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111.
Garima Singhal Riju Bhavesh Kunal Kasariya Ashish Ranjan Sharma Rajendra Pal Singh 《Journal of nanoparticle research》2011,13(7):2981-2988
Development of green nanotechnology is generating interest of researchers toward ecofriendly biosynthesis of nanoparticles.
In this study, biosynthesis of stable silver nanoparticles was done using Tulsi (Ocimum sanctum) leaf extract. These biosynthesized nanoparticles were characterized with the help of UV–vis spectrophotometer, Atomic Absorption
Spectroscopy (AAS), Dynamic light scattering (DLS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR),
and Transmission electron microscopy (TEM). Stability of bioreduced silver nanoparticles was analyzed using UV–vis absorption
spectra, and their antimicrobial activity was screened against both gram-negative and gram-positive microorganisms. It was
observed that O. sanctum leaf extract can reduce silver ions into silver nanoparticles within 8 min of reaction time. Thus, this method can be used
for rapid and ecofriendly biosynthesis of stable silver nanoparticles of size range 4–30 nm possessing antimicrobial activity
suggesting their possible application in medical industry. 相似文献
112.
Enhanced luminescence and degradation resistance in Tb modified Yttrium Borate core-nano silica shell phosphor under UV and VUV excitation 总被引:1,自引:0,他引:1
Santa Chawla RavishankerA.F. Khan Ashish YadavH. Chander V. Shanker 《Applied Surface Science》2011,257(16):7167-7171
Composition variation in optimized solid state reaction conditions has been done to achieve intense green emission in YTbxBO3 phosphor under UV and VUV (147 nm resonant Xe*, 172 nm Xe2* excimer band) excitation. Inert interface layer created by fabricating a shell of silica nanoparticles over individual phosphor grain protected the phosphor surface from deterioration and oxidation of luminescent ion (Tb3+) thus completely arresting phosphor degradation. At optimum Tb content of 20 mol%, integrated photoluminescence intensity of developed YTbxBO3 phosphor is four times higher than commercial green YBT. With short decay time of 4 ms, YTbxBO3 core-nano silica shell green emitting phosphor has great application potential in PDP panel and phosphor coated Xe lamps. 相似文献
113.
Ashish Jain R. Pankajavalli R. Babu S. Anthonysamy 《Journal of Thermal Analysis and Calorimetry》2014,115(2):1279-1287
The standard Gibbs energies of formation of Nd2TeO6 and M6TeO12 (where M = Nd, Sm) were determined from vapour pressure measurements. The vapour pressure of TeO2(g) was measured by employing thermogravimetry-based transpiration technique. The temperature dependence of the vapour pressure of TeO2(g) over the mixtures Nd2TeO6+Nd6TeO12, generated by the incongruent vapourisation reaction, 3Nd2TeO6(s) → Nd6TeO12(s)+2TeO2(g)+O2(g), was measured in the temperature range 1,408–1,495 K. Similarly, the vapour pressure of TeO2(g) over the mixtures M6TeO12+M2O3 (where M = Nd, Sm), generated by the incongruent vapourisation reaction, M6TeO12(s) → 3M2O3(s)+TeO2(g)+½O2(g), was measured in the temperature range 1,703–1,773 and 1,633–1,753 K for Nd6TeO12(s) and Sm6TeO12(s), respectively. Enthalpy increments of M2TeO6(s) (where M = Nd, Sm) were determined by inverse drop calorimetric method in the temperature range 573–1,273 K. The thermodynamic functions, viz., heat capacity, entropy and free energy functions, were derived from the measured values of enthalpy increments. A mean value of ?2,426.2 ± 0.6 and ?2,417.9 ± 1.1 kJ mol?1 was obtained for $ \Updelta_{\text{f} } H_{298}^{\text{o}} $ (Nd2TeO6, s) and $ \Updelta_{\text{f}} H_{298}^{\text{o}} $ (Sm2TeO6, s), respectively, by combining the value of $ \Updelta_{\text{f}} G^{\text{o}} $ (Nd2TeO6, s) and $ \Updelta_{\text{f}} G^{\text{o}} $ (Sm2TeO6, s) derived from vapour pressure data and the free energy functions derived from the drop calorimetric data. 相似文献
114.
Ambient UVA‐Induced Expression of p53 and Apoptosis in Human Skin Melanoma A375 Cell Line by Quinine
Neera Yadav Ashish Dwivedi Syed Faiz Mujtaba Hari Narayan Kushwaha Shio Kumar Singh Ratan Singh Ray 《Photochemistry and photobiology》2013,89(3):655-664
This study aimed to analyze the phototoxic mechanism and photostability of quinine in human skin cell line A375 under ambient intensities of UVA (320–400 nm). Photosensitized quinine produced a photoproduct 6‐methoxy‐quinoline‐4‐ylmethyl‐oxonium identified through LC‐MS/MS. Generation of 1O2, O2??, and ?OH was measured and further substantiated through their respective quenchers. Photosensitized Quinine (Q) caused degradation of 2‐deoxyguanosine, the most sensitive nucleotide to UV radiation. The intracellular ROS was increased in a concentration‐dependent manner. Significant reduction in metabolic status measured in terms of cell viability (54%) at 25 μg mL?1 was observed through MTT assay. Results of MTT assay accord NRU assay. Single strand DNA breaks and apoptosis were increased significantly (P < 0.01) as observed through comet assay and EB/AO double staining. Photosensitized quinine caused cells to arrest in G2 phase of cell cycle and induced apoptosis (5.08%) as revealed through FACS. Real‐Time PCR showed upregulation of p21 (4.56 folds) and p53 (2.811 folds) genes expression. Thus, our study suggests that generation of reactive oxygen species by quinine under ambient intensity of UVA may result into deleterious phototoxic effects among human population. 相似文献
115.
Shailesh Thakrar Abhay Bavishi Ashish Radadiya Shrey Parekh Dhairya Bhavsar Hardevsinh Vala Nilay Pandya Anamik Shah 《Journal of heterocyclic chemistry》2013,50(Z1):E73-E79
A new series of highly functionalized 1,5‐benzodiazepine derivatives 5a–x have been synthesized from 3‐[(1E)‐N‐(2‐aminophenyl) ethanimidoyl]‐4‐hydroxyl‐2H‐chromen‐2‐one 3a–c and pyrazole aldehyde 4a–h using catalytic amount of triflouro acetic acid under microwave irradiation. The main significant of the present procedure is shorter reaction time, easy work up procedure, and excellent yield with high purity. The structures of all the compounds were established on the basis of their IR, NMR, and mass spectral data and have been screened for their antimicrobial activity and antifungal activity. 相似文献
116.
Lakshmi Chandrasekharan Nair Ashish Awasthi 《Numerical Methods for Partial Differential Equations》2019,35(3):1269-1289
This paper presents a numerical method based on quintic trigonometric B‐splines for solving modified Burgers' equation (MBE). Here, the MBE is first discretized in time by Crank–Nicolson scheme and the resulting scheme is solved by quintic trigonometric B‐splines. The proposed method tackles nonlinearity by using a linearization process known as quasilinearization. A rigorous analysis of the stability and convergence of the proposed method are carried out, which proves that the method is unconditionally stable and has order of convergence O(h4 + k2). Numerical results presented are very much in accordance with the exact solution, which is established by the negligible values of L2 and L∞ errors. Computational efficiency of the scheme is proved by small values of CPU time. The method furnishes results better than those obtained by using most of the existing methods for solving MBE. 相似文献
117.
Richard A. Register Ashish Sen Robert A. Weiss Chi Li Stuart Cooper 《Journal of Polymer Science.Polymer Physics》1989,27(9):1911-1925
Carboxy-terminated polybutadiene neutralized with Cu2+ (CuPBD) and its blend with poly(styrene-co-4-vinylpyridine) (SVP) were examined by differential scanning calorimetry (DSC), transmission electron microscopy (TEM), small-angle x-ray scattering (SAXS), and extended x-ray absorption fine structure (EXAFS) spectroscopy. The DSC results indicate that in the blend substantial mixing occurs in the CuPBD-rich phase, although complete miscibility is not achieved, and the SVP-rich phase remains relatively pure. The TEM micrographs indicate that the morphology, while irregular, is reasonably described as bicontinuous, with a domain size of order 100 nm. The SAXS patterns show that the ionic aggregates present in CuPBD are destroyed upon blending, which is interpreted as being due to steric hindrances between ionic groups coordinated to vinylpyridine nitrogens. The EXAFS radial structure function of the blend exhibits a marked decrease in the Cu-Cu peak in comparison with CuPBD, indicating a change in local structure upon blending. The results indicate that some of the SVP is miscible with CuPBD owing to complexation between the pendant pyridine groups and the Cu2+ ions, which disrupts the ionic aggregates. However, the two materials are not fully miscible, leading to a rather coarse two-phase morphology. 相似文献
118.
Ashish Aneja Garth L. Wilkes Edward G. Rightor 《Journal of Polymer Science.Polymer Physics》2003,41(3):258-268
The morphological features of three flexible slabstock polyurethane foams based on varied contents of 2,4 and 2,6 toluene diisocyanate (TDI) isomers are investigated. The three commercially available TDI mixtures, that is, 65:35 2,4/2,6 TDI, 80:20 2,4/2,6 TDI, and 100:0 2,4/2,6 TDI were used. The foams were characterized at different length scales with several techniques. Differences in the cellular structure of the foams were noted with scanning electron microscopy. Small‐angle X‐ray scattering was used to demonstrate that all three foams were microphase‐separated and possessed similar interdomain spacings. Transmission electron microscopy revealed that the aggregation of the urea phase into large urea‐rich regions decreased systematically on increasing the asymmetric TDI isomer content. Fourier transform infrared spectroscopy showed that the level of bidentate hydrogen bonding of the hard segments increased with the 2,6 TDI isomer content. Differential scanning calorimetry and dynamic mechanical analysis (DMA) were used to note changes in the soft‐segment glass‐transition temperature of the foams on varying the diisocyanate ratios and suggested that the perfection of microphase separation was enhanced on increasing the 2,6 TDI isomer content. The preceding observations were used to explain why the foam containing the highest content of the symmetric 2,6 TDI isomer exhibited the highest rubbery storage modulus, as measured by DMA. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 258–268, 2003 相似文献
119.
Hu Z Chen L Betts DE Pandya A Hillmyer MA DeSimone JM 《Journal of the American Chemical Society》2008,130(43):14244-14252
Amphiphilic networks of perfluoropolyethers (PFPE) and poly(ethylene glycol) (PEG) have been achieved to yield optically transparent, mechanically robust films over a wide range of compositions. Telechelic diols of these oligomers were transformed to a photocurable dimethacryloxy form (DMA) and free radically cured at various composition weight ratios to yield free-standing films. Clear and colorless amphiphilic networks could be achieved when low molar mass versions of both the PFPE-DMA (1 kg/mol) and the PEG-DMA (550 g/mol) were used. The bulk morphologies of the samples were extensively characterized by a variety of techniques including ultraviolet-visible spectroscopy, differential scanning calorimetry, dynamic mechanic thermal analysis, small-angle X-ray scattering, atomic force microscopy, X-ray photoelectron spectroscopy, and optical microscopy, which strongly suggest that nanoscopic to macroscopic phase-separated materials could be achieved. By incorporating a threshold amount of PFPEs into PEG-based hydrogel networks, water swelling could be significantly reduced, which may offer a new strategy for a number of medical device applications. Along these lines, strong inhibition of nonspecific protein adsorption could be achieved with these amphiphilic network materials compared with an oligo(ethylene glycol)-based self-assembled monolayer coated surface. 相似文献
120.
Jha AK Lee J Tripathi A Bose A 《Langmuir : the ACS journal of surfaces and colloids》2008,24(12):6013-6017
The effect of three-dimensional confinement on the size and morphology of a vesicular surfactant mesophase obtained by mixing micellar solutions of cetyltrimethylammonium bromide and dodecylbenzenesulfonic acid has been studied using small-angle neutron scattering (SANS). The confined spaces were generated by the random close packing of polystyrene beads of radius Rb=1.5, 0.25, and 0.1 microm, creating voids of characteristic dimensions R approximately 0.22 Rb=3300, 550, and 220 A, respectively. These void length scales were comparable to or less than the radii of vesicles formed in the system under conditions of no confinement. Vesicles, made by mixing 0.8 wt % micellar solutions of surfactant in a water/D2O mixture that is contrast-matched with the polystyrene beads, were added in a SANS scattering cell without beads, as well as three cells with the different sized beads. The SANS data from the sample without confinement was best fitted by a core-shell model and not by spheres or disks, confirming the presence of vesicles. The data from samples in the confined domains also showed vesicles as the dominant structure. The most important result is that the mean size of these vesicles decreases as the confinement length scale is reduced. A simple thermodynamic model accounting for the balance between increased enthalpy when vesicles with curvature higher than the preferred one are formed, and increased free volume entropy for smaller vesicles supports the experimental data. While these results are focused on a specific vesicle system, the broad principles behind changes in microstructure produced by confinement are applicable to other surfactant aggregates. The results of this study are potentially important for understanding the flow of drug delivery vehicles through microcapillaries, in the recovery of oil from fine pores in rocks using surfactant containing fluids, micellar enhanced ultrafiltration, or in other situations where the size of surfactant aggregate structures approach the length scales between confining walls. 相似文献