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The Penrose triangle known as the Penrose tribar, or the impossible tribar, is a triangular impossible object, an optical illusion consisting of an object which can be depicted in a perspective drawing, but cannot exist as a solid object. It was first created by the Swedish artist Oscar Reutersvärd in 1934. Independently from Reutersvärd, the triangle was devised and popularized in the 1950s by psychiatrist Lionel Penrose and his son, prominent mathematician Roger Penrose, who described it as "impossibility in its purest form", it is featured prominently in the works of artist M. C. Escher, whose earlier depictions of impossible objects inspired it; the tribar appears to be a solid object, made of three straight beams of square cross-section which meet pairwise at right angles at the vertices of the triangle they form. The beams may be broken, forming cuboids; this combination of properties cannot be realized by any three-dimensional object in ordinary Euclidean space. Such an object can exist in certain Euclidean 3-manifolds.

There exist three-dimensional solid shapes each of which, when viewed from a certain angle, appears the same as the 2-dimensional depiction of the Penrose triangle on this page. The term "Penrose triangle" can refer to the 2-dimensional depiction or the impossible object itself. M. C. Escher's lithograph Waterfall depicts a watercourse that flows in a zigzag along the long sides of two elongated Penrose triangles, so that it ends up two stories higher than it began; the resulting waterfall, forming the short sides of both triangles, drives a water wheel. Escher helpfully points out that in order to keep the wheel turning some water must be added to compensate for evaporation. If a line is traced around the Penrose triangle, a 4-loop Möbius strip is formed.. Although the tribar is named one of the impossible objects, there exist many more that fit into the same category. Other impossible objects include the devil's fork, the Shepard elephant, impossible arch. While it is possible to construct analogies to the Penrose triangle with other shapes and regular polygons to create a Penrose polygon, the visual effect is not as striking, as the sides increase, the object seems to be warped or twisted.

Three hares Penrose steps Penrose square root law An article about impossible triangle sculpture in Perth Escher for Real constructions

Bostryx chusgonensis is a species of tropical air-breathing land snail, a pulmonate gastropod mollusk in the family Bulimulidae. Bostryx chusgonensis chusgonensis Weyrauch, 1960 Bostryx chusgonensis sipas Breure & Mogollón Avila, 2010 PeruThe nominate taxon was described from La Libertad Region, Río Chusgon area, at 1550–1900 m; the type locality of Bostryx chusgonensis sipas is Amazonas Region, Peru. The description of Bostryx chusgonensis sipas extends the range ca. 180 km more northward within the drainage system of the Río Marañon. The Bostryx chusgonensis sipas is separated by mountain ranges from the nominate subspecies. According to Weyrauch a ribbed form and a colour form with small brownish dots occur in the nominate subspecies. Subspecies Bostryx chusgonensis sipas differs from Bostryx chusgonensis chusgonensis by being larger, the less impressed suture, in streaked specimens, the axial streaks continuing till the base of the shell; the subspecific name sipas is derived from" sipas".

The epithet is used as a noun in apposition. It is characterized by spindle-shape, whitish colour and smooth surface; the height of the shell is up to 13.4 mm, three times as long as wide, spindle-shaped, with convex sides, rather thin. Colour is uniformly greyish-whitish or with axial streaks of light to dark-brown, the upper whorls somewhat darker. Surface is hardly shining, with incrassate growth striae. Protoconch is smooth; the shell has 6.5 whorls. The suture is impressed; the aperture is elongate-ovate, margins somewhat converging. Peristome simple, whitish. Columellar margin straight, hardly expanded. Dimension of the holotype of Bostryx chusgonensis sipas are as follows: The width of the shell is 4.7 mm. The height of the shell is 13.5 mm. The width of the aperture is 3.2 mm. The height of the aperture is 5.2 mm. The height of the last whorl is 8.39 mm. The shell has 6.5 whorls. This article incorporates CC-BY-3.0 text from the reference

T helper 17 cells are a subset of pro-inflammatory T helper cells defined by their production of interleukin 17. They are related to T regulatory cells and the signals that cause Th17s to differentiate inhibit Treg differentiation. However, Th17s are developmentally distinct from Th2 lineages. Th17 cells play an important role in maintaining mucosal barriers and contributing to pathogen clearance at mucosal surfaces, they have been implicated in autoimmune and inflammatory disorders. The loss of Th17 cell populations at mucosal surfaces has been linked to chronic inflammation and microbial translocation; these regulatory Th17 cells are generated by IL-6 in vitro. Like conventional regulatory T cells, induction of regulatory Treg17 cells could play an important role in modulating and preventing certain autoimmune diseases. Treg17 cells are generated from CD4+ T cells. Transforming growth factor beta, interleukin 6, interleukin 21 and interleukin 23 contribute to Th17 formation in mice and humans.

Key factors in the differentiation of Th17 cells are signal transducer and the activator of transcription 3 and retinoic acid receptor-related orphan receptors gamma and alpha. Th17 cells are differentiated; these cytokines are produced by activated antigen presenting cells after contact with pathogens. The Th17 cells can alter their differentiation program giving rise to either protective or pro-inflammatory pathogenic cells; the protective and non-pathogenic Th17 cells induced by IL-6 and TGF-β are termed as Treg17 cells. The pathogenic Th17 cells are induced by IL-23 and IL-1β. IL-21, produced by Th17 cells themselves, has been shown to initiate an alternative route for the activation of Th17 populations. Both interferon gamma and IL-4, the main stimulators of Th1 and Th2 differentiation have been shown to inhibit Th17 differentiation. Similar to Th17 cells the Treg17 development depended on the transcription factor Stat3. Th17 cells play a role in adaptive immunity protecting the body against pathogens.

However, anti-fungal immunity appears to be limited to particular sites with detrimental effects observed. Their main effector cytokines are IL-17A, IL-17F, IL-21, IL-22, as well as granulocyte-macrophage colony-stimulating factor. IL-17 family cytokines target innate immune cells and epithelial cells, among others, to produce G-CSF and IL-8, which leads to neutrophil production and recruitment. In this way, Th17 cell lineage appears to be one of the three major subsets of effector T cells, as these cells are involved in regulation of neutrophils, while Th2 cells regulate eosinophils and mast cells, Th1 cells regulate macrophages and monocytes. Thus, three T helper cell subsets are able to influence the myeloid part of the immune system responsible for innate defense against pathogens. Treg17 cells with regulatory phenotype with in vivo immune-suppressive properties in the gut have been identified as rTh17 cells. Treg17 cells produce IL-17 and IL-10 and low level of IL-22 and suppress autoimmune and other immune responses.

CD4+ T cells polarized with IL-23 and IL-6 are pathogenic upon adoptive transfer in type 1 diabetes while cells polarized with TGF-beta and IL-6 are not pathogenic. The intracellular aryl hydrocarbon receptor, activated by certain aromatic compounds, is expressed in Treg17 cells; these cells are regulated by TGF-beta. The production of IL-22 in this subset of Th17 cells is regulated by AhR and Treg17 cells are depend on activation of the transcription factor Stat3. In a steady state, TGF-beta and AhR ligands induce low expression of IL-22 along with high expression of AhR, c-MAF, IL-10, IL-21 that might play a protective role in cell regeneration and host microbiome homeostasis. Th17 cells mediate the regression of tumors in mice, but were found to promote tumor formation induced by colonic inflammation in mice. Like other T helper cells, Th17 cells interact with B cells in response to pathogens. Th17 cells are involved in B cell recruitment through CXCL13 chemokine signaling, Th17 activity may encourage antibody production.

Treg17 cells regulate the function of Th17 cells that are important role in the host defense against fungal and bacterial pathogens and participate in the pathogenesis of multiple inflammatory and autoimmune disorders. Selective deletion of Stat3 caused spontaneous severe colitis because of the lack of Treg17 cells and increase in pathogenic Th17 cells; the mechanism of Treg17 cell action is expression of chemokine receptor CCR6, which facilitates trafficking into areas of Th17 inflammation. This is seen in human disease such glomerulonephritis in the kidney. Conversion of pathogenic Th17 cells in vivo at the conclusion of an inflammatory disease process by TGF-β results in the generation of Treg17 like cells. There is conservation across species of Treg17 cells; the dysregulation of Th17 cells has been associated with autoimmune disorders and inflammation. In the case of autoimmune disorders, Th17 cell over activation can cause an inappropriate amount of inflammation, like in the case of rheumatoid arthritis.

Th17 cells have been shown to be necessary for maintenance of mucosal immunity. In HIV, the loss of Th17 cell populations can contribute to chronic infection. Th17 cells auto-specific Th17 cells, are associated with autoimmune disease such as multiple sclerosis, rheumatoid arthritis, psoriasis. Th17 overactivation against autoantigen will cause type 3 immune complex and comple

Velta Ruke-Dravina, was a Latvian-born Swedish linguist and folklorist, as well as a professor in Baltic languages at Stockholm University. Ruke-Dravina's research interests included children's language, language contact, dialectology, her doctoral thesis was about diminutives in Latvian language. She held the only professorship in Baltic languages outside the Baltics and had a leading role in developing the teaching program on the subject at Stockholm University. In 1980, she was elected as a member of the Royal Swedish Academy of Letters and Antiquities. Velta Tatjana Ruke was born January 1917, in Valmiera, she grew up in Latvia, graduating from Riga Secondary School No 2, from the Department of Baltic Philology at the Faculty of Philology and Philosophy of the University of Latvia in 1939. From 1938 and during World War II, Ruke-Dravina pursued doctoral studies in comparative Indo-European language research, but was not allowed to complete the studies as public defense of a thesis in this subject was not allowed in the German-fortified Latvia.

She worked for a while as a lecturer in phonetics and served as an assistant to the linguist Jānis Endzelīns. She was involved in a number of projects associated with land-targeting and place-name research at the Latvian language archive. In the autumn of 1944, Ruke-Dravina and her husband, like many others, fled to Sweden, she continued her academic activities at Lund University, where she taught in Baltic languages in the 1950s, at Stockholm University, where she earned a licentiate degree in Slavic languages in 1954, defended her doctorate in 1959. Between 1948 and 1970, Ruke-Dravina worked as a lecturer at the University of Lund, where she was an associate professor in Baltic and Slavic languages, she continued her career at the University of Stockholm, first as an associate professor in Slavic languages as an assistant professor of general linguistics, as a regular professor in Baltic languages. She became the chair of the Department of Baltic Language and Literature at the Institute of Slavs and Balts at the University of Stockholm before 1984.

She was a guest lecturer at universities in different countries. After retiring in 1983, Helge Rinholm became her successor. From 1982 to 1990, Ruke-Dravina was an editor of the literary yearbook Zari, she published over 300 scientific articles, was the author of several books on linguistic issues. She received several prizes for her activities. Ruke-Dravina is the mother of astronomer Dainis Dravins, she died May 7, 2003. Latviešu valodas dialektoloģijas atlanta materialu vākšanas programa, 1954 Laute und Nominalformen der Mundart von Stenden. 1, Akzent und Intonation, Lautlehre, 1955 Verbalformen und undeklinierbare Redeteile der Mundart von Stenden: Verben, Adverbien, Präpositionen und Präfixe, Konjunktionen, 1958 Diminutive im Lettischen, 1959 Interjektionen und Onomatopöie in der Mundart von Stenden, 1962 Zur Sprachentwicklung bei Kleinkindern. 1, Syntax: Beitrag auf der Grundlage lettischen Sprachmateriels, 1963 Rainis kā augšzemnieku valodas pārstāvis, 1965 Mehrsprachigkeit im Vorschulalter, 1967 Språk i kontakt.

1969 Initial consonant combinations in Lithuanian and Latvian, 1970 Place names in Kauguri county, Latvia: a synchronic-structural analysis of toponyms in an ancient Indo-European and Finno-Ugric contact area. 1971 Vārds īstā vietā: frazeologismu krājums = The right word in the right place, 1974 The standardization process in Latvian 16. Century to the present, 1977 Jān̨i latviešu literatūrā, 1978 No pieciem mēnešiem līdz pieciem gadiem, 1982 Cilvēks un daba latviešu tautasdziesmās, 1986 Rakstnieks un valoda, 1988 Svenska ortnamn i lettisk skönlitteratur, 1989 Valodniecība, 1991 Jāni latviešu literatūrā, 1991 Valodas jautājumi: rakstu krājums, 1992 Latviešu meitene apgūst savu pirmo valodu, 1993 Latviešu tautasdziesmu varianti: Kr. Barona "Latvju dainās", 1993 Darbu izlase, 2017 "Velta Tatjana Ruke-Dravina". Kungliga Vitterhets Historie och Antikvitets Akademien. Gustavsson, Sven. ”Velta Rūķe-Draviņa”. Kungl. Vitterhets historie och antikvitetsakademiens årsbok 2004: sid. -24. 0083-6796. ISSN 0083-6796.

Libris 9637340 Zirin, Mary. Women and Gender in Central and Eastern Europe and Eurasia: A Comprehensive Bibliography Volume I: Southeastern and East Central Europe Volume II: Russia, the Non-Russian Peoples of the Russian. Taylor & Francis. ISBN 978-1-317-45196-9

Ulrikke Pia Eikeri is a Norwegian tennis player. Eikeri has won 22 doubles titles on the ITF Women's Circuit. On 16 April 2018, she reached her best singles ranking of world No. 206. On 12 August 2019, she peaked at No. 118 in the doubles rankings. In 2010, Eikeri reached the semifinals of the Australian Open in girls' doubles, alongside Camila Silva, the finals of both singles and doubles at the Dunlop Orange Bowl. On the ITF junior tour, Eikeri has been ranked as high as No. 16 in the world. Playing for Norway at the Fed Cup, Eikeri has a win–loss record of 25–15. Ulrikke Eikeri at the Women's Tennis Association Ulrikke Eikeri at the International Tennis Federation Ulrikke Eikeri at the Fed Cup

"Monopoly" is a song by American singers Ariana Grande and Victoria Monét, released on April 1, 2019 through label Republic Records. The song was written by Grande, Monét, Charles Anderson, Michael Foster, Tim Suby, with production being handled by Social House and Suby; the music video, shot on March 30, 2019 at Mohegan Sun in the hours leading up to a concert scheduled that night, was released alongside the single, was directed by Alfredo Flores and Ricky Alvarez."Monopoly" was included on the Japanese deluxe edition of Grande's fifth studio album Thank U, Next as a bonus track, along with the official remix of "7 Rings" featuring 2 Chainz. It reached the top 10 in Greece and Israel and the top 20 in Ireland and New Zealand; the singers performed the song on some of the shows of the Sweetener World Tour. Monét and Grande decided to make a song titled "Monopoly", finding it funny since Monét dislikes the board game and declines to play whenever Grande asks; the song was recorded on February 1, 2019."Monopoly" was slated for a March 28, 2019 release but was pushed back to April 1, 2019 to celebrate "7 Rings" 8th week at number one on the Billboard Hot 100.

Grande said "Monopoly" is about "friendship, protecting your energy and staying right in your bag." "Monopoly" is a trap-pop song, leading Uproxx writer Chloe Gilke to call it the "spiritual successor" to Grande's single "7 Rings" which Monét co-wrote. The song is a celebration of Grande's success, much like "7 Rings", which charted at number one on the Hot 100 for eight weeks; the lyric "I like women and men" garnered significant attention since Monét came out as bisexual in November 2018, referencing Frank Ocean's 2017 single "Chanel", about his own bisexuality. Monét believed it was important to include this line, along with the lyrics "Swerve both ways, Dichotomy", to highlight her sexuality because of the lack of representation for bisexual black women in her industry. In response to the attention garnered by Grande for singing the "I like women and men" line, Grande opened up about her sexuality and revealed she doesn't label herself, tweeting "i haven’t before and still don’t feel the need to now ‍♂️, okay".

Grande sings “Even though we gave up that 90%,” referencing the fact that she had to give up 90% of the royalties for "7 Rings" to Rodgers & Hammerstein due to interpolating the melody of The Sound of Music's "My Favorite Things". Vulture praised the song and music video for being a "meme-heavy bisexual bop". NME wrote that following the release of Thank U, Next, "Monopoly" was refreshing to hear, describing the song as "flippant and fun"; the Washington Post and PinkNews reported that certain fans responded negatively to the song, accusing Grande of queerbaiting. Broadly writer Gabrielle Alexa criticized the accusations, stating "the act of speculating only perpetuates attitudes that contribute to the erasure of bisexual women. Grande doesn't have to date a girl, and we shouldn't try to make her prove her sexuality anyways." Credits adapted from Tidal. Ariana Grande – vocals, songwriting Victoria Monét – vocals, songwriting Tim Suby – production, programming Social House – co-production, programming Kyle Mann – engineering, studio personnel Brendan Morawski – engineering, studio personnel Victoria Monét's "Monopoly" Official Lyrics & Meaning, from Genius