Wave–particle duality<span> is the </span>concept<span> that every elementary </span>particle<span> or quantic entity may be partly described in terms not only of </span>particles, but also ofwaves. It expresses the inability of the classical concepts<span> "</span>particle" or "wave<span>" to fully </span>describe<span> the behavior of quantum-scale objects.</span>
Gynecomastia is an increase in the size of the mammary gland in men. The condition can occur in one or both breasts. It starts as a small mass under the nipple, which can be sensitive. One breast can be bigger than the other. Its cause is an imbalance between the stimulatory effects of estrogen (female sex hormones) and the inhibitory effects of androgens (male sex hormones) in the breast tissue, when the first ones increase, or the second ones descend.
Gynecomastia is a problem relatively common in the population, and there are three prevalence peaks throughout life:
Newborns: Between 60 and 90% of newborns have gynecomastia, produced by the passage of maternal estrogens through the placenta. It is a transient gynecomastia that disappears in about 2-3 weeks.
Puberty: Gynecomastia in puberty affects mainly young people aged between 10 and 14 years, and is due to the transient and physiological increase in estrogen that occurs at this age.
Elderly: Is due to an increase in fatty tissue with a greater peripheral aromatization ( a process that occurs in adipose tissue and that involves the conversion of androgens into estrogens), a decrease in the production of testosterone by the testes and the use of drugs.
<span>Noctilucent clouds (sometimes known as night clouds or mesopheric clouds) form in the mesosphere, a layer of the atmosphere located 47-59 miles above the Earth. </span>
<span>This is due to much of the energy that is consumed by lower trophic levels of the food chain/food web being used at that lower level. This energy is stored or used and, therefore, unavailable to the organisms higher up in the chain. As the chain lengthens, less energy is available, usually as a factor of 10 (1/10 of the energy taken in by the level below the consumer is available to the consumer's level, for example).</span>
