The recorder is a woodwind musical instrument in the group known as internal duct flutes—flutes with a whistle mouthpiece known as fipple flutes. A recorder can be distinguished from other duct flutes by the presence of a thumb-hole for the upper hand and seven finger-holes: three for the upper hand and four for the lower, it is the most prominent duct flute in the western classical tradition. Recorders are made in different sizes with names and compasses corresponding to different vocal ranges; the sizes most in use today are the soprano, alto and bass. Recorders are traditionally constructed from wood and ivory, while most recorders made in recent years are constructed from molded plastic; the recorders' internal and external proportions vary, but the bore is reverse conical to cylindrical, all recorder fingering systems make extensive use of forked fingerings. The recorder is first documented in Europe in the Middle Ages, continued to enjoy wide popularity in the Renaissance and Baroque periods, but was little used in the Classical and Romantic periods.

It was revived in the 20th century as part of the informed performance movement, became a popular amateur and educational instrument. Composers who have written for the recorder include Monteverdi, Purcell, Vivaldi, Johann Sebastian Bach, Paul Hindemith, Benjamin Britten, Leonard Bernstein, Luciano Berio, Arvo Pärt. Today, there are many professional recorder players who demonstrate the instrument's full solo range and a large community of amateurs; the sound of the recorder is described as clear and sweet, has been associated with birds and shepherds. It is notable for its quick response and its corresponding ability to produce a wide variety of articulations; this ability, coupled with its open finger holes, allow it to produce a wide variety of tone colors and special effects. Acoustically, its tone is pure and, when the edge is positioned in the center of the airjet, odd harmonics predominate in its sound; the instrument has been known by its modern English name at least since the 14th century.

David Lasocki reports the earliest use of "recorder" in the household accounts of the Earl of Derby in 1388, which register i. fistula nomine Recordour. By the 15th century, the name had appeared in English literature; the earliest references are in John Lydgate's Temple of Glas: These lytylle herdegromys Floutyn al the longe day.. In here smale recorderys, In floutys. and in Lydgate's Fall of Princes: Pan, god off Kynde, with his pipes seuene, / Off recorderis fond first the melodies. The instrument name "recorder" derives from the Latin recordārī, by way of Middle French recorder and its derivative MFr recordeur; the association between the various disparate, meanings of recorder can be attributed to the role of the medieval jongleur in learning poems by heart and reciting them, sometimes with musical accompaniment. The English verb "record" meant "to learn by heart, to commit to memory, to go over in one's mind, to recite" but it was not used in English to refer to playing music until the 16th century, when it gained the meaning "silently practicing a tune" or "sing or render in song", long after the recorder had been named.

Thus, the recorder cannot have been named after the sound of birds. The name of the instrument is uniquely English: in Middle French there is no equivalent noun sense of recorder referring to a musical instrument. Partridge indicates that the use of the instrument by jongleurs led to its association with the verb: recorder the minstrel's action, a "recorder" the minstrel's tool; the reason we know this instrument as the recorder and not one of the other instruments played by the jongleurs is uncertain. The introduction of the Baroque recorder to England by a group of French professionals in 1673 popularized the French name for the instrument, "flute douce", or "flute", a name reserved for the transverse instrument; until about 1695, the names "recorder" and "flute" overlapped, but from 1673 to the late 1720s in England, the word "flute" always meant recorder. In the 1720s, as the transverse flute overtook the recorder in popularity, English adopted the convention present in other European languages of qualifying the word "flute", calling the recorder variously the "common flute", "common English-flute", or "English flute" while the transverse instrument was distinguished as the "German flute" or "flute".

Until at least 1765, some writers still used "flute" to mean recorder. Until the mid 18th century, musical scores written in Italian refer to the instrument as flauto, whereas the transverse instrument was called flauto traverso; this distinction, like the English switch from "recorder" to "flute," has caused confusion among modern editors and performers. Indeed, in most European languages, the first term for the recorder was the word for flute alone. In the present day, cognates of the word "flute," when used without qualifiers, remain ambiguous and may refer to either the recorder, the modern concert flute, or other non-we

WD repeat-containing protein 3 is a protein that in humans is encoded by the WDR3 gene. This gene encodes a nuclear protein containing 10 WD repeats. WD repeats are 30- to 40-amino acid domains containing several conserved residues, which include a trp-asp at the C-terminal end. Proteins belonging to the WD repeat family are involved in a variety of cellular processes, including cell cycle progression, signal transduction and gene regulation. Model organisms have been used in the study of WDR3 function. A conditional knockout mouse line, called Wdr3tm1aWtsi was generated as part of the International Knockout Mouse Consortium program — a high-throughput mutagenesis project to generate and distribute animal models of disease to interested scientists. Male and female animals underwent a standardized phenotypic screen to determine the effects of deletion. Twenty four tests were carried out on mutant mice and two significant abnormalities were observed. No homozygous mutant embryos were identified during gestation, therefore none survived until weaning.

The remaining tests were carried out on heterozygous mutant adult mice.

The knot is a unit of speed equal to one nautical mile per hour 1.852 km/h. The ISO standard symbol for the knot is kn; the same symbol is preferred by the Institute of Electronics Engineers. The knot is a non-SI unit. Worldwide, the knot is used in meteorology, in maritime and air navigation—for example, a vessel travelling at 1 knot along a meridian travels one minute of geographic latitude in one hour. Etymologically, the term derives from counting the number of knots in the line that unspooled from the reel of a chip log in a specific time. 1 international knot = 1 nautical mile per hour, 1852.000 metres per hour, 0.51444 metres per second, 1.15078 miles per hour, 20.25372 inches per second 1.68781 feet per second. The length of the internationally agreed nautical mile is 1852 m; the US adopted the international definition in 1954, having used the US nautical mile. The UK adopted the international nautical mile definition in 1970, having used the UK Admiralty nautical mile; the speeds of vessels relative to the fluids in which they travel are measured in knots.

For consistency, the speeds of navigational fluids are measured in knots. Thus, speed over the ground and rate of progress towards a distant point are given in knots; until the mid-19th century, vessel speed at sea was measured using a chip log. This consisted of a wooden panel, attached by line to a reel, weighted on one edge to float perpendicularly to the water surface and thus present substantial resistance to the water moving around it; the chip log was cast over the stern of the line allowed to pay out. Knots placed at a distance of 47 feet 3 inches from each other, passed through a sailor's fingers, while another sailor used a 30-second sand-glass to time the operation; the knot count would be used in the sailing master's dead reckoning and navigation. This method gives a value for 1.85166 km/h. The difference from the modern definition is less than 0.02%. Derivation of knots spacing: 1 kn = 1852 m/h = 0.5144 m/s, so in 28 seconds, 14.40 metres per knot. Although the unit knot does not fit within the SI system, its retention for nautical and aviation use is important because the length of a nautical mile, upon which the knot is based, is related to the longitude/latitude geographic coordinate system.

As a result, nautical miles and knots are convenient units to use when navigating an aircraft or ship. Standard nautical charts are on the Mercator projection and the horizontal scale varies with latitude. On a chart of the North Atlantic, the scale varies by a factor of two from Florida to Greenland. A single graphic scale, of the sort on many maps, would therefore be useless on such a chart. Since the length of a nautical mile, for practical purposes, is equivalent to about a minute of latitude, a distance in nautical miles on a chart can be measured by using dividers and the latitude scales on the sides of the chart. Recent British Admiralty charts have a latitude scale down the middle to make this easier. Speed is sometimes incorrectly expressed as "knots per hour", which would mean "nautical miles per hour per hour" and thus would refer to acceleration. Prior to 1969, airworthiness standards for civil aircraft in the United States Federal Aviation Regulations specified that distances were to be in statute miles, speeds in miles per hour.

In 1969, these standards were progressively amended to specify that distances were to be in nautical miles, speeds in knots. The following abbreviations are used to distinguish between various measurements of airspeed: KTAS is "knots true airspeed", the airspeed of an aircraft relative to undisturbed air KIAS is "knots indicated airspeed", the speed shown on an aircraft's pitot-static airspeed indicator KCAS is "knots calibrated airspeed", the indicated airspeed corrected for position error and instrument error KEAS is "knots equivalent airspeed", the calibrated airspeed corrected for adiabatic compressible flow for the particular altitudeThe indicated airspeed is close to the true airspeed only at sea level in standard conditions and at low speeds. At 11000 m, an indicated airspeed of 300 kn may correspond to a true airspeed of 500 kn in standard conditions. Beaufort scale Hull speed, which deals with theoretical estimates of practical maximum speed of displacement hulls Knot count Knotted cord Metre per second Orders of magnitude Rope