Applied Transitional Studies

Smooth COSMO solvation model. We have recently extended our smooth COSMO solvation model with analytical gradients [71] to work with semiempirical QM and QM/MM methods within the CHARMM and MNDO programs [72, 73], The method is a considerably more stable implementation of the conventional COSMO method for geometry optimizations, transition state searches and potential energy surfaces [72], The method was applied to study dissociative phosphoryl transfer reactions [40], and native and thio-substituted transphosphorylation reactions [73] and compared with density-functional and hybrid QM/MM calculation results. The smooth COSMO method can be formulated as a linear-scaling Green s function approach [72] and was applied to ascertain the contribution of phosphate-phosphate repulsions in linear and bent-form DNA models based on the crystallographic structure of a full turn of DNA in a nucleosome core particle [74],... 

Resonance Raman spectroscopy has been applied to studies of polyenes for the following reasons. The Raman spectrum of a sample can be obtained even at a dilute concentration by the enhancement of scattering intensity, when the excitation laser wavelength is within an electronic absorption band of the sample. Raman spectra can give information about the location of dipole forbidden transitions, vibronic activity and structures of electronically excited states. A brief summary of vibronic theory of resonance Raman scattering is described here. 

An ab initio RHF/3-21 G study has shown that the decomposition of 3-hydroxy-3-methylbutan-2-one is a concerted process with hydrogen transfer and bond breaking via a five-membered cyclic transition state.AMI and PM3 methods using UHF calculations were applied to study the thermolysis of 2-cyanofuroxan. The reaction proceeds via a two-step pathway in which the second step is rate determining. The effect of solvent in the thermal decomposition reaction of fran -3,3-dimethyl-5,6-tetramethylene-l,2,4-trioxacyclohexane was studied. ... 

A better understanding of the molecular and structural changes that occur in starch and potatoes would enable effective control of their functional behavior during processing and consumption, as well as in the development of modified starch products. Modem techniques have been developed and applied to study starch stmcture, phase transitions, and interactions of starch... 

It has been found that the short-range interaction model can be applied to study the vibrational relaxation of molecules in condensed phases. This model is applied to treat vibrational relaxation and pure dephasing in condensed phases. For this purpose, the secular approximation is employed to Eq. (129). This assumption allows one to focus on several important system-heat bath induced processes such as the vibrational population transition processes, the vibrational coherence transfer processes, and the vibronic processes. 

The spectroscopic techniques described in this section include IR, Raman, and UV-visible spectroscopy, nuclear magnetic resonance (NMR) and electron spin resonance (ESR) spectroscopy, and extended X-ray absorption fine structure (EXAFS) spectroscopy. Techniques based on particle scattering, transitions in the nucleus, and radioisotope techniques that produce radiation that is a measure of the chemical environment are described in Sections IV.B and C. Some of these techniques, such as IR and UV-visible spectroscopy, have been applied to studies of catalysts for more than 30 years, whereas others, such as EXAFS, are relatively new to catalytic studies. 

In addition to freeze-fracture electron microscopy, a combination of DSC, NMR, and the monolayer technique has been applied to study the various aspects of the interaction of the class IV calcium antagonist flunarizine [150] with a range of phospholipids. DSC shows only limited interaction of flunarizine with PC. The drug destabilizes the Lp-phase without stabilizing the La-phase. In contrast, flunarizine influences not only the onset of phase transition but also the phase transition temperature and the completion of the transition of phosphatidylserine (PS), indicating... 

The origin of the electric dipole intensity for the AMj = 1 transitions studied merits further consideration. If the static magnetic field is 5 kG, the motional electric field has a magnitude of approximately 3 V cm-1 and is perpendicular to the applied magnetic field. This electric field mixes a state [./, Mj) with the states. J 1, Mj 1) and in order to obtain non-zero electric dipole transition moments for the transitions. /. Mj) o IJ, Mj 1), the oscillating electric field must be applied parallel to the static magnetic field. 

Both spin components of the lowest rotational transition were observed, and an improved value of the rotational constant obtained. The technique was also applied to study the rotational spectrum of the CN radical, produced when methyl cyanide was added to the helium beam. In this case the rotational transition exhibited splitting due to the spin-rotation and nuclear hyperfine interactions. The results were essentially the same as those described in chapter 10, obtained from a conventional microwave absorption experiment. 

Cation exchanged zeolites are successfully applied as catalysts or selective sorbents in separation technologies. " For both catalytic and sorption processes a concerted action of polarizing cations and basic oxygen atoms is important. In addition, transition metal cation embedded in zeolites exhibit peculiar redox properties because of the lower coordination in zeolite cavities compared to other supports." " Therefore, it is important to establish the strength and properties of active centers and their positions in the zeolite structure. Various experimental methods and simulation techniques have been applied to study the positions of cations in the zeolite framework and the interaction of the cations with guest molecules.Here, some of the most recent theoretical studies of cation exchanged zeolites are summarized. 

Studying the temperature evolution of UV Raman spectra was demonstrated to be an effective approach to determine the ferroelectric phase transition temperature in ferroelectric ultrathin films and superlattices, which is a critical but challenging step for understanding ferroelectricity in nanoscale systems. The T. determination from Raman data is based on the above mentioned fact that perovskite-type crystals have no first order Raman active modes in paraelectric phase. Therefore, Raman intensities of the ferroelectric superlattice or thin film phonons decrease as the temperature approaches Tc from below and disappear upon ti ansition into paraelectric phase. Above Tc, the spectra contain only the second-order features, as expected from the symmetry selection rules. This method was applied to study phase transitions in BaTiOs/SrTiOs superlattices. Figure 21.3 shows the temperature evolution of Raman spectra for two BaTiOs/SrTiOa superlattices. From the shapes and positions of the BaTiOs lines it follows that the BaTiOs layers remain in ferroelectric tetragonal... 

One of the remarkable demonstrations of the capabilities of ultraviolet Raman spectroscopy to probe extremely thin ferroelectric oxide layers reported so far has been its application for studies of ultrathin BaTi03 films [48]. In order to investigate the size effect on the ferroelectric phase transitions, variable temperature UV Raman spectroscopy was applied to studies of a series of BaTi03 films with layer thicknesses varied from 1.6 to 10 nm (4—25 unit cells). 

Temperature-programmed reduction and desorption (TPR, TPD) have been applied to study the stability of Pt-Co bimetallic particles entrapped in NaY zeolite cages upon O2 oxidation and reaction with surface protons generated during the reduction of transition metal cations. Oxidation of Pt/NaY catalyst with O2 at 573 K causes shift of TPR peak to lower temperature due to formation of partially oxidized Pt particles. Similar treatment for Pt-Co/NaY bimetallic catalysts results in complete isolation of Pt and Co in Pt-Co particles, leaving Pt and Co in supercages and sodalite cages, respectively. 

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