Effects of molasses grass,Melinis minutiflora volatiles on the foraging behavior of the cereal stemborer parasitoid,Cotesia sesamiae

Olfactory responses of the cereal stemborer parasitoid Cotesia sesamiae to volatiles emitted by gramineous host and nonhost plants of the stemborers were studied in a Y-tube olfactometer. The host plants were maize (Zea mays) and sorghum ( Sorghum bicolor), while the nonhost plant was molasses grass (Melinis minutiflora). In single-choice tests, females of C. sesamiae chose volatiles from infested and uninfested host plants and molasses grass over volatiles from the control (soil). In dual-choice tests, the wasp preferred volatiles from infested host plants to those from uninfested host plants. There was no discrimination between molasses grass volatiles and those of uninfested maize, uninfested sorghum, or infested maize. The wasp preferred sorghum volatiles over maize. Combining uninfested maize or sorghum with molasses grass did not make volatiles from the combination more attractive as compared to only uninfested host plants. Infested maize alone was as attractive as when combined with molasses grass. Infested sorghum was preferred over its combination with molasses grass. Local growth conditions of the molasses grasses influenced attractiveness to the parasitoids. Volatiles from Thika molasses grass were attractive, while those from Mbita molasses grass were not. Growing the Thika molasses grass in Mbita rendered it unattractive and vice versa with the Mbita molasses grass. This is a case of the same genotype expressing different phenotypes due to environmental factors.     

常压混合脱硅工艺生产种分精液

本文介绍了碳分、种分工艺对精液硅量指数A/S的不同要求,认为种分精液单独生产是很有必要的.本文从理论上分析了目前所应用的脱硅工艺,提出了一种常压生产种分精液的方法-常压混合脱硅工艺,并对某厂采用此工艺进行种分精液生产的情况进行了简单的介绍.     

Photochemical synthesis of bimetallic Au-Ag nanoparticles with "core-shell" type structure by seed mediated catalytic growth

The colloidal Au core/Ag shell structure composite nanoparticles were synthesized in PEG-acetone solution by photochemical route. The monodispersed Au nanoparticles with average diameter of 3.9 nm were used as growth seeds. The optical property of colloids and the sizes of composite nanoparticles were characterized when the molar ratio of Au to Ag ranges from 4 : 1 to 1 : 4. The results show that a composite nanoparticle structure similar to strawberry shape is formed at the molar ratio of Au to Ag from 4 : 1 to 1 : 1; the composite nanoparticles consisting of a core of Au and shell of Ag were generated at the 1: 4 molar ratio, having a striking feature of forming interconnected network structure.     

2014年灵丘春玉米生育期气象条件分析

根据灵丘县2014年4月下旬到9月下旬的气象观测资料和玉米获得高产所需的农业气象条件,对灵丘县春玉米生育期的气象条件进行了综合分析,得出2014-04—09的综合气象条件能满足春玉米生长发育的需求。其中,有3个时段的气象条件与春玉米生育阶段的需求不吻合,即5月上旬出现冷害、7月中下旬降水偏少、9月出现阶段性低温和阴雨寡照天气,这些不利气象条件都会对春玉米的发育造成不同程度的影响。     

不同灌溉量对退化草地的生态恢复作用

在希拉穆仁草原进行了为期3年的草地灌溉试验,对测试的试验地在灌溉3年期间及停灌后1年内进行了植被调查和土壤种子库发芽试验,结果表明：一是灌溉可以明显提高草地植被的生产性能且不同灌溉量间并无明显差异。当停止灌溉后,原灌溉样地的植被生产性能均略低于无灌溉对照区,且不同灌溉量间也无明显差异。二是不同灌溉量样地植被物种组成与无灌溉对照区的Bray-curtis相似性系数始终保持在0.8左右,表明灌溉期间群落结构并未发生很大变化。当停止灌溉后,原灌溉样地与无灌溉对照区的Bray-curtis相似性系数下降为充足灌溉区0.61和中度灌溉区0.55,表明灌溉对植物的生存策略有一定的影响且不同灌溉量基本相同。三是土壤中的种子总数量有所增加,但物种的数量有所减少。充足灌溉样地土壤种子库情况略差于无灌溉对照区,中度灌溉样地则略好于无灌溉对照区,表明不同灌溉量对植物的繁殖策略有一定的影响。     

一种变形表面的三维测量方法

提出一种新的利用标定图像进行三维测量的方法。利用SIFT算法找到初始的对应点,然后根据这些点生成三维空间中的种子点,再以这些种子点为中心,向外区域增长,直到完成整个物体表面测量。在每次增长的过程中,需要计算增长的三维空间平面在两个相机上的投影之间的图像相关系数。图像相关系数较大时认为是正确的增长,否则是错误的增长。实验证明,使用该方法能够得到很好的三维测量结果。     

使用线段表实现线段编码与种子填充快速算法

在图像处理中常用水平线段集表示区域,提出了一种采用线段表结构来表示区域,并给出使用线段表改进传统像素标记与种子填充算法的快速算法。该算法中,线段表的每个表项对应一条水平线段,它包含L、xL、xR、y和F 5个参数,即表示上下线段连通关系的标记,左、右端点的x坐标,线段的y坐标与表示线段特征或类型的标志。具有相同标记的线段表表项构成连通区域。以线段表为基础,水平与垂直方向的连通检测可分别进行,水平方向可通过行程编码实现,垂直方向则通过比较上下线段的端点坐标来确定。线段编码是像素标记的改进,由行程编码、线段标记、统一标记与标记排序4个步骤组成。采用线段表结构后,线段编码中利用桶排序,种子填充新算法中,利用队列结构并避免重复扫描来提高效率,与轮廓填充算法相比较效率都可提高近一倍。     

Detecting Overlapping Community Structures in Networks

Community structure has been recognized as an important statistical feature of networked systems over the past decade. A lot of work has been done to discover isolated communities from a network, and the focus was on developing of algorithms with high quality and good performance. However, there is less work done on the discovery of overlapping community structure, even though it could better capture the nature of network in some real-world applications. For example, people are always provided with varying characteristics and interests, and are able to join very different communities in their social network. In this context, we present a novel overlapping community structures detecting algorithm which first finds the seed sets by the spectral partition and then extends them with a special random walks technique. At every expansion step, the modularity function Q is chosen to measure the expansion structures. The function has become one of the popular standards in community detecting and is defined in Newman and Girvan (Phys. Rev. 69:026113, 2004). We also give a theoretic analysis to the whole expansion process and prove that our algorithm gets the best community structures greedily. Extensive experiments are conducted in real-world networks with various sizes. The results show that overlapping is important to find the complete community structures and our method outperforms the C-means in quality.     

Up in smoke: I. Smoke-derived germination cues for postfire annual,Nicotiana attenuata torr. Ex. Watson

Some postfire annuals with dormant seeds use heat or chemical cues from charred wood to synchronize their germination with the postfire environment. We report that wood smoke and polar extracts of wood smoke, but not the ash of burned wood, contain potent cue(s) that stimulate germination in the postfire annual plant,Nicotiana attenuata. We examined the responses of seeds from six populations of plants from southwest Utah to extracts of smoke and found the proportion of viable seeds that germinated in the presence of smoke cues to vary between populations but to be consistent between generations. With the most dormant genotypes, we examine three mechanisms by which smoke-derived chemical cues may stimulate germination (chemical scarification of the seed coat and nutritive- and signal-mediated stimulation of germination) and report that the response is consistent with the signal-mediated mechanism. The germination cue(s) found in smoke are produced by the burning of hay, hardwood branches, leaves, and, to a lesser degree, cellulose. Moreover, the cues are found in the common food condiment, liquid smoke, and we find no significant differences between brands. With a bioassay-driven fractionation of liquid smoke, we identified 71 compounds in active fractions by GC-MS and AA spectrometry. However, when these compounds were tested in pure form or in combinations that mimicked the composition of active fractions over a range of concentrations, they failed to stimulate germination to the same degree that smoke fractions did. Moreover, enzymatic oxidation of some of these compounds also failed to stimulate germination. In addition, we tested 43 additional compounds also reported from smoke, 85 compounds that were structurally similar to those reported from smoke and 34 compounds reported to influence germination in other species. Of the 233 compounds tested, 16 proved to inhibit germination at the concentrations tested, and none reproduced the activity of wood smoke. By thermally desorbing smoke produced by cellulose combustions that was trapped on Chromosorb 101, we demonstrate that the cue is desorbed between 125 and 150°C. We estimate that the germination cues are active at concentrations of less than 1 pg/seed and, due to their chromatographic behavior, infer that a number of different chemical structures are active. In separate experiments, we demonstrate that cues remain active for at least 53 days in soil under greenhouse conditions and that the application of aqucous extracts of smoke to soil containing seeds results in dramatic increases in germination of artificial seed banks. Hence, although the chemical nature of the germination cue remains elusive, the stability of the germination cues, their water-solubility, and their activity in low concentrations suggest that these cues could serve as powerful tools for the examination of dormant seed banks and the selective factors thought to be important in the evolution of postfire plant communities.     

A new method using feature extraction for identifying paddy rice species for quality seed selection

The purpose of this work was to explore a new feature extraction method for classifying paddy seeds using a feature extraction algorithm to achieve the area ratio, horizontal–slant and front–rear angles and find whether the proposed features have high discriminating power. Another objective was to find the smallest feature set that can ensure highly accurate recognition of seeds. A total of a 100 image features were extracted, and features having significant discriminating power were identified based on the analysis of variance (ANOVA). From the 100 features, 14 features were found to have high discriminating power and from these features, six were selected as the proposed features. Experimental results show that the proposed features and removal of redundant features enhanced the discriminating power of the feature set, and that the proposed features have an excellent discriminating property for seeds. The presented features resulted in the highest classification accuracy (98.8%) when compared to other methods.