title: VLAN

text: Although it was possible to use IP routing to connect multiple Ethernet networks together, it was expensive and relatively slow. Sincoskie started looking for alternatives that required less processing per packet. In the process, he independently reinvented transparent bridging, the technique used in modern Ethernet switches. However, using switches to connect multiple Ethernet networks in a fault-tolerant fashion requires redundant paths through that network, which in turn requires a spanning tree configuration. This ensures that there is only one "active" path from any source node to any destination on the network. This causes centrally located switches to become bottlenecks, limiting scalability as more networks are interconnected.


title: VLAN

text: To help alleviate this problem, Sincoskie invented VLANs by adding a tag to each Ethernet frame. These tags could be thought of as colors, say red, green, or blue. In this scheme, each switch could be assigned to handle frames of a single color, and ignore the rest. The networks could be interconnected with three spanning trees, one for each color. By sending a mix of different frame colors, the aggregate bandwidth could be improved. Sincoskie referred to this as a "multitree bridge". He and Chase Cotton created and refined the algorithms necessary to make the system feasible. This "color" is what is now known in the Ethernet frame as the IEEE 802.1Q header, or the VLAN tag. While VLANs are commonly used in modern Ethernet networks, they are not used in the manner first envisioned here.


title: VLAN

text: In 1998, Ethernet VLANs were described in the first edition of the IEEE 802.1Q-1998 standard. This was extended with IEEE 802.1ad to allow nested VLAN tags in service of provider bridging. This mechanism was improved with IEEE 802.1ah-2008.


title: VLAN

text: Early network designers often segmented physical LANs with the aim of reducing the size of the Ethernet collision domain—thus improving performance. When Ethernet switches made this a non-issue (because each switch port is a collision domain), attention turned to reducing the size of the data link layer broadcast domain. VLANs were first employed to separate several broadcast domains across one physical medium. A VLAN can also serve to restrict access to network resources without regard to physical topology of the network.


title: VLAN

text: VLANs operate at the data link layer of the OSI model. Administrators often configure a VLAN to map directly to an IP network, or subnet, which gives the appearance of involving the network layer. Generally, VLANs within the same organization will be assigned different non-overlapping network address ranges. This is not a requirement of VLANs. There is no issue with separate VLANs using identical overlapping address ranges (e.g. two VLANs each use the private network ). However, it is not possible to route data between two networks with overlapping addresses without delicate IP remapping, so if the goal of VLANs is segmentation of a larger overall organizational network, non-overlapping addresses must be used in each separate VLAN.


title: VLAN

text: A basic switch that is not configured for VLANs has VLAN functionality disabled or permanently enabled with a "default VLAN" that contains all ports on the device as members. The default VLAN typically uses VLAN identifier 1. Every device connected to one of its ports can send packets to any of the others. Separating ports by VLAN groups separates their traffic very much like connecting each group using a distinct switch for each group.


title: VLAN

text: Remote management of the switch requires that the administrative functions be associated with one or more of the configured VLANs.


title: VLAN

text: In the context of VLANs, the term "trunk" denotes a network link carrying multiple VLANs, which are identified by labels (or "tags") inserted into their packets. Such trunks must run between "tagged ports" of VLAN-aware devices, so they are often switch-to-switch or switch-to-router links rather than links to hosts. (Note that the term 'trunk' is also used for what Cisco calls "channels" : Link Aggregation or Port Trunking). A router (Layer 3 device) serves as the backbone for network traffic going across different VLANs. It is only when the VLAN port group is to extend to another device that tagging is used. Since communications between ports on two different switches travel via the uplink ports of each switch involved, every VLAN containing such ports must also contain the uplink port of each switch involved, and traffic through these ports must be tagged.


title: VLAN

text: Switches typically have no built-in method to indicate VLAN to port associations to someone working in a wiring closet. It is necessary for a technician to either have administrative access to the device to view its configuration, or for VLAN port assignment charts or diagrams to be kept next to the switches in each wiring closet.


title: VLAN

text: The protocol most commonly used today to support VLANs is IEEE 802.1Q. The IEEE 802.1 working group defined this method of multiplexing VLANs in an effort to provide multivendor VLAN support. Prior to the introduction of the 802.1Q standard, several proprietary protocols existed, such as Cisco Inter-Switch Link (ISL) and 3Com's Virtual LAN Trunk (VLT). Cisco also implemented VLANs over FDDI by carrying VLAN information in an IEEE 802.10 frame header, contrary to the purpose of the IEEE 802.10 standard.


title: VLAN

text: Both ISL and IEEE 802.1Q perform "explicit tagging" – the frame itself is tagged with VLAN identifiers. ISL uses an external tagging process that does not modify the Ethernet frame, while 802.1Q uses a frame-internal field for tagging, and therefore does modify the basic Ethernet frame structure. This internal tagging allows IEEE 802.1Q to work on both access and trunk links using standard Ethernet hardware.


title: VLAN

text: Under IEEE 802.1Q, the maximum number of VLANs on a given Ethernet network is 4,094 (4,096 values provided by the 12-bit field minus reserved values at each end of the range, 0 and 4,095). This does not impose the same limit on the number of IP subnets in such a network since a single VLAN can contain multiple IP subnets. IEEE 802.1ad extends the number of VLANs supported by adding support for multiple, nested VLAN tags. IEEE 802.1aq (Shortest Path Bridging) expands the VLAN limit to 16 million. Both improvements have been incorporated into the IEEE 802.1Q standard.


title: VLAN

text: Inter-Switch Link (ISL) is a Cisco proprietary protocol used to interconnect switches and maintain VLAN information as traffic travels between switches on trunk links. ISL is provided as an alternative to IEEE 802.1Q. ISL is available only on some Cisco equipment and has been deprecated.


title: VLAN

text: VLAN Trunking Protocol (VTP) is a Cisco proprietary protocol that propagates the definition of VLANs on the whole local area network. VTP is available on most of the Cisco Catalyst Family products. The comparable IEEE standard in use by other manufacturers is GARP VLAN Registration Protocol (GVRP) or the more recent Multiple VLAN Registration Protocol (MVRP).


title: VLAN

text: Multiple VLAN Registration Protocol is an application of Multiple Registration Protocol that allows automatic configuration of VLAN information on network switches. Specifically, it provides a method to dynamically share VLAN information and configure the needed VLANs.


title: VLAN

text: Static VLANs are also referred to as port-based VLANs. Static VLAN assignments are created by assigning ports to a VLAN. As a device enters the network, the device automatically assumes the VLAN of the port. If the user changes ports and needs access to the same VLAN, the network administrator must manually make a port-to-VLAN assignment for the new connection.


title: VLAN

text: Dynamic VLANs are created using software or by protocol. With a VLAN Management Policy Server (VMPS), an administrator can assign switch ports to VLANs dynamically based on information such as the source MAC address of the device connected to the port or the username used to log onto that device. As a device enters the network, the switch queries a database for the VLAN membership of the port that device is connected to. Protocol methods include Multiple VLAN Registration Protocol (MVRP) and the somewhat obsolete GARP VLAN Registration Protocol (GVRP).


title: VLAN

text: In a switch that supports protocol-based VLANs, traffic may be handled on the basis of its protocol. Essentially, this segregates or forwards traffic from a port depending on the particular protocol of that traffic; traffic of any other protocol is not forwarded on the port. This allows, for example, IP and IPX traffic to be automatically segregated by the network.


title: VLAN

text: VLAN cross connect (CC or VLAN-XC) is a mechanism used to create Switched VLANs, VLAN CC uses IEEE 802.1ad frames where the S Tag is used as a Label as in MPLS. IEEE approves the use of such a mechanism in part 6.11 of IEEE 802.1ad-2005.


title: Gospel of Peter

text: The Gospel of Peter (), or the Gospel according to Peter, is an ancient text concerning Jesus Christ, only partially known today. It is considered a non-canonical gospel and was rejected as apocryphal by the Church's synods of Carthage and Rome, which established the New Testament canon. It was the first of the non-canonical gospels to be rediscovered, preserved in the dry sands of Egypt.


title: Gospel of Peter

text: A major focus of the surviving fragment of the Gospel of Peter is the passion narrative, which ascribes responsibility for the crucifixion of Jesus to Herod Antipas rather than to Pontius Pilate.


title: Gospel of Peter

text: However, scholars generally agree that the Gospel of Peter is pseudepigraphical (bearing the name of an author who did not actually compose the text).


title: Gospel of Peter

text: The true author of the gospel remains a mystery. Although there are parallels with the three Synoptic Gospels, Peter does not use any of the material unique to Matthew or unique to Luke. Raymond E. Brown and others find that the author may have been acquainted with the synoptic gospels and even with the Gospel of John; Brown even suggests that the author's source in the canonical gospels was transmitted orally, through readings in the churches, i.e. that the text is based on what the author remembers about the other gospels, together with their own embellishments.


title: Gospel of Peter

text: Ron Cameron and others have further speculated the Gospel of Peter was written independently of the synoptic gospels using an early proto-gospel. A consequence of this is the potential existence of a source text that formed the basis of the passion narratives in Matthew, Luke, and Mark, as well as in Peter. Origen makes mention of the Gospel of Peter as agreeing with the tradition of the Hebrews. The relationship to the Gospel according to the Hebrews becomes more clear when Theodoret states that the Nazarenes made use of the Gospel of Peter, for it is known by the testimony of the Fathers generally that the Nazarene Gospel was commonly called the Gospel according to the Hebrews. The same Gospel was in use among the Ebionites, and, in fact, as almost all critics are agreed, the Gospel according to the Hebrews – under various names such as the Gospel according to Peter, according to the Apostles, the Nazarenes, Ebionites, Egyptians, etc. – was substantially the same work, circulated very widely throughout the early Church, though with modifications.


title: Gospel of Peter

text: The gospel is widely thought to date from after the composition of the four canonical gospels. Scholars are divided as to the exact date of the text, with Bart Ehrman placing it in the first half of the 2nd century and considering it to have been compiled based on oral traditions about Jesus, independent of the canonical gospels.<ref name="e/p 370–372">Ehrman and Pleše 2011, pp. 370–372.</ref> The dating of the text depends to a certain extent on whether the text condemned by Serapion, Bishop of Antioch upon inspection at Rhossus is the same as the text that was discovered in modern times.<ref name="e/p 371">Ehrman and Pleše 2011, p. 371.</ref> The Rhossus community had already been using it in their liturgy.


title: Gospel of Peter

text: John Dominic Crossan argues that the Gospel of Peter, as it is found in the modern day, was composed in the 2nd century but incorporates a passion narrative source that predates all other known passion accounts. He calls this primitive passion source the "Cross Gospel." Crossan asserts that this Cross Gospel was written before the synoptic gospels of Mark, Matthew, and Luke and that it influenced both them and the Gospel of Peter. Crossan's view is not accepted by mainstream Biblical scholars.


title: Gospel of Peter

text: Craig A. Evans argues that the Gospel of Peter was written in the 2nd century CE to counter anti-Christian polemics of that time (such as the ones found in Celsus's "The True Word").


title: Gospel of Peter

text: Later Western references, which condemn the work, such as Jerome and the , traditionally connected to Pope Gelasius I, are apparently based upon the judgment of Eusebius, not upon a direct knowledge of the text.


title: Gospel of Peter

text: The Second Epistle of Clement (an anonymous 2nd century homily erroneously attributed to Pope Clement I) refers to a passage thought to be from the Gospel of Peter:


title: Gospel of Peter

text: Origen mentions "the Gospel according to Peter, as it is called", together with "the Book of James" (believed by scholars to be the apocryphal Gospel of James), in support of the doctrine of the perpetual virginity of Mary. However, it is not clear that he was referring to what is known modernly as the Gospel of Peter because the extant fragments say nothing about this or about the birth of Jesus.


title: Gospel of Peter

text: In his "Church History", Eusebius writes that Bishop Serapion of Antioch had been informed that a Christian community in Rhosus was using the Gospel of Peter in their liturgy and had sent a letter authorizing them to do so, while also denying that such Gospel was actually written by Saint Peter. Later, however, Serapion was informed that the Gospel of Peter "hid a heresy", which he attributed to Marcian of Rhossos and that he identified with docetism. Serapion reports that he read the Gospel carefully and had the opportunity "to find, along with much of the Savior's true doctrine, some additions". Eusebius also states that several works had been attributed to Peter: the First Epistle of Peter, the Second Epistle of Peter, the Acts of Peter, the Gospel of Peter, the Preaching of Peter and the Apocalypse of Peter. He accepts the First Epistle of Peter as genuine, while he rejects all the others as spurious. Jerome mistakenly says in his that Serapion wrote the Gospel of Peter.


title: Gospel of Peter

text: In his "Compendium of Heretical Accounts", Theodoret states that the 4th century Nazarene sect used the Gospel of Peter in their liturgy, but this is considered to be highly unlikely and anachronistic. In his "Church History", Philip of Side states that "the ancients absolutely refused the Gospel of the Hebrews, the Gospel of Peter and the Gospel of Thomas, which they considered the work of heretics."


title: Gospel of Peter

text: The Gospel of Peter was recovered in 1886 by the French archaeologist Urbain Bouriant in the modern Egyptian city of Akhmim ( north of Nag Hammadi). The 8th- or 9th-century manuscript had been respectfully buried with an Egyptian monk. The fragmentary Gospel of Peter was the first non-canonical gospel to have been rediscovered, preserved in the dry sand of Egypt. Publication, delayed by Bouriant until 1892, occasioned intense interest. From the passion sequence that is preserved, it is clear that the gospel was a narrative gospel, but whether a complete narrative similar to the canonical gospels or simply a Passion cannot be said.


title: Gospel of Peter

text: Two other papyrus fragments from Oxyrhynchus (P.Oxy 4009 and P.Oxy. 2949) were uncovered later and published in 1972. They are possibly, but not conclusively, from the Gospel of Peter and would suggest, if they belonged, that the text was more than just a passion narrative. These small fragments both seem to give first person accounts of discussions between Jesus and Peter in situations prior to the Passion week. It has also been speculated that the Fayyum Fragment may be an excerpt from the Gospel of Peter.


title: Gospel of Peter

text: To date it is one of four early non-canonical narrative gospels, which exist only in fragmentary form: this Gospel of Peter, the Egerton Gospel, and the two very fragmentary Oxyrhynchus Gospels (P.Oxy. 840 and P.Oxy. 1224). The main point of interest from the first has resided in establishing its relationship to the four canonical gospels.


title: Gospel of Peter

text: J. Rendel Harris (1852–1941) decided to introduce the Gospel of Peter to the public in "A Popular Account of the Newly-Recovered Gospel of Peter." He opens with a description of its discovery, offering his opinions regarding its date and original language. Classifying the work as a Docetic gospel, Harris defines the community in which it arose as well as its use during the Patristic age. He translates the fragment and then proceeds to discuss the sources behind it. Harris is convinced that the author borrowed from the canonical accounts, and he lists other literature that may have incorporated the Gospel of Peter, with special emphasis on the "Diatessaron".


title: Gospel of Peter

text: Edgar J. Goodspeed stated that the main importance of this work is that it is the first of the Christian apologies, although on the next page he admits that only "bits" actually fall into that category.


title: Gospel of Peter

text: One of the chief characteristics of the work is that Pontius Pilate is exonerated of all responsibility for the Crucifixion, the onus being laid upon Herod Antipas, the scribes, and other Jews, who pointedly do not "wash their hands" like Pilate. However, the Gospel of Peter was condemned as heretical by for its alleged docetic elements.


title: Gospel of Peter

text: The opening leaves of the text are lost, so the Passion begins abruptly with the trial of Jesus before Pilate, after Pilate has washed his hands, and closes with its unusual and detailed version of the watch set over the tomb and the resurrection. The Gospel of Peter is more detailed in its account of the events after the Crucifixion than any of the canonical gospels, and it varies from the canonical accounts in numerous details: Herod gives the order for the execution, not Pilate, who is exonerated; Joseph (of Arimathea, which place is not mentioned) has been acquainted with Pilate; in the darkness that accompanied the crucifixion, "many went about with lamps, supposing that it was night, and fell down".


title: Gospel of Peter

text: Jesus' cry from the cross, which the Gospels of Mark and Matthew gives as "Eli, Eli, lama sabachthani?" which Mark and Matthew explains as meaning "My God, my God, why hast thou forsaken me?" is reported in Peter as "My power, my power, thou hast forsaken me". Immediately after, Peter states that "when he had said it he was taken up", suggesting that Jesus did not actually die. This, together with the claim that on the cross Jesus "remained silent, as though he felt no pain", has led many early Christians to accuse the text of docetism. F. F. Bruce writes:


title: Gospel of Peter

text: The account in Peter tells that the supposed writer and other disciples hid because they were being sought on suspicion of plotting to set fire to the temple, and totally rejects any possibility of their disloyalty. The centurion who kept watch at the tomb is given the name Petronius. Details of the sealing of the tomb, requested of Pilate by the elders of the Jewish community, elaborates upon Matthew 27:66, "So they went, and made the sepulchre sure, sealing the stone, and setting a watch", saying instead:


title: Gospel of Peter

text: Most importantly, the Resurrection and Ascension, which are described in detail, are not treated as separate events, but occur on the same day:


title: Gospel of Peter

text: The text is unusual at this point in describing the Cross itself as speaking, and even moving out of the tomb. Deane Galbraith shows that the Gospel of Peter has derived its unusual description of the talking and moving cross by interpreting the first six verses of LXX Psalm 18 (Psalm 19 in the Masoretic Text) as a prophecy of Jesus' resurrection. The text then proceeds to follow the Gospel of Mark, ending at the short ending (where the women flee the empty tomb in fear), adding on an extra scene set during the Feast of Unleavened Bread, where the disciples leave Jerusalem, and ends, like the short ending, without Jesus being physically seen.


title: GBU-53/B StormBreaker

text: The GBU-53/B StormBreaker, previously known as the Small Diameter Bomb II, is an American air-launched, precision-guided glide bomb.<ref name="urlGBU-53/B StormBreaker"></ref>


title: GBU-53/B StormBreaker

text: Development was started in 2006 for a class bomb that can identify and strike mobile targets from standoff distances in all weather conditions. It is integrated on the F-15E Strike Eagle and will be integregated into the F/A-18 Hornet and F-35 Lightning fighters. Its first flight was announced on May 1, 2009. A contract to start low rate initial production was awarded to Raytheon in June 2015.


title: GBU-53/B StormBreaker

text: The bomb is developed and manufactured by Raytheon. A Boeing/Lockheed Martin team attempted to develop it but lost in a U.S. Air Force competition. Boeing won the original competition but the project was on hold for several years due to a corruption scandal involving Darleen Druyun. The competition was reopened in September 2005.


title: GBU-53/B StormBreaker

text: The bomb can use GPS/INS to guide itself into the general vicinity of a moving target during the initial search phase, with course correction updates provided using a Link 16 over UHF data link. The bomb has three modes of target acquisition: millimeter-wave radar, infrared homing using an uncooled imaging seeker, and semi-active laser homing. The weapon is capable of fusing the information from the sensors to classify the target and can prioritize certain types of targets as desired when used in semi-autonomous mode.


title: GBU-53/B StormBreaker

text: The shaped charge warhead in the bomb has both blast and fragmentation effects, which makes it effective against infantry, armor (including MBTs), unhardened structures and buildings, as well as patrol craft sized boats and other soft targets. The bomb would be the first purpose-built no-drive zone enforcement weapon.


title: GBU-53/B StormBreaker

text: The use of uncooled imaging infrared has been cited as innovative and effective in reducing costs. An important feature of the new weapon is maximizing the number of bombs carried by the strike aircraft. A total of 28 GBU-53/B can be carried by the F-15E Strike Eagle using seven BRU-61/A suspension units, each carrying four bombs. Eight bombs along with two AIM-120 AMRAAM missiles can be carried in the weapons bay of the F-22 Raptor or the F-35 Lightning II (even the STOVL F-35B). The F-35 will not be able to operate the bomb until the aircraft receives the Block 4 software package in 2022. The SDB II bomb rack originally did not fit inside the smaller F-35B weapons bay. A modification will be provided to coincide with the software package. An F-35 can carry 24 total bombs, 8 internally and 16 externally.


title: GBU-53/B StormBreaker

text: The United States Air Force plans to use the bomb on the F-15E Strike Eagles as a no-drive zone enforcement weapon. The United States Navy and United States Marine Corps plan to use it on their versions of the F-35 Lightning II. Delivery for the first batch is planned for late 2014. Government requirements specify a 2016 delivery date. In October 2020, the Air Force approved the weapon for operational flight on the F-15E.


title: GBU-53/B StormBreaker

text: The U.S. Navy plans to first integrate the SDB II onto their F/A-18 Super Hornet jets, then onto the F-35B and C fighters. With the F-35 program experiencing continued delays from a naval perspective, the U.S. Navy has decided to change their integration strategy by using the L3Harris BRU-55 smart multiple carriage racks on F/A-18E/F to store and fire the SDB II for the U.S. Navy.


title: GBU-53/B StormBreaker

text: The L3Harris BRU-55/A smart rack enables the aircraft to carry two MIL-STD-1760 smart weapons, such as the SDB II, on each weapon station. The electronic control assembly and digital communications from the aircraft to the weapon are handled by the BRU-55 canted vertical ejector rack, which in turn is attached to a BRU-32/A bomb ejector rack connected to SUU-79 pylons, and then to the aircraft fuselage. The BRU-55/A is an upgrade, largely on the electronics, to the BRU-33 CVER (Canted Vertical) bomb ejection rack. The BRU-55 was developed as part of the Mk-82 Joint Direct Attack Munition (JDAM) program.


title: GBU-53/B StormBreaker

text: Current testing of this configuration will only be performed using the F/A-18E/F mid-board weapon stations, followed by testing SDB II and BRU-55 on in-board stations. The subsequent step will be to perform testing of the BRU-61/A Type 2 Universal Armament Interface (UAI) pneumatic rack, which will be the primary stores system for the F-35.


title: GBU-53/B StormBreaker

text: For U.S. Navy and U.S. Marine Corps integration with the F-35B and F-35C, the BRU-61/A will be utilized. The BRU-61/A is a pneumatic Multi-Stores Carriage System produced by Cobham Mission Systems. Each weapon station will be able to carry 4 SDB IIs. The BRU-61/A utilizes pneumatic ejection, which ejects the stores using compressed air, as opposed to previous systems which rely on pyrotechnic cartridges.


title: GBU-53/B StormBreaker

text: The original Small Diameter Bomb (SDB) was developed by Boeing and made for non-moving targets. The SDB II is designed to destroy moving targets in dust and bad weather. The Raytheon version was deployed successfully in 26 missions over 21 days. Raytheon was awarded the contract in August, 2010. The North American division of MBDA continues to produce the wings. The Raytheon contract is worth US$450 million. Boeing announced that it would not protest the Raytheon award.


title: GBU-53/B StormBreaker

text: On July 17, 2012 the SDB II successfully engaged and hit a moving target during a flight test at the White Sands Missile Range. The bomb was dropped from an F-15E Strike Eagle, then acquired, tracked, and guided itself onto a moving target using its tri-mode seeker, scoring a direct hit.


title: GBU-53/B StormBreaker

text: In January 2013 four SDB IIs were loaded into the weapons bay of an F-35 Lightning II alongside an AIM-120 AMRAAM missile. The successful fit check validated that the SDB II was compatible with the F-35 and gave adequate clearance in sweeps of inboard and outboard bay doors.


title: GBU-53/B StormBreaker

text: Two SDB IIs successfully conducted live fire tests against moving targets, one in September 2014 and the other in February 2015. Successful live fire tests qualified the weapon for the Air Force to make a Milestone C decision, leading to entering low-rate initial production (LRIP).


title: GBU-53/B StormBreaker

text: The SDB II received Milestone C approval in early May 2015, completing a five-year development program and clearing it for production and deployment with the F-15E. A handful of failed test shots prolonged development from four years to five, but per-unit cost was reduced from the goal of $180,000 to $115,000. Raytheon was awarded a $31 million contract on 12 June 2015 for the first LRIP lot of 144 SDB IIs.


title: GBU-53/B StormBreaker

text: Raytheon considered offering the SDB II to the United Kingdom for their Spear Capability 3 requirement to arm the Royal Air Force Eurofighter Typhoon and Royal Navy F-35B. To compete with MBDA's offer of a powered weapon, Raytheon considered a powered SDB II variant. In May 2016, the UK awarded a contract to MBDA to develop the SPEAR 3 missile, as it was the only weapon to meet the UK’s operational requirement.


title: GBU-53/B StormBreaker

text: The Republic of Korea Air Force is considering adopting the SDB II for use on its F-15K aircraft, as the bomb's capability to destroy moving targets more than 60 km away in all kinds of weather is useful to strike North Korean mobile missile launchers. In October 2017, the U.S. approved the sale of 3,900 SDBs to the Royal Australian Air Force for use on their F-35As.


title: GBU-53/B StormBreaker

text: In July 2018, Raytheon announced that the SDB II, recently renamed StormBreaker, had entered operational testing; the weapon had achieved a 90% success rate during developmental testing. The Air Force planned to declare the SDB II operational in September 2019, but a problem with the bomb's backup fin storage clips, other hardware and software issues, and the COVID-19 pandemic delayed its introduction. The StormBreaker was approved for operational use onboard the F-15E in September 2020.


title: Green Wing

text: Green Wing is a British sitcom set in the fictional East Hampton Hospital. It was created by the same team behind the sketch show "Smack the Pony" – Channel 4 commissioner Caroline Leddy and producer Victoria Pile – and stars Mark Heap, Tamsin Greig, Stephen Mangan and Julian Rhind-Tutt. Although set in a hospital, it uses no medical storylines; the action is produced by a series of soap opera-style twists and turns in the personal lives of the characters. They proceed through a series of often absurd sketch-like scenes, or by sequences where the film is slowed down or sped up, often emphasising the body language of the characters. The show had eight writers. Two series were made by the Talkback Thames production company for Channel 4.


title: Green Wing

text: The series ran between 3 September 2004 and 19 May 2006. One episode, filmed with the second series, was shown as a 90-minute-long special on 4 January 2007 in the UK, but was shown earlier in Australia and Belgium on 29 December 2006. Separate from the series, a sketch was made for Comic Relief and screened on 11 March 2005. Another was performed live at The Secret Policeman's Ball on 14 October 2006.


title: Green Wing

text: "Green Wing"<nowiki>'</nowiki>s plot revolves around the lives of the staff of the East Hampton Hospital Trust, a fictional NHS hospital with staff ranging from the slightly unusual to the completely surreal.


title: Green Wing

text: The series begins with a new arrival, surgical registrar Caroline Todd (Tamsin Greig). Caroline works alongside two other doctors: Guy Secretan (Stephen Mangan), an arrogant, half-Swiss, womanising anaesthetist, and "Mac" Macartney (Julian Rhind-Tutt), a suave, fashionable surgeon. It is not long before Caroline begins to develop feelings for both of them, though she is unsure as to which of the two she truly loves. Throughout the series, it becomes clear that Mac is her true love, but a range of misadventures prevent their relationship from flourishing. Other people Caroline meets include Martin Dear (Karl Theobald), a friendly house officer who is constantly failing his exams. He is unloved by his mother and is often bullied by Guy. Martin soon develops feelings for Caroline. There is also Angela Hunter (Sarah Alexander), a seemingly perfect, but irritating, senior registrar in pediatrics. Caroline dislikes Angela, but ends up taking her in as a lodger.


title: Green Wing

text: Caroline's main rival for Mac's affections is Sue White (Michelle Gomez), the Scottish staff liaison officer employed to listen and respond to the problems of East Hampton's staff. However, Sue is hostile and contemptuous towards most people. The only person she treats with any affection is Mac, whom she loves to the point of madness.


title: Green Wing

text: Perhaps the most eccentric member of staff is Alan Statham (Mark Heap), an overbearing, stuttering and pedantic consultant radiologist. He is in a relationship with Joanna Clore (Pippa Haywood), the 48-year-old head of human resources, although she despises him. Their relationship is an open secret, with student doctor Boyce (Oliver Chris) often hinting at it when goading Alan. Joanna's staff include Kim Alabaster (Sally Bretton); Naughty Rachel (Katie Lyons); Harriet Schulenburg (Olivia Colman), an overworked mother of four trapped in an unhappy marriage; and Karen Ball (Lucinda Raikes), who is often bullied by Kim and Rachel.


title: Green Wing

text: "Green Wing" was devised, created and produced by Victoria Pile. She was also the casting director, one of the writers and was involved in the editing, filming and post-production. She described "Green Wing" as "a sketch-meets-comedy-drama-meets-soap", and a continuation of her previous show, "Smack the Pony", where "Green Wing"<nowiki>'</nowiki>s crew also worked. Unusually for a British sitcom, which normally has only one or two writers, the show had eight: Pile, her husband Robert Harley, Gary Howe, Stuart Kenworthy, Oriane Messina, Richard Preddy, Fay Rusling and James Henry.


title: Green Wing

text: Pile and her co-writers initially used battery packs to represent characters, moving them around on her desk to develop scenarios for the show. The decision to make the characters doctors came later. Pile recalls that she mentioned to Peter Fincham that a hospital setting would work well and that he subsequently reported that Channel 4 were enthusiastic about a hospital location, which settled the matter. Even later still, a plot was developed and wall charts were used to mark up story arcs.


title: Green Wing

text: The show was directed and edited (along with Pile) by Tristram Shapeero and Dominic Brigstocke. Sketches were sped up or slowed down to create comic effect, often using body language to create humour. Editing was also used due to the amount of corpsing that occurred during the filming of the show. Tamsin Greig was said to corpse frequently, and episodes were written to minimise the contact between the characters of Caroline Todd and Alan Statham because Greig found it difficult not to laugh when acting alongside Mark Heap. The music, which plays prominently in the show, was written by Jonathan Whitehead (under the name "Trellis") and won him an RTS Craft & Design Award.


title: Green Wing

text: Following her success with "Smack the Pony", Channel 4 gave Pile a fairly free hand with her next project. Their only requirement was that it should have enough of a narrative thread to make it more of a sitcom than a sketch show.


title: Green Wing

text: The show had a half-hour pilot made in 2002 that was never aired. Scenes from the pilot were used in the first episode, "Caroline's First Day", and can be spotted due to the characters' appearance, most notably Rhind-Tutt's haircut. The pilot allowed the writers to experiment, such as using different filming techniques. In the pilot, Doon Mackichan played Joanna Clore and was meant to play her in the original series, but left when she became pregnant.


title: Green Wing

text: Although each script is fully written, the actors are allowed to improvise their own jokes, frequently adding to what has already been written. Normally workshops are used to allow actors to improvise their own material. One example of improvised material was Stephen Mangan's idea of Guy falling in love with Caroline. Rusling, Howe, Messina and Harley all have had speaking parts in the show, most notably Harley playing Charles Robertson, the hospital's CEO. The show's crew also make appearances in the show as extras. For example, Pile's former assistant Phil Secretan (after whom Guy is named) appears at the end of a scene in the first episode. Henry appears in the background during Martin's exam in the episode, "Tests".


title: Green Wing

text: The filming was done at two hospitals, the Northwick Park Hospital in Middlesex and the North Hampshire Hospital in Basingstoke. This presented a problem because the show had to work around the real-life hospitals, with their actual doctors, patients and emergency situations. In one scene in the final episode in series one, Guy (Mangan) was hitting squash balls behind him, and nearly hit a patient. However, some scenes, such as those in Sue's and Alan's offices, were filmed in a studio.


title: Green Wing

text: "Green Wing"<nowiki>'</nowiki>s title is said to have come from a small plastic green man with wings that was in executive producer Peter Fincham's top pocket, and fell on Pile's desk. Fincham claimed it was not his, so Pile kept it. This plastic man appears at the end of the credits on every show.


title: Green Wing

text: "Green Wing" had some plot lines that were never used. Unused storylines included Alan having an 80-year-old wife and step-grandchildren as old as him, and Guy suffering from impotence. Pile originally wanted the show to cover the entire hospital, not just doctors, but porters, car park attendants and kitchen staff. However, she decided that they had enough material with the eight main doctors and human resources workers.


title: Green Wing

text: Two endings were created for the special. The alternative ending is included on the DVD release of "Green Wing", along with deleted scenes from the episode. The alternative ending was planned to be used if a third series was going to be commissioned, as this ending was much more ambiguous. It is known that the actors wanted the alternative ending, but after some debate, it was not shown.


title: Green Wing

text: Caroline arrives at East Hampton for her first day of work and meets her colleagues Guy and Mac. She is forced to spend her second day on the job quashing rumours that she slept with Guy after he put her up for the night. Failing junior doctor Martin soon falls in love with Caroline. Meanwhile, Alan and Joanna maintain their relationship as the worst kept secret in the hospital. Alan wants to shout their relationship from the rooftops, whereas Joanna wants more spontaneity and danger, so quickly turns her affections to Lyndon Jones (Paterson Joseph), the hospital's head of I.T.


title: Green Wing

text: Martin is revealed to be the son of Joanna Clore; she does not want anyone at the hospital to find out. Joanna briefly believes that she is pregnant once again, only to find out that the test results had been mixed up and it was in fact Harriet who was pregnant. Alan, elated by the thought that he may become a father, become obsessed with babies and suggests that they try for one when he finds out that Joanna is not pregnant. Joanna, bored of Alan's predictable behaviour, finally decides to end her relationship with him.


title: Green Wing

text: Caroline starts to get broody, but is unsure as to whether it is Mac or Guy that she loves. Sue White, staff liaison officer, is deeply in love with Mac, threatening to kill her love rivals. Both women are devastated to find that Mac is intending to move to Sheffield with his new girlfriend to take up a consultancy position. Before he leaves, Mac bets Guy that he would not be able to sleep with Joanna, so Guy picks her up at the leaving party. Caroline accuses Emily of being a fraudster, which turn out to be a misunderstanding, but Emily breaks up with Mac after he is amused rather than angered by Caroline's accusations. Mac and Caroline later kiss.


title: Green Wing

text: As they are about to leave, Caroline and Mac find out that there is an emergency at Guy's flat. Martin discovered that Joanna was also Guy's birth mother. When Caroline and Mac arrive in an ambulance, Guy steals it in a drunken rage, with Mac and Martin in the back. Guy drives the ambulance to Wales, where, in an attempt to avoid a sheep, they drive onto a cliff edge. The series ends with the three of them balanced precariously on the cliff edge.


title: Green Wing

text: Mac fends off Sue's advances by saying he will only allow her to touch his arse if she can raise £10,000 for Comic Relief. Sue then proceeds to try to ask Martin, Joanna, Guy and Alan for the money, which she eventually manages to raise, though Mac runs off before she can get hold of him.


title: Green Wing

text: Eight weeks after the incident with the ambulance, Mac is in a coma and Guy has been suspended from his job. During his coma, Sue steals some of Mac's semen and tries to make herself pregnant. At the end of the first episode, Mac wakes up, but with amnesia which means he does not recall his nascent relationship with Caroline.


title: Green Wing

text: As Mac's memory returns, he and Caroline are on the verge of resuming their relationship when his former girlfriend Holly (Sally Phillips) returns to the hospital, to replace Angela, who has left to pursue a career in television. Holly has a son, called Mackenzie, who she says is Mac's. Caroline distances herself from Mac and starts dating Jake Leaf (Darren Boyd), a complementary therapist. Sue then discovers that Holly is lying, that Mac is not her son's father after all. Holly leaves the hospital. Caroline, excited by the news, leaves Jake.


title: Green Wing

text: When Alan becomes unusually happy after winning an internet caption competition, Joanna seeks to destroy his good humour. Using her dwarf cousin (Big Mick), dressed up in green body paint, she plans to scare him. The plan backfires when Alan is so scared that he beats Joanna's cousin to death with a stuffed heron. Alan and Joanna throw the body into the incinerator, but become paranoid that they will be discovered. Alan, however, learns from Boyce that the death is being viewed as a suicide, so Alan and Joanna go on a rampage, thinking themselves above the law.


title: Green Wing

text: After the death of a patient known as "Yo-yo Man" who offers them wise advice, Guy, Mac and Martin all decide to propose to Caroline. She rejects Martin, considers the offer from Guy, and Mac appears to be unable to form a proposal. Mac then tells Caroline to meet him at the railway station for a weekend away, but then suddenly discovers that he is terminally ill, and rides off into the distance on his motorbike. Guy goes to the railway station where he finds that Caroline is now willing to accept his proposal. Meanwhile, in the HR department, Karen is sitting on a windowsill, believing that there are Clangers in the office. Whilst on the phone to a friend, Rachel opens the window, tipping Karen out in the process. As the day continues, no one seems to notice her absence.


title: Green Wing

text: The police arrive at the hospital. Alan and Joanna believe that they will be arrested, and with Boyce's help escape from the hospital in a stolen camper van. When they discover that Martin is hidden in the back of the van, Alan, panicking, drives into a field, and series two ends in the same way as series one, with the van hanging over the edge of a cliff.


title: Green Wing

text: A sketch was performed for Amnesty International's Secret Policeman's Ball, with performances from Tamsin Greig, Stephen Mangan, Julian Rhind-Tutt and Michelle Gomez. Mangan and Rhind-Tutt appeared in two sketches.


title: Green Wing

text: When the announcer at the ball asks if there is a doctor in the house, Mac puts his hand up, to Caroline's embarrassment. Things get more embarrassing when Guy also volunteers, and asks why Caroline is sitting next to Mac when she is Guy's fiancée. An unconscious patient lies on an operating table. Guy touches her breasts, takes pictures of her naked body under the blanket, and kisses her. Caroline alleges that the patient is transgender, which repels Guy. Sue White then appears in a tutu, claiming that the patient is stalking Mac, and repeating the assertion that the patient is transgender.


title: Green Wing

text: The episode begins with the funeral of Angela, who departed the show during the second series, and was later killed by a moose. Mac, after a month's leave, discovers what has happened between Caroline and Guy, and although hurt, makes no attempt to interfere. Guy, on learning of Mac's terminal illness, tells Caroline to marry Mac instead of him.


title: Green Wing

text: Meanwhile, Alan and Joanna are still on the run, having abandoned Martin. Whilst on their journey, they accidentally kill three more people, a mechanic, a shop assistant and a policeman. Soon, they decide that, with no transport, money or employment, the only option is suicide. They are last seen, naked, walking hand-in-hand towards the sea. Meanwhile, Karen returns to work after her fall, but has changed drastically. She has become more confident and has developed better dress sense. Boyce ends up missing Alan, after finding that his replacement will not tolerate any misbehaviour. With Joanna gone, the office girls start to run riot. They form their own tribe and become hostile to anyone who enters the department.


title: Green Wing

text: Mac and Caroline finally marry, despite Mac's terminal illness (the exact nature of which is never disclosed, although Mac does tell Guy that its name has an "a" and an "e" in it). Sue gets over her obsession with Mac and finds love with a new man, who reciprocates her feelings. The episode concludes with Caroline being carried into the air by a mass of helium filled balloons at the wedding reception. The DVD box set extras include an alternative ending where Guy and Mac grab onto Caroline's ankles and are taken to the sky with her; this alternative ending ends with Mac saying, "Caroline, there's something I've been meaning to tell you."


title: Green Wing

text: The show received generally very positive reviews. The "Evening Standard" said that it was "a comedy as physically adroit as it was verbally sharp", and "The Guardian" said that "Channel 4’s hospital sitcom is the most innovative comedy since, well, "The Office"." In a review of television in 2006, Kathryn Flett in "The Observer" voted it one of the top ten TV programmes of the year. In "Broadcast magazine", the second series was voted joint-second best comedy series in 2006. In South Africa, where "Green Wing" is broadcast on BBC Prime, "The Sunday Times of South Africa" voted the show the best DStv programme of 2007. Composer Daniel Pemberton wrote that the soundtrack to "Green Wing" was, "One of the most innovative TV soundtracks in recent years."


title: Green Wing

text: Criticisms of "Green Wing" include the lazzi methods of filming and the overall length of the episodes, with some critics claiming that hour-long episodes are too long. The show won the 2005 and 2006 Comedy Tumbleweed Awards for "Worst Camerawork". Some were also critical of what was seen as a decline in quality when the second series began. Cathy Pryor in "The Independent on Sunday" said that, "Sadly, though, since I'm something of a fan, I have to report that the first episode of the second series is, disappointingly, rather flat. To be fair, there were a couple of laugh-out-loud moments - Dr Statham banging his head and falling down being one of them - but the whole [thing] didn't quite gel. Or should that be coagulate? I'll stop making bad jokes now since I'm still not as funny as anyone in the show. But I sincerely hope that the opener is a one- off and not a sign that Green Wing is going down the pan."


title: Green Wing

text: Similar comments were made by A. A. Gill. When the first series was broadcast, he praised the cast and characters, but commented negatively on the filming style and dramatic qualities. He also said:


title: Green Wing

text: "...it was one of the most freshly funny and crisply innovative comedies for years. The humour was all based in the character, not the situation. The story lines were negligible; there were no catch phrases; it was surreal in a way we hadn’t seen since "Monty Python"; and the cast were actors being funny from inside a characterisation, not stand-up comics bolting a cartoon persona onto the back of gags."


title: Green Wing

text: Subsequently, Gill critiqued the first episode of series two, in particular the use of a dream sequence at the beginning of the episode. He wrote,


title: Green Wing

text: "Now, every 11-year-old knows dream sequences are the lowest form of plotting solution, lower than unexplained superpowers such as the ability to stop time or become invisible; even lower than a magic get-better potion. Within two minutes, "Green Wing" had destroyed itself, lost its assured grip on the cliff of comedy and tumbled into the abyss of embarrassing overacting, formless gurning and pointless repetition. What had once looked Dada-ishly brilliant now looked like stoned improv from a show-off's drama school. The lack of plot and coherent narrative that previously had been a blessed freedom was revealed to be a formless free-for-all, brilliant performances as silly mannerisms. Nothing I've seen this year has disappointed me as sharply as the second series of "Green Wing". As Tom Paine so poignantly pointed out, only a step separates the sublime from the ridiculous."


title: Green Wing

text: The rest of the series received some praise and, in a 2009 article, Gill - writing about the current comedy output at the time - said: "Show me a funny indigenous comedy series; show me one that has been made in the past five years, other than "Green Wing"."


title: Green Wing

text: The first series scripts were released as "Green Wing: The Complete First Series Scripts" in paperback on 22 October 2006 (), by Titan Books. The book contains bonus material made exclusively for the book and previously unseen photos.


title: Green Wing

text: The soundtrack, entitled "" by Trellis was released by "Silva Screen" on 8 October 2007. It contains 23 tracks of the best of Jonathan Whitehead's Original Music created for the show.


title: Green Wing

text: It is available (both complete series) on Channel 4 on Demand and on the LoveFilm instant streaming service run by Amazon in the United Kingdom.


title: Green Wing

text: "Green Wing" won the first BAFTA Pioneer Audience Award in 2005. This is the only BAFTA award that is voted on by the general public. Pippa Haywood won the 2005 Rose d'Or for "Best Female Comedy Performance". Tamsin Greig won an award at the RTS Awards in 2005 for "Best Comedy Performance". Jonathan Whitehead won "Best Original Score" at the RTS Craft & Design Awards 2005. Greig received a BAFTA nomination for Best Comedy Performance in 2005, losing to David Walliams and Matt Lucas.


title: Green Wing

text: "Green Wing" has also won a number of times in "The Comedy.co.uk Awards", including the "Comedy of the Year" award in 2006.


title: Green Wing

text: The cast, crew and writers of "Green Wing" have shown no interest in creating a third series because of scheduling difficulties due to new projects being undertaken by the creators and talkbackTHAMES not having a big enough budget. However, creator Victoria Pile mentioned in a 2007 interview in the "Radio Times" that she may do a spin-off, saying, "I'm hoping to do another Channel 4 comedy imminently, possibly starring some of the same cast. Hopefully, it will be some kind of spin-off from "Green Wing"."


title: Green Wing

text: In 2009, Pile and most of the writing team behind "Green Wing" created a sitcom pilot set in a university entitled "Campus", which features similar concepts to "Green Wing", including improvisation. The motto of the university is "with wings", a reference to the show. The pilot was broadcast as part of Channel 4's "Comedy Showcase". A full series began in 2011, but was cancelled after one series.


title: Green Wing

text: A cocktail called the Green Wing was served at the 2005 BAFTAs. It was made using vodka, cloudy apple juice, elderflower cordial and sparkling mineral water. A "Green Wing" convention called "Wingin' It" was organised to raise money for Great Ormond Street Hospital, and took place on 13 January 2007 at the Brook Green Hotel, Hammersmith. There was a special appearance by "Green Wing" cast at the British Film Institute, on 17 January 2007; Pile, Greig, Mangan and Rhind-Tutt appeared. Some of the other writers, as well as Theobald and Heap, were in the audience. The event was hosted by John Lloyd. "Green Wing" appeared in an episode of the BBC documentary series "Imagine", entitled "A Funny Thing Happened on the Way to the Studio". Some of the funeral scenes from the special were shown, and the presenter of the show, Alan Yentob, appeared as one of the mourners.


title: Gums

text: The gums or gingiva (plural: "gingivae") consist of the mucosal tissue that lies over the mandible and maxilla inside the mouth. Gum health and disease can have an effect on general health.


title: Gums

text: The gums are part of the soft tissue lining of the mouth. They surround the teeth and provide a seal around them. Unlike the soft tissue linings of the lips and cheeks, most of the gums are tightly bound to the underlying bone which helps resist the friction of food passing over them. Thus when healthy, it presents an effective barrier to the barrage of periodontal insults to deeper tissue. Healthy gums are usually coral pink in light skinned people, and may be naturally darker with melanin pigmentation.


title: Gums

text: Changes in color, particularly increased redness, together with swelling and an increased tendency to bleed, suggest an inflammation that is possibly due to the accumulation of bacterial plaque. Overall, the clinical appearance of the tissue reflects the underlying histology, both in health and disease. When gum tissue is not healthy, it can provide a gateway for periodontal disease to advance into the deeper tissue of the periodontium, leading to a poorer prognosis for long-term retention of the teeth. Both the type of periodontal therapy and homecare instructions given to patients by dental professionals and restorative care are based on the clinical conditions of the tissue.


title: Gums

text: The marginal gum is the edge of the gums surrounding the teeth in collar-like fashion. In about half of individuals, it is demarcated from the adjacent, attached gums by a shallow linear depression, the free gingival groove. This slight depression on the outer surface of the gum does not correspond to the depth of the gingival sulcus but instead to the apical border of the junctional epithelium. This outer groove varies in depth according to the area of the oral cavity. The groove is very prominent on mandibular anteriors and premolars.


title: Gums

text: The marginal gum varies in width from 0.5 to 2.0 mm from the free gingival crest to the attached gingiva. The marginal gingiva follows the scalloped pattern established by the contour of the cementoenamel junction (CEJ) of the teeth. The marginal gingiva has a more translucent appearance than the attached gingiva, yet has a similar clinical appearance, including pinkness, dullness, and firmness. In contrast, the marginal gingiva lacks the presence of stippling, and the tissue is mobile or free from the underlying tooth surface, as can be demonstrated with a periodontal probe. The marginal gingiva is stabilized by the gingival fibers that have no bony support. The gingival margin, or free gingival crest, at the most superficial part of the marginal gingiva, is also easily seen clinically, and its location should be recorded on a patient's chart.


title: Gums

text: The attached gums are continuous with the marginal gum. It is firm, resilient, and tightly bound to the underlying periosteum of alveolar bone. The facial aspect of the attached gum extends to the relatively loose and movable alveolar mucosa, from which it is demarcated by the mucogingival junction. Attached gum may present with surface stippling. The tissue when dried is dull, firm, and immobile, with varying amounts of stippling. The width of the attached gum varies according to its location. The width of the attached gum on the facial aspect differs in different areas of the mouth. It is generally greatest in the incisor region (3.5 to 4.5 mm in the maxilla and 3.3 to 3.9 mm in the mandible) and less in the posterior segments, with the least width in the first premolar area (1.9 mm in the maxilla and 1.8 mm in the mandible). However, certain levels of attached gum may be necessary for the stability of the underlying root of the tooth.


title: Gums

text: The interdental gum lies between the teeth. They occupy the gingival embrasure, which is the interproximal space beneath the area of tooth contact. The interdental papilla can be pyramidal or have a "col" shape. Attached gums are resistant to the forces of chewing and covered in keratin.


title: Gums

text: The col varies in depth and width, depending on the expanse of the contacting tooth surfaces. The epithelium covering the col consists of the marginal gum of the adjacent teeth, except that it is nonkeratinized. It is mainly present in the broad interdental gingiva of the posterior teeth, and generally is not present with those interproximal tissue associated with anterior teeth because the latter tissue is narrower. In the absence of contact between adjacent teeth, the attached gum extends uninterrupted from the facial to the lingual aspect. The col may be important in the formation of periodontal disease but is visible clinically only when teeth are extracted.


title: Gums

text: Healthy gums usually have a color that has been described as "coral pink". Other colours like red, white, and blue can signify inflammation (gingivitis) or pathology. Smoking or drug use can cause discoloring as well (such as "meth mouth"). Although described as the colour coral pink, variation in colour is possible. This can be the result of factors such as: thickness and degree of keratinization of the epithelium, blood flow to the gums, natural pigmentation of the skin, disease, and medications.


title: Gums

text: Since the colour of the gums can vary, uniformity of colour is more important than the underlying color itself. Excess deposits of melanin can cause dark spots or patches on the gums (melanin gingival hyperpigmentation), especially at the base of the interdental papillae. Gum depigmentation (aka gum bleaching) is a procedure used in cosmetic dentistry to remove these discolorations.


title: Gums

text: Healthy gums have a smooth curved or scalloped appearance around each tooth. Healthy gums fill and fit each space between the teeth, unlike the swollen gum papilla seen in gingivitis or the empty interdental embrasure seen in periodontal disease. Healthy gums hold tight to each tooth in that the gum surface narrows to "knife-edge" thin at the free gingival margin. On the other hand, inflamed gums have a "puffy" or "rolled" margin.


title: Gums

text: Healthy gums have a firm texture that is resistant to movement, and the surface texture often exhibits surface stippling. Unhealthy gums, on the other hand, are often swollen and less firm. Healthy gums have an orange-peel like texture to it due to the stippling.


title: Gums

text: Healthy gums usually have no reaction to normal disturbance such as brushing or periodontal probing. Unhealthy gums, conversely, will show bleeding on probing (BOP) and/or purulent exudate.


title: Gums

text: The gingival cavity microecosystem, fueled by food residues and saliva, can support the growth of many microorganisms, of which some can be injurious to health. Improper or insufficient oral hygiene can thus lead to many gum and periodontal disorders, including gingivitis or periodontitis, which are major causes for tooth failure. Recent studies have also shown that anabolic steroids are also closely associated with gingival enlargement requiring a gingivectomy for many cases. Gingival recession is when there is an apical movement of the gum margin away from the biting (occlusal) surface. It may indicate an underlying inflammation such as periodontitis or pyorrhea, a pocket formation, dry mouth or displacement of the marginal gums away from the tooth by mechanical (such as brushing), chemical, or surgical means. Gingival retraction, in turn, may expose the dental neck and leave it vulnerable to the action of external stimuli, and may cause "root sensitivity".


title: WWF Invasion

text: WWF Invasion (also typeset as InVasion) was a professional wrestling pay-per-view (PPV) event produced by the World Wrestling Federation (WWF, now WWE). It took place on July 22, 2001, at the Gund Arena in Cleveland, Ohio. This event was initially planned to be the fourth Fully Loaded PPV, as it was advertised at the King of the Ring event, which immediately preceded Invasion, although the decision to replace Fully Loaded was made in May. Invasion was the first pay-per-view to feature the ongoing Invasion storyline, which featured wrestlers from the WWF taking on The Coalition, a combined force of wrestlers from World Championship Wrestling (WCW) and Extreme Championship Wrestling (ECW), later known as The Alliance. The event featured WWF wrestlers facing WCW and ECW wrestlers.


title: WWF Invasion

text: The main event, dubbed the "Inaugural Brawl," was a five-on-five tag team match between Team WWF and Team WCW/ECW. The other main match was a singles match for the WWF Hardcore Championship between Rob Van Dam and Jeff Hardy. With a buyrate of 775,000, the event is the highest grossing non-WrestleMania pay-per-view in WWE history.


title: WWF Invasion

text: Following the conclusion of the storyline, the event's July slot was given to Vengeance in 2002 when Armageddon returned that year; Vengeance temporarily replaced Armageddon in December 2001 due to the September 11 attacks.


title: WWF Invasion

text: From 1998 to 2000, the World Wrestling Federation (WWF, now WWE) held an event titled Fully Loaded. The WWF had planned to hold a fourth Fully Loaded pay-per-view (PPV) in 2001, but canceled it in order to hold an event titled Invasion for The Invasion storyline between the WWF and The Alliance, consisting of former World Championship Wrestling (WCW) and Extreme Championship Wrestling (ECW) talent. The event took place on July 22, 2001, at the Gund Arena in Cleveland, Ohio.


title: WWF Invasion

text: On March 23, the World Wrestling Federation (WWF) bought out its long-time rival, World Championship Wrestling (WCW). The last episode of "WCW Monday Nitro" aired on March 26, dubbed the "Night of Champions". "Nitro" started with WWF Owner Vince McMahon announcing a simulcast with "Raw Is War" later that night to address the future of WCW, during which it was revealed that Shane McMahon had bought WCW. At WrestleMania X-Seven on April 1, Shane defeated Vince in a Street Fight with some of the WCW talent in attendance, sitting in the upper-level seats at the Reliant Astrodome. During May and June, WCW wrestlers interfered in matches on WWF programming. At the 2001 King of the Ring, Booker T interfered during a Triple Threat match for the WWF Championship and tossed Steve Austin through the announcers table, nearly costing him the title.


title: WWF Invasion

text: On the following night, the June 25 episode of "Raw Is War", Shane declared his intention to invade the WWF, and the Invasion storyline started with Booker T performing a scissors kick to Vince. On the June 28 episode of "SmackDown!", it was decided that Fully Loaded was to be changed to Invasion, and would feature matches between WWF and WCW. The ultimate goal, reportedly, was for WCW to "take over" one of the WWF's two primary programs, either "Raw Is War" or "SmackDown!", and rebrand it as its own separate entity. To test the waters for this, the final twenty minutes of the July 2 "Raw Is War" telecast was given over to WCW, which brought in its own commentators (Scott Hudson and Arn Anderson), ring announcer (Stacy Keibler), referee (Nick Patrick), ring apron, and Chyron graphics, to present a match between Booker T and Buff Bagwell for Booker's WCW Championship (which he had won on the final episode of "Nitro"). This continued on "SmackDown!", where Gregory Helms lost the WCW Cruiserweight Championship against Billy Kidman and Booker defended the WCW Championship against Diamond Dallas Page. The Booker/Bagwell title match, however, was very poorly received both by television viewers and the live crowd in the arena; sports journalist Michael Landsberg reported that many have called the bout "the worst match ever". The two other WCW matches also received a negative fan reaction. The decision was thus made to make WCW a heel group who was out to destroy the WWF. On the July 9 on "Raw Is War", when then-face WCW owner Shane was scheduled to face Page in a street fight, the two instead attacked The Undertaker, turning Shane heel (Page had already debuted in WWF as a heel, as part of a stalker angle with Undertaker and his wife). Later that night, Chris Jericho and Kane (from the WWF) fought Lance Storm and Mike Awesome (from WCW) in a tag team match. It ended in a no contest when the ECW Alumni from both the WWF and WCW along with the debuting Rob Van Dam and Tommy Dreamer made their way to the ring. As it looked as though they were going after Storm and Awesome, they instead attacked Jericho and Kane. This led to the "Raw" color-commentator Paul Heyman leaving the announcer's booth and declared that Extreme Championship Wrestling (ECW) has joined the invasion and stated that the invasion has been taken to the extreme, leading to some WWF and WCW wrestlers (including Raven, Lance Storm, Rhyno, The Dudley Boyz, and Tazz) defecting to ECW. Shane appeared to co-operate with Vince against ECW, but later that night, it was revealed that WCW and ECW had merged, and that Stephanie McMahon-Helmsley (who was last seen on the May 21 episode of "Raw Is War") now owned ECW.


title: WWF Invasion

text: Earlier in the year, Austin had a change in character, becoming more emotional, and friendly with Vince. On the July 12 episode of "SmackDown!", Vince said he needed the "old" Austin, an anti-hero tough character, to lead the WWF at Invasion. After Vince pleaded with him, Austin shook his head and left. During the July 16 episode of "Raw is War", Austin was shown drinking in a bar. Later that night, a fight started between many WWF wrestlers, and WCW and ECW wrestlers. As WWF seemed to be disadvantaged, Austin arrived, and returned to his old character, fighting off the WCW and ECW wrestlers. The WWF wrestlers (Steve Austin, Kurt Angle, Chris Jericho, Kane, The Undertaker) then cleared out the ring, and were left standing tall. On the July 19 episode of "SmackDown!", Heyman says that he wants to bring back wrestling, and destroy sports entertainment by giving the WWF its last rites with The Alliance members, "In nomine Patris et Filii et Spiritus Sancti, Amen!", while proclaiming "Death to sports entertainment! Death to the WWF!".


title: WWF Invasion

text: Before the event officially began, Chavo Guerrero (WCW) defeated Scotty 2 Hotty (WWF) in a match taped for "Sunday Night Heat".


title: WWF Invasion

text: The first match of the event was between Lance Storm and Mike Awesome (ECW), and Edge and Christian (WWF). The match went back and forth until Awesome attempted a cheap shot at Edge from the apron. Edge avoided it, performed a dropkick, and sent Storm on top of him with a back body drop. Christian then leaped off Edge over the top rope onto Storm and Awesome. As Christian was on the top turnbuckle, Awesome tripped Christian, and attacked his back outside. Back in the ring, Storm and Awesome dominated Christian after Storm threw Christian's gut into the ringpost. Christian fought back with a crossbody, but Awesome tagged in, and performed a flapjack spinebuster. Storm and Awesome dominated Christian until Christian performed a back body drop to Awesome from the top rope. Edge and Storm tagged in, and Edge performed an Edge-O-Matic to Storm. Storm performed a jawbreaker, and attempted a double belly-to-back suplex with Awesome. Edge landed on his feet, and Christian performed a flying clothesline to both Storm and Awesome. Edge performed a spear to Awesome. Storm attempted a superkick to Christian, but Edge shoved Christian, and took the kick himself. As Awesome held Edge in a crucifix, Christian performed a spear to Awesome. Edge landed on top of Awesome, and pinned him for the victory.


title: WWF Invasion

text: The second match was between WCW Senior Referee Nick Patrick and WWF Senior Referee Earl Hebner with Mick Foley as the special guest referee. Other WCW and WWF referees accompanied them to the ring. The match started with Hebner delivering kicks in the corner, followed by punches, and knee drops to the midsection, but Patrick pulled Hebner outside. Back in the ring, Patrick stomped Hebner, but Hebner fought back with punches, and mounted punches. Patrick fought back by performing a low blow, and sent Hebner outside with a baseball slide. WCW referees stomped Hebner until Foley stopped them, and ejected them from ringside. Back in the ring, Patrick complained to Foley, allowing Hebner to perform a flying shoulder block, and pin Patrick for the victory. After the match, Patrick argued with Foley. Foley punched him, and applied the mandible claw.


title: WWF Invasion

text: The third match was between the APA (Faarooq and Bradshaw) (WWF), and Sean O'Haire and Chuck Palumbo (WCW). The teams were the tag team champions of their promotions. The match began with the APA performing a double spinebuster to Palumbo. Bradshaw had the advantage over Palumbo, then O'Haire. After Faarooq tagged in, O'Haire countered a belly-to-back suplex attempt, and performed a knee lift. Palumbo tagged in, and Faarooq performed a flying shoulder block. Bradshaw then tagged in, and performed a fallaway slam to Palumbo. O'Haire then kicked Bradshaw in the head, and performed a Widow Maker. Palumbo tagged in, and Bradshaw fought back with a DDT. After Faarooq tagged in, O'Haire pulled him out of the ring, and sent him into the ringsteps. They dominated Faarooq until Faarooq fought back with a spinebuster. Bradshaw and Palumbo tagged in, and Bradshaw performed a big boot, and a powerslam. As Bradshaw attempted a fallaway slam, O'Haire performed a superkick, and dropped Bradshaw onto the top turnbuckle. After Faarooq sent O'Haire outside, Palumbo performed a superkick to Faarooq, and Bradshaw pinned Palumbo after performing a Clothesline from Hell.


title: WWF Invasion

text: The fourth match was between the WWF Light Heavyweight Champion X-Pac and the WCW Cruiserweight Champion Billy Kidman. The match started back and forth until Kidman performed a hurricanrana, and an enzuigiri. X-Pac fought back after sending Kidman over the top rope, and performed a springboard reverse crossbody to the outside. Back in the ring, X-Pac applied the sleeper hold. Kidman escaped, and applied the sleeper hold, but X-Pac countered with a belly-to-back suplex. X-Pac went to the top rope, and performed a somersault legdrop, but Kidman avoided it. Kidman performed a B.K. Bomb, and mounted punches, which X-Pac countered with a powerbomb. X-Pac attempted another powerbomb, but Kidman reversed it into a sitout facebuster. X-Pac then countered an aerial attack with an X-Factor. As he attempted a Bronco buster, Kidman lifted his leg, performing a low blow. Kidman then pinned X-Pac after a shooting star press.


title: WWF Invasion

text: The fifth match was between Raven (ECW) and WWF commissioner William Regal (WWF). Regal gained the early advantage following a double underhook suplex, and a catapult, sending Raven outside. Back in the ring, Raven tossed Regal over top rope, and performed a baseball slide, and a Russian legsweep into the security wall. Back in the ring, Raven performed a diving punch to Regal's forehead. Regal countered another attempt, and performed a knee lift. Raven fought back with a corner clothesline, and a running bulldog. Regal fought back, countering a Raven Effect DDT into a Northern Lights suplex. After both collided, Raven rolled out of the ring, as Tazz came down. As the referee checked on Raven, Tazz performed a T-Bone suplex to Regal. Tazz left, and Raven pinned Regal after performing a Raven Effect DDT.


title: WWF Invasion

text: The sixth match was between The Big Show, Billy Gunn and Albert (WWF), and Chris Kanyon, Shawn Stasiak and Hugh Morrus (WCW). Before the match began, the WWF wrestlers gorilla pressed the WCW wrestlers. The match started with Kanyon attacking Gunn in the corner. Gunn performed an electric chair drop, but Stasiak hit a cheap shot, and Kanyon performed a Russian legsweep followed by a forward Russian legsweep. Stasiak tagged in, and Gunn performed a neckbreaker slam. After Albert tagged in, Kanyon and Morrus entered the ring, but Gunn and The Big Show threw them out. Albert performed a bicycle kick, and a Baldo Bomb to Stasiak. Morrus and Kanyon attacked Albert, and Morrus performed a DDT. Morrus tagged in, and Albert performed a powerslam before tagging in Gunn. Gunn performed a Fameasser to Morrus, and attempted the One and Only. Stasiak attacked him from behind, performing an inverted DDT, and Morrus pinned him for the victory. After the match, The Big Show performed chokeslams to Morrus and Stasiak, and an Alley Oop to Kanyon.


title: WWF Invasion

text: The seventh match was between Tazz (ECW) and Tajiri (WWF). The match started with Tajiri performing a spinning heel kick, and a standing moonsault. Tazz fought back with a head and arm suplex. Tajiri then escaped a suplex attempt, and performed kicks and punches. Tazz fought back with a clothesline. After Tazz applied a cross armbar, and performed a flapjack spinebuster, Tajiri fought back with a handspring back elbow. Tazz then pulled Tajiri off the apron, and sent him into the ringsteps. Back in the ring, Tajiri applied the Tarantula, and dropkicked Tazz, who was kneeling. Tazz then blocked a kick, and performed a capture suplex. He then shoved the referee out of the way, allowing Tajiri to spit green mist into Tazz's face, and pin him after a Buzzsaw Kick.


title: WWF Invasion

text: The eighth match was between Rob Van Dam (ECW) and Jeff Hardy (WWF) for the WWF Hardcore Championship. Before the match began, Van Dam attacked Matt Hardy from behind with a steel chair. The match started back and forth with a quick pace. Hardy gained the advantage after a dropkick to the back. After Hardy missed a crossbody, Van Dam performed a standing moonsault, a lifting double underhook facebuster, and a rolling thunder. Van Dam then climbed the turnbuckles, but Hardy shoved him outside. Outside, Hardy walked the barricade, but Van Dam sent him into the crowd. After a moonsault from the barricade, Hardy was placed over the barricade, and Van Dam performed a spinning heel kick off the apron. Hardy fought back with a sunset flip powerbomb from the apron, took out a ladder, and climbed it. However, Van Dam tipped the ladder, causing Hardy to fall. Van Dam attempted to use a chair, but Hardy used the ladder. After Hardy hit Van Dam with the chair, Van Dam came back with a Van Daminator, sending Hardy off the stage. Back in the ring, Van Dam performed a Chair Surf, and attempted a split-legged moonsault, but Hardy blocked it with his knees. Hardy followed with a DDT, a German suplex, and a sitout jawbreaker. Later on, Van Dam avoided a Swanton Bomb. Van Dam placed the Hardcore Championship belt on Hardy, and performed a Five Star Frog Splash onto the title. Van Dam then pinned Hardy to win the Hardcore Championship.


title: WWF Invasion

text: The ninth match was a Bra and Panties match between Torrie Wilson and Stacy Keibler (WCW), and Trish Stratus and Lita (WWF) with Mick Foley as the special guest referee. The match started with Lita and Stratus taking down Keibler and Wilson. Wilson dropkicked Stratus' back, and kicked her in the corner. Stratus fought back with a clothesline, and attempted to remove Wilson's shirt after a suplex. Keibler stopped her, and they attempted to double team, but Stratus performed a double clothesline. Lita tagged in, knocked Wilson off the apron, and removed Keibler's shirt after pulling her in. Keibler went outside the ring, and Lita chased after her. This allowed Wilson to stomp on Lita, and Keibler removed her shirt. Lita fought back with a snapmare, and attempted a diving crossbody. Wilson and Stratus tagged in, and performed a clothesline. Wilson fought back, and pulled Stratus up while stepping on her hair. She pulled down her top, but Stratus performed a roll-up, and removed Wilson's pants. Lita and Stratus then performed a Poetry in Motion, with Lita performing an aided clothesline to Wilson, before removing Wilson's shirt. Stratus then performed a bulldog to Keibler, and Lita performed a Litasault. They then removed Keibler's pants to win the match.


title: WWF Invasion

text: The main event was the "Inaugural Brawl", a no disqualification ten-man tag team match between Booker T, Diamond Dallas Page, The Dudley Boyz (Bubba Ray Dudley and D-Von Dudley) and Rhyno (Team WCW/ECW), and Stone Cold Steve Austin, Kurt Angle, The Undertaker, Kane and Chris Jericho (Team WWF). WCW Owner Shane McMahon, ECW Owner Stephanie McMahon-Helmsley, ECW General Manager Paul Heyman, and WWF Owner Vince McMahon were at ringside. The Undertaker attacked Page during his entrance, and all wrestlers fought at ringside. The match began with Team WWF having the advantage as Austin dominated Rhyno. Team WCW/ECW gained the advantage after Page performed a hangman to The Undertaker. Team WCW/ECW dominated The Undertaker until he performed a DDT. Team WWF kept the advantage until Booker performed a flapjack to Jericho with help from D-Von. Jericho fought back, knocking down the Dudley Boyz, and tagged in Angle. Angle fought the Dudley Boyz until Bubba Ray performed a Bubba Bomb. Angle was dominated by Team WCW/ECW until The Undertaker came in illegally, and attacked Page. All wrestlers entered the ring, and fought. The Undertaker fought with Page, and, after performing a chokeslam, they fought into the crowd. Austin was down holding his knee as Booker and Angle were lying in the ring. On the outside, Kane was double-teamed by the Dudley Boyz. Kane eventually fought back, performing a chokeslam to D-Von through the announce table. Bubba Ray and Rhyno then sent Kane through the other announce table with a double suplex. Jericho then sent Rhyno through a table with a shoulder block from the apron. In the ring, Bubba Ray and Booker double-teamed Angle until Angle fought back, performing a German suplex to Booker, and an Angle Slam to Bubba Ray. Angle attempted to apply the ankle lock on Booker, but Booker kicked him into the referee. Booker then performed a flapjack, and all three were down. Vince got the WWF Championship belt, and attempted to throw it to Angle. Shane took it, and hit Vince with it. Shane failed to hit Angle, and Angle threw both Shane and Bubba Ray out of the ring. Angle performed an Angle Slam on Booker, and applied the ankle lock. After sending the referee back in the ring, Austin turned on Team WWF by performing a Stone Cold Stunner to Angle. Booker then pinned Angle to win the match for Team WCW/ECW. After the match, Austin celebrated with Shane, Stephanie and Heyman.


title: WWF Invasion

text: After this pay-per-view, the Invasion storyline continued. The following night on "Raw is War", Steve Austin explained his defection was because he felt unappreciated. WCW/ECW, now referred to as The Alliance, had the momentum, holding the WWF Championship, the WWF Intercontinental Championship, and the WWF Hardcore Championship in addition to all of WCW's titles. The feud soon centered around the return of The Rock, and which team he would join, as both Vince and Shane attempted to persuade The Rock to join their team. The Rock remained with the WWF, and engaged in a feud with Booker T over the WCW Championship. Austin would begin a feud with Kurt Angle over the WWF Championship after the events at Invasion.


title: WWF Invasion

text: As the Invasion storyline concluded at Survivor Series in November, this was the only Invasion PPV held, and instead of reinstating Fully Loaded in July 2002, the WWF, which was renamed to World Wrestling Entertainment (WWE) in May 2002, moved Vengeance to the July slot; Vengeance had temporarily replaced Armageddon in December 2001 due to the September 11 attacks.


title: Solid oxide fuel cell

text: A solid oxide fuel cell (or SOFC) is an electrochemical conversion device that produces electricity directly from oxidizing a fuel. Fuel cells are characterized by their electrolyte material; the SOFC has a solid oxide or ceramic electrolyte.


title: Solid oxide fuel cell

text: Advantages of this class of fuel cells include high combined heat and power efficiency, long-term stability, fuel flexibility, low emissions, and relatively low cost. The largest disadvantage is the high operating temperature which results in longer start-up times and mechanical and chemical compatibility issues.


title: Solid oxide fuel cell

text: Solid oxide fuel cells are a class of fuel cells characterized by the use of a solid oxide material as the electrolyte. SOFCs use a solid oxide electrolyte to conduct negative oxygen ions from the cathode to the anode. The electrochemical oxidation of the hydrogen, carbon monoxide or other organic intermediates by oxygen ions thus occurs on the anode side. More recently, proton-conducting SOFCs (PC-SOFC) are being developed which transport protons instead of oxygen ions through the electrolyte with the advantage of being able to be run at lower temperatures than traditional SOFCs.


title: Solid oxide fuel cell

text: They operate at very high temperatures, typically between 500 and 1,000 °C. At these temperatures, SOFCs do not require expensive platinum catalyst material, as is currently necessary for lower temperature fuel cells such as PEMFCs, and are not vulnerable to carbon monoxide catalyst poisoning. However, vulnerability to sulfur poisoning has been widely observed and the sulfur must be removed before entering the cell through the use of adsorbent beds or other means.


title: Solid oxide fuel cell

text: Solid oxide fuel cells have a wide variety of applications, from use as auxiliary power units in vehicles to stationary power generation with outputs from 100 W to 2 MW. In 2009, Australian company, Ceramic Fuel Cells successfully achieved an efficiency of an SOFC device up to the previously theoretical mark of 60%. The higher operating temperature make SOFCs suitable candidates for application with heat engine energy recovery devices or combined heat and power, which further increases overall fuel efficiency.


title: Solid oxide fuel cell

text: Because of these high temperatures, light hydrocarbon fuels, such as methane, propane, and butane can be internally reformed within the anode. SOFCs can also be fueled by externally reforming heavier hydrocarbons, such as gasoline, diesel, jet fuel (JP-8) or biofuels. Such reformates are mixtures of hydrogen, carbon monoxide, carbon dioxide, steam and methane, formed by reacting the hydrocarbon fuels with air or steam in a device upstream of the SOFC anode. SOFC power systems can increase efficiency by using the heat given off by the exothermic electrochemical oxidation within the fuel cell for endothermic steam reforming process. Additionally, solid fuels such as coal and biomass may be gasified to form syngas which is suitable for fueling SOFCs in integrated gasification fuel cell power cycles.


title: Solid oxide fuel cell

text: Thermal expansion demands a uniform and well-regulated heating process at startup. SOFC stacks with planar geometry require on the order of an hour to be heated to operating temperature. Micro-tubular fuel cell design geometries promise much faster start up times, typically in the order of minutes.


title: Solid oxide fuel cell

text: Unlike most other types of fuel cells, SOFCs can have multiple geometries. The planar fuel cell design geometry is the typical sandwich type geometry employed by most types of fuel cells, where the electrolyte is sandwiched in between the electrodes. SOFCs can also be made in tubular geometries where either air or fuel is passed through the inside of the tube and the other gas is passed along the outside of the tube. The tubular design is advantageous because it is much easier to seal air from the fuel. The performance of the planar design is currently better than the performance of the tubular design, however, because the planar design has a lower resistance comparatively. Other geometries of SOFCs include modified planar fuel cell designs (MPC or MPSOFC), where a wave-like structure replaces the traditional flat configuration of the planar cell. Such designs are highly promising because they share the advantages of both planar cells (low resistance) and tubular cells.


title: Solid oxide fuel cell

text: A solid oxide fuel cell is made up of four layers, three of which are ceramics (hence the name). A single cell consisting of these four layers stacked together is typically only a few millimeters thick. Hundreds of these cells are then connected in series to form what most people refer to as an "SOFC stack". The ceramics used in SOFCs do not become electrically and ionically active until they reach very high temperature and as a consequence, the stacks have to run at temperatures ranging from 500 to 1,000 °C. Reduction of oxygen into oxygen ions occurs at the cathode. These ions can then diffuse through the solid oxide electrolyte to the anode where they can electrochemically oxidize the fuel. In this reaction, a water byproduct is given off as well as two electrons. These electrons then flow through an external circuit where they can do work. The cycle then repeats as those electrons enter the cathode material again.


title: Solid oxide fuel cell

text: Most of the downtime of a SOFC stems from the mechanical balance of plant, the air preheater, prereformer, afterburner, water heat exchanger, anode tail gas oxidizer, and electrical balance of plant, power electronics, hydrogen sulfide sensor and fans. Internal reforming leads to a large decrease in the balance of plant costs in designing a full system.


title: Solid oxide fuel cell

text: The ceramic anode layer must be very porous to allow the fuel to flow towards the electrolyte. Consequently, granular matter is often selected for anode fabrication procedures. Like the cathode, it must conduct electrons, with ionic conductivity a definite asset. The anode is commonly the thickest and strongest layer in each individual cell, because it has the smallest polarization losses, and is often the layer that provides the mechanical support. Electrochemically speaking, the anode's job is to use the oxygen ions that diffuse through the electrolyte to oxidize the hydrogen fuel.


title: Solid oxide fuel cell

text: The oxidation reaction between the oxygen ions and the hydrogen produces heat as well as water and electricity.


title: Solid oxide fuel cell

text: If the fuel is a light hydrocarbon, for example, methane, another function of the anode is to act as a catalyst for steam reforming the fuel into hydrogen. This provides another operational benefit to the fuel cell stack because the reforming reaction is endothermic, which cools the stack internally. The most common material used is a cermet made up of nickel mixed with the ceramic material that is used for the electrolyte in that particular cell, typically YSZ (yttria stabilized zirconia). These nanomaterial-based catalysts, help stop the grain growth of nickel. Larger grains of nickel would reduce the contact area that ions can be conducted through, which would lower the cells efficiency. Perovskite materials (mixed ionic/electronic conducting ceramics) have been shown to produce a power density of 0.6 W/cm2 at 0.7 V at 800 °C which is possible because they have the ability to overcome a larger activation energy.


title: Solid oxide fuel cell

text: However, there are a few disadvantages associated with YSZ as anode material. Ni coarsening, carbon deposition, reduction-oxidation instability, and sulfur poisoning are the main obstacles limiting the long-term stability of Ni-YSZ. Ni coarsening refers to the evolution of Ni particles in doped in YSZ grows larger in grain size, which decreases the surface area for the catalytic reaction. Carbon deposition occurs when carbon atoms, formed by hydrocarbon pyrolysis or CO disproportionation, deposit on the Ni catalytic surface. Carbon deposition becomes important especially when hydrocarbon fuels are used, i.e. methane, syngas. The high operating temperature of SOFC and the oxidizing environment facilitate the oxidation of Ni catalyst through reaction Ni + O = NiO. The oxidation reaction of Ni reduces the electrocatalytic activity and conductivity. Moreover, the density difference between Ni and NiO causes volume change on the anode surface, which could potentially lead to mechanical failure. Sulfur poisoning arises when fuel such as natural gas, gasoline, or diesel is used. Again, due to the high affinity between sulfur compounds (HS, (CH)S) and the metal catalyst, even the smallest impurities of sulfur compounds in the feed stream could deactivate the Ni catalyst on the YSZ surface.


title: Solid oxide fuel cell

text: Current research is focused on reducing or replacing Ni content in the anode to improve long-term performance. The modified Ni-YSZ containing other materials including CeO, YO, LaO, MgO, TiO, Ru, Co, etc. are invented to resist sulfur poisoning, but the improvement is limited due to the rapid initial degradation. Copper-based cerement anode is considered as a solution to carbon deposition because it is inert to carbon and stable under typical SOFC oxygen partial pressures (pO). Cu-Co bimetallic anodes in particular show a great resistivity of carbon deposition after the exposure to pure CH at 800C. And Cu-CeO-YSZ exhibits a higher electrochemical oxidation rate over Ni-YSZ when running on CO and syngas, and can achieve even higher performance using CO than H, after adding a cobalt co-catalyst. Oxide anodes including zirconia-based fluorite and perovskites are also used to replace Ni-ceramic anodes for carbon resistance. Chromite i.e. LaSrCrMnO (LSCM) is used as anodes and exhibited comparable performance against Ni–YSZ cermet anodes. LSCM is further improved by impregnating Cu and sputtering Pt as the current collector.


title: Solid oxide fuel cell

text: The electrolyte is a dense layer of ceramic that conducts oxygen ions. Its electronic conductivity must be kept as low as possible to prevent losses from leakage currents. The high operating temperatures of SOFCs allow the kinetics of oxygen ion transport to be sufficient for good performance. However, as the operating temperature approaches the lower limit for SOFCs at around the electrolyte begins to have large ionic transport resistances and affect the performance. Popular electrolyte materials include yttria-stabilized zirconia (YSZ) (often the 8% form 8YSZ), scandia stabilized zirconia (ScSZ) (usually 9 mol% ScO – 9ScSZ) and gadolinium doped ceria (GDC). The electrolyte material has crucial influence on the cell performances. Detrimental reactions between YSZ electrolytes and modern cathodes such as lanthanum strontium cobalt ferrite (LSCF) have been found, and can be prevented by thin (<100 nm) ceria diffusion barriers.


title: Solid oxide fuel cell

text: If the conductivity for oxygen ions in SOFC can remain high even at lower temperatures (current target in research ~500 °C), material choices for SOFC will broaden and many existing problems can potentially be solved. Certain processing techniques such as thin film deposition can help solve this problem with existing materials by:


title: Solid oxide fuel cell

text: The cathode, or air electrode, is a thin porous layer on the electrolyte where oxygen reduction takes place. The overall reaction is written in Kröger-Vink Notation as follows:


title: Solid oxide fuel cell

text: Cathode materials must be, at a minimum, electrically conductive. Currently, lanthanum strontium manganite (LSM) is the cathode material of choice for commercial use because of its compatibility with doped zirconia electrolytes. Mechanically, it has a similar coefficient of thermal expansion to YSZ and thus limits stress buildup because of CTE mismatch. Also, LSM has low levels of chemical reactivity with YSZ which extends the lifetime of the materials. Unfortunately, LSM is a poor ionic conductor, and so the electrochemically active reaction is limited to the triple phase boundary (TPB) where the electrolyte, air and electrode meet. LSM works well as a cathode at high temperatures, but its performance quickly falls as the operating temperature is lowered below 800 °C. In order to increase the reaction zone beyond the TPB, a potential cathode material must be able to conduct both electrons and oxygen ions. Composite cathodes consisting of LSM YSZ have been used to increase this triple phase boundary length. Mixed ionic/electronic conducting (MIEC) ceramics, such as perovskite LSCF, are also being researched for use in intermediate temperature SOFCs as they are more active and can make up for the increase in the activation energy of the reaction.


title: Solid oxide fuel cell

text: The interconnect can be either a metallic or ceramic layer that sits between each individual cell. Its purpose is to connect each cell in series, so that the electricity each cell generates can be combined. Because the interconnect is exposed to both the oxidizing and reducing side of the cell at high temperatures, it must be extremely stable. For this reason, ceramics have been more successful in the long term than metals as interconnect materials. However, these ceramic interconnect materials are very expensive when compared to metals. Nickel- and steel-based alloys are becoming more promising as lower temperature (600–800 °C) SOFCs are developed. The material of choice for an interconnect in contact with Y8SZ is a metallic 95Cr-5Fe alloy. Ceramic-metal composites called "cermet" are also under consideration, as they have demonstrated thermal stability at high temperatures and excellent electrical conductivity.


title: Solid oxide fuel cell

text: Polarizations, or overpotentials, are losses in voltage due to imperfections in materials, microstructure, and design of the fuel cell. Polarizations result from ohmic resistance of oxygen ions conducting through the electrolyte (iRΩ), electrochemical activation barriers at the anode and cathode, and finally concentration polarizations due to inability of gases to diffuse at high rates through the porous anode and cathode (shown as ηA for the anode and ηC for cathode). The cell voltage can be calculated using the following equation:


title: Solid oxide fuel cell

text: In SOFCs, it is often important to focus on the ohmic and concentration polarizations since high operating temperatures experience little activation polarization. However, as the lower limit of SOFC operating temperature is approached (~600 °C), these polarizations do become important.


title: Solid oxide fuel cell

text: Above mentioned equation is used for determining the SOFC voltage (in fact for fuel cell voltage in general). This approach results in good agreement with particular experimental data (for which


title: Solid oxide fuel cell

text: adequate factors were obtained) and poor agreement for other than original experimental working parameters. Moreover, most of the equations used require the addition of numerous factors which are difficult or impossible to determine. It makes very difficult any optimizing process of the SOFC working parameters as well as design architecture configuration selection. Because of those circumstances a few other equations were proposed:


title: Solid oxide fuel cell

text: This method was validated and found to be suitable for optimization and sensitivity studies in plant-level modelling of various systems with solid oxide fuel cells. With this mathematical description it is possible to account for different properties of the SOFC. There are many parameters which impact cell working conditions, e.g. electrolyte material, electrolyte thickness, cell temperature, inlet and outlet gas compositions at anode and cathode, and electrode porosity, just to name some. The flow in these systems is often calculated using the Navier–Stokes equations.


title: Solid oxide fuel cell

text: Ohmic losses in an SOFC result from ionic conductivity through the electrolyte and electrical resistance offered to the flow of electrons in the external electrical circuit. This is inherently a materials property of the crystal structure and atoms involved. However, to maximize the ionic conductivity, several methods can be done. Firstly, operating at higher temperatures can significantly decrease these ohmic losses. Substitutional doping methods to further refine the crystal structure and control defect concentrations can also play a significant role in increasing the conductivity. Another way to decrease ohmic resistance is to decrease the thickness of the electrolyte layer.


title: Solid oxide fuel cell

text: An ionic specific resistance of the electrolyte as a function of temperature can be described by the following relationship:


title: Solid oxide fuel cell

text: where: formula_18 and formula_19 – factors depended on electrolyte materials, formula_20 – electrolyte temperature, and formula_4 – ideal gas constant.


title: Solid oxide fuel cell

text: The concentration polarization is the result of practical limitations on mass transport within the cell and represents the voltage loss due to spatial variations in reactant concentration at the chemically active sites. This situation can be caused when the reactants are consumed by the electrochemical reaction faster than they can diffuse into the porous electrode, and can also be caused by variation in bulk flow composition. The latter is due to the fact that the consumption of reacting species in the reactant flows causes a drop in reactant concentration as it travels along the cell, which causes a drop in the local potential near the tail end of the cell.


title: Solid oxide fuel cell

text: The concentration polarization occurs in both the anode and cathode. The anode can be particularly problematic, as the oxidation of the hydrogen produces steam, which further dilutes the fuel stream as it travels along the length of the cell. This polarization can be mitigated by reducing the reactant utilization fraction or increasing the electrode porosity, but these approaches each have significant design trade-offs.