Merry-go-round

Disadvantages of these continuous countercurrent systems are associated primarily with the complexity of the equipment required and with the attrition resulting from the transpoiT of the ion exchanger. An effective alternative for intermediate scale processes is the use of merry-go-round systems and SMB units employing only packed-beds with no movement of the ion-exchanger. 

Small scale test runs prior to preparative irradiation experiments may be carried out in tubes which are either taped to the lamp housings (immersion wells) depicted in Figures 13-1 and 13-2 or placed in turntable reactors ( merry-go-rounds ). These arrangements permit the simultaneous irradiation of several samples, but only a fraction of the available light emission is used. In Figure 13-4 a simple reactor is shown which focusses almost all the emitted light into one sample which can be scaled up also to semi-preparative volumes. In this way the necessary irradiation time can be reduced sharply. 

To understand this simplification, imagine a man sitting on a merry-go-round with a large placard on which several sentences are written. As long as the merry-go-round is rotating rapidly, a stationary observer may not be able to read the words on the placard as it whirls round. However, if the observer were to jump onto the merry-go-round, then the apparent circular motion of the man with the placard would disappear to the observer since the two would now have the same angular velocity, and the words on the placard would be readable. 

A simpler but less versatile apparatus that is becoming increasingly popular is the merry-go-round diagrammed in Figure 2.22. 

Ultraviolet absorption spectra were obtained from a Cary 118C Spectrophotometer. Luminescence measurements were obtained from a Perkin-Elmer Model MPF-3 Fluorescence Spectrophotometer equipped with Corrected Spectra, Phosphorescence and Front Surface Accessories. A Tektronix Model 510N Storage Oscilloscope was used for luminescence lifetime measurements. Fiber irradiation photolyses were carried out in a Rayonet Type RS Model RPR-208 Preparative Photochemical Reactor equipped with a MGR-100 Merry-go-Round assembly. 

Analogous relationships are derived for SMB systems where each zone comprises a number of fixed beds operated in a merry-go-round sequence, as shown in Fig. 16-48. External flow velocities are calculated from Eqs. (16-209a) to (16-209d), replacing us with... 

Merry-go-round processes involving multiple C-H functionalizations and carbometallations have been described. In the example depicted, a rhodium hydride continues to be formed until steric factors prevail. The 2-norbornene moiety acts as a directing group (Equation (148)).125... 

Merry-go-round systems, 14 408 Mes, buffer for ion-exchange chromatography, 3 830t Mescaline, 2 84, 85 Mesh-belt furnace, 12 289 Mesh wick, 13 232... 

If the patient has done well on a previous antipsychotic for an extended period of time, and is willing to continue taking it, then it usually makes the most sense to restart or continue the same medication. This keeps the patient from unnecessarily starting on a merry-go-round of constant medication changes. An increase in dose or the addition of new psychosocial therapies may, however, be required. 

Although this simile is now known to miss the mark, its historical importance cannot be denied. The centrifugal force victoriously opposes the electrical attraction and conversely, for each electron. A wonderful merry-go-round (dynamical equilibrium) is the result. In this idyllic version, the revolving motion of the electrons would go on forever, if the atom were not subjected to external infiuences, namely, collisions with other atoms, electrons and photons. Deformed to varying degrees by these impacts, atoms always tend to restore themselves in the most harmonious way, evacuating the excess energy acquired from the collision. 

Figure 31-2 Merry-go-round diagram that summarizes the steps in the hydrogenation of ethene by Rh[(C6H5)3P]3CI. The key features are the flow of reactants into and the products out of the cycle, the loss and regaining of the ligand, and the regeneration of the catalyst. The ligand triphenylphosphine is represented by L.

Fluorine coordination degenerate fluorine migration in a Merry-Go-Round type mechanism... 

Despite the many wake-up calls over the past years, it seems we prefer to keep sleeping. It would be naive to think we humans could emerge from this merry-go-round unscathed, and that there will be no consequences for our DNA and the development of our children, given the daily use of an enormous amount of synthetic substances which have been shown to damage our living environment. 

Figure 1.2 Multilamp apparatus fitted with low-pressure mercury lamps and a rotating merry-go-round that ensures the uniform illumination of several test tubes. Alternatively, test tubes or other vessel(s) containing the solution to be irradiated can be accommodated.

Benzoyl azide (1 g, 6.8 mmol) and 6-methoxy-5,6-dihydropyran (11.4 g, 100 mmol) dissolved in acetonitrile (100 mL) are placed in 10 quartz test tubes and irradiated using light of wavelength 254 nm (mercury low pressure lamp) for 9h using a merry-go-round photoreactor. After removing the solvent and the olefin excess by vacuum evaporation, the reaction mixture... 

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