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Energy level

A quantum mechanical system or particle, bound—that is, confined spatially—can only take on certain discrete values of energy, called energy levels. This contrasts with classical particles; the term is used for the energy levels of electrons in atoms, ions, or molecules, which are bound by the electric field of the nucleus, but can refer to energy levels of nuclei or vibrational or rotational energy levels in molecules. The energy spectrum of a system with such discrete energy levels is said to be quantized. In chemistry and atomic physics, an electron shell, or principal energy level, may be thought of as the orbit of one or more electrons around an atom's nucleus; the closest shell to the nucleus is called the "1 shell", followed by the "2 shell" the "3 shell", so on farther and farther from the nucleus. The shells correspond with the principal quantum numbers or are labeled alphabetically with letters used in the X-ray notation; each shell can contain only a fixed number of electrons: The first shell can hold up to two electrons, the second shell can hold up to eight electrons, the third shell can hold up to 18 and so on.

The general formula is. Since electrons are electrically attracted to the nucleus, an atom's electrons will occupy outer shells only if the more inner shells have been filled by other electrons. However, this is not a strict requirement: atoms may have two or three incomplete outer shells. For an explanation of why electrons exist in these shells see electron configuration. If the potential energy is set to zero at infinite distance from the atomic nucleus or molecule, the usual convention bound electron states have negative potential energy. If an atom, ion, or molecule is at the lowest possible energy level, it and its electrons are said to be in the ground state. If it is at a higher energy level, it is said to be excited, or any electrons that have higher energy than the ground state are excited. If more than one quantum mechanical state is at the same energy, the energy levels are "degenerate", they are called degenerate energy levels. Quantized energy levels result from the relation between its wavelength.

For a confined particle such as an electron in an atom, the wave function has the form of standing waves. Only stationary states with energies corresponding to integral numbers of wavelengths can exist. Elementary examples that show mathematically how energy levels come about are the particle in a box and the quantum harmonic oscillator; the first evidence of quantization in atoms was the observation of spectral lines in light from the sun in the early 1800s by Joseph von Fraunhofer and William Hyde Wollaston. The notion of energy levels was proposed in 1913 by Danish physicist Niels Bohr in the Bohr theory of the atom; the modern quantum mechanical theory giving an explanation of these energy levels in terms of the Schrödinger equation was advanced by Erwin Schrödinger and Werner Heisenberg in 1926. In the formulas for energy of electrons at various levels given below in an atom, the zero point for energy is set when the electron in question has left the atom, i.e. when the electron's principal quantum number n = ∞.

When the electron is bound to the atom in any closer value of n, the electron's energy is lower and is considered negative. Assume there is one electron in a given atomic orbital in a hydrogen-like atom; the energy of its state is determined by the electrostatic interaction of the electron with the nucleus. The energy levels of an electron around a nucleus are given by: E n = − h c R ∞ Z 2 n 2, where R∞ is the Rydberg constant, Z is the atomic number, n is the principal quantum number, h is Planck's constant, c is the speed of light. For hydrogen-like atoms only, the Rydberg levels depend only on the principal quantum number n; this equation is obtained from combining the Rydberg formula for any hydrogen-like element with E = h ν = h c / λ assuming that the principal quantum number n above = n1 in the Rydberg formula and n2 = ∞. The Rydberg formula was derived from empirical spectroscopic emission data. 1 λ = R Z 2 An equivalent formula can be derived quantum mechanically from the time-independent Schrödinger equation with a kinetic energy Hamiltonian operator using a wave function as an eigenfunction to obtain the energy levels as eigenvalues, but the Rydberg constant would be replaced by other fundamental physics constants.

If there is more than one electron around the atom, electron-electron-interactions raise the energy level. These interactions are neglected if the spatial overlap of the electron wavefunctions is low. For multi-electron atoms, interactions between electrons cause the preceding equation to be no longer accurate as stated sim

Almere Poort

Almere Gate (. It is the newest part of what is a new city itself, with the first building completed only in 2005. Although Almere is a planned city, Almere Poort was not in the original city plans, but is rather a result of revised urban planning in accordance to Almere's more recent development plans assuming much higher target population and more prominent role as a satellite urban centre to Amsterdam. Almere Poort is located on the western bank of the IJmeer, with the Almeerderstrand beach forming the borough's western boundary, it borders Almere Haven to the south, Almere Stad to the east and the yet-undeveloped designated district of Almere Pampus to the North. The A6 motorway runs along the borough's southern border, with one exit at Poortdreef and one at Hogering, the latter of which runs along the eastern border; the Flevolijn railway line runs semi-diagonally across the borough, with local trains stopping at the borough's station Almere Poort railway station. The former Almere Strand railway station, serviced only during events at Almeerderstrand, was within the boundaries of Almere Poort.

It was demolished in 2012. Since buses run between Almere Poort station and Almeerderstrand during events. Almere Poort differs from the other boroughs and districts in that residential development does not follow the model typical for other districts of Almere, large-scale single-family housing developments built according to a common plan. Contrary to this, the district features both high-density apartment buildings, as well as land parcels available for free private housing development. Contrary to older districts of Almere, Almere-Poort refers to its residential areas as kwartieren rather than wijken; the designated parts of Almere Poort according to the official website of the municipality are: Homeruskwartier - featuring land plots for private housing development, with streets named after mythological beings and characters featured in the works of Homer Europakwartier - consisting of large-scale apartment buildings with an urban atmosphere, divided by the railway tracks into Europakwartier-West and Europakwartier-Oost.

The street naming after European countries follows the east-west geographic location of countries Columbuskwartier - this residential district has streets named after famous explorers such as Christopher Columbus himself Olympiakwartier and Olympia Office Park are to be constructed around the Almere Poort railway station to form the district's multi-functional and prestigious centre. Duin which will feature beach condo's and sand hills close to the beach of Almeerderstrand and Marina Muiderzand. Cascadepark - a park between Homeruskwartier and Europakwartier with its first trees planted in 2008 Kustzone - the coastal zone along the Almeerderstrand is designated for mixed development, including residential buildings, leisure facilities and some commerce Hogekant - this commercial area in the Western extremity of the district is designated for industrial use by small and mid-sized enterprises in the craft and service sectors Middenkant - separated with a canal from the Hogekant is to provide a more high-quality neighbourhood for SMEs Lagekant - this commercial area is designated for large and international companies in the service sector Almere Poort's section of the official webpage of the municipality of Almere

Morten Stræde

Morten Stræde is a Danish sculptor. He attended the Royal Danish Academy of Fine Arts from 1978–1985 and became a professor there. Morten Stræde had his breakthrough in the 1980s. In 2011, he created three new urban spaces in the Nørrebro borough in Copenhagen. Stræde was awarded the Premio Internazionale di scultura in 1999 and received the Eckersberg Medal in 2000, he has received the Thorvaldsen Medal. In its appraisal of Stræde's work, the academy noted his ability to assess the history of the place and the physical location where his public art is to be displayed. An example mentioned by the jury is Ulisse. Stræde is represented at the following art museums: National Gallery of Denmark Kobberstiksamlingen ARoS Aarhus Kunstmuseum Herning Museum of Art Horsens Museum of Art Kunstmuseet Køge Skitsesamling Vestsjællands Museum of Art Kunstmuseet Trapholt Esbjerg Art Museum Vejle Museum of Art Gothenburg Museum of Art, official site

National Geographic Endeavour

MS National Geographic Endeavour was a small expedition ship operated by Lindblad Expeditions for cruising in remote areas the polar regions. The ship was a fishing trawler built in 1966 as Marburg, converted to carry passengers in 1983. First named North Star Caledonian Star. On March 2, 2001, the ship was struck by a 30-metre-high rogue wave while crossing the Drake Passage, she was assisted by the Argentine Navy ocean fleet tug ARA Alferez Sobral and reached Ushuaia three days later. When National Geographic Endeavour was retired, the piano was donated to the Tomas de Berlanga school in Santa Cruz, Galapagos; the bridge ceiling, notched with polar bear sightings from her time in Svalbard, is with Sven Lindblad. The model, valuable art and other mementos were saved, some items were transferred to National Geographic Endeavour II. National Geographic Endeavour was scrapped on 6 May 2017. Details of the ship

Cunningham-Hall PT-6

The Cunningham-Hall Model PT-6 was an American six-seat cabin biplane aircraft of the late 1920s and was the first design of the Cunningham-Hall Aircraft Corporation of Rochester, New York. The Cunningham-Hall Aircraft Corporation was formed in 1928 and the first design was the PT-6, which first flew on April 3, 1929, it was flown to the Detroit Aircraft Show two days with minor alterations being made including a switch from a tailskid to a tailwheel. The PT-6 was a cabin biplane with an all-metal structure, stressed to meet military strength specifications rather than the much more lenient commercial requirements, however aside from the cabin, covered with corrugated aluminum, most of the airframe was fabric covered, it had a fixed landing gear with a tail wheel. The cockpit held a pilot and either a copilot or passenger, with a separate cabin for four passengers; the aircraft was powered by a 300 hp Wright J-6-9 Whirlwind radial engine. The company's final aircraft was a freighter conversion the PT-6F.

Built during 1937 and flown in 1938, the passenger cabin was modified as a cargo compartment with 156 cu ft of stowage space, an NACA cowling was fitted, along with a variable-pitch propeller. A freight door was fitted to a loading hatch fitted in the roof, it was powered by a Wright R-975E-1 radial engine of greater power. Only two PT-6s and one PT-6F were registered, however as many as six of each type may have been built; the discrepancy from many publications with higher numbers may indicate that from two to nine additional airframes were built, but scrapped without being registered or sold, due to the collapse of the aviation market with the deepening of the Great Depression. A production line had been set up, materials bought to produce 25 examples. Plans for a smaller 4-seat derivative to be named the PT-4, an armed military variant were cancelled. One example was used for charter flying by the Rochester - Buffalo Flying Service fitted with skis or floats. One customer was the Fairchild Aviation Corporation.

George Eastman of Kodak had his first flight in PT-6 The PT-6F was supposed to have been one of three built from parts still available from the original cancelled production run, for an expected Philippine customer, carried the Philippine registration of NPC-44, however a lack of funds caused that sale to be cancelled. The aircraft was sold for around $7,000, made its way to Alaska for a career as a bush plane with Byers Airways. PT-6 Six-seat cabin biplane powered by a 300 hp Wright J-6 Whirlwind radial engine. PT-6F Freighter version of the PT-6. PT-4 Cancelled 4 place version. PT-6 Bomber Cancelled bomber with turret. PT-6F s/n 381 NC444 NC16967 and NPC44 was restored to airworthy condition and as of 2008 was on display at the Golden Wings Museum at Anoka County-Blaine Airport, near Minneapolis. PT-6 s/n 2962 NC692W was restored to display-only status and cannot be flown, is at the Alaska Museum of Transportation and Industry in Wasilla and has been listed on the National Register of Historic Places.

Data from Aero Digest and JuptnerGeneral characteristics Crew: Two Capacity: Four Length: 29 ft 8 in Upper wingspan: 41 ft 8 in Upper Chord: 78 in Lower wingspan: 33 ft 8 in Lower Chord: 54 in Height: 9 ft 7 in Wing area: 378 sq ft Airfoil: Clark Y Empty weight: 2,670 lb Gross weight: 4,350 lb Fuel capacity: 90 US gal Oil capacity: 6 US gal Powerplant: 1 × Wright J-6-9-300 Whirlwind 9 cylinder air-cooled radial engine, 300 hp Propellers: 2-bladed metal propeller. Performance Maximum speed: 136 mph Cruise speed: 115 mph Stall speed: 40 mph landing speed: 45 mph Range: 690 mi Endurance: 6 hours Service ceiling: 17,500 ft Rate of climb: 900 ft/min initial rate Time to altitude: 1.5 minutes to 2,000 ft 5 minutes to 6,000 ft Wing loading: 10.5 lb/sq ft Power/mass: 0.08 hp/lb Eckland, K. O.. "Aircraft Cu to Cy". Retrieved 28 January 2020. George F. McLaughlin, ed.. "Cunningham-Hall biplane". Aero Digest. Vol. XIV no. 5. New York City: Aeronautical Digest Publishing Corp. pp. 106 and 108.

Hall, Randolph F.. "Cunningham-Hall Aircraft Corp. Story". AAHS Journal. American Aviation Historical Society. Pp. 90–97. Herrick, Greg. "Sole Survivor - Amazing restoration of the last Cunningham-Hall PT-6F biplane". Air Classics. Vol. 33 no. 10. Pp. 14-18 and 68-70. Juptner, Joseph P.. U. S. Civil Aircraft Vol. 2. Los Angeles, CA: Aero Publishers, Inc. pp. 220–221. LCCN 62-15967. George F. McLaughlin, ed.. "Cunningham-Hall biplane". Aero Digest. Vol. XIV no. 5. New York City: Aeronautical Digest Publishing Corp. pp. 106 and 108. Theobald, Mark. "Jas. Cunningham, Son & Co". Retrieved 3 February 2020. National Park Service. "National Park Service - Alaska - National Register of Historic Places". Retrieved 3 March 2020

Sara Poidevin

Sara Poidevin is a Canadian professional racing cyclist, who rides for UCI Women's Continental Team Rally Cycling. She raced mountain bikes before switching to road racing in 2013. 2016 1st Young rider classification Cascade Cycling Classic2017 1st Overall Colorado Classic 1st Points classification 1st Mountains classification 1st Young rider classification 1st Stage 2 2nd Overall Cascade Cycling Classic 1st Mountains classification 1st Young rider classification 1st Stage 52018 1st Young rider classification Tour Cycliste Féminin International de l'Ardèche 2nd Overall Tour of the Gila 1st Young rider classification 7th Overall Tour of California 1st Young rider classification List of 2016 UCI Women's Teams and riders Sara Poidevin at ProCyclingStats