Formation of radical species in photolyzed CH4:N2 ices

We report photochemical studies of thin cryogenic ice films composed of N₂, CH₄ and CO in ratios analogous to those on the surfaces of Neptune’s largest satellite, Triton, and on Pluto. Experiments were performed using a hydrogen discharge lamp, which provides an intense source of ultraviolet light to simulate the sunlight-induced photochemistry on these icy bodies. Characterization via infrared spectroscopy showed that C₂H₆ and C₂H₂, and HCO are formed by the dissociation of CH₄ into H, CH₂ and CH₃ and the subsequent reaction of these radicals within the ice. Other radical species, such as C₂, , CN, and CNN, are observed in the visible and ultraviolet regions of the spectrum. These species imply a rich chemistry based on formation of radicals from methane and their subsequent reaction with the N₂ matrix. We discuss the implications of the formation of these radicals for the chemical evolution of Triton and Pluto. Ultimately, this work suggests that , CN, HCO, and CNN may be found in significant quantities on the surfaces of Triton and Pluto and that new observations of these objects in the appropriate wavelength regions are warranted.     

Impacts of Global Emissions of CO, NOx, and CH4 on China Tropospheric Hydroxyl Free Radicals

Using the global chemistry and transport model MOZART,the simulated distributions of tropospheric hydroxyl free radicals(OH) over China and its sensitivities to global emissions of carbon monoxide(CO),nitrogen oxide(NO x),and methane(CH 4) were investigated in this study.Due to various distributions of OH sources and sinks,the concentrations of tropospheric OH in east China are much greater than in west China.The contribution of NO + perhydroxyl radical(HO 2) reaction to OH production in east China is more pronounced than that in west China,and because of the higher reaction activity of non-methane volatile organic compounds(NMVOCs),the contributions to OH loss by NMVOCs exceed those of CO and take the dominant position in summer.The results of the sensitivity runs show a significant increase of tropospheric OH in east China from 1990 to 2000,and the trend continues.The positive effect of double emissions of NO x on OH is partly offset by the contrary effect of increased CO and CH 4 emissions:the double emissions of NO x will cause an increase of OH of 18.1%-30.1%,while the increases of CO and CH 4 will cause a decrease of OH of 12.2%-20.8% and 0.3%-3.0%,respectively.In turn,the lifetimes of CH 4,CO,and NO x will increase by 0.3%-3.1% with regard to double emissions of CH 4,13.9%-26.3% to double emissions of CO and decrease by 15.3%-23.2% to double emissions of NO x.     

Analysis of high-resolution spectra of mildly metal-poor stars I. Spectral data and equivalent widths

A number of high resolution and high signal-to-noise ratio spectra of mildly metal-poor stars were obtained with the coudé echelle spectrograph attached to the 2.16m telescope at Xinglong Observation Base of Beijing Astronomical Observatory. The spectra of seven mildly metal-poor stars were processed with the MIDAS software package, and the equivalent widths of their spectral lines were measured. The measured equivalent widths together with an error analysis are presented.     

PNE: The Key to Chemical Evolution in BCDGs

Planetary Nebulae have proven to be an essential key to understand the long term chemical enrichment of the interstellar medium due to low mass stars. They allow to study the original abundances of the star, and the effect of the star on the interstellar medium. Blue compact dwarf galaxies are known to host violent star formation in very heavy element depleted environments. They also show traces of past star formation (Doublier et al., 1999; 2001), including AGB starsand red giants which are responsible for long term enrichment. However, models fails to reproduce the low metallicities observed if those stars are taken into account. We observed PNe in BCDGs, and made a comparative study of the abundances in the HII regions and of the PNe. This revised version was published online in September 2006 with corrections to the Cover Date.     

A study of faint young open clusters as tracers of spiral features in our galaxy paper 3: Collinder 97 (OC1 506)

Photoelectric and photographic photometry of twenty-nine stars was done in the field of the open cluster Collinder 97 ≡ OC1 506. Of these stars, a total of twenty-four have been found to be possible members. There is apparently no interstellar extinction in the direction of this cluster which is in the constellation of Monoceros: itsE(B-V) = 0.0 mag. This cluster is situated at a distance of 0.63 ± 0.01 kpc, which is well within the local arm of our Galaxy. The age of this cluster is in the range of 1 × 10⁸ to 5.9 × l0⁸ yr, which puts it in an older age group. Thus, it cannot be specifically considered as a spiral-arm tracer in the study of our Galaxy.     

XPer的新发射相：光谱与红外观测

ＸＰｅｒ的新发射相：光谱与红外观测杭恒荣，夏剑萍中国科学院紫金山天文台，南京２１０００８中国科学院光学天文联合实验室关键词Ｂｅ星／Ｘ射线双星，发射线，ＪＨＫ测光１引言ＸＰｅｒ是一颗Ｂｅ／Ｘ射线双星（４Ｕ０３５２＋３０）的光学对应体［１－３］，中子星的...     

安徽省旅游星级饭店地域差异研究

根据2000～2005年安徽省星级饭店统计资料,利用变异系数这一度量标准分析了安徽省饭店在时间序列上和星级结构上的地域差异,结果表明:随着时间的变化饭店总数在各市间的差异在渐渐缩小.星级结构上五星级饭店地域分异程度最大,其次依次为一星级、四星级、三星级和二星级,通过安徽省各市国内旅游收入区位商和餐饮住宿业就业人员区位商与各市星级饭店数量相对水平的比较,找出不符合一般趋势的城市加以讨论.最后,运用SPSS分析软件对安徽省17个地市的星级饭店发展水平进行聚类分析,并讨论了运行结果所分出的4类城市,提出了饭店业发展的若干建议.