AFM images of G1-phase premature condensed chromosomes: Evidence for 30 nm changed to 50 nm chromatin fibers

To gain evidence for 30 nm changed to 50 nm chromatin fibers, we used atomic force microscopy (AFM) to study the ultrastructural organization of G₁-phase premature condensed chromosomes (PCC). The surface of early G₁-phase PCC is smooth and fibrous structures exist around the chromatids. The height of early G₁-phase PCC is about 410 nm and the width is 1.07 ± 0.11 μm (n = 30). At late G₁-phase, the surface becomes globular. The height of late G1-phase PCC is about 370 nm and the width is 845.04 ± 82.84 nm (n = 30). Phase image reveals that early G₁-phase PCC is composed of 50 nm (48.91 ± 6.63 nm, n = 30) chromatin fibers and these 50 nm chromatin fibers tangle together, while late G₁-phase PCC is composed of 30 nm (30.96 ± 4.07 nm, n = 30) chromatin fibers. At high magnification, fibers existing around the chromatids become clear in early G₁-phase PCC. Chromatin fibers revealed by closer view of the end of chromatid are about 50 nm. In late G₁-phase PCC, the surface presents globular structures. The shape of these globular structures is regular and the diameter is 118.96 ± 11.70 nm (n = 30). Our results clearly show that 30 nm chromatin fibers change to 50 nm chromatin fibers in G₁-phase PCC and suggest that 50 nm chromatin fibers are the basic component of the mitotic chromosomes.     

The effect of C60 cluster ion beam bombardment in sputter depth profiling of organic-inorganic hybrid multiple thin films

The effects of C₆₀ cluster ion beam bombardment in sputter depth profiling of inorganic-organic hybrid multiple nm thin films were studied. The dependence of SIMS depth profiles on sputter ion species such as 500 eV Cs⁺, 10 keV C₆₀⁺, 20 keV C₆₀²⁺ and 30 keV C₆₀³⁺ was investigated to study the effect of cluster ion bombardment on depth resolution, sputtering yield, damage accumulation, and sampling depth.     

Nd:YVO4声光调Q腔内倍频457 nm蓝光激光器

脉冲蓝光激光器在水下探测、水下通信和遥感方面有着重要的应用前景。根据高斯光束传输的ABCD矩阵,设计了对热效应不灵敏的Z型谐振腔。利用808 nm激光二极管(LD)端面抽运Nd:YVO4晶棒,在室温下实现了4F3/2→4I9/2准三能级激光谱线跃迁。通过声光调Q和LBO腔内倍频,获得了稳定的高重复频率、高峰值功率457 nm蓝光激光输出。当抽运功率为30 W时,在重复频率为10 kHz下,获得最大单脉冲能量为56 μJ ,脉冲宽度为217 ns,峰值功率达258 W; 在重复频率为20 kHz下,获得最大平均功率为760 mW,脉冲宽度为261 ns,峰值功率为146 W。在最大平均输出功率下测量了脉冲457 nm蓝光激光器的功率稳定性,20 min之内其最大不稳定度小于2%。     

激光二极管侧抽运双棒串接准连续Nd∶YAG高功率绿光激光器

研制一台激光二极管(LD)侧面抽运双棒串接准连续Nd∶YAG折叠腔高功率绿光激光器,理论分析了热致双折射效应对系统的影响,并对用石英旋转片补偿前后的情况进行模拟对比。在考虑了补偿后的情况下设计了热稳定谐振腔。实验中采用两个串接的由30个20 W的LD阵列侧面抽运的Nd∶YAG棒和Ⅱ类临界相位匹配HGTR-KTP晶体,在抽运电流均为21.6 A,重复频率为27.2 kHz时,获得了最大平均输出功率为164 W,脉冲宽度为130 ns的532 nm绿光输出,光-光转换效率为13.7%,测得光束质量因子为M2x=9.52, M2y=9.86,不稳定度为2.3％。实验结果显示,经补偿后的激光系统能在宽的稳区范围内稳定运转。     

声光调Q的Nd:YVO4晶体1342 nm激光器

报道了采用光纤耦合激光二极管(LD)模块端面抽运Nd:YVO4晶体实现高功率、高重复频率声光调Q 1342 nm波长的激光输出,以及采用考虑增益频谱分布的调Q速率方程模型仿真研究该脉冲激光器的结果.在激光器注入总功率40 W的情况下,可得到最高工作重复频率100 kHz;在50 kHz重复频率工作条件下,可得到11.0 W的平均输出功率及稳定的脉冲输出.应用与介质增益频谱相关的调Q速率方程模型对该脉冲激光器进行了仿真研究,得到了脉冲宽度、脉冲峰值功率、脉冲建立时间等计算结果,还给出了输出在频谱上的分布以及谱宽,并与实验结果进行了比较.考虑增益频谱分布的调Q速率方程模型不仅可以应用于分析、设计脉冲激光器的频谱,而且由于考虑了增益在频谱上的实际分布,基于该模型的仿真计算可以获得比传统单频调Q速率方程更为接近实际的结果.     

LD end-pumped intracavity frequency doubled Yb:YAG laser

A laser diode end-pumped 10 at.% doped Yb:YAG microchip crystal intracavity frequency doubled all solid-stated green laser is reported in this paper. Using one plano-concave resonator, with the pump power of 1.2 W, 44.2 mW TEM₀₀ continuous wave (CW) laser at 525 nm was obtained, the optical conversion efficiency was about 3.7%. When a Cr:YAG crystal with initial transmission of 95.5% inserted in the resonator, the maximum output power of 6.4 mW, pulse duration width of 49.1 ns, pulse repetition rate of 2.45 kHz, and peak power of 53.1 W at 515 nm were achieved when the pump power was 1.2 W. The wavelength changed from 525 nm to 515 nm and the threshold was only 725 mW.     

BBO四倍频全固态Nd:YVO4紫外激光器

报道了用BBO晶体对激光二极管抽运Nd:YVO₄晶体声光调Q产生的1.064μm激光 进行四倍频,实现平均功率为63mW准连续波266nm紫外激光运转,重复频率为12.5kHz、单 脉冲能量5μJ、峰值功率达252W,绿光-紫外光转换效率达11%. 关键词： 266nm紫外激光 四倍频 全固态     

Polymer-Modified Single-Walled Carbon Nanotubes Affect Photosystem II Photochemistry,Intersystem Electron Transport Carriers and Photosystem I End Acceptors in Pea Plants

Single-walled carbon nanotubes (SWCNT) have recently been attracting the attention of plant biologists as a prospective tool for modulation of photosynthesis in higher plants. However, the exact mode of action of SWCNT on the photosynthetic electron transport chain remains unknown. In this work, we examined the effect of foliar application of polymer-grafted SWCNT on the donor side of photosystem II, the intersystem electron transfer chain and the acceptor side of photosystem I. Analysis of the induction curves of chlorophyll fluorescence via JIP test and construction of differential curves revealed that SWCNT concentrations up to 100 mg/L did not affect the photosynthetic electron transport chain. SWCNT concentration of 300 mg/L had no effect on the photosystem II donor side but provoked inactivation of photosystem II reaction centres and slowed down the reduction of the plastoquinone pool and the photosystem I end acceptors. Changes in the modulated reflection at 820 nm, too, indicated slower re-reduction of photosystem I reaction centres in SWCNT-treated leaves. We conclude that SWCNT are likely to be able to divert electrons from the photosynthetic electron transport chain at the level of photosystem I end acceptors and plastoquinone pool in vivo. Further research is needed to unequivocally prove if the observed effects are due to specific interaction between SWCNT and the photosynthetic apparatus.     

深紫外和频晶体CLBO产生193 nm激光的频率变换

 简述了深紫外和频晶体CLBO的光学特性。根据相位匹配角公式、非线性有效系数公式、走离角公式和允许角公式,详细计算了CLBO晶体和频产生193 nm激光时的相位匹配角、非线性有效系数、和频时谐波走离角、允许角的具体数值。根据这些数值,并考虑产业化的要求,对目前几种和频方式进行了比较,最终选定波长为λ₁=2 100 nm的o光和波长为λ₂=213 nm的e光作为基频光进行和频的匹配方式。此方式相位匹配角为51.6°,具有大的非线性有效系数0.97,小的走离角3.7°,大的允许角1.9×10^-6 rad·mm,是非常理想的产生193 nm激光的匹配方式。     

Bis(4,4′-dimethyl-2,2′-bipyridine)ruthenium(II) Complexes Containing 2-Arylimidazo-phenanthroline: Syntheses, Characterization and Third-order Nonlinear Optical Properties

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