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21) Nicole Oresme

Nicole Oresme (1 January 1325 – 11 July 1382), also known as Nicolas Oresme, Nicholas Oresme, or Nicolas d'Oresme, was a French philosopher of the later Middle Ages. He wrote influential works on economics, mathematics, physics, astrology, astronomy, philosophy, and theology. He served as Bishop of Lisieux, translated Aristotelian texts for King Charles V of France, and was a prominent scholar of 14th-century Europe.

Life

Nicole Oresme was born c. 1320–1325 in the village of Allemagnes (today's Fleury-sur-Orne) in the vicinity of Caen, Normandy, in the diocese of Bayeux. Little is known about his family background, but his attendance at the royally sponsored College of Navarre in Paris, which supported students of modest means, suggests he likely came from a peasant or modest family.

Oresme studied the "arts" in Paris, together with Jean Buridan (the so-called founder of the French school of natural philosophy), Albert of Saxony and perhaps Marsilius of Inghen, and there received the Magister Artium. By 1342, he was a regent master in arts during debates over William of Ockham's natural philosophy.

In 1348, he was a student of theology in Paris.

In 1356 he received his doctorate and in the same year he became grand master (grand-maître) of the College of Navarre.

In 1364 he was appointed dean of the Cathedral of Rouen. From 1369, at the request of Charles V, he translated Aristotelian works into French, receiving a pension in 1371. In 1377, with royal support, he became bishop of Lisieux, where he died in 1382.

Mathematics

Oresme's most important contributions to mathematics are contained in Tractatus de configurationibus qualitatum et motuum. In a quality, or accidental form, such as heat, he distinguished the intensio (the degree of heat at each point) and the extensio (as the length of the heated rod). These two terms were often replaced by latitudo and longitudo. For the sake of clarity, Oresme conceived the idea of visualizing these concepts by plane figures, approaching what we would now call rectangular coordinates. The intensity of the quality was represented by a length or latitudo proportional to the intensity erected perpendicular to the base at a given point on the base line, which represents the longitudo. Oresme proposed that the geometrical form of such a figure could be regarded as corresponding to a characteristic of the quality itself. Oresme defined a uniform quality as that which is represented by a line parallel to the longitude, and any other quality as difform. Uniformly varying qualities are represented by a straight line inclined to the axis of the longitude, while he described many cases of nonuniformly varying qualities. Oresme extended this doctrine to figures of three dimensions. He considered this analysis applicable to many different qualities such as hotness, whiteness, and sweetness. Significantly for later developments, Oresme applied this concept to the analysis of local motion where the latitudo or intensity represented the speed, the longitudo represented the time, and the area of the figure represented the distance travelled. He formulated a theorem for uniformly accelerated motion, showing distance traveled as the area under a velocity-time graph, predating Galileo. have been cited to credit Oresme with the discovery of "proto bar charts". He also proved the divergence of the harmonic series and introduced early concepts of curvature. Oresme was the first mathematician to prove this fact, and (after his proof was lost) it was not proven again until the 17th century by Pietro Mengoli. He explored fractional powers and probability over infinite sequences, concepts developed centuries later.

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2228) Louis E. Brus

Gist

Professor Louis Brus, a longtime professor and an alumnus of Columbia University, has been awarded the Nobel Prize in Chemistry. Brus was recognized along with two other scientists—Moungi G. Bawendi of MIT and Alexei I. Ekimov of Nanocrystals Technology Inc.—for his work on the “discovery and development of quantum dots, nanoparticles so tiny that their size determines their properties.”

Brus is currently the Samuel Latham Mitchill Professor Emeritus, and Special Research Scientist at Columbia. He is one of 87 Columbians—alumni, faculty, adjunct faculty, researchers, and administrators—to win a Nobel Prize.

Summary

Louis Brus (born August 10, 1943, Cleveland, Ohio, U.S.) is an American physical chemist who was awarded the 2023 Nobel Prize in Chemistry for his work in discovering and producing quantum dots, which are very small particles whose unusual quantum properties depend on their size. He shared the prize with Russian-born American physicist Alexei Ekimov and French-born American chemist Moungi Bawendi.

Brus spent his early life in Cleveland, but his father, an insurance executive, moved the family several times throughout the Midwest. He attended Shawnee Mission North High School in Roeland Park, Kansas, before enrolling at Rice University in Houston on a Naval Reserve Officers Training Corps (NROTC) scholarship. He completed his bachelor’s degree in chemical physics in 1965. After graduation, he was able to delay his active service in the United States Navy to complete a Ph.D. degree in chemical physics. Upon his graduation in 1969, he was made a lieutenant and stationed in Washington, D.C., as a science staff officer at the United States Naval Research Laboratory. After his service was completed in 1973, he served as a research technician at AT&T Bell Laboratories in Murray Hill, New Jersey, where he began to experiment with nanocrystals and semiconducting materials.

Since the 1930s, physicists and chemists have known that a material’s size has a significant effect on its properties. That is, in particles of matter a few nanometers in size (1 nanometer = 10−9 meter), quantum mechanical effects become significant. Particles of this size are called nanoparticles.

Brus’s discovery of quantum dots in late 1982 was accidental. He and his collaborators were interested in using semiconductors to drive chemical reactions. They worked with nanoparticles of cadmium sulfide (CdS) in a solution. Brus observed that the absorption spectra of newly produced CdS nanoparticles was different from those of particles that had been allowed to sit for a day. He suspected this happened because the nanoparticles grew in size. Upon measurement, new CdS nanoparticles proved to be about 4.5 nanometers across, and older (or “ripened”) CdS nanoparticles were about 12.5 nanometers across. (Ekimov had discovered quantum dots independently and had published his work in 1981, but, because Ekimov had published in a Soviet journal, Brus did not learn about his discovery until 1984.)

Brus and his group continued working on quantum dots. Bawendi was a postdoctoral fellow under Brus in the late 1980s, and later, as a professor at MIT (Massachusetts Institute of Technology), he developed a method for producing high-quality quantum dots of a consistent size. Today quantum dots are used in many applications, including in QLED (quantum-dot light-emitting diode) screens, in solar cells, and as markers in biomedical imaging.

Brus remained at Bell Laboratories until he joined the chemistry faculty at Columbia University in 1996. There he served as the scientific head of the complex films research group at the National Science Foundation’s Materials Research Science and Engineering Center from 1998 to 2008 and as codirector of the U.S. Department of Energy’s Energy Frontiers Research Center from 2009 to 2014.

Brus became an elected fellow of the American Physical Society in 1980 and of the American Academy of Arts and Sciences in 1998, and he was elected to the United States National Academy of Sciences in 2004. He was the recipient of the American Chemical Society’s Chemistry of Materials Prize in 2005 and of the Kavli Prize in Nanoscience in 2008. Brus shared the R.W. Wood Prize of the Optical Society of America (OSA, now Optica) with Russian scientist Alexander L. Efros and Ekimov in 2006 for their work with quantum dots. In addition, Brus received the National Academy of Sciences Award in Chemical Sciences in 2010 for his ongoing work with nanocrystals and investigations into the quantum effects that govern their optical properties.

Details

Louis Eugene Brus (born August 10, 1943) is an American chemist, and currently the Samuel Latham Mitchell Professor of Chemistry at Columbia University. He is the co-discoverer of the colloidal semi-conductor nanocrystals known as quantum dots. In 2023, he was awarded the Nobel Prize in Chemistry.

Early life and education

Louis Eugene Brus was born in 1943 in Cleveland, Ohio, United States of America. During high school in Roeland Park, Kansas, he developed an interest for chemistry and physics.

He entered Rice University in 1961 with a Naval Reserve Officers Training Corps (NROTC) college scholarship, which required him to participate in NROTC activities at sea as a midshipman. In 1965, he graduated at Rice with a B.S. degree in chemical physics, and then moved to Columbia University for his doctoral research. For his dissertation, he worked on the photodissociation of sodium iodide vapor, under the supervision of Richard Bersohn. After obtaining his Ph.D. degree in chemical physics in 1969, Brus returned to the Navy as a lieutenant and served as a scientific staff officer in collaboration with Lin Ming-chang, at the United States Naval Research Laboratory in Washington, D.C.

Under the recommendation of Bersohn, Brus left the Navy permanently and joined AT&T Bell Laboratories in 1973, where he did the work that led to the discovery of quantum dots. In 1996, Brus left Bell Labs and joined the faculty in the Department of Chemistry at Columbia University.

Work on quantum dots

Brus is a foundational figure in the research and development of quantum dots. Quantum dots are tiny semiconducting crystals whose nanoscale size gives them unique optical and electronic properties.

Brus was independently the first to synthesize them in a solution in 1982. At the time, he was studying organic photochemistry on cadmium sulfide particle surfaces using pump–probe Raman spectroscopy, looking for possible applications for solar-energy. He noticed that the optical properties of the crystals changed after leaving them for 24 hours. He attributed this change in band gap energy to Ostwald ripening when the crystal increased size.

Brus provided the theoretical framework for understanding the behavior of quantum dots in terms of quantum size effects. He identified the connection between the particle size of semiconductors and the wavelength of the light they emit, now known as the Brus equation.

Brus tried to contact researchers in the Soviet Union. It was in 1990, that he finally met Alexey Ekimov and Alexander Efros, who had first developed the semiconductor nanocrystals in glass in 1981 under more rudimentary conditions, however their research was not available in the United States.

At Bell Labs, Brus worked with postdoc researchers Paul Alivisatos and Moungi Bawendi in a research project with organometallic synthetic chemist Michael L. Steigerwald on reducing the size of the quantum dots.

Awards and honors

Brus was elected a fellow of the American Academy of Arts and Sciences in 1998, a member of the United States National Academy of Sciences in 2004, and is a member of the Norwegian Academy of Science and Letters.

He received the Distinguished Alumni Award from the Association of Rice University Alumni in 2010. He was co-recipient of the 2006 R. W. Wood Prize of the Optical Society of America "for the discovery of nanocrystal quantum dots and pioneering studies of their electronic and optical properties" shared with Alexander Efros and Alexey Ekimov. He also received the inaugural Kavli Prize for nanoscience along with Sumio Iijima in 2008 for "for their large impact in the development of the nanoscience field of the zero and one dimensional nanostructures in physics, chemistry and biology". In 2009 he was awarded the Willard Gibbs Award "for his leading role in the creation of chemical quantum dots". Brus was chosen for the 2010 NAS Award in Chemical Sciences. In 2012 he received the Franklin Institute's Bower Award and Prize for Achievement in Science, and was selected as a Clarivate Citation laureate in Chemistry "for discovery of colloidal semiconductor nanocrystals (quantum dots)".

In 2023, Brus was awarded the Nobel Prize in Chemistry jointly with Ekimov and Moungi Bawendi "for the discovery and synthesis of quantum dots". Bawendi had worked as a postdoc with Brus, when they were in Bell Labs.

2372) Dead Sea

Gist

The Dead Sea is one of the saltiest natural bodies of water on Earth. The special salt has been used in beauty products for thousands of years, but there's little chance of it running out!

The Dead Sea is called the "dead sea" because its extreme salinity, nearly ten times saltier than ocean water, prevents most aquatic life, such as fish and plants, from surviving in it. While most organisms cannot live there, some microorganisms like bacteria and algae have adapted to the harsh, mineral-rich waters, which are concentrated by intense evaporation in a hot desert climate.

Summary

The Dead Sea, also known by other names, is a landlocked salt lake bordered by Jordan to the east, the Israeli-occupied West Bank to the west and Israel to the southwest. It lies in the endorheic basin of the Jordan Rift Valley, and its main tributary is the Jordan River.

As of 2025, the lake's surface is 439.78 metres (1,443 ft) below sea level, making its shores the lowest land-based elevation on Earth. It is 304 m (997 ft) deep, the deepest hypersaline lake in the world. With a salinity of 342 g/kg, or 34.2% (in 2011), it is one of the world's saltiest bodies of water,[9] 9.6 times as salty as the ocean—and has a density of 1.24 kg/litre, which makes swimming similar to floating. This salinity makes for a harsh environment in which plants and animals cannot flourish, hence its name. The Dead Sea's main, northern basin is 50 kilometres (31 mi) long and 15 kilometres (9 mi) wide at its widest point.

The Dead Sea has attracted visitors from around the Mediterranean basin for thousands of years. It was one of the world's first health resorts, and it has been the supplier of a wide variety of products, from asphalt for Egyptian mummification to potash for fertilisers. Today, tourists visit the sea on its Israeli, Jordanian and West Bank coastlines.

The Dead Sea is receding at a swift rate; its surface area today is 605 sq km (234 sq mi), having been 1,050 sq km (410 sq mi) in 1930. Multiple canal and pipeline proposals, such as the scrapped Red Sea–Dead Sea Water Conveyance project, have been made to reduce its recession.

Details

Dead Sea, landlocked salt lake between Israel and Jordan in southwestern Asia. Its eastern shore belongs to Jordan, and the southern half of its western shore belongs to Israel. The northern half of the western shore lies within the Palestinian West Bank and has been under Israeli occupation since the 1967 Arab-Israeli war. The Jordan River, from which the Dead Sea receives nearly all its water, flows from the north into the lake.

The Dead Sea has the lowest elevation and is the lowest body of water on the surface of Earth. For several decades in the mid-20th century, the standard value given for the surface level of the lake was some 1,300 feet (400 metres) below sea level. Beginning in the 1960s, however, Israel and Jordan began diverting much of the Jordan River’s flow and increased the use of the lake’s water itself for commercial purposes. The result of those activities was a precipitous drop in the Dead Sea’s water level. By the mid-2010s, measurement of the lake level was more than 100 feet (some 30 metres) below the mid-20th-century figure—i.e., about 1,410 feet (430 metres) below sea level—but the lake continued to drop by about 3 feet (1 metre) annually.

Physical features:

Physiography and geology

The Dead Sea is situated between the hills of Judaea to the west and the Transjordanian plateaus to the east. Before the water level began dropping, the lake was some 50 miles (80 km) long, attained a maximum width of 11 miles (18 km), and had a surface area of about 394 square miles (1,020 square km). The peninsula of Al-Lisān (Arabic: “The Tongue”) divided the lake on its eastern side into two unequal basins: the northern basin encompassed about three-fourths of the lake’s total surface area and reached a depth of 1,300 feet (400 metres), and the southern basin was smaller and considerably shallower, less than 10 feet (3 metres) deep on average. During biblical times and until the 8th century ce, only the area around the northern basin was inhabited, and the lake was slightly lower than its present-day level. It rose to its highest level, 1,275 feet (389 metres) below sea level, in 1896 but receded again after 1935, stabilizing at about 1,300 feet (400 metres) below sea level for several decades.

The drop in the lake level in the late 20th and early 21st centuries changed the physical appearance of the Dead Sea. Most noticeably, the peninsula of Al-Lisān gradually extended eastward, until the lake’s northern and southern basins became separated by a strip of dry land. In addition, the southern basin was eventually subdivided into dozens of large evaporation pools (for the extraction of salt), so by the 21st century it had essentially ceased to be a natural body of water. The northern basin—effectively now the actual Dead Sea—largely retained its overall dimensions despite its great loss of water, mainly because its shoreline plunged downward so steeply from the surrounding landscape.

The Dead Sea region occupies part of a graben (a downfaulted block of Earth’s crust) between transform faults along a tectonic plate boundary that runs northward from the Red Sea–Gulf of Suez spreading centre to a convergent plate boundary in the Taurus Mountains of southern Turkey. The eastern fault, along the edge of the Moab Plateau, is more readily visible from the lake than is the western fault, which marks the gentler Judaean upfold.

In the Jurassic and Cretaceous periods (about 201 million to 66 million years ago), before the creation of the graben, an extended Mediterranean Sea covered Syria and Palestine. During the Miocene Epoch (23 million to 5.3 million years ago), as the Arabian Plate collided with the Eurasian Plate to the north, upheaval of the seabed produced the upfolded structures of the Transjordanian highlands and the central range of Palestine, causing the fractures that allowed the Dead Sea graben to drop. At that time the Dead Sea was probably about the size that it is today. During the Pleistocene Epoch (2,588,000 to 11,700 years ago), it rose to an elevation of about 700 feet (200 metres) above its modern level, forming a vast inland sea that stretched some 200 miles (320 km) from the H̱ula Valley area in the north to 40 miles (64 km) beyond its present southern limits. The Dead Sea did not spill over into the Gulf of Aqaba because it was blocked by a 100-foot (30-metre) rise in the highest part of Wadi Al-ʿArabah, a seasonal watercourse that flows in a valley to the east of the central Negev highlands.

Beginning about 2.5 million years ago, heavy streamflow into the lake deposited thick sediments of shale, clay, sandstone, rock salt, and gypsum. Later, strata of clay, marl, soft chalk, and gypsum were dropped onto layers of sand and gravel. Because the water in the lake evaporated faster than it was replenished by precipitation during the past 10,000 years, the lake gradually shrank to its present form. In so doing, it exposed deposits that now cover the Dead Sea valley to thicknesses of between about 1 and 4 miles (1.6 and 6.4 km).

The Al-Lisān region and Mount Sedom (historically Mount Sodom) resulted from movements of Earth’s crust. Mount Sedom’s steep cliffs rise up from the southwestern shore. Al-Lisān is formed of strata of clay, marl, soft chalk, and gypsum interbedded with sand and gravel. Both Al-Lisān and beds made of similar material on the western side of the Dead Sea valley dip to the east. It is assumed that the uplifting of Mount Sedom and Al-Lisān formed a southern escarpment for the Dead Sea. Later the sea broke through the western half of that escarpment to flood what is now the shallow southern remnant of the Dead Sea.

Another consequence resulting from the Dead Sea’s lower water level has been the appearance of sinkholes, especially in the southwestern part of the region. As the water in the lake dropped, it became possible for groundwater to rise up and dissolve large subterranean caverns in the overlying salt layer until the surface finally collapses. Several hundred sinkholes have formed, some of them in areas popular with tourists.

Climate and hydrology

The Dead Sea lies in a desert. Rainfall is scanty and irregular. Al-Lisān averages about 2.5 inches (65 mm) of rain a year, the industrial site of Sedom (near historical Sodom) only about 2 inches (50 mm). Because of the lake’s extremely low elevation and sheltered location, winter temperatures are mild, averaging 63 °F (17 °C) in January at the southern end at Sedom and 58 °F (14 °C) at the northern end; freezing temperatures do not occur. Summer is oppressively hot, averaging 93 °F (34 °C) in August at Sedom, with a recorded maximum of 124 °F (51 °C). Evaporation of the lake’s waters—estimated at about 55 inches (1,400 mm) per year—often creates a thick mist above the lake. On the rivers the atmospheric humidity varies from 45 percent in May to 62 percent in October. Lake and land breezes, which are relatively common, blow off the lake in all directions in the daytime and then reverse direction to blow toward the centre of the lake at night.

The inflow from the Jordan River, whose high waters occur in winter and spring, once averaged some 45.5 billion cubic feet (1.3 billion cubic metres) per year. However, the subsequent diversions of the Jordan’s waters reduced the river’s flow to a small fraction of the previous amount and became the principal cause for the drop in the Dead Sea’s water level. Four modest streams descend to the lake from Jordan to the east through deep gorges: the wadis (intermittent streams) Al-ʿUẓaymī, Zarqāʾ Māʿīn, Al-Mawjib, and Al-Ḥasā. Down numerous other wadis, streams flow spasmodically and briefly from the neighbouring heights as well as from the depression of Wadi Al-ʿArabah. Thermal sulfur springs also feed the rivers. Evaporation in summer and the inflow of water, especially in winter and spring, once caused noticeable seasonal variations of 12 to 24 inches (30 to 60 cm) in the level of the lake, but those fluctuations have been overshadowed by the more-dramatic annual drops in the Dead Sea’s surface level.

Salinity

The waters of the Dead Sea are extremely saline, and, generally, the concentration of salt increases toward the lake’s bottom. That phenomenon can create two different masses of water in the lake for extended periods of time. Such a situation existed for some three centuries, lasting until the late 1970s. Down to a depth of about 130 feet (40 metres), the temperature varied from 66 to 98 °F (19 to 37 °C), the salinity was slightly less than 300 parts per thousand, and the water was especially rich in sulfates and bicarbonates. Beneath a zone of transition located at depths between 130 and 330 feet (40 and 100 metres), the water had a uniform temperature of about 72 °F (22 °C) and a higher degree of salinity (approximately 332 parts per thousand); it contained hydrogen sulfide and strong concentrations of magnesium, potassium, chlorine, and bromine. The deep water was saturated with sodium chloride, which precipitated to the bottom. The deep water thus became fossilized (i.e., because it was highly salty and dense, it remained permanently on the bottom).

The dramatic reduction in inflow from the Jordan River that began in the 1960s gradually increased the salinity of the upper-layer waters of the Dead Sea. By the late 1970s that water mass had become more saline (and denser) than the lower layers, but, because it remained warmer than the layers beneath it, it did not sink. By the winter of 1978–79, however, the upper-level layer had become cool and saturated enough to sink, setting off an event known as an overturn (a mixing of the water layers). Since then the trend has been toward restoring the formerly stratified water layers, but with more instances of overturning.

The saline water has a high density that keeps bathers buoyant. The fresh water of the Jordan stays on the surface, and in the spring its muddy colour can be traced as it spreads southward from the point where the river empties into the Dead Sea. The lake’s extreme salinity excludes all forms of life except bacteria. Fish carried in by the Jordan or by smaller streams when in flood die quickly. Apart from the vegetation along the rivers, plant life along the shores is discontinuous and consists mainly of halophytes (plants that grow in salty or alkaline soil).

Human imprint

The name Dead Sea can be traced at least to the Hellenistic Age (323 to 30 bce). The Dead Sea figures in biblical accounts dating to the time of Abraham (first of the Hebrew patriarchs) and the destruction of Sodom and Gomorrah (the two cities along the lake, according to the Hebrew Bible, that were destroyed by fire from heaven because of their wickedness). The desolate wilderness beside the lake offered refuge to David (king of ancient Israel) and later to Herod I (the Great; king of Judaea), who at the time of the siege of Jerusalem by the Parthians in 40 bce barricaded himself in a fortress at Masada, Israel, just west of Al-Lisān. Masada was the scene of a two-year siege that culminated in the mass suicide of its Jewish Zealot defenders and the occupation of the fortress by the Romans in 73 ce. The Jewish sect that left the biblical manuscripts known as the Dead Sea Scrolls took shelter in caves at Qumrān, just northwest of the lake.

The Dead Sea constitutes an enormous salt reserve. Rock salt deposits also occur in Mount Sedom along the southwestern shore. The salt has been exploited on a small scale since antiquity. In 1929 a potash factory was opened near the mouth of the Jordan. Subsidiary installations were later built in the south at Sedom, but the original factory was destroyed during the 1948–49 Arab-Israeli war. A factory producing potash, magnesium, and calcium chloride was opened in Sedom in 1955. Another plant produces bromine and other chemical products. There are also chemical-processing facilities on the Jordanian side of the southern basin. Water for the extensive array of evaporation pools in the south, from which those minerals are extracted, is supplied by artificial canals from the northern basin.

Because of its location on the contested Jordanian-Israeli frontier, navigation on the Dead Sea is negligible. Its shores are nearly deserted, and permanent establishments are rare. Exceptions are the factory at Sedom, a few hotels and spas in the north, and, in the west, a kibbutz (an Israeli agricultural community) in the region of the ʿEn Gedi oasis. Small cultivated plots are also occasionally found on the lakeshore.

Concern mounted quickly over the continued drop in the Dead Sea’s water level, prompting studies and calls for greater conservation of the Jordan River’s water resources. In addition to proposals for reducing the amount of river water diverted by Israel and Jordan, those two countries discussed proposals for canals that would bring additional water to the Dead Sea. One such project, which received approval from both sides in 2015, would involve constructing a canal northward from the Red Sea. The plan, which would include desalinization and hydroelectric plants along the course of the canal, would deliver large quantities of brine (a by-product of the desalinization process) to the lake. However, the project met with skepticism and opposition from environmentalists and others who questioned the potentially harmful effects of mixing water from the two sources.

Additional Information

The Dead Sea is a lake located in the southwestern of Asia. It is the Earth's lowest surface, located 420 meters (1,380 feet) below sea level. The sea is drying up as basin countries use water from its tributaries for drinking water and processes like irrigation.

The Dead Sea is almost nine times as salty as the ocean because a lot of water evaporates out of it, leaving salt behind. Most life cannot survive its high salinity, which is why it is called the "Dead Sea". However, some microbes have adapted to the high salinity and are able to survive in the Dead Sea's harsh environment.

Because the water is so salty, it weighs more than fresh water. This allows people to float in the Dead Sea without any effort. Tourists come from around the world to float in the water.

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