Descending Processes

Three descending processes ensure the mass transfer in soils these process are  

Cheluviation. Cheluviation involves the transport of organo-metallic complexes (i.e., chelates) of iron and aluminum. Once transported to the lower horizon B, the iron and aluminum precipitate as iron and aluminum sesquioxides forming colored spodic horizons denoted B,. 

Lessivage. Lessivage involves the vertical transport of particles and colloids of clay minerals. The downward horizons where the accumulation of the transported clays occurs are called argillic (denoted B,) horizons. Usually, due to the swelling of clay minerals with water, the plugging of argillic horizons ensures an impermeabilization of lower horizons. 

Peat is the partly carbonized organic residue produced by decomposition of roots, trunks of trees, seeds, shrubs, grasses (reeds), ferns, mosses, and other vegetation. 

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In general, the calceous-dolomitic rocks from the Cambrian age are affected by their upper beds, by sulphide mineralization of lead, zinc and iron contemporaneous with sedimentation. The oxide lead and zinc minerals are disseminated through dolomitic limestone. As a consequence of the action of the descending process, these formations may assume different types of mineralization. According to the intensity of the oxidation process, which is associated with the different characteristics of the country rock, this country rock may be (a) principally calceous, (b) calceous with dolomitized zones and (c) primarily dolomitized. 

The second ceUulosic fiber process to be commercialized was invented by L. H. Despeissis (4) in 1890 and involved the direct dissolution of cotton fiber in ammoniacal copper oxide Uquor. This solvent had been developed by M. E. Schweizer in 1857 (5). The cuprammonium solution of ceUulose was spun into water, with dilute sulfuric acid being used to neutralize the ammonia and precipitate the ceUulose fibers. H. Pauly and co-workers (6) improved on the Despeissis patent, and a German company, Vereinigte Glanstoff Eabriken, was formed to exploit the technology. In 1901, Dr. Thiele at J. P. Bemberg developed an improved stretch-spinning system, the descendants of which survive today. 

Thus air cools as it rises and warms as it descends. Since we have assumed an adiabatic process, -ATIAz defines the dry adiabatic process lapse rate, a constant equal to 0.0098 K/m, is nearly 1 K/lOO m or 5.4°F/1000 ft. 

A National Transportation Safety Board Railroad Accident Report (1973) describes the accident which occurred in a shunting yard in East St. Louis, Illinois. Arriving cars are classified in the yard, then delivered to outbound carriers. On arrival, cars are inspected. They are then pushed up a mound, uncoupled, and allowed to roll down a descending grade onto one of the classification tracks. This process is called humping. Cars are directed and controlled by a computerized switching and speed-control system. 

Important processes commercially used are the Selexol, the Sulfinol, and the Rectisol processes. In these processes, no chemical reaction occurs between the acid gas and the solvent. The solvent, or absorbent, is a liquid that selectively absorbs the acid gases and leaves out the hydrocarbons. In the Selexol process for example, the solvent is dimethyl ether of polyethylene glycol. Raw natural gas passes countercurrently to the descending solvent. When the solvent becomes saturated with the acid gases, the pressure is reduced, and hydrogen sulfide and carbon dioxide are desorbed. The solvent is then recycled to the absorption tower. Figure 1-1 shows the Selexol process. ... 

In the moving bed processes, the preheated feed meets the hot catalyst, which is in the form of beads that descend by gravity to the regeneration zone. As in fluidized bed cracking, conversion of aromatics is low, and a mixture of saturated and unsaturated light hydrocarbon gases is produced. The gasoline product is also rich in aromatics and branched paraffins. 

The presentation finally descends on the very last of the listed chemical precipitation processes, and this pertains to precipitation implemented by carbonate anions (CO-). The dissolution of carbon dioxide takes place with the formation of the weak diabasic acid, H2C03. The overall dissociation of this acid (dissociation constant, KD) is represented by ... 

The application of pressure to a d-activated exchange process produces a decrease in n kP/k0) because the approach to the transition state requires an increase in volume, as indicated qualitatively by the one or two descending superscript arrows on kP in Fig. 3. The opposite is the case for an a-activated exchange process where the approach to the transition state requires a decrease in volume, indicated qualitatively by the one or two ascending superscript arrows on kP in Fig. 3. On this basis, it is clear that when M = V and Mn, water exchange on [M(H20)6]2+ is a-activated, but when M = Fe, Co, and Ni, it is d-activated. The origins of these differences are considered in more detail in Section III,B. 

O Pain is an unpleasant subjective experience that is the net effect of a complex interaction of the ascending and descending nervous systems involving biochemical, physiologic, psychological, and neocortical processes. 

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