高压下MgS的弹性性质、电子结构和光学性质的第一性原理研究

采用基于密度泛函理论(density functional theory)基础上的第一性原理赝势平面波方法, 计算研究了MgS晶体B2构型在不同压强下的几何结构、弹性性质、电子结构和光学性质. 计算结果表明, 在高压作用下, 该结构的导带能级有向高能级移动的趋势, 而价带能级有向低能级移动的趋势. 同时, 对照态密度分布图及高压下能级的移动情况, 分析了MgS B2构型在高压作用下的光学性质, 发现高压作用下, 吸收光谱发生了明显的蓝移.     

弱激光改善血液携氧功能机制分析及临床研究

本文用群论、量子力学、量子统计力学和非线性科学理论,结合血液中与携氧有关成分(卟啉)的结构功能对激光改善血液的携氧、输氧机制作了分析.量子统计和群论分析结果表明F-F’>0(F、F’分别为有、无激光作用时系统的自由能),这些结果能较好解释我们用激光血管内照射的临床治疗及血氧检测结果.     

问与答

<正> 什么是激光光电流效应?激光光电流效应有哪些应用? 当用激光照射气体放电管时,如果激光的频率和参与放电的粒子(原子、分子、离子)的某两个能级之     

HF和DF分子双光子布居转移过程中的同位素效应

通过求解含时薛定谔方程,研究了XF(X=H,D)分子体系双光子共振条件下布居转移过程中的同位素效应.对于这两个分子体系,基电子态上的振动能级v=0和v=2被考虑成初始态和目标态.详细讨论了激光场峰值强度和脉冲持续时间对布居转移过程的影响.脉冲持续时间需要长于860 fs才能保证DF分子体系可以获得较为显著的布居转移几率(大于80%),而对于HF分子体系,该参数只需长于460 fs.与HF分子体系相比,中间态v=1和较高的v=3振动态会对DF分子体系的双光子共振布居转移过程产生更重要的影响.     

激光与蛋白质孤子的非线性相互作用研究

在蛋白质分子一维分子链模型的基础上,引入了激光与蛋白质的相互作用项.讨论了激光对蛋白质分子孤立子的作用.表明在弱激光作用下蛋白质分子的集体振荡可能进入浑沌状态.     

通过双Σ型激光方案控制振动态布居转移

通过使用含时量子波包方法,对HF分子该类型的布居转移动力学进行了研究. 提出双Σ型激光控制方案,用于控制布居从|v=16>能级向|v=0>能级进行转移. 该方案的第一步是将布居从|v=16>经过中间能级|v=11>向|v=7>转移,第二步是将布居从|v=7>经过中间能级|v=3>向|v=0>转移. 在每一个步骤中,三个振动能级在两束重叠的激光脉冲作用下形成一个Σ型的布居转移路径. 通过优化激光的强度、频率和延迟时间,得到了最大的布居转移效率. 计算并比较了正序脉冲和反序脉冲两种情况,在这两种情况下,布居都可以超过90%从|v=16>能级向|v=0>能级进行转移.     

NO2分子内能传递和弛豫过程的光声和荧光光谱探测

将荧光光谱和光声光谱两种互补的探测技术结合起来,从辐射和无辐射跃迁两个方面,分析了 532nm激光作用下,NO2分子的激发和弛豫过程.发现NO2分子在激光作用下,将跃迁至第一激发电子态.当样品气压较低时,受激NO2分子除辐射荧光外,可通过快速的内能转移过程实现在几个振转能级的再布居;随样品气压的升高,分子间碰撞加剧,受激NO2分子通过分子间的碰撞,实现在多个振转能级的再布居.激光布居能级的荧光辐射效率随样品气压的升高逐渐降低,而长波区域的荧光辐射及光声信号强度逐渐增强,说明在高样品气压条件下,受激NO2分子的弛豫过程除辐射荧光外,还存在很强的碰撞弛豫过程,在碰撞弛豫过程中受激NO2分子将振动能转化为热运动的平动能,引起温度升高而产生很强的声信号.     

自辐射场下PuO分子光谱研究

在相对论有效原子实势近似下, 以Pu为SDD基组、O为6-311+G^*基组, 采用优选的密度泛函 B3LYP方法, 研究了用电场摸拟钚本身产生自辐射场(-0.005—0.005 a.u.) 作用下氧化钚(PuO)基态分子的最高占据轨道(HOMO)能级E_H、最低空轨道(LUMO)能级E_L、能隙E_g和费米能级E_F. 结果表明: 在所加的电场范围内, E_H随着电场的增加均逐渐减少, E_F随着电场的增加均逐渐增大, E_g始终处于增大的趋势, 费米能级E_F上升, 占据轨道的电子难以被激发至空轨道而形成激发态, PuO分子在自辐射场中更趋于稳定, 可以阻止O₂, H₂等扩散到表面内层而腐蚀钚表面, 有利于了钚在自辐射场中抗腐蚀.     

激光照射人血液荧光光谱变化的研究

采用OMA Ⅲ微弱信号检测系统研究了人血液荧光光谱在激光照射下的变化情况。结果表明 :在6 32 8nmHe Ne激光诱导下 ,不同血液在 6 70 ,730 ,981nm附近出现三个荧光峰 ;荧光强度在一定范围内与照射激光功率呈线性变化关系 ;随着激光照射时间的增加 ,三个峰位上的荧光强度下降 ,8min后趋于隐定值 ;在激光照射过程中 ,三个峰位出现不同数值的移动。     

分子对飞秒激光场响应的含时密度泛函理论研究

采用含时密度泛函理论方法研究线性分子碳化锂(Li2C2)对飞秒激光场响应的电子-离子动力学行为.在典型的近共振和非共振的激光频率作用下,分别对比分析了分子的共振和非共振电离过程.研究发现:分子在共振频率激光场的作用下发生更强的电离过程,并倾向于发生库伦爆炸,键长的振荡断裂与电离相互促进影响,而分子在较弱的激光场作用下发生单光子电离过程;随着双脉冲时间间隔的增加,离化电子数在一定范围内呈振荡上升趋势,随后趋于常数.     

Intracavity system design for IR multiphoton dissociation

An intracavity system for the infrared multiple photon dissociation (IRMPD) of molecules with high dissociation energy threshold has been designed and implemented. The system design based on a TEA CO₂ laser with a cavity folded in V-shape included the analysis of its stability varying the cavity dimensions as well as the analysis of the positions of the beam waists and of the beam size at them. The intracavity energy as a function of the total sample pressure has been measured and the laser-operation threshold has been determined. Intracavity IRMPD has been compared to traditional IRMPD performed in an irradiation geometry in which the radiation is focused into a photoreactor placed outside the laser cavity. Dissociation volumes in intracavity irradiation have resulted an order of magnitude larger than those obtained in experiments performed with the photoreactor outside the laser cavity.     

Using low intensity ultrasound to improve the efficiency of biological phosphorus removal

Low intensity ultrasound can produce various effects on biological materials, such as stimulating enzyme activity, cell growth, biosynthesis, etc., which may improve the efficiency of enhanced biological phosphorus removal (EBPR). We adopt total phosphorus (TP) and dehydrogenase activity (DHA) as indicators to confirm the feasibility of applying low intensity ultrasound in EBPR. Single-factor experiments and orthogonal test were conducted in batch anaerobic/oxic (A/O) process simulation to study the influence of ultrasonic intensity and exposure time in the EBPR process. The results showed that the optimal ultrasonic parameters were 0.2 W/cm² and 10 min under which condition the TP concentration in the effluent was 35–50% lower than that of the control (without ultrasonic irradiation). Changes of sludge activities after ultrasonic irradiation were examined. The improvement of sludge activity by ultrasound took 4 h after irradiation to reach the peak level, when an increase above 50% of DHA has been achieved by ultrasonic irradiation, and the enhancing effects induced by ultrasound disappeared in 16 h after irradiation. A tentative mechanism of biological phosphorus removal enhancement stimulated by ultrasound was discussed based on these phenomena.     

Influence of Low-Intensity Laser Radiation on the Rheological Characteristics of Human Blood

The influence of low-intensity laser radiation (LLR) on the rheological characteristics of human blood has been investigated. The results of the investigation of the blood velocity in the human skin capillaries, the erythrocyte aggregation time, and the spectral width of scattering intensity fluctuations depending on the irradiation time are presented. It has been shown that laser irradiation leads to a decrease in the degree of aggregation of erythrocytes and, accordingly, to an increase in the velocity of blood microcirculation, which can be used for laser therapy and diagnostics and treatment of cardiovascular diseases (CVD). To explain the results obtained, a method of the LLR–biotissue interaction is proposed.     

The electromagnetic interaction in the enzyme activity involving ATP

Summary A two-level model is considered to describe the dynamics of a biological system undergoing cyclic transformations between two states separated by an energy quantum interval. This is typically met in enzyme-activated reactions involving the transition from ATP to ADP and vice versa, the two molecules which play a key role in the energetics of biosystems. The model has been worked out with reference to the case of myosin ATPase, an enzyme involved in muscle contraction. General results can be obtained in analytical ways, when the dynamics of the system is investigated from an energetic point of view. A system of two coupled differential equations follows whose stationary solutions recover several fundamental aspects of biomatter: i) a non-linear response to energy supply, ii) a switch from non-cooperative to cooperative laser-induced behaviour, iii) phase transitions appearance, iv) the increase of the order parameter, sustained by resonant irradiation. This final result may be the key to the interpretation of experimental results of enzyme reactivation by laser irradiation, usually not effective on undamaged enzymes, which can be related to the claimed healing effect of low-power laser.     

Modelling chemical kinetics of small clusters after nanosecond laser ablation

Nanoclusters of various materials have recently been obtained by laser ablation. Strong evaporation of a condensed phase caused by laser irradiation is well known to generate an overcooled vapour. Further expansion thereof increases the oversaturation degree and facilitates homogeneous nucleation and cluster growth. To investigate homogeneous nucleation at very high expansion rates attained at nanosecond laser ablation, kinetic equations are applied describing all the possible gas-phase chemical reactions of dissociation and coalescing between small clusters. Additional cooling due to thermal emission by clusters is taken into account. Twenty smallest carbon molecules are considered. The model is applied to nanosecond laser ablation of graphite in vacuum. The resulted vapour molecular composition is characterised by dominating molecules C₃ and C₅ and an exponential drop of heavier clusters concentrations with their mass. The growth of heavier clusters is controlled by the balance between liberating the latent heat of their formation and the energy losses by expansion and thermal emission.     

Surface morphology of thin lysozyme films produced by matrix-assisted pulsed laser evaporation (MAPLE)

Thin films of the protein, lysozyme, have been deposited by the matrix-assisted pulsed laser evaporation (MAPLE) technique. Frozen targets of 0.3-1.0 wt.% lysozyme dissolved in ultrapure water were irradiated by laser light at 355 nm with a fluence of 2 J/cm². The surface quality of the thin lysozyme films of different thickness deposited on 7 mm × 7 mm Si-〈1 0 0〉-wafers was investigated with scanning electron microscopy and atomic force microscopy. Already at comparatively low thickness, ∼20 nm, the substrate is covered by intact lysozyme molecules and fragments. The concentration of lysozyme in the ice matrix apparently does not play any significant role for the morphology of the film. The morphology obtained with MAPLE has been compared with results for direct laser irradiation of a pressed lysozyme sample (i.e. pulsed laser deposition (PLD)).     

紫外激光和压力共同作用下C60-peapod的聚合相变研究

采用气相扩散方法将C₆₀分子填充到单壁碳纳米管(SWNTs)中，制备出高填充比率的豆荚形纳米材料C₆₀@SWNT，又称为peapod.用金刚石对顶砧(DAC)装置获得高压，在高压下同时利用紫外激光处理样品，通过激光和压力的共同作用研究了C₆₀分子在碳管内的聚合相变.在21.5GPa高压下，同时紫外激光(325nm)照射30min后，拉曼光谱表明C₆₀分子在碳管内发生了聚合，形成一维链状O相聚合结构，且该相变是不可逆的. 关键词： 60 peapod')" href="#">C₆₀ peapod 紫外激光 高压 拉曼光谱     

低强度激光辐照HeLa细胞诱导增殖效应的可见光谱特性

比较研究了可见波段405,514,633和785nm低强度激光辐照HeLa细胞的促增殖效应。实验采用100和1 000J.m-2两种有效能量密度的可见光波辐照细胞,照射后24,48,72h采用MTT法检测细胞活性。结果表明,405,633,785nm激光均能促进HeLa细胞增殖,且呈波长和时间依赖性;633nm激光辐照对细胞促增殖效应最显著;514nm激光辐照对HeLa细胞促增殖效应较不明显。不同光剂量对细胞增殖效应不同,405,633,785nm激光辐照时能量密度为1 000J.m-2的辐照组细胞增殖均较100J.m-2辐照组明显,而514nm激光辐照时1 000J.m-2辐照组与100J.m-2辐照组细胞增殖的差异不明显。     

Resonant laser ablation of copper and its application in microanalysis

Resonant laser ablation (RLA) is a two-step process, occurring within a pulse of a tunable laser, in which the leading edge of the laser pulse ablates a solid surface to produce neutral atoms or molecules that are then resonantly ionized by the trailing edge of the same laser pulse. The sensitivity and selectivity of RLA allow detection and quantitation at very low concentrations. In our preliminary RLA research, a sub-ppm detection level has been reached for copper in a standard aluminium sample. In addition, the threshold and saturation effects of RLA have been observed.     

Formation of polyelectrolyte microcapsules with chemically bound adsorbed molecules of fluorescein isotiocyanate and their destruction under laser action

Polyelectrolyte capsules with molecules of fluorescein isotiocyanate included in the shell have been obtained. The inclusion of dye molecules in the shell of the capsule allows the photosensibilized destruction of its structure. The measurements of the fluorescence intensity of a dye that was present in the shell revealed effective dissipation of the energy of photoexcited molecules by the surrounding organic matrix. The capsule suspension was irradiated by a laser in the absorption band of fluorescein isotiocyanate molecules. By measuring the size distribution of the capsules before and after irradiation with a laser it was shown that the capsules are destroyed under the effect of laser radiation.