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Movements, leaders, victories and the continuing fight for equality.
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Meet the people whose lives, choices and achievements shaped the journey.
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Wilmington, North Carolina once had a thriving Black middle class and an elected interracial government. In 1898 white supremacists used violence to overthrow that government, kill Black residents and drive many others from the city.
MORE →Reflects the personal views, recollections, and perspective of the author, Mike Davis.
This is a personal recollection on the Move fire on May 13, 1985
Diamond Reef System is a diving curriculum and safety program that uses a portable obstacle course to simulate reef structure for diver buoyancy skill training. It was founded by Peter Wallingford in 1989 to educate scuba divers on how to interact with coral reefs.[1] The program was adopted by the Environmental Protection Agency and the National Oceanic and Atmospheric Administration.[2]
In 1989, Peter Wallingford started a conservation organization called "Friends of the Reef" in response to customers of his store complaining about the state of the coral reefs.[3] He created an underwater obstacle course for buoyancy-control training, which was made of PVC pipe hoops shaped like diamonds.[4][5] The program was adopted by the National Oceanic Atmospheric Administration in 1989.[2] By 1991, Diamond Reef System had developed into an instructional program under the company, Buoyancy Training Systems, Inc.[3] Diamond Reef System was adopted into the Environmental Protection Agency's divers program in 1991.[2] It also received recognition from the University of California at Los Angeles diving program, University of North Carolina diving program and National Association of Underwater Instructors.[3]
The obstacle course kit for buoyancy training includes a set of buoyant hoops, each with a cord for tethering to a weight on the bottom, and a line holder to store the cord and adjust its operating length. Several alternative hoop geometries are covered in the patents (circular, triangular, octagonal and rectangular are mentioned),[6] but the one recommended and generally used is a square in a diamond-shaped orientation, tethered by a corner, allowing the open corner to float upwards. This is considered by the designer to be the most efficient shape considering the diver and equipment passing through the hoop. It also minimizes the amount of material and work required for an effective target, and the diamond configuration has better underwater stability than the other configurations.[7] Standard sized diamond hoops include 39 inches (1.0 m) and 48 inches (1.2 m) side lengths. These hoops can be made from any suitable material, but 1 inch (25 mm) diameter PVC pipe has been found adequate.
The target hoop is assembled from straight tubular sections with open ends connected by right angle elbows and the unconnected ends sealed by plugs or caps. The assembly can be glued together or held together by internal shock cord, allowing dislocation of the joints for compact storage.[6] The unconnected corner is generally deployed as the high point of the hoop and it allows a diver to escape upwards if unable to pass through the hoop.[6]
Slalom, escalator and rollercoaster obstacle course layouts can be laid out using the kit components. These courses are intended to be set up for buoyancy training in quiet, safe water with little or no current and more than fifteen feet of visibility. The recommended minimum depth of the water is 30 feet (9 m), allowing for a 10 feet (3 m) stop as the shallowest part of the obstacle course. A standard set comprises five identical hoops.[7]
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The system can be used for training and assessing diver buoyancy control and maneuvering skills.
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Diamond Reef System is a diving curriculum and safety program that uses a portable obstacle course to simulate reef structure for diver buoyancy skill training. It was founded by Peter Wallingford in 1989 to educate scuba divers on how to interact with coral reefs. The program was adopted by the Environmental Protection Agency and the National Oceanic and Atmospheric Administration.
A reef is a ridge or shoal of rock, coral, or similar relatively stable material lying beneath the surface of a natural body of water. Many reefs result from natural, abiotic (non-living) processes such as deposition of sand or wave erosion planing down rock outcrops. However, reefs such as the coral reefs of tropical waters are formed by biotic (living) processes, dominated by corals and coralline algae. Artificial reefs, such as shipwrecks and other man-made underwater structures, may occur intentionally or as the result of an accident. These are sometimes designed to increase the physical complexity of featureless sand bottoms to attract a more diverse range of organisms. They provide shelter to various aquatic animals which help prevent extinction. Another reason reefs are put in place is for aquaculture, and fish farmers who are looking to improve their businesses sometimes invest in them. Reefs are often quite near to the surface, but not all definitions require this. Earth's largest coral reef system is the Great Barrier Reef in Australia, at a length of over 2,300 kilometres (1,400 miles).
In vertebrates, the circulatory system is a system of organs that includes the heart, blood vessels, and blood which is circulated throughout the body. It includes the cardiovascular system, or vascular system, that consists of the heart and blood vessels (from Greek kardia meaning heart, and Latin vascula meaning vessels). The circulatory system has two divisions, a systemic circulation or circuit, and a pulmonary circulation or circuit. Some sources use the terms cardiovascular system and vascular system interchangeably with circulatory system. The network of blood vessels are the great vessels of the heart including large elastic arteries, and large veins; other arteries, smaller arterioles, capillaries that join with venules (small veins), and other veins. The circulatory system is closed in vertebrates, which means that the blood never leaves the network of blood vessels. Many invertebrates such as arthropods have an open circulatory system with a heart that pumps a hemolymph which returns via the body cavity rather than via blood vessels. Diploblasts such as sponges and comb jellies lack a circulatory system. Blood is a fluid consisting of plasma, red blood cells, white blood cells, and platelets; it is circulated around the body carrying oxygen and nutrients to the tissues and collecting and disposing of waste materials. Circulated nutrients include proteins and minerals and other components include hemoglobin, hormones, and gases such as oxygen and carbon dioxide. These substances provide nourishment, help the immune system to fight diseases, and help maintain homeostasis by stabilizing temperature and natural pH. In vertebrates, the lymphatic system is complementary to the circulatory system. The lymphatic system carries excess plasma (filtered from the circulatory system capillaries as interstitial fluid between cells) away from the body tissues via accessory routes that return excess fluid back to blood circulation as lymph. The lymphatic system is a subsystem that is essential for the functioning of the blood circulatory system; without it the blood would become depleted of fluid. The lymphatic system also works with the immune system. The circulation of lymph takes much longer than that of blood and, unlike the closed (blood) circulatory system, the lymphatic system is an open system. Some sources describe it as a secondary circulatory system. The circulatory system can be affected by many cardiovascular diseases. Cardiologists are medical professionals who specialise in the heart, and cardiothoracic surgeons specialise in operating on the heart and its surrounding areas. Vascular surgeons focus on disorders of the blood vessels, and lymphatic vessels.
A coral reef is an underwater ecosystem characterized by reef-building corals. Reefs are formed of colonies of coral polyps held together by calcium carbonate. Most coral reefs are built from stony corals, whose polyps cluster in groups. Coral belongs to the class Anthozoa in the animal phylum Cnidaria, which includes sea anemones and jellyfish. Unlike sea anemones, corals secrete hard carbonate exoskeletons that support and protect the coral. Most reefs grow best in warm, shallow, clear, sunny, and agitated water. Coral reefs first appeared 485 million years ago, at the dawn of the Early Ordovician, displacing the microbial and sponge reefs of the Cambrian. Sometimes called rainforests of the sea, shallow coral reefs form some of Earth's most diverse ecosystems. They occupy less than 0.1% of the world's ocean area, about half the area of France. Yet, they provide a home for at least 25% of all marine species, including fish, mollusks, worms, crustaceans, echinoderms, sponges, tunicates and other cnidarians. Coral reefs flourish in ocean waters that provide few nutrients. They are most commonly found at shallow depths in tropical waters, but deep water and cold water coral reefs exist on smaller scales in other areas. Shallow tropical coral reefs have declined by 50% since 1950, partly because they are sensitive to water conditions. They are under threat from excess nutrients (nitrogen and phosphorus), rising ocean heat content and acidification, overfishing (e.g., from blast fishing, cyanide fishing, spearfishing on scuba), sunscreen use, and harmful land-use practices, including runoff and seeps (e.g., from injection wells and cesspools). Coral reefs deliver ecosystem services for tourism, fisheries, and shoreline protection. The annual global economic value of coral reefs has been estimated at anywhere from US$30–375 billion (1997 and 2003 estimates) to US$2.7 trillion (a 2020 estimate) to US$9.9 trillion (a 2014 estimate).
Before the 1921 destruction of Tulsa’s Greenwood District, Black residents had created a remarkable center of business and community life. The district included stores, professional offices, entertainment venues and homes owned by Black citizens. Understanding Greenwood means learning what was built—not only what was burned.
MORE →Shirley Chisholm, elected in 1968.
