Avoiding Crystallization

The reading of data is performed optically, based on the difference in reflectivity between the well-reflecting crystalline and the opaque and lower reflecting amorphous phase. A low power laser beam is used to avoid crystallization (Eig. 15, Read). 

Rapid filtration is essential to avoid crystallization in the funnel and to decrease the time the filter paper is in contact with the concentrated acid. 

SBS and SIS can be subsequently hydrogenated to form SEBS and SEPS, respectively. SEBS is obtained from SBS with a higher vinyl content (typically around 30%) in order to avoid crystallization of the mid-block. The properties of all four of these common styrenic block copolymers are displayed in Table 2. 

The device was realized by deep reactive ion etching (DRIE) using the SU-8 technique, producing vertical side walls [72-74]. This fabrication route was chosen to avoid crystallization, which is known to occur at sharp channel edges. Using DRIE smooth, curved corners can be realized, unlike by conventional silicon wet etching. 

Although 550 suffices to dissolve the w-nitroacetophenone it is desirable to bring the alcoholic solution to a boil to avoid crystallization during filtration. 

Sutton [1.15] studied the question of how quickly solutions with certain CPAs (GL, dimethylsulfoxide (DMSO) and others] have to be cooled in order to avoid crystallization. At 100 °C/min concentration of 42.1 % DMSO and 48.5 % for GL are necessary to achieve the glass phase. With a 32.5 % solution of (2R.3R)-(-)butan-2,3-dio, the same effect can be accomplished at = 50 °C/min. In Fig. 1.18 Sutton (Fig. 11 from [1.114]) showed, that polyethylene glycol with a molecular weight of 400 (PEG 400) reduced the critical cooling rate down to approx. 25 °C/min. The addition of PEG 8000 [1.115] improved the protection of lactate dehydrogenase (LDH) by maltodextrins, if maltodextrins with low dextrose equivalents are used. 

Quick cooling is often advantageous, e. g. for recombinant DNA-proteins, in order to avoid crystallization of salts and to obtain the best possible, homogeneous cake. 

VF3), chlorotrifluoroethylene (CTFE), and hexafluoropropene (HFP), in order to avoid crystallization as described below. 

If self-forming cesium salt gradients are used, take care to be within the solubility of the salt at the given temperature to avoid crystallizations during centrifugation, since salt crystals may destroy the rotor during run (solubilities of cesium chloride and sulfate are given in Table 5.4). 

Fluids must be increased to 3 L/day to avoid crystallization in kidneys... 

The apparatus shown in Fig. 3, consisting of a 2-1. three-neckcd round-bottomed flask fitted with an efficient stirrer (Note 1), a gas inlet tube, a thermometer, and a reflux condenser is assembled in a ventilated hood. Bubbler tubes containing benzene are attached to the gas inlet tube and the top of the reflux condenser, and 500 ml. of dry benzene and 196 g. (2 moles) of maleic anhydride (Note 2) are placed in the flask. Stirring is begun, the flask is heated with a pan of hot water, and butadiene is introduced (from a commercial cylinder controlled by a needle valve) at a rapid rate (0.6-0.8 1. per minute). When the temperature of the solution has reached 50° (within 3-5 minutes) the pan of water is removed. The exothermic reaction causes the temperature to reach 70-75° in 15-25 minutes. The rapid stream of butadiene is nearly completely absorbed for 30-40 minutes, after which the rate is decreased until the reaction is completed (equal rates of bubbling in the two bubbler tubes) after 2-2.5 hours. The solution is poured into a 1-1. beaker at once to avoid crystallization of the product in the reaction flask. The beaker is covered and the mixture is kept at 0 5° overnight. 

The solution of [1.1.1 ]propellane should be warmed to -20-15°C to avoid crystallization of the 2,3-butanedione (which may not redissolve during the course of the irradiation). 

For certain formulations one of the components may crystallize upon cooling (e.g., certain bismaleimides, cyanates, etc.). In these cases, a thermal quench in liquid nitrogen may avoid crystallization, enabling the determination of Tg0 in a subsequent scan. 

The evaporator is normally needed to remove the majority of the water that is present in the AN solution. It must produce a solution with the required concentration at a temperature that avoids crystallization. The acceptable water content depends on the process that is used to make the finished product. It is... 

The funnel must be heated to avoid crystallization during filtration. 

According to the kinetic treatment of Lavayre et al (10) on two insoluble enantiomeric isomers, the relative initial velocities, V/VR were plotted against various ratios in the (S)-enantiomer. All of the initial velocity measurements were made at 50°C instead of 40°C to avoid crystallization of the acetate of pure (R)-HMPC, and at pH 6.0 to prevent spontaneous hydrolysis of the substrate at 50°C. The result gives a concave type of curve as illustrated in Figure 3. This implies that K mS < K mR and that the (S)-enantiomer is a strong competitive inhibitor. Thus, it is concluded that a very high optical purity of (R)-HMPC liberated with Arthrobacter lipase is entirely the result of the great catalytic constant of the (R)-HMPC ester. 

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