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991.
Tang F Wang J Liu D Yuan G Liu Y Jin Zhu C Fen Zhao Y 《Rapid communications in mass spectrometry : RCM》2002,16(11):1035-1039
The electrospray ionization tandem mass spectrometric (ESI-MS/MS) characteristics and fragmentation mechanisms of eight distamycin analogues containing N-methylpyrrole and N-methylimidazole were investigated. The members of two isomeric groups of distamycin analogues with the same elemental composition can be distinguished by MS/MS spectra of protonated molecules and of significant fragment ions. 相似文献
992.
Akikawa H Ajimura S Chrien RE Eugenio PM Franklin GB Franz J Gang L Imai K Khaustov P May M Pile PH Quinn B Rusek A Sasao J Sawafta RI Schmitt H Tamura H Tang L Tanida K Yuan L Zhou SH Zhu LH Zhu XF 《Physical review letters》2002,88(8):082501
With a germanium detector array (Hyperball), we observed two gamma-ray peaks corresponding to the two transitions (5/2(+)-->1/2(+) and 3/2(+)-->1/2(+)) in the (9)(Lambda)Be hypernucleus which was produced by the 9Be(K-,pi(-)) reaction. The energies of the gamma rays are 3029 +/- 2 +/- 1 keV and 3060 +/- 2 +/- 1 keV. The energy difference was measured to be 31.4(+2.5)(-3.6) keV, which indicates a very small Lambda-spin-dependent spin-orbit force between a Lambda and a nucleon. This is the smallest level splitting by far ever measured in a hypernucleus. 相似文献
993.
Tang L.C. Chang C.C. Chen T.C. Yau H.F. Ye P.X. 《Optical and Quantum Electronics》2002,34(12):1241-1249
We propose a novel geometry for a self-pumped phase conjugator that uses a +c-face incident configuration in a photorefractive pentagon-shaped 0°-cut BaTiO3 crystal for obtaining fast response in phase conjugation. A steady phase-conjugate output with a fast response time 0.4 s is obtained when the incident beam has a 4 W/cm2 intensity. The influences of position and angle on the temporal phase-conjugate response are also investigated. The advantage of this phase conjugator using this novel configuration is improved resolution of a phase-distorted image with a value as high as 128 lp/mm. 相似文献
994.
Molecular motions of polycrystalline cellobiose have been investigated by measuring proton spin–lattice relaxation times, T1 and T1ρ, and the second moment, M2, in both protonated and D2O exchanged forms over the temperature range 120–380 K. T1 relaxation is dominated by the motions of hydroxyl groups between 150 and 380 K, characterised by an activation energy of about 8.74 kJ/mol, whereas T1ρ relaxation is driven by the motions of the same groups between 120 and 300 K. T1ρ results suggest that hydroxyl groups have a distribution of dynamics. Motion of methylene groups was detected in the second-moment experiments at about 350 K, characterised by activation energy of about 40 kJ/mol. Consideration of the calculated and observed rigid-lattice second moments suggests that the reported X-ray data are incorrect for the inter-proton distance on C6′. 13C CPMAS spectra of both protonated and deuterated cellobiose have also been measured. Spectra of the deuterated material showed the existence of a second crystalline form in addition to the normal form. 相似文献
995.
Structural features of toxic chemicals for specific toxicity 总被引:1,自引:0,他引:1
We have studied the structural features of toxic chemicals from the RTECS database associated with specific toxicity. The frameworks, functional groups, and structure patterns of molecules are taken into account. Potential active frameworks, groups, and structure patterns for specific toxicity are gained by computational chemistry approaches. These structural features of toxic chemicals will be helpful in understanding activities of toxic chemicals and useful in predicting the toxicity of chemicals, especially in the early stage of drug design. 相似文献
996.
A practical scheme for polarization-insensitive and frequency-conversion interval-independent four-wave mixing in an optical loop configuration is proposed that uses one conventional semiconductor optical amplifier device and two perpendicular polarized pump sources. The significant advantages of this technique are simplicity of configuration, efficient conjugate power generation, effective suppression of the signal and one pump wave at the output port, and reduction in noise. 相似文献
997.
Ravi P. Agarwal X.H. Tang Z.C. Wang 《Journal of Mathematical Analysis and Applications》1999,240(2):1
In this paper, we shall consider a class of neutral differential equations of the form
where τ (0, ∞), σ [0, ∞), Q(t) C([t0, ∞), R + ), r(t) C([t0, ∞), (0, ∞)) with r(t) nondecreasing on [t0 − τ, ∞). We shall show that all positive solutions of ( * ) can be classified into four types, A, B, C, and D, and we shall obtain sufficient and necessary conditions for the existence of A-type, B-type, and D-type positive solutions of ( * ), respectively. A sufficient condition for the existence of C-type positive solutions of ( * ) is also given. Finally, we shall offer a sharp oscillation result for all solutions of ( * ). Our results generalize and improve those established in B. Yang and B. G. Zhang (Funkcial. Ekvac.39 (1996), 347–362). 相似文献
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998.
带模糊约束的最小费用流问题 总被引:4,自引:1,他引:3
本文首次提出了带模糊约束的最小费用流问题,建立了相应的数学模型并给出了求解这一模型的有关算法。最后,给出了一个具体实例。 相似文献
999.
一阶时滞微分方程解的零点分布 总被引:3,自引:0,他引:3
Abstract. The paper gives two estimates of the distance between adjacent zeros of solutions 相似文献
1000.