578 resultados para reductive paraphrase


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In natural languages multiple word sequences can represent the same underlying meaning. Only modelling the observed surface word sequence can result in poor context coverage, for example, when using n-gram language models (LM). To handle this issue, this paper presents a novel form of language model, the paraphrastic LM. A phrase level transduction model that is statistically learned from standard text data is used to generate paraphrase variants. LM probabilities are then estimated by maximizing their marginal probability. Significant error rate reductions of 0.5%-0.6% absolute were obtained on a state-ofthe-art conversational telephone speech recognition task using a paraphrastic multi-level LM modelling both word and phrase sequences.

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Strongly reducing organic substances (SROS) and iron oxides exist widely in soils and sediments and have been implicated in many soil and sediment processes. In the present work, the sorptive interaction between goethite and SROS derived from anaerobic decomposition of green manures was investigated by differential pulse voltammetry (DPV). Both green manures, Astragaltus sinicus (Astragalus) and Vicia varia (Vicia) were chosen to be anaerobically decomposed by the mixed microorganisms isolated from paddy soils for 30 d to prepare different SROS. Goethite used in experiments was synthesized in laboratory. The anaerobic incubation solutions from green manures at different incubation time were arranged to react with goethite, in which SROS concentration and Fe(II) species were analyzed. The anaerobic decomposition of Astragalus generally produced SROS more in amount but weaker in reducibility than that of Vicia in the same incubation time. The available SROS from Astragalus that could interact with goethite was 0.69 +/- 0.04, 0.84 +/- 0.04 and 1.09 +/- 0.03 cmol kg(-1) as incubated for 10, 15 and 30 d, respectively, for Vicia, it was 0.12 +/- 0.03, 0.46 +/- 0.02 and 0.70 +/- 0.02 cmol kg(-1). One of the fates of SROS as they interacted with goethite was oxidation. The amounts of oxidizable SROS from Astragalus decreased over increasing incubation time from 0.51 +/- 0.05 cmol kg(-1) at day 10 to 0.39 +/- 0.04 cmol kg(-1) at day 30, but for Vicia, it increased with the highest reaching to 0.58 +/- 0.04 cmol kg(-1) at day 30. Another fate of these substances was sorption by goethite. The SROS from Astragalus were sorbed more readily than those from Vicia, and closely depended upon the incubation time, whereas for those from Vicia, the corresponding values were remarkably less and apparently unchangeable with incubation time. The extent of goethite dissolution induced by the anaerobic solution from Vicia was greater than that from Astragalus, showing its higher reactivity. (c) 2008 Published by Elsevier Ltd.

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In this paper, the photochemical reduction process of Hg (II) in aqueous solution containing ferric iron and oxalate (Ox) has been studied. Under the radiation of a low-pressure mercury lamp (lambda = 253.7 nm, 8W), Fe(III)-oxalate complexes undergo photolysis to produce ferrous ions and other organic reductive species, which reduce Hg(II) subsequently. For 0.1 mg/L Hg (II), the photoreduction efficiency is comparatively higher in the solution at pH 5.0 than that over the range of 3.0 similar to 8.0. The photoreduction efficiency of Ho (II) in aqueous solution increases with increasing, initial concentration of ferric ions from 0.02 mmol/L to 0.2 mmol/L and initial concentration of oxalate from 0.96 mmol/L to 4.8 mmol/L and then gradually approaches to a steady state. CH3OH also contributes the reduction of Hg (II). We investigate the increase of the ferric, oxalate and CH3OH concentrations resulting from the increase of reduction efficiency of Hg (II). It can be seen that ferrous ions and other reactive species are reductants of Hg (II), and the reaction product with oxalate is mainly volatile metallic mercury.

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Vanadium dioxide thin films were fabricated by ion beam sputtering on Si3N4/SiO2/Si after a post reductive annealing process in a nitrogen atmosphere. X-ray Diffraction (XRD), scanning electron microscope (SEM), and X-ray photoelectron spectroscopy (XPS) were employed to analyze the effects of post annealing temperature on crystallinity, morphology, and composition of the vanadium oxide thin films. Transmission properties of vanadium dioxide thin films were measured by Fourier transform-infrared (FT-IR) spectroscopy. The results showed that the as-deposited vanadium oxide thin films were composed of non-crystalline V2O5 and a tetragonal rutile VO2. After annealing at 400 degrees C for 2 h, the mixed phase vanadium oxide (VOx) thin film changed its composition and structure to VO2 and had a (011) oriented monoclinic rutile structure. When increasing the temperature to 450 degrees C, nano VO2 thin films with smaller grains were obtained. FT-IR results showed that the transmission contrast factor of the nano VO2 thin film was more than 0.99 and the transmission of smaller grain nano VO2 thin film was near zero at its switched state. Nano VO2 thin film with smaller grains is an ideal material for application in optical switching devices.

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本文以土壤为介质,以2,4,4′-三氯联苯、2,2′,5,5′-四氯联苯、2,2′4,5,5′-五氯联苯、2,2′,3,4,4′,5-六氯联苯和2,2′,3,4,4′,5,5′-七氯联苯为目标污染物,对钯/铁双金属、微生物及其联合修复多氯联苯污染土壤进行了研究。 对钯/铁双金属还原脱氯多氯联苯的影响因素和动力学进行了研究,研究结果表明:较高的钯化率、反应温度,弱酸性pH条件对脱氯反应有促进作用;在实验所考察的初始浓度范围内,脱氯效果与多氯联苯的初始浓度关系较小;而钯/铁双金属投加量则存在一个适宜值,不宜太高或太低。多氯联苯催化脱氯符合准一级反应动力学。反应速率与多氯联苯初始浓度关系很小;反应速率随钯化率、钯/铁投加量和反应温度升高而增大;初始pH为5.5时反应速率最快。且联苯环上氯取代数越少,越难以脱氯。 从受多氯联苯长期污染的土样中筛选出一株高效降解多氯联苯的细菌(H1),菌株初步鉴定为芽胞杆菌属。在本实验条件下,微生物对土壤中多氯联苯的降解较为适宜的条件为:微生物接种量10%、反应温度在30℃左右、pH在7左右。在此条件下,微生物对PCBs的降解,随初始浓度的增加,降解速率逐渐降;且随氯取代数目的增加,降解率逐渐降低。 采用化学和微生物方法联合修复多氯联苯污染土壤是可行的。经过钯/铁双金属和好氧微生物连续处理后,2,4,4′-三氯联苯和2,2′,5,5′-四氯联苯几乎被完全降解,而2,2′4,5,5′-五氯联苯、2,2′,3,4,4′,5-六氯联苯和2,2′,3,4,4′,5,5′-七氯联苯还原脱氯后生成的低氯代同系物(2,2′,5-三氯联苯)也很容易被微生物所降解。 利用GC-MS对多氯联苯的中间产物及最终产物的分析,推测多氯联苯降解的反应机理为:在钯/铁双金属——水体系中,铁作为还原剂给出电子,水为质子供体。在催化剂钯作用下,H+与铁给出的电子在双金属表面结合,形成具有高反应活性的中间产物——新生态H*。H *攻击多氯联苯取代联苯环上的氯形成脱氯产物和氯离子。反应体系中的溶解氧与溶解铁结合在钯/铁表面形成氧化层,阻碍反应进行。过多的H2气泡也会覆盖活性反应位,对脱氯反应不利。

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胺及其衍生物是很多重要生物活性分子的结构单元,是合成天然产物和手性药物的重要中间体。 直接还原胺化由于其合成步骤简单而成为制备二级胺和三级胺的简便方法。为了发展一种较为简便的直接还原胺化反应,我们把研究的重点放在开发一种简便实用的有机小分子催化方法上。由文献调研可知,现已报道的直接还原胺化方法大多是催化醛或酮与一级胺或者脂肪二级胺的直接还原胺化,而醛或酮与芳香二级胺的直接还原胺化却尚无报道。在本文中,我们发现用简单的四甲基乙二胺(TEMED)在室温下以二氯甲烷为溶剂即可催化三氯氢硅对酮和芳香二级胺之间的直接还原胺化反应,并取得了高达92%的收率。该反应条件温和,底物普适性广,各种类型的酮均可以与芳香二级胺进行直接还原胺化,并且得到比较满意的收率。 同时,我们从手性Sulfoximine出发,设计和合成了一系列的Sulfoximine类新衍生物,并将其应用于间接还原胺化反应中。遗憾的是我们并没有得到预期的不对称催化效果。 Amines and their derivatives are basic structural motifs in natural products and pharmaceuticals and highly versatile building blocks for various organic substrates. Direct reductive amination (DRA) is a convenient method for the preparation of secondary and tertiary amines owing to its operational simplicity. In an effort to develop a simple and convenient procedure for direct reductive amination reaction, we focused our study on search for a mild and efficient organocatalytic system. In the literature, there are many reports concerning DRA between aldehydes or ketones and either primary amines or secondary aliphatic amines. But there are no reports concerning DRA between aldehydes or ketones and secondary aromatic amines. In this study, we have developed a highly practical method for the synthesis of tertiary amines by the direct reductive amination of ketones and secondary aromatic amines with tetramethylethylenediamine (TEMED) as the catalyst using HSiCl3 as the reducing agent in dichloromethane (affording up to 92% yield). This method can be carried out under mild conditions and is compatible with many functional groups. A variety of ketones were efficiently aminated with secondary aromatic amines to afford the corresponding amines in good to excellent yields. Starting from chiral sulfoximine, we designed and synthesized a series of new sulfoximine derivatives and tested their efficiencies as asymmetric organocatalysts for the reduction of imines, which, unfortunately, only exhibited low catalytic activity and enantioselectivity.

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过去十多年,世界手性药物市场需求迅速增长,手性制药工业的发展壮大,已经引起了各国政府、学术界,特别是企业界的高度重视。手性药物中含有大量的手性胺单元,因此研究高效构建手性胺结构单元的方法具有重要的意义和实用价值,而亚胺的不对称还原是合成手性胺最便捷的方法。 手性有机小分子路易斯碱催化三氯氢硅不对称还原亚胺是最近几年才发展起来的一类新的亚胺不对称还原方法。尽管在对映选择性和底物适用范围等方面已经获得了突破性的进展,但是,高性能的路易斯碱催化剂仅局限于N-甲酰氨基酸酰胺一种类型,而且其底物适用范围和催化活性仍不够理想。因此,发展新型催化剂很有必要。 手性硫氧化物作为手性诱导剂的应用已经有数十年的时间,广泛应用在不对称合成及天然产物的全合成中。理论上,硫氧结构单元也可以作为路易斯碱,对硅烷类试剂进行活化,而且硫氧键还有碳氧键难以比拟的先天优势,硫原子自带手性特征,在反应过程中,手性中心离反应位点更近,因此,从手性硫氧化合物出发,极有可能开发出新的高效手性路易斯碱催化剂。最近,Kobayashi和Khiar在亚胺的不对称烯丙基化反应中用手性亚砜活化烯丙基三氯硅烷,获得了较好的ee值,但反应中手性亚砜的用量都需要化学计量以上,因此还不能算做真正意义上的催化剂,进一步的文献调研也未见真正意义上的硫手性有机小分子催化剂。 本文首次成功将硫手性亚磺酰胺衍生物应用于催化三氯氢硅对亚胺的不对称还原,在经过对亚磺酰胺衍生物的多次结构优化,开发出了合成容易,催化活性和立体选择性都很优良,并且有着前所未有的底物普适性的新型手性路易斯碱催化剂。 我们首先尝试将商品化的20mol%叔丁基亚磺酰胺和对甲基亚磺酰胺直接用作催化剂催化三氯氢硅对亚胺的不对称还原,尽管仅获得中等的收率和很低的对映选择性,但证明我们的设计思路是可行的。在此基础上,我们以叔丁基亚磺酰胺为原料和基本骨架,设计合成了一系列的亚磺酰胺类催化剂,通过对催化剂的结构改造,发现当催化剂中存在较强酸性的酚羟基时,催化效果得到大幅提高。随着对催化剂的进一步结构优化,我们找到了一个结构简单,催化效果还不错的催化剂,经过反应条件优化以后,催化反应的收率最高能达到98%,对映选择性最高达93%,并且这个催化剂的底物适应范围比之前报道的催化剂都要广泛。针对酚羟基在催化剂中的重要作用,我们进行了仔细的机理研究后发现,在催化反应中,催化剂极有可能是通过双分子机理去活化三氯氢硅从而实现不对称催化的,而酚羟基的作用就是通过分子间氢键促进双分子催化剂与三氯氢硅的络合。受此启发,我们设计了一系列具有双齿结构的催化剂,通过对双齿催化剂的结构优化,最终筛选出了一个结构更加简单,但催化效果更好的双齿催化剂。10mol%该催化剂催化亚胺还原最高获得95%的收率和96%的ee值。这一结果也进一步验证了我们先前对催化剂机理的推测。 随后,我们还尝试将这些催化剂用于二级胺和芳香酮的直接还原胺化反应中,虽然能获得不错的收率,但对映选择性却很差,我们对反应条件进行了仔细的摸索,仍然没有获得突破。但这些实验为进一步研究二级胺和酮的不对称直接还原胺化反应奠定了良好的基础。 In the past decade, the rapid growth of the global chiral drug market and the significant development of the chiral pharmaceutical industry have attracted a great deal of attention from government, academia and enterprises. Chiral amine is an important structural motif of chiral drugs. Therefore, development of methods for the construction of this motif is of great importance. Catalytic enantioselective reduction of imines represents one of the most straightforward and efficient methods for the preparation of chiral amines. The chiral Lewis base organocatalysts promoted asymmetric reduction of imines by HSiCl3 has recently achieved significant advancements. Although big breakthroughs have been made in terms of substrate generality and enantioselectivity, the highly effective catalysts are limited to N-formyl amino acid amides, of which the efficiency and substrate scope remain unsatisfactory. Therefore, development of novel organocatalysts for this transformation is in great demand. Chiral sulfoxides have been well established as efficient and versatile stereocontrollers and have been extensively used in asymmetric synthesis and total synthesis of natural products. The S=O structural motif of sulfoxide could also behave as Lewis base activator for cholorsilane reagents, which, moreover, could be even better than caboxamide considering that the sulfur atom is chiral and thus the chirality center is closer to the reaction center. There exist great potentials that highly effective novel Lewis base organocatalysts could be developed starting from S-chiral sulfoxides. Recently, several S-chiral sulfoxides were reported by Kobayashi and Khiar to be used as Lewis base catalyst to activate allyltrichlorosilanes in asymmetric allylations and good enantioselectivities were obtained. However, these S-chiral sulfoxides were all used at a more than stoichiometric amount and were thus not authentically catalytic. A careful literature survey further revealed that there has been so far no S-chiral organocatalyst available. In this study, we, for the first time, successfully used S-chiral sulfinamides as Lewis base organocatalysts for the asymmetric reduction of ketimines by HSiCl3. After several rounds of structural optimization, we developed the first example of highly effective S-chiral organocatalysts, which promoted the asymmetric reduction of ketimines with trichlorosilane in high yield and excellent enantioselectivity with unprecedented substrate spectrum. In our initial practice, we examined 20mol% of the commercially available (R)-tert-butanesulfinamide and (S)-toluenesulfinamide as the catalyst in the hydrosilylation of ketimine. Although the product was only furnished in moderate yield and low ee, these results demonstrated that our strategy of catalyst design is on the right way. Next, starting from chiral tert-butanesulfinamide, we prepared a series of tert-butanesulfinamide derivatives via simple reductive amination and examined their catalytic efficiencies in the reduction of ketimine. We found that the catalyst bearing a phenolic hydroxyl group exhibited good reactivity and enantioselectivity. On the basis of which, we obtained a structurally simple and highly effective novel organocatalyst, affording the product in 98% yield and 93% ee under optimal reaction conditions. After careful exploration on the role of phenolic hydroxyl group in the catalyst, we speculated that two molecules of the catalyst be involved in the course of reaction, of which the assembly around the silicon center is facilitated by the intermolecular hydrogen bonding through the phenolic hydroxyl groups. Thus, we incorporated two units of sulfonamide into one molecular and prepared a new type of bissulfinamides organocatalysts and examined their catalytic efficiencies in the reduction of ketimine. After optimizing the structure of these catalysts, we finally obtained a novel organocatalyst which has even simpler molecular structure but showed better efficacies, 10mol% of which afforded up to 97% yield and 96% ee under optimal reaction conditions. These results further proved our speculation about the catalytic mechanism. We also examined the newly developed S-chiral organocatalysts in direct asymmetric reductive amination of secondary amines with aromatic ketone. The product was furnished in good yield but in low ee. No better results could be obtained despite our intense opimization efforts. Nevertheless, these experiments laid excellent foundations for eventual success.

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维生素(Vitamin)又称维他命,为“万年青”产品,是维持人体生命健康必需的一类低分子有机化合物质。维生素对人体健康的作用人们研究很多, 维生素可以增强人体对感染的抵抗力,降低出生缺陷及降低癌症和心脏病发病率等,一旦缺乏,肌体代谢就会失去平衡,免疫力下降,各种疾病,病毒就会趁虚而入;而维生素对作物影响的研究却很少。目前为止,尚无对用维生素浸种的方法来研究外源维生素是否对小麦种子萌发及幼苗生长起调节作用的报道,且对其在小麦抗逆性方面影响的研究甚少,对盐的胁迫抗性研究尚未有人报道。小麦(Triticum aestivum L.)属于拒盐的淡土性作物。盐害不利于小麦生长,严重影响小麦的产量和品质。本研究采用4 种不同维生素VB1、VC、VB6、VPP,分别对供试小麦品种川育12(红皮)、川育16(白皮)小麦浸种后,在一般自然条件下和逆境(盐胁迫条件)下,进行试验。探讨在正常情况下与在不同盐浓度条件下,各维生素及盐浓度对小麦发芽及幼苗生长的影响,并且比较两种不同皮色的小麦在相同盐胁迫条件下的差异表现,同时研究维生素处理的特异性,且哪种维生素对盐害缓解作用最佳。研究结果表明:在无盐胁迫(自然)条件下,对用4 种不同维生素VB1、VC、VB6、VPP 浸种小麦川育12、川育16 后的种子萌发及幼苗生长(幼苗的根长、根重、苗高、苗鲜重)的研究结果表明:4 种外源维生素浸种均对小麦发芽有调节作用,都能提高其最终发芽率。但是提高幅度有所差异。用VB6 浸种后的小麦提高幅度最多,VC 次之,VPP 提高幅度最小。同时,4 种外源维生素浸种对小麦种子的出芽速度及芽后长势也有一定的影响。VB6、VC 处理的小麦种子出芽速度最快,萌发后长势最好;VB1 出芽速度相对较慢,VPP 最慢,但都大于对照;VB1 处理长势略高于对照,VPP 处理的小麦长势则低于对照。从整体来看,VB6、VC处理促进效应明显, VB1 次之,而VPP 在某些方面无效甚至产生负效应。此外,相同的维生素处理对不同的品种的种子萌发、生长效果也存在差异,各种维生素作用于川育12 的效应均强于对川育16。进一步对幼苗根系TTC 还原力及幼苗叶片中硝酸还原酶活性进行测定、分析。研究发现:并非所有种类的维生素对幼苗根系TTC 还原力及幼苗叶片中硝酸还原酶活性的提高都有帮助。幼苗根系TTC 还原力在不同维生素处理下存在显著差异,而与小麦品种关系甚微。经VB6、VC 处理后,根系TTC 还原力测定值均显著高于对照,VB1 不明显,VPP 则略低于对照。VB6、VC 处理的幼苗叶片中硝酸还原酶的含量大于对照,VB1 与对照相差无几,而VPP 处理的川育12 幼苗叶片中的硝酸还原酶活性比对照CK 略高,而在川育16 中则略比对照CK 有所下降,呈现出抑制效应。综上结果表明:VB6、VC 具有促进种子发芽,幼苗生长及根系生长的作用,是较好的促生长剂;VPP 具有抑制作用,是较好的抑制剂,可进一步研究、开发利用。在盐胁迫条件下,对用4 种不同维生素VB1、VC、VB6、VPP 浸种川育12、川育16 后的种子萌发及幼苗生长(幼苗的根长、根重、苗高、苗鲜重)的研究结果表明:在不同盐浓度胁迫条件下, 各处理的种子萌发及幼苗生长均受到不同程度的抑制。随着盐浓度的增加, 发芽率、发芽指数和活力指数成下降趋势;幼苗的根长、根重、苗高、苗鲜重不断降低。4 种维生素处理间也表现出较大差异。VB6、VC 在每个处理中均保持对盐害的缓解作用,VB6 较VC 更易于促进发芽及幼苗生长。最终发芽率高,根系多、长、重,苗高高、重。而VB1、VPP 则表现出抑制作用。在高盐浓度150mM 时,4 种维生素浸种后的种子,其最终发芽率均不能达到40%,但VB6、VC 处理最终发芽率、苗重、根重均高于对照,VPP 最终发芽率、苗重、根重均低于对照。进一步对幼苗根系TTC 还原力及幼苗叶片中脯氨酸含量进行测定、分析。研究发现:不同盐浓度,不同维生素处理、不同品种间存在差异。随着盐浓度的增加(75mM,100mM,150mM),幼苗根系TTC 还原力活性成下降趋势,幼苗叶片中脯氨酸的积累量成上升趋势。VB6 处理脯氨酸含量增加最为明显,VC 次之,VPP 与对照接近,其变化幅度最小。经VB6、VC 处理后的幼苗根系还原强度,在不同盐浓度下,测定值均显著高于对照,VB1 不明显,VPP 则低于对照,产生负效应。此外,品种间表现不尽相同,相同的维生素处理,相同的盐浓度对不同的品种的种子萌发、生长效果也存在差异, 4 种维生素对川育16 的作用均强于川育12,但其影响趋势是一致的。说明VB6、VC 具有耐(抗)盐性,可以促进种子发芽和幼苗生长,是较好的耐(抗)盐拌种剂。 Vitamin is one kind of necessary low molecular compound for humans tosustain health and life. Lots of Studies have been done on the effectc of the vitaminsfor people. Vitamin can help people improve the body's natural resistance to disease,Drop the rate of birth defects、cacers and the incidence of the heart diseases. Ifpeople have less of them, the metabolism of the organism may throw off balance,immunity may drop off, and catch disease; Though the effects for Vitamin to thecrops are limited. up to now, there’s no one use soking seeds of wheats with vitaminsas a method, to study on how the effects will happen on the wheat seed germinationand seedling growth, and there are only few reserches on antireversion force forwheats ,none for the antireversion force in Sault stress condition.Wheat(Triticum aestivum L.)is sensitive to the salt, so the salt damage will doharm to wheat’s growth, it will have an unfavorable impact on the output and thequality of wheat.On this reaserch, we Soaking CHY12(red)、CHY16 (white) wheat seeds withVitamin C, B1, PP, B6 (50mg/L) as a pretreatment first. Then under two condition: one is in the normal environment the other is in different Salinity, we begin ourexperiments. Then disscuss on if the vitamin and salinity affect the wheat seedgermination and seedling growth, and what is the different between the two of them,the result shows that:Under the normal condition, after soaking seeds with VB1、VC、VB6、Vpp,we study on the their seed germination and the seeding growth(the root length andweights, The seedling heights and weights), it shows that all of those four kinds ofvitamin can adjust the seed germination, but different in The growth rate. VB6 isbest for increase, VC comes second,VPP is the worst. Meanwhile, those four vitaminalso have effect on the speed of the sprouting of the wheat. VB6、Vc can faster theseed germination most, and the seedlings are all doing well; VB1 do little effects onthe budding, Vpp is the worst, but all treatments are better than CK; but in Vi, VB1some what above the CK, while VPP lower than that. On the whole, the acceleratingeffect of VB6、VC are obvious, VB1 takes second place, but VPP in some aspects arenoneffective even have negative effect. Furthermore, different kind of seeds with thesame vitamin may different in seed germination and seedling growth, four vitaminson CHY16 is better than CHY12.More studies on TTC reductive capacity of roots and the activity of nitratereductase in the leaves, the reasult shows not all the vitamin can help the seedlings toimprove the TTC reductive capacity and the activity of nitrate reductase. TTCreductive capacity in different treatments shows significant differences,but notcorrelate to the variety of the wheat. The TTC reductive capacity of VB6、Vctreatments are all higher than CK, VB1 is nearly the same as CK, VPP is a littlelower than CK. Through the study of acivity of nitrate reductase, it shows that,VB6、VC are higher than CK ,VB1 is nearly the same as CK also, VPP is a little higher inthe CK of CHY12 but lower in CHY16. Through all the results above: VB6、Vc helpthe wheat seed germination, seedling growth and the growth of roots, is theperfectable factor of stimulating the growth; Vpp is a inhibition, that’ll be furtherreserch,and well develop and utilize in the future.Under the different Salinity condition, after soaking seeds with VB1、VC、VB6、Vpp,we study on the their seed germination and the seeding growth(the root lengthand weights, The seedling heights and weights), it shows that: under differentsalinity, the seed germination and the seedling growth of any treatment are inhibited.With the increase of the concentration, the germination rate, Vi、Gi all had fallen; theroot length and weight, the seedling heights and weights steadily sank down. There are also have pronounced difference between all treatments with four differentvitamins.VB6、VC in all treatments are alleviative the salt damage, VB6 is easier tocause to put forth buds than VC, and it’s quantitative value is the highest in theultimate germination rate, in root and seedlings’ hight and weight. Though the VPP、VB1 are seems to inhibite its growth. Under the high concentration150mM Nacl, theultimate germination rate in all treatments are below the 40%, but VB6、VC’squantitative values in any experiments are higher than CK,while VPP lower thanCK.Then we study on the TTC reductive capacity of roots and the content of Polinein leaves, the result shows that between the different salinity, different vitamintreatments, different varieties of the wheat have discrepancy.along with theincreasing concentraion of the salinity(75mM,100mM,150mM),TTC reductivecapacity of roots decreases, the accumulation of the content of Poline in leaves havean upward trend. The increase of VB6’s treatment are obviously, VC comessecond,VPP is nearly come up with CK, changes a little. In TTC reductive capacity of roots’s reserch, VB6、VC are higher than CK at any time,VB1 is not palpable,VPP is lower than CK, makes negative affect on wheat. In addition, varieties of thewheats are remain different, no matter it shows promoting or inhibiting, all fourvitamins have moreobvious effects on CHY16 than CHY12, but the tendency of theeffection are the same. It is say that VB6、VC can help wheat to standwith the saultwell, and promot in growth,they are the better reagent to mix with the seed.

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A series of commercially useful substituted pyridyl ureas have been synthesized via selenium dioxide-catalyzed reductive carbortylation of substituted nitrobenzene or substituted nitropyridine with amine as co-reagent and carbon monoxide as carbonyl reagent instead of phosgene in one-pot reaction. The recycling reusability of catalyst was also tested. It was also found that selenium dioxide-catalyzed reductive carbonylation of nitroaromatics exhibited reaction-controlled phase-transfer phenomena of the catalyst. (C) 2003 Elsevier B.V. All rights reserved.

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A series of cobalt-free and low cost perovskite oxygen permeable membranes based on BaCexFe1-xO3-delta (BCF) oxides was successfully synthesized and the membrane showed both high oxygen permeability and high stability under reductive atmosphere, which will be most suitable for constructing a membrane reactor for selective oxidation of light hydrocarbons to syngas or high value corresponding oxygenates.

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C-6-carboxylated chitosan obtained by oxidation of chitosan was selectively modified in order to obtain derivatives similar to bacterial antigens. Selective O-acetylation of 6-carboxyl chitosan afforded a modified polysaccharide with the 2-amino group available for further modifications to create carbonyl groups. A deaminative degradation reaction allowed the formation of oligosaccharides with terminal aldehyde groups. Reductive alkylation with lactose introduced lactityl branches which were oxidized with galactose oxidase to give aldehyde groups in its -galactose residues.

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The reaction mechanism of the Pd(0)-catalyzed alkyne cyanothiolation reaction is investigated by MP2, CCSD(T) and the density functional method B3LYP. The overall reaction mechanism is examined. The B3LYP results are consistent with the results of CCSD(T) and MP2 methods for the isomerization, acetylene insertion and reductive elimination steps, but not for the oxidative addition step. For the oxidative addition, the bisphosphine and monophosphine pathways are competitive in B3LYP, while the bisphosphine one is preferred for CCSD(T) and MP2 methods.

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During the reaction of reduced C-60 with benzyl bromide in benzonitrile, a novel cis-1 C-60 adduct, 1,4-dibenzyl-2,3-cyclic phenylimidate C-60 (1), Was obtained rather than the expected product of 1,4-dibenzyl C-60. The structure of compound 1 was analyzed by X-ray single-crystal diffraction, identifying the presence of a five-membered heterocycle at a [5,6] bond of C-60. One of the heteroatoms is assigned as a nitrogen atom; however, the identity of the other heteroatom cannot be determined unambiguously by crystallography due to similarity between the nitrogen and oxygen atoms.

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We reported a simple and effective green chemistry route for facile synthesis of nanowire-like Pt nanostructures atone step. In the reaction, dextran acted as a reductive agent as well as a protective agent for the synthesis of Pt nanostructures. Simple mixing of precursor aqueous solutions of dextran and K2PtCl4 at 80 degrees C could result in spontaneous formation of the Pt nanostructures. Optimization of the experiment condition could yield nanowire-like Pt nanostructures at 23:1 molar ratio of the dextran repeat unit to K2PtCl4.