title: The Circle (American season 1)

text: The British version of the show premiered in 2018, and was renewed for its second season a few months after the first season ended. After the first season was Channel 4's "youngest profiling" show in six years, according to the British TV industry magazine "Broadcast", talks began of international versions. On October 8, 2018, Netflix announced its partnership with All3Media to create three international versions of "The Circle" on Netflix, including the American version. Brandon Reigg, Netflix's Vice Principal of Unscripted Content, stated, "We think the show's combination of modern social media interaction and competition will captivate Netflix members around the world, in multiple languages, and we're delighted to partner with Studio Lambert and Motion to produce these three new local versions."


title: The Circle (American season 1)

text: In an interview with "Variety", Tim Harcourt, one of the executive producers for Studio Lambert, stated that "The Circle" format and premise allowed the casting team to search for all different kinds of people. He noted how the casting contrasted from casts on show like "Real Housewives" or "Jersey Shore" and how those shows are "all one gang of quite similar characters." He explained how there was no set cast for the show until it was over. The first eight players to enter were all predetermined and planned, but everything after that was all luck to whoever got on. Harcourt stated that the production team would decide who would be the right fit depending on who just left the game, acknowledging that with thirteen contestants, not all who were possible players end up on the show at all.


title: The Circle (American season 1)

text: In October 2019, it was reported that filming was completed. All filming was done in August 2019 before the British version's second season in September 2019, and was completed in fifteen days. It was also reported that the American version was filmed in Salford, England, using the same apartment building that was used in the second season of the British version. Attempts to obscure the filming location to appear to be in the United States were apparent, including overhead shots of the cities of Chicago and Milwaukee throughout the show, as well as aerial shots of the United Kingdom reversed so the cars appear to be driving on the right side of the road.


title: The Circle (American season 1)

text: According to participant Joey Sasso, filming of the show took about a month. The contestants' apartments were brightly-lit in part to allow the cameras to record them, but also to disorientate the players' perception of time; Sasso stated that they often had no idea what day or time of day it was, and he had taken to wearing sunglasses inside to cut off the glare from the lights which had been mistaken as a fashion statement by fans of the show. The contestants were given a few minutes each day to spend on the apartment complex's rooftop space.


title: The Circle (American season 1)

text: On December 10, 2019, a trailer for the American version was released, revealing the premiere date to be January 1, 2020, and the prize amount to be $100,000. On December 29, it was revealed by "The New York Times" that twelve episodes would be airing from January 1 to January 15 with four episodes being released every Wednesday as part of the "three week event." On December 30, 2019, in order to get more people interested in "The Circle", Netflix released a thirty-minute cut of the hour-long first episode of the season on its YouTube channel for free. Then, starting on January 1 and lasting until January 15, Netflix dropped four episodes every week on Wednesday.


title: The Circle (American season 1)

text: On January 8, 2020, via Twitter and Instagram, "The Circle" announced that voting had opened for the Fan Favorite award. The player who had received the most votes would win . Voting opened at midnight on January 8, 2020, PST, and lasted until midnight on January 17. The winner of the Fan Favorite vote was revealed to be Sammie Cimarelli on "The Circle"s Instagram on January 17.


title: The Circle (American season 1)

text: "The Circle" received positive reviews from critics. On the review aggregator website Rotten Tomatoes, the season holds an 80% approval rating with an average rating of 6 out of 10 based on 15 reviews. "The Circle" also became the topic of discussion on the sixth episode of "I Like to Watch", where drag queens Trixie Mattel and Katya Zamolodchikova reacted to the first episode. Because of the positive reviews and large number of viewers, Netflix renewed "The Circle" for a second and third season on March 24, 2020.


title: The Circle (American season 1)

text: Once the show began airing, it was well received. Megh Wright from "Vulture" proclaimed that "The Circle" is a "fascinating series" that gives a "brutally honest reflection of the fractured way we attempt to connect to each other today." Kate Knibbs from "Wired" declared it the "best TV show about the internet" that "actually takes its audience places, dramatizing the experience of online social interactions in all their fizz and slipperiness." The show was also praised for its diverse cast and personalities. According to Etan Smallman of "The New York Times", this type of diversity is what makes "The Circle" so unique among other reality TV shows.


title: The Circle (American season 1)

text: Meanwhile, Isaac Feldberg from "Fortune" told readers to skip "The Circle" because of "the aggressively irritating manner in which the series has been put together." Jerrica Tisdale from "Screen Rant" called the series a "must-see." She comments on how common it is to "develop entire relationships through solely digital interactions," and that is what "The Circle" is trying to explore.


title: The Circle (American season 1)

text: Nev Schulman, host and executive producer of "" criticized "The Circle" in an interview with "People". He said that when you remove the realistic circumstances and realistic people with normal personalities, it is less entertaining than realism. He also expressed disappointment at the use of the word "catfish"; he cites the definition to be "a complicated person who, for any number of reasons and personal struggles, has found themselves creating a profile of varying veracity or truths to explore, and interact, and discover themselves", whereas on "The Circle", players use it to simply call someone a liar. Despite these statements, he admits he still watches and enjoys the show.


title: The Circle (American season 1)

text: Aja Romano of "Vox" praised "The Circle" for embracing inauthenticity as a part of social media and human nature as a whole. She likens The Circle to a microcosm of social media, saying "Instead of treating 'being fake on the internet' as a shocking betrayal, "The Circle" embraces it as something we all do in big and small ways, often in the service of making friends and fitting in." She also praises the cast. She mentions how the cast shares very personal things frequently, even through the anonymity of The Circle. Romano states that the cast developed character arcs, and the production team could get away with making a narrative structure.


title: Saad Lamjarred

text: Saad Lamjarred (; born April 7, 1985) is a Moroccan singer-songwriter, multi-instrumentalist, dancer, record producer and actor. He grew up in an artist family and became famous after his songs broke YouTube audience records, making him a major figure in Arabic pop, and the first singer to popularize Moroccan pop.


title: Saad Lamjarred

text: Lamjarred was born to Bachir Abdou, a Moroccan classical singer, and Nezha Regragui, an actress and comedian.


title: Saad Lamjarred

text: From an early age, Lamjarred had a special interest in playing the piano, as well as singing as early as the age of four.


title: Saad Lamjarred

text: Lamjarred then went on to study at the Conservatory of Music in Rabat, where he studied music, art theory and dance. He would perform many productions wherein he would collaborate with his father.


title: Saad Lamjarred

text: Lamjarred moved to the US in 2001 and cites this as one of the main sources of inspiration for his music, crediting the experience for exposing him to western music and having a defining effect on his style and the type of artist he wanted to identify as.


title: Saad Lamjarred

text: In 2007, Lamjarred took part in "Super Star", a widely popular Arab talent TV show, and was placed second in season 4 of the series that was defeated by the Tunisian Marwan Ali. His participation earned him recognition.


title: Saad Lamjarred

text: In 2011, Lamjarred started his acting career, playing the male lead in "Ahlam Nassim", a Moroccan soap opera. He released an album in 2013, titled "Wala Aalik". That same year, he released two more EPs, namely "Salina" and "Enty". The title song of the latter, "Enty" (), became one of Lamjarred's biggest hits and earned him an award at the Méditel Morocco Music Awards 2014, as well as a nomination for the Best Middle East Act at the 2014 MTV Europe Music Awards.


title: Saad Lamjarred

text: Lamjarred was also nominated for the Best Middle East Act at the 2014 MTV Europe Music Awards. He won the Murex d'Or in the category of "Best Arabic Song" for his 2014 song "Enty".


title: Saad Lamjarred

text: The music video for Lamjarred's 2015 hit single, "Lm3allem" (), earned a Guinness World Record achievement after garnering 1 billion views on YouTube within three months of release.


title: Saad Lamjarred

text: A year later, Lamjarred released another single titled "Ana Machi Sahel" (), which he soon followed up with a black-and-white music video released on YouTube that features dozens of Lamjarred's fans, who have filmed themselves singing along to the song at home, in their cars and out and about. Lamjarred didn't wait too long to release another single by the name of "Ghaltana" () in the form of a video clip directed by Amr Rouani. The video caught eyes because of its Wild West, gritty feel, inspired by Rouani's childhood love of "Mad Max" films.


title: Saad Lamjarred

text: Following this success, Lamjarred's music production took a brief gap while he was on trial in Paris for "sexual assault", but soon made a come-back with his August 2017 comeback titled "Let Go". It was an immediate hit, it earned about half a million views on YouTube within an hour of its release. Lamjarred later released new hit songs such as "Ghazali" (), another big hit that earned more than half a million views only minutes after the video went live at an average of 50 thousand views every five minutes. "Ghazali" was then succeeded by "Casablanca", in which Lamjarred sings in French.


title: Saad Lamjarred

text: August 2018 saw Lamjarred incarcerated once more in Saint Tropez, halting his music career again until December 2018, in which he released another single, titled "Baddek Eih" (). Within 4 hours of publication, the official music video received over a million views on YouTube.


title: Saad Lamjarred

text: In July 2019, Lamjarred performed and released a duet with Egyptian actor and fellow singer Mohamed Ramadan titled "Ensay" (), which garnered over 100 million views within a month of publication.


title: Saad Lamjarred

text: On June 10, 2020, Lamjarred reached 10 million subscribers on his official YouTube channel, and becoming the first Arab African singer to get the Diamond Button. In May 2022, his 2015 hit single "Lm3allem" became the first Arabic song to surpass a billion views on YouTube.


title: Saad Lamjarred

text: Lamjarred leads a very private love life, but there were confirmed rumors that he was once married, and divorced around 2015. When asked about it by the media, he blamed jealousy, claiming that it could "really destroy lives", especially since he works in entertainment.


title: Saad Lamjarred

text: On 11 September 2022, he announced his engagement to businesswoman Ghita El Allaki. They married later in the same month.


title: Saad Lamjarred

text: In February 2010 while visiting the United States, Saad Lamjarred was accused of beating and raping a woman from Brooklyn, New York. Lamjarred fled the U.S. after posting bail and was in risk of being arrested if he returned. The case was dropped in 2016, after the accuser "stopped cooperating with prosecutors" and reached a settlement in a lawsuit.


title: Saad Lamjarred

text: Lamjarred was arrested at the Marriott Champs Elysées at the 17th arrondissement of Paris on October 25, 2016, where he appeared before a French prosecutor to face the charges about an alleged sexual assault against a French woman. He was scheduled to perform at the Palais des congrès de Paris on October 29, 2016. Lamjarred was released in April 2017, but still faced charges. In early 2017, he was "prohibited from performing in public, traveling and speaking to media". The King of Morocco, Mohammed VI, helped him cover his fees and hire a legal team. In 2017, a French-Moroccan woman accused him of sexual misconduct and abuse at an apartment in Casablanca, Morocco, back in 2015. She later withdrew the complaint "under pressure from her family".


title: Saad Lamjarred

text: On August 26, 2018, he was once again arrested in Saint-Tropez on a new rape allegation in France. Lamjarred, who has denied the allegations, was released on a bail of 150,000 euros and could not leave France. His release on bail was later appealed by the Parquet of Draguignan (public prosecutor). On September 18, 2018, he was incarcerated in France following a decision of the cour d'appel (court of appeal) from Aix-en-Provence. On November 20, 2018, it was announced that he had been cleared of rape charges, but would be tried for "crimes of sexual assault and willful violence". On December 6, 2018, it was announced that French authorities had released Lamjarred on a conditional release and that he was awaiting trial. His Moroccan passport was confiscated, he was not allowed to leave France and he had to report to the nearest precinct once a week.


title: Saad Lamjarred

text: Following the third allegation, a campaign started on the social media with the hashtags "Lamjarred out" and "masaktach" (A Moroccan term expressing refusal to be silenced), with the users demanding that his songs being taken off the radio stations. 2M and Hit Radio were among the first to take his songs off the airways, with the latter saying that they would ask their listeners whether they should keep the ban permanent or not.


title: Saad Lamjarred

text: In September 2018, after a campaign on social networks, some Moroccan media stopped their broadcast of Lamjarred's songs. In December 2018, he was released from jail after serving his sentence, but was unable to leave France until August 2019. In April 2019, the judge overseeing the case from October 2016 "redefined" the charges against him due to lack of evidence to prove him guilty and referred his case to the criminal court. On December 18, 2019, he had his first public concert in Riyadh after three years. Days before the concert, a number of Saudi users on Twitter expressed their disapproval of Lamjarred's upcoming concert in the country's capital.


title: Saad Lamjarred

text: In January 2020, the investigative chamber of the Paris Court of Appeal referred the case from October 2016 to the court of assizes. In April 2020, The Paris Court of Cassation annulled the decision made by the investigative chamber as "the code of criminal procedure was not respected and referred the case back to the criminal court.


title: Renormalization

text: Renormalization is a collection of techniques in quantum field theory, the statistical mechanics of fields, and the theory of self-similar geometric structures, that are used to treat infinities arising in calculated quantities by altering values of these quantities to compensate for effects of their self-interactions. But even if no infinities arose in loop diagrams in quantum field theory, it could be shown that it would be necessary to renormalize the mass and fields appearing in the original Lagrangian.


title: Renormalization

text: For example, an electron theory may begin by postulating an electron with an initial mass and charge. In quantum field theory a cloud of virtual particles, such as photons, positrons, and others surrounds and interacts with the initial electron. Accounting for the interactions of the surrounding particles (e.g. collisions at different energies) shows that the electron-system behaves as if it had a different mass and charge than initially postulated. Renormalization, in this example, mathematically replaces the initially postulated mass and charge of an electron with the experimentally observed mass and charge. Mathematics and experiments prove that positrons and more massive particles like protons exhibit precisely the same observed charge as the electron – even in the presence of much stronger interactions and more intense clouds of virtual particles.


title: Renormalization

text: Renormalization specifies relationships between parameters in the theory when parameters describing large distance scales differ from parameters describing small distance scales. Physically, the pileup of contributions from an infinity of scales involved in a problem may then result in further infinities. When describing spacetime as a continuum, certain statistical and quantum mechanical constructions are not well-defined. To define them, or make them unambiguous, a continuum limit must carefully remove "construction scaffolding" of lattices at various scales. Renormalization procedures are based on the requirement that certain physical quantities (such as the mass and charge of an electron) equal observed (experimental) values. That is, the experimental value of the physical quantity yields practical applications, but due to their empirical nature the observed measurement represents areas of quantum field theory that require deeper derivation from theoretical bases.


title: Renormalization

text: Renormalization was first developed in quantum electrodynamics (QED) to make sense of infinite integrals in perturbation theory. Initially viewed as a suspect provisional procedure even by some of its originators, renormalization eventually was embraced as an important and self-consistent actual mechanism of scale physics in several fields of physics and mathematics.


title: Renormalization

text: Today, the point of view has shifted: on the basis of the breakthrough renormalization group insights of Nikolay Bogolyubov and Kenneth Wilson, the focus is on variation of physical quantities across contiguous scales, while distant scales are related to each other through "effective" descriptions. All scales are linked in a broadly systematic way, and the actual physics pertinent to each is extracted with the suitable specific computational techniques appropriate for each. Wilson clarified which variables of a system are crucial and which are redundant.


title: Renormalization

text: Renormalization is distinct from regularization, another technique to control infinities by assuming the existence of new unknown physics at new scales.


title: Renormalization

text: The problem of infinities first arose in the classical electrodynamics of point particles in the 19th and early 20th century.


title: Renormalization

text: The mass of a charged particle should include the mass–energy in its electrostatic field (electromagnetic mass). Assume that the particle is a charged spherical shell of radius . The mass–energy in the field is


title: Renormalization

text: which becomes infinite as . This implies that the point particle would have infinite inertia and thus cannot be accelerated. Incidentally, the value of that makes formula_2 equal to the electron mass is called the classical electron radius, which (setting formula_3 and restoring factors of and formula_4) turns out to be


title: Renormalization

text: where formula_6 is the fine-structure constant, and formula_7 is the reduced Compton wavelength of the electron.


title: Renormalization

text: Renormalization: The total effective mass of a spherical charged particle includes the actual bare mass of the spherical shell (in addition to the mass mentioned above associated with its electric field). If the shell's bare mass is allowed to be negative, it might be possible to take a consistent point limit. This was called "renormalization", and Lorentz and Abraham attempted to develop a classical theory of the electron this way. This early work was the inspiration for later attempts at regularization and renormalization in quantum field theory.


title: Renormalization

text: When calculating the electromagnetic interactions of charged particles, it is tempting to ignore the "back-reaction" of a particle's own field on itself. (Analogous to the back-EMF of circuit analysis.) But this back-reaction is necessary to explain the friction on charged particles when they emit radiation. If the electron is assumed to be a point, the value of the back-reaction diverges, for the same reason that the mass diverges, because the field is inverse-square.


title: Renormalization

text: The Abraham–Lorentz theory had a noncausal "pre-acceleration". Sometimes an electron would start moving "before" the force is applied. This is a sign that the point limit is inconsistent.


title: Renormalization

text: The trouble was worse in classical field theory than in quantum field theory, because in quantum field theory a charged particle experiences Zitterbewegung due to interference with virtual particle–antiparticle pairs, thus effectively smearing out the charge over a region comparable to the Compton wavelength. In quantum electrodynamics at small coupling, the electromagnetic mass only diverges as the logarithm of the radius of the particle.


title: Renormalization

text: When developing quantum electrodynamics in the 1930s, Max Born, Werner Heisenberg, Pascual Jordan, and Paul Dirac discovered that in perturbative corrections many integrals were divergent (see The problem of infinities).


title: Renormalization

text: One way of describing the perturbation theory corrections' divergences was discovered in 1947–49 by Hans Kramers, Hans Bethe,


title: Renormalization

text: Julian Schwinger, Richard Feynman, and Shin'ichiro Tomonaga, and systematized by Freeman Dyson in 1949. The divergences appear in radiative corrections involving Feynman diagrams with closed "loops" of virtual particles in them.


title: Renormalization

text: While virtual particles obey conservation of energy and momentum, they can have any energy and momentum, even one that is not allowed by the relativistic energy–momentum relation for the observed mass of that particle (that is, formula_8 is not necessarily the squared mass of the particle in that process, e.g. for a photon it could be nonzero). Such a particle is called off-shell. When there is a loop, the momentum of the particles involved in the loop is not uniquely determined by the energies and momenta of incoming and outgoing particles. A variation in the energy of one particle in the loop can be balanced by an equal and opposite change in the energy of another particle in the loop, without affecting the incoming and outgoing particles. Thus many variations are possible. So to find the amplitude for the loop process, one must integrate over "all" possible combinations of energy and momentum that could travel around the loop.


title: Renormalization

text: These integrals are often "divergent", that is, they give infinite answers. The divergences that are significant are the "ultraviolet" (UV) ones. An ultraviolet divergence can be described as one that comes from


title: Renormalization

text: Shown in the pictures at the right margin, there are exactly three one-loop divergent loop diagrams in quantum electrodynamics:


title: Renormalization

text: The second class of divergence called an infrared divergence, is due to massless particles, like the photon. Every process involving charged particles emits infinitely many coherent photons of infinite wavelength, and the amplitude for emitting any finite number of photons is zero. For photons, these divergences are well understood. For example, at the 1-loop order, the vertex function has both ultraviolet and "infrared" divergences. In contrast to the ultraviolet divergence, the infrared divergence does not require the renormalization of a parameter in the theory involved. The infrared divergence of the vertex diagram is removed by including a diagram similar to the vertex diagram with the following important difference: the photon connecting the two legs of the electron is cut and replaced by two on-shell (i.e. real) photons whose wavelengths tend to infinity; this diagram is equivalent to the bremsstrahlung process. This additional diagram must be included because there is no physical way to distinguish a zero-energy photon flowing through a loop as in the vertex diagram and zero-energy photons emitted through bremsstrahlung. From a mathematical point of view, the IR divergences can be regularized by assuming fractional differentiation w.r.t. a parameter, for example:


title: Renormalization

text: is well defined at but is UV divergent; if we take the -th fractional derivative with respect to , we obtain the IR divergence


title: Renormalization

text: The diagram in Figure 2 shows one of the several one-loop contributions to electron–electron scattering in QED. The electron on the left side of the diagram, represented by the solid line, starts out with 4-momentum and ends up with 4-momentum . It emits a virtual photon carrying to transfer energy and momentum to the other electron. But in this diagram, before that happens, it emits another virtual photon carrying 4-momentum , and it reabsorbs this one after emitting the other virtual photon. Energy and momentum conservation do not determine the 4-momentum uniquely, so all possibilities contribute equally and we must integrate.


title: Renormalization

text: The various factors in this expression are gamma matrices as in the covariant formulation of the Dirac equation; they have to do with the spin of the electron. The factors of are the electric coupling constant, while the formula_12 provide a heuristic definition of the contour of integration around the poles in the space of momenta. The important part for our purposes is the dependency on of the three big factors in the integrand, which are from the propagators of the two electron lines and the photon line in the loop.


title: Renormalization

text: This has a piece with two powers of on top that dominates at large values of (Pokorski 1987, p. 122):


title: Renormalization

text: This integral is divergent and infinite, unless we cut it off at finite energy and momentum in some way.


title: Renormalization

text: The solution was to realize that the quantities initially appearing in the theory's formulae (such as the formula for the Lagrangian), representing such things as the electron's electric charge and mass, as well as the normalizations of the quantum fields themselves, did "not" actually correspond to the physical constants measured in the laboratory. As written, they were "bare" quantities that did not take into account the contribution of virtual-particle loop effects to "the physical constants themselves". Among other things, these effects would include the quantum counterpart of the electromagnetic back-reaction that so vexed classical theorists of electromagnetism. In general, these effects would be just as divergent as the amplitudes under consideration in the first place; so finite measured quantities would, in general, imply divergent bare quantities.


title: Renormalization

text: To make contact with reality, then, the formulae would have to be rewritten in terms of measurable, "renormalized" quantities. The charge of the electron, say, would be defined in terms of a quantity measured at a specific kinematic "renormalization point" or "subtraction point" (which will generally have a characteristic energy, called the "renormalization scale" or simply the energy scale). The parts of the Lagrangian left over, involving the remaining portions of the bare quantities, could then be reinterpreted as counterterms, involved in divergent diagrams exactly "canceling out" the troublesome divergences for other diagrams.


title: Renormalization

text: the fields and coupling constant are really "bare" quantities, hence the subscript above. Conventionally the bare quantities are written so that the corresponding Lagrangian terms are multiples of the renormalized ones:


title: Renormalization

text: Gauge invariance, via a Ward–Takahashi identity, turns out to imply that we can renormalize the two terms of the covariant derivative piece


title: Renormalization

text: A term in this Lagrangian, for example, the electron–photon interaction pictured in Figure 1, can then be written


title: Renormalization

text: The physical constant , the electron's charge, can then be defined in terms of some specific experiment: we set the renormalization scale equal to the energy characteristic of this experiment, and the first term gives the interaction we see in the laboratory (up to small, finite corrections from loop diagrams, providing such exotica as the high-order corrections to the magnetic moment). The rest is the counterterm. If the theory is "renormalizable" (see below for more on this), as it is in QED, the "divergent" parts of loop diagrams can all be decomposed into pieces with three or fewer legs, with an algebraic form that can be canceled out by the second term (or by the similar counterterms that come from and ).


title: Renormalization

text: The diagram with the counterterm's interaction vertex placed as in Figure 3 cancels out the divergence from the loop in Figure 2.


title: Renormalization

text: Historically, the splitting of the "bare terms" into the original terms and counterterms came before the renormalization group insight due to Kenneth Wilson. According to such renormalization group insights, detailed in the next section, this splitting is unnatural and actually unphysical, as all scales of the problem enter in continuous systematic ways.


title: Renormalization

text: To minimize the contribution of loop diagrams to a given calculation (and therefore make it easier to extract results), one chooses a renormalization point close to the energies and momenta exchanged in the interaction. However, the renormalization point is not itself a physical quantity: the physical predictions of the theory, calculated to all orders, should in principle be "independent" of the choice of renormalization point, as long as it is within the domain of application of the theory. Changes in renormalization scale will simply affect how much of a result comes from Feynman diagrams without loops, and how much comes from the remaining finite parts of loop diagrams. One can exploit this fact to calculate the effective variation of physical constants with changes in scale. This variation is encoded by beta-functions, and the general theory of this kind of scale-dependence is known as the renormalization group.


title: Renormalization

text: Colloquially, particle physicists often speak of certain physical "constants" as varying with the energy of interaction, though in fact, it is the renormalization scale that is the independent quantity. This "running" does, however, provide a convenient means of describing changes in the behavior of a field theory under changes in the energies involved in an interaction. For example, since the coupling in quantum chromodynamics becomes small at large energy scales, the theory behaves more like a free theory as the energy exchanged in an interaction becomes large – a phenomenon known as asymptotic freedom. Choosing an increasing energy scale and using the renormalization group makes this clear from simple Feynman diagrams; were this not done, the prediction would be the same, but would arise from complicated high-order cancellations.


title: Renormalization

text: Since the quantity is ill-defined, in order to make this notion of canceling divergences precise, the divergences first have to be tamed mathematically using the theory of limits, in a process known as regularization (Weinberg, 1995).


title: Renormalization

text: An essentially arbitrary modification to the loop integrands, or "regulator", can make them drop off faster at high energies and momenta, in such a manner that the integrals converge. A regulator has a characteristic energy scale known as the cutoff; taking this cutoff to infinity (or, equivalently, the corresponding length/time scale to zero) recovers the original integrals.


title: Renormalization

text: With the regulator in place, and a finite value for the cutoff, divergent terms in the integrals then turn into finite but cutoff-dependent terms. After canceling out these terms with the contributions from cutoff-dependent counterterms, the cutoff is taken to infinity and finite physical results recovered. If physics on scales we can measure is independent of what happens at the very shortest distance and time scales, then it should be possible to get cutoff-independent results for calculations.


title: Renormalization

text: Many different types of regulator are used in quantum field theory calculations, each with its advantages and disadvantages. One of the most popular in modern use is "dimensional regularization", invented by Gerardus 't Hooft and Martinus J. G. Veltman, which tames the integrals by carrying them into a space with a fictitious fractional number of dimensions. Another is "Pauli–Villars regularization", which adds fictitious particles to the theory with very large masses, such that loop integrands involving the massive particles cancel out the existing loops at large momenta.


title: Renormalization

text: Yet another regularization scheme is the "lattice regularization", introduced by Kenneth Wilson, which pretends that hyper-cubical lattice constructs our spacetime with fixed grid size. This size is a natural cutoff for the maximal momentum that a particle could possess when propagating on the lattice. And after doing a calculation on several lattices with different grid size, the physical result is extrapolated to grid size 0, or our natural universe. This presupposes the existence of a scaling limit.


title: Renormalization

text: A rigorous mathematical approach to renormalization theory is the so-called causal perturbation theory, where ultraviolet divergences are avoided from the start in calculations by performing well-defined mathematical operations only within the framework of distribution theory. In this approach, divergences are replaced by ambiguity: corresponding to a divergent diagram is a term which now has a finite, but undetermined, coefficient. Other principles, such as gauge symmetry, must then be used to reduce or eliminate the ambiguity.


title: Renormalization

text: Julian Schwinger discovered a relationship between zeta function regularization and renormalization, using the asymptotic relation:


title: Renormalization

text: as the regulator . Based on this, he considered using the values of to get finite results. Although he reached inconsistent results, an improved formula studied by Hartle, J. Garcia, and based on the works by E. Elizalde includes the technique of the zeta regularization algorithm


title: Renormalization

text: Using Hurwitz zeta regularization plus the rectangle method with step h (not to be confused with the Planck constant).


title: Renormalization

text: since for the Harmonic series formula_28 in the limit formula_29 we must recover the series formula_30


title: Renormalization

text: For multi-loop integrals that will depend on several variables formula_31 we can make a change of variables to polar coordinates and then replace the integral over the angles formula_32 by a sum so we have only a divergent integral, that will depend on the modulus formula_33 and then we can apply the zeta regularization algorithm, the main idea for multi-loop integrals is to replace the factor formula_34 after a change to hyperspherical coordinates so the UV overlapping divergences are encoded in variable . In order to regularize these integrals one needs a regulator, for the case of multi-loop integrals, these regulator can be taken as


title: Renormalization

text: so the multi-loop integral will converge for big enough using the Zeta regularization we can analytic continue the variable to the physical limit where and then regularize any UV integral, by replacing a divergent integral by a linear combination of divergent series, which can be regularized in terms of the negative values of the Riemann zeta function .


title: Renormalization

text: The early formulators of QED and other quantum field theories were, as a rule, dissatisfied with this state of affairs. It seemed illegitimate to do something tantamount to subtracting infinities from infinities to get finite answers.


title: Renormalization

text: Freeman Dyson argued that these infinities are of a basic nature and cannot be eliminated by any formal mathematical procedures, such as the renormalization method.


title: Renormalization

text: Another important critic was Feynman. Despite his crucial role in the development of quantum electrodynamics, he wrote the following in 1985:


title: Renormalization

text: Feynman was concerned that all field theories known in the 1960s had the property that the interactions become infinitely strong at short enough distance scales. This property called a Landau pole, made it plausible that quantum field theories were all inconsistent. In 1974, Gross, Politzer and Wilczek showed that another quantum field theory, quantum chromodynamics, does not have a Landau pole. Feynman, along with most others, accepted that QCD was a fully consistent theory.


title: Renormalization

text: The general unease was almost universal in texts up to the 1970s and 1980s. Beginning in the 1970s, however, inspired by work on the renormalization group and effective field theory, and despite the fact that Dirac and various others—all of whom belonged to the older generation—never withdrew their criticisms, attitudes began to change, especially among younger theorists. Kenneth G. Wilson and others demonstrated that the renormalization group is useful in statistical field theory applied to condensed matter physics, where it provides important insights into the behavior of phase transitions. In condensed matter physics, a "physical" short-distance regulator exists: matter ceases to be continuous on the scale of atoms. Short-distance divergences in condensed matter physics do not present a philosophical problem since the field theory is only an effective, smoothed-out representation of the behavior of matter anyway; there are no infinities since the cutoff is always finite, and it makes perfect sense that the bare quantities are cutoff-dependent.


title: Renormalization

text: If QFT holds all the way down past the Planck length (where it might yield to string theory, causal set theory or something different), then there may be no real problem with short-distance divergences in particle physics either; "all" field theories could simply be effective field theories. In a sense, this approach echoes the older attitude that the divergences in QFT speak of human ignorance about the workings of nature, but also acknowledges that this ignorance can be quantified and that the resulting effective theories remain useful.


title: Renormalization

text: In QFT, the value of a physical constant, in general, depends on the scale that one chooses as the renormalization point, and it becomes very interesting to examine the renormalization group running of physical constants under changes in the energy scale. The coupling constants in the Standard Model of particle physics vary in different ways with increasing energy scale: the coupling of quantum chromodynamics and the weak isospin coupling of the electroweak force tend to decrease, and the weak hypercharge coupling of the electroweak force tends to increase. At the colossal energy scale of 10 GeV (far beyond the reach of our current particle accelerators), they all become approximately the same size (Grotz and Klapdor 1990, p. 254), a major motivation for speculations about grand unified theory. Instead of being only a worrisome problem, renormalization has become an important theoretical tool for studying the behavior of field theories in different regimes.


title: Renormalization

text: If a theory featuring renormalization (e.g. QED) can only be sensibly interpreted as an effective field theory, i.e. as an approximation reflecting human ignorance about the workings of nature, then the problem remains of discovering a more accurate theory that does not have these renormalization problems. As Lewis Ryder has put it, "In the Quantum Theory, these [classical] divergences do not disappear; on the contrary, they appear to get worse. And despite the comparative success of renormalisation theory, the feeling remains that there ought to be a more satisfactory way of doing things."


title: Renormalization

text: From this philosophical reassessment, a new concept follows naturally: the notion of renormalizability. Not all theories lend themselves to renormalization in the manner described above, with a finite supply of counterterms and all quantities becoming cutoff-independent at the end of the calculation. If the Lagrangian contains combinations of field operators of high enough dimension in energy units, the counterterms required to cancel all divergences proliferate to infinite number, and, at first glance, the theory would seem to gain an infinite number of free parameters and therefore lose all predictive power, becoming scientifically worthless. Such theories are called "nonrenormalizable".


title: Renormalization

text: The Standard Model of particle physics contains only renormalizable operators, but the interactions of general relativity become nonrenormalizable operators if one attempts to construct a field theory of quantum gravity in the most straightforward manner (treating the metric in the Einstein–Hilbert Lagrangian as a perturbation about the Minkowski metric), suggesting that perturbation theory is not satisfactory in application to quantum gravity.


title: Renormalization

text: However, in an effective field theory, "renormalizability" is, strictly speaking, a misnomer. In nonrenormalizable effective field theory, terms in the Lagrangian do multiply to infinity, but have coefficients suppressed by ever-more-extreme inverse powers of the energy cutoff. If the cutoff is a real, physical quantity—that is, if the theory is only an effective description of physics up to some maximum energy or minimum distance scale—then these additional terms could represent real physical interactions. Assuming that the dimensionless constants in the theory do not get too large, one can group calculations by inverse powers of the cutoff, and extract approximate predictions to finite order in the cutoff that still have a finite number of free parameters. It can even be useful to renormalize these "nonrenormalizable" interactions.


title: Renormalization

text: Nonrenormalizable interactions in effective field theories rapidly become weaker as the energy scale becomes much smaller than the cutoff. The classic example is the Fermi theory of the weak nuclear force, a nonrenormalizable effective theory whose cutoff is comparable to the mass of the W particle. This fact may also provide a possible explanation for "why" almost all of the particle interactions we see are describable by renormalizable theories. It may be that any others that may exist at the GUT or Planck scale simply become too weak to detect in the realm we can observe, with one exception: gravity, whose exceedingly weak interaction is magnified by the presence of the enormous masses of stars and planets.


title: Renormalization

text: In actual calculations, the counterterms introduced to cancel the divergences in Feynman diagram calculations beyond tree level must be "fixed" using a set of " renormalisation conditions". The common renormalization schemes in use include:


title: Renormalization

text: Besides, there exists a "natural" definition of the renormalized coupling (combined with the photon propagator) as a propagator of dual free bosons, which does not explicitly require introducing the counterterms.


title: Renormalization

text: renormalization process, which goes beyond the dilatation group of conventional "renormalizable" theories, came from condensed matter physics. Leo P. Kadanoff's paper in 1966 proposed the "block-spin" renormalization group. The "blocking idea" is a way to define the components of the theory at large distances as aggregates of components at shorter distances.


title: Renormalization

text: This approach covered the conceptual point and was given full computational substance in the extensive important contributions of Kenneth Wilson. The power of Wilson's ideas was demonstrated by a constructive iterative renormalization solution of a long-standing problem, the Kondo problem, in 1974, as well as the preceding seminal developments of his new method in the theory of second-order phase transitions and critical phenomena in 1971. He was awarded the Nobel prize for these decisive contributions in 1982.


title: Renormalization

text: The most important information in the RG flow is its fixed points. A fixed point is defined by the vanishing of the beta function associated to the flow. Then, fixed points of the renormalization group are by definition scale invariant. In many cases of physical interest scale invariance enlarges to conformal invariance. One then has a conformal field theory at the fixed point.


title: Renormalization

text: If these fixed points correspond to free field theory, the theory is said to exhibit quantum triviality. Numerous fixed points appear in the study of lattice Higgs theories, but the nature of the quantum field theories associated with these remains an open question.


title: Kathleen Willey

text: Kathleen Willey (born June 2, 1946) is a former White House volunteer aide who, on March 15, 1998, alleged on the TV news program "60 Minutes" that Bill Clinton had sexually assaulted her on November 29, 1993, during his first term as President. She had been subpoenaed to testify in the Paula Jones sexual harassment case.


title: Kathleen Willey

text: According to Willey, during an early afternoon meeting on November 29, 1993, in the private study of the Oval Office, Clinton had embraced her tightly, kissed her on the lips, grabbed her breast, and forced her hand on his genitals. Clinton denied assaulting Willey. According to Monica Lewinsky's testimony, Clinton stated that the allegation was absurd because Willey is a small-breasted woman, so he would never pursue such a woman.


title: Kathleen Willey

text: According to Linda Tripp's grand jury testimony, she felt Willey pursued a romance with Clinton from the start of her White House affiliation. Willey had speculated with Tripp as to how she might be able to set up an assignation between herself and the president. She routinely attended events at which Clinton would be present and wore a black dress she believed he liked. According to Tripp's testimony, Willey wondered if she and Clinton could arrange to meet in a home to which she had access, on the Chesapeake Bay.


title: Kathleen Willey

text: The Final Report of the U.S. Office of the Independent Counsel report noted that "Willey and President Clinton are the only direct witnesses to their meeting, and their accounts differ substantially on the crucial facts of what occurred." It also stated that she gave false information to the FBI about her sexual relationship with a former boyfriend and acknowledged having lied about it when the agents confronted her with contradictory evidence. The probative value of this last aspect of Willey's testimony is highly uncertain beyond the unfavorable light it casts on her general credibility. Her claims regarding Clinton do not involve her former boyfriend.


title: Kathleen Willey

text: There were also some differences in Paula Jones’ and her grand jury testimony, but in both, she stated she had been harassed. Following Willey's acknowledgment of these lies about her boyfriend, "the Independent Counsel agreed not to prosecute Willey for any offense arising out of the investigation, including false statements in her Jones deposition, so long as she cooperated fully and truthfully with the investigation."


title: Kathleen Willey

text: According to Independent Counsel Robert Ray's report, "Willey's Paula Jones deposition testimony differed from her grand jury testimony on material aspects of the alleged incident."


title: Kathleen Willey

text: Ultimately, the Independent Counsel declined prosecution, and noted the absence of strong supporting evidence.


title: Kathleen Willey

text: According to a book critical of Clinton by Candice E. Jackson, Tripp told Larry King in February 1999 that Willey is "an honest person" who was "telling the truth" about having been sexually assaulted by Clinton. However, Tripp's grand jury testimony differs from Willey's claims regarding inappropriate sexual advances. She stated that Willey appeared excited about the alleged assault. Specifically, Tripp testified that Willey reported Clinton's sexual advances, which Clinton completely denied making. Tripp also noted that Willey stated that the force of the advances took her breath away, which is consistent with Willey's claim that she was not even given the opportunity to consent. However, Tripp further noted that Willey seemed pleased in some respects with what had happened.


title: Kathleen Willey

text: The Independent Counsel believed that Willey told a boyfriend that she was pregnant and she had a miscarriage when she did not. On the evening of March 19, 1998, Julie Hiatt Steele, a friend of Willey, released an affidavit, accusing the former White House aide of asking her to lie to corroborate Willey's account of being sexually groped by President Clinton in the Oval Office.


title: Kathleen Willey

text: An attempt by Starr to prosecute Steele for making false statements and obstructing justice ended in a mistrial, and Starr declined to seek a retrial after Steele sought an investigation against the former Independent Counsel for prosecutorial misconduct. Federal prosecutors are immune to such “misconduct” actions under longstanding Supreme Court precedent.


title: Kathleen Willey

text: In March 2000, U.S. District Court Judge Royce Lamberth ruled that President Clinton had "committed a criminal violation" of the Privacy Act of 1974 by releasing letters from Willey to the President that were written even after the alleged incident. A three-judge panel of the U.S. District Court of Appeals later criticized that aspect of Lamberth's ruling as “sweeping” and “superfluous,” but denied the White House motion before them. Willey filed suit against the White House over the issue.


title: Kathleen Willey

text: On November 6, 2007, her book "Target: Caught in the Crosshairs of Bill and Hillary Clinton" was published by WND Books, an imprint of World Ahead Media and WorldNetDaily. In her book, Willey claimed that on Labor Day weekend 2007, her house was burglarized, with the only thing stolen being a manuscript of her book. Willey stated that she believes individuals with ties to the Clintons were responsible for the break-in. She also filed a police report.


title: Kathleen Willey

text: Willey draws similarities in her book between the circumstances of her husband's death on November 29, 1993 and of the death of Vincent Foster, although she does not claim to know that any wrongdoing took place.


title: Kathleen Willey

text: In July 2015, Willey launched "A Scandal A Day," an anti-Clinton website; the website was set up by an Arizona-based private detective company Maverick Investigations, owned by Tom Watson.


title: Kathleen Willey

text: In October 2016, Willey joined Donald Trump for a press conference before the second presidential debate to air grievances against Hillary and Bill Clinton. The conference also included Juanita Broaddrick, Paula Jones, and Kathy Shelton. She was paid $2,500 for the appearance by a Political Action Committee headed by Roger Stone.


title: Kathleen Willey

text: While in high school, Willey became pregnant. She was sent to Ohio for the birth, and the child was placed for adoption. When she returned to school, it was said that her absence had been due to a car crash.


title: Kathleen Willey

text: Her first marriage was to Richard Dolsey, a medical student at the time. They had a daughter before divorcing in 1970.


title: Kathleen Willey

text: At the time of the alleged assault by President Clinton, Willey was married to Edward Eugene Willey Jr., a real estate lawyer. They had a son together. Edward Willey committed suicide on November 29, 1993.


title: Kathleen Willey

text: She was remarried in November 1999 to Bill Schwicker, whom she divorced in 2006. , she works and resides in Powhatan County, Virginia.


title: Kathleen Willey

text: In 2021, Willey was portrayed by Elizabeth Reaser in "", which focuses on the story of the Monica Lewinsky scandal, and portrays Willey's relationship with Linda Tripp.


title: Mo Hayder

text: Beatrice Clare Dunkel (born Clare Damaris Bastin; pen names, Mo Hayder and Theo Clare; 2 January 1962 – 27 July 2021) was a British author. Earlier in her life she worked as an actress and model under the name Candy Davis. She went on to write novels as Mo Hayder. One forthcoming book, "The Book of Sand", will be published in 2022 under the name Theo Clare. She won an Edgar Award in 2012. Her best-known work was "Birdman", which was followed by a sequel, "The Treatment".


title: Mo Hayder

text: Born in Essex on 2 January 1962, Hayder grew up in Loughton as the daughter of John Bastin, an astrophysicist, and Susan Hollins, a teacher. She had a younger brother, Richard. She left school and home for London shortly before her 16th birthday. Hayder was educated at The American University and Bath Spa University.


title: Mo Hayder

text: As Candy Davis, she won the Miss Nude beauty pageant in 1982 and became a Page 3 model. As an actress, her first credit was as a stripper in an episode of "Minder" although her best known role was playing secretary Miss Belfridge in the BBC sitcom "Are You Being Served?" in the final two series from 1983 to 1985. She also appeared in the music video for the ABC song "Poison Arrow".


title: Mo Hayder

text: After (in her own words) "a wild child phase" and a brief marriage to Gary Olsen she emigrated at 25 to Japan where she became a teacher of English as a foreign language in Tokyo. She was also a waitress at a nightclub and an amateur filmmaker.


title: Mo Hayder

text: Hayder sent the manuscript of her first book to several agents. To her surprise she was accepted by leading literary agent Jane Gregory who secured her an offer of nearly £200,000 from Transworld Publishers for a two-book deal. Patrick Janson-Smith of Transworld described the manuscript at the 1998 Frankfurt Book Fair as one of the most powerful and violent books he had come across, "a completely gripping story with believable characters". This debut novel, "Birdman", was published in December 1999 and was an international bestseller. Her second novel, "The Treatment", was a "Sunday Times" bestseller and won the 2002 WH Smith Thumping Good Read Award.


title: Mo Hayder

text: Her third novel, "Tokyo", was published in May 2004 and was another "Sunday Times" bestseller. "Tokyo" was published as "The Devil of Nanking" in the United States in March 2005. "Pig Island" was her fourth best seller, published in April 2006. "Pig Island" was nominated for both a Barry Award for Best British crime novel, and a CWA dagger. Her fifth book, "Ritual" was the first in "The Walking Man" series, and was nominated for CWA Ian Fleming Steel Dagger award. "Skin" is the second book in The Walking Man series, and was released in early 2009. "Gone", the third book in the series, was released in February 2011. "Gone" won the Edgar Award for Best Novel. Her novel "Hanging Hill" was published 2011, "Poppet" in 2013, and "Wolf" in 2014.


title: Mo Hayder

text: Her novels were controversial when published. "Birdman" was seen as violent and disturbing. Her second novel, "The Treatment" tackled themes of paedophilia. The "San Francisco Chronicle" called the novel a "disturbing journey into the pedophile mind".


title: Mo Hayder

text: Hayder also wrote the screenplay for "De Behandeling" (2014) which was a Belgian film of an adaptation of "The Treatment".


title: Mo Hayder

text: Shortly before her death, she completed a new novel "The Book of Sand," a speculative thriller written under the pseudonym Theo Clare, which will be published in 2022.


title: Mo Hayder

text: In 1985, she married the actor Gary Olsen, later the male lead in "2point4 children". The couple divorced in 1990.


title: Mo Hayder

text: Hayder lived in Cheltenham, England with her second husband, Bob Randall, a retired police sergeant whom she married in 2021. She had one daughter.


title: Mo Hayder

text: She died on 27 July 2021 from complications of motor neurone disease, aged 59, having been diagnosed the previous December.


title: Repentance

text: Repentance is reviewing one's actions and feeling contrition or regret for past wrongs, which is accompanied by commitment to and actual actions that show and prove a change for the better.


title: Repentance

text: In modern times, it is generally seen as involving a commitment to personal change and the resolve to live a more responsible and humane life. In other words, being sorry for one's misdeeds. It can also involve sorrow over a specific sin or series of sins that an individual feels guilt over, or conviction that they have committed. The practice of repentance plays an important role in the soteriological doctrines of Judaism, Christianity, and Islam. Analogous practices have been found in other world religions as well. In religious contexts, it often involves an act of confession to God or to a spiritual elder (such as a monk or priest). This confession might include an admission of guilt, a promise or intent not to repeat the offense, an attempt to make restitution for the wrong, or in some way reverse the harmful effects of the wrong where possible.


title: Repentance

text: Repentance typically requires an admission of guilt for committing a wrong or for omitting to do the right thing; a promise or resolve not to repeat the offense; an attempt to make restitution for the wrong, or in some way to reverse the harmful effects of the wrong or the omission where possible.


title: Repentance

text: Repentance (, literally, "return", pronounced "tshuva" or "teshuva") is one element of atoning for sin in Judaism. Judaism recognizes that everybody sins on occasion, but that people can stop or minimize those occasions in the future by repenting for past transgressions. Thus, the primary purpose of repentance in Judaism is ethical self transformation.


title: Repentance

text: A Jewish penitent is traditionally known as a "baal teshuva" ("lit.", "master of repentance" or "master of return") (; for a woman: , "baalat teshuva"; plural: , "baalei teshuva"). An alternative modern term is "hozer beteshuva" () ("lit.", "returning in repentance"). "In a place where "baalei teshuva" stand", according to halakha, "even the full-fledged righteous do not stand."


title: Repentance

text: Repentance is a stage in Christian salvation where the believer turns away from sin. As a distinct stage in the "ordo salutis" its position is disputed, with some theological traditions arguing it occurs prior to faith and the Reformed theological tradition arguing it occurs after faith. In Roman Catholic theology repentance is part of the larger theological concept of penance.


title: Repentance

text: "Tawba" is the Islamic concept of repenting to God due to performing any sins and misdeeds. It is a direct matter between a person and God, so there is no intercession. There is no original sin in Islam. It is the act of leaving what God has prohibited and returning to what he has commanded. The word denotes the act of being repentant for one's misdeeds, atoning for those misdeeds, and having a strong determination to forsake those misdeeds (remorse, resolution, and repentance). If someone sins against another person, restitution is required.


title: Repentance

text: The Buddha considered shame over doing wrong (Pali: "hiri") and fear of the consequences of wrongdoing (Pali:"otappa") as essential safeguards against falling into evil ways and further as extremely useful in the path of purification. Also recommended was the regular practice of self-assessment or wise reflection (Pali: "yoniso manasikara") on one's own actions in relation to others and the bigger picture.


title: Repentance

text: In Mahayana Buddhism, one of the most common repentance verses used for reflection is Samantabhadra's Repentance Verse taken from Chapter 40 of the Flower Adornment Sutra:


title: Repentance

text: "Hooponopono" (ho-o-pono-pono) is an ancient Hawaiian practice of reconciliation and forgiveness, combined with (repentance) prayers. Similar forgiveness practices were performed on islands throughout the South Pacific, including Samoa, Tahiti and New Zealand. Traditionally "hooponopono" is practiced by healing priests or "kahuna lapaau" among family members of a person who is physically ill. Modern versions are performed within the family by a family elder, or by the individual alone.


title: Capture the flag

text: Capture the flag (CTF) is a traditional outdoor sport where two or more teams each have a flag (or other markers) and the objective is to capture the other team's flag, located at the team's "base", and bring it safely back to their own base. Enemy players can be "tagged" by players in their home territory and, depending on the rules, they may be out of the game, become members of the opposite team, sent back to their own territory, or frozen in place ("in jail") until freed by a member of their own team.


title: Capture the flag

text: Capture the Flag requires a playing field of some sort. In both indoor and outdoor versions, the field is divided into two clearly designated halves, known as territories. Players form two teams, one for each territory. Each side has a "flag" which is most often a piece of fabric, but can be any object small enough to be easily carried by a person (night time games might use flashlights, glowsticks or lanterns as the "flags"). Sometimes teams wear dark colors at night to make it more difficult for their opponents to see them.


title: Capture the flag

text: The objective of the game is for players to venture into the opposing team's territory, grab the flag and return with it to their territory without being tagged. The flag is defended mainly by tagging opposing players who attempt to take it. Within their territory players are "safe", meaning that they cannot be tagged by opposing players. Once they cross into the opposing team's territory they are vulnerable.


title: Capture the flag

text: Rules for Capture the Flag appear in 1860 in the German gymnastic manual "Lehr- und Handbuch der deutschen Turnkunst" by Wilhelm Lübeck under the name "Fahnenbarlauf". In the 19th century, CTF was not an independent game but a variation of the European game of "Barlaufen" ("Barlauf mit Fahnenraub"), played in France and Germany.


title: Capture the flag

text: Descriptions of Capture the Flag in English language appeared in the early 20th century, e. g. in "Scouting For Boys" written in 1908 by Robert Baden-Powell, the founder of the Scouting Movement, under the title "Flag Raiding". They also appeared in the 1920 Edition of "The Official Handbook for Boys" published by the Boy Scouts of America.


title: Capture the flag

text: The flag is usually placed in a visibly obvious location at the rear of a team's territory. In a more difficult version, the flag is hidden in a place where it can only be seen from certain angles. It also might have some challenge involved. For example, the flag could be hidden in the leaves up in a tall tree, and the players have to see the flag, then knock it out and bring it to their base.


title: Capture the flag

text: Different versions of Capture the Flag have different rules, both for handling the flag and for what happens to tagged players. A player who is tagged may be eliminated from the game entirely (out of the game), be forced to join the opposing team, sent back to their own territory, or be placed in "jail" with or without a guard (according to the number of people in a team). The jail is a predesignated area of the group's territory which exists for holding tagged players and is normally towards the back of the group's territory.


title: Capture the flag

text: While tagged players may be confined to jail for a limited, predetermined time, the most common form of the game involves the option for a "jailbreak". In this version, players who are tagged remain in jail indefinitely. However, players from their own team may free them from jail by means of a jailbreak. Jailbreaks are accomplished by a player running from their own territory into the enemy's jail. Such action may, depending on the rules, free all jailed players or simply those who are physically touched by the one performing the jailbreak. But in some variants, teammates who got tagged can be jailed only 3 times, or they are kicked from the game until the next round. In general freed players are obligated to return directly to their own territory before attempting offensive action ("i.e.," attempting to grab the flag).


title: Capture the flag

text: While they return to their own side, freed players usually acquire "free walk-backs", in which they are safe from tagging until they reach their home territory. The player performing the jail break, on the other hand, is neither safe, nor restricted from performing other actions such as attempting to grab the flag or generally moving about enemy territory. Sometimes, players in jail form chains, so that if a teammate tags one person in the chain, everyone is free. Simply leaving jail without being freed is considered poor sportsmanship and is severely frowned upon, often leading to expulsion from the game. If all players on one team are jailed (meaning no teammate can free them from jail), then the other team will have all the time they want to find the other team's flag.


title: Capture the flag

text: The rules for the handling of the flag also vary from game to game and deal mostly with the disposition of the flag after a failed attempt at capturing it. In one variant, after a player is tagged while carrying the flag, it is returned to its original place. In another variant, the flag is left in the location where the player was tagged. This latter variant makes offensive play easier, as the flag will tend, over the course of the game, to be moved closer to the dividing line between territories. In some games, it is possible for the players to throw the flag to teammates. As long as the flag stays in play without hitting the ground, it is allowed for the players to pass. Normally the capture the flag looks like "flag_for_you".


title: Capture the flag

text: When the flag is captured by one player, they're not safe from being tagged, unless they trip. Sometimes, the flag holder may not be safe at all, even in their home territory, until they obtain both flags, thus ending the game. But they have the option to return to their own side or hand it off to a teammate who will then carry it to the other side. In most versions the flag may be handed off while running. The game is won when a player returns to their own territory with the enemy flag or both teams' flags, whether it be throw, place, toss, insert, etc. . Also, rarely the flag carrier may not attempt to free any of their teammates from jail.


title: Capture the flag

text: Alterations may include "one flag" CTF in which there is a defensive team and an offensive team, or games with three or more flags. In the case of the latter, one can only win when all flags are captured, not only one.


title: Capture the flag

text: Another variation is when the players put bandannas in their pockets with about six inches sticking out. Instead of tagging opponents, players must pull their opponent's bandanna out of their pocket. No matter where a player is when their bandanna is pulled, they're captured and must, depending on the preferences of the players, go to jail, or return to their base before returning to play. In this version there is no team territory, only a small base where the team's flag is kept. To win, one team must have both of the flags in their base.


title: Capture the flag

text: In some urban settings, the game is played indoors in an enclosed area with walls, similar to the walls in a hockey rink. There is also a spot sticking out of the back of the opposing ends which is connected to the playing area for the flag to be placed in. In this urban variation legal checking hockey style and legal checking against the boards is allowed. A player who commits a foul or illegal check is placed in a penalty box for a specified amount of time, depending on the severity of the foul. A player who deliberately injures an opponent is expelled from the rest of the game. Throwing the flag is allowed in this variation, as long as the flag is caught before it hits the ground. If the flag is thrown to a teammate but hits the ground before it can be caught, the flag is placed from the spot of the throw. If a player throws the flag, but is blocked or intercepted by a player from the opposing team, the flag is placed back at the base.


title: Capture the flag

text: New technologies have also led to a glow-in-the-dark version of CTF called Capture the Flag REDUX that includes two glowing orbs as the “flags,” color-coded LED bracelets to differentiate team members, and glowing jail markers.


title: Capture the flag

text: It is not uncommon for people to play airsoft, paintball, or Nerf variations of CTF. Typically there are no territories in these versions. Players who are "hit" must sit out a predetermined amount of time before returning to play (respawning).


title: Capture the flag

text: "Stealing sticks" is a similar game played in the British Isles, the United States, and Australia. However, instead of a flag, a number of sticks or other items such as coats or hats are placed in a "goal" on the far end of each side of the playing field or area. As in capture the flag, players are sent to a "prison" if tagged on the opponents' side, and may be freed by teammates. Each player may only take one of their opponents' sticks at a time. The first team to take all of the opponents' sticks to their own side wins.


title: Capture the flag

text: In 1984, Scholastic published Bannercatch for the Apple II and Commodore computers. An edutainment game with recognizable capture-the-flag mechanics, "Bannercatch" allows up to two humans (each alternating between two characters in the game world) to play capture the flag against an increasingly difficult team of four AI bots. "Bannercatch"s game world is divided into quadrants: home, enemy, and two "no-mans land" areas which hold the jails. A successful capture requires bringing the enemy flag into one team's "home" quadrant. Players can be captured when in an enemy territory, or in "no-mans land" while holding a flag. Captured players must be "rescued" from their designated jail by one of the other members of the team. Fallen flags remain where they dropped until a time-out period elapses, after which the flag returns to one of several starting locations in home territory. The 2D map also features walls, trees and a moving river, enabling a wide variety of strategies. Special locations in the play area allow humans to query the game state (such as flag status) using binary messages.


title: Capture the flag

text: In 1992, Richard Carr released an MS-DOS based game called "Capture the Flag". It is a turn-based strategy game with real time network / modem play (or play-by-mail) based around the traditional outdoor game. The game required players to merely move one of their characters onto the same square as their opponent's flag, as opposed to bringing it back to friendly territory, because of difficulties implementing the artificial intelligence that the computer player would have needed to bring the enemy flag home and intercept opposing characters carrying the flag.


title: Capture the flag

text: In computer security Capture the Flag (CTF), "flags" are secrets hidden in purposefully-vulnerable programs or websites. Competitors steal flags either from other competitors (attack/defense-style CTFs) or from the organizers (jeopardy-style challenges). Several variations exist, including hiding flags in hardware devices.


title: Capture the flag

text: Capture the Flag is among the games that have made a recent comeback among adults as part of the urban gaming trend (which includes games like Pac-Manhattan, Fugitive, Unreal Tournament and Manhunt). The game is played on city streets and players use cellphones to communicate. News about the games spreads virally through the use of blogs and mailing lists. Urban Capture the Flag has been played in cities throughout North America. One long running example occurs on the Northrop Mall at the University of Minnesota on Fridays with typical attendance ranging from 50 to several hundred.


title: Papillomaviridae

text: Papillomaviridae is a family of non-enveloped DNA viruses whose members are known as papillomaviruses. Several hundred species of papillomaviruses, traditionally referred to as "types", have been identified infecting all carefully inspected mammals, but also other vertebrates such as birds, snakes, turtles and fish. Infection by most papillomavirus types, depending on the type, is either asymptomatic (e.g. most Beta-PVs) or causes small benign tumors, known as papillomas or warts (e.g. human papillomavirus 1, HPV6 or HPV11). Papillomas caused by some types, however, such as human papillomaviruses 16 and 18, carry a risk of becoming cancerous.


title: Papillomaviridae

text: Papillomaviruses are usually considered as highly host- and tissue-tropic, and are thought to rarely be transmitted between species. Papillomaviruses replicate exclusively in the basal layer of the body surface tissues. All known papillomavirus types infect a particular body surface, typically the skin or mucosal epithelium of the genitals, anus, mouth, or airways. For example, human papillomavirus (HPV) type 1 tends to infect the soles of the feet, and HPV type 2 the palms of the hands, where they may cause warts. Additionally, there are descriptions of the presence of papillomavirus DNA in the blood and in the peripheral blood mononuclear cells.


title: Papillomaviridae

text: Papillomaviruses were first identified in the early 20th century, when it was shown that skin warts, or papillomas, could be transmitted between individuals by a filterable infectious agent. In 1935 Francis Peyton Rous, who had previously demonstrated the existence of a cancer-causing sarcoma virus in chickens, went on to show that a papillomavirus could cause skin cancer in infected rabbits. This was the first demonstration that a virus could cause cancer in mammals.


title: Papillomaviridae

text: There are over 100 species of papillomavirus recognised, though the ICTV officially recognizes a smaller number, categorized into 53 genera, as of 2019. All papillomaviruses (PVs) have similar genomic organizations, and any pair of PVs contains at least five homologous genes, although the nucleotide sequence may diverge by more than 50%. Phylogenetic algorithms that permit the comparison of homologies led to phylogenetic trees that have a similar topology, independent of the gene analyzed.


title: Papillomaviridae

text: Phylogenetic studies strongly suggest that PVs normally evolve together with their mammalian and bird host species, but adaptive radiations, occasional zoonotic events and recombinations may also impact their diversification. Their basic genomic organization appears maintained for a period exceeding 100 million years, and these sequence comparisons have laid the foundation for a PV taxonomy, which is now officially recognized by the International Committee on Taxonomy of Viruses. All PVs form the family "Papillomaviridae", which is distinct from the "Polyomaviridae" thus eliminating the term "Papovaviridae". Major branches of the phylogenetic tree of PVs are considered genera, which are identified by Greek letters. Minor branches are considered species and unite PV types that are genomically distinct without exhibiting known biological differences. This new taxonomic system does not affect the traditional identification and characterization of PV "types" and their independent isolates with minor genomic differences, referred to as "subtypes" and "variants", all of which are taxa below the level of "species". Additionally, phylogenetic groupings at higher taxonomic level have been proposed.


title: Papillomaviridae

text: This classification may need revision in the light of the existence of papilloma–polyoma virus recombinants. Additional species have also been described. Sparus aurata papillomavirus 1 has been isolated from fish.


title: Papillomaviridae

text: Over 170 human papillomavirus types have been completely sequenced. They have been divided into 5 genera: Alphapapillomavirus, Betapapillomavirus, Gammapapillomavirus, Mupapillomavirus and Nupapillomavirus. At least 200 additional viruses have been identified that await sequencing and classification.


title: Papillomaviridae

text: Individual papillomavirus types tend to be highly adapted to replication in a single animal species. In one study, researchers swabbed the forehead skin of a variety of zoo animals and used PCR to amplify any papillomavirus DNA that might be present. Although a wide variety of papillomavirus sequences were identified in the study, the authors found little evidence for inter-species transmission. One zookeeper was found to be transiently positive for a chimpanzee-specific papillomavirus sequence. However, the authors note that the chimpanzee-specific papillomavirus sequence could have been the result of surface contamination of the zookeeper's skin, as opposed to productive infection.


title: Papillomaviridae

text: Cottontail rabbit papillomavirus (CRPV) can cause protuberant warts in its native host, the North American rabbit genus "Sylvilagus". These horn-like warts may be the original basis for the urban legends of the American antlered rabbit the Jackalope and European "Wolpertinger". European domestic rabbits (genus "Oryctolagus") can be transiently infected with CRPV in a laboratory setting. However, since European domestic rabbits do not produce infectious progeny virus, they are considered an incidental or "dead-end" host for CRPV.


title: Papillomaviridae

text: Inter-species transmission has also been documented for bovine papillomavirus (BPV) type 1. In its natural host (cattle), BPV-1 induces large fibrous skin warts. BPV-1 infection of horses, which are an incidental host for the virus, can lead to the development of benign tumors known as sarcoids. The agricultural significance of BPV-1 spurred a successful effort to develop a vaccine against the virus.


title: Papillomaviridae

text: A few reports have identified papillomaviruses in smaller rodents, such as Syrian hamsters, the African multimammate rat and the Eurasian harvest mouse. However, there are no papillomaviruses known to be capable of infecting laboratory mice. The lack of a tractable mouse model for papillomavirus infection has been a major limitation for laboratory investigation of papillomaviruses.


title: Papillomaviridae

text: Four papillomaviruses are known to infect birds: Fringilla coelebs papillomavirus 1, Francolinus leucoscepus papillomavirus 1, Psittacus erithacus papillomavirus 1 and Pygoscelis adeliae papillomavirus 1. All these species have a gene (E9) of unknown function, suggesting a common origin.


title: Papillomaviridae

text: The evolution of papillomaviruses is thought to be slow compared to many other virus types, but there are no experimental measurements currently available. This is probably because the papillomavirus genome is composed of genetically stable double-stranded DNA that is replicated with high fidelity by the host cell's DNA replication machinery.


title: Papillomaviridae

text: It is believed that papillomaviruses generally co-evolve with a particular species of host animal over many years, although there are strong evidences against the hypothesis of coevolution. In a particularly speedy example, HPV-16 has evolved slightly as human populations have expanded across the globe and now varies in different geographic regions in a way that probably reflects the history of human migration. Cutaneotropic HPV types are occasionally exchanged between family members during the entire lifetime, but other donors should also be considered in viral transmission.


title: Papillomaviridae

text: Other HPV types, such as HPV-13, vary relatively little in different human populations. In fact, the sequence of HPV-13 closely resembles a papillomavirus of bonobos (also known as pygmy chimpanzees). It is not clear whether this similarity is due to recent transmission between species or because HPV-13 has simply changed very little in the six or so million years since humans and bonobos diverged.


title: Papillomaviridae

text: There are five main genera infecting humans (Alpha, Beta, Gamma, Mu and Nu). The most recent common ancestor of these genera evolved -. The most recent ancestor of the gamma genus was estimated to have evolved between and .


title: Papillomaviridae

text: Papillomaviruses are non-enveloped, meaning that the outer shell or capsid of the virus is not covered by a lipid membrane. A single viral protein, known as L1, is necessary and sufficient for formation of a 55–60 nanometer capsid composed of 72 star-shaped capsomers (see figure). Like most non-enveloped viruses, the capsid is geometrically regular and presents icosahedral symmetry. Self-assembled virus-like particles composed of L1 are the basis of a successful group of prophylactic HPV vaccines designed to elicit virus-neutralizing antibodies that protect against initial HPV infection. As such, papillomaviridæ are stable in the environment.


title: Papillomaviridae

text: The papillomavirus genome is a double-stranded circular DNA molecule ~8,000 base pairs in length. It is packaged within the L1 shell along with cellular histone proteins, which serve to wrap and condense DNA.


title: Papillomaviridae

text: The papillomavirus capsid also contains a viral protein known as L2, which is less abundant. Although not clear how L2 is arranged within the virion, it is known to perform several important functions, including facilitating the packaging of the viral genome into nascent virions as well as the infectious entry of the virus into new host cells. L2 is of interest as a possible target for more broadly protective HPV vaccines.


title: Papillomaviridae

text: The viral capsid consists of 72 capsomeres of which 12 are five-coordinated and 60 are six-coordinated capsomeres, arranged on a T = 7d icosahedral surface lattice.


title: Papillomaviridae

text: Papillomaviruses replicate exclusively in keratinocytes. Keratinocytes form the outermost layers of the skin, as well as some mucosal surfaces, such as the inside of the cheek or the walls of the vagina. These surface tissues, which are known as stratified squamous epithelia, are composed of stacked layers of flattened cells. The cell layers are formed through a process known as cellular differentiation, in which keratinocytes gradually become specialized, eventually forming a hard, crosslinked surface that prevents moisture loss and acts as a barrier against pathogens. Less-differentiated keratinocyte stem cells, replenished on the surface layer, are thought to be the initial target of productive papillomavirus infections. Subsequent steps in the viral life cycle are strictly dependent on the process of keratinocyte differentiation. As a result, papillomaviruses can only replicate in body surface tissues.


title: Papillomaviridae

text: Papillomaviruses gain access to keratinocyte stem cells through small wounds, known as microtraumas, in the skin or mucosal surface. Interactions between L1 and sulfated sugars on the cell surface promote initial attachment of the virus. The virus is then able to get inside from the cell surface via interaction with a specific receptor, likely via the alpha-6 beta-4 integrin, and transported to membrane-enclosed vesicles called endosomes. The capsid protein L2 disrupts the membrane of the endosome through a cationic cell-penetrating peptide, allowing the viral genome to escape and traffic, along with L2, to the cell nucleus.


title: Papillomaviridae

text: After successful infection of a keratinocyte, the virus expresses E1 and E2 proteins, which are for replicating and maintaining the viral DNA as a circular episome. The viral oncogenes E6 and E7 promote cell growth by inactivating the tumor suppressor proteins p53 and pRb. Keratinocyte stem cells in the epithelial basement layer can maintain papillomavirus genomes for decades.


title: Papillomaviridae

text: The expression of the viral late genes, L1 and L2, is exclusively restricted to differentiating keratinocytes in the outermost layers of the skin or mucosal surface. The increased expression of L1 and L2 is typically correlated with a dramatic increase in the number of copies of the viral genome. Since the outer layers of stratified squamous epithelia are subject to relatively limited surveillance by cells of the immune system, it is thought that this restriction of viral late gene expression represents a form of immune evasion.


title: Papillomaviridae

text: New infectious progeny viruses are assembled in the cell nucleus. Papillomaviruses have evolved a mechanism for releasing virions into the environment. Other kinds of non-enveloped animal viruses utilize an active lytic process to kill the host cell, allowing release of progeny virus particles. Often this lytic process is associated with inflammation, which might trigger immune attack against the virus. Papillomaviruses exploit desquamation as a stealthy, non-inflammatory release mechanism.


title: Papillomaviridae

text: Although some papillomavirus types can cause cancer in the epithelial tissues they inhabit, cancer is not a typical outcome of infection. The development of papillomavirus-induced cancers typically occurs over the course of many years. Papillomaviruses have been associated with the development of cervical cancer, penile cancer and oral cancers. An association with vulval cancer and urothelial carcinoma with squamous differentiation in patients with neurogenic bladder has also been noted. There are cancer causing papillomavirus genome that encodes two small proteins called E6 and E7 that mimic cancer causing oncogenes. The way they work is that they stimulate unnatural growth of cells and block their natural defenses. Also they act on many signaling proteins that control proliferation and apoptosis.


title: Papillomaviridae

text: The fact that the papillomavirus life cycle strictly requires keratinocyte differentiation has posed a substantial barrier to the study of papillomaviruses in the laboratory, since it has precluded the use of conventional cell lines to grow the viruses. Because infectious BPV-1 virions can be extracted from the large warts the virus induces on cattle, it has been a workhorse model papillomavirus type for many years. CRPV, rabbit oral papillomavirus (ROPV) and canine oral papillomavirus (COPV) have also been used extensively for laboratory studies. As soon as researchers discovered that these viruses cause cancer, they worked together to find a vaccine to it. Currently, the most effective way to go about it is to mimic a virus that is composed of L1 protein but lack the DNA. Basically, our immune system builds defenses against infections, but if these infections do not cause disease they can be used as a vaccine. PDB entry 6bt3 shows how antibodies surfaces attack the surface of the virus to disable it.


title: Papillomaviridae

text: Some sexually transmitted HPV types have been propagated using a mouse "xenograft" system, in which HPV-infected human cells are implanted into immunodeficient mice. More recently, some groups have succeeded in isolating infectious HPV-16 from human cervical lesions. However, isolation of infectious virions using this technique is arduous and the yield of infectious virus is very low.


title: Papillomaviridae

text: The differentiation of keratinocytes can be mimicked "in vitro" by exposing cultured keratinocytes to an air/liquid interface. The adaptation of such "raft culture" systems to the study of papillomaviruses was a significant breakthrough for "in vitro" study of the viral life cycle. However, raft culture systems are relatively cumbersome and the yield of infectious HPVs can be low.


title: Papillomaviridae

text: The development of a yeast-based system that allows stable episomal HPV replication provides a convenient, rapid and inexpensive means to study several aspects of the HPV lifecycle (Angeletti 2002). For example, E2-dependent transcription, genome amplification and efficient encapsidation of full-length HPV DNAs can be easily recreated in yeast (Angeletti 2005).


title: Papillomaviridae

text: Recently, transient high-yield methods for producing HPV pseudoviruses carrying reporter genes has been developed. Although pseudoviruses are not suitable for studying certain aspects of the viral life cycle, initial studies suggest that their structure and initial infectious entry into cells is probably similar in many ways to authentic papillomaviruses.


title: Papillomaviridae

text: Human papillomavirus binds to heparin molecules on the surface of the cells that it infects. Studies have shown that the crystal of isolated L1 capsomeres has the heparin chains recognized by lysines lines grooves on the surface of the virus. Also those with the antibodies show that they can block this recognition.


title: Papillomaviridae

text: The papillomavirus genome is divided into an early region (E), encoding six open reading frames (ORF) (E1, E2, E4, E5, E6, and E7) that are expressed immediately after initial infection of a host cell, and a late region (L) encoding a major capsid protein L1 and a minor capsid protein L2. All viral ORFs are encoded on one DNA strand (see figure). This represents a dramatic difference between papillomaviruses and polyomaviruses, since the latter virus type expresses its early and late genes by bi-directional transcription of both DNA strands. This difference was a major factor in establishment of the consensus that papillomaviruses and polyomaviruses probably never shared a common ancestor, despite the striking similarities in the structures of their virions.


title: Papillomaviridae

text: After the host cell is infected, HPV16 early promoter is activated and a polycistronic primary RNA containing all six early ORFs is transcribed. This polycistronic RNA contains three exons and two introns and undergoes active RNA splicing to generate multiple isoforms of mRNAs. One of the spliced isoform RNAs, E6*I, serves as an E7 mRNA to translate E7 oncoprotein. In contrast, an intron in the E6 ORF that remains intact without splicing is necessary for translation of E6 oncoprotein. However, viral early transcription subjects to viral E2 regulation and high E2 levels repress the transcription. HPV genomes integrate into host genome by disruption of E2 ORF, preventing E2 repression on E6 and E7. Thus, viral genome integration into host DNA genome increases E6 and E7 expression to promote cellular proliferation and the chance of malignancy.


title: Papillomaviridae

text: A major viral late promoter in viral early region becomes active only in differentiated cells and its activity can be highly enhanced by viral DNA replication. The late transcript is also a polycistronic RNA which contains two introns and three exons. Alternative RNA Splicing of this late transcript is essential for L1 and L2 expression and can be regulated by RNA cis-elements and host splicing factors.


title: Papillomaviridae

text: Genes within the papillomavirus genome are usually identified after similarity with other previously identified genes. However, some spurious open reading frames might have been mistaken as genes simply after their position in the genome, and might not be true genes. This applies specially to certain E3, E4, E5 and E8 open reading frames.


title: Papillomaviridae

text: Encodes a protein that binds to the viral origin of replication in the long control region of the viral genome. E1 uses ATP to exert a helicase activity that forces apart the DNA strands, thus preparing the viral genome for replication by cellular DNA replication factors.


title: Papillomaviridae

text: The E2 protein serves as a master transcriptional regulator for viral promoters located primarily in the long control region. The protein has a transactivation domain linked by a relatively unstructured hinge region to a well-characterized DNA binding domain. E2 facilitates the binding of E1 to the viral origin of replication. E2 also utilizes a cellular protein known as Bromodomain-4 (Brd4) to tether the viral genome to cellular chromosomes. This tethering to the cell's nuclear matrix ensures faithful distribution of viral genomes to each daughter cell after cell division. It is thought that E2 serves as a negative regulator of expression for the oncogenes E6 and E7 in latently HPV-infected basal layer keratinocytes. Genetic changes, such as integration of the viral DNA into a host cell chromosome, that inactivate E2 expression tend to increase the expression of the E6 and E7 oncogenes, resulting in cellular transformation and possibly further genetic destabilization.


title: Papillomaviridae

text: This small putative gene exists only in a few papillomavirus types. The gene is not known to be expressed as a protein and does not appear to serve any function.


title: Papillomaviridae

text: Although E4 proteins are expressed at low levels during the early phase of viral infection, expression of E4 increases dramatically during the late phase of infection. In other words, its "E" appellation may be something of a misnomer. In the case of HPV-1, E4 can account for up to 30% of the total protein at the surface of a wart. The E4 protein of many papillomavirus types is thought to facilitate virion release into the environment by disrupting intermediate filaments of the keratinocyte cytoskeleton. Viral mutants incapable of expressing E4 do not support high-level replication of the viral DNA, but it is not yet clear how E4 facilitates DNA replication. E4 has also been shown to participate in arresting cells in the G2 phase of the cell cycle.


title: Papillomaviridae

text: The E5 are small, very hydrophobic proteins that destabilise the function of many membrane proteins in the infected cell. The E5 protein of some animal papillomavirus types (mainly bovine papillomavirus type 1) functions as an oncogene primarily by activating the cell growth-promoting signaling of platelet-derived growth factor receptors. The E5 proteins of human papillomaviruses associated to cancer, however, seem to activate the signal cascade initiated by epidermal growth factor upon ligand binding. HPV16 E5 and HPV2 E5 have also been shown to down-regulate the surface expression of major histocompatibility complex class I proteins, which may prevent the infected cell from being eliminated by killer T cells.


title: Papillomaviridae

text: E6 is a 151 amino-acid peptide that incorporates a type 1 motif with a consensus sequence –(T/S)-(X)-(V/I)-COOH. It also has two zinc finger motifs.


title: Papillomaviridae

text: E6 is of particular interest because it appears to have multiple roles in the cell and to interact with many other proteins. Its major role, however, is to mediate the degradation of p53, a major tumor suppressor protein, reducing the cell's ability to respond to DNA damage.


title: Papillomaviridae

text: E6 has also been shown to target other cellular proteins, thereby altering several metabolic pathways. One such target is NFX1-91, which normally represses production of telomerase, a protein that allows cells to divide an unlimited number of times. When NFX1-91 is degraded by E6, telomerase levels increase, inactivating a major mechanism keeping cell growth in check. Additionally, E6 can act as a transcriptional cofactor—specifically, a transcription activator—when interacting with the cellular transcription factor, E2F1/DP1.


title: Papillomaviridae

text: E6 can also bind to PDZ-domains, short sequences which are often found in signaling proteins. E6's structural motif allows for interaction with PDZ domains on DLG (discs large) and hDLG (Drosophila large) tumor suppressor genes. Binding at these locations causes transformation of the DLG protein and disruption of its suppressor function. E6 proteins also interact with the MAGUK (membrane-associated guanylate kinase family) proteins. These proteins, including MAGI-1, MAGI-2, and MAGI-3 are usually structural proteins, and can help with signaling. More significantly, they are believed to be involved with DLG's suppression activity. When E6 complexes with the PDZ domains on the MAGI proteins, it distorts their shape and thereby impedes their function. Overall, the E6 protein serves to impede normal protein activity in such a way as to allow a cell to grow and multiply at the increased rate characteristic of cancer.


title: Papillomaviridae

text: Since the expression of E6 is strictly required for maintenance of a malignant phenotype in HPV-induced cancers, it is an appealing target of therapeutic HPV vaccines designed to eradicate established cervical cancer tumors.


title: Papillomaviridae

text: In most papillomavirus types, the primary function of the E7 protein is to inactivate members of the pRb family of tumor suppressor proteins. Together with E6, E7 serves to prevent cell death (apoptosis) and promote cell cycle progression, thus priming the cell for replication of the viral DNA. E7 also participates in immortalization of infected cells by activating cellular telomerase. Like E6, E7 is the subject of intense research interest and is believed to exert a wide variety of other effects on infected cells. As with E6, the ongoing expression of E7 is required for survival of cancer cell lines, such as HeLa, that are derived from HPV-induced tumors.