equator

An equator is the intersection of a sphere's surface with the plane perpendicular to the sphere's axis of rotation and midway between the poles. The Equator usually refers to the Earth's equator; an imaginary line on the Earth's surface equidistant from the North Pole and South Pole, dividing the Earth into the Northern Hemisphere and Southern Hemisphere. Other planets and astronomical bodies have equators similarly defined. The Equator is about 40,075 kilometers (24,901 mi) long; 78.7% is across water and 21.3% is over land.

The latitude of the Equator is by definition 0° (zero degrees). The Equator is one of the five notable circles of latitude on Earth, with the others being the two Polar Circles (the Arctic Circle and the Antarctic Circle) and the two Tropical Circles (The Tropic of Cancer and the Tropic of Capricorn). The Equator is the only line of latitude that is also a great circle. The imaginary circle obtained when the Earth's equator is projected onto the sky is called the celestial equator.

In its seasonal apparent movement across the sky the sun passes over the Equator twice each year, at the March and September equinoxes. At the moment of the equinox, light rays from the center of the sun are perpendicular to the surface of the earth at the point on the equator experiencing solar noon.

The Equator, like the Tropics, is not fixed. the true equatorial plane is always perpendicular to the Earth's spin axis; this axis is fairly stable but its position drifts about 15 meters (49 feet) during a year and the equator shifts likewise.

Equatorial seasons and climate
Seasons result from the yearly revolution of the Earth around the Sun and the tilt of the Earth's axis relative to the plane of revolution. During the year the northern and southern hemispheres are inclined toward or away from the sun according to Earth's position in its orbit. The hemisphere inclined toward the sun receives more sunlight and is in summer, while the other hemisphere receives less sun and is in winter (see solstice). At the equinox the Earth's axis is not tilted toward the sun and the day is about 12 hours long over most of the Earth.

The Equator lies mostly on the three largest oceans: the Pacific Ocean, the Atlantic Ocean, and the Indian Ocean. The highest point on the Equator is at the elevation of 4,690 meters (15,387 feet), found on the slopes of Volcán Cayambe [summit 5,790 meters (18,996 feet)] in Ecuador. This is slightly above the snow line, and is the only place on the Equator where snow lies on the ground.

Lowlands around the Equator generally have a tropical rainforest climate, also known as an equatorial climate, through cold currents cause some regions to have tropical monsoon climates with a dry season in the middle of the year. Usually, average annual temperature is around 30 °C (86 °F) during the day and 23 °C (73 °F) at night. Rainfall is very high, usually from 2,500 to 3,500 mm per year. Average rainy days are around 200 per year and average annual sunshine hours around 2000.

Equatorial countries and territories
The Equator traverses the land and/or territorial waters of 14 countries. Starting at the Prime Meridian and heading eastwards, the Equator passes through:

Coordinates	Country, territory or sea	Notes
0°N 0°E / 0°N 0°E / 0; 0 (Prime Meridian)	Atlantic Ocean	Gulf of Guinea
0°0′N 6°31′E / 0.000°N 6.517°E / 0.000; 6.517 (São Tomé and Príncipe)	São Tomé and Príncipe	Ilhéu das Rolas
0°0′N 6°31′E / 0.000°N 6.517°E / 0.000; 6.517 (Atlantic Ocean)	Atlantic Ocean	Gulf of Guinea
0°0′N 9°21′E / 0.000°N 9.350°E / 0.000; 9.350 (Gabon)	Gabon
0°0′N 13°56′E / 0.000°N 13.933°E / 0.000; 13.933 (Republic of the Congo)	Republic of the Congo	Passing through the town of Makoua.
0°0′N 17°46′E / 0.000°N 17.767°E / 0.000; 17.767 (Democratic Republic of the Congo)	Democratic Republic of the Congo	Passing 9 km south of central Butembo
0°0′N 29°43′E / 0.000°N 29.717°E / 0.000; 29.717 (Uganda)	Uganda	Passing 32 km south of central Kampala
0°0′N 32°22′E / 0.000°N 32.367°E / 0.000; 32.367 (Lake Victoria)	Lake Victoria	Passing through some islands of  Uganda
0°0′N 34°0′E / 0.000°N 34.000°E / 0.000; 34.000 (Kenya)	Kenya	Passing 6 km north of central Kisumu
0°0′N 41°0′E / 0.000°N 41.000°E / 0.000; 41.000 (Somalia)	Somalia
0°0′N 42°53′E / 0.000°N 42.883°E / 0.000; 42.883 (Indian Ocean)	Indian Ocean	Passing between Huvadhu Atoll and Fuvahmulah of the  Maldives
0°0′N 98°12′E / 0.000°N 98.200°E / 0.000; 98.200 (Indonesia)	Indonesia	The Batu Islands, Sumatra and the Lingga Islands
0°0′N 104°34′E / 0.000°N 104.567°E / 0.000; 104.567 (Karimata Strait)	Karimata Strait
0°0′N 109°9′E / 0.000°N 109.150°E / 0.000; 109.150 (Indonesia)	Indonesia	Borneo
0°0′N 117°30′E / 0.000°N 117.500°E / 0.000; 117.500 (Makassar Strait)	Makassar Strait
0°0′N 119°40′E / 0.000°N 119.667°E / 0.000; 119.667 (Indonesia)	Indonesia	Sulawesi (Celebes)
0°0′N 120°5′E / 0.000°N 120.083°E / 0.000; 120.083 (Gulf of Tomini)	Gulf of Tomini
0°0′N 124°0′E / 0.000°N 124.000°E / 0.000; 124.000 (Molucca Sea)	Molucca Sea
0°0′N 127°24′E / 0.000°N 127.400°E / 0.000; 127.400 (Indonesia)	Indonesia	Kayoa and Halmahera islands
0°0′N 127°53′E / 0.000°N 127.883°E / 0.000; 127.883 (Halmahera Sea)	Halmahera Sea
0°0′N 129°20′E / 0.000°N 129.333°E / 0.000; 129.333 (Indonesia)	Indonesia	Gebe Island
0°0′N 129°21′E / 0.000°N 129.350°E / 0.000; 129.350 (Pacific Ocean)	Pacific Ocean	Passing 570 m north of Waigeo island,  Indonesia Passing 13 km south of Aranuka atoll,  Kiribati Passing 21 km south of Baker Island,  United States Minor Outlying Islands
0°0′N 91°35′W / 0.000°N 91.583°W / 0.000; -91.583 (Ecuador)	Ecuador	Isabela Island in the Galápagos Islands
0°0′N 91°13′W / 0.000°N 91.217°W / 0.000; -91.217 (Pacific Ocean)	Pacific Ocean
0°0′N 80°6′W / 0.000°N 80.100°W / 0.000; -80.100 (Ecuador)	Ecuador	Passing 24 km north of central Quito, near Mitad del Mundo
0°0′N 75°32′W / 0.000°N 75.533°W / 0.000; -75.533 (Colombia)	Colombia	Passing 4.3 km north of the border with Peru
0°0′N 70°3′W / 0.000°N 70.050°W / 0.000; -70.050 (Brazil)	Brazil	Amazonas Roraima Amazonas Pará Amapá Pará - islands in the mouth of the Amazon River
0°0′N 49°20′W / 0.000°N 49.333°W / 0.000; -49.333 (Atlantic Ocean)	Atlantic Ocean

Despite its name, no part of Equatorial Guinea's territory lies on the Equator. However, its island of Annobón is 155 kilometers (100mi) south of the Equator, and the rest of the country lies to the north.

Latitude
Latitude (φ) is a geographic coordinate that specifies the north-south position of a point on the Earth's surface. Latitude is an angle (defined below) which ranges from 0° at the Equator to 90° (North or South) at the poles. Lines of constant latitude, or parallels, run east–west as circles parallel to the equator. Latitude is used together with longitude to specify the precise location of features on the surface of the Earth.

A graticule on a sphere or an ellipsoid. The lines from pole to pole are lines of constant longitude, or meridians. The circles parallel to the equator are lines of constant latitude, or parallels. The graticule determines the latitude and longitude of position on the surface.

The graticule, the mesh formed by the lines of constant latitude and constant longitude, is constructed by reference to the rotation axis of the Earth. The primary reference points are the poles where the axis of rotation of the Earth intersects the reference surface. Planes which contain the rotation axis intersect the surface in the meridians and the angle between any one meridian plane and that through Greenwich (the Prime Meridian) defines the longitude: meridians are lines of constant longitude. The plane through the centre of the Earth and orthogonal to the rotation axis intersects the surface in a great circle called the equator. Planes parallel to the equatorial plane intersect the surface in circles of constant latitude; these are the parallels. The equator has a latitude of 0°, the North pole has a latitude of 90° north (written 90° N or +90°), and the South pole has a latitude of 90° south (written 90° S or −90°). The latitude of an arbitrary point is the angle between the equatorial plane and the radius to that point.

A perspective view of the Earth showing how latitude (φ) and longitude (λ) are defined on a spherical model. The graticule spacing is 10 degrees.

Longitude
Longitude is a geographic coordinate that specifies the east-west position of a point on the Earth's surface. It is an angular measurement, usually expressed in degrees and denoted by the Greek letter lambda (λ). Points with the same longitude lie in lines running from the North Pole to the South Pole. By convention, one of these, the Prime Meridian, which passes through the Royal Observatory, Greenwich, England, was intended to establish the position of zero degrees longitude. The longitude of other places was to be measured as the angle east or west from the Prime Meridian, ranging from 0° at the Prime Meridian to +180° eastward and −180° westward. Specifically, it is the angle between a plane containing the Prime Meridian and a plane containing the North Pole, South Pole and the location in question.

Drawing of Earth with Longitudes

Circles of latitude
A circle of latitude on the Earth is an imaginary east-west circle connecting all locations (not taking into account elevation) having a given latitude. A location's position along a circle of latitude is given by its longitude.

Circles of latitude are often called parallels because they are parallel to each other – that is, any two parallels are everywhere the same distance apart. (Since the Earth is not spherical the distance from the equator to 10 degrees north is slightly less than the distance from 10 to 20 degrees north.)

Circles of latitude become smaller the farther they are from the equator and the closer they are to the poles. A circle of latitude is perpendicular to all meridians, and is hence a special case of a loxodrome.

The latitude of the circle is (roughly) the angle between the Equator and the circle, with the angle's vertex at the Earth's centre. The Equator is at 0°, and the North and South Pole are at 90° north and 90° south respectively. There are 89 integral (whole degree) circles of latitude between the Equator and the Poles in each hemisphere, but these can be divided into more precise measurements of latitude, and are often represented as a decimal degree (e.g. 34.637°N) or with minutes and seconds (e.g. 22°14'26"S). There is no limit to how precisely latitude can be measured, and so there are an infinite number of circles of latitude on Earth.

Great circle
A great circle, also known as an orthodrome or Riemannian circle, of a sphere is the intersection of the sphere and a plane which passes through the center point of the sphere. (A small circle is the intersection of the sphere and a plane which does not pass through the center.) Any diameter of any great circle coincides with a diameter of the sphere, and therefore all great circles have the same circumference as each other, and have the same center as the sphere. A great circle is the largest circle that can be drawn on any given sphere.

Solstice
A solstice is an astronomical event that occurs twice each year as the Sun reaches its highest or lowest excursion relative to the celestial equator on the celestial sphere. As a result, on the day of the solstice, the Sun appears to have reached its highest or lowest annual altitude in the sky above the horizon at local solar noon. The word solstice is derived from the Latin sol (sun) and sistere (to stand still), because at the solstices, the Sun stands still in declination; that is, the seasonal movement of the Sun's path (as seen from Earth) comes to a stop before reversing direction. The solstices, together with the equinoxes, are connected with the seasons. In many cultures the solstices mark either the beginning or the midpoint of winter and summer.

Illumination of Earth by Sun at the northern solstice.

Illumination of Earth by Sun at the southern solstice.

The term solstice can also be used in a broader sense, as the date (day) when this occurs. The day of the solstice is either the longest day of the year (in summer) or the shortest day of the year (in winter) for any place outside of the tropics.

Equinox
An equinox occurs twice a year (around 20 March and 22 September), when the plane of the Earth's equator passes the center of the Sun. At this time the tilt of the Earth's axis is inclined neither away from nor towards the Sun. The term equinox can also be used in a broader sense, meaning the date when such a passage happens. The name "equinox" is derived from the Latin aequus (equal) and nox (night), because around the equinox, night and day are about equal length. Times of sunset and sunrise vary with an observer's location (longitude and latitude), so these dates likewise depend on location and do not exist for locations close to the Equator. To avoid this ambiguity the term equilux is sometimes used in this sense.

During an equinox, the Earth is not tilted toward or away from the Sun and the length of the day is the same at all points on the Earth's surface.

During an equinox, the Earth is not tilted toward or away from the Sun and the length of the day is the same at all points on the Earth's surface.

Sources:

http://en.wikipedia.org/wiki/Equator
http://en.wikipedia.org/wiki/Latitude
http://en.wikipedia.org/wiki/Longitude
http://en.wikipedia.org/wiki/Circle_of_latitude
http://en.wikipedia.org/wiki/Great_circle
http://en.wikipedia.org/wiki/Solstice
http://en.wikipedia.org/wiki/Equinox

diabetes

Diabetes mellitus, or simply diabetes, is a group of metabolic diseases in which a person has high blood sugar, either because the pancreas does not produce enough insulin, or because cells do not respond to the insulin that is produced. This high blood sugar produces the classical symptoms of polyuria (frequent urination), polydipsia (increased thirst) and polyphagia (increased hunger).

There are three main types of diabetes mellitus (DM).

• Type 1 DM results from the body's failure to produce insulin, and currently requires the person to inject insulin or wear an insulin pump. This form was previously referred to as "insulin-dependent diabetes mellitus" (IDDM) or "juvenile diabetes".
• Type 2 DM results from insulin resistance, a condition in which cells fail to use insulin properly, sometimes combined with an absolute insulin deficiency. This form was previously referred to as non insulin-dependent diabetes mellitus (NIDDM) or "adult-onset diabetes".
• The third main form, gestational diabetes occurs when pregnant women without a previous diagnosis of diabetes of diabetes develop a high blood glucose level. It may precede development of type 2 DM.

Other forms of diabetes mellitus include cogenital diabetes, which is due to genetic defects of insulin secretion, cystic fibrosis-related diabetes, steroid diabetes induced by high doses of glucocorticoids, and several forms of monogenic diabetes.

Untreated, diabetes can cause many complications. Acute complications include diabetic ketoacidosis and nonketotic hyperosmolar coma. Serious long-term complications include cardiovascular disease, chronic renal failure, and diabetic retinopathy (retina damage). Adequate treatment of diabetes is thus important, as well as blood pressure control and lifestyle factors such as stopping smoking and maintaining a healthy body weight.

All forms of diabetes have been treatable since insulin became available in 1921, and type 2 diabetes may be controlled with medications. Insulin and some oral medications can cause hypoglycemia (low blood sugars), which can be dangerous if severe. Both types 1 and 2 are chronic conditions that cannot be cured. Pancreas transplants have been tried with limited success in type 1 DM; gastric bypass surgery has been successful in many with morbid obesity and type 2 DM. Gestational diabetes usually resolves after delivery.

Classification
Type 1 diabetes
Type 1 diabetes mellitus is characterized by loss of the insulin-producing beta cells of the islets of Langerhans in the pancreas, leading to insulin deficiency. This type can be further classified as immune-mediated or idiopathic. The majority of type 1 diabetes is of the immune-mediated nature, in which beta cell loss is a T-cello-mediated autoimmune attack. There is no known preventive measure against type 1 diabetes, which causes approximately 10% of diabetes mellitus cases in North America and Europe. Most affected people are otherwise healthy and of a healthy weight when onset occurs. Sensitivity and responsiveness to insulin are usually normal, especially in the early stages. Type 1 diabetes can affect children or adults, but was traditionally termed "juvenile diabetes" because a majority of these diabetes cases were in children.

Type 2 diabetes
Type 2 diabetes mellitus is characterized by insulin resistance, which may be combined with relatively reduced insulin secretion. The defective responsiveness of body tissues to insulin is believed to involve the insulin receptor. However, the specific defects are not known. Diabetes mellitus cases due to a known defect are classified separately. Type 2 diabetes is the most common type.

In the early stage of type 2, the predominantly abnormality is reduced insulin sensitivity. At this stage, hyperglycemia can be reversed by a variety of measures and medications that improve insulin sensitivity or reduce glucose production by the liver.

Gestational diabetes
Gestational diabetes mellitus (GDM) resembles type 2 diabetes in several respects, involving a combination of relatively inadequate insulin secretion and responsiveness. It occurs in about 2-5% of all pregnancies and may improve or disappear after delivery. Gestational diabetes is fully treatable, but requires careful medical supervision throughout the pregnancy. About 20-50% of affected women develop type 2 diabetes later in life.

Though it may be transient, untreated gestational diabetes can damage the health of the fetus or mother. Risks to the baby include macrosomia (high birth weight), congenital cardiac and central nervous system anomalities, and skeletal muscle malformations. Increased fetal insulin may inhabit fetal surfactant production and cause respiratory distress syndrome. Hyperbilirubinemia may result from red blood cell destruction. In severe cases, perinatal death may occur, most commonly as a result of poor placental perfusion due to vascular impairment. Labor induction may be indicated with decreased placental function. A Caesarean section may be performed if there is marked fetal distress or an increased risk of injury associated with macrosomia, such as shoulder dystocia.

Other types
Prediabetes indicates a condition that occurs when a person's blood glucose levels are higher than normal but not high enough for a diagnosis of type 2 DM. Many people destined to develop type DM 2 spend many years in a state of prediabetes which has been termed "America's largest healthcare epidemic."

Latent autoimmune diabetes of adults (LADA) is a condition in which type 1 DM develops in adults. Adults with LADA are frequently initially misdiagnosed as having type 2 DM, based on age rather than etiology.

Signs and symptoms
The classic symptoms of untreated diabetes are loss of weight, polyuria (frequent urination), polydipsia (increased thirst) and polyphagia (increased hunger). Symptoms may develop rapidly (weeks or months) in type 1 diabetes, while they usually develop much more slowly and may be subtle or absent in type 2 diabetes.

Prolonged high blood glucose can cause glucose absorption in the lens of the eye, which leads to changes in its shape, resulting in vision changes. Blurred vision is a common complaint leading to a diabetes diagnosis. A number of skin rashes that can occur in diabetes are collectively known as diabetic dermadromes.

Diabetic emergencies
People (usually with type 1 diabetes) may also present with diabetic ketoacidosis, a state of metabolic dysregulation characterized by the smell of acetone, a rapid, deep breathing kwnon as Kussmaul breathing, nausea, vomiting and abdominal pain, and altered states of consciousness.

A rare but equally severe possibility is hyperosmolar nonketotic state, which is more common in type 2 diabetes and is mainly the result of dehydration.

Complications
All forms of diabetes increase the risk of long-term complications. These typically develop after many years (10-20), but may be the first symptom in those who have otherwise not received a diagnosis before that time. The major long-term complications relate to damage to blood vessels. Diabetes doubles the risk of cardiovascular disease. The main "macrovascular" diseases (related to atherosclerosis of larger arteries) are ischemic heart disease (angina and myocardial infarction), stroke and peripheral vascular disease.

Diabetes also damages the capillaries (causes microangiopathy). Diabetic retinopathy, which affects blood vessel formation in the retina of the eye, can lead to visual symptoms including reduced vision and potentially blindness. Diabetic nephropathy, the impact of diabetes on the kidneys, can lead to scarring changes in the kidney tissue, loss of small or progressively larger amounts of protein in the urine, and eventually chronic kidney disease requiring dialysis.

Another risk is diabetic neuropathy, the impact of diabetes on the nervous system -- most commonly causing numbness, tingling and pain in the feet, and also increasing the risk of skin damage due to altered sensation. Together with vascular disease in the legs, neuropathy contributes to the risk of diabetes-related foot problems (such as diabetic foot ulcers) that can be difficult to treat and occasionally require amputation. As well, proximal diabetic neuropathy causes painful muscle wasting and weakness.

Several studies suggest a link between cognitive deficit and diabetes. Compared to those without diabetes, the research showed that those with the disease have a 1.2 to 1.5-fold greater rate of decline in cognitive function, and are at greater risk.

Causes
The cause of diabetes depends on the type.

Type 1 diabetes is partly inherited, and then triggered by certain infections, with some evidence pointing at Coxsackie B4 virus. A genetic element in individual susceptibility to some of these triggers has been traced to particular HLA genotypes (i.e., the genetic "self" identifiers relied upon by the immune system). However, even in those who have inherited the susceptibility, type 1 DM seems to require an environment trigger. The onset of type 1 diabetes is unrelated to lifestyle.

Type 2 diabetes is due primarily to lifestyle factors and genetics.

Diagnosis
Diabetes mellitus is characterized by recurrent or persistent hyperglycemia, and is diagnosed by demonstrating any one of the following:

• Fasting plasma glucose level = 7.0 mmol/l (126 mg/dl)
• Plasma glucose = 11.1 mmol/l (200 mg/dL) two hours after a 75 g oral glucose load as in a glucose tolerance test
• Symptoms of hyperglycemia and casual plasma glucose = 11.1 mmol/l (200 mg/dl)
• Glylcated hemoglobin (Hb A1C) = 6.5%

Management
Diabetes mellitus is a chronic disease, for which there is no known cure except in very specific situations. Management concentrates on keeping blood sugar levels as close to normal ("euglycemia") as possible, without causing hypoglycemia. This can usually be accomplished with diet, exercise, and use of appropriate medications (insulin in the case of type 1 diabetes; oral medications, as well as possibly insulin, in type 2 diabetes).

Patient education, understanding, and participation is vital, since the complications of diabetes are far less common and less severe in people who have well-managed blood sugar levels. The goal of treatment is an HbA1C level of 6.5%, but should not be lower than that, and may be set higher. Attention is also paid to other health problems that may accelerate the deleterious effects of diabetes. These include smoking, elevated cholesterol levels, obesity, high blood pressure, and lack of regular exercise.

Lifestyle
There are roles for patient education, dietetic support, and sensible exercise, with the goal of keeping both short-term and long-term blood glucose levels within acceptable bounds. In addition, given the associated higher risks of cardiovascular disease, lifestyle modifications are recommended to control blood pressure.

Medications
Metformin is generally recommended as a first line treatment for type 2 diabetes, as there is good evidence that it decreases mortality. Routine use of aspirin, however, has not been found to improve outcomes in uncomplicated diabetes.

Type 1 diabetes is typically treated with a combination of regular and NPH insulin, or synthetic insulin analogs. When insulin is used in type 2 diabetes, a long-acting formulation is usually added initially, while continuing oral medications. Doses of insulin are then increased to effect.

Support
In countries using a general practitioner system, such as the United Kingdom, care may take place mainly outside hospitals, with hospital-based specialist care used only in case of complications, difficult blood sugar control, or research projects. In other circumstances, general practitioners and specialists share care of a patient in a team approach. Home telehealth support can be an effective management technique.

Epidemiology
Globally, as of 2010, an estimated 285 million people had diabetes, with type 2 making up about 90% of the cases. Its incidence is increasing rapidly, and by 2030, this number is estimated to almost double. Diabetes mellitus occurs throughout the world, but is more common (especially type 2) in the more developed countries. The greatest increase in prevalence is, however, expected to occur in Asia and Africa, where most patients will probably be found by 2030. The increase in incidence in developing countries follows the trend of urbanization and lifestyle changes, perhaps most importantly a "Western-style" diet. This has suggested an environmental (i.e., dietary) effect, but there is little understanding of the mechanism(s) at present, though there is much speculation, some of it most compellingly presented.

Sources:

http://en.wikipedia.org/wiki/Diabetes

vehicle insurance

Vehicle insurance (also known as auto insurance, GAP insurance, car insurance, or motor insurance) is insurance purchased for cars, trucks, motorcycles, and other road vehicles. Its primary use is to provide financial protection against physical damage and/or bodily injury resulting from traffic collisions and against liability that could also arise therefrom. The specific terms of vehicle insurance vary with legal regulations in each region. To a lesser degree vehicle insurance may additionally offer financial protection against theft of the vehicle and possibly damage to the vehicle, sustained from things other than traffic collisions.

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.

Vehicle insurance, in the United States and elsewhere, is designed to cover risk of financial liability or the loss of a motor vehicle the owner may face if their vehicle is involved in a collision resulting in property or physical damages. Some states require a motor vehicle owner to carry some minimum level of liability insurance.

Insurance companies provide a motor vehicle owner with an insurance card for the particular coverage term which is to be kept in the vehicle in the event of a traffic collision as proof of insurance. Recently, states have started passing laws that electronic versions of proof of insurance can now be accepted by the authorities.

Coverage generally
Consumers may be protected by different levels of coverage depending on which insurance policy they purchase. Some states require drivers to carry at least liability insurance coverage to ensure that their drivers can cover the cost of damage to other people or property in the event of an accident. Some states, such as Wisconsin, have more flexible "proof of financial responsibility" requirements.

In the United States, automotive liability insurance covers claims against the policy holder and usually any other operator of an insured vehicle, provided they do not live at the same address as the policy holder and are not specifically excluded on the policy. Thus it is necessary, for example, when a young adult reaches driving age that they 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 another person's car you are not necessarily covered under their policy. Non-owners policies are also available. These policies insure drivers on any vehicle they drive, even if it belongs to someone else. 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. These policies are useful for people whose drivers' license has been suspended and they have to have insurance for their license to be reinstated.

Liability coverage
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 impairment to have the right to claim (or sue) under the insured driver's (or first party's) policy. If the third party sues the insured driver, liability coverage also covers court costs and damages that the insured driver may be deemed responsible for.

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 combined 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 into a maximum payment per person and a maximum payment per accident.

The limits are often expressed separated by slashes in the following form: "bodily injury per person"/"bodily injury per accident"/"property damage". For example, California requires this minimum coverage:

• $15,000 for injury/death to one person
• $30,000 for injury/death to more than one person
• $5,000 for damage to property

This would be expressed as "$15,000/$30,000/$5,000".

Another example, in the state of Oklahoma, drivers 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 person's medical bills but will not exceed $50,000 for other people injured in the accident. The insurance company will not pay more than $25,000 for property damage in repairs to the vehicle that the insured one hit.

In the state of Indiana, the minimum liability limits are $25,000/$50,000/$10,000, so there is a greater property damage exposure for only carrying the minimum limits.

Rental coverage
Generally, liability coverage purchased through a private insurer extends to rental cars. 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 rental transaction is processed using one of their cards. These benefits are restrictive in terms of the types of vehicles covered.

Full coverage
Full coverage is the term commonly used to refer to the combination of comprehensive and collision coverages (liability is generally also implied). The term full coverage is actually a misnomer because, even within traditional full coverage insurance, there are many types of coverage, and many optional amounts of each. "Full coverage" is a layman's misnomer that often results in drivers and vehicle owners being woefully underinsured. Most responsible insurance agents or brokers do not use this term when working with their clients.

One common misconception in the United States is that vehicles that are financed on credit through a bank or credit union are required to have "full" coverage in order for the financial institution to cover their losses in case of an accident. While most states do require additional coverage to be purchased, some such as Pennsylvania only require Comprehensive and Collision to be purchased in addition to liability and not "full" coverage. Vehicles purchased with cash or paid off by the owner are generally required to only carry liability. In some cases, vehicles financed through a "buy-here-pay-here" car dealership‒in which the consumer (generally those with poor credit) finances a car and pays the dealer directly without a bank‒also only require liability coverage.

Collision
Collision coverage provides coverage for vehicles involved in collisions. Collision coverage is 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 or totaled. 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 the car is paid off.  Collision Damage Waiver (CDW) or Loss Damage Waiver (LDW) is the term used by rental car companies for collision coverage.

Comprehensive
Comprehensive, also known as other than collision, coverage provides coverage, subject to a deductible, for cars 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.

Additionally, the majority of insurance companies list "Acts of God" as an aspect of comprehensive coverage. By definition, it includes any events or occurrences that are beyond human control. For example, a tornado, flood, hurricane, or hail storm would fall under this category.

Uninsured/underinsured motorist coverage
Uninsured/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, the insurance company pays the insured medical bills, then would subrogate from the at-fault party. This coverage is often overlooked and very important. In Colorado, for example, it was estimated in 2007 that 24% of drivers did not carry the state minimum liability limits required by law. Unfortunately, this number goes up significantly during recessions. In some areas, it is estimated that 1 out of every 3 drivers doesn't carry insurance. Usually the limits match the liability limits. Some insurance companies do offer UM/UIM in an umbrella policy.

Some states maintain unsatisfied judgment funds to provide compensation to those who cannot collect damages from uninsured drivers. Typically, the payout is not more than the minimum liability limits and the negligent driver remains responsible for reimbursing the state's fund.

In the United States, the definition of an uninsured/underinsured motorist, and corresponding coverages, are set by state laws. In some states it is mandatory. In the case of underinsured coverage, two different triggers apply: a damages trigger which is based on whether the limits are insufficient to cover the injured party's damages, and a limits trigger which applies when the limits are less than the injured party's limits. According to a 2009 survey by trade association Property Casualty Insurers Association of America, 29 states have a limits trigger while 20 states have a damages trigger. Another variation is whether a particular state requires stacking of policy limits of different vehicles or policies.

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, 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 a 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 auto dealerships as a comparatively low cost add-on to the car loan that provides coverage for the duration of the loan. GAP insurance does not always pay off the full loan value however. These cases include but are not limited to:

1. Any unpaid deliquent payment due at the time of loss
2. Payment deferrals or extensions (commonly called skips or skip a payment)
3. Refinancing of the vehicle loan after the policy was purchased
4. Late fees or other administrative fees assessed after loan commencement

Therefore, it is important for a policy holder to understand that they may still owe on the loan even though the GAP policy was purchased. Failure to understand this can result in the lender continuing their legal remedies to collect the balance and the potential of damaged credit.

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 $5,000, 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 $5,000. 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 $5,000, and then receive $5,000 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
Vehicle 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
Personal items in a vehicle that are damaged due to an accident would not be 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. However, some insurance companies will cover unattached GPS devices intended for automobile use.

Sources:

http://en.wikipedia.org/wiki/Vehicle_insurance
http://en.wikipedia.org/wiki/Vehicle_insurance_in_the_United_States

humidity

Humidity is the amount of water vapor in the air. Water vapor is the gas phase of water and is invisible. Humidity indicates the likelihood of precipitation, dew, or fog. Higher humidity reduces the effectiveness of sweating in cooling the body by reducing the rate of evaporation of moisture from the skin. This effect is calculated in a heat index table or humidex, used during summer weather.

There are three main measurements of humidity: absolute, relative, and specific. Absolute humidity is the water content of air. Relative humidity, expressed as a percent, measures the current absolute humidity relative to the maximum for that temperature. Specific humidity is a ratio of the water vapor content of the mixture to the total air content on a mass basis.

Measurement
There are various devices used to measure and regulate humidity. A device used to measure humidity is called a psychrometer or hygrometer. A humidistat is a humidity-triggered switch, often used to control a dehumidifier.

Humidity is also measured on a global scale using remotely placed satellites. These satellites are able to detect the concentration of water in the troposphere at altitudes between 4 and 12 kilometers. Satellites that can measure water vapor have sensors that are sensitive to infrared radiation. Water vapor specifically absorbs and re-radiates radiation in this spectral band. Satellite water vapor imagery plays an important role in monitoring climate conditions (like the formation of thunderstorms) and in the development of future weather forecasts.

Climate
While humidity itself is a climate variable, it also interacts strongly with other climate variables. The humidity is affected by winds and by rainfall. At the same time, humidity affects the energy budget and thereby influences temperatures in two major ways. First, water vapor in the atmosphere contains "latent" energy. During transpiration or evaporation, this latent heat is removed from surface liquid, cooling the earth's surface. This is the biggest non-radiative cooling effect at the surface. It compensates for roughly 70% of the average net radiative at the surface. Second, water vapor is the most important of all greenhouse gases. Water vapor, like a green lens that allows green light to pass through it but absorbs red light, is a "selective absorber". Along with other greenhouse gases, water vapor is transparent to most solar energy, as you can literally see. But it absorbs the infrared energy emitted (radiated) upward by the earth's surface, which is the reason that humid areas experience very little nocturnal cooling but dry desert regions cool considerably at night. This selective absorption causes the greenhouse effect. It raises the surface temperature substantially above its theoretical radiative equilibrium temperature with the sun, and water vapor is the cause of more of this warming that any other greenhouse gas.

The most humid cities on earth are generally located closer to the equator, near coastal regions. Cities in South and Southeast Asia are among the most humid. Kuala Lumpur and Singapore have very high humidity all year round because of their proximity to water bodies and the equator and oftentimes overcast weather. some places experience extreme humidity during their rainy seasons combined with warmth giving the feel of a lukewarm sauna, such as Kolkata, Chennai, and Cochin in India, and Lahore in Pakistan. Sukkur city located on the Indus River in Pakistan has some of the highest and most uncomfortable dew point in the country frequently exceeding 30° C (86 °F) in the Monsoon season. High temperatures couple up with bizarre dew point to create heat index in excess of 65 °C (149 °F). Darwin, Australia experiences an extremely humid wet season from December to April. Shanghai and Hong Kong in China also have an extreme humid period in their summer months. During the South-west and North-east Monsoon seasons (respectively, late May to September and November to March), expect heavy rains and a relatively high humidity post-rainfall. Outside the monsoon seasons, humidity is high (in comparison to countries North of the Equator), but completely sunny days abound. In cooler places such as Northern Tasmania, Australia, high humidity is experienced all year due to the ocean between mainland Australia and Tasmania. In the summer the hot dry air is absorbed by this ocean and the temperature rarely climbs above 35 °C (95 °F).

In the United States, the most humid cities, strictly in terms of relative humidity, are Forks and Olympia, Washington. This fact may come as a surprise to many, as the climate in this region rarely exhibits the discomfort usually associated with high humidity. This is because high dew points play a more significant role than relative humidity in discomfort, and so the air in these western cities usually does not feel "humid" as a result. In general, dew points are much lower in the Western U.S. than those in the Eastern U.S..

The highest dew points in the U.S. are found in coastal Florida and Texas. When comparing Key West and Houston, two of the most humid cities from those states, coastal Florida seems to have the higher dew points on average. However, Houston lacks the coastal breeze present in Key West, and, as a much larger city, it suffers from the urban heat island effect. A dew point of 88 °F (31 °C) was recorded in Moorhead, Minnesota on July 19, 2011, with a heat index of 133.5, although dew points over 80 °F (27 °C) are are there. The U.S. city with the lowest annual humidity is Las Vegas, Nevada, averaging 39% for a high and 21% as a low.

Air density and volume
Humidity depends on water vaporization and condensation, which, in turn, mainly depends on temperature. Therefore, when applying more pressure to a gas saturated with water, all components will initially decrease in volume approximately according to the ideal gas law. However, some of the water will condense until returning to almost the same humidity as before, giving the resulting total volume deviating from what the ideal gas law predicted. Conversely, decreasing temperature would also make some water condense, again making the final volume deviate from predicted by the ideal gas law. Therefore, gas volume may alternatively be expressed as the dry volume, excluding the humidity content. This fraction more accurately follows the ideal gas law. On the contrary the saturated volume is the volume a gas mixture would have if humidity was added to it until saturation (or 100% relative humidity).

Humid air is less dense than dry air because a molecule of water (M ≈ 18 u) is less massive than either a molecule of nitrogen (M ≈ 28 u) or a molecule of oxygen (M ≈ 32 u). About 78% of the molecules in dry air are nitrogen (N₂). Another 21% of the molecules in dry air are oxygen (O₂). The final 1% of dry air is a mixture of other gases.

For any gas, at a given temperature and pressure, the number of molecules present in a particular volume is constant -- see ideal gas law. So when water molecules (vapor) are introduced into that volume of dry air, the number of air molecules in the volume must decrease by the same number, if the temperature and pressure remain constant. (The addition of water molecules, or any other molecules, to a gas, without removal of an equal number of other molecules, will necessarily require a change in temperature, pressure, or total volume; that is, a change in at least one of these three parameters. If temperature and pressure remain constant, the volume increases, and the dry air molecules that were displaced will initially move out into the additional volume, after which the mixture will eventually become uniform through diffusion.) Hence the mass per unit volume of the gas -- its density -- decreases.

Effects
Animals and plants
Humidity is one of the fundamental abiotic factors that defines any habitat, and is a determinant of which animals and plants can thrive in a given environment.

The human body dissipates heat through perspiration and its evaporation. Heat convection to the surrounding air, and thermal radiation are the primary modes of heat transport from the body. Under conditions of high humidity, the rate of evaporation of sweat from the skin decreases. Also, if the atmosphere is as warm as or warmer than the skin during times of high humidity, blood brought to the body surface cannot dissipate heat by conduction to the air, and a condition called hyperpyrexia results. With so much blood going to the external surface of the body, relatively less goes to the active muscles, the brain and other internal organs. Physical strength declines, and fatigue occurs sooner than it would otherwise. Alertness and mental capacity also may be affected, resulting in heat stroke or hyperthermia.

Human comfort
Humans are sensitive to humid air because the human body uses evaporative cooling as the primary mechanism to regulate temperature. Under humid conditions, the rate at which perspiration evaporates on the skin is lower than it would be under arid conditions. Because humans perceive the rate of heat transfer from the body rather than temperature itself, we feel warmer when the relative humidity is high than when it is low.

Some people experience difficulty breathing in high humidity environments. Some cases may possibly be related to respiratory conditions such as asthma, while others may be the product of anxiety. Sufferers will often hyperventilate in response, causing sensations of numbness, faintness, and loss of concentration, among others.

Building construction
Traditional building designs typically had week insulation, and it allowed air moisture to flow freely between the interior and exterior. The energy-efficient, heavily-sealed architecture introduced in the 20th century also sealed off the movement of moisture, and this has resulted in a secondary problem of condensation forming in and around walls, which encourages the development of mold and mildew. Additionally, buildings with foundations not properly sealed will allow water to flow through the walls due to capillary action of pores found in masonry products. Solutions for energy-efficient buildings that avoid condensation are a current topic of architecture.

Sources:

http://en.wikipedia.org/wiki/Humidity

early-onset alzheimer's disease

Early-onset Alzheimer's disease, also called early-onset Alzheimer's or early-onset AD, is the term used for cases of Alzheimer's disease diagnosed before the age of 65. It is an uncommon form of Alzheimer's, accounting for only 5-10% of all Alzheimer's cases. Approximately 13% of the cases of early-onset Alzheimer's are Familial Alzheimer's disease, where a genetic predisposition leads to the disease. The other incidences of early-onset Alzheimer's, however, share the same traits as the 'late onset' form commonly referred to as "Alzheimer's disease", and little is understood about how it starts.

Non-Familial early onset Alzheimer's can develop in people who are in their thirties or forties, but that is extremely rare. The majority of people with early-onset Alzheimer's are in their fifties or early sixties.

Familial Alzheimer's disease
Familial Alzheimer's disease (FAD) or Early-onset Familial Alzheimer's disease (EOFAD) is an uncommon form of Alzheimer's disease that usually strikes earlier in life, defined as before the age of 65 (usually between 50 and 65 years of age, but can be early as 15) and is inherited in an autosomal dominant fashion, identified by genetics and other characteristics such as the age of onset. It accounts for approximately half the cases of early-onset Alzheimer's disease. Familial AD requires the patient to have at least one first degree relative with a history of AD.

Clinical features
Alzheimer's disease (AD) is the most common cause of dementia and usually occurs in old age. It is invariably fatal, generally within ten years of the first signs. Early signs of AD include memory loss, particularly in remembering recent events and the names of people and things. As the disease progresses the patient exhibits more serious problems, becoming subject to mood swings and unable to perform complex activities such as driving. In the latter stages they forget how to do simple things such as brushing their hair and then require full-time care.

Genetics
Familial Alzheimer's disease is caused by a mutation in one of at least 3 genes: presenlin 1, presenlin 2, and amyloid precursor protein (APP). Other gene mutations are in study.

Impact of Early-onset Alzheimer's
Early-onset Alzheimer's disease can have devastating effects on the careers, caretakers, and family members of patients.

As many patients are in the age range common to those raising children, patient's children who are not full grown suffer physically and emotionally as their parents are no longer able to care for them.

Those who are working lose their ability to perform their jobs competently, and are forced into early retirement. When this can be predicted, employees must discuss their future with their employers and the loss of skills they expect to face.

Those who are forced to retire early may not have access to the full rage of benefits available to those who retire at the minimum age set by the government.

With some jobs, a mistake may have devastating consequences on a large number of people, and cases have been reported in which a person with early-onset Alzheimer's who is unaware of their condition has caused distress.

People with Alzheimer's may also lose their ability to take care of their own needs, such as money management.

Sources:

http://en.wikipedia.org/wiki/Early-onset_Alzheimer's_disease

alzheimer's disease

Alzheimer's disease (AD), also known in medical literature as Alzheimer disease, is the most common form of dementia.  There is no cure for the disease, which worsens as it progresses, and eventually leads to death. It was first described by German psychiatrist and neuropathologist Alois Alzheimer in 1906 and was named after him. Most often, AD is diagnosed in people over 65 years of age, although the less-prevalent early-onset Alzheimer's can occur much earlier. In 2006, there were 26.6 million sufferers worldwide. Alzheimer's is predicted to affect 1 in 85 people globally by 2050.

Although Alzheimer's disease develops differently for every individual, there are many common symptoms. Early symptoms are often mistakenly thought to be 'age-related' concerns, or manifestations of stress. In the early stages, the most common symptom is difficulty in remembering recent events. When AD is suspected, the diagnosis is usually confirmed with tests that evaluate behavior and thinking abilities, often followed by a brain scan if available. As the disease advances, symptoms can include confusion, irritability, aggression, mood swings, trouble with language, and long-term memory loss. As the sufferer declines they often withdraw from family and society. Gradually, bodily functions are lost, ultimately leading to death. Since the disease is different for each individual, predicting how it will affect the person is difficult. AD develops for an unknown and variable amount of time before becoming fully apparent, and it can progress undiagnosed for years. On average, the life expectancy following diagnosis is approximately seven years. Fewer than three percent of individuals live more than fourteen years after diagnosis.

The cause and progress of Alzheimer's disease are not well understood. Research indicates that the disease is associated with plaques and tangles in the brain. Current treatments only help with the symptoms of the disease. There are no available treatments to stop or reverse the progression of the disease. Mental stimulation, exercise, and a balanced diet have been suggested as ways to delay cognitive symptoms (though not brain pathology) in healthy older individuals, but there is no conclusive evidence supporting an effect.

Because AD cannot be cured and is degenerative, the sufferer relies on others for assistance. The role of the main caregiver is often taken by the spouse or a close relative. Alzheimer's disease is known for placing a great burden on caregivers; the pressures can be wide-ranging, involving social, psychological, physical, and economic elements of the caregiver's life. In developed societies, AD is one of the most costly diseases to society.

Characteristics
The disease course is divided into four stages, with progressive patterns of cognitive and functional impairments.

Pre-dementia
The first symptoms are often mistakenly attributed to ageing or stress. Detailed neuropsychological testing can reveal mild cognitive difficulties up to eight years before a person fulfills the clinical criteria for diagnosis of AD. These early symptoms can affect the most complex daily living activities. The most noticeable deficit is memory loss, which shows up as difficulty in remembering recently learned facts and inability to acquire new information.

Subtle problems with the executive functions of attentiveness, planning, flexibility, and abstract thinking, or impairments in semantic memory (memory of meanings, and concept relationships) can also be symptomatic of the early stages of AD. Apathy can be observed at this stage, and remains the most persistent neuropsychiatric symptom throughout the course of the disease. Depressive symptoms, irritability and reduced awareness of subtle memory difficulties also occur commonly. The preclinical stage of the disease has also been termed mild cognitive impairment, but whether this term corresponds to a different diagnostic stage or identifies the first step of AD is a matter of dispute.

Early
In people with AD the increasing impairment of learning and memory eventually leads to a definitive diagnosis. In a small portion of them, difficulties of language, executive functions, perception (agnosia), or execution of movements (apraxia) are more prominent than memory problems. AD does not affect all memory capacities equally. Older memories of the person's life (episodic memory), facts learned (semantic memory), and implicit memory (the memory of the body on how to do things, such as using a fork to eat) are affected to a lesser degree than new facts or memories.

Language problems are mainly characterized by a shrinking vocabulary and decreased word fluency, which lead to a general impoverishment of oral and written language. In this stage, the person with Alzheimer's is usually capable of communicating basic ideas adequately. While performing fine motor tasks such as writing, drawing or dressing, certain movement coordination and planning difficulties (apraxia) may be present but they are commonly unnoticed. As the disease progresses, people with AD can often continue to perform many tasks independently, but may need assistance or supervision with the most cognitively demanding activities.

Moderate
Progressive deterioration eventually hinders independence, with subjects being unable to perform most common activities of daily living. Speech difficulties become evident due to an inability to recall vocabulary, which leads to frequent incorrect word substitutions (paraphasias). Reading and writing skills are also progressively lost. Complex motor sequences become less coordinated as time passes and AD progresses, so the risk of falling increases. During this phase, memory problems worsen, and the person may fail to recognize close relatives. Long-term memory, which was previously intact, becomes impaired.

Behavioral and neuropsychiatric changes become more prevalent. Common manifestations are wandering irritability and labile affect, leading to crying, outbursts of unpremeditated aggression, or resistance to caregiving. Sundowning can also appear. Approximately 30% of people with AD develop illusionary misidentifications and other delusional symptoms. Subjects also lose insight of their disease process and limitations (anosognosia). Urinary incontinence can develop. These symptoms create stress for relatives and caretakers, which can be reduced by moving the person from home care to other long-term care facilities.

Advanced
During the final stage of AD, the person is completely dependent upon caregivers. Language is reduced to simple phrases or even single words, eventually leading to complete loss of speech. Despite the loss of verbal language abilities, people can often understand and return emotional signals. Although aggressiveness can still be present, extreme apathy and exhaustion are more common results. People with AD will ultimately not be able to perform even the simplest tasks without assistance. Muscle mass and mobility deteriorate to the point where they are bedridden, and they lose the ability to feed themselves. AD is a terminal illness, with the cause of death typically being an external factor, such as infection of pressure ulcers or pneumonia, not the disease itself.

Cause
The cause for most Alzheimer's cases is essentially unknown (except for 1% to 5% of cases where genetic differences have been identified). Several competing hypotheses exist trying to explain the cause of the disease: cholinergic hypothesis, amyloid hypothesis, tau hypothesis, etc.

Management
There is no cure for Alzheimer's disease; available treatments offer relatively small symptomatic benefit but remain palliative in nature. Current treatments can be divided into pharmaceutical, psychosocial and caregiving.

Prognosis
The early stages of Alzheimer's disease are difficult to diagnose. A definitive diagnosis is usually made once cognitive impairment compromises daily living activities, although the person may still be living independently. The symptoms will progress from mild cognitive problems, such as memory loss through increasing stages of cognitive and non-cognitive disturbances, eliminating any possibility of independent living, especially in the late stages of the disease.

Life expectancy of the population with the disease is reduced. The mean life expectancy following diagnosis is approximately seven years. Fewer than 3% of people live more than fourteen years. Disease features significantly associated with reduced survival are an increased severity of cognitive impairment, decreased functional level, history of falls, and disturbances in the neurological examination. Other coincident diseases such as heart problems, diabetes or history of alcohol abuse are also related with shortened survival. While the earlier the age at onset the higher the total survival years, life expectancy is particularly reduced when compared to the healthy population among those who are younger. Men have a less favorable survival prognosis then women.

The disease is the underlying cause of death in 70% of all cases. Pneumonia and dehydration are the most frequent immediate causes of death, while cancer is a less frequent cause than in the general population.

Safety and culture
Social costs
Dementia, and specifically Alzheimer's disease, may be among the most costly diseases for society in Europe and the United States, while the cost in other countries such as Argentina, or South Korea, is also high and rising. The cost will probably increase with the ageing of society, becoming an important social problem. AD-associated costs include direct medical costs such as nursing home care, direct medical costs such as nursing home care, direct non-medical costs such as in-home day care, and indirect costs such as lost productivity of both patient and caregiver. Numbers vary between studies but dementia costs worldwide have been calculated around $160 billion, while costs of Alzheimer's disease in the United States may be $100 billion each year.

The greatest origin of costs for society is the long-term care by health are professionals and particularly institutionalization, which corresponds to two-thirds of the total costs for society. The costs of living at home is also very high, especially when informal costs for the family, such as caregiving time and caregiver's lost earnings, are taken into account.

Costs increase with dementia severity and the presence of behavioral disturbances, and are related to the increased caregiving time required for the provision of physical care. Therefore any treatment that slows cognitive decline, delays institutionalization or reduces caregivers' hours will have economic benefits. Economic evaluations of current treatments have shown positive results.

Caregiving burden
The role of the main caregiver is often taken by the spouse or a close relative. Alzheimer's disease is known for placing a great burden on caregivers which includes social, psychological, physical or economic aspects. Home care is usually preferred by people with AD and their families. This option also delays or eliminates the need for more professional and costly levels of care. Nevertheless two-thirds of nursing home residents have dementias.

Dementia caregivers are subject to high rates of physical and mental disorders. Factors associated with greater psychosocial problems of the primary caregivers include having an affected person at home, the carer being a spouse, demanding behaviors of the cared person such as depression, behavioral disturbances, hallucinations, sleep problems or walking disruptions and social isolation. Regarding economic problems, family caregivers often give up time from work to spend 47 hours per week on average with the person with AD, while the costs of caring for them are high. Direct and indirect costs of caring for an Alzheimer's patient average between $18,000 and $77,500 per year in the United States, depending on the study.

Sources:

http://en.wikipedia.org/wiki/Alzheimer's_disease