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21.
22.
Optically pumped laser emission has been observed on the NaK 2(A)1+ 1(X)1+ electronic state transition. The emission occurs between 1.015 and 1.035 m when a sodium-potassium heat-pipe oven is pumped with 695–745 nm pulsed dye laser radiation. The laser emission occurs on many ro-vibrational transitions without the use of cavity mirrors. However, the addition of a simple cavity increases both the number of observed lasing transitions and the amplitude of the emission on each line. We report our results for the dependence of the emission intensity on pump laser power, oven temperature, and buffer gas pressure. 相似文献
23.
The high temperature phase relations (20°C) of LiH2PO4, NaH2PO4, KH2PO4, RbH2PO4, CsH2PO4, NH4H2PO4, KH2AsO4, RbH2AsO4, CsH2AsO4 and NH4H2AsO4 have been studied. All materials decompose at higher temperatures. Solid—solid transitions are studied when present and transition temperatures, transition enthalpies, decomposition temperatures, decomposition enthalpies and decomposition products are discussed. 相似文献
24.
The ability to recover and purify natural and recombinant proteins, and the costs of doing so remain a major task in introducing
the potential products of biotechnology. The bases for separation range from specific binding onto tailored reagents to solubility
and partitioning behavior governed by a mixed bag of size, charge, and hydrophobicity. In most cases, a combination of methods
is used in sequence, and improvements in the selectivity at an early stage can enhance the effectiveness of subsequent (and
usually more costly) steps. Genetic engineering provides a means of improving the selectivity within the context of existing
separation methods.
By this strategy, improvements in selectivity are sought by bestowing a distinctive property on the protein of interest. The
primary sequence of amino acids is altered, such that the protein can be selectively removed from other components of the
multicomponent mixture in which such products are commonly found. In this article, the range of these “distinctive properties”
and their pairing with various separation methods will be reviewed. Specific examples from our work, in which a distinctive
charge is provided via a polypeptide “purification” fusion tail, will be discussed. Separation methods we have used with these
fusion proteins are precipitation, two-phase aqueous extraction, reversed micellar extraction, and ion exchange using both
resins and membranes. 相似文献
25.
Yu Gui Gu Xiaolin Zhang Richard F. Clark Stevan W. Djuric Zhenkun Ma 《Tetrahedron letters》2004,45(15):3051-3053
An intramolecular 1,3-dipolar cycloaddition of azomethine ylide, generated in situ via the reaction of C12-glycinate derivative of macrolide with formaldehyde, provided a novel tricyclic macrolide. The high stereoselectivity of this [2+3] reaction was achieved by introducing a suitable directing group at C-6 position of macrolide. 相似文献
26.
27.
Simon G. Bott Matthew Clark Joseph S. Thrasher Jerry L. Atwood 《Journal of chemical crystallography》1987,17(2):187-196
The X-ray structure of S-methyl(pentafluorosulfanyl)thiocarbamate, SF5NHC(O)SCH3, has been determined from three-dimensional diffractometer data and refined by full-matrix least-squares techniques. The crystals are monoclinic:P21/m,a=5.008 (5),b=7.811 (2),c=9.348 (4) Å, =99.08 (7)°, andZ=2; finalR=0.046 for 517 observed reflections. The structure comprises hydrogen-bonded (NHO) chains with the component monomers in thecis, cis-conformation, i.e., the arrangement of the nonhydrogen and nonfluorine atoms is nearly planar, the SF5 group and the O are in acis position with respect to the C-NH bond, and the O and the CH3 group are in acis position with respect to the C(O)-S bond. Theoretical methods including MNDO and molecular modeling were used to study the relative stabilities of the four possible conformations of SF5NHC(O)SCH3. 相似文献
28.
Aihara H Alston-Garnjost M Avery RE Barbaro-Galtieri A Barker AR Barnes AV Barnett BA Bauer DA Bengtsson H Bintinger DL Bobbink GJ Bolognese TS Bross AD Buchanan CD Buijs A Cain MP Caldwell DO Clark AR Cowan GD Crane DA Dahl OI Derby KA Eastman JJ Eberhard PH Eisner AM Enomoto R Erné FC Fujii T Gary JW Gorn W Hauptman JM Hofmann W Huth JE Hylen J Kamae T Kaye HS Kees KH Kenney RW Kerth LT Ko W Koda RI Kofler RR Kwong KK Lander RL Langeveld WG Layter JG Linde FL Lindsey CS Loken SC Lu A Lu X 《Physical review letters》1986,57(8):945-948
29.
The role of search theory in the exploitation of natural resources is discussed in this paper. After a brief history and taxonomy of search problems, the mathematics of search is discussed. This includes underlying probability distributions, the differential equations of search, Bayesian use of search information and optimization problems in search theory. The theory is illustrated by applications in fisheries, pest control, animal foraging, and oil and mineral exploration. 相似文献
30.