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51.
Abstract On radiolysis tris(acetylacetonato) cobalt(III) in aqueous solutions is found to get reduced by reaction with (1) hydrated electrons, (2) H atoms, (3) OH radicals and (4) C2H2OH radicals. The bimolecular rate constants for the first three reactions, determined by competition kinetics are: 4 × 1010, 2.3 × 109 and 4.7 × 109 M?1sec?1 respectively. Absorption spectra of the irradiated solutions indicate the formation of bis(acetylacetonato) cobalt(II) from reaction (1), but not from (3). The total cobaltous yield in air-free solutions is given byG(Co++) = 5.6 and 6.5 at pH 6.5 and 1 respectively. It appears that Geaq- ∽ H + GoH ∽ 2.8 in neutral solutions. Considerations of material balance for the primary yields of radiolysis of water suggest the possibility that the so-called independent H-atoms in neutral solutions are probably excited water molecules or ion-pairs. 相似文献
52.
Abstract It is shown that the McMillan parameter M = T SAN/T N1 (where T SAN and T NI are respectively the temperatures of the smectic A to nematic (SAN) and the nematic to isotropic (NI) phase transitions) is useful in analysing the crossover between second and first order behaviour of the SNN transition in the nO.m homologous liquid crystal series (the 4-n-alkoxybenzylidene-4′-n-alkylanilines). Using a phase diagram of orientational ordering versus M for this series, as obtained in this work (from E.S.R. and D.S.C), a symmetric tricritical point with mean field exponent β2 = 1 is demonstrated. In a preliminary study of E.S.R. linewidth parameters B and C of nitroxide spin probes dissolved in members of the nO.m series exhibiting a first order SAN transition, critical-type divergences are observed near this transition. In the case where M is closer to 0.959 (the value at the tricritical point), these divergences appear similar to those previously observed in related nO.m members with a second order SAN transition; however, they are considerably enhanced for an M value closer to unity (i.e. more removed from the tricritical point). This indicates the importance of coupling between orientational and positional order parameters in the observed critical-type divergences. 相似文献
53.
A series of N‐chloroacetyl‐2,6‐diarylpiperidin‐4‐ones (10–18) obtained from the corresponding 2,6‐diarylpiperidin‐4‐ones upon base‐catalyzed condensation with morpholine afforded N‐morpholinoacetyl‐2,6‐diarylpiperidin‐4‐ones (19–27). The synthesized compounds have been characterized by their elemental, analytical, and spectral data. 相似文献
54.
S. Krishna Prasad Yoji Maeda Corresponding author D. S. Shankar Rao S. Anitha Nagamani Uma S. Hiremath C. V. Yelamaggad 《Liquid crystals》2013,40(11):1277-1283
The phase behaviour of two achiral bent core banana-shaped compounds, the hexyloxy (compound I) and decyloxy (compound II) members of the 1,3-phenylene bis[N-(2-hydroxy-4-n-alkoxybenzylidene)-4′-aminobenzoate] series was investigated under hydrostatic pressures up to 300?MPa using high pressure differential thermal analysis and light transmission methods. The reversible transition sequence crystal (Cr1)–B1 phase–isotropic liquid (I), observed at room pressure for compound I, remains in the pressure region up to c 70?MPa. At higher pressures a pressure-induced crystalline phase (Cri) appears between the Cr1 and B1 phases, its temperature region becoming wider with increasing pressure. The temperature vs. pressure phase diagram shows a triple point of 72.9?MPa and 160.3°C for the Cr1, Cri and B1 phases, indicating the lower limit of pressure for the Cri phase. In compound II the reversible transition sequence crystal (Cr1)–B2 phase–I is seen over the whole pressure region, and the temperature range of the B2 phase remains unaltered. It is concluded that both the B1 and B2 banana phases are stable over the whole pressure region studied. 相似文献
55.
Abstract Variation of bulk modulus of Si, Ge and GaAs with pressure is studied using four semiempirical equations of state, two of which being proposed very recently. Hence an expression for bulk modulus for arbitrary pressure for the semiconductors similar to Cohen's formula for zero pressure is arrived at. The applicability of these equations of state for the high pressure phases of Si and Ge is tested using the recent experimental and theoretical pressure-volume data of these phases. 相似文献
56.
S. Chandrasekaran K. Gopal P. X. Franklin Balasubramanian Jaganatha Sivakumar Gajendra Singh Shridhar Narayanan B. Gopalan Ansar A. Khan 《Biomedical chromatography : BMC》2013,27(8):1018-1026
The present investigation describes the development and validation of a sensitive liquid chromatography–mass spectrometry/mass spectrometry (LC‐MS/MS) method for the estimation of dorsomorphin in rat plasma. A sensitive LC‐MS/MS method was developed using multiple reaction monitoring mode, with the transition of m/z (Q1/Q3) 400.2/289.3 for dorsomorphin and m/z (Q1/Q3) 306.2/236.3 for zaleplon. Chromatographic separation was achieved on a reverse phase Agilent XDB C18 column (100 × 4.6 mm, 5 µm). The mobile phase consisted of acetonitrile and 5 mm ammonium acetate buffer (pH 6.0) 90:10 v/v, at a flow rate of 0.8 mL/min. The effluence was ionized in positive ion mode by electrospray ionization (ESI) and quantitated by mass spectrometry. The retention times of dorsomorphin and internal standard were found to be 2.13 and 1.13 min, respectively. Mean extraction recovery of dorsomorphin and internal standard in rat plasma was above 80%. Dorsomorphin calibration curve in rat plasma was linear (r2 ≥ 0.99) ranging from 0.005 to 10 µg/mL. Inter‐day and intra‐day precision and accuracy were found to be within 85–115% (coefficient of variation). This method was successfully applied for evaluation of the oral pharmacokinetic profile of dorsomorphin in male Wistar rats. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
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Abstract In this study, the molecular weights of the polymer from vinyl benzoate has been reported for different dose rates and different temperatures. The mol.wt. remains around 4000. With increasing dose, the molecular weight increases to about 14,000. The degrees of polymerization and the kinetic chain lengths calculated from the experimentally determined G R values have been compared which show that the kinetic chain length is larger than the D ? Pn. From a plot of the (D ? Pn)?1 vs. R p , an intercept is obtained which is equal to 3.25 × 10?2 which is higher than obtained in conventional polymerization. By examining the effect of temperature on mol.wt., the dependence of R p on dose rate and the absence of induction period it has been concluded that chain transfer occurs to impurities that are generated during radiolysis. 相似文献
60.
Vijay Balasubramanian 《Foundations of Physics》2013,43(1):101-114
String theory has transformed our understanding of geometry, topology and space-time. Thus, for this special issue of Foundations of Physics commemorating “Forty Years of String Theory”, it seems appropriate to step back and ask what we do not understand. As I will discuss, time remains the least understood concept in physical theory. While we have made significant progress in understanding space, our understanding of time has not progressed much beyond the level of a century ago when Einstein introduced the idea of space-time as a combined entity. Thus, I will raise a series of open questions about time, and will review some of the progress that has been made as a roadmap for the future. 相似文献