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991.
Two New C—21 Steroidal Glycosides from Cynanchum aurichulatum 总被引:2,自引:0,他引:2
Two new C-21 steroidal glycosides, cynanauriculoside I and cynanauriculoside Ⅱ, were isolated from the roots of Cynanchum aurichulatum. Their structures were established using spectroscopic methods including one and two-dimensional NMR. 相似文献
992.
993.
研究了新显色剂5-(对羧基苯偶氮)-8-羟基喹啉(p-CPHQ)与U(Ⅵ)的显色反应条件,在阳离子表面活性剂CTMAB存在下,pH 4.0~6.0缓冲介质中,形成稳定的红色络合物,最大吸收波长为470nm,ε=4.39×10~4,含U(Ⅵ)量在0~55μg/25ml范围内符合比耳定律,结合TBP萃淋树脂分离富集,并以CyDTA、KF联合掩蔽,方法适用于岩石矿物中痕量铀的测定。 相似文献
994.
995.
Amidoxime-based adsorbents are widely studied as the main adsorbent in the recovery of uranium from seawater.However,the adsorption rate and loading capacity of such adsorbents should be further improved due to the economic viability consideration.In this paper,polyvinyl alcohol functionalized with amidoxime(PVA-g-AO)has been prepared as a new adsorbent for uranium(Ⅵ)adsorption from aqueous solution.The physicochemical properties of PVA-g-AO were investigated using infrared spectroscopy(IR),scanning electron microscope(SEM),X-ray diffraction(XRD),and X-ray photoelectron spectroscopy(XPS).Results showed that the ligand monomers were successfully grafted onto the matrixes.The XRD and XPS analysis showed that uranium was adsorbed in metal ionic form rather than in crystal form.Uranyl(U(Ⅵ))adsorption properties onto PVA-g-AO were evaluated.The adsorption of U(Ⅵ)by PVA-g-AO was fast,with an equilibrium time of less than 50 min.Additionally the maximum adsorption capacity reached 42.84 mg/g at pH 4.0. 相似文献
996.
利用一款标准的日盲型紫外探测传感器对枪击火焰进行了探测实验,结合紫外光传输特性,对实验数据进行分析,提出了探测枪击火焰紫外光谱的传感器技术指标。不考虑入射角度和响应时间的影响,1 km处要检测到步枪击发,传感器响应电流达到能明显检出的100 nA,则传感器的响应率和响应面积乘积至少达到0.002 AW-1m2。根据一种枪击探测装置原型方案,对紫外探测传感器的透光性、日盲特性、对紫外光的响应率、入射角和短路电流等技术指标进行了分析。采用分子束外延法制备了一种MgZnO紫外探测传感器,对其紫外光谱透光率、响应率和响应时间进行了测量,进一步优化性能后有望满足枪击探测要求。 相似文献
997.
998.
A method is proposed to rapidly predict the hydrogen bond cooperativity in N‐methylacetamide chains. The parameters needed are obtained from the fittings to the hydrogen bonding energies in the formamide chains containing 2 to 8 monomeric units. The scheme is then used to calculate the individual hydrogen bonding energies in N‐methylacetamide chains containing 2 to 7 monomeric units. The cooperativity predicted is in good agreement with those obtained from MP2/6‐31+G** calculations by including the BSSE correction. Our scheme is further employed to predict the individual hydrogen bonding energies in larger N‐methylacetamide chains containing up to 200 monomeric N‐methylacetamide units, to which the MP2 method cannot be applied. Based on our scheme, a cooperative effect of over 170 % of the dimer hydrogen bonding energy in long N‐methylacetamide chains is predicted. The method is also applied to heterogeneous chains containing formamide, acetamide, N‐methylformamide, and N‐methylacetamide. The individual hydrogen bonding energies in these heterogeneous chains are also in good agreement with those obtained from MP2 calculations with the BSSE correction, further demonstrating that our method is reasonable. 相似文献
999.
[Bis(imidazolyl)–BH2]+[Bis(triazolyl)–BH2]− Ionic Liquids with High Density and Energy Capacity
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Nianming Jiao Prof. Yanqiang Zhang Hao Li Dr. Long Liu Prof. Suojiang Zhang 《化学:亚洲杂志》2018,13(15):1932-1940
[Bis(imidazolyl)–BH2]+[bis(triazolyl)–BH2]? and [bis(imidazolyl)–BH2]+[tris(triazolyl)–BH]? were synthesized, the cations and anions of which were functionalized with B?H groups and azoles. As B?H groups contribute to the hypergolic activity and azole groups improve the energy output, the resulting ionic liquids exhibited ignition delay times as low as 20 ms and energy outputs as high as 461.1 kJ mol?1. In addition, densities (1.07–1.22 g cm?3) and density‐specific impulse (≈360 s g cm?3) values reached a relatively high level. These ionic liquids show great promise as sustainable rocket fuels. 相似文献
1000.
建立了生化药品、中成药和保健品中非法添加的13种消化类化学药的超高效液相色谱-Orbitrap高分辨质谱(UHPLC-HRMS)高通量筛查方法。供试品以甲醇-水(50∶50)为提取溶剂,经Hypersil Gold C18(2.1 mm×100 mm,3μm)色谱柱分离,以乙腈-0.1%甲酸水为流动相进行梯度洗脱,单次分析仅需10min。采用正离子检测,Full MS/dd-MS2扫描模式。通过比较供试品与对照品的色谱保留时间、高分辨一级和二级质谱,判断供试品中是否非法添加消化类药物,并对阳性样品进行定量分析。13种化合物的线性范围均为8.0~800μg/L,相关系数(r)均不低于0.998 5,回收率为94.6%~106.2%,相对标准偏差为1.2%~2.9%。该法快速简便、通量高、选择性好、灵敏度高,并已用于生化药品、中成药及保健品非法添加消化类化学药的高通量筛查和测定,在38批中成药中发现5批阳性样品,在43批保健品中发现3批阳性样品。 相似文献