Morphology of polyethylene crystallized under the simultaneous influence of pressure and orientation in a capillary viscometer

The morphology of high-density polyethylene crystallized under simultaneous pressure and shear in an Instron capillary viscometer has been examined by scanning electron microscopy, electron microscopy, and selected-area electron diffraction. Two distinct fibrous morphologies were observed in these unusually transparent strands. The outer sheath was composed of fibers, 3000 Å in diameter, aligned parallel to the extrusion direction and apparently interconnected by a lamellar cross texture. A highly crystalline ribbon texture composed of fine fibers, 200–250 Å in diameter, dominated the inner core. Sharp-spot electron diffraction patterns obtained from these central ribbons indicated a high degree of c-axis orientation parallel to the fibers and an extended-chain crystal structure. The melting behavior of both irradiated and unirradiated strands examined by differential scanning calorimetry was consistent with the formation of two distinct crystalline morphological units.     

Thermal Neutron damage in cadmium

The isochronal annealing of the damage produced by thermal neutron irradiation of cadmium at 3.6 °K has been studied for several initial doses which vary by a factor of 1000. The recovery results show a strong dependence upon initial dose. This effect, which is not seen to this extent in the fcc metals, cannot be accounted for by an irradiation annealing mechanism. In contrast to the observation of two processes involving long range defect migration for several fcc metals only one process, at high temperatures, is discernable from isochronal annealing of Cd. The presence of another process at low temperatures is clearly established by other means. Irradiation annealing effects observed during the production of damage at high defect concentrations indicate that the spontaneous annihilation volume between the defects of a new capture event and the defects from an earlier event is 80 atomic volumes. Other results suggest that damage production and recovery mechanisms may be associated with the anisotropic nature of the cadmium hexagonal lattice.     

井冈山自然保护区爬行动物初步调查

<正> 一地理概况井冈山自然保护区位于江西省西部,罗霄山脉中段。东接太和,东南连遂川,西接宁冈和湖南酃县,西北连永新,介于东径113°59′—114°23′。北纬26°27′—26°49′之间。地势西高东低,境内群山环抱,山体蜿蜒曲折,多呈西南向东北走向,形成山间峡谷和山间盆地。河溪     

湍流大气中高斯光束波前刃位错

在Rytov近似下 ,通过引入统计平均位错的概念研究了高斯光束通过近地面湍流大气传播时波前刃位错位置与湍流大气强度和传播距离等参数的关系。分别在远大于和远小于光波位相起伏周期的两种情况下 ,研究并得出了波前刃位错位置的湍流系综统计平均理论关系     

微量脉冲进样-导数火焰原子吸收光谱法测定调味品中锌

将微量脉冲进样技术和导数火焰原子吸收光谱法结合 ,建立了测定调味品中锌含量的新方法。探讨了微量进样体积和导数仪档位等影响因素。样品经离心、稀释后直接测定 ,该方法的灵敏度和检出限分别为 0 0 0 4和 0 0 13μg·mL-1,相对标准偏差为 3 0 %～ 4 4 % ,回收率 93 3%～ 113 3%。该方法准确和快速 ,结果令人满意。     

反应型三元铕配合物的合成及发光性能研究

文章以邻菲咯啉为第一配体 ,顺丁烯二酸酐、丙烯腈、十一烯酸、油酸和亚油酸为活性第二配体 ,合成了 5种新的反应型三元铕配合物。通过元素分析 ,EDTA配位滴定分析 ,红外、紫外和荧光光谱分析 ,对标题配合物的组成和结构进行了表征 ,并研究了它们的发光性能。结果表明 ,5种新的反应型三元配合物与相应的二元配合物相比发光强度大大提高 ,反应型配体产生“协同效应”的能力为 :亚油酸 >油酸 >丙烯腈 >顺丁烯二酸酐 >十一烯酸。且配合物中引入了能与其他单体共聚的活性第二配体 ,为合成具有优异发光性妮的键合型稀土高分子功能材料提供了一条新的途径     

用雅可比-傅里叶矩进行图像描述

提出了雅可比—傅里叶矩,它是用雅可比多项式作为径向函数,用傅里叶因子作为角向函数构造而成的,是广义正交傅里叶—梅林矩。经过归一化处理后的雅克比—傅立叶矩具有平移、尺度、旋转、灰度多畸不变性。从归一化图像重建误差、噪声灵敏度等方面对雅可比—傅里叶矩的图像描述能力进行了研究,结果显示雅可比—傅里叶矩在各种参量选择的情况下,具有良好的图像描述和抗噪声能力,是一个优良的图像特征。以前的研究多为单纯构建某一个函数,而现在将其扩展为构建一个函数族,开阔了矩描述量的研究视野。     

十八种清热解毒中草药中微量元素的测定

采用原子吸收分光光度法测定了十八种清热解毒中草药中人体必需微量元素含量。结果表明,这些中草药中含有丰富的人体必需微量元素。本方法具有操作简便、快速和准确度高等优点。     

Evaluation of lipid peroxidation inhibition and free radical scavenging abilities of 5,6,7-trimethoxy dihydroflavonols

Four naturally rare 5,6,7-trimethoxy-2,3-cis-dihydroflavonols(3-6) and two 5,6,7-trimethoxy-2,3-trans-dihydroflavonols(7-8) were designed and synthesized.Their antioxidative properties were evaluated by way of examining their scavenging capacities towards DPPH and O_2~(·-) free radicals,as well as by measuring their inhibitory ability against LPO.Both the 2,3-trans and the 2,3- cis conformers exhibited certain quenching abilities to DPPH and O_2~(·-) radicals,while most of the synthetic dihydroflavonols ...     

A new method for introduction ω-side chain of prostanoid using Barton radical reaction

A new method for introductionω-/side chain of prostanoid was described in this note.Starting from acid chloride(3),via Barton radical reaction,a transα,β-unsaturated ketone sython was introduced.