inferiority complex Acute sense of personal inferiority, often result¬ ing in either timidity or (through overcompensation) exaggerated aggres¬ siveness. Though once a standard psychological concept, particularly among followers of Alfred Adler, it has lost much of its usefulness through imprecise popular misuse.
infertility Inability of a couple to conceive and reproduce. It is defined as failure to conceive after one year of regular intercourse without con¬ traception. Inability to conceive when desired can result from a defect at any of the stages required for fertility (see reproductive system). About one in every eight couples is infertile. Most cases involve the female partner, 30^40% involve the male, and 10% are caused by unknown factors. In women, causes include ovulation or hormone problems, fallopian-tube disorders, and a chemical balance that is hostile to sperm; in men, causes include impotence, low sperm count, and sperm abnormalities. Either part¬ ner can have a blockage of the pathways the sperm must travel, often treatable by surgery. Emotional factors may contribute; return of normal fertility may require only counseling. Fertility drugs can stimulate the release of eggs (often more than one, leading to multiple births). Low sperm count may be overcome by limiting intercourse to the time of ovulation, the most fertile period. If these methods are unsuccessful, couples may try ARTIFICIAL insemination, in vitro fertilization, or SURROGATE motherhood, or they may choose adoption instead.
infinite series In mathematics, the sum of infinitely many numbers, whose relationship can typically be expressed as a formula or a function. An infinite series that results in a finite sum is said to converge (see con¬ vergence). One that does not, diverges. Mathematical analysis is largely taken up with studying the conditions under which a given function will result in a convergent infinite series. Such series (e.g., the Fourier series) are particularly useful in solving differential equations.
infinity In mathematics, the useful concept of a process with no end. As represented by the symbol «>, it is often mistakenly thought to be the largest number or a place on the real number line. Instead, it is the idea of a limit, as in the expression x —> ©°, which suggests that the variable x increases without bound. For example, the function/(x) = l/x, or the reciprocal of x, tends toward 0 as x approaches infinity as a limit. This process of approach¬ ing is crucial to the definition of the derivative and the integral in calculus, as well as to many other concepts of mathematical analysis.
inflammation Local reaction of living tissues to injury or illness, including burns, pneumonia, leprosy, tuberculosis, and rheumatoid arthri¬ tis. Its major signs are heat, redness, swelling, and pain. The process begins with brief contraction of nearby arterioles (see arteries). Dilation follows, flushing the capillaries with blood, from which fluid, plasma pro¬ teins, and leukocytes pass into the injured tissues, causing swelling as they attack the cause of injury. Initial acute inflammation can have any of four outcomes: resolution (return to normal), organization (new tissue buildup; see scar), suppuration (pus formation; see abscess), or chronic inflamma¬ tion. Sometimes treatment—including antibiotics for bacteria, or surgical removal of an irritating foreign body—can eliminate the cause. If not, anti-inflammatory drugs (e.g., cortisone or aspirin) may be given, or simple remedies (e.g., hot or cold compresses) may be applied.
inflation In cosmology, a hypothesized period of exponential expansion of the universe, shortly after the big bang, which may account for some of the universe’s observed properties, such as the distribution of energy and matter. Grand unified theories of the forces of nature suggest that infla¬ tion could have occurred during the first 10 -32 second after the universe began, when the strong force was decoupling from the weak and electro¬ magnetic forces. During this time, the universe would have expanded by
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more than 100 orders of magnitude. Interpreted in the context of general relativity, inflation occurred while the universe existed in a state of non¬ zero energy density (false vacuum).
inflation In economics, increases in the level of prices. Inflation is gen¬ erally thought of as an inordinate rise in the general level of prices. Four theories are commonly used to explain inflation. The first and oldest, the quantity theory, promoted in the 18th century by David Hume, assumes that prices will rise as the supply of money increases. Milton Friedman refined the quantity theory in the mid-20th century, arguing that the prescription for stable prices is to increase the money supply at a rate equal to that at which the economy is expanding. A second approach is John Maynard Keynes’s theory of income determination, which assumes that inflation occurs when the demand for goods and services is greater than the sup¬ ply. It calls for the government to control inflation by adjusting levels of spending and taxation and by raising or lowering interest rates. A third approach is the cost-push theory. It traces inflation to a phenomenon known as the price-wage spiral, in which workers’ demands for wage increases lead employers to increase prices to reflect their higher costs, thereby sowing the seeds of a further round of wage demands. A fourth approach is the structural theory, which emphasizes structural maladjust¬ ments in the economy, as when in developing countries imports tend to increase faster than exports, pushing down the international value of the developing country’s currency and causing prices to rise internally. See also DEFLATION, PRICE INDEX.
inflorescence \,in-fl9-'re-s 3 ns\ Cluster of flowers on one or a series of branches, which together make a large showy blossom. Categories depend on the arrangement of flowers on an elongated main axis (peduncle) or on sub-branches from the main axis, and on the timing and position of flowering. In determinate inflorescences, the youngest flowers are at the bottom or outside (e.g., onion flowers). In indeterminate inflorescences, the youngest flowers are at the top or in the center (e.g., snapdragon, lily of the valley, and Astilbe flowers). Other indeterminate inflorescences are the dangling male and female catkins of oak trees, the spike of barley, and the flat head (capitulum) of the dandelion.
influenza or flu or grippe Acute viral infection of the upper or lower respiratory tract. Influenza viRUSes A (the most common), B, and C pro¬ duce similar symptoms, but infection with or vaccination against one does not give immunity against the others. Chills, fatigue, and muscle aches begin abruptly. The temperature soon reaches 38-40 °C (101-104 °F). Head, muscle, abdominal, and joint aches may be accompanied by sore throat. Recovery starts in three to four days, and respiratory symptoms become more prominent. Bed rest, high fluid intake, and aspirin or other antifever drugs are standard treatment. Influenza A tends to occur in wave¬ like annual pandemics. Mortality is usually low, but in rare outbreaks (see influenza epidemic of 1918-19) it reaches immense proportions. Most deaths result from pneumonia or bronchitis.
influenza epidemic of 1918-19 or Spanish influenza epi¬ demic Most severe influenza outbreak of the 20th century. It apparently started as a fairly mild strain in a U.S. army camp in early March 1918. Troops sent to fight in World War I spread the virus to western Europe. Outbreaks occurred in nearly every inhabited part of the world, spread¬ ing from ports to cities along transportation routes. Pneumonia often devel¬ oped quickly and killed within two days. Among the most deadly epidemics in history, it left an estimated 25 million dead; unusually, half the deaths were among 20- to 40-year-olds.