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排序方式: 共有84条查询结果,搜索用时 15 毫秒
31.
In September 2019, two diseased plants of Campsis grandiflora showing the main symptom of witches' ‐broom (CgWB) were found in a nursery garden in Yangling, Shaanxi province, China. Partial 16S ribosomal RNA (F2nR2 region) and ribosomal protein (rp) genes of phytoplasmas were generated from the symptomatic plants by PCR amplification, and phytoplasma bodies were observed in the sieve tube elements of the CgWB samples under a transmission electron microscope, indicating phytoplasma infection in the two CgWB plants. Restriction fragment length polymorphism analysis of the F2nR2 region and similarity coefficient results suggested that the two associated phytoplasmas belong to two novel subgroups of 16SrI (aster yellows) group, designated as AK and AL. On the reconstructed phylogenetic trees based on F2nR2 regions and rp genes of phytoplasmas, respectively, the CgWB‐associated phytoplasmas clustered together with members of 16SrI subgroups. This was the first record of phytoplasmas infecting C. grandiflora worldwide. 相似文献
32.
通过电子衍射实验揭示了导电高聚物PPV(拉伸5倍)的次晶性;对弥散的层线强度分布进行了测量和分析,获取了表达单胞参数涨落的精确值,即Δ11(3)=Δ22(3)>0.027nm,Δ33(3)<0.012nm。此外,还推导了其取向分布函数值。 相似文献
33.
凹凸棒石吸附铜离子的机理 总被引:2,自引:0,他引:2
A single-factor experiment of copper ion adsorption on pure palygorskite was carried out to understand the Cu^2 sorption of palygorskite-an important clay mineral in soil and sedimentary rock. In addition, pH of the solution and the surface microstructure of palygorskite were investigated before and after adsorption. The experimental results indicated that efficiency of Cu^2 removal was related to the oscillation rate of the specimen shaker, sorption time, initial pH value and the amount of adsorbent added. Palygorskite induced Cu^2 hydrolysis and interaction between copper hydroxide colloids and palygorskite surfaces, as observed with transmission electron microscopy (TEM), were the main contributions to palygorskite removal of Cu^2 . This mechanism was different from adsorption at the mineral-water interface. It was proposed that surface hydrolysis of palygorskite raised the alkalinity of the palygorskite-water interface and suspension system. Thus, the induced pH of the solution was then high enough for Cu^2 hydrolysis on the mineral surface and in solution. 相似文献
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35.
The oriental armyworm, Mythimna separata (Walk), is one of the most serious pests of cereals in Asia and Australasia. The structure and distribution of the antennal sensilla of M. separata were studied by scanning electron microscopy and transmission electron microscopy. The results showed that antennae of both female and male M. separata are filiform in shape. Three groups and seven morphological sensillum types were recorded in both sexes, including uniporous sensilla (sensilla chaetica), multiporous sensilla (sensilla trichodea, basiconica, coeloconica, and styloconica), and aporous sensilla (sensilla squamiformia and Böhm bristles). S. trichodea, which were the most abundant sensilla, was made of three subtypes (ST I, ST II, and ST III) according to external features and two subtypes of s. basiconica (SB I and SB II) and s. coeloconica (SCo I and SCo II) were identified, respectively. Sexual dimorphisms in sensilla of M. separata were mainly perceived as the variations in the numbers of several sensilla subtypes. Also, the possible functions of the antennal sensilla were discussed. These results contribute to our understanding of the function of antennae in the behavior of M. separata. 相似文献
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37.
运用扫描与透射电镜对银鲳精子的超微结构进行了观察。银鲳精子由头部、中段和尾部(鞭毛)3部分组成。精子全长约39.51±1.64μm,头部长约1.98±0.30μm,表面粗糙。头部的主要结构包括细胞核和中心粒复合体。细胞核位于头部腹侧,卵圆形。细胞核中染色质致密,存在着不规则的网络状间隙。近端中心粒为9组三联微管结构,与远端中心粒相互垂直。中段的主要结构为袖套和线粒体。袖套与细胞核后端相连,含有4~5个线粒体及少量囊泡。尾部细长,长约37.52±1.68μm,至末端逐渐变细。尾部的主要结构为轴丝,为典型的"9+2"微管结构。尾部具有波纹状侧鳍,排列不对称。 相似文献
38.
为建立快速检测壳聚糖抑菌效果的方法,研究其对青枯菌生物膜形成的影响并探索其抑菌机理,利用酶标仪检测壳聚糖与菌悬液混合培养物的吸光值,计算抑菌率,同时利用结晶紫染色法对壳聚糖处理后青枯菌生物膜形成能力进行评价,并进行透射电镜观察.结果表明,在壳聚糖浓度低于0.15 mg/mL时,随浓度增加其抑菌效果亦显著增加,其浓度超过0.15 mg/mL之后,其抑菌效果达到同一水平,最高抑菌率为74.3%;而壳聚糖浓度对青枯菌生物膜形成能力未产生显著影响;透射电镜观察结果显示:壳聚糖通过破坏青枯菌细胞膜抑制细菌生长. 相似文献
39.
不同电性参数的三维地质体在中心回线瞬变电磁观测方式下的数值模拟是认识其电磁响应特征规律并进而开发新解释方法的理论基础。三维地质体的正演是瞬变电磁法研究的一个热点。通过一个具体的模型,讨论了利用 MAFIA 软件进行数值模拟计算的详细方法步骤。据此,可模拟计算任意具有不同电阻率、磁导率和介电常数的三维地质体在不同深度条件下的电磁响应。 相似文献
40.
Rasha Ragab Beheiry Hoda Foad Salem Mayada Wahid Karkit 《Anatomia, histologia, embryologia》2020,49(3):345-350
The aim of this research work was to study the histological structure of the pancreatic acini by transmission electron microscope in two avian species, duck and pigeon. The specimens were collected and processed for electron microscopic study. The results showed that the acini of the two avian species were two types; the first one was an electron dense and the second one an electron lucent. The light acinar cells were larger in size than the dark cells. These cells contained centrally located ovoid nuclei with prominent nucleoli and abundant euchromatin. The cytoplasm was electron lucent, with many rough endoplasmic reticulum, polymorphic mitochondria. Numerous zymogen granules were distributed in the basal part and around the nucleus, so these cells considered active cells. The dark acinar cells were characterized by an electron dense cytoplasm. The most prominent cell organelle in these cells were the zymogen granules that appeared in different sizes while other organelles as mitochondria, and rough endoplasmic reticulum were inconspicuous or few, so these cells were considered as inactive cells. The nucleus with indented nuclear membrane located centrally with prominent nucleoli and abundant heterochromatin. Prominent intercellular spaces between the individual acinar cells, as well as well-developed basement membrane separating the electron dense cells and the lumen contained the secretion between acinar cells. It could be concluded that the acinar cells in ducks and pigeons were divided into two types, that is, light and dark acinar cells which mainly attributed to the activity of these cells. 相似文献