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71.
We study the regularity of weak solutions to a class of second order parabolic system under only the assumption of continuous coefficients.We prove that the wea... 相似文献
72.
73.
Chiral chromanone lactones are a class of natural products with important biological activity. We report a direct diastereo- and enantioselective vinylogous conjugate addition of butenolide to 2-ester substituted chromones. The transformation proceeded well in the presence of as low as 1 mol% of a chiral N,N′-dioxide/ScIII complex, 3 Å MS and a catalytic amount of hexafluoroisopropanol (HFIP). The scope of Michael acceptors includes a variety of substituted chromones at different positions, and the desired chromanone lactones upon reduction are afforded in good yield and diastereoselectivity, and excellent enantioselectivity (up to 99% ee). The strategy could be used in the concise synthesis of blennolide C and gonytolide A, C and G.We report a direct, diastero- and enantioselective vinylogous 1,4-addition of butanolide to 2-ester chromones. A chiral ScIII complex enabled the reaction to proceed smoothly to give a variety of chraomanone lactones. 相似文献
74.
75.
以Zn(NO3)2· 6H2O和C6H12N4为原材料,采用二步水热法在碳纤维布上合成了形貌尺寸均匀的ZnO超细纳米线阵列。用 X 射线衍射(XRD)和扫描电镜(SEM)对其晶体结构和形貌进行了表征,利用恒流充放电测试等手段对其进行电化学性能测试。测试结果表明,材料表现出优异的电化学性能。在200 mA/g的电流密度下循环150次后,ZnO超细纳米线阵列仍然约有730 mAh/g的充放电比容量,库伦效率保持在95%以上。在1 200 mA/g的大倍率条件下,材料的充放电比容量依旧可达481 mAh/g左右,表现出十分良好的循环稳定性和可逆性能,是一种较为理想的锂离子电池负极复合材料。 相似文献
76.
Bin-Long Sun Ying-Ying Wang Sen Yang Min-Ting Tu Ying-Ying Shao Yi Hua Yi Zhou Cheng-Xia Tan 《Molecules (Basel, Switzerland)》2022,27(12)
To develop new compounds with high activity, broad spectrum and low-toxicity, 17 benzamides substituted with quinoline-linked 1,2,4-oxadiazole were designed using the splicing principle of active substructures and were synthesized. The biological activities were evaluated against 10 fungi, indicating that some of the synthetic compounds showed excellent fungicidal activities. For example, at 50 mg/L, the inhibitory activity of 13p (3-Cl-4-Cl substituted, 86.1%) against Sclerotinia sclerotiorum was superior to that of quinoxyfen (77.8%), and the inhibitory activity of 13f (3-CF3 substituted, 77.8%) was comparable to that of quinoxyfen. The fungicidal activities of 13f and 13p to Sclerotinia sclerotiorum were better than that of quinoxyfen (14.19 mg/L), with EC50 of 6.67 mg/L and 5.17 mg/L, respectively. Furthermore, the acute toxicity of 13p was 19.42 mg/L, classifying it as a low-toxic compound. 相似文献
77.
Yi Wang Xiangli Zhang Wenya Zhuang Yanlei Yu Xuanrong Sun Hong Wang Fengzhi Li Qingyong Li 《Molecules (Basel, Switzerland)》2022,27(12)
Irinotecan and Topotecan are two Camptothecin derivatives (CPTs) whose resistance is associated with the high expression of breast cancer resistance protein (BCRP) and P-glycoprotein (P-gp). To reverse this resistance, two novel CPTs, FL77-28 (7-(3-Fluoro-4-methylphenyl)-10,11-methylenedioxy-20(S)-CPT) and FL77-29 (7-(4-Fluoro-3-methylphenyl)-10,11-methylenedioxy-20(S)-CPT), were synthesized by our group. In this study, the anti-tumor activities of FL77-28, FL77-29, and their parent, FL118 (10,11-methylenedioxy-20(S)-CPT), were evaluated and the results showed that FL77-28 and FL77-29 had stronger anti-tumor activities than FL118. The transport and uptake of FL118, FL77-28, and FL77-29 were investigated in Caco-2 cells for the preliminary prediction of intestinal absorption. The apparent permeability coefficient from apical to basolateral (Papp AP-BL) values of FL77-28 and FL77-29 were (2.32 ± 0.04) × 10−6 cm/s and (2.48 ± 0.18) × 10−6 cm/s, respectively, suggesting that the compounds had moderate absorption. Since the transport property of FL77-28 was passive diffusion and the efflux ratio (ER) was less than 2, two chemical inhibitors were added to further confirm the involvement of efflux proteins. The results showed that FL77-28 was not a substrate of P-gp or BCRP, but FL77-29 was mediated by P-gp. In conclusion, FL77-28 might be a promising candidate to overcome drug resistance induced by multiple efflux proteins. 相似文献
78.
A new 2D metal coordination polymer(MCP),[Mn(pzdc)_(0.5)(L)]_n(1,pzdc=pyrazine-2,3-dicarboxylic acid,HL=3-(2-pyridyl)pyrazole),was synthesized under hydrothermal conditions and characterized by single-crystal X-ray diffraction,powder XRD,FT-IR,TG,fluorescence and elemental analysis techniques.Pale yellow crystals crystallize in orthorhombic system,space group Fdd2 with a=11.2368(6),b=38.280(2),c=10.5682(6) A,V=4545.9(4) A~3,C_(11)H_7MnN_4O_2,M_r=282.15,D_c=1.649 g/cm~3,μ(MoKα)=1.159 mm~(-1),F(000)=2272,Z=16,the final R=0.0613 and wR=0.1773 for 2856 observed reflections(I 2σ(I)).It shows a two-dimensional network structure and is further assembled into a three-dimensional supramolecular framework via hydrogen bonds and abundant π-π interactions.In addition,we analyzed natural bond orbital(NBO) of 1 in using the PBE0/LANL2DZ method established in Gaussian 03 Program.There is obvious covalent interaction between the coordinated atoms and Mn(Ⅱ) ions. 相似文献
79.
80.
作为一种洁净能源,硅锗合金的热电转换性能的研究越来越受到人们的重视.本文重点研究了不同Ge浓度的硅锗合金以及Si、Ge单晶在300~1100K温度范围内,Seebeck系数随温度的变化.并对组分相同导电类型不同、晶向不同以及结晶状态不同的样品的Seebeck系数进行了比较.在研究温度区间,Seebeck系数的绝对值大小一般在200~600μV/K之间,随温度不同连续变化.通过对比发现SiGe合金的Seebeck系数大小不仅与Ge的浓度和温度有关,其他因素对其绝对值也有影响,其中晶向最为明显,表现出了明显的各向异性.此外,材料本身的电阻率除了作为一个热电参数影响最优值外,其大小还对Seebeck系数的绝对值有影响,即掺杂济浓度对Seebeck系数的影响. 相似文献