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91.
Shivaji Sircar 《Adsorption》2006,12(4):259-266
An analytical mathematical model is used to investigate the influence of minute adsorbent temperature changes on the kinetics
of sorption of a gaseous adsorbate from mixture with a carrier gas using a differential closed loop recycle method. Isothermal
operation may not be achieved even when a very high gas circulation rate is used. Very small changes in the adsorbent temperature
during the process can cause substantial departure from isothermal uptake behavior. It is shown that the kinetic process can
be assumed to be isothermal only for trace adsorbate concentrations. A criterion for validity of isothermal data analysis
is proposed. 相似文献
92.
C.P. Singh M. Yousuf S.B. Qadri D.C. Turner B.P. Gaber B.R. Ratna 《Applied Physics A: Materials Science & Processing》2003,77(3-4):585-589
The synthesis of transparent monolithic silica with a structure consistent with a space group Pn3m )isdemonstratedusingatemplate-directedsynthesisapproach.TheprocedureisbasedonthehydrolysisandpolymerizationofsiliconalkoxideatlowpHinthepresenceofacationicsurfactant.Thelow-pHreactionrouteischosentoobtaintransparentmonolithicmesoporoussilica.AstructureconsistentwiththePn3m) space group with unit cell lattice parameter ranging from 60–64 Å was identified using small-angle X-ray diffraction. While the lattice parameter is observed to be a monotonically increasing function of surfactant-to-silica ratio, the surfactant-to-alkoxide ratio has a weak discernible effect on the lattice parameter. The Brunauer, Emmett, and Teller (BET) surface area, total pore volume and average pore diameter of the samples are in the range of 787–845 m2/g, 0.37–0.51 cc/g and 18–24 Å respectively. This synthesis approach offers a one-step formation of monolithic mesoporous silica of diverse dimensions for potential use in a variety of technological applications such as catalysis, controlled release and adsorption phenomena . PACS 36.10.Gr; 68.65.-k; 73.21.-b; 73.23.-b 相似文献
93.
The kinetics of oxidation of ascorbic acid by acidic hexacyanoferrate(III) have been investigated in presence of cationic surfactant viz. cetyltrimethylammonium bromide (CTAB). An inhibition effect of CTAB (below its critical micelle concentration) on the rate of oxidation has been observed. The spectrophotometric and kinetic data support a 1:1 premicellar association between substrate and surfactant. A mechanism has been proposed and a rate law consistent with kinetic results has been derived. 相似文献
94.
Rajat Sharma Vijaykumar Palled Ratna R. Sharma-Shivappa Jason Osborne 《Applied biochemistry and biotechnology》2013,169(3):761-772
Chemical pretreatment of lignocellulosic biomass has been extensively investigated for sugar generation and subsequent fuel production. Alkaline pretreatment has emerged as one of the popular chemical pretreatment methods, but most attempts thus far have utilized NaOH for the pretreatment process. This study aimed at investigating the potential of potassium hydroxide (KOH) as a viable alternative alkaline reagent for lignocellulosic pretreatment based on its different reactivity patterns compared to NaOH. Performer switchgrass was pretreated at KOH concentrations of 0.5–2 % for varying treatment times of 6–48 h, 6–24 h, and 0.25–1 h at 21, 50, and 121 °C, respectively. The pretreatments resulted in the highest percent sugar retention of 99.26 % at 0.5 %, 21 °C, 12 h while delignification up to 55.4 % was observed with 2 % KOH, 121 °C, 1 h. Six pretreatment conditions were selected for subsequent enzymatic hydrolysis with Cellic CTec2® for sugar generation. The pretreatment condition of 0.5 % KOH, 24 h, 21 °C was determined to be the most effective as it utilized the least amount of KOH while generating 582.4 mg sugar/g raw biomass for a corresponding percent carbohydrate conversion of 91.8 %. 相似文献
95.
D. Ratna V. Dalvi B. C. Chakraborty P. C. Deb 《Journal of polymer science. Part A, Polymer chemistry》2003,41(14):2166-2170
Copolymers of styrene and methyl acrylate were synthesized in the form of spherical beads (0.4–1.2 mm) and sulfonated with concentrated sulfuric acid. The sulfonated copolymer shows an in‐built acid–base indicator property; the yellow color in the acid medium changes to an intense pink color at the equivalence point. Also, the ion‐exchange capacity of the sulfonated copolymer increases with time, reaches a maximum, and decreases thereafter. The results were explained in terms of Fourier transform infrared spectroscopic analysis considering internal Friedel–Craft acylation followed by cyclic dehydration leading to a conjugated structure. The developed ion‐exchange resin also demonstrated better performance in demineralization of water as compared with the conventional polystyrene‐based beads. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2166–2170, 2003 相似文献
96.
97.
C. Nagabhushan Geetha G. Nair B. R. Ratna R. Shashidhar J. W. Goodby 《Liquid crystals》1988,3(2):175-183
Static dielectric constants, ε∥ and ε⊥ as well as the low frequency dielectric dispersion of ε∥ have been studied in the vicinity of the hexatic B-smectic A transition in n-hexyl-4'-pentyloxybiphenyl-4-carboxylate (65OBC) and n-butyl-4'-hexyloxybiphenyl-4-carboxylate (46OBC) and also near the crystal B-smectic A transition in n-(4-n-butyloxybenzylidene)-4-n-octylaniline (4O. 8). While the behaviour of the dielectric anisotropy is essentially similar for both transitions, the dispersion results show significant differences. 相似文献
98.
In liquid-crystalline elastomers, the nematic order parameter and the induced strain vary smoothly across the isotropic-nematic transition, without the expected first-order discontinuity. To investigate this smooth variation, we measure the strain as a function of temperature over a range of applied stress, for elastomers cross-linked in the nematic and isotropic phases, and analyze the results using a variation on Landau theory. This analysis shows that the smooth variation arises from quenched disorder in the elastomer, combined with the effects of applied stress and internal stress. 相似文献
99.
Ratna S. Phadke N. Vasanth Kumar R. V. Hosur Anil Saran Girjesh Govil 《International journal of quantum chemistry》1981,20(1):85-92
In our earlier studies using quantum chemical methods we had proposed that propranolol has an extended structure. These results were confirmed using proton NMR . We have now carried out extensive magnetic resonance and model building studies to examine the interaction of this drug with model membranes. The effect of propranolol on organization of lipid bilayers has been studied using ESR spin labeling technique. Spin label Tempo and spin labeled stearic acid (5 SASL ) have been used to monitor changes in the fluidity of model membranes. Presence of the drug is found to fluidize the lipids. In case of 0.2M dipalmitoyl phosphatidyl choline (DPPC), presence of drug (0.1M) is found to decrease the gel-liquid crystalline phase transition temperature by about 10°C. The order parameter measured from the spectrum of 5 SASL shows a 4% decrease on incorporation of the drug in membranes. 13C spin lattice relaxation time (T1) measurements have been carried out for different nuclear sites of the drug. The aromatic moiety shows a high degree of molecular rigidity when the drug is bound to the lipid bilayers. The oxypropanolamine group is however relatively flexible. It appears from these studies that the aromatic group binds strongly to the hydrophobic regions of the lipid bilayer, while the oxypropanolamine moiety remains relatively free and lies in the hydrophilic region. The 13C chemical shifts indicate the involvement of the β-hydroxyl group in hydrogen bonding with the lipids. The NH group may be involved in electrostatic interactions with the negatively charged phosphate group of the lipid bilayers. 相似文献
100.
A. V. Ratna Prasad K. Balakotesara Rao K. Mohana Rao K. Ramanaiah S. P. Kumar Gudapati 《International Journal of Polymer Analysis and Characterization》2015,20(6):541-556
Natural fiber-reinforced nanocomposites were prepared by incorporating wild cane grass fiber and organically modified montmorillonite (MMT) nanoclay into polyester resin. The composites were formulated up to a maximum volume of fiber of approximately 40% and their mechanical properties were investigated. The mean tensile strength and tensile modulus of nanoclay-filled wild cane grass fiber composites are 6.3% and 18.3% greater than those of wild cane grass fiber composites, respectively, without addition of nanoclay at maximum percentage volume of fiber. The mean flexural strength of nanocomposites at maximum percentage volume of fiber was increased to a maximum of 221 Mpa and flexural modulus to 4.2 Gpa. The mean impact strength of nanoclay-filled wild cane grass fiber composites was increased to 376.7 J/m at maximum percentage volume of fiber. The weight loss of nanoclay-filled wild cane grass fiber/polyester composites was 30% and 22% less than that of composites without nanoclay at maximum percentage volume of fiber. The results indicated that the use of nanoclay showed significant improvement in all the mechanical properties of wild cane grass fiber-reinforced composites. 相似文献