首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 15 毫秒
1.
2.
A proton microprobe capable of focusing proton beams with energies up to 6 million electron volts to a spot size of 2 x 2 square micrometers has been used for chemical analysis of small grains of minerals in lunar samples by proton-induced x-ray emission. The proton microprobe is preferable to the electron microprobe for analyzing trace elements whose concentrations are below the detection limit of the latter and for analyzing objects with numerous major and trace elements with a wide range of atomic numbers. Application of the proton microprobe to biological samples is feasible.  相似文献   

3.
4.
正The plant germplasm resources harboring abundant genetic variations are necessary wealth in developing new cultivars adapted to various geographic and seasonal conditions. Unraveling the complex genetic architecture underlying phenotypic diversity in germplasm population is essential  相似文献   

5.
6.
7.
Pest control is a major issue in agricultural management due to crop yield losses caused by pests. In this context, integrated pest management aims to suppress pest populations below an action threshold to minimize their impact. This paper presents the development of a web tool based on the Spanish regulations for the integrated pest management of table grapes; this provides decision support for evaluating when a particular pest action threshold has been crossed thus affecting table grape crops. The tool was built using a model-driven software development approach that enables software system generation from the problem’s knowledge model. The design of the knowledge bases which contain the system’s decision rules is also described. It is divided into knowledge bases that contain general knowledge related to the table grape crop as well as several specific knowledge bases (one per pest) containing the reasoning model that deduces the risk associated with a particular pest. The software has been designed by applying the model-driven development method thus making the system flexible, easy to evolve and adaptable whenever a new pest has to be incorporated into the software.  相似文献   

8.
9.
螺纹环套式新型渗灌毛管水力特性的试验研究   总被引:2,自引:0,他引:2  
文章针对渗灌毛管的易堵塞问题,设计了一种螺纹环套式新型渗灌毛管,并对其进行了水力特性的试验研究。结果表明,螺纹环套式渗灌毛管上螺纹式环套防护时沿程出流量均匀,灌水均匀度比较高,并且螺纹高度对出流均匀度的影响不大;渗灌的工作水头与其出流量呈幂函数关系。  相似文献   

10.
11.
利用microRNA靶位点预测网站结合小鼠胚胎着床芯片数据预测了mir-21的5个与着床相关的靶基因:Reck、F3、Upk1 b、Ggh、Tmed6,通过分别构建含有靶基因3′UTR的重组报告载体、pre-mir-21或/和mir-21inhibitor体外转染细胞、双荧光素酶活性分析初步确定mir-21的靶位点。pre-mir-21可显著降低转染上述5个重组载体的细胞内荧光素酶活性;mir-21 inhibitor可显著增加转染Reck、Upk1 b和Tmed63′UTR的重组载体的细胞内荧光素酶活性;pre-mir-21和mir-21 inhibitor共转染可分别显著增加转染含有Reck3′UTR、F33′UTR、Upk1 b3′UTR和Ggh3′UTR的重组载体的细胞内荧光素酶活性。Reck和Upk1b可能是mir-21的靶基因。  相似文献   

12.
农产品期货市场服务“三农”模式整合研究   总被引:2,自引:0,他引:2  
我国的农产品期货市场作为目前世界第一大的农产品市场,在价格发现、规避风险方面的作用越来越明显。探讨农产品期货市场服务三农的模式选择,不仅有利于促进三农整体的发展,对农产品期货市场本身的健康运行也有重要意义。借鉴生态学的生物链理论,将目前已有的服务模式整合在一起,并从生物链理论中得到一些对三农服务链有益的建议。  相似文献   

13.
Hirst E  Moyers JC 《Science (New York, N.Y.)》1973,179(4080):1299-1304
We described three uses of energy for which greater efficiency is feasible: transportation, space heating, and air conditioning. Shifts to less energy-intensive transportation modes could substantially reduce energy consumption; the magnitude of such savings would, of course, depend on the extent of such shifts and possible load factor changes. The hypothetical transportation scenario described here results in a 22 percent savings in energy for transportation in 1970, a savings of 2800 trillion Btu. To the homeowner, increasing the amount of building insulation and, in some cases, adding storm windows would reduce energy consumption and provide monetary savings. If all homes in 1970 had the "economic optimum" amount of insulation, energy consumption for residential heating would have been 42 percent less than if the homes were insulated to meet the pre-1971 FHA standards, a savings of 3100 trillion Btu. Increased utilization of energy-efficient air conditioners and of building insulation would provide significant energy savings and help to reduce peak power demands during the summer. A 67 percent increase in energy efficiency for room air conditioners would have saved 15.8 billion kilowatt-hours in 1970. In conclusion, it is possible-from an engineering point of view-to effect considerable energy savings in the United States. Increases in the efficiency of energy use would provide desired end results with smaller energy inputs. Such measures will not reduce the level of energy consumption, but they could slow energy growth rates.  相似文献   

14.
The molecular machinery mediating the fusion of synaptic vesicles (SVs) at presynaptic active zone (AZ) membranes has been studied in detail, and several essential components have been identified. AZ-associated protein scaffolds are viewed as only modulatory for transmission. We discovered that Drosophila Rab3-interacting molecule (RIM)-binding protein (DRBP) is essential not only for the integrity of the AZ scaffold but also for exocytotic neurotransmitter release. Two-color stimulated emission depletion microscopy showed that DRBP surrounds the central Ca(2+) channel field. In drbp mutants, Ca(2+) channel clustering and Ca(2+) influx were impaired, and synaptic release probability was drastically reduced. Our data identify RBP family proteins as prime effectors of the AZ scaffold that are essential for the coupling of SVs, Ca(2+) channels, and the SV fusion machinery.  相似文献   

15.
甘薯抗线虫病相关基因片段克隆及序列分析初步研究   总被引:4,自引:1,他引:4  
依据甜菜抗线虫病基因(Hs1pro-1)序列设计引物片段,对甘薯高抗线虫病品种金山25的总DNA进行PCR扩增,获得1条600 bp左右的特异片段.序列测定及同源性检索表明,克隆序列与甜菜的Hs1pro-1基因具有一定的同源性.  相似文献   

16.
本文简要剖析了动物布氏杆菌病试管凝集试验中的几点影响因素:血清样品的送检要求,试验过程中试剂的正确配制,试验中的注意事项,试验结果的判定以及操作过程中可能存在的问题及解决方法。  相似文献   

17.
文章综述了花粉管通道法进行遗传转化的发展历程及其在单子叶作物上的应用,对其在遗传转化中所涉及的机理进行了探讨,同时简要介绍了转化的操作步骤及存在的技术问题,并对其应用前景进行了展望。  相似文献   

18.
The amount of photosynthetically active radiation (PAR, 0.4–0.7 μm) absorbed by plants for photosynthesis relative to incident radiation is defined as the fraction of absorbed photosynthetically active radiation (fAPAR). This is an important variable in both plant biomass production and plant growth modeling. This study investigates the application of a newly developed, linear irradiance sensor (LightScout Quantum Bar Sensor, LightScout, Spectrum Technologies, Inc. USA), to quantify fAPAR for a demonstrator crop, Triticale (X Triticosecale Wittmack). A protocol was devised for sensor placement to determine reflected PAR components of fAPAR and to determine the optimal time of day and sensor orientation for data collection. Coincident, top of canopy, normalized difference vegetation index (NDVI) measurements were also acquired with a CropCircle? ACS-210 sensor and measurements correlated with derived fAPAR values. The optimum height of the linear irradiance sensor above soil or plant canopy was found to be 0.4 m while measuring reflected PAR. Measurement of fAPAR was found to be stable when conducted within 1 h of local solar noon in order to avoid significant bidirectional effects resulting from diurnal changes of leaf orientation relative to the vertically-placed sensor. In the row crop studied, averaging fAPAR readings derived from the linear irradiance sensor orientated across and along the plant row provided an R2 = 0.81 correlation with above-canopy NDVI. Across row sensor orientation also gave a similar correlation of R2 = 0.76 allowing the user to reduce sampling time.  相似文献   

19.
20.
An experiment was conducted on 120 human subjects to test the hypothesis that the probability distribution of serial errors is an invariant property of rote memorization. Contrary to the hypothesis, the relative difficulty function was significantly affected by ability to learn. There was a systematic tendency (p < .05) for fast learners to commit proportionately more errors in the middle of the sequence.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号