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51.
52.
Spinel systems with the composition of Cu1−xZnxCr2O4 [x = 0 CCr, x = 0.25 CZCr-1, x = 0.5 CZCr-2, x = 0.75 CZCr-3 and x = 1 ZCr] were prepared by homogeneous co-precipitation
method and were characterized by X-ray diffraction (XRD) and FT-IR spectroscopy. Elemental analysis was done by EDX, and surface
area measurements by the BET method. The redox behavior of these catalysts in cyclohexane oxidation at 243 K using TBHP as
oxidant was examined. Cyclohexanone was the major product over all catalysts with some cyclohexanol. 69.2% selectivity to
cyclohexanol and cyclohexanone at 23% conversion of cyclohexane was realized over zinc chromite spinels in 10 h. 相似文献
53.
54.
55.
Apart from serving as a parameter in describing the evolution of a system, time appears also as an observable property of
a system in experiments where one measures ‘the time of occurrence’ of an event associated with the system. However, while
the observables normally encountered in quantum theory (and characterized by self-adjoint operators or projection-valued measures)
correspond to instantaneous measurements, a time of occurrence measurement involves continuous observations being performed
on the system to monitor when the event occurs. It is argued that a time of occurrence observable should be represented by
a positive-operator-valued measure on the interval over which the experiment is carried out. It is shown that while the requirement
of time-translation invariance and the spectral condition rule out the possibility of a self-adjoint time operator (Pauli’s
theorem), they do allow for time of occurrence observables to be represented by suitable positive-operator-valued measures.
It is also shown that the uncertainty in the time of occurrence of an event satisfies the time-energy uncertainty relation
as a consequence of the time-translation invariance, only if the time of occurrence experiment is performed on the entire
time axis. 相似文献
56.
Prem K. Mehrotra Jayaraman Chandrasekhar Periakaruppan T. Manoharan Sankaran Subramanian 《Chemical physics letters》1979,68(1):219-221
The nonempirical NDDO MO method in its unrestricted form has been used to evaluate isotropic hyperfine coupling constants and nuclear spin-spin coupling constants. Satisfactory agreement with INDO and experimental results is obtained. 相似文献
57.
58.
Jayaraman Chandrasekhar Prem K. Mehrotra Sankaran Subramanian Periyakaruppan T. Manoharan 《Theoretical chemistry accounts》1979,52(4):303-310
Three valence-only schemes based on the Roby version of NDDO MO theory, which differ only in the core-valence treatment and the choice of the basis set, have been applied to the study of molecules containing first-row atoms. Orbital energies, charge distribution, dipole moments, field gradients, and a few other one-electron molecular properties are calculated to satisfactory accuracy. The schemes appear unreliable in the prediction of barriers to internal rotation in molecules, presumably due to errors in the core contribution to the total energy. An alternative treatment is suggested. 相似文献
59.
60.
Morita K Sankaran NB Huang W Seino T Sato Y Nishizawa S Teramae N 《Chemical communications (Cambridge, England)》2006,(22):2376-2378
An abasic site-containing DNA combined with lumiflavin allows amperometric determination of single nucleotide polymorphism through hydrogen bond-mediated nucleobase recognition in water by using abasic sites as a molecular recognition field. 相似文献