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81.
Paiva GS Pavão AC Alpes de Vasconcelos E Mendes O da Silva EF 《Physical review letters》2007,98(4):048501
We performed electric arc discharges in pure Si to generate luminous balls with lifetime in the order of seconds and several properties usually reported for natural ball lightning. This simple experiment does not rely on energy sources and excitation mechanisms that are improbable in the natural phenomenon and clearly demonstrates the role of vaporization and oxidation of Si, as proposed by the Abrahamson-Dinniss theory for ball-lightning formation. 相似文献
82.
We report on an optical arrangement capable of compensating angular dispersion of paraxial wave fields developed by diffractive optical elements (DOEs). Schematically, the system is a beam expander in which two phase-only zone plates have been inserted, remaining afocal the coupled system. The DOE, which induces a continuous set of dispersive tilted plane waves, is placed at a specific position within the proposed setup providing an output spectrum with achromatic angular deviation. A directional matching between phase fronts and pulse fronts of output wave packets is demonstrated. 相似文献
83.
Gouy wave modes are linear waves with finite energy that propagate without distortion at any phase and group velocity through a focal region in a dispersive medium. These features make them potentially useful for the onset and control of nonlinear interactions. 相似文献
84.
Given an excess demand function of an economy, say Z(p), a stable price adjustment mechanism (SPAM) guarantees convergence of solution path p(t,p0) to an equilibrium peq solution of Z(p)=0. Besides, all equilibrium points of Z(p) are asymptotically stable. Some SPAMs have been proposed, including Newton and transpose Jacobian methods. Despite this powerful stability property of SPAMs, their acceptation in the economics community has been limited by a lack of interpretation. This paper focuses on this issue. Specifically, feedback control theory is used to link SPAMs and price dynamics models with control inputs, which match the economically intuitive Walrasian Hypothesis (i.e., prices change with excess demand sign). Under mild conditions, it is shown the existence of a feedback function that transforms the price dynamics into a desired SPAM. Hence, a SPAM is interpreted as a fundamental (e.g., Walrasian) price dynamics under the action of a feedback function aimed to stabilize the equilibrium set of the excess demand function. 相似文献
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Frontispiece: A Multicomponent Conjugation Strategy to Unique N‐Steroidal Peptides: First Evidence of the Steroidal Nucleus as a β‐Turn Inducer in Acyclic Peptides 下载免费PDF全文
89.
Cover Picture: Insertion of a Single‐Molecule Magnet inside a Ferromagnetic Lattice Based on a 3D Bimetallic Oxalate Network: Towards Molecular Analogues of Permanent Magnets (Chem. Eur. J. 6/2014) 下载免费PDF全文
90.
S. C. Nunes V. T. Freitas R. A. S. Ferreira L. D. Carlos P. Almeida V. de Zea Bermudez 《Journal of Sol-Gel Science and Technology》2014,72(2):239-251
Ordered mono-amide cross-linked alkyl/siloxane hybrids (mono-amidosils) incorporating a Rhodamine (B) methyl ester perchlorate dye (Rh(B)CH3ClO4) have been synthesized through the sol–gel process and self-directed assembly. The host hybrid matrix m-A(14) is a lamellar bilayer hierarchically structured hybrid composed of short methyl-capped alkyl chains grafted to a siliceous framework through amide groups. At low dye concentration [n = 20, where n is the molar ratio of amide groups per Rh(B)CH3ClO4] a new lamellar structure with higher interlamellar distance than that of m-A(14) is formed, whereas at higher dye content (n = 5) this new lamellar structure coexists with that of m-A(14). The efficient encapsulation of Rh(B)CH3ClO4 provided by m-A(14) via hydrogen bonding interactions ensured the complete dissolution of the dye and induced a blue shift of the emission of the dye with respect to that of the isolated state, leading to an increase in the quantum yield from values below 0.01 % (measured for the isolated dye) to 4 % at n = 20. The formation of non-fluorescent H-type dimers in the sample with n = 5 accounts for the reduction of the quantum yield. The incorporation of Rh(B)CH3ClO4) into m-A(14) was clearly beneficial from the standpoint of the dye’s photostability, allowing to suppress photobleaching during the first 4 h. An intensification of the emission intensity by 50 and 25 % for the emission centered at 600 and 645 nm resulted, respectively, at n = 20. 相似文献