EDUCATION BLOG

Harp

2008-10-24T03:29:00.000-07:00

The harp is a stringed instrument which has the plane of its strings positioned perpendicular to the soundboard. All harps have a neck, resonator and strings. Some, known as frame harps, also have a forepillar; those lacking the forepillar are referred to as open harps. Depending on its size (which varies considerably), a harp may be played while held in the lap or while stood on the floor. Harp strings can be made of nylon (sometimes wound around copper), gut (more commonly used than nylon), wire, or silk. A person who plays the harp is called a harpist or a harper. Folk and Celtic musicians often use the term "harper," whereas classical/pedal musicians use "harpist."

Various types of harps are found in Africa, Europe, North, and South America, and a few parts of Asia. In antiquity harps and the closely related lyres were very prominent in nearly all musical cultures, but they lost popularity in the early 19^th century with Western music composers, being thought of primarily as a woman's instrument after Marie Antoinette popularised it as an activity for women.

The aeolian harp (wind harp), the autoharp, and all forms of the lyre and Kithara are not harps because their strings are not perpendicular to the soundboard; they are part of the zither family of instruments along with the piano and harpsichord. In blues music, the Harmonica is called a "Blues harp" or "harp", but it is a free reed wind instrument, not a stringed instrument.

Use in music

The harp is used sparingly in ballad (music), and most classical music, usually for special effects such as the glissando, arpeggios, and bisbigliando. It was commonly used on American pop music hits of the 1970s^{[citation needed]}. Italian and German opera uses harp for romantic arias and dances; an example of which is Musetta's Waltz from La bohème. French composers such as Claude Debussy and Maurice Ravel composed harp concertos and chamber music widely played today. In the 19^th century, the French composer and harpist Nicolas-Charles Bochsa composed hundreds of pieces of all kinds (opera transcriptions, chamber music, concertos, operas, harp methods). Henriette Renié and Marcel Grandjany have composed many lesser-known solo pieces and chamber music. Modern composers utilize the harp frequently, but while the pedals on a concert harp allow many sorts of non-diatonic scales and strange accidentals to be played, some modern pieces call for impractical pedal manipulations.

Many passages for solo harp can be found in 19^th century ballet music, which utilized the harp to a great extent in order to embellish the dancing of the ballerina. Elaborate cadenzas for harp were composed by Tchaikovsky for his ballets Swan Lake, The Nutcracker, and The Sleeping Beauty; as well as Alexander Glazunov for his score for the ballet Raymonda, which contains the variation titled Une fantaisie (a.k.a. Prélude et variations) which many modern conservatories utilize for the application and audition process.

In particular, the scores of Riccardo Drigo contained many compositions for harp which were renowned in their day (found in such works as Le Talisman and Les Millions d'Arlequin), as well as Cesare Pugni, whose ballets Éoline, ou La Dryade and Ondine, ou la Naïad included music written for harp to accompany the ballerina's numerous variations and enhance the atmosphere of the ballet's many fantastical scenes.

See the List of compositions for harp for the names of some notable pieces from the classical repertoire.

Alan Stivell is a well-known crossover and Celtic harpist. He first recorded an EP record, "Musique Gaélique," in 1959, then an LP in 1964 called "Telenn Geltiek " (available in CD). Following these, he has released 21 other albums including his harps, from 1970 until now (the last one is "Explore" - 2006- ). He recorded also some albums specially dedicated to the harp: the famous "Renaissance of the Celtic Harp" (1972), "Harpes du Nouvel Age" (1985), and "Beyond Words" (2002). He helped to promote developments in Electro-acoustic and Electric harps.

Harpists active in jazz, free improvisation, folk music, world music, and "Celtic dream" music, include:

Cobra..pssss

2008-10-19T06:13:00.000-07:00

Indian Spectacled Snake

Naje Naje

Types Of Cobras

The most common cobra is the Spectacled cobra Naja naja, native to the Indian subcontinent and associated with snake charming there. The Black cobra, found in Pakistan and North India, is generally considered to be a sub-species. The second most common cobra species is the Monocled cobra, Naja kaouthia, widespread in Asia.

In addition to a deadly bite, the Spitting cobra can incapacitate larger would-be predators by spraying venom into their eyes. This is extremely painful and can cause permanent blindness, but if washed out promptly rarely causes permanent damage.

The King cobra is ophiophagous i.e. it feeds almost entirely on other snakes, even venomous ones, although it sometimes preys on small rodents and birds. It will only attack humans if provoked or in other extreme circumstances that threaten its survival. If not treated, a king cobra's bite can kill a person in just half an hour. King Cobras may reach up to 5.2m (17.1ft) in length, making them the largest venomous snakes in the world.

In 2003, a new species of cobra was discovered at London Zoo in a shipment of illegal exotic pets. When zoo scientists thought they had a new species they brought in Dr. Wuster who confirmed their belief. Although bearing a resemblance to the Red Spitting Cobra DNA tests confirmed that it is in fact a new species altogether. Studies indicated that it originated from an area of Egypt and Sudan formerly known as Nubia. The new species, Naja nubiae or Nubian Spitting Cobra, has since bred at London Zoo.

Cobra venom

The snake will only attack a human if provoked or in other extreme circumstances which threaten its survival. Furthermore, for a dangerously venomous snake, the cobra's strikes are quite slow when compared to the extremely rapid strikes of such species as rattlesnakes. Additionally, not all bites result in envenomation and in the case of the Cobra the amount of "blank" strikes may be quite high: in one series of recorded bites in Malaysia only 55% of strikes have included envenomation. Cobra bites are fatal in about 10% of human cases. However, as with any venomous snake, any bite from a cobra should be treated as a potentially fatal injury and medical attention should be sought immediately after the bite occurs. As with all elapids, the venom of cobras is highly neurotoxic and dangerous. Therefore, any cobra bite must be regarded as life-threatening and professional medical assistance should be immediately sought. Early symptoms of a bite include ptosis, diplopia, dysphagia, and dizziness, followed by progressive respiratory muscle weakness, ultimately requiring endotracheal intubation. Cobra venom is a postsynaptic neurotoxin. It works by stopping the acetylcholine molecules in the diaphragm muscle from interacting. Without treatment death from respiratory failure may occur as early as 30 minutes after being bitten.

Standard treatment involves the use of antivenin. Additionally, it is possible to support bite victims via mechanical ventilation, using equipment of the type generally available at hospitals. Such support should be provided until the venom is metabolised and the victim can breathe unaided. If death occurs it takes place approximately 6 to 12 hours after the cobra bite. Cause of death is respiratory failure or suffocation caused by complete paralysis of the diaphragm.

Optical Fibres

2008-10-16T08:06:00.000-07:00

Intoduction

An optical fiber (or fibre) is a glass or plastic fiber that carries light along its length. Fiber optics is the overlap of applied science and engineering concerned with the design and application of optical fibers. Optical fibers are widely used in fiber-optic communications, which permits transmission over longer distances and at higher data rates (a.k.a "bandwidth"), than other forms of communications. Fibers are used instead of metal wires because signals travel along them with less loss, and they are immune to electromagnetic interference. Fibers are also used for illumination, and in bundles can be used to carry images, allowing viewing in tight spaces. Specially designed fibers are used for a variety of other applications, including as sensors and fiber lasers.

Light is kept in the "core" of the optical fiber by total internal reflection. This causes the fiber to act as a waveguide. Fibers which support many propagation paths or transverse modes are called multimode fibers (MMF). Fibers which support only a single mode are called singlemode fibers (SMF). Multimode fibers generally have a large-diameter core, and are used for short-distance communication links or for applications where high power must be transmitted. Singlemode fibers are used for most communication links longer than 200 meters.

Applications

Optical fiber can be used as a medium for telecommunication and networking because it is flexible and can be bundled as cables. It is especially advantageous for long-distance communications, because light propagates through the fiber with little attenuation compared to electrical cables.
Over short distances, such as networking within a building, fiber saves space in cable ducts because a single fiber can carry much more data than a single electrical cable. Fiber is also immune to electrical interference, which prevents cross-talk between signals in different cables and pickup of environmental noise.
Optical fibers can be used as sensors to measure strain, temperature, pressure and other quantities by modifying a fiber so that the quantity to be measured modulates the intensity, phase, polarization, wavelength or transit time of light in the fiber. Sensors that vary the intensity of light are the simplest, since only a simple source and detector are required. A particularly useful feature of such fiber optic sensors is that they can, if required, provide distributed sensing over distances of up to one meter.

Total internal reflection

When light traveling in a dense medium hits a boundary at a steep angle (larger than the "critical angle" for the boundary), the light will be completely reflected. This effect is used in optical fibers to confine light in the core. Light travels along the fiber bouncing back and forth off of the boundary. Because the light must strike the boundary with an angle less than the critical angle, only light that enters the fiber within a certain range of angles can travel down the fiber without leaking out. This range of angles is called the acceptance cone of the fiber. The size of this acceptance cone is a function of the refractive index difference between the fiber's core and cladding.

In simpler terms, there is a maximum angle from the fiber axis at which light may enter the fiber so that it will propagate, or travel, in the core of the fiber. The sine of this maximum angle is the numerical aperture (NA) of the fiber. Fiber with a larger NA requires less precision to splice and work with than fiber with a smaller NA. Single-mode fiber has a small NA.