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排序方式: 共有428条查询结果,搜索用时 15 毫秒
281.
R.T. De Silva Pooria Pasbakhsh K.L. Goh Siang-Piao Chai H. Ismail 《Polymer Testing》2013,32(2):265-271
Chitosan membranes reinforced by halloysite nanotubes (HNTs) at concentrations from 2 to 15 (w/w%) have been prepared by solution casting to investigate the optimal physico-chemical properties for biomedical applications. Tensile test data revealed that the membranes reinforced with 5 (w/w%) HNTs yielded the highest Young's modulus (0.52 ± 0.01 GPa) and strength (81.6 ± 4.4 MPa). Electron micrographs of the fractured surfaces implicated the interplay between individual HNTs and agglomerates of HNTs in the stress transfer mechanism. Infrared spectra revealed interaction between the HNT siloxane and chitosan functional groups. Thermogravimetric results demonstrated that the thermal stability of the membranes increased with HNT concentration. 相似文献
282.
Supramolecular side chain liquid crystalline polymers (SCLCPs) based on poly(3-carboxypropylmethylsiloxane-co-dimethylsiloxane) (PSIX, X=100, 76, 60, 41 or 23, denoting the mole percentage of 3-carboxypropylmethylsiloxane unit in the polymer) and stilbazole derivatives have been obtained through intermolecular hydrogen bonding (H-bonding) interactions between the carboxylic acid and the pyridyl moieties. The formation of H-bonding and self-assembly results in the formation of new mesogenic units, in which H-bonds function as molecular connectors. FTIR shows the existence of H-bonding in the complexes. The polymeric complexes behave as single component liquid crystalline polymers and exhibit stable and enantiotropic mesophases. The liquid crystalline properties of the supramolecular SCLCPs were studied using differential scanning calorimetry, polarizing optical microscopy and X-ray diffraction, and were found to exhibit smectic A phases with focal-conic textures. The thermal stability of the SCLCP increases on increasing the carboxylic acid content in the polysiloxane and the concentration of the stilbazole derivative in the complex. However, the thermal stability decreases on increasing the chain length of the stilbazole derivative. The crystal phase was not formed even on cooling to the glass transition temperature of the polymeric complex. 相似文献
283.
Ansgar Niehoff Alexandre Mantion Richard McAloney Alexandra Huber Jana Falkenhagen Cynthia M. Goh Andreas F. Thünemann Mitchell A. Winnik Henning Menzel 《Colloid and polymer science》2013,291(6):1353-1363
The synthesis, characterization, self-assembly, and gel formation of poly(γ-benzyl-l-glutamate) (PBLG) in a molecular weight range from ca. 7,000–100,000 g/mol and with narrow molecular weight distribution are described. The PBLG is synthesized by the nickel-mediated ring-opening polymerization and is characterized by size-exclusion chromatography coupled with multiple-angle laser light scattering, NMR, and Fourier transform infrared spectroscopy. The self-assembly and thermoreversible gel formation in the helicogenic solvent toluene is investigated by transmission electron microscopy, atomic force microscopy, small-angle X-ray scattering, and synchrotron powder X-ray diffraction. At concentrations significantly below the minimum gelation concentration, spherical aggregates are observed. At higher concentrations, gels are formed, which show a 3D network structure composed of nanofibers. The proposed self-assembly mechanism is based on a distorted hexagonal packing of PBLG helices parallel to the axis of the nanofiber. The gel network forms due to branching and rejoining of bundles of PBLG nanofibers. The network exhibits uniform domains with a length of 200?±?42 nm composed of densely packed PBLG helices. 相似文献
284.
An exceptional oxidizing behavior of sodium cyanoborohydride is observed where electron-withdrawing heterocyclic aldehydes are directly converted to their corresponding esters on treatment of sodium cyanoborohydride in methanol. The spectral analysis and single-crystal structure confirm the formation of esters.
285.
The detection of explosives in seawater is of great interest. We compared response single-, few-, and multilayer graphene
nanoribbons and graphite microparticle-based electrodes toward the electrochemical reduction of 2,4,6-trinitrotoluene (TNT).
We optimized parameters such as accumulation time, accumulation potential, and pH. We found that few-layer graphene exhibits
about 20% enhanced signal for TNT after accumulation when compared to multilayer graphene nanoribbons. However, graphite microparticle-modified
electrode provides higher sensitivity, and there was no significant difference in the performance of single-, few-, and multilayer
graphene nanoribbons and graphite microparticles for the electrochemical detection of TNT. We established the limit of detection
of TNT in untreated seawater at 1 μg/mL. 相似文献
286.
Goh CY Becker T Brown DH Skelton BW Jones F Mocerino M Ogden MI 《Chemical communications (Cambridge, England)》2011,47(21):6057-6059
Solution-phase and solid-state structural studies indicate that the remarkable hydrogelation properties of a proline-functionalised calix[4]arene emerge as a result of extended helical structures formed via inclusion of a proline moiety in a neighbouring calixarene cavity. 相似文献
287.
Shen ZL Goh KK Wong CH Yang YS Lai YC Cheong HL Loh TP 《Chemical communications (Cambridge, England)》2011,47(16):4778-4780
An efficient method for the synthesis of ester-containing indium homoenolate via a direct insertion of indium into β-halo ester in the presence of CuI/LiCl was described. The synthetic utility of the indium homoenolate was demonstrated by palladium-catalyzed cross-coupling with aryl halides in DMA with wide functional group compatibility. 相似文献
288.
Xiaojing Liu Qihang Chang Raquel Ferrer-Espada Leon G. Leanse Xueping Sharon Goh Xiuli Wang Jeffrey A. Gelfand Tianhong Dai 《Photochemistry and photobiology》2020,96(3):611-617
Moraxella catarrhalis is one of the major otopathogens of otitis media (OM) in childhood. M. catarrhalis tends to form biofilm, which contributes to the chronicity and recurrence of infections, as well as resistance to antibiotic treatment. In this study, we aimed to investigate the effectiveness of antimicrobial blue light (aBL; 405 nm), an innovative nonpharmacological approach, for the inactivation of M. catarrhalis OM. M. catarrhalis either in planktonic suspensions or 24-h old biofilms were exposed to aBL at the irradiance of 60 mW cm−2. Under an aBL exposure of 216 J cm−2, a >4-log10 colony-forming units (CFU) reduction in planktonic suspensions and a >3-log10 CFU reduction in biofilms were observed. Both transmission electron microscopy and scanning electron microscopy revealed aBL-induced morphological damage in M. catarrhalis. Ultraperformance liquid chromatography results indicated that protoporphyrin IX and coproporphyrin were the two most abundant species of endogenous photosensitizing porphyrins. No statistically significant reduction in the viability of HaCaT cells was observed after an aBL exposure of up to 216 J cm−2. Collectively, our results suggest that aBL is potentially an effective and safe alternative therapy for OM caused by M. catarrhalis. Further in vivo studies are warranted before this optical approach can be moved to the clinics. 相似文献
289.
Pin W. Koh Tiem L. Yoon Thong L. Lim Yee H. R. Chang Eong S. Goh 《International journal of quantum chemistry》2020,120(2):e26079
The structural and electronic properties of ternary AlxTiyNiz clusters, where x, y, and z are integers and x + y + z = 6 , are investigated. Both Slater, Vosko, Wilks, and Nusair and B3LYP exchange-correlation (XC) functionals are employed in a two-stage density functional theory (DFT) calculations to generate these clusters. In the first stage, a minimum energy cluster structure is generated by an unbiased global search algorithm coupled with a DFT code using a light XC functional and small basis sets. In the second stage, the obtained cluster structure is further optimized by another round of global minimization search coupled with a DFT calculator using a heavier XC functional and more costly basis set. Electronic properties of the structures are illustrated in the form of a ternary diagram. Our DFT calculations find that the thermodynamic stability of the clusters increases with the increment in the number of constituent nickel atoms. These results provide a new insight to the structure, stability, chemical order, and electronic properties for the ternary alloy nanoclusters. 相似文献
290.
Robert P. Boyer William M. Y. Goh 《Journal of Applied Mathematics and Computing》2011,37(1-2):421-442
It is well-known that the Fourier partial sums of a function exhibit the Gibbs phenomenon at a jump discontinuity. We study the same question for de la Vallée-Poussin sums. Here we find a new Gibbs function and a new Gibbs constant. When the function is continuous, a behavior similar to the Gibbs phenomenon also occurs at a kink. We call it the “generalized Gibbs phenomenon”. Let $F_{n}(x):=\frac{k_{n}(g,x)-g(x)}{k_{n}(g,x_{0})-g(x_{0})}$ , where x 0 is a kink and where k n (g,x) represents Fourier partial sums and de la Vallée-Poussin sums. We show that F n (x) exhibits the “generalized Gibbs phenomenon”. New universal Gibbs functions for both sums are derived. 相似文献