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Concentric eyewalls seen in Typhoon Haima as it travels west across the Pacific Ocean.. In meteorology, eyewall replacement cycles, also called concentric eyewall cycles, naturally occur in intense tropical cyclones with maximum sustained winds greater than 33 m/s (64 kn; 119 km/h; 74 mph), or hurricane-force, and particularly in major hurricanes of Saffir–Simpson category 3 to 5.
In tropical cyclones maximum wind speed of the storm, which occurs at the eyewall, is a primary indicator of its overall strength which is important in predicting overall intensity. Just beyond this eyewall is a moat which separates the inner rainbands (eventually the outer eyewall) from the (inner) eyewall.
drawing of a cone cell showing the invaginations of the outer segment that form the 'discs' Disc shedding is the process by which photoreceptor cells in the retina are renewed. The disc formations in the outer segment of photoreceptors, which contain the photosensitive opsins , are completely renewed every ten days.
In most cases, the outer eyewall begins to contract soon after its formation, which chokes off the inner eye and leaves a much larger but more stable eye. While the replacement cycle tends to weaken storms as it occurs, the new eyewall can contract fairly quickly after the old eyewall dissipates, allowing the storm to re-strengthen.
Dilated fundus examination (DFE) is a diagnostic procedure that uses mydriatic eye drops to dilate or enlarge the pupil in order to obtain a better view of the fundus of the eye. [1] Once the pupil is dilated, examiners use ophthalmoscopy to view the eye's interior, which makes it easier to assess the retina , optic nerve head , blood vessels ...
The visual cycle is a process in the retina that replenishes the molecule retinal for its use in vision. Retinal is the chromophore of most visual opsins, meaning it captures the photons to begin the phototransduction cascade. When the photon is absorbed, the 11-cis retinal photoisomerizes into all-trans retinal as it is ejected from the opsin ...
Visual phototransduction is the sensory transduction process of the visual system by which light is detected by photoreceptor cells (rods and cones) in the vertebrate retina.A photon is absorbed by a retinal chromophore (each bound to an opsin), which initiates a signal cascade through several intermediate cells, then through the retinal ganglion cells (RGCs) comprising the optic nerve.
The Parks–Bielschowsky three-step test, [1] also known as Park's three-step test or Bielschowsky head tilt test, [2] is a method used to isolate the paretic extraocular muscle, particularly superior oblique muscle and trochlear nerve (fourth cranial nerve), [3] in acquired vertical double vision. [4] It was originally described by Marshall M ...