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排序方式: 共有3343条查询结果,搜索用时 15 毫秒
1.
Mohd Akram Hira Lal Mohammad Osama Farah Ansari Sana Anwar Kabir-ud-Din Ajaz Ahmad Samreen Naved Azum Hadi M. Marwani Abdullah M. Asiri 《Journal of surfactants and detergents》2021,24(1):35-49
In this study, we prepared a novel series of diester-functionalized cationic gemini surfactants (Cm-E2O2-Cm) containing ethylene oxide as a spacer with varying alkyl chain lengths and characterized by 1H NMR, FT-IR, elemental analysis, and ESI-MS. The physicochemical properties of the geminis were explored by tensiometry, fluorescence, dye solubilization, and Krafft point. These geminis acquire superior surface activity than the conventional surfactants. Fluorescence spectroscopy analysis affirmed that the micropolarity and aggregation number of micelles diminished with increase in the alkyl chain length. These geminis represent a new group of amphiphiles of considerably high biodegradability, better cleavability, and low toxicity as assessed by BOD test, FT-IR analysis, and HC50 analysis, respectively. They also showed significant level of antimicrobial activity toward some specified bacterial strains of Gram-positive and Gram-negative by using agar well diffusion method. Furthermore, the thermogravimetric analysis provided information regarding thermal stabilities of the newly synthesized gemini surfactants. 相似文献
2.
Wan-Li Tan Dr. Chun Zhang Yang Li Dr. Kai Guo Dr. Xiao-Wei Gao Dr. Jun Wei Dr. Dong Yi Prof. Lin Pu Prof. Dr. Qin Wang 《ChemMedChem》2021,16(23):3569-3575
Forty samples of optically active falcarindiol analogues are synthesized by using the easily available C2 symmetric (R)- and (S)-1,1’-binaphth-2-ol (BINOL) in combination with Ti(OiPr)4, Zn powder and EtI. Their anticancer activities on Hccc-9810, HepG2, MDA-MB-231, Hela, MG-63 and H460 cells are assayed to elucidate their structure-activity relationships. These results showed that the falcarindiol analogue (3R,8S)- 2 i with the terminal double bond has the most potent anti-proliferation effect on Hccc-9810 cells with IC50 value of 0.46 μM. The falcarindiol analogue (3R,8S)- 2 i can induce obvious Hccc-9810 cell apoptosis in a concentration-dependent manner by Hoechst staining and flow cytometry analysis. The proposed mechanism suggests that the falcarindiol analogue (3R,8S)- 2 i increases LDH release and MDA content, and reduces the levels of SOD activity, which lead to the accumulation of oxidative stress and induce apoptosis in Hccc-9810 cells. 相似文献
3.
Bao-sheng LIU Miao-miao CAO Yue-zhong ZHANG Yong HU Chang-wei GONG Li-feng HOU Ying-hui WEI 《中国有色金属学会会刊》2021,31(2):358-370
To find suitable biodegradable materials for implant applications, Mg?6Zn?0.3Mn?xCa (x=0, 0.2 and 0.5, wt.%) alloys were prepared by semi-continuous casting followed by hot-extrusion technique. The microstructure and mechanical properties of Mg?6Zn?0.3Mn?xCa alloys were investigated using the optical microscope, scanning electron microscope and tensile testing. Results indicated that minor Ca addition can slightly refine grains of the extruded Mg?6Zn?0.3Mn alloy and improve its strength. When 0.2 wt.% and 0.5 wt.% Ca were added, the grain sizes of the as-extruded alloys were refined from 4.8 to 4.6 and 4.2 μm, respectively. Of the three alloys studied, the alloy with 0.5 wt.% Ca exhibits better combined mechanical properties with the ultimate tensile strength and elongation of 334 MPa and 20.3%. The corrosion behaviour, cell viability and antibacterial activities of alloys studied were also evaluated. Increasing Ca content deteriorates the corrosion resistance of alloys due to the increase of amount of effective cathodic sites caused by the formation of more Ca2Mg6Zn3 phases. Cytotoxicity evaluation with L929 cells shows higher cell viability of the Mg?6Zn?0.3Mn?0.5Ca alloy compared to Mg?6Zn?0.3Mn and Mg?6Zn?0.3Mn? 0.2Ca alloys. The antibacterial activity against Staphylococcus aureus is enhanced with increasing the Ca content due to its physicochemical and biological performance in bone repairing process. 相似文献
4.
河川径流是水资源重要组成部分,径流变化归因分析对于流域水资源安全及管理具有重要意义。基于白龙江中上游1960~2015年水文气象资料,采用多种统计学方法、基于Budyko假设的弹性分析法研究径流变化特征及归因分析。结果表明,径流呈显著下降趋势,线性倾向变化率为-2.69×108m3/10a,其临界突变发生在1986年,呈先上升后下降的趋势;径流量分布集中,6~10月占比63.59%,夏秋两季占比70.62%;径流减少受气候变化和人类活动影响,双累积曲线法影响率分别为33.02%、66.98%,累积量斜率变化率法影响率分别为44.17%、55.83%,弹性分析法影响率分别为35%~39%、61%~65%,可见人类活动为径流减少的主要影响因素,同时,弹性分析法计算结果介于其他两种方法计算结果之间,最为可靠。 相似文献
5.
采用高压均质辅助构筑十六烷基三甲基溴化铵(CTAB)改性植物精油/凹凸棒石复合抗菌材料,对其进行了FTIR、XRD、SEM、Zeta电位和TG测试表征.FTIR分析表明,植物精油负载于凹凸棒石并成功实现表面改性.随CTAB用量增加,复合抗菌材料的Zeta电位由负变正.最小抑菌浓度(MIC)测试结果表明,复合材料的抗菌性能随CTAB用量的增加而增强,CTAB改性明显提升了复合材料对革兰氏阳性菌的抗菌活性.当CTAB用量为2.5%(以凹凸棒石质量为基准,下同)时,CTAB改性香芹酚/凹凸棒石复合材料和肉桂醛/凹凸棒石复合材料对金黄色葡萄球菌的MIC值由未改性的1 g/L分别减小至0.125 g/L和0.5 g/L. 相似文献
6.
目的 针对未来时间内重大活动举办地鲜(冻)肉制品铅含量风险预测的问题,建立基于LSTM的时间序列预测模型,对当地鲜(冻)肉制品铅含量进行风险评估与预测预警。方法 通过收集2011-2020年国家市场监督管理总局日常食品监督管理抽检数据,筛选出北京的鲜(冻)肉制品的抽检数据,构建数据集并进行预处理,按照7:2:1的比例划分训练集、验证集和测试集,基于Tensorflow平台构建4层LSTM模型并进行训练,基于重大活动举办前10天的鲜(冻)制品铅含量数据,对未来1天的鲜(冻)制品铅含量风险进行预测。结果 实验表明,经过50轮模型迭代训练,训练集和测试集Loss指标收敛至0.084,经过5次训练后的模型评估参数RMSE为0.192,R2_score为0.916,模型误差较小、准确度较高。结论 基于LSTM的鲜(冻)肉制品铅含量风险预测模型整体性能较好,可应用于重大活动举办地的食品风险预测,并精准指导监督抽检。 相似文献
7.
为探究不同保鲜纸对采后枇杷货架品质及生理特性的影响。以"大五星"枇杷为试验材料,用不同处理的保鲜纸(500 mg·L-1纳他霉素、500 mg·L-1 ε-聚赖氨酸、500 mg·L-1二氧化氯)放入装有枇杷的保鲜箱内,在(20±0.5)℃货架条件下贮放,研究其枇杷在货架期品质及生理特性的变化。结果表明:与对照组(CK)比较,不同保鲜纸均能够延缓枇杷果实的腐烂率及失重率上升,抑制枇杷鲜果的VC含量、可滴定酸含量和可溶性固形物含量的下降,降低枇杷鲜果呼吸强度及乙烯生成速率,较好地抑制过多酚氧化酶(PPO)活性和氧化物酶(POD)活性。其中,在货架期12 d时,CK组、纳他霉素、ε-聚赖氨酸、二氧化氯的枇杷腐烂率分别为27.45%、22.56%、18.76%、14.62%。采后用二氧化氯型保鲜纸处理枇杷的保鲜效果最好,能够推迟枇杷的衰老进程,保持枇杷良好的货架期品质。 相似文献
8.
9.
In this study, 30 subjects were exposed to different combinations of air temperature (Ta: 24, 27, and 30°C) and CO2 level (8000, 10 000, and 12 000 ppm) in a high-humidity (RH: 85%) underground climate chamber. Subjective assessments, physiological responses, and cognitive performance were investigated. The results showed that as compared with exposure to Ta = 24°C, exposure to 30°C at all CO2 levels caused subjects to feel uncomfortably warm and experience stronger odor intensity, while increased mental effort and greater intensity of acute health symptoms were reported. However, no significant effects of Ta on task performance or physiological responses were found. This indicated that subjects had to exert more effort to maintain their performance in an uncomfortably warm environment. Increasing CO2 from 8000 to 12 000 ppm at all Ta caused subjects to report higher rates of headache, fatigue, agitation, and feeling depressed, although the results were statistically significant only at 24 and 27°C. The text typing performance and systolic blood pressure (SBP) decreased significantly at this exposure, whereas diastolic blood pressure (DBP) and thermal discomfort increased significantly. These effects suggest higher arousal/stress. No significant interaction effect of Ta and CO2 concentration on human responses was identified. 相似文献
10.
纳米硒的研究进展及其在食药领域的应用 总被引:1,自引:0,他引:1
硒(selenium,Se)是一种人体必需的微量营养元素,适量的补充可增强体内含硒酶(如谷胱甘肽过氧化酶等)的活性,清除过量自由基,预防和治疗心脑血管疾病及癌症等。红色零价态的纳米硒(selenium nanoparticle with valence state of zero,Se0NPs)不仅兼具氧化还原的基本性质,还可以通过设计不同的表面修饰剂(如多糖、蛋白、生物活性物质等)参数调控Se0NPs的功能性质,因此在食品、药品以及化妆品领域具有广泛的应用前景,可作为营养补充剂、抗癌制剂、抑菌剂等。但是Se0NPs在应用的过程中会面临着多种加工条件,可能导致Se0NPs的失效或硒释放造成的毒性风险,需要引起关注。本文主要对纳米硒的研究现状、表面修饰剂种类、功能性质、生物活性及其应用情况进行了总结,并对其未来的研究与发展进行了展望。 相似文献