活性氧化学──自由基与生命

本文扼要介绍了活性氧的化学机制及活性氧对人体及生物体的作用与危害，介绍了活性氧与自由基之间的关系以及人体清除活性氧的措施。

不同的WO3掺杂量对CeO_(2)的NH_(3)-SCR催化性能影响研究

针对二氧化铈(CeO_(2))活性低、活性温度范围窄的问题,提出了利用浸渍法合成不同三氧化钨(WO_(3))掺杂量的CeO_(2)催化剂的方法,发现4%WO_(3)/CeO_(2)(催化剂中W物质的量为Ce物质的量的4%)为最佳WO_(3)掺杂量的铈基催化剂。结果表明,该催化剂在150~425℃的宽温度区间表现出了90%以上的NO_(x)转化率和N_(2)选择性,同时也具有较好的抗SO_(2)和H_(2)O中毒性能。X射线光电子能谱(XPS)结果表明,4%WO_(3)掺杂能增加CeO_(2)表面化学活性氧物种,从而大幅提高中、低温催化活性。氨气程序升温脱附(NH_(3)-TPD)结果表明,4%WO_(3)掺杂能丰富CeO_(2)的表面酸性位、提高其酸性位强度,有利于反应物种的吸附和活化。因此,适量WO_(3)掺杂改性能够有效增强CeO_(2)的SCR催化性能。

High activity of a Pt decorated Ni/C nanocatalyst for hydrogen oxidation

The Pt decorated Ni/C nanocatalysts were prepared for hydrogen oxidation reaction（HOR） in fuel cell.By regulating the contents of Pt and Ni in the catalyst,both the composition and the structure affected the electrochemical catalytic characteristics of the Pt-Ni/C catalysts.When the Pt mass content was 3.1% percent and that of Ni was 13.9% percent,the Pt-Ni/C-3 catalyst exhibited a larger electrochemically active surface area and a higher exchange current density toward HOR than those of pure supported platinum sample.Our study demonstrates a feasible approach for designing the more efficient catalysts with lower content of noble metal for HOR in fuel cell.

Science Letters:Effect of nitrogen doping on the reduction of nitric oxide with activated carbon in the presence of oxygen

Nitrogen doping of activated carbon （AC） was performed by annealing both in ammonia and nitric oxide, and the activities of the modified carbons for NO reduction were studied in the presence of oxygen. Results show that nitrogen atoms were incorporated into the carbons, mostly in the form of pyridinic nitrogen or pyridonic nitrogen. The effect of nitrogen doping on the activities of the carbons can be ignored when oxygen is absent, but the doped carbons show desirable activities in the low temperature regime （≤500 ℃） when oxygen is present. The role of the surface nitrogen species is suggested to promote the formation of NO2 in the presence of oxygen, and NO2 can facilitate decomposition of the surface oxygen species in the low temperature regime

Preparation and electrochemical characterization of activated carbons by chemical-physical activation

A process was proposed based on the combination of chemical and physical activation for the production of activated carbons used as the electrode material for electric double layer capacitor (EDLC). By material characterization and electrochemical methods, the influences of the activitation process on the specific surface area, pore structure and electrochemical properties of the activated carbons were investigated. The results show that specific surface area, the mesopore volume, and the specific capacitance increase with the increase of the mass ratio of KOH to char (m(KOH)/m(char)) and the activation time, respectively. When m(KOH)/m(char) is 4.0, the specific surface area and the mesopore volume reach the maximum values, i.e. 1 960 m2/g and 0.308 4 cm3/g, and the specific capacitance is 120.7 F/g synchronously. Compared with the chemical activation, the activated carbons prepared by chemical-physical activation show a larger mesopore volume, a higher ratio of mesopore and a larger specific capacitance.

Response of Rice Varieties to Bound Residues of Metsulfuron-Methyl in a Paddy Soil

Metsulfuron-methyl is one of the widely used sulfonylurea herbicides. However, approximately half of the applied metsulfuron-methyl may remain as bound residues in soil. To characterize the response of rice plants to residual metsulfuron-methyl in soil, the activities of acetolactate synthase （ALS）, superoxide dismutase （SOD）, peroxidase （POD）, and catalase （CAT） were investigated in two rice varieties that differed in susceptibility to the herbicide. Changes in the activity of these enzymes in leaves and roots of Xiushui 63, a sensitive rice variety, were greater than those in a resistant variety Zhenong 952. Irrespective of variety, changes in the enzyme activity were greater in the roots than in the leaves. The activities of ALS and CAT decreased, while the SOD activity increased with the increase in the amounts of bound residues of metsulfuron-methyl （BRM） in soil. The POD activity increased at the BRM level of 0.025 mg kg^-1, but decreased at the BRM level of 0.05 mg kg^-1. The results showed that the bound residues of sulfonylurea herbicides may affect metabolism of rice plants.

Effect of Pre-oxidation on the Properties of Crushed Bituminous Coal and Activated Carbon Prepared Therefrom

The influence of a pre-oxidation process on the chemical properties of crushed bituminous coal and on adsorption properties of the subsequently formed char and activated carbon is discussed in this paper. Datong bituminous coal samples sized 6 mm were oxidized at different temperatures and for different times and then carbonized and activated by steam to obtain activated carbons. A Uniform Design method was used to arrange the experiments,IR and adsorption experiments were used to characterize these oxidized coals,chars and activated carbon samples. The results show that the carboxyl group disappeared and α-CH2 groups joined to alkenes decreased dramatically but the carbonyl group clearly increased in the coal sample oxidized at 543 K; The chemical composition of coal samples oxidized at lower temperature is different from that of coal oxidized at 543 K. Oxidizing coal samples at higher temperatures for a short time or at lower temperatures for a longer time resulted in activated carbon samples that tended toward the same adsorption properties: Iodine number 1100 mg/g and Methylene blue value 252 mg/g. The yield of activated carbon obtained from the pre-oxidized coal is 10% higher than the yield from parent coal but the activated carbons have the same adsorption properties.

Dynamical changing patterns of glycogen and enzyme histochemical activities in rat liver graft undergoing warm ischemia injury

AIM:To investigate the changing patterns of glycogen and enzyme histochemical activities in rat liver graft under a different warm ischemia time (WIT) and to predict the tolerant time limitation of the liver graft to warm ischemia injury. METHODS: The rats were randomized into five groups, WIT was 0,15,30,45,60 min, respectively, and histochemical staining of liver graft specimens was observed. The recovery changes of glycogen and enzyme histochemistry activities were measured respectively 6 and 24 h following liver graft implantation. RESULTS: The activities of succinic dehydrogenase, cytochrome oxidase, apyrase (Mg++-ATPase) and content of glycogen were decreased gradually after different WIT in a time-dependent manner. The changes were significant when WIT was over 30 min. CONCLUSION: Hepatic injury is reversible within 30 min of warm ischemia injury. Glycogen and enzyme histochemistry activities of liver grafts and their recovery potency after reperfusion may serve as criteria to evaluate the quality of liver grafts.

Effects of surface physicochemical properties on NH_3-SCR activity of MnO_2 catalysts with different crystal structures

α‐,β‐,δ‐,andγ‐MnO2nanocrystals are successfully prepared.We then evaluated the NH3selective catalytic reduction(SCR)performance of the MnO2catalysts with different phases.The NOx conversion efficiency decreased in the order:γ‐MnO2>α‐MnO2>δ‐MnO2>β‐MnO2.The NOx conversion with the use ofγ‐MnO2andα‐MnO2catalysts reached90%in the temperature range of140–200°C,while that based onβ‐MnO2reached only40%at200°C.Theγ‐MnO2andα‐MnO2nanowire crystal morphologies enabled good dispersion of the catalysts and resulted in a relatively high specific surface area.We found thatγ‐MnO2andα‐MnO2possessed stronger reducing abilities and more and stronger acidic sites than the other catalysts.In addition,more chemisorbed oxygen existed on the surface of theγ‐MnO2andα‐MnO2catalysts.Theγ‐MnO2andα‐MnO2catalysts showed excellent performance in the low‐temperature SCR of NO to N2with NH3.

Rose Essential Oil Extraction from Fresh Petals Using Synergetic Microwave ＆ Ultrasound Energy： Chemical Composition and Antioxidant Activity Assessment

The aim of the present work was to investigate the synergetic effect of microwave and ultrasound treatment on the production, chemical composition and antioxidant activity of rose essential oil. The rose essential oil was extracted from fresh Rosa x damciscena Mill. petals by four methods, hydrodistillation, steam distillation, organic solvent extraction and ultrasounds followed by microwave hydrodistillation. The chemical composition of the extracts was analysed by GC-MS, and the antioxidant capacity by DPPH. It was found that both chemical composition and the antioxidant activity of the extracts depend on the extraction method. Overall it was found that microwaves coupled with ultrasonic treatment can be used effectively for the intensification of the extraction of monoterpenes and sesquiterpenes--fragrance bearing molecules--and equally, for increased antioxidant activity while using about 4 time shorter extraction time. The scale-up of the method was also evaluated. The results obtained in this research support the possible use of the US/MW method for the extraction of rose essential oil for the pharmaceutical and fragrance industry.

Chemical Composition, Antioxidant and Antibacterial Activities of the Essential Oil and Methanol Extract from Mentha Iongifolia L. Hudson from North of Iran

This study was designed to evaluate antimicrobial and antioxidant activities of the essential oil and methanol extract from Mentha longifolia L. hudson. Antioxidant activity was evaluated through 2,2-diphenyl-l-picrylhydrazyl （DPPH） assay and β-carotene/linoleic acid assay. The essential oil and methanol extract were individually tested [disc-diffusion assay and evaluating minimum inhibition concentration （MIC）] against a number of bacteria. The essential oil showed strong antimicrobial activity against bacteria tested whereas the methanol extract almost remained inactive. In contrast, the extract showed much better activity than the essential oil in antioxidant activity assays employed, e.g. in the inhibition of free radical DPPH and β-carotene/linolcic acid systems. In the former, the extract was able to reduce the stable free radical DPPH with an IC50 of 55.3μg/mL while that of the oils were 10,630μg/mL. When compared to BHT （butylated hydroxytoluene）, a synthetic antioxidant, both showed weaker antioxidative potential. Similarly, in β-carotene/linoleic acid assay, these samples were not effectively able to inhibit the linoleic acid oxidation; exhibiting only 24% and 36% inhibitions at 2 mg/mL, respectively; both were far below than that of BHT. Total phenolic constituent of the extract was approximately 4.5 g/100 g as gallic acid equivalent. Gas chromatography-mass spectroscopy （GC-MS） analysis of the oil resulted in the identification of 45 constituents, ei^-piperitone epoxide, pulegone and piperitenone oxide being the main components. The results indicate that essential oil and extract ofM. longifolia L. hudson may be used as natural preservative in food against the agents of foodborne diseases and food spoilage.

Electrooxidative Degradation of an Anthraquinone Dye with in-situ Electrogenerated Active Chlorine in a Divided Flow Cell

The purpose of this paper was to investigate the possibility of treating C. I. Reactive Blue 19 wastewater by electrochemical oxidation via electrogenerated active chlorine, using metallic oxide coatings （dimensional stable anode, DSA） as anode. The electrolysis for the simulated wastewater was conducted at a constant current. Absorbances at 592 nm and 255 nm were measured to follow the decolorization of the dye and the degradatin of its aromatic ring. After 4 h of electrolysis under the experimental conditions： current density of 15 A·m^-2, 0.2 mol·L^-1 NaCl, 0.1 mol·L^-1 Na2SO4, 0.1 mmol·L^-1 dye, initial pH=6.4 and T=30℃, 100% decolorization of the dye and about 45% degradation of its aromatic ring were achieved, while no obvious change of total organic carbon was observed. The experimental results suggest that the decolorization of the dye and degradation of its aromatic ring were directly affected by current density, temperature, concentrations of the dye and sodium chloride, while slightly affected by initial pH and sodium sulfate concentration; the decolorization of the dye and degradation of its aromatic ring followed pseudo-first-order kinetics; and indirect electrooxidation, using electrogenerated active chlorine, predominated in the electrochemical oxidation.

Influence of CeO2 on Properties and Activity of Oxide Catalysts in Carbon Monoxide Oxidation

A series of catalysts on the basis of 10 wt.% CuO/y-AI203, 10 wt.% CuO ＋ 10 wt.% Cr2O3/y-AI203 and 15 wt.% MnO2/y -A1203 have been prepared and modified by CeO2 with contents up to 20 wt.%. Physico-chemical properties of the catalysts were determined by the methods of BET Adsorption, XRD, and TPR. Oxidative activity of the catalysts was studied at the temperature range 90-220 ℃and CO concentration of 3 mol.%. Addition of CeO2 led to changes in physico-chemical properties of the catalysts and formation of novel active centres that increased the activity of CuO and Cr203 containing catalysts, but decreased the activity of those, containing MnO2. The catalyst sample containing 10 wt.% CuO and 15 wt.% CeO2 has been shown to be the best one for complete conversion of CO. At the given conditions on this catalyst the complete oxidation of CO to CO2 occurred at 130 ~C during more than 500 h.

Manila clam Venerupis philippinarum as a biomonitor to metal pollution

The Manila clam Venerupis philippinarum is a good biomonitor/bioindicator to marine metal pollution and is frequently used in aquatic toxicology. Two dominant pedigrees (white and zebra) of clam are distributed in the Bohai Sea; however, little attention has been paid to potential biological differences between these two pedigrees. In this study, we tested the sensitivity of both pedigrees to marine metal (cadmium and zinc) pollution biomonitoring and marine environmental toxicology. Results demonstrate significant biological differences in gills of white and zebra clams based on metabolic profiles and antioxidant enzyme activities. In addition, we found that hypotaurine, malonate and homarine were relatively high in white clam gills, while alanine, arginine, glutamate, succinate, 4-aminobutyrate, taurine and betaine were high in zebra clam gills. Zebra clam gills were also more sensitive to a mixture of Cd and Zn, as shown by antioxidant enzyme activities and metabolic profiles, but white clam gills could accumulate more Zn. Therefore, we suggest that the white pedigree can be used as a biomonitor to marine Zn pollution, whereas the zebra pedigree can be used for toxicology studies on Cd and Zn mixed pollution.

Electroless Co-Zn Surface-Modified Nickel Hydroxide as an Active Material for Pasted Nickel Electrodes

Chemically precipitated β type nickel hydroxide powder was surface modified by electroless deposition of Co Zn coatings,and physical properties of both the modified and unmodified nickel hydroxide were characterized by scanning electron microscopy (SEM), specific surface area (BET), X ray diffraction (XRD) and X ray photoelectron spectroscopy (XPS). It has been found that Co and Zn components of the surface electroless coatings exist in the oxidized state. Electrochemical performances of pasted nickel electrodes using the modified nickel hydroxide as an active material were investigated, and compared with those of the electrodes prepared with the unmodified nickel hydroxide. Charge/discharge tests show that the modified nickel hydroxide electrodes exhibit better performances in the charge efficiency, specific discharge capacity and active material utilization. Their resistance to swelling with cycling is also superior to that of the unmodified nickel hydroxide electrodes. Cyclic voltammetric (CV) studies indicate that the modified electrodes have a higher electrochemical activity, and the porous pasted nickel electrodes have some distinguished CV characteristics in comparison with those of the thin film nickel electrodes.

Microbial processes and factors controlling their activities in alkaline lakes of the Mongolian plateau

A striking feature of the Mongolian plateau is the wide range of air temperatures during a year, -30 to 30~C. High summer temperatures, atmospheric weathering and the arid climate lead to formation of numerous alkaline soda lakes that are covered by ice during 6-7 months per year. During the study period, the lakes had pH values between 8.1 to 10.4 and salinity between 1.8 and 360 g/L. According to chemical composition, the lakes belong to sodium carbonate, sodium chloride-carbonate and sodium sulfate-carbonate types. This paper presents the data on the water chemical composition, results of the determination of the rates of microbial processes in microbial mats and sediments in the lakes studied, and the results of a Principal Component Analysis of environmental variables and microbial activity data. Temperature was the most important factor that influenced both chemical composition and microbial activity, pH and salinity are also important factors for the microbial processes. Dark CO2 fixation is impacted mostly by salinity and the chemical composition of the lake water. Total photosynthesis and sulfate-reduction are impacted mostly by pH. Photosynthesis is the dominant process of primary production, but the highest rate （386 mg C/（L.d）） determined in the lakes studied were 2-3 times lower than in microbial mats of lakes located in tropical zones. This can be explained by the relatively short warm period that lasts only 3-4 months per year. The highest measured rate of dark CO2 assimilation （59.8 mg C/（L·d）） was much lower than photosynthesis. The highest rate of sulfate reduction was 60 mg S/（L·d）, while that of methanogenesis was 75.6 μL CH4/（L·d） in the alkaline lakes of Mongolian plateau. The rate of organic matter consumption during sulfate reduction was 3-4 orders of magnitude higher than that associated with methanogenesis.

A REVIEW OF OXYGEN-CONTAINING SURFACE GROUPS AND SURFACE MODIFICATION OF ACTIVATED CARBON

This review focused on the recent reports related to the function, characterization and modification of oxygen-containing surface groups of activated carbon (AC). The Oxygen-containing surface groups were briefly described, and the most frequently used techniques for characterization of the oxygen-containing surface groups on ACs were also briefly stated. A detailed discussion of the effects of the oxygen-containing surface groups on the adsorptive capacity of AC was given. The recent progresses in modification of the oxygen-containing surface groups of AC were also reviewed.

Retinal ganglion cells of high cytochrome oxidase activity in the rat

Retinal ganglion cells in the rat were studied using the heavy metal intensified oytochrome oxidase and horseradish peroxidase histochemieal methods. The results show that a population of large retinal ganglion cells was consistently observed with the eyto3hrome oxidase staining method in retinas of normal rats or rats which received unilateral thalamotomy at birrth. These oytochrome oxidase rich ganglion cells appeared to have large somata, 3-6 primary dendrites and extensive dendritic arbors, and are comparable to ganglion cells labeled by the wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP). However, the morphological details of some of the cells revealed by the cytoahrome oxidase staining method are frequently better than those shown by the HRP histochemieal method. These results suggest that the mit03hondrial enzyme oytoohrome oxidase can be used as a simple but reliable marker for identifying and studying a population of retinal ganglion cells with high metabolie rate in the rat.

Chemical constituents and antioxidant activities of waste liquid extract from Apostichopus japonicus Selenka processing

Apostichopus japonicus Selenka is an ideal tonic food that is used traditionally in many Asian countries, and it contains many bioactive substances, such as antioxidant, antimicrobial, and anticancer materials. To convert waste liquid generated during production into a useful resource, extract from waste liquid was isolated by column chromatography and studied by the pyrogallol autoxidation and 1,10-phenanthroline-Fe^2＋ oxidation methods. Results show that the extract scavenged about 91% of the superoxide anion radical at a concentration of 1.4 mg/mL and 24% of the hydroxyl radical at 3.3 mg/mL. Four compounds were isolated and identified from the extract： 2,4-dihydroxy-5-methyl-1,3-azine; 2,4-dihydroxy- 1,3-diazine; 3-O-β-D-quinovopranosyl-（1→2）-4-O-sodium sulfate-β-D-xylopranosyl]-holosta-9（11）-ene313,12β,17α-triol; and 24-ethyl-5α-cholesta-7-ene-3β-O-β-D-xylopyranoside. All of these compounds are known in A. japonicus, and were found in the waste liquid for the first time.

Surface properties of activated carbon from different raw materials

Activated carbons （ACs） with different surface properties were prepared from different raw materials. N2 adsorption, pH value, Boehm titration, Temperature-programmed reduction （TPR） and FTIR were employed to characterize the pore structure and surface chemical properties of the ACs. The results show that AC from bituminous coal （AC-B） has more meso-pores, higher pH value, more carboxylic groups and basic site than ACs from coconut shell and hawthorn（AC-C, AC-H）. Oxygen in the mixture gas has great effect on S02 catalytic oxidation/oxidation ability of AC-B. In the absence of oxygen, the adsorbed SO2 on AC-B is 0.16 mmollg and the conversion ratio of adsorbed S02 to S03 is 22.07~; while in the presence of oxygen, the adsorbed amount of S02 is 0.42 retool/g, and all of the adsorbed S02 was totally converted to SO3. This feature of AC-B is consistent with its higher pH value, basic site and the reaction ability with H2 from TPR. The conversion ratios of S02 absorbed on both AC-C and AC-H were 100%, respectively.