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Van der Waals radius

The van der Waals radius, rw, of an atom is the radius of an imaginary hard sphere representing the distance of closest approach for another atom. It is named after Johannes Diderik van der Waals, winner of the 1910 Nobel Prize in Physics, as he was the first to recognise that atoms were not points and to demonstrate the physical consequences of their size through the van der Waals equation of state; the van der Waals volume, Vw called the atomic volume or molecular volume, is the atomic property most directly related to the van der Waals radius. It is the volume "occupied" by an individual atom; the van der Waals volume may be calculated. For a single atom, it is the volume of a sphere whose radius is the van der Waals radius of the atom: V w = 4 3 π r w 3. For a molecule, it is the volume enclosed by the van der Waals surface; the van der Waals volume of a molecule is always smaller than the sum of the van der Waals volumes of the constituent atoms: the atoms can be said to "overlap" when they form chemical bonds.

The van der Waals volume of an atom or molecule may be determined by experimental measurements on gases, notably from the van der Waals constant b, the polarizability α or the molar refractivity A. In all three cases, measurements are made on macroscopic samples and it is normal to express the results as molar quantities. To find the van der Waals volume of a single atom or molecule, it is necessary to divide by the Avogadro constant NA; the molar van der Waals volume should not be confused with the molar volume of the substance. In general, at normal laboratory temperatures and pressures, the atoms or molecules of a gas only occupy about ​1⁄1000 of the volume of the gas, the rest being empty space. Hence the molar van der Waals volume, which only counts the volume occupied by the atoms or molecules, is about 1000 times smaller than the molar volume for a gas at standard temperature and pressure; the following table shows the Van der Waals radii for the elements. Unless indicated otherwise, the data is given by Mathematica's ElementData function, from Wolfram Research, Inc..

The values are in picometers. The shade of the box ranges from red to yellow as the radius increases. Van der Waals radii may be determined from the mechanical properties of gases, from the critical point, from measurements of atomic spacing between pairs of unbonded atoms in crystals or from measurements of electrical or optical properties; these various methods give values for the van der Waals radius. Tabulated values of van der Waals radii are obtained by taking a weighted mean of a number of different experimental values, for this reason, different tables will have different values for the van der Waals radius of the same atom. Indeed, there is no reason to assume that the van der Waals radius is a fixed property of the atom in all circumstances: rather, it tends to vary with the particular chemical environment of the atom in any given case; the van der Waals equation of state is the simplest and best-known modification of the ideal gas law to account for the behaviour of real gases: = n R T,where p is pressure, n is the number of moles of the gas in question and a and b depend on the particular gas, V ~ is the volume, R is the specific gas constant on a unit mole basis and T the absolute temperature.

Their values vary from gas to gas. The van der Waals equation has a microscopic interpretation: molecules interact with one another; the interaction is repulsive at short distance, becomes mildly attractive at intermediate range, vanishes at long distance. The ideal gas law must be corrected when repulsive forces are considered. For example, the mutual repulsion between molecules has the effect of excluding neighbors from a certain amount of space around each molecule. Thus, a fraction of the total space becomes unavailable to each molecule as it executes random motion. In the equation of state, this volume of exclusion should be subtracted from the volume of the container, thus:; the other term, introduced in the van der Waals equation, a 2, describes a weak attractive force among molecules, which increases when n increases or V decreases and molecules become more crowded together. The van der Waals constant b volume can be used to calculate the van der Waals volume of an atom or molecule with experimental data derived from measurements on gases.

For helium, b = 23.7 cm3/mol. Helium is a monatomic gas, each mole of helium contains 6.022×1023 atoms: V w =

Sand Point, Alaska

Sand Point known as Popof Island, is a city in Aleutians East Borough, United States. At the 2010 census the population was 976, up from 952 in 2000, it is on one of the Shumagin Islands, off the Alaska Peninsula. It is the borough seat of Aleutians East Borough, is near the entrance to the Bering Sea; the Aleutians East Borough School District is in Southwestern Alaska along the Alaska Peninsula and Aleutian Chain The District was formed in 1988 from smaller districts that consolidated and formed a Borough with taxing authority. The Borough and District boundaries are the same, stretch over 15,000 square miles of roadless treeless tundra, from the middle of the Alaska Peninsula to the north and east, going southwest out to Akutan just east of Dutch Harbor. Sand Point was founded by a San Francisco fishing company in 1898 as a cod fishing station and trading post. Aleuts and Scandinavians were among the early residents. Gold mining was a part of the economy during the early 1900s. Fishing remains an important industry, as Sand Point is home to one of the largest fishing fleets in the Aleutian Chain.

Half the inhabitants are of Aleut descent - from the Qagan Tayagungin tribe, support themselves by fishing and fish processing. There is a cold storage and fish-processing plant owned and operated by Trident Seafoods and Peter Pan has a support facility. There is an airport with a 5,200 feet paved runway and daily flights to Anchorage, 575 nautical miles to the northeast; the town is above the treeline, there is a small herd of 120 bison which provides some meat for the island's inhabitants. It is notorious for the high winds caused by the meeting of cold air flows from the Bering Sea with the warm air over the Japan Current, it has a maritime climate, with temperature averages ranging from −9 to 76 °F, an average snowfall of 52 inches and an average rainfall of 33 inches. The Russian Orthodox St. Nicholas Chapel was built in Sand Point in 1933. Sand Point first appeared on the 1890 U. S. did not report a separate figure. It first reported a separate figure in 1900 as Sand Point, it returned in 1920 and in every successive census.

It formally incorporated in 1966 and with the formation of the Aleutians East Borough in 1987, became the seat of government. As of the census of 2000, there were 952 people, 229 households, 155 families residing in the city; the population density was 122.1 people per square mile. There were 282 housing units at an average density of 36.2 per square mile. The racial makeup of the city was 27.73% White, 1.47% Black or African American, 42.33% Native American, 23.21% Asian, 0.32% Pacific Islander, 2.21% from other races, 2.73% from two or more races. 13.55% of the population were Hispanic or Latino of any race. There were 229 households out of which 39.3% had children under the age of 18 living with them, 45.4% were married couples living together, 15.7% had a female householder with no husband present, 31.9% were non-families. 25.8% of all households were made up of individuals and 3.9% had someone living alone, 65 years of age or older. The average household size was 2.67 and the average family size was 3.17.

In the city, the age distribution of the population shows 20.4% under the age of 18, 8.6% from 18 to 24, 41.5% from 25 to 44, 26.3% from 45 to 64, 3.3% who were 65 years of age or older. The median age was 36 years. For every 100 females, there were 165.2 males. For every 100 females age 18 and over, there were 181.8 males. The median income for a household in the city was $55,417, the median income for a family was $58,000. Males had a median income of $20,000 versus $22,500 for females; the per capita income for the city was $21,954. About 10.3% of families and 16.0% of the population were below the poverty line, including 14.4% of those under age 18 and 32.1% of those age 65 or over. Like all of Southwest Alaska, Sand Point has a subpolar oceanic climate, though compared to most parts of the region it is a little less rainy and has fewer wet days - 145 as compared to over 220 throughout the Aleutian Islands and in most of Southeast Alaska. Sand Point is a mixed Native and non-Native community.

More than 50 % of the permanent residents in Sand Point are known as Unangan. Every July the town hosts a Culture Camp in which Aleut traditions such as dance, sewing Aleut dresses, playing drums, building kayaks, knot tying, weaving are taught. Culture Camp has an Aleut language component built into the program. According to the U. S. Census Bureau, the city has a total area of 28.9 square miles, of which, 7.8 square miles of it is land and 21.1 square miles of it is water. There is the Sand Point School, operated by the Aleutians East Borough School District. There are one hundred students in the Sand Point School. In addition to classroom space, the school houses a library media center, weight room, indoor pool and shop; the Sand Point School is part of the Aleutians East Borough School District. The superintendent of the AEBSD is Dr. Doug Conboy and the principal of the Sand Point School is Ralph Lindquist. Circa 1978 the school a part of the Aleutian Region School District, had a 13 teachers, 136 students.

Peninsula Airways offers expensive flights from Anchorage to Sand Point. It is difficult to obtain a plane ticket off of the island with costs reaching $1200 for a round-trip ticket. Cargo se

1994 Big Ten Conference Baseball Tournament

The 1994 Big Ten Conference Baseball Tournament was held at C. O. Brown Stadium in Battle Creek, Michigan from May 15 through 19; the top four teams from the regular season participated in the double-elimination tournament, the fourteenth annual tournament sponsored by the Big Ten Conference to determine the league champion. Ohio State won their second tournament championship and earned the Big Ten Conference's automatic bid to the 1994 NCAA Division I Baseball Tournament; the 1994 tournament was a 4-team double-elimination tournament, with seeds determined by conference regular season winning percentage only. Michigan and Michigan State claimed the third and fourth seeds by tiebreakers. * - Indicates game required 12 innings. The following players were named to the All-Tournament Team. Mike Repasky was named Most Outstanding Player. Repasky was an outfielder for Ohio State

Bay Challenge

The Bay Challenge is an annual open water swimming event from Sandy Cove, West Vancouver to Kitsilano Beach in Vancouver that crosses English Bay. The distance of the current course is 9 kilometers; the changing tides, cold temperatures and rough water make this race challenging. The event is held in the latter part of July every year, when the water temperature is between 16 and 20 degrees Celsius. Hosted by the Vancouver Open Water Swim Association, the focus is on an inclusive event that allows swimmers of all levels and abilities to participate; the Bay Challenge is open to both solo and relay participants to allow as many people as possible to experience the thrill of the challenge. The inaugural Bay Challenge known as the "Vancouver Sun Swimming Marathon," was designed as a publicity event to celebrate the opening of Kitsilano Pool in 1931; the event was organized by the Vancouver Amateur Swim Club and had 41 registrants – 12 women and 29 men. Of the 41 that committed to the race, 33 showed up on race day and 20 were reported to have finished.

Of those who finished, women came in 2nd, 3rd, 6th. [The Arthur P. Dawe trophy, sponsored by a local Irish sweepstakes winner, was awarded to the winner Percy Norman. Norman narrowly defeated Miss Roy Clark by 4 minutes in a winning time of 50 minutes. If the English Bay crossing became an annual event it was not recorded, it was not until 1983 that a crossing event was re-established and the first race won by local swimmer Tom Walker. For two years the route went from Lighthouse Park at Point Atkinson to Spanish Banks. In 1986, a course closer to original route was set. In that year only seven of the twenty competitors completed the swim between the distance shores; the race again was not held for several years. In 1989 a series of open water races was swum but an annual Bay Challenge proved elusive; the Vancouver Open Water Swim Association was established in 1991 and an enduring annual series has been the result. In 1993, Percy Norman's family donated the original Arthur P. Dawe cup to the Vancouver Open Water Swim Association and the association has been awarding it since to the winner of the annual Bay Challenge.

Vancouver Open Water Swim Association website Percy Norman BC Sports Hall of Fame & Museum Inductee

J. C. Seaman

Joseph Carryl Seaman Sr. known as J. C. Seaman, was a five-term member of the Louisiana House of Representatives from Waterproof in Tensas Parish in northeast Louisiana, having served from 1944 to 1964. During his tenure as representative, Lake Bruin State Park established in 1928 as a fish hatchery, opened near St. Joseph on Lake Bruin, an oxbow lake of the Mississippi River. A native of Waterproof, Seaman was the son of Horace P. Seaman, a federal employee on the Mississippi River levee system, the former Pearl Davidson, he graduated from the since defunct Waterproof High School. He was drafted into the United States Army near the end of World War I and hence never served in hostilities. Seaman was an insurance agent and banker with the former Bank of St. Joseph in Waterproof, now Cross Keys Bank, located near the Waterproof Town Hall. Seaman was first married to the former Evie Hinton Greaves, the couple had one son, J. C. Seaman Jr.. Evie was a daughter of the former Elizabeth R. "Vardie" Pitchford and Harry Percy "Hal" Greaves, a physician and the mayor of Waterproof from 1913-1924.

Evie Seaman died two months prior to her son's second birthday. On October 27, 1932, Seaman married Edith Gooding Post at Grace Episcopal Church in Waterproof. J. C. and Edith Seaman had Colin Davidson Seaman. Seaman served under Governors Jimmie Davis, Robert F. Kennon, Earl Kemp Long. In his last term in the House, his state senate colleague was Howard M. Jones of St. Joseph. In declining health, Seaman was unseated in the 1963 Democratic primary by S. S. DeWitt of Newellton and St. Joseph, who served two terms from 1964-1972. DeWitt had lost to Seaman in the 1959 party primary. Seaman died of cancer a month after leaving the office of representative. Services were held at a funeral home chapel in Ferriday in Concordia Parish. Seaman is interred at the Natchez City Cemetery in Natchez, Mississippi

Mossmorran

The Mossmorran Natural Gas Liquids plant is part of the northern North Sea Brent oil and gas field system and is located on the outskirts of Cowdenbeath, Fife. The Mossmorran facilities comprise two plants: the Fife NGL Plant operated by Shell and the Fife Ethylene Plant operated by ExxonMobil. Locally both plants are collectively known as Mossmorran. An associated sea-going tanker loading facility is located at 4 miles to the south. With the commissioning of the Shell Brent Field in 1976, Shell Expro and Exxon Chemicals sought permission to build processing plants at Mossmorran to process the natural gas liquids from the St Fergus gas terminal. A planning inquiry was completed in 1977; the Brent to St Fergus FLAGS pipeline was completed in 1980 and the Shell St Fergus terminal in 1981. Prior to this the associated gas from the Brent field had been flared offshore. Construction work started at Mossmorran in 1981. Shell Expro built the Fife Natural Gas Liquids plant and the Braefoot Bay Marine Terminal, Exxon Chemicals built the Fife Ethylene Plant adjacent to, using feedstock from, the NGL plant, together with the ethylene jetty at Braefoot Bay.

The plants were commissioned in 1985. In addition to gas from the Brent field the FLAGS pipeline carries gas from the Western Leg and Northern Leg Gas pipelines; the Fulmar gas line carries gas from the Central North Sea to St Fergus. Exxon and Mobil merged to form ExxonMobil in 1999; the Fife NGL plant covers an area of about 250 acres. The plant comprises three parallel fractionation trains on the east side of the site; the Ethylene plant is on the west side of the site and includes seven reaction furnaces with their associated chimneys, plus its own fractionation columns. The Mossmorran site overall includes about 11 product storage tanks; the flare from the Mossmorran site is visible and night, from any high point in Edinburgh at normal flaring rates and can be seen from many miles away when significant flaring is taking place. The plants operate the following flaring equipment: two 80-metre-high flares at Shell FNGL; the site is accessed east of the A909, off the south of the A92. The Braefoot Bay site is 7 km south on the Firth of Forth.

It includes marine loading jetties. After gas and oil are separated on the offshore platforms, the gas is routed ashore via pipelines to the gas terminal at St Fergus. At the terminal methane is separated from the rest of the gas product; the methane is sent to a neighbouring National Grid plant which controls the gas flow into the National Transmission System. The remaining natural gas liquids are piped south via a 223 kilometres pipeline to the Mossmorran site in Fife. NGL from the other gas terminals at St Fergus can be routed through the St Fergus - Mossmorran pipeline. At the Fife NGL plant natural gas liquid is separated into its component parts by distillation in three sequential fractionation columns; these comprise a de-ethaniser, a de-propaniser and a de-butaniser, the constituent components and products from the plant are: ethane, propane and pentane or natural gasoline. The ethane is piped to an adjacent ethylene cracker plant operated by ExxonMobil for processing and cracking; the propane and butane streams are chilled and stored on Mossmorran site within double wall insulated buried tanks, the gasoline is stored in floating-roof tanks.

These liquids are transported as required via pipeline to the marine terminal at Braefoot Bay on the Firth of Forth for loading onto ships for export. Vapour return lines from Braefoot Bay are provided for the butane facilities. Mossmorran has an adjacent road tanker terminal for road transportation of propane and butane; the LNG plant operated using two identical process modules with a capacity of 10,000 tonnes per day. This was increased to 15,000 tonnes per day by the addition of a third process module and a few other upgrades in 1992 at a cost of £100 million; the production capacity in 2014 was 12,500 tonnes/day. At the Fife Ethylene Plant ethane feedstock from the NGL plant is treated to remove carbon dioxide. An amine based solution is used to ‘wash’ the feedstock to remove CO2. Ethane is mixed with superheated steam and heated to 800-900°C in seven cracking furnaces to crack it into ethylene; the ethylene mixture is cooled to 25°C in a series of heat exchangers and routed to a quench tower where water cascades down through the gas to remove by-products such as tar.

The gas is next compressed and enters a ‘cold box’ comprising a further series of heat exchangers which chill the gas until it is liquefied. The liquid passes into a series of a reactor. In the first tower, the de-methaniser and methane are removed from the top and are used as fuel gas in the plant; the de-methanised product is taken from the bottom of the de-methaniser and passes to the second tower, the de-ethaniser. Ethylene and any remaining ethane are taken from the top of the de-ethaniser and are routed to the acetylene converters where hydrogen is added to convert acetylene to ethylene in the presence of a catalyst. A mixture called C5+ is removed from the bottom of the de-ethaniser and is used as a feedstock in the chemicals industry. From the acetylene converter the mixture passes to the third column, the ethylene splitter, un-reacted ethane is recycled back to the furnaces and ethylene product is pump