Spatial soliton by cascading χ(2) effect and its self-induced wave-guide in quasi-phase-matched media

The formation of the spatial solitons in the quadratic nonlinearity χ(2) media by cascading second harmonicgeneration (SHG) in quasi-phase-matched (QPM) sample is studied on the basis of nonlinear Schrodingerequation (NLSE). When the solitary wave propagates in the QPM media, it formed optical wave-guidesthrough cascading χ(2) effect called self-induced soliton wave-guide. Transverse refractive index distribu-tion of the self-induced soliton wave-guide of fundamental and SHG wave is obtained by cascading process.Analysis of guided-mode of such self-induced soliton wave-guide is first proposed to our knowledge. Be-cause the power needed for forming the spatial solitons in cascading process is much lower than that inKerr media, this kind of self-induced soliton wave-guide shows potential applications in all-optical signalprocess.     

Ultrafast solvation dynamics at internal sites of staphylococcal nuclease investigated by site-directed mutagenesis

Internal solvation of protein was studied by site-directed mutagenesis,with which an intrinsically fluorescent probe,tryptophan,is inserted into the desired position inside a protein molecule for ultrafast spectroscopic study.Here we review this unique method for protein dynamics research.We first introduce the frontiers of protein solvation,site-directed mutagenesis,protein stability and characteristics,and the spectroscopic methods.Then we present time-resolved spectroscopic dynamics of solvation dynamics inside cavities of active sites.The studies are carried out on a globular protein,staphylococcal nuclease.The solvation at sites inside the protein molecule’s cavities clearly reveals characteristics of the local environment.These solvation behaviors are directly correlated to enzyme activity.     

酶提取-单颗粒电感耦合等离子质谱法分析樱桃番茄纳米银颗粒及其吸收规律研究

为探究复合保鲜涂膜中AgNPs的迁移情况,采用酶提取的前处理方式,结合单颗粒电感耦合等离子体质谱（SP-ICP-MS）,考察了前处理方式、驻留时间、校准方式以及Ag+浓度等条件对AgNPs准确测定的影响。结果表明：0.1 g樱桃番茄样品在柠檬酸盐体系下使用0.2 g的R-10离析酶可达到消解最适酶剂量;当驻留时间小于100 μs时,测定结果有较好的积分条件以及较高的信背比;采用AgNP尺寸方式进行校准比单独用Ag+标准溶液校准方式的颗粒尺寸测定结果更加准确。采用该方法测定樱桃番茄中加标AgNPs颗粒回收率达到88.9%,粒径实测值为47.8±0.3 nm,粒径检出限为13 nm,颗粒浓度检出限为 7.5×104 particles/L。通过将樱桃番茄暴露于AgNPs涂膜中来探究AgNPs迁移行为,复合保鲜涂膜后的樱桃番茄通过三次洗涤后能够在表面去除大部分AgNPs,但仍有少量AgNPs穿过果表皮浸入果肉组织。该方法灵敏度高,操作简单,能够为揭示AgNPs在农产品及农业生产中的风险提供可靠、准确的表征方法。     

关于Yb~(3 )—Er~(3 )激活的上转换磷光体的效率

本文通过Er~(3 )离子激发过程的效率和最终发射过程的效率测定了Yb~(3 )—Er~(3 )激活的上转换磷光体的效率。激发过程依赖于红外激发强度。我们用不同的基质晶格,激发到选定的Er~(3 )能级,测量了发射过程的效率,而且作为Yb~(3 )和Er~(3 )浓度的函数。现在知道的最好的上转换磷光体之一,α-NaYF_4—0.20Yb—0.03Er的绿色发光效率约为6％。     

Mechanical Properties of Sialic Foamed Ceramic and Applications in Defense Structure

Mechanical properties of a closed-cellular sialic foamed ceramic are investigated by compressive tests. The sialic foamed ceramic under uniaxial stress compression shows brittleness and the flow stress increases with the strain rate. The engineering stress-engineering strain curve under uniaxial strain compression could be divided into three stages： linear elasticity, collapsed plateau and densification. The unloading elastic modulus, Poisson ratio and energy absorption ability are discussed. Shelly cellular material made by sialic foamed ceramic is applied into the stress distribution layer in the defense structure. Field explosion experiments are performed for the sand based stress distribution layer and shelly cellular material based layer. Compared with sand, the shelly cellular material reduces the peak stress of the blast wave.     

近红外光谱技术(NIRS)在牧草领域中的应用研究进展

牧草是草食动物最主要的营养来源。牧草品质的优劣不仅影响家畜的生长发育和生产效率,也决定着最终畜产品的产量与品质。牧草品质的优劣主要取决于牧草营养成分及其消化率、适口性、以及牧草中所含抗营养因子和真菌毒素、霉菌毒素的含量水平。近红外光谱技术(NIRS)是一种低成本、快速、简单、无损的定性、定量分析技术,已在许多领域广泛应用。该文简要介绍了NIRS的原理和特点,详细综述了NIRS在牧草品质分析、牧草育种、牧草品种鉴定和性状分类中的应用。通过较全面综述NIRS在牧草领域中的应用现状,以期有助于NIRS在我国牧草领域中的发展。     

纤维背板结构对B4C陶瓷复合装甲抗侵彻破碎特性的影响

以碳化硼陶瓷作为前置抗弹面板,以碳纤维T300、UHMWPE和Kevlar高性能纤维板的不同组合作为其复合背板,利用12.7 mm穿甲燃烧弹对不同结构的陶瓷/复合背板进行弹道冲击实验,通过回收破碎的弹体与陶瓷碎块,进行多级筛分称重,分析不同背板对应的陶瓷复合装甲的碎块分布规律与抗弹性能。研究表明：在陶瓷与纤维背板之间添加一层碳纤维板可以显著改善复合装甲的抗弹刚度梯度,提高整个抗弹靶板的结构刚度,进而改善弹体与整个面板之间的应力波传播形式,延长陶瓷锥体形成后与陶瓷面板脱离的时间和应力波在整个陶瓷面板内传播的作用时间,从而降低陶瓷面板内部拉伸波造成的拉伸断裂,延长弹体的驻留现象。利用Rosin-Rammler分布模型对陶瓷与弹体的碎块形式进行表征,结果表明：分别将一半厚度的UHMWPE纤维板和Kevlar纤维板替换为碳纤维背板,其陶瓷面板的半锥角分别增大了2.05%和4.20%,碎裂区整体平均特征尺寸分别下降了16.92%和42.96%;加入高抗弯强度的碳纤维作为复合装甲的中间过渡层后,背板的破坏形式改变,充分利用了纤维背板的高抗拉强度,从而提高整体复合装甲的抗弹性能。     

动物粪便近红外光谱的应用潜力

近红外光谱技术(NIRS)以其低成本、高效、环保、无损的优势在日粮和畜产品品质分析中得到广泛应用。饲料品质参数(如粗蛋白)的获取对于日粮营养的合理搭配不可或缺,传统的近红外光谱技术将日粮的近红外光谱与日粮品质参数的化学测定值进行回归,建立预测模型对日粮品质参数进行检测。然而,在放牧条件下日粮近红外光谱的难以获取限制了这一传统建模方法在动物营养中的应用。作为动物代谢性产物,动物粪便不仅包含有日粮信息也携带有动物自身信息。近年来,基于动物粪便近红外光谱和日粮信息(日粮植物学成分、化学成分及其消化率)建立的回归模型,也已被用于动物日粮信息的检测。简要介绍F.NIRS在动物性别、品种鉴定及繁殖和寄生虫感染状态检测中的应用。NIRS在动物粪肥分析中的应用结果表明NIRS能够对粪肥中主要成分含量进行快速分析。尽管F.NIRS预测准确性有待提高,但已显示出其作为快速、有效的分析工具用于检测日粮品质参数及动物生理状态的潜力。相关的英文评述性文章业已出版,但在中国F.NIRS的研究和应用非常欠缺。期望本文的呈现有助于F.NIRS在国内的发展。推荐将NIRS作为快速分析工具用于对粪肥主要成分(DM,OM,TS,VS,TN,TKN和NH₃-N)含量进行检测。