Electronic device that operates on the basis of the electric, magnetic, or optical properties of a solid material, especially one that uses a solid crystal in which an orderly three-dimensional arrangement of atoms, ions, or molecules is repeated throughout the entire crystal. Synthetic crystals of elements such as silicon, gallium arsenide, and germanium are used in transistors, rectifiers, and integrated circuits. The first solid-state device was the “cat's whisker” (1906), in which a fine wire was moved across a solid crystal to detect a radio signal. Seealso semiconductor.
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Any of various tools and instruments that generate and use compressed air. Examples include rock drills, pavement breakers, riveters, forging presses, paint sprayers, blast cleaners, and atomizers. Compressed-air power is flexible, economical, and safe. In general, pneumatic systems have relatively few moving parts, contributing to high reliability and low maintenance costs.
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A seal can mean a wax seal bearing an impressed figure, or an embossed figure in paper, with the purpose of authenticating a document, but the term can also mean any device for making such impressions or embossments, essentially being a mould that has the mirror image of the figure in counter-relief, such as mounted on rings known as signet rings. This article is concerned with devices and methods for making such imprints.
If the imprint is made as a relief resulting from the greater pressure on the paper where the high parts of the seal touch, the seal is known as a dry seal; in all other cases a liquid or liquified medium (such as ink or wax) is used, usually in another color than the paper's.
Sigillography is the term used for the study of seals.
The use of seals, in wax, in lacquer or embossed on paper, to authenticate documents, is a practice as old as writing itself. Seals of this nature were applied directly to the face of the document or attached to the document by cords in the owner's, or to a narrow strip of the document sliced and folded down as a tail but not detached from the document. This helped maintain authenticity by not allowing the reuse of the seal. If a forger tried to remove the seal in the first case, it would break. In the other cases, although the forger could remove the seal intact by ripping the cords from the paper, he would still have to separate the cords to attach it to another document, which would destroy the seal as well because the cords had knots tied in them inside the wax seal. Most governments still attach seals to letters patent. While many instruments required seals for validity (i.e. the deed or covenant) it is rather uncommon for private citizens to use seals anymore.
Seals were also applied to letters and parcels to indicate whether or not the item had been opened since the seal was applied. Seals were used both to seal the item to prevent tampering, as well as to provide proof that the item was actually from the sender and is not a forgery. To seal a letter, for example, a letter writer would compose the letter, fold it over, pour wax over the joint formed by the top of the page of paper, and then impress a ring, metal stamp, or other device. Governments would often send letters to citizens under the governmental seal for their eyes only. These were called letters secret. Seals are no longer commonly used in this way, except for ceremonial purposes.
The most common uses of the seal today are:
Recently, seals have come to light in South Arabia datable to the Himyarite age. One example shows a name written in Aramaic (Yitsḥaq bar Ḥanina) and engraved in reverse so as to be visible in the impression.
In the Indus Valley Civilization, rectangular seals were used to label trade goods and also had other purposes.
Known as 印章 (Pinyin: yin4zhang1) in China, dojang or ingam in Korea and inkan or hanko in Japan, ink seals have been used in East Asia as a form of written identification since the invention of writing. Even in modern times, seals are still commonly used instead of handwritten signatures to authenticate official documents or financial transactions. Both individuals and organizations have official seals, and they often have multiple seals in different sizes and styles for different situations. East Asian seals usually bear the name of the person or organization represented, but they can also bear a poem or a personal motto. Sometimes both types of seals, or one large seal that bears a name and a motto, are used to authenticate official documents. Seals are so important in East Asia that foreigners who frequently conduct business there also commission the engraving of a personal seal.
East Asian seals are carved from a variety of hard materials, including wood, soapstone, seaglass and jade. East Asian seals are traditionally used with a red oil-based paste consisting of finely ground cinnabar, which contrasts with the black ink traditionally used for the ink brush. Red chemical inks are more commonly used in modern times for sealing documents. Seal engraving is considered a form of calligraphy in East Asia. Like ink brush calligraphy, there are several styles of engraving. Some engraving styles emulate calligraphy styles, but many styles are so highly stylized that the characters represented on the seal are difficult for untrained readers to identify. Seal engravers are considered artists, and in the past, several famous calligraphers also became famous as engravers. Some seals, carved by famous engravers, or owned by famous artists or political leaders, have become valuable as works of art and history.
Because seals are commissioned by individuals and carved by artists, every seal is unique, and engravers often personalize the seals they create. The material of seal and the style of the engraving are typically matched to the personality of the owner. Seals can be traditional or modern, conservative or expressive. Seals are sometimes carved with a figure on the owner's zodiac animal on the top of the seal. Seals are also sometimes carved with images or calligraphy on the sides.
Although it is a utilitarian instrument of daily business in East Asia, Westerners and other non-Asians seldom see Asian seals except on Asian paintings and works of calligraphy. All traditional paintings in China, Japan, Korea, Vietnam, and the rest of East Asia are watercolor paintings on silk, paper, or some other surface that the red ink from seals can adhere to. East Asian paintings often bear multiple seals, including one or two seals from the artist, and the seals from the owners of the painting.
East Asian seals are the predecessors to block printing.
Signet rings, generally bearing a coat of arms, are made by intaglio engraving, either in metal or gems (generally semiprecious). Agate is a frequent material, especially carnelian or banded agate like sardonyx; the banding make the impression contrast with the ground.
Metal signet rings can also be cast, which is cheaper but yields a weaker material.
The wearing of signet rings (from Latin "signum" meaning sign) is a longstanding tradition among nobles in European and some other cultures. In contemporary usage, the signet ring is typically worn on the little finger of either the right or left hand (depending on the country), although some countries have different customs (French and German noblemen, and some Spanish nobles wear it on the ring finger of their left hand; Swiss wear it on the ring finger of their right hand). In the United Kingdom, signet rings are typically worn on the little finger of the left hand of the bearer and tend to be cast of gold. The ring should be worn with the seal facing outwards to enable wax impressions without removing the ring.
Because it is used to attest the authority of its bearer, the ring has also been seen as a symbol of his power, which is one explanation for its inclusion in the regalia of certain monarchies. After the death of a Pope, the smashing of his signet ring is a prescribed act clearing the way for the sedevacancy and subsequent election of a new Pope.
The wearing of a signet ring is declining as the European aristocracy diminishes, however noble families have upheld long standing traditions of wearing signet rings for centuries. Sometimes the initials of the individual are engraved into the ring if the person is not of noble descent and does not have the right to bear arms.
Later ecclesiastical synods require that letters under the bishop's seal should be given to priests when for some reason they lawfully quit their own proper diocese. So it was enacted at Chalon-sur-Saône in 813. Pope Nicholas I in the same century complains that the bishops of Dôle and Reims had contra morem sent their letters to him unsealed (Jaffé, "Regesta", nn. 2789, 2806, 2823). The custom of bishops possessing seals may from this date be assumed to have been pretty general. At first they were only used for securing the document from impertinent curiosity and the seal was commonly attached to the ties with which it was fastened. When the letter was opened by the addressee, the seal was necessarily broken. Later the seal served as an authentication and was attached to the face of the document. The deed was thus only held to be valid so long as the seal remained intact. It soon came to follow from this point of view that not only real persons like kings and bishops, but also every kind of body corporate, cathedral chapters, municipalities, monasteries etc., also required a common seal to validate the acts which were executed in their name.
During the early Middle Ages seals of lead, or more properly "bullae" (from the Latin for lead), were in common use both in East and West, but except in the case of the papal chancery, these leaden authentications soon went out of favour in western Christendom and it became the universal practice to take the impressions in wax. In England hardly any waxen seals have survived of earlier date than the Norman Conquest. In the British Museum collection the earliest bishop's seals preserved are those of William of St. Carileph, Bishop of Durham (1081-96) and of St. Anselm, Archbishop of Canterbury (1093-1109). The importance of the seal as a means of authentication necessitated that when authority passed into new hands the old seal should be destroyed and a new one made. When the pope dies it is the first duty of the Cardinal Camerlengo to obtain possession of the Fisherman's Ring, the papal signet, and to see that it is broken up. A similar practice prevailed in the Middle Ages and it is often alluded to by historians, as it seems to have been a matter of some ceremony. Thus we are concisely told: "There died in this year Robert de Insula, Bishop of Durham. After his burial, his seal was publicly broken up in the presence of all by Master Robert Avenel." (Histor. Dunel. Scrip. Tres., p. 63). Matthew Paris gives a similar description of the breaking of the seal of William of Trumpington, Abbot of St Albans, in 1235.
A related practice is found among blacksmiths: their touchmark (a stamp used on the hot metal to show who made it) is destroyed upon their death.
The expression "Seal of Approval" refers to a formal approval, regardless whether it involves a seal or other external marking, by an authoritative person or institute.
It is also part of the formal name of certain quality marks, such as: