伽马辐照对掺镱光纤材料特性影响的研究

掺镱光纤是高功率激光器的核心材料,但在高能射线辐照后其应用性能会显著下降,因此有必要对掺镱光纤材料在辐照环境下的性能变化进行深入研究。采用改进型化学气相沉积法结合稀土螯合物掺杂制备了系列光纤预制棒及光纤,测试了光纤在不同剂量下射线辐照前后的高功率输出性能,以及光纤预制棒辐照前后的吸收光谱及镱离子荧光寿命。结果表明：小剂量辐照后掺镱光纤的高功率输出显著下降,通过预制棒吸收光谱可看出主要是因为伽马辐照后使掺镱光纤材料中Al的相关缺陷浓度增多,在可见光区域吸收损耗增加。Ce离子的掺杂通过缓减辐致铝氧空位中心（Al-OHC）色心缺陷的增加,减少Yb离子荧光寿命的下降,可在一定程度上抑制高功率掺镱光纤的辐致暗化。     

层次分析中对数最小一乘排序法及其性质

利用最小一乘法原理 ,在层次分析中提出了一种新的排序方法——对数最小一乘法 ,并将其转化成线性规划问题求解 ,证明了对数最小一乘法的一些性质 .     

用仪器说明书培养学生自学能力和动手能力

中专物理教学中,实验是最重要的教学环节,而仪器说明书在学生实验中具有重要的地位和作用.1作用 可行性 教学仪器的说明书,或者说是技术资料.简单的由结构原理、用途、使用方法和注意事项四个部分组成.复杂的还有主要技术性能、指标、保养、维修等.显然,仪器说明     

厄米-高斯光束通过圆孔衍射的两种计算方法比较

应用Collins公式和硬边圆孔函数拓展为有限复高斯函数和的方法,推导出厄米-高斯（Hermite—Gaussian）光束通过圆孔的衍射场分布的近似解析公式．模拟结果表明使用该解析公式所得结果和直接对Collins公式进行数值计算的结果符合较好,并讨论两种方法的差异性以及各自的优缺点．     

Evaluation of diethylenetriaminepentaacetic acid-manganese(II) complexes modified by narrow molecular weight distribution of chitosan oligosaccharides as potential magnetic resonance imaging contrast agents

Novel conjugates of narrow molecular weight distribution of chitosan oligosaccharides (CSn; n=6, 8, 11) with manganese-diethylenetriaminepentaacetic acid (Mn-DTPA) as potential magnetic resonance imaging (MRI) contrast agents were synthesized. The structures were characterized by means of Fourier transform infrared spectra, ¹³C nuclear magnetic resonance, size exclusion chromatography and inductively coupled plasma atomic emission spectrometry. The characterization results showed that Mn-DTPA was successfully linked to aminated CSn by an amide function. The magnetic properties were characterized by in vitro and T₁-weighted FLASH image experiments. Relaxivities studies indicated that Mn-DTPA-CSn (n=8, 11) provided higher relaxivity, either in aqueous or bovine serum albumin solution (0.725 mM), than commercial contrast agent Gd-DTPA. The stability results showed that Mn-DTPA-CSn in aqueous were stable enough to prevent Mn^II ions from releasing. The preliminary in vitro and T₁-weighted FLASH image studies suggested that Mn-DTPA-CSn had the advantage of becoming promising MRI contrast agents.     

Elemental depth profile of faux bamboo paint in Forbidden City studied by synchrotron radiation confocal µ‐XRF

A three‐dimensional (3D) analysis of micro x‐ray fluorescence (XRF), namely confocal µ‐XRF, has been constructed at 4W1B beamline of the Beijing synchrotron radiation facility (BSRF). A KB mirror is applied to focus the incident beam and a polycapillary half‐lens in front of the Si(Li) detector is used to limit the visual field of the detector. The faux bamboo paint in Emperor Qianlong's Lodge of Retirement in Forbidden City was analyzed nondestructively by this method. A stratified structure in the paint is disclosed and the results show that the painting was probably restored once in the past, following the same painting technique as originally used. Copyright © 2008 John Wiley & Sons, Ltd.     

Ionic liquid-promoted multi-component reaction: novel and efficient preparation of pyrazolo[3,4-<Emphasis Type="Italic">b</Emphasis>]pyridinone,pyrazolo[3,4-<Emphasis Type="Italic">b</Emphasis>]-quinolinone and their hybrids with pyrimidine nucleoside

The utilization of an ionic liquid, [bmim][BF₄] as both reaction medium and promoter for a multi-component reaction of aldehyde (1) and 5-amino-3-methyl-1-phenylpyrazole (2) with Meldrum acid (3) or dimedone (5) is studied. From this reaction, pyrazolo[3,4-b]pyridinone (4) and pyrazolo[3,4-b]quinolinone (6) derivatives were prepared in high yields. This novel procedure showed such advantages as environmentally benign nature, enhanced efficiency, simple operation process, and mild reaction conditions. As an application, the procedure was successfully used in the preparation of a set of pyrimidine nucleoside–pyrazolo[3,4-b]pyridine and pyrazolo[3,4-b]quinolinone hybrids with potential biological activities.     

S2分子X^3—Σ^—g和B^3Σ^—u态的势能函数和振动光谱特征

应用实验光谱数据，导出了Ｓ２的基态分子Ｘ３Σ－ｇ和激发态Ｂ３Σ－ｕ的ＭｕｒｅｌＳｏｒｂｉｅ势能函数，并用ＱＣＩＳＤ（Ｔ）／６－３１１Ｇ方法对基态进行了计算，结果在吸引支出现了回避相交而产生了一个浅平极大，其他部位与实验结果符合甚好。计算了Ｂ３Σ－ｕ和Ｘ３Σ－ｇ态的全部振动能级，以及激发态（Ｂ３Σ－ｕ）振动能级≤９和基态（Ｘ３Σ－ｇ）振动能级≤３０之间的Ｄｅｓｌａｎｄｒｅｓ表。给出了Ｂ３Σ－ｕ－Ｘ３Σ－ｇ跃迁Ｃｏｎｄｏｎ抛物线，各振动态的计算结果与实验值很好符合。     

Experimental demonstration of joule-level non-collinear optical parametric chirped-pulse amplification in yttrium calcium oxyborate

In this Letter, we report on what is, to our knowledge, the first experimental demonstration of yttrium calcium oxyborate (YCOB) for joule-level and broadband non-collinear optical parametric chirped-pulse amplification centered at 800 nm. Based on a Ti:sapphire chirped-pulse amplification front end, an amplified signal energy of 3.36 J was generated with a pump of 35 J in the crystal. Compressed pulse duration of 44.3 fs, with a bandwidth of 49 nm, was achieved. The results confirm that YCOB crystal is another potential alternative as a final amplifier besides Ti:sapphire in a petawatt laser at 800 nm.