text:
Talk:Japanese Red Army

Untitled
No explanation on how their acts would overthrow Japan? Seems like much of it was in other parts of the world. Beetle B.

No one ever said terrorists had to make sense. --82.2.117.234 19:33, 12 January 2006 (UTC)

Ehh, the above was me, sorry, forgot to log in.--ScottishPinko 19:37, 12 January 2006 (UTC)

 * I think Fusako Shigenobu's logic was to work with existing terror networks, in solidarity with existing campaigns, rather than "starting from scratch." They were always a bit fuzzy (as far as I can tell) with how they planned a Japanese/world revolution, or what they wanted the post-revolutionary world to look like.  -Danspalding 00:50, 9 March 2006 (UTC)

More unbiased language please. Although politics is turbulent, I took liberty to change "murderers" to "members" because murder has negative (biased) rather than neutral and objective connotations.Aminatam 13:57, 23 February 2006 (UTC)

How could the JRA have been responsible for the 1970 JAL hijacking when the group wasn't founded until February 1971? Another source (http://japanfocus.org/113.html) credits this action to a different group, which would make more sense. —The preceding unsigned comment was added by 66.138.132.149 (talk • contribs) 20:58, 8 March 2006.

 * Good point; the 1970 JAL hijacking was actually the work of the Japanese Communist League - Red Army Faction. However, Fusako Shigenobu, founder of the JRA proper, and several members were originally part of the Red Army Faction.  The leadership of the RAF were on the plane that went to South Korea, and were out of the picture for years afterwards.  This should be clarified in the article.  -Danspalding 00:50, 9 March 2006 (UTC)

Under aliases is Holy War Brigade listed which is a pseudonym I don't believe a communist group would operate under. It is however a common problem that mentally unstable persons call the police after terrorist attacks and taking the blame on behalf of existing or even made up organisations. I strongly belive that this is one such incident. Good article, but no number of dead from the 1977 plane crash is cited. Neither any years on the last actions on the list. Please update. —The preceding unsigned comment was added by 84.210.117.113 (talk • contribs) 00:27, 30 March 2006.

BTW wasn't the two Lod attackers in '72 killed by israeli gunfire??? Did they really blow themselves up???. —The preceding unsigned comment was added by 84.210.117.113 (talk • contribs) 00:30, 30 March 2006.

Red Army-Faction, United Red Army, Japanese Red Army, Arab Japanese Red Army
Shigenobu left Japan as a leading member of the Red Army-Faction (which called itself a faction in 1969, because it then saw itself as a part of the new-left Communist League or Bund), when this "army" was in a rather sorry state. Its founder and the 1969 leadership was jailed or in North Korea, around 200 members had been put in prison. Merger-talks between the new leader of the Red Army-Faction and the leader of the Revolutionary Left Wing of the Japanese Communist Party (Kakusa) may have begun. In April the Red Army bought weapons from the maoist Left Wing and in July both groups declared themselves to be The Unified Red Army, which was soon changed to The United Red Army (in the half year of its existence all this group really achieved was to self-destruct in an ugly massacre of a third of its members and in the spring of 1972 the Red Army in Japan was kaputt. Shigenobu left with very few fighters for Lebanon and most or all of them belonged not to the Red Army, but to a Kyoto group, Kyoto Bandits (Patricia Steinhoff).

Also refered to as the Kyoto Partisans —Preceding unsigned comment added by 217.43.175.109 (talk) 20:32, 7 May 2011 (UTC)

 * As far as I know Shigenobu called her group Japanese Red Army only after the Lod attack in May, 1972. She also used Arab JRA. Only there was no Red Army at home any more.--Radh (talk) 17:35, 12 August 2009 (UTC)

in the Lebanon
Why keep people reverting to "in Lebanon"?--Radh (talk) 07:55, 24 September 2009 (UTC)

Mitsubishi attack
that was done by the East Asia Anti Japanese Armed Front —Preceding unsigned comment added by 217.43.175.109 (talk) 20:41, 7 May 2011 (UTC)

members
there's a nice, practical table in the Japanese article that encompasses the activities and posterior activities of the group's members: FoCuSandLeArN (talk) 21:08, 11 August 2012 (UTC)

Anti-Zionism
Are they against Jews and Rastas because it said Anti-Zionism (against Judaism and Rastafarian). Squidville1 (talk) 11:40, 5 September 2013 (UTC)

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Shigenobu scheduled release
source: https://unseenjapan.com/shigenobu-fusako-japanese-red-army-release-from-prison/ — Preceding unsigned comment added by 71.218.133.221 (talk) 21:43, 1 May 2022 (UTC)

title: Talk:Japanese Red Army


text:
Wikipedia:WikiProject Comics/Superherobox example

Example
Line(s) have been broken for readability.

Article text goes here. Infobox floats attractively at the right.

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/


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User:DianaS

Hello, I am new here.

title: User:DianaS


text:
Mirele Efros

Mirele Efros was an 1898 Yiddish play by Jacob Gordin. Some have called it "the Jewish Queen Lear".

The title character is a powerful matriarch who becomes bitterly estranged from her own family. Lulla Rosenfeld, in her commentary to Jacob Adler's memoir, describes the central character as part of a tradition running at least from Solomon Ettinger's Serkele (1825) to Clifford Odets' Awake and Sing (1935).

The title role was, according to Rosenfeld, "performed by every leading Yiddish actress". It was originally played by Keni Liptzin, during the first heyday of Yiddish theater in New York City. It was also notably played by Polish actress Esther Rachel Kaminska, who performed the part in New York in 1912. The Liptzin production had David Kessler as Mirele's son and Dinah Feinman (the former wife of Jacob Adler) as her daughter-in-law Shaindl.

A silent Yiddish film based on the play was produced in Warsaw, in 1912, directed by Andrzej Marek (Mark Arnstein) and starring Esther Rachel Kaminska, along with her daughter Ida Kaminska. A film adaptation of the play was made in the United States in 1939. It was directed by Josef Berne with Berta Gersten in the title role and Ruth Elbaum as Shaindl. It was made in Yiddish with English subtitles.

Plot
The title character, Mirele, is a fifty-year-old widow when the play begins who, over the last several decades, salvaged her late husband's failing business. Honest, hardworking, and astute, but also autocratic, her authority is challenged by her daughter-in-law Shaindl, who insists that it is time that her husband, Mirele's son, inherit the business. The inheritance is given—the house as well—but grudgingly, in such a manner as to cut off Mirele from her family. She takes refuge with her faithful steward, Kalman, towards whom she continues to behave as an autocrat.

Ten years later Shaindl, her marriage and the business both going poorly, attempts to heal the breach in time for her son's bar mitzvah. Mirele refuses, but after Shaindl's departure she collapses in grief. Ultimately, the boy successfully approaches her on the day of his bar mitzvah and convinces her to come. Despite its tragic, Shakespearean tone, the play, atypically for Gordin, ends happily, with song and dance.

Readings

 * Adler, Jacob, A Life on the Stage: A Memoir, translated and with commentary by Lulla Rosenfeld, Knopf, New York, 1999, ISBN 0-679-41351-0. 259-261 (commentary)

title: Mirele Efros


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Univalent function

In mathematics, in the branch of complex analysis, a holomorphic function on an open subset of the complex plane is called univalent if it is injective.

Examples
The function $$f \colon z \mapsto 2z + z^2$$ is univalent in the open unit disc, as $$f(z) = f(w)$$ implies that $$f(z) - f(w) = (z-w)(z+w+2) = 0$$. As the second factor is non-zero in the open unit disc, $$z = w$$ so $$f$$ is injective.

Basic properties
One can prove that if $$G$$ and $$\Omega$$ are two open connected sets in the complex plane, and

 * $$f: G \to \Omega$$

is a univalent function such that $$f(G) = \Omega$$ (that is, $$f$$ is surjective), then the derivative of $$f$$ is never zero, $$f$$ is invertible, and its inverse $$f^{-1}$$ is also holomorphic. More, one has by the chain rule

 * $$(f^{-1})'(f(z)) = \frac{1}{f'(z)}$$

for all $$z$$ in $$G.$$

Comparison with real functions
For real analytic functions, unlike for complex analytic (that is, holomorphic) functions, these statements fail to hold. For example, consider the function

 * $$f: (-1, 1) \to (-1, 1) \, $$

given by $$f(x)=x^3$$. This function is clearly injective, but its derivative is 0 at $$x=0$$, and its inverse is not analytic, or even differentiable, on the whole interval $$(-1,1)$$. Consequently, if we enlarge the domain to an open subset $$G$$ of the complex plane, it must fail to be injective; and this is the case, since (for example) $$f(\varepsilon \omega) = f(\varepsilon) $$ (where $$\omega $$ is a primitive cube root of unity and $$\varepsilon$$ is a positive real number smaller than the radius of $$G$$ as a neighbourhood of $$0$$).

title: Univalent function


text:
User talk:Ravenhook

Welcome
Welcome!

Hello,, and welcome to Wikipedia! Thank you for your contributions. I hope you like the place and decide to stay. Here are a few good links for newcomers: I hope you enjoy editing here and being a Wikipedian! Please sign your name on talk pages using four tildes (~~); this will automatically produce your name and the date. If you need help, check out Where to ask a question, ask me on my talk page, or place  on your talk page and someone will show up shortly to answer your questions. Again, welcome! Academic Challenger 06:03, 4 Apr 2005 (UTC)
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Jonathan Edwards College
Are you still in New Haven? In the JE dining hall there's a quote on the wall, something like "Do go into teaching. It is the only profession where anything short of total failure is a success." Could you possible check and add it to this article? Call me eccentric Old Blue, but I like that quotation. Jehochman (Talk/Contrib) 21:45, 24 March 2006 (UTC)

Could use your help
Behack, you edited my AIDS law clinic addition, and in a way I agreed with; afterall, in CLS's long history it didn't merit a full paragraph. But I need your help: my Floyd Abrams articles have been nominated for deletion. I explain the point behind them on the deletion page, but if you think this is important information I could sure use someone backing me up. I go into his legal strategy, his observations on the Supreme Court, his experience. I have spent so many countless hours working on it, that if it's deleted I'll have to taken an extended vacation from contributing, because I think it is very important. I'm all for deleting useless and vanity-fuelled articles, but this man is living history, and I took it upon myself to do this (after I read the book he gave me when I went to take his photograph for Wikipedia). I am writing a grant-proposal around the project; if it's deleted, well, that would hurt me a lot. http://en.wikipedia.org/wiki/Wikipedia:Articles_for_deletion/Floyd_Abrams_and_the_Pentagon_Papers_case --DavidShankBone 03:05, 18 September 2006 (UTC)

CLS Rankings
Sure, as long as you update the page next week.Ulpian 13:46, 28 March 2007 (UTC)

Fair use rationale for Image:JE-Shield.jpg
Thanks for uploading or contributing to Image:JE-Shield.jpg. I notice the image page specifies that the image is being used under fair use but there is no explanation or rationale as to why its use in Wikipedia articles constitutes fair use. In addition to the boilerplate fair use template, you must also write out on the image description page a specific explanation or rationale for why using this image in each article is consistent with fair use. Suggestions on how to do so can be found here.

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Image:JE-Shield.jpg
I have tagged Image:JE-Shield.jpg as no rationale, because it does not provide a fair use rationale. If you believe the image to be acceptable for fair use according to Wikipedia policy, please provide a rationale explaining as much, in accordance with the fair use rationale guideline, on the image description page. Some examples can be found at Use rationale examples. Please also consider using or one of the other tags listed at Image copyright tags/Non-free. Thank you. Rettetast (talk) 17:41, 28 July 2008 (UTC)

Neutral notice
As an editor with an interest in New York City articles, you are invited to participate in an RfC at The Dakota. --Tenebrae (talk) 21:35, 25 June 2013 (UTC)

ArbCom elections are now open!
MediaWiki message delivery (talk) 12:58, 23 November 2015 (UTC)

title: User talk:Ravenhook


text:
Talk:Neutrality of money

Neutrality and super-neutrality
is neutrality and super-neutrality of money the same thing? i had both terms in a lecture but i couldn't grasp if there is any difference between the two. — Preceding unsigned comment added by 141.44.163.84 (talk • contribs) 01:20, 23 February 2005 (UTC)
 * definately not the saem thing, superneutral when the rate at which the money supply changes affects the price level, neutral when the level of the money supply affects price, sorry cant explain it better.Bluemoose 08:52, 24 Feb 2005 (UTC)

Name change
I suggest changing the name of this article to Monetary neutrality. ~ UBeR 02:07, 30 October 2006 (UTC)
 * All the text books I've read call it the Neutrality of Money. --AtD 15:38, 30 October 2006 (UTC)

just bakwas —Preceding unsigned comment added by 117.102.8.130 (talk) 07:13, 15 January 2010 (UTC)

Counterfeiting
If the central bank can't affect the economy - why have it? Also why then is counterfeiting illegal? Hasn't money evolved from being a commonly traded commodity which use solves the coincidence of wants problem. Which means printing extra paper money and then using it, is taking something but not producing something in return (if the paper money isn't a claim on some commodity). How can that not distort the economy in favour of the money printer? — Preceding unsigned comment added by 135.196.109.220 (talk)

 * The theory of Neutrality of Money says that the central bank cannot effect the real macro-economy by changing the amount of money in circulation, as money is just paper and coin, not factories and such. It does not make any claims on other methods central banks use to control the economy. Summed up, it basically means printing money doesn't make factories and highways appear out of nowhere. Any changes in aggregate demand caused by a change in the money supply are "neutralised" by changes in the price level. The theory implies there are no long run problems caused by inflation, thus only holds true in a closed economy.

 * With regards to Counterfeiting, it's illegal because it unjustly transfers wealth to the Counterfeiter. Under the NoM theory, it doesn't change the size of the macro-economy in the long run, but could change the price level. --AtD 14:10, 21 February 2007 (UTC)

 * Well, the same happens when the Central Bank prints money - the money is not distributed equally to all people! It only gradually spreads throughout the economy. The effect is that the first receiving the money benefit twice: 1 when they use the money to buy the factors of production at old prices; 2 when they sell their products at new, post-inflation, prices. The idea of money neutrality is pure non-sense. The Central Bank is a legalized conterfeiter! — Preceding unsigned comment added by 86.121.5.166 (talk • contribs) 19:55, 24 December 2007 (UTC)

Citation overload
The 'evidence' section of this article contains the sentence 'Empirical studies have shown that money is neutral in the long-run.', followed by no fewer than 64 citations(!). This is utterly unnecessary. If such a result has been widely proved, it shouldn't be necessary to add so many citations to support it: a few citations to broad statements in reliable sources would be better than many citations to individual studies. At the moment, it breaks up the page and makes it harder to read, and paradoxically makes the sentence look less confidently stated due to the sheer number of citations the writer apparently felt the need to include. Robofish (talk) 17:13, 29 November 2011 (UTC)

Citation
is ridiculous.

the material here for reference.
 * References

When a statement (like "Empirical studies have shown that money is neutral in the long-run") is cited, the way to go about it is to find a reliable secondary source which supports it. Citing a bunch of individual studies is completely improper, and risks violating the "no original research" policy. Gabbe (talk) 10:51, 30 January 2012 (UTC)

You say that, but now when I replaced it with a single textbook reference in which the secondary source overviews the evidence, it got removed because "That doesn't constitute evidence". Tails non-neutrality wins, heads neutrality loses? Or is a reference to an ADVANCED textbook going to be sufficient? 109.145.191.56 (talk) 17:08, 10 November 2014 (UTC)

title: Talk:Neutrality of money


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Dinah Shtettin

Dinah Shtettin (akas: Dina Stettin and Dinah Feinman (דיינע פיינמאן); died 1946) was an English Yiddish theater actress. She was the second wife of Jacob Adler, with whom she had a daughter, Celia Adler, in 1889.

Early life
Dinah Shtettin was born in Poland to strict Orthodox Jewish parents. As a young child, her family moved to London. She began her theatrical career as a teenager in the chorus of Israel Grodner's London troupe in the mid-1880s, eventually winning small parts and joining the troupe when the Grodners went to Paris. When she was about sixteen, she met Jacob Adler, then a widower, who took a liking to her. At this time, he was in a relationship with Jenny Kaiser, with whom he had become romantically involved while still married to his first wife, Sonya. Adler and Kaiser had a son, Charles. Shtettin's father disapproved of both Adler and the theater, but did not restrict his daughter's wishes. He stated, "Let it be a divorce tomorrow, but marriage it must be!" The couple married in 1887, after which Adler and his troupe travelled to the United States. After he returned to London for seven months, he once again journeyed to New York in 1889 and was shortly followed by Dinah. Their daughter Celia was born in New York later that year. Shtettin divorced Adler when he eloped with Sara Heine two years later, in 1891. Despite acrimony between them, Shtettin went on to perform with her ex-husband's troupe on the American Yiddish stage. She travelled back to London to act to great popularity; in 1909, a woman was crushed to death in the effort to get the best seats to see her at the London Pavilion.

Shtettin later married playwright and actor Siegmund Feinman; they raised Celia together. Celia took her stepfather's surname in childhood, but took her father's name in her career, becoming a leading actress on the Yiddish stage. Shtettin and Feinman had another daughter, actress Lillie (Lili) Feinman, who married Yiddish actor Ludwig Satz. Siegmund Feinman died in 1909.

Stage career
Shtettin's New York debut was in the role of Fanya, the villain's daughter, in Jacob Gordin's Siberia (1892). Commercially unsuccessful at the time, this first play of Gordin's is now considered a landmark in the evolution of Yiddish theater.

title: Dinah Shtettin


text:
User:Dicejordan42

I try to be helpful.

title: User:Dicejordan42


text:
1973 in rail transport

January events

 * January 27 – MBTA purchases several rail lines in New England from Penn Central to form the basis of the new commuter system's network.

February events

 * February 26 – Chessie System is incorporated to become the parent corporation of a combined B&O/C&O/WM railroad system.

March events

 * March 13 – A riot breaks out at Ageo Station in Saitama, Japan as the National Railway Locomotive Engineers Union protests unsafe working conditions on the JNR.
 * March 30 – Toronto's Yonge Subway is extended to York Mills station.

May events

 * May 21 – Passenger traffic begins on the Bay Area Rapid Transit (BART) Concord line, through the 3.1 mi Berkeley Hills Tunnel between Oakland and Orinda, California beneath the Berkeley Hills.

June events

 * June 3 – The Norwegian State Railways open Lieråsen Tunnel on the Drammen Line between Asker and Lier (10.7 km).
 * June 22 – The EMD SDP40F diesel locomotive enters revenue service with Amtrak.

August events

 * August 17 – The last DB Class E 40 leaves the gates of the Krupp factory in Essen.

September events

 * September 28 – Amtrak's Turboliners make their first run on the Chicago–St Louis corridor.

November events

 * November 5 – Bay Area Rapid Transit Peninsula service starts between Downtown San Francisco and Daly City.
 * November 7 – Frontier Series Canadian ten-dollar note introduced depicting the Canadian passenger train hauled by an EMD F40PH diesel-electric locomotive.
 * November 27 – Toei Subway Line 6 (present-day Mita Line) is extended from Hibiya to Mita in Tokyo, Japan; its second extension since opening in 1968.

December events

 * December 19 – The Ealing rail crash occurred when an express train from London Paddington to Oxford derails at speed between Ealing Broadway and West Ealing. Ten passengers are killed and 94 injured

Unknown date events

 * The isolated coal hauler, the Black Mesa and Lake Powell Railroad, opens in Northern Arizona, the world's first line to use 50,000 V overhead line power.
 * Transcameroon Railway extended to N'Gaoundéré.
 * John W. Barriger III becomes president of the Boston and Maine Railroad.

title: 1973 in rail transport


text:
The Creation of the World and Other Business

The Creation of the World and Other Business is a play by Arthur Miller first performed in 1972.

Summary
The play is a parable that explores the theme of good-versus-evil by way of a comedic retelling of events in the Book of Genesis in the Bible. The first act is set in the Garden of Eden, where God creates Eve for Adam. God wants the couple to procreate, but doesn't know how to entice them into starting the process. Onto the scene comes Lucifer, who believes the existence of evil will make sex exciting, and he tempts the couple to eat the forbidden apple. God punishes Lucifer by tossing him into hell and punishes the couple by expelling them from paradise. In the second act, Eve gives birth to Cain. In the third act, Cain kills his brother Abel and is sent out as a wanderer.

Productions
Miller's first work since The Price five years earlier, Creation stumbled along during rehearsals. Original director Harold Clurman and most of the cast, including Barbara Harris and Hal Holbrook, were replaced, and the playwright rewrote most of the material. After 21 previews, the Broadway production, directed by Gerald Freedman, opened on November 30, 1972 at the Shubert Theatre, where it ran for 20 performances. The cast included Stephen Elliott as God, Bob Dishy as Adam, Zoe Caldwell as Eve, George Grizzard as Lucifer, and Mark Lamos as Abel.

In 1973, Tangent Theatre, an amateur theatre company from Walsall, won the rights to perform the play at the Edinburgh Festival Fringe. It was a critical success and Don Nunes, the director accepted the award for best production that year from Esther Rantzen. Tangent Theatre grew out of the West Midlands College of Education Theatre Society and performed all over Britain and Europe between 1969 and 1974.

Miller reworked the play into a musical, Up From Paradise, which opened in 1974 at the University of Michigan in Ann Arbor.

In 2004, Citizens of the Universe's production of Creation of the World and Other Business was banned from playing at Greenville Technical College.

In 2014, the Theater Department at Orange Coast College put on a rock and roll jukebox musical version of the play.


text:
Jurmo-class landing craft

The Jurmo-class landing craft is a type of military transport in use by the Finnish Navy. The manufacturer Marine Alutech designates it as Watercat M12.

History
The Jurmo was the result of modernisation in the Finnish Navy in the late 1990s. It was designed to replace the existing Uisko class landing craft. Its main purpose is landing and transportation operations for the Finnish Coastal Jaegers in all weather conditions. It has good maneuverability and can come to a full stop in only one ship length from top speed. Low draft makes it suitable for amphibious assault even in shallow waters.

The Jurmo can transport 3 tons of cargo or 22 men.

The Jurmo is currently being evaluated by the German and Greek navies. Ten of the slightly larger and more powerful M14 version were delivered to the Royal Malaysian Police.

Operators

 * 🇫🇮: Finnish Navy: U601-U638. An additional 17 units were ordered on 2023-06-29

 * 🇲🇾 Malaysia:Royal Malaysian Police: 10 vessels of the Watercat M14 version.

Related development

 * G class landing craft
 * Uisko class landing craft
 * Watercat M14 class landing craft

title: Jurmo-class landing craft


text:
Rudolph Marks

Rudolph Marks (circa 1867-1930; born in Odessa, Russian Empire, as Max Radkisson and A.K.A. Rudolph Marks Rodkinson) was a playwright, songwriter, and comedian. He rivaled Sigmund Mogulesko in Yiddish Theater in New York City in the 1890s, but had a less enduring career.

Biography
Marks arrived in New York aged 19, having spent four years in England after leaving Russia. In New York, he appeared with the Thalia Theatre and the United Hebrew Opera Company. By 1893, he was described as a "well known and clever comedian", and was one of two contenders for the title of "most popular young actor" in a contest run by a New York newspaper. He wrote several plays in Yiddish, including The Bowery Tramp, "the great comedy success" Chaim in America, and The Shop Girl. By 1893, Marks had begun studying law at University of the city of New York, and was admitted to the bar in 1898. For some years, reports of court cases he appeared in described him as "better known as a writer of Yiddish plays and as an actor of Shakepearean parts in the Bowery theaters than as a lawyer". He died in Manhattan on 6 May 1930.

title: Rudolph Marks


text:
Motion estimation

In computer vision and image processing, motion estimation is the process of determining motion vectors that describe the transformation from one 2D image to another; usually from adjacent frames in a video sequence. It is an ill-posed problem as the motion happens in three dimensions (3D) but the images are a projection of the 3D scene onto a 2D plane. The motion vectors may relate to the whole image (global motion estimation) or specific parts, such as rectangular blocks, arbitrary shaped patches or even per pixel. The motion vectors may be represented by a translational model or many other models that can approximate the motion of a real video camera, such as rotation and translation in all three dimensions and zoom.

Related terms
More often than not, the term motion estimation and the term optical flow are used interchangeably. It is also related in concept to image registration and stereo correspondence. In fact all of these terms refer to the process of finding corresponding points between two images or video frames. The points that correspond to each other in two views (images or frames) of a real scene or object are "usually" the same point in that scene or on that object. Before we do motion estimation, we must define our measurement of correspondence, i.e., the matching metric, which is a measurement of how similar two image points are. There is no right or wrong here; the choice of matching metric is usually related to what the final estimated motion is used for as well as the optimisation strategy in the estimation process.

Each motion vector is used to represent a macroblock in a picture based on the position of this macroblock (or a similar one) in another picture, called the reference picture.

The H.264/MPEG-4 AVC standard defines motion vector as:

motion vector: a two-dimensional vector used for inter prediction that provides an offset from the coordinates in the decoded picture to the coordinates in a reference picture.

Algorithms
The methods for finding motion vectors can be categorised into pixel based methods ("direct") and feature based methods ("indirect"). A famous debate resulted in two papers from the opposing factions being produced to try to establish a conclusion.

Direct methods

 * Block-matching algorithm
 * Phase correlation and frequency domain methods
 * Pixel recursive algorithms
 * Optical flow

Indirect methods
Indirect methods use features, such as corner detection, and match corresponding features between frames, usually with a statistical function applied over a local or global area. The purpose of the statistical function is to remove matches that do not correspond to the actual motion.

Statistical functions that have been successfully used include RANSAC.

Additional note on the categorization
It can be argued that almost all methods require some kind of definition of the matching criteria. The difference is only whether you summarise over a local image region first and then compare the summarisation (such as feature based methods), or you compare each pixel first (such as squaring the difference) and then summarise over a local image region (block base motion and filter based motion). An emerging type of matching criteria summarises a local image region first for every pixel location (through some feature transform such as Laplacian transform), compares each summarised pixel and summarises over a local image region again. Some matching criteria have the ability to exclude points that do not actually correspond to each other albeit producing a good matching score, others do not have this ability, but they are still matching criteria.

Affine motion estimation
Affine motion estimation is a technique used in computer vision and image processing to estimate the motion between two images or frames. It assumes that the motion can be modeled as an affine transformation (translation + rotation + zooming), which is a linear transformation followed by a translation.

Video coding
Applying the motion vectors to an image to synthesize the transformation to the next image is called motion compensation. It is most easily applied to discrete cosine transform (DCT) based video coding standards, because the coding is performed in blocks.

As a way of exploiting temporal redundancy, motion estimation and compensation are key parts of video compression. Almost all video coding standards use block-based motion estimation and compensation such as the MPEG series including the most recent HEVC.

3D reconstruction
In simultaneous localization and mapping, a 3D model of a scene is reconstructed using images from a moving camera.

title: Motion estimation


text:
File:Bill Bruford Gradually Going Tornado.jpg

Summary
Cover for the album Gradually Going Tornado by Bill Bruford


text:
Wikipedia:Articles for deletion/The Brink of Reality

 This page is an archive of the discussion about the proposed deletion of the article below. This page is no longer live. Further comments should be made on the article's talk page rather than here so that this page is preserved as an historic record. The result of the debate was delete. --Rhobite 19:05, Mar 7, 2005 (UTC)

The Brink of Reality
Vanity article on a non-notable web bulletin board. Foobaz · ✐ 01:47, 23 Feb 2005 (UTC)
 * Delete. Non-notable, vanity, currently deadend page. Zzyzx11 03:13, 23 Feb 2005 (UTC)
 * Keep. Its not deadend, and whether or not its non notable is your oppinion. The page contains a lot of site history, and is hardly an advertisement.Rangeley 11:33, 22 Feb 2005 (UTC)
 * Ok, but it still is non-notable. Zzyzx11 22:23, 23 Feb 2005 (UTC)
 * Delete, non-notable message board --nixie 05:11, 23 Feb 2005 (UTC)
 * Delete, non-notable. 550 members, one active in the past hour is better than the last forum someone insisted was worth an encyclopedia entry, but nowhere near the 50,000, 250 active I'd consider the minimum.  --Carnildo 08:37, 23 Feb 2005 (UTC)
 * Concur with Carnildo. Delete. (notability may be POV but we have consensual guidelines for it, too). Radiant! 08:50, Feb 23, 2005 (UTC)
 * Delete Completely non-notable even as web forums go. According to the article they only got their own domain a month ago(!!)  Agree with Carnildo that 50,000 members, 250 active is a pretty good minimum benchmark for forum notability. Andrew Lenahan - St ar bli nd  12:02, Feb 23, 2005 (UTC)
 * Delete, It's all been said. Inter 14:09, 23 Feb 2005 (UTC)
 * Delete. 500 (or even 600 or 700) members does not make a notable message board. -Aranel (" Sarah ") 22:25, 26 Feb 2005 (UTC)
 * Delete. --Paraphelion 01:47, 28 Feb 2005 (UTC)

Rangeley Note: For those who think 50,000 members is the benchmark, You will be hard pressed to find a forum over that. I can think of one, Gaia. Here is one with 8000 members, is that too low too? Why arent you going after all the forums with less then 50,000 members, or is this merely a double standard. And to those who say there is only one active user, that is because this is an American Board, and it was in the middle of the night when you said that... And while the main reason appears to be notability, I dont think this should be enough. The article goes pretty in depth. If this were an article with one paragraph, I would definately see your point, a non notable forum with a silly article. But this does have a lot of information in it, it wasnt thrown together in a few minutes, its taken quite a few days to get where it is.
 * (Note: the above by Rangely, the author of the article being VfDed.) Nonsense, there are numerous online communities over the 50,000 mark.  Slashdot, DeviantART, Kuro5hin, ChristianForums, Hardware.fr, Anandtech, and many many more.  As for why we aren't "going after" other non-notable forum artcles, we are.  It just takes time.  The vast majority of online message-board articles that come up for VfD get deleted for this very same reason.  In fact, I can't remember the last time that one was nominated and ended up being kept.  Andrew Lenahan - St ar bli nd  16:40, Feb 23, 2005 (UTC)

 * My benchmark comes from OCForums, a fairly active overclocking community, where the forum is only loosely attached to any non-forum websites. When I posted my last comment, it had 277 active users in the last however many minutes it counts, at 4AM Eastern (US) time. --Carnildo 00:19, 24 Feb 2005 (UTC)

 * Rangeley note: Che-lives has been up since August 31st, quite a lot of time and its still there. While the Brink of Reality isnt as active as some other forums, Is that reason to take a relatively in depth article down? I would think that the top way of judging these types of things is whether the article has a point or not. I could very well be wrong. The Che-Lives article is quite informative and I learned a lot about whats going on there from reading it, and I am not even a member there. I would want to judge that article by its content, not the 'active users' count. I would not mind if this was attempted to be deleted for its content, that I can fix and improve upon, but as is there is literally nothing I can do really. I dont really see this as fair, it should be the articles content not the active users. If there is an article about a small organisation with 100 people in it, is that reason to delete it even if the article is informative and you learn a lot from it? Basically what I am getting at is, if an article has content and informs, that should mean something, and in this case I feel that is being ignored, as noone has yet presented a reason for deletion as being the content. But if the content needs improving, by all means say so and I will get on it!
 * Ok, you bring up some very good points, and I'll try to address them. Point 1: For the most part, very small organisations do not generally deserve articles.  There's no official WP-approved number of members an org must have for an article, but usually an article about a 100-member group would really only be of interest to people already within that group.  There are exceptions, as always, but that's how it usually goes.  Point 2: I wish I could say that the content of this article is blameless in its VfDing.  It really focuses far too much on the internal politics of the forum, something that, again, only members of the board would care about.  For comparison's sake, let's look at the article for an indisputably notable organisation: the Salvation Army.  It's a very good article.  Notice that it covers basic history, mission, statistics, and activities of the org.  It doesn't get into the internal politics ("X was fired by Y", "X was elected over Y,Z, and N") that those not involved with the org wouldn't care about.  Some good questions to ask yourself when deciding what to include are: "Will anyone not inside this group have reason to know or care about this?"  "Will anyone need this information in 50 or 100 years?"  "How does this information relate to other information? Does it help explain anything?"  In my opinion, the first two paragraphs are fine, but the rest is only of interest to those involved in it (who, as a result, probably know it all already).  That part should be scrapped or condensed into a sentence or two.  If you need more help or advice, just let me know. Andrew Lenahan - St ar bli nd  01:43, Feb 24, 2005 (UTC)
 * (Rangeley)Alright, that type of advice is something I can follow up on. Edit: I have removed the questioned paragraph, and replaced with a few sentences in the Government and President sections. I have also added a statistics section.
 * That is indeed a vast improvement over the way the article was. By the way, I registered for a Brink of Reality account today as Starblind. Andrew Lenahan - St ar bli nd  23:27, Feb 24, 2005 (UTC)
 * I appreciate the fact that you continue to improve the article. However, for comparison, the game design forum I follow has 2470 members and 103662 posts. What I'm getting at is that, while your article is of decent quality, its subject is not encyclopedic. As an extreme example, I could write a lengthy informative article about my cat, but that doesn't make it worthy of encyclopedia inclusion. Poor articles on good subjects are tagged for improving, and kept. Consequently, good articles on poor subjects can be tagged for deletion. Radiant! 09:35, Feb 24, 2005 (UTC)
 * (Rangeley) Alright, lets look at the rules and guidelines for deletion deletion policyI dont see anything about a cut off point for forums, I do see things against Advertisements and Vanity articles. A vanity article would be like something on you, your cat, dog, family, your freind, that type of thing. An Advertisement would be 'Go to this site (link)' As we have clarified this article is not this, and I beleive the consensus is its a pretty good article instead, where is the base for deletion? I see many rules that say deletion is alright if the content is poor, but none in this case.
 * You're right, you'll never see a cut off point for groups in official WP policy. This is because WP generally prefers to take things on a case-by-case basis, like you see here on this VfD.  Under this system, each member votes using their own criteria (or perhaps no criteria at all).  It works much better than simply "All groups bigger than X need articles" or "all groups bigger than Y need articles".  Some WP members believe that anything that can be verified can be included, while others prefer relatively high imclusion criteria.  The ability to vote based on our own beliefs rather than a set-in-stone this-is-how-it-is set of rules, as well as the open incouragement of dialogue and discussion, keep the system generally balances and reasonable. Andrew Lenahan - St ar bli nd  23:27, Feb 24, 2005 (UTC)
 * (Rangeley) Im not sure it keeps it balanced and reasonable. The majority isnt always right, and sometimes some people judge unfairly. While you say discussion is encouraged, such as what is going on now, I am beginning to see that it has one flaw. Even as I have shown this wasnt a deadend site, wasnt a vanity article, and even made it information useful to others, rather then internal goings-on, it still comes down to what others think. And in this case the criteria is something unfixable. While we have discussed this for a day, the issue has been whittled down, and we have reached a point where regardless of the rules saying this article is good, personal oppinions will take it down. Even though the point of view for deletion has no rules to support it, it will win. As you said earlier, you cant remember the last time one of these was nominated for deletion and got off. I doubt this case will end any differently. I do think Wikipedia should add more guidelines for deletion, because when I made this I did look into them, and stayed in the rules. I wouldnt have bothered to make it if I knew that even if I followed the guidelines, it would get deleted because the deletion policy isnt actually written, but just ends up being any given persons own idea.
 * Sorry, but you are mistaken about the process. The guidelines for inclusion (or exclusion) are intentionally vague, because it would be patently impossible to provide for all occasions. There are a few non-debatable issues (e.g. copyvio), but the others will have to be decided on a case-by-case basis. We do not want the 'lawbook for wikipedia' to govern us (apart from the fact that creating it would take too much time). Therefore, a consensual majority will decide the case.
 * As is the case here. You have made your point. We have listened to you. And we disagree. Taking the case to extremes, we obviously want an article on Bill Gates, and we obviously don't want an article on my goldfish. We must draw a line somewhere, and that is called notability. There is too little that distinguishes your forum as being special amongst the thousands of other internet forums. Therefore, the vote to delete stands. Radiant! 22:13, Feb 25, 2005 (UTC)

This page is now preserved as an archive of the debate and, like some other VfD subpages, is no longer 'live'. Subsequent comments on the issue, the deletion, or the decision-making process should be placed on the relevant 'live' pages. Please do not edit this page.


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Saturn (store)

Saturn is a German chain of electronics stores in Germany. With Media Markt it constitutes Media-Saturn Holding, owned by the retail trade company Ceconomy, which was spun-off from Metro Group in 2017. The Saturn store in Hamburg is the biggest Electronicmarket in Europe.

Saturn is known for its slightly coarse German-language advertising slogan "Geiz ist geil!" ("Stinginess is cool!") which was used from 2002 to 2011 and sparked a nationwide debate about consumer behavior and the situation of the German economy. The slogan quickly became a common language and became synonymous with the German economic crisis.

History
The first Saturn-Hansa-Markt was opened in July 1961 by Friedrich Wilhelm and Anni Waffenschmidt at Cologne's Hansaring. Consumer electronics items were mainly sold to "diplomats from all over the world" on 120 m². In 1968 the two founded the company Hansa-Foto. Since 1969, private customers have also been able to shop at Saturn and Hansa-Foto. In 1972, the Waffenschmidts opened the first technical department store in Cologne with what they claimed to be the "largest phonograph record in the world". In the early 1980s, a large branch was opened on the Theresienhöhe in Munich, followed in 1985 by a branch in Frankfurt with the participation of Kaufhof. Saturn was acquired by the Media Markt holding company in 1990, both of which were merged into the MediaMarktSaturn Retail Group.

In 1992 there were seven Saturn Hansa stores (Cologne, Frankfurt, Munich, Dortmund, Hanover, Nuremberg, Gelsenkirchen).

The area of a market is usually between 2,000 m² and 10,000 m². An exception can be found in Hamburg with 18,000 m² and six floors which makes it one of the largest electronics stores in the world. Its origins relate to the merger of the Horten and Kaufhof department stores in 1995. In Hamburg, Kaufhof and Horten had stores side by side in Mönckebergstrasse, at the main train station. Both Saturn and Kaufhof were part of the Metro Group, so the Horten store was closed and occupied in 1999 with the electronics store.

Corporate affairs
As of December 2021, there are 137 Saturn stores in Germany and 2 in Luxembourg.

On 1 July 2011 the 34 Saturn stores in France were sold to the HTM Group.

Saturn stores in Austria, Belgium, Greece, Hungary, Luxembourg, the Netherlands, Poland, Russia, Spain, Switzerland and Turkey have been rebranded as Media Markt  and in Italy as Media World.

title: Saturn (store)


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Talk:Twentieth Air Force

Untitled
"Twentieth Air Force was formed during World War II, exclusively as a heavy strategic bombardment organization." Was this only a U.S. air force, or was it a coalition? Kingturtle 01:56, 23 Feb 2005 (UTC)
 * Exclusively USAAF. Arnold deliberately numbered the air force beyond the sequence 1-15 to demonstrate that it was a global strategic air force not subordinate to any theater command, and also commanded it himself for the same reason. He pledged to support theater commander requests (i.e. MacArthur or Nimitz) for support when necessary, but 20AF reported directly to the Joint Chiefs.--Reedmalloy (talk) 22:02, 17 June 2011 (UTC)

Adding the unreferenced template
I have added the unreferenced template to a couple of sections in this article and have also added one in the Notes section. For such a large detailed article it needs inline citations. I note in the reference section it says "This article incorporates text from 20th Air Force Website, a public domain work of the United States Government." Please see the articles Western Allied invasion of Germany and the Operation Matterhorn to see how the text that comes from a public domain work of the United States Government can be cited. --Philip Baird Shearer (talk) 12:09, 8 September 2008 (UTC)

Confusion with the 20th Air Division
What is the likelihood that someone giving a testimony would state that they were stationed at Malmstrom Air Force Base assigned to the 20th Air Division in March 1967, in the capacity of senior launch control officer, is telling the truth? Had they said the Twentieth Air Force everything would be fine, but from the outside it would seem hard to explain how such a person would mix up these two structures. __meco (talk) 14:06, 3 June 2010 (UTC)
 * No accounting for human memory, since neither organization was at Malmstrom in 1967. Bwmoll3 (talk) 20:01, 28 February 2012 (UTC)

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title: Talk:Twentieth Air Force


text: File:Painting of maxim gorki.jpg

title: File:Painting of maxim gorki.jpg


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Motion perception

Motion perception is the process of inferring the speed and direction of elements in a scene based on visual, vestibular and proprioceptive inputs. Although this process appears straightforward to most observers, it has proven to be a difficult problem from a computational perspective, and difficult to explain in terms of neural processing.

Motion perception is studied by many disciplines, including psychology (i.e. visual perception), neurology, neurophysiology, engineering, and computer science.

Neuropsychology
The inability to perceive motion is called akinetopsia and it may be caused by a lesion to cortical area V5 in the extrastriate cortex. Neuropsychological studies of a patient who could not see motion, seeing the world in a series of static "frames" instead, suggested that visual area V5 in humans is homologous to motion processing area V5/MT in primates.

First-order motion perception

Two or more stimuli that are switched on and off in alternation can produce two different motion percepts. The first, demonstrated in the figure to the right is "beta movement", and the basis for the technology of electronic news ticker displays. However, at faster alternation rates, and if the distance between the stimuli is just right, an illusory "object" the same colour as the background is seen moving between the two stimuli and alternately occluding them. This is called the phi phenomenon and is sometimes described as an example of "pure" motion detection uncontaminated, as in Beta movement, by form cues. This description is, however, somewhat paradoxical as it is not possible to create such motion in the absence of figural percepts.

The phi phenomenon has been referred to as "first-order" motion perception. Werner E. Reichardt and Bernard Hassenstein have modelled it in terms of relatively simple "motion sensors" in the visual system, that have evolved to detect a change in luminance at one point on the retina and correlate it with a change in luminance at a neighbouring point on the retina after a short delay. Sensors that are proposed to work this way have been referred to as either Hassenstein-Reichardt detectors after the scientists Bernhard Hassenstein and Werner Reichardt, who first modelled them, motion-energy sensors, or Elaborated Reichardt Detectors. These sensors are described as detecting motion by spatio-temporal correlation and are considered by some to be plausible models for how the visual system may detect motion. (Although, again, the notion of a "pure motion" detector suffers from the problem that there is no "pure motion" stimulus, i.e. a stimulus lacking perceived figure/ground properties). There is still considerable debate regarding the accuracy of the model and exact nature of this proposed process. It is not clear how the model distinguishes between movements of the eyes and movements of objects in the visual field, both of which produce changes in luminance on points on the retina.

Second-order motion perception
Second-order motion is when the moving contour is defined by contrast, texture, flicker or some other quality that does not result in an increase in luminance or motion energy in the Fourier spectrum of the stimulus. There is much evidence to suggest that early processing of first- and second-order motion is carried out by separate pathways. Second-order mechanisms have poorer temporal resolution and are low-pass in terms of the range of spatial frequencies to which they respond. (The notion that neural responses are attuned to frequency components of stimulation suffers from the lack of a functional rationale and has been generally criticized by G. Westheimer (2001) in an article called "The Fourier Theory of Vision.") Second-order motion produces a weaker motion aftereffect unless tested with dynamically flickering stimuli.

The aperture problem
The motion direction of a contour is ambiguous, because the motion component parallel to the line cannot be inferred based on the visual input. This means that a variety of contours of different orientations moving at different speeds can cause identical responses in a motion sensitive neuron in the visual system.

Motion integration
Some have speculated that, having extracted the hypothesized motion signals (first- or second-order) from the retinal image, the visual system must integrate those individual local motion signals at various parts of the visual field into a 2-dimensional or global representation of moving objects and surfaces. (It is not clear how this 2D representation is then converted into the perceived 3D percept) Further processing is required to detect coherent motion or "global motion" present in a scene.

The ability of a subject to detect coherent motion is commonly tested using motion coherence discrimination tasks. For these tasks, dynamic random-dot patterns (also called random dot kinematograms) are used that consist in 'signal' dots moving in one direction and 'noise' dots moving in random directions. The sensitivity to motion coherence is assessed by measuring the ratio of 'signal' to 'noise' dots required to determine the coherent motion direction. The required ratio is called the motion coherence threshold.

Motion in depth
As in other aspects of vision, the observer's visual input is generally insufficient to determine the true nature of stimulus sources, in this case their velocity in the real world. In monocular vision for example, the visual input will be a 2D projection of a 3D scene. The motion cues present in the 2D projection will by default be insufficient to reconstruct the motion present in the 3D scene. Put differently, many 3D scenes will be compatible with a single 2D projection. The problem of motion estimation generalizes to binocular vision when we consider occlusion or motion perception at relatively large distances, where binocular disparity is a poor cue to depth. This fundamental difficulty is referred to as the inverse problem.

Nonetheless, some humans do perceive motion in depth. There are indications that the brain uses various cues, in particular temporal changes in disparity as well as monocular velocity ratios, for producing a sensation of motion in depth. Two different binocular cues of the perception motion in depth are hypothesized: Inter-ocular velocity difference (IOVD) and changing disparity (CD) over time. Motion in depth based on inter-ocular velocity differences can be tested using dedicated binocularly uncorrelated random-dot kinematograms. Study results indicate that the processing of these two binocular cues – IOVD and CD – may use fundamentally different low-level stimulus features, which may be processed jointly that later stages. Additionally, as monocular cue, also the changing size of retinal images contributes to motion in depth detection.

Perceptual learning of motion
Detection and discrimination of motion can be improved by training with long-term results. Participants trained to detect the movements of dots on a screen in only one direction become particularly good at detecting small movements in the directions around that in which they have been trained. This improvement was still present 10 weeks later. However perceptual learning is highly specific. For example, the participants show no improvement when tested around other motion directions, or for other sorts of stimuli.

Cognitive map
A cognitive map is a type of mental representation which serves an individual to acquire, code, store, recall, and decode information about the relative locations and attributes of phenomena in their spatial environment. Place cells work with other types of neurons in the hippocampus and surrounding regions of the brain to perform this kind of spatial processing, but the ways in which they function within the hippocampus are still being researched.

Many species of mammals can keep track of spatial location even in the absence of visual, auditory, olfactory, or tactile cues, by integrating their movements—the ability to do this is referred to in the literature as path integration. A number of theoretical models have explored mechanisms by which path integration could be performed by neural networks. In most models, such as those of Samsonovich and McNaughton (1997) or Burak and Fiete (2009), the principal ingredients are (1) an internal representation of position, (2) internal representations of the speed and direction of movement, and (3) a mechanism for shifting the encoded position by the right amount when the animal moves. Because cells in the Medial Entorhinal Cortex (MEC) encode information about position (grid cells ) and movement (head direction cells and conjunctive position-by-direction cells ), this area is currently viewed as the most promising candidate for the place in the brain where path integration occurs.

Neurophysiology
Motion sensing using vision is crucial for detecting a potential mate, prey, or predator, and thus it is found both in vertebrates and invertebrates vision throughout a wide variety of species, although it is not universally found in all species. In vertebrates, the process takes place in retina and more specifically in retinal ganglion cells, which are neurons that receive input from bipolar cells and amacrine cells on visual information and process output to higher regions of the brain including, thalamus, hypothalamus, and mesencephalon.

The study of directionally selective units began with a discovery of such cells in the cerebral cortex of cats by David Hubel and Torsten Wiesel in 1959. Following the initial report, an attempt to understand the mechanism of directionally selective cells was pursued by Horace B. Barlow and William R. Levick in 1965. Their in-depth experiments in rabbit's retina expanded the anatomical and physiological understanding of the vertebrate visual system and ignited the interest in the field. Numerous studies that followed thereafter have unveiled the mechanism of motion sensing in vision for the most part. Alexander Borst and Thomas Euler's 2011 review paper, "Seeing Things in Motion: Models, Circuits and Mechanisms". discusses certain important findings from the early discoveries to the recent work on the subject, coming to the conclusion of the current status of the knowledge.

Direction selective (DS) cells
Direction selective (DS) cells in the retina are defined as neurons that respond differentially to the direction of a visual stimulus. According to Barlow and Levick (1965), the term is used to describe a group of neurons that "gives a vigorous discharge of impulses when a stimulus object is moved through its receptive field in one direction." This direction in which a set of neurons respond most strongly to is their "preferred direction". In contrast, they do not respond at all to the opposite direction, "null direction". The preferred direction is not dependent on the stimulus—that is, regardless of the stimulus' size, shape, or color, the neurons respond when it is moving in their preferred direction, and do not respond if it is moving in the null direction. There are three known types of DS cells in the vertebrate retina of the mouse, ON/OFF DS ganglion cells, ON DS ganglion cells, and OFF DS ganglion cells. Each has a distinctive physiology and anatomy. Analogous directionally selective cells are not thought to exist in the primate retina.

ON/OFF DS ganglion cells
ON/OFF DS ganglion cells act as local motion detectors. They fire at the onset and offset of a stimulus (a light source). If a stimulus is moving in the direction of the cell's preference, it will fire at the leading and the trailing edge. Their firing pattern is time-dependent and is supported by the Reichardt-Hassenstain model, which detects spatiotemporal correlation between the two adjacent points. The detailed explanation of the Reichardt-Hassenstain model will be provided later in the section. The anatomy of ON/OFF cells is such that the dendrites extend to two sublaminae of the inner plexiform layer and make synapses with bipolar and amacrine cells. They have four subtypes, each with its own preference for direction.

ON DS ganglion cells
Unlike ON/OFF DS ganglion cells that respond both to the leading and the trailing edge of a stimulus, ON DS ganglion cells are responsive only to a leading edge. The dendrites of ON DS ganglion cells are monostratified and extend into the inner sublamina of the inner plexiform layer. They have three subtypes with different directional preferences.

OFF DS ganglion cells
OFF DS ganglion cells act as a centripetal motion detector, and they respond only to the trailing edge of a stimulus. They are tuned to upward motion of a stimulus. The dendrites are asymmetrical and arbor in to the direction of their preference.

DS cells in insects
The first DS cells in invertebrates were found in flies in a brain structure called the lobula plate. The lobula plate is one of the three stacks of the neuropils in the fly's optic lobe. The "tangential cells" of the lobula plate composed of roughly about 50 neurons, and they arborize extensively in the neuropile. The tangential cells are known to be directionally selective with distinctive directional preference. One of which is Horizontally Sensitive (HS) cells, such as the H1 neuron, that depolarize most strongly in response to stimulus moving in a horizontal direction (preferred direction). On the other hand, they hyperpolarize when the direction of motion is opposite (null direction). Vertically Sensitive (VS) cells are another group of cells that are most sensitive to vertical motion. They depolarize when a stimulus is moving downward and hyperpolarize when it is moving upward. Both HS and VS cells respond with a fixed preferred direction and a null direction regardless of the color or contrast of the background or the stimulus.

The Hassenstein-Reichardt model
It is now known that motion detection in vision is based on the Hassenstein-Reichardt detector model. This is a model used to detect correlation between the two adjacent points. It consists of two symmetrical subunits. Both subunits have a receptor that can be stimulated by an input (light in the case of visual system). In each subunit, when an input is received, a signal is sent to the other subunit. At the same time, the signal is delayed in time within the subunit, and after the temporal filter, is then multiplied by the signal received from the other subunit. Thus, within each subunit, the two brightness values, one received directly from its receptor with a time delay and the other received from the adjacent receptor, are multiplied. The multiplied values from the two subunits are then subtracted to produce an output. The direction of selectivity or preferred direction is determined by whether the difference is positive or negative. The direction which produces a positive outcome is the preferred direction.

In order to confirm that the Reichardt-Hassenstein model accurately describes the directional selectivity in the retina, the study was conducted using optical recordings of free cytosolic calcium levels after loading a fluorescent indicator dye into the fly tangential cells. The fly was presented uniformly moving gratings while the calcium concentration in the dendritic tips of the tangential cells was measured. The tangential cells showed modulations that matched the temporal frequency of the gratings, and the velocity of the moving gratings at which the neurons respond most strongly showed a close dependency on the pattern wavelength. This confirmed the accuracy of the model both at the cellular and the behavioral level.

Although the details of the Hassenstein-Reichardt model have not been confirmed at an anatomical and physiological level, the site of subtraction in the model is now being localized to the tangential cells. When depolarizing current is injected into the tangential cell while presenting a visual stimulus, the response to the preferred direction of motion decreased, and the response to the null direction increased. The opposite was observed with hyperpolarizing current. The T4 and T5 cells, which have been selected as a strong candidate for providing input to the tangential cells, have four subtypes that each project into one of the four strata of the lobula plate that differ in the preferred orientation.

DS cells in vertebrates
One of the early works on DS cells in vertebrates was done on the rabbit retina by H. Barlow and W. Levick in 1965. Their experimental methods include variations to the slit-experiments and recording of the action potentials in the rabbit retina. The basic set-up of the slit experiment was they presented a moving black-white grating through a slit of various widths to a rabbit and recorded the action potentials in the retina. This early study had a large impact on the study of DS cells by laying down the foundation for later studies. The study showed that DS ganglion cells derive their property from the basis of sequence-discriminating activity of subunits, and that this activity may be the result of inhibitory mechanism in response to the motion of image in the null direction. It also showed that the DS property of retinal ganglion cells is distributed over the entire receptive field, and not limited to specific zones. Direction selectivity is contained for two adjacent points in the receptive field separated by as small as 1/4°, but selectivity decreased with larger separations. They used this to support their hypothesis that discrimination of sequences gives rise to direction selectivity because normal movement would activate adjacent points in a succession.

Molecular identity and structure of DS cells in mice
ON/OFF DS ganglion cells can be divided into 4 subtypes differing in their directional preference, ventral, dorsal, nasal, or temporal. The cells of different subtypes also differ in their dendritic structure and synaptic targets in the brain. The neurons that were identified to prefer ventral motion were also found to have dendritic projections in the ventral direction. Also, the neurons that prefer nasal motion had asymmetric dendritic extensions in the nasal direction. Thus, a strong association between the structural and functional asymmetry in ventral and nasal direction was observed. With a distinct property and preference for each subtype, there was an expectation that they could be selectively labeled by molecular markers. The neurons that were preferentially responsive to vertical motion were indeed shown to be selectively expressed by a specific molecular marker. However, molecular markers for other three subtypes have not been yet found.

Neural mechanism: starburst amacrine cells
The direction selective (DS) ganglion cells receive inputs from bipolar cells and starburst amacrine cells. The DS ganglion cells respond to their preferred direction with a large excitatory postsynaptic potential followed by a small inhibitory response. On the other hand, they respond to their null direction with a simultaneous small excitatory postsynaptic potential and a large inhibitory postsynaptic potential. Starburst amacrine cells have been viewed as a strong candidate for direction selectivity in ganglion cells because they can release both GABA and Ach. Their dendrites branch out radiantly from a soma, and there is a significant dendritic overlap. Optical measurements of Ca2+ concentration showed that they respond strongly to the centrifugal motion (the outward motion from the soma to the dendrites), while they don't respond well to the centripetal motion (the inward motion from the dendritic tips to the soma). When the starburst cells were ablated with toxins, direction selectivity was eliminated. Moreover, their release of neurotransmitters itself, specifically calcium ions, reflect direction selectivity, which may be presumably attributed to the synaptic pattern. The branching pattern is organized such that certain presynaptic input will have more influence on a given dendrite than others, creating a polarity in excitation and inhibition. Further evidence suggests that starburst cells release inhibitory neurotransmitters, GABA onto each other in a delayed and prolonged manner. This accounts for the temporal property of inhibition.

In addition to spatial offset due to GABAergic synapses, the important role of chloride transporters has started to be discussed. The popular hypothesis is that starburst amacrine cells differentially express chloride transporters along the dendrites. Given this assumption, some areas along the dendrite will have a positive chloride-ion equilibrium potential relative to the resting potential while others have a negative equilibrium potential. This means that GABA at one area will be depolarizing and at another area hyperpolarizing, accounting for the spatial offset present between excitation and inhibition.

Recent research (published March 2011) relying on serial block-face electron microscopy (SBEM) has led to identification of the circuitry that influences directional selectivity. This new technique provides detailed images of calcium flow and anatomy of dendrites of both starburst amacrine (SAC) and DS ganglion cells. By comparing the preferred directions of ganglion cells with their synapses on SAC's, Briggman et al. provide evidence for a mechanism primarily based on inhibitory signals from SAC's based on an oversampled serial block-face scanning electron microscopy study of one sampled retina, that retinal ganglion cells may receive asymmetrical inhibitory inputs directly from starburst amacrine cells, and therefore computation of directional selectivity also occurs postsynaptically. Such postsynaptic models are unparsimonious, and so if any given starburst amacrine cells conveys motion information to retinal ganglion cells then any computing of 'local' direction selectivity postsynaptically by retinal ganglion cells  is  redundant and dysfunctional. An acetylcholine (ACh) transmission model of directionally selective starburst amacrine cells provides a robust topological underpinning of a motion sensing in the retina.

Labs specialising in motion research

 * Visual Neuroscience, University of Nottingham
 * McGill Vision Research, McGill University
 * Purves Lab, Duke University
 * Center for Vision Research, York University
 * iLab, University of Southern California
 * Vision and Cognition, University of Tübingen

title: Motion perception


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