Muscle Rack 48″W x 24″D x 72″H 5-Shelf Steel Shelving, Black

24 may refer to:

• 24 (number), the natural number following 23 and preceding 25
• one of the years 24 BC, AD 24, 1924, 2024

48 may refer to:

• 48 (number)
• one of the years 48 BC, AD 48, 1948, 2048
• '48 (novel)
• '48 (magazine)
• "48", a song by Tyler, the Creator from the album Wolf
• 48, a phone network brand of Three Ireland
• "Forty Eight", a song by Karma to Burn from the album V, 2011
• 48 Doris, a main-belt asteroid

5 (five) is a number, numeral and digit. It is the natural number, and cardinal number, following 4 and preceding 6, and is a prime number.

Humans, and many other animals, have 5 digits on their limbs.

72 may refer to:

• 72 (number)
• One of the years 72 BC, AD 72, 1972, 2072
• "72", by James from the album Hey Ma
• 72 Feronia, a main-belt asteroid
• Tatra 72, an army off-road truck
• Audi 72, a compact executive car

Black is a color that results from the absence or complete absorption of visible light. It is an achromatic color, without hue, like white and grey. It is often used symbolically or figuratively to represent darkness. Black and white have often been used to describe opposites such as good and evil, the Dark Ages versus Age of Enlightenment, and night versus day. Since the Middle Ages, black has been the symbolic color of solemnity and authority, and for this reason it is still commonly worn by judges and magistrates.

Black was one of the first colors used by artists in Neolithic cave paintings. It was used in ancient Egypt and Greece as the color of the underworld. In the Roman Empire, it became the color of mourning, and over the centuries it was frequently associated with death, evil, witches, and magic. In the 14th century, it was worn by royalty, clergy, judges, and government officials in much of Europe. It became the color worn by English romantic poets, businessmen and statesmen in the 19th century, and a high fashion color in the 20th century. According to surveys in Europe and North America, it is the color most commonly associated with mourning, the end, secrets, magic, force, violence, fear, evil, and elegance.

Black is the most common ink color used for printing books, newspapers and documents, as it provides the highest contrast with white paper and thus is the easiest color to read. Similarly, black text on a white screen is the most common format used on computer screens. As of September 2019, the darkest material is made by MIT engineers from vertically aligned carbon nanotubes.

D, or d, is the fourth letter of the Latin alphabet, used in the modern English alphabet, the alphabets of other western European languages and others worldwide. Its name in English is dee (pronounced ), plural dees.

H, or h, is the eighth letter of the Latin alphabet, used in the modern English alphabet, including the alphabets of other western European languages and others worldwide. Its name in English is aitch (pronounced , plural aitches), or regionally haitch , plural haitches.

Muscle is a soft tissue, one of the four basic types of animal tissue. Muscle tissue gives skeletal muscles the ability to contract. Muscle is formed during embryonic development, in a process known as myogenesis. Muscle tissue contains special contractile proteins called actin and myosin which interact to cause movement. Among many other muscle proteins, present are two regulatory proteins, troponin and tropomyosin.

Muscle tissue varies with function and location in the body.

In vertebrates, the three types are:

1. skeletal,
2. cardiac (both striated), and
3. smooth muscle (non-striated).

Skeletal muscle tissue consists of elongated, multinucleate muscle cells called muscle fibers, and is responsible for movements of the body. Other tissues in skeletal muscle include tendons and perimysium. Smooth and cardiac muscle contract involuntarily, without conscious intervention. These muscle types may be activated both through the interaction of the central nervous system as well as by receiving innervation from peripheral plexus or endocrine (hormonal) activation. Striated or skeletal muscle only contracts voluntarily, upon the influence of the central nervous system. Reflexes are a form of non-conscious activation of skeletal muscles, but nonetheless arise through activation of the central nervous system, albeit not engaging cortical structures until after the contraction has occurred.

The different muscle types vary in their response to neurotransmitters and hormones such as acetylcholine, noradrenaline, adrenaline, and nitric oxide depending on muscle type and the exact location of the muscle.

Sub-categorization of muscle tissue is also possible, depending on among other things the content of myoglobin, mitochondria, and myosin ATPase etc.

Shelf (pl.: shelves) may refer to:

• Shelf (storage), a flat horizontal surface used for display and storage

Steel is an alloy of iron and carbon with improved strength and fracture resistance compared to other forms of iron. Because of its high tensile strength and low cost, steel is one of the most commonly manufactured materials in the world. Steel is used in buildings, as concrete reinforcing rods, in bridges, infrastructure, tools, ships, trains, cars, bicycles, machines, electrical appliances, furniture, and weapons.

Iron is always the main element in steel, but many other elements may be present or added. Stainless steels, which are resistant to corrosion and oxidation, typically need an additional 11% chromium.

Iron is the base metal of steel. Depending on the temperature, it can take two crystalline forms (allotropic forms): body-centred cubic and face-centred cubic. The interaction of the allotropes of iron with the alloying elements, primarily carbon, gives steel and cast iron their range of unique properties. In pure iron, the crystal structure has relatively little resistance to the iron atoms slipping past one another, and so pure iron is quite ductile, or soft and easily formed. In steel, small amounts of carbon, other elements, and inclusions within the iron act as hardening agents that prevent the movement of dislocations.

The carbon in typical steel alloys may contribute up to 2.14% of its weight. Varying the amount of carbon and many other alloying elements, as well as controlling their chemical and physical makeup in the final steel (either as solute elements, or as precipitated phases), impedes the movement of the dislocations that make pure iron ductile, and thus controls and enhances its qualities. These qualities include the hardness, quenching behaviour, need for annealing, tempering behaviour, yield strength, and tensile strength of the resulting steel. The increase in steel's strength compared to pure iron is possible only by reducing iron's ductility.

Steel was produced in bloomery furnaces for thousands of years, but its large-scale, industrial use began only after more efficient production methods were devised in the 17th century, with the introduction of the blast furnace and production of crucible steel. This was followed by the Bessemer process in England in the mid-19th century, and then by the open-hearth furnace. With the invention of the Bessemer process, a new era of mass-produced steel began. Mild steel replaced wrought iron. The German states were the major steel producers in Europe in the 19th century. American steel production was centered in Pittsburgh, Bethlehem, Pennsylvania, and Cleveland until the late 20th century.

Further refinements in the process, such as basic oxygen steelmaking (BOS), largely replaced earlier methods by further lowering the cost of production and increasing the quality of the final product. Today more than 1.6 billion tons of steel is produced annually. Modern steel is generally identified by various grades defined by assorted standards organizations. The modern steel industry is one of the largest manufacturing industries in the world, but also one of the most energy and greenhouse gas emission intense industries, contributing 8% of global emissions. However, steel is also very reusable: it is one of the world's most-recycled materials, with a recycling rate of over 60% globally.

W, or w, is the twenty-third letter of the Latin alphabet, used in the modern English alphabet, the alphabets of other western European languages and others worldwide. Its name in English is double-u, plural double-ues.

X, or x, is the twenty-fourth letter of the Latin alphabet, used in the modern English alphabet, the alphabets of other western European languages and others worldwide. Its name in English is ex (pronounced ), plural exes.