Medical apphcations

The use of metered-dose valves in aerosol medical appHcations permits an exact dosage of an active dmg to be deHvered to the respiratory system where it can act locally or be systemicaHy absorbed. For example, inhalers prescribed for asthmatics produce a fine mist that can penetrate into the bronchial tubes (see Antiasthmatic agents). 

Sulfur hexafluoride [2551-62-4] 6 molecular weight 146.07, is a colorless, odorless, tasteless gas. It is not flammable and not particularly reactive. Its high chemical stabiUty and excellent electrical characteristics have led to widespread use in various kinds of electrical and electronic equipment such as circuit breakers, capacitors, transformers, microwave components, etc (see Electronic materials). Other properties of the gas have led to limited usage in a variety of unique appHcations ranging from medical appHcations to space research. 

Medical appHcations of PFC emulsions for organ perfusion and intravenous uses have received much attention in recent years. The first commercial blood substitute (Fluosol DA 20%, trademark of the Green Cross Corp.) employed perfluorodecalin, and improved, second generation products based on this PFC, or perfluorooctylbromide, are now under development (20,21). The relatively high oxygen dissolving capabiHty of PFCs undedies these appHcations (see Blood, artificial). 

Larch Gum. Larch gum [37320-79-9] (larch arabinogalactan) is obtained by water extraction of the western larch tree, iLarix occidentalism the heartwood of which contains 5—35% on a dry wood basis. In the early 1960s, a countercurrent hot water extraction system was developed, and the gum was produced commercially by the St. Regis Paper Co. under the trade name Stractan. The potential production capacity of this gum is 10,000 t/yr based on the wood residues from the lumber industry. However, the product could not compete with gum arabic, and commercial production is now limited to small batches for a specific medical appHcation. 

In the late fifteenth century AD mercury was successfully used as a treatment for syphilis. In the late sixteenth century the development of the Patio process for the recovery of silver by amalgamation (see Silverand silveralloys) greatiy increased the consumption of mercury. Usage of mercury increased in 1643 when Torricelli invented the barometer, and again in 1720 when Fahrenheit invented the mercury thermometer. Other scientific and medical appHcations foUowed. Industrial usage after 1900, particularly in electrical appHcations, expanded rapidly, offsetting the sharp decline in its use in amalgamation. 

Microwaves have successfully been used for rewarming of blood for medical appHcations (157). Another successful appHcation, not commetciali2ed as of this writing, is the use of microwave heating for rapid tissue fixation (158,159). This procedure appears to reduce the time for tissue sample analysis... 

Most, if not all, microwave biological effects and potential medical appHcations are beheved to be the result of heating, ie, thermal effects. The phenomenon of microwave hearing, ie, the hearing of clicking sounds when exposed to an intense radar-like pulse, is generally beheved to be a thermoelastic effect (161). Excellent reviews of the field of microwave bioeffects are available (162,163). 

In medical apphcations, many test procedures have been developed for screening the efficiency of fabrics to block the passage of vimses, blood-home pathogens, etc. 

Medical Markets. In medical appHcations, progress has been made in the substitution of traditional materials with higher performing spunbondeds (67). Historically, flash spunbonded polyethylene was the first 100% spunbonded to find wider acceptance in medical uses such as disposable... 

LDPE is nontoxic, and is commonly used in food packaging (qv) where Food and Dmg Administration requirements, such as 21CFR in the case of thin films, must be met. It is also used in packaging pharmaceuticals and other medical appHcations such as iv bags and tubes. 

LLDPE by itself does not present any health-related hazard on account of its chemical inertness and low toxicity. Consequently, film, containers, and container Hds made from LLDPE are used on a large scale in food and dmg packaging. Some LLDPE grades produced with unsupported metallocene catalysts have an especially high purity due to high catalyst productivity and a low contamination level of resins with catalyst residue. FDA approved the use of film manufactured from these resins for food contact and for various medical appHcations (80). However, if LLDPE articles contain fillers, processing aids, or colorants, thek health factors must then be judged separately. 

Phthalocyanines are excellent lubricants at temperatures of 149—343°C (191). Combinations with other lubricants, like grease, molybdenum, or tungsten sulfides, have found appHcations in the automotive industry or professional drilling equipment (192—195). Further uses include indicators for iron(Il), molybdenum(V), and uranium(IV) (196) or redox reactions (197), medical appHcations like hemoglobin replacements (198) or sterilisation indicators (199), or uses like in gas filters for the removal of nitrogen oxides from cigarette smoke (200). 

Elastomers based on PTMEG have excellent microbial and fungus resistance. Their hydrolytic stabiUty make these elastomers prime candidates for use ia ground-contact appHcations, for example, as jacketing material for buried cables. Because of their good biocompatibiHty, they have also found uses ia medical appHcations, such as catheter tubiag. 

As vulcanizing agents, amino acids with or without sulfur are used for nipple mbber of babies botdes and mbbers used in medical appHcations... 

A monograph (1) covers the pioneering period of sulfa dmg development and describes over 5000 sulfanilamide derivatives, their preparation, properties, trade names, and biological testing. This review is remarkably complete through 1944. Several thousand additional derivatives have been made since, but no comparable coverage is available. A definitive account of medical appHcations up to 1960 has been pubHshed (2), and a review of experimental antibacterial aspects has been made (3). Chapters on general aspects of sulfonamides and sulfones have appeared (4,5). A review of the clinical efficacy of trimethoprim—sulfamethoxazole has been pubHshed (6). 

A family of PEO/PET copolymers has been synthesized and the characterized stmctures found to be close to those expected in theory (41). A wide degradation envelope has been achieved by adjusting the PEO-to-PET ratio. Mechanical properties prove useful for medical appHcations, and the 60/40 PEO/PET composition is reported as optimal. 

Cost. Price is an important consideration for most commodity types of mbber products, eg, tires, hoses, and belts. Eor specialty items, eg, mbber products for medical appHcations, cost is not a primary factor performance is more important. 

Examples of nir analysis are polymer identification (126,127), pharmaceutical manufacturing (128), gasoline analysis (129,130), and on-line refinery process chemistry (131). Nir fiber optics have been used as immersion probes for monitoring pollutants in drainage waters by attenuated total internal reflectance (132). The usefulness of nir for aqueous systems has led to important biological and medical appHcations (133). 

Chlorine dioxide gas generated from chlorite has been used as a chemosterilizing agent substitute for ethylene oxide in medical appHcations (174,175). Aqueous foam compositions containing chlorine dioxide have also been developed for the sanitization of hard surfaces (176). 

Maintenance hemodialysis has grown and expanded beyond the expectations of even the most enthusiastic of its eadiest proponents. Figure 7 is a plot of the overall estimated dialysis population by year siace 1970. The population at the end of 1992 exceeded 475,000 another 500,000 patients or so have received therapy at one time but have siace died or had transplants. Maintenance dialysis is now available to some extent ia all but the poorest nations ia economically advanced countries, excepting the United Kingdom, it is rendered as a virtual entitlement. The current worldwide mean cost of a single dialysis patient is about 30,000 per year (47) the aggregate economic magnitude of the medical appHcation of hemodialysis thus approaches 15 biUion. 

Whereas tests (186) indicated that ampholytes were effective in skin cleansing for preoperative use, for wound cleansing, and as an antiseptic in the oral cavity (187), as well as other medical appHcations, the food and beverage industries have proved to be the principal employers of these compounds. Ampholytes are used as sanitizers and disinfectants, not as food preservatives. Low toxicity, absence of skin irritation, and noncorrosiveness, along with antimicrobial activity, has given ampholytes acceptance in dairies, meat plants, and the brewing and soft drink industries. These disinfectants have been manufactured and distributed in Europe and Japan, but not in the United States. 

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