Chemical characterization of bohrium (element 107)

The arrangement of the chemical elements in the periodic table highlights resemblances in chemical properties, which reflect the elements' electronic structure. For the heaviest elements, however, deviations in the periodicity of chemical properties are expected: electrons in orbitals with a high probability density near the nucleus are accelerated by the large nuclear charges to relativistic velocities, which increase their binding energies and cause orbital contraction. This leads to more efficient screening of the nuclear charge and corresponding destabilization of the outer d and f orbitals: it is these changes that can give rise to unexpected chemical properties. The synthesis of increasingly heavy elements, now including that of elements 114, 116 and 118, allows the investigation of this effect, provided sufficiently long-lived isotopes for chemical characterization are available. In the case of elements 104 and 105, for example, relativistic effects interrupt characteristic trends in the chemical properties of the elements constituting the corresponding columns of the periodic table, whereas element 106 behaves in accordance with the expected periodicity. Here we report the chemical separation and characterization of six atoms of element 107 (bohrium, Bh), in the form of its oxychloride. We find that this compound is less volatile than the oxychlorides of the lighter elements of group VII, thus confirming relativistic calculations that predict the behaviour of bohrium, like that of element 106, to coincide with that expected on the basis of its position in the periodic table.     

Chemical characterization of element 112

The heaviest elements to have been chemically characterized are seaborgium (element 106), bohrium (element 107) and hassium (element 108). All three behave according to their respective positions in groups 6, 7 and 8 of the periodic table, which arranges elements according to their outermost electrons and hence their chemical properties. However, the chemical characterization results are not trivial: relativistic effects on the electronic structure of the heaviest elements can strongly influence chemical properties. The next heavy element targeted for chemical characterization is element 112; its closed-shell electronic structure with a filled outer s orbital suggests that it may be particularly susceptible to strong deviations from the chemical property trends expected within group 12. Indeed, first experiments concluded that element 112 does not behave like its lighter homologue mercury. However, the production and identification methods used cast doubt on the validity of this result. Here we report a more reliable chemical characterization of element 112, involving the production of two atoms of (283)112 through the alpha decay of the short-lived (287)114 (which itself forms in the nuclear fusion reaction of 48Ca with 242Pu) and the adsorption of the two atoms on a gold surface. By directly comparing the adsorption characteristics of (283)112 to that of mercury and the noble gas radon, we find that element 112 is very volatile and, unlike radon, reveals a metallic interaction with the gold surface. These adsorption characteristics establish element 112 as a typical element of group 12, and its successful production unambiguously establishes the approach to the island of stability of superheavy elements through 48Ca-induced nuclear fusion reactions with actinides.     

基于位移形函数和力形函数的梁柱单元理论对比研究

基于位移形函数的梁柱单元理论被广泛应用于框架结构梁柱单元的有限元分析,但其计算精度受到位移形函数的限制而难以提高.对比基于位移形函数的相关理论,总结基于力形函数的梁柱单元理论,进行有限元程序编制,计算过程中采用柱面弧长法来进行迭代求解.程序计算结果对比表明,基于力形函数的梁柱单元计算效率和计算精度均高于基于位移形函数的梁柱单元.     

零电阻温度为108K的(B_i,P_b)-S_r-C_a-C_u-O超导体

我们研究了名义组分为(B_(j1-x)P_(bx))_2 S_(r2)C_(a2)C_(u3)O_(10+y)(2223)材料的超导电性,对其中 x=0.1的样品,得到最高的零电阻温度为108K。     

Q_1~(rot)非协调元二网格法

在计算Possion方程特征值时,高效率更准确是我们追求的目标。本文在二维情况下用Qr1ot非协调元二网格法求得了Qr1ot元的特征值,并且与非二网格下得到的结果进行了比较,用数值例子说明了此方法具有高效性。     

反相高效液相色谱法测定氟草净

采用ＬＣ－６Ａ高效液相色谱仪，选用色谱柱Ｓｈｉｍ－ｐａｃｋＣＬＣ－ＯＤＳ，应用反相高效液相色谱法测定了新型除草剂－－氟草净的含量，回收率１００．４％，变异系数０．２９－０．３９．     

棘豆化学防除试验研究(二)

本文报导了87～89年以来,对棘豆化学防除的试验研究。筛选出的 JDC—Ⅱ药物,防效可达100%,并可使棘豆根部坏死。但缺点是,对有些伴生牧草有伤害。若先使用当年防效高、选择性好、成本低的2,4—DJ 酯控制棘豆蔓延生长,再使用根除性的 JDC—Ⅱ药物,可彻底消灭棘豆。若单独使用 JDC—Ⅱ药物,只要喷药时作好人工选择,药后作好轮牧及补播,亦可作到灭除毒草,改善草地生态。     

波浪作用下沉管管段沉放过程运动响应的试验研究

为研究波浪作用下沉管管段沉放过程的运动特性,开展了实验室沉管沉放的试验研究,量测了沉管管段的运动响应及沉放系统的缆绳受力,分析了管段运动位移和缆绳受力随相对波高H/h、相对宽度b/λ和相对沉深d/h的变化规律.结果表明:较小管段沉深情况下,管段的运动表现出强非线性特征;管段的运动响应随b/λ和d/h的增加而很快减小.管段沉深较小时,波高对管段的无量纲运动位移的影响较明显;迎浪侧的缆绳最大张力稍大于背浪侧的缆绳最大张力.较小的管段沉深情形下,两侧的缆绳张力相位差较明显;缆绳张力随b/λ的减小而增大,随H/h的减小和d/h的增大而减小.     

三乙醇胺(TEA)催化合成1,4-双(咪唑-1-基)丁烷的研究

文章研究了以三乙醇胺(Triethanolamine TEA)为相转移催化剂，在苯水体系中合成了1，4-双(咪唑-1-基)丁烷，在优化条件下产率92．6％．并详细考察了碱的浓度，反应时间，催化剂用量，反应温度等条件对反应的影响。     

聚氯代对亚苯基二亚甲基的化学气相沉积聚合及表征

用化学气相沉积(CVD)聚合法制备的聚氯代对亚苯基二亚甲基(PPX-C)膜,除了具有聚对亚苯基二亚甲基(PPX)膜的保形涂覆和物理性能外,还具有更好的粘附能力。研究表明:PPX-C膜具有优异的耐溶剂性和抗化学氧化性能;氯的引入使膜的玻璃化转变温度降低,室温柔性增强,动态力学阻尼性能增大,热降解起始温度比PPX膜低,主链降解温度与PPX膜相近。此外,氯的引入对膜的亲水性能影响不大,但膜的水汽渗透率却因此明显降低,与PPX膜相比PPX-C膜具有更好的防潮性能。     

青梅茎的化学成分研究(Ⅰ)

利用硅胶柱层析和葡聚糖凝胶柱层析分离和纯化,从青梅(Vatica mangachpoi Blanco)茎的乙醇提取物的乙酸乙酯部位分离得到5个化合物。经理化数据对照和波谱分析,确定它们分别为岩白菜素(1)、邻苯二甲酸二丁酯(2)、β-谷甾醇(3)、β-胡萝卜甙(4)和熊果酸(5)。其中化合物(2)、(4)和(5)首次从该属植物中分离得到,所有化合物均为首次从该植物中发现。     

二乙基二硫代氨基甲酸钠(DDC)的量子化学研究Ⅰ

本文采用量子化学的分子轨道理论研究了 DDC 及其一些过渡金属离子整合物的电子结构,应用微机专用改进的 CNDO 程序,计算了有关分子的分子轨道能量、电荷分布及键级,借以阐明有毒络合物[DDC—M~+]的电子结构与其抗癌功能之间的关系.     

瓜馥木化学成分研究

利用色谱技术进行分离纯化,从广西特色植物瓜馥木中分离得到7个单体化合物,根据光谱数据和理化性质等鉴定了它们的化学结构,分别为:5,6,7,8-四甲氧基黄酮(5,6,7,8-tetramethoxyflavone,)、(-)-表儿茶素((-)-epicatechin,)、丁香酸(syringic acid,)、大黄素甲醚(physcion,)、豆甾醇(stigmas-terol,)、胡萝卜苷(daucousterol,)和β-谷甾醇(β-sitosterol,),其中化合物为首次从瓜馥木属植物中分离得到,化合物和为首次从瓜馥木中分离得到。     

特厚板温度梯度轧制有限元模拟与实验研究

针对特厚板再结晶型轧制,板坯中心难以变形导致心部晶粒粗大的问题,使用Q345B钢,采用有限元方法建立了特厚板轧制的仿真模型,以研究在特厚板轧制过程中引入厚度方向上的温度梯度对钢板心部应变的影响,并与传统均温轧制进行对比,预测了两种温度场条件下奥氏体再结晶的晶粒尺寸.采用大试样平面应变实验对模拟结果进行验证.研究结果表明,温度梯度轧制有利于增加坯料心部应变量,最大增加了61.35%.计算和实验结果显示温度梯度轧制可以减小特厚板心部晶粒尺寸,晶粒度级别提高了一个等级,说明该工艺对提高特厚板中心区域性能有利.     

满足(幂零元)左-Zorn链条件的环

通过引进(幂零元)左zorn链条件,弱Her-(单侧)理想,K-商环等概念,讨论Her-环的性质,得到一系列结果.并给出环上Kothe猜测成立的一个充要条件,由此给出环上Herstein猜测成立的一个充要条件.     

美国《化学文摘》检索系统新探

介绍了CA光盘检索平台和SciFinder Scholar网上检索平台的概况、检索方法及特点,并对这两个平台作了较详细的比较。     

(RXN)4与(XNR)4立方簇合物的稳定性

用密度泛函理论DFT ,在B3LYP/CEP 1 2 1G水平上 ,对 (RXN) 4 (X =C ,Si,Ge ,Sn,Pb ;R =H ,CH3,C(CH3) 3,Si(CH3) 3,C6H5)立方簇合物的几何构型、电子结构、振动光谱和化学键性质进行了研究 .结果表明 ,(RXN) 4 的稳定性较差 ,(XNR) 4 的 5种结构的稳定性顺序为 :(PbNR) 4>(SnNR) 4 >(GeNR) 4 >(SiNR) 4 >(CNR) 4 .