Heart

The heart is a muscular organ in humans and other animals, which pumps blood through the blood vessels of the circulatory system. Blood provides the body with oxygen and nutrients, and also assists in the removal of metabolic wastes. The heart is located in the middle compartment of the mediastinum in the chest.

In humans, other mammals, and birds, the heart is divided into four chambers: upper left and right atria; and lower left and right ventricles. Commonly the right atrium and ventricle are referred together as the right heart and their left counterparts as the left heart. Fish in contrast have two chambers, an atrium and a ventricle, while reptiles have three chambers. In a healthy heart blood flows one way through the heart due to heart valves, which prevent backflow. The heart is enclosed in a protective sac, the pericardium, which also contains a small amount of fluid. The wall of the heart is made up of three layers: epicardium, myocardium, and endocardium.

Call

Call may refer to:

In arts and entertainment

In science and technology

Computing

Telecommunications

Other uses in science and technology

In finance

Rainbow

A rainbow is a meteorological phenomenon that is caused by reflection, refraction and dispersion of light in water droplets resulting in a spectrum of light appearing in the sky. It takes the form of a multicoloured arc. Rainbows caused by sunlight always appear in the section of sky directly opposite the sun.

Rainbows can be full circles; however, the average observer sees only an arc formed by illuminated droplets above the ground, and centred on a line from the sun to the observer's eye.

In a primary rainbow, the arc shows red on the outer part and violet on the inner side. This rainbow is caused by light being refracted when entering a droplet of water, then reflected inside on the back of the droplet and refracted again when leaving it.

In a double rainbow, a second arc is seen outside the primary arc, and has the order of its colours reversed, with red on the inner side of the arc.

Overview

A rainbow is not located at a specific distance from the observer, but comes from an optical illusion caused by any water droplets viewed from a certain angle relative to a light source. Thus, a rainbow is not an object and cannot be physically approached. Indeed, it is impossible for an observer to see a rainbow from water droplets at any angle other than the customary one of 42 degrees from the direction opposite the light source. Even if an observer sees another observer who seems "under" or "at the end of" a rainbow, the second observer will see a different rainbow—farther off—at the same angle as seen by the first observer.

Tom Clancy's Rainbow Six

Tom Clancy's Rainbow Six is a media franchise created by American author Tom Clancy about a fictional international counter-terrorist unit called "Rainbow." The franchise began with Clancy's novel Rainbow Six, which was adapted into a successful series of tactical first-person shooter video games.

Team Rainbow

Rainbow Six describes Rainbow as an international counter-terrorism operation hosted by NATO and funded by money funneled through the U.S. Department of the Interior.

The base of operations for Rainbow is located in Hereford, England (at the time, home to the SAS), due to the United Kingdom being one of the most accessible countries in the world and having one of the world's foremost special forces units. Most of the characters in Rainbow are American or British, though the NATO countries of France, Germany, Italy, Spain, Canada, and the NATO ally of Israel have at least one representative each.

Tom Clancy's Rainbow Six Siege

Tom Clancy's Rainbow Six Siege is a first-person shooter video game developed by Ubisoft Montreal and published by Ubisoft. Considered as a successor to the now cancelled Tom Clancy's Rainbow 6: Patriots, Siege puts heavy emphasis on environmental destruction and co-operation between players. Unlike previous entries in the series, the title has missions known as "situations" as well as an online mode.

Gameplay

Tom Clancy's Rainbow Six Siege is a first-person tactical shooter, in which players take control of an operator from the Rainbow team, a counter-terrorist unit. Different operators have different races, perks, bombs and gadgets. The game features an asymmetrical structure whereby the teams are not always balanced in their ability choices. The operators belong to the counter-terrorism units SWAT, SAS, GSG-9, Spetsnaz and GIGN, each of which has four operators. Canadian operators from Joint Task Force 2 have been added in a recent update. Players also have access to a "Recruit" operator whose gear and gadgets can be customized. Players pick an operator from any unit before a round starts, and are not allowed to change operators during a round. An in-game shop allows players to purchase operators using the in-game currency "Renown", which is earned from actions performed in-game. Each successive operator that is purchased from a single counter-terrorist unit costs an additional 500 Renown.