偏振模色散和时延抖动对啁啾光纤光栅色散补偿特性的影响

对存在偏振模色散(PMD)和群时延(GD)抖动的非理想线性啁啾光纤光栅的色散补偿特性进行了研究。实验测量了啁啾光纤光栅的群时延谱和偏振模色散光谱，理论分析和实验测量表明，啁啾光纤光栅差分群时延(DGD)抖动与其时延抖动密切相关。通过数值模拟方法，计算了线性啁啾光纤光栅偏振模色散眼图代价与入射到啁啾光纤光栅色散补偿器的光信号的偏振方向的关系，计算结果表明在使用啁啾光纤光栅色散补偿器时应对光信号的偏振方向进行调整，以获得最佳补偿效果。另外结合实验数据，模拟计算并讨论了非理想线性啁啾光纤光栅群时延抖动和偏振模色

Estimating Sighting Proportions of American Alligator Nests during Helicopter Survey

Proportions of American alligator (Alligator mississippiensis) nests sighted during aerial survey in Florida were estimated based upon multiple surveys by different observers. We compared sighting proportions across habitats, nesting seasons, and observer experience levels. The mean sighting proportion across all habitats and years was 0.736 (SE=0.024). Survey counts corrected by the mean sighting proportion reliably predicted total nest counts (R2=0.933). Sighting proportions did not differ by habitat type (P=0.668) or year P=0.328). Experienced observers detected a greater proportion of nests (P

傅立叶分解法荧光层析成像

本文提出一种基于结构光照明和傅立叶分解方法的荧光层析成像技术，该技术首先将激发光的强度沿着光轴方向调制成余弦函数，然后用此激发光对样品作传统的二维扫描，在每一个扫描位置余弦函数的频率在一定的范围内扫描，同时一一对应地记录下所发出的荧光强度。只要对所纪录的荧光序列做一个简单的傅立叶变换，即可以得到此位置样品沿着光轴方向的荧光团分布。这样通过一个传统的二维扫描，就可以得到一个三维的阳样品分布。

Nonlinear response and optical limiting in SrBi2Ta2O9 thin films

SrBi2Ta2O9 (SBT) thin films on quartz substrates were prepared by use of the pulsed-laser deposition technique. The nonlinear refractive indices, n(2), Of the SBT films were measured by use of z-scan techniques with picosecond pulses. Large negative nonlinear refractive indices of 3.84 and 3.58 cm(2)/GW were obtained for the wavelengths 532 nm and 1.064 mum, respectively. The two-photon absorption coefficient was determined to be 7.3 cm/GW for 532 nm. The limiting behavior of SBT thin film on a quartz substrate was investigated in an f/5 defocusing geometry by use of 38-ps-duration, 532-nm, 1.064-mum. laser excitation. (C) 2001 Optical Society of America.

国产掺镱双包层光纤的激光特性

采用MCVD方法研发了掺镱双包层光纤，并对其结构特性、荧光特性和激光特性进行了测试和研究。其D形内包层尺寸为400／450μm，数值孔径为0．36，纤芯直径约为16μm，数值孔径约为0．18。荧光谱线的范围为1000-1140nm，1030nm处的峰宽大于50nm。采用大功率激光二极管单端泵浦6m长的双包层光纤，在泵浦人纤功率为61W时，获得了32W的激光输出，斜率效率为64％。该光纤在高功率处未发现饱和现象，通过优化光纤参数与泵浦方式还可以提高转化效率和输出功率。实验表明该光纤可以取代进口光纤用作高功率

H-2-sensing characteristics of nanocrystalline La0.8Pb0.2FeO3 prepared by sol-gel method

Nanocrystalline La0.8Pb0.2FeO3 has been prepared by the sol-gel method. XRD patterns show that the nanocrystalline La0.8Pb0.2FeO3 is a perovskite phase with the orthorhombic structure and its mean crystallite size is about 19 nm. The influence of Pb ions which replaced the La ions on A-sites can be directly observed from the electrical and sensing properties to H-2 gas. The conductance of La0.8Pb0.2FeO3-based sensor is considerably higher than that of LaFeO3-based sensor, and Pb-doping can enhance the sensitivity to H2 gas. An empirical relationship of R = KCH2alpha with alpha = 0.668 was obtained.

977nm抽运下掺铒碲酸盐基氧卤玻璃的光谱特性

研究了掺铒TeO2-ZnO-PbCl2碲酸盐基氧卤玻璃在977nm激光二极管抽运下的发光和上转换发光特性，结果发现除红外1．53μm^4I13.2→^4I15/2发光外(荧光半高宽高达69nm)，该玻璃还存在很强的^2H11/2→^4I15/2(527nm)，^4S3/2→^4I15/2(549nm)和^4R9/2→^4I15/2(666nm)可见上转换发光．应用Judd-Ofelt理论计算得到玻璃强度参数Ω1(t=2，4，6)分别为Ω2=5．87×10^20cm^2,Ω4=2．08×10^2-cm^2，

The MLH1 c.1852_1853delinsGC (p.K618A) Variant in Colorectal Cancer: Genetic Association Study in 18,723 Individuals

Colorectal cancer is one of the most frequent neoplasms and an important cause of mortality in the developed world. Mendelian syndromes account for about 5% of the total burden of CRC, being Lynch syndrome and familial adenomatous polyposis the most common forms. Lynch syndrome tumors develop mainly as a consequence of defective DNA mismatch repair associated with germline mutations in MLH1, MSH2, MSH6 and PMS2. A significant proportion of variants identified by screening these genes correspond to missense or noncoding changes without a clear pathogenic consequence, and they are designated as "variants of uncertain significance'', being the c.1852_1853delinsGC (p.K618A) variant in the MLH1 gene a clear example. The implication of this variant as a low-penetrance risk variant for CRC was assessed in the present study by performing a case-control study within a large cohort from the COGENT consortium-COST Action BM1206 including 18,723 individuals (8,055 colorectal cancer cases and 10,668 controls) and a case-only genotype-phenotype correlation with several clinical and pathological characteristics restricted to the Epicolon cohort. Our results showed no involvement of this variant as a low-penetrance variant for colorectal cancer genetic susceptibility and no association with any clinical and pathological characteristics including family history for this neoplasm or Lynch syndrome.