Lepidoptera,with 0.16 million species,is the second largest order of insecta.This order includes silk worms,butterflies,and many agricultural pests.The cotton bollworm,Helicoverpa armigera(Hubner)is one of the pests i...Lepidoptera,with 0.16 million species,is the second largest order of insecta.This order includes silk worms,butterflies,and many agricultural pests.The cotton bollworm,Helicoverpa armigera(Hubner)is one of the pests in Lepidoptera that seriously harms cotton plant and other crops in China and other countries.This pest develops resistance to chemical insecticides rapidly.Bacillus thuringiensis(Bt)transgenic cotton plants are developed to control H.armigera population in the field.However,duri ng the past years,the rapid evoluti on of Bt toxi n resista nee is observed in H.armigera in tran sge nic cott on fields.New approaches for the development of new envir on mentally friendly insecticides to control H.armigera have become necessary,and the molecular mechanisms underlying the development and physiological processes of this species need to be further understood.Considerable progress in the study of H.armigera development and physiology has been achieved in the last decade.This mini-review summarizes the main fin dings on the molecular mechanisms of horm onal regulation of the development of H.armigera to present new target genes for developing new approaches to control the pest.展开更多
One of the primary forestry research interests lies in estimating forest stand parameters by applying empirical or semi-empirical model to establish the relationship between the forest stand parameters and remote sens...One of the primary forestry research interests lies in estimating forest stand parameters by applying empirical or semi-empirical model to establish the relationship between the forest stand parameters and remote sensing data. Using remote sensing image and the inventory data from 2 compartments in northeast Florida, U.S.A., this paper explored the correlation between forest stand parameters and Landsat TM spectral digital number （DN） value. Results showed that less than 50% of the total variance could be explained by linear regression models with only either a single band or such vegetation indices as vegetation index （VI） or normalized difference vegetation index （NDVI） as predicators. In consequence, multi-linear regression models which synthesized more predicators were introduced to estimate forest parameters. Regression results were tested in terms of the other group of data, and verification showed a better capability of explaining over 75% variance except for forest density. The weakness and further improvement of prediction models were also discussed in the article. This paper is expected to provide a better understanding of the relationship between TM spectral and forest characteristics展开更多
文摘后随X射线望远镜(follow-up X-ray telescope,FXT)是爱因斯坦探针卫星的主要载荷之一.为了获取高信噪比的数据,实现对观测天体的高精度定位,FXT使用Wolter-Ⅰ型X射线聚焦光学系统,该系统一直是X射线空间天文观测中的重要设备.根据Wolter-Ⅰ型的聚焦原理,结合实际的加工特点,利用蒙特卡罗模拟算法对影响光学成像质量的几个关键参量,如表面粗糙度、面形误差进行了模拟,结合模拟结果对各参量的作用效果进行了分析.之后利用PANTER实验室提供的聚焦镜性能测试结果对模拟方法进行了验证,同时对面形误差参量进行了限制.最终聚焦镜结构热控件半能量宽度(half energy width,HEW)模拟与实测结果基本一致.该模拟过程可以很有效地应用于聚焦镜加工工艺的摸索,为FXT的聚焦镜测试和标定工作提供参考.结合实测标定数据,该模拟方法生成的有效面积、渐晕和点扩散函数等可用于在轨观测标定数据库.
基金This study received the support from the National Natural Science Foundation of China(31730083 and 31572328).
文摘Lepidoptera,with 0.16 million species,is the second largest order of insecta.This order includes silk worms,butterflies,and many agricultural pests.The cotton bollworm,Helicoverpa armigera(Hubner)is one of the pests in Lepidoptera that seriously harms cotton plant and other crops in China and other countries.This pest develops resistance to chemical insecticides rapidly.Bacillus thuringiensis(Bt)transgenic cotton plants are developed to control H.armigera population in the field.However,duri ng the past years,the rapid evoluti on of Bt toxi n resista nee is observed in H.armigera in tran sge nic cott on fields.New approaches for the development of new envir on mentally friendly insecticides to control H.armigera have become necessary,and the molecular mechanisms underlying the development and physiological processes of this species need to be further understood.Considerable progress in the study of H.armigera development and physiology has been achieved in the last decade.This mini-review summarizes the main fin dings on the molecular mechanisms of horm onal regulation of the development of H.armigera to present new target genes for developing new approaches to control the pest.
文摘One of the primary forestry research interests lies in estimating forest stand parameters by applying empirical or semi-empirical model to establish the relationship between the forest stand parameters and remote sensing data. Using remote sensing image and the inventory data from 2 compartments in northeast Florida, U.S.A., this paper explored the correlation between forest stand parameters and Landsat TM spectral digital number （DN） value. Results showed that less than 50% of the total variance could be explained by linear regression models with only either a single band or such vegetation indices as vegetation index （VI） or normalized difference vegetation index （NDVI） as predicators. In consequence, multi-linear regression models which synthesized more predicators were introduced to estimate forest parameters. Regression results were tested in terms of the other group of data, and verification showed a better capability of explaining over 75% variance except for forest density. The weakness and further improvement of prediction models were also discussed in the article. This paper is expected to provide a better understanding of the relationship between TM spectral and forest characteristics
