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🔗 Mathematics

In number theory, the Green–Tao theorem, proved by Ben Green and Terence Tao in 2004, states that the sequence of prime numbers contains arbitrarily long arithmetic progressions. In other words, for every natural number k, there exist arithmetic progressions of primes with k terms. The proof is an extension of Szemerédi's theorem. The problem can be traced back to investigations of Lagrange and Waring from around 1770.

🔗 Technology 🔗 Military history 🔗 Military history/Military science, technology, and theory 🔗 Military history/Maritime warfare

Communication with submarines is a field within military communications that presents technical challenges and requires specialized technology. Because radio waves do not travel well through good electrical conductors like salt water, submerged submarines are cut off from radio communication with their command authorities at ordinary radio frequencies. Submarines can surface and raise an antenna above the sea level, then use ordinary radio transmissions, however this makes them vulnerable to detection by anti-submarine warfare forces. Early submarines during World War II mostly traveled on the surface because of their limited underwater speed and endurance; they dove mainly to evade immediate threats. During the Cold War, however, nuclear-powered submarines were developed that could stay submerged for months. Transmitting messages to these submarines is an active area of research. Very low frequency (VLF) radio waves can penetrate seawater a few hundred feet, and many navies use powerful VLF transmitters for submarine communications. A few nations have built transmitters which use extremely low frequency (ELF) radio waves, which can penetrate seawater to reach submarines at operating depths, but these require huge antennas. Other techniques that have been used include sonar and blue lasers.

🔗 Mathematics 🔗 Statistics

Anscombe's quartet comprises four data sets that have nearly identical simple descriptive statistics, yet have very different distributions and appear very different when graphed. Each dataset consists of eleven (x,y) points. They were constructed in 1973 by the statistician Francis Anscombe to demonstrate both the importance of graphing data when analyzing it, and the effect of outliers and other influential observations on statistical properties. He described the article as being intended to counter the impression among statisticians that "numerical calculations are exact, but graphs are rough."

🔗 Biography

Ward Christensen (born 1945 in West Bend, Wisconsin, United States) was the co-founder of the CBBS bulletin board, the first bulletin board system (BBS) ever brought online. Christensen, along with partner Randy Suess, members of the Chicago Area Computer Hobbyists' Exchange (CACHE), started development during a blizzard in Chicago, Illinois, and officially established CBBS four weeks later, on February 16, 1978. CACHE members frequently shared programs and had long been discussing some form of file transfer, and the two used the downtime during the blizzard to implement it.

Christensen was noted for building software tools for his needs. He wrote a cassette-based operating system before floppies and hard disks were common. When he lost track of the source code for some programs, he wrote ReSource, an iterative disassembler for the Intel 8080, to help him regenerate the source code. When he needed to send files to Randy Suess, he wrote XMODEM.

Jerry Pournelle wrote in 1983 of a collection of CP/M public-domain software that "probably 50 percent of the really good programs were written by Ward Christensen, a public benefactor." Christensen received two 1992 Dvorak Awards for Excellence in Telecommunications, one with Randy Suess for developing the first BBS, and a lifetime achievement award "for outstanding contributions to PC telecommunications." In 1993, he received the Pioneer Award from the Electronic Frontier Foundation.

Christensen worked at IBM from 1968 until his retirement in 2012. His last position with IBM was field technical sales specialist.

In May 2005, Christensen and Suess were both featured in BBS: The Documentary.

🔗 Guild of Copy Editors 🔗 Automobiles

The Chrysler Turbine Car is an experimental two-door hardtop coupe powered by a turbine engine and manufactured by Chrysler from 1963–1964. The bodywork was constructed by Italian design studio Carrozzeria Ghia and Chrysler completed the final assembly in Detroit. A total of 55 cars were manufactured: five prototypes and a limited run of 50 cars for a public user program. All have a signature metallic paint named "turbine bronze", roughly the color of root beer. The car was styled by Elwood Engel and the Chrysler studios and featured power brakes, power steering, and a TorqueFlite transmission.

The Chrysler turbine engine program that produced the Turbine Car began during the late 1930s and created prototypes that completed long-distance trips in the 1950s and early 1960s. The A-831 engines that powered the Ghia-designed Turbine Car could operate on many fuels, required less maintenance, and lasted longer than conventional piston engines, although they were much more expensive to produce.

After testing, Chrysler conducted a user program from October 1963 to January 1966 that involved 203 drivers in 133 cities in the United States cumulatively driving more than one million miles (1.6 million km). The program helped the company determine problems with the cars, notably with their complicated starting procedure, relatively unimpressive acceleration, and sub-par fuel economy and noise. The experience also revealed advantages of the turbine engines, including their remarkable durability, smooth operation, and relatively modest maintenance requirements.

After the user program ended in 1966, Chrysler reclaimed the cars and destroyed all but nine; Chrysler kept two cars, six are displayed at museums in the United States, and one is in a private collection. Chrysler's turbine engine program ended in 1979, largely due to the failure of the engines to meet government emissions regulations, relatively poor fuel economy, and as a condition of receiving a government loan in 1979.

🔗 Medicine 🔗 Skepticism 🔗 Alternative medicine

Coley's toxins (also called Coley's toxin, Coley's vaccine, Coley vaccine, Coley's fluid or mixed bacterial vaccine) is a mixture consisting of killed bacteria of species Streptococcus pyogenes and Serratia marcescens, named after William Coley, a surgical oncologist at the Hospital for Special Surgery who developed the mixture in the late 19th century as a treatment for cancer.

There is no evidence that Coley's toxins have any effectiveness in treating cancer, and use of them risks causing serious harm.

🔗 Germany 🔗 Motorcycling

The Daimler Petroleum Reitwagen ("riding car") or Einspur ("single track") was a motor vehicle made by Gottlieb Daimler and Wilhelm Maybach in 1885. It is widely recognized as the first motorcycle. Daimler is often called "the father of the motorcycle" for this invention. Even when the three steam powered two wheelers that preceded the Reitwagen, the Michaux-Perreaux and Roper of 1867–1869, and the 1884 Copeland, are considered motorcycles, it remains nonetheless the first petrol internal combustion motorcycle, and the forerunner of all vehicles, land, sea and air, that use its overwhelmingly popular engine type.

🔗 Economics 🔗 Basic Income 🔗 Taxation

In economics, a negative income tax (NIT) is a welfare system within an income tax where people earning below a certain amount receive supplemental pay from the government instead of paying taxes to the government.

Such a system has been discussed by economists but never fully implemented. According to surveys however, the consensus view among economists is that the "government should restructure the welfare system along the lines" of one. It was described by British politician Juliet Rhys-Williams in the 1940s and later by American free-market economist Milton Friedman.

Negative income taxes can implement a basic income or supplement a guaranteed minimum income system.

In a negative income tax system, people earning a certain income level would owe no taxes; those earning more than that would pay a proportion of their income above that level; and those below that level would receive a payment of a proportion of their shortfall, which is the amount their income falls below that level.

🔗 Architecture 🔗 Psychology 🔗 Sociology 🔗 Correction and Detention Facilities 🔗 Urban studies and planning 🔗 Hospitals

The Kirkbride Plan was a system of mental asylum design advocated by American psychiatrist Thomas Story Kirkbride (1809–1883) in the mid-19th century. The asylums built in the Kirkbride design, often referred to as Kirkbride Buildings (or simply Kirkbrides), were constructed during the mid-to-late-19th century in the United States. The structural features of the hospitals as designated by Kirkbride were contingent on his theories regarding the healing of the mentally ill, in which environment and exposure to natural light and air circulation were crucial. The hospitals built according to the Kirkbride Plan would adopt various architectural styles, but had in common the "bat wing" style floor plan, housing numerous wings that sprawl outward from the center.

The first hospital designed under the Kirkbride Plan was the Trenton State Hospital in Trenton, New Jersey, constructed in 1848. Throughout the remainder of the nineteenth century, numerous psychiatric hospitals were designed under the Kirkbride Plan across the United States. By the twentieth century, popularity of the design had waned, largely due to the economic pressures of maintaining the immense facilities, as well as contestation of Kirkbride's theories amongst the medical community.

Numerous Kirkbride structures still exist, though many have been demolished or partially-demolished and repurposed. At least 30 of the original Kirkbride buildings have been registered with the National Register of Historic Places in the United States, either directly or through their location on hospital campuses or in historic districts.

🔗 Spaceflight

Project Orion was a study of a spacecraft intended to be directly propelled by a series of explosions of atomic bombs behind the craft (nuclear pulse propulsion). Early versions of this vehicle were proposed to take off from the ground (with significant associated nuclear fallout); later versions were presented for use only in space. Six non-nuclear tests were conducted using models. The project was eventually abandoned for multiple reasons such as the Partial Test Ban Treaty which banned nuclear explosions in space as well as concerns over nuclear fallout.

The idea of rocket propulsion by combustion of explosive substance was first proposed by Russian explosives expert Nikolai Kibalchich in 1881, and in 1891 similar ideas were developed independently by German engineer Hermann Ganswindt. Robert A. Heinlein mentions powering spaceships with nuclear bombs in his 1940 short story "Blowups Happen." Real life proposals of nuclear propulsion were first made by Stanislaw Ulam in 1946, and preliminary calculations were made by F. Reines and Ulam in a Los Alamos memorandum dated 1947. The actual project, initiated in 1958, was led by Ted Taylor at General Atomics and physicist Freeman Dyson, who at Taylor's request took a year away from the Institute for Advanced Study in Princeton to work on the project.

The Orion concept offered high thrust and high specific impulse, or propellant efficiency, at the same time. The unprecedented extreme power requirements for doing so would be met by nuclear explosions, of such power relative to the vehicle's mass as to be survived only by using external detonations without attempting to contain them in internal structures. As a qualitative comparison, traditional chemical rockets—such as the Saturn V that took the Apollo program to the Moon—produce high thrust with low specific impulse, whereas electric ion engines produce a small amount of thrust very efficiently. Orion would have offered performance greater than the most advanced conventional or nuclear rocket engines then under consideration. Supporters of Project Orion felt that it had potential for cheap interplanetary travel, but it lost political approval over concerns with fallout from its propulsion.

The Partial Test Ban Treaty of 1963 is generally acknowledged to have ended the project. However, from Project Longshot to Project Daedalus, Mini-Mag Orion, and other proposals which reach engineering analysis at the level of considering thermal power dissipation, the principle of external nuclear pulse propulsion to maximize survivable power has remained common among serious concepts for interstellar flight without external power beaming and for very high-performance interplanetary flight. Such later proposals have tended to modify the basic principle by envisioning equipment driving detonation of much smaller fission or fusion pellets, in contrast to Project Orion's larger nuclear pulse units (full nuclear bombs) based on less speculative technology.

To Mars by A-Bomb: The Secret History of Project Orion was a 2003 BBC documentary film about the project.