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
Sunday, August 4, 2013
Thursday, August 1, 2013
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
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
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
Wednesday, June 19, 2013
existentialism
Existentialism is a term applied to the work of a number of late 19th- and 20th-century philosophers who, despite profound doctrinal differences, shared the belief that their philosophical thinking begins with the human subject - not merely the thinking subject, but the acting, feeling, living human individual. In existentialism, the individual's starting point is characterized by what has been called the “existential attitude”, or a sense of disorientation and confusion in the face of an apparently meaningless or absurd world. Many existentialists have also regarded traditional systematic or academic philosophies, in both style and content, as too abstract and remote from concrete human experience.
Søren Kierkegaard and Friedrich Nietzsche were two of the first philosophers considered fundamental to the existentialist movement, though neither used the term “existentialism” and it is unclear whether they would have supported the existentialism of the 20th century. They focus on subjective human experience rather than the objective truths of mathematics and science, which they believed were too detached or observational to truly get at the human experience. Like Pascal, they were interested in people's quiet struggle with the apparent meaninglessness of life and the use of diversion to escape from boredom.
Concepts
Existence precedes essence
A central proposition of existentialism is that existence precedes essence, which means that the most important consideration for the individual is the fact that he or she is an individual - an independently acting and responsible conscious being (“existence”) - rather than what labels, roles, stereotypes, definitions, or other preconceived categories the individual fits (“essence”). The actual life of the individual is what constitutes what could be called his or her “true essence” instead of there being an arbitrarily attributed essence used by others to define him or her. Thus, human beings, through their own consciousness, create their own values and determine a meaning to their life.
The Absurd
The notion of the Absurd contains the idea that there is no meaning to be found in the world beyond what meaning we give it. This meaninglessness also encompasses the amorality or “unfairness” of the world. This contrasts with the notion that “bad things don't happen to good people”; to the world, metaphorically speaking, there is no such thing as a good or a bad person; what happens happens, and it may just as well happen to a “good” person as to a “bad” person.
Because of the world's absurdity, at any point in time, anything can happen to anyone, and a tragic event could plummet someone into direct confrontation with the Absurd.
Facticity
Facticity is a concept defined by Sartre in Being and Nothingness as the “in-itself”, of which humans are in the mode of not being. This can be more easily understood when considering it in relation to the temporal dimension of the past: one's past is what one is in the sense that it co-constitutes oneself. However, to stay that one is only one's past would be to ignore a significant part of reality (the present and the future), while saying that one's past is only what one was, would entirely detach it from them now. A denial of one's own concrete past constitutes an inauthentic lifestyle, and the same goes for all other kinds of facticity (having a body - e.g., one that does not allow a person to run faster than the speed of sound - identity, values, etc.)
Facticity is both a limitation and a condition of freedom. It is a limitation in that a large part of one's facticity consists of things one couldn't have chosen (birthplace, etc.), but a condition in the sense that one's values most likely will depend on it. However, even though one's facticity is “set in stone” (as being past, for instance), it cannot determine a person: The value ascribed to one's facticity is still ascribed to it freely by that person. As an example, consider two men, one of whom has no memory of his past and the other remembers everything. They both have committed many crimes, but the first man, knowing nothing about this, leads a rather normal life while the second man, feeling trapped by his own past, continues a life of crime, blaming his own past for “trapping” him in his life There is nothing essential about his committing crimes, but he ascribes this meaning to his past.
However, to disregard one's facticity when one, in the continual process of self-making, projects oneself into the future, would be to put oneself in denial of oneself, and would thus be inauthentic. In other words, the origin of one's projection will still have to be one's facticity, although in the mode of not being it (essentially). Another aspect of facticity is that it entails angst, both in the sense that freedom “produces” angst when limited by facticity, and in the sense that the lack of the possibility of having facticity to “step in” for one to take responsibility for something one has done also produces angst.
Authenticity
The theme of authentic existence is common to many existentialist thinkers. It is often taken to mean that one has to “create oneself” and then lie in accordance with this self. What is meant by authenticity is that in acting, one should act as oneself, not as “one” acts or as “one's genes” or any other essence requires. The authentic act is one that is in accordance with one's freedom. Of course, as a condition of freedom is facticity, but not to the degree that this facticity can in any way determine one's choices (in the sense that one could blame one's background for making the choice one made) . The role of facticity in relation to authenticity involves letting one's actual values come into play when one makes a choice (instead of, like Kierkegaard's Aesthete, “choosing” randomly), so that one also takes responsibility for the act instead of choosing either-or without allowing the options to have different values.
In contrast to this, the inauthentic is the denial to live in accordance with one's freedom. this can take many forms, from pretending choices are meaningless or random, through convincing oneself that some form of determinism is true, a sort of “mimicry” where one acts as “one should”. How “one” should act is often determined by an image one has of how one such of oneself (say, a bank manager, lion tamer, prostitute, etc.) acts. This image usually corresponds to some sort of social norm, but this does not mean that all acting in accordance with social norms is inauthentic: The main point is the attitude that one takes to one's own freedom and responsibility, and the extent to which one acts in accordance with this freedom.
Angst
“Existential angst”, sometimes called dread anxiety, or anguish, is a term that is common to many existentialist thinkers. It is generally held to be a negative feeling arising from the experience of human freedom and responsibility. this archetypal example is the experience one has when standing on a cliff where one not only fears falling of it, but also dreads the possibility of throwing oneself off. In this experience that “nothing is holding me back”, one senses that the lack of anything that predetermines one to either throw oneself or to a stand still, and one experiences one's own freedom.
It can also be seen in relation to the previous point how angst is before nothing, and this is what sets it apart from fear that has an object. While in the case of fear, one can take definite measures to remove the object of fear, in the case of angst, no such “constructive” measures are possible. the use of the word “nothing” in this context relates both to the inherent insecurity about the consequences of one's actions, and to the fault that, in experiencing one's freedom as angst, one also realizes that one will be fully responsible for these consequences, there is no thing in a person (his or genes, for instance) that acts in her or his stead, and that he or she can “blame” if something goes wrong. Therefore, not every choice is perceived as having dreadful consequences (and, it can be claimed, human lives would be unbearable if every choice facilitated dread). However, this doesn't change the fact that freedom remains a condition of every action. Angst is often described as a drama an adolescent troubles with their drawing developmental years.
Despair
Despair, in existentialism, is generally defined as a loss of hope. More specifically, it is a loss of hope in reaction to a breakdown in one or more of the defining qualities of one's self or identity. If a person is invested in being a particular thing, such as a bus driver or an upstanding citizen, and then finds his being-thing compromised, he would normally be found in a state of despair - a hopeless state. For example, a singer who loses her ability to sing may despair if she has nothing else to fall back on, nothing on which to rely for her identity. She finds herself unable to be what defined her being.
What sets the existentialist notion of despair apart from the conventional definition is that existentialist despair is a state one is in even when he isn't overtly in despair. So long as a person's identity depends on qualities that can crumble, he is considered to be in perpetual danger.
Opposition to positivism and rationalism
Existentialists oppose definitions of human beings as primarily rational, and, therefore, oppose positivism and rationalism. Existentialism asserts that people actually make decisions based on subjective meaning rather than purely rationally. The rejection of reason as the source of meaning is a common theme of existentialist thought, as is the focus on the feelings of anxiety and dread that we feel in the face of our own radical freedom and our awareness of death. Kierkegaard advocated rationality as a means to interact with the objective world (e.g., in the natural sciences), but when it comes to existential problems, reason is sufficient: “Human reason has boundaries.”
Like Kierkegaard, Sartre saw problems with rationality, calling it a form of “bad faith”, an attempt by the self to impose structure on a world of phenomena - “the Other” - that is fundamentally irrational and random. According to Sartre, rationality and other forms of bad faith hinder people from finding meaning in freedom. To try to suppress their feelings of anxiety and dread, people confine themselves within everyday experience, Sartre asserts, thereby relinquishing their freedom and acquiescing to being possessed in one form or another by “the Look” of “the Other” (i.e., possessed by another person - or at least one's idea of that person).
Sources:
http://en.wikipedia.org/wiki/Existentialism
Søren Kierkegaard and Friedrich Nietzsche were two of the first philosophers considered fundamental to the existentialist movement, though neither used the term “existentialism” and it is unclear whether they would have supported the existentialism of the 20th century. They focus on subjective human experience rather than the objective truths of mathematics and science, which they believed were too detached or observational to truly get at the human experience. Like Pascal, they were interested in people's quiet struggle with the apparent meaninglessness of life and the use of diversion to escape from boredom.
Concepts
Existence precedes essence
A central proposition of existentialism is that existence precedes essence, which means that the most important consideration for the individual is the fact that he or she is an individual - an independently acting and responsible conscious being (“existence”) - rather than what labels, roles, stereotypes, definitions, or other preconceived categories the individual fits (“essence”). The actual life of the individual is what constitutes what could be called his or her “true essence” instead of there being an arbitrarily attributed essence used by others to define him or her. Thus, human beings, through their own consciousness, create their own values and determine a meaning to their life.
The Absurd
The notion of the Absurd contains the idea that there is no meaning to be found in the world beyond what meaning we give it. This meaninglessness also encompasses the amorality or “unfairness” of the world. This contrasts with the notion that “bad things don't happen to good people”; to the world, metaphorically speaking, there is no such thing as a good or a bad person; what happens happens, and it may just as well happen to a “good” person as to a “bad” person.
Because of the world's absurdity, at any point in time, anything can happen to anyone, and a tragic event could plummet someone into direct confrontation with the Absurd.
Facticity
Facticity is a concept defined by Sartre in Being and Nothingness as the “in-itself”, of which humans are in the mode of not being. This can be more easily understood when considering it in relation to the temporal dimension of the past: one's past is what one is in the sense that it co-constitutes oneself. However, to stay that one is only one's past would be to ignore a significant part of reality (the present and the future), while saying that one's past is only what one was, would entirely detach it from them now. A denial of one's own concrete past constitutes an inauthentic lifestyle, and the same goes for all other kinds of facticity (having a body - e.g., one that does not allow a person to run faster than the speed of sound - identity, values, etc.)
Facticity is both a limitation and a condition of freedom. It is a limitation in that a large part of one's facticity consists of things one couldn't have chosen (birthplace, etc.), but a condition in the sense that one's values most likely will depend on it. However, even though one's facticity is “set in stone” (as being past, for instance), it cannot determine a person: The value ascribed to one's facticity is still ascribed to it freely by that person. As an example, consider two men, one of whom has no memory of his past and the other remembers everything. They both have committed many crimes, but the first man, knowing nothing about this, leads a rather normal life while the second man, feeling trapped by his own past, continues a life of crime, blaming his own past for “trapping” him in his life There is nothing essential about his committing crimes, but he ascribes this meaning to his past.
However, to disregard one's facticity when one, in the continual process of self-making, projects oneself into the future, would be to put oneself in denial of oneself, and would thus be inauthentic. In other words, the origin of one's projection will still have to be one's facticity, although in the mode of not being it (essentially). Another aspect of facticity is that it entails angst, both in the sense that freedom “produces” angst when limited by facticity, and in the sense that the lack of the possibility of having facticity to “step in” for one to take responsibility for something one has done also produces angst.
Authenticity
The theme of authentic existence is common to many existentialist thinkers. It is often taken to mean that one has to “create oneself” and then lie in accordance with this self. What is meant by authenticity is that in acting, one should act as oneself, not as “one” acts or as “one's genes” or any other essence requires. The authentic act is one that is in accordance with one's freedom. Of course, as a condition of freedom is facticity, but not to the degree that this facticity can in any way determine one's choices (in the sense that one could blame one's background for making the choice one made) . The role of facticity in relation to authenticity involves letting one's actual values come into play when one makes a choice (instead of, like Kierkegaard's Aesthete, “choosing” randomly), so that one also takes responsibility for the act instead of choosing either-or without allowing the options to have different values.
In contrast to this, the inauthentic is the denial to live in accordance with one's freedom. this can take many forms, from pretending choices are meaningless or random, through convincing oneself that some form of determinism is true, a sort of “mimicry” where one acts as “one should”. How “one” should act is often determined by an image one has of how one such of oneself (say, a bank manager, lion tamer, prostitute, etc.) acts. This image usually corresponds to some sort of social norm, but this does not mean that all acting in accordance with social norms is inauthentic: The main point is the attitude that one takes to one's own freedom and responsibility, and the extent to which one acts in accordance with this freedom.
Angst
“Existential angst”, sometimes called dread anxiety, or anguish, is a term that is common to many existentialist thinkers. It is generally held to be a negative feeling arising from the experience of human freedom and responsibility. this archetypal example is the experience one has when standing on a cliff where one not only fears falling of it, but also dreads the possibility of throwing oneself off. In this experience that “nothing is holding me back”, one senses that the lack of anything that predetermines one to either throw oneself or to a stand still, and one experiences one's own freedom.
It can also be seen in relation to the previous point how angst is before nothing, and this is what sets it apart from fear that has an object. While in the case of fear, one can take definite measures to remove the object of fear, in the case of angst, no such “constructive” measures are possible. the use of the word “nothing” in this context relates both to the inherent insecurity about the consequences of one's actions, and to the fault that, in experiencing one's freedom as angst, one also realizes that one will be fully responsible for these consequences, there is no thing in a person (his or genes, for instance) that acts in her or his stead, and that he or she can “blame” if something goes wrong. Therefore, not every choice is perceived as having dreadful consequences (and, it can be claimed, human lives would be unbearable if every choice facilitated dread). However, this doesn't change the fact that freedom remains a condition of every action. Angst is often described as a drama an adolescent troubles with their drawing developmental years.
Despair
Despair, in existentialism, is generally defined as a loss of hope. More specifically, it is a loss of hope in reaction to a breakdown in one or more of the defining qualities of one's self or identity. If a person is invested in being a particular thing, such as a bus driver or an upstanding citizen, and then finds his being-thing compromised, he would normally be found in a state of despair - a hopeless state. For example, a singer who loses her ability to sing may despair if she has nothing else to fall back on, nothing on which to rely for her identity. She finds herself unable to be what defined her being.
What sets the existentialist notion of despair apart from the conventional definition is that existentialist despair is a state one is in even when he isn't overtly in despair. So long as a person's identity depends on qualities that can crumble, he is considered to be in perpetual danger.
Opposition to positivism and rationalism
Existentialists oppose definitions of human beings as primarily rational, and, therefore, oppose positivism and rationalism. Existentialism asserts that people actually make decisions based on subjective meaning rather than purely rationally. The rejection of reason as the source of meaning is a common theme of existentialist thought, as is the focus on the feelings of anxiety and dread that we feel in the face of our own radical freedom and our awareness of death. Kierkegaard advocated rationality as a means to interact with the objective world (e.g., in the natural sciences), but when it comes to existential problems, reason is sufficient: “Human reason has boundaries.”
Like Kierkegaard, Sartre saw problems with rationality, calling it a form of “bad faith”, an attempt by the self to impose structure on a world of phenomena - “the Other” - that is fundamentally irrational and random. According to Sartre, rationality and other forms of bad faith hinder people from finding meaning in freedom. To try to suppress their feelings of anxiety and dread, people confine themselves within everyday experience, Sartre asserts, thereby relinquishing their freedom and acquiescing to being possessed in one form or another by “the Look” of “the Other” (i.e., possessed by another person - or at least one's idea of that person).
Sources:
http://en.wikipedia.org/wiki/Existentialism
Monday, May 20, 2013
greenhouse effect
The greenhouse effect is a process by which thermal radiation from a planetary surface is absorbed by atmospheric greenhouse gases, and is re-radiated in all directions. Since part of this re-radiation is back towards the surface and the lower atmosphere, it results in an elevation of the average surface temperature above what it would be in the absence of the gases.
Solar radiation at the frequencies of visible light largely passes through the atmosphere to warm the planetary surface, which then emits this energy at the lower frequencies of infrared thermal radiation. Infrared radiation is absorbed by greenhouse gases, which in turn re-radiate much of the energy to the surface and lower atmosphere. The mechanism is named after the effect of solar radiation passing through glass and warming a greenhouse, but the way it retains heat is fundamentally different as a greenhouse works by reducing air flow, isolating the warm air inside the structure so that heat is not lost by convection.
If an ideal thermally conductive blackbody was the same distance from the sun as the Earth is, it would have a temperature of about 5.3 °C. However, since the Earth reflects about 30% of the incoming sunlight, this idealized planet's effective temperature (the temperature of a black body that would emit the same amount of radiation) would be about -18 °C. the surface temperature of this hypothetical planet is 33 °C below the Earth's actual surface temperature of approximately 14 °C. The mechanism that produces this difference between the actual surface temperature and the effective temperature is due to the atmosphere and is known as the greenhouse effect.
Earth's natural greenhouse effect makes life as we know it possible. However, human activities, primarily the burning of fossil fuels and clearing of forests, have intensified the natural greenhouse effect, causing global warming.
By their percentage contribution to the greenhouse effect on Earth, the four major gases are:
Greenhouse gas
A greenhouse (sometimes abbreviated GHG) is a gas in an atmosphere that absorbs and emits radiation within the thermal infrared range. This process is the fundamental cause of the greenhouse effect. The primary greenhouse gases in the Earth's atmosphere are water vapor, carbon dioxide, methane, nitrous oxide, and ozone. Greenhouse gases greatly affect the temperature of the Earth; without them, the Earth's surface would average about 33 °C colder than the present average of 14 °C (57 °F).
Since the beginning of the Industrial Revolution, the burning of fossil fuels has contributed to a 40% increase in the concentration of carbon dioxide in the atmosphere from 280ppm to 397ppm, despite the uptake of a large portion of the emissions by various natural "sinks" involved in the carbon cycle. Anthropogenic carbon dioxide (CO²) emissions (i.e., emissions produced by human activities) come from combustion of carbon-based fuels, principally wood, coal, oil, and natural gas.
Greenhouse
A greenhouse is a structural building with different types of covering materials that pass sunlight, usually glass, or plastic. It mainly heats up because the sun warms the ground inside, which then warms the air in the greenhouse. The air continues to heat because it is confined within the greenhouse, unlike the environment outside the greenhouse where warm air near the surface rises and mixes with cooler air aloft. In addition, the warmed structures and plants inside the greenhouse re-radiate some of their thermal energy in the infrared spectrum, to which glass is partly opaque, so some of this energy is also trapped inside the greenhouse. However, this latter process is a minor player compared with the former (convective) process. Thus, the primary heating mechanism of a greenhouse is convection. This can be demonstrated by opening a small window near the roof of a greenhouse; the temperature drops considerably. This principle is the basis of the autovent automatic cooling system. Thus, the glass used for a greenhouse works as a barrier to air flow, and its effect is to trap energy within the greenhouse. The air that is warmed near the ground is prevented from rising indefinitely and flowing away.
Although heat loss due to thermal conduction through the glass and other building materials occurs, net energy (and therefore temperature) increases inside the greenhouse.
Convection
Convection is the concerted, collective movement of ensembles of molecules within fluids (e.g., liquids, gases) and rheids. It is the circulatory motion that occurs in a fluid at a nonuniform temperature owing to the variation of its density and the action of gravity.
Blackbody
A blackbody is an idealized physical body that absorbs all incident electromagnetic radiation, regardless of frequency or angle of incidence.
Real materials emit energy at a fraction ‒ called the emissivity ‒ blackbody energy levels. By definition, a blackbody in thermal equilibrium has an emissivity of ε = 1.0. A source with lower emissivity independent of frequency often is referred to as a gray body. Construction of blackbodies with emissivity as close to one as possible remains a topic of current interest. A white body is one with a "rough surface that reflects all incident rays completely and uniformly in all directions."
Effective temperature
The effective temperature of a body such as a star or planet is the temperature of a blackbody that would emit the same total amount of electromagnetic radiation. Effective temperature is often used as an estimate of a body's temperature when the body's emissivity curve (as a function of wavelength) is not known.
When the star's or planet's net emissivity in the relevant wavelength band is less than unity (less than that of a blackbody), the actual temperature of the body will be higher than the effective temperature. The net emissivity may be low due to surface or atmospheric properties, including the greenhouse effect.
Emissivity
The emissivity of the material (usually written ε or e) is the relative ability of its surface to emit energy by radiation. It is the ratio of energy radiated by a particular material to energy radiated by a blackbody at the same temperature. A true blackbody would have an ε = 1 while any real object would have ε < 1. Emissivity is a dimensionless quantity.
In general, the duller and blacker a material is, the closer its emissivity is to 1. The more reflective a material is, the lower its emissivity. Highly polished silver has an emissivity of about 0.02.
Sources:
http://en.wikipedia.org/wiki/Greenhouse_effect
http://en.wikipedia.org/wiki/Greenhouse_gas
http://en.wikipedia.org/wiki/Greenhouse
http://en.wikipedia.org/wiki/Convection
http://en.wikipedia.org/wiki/Blackbody
http://en.wikipedia.org/wiki/Effective_temperature
http://en.wikipedia.org/wiki/Emissivity
Solar radiation at the frequencies of visible light largely passes through the atmosphere to warm the planetary surface, which then emits this energy at the lower frequencies of infrared thermal radiation. Infrared radiation is absorbed by greenhouse gases, which in turn re-radiate much of the energy to the surface and lower atmosphere. The mechanism is named after the effect of solar radiation passing through glass and warming a greenhouse, but the way it retains heat is fundamentally different as a greenhouse works by reducing air flow, isolating the warm air inside the structure so that heat is not lost by convection.
If an ideal thermally conductive blackbody was the same distance from the sun as the Earth is, it would have a temperature of about 5.3 °C. However, since the Earth reflects about 30% of the incoming sunlight, this idealized planet's effective temperature (the temperature of a black body that would emit the same amount of radiation) would be about -18 °C. the surface temperature of this hypothetical planet is 33 °C below the Earth's actual surface temperature of approximately 14 °C. The mechanism that produces this difference between the actual surface temperature and the effective temperature is due to the atmosphere and is known as the greenhouse effect.
Earth's natural greenhouse effect makes life as we know it possible. However, human activities, primarily the burning of fossil fuels and clearing of forests, have intensified the natural greenhouse effect, causing global warming.
By their percentage contribution to the greenhouse effect on Earth, the four major gases are:
- water vapor, 36-70%
- carbon dioxide, 9-26%
- methane, 4-9%
- ozone, 3-7%
Greenhouse gas
A greenhouse (sometimes abbreviated GHG) is a gas in an atmosphere that absorbs and emits radiation within the thermal infrared range. This process is the fundamental cause of the greenhouse effect. The primary greenhouse gases in the Earth's atmosphere are water vapor, carbon dioxide, methane, nitrous oxide, and ozone. Greenhouse gases greatly affect the temperature of the Earth; without them, the Earth's surface would average about 33 °C colder than the present average of 14 °C (57 °F).
Since the beginning of the Industrial Revolution, the burning of fossil fuels has contributed to a 40% increase in the concentration of carbon dioxide in the atmosphere from 280ppm to 397ppm, despite the uptake of a large portion of the emissions by various natural "sinks" involved in the carbon cycle. Anthropogenic carbon dioxide (CO²) emissions (i.e., emissions produced by human activities) come from combustion of carbon-based fuels, principally wood, coal, oil, and natural gas.
Greenhouse
A greenhouse is a structural building with different types of covering materials that pass sunlight, usually glass, or plastic. It mainly heats up because the sun warms the ground inside, which then warms the air in the greenhouse. The air continues to heat because it is confined within the greenhouse, unlike the environment outside the greenhouse where warm air near the surface rises and mixes with cooler air aloft. In addition, the warmed structures and plants inside the greenhouse re-radiate some of their thermal energy in the infrared spectrum, to which glass is partly opaque, so some of this energy is also trapped inside the greenhouse. However, this latter process is a minor player compared with the former (convective) process. Thus, the primary heating mechanism of a greenhouse is convection. This can be demonstrated by opening a small window near the roof of a greenhouse; the temperature drops considerably. This principle is the basis of the autovent automatic cooling system. Thus, the glass used for a greenhouse works as a barrier to air flow, and its effect is to trap energy within the greenhouse. The air that is warmed near the ground is prevented from rising indefinitely and flowing away.
Although heat loss due to thermal conduction through the glass and other building materials occurs, net energy (and therefore temperature) increases inside the greenhouse.
Convection
Convection is the concerted, collective movement of ensembles of molecules within fluids (e.g., liquids, gases) and rheids. It is the circulatory motion that occurs in a fluid at a nonuniform temperature owing to the variation of its density and the action of gravity.
Blackbody
A blackbody is an idealized physical body that absorbs all incident electromagnetic radiation, regardless of frequency or angle of incidence.
Real materials emit energy at a fraction ‒ called the emissivity ‒ blackbody energy levels. By definition, a blackbody in thermal equilibrium has an emissivity of ε = 1.0. A source with lower emissivity independent of frequency often is referred to as a gray body. Construction of blackbodies with emissivity as close to one as possible remains a topic of current interest. A white body is one with a "rough surface that reflects all incident rays completely and uniformly in all directions."
Effective temperature
The effective temperature of a body such as a star or planet is the temperature of a blackbody that would emit the same total amount of electromagnetic radiation. Effective temperature is often used as an estimate of a body's temperature when the body's emissivity curve (as a function of wavelength) is not known.
When the star's or planet's net emissivity in the relevant wavelength band is less than unity (less than that of a blackbody), the actual temperature of the body will be higher than the effective temperature. The net emissivity may be low due to surface or atmospheric properties, including the greenhouse effect.
Emissivity
The emissivity of the material (usually written ε or e) is the relative ability of its surface to emit energy by radiation. It is the ratio of energy radiated by a particular material to energy radiated by a blackbody at the same temperature. A true blackbody would have an ε = 1 while any real object would have ε < 1. Emissivity is a dimensionless quantity.
In general, the duller and blacker a material is, the closer its emissivity is to 1. The more reflective a material is, the lower its emissivity. Highly polished silver has an emissivity of about 0.02.
Sources:
http://en.wikipedia.org/wiki/Greenhouse_effect
http://en.wikipedia.org/wiki/Greenhouse_gas
http://en.wikipedia.org/wiki/Greenhouse
http://en.wikipedia.org/wiki/Convection
http://en.wikipedia.org/wiki/Blackbody
http://en.wikipedia.org/wiki/Effective_temperature
http://en.wikipedia.org/wiki/Emissivity
Sunday, May 12, 2013
antibiotic
An antibacterial is an agent that inhibits bacterial growth or kills bacteria. The term is often used synonymously with the term antibiotic(s). Today, however, with increased knowledge of the causative agents of various infectious diseases, antibiotic(s) has come to denote a broader range of antimicrobial compounds, including anti-fungal and other compounds.
The term antibiotic was first used in 1942 by Selman Waksman and his collaborators in journal articles to describe any substance produced by a microorganism that is antagonistic to the growth of other microorganisms in high dilution. This definition excluded substances that kill bacteria, but are not produced by microorganisms (such as gastric juices and hydrogen peroxide). It also excluded synthetic antibacterial compounds such as the sulfonamides. Many antibacterial compounds are relatively small molecules with a molecular weight of less than 2000 atomic units.
With advances in medicinal chemistry, most of today's antibacterials chemically are semisynthetic modifications of various natural compounds. Compounds that are still isolated from living organisms are the aminoglycosides, whereas other antibacterials -- for example, the sulfonamides, the quinolones, and the oxazolidinones -- are produced solely by chemical synthesis. In accordance with this, many antibacterial compounds are classified on the basis of chemical/biosynthetic origin into natural, semisynthetic, and synthetic. Another classification system is based on biological activity; in this classification, antibacterials are divided into two broad groups according to their biological effect on microorganisms: bactericidal agents kill bacteria, and bacteriostatic agents slow down or stall bacterial growth.
Antibiotic resistance is a form of drug resistance whereby some (or, less commonly, all) sub-populations of a microorganism, is usually a bacterial species, are able to survive after exposure to one or more antibiotics; pathogens resistant to multiple antibiotics are considered multidrug resistant (MDR) or, more colloquially, superbugs.
Antibiotic resistance is a serious and growing phenomenon in contemporary medicine and has emerged as one of the pre-eminent public health concerns of the 21st century, particularly as it pertains to pathogenic organisms (the term is especially relevant to organisms which cause disease in humans). In the simplest cases, drug-resistant organisms may have acquired resistance to first-line antibiotics, thereby necessitating the use of second-line agents. Typically, a first-line agent is selected on the basis of several factors including safety, availability and cost; a second-line agent is usually broader in spectrum, has a less favorable risk-benefit profile and is more expensive or, in dire circumstances, is locally unavailable.
It may take the form of a spontaneous or induced genetic mutation, or the acquisition of resistance genes from other bacterial species by horizontal gene transfer via conjugation, transduction, or transformation. Many antibiotic resistance genes reside on transmissible plasmids, facilitating their transfer. Exposure to an antibiotic naturally selects for the survival of the organisms with the genes for resistance. In this way, a gene for antibiotic resistance may readily spread through an ecosystem of bacteria. Antibiotic-resistance plasmids frequently contain genes conferring resistance to several different antibiotics.
Genes for resistance to antibiotics, like the antibiotics themselves, are ancient. However, the increasing prevalence of antibiotic-resistant bacterial infections seen in clinical practice stems from antibiotic use both within human medicine and veterinary medicine. Any use of antibiotics can increase selective pressure in a population of bacteria to allow the resistant bacteria to thrive and the susceptible bacteria to die off. As resistance towards antibiotics becomes more common, a greater need for alternative treatments arises. However, despite a push for new antibiotic therapies there has been a continued decline in the number of newly approved drugs. Antibiotic resistance therefore poses a significant problem.
Plasmid
A plasmid is a small DNA molecule that is physically separate from, and can replicate independently of, chromosomal DNA within a cell. Most commonly found as small circular, double stranded DNA molecules in bacteria, plasmids are sometimes present in archaea and eukaryotic organisms. In nature, plasmids carry genes that may benefit survival of the organism (e.g. antibiotic resistance), and can frequently be transmitted from one bacterium to another (even of another species) via horizontal gene transfer.
Plasmid sizes vary from 1 to 1000 kilo base pairs (kbp). The number of identical plasmids in a single cell can range anywhere from one to thousands under some circumstances. Plasmids can be considered part of the mobilome because they are often associated with conjugation, a mechanism of horizontal gene transfer.
Plasmid host-to-host transfer requires direct mechanical transfer by conjugation, or changes in incipient host gene expression allowing the intentional uptake of the genetic element by transformation. Plasmids provide a mechanism for horizontal gene transfer within a population of microbes and typically provide a selective advantage under a given environmental state. Plasmids may carry genes that provide resistance to naturally occurring antibiotics in a competitive environmental niche, or the proteins produced may act as toxins under similar circumstances.
Sources:
http://en.wikipedia.org/wiki/Antibacterial
http://en.wikipedia.org/wiki/Antibiotic_resistance
http://en.wikipedia.org/wiki/Plasmid
The term antibiotic was first used in 1942 by Selman Waksman and his collaborators in journal articles to describe any substance produced by a microorganism that is antagonistic to the growth of other microorganisms in high dilution. This definition excluded substances that kill bacteria, but are not produced by microorganisms (such as gastric juices and hydrogen peroxide). It also excluded synthetic antibacterial compounds such as the sulfonamides. Many antibacterial compounds are relatively small molecules with a molecular weight of less than 2000 atomic units.
With advances in medicinal chemistry, most of today's antibacterials chemically are semisynthetic modifications of various natural compounds. Compounds that are still isolated from living organisms are the aminoglycosides, whereas other antibacterials -- for example, the sulfonamides, the quinolones, and the oxazolidinones -- are produced solely by chemical synthesis. In accordance with this, many antibacterial compounds are classified on the basis of chemical/biosynthetic origin into natural, semisynthetic, and synthetic. Another classification system is based on biological activity; in this classification, antibacterials are divided into two broad groups according to their biological effect on microorganisms: bactericidal agents kill bacteria, and bacteriostatic agents slow down or stall bacterial growth.
Antibiotic resistance is a form of drug resistance whereby some (or, less commonly, all) sub-populations of a microorganism, is usually a bacterial species, are able to survive after exposure to one or more antibiotics; pathogens resistant to multiple antibiotics are considered multidrug resistant (MDR) or, more colloquially, superbugs.
Antibiotic resistance is a serious and growing phenomenon in contemporary medicine and has emerged as one of the pre-eminent public health concerns of the 21st century, particularly as it pertains to pathogenic organisms (the term is especially relevant to organisms which cause disease in humans). In the simplest cases, drug-resistant organisms may have acquired resistance to first-line antibiotics, thereby necessitating the use of second-line agents. Typically, a first-line agent is selected on the basis of several factors including safety, availability and cost; a second-line agent is usually broader in spectrum, has a less favorable risk-benefit profile and is more expensive or, in dire circumstances, is locally unavailable.
It may take the form of a spontaneous or induced genetic mutation, or the acquisition of resistance genes from other bacterial species by horizontal gene transfer via conjugation, transduction, or transformation. Many antibiotic resistance genes reside on transmissible plasmids, facilitating their transfer. Exposure to an antibiotic naturally selects for the survival of the organisms with the genes for resistance. In this way, a gene for antibiotic resistance may readily spread through an ecosystem of bacteria. Antibiotic-resistance plasmids frequently contain genes conferring resistance to several different antibiotics.
Genes for resistance to antibiotics, like the antibiotics themselves, are ancient. However, the increasing prevalence of antibiotic-resistant bacterial infections seen in clinical practice stems from antibiotic use both within human medicine and veterinary medicine. Any use of antibiotics can increase selective pressure in a population of bacteria to allow the resistant bacteria to thrive and the susceptible bacteria to die off. As resistance towards antibiotics becomes more common, a greater need for alternative treatments arises. However, despite a push for new antibiotic therapies there has been a continued decline in the number of newly approved drugs. Antibiotic resistance therefore poses a significant problem.
Plasmid
A plasmid is a small DNA molecule that is physically separate from, and can replicate independently of, chromosomal DNA within a cell. Most commonly found as small circular, double stranded DNA molecules in bacteria, plasmids are sometimes present in archaea and eukaryotic organisms. In nature, plasmids carry genes that may benefit survival of the organism (e.g. antibiotic resistance), and can frequently be transmitted from one bacterium to another (even of another species) via horizontal gene transfer.
Plasmid sizes vary from 1 to 1000 kilo base pairs (kbp). The number of identical plasmids in a single cell can range anywhere from one to thousands under some circumstances. Plasmids can be considered part of the mobilome because they are often associated with conjugation, a mechanism of horizontal gene transfer.
Plasmid host-to-host transfer requires direct mechanical transfer by conjugation, or changes in incipient host gene expression allowing the intentional uptake of the genetic element by transformation. Plasmids provide a mechanism for horizontal gene transfer within a population of microbes and typically provide a selective advantage under a given environmental state. Plasmids may carry genes that provide resistance to naturally occurring antibiotics in a competitive environmental niche, or the proteins produced may act as toxins under similar circumstances.
Sources:
http://en.wikipedia.org/wiki/Antibacterial
http://en.wikipedia.org/wiki/Antibiotic_resistance
http://en.wikipedia.org/wiki/Plasmid
Wednesday, February 27, 2013
curator
A curator (from Latin: curare meaning "take care") is a manager or overseer. Traditionally, a curator or keeper of a cultural heritage institution (e.g., gallery, museum, library or archive) is a content specialist responsible for an institution's collections and involved with the interpretation of heritage material. The object of a traditional curator's concern necessarily involves tangible objects of some sort, whether it be artwork, collectibles, historic items or scientific collections.
In smaller organizations, a curator may have sole responsibility for the acquisition and care of objects. The curator will make decisions regarding what objects to take, oversee their potential and documentations, conduct research based on the collection and history that provides propered packaging of art for transportation, and share that research with the public and polymath community through exhibitions and publications. In very small volunteer-based museums, such as local historical societies, a curator may be the only paid staff member.
In larger institutions, the curator's primary function is as a subject specialist, with the expectation that he or she will conduct original research on objects and guide the organization in its collecting. Such institutions can have multiple curators, each assigned to a specific collecting area (e.g., Curator of Ancient Art, Curator of Prints and Drawings, etc.) and often operating under the direction of a head curator. In such organizations, the physical care of the collection may be overseen by museum collection managers or museum conservators, and documentation and administrative matters (such as insurance and loans) are handled by a museum registrar.
Curators generally hold a higher academic degree in their subject, typically a Doctor of Philosophy or a Master's degree in subjects such as history, history of art, archaeology, anthropology, or classics. Curators are also expected to have contributed to their academic field, for example, by delivering public talks, publishing articles or presenting at specialist academic conferences. It is important that curators have knowledge of the current collecting market for their area of expertise, and are aware of current ethical practices and laws that may impact their organization's collecting.
Recently, the increased complexity of many museums and cultural organizations has prompted the emergence of professional programs in fields such as public history, museum studies, arts management, and curating/curatorial practice.
Sources:
http://en.wikipedia.org/wiki/Curator
In smaller organizations, a curator may have sole responsibility for the acquisition and care of objects. The curator will make decisions regarding what objects to take, oversee their potential and documentations, conduct research based on the collection and history that provides propered packaging of art for transportation, and share that research with the public and polymath community through exhibitions and publications. In very small volunteer-based museums, such as local historical societies, a curator may be the only paid staff member.
In larger institutions, the curator's primary function is as a subject specialist, with the expectation that he or she will conduct original research on objects and guide the organization in its collecting. Such institutions can have multiple curators, each assigned to a specific collecting area (e.g., Curator of Ancient Art, Curator of Prints and Drawings, etc.) and often operating under the direction of a head curator. In such organizations, the physical care of the collection may be overseen by museum collection managers or museum conservators, and documentation and administrative matters (such as insurance and loans) are handled by a museum registrar.
Curators generally hold a higher academic degree in their subject, typically a Doctor of Philosophy or a Master's degree in subjects such as history, history of art, archaeology, anthropology, or classics. Curators are also expected to have contributed to their academic field, for example, by delivering public talks, publishing articles or presenting at specialist academic conferences. It is important that curators have knowledge of the current collecting market for their area of expertise, and are aware of current ethical practices and laws that may impact their organization's collecting.
Recently, the increased complexity of many museums and cultural organizations has prompted the emergence of professional programs in fields such as public history, museum studies, arts management, and curating/curatorial practice.
Sources:
http://en.wikipedia.org/wiki/Curator
Sunday, December 30, 2012
church architecture
In architecture, the apse (Greek ἀψίς (apsis), then Latin absis: "arch, vault"; sometimes written apsis; plural apses) is a semicircular recess covered with a hemispherical vault or semi-dome. In Romanesque, Byzantine and Gothic Christian abbey, cathedral and church architecture, the term is applied to a semi-circular or polygonal termination of the main building at the liturgical east end (where the altar is), regardless of the shape of the roof, which may be flat, sloping, domed or hemispherical.
The apse is the semicircular or polygonal termination to the choir or aisles of a church. In relation to church architecture it is generally the name given to where the altar is placed or where the clergy are seated.
Nave
In Romanesque and Gothic Christian abbey, cathedral basilica and church architecture, the nave is the central approach to the high altar, the main body of the church. "Nave" (Medieval Latin navis, "ship") was probably suggested by the keel shape of its vaulting. The nave of a church, whether Romanesque, Gothic or Classical, extends from the entry -- which may have a separate vestibule, the narthex -- to the chancel and is flanked by lower aisles separated from the nave by an arcade. If the aisles are high and of a width comparable to the central nave, the structure is sometimes said to have three naves.
Transept
A transept (with two semitransepts) is a transverse section, of any building, which lies across the main body of the building. In Christian churches, a transept is an area set crosswise to the nave in a cruciform ("cross-shaped") building in a Romanesque and Gothic Christian church architecture. Each half of a transept is known as a semitransept.
The transept of a church separates the nave from the sanctuary, whether apse, choir, chevet, presbytery, or chancel. The transepts cross the nave at the crossing, which belongs equally to the main nave axis and to the transept. Upon its four piers, the crossing may support a spire (e.g., Salisbury Cathedral), a central tower (e.g., Gloucester Cathedral) or a crossing dome (e.g., Saint Paul's Cathedral).
Narthex
The narthex of a church is the entrance or lobby area, located at the end of the nave, at the far end from the church's main altar. Traditionally the narthex was part of the church building, but it was not considered part of the church proper. It is either an indoor area separated from the nave by a screen or rail, or an external structure such as a porch.
Chancel
The chancel (or presbytery) is the space around the altar in the sanctuary at the liturgical east end of a traditional Christian church building, possibly including the choir. It may terminate in an apse.
As well as the altar, the chancel usually houses the credence table and seats for officiating and assisting ministers. In Anglican and Methodist churches it will usually include the choir. In some traditions, the pulpit and lectern may be in the chancel, but in others these functions are considered proper to the nave.
The chancel is typically raised somewhat above the level of the nave, where the congregation gathers. It may be separated from the nave by a rood screen, a rail, or an open space. In some churches, the congregation may gather on three sides or in a semicircle around the chancel.
Sources:
http://en.wikipedia.org/wiki/Apse
http://en.wikipedia.org/wiki/Nave
http://en.wikipedia.org/wiki/Transept
http://en.wikipedia.org/wiki/Narthex
http://en.wikipedia.org/wiki/Chancel
crypt
In architecture, a crypt (from the Latin crypta and the Greek κρύπτη, kryptē; meaning concealed, private) is a stone chamber or vault beneath the floor of burial vault possibly containing sarcophagi, coffins or relics.
In more modern terms, a crypt is most often a stone chambered vault used to store the deceased. Crypts are usually found in cemeteries and under public religious buildings, such as churches and cathedrals, but are also occasionally found beneath mausolea or chapels on personal estates. Wealthy or prestigious families will often have a 'family crypt' or 'vault' in which all members of the family are interred. Many royal families, for example, have vast crypts containing bodies of dozens of former royals. In some localities an above ground crypt is more commonly called a mausoleum, which also refers to any elaborate building intended as a burial place, for one or any number of people.
Originally crypts were typically found below the apse of a church, such as the Abbey of Saint-Germain in Auxerre, but were later located beneath naves and transepts as well. Occasionally churches were raised high to accommodate a crypt at the ground level, such as Saint Michael's church in Hildesheim, Germany.
Burial Vault
A burial vault is a structural underground tomb.
It is a stone or brick-lined underground space or 'burial' chamber for the interment of a dead body or bodies. They were originally and are still often vaulted and usually have stone slab entrances. They are often privately owned and used for specific family or other groups, but usually stand beneath a public religious building, such as a church, or in a churchyard or cemetery. A crypt may be used as a burial vault.
Sarcophagus
A sarcophagus is a box-like funeral receptacle for a corpse, most commonly carved in stone, and displayed above ground through they may also be buried.
Sarcophagi were most often designed to remain above ground, hence were often ornately carved or elaborately constructed. Some were built to be freestanding, as part of an elaborate sealed tomb or series of tombs, while others were intended for placement in crypts and remain accessible to view.
Relic
In religion, a relic is a part of the body of a saint or a venerated person, or else another type of ancient religious object, carefully preserved for purposes of veneration or as a touchable or tangible memorial. Relics are an important aspect of some forms of Buddhism, Christianity, Hinduism, Shamanism, and many other religions. The word relic comes from the Latin reliquiae, meaning "remains" or "something left behind" (the same root as relinquish).
Mausoleum
A mausoleum is an external free-standing building constructed as a monument enclosing the interment space or burial chamber of a deceased person or persons. A monument without the interment is a cenotaph. A mausoleum may be considered a type of tomb or the tomb may be considered to be within the mausoleum. A Christian mausoleum sometimes include a chapel.
Sources:
http://en.wikipedia.org/wiki/Crypt
http://en.wikipedia.org/wiki/Vault_%28tomb%29
http://en.wikipedia.org/wiki/Sarcophagus
http://en.wikipedia.org/wiki/Relic
http://en.wikipedia.org/wiki/Mausoleum
In more modern terms, a crypt is most often a stone chambered vault used to store the deceased. Crypts are usually found in cemeteries and under public religious buildings, such as churches and cathedrals, but are also occasionally found beneath mausolea or chapels on personal estates. Wealthy or prestigious families will often have a 'family crypt' or 'vault' in which all members of the family are interred. Many royal families, for example, have vast crypts containing bodies of dozens of former royals. In some localities an above ground crypt is more commonly called a mausoleum, which also refers to any elaborate building intended as a burial place, for one or any number of people.
Originally crypts were typically found below the apse of a church, such as the Abbey of Saint-Germain in Auxerre, but were later located beneath naves and transepts as well. Occasionally churches were raised high to accommodate a crypt at the ground level, such as Saint Michael's church in Hildesheim, Germany.
Burial Vault
A burial vault is a structural underground tomb.
It is a stone or brick-lined underground space or 'burial' chamber for the interment of a dead body or bodies. They were originally and are still often vaulted and usually have stone slab entrances. They are often privately owned and used for specific family or other groups, but usually stand beneath a public religious building, such as a church, or in a churchyard or cemetery. A crypt may be used as a burial vault.
Sarcophagus
A sarcophagus is a box-like funeral receptacle for a corpse, most commonly carved in stone, and displayed above ground through they may also be buried.
Sarcophagi were most often designed to remain above ground, hence were often ornately carved or elaborately constructed. Some were built to be freestanding, as part of an elaborate sealed tomb or series of tombs, while others were intended for placement in crypts and remain accessible to view.
Relic
In religion, a relic is a part of the body of a saint or a venerated person, or else another type of ancient religious object, carefully preserved for purposes of veneration or as a touchable or tangible memorial. Relics are an important aspect of some forms of Buddhism, Christianity, Hinduism, Shamanism, and many other religions. The word relic comes from the Latin reliquiae, meaning "remains" or "something left behind" (the same root as relinquish).
Mausoleum
A mausoleum is an external free-standing building constructed as a monument enclosing the interment space or burial chamber of a deceased person or persons. A monument without the interment is a cenotaph. A mausoleum may be considered a type of tomb or the tomb may be considered to be within the mausoleum. A Christian mausoleum sometimes include a chapel.
Sources:
http://en.wikipedia.org/wiki/Crypt
http://en.wikipedia.org/wiki/Vault_%28tomb%29
http://en.wikipedia.org/wiki/Sarcophagus
http://en.wikipedia.org/wiki/Relic
http://en.wikipedia.org/wiki/Mausoleum
Sunday, December 2, 2012
rhetoric
Rhetoric is the art of speaking or writing effectively. It may entail the study of principles and rules of composition formulated by critics of ancient times and can involve the study of writing or speaking as a means of communication or persuasion.
As an art, rhetoric aims to improve the facility of speakers or writers who attempt to inform, persuade, or motivate particular audiences in specific situations. As a subject of formal study and a productive civic practice, rhetoric has played a central role in the Western tradition. Its best known definition comes from Aristotle, who considers it a counterpart of both logic and politics, and calls it "the faculty of observing in any given case the available means of persuasion." Rhetorics typically provide heuristics for understanding, discovering, and developing arguments for particular situations, such as Aristotle's three persuasive audience appeals, logos, pathos, and ethos. The five canons of rhetoric, which trace the traditional tasks in designing a persuasive speech, were first codified in classical Rome, invention (inventio), arrangement (dispositio), style (elocutio), memory (memoria), and delivery (pronuntiatio). Along with grammar and logic (or dialectic), rhetoric is one of the three ancient arts of discourse.
From ancient Greece to the late 19th century, rhetoric was a central part of Western education, filling the need to train public speakers and writers to move audiences to action with arguments. The word is derived from the Greek ῥητορικός (rhētorikós), "oratorical", from ῥήτωρ (rhḗtōr), "public speaker", related to ῥῆμα (rhêma), "that which is said or spoken, word, saying", and ultimately derived from the verb λέγω (loqui), "to speak, say."
Sources:
http://www.merriam-webster.com/dictionary/rhetoric
http://en.wikipedia.org/wiki/Rhetoric
As an art, rhetoric aims to improve the facility of speakers or writers who attempt to inform, persuade, or motivate particular audiences in specific situations. As a subject of formal study and a productive civic practice, rhetoric has played a central role in the Western tradition. Its best known definition comes from Aristotle, who considers it a counterpart of both logic and politics, and calls it "the faculty of observing in any given case the available means of persuasion." Rhetorics typically provide heuristics for understanding, discovering, and developing arguments for particular situations, such as Aristotle's three persuasive audience appeals, logos, pathos, and ethos. The five canons of rhetoric, which trace the traditional tasks in designing a persuasive speech, were first codified in classical Rome, invention (inventio), arrangement (dispositio), style (elocutio), memory (memoria), and delivery (pronuntiatio). Along with grammar and logic (or dialectic), rhetoric is one of the three ancient arts of discourse.
From ancient Greece to the late 19th century, rhetoric was a central part of Western education, filling the need to train public speakers and writers to move audiences to action with arguments. The word is derived from the Greek ῥητορικός (rhētorikós), "oratorical", from ῥήτωρ (rhḗtōr), "public speaker", related to ῥῆμα (rhêma), "that which is said or spoken, word, saying", and ultimately derived from the verb λέγω (loqui), "to speak, say."
Sources:
http://www.merriam-webster.com/dictionary/rhetoric
http://en.wikipedia.org/wiki/Rhetoric
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