Redox is a chemical reaction in which the oxidation states of atoms are changed. Any such reaction involves both a reduction process and a complementary oxidation process, two key concepts involved with electron transfer processes. Redox reactions include all chemical reactions; the chemical species from which the electron is stripped is said to have been oxidized, while the chemical species to which the electron is added is said to have been reduced. It can be explained in simple terms: Oxidation is the loss of electrons or an increase in oxidation state by a molecule, atom, or ion. Reduction is a decrease in oxidation state by a molecule, atom, or ion; as an example, during the combustion of wood, oxygen from the air is reduced, gaining electrons from carbon, oxidized. Although oxidation reactions are associated with the formation of oxides from oxygen molecules, oxygen is not included in such reactions, as other chemical species can serve the same function; the reaction can occur slowly, as with the formation of rust, or more in the case of fire.
There are simple redox processes, such as the oxidation of carbon to yield carbon dioxide or the reduction of carbon by hydrogen to yield methane, more complex processes such as the oxidation of glucose in the human body. "Redox" is a portmanteau of the words "reduction" and "oxidation". The word oxidation implied reaction with oxygen to form an oxide, since dioxygen was the first recognized oxidizing agent; the term was expanded to encompass oxygen-like substances that accomplished parallel chemical reactions. The meaning was generalized to include all processes involving loss of electrons; the word reduction referred to the loss in weight upon heating a metallic ore such as a metal oxide to extract the metal. In other words, ore was "reduced" to metal. Antoine Lavoisier showed. Scientists realized that the metal atom gains electrons in this process; the meaning of reduction became generalized to include all processes involving a gain of electrons. Though "reduction" seems counter-intuitive when speaking of the gain of electrons, it might help to think of reduction as the loss of oxygen, its historical meaning.
Since electrons are negatively charged, it is helpful to think of this as reduction in electrical charge. The electrochemist John Bockris has used the words electronation and deelectronation to describe reduction and oxidation processes when they occur at electrodes; these words are analogous to protonation and deprotonation, but they have not been adopted by chemists worldwide. The term "hydrogenation" could be used instead of reduction, since hydrogen is the reducing agent in a large number of reactions in organic chemistry and biochemistry. But, unlike oxidation, generalized beyond its root element, hydrogenation has maintained its specific connection to reactions that add hydrogen to another substance; the word "redox" was first used in 1928. The processes of oxidation and reduction occur and cannot happen independently of one another, similar to the acid–base reaction; the oxidation alone and the reduction alone are each called a half-reaction, because two half-reactions always occur together to form a whole reaction.
When writing half-reactions, the gained or lost electrons are included explicitly in order that the half-reaction be balanced with respect to electric charge. Though sufficient for many purposes, these general descriptions are not correct. Although oxidation and reduction properly refer to a change in oxidation state — the actual transfer of electrons may never occur; the oxidation state of an atom is the fictitious charge that an atom would have if all bonds between atoms of different elements were 100% ionic. Thus, oxidation is best defined as an increase in oxidation state, reduction as a decrease in oxidation state. In practice, the transfer of electrons will always cause a change in oxidation state, but there are many reactions that are classed as "redox" though no electron transfer occurs. In redox processes, the reductant transfers electrons to the oxidant. Thus, in the reaction, the reductant or reducing agent loses electrons and is oxidized, the oxidant or oxidizing agent gains electrons and is reduced.
The pair of an oxidizing and reducing agent that are involved in a particular reaction is called a redox pair. A redox couple is a reducing species and its corresponding oxidizing form, e.g. Fe2+/Fe3+ Substances that have the ability to oxidize other substances are said to be oxidative or oxidizing and are known as oxidizing agents, oxidants, or oxidizers; that is, the oxidant removes electrons from another substance, is thus itself reduced. And, because it "accepts" electrons, the oxidizing agent is called an electron acceptor. Oxygen is the quintessential oxidizer. Oxidants are chemical substances with elements in high oxidation states, or else electronegative elements that can gain extra electrons by oxidizing another substance. Substances that have the ability to reduce other substances are said to be reductive or reducing and are known as
A water wheel is a machine for converting the energy of flowing or falling water into useful forms of power in a watermill. A water wheel consists of a wheel, with a number of blades or buckets arranged on the outside rim forming the driving surface. Water wheels were still in commercial use well into the 20th century but they are no longer in common use. Uses included milling flour in gristmills, grinding wood into pulp for papermaking, hammering wrought iron, ore crushing and pounding fiber for use in the manufacture of cloth; some water wheels are fed by water from a mill pond, formed when a flowing stream is dammed. A channel for the water flowing to or from a water wheel is called a mill race; the race bringing water from the mill pond to the water wheel is a headrace. In the mid to late 18th century John Smeaton's scientific investigation of the water wheel led to significant increases in efficiency supplying much needed power for the Industrial Revolution. Water wheels began being displaced by the smaller, less expensive and more efficient turbine, developed by Benoît Fourneyron, beginning with his first model in 1827.
Turbines are capable of handling high heads, or elevations, that exceed the capability of practical-sized waterwheels. The main difficulty of water wheels is their dependence on flowing water, which limits where they can be located. Modern hydroelectric dams can be viewed as the descendants of the water wheel, as they too take advantage of the movement of water downhill. Water wheels come in two basic designs: a horizontal wheel with a vertical axle; the latter can be subdivided according to where the water hits the wheel into backshot overshot, breastshot and stream-wheels. The term undershot can refer to any wheel where the water passes under the wheel but it implies that the water entry is low on the wheel. Most water wheels in the United Kingdom and the United States are vertical wheels rotating about a horizontal axle, but in the Scottish highlands and parts of Southern Europe mills had a horizontal wheel. Overshot and backshot water wheels are used where the available height difference is more than a couple of meters.
Breastshot wheels are more suited to large flows with a moderate head. Undershot and stream wheel use large flows at no head. There is an associated millpond, a reservoir for storing water and hence energy until it is needed. Larger heads store more potential energy for the same amount of water so the reservoirs for overshot and backshot wheels tend to be smaller than for breast shot wheels. Overshot and pitchback water wheels are suitable where there is a small stream with a height difference of more than 2 meters in association with a small reservoir. Breastshot and undershot wheels can be used on high volume flows with large reservoirs. A horizontal wheel with a vertical axle. Called a tub wheel, Norse mill or Greek mill, the horizontal wheel is a primitive and inefficient form of the modern turbine; however if it delivers the required power the efficiency is of secondary importance. It is mounted inside a mill building below the working floor. A jet of water is directed on to the paddles of the water wheel.
This is a simple system without gearing so that the vertical axle of the water wheel becomes the drive spindle of the mill. The earliest known reference to water wheels dates to about 400 BCE, the earliest horizontal axis wheels date to about 200 BCE, so vertical axis mills pre-date horizontal axis mills by about two centuries. A stream wheel is a vertically mounted water wheel, rotated by the water in a water course striking paddles or blades at the bottom of the wheel; this type of water wheel is the oldest type of horizontal axis wheel. They are known as free surface wheels because the water is not constrained by millraces or wheel pit. Stream wheels are cheaper and simpler to build, have less of an environmental impact, than other type of wheel, they do not constitute a major change of the river. Their disadvantages are their low efficiency, which means that they generate less power and can only be used where the flow rate is sufficient. A typical flat board undershot wheel uses about 20 percent of the energy in the flow of water striking the wheel as measured by English civil engineer John Smeaton in the 18th century.
More modern wheels have higher efficiencies. Stream wheels gain little or no advantage from head, a difference in water level. Stream wheels mounted on floating platforms are referred to as ship wheels and the mill as a ship mill; the earliest were constructed by the Byzantine general Belisarius during the siege of Rome in 537. They were sometimes mounted downstream from bridges where the flow restriction of the bridge piers increased the speed of the current, they were inefficient but major advances were made in the eighteenth century. An undershot wheel is a vertically mounted water wheel with a horizontal axle, rotated by the water from a low weir striking the wheel in the bottom quarter. Most of the energy gain comparatively little from the head, they are similar in design to stream wheels. The term undershot is sometimes used with related but different meanings: all wheels where the water passes under the wheel wheels where the water enters in the bottom quarter. Wheels where paddles are placed into the flow of a stream.
See stream above. This is the oldest type of vertical water wheel; the word breastshot is used in a variety o
South Yorkshire is a metropolitan county in England. It is the southernmost county in the Yorkshire and the Humber region and had a population of 1.34 million in 2011. It has an area of 1,552 square kilometres and consists of four metropolitan boroughs, Doncaster and Sheffield. South Yorkshire was created on 1 April 1974 as a result of the Local Government Act 1972, its largest settlement is Sheffield. Lying on the east side of the Pennines, South Yorkshire is landlocked, borders Derbyshire to the west and south-west, West Yorkshire to the north-west, North Yorkshire to the north, the East Riding of Yorkshire to the north-east, Lincolnshire to the east and Nottinghamshire to the south-east; the Sheffield Urban Area is the tenth most populous conurbation in the UK, dominates the western half of South Yorkshire with over half of the county's population living within it. South Yorkshire lies within the Sheffield City Region with Barnsley being within the Leeds City Region, reflecting its geographical position midway between Yorkshire's two largest cities.
South Yorkshire County Council was abolished in 1986 and its metropolitan boroughs are now unitary authorities, although the metropolitan county continues to exist in law. As a ceremonial county, South Yorkshire has a High Sheriff. South Yorkshire was created from 32 local government districts of the West Riding of Yorkshire, with small areas from Derbyshire and Nottinghamshire. In the 2016 referendum on the United Kingdom's membership of the European Union, South Yorkshire voted 62% leave and 38% remain, making it one of the most Leave areas in the country. Although the modern county of South Yorkshire was not created until 1974, the history of its constituent settlements and parts goes back centuries. Prehistoric remains include a Mesolithic "house" dating to around 8000 BC, found at Deepcar, in the northern part of Sheffield. Evidence of earlier inhabitation in the wider region exists about 3 miles over the county boundary at Creswell Crags in Derbyshire, where artefacts and rock art found in caves have been dated by archaeologists to the late Upper Palaeolithic period, at least 12,800 years ago.
The region was on the frontier of the Roman Empire during the Roman period. The main settlements of South Yorkshire grew up around the industries of mining and steel manufacturing; the main mining industry was coal, concentrated to the north and east of the county. There were iron deposits which were mined in the area; the rivers running off the Pennines to the west of the county supported the steel industry, concentrated in the city of Sheffield. The proximity of the iron and coal made this an ideal place for steel manufacture. Although Christian nonconformism was never as strong in South Yorkshire as in the mill towns of West Yorkshire, there are still many Methodist and Baptist churches in the area. South Yorkshire has a high number of followers of spiritualism, it is the only county. The Local Government Commission for England presented draft recommendations, in December 1965, proposing a new county—York and North Midlands—roughly centred on the southern part of the West Riding of Yorkshire and northern parts of Derbyshire and Nottinghamshire.
The review was abolished in favour of the Royal Commission on Local Government before it was able to issue a final report. The Royal Commission's 1969 report, known as the Redcliffe-Maud Report, proposed the removal of much of the existing system of local government; the commission described the system of administering urban and rural districts separately as outdated, noting that urban areas provided employment and services for rural dwellers, open countryside was used by town dwellers for recreation. Redcliffe-Maud's recommendations were accepted by the Labour government in February 1970. Although the Redcliffe-Maud Report was rejected by the Conservative government after the 1970 general election, there was a commitment to local government reform, the need for a metropolitan county of South Yorkshire; the Local Government Act 1972 reformed local government in England by creating a system of two-tier metropolitan and non-metropolitan counties and districts throughout the country. The act formally established South Yorkshire on 1 April 1974, although South Yorkshire County Council had been running since elections in 1973.
The leading article in The Times on the day the Local Government Act came into effect noted that the "new arrangement is a compromise which seeks to reconcile familiar geography which commands a certain amount of affection and loyalty, with the scale of operations on which modern planning methods can work effectively". South Yorkshire had a two tier structure of local government with a strategic-level county council and four districts providing most services. In 1974, as part of the South Yorkshire Structure Plan of the environment and land use, South Yorkshire County Council commissioned a public attitudes survey covering job opportunities, educational facilities, leisure opportunities and medical services, shopping centres and transport in the county. In 1986, throughout England the metropolitan county councils were abolished; the functions of the county council were devolved to the boroughs. The joint boards continue to include the South Yorkshire Passenger Transport Executive; the South Yorkshire Police and Crime Commissioner oversees South Yorkshire Police.
Although the county council was abolished, Sou
Coke is a grey and porous fuel with a high carbon content and few impurities, made by heating coal or oil in the absence of air — a destructive distillation process. It is an important industrial product, used in iron ore smelting, but as a fuel in stoves and forges when air pollution is a concern; the unqualified term "coke" refers to the product derived from low-ash and low-sulfur bituminous coal by a process called coking. A similar product called pet coke, is obtained from crude oil in oil refineries. Coke may be formed by geologic processes. Historical sources dating to the 4th century describe the production of coke in ancient China; the Chinese first used coke for heating and cooking no than the ninth century. By the first decades of the eleventh century, Chinese ironworkers in the Yellow River valley began to fuel their furnaces with coke, solving their fuel problem in that tree-sparse region. In 1589, a patent was granted to Thomas Proctor and William Peterson for making iron and steel and melting lead with "earth-coal, sea-coal and peat".
The patent contains a distinct allusion to the preparation of coal by "cooking". In 1590, a patent was granted to the Dean of York to "purify pit-coal and free it from its offensive smell". In 1620, a patent was granted to a company composed of William St. John and other knights, mentioning the use of coke in smelting ores and manufacturing metals. In 1627, a patent was granted to Sir John Hacket and Octavius de Strada for a method of rendering sea-coal and pit-coal as useful as charcoal for burning in houses, without offense by smell or smoke. In 1603, Hugh Plat suggested that coal might be charred in a manner analogous to the way charcoal is produced from wood; this process was not employed until 1642. It was considered an improvement in quality, brought about an "alteration which all England admired"—the coke process allowed for a lighter roast of the malt, leading to the creation of what by the end of the 17th century was called pale ale. In 1709, Abraham Darby I established a coke-fired blast furnace to produce cast iron.
Coke's superior crushing strength allowed blast furnaces to become larger. The ensuing availability of inexpensive iron was one of the factors leading to the Industrial Revolution. Before this time, iron-making used large quantities of charcoal, produced by burning wood; as the coppicing of forests became unable to meet the demand, the substitution of coke for charcoal became common in Great Britain, coke was manufactured by burning coal in heaps on the ground so that only the outer layer burned, leaving the interior of the pile in a carbonized state. In the late 18th century, brick beehive ovens were developed, which allowed more control over the burning process. In 1768, John Wilkinson built a more practical oven for converting coal into coke. Wilkinson improved the process by building the coal heaps around a low central chimney built of loose bricks and with openings for the combustion gases to enter, resulting in a higher yield of better coke. With greater skill in the firing and quenching of the heaps, yields were increased from about 33% to 65% by the middle of the 19th century.
The Scottish iron industry expanded in the second quarter of the 19th century, through the adoption of the hot-blast process in its coalfields. In 1802, a battery of beehives was set up near Sheffield, to coke the Silkstone seam for use in crucible steel melting. By 1870, there were 14,000 beehive ovens in operation on the West Durham coalfields, capable of producing 4,000,000 long tons of coke; as a measure of the extent of the expansion of coke making, it has been estimated that the requirements of the iron industry were about 1,000,000 long tons a year in the early 1850s, whereas by 1880 the figure had risen to 7,000,000 long tons, of which about 5,000,000 long tons were produced in Durham county, 1,000,000 long tons in the South Wales coalfield, 1,000,000 long tons in Yorkshire and Derbyshire. In the first years of steam railway locomotives, coke was the normal fuel; this resulted from an early piece of environmental legislation. This was not technically possible to achieve until the firebox arch came into use, but burning coke, with its low smoke emissions, was considered to meet the requirement.
This rule was dropped, cheaper coal became the normal fuel, as railways gained acceptance among the public. In the US, the first use of coke in an iron furnace occurred around 1817 at Isaac Meason's Plumsock puddling furnace and rolling mill in Fayette County, Pennsylvania. In the late 19th century, the coalfields of western Pennsylvania provided a rich source of raw material for coking. In 1885, the Rochester and Pittsburgh Coal and Iron Company constructed the world's longest string of coke ovens in Walston, with 475 ovens over a length of 2 km, their output reached 22,000 tons per month. The Minersville Coke Ovens in Huntingdon County, were listed on the National Register of Historic Places in 1991. Between 1870 and 1905, the number of beehive ovens in the US skyrocketed from about 200 to 31,000, which produced nearly 18,000,000 tons of coke in the Pittsburgh area alone. One observer boasted that if loaded into a train, “the year's production would make up a train so long that the engine in front of it would go to
Stockholm is the capital of Sweden and the most populous urban area in the Nordic countries. The city stretches across fourteen islands. Just outside the city and along the coast is the island chain of the Stockholm archipelago; the area has been settled since the Stone Age, in the 6th millennium BC, was founded as a city in 1252 by Swedish statesman Birger Jarl. It is the capital of Stockholm County. Stockholm is the cultural, media and economic centre of Sweden; the Stockholm region alone accounts for over a third of the country's GDP, is among the top 10 regions in Europe by GDP per capita. It is an important global city, the main centre for corporate headquarters in the Nordic region; the city is home to some of Europe's top ranking universities, such as the Stockholm School of Economics, Karolinska Institute and Royal Institute of Technology. It hosts the annual Nobel Prize ceremonies and banquet at the Stockholm Concert Hall and Stockholm City Hall. One of the city's most prized museums, the Vasa Museum, is the most visited non-art museum in Scandinavia.
The Stockholm metro, opened in 1950, is well known for the decor of its stations. Sweden's national football arena is located north of the city centre, in Solna. Ericsson Globe, the national indoor arena, is in the southern part of the city; the city was the host of the 1912 Summer Olympics, hosted the equestrian portion of the 1956 Summer Olympics otherwise held in Melbourne, Australia. Stockholm is the seat of the Swedish government and most of its agencies, including the highest courts in the judiciary, the official residencies of the Swedish monarch and the Prime Minister; the government has its seat in the Rosenbad building, the Riksdag is seated in the Parliament House, the Prime Minister's residence is adjacent at Sager House. Stockholm Palace is the official residence and principal workplace of the Swedish monarch, while Drottningholm Palace, a World Heritage Site on the outskirts of Stockholm, serves as the Royal Family's private residence. After the Ice Age, around 8,000 BC, there were many people living in what is today the Stockholm area, but as temperatures dropped, inhabitants moved south.
Thousands of years as the ground thawed, the climate became tolerable and the lands became fertile, people began to migrate back to the North. At the intersection of the Baltic Sea and lake Mälaren is an archipelago site where the Old Town of Stockholm was first built from about 1000 CE by Vikings, they had a positive trade impact on the area because of the trade routes they created. Stockholm's location appears in Norse sagas as Agnafit, in Heimskringla in connection with the legendary king Agne; the earliest written mention of the name Stockholm dates from 1252, by which time the mines in Bergslagen made it an important site in the iron trade. The first part of the name means log in Swedish, although it may be connected to an old German word meaning fortification; the second part of the name means islet, is thought to refer to the islet Helgeandsholmen in central Stockholm. According to Eric Chronicles the city is said to have been founded by Birger Jarl to protect Sweden from sea invasions made by Karelians after the pillage of Sigtuna on Lake Mälaren in the summer of 1187.
Stockholm's core, the present Old Town was built on the central island next to Helgeandsholmen from the mid-13th century onward. The city rose to prominence as a result of the Baltic trade of the Hanseatic League. Stockholm developed strong economic and cultural linkages with Lübeck, Gdańsk, Visby and Riga during this time. Between 1296 and 1478 Stockholm's City Council was made up of 24 members, half of whom were selected from the town's German-speaking burghers; the strategic and economic importance of the city made Stockholm an important factor in relations between the Danish Kings of the Kalmar Union and the national independence movement in the 15th century. The Danish King Christian II was able to enter the city in 1520. On 8 November 1520 a massacre of opposition figures called the Stockholm Bloodbath took place and set off further uprisings that led to the breakup of the Kalmar Union. With the accession of Gustav Vasa in 1523 and the establishment of a royal power, the population of Stockholm began to grow, reaching 10,000 by 1600.
The 17th century saw Sweden grow into a major European power, reflected in the development of the city of Stockholm. From 1610 to 1680 the population multiplied sixfold. In 1634, Stockholm became the official capital of the Swedish empire. Trading rules were created that gave Stockholm an essential monopoly over trade between foreign merchants and other Swedish and Scandinavian territories. In 1697, Tre Kronor was replaced by Stockholm Palace. In 1710, a plague killed about 20,000 of the population. After the end of the Great Northern War the city stagnated. Population growth halted and economic growth slowed; the city was in shock after having lost its place as the capital of a Great power. However, Stockholm maintained its role as the political centre of Sweden and continued to develop culturally under Gustav III. By the second half of the 19th century, Stockholm had regained its leading economic role. New industries emerged and Stockholm was transformed into an important trade and service centre as well as a key gateway point within Sweden.
The population grew during this time through immigration. At the end
Taipingjing is the name of several different Daoist texts. At least two works were known by this title: Chinese: 天官歷包元太平經, it is considered to be a valuable resource for researching early Daoist beliefs and the society at the end of the Eastern Han dynasty. Zhang Jue, the leader of the Yellow Turban Rebellion, taught "Taiping Daoism" based on this work; the contents of the Taipingjing are diverse but deals with subjects such as heaven and earth, the five elements and yang and the sexagenary cycle. The Taipingjing is a guide that reveals the proper methods to bring forward an era of great peace or equality - the "Great Peace" -, an idea that dates back to the Warring States period; the idea of the "Great Peace" became more prominent during the Han period. The main idea brought forward by the scriptures is. There is a loss of cosmic balance, this is made obvious by omens such as droughts, famines and other natural disasters. There is chaos in the courts of the imperial house, proven by recorded events such as freakish births, all of which demonstrate Heaven's displeasure towards the mortal realm.
Humans have been polluted by their ancestors' sins. The Universe reciprocates the mortal realm's condition. Salvation lies in the hand of great princes known as Celestial Masters. Chinese antiquity was divided into three eras: High Antiquity, Middle Antiquity and Late Antiquity, but it was only High Antiquity that contained a time of Great Peace, maintained with the collaborative efforts of the rulers of that era and the Celestial Masters. There was no infant mortality, no bad harvests and the climate was convenient; this balance was so delicate that the suffering of one entity was enough to make things out of synch. The Taipingjing claimed that a better era than the one experienced by the Han dynasty can only begin with the emergence of a new healthy emperor, a new Heavenly Mandate and an end to evil omens. There was no definitive modern version of the Taipingjing until 1960, when Wang Ming published the Taipingjing Hejiao; the Taiping Jing once contained 170 chapters divided into 10 parts. Each "part" is labelled by the ten Celestial Stems.
However. The first two parts and the last three parts are missing in Ming's modern edition. So, in actuality, only five parts remain, of these parts, certain chapters have not been accounted for. Ming's edition includes "Magic Texts" and some images; some chapters follow the form of a dialogue between the Heavenly Teacher and the six zhenren, while others stick to the essay format, containing methods, instructions or notes. The Taipingjing had many authors, hence the various writing styles in the chapters. There are two known versions of the Taipingjing; the first one was presented to Emperor Cheng of Han under the title Tianguan li baoyuan Taiping jing It was written in this book that the House of Han was nearing the end of its cosmological cycle and that a new mandate was about to be presented to restore the dynasty. The book decrees that a man by the name of Chijing zi would bring and teach the ways of the Dao to the emperor. Emperor Shun of Han received similar scriptures called Taiping Qingling Shu, which would be used by the leader of the Yellow Turban Rebellion.
Xiang Zheng's memorial states that it was based on respect between Heaven and Earth and conformity with the Five Elements. Another version was called the Taiping Dongji jing and was introduced to the Celestial Master by Taishang Laojun. Tai-ping Jing 辑注类->太平经合校卷一至五十 - 东华理工大学图书馆 太平經合校