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41.
ζ-Oxo-α, β-enones react with lithium dimethylcuprate to give cyclic aldols such as hydroxydecalone 1 and hydroxyspiro[4.5]decanone 2 in a regio- and stereospecific manner. This new reaction, a combination of conjugate methyl addition to α, β-enones with directed intramolecular aldolisation, is suggested to proceed via either enoate anions, such as 8 and 11 , or radical anions, such as 9 → 10 and 12 → 13 , as intermediates. 相似文献
42.
A 980-nm pump-induced nonlinear refractive-index (n2) change in erbium-doped (20-m) and ytterbium-doped (20-m) fibers has been measured at 1064 nm by time-delayed photorefractive beam coupling in a co-propagating and counterpropagating geometry. It was found that n2 decreases at the wavelength of the probe beam when the pump beam is present. We present a semiclassical theory based on a four-state system that accounts for the pump-induced change of n2. Both theoretical and experimental results show that a significant index change, of the order of 10%, can be obtained for cw pump powers as small as 10 mW. 相似文献
43.
Bushev P Wilson A Eschner J Raab C Schmidt-Kaler F Becher C Blatt R 《Physical review letters》2004,92(22):223602
An excited-state atom whose emitted light is backreflected by a distant mirror can experience trapping forces, because the presence of the mirror modifies both the electromagnetic vacuum field and the atom's own radiation reaction field. We demonstrate this mechanical action using a single trapped barium ion. We observe the trapping conditions to be notably altered when the distant mirror is translated across an optical wavelength. The well-localized barium ion enables the spatial dependence of the forces to be measured explicitly. The experiment has implications for quantum information processing and may be regarded as the most elementary optical tweezers. 相似文献
44.
Dubnicková M Yaradaikin S Lacko I Devínsky F Gordeliy V Balgavý P 《Colloids and surfaces. B, Biointerfaces》2004,34(3):161-164
The influence of 1,4-butanediamonium-N,N'-dialkyl-N,N,N',N'-tetramethyl dibromides (CmA, m = 7-16 is the number of alkyl carbons) on the egg yolk phosphatidylcholine (EYPC) bilayer thickness and lipid surface area at the bilayer-aqueous phase interface is studied using X-ray diffraction on fluid lamellar CmA + EYPC + H2O phases as a function of CmA:EYPC and H2O:EYPC molar ratios and the alkyl chain length m. At the constant CmA:EYPC = 0.4 and H2O:EYPC = 18 molar ratios, the CmA induced bilayer thickness decrease shows a minimum and the lipid surface area increase a maximum at the alkyl chain length m = 9. The obtained results are discussed in the context of a structural perturbation model of the cut-off effect in biological potencies of surfactants which occurs when increasing the alkyl substituent chain length above the critical value. 相似文献
45.
The nonlinear refractive index n2 of silica fiber (24 m) and erbium-doped fiber (10 m) is measured to within an accuracy of 5% by use of time-delayed photorefractive beam coupling of intense 53-ps, 1.064-microm pulses that experience self-phase modulation in the fibers. The resultant induced grating autocorrelation response yields a value of n2/A(eff) and a calibration standard for the fiber. A phase shift of the order of 0.19pi can be detected and is limited only by laser amplitude fluctuations. A unique advantage of this technique is its ability to measure n2 accurately in short lengths (z < or = 25 m) of fiber, whereas other approaches typically use much longer lengths of fiber (z > or = 100 m). 相似文献
46.
Ferdinand Chovanec Mária Jurečková 《International Journal of Theoretical Physics》2003,42(9):1913-1926
Z. Rieanová proved that every D-lattice is a set-theoretical union of MV-algebras. These MV-algebras are blocks in the D-lattice. There is a dual question: How can we construct a D-poset from a given collection of MV-algebras. To solve this problem we use the pasting technique. We define an admissible system of MV-algebras and we prove that the pasting of this system is a D-poset. 相似文献
47.
During the last decade, striking improvements could be achieved for the precise control of deposition processes in optical coating technology. For example, as a consequence of enormous progresses in measure- ment and computer technology, direct optical monitoring in a broad spectral range can be considered as a common tool in many production environments nowadays. Besides the development of the corresponding hardware and measurement channels, advanced approaches for the evaluation of the acquired data and new multiple sensor monitoring strategies moved into the focus of modern research on the way towards de- terministic deposition techniques. In this context, also innovative concepts for the simulation of deposition processes to forecast the result for a specified coating design and automatic online correction algorithms gained of importance to reduce the risk of failure in coating production. The present contribution will be dedicated to selected aspects in this field, especially addressing broad band optical monitoring systems. A short review on examples for existing hardware configurations and software tools will be presented illus- trating the advantages of modern process control techniques. Novel approaches based on the modeling of thin film growth are discussed as an additional strategy to improve the predictability of coating processes. 相似文献
48.
In the above-mentioned paper, the total rate of generation is defined by
(unnumbered equation in Chapter 4.2 after Eq. (21)); in this equation the factor (1−cd+) is missing. As a consequence, Eqs. (22)–(30) and Fig. 4 in the original paper have to be revised which is presented in this corrigendum. Numbering of references remains unchanged. 相似文献
49.
A series of methyl hydronaphthyl alcohols, formates, acetates, and ketones were prepared and their odour properties evaluated. Minor structural changes, even opposite to the osmophoric group, were found to have major effects on the odour. 13C? NMR shift assignments of the hydronaphthyl derivatives are presented. 相似文献
50.
Spatial structures as a result of a modulational instability are obtained in the integrable discrete nonlinear Schrödinger equation (Ablowitz-Ladik equation). Discrete slow space variables are used in a general setting and the related finite differences are constructed. Analyzing the ensuing equation, we derive the modulational instability criterion from the discrete multiple scales approach. Numerical simulations in agreement with analytical studies lead to the disintegrations of the initial modulated waves into a train of pulses. 相似文献