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🔗 Mathematics

The Ulam spiral or prime spiral is a graphical depiction of the set of prime numbers, devised by mathematician Stanisław Ulam in 1963 and popularized in Martin Gardner's Mathematical Games column in Scientific American a short time later. It is constructed by writing the positive integers in a square spiral and specially marking the prime numbers.

Ulam and Gardner emphasized the striking appearance in the spiral of prominent diagonal, horizontal, and vertical lines containing large numbers of primes. Both Ulam and Gardner noted that the existence of such prominent lines is not unexpected, as lines in the spiral correspond to quadratic polynomials, and certain such polynomials, such as Euler's prime-generating polynomial x² − x + 41, are believed to produce a high density of prime numbers. Nevertheless, the Ulam spiral is connected with major unsolved problems in number theory such as Landau's problems. In particular, no quadratic polynomial has ever been proved to generate infinitely many primes, much less to have a high asymptotic density of them, although there is a well-supported conjecture as to what that asymptotic density should be.

In 1932, more than thirty years prior to Ulam's discovery, the herpetologist Laurence Klauber constructed a triangular, non-spiral array containing vertical and diagonal lines exhibiting a similar concentration of prime numbers. Like Ulam, Klauber noted the connection with prime-generating polynomials, such as Euler's.

🔗 Russia 🔗 Physics 🔗 Physics/relativity 🔗 Russia/science and education in Russia

The Novikov self-consistency principle, also known as the Novikov self-consistency conjecture and Larry Niven's law of conservation of history, is a principle developed by Russian physicist Igor Dmitriyevich Novikov in the mid-1980s. Novikov intended it to solve the problem of paradoxes in time travel, which is theoretically permitted in certain solutions of general relativity that contain what are known as closed timelike curves. The principle asserts that if an event exists that would cause a paradox or any "change" to the past whatsoever, then the probability of that event is zero. It would thus be impossible to create time paradoxes.

🔗 Technology 🔗 Architecture

A Matrioshka brain is a hypothetical megastructure of immense computational capacity powered by a Dyson sphere. It was proposed in 1997 by Robert J. Bradbury (1956–2011). It is an example of a Class B stellar engine, employing the entire energy output of a star to drive computer systems. This concept derives its name from the nesting Russian Matryoshka dolls. The concept was deployed by Bradbury in the anthology Year Million: Science at the Far Edge of Knowledge.

🔗 Aviation 🔗 Telecommunications 🔗 Guild of Copy Editors

In the U.S., Federal Communications Commission (FCC) regulations prohibit the use of mobile phones aboard aircraft in flight. Contrary to popular misconception, the Federal Aviation Administration (FAA) does not actually prohibit the use of personal electronic devices (including cell phones) on aircraft. Paragraph (b)(5) of 14 CFR 91.21 leaves it up to the airlines to determine if devices can be used in flight, allowing use of "Any other portable electronic device that the operator of the aircraft has determined will not cause interference with the navigation or communication system of the aircraft on which it is to be used."

In Europe, regulations and technology have allowed the limited introduction of the use of passenger mobile phones on some commercial flights, and elsewhere in the world many airlines are moving towards allowing mobile phone use in flight. Many airlines still do not allow the use of mobile phones on aircraft. Those that do often ban the use of mobile phones during take-off and landing.

Many passengers are pressing airlines and their governments to allow and deregulate mobile phone use, while some airlines, under the pressure of competition, are also pushing for deregulation or seeking new technology which could solve the present problems. On the other hand, official aviation agencies and safety boards are resisting any relaxation of the present safety rules unless and until it can be conclusively shown that it would be safe to do so. There are both technical and social factors which make the issues more complex than a simple discussion of safety versus hazard.

🔗 Medicine

A vaccine-preventable disease is an infectious disease for which an effective preventive vaccine exists. If a person acquires a vaccine-preventable disease and dies from it, the death is considered a vaccine-preventable death.

The most common and serious vaccine-preventable diseases tracked by the World Health Organization (WHO) are: diphtheria, Haemophilus influenzae serotype b infection, hepatitis B, measles, meningitis, mumps, pertussis, poliomyelitis, rubella, tetanus, tuberculosis, and yellow fever. The WHO reports licensed vaccines being available to prevent, or contribute to the prevention and control of, 27 vaccine-preventable infections.

🔗 Russia 🔗 Russia/demographics and ethnography of Russia 🔗 Russia/history of Russia

The Russian Cross is the name of a demographic trend that occurred in Russia and many other countries of the former Warsaw Pact. In Russia, starting in 1988, birth rates among native Russians (as well as most other ethnic groups of the European part of the former Soviet Union) were declining, while from 1991 the death rates started climbing.

In 1992, the number of deaths exceeded the number of births, and continued to do so to a greater or lesser degree until 2013. When this trend is plotted on a line graph starting from the mid-1980s, the lines cross at 1992, hence the name.

🔗 Technology 🔗 Computing 🔗 Telecommunications 🔗 Brands 🔗 Microsoft

Kin was a short-lived mobile phone line from Microsoft designed for users of social networking. The phones, aimed at people between ages 15 and 30, were manufactured by Sharp Corporation and sold through Verizon Wireless.

Microsoft invested two years and about US$1 billion developing the Kin platform, beginning with its acquisition of Danger Incorporated. The Kin was based on Windows CE.

The Kin ONE and TWO went on the market on May 14, 2010. Within two months, Verizon stopped selling the phones because of poor sales. Microsoft scrapped its planned European release, stopped promoting the devices, ceased production, and reassigned the Kin development team to other projects.

Microsoft updated its unsold Kin inventory with firmware that removed social and web-based features, and in December 2010 offered these re-purposed units through Verizon stores as limited feature phones, the Kin ONEm and the TWOm. In January 2011, Microsoft shut down the kin.com website, which controlled most of the earlier phones' features.

The Kin TWOm was discontinued in August 2011; unsold inventory could still be found for sale on deals sites as late as June 2013.

🔗 Science

In computing, tree shaking is a dead code elimination technique that is applied when optimizing code written in ECMAScript dialects like JavaScript or TypeScript into a single bundle that is loaded by a web browser. Often contrasted with traditional single-library dead code elimination techniques common to minifiers, tree shaking eliminates unused functions from across the bundle by starting at the entry point and only including functions that may be executed. It is succinctly described as "live code inclusion".

🔗 Cuba

Organopónicos or organoponics is a system of urban agriculture using organic gardens. It originated in Cuba and is still mostly focused there. It often consists of low-level concrete walls filled with organic matter and soil, with lines of drip irrigation laid on the surface of the growing media. Organopónicos is a labour-intensive form of local agriculture.

Organopónico farmers employ a wide variety of agroecological techniques including integrated pest management, polyculture, and crop rotation. Most organic materials are also produced within the gardens through composting. This allows production to take place with few petroleum-based inputs.

Organopónicos first arose as a community response to lack of food security during the Special Period after the collapse of the Soviet Union. It is publicly functioning in terms of ownership, access, and management, but heavily subsidized and supported by the Cuban government.

🔗 United States/U.S. Government 🔗 United States 🔗 Law 🔗 Open

Patentleft (also patent left, copyleft-style patent license or open patent) is the practice of licensing patents (especially biological patents) for royalty-free use, on the condition that adopters license related improvements they develop under the same terms. Copyleft-style licensors seek "continuous growth of a universally accessible technology commons" from which they, and others, will benefit.

Patentleft is analogous to copyleft, a license which allows distribution of a copyrighted work and derived works, but only under the same or equivalent terms.