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In organic chemistry, organocatalysis is a form of catalysis in which the rate of a chemical reaction is increased by an organic catalyst. This "organocatalyst" consists of carbon , hydrogen , sulfur and other nonmetal elements found in organic compounds.
In the legs, bypass grafting is used to treat peripheral vascular disease, acute limb ischemia, aneurysms and trauma.While there are many anatomical arrangements for vascular bypass grafts in the lower extremities depending on the location of the disease, the principle is the same: to restore blood flow to an area without normal flow.
A. Pelvic and lower extremity radiograph shows extensive calcification of the femoral arteries. B. Translumbar aortography shows near-total obstruction of the femoral arteries. Mönckeberg's arteriosclerosis, or Mönckeberg's sclerosis, is a non-inflammatory form of arteriosclerosis (artery hardening), which differs from atherosclerosis ...
Within the area of organocatalysis, (thio)urea organocatalysis describes the use of ureas and thioureas to accelerate and stereochemically alter organic transformations. The effects arise through hydrogen-bonding interactions between the substrate and the (thio)urea.
Proline organocatalysis is the use of proline as an organocatalyst in organic chemistry. This theme is often considered the starting point for the area of organocatalysis, even though early discoveries went unappreciated. [1] Modifications, such as MacMillan’s catalyst and Jorgensen's catalysts, proceed with excellent stereocontrol. [2]: 5574 [3]
The smaller arteries and arterioles have higher resistance, and confer the main blood pressure drop across major arteries to capillaries in the circulatory system. Illustration demonstrating how vessel narrowing, or vasoconstriction, increases blood pressure. In the arterioles blood pressure is lower than in the major arteries.
The tunica media may (especially in arteries) be rich in vascular smooth muscle, which controls the caliber of the vessel. Veins do not have the external elastic lamina, but only an internal one. The tunica media is thicker in the arteries rather than the veins. The outer layer is the tunica adventitia and the thickest layer in veins. It is ...
Hydrogen-bond catalysis is a type of organocatalysis that relies on use of hydrogen bonding interactions to accelerate and control organic reactions. In biological systems, hydrogen bonding plays a key role in many enzymatic reactions, both in orienting the substrate molecules and lowering barriers to reaction. [ 1 ]