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Sherman–Morrison formula | Alternative verification | Following is an alternate verification of the Sherman–Morrison formula using the easily verifiable identity (I+wvT)−1=I−wvT1+vTw .Let and A+uvT=A(I+wvT), then (A+uvT)−1=(I+wvT)−1A−1=(I−wvT1+vTw)A−1 .Substituting w=A−1u gives (A+uvT)−1=(I−A−1uvT1+vTA−1u)A−1=A−1−A−1uvTA−11+vTA−1u |
Sherman–Morrison formula | Generalization (Woodbury matrix identity) | Given a square invertible n×n matrix A , an n×k matrix U , and a k×n matrix V , let B be an n×n matrix such that B=A+UV . Then, assuming (Ik+VA−1U) is invertible, we have B−1=A−1−A−1U(Ik+VA−1U)−1VA−1. |
History of blogging | History of blogging | While the term "blog" was not coined until the late 1990s, the history of blogging starts with several digital precursors to it. Before "blogging" became popular, digital communities took many forms, including Usenet, commercial online services such as GEnie, BiX and the early CompuServe, e-mail lists and Bulletin Board Systems (BBS). In the 1990s, Internet forum software, such as WebEx, created running conversations with "threads". Threads are topical connections between messages on a metaphorical "corkboard". Some have likened blogging to the Mass-Observation project of the mid-20th century. |
History of blogging | 1983–1993 | Usenet was the primary serial medium included in the original definition of the Internet. It features the moderated newsgroup which allowed all posting in a newsgroup to be under the control of an individual or small group. Most such newsgroups were simply moderated discussion forums, however, in late 1983, mod.ber, was created, named after and managed by Brian E. Redman; he, and a few associates regularly posted summaries of interesting postings and threads taking place elsewhere on the net. Another moderated newsgroup, rec.humor.funny (rec.humor.funny via Google Groups), started on August 7, 1987. The group still exists; but is inactive, as no joke has been posted for over five years.In the early 1990s, when Tim Berners-Lee coined the term "World Wide Web" and defined the first standards for HTML and URLs, the specifications included "USENET newsgroups for serial publishing and discussions." Berners-Lee also created what is considered by Encyclopedia Britannica to be "the first 'blog'" in 1992 to discuss the progress made on creating the World Wide Web and software used for it. |
History of blogging | 1994–2001 | The modern blog evolved from the online diary, where people would keep a running account of their personal lives. Most such writers called themselves diarists, journalists, or journalers. A few called themselves "escribitionists". The Open Pages webring included members of the online-journal community. Justin Hall, who began eleven years of personal blogging in 1994 while a student at Swarthmore College, is generally recognized as one of the earliest bloggers, as is Jerry Pournelle. Another early blog was Wearable Wireless Webcam, an online shared diary of a person's personal life combining text, video, and pictures transmitted live from a wearable computer and EyeTap device to a web site in 1994. This practice of semi-automated blogging with live video together with text was referred to as sousveillance, and such journals were also used as evidence in legal matters. |
History of blogging | 1994–2001 | Other forms of journals kept online also existed. A notable example was game programmer John Carmack's widely read journal, published via the finger protocol. Some of the very earliest bloggers, like Steve Gibson of sCary's Quakeholio (now Shacknews) and Stephen Heaslip of Blue's News (still running since 1995 with online archives back to July 1996), evolved from the Quake scene and Carmack's .plan updates. Steve Gibson was hired to blog full-time by Ritual Entertainment on February 8, 1997, possibly making him the first hired blogger. Another example of early blogging was the Poster Children online tour diary, started in 1995 by Rose Marshack.The blog was independently invented by Ian Ring, in 1997. His online journal program was never called a "blog", and had very limited functionality, consisting of blobs of text associated with dates in an Access database. Ring experimented again with data-powered journalling in 2002, to provide a CMS for the popular health and wellness site SeekWellness.com, publishing weekly posts by fitness columnist Donald Ardell. Ring likes to claim that he "invented the blog", which is technically true even though there were other projects that could make the same claim with greater authority. |
History of blogging | 1994–2001 | Another early example of an early online entry into the evolution of blogging was created by Dave Winer. Winer is considered a pioneer of Web syndication techniques and has been considered one of the “fathers” of blogging. As the editor of Scripting News claims that his site “bootstrapped the blogging revolution and that it is the longest running Web Log in the internet.” Winer did not use the term "blog" and has never claimed the term. However he has gone on record as saying that “The first blogs were inspired by this blog, in fact many of them, including Barger's Robot Wisdom, used my software.” Websites, including both corporate sites and personal homepages, had and still often have "What's New" or "News" sections, often on the index page and sorted by date. One example of a news based "weblog" is the Drudge Report founded by the self-styled maverick reporter Matt Drudge, though apparently Drudge dislikes this classification. Two others—Institute for Public Accuracy and Arts & Letters Daily—began posting news releases featuring several news-pegged one-paragraph quotes several times a week beginning in 1998. One noteworthy early precursor to a blog was the tongue-in-cheek personal website that was frequently updated by Usenet legend Kibo. |
History of blogging | 1994–2001 | Early weblogs were simply manually updated components of common websites. However, the evolution of tools to facilitate the production and maintenance of web articles posted in reverse chronological order made the publishing process feasible to a much larger, less technical, population. Ultimately, this resulted in the distinct class of online publishing that produces blogs we recognize today. For instance, the use of some sort of browser-based software is now a typical aspect of "blogging". Blogs can be hosted by dedicated blog hosting services, or they can be run using, such as WordPress, Movable Type, Blogger or LiveJournal, or on regular web hosting services. |
History of blogging | 1994–2001 | The term "weblog" was coined by Jorn Barger on 17 December 1997. The short form, "blog," was coined by Peter Merholz, who jokingly broke the word weblog into the phrase we blog in the sidebar of his blog Peterme.com in April or May 1999. Shortly thereafter, Evan Williams at Pyra Labs used "blog" as both a noun and verb ("to blog," meaning "to edit one's weblog or to post to one's weblog") and devised the term "blogger" in connection with Pyra Labs' Blogger product, leading to the popularization of the terms.After a slow start, blogging rapidly gained in popularity. Blog usage spread during 1999 and the years following, being further popularized by the near-simultaneous arrival of the first hosted blog tools: Open Diary launched in October 1998, soon growing to thousands of online diaries. Open Diary innovated the reader comment, becoming the first blog community where readers could add comments to other writers' blog entries. |
History of blogging | 1994–2001 | SlashDot, a still-popular blog for tech "nerds" launched in September 1997.
Brad Fitzpatrick, a well known blogger started LiveJournal in March 1999.
Andrew Smales created Pitas.com in July 1999 as an easier alternative to maintaining a "news page" on a website, followed by DiaryLand in September 1999, focusing more on a personal diary community.
Drew Peloso and Steven Hatch launched Onclave in late 1999, a blogging and syndication platform scripted in Dave Winer's Frontier. |
History of blogging | 1994–2001 | In 2000, blogger Traciy Curry-Reyes started the blog Movies Based on True Stories Database. The site was the first to connect the real people with movies that were inspired by their cases. The information regarding her first blog in 1998 and based on the same subject has been lost. Traciy Curry-Reyes' 2000 blog was listed at (Geocities.org/traciy2000). That blog ended with the closing of Geocities. From there, she started the same blog with Blogger in 2008. |
History of blogging | 1994–2001 | Evan Williams and Meg Hourihan (Pyra Labs) launched blogger.com in August 1999 (purchased by Google in February 2003)Blogging combined the personal web page with tools to make linking to other pages easier — specifically permalinks, blogrolls and TrackBacks. This, together with weblog search engines enabled bloggers to track the threads that connected them to others with similar interests. |
History of blogging | 2001–2004 | Several broadly popular American political blogs emerged in 2001: Ron Gunzburger's Politics1, Taegan Goddard's Political Wire, Glenn Reynolds' Instapundit, Charles Johnson's Little Green Footballs, and Jerome Armstrong's MyDD. Andrew Sullivan's AndrewSullivan.com — now entitled "The Daily Dish" — launched in October 2000 and gained readership during 2001, especially in the wake of the September 11 attacks. (Two earlier popular American political blogs were Bob Somerby's Daily Howler, launched in 1998, and Mickey Kaus' Kausfiles, launched in 1999). |
History of blogging | 2001–2004 | By 2001, blogging was enough of a phenomenon that how-to manuals began to appear, primarily focusing on technique. The importance of the blogging community (and its relationship to larger society) increased rapidly. Established schools of journalism began researching blogging and noting the differences between journalism and blogging. |
History of blogging | 2001–2004 | Also in 2002, many blogs focused on comments by U.S. Senate Majority Leader Trent Lott. Senator Lott, at a party honoring U.S. Senator Strom Thurmond, praised Senator Thurmond by suggesting that the United States would have been better off had Thurmond been elected president. Lott's critics saw these comments as a tacit approval of racial segregation, a policy advocated by Thurmond's 1948 presidential campaign. This view was reinforced by documents and recorded interviews dug up by bloggers. (See Josh Marshall's Talking Points Memo.) Though Lott's comments were made at a public event attended by the media, no major media organizations reported on his controversial comments until after blogs broke the story. Blogging helped to create a political crisis that forced Lott to step down as majority leader. |
History of blogging | 2001–2004 | The impact of this story gave greater credibility to blogs as a medium of news dissemination. Though often seen as partisan gossips, bloggers sometimes lead the way in bringing key information to public light, with mainstream media having to follow their lead. More often, however, news blogs tend to react to material already published by the mainstream media.
After 2002, blogs gained increasing notice and coverage for their role in breaking, shaping, and spinning news stories. The Iraq war saw bloggers taking measured and passionate points of view that go beyond the traditional left-right divide of the political spectrum. |
History of blogging | 2001–2004 | Blogging was established by politicians and political candidates to express opinions on war and other issues and cemented blogs' role as a news source. (See Howard Dean and Wesley Clark.) Meanwhile, an increasing number of experts blogged, making blogs a source of in-depth analysis. (See Daniel Drezner and J. Bradford DeLong.) Blogging was used to draw attention to obscure news sources. For example, bloggers posted links to traffic cameras in Madrid as a huge anti-terrorism demonstration filled the streets in the wake of the March 11 attacks. |
History of blogging | 2001–2004 | Bloggers began to provide nearly-instant commentary on televised events, creating a secondary meaning of the word "blogging": to simultaneously transcribe and editorialize speeches and events shown on television. (For example, "I am blogging Rice's testimony" means "I am posting my reactions to Condoleezza Rice's testimony into my blog as I watch her on television.") Real-time commentary was sometimes referred to as "liveblogging." |
History of blogging | 2004–2013 | In 2004, the role of blogs became increasingly mainstream, as political consultants, news services and candidates began using them as tools for outreach and opinion forming. Even politicians not actively campaigning, such as the UK's Labour Party's MP Tom Watson, began to blog to bond with constituents. |
History of blogging | 2004–2013 | Minnesota Public Radio broadcast a program by Christopher Lydon and Matt Stoller called "The blogging of the President," which covered a transformation in politics that blogging seemed to presage. The Columbia Journalism Review began regular coverage of blogs and blogging. Anthologies of blog pieces reached print, and blogging personalities began appearing on radio and television. In the summer of 2004, both United States Democratic and Republican Parties' conventions credentialed bloggers, and blogs became a standard part of the publicity arsenal. Mainstream television programs, such as Chris Matthews' Hardball, formed their own blogs. Merriam-Webster's Dictionary declared "blog" as the word of the year in 2004.Blogs were among the driving forces behind the "Rathergate" scandal, to wit: (television journalist) Dan Rather presented documents (on the CBS show 60 Minutes) that conflicted with accepted accounts of President Bush's military service record. Bloggers declared the documents to be forgeries and presented evidence and arguments in support of that view, and CBS apologized for what it said were inadequate reporting techniques (see Little Green Footballs). Many bloggers view this scandal as the advent of blogs' acceptance by the mass media, both as a news source and opinion and as means of applying political pressure. |
History of blogging | 2004–2013 | Some bloggers have moved over to other media. The following bloggers (and others) have appeared on radio and television: Duncan Black (known widely by his pseudonym, Atrios), Glenn Reynolds (Instapundit), Markos Moulitsas Zúniga (Daily Kos), Alex Steffen (Worldchanging) and Ana Marie Cox (Wonkette). In counterpoint, Hugh Hewitt exemplifies a mass media personality who has moved in the other direction, adding to his reach in "old media" by being an influential blogger. Music blog publisher Jeff Davidson, Earvolution.com, now produces Sun Studio Sessions airing on PBS stations across the U.S. |
History of blogging | 2004–2013 | Some blogs were an important news source during the December 2004 Tsunami such as Médecins Sans Frontières, which used SMS text messaging to report from affected areas in Sri Lanka and Southern India. Similarly, during Hurricane Katrina in August 2005 and the aftermath a few blogs which were located in New Orleans, including the Interdictor and Gulfsails were able to maintain power and an Internet connection and disseminate information that was not covered by the mainstream media. |
History of blogging | 2004–2013 | In 2005, Global Voices Online, a site which "aggregates, curates, and amplifies the global conversation online – shining light on places and people other media often ignore" surfaced, bringing to light bloggers from around the world. Today, the site has a relationship with Reuters and is responsible for breaking many global news stories. |
History of blogging | 2004–2013 | In the United Kingdom, The Guardian newspaper launched a redesign in September 2005, which included a daily digest of blogs on page 2. Also in June 2006, BBC News launched a weblog for its editors, following other news companies.In January 2005, Fortune magazine listed eight bloggers that business people "could not ignore": Peter Rojas, Xeni Jardin, Ben Trott, Mena Trott, Jonathan Schwartz, Jason Goldman, Robert Scoble, and Jason Calacanis. |
History of blogging | 2004–2013 | In 2007, Tim O'Reilly proposed a Blogger's Code of Conduct. |
History of blogging | 2004–2013 | In 2011, Tom Knighton, owner of Knighton Media, Inc, announced that his company was purchasing The Albany Journal. Knighton Media was formed to managed Knighton's blog, Laws-n-Sausages, and this was the first known time that a blog had purchased a newspaper anywhere in the world.In 2012, Evan Williams of Pyra Labs launched Medium, a publishing platform for amateur and professional writers. In some ways this was the beginning of the end of the blog as a social platform. |
History of blogging | 2014 and After | The evolution of social media and the speed of people reacting to posted content led to increasing declarations of the death of the blog, even as it was acknowledged that what came after would contain a lot of the same DNA as the blog . |
History of blogging | 2014 and After | Even as the number of voices declaring blogs dead increased each year, others continued to see value, as for example in 2016 when the .blog domain name was launched. Depending on what one means by the word blog, blogging is alive and well - as of 2019, there are an estimated 500 million + blogs or blog-like sites in the world, including inactive websites. Not all platforms choose to share their data publicly, so the number of blogs on the web is likely much higher. |
Aleš Žiberna | Aleš Žiberna | Aleš Žiberna is a Slovene statistician, whose specialty is network analysis. His specific research interests include blockmodeling, multivariate analysis and computer intensive methods (e.g., computer simulations, resampling methods).Currently, he is employed at the Faculty of Social Sciences of the University of Ljubljana, specifically at the Chair of Social Informatics and Methodology, and Centre for Methodology and Informatics. |
Aleš Žiberna | Work | In 2007, he proposed a solution to the generalized valued blockmodeling by introducing homogeneity blockmodeling with the basic idea "that the inconsistency of an empirical block with its ideal block can be measured by within block variability of appropriate values". The newly-formed ideal blocks, which are appropriate for blockmodeling of valued networks, are then presented together with the definitions of their block inconsistencies.He also (in 2007/08) developed an implicit blockmodeling approach, based on previous work of Batagelj and Ferligoj (2000).: 16–17 In 2014, he proposed a new approach to the blockmodeling - blockmodeling linked networks. |
Aleš Žiberna | Selected bibliography | ŽIBERNA, Aleš. Generalized blockmodeling of valued networks. Social Networks. [Print ed.]. Jan. 2007, vol. 29, no. 1, str. 105-126. ISSN 0378-8733. |
Aleš Žiberna | Selected bibliography | ŽIBERNA, Aleš. Blockmodeling of multilevel networks. Social Networks. [Print ed.]. Oct. 2014, vol. 39, str. 46-61, ilustr. ISSN 0378-8733. DOI: 10.1016/j.socnet.2014.04.002. [COBISS.SI-ID 32697949] ŽIBERNA, Aleš. Generalized blockmodeling of sparse networks. Metodološki zvezki. [Tiskana izd.]. 2013, vol. 10, no. 2, str. 99-119, graf. prikazi. ISSN 1854-0023. http://www.stat-d.si/mz/mz10.1/Ziberna2013.pdf. [COBISS.SI-ID 32428893] MATJAŠIČ, Miha, CUGMAS, Marjan, ŽIBERNA, Aleš. Blockmodeling : an R package for generalized blockmodeling. Metodološki zvezki. [Tiskana izd.]. 2020, vol. 17, no. 2, str. 49-66, ilustr. ISSN 1854-0023. [COBISS.SI-ID 53164547] |
Brace (sailing) | Brace (sailing) | A brace on a square-rigged ship is a rope (line) used to rotate a yard around the mast, to allow the ship to sail at different angles to the wind. Braces are always used in pairs, one at each end of a yard (yardarm), termed port brace and starboard brace of a given yard or sail (e.g., the starboard main-brace is the brace fixed to the right end of the yard of the main sail). |
Brace (sailing) | Brace (sailing) | The braces are fixed to the outer ends of the yards, and are led to the deck as far aft as possible, to allow the crew to haul on them. The lower yards' braces can usually run directly to the deck, but to do so with those higher up would mean that most of the force was pulling downwards rather than backwards. Instead, the braces for the upper yards run to another mast and thence to the deck. On the aftermost mast, this may mean they have to be led forwards instead of backwards. Braces from the aftermost mast that run to the very stern of the ship often pass through blocks attached to short outriggers projecting from the side of the ship in order to improve their lead. These projections are called bumkins and can be seen in the picture. |
Brace (sailing) | Brace (sailing) | In many ways, braces are the equivalent of a modern yacht's sheets. However, where adjusting a sail on a yacht is a simple operation performed often, tacking or wearing ship using the braces usually requires the entire crew to be called to "bracing stations". This is because the braces carry heavy loads but have few blocks and hence each one needs many people hauling, and because most ships with braces have many sails and hence many such teams. For this reason, all manoeuvres require plenty of notice (one reason falling overboard is especially to be avoided from such a ship) and routine course changes may be planned well in advance for a time when as few of the crew as possible wish to be asleep. |
Brace (sailing) | Brace (sailing) | The sails on a tall ship's mast must all be turned together, because of all the gear that runs between them. The rate of turn is set by the course, the heaviest yard and hence the most difficult to move. The teams on the other braces for that mast must watch the course and keep their own yard in line with it. The braces may be marked with leather tags or twine seizings to indicate the centre ("square") position and the two extremes, though these marks may not always be accurate due to stretch in the line. |
Actoxumab | Actoxumab | Actoxumab is a human monoclonal antibody designed for the prevention of recurrence of Clostridium difficile infection.This drug, along with bezlotoxumab, was developed through Phase II efficacy trials by a partnership between Medarex Inc and MassBiologics of the University of Massachusetts Medical School. The project was then licensed to Merck & Co., Inc. for further development and commercialization.A study compared it with bezlotoxumab (that targets CD toxin-B) and found Actoxumab less effective. |
Fly-whisk | Fly-whisk | A fly-whisk (or fly-swish) is a tool that is used to swat flies. A similar device is used as a hand fan in hot tropical climates, sometimes as part of regalia, and is called a chowrie, chāmara, or prakirnaka in South Asia and Tibet.In Indonesian art, a fly-whisk is one of the items that is associated with Shiva. A fly-whisk is frequently seen as an attribute of Hindu, Jain, Daoist and Buddhist deities. The fly-whisk is evident in some configurations of the Ashtamangala, employed in some traditions of murti puja, particularly Gaudiya Vaishnavism. It is also used as an accessory in the ritual aspects of folk performance traditions, especially folk-theater forms like Pala Gaan, where it can double as a prop. |
Fly-whisk | Fly-whisk | Fly-whisks are in use in parts of the contemporary Middle East, such as Egypt, by some classes of society, e.g., outdoor merchants and shop keepers, especially in summer when flies become bothersome. Those have a wooden handle and plant fibers attached to them. The more expensive ones are made from horse hair. In the eastern parts of the Indian subcontinent, it is made from the tail-hairs of the yak. Yakut people from Siberia use fly-whisk called deybiir made of horse tail both for swating mosquitoes and as a sacred tool for shamanistic rituals. |
Fly-whisk | Fly-whisk | Fly-whisks appear frequently in the traditional regales of monarchs and nobility in many parts of the African continent. Fly whisks, called "ìrùkẹ̀rẹ̀" in Yoruba, were used by Yoruba monarchs and chiefs as a symbol of power and respect. This use has sometimes carried on into modern contexts: Kenyan leader Jomo Kenyatta carried a fly-whisk, a mark of authority in Maasai society, as did Malawian leader Hastings Banda, while South African jazz musician Jabu Khanyile also used a Maasai fly-whisk as a trademark when on stage.The fly-whisk is one of the traditional symbols of Buddhist monastic hierarchy in China and Japan, along with the khakkhara, jewel scepter, and begging bowl. The fly-whisk in Buddhism represents the symbolic "sweeping" of ignorance and mental afflictions. The Daoist fly-whisk is made of the root and twine of the smilax for the handle, and the hairs are made of palm fiber. The Chinese fly-whisk is also used in many Chinese martial arts such as Shaolin Kung Fu and Wudang quan, each corresponding to their own respective religious philosophy. |
Fly-whisk | Fly-whisk | A fly-whisk forms part of the royal regalia of Thailand. It consists of the tail hairs of a white elephant.
Fly-whisks were also used in Polynesian culture as a ceremonial mark of authority. |
Fly-whisk | Algeria incident | In 1827, the last Ottoman ruler of Algeria, Hussein Dey, struck the French consul, Pierre Deval in the face with a fly-whisk during a dispute over unpaid French debts to Algeria. That insult became a pretext for the French invasion of Algeria in 1830. |
Difference density map | Difference density map | In X-ray crystallography, a difference density map shows the spatial distribution of the difference between the measured electron density of the crystal and the electron density explained by the current model.These coefficients are derived from the gradient of the likelihood function of the observed structure factors on the basis of the current model. |
Difference density map | Display | Conventionally, they are displayed as isosurfaces with positive density—electron density where there's nothing in the model, usually corresponding to some constituent of the crystal that hasn't been modelled, for example a ligand or a crystallisation adjutant -- in green, and negative density—parts of the model not backed up by electron density, indicating either that an atom has been disordered by radiation damage or that it is modelled in the wrong place—in red. |
Difference density map | Calculation | Difference density maps are usually calculated using Fourier coefficients which are the differences between the observed structure factor amplitudes from the X-ray diffraction experiment and the calculated structure factor amplitudes from the current model, using the phase from the model for both terms (since no phases are available for the observed data). The two sets of structure factors must be on the same scale. It is now normal to also include weighting terms which take into account the estimated errors in the current model: Cdiffmap=(m|Fobs|−D|Fcalc|)exp(2πiϕcalc) where m is a figure of merit which is an estimate of the cosine of the error in the phase, and D is a scale factor. |
Colored matroid | Colored matroid | In mathematics, a colored matroid is a matroid whose elements are labeled from a set of colors, which can be any set that suits the purpose, for instance the set of the first n positive integers, or the sign set {+, −}.
The interest in colored matroids is through their invariants, especially the colored Tutte polynomial, which generalizes the Tutte polynomial of a signed graph of Kauffman (1989).There has also been study of optimization problems on matroids where the objective function of the optimization depends on the set of colors chosen as part of a matroid basis. |
Recombinant DNA | Recombinant DNA | Recombinant DNA (rDNA) molecules are DNA molecules formed by laboratory methods of genetic recombination (such as molecular cloning) that bring together genetic material from multiple sources, creating sequences that would not otherwise be found in the genome. |
Recombinant DNA | Recombinant DNA | Recombinant DNA is the general name for a piece of DNA that has been created by combining two or more fragments from different sources. Recombinant DNA is possible because DNA molecules from all organisms share the same chemical structure, differing only in the nucleotide sequence. Recombinant DNA molecules are sometimes called chimeric DNA because they can be made of material from two different species like the mythical chimera. rDNA technology uses palindromic sequences and leads to the production of sticky and blunt ends. |
Recombinant DNA | Recombinant DNA | The DNA sequences used in the construction of recombinant DNA molecules can originate from any species. For example, plant DNA can be joined to bacterial DNA, or human DNA can be joined with fungal DNA. In addition, DNA sequences that do not occur anywhere in nature can be created by the chemical synthesis of DNA and incorporated into recombinant DNA molecules. Using recombinant DNA technology and synthetic DNA, any DNA sequence can be created and introduced into living organisms. |
Recombinant DNA | Recombinant DNA | Proteins that can result from the expression of recombinant DNA within living cells are termed recombinant proteins. When recombinant DNA encoding a protein is introduced into a host organism, the recombinant protein is not necessarily produced. Expression of foreign proteins requires the use of specialized expression vectors and often necessitates significant restructuring by foreign coding sequences.Recombinant DNA differs from genetic recombination in that the former results from artificial methods while the latter is a normal biological process that results in the remixing of existing DNA sequences in essentially all organisms. |
Recombinant DNA | DNA creation | Molecular cloning is the laboratory process used to create recombinant DNA. It is one of two most widely used methods, along with polymerase chain reaction (PCR), used to direct the replication of any specific DNA sequence chosen by the experimentalist. There are two fundamental differences between the methods. One is that molecular cloning involves replication of the DNA within a living cell, while PCR replicates DNA in the test tube, free of living cells. The other difference is that cloning involves cutting and pasting DNA sequences, while PCR amplifies by copying an existing sequence. |
Recombinant DNA | DNA creation | Formation of recombinant DNA requires a cloning vector, a DNA molecule that replicates within a living cell. Vectors are generally derived from plasmids or viruses, and represent relatively small segments of DNA that contain necessary genetic signals for replication, as well as additional elements for convenience in inserting foreign DNA, identifying cells that contain recombinant DNA, and, where appropriate, expressing the foreign DNA. The choice of vector for molecular cloning depends on the choice of host organism, the size of the DNA to be cloned, and whether and how the foreign DNA is to be expressed. The DNA segments can be combined by using a variety of methods, such as restriction enzyme/ligase cloning or Gibson assembly. |
Recombinant DNA | DNA creation | In standard cloning protocols, the cloning of any DNA fragment essentially involves seven steps: (1) Choice of host organism and cloning vector, (2) Preparation of vector DNA, (3) Preparation of DNA to be cloned, (4) Creation of recombinant DNA, (5) Introduction of recombinant DNA into the host organism, (6) Selection of organisms containing recombinant DNA, and (7) Screening for clones with desired DNA inserts and biological properties.These steps are described in some detail in a related article (molecular cloning). |
Recombinant DNA | DNA expression | DNA expression requires the transfection of suitable host cells. Typically, either bacterial, yeast, insect, or mammalian cells (such as Human Embryonic Kidney cells or CHO cells) are used as host cells.Following transplantation into the host organism, the foreign DNA contained within the recombinant DNA construct may or may not be expressed. That is, the DNA may simply be replicated without expression, or it may be transcribed and translated and a recombinant protein is produced. Generally speaking, expression of a foreign gene requires restructuring the gene to include sequences that are required for producing an mRNA molecule that can be used by the host's translational apparatus (e.g. promoter, translational initiation signal, and transcriptional terminator).Specific changes to the host organism may be made to improve expression of the ectopic gene. In addition, changes may be needed to the coding sequences as well, to optimize translation, make the protein soluble, direct the recombinant protein to the proper cellular or extracellular location, and stabilize the protein from degradation. |
Recombinant DNA | Properties of organisms containing recombinant DNA | In most cases, organisms containing recombinant DNA have apparently normal phenotypes. That is, their appearance, behavior and metabolism are usually unchanged, and the only way to demonstrate the presence of recombinant sequences is to examine the DNA itself, typically using a polymerase chain reaction (PCR) test. Significant exceptions exist, and are discussed below. |
Recombinant DNA | Properties of organisms containing recombinant DNA | If the rDNA sequences encode a gene that is expressed, then the presence of RNA and/or protein products of the recombinant gene can be detected, typically using RT-PCR or western hybridization methods. Gross phenotypic changes are not the norm, unless the recombinant gene has been chosen and modified so as to generate biological activity in the host organism. Additional phenotypes that are encountered include toxicity to the host organism induced by the recombinant gene product, especially if it is over-expressed or expressed within inappropriate cells or tissues. |
Recombinant DNA | Properties of organisms containing recombinant DNA | In some cases, recombinant DNA can have deleterious effects even if it is not expressed. One mechanism by which this happens is insertional inactivation, in which the rDNA becomes inserted into a host cell's gene. In some cases, researchers use this phenomenon to "knock out" genes to determine their biological function and importance. Another mechanism by which rDNA insertion into chromosomal DNA can affect gene expression is by inappropriate activation of previously unexpressed host cell genes. This can happen, for example, when a recombinant DNA fragment containing an active promoter becomes located next to a previously silent host cell gene, or when a host cell gene that functions to restrain gene expression undergoes insertional inactivation by recombinant DNA. |
Recombinant DNA | Applications of recombinant DNA | Recombinant DNA is widely used in biotechnology, medicine and research. Today, recombinant proteins and other products that result from the use of DNA technology are found in essentially every western pharmacy, physician or veterinarian office, medical testing laboratory, and biological research laboratory. In addition, organisms that have been manipulated using recombinant DNA technology, as well as products derived from those organisms, have found their way into many farms, supermarkets, home medicine cabinets, and even pet shops, such as those that sell GloFish and other genetically modified animals. |
Recombinant DNA | Applications of recombinant DNA | The most common application of recombinant DNA is in basic research, in which the technology is important to most current work in the biological and biomedical sciences. Recombinant DNA is used to identify, map and sequence genes, and to determine their function. rDNA probes are employed in analyzing gene expression within individual cells, and throughout the tissues of whole organisms. Recombinant proteins are widely used as reagents in laboratory experiments and to generate antibody probes for examining protein synthesis within cells and organisms.Many additional practical applications of recombinant DNA are found in industry, food production, human and veterinary medicine, agriculture, and bioengineering. Some specific examples are identified below. |
Recombinant DNA | Applications of recombinant DNA | Recombinant chymosin Found in rennet, chymosin is an enzyme required to manufacture cheese. It was the first genetically engineered food additive used commercially. Traditionally, processors obtained chymosin from rennet, a preparation derived from the fourth stomach of milk-fed calves. Scientists engineered a non-pathogenic strain (K-12) of E. coli bacteria for large-scale laboratory production of the enzyme. This microbiologically produced recombinant enzyme, identical structurally to the calf derived enzyme, costs less and is produced in abundant quantities. Today about 60% of U.S. hard cheese is made with genetically engineered chymosin. In 1990, FDA granted chymosin "generally recognized as safe" (GRAS) status based on data showing that the enzyme was safe. |
Recombinant DNA | Applications of recombinant DNA | Recombinant human insulin Almost completely replaced insulin obtained from animal sources (e.g. pigs and cattle) for the treatment of insulin-dependent diabetes. A variety of different recombinant insulin preparations are in widespread use. Recombinant insulin is synthesized by inserting the human insulin gene into E. coli, or yeast (Saccharomyces cerevisiae) which then produces insulin for human use. Insulin produced by E. coli requires further post translational modifications (glycosylation) whereas yeast are able to perform these themselves by virtue of being a more complex host organism. The advantage of recombinant human insulin is after chronic use patients don't develop an immune defence against it the way animal sourced insulin stimulates the human immune system. |
Recombinant DNA | Applications of recombinant DNA | Recombinant human growth hormone (HGH, somatotropin) Administered to patients whose pituitary glands generate insufficient quantities to support normal growth and development. Before recombinant HGH became available, HGH for therapeutic use was obtained from pituitary glands of cadavers. This unsafe practice led to some patients developing Creutzfeldt–Jakob disease. Recombinant HGH eliminated this problem, and is now used therapeutically. It has also been misused as a performance-enhancing drug by athletes and others. DrugBank entry Recombinant blood clotting factor VIII A blood-clotting protein that is administered to patients with forms of the bleeding disorder hemophilia, who are unable to produce factor VIII in quantities sufficient to support normal blood coagulation. Before the development of recombinant factor VIII, the protein was obtained by processing large quantities of human blood from multiple donors, which carried a very high risk of transmission of blood borne infectious diseases, for example HIV and hepatitis B. DrugBank entry Recombinant hepatitis B vaccine Hepatitis B infection is controlled through the use of a recombinant hepatitis B vaccine, which contains a form of the hepatitis B virus surface antigen that is produced in yeast cells. The development of the recombinant subunit vaccine was an important and necessary development because hepatitis B virus, unlike other common viruses such as polio virus, cannot be grown in vitro. Vaccine information from Hepatitis B Foundation Recombinant antibodies Recombinant antibodies (rAbs) are produced in vitro by the means of expression systems based on mammalian cells. Their monospecific binding to a specific epitope makes rAbs eligible not only for research purposes, but also as therapy options against certain cancer types, infections and autoimmune diseases. |
Recombinant DNA | Applications of recombinant DNA | Diagnosis of infection with HIV Each of the three widely used methods for diagnosing HIV infection has been developed using recombinant DNA. The antibody test (ELISA or western blot) uses a recombinant HIV protein to test for the presence of antibodies that the body has produced in response to an HIV infection. The DNA test looks for the presence of HIV genetic material using reverse transcription polymerase chain reaction (RT-PCR). Development of the RT-PCR test was made possible by the molecular cloning and sequence analysis of HIV genomes. HIV testing page from US Centers for Disease Control (CDC) Golden rice A recombinant variety of rice that has been engineered to express the enzymes responsible for β-carotene biosynthesis. This variety of rice holds substantial promise for reducing the incidence of vitamin A deficiency in the world's population. Golden rice is not currently in use, pending the resolution of regulatory and intellectual property issues. |
Recombinant DNA | Applications of recombinant DNA | Herbicide-resistant crops Commercial varieties of important agricultural crops (including soy, maize/corn, sorghum, canola, alfalfa and cotton) have been developed that incorporate a recombinant gene that results in resistance to the herbicide glyphosate (trade name Roundup), and simplifies weed control by glyphosate application. These crops are in common commercial use in several countries. |
Recombinant DNA | Applications of recombinant DNA | Insect-resistant crops Bacillus thuringeiensis is a bacterium that naturally produces a protein (Bt toxin) with insecticidal properties. The bacterium has been applied to crops as an insect-control strategy for many years, and this practice has been widely adopted in agriculture and gardening. Recently, plants have been developed that express a recombinant form of the bacterial protein, which may effectively control some insect predators. Environmental issues associated with the use of these transgenic crops have not been fully resolved. |
Recombinant DNA | History | The idea of recombinant DNA was first proposed by Peter Lobban, a graduate student of Prof. Dale Kaiser in the Biochemistry Department at Stanford University Medical School. The first publications describing the successful production and intracellular replication of recombinant DNA appeared in 1972 and 1973, from Stanford and UCSF. In 1980 Paul Berg, a professor in the Biochemistry Department at Stanford and an author on one of the first papers was awarded the Nobel Prize in Chemistry for his work on nucleic acids "with particular regard to recombinant DNA". Werner Arber, Hamilton Smith, and Daniel Nathans shared the 1978 Nobel Prize in Physiology or Medicine for the discovery of restriction endonucleases which enhanced the techniques of rDNA technology. |
Recombinant DNA | History | Stanford University applied for a US patent on recombinant DNA in 1974, listing the inventors as Herbert W. Boyer (professor at the University of California, San Francisco) and Stanley N. Cohen (professor at Stanford University); this patent was awarded in 1980. The first licensed drug generated using recombinant DNA technology was human insulin, developed by Genentech and licensed by Eli Lilly and Company. |
Recombinant DNA | Controversy | Scientists associated with the initial development of recombinant DNA methods recognized that the potential existed for organisms containing recombinant DNA to have undesirable or dangerous properties. At the 1975 Asilomar Conference on Recombinant DNA, these concerns were discussed and a voluntary moratorium on recombinant DNA research was initiated for experiments that were considered particularly risky. This moratorium was widely observed until the National Institutes of Health (USA) developed and issued formal guidelines for rDNA work. Today, recombinant DNA molecules and recombinant proteins are usually not regarded as dangerous. However, concerns remain about some organisms that express recombinant DNA, particularly when they leave the laboratory and are introduced into the environment or food chain. These concerns are discussed in the articles on genetically modified organisms and genetically modified food controversies. Furthermore, there are concerns about the by-products in biopharmaceutical production, where recombinant DNA result in specific protein products. The major by-product, termed host cell protein, comes from the host expression system and poses a threat to the patient's health and the overall environment. |
Infusion | Infusion | Infusion is the process of extracting chemical compounds or flavors from plant material in a solvent such as water, oil or alcohol, by allowing the material to remain suspended in the solvent over time (a process often called steeping). An infusion is also the name for the resultant liquid. The process of infusion is distinct from both decoction—a method of extraction involving boiling the plant material—and percolation, in which water is passed through the material (as in a coffeemaker). |
Infusion | History | The first recorded use of essential oils was in the 10th or 11th century by the Persian polymath Avicenna, possibly in The Canon of Medicine.Tea is far older than this, dating back to the 10th century BC as the earliest recorded reference. |
Infusion | Preparation techniques | Infusion is a chemical process that uses botanicals (typically dried herbs, flowers or berries) that are volatile and release their active ingredients readily in water, oil, or alcohol. In this process, a liquid is typically boiled (or brought to another appropriate temperature) and poured over the herb. After the herb has been allowed to steep in the liquid for an appropriate period of time, it is removed (possibly by straining) leaving an infusion. Unless the infusion is to be consumed immediately, it is bottled and refrigerated for future use. |
Infusion | Preparation techniques | The amount of time the herbs are left in the liquid depends on the kind of infusion. Infusion times can range from seconds (for some kinds of Chinese tea) to hours, days, or months (for liqueurs like Sloe Gin). There are several accessories and techniques for removing the steeped or leftover botanicals that were used to infuse liquids, including metal steepers (which look like clamps), tea infusers (which act as strainers), and french presses (which are commonly used to infuse water with various teas and coffee). The most commonly used technique is the teabag, which is made with filter paper and filled with various tea flavors. |
Infusion | Examples | Tea is a common example of an infusion; most varieties of tea call for steeping the leaves in hot water, although some variants (e.g. Moroccan mint tea) call for decoction instead. Many herbal teas are prepared by infusion, as well; lemon, chamomile, senna, apple, ginger, rooibos, and many other plants are used individually or in combination.
Coffee can also be made through infusion (as in a French press), but is more often made through percolation.
Herbal remedies are commonly produced through infusions in water or oil. |
Infusion | Examples | Flavored oils: Plants with desirable flavors may be steeped in an edible oil or vinegar for an extended period; the infused oil or vinegar is often sold still containing the plant and is then used as flavoring. Chilis, lemon, garlic, and many other plants may be used. There can be ambiguity in the labeling of these oils: for example, what is described as sesame oil may be oil extracted from sesame seeds or another vegetable oil infused with sesame. |
Infusion | Examples | Cucumber water, a mix of sliced cucumber with citrus slices and herbs such as mint, is a popular infusion. It is sometimes known as "spa water" due to it being commonly served in day spas and similar personal care establishments. |
Triangular decomposition | Triangular decomposition | In computer algebra, a triangular decomposition of a polynomial system S is a set of simpler polynomial systems S1, ..., Se such that a point is a solution of S if and only if it is a solution of one of the systems S1, ..., Se. |
Triangular decomposition | Triangular decomposition | When the purpose is to describe the solution set of S in the algebraic closure of its coefficient field, those simpler systems are regular chains. If the coefficients of the polynomial systems S1, ..., Se are real numbers, then the real solutions of S can be obtained by a triangular decomposition into regular semi-algebraic systems. In both cases, each of these simpler systems has a triangular shape and remarkable properties, which justifies the terminology. |
Triangular decomposition | History | The Characteristic Set Method is the first factorization-free algorithm, which was proposed for decomposing an algebraic variety into equidimensional components. Moreover, the Author, Wen-Tsun Wu, realized an implementation of this method and reported experimental data in his 1987 pioneer article titled "A zero structure theorem for polynomial equations solving". To put this work into context, let us recall what was the common idea of an algebraic set decomposition at the time this article was written. |
Triangular decomposition | History | Let K be an algebraically closed field and k be a subfield of K. A subset V ⊂ Kn is an (affine) algebraic variety over k if there exists a polynomial set F ⊂ k[x1, ..., xn] such that the zero set V(F) ⊂ Kn of F equals V.
Recall that V is said irreducible if for all algebraic varieties V1, V2 ⊂ Kn the relation V = V1 ∪ V2 implies either V = V1 or V = V2. A first algebraic variety decomposition result is the famous Lasker–Noether theorem which implies the following.
Theorem (Lasker - Noether). For each algebraic variety V ⊂ Kn there exist finitely many irreducible algebraic varieties V1, ..., Ve ⊂ Kn such that we have V=V1∪⋯∪Ve. |
Triangular decomposition | History | Moreover, if Vi ⊈ Vj holds for 1 ≤ i < j ≤ e then the set {V1, ..., Ve} is unique and forms the irreducible decomposition of V.The varieties V1, ..., Ve in the above Theorem are called the irreducible components of V and can be regarded as a natural output for a decomposition algorithm, or, in other words, for an algorithm solving a system of equations in k[x1, ..., xn]. |
Triangular decomposition | History | In order to lead to a computer program, this algorithm specification should prescribe how irreducible components are represented. Such an encoding is introduced by Joseph Ritt through the following result. |
Triangular decomposition | History | Theorem (Ritt). If V ⊂ Kn is a non-empty and irreducible variety then one can compute a reduced triangular set C contained in the ideal ⟨F⟩ generated by F in k[x1, ..., xn] and such that all polynomials g in ⟨F⟩ reduces to zero by pseudo-division w.r.t C.We call the set C in Ritt's Theorem a Ritt characteristic set of the ideal ⟨F⟩ . Please refer to regular chain for the notion of a triangular set. |
Triangular decomposition | History | Joseph Ritt described a method for solving polynomial systems based on polynomial factorization over field extensions and computation of characteristic sets of prime ideals. |
Triangular decomposition | History | Deriving a practical implementation of this method, however, was and remains a difficult problem. In the 1980s, when the Characteristic set Method was introduced, polynomial factorization was an active research area and certain fundamental questions on this subject were solved recentlyNowadays, decomposing an algebraic variety into irreducible components is not essential to process most application problems, since weaker notions of decompositions, less costly to compute, are sufficient. |
Triangular decomposition | History | The Characteristic Set Method relies on the following variant of Ritt's Theorem. |
Triangular decomposition | History | Theorem (Wen-Tsun Wu). For any finite polynomial set F ⊂ k[x1, ..., xn], one can compute a reduced triangular set C⊂⟨F⟩ such that all polynomial g in F reduces to zero by pseudo-division w.r.t C.Different concepts and algorithms extended the work of Wen-Tsun Wu. In the early 1990s, the notion of a regular chain, introduced independently by Michael Kalkbrener in 1991 in his PhD Thesis and, by Lu Yang and Jingzhong Zhang led to important algorithmic discoveries. |
Triangular decomposition | History | In Kalkbrener's vision, regular chains are used to represent the generic zeros of the irreducible components of an algebraic variety. In the original work of Yang and Zhang, they are used to decide whether a hypersurface intersects a quasi-variety (given by a regular chain). Regular chains have, in fact, several interesting properties and are the key notion in many algorithms for decomposing systems of algebraic or differential equations. |
Triangular decomposition | History | Regular chains have been investigated in many papers.The abundant literature on the subject can be explained by the many equivalent definitions of a regular chain. Actually, the original formulation of Kalkbrener is quite different from that of Yang and Zhang. A bridge between these two notions, the point of view of Kalkbrener and that of Yang and Zhang, appears in Dongming Wang's paper.There are various algorithms available for obtaining triangular decomposition of V(F) both in the sense of Kalkbrener and in the sense of Lazard and Wen-Tsun Wu. The Lextriangular Algorithm by Daniel Lazard and the Triade Algorithm by Marc Moreno Maza together with the Characteristic Set Method are available in various computer algebra systems, including Axiom and Maple. |
Triangular decomposition | Formal definitions | Let k be a field and x1 < ... < xn be ordered variables. We denote by R = k[x1, ..., xn] the corresponding polynomial ring. For F ⊂ R, regarded as a system of polynomial equations, there are two notions of a triangular decomposition over the algebraic closure of k. The first one is to decompose lazily, by representing only the generic points of the algebraic set V(F) in the so-called sense of Kalkbrener. |
Triangular decomposition | Formal definitions | (F)=⋂i=1esat(Ti).
The second is to describe explicitly all the points of V(F) in the so-called sense of in Lazard and Wen-Tsun Wu.
V(F)=⋃i=1eW(Ti).
In both cases T1, ..., Te are finitely many regular chains of R and sat(Ti) denotes the radical of the saturated ideal of Ti while W(Ti) denotes the quasi-component of Ti. Please refer to regular chain for definitions of these notions. |
Triangular decomposition | Formal definitions | Assume from now on that k is a real closed field. Consider S a semi-algebraic system with polynomials in R. There exist finitely many regular semi-algebraic systems S1, ..., Se such that we have Zk(S)=Zk(S1)∪⋯∪Zk(Se) where Zk(S) denotes the points of kn which solve S. The regular semi-algebraic systems S1, ..., Se form a triangular decomposition of the semi-algebraic system S. |
Triangular decomposition | Examples | Denote Q the rational number field. In Q[x,y,z] with variable ordering x>y>z , consider the following polynomial system: S={x2+y+z=1x+y2+z=1x+y+z2=1 According to the Maple code: One possible triangular decompositions of the solution set of S with using RegularChains library is: {z=0y=1x=0∪{z=0y=0x=1∪{z=1y=0x=0∪{z2+2z−1=0y=zx=z |
Cross of Merit | Cross of Merit | A Cross of Merit is a personal decoration which is generally above the rank of medal and below that of knight, and may refer to: |
Cross of Merit | The Netherlands | Cross of Merit of the Order of the House of Orange Cross of Merit (Netherlands), a decoration for bravery Cross of Merit of the Netherlands Red Cross |
Cross of Merit | Poland | Cross of Merit (Poland) Cross of Merit with Swords (Poland) Cross of Merit for Bravery (Poland) Cross of Merit (Polish Scouting and Guiding Association) |
Cross of Merit | Ukraine | Cross of Merit (Ukrainian Insurgent Army) |
Cross of Merit | Other | Cross of Merit (EOHSJ) Cross of the Order pro Merito Melitensi, Sovereign Military Order of Malta |
Bus garage | Bus garage | A bus garage, also known as a bus depot, bus base or bus barn, is a facility where buses are stored and maintained. In many conurbations, bus garages are on the site of former car barns or tram sheds, where trams (streetcars) were stored, and the operation transferred to buses. In other areas, garages were built to replace horsebus yards or on virgin sites when populations were not as high as now. |
Bus garage | Description | Most bus garages will contain the following elements: Internal parking External parking Fueling point Fuel storage tanks Engineering section Inspection pits Bus wash Brake test lane Staff canteen/break room Administration officeSmaller garages may contain the minimum engineering facilities, restricted to light servicing capabilities only. Garages may also contain recovery vehicles, often converted buses, although their incidence has declined with the use of contractors to recover break-downs, and the increase in reliability. |
Bus garage | Description | Overnight, the more valuable or regularly in-service buses will usually be stored in the interior of the garage, with less used or older service vehicles, and vehicles withdrawn for storage or awaiting disposal, stored externally. During the day, internal and external areas will see a variety of movements. Heritage vehicles are almost exclusively stored inside the garage. |