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🔗 Medicine 🔗 Psychology

Type A and Type B personality hypothesis describes two contrasting personality types. In this hypothesis, personalities that are more competitive, highly organized, ambitious, impatient, highly aware of time management and/or aggressive are labeled Type A, while more relaxed, less 'neurotic', 'frantic', 'explainable', personalities are labeled Type B.

The two cardiologists who developed this theory came to believe that Type A personalities had a greater chance of developing coronary heart disease. Following the results of further studies and considerable controversy about the role of the tobacco industry funding of early research in this area, some reject, either partially or completely, the link between Type A personality and coronary disease. Nevertheless, this research had a significant effect on the development of the health psychology field, in which psychologists look at how an individual's mental state affects physical health.

🔗 Computing 🔗 Computing/Computer hardware

The Dadda multiplier is a hardware binary multiplier design invented by computer scientist Luigi Dadda in 1965. It uses a selection of full and half adders to sum the partial products in stages (the Dadda tree or Dadda reduction) until two numbers are left. The design is similar to the Wallace multiplier, but the different reduction tree reduces the required number of gates (for all but the smallest operand sizes) and makes it slightly faster (for all operand sizes).

Dadda and Wallace multipliers have the same three steps for two bit strings ${\displaystyle w_{1}}$ and ${\displaystyle w_{2}}$ of lengths ${\displaystyle \ell _{1}}$ and ${\displaystyle \ell _{2}}$ respectively:

1. Multiply (logical AND) each bit of ${\displaystyle w_{1}}$, by each bit of ${\displaystyle w_{2}}$, yielding ${\displaystyle \ell _{1}\cdot \ell _{2}}$ results, grouped by weight in columns
2. Reduce the number of partial products by stages of full and half adders until we are left with at most two bits of each weight.
3. Add the final result with a conventional adder.

As with the Wallace multiplier, the multiplication products of the first step carry different weights reflecting the magnitude of the original bit values in the multiplication. For example, the product of bits ${\displaystyle a_{n}b_{m}}$ has weight ${\displaystyle n+m}$.

Unlike Wallace multipliers that reduce as much as possible on each layer, Dadda multipliers attempt to minimize the number of gates used, as well as input/output delay. Because of this, Dadda multipliers have a less expensive reduction phase, but the final numbers may be a few bits longer, thus requiring slightly bigger adders.

🔗 Military history 🔗 Military history/North American military history 🔗 Military history/United States military history 🔗 Cold War 🔗 Military history/Asian military history 🔗 Military history/Southeast Asian military history 🔗 Vietnam

The Fall of Saigon, also known as the Liberation of Saigon by North Vietnamese, was the capture of Saigon, the capital of South Vietnam, by the People's Army of Vietnam (PAVN) and the Viet Cong on 30 April 1975. The event marked the end of the Vietnam War and the start of a transition period to the formal reunification of Vietnam into the Socialist Republic of Vietnam.

The PAVN, under the command of General Văn Tiến Dũng, began their final attack on Saigon on 29 April 1975, with the Army of the Republic of Vietnam (ARVN) forces commanded by General Nguyễn Văn Toàn suffering a heavy artillery bombardment. By the afternoon of the next day, the PAVN had occupied the important points of the city and raised their flag over the South Vietnamese presidential palace. The city was renamed Hồ Chí Minh City, after the late North Vietnamese President Hồ Chí Minh.

The capture of the city was preceded by Operation Frequent Wind, the evacuation of almost all American civilian and military personnel in Saigon, along with tens of thousands of South Vietnamese civilians who had been associated with the Republic of Vietnam. A few Americans chose not to be evacuated. United States ground combat units had left South Vietnam more than two years prior to the fall of Saigon and were not available to assist with either the defense of Saigon or the evacuation. The evacuation was the largest helicopter evacuation in history. In addition to the flight of refugees, the end of the war and the institution of new rules by the communists contributed to a decline in the city's population.

🔗 Medicine 🔗 Physiology

Exploding head syndrome (EHS) is a condition in which a person experiences unreal noises that are loud and of short duration when falling asleep or waking up. The noise may be frightening, typically occurs only occasionally, and is not a serious health concern. People may also experience a flash of light. Pain is typically absent.

The cause is unknown. Potential explanations include ear problems, temporal lobe seizure, nerve dysfunction, or specific genetic changes. Potential risk factors include psychological stress. It is classified as a sleep disorder or headache disorder. People often go undiagnosed.

There is no high quality evidence to support treatment. Reassurance may be sufficient. Clomipramine and calcium channel blockers have been tried. While the frequency of the condition is not well studied, some have estimated that it occurs in about 10% of people. Females are reportedly more commonly affected. The condition was initially described at least as early as 1876. The current name came into use in 1988.

🔗 United States/U.S. Government 🔗 United States 🔗 History 🔗 Computing 🔗 Cryptography 🔗 Cryptography/Computer science

In cryptography, the EFF DES cracker (nicknamed "Deep Crack") is a machine built by the Electronic Frontier Foundation (EFF) in 1998, to perform a brute force search of the Data Encryption Standard (DES) cipher's key space – that is, to decrypt an encrypted message by trying every possible key. The aim in doing this was to prove that the key size of DES was not sufficient to be secure.

🔗 Economics

"Assume a can opener" is a catchphrase used to mock economists and other theorists who base their conclusions on unjustified or oversimplified assumptions.

The phrase derives from a joke which dates to at least 1970 and possibly originated with British economists. The first book mentioning it is likely Economics as a Science (1970) by Kenneth E. Boulding:

There is a story that has been going around about a physicist, a chemist, and an economist who were stranded on a desert island with no implements and a can of food. The physicist and the chemist each devised an ingenious mechanism for getting the can open; the economist merely said, "Assume we have a can opener"!

The phrase was popularized in a 1981 book and has become sufficiently well known that many writers on economic topics use it as a catchphrase without further explanation.

🔗 Russia 🔗 Norway 🔗 Holidays 🔗 Sweden 🔗 Ethnic groups 🔗 Finland 🔗 Norse history and culture

The Sámi National Day is an ethnic national day for the Sámi (Saami) people that falls on February 6, the date when the first Sámi congress was held in 1917 in Trondheim, Norway. The congress was the first time that Norwegian and Swedish Sámi came together across national borders to work on finding solutions to common problems.

In 1992 at the 15th Sámi Conference in Helsinki, Finland, a resolution was passed that Sámi National Day should be celebrated on February 6 to commemorate the first Sámi congress in 1917, that Sami National Day is for all Sámi, regardless of where they live, and on that day the Sámi flag should be flown and the Sámi anthem sung in the local Sámi language. The first time Sami National Day was celebrated was in 1993, when the International Year of Indigenous People was proclaimed open in Jokkmokk, Sweden by the United Nations.

Since then, celebrating the day has become increasingly popular. In Norway, it is compulsory for municipal administrative buildings to fly the Norwegian flag, and optionally also the Sami flag, on February 6. Particularly notable is the celebration in Norway's capital Oslo, where the bells in the highest tower of Oslo City Hall play the Sami national anthem as the flags are raised. Some larger places have taken to arranging festivities in the week around the Sami National Day. The National Day has been included in the almanacs published by the University of Helsinki since 2004. The Norwegian, Swedish, and Finnish authorities recommend general flagging on the day.

By coincidence, February 6 was also the date representatives of the Sámi of the Kola Peninsula gathered annually to meet with Russian bureaucrats to debate and decide on issues of relevance to them. This assembly, called the Kola Sobbar, has been dubbed the "first Sámi Parliament" by the researcher Johan Albert Kalstad. However, the founding of the Kola Sobbar did not influence the choice of the date for Sámi People's Day, as the assembly existed only during the late 1800s and was largely forgotten until the early 2000s.

🔗 Computing 🔗 Trains 🔗 Trains/Rail transport modelling

The Tech Model Railroad Club (TMRC) is a student organization at the Massachusetts Institute of Technology (MIT). Historically it has been a wellspring of hacker culture and the oldest such hacking group in North America. Formed in 1946, its HO scale layout specializes in automated operation of model trains.

LOOP is a programming language designed by Uwe Schöning, along with GOTO and WHILE. The only operations supported in the language are assignment, addition and looping.

The key property of the LOOP language is that the functions it can compute are exactly the primitive recursive functions.

🔗 Computer science 🔗 Databases 🔗 Databases/Computer science

R-trees are tree data structures used for spatial access methods, i.e., for indexing multi-dimensional information such as geographical coordinates, rectangles or polygons. The R-tree was proposed by Antonin Guttman in 1984 and has found significant use in both theoretical and applied contexts. A common real-world usage for an R-tree might be to store spatial objects such as restaurant locations or the polygons that typical maps are made of: streets, buildings, outlines of lakes, coastlines, etc. and then find answers quickly to queries such as "Find all museums within 2 km of my current location", "retrieve all road segments within 2 km of my location" (to display them in a navigation system) or "find the nearest gas station" (although not taking roads into account). The R-tree can also accelerate nearest neighbor search for various distance metrics, including great-circle distance.