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  1. Human papillomavirus infection - Wikipedia

    en.wikipedia.org › wiki › Human_papillomavirus_infection

    Human papillomavirus infection ( HPV infection) is an infection caused by human papillomavirus ( HPV ), a DNA virus from the Papillomaviridae family. Many HPV infections cause no symptoms and 90% resolve spontaneously within two years. However, ...

    • Most people are infected at some point in time
    • None, warts
  2. Wart - Wikipedia

    en.wikipedia.org › wiki › Wart
    • Types
    • Cause
    • Pathophysiology
    • Prevention
    • Treatment
    • History

    A range of types of wart have been identified, varying in shape and site affected, as well as the type of human papillomavirus involved.These include: 1. Common wart (verruca vulgaris), a raised wart with roughened surface, most common on hands, but can grow anywhere on the body. Sometimes known as a Palmer wart or Junior wart. 2. Flat wart (verruca plana), a small, smooth flattened wart, flesh-coloured, which can occur in large numbers; most common on the face, neck, hands, wrists and knees. 3. Filiform or digitate wart, a thread- or finger-like wart, most common on the face, especially near the eyelids and lips. 4. Genital wart (venereal wart, condyloma acuminatum, verruca acuminata), a wart that occurs on the genitalia. 5. Periungual wart, a cauliflower-like cluster of warts that occurs around the nails. 6. Plantar wart (verruca, verruca plantaris), a hard, sometimes painful lump, often with multiple black specks in the center; usually only found on pressure points on the soles o...

    Warts are caused by the human papilloma virus (HPV). There are about 130 known types of human papilloma viruses. HPV infects the squamous epithelium, usually of the skin or genitals, but each HPV type is typically only able to infect a few specific areas on the body. Many HPV types can produce a benign growth, often called a "wart" or "papilloma", in the area they infect.[citation needed]Many of the more common HPV and wart types are listed below. 1. Common warts – HPV types 2 and 4 (most common); also types 1, 3, 26, 29, and 57 and others. 2. Cancers and genital dysplasia – "high-risk" HPV types are associated with cancers, notably cervical cancer, and can also cause some vulvar, vaginal, penile, anal and some oropharyngeal cancers. "Low-risk" types are associated with warts or other conditions. 1. 1.1. High-risk: 16, 18 (cause the most cervical cancer); also 31, 33, 35, 39, 45, 52, 58, 59, and others. 1. Plantar warts (verruca) – HPV type 1 (most common); also types 2, 3, 4, 27, 2...

    Common warts have a characteristic appearance under the microscope. They have thickening of the stratum corneum (hyperkeratosis), thickening of the stratum spinosum (acanthosis), thickening of the stratum granulosum, rete ridge elongation, and large blood vessels at the dermoepidermal junction.[citation needed]

    Gardasil 6 is an HPV vaccine aimed at preventing cervical cancers and genital warts. Gardasil is designed to prevent infection with HPV types 16, 18, 6, and 11. HPV types 16 and 18 currently cause about 70% of cervical cancer cases, and also cause some vulvar, vaginal, penile and anal cancers.HPV types 6 and 11 are responsible for 90% of documented cases of genital warts. Gardasil 9, approved in 2014 protects against HPV types 6, 11, 16, 18, 31, 33, 45, 52, and 58. HPV vaccines do not currently protect against the virus strains responsible for plantar warts(verrucae). Also, some of the ways for not spreading to other parts of the body. Follow simple guidelines to prevent warts. 1. Wash your hands regularly when you have been contacted with the person who is with warts. 2. Cover your warts with bandage 3. Do not pick your warts with hands 4. Have separate shower shoes

    There are many treatments and procedures associated with wart removal. A review of various skin wart treatments concluded that topical treatments containing salicylic acid were more effective than placebo. Cryotherapyappears to be as effective as salicylic acid, but there have been fewer trials.

    Surviving ancient medical texts show that warts were a documented disease since at least the time of Hippocrates, who lived ca. 460 – c. 370 BC. In the book De Medecia by the Roman physician Aulus Cornelius Celsus, who lived c. 25 BC – c. 50 AD, different types of warts were described. Celsus described myrmecia, today recognized as plantar wart, and categorized acrochordon (a skin tag) as wart. In the 13th century warts were described in books published by the surgeons William of Saliceto and Lanfranc of Milan. The word verruca to describe a wart was introduced by the physician Daniel Sennert, who described warts in his 1636 book Hypomnemata physicae. But the cause of warts was disputed in the medical profession. In the early 18th century the physician Daniel Turner, who published the first book on dermatology, suggested that warts were caused by damaged nerves close to the skin. Mid 18th century the surgeon John Hunter popularized the belief that warts were caused by a bacterial sy...

  3. Hepatitis B virus - Wikipedia

    en.wikipedia.org › wiki › Hepatitis_B_virus
    • Disease
    • Classification
    • Morphology
    • Evolution
    • Genome
    • Life Cycle
    • See Also

    Despite there being a vaccine to prevent Hepatitis B, HBV remains a global health problem. Hepatitis B can be acute and later become chronic, leading to other diseases and health conditions. In addition to causing hepatitis, infection with HBV can lead to cirrhosis and hepatocellular carcinoma. It has also been suggested that it may increase the risk of pancreatic cancer.

    Hepatitis B virus is classified in the genus Orthohepadnavirus, which contains 11 other species. The genus is classified as part of the Hepadnaviridae family, which contains four other genera, Avihepadnavirus, Herpetohepadnavirus, Metahepadnavirus and Parahepadnavirus. This family of viruses is the only member of the viral order Blubervirales. Viruses similar to hepatitis B have been found in all apes (orangutans, gibbons, gorillas and chimpanzees), in Old World monkeys, and in New World woolly monkeys (the woolly monkey hepatitis B virus), suggesting an ancient origin for this virus in primates. The virus is divided into four major serotypes (adr, adw, ayr, ayw) based on antigenic epitopes present on its envelope proteins. These serotypes are based on a common determinant (a) and two mutually exclusive determinant pairs (d/y and w/r). The viral strains have also been divided into ten genotypes (A–J) and forty subgenotypes according to overall nucleotide sequence variation of the ge...

    Structure

    Hepatitis B virus is a member of the Hepadnavirus family. The virus particle, called Dane particle (virion), consists of an outer lipid envelope and an icosahedral nucleocapsid core composed of protein. The nucleocapsid encloses the viral DNA and a DNA polymerase that has reverse transcriptase activity similar to retroviruses. The outer envelope contains embedded proteins which are involved in viral binding of, and entry into, susceptible cells. The virus is one of the smallest enveloped anim...

    Components

    It consists of: 1. HBsAg (Hepatitis B surface antigen) was the first hepatitis B virus protein to be discovered.It consists of small (S), medium (M) and large (L) protein. 2. HBcAg (Hepatitis B core antigen) is the main structural protein of HBV icosahedral nucleocapsid and it has function in replication of the virus. Capsid formation is the main factor for infection of the cell. HBcAg contributes to HBV clearance in vivo, but it is unknown whether HBcAg has to be in the capsid form to contri...

    The early evolution of the Hepatitis B, like that of all viruses, is difficult to establish. The divergence of orthohepadnavirus and avihepadnavirus occurred ~125,000 years ago (95% interval 78,297–313,500). Both the Avihepadnavirus and Orthohepadna viruses began to diversify about 25,000 years ago. The branching at this time lead to the emergence of the Orthohepadna genotypes A–H. Humanstrains have a most recent common ancestor dating back to 7,000 (95% interval: 5,287–9,270) to 10,000 (95% interval: 6,305–16,681) years ago. The Avihepadnavirus lack a X protein but a vestigial X reading frame is present in the genome of duck hepadnavirus. The X protein may have evolved from a DNA glycosylase. The rate of nonsynonymous mutations in this virus has been estimated to be about 2×10−5 amino acid replacements per site per year. The mean number of nucleotide substitutions/site/year is ~7.9×10−5. A second estimate of the origin of this virus suggests a most recent common ancestor of the hum...

    Size

    The genome of HBV is made of circular DNA, but it is unusual because the DNA is not fully double-stranded. One end of the full length strand is linked to the viral DNA polymerase. The genome is 3020–3320 nucleotideslong (for the full length strand) and 1700–2800 nucleotides long (for the short length strand).

    Encoding

    The negative-sense, (non-coding) strand is complementary to the viral mRNA. The viral DNA is found in the nucleus soon after infection of the cell. The partially double-stranded DNA is rendered fully double-stranded by completion of the (+) sense strand by cellular DNA polymerases(viral DNA polymerase is used for a later stage) and removal of the viral polymerase protein (P) from the (-) sense strand and a short sequence of RNA from the (+) sense strand. Non-coding bases are removed from the...

    Genotypes

    Genotypes differ by at least 8% of the sequence and have distinct geographical distributions and this has been associated with anthropological history. Within genotypes subtypes have been described: these differ by 4–8% of the genome. There are eight known genotypeslabeled A through H. A possible new "I" genotype has been described,but acceptance of this notation is not universal. Two further genotypes have since been recognised.The current (2014) listing now runs A though to J. Several subty...

    The life cycle of Hepatitis B virus is complex. Hepatitis B is one of a few known non-retroviral viruses which use reverse transcriptionas a part of its replication process. Attachment 1. The virus gains entry into the cell by binding to receptors on the surface of the cell and entering it by endocytosis mediated by either clathrin or caveolin-1. HBV initially binds to heparin sulfate proteoglycan. The pre-S1 segment of the HBV L protein then binds tightly to the cell surface receptor sodium taurocolate cotransporting polypeptide (NTCP), encoded by the SLC10A1gene. NTCP is mostly found in the sinusoidal membrane of liver cells. The presence of NTCP in liver cells correlates with the tissue specificity of HBV infection. Penetration 1. Following endocytosis, the virus membrane fuses with the host cell's membrane, releasing the nucleocapsid into the cytoplasm. Uncoating 1. Because the virus multiplies via RNA made by a host enzyme, the viral genomic DNA has to be transferred to the cel...

  4. Heat recovery ventilation - Wikipedia

    en.wikipedia.org › wiki › Heat_recovery_ventilation
    • Working Principle
    • Types
    • Applications
    • Environmental Impacts
    • External Links

    A heat recovery system is designed to supply conditioned air to the occupied space to continue the desired level of comfort. The heat recovery system keeps the house fully ventilated by recovering the heat which is coming from the inside environment. Heat recovery systems basically work by transferring the thermal energy (enthalpy) from one fluid to another fluid, from one fluid to a solid or from a solid surface to a fluid, at different temperatures and in thermal contact. Additionally, there is no direct interaction between fluid and fluid or fluid and solid in most of the heat recovery systems. In some application of heat recovery systems, fluid leakage is observed due to pressure differences which can cause mixture of the two fluids.

    Rotary thermal wheels

    Rotary thermal wheels are a mechanical means of heat recovery. A rotating porous metallic wheel transfers thermal energy from one air stream to another by passing through each fluid alternately. The system operates by working as a thermal storage mass whereby the heat from the air is temporarily stored within the wheel matrix until it is transferred to the cooler air stream. Two types of rotary thermal wheel exist, heat wheels and enthalpy (desiccant) wheels. Though there is geometrical simil...

    Fixed plate heat exchangers

    Fixed plate heat exchangers are the most commonly used type of heat exchanger and have been developed for 40 years. Thin metal plates are stacked with a small spacing between plates. Two different airstreams pass through these spaces, adjacent to each other. The heat transfer occurs as the temperature transfers through the plate from one airstream to the other. The efficiency of these devices have shown values of 90% sensible heat efficiency in transferring sensible heat from one air stream t...

    Heat pipes

    Heat pipes are a heat recovery device that use a multi-phase process to transfer heat from one airstream to another.Heat is transferred using an evaporator and condenser within a wicked, sealed pipe containing a fluid which undergoes constant phase change to transfer heat. The fluid within the pipes changes from a fluid to a gas in the evaporator section, absorbing the thermal energy from the warm airstream. The gas condenses back to a fluid in the condenser section where the thermal energy i...

    Rotary thermal wheel

    O’Connor et al.studied the effect that a rotary thermal wheel has on the supply air flow rates in to a building. A computational model was created to simulate the effects of a rotary thermal wheel on air flow rates when incorporated into a commercial wind tower system. The simulation was validated with a scale model experiment in a closed-loop subsonic wind tunnel. The data obtained from both tests were compared in order to analyse the flow rates. Although the flow rates were reduced compared...

    Fixed plate heat exchangers

    Mardiana et al.integrated a fixed plate heat exchanger into a commercial wind tower, highlighting the advantages of this type of system as a means of zero energy ventilation which can be simply modified. Full scale laboratory testing was undertaken in order to determine the effects and efficiency of the combined system. A wind tower was integrated with a fixed plate heat exchanger and was mounted centrally on a sealed test room. The results from this study indicate that the combination of a w...

    Heat pipes

    Due to the low pressure loss of heat pipe systems, more research has been conducted into the integration of this technology into passive ventilation than other heat recovery systems. Commercial wind towers were again used as the passive ventilation system for integrating this heat recovery technology. This further enhances the suggestion that commercial wind towers provide a worthwhile alternative to mechanical ventilation, capable of supplying and exhausting air at the same time.

    Energy saving is one of the key issues for both fossil fuel consumption and protection of global environment. The rising cost of energy and the global warming underlined that developing of the improved energy systems is necessary to increase the energy efficiency while reducing greenhouse gas emissions. The most effective way to reduce energy demand is to use energy more efficiently. Therefore, waste heat recovery is becoming popular in recent years since it improves energy efficiency. About 26% of industrial energy is still wasted as hot gas or fluid in many countries.However, during last two decades there has been remarkable attention to recover waste heat from various industries and to optimize the units which are used to absorb heat from waste gases. Thus, these attempts enhance reducing of global warming as well as of energy demand.

  5. Virus - Wikipedia

    en.wikipedia.org › wiki › Virus

    A virus is a submicroscopic infectious agent that replicates only inside the living cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea. Since Dmitri Ivanovsky's 1892 ...

  6. Hypothalamic–pituitary–adrenal axis - Wikipedia

    en.wikipedia.org › wiki › Hypothalamic–pituitary–adrenal_axis
    • Anatomy
    • Function
    • Immune System
    • Stress
    • External Links

    The key elements of the HPA axis are: 1. The paraventricular nucleus of the hypothalamus, which contains neuroendocrine neurons which synthesize and secrete vasopressin and corticotropin-releasing hormone (CRH). These two peptides regulate: 1.1. The anterior lobe of the pituitary gland. In particular, CRH and vasopressin stimulate the secretion of adrenocorticotropic hormone (ACTH), once known as corticotropin. ACTH in turn acts on: 1.2. the adrenal cortex, which produces glucocorticoid hormones (mainly cortisol in humans) in response to stimulation by ACTH. Glucocorticoids in turn act back on the hypothalamus and pituitary (to suppress CRH and ACTH production) in a negative feedbackcycle. CRH and vasopressin are released from neurosecretory nerve terminals at the median eminence. CRH is transported to the anterior pituitary through the portal blood vessel system of the hypophyseal stalk and vasopressin is transported by axonal transport to the posterior pituitary gland. There, CRH...

    Release of corticotropin-releasing hormone (CRH) from the hypothalamus is influenced by stress, physical activity, illness, by blood levels of cortisol and by the sleep/wake cycle (circadian rhythm). In healthy individuals, cortisol rises rapidly after wakening, reaching a peak within 30–45 minutes. It then gradually falls over the day, rising again in late afternoon. Cortisol levels then fall in late evening, reaching a trough during the middle of the night. This corresponds to the rest-activity cycle of the organism. An abnormally flattened circadian cortisol cycle has been linked with chronic fatigue syndrome, insomnia and burnout. The HPA axis has a central role in regulating many homeostatic systems in the body, including the metabolic system, cardiovascular system, immune system, reproductive system and central nervous system. The HPA axis integrates physical and psychosocial influences in order to allow an organism to adapt effectively to its environment, use resources, and o...

    There is bi-directional communication and feedback between the HPA axis and the immune system. A number of cytokines, such as IL-1, IL-6, IL-10 and TNF-alpha can activate the HPA axis, although IL-1 is the most potent. The HPA axis in turn modulates the immune response, with high levels of cortisol resulting in a suppression of immune and inflammatory reactions. This helps to protect the organism from a lethal overactivation of the immune system, and minimizes tissue damage from inflammation. The CNS is in many ways "immune privileged", but it plays an important role in the immune system and is affected by it in turn. The CNS regulates the immune system through neuroendocrine pathways, such as the HPA axis. The HPA axis is responsible for modulating inflammatory responsesthat occur throughout the body. During an immune response, proinflammatory cytokines (e.g. IL-1) are released into the peripheral circulation system and can pass through the blood brain barrier where they can intera...

    Stress and disease

    The HPA axis is involved in the neurobiology of mood disorders and functional illnesses, including anxiety disorder, bipolar disorder, insomnia, posttraumatic stress disorder, borderline personality disorder, ADHD, major depressive disorder, burnout, chronic fatigue syndrome, fibromyalgia, irritable bowel syndrome, and alcoholism. Antidepressants, which are routinely prescribed for many of these illnesses, serve to regulate HPA axis function. Sex differences are prevalent in humans with respe...

  7. Circumcision - Wikipedia

    en.wikipedia.org › wiki › Circumcision

    Circumcision is the removal of the foreskin from the human penis. In the most common procedure the foreskin is extended with forceps (in pre-pubescent children its normal adhesion to the glans must also be broken with a probe), then a ...

  8. Polyether ether ketone - Wikipedia

    en.wikipedia.org › wiki › Polyether_ether_ketone
    • Synthesis
    • Properties
    • Applications
    • Processing Options
    • Shape-Memory Peek in Biomechanical Applications

    PEEK polymers are obtained by step-growth polymerization by the dialkylation of bisphenolate salts. Typical is the reaction of 4,4'-difluorobenzophenone with the disodium salt of hydroquinone, which is generated in situ by deprotonation with sodium carbonate. The reaction is conducted around 300 °C in polar aprotic solvents - such as diphenyl sulphone.

    PEEK is a semicrystalline thermoplastic with excellent mechanical and chemical resistance properties that are retained to high temperatures. The processing conditions used to mold PEEK can influence the crystallinity and hence the mechanical properties. Its Young's modulus is 3.6 GPa and its tensile strength is 90 to 100 MPa. PEEK has a glass transition temperature of around 143 °C (289 °F) and melts around 343 °C (662 °F). Some grades have a useful operating temperature of up to 250 °C (482 °F). The thermal conductivity increases nearly linearly with temperature between room temperature and solidus temperature. It is highly resistant to thermal degradation, as well as to attack by both organic and aqueous environments. It is attacked by halogens and strong Brønsted and Lewis acids, as well as some halogenated compounds and aliphatic hydrocarbons at high temperatures. It is soluble in concentrated sulfuric acid at room temperature, although dissolution can take a very long time unle...

    PEEK is used to fabricate items for demanding applications, including bearings, piston parts, pumps, high-performance liquid chromatography columns, compressor plate valves, and electrical cable insulation. It is one of the few plastics compatible with ultra-high vacuum applications, which makes it suitable for aerospace, automotive, teletronic, and chemical industries. PEEK is used in medical implants, e.g., use with a high-resolution magnetic resonance imaging(MRI), for creating a partial replacement skull in neurosurgical applications. PEEK is used in spinal fusion devices and reinforcing rods. It is radiolucent, but it is hydrophobic causing it to not fully fuse with bone. PEEK seals and manifolds are commonly used in fluid applications. PEEK also performs well in high temperature applications (up to 500 °F/260 °C). Because of this and its low thermal conductivity, it is also used in FFFprinting to thermally separate the hot end from the cold end.

    PEEK melts at a relatively high temperature (343 °C / 649.4 °F) compared to most other thermoplastics. In the range of its melting temperature it can be processed using injection moulding or extrusion methods. It is technically feasible to process granular PEEK into filament form and 3D printing parts from the filament material using fused deposition modeling – FDM (or fused filament fabrication – FFF) technology.PEEK filaments have been demonstrated for producing medical devices up to class IIa. With this new filament, it is possible to use the FFF method for different medical applications like dentures. In its solid state PEEK is readily machinable, for example, by (CNC) milling machinesand is commonly used to produce high-quality plastic parts that are thermostable and both electrically and thermally insulating. Filled grades of PEEK can also be CNC machined, but special care must be taken to properly manage stresses in the material. PEEK is a high-performance polymer, but its hi...

    PEEK is not traditionally a shape-memory polymer; however, recent advances in processing have allowed shape-memory behavior in PEEK with mechanical activation. This technology has expanded to applications in orthopedic surgery.

  9. Glutaraldehyde - Wikipedia

    en.wikipedia.org › wiki › Glutaraldehyde
    • Uses
    • Safety
    • Mechanism of Action
    • Production and Reactions
    • History and Culture
    • External Links

    Disinfection

    Glutaraldehyde is used as a disinfectantand medication. Usually applied as a solution, it is used to sterilize surgical instrumentsand other areas.

    Fixative

    Glutaraldehyde is used in biochemistry applications as an amine-reactive homobifunctional crosslinker and fixative prior to SDS-PAGE, staining, or electron microscopy. It kills cells quickly by crosslinking their proteins. It is usually employed alone or mixed with formaldehyde as the first of two fixative processes to stabilize specimens such as bacteria, plant material, and human cells. A second fixative procedure uses osmium tetroxide to crosslink and stabilize cell and organelle membrane...

    Wart treatment

    As a medication it is used to treat plantar warts. For this purpose, a 10% w/v solution is used. It dries the skin, facilitating physical removal of the wart. Trade names include Diswart Solution and Glutarol.[citation needed]

    Side effects include skin irritation. If exposed to large amounts, nausea, headache, and shortness of breath may occur. Protective equipment is recommended when used, especially in high concentrations. Glutaraldehyde is effective against a range of microorganisms including spores. As a strong sterilant, glutaraldehyde is toxic and a strong irritant. There is no strong evidence of carcinogenic activity.Some occupations that work with this chemical have an increased risk of some cancers.

    A number of mechanisms have been invoked to explain the biocidal properties of glutaraldehyde.Like many other aldehydes, it reacts with amines and thiol groups, which are common functional groups in proteins. Being bi-function, it is also a potential crosslinker.

    Glutaraldehyde is produced industrially by the oxidation of cyclopentene. Alternatively it can be made by the Diels-Alder reaction of acrolein and vinyl ethersfollowed by hydrolysis. Like many other dialdehydes, (e.g., glyoxal) and simple aldehydes (e.g., formaldehyde), glutaraldehyde converts in aqueous solution to various hydrates that in turn convert to other equilibrating species.[clarification needed] Monomeric glutaraldehyde polymerizes by aldol condensationreaction yielding alpha, beta-unsaturated poly-glutaraldehyde. This reaction usually occurs at alkaline pH values. [medical citation needed]

    Glutaraldehyde came into medical use in the 1960s. It is on the World Health Organization's List of Essential Medicines, the safest and most effective medicines needed in a health system. There are a number of other commercial uses such as leather tanning. A glutaraldehyde solution of 0.1% to 1.0% concentration may be used as a biocide for system disinfection and as a preservative for long-term storage. It is a sterilant, killing endospores in addition to many microorganisms and viruses. As a biocide, glutaraldehyde is a component of hydraulic fracturing ("fracking") fluid. It is included in the additive called Alpha 1427.Bacterial growth impairs extraction of oil and gas from these wells. Glutaraldehyde is pumped as a component of the fracturing fluid to inhibit microbial growth. [medical citation needed]

  10. Pulse-width modulation - Wikipedia

    en.wikipedia.org › wiki › Pulse-width_modulation
    • Duty Cycle
    • History
    • Principle
    • Applications
    • See Also
    • External Links

    The term duty cycledescribes the proportion of 'on' time to the regular interval or 'period' of time; a low duty cycle corresponds to low power, because the power is off for most of the time. Duty cycle is expressed in percent, 100% being fully on. When a digital signal is on half of the time and off the other half of the time, the digital signal has a duty cycle of 50% and resembles a "square" wave. When a digital signal spends more time in the on state than the off state, it has a duty cycle of >50%. When a digital signal spends more time in the off state than the on state, it has a duty cycle of <50%. Here is a pictorial that illustrates these three scenarios:

    Some machines (such as a sewing machine motor) require partial or variable power. In the past, control (such as in a sewing machine's foot pedal) was implemented by use of a rheostat connected in series with the motor to adjust the amount of current flowing through the motor. It was an inefficient scheme, as this also wasted power as heat in the resistor element of the rheostat, but tolerable because the total power was low. While the rheostat was one of several methods of controlling power (see autotransformers and Variac for more info), a low cost and efficient power switching/adjustment method was yet to be found. This mechanism also needed to be able to drive motors for fans, pumps and robotic servos, and needed to be compact enough to interface with lamp dimmers. PWM emerged as a solution for this complex problem. One early application of PWM was in the SinclairX10, a 10 W audio amplifier available in kit form in the 1960s. At around the same time PWM started to be used in AC m...

    Pulse-width modulation uses a rectangular pulse wave whose pulse width is modulated resulting in the variation of the average value of the waveform. If we consider a pulse waveform f ( t ) {\\displaystyle f(t)} , with period T {\\displaystyle T} , low value y min {\\displaystyle y_{\\text{min}}} , a high value y max {\\displaystyle y_{\\text{max}}} and a duty cycleD (see figure 1), the average value of the waveform is given by: 1. y ¯ = 1 T ∫ 0 T f ( t ) d t {\\displaystyle {\\bar {y}}={\\frac {1}{T}}\\int _{0}^{T}f(t)\\,dt} As f ( t ) {\\displaystyle f(t)} is a pulse wave, its value is y max {\\displaystyle y_{\\text{max}}} for 0 < t < D ⋅ T {\\displaystyle 0

    Servos

    PWM is used to control servomechanisms; see servo control.

    Telecommunications

    In telecommunications, PWM is a form of signal modulationwhere the widths of the pulses correspond to specific data values encoded at one end and decoded at the other. Pulses of various lengths (the information itself) will be sent at regular intervals (the carrier frequency of the modulation). The inclusion of a clock signalis not necessary, as the leading edge of the data signal can be used as the clock if a small offset is added to each data value in order to avoid a data value with a zero...

    Power delivery

    PWM can be used to control the amount of power delivered to a load without incurring the losses that would result from linear power delivery by resistive means. Drawbacks to this technique are that the power drawn by the load is not constant but rather discontinuous (see Buck converter), and energy delivered to the load is not continuous either. However, the load may be inductive, and with a sufficiently high frequency and when necessary using additional passive electronic filters, the pulse...

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