title: Retina display

text: Retina Display is a brand name used by Apple for its series of IPS LCD and OLED displays that have a higher pixel density than traditional Apple displays. Apple has registered the term "Retina" as a trademark with regard to computers and mobile devices with the United States Patent and Trademark Office and Canadian Intellectual Property Office. The applications were approved in 2012 and 2014 respectively. The Canadian application cited a 2010 application in Jamaica.


title: Retina display

text: The Retina display debuted in 2010 with the iPhone 4 and the iPod Touch (4th Generation), and later the iPad (3rd generation) where each screen pixel of the iPhone 3GS, iPod touch (3rd generation), iPad 2 was replaced by four smaller pixels, and the user interface scaled up to fill in the extra pixels. Apple calls this mode "HiDPI mode". In simpler words, it is one logical pixel = four physical pixels. The scale factor is tripled for devices with even higher pixel densities, such as the iPhone 6 Plus and iPhone X. The advantage of this equation is that the CPU "sees" a small portion of the data and calculates the relative positions of each element, and the GPU renders these elements with high quality assets to make the output much sharper and clearer. The goal of Retina displays is to make the text and images being displayed extremely crisp, so that pixels are not visible to the naked eye or at viewing distance. This allows displays to rival the smooth curves and sharpness of printed text and immediacy of photographic prints.


title: Retina display

text: The Retina display has since expanded to most Apple product lines, such as Apple Watch, iPhone, iPod Touch, iPad, iPad Mini, iPad Air, iPad Pro, MacBook, MacBook Air, MacBook Pro, iMac, and Pro Display XDR, some of which have never had a comparable non-Retina display. Apple uses various marketing terms to differentiate between its LCD and OLED displays having various resolutions, contrast levels, color reproduction, or refresh rates. It is known as "Liquid Retina display" for the iPhone XR, iPad Air 4th Generation, iPad Mini 6th Generation, iPad Pro 3rd Generation and later versions, and "Retina 4.5K display" for the iMac.


title: Retina display

text: Apple's Retina displays are not an absolute standard for display sharpness, but vary depending on the size of the display on the device, and at what distance the user would typically be viewing the screen. Where on smaller devices with smaller displays users would view the screen at a closer distance to their eyes, the displays have more PPI (Pixels Per Inch), while on larger devices with larger displays where the user views the screen further away, the screen uses a lower PPI value. Later device versions have had additional improvements, whether an increase in the screen size (the iPhone 12 Pro Max), contrast ratio (the 12.9” iPad Pro 5th Generation, and iMac with Retina 4.5K display), and/or, more recently, PPI count (OLED iPhones); as a result, Apple uses the names “Retina HD display", "Retina 4K/5K display", “Retina 4.5K display", "Super Retina HD display", “Super Retina XDR display”, and "Liquid Retina display" for each successive version.


title: Retina display

text: When introducing the iPhone 4, Steve Jobs said the number of pixels needed for a Retina display is about 300 PPI for a device held 10 to 12 inches from the eye. One way of expressing this as a unit is pixels-per-degree (PPD) which takes into account both the screen resolution and the distance from which the device is viewed. Based on Jobs' predicted number of 300, the threshold for a Retina display starts at the PPD value of 57 PPD. 57 PPD means that a tall skinny triangle with a height equal to the viewing distance and a top angle of one degree will have a base on the device's screen that covers 57 pixels. Any display's viewing quality (from phone displays to huge projectors) can be described with this size-independent universal parameter. Note that the PPD parameter is not an intrinsic parameter of the display itself, unlike absolute pixel resolution (e.g. 1920×1080 pixels) or relative pixel density (e.g. 401 PPI), but is dependent on the distance between the display and the eye of the person (or lens of the device) viewing the display; moving the eye closer to the display reduces the PPD, and moving away from it increases the PPD in proportion to the distance.


title: Retina display

text: where formula_2 is the distance to the screen, formula_3 is the resolution of the screen in pixels per unit length, and formula_4 is the aperture of a cone having the apex on focus, height formula_2, and the base in the eye lens —the optical correspondent to a cone inside the eye having the same base and the apex in the other focus, the fovea. That aperture, which can be measured by visual field tests, varies widely among different human subjects.


title: Retina display

text: In practice, thus far Apple has converted a device's display to Retina by doubling the number of pixels in each direction, quadrupling the total resolution. This increase creates a sharper interface at the same physical dimensions. The sole exception to this has been the iPhone 6 Plus, 6S Plus, 7 Plus, and 8 Plus, which renders its display at triple the number of pixels in each direction, before down-sampling to a 1080p resolution.


title: Retina display

text: The displays are manufactured worldwide by different suppliers. Currently, the iPad's display comes from Samsung, while the MacBook Pro and iPod Touch displays are made by LG Display and Japan Display Inc. There was a shift of display technology from twisted nematic (TN) liquid-crystal displays (LCDs) to in-plane switching (IPS) LCDs starting with the iPhone 4 models in June 2010.


title: Retina display

text: Apple markets the following devices as having a Retina display, Retina HD display, Liquid Retina display, Liquid Retina XDR display, Super Retina HD display, Super Retina XDR display or Retina 4K/5K/6K display:


title: Retina display

text: Reviews of Apple devices with Retina displays have generally been positive on technical grounds, with comments describing it as a considerable improvement on earlier screens and praising Apple for driving third-party application support for high-resolution displays more effectively than on Windows. While high-dpi displays such as IBM's T220 and T221 had been sold in the past, they had seen little take-up due to their cost of around $8400.


title: Retina display

text: "to our eyes, there has never been a more detailed, clear, or viewable screen on any mobile device. Not only are the colors and blacks deep and rich, but you simply cannot see pixels on the screen…webpages that would be line after line of pixelated content when zoomed out on a 3GS are completely readable on the iPhone 4, though the text is beyond microscopic."


title: Retina display

text: That much resolution is stunning. To see it on a mainstream device like the iPad—rather than a $13,000 exotic monitor—is truly amazing, and something I've been waiting more than a decade to see. It will set a bar for future resolution that every other manufacturer of devices and PCs will have to jump.


title: Retina display

text: Writer John Gruber suggested that the arrival of Retina displays on computers would trigger a need to redesign interfaces and designs for the new displays:


title: Retina display

text: The sort of rich, data-dense information design espoused by Edward Tufte can now not only be made on the computer screen but also enjoyed on one. Regarding font choices, you not only need not choose a font optimized for rendering on screen, but should not. Fonts optimized for screen rendering look cheap on the retina MacBook Pro—sometimes downright cheesy—in the same way they do when printed in a glossy magazine.


title: Retina display

text: Raymond Soneira, president of DisplayMate Technologies, has challenged Apple's claim. He says that the physiology of the human retina is such that there must be at least 477 pixels per inch in a pixelated display for the pixels to become imperceptible to the human eye at a distance of . Astronomer and science blogger Phil Plait notes, however, that, "if you have [better than 20/20] eyesight, then at one foot away the iPhone 4S's pixels are resolved. The picture will look pixelated. If you have average eyesight [20/20 vision], the picture will look just fine... So in my opinion, what Jobs said was fine. Soneira, while technically correct, was being picky." The retinal neuroscientist Bryan Jones offers a similar analysis of more detail and comes to a similar conclusion: "I'd find Apple's claims stand up to what the human eye can perceive."


title: Retina display

text: Apple fan website "CultOfMac" hosts an article by John Brownlee who incorrectly stated that the resolution the human eye can discern at 12 inches is 900 PPI, concluding ""Apple's Retina Displays are only about 33% of the way there."" On the topic of 20/20 vision, Brownlee misrepresented visual acuity in the population saying ""most research suggests that normal vision is actually much better than 20/20"" when in truth the majority have worse than 20/20 vision, and the WHO considers average vision as 20/40. Brownlee also stated that people do not always view displays at a constant distance, and claimed a close-viewed display could no longer be classed as Retina. However, near visual acuity is usually poor due to presbyopia in nearly everyone over 40, such that decreasing reading distance can actually reduce perceivable resolution.


title: Retina display

text: The first smartphone following the iPhone 4 to ship with a display of a comparable pixel density was the Nokia E6, running Symbian Anna, with a resolution of 640 × 480 at a screen size of 62.5mm. This was an isolated case for the platform however, as all other Symbian-based devices had larger displays with lower resolutions. Some older Symbian smartphones, including the Nokia N80 and N90, featured a 2.1 inch display at 259 ppi, which was one of the sharpest at the time. The first Android smartphones with the same display - Meizu M9 was launched a few months later in beginning of 2011. In October of the same year Galaxy Nexus was announced, which had a display with a better resolution. By 2013 the 300+ ppimark was found on midrange phones such as the Moto G. From 2013 to 2014, many flagship devices such as the Samsung Galaxy S4 and HTC One (M8) had 1080p (FHD) screens around 5-inches for a 400+ PPI which surpassed the Retina density on the iPhone 5. The second major redesign of the iPhone, the iPhone 6, has a 1334 × 750 resolution on a 4.7-inch screen, while rivals such as the Samsung Galaxy S6 have a QHD display of 2560 × 1440 resolution, close to four times the number of pixels found in the iPhone 6, giving the S6 a 577 PPI that is almost twice that of the iPhone 6's 326 PPI. The Sony Xperia Z5 Premium launched in late 2015 had 806 PPI.


title: Retina display

text: The larger iPhone 6 Plus features a "Retina HD display", which is a 5.5-inch 1080p screen with 401 PPI. Aside from resolution, all generations of iPhone Retina displays receive high ratings for other aspects such as brightness and color accuracy, compared to those of contemporary smartphones, while some Android devices such as the LG G3 have sacrificed screen quality and battery life for high resolution. "Ars Technica" suggested the "superfluousness of so many flagship phone features—the move from 720p to 1080p to 1440p and beyond...things are all nice to have, but you’d be hard-pressed to argue that any of them are essential". Furthermore, developers can better optimize content for iOS due to Apple's few screen sizes in contrast to Android's wide display format variations.


title: Retina display

text: Many Windows-based Ultrabook models have offered 1080p (FHD) screens standard since 2012 and often QHD or QHD+ as optional upgrade displays.


title: Volkswagen Transporter (T5)

text: The Volkswagen Transporter T5 range is the fifth generation of Volkswagen Commercial Vehicles (VWCV/VWN) 'Transporter' series of medium-sized light commercial vehicles and the people mover Caravelle/Multivan range. It was launched 6 October 2002, and went into full production on 25 April 2003, replacing the fourth generation T4 Transporter range.


title: Volkswagen Transporter (T5)

text: Key markets for the T5 range are Germany, the United Kingdom, Taiwan, Russia, France, Turkey and Singapore. The T5 range was not sold in the United States and Canada due to poor sales of the T4-based Volkswagen EuroVan. In lieu of the T5, Volkswagen marketed the Canadian-built Routan, a minivan derived from the Chrysler RT platform.


title: Volkswagen Transporter (T5)

text: The Transporter is the commercial workhorse in the T5 range, available in over 100 combinations. Variants include short- (SWB), or long-wheelbases (LWB); along with low-, medium-, or high-rooflines; and can be configured as a van, minibus, single-cab, double-cab, drop side or chassis truck.


title: Volkswagen Transporter (T5)

text: Apart from these factory variants there are a multitude of third-party conversions available, some of which are offered through the VWCV/VWN dealer organisation. They include refrigerated vans, ambulances, police vans, fire engines, ladder trucks, campervans and so on.


title: Volkswagen Transporter (T5)

text: The full cargo payload potential of the Transporter is between to 1.4 tonnes. Load compartment volumes range from to .


title: Volkswagen Transporter (T5)

text: The T5 is also available in six- to eleven-seat configurations called Shuttle, Kombi, Caravelle, and Multivan.


title: Volkswagen Transporter (T5)

text: The Transporter Sportline is the range-topping trim level of the Transporter panel and Kombi van. It comes as standard with a Turbocharged Direct Injection (TDI) diesel engine, generating torque of at 2,000 rpm, and is mated to a six-speed manual gearbox.


title: Volkswagen Transporter (T5)

text: The vehicles have a wide range of options including an acoustic cabin option which makes the van feel more like a car.


title: Volkswagen Transporter (T5)

text: Other standard features on the Sportline include 18-inch weight-rated alloy wheels, body-coloured bumpers, door mirrors and handles. It features suspension which is lowered by over standard variants, and has chrome side bars and grille, a roof spoiler, as well as a special Volkswagen badge.


title: Volkswagen Transporter (T5)

text: The Sportline featured in an episode of Top Gear TV series; where Clarkson, Hammond and May had to choose three vans to compete in a series of challenges, including transporting equipment for The Who. Jeremy Clarkson claimed the Sportline to be "the fastest van in Britain".


title: Volkswagen Transporter (T5)

text: This claim was put to the test by competitor TV programme "Fifth Gear" where the Sportline has been put head to head with The A-Team van, as well as the Mercedes-Benz Vito Sport-X. The Sportline comfortably won a race against the A-Team GMC van, even with Tiff Needell cutting corners and using short cuts in the vein of the television series. Against the Sport-X, even though the Mercedes had a more powerful engine, it was found that the traction control was too sensitive and overtly intrusive to be able to make quick progress around a track.


title: Volkswagen Transporter (T5)

text: The California and California (Kombi) Beach constitute the Volkswagen Commercial Vehicles campervan range, designed and built in-house on the T5 platform.


title: Volkswagen Transporter (T5)

text: The 'California' is a fully equipped camper with beds, sink, and fold-up seat and tables. The 'California Beach' is an entry level model that comes with just a fold-up bed.


title: Volkswagen Transporter (T5)

text: In September 2009, Volkswagen Commercial Vehicles launched a revamped and facelifted T5 range, which is sold under four main labels the Transporter, Caravelle, Multivan and California.


title: Volkswagen Transporter (T5)

text: The revised range showcases new technology dealers claimed it was their best earner. The medium van segment, which includes a world-first with the dual clutch transmission named Direct-Shift Gearbox (DSG) – which is also available with 4motion four-wheel drive, Side Lane Assist for monitoring blind spots when changing lanes, tyre pressure monitor display for monitoring tyre pressures (TPMS), Bi-Xenon Head Lights with LED Daytime Running Lights and touchscreen Radio Navigation System (RNS) and a reversing camera that worked in conjunction with RNS.


title: Volkswagen Transporter (T5)

text: Engines powering the revised range are now all inline-four-cylinder designs; and all are 2.0 L in cubic capacity which includes one petrol option, and four newly developed high-efficiency Turbocharged Direct Injection (TDI) diesel options, all with common rail, replacing the former Pumpe Düse (PD) Unit Injector fuel system. Volkswagen Commercial Vehicles claim that this new diesel engine range is twenty percent more efficient than the outgoing TDI range.


title: Volkswagen Transporter (T5)

text: It is a version commemorating 25th anniversary of Multivan, covering 2.0L petrol, 2.0L TSI (150 kW), 2.0L TSI 4MOTION (150 kW), 2.0L TDI (75 kW), 2.0L TDI (103 kW), 2.0L TDI 4MOTION (103 kW), 2.0L BiTDI (132 kW), 2.0L BiTDI 4MOTION (132 kW) models. It was limited to 225 models worldwide and includes a matte black roof and black 18-inch alloy wheels, black door handles, matte black paint on the underside of the front bumper, black decal trim at the back and side sills; choice of Candy White, Salsa Red or Metallic Silver body colour; sport chassis and upgraded anti-roll bar.


title: Annalise Basso

text: Annalise Nicole Basso (born December 2, 1998) is an American actress. She currently stars in "Snowpiercer" (2020).


title: Annalise Basso

text: She has starred in the films "Bedtime Stories" (2008), "Love Takes Wing" (2009), "Standing Up" (2013), "Oculus" (2013), and "" (2016). From 2014 until 2015, she starred in the television series "The Red Road". She graduated from Campbell Hall School in Studio City, Los Angeles.


title: Annalise Basso

text: Annalise Basso is the youngest child of Marcia and Louis Joseph Basso, and has an older sister and brother, Alexandria and Gabriel Basso, who are also actors. Most of her initial roles have been on television commercials or small guest appearances on television series. Her first role that garnered attention was her role as Eden Hamby on "True Blood". In 2009, she starred in the television film "Love Takes Wing" from the "Love Comes Softly" series. When she was 10, she took part in "Are You Smarter Than a 5th Grader?" as a student. More recently, she has had roles in episodes of "New Girl" and "Nikita".


title: Annalise Basso

text: Basso's first lead role in a feature film was in D. J. Caruso's "Standing Up", a coming-of-age story based on the novel "The Goats" by Brock Cole. The film debuted at the 2012 Cannes Film Festival. The story centers on two children, played by Basso and Chandler Canterbury, who are stripped naked and left stranded together on an island as part of a summercamp prank.


title: Annalise Basso

text: In 2014, she starred in the horror film "Oculus" as a younger version of Karen Gillan's character. Basso gained greater recognition and attention for the critically successful horror film "" in 2016.


title: Annalise Basso

text: In 2019, she played Heaven Casteel in series of Lifetime movies based on the Casteel saga by V.C. Andrews.


title: Annalise Basso

text: She currently stars as LJ Folger in TNT's apocalyptic crime thriller "Snowpiercer", adapted from the movie of the same name.


title: Emmanuel Lubezki

text: Emmanuel Lubezki Morgenstern (; born November 30, 1964) is a Mexican cinematographer. He sometimes goes by the nickname Chivo, which means "goat" in Spanish. Lubezki has worked with many acclaimed directors, including Mike Nichols, Tim Burton, Michael Mann, Joel and Ethan Coen, David O. Russell, and frequent collaborators Terrence Malick, Alfonso Cuarón, and Alejandro González Iñárritu.


title: Emmanuel Lubezki

text: Lubezki is known for groundbreaking uses of natural lighting and continuous uninterrupted shots in cinematography, often utilizing a Steadicam, a 3-axis gimbal, or hand-held camera to orchestrate fluid, uninterrupted camera movements during particularly significant scenes. Lubezki is a member of both the Mexican Society of Cinematographers and the American Society of Cinematographers. His work has been praised by audiences and critics alike, which earned him multiple awards, including eight Academy Award nominations for Best Cinematography. He won in this category three times, becoming the first person to do so in three consecutive years, for "Gravity" (2013), "Birdman" (2014), and "The Revenant" (2015).


title: Emmanuel Lubezki

text: In 2020, he shot and narrated a short film for Apple displaying the camera capabilities of the iPhone 12 Pro, the first device ever to capture, edit and playback in Dolby Vision.


title: Emmanuel Lubezki

text: Lubezki was born to a Jewish family in Mexico City, Mexico. His father was actor and producer Muni Lubezki. His paternal grandfather is Lithuanian Jewish while his grandmother is also Jewish, from Russia. Lubezki studied film at Mexico's Centro Universitario de Estudios Cinematográficos (CUEC), where he met Alfonso Cuarón.


title: Emmanuel Lubezki

text: Lubezki began his career in Mexican film and television productions in the late 1980s. His first international production was the 1993 independent film "Twenty Bucks", which followed the journey of a single twenty-dollar bill.


title: Emmanuel Lubezki

text: Lubezki is a frequent collaborator with fellow Mexican filmmaker Alfonso Cuarón. The two have been friends since they were teenagers and attended the same film school at the National Autonomous University of Mexico. Together they have worked on six motion pictures: "Sólo Con Tu Pareja", "A Little Princess", "Great Expectations", "Y Tu Mamá También", "Children of Men", and "Gravity".


title: Emmanuel Lubezki

text: His work with Cuarón on "Children of Men" (2006) has received universal acclaim. The film utilized a number of new technologies and distinctive techniques. The "roadside ambush" scene was shot in one extended take utilizing a special camera rig invented by Doggicam systems, developed from the company's Power Slide system. For the scene, a vehicle was modified to enable seats to tilt and lower actors out of the way of the camera. The windshield of the car was designed to tilt out of the way to allow camera movement in and out through the front windscreen. A crew of four, including Lubezki, rode on the roof. "Children of Men" also features a seven-and-a-half-minute battle sequence composed of roughly five seamless edits.


title: Emmanuel Lubezki

text: Lubezki won his first Academy Award for Best Cinematography for his work on Cuarón's "Gravity", a thriller set in outer space. The film was praised for the way it combined two shots through digital backgrounds of space to create the illusion of scenes done in a single shot. Lubezki won his second Academy Award for Best Cinematography in the following year for his work on Alejandro González Iñárritu's "Birdman". The film used a similar technique from "Gravity", being very unusual in the way the entire movie was shot so as to appear to be photographed in one continuous take. Lubezki won the award again in 2015 for Iñárritu's "The Revenant", becoming a milestone for his third consecutive win and for being the first cinematographer to do so. The film was shot entirely in the wilderness during a cold season, minimizing the amount of CGI and using only natural lighting. It was an extremely difficult process that required a limited amount of time to shoot each scene, which delayed the production, causing budget overruns and changes of locations for proper settings. However, "The Revenant" earned over $500 million at the box office and received critical acclaim, with much praise for the film's atmospheric tone and realism.


title: Emmanuel Lubezki

text: Lubezki won the Royal Photographic Society Lumière Award for major achievement in cinematography, video or animation in 2016.


title: Truss bridge

text: A truss bridge is a bridge whose load-bearing superstructure is composed of a truss, a structure of connected elements, usually forming triangular units. The connected elements (typically straight) may be stressed from tension, compression, or sometimes both in response to dynamic loads. The basic types of truss bridges shown in this article have simple designs which could be easily analyzed by 19th and early 20th-century engineers. A truss bridge is economical to construct because it uses materials efficiently.


title: Truss bridge

text: The nature of a truss allows the analysis of its structure using a few assumptions and the application of Newton's laws of motion according to the branch of physics known as statics. For purposes of analysis, trusses are assumed to be pin jointed where the straight components meet, meaning that taken alone, every joint on the structure is functionally considered to be a flexible joint as opposed to a rigid joint with strength to maintain its own shape, and the resulting shape and strength of the structure is only maintained by the interlocking of the components. This assumption means that members of the truss (chords, verticals and diagonals) will act only in tension or compression. A more complex analysis is required where rigid joints impose significant bending loads upon the elements, as in a Vierendeel truss.


title: Truss bridge

text: In the bridge illustrated in the infobox at the top, vertical members are in tension, lower horizontal members in tension, shear, and bending, outer diagonal and top members are in compression, while the inner diagonals are in tension. The central vertical member stabilizes the upper compression member, preventing it from buckling. If the top member is sufficiently stiff then this vertical element may be eliminated. If the lower chord (a horizontal member of a truss) is sufficiently resistant to bending and shear, the outer vertical elements may be eliminated, but with additional strength added to other members in compensation. The ability to distribute the forces in various ways has led to a large variety of truss bridge types. Some types may be more advantageous when wood is employed for compression elements while other types may be easier to erect in particular site conditions, or when the balance between labor, machinery and material costs have certain favorable proportions.


title: Truss bridge

text: The inclusion of the elements shown is largely an engineering decision based upon economics, being a balance between the costs of raw materials, off-site fabrication, component transportation, on-site erection, the availability of machinery and the cost of labor. In other cases the appearance of the structure may take on greater importance and so influence the design decisions beyond mere matters of economics. Modern materials such as prestressed concrete and fabrication methods, such as automated welding, and the changing price of steel relative to that of labor have significantly influenced the design of modern bridges.


title: Truss bridge

text: A pure truss can be represented as a pin-jointed structure, one where the only forces on the truss members are tension or compression, not bending. This is used in the teaching of statics, by the building of model bridges from spaghetti. Spaghetti is brittle and although it can carry a modest tension force, it breaks easily if bent. A model spaghetti bridge thus demonstrates the use of a truss structure to produce a usefully strong complete structure from individually weak elements.


title: Truss bridge

text: Because wood was in abundance, early truss bridges would typically use carefully fitted timbers for members taking compression and iron rods for tension members, usually constructed as a covered bridge to protect the structure. In 1820 a simple form of truss, Town's lattice truss, was patented, and had the advantage of requiring neither high labor skills nor much metal. Few iron truss bridges were built in the United States before 1850.


title: Truss bridge

text: Truss bridges became a common type of bridge built from the 1870s through the 1930s. Examples of these bridges still remain across the US, but their numbers are dropping rapidly as they are demolished and replaced with new structures. As metal slowly started to replace timber, wrought iron bridges in the US started being built on a large scale in the 1870s. Bowstring truss bridges were a common truss design during this time, with their arched top chords. Companies like the Massillon Bridge Company of Massillon, Ohio, and the King Bridge Company of Cleveland, Ohio, became well-known, as they marketed their designs to cities and townships. The bowstring truss design fell out of favor due to a lack of durability, and gave way to the Pratt truss design, which was stronger. Again, the bridge companies marketed their designs, with the Wrought Iron Bridge Company in the lead. As the 1880s and 1890s progressed, steel began to replace wrought iron as the preferred material. Other truss designs were used during this time, including the camel-back. By the 1910s, many states developed standard plan truss bridges, including steel Warren pony truss bridges. As the 1920s and 1930s progressed, some states, such as Pennsylvania, continued to build steel truss bridges, including massive steel through-truss bridges for long spans. Other states, such as Michigan, used standard plan concrete girder and beam bridges, and only a limited number of truss bridges were built.


title: Truss bridge

text: The truss may carry its roadbed on top, in the middle, or at the bottom of the truss. Bridges with the roadbed at the top or the bottom are the most common as this allows both the top and bottom to be stiffened, forming a box truss. When the roadbed is atop the truss it is called a deck truss (an example of this was the I-35W Mississippi River bridge). When the truss members are both above and below the roadbed it is called a through truss (an example of this application is the Pulaski Skyway), and where the sides extend above the roadbed but are not connected, a pony truss or half-through truss.


title: Truss bridge

text: Sometimes both the upper and lower chords support roadbeds, forming a double-decked truss. This can be used to separate rail from road traffic or to separate the two directions of road traffic.


title: Truss bridge

text: Since through truss bridges have supports located over the bridge deck, they are susceptible to being hit by overheight loads when used on highways. The I-5 Skagit River bridge collapsed after such a strike; before the collapse, similar incidents had been common and had necessitated frequent repairs.


title: Truss bridge

text: Truss bridges consisting of more than one span may be either a continuous truss or a series of simple trusses. In the simple truss design, each span is supported only at the ends and is fully independent of any adjacent spans. Each span must fully support the weight of any vehicles traveling over it (the live load).


title: Truss bridge

text: In contrast, a continuous truss functions as a single rigid structure over multiple supports. This means that the live load on one span is partially supported by the other spans, and consequently it is possible to use less material in the truss. Continuous truss bridges were not very common before the mid-20th century because they are statically indeterminate, which makes them difficult to design without the use of computers.


title: Truss bridge

text: A multi-span truss bridge may also be constructed using cantilever spans, which are supported at only one end rather than both ends like other types of trusses. Unlike a continuous truss, a cantilever truss does not need to be connected rigidly, or indeed at all, at the center. Many cantilever bridges, like the Quebec Bridge shown below, have two cantilever spans supporting a simple truss in the center. The bridge would remain standing if the simple truss section were removed.


title: Truss bridge

text: Bridges are the most widely known examples of truss use. There are many types, some of them dating back hundreds of years. Below are some of the more common designs.


title: Truss bridge

text: The Allan truss, designed by Percy Allan, is partly based on the Howe truss. The first Allan truss was completed on 13 August 1894 over Glennies Creek at Camberwell, New South Wales and the last Allan truss bridge was built over Mill Creek near Wisemans Ferry in 1929. Completed in March 1895, the Tharwa Bridge located at Tharwa, Australian Capital Territory, was the second Allan truss bridge to be built, the oldest surviving bridge in the Australian Capital Territory and the oldest, longest continuously used Allan truss bridge. Completed in November 1895, the Hampden Bridge in Wagga Wagga, New South Wales, Australia, the first of the Allan truss bridges with overhead bracing, was originally designed as a steel bridge but was constructed with timber to reduce cost. In his design, Allan used Australian ironbark for its strength. A similar bridge also designed by Percy Allen is the Victoria Bridge on Prince Street, Picton, New South Wales. Also constructed of ironbark, the bridge is still in use today for pedestrian and light traffic.


title: Truss bridge

text: The Bailey truss was designed by the British in 1940-1941 for military uses during World War II. A short selection of prefabricated modular components could be easily and speedily combined on land in various configurations to adapt to the needs at the site and allow rapid deployment of completed trusses. In the image, note the use of pairs of doubled trusses to adapt to the span and load requirements. In other applications the trusses may be stacked vertically, and doubled as necessary.


title: Truss bridge

text: The Baltimore truss is a subclass of the Pratt truss. A Baltimore truss has additional bracing in the lower section of the truss to prevent buckling in the compression members and to control deflection. It is mainly used for rail bridges, showing off a simple and very strong design. In the Pratt truss the intersection of the verticals and the lower horizontal tension members are used to anchor the supports for the short-span girders under the tracks (among other things). With the Baltimore truss, there are almost twice as many points for this to happen because the short verticals will also be used to anchor the supports. Thus the short-span girders can be made lighter because their span is shorter. A good example of the Baltimore truss is the Amtrak Old Saybrook – Old Lyme Bridge in Connecticut, United States.


title: Truss bridge

text: The Bollman Truss Railroad Bridge at Savage, Maryland, United States is the only surviving example of a revolutionary design in the history of American bridge engineering. The type was named for its inventor, Wendel Bollman, a self-educated Baltimore engineer. It was the first successful all-metal bridge design (patented in 1852) to be adopted and consistently used on a railroad. The design employs wrought iron tension members and cast iron compression members. The use of multiple independent tension elements reduces the likelihood of catastrophic failure. The structure was also easy to assemble.


title: Truss bridge

text: The Wells Creek Bollman Bridge is the only other bridge designed by Wendel Bollman still in existence, but it is a Warren truss configuration.


title: Truss bridge

text: The bowstring truss bridge was patented in 1841 by Squire Whipple. While similar in appearance to a tied-arch bridge, a bowstring truss has diagonal load-bearing members: these diagonals result in a structure that more closely matches a Parker truss or Pratt truss than a true arch.


title: Truss bridge

text: In the Brown truss all vertical elements are under tension, with exception of the end posts. This type of truss is particularly suited for timber structures that use iron rods as tension members.


title: Truss bridge

text: Most trusses have the lower chord under tension and the upper chord under compression. In a cantilever truss the situation is reversed, at least over a portion of the span. The typical cantilever truss bridge is a "balanced cantilever", which enables the construction to proceed outward from a central vertical spar in each direction. Usually these are built in pairs until the outer sections may be anchored to footings. A central gap, if present, can then be filled by lifting a conventional truss into place or by building it in place using a "traveling support". In another method of construction, one outboard half of each balanced truss is built upon temporary falsework. When the outboard halves are completed and anchored the inboard halves may then be constructed and the center section completed as described above.


title: Truss bridge

text: The Fink truss was designed by Albert Fink of Germany in 1854. This type of bridge was popular with the Baltimore and Ohio Railroad. The Appomattox High Bridge on the Norfolk and Western Railway included 21 Fink deck truss spans from 1869 until their replacement in 1886.


title: Truss bridge

text: The Howe truss, patented in 1840 by Massachusetts millwright William Howe, includes vertical members and diagonals that slope up towards the center, the opposite of the Pratt truss.


title: Truss bridge

text: In contrast to the Pratt truss, the diagonal web members are in compression and the vertical web members are in tension. Few of these bridges remain standing. Examples include Jay Bridge in Jay, New York; McConnell's Mill Covered Bridge in Slippery Rock Township, Lawrence County, Pennsylvania; Sandy Creek Covered Bridge in Jefferson County, Missouri; and Westham Island Bridge in Delta, British Columbia, Canada.


title: Truss bridge

text: The K-truss is named after the "K" formed in each panel by the vertical member and two oblique members. Examples are the Südbrücke rail bridge over the River Rhine, Mainz, Germany, the bridge on I-895 (Baltimore Harbor Tunnel Thruway) in Baltimore, Maryland, the Long–Allen Bridge in Morgan City, Louisiana (Morgan City Bridge) with three 600-foot-long spans, and the Wax Lake Outlet bridge in Calumet, Louisiana


title: Truss bridge

text: One of the simplest truss styles to implement, the king post consists of two angled supports leaning into a common vertical support.


title: Truss bridge

text: This type of bridge uses a substantial number of lightweight elements, easing the task of construction. Truss elements are usually of wood, iron, or steel.


title: Truss bridge

text: A lenticular truss bridge includes a lens-shape truss, with trusses between an upper chord (functioning as an arch) that curves up and then down to end points, and a lower chord (functioning as a suspension cable) that curves down and then up to meet at the same end points. Where the arches extend above and below the roadbed, it is called a lenticular pony truss bridge. The Pauli truss bridge is a specific variant of the lenticular truss, but the terms are not interchangeable.


title: Truss bridge

text: One type of lenticular truss consists of arcuate upper compression chords and lower eyebar chain tension links. Brunel's Royal Albert Bridge over the River Tamar between Devon and Cornwall uses a single tubular upper chord. As the horizontal tension and compression forces are balanced these horizontal forces are not transferred to the supporting pylons (as is the case with most arch types). This in turn enables the truss to be fabricated on the ground and then to be raised by jacking as supporting masonry pylons are constructed. This truss has been used in the construction of a stadium, with the upper chords of parallel trusses supporting a roof that may be rolled back. The Smithfield Street Bridge in Pittsburgh, Pennsylvania, is another example of this type.


title: Truss bridge

text: An example of a lenticular pony truss bridge that uses regular spans of iron is the Turn-of-River Bridge designed and manufactured by the Berlin Iron Bridge Co.


title: Truss bridge

text: The Pauli truss is a variant of the lenticular truss, "with the top chord carefully shaped so that it has a constant force along the entire length of the truss." It is named after , whose 1857 railway bridge (the ) spanned the Isar near Munich. ("See also Grosshesselohe Isartal station".) The term Pauli truss is not interchangeable with the term lenticular truss and, according to Thomas Boothby, the casual use of the term has clouded the literature.


title: Truss bridge

text: The Long truss was designed by Stephen H. Long in 1830. The design resembles a Howe truss, but is entirely made of wood instead of a combination of wood and metal. The longest surviving example is the Eldean Covered Bridge north of Troy, Ohio, spanning . One of the earliest examples is the Old Blenheim Bridge, which with a span of and a total length of long was the second-longest covered bridge in the United States, until its destruction from flooding in 2011.


title: Truss bridge

text: The Busching bridge, often erroneously used as an example of a Long truss, is an example of a Howe truss, as the verticals are metal rods.


title: Truss bridge

text: A Parker truss bridge is a Pratt truss design with a polygonal upper chord. A "camelback" is a subset of the Parker type, where the upper chord consists of exactly five segments. An example of a Parker truss is the Traffic Bridge in Saskatoon, Canada. An example of a camelback truss is the Woolsey Bridge near Woolsey, Arkansas.


title: Truss bridge

text: Designed and patented in 1872 by Reuben Partridge, after local bridge designs proved ineffective against road traffic and heavy rains. It became the standard for covered bridges built in central Ohio in the late 1800s and early 1900s.


title: Truss bridge

text: The Pegram truss is a hybrid between the Warren and Parker trusses where the upper chords are all of equal length and the lower chords are longer than the corresponding upper chord. Because of the difference in upper and lower chord length, each panel is not square. The members which would be vertical in a Parker truss vary from near vertical in the center of the span to diagonal near each end (like a Warren truss). George H. Pegram, while the chief engineer of Edge Moor Iron Company in Wilmington, Delaware, patented this truss design in 1885.


title: Truss bridge

text: The Pegram truss consists of a Parker type design with the vertical posts leaning towards the center at an angle between 60 and 75°. The variable post angle and constant chord length allowed steel in existing bridges to be recycled into a new span using the Pegram truss design. This design also facilitated reassembly and permitted a bridge to be adjusted to fit different span lengths. There are twelve known remaining Pegram span bridges in the United States with seven in Idaho, two in Kansas, and one each in California, Washington, and Utah.


title: Truss bridge

text: The Pennsylvania (Petit) truss is a variation on the Pratt truss. The Pratt truss includes braced diagonal members in all panels; the Pennsylvania truss adds to this design half-length struts or ties in the top, bottom, or both parts of the panels. It is named after the Pennsylvania Railroad, which pioneered this design. It was once used for hundreds of bridges in the United States, but fell out of favor in the 1930s, and very few bridges of this design remain. Examples of this truss type include the Lower Trenton Bridge in Trenton, New Jersey, the Fort Wayne Street Bridge in Goshen, Indiana, the Schell Bridge in Northfield, Massachusetts, the Inclined Plane Bridge in Johnstown, Pennsylvania, the Easton–Phillipsburg Toll Bridge in Easton, Pennsylvania, the Connecticut River Bridge in Brattleboro, Vermont, the Metropolis Bridge in Metropolis, Illinois, and the Healdsburg Memorial Bridge in Healdsburg, California.


title: Truss bridge

text: A Post truss is a hybrid between a Warren truss and a double-intersection Pratt truss. Invented in 1863 by Simeon S. Post, it is occasionally referred to as a "Post patent truss" although he never received a patent for it. The Ponakin Bridge and the Bell Ford Bridge are two examples of this truss.


title: Truss bridge

text: A Pratt truss includes vertical members and diagonals that slope down towards the center, the opposite of the Howe truss. The interior diagonals are under tension under balanced loading and vertical elements under compression. If pure tension elements are used in the diagonals (such as eyebars) then crossing elements may be needed near the center to accept concentrated live loads as they traverse the span. It can be subdivided, creating Y- and K-shaped patterns. The Pratt truss was invented in 1844 by Thomas and Caleb Pratt. This truss is practical for use with spans up to and was a common configuration for railroad bridges as truss bridges moved from wood to metal. They are statically determinate bridges, which lend themselves well to long spans. They were common in the United States between 1844 and the early 20th century.


title: Truss bridge

text: Examples of Pratt truss bridges are the Governor's Bridge in Maryland, Dearborn River High Bridge near Augusta, Montana, built in 1897, and the Fair Oaks Bridge in Fair Oaks, California, built 1907–09.


title: Truss bridge

text: The Scenic Bridge near Tarkio, Montana, is an example of a Pratt deck truss bridge, where the roadway is on top of the truss.


title: Truss bridge

text: The queenpost truss, sometimes called "queen post" or "queenspost", is similar to a king post truss in that the outer supports are angled towards the center of the structure. The primary difference is the horizontal extension at the center which relies on beam action to provide mechanical stability. This truss style is only suitable for relatively short spans.


title: Truss bridge

text: The Smith truss, patented by Robert W Smith on July 16, 1867, has mostly diagonal criss-crossed supports. Smith's company used many variations of this pattern in the wooden covered bridges it built.


title: Truss bridge

text: While most all of the bridges built in the 19th century in the Jackson County, Ohio, area used the Smith truss design, the Johnson Road Covered Bridge is the last known surviving example in the state.


title: Truss bridge

text: The Thacher truss combines some of the characteristics of a Pratt truss with diagonals under tension and of a Howe truss with diagonals under compression. It is quite rare.


title: Truss bridge

text: A truss arch may contain all horizontal forces within the arch itself, or alternatively may be either a thrust arch consisting of a truss, or of two arcuate sections pinned at the apex. The latter form is common when the bridge is constructed as cantilever segments from each side as in the Navajo Bridge.


title: Truss bridge

text: The Vierendeel truss, unlike common pin-jointed trusses, imposes significant bending forces upon its members—but this in turn allows the elimination of many diagonal elements. It is a structure where the members are not triangulated but form rectangular openings, and is a frame with fixed joints that are capable of transferring and resisting bending moments. While rare as a bridge type due to higher costs compared to a triangulated truss, it is commonly employed in modern building construction as it allows the resolution of gross shear forces against the frame elements while retaining rectangular openings between columns. This is advantageous both in allowing flexibility in the use of the building space and freedom in selection of the building's outer curtain wall, which affects both interior and exterior styling aspects.


title: Truss bridge

text: Patented 1894 (); its simplicity eases erection at the site. It was intended to be used as a railroad bridge.


title: Truss bridge

text: The Warren truss was patented in 1848 by James Warren and Willoughby Theobald Monzani, and consists of longitudinal members joined only by angled cross-members, forming alternately inverted equilateral triangle-shaped spaces along its length, ensuring that no individual strut, beam, or tie is subject to bending or torsional straining forces, but only to tension or compression. Loads on the diagonals alternate between compression and tension (approaching the center), with no vertical elements, while elements near the center must support both tension and compression in response to live loads. This configuration combines strength with economy of materials and can therefore be relatively light. The girders being of equal length, it is ideal for use in prefabricated modular bridges. It is an improvement over the Neville truss which uses a spacing configuration of isosceles triangles.


title: Truss bridge

text: A Whipple truss, named after its inventor Squire Whipple, is usually considered a subclass of the Pratt truss because the diagonal members are designed to work in tension. The main characteristic of a Whipple truss is that the tension members are elongated, usually thin, and at a shallow angle, and cross two or more bays (rectangular sections defined by the vertical members).


title: Truss bridge

text: The Wichert truss is a modified type of continuous truss which is statically determinate and helps avoid some of the other shortcomings of continuous trusses. It was patented in 1930 by Pittsburgh-based civil engineer Edward Martin Wichert (1883–1955). The defining feature of this truss type is a hinged kite-shaped section above each intermediate support. Only about ten Wichert truss bridges were ever built, mostly in Pennsylvania and Maryland. Of these, one of the best known is the Homestead Grays Bridge in Pittsburgh.


title: Truss bridge

text: Driving across a truss bridge: The video shows the roadway perspective of a through truss bridge over the Willamette River in Harrisburg, Oregon, USA. The bridge features three simply supported Parker Truss spans.


title: George Herbert, 5th Earl of Carnarvon

text: George Edward Stanhope Molyneux Herbert, 5th Earl of Carnarvon, (26 June 1866 – 5 April 1923), styled Lord Porchester until 1890, was an English peer and aristocrat best known as the financial backer of the search for and excavation of Tutankhamun's tomb in the Valley of the Kings.


title: George Herbert, 5th Earl of Carnarvon

text: Styled Lord Porchester from birth, he was born at 66 Grosvenor Street, Mayfair, London, the only son of Henry Herbert, 4th Earl of Carnarvon, a distinguished Tory statesman, by his first wife Lady Evelyn Stanhope, daughter of Anne and George Stanhope, 6th Earl of Chesterfield. Aubrey Herbert was his half-brother. He was educated at Eton College and Trinity College, Cambridge. He inherited the Bretby Hall estate in Derbyshire from his maternal grandmother, Anne Elizabeth, Dowager Countess of Chesterfield in 1885, and succeeded his father in the earldom in 1890.


title: George Herbert, 5th Earl of Carnarvon

text: Lord Carnarvon married Almina Victoria Maria Alexandra Wombwell, alleged to be the illegitimate daughter of millionaire banker Alfred de Rothschild, of the Rothschild family, at St. Margaret's Church, Westminster, on 26 June 1895. Rothschild provided a marriage settlement of £500,000 (equivalent to £ in pounds), and paid off all Lord Carnarvon’s existing debts. The Carnarvons had two children:


title: George Herbert, 5th Earl of Carnarvon

text: Exceedingly wealthy due to his marriage settlement, Carnarvon was at first best known as an owner of racehorses, and in 1902 he established Highclere Stud to breed thoroughbred racehorses. He joined the Jockey Club and, in 1905, was appointed one of the stewards at the new Newbury Racecourse, and acted as a steward at other racecourses. His family has maintained the connection ever since. His grandson, the 7th Earl, was racing manager to Queen Elizabeth II from 1969 until his death in 2001.


title: George Herbert, 5th Earl of Carnarvon

text: Lord Carnarvon was a keen motor car driver. In 1903, he suffered a serious motoring accident near Bad Schwalbach in Germany, after which he never fully recovered his health. After a lengthy convalescence, his doctors advised that he winter out of England, and from then on he and Lady Carnarvon often spent their winters in Egypt. Here, he became an enthusiastic amateur Egyptologist, and also bought Egyptian antiquities for their collection in England.


title: George Herbert, 5th Earl of Carnarvon

text: In 1907, Lord Carnarvon undertook to sponsor the excavation of nobles' tombs in Deir el-Bahri, near Thebes. He employed Howard Carter to undertake the work, on the recommendation of Gaston Maspero, director of the Egyptian Antiquities Department. In 1912, Carnarvon published "Five Years’ Exploration at Thebes", co-written with Carter, describing their excavations.


title: George Herbert, 5th Earl of Carnarvon

text: In 1914, Lord Carnarvon received the concession to dig in the Valley of the Kings, replacing Theodore Davis who had resigned. Carter again led the work, undertaking a systematic search of the Valley for any tombs missed by previous expeditions, in particular that of the Pharaoh Tutankhamun. Excavations were interrupted during the First World War, but resumed in late 1917. By 1922, little of significance had been found and Lord Carnarvon decided this would be the final year he would fund the work. However, on 4 November 1922, Carter was able to send a telegram to Lord Carnarvon, in England, saying: "At last we have made wonderful discovery in Valley; a magnificent tomb with seals intact; re-covered same for your arrival; congratulations".


title: George Herbert, 5th Earl of Carnarvon

text: Lord Carnarvon, accompanied by his daughter Lady Evelyn Herbert, returned to Egypt, arriving at Luxor on 23 November 1922. Both were present the next day when the full extent of the stairway to the tomb was cleared and a seal containing Tutankhamun's cartouche found on the outer doorway. This door was removed and the rubble filled corridor behind cleared, revealing the door of the tomb itself. Carnarvon was also present when, on 26 November, Carter made a tiny breach in the top left hand corner of this doorway, enabling him to peer in by the light of a candle. When Carnarvon asked, "Can you see anything?" Carter replied "Yes, wonderful things!”. The tomb was then secured, to be entered in the presence of an official of the Egyptian Department of Antiquities the next day. However that night, Carter, his assistant Arthur Callender, Carnarvon and Lady Evelyn apparently made an unauthorised visit, becoming the first people in modern times to enter the tomb. Some sources suggest that the group also entered the inner burial chamber. In this account, a small hole was found in the chamber's sealed doorway and Carter, Carnarvon and Lady Evelyn crawled through.


title: George Herbert, 5th Earl of Carnarvon

text: The next morning, the 27 November, saw an inspection of the tomb in the presence of an Egyptian official. Callender rigged up electric lighting, illuminating a vast haul of items, including gilded couches, chests, thrones, and shrines. They also saw evidence of two further chambers, including the sealed doorway to the inner burial chamber, guarded by two life-size statues of Tutankhamun. In spite of evidence of break-ins in ancient times, the tomb was virtually intact, and would ultimately be found to contain over 5,000 items.


title: George Herbert, 5th Earl of Carnarvon

text: On 29 November, the tomb was officially opened in the presence of a number of invited dignitaries and Egyptian officials.


title: George Herbert, 5th Earl of Carnarvon

text: Lord Carnarvon travelled to England in December 1922, returning in January 1923 to be present at the official opening of the inner burial chamber on 16 February. Before the opening Carnarvon had sold the exclusive newspaper rights to report the excavation to "The Times". While this helped finance the work, it created resentment both from other newspapers and from the Egyptian authorities, whose own press was also excluded.


title: George Herbert, 5th Earl of Carnarvon

text: Towards the end of February, a rift with Carter, probably caused by a disagreement on how to manage the supervising Egyptian authorities, temporarily closed excavation. Work recommenced in early March after Carnarvon apologised. This was to be Lord Carnarvon's last significant involvement in the excavation project, he falling seriously ill shortly afterwards.


title: George Herbert, 5th Earl of Carnarvon

text: On 19 March 1923, Carnarvon suffered a severe mosquito bite which became infected by a razor cut. On 5 April, he died in the Continental-Savoy Hotel in Cairo caused, according to contemporaneous reports, by blood poisoning progressing to pneumonia. On 14 April, Lady Almina Carnarvon moved Lord Carnarvon's remains to England. His tomb appropriately reflects his archaeological interest, nestled within an ancient hill fort overlooking his family seat at Beacon Hill, Burghclere, Hampshire. Carnarvon was survived by his wife Almina, who subsequently remarried, and their two children.


title: George Herbert, 5th Earl of Carnarvon

text: After Lord Carnarvon's death, Carter continued the excavation. The Egyptian government however took ownership of the tomb's contents, and in April 1930 provided a grant of £35,000 to his heirs (equivalent to £ in pounds).


title: George Herbert, 5th Earl of Carnarvon

text: Encouraged by newspaper speculation, the "Curse of Tutankhamun," or, the "Mummy's Curse," entered popular culture and was fuelled further by author Sir Arthur Conan Doyle's suggestion that Carnarvon's death had been caused by "elementals" created by Tutankhamun's priests to guard the royal tomb. Howard Carter dismissed such speculation as , commenting that "the sentiment of the Egyptologist ... is not one of fear, but of respect and awe ... entirely opposed to foolish superstitions".


title: George Herbert, 5th Earl of Carnarvon

text: Some of the stories were clearly fabricated, including that a curse had been found inscribed on the wall of the tomb, while a study showed that those involved in the tomb's discovery and clearance did not, on average, have a lower than average life expectancy. A study of documents and scholarly sources led "The Lancet" to conclude as unlikely that Carnarvon's death had anything to do with Tutankhamun's tomb, refuting another theory that exposure to toxic fungi (mycotoxins) had contributed to his demise. Although he was one of those to enter the tomb on several occasions, none of the other 25 from Europe were affected in the months after their entries. The cause of Carnarvon's death was reported as "'pneumonia supervening on [facial] erysipelas,' (a streptococcal infection of the skin and underlying soft tissue). Pneumonia was thought to be only one of various complications, arising from the progressively invasive infection, that eventually resulted in multiorgan failure." The Earl had been "prone to frequent and severe lung infections" according to "The Lancet" and there had been a "general belief ... that one acute attack of bronchitis could have killed him. In such a debilitated state, the Earl's immune system was easily overwhelmed by erysipelas".


title: Gigguk

text: Garnt Maneetapho (born 31 May 1990), better known as Gigguk, is a Thai-British YouTuber and podcaster who is known for his comedic rants and reviews on anime and otaku culture. He is affiliated with the Kadokawa-backed agency GeeXPlus.


title: Gigguk

text: He used the online pseudonym "Gigguk," a combination of his family nickname "Gigg" and UK, his place of residence, and called his channel The Anime Zone. In 2012, he was a producer in abridging popular anime, starting with "Evangelion" into the "EvAbridged" series.


title: Gigguk

text: During 2017, Maneetapho retired the Anime Zone moniker for his channel, using just Gigguk. In February 2018, Maneetapho presented the Best Comedy award at the 2nd Crunchyroll Anime Awards, alongside YouTuber LilyPichu, at the Ricardo Montalbán Theatre in Los Angeles.


title: Gigguk

text: In November 2019, Maneetapho, along with YouTuber Sydney Poniewaz (Sydsnap), moved to northwestern Tokyo, Japan to begin working as an influencer for GeeXPlus. The effort was to help promote/introduce anime and Japanese culture to the rest of the world through his content.


title: Gigguk

text: In February 2020, Maneetapho joined alongside Connor Colquhoun (CDawgVA) and Joey Bizinger (The Anime Man) in creating and hosting a weekly audio and video podcast called "Trash Taste", where they discuss anime, manga, otaku culture, and their experiences while living in Japan. The first episode was released on 5 June 2020 with new episodes available on YouTube and major podcast platforms every Friday. In August 2020 Maneetapho participated in a chess tournament hosted by Chess.com for anime YouTubers. Reaching the finals, Maneetapho beat fellow "Trash Taste" co-host Connor Colquhoun. In July 2021, Maneetapho successfully defended his title in "Tournament Arc 2", hosted again by Chess.com.


title: Gigguk

text: Maneetapho's parents are from Thailand, and he was born and raised in the United Kingdom. He is a practicing Buddhist, and has served as a monk twice in his life. Maneetapho became engaged to fellow YouTuber Sydney Poniewaz on 12 April 2019. On 5 June 2022, they were married at a ceremony in the UK.


title: Gabby's Dollhouse

text: Gabby's Dollhouse is an American live-action/animated/interactive preschool series created by Traci Paige Johnson and Jennifer Twomey for Netflix. In the series, which first aired on January 5, 2021, Gabby (voiced by Laila Lockhart Kraner) and her cat friends go on adventures within her dollhouse.


title: Gabby's Dollhouse

text: The first episode was released as a sneak peek on YouTube on August 22, 2020, while the series itself was released on January 5, 2021. The second season premiered on August 10, 2021, while the third season premiered on October 19, 2021. The fourth season premiered on February 1, 2022, the fifth season premiered on July 25, 2022, and the sixth season premiered on November 1, 2022. The series was later renewed for a seventh season.


title: Gabby's Dollhouse

text: "Gabby’s Dollhouse" made its linear debut on Cartoonito Latin America on April 18, 2022 and on Tiny Pop in the UK on October 17, 2022.


title: Gabby's Dollhouse

text: Like "Blue's Clues" and most interactive preschool shows, "Gabby's Dollhouse" has built-in silences designed to encourage audience participation.


title: Gabby's Dollhouse

text: Each episode begins with the live-action Gabby playing in her bedroom. She then unboxes a miniature that is the catalyst for an adventure inside the animated world of her dollhouse. Gabby puts on her cat ears headband and shrinks down with her stuffed toy, Pandy Paws, who comes alive to surprise Gabby with a “hug attack.” Common rituals may involve an encounter with CatRat, who often randomly appears in one of the rooms in the dollhouse.


title: Gabby's Dollhouse

text: The dollhouse has seven key cat-themed rooms where Gabby’s adventures take place with the various Gabby Cats:


title: Gabby's Dollhouse

text: At the end of each episode is a “Cat of the Day” segment, where one of the Gabby Cats is selected to guide the viewer one-on-one in crafting, cooking, or singing.


title: Gabby's Dollhouse

text: "Gabby's Dollhouse: Cat-tastic Dance Along" was released on DVD and digital download on February 1, 2022 by Universal Pictures Home Entertainment (through Studio Distribution Services LLC). It features 20 songs from the show with a group of kids dancing which is inspired by TikTok's sensation of dance challenges. The DVD and digital download also feature meditation sessions each one feature a Gabby Cat going into mindfulness mode. In United States. and released on DVD and digital download on TBA 2023 by Mediumrare Entertainment in United Kingdom and Ireland.


title: Gabby's Dollhouse

text: The show was nominated for a Kidscreen award in 2021 and released a series of show-themed toys for the 2021 holiday season.


title: Galvanic cell

text: A galvanic cell or voltaic cell, named after the scientists Luigi Galvani and Alessandro Volta, respectively, is an electrochemical cell in which an electric current is generated from spontaneous Oxidation-Reduction reactions. A common apparatus generally consists of two different metals, each immersed in separate beakers containing their respective metal ions in solution that are connected by a salt bridge or separated by a porous membrane.


title: Galvanic cell

text: Volta was the inventor of the voltaic pile, the first electrical battery. In common usage, the word "battery" has come to include a single galvanic cell, but a battery properly consists of multiple cells.


title: Galvanic cell

text: In 1780, Luigi Galvani discovered that when two different metals (e.g., copper and zinc) are in contact and then both are touched at the same time to two different parts of a muscle of a frog leg, to close the circuit, the frog's leg contracts. He called this "animal electricity". The frog's leg, as well as being a detector of electrical current, was also the electrolyte (to use the language of modern chemistry).


title: Galvanic cell

text: A year after Galvani published his work (1790), Alessandro Volta showed that the frog was not necessary, using instead a force-based detector and brine-soaked paper (as electrolyte). (Earlier Volta had established the law of capacitance with force-based detectors). In 1799 Volta invented the voltaic pile, which is a stack of galvanic cells each consisting of a metal disk, an electrolyte layer, and a disk of a different metal. He built it entirely out of non-biological material to challenge Galvani's (and the later experimenter Leopoldo Nobili)'s animal electricity theory in favor of his own metal-metal contact electricity theory. Carlo Matteucci in his turn constructed a battery entirely out of biological material in answer to Volta. Volta's contact electricity view characterized each electrode with a number that we would now call the work function of the electrode. This view ignored the chemical reactions at the electrode-electrolyte interfaces, which include H formation on the more noble metal in Volta's pile.


title: Galvanic cell

text: Although Volta did not understand the operation of the battery or the galvanic cell, these discoveries paved the way for electrical batteries; Volta's cell was named an IEEE Milestone in 1999.


title: Galvanic cell

text: Some forty years later, Faraday (see Faraday's laws of electrolysis) showed that the galvanic cell—now often called a voltaic cell—was chemical in nature. Faraday introduced new terminology to the language of chemistry: electrode (cathode and anode), electrolyte, and ion (cation and anion). Thus Galvani incorrectly thought the source of electricity (or source of electromotive force (emf), or seat of emf) was in the animal, Volta incorrectly thought it was in the physical properties of the isolated electrodes, but Faraday correctly identified the source of emf as the chemical reactions at the two electrode-electrolyte interfaces. The authoritative work on the intellectual history of the voltaic cell remains that by Ostwald.


title: Galvanic cell

text: It was suggested by Wilhelm König in 1940 that the object known as the Baghdad battery might represent galvanic cell technology from ancient Parthia. Replicas filled with citric acid or grape juice have been shown to produce a voltage. However, it is far from certain that this was its purpose—other scholars have pointed out that it is very similar to vessels known to have been used for storing parchment scrolls.


title: Galvanic cell

text: Galvanic cells are extensions of spontaneous redox reactions, but have been merely designed to harness the energy produced from said reaction. For example, when one immerses a strip of zinc metal (Zn) in an aqueous solution of copper sulfate (CuSO), dark-colored solid deposits will collect on the surface of the zinc metal and the blue color characteristic of the Cu ion disappears from the solution. The depositions on the surface of the zinc metal consist of copper metal, and the solution now contains zinc ions. This reaction is represented by


title: Galvanic cell

text: In this redox reaction, Zn is oxidized to Zn and Cu is reduced to Cu. When electrons are transferred directly from Zn to Cu , the enthalpy of reaction is lost to the surroundings as heat. However, the same reaction can be carried out in a galvanic cell, allowing some of the chemical energy released to be converted into electrical energy. In its simplest form, a half-cell consists of a solid metal (called an electrode) that is submerged in a solution; the solution contains cations (+) of the electrode metal and anions (−) to balance the charge of the cations. The full cell consists of two half-cells, usually connected by a semi-permeable membrane or by a salt bridge that prevents the ions of the more noble metal from plating out at the other electrode.


title: Galvanic cell

text: A specific example is the Daniell cell (see figure), with a zinc (Zn) half-cell containing a solution of ZnSO (zinc sulfate) and a copper (Cu) half-cell containing a solution of CuSO (copper sulfate). A salt bridge is used here to complete the electric circuit.


title: Galvanic cell

text: If an external electrical conductor connects the copper and zinc electrodes, zinc from the zinc electrode dissolves into the solution as Zn ions (oxidation), releasing electrons that enter the external conductor. To compensate for the increased zinc ion concentration, via the salt bridge zinc ions leave and anions enter the zinc half-cell. In the copper half-cell, the copper ions plate onto the copper electrode (reduction), taking up electrons that leave the external conductor. Since the Cu ions (cations) plate onto the copper electrode, the latter is called the cathode. Correspondingly the zinc electrode is the anode. The electrochemical reaction is


title: Galvanic cell

text: This is the same reaction as given in the previous example. In addition, electrons flow through the external conductor, which is the primary application of the galvanic cell.


title: Galvanic cell

text: As discussed under cell voltage, the electromotive force of the cell is the difference of the half-cell potentials, a measure of the relative ease of dissolution of the two electrodes into the electrolyte. The emf depends on both the electrodes and on the electrolyte, an indication that the emf is chemical in nature.


title: Galvanic cell

text: A half-cell contains a metal in two oxidation states. Inside an isolated half-cell, there is an oxidation-reduction (redox) reaction that is in chemical equilibrium, a condition written symbolically as follows (here, "M" represents a metal cation, an atom that has a charge imbalance due to the loss of ""n"" electrons):


title: Galvanic cell

text: A galvanic cell consists of two half-cells, such that the electrode of one half-cell is composed of metal A, and the electrode of the other half-cell is composed of metal B; the redox reactions for the two separate half-cells are thus:


title: Galvanic cell

text: In other words, the metal atoms of one half-cell are oxidized while the metal cations of the other half-cell are reduced. By separating the metals in two half-cells, their reaction can be controlled in a way that forces transfer of electrons through the external circuit where they can do useful work.


title: Galvanic cell

text: Galvanic cells, by their nature, produce direct current. The Weston cell has an anode composed of cadmium mercury amalgam, and a cathode composed of pure mercury. The electrolyte is a (saturated) solution of cadmium sulfate. The depolarizer is a paste of mercurous sulfate. When the electrolyte solution is saturated, the voltage of the cell is very reproducible; hence, in 1911, it was adopted as an international standard for voltage.


title: Galvanic cell

text: A battery is a set of galvanic cells that are connected together to form a single source of voltage. For instance, a typical 12V lead–acid battery has six galvanic cells connected in series with the anodes composed of lead and cathodes composed of lead dioxide, both immersed in sulfuric acid. Large battery rooms, for instance in a telephone exchange providing central office power to user's telephones, may have cells connected in both series and parallel.


title: Galvanic cell

text: The voltage (electromotive force "E") produced by a galvanic cell can be estimated from the standard Gibbs free energy change in the electrochemical reaction according to:


title: Galvanic cell

text: where "ν" is the number of electrons transferred in the balanced half reactions, and "F" is Faraday's constant. However, it can be determined more conveniently by the use of a standard potential table for the two half cells involved. The first step is to identify the two metals and their ions reacting in the cell. Then one looks up the standard electrode potential, "E", in volts, for each of the two half reactions. The standard potential of the cell is equal to the more positive "E" value minus the more negative "E" value.


title: Galvanic cell

text: For example, in the figure above the solutions are CuSO and ZnSO. Each solution has a corresponding metal strip in it, and a salt bridge or porous disk connecting the two solutions and allowing ions to flow freely between the copper and zinc solutions. To calculate the standard potential one looks up copper and zinc's half reactions and finds:


title: Galvanic cell

text: The standard potential for the reaction is then +0.34 V − (−0.76 V) = 1.10 V. The polarity of the cell is determined as follows. Zinc metal is more strongly reducing than copper metal because the standard (reduction) potential for zinc is more negative than that of copper. Thus, zinc metal will lose electrons to copper ions and develop a positive electrical charge. The equilibrium constant, "K", for the cell is given by:


title: Galvanic cell

text: where "F" is the Faraday constant, "R" is the gas constant and "T" is the temperature in kelvins. For the Daniell cell "K" is approximately equal to . Thus, at equilibrium, a few electrons are transferred, enough to cause the electrodes to be charged.


title: Galvanic cell

text: Actual half-cell potentials must be calculated by using the Nernst equation as the solutes are unlikely to be in their standard states:


title: Galvanic cell

text: where "Q" is the reaction quotient. When the charges of the ions in the reaction are equal, this simplifies to:


title: Galvanic cell

text: where {M} is the activity of the metal ion in solution. In practice concentration in mol/L is used in place of activity. The metal electrode is in its standard state so by definition has unit activity. The potential of the whole cell is obtained as the difference between the potentials for the two half-cells, so it depends on the concentrations of both dissolved metal ions. If the concentrations are the same, formula_5and the Nernst equation is not needed under the conditions assumed here.


title: Galvanic cell

text: The value of 2.303 is , so at 25 °C (298.15 K) the half-cell potential will change by only 0.05918 V/"ν" if the concentration of a metal ion is increased or decreased by a factor of 10.


title: Galvanic cell

text: These calculations are based on the assumption that all chemical reactions are in equilibrium. When a current flows in the circuit, equilibrium conditions are not achieved and the cell voltage will usually be reduced by various mechanisms, such as the development of overpotentials. Also, since chemical reactions occur when the cell is producing power, the electrolyte concentrations change and the cell voltage is reduced. A consequence of the temperature dependency of standard potentials is that the voltage produced by a galvanic cell is also temperature dependent.


title: Galvanic cell

text: Galvanic corrosion is the electrochemical erosion of metals. Corrosion occurs when two dissimilar metals are in contact with each other in the presence of an electrolyte, such as salt water. This forms a galvanic cell, with hydrogen gas forming on the more noble (less active) metal. The resulting electrochemical potential then develops an electric current that electrolytically dissolves the less noble material. A concentration cell can be formed if the same metal is exposed to two different concentrations of electrolyte.


title: Adaptive immune system

text: The adaptive immune system, also known as the acquired immune system, is a subsystem of the immune system that is composed of specialized, systemic cells and processes that eliminate pathogens or prevent their growth. The acquired immune system is one of the two main immunity strategies found in vertebrates (the other being the innate immune system).


title: Adaptive immune system

text: Like the innate system, the adaptive immune system includes both humoral immunity components and cell-mediated immunity components and destroys invading pathogens. Unlike the innate immune system, which is pre-programmed to react to common broad categories of pathogen, the adaptive immune system is highly specific to each particular pathogen the body has encountered.


title: Adaptive immune system

text: Adaptive immunity creates immunological memory after an initial response to a specific pathogen, and leads to an enhanced response to future encounters with that pathogen. Antibodies are a critical part of the adaptive immune system. Adaptive immunity can provide long-lasting protection, sometimes for the person's entire lifetime. For example, someone who recovers from measles is now protected against measles for their lifetime; in other cases it does not provide lifetime protection, as with chickenpox. This process of adaptive immunity is the basis of vaccination.


title: Adaptive immune system

text: The cells that carry out the adaptive immune response are white blood cells known as lymphocytes. B cells and T cells, two different types of lymphocytes, carry out the main activities: antibody responses, and cell-mediated immune response. In antibody responses, B cells are activated to secrete antibodies, which are proteins also known as immunoglobulins. Antibodies travel through the bloodstream and bind to the foreign antigen causing it to inactivate, which does not allow the antigen to bind to the host. Antigens are any substances that elicit the adaptive immune response. Sometimes the adaptive system is unable to distinguish harmful from harmless foreign molecules; the effects of this may be hayfever, asthma, or any other allergy.


title: Adaptive immune system

text: In adaptive immunity, pathogen-specific receptors are "acquired" during the lifetime of the organism (whereas in innate immunity pathogen-specific receptors are already encoded in the genome). This acquired response is called "adaptive" because it prepares the body's immune system for future challenges (though it can actually also be maladaptive when it results in allergies or autoimmunity).


title: Adaptive immune system

text: The system is highly adaptable because of two factors. First, somatic hypermutation is a process of accelerated random genetic mutations in the antibody-coding genes, which allows antibodies with novel specificity to be created. Second, V(D)J recombination randomly selects one variable (V), one diversity (D), and one joining (J) region for genetic recombination and discards the rest, which produces a highly unique combination of antigen-receptor gene segments in each lymphocyte. This mechanism allows a small number of genetic segments to generate a vast number of different antigen receptors, which are then uniquely expressed on each individual lymphocyte. Since the gene rearrangement leads to an irreversible change in the DNA of each cell, all progeny (offspring) of that cell inherit genes that encode the same receptor specificity, including the memory B cells and memory T cells that are the keys to long-lived specific immunity.


title: Adaptive immune system

text: The term "adaptive" was first used by Robert Good in reference to antibody responses in frogs as a synonym for "acquired immune response" in 1964. Good acknowledged he used the terms as synonyms but explained only that he preferred to use the term "adaptive". He might have been thinking of the then not implausible theory of antibody formation in which antibodies were plastic and could adapt themselves to the molecular shape of antigens, and/or to the concept of "adaptive enzymes" as described by Monod in bacteria, that is, enzymes whose expression could be induced by their substrates. The phrase was used almost exclusively by Good and his students and a few other immunologists working with marginal organisms until the 1990s when it became widely used in tandem with the term "innate immunity" which became a popular subject after the discovery of the Toll receptor system in "Drosophila", a previously marginal organism for the study of immunology. The term "adaptive" as used in immunology is problematic as acquired immune responses can be both adaptive and maladaptive in the physiological sense. Indeed, both acquired and innate immune responses can be both adaptive and maladaptive in the evolutionary sense. Most textbooks today, following the early use by Janeway, use "adaptive" almost exclusively and noting in glossaries that the term is synonymous with "acquired".


title: Adaptive immune system

text: The classic sense of "acquired immunity" came to mean, since Tonegawa's discovery, "antigen-specific immunity mediated by somatic gene rearrangements that create clone-defining antigen receptors". In the last decade, the term "adaptive" has been increasingly applied to another class of immune response not so-far associated with somatic gene rearrangements. These include expansion of natural killer (NK) cells with so-far unexplained specificity for antigens, expansion of NK cells expressing germ-line encoded receptors, and activation of other innate immune cells to an activated state that confers a short-term "immune memory". In this sense, "adaptive immunity" more closely resembles the concept of "activated state" or "heterostasis", thus returning in sense to the physiological sense of "adaptation" to environmental changes.


title: Adaptive immune system

text: Acquired immunity is triggered in vertebrates when a pathogen evades the innate immune system and (1) generates a threshold level of antigen and (2) generates "stranger" or "danger" signals activating dendritic cells.


title: Adaptive immune system

text: T and B lymphocytes are the cells of the adaptive immune system. The human body has about 2 trillion lymphocytes, which are 20–40% of white blood cells; their total mass is about the same as the brain or liver. The peripheral bloodstream contains only 2% of all circulating lymphocytes; the other 98% move within tissues and the lymphatic system, which includes the lymph nodes and spleen. In humans, approximately 1–2% of the lymphocyte pool recirculates each hour to increase the opportunity for the cells to encounter the specific pathogen and antigen that they react to.


title: Adaptive immune system

text: B cells and T cells are derived from the same multipotent hematopoietic stem cells, and look identical to one another until after they are activated. B cells play a large role in the humoral immune response, whereas T cells are intimately involved in cell-mediated immune responses. In all vertebrates except Agnatha, B cells and T cells are produced by stem cells in the bone marrow. T cell progenitors then migrate from the bone marrow to the thymus, where they develop further.


title: Adaptive immune system

text: In an adult animal, the peripheral lymphoid organs contain a mixture of B and T cells in at least three stages of differentiation:


title: Adaptive immune system

text: Acquired immunity relies on the capacity of immune cells to distinguish between the body's own cells and unwanted invaders.


title: Adaptive immune system

text: The host's cells express "self" antigens. These antigens are different from those on the surface of bacteria or on the surface of virus-infected host cells ("non-self" or "foreign" antigens). The acquired immune response is triggered by recognizing foreign antigen in the cellular context of an activated dendritic cell.


title: Adaptive immune system

text: With the exception of non-nucleated cells (including erythrocytes), all cells are capable of presenting antigen through the function of major histocompatibility complex (MHC) molecules. Some cells are specially equipped to present antigen, and to prime naive T cells. Dendritic cells, B-cells, and macrophages are equipped with special "co-stimulatory" ligands recognized by co-stimulatory receptors on T cells, and are termed professional antigen-presenting cells (APCs).


title: Adaptive immune system

text: Several T cells subgroups can be activated by professional APCs, and each type of T cell is specially equipped to deal with each unique toxin or microbial pathogen. The type of T cell activated, and the type of response generated, depends, in part, on the context in which the APC first encountered the antigen.


title: Adaptive immune system

text: Dendritic cells engulf exogenous pathogens, such as bacteria, parasites or toxins in the tissues and then migrate, via chemotactic signals, to the T cell-enriched lymph nodes. During migration, dendritic cells undergo a process of maturation in which they lose most of their ability to engulf other pathogens, and develop an ability to communicate with T-cells. The dendritic cell uses enzymes to chop the pathogen into smaller pieces, called antigens. In the lymph node, the dendritic cell displays these non-self antigens on its surface by coupling them to a receptor called the major histocompatibility complex, or MHC (also known in humans as human leukocyte antigen (HLA)). This MHC-antigen complex is recognized by T-cells passing through the lymph node. Exogenous antigens are usually displayed on MHC class II molecules, which activate CD4+T helper cells.


title: Adaptive immune system

text: Endogenous antigens are produced by intracellular bacteria and viruses replicating within a host cell. The host cell uses enzymes to digest virally associated proteins and displays these pieces on its surface to T-cells by coupling them to MHC. Endogenous antigens are typically displayed on MHC class I molecules, and activate CD8+ cytotoxic T-cells. With the exception of non-nucleated cells (including erythrocytes), MHC class I is expressed by all host cells.


title: Adaptive immune system

text: Cytotoxic T cells (also known as TC, killer T cell, or cytotoxic T-lymphocyte (CTL)) are a sub-group of T cells that induce the death of cells that are infected with viruses (and other pathogens), or are otherwise damaged or dysfunctional.


title: Adaptive immune system

text: Naive cytotoxic T cells are activated when their T-cell receptor (TCR) strongly interacts with a peptide-bound MHC class I molecule. This affinity depends on the type and orientation of the antigen/MHC complex, and is what keeps the CTL and infected cell bound together. Once activated, the CTL undergoes a process called clonal selection, in which it gains functions and divides rapidly to produce an army of "armed" effector cells. Activated CTL then travels throughout the body searching for cells that bear that unique MHC Class I + peptide.


title: Adaptive immune system

text: When exposed to these infected or dysfunctional somatic cells, effector CTL release perforin and granulysin: cytotoxins that form pores in the target cell's plasma membrane, allowing ions and water to flow into the infected cell, and causing it to burst or lyse. CTL release granzyme, a serine protease encapsulated in a granule that enters cells via pores to induce apoptosis (cell death). To limit extensive tissue damage during an infection, CTL activation is tightly controlled and in general requires a very strong MHC/antigen activation signal, or additional activation signals provided by "helper" T-cells (see below).


title: Adaptive immune system

text: On resolution of the infection, most effector cells die and phagocytes clear them away—but a few of these cells remain as memory cells. On a later encounter with the same antigen, these memory cells quickly differentiate into effector cells, dramatically shortening the time required to mount an effective response.


title: Adaptive immune system

text: CD4+ lymphocytes, also called "helper" T cells, are immune response mediators, and play an important role in establishing and maximizing the capabilities of the acquired immune response. These cells have no cytotoxic or phagocytic activity; and cannot kill infected cells or clear pathogens, but, in essence "manage" the immune response, by directing other cells to perform these tasks.


title: Adaptive immune system

text: Helper T cells express T cell receptors (TCR) that recognize antigen bound to Class II MHC molecules. The activation of a naive helper T-cell causes it to release cytokines, which influences the activity of many cell types, including the APC (Antigen-Presenting Cell) that activated it. Helper T-cells require a much milder activation stimulus than cytotoxic T cells. Helper T cells can provide extra signals that "help" activate cytotoxic cells.


title: Adaptive immune system

text: Classically, two types of effector CD4 T helper cell responses can be induced by a professional APC, designated Th1 and Th2, each designed to eliminate different types of pathogens. The factors that dictate whether an infection triggers a Th1 or Th2 type response are not fully understood, but the response generated does play an important role in the clearance of different pathogens.


title: Adaptive immune system

text: The Th1 response is characterized by the production of Interferon-gamma, which activates the bactericidal activities of macrophages, and induces B cells to make opsonizing (marking for phagocytosis) and complement-fixing antibodies, and leads to "cell-mediated immunity". In general, Th1 responses are more effective against intracellular pathogens (viruses and bacteria that are inside host cells).


title: Adaptive immune system

text: The Th2 response is characterized by the release of Interleukin 5, which induces eosinophils in the clearance of parasites. Th2 also produce Interleukin 4, which facilitates B cell isotype switching. In general, Th2 responses are more effective against extracellular bacteria, parasites including helminths and toxins. Like cytotoxic T cells, most of the CD4 helper cells die on resolution of infection, with a few remaining as CD4 memory cells.


title: Adaptive immune system

text: Increasingly, there is strong evidence from mouse and human-based scientific studies of a broader diversity in CD4 effector T helper cell subsets. Regulatory T (Treg) cells, have been identified as important negative regulators of adaptive immunity as they limit and suppress the immune system to control aberrant immune responses to self-antigens; an important mechanism in controlling the development of autoimmune diseases. Follicular helper T (Tfh) cells are another distinct population of effector CD4 T cells that develop from naive T cells post-antigen activation. Tfh cells are specialized in helping B cell humoral immunity as they are uniquely capable of migrating to follicular B cells in secondary lymphoid organs and provide them positive paracrine signals to enable the generation and recall production of high-quality affinity-matured antibodies. Similar to Tregs, Tfh cells also play a role in immunological tolerance as an abnormal expansion of Tfh cell numbers can lead to unrestricted autoreactive antibody production causing severe systemic autoimmune disorders.


title: Adaptive immune system

text: The relevance of CD4 T helper cells is highlighted during an HIV infection. HIV is able to subvert the immune system by specifically attacking the CD4 T cells, precisely the cells that could drive the clearance of the virus, but also the cells that drive immunity against all other pathogens encountered during an organism's lifetime.


title: Adaptive immune system

text: Gamma delta T cells (γδ T cells) possess an alternative T cell receptor (TCR) as opposed to CD4+ and CD8+ αβ T cells and share characteristics of helper T cells, cytotoxic T cells and natural killer cells. Like other 'unconventional' T cell subsets bearing invariant TCRs, such as CD1d-restricted natural killer T cells, γδ T cells exhibit characteristics that place them at the border between innate and acquired immunity. On one hand, γδ T cells may be considered a component of adaptive immunity in that they rearrange TCR genes via V(D)J recombination, which also produces junctional diversity, and develop a memory phenotype. On the other hand, however, the various subsets may also be considered part of the innate immune system where a restricted TCR or NK receptors may be used as a pattern recognition receptor. For example, according to this paradigm, large numbers of Vγ9/Vδ2 T cells respond within hours to common molecules produced by microbes, and highly restricted intraepithelial Vδ1 T cells respond to stressed epithelial cells.


title: Adaptive immune system

text: B Cells are the major cells involved in the creation of antibodies that circulate in blood plasma and lymph, known as humoral immunity. Antibodies (also known as immunoglobulin, Ig), are large Y-shaped proteins used by the immune system to identify and neutralize foreign objects. In mammals, there are five types of antibody: IgA, IgD, IgE, IgG, and IgM, differing in biological properties; each has evolved to handle different kinds of antigens. Upon activation, B cells produce antibodies, each of which recognize a unique antigen, and neutralizing specific pathogens.


title: Adaptive immune system

text: Like the T cell, B cells express a unique B cell receptor (BCR), in this case, a membrane-bound antibody molecule. All the BCR of any one clone of B cells recognizes and binds to only one particular antigen. A critical difference between B cells and T cells is how each cell "sees" an antigen. T cells recognize their cognate antigen in a processed form – as a peptide in the context of an MHC molecule, whereas B cells recognize antigens in their native form. Once a B cell encounters its cognate (or specific) antigen (and receives additional signals from a helper T cell (predominately Th2 type)), it further differentiates into an effector cell, known as a plasma cell.


title: Adaptive immune system

text: Plasma cells are short-lived cells (2–3 days) that secrete antibodies. These antibodies bind to antigens, making them easier targets for phagocytes, and trigger the complement cascade. About 10% of plasma cells survive to become long-lived antigen-specific memory B cells. Already primed to produce specific antibodies, these cells can be called upon to respond quickly if the same pathogen re-infects the host, while the host experiences few, if any, symptoms.


title: Adaptive immune system

text: Primitive jawless vertebrates, such as the lamprey and hagfish, have an adaptive immune system that shows 3 different cell lineages, each sharing a common origin with B cells, αβ T cells, and innate-like γΔ T cells. Instead of the classical antibodies and T cell receptors, these animals possess a large array of molecules called variable lymphocyte receptors (VLRs for short) that, like the antigen receptors of jawed vertebrates, are produced from only a small number (one or two) of genes. These molecules are believed to bind pathogenic antigens in a similar way to antibodies, and with the same degree of specificity.


title: Adaptive immune system

text: For a long time it was thought that insects and other invertebrates possess only innate immune system. However, in recent years some of the basic hallmarks of adaptive immunity have been discovered in insects. Those traits are immune memory and specificity. Although the hallmarks are present the mechanisms are different from those in vertebrates.


title: Adaptive immune system

text: Immune memory in insects was discovered through the phenomenon of priming. When insects are exposed to non-lethal dose or heat killed bacteria they are able to develop a memory of that infection that allows them to withstand otherwise lethal dose of the same bacteria they were exposed to before. Unlike in vertebrates, insects do not possess cells specific for adaptive immunity. Instead those mechanisms are mediated by hemocytes. Hemocytes function similarly to phagocytes and after priming they are able to more effectively recognize and engulf the pathogen. It was also shown that it is possible to transfer the memory into offspring. For example, in honeybees if the queen is infected with bacteria then the newly born workers have enhanced abilities in fighting with the same bacteria. Other experimental model based on red flour beetle also showed pathogen specific primed memory transfer into offspring from both mothers and fathers.


title: Adaptive immune system

text: Most commonly accepted theory of the specificity is based on "Dscam" gene. "Dscam" gene also known as Down syndrome cell adhesive molecule is a gene that contains 3 variable Ig domains. Those domains can be alternatively spliced reaching high numbers of variations. It was shown that after exposure to different pathogens there are different splice forms of dscam produced. After the animals with different splice forms are exposed to the same pathogen only the individuals with the splice form specific for that pathogen survive.


title: Adaptive immune system

text: Other mechanisms supporting the specificity of insect immunity is RNA interference (RNAi). RNAi is a form of antiviral immunity with high specificity. It has several different pathways that all end with the virus being unable to replicate. One of the pathways is siRNA in which long double stranded RNA is cut into pieces that serve as templates for protein complex Ago2-RISC that finds and degrades complementary RNA of the virus. MiRNA pathway in cytoplasm binds to Ago1-RISC complex and functions as a template for viral RNA degradation. Last one is piRNA where small RNA binds to the Piwi protein family and controls transposones and other mobile elements. Despite the research the exact mechanisms responsible for immune priming and specificity in insects are not well described.