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101.
Zusammenfassung Junge Pflanzen von Nicotiana tabacum wurden mit Tabakmosaikvirus (TMV) infiziert und die Konzentration an pufferlöslicher und an pufferunlöslicher Pflanzen-Nucleinsäure zu verschiedenen Zeiten nach der Infektion bestimmt.In der Fraktion der pufferlöslichen Pflanzen-Nucleinsäure (DNS und RNS) konnten keine mit der TMV-Infektion zusammenhängenden Konzentrationsänderungen festgestellt werden. Hingegen wird in der pufferunlöslichen Fraktion eine beträchtliche Verminderung an RNS gefunden. In dieser Fraktion bleibt die Konzentration an DNS mit der Dauer der Virusinfektion annähernd konstant. Es ist daher wahrscheinlich, daß die pufferunlösliche RNS zumindest einen Teil des für die Synthese der Virusnucleinsäure notwendigen Materials liefert. 相似文献
102.
A procedure is described for recovering silver from industrial sewage (mining and photo-industry etc) with the aid of the ion-exchanger potassium cyanocobalt(II)ferrate(II) (KCFC). Silver is easily removed by simple mixing with KCFC, even from solutions containing less than 1 g of silver per ton of solution. The process is performed at room temperature at pH < 7. There is no interference from a 600-fold amount of Ca, Cu(II), Zn, Cd, Pb, and Fe(II). Pure silver may be obtained by dissolution of the ion-exchanger in potassium cyanide solution, subsequent precipitation as sulphide, and roasting, or by melting it out of the ion-exchanger after heat treatment in a high-frequency furnace. With 1 kg of KCFC, 1.25 kg of silver may be extracted from solution. The process is simple and economic. 相似文献
103.
[reaction: see text] A general process for the efficient synthesis of sulfinyl transfer agents has been developed using cinchona alkaloids quinine and quinidine as chiral auxiliaries. The importance of these new and unique sulfinyl transfer agents is exemplified by the expedient synthesis of several sulfoxides in excellent enantiopurities and high yields. 相似文献
104.
Fillmore Freeman Phuong Dang Angela C. Huang Aline Mack Kara Wald 《Tetrahedron letters》2005,46(12):1993-1995
B3LYP/6-311 + G(d,p) has been used to calculate the relative energies and geometrical parameters of the respective reactants, transition states, and cycloadducts from the cycloadditions of azomethine ylide and ethene, (Z)-2-butene, and (E)-2-butene. The half-chair (envelope) transition state structures are consistent with a synchronous concerted cycloaddition mechanism. 相似文献
105.
To make sense of quantum field theory in an arbitrary (globally hyperbolic) curved spacetime, the theory must be formulated
in a local and covariant manner in terms of locally measurable field observables. Since a generic curved spacetime does not
possess symmetries or a unique notion of a vacuum state, the theory also must be formulated in a manner that does not require
symmetries or a preferred notion of a “vacuum state” and “particles”. We propose such a formulation of quantum field theory,
wherein the operator product expansion (OPE) of the quantum fields is elevated to a fundamental status, and the quantum field
theory is viewed as being defined by its OPE. Since the OPE coefficients may be better behaved than any quantities having
to do with states, we suggest that it may be possible to perturbatively construct the OPE coefficients—and, thus, the quantum
field theory. By contrast, ground/vacuum states—in spacetimes, such as Minkowski spacetime, where they may be defined—cannot
vary analytically with the parameters of the theory. We argue that this implies that composite fields may acquire nonvanishing
vacuum state expectation values due to nonperturbative effects. We speculate that this could account for the existence of
a nonvanishing vacuum expectation value of the stress-energy tensor of a quantum field occurring at a scale much smaller than
the natural scales of the theory.
Fourth Award in the 2008 Essay Competition of the Gravity Research Foundation. 相似文献
106.
We establish the existence of local, covariant time ordered products of local Wick polynomials for a free scalar field in
curved spacetime. Our time ordered products satisfy all of the hypotheses of our previous uniqueness theorem, so our construction
essentially completes the analysis of the existence, uniqueness, and renormalizability of the perturbative expansion for nonlinear
quantum field theories in curved spacetime. As a byproduct of our analysis, we derive a scaling expansion of the time ordered
products about the total diagonal that expresses them as a sum of products of polynomials in the curvature times Lorentz invariant
distributions, plus a remainder term of arbitrarily low scaling degree.
Received: 6 December 2001 / Accepted: 10 June 2002 Published online: 21 October 2002 相似文献
107.
A procedure for using ionic liquids to determine volatile impurities in compounds or matrices that are soluble in an ionic liquid is described. Using a conventional autosampler a droplet of ionic liquid solution is suspended in the inlet of the gas chromatograph and analytes are desorbed onto a GC column using splitless injection conditions. Results are presented for 1,2-propanediol, nonane, N,N-dimethylacetamide, and mesitylene in two different compounds in the ionic liquids trihexyltetradecylphosphonium bis(trifluoromethylsulfonyl)imide and trihexyltetradecylphosphonium dicyanamide. 相似文献
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