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排序方式: 共有1434条查询结果,搜索用时 15 毫秒
161.
Samsul Rizal E. M. Mistar A. A. Oyekanmi Abdul Khalil H.P.S. Tata Alfatah N. G. Olaiya C. K. Abdullah 《Molecules (Basel, Switzerland)》2021,26(14)
The use of chemical modification of cellulosic fibre is applied in order to increase the hydrophobicity, hence improving the compatibility between the fibre and matrix bonding. In this study, the effect of propionic anhydride modification of kenaf fibre was investigated to determine the role of bionanocarbon from oil palm shell agricultural wastes in the improvement of the functional properties of bionanocomposites. The vinyl esters reinforced with unmodified and propionic anhydride modified kenaf fibres bio nanocomposites were prepared using 0, 1, 3, 5 wt% of bio-nanocarbon. Characterisation of the fabricated bionanocomposite was carried out using FESEM, TEM, FT-IR and TGA to investigate the morphological analysis, surface properties, functional and thermal analyses, respectively. Mechanical performance of bionanocomposites was evaluated according to standard methods. The chemical modification of cellulosic fibre with the incorporation of bionanocarbon in the matrix exhibited high enhancement of the tensile, flexural, and impact strengths, for approximately 63.91%, 49.61% and 54.82%, respectively. The morphological, structural and functional analyses revealed that better compatibility of the modified fibre–matrix interaction was achieved at 3% bionanocarbon loading, which indicated improved properties of the bionanocomposite. The nanocomposites exhibited high degradation temperature which signified good thermal stability properties. The improved properties of the bionanocomposite were attributed to the effect of the surface modification and bionanocarbon enhancement of the fibre–matrix networks. 相似文献
162.
The paper discusses an infrared thermography (IRT) based procedure for quantification of annular air-gap in cylindrical geometries. Different annular air-gaps are simulated using aluminum hollow cylinders and solid stainless steel inserts of varying diameters. The specimens are externally heated using a hot air-gun and the temperature of the specimens are monitored during cooling using an infrared camera. The temperature decay during the cooling cycle follows an exponential profile in all the cases where the decay constant is air-gap dependent. The rate of temperature decay is fastest for the empty cases (without inserts) and lower for smaller air-gaps. The system is analyzed using a lumped system model by measuring the temperature over a time scale significantly higher than the transition time of the lumped system. It is observed that the Biot number of the system is less than unity, allowing analysis of the system in terms of a single time constant, neglecting internal temperature transients. It is observed that the time constant of temperature decay increases with decreasing annular air-gap. An empirical relation between the inverse of time constant of temperature decay and annular air-gaps is established. Using this calibration curve, unknown air-gaps up to 20 μm could be measured with good accuracy. Applications of this newly developed technique include detection of misalignment of concentric machineries and determination of fuel-to-clad gap of nuclear reactor fuels. 相似文献
163.
Sie-Tiong Ha Teck-Ming Koh Guan-Yeow Yeap Hong-Cheu Lin Siew-Ling Lee Yip-Foo Win 《Phase Transitions》2013,86(3):195-204
A series of new rod-shaped mesomorphic compounds, 6-ethoxy-2-(4-alkanoyloxybenzylidenamino)benzothiazoles, consisting of a 2,6-disubstituted benzothiazole core and a Schiff base central linkage, were synthesized and their structures were ascertained via elemental analysis and spectroscopic techniques. Their mesomorphic properties were studied using differential scanning calorimetry (DSC), polarized optical microscopy (POM) and X-ray diffraction (XRD) analysis. All compounds showed enantiotropic mesomorphism. Whilst the lower members of the series, hexanoyloxy and octanoyloxy derivatives exhibited nematic phase, the higher members (decanoyloxy, dodecanoyloxy, tetradecanoyloxy, hexadecanoyloxy and octadecanoyloxy derivatives) exhibited nematic and smectic C phases. 相似文献
164.
《Journal of Physics and Chemistry of Solids》2002,63(6-8):1281-1284
NMR relaxation rate, T1−1, of the metallic carbon nanotube is discussed based on Tomonaga–Luttinger-liquid theory. It is found that the Coulomb interaction leads to increase of (T1T)−1 by a power law with decreasing temperature, T. The dependence on temperature of (T1T)−1 in the multi-wall nanotube (MWNT) is shown to be strongly suppressed by existence of the metallic shells in the MWNTs. 相似文献
165.
《Polyhedron》2002,21(5-6):549-552
Reaction of BCl3 with 2-methoxyaniline (1:6 equiv.) in toluene, and subsequent metallation with nBuLi (3 equiv.) produces {[Li4B(NR)3·THF]+[BnBu4]−·toluene}2 (R=2-methoxyphenyl), which contains the first example of a trisimido borate trianion—the imido analogue of the orthoborate trianion, [BO3]3−. 相似文献
166.
Halichonic acid,a new rearranged bisabolene-type sesquiterpene from a marine sponge Halichondria sp.
Kenta Raiju Yuki Hitora Hikaru Kato Yuji Ise Esther D. Angkouw Remy E.P. Mangindaan Sachiko Tsukamoto 《Tetrahedron letters》2019,60(15):1079-1081
A new compound, halichonic acid (1), was isolated from a marine sponge Halichondria sp., together with (6R,7S)-7-amino-7,8-dihydro-α-bisabolene (2). The structure of 1 was elucidated by spectroscopic analysis and ECD spectrum calculation to be a rearranged bisabolene-type sesquiterpene having a 3-azabicyclo[3.3.1]nonene moiety. Compound 2 was cytotoxic against HeLa cells with an IC50 value of 50?μM, whereas 1 did not show cytotoxicity even at 50?μM. It is possible that 1 is biosynthesized from farnesyl pyrophosphate and glycine, with rearrangement. 相似文献
167.
PPD emulsion product is advantageous for use in sub-ambient temperature as it improve the physical handling characteristic compared to traditional product. However, existing PPD emulsion system is solely implementing a single anionic surfactant system which leads instability towards a series of temperature changes. Therefore, mixed surfactant (anionic and non-ionic) surfactant was introduced to overcome this problem. Through this research, sodium dodecyl sulfate (SDS) act as anionic surfactant and Tween 80 used as non-ionic surfactant in this study. The stability of an emulsion was identified through particle size and zeta potential. For the mixed surfactant composition, the result show the presence of SDS content contributes in reduction on particle size. Furthermore, the study on effectiveness of surfactant on EVA emulsion was evaluated. The result indicates with present of surfactant, interfacial surface tension was reduced. The freezing point and pour point depressant test of the EVA emulsion was evaluated. Present of non-ionic surfactant help in stability and flow-respond at low temperature. Mixed surfactant system provides sufficient protection from droplet size growth caused by the temperature changes which eventually leads to instability. 相似文献
168.
Aqsa Habib Mansoureh Nazari V. Muhammad Adnan Iqbal Haq Nawaz Bhatti M.B. Khadeer Ahmed A.M.S. Abdul Majid 《Journal of Saudi Chemical Society》2019,23(7):795-808
The promising biomedical applications of silver complexes stimulated the researchers to test these compounds against cancer. The present research work was designed to achieve this goal. In this work, a series of 5-methyl benzimidazole based N-Heterocyclic carbene ligands and respective silver(I) complexes were synthesized and tested on cancer cell lines to assess their anticancer activity. Unsymmetrically substituted benzimidazole was found unique in its reactivity and generation of a single product during NHC ligand formation was only possible after two successive alkylations with same alkyl halide. The corresponding Ag(I)-NHC adducts were obtained by in situ deprotonation of the NHC ligands. Synthesized compounds were characterized by various physcio-chemical and spectroscopic methods. Single crystal X-ray diffraction study of complex 7 revealed its mononuclear structure. Preliminary in vitro anticancer study of azolium salts and respective Ag(I)-NHC complexes against human breast cancer (MDA-MB-231), colon cancer (HCT-116) and normal endothelial cells (EA.hy926) cells revealed that all the compounds are more cytotoxic to cancer cells than normal cells and the complexes are relatively more potent compared to the corresponding NHC ligands. It was found that increased chain length and presence of methyl substituent on benzimidazole ring enhance the biopotency of Ag(I)-NHC complexes. The synthesized compounds were further studied for pro-apoptotic mechanism of action via Rhodamine 123 test. The tested compounds were found to induce apoptosis via extrinsic mitochondrial pathway. 相似文献
169.
Heracleum sphondylium L. subsp. ternatum (Velen.) Brummitt. commonly known as “hogweed” is traditionally used to manage several human ailments. This investigation assessed, for the first time, the enzyme inhibitory properties, antioxidant activity, phytochemical profile, antimutagenic, and antimicrobial potential of the ethyl acetate, methanol, and water extracts of H. sphondylium. We also established the possible interactions of identified phenolic compounds with cholinesterases, amylase, glucosidase, and tyrosinase using in silico docking studies. Chlorogenic acid was found in high amounts in the methanol extract of H. sphondylium. The methanol extract was an effective inhibitor of acetylcholinesterase (1.70 mg galantamine equivalent (GALAE)/g extract) while the ethyl acetate extract showed pronounced inhibitory action against butyrylcholinesterase (1.77 mg GALAE/g extract). The extracts exhibited low inhibition against amylase (0.12-0.84 mmol acarbose equivalent (ACAE)/g extract) and a more pronounced inhibition against glucosidase (2.29–3.65 mmol ACAE/g extract). In silico results showed that rutin and quercetin (-70.4 and -72.2 Kcal/mol, for rutin and quercetin respectively) docked to the enzymatic cavity of acetylcholinesterase but these phenolic compounds showed less affinity with butyrylcholinesterase (-15.0 and -5.2 Kcal/mol, for rutin and quercetin respectively). The extracts did not induce any mutations on the bacterial strains, while they have excellent antimutagenic capacity against well-known mutagens (inhibition values 98%, 97% and 96%). The methanol extract (0.78 mg/ml) showed moderate antifungal activity while the ethyl acetate extract (0.78–3.12 mg/ml) showed weak to moderate antimicrobial activity. This study provides valuable baseline data which might serve for the development of future pharmacophores for the management of human ailments. 相似文献
170.
Conductivity studies of plasticized anhydrous PEO-KOH alkaline solid polymer electrolyte 总被引:1,自引:0,他引:1
Polyethylene oxide (PEO)–potassium hydroxide (KOH)-based alkaline solid polymer electrolyte films have been prepared by using
methanol as solvent. The highest room temperature ionic conductivity of (2.1 ± 0.5) × 10−8 S cm−1 was achieved for the composition of 70 wt% PEO:30 wt% KOH. The addition of plasticizer, ethylene carbonate, propylene carbonate,
or polyethylene glycol to the highest conductivity of PEO–KOH system helps to increase the ambient ionic conductivity to the
order of 10−6–10−4 S cm−1. The log σ vs 1/T plot of PEO–KOH showed a small conductivity decrease at 50–60 °C range. The small decrease and the hysteresis that occur
during the heating–cooling cycle was overcome by the presence of the plasticizer. X-ray diffraction observation supports the
conductivity results. 相似文献