High fidelity is a term used by listeners and home audio enthusiasts to refer to high-quality reproduction of sound. This is in contrast to the lower quality sound produced by inexpensive audio equipment, or the inferior quality of sound reproduction that can be heard in recordings made until the late 1940s. Ideally, high-fidelity equipment has inaudible noise and distortion, a flat frequency response within the human hearing range. Bell Laboratories began experimenting with a range of recording techniques in the early 1930s. Performances by Leopold Stokowski and the Philadelphia Orchestra were recorded in 1931 and 1932 using telephone lines between the Academy of Music in Philadelphia and the Bell labs in New Jersey; some multitrack recordings were made on optical sound film, which led to new advances used by MGM and Twentieth Century Fox Film Corporation. RCA Victor began recording performances by several orchestras using optical sound around 1941, resulting in higher-fidelity masters for 78-rpm discs.
During the 1930s, Avery Fisher, an amateur violinist, began experimenting with audio design and acoustics. He wanted to make a radio that would sound like he was listening to a live orchestra—that would achieve high fidelity to the original sound. After World War II, Harry F. Olson conducted an experiment whereby test subjects listened to a live orchestra through a hidden variable acoustic filter; the results proved that listeners preferred high-fidelity reproduction, once the noise and distortion introduced by early sound equipment was removed. Beginning in 1948, several innovations created the conditions that made major improvements of home-audio quality possible: Reel-to-reel audio tape recording, based on technology taken from Germany after WWII, helped musical artists such as Bing Crosby make and distribute recordings with better fidelity; the advent of the 33⅓ rpm Long Play microgroove vinyl record, with lower surface noise and quantitatively specified equalization curves as well as noise-reduction and dynamic range systems.
Classical music fans, who were opinion leaders in the audio market adopted LPs because, unlike with older records, most classical works would fit on a single LP. FM radio, with wider audio bandwidth and less susceptibility to signal interference and fading than AM radio. Better amplifier designs, with more attention to frequency response and much higher power output capability, reproducing audio without perceptible distortion. New loudspeaker designs, including acoustic suspension, developed by Edgar Villchur and Henry Kloss with improved bass frequency response. In the 1950s, audio manufacturers employed the phrase high fidelity as a marketing term to describe records and equipment intended to provide faithful sound reproduction. While some consumers interpreted high fidelity as fancy and expensive equipment, many found the difference in quality compared to the then-standard AM radios and 78-rpm records apparent and bought high-fidelity phonographs and 33⅓ LPs such as RCA's New Orthophonics and London's ffrr.
Audiophiles paid attention to technical characteristics and bought individual components, such as separate turntables, radio tuners, power amplifiers and loudspeakers. Some enthusiasts assembled their own loudspeaker systems. In the 1950s, hi-fi became a generic term for home sound equipment, to some extent displacing phonograph and record player. In the late 1950s and early 1960s, the development of the Westrex single-groove stereophonic record cutterhead led to the next wave of home-audio improvement, in common parlance stereo displaced hi-fi. Records were now played on a stereo. In the world of the audiophile, the concept of high fidelity continued to refer to the goal of accurate sound reproduction and to the technological resources available for approaching that goal; this period is regarded as the "Golden Age of Hi-Fi", when vacuum tube equipment manufacturers of the time produced many models considered endearing by modern audiophiles, just before solid state equipment was introduced to the market, subsequently replacing tube equipment as the mainstream technology.
The metal-oxide-semiconductor field-effect transistor was adapted into a power MOSFET for audio by Jun-ichi Nishizawa at Tohoku University in 1974. Power MOSFETs were soon manufactured by Yamaha for their hi-fi audio amplifiers. JVC, Pioneer Corporation and Toshiba began manufacturing amplifiers with power MOSFETs in 1974. In 1977, Hitachi introduced the LDMOS, a type of power MOSFET. Hitachi was the only LDMOS manufacturer between 1977 and 1983, during which time LDMOS was used in audio power amplifiers from manufacturers such as HH Electronics and Ashly Audio, were used for music and public address systems. Class-D amplifiers became successful in the mid-1980s when low-cost, fast-switching MOSFETs were made available. Many transistor amps use MOSFET devices in their power sections, because their distortion curve is more tube-like. A popular type of system for reproducing music beginning in the 1970s was the integrated music centre—which combined a phonograph turntable, AM-FM radio tuner, tape player and power amplifier in one package sold with its own separate, detachable or integrated speakers.
These systems advertised their simplicity. The consumer did not have to select and assemble individual components, or be familiar with impedance and power ratings. Purists avoid referring to these systems as high fidelity, though some are capable of good quality sound reproduction. Audiophiles in the 1970s and 1980s preferred to buy each compo
Gloucester City Hall is located at 9 Dale Avenue in Gloucester, Massachusetts. It was built in 1870 and dedicated the following year, has served as the main location for the city's offices since then. Built to a design by Bryant and Rogers, it is a two-story Second Empire brick building; each of the rectangular building's four corners is topped by its own pyramidal roof structure, above, a small rectangular cupola with its own roof. Centered on the front elevation is a clock tower, brick in its lower levels, decorated wood above, ending in a copper dome; the building was listed on the National Register of Historic Places in 1973, included in the Central Gloucester Historic District in 1982. National Register of Historic Places listings in Gloucester, Massachusetts National Register of Historic Places listings in Essex County, Massachusetts Website about the building
A vaccine vial monitor is a thermochromic label put on vials containing vaccines which gives a visual indication of whether the vaccine has been kept at a temperature which preserves its potency. The labels were designed in response to the problem of delivering vaccines to developing countries where the cold chain is difficult to preserve, where vaccines were being rendered inactive and administered ineffectively due to their having been denatured by exposure to ambient temperature; when international vaccine care standards were being designed in the 1970s, the manuals generalized from the needs of care for the oral polio vaccine since, the most delicate vaccine in wide use. In the 1970s PATH began working with the WHO to develop a system for identifying vaccines which had expired from improper storage. In 1996 the vaccine vial monitor was first used in a vaccine project, by the next year it was accepted for use on many vaccine projects. In 2007 in Geneva the World Health Organization hosted a commemoration of the 10-year anniversary of the introduction of VVMs.
In 2007 PATH won a Tech Award for the development of the VVM. The vaccine vial monitor consists of a heat sensitive square within a circle. If the monitor is exposed to heat it changes color with time and with increasing speed in hotter conditions. If the square becomes the same color as the circle or becomes darker than the circle the vaccine contained in the vial is damaged and the vial should be discarded. Studies have shown that health workers without proper training sometimes do not understand what a VVM is or how it works. A 2007 study in urban areas of Valsad in India showed that vaccine administrators were unaware of the purpose of the monitors; the vaccine vial monitor is intended for use on vaccines which may travel outside of the cold chain, but its use on certain vaccines has had an notable impact. Manufacturers recommend that hepatitis B vaccines be stored at 2-8 °C, but the vaccines tolerate ambient and high temperatures for some amount of time; the use of vaccine vial monitors has helped health workers remain confident in vaccines being stored outside the cold chain.
The World Health Organization has described VVMs as crucial in the spread of polio vaccination programs. Electronic time–temperature indicators can detect all temperature changes, including issues of freezing vaccines which heat-detecting VVMs would not detect. Project page at PATH World Health Organization page on VVMs
Hibera is an ancient city, known for being a strategic point from which the Second Punic War is said to have originated. It was fought over by the Carthaginians and the Romans during this period. According to the texts, most of them from Titus Livius's History of Rome, the city was situated in the north east of the Iberian Peninsula, near the mouth of the Ebro river. After the occupation and rule of both nations the city adopted the name Dertosa. For a long time nobody had found any trace that this city existed, with its foundations concealed underground; this led to its existence being disputed. In August 2007, archaeologists brought to light the remains of some of the city walls, dating from the 7th century BC near to the city of Tortosa; the walls provided sufficient evidence that this city existed where it was written, defended its remains from external attacks on the site. Transito amne cum diu consultassent, utrum castra castris conferrent an satis haberent sociis Carthaginiensium oppugnandis morari ab itinere proposito hostem, urbem a propinquo flumine Hiberam appellatam, opulentissimam ea tempestate regionis eius, oppugnare parant.
Quod ubi sensit Hasdrubal, pro ope ferenda sociis pergit ire ipse ad urbem deditam nuper in fidem Romanorum oppugnandam. Ita iam coepta obsidio omissa ab Romanis est et in ipsum Hasdrubalem versum bellum. "After crossing the river, they long debated whether to bring their camp closer to Hasdrubal’s or whether it would suffice for them to delay the enemy’s projected march by launching attacks on Carthaginian allies. They prepared to attack what was at that time the richest city in the region, named after the nearby river; when Hasdrubal heard about this, instead of bringing assistance to his allies, he chose rather to proceed himself with an attack on a town that had surrendered to the Romans. The blockade of Hibera, which had commenced, was therefore abandoned by the Romans, whose operations were now focused directly on Hasdrubal himself."
Wildstar is a fictional superheroine in comic books published by DC Comics. She is the 21st century ancestor of Dawnstar of the Legion of Super-Heroes, her powers are a combination of Wildfire. Wildstar was born on the planet Starhaven a planet colonized by people of Anasazi Indian heritage from Earth; the Anasazi tribe was abducted by the Athranian genetic engineers, who hoped to use them as test subjects. However, the Athranians were overthrown by Spider Guild; the Anasazi tribe were left to their own devices. The genetic experiments endow them with wings and the ability to survive in space without oxygen or protection from the rigours of space. Wildstar was born a mutant of her people as she had the innate tracking ability, which manifested itself as the knack to find anyone in her village and see hidden things. However, she was born with deformed wings, which led to her being shunned by her tribe. Mocked and ignored by her peers, she lived alone; some time around the Final Crisis, Vril Dox came to Starhaven seeking a volunteer for his second R.
E. B. E. L. S. Team to combat L. E. G. I. O. N.. The chief, Chief Night Sky seeing a way to rid himself of a nuisance, sent the old woman out with the alien. Vril Dox saw great potential in her power for tracking people. Vril Dox promised her that if she comes with him and joins the team he will give her the power of flight. Wildstar with this knowledge agrees to go with the strange visitor. Subsequently, Vril Dox kept his promise, but not in the way Wildstar expected, he strapped her into a machine and turned her into an anti-energy being similar to Wildfire and placed her in a containment suit which gave her the power of flight as well as powerful anti-energy blasts from her visor. They go to the planet Cairn, where L. E. G. I. O. N. has driven off Garv and Garryn Bek. They begin their investigation into Starro. Wildstar and the other Starhavenites are genetically altered humans. Vril Dox II turned her into an anti-energy being similar to Wildfire, placed her in a containment suit, she is now able to produce powerful anti-energy blasts from her visor.
In her anti-energy form she is able to fly. The anti-energy is channelled out her back allowing her to construct large wings, she can survive in deep space for long periods of time without a oxygen. Wildstar is a master tracker and can track life forms and objects across light years of distance and through interstellar space, she can use this ability while unconscious, under mind control and sensory blinded. Starhavenites have pairs of large, white-feathered wings that grow out of their upper backs, the result of genetic engineering. Wildstar's wings were born deformed causing her to be an outcast. Wildstar must wear a containment suit at all time due to her anti-energy form; the suit allows her to channel the energy into wing like constructs and the visor helps her focus the energy in to a concussive blast
In optics, a thin lens is a lens with a thickness, negligible compared to the radii of curvature of the lens surfaces. Lenses whose thickness is not negligible are sometimes called thick lenses; the thin lens approximation ignores optical effects due to the thickness of lenses and simplifies ray tracing calculations. It is combined with the paraxial approximation in techniques such as ray transfer matrix analysis; the focal length, f, of a lens in air is given by the lensmaker's equation: 1 f =, where n is the index of refraction of the lens material, R1 and R2 are the radii of curvature of the two surfaces. For a thin lens, d is much smaller than one of the radii of curvature. In these conditions, the last term of the Lensmaker's equation becomes negligible, the focal length of a thin lens in air can be approximated by 1 f ≈. Here R1 is taken to be positive if the first surface is convex, negative if the surface is concave; the signs are reversed for the back surface of the lens: R2 is positive if the surface is concave, negative if it is convex.
This is an arbitrary sign convention. Certain rays follow simple rules when passing through a thin lens, in the paraxial ray approximation: Any ray that enters parallel to the axis on one side of the lens proceeds towards the focal point F on the other side. Any ray that arrives at the lens after passing through the focal point on the front side, comes out parallel to the axis on the other side. Any ray that passes through the center of the lens will not change its direction. By tracing these rays, the relationship between the object distance s and the image distance s′ can be shown to be 1 s + 1 s ′ = 1 f,which is known as the thin lens equation. In scalar wave optics a lens is a part. Mathematically this can be understood as a multiplication of the wave-front with the following function: exp