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排序方式: 共有298条查询结果,搜索用时 15 毫秒
1.
Karishma Tiwari Pulak Sarkar Solagna Modak Harwinder Singh Sumit Kumar Pramanik Santanu Karan Amitava Das 《Advanced materials (Deerfield Beach, Fla.)》2020,32(8):1905621
Separation membranes with higher molecular weight cut-offs are needed to separate ions and small molecules from a mixed feed. The molecular sieving phenomenon can be utilized to separate smaller species with well-defined dimensions from a mixture. Here, the formation of freestanding polyimine nanofilms with thicknesses down to ≈14 nm synthesized via self-assembly of pre-synthesized imine oligomers is reported. Nanofilms are fabricated at the water–xylene interface followed by reversible condensation of polymerization according to the Pieranski theory. Polyimine nanofilm composite membranes are made via transferring the freestanding nanofilm onto ultrafiltration supports. High water permeance of 49.5 L m-2 h−1 bar−1 is achieved with a complete rejection of brilliant blue-R (BBR; molecular weight = 825 g mol−1) and no more than 10% rejection of monovalent and divalent salts. However, for a mixed feed of BBR dye and monovalent salt, the salt rejection is increased to ≈18%. Membranes are also capable of separating small dyes (e.g., methyl orange; MO; molecular weight = 327 g mol−1) from a mixed feed of BBR and MO. Considering a thickness of ≈14 nm and its separation efficiency, the present membrane has significance in separation processes. 相似文献
2.
DJ Hazuda PJ Felock JC Hastings B Pramanik AL Wolfe 《Canadian Metallurgical Quarterly》1997,71(9):7005-7011
Previous in vitro analyses have shown that the human immunodeficiency virus type 1 (HIV-1) integrase uses either manganese or magnesium to assemble as a stable complex on the donor substrate and to catalyze strand transfer. We now demonstrate that subsequent to assembly, catalysis of both 3' end processing and strand transfer requires a divalent cation cofactor and that the divalent cation requirements for assembly and catalysis can be functionally distinguished based on the ability to utilize calcium and cobalt, respectively. The different divalent cation requirements manifest by these processes are exploited to uncouple assembly and catalysis, thus staging the reaction. Staged 3' end processing and strand transfer assays are then used in conjunction with exonuclease III protection analysis to investigate the effects of integrase inhibitors on each step in the reaction. Analysis of a series of related inhibitors demonstrates that these types of compounds affect assembly and not either catalytic process, therefore reconciling the apparent disparate results obtained for such inhibitors in assays using isolated preintegration complexes. These studies provide evidence for a distinct role of the divalent cation cofactor in assembly and catalysis and have implications for both the identification and characterization of integrase inhibitors. 相似文献
3.
Development of nano indium tin oxide (ITO) grains by alkaline hydrolysis of In(III) and Sn(IV) salts
Indium tin oxide (ITO) nano powders of different compositions (In: Sn = 90: 10, 70: 30 and 50: 50) were prepared by heat treatment
(300-450°C) of mixed hydroxides of In(III) and Sn(IV). The hydroxides were obtained by the reaction of aq. NH3 with mixed aq. solutions of In(NO3)3 and SnCl4. FTIR and TG/DTA studies revealed that powders existed as In(OH)3H2O—SnO3H2H2O in the solid state and then they transformed to In2O3—SnO2 via some metastable intermediates after 300°C. Cubic phase of In2O3 was identified by XRD for the oxides up to 30% of Sn. Particle size measurements of the solid dispersed in acetone and SEM
study for microstructure showed that the oxides were in the nano range (55-75 nm) whereas the size range determined from Debye-Scherrer
equation were 11–24 nm. 相似文献
4.
P Pramanik 《Bulletin of Materials Science》1995,18(6):819-829
Ultrafine (⩽ 150 nm) powders of spinels [MFe2O4 where M = Ni(II), Co(II) and Zn(II)]; rare-earth orthoferrites [RFeO3 where R = Sm, Nd and Gd], and rare-earth garnets [R3Fe3O12 where R = Sm, Nd and Gd] with good purity and chemical homogeneity were prepared through two new versatile chemical routes.
The first route involved the coprecipitation of the desired metal nitrates from their aqueous solution, in presence of a water
soluble polymer-polyvinyl alcohol (PVA), by triethyl ammonium carbonate solution. The other process involved complete evaporation
of a mixture of optimum amounts of PVA and the desired aqueous metal nitrate solutions, with and without the addition of optimum
amounts of urea when the mixture was evaporated to a pasty mass. In addition, detailed study on the reported potassium ferricyanide
route was also carried out for the production of the rare-earth orthoferrite powders. The various precursor as well as the
heat-treated mixed-oxide powders, prepared through each of the routes, were compared by the physical characterization studies
involving thermal gravimetry and differential scanning calorimetry, infrared spectroscopy, X-ray powder diffraction, transmission
electron microscopy, and room temperature magnetic measurements. 相似文献
5.
Bi2 Te3 -based alloys are currently best-known, technologically important thermoelectric materials near room temperature. In this paper, nanocrystalline Bi2 Te3 was synthesized by an aqueous solution technique based on the reaction between the aqueous solution of Bi-ethylenediamine tetraaceticacid (EDTA), TeO-EDTA, and NaBH4 at room temperature. NaBH4 was used as a reducing agent. TeO-EDTA was prepared from TeO2 after satisfactory purification. The sample purity was examined by selected area energy dispersive X-ray analysis. The products were characterized by X-ray diffraction and high-resolution transmission electron microscopy by which the particle morphologies and size were studied. The particle size ranges from 60 to 90 nm. 相似文献
6.
V. Rao S. Pramanik C. R. Tewari S. R. Singh O. N. Mohanty 《Journal of Materials Science》1989,24(11):4088-4093
Phase transformation studies have been made of the Mn-Al alloys with compositions near the equiatomic range with or without small amounts of carbon, copper and nickel, using differential thermal analysis, X-ray diffraction and optical and electron microscopy. The high temperature hexagonal phase obtained by quenching, transforms to the ferromagnetic phase between 500 and 550° C and on further heating transforms back to the hexagonal phase between 750 and 950° C. Also, on controlled cooling of the phase from about 900° C, the ferromagnetic phase is formed between 800 and 670° C. TEM studies have shown the presence of the B19 ordered phase, ferromagnetic phase and Mn5Al8 precipitates even in quenched alloys. 相似文献
7.
Dibyajyoti Pramanik Rahul Mahadev Shelake Jiyeon Park Mi Jung Kim Indeok Hwang Younghoon Park Jae-Yean Kim 《International journal of molecular sciences》2021,22(4)
Tomato is one of the major vegetable crops consumed worldwide. Tomato yellow leaf curl virus (TYLCV) and fungal Oidium sp. are devastating pathogens causing yellow leaf curl disease and powdery mildew. Such viral and fungal pathogens reduce tomato crop yields and cause substantial economic losses every year. Several commercial tomato varieties include Ty-5 (SlPelo) and Mildew resistance locus o 1 (SlMlo1) locus that carries the susceptibility (S-gene) factors for TYLCV and powdery mildew, respectively. The clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein (Cas) is a valuable genome editing tool to develop disease-resistant crop varieties. In this regard, targeting susceptibility factors encoded by the host plant genome instead of the viral genome is a promising approach to achieve pathogen resistance without the need for stable inheritance of CRISPR components. In this study, the CRISPR/Cas9 system was employed to target the SlPelo and SlMlo1 for trait introgression in elite tomato cultivar BN-86 to confer host-mediated immunity against pathogens. SlPelo-knockout lines were successfully generated, carrying the biallelic indel mutations. The pathogen resistance assays in SlPelo mutant lines confirmed the suppressed accumulation of TYLCV and restricted the spread to non-inoculated plant parts. Generated knockout lines for the SlMlo1 showed complete resistance to powdery mildew fungus. Overall, our results demonstrate the efficiency of the CRISPR/Cas9 system to introduce targeted mutagenesis for the rapid development of pathogen-resistant varieties in tomato. 相似文献
8.
Monoj Pramanik Suneel Kumar Srivastava Biswas Kumar Samantaray Anil Kumar Bhowmick 《应用聚合物科学杂志》2003,87(14):2216-2220
Ethylene vinyl acetate rubber (45% vinyl acetate content, EVA‐45) and organomodified clay (12Me‐MMT) composites were prepared by solution blending of the rubber and the clay. A combination of X‐ray diffraction, scanning electron microscopy, and transmission electron microscopy studies showed that the composites obtained are on the nanometer scale. The measurements of the dynamic mechanical properties for different compositions over a temperature range (?100 to +100°C) showed that the storage moduli of these rubber–clay nanocomposites are higher above the glass to rubber transition temperature compared to the neat rubber. The tensile strength of the nanocomposites is about 1.6 times higher than that of the EVA‐45. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 2216–2220, 2003 相似文献
9.
To determine effects of very low levels of linolenic acid on frying stabilities of soybean oils, tests were conducted with
2% (low) linolenic acid soybean oil (LLSBO) and 0.8% (ultra-low) linolenic acid soybean oil (ULLSBO) in comparison with cottonseed
oil (CSO). Potato chips were fried in the oils for a total of 25 h of oil use. No significant differences were found for either
total polar compounds or FFA between samples of LLSBO and ULLSBO; however, CSO had significantly higher percentage of polar
compounds and FFA than the soybean oils at all sampling times. Flavor evaluations of fresh and aged (1, 3, 5, and 7 wk at
25°C) potato chips showed some differences between potato chips fried in different oil types. Sensory panel judges reported
that potato chips fried in ULLSBO and aged for 3 or 7 wk at 25°C had significantly lower intensities of fishy flavor than
did potato chips fried in LLSBO with the same conditions. Potato chips fried in ULLSBO that had been used for 5 h and then
aged 7 wk at 25°C had significantly better quality than did potato chips fried 5 h in LLSBO and aged under the same conditions.
Hexanal was significantly higher in the 5-h LLSBO sample than in potato chips fried 5 h in ULLSBO. The decrease in linolenic
acid from 2 to 0.8% in the oils improved flavor quality and oxidative stability of some of the potato chip samples. 相似文献
10.
Polyacrylonitrile solution homogeneity study by dynamic shear rheology and the effect on the carbon fiber tensile strength
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Bradley A. Newcomb Prabhakar V. Gulgunje Yaodong Liu Kishor Gupta Manjeshwar G. Kamath Chandrani Pramanik Sushanta Ghoshal Han Gi Chae Satish Kumar 《Polymer Engineering and Science》2016,56(3):361-370
Poly(acrylonitrile‐co‐methacrylic acid) (PAN‐co‐MAA)/N,N‐dimethylformamide (DMF) solutions were prepared and dynamic shear rheology of these solutions were investigated. With increasing stirring time up to 72 h at 70°C, the polymer solution became less elastic (more liquid‐like) with a ~60% reduction in the zero‐shear viscosity. Relaxation spectra of the PAN‐co‐MAA/DMF solutions yield a decrease in relaxation time (disentanglement time, τd), corresponding to an about 8% decrease in viscosity average molecular weight. The log‐log plot of G′ (storage modulus) versus G″ (loss modulus) exhibited an increase in slope as a function of stirring time, suggesting that the molecular level solution homogeneity increased. In order to study the effect of solution homogeneity on the resulting carbon fiber tensile strength, multiple PAN‐co‐MAA/DMF solutions were prepared, and the precursor fibers were processed using gel‐spinning, followed by continuous stabilization and carbonization. The rheological properties of each solution were also measured and correlated with the tensile strength values of the carbon fibers. It was observed that with increasing the slope of the G′ versus G″ log‐log plot from 1.471 to 1.552, and reducing interfilament fiber friction during precursor fiber drawing through the addition of a fiber washing step prior to fiber drawing, the carbon fiber strength was improved (from 3.7 to 5.8 GPa). This suggests that along with precursor fiber manufacturing and carbonization, the solution homogeneity is also very important to obtain high strength carbon fiber. POLYM. ENG. SCI., 56:361–370, 2016. © 2016 Society of Plastics Engineers 相似文献