Snowpack permittivity profile retrieval from tomographic SAR data

This work deals with 3D structure characterization and permittivity profile retrieval of snowpacks by tomographic SAR data processing. The acquisition system is a very high resolution ground based SAR system, developed and operated by the SAPHIR team, of IETR, University of Rennes-1 (France). It consists mainly of a vector network analyser and a multi-static antenna system, moving along two orthogonal directions, so as to obtain a two-dimensional synthetic array. Data were acquired during the AlpSAR campaign carried by the European Space Agency and led by ENVEO. In this study, tomographic imaging is performed using Time Domain Back Projection and consists in coherently combining the different recorded backscatter contributions. The assumption of free-space propagation during the focusing process is discussed and illustrated by focusing experimental data. An iterative method for estimating true refractive indices of the snow layers is presented. The antenna pattern is also compensated for. The obtained tomograms after refractive index correction are compared to the stratigraphy of the observed snowpack.     

A complex target terrain SAR raw data generation and evaluation based on inversed equalized hybrid-domain algorithm processing

In this paper, synthetic aperture radar raw data generation of complex target terrain based on inverse equalized hybrid-domain processing technique is proposed. Firstly, the basic synthetic aperture radar (SAR) echo model is derived via spectral analysis of extended chirp scaling. Then, the inverse equalized extended chirp scaling algorithm (ECSA) procedure is applied directly step by step to a real input SAR image in order to generate the raw data of the reference SAR image. The whole raw data generation (RDG) procedure only consists of Inverse Equalized ECSA (IEECSA) without integral equation and computation complexity, which means easier implementation and higher efficiency. By applying the resulted RDG into different image formation algorithms (IFAs), not only the final images are reconstructed but also the resulted RDG is evaluated in practice. Finally, valid image quality assessment techniques are implemented on the reconstructed images. The simulations not only confirm the validity of the proposed RDG method based on inverse equalized hybrid-domain technique but also evaluate the quality metrics of reconstructed images as a method of reliability assurance.     

结构多样性与构效关系——雷公藤新药研究与开发

雷公藤是我国拥有的一种资源比较丰富的传统中草药。其中的主要活性成分雷公藤内酯醇是一种具有3个环氧基团以及一个α, β-不饱和五元内酯环结构的构型独特的松香烷型二萜化合物,具有明显的抗炎、免疫抑制、抗肿瘤及抗雄性生育等生物活性,自被发现以来,吸引了众多药物化学家及药理学家的广泛关注。通过对雷公藤内酯醇结构多样性改造和修饰,包括对C14-位羟基、C12, C13-位环氧、α, β-不饱和五元内酯环、C7,C8-位环氧、C5,C6-位的修饰,以及三环氧开环的改造,合成出了一系列雷公藤内酯醇衍生物,并进行了相关的药理活性测试。总结雷公藤环氧二萜类结构类似物的药理测试结果,初步得出了一些构效关系的特点。随着针对雷公藤内酯醇各个位点进行结构多样性改造所获得的衍生物以及相应的系统性药理活性测试的不断积累与深化,雷公藤内酯醇的结构与活性关系(SAR)也必定越来越明朗。合成低毒性、高活性、宽治疗视窗的雷公藤内酯醇衍生物是该领域众多药物化学家和药理学家的共同目标,从而使雷公藤在更多的领域中具有更广阔的应用前景。     

Interaction of a submerged horseshoe vortex with a free surface

In this paper a submerged horseshoe vortex under a free surface is discussed and the algebraic expression of the wave elevation is obtained. From this expression, some characteristics of the ship wave are described. There exists a smooth region near $\theta = 0^\circ$, but when the uniform stream passes the other singularities (source, sink, doublet, etc.) there is no smooth region. The mechanism of synthetic aperture radar (SAR) images of the narrow ship wakes is also explained.     

含氟新农药的构效关系研究Ⅰ.经典QSAR分析

为了能更深入地认识含氟新化合物作为农药的生物活性和其结构间的关系,建立有意义的构效关系模型,我们用经典QSAR(定量构效关系)方法研究了三十三个含氟化合物的两种不同的生物活性与结构的关系,其对抗黄瓜疫病活性模型有很好的解释能力和预测能力,并根据这个模型设计了一些新的活性结构.而对抑制西瓜白绢病的活性数据的处理未能获得理想模型.通过这一工作确立了先应用聚类等定性分析方法,再用多元统计分析方法作更深入研究的QSAR研究模式.     

Synthesis and biological evaluation of a des-dihydropyran laulimalide analog

The preparation of a novel simplified Laulimalide analog via a highly convergent and efficient route and its biological evaluation are presented. The outlined route enables the synthesis of C₅–C₉ modified analog 2 and uses Julia–Kocienski olefination for fragment assembly and a regioselective Yamaguchi macrolactonization for ring closure. This strategy should be suitable for the generation of various new C₅–C₉ des-dihydropyran laulimalide derivatives for further SAR studies.     

从SAR遥感图像中提取水域的一种双模式结合方法

水域是SAR图像的一个重要特征,针对SAR图像水域的检测问题,提出了一种利用形态学和信息跟踪双模式相结合的检测方法。采用形态学的开运算,提取基本的水域轮廓,再结合改进的信息编码,进行跟踪检测,进一步精确定位水域区域。实验结果表明,双模式结合的水域检测方法,可以较准确的提取SAR图像的水域区域,效果要优于单一模式的检测方法,而且跟信息熵方法相比较还提高了运算效率。     

HF SAR image cross-correlation technique for high accuracy orbit positioning

A novel technique to determine the position of spacecraft orbits is proposed. The technique is based on the cross-correlation function of HF SAR images and is able to determine the relative position of orbits with an accuracy of ～ /4 or better, where is the wavelength of the HF radar pulse at its center frequency. The performance of the proposed technique was confirmed by simulation which was carried out under the condition of design facts of the SELENE LRS mission. The highly accurate orbit positioning ena...     

Aryl-oxadiazole Schiff bases: Synthesis, α-glucosidase in vitro inhibitory activity and their in silico studies

α-Glucosidase enzyme is a therapeutic target for diabetes mellitus and its inhibitors play a vital role in the treatment of this disease. A new series of aryl-oxadiazole Schiff bases (1–18) were synthesized and evaluated for α-glucosidase inhibitory potential. Fifteen compounds 1–8, 11–13, and 15–18 showed excellent inhibition with IC₅₀ values ranging from 0.30 ± 0.2 to 35.1 ± 0.80 µM as compared to the standard inhibitor acarbose (IC₅₀ = 38.45 ± 0.80 µM), nonetheless, the remaining compounds were found to have moderate activity. Among the series, compounds 7 (IC₅₀ = 0.30 ± 0.2 μM) with hydroxy groups at phenyl rings on either side of the oxadiazole ring was identified as the most potent inhibitor of α-glucosidase. The molecular docking studies were conducted to understand the binding mode of active inhibitors with the active site of enzyme and results supported the experimental data.     

Plasmodial Kinase Inhibitors Targeting Malaria: Recent Developments

Recent progress in reducing malaria cases and ensuing deaths is threatened by factors like mutations that induce resistance to artemisinin derivatives. Multiple drugs are currently in clinical trials for malaria treatment, including some with novel mechanisms of action. One of these, MMV390048, is a plasmodial kinase inhibitor. This review lists the recently developed molecules which target plasmodial kinases. A systematic review of the literature was performed using CAPLUS and MEDLINE databases from 2005 to 2020. It covers a total of 60 articles and describes about one hundred compounds targeting 22 plasmodial kinases. This work highlights the strong potential of compounds targeting plasmodial kinases for future drug therapies. However, the majority of the Plasmodium kinome remains to be explored.