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Casimir element
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Symmetric invariant tensors of simple Lie algebras
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A Casimir element of order m corresponds to a symmetric invariant tensor of the same order via C(m)=κi1i2⋯imXi1Xi2⋯Xim . Constructing and relating Casimir elements is equivalent to doing the same for symmetric invariant tensors.
Construction of symmetric invariant tensors Symmetric invariant tensors may be constructed as symmetrized traces in the defining representation Tr (X(i1Xi2⋯Xim)) where indices are raised and lowered by the Killing form, and symmetrized under all permutations.
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Casimir element
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Symmetric invariant tensors of simple Lie algebras
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It is also possible to construct symmetric invariant tensors from the antisymmetric invariant tensors of the type Ωi1i2⋯i2m−1(2m−1)=fi1[i2j1⋯fi2m−3i2m−2]jm−1kj1⋯jm−1i2m−1(m) The symmetric invariant tensor ti1i2⋯im(m)=Ωj1j2⋯j2m−2im(2m−1)fi1j1j2⋯fim−1j2m−2j2m−3 is traceless for m>2 . Such invariant tensors are orthogonal to one another in the sense that ti1i2⋯im(m)(t(n))i1i2⋯imim+1⋯in=0 if n>m In the case of the simple Lie algebra Al=sll+1 , let us introduce the fully symmetric tensor of order three dijk such that, in the defining representation, XiXj=2ℓ+1δij+fijkXk+dijkXk Then the Sudbery symmetric invariant tensors are di1i2(2)=δi1i2 di1i2i3(3)=di1i2i3 di1i2i3i4(4)=d(i1i2jdi3i4)j di1i2i3i4i5(5)=d(i1i2jdji3kdi4i5)k Relations between symmetric invariant tensors For a simple Lie algebra of rank r , there are r algebraically independent symmetric invariant tensors. Therefore, any such tensor can be expressed in terms of r given tensors. There is a systematic method for deriving complete sets of identities between symmetric invariant tensors.In the case of the Lie algebra Al , the symmetric invariant tensors t(m) obey t(m>l+1)=0 . Reexpressing these tensors in terms of other families such as d(m) or k(m) gives rise to nontrivial relations within these other families. For example, the Sudbery tensors d(m>l+1) may be expressed in terms of d(2),⋯,d(l+1) , with relations of the type di1i2i3i4(4)=l=213δ(i1i2δi3i4) di1i2i3i4i5(5)=l=213d(i1i2i3δi4i5) di1i2i3i4i5(5)=l=323d(i1i2i3δi4i5) Structure constants also obey identities that are not directly related to symmetric invariant tensors, for example 3dabedcde−facefbde−fadefbce=l=2δacδbd+δadδbc−δabδcd
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Casimir element
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Examples
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Case of sl(2) The Lie algebra sl2C consists of two-by-two complex matrices with zero trace. There are three standard basis elements, e ,f , and h , with e=[0100],f=[0010],h=[100−1].
The commutators are [e,f]=h,[h,f]=−2f,[h,e]=2e.
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Casimir element
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Examples
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One can show that the Casimir element is Case of so(3) The Lie algebra so(3) is the Lie algebra of SO(3), the rotation group for three-dimensional Euclidean space. It is simple of rank 1, and so it has a single independent Casimir. The Killing form for the rotation group is just the Kronecker delta, and so the Casimir invariant is simply the sum of the squares of the generators Lx,Ly,Lz of the algebra. That is, the Casimir invariant is given by L2=Lx2+Ly2+Lz2.
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Casimir element
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Examples
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Consider the irreducible representation of so(3) in which the largest eigenvalue of Lz is ℓ , where the possible values of ℓ are {\textstyle 0,\,{\frac {1}{2}},\,1,\,{\frac {3}{2}},\,\ldots } . The invariance of the Casimir operator implies that it is a multiple of the identity operator I . This constant can be computed explicitly, giving the following result L2=Lx2+Ly2+Lz2=ℓ(ℓ+1)I.
In quantum mechanics, the scalar value ℓ is referred to as the total angular momentum. For finite-dimensional matrix-valued representations of the rotation group, ℓ always takes on integer values (for bosonic representations) or half-integer values (for fermionic representations).
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Casimir element
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Examples
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For a given value of ℓ , the matrix representation is (2ℓ+1) -dimensional. Thus, for example, the three-dimensional representation for so(3) corresponds to ℓ=1 , and is given by the generators Lx=i(00000−1010);Ly=i(001000−100);Lz=i(0−10100000), where the factors of i are needed for agreement with the physics convention (used here) that the generators should be skew-self-adjoint operators.The quadratic Casimir invariant can then easily be computed by hand, with the result that L2=Lx2+Ly2+Lz2=2(100010001) as ℓ(ℓ+1)=2 when ℓ=1 This is what is meant when we say that the eigenvalues of the Casimir operator is used to classify the irreducible representations of a Lie algebra (and of an associated Lie Group Lie Group): two irreducible representations of a Lie Algebra are equivalent if and only if their Casimir element have the same eigenvalue. In this case, the irreps of so(3) are completely determined by the value of ℓ , or equivalently, by the value of ℓ(ℓ+1) Similarly, the two dimensional representation has a basis given by the Pauli matrices, which correspond to spin 1⁄2, and one can again check the formula for the Casimir by direct computation.
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PLATO (computer system)
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PLATO (computer system)
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PLATO (Programmed Logic for Automatic Teaching Operations), also known as Project Plato and Project PLATO, was the first generalized computer-assisted instruction system. Starting in 1960, it ran on the University of Illinois' ILLIAC I computer. By the late 1970s, it supported several thousand graphics terminals distributed worldwide, running on nearly a dozen different networked mainframe computers. Many modern concepts in multi-user computing were first developed on PLATO, including forums, message boards, online testing, email, chat rooms, picture languages, instant messaging, remote screen sharing, and multiplayer video games.
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PLATO (computer system)
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PLATO (computer system)
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PLATO was designed and built by the University of Illinois and functioned for four decades, offering coursework (elementary through university) to UIUC students, local schools, prison inmates, and other universities. Courses were taught in a range of subjects, including Latin, chemistry, education, music, Esperanto, and primary mathematics. The system included a number of features useful for pedagogy, including text overlaying graphics, contextual assessment of free-text answers, depending on the inclusion of keywords, and feedback designed to respond to alternative answers.
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PLATO (computer system)
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PLATO (computer system)
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Rights to market PLATO as a commercial product were licensed by Control Data Corporation (CDC), the manufacturer on whose mainframe computers the PLATO IV system was built. CDC President William Norris planned to make PLATO a force in the computer world, but found that marketing the system was not as easy as hoped. PLATO nevertheless built a strong following in certain markets, and the last production PLATO system was in use until 2006.
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PLATO (computer system)
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Innovations
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PLATO was either the first or an earlier example of many now-common technologies: Hardware Plasma display (PLATO IV), c. 1964. Donald Bitzer Touchscreen (PLATO IV), c. 1964. Donald Bitzer Gooch Synthetic Woodwind (music device for the terminal), c. 1972 Display Graphics Charset Editor (bitmapped picture drawing program) storing in downloadable fonts.
Show Display Mode (graphics application generator (TUTOR)), 1975.
Online communities Pad (General-purpose computer message board), 1973 Notesfiles (precursor to newsgroups), 1973.
Talkomatic (real-time text-based chat, with six rooms each allowing five participants), 1973 Term-talk (1:1 chat) Screen software sharing: Monitor Mode, 1974, used by instructors to help students, precursor of Timbuktu.
Common Computer Game Genres, including many of the early (first?) real time multi-player games Multiplayer Games Spacewar! (Multiplayer space battle game), c. 1969. Rick Bloome Dungeon Games dnd (dungeon crawl game), 1974–75. Included the first video game boss.
Pedit5, c. 1974, likely the first graphical dungeon computer game.
Avatar (60-player 2.5-D graphical Multi-User Dungeon (MUD)), c. 1978.
Space combat Empire (30 person multi-player inter-terminal 2-D real-time space simulation), c. 1974 Spasim (32-player first-person 3D space battle game), c. 1974 Flight Simulation: Fortner, Brand (1974), Airfight (3-D flight simulator); this probably inspired UIUC student Bruce Artwick to start Sublogic which was acquired and later became Microsoft Flight Simulator.
Military simulations: Haefeli, John (c. 1975), Panther (3-D tank simulation).
3D Maze games: Wallace, Bruce (1975), Build-Up, based on a story by J. G. Ballard, the first PLATO 3-D walkthru maze game.
Quest Simulation: Think15 (2-D outdoor wilderness quest simulation), c. 1977, like Trek with monsters, trees, treasures.
Solitaire: Alfille, Paul (1979), Freecell solitaire, Lockard, Brodie (1981), Mahjong solitaire Educational Answer Judging Machinery (set of about 25 commands in TUTOR that made it easy to test a student's understanding of a complex concept).
Training systems; Kaven, Luke (1979), The Procedure Logic Simulator (PLS) (intelligent CAI authoring system) an ambitious ICAI programming system featuring partial-order plans, used to train Con Edison steam plant operators.
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PLATO (computer system)
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History
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Impetus Before the 1944 G.I. Bill that provided free college education to World War II veterans, higher education was limited to a minority of the US population, though only 9% of the population was in the military. The trend towards greater enrollment was notable by the early 1950s, and the problem of providing instruction for the many new students was a serious concern to university administrators. To wit, if computerized automation increased factory production, it could do the same for academic instruction.
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PLATO (computer system)
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History
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The USSR's 1957 launching of the Sputnik I artificial satellite energized the United States' government into spending more on science and engineering education. In 1958, the U.S. Air Force's Office of Scientific Research had a conference about the topic of computer instruction at the University of Pennsylvania; interested parties, notably IBM, presented studies.
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PLATO (computer system)
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History
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Genesis Around 1959, Chalmers W. Sherwin, a physicist at the University of Illinois, suggested a computerised learning system to William Everett, the engineering college dean, who, in turn, recommended that Daniel Alpert, another physicist, convene a meeting about the matter with engineers, administrators, mathematicians, and psychologists. After weeks of meetings they were unable to agree on a single design. Before conceding failure, Alpert mentioned the matter to laboratory assistant Donald Bitzer, who had been thinking about the problem, suggesting he could build a demonstration system.
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PLATO (computer system)
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History
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Project PLATO was established soon afterwards, and in 1960, the first system, PLATO I, operated on the local ILLIAC I computer. It included a television set for display and a special keyboard for navigating the system's function menus; PLATO II, in 1961, featured two users at once, one of the first implementations of multi-user time-sharing.The PLATO system was re-designed, between 1963 and 1969; PLATO III allowed "anyone" to design new lesson modules using their TUTOR programming language, conceived in 1967 by biology graduate student Paul Tenczar. Built on a CDC 1604, given to them by William Norris, PLATO III could simultaneously run up to 20 terminals, and was used by local facilities in Champaign–Urbana that could enter the system with their custom terminals. The only remote PLATO III terminal was located near the state capitol in Springfield, Illinois at Springfield High School. It was connected to the PLATO III system by a video connection and a separate dedicated line for keyboard data.
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PLATO (computer system)
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History
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PLATO I, II, and III were funded by small grants from a combined Army-Navy-Air Force funding pool. By the time PLATO III was in operation, everyone involved was convinced it was worthwhile to scale up the project. Accordingly, in 1967, the National Science Foundation granted the team steady funding, allowing Alpert to set up the Computer-based Education Research Laboratory (CERL) at the University of Illinois Urbana–Champaign campus. The system was capable of supporting 20 time-sharing terminals.
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PLATO (computer system)
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History
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Multimedia experiences (PLATO IV) In 1972, with the introduction of PLATO IV, Bitzer declared general success, claiming that the goal of generalized computer instruction was now available to all. However, the terminals were very expensive (about $12,000). The PLATO IV terminal had several major innovations: Plasma Display Screen: Bitzer's orange plasma display, incorporated both memory and bitmapped graphics into one display. The display was a 512×512 bitmap, with both character and vector plotting done by hardwired logic. It included fast vector line drawing capability, and ran at 1260 baud, rendering 60 lines or 180 characters per second. . Users could provide their own characters to support rudimentary bitmap graphics.
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PLATO (computer system)
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History
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Touch panel: A 16×16 grid infrared touch panel, allowing students to answer questions by touching anywhere on the screen.
Microfiche images: Compressed air powered a piston-driven microfiche image selector that permitted colored images to be projected on the back of the screen under program control.
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PLATO (computer system)
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History
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A hard drive for Audio snippets: The random-access audio device used a magnetic disc with a capacity to hold 17 total minutes of pre-recorded audio. It could retrieve for playback any of 4096 audio clips within 0.4 seconds. By 1980, the device was being commercially produced by Education and Information Systems, Incorporated with a capacity of just over 22 minutes.
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PLATO (computer system)
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History
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A Votrax voice synthesizer The Gooch Synthetic Woodwind (named after inventor Sherwin Gooch), a synthesizer that offered four-voice music synthesis to provide sound in PLATO courseware. This was later supplanted on the PLATO V terminal by the Gooch Cybernetic Synthesizer, which had sixteen voices that could be programmed individually, or combined to make more complex sounds.Bruce Parello, a student at the University of Illinois in 1972, created the first digital emojis on the PLATO IV system.
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PLATO (computer system)
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History
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Influence on PARC and Apple Early in 1972, researchers from Xerox PARC were given a tour of the PLATO system at the University of Illinois. At this time, they were shown parts of the system, such as the Insert Display/Show Display (ID/SD) application generator for pictures on PLATO (later translated into a graphics-draw program on the Xerox Star workstation); the Charset Editor for "painting" new characters (later translated into a "Doodle" program at PARC); and the Term Talk and Monitor Mode communications programs. Many of the new technologies they saw were adopted and improved upon, when these researchers returned to Palo Alto, California. They subsequently transferred improved versions of this technology to Apple Inc.
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PLATO (computer system)
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History
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CDC years As PLATO IV reached production quality, William Norris (CDC) became increasingly interested in it as a potential product. His interest was twofold. From a strict business perspective, he was evolving Control Data into a service-based company instead of a hardware one, and was increasingly convinced that computer-based education would become a major market in the future. At the same time, Norris was troubled by the unrest of the late 1960s, and felt that much of it was due to social inequalities that needed to be addressed. PLATO offered a solution by providing higher education to segments of the population that would otherwise never be able to afford a university education.
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PLATO (computer system)
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History
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Norris provided CERL with machines on which to develop their system in the late 1960s. In 1971, he set up a new division within CDC to develop PLATO "courseware", and eventually many of CDC's own initial training and technical manuals ran on it. In 1974, PLATO was running on in-house machines at CDC headquarters in Minneapolis, and in 1976, they purchased the commercial rights in exchange for a new CDC Cyber machine.
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PLATO (computer system)
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History
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CDC announced the acquisition soon after, claiming that by 1985, 50% of the company's income would be related to PLATO services. Through the 1970s, CDC tirelessly promoted PLATO, both as a commercial tool and one for re-training unemployed workers in new fields. Norris refused to give up on the system, and invested in several non-mainstream courses, including a crop-information system for farmers, and various courses for inner-city youth. CDC even went as far as to place PLATO terminals in some shareholder's houses, to demonstrate the concept of the system.
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PLATO (computer system)
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History
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In the early 1980s, CDC started heavily advertising the service, apparently due to increasing internal dissent over the now $600 million project, taking out print and even radio ads promoting it as a general tool. The Minneapolis Tribune was unconvinced by their ad copy and started an investigation of the claims. In the end, they concluded that while it was not proven to be a better education system, everyone using it nevertheless enjoyed it, at least. An official evaluation by an external testing agency ended with roughly the same conclusions, suggesting that everyone enjoyed using it, but it was essentially equal to an average human teacher in terms of student advancement.
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PLATO (computer system)
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History
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Of course, a computerized system equal to a human should have been a major achievement, the very concept for which the early pioneers in CBT were aiming. A computer could serve all the students in a school for the cost of maintaining it, and wouldn't go on strike. However, CDC charged $50 an hour for access to their data center, in order to recoup some of their development costs, making it considerably more expensive than a human on a per-student basis. PLATO was, therefore, a failure as a profitable commercial enterprise, although it did find some use in large companies and government agencies willing to invest in the technology.
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PLATO (computer system)
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History
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An attempt to mass-market the PLATO system was introduced in 1980 as Micro-PLATO, which ran the basic TUTOR system on a CDC "Viking-721" terminal and various home computers. Versions were built for the TI-99/4A, Atari 8-bit family, Zenith Z-100 and, later, Radio Shack TRS-80 and IBM Personal Computer. Micro-PLATO could be used stand-alone for normal courses, or could connect to a CDC data center for multiuser programs. To make the latter affordable, CDC introduced the Homelink service for $5 an hour.
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PLATO (computer system)
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History
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Norris continued to praise PLATO, announcing that it would be only a few years before it represented a major source of income for CDC as late as 1984. In 1986, Norris stepped down as CEO, and the PLATO service was slowly killed off. He later claimed that Micro-PLATO was one of the reasons PLATO got off-track. They had started on the TI-99/4A, but then Texas Instruments pulled the plug and they moved to other systems like the Atari, who soon did the same. He felt that it was a waste of time anyway, as the system's value was in its online nature, which Micro-PLATO lacked initially.
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PLATO (computer system)
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History
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Bitzer was more forthright about CDC's failure, blaming their corporate culture for the problems. He noted that development of the courseware was averaging $300,000 per delivery hour, many times what the CERL was paying for similar products. This meant that CDC had to charge high prices in order to recoup their costs, prices that made the system unattractive. The reason, he suggested, for these high prices was that CDC had set up a division that had to keep itself profitable via courseware development, forcing them to raise the prices in order to keep their headcount up during slow periods.
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PLATO (computer system)
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History
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PLATO V: multimedia Intel 8080 microprocessors were introduced in the new PLATO V terminals. They could download small software modules and execute them locally. It was a way to augment the PLATO courseware with rich animation and other sophisticated capabilities.
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PLATO (computer system)
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Online community
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Although PLATO was designed for computer-based education, perhaps its most enduring legacy is its place in the origins of online community. This was made possible by PLATO's groundbreaking communication and interface capabilities, features whose significance is only lately being recognized by computer historians. PLATO Notes, created by David R. Woolley in 1973, was among the world's first online message boards, and years later became the direct progenitor of Lotus Notes.PLATO's plasma panels were well suited to games, although its I/O bandwidth (180 characters per second or 60 graphic lines per second) was relatively slow. By virtue of 1500 shared 60-bit variables per game (initially), it was possible to implement online games. Because it was an educational computer system, most of the user community were keenly interested in games.
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PLATO (computer system)
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Online community
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In much the same way that the PLATO hardware and development platform inspired advances elsewhere (such as at Xerox PARC and MIT), many popular commercial and Internet games ultimately derived their inspiration from PLATO's early games. As one example, Castle Wolfenstein by PLATO alum Silas Warner was inspired by PLATO's dungeon games (see below), in turn inspiring Doom and Quake. Thousands of multiplayer online games were developed on PLATO from around 1970 through the 1980s, with the following notable examples: Daleske's Empire a top-view multiplayer space game based on Star Trek. Either Empire or Colley's Maze War is the first networked multiplayer action game. It was ported to Trek82, Trek83, ROBOTREK, Xtrek, and Netrek, and also adapted (without permission) for the Apple II computer by fellow PLATO alum Robert Woodhead (of Wizardry fame), as a game called Galactic Attack.
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PLATO (computer system)
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Online community
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The original Freecell by Alfille (from Baker's concept).
Fortner's Airfight, probably the direct inspiration for (PLATO alum) Bruce Artwick's Microsoft Flight Simulator.
Haefeli and Bridwell's Panther (a vector graphics-based tankwar game, anticipating Atari's Battlezone).
Many other first-person shooters, most notably Bowery's Spasim and Witz and Boland's Futurewar, believed to be the first FPS.
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PLATO (computer system)
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Online community
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Countless games inspired by the role-playing game Dungeons & Dragons, including the original Rutherford/Whisenhunt and Wood dnd (later ported to the PDP-10/11 by Lawrence, who earlier had visited PLATO). and is believed to be the first dungeon crawl game and was followed by: Moria, Rogue, Dry Gulch (a western-style variation), and Bugs-n-Drugs (a medical variation)—all presaging MUDs (Multi-User Domains) and MOOs (MUDs, Object Oriented) as well as popular first-person shooters like Doom and Quake, and MMORPGs (Massively multiplayer online role-playing game) like EverQuest and World of Warcraft. Avatar, PLATO's most popular game, is one of the world's first MUDs and has over 1 million hours of use.. The games Doom and Quake can trace part of their lineage back to PLATO programmer Silas Warner.PLATO's communication tools and games formed the basis for an online community of thousands of PLATO users, which lasted for well over twenty years. PLATO's games became so popular that a program called "The Enforcer" was written to run as a background process to regulate or disable game play at most sites and times – a precursor to parental-style control systems that regulate access based on content rather than security considerations.
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PLATO (computer system)
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Online community
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In September 2006 the Federal Aviation Administration retired its PLATO system, the last system that ran the PLATO software system on a CDC Cyber mainframe, from active duty. Existing PLATO-like systems now include NovaNET and Cyber1.org.
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PLATO (computer system)
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Online community
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By early 1976, the original PLATO IV system had 950 terminals giving access to more than 3500 contact hours of courseware, and additional systems were in operation at CDC and Florida State University. Eventually, over 12,000 contact hours of courseware was developed, much of it developed by university faculty for higher education. PLATO courseware covers a full range of high-school and college courses, as well as topics such as reading skills, family planning, Lamaze training and home budgeting. In addition, authors at the University of Illinois School of Basic Medical Sciences (now, the University of Illinois College of Medicine) devised a large number of basic science lessons and a self-testing system for first-year students. However the most popular "courseware" remained their multi-user games and role-playing video games such as dnd, although it appears CDC was uninterested in this market. As the value of a CDC-based solution disappeared in the 1980s, interested educators ported the engine first to the IBM PC, and later to web-based systems.
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PLATO (computer system)
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Custom character sets
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In the early 1970s, some people working in the modern foreign languages group at the University of Illinois began working on a set of Hebrew lessons, originally without good system support for leftward writing. In preparation for a PLATO demo in Tehran, that Bruce Sherwood would participate in, Sherwood worked with Don Lee to implement support for leftward writing, including Persian (Farsi), which uses the Arabic script. There was no funding for this work, which was undertaken only due to Sherwood's personal interest, and no curriculum development occurred for either Persian or Arabic. However, Peter Cole, Robert Lebowitz, and Robert Hart used the new system capabilities to re-do the Hebrew lessons. The PLATO hardware and software supported the design and use of one's own 8-by-16 characters, so most languages could be displayed on the graphics screen (including those written right-to-left).
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PLATO (computer system)
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University of Illinois School of Music PLATO Project (Technology and Research-based Chronology)
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A PLATO-compatible music language known as OPAL (Octave-Pitch-Accent-Length) was developed for these synthesizers, as well as a compiler for the language, two music text editors, a filing system for music binaries, programs to play the music binaries in real time, and print musical scores, and many debugging and compositional aids. A number of interactive compositional programs have also been written. Gooch's peripherals were heavily used for music education courseware as created, for example, by the University of Illinois School of Music PLATO Project.
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PLATO (computer system)
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University of Illinois School of Music PLATO Project (Technology and Research-based Chronology)
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From 1970 to 1994, the University of Illinois (U of I) School of Music explored the use of the Computer-based Education Research Laboratory (CERL) PLATO computer system to deliver online instruction in music. Led by G. David Peters, music faculty and students worked with PLATO’s technical capabilities to produce music-related instructional materials and experimented with their use in the music curriculum.Peters began his work on PLATO III. By 1972, the PLATO IV system made it technically possible to introduce multimedia pedagogies that were not available in the marketplace until years later.
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PLATO (computer system)
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University of Illinois School of Music PLATO Project (Technology and Research-based Chronology)
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Between 1974 and 1988, 25 U of I music faculty participated in software curriculum development and more than 40 graduate students wrote software and assisted the faculty in its use. In 1988, the project broadened its focus beyond PLATO to accommodate the increasing availability and use of microcomputers. The broader scope resulted in renaming the project to The Illinois Technology-based Music Project. Work in the School of Music continued on other platforms after the CERL PLATO system shutdown in 1994. Over the 24-year life of the music project, its many participants moved into educational institutions and into the private sector. Their influence can be traced to numerous multimedia pedagogies, products, and services in use today, especially by musicians and music educators.
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PLATO (computer system)
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University of Illinois School of Music PLATO Project (Technology and Research-based Chronology)
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Significant early efforts Pitch recognition/performance judging In 1969, G. David Peters began researching the feasibility of using PLATO to teach trumpet students to play with increased pitch and rhythmic precision. He created an interface for the PLATO III terminal. The hardware consisted of (1) filters that could determine the true pitch of a tone, and (2) a counting device to measure tone duration. The device accepted and judged rapid notes, two notes trilled, and lip slurs. Peters demonstrated that judging instrumental performance for pitch and rhythmic accuracy was feasible in computer-assisted instruction.
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PLATO (computer system)
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University of Illinois School of Music PLATO Project (Technology and Research-based Chronology)
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Rhythm notation and perception By 1970, a random access audio device was available for use with PLATO III.In 1972, Robert W. Placek conducted a study that used computer-assisted instruction for rhythm perception. Placek used the random access audio device attached to a PLATO III terminal for which he developed music notation fonts and graphics. Students majoring in elementary education were asked to (1) recognize elements of rhythm notation, and (2) listen to rhythm patterns and identify their notations. This was the first known application of the PLATO random-access audio device to computer-based music instruction.
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PLATO (computer system)
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University of Illinois School of Music PLATO Project (Technology and Research-based Chronology)
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Study participants were interviewed about the experience and found it both valuable and enjoyable. Of particular value was PLATO’s immediate feedback. Though participants noted shortcomings in the quality of the audio, they generally indicated that they were able to learn the basic skills of rhythm notation recognition.These PLATO IV terminal included many new devices and yielded two notable music projects: Visual diagnostic skills for instrumental music educators By the mid-1970s, James O. Froseth (University of Michigan) had published training materials that taught instrumental music teachers to visually identify typical problems demonstrated by beginning band students. For each instrument, Froseth developed an ordered checklist of what to look for (i.e., posture, embouchure, hand placement, instrument position, etc.) and a set of 35mm slides of young players demonstrating those problems. In timed class exercises, trainees briefly viewed slides and recorded their diagnoses on the checklists which were reviewed and evaluated later in the training session.
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PLATO (computer system)
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University of Illinois School of Music PLATO Project (Technology and Research-based Chronology)
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In 1978, William H. Sanders adapted Froseth’s program for delivery using the PLATO IV system. Sanders transferred the slides to microfiche for rear-projection through the PLATO IV terminal’s plasma display. In timed drills, trainees viewed the slides, then filled in the checklists by touching them on the display. The program gave immediate feedback and kept aggregate records. Trainees could vary the timing of the exercises and repeat them whenever they wished.
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PLATO (computer system)
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University of Illinois School of Music PLATO Project (Technology and Research-based Chronology)
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Sanders and Froseth subsequently conducted a study to compare traditional classroom delivery of the program to delivery using PLATO. The results showed no significant difference between the delivery methods for a) student post-test performance and b) their attitudes toward the training materials. However, students using the computer appreciated the flexibility to set their own practice hours, completed significantly more practice exercises, and did so in significantly less time.
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PLATO (computer system)
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University of Illinois School of Music PLATO Project (Technology and Research-based Chronology)
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Musical instrument identification In 1967, Allvin and Kuhn used a four-channel tape recorder interfaced to a computer to present pre-recorded models to judge sight-singing performances.In 1969, Ned C. Deihl and Rudolph E. Radocy conducted a computer-assisted instruction study in music that included discriminating aural concepts related to phrasing, articulation, and rhythm on the clarinet. They used a four-track tape recorder interfaced to a computer to provide pre-recorded audio passages. Messages were recorded on three tracks and inaudible signals on the fourth track with two hours of play/record time available. This research further demonstrated that computer-controlled audio with four-track tape was possible.In 1979, Williams used a digitally controlled cassette tape recorder that had been interfaced to a minicomputer (Williams, M.A. "A comparison of three approaches to the teaching of auditory-visual discrimination, sight singing and music dictation to college music students: A traditional approach, a Kodaly approach, and a Kodaly approach augmented by computer-assisted instruction," University of Illinois, unpublished). This device worked, yet was slow with variable access times.
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PLATO (computer system)
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University of Illinois School of Music PLATO Project (Technology and Research-based Chronology)
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In 1981, Nan T. Watanabe researched the feasibility of computer-assisted music instruction using computer-controlled pre-recorded audio. She surveyed audio hardware that could interface with a computer system.Random-access audio devices interfaced to PLATO IV terminals were also available. There were issues with sound quality due to dropouts in the audio. Regardless, Watanabe deemed consistent fast access to audio clips critical to the study design and selected this device for the study.
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PLATO (computer system)
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University of Illinois School of Music PLATO Project (Technology and Research-based Chronology)
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Watanabe’s computer-based drill-and-practice program taught elementary music education students to identify musical instruments by sound. Students listened to randomly selected instrument sounds, identified the instrument they heard, and received immediate feedback. Watanabe found no significant difference in learning between the group who learned through computer-assisted drill programs and the group receiving traditional instruction in instrument identification. The study did, however, demonstrate that use of random-access audio in computer-assisted instruction in music was feasible.
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PLATO (computer system)
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University of Illinois School of Music PLATO Project (Technology and Research-based Chronology)
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The Illinois Technology-based music project By 1988, with the spread of micro-computers and their peripherals, the University of Illinois School of Music PLATO Project was renamed The Illinois Technology-based Music Project. Researchers subsequently explored the use of emerging, commercially available technologies for music instruction until 1994.
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PLATO (computer system)
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University of Illinois School of Music PLATO Project (Technology and Research-based Chronology)
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Influences and impacts Educators and students used the PLATO System for music instruction at other educational institutions including Indiana University, Florida State University, and the University of Delaware. Many alumni of the University of Illinois School of Music PLATO Project gained early hands-on experience in computing and media technologies and moved into influential positions in both education and the private sector.
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PLATO (computer system)
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University of Illinois School of Music PLATO Project (Technology and Research-based Chronology)
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The goal of this system was to provide tools for music educators to use in the development of instructional materials, which might possibly include music dictation drills, automatically graded keyboard performances, envelope and timbre ear-training, interactive examples or labs in musical acoustics, and composition and theory exercises with immediate feedback. One ear-training application, Ottaviano, became a required part of certain undergraduate music theory courses at Florida State University in the early 1980s.
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PLATO (computer system)
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University of Illinois School of Music PLATO Project (Technology and Research-based Chronology)
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Another peripheral was the Votrax speech synthesizer, and a "say" instruction (with "saylang" instruction to choose the language) was added to the Tutor programming language to support text-to-speech synthesis using the Votrax.
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PLATO (computer system)
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Other Efforts
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One of CDC's greatest commercial successes with PLATO was an online testing system developed for National Association of Securities Dealers (now the Financial Industry Regulatory Authority), a private-sector regulator of the US securities markets. During the 1970s Michael Stein, E. Clarke Porter and PLATO veteran Jim Ghesquiere, in cooperation with NASD executive Frank McAuliffe, developed the first "on-demand" proctored commercial testing service. The testing business grew slowly and was ultimately spun off from CDC as Drake Training and Technologies in 1990. Applying many of the PLATO concepts used in the late 1970s, E. Clarke Porter led the Drake Training and Technologies testing business (today Thomson Prometric) in partnership with Novell, Inc. away from the mainframe model to a LAN-based client server architecture and changed the business model to deploy proctored testing at thousands of independent training organizations on a global scale. With the advent of a pervasive global network of testing centers and IT certification programs sponsored by, among others, Novell and Microsoft, the online testing business exploded. Pearson VUE was founded by PLATO/Prometric veterans E. Clarke Porter, Steve Nordberg and Kirk Lundeen in 1994 to further expand the global testing infrastructure. VUE improved on the business model by being one of the first commercial companies to rely on the Internet as a critical business service and by developing self-service test registration. The computer-based testing industry has continued to grow, adding professional licensure and educational testing as important business segments.
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PLATO (computer system)
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Other Efforts
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A number of smaller testing-related companies also evolved from the PLATO system. One of the few survivors of that group is The Examiner Corporation. Dr. Stanley Trollip (formerly of the University of Illinois Aviation Research Lab) and Gary Brown (formerly of Control Data) developed the prototype of The Examiner System in 1984.
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PLATO (computer system)
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Other Efforts
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In the early 1970s, James Schuyler developed a system at Northwestern University called HYPERTUTOR as part of Northwestern's MULTI-TUTOR computer assisted instruction system. This ran on several CDC mainframes at various sites.Between 1973 and 1980, a group under the direction of Thomas T. Chen at the Medical Computing Laboratory of the School of Basic Medical Sciences at the University of Illinois at Urbana Champaign ported PLATO's TUTOR programming language to the MODCOMP IV minicomputer. Douglas W. Jones, A.B. Baskin, Tom Szolyga, Vincent Wu and Lou Bloomfield did most of the implementation. This was the first port of TUTOR to a minicomputer and was largely operational by 1976. In 1980, Chen founded Global Information Systems Technology of Champaign, Illinois, to market this as the Simpler system. GIST eventually merged with the Government Group of Adayana Inc. Vincent Wu went on to develop the Atari PLATO cartridge.
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PLATO (computer system)
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Other Efforts
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CDC eventually sold the "PLATO" trademark and some courseware marketing segment rights to the newly formed The Roach Organization (TRO) in 1989. In 2000 TRO changed their name to PLATO Learning and continue to sell and service PLATO courseware running on PCs. In late 2012, PLATO Learning brought its online learning solutions to market under the name Edmentum.CDC continued development of the basic system under the name CYBIS (CYber-Based Instructional System) after selling the trademarks to Roach, in order to service their commercial and government customers. CDC later sold off their CYBIS business to University Online, which was a descendant of IMSATT. University Online was later renamed to VCampus.
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PLATO (computer system)
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Other Efforts
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The University of Illinois also continued development of PLATO, eventually setting up a commercial on-line service called NovaNET in partnership with University Communications, Inc. CERL was closed in 1994, with the maintenance of the PLATO code passing to UCI. UCI was later renamed NovaNET Learning, which was bought by National Computer Systems (NCS). Shortly after that, NCS was bought by Pearson, and after several name changes now operates as Pearson Digital Learning.
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PLATO (computer system)
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Other Efforts
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The Evergreen State College received several grants from CDC to implement computer language interpreters and associated programming instruction. Royalties received from the PLATO computer-aided instruction materials developed at Evergreen support technology grants and an annual lecture series on computer-related topics.
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PLATO (computer system)
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Other versions
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In South Africa During the period when CDC was marketing PLATO, the system began to be used internationally. South Africa was one of the biggest users of PLATO in the early 1980s. Eskom, the South African electrical power company, had a large CDC mainframe at Megawatt Park in the northwest suburbs of Johannesburg. Mainly this computer was used for management and data processing tasks related to power generation and distribution, but it also ran the PLATO software. The largest PLATO installation in South Africa during the early 1980s was at the University of the Western Cape, which served the "native" population, and at one time had hundreds of PLATO IV terminals all connected by leased data lines back to Johannesburg. There were several other installations at educational institutions in South Africa, among them Madadeni College in the Madadeni township just outside Newcastle.
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PLATO (computer system)
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Other versions
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This was perhaps the most unusual PLATO installation anywhere. Madadeni had about 1,000 students, all of them who were original inhabitants i.e. native population and 99.5% of Zulu ancestry. The college was one of 10 teacher preparation institutions in kwaZulu, most of them much smaller. In many ways Madadeni was very primitive. None of the classrooms had electricity and there was only one telephone for the whole college, which one had to crank for several minutes before an operator might come on the line. So an air-conditioned, carpeted room with 16 computer terminals was a stark contrast to the rest of the college. At times the only way a person could communicate with the outside world was through PLATO term-talk.
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PLATO (computer system)
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Other versions
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For many of the Madadeni students, most of whom came from very rural areas, the PLATO terminal was the first time they encountered any kind of electronic technology. Many of the first-year students had never seen a flush toilet before. There initially was skepticism that these technologically illiterate students could effectively use PLATO, but those concerns were not borne out. Within an hour or less most students were using the system proficiently, mostly to learn math and science skills, although a lesson that taught keyboarding skills was one of the most popular. A few students even used on-line resources to learn TUTOR, the PLATO programming language, and a few wrote lessons on the system in the Zulu language.
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PLATO (computer system)
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Other versions
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PLATO was also used fairly extensively in South Africa for industrial training. Eskom successfully used PLM (PLATO learning management) and simulations to train power plant operators, South African Airways (SAA) used PLATO simulations for cabin attendant training, and there were a number of other large companies as well that were exploring the use of PLATO.
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PLATO (computer system)
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Other versions
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The South African subsidiary of CDC invested heavily in the development of an entire secondary school curriculum (SASSC) on PLATO, but unfortunately as the curriculum was nearing the final stages of completion, CDC began to falter in South Africa—partly because of financial problems back home, partly because of growing opposition in the United States to doing business in South Africa, and partly due to the rapidly evolving microcomputer, a paradigm shift that CDC failed to recognize.
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PLATO (computer system)
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Other versions
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Cyber1 In August 2004, a version of PLATO corresponding to the final release from CDC was resurrected online. This version of PLATO runs on a free and open-source software emulation of the original CDC hardware called Desktop Cyber. Within six months, by word of mouth alone, more than 500 former users had signed up to use the system. Many of the students who used PLATO in the 1970s and 1980s felt a special social bond with the community of users who came together using the powerful communications tools (talk programs, records systems and notesfiles) on PLATO.The PLATO software used on Cyber1 is the final release (99A) of CYBIS, by permission of VCampus. The underlying operating system is NOS 2.8.7, the final release of the NOS operating system, by permission of Syntegra (now British Telecom [BT]), which had acquired the remainder of CDC's mainframe business. Cyber1 runs this software on the Desktop Cyber emulator. Desktop Cyber accurately emulates in software a range of CDC Cyber mainframe models and many peripherals.Cyber1 offers free access to the system, which contains over 16,000 of the original lessons, in an attempt to preserve the original PLATO communities that grew up at CERL and on CDC systems in the 1980s. The load average of this resurrected system is about 10–15 users, sending personal and notesfile notes, and playing inter-terminal games such as Avatar and Empire (a Star Trek-like game), which had both accumulated more than 1.0 million contact hours on the original PLATO system at UIUC.
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Eptapirone
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Eptapirone
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Eptapirone (F-11,440) is a very potent and highly selective 5-HT1A receptor full agonist of the azapirone family. Its affinity for the 5-HT1A receptor was reported to be 4.8 nM (Ki) (or 8.33 (pKi)), and its intrinsic activity approximately equal to that of serotonin (i.e., 100%).Eptapirone and related high-efficacy 5-HT1A full and super agonists such as befiradol and F-15,599 were developed under the hypothesis that the maximum exploitable therapeutic benefits of 5-HT1A receptor agonists might not be able to be seen without the drugs employed possessing sufficiently high intrinsic activity at the receptor. As 5-HT1A receptor agonism, based on animal and other research, looked extremely promising for the treatment of depression from a theoretical perspective, this idea was developed as a potential explanation for the relatively modest clinical effectiveness seen with already available 5-HT1A receptor agonists like buspirone and tandospirone, which act merely as weak-to-moderate partial agonists of the receptor.
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Eptapirone
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Animal studies
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In the Porsolt forced swimming test, eptapirone was found to suppress immobility more robustly than buspirone, ipsapirone, flesinoxan, paroxetine, and imipramine, which was suggestive of strong antidepressant-like effects. In this assay, unlike the other drugs screened, buspirone actually increased the immobility time with a single administration, while repeated administration decreased it, an effect that may have been related to buspirone's relatively weak intrinsic activity (~30%) at the 5-HT1A receptor and/or its preferential activation of 5-HT1A somatodendritic autoreceptors over postsynaptic receptors.After repeated administration, high dose paroxetine was able to rival the reduction in immobility seen with eptapirone. However, efficacy was seen on the first treatment with eptapirone, which suggested that eptapirone may have the potential for a more rapid onset of antidepressant effectiveness in comparison. Imipramine was unable to match the efficacy of eptapirone or high dose paroxetine, which was probably the result of the fact that higher doses were fatal.In the conflict procedure, eptapirone produced substantial increases in punished responding without affecting unpunished responding, which was suggestive of marked anxiolytic-like effects. In addition, the efficacy of eptapirone in this assay was more evident than that of buspirone, ipsapirone, and flesinoxan.
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Eptapirone
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Human studies
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Eptapirone has been assayed in humans in preclinical trials at an oral dose of 1.5 mg. In these studies, eptapirone reduced body temperature, prolonged REM sleep, increased cortisol and growth hormone levels, and produced side effects such as dizziness and drowsiness while being overall well tolerated. It peaked rapidly within 30–60 minutes and had an estimated half-life of two hours, with a total duration of approximately three hours.
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Conway triangle notation
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Conway triangle notation
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In geometry, the Conway triangle notation, named after John Horton Conway, allows trigonometric functions of a triangle to be managed algebraically. Given a reference triangle whose sides are a, b and c and whose corresponding internal angles are A, B, and C then the Conway triangle notation is simply represented as follows: sin sin sin C where S = 2 × area of reference triangle and cot φ.
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Conway triangle notation
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Conway triangle notation
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in particular cot cos A=b2+c2−a22 cot cos B=a2+c2−b22 cot cos C=a2+b2−c22 cot ω=a2+b2+c22 where ω is the Brocard angle. The law of cosines is used: cos A cot π3=S33 S2φ=Sφ2−S22SφSφ2=Sφ+Sφ2+S2 for values of φ where 0<φ<π Sϑ+φ=SϑSφ−S2Sϑ+SφSϑ−φ=SϑSφ+S2Sφ−Sϑ.
Furthermore the convention uses a shorthand notation for SϑSφ=Sϑφ and SϑSφSψ=Sϑφψ.
Hence: sin cos tan A=SSA a2=SB+SCb2=SA+SCc2=SA+SB.
Some important identities: cyclic SA=SA+SB+SC=Sω S2=b2c2−SA2=a2c2−SB2=a2b2−SC2 SBC=SBSC=S2−a2SASAC=SASC=S2−b2SBSAB=SASB=S2−c2SC SABC=SASBSC=S2(Sω−4R2)Sω=s2−r2−4rR where R is the circumradius and abc = 2SR and where r is the incenter, s=a+b+c2 and a+b+c=Sr.
Some useful trigonometric conversions: sin sin sin cos cos cos C=Sω−4R24R2 cyclic sin cyclic cos cyclic tan tan tan tan C.
Some useful formulas: cyclic cyclic a4=2(Sω2−S2) cyclic cyclic cyclic cyclic b2c2=Sω2+S2.
Some examples using Conway triangle notation: Let D be the distance between two points P and Q whose trilinear coordinates are pa : pb : pc and qa : qb : qc. Let Kp = apa + bpb + cpc and let Kq = aqa + bqb + cqc. Then D is given by the formula: cyclic a2SA(paKp−qaKq)2.
Using this formula it is possible to determine OH, the distance between the circumcenter and the orthocenter as follows: For the circumcenter pa = aSA and for the orthocenter qa = SBSC/a cyclic cyclic SBSC=S2.
Hence: cyclic cyclic cyclic cyclic cyclic cyclic cyclic cyclic cyclic a2−32(Sω−4R2)=3R2−12Sω−32Sω+6R2=9R2−2Sω.
This gives: OH=9R2−2Sω.
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All Sky Automated Survey for SuperNovae
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All Sky Automated Survey for SuperNovae
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The All Sky Automated Survey for SuperNovae (ASAS-SN) is an automated program to search for new supernovae and other astronomical transients, headed by astronomers from the Ohio State University, including Christopher Kochanek and Krzysztof Stanek. It has 20 robotic telescopes in both the northern and southern hemispheres. It can survey the entire sky approximately once every day.Initially, there were four ASAS-SN telescopes at Haleakala and another four at Cerro Tololo, a Las Cumbres Observatory site. Twelve more telescopes were deployed in 2017 in Chile, South Africa and Texas, with funds from the Gordon and Betty Moore Foundation, the Ohio State University, the Mount Cuba Astronomical Foundation, China, Chile, Denmark, and Germany. All the telescopes (Nikon telephoto 400mm/F2.8 lenses) have a diameter of 14 cm and ProLine PL230 CCD cameras. The pixel resolution in the cameras is 7.8 arc seconds, so follow-up observations on other telescopes are usually required to get a more accurate location.The main goal of the project is to look for bright supernovae, and its discoveries have included the most powerful supernova event ever discovered, ASASSN-15lh. However, other transient objects are frequently discovered, including nearby tidal disruption events (TDEs) (e.g., ASASSN-19bt), Galactic novae (e.g., ASASSN-16kt, ASASSN-16ma, and ASASSN-18fv), cataclysmic variables, and stellar flares, including several of the largest flares ever seen. In July 2017 ASAS-SN discovered its first comet, ASASSN1, and in July 2019 it provided crucial data for the near-Earth asteroid 2019 OK. It can detect new objects with magnitudes between 18 and 8.Objects discovered receive designations starting with ASASSN followed by a dash, a two digit year and letters, for example ASASSN-19bt.
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Thia-crown ether
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Thia-crown ether
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In organic chemistry, thia-crown ethers are organosulfur compounds which are the thia analogues of crown ethers (cyclic polyethers). That is, they have a sulfur atom (sulfide linkage, −S−) in place of each oxygen atom (ether linkage, −O−) around the ring. While the parent crown ethers have the formulae (CH2CH2O)n, the parent thia-crown ethers have the formulae (CH2CH2S)n, where n = 3, 4, 5, 6. They have trivial names "x-ane-Sy", where x and y are the number of atoms in the ring and the number of those atoms that are sulfur, respectively. Thia-crown ethers exhibit affinities for transition metals.
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Thia-crown ether
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Thia-crown ether
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1,4,7-Trithiacyclononane (9-ane-S3) is a tridentate ligand and forms complexes with many metal ions, including those considered hard, such as copper(II) and iron(II).Tetradentate 14-ane-S4 and the hexadentate 18-ane-S6 are also known.
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Open microfluidics
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Open microfluidics
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Microfluidics refers to the flow of fluid in channels or networks with at least one dimension on the micron scale. In open microfluidics, also referred to as open surface microfluidics or open-space microfluidics, at least one boundary confining the fluid flow of a system is removed, exposing the fluid to air or another interface such as a second fluid.
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Open microfluidics
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Types of open microfluidics
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Open microfluidics can be categorized into various subsets. Some examples of these subsets include open-channel microfluidics, paper-based, and thread-based microfluidics.
Open-channel microfluidics In open-channel microfluidics, a surface tension-driven capillary flow occurs and is referred to as spontaneous capillary flow (SCF). SCF occurs when the pressure at the advancing meniscus is negative. The geometry of the channel and contact angle of fluids has been shown to produce SCF if the following equation is true.
pfpw<cos(θ) Where pf is the free perimeter of the channel (i.e., the interface not in contact with the channel wall), and pw is the wetted perimeter (i.e., the walls in contact with the fluid), and θ is the contact angle of the fluid on the material of the device.
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Open microfluidics
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Types of open microfluidics
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Paper-based microfluidics Paper-based microfluidics utilizes the wicking ability of paper for functional readouts. Paper-based microfluidics is an attractive method because paper is cheap, easily accessible, and has a low environmental impact. Paper is also versatile because it is available in various thicknesses and pore sizes. Coatings such as wax have been used to guide flow in paper microfluidics. In some cases, dissolvable barriers have been used to create boundaries on the paper and control the fluid flow. The application of paper as a diagnostic tool has shown to be powerful because it has successfully been used to detect glucose levels, bacteria, viruses, and other components in whole blood. Cell culture methods within paper have also been developed. Lateral flow immunoassays, such as those used in pregnancy tests, are one example of the application of paper for point of care or home-based diagnostics. Disadvantages include difficulty of fluid retention and high limits of detection.
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Open microfluidics
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Types of open microfluidics
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Thread-based microfluidics Thread-based microfluidics, an offshoot from paper-based microfluidics, utilizes the same capillary based wicking capabilities. Common thread materials include nitrocellulose, rayon, nylon, hemp, wool, polyester, and silk. Threads are versatile because they can be woven to form specific patterns. Additionally, two or more threads can converge together in a knot bringing two separate ‘streams’ of fluid together as a reagent mixing method. Threads are also relatively strong and difficult to break from handling which makes them stable over time and easy to transport. Thread-based microfluidics has been applied to 3D tissue engineering and analyte analysis.
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Open microfluidics
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Capillary filaments in open microfluidics
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Open capillary microfluidics are channels that expose fluids to open air by excluding the ceiling and/or floor of the channel. Rather than rely on using pumps or syringes to maintain flow, open capillary microfluidics uses surface tension to facilitate the flow. The elimination of and infusion source reduces the size of the device and associated apparatus, along with other aspects that could obstruct their use. The dynamics of capillary-driven flow in open microfluidics are highly reliant on two types of geometric channels commonly known as either rectangular U-grooves or triangular V-grooves. The geometry of the channels dictates the flow along the interior walls fabricated with various ever-evolving processes.
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Open microfluidics
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Capillary filaments in open microfluidics
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Capillary filaments in U-groove Rectangular open-surface U-grooves are the easiest type of open microfluidic channel to fabricate. This design can maintain the same order of magnitude velocity in comparison to V-groove. Channels are made of glass or high clarity glass substitutes such as polymethyl methacrylate (PMMA), polycarbonate (PC), or cyclic olefin copolymer (COC). To eliminate the remaining resistance after etching, channels are given hydrophilic treatment using oxygen plasma or deep reactive-ion etching(DRIE).
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Open microfluidics
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Capillary filaments in open microfluidics
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Capillary filaments in V-groove V-groove, unlike U-groove, allows for a variety of velocities depending on the groove angle. V-grooves with sharp groove angle result in the interface curvature at the corners explained by reduced Concus-Finn conditions. In a perfect inner corner of a V-groove, the filament will advance indefinitely in the groove allowing the formation of capillary filament depending on the wetting conditions. The width of the groove plays an important role in controlling the fluid flow. The narrower the V-groove is, the better the capillary flow of liquids is even for highly viscous liquids such as blood; this effect has been used to produce an autonomous assay. The fabrication of a V-groove is more difficult than a U-groove as it poses a higher risk for faulty construction, since the corner has to be tightly sealed.
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Open microfluidics
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Advantages
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One of the main advantages of open microfluidics is ease of accessibility which enables intervention (i.e., for adding or removing reagents) to the flowing liquid in the system. Open microfluidics also allows simplicity of fabrication thus eliminating the need to bond surfaces. When one of the boundaries of a system is removed, a larger liquid-gas interface results, which enables liquid-gas reactions. Open microfluidic devices enable better optical transparency because at least one side of the system is not covered by the material which can reduce autofluorescence during imaging. Further, open systems minimize and sometimes eliminate bubble formation, a common problem in closed systems.In closed system microfluidics, the flow in the channels is driven by pressure via pumps (syringe pumps), valves (trigger valves), or electrical field. An example of one of these methods for achieving low flow rates using temperature-controlled evaporation has been described for an open microfluidics system, allowing for long incubation hours for biological applications and requiring small sample volumes. Open system microfluidics enable surface-tension driven flow in channels thereby eliminating the need for external pumping methods. For example, some open microfluidic devices consist of a reservoir port and pumping port that can be filled with fluid using a pipette. Eliminating external pumping requirements lowers cost and enables device use in all laboratories with pipettes.
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Open microfluidics
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Advantages
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Materials Solutions Thankfully, while many problems exist with PDMS, many solutions have also been developed. To address the negative hydrophobicity and porosity that PDMS exhibits, researchers have started to use coatings such as BSA (bovine serum albumin) or charged molecules to create a layer between the native PDMS and the cells. Other researchers have successfully employed several of the Pluronic surfactants, a tri-block copolymer that has two hydrophilic blocks surrounding a hydrophobic core often used to increase the hydrophilic nature of numerous substrates, and even borosilicate glass coatings to address the hydrophobicity problem. Interestingly, treatment with either of the prior two compounds can result in prevention of non-specific protein adsorption, as they (and other coatings) form stable adsorption interactions with the PDMS, which aides in reducing PDSM interference with cell culture media. These compounds and materials can affect surface properties and should be carefully tested to note the impact on cultured cells. Researchers developed 3D scaffolding systems to mimic in vivo environments so that more cells and cell types can grow in an effort to address the problem that not all cell types can grow on PDMS. Like coating the PDMS, 3D scaffolding systems employ alternatives materials like ECM (extracellular matrix) proteins so rather than not binding the native PDMS, cells are more likely to bind to the proteins. Lastly, researchers have addressed the permeability of PDMS to water vapor using some elegant solutions. For example, a portion of the microfluidic system can be designated for humidification and cast in PDMS, or other material like glass.
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Open microfluidics
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Disadvantages
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Some drawbacks of open microfluidics include evaporation, contamination, and limited flow rate. Open systems are susceptible to evaporation which can greatly affect readouts when fluid volumes are on the microscale. Additionally, due to the nature of open systems, they are more susceptible to contamination than closed systems. Cell culture and other methods where contamination or small particulates are a concern must be carefully performed to prevent contamination. Lastly, open systems have a limited flow rate because induced pressures cannot be used to drive flow.
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Open microfluidics
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Disadvantages
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Materials Polydimethylsiloxane (PDMS) is an ideal material to fabricate microfluidic devices for cell culture applications due to several advantageous properties such as low processing costs, ease of manufacture, rapid prototyping, ease of surface modification, and cellular non-toxicity. While there are several benefits that arise from using native Polydimethylsiloxane (PDMS), there are also some drawbacks that researchers must account for in their experiments. First, PDMS is both hydrophobic and porous, meaning that small molecules or other hydrophobic molecules can be adsorbed onto it. Such molecules include anything from methyl- or alkyl-containing molecules, and even certain dyes like Nile Red. Researchers identified in 2008 that plasma could be used to reduce the hydrophobicity of PDMS, though it returned about two weeks after treatment. Some researchers postulate that integrating removable polycaprolactone (PCL) fiber-based electrospun scaffolds under NaOH treatment enhances hydrophilicity as well as mitigating hydrophobicity, while promoting more efficient cell communication. Another problem that arises with PDMS is that it can interfere with the media that circulates in the channels. Incomplete curing of PDMS channels can lead to PDMS leaching into the media and, even when complete curing takes place, components of the media can still unintentionally attach to free hydrophobic sites on the PDMS walls. Yet another problem arises with the gas permeability of PDMS. Most researchers take advantage of this to oxygenate both the PDMS and the circulating media, but this trait also makes the microfluidic system especially vulnerable to water vapor loss. Lastly, not all cell types can grow, or will grow at the same levels, on native PDMS. For instance, high levels of rapid cell death in two fibroblast types grown on native PDMS were observed as early as 1994, which posed problems for the widespread use of PDMS in microfluidic cell culture.
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Open microfluidics
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Applications
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Like many microfluidic technologies, open system microfluidics has been applied to nanotechnology, biotechnology, fuel cells, and point of care (POC) testing. For cell-based studies, open-channel microfluidic devices enable access to cells for single cell probing within the channel. Other applications include capillary gel electrophoresis, water-in-oil emulsions, and biosensors for POC systems. Suspended microfluidic devices, open microfluidic devices where the floor of the device is removed, have been used to study cellular diffusion and migration of cancer cells. Suspended and rail-based microfluidics have been used for micropatterning and studying cell communication.
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Open microfluidics
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Applications
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Materials Solutions Applications Applications of these solutions are still in use today, as seen by the following examples. In 2014, Lei et al was testing the impedance of human oral cancer cells in the presence of cisplatin, a known anti-cancer drug, by molding the cells into a 3D scaffolding. The authors had noted from previous studies that cellular impedance could be correlated to cellular viability and proliferation in 2D cell culture and hoped to translate that correlation into 3D cell culture. Using agarose to create the 3D scaffolding, the researchers measured the growth and proliferation of human oral cancer cells in the presence and absence of cisplatin using fluorescent DNA assays and observed that there was indeed a correlation like that observed in 2D model. Not only did this prove that principles from 2D cell culture could be translated to 3D open microfluidic cell culture, but it also potentially lays the foundation for a more personalized treatment plan for cancer patients. They postulated that future developments could transform this method into an assay that could test patient cancer cell response to known anti-cancer drugs. Another group used a similar method, but instead of creating a 3D scaffolding, they employed several different PDMS coatings to determine the best option for studying cancer stem cells. The group looked at BSA and ECM proteins and found that, while their experimental evidence supported BSA as the best coating for circulating cancer cells (CSC’s), phenotypic changes did occur to the cells (namely, elongation), but did not impact the cells’ ability to perform normal cell functions. A key caveat to note here is that BSA is not a blanket solution that works for every cell type- different coatings work better or worse for certain cell types and these differences should be considered when developing an experiment.
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Music criticism
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Music criticism
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The Oxford Companion to Music defines music criticism as "the intellectual activity of formulating judgments on the value and degree of excellence of individual works of music, or whole groups or genres". In this sense, it is a branch of musical aesthetics. With the concurrent expansion of interest in music and information media over the past century, the term has come to acquire the conventional meaning of journalistic reporting on musical performances.
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Music criticism
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Nature of music criticism
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The musicologist Winton Dean has suggested that "music is probably the most difficult of the arts to criticise." Unlike the plastic or literary arts, the 'language' of music does not specifically relate to human sensory experience – Dean's words, "the word 'love' is common coin in life and literature: the note C has nothing to do with breakfast or railway journeys or marital harmony." Like dramatic art, music is recreated at every performance, and criticism may, therefore, be directed both at the text (musical score) and the performance. More specifically, as music has a temporal dimension that requires repetition or development of its material "problems of balance, contrast, expectation and fulfilment... are more central to music than to other arts, supported as these are by verbal or representational content." The absence of a systematic or consensus-based musical aesthetics has also tended to make music criticism a highly subjective issue. "There is no counter-check outside the critic's own personality."
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Music criticism
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History
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To end of 18th century Critical references to music (often deprecating performers or styles) can be found in early literature, including, for example, in Plato's Laws and in the writings of medieval music theorists.
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Music criticism
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History
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According to Richard Taruskin, the active concert life of late 18th-century London meant that "the role and the function of arts criticism as we know it today were the creations of the English public." However, the first magazines specifically devoted to music criticism seem to have developed in Germany, for example, Georg Philipp Telemann's Der getreue Music-Meister (1728), which included publications of new compositions, and Der kritische Musikus which appeared in Hamburg between 1737 and 1740. In France in the 1750s, the Querelle des Bouffons (the dispute between supporters of French and Italian opera styles as represented by Jean-Philippe Rameau and Jean-Baptiste Lully respectively) generated essays from Jean-Jacques Rousseau and others, including Denis Diderot's Rameau's Nephew (1761). The English composer Charles Avison (1709–1770) published the first work on musical criticism in the English language – an Essay on Musical Expression published in 1752. In it, Avison claims that since the time of Palestrina and Raphael, music had improved in status whilst pictorial art had declined. However, he believes that George Frideric Handel is too much concerned with naturalistic imitation than with expression, and criticises the habit, in Italian operas, of that egregious absurdity of repeating, and finishing many songs with the first part; when it often happens, after the passions of anger and revenge have been sufficiently expressed, that reconcilement and love are the subjects of the second, and, therefore, should conclude the performance. Typically, until the late eighteenth century, music criticism centred on vocal rather than instrumental music – "vocal music ... was the apex of [the] aesthetic hierarchy. One knew what music was expressing." Age of Romanticism The last years of the eighteenth century reflected both a change of patronage of music from the aristocracy to the rising middle-classes, and the rise of Romanticism in the arts. Both of these had consequences for the practice of music criticism; "the tone of the critic was lowered as his audience expanded: he began to approach the reader as a colleague rather than a pedagogue", and a new generation of critics began to widen their consideration to other aspects of music than its pure representative aspects, becoming increasingly interested in instrumental music. Prominent amongst these was E. T. A. Hoffmann, who wrote in 1809That instrumental music has now risen to a level of which one probably had no inkling not long ago and that the symphony, especially following...Haydn and Mozart, has become the ultimate form of instrumental music – the opera of instruments, as it were – all this is well-known to every music-lover.
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Music criticism
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History
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A further impetus to the direction of music criticism was given by the changing nature of concert programming with the establishment of the European classical music canon; indeed it is at this period that the word 'classical' is first applied to a received musical tradition. At the same time, the proportion of new music to 'canonic' music in concert programming began to decline, meaning that living composers were increasingly in competition with their dead predecessors. This was particularly the case in respect of the rise of Beethoven's reputation in his last year and posthumously. This gave rise both to writings on the value of the 'canon' and also to writings by composers and their supporters defending newer music.
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Music criticism
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History
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In 1798 the Allgemeine musikalische Zeitung, edited by Friedrich Rochlitz (1769–1842), began publication in Leipzig, and this is often regarded as the precursor of a new genre of criticism aimed at a wider readership than qualified connoisseurs. In subsequent years several regular journals dedicated to music criticism and reviews began to appear in major European centres, including The Harmonicon (London 1823–33), The Musical Times (London, 1844-date), the Revue et gazette musicale de Paris (Paris 1827–1880, founded by François-Joseph Fétis), the Berliner allgemeine musikalische Zeitung founded in 1825 by A.M. Schlesinger and edited by A. B. Marx, and the Neue Zeitschrift für Musik founded in 1834 in Leipzig by Robert Schumann and Friedrich Wieck, and later edited by Franz Brendel. Other journals at this period also began to carry extensive writings on music: Hector Berlioz wrote for the Parisian Journal des débats, Heinrich Heine reported on music and literature in Paris for the Stuttgart Allgemeine Zeitung, the young Richard Wagner wrote articles for Heinrich Laube's magazine Zeitung für die elegante Welt and during his 1839–42 stay in Paris for Schlesinger's publishing house and German newspapers. The writer George Henry Caunter (1791–1843) was called "one of the first musical critics in the metropolis [London]". In 1835 James William Davison (1813–85) began his lifelong career as a music critic, writing 40 years for The Times.
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Music criticism
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Sources
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Avison, Charles (1752). Essay on Musical Expression. London. Downloadable from IMSLP.
Bujic, Bojan (n.d.) "Criticism of Music" in The Oxford Companion to Music, Oxford Music Online, accessed 1 January 2013.
Charlton, David (2003). "Hoffmann as a Writer on Music", in Hoffmann (2003, 1–22).
Conway, David (2012). Jewry in Music: Entry to the Profession from the Enlightenment to Richard Wagner. Cambridge: Cambridge University Press. ISBN 978-1-107-01538-8.
Davison, J.W., ed. Henry Davison (1912). FromMendelssohnto Wagner: Memoirs of J. W. Davison". London: William Reeves.
Dean, Winton (1980). "Criticism", in New Grove Dictionary of Music and Musicians (ed. Stanley Sadie) vol. 5, 36–50. London: Macmillan ISBN 0-333-23111-2.
Hoffmann, E. T. A., ed. David Charlton (2003).E. T. A. Hoffmann's Musical Writings. Cambridge: Cambridge University Press. ISBN 0 521 23520 0.
Taruskin, Richard (2010). Music in the Seventeenth and Eighteenth Centuries, Oxford: Oxford University Press ISBN 978-0-19-538482-6.
Urban, Sylvanus, ed. (1843). "Deaths", in The Gentleman's Magazine. London: William Pickering; John Bowyer Nichols and Son.
Weber, William (2001). "From Miscellany to Homogeneity in Concert Programming", in Poetics 29, 127–34.
Weber, William (2003). "Consequences of Canon: The Institutionalization of Enmity between Contemporary and Classical Music", Common Knowledge 9/2, 78–99.
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Exploding-bridgewire detonator
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Exploding-bridgewire detonator
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The exploding-bridgewire detonator (EBW, also known as exploding wire detonator) is a type of detonator used to initiate the detonation reaction in explosive materials, similar to a blasting cap because it is fired using an electric current. EBWs use a different physical mechanism than blasting caps, using more electricity delivered much more rapidly, and explode in a much more precise timing after the electric current is applied, by the process of exploding wire method. This has led to their common use in nuclear weapons.The slapper detonator is a more recent development along similar lines.
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Exploding-bridgewire detonator
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History
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The EBW was invented by Luis Alvarez and Lawrence Johnston for the Fat Man–type bombs of the Manhattan Project, during their work in Los Alamos National Laboratory. The Fat Man Model 1773 EBW detonators used an unusual, high reliability detonator system with two EBW "horns" attached to a single booster charge, which then fired each of the 32 explosive lens units.
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Exploding-bridgewire detonator
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Description
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EBWs were developed as a means of detonating multiple explosive charges simultaneously, mainly for use in plutonium-based nuclear weapons in which a plutonium core (called a pit) is compressed very rapidly. This is achieved via conventional explosives placed uniformly around the pit. The implosion must be highly symmetrical or the plutonium would simply be ejected at the low-pressure points. Consequently, the detonators must have very precise timing.
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Exploding-bridgewire detonator
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Description
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An EBW has two main parts: a piece of fine wire which contacts the explosive, and a high-voltage high-current low-impedance electricity source; it must reliably and consistently supply a rapid starting pulse. When the wire is connected across this voltage, the resulting high current melts and then vaporizes the wire in a few microseconds. The resulting shock and heat initiate the high explosive.
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Exploding-bridgewire detonator
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Description
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This accounts for the heavy cables seen in photos of the Trinity "Gadget"; high voltage cable requires good insulation and they had to deliver a large current with little voltage drop, lest the EBW not achieve the phase transition quickly enough.
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Exploding-bridgewire detonator
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Description
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The precise timing of EBWs is achieved by the detonator using direct physical effects of the vaporized bridgewire to initiate detonation in the detonator's booster charge. Given a sufficiently high and well known amount of electric current and voltage, the timing of the bridgewire vaporization is both extremely short (a few microseconds) and extremely precise and predictable (standard deviation of time to detonate as low as a few tens of nanoseconds).
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Exploding-bridgewire detonator
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Description
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Conventional blasting caps use electricity to heat a bridge wire rather than vaporize it, and that heating then causes the primary explosive to detonate. Imprecise contact between the bridgewire and the primary explosive changes how quickly the explosive is heated up, and minor electrical variations in the wire or leads will change how quickly it heats up as well. The heating process typically takes milliseconds to tens of milliseconds to complete and initiate detonation in the primary explosive. This is roughly 1,000 to 10,000 times longer and less precise than the EBW electrical vaporization.
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Exploding-bridgewire detonator
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Description
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Use in nuclear weapons Since explosives detonate at typically 7–8 kilometers per second, or 7–8 meters per millisecond, a 1 millisecond delay in detonation from one side of a nuclear weapon to the other would be longer than the time the detonation would take to cross the weapon. The time precision and consistency of EBWs (0.1 microsecond or less) are roughly enough time for the detonation to move 1 millimeter at most, and for the most precise commercial EBWs this is 0.025 microsecond and about 0.2 mm variation in the detonation wave. This is sufficiently precise for very tight tolerance applications such as nuclear weapon explosive lenses.
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Exploding-bridgewire detonator
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Description
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In the US, due to their common use in nuclear weapons, these devices are subject to the nuclear control authorities in every state, according to the Guidelines for the Export of Nuclear Material, Equipment and Technology. EBWs are on the United States Munitions List, and exports are highly regulated.
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