title: Pepin of Herstal

text: Pepin's statesmanship was notable for the further diminution of Merovingian royal authority, and for the acceptance of the undisputed right to rule for his family. Therefore, Pepin was able to name as heir his grandson Theudoald. But this was not accepted by his powerful son Charles Martel, leading to a civil war after his death in which the latter emerged victorious.


title: Pepin of Herstal

text: Pepin, sometimes called Pepin II and Pepin the Middle, was the grandson and namesake of Pepin I the Elder through the marriage of Pepin I's daughter Begga to Ansegisel. He was also the grandfather of Pepin the Short and great-grandfather of Charlemagne. That marriage united the two houses of the Pippinids and the Arnulfings which created what would be called the Carolingian dynasty. Pepin II was probably born in Herstal (Héristal), modern Belgium (where his centre of power lay), whence his byname (sometimes "of Heristal").


title: Pepin of Herstal

text: As mayor of Austrasia, Pepin and Martin, the duke of Laon, fought the Neustrian mayor Ebroin, who had designs on all Francia. Ebroin defeated the Austrasians in the Battle of Lucofao and came close to uniting all the Franks under his rule; however, he was assassinated in 681, the victim of a combined attack by his numerous enemies Pepin immediately made peace with his successor, Waratton.


title: Pepin of Herstal

text: However, Waratton's successor, Berchar, and the Neustrian king Theuderic III, who, since 679, was nominal king of all the Franks, made war on Austrasia. The king and his mayor were decisively defeated at the Battle of Tertry (Textrice) in the Vermandois in 687. Berchar and Theuderic withdrew themselves to Paris, where Pepin followed and eventually forced on them a peace treaty with the condition that Berchar leave his office. Pepin was created mayor in all three Frankish kingdoms (Austrasia, Neustria, and Burgundy) and began calling himself Duke and Prince of the Franks ("dux et princeps Francorum"). In the ensuing quarrels, Berchar killed his mother-in-law Ansfled and fled. His wife Anstrude married Pepin's eldest son Drogo, Duke of Champagne, and Pepin's place in Neustria was secured.


title: Pepin of Herstal

text: The Neustrians barely tolerated an Austrasian overlord, but Pepin preferred to put these local resistances aside to deal with Germany.


title: Pepin of Herstal

text: Over the next several years, Pepin subdued the Alemanni, Frisians, and Franconians, bringing them within the Frankish sphere of influence. Between 690 and 692, Utrecht fell. This gave the Franks control of important trade routes on the Rhine to the North Sea. He also supported the missionary work of Willibrord. In 695, he placed Drogo in the Burgundian mayorship and his other son, Grimoald, in the Neustrian one.


title: Pepin of Herstal

text: Around 670, Pepin had married Plectrude, who had inherited substantial estates in the Moselle region. She was the mother of Drogo of Champagne and Grimoald II, both of whom died before their father. However, Pepin also had a mistress (or possibly, a second wife) named Alpaida (or Chalpaida) who bore him two more sons: Charles Martel and Childebrand.


title: Pepin of Herstal

text: Just before Pepin's death, Plectrude convinced him to disinherit the sons he had with his mistress Alpaida in favour of his grandson, Theudoald (the son of Pepin and Plectrude's son Grimoald), who was still a young child (and amenable to Plectrude's control). Pepin died suddenly at the age of 79 on 16 December 714, at Jupille (in modern Belgium). His grandchildren through Plectrude claimed themselves to be Pepin's true successors and, with the help of Plectrude, tried to maintain the position of mayor of the palace after Pepin's death. However, Charles (son of Pepin and Alpaida) had gained favour among the Austrasians, primarily for his military prowess and ability to keep them well supplied with booty from his conquests. Despite the efforts of Plectrude to silence her child's rival by imprisoning him, he became the sole mayor of the palace—and "de facto" ruler of Francia—after a civil war which lasted for more than three years after Pepin's death.


title: Pepin of Herstal

text: In 2018, the Dutch production company Farmhouse released a movie called Redbad (film), based on the historical Redbad and directed by Roel Reiné. Jonathan Banks played Pepin of Herstal, who is the main villain in this movie.


title: Wireless sensor network

text: Wireless sensor networks (WSNs) refer to networks of spatially dispersed and dedicated sensors that monitor and record the physical conditions of the environment and forward the collected data to a central location. WSNs can measure environmental conditions such as temperature, sound, pollution levels, humidity and wind.


title: Wireless sensor network

text: These are similar to wireless ad hoc networks in the sense that they rely on wireless connectivity and spontaneous formation of networks so that sensor data can be transported wirelessly. WSNs monitor physical conditions, such as temperature, sound, and pressure. Modern networks are bi-directional, both collecting data and enabling control of sensor activity. The development of these networks was motivated by military applications such as battlefield surveillance. Such networks are used in industrial and consumer applications, such as industrial process monitoring and control and machine health monitoring.


title: Wireless sensor network

text: A WSN is built of "nodes" – from a few to hundreds or thousands, where each node is connected to other sensors. Each such node typically has several parts: a radio transceiver with an internal antenna or connection to an external antenna, a microcontroller, an electronic circuit for interfacing with the sensors and an energy source, usually a battery or an embedded form of energy harvesting. A sensor node might vary in size from a shoebox to (theoretically) a grain of dust, although microscopic dimensions have yet to be realized. Sensor node cost is similarly variable, ranging from a few to hundreds of dollars, depending on node sophistication. Size and cost constraints constrain resources such as energy, memory, computational speed and communications bandwidth. The topology of a WSN can vary from a simple star network to an advanced multi-hop wireless mesh network. Propagation can employ routing or flooding.


title: Wireless sensor network

text: In computer science and telecommunications, wireless sensor networks are an active research area supporting many workshops and conferences, including International Workshop on Embedded Networked Sensors (EmNetS), IPSN, SenSys, MobiCom and EWSN. As of 2010, wireless sensor networks had deployed approximately 120million remote units worldwide.


title: Wireless sensor network

text: Area monitoring is a common application of WSNs. In area monitoring, the WSN is deployed over a region where some phenomenon is to be monitored. A military example is the use of sensors to detect enemy intrusion; a civilian example is the geo-fencing of gas or oil pipelines.


title: Wireless sensor network

text: There are several types of sensor networks for medical applications: implanted, wearable, and environment-embedded. Implantable medical devices are those that are inserted inside the human body. Wearable devices are used on the body surface of a human or just at close proximity of the user. Environment-embedded systems employ sensors contained in the environment. Possible applications include body position measurement, location of persons, overall monitoring of ill patients in hospitals and at home. Devices embedded in the environment track the physical state of a person for continuous health diagnosis, using as input the data from a network of depth cameras, a sensing floor, or other similar devices. Body-area networks can collect information about an individual's health, fitness, and energy expenditure. In health care applications the privacy and authenticity of user data has prime importance. Especially due to the integration of sensor networks, with IoT, the user authentication becomes more challenging; however, a solution is presented in recent work.


title: Wireless sensor network

text: Wireless sensor networks have been used to monitor various species and habitats, beginning with the Great Duck Island Deployment, including marmots, cane toads in Australia and zebras in Kenya.


title: Wireless sensor network

text: There are many applications in monitoring environmental parameters, examples of which are given below. They share the extra challenges of harsh environments and reduced power supply.


title: Wireless sensor network

text: Experiments have shown that personal exposure to air pollution in cities can vary a lot. Therefore, it is of interest to have higher temporal and spatial resolution of pollutants and particulates. For research purposes, wireless sensor networks have been deployed to monitor the concentration of dangerous gases for citizens (e.g., in London). However, sensors for gases and particulate matter suffer from high unit-to-unit variability, cross-sensitivities, and (concept) drift. Moreover, the quality of data is currently insufficient for trustworthy decision-making, as field calibration leads to unreliable measurement results, and frequent recalibration might be required. A possible solution could be blind calibration or the usage of mobile references.


title: Wireless sensor network

text: A network of Sensor Nodes can be installed in a forest to detect when a fire has started. The nodes can be equipped with sensors to measure temperature, humidity and gases which are produced by fire in the trees or vegetation. The early detection is crucial for a successful action of the firefighters; thanks to Wireless Sensor Networks, the fire brigade will be able to know when a fire is started and how it is spreading.


title: Wireless sensor network

text: A landslide detection system makes use of a wireless sensor network to detect the slight movements of soil and changes in various parameters that may occur before or during a landslide. Through the data gathered it may be possible to know the impending occurrence of landslides long before it actually happens.


title: Wireless sensor network

text: Water quality monitoring involves analyzing water properties in dams, rivers, lakes and oceans, as well as underground water reserves. The use of many wireless distributed sensors enables the creation of a more accurate map of the water status, and allows the permanent deployment of monitoring stations in locations of difficult access, without the need of manual data retrieval.


title: Wireless sensor network

text: Wireless sensor networks can be effective in preventing adverse consequences of natural disasters, like floods. Wireless nodes have been deployed successfully in rivers, where changes in water levels must be monitored in real time.


title: Wireless sensor network

text: Wireless sensor networks have been developed for machinery condition-based maintenance (CBM) as they offer significant cost savings and enable new functionality.


title: Wireless sensor network

text: Wireless sensors can be placed in locations difficult or impossible to reach with a wired system, such as rotating machinery and untethered vehicles.


title: Wireless sensor network

text: Wireless sensor networks also are used for the collection of data for monitoring of environmental information. This can be as simple as monitoring the temperature in a fridge or the level of water in overflow tanks in nuclear power plants. The statistical information can then be used to show how systems have been working. The advantage of WSNs over conventional loggers is the "live" data feed that is possible.


title: Wireless sensor network

text: Monitoring the quality and level of water includes many activities such as checking the quality of underground or surface water and ensuring a country's water infrastructure for the benefit of both human and animal. It may be used to protect the wastage of water.


title: Wireless sensor network

text: Wireless sensor networks can be used to monitor the condition of civil infrastructure and related geo-physical processes close to real time, and over long periods through data logging, using appropriately interfaced sensors.


title: Wireless sensor network

text: The Wide Area Tracking System (WATS) is a prototype network for detecting a ground-based nuclear device such as a nuclear "briefcase bomb." WATS is being developed at the Lawrence Livermore National Laboratory (LLNL). WATS would be made up of wireless gamma and neutron sensors connected through a communications network. Data picked up by the sensors undergoes "data fusion", which converts the information into easily interpreted forms; this data fusion is the most important aspect of the system.


title: Wireless sensor network

text: The data fusion process occurs "within" the sensor network rather than at a centralized computer and is performed by a specially developed algorithm based on Bayesian statistics. WATS would not use a centralized computer for analysis because researchers found that factors such as latency and available bandwidth tended to create significant bottlenecks. Data processed in the field by the network itself (by transferring small amounts of data between neighboring sensors) is faster and makes the network more scalable.


title: Wireless sensor network

text: An important factor in WATS development is "ease of deployment", since more sensors both improves the detection rate and reduces false alarms. WATS sensors could be deployed in permanent positions or mounted in vehicles for mobile protection of specific locations. One barrier to the implementation of WATS is the size, weight, energy requirements and cost of currently available wireless sensors. The development of improved sensors is a major component of current research at the Nonproliferation, Arms Control, and International Security (NAI) Directorate at LLNL.


title: Wireless sensor network

text: WATS was profiled to the U.S. House of Representatives' Military Research and Development Subcommittee on October 1, 1997, during a hearing on nuclear terrorism and countermeasures. On August 4, 1998, in a subsequent meeting of that subcommittee, Chairman Curt Weldon stated that research funding for WATS had been cut by the Clinton administration to a subsistence level and that the program had been poorly re-organized.


title: Wireless sensor network

text: There are studies that show that using sensors for incident monitoring improve in a great way the response of firefighters and police to an unexpected situation. For an early detection of incidents we can use acoustic sensors to detect a spike in the noise of the city because of a possible accident, or use termic sensors to detect a possible fire.


title: Wireless sensor network

text: Using low-power electronics, WSN:s can be cost-efficiently applied also in supply chains in various industries.


title: Wireless sensor network

text: Cross-layer is becoming an important studying area for wireless communications. In addition, the traditional layered approach presents three main problems:


title: Wireless sensor network

text: So the cross-layer can be used to make the optimal modulation to improve the transmission performance, such as data rate, energy efficiency, quality of service (QoS), etc. Sensor nodes can be imagined as small computers which are extremely basic in terms of their interfaces and their components. They usually consist of a "processing unit" with limited computational power and limited memory, "sensors" or MEMS (including specific conditioning circuitry), a "communication device" (usually radio transceivers or alternatively optical), and a power source usually in the form of a battery. Other possible inclusions are energy harvesting modules, secondary ASICs, and possibly secondary communication interface (e.g. RS-232 or USB).


title: Wireless sensor network

text: The base stations are one or more components of the WSN with much more computational, energy and communication resources. They act as a gateway between sensor nodes and the end user as they typically forward data from the WSN on to a server. Other special components in routing based networks are routers, designed to compute, calculate and distribute the routing tables.


title: Wireless sensor network

text: One major challenge in a WSN is to produce "low cost" and "tiny" sensor nodes. There are an increasing number of small companies producing WSN hardware and the commercial situation can be compared to home computing in the 1970s. Many of the nodes are still in the research and development stage, particularly their software. Also inherent to sensor network adoption is the use of very low power methods for radio communication and data acquisition.


title: Wireless sensor network

text: In many applications, a WSN communicates with a local area network or wide area network through a gateway. The Gateway acts as a bridge between the WSN and the other network. This enables data to be stored and processed by devices with more resources, for example, in a remotely located server. A wireless wide area network used primarily for low-power devices is known as a Low-Power Wide-Area Network (LPWAN).


title: Wireless sensor network

text: There are several wireless standards and solutions for sensor node connectivity. Thread and ZigBee can connect sensors operating at 2.4 GHz with a data rate of 250kbit/s. Many use a lower frequency to increase radio range (typically 1 km), for example Z-wave operates at 915 MHz and in the EU 868 MHz has been widely used but these have a lower data rate (typically 50 kbit/s). The IEEE 802.15.4 working group provides a standard for low power device connectivity and commonly sensors and smart meters use one of these standards for connectivity. With the emergence of Internet of Things, many other proposals have been made to provide sensor connectivity. LoRa is a form of LPWAN which provides long range low power wireless connectivity for devices, which has been used in smart meters and other long range sensor applications. Wi-SUN connects devices at home. NarrowBand IOT and LTE-M can connect up to millions of sensors and devices using cellular technology.


title: Wireless sensor network

text: Energy is the scarcest resource of WSN nodes, and it determines the lifetime of WSNs. WSNs may be deployed in large numbers in various environments, including remote and hostile regions, where ad hoc communications are a key component. For this reason, algorithms and protocols need to address the following issues:


title: Wireless sensor network

text: Lifetime maximization: Energy/Power Consumption of the sensing device should be minimized and sensor nodes should be energy efficient since their limited energy resource determines their lifetime. To conserve power, wireless sensor nodes normally power off both the radio transmitter and the radio receiver when not in use.


title: Wireless sensor network

text: Wireless sensor networks are composed of low-energy, small-size, and low-range unattended sensor nodes. Recently, it has been observed that by periodically turning on and off the sensing and communication capabilities of sensor nodes, we can significantly reduce the active time and thus prolong network lifetime. However, this duty cycling may result in high network latency, routing overhead, and neighbor discovery delays due to asynchronous sleep and wake-up scheduling. These limitations call for a countermeasure for duty-cycled wireless sensor networks which should minimize routing information, routing traffic load, and energy consumption. Researchers from Sungkyunkwan University have proposed a lightweight non-increasing delivery-latency interval routing referred as LNDIR. This scheme can discover minimum latency routes at each non-increasing delivery-latency interval instead of each time slot. Simulation experiments demonstrated the validity of this novel approach in minimizing routing information stored at each sensor. Furthermore, this novel routing can also guarantee the minimum delivery latency from each source to the sink. Performance improvements of up to 12-fold and 11-fold are observed in terms of routing traffic load reduction and energy efficiency, respectively, as compared to existing schemes.


title: Wireless sensor network

text: Operating systems for wireless sensor network nodes are typically less complex than general-purpose operating systems. They more strongly resemble embedded systems, for two reasons. First, wireless sensor networks are typically deployed with a particular application in mind, rather than as a general platform. Second, a need for low costs and low power leads most wireless sensor nodes to have low-power microcontrollers ensuring that mechanisms such as virtual memory are either unnecessary or too expensive to implement.


title: Wireless sensor network

text: It is therefore possible to use embedded operating systems such as eCos or uC/OS for sensor networks. However, such operating systems are often designed with real-time properties.


title: Wireless sensor network

text: TinyOS, developed by David Culler, is perhaps the first operating system specifically designed for wireless sensor networks. TinyOS is based on an event-driven programming model instead of multithreading. TinyOS programs are composed of "event handlers" and "tasks" with run-to-completion semantics. When an external event occurs, such as an incoming data packet or a sensor reading, TinyOS signals the appropriate event handler to handle the event. Event handlers can post tasks that are scheduled by the TinyOS kernel some time later.


title: Wireless sensor network

text: LiteOS is a newly developed OS for wireless sensor networks, which provides UNIX-like abstraction and support for the C programming language.


title: Wireless sensor network

text: Contiki, developed by Adam Dunkels, is an OS which uses a simpler programming style in C while providing advances such as 6LoWPAN and Protothreads.


title: Wireless sensor network

text: PreonVM is an OS for wireless sensor networks, which provides 6LoWPAN based on Contiki and support for the Java programming language.


title: Wireless sensor network

text: Online collaborative sensor data management platforms are on-line database services that allow sensor owners to register and connect their devices to feed data into an online database for storage and also allow developers to connect to the database and build their own applications based on that data. Examples include Xively and the Wikisensing platform. Such platforms simplify online collaboration between users over diverse data sets ranging from energy and environment data to that collected from transport services. Other services include allowing developers to embed real-time graphs & widgets in websites; analyse and process historical data pulled from the data feeds; send real-time alerts from any datastream to control scripts, devices and environments.


title: Wireless sensor network

text: The architecture of the Wikisensing system describes the key components of such systems to include APIs and interfaces for online collaborators, a middleware containing the business logic needed for the sensor data management and processing and a storage model suitable for the efficient storage and retrieval of large volumes of data.


title: Wireless sensor network

text: At present, agent-based modeling and simulation is the only paradigm which allows the simulation of complex behavior in the environments of wireless sensors (such as flocking). Agent-based simulation of wireless sensor and ad hoc networks is a relatively new paradigm. Agent-based modelling was originally based on social simulation.


title: Wireless sensor network

text: Network simulators like Opnet, Tetcos NetSim and NS can be used to simulate a wireless sensor network.


title: Wireless sensor network

text: Network localization refers to the problem of estimating the location of wireless sensor nodes during deployments and in dynamic settings. For ultra-low power sensors, size, cost and environment precludes the use of Global Positioning System receivers on sensors. In 2000, Nirupama Bulusu, John Heidemann and Deborah Estrin first motivated and proposed a radio connectivity based system for localization of wireless sensor networks. Subsequently, such localization systems have been referred to as range free localization systems, and many localization systems for wireless sensor networks have been subsequently proposed including AHLoS, APS, and Stardust.


title: Wireless sensor network

text: Sensors and devices used in wireless sensor networks are state-of-the-art technology with the lowest possible price. The sensor measurements we get from these devices are therefore often noisy, incomplete and inaccurate. Researchers studying wireless sensor networks hypothesize that much more information can be extracted from hundreds of unreliable measurements spread across a field of interest than from a smaller number of high-quality, high-reliability instruments with the same total cost.


title: Wireless sensor network

text: Macro-programming is a term coined by Matt Welsh. It refers to programming the entire sensor network as an ensemble, rather than individual sensor nodes. Another way to macro-program a network is to view the sensor network as a database, which was popularized by the TinyDB system developed by Sam Madden.


title: Wireless sensor network

text: Reprogramming is the process of updating the code on the sensor nodes. The most feasible form of reprogramming is remote reprogramming whereby the code is disseminated wirelessly while the nodes are deployed. Different reprogramming protocols exist that provide different levels of speed of operation, reliability, energy expenditure, requirement of code resident on the nodes, suitability to different wireless environments, resistance to DoS, etc. Popular reprogramming protocols are Deluge (2004), Trickle (2004), MNP (2005), Synapse (2008), and Zephyr (2009).


title: Wireless sensor network

text: Infrastructure-less architecture (i.e. no gateways are included, etc.) and inherent requirements (i.e. unattended working environment, etc.) of WSNs might pose several weak points that attract adversaries. Therefore, security is a big concern when WSNs are deployed for special applications such as military and healthcare. Owing to their unique characteristics, traditional security methods of computer networks would be useless (or less effective) for WSNs. Hence, lack of security mechanisms would cause intrusions towards those networks. These intrusions need to be detected and mitigation methods should be applied.


title: Wireless sensor network

text: There have been important innovations in securing wireless sensor networks. Most wireless embedded networks use omni-directional antennas and therefore neighbors can overhear communication in and out of nodes. This was used this to develop a primitive called “"local monitoring"” which was used for detection of sophisticated attacks, like blackhole or wormhole, which degrade the throughput of large networks to close-to-zero. This primitive has since been used by many researchers and commercial wireless packet sniffers. This was subsequently refined for more sophisticated attacks such as with collusion, mobility, and multi-antenna, multi-channel devices.


title: Wireless sensor network

text: If a centralized architecture is used in a sensor network and the central node fails, then the entire network will collapse, however the reliability of the sensor network can be increased by using a distributed control architecture. Distributed control is used in WSNs for the following reasons:


title: Wireless sensor network

text: As for the distributed filtering over distributed sensor network. the general setup is to observe the underlying process through a group of sensors organized according to a given network topology, which renders the individual observer estimates the system state based not only on its own measurement but also on its neighbors’.


title: Wireless sensor network

text: The data gathered from wireless sensor networks is usually saved in the form of numerical data in a central base station. Additionally, the Open Geospatial Consortium (OGC) is specifying standards for interoperability interfaces and metadata encodings that enable real time integration of heterogeneous sensor webs into the Internet, allowing any individual to monitor or control wireless sensor networks through a web browser.


title: Wireless sensor network

text: To reduce communication costs some algorithms remove or reduce nodes' redundant sensor information and avoid forwarding data that is of no use. This technique has been used, for instance, for distributed anomaly detection or distributed optimization. As nodes can inspect the data they forward, they can measure averages or directionality for example of readings from other nodes. For example, in sensing and monitoring applications, it is generally the case that neighboring sensor nodes monitoring an environmental feature typically register similar values. This kind of data redundancy due to the spatial correlation between sensor observations inspires techniques for in-network data aggregation and mining. Aggregation reduces the amount of network traffic which helps to reduce energy consumption on sensor nodes. Recently, it has been found that network gateways also play an important role in improving energy efficiency of sensor nodes by scheduling more resources for the nodes with more critical energy efficiency need and advanced energy efficient scheduling algorithms need to be implemented at network gateways for the improvement of the overall network energy efficiency.


title: Wireless sensor network

text: This is a form of in-network processing where sensor nodes are assumed to be unsecured with limited available energy, while the base station is assumed to be secure with unlimited available energy. Aggregation complicates the already existing security challenges for wireless sensor networks and requires new security techniques tailored specifically for this scenario. Providing security to aggregate data in wireless sensor networks is known as "secure data aggregation in WSN". were the first few works discussing techniques for secure data aggregation in wireless sensor networks.


title: Wireless sensor network

text: Two main security challenges in secure data aggregation are confidentiality and integrity of data. While encryption is traditionally used to provide end to end confidentiality in wireless sensor network, the aggregators in a secure data aggregation scenario need to decrypt the encrypted data to perform aggregation. This exposes the plaintext at the aggregators, making the data vulnerable to attacks from an adversary. Similarly an aggregator can inject false data into the aggregate and make the base station accept false data. Thus, while data aggregation improves energy efficiency of a network, it complicates the existing security challenges.


title: Soman Chainani

text: Soman Chainani is an American author and filmmaker, best known for writing the children's book series "The School for Good and Evil".


title: Soman Chainani

text: Soman's series, "The School for Good and Evil", debuted on the New York Times Bestseller List, has sold more than 3.5 million copies, been translated into 32 languages across 6 continents, and has been adapted into a major motion picture from Netflix that debuted at #1 in over 80 countries.


title: Soman Chainani

text: His other books in the School for Good and Evil series – "A World Without Princes", "The Last Ever After", "Quests for Glory", "A Crystal of Time" and "One True King" – have all debuted on the New York Times Bestseller List as well.


title: Soman Chainani

text: His book of retold fairytales, "Beasts and Beauty," was released on September 21, 2021, to wide acclaim, with Kirkus Reviews calling the collection "expertly crafted... evoking the wonder, terror, and magic of the fantasy realms." "Beasts & Beauty" was an instant New York Times bestseller, Soman’s seventh New York Times bestseller in a row, and is slated to be a limited television series from Sony 3000, with Soman writing and executive producing. Together, Chainani's books have been on the New York Times Bestseller List for 44 weeks.


title: Soman Chainani

text: His most recent book, "Rise of the School for Good and Evil" was released on May 31, 2022, to high acclaim and the New York Times Bestseller list. Publishers Weekly described it as “an episodic, adventurous fantasy offering.” A sequel, "Fall of the School for Good and Evil" is expected in May 2023.


title: Soman Chainani

text: Chainani grew up in Key Biscayne, Florida, where his family was one of the few of Indian descent. He attended Harvard University, where he graduated with a degree in English and American Literature in 2001. As of 2003 he resided in New York City. After graduation, he went on to attend Columbia University, where he participated in their MFA Film Program.


title: Kris Paronto

text: Kristian Joaquin "Tanto" Paronto (Born 1971) is an American author, businessman, and former U.S. Army Ranger and CIA security contractor. He is known for his actions while part of the CIA annex security team during the 2012 terrorist attack on the U.S. Ambassador to Libya, J. Chris Stevens and the CIA compound in Benghazi. He is featured in the book "13 Hours: The Inside Account of What Really Happened in Benghazi" and is credited as a co-author, and is author of the self-help books "The Patriot's Creed: Inspiration and Advice for Living a Heroic Life" and "."


title: Kris Paronto

text: Paronto was born in Alamosa, Colorado. His parents were educators and his mother taught his first-grade class. His father James Paronto was a football coach and athletic director. Paronto played football, baseball and basketball. A football scholarship helped pay for his college degrees which include an associates, bachelor and master degrees.


title: Kris Paronto

text: Paronto served four years as an Army Ranger followed by four years in the Army National Guard. He reached the enlisted rank of Sergeant before receiving a commission in 2003.


title: Kris Paronto

text: Paronto was a CIA private security contractor guarding the Benghazi, Libya CIA annex, during the 2012 Benghazi attack. CIA contractors Tyrone S. Woods and Glen Doherty were killed in the attack along with the U.S. Ambassador to Libya J. Christopher Stevens and U.S. Foreign Service Information Management Specialist Sean Smith. After Benghazi, Paronto served as a security contractor in Yemen before leaving the CIA.


title: Kris Paronto

text: Following his exit from the CIA, Kris Paronto became an author and public speaker. After the U.S. captured Ahmed Abu Khatallah for his role in the Benghazi attack and brought him to the U.S., Paronto was critical of the decision made by the Obama Administration to have him tried before a jury in Federal court. In protest of that decision, Paronto refused to testify at his trial. Along with Mitchell Zuckoff and other members of the Annex Security Team stationed in Benghazi, Paronto co-wrote the book "13 Hours:" "The Inside Account of What Really Happened In Benghazi". The book was the basis for the Michael Bay-directed film "".


title: Kris Paronto

text: In 2017, Paronto released his second book, "", a self-help book and survival guide based on Paronto's military experiences.


title: Kris Paronto

text: Paronto hosted the pilot episode of "War Heroes", a documentary series about American military personnel, produced by Fox Trail Productions.


title: Kris Paronto

text: In November of 2019, Paronto launched "Battleline Podcast" with Ian Scotto which has continued since.


title: Kris Paronto

text: Paronto is co-founder of the 14th Hour Foundation, a non-profit organization "committed to raising and dispersing funds to help the lives and futures of Veterans, Military Contractor Personnel, and First Responders who have served and sacrificed to protect the American Homeland."


title: Kris Paronto

text: Paronto is married to former Maverick Assistant Volleyball Coach Tanya Cate. They have three children.


title: Pitot-static system

text: A pitot-static system is a system of pressure-sensitive instruments that is most often used in aviation to determine an aircraft's airspeed, Mach number, altitude, and altitude trend. A pitot-static system generally consists of a pitot tube, a static port, and the pitot-static instruments. Other instruments that might be connected are air data computers, flight data recorders, altitude encoders, cabin pressurization controllers, and various airspeed switches. Errors in pitot-static system readings can be extremely dangerous as the information obtained from the pitot static system, such as altitude, is potentially safety-critical. Several commercial airline disasters have been traced to a failure of the pitot-static system.


title: Pitot-static system

text: The pitot-static system of instruments uses the principle of air pressure gradient. It works by measuring pressures or pressure differences and using these values to assess the speed and altitude. These pressures can be measured either from the static port (static pressure) or the pitot tube (pitot pressure). The static pressure is used in all measurements, while the pitot pressure is used only to determine airspeed.


title: Pitot-static system

text: The pitot pressure is obtained from the pitot tube. The pitot pressure is a measure of ram air pressure (the air pressure created by vehicle motion or the air ramming into the tube), which, under ideal conditions, is equal to stagnation pressure, also called total pressure. The pitot tube is most often located on the wing or front section of an aircraft, facing forward, where its opening is exposed to the relative wind. By situating the pitot tube in such a location, the ram air pressure is more accurately measured since it will be less distorted by the aircraft's structure. When airspeed increases, the ram air pressure is increased, which can be translated by the airspeed indicator.


title: Pitot-static system

text: The static pressure is obtained through a static port. The static port is most often a flush-mounted hole on the fuselage of an aircraft, and is located where it can access the air flow in a relatively undisturbed area. Some aircraft may have a single static port, while others may have more than one. In situations where an aircraft has more than one static port, there is usually one located on each side of the fuselage. With this positioning, an average pressure can be taken, which allows for more accurate readings in specific flight situations. An alternative static port may be located inside the cabin of the aircraft as a backup for when the external static port(s) are blocked. A pitot-static tube effectively integrates the static ports into the pitot probe. It incorporates a second coaxial tube (or tubes) with pressure sampling holes on the sides of the probe, outside the direct airflow, to measure the static pressure. When the aircraft climbs, static pressure will decrease.


title: Pitot-static system

text: Some pitot-static systems incorporate single probes that contain multiple pressure-transmitting ports that allow for the sensing of air pressure, angle of attack, and angle of sideslip data. Depending on the design, such air data probes may be referred to as 5-hole or 7-hole air data probes. Differential pressure sensing techniques can be used to produce angle of attack and angle of sideslip indications.


title: Pitot-static system

text: The pitot-static system obtains pressures for interpretation by the pitot-static instruments. While the explanations below explain traditional, mechanical instruments, many modern aircraft use an air data computer (ADC) to calculate airspeed, rate of climb, altitude and Mach number. In some aircraft, two ADCs receive total and static pressure from independent pitot tubes and static ports, and the aircraft's flight data computer compares the information from both computers and checks one against the other. There are also "standby instruments", which are back-up pneumatic instruments employed in the case of problems with the primary instruments.


title: Pitot-static system

text: The airspeed indicator is connected to both the pitot and static pressure sources. The difference between the pitot pressure and the static pressure is called dynamic pressure. The greater the dynamic pressure, the higher the airspeed reported. A traditional mechanical airspeed indicator contains a pressure diaphragm that is connected to the pitot tube. The case around the diaphragm is airtight and is vented to the static port. The higher the speed, the higher the ram pressure, the more pressure exerted on the diaphragm, and the larger the needle movement through the mechanical linkage.


title: Pitot-static system

text: The pressure altimeter, also known as the barometric altimeter, is used to determine changes in air pressure that occur as the aircraft's altitude changes. Pressure altimeters must be calibrated prior to flight to register the pressure as an altitude above sea level. The instrument case of the altimeter is airtight and has a vent to the static port. Inside the instrument, there is a sealed aneroid barometer. As pressure in the case decreases, the internal barometer expands, which is mechanically translated into a determination of altitude. The reverse is true when descending from higher to lower altitudes.


title: Pitot-static system

text: Aircraft designed to operate at transonic or supersonic speeds will incorporate a machmeter. The machmeter is used to show the ratio of true airspeed in relation to the speed of sound. Most supersonic aircraft are limited as to the maximum Mach number they can fly, which is known as the "Mach limit". The Mach number is displayed on a machmeter as a decimal fraction.


title: Pitot-static system

text: The variometer, also known as the vertical speed indicator (VSI) or the vertical velocity indicator (VVI), is the pitot-static instrument used to determine whether or not an aircraft is flying in level flight. The vertical speed specifically shows the rate of climb or the rate of descent, which is measured in feet per minute or meters per second. The vertical speed is measured through a mechanical linkage to a diaphragm located within the instrument. The area surrounding the diaphragm is vented to the static port through a calibrated leak (which also may be known as a "restricted diffuser"). When the aircraft begins to increase altitude, the diaphragm will begin to contract at a rate faster than that of the calibrated leak, causing the needle to show a positive vertical speed. The reverse of this situation is true when an aircraft is descending. The calibrated leak varies from model to model, but the average time for the diaphragm to equalize pressure is between 6 and 9 seconds.


title: Pitot-static system

text: There are several situations that can affect the accuracy of the pitot-static instruments. Some of these involve failures of the pitot-static system itself—which may be classified as "system malfunctions"—while others are the result of faulty instrument placement or other environmental factors—which may be classified as "inherent errors".


title: Pitot-static system

text: A blocked pitot tube is a pitot-static problem that will only affect airspeed indicators. A blocked pitot tube will cause the airspeed indicator to register an increase in airspeed when the aircraft climbs, even though actual airspeed is constant. (As long as the drain hole is also blocked, as the air pressure would otherwise leak out to the atmosphere.) This is caused by the pressure in the pitot system remaining constant when the atmospheric pressure (and static pressure) are decreasing. Conversely, the airspeed indicator will show a decrease in airspeed when the aircraft descends. The pitot tube is susceptible to becoming clogged by ice, water, insects or some other obstruction. For this reason, aviation regulatory agencies such as the U.S. Federal Aviation Administration (FAA) recommend that the pitot tube be checked for obstructions prior to any flight. To prevent icing, many pitot tubes are equipped with a heating element. A heated pitot tube is required in all aircraft certificated for instrument flight except aircraft certificated as Experimental Amateur-Built.


title: Pitot-static system

text: A blocked static port is a more serious situation because it affects all pitot-static instruments. One of the most common causes of a blocked static port is airframe icing. A blocked static port will cause the altimeter to freeze at a constant value, the altitude at which the static port became blocked. The vertical speed indicator will read zero and will not change at all, even if vertical speed increases or decreases. The airspeed indicator will reverse the error that occurs with a clogged pitot tube and cause the airspeed to be read less than it actually is as the aircraft climbs. When the aircraft is descending, the airspeed will be over-reported. In most aircraft with unpressurized cabins, an alternative static source is available and can be selected from within the cockpit.


title: Pitot-static system

text: Inherent errors may fall into several categories, each affecting different instruments. "Density errors" affect instruments metering airspeed and altitude. This type of error is caused by variations of pressure and temperature in the atmosphere. A "compressibility error" can arise because the impact pressure will cause the air to compress in the pitot tube. At standard sea level pressure altitude the calibration equation (see calibrated airspeed) correctly accounts for the compression so there is no compressibility error at sea level. At higher altitudes the compression is not correctly accounted for and will cause the instrument to read greater than equivalent airspeed. A correction may be obtained from a chart. Compressibility error becomes significant at altitudes above and at airspeeds greater than . "Hysteresis" is an error that is caused by mechanical properties of the aneroid capsules located within the instruments. These capsules, used to determine pressure differences, have physical properties that resist change by retaining a given shape, even though the external forces may have changed. "Reversal errors" are caused by a false static pressure reading. This false reading may be caused by abnormally large changes in an aircraft's pitch. A large change in pitch will cause a momentary showing of movement in the opposite direction. Reversal errors primarily affect altimeters and vertical speed indicators.


title: Pitot-static system

text: Another class of inherent errors is that of position error. A position error is produced by the aircraft's static pressure being different from the air pressure remote from the aircraft. This error is caused by the air flowing past the static port at a speed different from the aircraft's true airspeed. Position errors may provide positive or negative errors, depending on one of several factors. These factors include airspeed, angle of attack, aircraft weight, acceleration, aircraft configuration, and in the case of helicopters, rotor downwash. There are two categories of position errors, which are "fixed errors" and "variable errors". Fixed errors are defined as errors which are specific to a particular model of aircraft. Variable errors are caused by external factors such as deformed panels obstructing the flow of air, or particular situations which may overstress the aircraft.


title: Pitot-static system

text: Lag errors are caused by the fact that any changes in the static or dynamic pressure outside the aircraft require a finite amount of time to make their way down the tubing and affect the gauges. This type of error depends on the length and diameter of the tubing as well as the volume inside the gauges. Lag error is only significant around the time when the airspeed or altitude are changing. It is not a concern for steady level flight.


title: NCIS (season 7)

text: The seventh season of the police procedural drama "NCIS" premiered on September 22, 2009 with "" Season 1 premiering afterwards. At the end of season six, Ziva had left the "NCIS" team in Israel, returning to work as a Mossad officer. In the closing seconds of that season, Ziva was shown to have been captured and tortured for information about "NCIS".


title: NCIS (season 7)

text: In the first episode of season seven, Ziva is rescued by Gibbs, Tony and McGee and upon her return to Washington, she eventually becomes an NCIS agent after resigning from Mossad for good. Much of the season's story arc then focuses on the Mexican Drug War and Colonel Merton Bell (Robert Patrick), a suspected murderer who hired the lawyer M. Allison Hart to represent him. Hart quickly becomes a thorn in Gibbs' side by regularly showing up and protecting possible suspects while they are being investigated, claiming that they were her clients.


title: NCIS (season 7)

text: The season draws to a close as Gibbs is later kidnapped by someone working for Paloma Reynosa, the daughter of the late Pedro Hernandez, a drug dealer Gibbs himself shot dead twenty years previously as Hernandez had been responsible for killing Gibbs' first wife Shannon and daughter Kelly. While Gibbs is held prisoner, Paloma informs him that he would work for her or she would have everyone he ever knew and cared about die if he did not go through with her demands.


title: NCIS (season 7)

text: It also ends in a cliffhanger with Paloma herself traveling to Stillwater and confronting Jackson Gibbs in his shop, leaving his fate unknown.


title: NCIS (season 7)

text: The series aired alongside season one of "", and the NCIS episode "Endgame" continued on the events that had taken place in the "NCIS: Los Angeles" episode "Killshot".


title: Stebin Ben

text: Stebin Ben is an Indian playback singer and performer from Bhopal. He has given voice for films, "Shimla Mirchi" (2020), "Hotel Mumbai" (2019), TV series, "Class of 2017" and "Kaisi Yeh Yaariaan". He also sung singles, "Rula Ke Gaya Ishq" (2019) and "Mera Mehboob" (2019), released by Zee Music Company and Sony Music India.


title: Stebin Ben

text: Stebin began his music career by singing covers of songs like "Mera Dil Bhi Kitna Pagal Hain" (from Venus Music), "Bheegi Bheegi Raaton Mein", "Yeh Jo Halka Halka Suroor Hai" and "Chupana Bhi Nahi Aata". He made his debut in playback singing with 2017 Hindi web series, "Class of 2017" and lent his voice for "Kaisi Yeh Yaariaan". He did a cover of "Ye Jo Halka Halka Suroor Hai", featuring Niti Taylor, received over 6 million views on YouTube.


title: Stebin Ben

text: In 2019, he made his film debut in playback singing with the song "Humein Bharat Kehte Hain" in the film "Hotel Mumbai", followed "Ishq Di Feeling" for 2020 film "Shimla Mirchi", composed by Meet Bros.


title: Stebin Ben

text: In September 2018, he was awarded "Best Bollywood Artist of the year" at India Nightlife Awards 2018. He is the winner of T-Series StageWorks's singing contest The Stage in 2016. In October 2014, Stebin Ben won the Best Performance Award at MTV Asia's "Project Aloft Star India" (season 1).


title: IBM PC compatible

text: IBM PC compatible computers are similar to the original IBM PC, XT, and AT, all from computer giant IBM, that are able to use the same software and expansion cards. Such computers were referred to as PC clones, IBM clones or IBM PC clones. The term "IBM PC compatible" is now a historical description only, since IBM no longer sells personal computers after it sold its personal computer division in 2005 to Chinese technology company Lenovo. The designation "PC", as used in much of personal computer history, has not meant "personal computer" generally, but rather an x86 computer capable of running the same software that a contemporary IBM PC could. The term was initially in contrast to the variety of home computer systems available in the early 1980s, such as the Apple II, TRS-80, and Commodore 64. Later, the term was primarily used in contrast to Apple's Macintosh computers.


title: IBM PC compatible

text: These "clones" duplicated almost all the significant features of the original IBM PC architectures. This was facilitated by IBM's choice of commodity hardware components, which were cheap, and by various manufacturers' ability to reverse-engineer the BIOS firmware using a "clean room design" technique. Columbia Data Products built the first clone of the IBM personal computer, the MPC 1600 by a clean-room reverse-engineered implementation of its BIOS. Other rival companies, Corona Data Systems, Eagle Computer, and the Handwell Corporation were threatened with legal action by IBM, who settled with them. Soon after in 1982, Compaq released the very successful Compaq Portable in 1982, also with a clean-room reverse-engineered BIOS, and also not challenged legally by IBM.


title: IBM PC compatible

text: Some early IBM PC compatibles used the same 8-bit computer bus as the original PC and XT models, but many soon adopted the 16-bit IBM AT bus. It was later re-named the Industry Standard Architecture (ISA) bus, after the Extended Industry Standard Architecture bus open standard for IBM PC compatibles was announced in September 1988 by a consortium of PC clone vendors, led by Compaq and called the Gang of Nine, as an alternative to IBM's proprietary Micro Channel architecture (MCA) introduced in its PS/2 series. Soon after the industry adopted new bus standards in a similar, cooperative way: the VESA Local Bus (VLB), Peripheral Component Interconnect (PCI) and the Accelerated Graphics Port (AGP).


title: IBM PC compatible

text: Descendants of the x86 IBM PC compatibles, namely 64-bit computers based on "x86-64/AMD64" chips comprise the majority of desktop computers on the market as of 2021, with the dominant operating system being Microsoft Windows. Interoperability with the bus structure and peripherals of the original PC architecture may be limited or non-existent. Many modern computers are unable to use old software or hardware that depends on portions of the IBM PC compatible architecture which are missing or do not have equivalents in modern computers. For example, computers which boot using Unified Extensible Firmware Interface-based firmware that lack a Compatibility Support Module, or CSM, required to emulate the old BIOS-based firmware interface, or have their CSMs disabled, cannot natively run MS-DOS since MS-DOS depends on a BIOS interface to boot.


title: IBM PC compatible

text: Only the Macintosh had kept significant market share without having compatibility with the IBM PC, although that changed with Intel Macs running Mac OS X, often dual-booting Windows with Boot Camp.


title: IBM PC compatible

text: IBM decided in 1980 to market a low-cost single-user computer as quickly as possible. On 12 August 1981, the first IBM PC went on sale. There were three operating systems (OS) available for it. The least expensive and most popular was PC DOS made by Microsoft. In a crucial concession, IBM's agreement allowed Microsoft to sell its own version, MS-DOS, for non-IBM computers. The only component of the original PC architecture exclusive to IBM was the BIOS (Basic Input/Output System).


title: IBM PC compatible

text: IBM at first asked developers to avoid writing software that addressed the computer's hardware directly and to instead make standard calls to BIOS functions that carried out hardware-dependent operations. This software would run on any machine using MS-DOS or PC DOS. Software that directly addressed the hardware instead of making standard calls was faster, however; this was particularly relevant to games. Software addressing IBM PC hardware in this way would not run on MS-DOS machines with different hardware. The IBM PC was sold in high enough volumes to justify writing software specifically for it, and this encouraged other manufacturers to produce machines that could use the same programs, expansion cards, and peripherals as the PC. The 808x computer marketplace rapidly excluded all machines which were not hardware- and software-compatible with the PC. The 640 KB barrier on "conventional" system memory available to MS-DOS is a legacy of that period; other non-clone machines, while subject to a limit, could exceed 640 KB.


title: IBM PC compatible

text: Rumors of "lookalike", compatible computers, created without IBM's approval, began almost immediately after the IBM PC's release. "InfoWorld" wrote on the first anniversary of the IBM PC that


title: IBM PC compatible

text: By June 1983 "PC Magazine" defined "PC 'clone'" as "a computer [that can] accommodate the user who takes a disk home from an IBM PC, walks across the room, and plugs it into the 'foreign' machine". Because of a shortage of IBM PCs that year, many customers purchased clones instead. Columbia Data Products produced the first computer more or less compatible with the IBM PC standard during June 1982, soon followed by Eagle Computer. Compaq announced its first product, an IBM PC compatible in November 1982, the Compaq Portable. The Compaq was the first sewing machine-sized portable computer that was essentially 100% PC-compatible. The court decision in "Apple v. Franklin", was that BIOS code was protected by copyright law, but it could reverse-engineer the IBM BIOS and then write its own BIOS using clean room design. Note this was over a year after Compaq released the Portable. The money and research put into reverse-engineering the BIOS was a calculated risk.


title: IBM PC compatible

text: At the same time, many manufacturers such as Tandy/RadioShack, Xerox, Hewlett-Packard, Digital Equipment Corporation, Sanyo, Texas Instruments, Tulip, Wang and Olivetti introduced personal computers that supported MS-DOS, but were not completely software- or hardware-compatible with the IBM PC.


title: IBM PC compatible

text: Tandy described the Tandy 2000, for example, as having a "'next generation' true 16-bit CPU", and with "More speed. More disk storage. More expansion" than the IBM PC or "other MS-DOS computers". While admitting in 1984 that many PC-DOS programs did not work on the computer, the company stated that "the most popular, sophisticated software on the market" was available, either immediately or "over the next six months".


title: IBM PC compatible

text: Like IBM, Microsoft's apparent intention was that application writers would write to the application programming interfaces in MS-DOS or the firmware BIOS, and that this would form what would now be termed a hardware abstraction layer. Each computer would have its own Original Equipment Manufacturer (OEM) version of MS-DOS, customized to its hardware. Any software written for MS-DOS would operate on any MS-DOS computer, despite variations in hardware design.


title: IBM PC compatible

text: This expectation seemed reasonable in the computer marketplace of the time. Until then Microsoft's business was based primarily on computer languages such as BASIC. The established small system operating software was CP/M from Digital Research which was in use both at the hobbyist level and by the more professional of those using microcomputers. To achieve such widespread use, and thus make the product viable economically, the OS had to operate across a range of machines from different vendors that had widely varying hardware. Those customers who needed other applications than the starter programs could reasonably expect publishers to offer their products for a variety of computers, on suitable media for each.


title: IBM PC compatible

text: Microsoft's competing OS was intended initially to operate on a similar varied spectrum of hardware, although all based on the 8086 processor. Thus, MS-DOS was for several years sold only as an OEM product. There was no Microsoft-branded MS-DOS: MS-DOS could not be purchased directly from Microsoft, and each OEM release was packaged with the trade dress of the given PC vendor. Malfunctions were to be reported to the OEM, not to Microsoft. However, as machines that were compatible with IBM hardware—thus supporting direct calls to the hardware—became widespread, it soon became clear that the OEM versions of MS-DOS were virtually identical, except perhaps for the provision of a few utility programs.


title: IBM PC compatible

text: MS-DOS provided adequate functionality for character-oriented applications such as those that could have been implemented on a text-only terminal. Had the bulk of commercially important software been of this nature, low-level hardware compatibility might not have mattered. However, in order to provide maximum performance and leverage hardware features (or work around hardware bugs), PC applications quickly developed beyond the simple terminal applications that MS-DOS supported directly. Spreadsheets, WYSIWYG word processors, presentation software and remote communication software established new markets that exploited the PC's strengths, but required capabilities beyond what MS-DOS provided. Thus, from very early in the development of the MS-DOS software environment, many significant commercial software products were written directly to the hardware, for a variety of reasons:


title: IBM PC compatible

text: During development, Compaq engineers found that "Microsoft Flight Simulator" would not run because of what subLOGIC's Bruce Artwick described as "a bug in one of Intel's chips", forcing them to make their new computer bug compatible with the IBM PC. At first, few clones other than Compaq's offered truly full compatibility. Jerry Pournelle purchased an IBM PC in mid-1983, "rotten keyboard and all", because he had "four cubic feet of unevaluated software, much of which won't run on anything but an IBM PC. Although a lot of machines claim to be 100 percent IBM PC compatible, I've yet to have one arrive ... Alas, a lot of stuff doesn't run with Eagle, Z-100, Compupro, or anything else we have around here". Columbia Data Products's November 1983 sales brochure stated that during tests with retail-purchased computers in October 1983, its own and Compaq's products were compatible with all tested PC software, while Corona and Eagle's were less compatible. Columbia University reported in January 1984 that Kermit ran without modification on Compaq and Columbia Data Products clones, but not on those from Eagle or Seequa. Other MS-DOS computers also required custom code.


title: IBM PC compatible

text: Future Computing said in February 1984 that some computers were "press-release compatible", exaggerating their actual compatibility with the IBM PC. Many companies were reluctant to have their products' PC compatibility tested. When "PC Magazine" requested samples from computer manufacturers that claimed to produce compatibles for an April 1984 review, 14 of 31 declined. Corona Data Systems specified that "Our systems run all software that conforms to IBM PC programming standards. And the most popular software does." When a "BYTE" journalist asked to test Peachtext at the Spring 1983 COMDEX, Corona representatives "hemmed and hawed a bit, but they finally led me ... off in the corner where no one would see it should it fail". The magazine reported that "Their hesitancy was unnecessary. The disk booted up without a problem". Zenith Data Systems was bolder, bragging that its Z-150 ran all applications people brought to test with at the 1984 West Coast Computer Faire.


title: IBM PC compatible

text: "Creative Computing" in 1985 stated, "we reiterate our standard line regarding the IBM PC compatibles: try the package you want to use before you buy the computer." Companies modified their computers' BIOS to work with newly discovered incompatible applications, and reviewers and users developed stress tests to measure compatibility; by 1984 the ability to operate Lotus 1-2-3 and "Flight Simulator" became the standard, with compatibles specifically designed to run them.


title: IBM PC compatible

text: IBM believed that some companies such as Eagle, Corona, and Handwell infringed on its copyright, and after "Apple Computer, Inc. v. Franklin Computer Corp." successfully forced the clone makers to stop using the BIOS. The Phoenix BIOS in 1984, however, and similar products such as AMI BIOS, permitted computer makers to legally build essentially 100%-compatible clones without having to reverse-engineer the PC BIOS themselves. A September 1985 "InfoWorld" chart listed seven compatibles with RAM, two disk drives, and monochrome monitors for to , while the equivalent IBM PC cost . The inexpensive Leading Edge Model D is even compatible with IBM proprietary diagnostic software, unlike the Compaq Portable. By 1986 "Compute!" stated that "clones are generally reliable and about 99 percent compatible", and a 1987 survey in the magazine of the clone industry did not mention software compatibility, stating that "PC by now has come to stand for a computer capable of running programs that are managed by MS-DOS".


title: IBM PC compatible

text: In February 1984 "Byte" wrote that "IBM's burgeoning influence in the PC community is stifling innovation because so many other companies are mimicking Big Blue", but "The Economist" stated in November 1983, "The main reason why an IBM standard is not worrying is that it can help competition to flourish".


title: IBM PC compatible

text: By 1983, IBM had about 25% of sales of personal computers between and , and computers with some PC compatibility were another 25%. As the market and competition grew IBM's influence diminished. In November 1985 "PC Magazine" stated "Now that it has created the [PC] market, the market doesn't necessarily need IBM for the machines. It may depend on IBM to set standards and to develop higher-performance machines, but IBM had better conform to existing standards so as to not hurt users". In January 1987, Bruce Webster wrote in "Byte" of rumors that IBM would introduce proprietary personal computers with a proprietary operating system: "Who cares? If IBM does it, they will most likely just isolate themselves from the largest marketplace, in which they really can't compete anymore anyway". The magazine predicted that in 1987 the market "will complete its transition from an IBM standard to an Intel/MS-DOS/expansion bus standard ... Folks aren't so much concerned about IBM compatibility as they are about Lotus 1-2-3 compatibility". By 1992, "Macworld" stated that because of clones, "IBM lost control of its own market and became a minor player with its own technology".


title: IBM PC compatible

text: "The Economist" predicted in 1983 that "IBM will soon be as much a prisoner of its standards as its competitors are", because "Once enough IBM machines have been bought, IBM cannot make sudden changes in their basic design; what might be useful for shedding competitors would shake off even more customers". After IBM announced the OS/2-oriented PS/2 line in early 1987, sales of existing DOS-compatible PC compatibles rose, in part because the proprietary operating system was not available. In 1988, Gartner Group estimated that the public purchased 1.5 clones for every IBM PC. By 1989 Compaq was so influential that industry executives spoke of "Compaq compatible", with observers stating that customers saw the company as IBM's equal or superior.


title: IBM PC compatible

text: After 1987, IBM PC compatibles dominated both the home and business markets of commodity computers, with other notable alternative architectures being used in niche markets, like the Macintosh computers offered by Apple Inc. and used mainly for desktop publishing at the time, the aging 8-bit Commodore 64 which was selling for $150 by this time and became the world's best-selling computer, the 32-bit Commodore Amiga line used for television and video production and the 32-bit Atari ST used by the music industry. However, IBM itself lost the main role in the market for IBM PC compatibles by 1990. A few events in retrospect are important:


title: IBM PC compatible

text: Despite popularity of its ThinkPad set of laptop PC's, IBM finally relinquished its role as a consumer PC manufacturer during April 2005, when it sold its laptop and desktop PC divisions (ThinkPad/ThinkCentre) to Lenovo for .


title: IBM PC compatible

text: As of October 2007, Hewlett-Packard and Dell had the largest shares of the PC market in North America. They were also successful overseas, with Acer, Lenovo, and Toshiba also notable. Worldwide, a huge number of PCs are "white box" systems assembled by myriad local systems builders. Despite advances of computer technology, the IBM PC compatibles remained very much compatible with the original IBM PC computers, although most of the components implement the compatibility in special backward compatibility modes used only during a system boot. It was often more practical to run old software on a modern system using an emulator rather than relying on these features.


title: IBM PC compatible

text: One of the strengths of the PC compatible design is its modular hardware design. End-users could readily upgrade peripherals and, to some degree, processor and memory without modifying the computer's motherboard or replacing the whole computer, as was the case with many of the microcomputers of the time. However, as processor speed and memory width increased, the limits of the original XT/AT bus design were soon reached, particularly when driving graphics video cards. IBM did introduce an upgraded bus in the IBM PS/2 computer that overcame many of the technical limits of the XT/AT bus, but this was rarely used as the basis for IBM compatible computers since it required licence payments to IBM both for the PS/2 bus and any prior AT-bus designs produced by the company seeking a license. This was unpopular with hardware manufacturers and several competing bus standards were developed by consortiums, with more agreeable license terms. Various attempts to standardize the interfaces were made, but in practice, many of these attempts were either flawed or ignored. Even so, there were many expansion options, and despite the confusion of its users, the PC compatible design advanced much faster than other competing designs of the time, even if only because of its market dominance.


title: IBM PC compatible

text: During the 1990s, IBM's influence on PC architecture started to decline. "IBM PC compatible" becomes "Standard PC" in 1990s, and later "ACPI PC" in 2000s. An IBM-brand PC became the exception rather than the rule. Instead of placing importance on compatibility with the IBM PC, vendors began to emphasize compatibility with Windows. In 1993, a version of Windows NT was released that could operate on processors other than the x86 set. While it required that applications be recompiled, which most developers did not do, its hardware independence was used for Silicon Graphics (SGI) x86 workstations–thanks to NT's Hardware abstraction layer (HAL), they could operate NT (and its vast application library).


title: IBM PC compatible

text: No mass-market personal computer hardware vendor dared to be incompatible with the latest version of Windows, and Microsoft's annual WinHEC conferences provided a setting in which Microsoft could lobby for—and in some cases dictate—the pace and direction of the hardware of the PC industry. Microsoft and Intel had become so important to the ongoing development of PC hardware that industry writers began using the word Wintel to refer to the combined hardware-software system.


title: IBM PC compatible

text: This terminology itself is becoming a misnomer, as Intel has lost absolute control over the direction of x86 hardware development with AMD's AMD64. Additionally, non-Windows operating systems like macOS and Linux have established a presence on the x86 architecture.


title: IBM PC compatible

text: Although the IBM PC was designed for expandability, the designers could not anticipate the hardware developments of the 1980s, nor the size of the industry they would engender. To make things worse, IBM's choice of the Intel 8088 for the CPU introduced several limitations for developing software for the PC compatible platform. For example, the 8088 processor only had a 20-bit memory addressing space. To expand "PC"s beyond one megabyte, Lotus, Intel, and Microsoft jointly created expanded memory (EMS), a bank-switching scheme to allow more memory provided by add-in hardware, and accessed by a set of four 16-kilobyte "windows" inside the 20-bit addressing. Later, Intel CPUs had larger address spaces and could directly address 16 MB (80286) or more, causing Microsoft to develop extended memory (XMS) which did not require additional hardware.


title: IBM PC compatible

text: "Expanded" and "extended" memory have incompatible interfaces, so anyone writing software that used more than one megabyte had to provide for both systems for the greatest compatibility until MS-DOS began including EMM386, which simulated EMS memory using XMS memory. A protected mode OS can also be written for the 80286, but DOS application compatibility was more difficult than expected, not only because most DOS applications accessed the hardware directly, bypassing BIOS routines intended to ensure compatibility, but also that most BIOS requests were made by the first 32 interrupt vectors, which were marked as "reserved" for protected mode processor exceptions by Intel.


title: IBM PC compatible

text: Video cards suffered from their own incompatibilities. There was no standard interface for using higher-resolution SVGA graphics modes supported by later video cards. Each manufacturer developed their own methods of accessing the screen memory, including different mode numberings and different bank switching arrangements. The latter were used to address large images within a single 64 KB segment of memory. Previously, the VGA standard had used planar video memory arrangements to the same effect, but this did not easily extend to the greater colour depths and higher resolutions offered by SVGA adapters. An attempt at creating a standard named VESA BIOS Extensions (VBE) was made, but not all manufacturers used it.


title: IBM PC compatible

text: When the 386 was introduced, again a protected mode OS could be written for it. This time, DOS compatibility was much easier because of virtual 8086 mode. Unfortunately programs could not switch directly between them, so eventually, some new memory-model APIs were developed, VCPI and DPMI, the latter becoming the most popular.


title: IBM PC compatible

text: Because of the great number of third-party adapters and no standard for them, programming the PC could be difficult. Professional developers would operate a large test-suite of various known-to-be-popular hardware combinations.


title: IBM PC compatible

text: Meanwhile, consumers were overwhelmed by the competing, incompatible standards and many different combinations of hardware on offer. To give them some idea of what sort of PC they would need to operate their software, the Multimedia PC (MPC) standard was set during 1990. A PC that met the minimum MPC standard could be marketed with the MPC logo, giving consumers an easy-to-understand specification to look for. Software that could operate on the most minimally MPC-compliant PC would be guaranteed to operate on any MPC. The MPC level 2 and MPC level 3 standards were set later, but the term "MPC compliant" never became popular. After MPC level 3 during 1996, no further MPC standards were established.


title: IBM PC compatible

text: By the late 1990s, the success of Microsoft Windows had driven rival commercial operating systems into near-extinction, and had ensured that the "IBM PC compatible" computer was the dominant computing platform. This meant that if a developer made their software only for the Wintel platform, they would still be able to reach the vast majority of computer users. The only major competitor to Windows with more than a few percentage points of market share was Apple, Inc.'s Macintosh. The Mac started out billed as "the computer for the rest of us", but high prices and closed architecture drove the Macintosh into an education and desktop publishing niche, from which it only emerged in the mid-2000s. By the mid-1990s the Mac's market share had dwindled to around 5% and introducing a new rival operating system had become too risky a commercial venture. Experience had shown that even if an operating system was technically superior to Windows, it would be a failure in the market (BeOS and OS/2 for example). In 1989, Steve Jobs said of his new NeXT system, "It will either be the last new hardware platform to succeed, or the first to fail." Four years later in 1993, NeXT announced it was ending production of the NeXTcube and porting NeXTSTEP to Intel processors.


title: IBM PC compatible

text: Very early on in PC history, some companies introduced their own XT-compatible chipsets. For example, Chips and Technologies introduced their 82C100 XT Controller which integrated and replaced six of the original XT circuits: one 8237 DMA controller, one 8253 interrupt timer, one 8255 parallel interface controller, one 8259 interrupt controller, one 8284 clock generator, and one 8288 bus controller. Similar non-Intel chipsets appeared for the AT-compatibles, for example OPTi's 82C206 or 82C495XLC which were found in many 486 and early Pentium systems. The x86 chipset market was very volatile though. In 1993, VLSI Technology had become the dominant market player only to be virtually wiped out by Intel a year later. Intel has been the uncontested leader ever since. As the "Wintel" platform gained dominance Intel gradually abandoned the practice of licensing its technologies to other chipset makers; in 2010 Intel was involved in litigation related to their refusal to license their processor bus and related technologies to other companies like Nvidia.


title: IBM PC compatible

text: Companies such as AMD and Cyrix developed alternative x86 CPUs that were functionally compatible with Intel's. Towards the end of the 1990s, AMD was taking an increasing share of the CPU market for PCs. AMD even ended up playing a significant role in directing the development of the x86 platform when its Athlon line of processors continued to develop the classic x86 architecture as Intel deviated with its Netburst architecture for the Pentium 4 CPUs and the IA-64 architecture for the Itanium set of server CPUs. AMD developed AMD64, the first major extension not created by Intel, which Intel later adopted as x86-64. During 2006 Intel began abandoning Netburst with the release of their set of "Core" processors that represented a development of the earlier Pentium III.


title: IBM PC compatible

text: A major alternative to Wintel domination is the rise of alternative operating systems since the early 2000s, which has been marked as the start of a post-PC era.


title: IBM PC compatible

text: The term "IBM PC compatible" is not commonly used presently because many current mainstream desktop and laptop computers are based on the PC architecture, and IBM no longer makes PCs. The competing hardware architectures have either been discontinued or, like the Amiga, have been relegated to niche, enthusiast markets. In the past, the most successful exception was Apple's Macintosh platform, which used non-Intel processors from its inception. Although Macintosh was initially based on the Motorola 68000 series, then transitioned to the PowerPC architecture, Macintosh computers transitioned to Intel processors beginning in 2006. Until 2020 Macintosh computers shared the same system architecture as their Wintel counterparts and could boot Microsoft Windows without a DOS Compatibility Card. However, with the announcement of the internally developed ARM-based M1 CPU, they are again the exception to IBM compatibility.


title: IBM PC compatible

text: The processor speed and memory capacity of modern PCs are many orders of magnitude greater than they were for the original IBM PC and yet backwards compatibility has been largely maintained a 32-bit operating system can still operate many of the simpler programs written for the OS of the early 1980s without needing an emulator, though an emulator like DOSBox now has near-native functionality at full speed (and is necessary for certain games which may run too fast on modern processors). Additionally, many modern PCs can still run DOS directly, although special options such as USB legacy mode and SATA-to-PATA emulation may need to be set in the BIOS setup utility. Computers using the UEFI might need to be set at legacy BIOS mode to be able to boot DOS. However, the BIOS/UEFI options in most mass-produced consumer-grade computers are very limited and cannot be configured to truly handle OSes such as the original variants of DOS.


title: IBM PC compatible

text: The spread of the x86-64 architecture has further distanced current computers' and operating systems' internal similarity with the original IBM PC by introducing yet another processor mode with an instruction set modified for 64-bit addressing, but x86-64 capable processors also retain standard x86 compatibility.


title: Lara Lewington

text: Lara Lewington (born 10 May 1979) is a British television presenter, journalist and former weather presenter. She co-presents the BBC's technology programme "Click".


title: Lara Lewington

text: Lewington attended Surbiton High School, an independent school in Surbiton, Greater London. She studied at St Mary's University, Twickenham. She reports working as a runner on the game show "It's a Knockout" while at the university.


title: Lara Lewington

text: Lewington joined Five in January 2003, as their weather presenter. She spent six years at the channel, also becoming the showbiz correspondent for "Five News," before a stint as showbiz correspondent on Sky News.


title: Lara Lewington

text: She contributed to various shows including "The Weakest Link" News and Weather special, ITV1's "Celebrities Exposed and" E!'s "101 Greatest" programmes. She has also appeared weekly on ITV's "The Impressionable Jon Culshaw", was a panellist on ITV's "Win, Lose or Draw", and has appeared on BBC Two's "Newsnight", Channel 4's "", "Big Brother's Big Mouth", ITV's "Britain's Best Dish", the BBC's "Let's Dance For Sports Relief" and appeared as one of the four representatives of Five TV on the BBC One "Sport Relief" "Superstars" special.


title: Lara Lewington

text: Lewington joined BBC's "Click" in 2011 as a reporter and later became a presenter in 2018. She co-presents the show with Spencer Kelly and appears on other radio and TV shows talking about technology. She has also been the technology columnist for "Woman" magazine.


title: Lara Lewington

text: Lewington can be seen presenting the weather on a background monitor in the "Daily Planet" newsroom in the 2006 film "Superman Returns". She appeared in British comedy feature film "Shouting Men" (2010) and BBC2's "Happiness".


title: Lara Lewington

text: Lewington married financial journalist and broadcaster Martin Lewis in 2009. They have one daughter born in 2012.


title: Xenotransplantation

text: Xenotransplantation ("xenos-" from the Greek meaning "foreign" or strange), or heterologous transplant, is the transplantation of living cells, tissues or organs from one species to another. Such cells, tissues or organs are called xenografts or xenotransplants. It is contrasted with allotransplantation (from other individual of same species), syngeneic transplantation or isotransplantation (grafts transplanted between two genetically identical individuals of the same species) and autotransplantation (from one part of the body to another in the same person).


title: Xenotransplantation

text: Xenotransplantation of human tumor cells into immunocompromised mice is a research technique frequently used in pre-clinical oncology research.


title: Xenotransplantation

text: Human xenotransplantation offers a potential treatment for end-stage organ failure, a significant health problem in parts of the industrialized world. It also raises many novel medical, legal and ethical issues. A continuing concern is that many animals, such as pigs, have a shorter lifespan than humans, meaning that their tissues age at a quicker rate. (Pigs have a maximum life span of about 27 years.) Disease transmission (xenozoonosis) and permanent alteration to the genetic code of animals are also causes for concern. Similarly to objections to animal testing, animal rights activists have also objected to xenotransplantation on ethical grounds. A few temporarily successful cases of xenotransplantation are published.


title: Xenotransplantation

text: It is common for patients and physicians to use the term "allograft" imprecisely to refer to either allograft (human-to-human) or xenograft (animal-to-human), but it is helpful scientifically (for those searching or reading the scientific literature) to maintain the more precise distinction in usage.


title: Xenotransplantation

text: The first serious attempts at xenotransplantation (then called heterotransplantation) appeared in the scientific literature in 1905, when slices of rabbit kidney were transplanted into a child with chronic kidney disease. In the first two decades of the 20th century, several subsequent efforts to use organs from lambs, pigs, and primates were published.


title: Xenotransplantation

text: Scientific interest in xenotransplantation declined when the immunological basis of the organ rejection process was described. The next waves of studies on the topic came with the discovery of immunosuppressive drugs. Even more studies followed Joseph Murray's first successful renal transplantation in 1954 and scientists, facing the ethical questions of organ donation for the first time, accelerated their effort in looking for alternatives to human organs.


title: Xenotransplantation

text: In 1963, doctors at Tulane University attempted chimpanzee-to-human renal transplantations in six people who were near death; after this and several subsequent unsuccessful attempts to use primates as organ donors and the development of a working cadaver organ procuring program, interest in xenotransplantation for kidney failure dissipated. Out of 13 such transplants performed by Keith Reemtsma, one kidney recipient lived for nine months, returning to work as a schoolteacher. At autopsy, the chimpanzee kidneys appeared normal and showed no signs of acute or chronic rejection.


title: Xenotransplantation

text: An American infant girl known as "Baby Fae" with hypoplastic left heart syndrome was the first infant recipient of a xenotransplantation, when she received a baboon heart in 1984. The procedure was performed by Leonard Lee Bailey at Loma Linda University Medical Center in Loma Linda, California. Fae died 21 days later due to a humoral-based graft rejection thought to be caused mainly by an ABO blood type mismatch, considered unavoidable due to the rarity of type O baboons. The graft was meant to be temporary, but unfortunately a suitable allograft replacement could not be found in time. While the procedure itself did not advance the progress on xenotransplantation, it did shed a light on the insufficient amount of organs for infants. The story made such an impact that the crisis of infant organ shortage improved for that time.


title: Xenotransplantation

text: The first transplant of a non-genetically modified pig's heart, lungs and kidneys into a human was performed in Sonapur, Assam in India in mid-December 1996, and was announced in January 1997. The recipient was Purno Saikia, a 32-year-old terminally-ill man; he died shortly after the operation of multiple infections. The Indian cardiothoracic surgeon Dhani Ram Baruah and two of his associates, Jonathan Ho Kei-shing (of the Hong Kong-based Prince of Wales Medical Institute) and C.S. James, performed the surgeries. Baruah claimed that Saikia had failed to respond to conventional surgery, and that the patient and his family had consented to the procedure.


title: Xenotransplantation

text: All three involved in the surgery were arrested on January 9, 1997, for the alleged violation of the Transplantation of Human Organs and Tissues Act of 1994. Baruah was dismissed in medical circles as a "mad scientist" and the procedure was dubbed a "hoax". Baruah himself signed a statement saying he had done no transplant, but then alleged that the confession was forced from him. They were found guilty of unethical procedure and culpable homicide and imprisoned for 40 days. Dhani Ram Baruah's surgical institute was also found to be without necessary registration.


title: Xenotransplantation

text: Critics said Dhani Bam Baruah's claims and medical procedures were neither taken seriously nor accepted by the scientific community because he never got his findings scientifically peer-reviewed. Past complaints of ethics violations during surgeries in Hong Kong by Baruah and Ho had occurred in 1992, when they had implanted heart valves, developed by Baruah, made of animal tissue. A year later, six patients died. The Asian Medical News reported that "grave concerns" were expressed "over the procedure and ethics of the implementation".


title: Xenotransplantation

text: In September 2021, surgeons led by Robert Montgomery performed the first genetically engineered pig kidney xenotransplant to a brain-dead human at NYU Langone Health with no sign of immediate rejection (partly because the pig thymus gland was transplanted as well). The kidney was procured from a pig with only a single gene modification: the removal of alpha-gal.


title: Xenotransplantation

text: In January 2022, doctors led by cardiothoracic surgeon Bartley P. Griffith and Muhammad M. Mohiuddin at the University of Maryland Medical Center and University of Maryland School of Medicine performed a heart transplant from a genetically modified pig to a terminally ill patient, David Bennett Sr., who was ineligible for a standard human heart transplant. The pig had undergone specific gene editing to remove enzymes responsible for producing sugar antigens that lead to hyperacute organ rejection in humans. The US medical regulator gave special dispensation to carry out the procedure under compassionate use criteria. The recipient died two months after the transplantation.


title: Xenotransplantation

text: In June and July 2022, surgeons at NYU Langone Health performed two genetically modified pig heart transplants into recently deceased humans. The hearts were from pigs that had the identical 10 genetic modifications used in the University of Maryland Medical Center heart xenotransplantation in January 2022. All three hearts came from Revivicor, Inc., a facility based in Blacksburg, Va., and a subsidiary of United Therapeutics.


title: Xenotransplantation

text: A worldwide shortage of organs for clinical implantation causes about 20–35% of patients who need replacement organs to die on the waiting list. Certain procedures, some of which are being investigated in early clinical trials, aim to use cells or tissues from other species to treat life-threatening and debilitating illnesses such as cancer, diabetes, liver failure and Parkinson's disease. If vitrification can be perfected, it could allow for long-term storage of xenogenic cells, tissues and organs so that they would be more readily available for transplant.


title: Xenotransplantation

text: Xenotransplants could save thousands of patients waiting for donated organs. The animal organ, probably from a pig or baboon could be genetically altered with human genes to trick a patient's immune system into accepting it as a part of its own body. They have re-emerged because of the lack of organs available and the constant battle to keep immune systems from rejecting allotransplants. Xenotransplants are thus potentially a more effective alternative.


title: Xenotransplantation

text: Xenotransplantation of human tumor cells into immunocompromised mice is a research technique frequently used in oncology research. It is used to predict the sensitivity of the transplanted tumor to various cancer treatments; several companies offer this service, including the Jackson Laboratory.


title: Xenotransplantation

text: Human organs have been transplanted into animals as a powerful research technique for studying human biology without harming human patients. This technique has also been proposed as an alternative source of human organs for future transplantation into human patients. For example, researchers from the Ganogen Research Institute transplanted human fetal kidneys into rats which demonstrated life supporting function and growth.


title: Xenotransplantation

text: Since they are the closest relatives to humans, non-human primates were first considered as a potential organ source for xenotransplantation to humans. Chimpanzees were originally considered the best option since their organs are of similar size, and they have good blood type compatibility with humans, which makes them potential candidates for xenotransfusions. However, since chimpanzees are listed as an endangered species, other potential donors were sought. Baboons are more readily available, but impractical as potential donors. Problems include their smaller body size, the infrequency of blood group O (the universal donor), their long gestation period, and their typically small number of offspring. In addition, a major problem with the use of nonhuman primates is the increased risk of disease transmission, since they are so closely related to humans.


title: Xenotransplantation

text: Pigs ("Sus scrofa domesticus") are currently thought to be the best candidates for organ donation. The risk of cross-species disease transmission is decreased because of their increased phylogenetic distance from humans. Pigs have relatively short gestation periods, large litters, and are easy to breed, making them readily available.


title: Xenotransplantation

text: They are inexpensive and easy to maintain in pathogen-free facilities, and current gene editing tools are adapted to pigs to combat rejection and potential zoonoses. Pig organs are anatomically comparable in size, and new infectious agents are less likely since they have been in close contact with humans through domestication for many generations. Treatments sourced from pigs have proven to be successful such as porcine-derived insulin for patients with diabetes mellitus. Increasingly, genetically engineered pigs are becoming the norm, which raises moral qualms, but also increases the success rate of the transplant.


title: Xenotransplantation

text: Current experiments in xenotransplantation most often use pigs as the donor, and baboons as human models. In 2020 the U.S. Food and Drug Administration approved a genetic modification of pigs so they do not produce alpha-gal sugars. Pig organs have been used for kidney and heart transplants into humans.


title: Xenotransplantation

text: In the field of regenerative medicine, pancreatogenesis- or nephrogenesis-disabled pig embryos, unable to form a specific organ, allow experimentation toward the "in vivo" generation of functional organs from xenogenic pluripotent stem cells in large animals via compensation for an empty developmental niche (blastocyst complementation). Such experiments provide the basis for potential future application of blastocyst complementation to generate transplantable human organs from the patient's own cells, using livestock animals, to increase quality of life for those with end-stage organ failure.


title: Xenotransplantation

text: To date, no xenotransplantation trials have been entirely successful due to the many obstacles arising from the response of the recipient's immune system. "Xenozoonoses" are one of the biggest threats to rejections, as they are xenogenetic infections. The introduction of these microorganisms are a big issue that lead to the fatal infections and then rejection of the organs. This response, which is generally more extreme than in allotransplantations, ultimately results in rejection of the xenograft, and can in some cases result in the immediate death of the recipient. There are several types of rejection organ xenografts are faced with, these include hyperacute rejection, acute vascular rejection, cellular rejection, and chronic rejection.


title: Xenotransplantation

text: A rapid, violent, and hyperacute response comes as a result of antibodies present in the host organism. These antibodies are known as xenoreactive natural antibodies (XNAs).


title: Xenotransplantation

text: This rapid and violent type of rejection occurs within minutes to hours from the time of the transplant. It is mediated by the binding of XNAs (xenoreactive natural antibodies) to the donor endothelium, causing activation of the human complement system, which results in endothelial damage, inflammation, thrombosis and necrosis of the transplant. XNAs are first produced and begin circulating in the blood in neonates, after colonization of the bowel by bacteria with galactose moieties on their cell walls. Most of these antibodies are the IgM class, but also include IgG, and IgA.


title: Xenotransplantation

text: The epitope XNAs target is an α-linked galactose moiety, galactose-alpha-1,3-galactose (also called the α-Gal epitope), produced by the enzyme alpha-galactosyltransferase. Most non-primates contain this enzyme thus, this epitope is present on the organ epithelium and is perceived as a foreign antigen by primates, which lack the galactosyl transferase enzyme. In pig to primate xenotransplantation, XNAs recognize porcine glycoproteins of the integrin family.


title: Xenotransplantation

text: The binding of XNAs initiate complement activation through the classical complement pathway. Complement activation causes a cascade of events leading to: destruction of endothelial cells, platelet degranulation, inflammation, coagulation, fibrin deposition, and hemorrhage. The result is thrombosis and necrosis of the xenograft.


title: Xenotransplantation

text: Since hyperacute rejection presents such a barrier to the success of xenografts, several strategies to overcome it are under investigation:


title: Xenotransplantation

text: Also known as delayed xenoactive rejection, this type of rejection occurs in discordant xenografts within 2 to 3 days, if hyperacute rejection is prevented. The process is much more complex than hyperacute rejection and is currently not completely understood. Acute vascular rejection requires de novo protein synthesis and is driven by interactions between the graft endothelial cells and host antibodies, macrophages, and platelets. The response is characterized by an inflammatory infiltrate of mostly macrophages and natural killer cells (with small numbers of T cells), intravascular thrombosis, and fibrinoid necrosis of vessel walls.