During the past forty years, disposable diapers have become an important part of the economy. Since the average baby uses at least ten diapers per day for an average of two years, the convenience of the product has made it a very popular as well as controversial item.
Before one cell can divide into two cells, the cell must make a copy of the cellular DNA so that after cell division, each cell will contain a complete complement of the genetic material. Replication is the cellular process by which DNA or the cellular genome is duplicated with almost perfect (and sometimes perfect) fidelity.
Dopamine belongs to a family of biological compounds called catecholamines (see Figure 1). Dopamine is synthesized from the compound L-dihydroxyphenylalanine (L-dopa) via the enzyme dopa decarboxylase.
Described in 1953 by James Watson and Francis Crick, the double helix of DNA (deoxyribonucleic acid) is the cellular storehouse of genetic information.
The great appeal of textiles lies in their colors and the way that color is used to create patterned effects. Color is applied by the process of dyeing, which in its simplest form involves the immersion of a fabric in a solution of a dyestuff in water.
Dysprosium, taking its name from the Greek word dysprositos, meaning "hard to obtain," is a metallic element, discovered, but not isolated, in 1886 in Paris by the French scientist Paul-Émile Lecoq de Boisbaudran. Its isolation was made possible by the development of ion-exchange separation in the 1950s.
Einsteinium, the tenth member of the actinide series, was discovered in 1952. Einsteinium and fermium (element 100) were most unexpectedly produced in the explosion of the first U.S.
Electrochemistry deals with the links between chemical reactions and electricity. This includes the study of chemical changes caused by the passage of an electric current across a medium, as well as the production of electric energy by chemical reactions.
Endorphins are small neuropeptides that are produced by the body and act to reduce pain—hence, the name endorphin (a shortened version of endogenous morphine). The term "enkephalin" (meaning literally "in the head") is also applied to endorphins, but usually refers to smaller molecules that have pain-relieving properties.
In the discussion of energy, the fundamental concept is that of work, which is motion against an opposing force. Energy is the capacity to do work.
Modern societies rely on a variety of energy sources to heat homes, propel transportation vehicles, and produce goods for shelter, food, health care, and entertainment. Some of these sources are renewable, whereas others are nonrenewable.
Environmental pollution is the release of chemical waste that causes detrimental effects on the environment. Environmental pollution is often divided into pollution of water supplies, the atmosphere, and the soil.
Enzymes are (mostly) proteins that catalyze biochemical reactions; that is, they increase the rate of a reaction but are not used up in the process. Their importance to life is underscored by the fact that many severe or fatal genetic diseases involve a missing or defective enzyme.
Epinephrine, also known as adrenalin, is a hormone that is responsible for the "fight or flight" reaction in mammals. Chemically, it mobilizes the body's defense system, inducing the release into the blood of large amounts of glucose from stores in the liver and muscles.
A state of equilibrium exists in a process when the rate of the forward process equals the rate of the reverse process. The equilibrium condition exists in relation to thermal, mechanical, and chemical changes.
Erbium is a chemical element. Its ground state electronic configuration is [Xe]4f12 6s2.
Estrogen is not one hormone, it is the name used to denote either of two steroid hormones. These hormones are noted for their role in the development of the secondary sexual characteristics of females.
Chemistry, like any discipline, has a social structure. It relies on the interactions, behaviors, and expectations of individuals in order to function.
Europium is a metallic element discovered in 1901 in Paris by the French scientist Eugène-Anatole Demarcay. It belongs to a series of elements called lanthanides, or 4f elements, extending from lanthanum (atomic number 57) to lutetium (atomic number 71).
An explosion is a sudden, violent change of potential energy to work, which transfers to its surroundings in the form of a rapidly moving rise in pressure called a blast wave or shock wave. The shock wave can cause substantial damage.
Fats occur naturally in food and play a significant role in human nutrition. Fats are used to store energy in the body, insulate body tissues, cushion internal organs, and transport fat-soluble vitamins in the blood.
Éleuthère Irénée du Pont was born in France on June 24, 1771, and died on October 31, 1834, in the United States. He was the son of Pierre du Pont, an active member of the French government in the 1780s and 1790s before, during, and after the French Revolution.
Paul Ehrlich made notable contributions in several areas of medicine including selective dye staining of cells, immunology, cancer research, and chemical therapy of infectious diseases.
For most people asked to name a scientist, "Albert Einstein" is the first name that comes to mind. Einstein's life story, including his difficulties with math in high school, his time spent as a patent clerk in the Swiss Patent Office, his development of the theory of relativity, and his influence on the development of the nuclear bomb, is the stuff of legends.
The Nobel Prize Committee rarely honors the work of scientists who develop new drugs.
Chemical reactions convert reactants to products, whose properties differ from those of the reactants. Chemical equations are a compact and convenient way to represent chemical reactions.
Observations are the heart of the scientific method, but human perception is faulty when it comes to observing "absolutes." That is, one may be able to say that this liquid is hotter than that liquid, but not by how much, nor their exact temperatures. For science to be meaningful and its results reproducible, some external mechanism for making (and comparing) measurements that can be used by scientists must exist.