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171.
K.V. Anand Aviral Roy Irfan Mulla Kishor Balbudhe K. Jayaraman S.R. Chakravarthy 《Proceedings of the Combustion Institute》2013,34(2):2139-2146
Sixteen propellant formulations based on ammonium perchlorate (AP), hydroxyl-terminated polybutadiene, and aluminium particles have been tested for size distribution of aluminium agglomerates emerging from their burning surface. The formulations are based on a bimodal size distribution of AP particles. Ten of the formulations exhibit one or two plateaus/mesa in their burning rate variation with pressure (zero/negative pressure exponent of burning rate). The relevant formulation variables, namely, coarse and fine AP sizes and coarse-to-fine ratio, aluminium size and content, and two different curing agents, have been varied. Tests are performed in the 1–10 MPa pressure range. A direct correlation between burning rate and agglomerate size exists for propellants with normal burning rate trends but a neutral or inverse correlation is observed for those exhibiting plateau burning behaviour. Larger the parent aluminium size, lesser the agglomeration, as expected; but the effect of aluminium content is non-monotonic. The coarse AP size influences the aluminium agglomerate size as expected from the pocket model regardless of plateau burning effects. The agglomerate size decreases with increase in fine AP size, however. A computer model developed earlier at this laboratory for prediction of aluminium agglomerates based on three-dimensional packing of particles and deduction of AP particles with attached leading edge diffusion flames is applied to the present formulations. The model under-predicts the agglomerate size, only marginally for propellants that do not exhibit plateau burning rate trends, but substantially, otherwise. This is because it does not take into account effects of binder melt flow and is independent of the curing agent of the binder. 相似文献
172.
Chockalingam Karunakaran Jayaraman Jayabharathi Marimuthu Venkatesh Perumal Venugopal Thanikachalam Prasoon Kumar Thakur 《Journal of Physical Organic Chemistry》2013,26(5):386-406
Phenanthrimidazoles as hole transport materials have been synthesized, characterized, and applied as nondoping emitters in organic light emitting devices. The synthesized molecules possess high fluorescent quantum yield and thermal properties and display film forming abilities. The highest occupied molecular orbital (HOMO) energies of these materials are shallower than the reported tris(8‐hydroxyquinoline)aluminum (Alq3), which enables the hole transport ability of these phenanthrimidazoles. Taking advantage of the thermal stability and hole transporting ability, these compounds can be used as a functional layer between NPB [4,4‐bis(N‐(1‐naphthyl)‐N‐phenylamino)biphenyl] and Alq3 layers and show that these phenanthrimidazoles can be alternatively used as novel hole transport materials and to improve the device performances. Geometrical, optical, electrical, and electroluminescent properties of these molecules have been probed. Further, natural bond orbital, nonlinear optical materials (NLO), molecular electrostatic potential, and HOMO–lowest unoccupied molecular orbital (LMO) energy analysis have been made by density functional theory (DFT) method to support the experimental results. Hyperpolarizability analysis reveals that the synthesized phenanthrimidazoles possess NLO behavior. The chemical potential, hardness, and electrophilicity index of phenanthrimidazoles have also been computed by DFT method. Photoinduced electron transfer explains the enhancement of fluorescence by nanoparticulate ZnO, and the apparent binding constant has been obtained. Adsorption of the fluorophore on ZnO nanoparticle lowers the HOMO and LUMO energy levels of the fluorophore. The strong adsorption of the phenanthrimidazoles on the surface of ZnO nanocrystals is likely due to the chemical affinity of the nitrogen atom of the organic molecule to Zn(II) on the surface of nanocrystal. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
173.
Synthesis and Photophysics of Some Novel Imidazole Derivatives Used as Sensitive Fluorescent Chemisensors 总被引:1,自引:0,他引:1
Kanagarathinam Saravanan Natesan Srinivasan Venugopal Thanikachalam Jayaraman Jayabharathi 《Journal of fluorescence》2011,21(1):65-80
Some novel imidazole derivatives were developed for highly sensitive chemisensors for transition metal ions. Since these compounds are sensitive to different external stimulations such as UV irradiation, heat, increasing pressure and changing the environmental pH causing colour change and so they can be used as a ??multi-way?? optically switchable material. A prominent fluorescence enhancement was found in the presence of transition metal ions such as Hg2+, Pb2+ and Cu2+ and this was suggested to result from the suppression of radiationless transitions from the n-??* state in the chemisensors. The existence of C-H??.O intramolecular hydrogen bonding in dmphnpi is confirmed by the Natural Bond Orbital analysis (NBO). The Mulliken, NBO charge analysis and the HOMO-LUMO energies were also calculated. The electric dipole moment (??) and the first-hyperpolarisability (??) value of the investigated molecules have been studied both experimentally and theoretically which reveal that the synthesized molecules have microscopic non-linear optical (NLO) behaviour with non-zero values. Ground and excited state DFT calculation were carried out in order to find out dipole moment and energy. 相似文献
174.
Manivannan A. Sudha R. Maharajan S. Shaji Dinu Maheswari R. Uma Joseph Kitheri Jayaraman V. 《Journal of Radioanalytical and Nuclear Chemistry》2021,328(2):591-604
Journal of Radioanalytical and Nuclear Chemistry - In this study, the natural luffa fiber was easily modified by chemical method with amide groups and phosphoric acid (LF-A2-M1/P). SEM, XRD, FTIR... 相似文献
175.
Muthusamy Jayaraman Steven M. Ansell Barbara L. Mui Ying K. Tam Jianxin Chen Xinyao Du David Butler Laxman Eltepu Shigeo Matsuda Jayaprakash K. Narayanannair Kallanthottathil G. Rajeev Ismail M. Hafez Akin Akinc Martin A. Maier Mark A. Tracy Pieter R. Cullis Thomas D. Madden Muthiah Manoharan Michael J. Hope 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2012,124(34):8657-8661
176.
Nabil Tahiri Peter Fodran Dhineshkumar Jayaraman Jeffrey Buter Martin D. Witte Tonatiuh A. Ocampo D. Branch Moody Ildiko Van Rhijn Adriaan J. Minnaard 《Angewandte Chemie (International ed. in English)》2020,59(19):7555-7560
In Mycobacterium tuberculosis, mycolic acids and their glycerol, glucose, and trehalose esters (“cord factor”) form the main part of the mycomembrane. Despite their first isolation almost a century ago, full stereochemical evaluation is lacking, as is a scalable synthesis required for accurate immunological, including vaccination, studies. Herein, we report an efficient, convergent, gram‐scale synthesis of four stereo‐isomers of a mycolic acid and its glucose ester. Binding to the antigen presenting protein CD1b and T cell activation studies are used to confirm the antigenicity of the synthetic material. The absolute stereochemistry of the syn‐methoxy methyl moiety in natural material is evaluated by comparing its optical rotation with that of synthetic material. 相似文献
177.
Organophotocatalysis: Insights into the Mechanistic Aspects of Thiourea‐Mediated Intermolecular [2+2] Photocycloadditions 下载免费PDF全文
Nandini Vallavoju Dr. Sermadurai Selvakumar Dr. Barry C. Pemberton Dr. Steffen Jockusch Prof. Dr. Mukund P. Sibi Prof. Dr. Jayaraman Sivaguru 《Angewandte Chemie (International ed. in English)》2016,55(18):5446-5451
Mechanistic investigations of the intermolecular [2+2] photocycloaddition of coumarin with tetramethylethylene mediated by thiourea catalysts reveal that the reaction is enabled by a combination of minimized aggregation, enhanced intersystem crossing, and altered excited‐state lifetime(s). These results clarify how the excited‐state reactivity can be manipulated through catalyst–substrate interactions and reveal a third mechanistic pathway for thiourea‐mediated organo‐photocatalysis. 相似文献
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