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Showing posts with label electromedical. Show all posts
Showing posts with label electromedical. Show all posts

Monday, November 10, 2008

spectrophotometer

In physics, spectrophotometry is the quantitative study of electromagnetic spectra. It is more specific than the general term electromagnetic spectroscopy in that spectrophotometry deals with visible light,

near-ultraviolet, and near-infrared. Also, the term does not cover time-resolved spectroscopic techniques.
Spectrophotometry involves the use of a spectrophotometer. A spectrophotometer is a photometer (a device for measuring light intensity) that can measure intensity as a function of the color, or more specifically, the wavelength of light. There are many kinds of spectrophotometers. Among the most important distinctions used to classify them are the wavelengths they work with, the measurement techniques they use, how they acquire a spectrum, and the sources of intensity variation they are designed to measure. Other important features of spectrophotometers include the spectral bandwidth and linear range.
Perhaps the most common application of spectrophotometers is the measurement of light absorption, but they can be designed to measure diffuse or specular reflectance. Strictly, even the emission half of a luminescence instrument is a kind of spectrophotometer.
The use of spectrophotometers is not limited to studies in physics. They are also commonly used in other scientific fields such as chemistry, biochemistry, and molecular biology.[1]

Design
There are two major classes of spectrophotometers; single beam and double beam. A double beam spectrophotometer measures the ratio of the light intensity on two different light paths, and a single beam spectrophotometer measures the absolute light intensity. Although ratio measurements are easier, and generally more stable, single beam instruments have advantages; for instance, they can have a larger dynamic range, and they can be more compact.
Historically, spectrophotometers use a monochromator to analyze the spectrum, but there are also spectrophotometers that use arrays of photosensors. Especially for infrared spectrophotometers, there are spectrophotometers that use a Fourier transform technique to acquire the spectral information quicker in a technique called Fourier Transform InfraRed.
The spectrophotometer measures quantitatively the fraction of light that passes through a given solution. In a spectrophotometer, a light from the lamp is guided through a monochromator, which picks light of one particular wavelength out of the continuous spectrum. This light passes through the sample that is being measured. After the sample, the intensity of the remaining light is measured with a photodiode or other light sensor, and the transmittance for this wavelength is then calculated.
In short, the sequence of events in a spectrophotometer is as follows:
1. The light source shines through the sample.
2. The sample absorbs light.
3. The detector detects how much light the sample has absorbed.
4. The detector then converts how much light the sample absorbed into a number.
5. The numbers are either plotted straight away, or are transmitted to a computer to be further manipulated (e.g. curve smoothing, baseline correction)
Many spectrophotometers must be calibrated by a procedure known as "zeroing." The absorbency of some standard substance is set as a baseline value, so the absorbencies of all other substances are recorded relative to the initial "zeroed" substance. The spectrophotometer then displays % absorbency (the amount of light absorbed relative to the initial substance).[1]

UV and IR spectrophotometers
The most common spectrophotometers are used in the UV and visible regions of the spectrum, and some of these instruments also operate into the near-infrared region as well.
Visible region 400-700nm spectrophotometry is used extensively in colorimetry science. Ink manufacturers, printing companies, textiles vendors, and many more, need the data provided through colorimetry. They usually take readings every 20 nanometers along the visible region, and produce a spectral reflectance curve. These curves can be used to test a new batch of colorant to check if it makes a match to specifications.
Traditional visual region spectrophotometers cannot detect if a colorant has fluorescence. This can make it impossible to manage color issues if one or more of the printing inks is fluorescent. Where a colorant contains fluorescence, a bi-spectral fluorescent spectrophotometer is used. There are two major setups for visual spectrum spectrophotometers, d/8 (spherical) and 0/45. The names are due to the geometry of the light source, observer and interior of the measurement chamber. Scientists use this machine to measure the amount of compounds in a sample. If the compound is more concentrated more light will be absorbed by the sample; within small ranges, the Beer-Lambert law holds and the absorbance between samples vary with concentration linearly.
Samples are usually prepared in cuvettes; depending on the region of interest, they may be constructed of glass, plastic, or quartz.

IR spectrophotometry
Spectrophotometers designed for the main infrared region are quite different because of the technical requirements of measurement in that region. One major factor is the type of photosensors that are available for different spectral regions, but infrared measurement is also challenging because virtually everything emits IR light as thermal radiation, especially at wavelengths beyond about 5 µm.
Another complication is that quite a few materials such as glass and plastic absorb infrared light, making it incompatible as an optical medium. Ideal optical materials are salts, which do not absorb strongly. Samples for IR spectrophotometry may be smeared between two discs of potassium bromide or ground with potassium bromide and pressed into a pellet. Where aqueous solutions are to be measured, insoluble silver chloride is used to construct the cell.

Spectroradiometers
Spectroradiometers, which operate almost like the visible region spectrophotometers, are designed to measure the spectral density of illuminants in order to evaluate and categorize lighting for sales by the manufacturer, or for the customers to confirm the lamp they decided to purchase is within their specifications. Components:
1. The light source shines onto or through the sample.
2. The sample transmits or reflects light.
3. The detector detects how much light was reflected from or transmitted through the sample.
4. The detector then converts how much light the sample transmitted or reflected into a number.

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Otolaryngology

Otolaryngology is the branch of medicine that specializes in the diagnosis and treatment of ear, nose, throat, and head and neck disorders.

The full name of the specialty is otolaryngology-head and neck surgery. Practitioners are called otolaryngologists-head and neck surgeons, or sometimes otorhinolaryngologists (ORL). A commonly used term for this specialty is ENT (ear, nose and throat). The term comes from the Greek ?t??a?????????a (oto = genitive for ear, laryngo = genitive for larynx/throat, logy = study), and it literally means the study of ear and neck. The full term ?t???????a?????????a (otorhinolaryngology), also includes rhino, which is the genitive of nose.

Explanation
Otolaryngologists are medical doctors (MD, MBBS, MBChB, etc.) or osteopathic doctors (DO) who complete at least five years of surgical residency training. This is composed of one year in general surgical training and four years in otolaryngology - head and neck surgery; in the past it varied between two and three years of each.
Following residency training some otolaryngologists elect to complete advanced subspeciality fellowship training which can range from as little as 2 weekend courses (Allergy)[1] or as long as 1-2 years in duration (pediatric otolaryngology)[2].[citat

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Light Cure

Dental restorative materials are specially fabricated materials, designed for use as dental restorations (fillings),

which are used to restore tooth structure loss, usually resulting from but not limited to dental caries (dental cavities). There are many challenges for the physical properties of the ideal dental restorative material.

Restorative material development
The goal of research and development is to develop the ideal restorative material. The ideal restorative material would be identical to natural tooth structure, in strength adherence and appearance. The properties of an ideal filling material can be divided into four categories: physical properties, biocompatibility, aesthetics and application.

Physical properties
The physical properties include heat insulation, resistance to different categories of forces, and wear, bond strength, and chemical resistance. The material needs to withstand everyday forces and conditions on it without fatiguing.

Biocompatibility
Biocompatibility refers to how well the material coexists with the biological equilibrium of the tooth and body systems. Since fillings are in close contact with mucosa, tooth, and pulp, biocompatibility is very important. Common problems with some of the current dental materials include allergies, chemical leakage from the material, and pulpal irritation. Some of the byproducts of the chemical reactions during different stages of material hardening need to be considered.

Aesthetics
Filling materials ideally would match the surrounding tooth structure in shade translucency and texture.

Application
Dental operators require materials that are easy to manipulate and shape, where the chemistry of any reactions that need to occur are predictable or controllable.

Direct restorative materials
The chemistry of the setting reaction for direct restorative materials is designed to be more biologically compatible. Heat and byproducts generated cannot damage the tooth or patient, since the reaction needs to take place while in contact with the tooth during restoration. This ultimately limits the strength of the materials, since harder materials need more energy to manipulate.

Amalgam
Amalgam fillings, (also called silver fillings) are a mixture of mercury (from 43% to 54%) and powdered alloy made mostly of silver, tin, zinc and copper commonly called the amalgam alloy.[1] Due to the known toxicity of the element mercury, there is some controversy about the use of amalgams. see Amalgam controversy.

History
The Chinese were the first to use a silver amalgam to fill teeth in the 7th century; in 1816, Auguste Taveau developed his own dental amalgam from silver coins and mercury. This amalgam contained a very small amount of mercury and had to be heated in order for the silver to dissolve at an appreciable rate. Taveau's formula offered lower cost and greater ease of use compared to existing materials such as gold, but had many practical problems, including a tendency to significantly expand after setting. Because of these problems, this formula was abandoned in France. In 1833, however, two untrained Europeans, the Crawcour brothers, brought Taveau's amalgam to the United States under the name "Royal Mineral Succedaneum".[2]

Aesthetics
Most of the patients don't like the silvery glossy appearance of dental amalgams to be visible. So dental amalgams are mostly not used for the restoration of incisors or canines. Composites are given preference in such cases.

Gamma 2 phase amalgams
After widespread adoption and wildly varying standards, the multitude of formulas for making amalgams were standardised into the gamma-2-phase amalgam formula in 1895.

The gamma-2-phase amalgams contain approximately equal parts 50% of liquid mercury and 50% of an alloy powder containing:
* > 65% silver (Ag)
* < 29% tin (Sn)
* < 6% copper (Cu)
* < 2% zinc (Zn)
* < 3% mercury (Hg)

The resulting amalgam is composed of the gamma phase (the silver-tin eutectic Ag3Sn, which reacts with mercury, yielding the gamma-1 phase (Ag2Hg3) and gamma-2 phase (Sn7-8Hg). The gamma phase is prone to corrosion and its mechanical strength is low. The alloy tends to undergo crevice corrosion and form local galvanic cells.
Around 1970, the ingredients changed to the new non-gamma-2 form, with lower manufacturing cost, greater mechanical strength, and better corrosion resistance. The reduced-gamma-2 amalgams (sometimes referred to as "high-copper" amalgams) contain approximately equal parts 50% of liquid mercury and 50% of an alloy powder containing:
* > 40% silver (Ag)
* < 32% tin (Sn)
* < 30% copper (Cu)
* < 2% zinc (Zn)
* < 3% mercury (Hg)

The amalgam alloy is strengthened by presence of Ag-Cu particles. The gamma-2 phase reacts with the Ag-Cu particles to form eta phase Cu6Sn5 and gamma-1 phase.
The possible difference in toxicology between the two has not been studied conclusively. Amalgams continue to be used today because they are hard, durable and inexpensive.

Galvanic shock
When aluminium foil makes contact with some amalgam fillings, saliva in the mouth can act as an electrolyte. This can generate small electrical currents which are felt through the nerves in the tooth as (often extremely painful) electrical "jolts" or shocks.

Composite resin (also called white or plastic filling)
Composite resin fillings (also called white fillings) are a mixture of powdered glass and plastic resin, and can be made to resemble the appearance of the natural tooth. They are strong, durable and cosmetically superior to silver or dark grey colored amalgam fillings. Composite resin fillings are usually more expensive than silver amalgam fillings. Bis-GMA based materials contain Bisphenol A, a known endocrine disrupter chemical, and may contribute to the development of breast cancer. PEX-based materials do not.
Most modern composite resins are light-cured photopolymers. Once the composite hardens completely, the filling can then be polished to achieve maximum aesthetic results. Composite resins experience a very small amount of shrinkage upon curing, causing the material to pull away from the walls of the cavity preparation. This makes the tooth slightly more vulnerable to microleakage and recurrent decay. With proper technique and material selection, microleakage can be minimized or eliminated altogether.
Besides the aesthetic advantage of composite fillings over amalgam fillings, the preparation of composite fillings requires less removal of tooth structure to achieve adequate strength. This is because composite resins bind to enamel (and dentin too, although not as well) via a micromechanical bond. As conservation of tooth structure is a key ingredient in tooth preservation, many dentists prefer placing composite instead of amalgam fillings whenever possible.
Generally, composite fillings are used to fill a carious lesion involving highly visible areas (such as the central incisors or any other teeth that can be seen when smiling) or when conservation of tooth structure is a top priority.
Composite resin fillings require a clean and dry surface to bond correctly with the tooth, so cavities in areas that are harder to keep totally dry during the filling procedure may require a less moisture-sensitive filling. The use of a rubber dam is highly recommended.

Glass Ionomer Cement
See main article Glass ionomer cement
These fillings are a mixture of glass and an organic acid. Although they are tooth-colored, glass ionomers vary in translucency. Although glass ionomers can be used to achieve an aesthetic result, their aesthetic potential does not measure up to that provided by composite resins.
The cavity preparation of a glass ionomer filling is the same as a composite resin; it is considered a fairly conservative procedure as the bare minimum of tooth structure should be removed.
Conventional glass ionomers are chemically set via an acid-base reaction. Upon mixing of the material components, there is no light cure needed to harden the material once placed in the cavity preparation. After the initial set, glass ionomers still need time to fully set and harden.
Glass ionomers do have their advantages over composite resins:
1. They are not subject to shrinkage and microleakage, as the bonding mechanism is an acid-base reaction and not a polymerization reaction.
2. Glass ionomers contain and release fluoride, which is important to preventing carious lesions. Furthermore, as glass ionomers release their fluoride, they can be "recharged" by the use of fluoride-containing toothpaste. Hence, they can be used as a treatment modality for patients who are at high risk for caries. Newer formulations of glass ionomers that contain light-cured resins can achieve a greater aesthetic result, but do not release fluoride as well as conventional glass ionomers.
Glass ionomers are about as expensive as composite resin. The fillings do not wear as well as composite resin fillings. Still, they are generally considered good materials to use for root caries and for sealants.

Resin modified Glass-Ionomer Cement (Compomer)
A combination of glass-ionomer and composite resin, these fillings are a mixture of glass, an organic acid, and resin polymer that harden when light cured. (The light activates a catalyst in the cement that causes it to cure in seconds.) The cost is similar to composite resin. It holds up better than glass ionomer, but not as well as composite resin, and is not recommended for biting surfaces of adult teeth.
In general, resin modified glass-ionomer cements can achieve a better aesthetic result than conventional glass ionomers, but not as good as pure composites.

Indirect Restorative materials

Porcelain (ceramic)
Porcelain fillings are hard, but can cause wear on opposing teeth. They are brittle and are not always recommended for molar fillings.

Gold
Gold fillings have excellent durability, wear well, and do not cause excessive wear to the opposing teeth, but they do conduct heat and cold, which can be irritating. There are two categories of gold fillings, cast gold fillings (gold inlays and onlays) made with 14 or 18 kt gold, and gold foil made with pure 24 kt gold that is burnished layer by layer. For years, they have been considered the benchmark of restorative dental materials. Recent advances in dental porcelains and consumer focus on aesthetic results have caused demand for gold fillings to drop in favor of advanced composites and porcelain veneers and crowns. Gold fillings are usually quite expensive, although they do last a very long time. It is not uncommon for a gold crown to last 30 years in a patient's mouth.

Other historical fillings
Lead fillings were used in the 1700s, but became unpopular in the 1800s because of their softness. This was before lead poisoning was understood.
According to American Civil War-era dental handbooks from the mid-1800s, since the early 1800s metallic fillings had been used, made of lead, gold, tin, platinum, silver, aluminum, or amalgam. A pellet was rolled slightly larger than the cavity, condensed into place with instruments, then shaped and polished in the patient's mouth. The filling was usually left "high", with final condensation — "tamping down" — occurring while the patient chewed food. Gold foil was the most popular and preferred filling material during the Civil War. Tin and amalgam were also popular due to lower cost, but were held in lower regard.
One survey of dental practices in the mid-1800s catalogued dental fillings found in the remains of seven Confederate soldiers from the U.S. Civil War; they were made of:
* Gold foil: Preferred because of its durability and safety.
* Platinum: Was rarely used because it was too hard, inflexible and difficult to form into foil.
* Aluminum: A material which failed because of its lack of malleability but has been added to some amalgams.
* Tin and iron: Believed to have been a very popular filling material during the Civil War. Tin foil was recommended when a cheaper material than gold was requested by the patient, however tin wore down rapidly and even if it could be replaced cheaply and quickly, there was a concern, specifically from Harris, that it would oxidise in the mouth and thus cause a recurrence of caries. Due to the blackening, tin was only recommended for posterior teeth.
* Thorium: Radioactivity was unknown at that time, and the dentist probably thought he was working with tin.
* Lead and tungsten mixture, probably coming from shotgun pellets. Lead was rarely used in the 19th century, it is soft and quickly worn down by mastication, and had known harmful health effects.
* Amalgam: The most popular amalgam was a mixture of silver, tin and mercury. According to the authors of the article " It set very hard and lasted for many years, the major contradiction being that it oxidized in the mouth, turning teeth black. Also the mercury contained in the amalgam was thought at that time to be harmful." as explained in the pre-eminent dental textbook of that century, The Principles and Practice of Dental Surgery by Chapin A. Harris A.M., M.D., D.D.S..[3]

Replacement fillings
Fillings have a finite lifespan: an average of 12.8 years for amalgam and 7.8 years for composite resins.[4] Fillings fail because of changes in the filling, tooth or the bond between them.
Amalgam fillings expand with age, possibly cracking the tooth and requiring repair and filling replacement. Composite fillings shrink with age and may pull away from the tooth allowing leakage. As chewing applies considerable pressure on the tooth, the filling may crack, allowing seepage and eventual decay in the tooth underneath.
The tooth itself may be weakened by the filling and crack under the pressure of chewing. That will require further repairs to the tooth and replacement of the filling.
If fillings leak or if the original bond is inadequate, the bond may fail even if the filling and tooth are otherwise unchanged.

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Infra Red Lamp

An infrared heater is a body with a higher temperature which transfers energy to a body with a lower temperature through electromagnetic radiation.

Depending on the temperature of the emitting body, the wavelength of the infrared radiation ranges from 780 nm to 1 mm. The relationship between temperature and wavelength is expressed by the Stefan-Boltzmann Law. No contact or medium between the two bodies is needed for the energy transfer. A rough classification of infrared heaters is connected to wavelength bands of major emission of the energy: short wave or near infrared for the range from 780 nm to 1400 nm, these emitters are also named bright because still some visible light with glare is emitted; medium infrared for the range between 1400 nm and 3000 nm; far infrared or dark emitters for everything above 3000 nm.

Elements of infrared heaters
For practical purposes, most infrared heaters are constructed by either using the emission of a flame (usually soot or a heated matrix) or an electrically heated filament as the emitting body. If an electrically operated infrared heater (infrared lamp) is used, the filament is usually protected by a heat-resistant quartz glass tube. Depending on the filament temperature, a filling of the quartz tube with inert gas (e.g. halogen) may be required to prevent filament degradation. These emitters use the same materials and principle as a light bulb.

The most common filament material used for electrical infrared heaters is tungsten wire, which is coiled to provide more surface area. Low temperature alternatives for tungsten are carbon , or alloys of iron, chromium and aluminium (brand name ‘kanthal’). While carbon filaments are more fickle to produce, they heat up much quicker than a comparable medium-wave heater based on a FeCrAl filament.

Industrial infrared heaters sometimes use a gold coating on the quartz tube that reflects the infrared radiation and directs it towards the product to be heated. Consequently the infrared radiation impinging on the product is virtually doubled. Gold is used because of its oxidation resistance and very high IR reflectivity of approximately 95 %

Types of infrared heaters
Infrared heaters are commonly used in infrared modules (or emitter banks) combining several heaters to achieve larger heated areas.
Infrared heaters are usually classified by the wavelength they emit. Near infrared (NIR) or short-wave infrared heaters operate at high filament temperatures above 1800 °C and when arranged in a field reach high power densities of some 100s of kW/m². Their peak wavelength is well below the absorption spectrum for water, making them unsuitable for many drying applications. They are well suited for heating of silica where a deep penetration is needed.

Medium-wave and carbon (CIR) infrared heaters operate at filament temperatures of around 1000 °C. They reach maximum power densities of up to 60 kW/m² (medium-wave) and 150 kW/m² (CIR).

Efficiency of infrared heaters

Theoretically, the efficiency of an infrared heater is 100% as it converts nearly all electrical energy into heat in the filament. The filament then emits its heat by infrared radiation that is directly or via a reflector impinging on the product to be heated. Some energy is lost due to conduction or convection.

For practical applications, the efficiency of the infrared heater depends on matching the emitted wavelength and the absorption spectrum of the material to be heated.

For example, the absorption spectrum for water has its peak at around 3000 nm. This means that emission from medium-wave or carbon infrared heaters are much better absorbed by water and water-based coatings than NIR or short-wave infrared radiation.

The same is true for many plastics like PVC or polyethylene. Their peak absorption is around 3500 nm. On the other hand, some metals absorb only in the short-wave range and show a strong reflectivity in the medium and far infrared. This makes a careful selection of the right infrared heater type important for energy efficiency in the heating process.

Applications of infrared heaters

IR heaters are used in industrial manufacturing processes including curing of coatings; heating of plastic prior to forming; plastic welding; processing glass; cooking and browning food. They are used when high temperatures are required, fast responses or temperature gradients are needed or products need to be heated in certain areas in a targeted way. Their application is difficult for objects with undercuts.

They are also used to provide warmth to suckling animals whose mother cannot or will not provide them with natural warmth as well as to captive animals in zoos or veterinary clinics, especially for lizards and other reptiles, and tropical animals such as birds.

IR heaters are used in low-temperature infrared saunas.

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Diathermy

Dielectric heating (also known as electronic heating, RF heating, high-frequency heating) is

the phenomenon in which radiowave or microwave electromagnetic radiation heats a dielectric material, especially as caused by dipole rotation.

Mechanisms
There are two principal mechanisms by which a non-conductive material can be warmed in an EM field:
1. Electrical conduction: current flow in the material induced by the oscillating electric field generates heat by ohmic losses in the material.
2. Dipole rotation: Molecular rotation occurs in materials containing polar molecules having an electrical dipole moment, which will align themselves in the field by rotating; as the field alternates, the molecules reverse direction and accelerate the motion of individual molecules or atoms. Heat is a form of energy possessed by a substance by virtue of the vibrational movement, i.e. kinetic energy, of its molecules or atoms.
Dipole rotation is the mechanism normally referred to as dielectric heating, and is most widely observable in the microwave oven where it operates most efficiently on liquid water, and much less so on fats, sugars, and frozen water. This is caused by fats and sugars being far less polar than water molecules, and are thus less affected by the forces generated by the alternating electromagnetic fields. Meanwhile, frozen water molecules are fixed in place in a crystal lattice, and cannot freely rotate and absorb heat from molecular friction. Outside of cooking, the effect can be used to heat solids, liquids, or gases (see states of matter).
Communication microwave frequencies penetrate semi-solid substances like meat, and living tissue to a distance proportional to its power density. Some environmentalists are concerned that the widespread adoption of microwave-emitting mobile phones could harm human and animal health through dielectric heating.

Dielectric heating power
For dielectric heating the generated power density per volume is calculated by
p = \omega \cdot \varepsilon_r'' \cdot \varepsilon_0 \cdot E^2,
where ? is the angular frequency, er'' is the imaginary part of the complex relative permittivity, e0 is the permittivity of free space and E the electric field strength. The imaginary part of the complex relative permittivity is a measure for the ability of dielectric material to convert radio frequency electromagnetic field energy into heat.

Surgical uses
Main article: Electrosurgery
Surgical diathermy is usually better known as electrosurgery, and is also referred to occasionally as electrocautery. Electrosurgery involves the use of high frequency alternating current in surgery as either a cutting modality, or else to cauterize small blood vessels to stop bleeding. This technique induces localized tissue burning and damage, the zone of which is controlled by the frequency and power of the device.[1]

Heating uses
In the natural sciences, the term diathermy means "electrically induced heat" and is commonly used for muscle relaxation. It is also a method of heating tissue electromagnetically or ultrasonically for therapeutic purposes in medicine. [2]
Ultrasonic diathermy refers to heating of tissues by ultrasound for the purpose of therapeutic deep heating. No tissue is ordinarily damaged hence it is generally used in biomedical applications. [3][4]
Electric diathermy uses high frequency alternating electric or magnetic fields, sometimes with no electrode or device contact to the skin, to induce gentle deep tissue heating by induction or dipole rotation. No tissue is ordinarily damaged. [3][5]

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Dental X-ray

Dental X-rays are pictures of the teeth, bones, and surrounding soft tissues to screen for and help identify problems with the teeth, mouth, and jaw.

X-ray pictures can show cavities, hidden dental structures (such as wisdom teeth), and bone loss that cannot be seen during a visual examination. Dental X-rays may also be done as follow-up after dental treatments.
A radiographic image is formed by a controlled burst of X-ray radiation which penetrates oral structures at different levels, depending on varying anatomical densities, before striking the film or sensor. Teeth appear lighter because less radiation penetrates them to reach the film. Dental caries, tooth decay, infections and other changes in the bone density, and the periodontal ligament, appear darker because X-rays readily penetrate these less dense structures. Dental restorations (fillings, crowns) may appear lighter or darker, depending on the density of the material.
The dosage of X-ray radiation received by a dental patient is typically small, equivalent to a few days' worth of background radiation environmental radiation exposure, or similar to the dose received during a cross-country airplane flight. Incidental exposure is further reduced by the use of a lead shield, lead apron, sometimes with a lead thyroid collar. Technician exposure is reduced by stepping out of the room, or behind adequate shielding material, when the X-ray source is activated.
Once photographic film has been exposed to X-ray radiation, it needs to be developed, traditionally using a process where the film is exposed to a series of chemicals in a dark room, as the films are sensitive to normal light. This can be a time-consuming process, and incorrect exposures or mistakes in the development process can necessitate retakes, exposing the patient to additional radiation. Digital x-rays, which replace the film with an electronic sensor, address some of these issues, and are becoming widely used in dentistry as the technology evolves. They may require less radiation and are processed much quicker than conventional radiographic films, often instantly viewable on a computer. However digital sensors are extremely costly and have historically had poor resolution, though this is much improved in modern sensors.
This preoperative photo of tooth #3, (A), reveals no clinically apparent decay other than a small spot within the central fossa. In fact, decay could not be detected with an explorer. Radiographic evaluation, (B), however, revealed an extensive region of demineralization within the dentin (arrows) of the mesial half of the tooth. When a bur was used to remove the occlusal enamel overlying the decay, (C), a large hollow was found within the crown and it was discovered that a hole in the side of the tooth large enough to allow the tip of the explorer to pass was contiguous with this hollow. After all of the decay had been removed, (D), the pulp chamber had been exposed and most of the mesial half of the crown was either missing or poorly supported.
It is possible for both tooth decay and periodontal disease to be missed during a clinical exam, and radiographic evaluation of the dental and periodontal tissues is a critical segment of the comprehensive oral examination. The photographic montage at right depicts a situation in which extensive decay had been overlooked by a number of dentists prior to radiographic evaluation of the area.

Intraoral radiographic views
Placing the radiographic film or sensor inside the mouth produces an intraoral radiographic view.

Periapical view
The periapical view is taken of both anterior and posterior teeth. The objective of this type of view is to capture the tip of the root on the film. This is often helpful in determining the cause of pain in a specific tooth, because it allows a dentist to visualize the tooth as well as the surrounding bone in their entirety. This view is often used to determine the need for endodontic therapy as well as to visualize the successful progression of endodontic therapy once it is initiated.
The name periapical is derived from the Latin peri, which means "around," and apical, which means "tip."

Bitewing view
The bitewing view is taken to visualize the crowns of the posterior teeth and the height of the alveolar bone in relation to the cementoenamel junctions, which are the demarcation lines on the teeth which separate tooth crown from tooth root. When there is extensive bone loss, the films may be situated with their longer dimension in the vertical axis so as to better visualize their levels in relation to the teeth. Because bitewing views are taken from a more or less perpendicular angle to the buccal surface of the teeth, they more accurately exhibit the bone levels than do periapical views. Bitewings of the anterior teeth are not taken.
The name bitewing refers to a little tab of paper or plastic situated in the center of the X-ray film, which when bitten on, allows the film to hover so that it captures an even amount of maxillary and mandibular information.

Occlusal view
The occlusal view is not taken very often -- it is indicated when there is a desire to reveal the skeletal or pathologic anatomy of either the floor of the mouth or the palate. The occlusal film, which is about three to four times the size of the film used to take a periapical or bitewing, is inserted into the mouth so as to entirely separate the maxillary and mandibular teeth, and the film is exposed either from under the chin or angled down from the top of the nose. Sometimes, it is placed in the inside of the cheek to confirm the presence of a sialolith in Stenson's duct, which carries saliva from the parotid gland. The occlusal view is not included in the standard full mouth series.

Full mouth series
A full mouth series is a complete set of intraoral X-rays taken of a patients' teeth and adjacent hard tissue.[1] This is often abbreviated as either FMS or FMX. The full mouth series is composed of 18 films:
* four bitewings
o two molar bitewings (left and right)
o two premolar bitewings (left and right)
* eight posterior periapicals
o two maxillary molar periapicals (left and right)
o two maxillary premolar periapicals (left and right)
o two mandibular molar periapicals (left and right)
o two mandibular premolar periapicals (left and right)
* six anterior periapicals
o two maxillary canine-lateral incisor periapicals (left and right)
o two mandibular canine-lateral incisor periapicals (left and right)
o two central incisor periapicals (maxillary and mandibular)

The Faculty of General Dental Practice of the Royal College of Surgeons of England publication Selection Criteria in Dental Radiography holds that given current evidence full mouth series are to be discouraged due to the large numbers of radiographs involved, many of which will not be necessary for the patients treament. An alternative approach using bitewing screening with selected periapical views is suggested as a method of minimising radiation dose to the patient while maximizing diagnostic yield.

Extraoral radiographic views
Placing the radiographic film or sensor outside the mouth, on the opposite side of the head from the X-ray source, produces an extra-oral radiographic view.
A lateral cephalogram is used to evaluate dentofacial proportions and clarify the anatomic basis for a malocclusion, and an antero-posterior radiograph provides a face-forward view.

Panoramic films
A panoramic film, able to show a greater field of view, including the heads and necks of the mandibular condyles, the coronoid processes of the mandible, as well as the nasal antrum and the maxillary sinuses.
Panoramic films are extraoral films, in which the film is exposed while outside the patients' mouth, and they were developed by the United States Army as a quick way to get an overall view of a soldiers' oral health. Exposing eighteen films per soldier was very time consuming, and it was felt that a single panoramic film could speed up the process of examining and assessing the dental health of the soldiers; soldiers with toothaches are not very effective. It was later discovered that while panoramic films can prove very useful in detecting and localizing mandibular fractures and other pathologic entities of the mandible, they were not very good at assessing periodontal bone loss or tooth decay.[2]

Computed Tomography
There is increasing use of CT (computed tomography) scans in dentistry, particularly to plan dental implants; there may be significant levels of radiation and potential risk. Specially designed CBCT (cone beam CT) scanners can be used instead, which produce adequate imaging with a tenfold reduction in radiation.(Dr. Bernard Friedland, Harvard School of Dental Medicine, 1dec07)

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Centrifuge

A centrifuge is a piece of equipment, generally driven by a motor, that puts an object in rotation around a fixed axis, applying a force perpendicular to the axis. The centrifuge works using the sedimentation principle,

where the centripetal acceleration is used to evenly distribute substances (usually present in a solution for small scale applications) of greater and lesser density. There are many different kinds of centrifuges, including those for very specialised purposes. It can be used for viable counts, when shaking the culture e.g. yeast, out of suspension.

Theory
Protocols for centrifugation typically specify the amount of acceleration to be applied to the sample, rather than specifying a rotational speed such as revolutions per minute. The acceleration is often quoted in multiples of g, the standard acceleration due to gravity at the Earth's surface. This distinction is important because two rotors with different diameters running at the same rotational speed will subject samples to different accelerations.
The acceleration can be calculated as the product of the radius and the square of the angular velocity.

History and predecessors
A 19th century hand cranked laboratory centrifuge.
English military engineer Benjamin Robins (1707-1751) invented a whirling arm apparatus to determine drag. In 1864, Antonin Prandtl invented the first dairy centrifuge in order to separate cream from milk. And in 1879, Gustaf de Laval demonstrated the first continuous centrifugal separator, making its commercial application feasible.

Types
There are at least five types of centrifuge:

* Tabletop/clinical/desktop centrifuge or microcentrifuge
* High-speed centrifuge
* Cooling centrifuge
* Ultracentrifuge
* Geotechnical centrifuge

Industrial centrifuges may otherwise be classified according to the type of separation of the high density fraction from the low density one :
* Screen centrifuges, where the centrifugal acceleration allows the liquid to pass through a screen of some sort, through which the solids cannot go (due to granulometry larger than the screen gap or due to agglomeration). Common types are :
o Pusher centrifuges
o Peeler centrifuges
* Decanter centrifuges, in which there is no physical separation between the solid and liquid phase, rather an accelerated settling due to centrifugal acceleration. Common types are :
o Solid bowl centrifuges
o Conical plate centrifuges

Uses
Isolating suspensions
Simple centrifuges are used in chemistry, biology, and biochemistry for isolating and separating suspensions. They vary widely in speed and capacity. They usually comprise a rotor containing two, four, six, or many more numbered wells within which the samples containing centrifuge tips may be placed.

Isotope separation
Other centrifuges, the first being the Zippe-type centrifuge, separate isotopes, and these kinds of centrifuges are in use in nuclear power and nuclear weapon programs.
Gas centrifuges are used in uranium enrichment. The heavier isotope of uranium (uranium-238) in the uranium hexafluoride gas tend to concentrate at the walls of the centrifuge as it spins, while the desired uranium-235 isotope is extracted and concentrated with a scoop selectively placed inside the centrifuge. It takes many thousands of centrifuges to enrich uranium enough for use in a nuclear reactor (around 3.5% enrichment), and many thousands more to enrich it to weapons-grade (around 90% enrichment) for use in nuclear weapons.
The 20 G centrifuge at the NASA Ames Research Center

Aeronautics and astronautics
Human centrifuges are exceptionally large centrifuges that test the reactions and tolerance of pilots and astronauts to acceleration above those experienced in the Earth's gravity.
The US Air Force at Holloman Air Force Base, NM operates a human centrifuge. The centrifuge at Holloman AFB is operated by the aerospace physiology department for the purpose of training and evaluating prospective fighter pilots for high-g flight in Air Force fighter aircraft. It is important to note that the centrifuge at Holloman AFB is unrealistic in that it is far more difficult for a pilot to tolerate the high-g environment in the centrifuge than in a real fighter aircraft. This well-known fact is based on countless accounts from experienced operational fighter pilots.[citation needed]
The use of large centrifuges to simulate a feeling of gravity has been proposed for future long-duration space missions. Exposure to this simulated gravity would prevent or reduce the bone decalcification and muscle atrophy that affect individuals exposed to long periods of freefall. An example of this can be seen in the film 2001: A Space Odyssey.

Earthquake and blast simulation
The geotechnical centrifuge is used for simulating blasts and earthquake phenomena.[1] For a discussion of their design, see Geotechnical Centrifuges by Philip Turner.

Commercial applications
* Standalone centrifuges for drying (hand-washed) clothes - usually with a water outlet.
* Centrifuges are used in the attraction Mission: SPACE, located at Epcot in Walt Disney World, which propels riders using a combination of a centrifuge and a motion simulator to simulate the feeling of going into space.
* In soil mechanics, centrifuges utilize centrifugal acceleration to match soil stresses in a scale model to those found in reality.
* Large industrial centrifuges are commonly used in water and wastewater treatment to dry sludges. The resulting dry product is often termed cake, and the water leaving a centrifuge after most of the solids have been removed is called centrate.
* Large industrial centrifuges are also used in the oil industry to remove solids from the drilling fluid.
* Disc-stack centrifuges used by some companies in Oil Sands industry to separate small amounts of water and solids from bitumen before it's sent to Upgrading.

Calculating relative centrifugal force (RCF)
Relative centrifugal force is the measurement of the force applied to a sample within a centrifuge. This can be calculated from the speed (RPM) and the rotational radius (cm) using the following calculation.

g = RCF = 0.00001118\,r \, N^2 \,

where
g = Relative centrifuge force
r = rotational radius (centimetres, cm)
N = rotating speed (revolutions per minute, r/min)

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Audiometry

Audiometry is the testing of hearing ability. Typically, audiometric tests determine a subject's hearing levels with the help of an audiometer,

but may also measure ability to discriminate between different sound intensities, recognize pitch, or distinguish speech from background noise. Acoustic reflex and otoacoustic emissions may also be measured. Results of audiometric tests are used to diagnose hearing loss or diseases of the ear, and often make use of an Audiogram.
Type A. Subjective audiometry 1. Pure tone audiometry 2. Speech audiometry B. Objective audiometry 1. Electronic response audiometry.

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Audiometer

An audiometer is a machine used for evaluating hearing loss. The invention of this machine is generally credited to Dr.


Harvey Fletcher of Brigham Young University. Audiometers are standard equipment at ENT clinics and in audiology centers. They usually consist of an embedded hardware unit connected to a pair of headphones and a feedback button, sometimes controlled by a standard PC. Audiometer requirements are specified in IEC 60645, ISO 8253, and ANSI S3.6 standards.
An alternative to hardware audiometers are software audiometers, which are available in many different configurations.
Screening PC-based audiometer These use a standard computer and can be run by anybody in their home to test their hearing, although their accuracy is not as high due to lack of a standard for calibration. Some of these audiometers are even available on a handheld Windows driven device.
Clinical PC-based audiometer These are generally more expensive than hardware audiometers, but are much more accurate and efficient. They are most commonly used in hospitals, upper-class audiology centers and research communities. Because these audiometers can be calibrated to 1/10 of a dB, calibration is more accurate than hardware audiometers. Some audiometers even provide you with a software developer's kit that provides researchers with the capability to create their own diagnostic tests.

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Friday, November 07, 2008

Vehicle Insurance

Vehicle insurance (also known as auto insurance, car insurance, or motor insurance) is insurance purchased for cars, trucks, and other vehicles.

Its primary use is to provide protection against losses incurred as a result of traffic accidents and against liability that could be incurred in an accident.

Public policy

In many jurisdictions it is compulsory to have vehicle insurance before using or keeping a motor vehicle on public roads. Most jurisdictions relate insurance to both the car and the driver, however the degree of each varies greatly.

A 1994 study by Jeremy Jackson and Roger Blackman[1] showed, consistent with the risk homeostasis theory, that increased accident costs caused large and significant reductions in accident frequencies.

Australia

In South Australia, Third Party Personal insurance from the State Government Insurance Corporation (SGIC) is included in the licence registration fee for people over 16. A similar scheme applies in Western Australia.

In Victoria, Third Party Personal insurance from the Transport Accident Commission is similarly included, through a levy, in the vehicle registration fee.

In New South Wales, Compulsory Third Party Insurance (commonly known as CTP Insurance) is a mandatory requirement and each individual car must be insured or the vehicle will not be considered legal. Therefore, a motorist cannot drive the vehicle until it is insured. A 'Green Slip,' another name CTP Insurance is commonly known by due to the colour of the pages the form is printed on, must be obtained through one of the seven main insurers in New South Wales.



Canada

Several Canadian provinces (British Columbia, Saskatchewan, Manitoba and Quebec) provide a public auto insurance system while in the rest of the country insurance is provided privately. Basic auto insurance is mandatory throughout Canada with each province's government determining which benefits are included as minimum required auto insurance coverage and which benefits are options available for those seeking additional coverage. Accident benefits coverage is mandatory everywhere except for Newfoundland and Labrador. All provinces in Canada have some form of no-fault insurance available to accident victims. The difference from province to province is the extent to which tort or no-fault is emphasized.[2] Typically, coverage against loss of or damage to the driver's own vehicle is optional - one notable exception to this is in Saskatchewan, where SGI provides collision coverage (less than a $700 deductible, such as a collision damage waiver) as part of its basic insurance policy. In Saskatchewan, residents have the option to have their auto insurance through a tort system but less than 0.5% of the population have taken this option.[2]



Ireland

The Road Traffic Act, 1933 requires all drivers of mechanically propelled vehicles in public places to have at least third-party insurance, or to have obtained exemption - generally by depositing a (large) sum of money with the High Court as a guarantee against claims. In 1933 this figure was set at £15,000. The Road Traffic Act, 1961 [1] (which is currently in force) repealed the 1933 act but replaced these sections with functionally identical sections.

From 1968, those making deposits require the consent of the Minister for Transport to do so, with the sum specified by the Minister.

Those not exempted from obtaining insurance must obtain a certificate of insurance from their insurance provider, and display a portion of this (an insurance disc) on their vehicles windscreen (if fitted). The certificate in full must be presented to a police station within ten days if requested by an officer. Proof of having insurance or an exemption must also be provided to pay for your motor tax.

Those injured or suffering property damage/loss due to uninsured drivers can claim against the Motor Insurance Bureau of Ireland's uninsured drivers fund, as can those injured (but not those suffering damage or loss) from hit and run offences.



South Africa

South Africa allocates a percentage of the money from petrol into the Road Accidents Fund, which goes towards compensating third parties in accidents.[3]



[United Kingdom

In 1930, the UK government introduced a law that required every person who used a vehicle on the road to have at least third party personal injury insurance. Today UK law is defined by The Road Traffic Act 1988, which was last modified in 1991. The act requires that motorists either be insured, have a security, or have made a specified deposit (£500,000 as of 1991) with the Accountant General of the Supreme Court, against their liability for injuries to others (including passengers) and for damage to other persons' property resulting from use of a vehicle on a public road or in other public places.

The minimum level of insurance cover commonly available and which satisfies the requirement of the act is called third party only insurance. The level of cover provided by Third party only insurance is basic but does exceed the requirements of the act.

Road Traffic Act Only Insurance is not the same as Third Party Only Insurance and is not often sold. It provides the very minimum cover to satisfy the requirements of the act. For example Road Traffic Act Only Insurance has a limit of £250,000 for damage to third party property and does not cover emergency treatment fees. Third party insurance has a far greater limit for third party property damage and will cover emergency treatment fees.

It is an offence to drive a car, or allow others to drive it, without at least third party insurance whilst on the public highway (or public place Section 143(1)(a) RTA 1988 as amended 1991); however, no such legislation applies on private land.

Vehicles which are exempted by the act, from the requirement to be covered, include those owned by certain councils and local authorities, national park authorities, education authorities, police authorities, fire authorities, heath service bodies and security services.

The insurance certificate or cover note issued by the insurance company constitutes legal evidence that the vehicle specified on the document is insured. The law says that an authorised person, such as the police, may require a driver to produce an insurance certificate for inspection. If the driver cannot show the document immediately on request, then the driver will usually be issued a HORT/1 with seven days, as of midnight of the date of issue, to take a valid insurance certificate (and usually other driving documents as well) to a police station of the driver's choice. Failure to produce an insurance certificate is an offence.

Insurance is more expensive in Northern Ireland than in other parts of the UK.[vague][citation needed]

Most motorists in the UK are required to prominently display a vehicle licence (tax disc) on their vehicle when it is kept or driven on public roads. This helps to ensure that most people have adequate insurance on their vehicles because you are required to produce an insurance certificate when you purchase the disc.

The Motor Insurers Bureau compensates the victims of road accidents caused by uninsured and untraced motorists. It also operates the Motor Insurance Database, which contains details of every insured vehicle in the country.



United States

In the United States, auto insurance covering liability for injuries and property damage done to others is compulsory in most states, though enforcement of the requirement varies from state to state. The state of New Hampshire, for example, does not require motorists to carry liability insurance (the ballpark model), while in Virginia residents must pay the state a $500 annual fee per vehicle if they choose not to buy liability insurance.[4] Penalties for not purchasing auto insurance vary by state, but often involve a substantial fine, license and/or registration suspension or revocation, as well as possible jail time in some states. Usually, the minimum required by law is third party insurance to protect third parties against the financial consequences of loss, damage or injury caused by a vehicle.

Some states, such as North Carolina, require that a driver hold liability insurance before a license can be issued.

Arizona Department of Transportation Research Project Manager John Semmens has recommended that car insurers issue license plates, and that they be held responsible for the full cost of injuries and property damages caused by their licensees under the Disneyland model. Plates would expire at the end of the insurance coverage period, and licensees would need to return their plates to their insurance office in order to receive a refund on their premiums. Vehicles driving without insurance would thus be easy to spot because they would not have license plates, or the plates would be past the marked expiration date.[5]



Coverage levels

Vehicle insurance can cover some or all of the following items:

* The insured party
* The insured vehicle
* Third parties (car and people)
* In some States coverage for injuries to persons riding in the insured vehicle is available without regard to fault in the auto accident (No Fault Auto Insurance)

Different policies specify the circumstances under which each item is covered. For example, a vehicle can be insured against theft, fire damage, or accident damage independently.



Excess

An excess payment, also known as a deductible, is the fixed contribution you must pay each time your car is repaired through your car insurance policy. Normally the payment is made directly to the accident repair "garage" (The term "garage" refers to an establishment where vehicles are serviced and repaired) when you collect the car. If one's car is declared to be a "write off" or "total loss"("write off" is commonly used in motor insurance to describe a vehicle the worth of which is less than the cost of repair), the insurance company will deduct the excess agreed on the policy from the settlement payment it makes to you.

If the accident was the other driver's fault, and this is accepted by the third party's insurer, you'll be able to reclaim your excess payment from the other person's insurance company.



Compulsory excess

A compulsory excess is the minimum excess payment your insurer will accept on your insurance policy. Minimum excesses vary according to your personal details, driving record and insurance company.



Voluntary excess

In order to reduce your insurance premium, you may offer to pay a higher excess than the compulsory excess demanded by your insurance company. Your voluntary excess is the extra amount over and above the compulsory excess that you agree to pay in the event of a claim on the policy. As a bigger excess reduces the financial risk carried by your insurer, your insurer is able to offer you a significantly lower premium.



Basis of premium charges

Main article: auto insurance risk selection

Depending on the jurisdiction, the insurance premium can be either mandated by the government or determined by the insurance company in accordance to a framework of regulations set by the government. Often, the insurer will have more freedom to set the price on physical damage coverages than on mandatory liability coverages.

When the premium is not mandated by the government, it is usually derived from the calculations of an actuary based on statistical data. The premium can vary depending on many factors that are believed to have an impact on the expected cost of future claims.[6] Those factors can include the car characteristics, the coverage selected (deductible, limit, covered perils), the profile of the driver (age, gender, driving history) and the usage of the car (commute to work or not, predicted annual distance driven).[7][8]



Gender

Men average more miles driven per year than women do, and have a proportionally higher accident involvement at all ages. Insurance companies cite women's lower accident involvement in keeping the youth surcharge lower for young women drivers than for their male counterparts, but adult rates are generally unisex. Reference to the lower rate for young women as "the women's discount" has caused confusion that was evident in news reports on a recently defeated EC proposal to make it illegal to consider gender in assessing insurance premiums.[9] Ending the discount would have made no difference to most women's premiums.



Age

Teenage drivers who have no driving record will have higher car insurance premiums. However, young drivers are often offered discounts if they undertake further driver training on recognised courses, such as the Pass Plus scheme in the UK. In the U.S. many insurers offer a good grade discount to students with a good academic record and resident student discounts to those who live away from home. Generally insurance premiums tend to become lower at the age of 25. Senior drivers are often eligible for retirement discounts reflecting lower average miles driven by this age group.



Marital Status

Drivers who are unmarried are often charged higher insurance premiums as opposed to married drivers.



Vehicle Classification

Owners of sports cars, muscle cars, some sport utility vehicles, and motorcycles would have higher insurance premiums as opposed to compact cars or luxury cars. However, in the case of motorcycles, the chance of causing extensive damage to other vehicles is relatively low (as opposed to damage to oneself) and thus liability insurance premiums are often lower.



Distance

Some car insurance plans do not differentiate in regard to how much the car is used. However, methods of differentiation would include:



Reasonable estimation

Several car insurance plans rely on a reasonable estimation of the average annual distance expected to be driven which is provided by the insured. This discount benefits drivers who drive their cars infrequently but has no actuarial value since it is unverified.



Odometer-based systems

Cents Per Mile Now[10](1986) advocates classified odometer-mile rates. After the company's risk factors have been applied and the customer has accepted the per-mile rate offered, customers buy prepaid miles of insurance protection as needed, like buying gallons of gasoline. Insurance automatically ends when the odometer limit (recorded on the car’s insurance ID card) is reached unless more miles are bought. Customers keep track of miles on their own odometer to know when to buy more. The company does no after-the-fact billing of the customer, and the customer doesn't have to estimate a "future annual mileage" figure for the company to obtain a discount. In the event of a traffic stop, an officer could easily verify that the insurance is current by comparing the figure on the insurance card to that on the odometer.

Critics point out the possibility of cheating the system by odometer tampering. Although the newer electronic odometers are difficult to roll back, they can still be defeated by disconnecting the odometer wires and reconnecting them later. However, as the Cents Per Mile Now website points out:

As a practical matter, resetting odometers requires equipment plus expertise that makes stealing insurance risky and uneconomical. For example, in order to steal 20,000 miles (32,000 km) of continuous protection while paying for only the 2,000 miles (3,200 km) from 35,000 miles (56,000 km) to 37,000 miles (60,000 km) on the odometer, the resetting would have to be done at least nine times to keep the odometer reading within the narrow 2,000-mile (3,200 km) covered range. There are also powerful legal deterrents to this way of stealing insurance protection. Odometers have always served as the measuring device for resale value, rental and leasing charges, warranty limits, mechanical breakdown insurance, and cents-per-mile tax deductions or reimbursements for business or government travel. Odometer tampering—detected during claim processing—voids the insurance and, under decades-old state and federal law, is punishable by heavy fines and jail.

Under the cents-per-mile system, rewards for driving less are delivered automatically without need for administratively cumbersome and costly GPS technology. Uniform per-mile exposure measurement for the first time provides the basis for statistically valid rate classes. Insurer premium income automatically keeps pace with increases or decreases in driving activity, cutting back on resulting insurer demand for rate increases and preventing today's windfalls to insurers when decreased driving activity lowers costs but not premiums.



GPS-based system

In 1998, Progressive Insurance started a pilot program in Texas in which drivers received a discount for installing a GPS-based device that tracked their driving behavior and reported the results via cellular phone to the company.[11] Policyholders were reportedly more upset about having to pay for the expensive device than they were over privacy concerns.[12] The program was discontinued in 2000.



OBDII-based system

In 2008, The Progressive Corporation launched MyRate to give drivers a customized insurance rate based on how, how much, and when their car is driven. MyRate is currently available in Alabama, Kentucky, Louisiana, Michigan, Minnesota, Maryland, New Jersey and Oregon. Driving data is transmitted to the company using an on-board telematic device. The device connects to a car's OnBoard Diagnostic (OBD-II) port (all automobiles built after 1996 have an OBD-II.) and transmits speed, time of day and number of miles the car is driven. There is no GPS in the MyRate device, so no location information is collected. Cars that are driven less often, in less risky ways and at less risky times of day can receive large discounts. Progressive has received patents on its methods and systems of implementing usage-based insurance and has licensed these methods and systems to other companies. Progressive has service marks pending on the terms Pay As You Drive and Pay How You Drive.



Auto insurance in the United States



Coverage available

The consumer may be protected with different coverage types depending on what coverage the insured purchases. Some states require that motorists carry liability insurance coverage in order to ensure that its drivers can cover the cost of damages to people or property in the event of an automobile accident. Some states, such as Wisconsin, have more flexible “proof of financial responsibility” requirements.[13]

In the United States, liability insurance covers claims against the policy holder and generally, any other operator of the insured vehicles, provided they do not live at the same address as the policy holder, and are not specifically excluded on the policy. In the case of those living at the same address, they must specifically be covered on the policy. Thus it is necessary, for example, when a family member comes of driving age they must be added to the policy. Liability insurance sometimes does not protect the policy holder if they operate any vehicles other than their own. When you drive a vehicle owned by another party, you are covered under that party’s policy. Non-owners policies may be offered that would cover an insured on any vehicle they drive. This coverage is available only to those who do not own their own vehicle and is sometimes required by the government for drivers who have previously been found at fault in an accident. Non-owners policies are also known as Named Operator Policies. The policies are useful for people whose drivers license has been suspended and they have to have insurance for their licensed to be reinstated.

Generally, liability coverage extends when you rent a car. Comprehensive policies ("full coverage") usually also apply to the rental vehicle, although this should be verified beforehand. Full coverage premiums are based on, among other factors, the value of the insured’s vehicle. This coverage, however, cannot apply to rental cars because the insurance company does not want to assume responsibility for a claim greater than the value of the insured’s vehicle, assuming that a rental car may be worth more than the insured’s vehicle. Most rental car companies offer insurance to cover damage to the rental vehicle. These policies may be unnecessary for many customers as credit card companies, such as Visa and MasterCard, now provide supplemental collision damage coverage to rental cars if the transaction is processed using one of their cards. These benefits are restrictive in terms of the types of vehicles covered.[14]



Liability

Liability coverage is offered for bodily injury (BI) or property damage (PD) for which the insured driver is deemed responsible. The amount of coverage provided (a fixed dollar amount) will vary from jurisdiction to jurisdiction. Whatever the minimum, the insured can usually increase the coverage (prior to a loss) for an additional charge.

An example of Property Damage is where an insured driver (or 1st party) drives into a telephone pole and damages the pole, liability coverage pays for the damage to the pole. In this example, the drivers insured may also become liable for other expenses related to damaging the telephone pole, such as loss of service claims (by the telephone company), depending on the jurisdiction. An example of Bodily Injury is where an insured driver causes bodily harm to a third party and the insured driver is deemed responsible for the injuries. However, in some jurisdictions, the third party would first exhaust coverage for accident benefits through their own insurer (assuming they have one) and/or would have to meet a legal definition of severe imparement to have the right to claim (or sue) under the insured driver's (or 1st Party's) policy.

In some jurisdictions: Liability coverage is available either as a combined single limit policy, or as a split limit policy:



Combined single limit

A combined single limit combines property damage liability coverage and bodily injury coverage under one single combined limit. For example, an insured driver with a combine single liability limit strikes another vehicle and injures the driver and the passenger. Payments for the damages to the other driver's car, as well as payments for injury claims for the driver and passenger, would be paid out under this same coverage.



Split limits

A split limit liability coverage policy splits the coverages into property damage coverage and bodily injury coverage. In the example given above, payments for the other driver's vehicle would be paid out under property damage coverage, and payments for the injuries would be paid out under bodily injury coverage.

Bodily injury liability coverage is also usually split as well into a maximum payment per person and a maximum payment per accident.

In the state of Oklahoma, you must carry at least state minimum liability limits of $25,000/50,000/25,000. If an insured driver hits a car full of people and is found by the insurance company to be liable, the insurance company will pay $25,000 of one persons medical bills but will not exceed 50,000 for other people injured in the accident. The insurance company will pay porperty damage not to exceed 25,000 in repairs to the vehicle that the insured hit.



Full Coverage

Full coverage is the name commonly referred to as Comprehensive and Collision. The insurance companies want to get away from the term because there is no such thing as full coverage.



Collision

Collision coverage provides coverage for an insured's vehicle that is involved in an accident, subject to a deductible. This coverage is designed to provide payments to repair the damaged vehicle, or payment of the cash value of the vehicle if it is not repairable. Collision coverage is optional, however if you plan on financing a car or taking a car loan, the lender will usually insist you carry collision for the finance term or until your car is paid off. Collision Damage Waiver (CDW) is the term used by rental car companies for collision coverage.



Comprehensive

Comprehensive (a.k.a. - Other Than Collision) coverage provides coverage, subject to a deductible, for an insured's vehicle that is damaged by incidents that are not considered Collisions. For example, fire, theft (or attempted theft), vandalism, weather, or impacts with animals are types of Comprehensive losses.



Uninsured/underinsured coverage

Underinsured coverage, also known as UM/UIM, provides coverage if an at-fault party either does not have insurance, or does not have enough insurance. In effect, your insurance company pays your medical bills, then would subrogate from the at fault party.

In the United States, the definition of an uninsured/underinsured motorist, and corresponding coverages, are set by state laws.



Loss of use

Loss of use coverage, also known as rental coverage, provides reimbursement for rental expenses associated with having an insured vehicle repaired due to a covered loss.



Loan/lease payoff

Loan/lease payoff coverage, also known as GAP coverage or GAP insurance,[15][16] was established in the early 1980s to provide protection to consumers based upon buying and market trends.

Due to the sharp decline in value immediately following purchase, there is generally a period in which the amount owed on the car loan exceeds the value of the vehicle, which is called "upside-down" or negative equity. Thus, if the vehicle is damaged beyond economical repair at this point, the owner will still owe potentially thousands of dollars on the loan. The escalating price of cars, longer-term auto loans, and the increasing popularity of leasing gave birth to GAP protection. GAP waivers provide protection for consumers when a "gap" exists between the actual value of their vehicle and the amount of money owed to the bank or leasing company. In many instances, this insurance will also pay the deductible on the primary insurance policy. These policies are often offered at the auto dealership as a comparatively low cost add on that can be put into the car loan which provides coverage for the duration of the loan.

Consumers should be aware that a few states, including New York, require lenders of leased cars to include GAP insurance within the cost of the lease itself. This means that the monthly price quoted by the dealer must include GAP insurance, whether it is delineated or not. Nevertheless, unscrupulous dealers sometimes prey on unsuspecting individuals by offering them GAP insurance at an additional price, on top of the monthly payment, without mentioning the State's requirements.

In addition, some vendors and insurance companies offer what is called "Total Loss Coverage." This is similar to ordinary GAP insurance but differs in that instead of paying off the negative equity on a vehicle that is a total loss, the policy provides a certain amount, usually up to $5000, toward the purchase or lease of a new vehicle. Thus, to some extent the distinction makes no difference, i.e., in either case the owner receives a certain sum of money. However, in choosing which type of policy to purchase, the owner should consider whether, in case of a total loss, it is more advantageous for him or her to have the policy pay off the negative equity or provide a down payment on a new vehicle.

For example, assuming a total loss of a vehicle valued at $15,000, but on which the owner owes $20,000, is the "gap" of $5000. If the owner has traditional GAP coverage, the "gap" will be wiped out and he or she may purchase or lease another vehicle or choose not to. If the owner has "Total Loss Coverage," he or she will have to personally cover the "gap" of $5000, and then receive $5000 toward the purchase or lease of a new vehicle, thereby either reducing monthly payments, in the case of financing or leasing, or the total purchase price in the case of outright purchasing. So the decision on which type of policy to purchase will, in most instances, be informed by whether the owner can pay off the negative equity in case of a total loss and/or whether he or she will definitively purchase a replacement vehicle.



Towing

Car towing coverage is also known as Roadside Assistance coverage. Traditionally, automobile insurance companies have agreed to only pay for the cost of a tow that is related to an accident that is covered under the automobile policy of insurance. This had left a gap in coverage for tows that are related to mechanical breakdowns, flat tires and gas outages. To fill that void, insurance companies started to offer the car towing coverage, which pays for non-accident related tows.



Personal Property

If personal items in a vehicle are damaged due to an accident that would not be a covered under the auto policy. Any type of property that is not attached to the vehicle should be claimed under a homeowners or renters policy.


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Student Loans

The Student Loans Company Limited is a non-departmental public body of the United Kingdom government, responsible for the provision of financial support to students attending university.

The company offers loans to students at the rate of inflation - as measured by the retail price index - and administers repayment once the student has entered employment and is earning a salary in excess of a defined threshold.

Historically loans were collected directly from the student by direct debit (mortgage style loans), more recently Income Contingent Repayment (ICR) loans have been introduced. ICR loans are paid back via Her Majesty's Revenue and Customs who actually collect the repayments and send the details of the repayment collected back to the Student Loans Company. Borrowers outside the UK tax system repay directly to the Student Loans Company.

The Company was established in 1990 when it lent out £190 million to eligible students. Since then, changes in the provision of higher education have seen the phasing out of non repayable maintenance grants, and the charging of tuition fees. In the financial year 2004-05, the Company lent out £2,712 million, with total outstanding loans valued at £15,974.6 million at the end of that financial year. [1]

The Student Loans Company is based at Bothwell Street, Glasgow, Scotland, and also has offices at Hillington, Darlington and Colwyn Bay.

The UK Government sold off two tranches of debtor accounts in 1998 and 1999 to Finance for Higher Education (FFHE), a company formed by Greenwich NatWest, and Honours Student Loans Company a trading name of Honours Trustee Limited, a private limited company.

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Divorce Attorney

Divorce or dissolution of marriage is a legal process leading to the termination of a marriage.



Divorce laws vary considerably around the world. Divorce is not permitted in some countries, such as in Malta and in the Philippines, though an annulment is permitted.

The legal process for divorce may also involve an application and award of spousal support, child custody, child support, distribution of property and division of debt, though these matters are only ancillary to the dissolution of the marriage.

No fault divorce describes a divorce process which does not required a court to find either party at fault for the breakdown of a marriage when granting the divorce. No fault divorce does not mean a court will ignore the behaviour of the parties when dividing property, debts, evaluating custody, and support. Rather, the typical no fault statute prohibits a court from denying a divorce or allowing a party to raise a defense for divorce.

In some jurisdictions, a divorce must be certified by a court of law, as a legal action is needed to dissolve the prior legal act of marriage. The terms of the divorce are also determined by the court, though they may take into account prenuptial agreements or postnuptial agreements, or simply ratify terms that the spouses have agreed on privately. Often, however, the spouses disagree about the terms of the divorce, which can lead to stressful and expensive litigation. Less adversarial approaches to divorce settlements have recently emerged, such as mediation and collaborative divorce, which negotiate mutually acceptable resolution to conflicts. In some other countries, like Portugal, when the spouses agree to divorce and to the terms of the divorce, it can be certified by a non judiciary administrative entity, where also can be served an Electronic Divorce since March 2008.

In cases involving children, governments have a pressing interest in ensuring that disputes between parents do not spill over into the family courts. One way of doing this is through the encouragement of a parenting plan. In the United States, all states now require parents to file a parenting plan when they legally separate or divorce.

The subject of divorce as a social phenomenon is an important research topic in sociology. In many developed countries, divorce rates increased markedly during the twentieth century. Among the nations in which divorce has become commonplace are the United States, Canada, and members of the European Union. Japan retains a markedly lower divorce rate, though it has increased in recent years.


Types of divorce

The approach to divorce varies by jurisdiction. There are two basic approaches to divorce: fault based and no-fault based.

Fault divorce can affect the distribution of property, and will allow an immediate divorce, in states where there is a waiting period required for no-fault divorce.

Residency requirements vary from state to state, and a couple may separate, one spouse may move to a state with divorce laws of their choice, establish residency, and then apply for divorce. However, this typically does not change the state in which property and other issues are decided.


No fault divorce

Under a no-fault divorce system the dissolution of a marriage does not require an allegation or proof of fault of either party to be shown. No-fault divorce has been in operation in Australia since 1975 and the only thing the applicant needs to show is separation (or "deemed separation") for 12 months, and the divorce application can be made by either party or by both parties jointly.

Forty-nine states of the United States have adopted unilateral no-fault divorce laws. Common reasons for no-fault divorce include incompatibility, irreconcilable differences, and irremediable breakdown of the marriage. No-fault divorce can be a unilateral divorce action forced upon the non-initiating spouse by the initiator with the support of the court system. The non-initiating spouse may be divorced against his or her will, though "not at fault".

In England a to obtain a no fault divorce the time scales are 2 years if both parties agree and 5 years if one party does not agree.


At-fault divorce

Fault divorces used to be the only way to break a marriage, and people who had differences, but did not qualify as "at fault", only had the option to separate (and were prevented from legally remarrying).

In the United States, New York is the only state that still requires fault for a divorce.

However there are ways (defenses) to prevent a fault divorce:

* Condonation
* Connivance
* Provocation
* Collusion

A defence is expensive, and not usually practical as eventually most divorces are granted.

Comparative rectitude is a doctrine used to determine which spouse is more at fault when both spouses are guilty of breaches.


Summary divorce

A summary (or simple) divorce, available in some jurisdictions, is used when spouses meet certain eligibility requirements, or can agree on key issues beforehand.

Key factors:

* Short marriage (under 5 years)
* No children (or, in some states, they have resolved custody and set child support payments)
* Minimal or no real property (no mortgage)
* Marital property is under a threshold (around $35,000 not including vehicles)
* Each spouse's personal property is under a threshold (typically the same as marital property)


Uncontested divorce

It is estimated that upwards of 95% of divorces in the US are "uncontested," because the two parties are able to come to an agreement (either with or without lawyers/mediators/collaborative counsel) about the property, children and support issues. When the parties can agree and present the court with a fair and equitable agreement, approval of the divorce is almost guaranteed. If the two parties cannot come to an agreement, they may ask the court to decide how to split property, deal with the custody of their children.


Collaborative divorce

Collaborative divorce is becoming a popular method for divorcing couples to come to agreement on divorce issues. In a collaborative divorce, the parties negotiate an agreed resolution with the assistance of attorneys who are trained in the collaborative divorce process and in mediation, and often with the assistance of a neutral financial specialist and/or divorce coach(es). The parties are empowered to make their own decisions based on their own needs and interests, but with complete information and full professional support. Once the collaborative divorce starts, the lawyers are disqualified from representing the parties in a contested legal proceeding, should the collaborative law process end prematurely. Most attorneys who practice collaborative divorce claim that it can be substantially less expensive than other divorce methods (regular divorce or mediation). However, should the parties not reach any agreements, any documents or information exchanged during the collaborative process cannot later be used in further legal proceedings, as the collabrative process is confidential proceedings. Furthermore, there are no set enforceable timelines for completion of a divorce using collabrative divorce.


Mediated divorce

Divorce mediation is an alternative to traditional divorce litigation. [1] In a divorce mediation session, a mediator facilitates the discussion between the husband and wife by assisting with communication and providing information and suggestions to help resolve differences. At the end of the mediation process, the separating parties have typically developed a tailored divorce agreement that can be submitted to the court. Mediation sessions can include the party's attorneys or a neutral attorney or an attorney-mediator who can inform both parties of their legal rights, but does not provide advice to either, or can be conducted without attorneys. Divorce mediators may be attorneys who have experience in divorce cases. Divorce mediation can be significantly less expensive than litigation. [2]. The adherence rate to mediated agreements is much higher than that of adherence to court orders.


History
Henry VIII of England is known for breaking with the Roman Catholic Church partly in order to obtain a divorce

Divorce existed in antiquity, dating at least back to ancient Mesopotamia. The ancient Athenians liberally allowed divorce, but the person requesting divorce had to submit the request to a magistrate, and the magistrate could determine whether the reasons given were sufficient.

Divorce was rare in early Roman culture however. But as their empire grew in power and authority Roman civil law embraced the maxim, “matrimonia debent esse libera” ("marriages ought to be free"), and either husband or wife could renounce the marriage at will. Though civil authority rarely intervened in divorces, social and familial taboos guaranteed that divorce occurred only after serious circumspection.

The Christian emperors Constantine and Theodosius restricted the grounds for divorce to grave cause, but this was relaxed by Justinian in the sixth century. After the fall of the empire, familial life was regulated more by ecclesiastical authority than civil authority. By the ninth or tenth century, the divorce rate had been greatly reduced under the influence of the Christian Church,[1] which considered marriage a sacrament instituted by God and Christ indissoluble by mere human action.[2]

Although divorce, as known today, was generally prohibited after the tenth century, separation of husband and wife and the annulment of marriage were well-known. What is today referred to as “separate maintenance” (or "legal separation") was termed “divorce a mensa et thoro” (“divorce from bed-and-board”). The husband and wife physically separated and were forbidden to live or cohabit together; but their marital relationship did not fully terminate.[3] Civil courts had no power over marriage or divorce. The grounds for annulment were determined by Church authority and applied in ecclesiastical courts. Annulment was known as “divorce a vinculo matrimonii,” or “divorce from all the bonds of marriage,” for canonical causes of impediment existing at the time of the marriage. “For in cases of total divorce, the marriage is declared null, as having been absolutely unlawful ab initio.” [4][5][6] The Church held that the sacrament of marriage produced one person from two, inseparable from each other: “By marriage the husband and wife are one person in law: that is, the very being of legal existence of the woman is suspended during the marriage or at least incorporated and consolidated into that of the husband: under whose wing, protection and cover, she performs everything.” [7] Since husband and wife became one person upon marriage, that oneness could only be annulled if the parties improperly entered into the marriage initially.

Marriage later came to be considered a civil contract, and on that basis civil authorities gradually asserted their power to decree divorce. Since no precedents existed defining the circumstances under which marriage could be dissolved, civil courts heavily relied on the previous determinations of the ecclesiastic courts and freely adopted the requirements set down by those courts. As the civil courts assumed the power to dissolve marriages, courts still strictly construed the circumstances under which they would grant a divorce,[8] and now considered divorce to be contrary to public policy. Because divorce was considered to be against the public interest, civil courts refused to grant a divorce if evidence revealed any hint of complicity between the husband and wife to divorce, or if they attempted to manufacture grounds for a divorce. Divorce was granted only because one party to the marriage had violated a sacred vow to the "innocent spouse." If both husband and wife were guilty, "neither would be allowed to escape the bonds of marriage."[9] Eventually, the idea that a marriage could be dissolved in cases in which one of the parties violated the sacred vow gradually allowed expansion of the grounds upon which divorce could be granted from those grounds which existed at the time of the marriage to grounds which occurred after the marriage, but which exemplified violation of that vow, such as abandonment, adultery, or “extreme cruelty.”[10]

In post Victorian America divorce rates sky rocketed as was shown in Elaine Tyler May's Great Expectations: Divorce in post Victorian America which argued that the shift from the repression of desire to pursuing it due to increased leisure time and the eight hour day, Americans expected more than duty from their spouses. The American home was no longer an abode for discipline and suppression of desire but a place for the pursuit of happiness and satisfaction. Divorce before the 1920's was based on the husband not providing 'life' necessities' for his child and wife. Later it became clear that men and women wanted to be sexually satisfied in their marriages as well as have the public chaste image. This clash in expecting old values with the best of the modern values cause much grief between couples leading to monetary problems and problems sexually, leading to divorce. The shift in the 1920's, to expect more from married life other than duty and chastity from the wife and hard work and suppression of vice from the husband leads us into the present predicament of the high divorce rates in this country.


Initiation

The National Center for Health Statistics reports that from 1975 to 1988 in the US, in families with children present, wives file for divorce in approximately two-thirds of cases. In 1975, 71.4% of the cases were filed by women, and in 1988, 65% were filed by women.[11]

According to a study published in the American Law and Economics Review, women currently file slightly more than two-thirds of divorce cases in the US.[12] There is some variation among states, and the numbers have also varied over time, with about 60% of filings by women in most of the 19th century, and over 70% by women in some states just after no-fault divorce was introduced, according to the paper. Evidence is given that among college-educated couples, the percentages of divorces initiated by women is approximately 90%.

In their study titled "Child Custody Policies and Divorce Rates in the US," Kuhn and Guidubaldi find it reasonable to conclude that women anticipate advantages to being single, rather than remaining married.[13]

When women anticipate a clear gender bias in the courts regarding custody, they expect to be the primary residential parent for the children and recipient of the resulting financial child support, maintaining the marital residence, receiving half of all marital property, and gaining total freedom to establish new social relationships. In their detailed analysis of divorce rates, Kuhn and Guidubaldi conclude that acceptance of joint physical custody may reduce divorce. States whose family law policies, statutes, or judicial practice encourage joint custody have shown a greater decline in their divorce rates than those that favor sole custody.

In divorce adjustment evidence shows that males reported less stress prior to the decision to divorce than do females, and that females fare better after separation and divorce than do males.[14]


Divorce avoidance

Main article: Relationship counseling
See also: Legal separation


Religious/cultural attitudes

Main article: Religion and divorce

Many religions have varied attitudes towards divorce, ranging from prohibited to acceptable behavior.

At times these religious attitudes may create a conflict with secular legal systems.


Implications of divorce

Main article: Implications of divorce

There are significant emotional, financial, medical and psychological implications of divorce.


Divorce laws in different countries

Main article: Law and divorce around the world

Different societies and legal jurisdictions have varying attitudes towards divorce.

Only Malta, the Philippines and the Vatican don't allow divorce at all.


Incidence

Main article: Divorce demography


Divorce party

Main article: Divorce party

A divorce party is a ceremony that celebrates the end of a marriage or civil union. Increasingly many people undergoing a divorce choose to hold a party or ceremony in order to bring closure to the marriage. In the case of an amiable divorce, couples may choose to hold a joint divorce ceremony together to signify the dissolution of a marriage but to emphasize their continuing friendship and good relations afterwards.



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