Polymer degradationPolymer degradation is the reduction in the physical properties of a polymer, such as strength, caused by changes in its chemical composition. Polymers and particularly plastics are subject to degradation at all stages of their product life cycle, including during their initial processing, use, disposal into the environment and recycling. The rate of this degradation varies significantly; biodegradation can take decades, whereas some industrial processes can completely decompose a polymer in hours.
Jet airlinerA jet airliner or jetliner is an airliner powered by jet engines (passenger jet aircraft). Airliners usually have two or four jet engines; three-engined designs were popular in the 1970s but are less common today. Airliners are commonly classified as either the large wide-body aircraft, medium narrow-body aircraft and smaller regional jet. Most airliners today are powered by jet engines, because they are capable of safely operating at high speeds and generate sufficient thrust to power large-capacity aircraft.
CavitationCavitation is a phenomenon in which the static pressure of a liquid reduces to below the liquid's vapour pressure, leading to the formation of small vapor-filled cavities in the liquid. When subjected to higher pressure, these cavities, called "bubbles" or "voids", collapse and can generate shock waves that may damage machinery. These shock waves are strong when they are very close to the imploded bubble, but rapidly weaken as they propagate away from the implosion. Cavitation is a significant cause of wear in some engineering contexts.
Bubble (physics)A bubble is a globule of a gas substance in a liquid. In the opposite case, a globule of a liquid in a gas, it's called a drop. Due to the Marangoni effect, bubbles may remain intact when they reach the surface of the immersive substance. Bubbles are seen in many places in everyday life, for example: As spontaneous nucleation of supersaturated carbon dioxide in soft drinks As water vapor in boiling water As air mixed into agitated water, such as below a waterfall As sea foam As a soap bubble As given off in chemical reactions, e.
Therapeutic indexThe therapeutic index (TI; also referred to as therapeutic ratio) is a quantitative measurement of the relative safety of a drug. It is a comparison of the amount of a therapeutic agent that causes the therapeutic effect to the amount that causes toxicity. The related terms therapeutic window or safety window refer to a range of doses optimized between efficacy and toxicity, achieving the greatest therapeutic benefit without resulting in unacceptable side-effects or toxicity.
AgonistAn agonist is a chemical that activates a receptor to produce a biological response. Receptors are cellular proteins whose activation causes the cell to modify what it is currently doing. In contrast, an antagonist blocks the action of the agonist, while an inverse agonist causes an action opposite to that of the agonist. From the Greek αγωνιστής (agōnistēs), contestant; champion; rival < αγων (agōn), contest, combat; exertion, struggle < αγω (agō), I lead, lead towards, conduct; drive Receptors can be activated by either endogenous agonists (such as hormones and neurotransmitters) or exogenous agonists (such as drugs), resulting in a biological response.
Receptor antagonistA receptor antagonist is a type of receptor ligand or drug that blocks or dampens a biological response by binding to and blocking a receptor rather than activating it like an agonist. Antagonist drugs interfere in the natural operation of receptor proteins. They are sometimes called blockers; examples include alpha blockers, beta blockers, and calcium channel blockers. In pharmacology, antagonists have affinity but no efficacy for their cognate receptors, and binding will disrupt the interaction and inhibit the function of an agonist or inverse agonist at receptors.
Sharps wasteSharps waste is a form of biomedical waste composed of used "sharps", which includes any device or object used to puncture or lacerate the skin. Sharps waste is classified as biohazardous waste and must be carefully handled. Common medical materials treated as sharps waste are hypodermic needles, disposable scalpels and blades, contaminated glass and certain plastics, and guidewires used in surgery. In addition to needles and blades, anything attached to them, such as syringes and injection devices, is also considered sharps waste.
Needlestick injuryA needlestick injury is the penetration of the skin by a hypodermic needle or other sharp object that has been in contact with blood, tissue or other body fluids before the exposure. Even though the acute physiological effects of a needlestick injury are generally negligible, these injuries can lead to transmission of blood-borne diseases, placing those exposed at increased risk of infection from disease-causing pathogens, such as the hepatitis B virus (HBV), hepatitis C virus (HCV), and human immunodeficiency virus (HIV).
Injection (medicine)An injection (often and usually referred to as a "shot" in US English, a "jab" in UK English, or a "jag" in Scottish English and Scots) is the act of administering a liquid, especially a drug, into a person's body using a needle (usually a hypodermic needle) and a syringe. An injection is considered a form of parenteral drug administration; it does not involve absorption in the digestive tract. This allows the medication to be absorbed more rapidly and avoid the first pass effect.
