A proton is a stable subatomic particle, symbol
p
, H+, or 1H+ with a positive electric charge of +1 e (elementary charge). Its mass is slightly less than that of a neutron and 1,836 times the mass of an electron (the proton-to-electron mass ratio). Protons and neutrons, each with masses of approximately one atomic mass unit, are jointly referred to as "nucleons" (particles present in atomic nuclei).
The gravitational constant, denoted by the capital letter G, is an empirical physical constant involved in the calculation of gravitational effects in Sir Isaac Newton's law of universal gravitation and in Albert Einstein's theory of general relativity.
The dalton or unified atomic mass unit is a non-SI unit of mass defined as 1/12 of the mass of an unbound neutral atom of carbon-12 in its nuclear and electronic ground state and at rest. The atomic mass constant, denoted mu, is defined identically, giving mu = 1/12 m(12C) = 1 Da.
The Digital Signature Algorithm (DSA) is a public-key cryptosystem and Federal Information Processing Standard for digital signatures, based on the mathematical concept of modular exponentiation and the discrete logarithm problem. DSA is a variant of the Schnorr and ElGamal signature schemes.
The Washington Monument is an obelisk on the National Mall in Washington, D.C., built to commemorate George Washington, a Founding Father of the United States, victorious commander-in-chief of the Continental Army from 1775 to 1783 in the American Revolutionary War, and the first President of the United States from 1789 to 1797. Standing east of the Reflecting Pool and the Lincoln Memorial, the monument, made of marble, granite, and bluestone gneiss, is both the world's tallest predominantly stone structure and the world's tallest obelisk, standing 554 feet 7+11⁄32 inches (169.046 m) tall, according to the U.S. Geodetic Survey measurements in 2013–2014. It is the tallest monumental column in the world if all are measured above their pedestrian entrances. It was the world's tallest structure between 1884 and 1889, after which it was overtaken by the Eiffel Tower, in Paris. Previously, the tallest structure was the Cologne Cathedral.
Stonemasonry or stonecraft is the creation of buildings, structures, and sculpture using stone as the primary material. Stonemasonry is the craft of shaping and arranging stones, often together with mortar and even the ancient lime mortar, to wall or cover formed structures.
Mortar is a workable paste which hardens to bind building blocks such as stones, bricks, and concrete masonry units, to fill and seal the irregular gaps between them, spread the weight of them evenly, and sometimes to add decorative colors or patterns to masonry walls. In its broadest sense, mortar includes pitch, asphalt, and soft mud or clay, as those used between mud bricks, as well as cement mortar. The word "mortar" comes from Old French mortier, "builder's mortar, plaster; bowl for mixing." (13c.).
The Gallarus Oratory (Irish: Séipéilín Ghallarais, Gallarus being interpreted as either 'rocky headland' or 'house or shelter for foreigner ' is a chapel on the Dingle Peninsula, County Kerry, Ireland. It has been presented variously as an early-Christian stone church by antiquary Charles Smith, in 1756; a 12th-century Romanesque church by archaeologist Peter Harbison in 1970; a shelter for pilgrims by the same in 1994. The local tradition prevalent at the time of Charles Smith attributed it to one Griffith More, being a funerary chapel built by him or his family at their burial place.
Building material is material used for construction. Many naturally occurring substances, such as clay, rocks, sand, wood, and even twigs and leaves, have been used to construct buildings. Apart from naturally occurring materials, many man-made products are in use, some more and some less synthetic. The manufacturing of building materials is an established industry in many countries and the use of these materials is typically segmented into specific specialty trades, such as carpentry, insulation, plumbing, and roofing work. They provide the make-up of habitats and structures including homes.
Retaining walls are relatively rigid walls used for supporting soil laterally so that it can be retained at different levels on the two sides. Retaining walls are structures designed to restrain soil to a slope that it would not naturally keep to. They are used to bound soils between two different elevations often in areas of terrain possessing undesirable slopes or in areas where the landscape needs to be shaped severely and engineered for more specific purposes like hillside farming or roadway overpasses. A retaining wall that retains soil on the backside and water on the frontside is called a seawall or a bulkhead.
Cordwood construction is a term used for a natural building method in which short logs are piled crosswise to build a wall, using mortar or cob to permanently secure them. This technique can use local materials at minimal cost.
The heating value of a substance, usually a fuel or food, is the amount of heat released during the combustion of a specified amount of it.
Repointing is the process of renewing the pointing, which is the external part of mortar joints, in masonry construction. Over time, weathering and decay cause voids in the joints between masonry units, usually in bricks, allowing the undesirable entrance of water. Water entering through these voids can cause significant damage through frost weathering and from salt dissolution and deposition. Repointing is also called pointing, or pointing up, although these terms more properly refer to the finishing step in new construction.
NIST-F1 is a cesium fountain clock, a type of atomic clock, in the National Institute of Standards and Technology (NIST) in Boulder, Colorado, and serves as the United States' primary time and frequency standard. The clock took less than four years to test and build, and was developed by Steve Jefferts and Dawn Meekhof of the Time and Frequency Division of NIST's Physical Measurement Laboratory.
Lime mortar or torching is a masonry mortar composed of lime and an aggregate such as sand, mixed with water. It is one of the oldest known types of mortar, used in ancient Rome and Greece, when it largely replaced the clay and gypsum mortars common to ancient Egyptian construction.
Stone walls are a kind of masonry construction that has been used for thousands of years. The first stone walls were constructed by farmers and primitive people by piling loose field stones into a dry stone wall. Later, mortar and plaster were used, especially in the construction of city walls, castles, and other fortifications before and during the Middle Ages. These stone walls are spread throughout the world in different forms. One of the best example is the Cyclopean Wall in Rajgir, India.
Structural dampness is the presence of unwanted moisture in the structure of a building, either the result of intrusion from outside or condensation from within the structure. A high proportion of damp problems in buildings are caused by ambient climate dependent factors of condensation and rain penetration. Capillary penetration of fluid from the ground up through concrete or masonry is known as "rising damp" and is governed by the shape and porosity of the construction materials through which this evaporation-limited capillary penetration takes place. Structural damp, regardless of the mechanisms through which it takes place, is exacerbated by higher levels of humidity.
The Mortier de 58 mm type 2 or Mortier de 58 mm T N°2, also known as the Crapouillot or "little toad" from its appearance, was the standard French medium trench mortar of World War I.
An atomic clock is a clock that measures time by monitoring the resonant frequency of atoms. It is based on atoms having different energy levels. Electron states in an atom are associated with different energy levels, and in transitions between such states they interact with a very specific frequency of electromagnetic radiation. This phenomenon serves as the basis for the International System of Units' (SI) definition of a second:
The second, symbol s, is the SI unit of time. It is defined by taking the fixed numerical value of the caesium frequency, , the unperturbed ground-state hyperfine transition frequency of the caesium 133 atom, to be 9192631770 when expressed in the unit Hz, which is equal to s−1.
The 12-inch coast defense mortar was a weapon of 12-inch (305 mm) caliber emplaced during the 1890s and early 20th century to defend US harbors from seaborne attack. In 1886, when the Endicott Board set forth its initial plan for upgrading the coast defenses of the United States, it relied primarily on mortars, not guns, to defend American harbors. Over the years, provision was made for fortifications that would mount some 476 of these weapons, although not all of these tubes were installed. Ninety-one of these weapons were remounted as railway artillery in 1918-1919, but this was too late to see action in World War I. The railway mortars were only deployed in small quantities, and none overseas. The fixed mortars in the Philippines saw action in the Japanese invasion in World War II. All of the fixed mortars in the United States were scrapped by 1944, as new weapons replaced them, and the railway mortars were scrapped after the war. Today, the only remaining mortars of this type in the 50 states are four at Battery Laidley, part of Fort Desoto near St. Petersburg, Florida, but the remains of coast defense mortar emplacements can be seen at many former Coast Artillery forts across the United States and its former territories. Additional 12-inch mortars and other large-caliber weapons remain in the Philippines.
