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61.
The kinetic results of the oxidation of lactic acid by CrVI in the absence and presence of ethylenediaminetetraacetic acid (EDTA), 2,2-bipyridyl (bpy), MnII and CeIV are presented. EDTA, bpy and MnII catalyse the reaction, whereas CeIV acts as an inhibitor. Irrespective of the conditions, the order with respect to [lactic acid] was found to lie between one and two, and one in [CrVI]. In the EDTA, bpy and MnII-catalysed paths, CrVI–EDTA, CrVI–bpy and lactic acid–MnII complexes have respectively been suggested as the active oxidant and reductant. The kinetic and cerium(IV) effect studies are consistent with a one-step two-electron transfer mechanism in the absence/presence of EDTA and bpy where a chromate–ester mechanism experiences a redox decomposition (C—H cleavage) in the rate-determining step. On the other hand, the catalytic effect of MnII is described as a one-step three-electron redox decomposition (C—C cleavage) mechanism. Mechanisms in accordance with the experimental data have been proposed for the reactions. Activation parameters have also been evaluated and discussed. 相似文献
62.
63.
Maurya MR Agarwal S Abid M Azam A Bader C Ebel M Rehder D 《Dalton transactions (Cambridge, England : 2003)》2006,(7):937-947
Binuclear, mu-bis(oxo)bis{oxovanadium(V)} complexes [(VOL)2(mu-O)2](2 and 7)(where HL are the hydrazones Hacpy-nah I or Hacpy-fah II; acpy = 2-acetylpyridine, nah = nicotinic acid hydrazide and fah = 2-furoic acid hydrazide) were prepared by the reaction of [VO(acac)2] and the ligands in methanol followed by aerial oxidation. The paramagnetic intermediate complexes [VO(acac)(acpy-nah)](1) and [VO(acac)(acpy-fah)](6) have also been isolated. Treatment of [VO(acac)(acpy-nah)] and [VO(acac)(acpy-fah)] with aqueous H2O2 yields the oxoperoxovanadium(V) complexes [VO(O2)(acpy-nah)](3) and [VO(O2)(acpy-fah)](8). In the presence of catechol (H2cat) or benzohydroxamic acid (H2bha), 1 and 6 give the mixed chelate complexes [VO(cat)L](HL =I: 4, HL =II: 9) or [VO(bha)L](HL =I: 5, HL =II: 10). Complexes 4, 5, 9 and 10 slowly convert to the corresponding oxo-mu-oxo species 2 and 7 in DMF solution. Ascorbic acid enhances this conversion under aerobic conditions, possibly through reduction of these complexes with concomitant removal of coordinated catecholate or benzohydroxamate. Acidification of 7 with HCl dissolved in methanol afforded a hydroxo(oxo) complex. The crystal and molecular structure of 2.1.5H2O has been determined, and the structure of 7 re-determined, by single crystal X-ray diffraction. Both of these binuclear complexes contain the uncommon asymmetrical {VO(mu-O)}2 diamond core. The in vitro tests of the antiamoebic activity of ligands I and II and their binuclear complexes 2 and 7 against the protozoan parasite Entamoeba histolytica show that the ligands have no amoebicidal activity while their vanadium complexes 2 and 7 display more effective amoebicidal activity than the most commonly used drug metronidazole (IC50 values are 1.68 and 0.45 microM, respectively vs 1.81 microM for metronidazole). Complexes 2 and 7 catalyse the oxidation of styrene and ethyl benzene effectively. Oxidation of styrene, using H2O2 as an oxidant, gives styrene epoxide, 2-phenylacetaldehyde, benzaldehyde, benzoic acid and 1-phenyl-ethane-1,2-diol, while ethyl benzene yields benzyl alcohol, benzaldehyde and 1-phenyl-ethane-1,2-diol. 相似文献
64.
In the optical model (OM) approach for fusion, absorption of flux occuring beyond the barrier position is presented in detail
at low energies. It has been shown that the OM transmission can be well approximated as a sum of the WKB transmission and
a long range absorption (LRA) contribution. Owing to absence of LRA, the fusion predictions of coupled channel codes based
on transmission approach like the CCFUS code, do not agree with the predictions of complete coupled reaction channel (CRC)
calculations based on OM approach using the code FRESCO. The CCFUS code with a modified transmission which includes LRA contribution
is shown to be consistent with the CRC results using FRESCO. The static deformation of the colliding nuclei strongly influences
the fusion imaginary potential and therefore the deep sub-barrier fusion cross sections. 相似文献
65.
M J Singh S K Goel R Shanker D O Kataria N Madhavan P Sugathan J J Das D K Avasthi A K Sinha 《Pramana》1997,49(5):521-533
An on-line facility to measure coincidences between the recoil ions and the scattered projectiles (SCORPION) has been designed,
fabricated and commissioned at Nuclear Science Centre (NSC), New Delhi. The facility consists of a four jaw slit assembly,
a time of flight (TOF) spectrometer, a parallel plate electrostatic charge analyser and a one dimensional position sensitive
parallel plate avalanche counter (PPAC). Details of the design and working principles of various components and the test results
obtained for the Si
q+-Ar collision system are presented to highlight the performance of the system. A multiple loss of up to four electrons has
been observed for 60 MeV Si4+ ions colliding with argon atoms in a single collision condition. Spectra of recoil ions detected in coincidence with a particular
charge state of the scattered projectile show a bell shaped distribution as a function of the recoil charge state (r) for the electron loss events. However, the yield of recoil ions drops asr increases for the direct ionization channel. Also for electron loss, the peak of the recoil ion distribution is seen to shift
to a higher recoil charge state as the number of lost electrons from the projectile increases. 相似文献
66.
A general leptodermous expansion for the density of single-particle levels in thin-skinned potential wells is derived and is used to study the finite size corrections to the macroscopic level density parameters of nuclei. With droplet model values for the potential parameters, the calculated level density parameters for nuclei along the β-stability line show systematic deviations from the experimental estimates. Possible reasons for these deviations are also discussed. 相似文献
67.
Singh Varun Kumar Singh Shishir Kumar Gupta Himani Shalu Balo Liton Tripathi Alok Kumar Verma Yogendra Lal Singh Rajendra Kumar 《Journal of Solid State Electrochemistry》2018,22(6):1909-1919
Journal of Solid State Electrochemistry - We report herein the development of a sodium polymer battery consisting of solid polymer electrolyte (SPE) system (polymer + ionic liquid and salt) as an... 相似文献
68.
It is well known that the expression for fixed-J level densityI ?(E, J)=?I(E) $\frac{\partial }{{\partial M}}$ I(M|E)| M=J+1/2 reduces to familiar Bethe’s formula provided the conditionalM-distributionI(M|E) is approximated by a Gaussian form, so called spin cut-off approximation (M is thez-component of total angular momentumJ andE is the excitation energy). After a detailed analysis, we find that the Bethe’s formula which overestimatesI?(E, J) at highJ values, in particular near the yrast line, can be significantly improved by including a few higher-order moment terms in a suitable expansion forI(M|E) with the lowest-order term to be a Gaussian, e.g., Edgeworth expansions. We also find that, except at very low excitation energies, reasonable values (close to exact) of the moments ofI(M|E) can easily be obtained when multiple Laplace-back transform of the partition function for grand canonical ensemble is evaluated within the saddle point approximation. Furthermore, we study the effects of shell structure as well as residual interaction on the excitation energy dependence of these moments. 相似文献
69.
The current-voltage characteristics for Bi-Sr-Ca-Cu-O bulk specimen incorporating manually carved constriction show both zero
voltage pair current and quasiparticle tunnelling current. The pair current amplitude modulates with applied d.c. magnetic
fields. Microwave-induced Shapiro steps are clearly seen in the I-V curves. The Josephson effects arise due to the presence
of arrays of grain boundary Josephson junctions. 相似文献
70.
A K Gupta N S Natarajan V S Tomar N D Kataria V K Batra A V Narlikar K Chandra 《Pramana》1987,28(5):517-527
A C Josephson effect is now used by several countries as the reference standard for the unit of d.c. voltage. This paper describes the work done at the National Physical Laboratory (NPL), New Delhi in the realization of the unit of volt based on the a.c Josephson effect. A voltage standard at 1 mV level using a Nb-Nb point contact junction has been established and the as-maintained volt based on a bank of standard cells has been intercompared against it using a 1:1000 voltage divider. The experimental set-up used in this comparison and the results of recent measurements are described. The overall uncertainty in assigning the value of emf to a standard cell is about 1 ppm. The as-maintained volt has been found to agree with the Josephson voltage within overall uncertainty. 相似文献