Study of Energetic Nitramine Extruded Double-Base Propellants

This paper gives the results of an experimental study on nitramine extruded double-base (EDB)fonnulationscontaining up to 25 percent RDXin low and high calorimetric value double-base(DB)propellants. The effect of ballistic modifiers on the burn rate and pressure exponent ( 11) of promisingfonnulations has also been investigated. The data generated on various parameters reveal that ( i)nitraniine EDB propellants exhibit relatively superior thennal stability,' (ii) tensile strength andpercentage elongation are drastically altered if RDX concentration exceeds 15 per cent, (iii) 11 islowered significantly in the presence of ballistic modifiers, (iv) characteristic velocity (C*) values arehigher to that for the control tonnulation, and ( v) temperature sensitivity of burn rate is on the lowerside (0,20 -0.25 % / °C as against 0.40 % / °C) in the presence of ballistic modifiers

An ab initio topographical investigation on the molecular electrostatic potential of some chemical mutagens

A detailed topographical investigation on the molecular electrostatic potentials (MESPs) of different conformers of acetaldehyde, nitrous acid and hydroxylamine has been carried out at the ab initio SCF level using TZ2p, 6-31G* and STO-3G basis sets. In general, large regions of negative potential have been observed. An attempt has been made to correlate these potentials with biological activities of the molecules. Mutagenic and toxicological properties appear to be related to the presence of these large negative zones

Deep-desulfurization of the petroleum diesel using the heterogeneous carboxyl functionalized poly-ionic liquid

Acidic carboxyl functionalized poly(ionic liquid) (CFPIL) has been synthesized and characterized by various techniques like FT-NMR, Fourier transform infrared spectroscopy (FTIR). In this work, deep oxidative desulfurization of model oil (thiophene dissolved in iso-octane) by CFPIL catalyst was carried out in presence of 30 wt% H2O2 solution as an oxidant. The effects of the hydrogen peroxide, amount of CFPIL, temperature-time and recyclability are scrutinized systematically. It was found that the effective molar proportion of H2O2 to sulfur was 4:1 at 70 °C in 180 min with 0.6 g catalyst, removing 100% thiophene from model oil. This method has shown high efficiency for the removal of thiophene, which is difficult to remove from the oil than benzothiophene and dibenzothiophene. Additionally, an oxidative desulfurization mechanism has been proposed according to the experimental results. This catalytic system by CFPIL offers advantages such as higher efficiency, low amount of ionic liquid, simple work up for separating oil from the catalyst and ease of recycling. This protocol inclines to show that diesel fuels in industry can be purified to sulfur-free or ultra-low sulfur fuels by further deep oxidative desulfurization with CFPILs after hydrodesulfurization

Influence of cobalt salts of organic acids on the burning rate behaviour of double base propellants

271-274<span style="font-size:11.0pt;line-height:115%; font-family:" calibri","sans-serif";mso-ascii-theme-font:minor-latin;mso-fareast-font-family:="" "times="" new="" roman";mso-fareast-theme-font:minor-fareast;mso-hansi-theme-font:="" minor-latin;mso-bidi-font-family:"times="" roman";mso-ansi-language:en-us;="" mso-fareast-language:en-us;mso-bidi-language:ar-sa"="">Influence of cobalt salts of aliphatic and aromatic acids has been studied on the burning rates of NC-NG based double phase propellants in the pressure range of 35-140 kg/cm2. Cobalt-b-resorcylate has the highest burning rates, followed by cobalt salicylate. Both the compounds show plateau effect in 105-140kg/cm2 pressure region. Cobalt stearate is found to be effective in low pressure region, whereas cobalt benzoate is most effective in higher pressure. Cobalt gallate is ineffective towards any catalytic or plateau effect. The results have been explained on the basis of thermal decomposition studies of catalyzed double base propellants.</span

Topographical analysis of electron density and molecular electrostatic potential for cyclopropa- and cyclobutabenzenes

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Complementary electrostatics for the study of DNA base-pair interactions

The complementary "lock and key" patterns of weakly interacting molecules are explored by mapping the topography of respective molecular electrostatic potentials (MESP). A new model, viz., electrostatic potential for intermolecular complexation (EPIC), which incorporates such MESP features, has been employed for studying interactions between DNA base pairs. A wide variety of pairs of bases involving adenine (A), guanine (G), and cytosine (C) are chosen as test cases. The interaction energy within the EPIC model is expressed as (&#189;){&#8721;VA,iqB,i + &#8721;VB,iqA,i}, where VA,i is the MESP value due to A at the ith atom of molecule B and qB,i is the MESP-derived charge at this site. The interaction energies and geometrical parameters obtained by this model agree remarkably well with the corresponding literature values obtained by full geometry optimization at the ab initio level. Being intuitively appealing and simple in application, the EPIC model seems to have the potential of being a good predictive tool for investigating weak intermolecular interactions

Structure and stability of DNA base trimers: an electrostatic approach

Triplexes involving major groove binding of a third oligomer to the DNA duplex structure have gathered much interest in recent years. The study of base trimer interactions in the gas phase is expected to provide useful information regarding orientational preferences and inherent stabilities. A recently developed electrostatic potential for intermolecular complexation (EPIC) model has been found to be quite useful for exploring the structures and energetics in base pairs [Gadre, S. R.; Pundlik, S. S. J. Phys. Chem. 1996, 101, 3298]. This model makes use of complementary electrostatic features of the interacting species that are determined by ab initio theory. We report here the investigations on various trimers including TAT, TAG, ATG, CGG, and TCG using this model. The overall good agreement of the trimer interaction energies with the corresponding single-point SCF values made at the model-predicted geometries reveals the suitability of the EPIC model for studying DNA base complexes

A "critical" appraisal of electrostatic charge models for molecules

The conventional electrostatic charge models (PD-AC) are constructed so as to reproduce the molecular electrostatic potential (MESP) on and beyond the van der Waals' (vdW) surface. The MESP distribution has recently [S R Gadre, S A Kulkarni and I H Shrivastava (1992)J. Chem. Phys. 96 5253] been shown to exhibit rich topographical features. With this in view, a detailed topographical comparison of the MESP derived from the charge models, with the respectiveab initio (MO) ones is taken up for water, hydrogen sulphide, methane and benzene molecules as test cases. It is shown that the point charge models have a fundamental lacuna, viz. they fail to mimic the essential topographical features of MESP. A new model incorporating a small number of floating spherical Gaussians is shown to restore all the critical features of the molecules under study. A comparative study of the standard deviations of MESP derived from charge models on scaled vdW surfaces further reveals that the present model leads to a better representation ofab initio MESP