Potential bile acid metabolites. 1. The epimeric 3ϵ,7α,12β-trihydroxy-5β-cholanic acids. Raney nickel as an epimerizing catalyst.

The epimeric 3α,7α,12β- and 3β,7α,12β-trihydroxy-5β-cholanic acids have been prepared. Under ambient hydrogenation conditions with Raney nickel as catalyst the axial 3β-ester ($\text{4b}$) is epimerized to the 3α-compound ($\text{2b}$).     

SciFinder-guided rational design of fluorescent carbon dots for ratiometric monitoring intracellular pH fluctuations under heat shock

Intracellular pH plays a significant role in various biological processes, including cell proliferation, apoptosis, metabolism, enzyme activity and homeostasis. In this work, a novel design strategy for the preparation of pH responsive carbon dots (CDs-pH) for ratiometric intracellular imaging was reported. By using SciFinder database, fluorescent CDs-pH with the required pK_a value of 6.84 were rationally designed, which is vital important for precise sensing of intracellular pH. As a result, the synthesized CDs-pH demonstrated robust ability to test pH fluctuations within the physiological range of 5.4-7.4. The CDs-pH was further utilized for fluorescent ratiometric imaging of pH in living HeLa cells, effectively avoided the influence of autofluorescence from native cellular species. Moreover, real-time monitoring of intracellular pH fluctuation under heat shock was successfully realized. This SciFinder-guided design strategy is simple and flexible, which has a great potential to be used for the development of other types of CDs for various applications.     

Oxidations of 4- and 3-Aminopyridinepentaammineruthenium(ii) Complexes by Ethylenediaminetetraacetatocobaltate(III)

Redox reactions of Co(edta)^? with Ru(NH₃)₅L²⁺ (L = 3- and 4-aminopyridine (AmPy)) were found to follow an outer-sphere electron transfer mechanism. The specific rate constants are (3.26 ± 0.03) × 10² and (3.07 ± 0.04) × 10₃ M^?1S^?1, for L = 3- and 4-AmPy, respectively, at μ, = 0.10 M LiClO₄, pH = 8.0 (tris) and T = 25 °C. The rate constants of oxidations for a series of Ru(NH₃)₅L²⁺ complexes are higher than those of the corresponding Fe(CN)₅L_3- complexes by factors of 4 to 15 even after corrections for differences in reduction potentials and in charges of the complexes. Nonadiabaticity in the reactions of Fe(CN)₅L3 complexes may account for the difference in the relative reactivities.     

便携式微波等离子体离子化检测器气相色谱仪用于气体分析的研究

本文使用自制的便携式微波诱导等离子体离子化检测器气相色谱仪对可燃气体中N_2、O_2、H_2和CH_4的测定方法进行了研究。以氩气为载气和工作气体,考察了改进后的微波诱导等离子体离子化检洲器(MIPID)的工作参数对测定的影响。对煤气和乙炔中的O_2、N_2、H_2和CH_4进行了测定,分析结果与热导池检测器(TCD)的气相色谱法一致。讨论了高电离电位(>11.7ev)气体组分在MIPID中响应特性。     

Determination of trace elements in drinking tea by various analytical techniques

Tea has been one of the most popular simulating beverages which is both heavily produced and consumed in Taiwan. The determination of minor or trace elements in drinking tea and tea leaves is therefore important for estimating the daily intake of Taiwanese considered as a safety indicator. In order to accurately and precisely determine the concentrations of trace elements in samples, several analytical methods such as AAS, NAA and ICP-AES are suggested. This paper attempts to utilize all three methods to determine the concentrations of minor or trace elements in different types of tea leaves and the extracts percolated from them. The influence of fermentation processes on the concentration levels of minor or trace elements in tea samples is investigated. Because only free metal ions are bioavailable for the human body, it is necessary to determine their concentrations in drinking tea. The dissolution of trace elements in drinking tea is therefore studied by simulating the common Chinese style of tea percolation. Concentrations of thirteen elements including Zn, Mn, Ca, Cu, Ni, Al, K, Mg, Cd, Pb, Na, Co and Sc are determined.     

钒、铬、锰磷桥络合物中31P NMR化学位移的研究

ISSIe山和W6flSChllh山子1960年首次用pdCI。和二苯基磷合成出黄色的二聚络合物，后被H。yieY＊确认为具有pRZ的桥式结构．此后一系列该类结构的化合物被合成并引起了广泛的兴趣．磷可以和两个甚至多个金属原子络合构成多核金属络合物，在催化反应中有重要应用．磷原子存在多种电子态，其3d空轨道也能参与成键．P乃1的NMR谱是研究含磷化合物立体结构的有力工具．P－31与其它核素之间的耦合常数以及P－31的化学位移对阐明化合物的立体构象以及电子结构具有重要作用．近年来，West饲用计算机神经网络技术预测P－：if的化学位移，但仅…     

功能液晶膜的新进展

论述了功能液晶膜的新近研究结果和发展动向,指出功能液晶膜具有优异的气体分离、液体分离和电光性能,可望作为高效气体分离膜、高效液体分离膜和大面积光控膜,具有较重大的理论与实际意义。     

Elucidating dominant factors of PO43-, Cd2+ and nitrobenzene removal by biochar: A comparative investigation based on distinguishable biochars

Four distinct biochars were employed to remove three typical pollutants, meanwhile, path analysis, a multi-statistical regression method, was performed to elucidate the dominant factors of biochar adsorption. This work can provide a new insight to prepare a targeted biochar as adsorbents.     

含二苯甲烷结构四元共缩聚杂萘聚芳酰胺的合成与性能

采用自制二胺1,2-二氢-2-(4-氨基苯基)-4-[4-(4-氨基苯氧基)-苯基]-二氮杂萘-1-酮、商品二胺4,4′-二氨基二苯甲烷和对苯二胺与对苯二甲酰氯进行低温溶液缩聚反应,改变三种二胺的比例,得到了一系列共聚酰胺树脂,其特性粘数为1·24~2·32dL/g,用FT-IR、1H-NMR手段研究了聚合物的结构;利用DSC和TGA研究了聚合物的耐热性能,结果表明,该类聚合物具有较高玻璃转化温度(301℃以上);氮气气氛中5%热失重温度在438℃以上;用一定比例的二胺制得的聚合物分别能溶于N-甲基吡咯烷酮、N,N-二甲基乙酰胺等非质子极性溶剂中并浇注得到韧性薄膜.     

Bis(crown-6)calix[4]arene/Cs+ Coordination Chemistry in NPME Solution

NMR spectroscopy was used to show that the symmetry of the crown ether bis(C6) is increased by an increase of the alkali metal cation radius. The EXAFS spectrum demonstrates that a seven oxygen atom coordinated configuration is present in the bis(C6)/Cs⁺/NPME system, where NPME denotes o-nitrophenylmethyl ether. The seventh oxygen in this complex, besides the six crown ether oxygens of bis(C6), may come either from a H₂O molecule or an NO₃⁻ ion.