Coulometric determination of dissolved hydrogen with a multielectrolytic modified carbon felt electrode-based sensor

A multielectrolytic modified carbon electrode （MEMCE） was fabricated by the electrolytic-oxidation/reduction processes. First, the functional groups containing nitrogen atoms such as amino group were introduced by the electrode oxidation of carbon felt electrode in an ammonium carbamate aqueous solution, and next, this electrode was electroreduced in sulfuric acid. The redox waves between hydrogen ion and hydrogen molecule at highly positive potential range appeared in the cyclic voltammogram obtained by MEMCE. A coulometric cell using MEMCE with a catalytic activity of electrooxidation of hydrogen molecule was constructed and was used for the measurement of dissolved hydrogen. The typical current vs. time curve was obtained by the repetitive measurement of the dissolved hydrogen. These curves indicated that the measurement of dissolved hydrogen was finished completely in a very short time （ca. 10 sec）. A linear relationship was obtained between the electrical charge needed for the electrooxidation process of hydrogen molecule and dissolved hydrogen concentration. This indicates that the developed coulometric method can be used for the determination of the dissolved hydrogen concentration.

Effects of urea plus nitrate pretreated rice straw and corn oil supplementation on fiber digestibility,nitrogen balance,rumen fermentation,microbiota and methane emissions in goats

Background: Urea pretreatment is an efficient strategy to improve fiber digestibility of low quality roughages for ruminants. Nitrate and oil are usually used to inhibit enteric methane(CH4) emissions from ruminants. The objective of this study was to examine the combined effects of urea plus nitrate pretreated rice straw and corn oil supplementation to the diet on nutrient digestibility, nitrogen(N) balance, CH4 emissions, ruminal fermentation characteristics and microbiota in goats. Nine female goats were used in a triple 3 × 3 Latin Square design(27 d periods). The treatments were: control(untreated rice straw, no added corn oil), rice straw pretreated with urea and nitrate(34 and 4.7 g/kg of rice straw on a dry matter [DM] basis, respectively, UN), and UN diet supplemented with corn oil(15 g/kg soybean and15 g/kg corn were replaced by 30 g/kg corn oil, DM basis, UNCO).Results: Compared with control, UN increased neutral detergent fiber(NDF) digestibility(P < 0.001) and copies of protozoa(P < 0.001) and R. albus(P < 0.05) in the rumen, but decreased N retention(-21.2%, P < 0.001), dissolved hydrogen concentration(-22.8%, P < 0.001), molar proportion of butyrate(-18.2%, P < 0.05),(acetate + butyrate) to propionate ratio(P < 0.05) and enteric CH4 emissions(-10.2%, P < 0.05). In comparison with UN, UNCO increased N retention(+34.9%, P < 0.001) and decreased copies of protozoa(P < 0.001) and methanogens(P < 0.001). Compared with control, UNCO increased NDF digestibility(+8.3%, P < 0.001), reduced ruminal dissolved CH4 concentration(-24.4%, P < 0.001) and enteric CH4 emissions(-12.6%, P < 0.05).Conclusions: A combination of rice straw pretreated with urea plus nitrate and corn oil supplementation of the diet improved fiber digestibility and lowered enteric CH4 emissions without negative effects on N retention. These strategies improved the utilization of rice straw by goats.

Optical evodiamine derivatives:Asymmetric synthesis and antitumor activity

Evodiamine and its derivatives have an asymmetric center at the C13 b position.Herein,isomers of evodiamine derivatives 2 and 3 were obtained by straightforward asymmetric total synthesis.Their inhibitory activities toward topoisomerases Ⅰ and Ⅱ and their cytotoxicities in cancer cell lines were evaluated.All the four isomers exhibited good to excellent antitumor potency and the（S）-isomers were generally more active than the（R）-isomers.The binding modes of（S）-2 with topoisomerases Ⅰ and Ⅱ were also clarified by molecular docking.