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1.
非计算机专VFP程序设计语言教学实践与探索   总被引:2,自引:0,他引:2  
VFP程序设计语言是一种能处理大量的数据和进行管理系统开发的常用工具。它是很多高校非计算机专业的计算机基础课程,如何教好这门课程是计算机基础课教师非常关心的问题。本文对重视课前准备,精心制作多媒体课件、注重课堂教学,激发学习兴趣、重视上机实验指导、“无纸化”上机考核方式等几个方面进行了探讨。  相似文献   

2.
Knowing the behavior of a fluid in small volumes is essential for the understanding of a vast array of common problems in science, such as biological interactions, fracture propagation, and molecular tribology and adhesion, as well as pressure solvation and other geophysical processes. When a fluid is confined, its phase behavior is altered and excluded-volume effects become apparent. Pioneering measurements performed with the surface forces apparatus have revealed so-called structural or oscillatory solvation forces as well as the occurrence of a finite shear stress, which was interpreted as a solidification transition. Here, we report measurements obtained with an extended surface forces apparatus, which makes use of fast spectral correlation to gain insight into the behavior of a thin film of cyclohexane confined within attoliter volumes, with simultaneous measurement of film thickness and refractive index. With decreasing pore width, cyclohexane is found to undergo a drastic transition from a three-dimensional bulk fluid to a two-dimensional adsorbate with strikingly different properties. Long-range density fluctuations of unexpected magnitude are observed.  相似文献   

3.
Cao YC  Jin R  Mirkin CA 《Science (New York, N.Y.)》2002,297(5586):1536-1540
Multiplexed detection of oligonucleotide targets has been performed with gold nanoparticle probes labeled with oligonucleotides and Raman-active dyes. The gold nanoparticles facilitate the formation of a silver coating that acts as a surface-enhanced Raman scattering promoter for the dye-labeled particles that have been captured by target molecules and an underlying chip in microarray format. The strategy provides the high-sensitivity and high-selectivity attributes of gray-scale scanometric detection but adds multiplexing and ratioing capabilities because a very large number of probes can be designed based on the concept of using a Raman tag as a narrow-band spectroscopic fingerprint. Six dissimilar DNA targets with six Raman-labeled nanoparticle probes were distinguished, as well as two RNA targets with single nucleotide polymorphisms. The current unoptimized detection limit of this method is 20 femtomolar.  相似文献   

4.
采用酚-硫酸法测定木素磺酸铵中糖含量,以葡萄糖为对照,苯酚-硫酸作显色剂,用紫外分光光度计在490 nm处测定吸光度。结果显示:葡萄糖浓度为20~120μg/mL时线性关系显著,R2=0.995 9;精密度RSD=0.034%,稳定性RSD=0.102%,回收率98.99%,RSD=0.871%,重现性RSD=0.336%。酚-硫酸法测定木素磺酸铵中糖含量简便易行,精密度、稳定性、回收性、重现性良好。  相似文献   

5.
State-selected rubidium-87 molecules were created at rest in a dilute Bose-Einstein condensate of rubidium-87 atoms with coherent free-bound stimulated Raman transitions. The transition rate exhibited a resonance line shape with an extremely narrow width as small as 1.5 kilohertz. The precise shape and position of the resonance are sensitive to the mean-field interactions between the molecules and the atomic condensate. As a result, we were able to measure the molecule-condensate interactions. This method allows molecular binding energies to be determined with unprecedented accuracy and is of interest as a mechanism for the generation of a molecular Bose-Einstein condensate.  相似文献   

6.
为探明腐植酸与磷肥施用方式对土壤磷素移动性和淋失量的影响,通过室内土柱淋溶试验,分别设计了不施肥(CK)、基施腐植酸钾追施/不追施磷肥(HA-P、HA)、基施磷肥追施/不追施腐植酸钾(P-HA、P)和磷肥腐植酸钾共同基施(P+HA)共6个处理,来探讨将腐植酸水溶性肥料中的主要原料腐植酸钾与磷肥按照不同施用方式施入土壤后对土壤磷素剖面迁移能力和淋出的影响。结果表明:在相同的灌溉条件下,HA-P处理显著增加了土壤磷素的淋出,分别比P-HA、P和P+HA 3个处理的磷素淋出总量高244.08%、78.51%和35.34%,而P-HA则显著降低了土壤磷素的淋出量;P+HA和P-HA处理土壤剖面的速效磷和全磷含量均随土层深度的增加而显著增加,与P处理结果相似,而HA-P处理剖面各层土壤的速效磷和全磷含量差异较小;HA处理会使土壤磷素淋出略有增加。研究表明,腐植酸钾与磷肥等量输入时,以腐植酸钾为基肥、磷溶液进行追肥的施用方式对土壤磷素移动的促进作用最大,有较高的淋失风险,而基施磷肥、追施腐植酸钾则可以显著控制土壤剖面磷素移动,降低土壤磷素的淋出量。  相似文献   

7.
Breeding Technology of eui-hybrids of Rice   总被引:1,自引:0,他引:1  
Induced mutants of elongated uppermost internode (eui) were directly obtained after irradiation on maintainer (B) and restorer (R) lines of hybrid rice. CMS lines(A) with eui (referred to as eA), restorer lines with eui (referred to as eR) as well as hybrid rice with eui gene (referred to as e-hybrids)were developed. The results showed that the eui mutation frequency averaged 0.10‰ at a range of 0.02‰ - 0.47‰,varying with applied dosage and mutated materials. Genetic diversities of eui stock, and a new eui gene, temporarily designated as eui2(t), was identified. eA lines have a significantly elongated uppermost internode causing better panicle exsertion and possessing higher outcrossing potential. e-hybrids increased plant height by 3 - 10 cm and headed 2 - 3 days earlier, as well as showed greater grain weight resulting in higher yield potential than that of corresponding original hybrids. The technology systems without GA3, a few of using GA3 in hybrid rice seed production, and the establishment of e-hybrid rice breeding system were also discussed in this paper.  相似文献   

8.
[目的]研究丛枝菌根对黄檗氮素及含氮物质含量的影响。[方法]通过盆栽试验,用丛枝菌根真菌接种黄檗一年生实生苗,研究丛枝菌根对黄檗(Phellodendron amurense Rupr).氮素及含氮物质含量的影响。[结果]黄檗幼苗形成丛枝菌根后,增加了叶片氮素含量,接种G.mosseae的苗木叶片氮素含量比对照提高了1.28~1.60倍,光合能力增强。接种丛枝菌根菌后,显著提高了黄檗叶绿素含量及叶绿素a和b的比值,增强了黄檗光合作用的能力,叶绿素a含量提高了25%以上;同时,增加了植物体内吲哚乙酸的含量,增加比例在1.65~2.41倍之间;增强植物体内硝酸还原酶的活性,增加了可溶性蛋白含量,增加比例在1.67~2.49倍之间,增强了植物氮素代谢能力,促进植物生长,增强植物的次生代谢能力。[结论]该研究结果为丛枝菌根真菌在黄檗上的应用提供了理论依据。  相似文献   

9.
Inoculation of the cornea, lip, or footpad of mice with herpes simplex virus type 1 resulted in a latent infection of the local sensory ganglia. Inoculation of the vagina and cervix with herpes simplex virus type 2, as well as type 1, also induced a latent ganglionic infection. With the use of sciatic nerve section as a stimulus, a reproducible model of viral reactivation in vivo was established.  相似文献   

10.
The fabrication and characterization of a glass containing a regular parallel array of submicrometer channels or capillaries are described. The capillaries are arranged in a two-dimensional hexagonal close packing configuration with channel diameters as small as 33 nanometers and packing densities as high as 3 x 10(10) channels per square centimeter. The high-temperature stability of the nanochannel glass array is well suited as a host or template for the formation of quantum confined semiconductor structures or as a mask for massively parallel patterned lithographic applications.  相似文献   

11.
美国终身教职制度作为实现学术自由的手段,使大学教师享受到了教学自由、研究自由和对外活动自由,并为大学教师提供了经济保障,对教师形成了一定的职业吸引力。借鉴美国终身教职制度理论和实践经验,可以引导我国高校建立适合其自身发展的教师职业管理制度。  相似文献   

12.
Yield maps are recognized as a valuable tool with regard to managing upcoming crop production but can contain a large amount of defective data that might result in misleading decisions. These anomalies must be removed before further processing to ensure the quality of future decisions. This paper proposes a new holistic methodology to filter out defective observations likely to be present in yield datasets. The notion of spatial neighbourhood has been refined to embrace the specific characteristics of such on-the-go vehicle based datasets. Observations are compared with their newly-defined spatial neighbourhood and the most abnormal ones are classified as defective observations based on a density-based clustering algorithm. The approach was conceived to be as non-parametric and automated as far as possible to pre-process a growing number of datasets without supervision. The proposed approach showed promising results on real yield datasets with the detection of well-known sources of errors such as filling and emptying times, speed changes and non-fully used cutting bar.  相似文献   

13.
平峪村位于北京市房山区十渡镇,是一个以旅游为主导产业的山区村。近年随着旅游市场的变化,该村产业结构不合理、产品特色不明显、基础设施不健全、人才缺乏等问题突显。基于SWOT分析法,从规划、产品、品牌、人才等方面对平峪村进行分析,提出建立有机农业为核心、休闲农业为主导的“绿色体验,岩溶山水”发展模式,发展内驱力强、多盈利点、可持续发展的绿色休闲产业,将平峪村打造成休闲农业示范村。  相似文献   

14.
取精噁唑禾草灵废水处理系统进水口处污泥进行驯化培养,分离到8株有效菌株,通过高效液相色谱分析这8株菌株降解精噁唑禾草灵的残存量,确定其中降解精噁唑禾草灵最好的一株菌株为本实验菌株,通过传统的微生物鉴定方法,将其鉴定为产碱菌属(Alcaligenes sp.),标记为Alcaligenes sp.H.分离菌株H可以以精噁唑禾草灵为唯一碳源和能源生长;在纯培养条件下,分离菌株H对较高浓度的精噁唑禾草灵(50 mg·mL-1和100 mg·mL-1)均能较好地降解.  相似文献   

15.
Myers N 《Science (New York, N.Y.)》1972,178(4067):1255-1263
A national park is as integral to its regional environment as it is to the nation. Whether one wants to manage it that way or not, a park is dependent on the resources-human and physiobiological-of the environs, just as the environs are modified by the park's existence. This view may not jibe with the spirit of those who strive to protect a patch of old-time Africa as a refuge of serenity and stability in a world of tumult and change. But the park has its own ecology, just as does any creature within it, although the park's, being more abstract, is more difficult to discern. Planned or not, a park's future is even more enmeshed with the region's future than with the nation's. The ramifications of this relationship, especially the socioeconomic ones, are not always recognized, with the result that the enmeshing process sometimes sounds like a crunching of the gears. The worlds on both sides of the park boundary would get along better if there were a clear indication of what each can do for the other. By contrast, if they spend their energy resisting one another, there is little doubt as to which must be the ultimate "winner."  相似文献   

16.
17.
三维有序大孔径介孔二氧化硅载体的仿生合成   总被引:1,自引:0,他引:1  
介孔二氧化硅作为固定漆酶的载体,在降解氯酚农药研究中意义重大。以正硅酸乙酯(TEOS)为硅源,以不同链长的长链烷基三甲基溴化铵(CnTAB,n = 12,14,16,18)和两性生物表面活性剂椰油基甘氨酸钠(YCS)为混合模板剂,仿生合成了具有三维六方结构的有序介孔二氧化硅。和传统介孔二氧化硅载体相比,三维六方介孔二氧化硅具有较大的孔径及比表面积,且相邻孔道之间发生相互的连通。当使用链长为C16以上的阳离子表面活性剂和YCS混合时,得到孔径为9 nm左右,且具有不同形貌的大孔径介孔二氧化硅,为酶的固定化提供了优良载体。图8表2参22  相似文献   

18.
李争鸣  高启杰 《安徽农业科学》2011,39(33):20829-20830
通过对中国农业大学曲周农业技术推广团队的实地调研,研究和总结了以农业技术推广为运作载体的研究生培养循环发展模式。该模式以基地为平台,采用理论与实践相结合、学习与服务相结合的培养方式,实现了学科链与农业生产链的有效对接,有助于为国家培养高水平、有综合素质的应用型农科研究生。该模式依靠有效的制度,以及大学与县政府、大学与农户互动激励机制保证了研究生培养的持续发展,是农业类院校研究生培养可以借鉴的新模式。  相似文献   

19.
Animals receiving low-intensity electrical stimulation of the basolateral nucleus of the amygdala while drinking plain tap water were injected with toxic doses of lithium chloride to examine whether brain stimulation can serve as a conditioned stimulus in a bait-shyness paradigm. Subjects receiving this pairing greatly reduced their water intake in a retention test, in a similar manner to a group in which saccharin was paired with poisoning. Pairing lithium chloride with stimulation of the amygdala had no effect on subsequent water intake in the absence of brain stimulation. This effect appears to be locus specific, as caudate stimulation could not serve as a conditioned stimulus.  相似文献   

20.
Gibbs JB 《Science (New York, N.Y.)》2000,287(5460):1969-1973
Cancer as a disease in the human population is becoming a larger health problem, and the medicines used as treatments have clear limitations. In the past 20 years, there has been a tremendous increase in our knowledge of the molecular mechanisms and pathophysiology of human cancer. Many of these mechanisms have been exploited as new targets for drug development in the hope that they will have greater antitumor activity with less toxicity to the patient than is seen with currently used medicines. The fruition of these efforts in the clinic is just now being realized with a few encouraging results.  相似文献   

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