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🔗 Mathematics

The number e is a mathematical constant approximately equal to 2.71828 and is the base of the natural logarithm: the unique number whose natural logarithm is equal to one. It is the limit of (1 + 1/n)ⁿ as n approaches infinity, an expression that arises in the study of compound interest. It can also be calculated as the sum of the infinite series

${\displaystyle e=\sum \limits _{n=0}^{\infty }{\frac {1}{n!}}={\frac {1}{1}}+{\frac {1}{1}}+{\frac {1}{1\cdot 2}}+{\frac {1}{1\cdot 2\cdot 3}}+\cdots }$

The constant can be characterized in many different ways. For example, it can be defined as the unique positive number a such that the graph of the function y = a^x has unit slope at x = 0. The function f(x) = e^x is called the (natural) exponential function, and is the unique exponential function equal to its own derivative. The natural logarithm, or logarithm to base e, is the inverse function to the natural exponential function. The natural logarithm of a number k > 1 can be defined directly as the area under the curve y = 1/x between x = 1 and x = k, in which case e is the value of k for which this area equals one (see image). There are alternative characterizations.

e is sometimes called Euler's number after the Swiss mathematician Leonhard Euler (not to be confused with γ, the Euler–Mascheroni constant, sometimes called simply Euler's constant), or as Napier's constant. However, Euler's choice of the symbol e is said to have been retained in his honor. The constant was discovered by the Swiss mathematician Jacob Bernoulli while studying compound interest.

The number e has eminent importance in mathematics, alongside 0, 1, π, and i. All five of these numbers play important and recurring roles across mathematics, and these five constants appear in one formulation of Euler's identity. Like the constant π, e is also irrational (i.e. it cannot be represented as ratio of integers) and transcendental (i.e. it is not a root of any non-zero polynomial with rational coefficients). The numerical value of e truncated to 50 decimal places is

🔗 Electronics

The 555 timer IC is an integrated circuit (chip) used in a variety of timer, delay, pulse generation, and oscillator applications. Derivatives provide two (556) or four (558) timing circuits in one package. Introduced in 1972 by Signetics, the 555 is still in widespread use due to its low price, ease of use, and stability. Numerous companies have made the original bipolar timers and similar low-power CMOS timers too. As of 2003, it was estimated that 1 billion units were manufactured every year. The 555 is the most popular integrated circuit ever manufactured.

🔗 Psychology

Learned helplessness is behavior exhibited by a subject after enduring repeated aversive stimuli beyond their control. It was initially thought to be caused from the subject's acceptance of their powerlessness: discontinuing attempts to escape or avoid the aversive stimulus, even when such alternatives are unambiguously presented. Upon exhibiting such behavior, the subject was said to have acquired learned helplessness. Over the past few decades, neuroscience has provided insight into learned helplessness and shown that the original theory actually had it backwards: the brain's default state is to assume that control is not present, and the presence of "helpfulness" is what is actually learned.

In humans, learned helplessness is related to the concept of self-efficacy; the individual's belief in their innate ability to achieve goals. Learned helplessness theory is the view that clinical depression and related mental illnesses may result from such real or perceived absence of control over the outcome of a situation.

🔗 Biography 🔗 Espionage 🔗 Military history 🔗 Military history/Military biography 🔗 Biography/military biography 🔗 Military history/Intelligence 🔗 United Kingdom 🔗 Military history/World War II 🔗 Military history/German military history 🔗 Military history/Spanish military history 🔗 Spain 🔗 Military history/European military history 🔗 Military history/British military history

Juan Pujol García (Spanish: [ˈxwan puˈʝol ɣaɾˈθi.a]; 14 February 1912 – 10 October 1988), also known as Joan Pujol i García (Catalan: [ʒuˈan puˈʒɔl i ɣəɾˈsi.ə]), was a Spanish spy who acted as a double agent loyal to Great Britain against Nazi Germany during World War II, when he relocated to Britain to carry out fictitious spying activities for the Germans. He was given the codename Garbo by the British; their German counterparts codenamed him Alaric and referred to his non-existent spy network as "Arabal".

After developing a loathing of political extremism of all sorts during the Spanish Civil War, Pujol decided to become a spy for Britain as a way to do something "for the good of humanity". Pujol and his wife contacted the British Embassy in Madrid, which rejected his offer.

Undeterred, he created a false identity as a fanatically pro-Nazi Spanish government official and successfully became a German agent. He was instructed to travel to Britain and recruit additional agents; instead he moved to Lisbon and created bogus reports about Britain from a variety of public sources, including a tourist guide to Britain, train timetables, cinema newsreels and magazine advertisements.

Although the information would not have withstood close examination, Pujol soon established himself as a trustworthy agent. He began inventing fictitious sub-agents who could be blamed for false information and mistakes. The Allies finally accepted Pujol when the Germans expended considerable resources attempting to hunt down a fictitious convoy. Following interviews by Desmond Bristow of Section V MI6 Iberian Section, Juan Pujol was taken on. The family were moved to Britain and Pujol was given the code name "Garbo". Pujol and his handler Tomás Harris spent the rest of the war expanding the fictitious network, communicating to the German handlers at first by letters and later by radio. Eventually the Germans were funding a network of 27 agents, all fictitious.

Pujol had a key role in the success of Operation Fortitude, the deception operation intended to mislead the Germans about the timing, location and scale of the invasion of Normandy in 1944. The false information Pujol supplied helped persuade the Germans that the main attack would be in the Pas de Calais, so that they kept large forces there before and even after the invasion. Pujol had the distinction of receiving military decorations from both sides of the war – being awarded the Iron Cross and becoming a Member of the Order of the British Empire.

🔗 Geology 🔗 Rocks and minerals 🔗 Iceland

Iceland spar, formerly called Iceland crystal (Icelandic: silfurberg [ˈsɪlvʏrˌpɛrk], lit. 'silver-rock') and also called optical calcite, is a transparent variety of calcite, or crystallized calcium carbonate, originally brought from Iceland, and used in demonstrating the polarization of light.

🔗 Electronic music 🔗 Music/Music genres

Lowercase is an extreme form of ambientminimalism where very quiet, usually unheard sounds are amplified to extreme levels. Minimal artist Steve Roden popularized the movement with an album entitled Forms of Paper, in which he made recordings of himself handling paper in various ways. These recordings were commissioned by the Hollywood branch of the Los Angeles Public Library.

🔗 Psychology

The need for cognition (NFC), in psychology, is a personality variable reflecting the extent to which individuals are inclined towards effortful cognitive activities.

Need for cognition has been variously defined as "a need to structure relevant situations in meaningful, integrated ways" and "a need to understand and make reasonable the experiential world". Higher NFC is associated with increased appreciation of debate, idea evaluation, and problem solving. Those with a high need for cognition may be inclined towards high elaboration. Those with a lower need for cognition may display opposite tendencies, and may process information more heuristically, often through low elaboration.

Need for cognition is closely related to the five factor model domain openness to experience, typical intellectual engagement, and epistemic curiosity (see below).

🔗 Architecture

A saw-tooth roof is a roof comprising a series of ridges with dual pitches either side. The steeper surfaces are glazed to admit daylight and face away from the equator to shield workers and machinery from direct sunlight. This kind of roof admits natural light into a deep plan building or factory. It was therefore most commonly built during the Machine Age from the mid-nineteenth century to the mid-twentieth, when electrification of factories was not yet common.

Many factories of the era had little or no electrical wiring; their main power sources for the machinery were often steam engines driving line shafting, and the lighting was chiefly via daylighting through the windows. Work done at night, when necessary, was typically lit by oil lamps and candles, but many factories closed for the night. Their norm of an early working day (for example, 6 a.m. to 4 p.m.) was not merely a tradition but a functional decision based on this reliance on daylighting. The same was true of the farmer's workday, for the same reason.

The Object Oriented Role Analysis and Modeling (OOram) is a method, based on the concept of role, for performing object-oriented modeling.

Originally (1989) coined Object Oriented Role Analysis, Synthesis and Structuring (OORASS), the method focuses on describing patterns of interaction without connecting the interaction to particular objects/instances. OOram was originally developed by Trygve Reenskaug (1996), a professor at the University of Oslo and the founder of the Norwegian IT company Taskon. The use of "roles" in OOram is similar in application to that of Agent-oriented programming.

Enterprise models created according to OOram may have a number of views, with each view presenting certain aspects of a model. The following ten views are proposed:

1. Area of concern view: Textual description of a phenomenon represented in the role model.
2. Stimulus-response view: Describes how environment roles may trigger activities in the organization (stimulus), together with the effect (response).
3. Role list view: List describing all roles of a role model together with attributes and textual explanation.
4. Semantic view: Describes meaning of roles and relationships between roles.
5. Collaboration view: Describes patterns of roles and message paths.
6. Interface view: Describes all messages that can be sent along a message path.
7. Scenario view: Provides a sample sequence of messages flowing between roles (a concrete example).
8. Process view: Describes data flow between roles and associated activities performed by the roles.
9. State diagram view: For each role, the legal states can be described together with messages that trigger transitions.
10. Method specification view: Describes what messages to send for each method belonging to a role. May also specify procedures to perform.

OOram suggests a varied mix of formal and informal notations and languages for representing and communicating models. Which view to use depends upon the needs in a particular situation.