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海绵Phacelliafusca中含氮化合物的分离与结构鉴定 总被引:1,自引:0,他引:1
从采自中国南海西沙群岛海域的海绵Phacellia fusca Schmidt中得到4个含氮 化合物。经~1H NMR,~(13)C NMR,HMQC,HMBC,~1H-~1HCOSY,FABMS和EIMS等光谱分析 ,确证其结构分别为:N,N'-二[2-乙氧基-1(Z)-乙烯基]脲(1),2- Bromoaldisin(2),Aldisin(3)Dibromophakellin盐酸盐(4)。其中化合物1为一具有 对称结构的新脲类化合物,命名Phacelliaurea A;化合物4是首次从该海绵中分离 得到的已知胍基生物碱,首次报到了它的~(13)C NMR数据及其归属。 相似文献
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The title compound(zifaxaban 2, C20H16ClN3O4 S, Mr = 429.87) was synthesized and its crystal structure was determined by single-crystal X-ray diffraction. Zifaxaban crystallizes in monoclinic, space group P21 with a = 5.7900(12), b = 13.086(3), c = 12.889(3) A, β = 100.86(3)°, V = 959.1(3) A3, Z = 2, Dc = 1.489 g/cm3, F(000) = 444, μ = 0.342 mm-1, the final R = 0.0320 and wR = 0.0640 for 2717 observed reflections(I 2σ(I)). The absolute configuration of the stereogenic center in the title compound was confirmed to be S by single-crystal X-ray diffraction. Four existing intermolecular hydrogen bonds help to stabilize the lattice and the molecule in the lattice to adopt an L-shape conformation. Zifaxaban was slightly more active than rivaroxaban 1 in in vitro assay against human FXa and therefore is promising as a drug candidate. 相似文献
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Ferroelectric behaviour of 30nm BaTiO3 ceramics prepared by high pressure assisted sintering 下载免费PDF全文
Dense nanocrystalline BaTiO3 ceramics with a homogeneous grain size of 30 nm was obtained by pressure assisted sintering. The ferroelectric behaviour of the ceramics was characterized by the dielectric peak at around 120 ℃, the P-E hysteresis loop and some ferroelectric domains. These experimental results indicate that the critical grain size for the disappearance of ferroelectricity in nanocrystalline BaTiO3 ceramics fabricated by pressure assisted sintering is below 30 nm. The ferroelectric property decreasing with decreasing grain size can be explained by the lowered tetragonality and the 'dilution' effect of grain boundaries. 相似文献
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Two ruthenium atoms are covalently connected to the para positions of a phenyl ring in 1,2,4,5-tetra(2-pyridyl)benzene (tpb) to form a linear Ru-tpb-Ru arrangement. This unique structure leads to appealing electronic properties for the biscyclometalated complex [(tpy)Ru(tpb)Ru(tpy)](2+), where tpy is 2,2';6',2″-terpyridine. It could be stepwise oxidized at substantially low potential (+0.12 and +0.55 V vs Ag/AgCl) and with a noticeably large comproportionation constant (1.94 × 10(7)). In addition to the routinely observed metal-to-ligand charge-transfer transitions, [(tpy)Ru(tpb)Ru(tpy)](2+) displays a separate and distinct absorption band at 805 nm with appreciable absorptivity (ε = 9000 M(-1) cm(-1)). This band is assigned to the charge transition from the Ru-tpb-Ru motif to the pyridine rings of tpb with the aide of density functional theory (DFT) and time-dependent DFT calculations. Complex [(tpy)Ru(tpb)Ru(tpy)](2+) was precisely titrated with 1 equiv of cerium ammonium nitrate to produce [(tpy)Ru(tpb)Ru(tpy)](3+), which shows intense multiple NIR transitions. The electronic coupling parameters H(ab) of individual NIR components are determined to be 5812, 4942, 4358, and 3560 cm(-1). DFT and TDDFT calculation were performed on [(tpy)Ru(tpb)Ru(tpy)](3+) to elucidate its electronic structure and spin density population and the nature of the observed NIR transitions. Electron paramagnetic resonance studies of [(tpy)Ru(tpb)Ru(tpy)](3+) exhibit a discernible rhombic signal with the isotropic g factor of ?g? = 2.144. These results point to the strong orbital interaction of tpb with metal centers and that tpb behaves as a redox noninnocent bridging ligand in [(tpy)Ru(tpb)Ru(tpy)](2+). Complex [(tpy)Ru(tpb)Ru(tpy)](3+) is determined to be a Robin-Day class III system with full charge delocalization across the Ru-tpb-Ru motif. 相似文献
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为研制大功率太赫兹源, 提出以切连科夫表面波振荡器为基础, 采用过模结构来研究0.34 THz信号的产生. 重点研究了慢波结构的各参数对器件输出性能的影响, 对慢波结构进行了优化设计, 并采用数值模拟方法, 对慢波结构实际参数的选取和实验中所允许的加工精度提了具体要求; 最后采用粒子模拟对该结构进行了"热腔"模拟计算. 结果表明该结构能够产生频率为0.34 THz, 输出功率约为7.8 MW的太赫兹信号, 并且稳定工作于表面波振荡器状态. 该结果为下一步0.34 THz太赫兹源的研制奠定了基础.
关键词:
表面波振荡器
慢波结构
太赫兹
粒子模拟 相似文献
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提出了采用截止波导法与谐波混频法相结合的方式,进行0.14THz高功率短脉冲的频率测量.首先将两个截止频率分别为0.125和0.15THz的非标准矩形波导作为接收端,通过截止波导滤波法获得了太赫兹辐射源的频率范围.然后根据已知的频率范围,将本振频率选择为15—20GHz,则谐波混频的谐波次数确定为8.随后的Ka波段的脉冲测试和0.14THz连续波测试表明,该8次谐波混频器可用于0.14THz脉冲的混频测量.最后,0.14THz脉冲频率测量实验给出了太赫兹辐射源的准确频率为0.1465THz.该方法大大降低了对本振信号的频率要求,且结果准确可信,为长波段太赫兹脉冲的频率测量提供了一种新的思路. 相似文献