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Bent bond

In organic chemistry, a bent bond known as a banana bond, is a type of covalent chemical bond with a geometry somewhat reminiscent of a banana. The term itself is a general representation of electron density or configuration resembling a similar "bent" structure within small ring molecules, such as cyclopropane or as a representation of double or triple bonds within a compound, an alternative to the sigma and pi bond model. Bent bonds are a special type of chemical bonding in which the ordinary hybridization state of two atoms making up a chemical bond are modified with increased or decreased s-orbital character in order to accommodate a particular molecular geometry. Bent bonds are found in strained organic compounds such as cyclopropane and aziridine. In these compounds, it is not possible for the carbon atoms to assume the 109.5° bond angles with standard sp3 hybridization. Increasing the p-character to sp5 makes it possible to reduce the bond angles to 60°. At the same time, the carbon-to-hydrogen bonds gain more s-character.

In cyclopropane, the maximum electron density between two carbon atoms does not correspond to the internuclear axis, hence the name bent bond. In cyclopropane, the interorbital angle is 104°; this bending can be observed experimentally by X-ray diffraction of certain cyclopropane derivatives: the deformation density is outside the line of centers between the two carbon atoms. The carbon–carbon bond lengths are shorter than in a regular alkane bond: 151 pm versus 153 pm. Cyclobutane still has bent bonds. In this molecule, the carbon bond angles are 90° for the planar conformation and 88° for the puckered one. Unlike in cyclopropane, the C–C bond lengths increase rather than decrease. In terms of reactivity, cyclobutane is inert and behaves like ordinary alkanes. An alternative model utilizes semi-localized Walsh orbitals in which cyclopropane is described as a carbon sp2 sigma bonding and in-plane pi bonding system. Critics of the Walsh orbital theory argue that this model does not represent the ground state of cyclopropane as it cannot be transformed into the localized or delocalized descriptions via a unitary transformation.

Two different explanations for the nature of double and triple covalent bonds in organic molecules were proposed in the 1930s. Linus Pauling proposed that the double bond results from two equivalent tetrahedral orbitals from each atom, which came to be called banana bonds or tau bonds. Erich Hückel proposed a representation of the double bond as a combination of a sigma bond plus a pi bond; the Hückel representation is the better-known one, it is the one found in most textbooks since the late-20th century. Both models represent the same total electron density, with the orbitals related by a unitary transformation. We can construct the two equivalent bent bond orbitals h and h' by taking linear combinations h = c1σ + c2π and h' = c1σ – c2π for an appropriate choice of coefficients c1 and c2. In a 1996 review, Kenneth B. Wiberg concluded that "although a conclusive statement cannot be made on the basis of the available information, it seems that we can continue to consider the σ/π and bent-bond descriptions of ethylene to be equivalent."

Ian Fleming goes further in a 2010 textbook, noting that "the overall distribution of electrons is the same" in the two models. The bent bond theory can explain other phenomena in organic molecules. In fluoromethane, for instance, the experimental F–C–H bond angle is 109°, greater than the calculated value; this is because according to Bent's rule, the C–F bond gains p-orbital character leading to high s-character in the C–H bonds, H–C–H bond angles approaching those of sp2 orbitals – e.g. 120° – leaving less for the F–C–H bond angle. The difference is again explained in terms of bent bonds. Bent bonds come into play in the gauche effect, explaining the preference for gauche conformations in certain substituted alkanes and the alkene cis effect associated with some unusually stable alkene cis isomers. NMR experiment

AirPort Extreme

The AirPort Extreme is a residential gateway combining the functions of a router, network switch, wireless access point and NAS as well as varied other functions, one of Apple's former AirPort products. The latest model, the 6th generation, supports 802.11ac networking in addition to older standards. Versions of the same system with a built-in network-accessible hard drive are known as the AirPort Time Capsule; the name "AirPort Extreme" referred to any one of Apple's AirPort products that implemented the newly introduced 802.11g Wi-Fi standard, differentiating it from earlier devices that ran the slower 802.11a and b standards. At that time the gateway part of this lineup was known as the AirPort Extreme Base Station. With the addition of the faster Draft-N standards in early 2009 this naming was dropped, from on only the gateway has been known as the AirPort Extreme. Several minor upgrades followed to change antenna and power in the Wi-Fi. In 2013, a major upgrade added more internal antennas.

The AirPort Extreme has gone through three distinct physical forms. The earliest models were packaged similar to the original AirPort Base Station, in a round housing known as the "flying saucer". From 2007 to 2013 the Extreme was packaged in a rounded-rectangle white plastic housing, similar in layout and size to the Mac mini or earlier Apple TVs; the 2013 802.11 ac model was re-packaged into taller than it is square. According to a Bloomberg report on November 21, 2016, "Apple Inc. has disbanded its division that develops wireless routers, another move to try to sharpen the company’s focus on consumer products that generate the bulk of its revenue, according to people familiar with the matter."In an April 2018 statement to 9to5Mac, Apple announced the discontinuation of its AirPort line leaving the consumer router market. Apple will continue supporting the AirPort Extreme, however the company now provides a list of recommended features when consumers are searching for a new wireless router.

Featured 802.11ac Wi-Fi base station Sleep Proxy Service 4 Ethernet ports — all ports are gigabit Ethernet on newer versions USB interface for disk and printer sharing Built-in file server Runs VxWorks Operating System by WindRiver or a customized version of NetBSD. The AirPort Disk feature allows users to plug a USB hard drive into the AirPort Extreme for use as a network-attached storage device for Mac OS X and Microsoft Windows clients. Users may connect a USB hub and printer; the performance of USB hard drives attached to an AirPort Extreme is slower than if the drive were connected directly to a computer. This is due to the processor speed on the AirPort Extreme. Depending on the setup and types of reads and writes, performance ranges from 0.5 to 17.5 MB/s for writing and 1.9 to 25.6 MB/s for reading. Performance for the same disk connected directly to a computer would be 6.6 to 31.6 MB/s for writing and 7.1 to 37.2 MB/s for reading. NTFS-formatted drives are not supported; the original AirPort Extreme Base Station was so named because of its support for the 802.11g standard of the day, as well as for its ability to serve up to 50 Macs or PCs simultaneously.

One feature found in most models of this generation was an internal 56K dial-up modem, allowing homes that lacked a broadband connection to enjoy wireless connectivity, albeit at dial-up speeds. It was the last generation to retain the "flying saucer" form factor. Generations would adopt the short, rounded-square form factor that would be seen until 2013. On January 9, 2007 the AirPort Extreme began shipping, with support for 802.11n draft specification, built-in wireless print and storage server. On March 19, 2008, Apple released a firmware update for both models of the AirPort Extreme that, according to third-party reports, allowed AirPort Disks to be used in conjunction with Time Machine, similar to the functionality provided by AirPort Time Capsule. On March 3, 2009, Apple unveiled a new AirPort Extreme with simultaneous dual-band 802.11 Draft-N radios. This allowed full 802.11 Draft-N 2x2 communication in both 802.11 Draft-N bands at the same time. On October 20, 2009, Apple unveiled an updated AirPort Extreme with antenna improvements.

On June 21, 2011, Apple unveiled an updated AirPort Extreme, referred to as AirPort Extreme 802.11n. The detailed table of output power comparison between the 4th generation model MC340LL/A and the 5th generation model MD031LL/A can be seen below: Note: 3dB more equals a doubling of power output On June 10, 2013, Apple unveiled an updated AirPort Extreme, referred to as AirPort Extreme 802.11ac. The 6th generation AirPort Extreme features three-stream 802.11ac Wi-Fi technology with a maximum data rate of 1.3Gbit/s, nearly three times faster than 802.11n. Time Machine is now supported using an external USB hard drive connected to AirPort Extreme. *802.11n draft-specification support in 1st- to 3rd-generation models. **802.11ac draft-specification support in 6th-generation model. ***All models support IPv6 tunnel mode. ****Supported by Apple. AirPort Express AirPort Time Capsule

Khao Ang Rue Nai Wildlife Sanctuary

The Khao Ang Rue Nai Wildlife Sanctuary is a protected area at the western extremities of the Cardamom Mountains in Chachoengsao Province, Thailand. Founded in 1977, it is an IUCN Category IV wildlife sanctuary, measuring over 1,000 km2 in area. South-east of, connected with, the wildlife sanctuary is the Khao Sip Ha Chan National Park. South-west of the protection is the Khao Chamao–Khao Wong National Park; the sanctuary is covered by low-lying evergreen forest, along with dry and moist evergreens, mixed deciduous, deciduous dipterocarp, as well as grassland. The Thai Department of National Parks has estimated that in 2008 the elephant population of Khao Ang Rue Nai was just 219 animals. In recent years this number has grown by 9.83 percent per year, meaning that the reserve now has 275 or so elephants. The twenty new animals born every year exceed the death rate, their expanding population has meant. Thus the villages that border the sanctuary are subject to about 25 raids on crops per month.

Due to the average crop damage of six rai per year per household, crop damage costs each household nearly 35,000 baht or 19 percent of average household income. Affected households spend an average of 212 nights awake per year guarding their fields; the DNP has resorted to various measures to reduce the conflict, including growing food crops in the forest for the animals. A spokesman for the DNP noted, on behalf of the elephants, that, "We are encroaching into forest, making it harder for elephants, which face limited food sources....it is our task not to invade their homes." Khao Angruenai in Thailand

Euro gold and silver commemorative coins (Monaco)

Euro gold and silver commemorative coins are special euro coins minted and issued by member states of the Eurozone in gold and silver, although other precious metals are used in rare occasions. Monaco was one of the first countries allowed to introduced the euro on 1 January 2002, although they are not part of the Eurozone. Since the Monnaie de Paris in France have been minting both normal issues of Monégasque euro coins, which are intended for circulation, commemorative euro coins in gold and silver; these special coins have a legal tender only in Monaco, unlike the normal issues of the Monegasque euro coins, which have a legal tender in every country of the Eurozone. This means that the commemorative coins made of gold and silver cannot be used as money in other countries. Furthermore, as their bullion value and collectable value vastly exceeds their face value, these coins are not intended to be used as means of payment at all—although it remains possible. For this reason, they are named Collectors' coins.

The coins commemorate the anniversaries of historical events or draw attention to current events of special importance. Monaco mints one of these coins on average per year, in both gold and silver, with face value ranging from 5 to 100 euros; as of 28 December 2008, seven variations of Monegasque euro commemorative coins have been minted: one in 2002, two in 2003, one in 2004, one in 2005 and two in 2008. These special high-value commemorative coins are not to be confused with €2 commemorative coins, which are coins designated for circulation and do have legal tender status in all countries of the Eurozone; the following table shows the number of coins minted per year. In the first section, the coins are grouped by the metal used, while in the second section they are grouped by their face value

Tinsel (TV series)

Tinsel is a Nigerian soap opera that began airing in August 2008. On May 23, 2013, the show's 1000th episode aired, it has been called "the most successful television drama on Nigerian television in recent times". Tinsel's plot revolves around two rival film companies: Reel Studios, founded by Fred Ade-Williams, Odyssey Pictures, headed by Brenda "Nana" Mensah. Tinsel is a tale of drama, romance and triumph; the show returned for its eighth season on the 25th of May, 2015. Tinsel is available for streaming on Demand Africa. Maltida Obaseki as Angela Dede Funlola Aofiyebi-Raimi as Brenda Nana Mensah Ireti Doyle as Sheila Ade-Williams Linda Ejiofor as Bimpe Kalu Ikeagwu as Masters Anne Njemanze as Sankey Ashionye Michelle Raccah as Monica Ade-Williams Funmi Holder as Amaka Ade-Williams Tomi Odunsi as Salewa Yewande Lawal as Shoshanna Dozie Onyiriuka as Freddy Abiola Segun-Williams as Titi Florence Uwaleke as Ene Ike Okechukwu as Chuks Obi Ibrahim Suleiman as Damini Jumoke Bello as Peju Ifeanyi William as Obiora Charles Ujomu as Frank Kunle Remi as Zane Tope Tedela Kolade Shasi as Gym Coach Yemisi Fancy as Helen Christina Okorojie as Yvonne Nancy Isime as Serena Mena Sodje as Pippa Cheng Fuller as Barrister Taylor Tinsel was in pre-production for over ninety months.

Over 500 actors were auditioned for the lead role of Fred Ade-Williams before the decision to cast Victor Olaotan was made. As of June 2013, the show's production cost per minute is 900 dollars, total costs have exceeded four billion naira; the show was shot in a studio in Lagos until March 2013 when a fire destroyed that location. Since the show has been shot at a studio and a private residence in Ikeja, Lagos. Note:The Series is still ongoing and it airs on AM Urban and AM Family. Tinsel on IMDb Tinsel on Demand Africa

Portsmouth Community Library

Portsmouth Community Library known as the Portsmouth Colored Community Library, is a historic library building located at Portsmouth, Virginia. It was built in 1945 at 804 South Street, it is a three bay, brick building with a hipped roof. It was built to provide for the reading needs of Portsmouth's African Americans. In 1959, two local dentists, Dr. James Holley and Dr. Hugo A. Owens sued the City of Portsmouth and the Portsmouth Public Library to integrate the public library, which resulted in the closure of the Portsmouth Community Library; the building has been relocated twice since it was closed in 1962 after integration of the public library system. It was listed on the National Register of Historic Places in 2010; the library is now operated as a museum of local African-American history by the City of Portsmouth. Displays include photographs and memorabilia, as well as African-American books and journals from the former library; the African American Historical Society of Portsmouth led efforts to dedicate the historic library as a museum, which opened in 2013.

Portsmouth Community Colored Library Museum - official site