从太空探测万里长城

2004年5月11日,欧空局网站发布了题为“从太空看长城”的公告,引起广泛关注和热烈争论.争论焦点涉及如何正确认识人眼视觉原理,如何准确理解卫星遥感应用潜力等问题.文章从人眼结构、产生光觉、视觉和形觉的基本条件以及眼睛分辨率等基本概念入手,判定肉眼从太空不可能看到长城.同时通过理论分析与实验,揭示了空间分辨率达到米级的SPOT-5全色图像能够清楚地展现北京密云水库北面的各段野长城.在分辨率为10m和20m的多光谱图像上,无法辨别出长城.而在全色（2.5m,5m）与多光谱进行融合处理的图像上,各段野长城及其周围背景都能十分清晰地显示出来.     

Toxaphene analysis in Great Lakes fish: a comparison of GC-EI/MS/MS and GC-ECNI-MS, individual congener standard and technical mixture for quantification of toxaphene

Toxaphene is considered to be a problematic organochlorine pollutant because of its bioaccumulation potential and persistence in aquatic environments. In this study, whole lake trout and walleye composites were used to evaluate two analytical techniques for total toxaphene and selected congener analysis. The efficacy of using gas chromatography electron ionization tandem mass spectrometry (GC-EI/MS/MS) and electron capture negative ionization mass spectrometry (GC-ECNI-MS) were compared. Although the sensitivity using GC-ECNI-MS was approximately five times greater than GC-EI/MS/MS, the latter provided more consistent inter-Parlar relative response factors (RRF). When using technical calibration mixtures, these results suggest a more accurate total toxaphene measurement was obtained using the GC-EI/MS/MS method. Total toxaphene concentrations in lake trout composites from both methods were highly correlated (R ² = 0.985) with the MS/MS concentrations approximately half of those determined by ECNI, suggesting systematic high bias in toxaphene concentrations when measured using GC-ECNI.     

Structure and bonding in proteins: Part 1. The electron organisation in the amide unit

A consistent set of numerical information on the electron organisation in the amide unit has been obtained for a number of small amides, using the readily available Gaussian-70 computer package and a modest amount of computer time. There is good agreement with experimental facts concerning bond lengths, bond angles, rotation barriers and cis/trans energy differences. The results have been analysed in terms of simple molecular orbital theory and other simple valence ideas to make the results intelligible in a physical sense, so that they may be used in larger molecules. The rotation barrier about the CN bond seems to be a simple π-electron conjugation effect, whose magnitude is influenced in the main by the internal geometry of the CNO fragment rather than by substituents.     

A. C. conductivity due to intimate pairs of charged defect centres

The influence of the association of charged defects into intimate pairs on a.c. conduction is discussed in the light of the fundamental mechanism being that of the simultaneous hopping of two electrons over the barrier separating two oppositely charged defect centres, the barrier height being correlated with the intersite separation via the Coulomb interaction. The behaviour of chalcogenide glasses is discussed in terms of the present theory, and it is concluded that the existence of two classes of a.c. conductivity behaviour into which these materials generally fall can be simply explained by the predominance of either intimate pairs or non-intimate pairs of charged defect states according to the conditions of preparation.     

以“大旅游”战略格局发展桐庐旅游业

本文通过对桐庐县旅游资源的特点、旅游业发展现状的分析 ,提出以“大旅游”战略格局发展桐 庐旅游业的思路 .     

Post-Gondwana break-up record constraints from apatite fission track thermochronology in NW Namibia

The break-up of Western Gondwana Supercontinent was responsible in NW Namibia for significant tectono-thermal events at Early Cretaceous. In the Kaoko Belt and Walvis Basin, several evidences of this plate readjustment are registered: Etendeka Province, Great Escarpment Mountains, Precambrian structure reactivations, unconformities of surfaces in both continental area and margin basins. Apatite fission track thermochronology applied to the Kaoko basement rocks provides evidence of long-lived cooling history since the Early Cretaceous. The thermal modelings indicate accelerated uplift and/or upwarping of the local crust at followed by a gradual and continuous cooling history.     

Polymerisation of pentadienyl compounds in the presence of transition-metal compounds: the polymorphic compound deca-1,3,7,9-tetraenediiron hexacarbonyl

The reaction between Fe(CO)₅ and penta-1,4-dien-3-ol gives two forms of di(pentadienyliron tricarbonyl).     

X-ray photoelectron spectra of inorganic molecules: XXX. Organometallic derivatives of tungsten(O) and tungsten(II)

The W 4f binding energies of various carbonyl-containing complexes of tungsten are reported. Comparisons between W^II complexes containing the [(η³-allyl)W(CO)₂] moiety and neutral derivatives of the type W(CO)_6-xL_x are made. The absence of a clear-cut correlation between the W 4f binding energies and the value of x in W(CO)_6-xL_x is discussed and these results compared with those obtained for the analogous molybdenum complexes.     

STUDY ON THE MOISTURE PASSAGE ON THE LOWER REACHES OF THE YARLUNG ZANGBO RIVER

A series of gorges on the lower reaches of the Yarlung Zangbo River is like an enormous crevice splitting the southeastern Qinghai-Xizang (Tibet)Plateau to create a passage through which warm, wet air flow from the Indian Ocean reaches the inner part of the plateau. This moisture passage was mainly strengthened after the Pleistocene epoch in the Quaternary period and has played a major role in affecting the beginning date of the rainy season and the amount of the plateau's rainfall. It has also served as a corridor for the living things on the southern and the northern sides of the Himalayas to mingle with each other. The region along this passage is abundant in evidences of species of differentiation, variation and biological division. Also the passage has provided a favorable environment for human beings and affected natural phenomena there.     

Photochemische reaktionen von übergangsmetall-olefin-komplexen: XI. [4+ 6]-cycloaddition von tricyclo[6.3.0.02,7]undeca-3,5-dien antricarbonyl-η6-1,3,5-cycloheptatrien-chrom(0)

The photochemical reaction of tricarbonyl-η⁶-1,3,5-cycloheptatriene-chromium(0) (I) with tricyclo[6.3.0.0^2,7]undeca-3,5-diene (II) in n-pentane at 248 K yields the [4 + 6]-cycloadduct tricarbonyl-η⁶-pentacyclo[7.6.2.1^10,15.0^2,8.0^3,7]octadeca-11,13,16-triene-chromium(0) (III). Detachment of the pentacyclic triene ligand from chromium can be achieved with trimethylphosphite. The constitutions of complex III and of the pentacyclic hydrocarbon IV were determined by spectroscopic means.