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101.
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Electron Spin Resonance (ESR) spectra of gamma irradiated methylacrylamide-2-acrylamido-2-methyl-propanesulphonic acid (MA-AMPS) are recorded to identify the radical species formed during the irradiation of the copolymer. The ESR spectrum observed for irradiated MA-AMPS copolymer at liquid nitrogen temperature (LNT) (77 r K) is an asymmetric triplet; while the spectrum observed at room temperature (RT) is a quintet. The intensity distribution of both the spectra deviated appreciably from the expected theoretical values. Computer simulations are employed to analyze the ESR spectra observed at different temperatures. The triplet spectrum observed at LNT is simulated to be a superposition of component spectra arising from macroradicals of the type~CH 2 - \dot {\rm C} H-CH 2 ~ (I), radicals of the type \dot {\rm C} H 2 SO 3 H (II), and peroxy radicals (III). In contrast, the RT spectrum is simulated to be a superposition of component spectra arising due to radicals I, II, III together with the component quartet assigned to methyl radicals ( \dot {\rm C} H 3 ). The formation of such free radicals in irradiated copolymer is discussed. 相似文献
104.
Quantum dots (3–4?nm) of Zn1? x Cd x S (both free of Mn2+ and with Mn2+ incorporated) were synthesized through a novel solvothermal-microwave irradiation technique. Detailed structural analysis of the Zn1? x Cd x S and Zn1? x Cd x S:Mn2+ (x?=?0, 0.25, 0.5, 0.75 and 1) materials was carried out using powder X-ray diffraction technique. For all the compositions, the crystallite size was controlled to less than 1.5?nm. The optical energy gap for Zn1? x Cd x S was found to vary from 3.878 to 2.519?eV and for Zn1?x Cd x S:Mn2+ it varies from 3.830 to 2.442?eV when x is increased from 0 to 1. Overall, the optical energy gap could be tuned from a minimum of 2.442?eV to a maximum of 3.878?eV. DC conductivity analysis (from 40°C to 150°C) and electrical energy gap analysis for all the compositions were also performed. The dc conductivity for Zn1? x Cd x S solid solutions varies from 0.3840?×?10?10 to 8.7782?×?10?10?mho/m at 150°C and for Zn1? x Cd x S:Mn2+ it varies from 0.5751?×?10?10 to 9.8078?×?10?10 mho /m at 150°C (for x?=?0 to x?=?1). The method of synthesis and the results observed in this investigation may assist in the fabrication of optical devices when the required operational performance falls under the range observed in the study. 相似文献
105.
Confocal scanning laser microscopy (CSLM) was used in real-time observation of alloy element oxidation of a Mn/Al TRIP steel in an Ar–O2 atmosphere. CSLM images reveal a marked role of grain boundaries in the overall initial oxidation kinetics of the alloy, and consequently in the morphology of the initial surface oxide. The oxidation on the alloy surface is dominated by the formation of Mn-rich oxide ridges along grain boundary traces on the surface. Oxide ridge formation kinetics was quantified by measurements on images extracted from real-time recordings of surface oxide evolution. Oxide ridge growth was found to take place at a constant rate. Scanning electron microscopy (SEM) images of the oxidized surfaces showed homogenous oxide ridges along straight grain boundary traces and heterogeneous oxide ridges along non-straight grain boundary traces. A transport mechanism of Mn to the surface is proposed, which relies on grain boundary segregation of Mn and on a relationship between grain boundary diffusivity and grain boundary character. It is suggested that when regarding alloys with significant grain boundary segregation of a solute, separate Wagner balances for internal vs. external oxidation is required for the grain lattices and the grain boundaries, respectively. 相似文献
106.
Venkata Naresh Vema Y. Bharathi Kumari Sridhar Musulla Rama Krishnam Raju Addada Srinivasa Rao Alapati 《Tetrahedron letters》2019,60(14):986-988
A concise total synthesis of (3R),(5R)-5-hydroxy-de-O-methyllasiodiplodin and its epimer have been synthesized from commercially available (R)-propylene oxide and Orsellinic acid as starting materials. The key steps involved in the synthesis are Wittig reaction, epoxide ring opening with 1,3-dithiane intermediate and Yamaguchi macrolactonization. 相似文献
107.
Kalluri S Depireux DA Shamma SA 《The Journal of the Acoustical Society of America》2008,123(5):2701-2716
This study examined the perception and cortical representation of harmonic complex tones, from the perspective of the spectral fusion evoked by such sounds. Experiment 1 tested whether ferrets spontaneously distinguish harmonic from inharmonic tones. In baseline sessions, ferrets detected a pure tone terminating a sequence of inharmonic tones. After they reached proficiency, a small fraction of the inharmonic tones were replaced with harmonic tones. Some of the animals confused the harmonic tones with the pure tones at twice the false-alarm rate. Experiment 2 sought correlates of harmonic fusion in single neurons of primary auditory cortex and anterior auditory field, by comparing responses to harmonic tones with those to inharmonic tones in the awake alert ferret. The effects of spectro-temporal filtering were accounted for by using the measured spectrotemporal receptive field to predict responses and by seeking correlates of fusion in the predictability of responses. Only 12% of units sampled distinguished harmonic tones from inharmonic tones, a small percentage that is consistent with the relatively weak ability of the ferrets to spontaneously discriminate harmonic tones from inharmonic tones in Experiment 1. 相似文献
108.
Cherukumalli Purna Koteswara Rao Tadiboina Bhaskara Rao Gulipalli Kali Charan Bodige Srinu Gangarapu Kiran Sridhar Gattu 《Russian Journal of General Chemistry》2020,90(10):1981-1989
Russian Journal of General Chemistry - A novel series of bis-isoxazole incorporated benzothiazole derivatives has been designed and synthesized. Molecular structures of the compounds have been... 相似文献
109.
110.
Synthesis of new β3-amino acid, peptides and conformational analysis are reported from d-ribose, using Wittig olefination and Aza-Michael addition. 相似文献