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321.
食饵种群具有常数收获率的捕食—食饵模型分析 总被引:3,自引:0,他引:3
本文研究食饵种群具有常数收获效的捕食-食饵模型:{dx/dt=bx^2(1-x/k)-βxy-hdy/dt=-cy+dxy讨论了极限环的存在性、唯一性和正平衡点的全局稳定性以及分界线环的存在性。 相似文献
322.
Delong Zhang Xiaojun ChenYufang Wang Dengsong ZhuBo Wu Guoxiang Lan 《Journal of Physics and Chemistry of Solids》2002,63(2):345-358
Raman spectra of as-grown and vapor transport equilibration (VTE) treated Er:LiNbO3 crystals, which have different cut orientations (X-cut and Z-cut), different Er-doping levels (Er:(0.2, 0.4 and 2.0 mol%)LiNbO3) and different VTE durations (80, 120, 150 and 180 h), were recorded at room temperature in the wavenumber range 50-1000 cm−1 by using backward scattering geometry. The spectra were attributed on the basis of their spectral features and the previous experimental work and the most recent theoretical progress in lattice dynamics on pure LiNbO3. In comparison with the pure crystal the most remarkable effect of Er-doping on the Raman spectrum is observed for the E(TO9) mode. It does not appear at 610 cm−1 as the pure crystal, but locates at 633 cm−1. In addition, the doping also results in the lowering of the Raman phonon frequency, the broadening of the Raman linewidth and the changes of the relative Raman intensity of some peaks. The VTE treatment results in the narrowing of the linewidth, the recovery of the lowered phonon frequency and the further changes of relative Raman intensity. The narrowing of Raman linewidth indicates that the VTE processing has brought these crystals closer to stoichiometric composition. The VTE treatment has induced the formation of a precipitate ErNbO4 in the high-doped Er(2.0%):LiNbO3 crystals whether X- or Z-cut. For these precipitated crystals, besides above linewidth and phonon frequency features, they also display more significant Raman intensity changes compared with those not precipitated crystals. In addition, a slight mixing between A1(TO) and E(TO) spectra is also observed for these precipitated crystals. Above doping and VTE effects on Raman spectra were quantitatively or qualitatively correlated with the characteristics of the crystal structure and phonon vibrational system. 相似文献
323.
Inthecourseofourscreeningnewantifungalandanticancercompoundsusingthebioassaysystembasedonmorphologicaldeformationorgrowthinhibiti0n0fPyriculariaoryzae,anovelactivecomPoundWAwasobtainedfromthemetab0litesofthefungusstrain38isolatedfromasoilsample'.ItSminimalinhibitionc0ncentrationwas288.4pglml.InthispaPer,wedescribethephysic0-chemicalpr0pertiesandstructureelucidationofWA.Comp0undWAwasobtainedaswhitep0wderhavingmeltingpointl2ful28"C.Itsm0lecularformula,Cl1HIo04,wasdeterminedbyCI-MS[Inlz20… 相似文献
324.
多元复合原油破乳剂的研究和应用 总被引:2,自引:0,他引:2
本文评价了几种破乳剂对克拉玛依原油的破乳效果。进行了单剂和复配剂的化学破乳及除油率的筛选。结果表明复配破乳剂在加药浓度、净化油含水和净化水含油、脱水速度等方面均优于单剂。表明复配破乳剂是高效原油破乳剂的研究方向之一。 相似文献
325.
Using D-proline (D-Pro) as the reducing agent and capper, D-Pro@AuNCs was rapidly constructed. Its fluorescence could be quenched by AuNPs. Due to the electrostatic interaction between anticancer drug Raltitrexed (RTX) and AuNPs induced fluorescence "turn-on" principle, the resultant fluorescent probe exhibited good selectivity and sensitivity for detecting RTX in rat serums. 相似文献
326.
Matsukevich DN Chanelière T Bhattacharya M Lan SY Jenkins SD Kennedy TA Kuzmich A 《Physical review letters》2005,95(4):040405
We describe a new experimental approach to probabilistic atom-photon (signal) entanglement. Two qubit states are encoded as orthogonal collective spin excitations of an unpolarized atomic ensemble. After a programmable delay, the atomic excitation is converted into a photon (idler). Polarization states of both the signal and the idler are recorded and are found to be in violation of the Bell inequality. Atomic coherence times exceeding several microseconds are achieved by switching off all the trapping fields--including the quadrupole magnetic field of the magneto-optical trap--and zeroing out the residual ambient magnetic field. 相似文献
327.
M. Novotný M. Jelínek J. Bulíř J. Lančok V. Vorlíček J. Bonarski 《Applied Physics A: Materials Science & Processing》2004,79(4-6):1267-1270
Pulsed laser deposition (PLD) and hybrid pulsed laser deposition (HPLD) systems were used for nanocrystalline diamond (NCD) film growth on Si(100) and sapphire(0001) substrates. The PLD system was based on a KrF excimer laser (=248 nm,20 ns), which ablated a graphite target in pure oxygen or hydrogen ambient. The HPLD system was based on a combination of PLD and additional capacitively coupled radio-frequency discharges (13.56 MHz) in argon–hydrogen ambient. Radio-frequency power was applied to two plane parallel electrodes or directly to the substrate holder. The working atmosphere pressure was varied from 1 Pa to 220 Pa and the substrate temperature was varied from 20 °C to 660 °C. X-ray diffraction analysis, Raman spectroscopy and a profilometer were used to study the deposited film properties. A band around 1180 cm-1, which can be attributed to NCD, occurred in the Raman spectra. A characteristic diamond peak at 1332 cm-1 was not observed. Films prepared by HPLD showed better compositional homogeneity (from Raman analysis) than films created by PLD. PACS 52.80.Pi; 81.07.Bc; 81.15.Fg 相似文献
328.
We experimentally observe the formation of high-order transverse patterns in a microchip laser with a high degree of frequency degeneracy. With a doughnut pump profile the spontaneous transverse patterns are well localized in the Lissajous trajectories. The observed transverse patterns are reconstructed with a high degree of accuracy by use of the coherent state of quantum theory. The accurate reconstruction suggests that laser resonators can be designed to obtain a more thorough understanding of the quantum-classical connection. 相似文献
329.
High-temperature generalized synthesis of stable ordered mesoporous silica-based materials by using fluorocarbon-hydrocarbon surfactant mixtures 总被引:4,自引:0,他引:4
330.
You JS Yu XQ Zhang GL Xiang QX Lan JB Xie RG 《Chemical communications (Cambridge, England)》2001,(18):1816-1817
Novel chiral imidazole cyclophane receptors were synthesized by highly selective N-alkylation of the imadazolyl 1N-position of the bridged histidine diester 2 with the dibromide in the presence of NaH; these receptors exhibit good chiral recognition toward the enantiomers of L- and D-amino acid derivatives (up to KD/KL = 3.52, delta delta G0 = -3.11 kJ mol-1) in CHCl3 at 25.0 degrees C. 相似文献