共查询到20条相似文献,搜索用时 46 毫秒
1.
ZHOU Lei TIAN Jiwei ZHANG Xiaoqian 《科学通报(英文版)》2005,50(24):2885-2890
The turbulent dissipation along with temperature and salinity was measured on board R/V Dong Fang Hong 2 over the shelf break of the East China Sea from March 7 to 9, 2004. Applying the Turner angle, it is found that the 'diffusive' double diffusion, salt-fingering, and stable stratification coexist in the upper water column of about 50 m. Below that depth, there exists weak salt-fingering. The turbulent dissipation rates are enhanced along the ray paths of M2 internal tides emanating from the shelf break with values ranging from 1.0×10^-9 W·kg^-1 to 1.2×10^-6 W·kg^-1. The corresponding diapycnal mixing rates are from 1×10^-6 m^2· s^-1 to 1×10^-2 m^2· s^-1. The spatially averaged mixing rate over the whole observation section is 2.3×10^-3 m^2· s^-1, which is much larger than 1×10^-5 m^2·s^-1 of the background diapycnal mixing rate in the open ocean. 相似文献
2.
Zhenrong Sun Shenyi Wang Yanping Huang Jiyun Lin Liangen Ding Zugeng Wang 《科学通报(英文版)》1998,43(5):399-402
The nonlinear refractive indexesn
2 for the ethanol solutions of 1, 10-phenanthroline (2.0 × 10−3 mol · L−1), [bis(l, 10-phenanthroline) lanthanum (III)] nitrate (1.0 × 10−3 mol · L−1), and [nitrato-fluoracil-bis (1, 10-phenanthroline) lanthanum (III) ] nitrate (1.0 × 10−3 mol · L−1) are first measured, the third-order nonlinear optical susceptibilities χ(3) and 〈γ〉 are calculated, and the mechanisms of the third-order optical nonlinearities enhanced by lanthanum (III) are discussed
preliminarily. 相似文献
3.
Methane emissions from wetlands on the Qinghai-Tibet Plateau 总被引:4,自引:0,他引:4
The areal extent of cold freshwater wetlands on the Qinghai-Tibet Plateau (QTP) is estimated at 0.133 × 106 km2, suggesting a significant methane potential. Methane fluxes from wet alpine meadows, peatlands,Hippuris vulgaris mires and secondary marshes were 43.18, 12.96, −0.28 and 45.90 mg · m−2 · d−1, respectively based on the transect flux studies at the Huashixia Permafrost Station (HPS) from July to August 1996. Average
CH4 fluxes in the thaw season were extrapolated at 5.68 g · m−2 according to the areal percentage of wetland areas in the Huashixia region. The CH4 fluxes at four fixed sites, representative of similar ecosystems, ranged from −19.384–347.15 mg · m−2 · d−1, and the average CH4 fluxes varied from 6.54 to 71.97 mg · m−2 · d−1 at each site during the observation period from April to September 1997. The CH4 emissions at each site during the entire thaw season was estimated from 1.21 to 10.65 g · m−2, displaying strong spatial variations. Seasonal variations of CH4 fluxes also were observed at four sites: CH4 outbursts occurred upon the spring thaw in May and June, CH4 fluxes increased afterwards with rising soil temperatures. Episodic fluxes were observed in summer, which influenced the
average CH4 fluxes considerably. Annual CH4 emissions from cold wetlands on the QTP were estimated at about 0.7–0.9 Tg based on the distribution of wetlands, representative
CH4 fluxes, and number of thaw days. The centers of CH4 releasing were located in the sources of the Yangtze and Yellow rivers, and Zoigê Peatlands. 相似文献
4.
Export and remineralization of POM in the Southern Ocean and the South China Sea estimated from 210Po/210Pb disequilibria 总被引:1,自引:0,他引:1
Disequilibria between ^210Po and ^210Pb in the upper water and their potential applications as a proxy of particle export and remineralization were examined in the Southern Ocean (station IV3) and the South China Sea (NS44). ^210po was deficit in surface waters but excessive relative to ^210Pb in subsurface waters. Good positive correlation between ^210Po and particulate organic carbon (POC) indicated deficits and excess of ^210Po resulted from particulate organic matter (POM) export and remJneralization respectively, which was also supported by the decreased δ^13C and increased δ^15N downwards as a result of particle remineralization. On the basis of ^210Po/^210Pb box-model, POC export flux out of the surface waters were 1.2 mmol C. m^-2. d^-1 and 2.3 mmol C. m^-2. d^-1 for station NS44 and IV3, respectively. In the subsurface waters, remineralization fluxes of ^210Po were 0.062 Bq. m^-2.d^-1 and 0.566 Bq.m^-2.d^-1 for station NS44 and IV3 along with the recycle efficiency of 52±26% and 119±52%, respectively. Remineralized fluxes of POM derived from ^210Po and exported POC were 0.6 mmol C.m^-2.d^-1 and 2.7 mmol C. m^-2. d^-1 for NS44 and IV3. This study suggested that ^210Po was a powerful tracer of particle export and remineralization. 相似文献
5.
Synthesis of a new high sensitive water soluble chromogenic reagent meso-tetra-(2-chloro-4-sulfophenyl) prophyrin and the
conditions for the reaction of this reagent with cadmium (I) were studied. The apparent molar absorption coefficient at 434 nm is 5.20×105 L·mol−1·cm−1. The method has been applied to the determination of 5.0×10−9 (content by weight) Cadmium (I) in honey.
Supported by the National Natural Science Foundatyion of China
Xiao Ling: born in Oct. 1962, Ph.D gradute student 相似文献
6.
CHEN Lihua~ ZHANG Yongkang~ YIN Hong~ LIU Liuzhan~ YANG Zhaoxia~ SHEN Hanxi~ . College of Chemistry Chemical Engineering Jishou University Jishou Hunan China . College of Chemistry Nankai University Tianjin China 《武汉大学学报:自然科学英文版》2006,11(3):704-708
0 IntroductionMaalnadria siusb atr ompajicosr .he aAltrthe pmrisoibnlienmi (n qtihneghtraoopsiucs,QHS,Fig.1) is a sesquiterpene endoperoxide isola-ted fromArtemisia annuaL., an ancient Chineseherbal medicine usedfor treatment of fever and ma-laria.Studies of the structure and activity relation-ship have shownthat endoperoxide groupis essentialfor anti malarial activity of QHS and absence of thismoiety lead to completely loss in activity of thedrug. Many techniques have been developed to de… 相似文献
7.
A rapid and sensitive on-line preconcentration method for spectrophotometric determination of chromium (VI) in nature water
is described. Preconcentration and determination are based on (i) the quantitative and fast adsorption of chromium (VI) on
the high surface area nanometer-size TiO2 (anatase) powders, which prepared by a sol-gel method from hydrolysis of TiCl4 and (ii) the quantitative and reproducible elution of Cr (VI) by 2.0 mol·L−1 HCl. A mini-column system for preconcentration is developed, Cr(VI) on the mini-column is eluted and merged with a stream
water and DPCB (1,5-diphenylcarbazide) as the chromogenic reagent. The proposed system permits throughputs of 6 sample h−1 (0.001 μg·mL−1 Cr(VI)) or 20 sample h−1 (0.1 μg·mL−1 Cr(VI)). The preconcentration factor is 55. The detection limit is 0.8 ng · mL−1 Cr(VI). The reproducibility is satisfactory with a relative standard deviation of less than 3.35% (0.01 μg·mL−1 Cr(VI),n=5).
Supported by the National Natural Science Foundation of China
Ma Wanhong: born in 1961, Ph. D. Graduate student, Associate professor 相似文献
8.
QIN Yimin PAN Nina ZOU GuolinCollege of Life Sciences Wuhan University Wuhan Hubei China 《武汉大学学报:自然科学英文版》2006,11(2):432-436
0Introduction Porphyrinderivativeshavebeenusedasphotosensitizersinphotodynamictherapy(PDT),anewapproachdevel opedforthetreatmentofcancer[1].Cationwater solublepor phyrinsareofconsiderableinterestowingtotheirpossiblebio medicalapplications[2].Inwhich,theinhibiteffectonthe growthmetabolismofE.coliandcancercellHL60ofmeso tetra(4N ethylacetatepyridyl)porphyrin(H2NEAE pp)and itsZn(Ⅱ)complexform(ZnNEAE pp)havebeenrecentlyin vestigated[3,4].Toenhancetumor locationandanticancerac tivitiesofdr… 相似文献
9.
The photodegradation of bisphenol A (BPA) in aqueous solution containing metal ions and ascorbic acid (AsA) was investigated.
After strong irradiation, the aqueous solution containing AsA and Cu2+ could produce hydroxyl radicals that induced the photodegradation of BPA. The photodegradation efficiency of BPA in the solution
containing 70 μmol·L−1 Cu2+ and 15 mg·L−1 AsA reached 59% at pH 6.0 after 4 hours irradiation with high pressure mercury lamp. The photodegradation efficiency of BPA
reached 10% after 4 hours irradiation with daylight lamp in the presence of 70 μmol·L−1 Cu2+ and 15 mg·L−1 ascorbic acid. BPA was not degraded in the aqueous solution only containing AsA or Cu2+. The BPA photodegradation in aqueous solution containing AsA and Fe3+ was weaker than in aqueous solution that containing AsA and Cu2+ at the same concentration. This work showed a new route of the BPA photodegradation in aqueous environment.
Biography: PENG Zhang’e (1970–), female, Ph. D. candidate, research direction: aquatic environmental chemistry. 相似文献
10.
Kinetic studies of the decomposition reaction of dinuclear Fe(Ⅱ) adducts [Fe2(N-Et-HPTB){O2P(OPh)2}](Cl- O4)2 (1) and [Fe2(N-Et-HPTB) {O2P(Ph)2}] (ClO4)2 (2) with O2 have been carried out at low temperature using UV-vis spectra. The decomposition reaction of Fe(Ⅱ)/O2 adducts was first-order in the experimental conditions, and the activation parameters were obtained. ?H¹ = 85.62 kJ·mol-1, ?S¹ = 19.43 J·mol-1·K-1 for compound (1) and ?H¹ = 97.97 kJ·mol-1, ?S¹ = 55.68 J·mol-1·K-1 for compound (2). These results are similar to those of dioxygen adducts of other metals complexes and natural enzymes such as methane mono- oxygenase (MMOH). 相似文献
11.
The contribution of root respiration to soil CO2 efflux in Puccinellia tenuiflora dominated community in a semi-arid meadow steppe 总被引:3,自引:1,他引:3
WANG Wei GUO Jixun 《科学通报(英文版)》2006,51(6):697-703
Rising atmospheric CO2 and temperature are altering ecosystem carbon cycling. Grasslands play an important role in regional climate change and global carbon cycle. Below-ground processes play a key role in the grassland carbon cycle because they regulate … 相似文献
12.
There are many sediment trapping reservoirs in the Hill Loess Plateau. The Huangtuwa small catchment is selected as a research field where samples were collected in a sediment deposit profile with a vertical length of 12.73 m. By the variation of fine particle content and pollen concentration, 54 flood couples were identified. Taking the freeze-thawing disturbed texture as the sign of the latest flood couple in a year, it is ascertained that those 54 floods should happen in 31 years. Using pyramid volume calculation formula, the sediment yields of flood ranged between 716-30376 t· km^-2, The average sediment yield was 7106 t· km^-2, The annual sediment yields varied between 968-55579 t· (km^2· a)^-1, and the average value is 12629 t· (km^2· a)^-1. Compared with the modern annual sediment discharge of the Huaining River, the erosion rate in the Huangtuwa region 450 years ago was similar to the modern erosion rate. In the period from the 27th year to the 31st year, the average annual sediment yield increased sharply to 31309 t· (km^2· a)^-1. It implied that re-reclamation of the abandoned land in the catchment since the landslide disaster, where vegetation had rehabilitated already, caused very severe soil erosion in the catchment. 相似文献
13.
Highly sensitive voltammetric method for the determination of estrogens, based on the enhancement effect of cetyltrimethylammonium
bromide (CTAB) has been described. In the presence of CTAB, the oxidation peak currents of estrogens (estradiol, estrone,
estriol, estradiol valerate and diethylstilbestrol) as the carbon paste electrode (CPE) increased significantly after open-circuit
accumulation. The peak current was proportional to the concentration of estradiol over the range from 5×10−9 to 2.5×10−6 mol·L−1. The detection limit was 8×10−10 mol·L−1 at 6 min of accumulation. The total amounts of estrogens in the blood serums were determined and the average recovery was
104.92%. Under the conditions used, the electrode process of estradiol was examined the mechanism for peak current enhancement
was also discussed.
Foundation item: Supported by the National Natural Science Foundation of China (60171023) and the Natural Science Foundation
of Hubei Province (99J060)
Biography: Wu Kang-bing(1977-), male, Ph.D. candidate. research direction: bioelectrochemistry. 相似文献
14.
Preliminary results of the study on wind erosion in the Qinghai-Tibetan Plateau using137Cs technique
The worldwide fallout of caesium-137 (137Cs) associated with the nuclear weapon tests during the 1950s and 1960s has provided a valuable man-made tracer for studies
of soil erosion and sediment delivery. But relatively few researchers have used it to estimate wind erosion. In this note,
the137Cs technique is introduced into the studies of wind erosion and its modern processes in the Qinghai-Tibetan Plateau. Two137Cs reference inventories of 982.11 and 2 376.04 Bq · m−2 were established preminarily, distributed in the south and middle-north parts of the studied area respectively. By analyzing
the patterns of137Cs depth profiles from sampling sites, the aeolian processes of erosion and deposition in nearly 40 years have been revealed,
i.e. the shrub coppice dunes (S1) and semi-fixed dunefields (S3) experienced the alternation of erosion and deposition, while
the grasslands (S4, S6 and S7) and dry farmlands (S5) suffered erosion only. By using137Cs model, the average wind erosion rates for shrub coppice dune (S1), semi-fixed dune fields (S3), dry farmlands (S5) and
grasslands (S4, S6 and S7) were estimated to be 84.14, 69.43, 30.68 and 21.84 t · ha1 · a−1 respectively, averaging 47.59 t · ha−1 · a−1 for the whole plateau, which can be regarded as of the medium erosion standard. These results derived from Cs for the first
time have significant implications for the further research of wind erosion and desertification control in the Qinghai-Tibetan
Plateau. 相似文献
15.
Fluxes of carbon dioxide and methane from swamp and impact factors in Sanjiang Plain,China 总被引:16,自引:0,他引:16
SONG Changchun YAN Baixing WANG Yuesi WANG Yiyong LOU Yanjing & ZHAO Zhichun . Northeast Institute of Geography Agricultural Ecology Chinese Academy of Sciences Changchun China . Institute of Atmospheric Physics Chinese Academy of Sciences Beijing China Correspondence should be addressed to Song Changchun 《科学通报(英文版)》2003,48(24):2749-2753
Incomplete decomposition of organic matter results in the accumulation of the carbon and other nutriments in wetlands. The wetland ecosystem gains a large amount of carbon from atmosphere CO2 by photosynthesis, and it loses much of which back into the atmosphere as CO2 and CH4 emission through the decomposition and respiration. Climate change, such as global warming and reduction of precipitation could drive the wetlands from carbon sink to source[1,2]. Wetland plays an important role in car… 相似文献
16.
为研究He-Ne激光对增强UV-B辐射后损伤的修复作用,采用5 mW.mm-2He-Ne激光辐照、10.08 kJ.m2.d1的UV-B辐射及二者组合对舜麦1718号小麦幼苗进行处理,测定各处理组小麦幼苗硝酸还原酶活性、一氧化氮合成酶含量和膜透性的变化.分析结果显示:He-Ne激光辐照可使UV-B辐射后小麦幼苗硝酸还原酶活力升高1.2倍,显著改善了增强UV-B辐射后硝酸还原酶活性降低的程度;而一氧化氮合成酶(NOS)含量B组和BL组分别高于CK组45.1%和17.8%,现促进作用. 相似文献
17.
DU JinFeng LI Ying ZHANG Qi YAO XiaoJun 《科学通报(英文版)》2007,52(2):200-204
The presence of several high affinity binding sites on human serum albumin (HSA) makes it a possible target for many drugs. This study is designed to examine the effect of aloe-emodin on HSA by fluo-rescence, CD spectroscopy and molecular modeling. The results of fluorescence measurements sug-gested that the hydrophobic interaction was the predominant intermolecular force stabilizing the AE-HSA complex, which was in good agreement with the result of molecular modeling study. And the enthalpy change ΔH0 and the entropy change ΔS0 were calculated to be -7.041 kJ·mol-1 and 76.619 J·mol-1·K-1 according to the Van't Hoff equation. The alterations of protein secondary structure in the presence of AE in aqueous solution were quantitatively calculated from CD spectra, and the content of α-helices obviously increased. 相似文献
18.
A carbon paste electrode modified with multi-walled carbon nanotubes (MWCNT) was prepared and the determination of ultra trace amount of zirconium based on the anodic adsorptive voltammetry of the zirconium-calcium-alizarin red S mix-polynuclear complex is described in this paper for the first time. The results showed that the sensitivity and the selectivity of the method are excellent. The second derivative linear scan voltammograms of the complex were recorded by polarographic analyzer from 200 to 1200 mV (vs. SCE) and it was found that the complex can be adsorbed on the surface of the electrode, yielding a peak at about 840 mV, corresponding to the oxidation of ARS in the complex. The peak current increases linearly with Zr (IV) concentration in the range of 6.0×10^-12--6.0×10^-11 mol. L^-1 (accumulation time 120 s), 6.0×10^-11--2.0×10^-9 mol. L-1 (accumulation time 90 s) and 2.0×10^-9--1.0×10^-7 mol. L^-1 (accumulation time 60 s) and the detection limit (S/N = 3) is 2.0×10^-12 mol. L^-1 (accumulation time 180 s). The procedure has been successfully applied to the determination of zirconium in the ore samples. 相似文献
19.
An electrochemical method for the simultaneous determination of lead(II) and Cadmium(II) with a calix[6]arene modified carbon
paste electrode (CPE) has been developed. Pb2+ and Cd2+ were accumulated at the surface of the modified electrode via formation of chemical complexes with calix[6]arene, and reduced
at 1.40 V. During the following anodic potential sweep, reduced lead and cadmium were oxidized, and two well-defined striping
peaks appeared at about −0.60 V and −0.84 V. Compared with a bare carbon paste electrode, the calix[6]arene modified CPE greatly
improves the sensitivity of determining lead and cadmium. The stripping peak currents change linearly with the concentration
of Pb2+ 3.0×10−8–8.0×10−6 mol·L−1 and with that of Cd2+ 6.0×10−8–1.0×10−5 mol ·L−1. The detection limits of Pb2+ and Cd2+ are found to be 8.0×10−9 mol·L−1 and 2.0×10−8 mol·L−1, respectively. The modified carbon paste electrode was applied to determine trace levels of lead and cadmium in water samples.
Comparing with that of atomic absorption spectrometry, the results suggests that the calix[6]arene modified CPE has great
potential for the practical sample analysis.
Foundation item: Supported by the National Natural Science Foundation of China (60171023)
Biography: JI Xiao-bo (1980-), male, Master, research direction: electroanalytical chemistry. 相似文献
20.
ZHAO Chungui YANG Binsheng ZHANG Wei BAI Haijing & LIU Wen . Institute of Biological Technology Shanxi University Taiyuan China . Institute of Molecular Science Shanxi University Taiyuan China . Chinese Institute of Radiation Protection Taiyuan China Correspondence should be addressed to Yang Binsheng 《科学通报(英文版)》2003,48(2):127-130
Human serum apotransferrin is the major iron-tran- sport protein in blood. The protein binds iron as Fe3+ at two similar, but not identical, high-affinity binding sites. Although iron bound to human serum apotransferrin is less then 0.1% (~3 mg) of the total body iron, dynamically it is the most important iron pool with the highest rate of turnover. The turnover of transferrin iron is in the order of 30 mg per day and, normally, about 80% of this iron are transported to the bone marrow for hem… 相似文献