Flash cooling

ThermalLkjucfaction Process. In the thermal Hquefaction process (see Eig. 1), a starch slurry containing no enzyme or added calcium is heated for several minutes. The slurry is slightly acidic and sufficient acid Hquefaction is achieved to reduce viscosity. The hydrolyzate (at essentially zero DE) is flash-cooled to 95—100°C, a-amylase is added, and the pH is adjusted. The reaction then goes to completion. 

Except for in house preliminary studies, the intensities of X-rays diffracted by hydrogenase crystals are now usually obtained with synchrotron radiation (Fig. 6.2) and detected by image plate or charge coupled device (CCD) detectors. To limit the damage induced by the powerful photon flux of synchrotrons, the crystals are usually mounted in a small loop, flash cooled in either liquid propane or nitrogen and stored... 

Kriminski, S., Kazmierczak, M. and Thorne, R. E. (2003). Heat transfer from protein crystals impUcations for flash-cooling and X-ray beam heating. Acta Crystallogr. D 59,697-708. 

Kwong, P. D. and Liu, Y. (1999). Use of cryoprotectants in combination with immiscible oils for flash cooling macromolecular crystals. J. Appl. Cryst. 32,102-105. 

Flash cooling of samples, the use of field-emission guns to generate more coherent electron beams, and improved software has radically extended the power of electron microscopy, so that it is now almost routine to provide structural information for viruses to better than 10 A, and sometimes 7 A resolution (Conway et al., 1997). The major strength... 

Only one polymorphic form of the substance has been observed. A study was undertaken to attempt to produce different forms by flash cooling and slow evaporation from various solvents (V, V-dimethylformamide, acetonitrile,ethanol, dichloromethane,2-propanol, water (neutral pH, pH 5, and pH 9), ethanol/watermixtures (1 1, neutral and at pH 5 and 9). No additional forms were observed upon examination of the resulting crystals by x-ray powder diffraction. 

Cooling Section For the cooling section, a quench cooler with adequate heat removal capacity is effective. Another technique is to inject the hot medium through an expansion valve into a vacuum chamber, which is known as flash cooling. Both of these take a very short time therefore, the sterilization during the cooling period can be assumed to be negligible. 

The X value calculated is valid only over a range in which the pressure loss in the pipe does not exceed 15% of inlet value. This is a considerable handicap if the case involves a large pressure loss. Here the objective is to divide the pipe run into several segments. Each segment will have a different pressure inlet and probably a different temperature due to the gas-flashing cooling effect. This makes the solution longer, but consider the fact that this is a two-phase flow, not subject to easy or short solution in any case. 

The product stream from the reactor (Bl) was flash cooled using a flash drum (B3) to separate vapors from the liquid phase. The flash models available in ASPEN-Plus determine the thermal and phase conditions of a mixture with one or more inlet streams. A separator (B6) was employed to separate C02 and steam. The resulting recycle streams no. 10 and no. 9 were sent to B13 and B7, respectively. The liquid stream (no. 14) from the flash drum was sent to a Pneumapress filter (B10), where it was separated into filter cake (stream no. 13) and filtrate (streamno. 8). This separation was done to facilitate heat extraction from the product stream for heat exchanger Bll. 

The experiments with N2 cryostats are usually run at temperatmes between 100 and 170K the desire for the lowest possible temperatme is balanced by the necessity to avoid icing. Such temperatmes are almost always sufficient to prevent both the chemical (or photochemical) decomposition of the sample and the solvent loss. The choice between rapid (flash) and slow cooling depends on the natme of the sample. When the thermal expansion coefficient is likely to be high, as is usually the case with conformationally flexible molecules, slow cooling is preferable if the crystal stability permits it. On the other hand, flash-cooling is the only technique possible for protein crystals, because slow cooling will allow the crystallization water to form ice crystals,... 

After the strands leave the die, they are run through a cold water bath to solidify the polystyrene. The strands are then run up through a helical rotary cutter that cleaves the strands to a length of approximately 6-9 mm. The resultant beads or pellets are passed through an annealing unit and flash cooled to set nucleation sites and cell size. 

The X-ray beam from the source is monochromated, focused, and collimated to deliver a parallel beam of defined size and wavelength to the crystal. Because of the intrinsically superior optical qualities of synchrotron beams, the radiation delivered to the crystal is also superior to that from conventional sources. The crystal is mounted on a goniostat, which allows the crystal to be rotated. The crystal is usually flash-cooled to a temperature of 100 K by a cold stream of nitrogen gas to reduce radiation damage. X-rays are ionizing radiation and the free radicals produced as they pass through the protein destroy the crystal. Without flash cooling, protein crystals last only seconds on a synchrotron beamline. 

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