C20富勒烯的Ar+离子辐照合成

Ar+离子辐照聚乙烯靶表面在室温情况下合成的C20,已采用高分辨率透射电子显微镜/电子衍射装置、飞行时间质谱、红外和拉曼谱仪进行了研究.结果认为,辐照诱发的微晶体由笼式C20组成.     

氢分子在几种高铬镍合金钢中微扩散所引起的内耗峰

用扭摆作内耗测量,发现八种高铬镍合金钢中含氢可以引起内耗峰。当振动频率约为每秒1.5周时,内耗峰的巅值温度在610—640℃附近。用其中一种高铬镍合金钢试样(18Cr 12Ni)进行了系统的实验,指出这个内耗峰的基元过程是一种弛豫过程,所包含的激活能约为46,000—50,000卡/克分子。根据激活能的数值以及内耗峰在升温、降温和保温时的变化情况,可以认为这个新内耗峰是由於氢分子在钢中微扩散所引起来的。内耗测量的结果也指出了在18Cr 12Ni钢中在特定的升温、降温速度下氢分子舆氢原子的转变温度范围,所得的结果舆资料上的相合。     

重庆地区露天石刻早期封护材料老化产物及其影响研究

重庆市市委会办公大楼旧址前有一组露天存放的清代砂岩石狮子,表面覆盖着黑色硬壳状物质, 发生大面积脱落,起翘和卷曲。为了揭示黑色硬壳状结构组成,研究其形成过程及对文物产生的影响,利用环境扫描电子显微镜(SEM),X-射线衍射仪(XRD),X-射线荧光光谱仪(XRF),傅里叶变换红外光谱仪(FTIR)和X-射线光电子能谱(XPS)对黑色硬壳及文物表层砂岩样品进行了检测分析研究。结果发现：黑色硬壳断面Mapping元素分布图显示其分为底漆层,中间层和表层,系石刻早期封护层的老化产物;中间层含有立德粉(硫化锌和硫酸钡),黑色外观源于表层中含铅颜料(铅白)变色形成黑色硫化铅及树脂碳化所致;红外光谱与光电子能谱显示出黑色硬壳中含有强的羟基(-OH)特征峰,说明封护层中有机物老化后形成了大量羟基,从而增强了自身亲水性,造成易吸水溶胀与干燥收缩情况,导致大面积脱落,起翘和卷曲现象;黑色硬壳起翘和卷曲部位与下层石刻表面之间形成了易于积水的微空隙,能够聚集雨水中的有害物质,造成石刻表层岩石发生腐蚀,例如黑色硬壳背面及下层岩石表面中高含量硬石膏(CaSO₄),经生水化作用后转化为石膏(CaSO₄·2H₂O),发生体积膨胀造成岩石表面松动和酥粉。因此,当露天文物表面上封护层已老化时,及时地进行清除是十分必要的。     

正电子冲击下氦电离三重微分截面的理论计算

我们发展了一种正电子碰撞原子电离的畸变波Born近似方法, 在这个方法中,正负电子偶素通道通过一个ab initio的光学势附加到入射粒子和靶的相互作用势上,且通道对电离作用被第一次被考虑在正电子碰撞原子电离的过程中. 应用这个方法计算了在50 eV入射能量范围氦的电离的三重微分截面,计算结果和实验数据很好的符合.     

激光在雨中传输的分析与计算

本文通过分析雨滴其对激光的散射和吸收作用,研究激光在大气中传输时受雨滴作用的影响,计算不同雨滴对激光光强的影响,在不同降雨下,测试激光光强的变化,并通过软件仿真实时显示光斑的闪烁、漂移,为进一步优化激光通信系统性能设计、最终实现全天候超视距的大气激光通信做有意义的探索。     

Recovery of spectral features readout with frequency-chirped laser fields

A data-processing technique is proposed for use with conventional frequency-chirped absorption spectroscopy to ensure accurate mapping of spectral features into time-domain signatures with arbitrarily fast readout chirp rates. This technique recovers the spectrum from a signal that is distorted owing to the fast chirp rate and therefore facilitates fast measurement of the spectral features over a broad spectral range with high resolution. Both numerical simulations and experimental results are presented.     

Structural characterization of crystalline ternary inclusion compounds at the air-water interface

Crystalline ternary inclusion monolayers consisting of a two-dimensional hydrogen-bonded host network of guanidinium (G) ions and organosulfonate (S) amphiphiles, and biphenylalkane guests, can be generated at the air-water interface through synergistic structural enforcement by hydrogen bonding and host-guest packing. Surface pressure-area isotherms of the 4'-hexadecylbiphenyl-4-sulfonate (C16BPS) amphiphile in the presence of G, with or without guest, are characterized by lift-off molecular areas expected for the GS sheet based on single-crystal X-ray structures of homologous bulk crystals. Intercalation of biphenylalkane guests (4-C(n)()H(2)(n)()(+1)-C(6)H(4)-C(6)H(5), n = 1, 4, 6, 10, 16; denoted CnBP) between organosulfonate hydrophobes, which define pocketlike cavities in the GS monolayer host, afford ternary inclusion monolayers with a 1:1 host-guest stoichiometry. These inclusion monolayers are less compressible than the guest-free host, consistent with dense packing of the biphenylalkane moieties of the host and the biphenylalkane guests. The inclusion monolayers are distinguished from the amorphous guest-free host and from selected guanidinium-free mixed monolayers by structural characterization with grazing-angle incidence X-ray diffraction (GIXD). The GIXD data for the ternary (G)C16BPS:C16BP and (G)C16BPS:C6BP inclusion monolayers obtained upon compression are consistent with a rectangular unit cell. The dimensions of these unit cells and refinement of the GIXD data suggest a "rotated shifted ribbon" GS hydrogen-bonding motif similar to that observed in some bulk GS crystals, including (G)(ethylbiphenylsulfonate). GIXD reveals that (G)C16BPS:C16BP and (G)C16BPS:C6BP are more crystalline than the corresponding guanidinium-free mixed monolayers. The (G)C16BPS:C6BP inclusion monolayer is stable upon compression, even though the alkyl-alkyl host-guest interactions are reduced due to the shorter hexyl substituents of the guest, demonstrating an important reinforcing role for the hydrogen-bonded GS sheet. The structure of a C16BPS:tetracosane (C24) mixed monolayer is independent of G; the unit cell symmetry and dimensions suggest a structure governed by alkyl-alkane interactions that prohibit formation of a GS network. These results illustrate that the existence of ternary inclusion monolayers with an intact GS network requires guest molecules that are structurally homologous with the hydrophobes of the host, in this case biphenylalkanes. The observation of these inclusion compounds suggests an approach for introducing functional nonamphiphilic molecules to an air-water interface through inclusion in a well-defined host.     

Continuity of Information Transport in Surjective Cellular Automata

We introduce a local version of the Shannon entropy in order to describe information transport in spatially extended dynamical systems, and to explore to what extent information can be viewed as a local quantity. Using an appropriately defined information current, this quantity is shown to obey a local conservation law in the case of one-dimensional reversible cellular automata with arbitrary initial measures. The result is also shown to apply to one-dimensional surjective cellular automata in the case of shift-invariant measures. Bounds on the information flow are also shown.     

A Proton Beam Delivery System for Conformal Therapyand Intensity Modulated Therapy

A scattering proton beam delivery system for conformal therapy and intensity modulated therapy is described. The beam is laterally spread out by a dual-ring doublescattering system and collimated by a program-controlled multileaf collimator and patientspecific fixed collimators. The proton range is adjusted and modulated by a programcontrolled binary filter and ridge filters.