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Phase response curves for light and for melatonin administration. In humans and animals, there is a regulatory system that governs the phase relationship of an organism's internal circadian clock to a regular periodicity in the external environment (usually governed by the solar day).
A Morse code light is light in which appearances of light of two clearly different durations (dots and dashes) are grouped to represent a character or characters in the Morse Code. For example, "Mo(A)" is a light in which in each period light is shown for a short period (dot) followed by a long period (dash), the Morse Code for "A".
A sinus rhythm is any cardiac rhythm in which depolarisation of the cardiac muscle begins at the sinus node. [1] It is necessary, but not sufficient, for normal electrical activity within the heart. [2] On the electrocardiogram (ECG), a sinus rhythm is characterised by the presence of P waves that are normal in morphology. [2]
He also cautions against taking the mere repetition of a movement to indicate a rhythm. The object of rhythmanalysis is to access the obscure property of the rhythm called ‘presence.’ The sensory events through which the rhythmanalyst perceives the rhythm are called ‘simulacra,’ or simply ‘the present.’ The need for rhythmanalysis ...
Wiggers diagram of various events of a cardiac cycle, with 2nd heart sound at bottom.. A split S2 is a finding upon auscultation of the S2 heart sound. [1]It is caused when the closure of the aortic valve (A 2) and the closure of the pulmonary valve (P 2) are not synchronized during inspiration.
An idioventricular rhythm is a cardiac rhythm characterized by a rate of <50 beats per minute (bpm), absence of conducted P waves and widening of the QRS complex. [1] In cases where the heart rate is between 50 and 110 bpm, it is known as accelerated idioventricular rhythm and ventricular tachycardia if the rate exceeds 120 bpm.
In vertebrates, the master circadian clock is contained within the suprachiasmatic nucleus (SCN), a bilateral nerve cluster of about 20,000 neurons. [10] [11] The SCN itself is located in the hypothalamus, a small region of the brain situated directly above the optic chiasm, where it receives input from specialized photosensitive ganglion cells in the retina via the retinohypothalamic tract.
The Code Book: The Science of Secrecy from Ancient Egypt to Quantum Cryptography is a book by Simon Singh, published in 1999 by Fourth Estate and Doubleday. The Code Book describes some illustrative highlights in the history of cryptography , drawn from both of its principal branches, codes and ciphers .