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81.
82.
Dynamics of femtosecond laser interactions with dielectrics   总被引:1,自引:0,他引:1  
Femtosecond laser pulses appear as an emerging and promising tool for processing wide bandgap dielectric materials for a variety of applications. This article aims to provide an overview of recent progress in understanding the fundamental physics of femtosecond laser interactions with dielectrics that may have the potential for innovative materials applications. The focus of the overview is the dynamics of femtosecond laser-excited carriers and the propagation of femtosecond laser pulses inside dielectric materials. PACS 61.80.Ba; 52.38.Mf; 42.65.Jx; 78.47.+p; 71.35.-y  相似文献   
83.
84.
A C-glycoside mimetic of l-galactose 1-diphosphate, a potential ligand of GDP-l-galactose hydrolase, an enzyme involved in the biosynthesis of vitamin C, has been designed, stereoselectively synthesised by C-allylation of tribenzylated l-fucose, by periodate-osmium tetroxide degradation of the double bond, by condensation of the obtained aldehydes with benzylacetate and by deprotection. The obtained mimetic was linked to a sepharose resin.  相似文献   
85.
Aziridinyl ethers are selectively and easily converted to either amino vinyl ethers or alkoxy allylamines by treatment with mixed metal bases (superbases).  相似文献   
86.
A nanosecond-time-resolution pyrometer has been developed for measuring the transient surface temperature of a solid material heated by pulsed excimer-laser irradiation. Fast germanium diodes are employed to capture the transient thermal emission signals in the wavelength range between 1.2 and 1.6 pm. The surface temperature is derived from the measured spectral thermal emission. The directional spectral emissivity is determined in situ by measuring the transient directional spectral reflectivity and applying Kirchhoffs law. The experimental results are in good agreement with numerical thermal modeling predictions. The pyrometric thermal emission measurement also yields the solid/liquid interface temperature during the pulsed excimer-laser-induced melting. The relation between the measured interface superheating temperature and the interface velocity reveals the melting kinetic relation during the high-power, short-pulse laser-induced phase-change processes.  相似文献   
87.
Observations of self-induced steps in the d.c. current-voltage characteristic of light-sensitive Josephson junctions are reported. The appearance of the structure is induced by light. Preliminary experimental data show a reasonable agreement with the theory developed for oxide barrier junctions. A shift in the positions of the resonant peaks has been observed increasing the illumination level.  相似文献   
88.
The values of drawing dependence of the density ρ, axial elastic modulus E, and maximum draw ratio λ of crosslinked low-density polyethylene (CLPE) rather similar to those obtained with un-crosslinked branched material of similarly low density. Very much the same applies to the equilibrium concentration of sorbed methylene chloride in the amorphous component and the zero-concentration diffusion coefficient D0. The exponential concentration coefficient γD , however, even at the maximum draw ratio, shows no indication of the rapid increase so characteristic of the completed transformation from the lamellar to the fibrous structure. On the basis of this finding, one can understand the small deviations in the dependence of the mechanical properties between the crosslinked and uncrosslinked branched material. The segments between the crosslinks, much shorter than the free molecules, favor the formation of the interfibrillar tie molecules that limit the drawability of the sample. But since they cannot be extended to the same length as the free molecules, they contribute less to the total fraction of tie molecules per amorphous layer and hence yield a smaller axial elastic modulus.  相似文献   
89.
1,3-Dipolar cycloadditions of nitrones with alkenes afforded the corresponding isoxazolidines in ionic liquids in the presence of Er(OTf)3. The ionic liquid and the catalyst are recycled up to five times without any specific treatment or loss of activity. Extension of the procedure to the synthesis of isoxazolidinyl nucleosides has been investigated.  相似文献   
90.
Recently a method termed constrained fluid lambda-integration was proposed for calculating the free energy difference between bulk solid and liquid reference states via the construction of a reversible thermodynamic integration path; coupling the two states in question. The present work shows how the application of the constrained fluid lambda-integration concept to solid/liquid slab simulation cells makes possible a generally applicable computer simulation methodology for calculating the free energy of any surface and/or surface defect structure, including surfaces requiring variations in surface atom or density number, such as the (1 x 5) Au(100) or (1 x 2) missing row Au(110) reconstructed surfaces or excess adatom/vacancy/step populated surfaces. We evaluate the methodology by calculating the free energy of various disordered high temperature Au(110) embedded atom method surfaces constrained to differing excess surface atom numbers [including those corresponding to the (1 x 2) missing row reconstructed surface] and obtained the interesting result that at 1000 K (as distinct from lower temperatures) the free energy difference between these surfaces is reduced to zero; a result which is consistent with an expected order-disorder phase transition for the Au(110) surface at such high temperatures.  相似文献   
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