Reaction of hydrated electrons with ferricytochrome C

The reaction of ferricytochrome c with hydrated electrons produced at pH 6.8 by radiolysis with electron pulses lasting 50 to 1000 nanoseconds has a specific rate constant of 5.5 x 10(10) liter mole(-1) sec(-1) for the formation of the primary adduct. By using appropriate wavelengths, another fast, consecutive process was demonstrated, with the pure first order rate constant 1.0 x 10(5) sec(-1). Its characteristics agree with it being an intramolecular process within the enzyme. Approximately 50 percent of all electrons which add to ferricytochrome c end in forming ferrocytochrome c.     

Electron diffraction of frozen, hydrated protein crystals

High-resolution electron diffraction patterns have been obtained from frozen, hydrated catalase crystals to demonstrate the feasibility of using a frozen specimen hydration technique. The use of frozen specimens to maintain the hydration of complex biological structures has certain advantages over previously developed liquid hydration techniques.     

Microheterogeneity of singlet oxygen distributions in irradiated humic acid solutions

Singlet oxygen (1O2) is a highly reactive species formed through solar irradiation of organic matter in environmental waters. Implicated in a range of reactions, it has proven difficult to quantify its spatial distribution in natural waters. We assessed the microheterogeneous distribution of 1O2 in irradiated solutions containing chromophoric dissolved organic matter (CDOM) by using molecular probes of varying hydrophobicity. The apparent 1O2 concentrations ([1O2]app), measured by recently developed hydrophobic trap-and-trigger chemiluminescent probe molecules, were orders of magnitude higher than those measured by the conventional hydrophilic probe molecule furfuryl alcohol. The differential [1O2]app values measured by these probes reflect a steep concentration gradient between the CDOM macromolecules and the aqueous phase. A detailed kinetic model based on the data predicts probabilistic 1O2 distributions under different solvent conditions.     

Temperature dependence of optical activity of sugar solutions

The temperature dependence of optical activity of solutions of metabolic sugars is investigated and the activation energy of the reaction of association into supramolecular structures is determined. On the basis of the values of the activation energy and with consideration of the effect of time and place and orientation of the instrument on the optical activity of sugars, a suggestion is expressed concerning their key role in the mechanism of adaptation of living systems to environmental changes.     

真空渗糖对冷冻菜用大豆部分玻璃化转变温度和硬度的影响

中国是世界上最大的菜用大豆生产国和出口国,菜用大豆的生产主要集中在长江流域和东南沿海一带[1]。在中国东部沿海地区,鲜食大豆的种植、生产和加工已具规模,其已成为当前出口创汇的重要农产品[2]。鲜食菜用大豆又称毛豆,是在豆荚鼓粒饱满及荚色、籽粒呈翠绿色时采青剥仁食用[3]。随着人民生活质量的逐步提高,消费者对食品的     

Volatilization of high molecular weight DNA by pulsed laser ablation of frozen aqueous solutions

DNA has been volatilized by pulsed laser ablation of a thin film of a frozen aqueous DNA solution. The target film was irradiated in vacuum by a pulsed laser at power densities sufficient to ablate the ice matrix. The expanding ablated water vapor entrained embedded DNA molecules and expelled them into the gas phase. Ejection of DNA molecules as large as 410 kilodaltons was verified by collection of the ablation products and subsequent mass analysis by polyacrylamide gel electrophoresis with autoradiographic detection.     

Mobility of the hydrated electron

The transient change in conductivity in diluted barium hydroxide solutions during and immediately after irradiation with single pulses of electrons from a 15-million-electron-volt linear accelerator was measured. Ionic mobility of the radiation-produced hydrated electrons was 1.84 x 10(-3)cm(-2) volt(-1) sec(-1) +/- 10 percent. This value corresponds to a diffusion constant of 4.75 x 10(-5) cm(2) sec(-1).     

Dechlorination of DDT in frozen blood

Dechilorination of a commercial mixture of o, p'-DDT and p, ppDDT to p, p'-DDD and p, p'-DDE occiurs in avian blood stored at-20 degrees C, indicatinig nonenzymalic degradation. The subsequent disappearance of these two metabolites suggests conversion to other metabolites which cannot be detected by gas chromatography with an electron-captutre detector.     

芦荟汁中芦荟苷的稳定化技术研究

主要对芦荟苷在高温、强光以及不同pH、不同介质等条件下稳定性进行研究。结果表明：加热的温度越高,时间越长,芦荟苷的热稳定性越差,而在室温下（20℃）芦荟苷的吸光度基本不随时间改变;芦荟苷具有光敏性,在太阳光照射下,2小时后便出现黄绿色沉淀物;芦荟溶液随着pH的升高,其稳定性下降;低浓度的氯化钠和蔗糖对芦荟汁液稳定性的维持比高浓度的效果明显。复合抗氧化剂的最佳比例为：柠檬酸0．5％,抗坏血酸0．2％,乙二铵四乙酸二钠（EDTA—Na）0．05％。     

洛美沙星在常用输液中的稳定性

目的:探讨洛美沙星在5%葡萄糖注射液、10%葡萄糖注射液、5%葡萄糖氯化钠注射液、0.9%氯化钠注射液4种输液配伍中的稳定性.方法:应用紫外分光光度计、酸度计分别测定洛美沙星与4种输液在25℃和37℃的条件下配伍后,在24h内含量、pH值等变化情况.结果:在25℃、37℃条件下,洛美沙星与4种输液配伍后在24h内含量、pH值和外观无显著变化. 结论:在25℃、37℃条件下,洛美沙星与4种输液配伍后在24h内比较稳定.     

Regulation of sucrose synthase activity and sugar yield by nitrogen in sugar beet

The content of sugar is influenced by sucrose synthase (SS) activity in roots. The effects of nitrogen level in the amino- nitrate ratio on SS activity of leaves and roots, roots yield and sugar content in sugar beet were studied in the field experiment by nutrient solution culture. The results showed that SS activity in leaves was lower than that in roots. With nitrogen level increasing, SS decomposition activity enhanced, and synthesis activity reduced. SS activity was regulated by different nitrogen forms and the ratio of NO3– and NH4 . SS synthesis activity was enhanced as NH4 increasing when NO3–: NH4 ≥1, and it decreased as increasing NH4 when NO3–: NH4 ≤1, and it was the highest when NO3–: NH4 =1. SS decomposition activity was enhanced as NO3– increasing. Sucrose content in root was lowed as nitrogen level increasing, but it was enhanced as NH4 increasing in the same nitrogen level. Root and sugar yield were the highest in the medium nitrogen level and NO3–: NH4 =1. The result in field experiment corresponded with that in the nutrient fluid culture. It provides a basis for using reasonably nitrogen fertilizer in sugar beet production.     

Phase transitions of Dirac electrons in bismuth

The Dirac Hamiltonian, which successfully describes relativistic fermions, applies equally well to electrons in solids with linear energy dispersion, for example, in bismuth and graphene. A characteristic of these materials is that a magnetic field less than 10 tesla suffices to force the Dirac electrons into the lowest Landau level, with resultant strong enhancement of the Coulomb interaction energy. Moreover, the Dirac electrons usually come with multiple flavors or valley degeneracy. These ingredients favor transitions to a collective state with novel quantum properties in large field. By using torque magnetometry, we have investigated the magnetization of bismuth to fields of 31 tesla. We report the observation of sharp field-induced phase transitions into a state with striking magnetic anisotropy, consistent with the breaking of the threefold valley degeneracy.     

Energetic electrons in the magnetosphere of jupiter

Observations of energetic electrons ( greater, similar 0.07 million electron volts) show that the outer magnetosphere of Jupiter consists of a thin disklike, quasitrapping region extending from about 20 to 100 planetary radii (R(J)). This magnetodisk is confined to the vicinity of the magnetic equatorial plane and appears to be an approximate figure of revolution about the magnetic axis of the planet. Hard trapping is observed within a radial distance of about 20 R(J). The omnidirectional intensity J(0) of electrons with energy greater, similar 21 million electron volts within the region 3 r 20 R(J) is given by the following provisional expression in terms of radial distance r and magnetic latitude theta: J(0) = 2.1 x 10(8) exp[-(r/a) - (theta/b)(2)]. In this expression J(0) is particles per square centimeter per second; a = 1.52 R(J) for 3 相似文献   

药剂稳定化技术处理典型重金属污染废物研究

综述了药剂稳定化技术在pH、沉淀、吸附、离子交换和氧化/还原电位控制方面处理污染土壤、污泥及飞灰等典型重金属污染废物的研究与应用进展,并指出了药剂稳定化技术在上述研究领域存在的问题和今后发展的方向。     

Bidirectional counting of single electrons

A bidirectional single-electron counting device is demonstrated. Individual electrons flowing in forward and reverse directions through a double quantum dot are detected with a quantum point contact acting as a charge sensor. A comprehensive statistical analysis in the frequency and time domains and of higher order moments of noise reveals antibunching correlation in single-electron transport through the device itself. The device can also be used to investigate current flow in the attoampere range, which cannot be measured by existing current meters.     

果树果实中的糖代谢

糖分是果树果实的重要组成成分。有关果实中糖代谢的研究一直是果树研究的重点,并且取得了一定的进展。为更好地认识果树果实中糖代谢的研究以及提供调控糖代谢提高果实品质的理论依据,文章综述了果实发育过程中糖的种类及含量、糖进入果实的途径及运输,果实糖代谢的相关反应,果实糖代谢的方式、糖代谢相关酶的活性与糖积累的关系以及果实中糖代谢的调控等。