基于等离子体镜的太赫兹单脉冲选择方法

研究了一种用于中国工程物理研究院太赫兹自由电子激光装置(CTFEL)输出的太赫兹的单脉冲选择方法,以满足一些对太赫兹脉冲的时间分辨率和峰值强度提出较高要求同时要保证较低平均功率的实验的需要。利用自诱导等离子体开关技术,太赫兹能够被短脉冲激光打靶产生的等离子体镜反射,从而使等离子体镜可以作为门控开关,选出单个太赫兹微脉冲。通过理论分析计算出等离子体临界密度和激光功率密度阈值,采用辐射流体模拟软件对激光打靶过程进行数值模拟。模拟结果表明,激光激发出的等离子体密度远大于临界密度。由此证明了实验的可行性,进而给出实验所需装置的参数指标以及实验光路设计。

高功率超短脉冲系统等离子体镜的焦斑退化分析

等离子体镜是一种有效提升高功率超短脉冲激光信噪比的方法,但在一部分实验中使用等离子体镜后焦斑出现了退化现象。为了定量研究等离子体镜的焦斑退化问题,提出基于等离子体膨胀和衍射传输的时空聚焦多步传输算法,通过光束质量评价函数定量分析等离子体膨胀时间、波前误差幅值和空间频率对焦斑退化的影响。仿真结果表明,等离子体镜引起的远场焦斑退化主要是由等离子体膨胀时间和波前误差引起的等离子体膨胀不均匀所致,其中,等离子体膨胀时间是主导因素。并且波前误差的幅度越大、空间频率越低,对聚焦能力的影响相对越大。从高信噪比、高功率激光系统输出能力的角度考虑,对于使用等离子体镜的高功率超短脉冲激光系统提出时空上的光束质量要求,以避免远场焦斑的退化问题。

气管镜下氩等离子体凝切术联合冷冻治疗气道良性肿瘤五例临床分析

原发性气管支气管良性肿瘤临床少见，既往由于技术限制，多数患者采取开胸手术治疗。近几年随着气管镜介入治疗的进展，激光、高频电、氩等离子体凝切术、冷冻、微波及光动力等技术均可用于治疗（支）气管腔内良性肿瘤。

拍瓦激光驱动纳米刷靶高品质质子束的产生

超强激光加速产生的高能质子束源在基础物理研究、材料科学、生物医疗等领域具有广泛应用前景。基于激光聚变研究中心的SILEX-II装置,开展了高对比度飞秒激光驱动纳米刷靶质子加速实验研究。采用等离子体镜技术进一步提升激光对比度,有效降低了预脉冲对纳米刷靶结构的影响。相比于平面靶,采用纳米刷靶质子截止能量提高到1.5倍,质子束产额增加近一个量级,成功验证了超高功率密度下纳米刷靶对激光离子加速的增强效果,并且有效提升了质子束空间分布的均匀性。研究结果为高品质质子束源的产生和应用提供了技术途径。

可视下尿道腔内内切开术治疗尿道狭窄29例

目的:探讨尿道狭窄的腔内手术治疗疗效及其安全性。方法:回顾性分析直视下采用肾镜、英国Gyrus公司生产的超脉冲等离子体切割镜对29例尿道狭窄患者进行腔内内切开治疗。结果:本组尿道内切开术1次者27例,2次者2例。29例全部成功。结论:术前完善各项术前检查,详细了解尿道狭窄段长度、狭窄程度、位置、数目、有无合并假道;术中充分切开瘢痕组织,超脉冲等离子切割镜(内鞘F24、30°切割镜)弧形电切襻彻底去除瘢痕组织;术后积极预防感染、正确把握保留导尿管时间是保证手术成功的关键。

Organotemplate-free Hydrothermal Synthesis of SUZ-4 Zeolite: Influence of Synthesis Conditions

Various conditions were investigated in detail for the novel organic template-free static hydrothermal synthesis of SUZ-4 zeolite in the presence of seeds. The obtained samples were characterized by XRD （X-ray diffraction）, SEM （scanning electron microscope）, TG （thermal gravimetric analysis）, ICP （inductively coupling plasma） elemental analysis, nitrogen sorption isotherm and surface area. The results show that pure SUZ-4 zeolites with high crystallinity are obtained in a broad window of synthesis conditions： seed mass concentration 0.2%-2%, SIO2/A1203 molar ratio 21 25, KOH/SiO2 molar ratio 0.33 0.43, H20/SiO2 molar ratio 7.14-38.1, aging time 24 h, crystallization temperature 160℃, and crystallization time 6-10 d. Also, crystallinity and size of the rod-like SUZ-4 zeolite crystals are found to alter with the conditions.

Promoting Effects of Pt on the Catalytic Performance of Supported NiB Amorphous Alloy Catalysts for Benzene Hydrogenation

A support(denoted AM) was prepared using pseudo-boehmite and mordenite.Ni-B and NiPtB amorphous catalysts were prepared on the support by the impregnation method followed by chemical reduction with a KBH4 solution.And the catalysts were characterized by X-ray diffraction(XRD),environment scanning electron microscope(ESEM),inductively coupled plasma(ICP),H2-temperature programmed reduction(H2-TPR),differential thermal analysis(DTA),and BET.Benzene hydrogenation was used as a probe reaction to evaluate the effect of addition of small quantities of Pt on the NiB/AM catalyst.The results show that Pt can promote the reduction of NiO and the formation of active sites,leading to smaller catalyst particles and better dispersion of active metal particles on the support.The catalytic activity,sulfur resistance and thermal stability were remarkably improved by Pt doping of the NiB/AM catalyst.

Corrosion detection of tinplate cans containing coffee using EIS/EN sensor

The corrosion behavior of tinplate cans containing coffee was investigated using novel electrochemical impedance spectroscopy(EIS) and electrochemical noise(EN) sensors.The contents of iron and tin dissolved in cans were detected by inductively coupled plasma mass spectrometer(ICP-MS),and the morphology of corroded surface was observed by optical microscopy and scanning probe microscopy(SPM).The results reveal that the coating resistance,charge transfer resistance and noise resistance decrease with the prolongation of storage time.The iron and tin contents in cans increase with the storage time,while the bump height of coating surface increases from 30 nm to 80 nm during the corrosion of twelve months.The existence of deformation would enhance the corrosion process of tinplate cans.Finally,the corrosion mechanism of tinplate cans in coffee was proposed.

Nitrogen Plasma Treatment Effect on Graphene Sheeted Vertically Aligned Carbon Nanofibers

Nitrogen plasma treatment effect on GS-CNFs （graphene seeted vertically aligned carbon nanofibers） has been studied. GS-CNFs were grown on nickel coated cupper substrates by DC-plasma CVD （chemical vapor deposition） at relatively low temperature. GS-CNFs were studied by SEM （scanning electron microscopy）, HR-TEM （high-resolution transmission electron microscopy）, XPS and Raman measurements. GS-CNFs are composed of cylindrical shaped having pure graphite sheets with about 5 μm length and nanometer size tips and roots diameter. Nitrogen plasma treatment causes nitrogen chemical etching on the graphene seeted carbon nanofibers were disordered its fine shape and increase the graphetization due to nitrogen incorporation.

相对传播的双脉冲激光与薄膜靶作用产生的强单色谐波

研究了相对传播的双脉冲激光与薄膜靶的作用,观察到很强的谐波产生.其物理图像是:圆偏振高对比度强激光脉冲作用于薄膜靶,由光压推动产生的高密度等离子体靶向前运动,同时由于电荷分离场的作用,使得离子束和电子束在纵向上都有好的聚束,从而产生以相对论速度向前运动的等离子体镜;反向入射一个探测光到已被加速的等离子体镜上,由多普勒频移产生强的单色N次谐波,探测光脉冲被"压缩"至原来的1/N.还讨论了激光和等离子体参数对等离子体镜的运动和谐波级次的影响,以及相对论运动等离子体镜的稳定性对谐波的影响.

Size-tunable synthesis of gold nanorods using pyrogallol as a reducing agent

A novel and facile seed-mediated method for the preparation of monodispersed gold nanorods(GNRs) is presented by introducing pyrogallol as a reductant. Fast Fourier transformation of high-resolution transmission electron microscopy reveals that the synthesized GNRs are single crystalline. The longitudinal surface plasmon resonance of GNRs can be finely tuned by varying silver ion concentrations or seed amounts. Also, both thick(diameter >30 nm) and thin(diameter <10 nm) GNRs with exceptional monodispersity can be well prepared by this method. These findings indicate that this method has a greater performance in controlling the morphology of GNRs than that of traditional approach with ascorbic acid as a reductant.

Three-dimensional hierarchical Pt-Cu superstructures

Three-dimensional （3D） hierarchical Pt-Cu tetragonal, highly branched, and dendritic superstructures have been synthesized by a facile template-free hydrothermal approach, showing growth patterns along （111, 110）, （111）, and （100） planes, respectively. These structures have been characterized by transmission electron microscopy （TEM）, X-ray diffraction （XRD）, energy dispersive X-ray spectroscopy （EDX）, inductively coupled plasma optical emission spectrometry （ICP-OES） and a detailed formation mechanism has been developed, which shows that the in situ formed 12 and the galvanic replacement reaction between Cu and Pt4, may guide the formation of these superstructures. The comparative electrocatalytic properties have been investigated for methanol and ethanol oxidation. Due to their interconnected arms, sufficient absorption sites, and exposed surfaces, these superstructures exhibit enhanced electrocatalytic performance for electro-oxidation of methanol and ethanol when compared with commercial Pt/C and Pt black.

Mapping carbon distribution in 35SiMn steel by energy-filtered transmission electron microscopy

In this study,the three-windows method,the jump-ratio method and the R-map method in energy-filtered transmission electron microscopy(EFTEM) have been applied to mapping carbon distribution in 35SiMn steel after a quenching-partitioning treatment.The carbon contamination is successfully suppressed by using EFTEM and plasma-cleaning TEM samples.Compared to the three-windows method and the jump-ratio method,the R-map method provides carbon distribution with less noises,and is insensitive to changes in sample thickness.We have demonstrated that the R-map method is a better way for carbon mapping in middle-carbon steel without the influence of carbon contamination.

Distribution, occurrence and enrichment causes of gallium in coals from the Jungar Coalfield, Inner Mongolia

We collected eleven bench samples of No. 6 coal from the Heidaigou Surface Mine, Jungar Coalfield, Inner Mongolia, China, and four samples from the affiliated coal preparation plant. Based on these samples, we used inductively coupled-plasma mass spectroscopy, X-ray diffraction, scanning electron microscope with an energy-dispersive X-ray spectrometer techniques, and borehole exploration data, to investigate the distribution, occurrence and enrichment causes of gallium （Ga） in the coals. Our results show： （1） Gallium is significantly enriched in the coal seams from the study area, with an average content of 18.8-26.0 ppm. Gallium is distributed heterogeneously in the coals, and reaches ore-forming scales only in No. 6 coal of Heidaigou Surface Mine, not in the other mining districts of Jungar Coalfield. （2） On the horizontal plane, Ga is enriched in the main minable coals from the northern and middle part of the coalfield. In the vertical profile, Ga content in the coal seams is higher at the base of Taiyuan Formation （Nos. 8 and 9） and Shanxi Formation （Nos. 3 and 4） than at the top of the Taiyuan Formation. Within the identical coal seam, Ga content is higher in the benches near the roof and floor than in the middle section. （3） Gallium in the coals is associated mainly with kaolinite and boehmite. Additionally, Ga may be adsorbed to some extent by humic acid, resulting in a high level in weathering coal. （4） Geological factors affect Ga enrichment in coal, such as the prop- erty of parent rocks in the source area, the sedimentary environment, organic matter, structure, and past magmatic hydrothermal activity. Especially, Ga content in parent rocks plays a leading role. （5） The mobility and precipitation of trace elements like Ga are controlled principally by the geochemical behavior of the major element A1. Terrestrial and transgressive environments can cause the precipitation of bauxite, whereas marine-continental depositional environments may cause the separation of Ga from A1. In addition, Ga may migrate in the form of gas tively enriched in high-volatile coal. and may be affected by the ground temperature. Thus, it is relatively enriched in high-volatile coal.

Electron dynamics and wave activities associated with mirror mode structures in the near-Earth magnetotail

We report the observation of mirror mode structures by Cluster spacecraft at around X^-16 RE in the Earth’s magnetotail.The wavelength of the mirror structure is larger than 7000 km,corresponding to tens of ion gyroradii.Features of the mirror structures are similar to those detected in the magnetosheath:the anti-correlation between the magnetic field strength and plasma density,zero phase velocity in the plasma rest frame and linear polarization.The structures were observed in a region bounded by two dipolarizations during a substorm intensification.Thus,the dipolarization process may provide a plasma condition facilitating the growth of the mirror mode structures.Another interesting feature is the electron dynamics within the mirror structures.Thermal electron energy flux has an enhancement at 0°and 180°pitch angles inside the magnetic dips of the first three mirror structures and an enhancement at 90°pitch angle inside the magnetic dip of the last structure.The different electron distribution inside the mirror structures might be a result of different evolution stages of the mirror wave.The last structure may be in the nonlinear stage of the mirror instability,whereas the three others with quasi-sinusoidal waveforms may be in the linear stage.In addition,we found that intense whistler waves were confined within the magnetic dips.We conjecture that whistler waves observed in the first three dips were generated in a remote region,then they were trapped in the mirror mode troughs and transported toward the spacecraft;while the whistler wave detected in the last dip was excited locally by the electron anisotropy instability.

Fluorescence enhancement of Tb^(3+) complexes by adding silica-coated silver nanoparticles

Six kinds of terbium ternary complexes with halo-benzoic acids were synthesized. Their compositions were determined by C, H elemental analyzer and EDTA titration. The infrared spectra, ultraviolet absorption spectra, and fluorescence spectra were also measured to identify the complexes. Elemental analysis showed that the compositions of these complexes were Tb（p-BrBA）3- H20, Tb（p-CIBA）3- 2H20, Tb（p-FBA）3- H20, Tb（o-FBA）3·2H20, Tb（o-CIBA）3· H20, and Tb（o-BrBA）3. H20, respectively. The monodispersed Ag@SiO2 core-shell nanoparticles with silica thicknesses of 10, 15, and 25 nm were success- fully prepared and characterized by transmission-electron microscopy. Fluorescence intensities of the complexes were detected before and after Ag@SiO2core-shell nanoparticles were added; the enhancement times were related to the silica-shell thick- ness. The fluorescence enhancement times were largest when the thickness of the silica shell was 25 nm. The mechanism may be attributed to the localized surface-plasmon resonance. Furthermore, the enhancement effect of terbium fluoro-benzoate complexes was the strongest in these complexes. This result may be attributed to the hydrogen bond between the hydroxyl on the surface of the silica shell and the fluorine atom.