997 resultados para HD5014 .N3


Relevância:

10.00% 10.00%

Publicador:

Resumo:

采用全相对论扭曲波方法,系统地计算了类N3+和O4+离子从基态到2s2p和2p2的各激发态以及从亚稳态到2p2各激发态的电子碰撞激发截面,详细地讨论了靶态的关联效应对激发截面的影响.结果表明:对于2s-2p的单电子激发,在低能碰撞时,靶态的电子关联效应起非常重要的作用,且使得激发截面降低;而高能碰撞时,靶态波函数的描述对连续态波函数的影响比较小,对激发截面影响也比较小.对于2s2-2p2的双电子激发,其中基态2s21S0到J=0的2p23P0,1S0的激发截面较大,其主要原因是末离子态波函数与基组态波函数的混合,但是其他几个激发的激发截面较小.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

针对污染地表水的特点,从辽河油田受石油污染的缓流河床底泥中筛选出一株能有效去除CODCr的微球菌(Micrococcussp.N3-9P),并对其进行了化学包埋法固定化.通过实验,确定了改进的聚乙烯醇-海藻酸钠共固定工艺配方(质量分数)聚乙烯醇10.5%,海藻酸钠0.5%,活性碳3%及微量生长素,优化了过程控制参数.地表水修复实验表明,96h后固定化颗粒对污染地表水中CODCr的去除率为70.9%,明显高于游离菌的33.6%.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

A series of single-component cobalt salen complexes, N,N'-bis(salicylidene)-1,2phenylenediamino cobaltIII X(X = Cl (1a), Br (1b), NO3 (1c), CF3COO (1d), BF4 (le), and N3 (If)) (SalphCoX), were prepared for alternating copolymerization of carbon dioxide and propylene oxide(PO) under mild condition. The axial anion X group of the SalenphCoX played important role in tailoring the catalytic activity, polymeric/cyclic carbonate selectivity, as well as stereochemistry of carbonate unit sequence in the polymer chain. SalenphCoX with an electron-withdrawing axial X group (complex 1c) was an ideal catalyst for the copolymerization of CO2 and PO to selectively produce polycarbonate with similar to 99% carbonate linkage and over 81% head-to-tail structure.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

一种素食者食用的调和油是由富含饱和脂肪酸的油脂、富含单不饱和脂肪酸的油脂、富含N6系列多不饱和脂肪酸的油脂、富N3系列多不饱和脂肪酸的油脂在10~60℃条件下调和而成,调和油中脂肪酸的重量百分含量为饱和脂肪酸25~30wt%,单不饱和脂肪酸33~39wt%,多不饱和脂肪酸33~39wt%,其中N6系列多不饱和脂肪酸29~33wt%N3系列多不饱和脂肪酸wt5~8%,并N3、N6系列不饱和脂肪酸重量比例为1:4~6。本发明具有价格低廉,营养均衡,脂肪酸比例协调,适合素食者食用的优点。

Relevância:

10.00% 10.00%

Publicador:

Resumo:

The interaction of antitumor antibiotic, echinomycin (Echi) with guanine (Gua) was thoroughly investigated by adsorptive transfer stripping cyclic voltammetry, ultraviolet and visible adsorption spectra (UV/Vis) and Fourier-transform infrared spectroscopy (FTIR). Electrochemistry provided a simple tool for verifying the occurrence of interaction between Echi and Gua. Echi could be accumulated from the solution and give well-defined electrochemical signals in 0.1 M phosphate buffer solution (pH 7.0) only when Gua was present on the surface of the electrochemically pretreated glass carbon electrode (GCE), suggesting a strong binding of Echi to Gua. All the acquired spectral data showed that a new adduct between Echi and Gua was formed, and two pairs of adjacent intermolecular hydrogen bonds between the Ala backbone atoms in Echi and Gua (Ala-NH to Gua-N3 and Gua-NH2 to Ala-CO) played a dominating role in the interaction. Electrochemistry coupled with spectroscopy techniques could provide a relatively easy way to obtain useful insights into the molecular mechanism of drug-DNA interactions, which should be important in the development of new anticancer drugs with specific base recognition.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Oxochromium (V) tetraphenylporphyrin complexes, O = Cr (V) TPP (Cl) PhI. O = Cr-(V) TPP (N3) PhI and O = Cr (V)TPP (p-CH3OC6H4O)1/2PhI were isolated from the reaction of Cr (III) TPP (Cl). Cr (III) TPP (N3) Py or Cr (III) TPP (p-CH3OC6H4O) THF with iodosy

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Linxia Basin, situated in the northeast belt of the Tibetan Plateau, is a late Cenozoic depression basin bounded by the Tibetan Plateau and the Chinese Loess Plateau. The Cenozoic deposition, spanning over 30Ma, in which very abundant mammal fossils were discovered, is very suitable for study of uplift processes and geo-morphological evolution of the Tibetan Plateau. The Longdan section (35°31′31.6″N,103°29′0.6″E) is famous for the middle Miocene Platybelodon fauna and the late Miocene Hipparion fauna for a long time and is also one of the earliest known places for wooly rhino, which lies on the east slope of Longdan, a small village of township Nalesi in the south of the Dongxiang Autonomous County, Linxia Hui Nationallity Autonomous Prefecture. The Longdan mammal fauna was discovered at the base of the Early Pleistocene loess deposits at Dongxiang, where the lithology is different from the typical Wucheng Loess on the Chinese Loess Plateau. The rich fossils contain many new species and the major two layers of fossils are in the loess beds. Geologically the fossiliferous area is located in the central part of the Linxia Cenozoic sedimentary basin. Tectonically the Linxia Basin is an intermountain fault basin, bordered by the Leijishan major fault in the south and the north Qinling and Qilianshan major faults in the north. The section is 51.6m thick above the gravel layer, including the 1.6m Late Pleistocene Malan Loess on the top and the other loess-paleosol sequences in the middle of the section. The base of the section is the Jishi Formation, consisting of gravel layer of 13 ~ 17m thick. In this study, 972 bulk samples were collected with an interval of 5cm and other 401 orientied samples were taken with a magnetic compass. In the laboratory, the paleomagnetism, medium grain size, susceptibility, color, micromorphology, anisotropy of magnetic susceptibility were analyzed. From the stratigraphic analysis, the Longdan section from the top 0.3m to the bottom 51.6m, containing 5 normal polarities (N1-N5) and 5 reversal polarities (R1-R5). The paleomagnetic results show N3 is the Olduvai subchron in the middle of the Matuyama chron, and then the chronology of the Longdan mammal fauna is constructed along the section. The Matuyama-Gauss boundary is 45m and N5 enters Gauss chron. The Olduvai subchron with the age of 1.77 ~ 1.95Ma is found just in the upper fossiliferous level of Longdan mammal fauna. Taking the deposit rate of the section into account, the geological age of the upper fossiliferous level of Longdan mammal fauna is estimated to be about 1.9Ma. The lower fossiliferous level is just below the Reunion subchron and its age is estimated to be 2.25Ma. In addition, anisotropy of magnetic susceptibility of the loess-paleosol and other climatic indexes were used for discussing the late Cenozoic paleoenvironmental changes at Longdan, from which the Longdan area should have been an area of predominantly steppe the same as the Longdan mammal fauna.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

运用MINTEQ 化学平衡软件对巢湖、龙感湖中溶解态稀土的形态进行模拟。模拟结果表明, 在巢湖和龙感湖中Ln (CO3) 2- , LnCO3+ 是溶解态稀土的最主要的存在形式, 当8 > pH > 7. 19 时, REE 主要以LnCO3+ 形式存在, 当pH > 8 时, REE 主要以Ln (CO3) 2- 形式存在, 并且ΣLn (CO3) n3 - 2 n ( n = 1 和2) 形态的稀土基本上占溶解态稀土总含量的93 %以上。Ln3 + 在巢湖和龙感湖水体中平均丰度为5. 03 % , Ln3 + 的丰度和pH 值成反相关关系。LnPO4 在湖水中平均丰度为1. 61 % , 但这种形式的稀土在巢湖和龙感湖中非常重要。巢湖和龙感湖中LREE 的LnPO4 均处于过饱和状态, 甚至巢湖西半湖区丰水期HREE 的LnPO4 的也都处于过饱和状态, PO43 - 对稀土的存在有很强的限制作用。LnSO4 , LnF2 + , LnOH2 + , LnCl2 + 等形态的各元素平均丰度均小于1 % , 在富营养化的淡水中通常可以忽略不计。

Relevância:

10.00% 10.00%

Publicador:

Resumo:

随着人口数量的急剧膨胀和工业化、城市化进程日益加快,水环境问题成为一个令人关注的全球性问题。众所周知,人类可利用的淡水有90%以上集中在湖泊中,而湖泊自身的自然特征使其成为一个极易受到污染的水体,一旦污染,治理与恢复将是一项困难且耗时的工程。虽然这一问题已经引起人们的高度重视,但相关的研究仍然滞后。人们至今还无法彻底弄清楚污染物在湖泊水体中是如何迁移转化的,污染物又如何的发生自净化作用,又会在什么样的条件下对湖泊产生二次污染等一系列问题。但人们逐渐认识到悬浮颗粒物在污染物的产生、迁移、沉淀过程中扮演了重要角色,因此水/粒相互作用过程成为研究污染物在湖泊中环境行为特征的关键课题。 稀土元素(REEs)由原子序数57~71的镧系元素(La~Lu)和39号元素Y组成,因其具有非常相似但又有细微差别的特殊化学性质,被广泛用来示踪各类地球化学过程。由于稀土元素在地球化学过程中的变化是随原子序数的增加而连续变化的,它比单个微量元素示踪体系有更好的示踪性。同时, REE对水/粒相互作用过程的响应比较敏感,这是因为稀土元素在水体中主要以胶体方式存在,易于被吸附或解吸,在这个过程中,轻重稀土元素又因它们的吸附及络合行为不同而发生分异,所以表生水体中的稀土元素还具有明显的过程特征,可以用来示踪水体的水/粒相互作用过程。 本项研究的主要目的是通过对湖泊中稀土元素的地球化学行为研究,认识元素在湖泊水体中的水粒相互作用过程,了解它们在水体中的分布特征以及存在形式,并对比不同特征湖泊中稀土元素的地球化学迁移过程,为有关水环境的治理及决策提供科学依据。通过对稀土元素的萃取方法和太湖、巢湖、龙感湖、红枫湖、阿哈湖五个不同湖泊及其周边河流中水化学和稀土元素的研究,得出以下初步结论: 1.从有机膦萃取稀土实验来看,pH是影响有机膦萃取效率的主要因素。实际环境体系中,各种物理、化学参数均不相同,针对不同的表生水体需要调到特定的pH值才能得到最佳的萃取效果。 2.红枫湖和阿哈湖的溶解态稀土平均含量低于世界平均淡水的稀土含量,红枫湖为18.2ng/kg,阿哈湖为6.5ng/kg。太湖、巢湖、龙感湖的溶解态稀土平均含量较高,分别为74. 7ng/kg、104.8ng/kg、64.8ng/kg。环太湖河流丰水期和枯水期溶解态稀土的平均含量分别为649.2ng/kg、35.0ng/kg。丰水期河流的溶解态稀土浓度普遍比枯水期浓度高50%-100%,但合溪和城南河高出110倍和46倍,显然严重的污染导致了这一结果。 3.红枫湖及环红枫湖河流、阿哈湖、太湖流域水体的稀土配分模式为重稀土富集型,但合溪、直湖港、望虞河、胥江、横泾塘、太浦运河和阿哈湖入湖游鱼河等七条河流呈现出有趣的中稀土富集模式。巢湖和龙感湖溶解态稀土为平坦型的配分模式。巢湖稀土元素在丰水期和枯水期的分异在整个湖泊中具有规律性:从西到东(La/Yb)SN值逐渐增大,即轻稀土的相对含量逐渐增高。藻类的吸收作用可能是造成这种现象的主要原因。同时说明,轻稀土可能是促进藻类生长的“催化剂”之一。 4.红枫湖及环红枫湖河流和阿哈湖水体溶解态Ce出现负异常,氧化还原作用是产生这种现象的主要原因之一;化学风化作用可能是红枫湖发生Ce异常现象的另一原因。太湖、巢湖、龙感湖中δCe值约为1,主要原因是四价铈在强的水动力条件下无法通过颗粒物的净化作用而除去,它们仍然以细微颗粒物或胶体的形式保留在水体中。 5.颗粒物含量和pH是控制水体中稀土含量的重要因素。在龙感湖和巢湖,稀土元素的含量均随着pH值的增大而减小;但颗粒物在这两个湖泊中对水体中的溶解态稀土表现出不同的吸附解吸作用。而太湖、红枫湖、阿哈湖这样高碱度水体中,HCO3-通过平衡反应和络合竞争作用使得H+的调节功能和颗粒物的吸附解吸作用大大削弱。 6.碳酸根的络合作用是造成太湖流域、红枫湖流域、阿哈湖水体中稀土元素呈重稀土富集型的主要原因。而水体中细微胶体过多,使得巢湖和龙感湖水体中稀土元素呈现出平坦型的稀土配分模式。阿哈湖入湖河流的中稀土富集现象则反应了矿山开采导致入湖水体受到污染的事实,而太湖周边河流丰水期的中稀土富集则说明了地表径流向河流中输入了大量有机污染物产生的影响。 7.在碱性或中性水体中,Ln(CO3)n3-2n是REE无机络合物中的主要存在形式,五个湖泊流域的平均含量在90.6%-99.8%之间。并且∑Ln(CO3)n3-2n所占的比例越高,其重稀土富集程度也就越高。在富营养化水体中,LnPO4形态稀土含量在1.00%-8.31%之间,LnPO4通常处于过饱和状态,并以无定形沉淀和胶体态的形式保留在水体中。PO43-对水体中溶解态稀土的存在有着很强的限制性作用,反过来颗粒物及胶体上的稀土也可能通过共沉淀作用影响水体中溶解态PO43-的含量。 8.模拟显示在DOC含量高的水体中,稀土有机络合形态将取代碳酸盐的络合形态占主导地位。从整个稀土序列来看,无论是随着溶解有机质浓度还是pH的变化,稀土的有机络合形态的均呈现总体自轻稀土向重稀土增加的趋势,但自Eu至Dy中稀土部分呈现一个上凸的趋势,显示了中稀土与溶解有机质较强的络合作用。 9.悬浮颗粒物相态提取研究结果显示:①铁锰氧化物相富集轻稀土(和中稀土),AEC态更多地富集中稀土,而有机相则明显优先富集重稀土和中稀土,残渣相则大多显示近似平直的类似于页岩的稀土配分模式;②从各相态中相对比例来看,基本的递减顺序为残渣相≥铁锰氧化物相>AEC态和有机结合态。悬浮物携带的稀土中,30%或更少是潜在生物有效的。但是,这个比例对不同的元素和不同的湖泊变化很大。从湖泊颗粒物的相态提取分析,悬浮颗粒物是重金属类物质的主要迁移介质,在迁移和归宿的模式中仍然必须加以考虑。③从颗粒物中稀土元素赋存形态和配分模式,可以精确的示踪水体中的物质来源,并可以对水体中颗粒物的组成进行预测和判断。④由于水体污染程度越重,轻重稀土相对比例在不同相态中变化越明显,残渣态稀土的所占相对比例越小,因此颗粒物中不同形态稀土的相对比例可以作为判断水体的污染轻重的新标准,并可以进行污染负荷量趋势的常规评价。

Relevância:

10.00% 10.00%

Publicador:

Resumo:

The Coulomb explosion of ammonia clusters induced by nanosecond laser at 532 not with an intensity of similar to 10(12) Wcm(-2) has been studied by time of flight mass spectrometry. The dominant multiply charged ions are N3+ and N2+ with kinetic energies of 110 and 50 eV respectively. The electrons generated from the multiphoton ionization are heated through inverse bremsstrahlung by the laser field when colliding with neutral or ionic particles. When their energies surpass the corresponding ionization potentials of the molecules or ions, the subsequent electron impact ionization may take place thus resulting in multi-charged nitrogen ions. Covariance analysis is made to study the possible pathways of the Coulomb explosion.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

This paper investigates the power of genetic algorithms at solving the MAX-CLIQUE problem. We measure the performance of a standard genetic algorithm on an elementary set of problem instances consisting of embedded cliques in random graphs. We indicate the need for improvement, and introduce a new genetic algorithm, the multi-phase annealed GA, which exhibits superior performance on the same problem set. As we scale up the problem size and test on \hard" benchmark instances, we notice a degraded performance in the algorithm caused by premature convergence to local minima. To alleviate this problem, a sequence of modi cations are implemented ranging from changes in input representation to systematic local search. The most recent version, called union GA, incorporates the features of union cross-over, greedy replacement, and diversity enhancement. It shows a marked speed-up in the number of iterations required to find a given solution, as well as some improvement in the clique size found. We discuss issues related to the SIMD implementation of the genetic algorithms on a Thinking Machines CM-5, which was necessitated by the intrinsically high time complexity (O(n3)) of the serial algorithm for computing one iteration. Our preliminary conclusions are: (1) a genetic algorithm needs to be heavily customized to work "well" for the clique problem; (2) a GA is computationally very expensive, and its use is only recommended if it is known to find larger cliques than other algorithms; (3) although our customization e ort is bringing forth continued improvements, there is no clear evidence, at this time, that a GA will have better success in circumventing local minima.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

The research described in this thesis involved the chemistry of borane-species which contain one or more halide or pseudohalide groups. Both monoboron species e.g. [BH3X]- and "cluster" borane species e.g. [B10H9X]2- and I-Se B11H10 were studied. The first chapter is a review of the syntheses, properties and reactions of halide and pseudohalide species containing from one to ten boron atoms. Chapter Two is a theoretical investigation of' the electronic and molecular structures of two series of boranes i. e. [BH3X]- and [B10H9X]2- where X = H, CI, CN, NCS, SCN and N3. The calculational method used was the Modified Neglect of Differential Overlap (MNDO) method of Dewar et al. The results were compared where possible with experimental results such as the X-ray crystallographically determined structures of [BH3CI]- and [B10H10]2-. Chapter Three concerns halogenated selenaborane clusters and reports an improved synthesis of 12-Br-SeB11H10 and the first structural data for a simple non-metal containing selenaborane cage with the X-ray crystallographically determined structure of 12-1-SeB11H10. Finally, an indepth n.m.r. study of Se2B9H9 is also reported together with attempts to halogenate this compound. The last two chapters are based on single boron systems. Chapter Four concerns the synthetic routes to amine-boranes and -cyanoboranes from [BH4]- and [BH3CN]- substrates. This chapter discusses some difficulties encountered when polyamines were used in these reactions. The characterisation of an unusual ketone isolated from some of these reactions, the X-ray crystallographically determined structure of 4-dimethylamino-pyridine-cyanoborane and a new route to pyrazabole dimeric species are also discussed. The final chapter reports on work carried out at producing BH2X (X = H, CN) adducts of aminophosphines. Three routes were attempted to generate P-B and N-B bonded species with varying degrees of success. Some unusual products of these reactions are discussed including [Ph2(O) PPPh2 ] [Ph2NH]2, the structure of which was determined by X-ray crystallography.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

The global increase in atmospheric carbon dioxide concentration is potentially threatening marine biodiversity in two ways. First, carbon dioxide and other greenhouse gases accumulating in the atmosphere are causing global warming1. Second, carbon dioxide is altering sea water chemistry, making the ocean more acidic2. Although temperature has a cardinal influence on all biological processes from the molecular to the ecosystem level3, acidification might impair the process of calcification or exacerbate dissolution of calcifying organisms4. Here, we show however that North Atlantic calcifying plankton primarily responded to climate-induced changes in temperatures during the period 1960–2009, overriding the signal from the effects of ocean acidification. We provide evidence that foraminifers, coccolithophores, both pteropod and nonpteropod molluscs and echinoderms exhibited an abrupt shift circa 1996 at a time of a substantial increase in temperature5 and that some taxa exhibited a poleward movement in agreement with expected biogeographical changes under sea temperature warming6,7. Although acidification may become a serious threat to marine calcifying organisms, our results suggest that over the study period the primary driver of North Atlantic calcifying planktonwas oceanic temperature.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Hyperadrenocorticism is a rare endocrine disease in the cat; it is characterized by elevated blood cortisol level that generates numerous clinical signs including hyperglycemia, polyuria, polydipsia, polyphagia and skin diseases. The average age of onset is around 10 years. This disease usually occurs link with other endocrine disorders such as diabetes mellitus.The disease can be produced by functional alteration of the pituitary gland or the adrenal. A case report, with differential diagnosis and review of the literature, is presented.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Existen diferentes definiciones del concepto de masculinidad. Por un lado están las normativas, que la entienden como lo que los hombres deberían ser y, por otro, los enfoques semióticos, que la definen como no-feminidad. Partiendo de este último enfoque y teniendo en cuenta que la feminidad ha evolucionado en los últimos años junto con la sociedad desdibujando la frontera entre lo que forma parte del rol femenino y lo que no, se puede afirmar que han surgido a partir de los renovados modelos de feminidad, diferentes y nuevas masculinidades entre las que se encuentra la del hombre metrosexual. Es en este tipo de masculinidad en concreto en la que se centra la presente investigación y en cómo se construye la narración de dicha masculinidad en el discurso publicitario actual recurriendo a la figura mítica de Narciso. Así, a partir de una revisión bibliográfica y de un análisis de contenido, se pretende analizar la influencia de la publicidad en la aparición del hombre metrosexual como nueva masculinidad en respuesta a la transformación de la feminidad, a la par que confirmar la presencia de la figura de Narciso como recurso en la construcción de la masculinidad en la publicidad actual.