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31.
Micro-blast waves emerging from the open end of a detonation transmission tube were experimentally visualized in this study. A commercially available detonation transmission tube was used (Nonel tube, M/s Dyno Nobel, Sweden), which is a small diameter tube coated with a thin layer of explosive mixture (HMX $+$ traces of Al) on its inner side. The typical explosive loading for this tube is of the order of 18 mg/m of tube length. The blast wave was visualized using a high speed digital camera (frame rate 1 MHz) to acquire time-resolved schlieren images of the resulting flow field. The visualization studies were complemented by computational fluid dynamic simulations. An analysis of the schlieren images showed that although the blast wave appears to be spherical, it propagates faster along the tube axis than along a direction perpendicular to the tube axis. Additionally, CFD analysis revealed the presence of a barrel shock and Mach disc, showing structures that are typical of an underexpanded jet. A theory in use for centered large–scale explosions of intermediate strength $(10\, < \Delta {p}/{p}_0 \lesssim \, 0.02)$ gave good agreement with the blast trajectory along the tube axis. The energy of these micro-blast waves was found to be $1.25 \pm 0.94$ J and the average TNT equivalent was found to be $0.3$ . The repeatability in generating these micro-blast waves using the Nonel tube was very good $(\pm 2~\%)$ and this opens up the possibility of using this device for studying some of the phenomena associated with muzzle blasts in the near future. 相似文献
32.
We consider a collapsing spherically symmetric inhomogeneous dust cloud in higher dimensional space-time. We show that the
central singularity of collapse can be a strong curvature or a weak curvature naked singularity depending on the initial density
distribution. 相似文献
33.
Paruchuri Kondaiah S.V. Jagadeesh Chandra Elvira Fortunato Choi Chel Jong G. Mohan Rao D.V. Rama Koti Reddy S. Uthanna 《Surface and interface analysis : SIA》2020,52(9):541-546
The effect of substrate temperature on the direct current magnetron-sputtered zirconium oxide (ZrO2) dielectric films was investigated. Stoichiometric of the ZrO2 thin films was obtained at an oxygen partial pressure of 4.0 × 10−2 Pa. X-ray diffraction studies revealed that the crystallite size in the layer was increased from 4.8 to 16.1 nm with increase of substrate temperature from 303 to 673 K. Metal-oxide-semiconductor devices were fabricated on ZrO2/Si stacks with Al gate electrode. The dielectric properties of ZrO2 layer and interface quality at ZrO2/Si were significantly influenced by the substrate temperature. The dielectric constant increased from 15 to 25, and the leakage current density decreased from 0.12 × 10−7 to 0.64 × 10−9 A cm−2 with the increase of substrate temperature from 303 to 673 K. 相似文献
34.
35.
Ashok Kale Nagaraju Medishetti Jagadeesh Babu Nanubolu Krishnaiah Atmakur 《Tetrahedron letters》2018,59(47):4168-4171
Regioselective synthesis of 2-benzoyl-6,6-dimethyl-6,7-dihydrobenzofuran-4(5H)-ones have been accomplished through a novel protocol involving β-amino enone, N-chlorosuccinimide and dimedone in a one pot catalyst-free reaction at an ambient temperature. On the other hand, the same reaction when conducted with two equivalents of N-chlorosuccinimide under similar reaction conditions, exclusive formation of 2-benzoyl-3-(dimethylamino)-6,6-dimethyl-6,7-dihydrobenzofuran-4(5H)-ones were observed. Simple and metal-free reaction conditions, selective product formation and excellent yields are the advantages of this protocol. 相似文献
36.
Balasubramanian Sridhar Jagadeesh Babu Nanubolu Krishnan Ravikumar 《Acta Crystallographica. Section C, Structural Chemistry》2013,69(10):1164-1169
Lamotrigine, an antiepileptic drug, has been complexed with three aromatic carboxylic acids. All three compounds crystallize with the inclusion of N,N‐dimethylformamide (DMF) solvent, viz. lamotriginium [3,5‐diamino‐6‐(2,3‐dichlorophenyl)‐1,2,4‐triazin‐2‐ium] 4‐iodobenzoate N,N‐dimethylformamide monosolvate, C9H8Cl2N5+·C7H4IO2−·C3H7NO, (I), lamotriginium 4‐methylbenzoate N,N‐dimethylformamide monosolvate, C9H7Cl2N5+·C8H8O2−·C3H7NO, (II), and lamotriginium 3,5‐dinitro‐2‐hydroxybenzoate N,N‐dimethylformamide monosolvate, C9H8Cl2N5+·C7H3N2O7−·C3H7NO, (III). In all three structures, proton transfer takes place from the acid to the lamotrigine molecule. However, in (I) and (II), the acidic H atom is disordered over two sites and there is only partial transfer of the H atom from O to N. In (III), the corresponding H atom is ordered and complete proton transfer has occurred. Lamotrigine–lamotrigine, lamotrigine–acid and lamotrigine–solvent interactions are observed in all three structures and they thereby exhibit isostructurality. The DMF solvent extends the lamotrigine–lamotrigine dimers into a pseudo‐quadruple hydrogen‐bonding motif. 相似文献
37.
The first synthesis of cell wall-active lipopeptide diastereomers from easily accessible starting materials has been reported. The synthetic strategy involves Jacobsen resolution, TEMPO/BAIB & 2C-Wittig (one pot reaction), and peptide couplings. 相似文献
38.
Krishnan Ravikumar Balasubramanian Sridhar Jagadeesh Babu Nanubolu Govindaraju Karthik Basi Venkata Subba Reddy 《Acta Crystallographica. Section C, Structural Chemistry》2015,71(8):721-727
The challenging molecular architecture of spirooxindoles is appealing to chemists because it evokes novel synthetic strategies that address configurational demands and provides platforms for further reaction development. The [3+2] cycloaddition of the carbonyl ylide with arylideneoxindole via a five‐membered cyclic transition state gave a novel class of dispirooxindole derivatives, namely tert‐butyl 4′‐(4‐bromophenyl)‐1′′‐methyl‐2,2′′‐dioxo‐5′‐phenyl‐4′,5′‐dihydrodispiro[indoline‐3,2′‐furan‐3′,3′′‐indoline]‐1‐carboxylate, C36H31BrN2O, (Ia), 5′‐(4‐bromophenyl)‐1,1′′‐dimethyl‐4′‐phenyl‐4′,5′‐dihydrodispiro[indoline‐3,2′‐furan‐3′,3′′‐indoline]‐2,2′′‐dione, C32H25BrN2O3, (Ib), and tert‐butyl 1′′‐methyl‐2,2′′‐dioxo‐4′‐phenyl‐5′‐(p‐tolyl)‐4′,5′‐dihydrodispiro[indoline‐3,2′‐furan‐3′,3′′‐indoline]‐1‐carboxylate, C37H34N2O5, (Ic). Crystal structure analyses of these dispirooxindoles revealed the formation of two diastereoisomers selectively and confirmed their relative stereochemistry (SSSR and RRRS). In all three structures, intramolecular C—H...O and π–π interactions between oxindole and dihydrofuran rings are the key factors governing the regio‐ and stereoselectivity, and in the absence of conventional hydrogen bonds, their crystal packings are strengthened by intermolecular C—H...π interactions. 相似文献
39.
Prasanna SJ Sharma HK Mukkanti K Kumar VJ Raja G Sivakumaran M 《Journal of chromatographic science》2010,48(10):830-834
The present study relates to a new capillary electrophoresis method for the determination of N-methylpyrrolidine, an impurity considered to be toxic and also potential degradation impurity in cefepime hydrochloride drug substance. The newly developed capillary electrophoresis method for determining the content of N-methylpyrrolidine in cefepime for injection has been validated as per International Conference on Harmonization (ICH) guidelines to prove the selectivity, sensitivity, suitability, robustness, and ruggedness of the method. This simple, efficient, and rapid methodology may be used by pharmaceutical industry for routine analysis as well as during stability studies. The newly developed capillary electrophoresis method to determine the content of N-methylpyrrolidine in cefepime for injection requires 10 min for data acquisition, and uses an indirect UV photometry method to detect the analyte signal at 240 nm against the reference signal at 210 nm. The electrophoretic system is optimized to get stable base line, higher signal to noise ratio and peaks with narrow peak width. The method employs bare fused silica capillary with extended light path, effective length of capillary is 56 cm and inner diameter of capillary is 50 μm, 5 mmole of imidazole buffer adjusted to pH 5.1 with 3 molar acetic acid solution is used as background electrolyte. The sample is introduced in hydrodynamic mode employing pressure of 50 mbar for 5 s, and the desired separation is achieved with constant applied voltage of 25 kV at ambient temperature (~25°C). 相似文献
40.
The scattering of incident plane elastic waves by a varietyof different defects that lie upon a fluid-solid interface isconsidered here using matched asymptotic expansions. The expansionscheme is developed in terms of a parameter , the ratio of typicaldefect length scale to a typical wavelength of the incidentfield, taken to be small. Three different canonical situations occur and these are illustratedvia three specific examples treated here: a rigid strut, anedge crack, and a rigid strip. In each case the leading-ordermatching is performed to identify the leading-order contributionof the defect to the acoustic field in the far field. In particular,each defect is identified with a source of dipole response ininterfacial stress of displacement. It is shown in the limit as s<<s1 that in the inner problemsthe fluid and solid pieces uncouple in a particularly convenientmanner allowing analytical solutions to be deduced. These arethen matched with appropriate outer solutions. 相似文献