Symbiosis

Symbiosis (from Greek σύν "together" and βίωσις "living") is close and often long-term interaction between two different biological species. In 1877 Albert Bernhard Frank used the word symbiosis (which previously had been used to depict people living together in community) to describe the mutualistic relationship in lichens. In 1879, the German mycologist Heinrich Anton de Bary defined it as "the living together of unlike organisms."

The definition of symbiosis has varied among scientists. Some believe symbiosis should only refer to persistent mutualisms, while others believe it should apply to any type of persistent biological interaction (in other words mutualistic, commensalistic, or parasitic). After 130 years of debate, current biology and ecology textbooks now use the latter "de Bary" definition or an even broader definition (where symbiosis means all species interactions), with the restrictive definition no longer used (in other words, symbiosis means mutualism).

Some symbiotic relationships are obligate, meaning that both symbionts entirely depend on each other for survival. For example, many lichens consist of fungal and photosynthetic symbionts that cannot live on their own. Others are facultative (optional): they can, but do not have to live with the other organism.

Symbiosis (Star Trek: The Next Generation)

"Symbiosis" is the 22nd episode of the American science fiction television series Star Trek: The Next Generation. It first aired on April 18, 1988, in broadcast syndication. The teleplay was written by Robert Lewin, Richard Manning, and Hans Beimler, based on a story by Lewin, and the episode was directed by Win Phelps.

Set in the 24th century, the series follows the adventures of the crew of the Starfleet starship Enterprise-D. In this episode, Captain Jean-Luc Picard (Patrick Stewart) tries to mediate a trade dispute between two co-dependent neighbouring planets regarding medical supplies which turn out to be narcotic drugs.

The episode was written after executive producer Maurice Hurley worked on Miami Vice, which he credited for resulting in a narcotic theme in the episode. The guest cast included Judson Scott and Merritt Butrick who had both appeared in Star Trek II: The Wrath of Khan (1982). "Symbiosis" marked the final filmed appearance of Denise Crosby as Tasha Yar until her return in "Yesterday's Enterprise". The episode received mixed reviews with criticism directed at the subject matter and the unsubtle nature of the presentation.

Forma

Forma is a Latin word meaning "form". Both the word "forma" and the word "form" are used interchangeably as informal terms in biology:

Formwork

Formwork is the term given to either temporary or permanent molds into which concrete or similar materials are poured. In the context of concrete construction, the falsework supports the shuttering moulds.

Formwork and concrete form types

Formwork comes in several types:

Homogeneous polynomial

In mathematics, a homogeneous polynomial is a polynomial whose nonzero terms all have the same degree. For example, is a homogeneous polynomial of degree 5, in two variables; the sum of the exponents in each term is always 5. The polynomial is not homogeneous, because the sum of exponents does not match from term to term. A polynomial is homogeneous if and only if it defines a homogeneous function. An algebraic form, or simply form, is a function defined by a homogeneous polynomial. A binary form is a form in two variables. A form is also a function defined on a vector space, which may be expressed as a homogeneous function of the coordinates over any basis.

A polynomial of degree 0 is always homogeneous; it is simply an element of the field or ring of the coefficients, usually called a constant or a scalar. A form of degree 1 is a linear form. A form of degree 2 is a quadratic form. In geometry, the Euclidean distance is the square root of a quadratic form.

Homogeneous polynomials are ubiquitous in mathematics and physics. They play a fundamental role in algebraic geometry, as a projective algebraic variety is defined as the set of the common zeros of a set of homogeneous polynomials.