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🔗 Economics 🔗 Statistics

The Herfindahl index (also known as Herfindahl–Hirschman Index, HHI, or sometimes HHI-score) is a measure of the size of firms in relation to the industry and an indicator of the amount of competition among them. Named after economists Orris C. Herfindahl and Albert O. Hirschman, it is an economic concept widely applied in competition law, antitrust and also technology management. It is defined as the sum of the squares of the market shares of the firms within the industry (sometimes limited to the 50 largest firms), where the market shares are expressed as fractions. The result is proportional to the average market share, weighted by market share. As such, it can range from 0 to 1.0, moving from a huge number of very small firms to a single monopolistic producer. Increases in the Herfindahl index generally indicate a decrease in competition and an increase of market power, whereas decreases indicate the opposite. Alternatively, if whole percentages are used, the index ranges from 0 to 10,000 "points". For example, an index of .25 is the same as 2,500 points.

The major benefit of the Herfindahl index in relationship to such measures as the concentration ratio is that it gives more weight to larger firms.

The measure is essentially equivalent to the Simpson diversity index, which is a diversity index used in ecology; the inverse participation ratio (IPR) in physics; and the effective number of parties index in politics.

🔗 Biography 🔗 Mathematics 🔗 Physics 🔗 Biography/science and academia 🔗 Robotics 🔗 United Kingdom 🔗 Physics/Biographies 🔗 Christianity

Freeman John Dyson (15 December 1923 – 28 February 2020) was an English-born American theoretical physicist and mathematician known for his work in quantum electrodynamics, solid-state physics, astronomy and nuclear engineering. He was professor emeritus in the Institute for Advanced Study in Princeton, a member of the Board of Visitors of Ralston College and a member of the Board of Sponsors of the Bulletin of the Atomic Scientists.

Dyson originated several concepts that bear his name, such as Dyson's transform, a fundamental technique in additive number theory, which he developed as part of his proof of Mann's theorem; the Dyson tree, a hypothetical genetically-engineered plant capable of growing in a comet; the Dyson series, a perturbative series where each term is represented by Feynman diagrams; the Dyson sphere, a thought experiment that attempts to explain how a space-faring civilization would meet its energy requirements with a hypothetical megastructure that completely encompasses a star and captures a large percentage of its power output; and Dyson's eternal intelligence, a means by which an immortal society of intelligent beings in an open universe could escape the prospect of the heat death of the universe by extending subjective time to infinity while expending only a finite amount of energy.

Dyson believed global warming is caused merely by increased carbon dioxide but that some of the effects of this are favourable and not taken into account by climate scientists, such as increased agricultural yield. He was skeptical about the simulation models used to predict climate change, arguing that political efforts to reduce causes of climate change distract from other global problems that should take priority. He also signed the World Climate Declaration that there "is no Climate Emergency".

🔗 Zoo 🔗 Primates

Ken Allen (February 13, 1971 – December 1, 2000) was a Bornean orangutan at the San Diego Zoo. He became one of the most popular animals in the history of the zoo because of his many successful escapes from his enclosures. He was nicknamed "the hairy Houdini".

Ken Allen was born in captivity at the San Diego Zoo in 1971. During the 1980s, Ken Allen gained worldwide attention for a series of three escapes from his enclosure, which had been thought to be escape-proof. During some of his escapes, his female companions would join him. Ken Allen's ability to outwit his keepers, as well as his docile demeanor during his escapes, resulted in fame. He had his own fan club, and was the subject of T-shirts and bumper stickers (most reading "Free Ken Allen"). A song, The Ballad of Ken Allen, was written about him.

Ken Allen developed prostate cancer and was euthanized on December 1, 2000. He was 29 years old.

🔗 Physiology

Monocular rivalry is a phenomenon of human visual perception that occurs when two different images are optically superimposed. During prolonged viewing, one image becomes clearer than the other for a few moments, then the other image becomes clearer than the first for a few moments. These alternations in clarity continue at random for as long as one looks. Occasionally one image will become exclusively visible and the other image invisible.

In the demonstration, one image is a green grating and the other is a red grating. During prolonged inspection, the viewer can see the green grating as clearer than the red grating for a few moments, then the reverse. Occasionally the green grating will be all that is visible and occasionally the red grating will be all that is visible. Occasionally, at transitions, one will briefly see irregular composites of the two gratings (such as the red and green gratings superimposed but with one or two bars of the green grating invisible).

Monocular rivalry is easier to see when the component stimuli are of opposite colors, but it also occurs when the component stimuli have the same colors. As long as the two component stimuli differ spatiotemporally in some way, such as orientation (as shown), spatial frequency, or direction of movement, monocular rivalry can be seen.

A hydraulic telegraph (Greek: υδραυλικός τηλέγραφος) is either of two different hydraulic-telegraph telecommunication systems. The earliest one was developed in 4th-century BC Greece, while the other was developed in 19th-century AD Britain. The Greek system was deployed in combination with semaphoric fires, while the latter British system was operated purely by hydraulic fluid pressure.

Although both systems employed water in their sending and receiver devices, their transmission media were completely different. The ancient Greek system transmitted its semaphoric information to the receiver visually, which limited its use to line-of-sight distances in good visibility weather conditions only. The 19th-century British system used water-filled pipes to effect changes to the water level in the receiver unit (similar to a transparent water-filled flexible tube used as a level indicator), thus limiting its range to the hydraulic pressure that could be generated at the transmitter's device.

While the Greek device was extremely limited in the codes (and hence the information) it could convey, the British device was never deployed in operation other than for very short-distance demonstrations. Although the British device could be used in any visibility within its range of operation, it could not work in sub-zero temperatures without additional infrastructure to heat the pipes. This contributed to its impracticality.

🔗 Europe 🔗 Sexology and sexuality 🔗 Sexology and sexuality/Sex work

A sex drive-in or sex box is a car garage (or similarly shielded location) that is designed to allow prostitution to take place using cars, and can be found in a few countries in Europe. Generally the facilities are created by local authorities to put some control on where prostitution occurs and to provide increased safety.

🔗 Companies 🔗 Lists 🔗 Disney

The following is a list of assets owned and operated by The Walt Disney Company, unless otherwise indicated.

🔗 New York City 🔗 Architecture

75½ Bedford Street is a house located in the West Village neighborhood of New York City that is only 9 feet 6 inches (2.9 meters) wide. Built in 1873, it is often described as the narrowest house in New York. Its past tenants have included Edna St. Vincent Millay, Ann McGovern, cartoonist William Steig and anthropologist Margaret Mead. It is sometimes referred to as the Millay House, indicated by a plaque on the outside of the house. The house is located in the Greenwich Village Historic District, but is not an individually designated New York City Landmark.

🔗 Volcanoes 🔗 Meteorology

The year 1816 is known as the Year Without a Summer (also the Poverty Year and Eighteen Hundred and Froze To Death) because of severe climate abnormalities that caused average global temperatures to decrease by 0.4–0.7 °C (0.72–1.26 °F). This resulted in major food shortages across the Northern Hemisphere.

Evidence suggests that the anomaly was predominantly a volcanic winter event caused by the massive 1815 eruption of Mount Tambora in April in the Dutch East Indies (now Indonesia). This eruption was the largest eruption in at least 1,300 years (after the hypothesized eruption causing the extreme weather events of 535–536), and perhaps exacerbated by the 1814 eruption of Mayon in the Philippines.

🔗 Novels 🔗 Novels/Science fiction

Last and First Men: A Story of the Near and Far Future is a "future history" science fiction novel written in 1930 by the British author Olaf Stapledon. A work of unprecedented scale in the genre, it describes the history of humanity from the present onwards across two billion years and eighteen distinct human species, of which our own is the first. The book employs a narrative conceit that, under subtle inspiration, the novelist has unknowingly been dictated a channelled text from the last human species.

Stapledon's conception of history is based on the Hegelian Dialectic, following a repetitive cycle with many varied civilisations rising from and descending back into savagery over millions of years, but it is also one of progress, as the later civilisations rise to far greater heights than the first. The book anticipates the science of genetic engineering, and is an early example of the fictional supermind; a consciousness composed of many telepathically linked individuals.

In 1932, Stapledon followed Last and First Men with the far less acclaimed Last Men in London. Another Stapledon novel, Star Maker (1937), could also be considered a sequel to Last and First Men (mentioning briefly man's evolution on Neptune), but is even more ambitious in scope, being a history of the entire universe.

It is the 11th title in the SF Masterworks series.