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Sildenafil, sold under the brand name Viagra, among others, is a medication used to treat erectile dysfunction and pulmonary arterial hypertension. [4] [8] It is also sometimes used off-label for the treatment of certain symptoms in secondary Raynaud's phenomenon. [9]
Khelif was born in Aïn Sidi Ali, Laghouat Province. [11] [12] When she was two months old, her family moved to Biban Mesbah, a rural village in Tiaret Province, where she would grow up.
The four pigments in a bird's cone cells (in this example, estrildid finches) extend the range of color vision into the ultraviolet. [1]Tetrachromacy (from Greek tetra, meaning "four" and chroma, meaning "color") is the condition of possessing four independent channels for conveying color information, or possessing four types of cone cell in the eye.
The word purpura (/ ˈ p ɜːr p ɜːr ə /) comes from Latin purpura, "purple", which came from ancient Greek πορφύρα. Purpura is a mass noun naming the condition or state, not the name of an individual spot (thus there is no *purpurum, *purpura or *purpura, *purpurae count declension).
Fermentation can only occur in an anaerobic (oxygen-free) environment. The evolution of photosynthesis made it possible for cells to derive energy from the Sun. [106]: 377 Most of the life that covers the surface of the Earth depends directly or indirectly on photosynthesis.
Cats have excellent night vision and can see at one sixth the light level required for human vision. [ 53 ] : 43 This is partly the result of cat eyes having a tapetum lucidum , which reflects any light that passes through the retina back into the eye, thereby increasing the eye's sensitivity to dim light. [ 69 ]
The Gibbs free energy relates the tendency of a physical or chemical system to simultaneously lower its energy and increase its disorder, or entropy, in a spontaneous natural process. Gibbs's approach allows a researcher to calculate the change in free energy in the process, such as in a chemical reaction, and how fast it will happen.
Although the concept of correlated color temperature extends the definition to any visible light, the color temperature of a green or a purple light rarely is useful information. Color temperature is conventionally expressed in kelvins, using the symbol K, a unit for absolute temperature.