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Preservation Of Magnetic Audiotape
Preservation of magnetic audiotape comprises techniques for handling, cleaning and storage of magnetic audiotapes in an archival repository. Multiple types of magnetic media exist but are mainly in the form of open reels or enclosed cassettes. Although digitization of materials on fragile magnetic media in library and information science is a common practice, there remains a need for conserving the actual physical magnetic tape and playback equipment as artifacts. Structure of magnetic tape The first magnetic tapes were manufactured by BASF in Germany in 1932. They were designed with iron carbonyl as the magnetic pigment mixed into the cellulose acetate carrier. Production soon moved to iron oxide coated onto cellulose acetate rolls cut into uniform strips wound onto plastic or metal hubs. Recordists began recording sound on magnetic media in the twenties in the form of magnetic wire. After World War II, the advantages of tape in terms of sturdiness and the ability to edit b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Magnetic Tape
Magnetic tape is a medium for magnetic storage made of a thin, magnetizable coating on a long, narrow strip of plastic film. It was developed in Germany in 1928, based on the earlier magnetic wire recording from Denmark. Devices that use magnetic tape could with relative ease record and playback audio, visual, and binary computer data. Magnetic tape revolutionized sound recording and reproduction and broadcasting. It allowed radio, which had always been broadcast live, to be recorded for later or repeated airing. Since the early 1950s, magnetic tape has been used with computers to store large quantities of data and is still used for backup purposes. Magnetic tape begins to degrade after 10–20 years and therefore is not an ideal medium for long-term archival storage. Durability While good for short-term use, magnetic tape is highly prone to disintegration. Depending on the environment, this process may begin after 10–20 years. Over time, magnetic tape made in the 1970 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Library Of Congress
The Library of Congress (LOC) is the research library that officially serves the United States Congress and is the ''de facto'' national library of the United States. It is the oldest federal cultural institution in the country. The library is housed in three buildings on Capitol Hill in Washington, D.C.; it also maintains a conservation center in Culpeper, Virginia. The library's functions are overseen by the Librarian of Congress, and its buildings are maintained by the Architect of the Capitol. The Library of Congress is one of the largest libraries in the world. Its "collections are universal, not limited by subject, format, or national boundary, and include research materials from all parts of the world and in more than 470 languages." Congress moved to Washington, D.C., in 1800 after holding sessions for eleven years in the temporary national capitals in New York City and Philadelphia. In both cities, members of the U.S. Congress had access to the sizable co ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lubricant
A lubricant (sometimes shortened to lube) is a substance that helps to reduce friction between surfaces in mutual contact, which ultimately reduces the heat generated when the surfaces move. It may also have the function of transmitting forces, transporting foreign particles, or heating or cooling the surfaces. The property of reducing friction is known as lubricity. In addition to industrial applications, lubricants are used for many other purposes. Other uses include cooking ( oils and fats in use in frying pans, in baking to prevent food sticking), bioapplications on humans (e.g. lubricants for artificial joints), ultrasound examination, medical examination, and sexual intercourse. It is mainly used to reduce friction and to contribute to a better and efficient functioning of a mechanism. History Lubricants have been in some use for thousands of years. Calcium soaps have been identified on the axles of chariots dated to 1400 BC. Building stones were slid on oil-impregrate ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Relative Humidity
Humidity is the concentration of water vapor present in the air. Water vapor, the gaseous state of water, is generally invisible to the human eye. Humidity indicates the likelihood for precipitation, dew, or fog to be present. Humidity depends on the temperature and pressure of the system of interest. The same amount of water vapor results in higher relative humidity in cool air than warm air. A related parameter is the dew point. The amount of water vapor needed to achieve saturation increases as the temperature increases. As the temperature of a parcel of air decreases it will eventually reach the saturation point without adding or losing water mass. The amount of water vapor contained within a parcel of air can vary significantly. For example, a parcel of air near saturation may contain 28 g of water per cubic metre of air at , but only 8 g of water per cubic metre of air at . Three primary measurements of humidity are widely employed: absolute, relative, and specific. A ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Preservation (library And Archival Science)
In library and archival science, preservation is a set of preventive conservation activities aimed at prolonging the life of a record, book, or object while making as few changes as possible. Preservation activities vary widely and may include monitoring the condition of items, maintaining the temperature and humidity in collection storage areas, writing a plan in case of emergencies, digitizing items, writing relevant metadata, and increasing accessibility. Preservation, in this definition, is practiced in a library or an archive by a librarian, archivist, or other professional when they perceive a record is in need of maintenance. Preservation should be distinguished from interventive conservation and restoration, which refers to the treatment and repair of individual items to slow the process of decay, or restore them to a usable state. Preventive conservation is occasionally used interchangeably with preservation, particularly outside the professional literature. Fundamenta ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
National Library Of Canada
Library and Archives Canada (LAC; french: Bibliothèque et Archives Canada) is the federal institution, tasked with acquiring, preserving, and providing accessibility to the documentary heritage of Canada. The national archive and library is the fifth largest library in the world. The LAC reports to the Parliament of Canada through the Minister of Canadian Heritage. The LAC traces its origins to the Dominion Archives, formed in 1872, and the National Library of Canada, formed in 1953. The former was later renamed as the Public Archives of Canada in 1912, and the National Archives of Canada in 1987. In 2004, the National Archives of Canada and the National Library of Canada were merged to form Library and Archives Canada. History Predecessors The Dominion Archives was founded in 1872 as a division within the Department of Agriculture tasked with acquiring and transcribing documents related to Canadian history. In 1912, the division was transformed into an autonomous orga ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oxide
An oxide () is a chemical compound that contains at least one oxygen atom and one other element in its chemical formula. "Oxide" itself is the dianion of oxygen, an O2– (molecular) ion. with oxygen in the oxidation state of −2. Most of the Earth's crust consists of oxides. Even materials considered pure elements often develop an oxide coating. For example, aluminium foil develops a thin skin of Al2O3 (called a passivation layer) that protects the foil from further corrosion.Greenwood, N. N.; & Earnshaw, A. (1997). Chemistry of the Elements (2nd Edn.), Oxford:Butterworth-Heinemann. . Stoichiometry (the measurable relationship between reactants and chemical equations of a equation or reaction) Oxides are extraordinarily diverse in terms of stoichiometries and in terms of the structures of each stoichiometry. Most elements form oxides of more than one stoichiometry. A well known example is carbon monoxide and carbon dioxide.Greenwood, N. N.; & Earnshaw, A. (1997). Chemistry ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tape Baking
Sticky-shed syndrome is a condition created by the deterioration of the binders in a magnetic tape, which hold the ferric oxide magnetizable coating to its plastic carrier, or which hold the thinner back-coating on the outside of the tape. This deterioration renders the tape unusable. Some kinds of binder are known to break down over time, due to the absorption of moisture (hydrolysis). The symptoms of this breakdown can be immediately obvious even when rewinding the tape: tearing sounds and sluggish behavior. If a tape with sticky-shed syndrome is played, the reels will make screeching or squeaking sounds, and the tape will leave dusty, rusty particles on the guides and heads. In some cases, particularly with digital tapes, the symptoms are more subtle, causing intermittent dropouts. Cause Some tapes may deteriorate because of a breakdown in the binder (the glue) that holds the oxide particles on the tape, or the back coating on the reverse side, if the tape was from any of th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sticky-shed Syndrome
Sticky-shed syndrome is a condition created by the deterioration of the binders in a magnetic tape, which hold the ferric oxide magnetizable coating to its plastic carrier, or which hold the thinner back-coating on the outside of the tape. This deterioration renders the tape unusable. Some kinds of binder are known to break down over time, due to the absorption of moisture (hydrolysis). The symptoms of this breakdown can be immediately obvious even when rewinding the tape: tearing sounds and sluggish behavior. If a tape with sticky-shed syndrome is played, the reels will make screeching or squeaking sounds, and the tape will leave dusty, rusty particles on the guides and heads. In some cases, particularly with digital tapes, the symptoms are more subtle, causing intermittent dropouts. Cause Some tapes may deteriorate because of a breakdown in the binder (the glue) that holds the oxide particles on the tape, or the back coating on the reverse side, if the tape was from any of th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hygroscopic
Hygroscopy is the phenomenon of attracting and holding water molecules via either absorption or adsorption from the surrounding environment, which is usually at normal or room temperature. If water molecules become suspended among the substance's molecules, adsorbing substances can become physically changed, e.g., changing in volume, boiling point, viscosity or some other physical characteristic or property of the substance. For example, a finely dispersed hygroscopic powder, such as a salt, may become clumpy over time due to collection of moisture from the surrounding environment. ''Deliquescent'' materials are sufficiently hygroscopic that they absorb so much water that they become liquid and form an aqueous solution. Etymology and pronunciation The word ''hygroscopy'' () uses combining forms of '' hygro-'' and '' -scopy''. Unlike any other ''-scopy'' word, it no longer refers to a viewing or imaging mode. It did begin that way, with the word ''hygroscope'' referring in the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Base (chemistry)
In chemistry, there are three definitions in common use of the word base, known as Arrhenius bases, Brønsted bases, and Lewis bases. All definitions agree that bases are substances that react with acids, as originally proposed by G.-F. Rouelle in the mid-18th century. In 1884, Svante Arrhenius proposed that a base is a substance which dissociates in aqueous solution to form Hydroxide ions OH−. These ions can react with hydrogen ions (H+ according to Arrhenius) from the dissociation of acids to form water in an acid–base reaction. A base was therefore a metal hydroxide such as NaOH or Ca(OH)2. Such aqueous hydroxide solutions were also described by certain characteristic properties. They are slippery to the touch, can taste bitter and change the color of pH indicators (e.g., turn red litmus paper blue). In water, by altering the autoionization equilibrium, bases yield solutions in which the hydrogen ion activity is lower than it is in pure water, i.e., the water ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
