Wayback Machine

The Wayback Machine is a digital archive of the World Wide Web, founded by the Internet Archive, a nonprofit organization based in San Francisco. Its founders, Brewster Kahle and Bruce Gilliat developed the Wayback Machine with the intention of providing "universal access to all knowledge" by preserving archived copies of defunct webpages. Since its launch in 2001, over 452 billion pages have been added to the archive; the service has sparked controversy over whether or not creating archived pages without the owner's permission constitutes copyright infringement in certain jurisdictions. Internet Archive founders Brewster Kahle and Bruce Gilliat launched the Wayback Machine in 2001 to address the problem of website content vanishing whenever it gets changed or shut down; the service enables users to see archived versions of web pages across time, which the archive calls a "three dimensional index". Kahle and Gilliat created the machine hoping to archive the entire Internet and provide "universal access to all knowledge."The name Wayback Machine was chosen as a reference to the "WABAC machine", a fictional time-traveling device used by the characters Mister Peabody and Sherman in The Rocky and Bullwinkle Show, an animated cartoon.

In one of the animated cartoon's component segments, Peabody's Improbable History, the characters used the machine to witness, participate in, alter famous events in history. The Wayback Machine began archiving cached web pages in 1996, with the goal of making the service public five years later. From 1996 to 2001, the information was kept on digital tape, with Kahle allowing researchers and scientists to tap into the clunky database; when the archive reached its fifth anniversary in 2001, it was unveiled and opened to the public in a ceremony at the University of California, Berkeley. By the time the Wayback Machine launched, it contained over 10 billion archived pages. Today, the data are stored on the Internet Archive's large cluster of Linux nodes, it archives new versions of websites on occasion. Sites can be captured manually by entering a website's URL into the search box, provided that the website allows the Wayback Machine to "crawl" it and save the data. Software has been developed to "crawl" the web and download all publicly accessible World Wide Web pages, the Gopher hierarchy, the Netnews bulletin board system, downloadable software.

The information collected by these "crawlers" does not include all the information available on the Internet, since much of the data is restricted by the publisher or stored in databases that are not accessible. To overcome inconsistencies in cached websites, was developed in 2005 by the Internet Archive as a means of allowing institutions and content creators to voluntarily harvest and preserve collections of digital content, create digital archives. Crawls are contributed from various sources, some imported from third parties and others generated internally by the Archive. For example, crawls are contributed by the Sloan Foundation and Alexa, crawls run by IA on behalf of NARA and the Internet Memory Foundation, mirrors of Common Crawl; the "Worldwide Web Crawls" have capture the global Web. The frequency of snapshot captures varies per website. Websites in the "Worldwide Web Crawls" are included in a "crawl list", with the site archived once per crawl. A crawl can take months or years to complete depending on size.

For example, "Wide Crawl Number 13" started on January 9, 2015, completed on July 11, 2016. However, there may be multiple crawls ongoing at any one time, a site might be included in more than one crawl list, so how a site is crawled varies widely; as of October 2019, users are limited to 5 archival retrievals per minute. As technology has developed over the years, the storage capacity of the Wayback Machine has grown. In 2003, after only two years of public access, the Wayback Machine was growing at a rate of 12 terabytes/month; the data is stored on PetaBox rack systems custom designed by Internet Archive staff. The first 100TB rack became operational in June 2004, although it soon became clear that they would need much more storage than that; the Internet Archive migrated its customized storage architecture to Sun Open Storage in 2009, hosts a new data center in a Sun Modular Datacenter on Sun Microsystems' California campus. As of 2009, the Wayback Machine contained three petabytes of data and was growing at a rate of 100 terabytes each month.

A new, improved version of the Wayback Machine, with an updated interface and a fresher index of archived content, was made available for public testing in 2011. In March that year, it was said on the Wayback Machine forum that "the Beta of the new Wayback Machine has a more complete and up-to-date index of all crawled materials into 2010, will continue to be updated regularly; the index driving the classic Wayback Machine only has a little bit of material past 2008, no further index updates are planned, as it will be phased out this year." In 2011, the Internet Archive installed their sixth pair of PetaBox racks which increased the Wayback Machine's storage capacity by 700 terabytes. In January 2013, the company announced a ground-breaking milestone of 240 billion URLs. In October 2013, the company announced the "Save a Page" feature which allows any Internet user to archive the contents of a URL; this became a threat of abuse by the service for hosting malicious binaries. As of December 2014, the Wayback Machine contained 435 billion web pages—almost nine petabytes of data, was growing at about 20 terabytes a week.

As of July 2016, the Wayback Machine contained around 15 petabytes of data. As of September

Surface properties of transition metal oxides

Transition metal oxides are compounds composed of oxygen atoms bound to transition metals. They are utilized for their catalytic activity and semiconductive properties. Transition metal oxides are frequently used as pigments in paints and plastics, most notably titanium dioxide. Transition metal oxides have a wide variety of surface structures which affect the surface energy of these compounds and influence their chemical properties; the relative acidity and basicity of the atoms present on the surface of metal oxides are affected by the coordination of the metal cation and oxygen anion, which alter the catalytic properties of these compounds. For this reason, structural defects in transition metal oxides influence their catalytic properties; the acidic and basic sites on the surface of metal oxides are characterized via infrared spectroscopy, calorimetry among other techniques. Transition metal oxides can undergo photo-assisted adsorption and desorption that alter their electrical conductivity.

One of the more researched properties of these compounds is their response to electromagnetic radiation, which makes them useful catalysts for redox reactions, isotope exchange and specialized surfaces. There is little known about the surface structures of transition metal oxides, but their bulk crystal structures are well researched; the approach to determine the surface structure is to assume the oxides are ideal crystal, where the bulk atomic arrangement is maintained up to and including the surface plane. The surfaces will be generated by cleavages along the planes of the bulk crystal structure. However, when a crystal is cleaved along a particular plane, the position of surface ions will differ from the bulk structure. Newly created surfaces will tend to minimize the surface Gibbs energy, through reconstruction, to obtain the most thermodynamically stable surface; the stability of these surface structures are evaluated by surface polarity, the degree of coordinative unsaturation and defect sites.

The oxide crystal structure is based on a close-pack array of oxygen anions, with metal cations occupying interstitial sites. The close-packed arrays, such as face-centered-cubic and hexagonal-close packed, have both octahedral and tetrahedral interstices. Many compounds from first row of transition metal monoxides, from TiO to NiO, have a rocksalt structure; the rock salt structure is generated by filling all octahedral sites with cations in an oxygen anion fcc array. The majority of transition metal dioxides have the rutile structure, seen to the right. Materials of this stoichiometry exist for Ti, Cr, V and Mn in the first row transition metal and for Zr to Pd in the second; the rutile structure is generated by filling half of the octahedral sites with cations of the hcp oxygen anion array. Few transition metals can achieve the +6 oxidation state in an oxide, so oxides with the stoichiometry MO3 are rare; the structure of binary oxides can be predicted on the basis of the relative sizes of the metal and oxide ions and the filling of holes in a close packed oxide lattice.

However, the predictions of structure are more difficult for ternary oxides. The combination of two or more metals in an oxide creates a lot of structural possibilities; the stoichiometry of ternary oxide may be changed by varying the proportions of the two components and their oxidation states. For example, at least twenty ternary oxide phases are formed between strontium and vanadium including SrV2O6, Sr2V2O5, SrVO3 and Sr2VO4; the structural chemistry of ternary and more complex oxides is an extensive subject, but there are a few structures that are adopted by ternary oxides, such as the perovskite structure. The perovskite structure, ABO3, is the most widespread ternary phase; the perovskite structure is found for ternary oxides formed with one large and one small cation. In this structure, there is a simple cubic array of B cations, with the A cations occupying the center of the cube, the oxide atoms are sited at the center of the 12 edges of the simple cube. Since little is known about the surface Gibbs energy of transition metal oxides, polarity of the surface and the degree of coordinative unsaturation of a surface cation are used to compare the stabilities of different surface structures.

Defect sites can have a huge impact on the surface stability. When a crystal of a binary oxide is cleaved to generate two new surfaces, each solid’s charge remains neutral. However, the structure of the two newly created surfaces may not be the same. If the structures are identical, the surface will be dipoleless and is considered a nonpolar surface. If the structures are different, the surface will have a strong dipole and is considered a polar surface. Examples of nonpolar surfaces include the rocksalt surface, the rutile, surfaces and the pervoskite surface. An example of a polar surface is the rocksalt surface. In general, a polar surface is less stable than a nonpolar surface because a dipole moment increases the surface Gibbs energy. Oxygen polar surfaces are more stable than metal polar surfaces because oxygen ions are more polarizable, which lowers the surface energy; the degree of coordinative unsaturation of a surface cation measures the number of bonds involving the cation that have to be broken to form a surface.

As the degree of coordinative unsaturation increases, more bonds are broken and the metal cation becomes destabilized. The destabilization of the cation increases the surface Gibbs energy, which decreases the overall stability. For example, the rutile surface is more stable than the rutile and surfaces because it has a lower degree of coordinative unsaturation. Defect sites can interfere with the stability of metal oxid

Pedro Duque

Pedro Francisco Duque Duque, OF, OMSE is a Spanish astronaut and aeronautics engineer who serves as Minister of Science and Universities of the Government of Spain. He is Member of the Congress of Deputies since May 2019, he was the first Spanish astronaut. He was born in Madrid in 1963, as the son of an agricultural engineer who worked as an air traffic controller, a housewife from Badajoz. In 1986 Duque earned a degree in Aeronautical Engineering from the Universidad Politécnica de Madrid. In 1986 he worked for GMV and for the European Space Agency for six years before being selected as an astronaut candidate in 1992. Duque underwent training in the United States, his first spaceflight was as a mission specialist aboard space shuttle mission STS-95, during which Duque supervised ESA experimental modules. In October 2003, Duque visited the International Space Station on board of a Soyuz TMA Ship for several days during a crew changeover; the scientific program of this visit was called by ESA/Spain Misión Cervantes.

In 2003 he started working at UPM School of Aeronautical Engineers as head of operations of the Spanish USOC lecturing students on space science and operations. In 2006 Duque was named managing director of Deimos Imaging, a private company, that in 2009 put in orbit the first Spanish earth observation satellite with uses in agriculture, forestry wildfire detection and control. In 2011 he was named CEO of the Company. In October 2011 Duque returned to his position in the European Space Agency, retaking his position as an astronaut; until 2015 he was the leader of the Flight Operations Office, with responsibility for ESA operations in the ISS. After that he assumed the responsibility of the review of future ESA manned flights, within the ESA's astronaut corps. After the success of the motion of no confidence against the government of Mariano Rajoy in June 2018, President Pedro Sanchez named Pedro Duque Minister of Science and Universities. In April 2019, Duque announce that his ministry was going to increase Spain's contribution to the European Space Agency by €701 million between 2020 and 2026 to ensure a proper contribution regarding the Spanish economy size.

As the rest of the Sánchez cabinet, Duque ran for the April 2019 general election, being elected MP for Alicante. Order Of Friendship of the Russian Federation Grand Cross of Aeronautical Merit Prince of Asturias Award of International Cooperation Doctor Honoris Causa of the Technical University of Valencia Medal "For Merit in Space Exploration" of the Russian federation Doctor Honoris Causa of the European University of Madrid Doctor Honoris Causa of the National University of Distance Education Doctor Honoris Causa of the University of Almería List of astronauts List of Hispanic astronauts ESA profile page NASA Biography Spacefacts biography of Pedro Duque Events and Conferences Telescope Hosting site in Nerpio, Spain España: quién es Pedro Duque, el primer astronauta español y nuevo ministro de Ciencia