title: Stem-cell therapy

text: Use of mesenchymal stem cells (MSCs) derived from adult stem cells is under preliminary research for potential orthopedic applications in bone and muscle trauma, cartilage repair, osteoarthritis, intervertebral disc surgery, rotator cuff surgery, and musculoskeletal disorders, among others. Other areas of orthopedic research for uses of MSCs include tissue engineering and regenerative medicine.


title: Stem-cell therapy

text: Stem cells can also be used to stimulate the growth of human tissues. In an adult, wounded tissue is most often replaced by scar tissue, which is characterized in the skin by disorganized collagen structure, loss of hair follicles and irregular vascular structure. In the case of wounded fetal tissue, however, wounded tissue is replaced with normal tissue through the activity of stem cells. A possible method for tissue regeneration in adults is to place adult stem cell "seeds" inside a tissue bed "soil" in a wound bed and allow the stem cells to stimulate differentiation in the tissue bed cells. This method elicits a regenerative response more similar to fetal wound-healing than adult scar tissue formation. Researchers are still investigating different aspects of the "soil" tissue that are conducive to regeneration. Because of the general healing capabilities of stem cells, they have gained interest for the treatment of cutaneous wounds, such as in skin cancer.


title: Stem-cell therapy

text: Destruction of the immune system by the HIV is driven by the loss of CD4+ T cells in the peripheral blood and lymphoid tissues. Viral entry into CD4+ cells is mediated by the interaction with a cellular chemokine receptor, the most common of which are CCR5 and CXCR4. Because subsequent viral replication requires cellular gene expression processes, activated CD4+ cells are the primary targets of productive HIV infection. Recently scientists have been investigating an alternative approach to treating HIV-1/AIDS, based on the creation of a disease-resistant immune system through transplantation of autologous, gene-modified (HIV-1-resistant) hematopoietic stem and progenitor cells (GM-HSPC).


title: Stem-cell therapy

text: Stem cells are thought to mediate repair via five primary mechanisms: 1) providing an anti-inflammatory effect, 2) homing to damaged tissues and recruiting other cells, such as endothelial progenitor cells, that are necessary for tissue growth, 3) supporting tissue remodeling over scar formation, 4) inhibiting apoptosis, and 5) differentiating into bone, cartilage, tendon, and ligament tissue.


title: Stem-cell therapy

text: To further enrich blood supply to the damaged areas, and consequently promote tissue regeneration, platelet-rich plasma could be used in conjunction with stem cell transplantation. The efficacy of some stem cell populations may also be affected by the method of delivery; for instance, to regenerate bone, stem cells are often introduced in a scaffold where they produce the minerals necessary for generation of functional bone.


title: Stem-cell therapy

text: Stem cells have also been shown to have a low immunogenicity due to the relatively low number of MHC molecules found on their surface. In addition, they have been found to secrete chemokines that alter the immune response and promote tolerance of the new tissue. This allows for allogeneic treatments to be performed without a high rejection risk.


title: Stem-cell therapy

text: The ability to grow up functional adult tissues indefinitely in culture through Directed differentiation creates new opportunities for drug research. Researchers are able to grow up differentiated cell lines and then test new drugs on each cell type to examine possible interactions "in vitro" before performing "in vivo" studies. This is critical in the development of drugs for use in veterinary research because of the possibilities of species-specific interactions. The hope is that having these cell lines available for research use will reduce the need for research animals used because effects on human tissue "in vitro" will provide insight not normally known before the animal testing phase.


title: Stem-cell therapy

text: Stem cells are being explored for use in conservation efforts. Spermatogonial stem cells have been harvested from a rat and placed into a mouse host and fully mature sperm were produced with the ability to produce viable offspring. Currently research is underway to find suitable hosts for the introduction of donor spermatogonial stem cells. If this becomes a viable option for conservationists, sperm can be produced from high genetic quality individuals who die before reaching sexual maturity, preserving a line that would otherwise be lost.


title: Stem-cell therapy

text: Most stem cells intended for regenerative therapy are generally isolated either from the patient's bone marrow or from adipose tissue. Mesenchymal stem cells can differentiate into the cells that make up bone, cartilage, tendons, and ligaments, as well as muscle, neural and other progenitor tissues. They have been the main type of stem cells studied in the treatment of diseases affecting these tissues. The number of stem cells transplanted into damaged tissue may alter the efficacy of treatment. Accordingly, stem cells derived from bone marrow aspirates, for instance, are cultured in specialized laboratories for expansion to millions of cells. Although adipose-derived tissue also requires processing prior to use, the culturing methodology for adipose-derived stem cells is not as extensive as that for bone marrow-derived cells. While it is thought that bone-marrow-derived stem cells are preferred for bone, cartilage, ligament, and tendon repair, others believe that the less challenging collection techniques and the multi-cellular microenvironment already present in adipose-derived stem cell fractions make the latter the preferred source for autologous transplantation.


title: Stem-cell therapy

text: New sources of mesenchymal stem cells are being researched, including stem cells present in the skin and dermis which are of interest because of the ease at which they can be harvested with minimal risk to the animal. Hematopoietic stem cells have also been discovered to be travelling in the blood stream and possess equal differentiating ability as other mesenchymal stem cells, again with a very non-invasive harvesting technique.


title: Stem-cell therapy

text: There has been more recent interest in the use of extra embryonic mesenchymal stem cells. Research is underway to examine the differentiating capabilities of stem cells found in the umbilical cord, yolk sac and placenta of different animals. These stem cells are thought to have more differentiating ability than their adult counterparts, including the ability to more readily form tissues of endodermal and ectodermal origin.


title: Stem-cell therapy

text: There is widespread controversy over the use of human embryonic stem cells. This controversy primarily targets the techniques used to derive new embryonic stem cell lines, which often requires the destruction of the blastocyst. Opposition to the use of human embryonic stem cells in research is often based on philosophical, moral, or religious objections. There is other stem cell research that does not involve the destruction of a human embryo, and such research involves adult stem cells, amniotic stem cells, and induced pluripotent stem cells.


title: Stem-cell therapy

text: On 23 January 2009, the US Food and Drug Administration gave clearance to Geron Corporation for the initiation of the first clinical trial of an embryonic stem-cell-based therapy on humans. The trial aimed to evaluate the drug GRNOPC1, embryonic stem cell-derived oligodendrocyte progenitor cells, on people with acute spinal cord injury. The trial was discontinued in November 2011 so that the company could focus on therapies in the "current environment of capital scarcity and uncertain economic conditions". In 2013 biotechnology and regenerative medicine company BioTime () acquired Geron's stem cell assets in a stock transaction, with the aim of restarting the clinical trial.


title: Stem-cell therapy

text: Scientists have reported that MSCs when transfused immediately within few hours post thawing may show reduced function or show decreased efficacy in treating diseases as compared to those MSCs which are in log phase of cell growth (fresh), so cryopreserved MSCs should be brought back into log phase of cell growth in invitro culture before administration. Re-culturing of MSCs will help in recovering from the shock the cells get during freezing and thawing. Various MSC clinical trials which used cryopreserved product immediately post thaw have failed as compared to those clinical trials which used fresh MSCs.


title: Stem-cell therapy

text: Research has been conducted on horses, dogs, and cats can benefit the development of stem cell treatments in veterinary medicine and can target a wide range of injuries and diseases such as myocardial infarction, stroke, tendon and ligament damage, osteoarthritis, osteochondrosis and muscular dystrophy both in large animals, as well as humans. While investigation of cell-based therapeutics generally reflects human medical needs, the high degree of frequency and severity of certain injuries in racehorses has put veterinary medicine at the forefront of this novel regenerative approach. Companion animals can serve as clinically relevant models that closely mimic human disease.


title: Stem-cell therapy

text: Veterinary applications of stem cell therapy as a means of tissue regeneration have been largely shaped by research that began with the use of adult-derived mesenchymal stem cells to treat animals with injuries or defects affecting bone, cartilage, ligaments and/or tendons. There are two main categories of stem cells used for treatments: allogeneic stem cells derived from a genetically different donor within the same species and autologous mesenchymal stem cells, derived from the patient prior to use in various treatments. A third category, xenogenic stem cells, or stem cells derived from different species, are used primarily for research purposes, especially for human treatments.


title: Stem-cell therapy

text: Bone has a unique and well documented natural healing process that normally is sufficient to repair fractures and other common injuries. Misaligned breaks due to severe trauma, as well as treatments like tumor resections of bone cancer, are prone to improper healing if left to the natural process alone. Scaffolds composed of natural and artificial components are seeded with mesenchymal stem cells and placed in the defect. Within four weeks of placing the scaffold, newly formed bone begins to integrate with the old bone and within 32 weeks, full union is achieved. Further studies are necessary to fully characterize the use of cell-based therapeutics for treatment of bone fractures.


title: Stem-cell therapy

text: Stem cells have been used to treat degenerative bone diseases. The normally recommended treatment for dogs that have Legg–Calve–Perthes disease is to remove the head of the femur after the degeneration has progressed. Recently, mesenchymal stem cells have been injected directly in to the head of the femur, with success not only in bone regeneration, but also in pain reduction.


title: Stem-cell therapy

text: Autologous stem cell-based treatments for ligament injury, tendon injury, osteoarthritis, osteochondrosis, and sub-chondral bone cysts have been commercially available to practicing veterinarians to treat horses since 2003 in the United States and since 2006 in the United Kingdom. Autologous stem cell based treatments for tendon injury, ligament injury, and osteoarthritis in dogs have been available to veterinarians in the United States since 2005. Over 3000 privately owned horses and dogs have been treated with autologous adipose-derived stem cells. The efficacy of these treatments has been shown in double-blind clinical trials for dogs with osteoarthritis of the hip and elbow and horses with tendon damage.


title: Stem-cell therapy

text: Race horses are especially prone to injuries of the tendon and ligaments. Conventional therapies are very unsuccessful in returning the horse to full functioning potential. Natural healing, guided by the conventional treatments, leads to the formation of fibrous scar tissue that reduces flexibility and full joint movement. Traditional treatments prevented a large number of horses from returning to full activity and also have a high incidence of re-injury due to the stiff nature of the scarred tendon. Introduction of both bone marrow and adipose derived stem cells, along with natural mechanical stimulus promoted the regeneration of tendon tissue. The natural movement promoted the alignment of the new fibers and tendocytes with the natural alignment found in uninjured tendons. Stem cell treatment not only allowed more horses to return to full duty and also greatly reduced the re-injury rate over a three-year period.


title: Stem-cell therapy

text: The use of embryonic stem cells has also been applied to tendon repair. The embryonic stem cells were shown to have a better survival rate in the tendon as well as better migrating capabilities to reach all areas of damaged tendon. The overall repair quality was also higher, with better tendon architecture and collagen formed. There was also no tumor formation seen during the three-month experimental period. Long-term studies need to be carried out to examine the long-term efficacy and risks associated with the use of embryonic stem cells. Similar results have been found in small animals.


title: Stem-cell therapy

text: Osteoarthritis is the main cause of joint pain both in animals and humans. Horses and dogs are most frequently affected by arthritis. Natural cartilage regeneration is very limited. Different types of mesenchymal stem cells and other additives are still being researched to find the best type of cell and method for long-term treatment.


title: Stem-cell therapy

text: Adipose-derived mesenchymal cells are currently the most often used for stem cell treatment of osteoarthritis because of the non-invasive harvesting. This is a recently developed, non-invasive technique developed for easier clinical use. Dogs receiving this treatment showed greater flexibility in their joints and less pain.


title: Stem-cell therapy

text: Stem cells have successfully been used to ameliorate healing in the heart after myocardial infarction in dogs. Adipose and bone marrow derived stem cells were removed and induced to a cardiac cell fate before being injected into the heart. The heart was found to have improved contractility and a reduction in the damaged area four weeks after the stem cells were applied.


title: Stem-cell therapy

text: A different trial is underway for a patch made of a porous substance onto which the stem cells are "seeded" in order to induce tissue regeneration in heart defects. Tissue was regenerated and the patch was well incorporated into the heart tissue. This is thought to be due, in part, to improved angiogenesis and reduction of inflammation. Although cardiomyocytes were produced from the mesenchymal stem cells, they did not appear to be contractile. Other treatments that induced a cardiac fate in the cells before transplanting had greater success at creating contractile heart tissue.


title: Stem-cell therapy

text: Recent research, such as the European nTRACK research project, aims to demonstrate that multimodal nanoparticles can structurally and functionally track stem cell in muscle regeneration therapy. The idea is to label stem cells with gold nano-particles that are fully characterised for uptake, functionality, and safety. The labelled stem cells will be injected into an injured muscle and tracked using imaging systems. However, the system still needs to be demonstrated at lab scale.


title: Stem-cell therapy

text: Spinal cord injuries are one of the most common traumas brought into veterinary hospitals. Spinal injuries occur in two ways after the trauma: the primary mechanical damage, and in secondary processes, like inflammation and scar formation, in the days following the trauma. These cells involved in the secondary damage response secrete factors that promote scar formation and inhibit cellular regeneration. Mesenchymal stem cells that are induced to a neural cell fate are loaded onto a porous scaffold and are then implanted at the site of injury. The cells and scaffold secrete factors that counteract those secreted by scar forming cells and promote neural regeneration. Eight weeks later, dogs treated with stem cells showed immense improvement over those treated with conventional therapies. Dogs treated with stem cells were able to occasionally support their own weight, which has not been seen in dogs undergoing conventional therapies.


title: Stem-cell therapy

text: In a study to evaluate the treatment of experimentally induced MS in dogs using laser activated non-expanded adipose derived stem cells. The results showed amelioration of the clinical signs over time confirmed by the resolution of the previous lesions on MRI. Positive migration of the injected cells to the site of lesion, increased remyelination detected by Myelin Basic Proteins, positive differentiation into Olig2 positive oligodendrocytes, prevented the glial scar formation and restored axonal architecture.


title: Stem-cell therapy

text: Treatments are also in clinical trials to repair and regenerate peripheral nerves. Peripheral nerves are more likely to be damaged, but the effects of the damage are not as widespread as seen in injuries to the spinal cord. Treatments are currently in clinical trials to repair severed nerves, with early success. Stem cells induced to a neural fate injected in to a severed nerve. Within four weeks, regeneration of previously damaged stem cells and completely formed nerve bundles were observed.


title: Stem-cell therapy

text: Stem cells are also in clinical phases for treatment in ophthalmology. Hematopoietic stem cells have been used to treat corneal ulcers of different origin of several horses. These ulcers were resistant to conventional treatments available, but quickly responded positively to the stem cell treatment. Stem cells were also able to restore sight in one eye of a horse with retinal detachment, allowing the horse to return to daily activities.


title: Stem-cell therapy

text: In the late 1990s and early 2000s, there was an initial wave of companies and clinics offering stem cell therapy, while not substantiating health claims or having regulatory approval. By 2012, a second wave of companies and clinics had emerged, usually located in developing countries where medicine is less regulated and offering stem cell therapies on a medical tourism model. Like the first wave companies and clinics, they made similar strong, but unsubstantiated, claims, mainly by clinics in the United States, Mexico, Thailand, India, and South Africa. By 2016, research indicated that there were more than 550 stem cell clinics in the US alone selling generally unproven therapies for a wide array of medical conditions in almost every state in the country, altering the dynamic of stem cell tourism. In 2018, the FDA sent a warning letter to StemGenex Biologic Laboratories in San Diego, which marketed a service in which it took body fat from people, processed it into mixtures it said contained various forms of stem cells, and administered it back to the person by inhalation, intravenously, or infusion into their spinal cords; the company said the treatment was useful for many chronic and life-threatening conditions.


title: Stem-cell therapy

text: Costs of stem cell therapies range widely by clinic, condition, and cell type, but most commonly range between $10,000-$20,000. Insurance does not cover stem cell injections at clinics so patients often use on-line fundraising. In 2018, the US Federal Trade Commission found health centers and an individual physician making unsubstantiated claims for stem cell therapies, and forced refunds of some $500,000. The FDA filed suit against two stem cell clinic firms around the same time, seeking permanent injunctions against their marketing and use of unapproved adipose stem cell products.


title: Stem-cell therapy

text: Although according to the NIH no stem cell treatments have been approved for COVID-19 and the agency recommends against the use of MSCs for the disease, some stem cell clinics began marketing both unproven and non-FDA-approved stem cells and exosomes for COVID-19 in 2020. The FDA took prompt action by sending letters to the firms in question. The FTC also warned a stem cell firm for COVID-19-related marketing.


title: Endangered language

text: An endangered language or moribund language is a language that is at risk of disappearing as its speakers die out or shift to speaking other languages. Language loss occurs when the language has no more native speakers and becomes a "dead language". If no one can speak the language at all, it becomes an "extinct language". A dead language may still be studied through recordings or writings, but it is still dead or extinct unless there are fluent speakers. Although languages have always become extinct throughout human history, they are currently dying at an accelerated rate because of globalization, imperialism, neocolonialism and linguicide (language killing).


title: Endangered language

text: Language shift most commonly occurs when speakers switch to a language associated with social or economic power or spoken more widely, the ultimate result being language death. The general consensus is that there are between 6,000 and 7,000 languages currently spoken. Some linguists estimate that between 50% and 90% of them will be severely endangered or dead by the year 2100. The 20 most common languages, each with more than 50 million speakers, are spoken by 50% of the world's population, but most languages are spoken by fewer than 10,000 people. On a more general level, 0.2% of the world's languages are spoken by half of the world's population. Furthermore, 96% of the world's languages are spoken by 4% of the population.


title: Endangered language

text: The first step towards language death is "potential endangerment". This is when a language faces strong external pressure, but there are still communities of speakers who pass the language to their children. The second stage is "endangerment". Once a language has reached the endangerment stage, there are only a few speakers left and children are, for the most part, not learning the language. The third stage of language extinction is "seriously endangered". During this stage, a language is unlikely to survive another generation and will soon be extinct. The fourth stage is "moribund", followed by the fifth stage "extinction".


title: Endangered language

text: Many projects are under way aimed at preventing or slowing language loss by revitalizing endangered languages and promoting education and literacy in minority languages, often involving joint projects between language communities and linguists. Across the world, many countries have enacted specific legislation aimed at protecting and stabilizing the language of indigenous speech communities. Recognizing that most of the world's endangered languages are unlikely to be revitalized, many linguists are also working on documenting the thousands of languages of the world about which little or nothing is known.


title: Endangered language

text: The total number of contemporary languages in the world is not known, and it is not well defined what constitutes a separate language as opposed to a dialect. Estimates vary depending on the extent and means of the research undertaken, and the definition of a distinct language and the current state of knowledge of remote and isolated language communities. The number of known languages varies over time as some of them become extinct and others are newly discovered. An accurate number of languages in the world was not yet known until the use of universal, systematic surveys in the later half of the twentieth century. The majority of linguists in the early twentieth century refrained from making estimates. Before then, estimates were frequently the product of guesswork and very low.


title: Endangered language

text: One of the most active research agencies is SIL International, which maintains a database, Ethnologue, kept up to date by the contributions of linguists globally.


title: Endangered language

text: Ethnologue's 2005 count of languages in its database, excluding duplicates in different countries, was 6,912, of which 32.8% (2,269) were in Asia, and 30.3% (2,092) in Africa. This contemporary tally must be regarded as a variable number within a range. Areas with a particularly large number of languages that are nearing extinction include: Eastern Siberia, Central Siberia, Northern Australia, Central America, and the Northwest Pacific Plateau. Other hotspots are Oklahoma and the Southern Cone of South America.


title: Endangered language

text: Almost all of the study of language endangerment has been with spoken languages. A UNESCO study of endangered languages does not mention sign languages. However, some sign languages are also endangered, such as Alipur Village Sign Language (AVSL) of India, Adamorobe Sign Language of Ghana, Ban Khor Sign Language of Thailand, and Plains Indian Sign Language. Many sign languages are used by small communities; small changes in their environment (such as contact with a larger sign language or dispersal of the deaf community) can lead to the endangerment and loss of their traditional sign language. Methods are being developed to assess the vitality of sign languages.


title: Endangered language

text: While there is no definite threshold for identifying a language as endangered, UNESCO's 2003 document entitled "Language vitality and endangerment" outlines nine factors for determining language vitality:


title: Endangered language

text: Many languages, for example some in Indonesia, have tens of thousands of speakers but are endangered because children are no longer learning them, and speakers are shifting to using the national language (e.g. Indonesian) in place of local languages. In contrast, a language with only 500 speakers might be considered very much alive if it is the primary language of a community, and is the first (or only) spoken language of all children in that community.


title: Endangered language

text: Asserting that "Language diversity is essential to the human heritage", UNESCO's Ad Hoc Expert Group on Endangered Languages offers this definition of an endangered language: "... when its speakers cease to use it, use it in an increasingly reduced number of communicative domains, and cease to pass it on from one generation to the next. That is, there are no new speakers, adults or children."


title: Endangered language

text: UNESCO operates with four levels of language endangerment between "safe" (not endangered) and "extinct" (no living speakers), based on intergenerational transfer: "vulnerable" (not spoken by children outside the home), "definitely endangered" (children not speaking), "severely endangered" (only spoken by the oldest generations), and "critically endangered" (spoken by few members of the oldest generation, often semi-speakers).


title: Endangered language

text: UNESCO's "Atlas of the World's Languages in Danger" categorises 2,473 languages by level of endangerment.


title: Endangered language

text: Using an alternative scheme of classification, linguist Michael E. Krauss defines languages as "safe" if it is considered that children will probably be speaking them in 100 years; "endangered" if children will probably not be speaking them in 100 years (approximately 60–80% of languages fall into this category) and "moribund" if children are not speaking them now.


title: Endangered language

text: Many scholars have devised techniques for determining whether languages are endangered. One of the earliest is GIDS (Graded Intergenerational Disruption Scale) proposed by Joshua Fishman in 1991. In 2011 an entire issue of "Journal of Multilingual and Multicultural Development" was devoted to the study of ethnolinguistic vitality, Vol. 32.2, 2011, with several authors presenting their own tools for measuring language vitality. A number of other published works on measuring language vitality have been published, prepared by authors with varying situations and applications in mind.


title: Endangered language

text: According to the Cambridge Handbook of Endangered Languages, there are four main types of causes of language endangerment:


title: Endangered language

text: Often multiple of these causes act at the same time. Poverty, disease and disasters often affect minority groups disproportionately, for example causing the dispersal of speaker populations and decreased survival rates for those who stay behind.


title: Endangered language

text: Among the causes of language endangerment cultural, political and economic marginalization accounts for most of the world's language endangerment. Scholars distinguish between several types of marginalization: Economic dominance negatively affects minority languages when poverty leads people to migrate towards the cities or to other countries, thus dispersing the speakers. Cultural dominance occurs when literature and higher education is only accessible in the majority language. Political dominance occurs when education and political activity is carried out exclusively in a majority language.


title: Endangered language

text: Historically, in colonies, and elsewhere where speakers of different languages have come into contact, some languages have been considered superior to others: often one language has attained a dominant position in a country. Speakers of endangered languages may themselves come to associate their language with negative values such as poverty, illiteracy and social stigma, causing them to wish to adopt the dominant language which is associated with social and economical progress and modernity. Immigrants moving into an area may lead to the endangerment of the autochthonous language.


title: Endangered language

text: Language endangerment affects both the languages themselves and the people that speak them. Also, this affects the essence of a culture.


title: Endangered language

text: As communities lose their language they often also lose parts of their cultural traditions which are tied to that language, such as songs, myths, poetry, local remedies, ecological and geological knowledge and language behaviors that are not easily translated. Furthermore, the social structure of one's community is often reflected through speech and language behavior. This pattern is even more prominent in dialects. This may in turn affect the sense of identity of the individual and the community as a whole, producing a weakened social cohesion as their values and traditions are replaced with new ones. This is sometimes characterized as anomie. Losing a language may also have political consequences as some countries confer different political statuses or privileges on minority ethnic groups, often defining ethnicity in terms of language. That means that communities that lose their language may also lose political legitimacy as a community with special collective rights. Language can also be considered as scientific knowledge in topics such as medicine, philosophy, botany, and many more. It reflects a community's practices when dealing with the environment and each other. When a language is lost, this knowledge is lost as well.


title: Endangered language

text: In contrast, language revitalization is correlated with better health outcomes in indigenous communities.


title: Endangered language

text: During language loss—sometimes referred to as "obsolescence" in the linguistic literature—the language that is being lost generally undergoes changes as speakers make their language more similar to the language that they are shifting to. For example, gradually losing grammatical or phonological complexities that are not found in the dominant language.


title: Endangered language

text: Generally the accelerated pace of language endangerment is considered to be a problem by linguists and by the speakers. However, some linguists, such as the phonetician Peter Ladefoged, have argued that language death is a natural part of the process of human cultural development, and that languages die because communities stop speaking them for their own reasons. Ladefoged argued that linguists should simply document and describe languages scientifically, but not seek to interfere with the processes of language loss. A similar view has been argued at length by linguist Salikoko Mufwene, who sees the cycles of language death and emergence of new languages through creolization as a continuous ongoing process.


title: Endangered language

text: A majority of linguists do consider that language loss is an ethical problem, as they consider that most communities would prefer to maintain their languages if given a real choice. They also consider it a scientific problem, because language loss on the scale currently taking place will mean that future linguists will only have access to a fraction of the world's linguistic diversity, therefore their picture of what human language is—and can be—will be limited.


title: Endangered language

text: Some linguists consider linguistic diversity to be analogous to biological diversity, and compare language endangerment to wildlife endangerment.


title: Endangered language

text: Linguists, members of endangered language communities, governments, nongovernmental organizations, and international organizations such as UNESCO and the European Union are actively working to save and stabilize endangered languages. Once a language is determined to be endangered, there are three steps that can be taken in order to stabilize or rescue the language. The first is language documentation, the second is language revitalization and the third is language maintenance.


title: Endangered language

text: Language documentation is the documentation in writing and audio-visual recording of grammar, vocabulary, and oral traditions (e.g. stories, songs, religious texts) of endangered languages. It entails producing descriptive grammars, collections of texts and dictionaries of the languages, and it requires the establishment of a secure archive where the material can be stored once it is produced so that it can be accessed by future generations of speakers or scientists.


title: Endangered language

text: Language revitalization is the process by which a language community through political, community, and educational means attempts to increase the number of active speakers of the endangered language. This process is also sometimes referred to as language revival or reversing language shift. For case studies of this process, see Anderson (2014). Applied linguistics and education are helpful in revitalizing endangered languages. Vocabulary and courses are available online for a number of endangered languages.


title: Endangered language

text: Language maintenance refers to the support given to languages that need for their survival to be protected from outsiders who can ultimately affect the number of speakers of a language. UNESCO's strides towards preventing language extinction involves promoting and supporting the language in aspects such as education, culture, communication and information, and science.


title: Endangered language

text: Another option is "post-vernacular maintenance": the teaching of some words and concepts of the lost language, rather than revival proper.


title: Endangered language

text: As of June 2012 the United States has a "J-1 specialist visa, which allows indigenous language experts who do not have academic training to enter the U.S. as experts aiming to share their knowledge and expand their skills".


title: Fluticasone

text: Fluticasone is a manufactured glucocorticoid used to treat nasal symptoms. Both the esters, fluticasone propionate (a brand name for which is Flovent) and fluticasone furoate, are also used as topical anti-inflammatories and inhaled corticosteroids, and are used much more commonly in comparison.


title: Fluticasone

text: It is on the World Health Organization's List of Essential Medicines. In 2020, it was the 23rd most commonly prescribed medication in the United States, with more than 24million prescriptions, although it is also sold over the counter.


title: Capacitor types

text: Capacitors are manufactured in many styles, forms, dimensions, and from a large variety of materials. They all contain at least two electrical conductors, called "plates", separated by an insulating layer ("dielectric"). Capacitors are widely used as parts of electrical circuits in many common electrical devices.


title: Capacitor types

text: Capacitors, together with resistors and inductors, belong to the group of "passive components" in electronic equipment. Small capacitors are used in electronic devices to couple signals between stages of amplifiers, as components of electric filters and tuned circuits, or as parts of power supply systems to smooth rectified current. Larger capacitors are used for energy storage in such applications as strobe lights, as parts of some types of electric motors, or for power factor correction in AC power distribution systems. Standard capacitors have a fixed value of capacitance, but adjustable capacitors are frequently used in tuned circuits. Different types are used depending on required capacitance, working voltage, current handling capacity, and other properties.


title: Capacitor types

text: While, in absolute figures, the most commonly manufactured capacitors are integrated into dynamic random-access memory, flash memory, and other device chips, this article covers the discrete components.


title: Capacitor types

text: A conventional capacitor stores electric energy as static electricity by charge separation in an electric field between two electrode plates. The charge carriers are typically electrons, The amount of charge stored per unit voltage is essentially a function of the size of the plates, the plate material's properties, the properties of the dielectric material placed between the plates, and the separation distance (i.e. dielectric thickness). The potential between the plates is limited by the properties of the dielectric material and the separation distance.


title: Capacitor types

text: Nearly all conventional industrial capacitors except some special styles such as "feed-through capacitors", are constructed as "plate capacitors" even if their electrodes and the dielectric between are wound or rolled. The capacitance, "C", of a plate capacitors is:


title: Capacitor types

text: The capacitance increases with the area "A" of the plates and with the permittivity "ε" of the dielectric material, and decreases with the plate separation distance "d". The capacitance is therefore greatest in devices made from materials with a high permittivity, large plate area, and small distance between plates.


title: Capacitor types

text: Another type – the electrochemical capacitor – makes use of two other storage principles to store electric energy. In contrast to ceramic, film, and electrolytic capacitors, supercapacitors (also known as electrical double-layer capacitors (EDLC) or ultracapacitors) do not have a conventional dielectric. The capacitance value of an electrochemical capacitor is determined by two high-capacity storage principles. These principles are:


title: Capacitor types

text: The ratio of the storage resulting from each principle can vary greatly, depending on electrode design and electrolyte composition. Pseudocapacitance can increase the capacitance value by as much as an order of magnitude over that of the double-layer by itself.


title: Capacitor types

text: Capacitors are divided into two mechanical groups: Fixed-capacitance devices with a constant capacitance and variable capacitors.


title: Capacitor types

text: Variable capacitors are made as "trimmers", that are typically adjusted only during circuit calibration, and as a device tunable during operation of the electronic instrument.


title: Capacitor types

text: The most common group is the fixed capacitors. Many are named based on the type of dielectric. For a systematic classification these characteristics cannot be used, because one of the oldest, the electrolytic capacitor, is named instead by its cathode construction. So the most-used names are simply historical.


title: Capacitor types

text: In addition to the above shown capacitor types, which derived their name from historical development, there are many individual capacitors that have been named based on their application. They include:


title: Capacitor types

text: Often, more than one capacitor family is employed for these applications, e.g. interference suppression can use ceramic capacitors or film capacitors.


title: Capacitor types

text: All of them store their electrical charge statically within an electric field between two (parallel) electrodes.


title: Capacitor types

text: Beneath this conventional capacitors a family of electrochemical capacitors called supercapacitors was developed. Supercapacitors do not have a conventional dielectric. They store their electrical charge statically in Helmholtz double-layers and faradaically at the surface of electrodes


title: Capacitor types

text: The most important material parameters of the different dielectrics used and the approximate Helmholtz-layer thickness are given in the table below.


title: Capacitor types

text: The capacitor's plate area can be adapted to the wanted capacitance value. The permittivity and the dielectric thickness are the determining parameter for capacitors. Ease of processing is also crucial. Thin, mechanically flexible sheets can be wrapped or stacked easily, yielding large designs with high capacitance values. Razor-thin metallized sintered ceramic layers covered with metallized electrodes however, offer the best conditions for the miniaturization of circuits with SMD styles.


title: Capacitor types

text: Capacitance ranges from picofarads to more than hundreds of farads. Voltage ratings can reach 100 kilovolts. In general, capacitance and voltage correlate with physical size and cost.


title: Capacitor types

text: As in other areas of electronics, volumetric efficiency measures the performance of electronic function per unit volume. For capacitors, the volumetric efficiency is measured with the "CV product", calculated by multiplying the capacitance (C) by the maximum voltage rating (V), divided by the volume. From 1970 to 2005, volumetric efficiencies have improved dramatically.


title: Capacitor types

text: These individual capacitors can perform their application independent of their affiliation to an above shown capacitor type, so that an overlapping range of applications between the different capacitor types exists.


title: Capacitor types

text: A ceramic capacitor is a non-polarized fixed capacitor made out of two or more alternating layers of ceramic and metal in which the ceramic material acts as the dielectric and the metal acts as the electrodes. The ceramic material is a mixture of finely ground granules of paraelectric or ferroelectric materials, modified by mixed oxides that are necessary to achieve the capacitor's desired characteristics. The electrical behavior of the ceramic material is divided into two stability classes:


title: Capacitor types

text: The great plasticity of ceramic raw material works well for many special applications and enables an enormous diversity of styles, shapes and great dimensional spread of ceramic capacitors. The smallest discrete capacitor, for instance, is a "01005" chip capacitor with the dimension of only 0.4 mm × 0.2 mm.


title: Capacitor types

text: The construction of ceramic multilayer capacitors with mostly alternating layers results in single capacitors connected in parallel. This configuration increases capacitance and decreases all losses and parasitic inductances. Ceramic capacitors are well-suited for high frequencies and high current pulse loads.


title: Capacitor types

text: Because the thickness of the ceramic dielectric layer can be easily controlled and produced by the desired application voltage, ceramic capacitors are available with rated voltages up to the 30 kV range.


title: Capacitor types

text: Some ceramic capacitors of special shapes and styles are used as capacitors for special applications, including RFI/EMI suppression capacitors for connection to supply mains, also known as safety capacitors, X2Y® and three-terminal capacitors for bypassing and decoupling applications, feed-through capacitors for noise suppression by low-pass filters and ceramic power capacitors for transmitters and HF applications.


title: Capacitor types

text: Film capacitors or plastic film capacitors are non-polarized capacitors with an insulating plastic film as the dielectric. The dielectric films are drawn to a thin layer, provided with metallic electrodes and wound into a cylindrical winding. The electrodes of film capacitors may be metallized aluminum or zinc, applied on one or both sides of the plastic film, resulting in metallized film capacitors or a separate metallic foil overlying the film, called film/foil capacitors.


title: Capacitor types

text: Metallized film capacitors offer self-healing properties. Dielectric breakdowns or shorts between the electrodes do not destroy the component. The metallized construction makes it possible to produce wound capacitors with larger capacitance values (up to 100 µF and larger) in smaller cases than within film/foil construction.


title: Capacitor types

text: Film/foil capacitors or metal foil capacitors use two plastic films as the dielectric. Each film is covered with a thin metal foil, mostly aluminium, to form the electrodes. The advantage of this construction is the ease of connecting the metal foil electrodes, along with an excellent current pulse strength.


title: Capacitor types

text: A key advantage of every film capacitor's internal construction is direct contact to the electrodes on both ends of the winding. This contact keeps all current paths very short. The design behaves like a large number of individual capacitors connected in parallel, thus reducing the internal ohmic losses (equivalent series resistance or ESR) and equivalent series inductance (ESL). The inherent geometry of film capacitor structure results in low ohmic losses and a low parasitic inductance, which makes them suitable for applications with high surge currents (snubbers) and for AC power applications, or for applications at higher frequencies.


title: Capacitor types

text: The plastic films used as the dielectric for film capacitors are polypropylene (PP), polyester (PET), polyphenylene sulfide (PPS), polyethylene naphthalate (PEN), and polytetrafluoroethylene (PTFE). Polypropylene has a market share of about 50% and polyester with about 40% are the most used film materials. The other 10% use all the other materials, including PPS and paper with roughly 3% each.


title: Capacitor types

text: Some film capacitors of special shapes and styles are used as capacitors for special applications, including RFI/EMI suppression capacitors for connection to the supply mains, also known as safety capacitors, snubber capacitors for very high surge currents, motor run capacitors and AC capacitors for motor-run applications.


title: Capacitor types

text: A related type is the power film capacitor. The materials and construction techniques used for large power film capacitors mostly are similar to those of ordinary film capacitors. However, capacitors with high to very high power ratings for applications in power systems and electrical installations are often classified separately, for historical reasons. The standardization of ordinary film capacitors is oriented on electrical and mechanical parameters. The standardization of power capacitors by contrast emphasizes the safety of personnel and equipment, as given by the local regulating authority.


title: Capacitor types

text: As modern electronic equipment gained the capacity to handle power levels that were previously the exclusive domain of "electrical power" components, the distinction between the "electronic" and "electrical" power ratings blurred. Historically, the boundary between these two families was approximately at a reactive power of 200 volt-amperes.


title: Capacitor types

text: Film power capacitors mostly use polypropylene film as the dielectric. Other types include metallized paper capacitors (MP capacitors) and mixed dielectric film capacitors with polypropylene dielectrics. MP capacitors serve for cost applications and as field-free carrier electrodes (soggy foil capacitors) for high AC or high current pulse loads. Windings can be filled with an insulating oil or with epoxy resin to reduce air bubbles, thereby preventing short circuits.


title: Capacitor types

text: They find use as converters to change voltage, current or frequency, to store or deliver abruptly electric energy or to improve the power factor. The rated voltage range of these capacitors is from approximately 120 V AC (capacitive lighting ballasts) to 100 kV.


title: Capacitor types

text: Electrolytic capacitors have a metallic anode covered with an oxidized layer used as dielectric. The second electrode is a non-solid (wet) or solid electrolyte. Electrolytic capacitors are polarized. Three families are available, categorized according to their dielectric.


title: Capacitor types

text: The anode is highly roughened to increase the surface area. This and the relatively high permittivity of the oxide layer gives these capacitors very high capacitance per unit volume compared with film- or ceramic capacitors.


title: Capacitor types

text: The permittivity of tantalum pentoxide is approximately three times higher than aluminium oxide, producing significantly smaller components. However, permittivity determines only the dimensions. Electrical parameters, especially conductivity, are established by the electrolyte's material and composition. Three general types of electrolytes are used:


title: Capacitor types

text: Internal losses of electrolytic capacitors, prevailing used for decoupling and buffering applications, are determined by the kind of electrolyte.


title: Capacitor types

text: The large capacitance per unit volume of electrolytic capacitors make them valuable in relatively high-current and low-frequency electrical circuits, e.g. in power supply filters for decoupling unwanted AC components from DC power connections or as coupling capacitors in audio amplifiers, for passing or bypassing low-frequency signals and storing large amounts of energy. The relatively high capacitance value of an electrolytic capacitor combined with the very low ESR of the polymer electrolyte of polymer capacitors, especially in SMD styles, makes them a competitor to MLC chip capacitors in personal computer power supplies.


title: Capacitor types

text: Bipolar aluminum electrolytic capacitors (also called Non-Polarized capacitors) contain two anodized aluminium foils, behaving like two capacitors connected in series opposition.


title: Capacitor types

text: Electrolytic capacitors for special applications include motor start capacitors, flashlight capacitors and audio frequency capacitors.


title: Capacitor types

text: Supercapacitors (SC), comprise a family of electrochemical capacitors. Supercapacitor, sometimes called ultracapacitor is a generic term for electric double-layer capacitors (EDLC), pseudocapacitors and hybrid capacitors. They don't have a conventional solid dielectric. The capacitance value of an electrochemical capacitor is determined by two storage principles, both of which contribute to the total capacitance of the capacitor:


title: Capacitor types

text: The ratio of the storage resulting from each principle can vary greatly, depending on electrode design and electrolyte composition. Pseudocapacitance can increase the capacitance value by as much as an order of magnitude over that of the double-layer by itself.


title: Capacitor types

text: Supercapacitors bridge the gap between conventional capacitors and rechargeable batteries. They have the highest available capacitance values per unit volume and the greatest energy density of all capacitors. They support up to 12,000 farads/1.2 volt, with capacitance values up to 10,000 times that of electrolytic capacitors. While existing supercapacitors have energy densities that are approximately 10% of a conventional battery, their power density is generally 10 to 100 times greater. Power density is defined as the product of energy density, multiplied by the speed at which the energy is delivered to the load. The greater power density results in much shorter charge/discharge cycles than a battery is capable, and a greater tolerance for numerous charge/discharge cycles. This makes them well-suited for parallel connection with batteries, and may improve battery performance in terms of power density.


title: Capacitor types

text: Within electrochemical capacitors, the electrolyte is the conductive connection between the two electrodes, distinguishing them from electrolytic capacitors, in which the electrolyte only forms the cathode, the second electrode.


title: Capacitor types

text: Supercapacitors are polarized and must operate with correct polarity. Polarity is controlled by design with asymmetric electrodes, or, for symmetric electrodes, by a potential applied during the manufacturing process.


title: Capacitor types

text: Supercapacitors support a broad spectrum of applications for power and energy requirements, including:


title: Capacitor types

text: Supercapacitors are rarely interchangeable, especially those with higher energy densities. IEC standard 62391-1 "Fixed electric double layer capacitors for use in electronic equipment" identifies four application classes:


title: Capacitor types

text: Exceptional for electronic components like capacitors are the manifold different trade or series names used for supercapacitors like: "APowerCap, BestCap, BoostCap, CAP-XX, DLCAP, EneCapTen, EVerCAP, DynaCap, Faradcap, GreenCap, Goldcap, HY-CAP, Kapton capacitor, Super capacitor, SuperCap, PAS Capacitor, PowerStor, PseudoCap, Ultracapacitor" making it difficult for users to classify these capacitors.


title: Capacitor types

text: Many safety regulations mandate that Class X or Class Y capacitors must be used whenever a "fail-to-short-circuit" could put humans in danger,


title: Capacitor types

text: Safety capacitors protect humans and devices from high voltage surges by shunting the surge energy to ground.


title: Capacitor types

text: In particular, safety regulations mandate a particular arrangement of Class X and Class Y mains filtering capacitors.


title: Capacitor types

text: In principle, any dielectric could be used to build Class X and Class Y capacitors; perhaps by including an internal fuse to improve safety.


title: Capacitor types

text: Beneath the above described capacitors covering more or less nearly the total market of discrete capacitors some new developments or very special capacitor types as well as older types can be found in electronics.


title: Capacitor types

text: Specialized devices such as built-in capacitors with metal conductive areas in different layers of a multi-layer printed circuit board and kludges such as twisting together two pieces of insulated wire also exist.


title: Capacitor types

text: Variable capacitors may have their capacitance changed by mechanical motion. Generally two versions of variable capacitors has to be to distinguished


title: Capacitor types

text: Variable capacitors include capacitors that use a mechanical construction to change the distance between the plates, or the amount of plate surface area which overlaps. They mostly use air as dielectric medium.


title: Capacitor types

text: Semiconductive variable capacitance diodes are not capacitors in the sense of passive components but can change their capacitance as a function of the applied reverse bias voltage and are used like a variable capacitor. They have replaced much of the tuning and trimmer capacitors.


title: Capacitor types

text: Discrete capacitors deviate from the ideal capacitor. An ideal capacitor only stores and releases electrical energy, with no dissipation. Capacitor components have losses and parasitic inductive parts. These imperfections in material and construction can have positive implications such as linear frequency and temperature behavior in class 1 ceramic capacitors. Conversely, negative implications include the non-linear, voltage-dependent capacitance in class 2 ceramic capacitors or the insufficient dielectric insulation of capacitors leading to leakage currents.


title: Capacitor types

text: All properties can be defined and specified by a series equivalent circuit composed out of an idealized capacitance and additional electrical components which model all losses and inductive parameters of a capacitor. In this series-equivalent circuit the electrical characteristics are defined by:


title: Capacitor types

text: Using a series equivalent circuit instead of a parallel equivalent circuit is specified by IEC/EN 60384-1.


title: Capacitor types

text: The rated capacitance C or nominal capacitance C is the value for which the capacitor has been designed. Actual capacitance depends on the measured frequency and ambient temperature. Standard measuring conditions are a low-voltage AC measuring method at a temperature of 20 °C with frequencies of


title: Capacitor types

text: Capacitors are available in geometrically increasing preferred values (E series standards) specified in IEC/EN 60063. According to the number of values per decade, these were called the E3, E6, E12, E24 etc. series. The range of units used to specify capacitor values has expanded to include everything from pico- (pF), nano- (nF) and microfarad (µF) to farad (F). Millifarad and kilofarad are uncommon.


title: Capacitor types

text: The percentage of allowed deviation from the rated value is called tolerance. The actual capacitance value should be within its tolerance limits, or it is out of specification. IEC/EN 60062 specifies a letter code for each tolerance.


title: Capacitor types

text: The required tolerance is determined by the particular application. The narrow tolerances of E24 to E96 are used for high-quality circuits such as precision oscillators and timers. General applications such as non-critical filtering or coupling circuits employ E12 or E6. Electrolytic capacitors, which are often used for filtering and bypassing capacitors mostly have a tolerance range of ±20% and need to conform to E6 (or E3) series values.


title: Capacitor types

text: Capacitance typically varies with temperature. The different dielectrics express great differences in temperature sensitivity. The temperature coefficient is expressed in parts per million (ppm) per degree Celsius for class 1 ceramic capacitors or in % over the total temperature range for all others.


title: Capacitor types

text: Most discrete capacitor types have more or less capacitance changes with increasing frequencies. The dielectric strength of class 2 ceramic and plastic film diminishes with rising frequency. Therefore, their capacitance value decreases with increasing frequency. This phenomenon for ceramic class 2 and plastic film dielectrics is related to dielectric relaxation in which the time constant of the electrical dipoles is the reason for the frequency dependence of permittivity. The graphs below show typical frequency behavior of the capacitance for ceramic and film capacitors.


title: Capacitor types

text: For electrolytic capacitors with non-solid electrolyte, mechanical motion of the ions occurs. Their movability is limited so that at higher frequencies not all areas of the roughened anode structure are covered with charge-carrying ions. As higher the anode structure is roughened as more the capacitance value decreases with increasing frequency. Low voltage types with highly roughened anodes display capacitance at 100 kHz approximately 10 to 20% of the value measured at 100 Hz.


title: Capacitor types

text: Capacitance may also change with applied voltage. This effect is more prevalent in class 2 ceramic capacitors. The permittivity of ferroelectric class 2 material depends on the applied voltage. Higher applied voltage lowers permittivity. The change of capacitance can drop to 80% of the value measured with the standardized measuring voltage of 0.5 or 1.0 V. This behavior is a small source of non-linearity in low-distortion filters and other analog applications. In audio applications this can cause distortion (measured using THD).


title: Capacitor types

text: The voltage at which the dielectric becomes conductive is called the breakdown voltage, and is given by the product of the dielectric strength and the separation between the electrodes. The dielectric strength depends on temperature, frequency, shape of the electrodes, etc. Because a breakdown in a capacitor normally is a short circuit and destroys the component, the operating voltage is lower than the breakdown voltage. The operating voltage is specified such that the voltage may be applied continuously throughout the life of the capacitor.


title: Capacitor types

text: In IEC/EN 60384-1 the allowed operating voltage is called "rated voltage" or "nominal voltage". The rated voltage (UR) is the maximum DC voltage or peak pulse voltage that may be applied continuously at any temperature within the rated temperature range.


title: Capacitor types

text: The voltage proof of nearly all capacitors decreases with increasing temperature. Some applications require a higher temperature range. Lowering the voltage applied at a higher temperature maintains safety margins. For some capacitor types therefore the IEC standard specify a second "temperature derated voltage" for a higher temperature range, the "category voltage". The category voltage (UC) is the maximum DC voltage or peak pulse voltage that may be applied continuously to a capacitor at any temperature within the category temperature range.


title: Capacitor types

text: In general, a capacitor is seen as a storage component for electric energy. But this is only one capacitor function. A capacitor can also act as an AC resistor. In many cases the capacitor is used as a decoupling capacitor to filter or bypass undesired biased AC frequencies to the ground. Other applications use capacitors for capacitive coupling of AC signals; the dielectric is used only for blocking DC. For such applications the AC resistance is as important as the capacitance value.


title: Capacitor types

text: The frequency dependent AC resistance is called impedance formula_2 and is the complex ratio of the voltage to the current in an AC circuit. Impedance extends the concept of resistance to AC circuits and possesses both magnitude and phase at a particular frequency. This is unlike resistance, which has only magnitude.


title: Capacitor types

text: The magnitude formula_4 represents the ratio of the voltage difference amplitude to the current amplitude, formula_5 is the imaginary unit, while the argument formula_6 gives the phase difference between voltage and current.


title: Capacitor types

text: In capacitor data sheets, only the impedance magnitude |Z| is specified, and simply written as "Z" so that the formula for the impedance can be written in Cartesian form


title: Capacitor types

text: where the real part of impedance is the resistance formula_8 (for capacitors formula_9) and the imaginary part is the reactance formula_10.


title: Capacitor types

text: As shown in a capacitor's series-equivalent circuit, the real component includes an ideal capacitor formula_11, an inductance formula_12 and a resistor formula_13. The total reactance at the angular frequency formula_14 therefore is given by the geometric (complex) addition of a capacitive reactance (Capacitance) formula_15 and an inductive reactance (Inductance): formula_16.


title: Capacitor types

text: To calculate the impedance formula_2 the resistance has to be added geometrically and then formula_18 is given by


title: Capacitor types

text: The impedance specified in the datasheets often show typical curves for the different capacitance values. With increasing frequency as the impedance decreases down to a minimum. The lower the impedance, the more easily alternating currents can be passed through the capacitor. At the apex, the point of resonance, where XC has the same value than XL, the capacitor has the lowest impedance value. Here only the ESR determines the impedance. With frequencies above the resonance the impedance increases again due to the ESL of the capacitor. The capacitor becomes an inductance.


title: Capacitor types

text: As shown in the graph, the higher capacitance values can fit the lower frequencies better while the lower capacitance values can fit better the higher frequencies.


title: Capacitor types

text: Aluminum electrolytic capacitors have relatively good decoupling properties in the lower frequency range up to about 1 MHz due to their large capacitance values. This is the reason for using electrolytic capacitors in standard or switched-mode power supplies behind the rectifier for smoothing application.


title: Capacitor types

text: Ceramic and film capacitors are already out of their smaller capacitance values suitable for higher frequencies up to several 100 MHz. They also have significantly lower parasitic inductance, making them suitable for higher frequency applications, due to their construction with end-surface contacting of the electrodes. To increase the range of frequencies, often an electrolytic capacitor is connected in parallel with a ceramic or film capacitor.


title: Capacitor types

text: Many new developments are targeted at reducing parasitic inductance (ESL). This increases the resonance frequency of the capacitor and, for example, can follow the constantly increasing switching speed of digital circuits. Miniaturization, especially in the SMD multilayer ceramic chip capacitors (MLCC), increases the resonance frequency. Parasitic inductance is further lowered by placing the electrodes on the longitudinal side of the chip instead of the lateral side. The "face-down" construction associated with multi-anode technology in tantalum electrolytic capacitors further reduced ESL. Capacitor families such as the so-called MOS capacitor or silicon capacitors offer solutions when capacitors at frequencies up to the GHz range are needed.


title: Capacitor types

text: ESL in industrial capacitors is mainly caused by the leads and internal connections used to connect the capacitor plates to the outside world. Large capacitors tend to have higher ESL than small ones because the distances to the plate are longer and every mm counts as an inductance.


title: Capacitor types

text: For any discrete capacitor, there is a frequency above DC at which it ceases to behave as a pure capacitor. This frequency, where formula_24 is as high as formula_25, is called the self-resonant frequency. The self-resonant frequency is the lowest frequency at which the impedance passes through a minimum. For any AC application the self-resonant frequency is the highest frequency at which capacitors can be used as a capacitive component.


title: Capacitor types

text: This is critically important for decoupling high-speed logic circuits from the power supply. The decoupling capacitor supplies transient current to the chip. Without decouplers, the IC demands current faster than the connection to the power supply can supply it, as parts of the circuit rapidly switch on and off. To counter this potential problem, circuits frequently use multiple bypass capacitors—small (100 nF or less) capacitors rated for high frequencies, a large electrolytic capacitor rated for lower frequencies and occasionally, an intermediate value capacitor.


title: Capacitor types

text: The summarized losses in discrete capacitors are ohmic AC losses. DC losses are specified as "leakage current" or "insulating resistance" and are negligible for an AC specification. AC losses are non-linear, possibly depending on frequency, temperature, age or humidity. The losses result from two physical conditions:


title: Capacitor types

text: The largest share of these losses in larger capacitors is usually the frequency dependent ohmic dielectric losses. For smaller components, especially for wet electrolytic capacitors, conductivity of liquid electrolytes may exceed dielectric losses. To measure these losses, the measurement frequency must be set. Since commercially available components offer capacitance values cover 15 orders of magnitude, ranging from pF (10 F) to some 1000 F in supercapacitors, it is not possible to capture the entire range with only one frequency. IEC 60384-1 states that ohmic losses should be measured at the same frequency used to measure capacitance. These are:


title: Capacitor types

text: A capacitor's summarized resistive losses may be specified either as ESR, as a dissipation factor(DF, tan δ), or as quality factor (Q), depending on application requirements.


title: Capacitor types

text: Capacitors with higher ripple current formula_26 loads, such as electrolytic capacitors, are specified with equivalent series resistance ESR. ESR can be shown as an ohmic part in the above vector diagram. ESR values are specified in datasheets per individual type.


title: Capacitor types

text: The losses of film capacitors and some class 2 ceramic capacitors are mostly specified with the dissipation factor tan δ. These capacitors have smaller losses than electrolytic capacitors and mostly are used at higher frequencies up to some hundred MHz. However the numeric value of the dissipation factor, measured at the same frequency, is independent of the capacitance value and can be specified for a capacitor series with a range of capacitance. The dissipation factor is determined as the tangent of the reactance (formula_27) and the ESR, and can be shown as the angle δ between imaginary and the impedance axis.


title: Capacitor types

text: Capacitors with very low losses, such as ceramic Class 1 and Class 2 capacitors, specify resistive losses with a quality factor (Q). Ceramic Class 1 capacitors are especially suitable for LC resonant circuits with frequencies up to the GHz range, and precise high and low pass filters. For an electrically resonant system, Q represents the effect of electrical resistance and characterizes a resonator's bandwidth formula_30 relative to its center or resonant frequency formula_31. Q is defined as the reciprocal value of the dissipation factor.


title: Capacitor types

text: A capacitor can act as an AC resistor, coupling AC voltage and AC current between two points. Every AC current flow through a capacitor generates heat inside the capacitor body. These dissipation power loss formula_33 is caused by formula_34 and is the squared value of the effective (RMS) current formula_35


title: Capacitor types

text: The internal generated heat has to be distributed to the ambient. The temperature of the capacitor, which is established on the balance between heat produced and distributed, shall not exceed the capacitors maximum specified temperature. Hence, the ESR or dissipation factor is a mark for the maximum power (AC load, ripple current, pulse load, etc.) a capacitor is specified for.


title: Capacitor types

text: Ripple and AC currents mainly warms the capacitor body. By this currents internal generated temperature influences the breakdown voltage of the dielectric. Higher temperature lower the voltage proof of all capacitors. In wet electrolytic capacitors higher temperatures force the evaporation of electrolytes, shortening the life time of the capacitors. In film capacitors higher temperatures may shrink the plastic film changing the capacitor's properties.


title: Capacitor types

text: Pulse currents, especially in metallized film capacitors, heat the contact areas between end spray (schoopage) and metallized electrodes. This may reduce the contact to the electrodes, heightening the dissipation factor.


title: Capacitor types

text: For safe operation, the maximal temperature generated by any AC current flow through the capacitor is a limiting factor, which in turn limits AC load, ripple current, pulse load, etc.


title: Capacitor types

text: A "ripple current" is the RMS value of a superimposed AC current of any frequency and any waveform of the current curve for continuous operation at a specified temperature. It arises mainly in power supplies (including switched-mode power supplies) after rectifying an AC voltage and flows as charge and discharge current through the decoupling or smoothing capacitor. The "rated ripple current" shall not exceed a temperature rise of 3, 5 or 10 °C, depending on the capacitor type, at the specified maximum ambient temperature.


title: Capacitor types

text: Ripple current generates heat within the capacitor body due to the ESR of the capacitor. The components of capacitor ESR are: the dielectric losses caused by the changing field strength in the dielectric, the resistance of the supply conductor, and the resistance of the electrolyte. For an electric double layer capacitor (ELDC) these resistance values can be derived from a Nyquist plot of the capacitor's complex impedance.


title: Capacitor types

text: ESR is dependent on frequency and temperature. For ceramic and film capacitors in generally ESR decreases with increasing temperatures but heighten with higher frequencies due to increasing dielectric losses. For electrolytic capacitors up to roughly 1 MHz ESR decreases with increasing frequencies and temperatures.


title: Capacitor types

text: The types of capacitors used for power applications have a specified rated value for maximum ripple current. These are primarily aluminum electrolytic capacitors, and tantalum as well as some film capacitors and Class 2 ceramic capacitors.


title: Capacitor types

text: Aluminum electrolytic capacitors, the most common type for power supplies, experience shorter life expectancy at higher ripple currents. Exceeding the limit tends to result in explosive failure.


title: Capacitor types

text: Tantalum electrolytic capacitors with solid manganese dioxide electrolyte are also limited by ripple current. Exceeding their ripple limits tends to shorts and burning components.


title: Capacitor types

text: For film and ceramic capacitors, normally specified with a loss factor tan δ, the ripple current limit is determined by temperature rise in the body of approximately 10 °C. Exceeding this limit may destroy the internal structure and cause shorts.


title: Capacitor types

text: The rated pulse load for a certain capacitor is limited by the rated voltage, the pulse repetition frequency, temperature range and pulse rise time. The "pulse rise time" formula_39, represents the steepest voltage gradient of the pulse (rise or fall time) and is expressed in volts per μs (V/μs).


title: Capacitor types

text: The rated pulse rise time is also indirectly the maximum capacity of an applicable peak current formula_40. The peak current is defined as:


title: Capacitor types

text: The permissible pulse current capacity of a metallized film capacitor generally allows an internal temperature rise of 8 to 10 K.


title: Capacitor types

text: In the case of metallized film capacitors, pulse load depends on the properties of the dielectric material, the thickness of the metallization and the capacitor's construction, especially the construction of the contact areas between the end spray and metallized electrodes. High peak currents may lead to selective overheating of local contacts between end spray and metallized electrodes which may destroy some of the contacts, leading to increasing ESR.


title: Capacitor types

text: For metallized film capacitors, so-called pulse tests simulate the pulse load that might occur during an application, according to a standard specification. IEC 60384 part 1, specifies that the test circuit is charged and discharged intermittently. The test voltage corresponds to the rated DC voltage and the test comprises 10000 pulses with a repetition frequency of 1 Hz. The pulse stress capacity is the pulse rise time. The rated pulse rise time is specified as 1/10 of the test pulse rise time.


title: Capacitor types

text: The pulse load must be calculated for each application. A general rule for calculating the power handling of film capacitors is not available because of vendor-related internal construction details. To prevent the capacitor from overheating the following operating parameters have to be considered:


title: Capacitor types

text: Examples for calculations of individual pulse loads are given by many manufactures, e.g. WIMA and Kemet.


title: Capacitor types

text: An AC load only can be applied to a non-polarized capacitor. Capacitors for AC applications are primarily film capacitors, metallized paper capacitors, ceramic capacitors and bipolar electrolytic capacitors.


title: Capacitor types

text: The rated AC load for an AC capacitor is the maximum sinusoidal effective AC current (rms) which may be applied continuously to a capacitor within the specified temperature range. In the datasheets the AC load may be expressed as


title: Capacitor types

text: The rated AC voltage for film capacitors is generally calculated so that an internal temperature rise of 8 to 10 °K is the allowed limit for safe operation. Because dielectric losses increase with increasing frequency, the specified AC voltage has to be derated at higher frequencies. Datasheets for film capacitors specify special curves for derating AC voltages at higher frequencies.


title: Capacitor types

text: If film capacitors or ceramic capacitors only have a DC specification, the peak value of the AC voltage applied has to be lower than the specified DC voltage.


title: Capacitor types

text: AC loads can occur in AC motor run capacitors, for voltage doubling, in snubbers, lighting ballast and for PFC for phase shifting to improve transmission network stability and efficiency, which is one of the most important applications for large power capacitors. These mostly large PP film or metallized paper capacitors are limited by the rated reactive power VAr.


title: Capacitor types

text: Bipolar electrolytic capacitors, to which an AC voltage may be applicable, are specified with a rated ripple current.


title: Capacitor types

text: The resistance of the dielectric is finite, leading to some level of DC "leakage current" that causes a charged capacitor to lose charge over time. For ceramic and film capacitors, this resistance is called "insulation resistance R". This resistance is represented by the resistor R in parallel with the capacitor in the series-equivalent circuit of capacitors.


title: Capacitor types

text: Insulation resistance must not be confused with the outer isolation of the component with respect to the environment.


title: Capacitor types

text: The time curve of self-discharge over insulation resistance with decreasing capacitor voltage follows the formula


title: Capacitor types

text: The self-discharge constant is an important parameter for the insulation of the dielectric between the electrodes of ceramic and film capacitors. For example, a capacitor can be used as the time-determining component for time relays or for storing a voltage value as in a sample and hold circuits or operational amplifiers.


title: Capacitor types

text: Class 1 ceramic capacitors have an insulation resistance of at least 10 GΩ, while class 2 capacitors have at least 4 GΩ or a self-discharge constant of at least 100 s. Plastic film capacitors typically have an insulation resistance of 6 to 12 GΩ. This corresponds to capacitors in the uF range of a self-discharge constant of about 2000–4000 s.


title: Capacitor types

text: Insulation resistance respectively the self-discharge constant can be reduced if humidity penetrates into the winding. It is partially strongly temperature dependent and decreases with increasing temperature. Both decrease with increasing temperature.


title: Capacitor types

text: For electrolytic capacitors the insulation resistance of the dielectric is termed "leakage current". This DC current is represented by the resistor R in parallel with the capacitor in the series-equivalent circuit of electrolytic capacitors. This resistance between the terminals of a capacitor is also finite. R is lower for electrolytics than for ceramic or film capacitors.


title: Capacitor types

text: The leakage current includes all weak imperfections of the dielectric caused by unwanted chemical processes and mechanical damage. It is also the DC current that can pass through the dielectric after applying a voltage. It depends on the interval without voltage applied (storage time), the thermic stress from soldering, on voltage applied, on temperature of the capacitor, and on measuring time.


title: Capacitor types

text: The leakage current drops in the first minutes after applying DC voltage. In this period the dielectric oxide layer can self-repair weaknesses by building up new layers. The time required depends generally on the electrolyte. Solid electrolytes drop faster than non-solid electrolytes but remain at a slightly higher level.


title: Capacitor types

text: The leakage current in non-solid electrolytic capacitors as well as in manganese oxide solid tantalum capacitors decreases with voltage-connected time due to self-healing effects. Although electrolytics leakage current is higher than current flow over insulation resistance in ceramic or film capacitors, the self-discharge of modern non solid electrolytic capacitors takes several weeks.


title: Capacitor types

text: A particular problem with electrolytic capacitors is storage time. Higher leakage current can be the result of longer storage times. These behaviors are limited to electrolytes with a high percentage of water. Organic solvents such as GBL do not have high leakage with longer storage times.


title: Capacitor types

text: All ferroelectric materials exhibit a piezoelectric effect. Because Class 2 ceramic capacitors use ferroelectric ceramics dielectric, these types of capacitors may have electrical effects called microphonics. Microphonics (microphony) describes how electronic components transform mechanical vibrations into an undesired electrical signal (noise). The dielectric may absorb mechanical forces from shock or vibration by changing thickness and changing the electrode separation, affecting the capacitance, which in turn induces an AC current. The resulting interference is especially problematic in audio applications, potentially causing feedback or unintended recording.


title: Capacitor types

text: In the reverse microphonic effect, varying the electric field between the capacitor plates exerts a physical force, turning them into an audio speaker. High current impulse loads or high ripple currents can generate audible sound from the capacitor itself, draining energy and stressing the dielectric.


title: Capacitor types

text: Dielectric absorption occurs when a capacitor that has remained charged for a long time discharges only incompletely when briefly discharged. Although an ideal capacitor would reach zero volts after discharge, real capacitors develop a small voltage from time-delayed dipole discharging, a phenomenon that is also called dielectric relaxation, "soakage" or "battery action".


title: Capacitor types

text: In many applications of capacitors dielectric absorption is not a problem but in some applications, such as long-time-constant integrators, sample-and-hold circuits, switched-capacitor analog-to-digital converters, and very low-distortion filters, the capacitor must not recover a residual charge after full discharge, so capacitors with low absorption are specified.


title: Capacitor types

text: The voltage at the terminals generated by the dielectric absorption may in some cases possibly cause problems in the function of an electronic circuit or can be a safety risk to personnel. In order to prevent shocks most very large capacitors are shipped with shorting wires that need to be removed before they are used.


title: Capacitor types

text: The capacitance value depends on the dielectric material (ε), the surface of the electrodes (A) and the distance (d) separating the electrodes and is given by the formula of a plate capacitor:


title: Capacitor types

text: The separation of the electrodes and the voltage proof of the dielectric material defines the breakdown voltage of the capacitor. The breakdown voltage is proportional to the thickness of the dielectric.


title: Capacitor types

text: Theoretically, given two capacitors with the same mechanical dimensions and dielectric, but one of them have half the thickness of the dielectric. With the same dimensions this one could place twice the parallel-plate area inside. This capacitor has theoretically 4 times the capacitance as the first capacitor but half of the voltage proof.


title: Capacitor types

text: thus a capacitor having a dielectric half as thick as another has 4 times higher capacitance but ½ voltage proof, yielding an equal maximum energy density.


title: Capacitor types

text: Therefore, dielectric thickness does not affect energy density within a capacitor of fixed overall dimensions. Using a few thick layers of dielectric can support a high voltage, but low capacitance, while thin layers of dielectric produce a low breakdown voltage, but a higher capacitance.


title: Capacitor types

text: This assumes that neither the electrode surfaces nor the permittivity of the dielectric change with the voltage proof. A simple comparison with two existing capacitor series can show whether reality matches theory. The comparison is easy, because the manufacturers use standardized case sizes or boxes for different capacitance/voltage values within a series.


title: Capacitor types

text: In reality modern capacitor series do not fit the theory. For electrolytic capacitors the sponge-like rough surface of the anode foil gets smoother with higher voltages, decreasing the surface area of the anode. But because the energy increases squared with the voltage, and the surface of the anode decreases lesser than the voltage proof, the energy density increases clearly. For film capacitors the permittivity changes with dielectric thickness and other mechanical parameters so that the deviation from the theory has other reasons.


title: Capacitor types

text: Comparing the capacitors from the table with a supercapacitor, the highest energy density capacitor family. For this, the capacitor 25  F/2.3 V in dimensions D × H = 16 mm × 26 mm from Maxwell HC Series, compared with the electrolytic capacitor of approximately equal size in the table. This supercapacitor has roughly 5000 times higher capacitance than the 4700/10 electrolytic capacitor but ¼ of the voltage and has about 66,000 mWs (0.018 Wh) stored electrical energy, approximately 100 times higher energy density (40 to 280 times) than the electrolytic capacitor.


title: Capacitor types

text: Electrical parameters of capacitors may change over time during storage and application. The reasons for parameter changings are different, it may be a property of the dielectric, environmental influences, chemical processes or drying-out effects for non-solid materials.


title: Capacitor types

text: In ferroelectric Class 2 ceramic capacitors, capacitance decreases over time. This behavior is called "aging". This aging occurs in ferroelectric dielectrics, where domains of polarization in the dielectric contribute to the total polarization. Degradation of polarized domains in the dielectric decreases permittivity and therefore capacitance over time. The aging follows a logarithmic law. This defines the decrease of capacitance as constant percentage for a time decade after the soldering recovery time at a defined temperature, for example, in the period from 1 to 10 hours at 20 °C. As the law is logarithmic, the percentage loss of capacitance will twice between 1 h and 100 h and 3 times between 1 h and 1,000 h and so on. Aging is fastest near the beginning, and the absolute capacitance value stabilizes over time.


title: Capacitor types

text: The rate of aging of Class 2 ceramic capacitors depends mainly on its materials. Generally, the higher the temperature dependence of the ceramic, the higher the aging percentage. The typical aging of X7R ceramic capacitors is about 2.5% per decade. The aging rate of Z5U ceramic capacitors is significantly higher and can be up to 7% per decade.


title: Capacitor types

text: The aging process of Class 2 ceramic capacitors may be reversed by heating the component above the Curie point.


title: Capacitor types

text: Class 1 ceramic capacitors and film capacitors do not have ferroelectric-related aging. Environmental influences such as higher temperature, high humidity and mechanical stress can, over a longer period, lead to a small irreversible change in the capacitance value sometimes called aging, too.


title: Capacitor types

text: The change of capacitance for P 100 and N 470 Class 1 ceramic capacitors is lower than 1%, for capacitors with N 750 to N 1500 ceramics it is ≤ 2%. Film capacitors may lose capacitance due to self-healing processes or gain it due to humidity influences. Typical changes over 2 years at 40 °C are, for example, ±3% for PE film capacitors and ±1% PP film capacitors.


title: Capacitor types

text: Electrolytic capacitors with non-solid electrolyte age as the electrolyte evaporates. This evaporation depends on temperature and the current load the capacitors experience. Electrolyte escape influences capacitance and ESR. Capacitance decreases and the ESR increases over time. In contrast to ceramic, film and electrolytic capacitors with solid electrolytes, "wet" electrolytic capacitors reach a specified "end of life" reaching a specified maximum change of capacitance or ESR. End of life, "load life" or "lifetime" can be estimated either by formula or diagrams or roughly by a so-called "10-degree-law". A typical specification for an electrolytic capacitor states a lifetime of 2,000 hours at 85 °C, doubling for every 10 degrees lower temperature, achieving lifespan of approximately 15 years at room temperature.


title: Capacitor types

text: Supercapacitors also experience electrolyte evaporation over time. Estimation is similar to wet electrolytic capacitors. Additional to temperature the voltage and current load influence the life time. Lower voltage than rated voltage and lower current loads as well as lower temperature extend the life time.


title: Capacitor types

text: Capacitors are reliable components with low failure rates, achieving life expectancies of decades under normal conditions. Most capacitors pass a test at the end of production similar to a "burn in", so that early failures are found during production, reducing the number of post-shipment failures.


title: Capacitor types

text: Reliability for capacitors is usually specified in numbers of Failures In Time (FIT) during the period of constant random failures. FIT is the number of failures that can be expected in one billion (10) component-hours of operation at fixed working conditions (e.g. 1000 devices for 1 million hours, or 1 million devices for 1000 hours each, at 40 °C and 0.5 U). For other conditions of applied voltage, current load, temperature, mechanical influences and humidity the FIT can recalculated with terms standardized for industrial or military contexts.


title: Capacitor types

text: Capacitors may experience changes to electrical parameters due to environmental influences like soldering, mechanical stress factors (vibration, shock) and humidity. The greatest stress factor is soldering. The heat of the solder bath, especially for SMD capacitors, can cause ceramic capacitors to change contact resistance between terminals and electrodes; in film capacitors, the film may shrink, and in wet electrolytic capacitors the electrolyte may boil. A recovery period enables characteristics to stabilize after soldering; some types may require up to 24 hours. Some properties may change irreversibly by a few per cent from soldering.


title: Capacitor types

text: Electrolytic capacitors with non-solid electrolyte are "aged" during manufacturing by applying rated voltage at high temperature for a sufficient time to repair all cracks and weaknesses that may have occurred during production. Some electrolytes with a high water content react quite aggressively or even violently with unprotected aluminum. This leads to a "storage" or "disuse" problem of electrolytic capacitors manufactured before the 1980s. Chemical processes weaken the oxide layer when these capacitors are not used for too long. New electrolytes with "inhibitors" or "passivators" were developed during the 1980s to solve this problem.


title: Capacitor types

text: As of 2012 the standard storage time for electronic components of two years at room temperature substantiates (cased) by the oxidation of the terminals will be specified for electrolytic capacitors with non-solid electrolytes, too. Special series for 125 °C with organic solvents like GBL are specified up to 10 years storage time ensure without pre-condition the proper electrical behavior of the capacitors.


title: Capacitor types

text: For antique radio equipment, "pre-conditioning" of older electrolytic capacitors may be recommended. This involves applying the operating voltage for some 10 minutes over a current limiting resistor to the terminals of the capacitor. Applying a voltage through a safety resistor repairs the oxide layers.


title: Capacitor types

text: The tests and requirements to be met by capacitors for use in electronic equipment for approval as standardized types are set out in the generic specification IEC/EN 60384-1 in the following sections.


title: Capacitor types

text: Capacitors, like most other electronic components and if enough space is available, have imprinted markings to indicate manufacturer, type, electrical and thermal characteristics, and date of manufacture. If they are large enough the capacitor is marked with:


title: Capacitor types

text: Polarized capacitors have polarity markings, usually "−" (minus) sign on the side of the negative electrode for electrolytic capacitors or a stripe or "+" (plus) sign, see #Polarity marking. Also, the negative lead for leaded "wet" e-caps is usually shorter.


title: Capacitor types

text: Smaller capacitors use a shorthand notation. The most commonly used format is: XYZ J/K/M VOLTS V, where XYZ represents the capacitance (calculated as XY × 10 pF), the letters J, K or M indicate the tolerance (±5%, ±10% and ±20% respectively) and VOLTS V represents the working voltage.


title: Capacitor types

text: Capacitance, tolerance and date of manufacture can be indicated with a short code specified in IEC/EN 60062. Examples of short-marking of the rated capacitance (microfarads): µ47 = 0,47 µF, 4µ7 = 4,7 µF, 47µ = 47 µF


title: Capacitor types

text: For very small capacitors like MLCC chips no marking is possible. Here only the traceability of the manufacturers can ensure the identification of a type.


title: Capacitor types

text: Aluminum e-caps with "non-solid" electrolyte have a polarity marking at the cathode ("minus") side. Aluminum, tantalum, and niobium e-caps with "solid" electrolyte have a polarity marking at the anode ("plus") side. Supercapacitors are marked at the "minus" side.


title: Capacitor types

text: Discrete capacitors today are industrial products produced in very large quantities for use in electronic and in electrical equipment. Globally, the market for fixed capacitors was estimated at approximately US$18 billion in 2008 for 1,400 billion (1.4 × 10) pieces. This market is dominated by ceramic capacitors with estimate of approximately one trillion (1 × 10) items per year.


title: Capacitor types

text: All other capacitor types are negligible in terms of value and quantity compared with the above types.


title: Boeing AH-6

text: The Boeing AH-6 is a series of light helicopter gunships based on the MH-6 Little Bird and MD 500 family. Developed by Boeing Rotorcraft Systems, these include the Unmanned Little Bird (ULB) demonstrator, the A/MH-6X Mission Enhanced Little Bird (MELB), and the proposed AH-6I and AH-6S.


title: Boeing AH-6

text: The Unmanned Little Bird demonstrator, which Boeing built from a civilian MD 530F, first flew on September 8, 2004, and made its first autonomous flight (with safety pilot) on October 16, 2004.


title: Boeing AH-6

text: In April 2006, Boeing used the ULB to demonstrate the ability of another helicopter, in this case an AH-64 Apache to remotely control the ULB's weapons payload as a part of Boeing's Airborne Manned/Unmanned System Technology Demonstration (AMUST-D) program. For the initial test, the Apache Longbow was on the ground, while the ULB was airborne several miles away and Hellfire missiles were fired from the ULB by a tester sitting at the co-pilot's station in the Apache. Both aircraft are equipped with tactical common data link equipment and technologies manufactured by L-3 Communications.


title: Boeing AH-6

text: The ULB Demonstrator first flew in the unmanned mode on June 30, 2006 from the United States Army's Yuma Proving Ground, flying a pre-programmed 20-minute armed intelligence, surveillance and reconnaissance mission around the facility. All previous flights during the 450 flight hour engineering development phase had a safety pilot on board, although the aircraft was typically flown remotely from the ground.


title: Boeing AH-6

text: With the successes of the ULB, Boeing incorporated its technologies into an A/MH-6, designating it the A/MH-6X. On September 20, 2006, the first A/MH-6X lifted off on its maiden flight from Boeing Rotorcraft Systems' Mesa, Arizona facility with a pilot on board. While the ULB Demonstrator had a payload of 2,400 pounds, the MELB has an additional 1,000 pounds of payload capacity. The A/MH-6X is similar to the A/MH-6M, but includes a prototype glass cockpit and a number of upgrades to the electronics and avionics. The A/MH-6X is an optionally manned or unmanned aircraft which is a hybrid of the ULB demonstrator and the A/MH-6M mission-enhanced Little Bird which is used by US Army Special Operations Command.