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991.
M.E. Garcia 《Applied Physics A: Materials Science & Processing》2001,72(3):261-271
A theoretical study of different ultrafast nonequilibrium processes taking place during and after ultrashort excitation of
clusters is presented. We discuss similarities and differences for several processes involving nonequilibrium ultrafast motion
of atoms and electrons. We study ultrashort relaxation of clusters in response to excitations produced by femtosecond laser
pulses of different intensities. We show how different relaxation processes, such as bond breaking, melting, fragmentation,
emission of atoms, or Coulomb explosion, can be induced, depending on the laser intensity and laser pulse duration. We also
discuss processes involving nonequilibrium electron dynamics, such as intraband Auger decay in clusters and ultrafast electronic
motion during collisions between clusters and surfaces. We show that this electron dynamics leads to Stückelberg-like oscillations
of measurable quantities, such as the electron emission yield.
Received: 4 April 2000 / Accepted: 6 November 2000 / Published online: 9 February 2001 相似文献
992.
Karen A. Ketcham John K. Swearingen Alfonso Castieiras Isabel Garcia Elena Bermejo Douglas X. West 《Polyhedron》2001,20(28):19-3273
Reduction of 2-cyanopyridine by sodium in the presence of 3-piperidylthiosemicarbazide produces 2-pyridineformamide 3-piperidylthiosemicarbazone, HAmpip. Complexes with iron(III), cobalt(II,III) copper(II) and zinc(II) have been prepared and characterized by molar conductivities, magnetic susceptibilities and spectroscopic techniques. In addition, the crystal structures of HAmpip, [Fe(Ampip)2]ClO4, [Cu(HAmpip)Cl2]·CH3OH and [Zn(HAmpip)Br2]·C2H6SO have been determined. Coordination is via the pyridyl nitrogen, imine nitrogen and thiolato or thione sulfur when coordinating as the anionic or neutral ligand, respectively. 相似文献
993.
E Oset D Cabrera H C Chiang C Garcia Recio S Hirenzaki S S Kamalov J Nieves Y Okumura A Ramos H Toki M J Vicente Vacas 《Pramana》2001,57(2-3):417-431
In this talk we briefly describe some basic elements of chiral perturbation theory, xPT, and how the implementation of unitarity and other novel elements lead to a better expansion of the T-matrix for meson-meson and meson-baryon interactions. Applications are then done to the ππ interaction in nuclear matter
in the scalar and vector channels, antikaons in nuclei and K
− atoms, and how the φ meson properties are changed in a nuclear medium. 相似文献
994.
995.
Fourier transform infrared (FTIR) and 13C solid state nuclear magnetic resonance (NMR) spectroscopy were used to study dextrin structural changes occurring upon hydrogel formation by vinyl acrylate (VA) grafting and subsequent free radical polymerization. The degrees of VA substitution (DS) and polymerization (DP) were quantified up to 40%VA by FTIR intensity measurements and partial least squares (PLS)/FTIR, the latter being a faster and less error-prone method. Above 40%VA, both parameters are underestimated by FTIR. A spin counting NMR experiment showed high carbon observabilities for hydrogels and improved PLS/NMR models were achieved for DS and DP determination. Alternative NMR integration methods are hindered by the broad VA peaks and need for area correction, due to their CP dynamics. NMR changes in C1 profile showed that a single helical conformation predominates at lower %VA, being replaced by disordered conformations as %VA increases. Furthermore, a correlation FTIR/NMR study indicated that ring conformations are significantly affected in hydrogels, compared to unpolymerized dextrin. 相似文献
996.
Ronaldo Dias Nancy L. Garcia Adriano Z. Zambom 《Computational Optimization and Applications》2010,45(3):521-541
The objective of this study is to find a smooth function joining two points A and B with minimum length constrained to avoid fixed subsets. A penalized nonparametric method of finding the best path is proposed.
The method is generalized to the situation where stochastic measurement errors are present. In this case, the proposed estimator
is consistent, in the sense that as the number of observations increases the stochastic trajectory converges to the deterministic
one. Two applications are immediate, searching the optimal path for an autonomous vehicle while avoiding all fixed obstacles
between two points and flight planning to avoid threat or turbulence zones. 相似文献
997.
In 1989 work began on merging finite and discrete elements. During 1990 algorithmic solutions for the new combined method were developed, together with a C-based implementation known as the Y code. In 2004 these developments and implementations were published as a textbook. Queen Mary University of London (QMUL) and Imperial College are currently engaged in a research project to make Y codes in both 2D and 3D available in Open Source format and with mainly geoscience problems in mind. The result is a set of... 相似文献
998.
999.
A number of derivatives of isoxazolo-[2,3-c] quinazoline ring system have been prepared by reaction of 2-aryl-4-methylthioquinazoline-3-oxides with activated acetonitriles or 1,3-dicarbonyl compounds in basic medium. 相似文献
1000.