多羟基甾醇的合成及其结构与抗肿瘤细胞活性关系研究

报道了6个具有类似结构的多羟基甾醇的合成和它们的抗肿瘤细胞活性.发现此类化合物的细胞毒性与其分子中双键存在与否有着密切关系.当甾核或支链中双键被饱和时,其细胞毒性均明显降低.甾醇(5)和(8)对胃癌(MGC)、宫颈癌(HELA)细胞的生长具有一定的抑制作用.     

极端干旱地区人地关系历史演变的初步研究--以新疆塔里木盆地为例

论述了极端干旱环境背景下的人地关系性质以及演变的主要特征 ,指出在此地区资源是决定人地关系性质和特征的首要因素 ,而气候的自然演变、人类活动的影响等是在不同时空尺度上制约着干旱区人类的生存空间、活动空间以及人类的生存活动、社会生产活动与自然环境的物质、能量、信息交流等方面的更深层次的因素 .从原始社会 ,农业社会到工业社会 ,这种关系的表现形式一直不断地发生着变化 ,大致经历了依附自然 ,干预——顺应自然 ,干预自然 ,回归自然四个阶段 .各个阶段以气候环境变化为背景 ,以水资源为主线 ,表现出人地关系演变的时空特征     

Conformational effect on fluorescence emission of tetraphenylethylene-based metallacycles

Herein, we designed and constructed two metallacycles, 1 and 2, to illustrate the conformational effect of isomeric AIE fluorophores on the platform of supramolecular coordination complexes (SCCs). Speci?cally, the dangling phenyl rings in TPE units of the metallacycle 1 align completely outside the main cyclic structure, while in the metallacycle 2, these phenyl rings align half inside and half outside. The experimental results showed that two metallacycles exhibited different behaviors in terms of AIE fluorescence and chemical sensing, which could be attributed to the subtle structural difference of the TPE units. This work represents the unification of topics such as self-assembly, AIE, and chemical sensing, and further promotes the understanding for the structure-property relationship of isomeric AIE fluorophores.     

Formation mechanism of the hierarchic structure in the lath martensite phase in steels

Martensitic transformation is the phase transformation accompanying orderly shear deformation without atomic diffusion. The structures made by martensitic transformation are classified as thin plate, lens or lath in steels. The mechanism by which the hierarchic microstructure in the lath martensite phase forms has heretofore not been understood. We have made clear the mechanism by considering, independently, two plastic deformations using the slip deformation model proposed by Khachaturyan, and present herein a deformation matrix for each of the six crystallographic variants in a packet of the hierarchic structure. Our results are quantitatively consistent with experimental results for the Kurdjumov–Sachs (K-S) crystal orientation relationship and habit plane. Furthermore, the important points of our study are as follows: the origin of the sub-block structure and the specific combination of the sub-block structure are clarified; the laths existing in a block can be explained; and deviations between the directional parallel and plane parallel are obtained quantitatively, without any adjustable parameters.     

Carbon-content dependent effect of magnetic field on austenitic decomposition of steels

The transformed microstructures of the high-purity Fe-0.12C alloy and Fe-0.36C alloy heat treated without and with a 12 T magnetic field have been investigated to explore the carbon-content dependent field effect on austenitic decomposition in steels. Results show that, the field-induced transformed morphology characteristics in different alloys differ from each other. In the Fe-0.12C alloy, the pearlite colonies are elongated along the field direction, and shaped by the chained and elongated proeutectoid ferrite grains in the field direction. However, in the Fe-0.36C alloy, the field mainly reduces the amount of Widmänstatten ferrite and elongates the formed proeutectoid ferrite grains in the field direction. No clear field direction alignment is obtained. The magnetic field also demonstrates carbon-content dependent effect on the texture of the formed ferrite. It clearly enhances the 〈001〉 fiber of the ferrite in the transverse field direction in the Fe-0.36C alloy. This field effect is related to the crystal lattice distortion induced by carbon solution and this impact becomes stronger with the increase of the carbon content. For the Fe-0.12C alloy, this field effect is greatly reduced due to the reduced carbon oversaturation in ferrite and elevated formation temperature. The orientation relationships (ORs) between the pearlitic ferrite and the pearlitic cementite in both alloys are less affected by the magnetic field. No obvious changes in the either type of the appearing ORs and their number of occurrences are detected.     

秦岭大熊猫主食竹叶片不同花期内源激素变化及与高光谱的响应关系

选取佛坪保护区不同开花状态的大熊猫主食竹种巴山木竹(Bashania fargesii)、秦岭箭竹(Farge-sia qinlingensis)和龙头竹(Fargesia dracocephala)进行高光谱测定,并利用酶联免疫吸附法测定分析竹叶的内源激素(赤霉素、生长素、玉米素核苷和脱落酸)的差异,并建立关系模型。结果为:(1)巴山木竹和龙头竹在未开花状态下的赤霉素含量高于开花状态下的,而秦岭箭竹相反;三种竹子未开花竹的生长素和脱落酸含量都低于开花竹;未开花竹的玉米素核苷高于开花竹的。(2)除巴山木竹的生长素和玉米素核苷含量与一定波段的原始光谱显著相关,三种竹子的其他激素含量仅与光谱一阶导数在一定波段极显著相关。(3)利用特征波段得到的线性模型精度高。研究表明激素含量与光谱的相关性能预测竹子开花。     

Total Synthesis and Functional Evaluation of Fourteen Derivatives of Lysocin E: Importance of Cationic,Hydrophobic, and Aromatic Moieties for Antibacterial Activity

Lysocin E ( 1 ) is a structurally complex 37‐membered depsipeptide comprising 12 amino‐acid residues with an N‐methylated amide and an ester linkage. Compound 1 binds to menaquinone (MK) in the bacterial membrane to exert its potent bactericidal activity. To decipher the biologically important functionalities within this unique antibiotic, we performed a comprehensive structure‐activity relationship (SAR) study by systematically changing the side‐chain structures of l ‐Thr‐1, d ‐Arg‐2, N‐Me‐d ‐Phe‐5, d ‐Arg‐7, l ‐Glu‐8, and d ‐Trp‐10. First, we achieved total synthesis of the 14 new side‐chain analogues of 1 by employing a solid‐phase strategy. We then evaluated the MK‐dependent liposomal disruption and antimicrobial activity against Staphylococcus aureus by 1 and its analogues. Correlating data between the liposome and bacteria experiments revealed that membrane lysis was mainly responsible for the antibacterial functions. Altering the cationic guanidine moiety of d ‐Arg‐2/7 to a neutral amide, and the C7‐acyl group of l ‐Thr‐1 to the C2 or C11 counterpart decreased the antimicrobial activities four‐ or eight‐fold. More drastically, chemical mutation of d ‐Trp‐10 to d ‐Ala‐10 totally abolished the bioactivities. These important findings led us to propose the biological roles of the side‐chain functionalities.     

高中物理实验中线性关系的建立与应用

高中物理实验是高考的重要考点,而在实验中合理应用图像解决问题更是热点.在高中物理实验中,各个物理量的关系错综复杂,多为非线性关系,因此,绘制出有关两个物理量的图像也多以曲线为主,很难利用图像解决实际问题.此文意从如何适当地转化物理量的形式,从而建立起它们之间的线性关系等相关问题进行研讨.     

离子液体的黏度与其扩散系数和电导率的新型关系方程

离子液体的传递性质对其在化学化工等领域的研究和应用至关重要,但迄今文献中缺乏可靠的理论预测模型或传递性质间的相互关系式,因此,有必要建立传递性质间的相互关系以便应用.本文建立了离子液体黏度与扩散系数或电导率间的定量关系,并利用文献实验数据进行了系统检验.结果表明,新方程可由离子液体黏度数据准确预测其扩散系数和电导率.与Stokes-Einstein方程相比,新方程不仅可解释离子液体中的许多实验现象,而且实现了定量预测(无需离子的有效流体力学半径数据).