微囊藻毒素[Dha~7]MCRR的制备及鉴定

以野外收集的水华蓝藻为原料,经过75%甲醇溶液浸提,快速色谱分离和半制备色谱纯化,从滇池水华蓝藻中分离纯化出1种微囊藻毒素变体.电喷雾质谱、紫外分光光度计和HPLC检测结果表明,所得毒素为[Dha7]MCRR,是MCRR的1种去甲基化变体,其纯度大于95%.该毒素的分子组成为环(Ala-Arg-MeAsp-Arg-Adda-Glu-Dha),分子量为1 023,其紫外扫描光谱(200~300 nm)在239 nm处有特征吸收.[Dha7]MCRR在滇池水华蓝藻中普遍存在,有时会成为MC的主要种类.

~(14)C标记1,2,7,8-TCDD在鲤体内分布及代谢的初步研究

利用14C标记1,2,7,8-四氯代二苯并二噁英(1,2,7,8Tetrachloro[U—14C]dibenzodioxin,14C1,2,7,8TCDD)初步研究了其在鲤体内的分布和代谢规律。14C1,2,7,8-TCDD溶解于丙酮/植物油中,腹腔暴露。暴露1、2、4、8、12d后取样,肝脏、胆汁、腹腔脂肪等消化制样后用液闪仪测量放射性活度。肝脏和胆汁内的放射性活度同步变化,都是第8d达到峰值后下降。腹腔脂肪内1—2d放射性明显高于随后取样的样品。肝和腹腔脂肪的分布量之比呈现“S”型变化趋势。暴露4d

2,3,7,8-四氯代二苯并二英(TCDD)和苯并芘(B[a]P)对原代培养鲫鱼肝细胞中卵黄蛋白原诱导的影响

通过测定原代培养鲫鱼(Carassius auratus)肝细胞中雌激素受体所介导的卵黄蛋白原(Vtg)生成以及芳香烃受体所介导的CYP1A1基因转录水平的变化, 建立了一种类雌激素体外实验模型. 实验结果表明, Vtg和Vtg mRNA的表达与己烯雌酚(DES)之间均有很好的剂量-效应关系, Vtg和Vtg mRNA均可作为指示类雌激素毒性的生物标志物. TCDD, B[a]P可显著抑制鱼肝细胞中DES诱导的Vtg和Vtg mRNA的表达, 呈明显的抗雌激素效应, 并同时激活了CYP1A1 基因的表达;

Magnetocaloric effect in nano- and polycrystalline manganite $La_{0.7}Ca_{0.3}MnO_3$

$La_{0.7}Ca_{0.3}MnO_3$ samples were prepared in nano- and polycrystalline forms by sol-gel and solid state reaction methods, respectively, and structurally characterized by synchrotron X-ray diffraction. The magnetic properties determined by ac susceptibility and dc magnetization measurements are discussed. The magnetocaloric effect in this nanocrystalline manganite is spread over a broader temperature interval than in the polycrystalline case. The relative cooling power of the poly- and nanocrystalline manganites is used to evaluate a possible application for magnetic cooling below room temperature.

Unusual resistivity hysteresis in a bulk magnetoresistive ferromagnetic/ferrimagnetic composite (La0.7 Ca0.3 Mn O3 Mn3 O4): Role of demagnetization effects

The authors report an intriguing resistivity versus magnetic field dependence in polycrystalline composite samples containing a magnetoresistive manganite (ferromagnetic/conducting La0.7 Ca0.3 Mn O3) and a magnetic manganese oxide (ferrimagnetic/insulating Mn3 O4). At 10 K, when the magnetic field is scanned from positive to negative values, the resistance peak occurs at positive magnetic field, instead of zero or negative field as usually observed in polycrystalline manganite samples. The position of the resistance peak agrees well with the cancellation of the internal magnetic field, suggesting that the demagnetization effects are responsible for this behavior. © 2007 American Institute of Physics.

YBa 2Cu 3O 7-δ thick films on Ag prepared by the Electrophoretic Deposition technique

YBa 2Cu 3O 7-δ thick films have been deposited onto Ag substrates by the Electrophoretic Deposition (EPD) technique. Different microstructures and electrical behaviours were observed depending on the starting powder. Coatings prepared from commercial powder displayed significant porosity and the superconducting transition width was found to be magnetic-field dependent. Films produced from home-made coprecipitated powder are denser but contain some secondary phases. No dependence of the resistive transition as a function of magnetic field (H 20 Oe) was observed in that case. © 2006 IOP Publishing Ltd.

Spin-cluster effect and lattice-deformation-induced Kondo effect, spin-glass freezing, and strong phonon scattering in La 0.7 Ca 0.3Mn 1-xCr xO 3

Besides the Kondo effect observed in dilute magnetic alloys, the Cr-doped perovskite manganate compounds La0.7 Ca0.3 Mn1-x Crx O3 also exhibit Kondo effect and spin-glass freezing in a certain composition range. An extensive investigation for the La0.7 Ca0.3 Mn1-x Crx O3 (x=0.01, 0.05, 0.10, 0.3, 0.6, and 1.0) system on the magnetization and ac susceptibility, the resistivity and magnetoresistance, as well as the thermal conductivity is done at low temperature. The spin-glass behavior has been confirmed for these compounds with x=0.05, 0.1, and 0.3. For temperatures above Tf (the spin-glass freezing temperature) a Curie-Weiss law is obeyed. The paramagnetic Curie temperature θ is dependent on Cr doping. Below Tf there exists a Kondo minimum in the resistivity. Colossal magnetoresistance has been observed in this system with Cr concentration up to x=0.6. We suppose that the substitution of Mn with Cr dilutes Mn ions and changes the long-range ferromagnetic order of La0.7 Ca0.3 MnO3. These behaviors demonstrate that short-range ferromagnetic correlation and fluctuation exist among Mn spins far above Tf. Furthermore, these interactions are a precursor of the cooperative freezing at Tf. The "double bumps" feature in the resistivity-temperature curve is observed in compounds with x=0.05 and 0.1. The phonon scattering is enhanced at low temperatures, where the second peak of double bumps comes out. The results indicate that the spin-cluster effect and lattice deformation induce Kondo effect, spin-glass freezing, and strong phonon scattering in mixed perovskite La0.7 Ca0.3 Mn1-x Crx O3. © 2005 American Institute of Physics.

人工湿地生态系统的除藻研究

国家杰出青年科学基金(3992 50 0 7); 欧盟国际合作项目(ERBIC 1 8CT 960 0 59)

人工四倍体鲤鲫的产生

在人工诱导的复合三倍体鲤鱼成熟个体中有极个别个体产出的卵既保留了原有的3套染色体,又能与一套外来精核融合产生四倍体。1997年人工产生的8000多尾鲤鲫四倍体鱼经细胞遗传学研究分析鉴定,结果所有的个体都有4套染色体组,染色体数目在185～210之间,众数为200,四倍体比率为100％。这表明人工复合三倍体鲤鱼的生殖方式十分独特,绝大部分个体的成熟卵可借助于外来精子的激动进行自然雌核发育;而有极个别个体的成熟卵能与外来精子融合产生四倍体个体。四倍体鲤鲫的形态特征像鲫鱼。

7种鲟形目鱼类亲缘关系的随机扩增多态性DNA研究

为阐明鲟形目鱼类的系统发育关系,采用随机扩增多态性DNA(RAPD)技术对中华鲟、达氏鲟、史氏鲟、意大利鲟、短吻鲟、长江白鲟和匙吻鲟的基因组进行了研究。13个引物在每个种共产生127个信息座位。按UPGMA聚类法构建这7种鲟形目鱼类的分子系统树。分子系统树首先分成两大支,即长江白鲟和匙吻鲟为一支,其他5种鲟科鱼类为对应的另一支。在5种鲟科鱼类中,我国3种鲟科鱼类中华鲟、达氏鲟和史氏鲟聚在一起,与意大利鲟和短吻鲟分开。我国3种鲟科鱼类又可分成两小支,中华鲟和达氏鲟为一支与史氏鲟相对应。由分子系统树得到的各个

2,3,7,8-TCDD对稀有鮈鲫幼体超微结构影响的观察

国家自然科学基金29607004

Determinations of MC-LR and [Dha(7)] MC-LR Concentrations and Physicochemical Properties by Liquid Chromatography-Tandem Mass Spectrometry

A liquid chromatography electrospray mass spectrometry (LC/ESI/MS) method working in multiple reactions monitoring mode for the determination of trace amounts of microcystin variants (MC-LR and [Dha(7)] MC-LR) in waters was developed. The limit of quantification was 0.05 mu g/L and the limit of detection was 0.015 mu g/L for MC-LR and [Dha(7)] MC-LR, respectively. Recoveries for MCs were in the range of 68%-81%. MC-LR and [Dha(7)] MC-LR were chemically stable with similar physiochemical behavior.

Measurement of residual stresses in ferroelectric Pb(Zr 0.3Ti0.7)O3 thin films by X-ray diffraction

The residual stresses in Pb(Zr0.3Ti0.7)O3 thin films were measured by the sin2 Ψ method using the normal X-ray incidence. The spacing of different planes (hkl) parallel to the film surface were converted to the spacing of a set of inclined planes (100). The angles between (100) and (hkl) were equivalent to the tilting angles of (100) from the normal of film surface. The residual stresses were extracted from the linear slope of the strain difference between the equivalent inclined direction and normal direction with respect to the sin2 Ψ. The results were in consistency with that derived from the conventional sin2 Ψ method. © 2013 The Japan Society of Applied Physics.