Retrograde

The diagram (Fig. 5.21) shows that as the pressure is reduced below the dew point, the volume of liquid in the two phase mixture initially increases. This contradicts the common observation of the fraction of liquids in a volatile mixture reducing as the pressure is dropped (vaporisation), and explains why the fluids are sometimes referred to as retrograde gas condensates. 

Condensable Hquids also are recovered from high pressure gas reservoirs by retrograde condensation. In this process, the high pressure fluid from the reservoir produces a Hquid phase on isothermal expansion. As the pressure decreases isotherm ally the quantity of the Hquid phase increases to a maximum and then decreases to disappearance. In the production of natural gas Hquids from these high pressure wells, the well fluids are expanded to produce the optimum amount of Hquid. The Hquid phase then is separated from the gas for further processing. The gas phase is used as a raw material for one of the other recovery processes, as fuel, or is recompressed and returned to the formation. 

Hydroxyethyl group introduction at low DS results in distinct modification of physical properties. Among these are decreased gelatinization temperature range (126), increased granule swelling rate (127), and decreased abiUty of starch pastes to gel and retrograde. 

Cationic starches show decreased gelatinization temperature range and increased hot paste viscosity. Pastes remain clear and fluid even at room temperatures and show no tendency to retrograde. This stabiUty is due to Coulombic repulsion between positively charged starch molecules in dispersion. 

Compared to native starches, monophosphate esters have a decreased gelatinization temperature range and swell in cold water at a DS of 0.07. Starch phosphates have increased paste viscosity and clarity and decreased retrogradation. Their properties are in many ways similar to those of potato starch, which naturally contains phosphate groups. 

Low DS starch acetates have reduced gelatinization temperature ranges and reduced tendency to retrograde after pasting and cooling. Gelling may be completely inhibited if the DS is sufficiently high. Low DS starch acetate polymers also form films which are useful in textile and paper manufacture. 

Scale. Scale deposits are formed by precipitation and crystal growth at a surface in contact with water. Precipitation occurs when solubiUties are exceeded either in the bulk water or at the surface. The most common scale-forming salts that deposit on heat transfer surfaces are those that exhibit retrograde solubiUty with temperature. 

An aqueous dispersion of an unmodified starch containing amylose wiU gradually form an insoluble precipitate through association of linear segments. This process is called retrogradation or set-back. 

In general, derivatization increases solution and gel clarity, reduces the tendency to gel, improves water binding, increases freeze—thaw stabiHty, reduces the gelatinization temperature, increases peak viscosity, and reduces the tendency to retrograde. Combinations of substitutions are used to obtain desiredproperti.es for specific appHcations. 

There are those who see the emergence of sector standards as a retrograde step, having reached the stage where we have condensed all the world s national quality system standards into one group of 20 standards. Those following the development of ISO 9000 will already be aware that the 20 standards in the ISO 9000 family are soon to be reduced to four (ISO 9000, ISO 9001, ISO 9004, and a replacement for ISO 10011). It... 

Ruckwkrtsbewegung, /. retrograde motion. Riickweg, m. return path, ruckweise, adv. by jerks intermittently, riickwerfen, v.t. throw back reflect, riickwirken. v.i. react. 

Mechanism 2 of Figure 8-122B becomes apparent when the flow recirculation on the tray increases with increasing underflow clearance. The curvature of the column wall influences the movement of the liquid toward the center. High underflow clearance does not even out maldistribution due to backup where the irregular flow pattern enters into the tray below. This allows flow separation to occur on the downcomer floor, and leads to enhanced retrograde flow. 

A natural gas reservoir in which retrograde condensation will take place as it is depleted and from which liquids can be commercially recovered in surface facilities. 

Reservoir de gaz naturel dans lequel se produit une condensation retrograde a mesure de son epuisement et a partir duquel on pent recuperer commer-cialement des liquides en surface. 

They also argued that the polymerization of the adduct proceeded only when the retrograde reaction giving back the two monomers was occurring, i.e. at higher temperatures and thus the real monomer was the charge-transfer complex. 

Protein toxins acting intracellularly are often composed of two subunits (A/B model). One subunit is catalytic (A-subunit) and the other is responsible for binding and cell entry (B-subunit). Following binding to an extracellular membrane receptor, the toxins are endocytosed. From the endosomes, the A-subunit is directly (pH dqDendent) transferred into the cytosol (e.g., diphtheria toxin and anthrax toxin) or the toxin is transported in a retrograde manner via the golgi to the ER (e.g., cholera toxin), where translocation into the cytosol occurs [1]. 

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