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排序方式: 共有755条查询结果,搜索用时 15 毫秒
681.
Fruchter JS Robertson DE Evans JC Olsen KB Lepel EA Laul JC Abel KH Sanders RW Jackson PO Wogman NS Perkins RW VAN Tuyl HH Beauchamp RH Shade JW Daniel JL Erikson RL Sehmel GA Lee RN Robinson AV Moss OR Briant JK Cannon WC 《Science (New York, N.Y.)》1980,209(4461):1116-1125
Samples of ash from the 18 May 1980 eruption of Mount St. Helens were collected from several locations in eastern Washington and Montana. The ash was subjected to a variety of analyses to determine its chemical, physical, mineralogical, and biological characteristics. Chemically, the ash samples were of dacitic composition. Particle size data showed bimodal distributions and differed considerably with location. However, all samples contained comparable amounts of particles less than 3.5 micrometers in diameter (respirable fraction). Mineralogically, the samples ranged from almost totally glassy to almost totally crystalline. Crystalline samples were dominated by plagioclase feldspar (andesine) and orthopyroxene (hypersthene), with smaller amounts of titanomagnetite and hornblende. All but one of the samples contained from less than 1 percent to 3 percent free crystalline silica (quartz, trydimite, or cristobalite) in both the bulk samples and 1 to 2 percent in the fractions smaller than 3.5 micrometers. The long-lived natural radionuclide content of the ash was comparable to that of crustal material; however, relatively large concentrations of short-lived radon daughters were present and polonium-210 content was inversely correlated with particle size. In vitro biological tests showed the ash to be nontoxic to alveolar macrophages, which are an important part of the lungs' natural clearance mechanism. On the basis of a substantial body of data that has shown a correlation between macrophage cytotoxicity and fibrogenicity of minerals, the ash is not predicted to be highly fibrogenic. 相似文献
682.
Horsch RB Fraley RT Rogers SG Sanders PR Lloyd A Hoffmann N 《Science (New York, N.Y.)》1984,223(4635):496-498
Morphologically normal plants were regenerated from Nicotiana plumbaginifolia cells transformed with an Agrobacterium tumefaciens strain containing a tumor-inducing plasmid with a chimeric gene for kanamycin resistance. The presence of the chimeric gene in regenerated plants was demonstrated by Southern hybridization analysis, and its expression in plant tissues was confirmed by the ability of leaf segments to form callus on media containing kanamycin at concentrations that were normally inhibitory. Progeny derived from several transformed plants inherited the foreign gene in a Mendelian manner. 相似文献
683.
[目的]确定玉米对土壤中老化滴滴涕和六六六的累积、迁移和转化能力。[方法]温室盆栽试验。取均匀掺入梯度浓度滴滴涕和六六六农药的科研土壤装盆,收集持续盆栽过程中不同时段的土壤和植物样品进行残留测试。[结果]所选择的玉米植株在所设计的土壤污染浓度范围内具有宽域的滴滴涕和六氯环己烷清除能力,其茎秆、根系的生物浓缩系数分别介于0.004至0.027和0.036到0.097之间,但去除率均低于0.1,滴滴涕和六六六梯度处理间无显著差异。滴滴涕可通过被动吸附和主动吸收被玉米植体积累,且由还原性脱卤化介导,p,p’-DDT向p,p’-DDE转化。[结论]玉米对土壤有机氯农药具有清除修复能力,且有机氯农药的对玉米脂肪的亲和力是影响其在植物体内的吸收和转运的主要因素之一。 相似文献
684.
685.
2008年沈阳市花生新品种比较试验 总被引:1,自引:0,他引:1
通过丰产性、抗逆性及适应性等方面对沈阳市引进的花生新品种进行品比试验,结果表明:鲁花11、花育23、铁引花1、阜花11、花育22、花育16、连花6等品种可推广应用,本试验为筛选适合沈阳市大面积种植的高产、稳产、优质、高抗的花生品种提供科学依据。 相似文献
686.
Tiago Leo Mingxun Wang Nathan Moss Ricardo da Silva Jon Sanders Sergey Nurk Alexey Gurevich Gregory Humphrey Raphael Reher Qiyun Zhu Pedro Belda-Ferre Evgenia Glukhov Syrena Whitner Kelsey L. Alexander Robert Rex Pavel Pevzner Pieter C. Dorrestein Rob Knight Nuno Bandeira William H. Gerwick Lena Gerwick 《Marine drugs》2021,19(1)
Microbial natural products are important for the understanding of microbial interactions, chemical defense and communication, and have also served as an inspirational source for numerous pharmaceutical drugs. Tropical marine cyanobacteria have been highlighted as a great source of new natural products, however, few reports have appeared wherein a multi-omics approach has been used to study their natural products potential (i.e., reports are often focused on an individual natural product and its biosynthesis). This study focuses on describing the natural product genetic potential as well as the expressed natural product molecules in benthic tropical cyanobacteria. We collected from several sites around the world and sequenced the genomes of 24 tropical filamentous marine cyanobacteria. The informatics program antiSMASH was used to annotate the major classes of gene clusters. BiG-SCAPE phylum-wide analysis revealed the most promising strains for natural product discovery among these cyanobacteria. LCMS/MS-based metabolomics highlighted the most abundant molecules and molecular classes among 10 of these marine cyanobacterial samples. We observed that despite many genes encoding for peptidic natural products, peptides were not as abundant as lipids and lipopeptides in the chemical extracts. Our results highlight a number of highly interesting biosynthetic gene clusters for genome mining among these cyanobacterial samples. 相似文献
687.
黑龙江农垦水稻高产攻关出现了小面积折合稻谷产量超过14.7t/hm^2的高产典型。从品种、土壤、栽培技术和气候条件等方面,采取与其它地区高产典型对比的方法,分析了寒地气候条件下出现这种高产典型的原因。分析了产量构成各项指标的特点及高产攻关研究的现实意义。指出综合栽培技术应该是高产攻关研究的要点。提高我国水稻单产,不仅要重视生产技术创新,还要重视生产机制创新。黑龙江农垦总局大面积水稻获得高产经验值得深入总结。 相似文献
688.
689.
基于Logistic方程的大豆产量预报方法 总被引:1,自引:0,他引:1
基于Logistic方程建立大豆干物质累积曲线用来描述大豆干物质累积过程,由于气候条件处于非理想状态,因此对其干物质累积过程进行气象条件订正,并分析干物质累积量与气候产量的关系.在以上分析的基础上,建立大豆农业气象产量预测模式.通过计算分析温度和水分订正系数发现:在不同热量带、不同年份、不同发育时段,温度和水分订正系数不同,说明温度和水分条件是影响大豆生长发育和产量形成的重要限制因子.利用大豆主产区2004-2006年的气象和产量资料进行预报,预报精确度在95.9%左右,且预测产量与实际产量相关性较好,R2在0.903~0.948之间,通过α=0.01的显著性检验,说明模型预测的产量比较准确,模型可用. 相似文献
690.
荧光指示剂检测甜菜胞内钙离子的条件优化 总被引:2,自引:0,他引:2
胞内钙离子信号做为第二信使参与植物抗病信号转导途径。以甜菜叶片为试验材料,用孵育方法将Ca2+荧光探针Fluo-3/AM载入甜菜细胞中,并结合激光共聚焦扫描显微技术,研究甜菜叶片胞质游离Ca2+的测定方法。结果表明,采用20μmol·L-1的钙离子荧光指示剂Fluo-3/AM装载顺次进行低温4℃孵育120 min,25℃孵育120 min,可获得较为理想的甜菜叶片胞质游离Ca2+染色结果。该方法可用于检测BNYVV侵染甜菜叶片胞质游离钙离子的变化,为研究甜菜BNYVV入侵甜菜后胞内钙信号作用提供理论研究基础。 相似文献