒脉冲对比度的三阶自相关法测试技术

为了测试单发次皮秒脉冲对比度,设计并研制了非共轴三阶自相关仪。三阶自相关仪参数优化设计中,在确保获得正确的相关耦合信号的前提下,充分利用KDP晶体的极化张量,寻找有效非线性系数相对较高的相位匹配点,在满足非共线相位匹配条件的同时兼顾群速匹配,为增大时间测试范围,选取较大的入射光夹角。采用分区测试和图形重构技术,增大对比度测试的动态范围,结果显示采用两个科学级CCD测试的脉冲对比度在105左右。     

Assessment of transmission of the shear stress in potted anchors for composite rods 1. Sleeve of constant thickness

The key problem facing the application of fiber-reinforced polymer (FRP) stay cables and tendons is the anchorage. Potted (bond-type) anchors have been used more extensively than anchors of any other type. The main aim in the design of anchors is to minimize the peak shear stress at the FRP rod-pottant interface. To this end, parametric analyses of the stress state in the anchors are carried out. Since parametric studies can not be easily performed by the finite-element method, an analytical model of the anchor is proposed. The model involves significant simplifying assumptions and allows one to obtain a relatively simple analytical solution for shear-stress distributions at the FRP rod-pottant interface. The use of this solution at various boundary conditions and various geometrical and mechanical parameters of anchor components enables one to search for and evaluate, at least qualitatively, different methods for decreasing the peak interfacial shear stress in the anchor. In this part of the investigation, an anchor consisting of a sleeve of constant thickness is considered. Russian tanslation published in Mekhanika Kompozitnykh Materialov, Vol. 45, No. 3, pp. 321-346, May-June, 2009.     

Semisynthesis of Functional Glycosylphosphatidylinositol-Anchored Proteins

Glypiation is a common posttranslational modification of eukaryotic proteins involving the attachment of a glycosylphosphatidylinositol (GPI) glycolipid. GPIs contain a conserved phosphoglycan that is modified in a cell- and tissue-specific manner. GPI complexity suggests roles in biological processes and effects on the attached protein, but the difficulties to get homogeneous material have hindered studies. We disclose a one-pot intein-mediated ligation (OPL) to obtain GPI-anchored proteins. The strategy enables the glypiation of folded and denatured proteins with a natural linkage to the glycolipid. Using the strategy, glypiated eGFP, Thy1, and the Plasmodium berghei protein MSP1₁₉ were prepared. Glypiation did not alter the structure of eGFP and MSP1₁₉ proteins in solution, but it induced a strong pro-inflammatory response in vitro. The strategy provides access to glypiated proteins to elucidate the activity of this modification and for use as vaccine candidates against parasitic infections.     

Shot noise in electron transport through a double quantum dot: a master equation approach

We study shot noise in tunneling current through a double quantum dot connected to two electric leads.We derive two master equations in the occupation-state basis and the eigenstate basis to describe the electron dynamics.The approach based on the occupation-state basis,despite being widely used in many previous studies,is valid only when the interdot coupling strength is much smaller than the energy difference between the two dots.In contrast,the calculations using the eigenstate basis are valid for an arbitrary interdot coupling.Using realistic model parameters,we demonstrate that the predicted currents and shot-noise properties from the two approaches are significantly different when the interdot coupling is not small.Furthermore,properties of the shot noise predicted using the eigenstate basis successfully reproduce qualitative features found in a recent experiment.     

散弹噪声极限稳定度优于1×10-13τ-1/2的铷频标物理系统

近年来,铷原子频标研究取得长足进展,频率稳定度达到10^-13τ^-1/2量级.为进一步改善铷频标稳定度性能,本文设计了一种高信噪比物理系统.物理系统中的腔泡组件采用微波场磁力线与量子化轴方向高度平行的开槽管式微波腔,滤光泡和吸收泡独立控温.抽运光源采用了光学滤光和同位素滤光双重滤光方案.本文实测了背景光电流I₀和鉴频斜率K_d,结果分别为95 μA和7.7 nA/Hz,在此基础上计算物理系统的散弹噪声极限稳定度为7.5×10^-14τ^-1/2.研究结果表明,只要锁频环路的电子学噪声得到有效控制,铷频标的频率稳定度突破1×10^-13τ^-1/2,进入10^-14τ^-1/2量级是完全可能的.     

两种求铅球最佳出手角的方法比较

本文提出了利用运动叠加原理分析铅球最佳出手角的简便方法,与传统方法就两种不同情形下求解最佳出手角进行了对比,说明了叠加原理法的简洁性．同时通过对两组理论数据的对比,说明分析铅球最佳出手角可将出手高度视为独立变量．     

非稳散粒噪音相位依赖特性的实验研究

为了抑制相位调制引起的散粒噪音,实验研究了通过调制二极管激光器输出光强度,使用相位解调技术得到的不同解调相位下非稳散粒噪音的功率谱.在最小散粒噪音处,得到了相比于无调制情况下的散粒噪音减小3 dB的灵敏测量结果.实验结果表明,选择合适的调制相位可以在一定程度上抑制散粒噪音.研究结果与理论分析一致.     

Effects of polymerization method on structure and properties of thermoplastic polyurethanes

The effects of the dynamic polymerization method and temperature on the molecular aggregation structure and the mechanical and melting properties of thermoplastic polyurethanes (TPUs) were successfully clarified. TPUs were prepared from poly (ethylene adipate) glycol (M_n = 2074), 4,4′‐diphenylmethane diisocyanate and 1,4‐butanediol by the one‐shot (OS) and the prepolymer (PP) methods in bulk at dynamic polymerization temperatures ranging from 140 to 230 °C. Glass‐transition temperatures (T_gs) of the soft segment and melting points (T_ms) of the hard segment domains of OS‐TPUs increased and decreased, respectively, with increasing polymerization temperatures, but those of PP‐TPUs were almost independent of the polymerization temperature. T_gs of the soft segment and T_ms of the hard segment domains of these TPUs polymerized above 190 °C were almost the same regardless of the polymerization method. Solid‐state nuclear magnetic resonance spectroscopy (NMR) analyses of OS‐ and PP‐TPUs showed that the relative proton content of fast decay components, which corresponds to the hard segment domains, in these TPUs decreased with increasing polymerization temperatures. These results clearly show that the degree of microphase separation becomes weaker with increasing polymerization temperatures. The temperature dependence of dynamic storage modulus and loss tangent of OS‐TPUs coincided with those of PP‐TPUs at polymerization temperature above 190 °C. The apparent shear viscosity for OS‐ and PP‐TPUs polymerized above 190 °C approached a Newtonian behavior at low shear rates regardless of the polymerization method. These results indicate that TPUs polymerized at higher temperatures form almost the same molecular aggregation structures irrespective of the dynamic polymerization method. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 800–814, 2007     

Modelling the temporal intensity distribution of laser ablation inductively coupled plasma mass spectrometry in single shot mode

A transport model is proposed that describes the temporal intensity distribution observed in laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) in single-shot mode using quantitative signal equations. Calculations aim on the deduction of the dispersion function describing the time-dependent part of the signal equation.

The dispersion function depends on transport time in the centre of the transport tube, as related to carrier gas flow rate and tube volume and on the relation between carrier gas flow rate and ablation chamber volume. The equations describing the signal shape standardize signals from different systems and allow quantitative optimization of the ablation chamber, the transport tube and the detector.

Application of the model to ICP-MS shows that only a part of the area filled by the transported vaporization product and thus only a part of the transported vaporization product can be observed at the detector. The model is able to quantify both fractions.

As was calculated, the observed fraction of analyte is always higher than the observed fraction of the sample containing cross section and depends on the chosen transport parameters characterising the dispersion function. Thus, the determination of the signal integrals in the usual way can lead to systematic errors if the parameters influencing the dispersion function are variable.

Therefore, a different method of analysis based on signal equations is proposed and demonstrated. By this method of data treatment, all important system parameters influencing the dispersion function could be calculated and matched with theoretical ones. Furthermore, a complete integral of the transient signal including its statistical variation can be generated from a limited number of measurement points. For example, this can be applied to signals detected incompletely because of detector saturation and enables the use of high-abundance elements as internal standards.

Furthermore, the method can be used to monitor system performance, to identify the flow regime inside the ablation chamber, to take into account the sample volume for quantitative analysis and finally, to detect anomalous signal distributions that would lead to systematic errors. The prospects and limitations of the model are discussed for LA-ICP-MS in single shot mode.     

Hydrophile Polymergele mit reaktiven Gruppen, 2. Mitt.: Chelatharze auf Basis von Glucose- und Saccharosemethacrylaten

A widely applicable method for the preparation of chelating resins based on glucose- and sucrosemethacrylate-gels is described. Primary aromatic amino groups were bonded to the carrier by esterification with 4-nitrobenzoylchloride and subsequent reduction of the nitro groups with sodium dithionite. Diazotation and coupling with various chelating ligands (8-hydroxyquinoline, dithizone, anthranilic acid, salicylic acid and pyrogallol) afforded chelating resins with capacities of max. 1.7 mmol/g. Sucrosemethacrylate-gels were etherified with 4-nitrobenzylchloride, epichlorohydrin, 4-nitrophenyl glycide ether (IIb), acrylonitrile and 4-nitrophenylacrylamide (IVb). Reaction of the gels with IIb or IVb and subsequent reduction of the nitro groups yielded reactive carriers with ether-linked primary aromatic amino groups. Diazotation and coupling with 8-hydroxyquinoline yielded chelating resins. The capacities of the gels were 0.6–0.7 mmol/g and these resins were extremely stable to changes inpH.