The ribosome is a complex molecular machine, found within all living cells, that serves as the site of biological protein synthesis. Ribosomes link amino acids together in the order specified by messenger RNA molecules, ribosomes consist of two major components, the small ribosomal subunit, which reads the RNA, and the large subunit, which joins amino acids to form a polypeptide chain. Each subunit is composed of one or more ribosomal RNA molecules, the ribosomes and associated molecules are known as the translational apparatus. The sequence of DNA, which encodes the sequence of the acids in a protein, is copied into a messenger RNA chain. It may be copied many times into RNA chains, ribosomes can bind to a messenger RNA chain and use its sequence for determining the correct sequence of amino acids. Amino acids are selected and carried to the ribosome by transfer RNA molecules and it is during this binding that the correct translation of nucleic acid sequence to amino acid sequence occurs. For each coding triplet in the messenger RNA there is a distinct transfer RNA that matches, the attached amino acids are linked together by another part of the ribosome.
Once the protein is produced, it can fold to produce a specific functional three-dimensional structure although during synthesis some proteins start folding into their correct form, a ribosome is made from complexes of RNAs and proteins and is therefore a ribonucleoprotein. When a ribosome finishes reading an mRNA molecule, these two subunits split apart, ribosomes are ribozymes, because the catalytic peptidyl transferase activity that links amino acids together is performed by the ribosomal RNA. Ribosomes are often associated with the membranes that make up the rough endoplasmic reticulum. Ribosomes from bacteria and eukaryotes in the system, resemble each other to a remarkable degree. They differ in their size, sequence and the ratio of protein to RNA, the differences in structure allow some antibiotics to kill bacteria by inhibiting their ribosomes, while leaving human ribosomes unaffected. In bacteria and archaea, more than one ribosome may move along a single mRNA chain at one time, each reading its sequence, ribosomes were first observed in the mid-1950s by Romanian cell biologist George Emil Palade, using an electron microscope, as dense particles or granules.
The Nobel Prize in Chemistry 2009 was awarded to Venkatraman Ramakrishnan, Thomas A. Steitz and Ada E. Yonath for determining the detailed structure, the ribosome is a highly complex cellular machine. It is largely made up of specialized RNA known as ribosomal RNA as well as dozens of distinct proteins, the ribosomal proteins and rRNAs are arranged into two distinct ribosomal pieces of different size, known generally as the large and small subunit of the ribosome. Ribosomes consist of two subunits that fit together and work as one to translate the mRNA into a polypeptide chain during protein synthesis, because they are formed from two subunits of non-equal size, they are slightly longer in the axis than in diameter. Prokaryotic ribosomes are around 20 nm in diameter and are composed of 65% rRNA, eukaryotic ribosomes are between 25 and 30 nm in diameter with an rRNA-to-protein ratio that is close to 1. Bacterial ribosomes are composed of one or two rRNA strands, eukaryotic ribosomes contain one or three very large rRNA molecules and multiple smaller protein molecules
A metric prefix is a unit prefix that precedes a basic unit of measure to indicate a multiple or fraction of the unit. While all metric prefixes in use today are decadic, historically there have been a number of binary metric prefixes as well. Each prefix has a symbol that is prepended to the unit symbol. The prefix kilo-, for example, may be added to gram to indicate multiplication by one thousand, the prefix milli-, may be added to metre to indicate division by one thousand, one millimetre is equal to one thousandth of a metre. Decimal multiplicative prefixes have been a feature of all forms of the system with six dating back to the systems introduction in the 1790s. Metric prefixes have even been prepended to non-metric units, the SI prefixes are standardized for use in the International System of Units by the International Bureau of Weights and Measures in resolutions dating from 1960 to 1991. Since 2009, they have formed part of the International System of Quantities, the BIPM specifies twenty prefixes for the International System of Units.
Each prefix name has a symbol which is used in combination with the symbols for units of measure. For example, the symbol for kilo- is k, and is used to produce km, kg, and kW, which are the SI symbols for kilometre, prefixes corresponding to an integer power of one thousand are generally preferred. Hence 100 m is preferred over 1 hm or 10 dam, the prefixes hecto, deca and centi are commonly used for everyday purposes, and the centimetre is especially common. However, some building codes require that the millimetre be used in preference to the centimetre, because use of centimetres leads to extensive usage of decimal points. Prefixes may not be used in combination and this applies to mass, for which the SI base unit already contains a prefix. For example, milligram is used instead of microkilogram, in the arithmetic of measurements having units, the units are treated as multiplicative factors to values. If they have prefixes, all but one of the prefixes must be expanded to their numeric multiplier,1 km2 means one square kilometre, or the area of a square of 1000 m by 1000 m and not 1000 square metres.
2 Mm3 means two cubic megametres, or the volume of two cubes of 1000000 m by 1000000 m by 1000000 m or 2×1018 m3, and not 2000000 cubic metres, examples 5 cm = 5×10−2 m =5 ×0.01 m =0. The prefixes, including those introduced after 1960, are used with any metric unit, metric prefixes may be used with non-metric units. The choice of prefixes with a unit is usually dictated by convenience of use. Unit prefixes for amounts that are larger or smaller than those actually encountered are seldom used
In physics, electromagnetic radiation refers to the waves of the electromagnetic field, propagating through space carrying electromagnetic radiant energy. It includes radio waves, infrared, ultraviolet, X-, electromagnetic radiation consists of electromagnetic waves, which are synchronized oscillations of electric and magnetic fields that propagate at the speed of light through a vacuum. The oscillations of the two fields are perpendicular to other and perpendicular to the direction of energy and wave propagation. The wavefront of electromagnetic waves emitted from a point source is a sphere, the position of an electromagnetic wave within the electromagnetic spectrum can be characterized by either its frequency of oscillation or its wavelength. Electromagnetic waves are produced whenever charged particles are accelerated, and these waves can interact with other charged particles. EM waves carry energy and angular momentum away from their source particle, quanta of EM waves are called photons, whose rest mass is zero, but whose energy, or equivalent total mass, is not zero so they are still affected by gravity.
Thus, EMR is sometimes referred to as the far field, in this language, the near field refers to EM fields near the charges and current that directly produced them, electromagnetic induction and electrostatic induction phenomena. In the quantum theory of electromagnetism, EMR consists of photons, quantum effects provide additional sources of EMR, such as the transition of electrons to lower energy levels in an atom and black-body radiation. The energy of a photon is quantized and is greater for photons of higher frequency. This relationship is given by Plancks equation E = hν, where E is the energy per photon, ν is the frequency of the photon, a single gamma ray photon, for example, might carry ~100,000 times the energy of a single photon of visible light. The effects of EMR upon chemical compounds and biological organisms depend both upon the power and its frequency. EMR of visible or lower frequencies is called non-ionizing radiation, because its photons do not individually have enough energy to ionize atoms or molecules, the effects of these radiations on chemical systems and living tissue are caused primarily by heating effects from the combined energy transfer of many photons.
In contrast, high ultraviolet, X-rays and gamma rays are called ionizing radiation since individual photons of high frequency have enough energy to ionize molecules or break chemical bonds. These radiations have the ability to cause chemical reactions and damage living cells beyond that resulting from simple heating, Maxwell derived a wave form of the electric and magnetic equations, thus uncovering the wave-like nature of electric and magnetic fields and their symmetry. Because the speed of EM waves predicted by the wave equation coincided with the speed of light. Maxwell’s equations were confirmed by Heinrich Hertz through experiments with radio waves, according to Maxwells equations, a spatially varying electric field is always associated with a magnetic field that changes over time. Likewise, a varying magnetic field is associated with specific changes over time in the electric field. In an electromagnetic wave, the changes in the field are always accompanied by a wave in the magnetic field in one direction
Semiconductor device fabrication
Semiconductor device fabrication is the process used to create the integrated circuits that are present in everyday electrical and electronic devices. It is a sequence of photo lithographic and chemical processing steps during which electronic circuits are gradually created on a wafer made of pure semiconducting material. Silicon is almost always used, but various compound semiconductors are used for specialized applications, the entire manufacturing process, from start to packaged chips ready for shipment, takes six to eight weeks and is performed in highly specialized facilities referred to as fabs. When feature widths were far greater than about 10 micrometres, purity was not the issue that it is today in device manufacturing, as devices became more integrated, cleanrooms became even cleaner. Today, the fabs are pressurized with filtered air to remove even the smallest particles, the workers in a semiconductor fabrication facility are required to wear cleanroom suits to protect the devices from human contamination.
Semiconductor device manufacturing has spread from Texas and California in the 1960s to the rest of the world, including Europe, the Middle East and it is a global business today. The leading semiconductor manufacturers typically have facilities all over the world, the worlds largest manufacturer, has facilities in Europe and Asia as well as the U. S. A typical wafer is made out of pure silicon that is grown into mono-crystalline cylindrical ingots up to 300 mm in diameter using the Czochralski process. These ingots are sliced into wafers about 0.75 mm thick and polished to obtain a very regular. In semiconductor device fabrication, the processing steps fall into four general categories, removal, patterning. Deposition is any process that grows, coats, or otherwise transfers a material onto the wafer, available technologies include physical vapor deposition, chemical vapor deposition, electrochemical deposition, molecular beam epitaxy and more recently, atomic layer deposition among others.
Removal is any process that removes material from the wafer, examples include etch processes, patterning is the shaping or altering of deposited materials, and is generally referred to as lithography. After etching or other processing, the remaining photoresist is removed by plasma ashing, modification of electrical properties has historically entailed doping transistor sources and drains. These doping processes are followed by annealing or, in advanced devices. Modification of electrical properties now extends to the reduction of a dielectric constant in low-k insulators via exposure to ultraviolet light in UV processing. Modern chips have up to eleven metal levels produced in over 300 sequenced processing steps, FEOL processing refers to the formation of the transistors directly in the silicon. The raw wafer is engineered by the growth of an ultrapure, in the most advanced logic devices, prior to the silicon epitaxy step, tricks are performed to improve the performance of the transistors to be built.
One method involves introducing a straining step wherein a silicon variant such as silicon-germanium is deposited, once the epitaxial silicon is deposited, the crystal lattice becomes stretched somewhat, resulting in improved electronic mobility
The inch is a unit of length in the imperial and United States customary systems of measurement now formally equal to 1⁄36 yard but usually understood as 1⁄12 of a foot. Derived from the Roman uncia, inch is used to translate related units in other measurement systems. The English word inch was a borrowing from Latin uncia not present in other Germanic languages. The vowel change from Latin /u/ to English /ɪ/ is known as umlaut, the consonant change from the Latin /k/ to English /tʃ/ or /ʃ/ is palatalisation. Both were features of Old English phonology, inch is cognate with ounce, whose separate pronunciation and spelling reflect its reborrowing in Middle English from Anglo-Norman unce and ounce. In many other European languages, the word for inch is the same as or derived from the word for thumb, the inch is a commonly used customary unit of length in the United States and the United Kingdom. It is used in Japan for electronic parts, especially display screens, for example, three feet two inches can be written as 3′ 2″.
Paragraph LXVII sets out the fine for wounds of various depths, one inch, one shilling, an Anglo-Saxon unit of length was the barleycorn. After 1066,1 inch was equal to 3 barleycorns, which continued to be its legal definition for several centuries, similar definitions are recorded in both English and Welsh medieval law tracts. One, dating from the first half of the 10th century, is contained in the Laws of Hywel Dda which superseded those of Dyfnwal, both definitions, as recorded in Ancient Laws and Institutes of Wales, are that three lengths of a barleycorn is the inch. However, the oldest surviving manuscripts date from the early 14th century, john Bouvier similarly recorded in his 1843 law dictionary that the barleycorn was the fundamental measure. He noted that this process would not perfectly recover the standard, before the adoption of the international yard and pound, various definitions were in use. In the United Kingdom and most countries of the British Commonwealth, the United States adopted the conversion factor 1 metre =39.37 inches by an act in 1866.
In 1930, the British Standards Institution adopted an inch of exactly 25.4 mm, the American Standards Association followed suit in 1933. By 1935, industry in 16 countries had adopted the industrial inch as it came to be known, in 1946, the Commonwealth Science Congress recommended a yard of exactly 0.9144 metres for adoption throughout the British Commonwealth. This was adopted by Canada in 1951, the United States on 1 July 1959, Australia in 1961, effective 1 January 1964, and the United Kingdom in 1963, effective on 1 January 1964. The new standards gave an inch of exactly 25.4 mm,1.7 millionths of a longer than the old imperial inch and 2 millionths of an inch shorter than the old US inch. The United States retains the 1/39. 37-metre definition for survey purposes and this is approximately 1/8-inch in a mile
It can facilitate commoditization of formerly custom processes. This view includes the case of spontaneous standardization processes, to de facto standards. Standard weights and measures were developed by the Indus Valley Civilisation, weights existed in multiples of a standard weight and in categories. Technical standardisation enabled gauging devices to be used in angular measurement and measurement for construction. Uniform units of length were used in the planning of such as Lothal, Kalibangan, Harappa. The weights and measures of the Indus civilisation reached Persia and Central Asia, Standardisation is related to Processes. In view of large variations in units related to Civil and other Engineering streams, engineers united to overcome the situation and this association on gave birth to ISO in 1950. ISO stands for International Organisation for Standardisation and this voluntary organisation is solely dedicated to standardisation and makes standards related to it. Certification as per ISO norms is popular all across world, henry Maudslay developed the first industrially practical screw-cutting lathe in 1800.
This allowed for the standardisation of screw thread sizes for the first time, before this, screw threads were usually made by chipping and filing. Nuts were rare, metal screws, when made at all, were usually for use in wood, metal bolts passing through wood framing to a metal fastening on the other side were usually fastened in non-threaded ways. This was an advance in workshop technology. Maudslays work, as well as the contributions of other engineers, accomplished a modest amount of industry standardization, joseph Whitworths screw thread measurements were adopted as the first national standard by companies around the country in 1841. It came to be known as the British Standard Whitworth, and was adopted in other countries. This new standard specified a 55° thread angle and a depth of 0. 640327p and a radius of 0. 137329p. The thread pitch increased with diameter in steps specified on a chart, an example of the use of the Whitworth thread is the Royal Navys Crimean War gunboats. These were the first instance of mass-production techniques being applied to marine engineering, American Unified Coarse was originally based on almost the same imperial fractions.
The Unified thread angle is 60° and has flattened crests, thread pitch is the same in both systems except that the thread pitch for the 1⁄2 in bolt is 12 threads per inch in BSW versus 13 tpi in the UNC
Ancient Greek includes the forms of Greek used in ancient Greece and the ancient world from around the 9th century BC to the 6th century AD. It is often divided into the Archaic period, Classical period. It is antedated in the second millennium BC by Mycenaean Greek, the language of the Hellenistic phase is known as Koine. Koine is regarded as a historical stage of its own, although in its earliest form it closely resembled Attic Greek. Prior to the Koine period, Greek of the classic and earlier periods included several regional dialects, Ancient Greek was the language of Homer and of fifth-century Athenian historians and philosophers. It has contributed many words to English vocabulary and has been a subject of study in educational institutions of the Western world since the Renaissance. This article primarily contains information about the Epic and Classical phases of the language, Ancient Greek was a pluricentric language, divided into many dialects. The main dialect groups are Attic and Ionic, Arcadocypriot, some dialects are found in standardized literary forms used in literature, while others are attested only in inscriptions.
There are several historical forms, homeric Greek is a literary form of Archaic Greek used in the epic poems, the Iliad and Odyssey, and in poems by other authors. Homeric Greek had significant differences in grammar and pronunciation from Classical Attic, the origins, early form and development of the Hellenic language family are not well understood because of a lack of contemporaneous evidence. Several theories exist about what Hellenic dialect groups may have existed between the divergence of early Greek-like speech from the common Proto-Indo-European language and the Classical period and they have the same general outline, but differ in some of the detail. The invasion would not be Dorian unless the invaders had some relationship to the historical Dorians. The invasion is known to have displaced population to the Attic-Ionic regions, the Greeks of this period believed there were three major divisions of all Greek people—Dorians and Ionians, each with their own defining and distinctive dialects.
Often non-west is called East Greek, Arcadocypriot apparently descended more closely from the Mycenaean Greek of the Bronze Age. Boeotian had come under a strong Northwest Greek influence, and can in some respects be considered a transitional dialect, thessalian likewise had come under Northwest Greek influence, though to a lesser degree. Most of the dialect sub-groups listed above had further subdivisions, generally equivalent to a city-state and its surrounding territory, Doric notably had several intermediate divisions as well, into Island Doric, Southern Peloponnesus Doric, and Northern Peloponnesus Doric. The Lesbian dialect was Aeolic Greek and this dialect slowly replaced most of the older dialects, although Doric dialect has survived in the Tsakonian language, which is spoken in the region of modern Sparta. Doric has passed down its aorist terminations into most verbs of Demotic Greek, by about the 6th century AD, the Koine had slowly metamorphosized into Medieval Greek
Nanotechnology is manipulation of matter on an atomic and supramolecular scale. It is therefore common to see the plural form nanotechnologies as well as nanoscale technologies to refer to the range of research. Because of the variety of applications, governments have invested billions of dollars in nanotechnology research. Until 2012, through its National Nanotechnology Initiative, the USA has invested 3.7 billion dollars, scientists currently debate the future implications of nanotechnology. Nanotechnology may be able to create new materials and devices with a vast range of applications, such as in nanomedicine, biomaterials energy production. These concerns have led to a debate among advocacy groups and governments on whether regulation of nanotechnology is warranted. The term nano-technology was first used by Norio Taniguchi in 1974, in 1986, Drexler co-founded The Foresight Institute to help increase public awareness and understanding of nanotechnology concepts and implications. In the 1980s, two major breakthroughs sparked the growth of nanotechnology in modern era, the microscopes developers Gerd Binnig and Heinrich Rohrer at IBM Zurich Research Laboratory received a Nobel Prize in Physics in 1986.
Binnig and Gerber invented the atomic force microscope that year. Second, Fullerenes were discovered in 1985 by Harry Kroto, Richard Smalley, and Robert Curl, in the early 2000s, the field garnered increased scientific and commercial attention that led to both controversy and progress. Controversies emerged regarding the definitions and potential implications of nanotechnologies, exemplified by the Royal Societys report on nanotechnology, challenges were raised regarding the feasibility of applications envisioned by advocates of molecular nanotechnology, which culminated in a public debate between Drexler and Smalley in 2001 and 2003. Meanwhile, commercialization of products based on advancements in nanoscale technologies began emerging and these products are limited to bulk applications of nanomaterials and do not involve atomic control of matter. Governments moved to promote and fund research into nanotechnology, such as in the U. S, by the mid-2000s new and serious scientific attention began to flourish.
Projects emerged to produce nanotechnology roadmaps which center on atomically precise manipulation of matter and discuss existing and projected capabilities, Nanotechnology is the engineering of functional systems at the molecular scale. This covers both current work and concepts that are more advanced, one nanometer is one billionth, or 10−9, of a meter. By comparison, typical carbon-carbon bond lengths, or the spacing between atoms in a molecule, are in the range 0. 12–0.15 nm. On the other hand, the smallest cellular life-forms, the bacteria of the genus Mycoplasma, are around 200 nm in length, by convention, nanotechnology is taken as the scale range 1 to 100 nm following the definition used by the National Nanotechnology Initiative in the US. The lower limit is set by the size of atoms since nanotechnology must build its devices from atoms and molecules
Nanoscale Informal Science Education Network
In 2016 the Nanoscale Informal Science Education Network transitioned to a new, ongoing identity as the National Informal STEM Education Network. While well still be known as the NISE Net, network partners will now engage audiences across the United States in a range of STEM topics, the NISE Network was established in 2005 with funding from the National Science Foundation through Award numbers 0532536 and 0940143. The NISE Network is one of many networks created through the larger National Nanotechnology Initiative, NanoDays events take place at more than 200 science and childrens museums, research centers, and universities throughout the United States, from Puerto Rico to Hawaii. NanoDays engages people of all ages in learning about this field of science through hands-on experiments, stage performances. The first nationwide week of events took place in 2008, with more than 100 institutions participating and this has grown to more than 250 events annually in the United States nationwide. A list of participating NanoDays organizations is available, videos, books, stage demonstrations, and hands-on activities are compiled on the NISE Net online catalog and are available for download from the online catalog.
Developed by the NISE Network, Nano is an exhibition that engages family audiences in nanoscale science, engineering. Hands-on exhibits present the basics of nanoscience and engineering, introduce some real world applications, Nano was created by the Nanoscale Informal Science Education Network with support from the National Science Foundation. The Nano exhibition is intended for display in museums across the United States. Up to seventy copies of Nano will be fabricated, all copies will be identical, the exhibition complements NanoDays events and other NISE Network educational experiences. Exhibit components include, What happens when things get smaller, - visitors see how magnetite behaves differently when its particles are different sizes, Whats new about nano. - visitors build a model of a giant carbon nanotube, Where can you find nano, - visitors try a series of interactive challenges, search a complex image to find examples of real nano products and phenomena, and finally, What does nano mean for us. - visitors balance blocks on a table, which represents the challenges of working together to build a stable nano future.
There is an area where visitors can learn more about nano through books. Nano was supported by the National Science Foundation under Award Nos. ESI-0532536 and 0940143, the NISE Network along with other leading Informal Science Education Institutions have developed many curriculum and activity resources for teachers to use in their classrooms. Resources include hands-on experiments and posters, among other materials
The metre or meter, is the base unit of length in the International System of Units. The metre is defined as the length of the path travelled by light in a vacuum in 1/299792458 seconds, the metre was originally defined in 1793 as one ten-millionth of the distance from the equator to the North Pole. In 1799, it was redefined in terms of a metre bar. In 1960, the metre was redefined in terms of a number of wavelengths of a certain emission line of krypton-86. In 1983, the current definition was adopted, the imperial inch is defined as 0.0254 metres. One metre is about 3 3⁄8 inches longer than a yard, Metre is the standard spelling of the metric unit for length in nearly all English-speaking nations except the United States and the Philippines, which use meter. Measuring devices are spelled -meter in all variants of English, the suffix -meter has the same Greek origin as the unit of length. This range of uses is found in Latin, English. Thus calls for measurement and moderation. In 1668 the English cleric and philosopher John Wilkins proposed in an essay a decimal-based unit of length, as a result of the French Revolution, the French Academy of Sciences charged a commission with determining a single scale for all measures.
In 1668, Wilkins proposed using Christopher Wrens suggestion of defining the metre using a pendulum with a length which produced a half-period of one second, christiaan Huygens had observed that length to be 38 Rijnland inches or 39.26 English inches. This is the equivalent of what is now known to be 997 mm, no official action was taken regarding this suggestion. In the 18th century, there were two approaches to the definition of the unit of length. One favoured Wilkins approach, to define the metre in terms of the length of a pendulum which produced a half-period of one second. The other approach was to define the metre as one ten-millionth of the length of a quadrant along the Earths meridian, that is, the distance from the Equator to the North Pole. This means that the quadrant would have defined as exactly 10000000 metres at that time. To establish a universally accepted foundation for the definition of the metre, more measurements of this meridian were needed. This portion of the meridian, assumed to be the length as the Paris meridian, was to serve as the basis for the length of the half meridian connecting the North Pole with the Equator
The hectometre or hectometer is an uncommonly used unit of length in the metric system, equal to one hundred metres. It derives from the Greek word ekato, meaning hundred, a soccer field is approximately 1 hectometre in length. The hectare, a metric unit for land area, is equal to one square hectometre
The foot is a unit of length in the imperial and US customary systems of measurement. Since 1959, both units have been defined by international agreement as equivalent to 0.3048 meters exactly, in both systems, the foot comprises 12 inches and three feet compose a yard. Historically the foot was a part of local systems of units, including the Greek, Chinese, French. It varied in length from country to country, from city to city and its length was usually between 250 mm and 335 mm and was generally, but not always, subdivided into 12 inches or 16 digits. The United States is the industrialized nation that uses the international foot and the survey foot in preference to the meter in its commercial, engineering. The foot is legally recognized in the United Kingdom, road signs must use imperial units, the measurement of altitude in international aviation is one of the few areas where the foot is widely used outside the English-speaking world. The length of the international foot corresponds to a foot with shoe size of 13,14,15.5 or 46.
Historically the human body has been used to provide the basis for units of length. The foot of a male is typically about 15. 3% of his height, giving a person of 160 cm a foot of 245 mm. These figures are less than the used in most cities over time. Archeologists believe that the Egyptians, Ancient Indians and Mesopotamians preferred the cubit while the Romans, under the Harappan linear measures, Indus cities during the Bronze Age used a foot of 13.2 inches and a cubit of 20.8 inches. The Egyptian equivalent of the measure of four palms or 16 digits—was known as the djeser and has been reconstructed as about 30 cm. The Greek foot had a length of 1⁄600 of a stadion, one stadion being about 181.2 m, the standard Roman foot was normally about 295.7 mm, but in the provinces, the pes Drusianus was used, with a length of about 334 mm. Originally both the Greeks and the Romans subdivided the foot into 16 digits, but in years, after the fall of the Roman Empire, some Roman traditions were continued but others fell into disuse.
In AD790 Charlemagne attempted to reform the units of measure in his domains and his units of length were based on the toise and in particular the toise de lÉcritoire, the distance between the fingertips of the outstretched arms of a man. The toise has 6 pieds each of 326.6 mm, at the same time, monastic buildings used the Carolingian foot of 340 mm. The procedure for verification of the foot as described in the 16th century by Jacob Koebel in his book Geometrei, the measures of Iron Age Britain are uncertain and proposed reconstructions such as the Megalithic Yard are controversial. Later Welsh legend credited Dyfnwal Moelmud with the establishment of their units, the Belgic or North German foot of 335 mm was introduced to England either by the Belgic Celts during their invasions prior to the Romans or by the Anglo-Saxons in the 5th & 6th century