A photomicrograph thin section of the aggregate is featured above. Aeolian lava is studied to understand how magma forms at depth and the level of risk of its eruption. This particular glomerocryst is made of two minerals; plagioclase and pyroxene, whose chemical compositions, textures and melt inclusions help decipher just what happens in a magma chamber.
But, if you look closely at its shape, you might learn something more — that even something as hard as a rock has a heart. — Bernardo Cesare
A Cardiod, a lovely mathsy heart shape, can be constructed as shown in the animation as the combination of many circles generated from a single underlying circle. This shape describes the sensitivity regions of many directional microphones. [more] [code]
Sinus pause describes a condition where the SA node fails to generate an electrical impulse for what is generally a brief period of time. In the above example, the initial rate is 88 beats per minute (the first two beats are normal), then there is a 1.8 second sinus pause before the heart resumes, initially at a somewhat slower rate of 52 beats per minute. A related rhythm is SA block which is often hard to distinguish from a sinus pause. In SA block, the SA node creates an impulse, but it is blocked from leaving the SA node. The differences are beyond the scope of this discussion.
Patients who have sinus pauses may complain of missed or skipped beats, flutters, palpitations, hard beats or may feel faint, dizzy or lightheaded or experience a syncopal episode (passing out). Frequent pauses would heighten these symptoms. This is a result of patients actually missing or dropping beats. Obviously, if the heart misses a beat, blood does not flow during that time period resulting in a lack of oxygen or perfusion throughout the body.
Treatment and prognosis depend on the cause and cardiac status of the patient. This condition may be drug induced or it may be a result of cardiac disease. Treatment may involve the use of medications or the use of a temporary or permanent pacemaker.
Photographer Julien Girard drew the heart in the air with a tiny flashlight at ESO’s Paranal Observatory in northern Chile. The VLT telescopes are barely visible on the hill at lower right. This image was taken in October 2011 and released for Valentine’s Day on Feb. 13, 2012.
These microscopy images demonstrate the effects of Notch signalling on the hearts of newborn mice (top) and of adult mice after a heart attack (bottom). In a normal neonatal heart (top left), the two major heart chambers (ventricles) are clearly separated by tissue (septum). But when Notch signalling was inactivated in an embryo’s heart muscle cells, the septum between the ventricles of the newborn mouse’s heart was incomplete (asterisk). The same defect commonly occurs in humans with congenital heart disease, often leading to circulatory distress. In the images of adult hearts (bottom), healthy tissue is shown in red and damaged tissue in blue. Normally (bottom left), a heart attack causes extensive tissue damage to the left ventricle (right-hand cavity), but mice in which Notch was re-activated after the heart attack had reduced tissue damage (bottom right) and improved cardiac function.
Continuing with the heart, today we have two words: systole and diastole. Both entered Modern English around 1570, a time of great advances in medicine and science. Both words use the Ancient Greek stellein meaning to contract. Adding the prefix dia- gave the Ancient Greek word diastellein meaning to make ready or prepare. Adding the prefix syn- gave the Ancient Greek word systole meaning contraction. English doctor William Harvey and his medical professor Hieronymous Fabricius worked out the movement of blood through the atria and ventricles. Two things slowed their progress-inability to see the action of the valves that keep blood flowing in one direction and inability to see the microscopic aterioles and venules (capillaries that act as the transfer point between oxygen rich blood entering a cell and the oxygen depleted and carbon dioxide laden blood leaving the cell). Today measure of systole and diastole as blood pressure is one of the key vital signs of health.
The bioluminescent algae Noctiluca scintillans is also known as “sea sparkle” because of its magical appearance. These dinoflagellates become illuminated when they are disturbed by motion in the water — whether it’s the result of natural waves or a fish swimming by. The above romantic “light display” was created by the photographer moving an object through the water in a heart shape.
Located in the Perseus arm of the Galaxy in the constellation Cassiopeia. This is an emission nebula showing glowing gas and darker dust lanes. The nebula is formed by plasma of ionized hydrogen and free electrons. The nebula’s intense red output and its configuration are driven by the radiation emanating from a small group of stars near the nebula’s center.