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31.
The experimental performance of a gain-switched Ti:sapphire laser oscillator pumped by a frequency-doubled Q -switched Nd:YAG laser system is presented for a variety of operating conditions. A theoretical model developed for this oscillator predicts well its performance. The observed curved input-output energy plots for the oscillator result from the kinetics of gain switching and fluorescence decay during the gain buildup period. Fluorescence decay also produces observed oscillator thresholds higher than those normally predicted by the standard gain-equals-loss condition. Gain-switched parasitic modes, with a higher threshold but shorter round-trip time than the resonator mode, cause the resonator mode to oscillate only over a finite range of pump energies. Spectroscopic investigations show that the Ti:sapphire cross-section spectrum is well fit by a Poisson distribution, giving a peak cross section of 3×10-19 cm2 for the π polarization 相似文献
32.
33.
Donald A. Kangas Ronald R. Pelletier 《Journal of polymer science. Part A, Polymer chemistry》1970,8(12):3543-3555
Copolymers of 2-sulfoethyl methacrylate, (SEM) were prepared with ethyl methacrylate, ethyl acrylate, vinylidene chloride, and styrene in 1,2-dimethoxyethane solution with N,N′-azobisisobutyronitrile as initiator. The monomer reactivity ratios with SEM (M1) were: vinylidene chloride, r1 = 3.6 ± 0.5, r2 = 0.22 ± 0.03; ethyl acrylate, r1 = 3.2 ± 0.6, r2 = 0.30 ± 0.05; ethyl methacrylate, r1 = 2.0 ± 0.4, r2 = 1.0 ± 0.1; styrene, r1 = 0.6 ± 0.2, r2 = 0.37 ± 0.03. The values of the copolymerization parameters calculated from the monomer reactivity ratios were e = +0.6 and Q = 1.4. Comparison of the monomer reactivities indicates that SEM is similar to ethyl methacrylate with regard to copolymerization reactivity in 1,2-dimethoxyethane solution. The sodium salt of 2-sulfoethyl methacrylate, SEM?Na⊕, was copolymerized with 2-hydroxyethyl methacrylate (M2) in water solution. Reactivity ratios of r1 = 0.7 ± 0.1 and r2 = 1.6 ± 0.1 were obtained, indicating a lower reactivity of SEM?Na⊕ in water as compared to SEM in 1,2-dimethoxyethane. This decreased reactivity was attributed to greater ionic repulsion between reacting species in the aqueous medium. 相似文献
34.
Tero Tuuttila 《Tetrahedron》2008,64(46):10590-10597
Eight bischromophoric bisMPA based polyester Janus dendrimers emanating from a pentaerythritol core were synthesized and their properties evaluated. 4-((4-(Ethyl(2-(2-(6-methoxynaphthalen-2-yl)propanoyloxy)ethyl)amino)-phenyl)diazenyl)-benzoic acid and 4-((4-(ethyl(2-(2-(6-methoxynaphthalen-2-yl)propanoyloxy)-ethyl)-amino)phenyl)diazenyl)-3-nitrobenzoic acid were attached to the dendritic polyester skeleton to make chiral dendrimers up to the second generation. The structures and the purity of the molecules were verified with 1H NMR, 13C NMR, ESI TOF mass spectrometry, and elemental analysis. Spectral properties were evaluated with UV-vis and CD spectrometer. The compounds displayed broad absorption maxima in the visible region. The CD spectra confirmed the optical purity of the compounds. The thermal properties were evaluated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). 相似文献
35.
Sobolev Spaces with Zero Boundary Values on Metric Spaces 总被引:6,自引:0,他引:6
We generalize the definition of the first order Sobolev spaces with zero boundary values to an arbitrary metric space endowed with a Borel regular measure. We show that many classical results extend to the metric setting. These include completeness, lattice properties and removable sets. 相似文献
36.
A nonliner potenitial theory for the supersolutions of equations similar to the p-Laplacian is studied on quasi open setes. We also introduce Sobolev spaces W1, p(U) and W1 p o on quasi sets. The equivalence of several possible definitions of such spaces, as well as completencess, density results and an analogue of Baby's theorem, are proved. The basic probperties of supersolutions to the above equation on quasi open sets and corresponding finely A-superharmonic functions (a nonlinear version of Fugleds's concept) are investigated. We prove that each bounded finely superharmonic function is a fine supersoluan asymptotic corrdinate path along which an unbounded A-subharmonie function grows to indinity 相似文献
37.
We prove that mappings of bounded length distortion are local homeomorphisms if they have -integrable weak second derivatives.
Received March 31, 1999 / Revised December 12, 1999 / Published online July 20, 2000 相似文献
38.
H Kangas Franz n R J Tois J Taskinen R Kostiainen 《Rapid communications in mass spectrometry : RCM》1999,13(16):1680-1684
Tandem mass spectrometric behaviour was studied for a small combinatorial library of alkyl 3-hydroxy-5-(4'-nitrophenoxy) benzoates (A1-A5) and alkyl 3-hydroxy-5-(2', 4'-dinitrophenoxy) benzoates (B1-B5). The spectra were recorded by negative ion electrospray low-energy collision induced dissociation (CID) tandem mass spectrometry. The product ion spectra of [M - H](-) of the benzoates A1-A5 are similar, as are those of benzoates B1-B5. However, the spectra of the B series compounds differ significantly from those of the A series owing to the second electron-withdrawing nitro substituent in the B compounds. In addition, the length of the alkyl chain has an effect on the fragmentation. However, both series of compounds exhibit an abundant nitrophenoxy ion formed by the loss of 3-hydroxybenzoate. This is at m/z 138 in A1-A5 and at m/z 183 in B1-B5. A precursor ion scan of the nitrophenoxy ion provides a rapid method to identify the synthesised compounds in this type of combinatorial mixture. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
39.
Tero Taipale Monika Österberg Antti Nykänen Janne Ruokolainen Janne Laine 《Cellulose (London, England)》2010,17(5):1005-1020
Different types of microfibrillated cellulose (MFC) and fines suspensions were produced, characterized, and then added to
a papermaking pulp suspension. High and medium molar mass cationic polyelectrolytes were used as fixatives. The drainage behavior
of the pulp suspensions with additives were evaluated against the strength properties of hand sheets made thereof. The effects
of salt concentration, pH, fixative type, dosage and type of fibrillar material on drainage were examined. All the MFC and
fines samples produced had clearly different properties due to their dissimilar production methods, and they also introduced
specific responses on the measured drainage and paper strength. Generally, the addition of MFC decreased the drainage rate
of pulp suspension and increased the strength of paper. However, it was shown that by optimum selection of materials and process
conditions an enhancement of the strength properties could be achieved without simultaneously deteriorating the drainage. 相似文献
40.
Let G=(V, E) be an undirected graph and C a subset of vertices. If the sets B
r
(F)C are distinct for all subsets FV with at most k elements, then C is called an (r,k)-identifying code in G. Here B
r
(F) denotes the set of all vertices that are within distance r from at least one vertex in F. We consider the two-dimensional square lattice with diagonals (the king lattice). We show that the optimal density of an (r,2)-identifying code is 1/4 for all r3. For r=1,2, we give constructions with densities 3/7 and 3/10, and we prove the lower bounds 9/22 and 31/120, respectively.
The research of the authors was supported by the Academy of Finland under grants 44002 and 46186 相似文献