Studies on Poplar Parthenogenesis Induced by Laser

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大豆愈伤组织超弱光子辐射的双指数模型

在研究生物超弱光子辐射机理的基础上,建立了大豆愈伤组织超弱光子辐射的双指数模型.用20μW/cm2的UV-B辐射处理大豆愈伤组织2 h,测定处理后4 d内的超弱光子辐射.结果显示,双指数模型准确描述了大豆愈伤组织的超弱光子辐射及其在UV-B辐射下的变化,表明大豆愈伤组织的超弱光子辐射由快项和慢项两个部分组成;通过对双指...     

He-Ne激光诱变选育高产白藜芦醇细胞系

以葡萄皮脱分化组织为最初材料,用根癌农杆菌702菌株感染,通过纸电泳证明胭脂碱合成醇基因的存在,并在无激素培养基上培养5～6代以上,将此组织(MS)作为本次实验的研究对象.用He-Ne激光辐照,对MS进行诱变处理,通过继代选育,得到优良细胞系T₁₂,其特点是:生长迅速,生长周期比对照组(CK)缩短10～15天;生长曲线的稳定期明显延长,白藜芦醇平均产量比MS组提高40%.通过稳定性实验证明T₁₂组遗传性状是可靠的.     

Laser texturing of Hastelloy C276 alloy surface for improved hydrophobicity and friction coefficient

Laser treatment of Hastelloy C276 alloy is carried out under the high pressure nitrogen assisting gas environment. Morphological and metallurgical changes in the laser treated layer are examined using the analytical tools including, scanning electron and atomic force microscopes, X-ray diffraction, energy dispersive spectroscopy, and Fourier transform infrared spectroscopy. Microhardness is measured and the residual stress formed in the laser treated surface is determined from the X-ray data. The hydrophibicity of the laser treated surface is assessed using the sessile drop method. Friction coefficient of the laser treated layer is obtained incorporating the micro-tribometer. It is found that closely spaced laser canning tracks create a self-annealing effect in the laser treated layer and lowers the thermal stress levels through modifying the cooling rates at the surface. A dense structure, consisting of fine size grains, enhances the microhardness of the surface. The residual stress formed at the surface is compressive and it is in the order of −800 MPa. Laser treatment improves the surface hydrophobicity significantly because of the formation of surface texture composing of micro/nano-pillars.     

Nano-second pulse laser treatment of Incoloy 800 HT alloy-corrosion properties

Incoloy alloy 800 HT is widely used material of construction for equipment that must resist corrosion. Moreover, the corrosion properties of the alloy reduce considerably when the alloy is heat treated. However, the short pulse laser treatment of the alloy may offer alternative technique to improve the corrosion properties of the alloy. In the present study, nano-second pulse heating of Incoloy 800 HT alloy is carried out using a Nd-YAG laser. The heating rate and the temperature rise during the laser treatment are predicted theoretically. Electrochemical techniques are applied to determine the corrosion rates of the laser treated and untreated Incoloy 800 HT samples. SEM and EDS are introduced for metallographic examination of the treated alloy surface. It is found that the fine dentritic structures occur at the surface after the laser treatment. The local pitting is observed for the laser melted and re-solidified regions while the scattering of the pits are resulted for the laser heated and unmelted regions. In addition, the corrosion rate reduces for the laser-treated samples.     

Cemented carbide cutting tool: Laser processing and thermal stress analysis

Laser treatment of cemented carbide tool surface consisting of W, C, TiC, TaC is examined and thermal stress developed due to temperature gradients in the laser treated region is predicted numerically. Temperature rise in the substrate material is computed numerically using the Fourier heating model. Experiment is carried out to treat the tool surfaces using a CO₂ laser while SEM, XRD and EDS are carried out for morphological and structural characterization of the treated surface. Laser parameters were selected include the laser output power, duty cycle, assisting gas pressure, scanning speed, and nominal focus setting of the focusing lens. It is found that temperature gradient attains significantly high values below the surface particularly for titanium and tantalum carbides, which in turn, results in high thermal stress generation in this region. SEM examination of laser treated surface and its cross section reveals that crack initiation below the surface occurs and crack extends over the depth of the laser treated region.     

Laser controlled melting of pre-prepared inconel 718 alloy surface

Laser treatment of Inconel 718 alloy surface is carried out. The alloy surface is coated with a carbon layer containing 7% TiC particles prior to the laser treatment. The carbon coating provides increased absorption of the incident laser beam and holds TiC particles. The microstrutural and morphological changes in the laser treated region are examined using optical and scanning electron microscopes, energy dispersive spectroscopy, and X-ray diffraction. The microhardness of the surface is measured and the residual stress formed at the surface vicinity is determined from the XRD technique. It is found that partial dissolution of carbide particles takes place at the surface. The composition of fine grains at the surface vicinity, nitride compounds formed, and dissolution of Laves phase at the surface region enhances the hardness at the treated surface. In addition, laser treated surface is free from the micro-crack network and cavities.     

激光冲击与渗碳复合工艺改善12CrNi3A钢磨损性能

为了提高12CrNi3A钢渗碳层质量及其抗磨损性能,提出了激光冲击与渗碳不同顺序复合的工艺方法。球磨实验结果表明,相比渗碳处理,激光冲击后渗碳试样的比磨损率降低了51%,而渗碳后激光冲击强化试样的比磨损率降低了13%,说明激光冲击后渗碳的复合工艺能更好地改善抗磨损性能。在摩擦系数差别不大的情况下,抗磨损性能的提升与显微硬度提高、微观组织变化有关,从这两方面讨论抗磨损性能提升的机理。研究表明:激光冲击强化可促进渗碳的过程,强化后渗碳形成的渗碳层结构致密,大量细小碳化物形成,固溶强化、第二相强化作用增强,显微硬度增大,从而提高抗磨损性能;而渗碳后激光冲击强化只使渗层表面发生了形变强化,与渗碳工艺相比,显微硬度略有提高,抗磨损性能提高有限。     

Laser controlled melting of pre-treated zirconia surface

Laser treatment of pre-prepared zirconia surface is carried out. The pre-prepared surface, prior to laser treatment, consists of 50 μm carbon film and 7% titanium carbide particles, which are imbedded in the carbon film. The microstructural and morphological changes in the laser treated surface layer are examined using optical and scanning electron microscopes, energy dispersive spectroscopy, and X-ray diffraction. The fracture toughness of the laser treated surface is measured and the residual stress formed at the surface vicinity is determined from the X-ray diffraction technique. It is found that the microhardness of the laser treated surface increased slightly due to the dense layer formed at the surface vicinity. However, the laser treatment process reduces the fracture toughness of the surface due to improved surface hardness and the residual stress formed in the surface vicinity.     

A ponderomotive guiding center particle-in-cell code for efficientmodeling of laser-plasma interactions

A novel particle simulation code is described that self-consistently models certain classes of laser-plasma interactions without resolving the optical cycles of the laser. This is accomplished by separating the electromagnetic field into a laser component and a wake component. Although the wake component is treated as in a fully explicit particle-in-cell (PIC) code, the laser component is treated in the high-frequency limit, which allows the optical cycles to be averaged out. This leads to enormous reductions in computer time when the laser frequency is much greater than all other frequencies of interest. This work is an extension of the work of Mora and Antonsen, Jr. (1996 and 1997), who derived the time-averaged equations coupling the laser with the particles and developed a code to solve these equations in the quasi-static limit. The code presented is distinguished by the fact that it is useful when the plasma length is much less than the laser pulse length. Also, it is already parallelized and should be straightforward to extend to three dimensions     

激光辐照加电场激励对滇稻生长发育的影响

用激光辐照加电场激励处理滇稻种子,并对之进行育秧和田间种植试验.多年来试验表明,在出苗率、有效分、结实率和千粒重等诸多方面均优于单纯用激光处理的稻种和对照(CK).本文分析了激光和电场对生物分子共同作用的机制.     

Numerical calculations of temperature distribution of double layer metallic surface treated by laser beams

A mathematical model of laser beam treatment of double layer alloys (Ni/Fe, Al/Fe and Cr/Fe systems) describing the effect of laser beam on different physical and geometrical parameters of coated layer system has been adapted. The numerical solutions of the non-homogeneous heat-transport differential equation could estimate the temperature of the treated region.The suggested model allows investigation of the temperature distribution as a function of treated surface and laser parameters. The physical parameters of the treated materials were taken as functions of temperature due to the change in the temperature of the treated double layer materials.     

The effect of laser surface treatment of Al-Si alloy on the surface hardness and structure

In this paper, some samples of Al-Si alloy with various silicon content were treated by laser beam. The effects on structure, hardness and substructure of samples were investigated. The experimental results show that the primary crystal Al and eutectic silicon in the laser treated samples is got thinning obviously, the mosaic dimension is decreased and the dislocation density is increased.     

Evaluation of laser-assisted bremsstrahlung with Dirac-Volkov propagators

We study spontaneous bremsstrahlung emission in a highly intense laser field. In this regime the interaction with the laser field has to be treated nonperturbatively by using the relativistic formalism including Dirac-Volkov propagators, while the interaction with the Coulomb field and the bremsstrahlung radiation can be treated in first-order perturbation theory. For the intermediate electron state a fully laser-dressed propagator is used, including radiative corrections to avoid singularities on the mass shell. We find that the use of the Dirac-Volkov propagator is crucial to obtain correct numerical results. The cross section of the process is evaluated for laser intensities of order 10(20) W/cm(2) and relativistic energies of the initial electron.     

Laser gas-assisted processing of carbon coated and TiC embedded Ti-6Al-4V alloy surface

Laser gas-assisted treatment of Ti-6Al-4V alloy surface is carried out. The alloy surface is initially coated by a carbon layer, in which the TiC particles are embedded prior to laser processing of the surface. The carbon coating with the presence of TiC particles on the workpiece surface is expected to result in carbonitride compound in the surface vicinity after the laser treatment process. Optical and scanning electron microscopes are used to examine the morphological and the metallurgical changes in the laser treated layer. The residual stress formed in the surface region after the laser treatment process is critical for the practical applications of the resulting surface. Therefore, the residual stress formed in the laser treated region is predicted from the analytically equation. The X-ray diffraction technique is incorporated to obtain the residual stress formed in the surface region. It is found that the residual stress predicted agrees with the X-ray diffraction data. The dense structures consisting of TiC_xN_1−x, TiN_x, Ti₂N, and TiC compounds are formed in the surface region of the treated layer. This, in turn, significantly increases the microhardness at the surface.     

绿激光汽化前列腺的临床应用研究

比较了绿激光经尿道水下汽化前列腺手术与其它传统几种手术的性能、特点，阐述了绿激光汽化前列腺的优势：手术属微创，手术时间短，无出血，无需或只需短时间插尿管，恢复快，副作用较小，比较安全等．绿激光前列腺手术的特点是由绿激光水下汽化生物组织的机理决定的．532nm波长的绿激光在汽化前列腺时，几乎可以透过水，激光能量主要集中于组织表面的，表面效应好，同时又有一定的体效应，可以较快地汽化组织，又具有较好的止血效果．     

The applicability of Fourier's theory of heat conduction on laser produced plasmas

Thermal conduction in laser produced plasmas is usually treated by the macroscopic heat conduction equation. It is shown that this treatment can be incorrect in the case of a laser ablative implosion.     

UV-B诱导的大豆愈伤组织超弱光子辐射的动力学分析

为了研究细胞超弱光子辐射的动力学特征及其所揭示的生物学意义,用20 μW/cm2UV-B辐射大豆愈伤组织2 h,测定停止辐射后4 d内大豆愈伤组织在LED光诱导下的延迟发光.通过建立延迟发光动力学方程和数学拟合得到了大豆愈伤组织超弱光子辐射中的延迟发光积分强度、初始光子数、衰减参数和自发发光,讨论了这些发光动力学参数的生物学意义.研究结果表明,在停止UV-B辐射后的4 d内,大豆愈伤组织的光诱导延迟发光服从双曲线弛豫.动力学分析发现,延迟发光积分强度和初始光子数随处理后时间的进行呈现波动变化,停止UV-B辐射后,自发发光和丙二醛（MDA）含量均呈现升高的趋势,在辐射后2 d附近达到峰值,此后同步下降.用延迟发光积分强度和自发发光的比值定义细胞的状态参量Q和序参量R,发现UV-B辐射后大豆愈伤组织细胞Q值或R值的变化反映了UV-B辐射对大豆愈伤组织细胞的损伤以及细胞的恢复过程.     

激光磁共振方法测量CO激光器的频率稳定度

对于频率不能连续调谐的CO激光器,采用一种新的激光频率稳定度的测量方法是以分子的激光磁共振谱线为基准,通过测量分子的激光磁共振谱线线宽及其变化,然后用阿仑方差进行数据处理,即得出了一系列时畴下的CO激光频率稳定度,并用计算机对取样时间从0.1秒-1000秒的频率稳定度进行幂函数拟合,获得了频畴的CO激光频率稳定度的表达式。     

激光磁共振方法测量C0激光器的频率稳定度

对于频率不能连续调谐的CO激光器,采用一种新的激光频率稳定度的测量方法是以分子的激光磁共振谱线为基准,通过测量分子的激光磁共振谱线线宽及其变化,然后用阿仑方差进行数据处理,即得出了一系列时畴下的CO激光频率稳定度,并用计算机对取样时间从0.1秒-1000秒的频率稳定度进行幂函数拟合,获得了频畴的CO激光频率稳定度的表达式。