Ablation
Encyclopedia
Ablation is removal of material from the surface of an object by vaporization
, chipping, or other erosive
processes. This occurs in spaceflight
during ascent and atmospheric reentry
, glaciology
, medicine
, and passive fire protection
.
design, ablation is used to both cool and protect mechanical parts and/or payloads that would otherwise be damaged by extremely high temperatures. Two principal applications are heat shield
s for spacecraft entering a planetary atmosphere
from space and cooling of rocket engine nozzles. Examples include the Apollo Command Module
that protected astronauts from the heat
of atmospheric reentry
and the Kestrel
second stage
rocket engine
designed for exclusive use in an environment of space vacuum since no heat convection
is possible.
In a basic sense, ablative material is designed to slowly burn away in a controlled manner, so that heat can be carried away from the spacecraft by the gases generated by the ablative process; while the remaining solid material insulates the craft from superheated gases. There is an entire branch of spaceflight
research involving the search for new fireproofing
materials to achieve the best ablative performance; this function is critical to protect the spacecraft occupants and payload from otherwise excessive heat loading. The same technology is used in some passive fire protection
applications, in some cases by the same vendors, who offer different versions of these fireproofing
products, some for aerospace and some for structural fire protection
.
, sublimation, calving
, or erosive removal of snow by wind. Air temperature is typically the dominant control of ablation with precipitation exercising secondary control. In a temperate climate during ablation season, ablation rates typically average around 2 mm/hr.
Ablation can refer either to the processes removing ice and snow or to the quantity of ice and snow removed.
, usually by surgery
. Surface ablation of the skin
(dermabrasion
, also called resurfacing because it induces regeneration
) can be carried out by chemicals (which cause peeling) or by lasers. Its purpose is to remove skin spots, aged skin, wrinkles, thus rejuvenating
it. Surface ablation is also employed in otolaryngology
for several kinds of surgery, such as for snoring
. Ablation therapy using radio frequency waves on the heart is used to cure a variety of cardiac arrhythmia such as supraventricular tachycardia
, Wolff–Parkinson–White syndrome (WPW), ventricular tachycardia, and more recently as management of atrial fibrillation
. The term is often used in the context of laser ablation
, a process in which a laser
dissolves a material's molecular bonds
. For a laser to ablate tissues, the power density or fluence
must be high, otherwise thermocoagulation occurs, which is simply thermal vaporization of the tissues.
Rotoablation is a type of arterial cleansing that consists of inserting a tiny, diamond-tipped, drill-like device into the affected artery to remove fatty deposits or plaque. The procedure is used in the treatment of coronary heart disease
to restore blood flow.
Radiofrequency ablation
(RF) is a method of removing aberrant tissue from within the body via minimally invasive procedures. I.e., RF ablation in an electrophysiology study
to remove cells that are issuing abnormal electrical activity leading to arrhythmia.
Bone marrow
ablation is a process whereby the human bone marrow cells are eliminated in preparation for a bone marrow transplant
. This is performed using high-intensity chemotherapy
and total body irradiation
. As such it has nothing to do with the vaporization techniques described in the rest of this article.
Ablation of brain tissue
is used for treating certain neurological disorder
s, particularly Parkinson's disease
, and sometimes for psychiatric disorders as well.
Recently, some researchers reported successful results with genetic ablation. In particular, genetic ablation is potentially a much more efficient method of removing unwanted cells, such as tumor
cells, because large numbers of animals lacking specific cells could be generated. Genetically ablated lines can be maintained for a prolonged period of time and shared within the research community. Researchers at Columbia University report of reconstituted caspases combined from C. elegans and humans, which maintain a high degree of target specificity. The genetic ablation techniques described could prove useful in battling cancer.
Genetic ablation is another term for gene silencing
, in which gene expression
is abolished through the alteration or deletion of genetic sequence information. In cell ablation, individual cells in a population or culture are destroyed or removed. Both can be used as experimental tools, as in loss-of-function experiments.
Laser ablation
is greatly affected by the nature of the material and its ability to absorb energy, therefore the wavelength of the ablation laser should have a minimum absorption depth. While these lasers can average a low power, they can offer peak intensity and fluence given by:
while the peak power is
Surface ablation of the cornea
for several types of eye refractive surgery
is now common, using an excimer laser
system (LASIK
and LASEK
). Since the cornea does not grow back, laser is used to remodel the cornea refractive
properties to correct refraction errors, such as astigmatism
, myopia
, and hyperopia
. Laser ablation is also used to remove part of the uterine
wall in women with menstruation
and adenomyosis
problems in a process called endometrial ablation
.
ping and fireproofing
products can be ablative in nature. This can mean endothermic
materials, or merely materials that are sacrificial and become "spent" over time while exposed to fire
such as silicone
firestop products.
Given sufficient time under fire or heat conditions, these products char away, crumble, and disappear. The idea is to put enough of this material in the way of the fire that a level of fire-resistance rating
can be maintained, as demonstrated in a fire test
. Ablative materials usually have a large concentration of organic matter that is reduced by fire to ashes. In the case of silicone, organic rubber
surrounds very finely divided silica dust
(up to 380 m² of combined surface area of all the dust particles per gram of this dust). When the organic rubber is exposed to fire it burns to ash and leaves behind the silica dust with which the product started.
s for the bottom hull surfaces of recreational, commercial and military sea vessels. Ablative paints are often utilized for this purpose to prevent the dilution or deactivation of the antifouling agent. Over time, the paint will slowly decompose in the water, exposing fresh antifouling compounds on the surface. Engineering the antifouling agents and the ablation rate can produce long-lived protection from the deleterious effects of biofouling.
Vaporization
Vaporization of an element or compound is a phase transition from the liquid or solid phase to gas phase. There are three types of vaporization: evaporation, boiling and sublimation....
, chipping, or other erosive
Erosion
Erosion is when materials are removed from the surface and changed into something else. It only works by hydraulic actions and transport of solids in the natural environment, and leads to the deposition of these materials elsewhere...
processes. This occurs in spaceflight
Spaceflight
Spaceflight is the act of travelling into or through outer space. Spaceflight can occur with spacecraft which may, or may not, have humans on board. Examples of human spaceflight include the Russian Soyuz program, the U.S. Space shuttle program, as well as the ongoing International Space Station...
during ascent and atmospheric reentry
Atmospheric reentry
Atmospheric entry is the movement of human-made or natural objects as they enter the atmosphere of a celestial body from outer space—in the case of Earth from an altitude above the Kármán Line,...
, glaciology
Glaciology
Glaciology Glaciology Glaciology (from Middle French dialect (Franco-Provençal): glace, "ice"; or Latin: glacies, "frost, ice"; and Greek: λόγος, logos, "speech" lit...
, medicine
Medicine
Medicine is the science and art of healing. It encompasses a variety of health care practices evolved to maintain and restore health by the prevention and treatment of illness....
, and passive fire protection
Passive fire protection
Passive fire protection is an integral component of the three components of structural fire protection and fire safety in a building. PFP attempts to contain fires or slow the spread, through use of fire-resistant walls, floors, and doors...
.
Spaceflight
In spacecraftSpacecraft
A spacecraft or spaceship is a craft or machine designed for spaceflight. Spacecraft are used for a variety of purposes, including communications, earth observation, meteorology, navigation, planetary exploration and transportation of humans and cargo....
design, ablation is used to both cool and protect mechanical parts and/or payloads that would otherwise be damaged by extremely high temperatures. Two principal applications are heat shield
Heat shield
A heat shield is designed to shield a substance from absorbing excessive heat from an outside source by either dissipating, reflecting or simply absorbing the heat...
s for spacecraft entering a planetary atmosphere
Atmosphere
An atmosphere is a layer of gases that may surround a material body of sufficient mass, and that is held in place by the gravity of the body. An atmosphere may be retained for a longer duration, if the gravity is high and the atmosphere's temperature is low...
from space and cooling of rocket engine nozzles. Examples include the Apollo Command Module
Apollo Command/Service Module
The Command/Service Module was one of two spacecraft, along with the Lunar Module, used for the United States Apollo program which landed astronauts on the Moon. It was built for NASA by North American Aviation...
that protected astronauts from the heat
Heat
In physics and thermodynamics, heat is energy transferred from one body, region, or thermodynamic system to another due to thermal contact or thermal radiation when the systems are at different temperatures. It is often described as one of the fundamental processes of energy transfer between...
of atmospheric reentry
Atmospheric reentry
Atmospheric entry is the movement of human-made or natural objects as they enter the atmosphere of a celestial body from outer space—in the case of Earth from an altitude above the Kármán Line,...
and the Kestrel
Kestrel (rocket engine)
The Kestrel engine is an LOX/RP-1 pressure-fed rocket engine. The Kestrel engine was developed by SpaceX for upper stage use on the Falcon 1 rocket....
second stage
Multistage rocket
A multistage rocket is a rocket that usestwo or more stages, each of which contains its own engines and propellant. A tandem or serial stage is mounted on top of another stage; a parallel stage is attached alongside another stage. The result is effectively two or more rockets stacked on top of or...
rocket engine
Rocket engine
A rocket engine, or simply "rocket", is a jet engineRocket Propulsion Elements; 7th edition- chapter 1 that uses only propellant mass for forming its high speed propulsive jet. Rocket engines are reaction engines and obtain thrust in accordance with Newton's third law...
designed for exclusive use in an environment of space vacuum since no heat convection
Convection
Convection is the movement of molecules within fluids and rheids. It cannot take place in solids, since neither bulk current flows nor significant diffusion can take place in solids....
is possible.
In a basic sense, ablative material is designed to slowly burn away in a controlled manner, so that heat can be carried away from the spacecraft by the gases generated by the ablative process; while the remaining solid material insulates the craft from superheated gases. There is an entire branch of spaceflight
Spaceflight
Spaceflight is the act of travelling into or through outer space. Spaceflight can occur with spacecraft which may, or may not, have humans on board. Examples of human spaceflight include the Russian Soyuz program, the U.S. Space shuttle program, as well as the ongoing International Space Station...
research involving the search for new fireproofing
Fireproofing
Fireproofing, a passive fire protection measure, refers to the act of making materials or structures more resistant to fire, or to those materials themselves, or the act of applying such materials. Applying a certification listed fireproofing system to certain structures allows these to have a...
materials to achieve the best ablative performance; this function is critical to protect the spacecraft occupants and payload from otherwise excessive heat loading. The same technology is used in some passive fire protection
Passive fire protection
Passive fire protection is an integral component of the three components of structural fire protection and fire safety in a building. PFP attempts to contain fires or slow the spread, through use of fire-resistant walls, floors, and doors...
applications, in some cases by the same vendors, who offer different versions of these fireproofing
Fireproofing
Fireproofing, a passive fire protection measure, refers to the act of making materials or structures more resistant to fire, or to those materials themselves, or the act of applying such materials. Applying a certification listed fireproofing system to certain structures allows these to have a...
products, some for aerospace and some for structural fire protection
Fire protection
Fire protection is the study and practice of mitigating the unwanted effects of fires. It involves the study of the behaviour, compartmentalisation, suppression and investigation of fire and its related emergencies, as well as the research and development, production, testing and application of...
.
Glaciology
In glaciology and meteorology, ablation—the opposite of accumulation—refers to all processes that remove snow, ice, or water from a glacier or snowfield. Ablation refers to the melting of snow or ice that runs off the glacier, evaporationEvaporation
Evaporation is a type of vaporization of a liquid that occurs only on the surface of a liquid. The other type of vaporization is boiling, which, instead, occurs on the entire mass of the liquid....
, sublimation, calving
Ice calving
Ice calving, also known as glacier calving or iceberg calving, is a form of ice ablation or ice disruption. It is the sudden release and breaking away of a mass of ice from a glacier, iceberg, ice front, ice shelf, or crevasse...
, or erosive removal of snow by wind. Air temperature is typically the dominant control of ablation with precipitation exercising secondary control. In a temperate climate during ablation season, ablation rates typically average around 2 mm/hr.
Ablation can refer either to the processes removing ice and snow or to the quantity of ice and snow removed.
Medicine
In medicine, ablation is the same as removal of a part of biological tissueBiological tissue
Tissue is a cellular organizational level intermediate between cells and a complete organism. A tissue is an ensemble of cells, not necessarily identical, but from the same origin, that together carry out a specific function. These are called tissues because of their identical functioning...
, usually by surgery
Surgery
Surgery is an ancient medical specialty that uses operative manual and instrumental techniques on a patient to investigate and/or treat a pathological condition such as disease or injury, or to help improve bodily function or appearance.An act of performing surgery may be called a surgical...
. Surface ablation of the skin
Skin
-Dermis:The dermis is the layer of skin beneath the epidermis that consists of connective tissue and cushions the body from stress and strain. The dermis is tightly connected to the epidermis by a basement membrane. It also harbors many Mechanoreceptors that provide the sense of touch and heat...
(dermabrasion
Dermabrasion
Dermabrasion is a surgical procedure that involves the controlled abrasion of the upper layers of the skin with sandpaper or other mechanical means. Nowadays it has become common to use CO2 or Erbium:YAG laser as well. The procedure requires a local anaesthetic...
, also called resurfacing because it induces regeneration
Regeneration (biology)
In biology, regeneration is the process of renewal, restoration, and growth that makes genomes, cells, organs, organisms, and ecosystems resilient to natural fluctuations or events that cause disturbance or damage. Every species is capable of regeneration, from bacteria to humans. At its most...
) can be carried out by chemicals (which cause peeling) or by lasers. Its purpose is to remove skin spots, aged skin, wrinkles, thus rejuvenating
Rejuvenation
Rejuvenation may refer to:*Rejuvenation , reversing the aging process*Rejuvenation , when the base level that a river is flowing down to is lowered*Rejuvenation , 1974*Rejuvenation , 2009...
it. Surface ablation is also employed in otolaryngology
Otolaryngology
Otolaryngology or ENT is the branch of medicine and surgery that specializes in the diagnosis and treatment of ear, nose, throat, and head and neck disorders....
for several kinds of surgery, such as for snoring
Snoring
Snoring is the vibration of respiratory structures and the resulting sound, due to obstructed air movement during breathing while sleeping. In some cases the sound may be soft, but in other cases, it can be loud and unpleasant...
. Ablation therapy using radio frequency waves on the heart is used to cure a variety of cardiac arrhythmia such as supraventricular tachycardia
Supraventricular tachycardia
Supraventricular tachycardia is a general term that refers to any rapid heart rhythm originating above the ventricular tissue. Supraventricular tachycardias can be contrasted to the potentially more dangerous ventricular tachycardias - rapid rhythms that originate within the ventricular...
, Wolff–Parkinson–White syndrome (WPW), ventricular tachycardia, and more recently as management of atrial fibrillation
Management of atrial fibrillation
The main goals in the management of atrial fibrillation are to prevent temporary circulatory instability and to prevent stroke. Control of heart rate and rhythm are principally used to achieve the former, while anticoagulation may be required to decrease the risk of stroke...
. The term is often used in the context of laser ablation
Laser ablation
Laser ablation is the process of removing material from a solid surface by irradiating it with a laser beam. At low laser flux, the material is heated by the absorbed laser energy and evaporates or sublimates. At high laser flux, the material is typically converted to a plasma...
, a process in which a laser
Laser
A laser is a device that emits light through a process of optical amplification based on the stimulated emission of photons. The term "laser" originated as an acronym for Light Amplification by Stimulated Emission of Radiation...
dissolves a material's molecular bonds
Covalent bond
A covalent bond is a form of chemical bonding that is characterized by the sharing of pairs of electrons between atoms. The stable balance of attractive and repulsive forces between atoms when they share electrons is known as covalent bonding....
. For a laser to ablate tissues, the power density or fluence
Fluence
In physics, fluence is the flux integrated over time. For particles, it is defined as the total number of particles that intersect a unit area in a specific time interval of interest, and has units of m–2...
must be high, otherwise thermocoagulation occurs, which is simply thermal vaporization of the tissues.
Rotoablation is a type of arterial cleansing that consists of inserting a tiny, diamond-tipped, drill-like device into the affected artery to remove fatty deposits or plaque. The procedure is used in the treatment of coronary heart disease
Coronary heart disease
Coronary artery disease is the end result of the accumulation of atheromatous plaques within the walls of the coronary arteries that supply the myocardium with oxygen and nutrients. It is sometimes also called coronary heart disease...
to restore blood flow.
Radiofrequency ablation
Radiofrequency ablation
Radio frequency ablation is a medical procedure where part of the electrical conduction system of the heart, tumor or other dysfunctional tissue is ablated using the heat generated from the high frequency alternating current to treat a medical disorder...
(RF) is a method of removing aberrant tissue from within the body via minimally invasive procedures. I.e., RF ablation in an electrophysiology study
Electrophysiology study
An electrophysiology study is a minimally invasive procedure which tests the electrical conduction system of the heart to assess the electrical activity and conduction pathways of the heart. The study is indicated to investigate the cause, location of origin, and best treatment for various...
to remove cells that are issuing abnormal electrical activity leading to arrhythmia.
Bone marrow
Bone marrow
Bone marrow is the flexible tissue found in the interior of bones. In humans, bone marrow in large bones produces new blood cells. On average, bone marrow constitutes 4% of the total body mass of humans; in adults weighing 65 kg , bone marrow accounts for approximately 2.6 kg...
ablation is a process whereby the human bone marrow cells are eliminated in preparation for a bone marrow transplant
Bone marrow transplant
Hematopoietic stem cell transplantation is the transplantation of multipotent hematopoietic stem cell or blood, usually derived from bone marrow, peripheral blood stem cells, or umbilical cord blood...
. This is performed using high-intensity chemotherapy
Chemotherapy
Chemotherapy is the treatment of cancer with an antineoplastic drug or with a combination of such drugs into a standardized treatment regimen....
and total body irradiation
Total body irradiation
Total body irradiation is a form of radiotherapy used primarily as part of the preparative regimen for haematopoietic stem cell transplantation. As the name implies, TBI involves irradiation of the entire body, though in modern practice the lungs are often partially shielded to lower the risk of...
. As such it has nothing to do with the vaporization techniques described in the rest of this article.
Ablation of brain tissue
Ablative brain surgery
Ablative brain surgery is the surgical ablation by burning or freezing of brain tissue to treat neurological or psychological disorders. The lesions it causes are irreversible....
is used for treating certain neurological disorder
Neurological disorder
A neurological disorder is a disorder of the body's nervous system. Structural, biochemical or electrical abnormalities in the brain, spinal cord, or in the nerves leading to or from them, can result in symptoms such as paralysis, muscle weakness, poor coordination, loss of sensation, seizures,...
s, particularly Parkinson's disease
Parkinson's disease
Parkinson's disease is a degenerative disorder of the central nervous system...
, and sometimes for psychiatric disorders as well.
Recently, some researchers reported successful results with genetic ablation. In particular, genetic ablation is potentially a much more efficient method of removing unwanted cells, such as tumor
Tumor
A tumor or tumour is commonly used as a synonym for a neoplasm that appears enlarged in size. Tumor is not synonymous with cancer...
cells, because large numbers of animals lacking specific cells could be generated. Genetically ablated lines can be maintained for a prolonged period of time and shared within the research community. Researchers at Columbia University report of reconstituted caspases combined from C. elegans and humans, which maintain a high degree of target specificity. The genetic ablation techniques described could prove useful in battling cancer.
Biology
Biological ablation is the removal of a biological structure or functionality.Genetic ablation is another term for gene silencing
Gene silencing
Gene silencing is a general term describing epigenetic processes of gene regulation. The term gene silencing is generally used to describe the "switching off" of a gene by a mechanism other than genetic modification...
, in which gene expression
Gene expression
Gene expression is the process by which information from a gene is used in the synthesis of a functional gene product. These products are often proteins, but in non-protein coding genes such as ribosomal RNA , transfer RNA or small nuclear RNA genes, the product is a functional RNA...
is abolished through the alteration or deletion of genetic sequence information. In cell ablation, individual cells in a population or culture are destroyed or removed. Both can be used as experimental tools, as in loss-of-function experiments.
Laser ablation
Laser ablation
Laser ablation is the process of removing material from a solid surface by irradiating it with a laser beam. At low laser flux, the material is heated by the absorbed laser energy and evaporates or sublimates. At high laser flux, the material is typically converted to a plasma...
is greatly affected by the nature of the material and its ability to absorb energy, therefore the wavelength of the ablation laser should have a minimum absorption depth. While these lasers can average a low power, they can offer peak intensity and fluence given by:
while the peak power is
Surface ablation of the cornea
Cornea
The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber. Together with the lens, the cornea refracts light, with the cornea accounting for approximately two-thirds of the eye's total optical power. In humans, the refractive power of the cornea is...
for several types of eye refractive surgery
Refractive surgery
Refractive eye surgery is any eye surgery used to improve the refractive state of the eye and decrease or eliminate dependency on glasses or contact lenses. This can include various methods of surgical remodeling of the cornea or cataract surgery. The most common methods today use excimer lasers to...
is now common, using an excimer laser
Excimer laser
An excimer laser is a form of ultraviolet laser which is commonly used in the production of microelectronic devices , eye surgery, and micromachining....
system (LASIK
LASIK
LASIK or Lasik , commonly referred to simply as laser eye surgery, is a type of refractive surgery for correcting myopia, hyperopia, and astigmatism...
and LASEK
Lasek
Lasek may refer to:*LASEK or photorefractive keratectomy, a laser eye surgery technique*Lasek, Lower Silesian Voivodeship *Lasek, Kuyavian-Pomeranian Voivodeship *Lasek, Łódź Voivodeship...
). Since the cornea does not grow back, laser is used to remodel the cornea refractive
Refraction
Refraction is the change in direction of a wave due to a change in its speed. It is essentially a surface phenomenon . The phenomenon is mainly in governance to the law of conservation of energy. The proper explanation would be that due to change of medium, the phase velocity of the wave is changed...
properties to correct refraction errors, such as astigmatism
Astigmatism (eye)
Astigmatism is an optical defect in which vision is blurred due to the inability of the optics of the eye to focus a point object into a sharp focused image on the retina. This may be due to an irregular or toric curvature of the cornea or lens. There are two types of astigmatism: regular and...
, myopia
Myopia
Myopia , "shortsightedness" ) is a refractive defect of the eye in which collimated light produces image focus in front of the retina under conditions of accommodation. In simpler terms, myopia is a condition of the eye where the light that comes in does not directly focus on the retina but in...
, and hyperopia
Hyperopia
Hyperopia, also known as farsightedness, longsightedness or hypermetropia, is a defect of vision caused by an imperfection in the eye , causing difficulty focusing on near objects, and in extreme cases causing a sufferer to be unable to focus on objects at any distance...
. Laser ablation is also used to remove part of the uterine
Uterus
The uterus or womb is a major female hormone-responsive reproductive sex organ of most mammals including humans. One end, the cervix, opens into the vagina, while the other is connected to one or both fallopian tubes, depending on the species...
wall in women with menstruation
Menstruation
Menstruation is the shedding of the uterine lining . It occurs on a regular basis in sexually reproductive-age females of certain mammal species. This article focuses on human menstruation.-Overview:...
and adenomyosis
Adenomyosis
Adenomyosis is a medical condition characterized by the presence of ectopic glandular tissue found in muscle. The term adenomyosis is derived from the terms adeno- , myo- , and -osis...
problems in a process called endometrial ablation
Endometrial ablation
Endometrial ablation is a medical procedure that is used to remove or destroy the endometrial lining of a uterus. This technique is most often employed for people who suffer from excessive or prolonged bleeding during their menstrual cycle but cannot or do not wish to undergo a hysterectomy. ...
.
Passive fire protection
FirestopFirestop
A firestop is a passive fire protection system of various components used to seal openings and joints in fire-resistance rated wall and/or floor assemblies, based on fire testing and certification listings....
ping and fireproofing
Fireproofing
Fireproofing, a passive fire protection measure, refers to the act of making materials or structures more resistant to fire, or to those materials themselves, or the act of applying such materials. Applying a certification listed fireproofing system to certain structures allows these to have a...
products can be ablative in nature. This can mean endothermic
Endothermic
In thermodynamics, the word endothermic describes a process or reaction in which the system absorbs energy from the surroundings in the form of heat. Its etymology stems from the prefix endo- and the Greek word thermasi,...
materials, or merely materials that are sacrificial and become "spent" over time while exposed to fire
Fire
Fire is the rapid oxidation of a material in the chemical process of combustion, releasing heat, light, and various reaction products. Slower oxidative processes like rusting or digestion are not included by this definition....
such as silicone
Silicone
Silicones are inert, synthetic compounds with a variety of forms and uses. Typically heat-resistant and rubber-like, they are used in sealants, adhesives, lubricants, medical applications , cookware, and insulation....
firestop products.
Given sufficient time under fire or heat conditions, these products char away, crumble, and disappear. The idea is to put enough of this material in the way of the fire that a level of fire-resistance rating
Fire-resistance rating
A fire-resistance rating typically means the duration for which a passive fire protection system can withstand a standard fire resistance test. This can be quantified simply as a measure of time, or it may entail a host of other criteria, involving other evidence of functionality or fitness for...
can be maintained, as demonstrated in a fire test
Fire test
A fire test is a means of determining whether or not fire protection products meet minimum performance criteria as set out in a building code or other applicable legislation. Successful tests in laboratories holding national accreditation for testing and certification result in the issuance of a...
. Ablative materials usually have a large concentration of organic matter that is reduced by fire to ashes. In the case of silicone, organic rubber
Rubber
Natural rubber, also called India rubber or caoutchouc, is an elastomer that was originally derived from latex, a milky colloid produced by some plants. The plants would be ‘tapped’, that is, an incision made into the bark of the tree and the sticky, milk colored latex sap collected and refined...
surrounds very finely divided silica dust
Dust
Dust consists of particles in the atmosphere that arise from various sources such as soil dust lifted up by wind , volcanic eruptions, and pollution...
(up to 380 m² of combined surface area of all the dust particles per gram of this dust). When the organic rubber is exposed to fire it burns to ash and leaves behind the silica dust with which the product started.
Marine surface coatings
Antifouling paints and other related coatings are routinely used to prevent the buildup of microorganisms and other animals, such as barnacleBarnacle
A barnacle is a type of arthropod belonging to infraclass Cirripedia in the subphylum Crustacea, and is hence related to crabs and lobsters. Barnacles are exclusively marine, and tend to live in shallow and tidal waters, typically in erosive settings. They are sessile suspension feeders, and have...
s for the bottom hull surfaces of recreational, commercial and military sea vessels. Ablative paints are often utilized for this purpose to prevent the dilution or deactivation of the antifouling agent. Over time, the paint will slowly decompose in the water, exposing fresh antifouling compounds on the surface. Engineering the antifouling agents and the ablation rate can produce long-lived protection from the deleterious effects of biofouling.
External links
- Physics of laser ablation
- Lasik Laser Eye Surgery. USA Food an Drugs Administration info.
- Physical Modalities, Including Laser. eMedicine index of articles on the subject.
- Chemical Peeling. American Society for Dermatological Surgery.
- Heart Arrhythmias Respond to Ablation UCLA Healthcare