Quasi-modes

Ulness D J, Stimson M J, Kirkwood J C and Albrecht A C 1997 Interferometric downconversion of high frequency molecular vibrations with time-frequency-resolved coherent Raman scattering using quasi-cw noisy laser light C-H stretching modes of chloroform and benzene J. Rhys. Chem. A 101 4587-91... 

B2.5.351 after multiphoton excitation via the CF stretching vibration at 1070 cm. More than 17 photons are needed to break the C-I bond, a typical value in IR laser chemistry. Contributions from direct absorption (i) are insignificant, so that the process almost exclusively follows the quasi-resonant mechanism (iii), which can be treated by generalized first-order kinetics. As an example, figure B2.5.15 illustrates the fonnation of I atoms (upper trace) during excitation with the pulse sequence of a mode-coupled CO2 laser (lower trace). In addition to the mtensity, /, the fluence, F, of radiation is a very important parameter in IR laser chemistry (and more generally in nuiltiphoton excitation) ... 

The next problem to consider is how chaotic attractors evolve from tire steady state or oscillatory behaviour of chemical systems. There are, effectively, an infinite number of routes to chaos [25]. However, only some of tliese have been examined carefully. In tire simplest models tliey depend on a single control or bifurcation parameter. In more complicated models or in experimental systems, variations along a suitable curve in the control parameter space allow at least a partial observation of tliese well known routes. For chemical systems we describe period doubling, mixed-mode oscillations, intennittency, and tire quasi-periodic route to chaos. 

In addition to tire period-doubling route to chaos tliere are otlier routes tliat are chemically important mixed-mode oscillations (MMOs), intennittency and quasi-periodicity. Their signature is easily recognized in chemical experiments, so tliat tliey were seen early in the history of chemical chaos. 

I he eigenvector-following (or Hessian mode) method implemented in HyperChem is based on an effieien t quasi-Newton like algorithm for loca tin g tran sitiori states, wh ieh can locate tran si-tion states for alternative rearran gern eri t/dissoeiation reactions, even when startin g from th e wron g regio n on th e poten tial en ergy surface. 

FI and FD are mild or soft methods of ionization that produce abundant molecular or quasi-molecular positive or negative ions from a very wide range of substances. In the FD mode, it is particularly useful for high-molecular-mass and/or thermally labile substances such as polymers, peptides, and carbohydrates. 

Mostly, positive-ion FAB yields protonated quasi-molecular ions [M -i- H]+, and the negative-ion mode yields [M - H]. In the presence of metal salts (e.g., KCl) that are sometimes added to improve efficiency in the LC column, ions of the type [M -i- X]+are common, where X is the metal. Another type of ion that is observed is the so-called cluster, a complex of several molecules with one proton, [M -i- H]+ with n = 1, 2, 3,. .., etc. Few fragment ions are produced. 

The Q in Q/TOF stands for quadrupole (see Chapter 25, Quadrupole Ion Optics ). A Q/TOF instrument — normally used with an electrospray ion inlet — measures mass spectra directly to obtain molecular or quasi-molecular mass information, or it can be switched rapidly to MS/MS mode to examine structural features of ions. The analyzer layout is presented in Figure 20.2. 

A2) In spite of the high individual frequencies, bond length and bond angle vibrations participate in quasi-classical low frequency collective normal modes. Bond angle bending is necessary for the flexibility of five-membered rings, which plays a key role in the polymorphism of nucleic acids. 

Figure 3 Anharmonicity factor versus quasi-harmomc mode number from a 200 ps vacuum simulation of BPTI. It can be seen that beyond about the 200th mode the anharmonicity factors are about 1.0, indicating harmomcity. Those below mode number 200 show progressively greater anharmonicity factors, indicating that they span a space within which energy barriers are crossed. A similar picture was found for a I ns simulation of human lysozyme m water [61]. (Adapted from Ref. II.)...

As examples of such quasi-equivalent arrangement of subunits, we will examine the T = 3 and T = 4 packing modes, both of which are found in known virus particles. In the T = 3 structure, which has 180 subunits (3 x 60),... 

A15 Watt, ZVS Quasi-resonant, Current-mode Controlled Flyback Converter... 

This eompensation is intended for voltage-mode eontrolled forward eonverters whieh exliibit a seeond order output filter pole eharaeteristie. This would also inelude a quasi-resonant forward-mode eonverter that uses variable frequency, voltage-mode control. The T-C filter has a severe 180 degree phase lag and a -40dB/decade gain rolloff. To get any sort of wide bandwidth from the supply at all, this type of compensation must be used. 

Oscillations of black holes. Non-radial oscillations of black holes can be excited when a mass is captured by the black hole. The so called quasinormal modes have eigenfrequencies and damping times which are characteristic of black holes, and very different of eigenfrequencies and damping times of quasi normal modes of stars having the same mass. Also the eigenmodes being different for a star and a black hole, the associated gw will also exhibit characteristic features. 

We started by analyzing the dominant modes of oscillation showed by oxygen content, streamflow, and ENSO using the Maximum Entropy Method (MEM) (Table 1). It is remarkable that both the streamflow to the reservoir and the AF showed common oscillations with ENSO at fi-equencies between 0.016 and 0.035 cycles month These frequencies are very close to the two main periods of ENSO (the quasi-biennial and quasi-quadrennial periods) [56]. Although we do not have a mechanistic explanation for this teleconnection (in fact the extratropical influence of ENSO is a hot topic in climate research, Merkel and Latif [57]), it is certainly difficult to propose an alternative explanation for the oscillations in AF and stream-flow observed at these frequencies. 

HOMO Amplitudes, Quasi-Intermediate Structures, and Mode Selectivities... 

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