【正文】 on passes readily the outer air, slightly through liquid, and only poorly through solid, the object to be disinfected must be directly exposed to it for full effect. ? Applications of UV Radiation UV radiation is usually directed at disinfection rather than sterilization. Germicidal(殺菌的 ) lamps can cut down on the concerntration of airborne(空中的 ) microbes as much as 99%.They are used in hospital rooms, operating rooms, schools, food preparation rooms and dental offices. SOUND WAVES IN MICROBIAL CONTROL ? Highfrequency sound (sonic超聲 ) waves beyond the sensitivity of the human ear known to disrupt cells. These frequencies range from 15， 000 to more than 200,000 cycles per second (supersonic to ultrasonic). Sonication transmits vibrations through a waterfilled Chamber to induce pressure changes and create intense points of turbulence（動(dòng)亂 ） that can stress and burst cells In the vicinity（近傍 ） . Gramnegative rods（桿菌） are most sensitive to ultrasonic vibrations and grampositive cocci(球菌 ), fungal spores, and bacterial spores are most resistant to them. ? STERILIZATION BY FILTRATION: ? TECHNIQUES FOR REMOVING MICROBES ? Filtration(過濾 ) is an effective method to remove microbes from air and liquids. In practice, A fluid is stained through a filter with openings large enough for the fluid to pass through but too small for microanisms to pass through (figure ). ? Most modern microbiological filters are thin membranes of cellulose acctatc, polycarbonate (聚碳酸酯 )and a variety of plastic materials (Teflon, nylon) whose pore size can be carefully controlled and standardized. Ordinary substances such as charcoal(活性碳 ), diatomaceous earth(硅藻土的 ), or porcelain(瓷器 ) are also used in some applications. Viewed microscopically, most filter are perforated by very precise, uniform pores (figure ).. ? The pore diameters vary from coarse(8um)to ultrafine（ ），permiting selection of the minimum particle size to be trapped. Those with the smallest pore diameters permit ture sterilization by removing viruses, and some will even remove large proteins ? Applications of Filtration Sterilization Filtration sterilization is used to prepare liquids that cannot withstand heat, including serum and other blood products, Vaccines, drugs, fluids ,enzymes, and media. Filtration has been employed as an alternative to sterilize milk and beer without altering their flavor. It is also an important step in water purification. Chemical Agents in Microbial Control ? Chemical control of microbes probably ? Emerged as a serious science in the early 1800s,when physicians used chloride of lime and iodine solutions to treat wounds and to wash their hands before surgery. At the present time, approximately 10,000 different antimicrobial chemical agents are manufactured。 probably 1,000 of them are used routinely in the allied health sciences and the home. ? Antimicerobial chemicals occur in the liquid, gaseous, or even solid state and vary from disinfectantes and antiscptics to sterilantes and preservatives. For the sakeof convenience many solid or gaseouse antimicrobial chemicals are dissolved in water, alcohol, or a mixture of the two to produce a liquid solution. CHOOSING A MINCROBICIDAL CHEMICAL ? The choice and appropriate use of a antimicrobial chemical agents is of constant concern in medicine. Although actual clinical practices of chemical decontamination vary widely, some desirable qualities in a germicide have been identified, including: 1. rapid action even in low concentrations, 2. solubility in water or alchol and longterm stability, 3. broadspectrum micerobicidal action without being toxic to human and animal tissues, 4. peration of inanimate surfaces to sustain a cumulative(累積的 ) or persistent action, 5. resistance to being inactivated by anic matter, 6. noncorrosive(非腐蝕性的 ) or nonstaining properties, 7. Sanitizing（消毒 ） and deodorizing（除臭 ） properties,and 8. inexpensiveness and ready availability. ? Germicides（殺菌劑 ） are evaluated in terms of their effectiveness in destroying microbes in medical and dental（牙齒的 ） settings. The three levels of chemical deamination(凈化 ) procedurces are high, intermediate, and low (table ).Highlevel germicides cill endospores,and,if properly used, are sterilants. ? Materials that access it at highlevel control are medical Devices—for example, catheters(醫(yī)用導(dǎo)管 ), heartlung Equipment, and implants—that are heatsterilizable and are intended to enter body tissues during medical procedures. Intermediatelevel germicides kill fungal (but not bacterial) sporec, resistant pathogens. ? Low levels of disinfectipn eliminate only vegetative bacteria, vegetative fungal cells, and some viruses. They are used to clean materials such as electrodes(電極 ), and furniture that touch the skin surfaces. FACTORS THAT AFFECT THE GERMICIDAL ACTIVITY OF CHEMICALS ? Factors that control the effect of a germicide include the nature of the microanisms being treated, the nature of the material being treated, the degree of contamination, the time of exposure, and the strength and chemical action of the germicide. ? A chemical’ s strength or concentration is expressed in various ways, depending upon convention and the method of preparation. The content of many chemical agents can be expressed by more than one notation. 謝謝觀看 /歡迎下載 BY FAITH I MEAN A VISION OF GOOD ONE CHERISHES AND THE ENTHUSIASM THAT PUSHES ONE TO SEEK ITS FULFILLMENT REGARDLESS OF OBSTACLES. BY FAITH I BY FAITH