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Encyclopedia > Ablation

Ablation is defined as the removal of material from the surface of an object by vaporization, chipping, or other erosive processes. The term occurs in space physics associated with atmospheric reentry, in glaciology, medicine and passive fire protection. Evaporation is the process whereby atoms or molecules in a liquid state (or solid state if the substance sublimes) gain sufficient energy to enter the gaseous state. ... Chipping is a prefix used in a number of place names in England, probably derived from ceapen, an Old English word meaning market, though the meaning may alternatively come from (or via) the Medieval English word chepynge with a more specific meaning of long market square. Examples include: Chipping Campden... Severe soil erosion in a wheat field near Washington State University, USA. For erosion as understood by materials science, see Erosion (materials science) For erosion as an English analogy, see Erosion (figurative) For erosion as an operation of Mathematical morphology, see Erosion (morphology) Erosion is the displacement of solids (soil... Space physics, also known as space plasma physics, is the study of plasmas as they occur naturally in the universe. ... Reentry redirects here. ... Lateral moraine on a glacier joining the Gorner Glacier, Zermatt, Switzerland. ... medicines, see medication and pharmacology. ... Fire-resistance rated wall assembly with fire door, cable tray penetration and intumescent [1] cable coating. ...

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Space physics

In space physics, ablation occurs to heat shields that are used to protect payloads from heat, such as the heat shields used by the Apollo Command Module on atmospheric reentry. 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 generated gases; while the remaining solid material insulates the craft from superheated gases. There is an entire branch of space physics 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. Space physics, also known as space plasma physics, is the study of plasmas as they occur naturally in the universe. ... In aeronautics, a heat shield is a protective layer on a spacecraft or ballistic missile that is designed to protect it from high temperatures, usually those that result from aerobraking during entry into a planets atmosphere. ... In physics, heat, symbolized by Q, is defined as energy in transit. ... Description Role: Earth and Lunar Orbit Crew: 3; CDR, CM pilot, LM pilot Dimensions Height: 36. ... Reentry redirects here. ... Fireproofing, a passive fire protection measure, subject to bounding, refers to the act of making materials or structures more resistant to fire, or to those materials themselves. ... Fire-resistance rated wall assembly with fire door, cable tray penetration and intumescent [1] cable coating. ... Fireproofing, a passive fire protection measure, subject to bounding, refers to the act of making materials or structures more resistant to fire, or to those materials themselves. ... Fire protection is the prevention and reduction of the hazards associated with fires. ...


Glaciology

In glaciology, ablation is used to define the removal of ice or snow from the surface of a mass of ice. Ablation may refer to melting and runoff or evaporation and sublimation of the ice, resulting in a thinning of the ice if it is not replenished by some other process. Ablation deposits are the masses of detritus left after surface melting of glacial ice. This article or section is in need of attention from an expert on the subject. ... Sublimation of an element or substance is a conversion between the solid and the gaseous phases of matter, with no intermediate liquid stage. ...


Medicine

In medicine, ablation is the same as removal of a part of biological tissue, usually by surgery. The American Heritage Stedman's Medical Dictionary defines ablation as "Removal of a body part or the destruction of its function, as by a surgery, disease, or noxious substance." [1] Biological tissue is a collection of interconnected cells that perform a similar function within an organism. ... A cardiothoracic surgeon performs a mitral valve replacement at the Fitzsimons Army Medical Center. ...


Surface ablation in the skin (also called resurfacing, because it induces regeneration) can be carried out by chemicals (peeling) or by lasers. Its purpose is to remove skin spots, aged skin, wrinkles, thus rejuvenating it. Surface ablation is also employed in otolaringology for several kinds of surgery, such as for snoring. Ablation therapy using radiofrequency waves on the heart is used to cure a variety of cardiac arrhythmias such as supraventricular tachycardia, WPW syndrome, ventricular tachycardia and more recently atrial fibrillation. The term is often used in the context of laser ablation, a process by which the molecular bonds of a material are dissolved by a laser. It has been suggested that this article or section be merged with Epidermis (skin). ... Regeneration is a form of tissue repair; the restoration of lost or damaged tissues, organs or limbs. ... Ageing or aging is the process of getting older. ... A wrinkle is a ridge or crease of a surface. ... Rejuvenation is the procedure of reversing the aging process, thus regaining youth. ... Snoring is the act of breathing through the open mouth in such a way as to cause a vibration of the uvula and soft palate, thus giving rise to a sound which may vary from a soft noise to a loud unpleasant sound. ... Atrial fibrillation (AF or afib) is an abnormal heart rhythm (cardiac arrhythmia) which involves the two small, upper heart chambers (the atria). ... Guo et al. ... Covalent bonding is a description of chemical bonding that is characterized by the sharing of pairs of electrons between atoms. ... A laser (acronym for light amplification by stimulated emission of radiation) is an optical source that emits photons in a coherent beam. ...


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. This article or section does not adequately cite its references or sources. ...


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 vaporisation techniques described in the rest of this article. Grays Anatomy illustration of cells in bone marrow. ... Bone marrow transplantation or hematopoietic stem cell transplantation (HSCT) is a medical procedure in the field of hematology and oncology that involves transplantation of hematopoietic stem cells (HSC). ... Chemotherapy is the use of chemical substances to treat disease. ... Total Body Irradiation (TBI) is a radiotherapy technique used to ablate the bone marrow and immune system prior to bone marrow transplantation or peripheral blood stem cell transplantation. ...


Biology

Ablation in biology can refer to genetic or cell ablation, for example. Genetic ablation describes a gene that has been silenced. It can be used on purpose in experiments where scientists can observe the effect of genetic silencing. Cell ablation is where individual cells are destroyed for experimental reasons.[2]


Laser ablation

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: Guo et al. ...

Fluence  (mathrm{J}/mathrm{cm}^2) = laser  pulse  energy  (mathrm{J}) / focal  spot  area  (mathrm{cm}^2) ,

while the peak power is

Peak  power  (mathrm{W}) = pulse  energy  (mathrm{J}) / pulse  duration  (mathrm{s})

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, in order to correct refraction errors, such as astigmatism, myopia and hyperopia. The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber, providing most of an eyes optical power [1]. Together with the lens, the cornea refracts light and, as a result, helps the eye to focus. ... Refractive eye surgery is any eye surgery used to improve the refractive state of the eye and decrease dependency on glasses or contact lenses. ... An excimer laser is a form of ultraviolet chemical laser which is commonly used in eye surgery and semiconductor manufacturing. ... LASIK, an acronym for Laser-Assisted in Situ Keratomileusis, is a form of refractive laser eye surgery procedure performed by ophthalmologists intended for correcting myopia, hyperopia, and astigmatism. ... This article or section should be merged with Photorefractive keratectomy LASEK, an acronym for Laser-Assisted Sub-Epithelial Keratectomy, is an eye surgery procedure intended to reduce a persons dependency on glasses or contact lenses. ... The straw seems to be broken, due to refraction of light as it emerges into the air. ... Refraction error is an error in the focussing of light by the human eye. ... Astigmatism is an affliction of the eye, where vision is blurred by an irregularly shaped cornea. ... Normal vision. ... Hyperopia, also known as hypermetropia or colloquially as farsightedness or longsightedness, is a defect of vision caused by an imperfection in the eye (often when the eyeball is too short or when the lens cannot become round enough), causing inability to focus on near objects, and in extreme cases causing...


Passive fire protection

Firestopping and fireproofing products can be ablative in nature. This can mean endothermic materials, or merely materials that are sacrificial and become "spent" over time spent while exposed to fire. The latter version has also been used to describe silicone firestop products, which, by themselves, are sacrificial. In other words, given sufficient time under fire or heat conditions, these products actually char away, crumble and disappear. The idea is to put enough of this material in the way of the fire, so that a prescribed fire-resistance rating can be maintained, as proven in a fire test. Usually, ablative materials have a large concentration of organic matter, which 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 fire comes, it reduces the organic rubber to ash and leaves the silica dust, that the product started with, behind. If you burn some silicone caulking and then subsequently crush the remaining ashes, you will find that the interior of the black piece of ash is actually white. The silica was white to begin with. The black stuff is the carbonaceous remains of the organic rubber that surrounded each silica dust particle. A firestop is a passive fire protection system of various components used to seal openings in fire-resistance rated wall and/or floor assemblies through bounding. ... Fireproofing, a passive fire protection measure, subject to bounding, refers to the act of making materials or structures more resistant to fire, or to those materials themselves. ... In thermodynamics, the word endothermic describes a process or reaction that absorbs energy in the form of heat. ... It has been suggested that this article or section be merged with Flame. ... Silicone caulking can be used as a basic sealant against water and air penetration. ... A firestop is a passive fire protection system of various components used to seal openings in fire-resistance rated wall and/or floor assemblies through bounding. ... A pocket watch, a device used to keep time There are two distinct views on the meaning of time. ... In physics, heat, symbolized by Q, is defined as energy in transit. ... An idea (Greek: ιδέα) is a specific thought which arises in the mind. ... International time/temperature curves used to run commercial furnaces for testing the Fire-resistance rating of passive fire protection systems, such as firestops, fire doors, wall and floor assemblies, etc. ... 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. ... Latex being collected from a tapped rubber tree Rubber is an elastic hydrocarbon polymer which occurs as a milky colloidal suspension (known as latex) in the sap of several varieties of plants. ... The chemical compound silicon dioxide, also known as silica, is the oxide of silicon, chemical formula SiO2. ... After just three years of use dust has blocked this laptop heat sink, making the computer unusable Dust is a general name for minute solid particles with diameters less than 500 micrometers (otherwise, see sand or granulates) and, more generally, for finely divided matter. ... General Name, Symbol, Number carbon, C, 6 Chemical series nonmetals Group, Period, Block 14, 2, p Appearance black (graphite) colorless (diamond) Atomic mass 12. ...


External links

References

  1. ^ The American Heritage Stedman's Medical Dictionary. KMLE Medical Dictionary Definition of ablation.
  2. ^ Cell Ablation definition at Change Bioscience.

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