Tubes, artificial

The blood of the patient, withdrawn from an artery near the wrist, is allowed to flow through the blood circuit, which includes the dialyzer, usually a blood pump plus monitoring instruments, and is returned to a nearby vein. The connections to the blood vessels are made via the so-called subcutaneous arteriovenous shunt this involves an artificial tube that connects the artery and vein underneath the wrist skin. 

The theoretical background of the confinement effect in (artificial) tubes was recently examined in detail with the aid of an analytical theory as well as with Monte Carlo simulations [70]. The analytical treatment referred to a polymer chain confined to a harmonic radial tube potential. The computer simulation mimicked the dynamics of a modified Stockmayer chain in a tube with hard pore walls. In both treatments, the characteristic laws of the tube/reptation model were reproduced. Moreover, the crossover from reptation (tube diameter equal to a few Kuhn segment lengths) to Rouse dy-... 

The figures show typical signals obtained from an ID inspection of non-ferromagnetic tubing with artificial flaws, Figure 1, and actual results on steel tubing. Figure 2. 

Fig. 1 The view of the polar display with monitors arcs and control panel for SFT6000N board parameters. Recorded signal is from the eddy current probe moved along in a brass tube of inner diameter 20 mm with 2 mm holes as artificial flaws. SFT6000N card operates with 40 kHz injection voltage firequency.

Spira.1- Wound Modules. Spiral-wound modules were used originally for artificial kidneys, but were fuUy developed for reverse osmosis systems. This work, carried out by UOP under sponsorship of the Office of Saline Water (later the Office of Water Research and Technology) resulted in a number of spiral-wound designs (63—65). The design shown in Figure 21 is the simplest and most common, and consists of a membrane envelope wound around a perforated central coUection tube. The wound module is placed inside a tubular pressure vessel, and feed gas is circulated axiaUy down the module across the membrane envelope. A portion of the feed permeates into the membrane envelope, where it spirals toward the center and exits through the coUection tube. 

In most cases, artificial destratification is carried out throughout the summer. However, work in the Lund Tubes in Blelham Tarn suggests that intermittent destratification could provide further enhancement to this method of control by creating an unstable environment. This instability causes disruption of growth patterns of the algal community and, consequently, no species becomes dominant. 

Artificial ice rinks are frozen shallow ponds, formed and maintained using a brine in tubes buried under the surface. Tubes may be steel or plastic for a permanent rink or plastic for a temporary installation. The brine temperature within the pipes will be about - 11°C, and must be lower for rinks in the open air, owing to high solar radiation loads. Packaged liquid chillers are now generally used, and will be transportable, complete with brine pumps and other apparatus, for temporary installations. 

While it would be difficult to enumerate all of the efforts in the area of implants where plastics are involved, some of the significant ones are (1) the implanted pacemaker, (2) the surgical prosthesis devices to replace lost limbs, (3) the use of plastic tubing to support damaged blood vessels, and (4) the work with the portable artificial kidney. The kidney application illustrates an area where more than the mechanical characteristics of the plastics are used. The kidney machine consists of large areas of a semi-permeable membrane, a cellulosic material in some machines, where the kidney toxins are removed from the body fluids by dialysis based on the semi-permeable characteristics of the plastic membrane. A number of other plastics are continually under study for use in this area, but the basic unit is a device to circulate the body fluid through the dialysis device to separate toxic substances from the blood. The mechanical aspects of the problem are minor but do involve supports for the large amount of membrane required. 

In Vitio—Isolated from the living organism and artificially maintained, as in a test tube. 

An alternative approach is to synthesize an artificial gene in the test-tube starting with the appropriate deoxyribonucleotides. This approach, which demands that the entire amino acid sequence be known, has been used to clone genes encoding proteins 200 amino acids long. 

Aluminum is very malleable, as anyone can see from the thin rolls of aluminum foil (sometimes wrongly called tin foil ) used in modem kitchens. Toothpaste tubes are made of aluminum, and so are many toys and various parts of cars. There is even an artificial ruby made of a compound of aluminum, used in jeweled watches. Aluminum does not corrode, and so it is used for kitchenware and for many items in the construction industry. Because aluminum is light, it is used a great deal in airplane construction. 

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