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81.
Ekaterina V. Bartashevich Svetlana E. Mukhitdinova Iliya V. Klyuev Vladimir G. Tsirelson 《Molecules (Basel, Switzerland)》2022,27(17)
Using the orbital-free quantum crystallography approach, we have disclosed the quantitative trends in electronic features for bonds of different strengths formed by tetrel (Tt) atoms in stable molecular complexes consisting of electrically neutral tetrahedral molecules and halide anions. We have revealed the role of the electrostatic and exchange-correlation components of the total one-electron static potential that are determined by the equilibrium atomic structure and by kinetic Pauli potential, which reflects the spin-dependent electron motion features of the weak and strong bonds. The gap between the extreme positions in the electrostatic and total static potentials along the line linking the Tt atom and halide anion is wide for weak bonds and narrow for strong ones. It is in very good agreement with the number of minima in the Pauli potential between the bounded atoms. This gap exponentially correlates with the exchange-correlation potential in various series with a fixed nucleophilic fragment. A criterion for categorizing the noncovalent tetrel bonds (TtB) based on the potential features is suggested. 相似文献
82.
Pawee Sitthichai Setinee Chanpirom Tharakorn Maneerat Rawiwan Charoensup Thapakorn Tree-Udom Punyawatt Pintathong Surat Laphookhieo Tawanun Sripisut 《Molecules (Basel, Switzerland)》2022,27(14)
Kaempferia parviflora (Black ginger) is used widely in medical fields as an anti-microorganism and anti-inflammation. In this study, the aim was to evaluate the in vitro and in vivo anti-acne efficacy of black ginger extract. The results indicate that the methanol and ethanol extracts showed the highest total phenolic contents, without a significant difference, whereas the n-hexane extract showed the highest total flavonoid content. Nine flavones were detected using UPLC−QTOF−MS, and the ethyl acetate extract showed the highest amount of 5,7-dimethoxyflavone (DMF) according to HPLC. Antibacterial activity against Staphylococcus aureus, S. epidermidis, and Cutibacterium acnes was observed. All the extracts showed antimicrobial activity against C. acnes, revealing MICs in the range of 0.015 to 0.030 mg/mL, whereas the ethyl acetate extract inhibited the growth of S. epidermidis with a MIC of 3.84 mg/mL. In addition, the ethyl acetate extract showed the highest activity regarding nitric oxide inhibition (IC50 = 12.59 ± 0.35 µg/mL). The ethyl acetate extract was shown to be safe regarding cell viability at 0.1 mg/mL. The anti-acne efficacy was evaluated on volunteers. The volunteers were treated in two groups: one administered a 0.02% ethyl acetate extract gel-cream (n = 9) and one administered a placebo (n = 9) for 6 weeks. The group treated with the gel-cream containing the extract showed 36.52 and 52.20% decreases in acne severity index (ASI) after 4 and 6 weeks, respectively, and 18.19 and 18.54% decreases in erythema, respectively. The results suggest that K. parviflora could be a potent active ingredient in anti-inflammatory and anti-acne products. 相似文献
83.
Arjun H. Banskota Sean M. Tibbetts Alysson Jones Roumiana Stefanova Joerg Behnke 《Molecules (Basel, Switzerland)》2022,27(15)
Hemp (Cannabis sativa L.) processing by-products (hemp cake and hemp seed hulls) were studied for their protein content, extraction of protein isolates (PIs), and their in vitro protein digestibility (IVPD). Crude protein contents of hemp cake and hemp seed hulls were 30.4% and 8.6%, respectively, calculated based on generalized N-to-P conversion factor (N × 5.37). Extraction efficiency of PIs from defatted biomass ranged from 56.0 to 67.7% with alkaline extraction (0.1 M NaOH) followed by isoelectric precipitation (1.0 M HCl). Nitrogen analysis suggested that the total protein contents of PIs extracted using three different alkaline conditions (0.5 M, 0.1 M, and pH 10.0 with NaOH) were >69.7%. The hemp by-product PIs contained all essential amino acids (EAAs) required for fish with leucine, valine, and phenylalanine belonging to the five dominant amino acids. Overall, glutamate was the dominant non-EAA followed by aspartate. Coomassie staining of an SDS-PAGE gel revealed strong presence of the storage protein edestin. High IVPD of >88% was observed for PIs extracted from hemp seeds and by-products when evaluated using a two-phase in vitro gastric/pancreatic protein digestibility assay. PIs extracted from by-products were further tested for their antioxidant activities. The tested PIs showed dose-dependent DPPH radical scavenging activity and possessed strong ORAC values > 650 μM TE/g. 相似文献
84.
基于Fluent软件平台,采用数值模拟方法对非稳态圆柱体结构尾流流动特性进行了研究。对在Re=50~200范围内,双旋转附属圆柱的转速对主圆柱体尾流流动特性的影响进行了分析。研究结果表明:随着附属圆柱旋转速率的增加,主圆柱体表面所受阻力系数平均值与均方根值、升力系数均方根值均会减小。同时,旋转速率的变化对柱体结构表面压力分布的影响显著,压力系数在附属圆柱的位置产生了跳跃性变化。另外,当附属圆柱转速达到临界值时,尾流涡街变窄,涡脱落现象消失,并且系统的能量效率到达最佳状态。 相似文献
85.
甲基苯基乙烯硅橡胶具有耐高低温、防震等独特优势,在航天器的减震、密封等领域具有广泛应用前景。研究了甲基苯基乙烯基硅橡胶的电离总剂量效应。结果表明,随着辐射剂量的增加,甲基苯基乙烯基硅橡胶的力学性能出现了不同程度的退化。拉伸强度和撕裂强度变化规律以1106 Gy(Si)剂量点为分界点。低于该剂量,拉伸和撕裂随剂量增加快速下降;高于该剂量时,随辐照剂量增加,拉伸强度出现一定程度反弹,呈现出宽U形,而撕裂强度则是先增加后下降。拉断伸长率和邵氏硬度A随辐照剂量增加分别出现快速下降和增加,最终接近饱和。最后,从辐射交联和裂解方面讨论了甲基苯基乙烯基硅橡胶电离总剂量效应的潜在物理机制。 相似文献
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88.
ATR-FTIR光谱技术在聚合物膜研究中的应用 总被引:7,自引:0,他引:7
红外光谱是聚合物研究中常用的一种表征手段,而衰减全反射红外光谱(ATR-FTIR)更是由于在研究聚合物薄膜方面具有显著的优势而被广泛使用。逐层组装(layer-by-layer Assembly)技术是一种常用的组装聚合物超薄膜的方法,ATR-FTIR光谱技术的引入可以在获取膜组装过程中相应信息的同时有效地避免表征过程中对样品的损害。另一方面,ATR-FTIR方法与二维相关光谱技术(two-dimensional correlation spectroscopy, 2D correlation spectroscopy)相结合也是研究小分子(主要是水分子)在聚合物薄膜中的渗透行为的有效手段。本文对ATR-FTIR的基本原理和显著特点作了介绍,并以实例阐述该方法在逐层组装技术和水分子在薄膜内渗透行为研究两方面的应用。 相似文献
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90.
A pentamodule assembly approach has been established for total synthesis of the naturally occurring (–)‐palmyrolide A and (+)‐5,7‐epi‐palmyrolide A. By using the racemic tert‐butyl carbinol‐containing alkyl iodide, the two diastereoisomeric macrolides could be obtained from the same sequence of reactions, demonstrating the flexibility of the multimodule assembly strategy for diverted total synthesis. 相似文献