核碎裂在离子与生物分子相互作用中的效应

讨论了重离子辐照生物中核碎裂效应,给出与此相关的核碎裂研究现状和进展。The effect of nuclear fragmentation discussed. The status and perspectives of this data. in the topic interactions of heavy ions with biological are presented based On calculations and molecules is experimental.     

Optimization of the Water-PRESS Pulse Sequence and Its Integration into Pulse Sequences for Studying Biological Macromolecules

In this paper, the recently developed “Water-PRESS” method of water suppression [W. S. Price and Y. Arata (1996),J. Magn. Reson. B112,190] in which homospoil pulses are used to manipulate the effects of radiation damping on the water resonance and thereby selectively alter the effective relaxation times of the water resonance with respect to the solute (e.g., biological macromolecules) resonances is further developed and applied. In the present work, methods for optimization in terms of degree of water suppression and in temporal terms (important for the application of Water-PRESS to multidimensional experiments) are considered so that recycle delays of less than 2.3 s (including the acquisition time) are possible. Also, a simple modification which allows the observation of solute resonances with relaxation times similar to that of the water resonance is presented. Finally, the inclusion into more complicated pulse sequences is also discussed. Experimental examples using aqueous samples of lysozyme and immunoglobulin are given. Compared to most other NMR water suppression techniques, this method is extremely simple to implement and optimize and does not require accurately calibrated RF pulses or perfect lineshape.     

Dynamic NMR q-space studies of microstructure with the multigrade CPMG sequence

A new approach to q-space studies of microstructure is proposed, which exploits the combined information contained in the water proton transverse relaxation time distribution and the frequency dependence of the apparent water diffusivity in heterogeneous systems. Using an automated two-dimensional multigrade CPMG sequence, both the pulse spacing and the amplitude of the applied field gradient are varied systematically and used to measure the frequency and wave vector dependence of the multiple exponential echo decay constants and amplitudes. Undesirable crossterms in the applied and background field gradients are eliminated by a simple procedure involving a sign reversal in the applied gradient. Nonlinear, local susceptibility-induced field gradients are shown to lead to enhanced, frequency-dependent apparent water diffusivities that are sensitive to the local microstructure.     

V型稠密介质中脉宽对超短脉冲和频谱及其CEP依赖性的影响

利用不含慢变包络近似和旋波近似的全波Maxwell-Bloch方程组的数值解,研究脉宽对稠密V型三能级原子介质中超短激光脉冲和频谱及其载波包络位相(CEP)依赖性的影响.结果表明:脉宽较小时,脉冲分裂数目少,频谱较宽,高频部分显著,CEP的变化对脉冲及频谱的影响较大,尤其对子脉冲间的时间间隔及频谱高频部分强度大小的影响更为显著;随着脉宽的增大,脉冲分裂数目增多,频谱宽度变窄,高频部分强度明显降低,CEP的变化对脉冲及频谱的影响减弱.     

Motional Stark Effect and Its Active Cancellation in Diamagnetic Spectrum of Barium

With time-of-flight and electric field ionization detection technique, we investigate the motional Stark effect for highly excited Rydberg barium in high magnetic field and its active cancellation experimentally. In the experiment, the atom beam is aligned at a small angle of 15° with respect to the magnetic field. The motional Stark effect cancellation is demonstrated on two sets of. circularly polarized spectra in static magnetic field B = 1.00000 Tesla and B = 1.70000 Tesla, respectively, although the effect is very small （- 3.5 Vcm^-1） in our apparatus configuration.     

啁啾系数对飞秒脉冲的分裂及光谱性质的影响

利用预估校正-时域有限差分法求得不含慢变包络近似和旋转波近似的全波Maxwell-Bloch方程的数值解,在Λ型三能级原子介质中研究了啁啾系数C对传播中的飞秒Gauss型脉冲分裂情况及光谱性质的影响.结果表明:面积小于等于3π的啁啾脉冲在介质中不出现分裂,但脉冲啁啾会引起脉冲频谱的震荡;对于4π面积啁啾脉冲,啁啾系数C较小时脉冲在介质中发生分裂,C较大的脉冲不再产生分裂,即分裂的子脉冲数量减少;随着C增大,脉冲中心频率附近频谱震荡愈加剧烈,高频成分的范围及强度明显减小;对于大面积8π脉冲,脉冲分裂情况与4π情况相似,但随C增大,脉冲高频成分的范围和强度没有明显变化,而高频成分中的峰值分布却显著不同.     

Theoretical Semiempirical Study of the Biomolecules Interaction with Carbon Nanotubes

Modeling of the quantum interaction properties of glycine radicals on the sidewalls of the single-walled carbon nanotubes (CNTs) is investigated by MINDO/3 (Modified Intermediate Neglect of Differential Overlap version 3) calculations. It is found that the interaction potential of the N-centered glycine radical with the tubes results in stable complexes when it reacts with the nitrogen atom (N² centered) and metastable conformations with C² atoms. We have studied the effect of the diameter–length characteristics of the CNT on binding the amino acid. Our results suggest that the binding energy is lower as the CNT diameter increases, while as the CNT length increases, the binding energy initially increases and then slightly fluctuates.     

Generalized Toda Mechanics Associated with Classical Lie Algebras and Their Reductions

For any classical Lie algebra $\mathfrak{g}$, we construct a family of integrable generalizations of Toda mechanics labeled a pair of ordered integers $(m,n)$. The universal form of the Lax pair, equations of motion, Hamiltonian as well as Poisson brackets are provided, and explicit examples for $\mathfrak{g}=B_{r},C_{r},D_{r}$ with $m,n\leq3$ are also given. For all $m,n$, it is shown that the dynamics of the $(m,n-1)$- and the $(m-1,n)$-Toda chains are natural reductions of that of the $(m,n)$-chain, and for $m=n$, there is also a family of symmetrically reduced Toda systems, the $(m,m)_{\mathrm{Sym}}$-Toda systems, which are also integrable. In the quantum case, all $(m,n)$-Toda systems with $m>1$ or $n>1$ describe the dynamics of standard Toda variables coupled to noncommutative variables. Except for the symmetrically reduced cases, the integrability for all $(m,n)$-Toda systems survive after quantization.     

激光脉冲宽度对有质动力加速电子的影响

基于真空中单电子运动模型,编程计算得到了高斯激光脉冲与初始位于激光传播轴上电子的相互作用结果。不同激光参鼍条件下,得到了电子的能量增益与激光强度、焦斑大小和脉冲宽度关系。结果表明,高斯激光脉冲焦斑较大时,电子没有明显的能量增益,高斯激光脉冲焦斑太小时,电子也没有明显的能量增益。电子的能量增益有一个最佳焦斑大小。在相同激光强度下,电子能量增益的最佳焦斑大小随脉冲宽度的增大而增大,但最佳焦斑大小与脉冲宽度的比值基本上是不变的。     

Method of Eliminating Systematic Errors of Atomic Absorption Analysis in Atomization of a Material in a Graphite Furnace

By taking as an example the obtaining of the spectra of the gas phase over alkali metal iodides and calcium fluoride, we show the possibility of eliminating systematic errors of atomic absorption analysis which are due to nonselective absorption of light. It is been suggested that it makes sense to create a database that would contain molecular absorption spectra of the most abundant substances and would be intended for use by chemistsanalysts.     

Influence of High Orientational Order on the Shape of the Echo Response from a Hahn Pulse Sequence

The amplitude modulations in the simulations of the Hahn echo responses from cholestane spin labels in samples characterized by a high degree of orientational order are shown to arise from the use of “soft” pulses. Soft pulses have a limited spectral range and cover only a small portion of the CW-ESR spectra, so that not all the spins are on-resonance. The magnetization vectors of the off-resonance spins only partially tilted away from the laboratoryzaxis, the direction of the applied static magnetic field. They thus contribute oscillating components to the magnetization in thexyplane. The contribution from the off-resonance spins to the Hahn echo formation is significant in highly oriented samples, but cancels out in samples exhibiting a small degree of order. Experimental echo responses obtained from CSL molecules embedded in rigid matrices of eggPC bilayers and the liquid crystalline materials ZLI and MBBA confirm the theoretical predictions.     

Pulse wave velocity with 4D flow MRI: Systematic differences and age-related regional vascular stiffness

Purpose

The objective of this study was to compare multiple methods for estimation of PWV from 4D flow MRI velocity data and to investigate if 4D flow MRI-based PWV estimation with piecewise linear regression modeling of travel-distance vs. travel time is sufficient to discern age-related regional differences in PWV.

Methods

4D flow MRI velocity data were acquired in 8 young and 8 older (age: 23 ± 2 vs. 58 ± 2 years old) normal volunteers. Travel-time and travel-distance were measured throughout the aorta and piecewise linear regression was used to measure global PWV in the descending aorta and regional PWV in three equally sized segments between the top of the aortic arch and the renal arteries. Six different methods for extracting travel-time were compared.

Results

Methods for estimation of travel-time that use information about the whole flow waveform systematically overestimate PWV when compared to methods restricted to the upslope-portion of the waveforms (p < 0.05). In terms of regional PWV, a significant interaction was found between age and location (p < 0.05). The age-related differences in regional PWV were greater in the proximal compared to distal descending aorta.

Conclusion

Care must be taken as different classes of methods for the estimation of travel-time produce different results. 4D flow MRI-based PWV estimation with piecewise linear regression modeling of travel-distance vs. travel time can discern age-related differences in regional PWV well in line with previously reported data.     

能动变形反射镜波面误差特性分析及实验研究

对能动变形反射镜波面误差进行了理论分析和实验研究.在对能动变形反射镜波面误差进行理论分析和实验研究的基础上,利用有限元对37单元能动变形反射镜低频象差补偿能力进行了相关的分析和计算,结合相关实验确定了能动变形反射镜的主要参数,成功研制出了曲率半径1926 mm、口径300 mm的37单元球面能动变形反射镜.经实验测定校正误差前、后镜面面形的PV值(波前峰谷差值)和RMS值分别为:0.545γ、0.08γ及0.239γ、0.031γ,从实测结果口I以看到取得了明显的校正效果.并且在研制过程中对镜面加工、驱动器极头粘接等技术和工艺问题进行了有效地探索和研究,从而为能动变形反射镜进一步的研制工作奠定了良好的基础.     

Constants of Motion for Several One-Dimensional Systems and Problems Associated with Getting Their Hamiltonians

The constants of motion of the following systems are deduced: a relativistic particle with linear dissipation; a no-relativistic particle with a time explicitly depending force; a no-relativistic particle with a constant force and time depending mass; and a relativistic particle under a conservative force with position depending mass. The Hamiltonian for these systems, which is determined by getting the velocity as a function of position and generalized linear momentum, can be found explicitly at first approximation for the first system. The Hamiltonians for the other systems are kept implicitly in their expressions for their constants of motion.     

超短脉冲激光对硅膜的热力效应分析

为了研究超短脉冲激光辐照下半导体材料的热力效应,在热电子崩力和自洽场两种模型的基础上,得到了完全耦合的非线性热弹方程组。在单轴应力条件下,采用有限差分法,讨论了不同脉宽的超短脉冲激光辐照下,硅膜内载流子温度、晶格温度、热应力以及热电子崩力随时间及膜深度的变化情况。结果表明,脉冲宽度对硅膜的热力损伤过程起重要作用。能量密度一定时,载流子和晶格达到热平衡所需时间随脉冲宽度的增加而增加;热电子崩力呈现明显的双峰结构,同时脉冲宽度对第二个峰值的影响较大;脉宽越窄,热应力的峰值越大,越容易对材料造成损伤,为激光加工和光电器件的损伤提供了理论参考。     

编码模板误差引起测量光谱图像改变的分析

针对编码模板存在的各种不同误差情况,确定了相应的循环编码矩阵.根据阿达玛变换成像光谱仪的编码和解码原理,通过比较解码得到光谱图像和原始图像.分析了光谱图像在编码模板存在各种不同误差的情况下,随编码模板误差的变化情况,得到了光谱图像随编码模板误差变化的大致范围和基本关系.     

从微观角度分析电磁感应中的动生电动势和感应电流的形成及能量的转化

以"动电动模型"和"电动电模型"为例,从微观的角度出发,对感应电动势、感应电流的形成以及能量的转化进行分析,目的在于将宏观的认知和微观的内在本质统一起来,以期深入浅出地进行有效教学.     

啁啾高斯光脉冲对带前置放大器光接收机灵敏度的影响研究

研究了不同程度啁啾分量高斯形光脉冲信号对带前置放大器光接收机灵敏度的影响，同时进行了理论分析和数值摸拟。发现适当选取高斯形光脉冲信号归一化相对脉宽因了、啁啾分量、接收机均衡滤波器输出的升余弦频谱波形滚降因子的值可以提高光接收机灵敏度，其结果对实际光接收机的分析和设计有一定指导意义。     

Spectrum Transformation of Gaussian Pulse in Waveguide by FDTD and Its Effect on Analysis of Discontinuity Problem

An interesting, surprising phenomenon, spectrum transformation of Gaussian pulse propagating in waveguide, is revealed in this paper. It is found that the spectrum power of zero frequency of Gaussian pulse is changed into the spectrum power of cut-off frequency of H₁₀ mode in rectangular waveguide when FDTD simulation is implemented in the absence of nonlinear material in waveguide. The cause of the spectrum transformation is explained based on the mode field structure at cut-off. Its effect on the correctness of analyzing waveguide discontinuity problem is presented too.