click links in text for more info


A bolometer is a device for measuring the power of incident electromagnetic radiation via the heating of a material with a temperature-dependent electrical resistance. It was invented in 1878 by the American astronomer Samuel Pierpont Langley. A bolometer consists of an absorptive element, such as a thin layer of metal, connected to a thermal reservoir through a thermal link; the result is that any radiation impinging on the absorptive element raises its temperature above that of the reservoir – the greater the absorbed power, the higher the temperature. The intrinsic thermal time constant, which sets the speed of the detector, is equal to the ratio of the heat capacity of the absorptive element to the thermal conductance between the absorptive element and the reservoir; the temperature change can be measured directly with an attached resistive thermometer, or the resistance of the absorptive element itself can be used as a thermometer. Metal bolometers work without cooling, they are produced from thin foils or metal films.

Today, most bolometers use superconductor absorptive elements rather than metals. These devices can be operated at cryogenic temperatures, enabling greater sensitivity. Bolometers are directly sensitive to the energy left inside the absorber. For this reason they can be used not only for ionizing particles and photons, but for non-ionizing particles, any sort of radiation, to search for unknown forms of mass or energy; the most sensitive bolometers are slow to reset. On the other hand, compared to more conventional particle detectors, they are efficient in energy resolution and in sensitivity, they are known as thermal detectors. The first bolometers made by Langley consisted of two steel, platinum, or palladium foil strips covered with lampblack. One strip was shielded from one exposed to it; the strips formed two branches of a Wheatstone bridge, fitted with a sensitive galvanometer and connected to a battery. Electromagnetic radiation falling on the exposed strip would change its resistance. By 1880, Langley's bolometer was refined enough to detect thermal radiation from a cow a quarter of a mile away.

This radiant-heat detector is sensitive to differences in temperature of one hundred-thousandth of a degree Celsius. This instrument enabled him to thermally detect across a broad spectrum, noting all the chief Fraunhofer lines, he discovered new atomic and molecular absorption lines in the invisible infrared portion of the electromagnetic spectrum. Nikola Tesla asked Dr. Langley if he could use his bolometer for his power transmission experiments in 1892. Thanks to that first use, he succeeded in making the first demonstration between West Point and his laboratory on Houston Street. While bolometers can be used to measure radiation of any frequency, for most wavelength ranges there are other methods of detection that are more sensitive. For sub-millimeter wavelengths, bolometers are among the most sensitive available detectors, are therefore used for astronomy at these wavelengths. To achieve the best sensitivity, they must be cooled to a fraction of a degree above absolute zero. Notable examples of bolometers employed in submillimeter astronomy include the Herschel Space Observatory, the James Clerk Maxwell Telescope, the Stratospheric Observatory for Infrared Astronomy.

The term bolometer is used in particle physics to designate an unconventional particle detector. They use the same principle described above; the bolometers are sensitive not only to every form of energy. The operating principle is similar to that of a calorimeter in thermodynamics. However, the approximations, ultra low temperature, the different purpose of the device make the operational use rather different. In the jargon of high energy physics, these devices are not called "calorimeters", since this term is used for a different type of detector, their use as particle detectors was proposed from the beginning of the 20th century, but the first regular, though pioneering, use was only in the 1980s because of the difficulty associated with cooling and operating a system at cryogenic temperature. They can still be considered to be at the developmental stage. A microbolometer is a specific type of bolometer used as a detector in a thermal camera, it is a grid of vanadium oxide or amorphous silicon heat sensors atop a corresponding grid of silicon.

Infrared radiation from a specific range of wavelengths strikes the vanadium oxide or amorphous silicon, changes its electrical resistance. This resistance change is measured and processed into temperatures which can be represented graphically; the microbolometer grid is found in three sizes, a 640×480 array, a 320×240 array or less expensive 160×120 array. Different arrays provide the same resolution with larger array providing a wider field of view. Larger, 1024×768 arrays were announced in 2008; the hot electron bolometer operates at cryogenic temperatures within a few degrees of absolute zero. At these low temperatures, the electron system in a metal is weakly coupled to the phonon system. Power coupled to the electron system drives it out of thermal equilibrium with the phonon system, creating hot electrons. Phonons in the metal are well-coupled to substrate phonons and act as a thermal reservoir. In describing the performance of the HEB, the relevant heat capacity is the electronic heat capacity and the


Navizon, Inc. is a provider of location-based services and products. Navizon was an early developer of technology that makes it possible to determine the geographic position of a mobile device using as reference the location of cell phone towers and Wi-Fi-based wireless access points instead of GPS. Navizon developed technology for locating mobile devices indoors with room and floor-level accuracy. Navizon known as Mexens Technology, was founded by a team from the Internet Protocol geolocation market, its founder and CEO, Cyril Houri, was founder and CEO of Infosplit, a provider of IP address geolocation services started in 1999, acquired in 2004. In 2005, Mexens Technology, as Navizon, Inc. was named, introduced Navizon, a hybrid positioning system combining GPS, Wi-Fi and cellular positioning. Mobile device users obtain their position through the Navizon app, which calculates the locations of cell sites and Wi-Fi access points by analyzing the signal strength at different locations. Navizon's database of cellular tower and Wi-Fi access point locations was built by a global community of users through crowdsourcing.

The Navizon app provides access to features such as Buddy Finder, which allows users to find the location of other registered users, incentives through the Navizon Rewards System, which allows users to earn rewards for contributing data through Navizon's crowdsourcing initiative. Navizon's positioning products and services include the Navizon app, for individuals, wireless positioning systems for corporations. In March 2009, the Navizon Wi-Fi positioning system was licensed by Yahoo Mobile and in March 2010 Microsoft selected Navizon for Wi-Fi and Cellular positioning. In 2011, Navizon unveiled Indoor Triangulation System, a location based service for businesses that tracks Wi-Fi enabled smart phones and notebooks, gives a view of people traffic inside a building or throughout a campus with room-and floor-level accuracy. In 2006, Mexens Technology, Inc. received United States Patent No. 7,397,424 for its “System and Method for Enabling Continuous Geographic Location Estimation for Wireless Computing Devices”.

In 2008, Mexens Technology, Inc. received a second patent, United States Patent No. 7,696,923 for its “System and method for determining geographic location of wireless computing devices”. Official website

Al Schwartz (writer)

Albert "Al" Schwartz was an American screenwriter, television producer, director. He was a writer for The Red Skelton Show, where he and other writers won a Primetime Emmy Award for Outstanding Writing for a Comedy Series in 1961 and were nominated for the same award in 1962, he wrote scripts for The Jackie Gleason Show, The Milton Berle Show, The Brady Bunch, Gilligan's Island, Petticoat Junction, other television shows and made-for-TV movies throughout the 1950s, 1960s and 1970s. Earlier in his career, Schwartz wrote for Bob Hope's radio program, The Pepsodent Show Starring Bob Hope, he was the brother of Sherwood Schwartz, the creator and producer of Gilligan's Island and The Brady Bunch, Elroy Schwartz, a comedy and television writer. Al Schwartz on IMDb

National Postal Museum

The National Postal Museum, located opposite Union Station in Washington, D. C. United States, was established through joint agreement between the United States Postal Service and the Smithsonian Institution and opened in 1993; the museum is located across the street from Union Station, in the building that once served as the main post office of Washington, D. C. from 1914, when it was constructed, until 1986. The building was designed by the Graham and Burnham architectural firm, led by Ernest Graham following the death of Daniel Burnham in 1912; the building in which the museum is housed serves as the headquarters of the United States Department of Labor's Bureau of Labor Statistics, as well as a data center for the United States Senate. The museum stores the National Philatelic Collection and hosts many interactive displays about the history of the United States Postal Service and of mail service around the world; the museum houses a gift shop and a United States Postal Service philatelic sales window, along with exhibits on the Pony Express, the use of railroads with the mail, the preserved remains of Owney, an exhibit on direct marketing called, "What's in the Mail for You," that produces a souvenir envelope with a visitor's name printed on it and a coupon for the gift shop.

As a Smithsonian museum, admission is free. This museum houses a library. In 2005, the museum acquired John Lennon's childhood stamp collection. From June 2015 until December 2018 the museum displayed the 1856 British Guiana One-Cent Magenta, the world's most valuable stamp, which sold for nearly $10 million. In September 2009, the museum received an $8 million gift from investment firm founder William H. Gross to help finance an expansion project; the museum now hosts the William H. Gross Stamp Gallery named in his honor. Since 2002, the museum has presented the Smithsonian Philatelic Achievement Award every two years. List of philatelic libraries Owney U. S. Postal Museums Postal Museum National Postal Museum official website National Postal Museum Library Official website Smithsonian's National Postal Museum at Google Cultural Institute Arago: People, Postage & the Post

Sybille of Bâgé

Sybille de Baugé, Lady of Bâgé, was the daughter of Guy I Damas de Baugé, Baron of Couzan and Dauphine de Lavieu. She was a Countess Consort of Savoy, being married to Amadeus V, Count of Savoy in 1272. Issue: Bonne of Savoy, married firstly, John I of Viennois, Dauphin of Viennois, secondly, Hugh of Burgundy, Lord of Montbauson, the son of Hugh III, Count of Burgundy. John of Savoy Beatrice of Savoy Edward, Count of Savoy Eleonor of Savoy, married: firstly, William of Chalon, Count of Auxerre and Tonnerre, her daughter, Marguerite of Mello, married John II of Chalon-Arlay. Margaret of Savoy, married John I of Montferrat. Agnes of Savoy, married William III of Geneva, their son was Amadeus III of Geneva. Aymon, Count of Savoy

ASM-N-6 Omar

The ASM-N-6 Omar was a short-range air-to-surface missile developed for and evaluated by the United States Navy in the early 1950s. Intended to use existing unguided rockets as a basis and using a novel guidance system involving optical beam-riding, the program was unable to resolve difficulties with the guidance system and was cancelled without entering service. Designed by Eastman Kodak in response to an urgent requirement by the U. S. Navy for a stand-off air-to-ground weapon for use in the Korean War, the Omar, designated XASM-N-6, was authorized for development on 20 August 1951. Based on the airframe of the standard 5 in High Velocity Aircraft Rocket, cruciform fins were mounted at the mid and aft portions of the rocket body to provide stabilization and control. An optical beam riding guidance system was developed for use with Omar; the Omar shared some parts of its control system with the AAM-N-7 Sidewinder air-to-air missile. Test launches of Omar began in late 1951. Issues were found with the beam of light "spreading" as it covered the distance to the target, the issue of the launching aircraft having to remain on course to the target, a common issue with early guided missiles, could not be solved.

The following year a modification of the seeker head, nicknamed "Ramo" was tested, evaluating a frequency modulation system to encode the light beam to refine the guidance. This proved no more effective, the system was cancelled although some details of the frequency encoding were used in the development of the SAM-N-7 Terrier program. Media related to ASM-N-6 Omar at Wikimedia Commons