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.     

A Review on Mechanistic Insight of Plant Derived Anticancer Bioactive Phytocompounds and Their Structure Activity Relationship

Cancer is a disorder that rigorously affects the human population worldwide. There is a steady demand for new remedies to both treat and prevent this life-threatening sickness due to toxicities, drug resistance and therapeutic failures in current conventional therapies. Researchers around the world are drawing their attention towards compounds of natural origin. For decades, human beings have been using the flora of the world as a source of cancer chemotherapeutic agents. Currently, clinically approved anticancer compounds are vincristine, vinblastine, taxanes, and podophyllotoxin, all of which come from natural sources. With the triumph of these compounds that have been developed into staple drug products for most cancer therapies, new technologies are now appearing to search for novel biomolecules with anticancer activities. Ellipticine, camptothecin, combretastatin, curcumin, homoharringtonine and others are plant derived bioactive phytocompounds with potential anticancer properties. Researchers have improved the field further through the use of advanced analytical chemistry and computational tools of analysis. The investigation of new strategies for administration such as nanotechnology may enable the development of the phytocompounds as drug products. These technologies have enhanced the anticancer potential of plant-derived drugs with the aim of site-directed drug delivery, enhanced bioavailability, and reduced toxicity. This review discusses mechanistic insights into anticancer compounds of natural origins and their structural activity relationships that make them targets for anticancer treatments.     

Synthesis and Biochemical Evaluation of 8H-Indeno[1,2-d]thiazole Derivatives as Novel SARS-CoV-2 3CL Protease Inhibitors

The COVID-19 pandemic caused by SARS-CoV-2 is a global burden on human health and economy. The 3-Chymotrypsin-like cysteine protease (3CL^pro) becomes an attractive target for SARS-CoV-2 due to its important role in viral replication. We synthesized a series of 8H-indeno[1,2-d]thiazole derivatives and evaluated their biochemical activities against SARS-CoV-2 3CL^pro. Among them, the representative compound 7a displayed inhibitory activity with an IC₅₀ of 1.28 ± 0.17 μM against SARS-CoV-2 3CL^pro. Molecular docking of 7a against 3CL^pro was performed and the binding mode was rationalized. These preliminary results provide a unique prototype for the development of novel inhibitors against SARS-CoV-2 3CL^pro.     

基于非线性预处理的SAR图像浮点数据压缩

提出了一种基于非线性预处理和DCT的SAR图像浮点数据压缩方法,通过对预处理前后DCT系数的熵和恢复图像信噪比的分析,确定符合SAR数据特征的预处理方法,再应用区域编码对其进行定值压缩。实验表明该方法可取得非常明显的效果。     

Structure-based linker optimization of 6-(2-cyclohexyl-1-alkyl)-2-(2-oxo-2-phenylethylsulfanyl)pyrimidin-4(3H)-ones as potent non-nucleoside HIV-1 reverse transcriptase inhibitors

In continuation of our efforts toward the discovery of potent HIV-1 NNRTIs with diverse structures,a series of novel S-DACO analogues of 6-(2-cyclohexyl-1-allkyl)-2-(2-oxo-2-phenyl-ethylsulfanyl)pyrimidin-4(3 H)-ones were designed,synthesized and evaluated for their antiviral activities in MT-4 cells.Most of these new compounds showed moderate to good activities against wild type HIV-1 with IC_(50) values ranging from 7.55 μmol/L to 0.018 μmol/L.Among them,compound 5 c was identified as the most promising inhibitor against HIV-1 replication with an IC_(50)=0.018 μmol/L,CC_(50)=194 μmol/L,and SI=12791,which was much more potent than the reference drugs NVP and DLV and comparable to AZT and EFV.In addition,5 c also exhibited improved activity against double mutant HIV-1 strain RES056 compared to that of the reference drugs NVP/DLV and DB02.The preliminary structure-activity relationship(SAR) and molecular modeling studies were also discussed,which provides some useful indications for guiding the further rational design of new S-DACO analogues.     

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...