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排序方式: 共有236条查询结果,搜索用时 15 毫秒
51.
Abdul Al MortuzaMd. Hafijur Rahman Sinthia Shabnam MouMd. Johurul Islam Abu Bakar Md. Ismail 《Current Applied Physics》2012,12(2):565-569
The structural, electrical and optical characteristics of porous silicon (PS) due to the impregnation of LaF3 into PS by a novel chemical-bath deposition (CBD) technique have been investigated in this article. Without removing the PS from the anodization chamber the impregnation with LaF3 has been done by reacting LaCl3 with HF in the same chamber at room temperature. The impregnation of LaF3 was confirmed by the SEM on the cross-section of the LaF3/PS/Si system and EDX. The modification of PS surface by LaF3 had direct influence on the electrical and optical properties of PS. Electrical properties of Ag/LaF3/PS/p-Si/Ag structures were studied through the current-voltage (I-V) and capacitance-voltage (C-V) characteristics. Formation of metal-insulator-semiconductor (MIS) diode was evident whose forward current increased with annealing. A diode factor of about 2.4 has been obtained for the annealed heterostructure indicating a high density of trap states. The C−2-V curves of all samples showed negative flat band voltage of around −2 V confirming a large number of fixed positive charges in the LaF3. The photoluminescence (PL) intensity of the LaF3-impregnated PS showed aging for the as-deposited samples, but when annealed PS structure recovered the PL intensity. Experimental results show that the optimized chemical bath passivation process for the LaF3 on porous silicon could enable the porous silicon to be an important material for photonic application. 相似文献
52.
Hussain H Krohn K Schulz B Draeger S Nazir M Saleem M 《Natural product communications》2012,7(3):293-294
Two new acaranoic acids, named seimatoporic acid A and B (1, and 2), together with six known compounds, R-(-)-mellein (3), cis-4-hydroxymellein (4), trans-4-hydroxymellein (5), 4R-hydroxy-5-methylmellein (6), (-)-5-hydroxymethylmellein (7), and ergosterol (8) were isolated from an endophytic fungus, Seimatosporium sp, by a bioassay-guided procedure. The structures of the new compounds have been assigned from analysis of the 1H and 13C NMR spectra, DEPT, and by 2D COSY, HMQC, HMBC and NOESY experiments. A mixture of compounds 1 and 2 showed strong antifungal activity against Botrytis cinerea, Septoria tritici, and Pyricularia oryzae. 相似文献
53.
Pierre-Antoine Gédouin Shabnam Arbab Chirani Sylvain Calloch 《International Journal of Plasticity》2010
The microstructure of shape memory alloys changes with the thermomechanical history of the material. During thermomechanical loading, austenite, thermally-induced martensite or stress-induced martensite can be simultaneously present in the material. In applications integrating SMA parts, utilization conditions seriously affect the microstructure and can generate macroscopic strain or stress. Consequently, during thermomechanical loadings, it is important to be able to proportion the different phases and consequently to understand the kinetic transformation. This is very useful in the development of constitutive equations. This study shows, by a series of tests, that the proposed experimental method, based on the measurement of the variation of electric resistance of CuAlBe wires, permits to determine the volume fraction of the different phases present in the material (i.e., austenite, stress-induced martensite and thermally-induced martensite). The proposed method is applied to the most common thermomechanical behavior met in engineering applications of shape memory alloys: pseudoelasticity, pseudoplasticity, recovery-stress and stress-assisted two-way shape memory effect. The proportioning method based on a mixture law integrating the resistivity of pure phases present in the SMA is first performed on different two-phase mixture cases and then applied to a three phase mixture case. 相似文献
54.
Muhammad Imran Tousif Mamona Nazir Muhammad Saleem Saba Tauseef Nusrat Shafiq Laiba Hassan Hidayat Hussian Domenico Montesano Daniele Naviglio Gokhan Zengin Ishtiaq Ahmad 《Molecules (Basel, Switzerland)》2022,27(20)
Psidium guajava L. (guava) is a small tree known for its fruit flavor that is cultivated almost around the globe in tropical areas. Its fruit is amazingly rich in antioxidants, vitamin C, potassium, and dietary fiber. In different parts of the world, this plant holds a special place with respect to fruit and nutritional items. Pharmacological research has shown that this plant has more potential than just a fruit source; it also has beneficial effects against a variety of chronic diseases due to its rich nutritional and phytochemical profile. The primary goal of this document is to provide an updated overview of Psidium guajava L. and its bioactive secondary metabolites, as well as their availability for further study, with a focus on the health benefits and potential industrial applications. There have been several studies conducted on Psidium guajava L. in relation to its use in the pharmaceutical industry. However, its clinical efficacy and applications are still debatable. Therefore, in this review a detailed study with respect to phytochemistry of the plant through modern instruments such as GC and LC-MS has been discussed. The biological activities of secondary metabolites isolated from this plant have been extensively discussed. In order to perform long-term clinical trials to learn more about their effectiveness as drugs and applications for various health benefits, a structure activity relationship has been established. Based on the literature, it is concluded that this plant has a wide variety of biopharmaceutical applications. As a whole, this article calls for long-term clinical trials to obtain a greater understanding of how it can be used to treat different diseases. 相似文献
55.
Rabia Hassan Farzana Nazir Mah Roosh Arshemah Qaisar Uzma Habib Abdulrahim A. Sajini Mudassir Iqbal 《Molecules (Basel, Switzerland)》2022,27(19)
Ionic liquids (ILs) have emerged as active pharmaceutical ingredients because of their excellent antibacterial and biological activities. Herein, we used the green-chemistry-synthesis procedure, also known as the metathesis method, to develop three series of ionic liquids using 1-methyl-3-butyl imidazolium, butyl pyridinium, and diethyldibutylammonium as cations, and bromide (Br−), methanesulfonate (CH3SO3−), bis(trifluoromethanesulfonyl)imide (NTf2−), dichloroacetate (CHCl2CO2−), tetrafluoroborate (BF4−), and hydrogen sulfate (HSO4−) as anions. Spectroscopic methods were used to validate the structures of the lab-synthesized ILs. We performed an agar well diffusion assay by using pathogenic bacteria that cause various infections (Escherichia coli; Enterobacter aerogenes; Klebsiella pneumoniae; Proteus vulgaris; Pseudomonas aeruginosa; Streptococcus pneumoniae; Streptococcus pyogenes) to scrutinize the in vitro antibacterial activity of the ILs. It was established that the nature and unique combination of the cations and anions were responsible for the antibacterial activity of the ILs. Among the tested ionic liquids, the imidazolium cation and NTf2− and HSO4− anions exhibited the highest antibacterial activity. The antibacterial potential was further investigated by in silico studies, and it was observed that bis(trifluoromethanesulfonyl)imide (NTf2−) containing imidazolium and pyridinium ionic liquids showed the maximum inhibition against the targeted bacterial strains and could be utilized in antibiotics. These antibacterial activities float the ILs as a promising alternative to the existing antibiotics and antiseptics. 相似文献
56.
57.
Arif Rafiq Nazir Ahmad Mir Farooq Ahmad .Mathematics Department COMSATS Institute of Information Technology Islamabad Pakistan .Centre for Advanced Studies in Pure Applied Mathematics Bahauddin Zakariya University Multan Pakistan 《应用数学和力学(英文版)》2007,(7)
In account of the famous ebyev inequality,a rich theory has appeared in the literature.We establish some new weighted ebyev type integral inequalitíes.Our proofs are of independent interest and provide new estimates on these types of inequalities. 相似文献
58.
Nitin H. Andhare Yogesh Thopate Lalit Kumar Tanuj Sharma M.I. Siddiqi Arun K. Sinha Aamir Nazir 《Tetrahedron》2018,74(14):1655-1667
A concise, one pot and regioselective access to (E)-distyrylbenzenes (DSBs) from arylhalide and secondary phenylenediethanol, a stable precursor for in situ generation of divinylbenzene (DVB) to avoid its polymerization, is described for construction of double CC bond formation via tandem double-dehydrative-double-Heck (D-D-D-H) reaction using Palladium and ionic liquid [hmim]Br as a cooperative catalyst. It is noteworthy that this pot-economy approach also provides direct synthesis of hydroxylated distyrylbenzenes without requirement of protection-deprotection strategy. Importantly, the synthesized DSBs are tested for their protective activity against β amyloid reduction, acetylcholine esterase inhibition, lipid lowering and reactive oxygen species (ROS) reduction properties in transgenic Caenorhabditis elegans model wherein 1,3-bis((E)-4-(trifluoromethyl)styryl)benzene (5c) is found to be active across all above factors thus presenting lead molecule within multi-target-directed ligands (MTDLs) approach. Molecular docking studies were also performed to understand the interactions of potent DSBs with receptors. 相似文献
59.
Analysis of Solvent Effect on Mechanical Properties of Poly(ether ether ketone) Using Nano-indentation 下载免费PDF全文
Tanveer Iqbal Saima Yasin Ahmad Shakeel Hamayoun Mahmood Fahad Nazir Paul F. Luckham 《化学物理学报(中文版)》2018,31(2):211-215
Poly (ether ether ketone)(PEEK) is a high-performance semi-crystalline thermoplastic polymer.Exposure of the polymeric surface to solvents can have a strong effect like softening/swelling of polymeric network or dissolution.In this study, nano-indentation analysis was performed to study the effect of acetone on the surface mechanical properties of PEEK using different exposure time.The experiments were performed with a constant loading rate (10 nm/s) to a maximum indentation displacement (1000 nm).A 30-second hold segment was included at the maximum load to account for any creep effects followed by an unloading segment to 80% unloading.The indentation hardness and the elastic modulus were computed as a continuous function of the penetration displacement in the continuous stiffness mode (CSM) indentation.The experimental data showed that the peak load decreased from ~5.2 mN to ~1.7 mN as exposure time in solvent environment increased from 0 to 18 days.The elastic modulus and the hardness of PEEK samples also displayed a decreasing trend as a function of exposure time in the solvent environment.Two empirical models were used to fit the experimental data of hardness as a function of exposure time which showed a good agreement with the experimental values. 相似文献
60.
Huang J Virji S Weiller BH Kaner RB 《Chemistry (Weinheim an der Bergstrasse, Germany)》2004,10(6):1314-1319
The conjugated polymer polyaniline is a promising material for sensors, since its conductivity is highly sensitive to chemical vapors. Nanofibers of polyaniline are found to have superior performance relative to conventional materials due to their much greater exposed surface area. A template-free chemical synthesis is described that produces uniform polyaniline nanofibers with diameters below 100 nm. The interfacial polymerization can be readily scaled to make gram quantities. Resistive-type sensors made from undoped or doped polyaniline nanofibers outperform conventional polyaniline on exposure to acid or base vapors, respectively. The nanofibers show essentially no thickness dependence to their sensitivity. 相似文献