History.

Eve Ensler wrote the first draft of the monologues in 1996 (there have been several revisions since) following interviews she conducted with 200 women about their views on sex, relationships, and violence against women. The interviews began as casual conversations with her friends, who then brought up anecdotes they themselves had been told by other friends; this began a continuing chain of referrals. In an interview with Women.com, Ensler said that her fascination with vaginas began because of "growing up in a violent society". "Women's empowerment is deeply connected to their sexuality." She also stated, "I'm obsessed with women being violated and raped, and with incest. All of these things are deeply connected to our vaginas."  Ensler wrote the piece to "celebrate the vagina". Ensler states that in 1998, the purpose of the piece changed from a celebration of vaginas and femininity to a movement to stop violence against women. This was the start of the V-Day movement which has continued strong every year since, has turned into a worldwide phenomenon, and a very successful non-profit organization.  The play opened at HERE Arts Center in New York City on October 3, 1996, with a limited run that was scheduled to end November 15 but was extended to December 31. The play gained popularity through a sold-out performances, media coverage and word of mouth. "In 2001, V-Day sold out New York’s Madison Square Garden with more than seventy actors performing. The evening raised $1 million raised for groups working to end violence against women and girls."  "After "The Vagina Monologues" debuted in 1996, it quickly became a hit. Soon, Eve Ensler's episodic play had graduated from off-off Broadway to Madison Square Garden to college stages the world over."  In 2004, the first all-transgender performance of "The Vagina Monologues" was held, resulting in the creation of the documentary "Beautiful Daughters" (2006)"," which displays the hardships the all-transgender cast faced with the production. The monologues were read by eighteen notable transgender women, and a new monologue revolving around the experiences and struggles of transgender women was included.  The play was also adapted into a Marathi play called "Yonichya Maneechya Gujagoshti" by feminist writer-activist Vandana Khare in the year 2009.  Gabriela Youth, the one and only national democratic mass organization for young women in the Philippines also adapted the play into a Tagalog theatrical show called "Ang Usapang Puke" with its student members from the Polytechnic University of the Philippines in the year 2018.

Plot summary.

"The Vagina Monologues" is made up of various personal monologues read by a diverse group of women. Originally, Eve Ensler performed every monologue herself, with subsequent performances featuring three actresses, and more recent versions featuring a different actress for every role. Each of the monologues deals with an aspect of the feminine experience, touching on matters such as sex, sex work, body image, love, rape, menstruation, female genital mutilation, masturbation, birth, orgasm, the various common names for the vagina or simply as a physical aspect of the body. A recurring theme throughout the piece is the vagina as a tool of female empowerment, and the ultimate embodiment of individuality.  Some monologues include:  Every year a new monologue is added to highlight a current issue affecting women around the world. In 2003, for example, Ensler wrote a new monologue, called "Under the Burqa", about the plight of women in Afghanistan under Taliban rule. In 2004, Ensler also wrote a monologue called "They Beat the Girl Out of My Boy...Or So They Tried" after interviewing a group of women whose gender identity differed from their assigned gender at birth. Every V-Day thousands of local benefit productions are staged to raise funds for local groups, shelters, and crisis centers working to end violence against women.

V-Day.

V-Day is a non-profit 501(c)(3) organization that distributes funds to national and international grassroot organizations and programs that work to stop violence against girls and women. "The Vagina Monologues" is the cornerstone of the V-Day movement, whose participants stage benefit performances of the show and/or host other related events in their communities. Such events take place worldwide each year between 1 February and 30 April, many on college campuses as well. All performances must stick to the annual script that V-Day puts out specifically for the V-Day productions of "The Vagina Monologues". The V-Day organization encourages the renditions to include as many diverse actors as possible. With a minimum of 5 actors required by V-Day, the organization also has no maximum limit on the number of actors that can be included in the productions and encourages inclusion of as many actors as possible. The performances generally benefit rape crisis centers and shelters for women, as well as similar resource centers for women and girls experiencing violence against them.  On 21 February 2004 Ms. Ensler in conjunction with Jane Fonda and Deep Stealth Productions produced and directed the first all-transgender performance of "The Vagina Monologues", with readings by eighteen notable transgender women and including a new monologue documenting the experiences of transgender women. It debuted in connection with "LA V-DAY Until the Violence Stops" with monologues documenting the violence against transgender women. Since that debut, many university and college productions have included these three "Transgender Monologues". "Beautiful Daughters" (2006) is a documentary about the cast of the first performance by transgender women.

Support.

An article in "Signs" by Christine M. Cooper begins by applauding "The Vagina Monologues" for benefit performances done within the first six years (1998–2004). These performances raised over $20 million, 85 percent of which was donated to grassroots organizations that fight against violence towards women.

Criticism.

Criticism from feminists.

"The Vagina Monologues" has been criticized by some within the feminist movement, including pro-sex feminists and individualist feminists. Sex-positive feminist Betty Dodson, author of several books about female sexuality, saw the play as having a narrow and restrictive view of sexuality. Dodson's main concern seemed to be the lack of the term "clitoris" throughout the play. She believes that the play sends a message that the vagina is the main sex organ, not the clitoris. There is also criticism of "The Vagina Monologues" about its conflation of vaginas as women, more specifically for the message of the play that women are their vaginas, as Susan E. Bell and Susan M. Reverby argue, "Generations of feminists have argued that we are more than our bodies, more than a vagina or 'the sex'. Yet, TVM re-inscribes women's politics in our bodies, indeed in our vaginas alone". The focus on women finding themselves through their vaginas, many say, seems more like a Second Wave consciousness-raising group rather than a ground-breaking, inter-sectional, Third Wave cornerstone.

Criticism for being anti-transgender.

Because of the title and content of "The Vagina Monologues" being body-centric, American University chose to change their production of it to a new show including all-original pieces, giving the production the name of "Breaking Ground Monologues." Although members of American University's Women's Initiative believe that the show "was" revolutionary in the 1990s, they concluded that equating having a vagina with being a woman is not an accurate display of womanhood today, suggesting that "The Vagina Monologues" continues to perpetuate the gender binary and erase the identity of those who are genderqueer.  In 2015 a student organization at Mount Holyoke College canceled its annual performance of the play for being, in its opinion, insufficiently inclusive of transgender people. "At its core", Erin Murphy, the president of the school's theater group, said, "the show offers an extremely narrow perspective on what it means to be a woman.... Gender is a wide and varied experience, one that cannot simply be reduced to biological or anatomical distinctions, and many of us who have participated in the show have grown increasingly uncomfortable presenting material that is inherently reductionist and exclusive." The traditionally all-female college had begun admitting students designated male at birth who identified as female the previous year, but the college denied that had anything to do with the decision to discontinue the annual performances of the play.

Criticism for being colonial.

Kim Hall, a professor of Philosophy at Appalachian State University, further criticizes the play, particularly the sections dealing with women in developing countries, for contributing to "colonialist conceptions of non-Western women," such as the piece "My Vagina Was My Village." Although she supports frank discussions about sex, Hall rescales many of the same critiques leveled by feminists of color at white privilege among second-wave feminists: "premature white feminist assumptions and celebrations of a global'sisterhood.'"  In "The Vagina Monologues," depictions of sexual violence are told through mostly non-white and non-US centered stories, as Srimati Basu states, "While a few of these forms of violence, such as sexual assault and denigration of genitalia, are depicted in U.S. locations, violence is the primary register through which 'the global' is evoked, the main lens for looking outside the United States. These global locations serve to signify the terror that is used to hold the laughter in balance, to validate the seriousness of the enterprise, while the 'vagina' pieces are more directly associated with pleasure and sexuality and set in the United States".  In 2013, Columbia University's V-Day decided to stage the play with a cast entirely of non-white women because of the misrepresentation. That decision, too, was controversial.

Social conservative criticism.

The play has also been criticized by social conservatives, such as the American Society for the Defense of Tradition, Family and Property (TFP) and the Network of Enlightened Women. The TFP denounced it as "a piece replete with sexual encounters, lust, graphic descriptions of masturbation and lesbian behavior", urging students and parents to protest. Following TFP and other protests, performances were cancelled at sixteen Catholic colleges. Saint Louis University made the decision not to endorse the 2007 production, claiming the yearly event was getting to be "redundant." The response of the university's student-led feminist organization was to continue the production at an off-campus location.

Robert Swope critique.

In 2000, Robert Swope, a conservative contributor to a Georgetown University newspaper, "The Hoya", wrote an article critical of the play. He suggested there was a contradiction between the promotion of rape awareness on V-Day and the monologue "The Little Coochie Snorcher That Could", in which an adult woman recalls being given alcohol and statutorily raped at 13 by a 24-year-old woman as a positive, healing experience, ending the segment with the proclamation "It was a good rape." Outcry from the play's supporters resulted in Swope's being fired from the staff of "The Hoya", before the piece was even run. Swope had previously criticized the play in an article he wrote entitled "Georgetown Women's Center: Indispensable Asset or Improper Expenditure?" His termination received critical editorial coverage in "The Wall Street Journal", "Salon", "National Review", "The Atlantic Monthly", "The Washington Times", "The Weekly Standard", and by Wendy McElroy of iFeminists.

College performances.

Every year, the play is performed on hundreds of college campuses as part of V-Day's College campaign.  Inspired by "The Vagina Monologues", many colleges have gone on to develop their own plays. Performances at colleges are always different, not always pre-written but with some actors writing their own monologue, and variations based on the campus.  The Cardinal Newman Society has criticized the performance of the play on Catholic college campuses. In 2011 ten of the fourteen Catholic universities hosting the "Monologues" were Jesuit institutions. The Jesuit Tim Clancy, pastor and philosophy professor at Gonzaga University, explains why he supports VM performances on campus: “They are not arguments – they are stories... stories of pain and suffering, stories of shame, violation and impotence” that lead to discussions on “the extremes of the human condition”, responding to the call of Pope Benedict for Jesuits in their work to explore “the boundaries resulting from an erroneous or superficial vision of God and man that stand between faith and human knowledge”.

The Vagina Monologues is an episodic play written by Eve Ensler which developed and premiered at HERE Arts Center, Off-Off-Broadway in New York and was followed by an Off-Broadway run in 1996 at Westside Theatre. The play explores consensual and nonconsensual sexual experiences, body image, genital mutilation, direct and indirect encounters with reproduction, vaginal care, menstrual periods, sex work, and several other topics through the eyes of women with various ages, races, sexualities, and other differences.

Monology vagíny (anglicky: The Vagina Monologues) je divadelní hra, kterou napsala Eve Ensler v roce 1996. Původně Eve hrála všechny role žen, které vypovídaly své monology; poté, co přestala v této titulní roli vystupovat, se ve hře vystřídalo mnoho celebrit.


Etymology.

The term "paraphyly", or "paraphyletic", derives from the two Ancient Greek words (), meaning "beside, near", and (), meaning "genus, species", and refers to the situation in which one or several monophyletic subgroups of organisms (e.g., genera, species) are "left apart" from all other descendants of a unique common ancestor.  Conversely, the term "monophyly", or "monophyletic", builds on the Ancient Greek prefix (), meaning "alone, only, unique", and refers to the fact that a monophyletic group includes organisms consisting of "all" the descendants of a "unique" common ancestor.  By comparison, the term "polyphyly", or "polyphyletic", uses the Ancient Greek prefix (), meaning "many, a lot of", and refers to the fact that a polyphyletic group includes organisms arising from "multiple" ancestral sources.

Phylogenetics.

In cladistics.

Groups that include all the descendants of a common ancestor are said to be "monophyletic". A paraphyletic group is a monophyletic group from which one or more subsidiary clades (monophyletic groups) are excluded to form a separate group. Ereshefsky has argued that paraphyletic taxa are the result of anagenesis in the excluded group or groups.  A group whose identifying features evolved convergently in two or more lineages is "polyphyletic" (Greek πολύς ["polys"], "many"). More broadly, any taxon that is not paraphyletic or monophyletic can be called polyphyletic.  These terms were developed during the debates of the 1960s and 1970s accompanying the rise of cladistics.  Paraphyletic groupings are considered problematic by many taxonomists, as it is not possible to talk precisely about their phylogenetic relationships, their characteristic traits and literal extinction. Related terminology that may be encountered are stem group, chronospecies, budding cladogenesis, anagenesis, or 'grade' groupings. Paraphyletic groups are often a relic from previous erroneous assessments about phylogenic relationships, or from before the rise of cladistics.

Examples.

The prokaryotes (single-celled life forms without cell nuclei), because they exclude the eukaryotes, a descendant group. Bacteria and Archaea are prokaryotes, but archaea and eukaryotes share a common ancestor that is not ancestral to the bacteria. The prokaryote/eukaryote distinction was proposed by Edouard Chatton in 1937 and was generally accepted after being adopted by Roger Stanier and C.B. van Niel in 1962. The botanical code (the ICBN, now the ICN) abandoned consideration of bacterial nomenclature in 1975; currently, prokaryotic nomenclature is regulated under the ICNB with a starting date of 1 January 1980 (in contrast to a 1753 start date under the ICBN/ICN).  Among plants, dicotyledons (in the traditional sense) are paraphyletic because the group excludes monocotyledons. "Dicotyledon" has not been used as a botanic classification for decades, but is allowed as a synonym of Magnoliopsida. Phylogenetic analysis indicates that the monocots are a development from a dicot ancestor. Excluding monocots from the dicots makes the latter a paraphyletic group.  Among animals, several familiar groups are not, in fact, clades. The order Artiodactyla (even-toed ungulates) is paraphyletic because it excludes Cetaceans (whales, dolphins, etc.). In the ICZN Code, the two taxa are orders of equal rank. Molecular studies, however, have shown that the Cetacea descend from artiodactyl ancestors, although the precise phylogeny within the order remains uncertain. Without the Cetacean descendants the Artiodactyls must be paraphyletic. The class Reptilia "as traditionally defined" is paraphyletic because it excludes birds (class Aves) and mammals. In the ICZN Code, the three taxa are classes of equal rank. However, mammals hail from the synapsids (which were once described as "mammal-like reptiles") and birds are descended from the dinosaurs (a group of Diapsida), both of which are reptiles. Alternatively, reptiles are paraphyletic because they gave rise to (only) birds. Birds and reptiles together make Sauropsids. Osteichthyes, bony fish, are paraphyletic when they include only Actinopterygii (ray-finned fish) and Sarcopterygii (lungfish, etc.), excluding tetrapods; more recently, Osteichthyes is treated as a clade, including the tetrapods. The wasps are paraphyletic, consisting of the narrow-waisted Apocrita without the ants and bees. The sawflies (Symphyta) are similarly paraphyletic, forming all of the Hymenoptera except for the Apocrita, a clade deep within the sawfly tree. Crustaceans are not a clade because the Hexapoda (insects) are excluded. The modern clade that spans all of them is the Tetraconata.

Paraphyly in species.

Species have a special status in systematics as being an observable feature of nature itself and as the basic unit of classification. The phylogenetic species concept requires species to be monophyletic, but paraphyletic species are common in nature. Paraphyly is common in speciation, whereby a mother species (a paraspecies) gives rise to a daughter species without itself becoming extinct. Research indicates as many as 20 percent of all animal species and between 20 and 50 percent of plant species are paraphyletic. Accounting for these facts, some taxonomists argue that paraphyly is a trait of nature that should be acknowledged at higher taxonomic levels.

Uses for paraphyletic groups.

When the appearance of significant traits has led a subclade on an evolutionary path very divergent from that of a more inclusive clade, it often makes sense to study the paraphyletic group that remains without considering the larger clade. For example, the Neogene evolution of the Artiodactyla (even-toed ungulates, like deer) has taken place in an environment so different from that of the Cetacea (whales, dolphins, and porpoises) that the Artiodactyla are often studied in isolation even though the cetaceans are a descendant group. The prokaryote group is another example; it is paraphyletic because it excludes many of its descendant organisms (the eukaryotes), but it is very useful because it has a clearly defined and significant distinction (absence of a cell nucleus, a plesiomorphy) from its excluded descendants.  Also, paraphyletic groups are involved in evolutionary transitions, the development of the first tetrapods from their ancestors for example. Any name given to these ancestors to distinguish them from tetrapods—"fish", for example—necessarily picks out a paraphyletic group, because the descendant tetrapods are not included.  The term "evolutionary grade" is sometimes used for paraphyletic groups. Moreover, the concepts of monophyly, paraphyly, and polyphyly have been used in deducing key genes for barcoding of diverse group of species.

Independently evolved traits.

Viviparity, the production of offspring without the laying of a fertilized egg, developed independently in the lineages that led to humans ("Homo sapiens") and southern water skinks ("Eulampus tympanum", a kind of lizard). Put another way, at least one of the lineages that led to these species from their last common ancestor contains nonviviparous animals, the pelycosaurs ancestral to mammals; vivipary appeared subsequently in the mammal lineage.  Independently-developed traits like these cannot be used to distinguish paraphyletic groups because paraphyly requires the excluded groups to be monophyletic. Pelycosaurs were descended from the last common ancestor of skinks and humans, so vivipary could be paraphyletic only if the pelycosaurs were part of an excluded monophyletic group. Because this group is monophyletic, it contains all descendants of the pelycosaurs; because it is excluded, it contains no viviparous animals. This does not work, because humans are among these descendants. Vivipary in a group that includes humans and skinks cannot be paraphyletic.

Non-exhaustive list of paraphyletic groups.

The following list recapitulates a number of paraphyletic groups proposed in the literature, and provides the corresponding monophyletic taxa.

Linguistics.

The concept of paraphyly has also been applied to historical linguistics, where the methods of cladistics have found some utility in comparing languages. For instance, the Formosan languages form a paraphyletic group of the Austronesian languages because they consist of the nine branches of the Austronesian family that are not Malayo-Polynesian and are restricted to the island of Taiwan.

In taxonomy, a group is paraphyletic if it consists of the group's last common ancestor and all descendants of that ancestor excluding a few—typically only one or two—monophyletic subgroups. The group is said to be paraphyletic "with respect to" the excluded subgroups. The arrangement of the members of a paraphyletic group is called a paraphyly. The term is commonly used in phylogenetics (a subfield of biology) and in linguistics.

Parafyletismus je stav nějaké člověkem definované skupiny organismů, ve kterém se skupina nachází, pokud zahrnuje jejího společného předka, ale ne všechny jeho potomky. Taxon (skupina) se pak nazývá parafyletický a není přirozený. Velké procento taxonů, které běžně známe, je parafyletické. V současné systematice (taxonomii) je snaha tyto umělé taxony, které se neslučují se stavem věcí v přírodě, nahradit taxony monofyletickými. Typickým parafyletickým taxonem bývá skupina složená z více primitivních monofyletických skupin, které např. postrádají důležitou apomorfii, která definuje skupinu odvozenou. Takovou skupinou jsou třeba širopasí (blanokřídlí), skupina je tedy na rozdíl od štíhlopasých nepřirozená.


Taxonomy.

The name "Megalania prisca" was coined in 1859 by Sir Richard Owen to mean "ancient great roamer"; the name was chosen "in reference to the terrestrial nature of the great Saurian". Owen used a modification of the Greek word ἠλαίνω "ēlainō" ("I roam"). The close similarity to the Latin word: "lania" (feminine form of "butcher") has resulted in numerous taxonomic and popular descriptions of megalania mistranslating the name as "ancient giant butcher."  Owen introduced the genus "Megalania" to accommodate the species "Megalania prisca". Its status as a valid genus remains controversial, with many authors preferring to consider it a junior synonym of "Varanus", which encompasses all living monitor lizards. As the gender of the genera "Megalania" and "Varanus" are respectively feminine and masculine, the specific name "prisca" (fem.)/"priscus" (masc.) follows suit.  The genus "Megalania" is included as a synonym of "Varanus" by many researchers due to the relationships of the many "Varanus" species; "M. prisca" is closely related to other Australian monitors classified as "Varanus", so excluding "M. prisca" from "Varanus" renders the latter genus an unnatural grouping. Ralph Molnar noted in 2004 that, even if every species of the genus "Varanus" were divided into groups currently designated as subgenera, "V. priscus" would still be classified in the genus "Varanus", because this is the current subgenus name, as well as genus name, for all Australian monitors. Unless other Australian monitor species were each also classified their own exclusive genera, "Megalania" would not be a valid genus name. However, Molnar noted that "megalania" is suitable for use as a vernacular, rather than scientific name, for the species "Varanus priscus".

Phylogeny.

Several studies have attempted to establish the phylogenetic position of megalania within the Varanidae. An affinity with the perentie "Varanus giganteus", Australia's largest living lizard, has been suggested based on skull-roof morphology. The most recent comprehensive study proposes a sister-taxon relationship with the large Indonesian dragon, "Varanus komodoensis", based on neurocranial similarities, with the lace monitor as the closest living Australian relative. Conversely, the perentie is considered more closely related to Gould's and the argus monitors.

Size.

The lack of complete or nearly complete fossil skeletons has made it difficult to determine the exact dimensions of megalania. Early estimates placed the length of the largest individuals at, with a maximum weight of approximately. In 2002, Stephen Wroe considerably downsized megalania, suggesting a maximum length of and a weight of with averages of and. decrying the earlier maximum length estimate of as exaggerations based on flawed methods. However, in 2009, Wroe, along with other researchers revised upwards their estimates to at least and.  In a book published in 2004, Ralph Molnar determined a range of potential sizes for megalania, made by scaling up from dorsal vertebrae, after he determined a relationship between dorsal vertebrae width and total body length. If it had a long, thin tail like the lace monitor ("Varanus varius"), then it would have reached a length of, while if its tail-to-body proportions were more similar to that of the Komodo dragon ("V. komodoensis"), then a length around is more likely. Taking the maximal length, he estimated a weight of, with a leaner being average.

Palaeobiology.

Megalania is the largest terrestrial lizard known to have existed. Judging from its size, it would have fed mostly upon medium- to large-sized animals, including any of the giant marsupials such as "Diprotodon", along with other reptiles and small mammals, as well as birds and their eggs and chicks. It had heavily built limbs and body and a large skull complete with a small crest between the eyes, and a jaw full of serrated, blade-like teeth.  Some scientists regard with skepticism the contention that megalania was the only, or even principal, predator of the Australian Pleistocene megafauna. They note that the "marsupial lion" ("Thylacoleo carnifex") has been implicated with the butchery of very large Pleistocene mammals, while megalania has not. In addition, they note that megalania fossils are extremely uncommon, in contrast to "T. carnifex" with its wide distribution across Australian Pleistocene deposits. "Quinkana", a genus of terrestrial crocodiles that grew up to 6 m and was present until around 40,000 years ago, has also been marked as another apex predator of Australian megafauna.  If one were to reconstruct the ecosystems that existed before the arrival of the humans on Australia, introducing Komodo dragons to represent megalania has been suggested to be desirable.  A study published in 2009 using Wroe's earlier size estimates and an analysis of 18 closely related lizard species estimated a sprinting speed of. This speed is comparable to that of the extant freshwater crocodile ("Crocodylus johnstoni").  The scales of megalania would possibly be similar to those of their extant relatives possessing a honeycomb microstructure and be durable and resilient to water evaporation.

Venom.

Along with other varanid lizards, such as the Komodo dragon and the Nile monitor, megalania belongs to the proposed clade Toxicofera, which contains all known reptile clades possessing toxin-secreting oral glands, as well as their close, venomous and nonvenomous relatives, including Iguania, Anguimorpha, and snakes. Closely related varanids use a potent venom found in glands inside the jaw. The venom in these lizards have been shown to be a hemotoxin. The venom would act as an anticoagulant and would greatly increase the bleeding the prey received from its wounds. This would rapidly decrease the prey's blood pressure and lead to systemic shock. Being a member of Anguimorpha, megalania may have been venomous and if so, would be the largest venomous vertebrate known.

Extinction.

Recent paleontological analysis using accelerator mass spectrometry C dating of known fossils shows megalania to have been alive around the Pleistocene epoch 50,000 years ago. An affiliate hypothesis to this dating is that anthropogenic extirpation was the cause of the downfall of megalania and other Australian megafauna in the similar vein as to how a large factor of the extinction of the Northern Hemisphere's megafauna at the end of the Pleistocene epoch was caused by early humans. In addition, a study, which examined the morphology of nine closely related extant varanid lizards and then allometrically scaled and compared them to "V. prisca", found that the musculature of the limbs, posture, muscular mass, and possible muscular composition of the animal would most likely have been inefficient when attempting to outrun the early human settlers who colonized Australia during that time. This, in coordination with other megafauna that lived at that time such as "Quinkana" and "Thylacoleo carnifex", and possible climate change, could have led to the species' extinction.

Megalania refers to an extinct giant goanna or monitor lizard, recognised as either Megalania prisca or Varanus priscus. They were part of the megafaunal assemblage that inhabited southern Australia during the Pleistocene. The youngest fossil remains dated to around 50,000 years ago. The first aboriginal settlers of Australia might have encountered them and been a factor in their extinction.

Varanus priscus (též Megalania prisca) je vyhynulý australský varan, který dosahoval délky přes 4,5 metru a hmotnosti kolem 600 kilogramů, je tak považován za největšího suchozemského ještěra, který kdy existoval. Původně byl popsán jako jediný zástupce rodu Megalania, ale kromě velikosti se nijak výrazně neodlišuje od dnešních varanů ("Varanus" sensu stricto) a recentní studie ho proto řadí do rodu "Varanus" (Pianka and King, 2004).


Etymology.

The term "roller container" has been introduced in the English summary of the DIN standards that refer to the prominent feature of steel wheels - such wide wheels are commonly known in English as rollers. It does also refer to the verb "to roll" which has the same meaning in German - the particle "ab-" in German "abroll container" designates downward/pushback operations so that the German "Abrollcontainer" is sometimes translated to English as "roll-off container".  The DIN standard uses the German term "Abrollbehälter" where the generic Germanic "behälter" has replaced the Romanic "container" - the latter is more associated with transport containers in the German language so that the ACTS designation has picked up "Abrollcontainer" instead of the synonymous "Abrollbehälter". With "Abrollcontainer" associated to transport systems the various "Abrollbehälter" types are usually denoting firefighting equipment. In British English the firefighting containers are generically called "demountable pod" or just "pod" for example "foam pod" and while being a generic term these are universally roller containers as well.  There is an additional term "hooklift container" that is related to the common designation of the hoist gear on trucks used for roller containers to be called "hook lift". This has influenced languages like Dutch where the truck is called "haakarmvoertuig" (hook arm vehicle) and the container being a "haakarmbak" (hook arm pod). These terms refer to the level arm that matches with the grip hook on the container to lift it from the ground. Note that the term hooklift container may refer to any container type with an additional hook bar which "does not" necessarily include roller wheels - this includes the NATO standard STANAG 2413 variations of 20' ISO containers having an additional hook bar.

History.

Solutions for intermodal transport containers in road and rail transport already appeared in the 1930s. One of the systems was used since 1934 in the Netherlands to carry waste transportation and consumer goods. These "Laadkisten" had a permissible gross mass of and dimensions of. Reloading held by dragging rope winch tow car.  After World War II that system was used for transports between Switzerland and the Netherlands. On 14–23 April 1951 in Zurich Tiefenbrunnen under the auspices of the Club «Museum of Transport, Switzerland, Swiss Transportation" and Bureau International des Containers "(BIC) held demonstrations container systems aim to select the best solution for Western Europe. There were representatives Belgium, France, the Netherlands, Germany, Switzerland, Sweden, Great Britain, Italy and the USA. The result of this meeting had been the first after World War II European standard UIC 590, also known as "Pa-Behälter" (porteur-aménagé-Behälter). This system has been implemented in Denmark, Belgium, the Netherlands, Luxembourg, West Germany, Switzerland and Sweden. In Germany it was widely marketed as the "haus zu haus" (house to house) transport system which did include a variety of pod types.  Along with the gradual popularization of large container type ISO (first seen in Europe in 1966), the "Pa-Behälter" system fell out of use and it was subsequently withdrawn by the railways (no new containers produced after 1975, scrapped in the 2000s). The transport of waste containers was moved completely to road transportation in the 1970s. Previously the open-top middle-sized container Eoskrt of the "haus zu haus" series was widely used for waste transport by rail. It could be moved on four small wheels on to the flat car fitting into comparably narrow guide rails that were mounted on them. These early roll containers types had standard steel wheels of 75 mm in width with a diameter size of 200 mm. The axle track was 1400 mm across and the wheel base 1950 mm at length. Lashing eyelets are attached to every wheel case allowing to move and lock the container in place.

Standardization.

Roller containers have been standardized in DIN 30722 by the Municipal Services Standards Committee (German "Normenausschuss Kommunale Technik" / NKT). The first parts are subdivisions of different weight classes (part 1 up to, part 2 up to, part 3 up to ) that had been first published in April 1993 and the latest revision being published in February 2007. The part 4 of the standard series covers the intermodal transport between rail and road with the issue of July 1994 being still current.  The DIN roller containers have a hook that is directed 45° upwards with the handle bar positioned at a height of. The roller wheels have an inner distance of and an outer distance of. The width of the containers does mostly follow intermodal shipping containers and there are undercarriage frames available for twenty-foot containers to be handled as a roller container. The length of DIN roller containers is standardized in steps of from an overall length of. The height has not been standardized and roller containers are commonly not used for stacking.  The NATO standard STANAG 2413 "demountable load carrying platforms (dlcp/flatracks)" references the DIN 30722 for the definition of the "hookbar". The LHS rollers and ISO container twistlock pockets are optional in STANAG 2413 - the LHS designation references the Load Handling System (German "Hakenladesystem" / hook load system) derived from the DIN roller containers in use for firefighting equipment.

Container types and applications.

The roller containers come in a larger variety for specific usages. For bulk waste a common type has additional impermeable doors on one side. There are low height containers that allow easy dumping of green care waste. There are squeeze containers that compress the garbage. Roller containers for construction waste need additional stability. The DIN standard does not define the height nor most of the other sizes - it concentrates on the hook for lifting the container and the wheels that allow sliding on the ground.  According to Marrel they have invented hooklift trucks marketing them since 1969 in the USA. There have been various heights and sizes of the hook with the ACTS roller container system standardizing on (rounded to for the US market at Stellar Industries). Hook heights of 54" and 36" are also in common use.

ACTS intermodal transport system.

The ACTS (from German "Abrollcontainer Transportsystem" / roller container transport system) offers a loading principle from a roller container truck directly on to a rail car. There is no additional installation required for the process as the level arm of the truck can push the container on to a transport frame that is mounted on the rail car. The transport frame consists of two U-profile rail bars and a central pivot - this allows the frame to swing out for loading and to swing back to be parallel with the rail car for distance travel by rail.  The ACTS found wider usage first in Switzerland where rail transport to remote villages is often easier than running large trucks through narrow streets. Rail transport of roller containers is now prevalent in German-speaking countries and neighbouring countries like the Netherlands and the Czech Republic.

Containerized firefighting equipment.

The roller container standards have become the basis of containerized firefighting equipment throughout Europe. The permanent mounting of equipment creates a large number of specialized fire trucks while containerization allows the use of only one transport truck with a level arm - in Germany it is called WLF (German "Wechselladerfahrzeug" / swap loader vehicle). In practical usage there are lighter specialized fire trucks for everyday usage while larger fire and catastrophic situations can be handled by using WLF in a shuttle operation bringing as much equipment to the scene as needed.  The containers come in a great variety with national regulations to control common types, for example in Germany one may find  For the most part the replacement of older fire trucks takes the form of new AB units in Germany. The AB units may be built from standard containers with equipment installed from different suppliers as required by the fire department. The WLF loader vehicle can be purchased independently with the availability of a wide variety of trucks on the market (that are not originally designed for firefighting) - the trucks are sent to specialized workshops that can convert them to WLF fire trucks by adding a hook lift, siren and communications. The AB units may be used far longer than the WLF trucks as the latter can be exchanged independently - this makes maintenance cheaper especially for special equipment that is only rarely needed. Additionally some firefighting equipment like the decontamination pod have advantages for military conversion dispatching them by standard NATO container transport.

Military.

In the US the Heavy Expanded Mobility Tactical Truck (HEMTT) was produced in a version with a hooklift hoist gear named Load Handling System (LHS). The M1120 HEMTT LHS is the basis of the Palletized Load System using a flatbed platform to be mounted under ISO containers as a Container Handling Unit (CHU). This allows containers to be unloaded without the help of a forklift. Current NATO agreements require PLS to maintain interoperability with comparable British, German and French systems through the use of a common flatrack.  The British Army has developed the Demountable Rack Offload and Pickup System (DROPS) using the Medium Mobility Load Carrier (MMLC) as an all-terrain truck with a hook loader system. As in the Palletized Load System a flatrack can be used to transport ISO containers. After an evolutionary step with the Improved Medium Mobility Load Carrier (IMMLC) the British Army is now transitioning the Enhanced Pallet Load System (EPLS). In the ELPS there is a different Container Handling Unit that is not put under the container but it uses an H Frame that fits into the corner locks of an ISO container on the back side.

Disadvantages.

Although roller containers are very easy to load/unload they do have some problems. The steel rollers that contact the ground can cause damage to asphalt pavement, a concrete surface is more suitable. The angle that the container is tilted can cause loads to move if they are not secured. A swap body may be used where the container needs to be kept level.

A roller container is a container type that can be carried by trucks to be pushed to ground level by help of a hook and level arm with the container possibly sliding on steel roller wheels.

ACTS (zkratka z německého Abroll-Container-Transport-System) je přepravní systém pro kombinovanou dopravu silnice-železnice. V rámci tohoto systému jsou používány speciální odvalovací kontejnery, které jsou přepravovány na speciálních železničních vozech nebo na automobilových nosičích.


Family.

Metis was an Oceanid, the daughters of Oceanus and his sister Tethys, who were three thousand in number, and was of an earlier age than Zeus and his siblings. Metis was the first great spouse of Zeus, and also his cousin. Zeus is himself titled "Mêtieta" ("the wise counsellor"), in the Homeric poems.

Mythology.

Metis was the one who gave Zeus a potion to cause Cronus to vomit out Zeus' siblings.  Metis was both a threat to Zeus and an indispensable aid:"Zeus lay with Metis but immediately feared the consequences. It had been prophesied that Metis would bear extremely powerful children: the first, Athena and the second, a son more powerful than Zeus himself, who would eventually overthrow Zeus."In order to forestall these dire consequences, Zeus tricked her into turning herself into a fly and promptly swallowed her. He was too late: Metis had already conceived a child. In time she began making a helmet and robe for her fetal daughter. The hammering as she made the helmet caused Zeus great pain, and Hephaestus either clove Zeus's head with an axe, or hit it with a hammer at the river Triton, giving rise to Athena's birth. Athena leaped from Zeus's head, fully grown, armed, and armoured. Zeus was none the worse for this experience.  The similarities between Zeus swallowing Metis and Cronus swallowing his children have been noted by several scholars. This also caused some controversy in regard to reproduction myths and the lack of a need for women as a means of reproduction.  Hesiod's account is followed by Acusilaus and the Orphic tradition, which enthroned Metis side by side with Eros as primal cosmogenic forces. Plato makes "Poros", or "creative ingenuity", the child of Metis.

Metis (;, "wisdom", "skill", or "craft"), in ancient Greek religion, was a mythical Titaness belonging to the second generation of Titans.

Métis (latinsky "Mens") je v řecké mytologii dcerou Titána Ókeana a jeho manželky a sestry Téthys. Je bohyní rozumu. Métis žila blízko Ókeanových proudů, tam ji také navštívil Zeus, když dospěl a pojal úmysl svrhnout Krona. Métis mu poradila, aby navštívil matku země Rheiu a požádal ji, aby z něho udělala Kronova číšníka. Pak podle Métidiny rady smíchal medový nápoj s dávidlem a to podal Kronovi. Pak už Kronos zvrátil všechny Diovy bratry a sestry v pořadí Poseidón, Hádés, Héra, Démétér a Hestiá.


Advertising-supported software.

In legitimate software, the advertising functions are integrated into or bundled with the program. Adware is usually seen by the developer as a way to recover development costs, and to generate revenue. In some cases, the developer may provide the software to the user free of charge or at a reduced price. The income derived from presenting advertisements to the user may allow or motivate the developer to continue to develop, maintain and upgrade the software product. The use of advertising-supported software in business is becoming increasingly popular, with a third of IT and business executives in a 2007 survey by McKinsey & Company planning to be using ad-funded software within the following two years. Advertisement-funded software is also one of the business models for open-source software.

Application software.

Some software is offered in both an advertising-supported mode and a paid, advertisement-free mode. The latter is usually available by an online purchase of a license or registration code for the software that unlocks the mode, or the purchase and download of a separate version of the software.  Some software authors offer advertising-supported versions of their software as an alternative option to business organizations seeking to avoid paying large sums for software licenses, funding the development of the software with higher fees for advertisers.  Examples of advertising-supported software include Adblock Plus ("Acceptable Ads"), the Windows version of the Internet telephony application Skype, and the Amazon Kindle 3 family of e-book readers, which has versions called "Kindle with Special Offers" that display advertisements on the home page and in sleep mode in exchange for substantially lower pricing.  In 2012, Microsoft and its advertising division, Microsoft Advertising, announced that Windows 8, the major release of the Microsoft Windows operating system, would provide built-in methods for software authors to use advertising support as a business model. The idea had been considered since as early as 2005.

Software as a service.

Support by advertising is a popular business model of software as a service (SaaS) on the Web. Notable examples include the email service Gmail and other Google Apps (now G Suite) products, and the social network Facebook. Microsoft has also adopted the advertising-supported model for many of its social software SaaS offerings. The Microsoft Office Live service was also available in an advertising-supported mode.  In the view of Federal Trade Commission staff, there appears to be general agreement that software should be considered "spyware" only if it is downloaded or installed on a computer without the user's knowledge and consent. However, unresolved issues remain concerning how, what, and when consumers need to be told about software installed on their computers for consent to be adequate. For instance, distributors often disclose in an end-user license agreement that there is additional software bundled with primary software, but some panelists and commenters did not view such disclosure as sufficient to infer consent to the installation of the bundled software.

Malware.

The term "adware" is frequently used to describe a form of malware (malicious software) which presents unwanted advertisements to the user of a computer. The advertisements produced by adware are sometimes in the form of a pop-up or sometimes in an "unclosable window".  When the term is used in this way, the severity of its implication varies. While some sources rate adware only as an "irritant", others classify it as an "online threat" or even rate it as seriously as computer viruses and trojans. The precise definition of the term in this context also varies. Adware that observes the computer user's activities without their consent and reports it to the software's author is called spyware. However most adware operates legally and some adware manufacturers have even sued antivirus companies for blocking adware.  Programs have been developed to detect, quarantine, and remove advertisement-displaying malware, including Ad-Aware, Malwarebytes' Anti-Malware, Spyware Doctor and Spybot – Search & Destroy. In addition, almost all commercial antivirus software currently detect adware and spyware, or offer a separate detection module.  A new wrinkle is adware (using stolen certificates) that disables anti-malware and virus protection; technical remedies are available.  Adware has also been discovered in certain low-cost Android devices, particularly those made by small Chinese firms running on Allwinner systems-on-chip. There are even cases where adware code is embedded deep into files stored on the system and boot partitions, to which removal involves extensive (and complex) modifications to the firmware.

Adware, or advertising-supported software, is software that generates revenue for its developer by automatically generating online advertisements in the user interface of the software or on a screen presented to the user during the installation process. The software may generate two types of revenue: one is for the display of the advertisement and another on a "pay-per-click" basis, if the user clicks on the advertisement. The software may implement advertisements in a variety of ways, including a static box display, a banner display, full screen, a video, pop-up ad or in some other form.

Adware (z angl. "reklamní software", zkratka " advertising-supported software") je označení pro produkty znepříjemňující práci nějakou reklamní aplikací. Ty mohou mít různou úroveň agresivity - od běžných bannerů až po neustále vyskakující pop-up okna nebo ikony v oznamovací oblasti. Další nepříjemnou věcí je např. změna domovské stránky v Windows Internet Exploreru, aniž by o to uživatel měl zájem.


Example.

As an example, assume this transmitted bit sequence:  0 1 1 0 0 0 1 0 1 1  and the following received bit sequence:  0 0 1 0 1 0 1 0 0 1,  The number of bit errors (the underlined bits) is, in this case, 3. The BER is 3 incorrect bits divided by 10 transferred bits, resulting in a BER of 0.3 or 30%.

Packet error ratio.

The packet error ratio (PER) is the number of incorrectly received data packets divided by the total number of received packets. A packet is declared incorrect if at least one bit is erroneous. The expectation value of the PER is denoted packet error probability "p", which for a data packet length of "N" bits can be expressed as  assuming that the bit errors are independent of each other. For small bit error probabilities and large data packets, this is approximately  Similar measurements can be carried out for the transmission of frames, blocks, or symbols.

Factors affecting the BER.

In a communication system, the receiver side BER may be affected by transmission channel noise, interference, distortion, bit synchronization problems, attenuation, wireless multipath fading, etc.  The BER may be improved by choosing a strong signal strength (unless this causes cross-talk and more bit errors), by choosing a slow and robust modulation scheme or line coding scheme, and by applying channel coding schemes such as redundant forward error correction codes.  The "transmission BER" is the number of detected bits that are incorrect before error correction, divided by the total number of transferred bits (including redundant error codes). The "information BER", approximately equal to the decoding error probability, is the number of decoded bits that remain incorrect after the error correction, divided by the total number of decoded bits (the useful information). Normally the transmission BER is larger than the information BER. The information BER is affected by the strength of the forward error correction code.

Analysis of the BER.

The BER may be evaluated using stochastic (Monte Carlo) computer simulations. If a simple transmission channel model and data source model is assumed, the BER may also be calculated analytically. An example of such a data source model is the Bernoulli source.  Examples of simple channel models used in information theory are:  A worst-case scenario is a completely random channel, where noise totally dominates over the useful signal. This results in a transmission BER of 50% (provided that a Bernoulli binary data source and a binary symmetrical channel are assumed, see below).  In a noisy channel, the BER is often expressed as a function of the normalized carrier-to-noise ratio measure denoted Eb/N0, (energy per bit to noise power spectral density ratio), or Es/N0 (energy per modulation symbol to noise spectral density).  For example, in the case of QPSK modulation and AWGN channel, the BER as function of the Eb/N0 is given by: formula_3.  People usually plot the BER curves to describe the performance of a digital communication system. In optical communication, BER(dB) vs. Received Power(dBm) is usually used; while in wireless communication, BER(dB) vs. SNR(dB) is used.  Measuring the bit error ratio helps people choose the appropriate forward error correction codes. Since most such codes correct only bit-flips, but not bit-insertions or bit-deletions, the Hamming distance metric is the appropriate way to measure the number of bit errors. Many FEC coders also continuously measure the current BER.  A more general way of measuring the number of bit errors is the Levenshtein distance. The Levenshtein distance measurement is more appropriate for measuring raw channel performance before frame synchronization, and when using error correction codes designed to correct bit-insertions and bit-deletions, such as Marker Codes and Watermark Codes.

Mathematical draft.

The BER is the likelihood of a bit misinterpretation due to electrical noise formula_4. Considering a bipolar NRZ transmission, we have  formula_5 for a "1" and formula_6 for a "0". Each of formula_7 and formula_8 has a period of formula_9.  Knowing that the noise has a bilateral spectral density formula_10,  formula_7 is formula_12  and formula_8 is formula_14.  Returning to BER, we have the likelihood of a bit misinterpretation formula_15.  formula_16 and formula_17  where formula_18 is the threshold of decision, set to 0 when formula_19.  We can use the average energy of the signal formula_20 to find the final expression :  formula_21

Bit error rate test.

BERT or bit error rate test is a testing method for digital communication circuits that uses predetermined stress patterns consisting of a sequence of logical ones and zeros generated by a test pattern generator.  A BERT typically consists of a test pattern generator and a receiver that can be set to the same pattern. They can be used in pairs, with one at either end of a transmission link, or singularly at one end with a loopback at the remote end. BERTs are typically stand-alone specialised instruments, but can be personal computer–based. In use, the number of errors, if any, are counted and presented as a ratio such as 1 in 1,000,000, or 1 in 1e06.

Bit error rate tester.

A bit error rate tester (BERT), also known as a "bit error ratio tester" or "bit error rate test solution" (BERTs) is electronic test equipment used to test the quality of signal transmission of single components or complete systems.  The main building blocks of a BERT are:

In digital transmission, the number of bit errors is the number of received bits of a data stream over a communication channel that have been altered due to noise, interference, distortion or bit synchronization errors.

Bitová chybovost neboli Bit Error Rate (BER) vyjadřuje četnost chyb v telekomunikacích a je definována poměrem chybně přijatých bitů bE ku celkovému počtu přijatých bitů za určitou dobu měření.


History.

The idea of a correlation between molecular geometry and number of valence electron pairs (both shared and unshared pairs) was originally proposed in 1939 by Ryutaro Tsuchida in Japan, and was independently presented in a Bakerian Lecture in 1940 by Nevil Sidgwick and Herbert Powell of the University of Oxford. In 1957, Ronald Gillespie and Ronald Sydney Nyholm of University College London refined this concept into a more detailed theory, capable of choosing between various alternative geometries.  In recent years, VSEPR theory has been criticized as an outdated model from the standpoint of both scientific accuracy and pedagogical value. In particular, the equivalent lone pairs of water and carbonyl compounds in VSEPR theory neglect fundamental differences in the symmetries (σ vs. π) of molecular orbitals and natural bond orbitals that correspond to them, a difference that is sometimes chemically significant. Furthermore, there is little evidence, computational or experimental, proposing that lone pairs are "bigger" than bonding pairs. It has been suggested that Bent's rule is capable of replacing VSEPR as a simple model for explaining molecular structure. Nevertheless, VSEPR theory captures many of the essential features of the structure and electron distribution of simple molecules, and most undergraduate general chemistry courses continue to teach it.

Overview.

VSEPR theory is used to predict the arrangement of electron pairs around non-hydrogen atoms in molecules, especially simple and symmetric molecules, where these key, central atoms participate in bonding to two or more other atoms; the geometry of these key atoms and their non-bonding electron pairs in turn determine the geometry of the larger whole.  The number of electron pairs in the valence shell of a central atom is determined after drawing the Lewis structure of the molecule, and expanding it to show all bonding groups and lone pairs of electrons. In VSEPR theory, a double bond or triple bond are treated as a single bonding group. The sum of the number of atoms bonded to a central atom and the number of lone pairs formed by its nonbonding valence electrons is known as the central atom's steric number.  The electron pairs (or groups if multiple bonds are present) are assumed to lie on the surface of a sphere centered on the central atom and tend to occupy positions that minimize their mutual repulsions by maximizing the distance between them. The number of electron pairs (or groups), therefore, determines the overall geometry that they will adopt. For example, when there are two electron pairs surrounding the central atom, their mutual repulsion is minimal when they lie at opposite poles of the sphere. Therefore, the central atom is predicted to adopt a "linear" geometry. If there are 3 electron pairs surrounding the central atom, their repulsion is minimized by placing them at the vertices of an equilateral triangle centered on the atom. Therefore, the predicted geometry is "trigonal". Likewise, for 4 electron pairs, the optimal arrangement is "tetrahedral".

Degree of repulsion.

The overall geometry is further refined by distinguishing between "bonding" and "nonbonding" electron pairs. The bonding electron pair shared in a sigma bond with an adjacent atom lies further from the central atom than a nonbonding (lone) pair of that atom, which is held close to its positively charged nucleus. VSEPR theory therefore views repulsion by the lone pair to be greater than the repulsion by a bonding pair. As such, when a molecule has 2 interactions with different degrees of repulsion, VSEPR theory predicts the structure where lone pairs occupy positions that allow them to experience less repulsion. Lone pair–lone pair (lp–lp) repulsions are considered stronger than lone pair–bonding pair (lp–bp) repulsions, which in turn are considered stronger than bonding pair–bonding pair (bp–bp) repulsions, distinctions that then guide decisions about overall geometry when 2 or more non-equivalent positions are possible. For instance, when 5 valence electron pairs surround a central atom, they adopt a trigonal bipyramidal molecular geometry with two collinear "axial" positions and three "equatorial" positions. An electron pair in an axial position has three close equatorial neighbors only 90° away and a fourth much farther at 180°, while an equatorial electron pair has only two adjacent pairs at 90° and two at 120°. The repulsion from the close neighbors at 90° is more important, so that the axial positions experience more repulsion than the equatorial positions; hence, when there are lone pairs, they tend to occupy equatorial positions as shown in the diagrams of the next section for steric number five.  The difference between lone pairs and bonding pairs may also be used to rationalize deviations from idealized geometries. For example, the HO molecule has four electron pairs in its valence shell: two lone pairs and two bond pairs. The four electron pairs are spread so as to point roughly towards the apices of a tetrahedron. However, the bond angle between the two O–H bonds is only 104.5°, rather than the 109.5° of a regular tetrahedron, because the two lone pairs (whose density or probability envelopes lie closer to the oxygen nucleus) exert a greater mutual repulsion than the two bond pairs.  A bond of higher bond order also exerts greater repulsion since the pi bond electrons contribute. For example in isobutylene, (HC)C=CH, the HC−C=C angle (124°) is larger than the HC−C−CH angle (111.5°). However, in the carbonate ion,, all three C−O bonds are equivalent with angles of 120° due to resonance.

AXE method.

The "AXE method" of electron counting is commonly used when applying the VSEPR theory. The electron pairs around a central atom are represented by a formula AXE, where "A" represents the central atom and always has an implied subscript one. Each "X" represents a ligand (an atom bonded to A). Each "E" represents a "lone pair" of electrons on the central atom. The total number of "X" and "E" is known as the steric number. For example in a molecule AXE, the atom A has a steric number of 5.  Based on the steric number and distribution of "X"s and "E"s, VSEPR theory makes the predictions in the following tables. Note that the geometries are named according to the atomic positions only and not the electron arrangement. For example, the description of AXE as a bent molecule means that the three atoms AX are not in one straight line, although the lone pair helps to determine the geometry.  When the substituent (X) atoms are not all the same, the geometry is still approximately valid, but the bond angles may be slightly different from the ones where all the outside atoms are the same. For example, the double-bond carbons in alkenes like CH are AXE, but the bond angles are not all exactly 120°. Likewise, SOCl is AXE, but because the X substituents are not identical, the X–A–X angles are not all equal.  As a tool in predicting the geometry adopted with a given number of electron pairs, an often used physical demonstration of the principle of minimal electron pair repulsion utilizes inflated balloons. Through handling, balloons acquire a slight surface electrostatic charge that results in the adoption of roughly the same geometries when they are tied together at their stems as the corresponding number of electron pairs. For example, five balloons tied together adopt the trigonal bipyramidal geometry, just as do the five bonding pairs of a PCl molecule (AX) or the two bonding and three non-bonding pairs of a XeF molecule (AXE). The molecular geometry of the former is also trigonal bipyramidal, whereas that of the latter is linear.  Possible geometries for steric numbers of 10, 11, 12, or 14 are bicapped square antiprismatic (or bicapped dodecadeltahedral), octadecahedral, icosahedral, and bicapped hexagonal antiprismatic, respectively. No compounds with steric numbers this high involving monodentate ligands exist, and those involving multidentate ligands can often be analysed more simply as complexes with lower steric numbers when some multidentate ligands are treated as a unit.

Examples.

The methane molecule (CH) is tetrahedral because there are four pairs of electrons. The four hydrogen atoms are positioned at the vertices of a tetrahedron, and the bond angle is cos(−) ≈ 109° 28′. This is referred to as an AX type of molecule. As mentioned above, A represents the central atom and X represents an outer atom.  The ammonia molecule (NH) has three pairs of electrons involved in bonding, but there is a lone pair of electrons on the nitrogen atom. It is not bonded with another atom; however, it influences the overall shape through repulsions. As in methane above, there are four regions of electron density. Therefore, the overall orientation of the regions of electron density is tetrahedral. On the other hand, there are only three outer atoms. This is referred to as an AXE type molecule because the lone pair is represented by an E. By definition, the molecular shape or geometry describes the geometric arrangement of the atomic nuclei only, which is trigonal-pyramidal for NH.  Steric numbers of 7 or greater are possible, but are less common. The steric number of 7 occurs in iodine heptafluoride (IF); the base geometry for a steric number of 7 is pentagonal bipyramidal. The most common geometry for a steric number of 8 is a square antiprismatic geometry. Examples of this include the octacyanomolybdate () and octafluorozirconate () anions. The nonahydridorhenate ion () in potassium nonahydridorhenate is a rare example of a compound with a steric number of 9, which has a tricapped trigonal prismatic geometry.

Exceptions.

There are groups of compounds where VSEPR fails to predict the correct geometry.

Some AXE molecules.

The shapes of heavier Group 14 element alkyne analogues (RM≡MR, where M = Si, Ge, Sn or Pb) have been computed to be bent.

Some AXE molecules.

One example of the AXE geometry is molecular lithium oxide, LiO, a linear rather than bent structure, which is ascribed to its bonds being essentially ionic and the strong lithium-lithium repulsion that results. Another example is O(SiH) with an Si–O–Si angle of 144.1°, which compares to the angles in ClO (110.9°), (CH)O (111.7°), and N(CH) (110.9°). Gillespie and Robinson rationalize the Si–O–Si bond angle based on the observed ability of a ligand's lone pair to most greatly repel other electron pairs when the ligand electronegativity is greater than or equal to that of the central atom. In O(SiH), the central atom is more electronegative, and the lone pairs are less localized and more weakly repulsive. The larger Si–O–Si bond angle results from this and strong ligand-ligand repulsion by the relatively large -SiH ligand. Burford et al showed through X-ray diffraction studies that ClAl–O–PCl has a linear Al–O–P bond angle and is therefore a non-VSEPR molecule.

Some AXE and AXE molecules.

Some AXE molecules, e.g. xenon hexafluoride (XeF) and the Te(IV) and Bi(III) anions,,,, and, are octahedra, rather than pentagonal pyramids, and the lone pair does not affect the geometry to the degree predicted by VSEPR. Similarly, the octafluoroxenate ion () in nitrosonium octafluoroxenate(VI) is a square antiprism and not a bicapped trigonal prism (as predicted by VSEPR theory for an AXE molecule), despite having a lone pair. One rationalization is that steric crowding of the ligands allows little or no room for the non-bonding lone pair; another rationalization is the inert pair effect.

Transition metal molecules.

Many transition metal compounds have unusual geometries, which can be ascribed to ligand bonding interaction with the d subshell and to absence of valence shell lone pairs. Gillespie suggested that this interaction can be weak or strong. Weak interaction is dealt with by the Kepert model, while strong interaction produces bonding pairs that also occupy the respective antipodal points (ligand opposed) of the sphere. This is similar to predictions based on sd hybrid orbitals using the VALBOND theory. The repulsion of these bidirectional bonding pairs leads to a different prediction of shapes.  The Kepert model cannot explain the formation of square planar complexes.

Heavier alkaline earth halides.

The gas phase structures of the triatomic halides of the heavier members of group 2, (i.e., calcium, strontium and barium halides, MX), are not linear as predicted but are bent, (approximate X–M–X angles: CaF, 145°; SrF, 120°; BaF, 108°; SrCl, 130°; BaCl, 115°; BaBr, 115°; BaI, 105°). It has been proposed by Gillespie that this is caused by interaction of the ligands with the electron core of the metal atom, polarising it so that the inner shell is not spherically symmetric, thus influencing the molecular geometry. Ab initio calculations have been cited to propose that contributions from the d subshell are responsible, together with the overlap of other orbitals.

Odd-electron molecules.

The VSEPR theory can be extended to molecules with an odd number of electrons by treating the unpaired electron as a "half electron pair" — for example, Gillespie and Nyholm suggested that the decrease in the bond angle in the series (180°), NO (134°), (115°) indicates that a given set of bonding electron pairs exert a weaker repulsion on a single non-bonding electron than on a pair of non-bonding electrons. In effect, they considered nitrogen dioxide as an AXE molecule, with a geometry intermediate between and. Similarly, chlorine dioxide (ClO) is an AXE molecule, with a geometry intermediate between and.  Finally, the methyl radical (CH) is predicted to be trigonal pyramidal like the methyl anion (), but with a larger bond angle (as in the trigonal planar methyl cation ()). However, in this case, the VSEPR prediction is not quite true, as CH is actually planar, although its distortion to a pyramidal geometry requires very little energy.

Valence shell electron pair repulsion theory, or VSEPR theory (, ), is a model used in chemistry to predict the geometry of individual molecules from the number of electron pairs surrounding their central atoms. It is also named the Gillespie-Nyholm theory after its two main developers, Ronald Gillespie and Ronald Nyholm. The premise of VSEPR is that the valence electron pairs surrounding an atom tend to repel each other and will, therefore, adopt an arrangement that minimizes this repulsion. This in turn decreases the molecule's energy and increases its stability, which determines the molecular geometry. Gillespie has emphasized that the electron-electron repulsion due to the Pauli exclusion principle is more important in determining molecular geometry than the electrostatic repulsion.

Teorie VSEPR (Valence Shell Electron Pair Repulsion = odpuzování elektronových párů valenční sféry) je model užívaný v chemii k předpovídáni geometrie molekul na základě počtu a druhu elektronových párů obklopujících centrální atomy. Je také označován jako Gillespieho-Nyholmova teorie, podle hlavních tvůrců.


Types.

In most species, the sex ratio varies according to the age profile of the population.  It is generally divided into four subdivisions:  These definitions can be somewhat subjective since they lack clear boundaries.

Sex ratio theory.

The theory of sex ratio is a field of study concerned with the accurate prediction of sex ratios in all sexual species, based on a consideration of their natural history. The field continues to be heavily influenced by Eric Charnov’s 1982 book, "Sex Allocation". He defines five major questions, both for his book and the field in general (slightly abbreviated here):  Biological research mostly concerns itself with sex "allocation" rather than sex ratio, sex allocation denoting the allocation of energy to either sex. Common research themes are the effects of local mate and resource competition (often abbreviated LMC and LRC, respectively).

Fisher's principle.

Fisher’s principle explains why for most species, the sex ratio is approximately 1:1. Bill Hamilton expounded Fisher’s argument in his 1967 paper on “Extraordinary sex ratios” as follows, given the assumption of equal parental expenditure on offspring of both sexes.  In modern language, the 1:1 ratio is the evolutionarily stable strategy (ESS). This ratio has been observed in many species, including the bee Macrotera portalis. A study performed by Danforth observed no significant difference in the number of males and females from the 1:1 sex ratio.

Examples in non-human species.

Environmental and individual control.

Spending equal amounts of resources to produce offspring of either sex is an evolutionarily stable strategy: if the general population deviates from this equilibrium by favoring one sex, one can obtain higher reproductive success with less effort by producing more of the other. For species where the cost of successfully raising one offspring is roughly the same regardless of its sex, this translates to an approximately equal sex ratio.  Bacteria of the genus "Wolbachia" cause skewed sex ratios in some arthropod species as they kill males. Sex-ratio of adult populations of pelagic copepods is usually skewed towards dominance of females. However, there are differences in adult sex ratios between families: in families in which females require multiple matings to keep producing eggs, sex ratios are less biased (close to 1); in families in which females can produce eggs continuously after only one mating, sex ratios are strongly skewed towards females.  Several species of reptiles have temperature-dependent sex determination, where incubation temperature of eggs determines the sex of the individual. In the American alligator, for example, females are hatched from eggs incubated between, whereas males are hatched from eggs. In this method, however, all eggs in a clutch (20–50) will be of the same sex. In fact, the natural sex ratio of this species is five females to one male.  In birds, mothers can influence the sex of their chicks. In peafowl, maternal body condition can influence the proportion of daughters in the range from 25% to 87%.  In several different groups of fish, such as wrasses, parrotfish and clownfish, dichogamy — or sequential hermaphoditism — is normal. This can cause a discrepancy in the sex ratios as well. In the bluestreak cleaner wrasse, there is only one male for every group of 6-8 females. If the male fish dies, the strongest female changes its sex to become the male for the group. All of these wrasse are born female, and only become male in this situation. Other species, like clownfish, do this in reverse, where all start out as non-reproductive males, and the largest male becomes a female, with the second-largest male maturing to become reproductive.

Domesticated animals.

Traditionally, farmers have discovered that the most economically efficient community of animals will have a large number of females and a very small number of males. A herd of cows with a few bulls or a flock of hens with one rooster are the most economical sex ratios for domesticated livestock.

Dioecious plants secondary sex ratio and amount of pollen.

It was found that the amount of fertilizing pollen can influence secondary sex ratio in dioecious plants. Increase in pollen amount leads to decrease in number of male plants in the progeny. This relationship was confirmed on four plant species from three families – "Rumex acetosa" ("Polygonaceae"), "Melandrium album" ("Cariophyllaceae"), "Cannabis sativa" and "Humulus japonicus" ("Cannabinaceae").

Polyandrous and cooperatively breeding homeotherms.

In charadriiform birds, recent research has shown clearly that polyandry and sex-role reversal (where males care and females compete for mates) as found in phalaropes, jacanas, painted snipe and a few plover species is clearly related to a strongly male-biased adult sex ratio. Those species with male care and polyandry invariably have adult sex ratios with a large surplus of males, which in some cases can reach as high as six males per female.  Male-biased adult sex ratios have also been shown to correlate with cooperative breeding in mammals such as alpine marmots and wild canids. This correlation may also apply to cooperatively breeding birds, though the evidence is less clear. It is known, however, that both male-biased adult sex ratios and cooperative breeding tend to evolve where caring for offspring is extremely difficult due to low secondary productivity, as in Australia and Southern Africa. It is also known that in cooperative breeders where both sexes are philopatric like the varied sittella, adult sex ratios are equally or more male-biased than in those cooperative species, such as fairy-wrens, treecreepers and the noisy miner where females always disperse.

See also.

Humans: Institutions:

The sex ratio is the ratio of males to females in a population. In most sexually reproducing species, the ratio tends to be 1:1. This tendency is explained by Fisher's principle. For various reasons, however, many species deviate from anything like an even sex ratio, either periodically or permanently. Examples include parthenogenic species, periodically mating organisms such as aphids, some eusocial wasps such as "Polistes fuscatus" and "Polistes exclamans", bees, ants, and termites.

Poměr pohlaví je název pro poměr počtu mužů ku počtu žen v populaci. Primární poměr pohlaví je poměr při početí, sekundární poměr pohlaví je poměr při narození, terciární je poměr v reprodukčním věku a kvartární v poreprodukčním věku (ten je ovlivněn tím, že je různá střední délka života obou pohlaví). U lidí se obvykle předpokládá poměr zhruba 105 chlapců na 100 dívek. V Česku (stejně jako ve většině Evropy) je celkový počet mužů menší než celkový počet žen. V některých lidských společenstvích může být tento poměr vychýlen různými vlivy jako jsou potraty závislými na testech pohlaví a infanticidou (např. Čína). U lidí, ale i u jiných savců, je také ovlivněn společenskou situací. V obdobích a místech nouze (krize, války) se rodí více dívek, kdežto v obdobích prosperity a u bohatých lidí zase více chlapců.


Characteristics.

The price of an expansion pack is usually much less than that of the original game. As expansion packs consist solely of additional content, most require the original game in order to play. Games with many expansions often begin selling the original game with prior expansions, such as "The Sims Deluxe Edition" ("The Sims" with ""). These bundles make the game more accessible to new players. When games reach the end of their lifespan, the publisher often releases a 'complete' or 'gold' collection which includes the game and all its subsequent expansions.

Stand-alone expansion packs.

Some expansion packs do not require the original game in order to use the new content, as is the case with "", "" or "Sonic & Knuckles". The same art and sound and code is used from the original game, and it takes place in the same active story as the original. In some cases, a stand-alone expansion such as "", or "" includes the original game.

Console game expansion packs.

Expansion packs are most commonly released for PC games, but are becoming increasingly prevalent for video game consoles, particularly due to the popularity of downloadable content. The increasing number of multi-platform games has also led to the release of more expansion packs on consoles, especially stand-alone expansion packs (as described above). "", for example, requires the original "" to play on the PC, but Xbox 360 versions of both the original "Tiberium Wars" and "Kane's Wrath" are available, neither of which require one another.  "" was the first expansion pack released for the PlayStation. The game required the player to insert the "London" disc, remove it, insert the original "Grand Theft Auto" disc, remove it, then insert the "London" media again in order to play.  "Sonic & Knuckles" for the Mega Drive/Genesis was unusual in that it functioned as both a stand-alone cartridge and as an expansion pack for both "Sonic the Hedgehog 2" and "Sonic the Hedgehog 3".

Collectible card game expansions.

Collectible card games, or CCGs for short, are typically released as expansion sets, composed of booster packs. CCGs may be referred to as "living" or "dead", and living CCGs are routinely published with supplementary expansions. CCGs generally don't have a core set that is reprinted indefinitely, instead, they are retired and replaced with new expansions on a quarterly or bi-annual basis. Expansions usually introduce new rules, or game mechanics, expanding the games library of cards and rules set.

An expansion pack, expansion set, supplement, or simply expansion is an addition to an existing role-playing game, tabletop game, video game or collectible card game. These add-ons usually add new game areas, weapons, objects, characters, or an extended storyline to an already-released game. While board game expansions are typically designed by the original creator, video game developers sometimes contract out development of the expansion pack to a third-party company, it may choose to develop the expansion itself, or it may do both. Board games and tabletop RPGs may have been marketing expansions since the 1970s, and video games have been releasing expansion packs since the 1980s, early examples being the "Dragon Slayer" games "" and "Sorcerian". Other terms for the concept are module and, in certain games' marketing, adventure.

Rozšíření hry je doplněk k již vydané hře. Rozšíření hry obsahuje nová herní prostředí, mapy, funkce, zbraně, objekty, pokračování v herním příběhu apod. K používání rozšíření je zpravidla nutná původní hra, někdy lze však rozšíření hrát samostatně. U stolních her může být příkladem Carcassonne a na jedné straně rozšíření "Hostince a katedrály, Kupci a stavitelé, Princezna a drak, Věž", která jsou vázána na původní hru, a na druhé straně svébytná rozšíření "Lovci a sběrači, Hrad, Město, Objevitelé", která lze hrát bez původní hry, přičemž jsou založená na obdobných herních principech původní hry. A speciální situace vzniká u hry Dominion, kde vlastně existují dvě základní hry (originální Dominion a Dominion: Intriky), které je možné kombinovat, a všechna rozšíření je možné použít k jakékoli z nich.


Biography.

Early life.

Carmack was born in Shawnee Mission, Kansas, the son of local television news reporter Stan Carmack. He grew up in the Kansas City metropolitan area, where he became interested in computers at an early age. He attended Shawnee Mission East High School in Prairie Village, Kansas and Raytown South High School in nearby Raytown, Missouri.  Carmack was introduced to video games with the 1978 shoot 'em up title "Space Invaders" in the arcades during a summer vacation as a child. The 1980 maze chase arcade game "Pac-Man" also left a strong impression on him. He cited Shigeru Miyamoto as the game developer he most admired.  As reported in David Kushner's "Masters of Doom", when Carmack was 14, he broke into a school to help a group of children steal Apple II computers. To gain entry to the building, Carmack concocted a sticky substance of thermite mixed with Vaseline that melted through the windows. However, an overweight accomplice struggled to get through the hole, and opened the window, setting off a silent alarm and alerting police. Carmack was arrested, and sent for psychiatric evaluation (the report mentions "no empathy for other human beings" and describes Carmack as "a brain on legs"). Carmack was then sentenced to a year in a juvenile home.  He attended the University of Missouri–Kansas City for two semesters before withdrawing to work as a freelance programmer.

Career.

Softdisk, a computer company in Shreveport, Louisiana, hired Carmack to work on "Softdisk G-S" (an Apple II publication), introducing him to John Romero and other future key members of id Software such as Adrian Carmack (not related). Later, Softdisk would place this team in charge of a new, but short-lived, bi-monthly game subscription product called "Gamer's Edge" for the IBM PC (DOS) platform. In 1990, while still at Softdisk, Carmack, Romero, and others created the first of the "Commander Keen" games, a series that was published by Apogee Software, under the shareware distribution model, from 1991 onwards. Afterwards, Carmack left Softdisk to co-found id Software.  Carmack has pioneered or popularized the use of many techniques in computer graphics, including "adaptive tile refresh" for "Commander Keen", ray casting for "Hovertank 3-D", "Catacomb 3-D", and "Wolfenstein 3-D", binary space partitioning which "Doom" became the first game to use, surface caching which he invented for "Quake", Carmack's Reverse (formally known as z-fail stencil shadows) which he devised for "Doom 3", and MegaTexture technology, first used in "".  Carmack's engines have also been licensed for use in other influential first-person shooters such as "Half-Life", "Call of Duty" and "Medal of Honor". In 2007, when Carmack was on vacation with his wife, he ended up playing some games on his cellphone, and decided he was going to make a "good" mobile game.  On August 7, 2013, Carmack joined Oculus VR as their CTO. On November 22, 2013, he resigned from id Software to work full-time at Oculus VR. Carmack's reason for leaving was because id's parent company ZeniMax Media didn't want to support Oculus Rift. Carmack's role at both companies later became central to a ZeniMax lawsuit against Oculus parent company Facebook, claiming that Oculus stole ZeniMax's virtual reality intellectual property. The trial jury absolved Carmack of liability, though Oculus and other corporate officers were held liable for trademark, copyright, and contract violations.  In February 2017, Carmack sued ZeniMax, claiming the company had refused to pay him the remaining $22.5 million owed him from their purchase of id Software. By October 2018, Carmack stated that he and ZeniMax reached an agreement and that "Zenimax has fully satisfied their obligations to me", ending the suit.  On November 13, 2019, Carmack announced that he is stepping down from the Oculus CTO role to become a "Consulting CTO" in order to allocate more time to his work on artificial general intelligence (AGI).

Armadillo Aerospace.

Around 2000, Carmack became interested in rocketry, a hobby of his youth. Reviewing how much money he was spending on customizing Ferraris, Carmack realized he could do significant work in hobby aerospace. He began by giving financial support to a few local amateur engineers. Carmack funded the company out of his own pocket, for "something north of a million dollars a year." The company of hobbyists made steady progress toward their goals of suborbital space flight and eventual orbital vehicles. In October 2008, Armadillo Aerospace competed in a NASA contest known as the Lunar Lander Challenge, winning first place in the Level 1 competition along with $350,000. In September 2009, they completed Level 2 and were awarded $500,000. The company went into "hibernation mode" in 2013.

Open-source software.

Carmack is a well-known advocate of open-source software, and has repeatedly voiced his opposition to software patents, equating them to robbery. He has also contributed to open source projects, such as starting the initial port of the X Window System to Mac OS X Server and working to improve the OpenGL drivers for Linux through the Utah GLX project.  Carmack released the source code for "Wolfenstein 3D" in 1995 and the "Doom" source code in 1997. When the source code to "Quake" was leaked and circulated among the "Quake" community underground in 1996, a programmer unaffiliated with id Software used it to port "Quake" to Linux, and subsequently sent the patches to Carmack. Instead of pursuing legal action, id Software, at Carmack's behest, used the patches as the foundation for a company-sanctioned Linux port. id Software has since publicly released the source code to "Quake", "Quake 2", "Quake 3" and lastly "Doom 3" (and later the "BFG Edition"), all under the GNU General Public License (GPL). The "Doom" source code was also re-released under the GPL in 1999. The id Tech 4 engine, more commonly known as the "Doom 3 engine", has also been released as open-source license under the GPL. The source code for "Hovertank 3D" and "Catacomb 3D" (as well as Carmack's earlier "Catacomb") was released in June 2014 by Flat Rock Software with Carmack's blessing. On the other hand, Carmack has several times over the years voiced a skeptical opinion about Linux as a gaming platform; for instance in 2013 he argued for emulation ""as proper technical direction for gaming on linux"" and in 2014 he voiced the opinion that Linux might be the biggest problem for the success of the Steam Machine.  Carmack contributes to charities and gaming communities. Some of the recipients of Carmack's charitable contributions include his former high school, promoters of open-source software, opponents of software patents, and game enthusiasts.

Personal life.

Carmack was so successful at id that by mid-1994 he had purchased 2 Ferraris; a 328 and a Ferrari Testarossa. In 1997, he gave away one of his Ferrari (a 328 model) as a prize to Dennis Fong, the winner of the "Quake" tournament "Red Annihilation".  He met his wife Katherine Anna Kang at the 1997 QuakeCon when she visited id's offices. As a bet, Kang challenged Carmack to sponsor the first All Female Quake Tournament if she was able to produce a significant number of participants. Carmack predicted a maximum of 25 participants, but there were 1,500. Carmack and Kang married on January 1, 2000 and planned a ceremony in Hawaii. Steve Jobs requested that they would postpone the ceremony so he could attend the MacWorld Expo on January 5, 2000. Carmack declined and suggested making a video instead. Carmack and his wife had a son in 2004. Carmack has a blog last updated in 2006 (previously a.plan), an active Twitter account, and also occasionally posts comments to Slashdot.  As a game developer, he differs from many of his contemporaries by avoiding commitment to a final release date for any game he is developing. Instead, when asked for a release date on a new title, Carmack will usually reply that the game will be released "when it's done." Employees at Apogee, in their past years the publishers of games by id Software, adopted this business practice as well.  Carmack supported the 2012 presidential campaign of Libertarian Ron Paul.  Carmack is an atheist.  Carmack loves pizza. During his time at id Software, a medium pepperoni pizza would arrive for Carmack from Domino's Pizza almost every day, carried by the same delivery person for more than 15 years. Carmack had been such a regular customer that they continued to charge him 1995 prices.  On occasion he has commended the efforts of similarly focused programmers — first Ken Silverman, who wrote the Build engine for 3D Realms, and later with Tim Sweeney of Epic Games, who writes the Unreal Engine.

Games.

Titles are listed below in reverse chronological order.

John D. Carmack II (born August 20, 1970) is an American computer programmer, video game developer and engineer. He co-founded the video game company id Software and was the lead programmer of its games "Commander Keen", "Wolfenstein 3D", "Doom" and "Quake" and their sequels. Carmack made innovations in 3D graphics, such as his Carmack's Reverse algorithm for shadow volumes. In 2013, he resigned from id to work full-time at Oculus VR, where he served as CTO and later Consulting CTO in 2019.

John D. Carmack II (* 20. srpna 1970) je americký programátor, který je znám pro svou práci na 3D hrách jako Wolfenstein 3D, Quake či Doom. V roce 1991 spoluzakládal firmu Id Software, která vytváří 3D hry a licencuje 3D enginy. Od roku 2013 pracuje pro Oculus VR. Nedostudoval vysokou školu. Je ženatý a má syna.