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排序方式: 共有270条查询结果,搜索用时 62 毫秒
91.
Huda Abdullah Mohd Syafiq Zulfakar Wan Nasarudin Wan Jalal Mohammad Tariqul Islam Sahbudin Shaari 《Journal of Sol-Gel Science and Technology》2014,69(1):183-192
Zinc aluminate compounds have been dispersed in silica matrix prepared by sol-gel method with different compositions for (1 ? x)ZnAl2O4–xSiO2. Continuous stirring of ethylene glycol solution contained zinc nitrate, aluminium nitrate and silicon dioxide to produces gel precursor. Structural and morphological studies of (1 ? x)ZnAl2O4–xSiO2 thin films were examined by field emission scanning electron microscopy (FESEM) and X-ray diffractometer (XRD) analysis. The FESEM images showed the spherical structures with porosity for (1 ? x)ZnAl2O4–xSiO2 thin films. XRD analysis indicated that the crystallite size for (1 ? x)ZnAl2O4–xSiO2 increased from 39.79 to 44.34 nm. Fourier transform infra-red analysis showed that the existence of H2O molecules and the presence of nitrate group within the samples. Dielectric permittivity (ε r ) of (1 ? x)ZnAl2O4–xSiO2 samples were measured within frequency range from 1 Hz to 1 MHz. The dielectric permittivity, ε r decreased as frequency was applied to the sample. The performance of the patch antenna can be measured using return loss analysis. The highest result shows that the patch antenna resonated at frequency 3.46 GHz and gives ?14.25 dB return loss bandwidth. 相似文献
92.
Ahmed Jalal Uddin Norihiro Katayama Yutaka Ohkoshi Yasuo Gotoh Masanobu Nagura 《Journal of Polymer Science.Polymer Physics》2002,40(21):2449-2462
For monofilament biodegradable sutures fabricated from the L ‐lactide–ε‐caprolactone (75/25) copolymer [P(LLA/CL)], there have been some concerns regarding their mechanical properties, such as the knot‐pull strength and stiffness. This article demonstrates the further potentiality of these sutures through improvements in those properties. With the aim of diminishing the molecular orientation, particularly in the suture surface region, we adopted an expedient method to treat P(LLA/CL) sutures with an acetone/water mixture, using different times and time patterns. The changes in the molecular orientation distributions across the suture cross sections were characterized by the specific index of birefringence measured with an interference microscope. The crystal orientations, knot‐pull strengths, tensile strengths, and bending rigidity were measured. The conformational changes in suture breaking during knot‐pull tests were analyzed with high‐speed‐video observations. Morphological analyses of the fractural surfaces were performed with scanning electron microscopy. The knot‐pull strength tended to rise, in comparison with that of untreated samples, up to a certain treatment time and was accompanied by a minimal decrement of the tensile strength. The knot‐pull strength did not show an increasing trend with further treatment, whereas the tensile strength declined remarkably. The birefringence, crystal orientation, bending rigidity, fractured surface analysis, and high‐speed‐video observations revealed molecular disorientation mainly in the filament outer layers for that particular treatment causing the sutures to be considerably softer. The suture softness played a role in changing the deformation behavior of the knot when a load was applied and caused the knot‐pull strength to rise. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2449–2462, 2002 相似文献
93.
94.
Basic Ionic Liquid as Catalyst and Reaction Media for the One‐pot Three‐component Regioselective Synthesis of Various Thiazol‐2‐imine Derivatives
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Jafar Abbasi Shiran Asieh Yahyazadeh Bohari M. Yamin Manouchehr Mamaghani Jalal Albadi 《Journal of heterocyclic chemistry》2016,53(4):1009-1016
Thiazol‐2‐imine derivatives were synthesized in an easy and efficient route from the regioselective one‐pot three‐component reaction of aryl amine, alkylisothiocyanate, and various α‐haloketones in [omim][OH] basic ionic liquid. Recyclable reaction media, catalyst free, and short reaction times are the main advantages of this protocol. This method produces the products at room temperature in excellent yields (68–96%). Furthermore, the target compound 6b was determined by X‐ray crystallographic analysis. 相似文献
95.
Tahira?Batool Essam?A.?MakkyEmail author Muna?Jalal Mashitah?M.?Yusoff 《Applied biochemistry and biotechnology》2016,180(5):900-916
l-asparaginase (LA) catalyzes the degradation of asparagine, an essential amino acid for leukemic cells, into ammonia and aspartate. Owing to its ability to inhibit protein biosynthesis in lymphoblasts, LA is used to treat acute lymphoblastic leukemia (ALL). Different isozymes of this enzyme have been isolated from a wide range of organisms, including plants and terrestrial and marine microorganisms. Pieces of information about the three-dimensional structure of l-asparaginase from Escherichia coli and Erwinia sp. have identified residues that are essential for catalytic activity. This review catalogues the major sources of l-asparaginase, the methods of its production through the solid state (SSF) and submerged (SmF) fermentation, purification, and characterization as well as its biological roles. In the same breath, this article explores both the past and present applications of this important enzyme and discusses its future prospects. 相似文献
96.
In this study, a new way of understanding the shear-thickening phenomenon in self-assembled solutions is introduced. The near-
and out-of-equilibrium behavior is investigated in four aqueous micellar solutions containing surfactants of the same family:
the alkyltrimethylammonium bromide mixed with an ionic salt at equimolar concentration. Thus, the four molecules of surfactants
have the same polar head but different aliphatic chain length containing 12, 14, 16, and 18 carbon atoms. In aqueous solutions,
the attractive forces between the surfactant molecules depend on the length of the aliphatic chain, thus, varying this parameter
will have a definite influence on the aggregation number, the shape and dimension of the micelles. According to our results,
the evolution of the low shear viscosity is affected by the chain length. The rheometric measurements performed in steady
and time-dependent flows show that the emergence, the range, and the amplitude of the shear thickening also depend on this
parameter. However, in the domain of high shear rates, after reaching the maximum of viscosity, all flow curves superimpose
irrespective of the chain length. The rheo-optic measurements confirm the apparition of the shear-induced structure (SIS);
this new phase is locally oriented and the chain length affects strongly the micelles orientation and the birefringence intensity.
These results undoubtedly demonstrate that the chain length plays an important role in the behavior near equilibrium and under
shear flow of the micellar systems.
Paper presented at the third Annual European Rheology Conference (AERC 2006) on April 27–29, 2006, Crete, Greece. 相似文献
97.
A new method has been developed for the chemoselective acetylation of alcohols with acetic anhy‐dride in the presence of phenols using a novel,recyclable Cu O‐Zn O nanocatalyst.The catalyst was synthesized using the co‐precipitation method and characterized by N2 adsorption‐desorption,X‐ray diffraction,scanning electron microscopy,transmission electron microscopy and energy dis‐persion scanning analyses.Furthermore,this catalyst could be recycled up to six times without significant loss in its activity. 相似文献
98.
A new three-dimensional microporous metal-organic framework Cu(BDC-OH)(4,4'-bipy)·G(x) (UTSA-15; H(2)BDC-OH = 2-hydroxy-benzenedicarboxylic acid, 4,4'-bipy =4,4'-bipyridine, G = guest molecules) with functional -OH groups on the pore surfaces was solvothermally synthesized and structurally characterized. UTSA-15 features a three-dimensional structure having 2D intercrossed channels of about 4.1 × 7.8 and 3.7 × 5.1 ?(2), respectively. The small pores and the functional -OH groups on the pore surfaces within the activated UTSA-15a have enabled their strong interactions with CO(2) and C(2)H(2) which have been revealed in their large adsorption enthalpies of 39.5 and 40.6 kJ/mol, respectively, highlighting UTSA-15a as the highly selective microporous metal-organic framework for the CO(2)/CH(4) and C(2)H(2)/CH(4) gas separation with separation selectivity of 24.2 and 55.6, respectively, at 296 K. 相似文献
99.
Poly(4-vinyl pyridine) supported nanoparticle of copper(Ⅰ) iodide is reported as a green and recyclable catalyst for the regioselective synthesis of 1,4-disubstituted-1H-1,2,3-triazoles from benzyl halides,sodium azide and terminal alkynes in water. This catalyst can be recovered by simple filtration and recycled up to 8 consecutive runs without any loss of its efficiency. 相似文献
100.
BV Reddy S Jalal P Borkar JS Yadav PP Reddy AC Kunwar B Sridhar 《Organic & biomolecular chemistry》2012,10(32):6562-6568
A novel intramolecular Prins cyclization of (Z)-2-(5-hydroxypent-2-enyl)phenol with various aldehydes has been achieved using 10 mol% In(OTf)(3) and 30 mol% TsOH to produce the cis-fused hexahydropyrano[4,3-b]chromene derivatives in good yields, while the coupling of (E)-2-(5-hydroxypent-2-enyl)phenol with aldehydes under similar conditions affords the corresponding trans-fused hexahydropyrano[4,3-b]chromene derivatives. 相似文献