Depot distribution system

Logistics by its very nature tends to be fixed asset intensive . Trucks, distribution centres and automated handling systems involve considerable investment and, consequently, will often depress return on investment. In conventional multi-echelon distribution systems, it is not unusual to find factory warehouses, regional distribution centres and local depots, all of which represent significant fixed investment. 

Though the stock control system led to marked improvement in the issue of items, a serious deficiency in the distribution system still remained. That deficiency was failure to control the flow of materials from production lines to the depots. "That, said General Lutes after the close of World War II, "is an excellent illustration of one of the most important lessons about Army supply that is, that the supply process is an individual entity and cannot be broken down into un-co-ordinated phases such as production, stock control, and distribution. With the advent of the supply control system in the Army in the spring of 1944 came a concerted effort to co-ordinate the various phases of the supply process. ... 

Insecticides with systemic action are taken up relatively quickly by the plants and transported into the vascular system. According to the type of application, uptake occurs through the roots or the parts of the plant above ground. Distribution is chiefly by the xylem, but is also possible by the phloem and by diffusion from cell to cell. The persistence of activity is dependent on the type of substance, the intensity of breakdown in the plant or the soil, and environmental conditions. A much longer period of protection can be maintained if, by application of granulates at drilling or planting out, a depot of the substance is created in the soil from which the active substance is released slowly and taken up by the plants. 

One class of compounds does deserve special attention—those chemicals that are very fat soluble. These include the older chlorinated pesticides, such as DDT, and some environmental contaminants, such as the PCBs (the polychlorinated biphenyls) and dioxins. In these cases, low levels of intact chemicals, if absorbed, may encounter the body s final defense mechanism. This defense is to store the compounds in fat and milk, a paradoxical strategy that the body uses to sequester away chemicals into a storage site (or depot) where they can do no harm to the rest of the body, ft s conceptually the prison system of the body. The absorption and distribution into fat greatly reduces the concentration of chemicals at other body sites and thus serves to blunt the impact of the exposure. Similarly, this simple method of diluting the absorbed chemical often keeps the concentration below an effect level and gives the overworked liver time to try to destroy them. 

On the other hand, if the compound only slightly penetrates the skin, the risk of tissue residues should be minimal. Under all circumstances, residues at the application site must be considered separately from tissue residues resulting from systemic distribution. If depots form, the nature of the binding (reversible or irreversible-covalent) must be assessed. Although this list seems formidable, it is amenable to straightforward experimental procedures. 

The most widely used parenteral administration avenues are intravenous (iv), intramuscular (im), and subcutaneous (sc). In addition, there are several minor applications (e.g. intraarterial). Application of a protein drug by the different main parenteral administration routes may have profound effects on the pharmacological performances. When the drug is administered iv, it is immediately available for action in the circulation, while drugs administered im or sc need more time to reach the blood (depot effect), and consequently the pharmacokinetic (PK) profiles could be different. Besides the PK, the route of administration may have influence on the primary distribution of the drug. For example, when administered sc, smaller and hydrophiUic proteins tend to enter the venous system, while larger and/or more hydrophobic proteins tend to... 

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