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71.
72.
The principle luminescence bands excited in additively coloured MgO by radiation in the wavelength range 170–400 nm are observed at wavelengths of 520, 475, 441 and 375 nm. Polarised luminescence and uniaxial stress measurements on the 441 nm band, the radiative lifetime of 25 msec at 1.6 K and temperature dependence of luminescence intensities of the 375, 441 and 375 nm bands are consistent with the 441 nm band being due to 3B1u → 1Ag transitions of the F2+2 centre. 相似文献
73.
Acid treatment of 2-(β-Benzoylethyl)-cyclopentanone (III) leads directly to a phenylcycloheptene carboxylic acid (VII) and the related lactone (XI), via a bicyclic intermediate. 相似文献
74.
Alexander McKillop Alan Henderson Partha S. Ray Carmen Avendano Encarnacion G. Molinero 《Tetrahedron letters》1982,23(33):3357-3360
Ethyl carboethoxyformimidate is shown to be a versatile reagent for the synthesis of a variety of mono- and bicyclic heterocyclic systems. 相似文献
75.
Denote by σ the subspace of Hilbert space {(xi)?l2:xi=0 for all but finitely many i}. Examples of cell-like decompositions of σ are constructed that have decomposition spaces that are not homeomorphic to σ. At one extreme is a cell-like decomposition G of σ produced using ghastly finite dimensional examples such that the decomposition space σ?G contains no embedded 2-cell but (σ?G)× is homeomorphic to σ. At the other extreme is a cell-like decomposition G of σ satisfying: (a) the nondegeneracy set NG={g?G:g≠point} consists of countably many arcs (necessarily tame); (b) the nondegeneracy set NG is a closed subset of the decomposition space σ?G; (c) each map f:B2→σ?G of a 2-cell into σ?G can be approximated arbitrarily closely by an embedding; (d) σ?G is not homeomorphic to σ but (σ?G)× is homeomorphic to σ. The fact that both conditions (a) and (b) can be satisfied (and have (d) hold) is directly attributable to σ’s incompleteness as a topological space. 相似文献
76.
77.
Mihailov SJ Smelser CW Lu P Walker RB Grobnic D Ding H Henderson G Unruh J 《Optics letters》2003,28(12):995-997
High-quality retroreflecting fiber Bragg gratings were written in standard Ge-doped telecom fiber (Corning SMF-28) after a few minutes exposure with pulsed 800-nm, 120-fs laser radiation by use of a deep-etch silica zero-order nulled phase mask optimized for 800 nm. Induced index modulations of 1.9 x 10(-3) were achieved with peak power intensities of 1.2 x 10(13) W/cm2 without any fiber sensitization. The fiber gratings are stable and did not erase after 2 weeks at 300 degrees C. The primary mechanism of induced index change results from a structural modification to the fiber core. 相似文献
78.
Back BB Baker MD Ballintijn M Barton DS Becker B Betts RR Bickley AA Bindel R Budzanowski A Busza W Carroll A Decowski MP García E Gburek T George N Gulbrandsen K Gushue S Halliwell C Hamblen J Harrington AS Henderson C Hofman DJ Hollis RS Hołyński R Holzman B Iordanova A Johnson E Kane JL Khan N Kulinich P Kuo CM Lee JW Lin WT Manly S Mignerey AC Noell A Nouicer R Olszewski A Pak R Park IC Pernegger H Reed C Remsberg LP Roland C Roland G Sagerer J Sarin P Sawicki P Sedykh I Skulski W Smith CE 《Physical review letters》2003,91(7):072302
We have measured transverse momentum distributions of charged hadrons produced in d+Au collisions at sqrt[s(NN)]=200 GeV. The spectra were obtained for transverse momenta 0.25
相似文献
79.
The lithiated (organo)sulfonylacetonitrile complex [MeSO(2)CHCNLi.THF] (3) has been prepared and structurally characterized in order to demonstrate that well-known molecular aggregates of s-block metals may be used as building blocks in the controlled assembly of complex supramolecular architectures. The solid state structure of 3 can be described as a novel basket-weaved, 2-D network, composed of (SO(2)Li)(2) "dimeric" rings joined via "interdimer" donation of nitrile units. 相似文献
80.
A procedure for the preparation of high-quality single crystals from concentrated glyme mixtures is presented. Anhydrous single crystals of LiNO(3) and LiClO(4) were prepared in this manner, and the single-crystal structure of LiClO(4) (orthorhombic, Pnma, a = 8.6447(12) A, b = 6.8512(10) A, c = 4.8254(7) A, Z = 4) was determined as an example. This procedure is expected to be widely applicable for not only salts but also a wide range of other materials solvated by glymes. 相似文献