27 resultados para 39-357


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Firstly reported for Fe-containing transition metal substituted polyoxometalates was an unusual Fe-centered demetalation process induced by the reduction of ZnW11FeIII to ZnW11FeII which resulted in a new couple of Fe-relating redox waves at positive potentials. (C) 1999 Elsevier Science S.A. All rights reserved.

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The electrochemical behavior of a series of undecatungstozincates monosubstituted by first-row transition metals, ZnW11M(H2O)O-39(n-) (M=Cr, Mn, Fe, Co, Ni, Cu or Zn), was investigated systematically and comparably in aqueous solutions by electrochemical and in situ UV-visible-near-IR spectroelectrochemical methods. These compounds exhibit not only successive reduction processes of the addenda atoms (W) in a negative potential range, but some of them also involve redox reactions originating from the substituted transition metals (M) such as the reduction of Fe-III and Cu-II at less negative potentials and the oxidation of Mn-II at a more positive potential. Some interesting results and phenomena, especially of the transition metals, were found for the first time. Moreover, possible reaction mechanisms are proposed based on the experimental results.

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采用电解法制备了未见文献报道的杂多蓝H8[SiMo11Co(H2O)O39]·20H2O,通过X-射线衍射测定了其晶体结构,该晶体属单斜晶系,空间群P21;。晶胞参数全矩阵最小二乘法修正至中心原子Si与4个氧形成四面体结构,配原子M(M=11/12Mo+1/12Co)与O形成12个MO6八面体结构3个MO6共边形成4个M3O13三金属簇,4个三金属簇与SiO4四面体共角相连形成阴离子结构。

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采用水热合成与离子交换方法,将中心原子为过渡金属(Fe)的钨系过渡金属取代型杂多阴离子FeW_(11)NiO_(39)(H_2O) ̄(7-)(缩写为FeW_(11)Ni)嵌入ZnAl型阴离子层状结构粘土间,获得了大层间距、通道高度达1.32nm的新型层柱微孔化合物。通过XRD、IR及ESR等手段进行了表征。以ZnAl-Few_(11)Ni为催化剂合成邻苯二甲酸二辛酯(DOP),选择性大于99%,转化率由嵌入前的12%提高到近50%,催化活性明显提高。

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合成及制备了K_7H_6[Nd(GeMo_(11)O_(39))_2]·27H_2O单晶,测定其晶体结构,空间群属P2_1/n,晶胞参数:α=1.7095(4),b=2.6895(3),c=2.1214(5)nm,β=103.11(2)°;V=9.4994(3)nm~3;Z=4;D_m=3.14g/cm~3,D_c=3.05g/cm~3;μ(MoKα)=43.70cm~(-1)。利用结构分析的结果,研究配合物的IR光谱性质,提出利用IR光谱推测杂多配合物分子结构特征的实验证据和理论根据。电子光谱证实配合物中Nd~(3+)的f轨道参与成键。

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本文采用低温技术,在—90℃的干燥氮气保护下,收集标题化合物晶体的衍射数据,用重原子法解出结构。P2_1/n空间群,a=17.504(2),b=27.323(5),c=21.616(4),β=104.49(2)°,z=4.8320个衍射参与精修,最后的R值为0.088。中心离子Pr(Ⅲ)同2个钼硅杂多酸根中的8个氧原子键合,形成正方反棱柱配位多面体。Pr—O的平均键长为2.44(2)。钼硅杂多酸根配体具有缺位的α型Keggin结构。

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Rel/NF kappa B is a family of transcription factors. In the present study, a Rel/NF kappa B family member, Dorsal homolog (FcDorsal) was cloned from the Chinese shrimp Fenneropenaeus chinensis. The full length cDNA of FcDorsal consists of 1627 bp, revealed a 1071 bp open reading frame encoding 357 aa. The predicted molecular weight (MW)of the deduced amino acid sequence of FcDorsal was 39.78 kDa, and its theoretical pl was 8.85. Amino acid sequence analysis showed that FcDorsal contains a Rel homolog domain (RHD) and an IPT/TIG (Ig-like, plexins and transcriptions factors) domain. The signature sequence of dorsal protein existed in the deduced amino acid sequence. Spatial expression profiles showed that FcDorsal had the highest expression level in the hemocytes and lymphoid organ (Oka). The expression profiles in the hemocytes and lymphoid organ were apparently modulated when shrimp were stimulated by bacteria or WSSV. Both Gram-positive (G(+)) bacteria (Micrococcus lysodeikticus) and Gram-negative (G(-)) bacteria (Vibrio anguillarium) injection to shrimp caused the up-regulation of FcDorsal at the transcription level. DsRNA approach was used to study the function of FcDorsal and the data showed that FcDorsal was related to the transcription of Penaeidin 5 in shrimp. The present data provide clues that FcDorsal might play potential important roles in the innate immunity of shrimp. Through comparison of the expression profiles between FcDorsal and another identified Rel/NF kappa B member (FcRelish) in shrimp responsive to WSSV challenge, we speculate that FcDorsal and FcRelish might play different roles in shrimp immunity. (C) 2010 Elsevier Ltd. All rights reserved.

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过量氮和磷引起的海水富营养化引起了一系列的生态环境效应,探讨二者的耦合关系对阐明全球海洋生态环境变化机制意义重大。本论文首次探讨了过量氮和磷引起的富营养化对海水无机碳体系的影响,通过室内系统模拟实验,构筑了过量氮和磷与无机碳体系变化的定量耦合关系,在此基础上获得了中国近海典型海域特别是南黄海近十年氮和磷演变引起的无机碳源汇格局变化,获得了以下一系列新的结果和认识: 1、不同营养盐(NO3-、NH4+、NO2-和PO43-)对水体溶解无机碳体系均有重要影响,且影响程度有较大的差异。 在模拟实验中,当NO3-<188 μmol/L,NH4+<126 μmol/L,NO2-<39.5 μmol/L时均可明显提高水体的固碳能力,相应水体中的DIC、HCO3-和 pCO2均较空白对照组时有一定程度的下降。当N浓度达到一定值后,其固碳能力减弱,DIC、HCO3-和pCO2出现相反变化。当NH4+>126 μmol/L和NO2->39.5 μmol/L时pCO2增加,向大气释放CO2。在PO43-添加组中,当浓度小于19.5μmol/L时DIC、pCO2较空白对照组下降,水体表现为大气CO2的汇,其固碳能力高于N组。在孔石莼添加组中,各营养盐组水体的固碳能力均高于空白对照组,相应水体中DIC、HCO3-和pCO2的下降明显。其中,同一营养盐浓度水平下,NH4+组中各无机碳组分的变化幅度明显高于NO3-和NO2-组,PO43-组的无机碳体系变化幅度低于N组。其中,当NO3-、NH4+和NO2-浓度分别在71 μmol/L,49.7 μmol/L和11.7 μmol/L时,pCO2下降明显,水体表现为大气CO2的强汇。对无机碳各参数的变化量与营养盐进行多元回归分析,得到以下统计关系: ⊿DIC=-0.937(⊿PO43-)-0.34(⊿NO3-)-0.46(⊿NH4+)+0.11(⊿NO2-)(R2=0.69, n=30,Sig.<0.05) ⊿HCO3-=-1.357(⊿PO43-)-0.35(⊿NO3-)-0.57(⊿NH4+)-0.013(⊿NO2-)(R2=0.76, n=32, Sig.<0.05) ⊿CO32-=0.344(⊿PO43-)+0.16(⊿NO3-)+0.18(⊿NH4+)+0.076(⊿NO2-)(R2=0.69, n=32, Sig.<0.05) ⊿pCO2=-1.321(⊿PO43-)-0.12(⊿NO3-)-0.31(⊿NH4+)-0.032(⊿NO2-)(R2=0.84, n=35, Sig.<0.01) 2.氮、磷对海水无机碳体系的源汇格局影响主要受控于水体浮游藻类对营养盐的利用。 模拟实验各种情况下Chl-a的浓度均有不同程度的变化。在N组中,当NH4+<126 μmol/L,随着NH4+浓度的增加,Chl-a浓度增加,而高浓度(NH4+>126 μmol/L)的实验组中,Chl-a则随浓度的增加而下降。当NO2-和PO43-的浓度分别大于39.5 μmol/L和19.5 μmol/L时,水体中Chl-a随营养盐浓度的增加而出现下降趋势,不同的是NO3-添加组在实验浓度范围内藻类均出现了不同程度的增长,这可能与浮游藻类对过量营养盐的耐受性不同有关。在低浓度时,PO43-组pCO2的下降最为明显,这与 PO43-组Chl-a的含量较高相一致,其次为NH4+,NO3-高于NO2-,可见在实验水体中PO43-对于藻类新陈代谢作用影响明显,从而作用到无机碳上的影响也就最为明显。对各实验水体⊿Chl-a与无机碳各组分作相关性分析发现,⊿Chl-a与⊿pCO2的相关性最为明显(R2=0.75,p<0.0001),这可能是因为浮游藻类光合作用和分解作用消耗或生成的首先是海水中的游离CO2(即pCO2)。在孔石莼组中,由于大藻对过量营养盐的耐受性较强,因此各组中藻类干重均有一定程度的增长。藻类干重的增加以NH4+最为明显,其次为NO3-和NO2-,这可能与其对N盐的优先吸收顺序NH4+>NO3->NO2-有关。加PO43-组中藻类的干重增加量低于NH4+和NO3-组,这与大藻的生理特性有关。对藻类干重增加量⊿m与⊿DIC作相关性发现,二者相关性明显(R2=0.64,p<0.01),这是由于孔石莼光合作用同时吸收HCO3-和CO2为碳源有关。 3、近年来,中国近海由于海水过量氮磷引起的富营养化,可使大部分海域海水无机碳汇强度增加 应用室内模拟获得的无机碳与氮、磷之间的定量耦合关系,估算了过量氮、磷引起的富营养化条件下,中国近海水体无机碳源汇的变化情况。结果表明,近十年来,由于氮、磷浓度的增加而导致渤海、南黄海、北黄海和东海每年从大气中多吸收0.197×106t C、0.302×106t C、0.039×106t C和2.233×106t C,东中国近海营养要素的含量的变化及组成比例的时间性和地区性差异是造成各海区碳通量差异的重要因素;对2006年南黄海水文、化学、生物与无机碳体系之间的相互关系进行综合分析,可知水体无机碳体系与营养盐水平密切相关。

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用0.5mol/LHCl提取黄土、古土壤中的酸溶相成分,并用混合树脂法和硼特效树脂法两方法叠加以硼进行分离和纯化,Cs2BO2^+法测同位素比值。结果表明,虽然混合树脂法和硼特效脂法都是较成熟的方法,但用来处理杂质离子含量相对高而硼含量低的样品深液并不成功。两种方法叠加处理后达到理想的效果,重复处理黄土-古土壤样品的精度(2RSD)在0.4‰~0.4‰之间,,这与标样(mST SRM 951)水平(0.3‰)接近,说明处理方法是可行的。用此方法首次测定了洛川黄土.古土壤沉积物中酸溶相的硼同位煮组成。

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~(40)Ar-~(39)Ar法是继K-Ar法后发展起来的一个新的年代学分支,自1962年Sigurgeirssion正式提出~(40)Ar-~(39)Ar计时理论以来,经C. M. Merrihue, G. Turner, G. B. Dalrymple, M. A. Lanphere, I. McDougall, J. G. Mitchell等人的不断改造和完善,现已发展成为一门较为成熟的学科。~(40)Ar-~(39)Ar法以其独特的优点而倍受地质学家的偏爱,其中阶段加热技术是~(40)Ar-~(39)Ar法得以广泛应用的关键,它不仅可以提供一般的年代学资料,同时,还提供诸如样品的受热历史、过剩Ar、封闭温度以及岩体的隆起速率等许多信息。近十年来,对这一领域的研究,无论是在理论方面,还是在实验技术方面,都取得了可喜的进展。