New parameterization of the trinucleon wave function and its application to the π <Superscript>3</Superscript>He scattering length

We present a new parameterization of the trinucleon wave function. As a novel feature a separable parameterization for the complete wave function is given. In this way any calculation that considers two-body currents only is largely simplified. To demonstrate this we calculate the π³He scattering length in chiral-perturbation theory. We find reasonable agreement with experimental values inferred from data on level shifts in pionic ³He bound states. The relevance of the π-triton system for an alternative determination of the πN scattering lengths is discussed. Received: 12 August 2002 / Accepted: 25 November 2002 / Published online: 25 February 2003 RID="a" ID="a"e-mail: c.hanhart@fz.juelich.de Communicated by V. Vento     

Photoacoustic signal enhancement at visible and X-ray wavelengths

Good agreement between theory and experiment is found for photoacoustic (PA) signal enhancement by volatile liquids adsorbed on solid samples in a microphonic cell illuminated with visible light. When the same solid samples are illuminated with synchrotron X-radiation significantly smaller PA signal enhancements are observed than are predicted by theory because of radiolysis of the liquid vapors. The introduction of the volatile liquids is nevertheless valuable for the X-ray photoacoustic measurements because it raises the signal above the threshold for detectability.     

Acousto-optic amplitude modulation and demodulation of electromagnetic wave in magnetised diffusive semiconductors

Using hydrodynamical model of semiconductor plasma analytical investigations are made for the amplitude modulation as well as demodulation of an electromagnetic wave in a transversely magnetised acousto-optic semiconducting plasma. The inclusion of carriers diffusion adds new dimension in the analysis presented here. Analysis are made under different wave number regions over a wide range of cyclotron frequency. It has been seen that diffusion of charge carriers modifies amplitude modulation and demodulation processes effectively. Numerical estimations are made for n-InSb crystal irradiated by pump wave of frequency 1.6 T s^-1. Complete absorption of the waves takes place in all the possible wave lengths regimes when the cyclotron frequency becomes exactly equal to (v ² + )^1/2. Received 28 February 2002 Published online 19 July 2002     

A theory for the enhancement of the photoacoustic signals by volatile liquids

It has been shown experimentally that photoacoustic signals can be enhanced by introduction of a volatile liquid into the cell. Korpiun developed a theory which predicted the enhancement to be proportional to the mole fraction of the volatile component (y ₀) in the gas phase. His theory is, however, based on a species conservation equation valid for dilute solutions only. We present a rigorous theory for predicting the enhancement of potoacoustic signal. Our theory shows the enhancement to be proportional toy ₀/(1–y ₀) which compares well with observations of Ganguly and Somasundaram.     

Thermal wave electroacoustic calorimetry in a Si photovoltaic cell

Power dissipation in a p–n ⁺ Si solar cell has been monitored using the electroacoustic technique. Experimental results are described by a vector model which takes into account the different physical locations of the several heat-generating or heat-consuming processes. Analysis of experimental data based on this model allows separation of the different contributions to the power dissipated in the cell and a direct insight into the power loss mechanisms in the device.Symbols Used in the Text D _th thermal diffusion coefficient of the sample - EA electroacoustic - E _gap energy of the gap of the semiconductor - hv energy of the incident light - i _dark cell current density in the dark - i ₀ saturation current density of the device - l sample thickness - n quality factor of the device - P total power dissipated in the cell in PA experiments - PA photoacoustic - P _dark total power dissipated in the solar cell in the dark in EA experiments - P _{fs, inj}, P _{bs, inj} cooling of front and back surface of the cell by injected carriers - P _{fs, photo}, P _{bs, photo} heating of front and back surface of the cell by photogenerated carriers - P _inj power dissipated in the recombination of injected carriers - P _jc power absorbed in the junction cooling process - P _light total power dissipated in the illuminated solar cell in EA experiments - P _photo power dissipated by photogenerated carriers when drifting along the potential slope - P _therm power dissipated by thermalization of photocarriers in the conduction band - V amplitude of the modulated potential applied to the cell - , phase angles between vector contributions to the total dissipated power in the cell - E _c, E _v energy difference between the quasi-Fermi levels of the n(p) semiconductor and the bottom (top) of the conduction (valence) band - _th=(2D _th/)^1/2 thermal diffusion length of the sample - _d phase of EA signal in the dark - ₁ phase of EA signal with light - frequency of the modulated voltage applied to the cell.     

色谱技术在肝素结构分析中的研究进展

肝素（heparin, Hp）是目前临床应用最为广泛的抗凝剂,是由重复二糖单元组成的多硫酸化酸性直链多糖。低分子量肝素（LMWHs）是以肝素为原料,经过化学或酶降解获得的相对分子质量相对较小的肝素衍生物,相对肝素,它们的出血副作用和免疫原性更小,皮下注射时生物利用度更高。肝素及低分子量肝素具有一系列结构特点,如相对分子质量偏大且有一定分布,多种糖残基同时存在,硫酸酯位置和数量呈现多样化,以及不同工艺产生的特殊残基的种类和含量不一等。该类药物结构的复杂性对分析方法提出了巨大的挑战,也限制了其质量控制提升、工艺优化、临床用药安全和新适应证拓展等。该文以色谱分析方法为中心,从结构分析的不同角度,包括单糖、二糖、寡糖、多糖的识别、组成分析和不同层次,系统地梳理和阐述近年来肝素类药物在色谱分析方法上的进展,并对这些方法的应用范畴、创新性、局限性等进行总结。该文将为肝素类药物的结构分析、质量控制提供较系统的方法学参考,为更多新方法开发提供思路,为更深入地研究肝素类药物结构、拓展其应用提供有力支撑。     

Optimization of EUV radiation yield from laser-produced plasma

We optimize the conversion of laser energy into extreme ultraviolet (EUV) radiation by tailoring the laser parameters for a laser-produced plasma generated from 20 μm diameter water droplets. It is shown that mass-limited targets require careful adaption of laser-pulse energy and laser-pulse duration separately, rather than laser intensity, which seems to be adequate for bulk targets. The optimal pulse duration scales with the droplet radius, and the optimal pulse energy with the droplet volume. With optimized parameters, we obtain a conversion efficiency of 0.23% in 4π and 2.5% bandwidth for 13 nm radiation, the future EUV lithography light. Received: 16 July 2001 / Revised version: 25 September 2001 / Published online: 7 November 2001     

Dynamics of BF 4 - anion reorientation in the spin-crossover compound [Fe(1-n-propyl-1H-tetrazole) 6 ](BF 4 ) 2 and in its Zn II analogue

¹⁹ F and ¹¹ B spin-lattice relaxation times were measured in [ Zn ( ptz ) ₆ ] ( BF ₄ ) ₂ and in the spin-crossover compound [ Fe ( ptz ) ₆ ] ( BF ₄ ) ₂ . For both compounds BF ₄ ^- anion reorientation is active above 50 K. For [ Zn ( ptz ) ₆ ] ( BF ₄ ) ₂ , the anion-reorientation dynamics is different in the temperature regions of 50-90 K, 90-120 K, and above 150 K; between 120 and 150 K it changes rapidly reflecting a structural change. In [ Fe ( ptz ) ₆ ] ( BF ₄ ) ₂ the mechanism for the paramagnetic relaxation involving the ¹⁹ F nuclei is found to be of the diffusion-limited type according to the theory of Lowe and Tse. The present results prove that the spin-crossover takes place in a dynamic surrounding and not in a static crystal lattice. Received 09 February 1999 and Received in final form 14 June 1999     

Fragmentation of dodecanethiol molecules: application to self-assembled monolayer damage in atom lithography

Atom lithography commonly employs self-assem- bled monolayers (SAMs) of alkanethiols which act as resists to protect prepared surfaces. Metastable atomic species such as helium are used to damage the resist, enabling pattern transfer via mask lithography, followed by wet chemical etching. The damage mechanism is, however, not well understood. Here we report studies of fragmentation of dodecanethiol (DDT) molecules embedded in helium nano-droplets that have been irradiated by an electron beam. The results of the charge-transfer fragmentation process provide the first experimental data on the damage mechanisms that occur in the metastable helium/SAM interaction. Received: 20 September 1999 / Revised version: 6 December 1999 / Published online: 8 March 2000     

An incoherent optical correlator based on photoanisotropy

We describe theoretically the function of a nonlinear optical element based on photoanisotropy in azo-dye-doped polymers for optical correlation. This element allows the realization of a matched filter with two incoherent light beams. The described technique involves the insertion of a photoanisotropic polymer sample in the Fourier plane of the optical element. Due to the specific features of photoanisotropic materials the output is characterized by the convolution of the first wave with the autocorrelation function of the second wave. Received: 29 March 1999 / Revised version: 14 June 1999 / Published online: 16 September 1999