自然土壤环境下脐橙植物体稀土累积特征

在赣南稀土高背景区(稀土矿区)和稀土低背景区不同土壤脐橙果园分别取岩、土、植物样32组,用ICP-MS法测定样品中15个稀土元素的含量,并对稀土元素在土壤和脐橙植物体内的分布、迁移、累积特征进行研究.结果表明,稀土元素在脐橙植物体内的分布特征是:根>叶>枝>果皮>果肉;稀土元素从A层土→A层土可溶态→根→枝→叶(以及枝→果皮,枝→果肉)的演化、迁移过程中,总的趋势是轻稀土元素所占百分比逐渐增高,重稀土元素所占百分比逐渐降低;高、低稀土背景区脐橙植物体各器官的稀土含量差别由根至果实逐渐缩小,根的稀土含量差别很大,到果肉则差别很小,高、低稀土背景区脐橙果肉的稀土含量均低于限量标准.     

稀土元素对农业增产作用的研究——1.稀土元素在植物体内的含量和分布规律初探

稀土元素对调节作物生长有特殊的作用,在农作物的栽培试验中有增产效果。为探讨稀土元素对农作物增产的生理效应,本文调查了某稀土矿区的植物种类,并与非矿区进行了对比。矿区与非矿区植物种类基本相同,但采集的植物叶片中稀土含量却有显著差别。如矿区马尾松叶子中稀土含量高于一般地区2.5～22倍。用水培法研究了单一稀土元素在黄瓜植株内的分布规律,镧在植株不同部分的分布有一定规律,以稀土占灰分的重量百分比计,植物幼嫩部分有较多镧。 本文采用示波极谱络合物吸附波的方法测定植物中的单一稀土及稀土总量。     

土壤-植物体系稀土元素的分异现象

用仪器中子活化分析测定了从同一地点采集的9种不同植物根和叶中8个稀土元素（La,Ce,Nd,Sm,Eu,Tb,Yb和Lu)的含量，研究了稀土元素在植物根、叶及相应母土中的分布特征。结果表明，同一植物的根、叶和母土中稀土分布模式均有较大差异。生长在同一地点不同植物根中稀土分布模式非常相似，而叶中分布规模差别较明显。说明根对单一稀土元素的吸收主要取决于这个元素在土壤中有效态的含量，而在稀土从根到叶的运输和积累过程中出现的分异则由植物自身的结构特征决定。     

重稀土矿区芒萁稀土元素精细定位及光抑制对其光合活性的影响

分析了中国江西省龙南县足洞乡重稀土矿区及非矿区稀土元素富集植物芒萁体内稀土元素的精细定位及光抑制对芒萁光合特性影响。结果表明,稀土元素主要分布在芒萁的根部和叶片中,矿区芒萁叶片中的重稀土含量显著高于非矿区芒萁叶片。电镜观察表明,稀土元素主要分布在细胞壁外,细胞质中只含有微量稀土元素。与非矿区芒萁叶片相比,重稀土矿区芒萁叶片中的色素含量显著降低,但β-胡萝卜素含量显著增高。正常光照条件下,矿区芒萁光系统II(PS II)的光化学特性比非矿区芒萁略有提高。光抑制实验表明,400μmol photons.m-2.s-2的光照强度对矿区芒萁光化学活性影响很小而非矿区芒萁光化学活性显著下降。综上所述,矿区芒萁富集重稀土元素的机制是:(1)通过产生的稀土结合多糖、蛋白等物质将稀土元素固定在细胞壁外;(2)通过改变叶片内部的叶黄素循环色素含量避免高光强对光系统的伤害作用。     

内蒙古白云鄂博矿区优势植物重金属和稀土元素富集特征

为筛选适合内蒙古白云鄂博矿区重金属-稀土复合污染土壤修复治理及生态环境恢复的植物材料,本研究采用野外调查法,确定样方区域内的植物种,从中选取长势良好且具有多度和频度优势的植物种,采集植物样品及其相应的根际和非根际土壤,测定重金属和稀土元素含量,分析植物对重金属和稀土元素的富集特征。结果表明,矿区样方区域内共采集到植物53种,分属21科、46属,并筛选出11种优势草本植物。矿区优势植物根际土壤和非根际土壤中重金属和总稀土的平均含量均高于内蒙古土壤背景值,矿区土壤受到不同程度的重金属-稀土复合污染。植物不同部位对重金属和稀土元素的吸收能力不同,除Cu以外,其余重金属和稀土元素在植物地下部分的平均含量高于地上部分。植物体内多种重金属的最高值均高于植物体内正常含量范围,但未达到超富集植物标准。猪毛菜（Salsola collina）对Cu和Hg,艾（Artemisia argyi）对Cu,凤毛菊（Saussurea japonica）对Cu和大多数稀土元素以及蓼子朴（Inula salsoloides）对La,Ce,Pr,Nd,Sm,Eu和Gd的生物富集系数及转运系数均大于1,属于富集型植物,...     

稀土在天然植物铁芒萁体内结合形式的光谱学研究

利用ICP-MS研究了江西赣州沙河稀土矿区天然植物铁芒萁体内稀土元素的分布规律,发现叶片和叶绿素中Ce含量最高,分别占其稀土总量的79.43%和66.71%。铁芒萁叶片光系统（Ⅱ）（PSⅡ）荧光发射峰较普通植物紫移15-25nm,且峰强是PSⅠ的6.79倍,表明PSⅡ活性提高。由于铁芒萁叶绿素中稀土叶绿素含量较低（约占叶绿素总量的0.1%）,测定的UV-Vis和FTIR光谱特征与标样叶绿素a相似,未能反映出稀土的配位信息。而利用EXAFS则表征出在铁芒萁叶绿素中Ce为八配位,Ce-N键长为0.252nm,推测Ce是与两个卟啉环配位的,为一双层结构。     

稀土元素在植物中的分异研究进展

有关对稀土农用的理论和实践、天然和农业生态系统中稀土的地球化学行为及稀土的增产生理过程与毒理等方面已开展了大量研究,而对稀土进入植物体内的迁移过程、分布分异现象和机制缺乏必要的了解。稀土元素在植物中的分异研究有助于“示踪”稀土元素在土壤(溶液)-植物系统中的迁移路径,进而查明控制稀土元素迁移和积累的体外和体内敏感因素。本文结合近5年的研究工作,就近年来国内外有关稀土元素在植物中的分异现象、机制及其研究意义进行了综述,并展望了此方面的研究趋势,期望能为稀土以及重金属的生物有效性研究开辟一条新思路。     

稀土在植物抗逆中的生理作用

论述了近年来关于稀土元素在植物抵抗干旱、高温、低温、盐渍、病虫害、重金属污染等逆境中的作用。稀土元素在植物抗逆中可能的生理作用机制为：稀土离子与细胞膜上的磷脂结合，调节钙代谢，改变细胞膜的通透性和稳定性，提高细胞膜的保护功能；稀土离子能提高植物体内的保护酶活性，减少自由基积累，增强植物的抗逆性。     

黄土高原表层土壤中稀土元素含量及其对稀土农用效果的影响

用中子活化法（ＩＮＡＡ）测定了黄土高原地区主要类型土壤（表层）１０４个样品中８个稀土元素（Ｌａ，Ｃｅ，Ｎｄ，Ｓｍ，Ｅｕ，Ｔｂ，Ｙｂ，Ｌｕ），初步探讨了该区土壤中稀土元素的区域分布及对稀土农用效果的影响。结果表明，黄土高原土壤中稀土元素的含量接近全国土壤中的平均含量：主要类型土壤的稀土元素含量分布规律为：灰褐土，娄土＞黑垆土，黄绵土＞灰钙土，与土壤粘粒含量相似，由东南向西北呈下降趋势：该区较适合于农用稀土的推广应用。     

我国主要土壤中稀土元素的含量和分布

我国主要土壤Ｌａ，Ｃｅ，Ｎｄ，Ｓｍ和Ｙ的平均含量分别为４３．７、８６．２、３５．８、８．２１．８μｇ／ｇ，稀土总量为２６４μｇ／ｇ。稀土元素在成土过程中产生不同程度的富集和淋溶，但其含量末表现有地带性差异。在６１个土样中可给态稀土的平均含量为２４．９μｇ／ｇ，有从南向北降低的趋势；其中低于１０μｇ／ｇ的中酸性土壤占酸性土壤样品总数的１７％，低于１０μｇ／ｇ的中性、石灰性土壤占中性和石灰性土壤样品总     

二氧化碳和丙烯直接合成甲基丙烯酸的NiPMo/TiO2催化剂的研究

用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%.     

Synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives

Different approaches for the synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives from simple amino acids have been investigated. A library of 33 precursors for the preparation of N-hydroxy pyrazinones was obtained in moderate to good yields.     

Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction

In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments.     

CoFe2O4自形成磁性液体场致结构化对磁化的影响

The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula.     

Highly regioselective Buchwald–Hartwig amination at C-2 of 2,4-dichloropyridine enabling a novel approach to 2,4-bisanilinopyridine (BAPyd) libraries

The highly regioselective Buchwald–Hartwig amination at C-2 of the cheap and readily accessible reagent, 2,4-dichloropyridine with a range of anilines and heterocyclic amines is described. This new methodology is robust and provides a facile access to 4-chloro-N-phenylpyridin-2-amines on 0.25 mol scale. These intermediates undergo a further Buchwald–Hartwig amination at higher temperature to enable rapid exploration of the chemical space at C-4 and to provide a library of 2,4-bisaminopyridines.     

KMnO4-mediated oxidative CN bond cleavage of tertiary amines: Synthesis of amides and sulfonamides

KMnO₄-mediated oxidative CN bond cleavage of tertiary amines producing secondary amine was introduced, which was trapped by electrophiles (acyl chloride and sulfonyl chloride) to form amides and sulfonamides. The reaction could take place at mild condition, tolerating a wide range of function groups and affording products in moderate to excellent yields.     

Chemistry of heterocyclic compounds at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, over 50 years (Review)

The review contains a concise historical account and information on the most significant researches undertaken by the staff at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences on the Chemistry of Heterocyclic Compounds. Dedicated to Academician of the Russian Academy of Sciences B. A. Trofimov on his 70th jubilee. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1443–1502, October, 2008.     

Sulfur-directed metal-free and regiospecific methyl C(sp3)–H imidation of thioanisoles

Regiospecific and direct imidation of the methyl C(sp³)–H bond of thioanisoles is realized under mild and metal-free conditions with N-fluorobis(benzenesulfonyl)imide as an oxidant and nitrogen source. Proposed mechanism suggests that thionium ion intermediates and a Pummerer-type reaction are involved. The imidation has advantages such as high step-economy, excellent functionality tolerance, and regiospecificity, giving structurally diverse imidation products.     

A general and convenient synthesis of 4-(tosylmethyl)semicarbazones and their use in amidoalkylation of hydrogen,heteroatom, and carbon nucleophiles

A general synthesis of previously unknown semicarbazone-based α-amidoalkylating reagents, 4-(tosylmethyl)semicarbazones, has been developed. The synthesis involved three-component condensation of semicarbazones of aliphatic or aromatic aldehydes with the same or other aldehydes and p-toluenesulfinic acid. The scope and limitations of this reaction were investigated. The compounds obtained were demonstrated to be an efficient α-(4-semicarbazono)alkylating agents. They were reacted with H- (sodium borohydride), O- (sodium methylate), S- (sodium phenylthiolate), N- (pyrrolidine, sodium succinimide), P- (trialkyl phosphites), and C-nucleophiles (sodium diethyl malonate) to give the corresponding products of the tosyl group substitution, 4-substituted semicarbazones, including analogues of nitrofurazone. Among the prepared compounds tested in vitro for antibacterial and antifungal activity, three nitrofuryl-containing semicarbazones exhibited high biological activities with minimum inhibitory concentration (MIC) values of 8–32 μg/mL.     

Synthesis of novel chiral bidentate hydroxyalkyl-N-heterocyclic carbene ligands and their application in palladium-catalyzed Mizoroki–Heck couplings and asymmetric addition of diethylzinc to benzaldehyde

A small library of new chiral bidentate hydroxyalkyl-imidazolium salts 1 is conveniently synthesized on multi-gram scale from inexpensive and commercially available chiral pool amino acids. The corresponding carbenes, generated by deprotonation of imidazolium salts 1, in combination with palladium(II) chloride were tested in the Mizoroki–Heck coupling reaction. The most significant results in terms of yields and reactivities were achieved with low catalyst loading. The catalytic activities of these imidazolium salts were also investigated in the asymmetric addition of diethylzinc to benzaldehyde. The use of MgO nanoparticles as an additive in conjunction with these ligands played a crucial role in increasing the efficiency of these reactions.