History.

The earliest examples of dead ends were unearthed in the El-Lahun workers' village in Egypt, which was built circa 1885 BC. The village is laid out with straight streets that intersect at right angles, akin to a grid but irregular. The western part of the excavated village, where the workers lived, shows fifteen narrow and short dead-ends laid out perpendicularly on either side of a wider, straight street; all terminate at the enclosing walls.  Dead-end streets also appeared during the classical period of Athens and Rome. The 15th century architect and planner Leon Battista Alberti implies in his writings that dead-end streets may have been used intentionally in antiquity for defense purposes. He writes:  The Ancients in All Towns were for having some intricate Ways and turn again Streets [i.e., dead ends or loops], without any Passage through them, that if an Enemy comes into them, he may be at a Loss, and be in Confusion and Suspense; or if he pushes on daringly, may be easily destroyed.  The same opinion is expressed by an earlier thinker, Aristotle, when he criticized the Hippodamian grid: ... but for security in war [the arrangement is more useful if it is planned in] the opposite [manner], as it used to be in ancient times. For that [arrangement] is difficult for foreign troops to enter and find their way about when attacking.  In the UK, their prior existence is implied by the Public Health Act 1875 which banned their use in new developments.  Inferential evidence of their earlier use can also be drawn from the text of a German architect, Rudolf Eberstadt, that explains their purpose and utility:  We have, in our medieval towns, showing very commendable methods of cutting up the land. I ought to mention here that to keep traffic out of residential streets is necessary not only in the general interest of the population, but, above all, for the sake of the children, whose health (amongst the working classes) is mainly dependent on the opportunity of moving about in close connection with their dwelling places, without the danger of being run over. In the earlier periods, traffic was excluded from residential streets simply by gates or by employing the cul-de-sac.  It was in the United Kingdom that the cul-de-sac street type was first legislated into use, with the Hampstead Garden Suburb Act 1906. The proponents of the Act, Raymond Unwin and Barry Parker, thus gained permission to introduce culs-de-sac in their subsequent site plans, and they promoted it as a suitable street type for Garden Suburbs. Unwin's applications of the cul-de-sac and the related crescent always included pedestrian paths independent of the road network. This design feature reflects the predominance of pedestrian movement for local trips at the turn of the 20th century, and presages the current planning priority for increased pedestrian accessibility. The 1906 Act defined the nature of the cul-de-sac as a non-through road and restricted its length to. Garden cities in the UK that followed Hampstead, such as Welwyn Garden City, all included culs-de-sac (see photo).  In the 1920s, the garden city movement gained ground in the United States and, with it, came its design elements, such as the cul-de-sac. Clarence Stein, a main proponent of the movement, incorporated it in the Radburn, New Jersey subdivision, which was to become a model for subsequent neighborhood developments. The country's Federal Housing Authority (FHA) recommended and promoted their use through their 1936 guidelines and the power of lending development funds.  In Canada, a variation of Stein's Radburn 1929 plan that used crescents (loops) instead of culs-de-sac was built in 1947: Wildwood Park, Winnipeg, designed by Hubert Bird. In 1954, the Central Mortgage and Housing Corporation published its own guidelines in which the cul-de-sac was strongly recommended for local streets and, as the FHA in the US, used its lending power to see its inclusion in development plans. The Varsity Village and Braeside, subdivisions in Calgary, Alberta also used the Radburn model in the late 1960s.  In the 1960s the cul-de-sac attained systematic international application in planned new cities such as Doxiadis' Islamabad (1960). In the UK, new towns such as Harlow (1947) by Sir Frederick Gibberd and Milton Keynes (1967) incorporated culs-de-sac and crescents in their layouts. Planning theorists have suggested the use alternatives to culs-de-sac. Most notably, Christopher Alexander et al., in his "A Pattern Language" 1977 book (pattern #49) suggests the use of looped local roads which do not abruptly stop. Although dead end streets (culs-de-sac), would fit his definition of looped local roads Alexander suggestions that "culs-de-sacs are very bad from a social standpoint–they force interaction and they feel claustrophobic, because there is only one entrance". Doxiadis has additionally argued their important role in separating man from machine.

Originally-unplanned dead ends.

Originally-unplanned dead ends have been created in city centers that are laid out on a grid by blocking through traffic. Whole neighbourhood street reconfigurations emerged in several cities, mainly concentrated in North America and the UK, which include Berkeley, California; Seattle, Washington; and Vancouver, British Columbia. The transformation of grid plans since the 1970s limits access to an existing road that is newly designated as a major artery, enabling traffic to move smoothly on it, alleviating residents' concerns.  This selective, sporadic transformation is continuing. As traffic volumes increase and as cities decide to remove or reduce traffic on specific streets of central areas, streets are closed off using bollards or landscaping thus creating new, originally unplanned dead ends and producing a new, functional blend of the inherited grid with newer street types. A recent variation of limiting traffic is the managed closure by using retractable bollards that are activated only by designated card holders. However, besides cars, they also stop ambulances and other emergency vehicles, and they often lack adequate turning.

Suburban use and benefits.

Since the end of World War II, new subdivisions in the United States and Canada, as well as New Towns in England and other countries have made extensive use of the cul-de-sac and crescent (loops) street types. Typically, there is one or several central roads in the subdivision with many cul-de-sac streets of varying length, branching out from the main roads, to fill the land in the subdivision, a dendrite or hierarchical pattern. Since the 1960s, the pattern has been the dominant road network structure of suburbs and exurbs in the United States, Canada, and Australia. It is also increasingly popular in Latin America, Western Europe, and China. In this pattern, there are only a few roads (relative to the number of cul-de-sac streets) leading out of the subdivision and into other subdivisions or onto major roads.  In the US, these changes can be attributed to real-estate developers' desire to meet FHA guidelines and make federal home loans available to their consumers. In Canada, a similar incentive was provided to developers by CMHC. The incentives, which were discontinued in the 1970s, gave the initial impetus for the application of the hierarchical pattern. In other countries, such incentives do not exist, and adoption is motivated by consumer preferences.  American urban planning, in the 19th and the early 20th centuries, emphasized a grid plan, partly out of extensive reliance on foot, horse and trams for transportation. In such earlier urban development, alleys were included to allow for deliveries of soiled supplies, such as coal, to the rear of houses that are now heated by electricity, piped natural gas or oil. The use of culs-de-sac reduces the amount of car traffic on residential streets within the subdivision, thus reducing noise, air pollution and the probability of accidents. Ben-Joseph (1995) and Lovegrove/Sayed (2006) indicate a substantially lower collision rate for street networks based on the cul-de-sac street type. Dumbaugh and Rae (2009) suggest that land use patterns play a significant role in traffic safety and should be considered in conjunction with the network pattern. While all intersection types in general increase the incidence of fatal crashes, four-way intersections, which rarely occur in a network with cul-de-sac or loop streets, increase total and injurious crashes significantly. The study recommends hybrid street networks with dense concentrations of T-intersections and concludes that a return to the 19th century gridiron is undesirable.  The decrease in traffic, in turn, is thought to lower the incidence of crime and increase desirability, because in most cases the people who traverse the cul-de-sac either live there or are guests of those who do. CPTED planning principles suggest increased natural surveillance and sense of ownership as a means of fostering security in a neighbourhood. Both of these phenomena occur naturally on a cul-de-sac street as does social networking. Design guidelines based on the CPTED perspective recommend its use for those reasons.  Cul-de-sac streets increase spontaneous outdoor activity by children. A study in California examined the amount of child play that occurred on the streets of neighbourhoods with different characteristics; grid pattern and culs-de-sac. The findings indicate that culs-de-sac showed substantial increase in play activity than the open grid street pattern. Culs-de-sac reduce perceived danger from traffic, thereby encouraging more outdoor play.  Similar studies in Europe and Australia found that children's outdoor play is significantly reduced on through roads where traffic is, or perceived by parents to be, a risk. In addition, they confirmed the results of the seminal Donald Appleyard 1982 study, which showed the negative correlation between amount of traffic and social networks. The inverse correlation between amounts of traffic and sociability of streets was reconfirmed by a newer study that repeated Appleyard’s San Francisco analysis in Bristol, UK. It showed that the cul-de-sac street with the lowest traffic of the three streets had the highest level of social interaction.  The studies recommend the use of the cul-de-sac or strong traffic calming measures. When culs-de-sac are interconnected with foot and bike paths, as for example in Vauban, Freiburg and Village Homes in Davis, California, they can increase active modes of mobility among their residents.  Real estate developers prefer culs-de-sac because they allow builders to fit more houses into oddly-shaped tracts of land and facilitate building to the edges of rivers and property lines. They also choose these discontinuous network patterns of cul-de-sac and loop streets because of the often significant economies in infrastructure costs compared to the grid plan.  From an environmental perspective, culs-de-sac allow greater flexibility than the common grid in adapting to the natural grades of a site and to its ecologically sensitive features, such as streams creeks and mature forest growth.  The desirability of the cul-de-sac street type among home buyers is implied by the evidence that they often pay up to a 20% premium for a home on such a street, according to one study. That could be because there is considerably less passing traffic, resulting in less noise and reduced actual or perceived risk, increasing the sense of tranquility. A survey of residents on three types of streets: cul-de-sac, loop, and through (grid) recorded their preferences among these types. It found that 82% of cul-de-sac residents preferred their own street type, 18% preferred a loop, and 0% the grid. Only 13% of grid street residents preferred their own type and 54% would choose a cul-de-sac. Two other studies, reported in 1990 and 2009 respectively, confirmed the upward trend and determined the premium that cul-de-sac streets command. The first found a 29% premium over the streets in a grid. The second, focused on trails and greenbelts, found that other amenities including cul-de-sac streets add significantly to the home value.  The positive feelings that a cul-de-sac street could evoke, that residents value, are expressed vividly by Allan Jacobs in describing Roslyn Place, a short (), narrow (), densely built (), and wood-paved cul-de-sac in the Shadyside neighborhood of Pittsburgh, Pennsylvania: "Step into Roslyn Place and you are likely to sense, immediately, that you are in a "place", a special place, a handsome place, a safe place, a welcoming place, a place where you might wish to live." "..."narrowness and enclosure and intimacy bring a feeling of safety to Roslyn Place... “Stay on our street” is all the kids have to know.  Gated communities, whose numbers steadily increase worldwide, use cul-de-sac and loop street networks because the dendrite structure reduces the number of through roads and thus the corresponding number of entries and exits that need to be controlled.

Criticisms and discussion.

Traffic safety issues.

Dead ends are traditionally considered safer traffic environments for children than normal streets, but research shows that areas with many dead ends in fact have higher rates of traffic accidents involving young children.  This increased risk of death is due to multiple factors, including:

Environmental, health, and crime issues.

Culs-de-sac are criticised by urban designers like those of the Foundation for the Built Environment in the UK for encouraging car transport for even short distances, as more direct connections are precluded by the geometry, which necessitates long travel distances even to physically-nearby locations. This increases fuel consumption and vehicle emissions and has negative effects on health by reducing walking and cycling rates. Related research in the United States by Richard Jackson has shown that people in car-based (cul-de-sac heavy) communities weigh on average more than those in traditional towns (with open grid networks).  An extensive analysis of the research evidence by TRB, however, shows only an association between the built environment and physical activity levels, not causal connections. The evidence also does not identify with certainty which characteristics of the built environment are most closely associated with physical activity behaviour. The study also warns against confusing inadequate physical activity with obesity which is the outcome of an energy imbalance. Many contemporary lifestyle trends, some inevitable (sedentary work) and some avoidable (frequent energy-rich food consumption or the watching of television [4 h/d]), contribute to the imbalance and must be considered in understanding and combating obesity.  The impermeability deficiency of the typical cul-de-sac street can be addressed by applying a modified, improved version of it, mentioned above, that enables pedestrian and bicycle through movement. While this more permeable version can be applied in new developments easily, modifying existing impermeable cul-de-sac streets is problematic as it encounters property ownership issues. Efforts in that direction are, however, being made. Because of the complicated legal process and the sheer number of existing cul-de-sac streets, however, such efforts would be slow to produce results and may have little impact in changing the landscape of existing districts. Conversely, transforming existing streets that are part of a grid plan into permeable, linked culs-de-sac, as was done in Berkeley, California, and Vancouver, British Columbia, is physically and administratively easy due to the public ownership of the street right-of-way. However, residents on adjacent through roads may resent the potential traffic increase and delay the process. In Berkeley, the barriers used were permeable to both pedestrian and bicycle traffic and became the backbone of the bicycle boulevard system in that region.  Increases in pedestrian and bicycle permeability may result in a displacement of local car trips for short distance destinations and consequently a reduction in neighbourhood vehicle emissions. The impermeable cul-de-sac not only discourages walking and biking but also increases the length of car trips by the circuitous geometry of the dendrite network structure of which it is a part. Research studies examined the influence of several variables on the amount of car travel that residents of several types of districts recorded. Results vary considerably among them, but there is general agreement on a number of key correlations: a) the wealthier and the larger the family is the more cars they own and the more they drive, b) the farther away a family lives from the city centre and the fewer the jobs in the vicinity plus a slow bus service the more they drive, and c) street patterns may add a 10% length to "local trips" but the total VKTs are affected more by the "macro" urban than the "micro" neighbourhood structure.  Culs-de-sac, especially those that also cut off pedestrian connections instead of limiting only road traffic, have also been criticised for negative effects on safety because they decrease the amount of through traffic (vehicular or pedestrian) that might spot an accident or crime victim in need of help. Proponents of culs-de-sac and gated communities have in turn countered that the reduction in through traffic makes any "stranger" much more recognisable in the closed local environment and thus reduces crime danger. That view has in turn been characterized as unrealistic. It is argued that, since only very few of all non-locals passing through the area are potential criminals, increased traffic should increase rather than decrease safety.  New research has expanded the discussion on the disputed issue. A recent study did extensive spatial analysis and correlated several building, site plan and social factors with crime frequencies and identified subtle nuances to the contrasting positions. The study looked at, among others, a) dwelling types, b) unit density (site density) c) movement on the street, d) culs-de-sac or grids, and e) the permeability of a residential area. Among its conclusions are, respectively, that a) flats are always safer than houses and the wealth of inhabitants matters, b) density is generally beneficial but more so at ground level, c) local movement is beneficial but larger scale movement not so, d) relative affluence and the number of neighbours has a greater effect than either being on a cul-de-sac or being on a through street. It also established again that simple, linear culs-de-sac with good numbers of dwellings that are joined to through streets tend to be safe. As for permeability, it suggests that residential areas should be permeable enough to allow movement in all directions but no more. The overprovision of poorly used permeability is a crime hazard.  More generally, the New Urbanism movement has offered criticism of the cul-de-sac and crescent (loop) street types not intended to network with each other. It has been suggested that such street layouts can cause increased traffic on the collector streets. It is recognized that cul-de-sacs and looped streets inherently remove car traffic through them and restrict access to residents only. Resident traffic is naturally channelled to minor residential collectors and to arterials that provide inter-neighbourhood and inter-district connectivity. A study, reported in 1990, compared the traffic performance in a development that was laid out using two approaches, one with and the other without hierarchy or cul-de-sac streets. It concluded that the non-hierarchical, traditional layout generally shows lower peak speed and shorter, more frequent intersection delays than the hierarchical pattern. The traditional pattern is not as friendly to the long trips as the hierarchical but friendlier to short trips. Local trips in it are shorter in distance but about equivalent in time with the hierarchical layout. A later similar comparative traffic study of about concluded that all types of layouts perform adequately in most land use scenarios and that a refined hierarchical, dendrite network can improve traffic performance.  Anecdotal and research evidence suggests that navigation (especially on foot) in a disconnected network of cul-de-sac and looped streets is inconvenient and non-intuitive, particularly when combined with curvilinear geometry. Loss of orientation and sense of direction is also a common experience in older cities with cul-de-sac streets (Medina of Arab cities or Mediterranean hill towns) as well as in cities with highly irregular block geometries and sizes and corresponding street alignments that produce a labyrinthine effect. The long history of such cities implies that an irregular, complicated street network that appears entirely illegible to a visitor is well understood and used by the inhabitants. More convincing about its workability for their permanent residents are the case histories of cities such as Regensburg that show a gradual transformation of an imported or imposed orthogonal, "legible" grid to the traditional "confusing" street networks.  Cul-de-sac and loop streets can reduce the size of any given neighbourhood to a single street. Neighbourhoods can be defined by geographic boundaries but more often it is shared ethnic, socioeconomic and cultural characteristics that create social cohesion irrespective of apparent physical "boundaries." Mehaffy "et al." (2010), who propose a model for structuring an urban network, suggest that neighbourhoods cannot be designed into being. "Community" is viewed as a dynamic social and cultural construct, especially in contemporary, open, multicultural cities. Residential area street configuration can assist its emergence only by reducing through traffic and increasing local pedestrian movement; a design goal for which connected cul-de-sac and looped streets are suited.  Issues of pedestrian trip length and isolation are sharply evident in the back-to-front housing arrangement where the front of the house fronts onto the cul-de-sac street while the rear fronts onto the main roads. Some of the problems can be mitigated by the newer practice of connecting the neighbouring roads and culs-de-sac with public pedestrian/cycle paths. In effect, this removes the discontinuity aspect for these modes of transport. Built examples of such connected culs-de-sac can be found in the United States (such as Radburn, New Jersey, and Village Homes, California), England (such as Milton Keynes), and Greece (such as Papagou, a suburb of Athens) (see photo). Acknowledging their use, Germany, under the 2009 amendment to the Road Traffic Act, introduced an additional sign for culs-de-sac that are permeable to pedestrians and cyclists (see under signage below). A new system for organizing connected, permeable culs-de-sac into complete neighbourhoods, the fused grid, has been developed by Canada Mortgage and Housing Corporation.  In the development context and planning literature of North America, cul-de-sacs have been associated with low-density residential development. Sustainable development theorists and proponents claim that to be, in some undefined way, inefficient. The increased prevalence of cul-de-sac streets occurred in the 1960s and 1970s, a period of rapid economic and city expansion, when a detached house on a large lot meant an ideal form of habitation. The temporal coincidence of the wide adoption of a street type and an increasing demand for large lots and houses creates the impression of a necessary relationship between street type and unit density. Historically, however, the earliest systematic application of the cul-de-sac street type by Raymond Unwin (1909) had a unit density between, considerably higher than mid-to-late 20th century. Even in the 21st century, developments rarely achieve densities above in the suburbs. Conversely, early 1950s suburban developments that were laid out on a grid exhibit similar low densities. Evidently, street, network type and density are not linked causally; other factors, such as land scarcity and income influence the outcome as, for example, in cities that are landlocked or that have low average incomes.  Another concern is often raised by emergency services, which can have difficulty locating streets when a community consists of a large number of similarly named culs-de-sac; also, large fire response vehicles, in particular, can have great difficulty with turning around in a cul-de-sac. However, confusing street naming is not a necessary outcome of street network design and can be improved. The practice of naming orthogonal networks by numbers and letters in the corresponding cardinal directions has been criticized by Camilo Sitte as lacking imagination. Nonetheless, police and fire departments now use advanced GPS systems that quickly locate the destination and the shortest path to follow.  School buses can also have a hard time turning around, which means that children who live in a cul-de-sac must often walk to a bus stop on a main through road. However, recent research on obesity and urban planning suggests that to be a possible advantage because it enables children to get daily physical activity. Longer walking distances, however, reduce interest to use buses especially when a car is available. This disincentive to walking to the school bus stop can be overcome in planned cul-de-sac streets by regulating their maximum length to about, as was recommended and practiced by R. Unwin and others.  Weighing available evidence has led a few US cities including Austin, Texas; Charlotte, North Carolina; and Portland, Oregon, to restrict and regulate the inclusion of cul-de-sac streets in new suburbs. However, a 2010 study on Sprawl in NA by a legal expert concludes that "neighborhoods dominated by culs-de-sac are less walkable than those that include street grids... On the other hand, culs-de-sac do have a countervailing public benefit: because of their very inaccessibility, they tend to have less automobile traffic. Given the existence of important public policy goals on both sides, a city seeking to maximize walkability should not favor culs-de-sac over grids, but should also allow some culs-de-sac as a legitimate residential option.... In addition, there are "middle ground" alternatives between prohibiting culs-de-sac and mandating them. For example, a city could encourage culs-de-sac combined with pedestrian walkways." This design combination is shown in the Village Homes layout and is an integral part of the Fused Grid.

Terminology.

George Orwell wrote in his 1946 article "Politics and the English Language" that the term "cul de sac" is another foreign word used in English as pretentious diction and is unnecessary.  The word "cul-de-sac" and its synonyms or near synonyms "dead end" and "no exit" have inspired metaphorical uses in literature and in culture, often with the result that a word or phrase seeming to have a negative connotation is replaced in street signs with a new coinage. ("No outlet" is another alternative name used on street signs.)  The expression "cul-de-sac" comes from French, where it originally meant "bottom of the sack". It was first used in English in anatomy (since 1738). It was used for dead-end streets since 1800 in English (since the 14th century in French). The often heard erroneous folk etymology "arse/ass [buttocks] of the sack" is based on the modern meaning of "cul" in French, Catalan, and Occitan, but "cul" doesn't have that meaning in "cul-de-sac", which is still used to refer to dead ends in modern French although the terms and are more common in modern French.  J. R. R. Tolkien used the name Bag End as a translation of "cul-de-sac" to poke fun at the British use of French terms.

Canada.

In Canada, "cul-de-sac" is commonly used in speech but "no exit" or "no through road" is more common in road signs, especially in western Canada. In Quebec and Newfoundland, "Cul-de-Sac" is in far more common use, though Quebec is increasingly using "Impasse" instead.

Australia.

In Australia, dead-end streets are signposted as and often referred to as a "No Through Road". Suffixes for these types of streets include "court", "close" or "place". The term "cul-de-sac" generally only refers to a reasonably short street with a bulbous end, or even only to the end portion. A long road that is a no-through road and terminates abruptly is usually called a dead end.

New Zealand.

In New Zealand dead-end streets are sometimes signposted as "No Exit", but are often not signposted at all. The terms 'cul-de-sac' and 'dead end' have the same senses as in Australia.

United States.

U.S. Federal Highway Administration rules state: "The "Dead End" sign may be used at the entrance of a single road or street that terminates in a dead end or cul-de-sac. The "No Outlet" sign may be used at the entrance to a road or road network from which there is no other exit." There is no federal regulation on "no exit".  The phrase "No Exit" is also preferred for Chicago signs, although "dead end" is still used there. New York City has favored "dead end" since at least the 1930s, when Sidney Kingsley used the phrase to title his Broadway play about poor, tough East Side youths with lives of little promise, in contrast to the dead-end streets of the nearby Sutton Place neighborhood. (Similarly, French existentialist Jean-Paul Sartre titled a play about three damned sinners, "Huis Clos", translated into English as "No Exit".) Kingsley's play was later made into a movie, "Dead End", which proved so popular that it spawned similar movies, many starring a group of recurring characters known as the Dead End Kids. The play and movies created such a strong image of bleak futures and an unfair society that some municipalities changed the sign terminology for culs-de-sac, often to "no outlet" or "no exit". (The "dead end" signs currently at Sutton Place are bright yellow with black lettering.)  In New York City, as of 2008, there were 4,659 "dead end" traffic signs, along with 160 "no outlet" signs. The city records, which go back to the 1960s, show only a couple of "no exit" signs once existing near the approaches to the Midtown Tunnel, and which are no longer there. "We hear that some towns use 'no outlet' instead of 'dead end' because they think it sounds less morbid," New York City Commissioner of Transportation Janette Sadik-Khan said in 2008. "We tell New Yorkers the truth: it's a 'dead end', and we think that motorists get the point quickly."  California uses the phrase "Not a Through Street" or "Not a Through Road" to mark roads or road systems that end in culs-de-sac. More recently, "No Outlet" has been shown on some signs as well (an example being Meyers Avenue south of Eureka Street in the Pine Hills area).

Other uses.

In military parlance, a "cul-de-sac" refers to a situation where an army is ""hemmed in on all sides but behind"". "Cul-de-sac" is also used metaphorically to mean a line of thought or action that leads nowhere.  In medicine, the expression is used to refer to the recto-uterine pouch, also known as the Pouch of Douglas, the deepest point of the female peritoneal cavity.

A dead end, also known as a cul-de-sac (, from French for "bottom of bag"), no through road or no exit road, is a street with only one inlet or outlet.

死路是指仅有一边可以出入的道路,因有尽头之处而以「死」称之。通常见于街道、巷道或野外道路上,多为不同年代的都市设计或道路规划产生差异下,导致道路无法延续而成,但也有因交通宁静、社区安全防护等缘由而特别设计的,例如囊底路。假若路人不熟悉道路,误入死路会浪费时间,因为路有尽头,非原路折返不可,所以不少死路都会在路口处安装单程路或「此路不通」等路标,以警告用路人。


Names.

The Protestant Episcopal Church in the United States of America (PECUSA) and "The Episcopal Church" (TEC) are both official names specified in the church's constitution. The latter is much more commonly used. In other languages, an equivalent is used. For example, in Spanish, the church is called "La Iglesia Episcopal Protestante de los Estados Unidos de América" or "La Iglesia Episcopal". and in French "L'Église protestante épiscopale des États-Unis d'Amérique" or "L'Église épiscopale".  Until 1964, "The Protestant Episcopal Church in the United States of America" was the only official name in use. In the 19th century, High Church members advocated changing the name, which they felt did not acknowledge the church's Catholic heritage. They were opposed by the church's evangelical wing, which felt that the "Protestant Episcopal" label accurately reflected the Reformed character of Anglicanism. After 1877, alternative names were regularly proposed and rejected by the General Convention. One proposed alternative was "the American Catholic Church". By the 1960s, opposition to dropping the word "Protestant" had largely subsided. In

History.

Colonial era.

The Episcopal Church has its origins in the Church of England in the American colonies, and it stresses continuity with the early universal Western Church and claims to maintain apostolic succession (though the Catholic and Orthodox churches do not recognize this claim).  The first parish was founded in Jamestown, Virginia in 1607, under the charter of the Virginia Company of London. The tower of Jamestown Church ( 1639–43) is one of the oldest surviving Anglican church structures in the United States. The Jamestown church building itself is

Revolutionary era.

Embracing the symbols of the British presence in the American colonies, such as the monarchy, the episcopate, and even the language of the "Book of Common Prayer", the Church of England almost drove itself to extinction during the upheaval of the American Revolution. More than any other denomination, the War of Independence internally divided both clergy and laity of the Church of England in America, and opinions covered a wide spectrum of political views: patriots, conciliators, and loyalists. While many Patriots were suspicious of Loyalism in the church, about three-quarters of the signers of the Declaration of Independence were nominally Anglican laymen, including Thomas Jefferson, William Paca, and George Wythe. It was often assumed that persons considered "High Church" were Loyalists, whereas persons considered "Low Church" were Patriots: assumptions with possibly dangerous implications for the time. Of the approximately three hundred clergy in the Church of England in America

Early Republic era.

In the wake of the Revolution, American Episcopalians faced the task of preserving a hierarchical church structure in a society infused with republican values. When the clergy of Connecticut elected Samuel Seabury as their bishop in 1783, he sought consecration in England. The Oath of Supremacy prevented Seabury's consecration in England, so he went to Scotland; the non-juring bishops of the Scottish Episcopal Church consecrated him in Aberdeen on November 14, 1784, making him, in the words of scholar Arthur

Nineteenth century.

In 1856 the first society for African Americans in the Episcopal Church was founded by James Theodore Holly. Named "The Protestant Episcopal Society for Promoting The Extension of The Church Among Colored People", the society argued that blacks should be allowed to participate in seminaries and diocesan conventions. The group lost its focus when Holly emigrated to Haiti, but other groups followed after the Civil War. The current Union of Black Episcopalians traces its history to the society. Holly went on to found the Anglican Church in Haiti, where he became the first African-American bishop on November 8, 1874. As Bishop of Haiti, Holly was the first African American to attend the Lambeth Conference. However, he was consecrated by the American Church Missionary Society, an Evangelical Episcopal branch of the Church.  Episcopal missions chartered by African-Americans in this era were chartered as a Colored Episcopal Mission. All other missions (white) were chartered as an Organized Episcopal Mission. Many historically Black parishes are still in existence to date. When the American Civil War began

Era of change (1958–1970s).

At the 1958 general convention, a coalition of liberal church members succeeded in passing a resolution recognizing "the natural dignity and value of every man, of whatever color or race, as created in the image of God". It called on Episcopalians "to work together, in charity and forbearance, towards the establishment... of full opportunities in fields such as education, housing, employment and public accommodations". In response, the Episcopal Society for Cultural and Racial Unity (ESCRU) was founded in December 1959 in order

Recent history.

In recent decades, the Episcopal Church, like other mainline churches, has experienced a decline in membership as well as internal controversy over women's ordination and the place of homosexuals in the church. The 1976 General Convention also passed a resolution calling for an end to apartheid in South Africa and in 1985 called for "dioceses, institutions, and agencies" to create equal opportunity employment and affirmative action policies to address any potential "racial inequities" in clergy placement. Because of these and other controversial issues including abortion, individual members and clergy can and do frequently disagree with the stated position of the church's leadership. In January 2016, the Anglican Primates Meeting at Canterbury decided that in response to the "distance" caused by what it called "unilateral action on matters of doctrine without catholic unity", "for a period of three years, The Episcopal Church [would neither] represent [the Communion] on ecumenical and interfaith bodies... [nor] take part in decision making on any issues pertaining to doctrine or polity."

Revised prayer book.

In 1976, the General Convention adopted a new prayer book, which was a substantial revision and modernization of the previous 1928 edition. It incorporated many principles of

Ordination of women.

On July 29, 1974, a group of women known as the Philadelphia Eleven were irregularly ordained as priests in the Episcopal Church by bishops Daniel Corrigan, Robert L. DeWitt, and Edward R. Welles, assisted by Antonio Ramos. On September 7, 1975, four more women (the "Washington Four") were irregularly ordained by retired bishop George W. Barrett. In the wake of the controversy over the ordination of the Philadelphia Eleven, the General Convention permitted the ordination of women in 1976 and recognized the ordinations of the 15 forerunners. The first women were canonically ordained to the priesthood in 1977. The first woman to become a bishop, Barbara Harris, was consecrated on February 11, 1989.  At the same time, there was still tolerance for those dioceses

Affirmation of LGBT people.

The Episcopal Church affirmed at the 1976 General Convention that homosexuals are "children of God" who deserve acceptance and pastoral care from the church and equal protection under the law. The first openly gay person ordained as a priest was Ellen Barrett in 1977. Despite such an affirmation of gay rights, the General Convention affirmed in 1991 that "physical sexual expression" is only appropriate within the monogamous lifelong "union of husband and wife". The church elected its first openly gay

Separations from the church.

Following the ordination of Bp. Gene Robinson in 2003, some members of a number of congregations left the Episcopal Church. For example, in Cleveland, Ohio, four parishes "with about 1,300 active members, decided to leave the U.S. church and the local diocese because of 'divergent understandings of the authority of scripture and traditional Christian teaching.'" Four dioceses also voted to leave the church; Pittsburgh, Quincy, Fort Worth, and San Joaquin. The stated reasons included those expressed by the Pittsburgh diocese, which complained that the church had been "hijacked" by liberal bishops. A few years later, in 2012, the Diocese of South Carolina voted to withdraw.  The Episcopal Church did not acknowledge any of the purported diocesan withdrawals, stating that under canon law an Episcopal diocese cannot withdraw itself from the larger Episcopal Church. In a "pastoral letter" to the South Carolina diocese, Presiding Bishop Schori wrote that "While some leaders have expressed a desire to leave The Episcopal Church, the Diocese has not left. It cannot, by its own

Church property disputes.

In a letter to the House of Bishops during summer 2009, Presiding Bishop Katharine Jefferts Schori instructed local dioceses not to sell parish property to departing groups. She stated: "We do not make settlements that encourage religious bodies who seek to replace The Episcopal Church".  Before Schori took this stand, prior bishops had treated parish property disputes as internal diocesan matters that are "not subject to the review or oversight of the presiding bishop". One example was when then-Presiding Bishop Frank Griswold told the Diocese of Western Louisiana on May 11, 2006, that the national church involved itself in

Membership.

, the Episcopal Church reported 1,835,931 baptized members. The majority of members are in the United States, where the Church has 1,676,349 members. Outside of the U.S. the Church has 159,582. Total average Sunday attendance (ASA) for 2018 was 562,529 (533,206 in the U.S. and 29,323 outside the U.S.), a decrease of 24.7% percent from 2008.  According to a report by ARIS/Barna in 2001, 3.5 million Americans self–identified as Episcopalians, highlighting "a gap between those who are affiliated with the church (on membership rolls), versus those who self-identify [as Episcopalians]". Church Pension Group also cited having 3.5 million adherents in 2002. More recently, in 2014, Pew Research found that approximately 1.2 percent of 245 million U.S adults, around 3 million people, self–identified as mainline Episcopalian/Anglican.  According to data collected in 2000, the District of Columbia, Rhode Island, Connecticut, and Virginia have the highest rates of adherents per capita, and states along the East Coast generally have a higher number of adherents per capita than in other parts of the country. New York was the

Influence.

In the twentieth century, Episcopalians tended to be wealthier and more educated (having more graduate and postgraduate degrees per capita) than most other religious groups in the United States, and were disproportionately represented in the upper reaches of American business, law, and politics. According to Pew Research Center Episcopal Church "has often been seen as the religious institution most closely associated with the American establishment, producing many of the nation’s most important leaders in politics and business." And about a quarter of

Structure.

The Episcopal Church is governed according to episcopal polity with its own system of canon law. This means that the church is organized into dioceses led by bishops in consultation with representative bodies. It is a unitary body, in that the power of the General Convention is not limited by the individual dioceses. The church has, however, a highly decentralized structure and characteristics of a confederation.

Parishes and dioceses.

At the local level, there are 6,447 Episcopal congregations, each of which elects a vestry or bishop's committee. Subject to the approval of its diocesan bishop, the vestry of each parish elects a priest, called the rector, who has spiritual jurisdiction in the parish and selects assistant clergy, both deacons and priests. (There is a difference between vestry and clergy elections – clergy are ordained members usually selected from outside the parish, whereas any member in good standing of a parish is eligible to serve on the vestry.) The diocesan bishop, however, appoints the clergy for all missions and may choose to do so for non-self-supporting parishes.  The middle

National church.

The Washington National Cathedral is the seat of the Presiding Bishop of the Episcopal Church as well as the bishop of the Episcopal Diocese of Washington.  The highest legislative body of the Episcopal Church is the triennial General Convention, consisting of the House of Deputies and the House of Bishops. All active (whether diocesan, coadjutor, suffragan, or assistant) and retired bishops make up the over 300 members of the House of Bishops. Diocesan conventions elect over 800 representatives (each diocese elects four laity and four clergy) to the House of Deputies. The House of Deputies elects a president and vice-president to preside at meetings. General Convention enacts two types of legislation. The first type is the rules by which the church is governed as contained in the Constitution and Canons; the second type are broad guidelines on church policy called resolutions. Either house may propose legislation. The House of Deputies only meets as a full body once every three years; however, the House of Bishops meets regularly throughout the triennium between conventions.  The real work of General Convention is done by interim bodies, the most powerful being the Executive Council, which

Worship and liturgy.

Worship according to the Book of Common Prayer (BCP) is central to the Episcopal Church's identity and its main source of unity. The current edition of the BCP was published in 1979 and is similar to other Anglican prayer books in use around the world. It contains most of the worship services (or liturgies) used in the Episcopal Church.  The Episcopal Church has a sacramental understanding of worship. The Episcopal catechism defines a sacrament as "an outward and visible sign of an inward and spiritual grace given to us". Episcopalians believe that sacraments are material things that God uses to act in human lives. The BCP identifies Baptism and the Eucharist as the "two great sacraments of the Gospel". Confirmation, ordination, holy matrimony, reconciliation of a penitent, and unction are identified as "sacramental rites". Private confession of sin is available in the Episcopal Church, though it is not as commonly practiced as in the Roman Catholic Church. This is in part due to the general confession provided for in Episcopal services.  The prayer book specifies that the Eucharist or Holy Communion is "the principal act of Christian worship on the Lord's Day". The service has two parts. The first is centered on Bible readings and preaching. At each service, four scripture passages are

Belief and practice.

The center of Episcopal teaching is the life and resurrection of Jesus Christ. The Doctrine of the Episcopal Church is found in the Canon of Holy Scripture as understood in the Apostles' and Nicene Creeds and in the sacramental rites, the Ordinal and Catechism of the Book of Common Prayer. Some of these teachings include:  The full catechism is included in the Book of Common Prayer and is posted on the Episcopal website. In practice, not all Episcopalians hold all of these beliefs, but ordained clergy are required to "solemnly engage to conform" to this doctrine.  The Episcopal Church follows the "via media" or "middle way" between Protestant and Roman Catholic doctrine and practices: that is both Catholic and Reformed. Although many Episcopalians identify with this concept, those whose convictions lean toward either evangelical Anglicanism or Anglo-Catholicism may not.  A broad spectrum of theological views is represented within the Episcopal Church. Some Episcopal members or theologians hold evangelical positions, affirming the authority of scripture over all. The Episcopal Church website glossary defines the sources of authority as a balance between scripture, tradition, and reason. These three are characterized as a "three-legged stool" which will topple if any one overbalances the other. It also notes  This balance of scripture, tradition and reason is traced to the work of Richard Hooker, a 16th-century apologist. In Hooker's model, scripture is the primary means of arriving at doctrine and things stated plainly in scripture are accepted as true. Issues that are ambiguous are determined by tradition, which is checked by reason. Noting the role of personal experience in Christian life, some Episcopalians have advocated following the example of the Wesleyan Quadrilateral of Methodist theology by thinking in terms of a "Fourth Leg" of "experience". This understanding is highly dependent on the work of Friedrich Schleiermacher.  A public example of this struggle between different Christian positions in the church has been the 2003 consecration of Gene Robinson, an openly gay man living with a long-term partner. The acceptance/rejection of his consecration is motivated by different views on the understanding of scripture. This struggle has some members concerned that the church may not continue its relationship with the larger Anglican Church. Others, however, view this pluralism as an asset, allowing a place for both sides to balance each other.  Comedian and Episcopalian Robin Williams once described the Episcopal faith (and, in a performance in London, specifically the Church of England) as "Catholic Lite – same rituals, half the guilt".

Agencies and programs.

The Society for the Increase of the Ministry (SIM) is the only organization raising funds on a national basis for Episcopal seminarian support. SIM's founding purpose in 1857 – "to find suitable persons for the Episcopal ministry and aid them in acquiring a thorough education". SIM has awarded scholarships to qualified full-time seminary students.  Episcopal Relief & Development is the international relief and development agency of the Episcopal Church of the United States. It helps to rebuild after disasters and aims to empower people by offering lasting solutions that fight poverty, hunger and disease. Episcopal Relief and Development programs focus on alleviating hunger, improving food supply, creating economic

Ecumenical relations.

Like the other churches of the Anglican Communion, the Episcopal Church has entered into full communion with the Old Catholic Churches of the Union of Utrecht, the Philippine Independent Church, and the Mar Thoma Syrian Church of Malabar. The Episcopal Church is also in a relationship of full communion with the Evangelical Lutheran Church in America and the Northern and Southern Provinces of the Moravian Church in America. The Episcopal Church entered into a full communion agreement with the Church of Sweden at its General Convention in Salt Lake City on June 28, 2015.  The Episcopal Church maintains ecumenical dialogues with the United Methodist Church and the Moravian Church in America, and participates in pan-Anglican dialogues with the Oriental Orthodox Churches, the World Alliance of Reformed Churches, and the Roman Catholic Church. In 2006 a relation of interim Eucharistic sharing was inaugurated with the United Methodist Church, a step that may ultimately lead to full communion.  Historically Anglican churches have had strong ecumenical ties with the Eastern Orthodox Churches, and the Episcopal Church particularly with the Russian Orthodox Church, but relations in more recent years have been strained by the ordination of women and the ordination of Gene Robinson to the episcopate. A former relation of full communion with the Polish National Catholic Church (once a part of the Union of Utrecht) was broken off by the PNCC in 1976 over the ordination of women.  The Episcopal Church was a founding member of the Consultation on Church Union and participates in its successor, Churches Uniting in Christ. The Episcopal Church is a founding member of the National Council of Churches, the World Council of Churches, and the new Christian Churches Together in the USA. Dioceses and parishes are frequently members of local ecumenical councils as well.

The Episcopal Church (TEC) is a member church of the worldwide Anglican Communion and is based in the United States with additional dioceses elsewhere. It is a mainline Christian denomination divided into nine provinces. The presiding bishop of the Episcopal Church is Michael Bruce Curry, the first African-American bishop to serve in that position.

美国圣公会(The Episcopal Church)是普世圣公宗在美国、洪都拉斯、台湾、哥伦比亚、厄瓜多尔、海地、多米尼加共和国、委内瑞拉、英属维尔京群岛和部分欧洲地区的一个教区,教会体制采主教制。总部位于纽约市。


Anatomy.

Myriapods have a single pair of antennae and, in most cases, simple eyes. Exceptions include the large and well-developed compound eyes of Scutigera The mouthparts lie on the underside of the head, with an "epistome" and labrum forming the upper lip, and a pair of maxillae forming the lower lip. A pair of mandibles lie inside the mouth. Myriapods breathe through spiracles that connect to a tracheal system similar to that of insects. There is a long tubular heart that extends through much of the body, but usually few, if any, blood vessels.  Malpighian tubules excrete nitrogenous waste into the digestive system, which typically consists of a simple tube. Although the ventral nerve cord has a ganglion in each segment, the brain is relatively poorly developed.  During mating, male myriapods produce a packet of sperm, or spermatophore, which they must transfer to the female externally; this process is often complex and highly developed. The female lays eggs which hatch as much-shortened versions of the adults, with only a few segments and as few as three pairs of legs. The young add additional segments and limbs as they repeatedly moult to reach the adult form.

Ecology.

Myriapods are most abundant in moist forests, where they fulfill an important role in breaking down decaying plant material, although a few live in grasslands, semi-arid habitats or even deserts. A very small percentage of species are littoral (found along the sea shore). The majority are detritivorous, with the exception of centipedes, which are chiefly nocturnal predators. A few species of centipedes and millipedes are able to produce light and are therefore bioluminescent Pauropodans and symphylans are small, sometimes microscopic animals that resemble centipedes superficially and live in soils. Millipedes differ from the other groups in having their body segments fused into pairs, giving the appearance that each segment bears two pairs of legs, while the other three groups have a single pair of legs on each body segment.  Although not generally considered dangerous to humans, many millipedes produce noxious secretions (often containing benzoquinones) which in rare cases can cause temporary blistering and discolouration of the skin. Large centipedes, however, can bite humans, and although the bite may cause intense pain and discomfort, fatalities are extremely rare.

Classification.

There has been much debate as to which arthropod group is most closely related to the Myriapoda. Under the Mandibulata hypothesis, Myriapoda is the sister taxon to Pancrustacea, a group comprising the Crustacea and Hexapoda (insects and their close relatives). Under the Atelocerata hypothesis, Hexapoda is the closest, whereas under the Paradoxopoda hypothesis, Chelicerata is the closest. This last hypothesis, although supported by few, if any, morphological characters, is supported by a number of molecular studies. A 2020 study found numerous characters of the eye and preoral region suggesting that the closest relatives to crown myriapods are the extinct Euthycarcinoids. There are four classes of extant myriapods, Chilopoda (centipedes), Diplopoda, Pauropoda and Symphyla, containing a total of around 12,000 species. While each of these groups of myriapods is believed to be monophyletic, relationships among them are less certain.

Centipedes.

Centipedes make up the class Chilopoda. They are fast, predatory and venomous, hunting mostly at night. There are around 3,300 species, ranging from the diminutive "Nannarrup hoffmani" (less than 12 mm or in in length) to the giant "Scolopendra gigantea", which may exceed.

Millipedes.

Millipedes form the class Diplopoda. Most millipedes are slower than centipedes, and feed on leaf litter and detritus. They are distinguished by the fusion of each pair of body segments into a single unit, giving the appearance of having two pairs of legs per segment. Around 12,000 species have been described, which may represent less than a tenth of the true global millipede diversity. The name "millipede" is a compound word formed from the Latin roots "millia" ("thousand") and "pes" (gen. "pedis") ("foot"), although millipedes typically have between 36 and 400 legs. One species, "Illacme plenipes", has the greatest number of legs of any animal, with 750. Pill millipedes are much shorter, and are capable of rolling up into a ball, like pillbugs.

Symphyla.

About 200 species of them are known worldwide. They resemble centipedes but are smaller and translucent. Many spend their lives as soil infauna, but some live arboreally. Juveniles have six pairs of legs, but, over a lifetime of several years, add an additional pair at each moult so that the adult instar has twelve pairs of legs.

Pauropoda.

Pauropoda is another small group of small myriapods. They are typically 0.5–2.0 mm long and live in the soil on all continents except Antarctica. Over 700 species have been described. They are believed to be the sister group to millipedes, and have the dorsal tergites fused across pairs of segments, similar to the more complete fusion of segments seen in millipedes.

Arthropleuridea.

Arthropleurideans were ancient myriapods that are now extinct, known from the late Silurian to the Permian. The most famous members are from the genus "Arthropleura", which was a giant, probably herbivorous, animal that could be up to long, but the group also includes species less than. Arthropleuridea was historically considered a distinct class of myriapods, but since 2000 scientific consensus has viewed the group as a subset of millipedes, although the relationship of arthropleurideans to other millipedes and to each other is debated.

Myriapod relationships.

A variety of groupings (clades) of the myriapod classes have been proposed, and married, some of which are mutually exclusive, and all of which represent hypotheses of evolutionary relationships. Traditional relationships supported by morphological similarities (anatomical or developmental similarities) are challenged by newer relationships supported by molecular evidence (including DNA sequence and amino acid similarities).

Myriapoda is a subphylum of arthropods containing millipedes, centipedes, and others. The group contains over 16,000 species, most of which are terrestrial. Although their name suggests they have myriad (10,000) legs, myriapods range from having up to 750 legs (the millipede "Illacme plenipes") to having fewer than ten legs.

多足亚门(或称多足类、多足纲,学名Myriapoda,来自古希腊语μυριάς一万和 πούς脚、腿),是节肢动物门下的一类,包含了马陆及蜈蚣等。多足类有超过13000个物种,都是陆地动物。虽然学名Myriapoda的词源是一万条腿,但实际上多足类最多只有约750条腿("Illacme plenipes"),少至10只以下。牠们有一对触角及单眼。


History.

According to popular legend, the coffee plant was discovered in Ethiopia by a goatherd named Kaldi.  South America is now responsible for about 45% of the world's total coffee exports. Most of this coffee is grown in Brazil.  The United States imports more coffee than any other nation. The per capita consumption of coffee in the United States in 2011 was 4.24 kg (9 lbs), and the value of coffee imported exceeded $8 billion. As of 2015, Americans consumed approximately 400 million cups of coffee per day, making the United States the leading consumer of coffee in the world.  Coffee plants grow within a defined area between the Tropics of Cancer and Capricorn, termed the bean belt or coffee belt.

Etymology.

The Oxford English Dictionary suggests that the European languages generally appear to have gotten the name from Turkish "kahveh", about 1600, perhaps through Italian "caffè". Arab "qahwah", in Turkish pronounced "kahveh", the name of the infusion or beverage; said by Arab lexicographers to have originally meant "wine" or some type of wine, and to be a derivative of a verb-root "qahiya" "to have no appetite". Another common theory is that the name derives from Kaffa Province, Ethiopia, where the species may have originated.

Coffee plant.

The coffee tree averages from in height. As the tree gets older, it branches less and less and bears more leaves and fruits.  Coffee plants are grown in rows several feet apart. Some farmers plant fruit trees around them or plant the coffee on the sides of hills, because they need specific conditions to flourish. Ideally, Arabica coffee beans are grown at temperatures between and Robusta at and receive between of rainfall per year. Heavy rain is needed in the beginning of the season when the fruit is developing and less later in the season as it ripens.

Processing.

When the fruit is ripe, it is almost always handpicked, using either "selective picking", where only the ripe fruit is removed, or "strip-picking", where all of the fruit is removed from a limb all at once. This selective picking gives the growers reason to give their coffee a certain specification called "operation cherry red" (OCR). In rare circumstances, the Asian palm civet eats coffee berries and excretes the beans. These beans are called "kopi luwak", and can be processed further into a rare and expensive coffee.  Two methods are primarily used to process coffee berries. The first, "wet" or "washed" process, has historically usually been carried out in Central America and areas of Africa. The flesh of the cherries is separated from the seeds and then the seeds are fermented – soaked in water for about two days. This softens the mucilage, which is a sticky pulp residue that is still attached to the seeds. Then this mucilage is washed off with water.  The "dry processing" method, cheaper and simpler, was historically used for lower-quality beans in Brazil and much of Africa, but now brings a premium when done well. Twigs and other foreign objects are separated from the berries and the fruit is then spread out in the sun on concrete, bricks or raised beds for 2–3 weeks, turned regularly for even drying.

Composition.

The term "green coffee bean" refers to unroasted mature or immature coffee beans. These have been processed by wet or dry methods to remove the outer pulp and mucilage and have an intact wax layer on the outer surface. When immature, they are green. When mature, they have a brown to yellow or reddish color and typically weigh 300 to 330 mg per dried coffee bean. Nonvolatile and volatile compounds in green coffee beans, such as caffeine, deter many insects and animals from eating them. Further, both nonvolatile and volatile compounds contribute to the flavor of the coffee bean when it is roasted. Nonvolatile nitrogenous compounds (including alkaloids, trigonelline, proteins, and free amino acids) and carbohydrates are of major importance in producing the full aroma of roasted coffee and for its biological action. Since the mid 2000s, green coffee extract has been sold as a nutritional supplement and has been clinically studied for its chlorogenic acid content and for its lipolytic and weight-loss properties.

Nonvolatile alkaloids.

Caffeine ("1,3,7-trimethyl-xanthine") is the alkaloid most present in green and roasted coffee beans. The content of caffeine is between 1.0% and 2.5% by weight of dry green coffee beans. The content of caffeine does not change during maturation of green coffee beans. Lower concentrations of theophylline, theobromine, paraxanthine, liberine, and methylliberine can be found. The concentration of theophylline, an alkaloid noted for its presence in green tea, is reduced during the roasting process, usually about 15 minutes at, whereas the concentrations of most other alkaloids are not changed. The solubility of caffeine in water increases with temperature and with the addition of chlorogenic acids, citric acid, or tartaric acid, all of which are present in green coffee beans. For example, of caffeine dissolves in of water at room temperature, and at. The xanthine alkaloids are odorless, but have a bitter taste in water, which is masked by organic acids present in green coffee.  Trigonelline ("N"-methyl-nicotinate) is a derivative of vitamin B that is not as bitter as caffeine. In green coffee beans, the content is between 0.6% and 1.0%. At a roasting temperature of, 85% of the trigonelline is degraded to nicotinic acid, leaving small amounts of the unchanged molecule in the roasted beans.

Proteins and amino acids.

Proteins account for 8% to 12% of dried green coffee beans. A majority of the proteins are of the 11-S storage kind (alpha – component of 32 kDa, beta – component of 22 kDa), most of which are degraded to free amino acids during maturation of green coffee beans. Further, 11-S storage proteins are degraded to their individual amino acids under roasting temperature, thus are an additional source of bitter components due to generation of Maillard reaction products. High temperature and oxygen concentration and low pH degrade 11-S storage proteins of green coffee beans to low-molecular-weight peptides and amino acids. The degradation is accelerated in the presence of organic acids such as chlorogenic acids and their derivatives. Other proteins include enzymes, such as catalase and polyphenol oxidase, which are important for the maturation of green coffee beans. Mature coffee contains free amino acids (4.0 mg amino acid/g robusta coffee and up to 4.5 mg amino acid/g arabica coffee). In "Coffea arabica", alanine is the amino acid with the highest concentration, i.e. 1.2 mg/g, followed by asparagine of 0.66 mg/g, whereas in "C. robusta", alanine is present at a concentration of 0.8 mg/g and asparagine at 0.36 mg/g. The free hydrophobic amino acids in fresh green coffee beans contribute to the unpleasant taste, making it impossible to prepare a desirable beverage with such compounds. In fresh green coffee from Peru, these concentrations have been determined as: isoleucine 81 mg/kg, leucine 100 mg/kg, valine 93 mg/kg, tyrosine 81 mg/kg, phenylalanine 133 mg/kg. The concentration of gamma-aminobutyric acid (a neurotransmitter) has been determined between 143 mg/kg and 703 mg/kg in green coffee beans from Tanzania. Roasted coffee beans do not contain any free amino acids; the amino acids in green coffee beans are degraded under roasting temperature to Maillard products (reaction products between the aldehyde group of sugar and the alpha-amino group of the amino acids). Further, diketopiperazines, e.g. cyclo(proline-proline), cyclo(proline-leucine), and cyclo(proline-isoleucine), are generated from the corresponding amino acids, and are the major source of the bitter taste of roasted coffee. The bitter flavor of diketopiperazines is perceptible at around 20 mg/liter of water. The content of diketopiperazines in espresso is about 20 to 30 mg, which is responsible for its bitterness.

Carbohydrates.

Carbohydrates make up about 50% of the dry weight of green coffee beans. The carbohydrate fraction of green coffee is dominated by polysaccharides, such as arabinogalactan, galactomannan, and cellulose, contributing to the tasteless flavor of green coffee. Arabinogalactan makes up to 17% of dry weight of green coffee beans, with a molecular weight of 90 kDa to 200 kDa. It is composed of beta-1-3-linked galactan main chains, with frequent members of arabinose (pentose) and galactose (hexose) residues at the side chains comprising immunomodulating properties by stimulating the cellular defense system (Th-1 response) of the body. Mature brown to yellow coffee beans contain fewer residues of galactose and arabinose at the side chain of the polysaccharides, making the green coffee bean more resistant to physical breakdown and less soluble in water. The molecular weight of the arabinogalactan in coffee is higher than in most other plants, improving the cellular defense system of the digestive tract compared to arabinogalactan with lower molecular weight. Free monosaccharides are present in mature brown to yellow-green coffee beans. The free part of monosaccharides contains sucrose (gluco-fructose) up to 9000 mg/100g of arabica green coffee bean, a lower amount in robustas, i.e. 4500 mg/100g. In arabica green coffee beans, the content of free glucose was 30 to 38 mg/100g, free fructose 23 to 30 mg/100g; free galactose 35 mg/100g and mannitol 50 mg/100g dried coffee beans, respectively. Mannitol is a powerful scavenger for hydroxyl radicals, which are generated during the peroxidation of lipids in biological membranes.

Lipids.

The lipids found in green coffee include: linoleic acid, palmitic acid, oleic acid, stearic acid, arachidic acid, diterpenes, triglycerides, unsaturated long-chain fatty acids, esters, and amides. The total content of lipids in dried green coffee is between 11.7 and 14 g/100 g. Lipids are present on the surface and in the interior matrix of green coffee beans. On the surface, they include derivatives of carboxylic acid-5-hydroxytryptamides with an amide bond to fatty acids (unsaturated C6 to C24) making up to 3% of total lipid content or 1200 to 1400 microgram/g dried green coffee bean. Such compounds form a wax-like cover on the surface of the coffee bean (200 to 300 mg lipids/100 g dried green coffee bean) protecting the interior matrix against oxidation and insects. Further, such molecules have antioxidative activity due to their chemical structure. Lipids of the interior tissue are triglycerides, linoleic acid (46% of total free lipids), palmitic acid (30% to 35% of total free lipids), and esters. Arabica beans have a higher content of lipids (13.5 to 17.4 g lipids/100 g dried green coffee beans) than robustas (9.8 to 10.7 g lipids/100 g dried green coffee beans). The content of diterpenes is about 20% of the lipid fraction. The diterpenes found in green coffee include cafestol, kahweol and 16-O-methylcafestol. Some of these diterpenes have been shown in "in vitro" experiments to protect liver tissue against chemical oxidation. In coffee oil from green coffee beans the diterpenes are esterified with saturated long chain fatty acids.

Nonvolatile chlorogenic acids.

Chlorogenic acids belong to a group of compounds known as phenolic acids, which are antioxidants. The content of chlorogenic acids in dried green coffee beans of arabica is 65 mg/g and of robusta 140 mg/g, depending on the timing of harvesting. At roasting temperature, more than 70% of chlorogenic acids are destroyed, leaving a residue less than 30 mg/g in the roasted coffee bean. In contrast to green coffee, green tea contains an average of 85 mg/g polyphenols. These chlorogenic acids could be a valuable, inexpensive source of antioxidants. Chlorogenic acids are homologous compounds comprising caffeic acid, ferulic acid and 3,4-dimethoxycinnamic acid, which are connected by an ester bond to the hydroxyl groups of quinic acid. The antioxidant capacity of chlorogenic acid is more potent than of ascorbic acid (vitamin C) or mannitol, which is a selective hydroxy-radical scavenger. Chlorogenic acids have a bitter taste in low concentrations such as 50 mg/l water. At higher concentrations of 1 g/l water, they have a sour taste. Chlorogenic acids increase the solubility of caffeine and are important modulators of taste.

Volatile compounds.

Volatile compounds of green coffee beans include short-chain fatty acids, aldehydes, and nitrogen-containing aromatic molecules, such as derivatives of pyrazines (green-herbeaceous-earthy odor). Briefly, such volatile compounds are responsible for the less pleasing odor and taste of green coffee versus roasted coffee. Commercial success was realized by Starbucks in creating Green Bean Refreshers using a process that primarily isolates the caffeine from the green beans but does not actually use steeped liquid from the beans. Many consumers experiment with creating green bean "extract" by steeping green coffee beans in hot water. Often, the recommended times of steeping (20 minutes to 1 hour) extract too much caffeine to provide a pleasant taste. A steeping time of 12 minutes or under provides a more palatable liquid that can be used as a base for a drink containing more of the nutrients and less caffeine that using just isolated caffeine extract. The alkaline stock base that results can be paired with acidic or fruity extracts, with or without sweetener, to mask the vegetable-like taste of the extract.  When green coffee beans are roasted, other molecules with the typical pleasant aroma of coffee are generated, which are not present in fresh green coffee. During roasting, the major part of the unpleasant-tasting volatile compounds are neutralised. Unfortunately, other important molecules such as antioxidants and vitamins present in green coffee are destroyed. Volatile compounds with nauseating odor for humans have been identified, including acetic acid (pungent, unpleasant odor), propionic acid (odor of sour milk, or butter), butanoic acid (odor of rancid butter, present in green coffee with 2 mg/100 g coffee beans), pentanoic acid (unpleasant fruity flavor, present in green coffee at 40 mg/100 g in coffee beans), hexanoic acid (fatty-rancid odor), heptanoic acid (fatty odor), octanoic acid (repulsive oily rancid odor); nonanoic acid (mild nut-like fatty odor); decanoic acid (sour repulsive odor), and derivatives of such fatty acids – 3-methyl-valeric acid (sour, green-herbaceous, unpleasant odor), acetaldehyde (pungent-nauseating odor, even when highly diluted, present in dried green coffee beans at concentrations of about 5 mg/kg), propanal (choking effect on respiratory system, penetrating-nauseating), butanal (nauseating effect, present in dried green coffee beans at 2 to 7 mg/kg), or pentanal (very repulsive nauseating effect).

A coffee bean is a seed of the "Coffea" plant and the source for coffee. It is the pit inside the red or purple fruit often referred to as a cherry. Just like ordinary cherries, the coffee fruit is also a so-called stone fruit. Even though the coffee beans are not technically beans, they are referred to as such because of their resemblance to true beans. The fruits – coffee cherries or coffee berries – most commonly contain two stones with their flat sides together. A small percentage of cherries contain a single seed, instead of the usual two. This is called a "peaberry". The peaberry occurs only between 10 and 15% of the time, and it is a fairly common (yet scientifically unproven) belief that they have more flavour than normal coffee beans. Like Brazil nuts (a seed) and white rice, coffee beans consist mostly of endosperm.

咖啡豆是咖啡属植物的种子,咖啡属植物的果实大小类似樱桃,咖啡豆即为其中的核果。将咖啡豆烘焙加工后再磨碎成咖啡粉,即可烹制咖啡。


特奥巴尔德·冯·贝特曼-霍尔韦格

Ancestry.

Bethmann-Hollweg was born in Hohenfinow, Brandenburg, the son of Prussian official Felix von Bethmann-Hollweg. His grandfather was August von Bethmann-Hollweg, who had been a prominent law scholar, president of Frederick William University in Berlin, and Prussian Minister of Culture. His great-grandfather was Johann Jakob Hollweg, who had married a daughter of the wealthy Frankfurt am Main banking family of Bethmann, founded in 1748.  Cosima Wagner was a relative on the Bethmann side, and his mother, Isabella de Rougemont, was a French Swiss.

Early life.

He was educated at the boarding school of Schulpforta and at the Universities of Strasbourg, Leipzig and Berlin. Entering the Prussian administrative service in 1882, Bethmann-Hollweg rose to the position of the President of the Province of Brandenburg in 1899. He married Martha von Pfuel, the niece of Ernst von Pfuel, Prime Minister of Prussia. From 1905 to 1907, Bethmann-Hollweg served as Prussian Minister of the Interior and then as Imperial State Secretary for the Interior from 1907 to 1909. On the resignation of Chancellor Bernhard von Bülow in 1909, Bethmann-Hollweg was appointed to succeed him.

Chancellor.

In foreign policy he pursued a policy of détente with Britain, hoping to come to some agreement that would put a halt to the two countries' ruinous naval arms race and give Germany a free hand to deal with France. The policy failed, largely from the opposition of German Naval Minister Alfred von Tirpitz. Despite the increase in tensions because of the Second Moroccan Crisis of 1911, Bethmann-Hollweg improved relations with Britain to some extent, working with British foreign secretary Sir Edward Grey to alleviate tensions during the Balkan Crises of 1912–1913. He did not learn of the Schlieffen Plan until December 1912, after he had received the Second Haldane Mission. He negotiated treaties over an eventual partition of the Portuguese colonies and the projected Berlin-Baghdad railway, the latter aimed in part at securing Balkan countries' support for a German-Ottoman alliance. The crisis came to a head on 5 July 1914 when the Count Hoyos Mission arrived in Berlin in response to Berchtold's plea for friendship. Bethmann-Hollweg was assured that Britain would not intervene in the frantic diplomatic rounds across the European powers. However, reliance on that assumption encouraged Austria to demand Serbian concessions. His main concern was Russian border manoeuvres, conveyed by his ambassadors at a time when Raymond Poincaré himself was preparing a secret mission to St Petersburg. He wrote to Count Sergey Sazonov:Russian mobilisation measures would compel us to mobilise and that then European war could scarcely be prevented.  When War Minister Erich von Falkenhayn wanted to mobilise for war on 29 July, Bethmann was still against it but used his veto to prevent the Reichstag debating it. Pourtales telegram of 31 July was what Helmuth von Moltke the Younger, who declared a "Zustand drohender Kriegsgefahr" (state of imminent danger of war) wanted to hear; to Bethmann-Hollweg's dismay, the other powers had failed to communicate Russia's provocation.  In domestic politics, Bethmann-Hollweg's record was also mixed, and his compromising of socialists and liberals on the left and nationalists on the right alienated most of the German political establishment.  Following the assassination of Archduke Franz Ferdinand in Sarajevo on 28 June 1914, Bethmann-Hollweg and his foreign minister, Gottlieb von Jagow, were instrumental in assuring Austria-Hungary of Germany's unconditional support, regardless of Austria's actions against Serbia. While Grey was suggesting a mediation between Austria-Hungary and Serbia, Bethmann-Hollweg wanted Austria-Hungary to attack Serbia and so he tampered with the British message and deleted the last line of the letter: When the Austro-Hungarian ultimatum was presented to Serbia, Kaiser Wilhelm II ended his cruise of the North Sea and hurried back to Berlin.  Bethmann-Hollweg, much of whose foreign policy before the war had been guided by his desire to establish good relations with Britain, was particularly upset by Britain's declaration of war following the German violation of Belgium's neutrality during its invasion of France. He reportedly asked the departing British Ambassador Edward Goschen how Britain could go to war over a "scrap of paper" (""ein Fetzen Papier""), which was the 1839 Treaty of London guaranteeing Belgium's neutrality.  A Published Interview Explaining the "Scrap of Paper" Phrase said by German Chancellor Theobald von Bethmann-Hollweg [translation]  Bethmann-Hollweg had made some plans in the event Britain came into the war and was involved closely in the plans to destabilise Britain's colonies, most notably the Hindu–German Conspiracy.  A tall, gaunt, sombre, well-trimmed aristocratic figure, Bethmann-Hollweg sought approval from a declaration of war. His civilian colleagues pleaded for him to register some febrile protest, but he was frequently outflanked by the military leaders, who played an increasingly important role in the direction of all German policy. However, historian Fritz Fischer, in the 1960s, showed that Bethmann-Hollweg made more concessions to the nationalist right than had previously been thought. He supported the ethnic cleansing of Poles from the Polish Border Strip as well as Germanisation of Polish territories by settlement of German colonists.  Bethmann presented the Septemberprogramm, which was a survey of ideas from the Elite should Germany win the war. Bethmann-Hollweg, with all credibility and power now lost, conspired over Falkenhayn's head with Paul von Hindenburg and Erich Ludendorff (respectively commander-in-chief and chief of staff for the Eastern Front) for an Eastern Offensive. They then succeeded, in August 1916 in securing Falkenhayn's replacement by Hindenburg as Chief of the General Staff, with Ludendorff as First Quartermaster-General (Hindenburg's deputy). Thereafter, Bethmann-Hollweg's hopes for US President Woodrow Wilson's mediation at the end of 1916 came to nothing. Over Bethmann-Hollweg's objections, Hindenburg and Ludendorff forced the adoption of unrestricted submarine warfare in March 1917, adopted as a result of Henning von Holtzendorff's memorandum. Bethmann-Hollweg had been a reluctant participant and opposed it in cabinet. The US entered the war in April 1917, perhaps the inevitability that they had wished to avoid.  Bethmann-Hollweg remained in office until July 1917, when a Reichstag revolt resulted in the passage of the Social Democrat Matthias Erzberger's Peace Resolution by an alliance of the Social Democratic, Progressive, and Centre Parties, which forced his resignation and replacement by a relatively unknown figure, Georg Michaelis.

German Revolution.

During 1918, German support for the war was increasingly challenged by strikes and political agitation. In October sailors in the German Imperial Navy mutinied when ordered to set sail for a final confrontation with the British Navy. The Kiel Mutiny sparked off the November Revolution which brought the war to an end. Bethmann-Hollweg tried to persuade the Reichstag to opt to moderate for peace.

Later life.

His plan to dominate European hegemony through Pan-Germanism in the east and Mitteleuropa in the west disintegrated at the Treaty of Brest-Litovsk. It signalled a long-term development of racially expansive policies of Germanification that presaged the conflict 20 years later.  Intellectual supporters of the policy in Berlin, Arnold Wahnschaffe (1865–1941), undersecretary in the chancellery, and Arthur Zimmermann, were his closest and ablest colleagues. Bethmann-Hollweg was directly responsible for devising the "Flamenpolitik" on the Western Front carried out in the Schlieffen Plan, yet this strategy's ultimate failure as a mode of occupation brought economic collapse and military defeat, as was clearly identified by the Bryce Report. The Chancellor's justification lay in the refrain that Germany was fighting a war of national survival.  Bethmann-Hollweg received prominent attention throughout the world in June 1919, when he formally asked the Allied and the Associated Powers to place him on trial instead of the Kaiser. The Supreme War Council decided to ignore his request. He was often mentioned as among those who might be tried by Allies for political offences in connection with the origin of the war.  In 1919, reports from Geneva said he was credited in diplomatic circles there as leading the monarchists for both the Hohenzollerns and the Habsburgs, the nucleus of which was said to be located in Switzerland.  The ex-Chancellor spent the short remainder of his life in retirement, writing his memoirs. A little after Christmas 1920, he caught a cold, which developed into acute pneumonia from which he died on 1 January 1921. His wife had died in 1914, and he had lost his eldest son in the war.  He was survived by a daughter, Countess Zeech, the wife of the Secretary of the Russian Legation at Munich.  Bethmann-Hollweg is buried in Hohenfinow.

References.

In German.

Essays

Theobald Theodor Friedrich Alfred von Bethmann-Hollweg (29 November 1856 – 1 January 1921) was a German politician who was the Chancellor of the German Empire from 1909 to 1917.

特奥巴尔德·冯·贝特曼-霍尔韦格(,1856年-11月29日-1921年-1月1日),德国政治家,曾于1909年至1917年间任德意志帝国总理。


History.

Theoretical considerations of the feasibility of correcting chromatic aberration were debated in the 18th century following Newton's statement that such a correction was impossible (see History of the telescope). Credit for the invention of the first achromatic doublet is often given to an English barrister and amateur optician named Chester Moore Hall. Hall wished to keep his work on the achromatic lenses a secret and contracted the manufacture of the crown and flint lenses to two different opticians, Edward Scarlett and James Mann. They in turn sub-contracted the work to the same person, George Bass. He realized the two components were for the same client and, after fitting the two parts together, noted the achromatic properties. Hall used the achromatic lens to build the first achromatic telescope, but his invention did not become widely known at the time.  In the late 1750s, Bass mentioned Hall's lenses to John Dollond, who understood their potential and was able to reproduce their design. Dollond applied for and was granted a patent on the technology in 1758, which led to bitter fights with other opticians over the right to make and sell achromatic doublets.  Dollond's son Peter invented the apochromat, an improvement on the achromat, in 1763.

Types.

Several different types of achromat have been devised. They differ in the shape of the included lens elements as well as in the optical properties of their glass (most notably in their optical dispersion or Abbe number).  In the following, "R" denotes the radius of the spheres that define the optically relevant refracting lens surfaces. By convention, "R" denotes the first lens surface counted from the object. A doublet lens has four surfaces with radii "R" to "R".

Littrow doublet.

Uses an equiconvex crown glass lens with, and a second flint glass lens with. The back of the flint glass lens is flat. A Littrow doublet can produce a ghost image between "R" and "R" because the lens surfaces of the two lenses have the same radii.

Fraunhofer doublet (Fraunhofer objective).

The first lens has positive refractive power, the second negative. "R" is set greater than "R", and "R" is set close to, but not equal to, "R". "R" is usually greater than "R". In a Fraunhofer doublet, the dissimilar curvatures of "R" and "R" are mounted close, but not in contact. This design yields more degrees of freedom (one more free radius, length of the air space) to correct for optical aberrations.

Clark doublet.

Early Clark lenses follow the Fraunhofer design. After the late 1860s, they changed to the Littrow design, approximately equiconvex crown,, and a flint with and. By about 1880, Clark lenses had "R" set slightly shorter than "R" to create a focus mismatch between "R" and "R", thereby reducing ghosting caused by reflections within the airspace.

Oil-spaced doublet.

The use of oil between the crown and flint eliminates the effect of ghosting, particularly where. It can also increase light transmission slightly and reduce the impact of errors in "R" and "R".

Steinheil doublet.

The Steinheil doublet, devised by Carl August von Steinheil, is a flint-first doublet. In contrast to the Fraunhofer doublet, it has a negative lens first followed by a positive lens. It needs stronger curvature than the Fraunhofer doublet.

Dialyte.

Dialyte lenses have a wide air space between the two elements. They were originally devised in the 19th century to allow much smaller flint glass elements down stream since flint glass was hard to produce and expensive. They are also lenses where the elements can not be cemented because "R" and "R" have different absolute values.

Design.

The first-order design of an achromat involves choosing the overall power formula_1 of the doublet and the two glasses to use. The choice of glass gives the mean refractive index, often written as formula_2 (for the refractive index at the Fraunhofer "d" spectral line wavelength), and the Abbe number formula_3 (for the reciprocal of the glass dispersion). To make the linear dispersion of the system zero, the system must satisfy the equations  where the lens power is formula_5 for a lens with focal length formula_6. Solving these two equations for formula_7 and formula_8 gives  Since formula_10, and the Abbe numbers are positive-valued, the power of the second element in the doublet is negative when the first element is positive.

Evolutions.

More complex achromatic lens designs can improve the precision of color images by bringing more wavelengths into exact focus. An apochromatic lens brings three wavelengths into a common focus and requires costly materials, while a superachromatic lens brings four wavelengths into focus and must be manufactured with even more expensive fluoride glass and to tight tolerances.

An achromatic lens or achromat is a lens that is designed to limit the effects of chromatic and spherical aberration. Achromatic lenses are corrected to bring two wavelengths (typically red and blue) into focus on the same plane.

消色差透镜或复消色差透镜(achromat)是被设计用来将色差和球面像差减至最小的透镜,属于消色差透镜组。