During what war did French officers setup headquarters in CAR?

In September 1940, during the Second World War, pro-Gaullist French officers took control of Ubangi-Shari and General Leclerc established his headquarters for the Free French Forces in Bangui. In 1946 Barthélémy Boganda was elected with 9,000 votes to the French National Assembly, becoming the first representative for CAR in the French government. Boganda maintained a political stance against racism and the colonial regime but gradually became disheartened with the French political system and returned to CAR to establish the Movement for the Social Evolution of Black Africa (MESAN) in 1950.


Who was elected in 1946 as the first representative?


What was Bogandas platform that he ran for?


What caused Boganda to leave his elected post?


What was the overwhelming amount of votes MESAN captured?

In the Ubangi-Shari Territorial Assembly election in 1957, MESAN captured 347,000 out of the total 356,000 votes, and won every legislative seat, which led to Boganda being elected president of the Grand Council of French Equatorial Africa and vice-president of the Ubangi-Shari Government Council. Within a year, he declared the establishment of the Central African Republic and served as the country's first prime minister. MESAN continued to exist, but its role was limited. After Boganda's death in a plane crash on 29 March 1959, his cousin, David Dacko, took control of MESAN and became the country's first president after the CAR had formally received independence from France. Dacko threw out his political rivals, including former Prime Minister and Mouvement d'évolution démocratique de l'Afrique centrale (MEDAC), leader Abel Goumba, whom he forced into exile in France. With all opposition parties suppressed by November 1962, Dacko declared MESAN as the official party of the state.


Who was elected president of the Grand Council?


In April 1979, young students protested against Bokassa's decree that all school attendees would need to buy uniforms from a company owned by one of his wives. The government violently suppressed the protests, killing 100 children and teenagers. Bokassa himself may have been personally involved in some of the killings. In September 1979, France overthrew Bokassa and "restored" Dacko to power (subsequently restoring the name of the country to the Central African Republic). Dacko, in turn, was again overthrown in a coup by General André Kolingba on 1 September 1981.


How many were killed in the April 1979 protests?


Who overthrew Bokassa after this incident?


What was inspired by the fall of the Berlin wall?

By 1990, inspired by the fall of the Berlin Wall, a pro-democracy movement arose. Pressure from the United States, France, and from a group of locally represented countries and agencies called GIBAFOR (France, the USA, Germany, Japan, the EU, the World Bank, and the UN) finally led Kolingba to agree, in principle, to hold free elections in October 1992 with help from the UN Office of Electoral Affairs. After using the excuse of alleged irregularities to suspend the results of the elections as a pretext for holding on to power, President Kolingba came under intense pressure from GIBAFOR to establish a "Conseil National Politique Provisoire de la République" (Provisional National Political Council, CNPPR) and to set up a "Mixed Electoral Commission", which included representatives from all political parties.[citation needed]


What large country pressured CAR to hold elections?


What excuse did Kolingba use to deny the election results?


When was a second democratic election held?

When a second round of elections were finally held in 1993, again with the help of the international community coordinated by GIBAFOR, Ange-Félix Patassé won in the second round of voting with 53% of the vote while Goumba won 45.6%. Patassé's party, the Mouvement pour la Libération du Peuple Centrafricain (MLPC) or Movement for the Liberation of the Central African People, gained a simple but not an absolute majority of seats in parliament, which meant Patassé's party required coalition partners.[citation needed]


Who became the first democratically elected president?


Did Patasse get a majority of the votes?


When was the new constitution for CAR approved?

Patassé purged many of the Kolingba elements from the government and Kolingba supporters accused Patassé's government of conducting a "witch hunt" against the Yakoma. A new constitution was approved on 28 December 1994 but had little impact on the country's politics. In 1996–1997, reflecting steadily decreasing public confidence in the government's erratic behaviour, three mutinies against Patassé's administration were accompanied by widespread destruction of property and heightened ethnic tension. During this time (1996) the Peace Corps evacuated all its volunteers to neighboring Cameroon. To date, the Peace Corps has not returned to the Central African Republic. The Bangui Agreements, signed in January 1997, provided for the deployment of an inter-African military mission, to Central African Republic and re-entry of ex-mutineers into the government on 7 April 1997. The inter-African military mission was later replaced by a U.N. peacekeeping force (MINURCA).


The mutinies caused what effects on the country?


What agreement gave the authority for deployment of military intervention?


In the aftermath of the failed coup, militias loyal to Patassé sought revenge against rebels in many neighborhoods of Bangui and incited unrest including the murder of many political opponents. Eventually, Patassé came to suspect that General François Bozizé was involved in another coup attempt against him, which led Bozizé to flee with loyal troops to Chad. In March 2003, Bozizé launched a surprise attack against Patassé, who was out of the country. Libyan troops and some 1,000 soldiers of Bemba's Congolese rebel organization failed to stop the rebels and Bozizé's forces succeeded in overthrowing Patassé.[citation needed]


Which General was involved in another coup?


Where did General Bozize flee to escape?


When did Bozize finally attempt his coup?


Who succeeded in finally overthrowing Patasse?


In 2004 the Central African Republic Bush War began as forces opposed to Bozizé took up arms against his government. In May 2005 Bozizé won a presidential election that excluded Patassé and in 2006 fighting continued between the government and the rebels. In November 2006, Bozizé's government requested French military support to help them repel rebels who had taken control of towns in the country's northern regions. Though the initially public details of the agreement pertained to logistics and intelligence, the French assistance eventually included strikes by Mirage jets against rebel positions.


In what way did Bozize made his rule legitimate?


When did CAR ask for assistance from the French against rebels?


How did the French assist against the rebels?


What agreement called for the stop of Hostilities?

The Syrte Agreement in February and the Birao Peace Agreement in April 2007 called for a cessation of hostilities, the billeting of FDPC fighters and their integration with FACA, the liberation of political prisoners, integration of FDPC into government, an amnesty for the UFDR, its recognition as a political party, and the integration of its fighters into the national army. Several groups continued to fight but other groups signed on to the agreement, or similar agreements with the government (e.g. UFR on 15 December 2008). The only major group not to sign an agreement at the time was the CPJP, which continued its activities and signed a peace agreement with the government on 25 August 2012.


What did the Birao Peace Agreement call for?


What major group did not sign the peace agreement immediately?


When did the CPJP finally sign the peace agreement?


When was the Birao Peace Agreement signed?


Michel Djotodia took over as president and in May 2013 Central African Republic's Prime Minister Nicolas Tiangaye requested a UN peacekeeping force from the UN Security Council and on 31 May former President Bozizé was indicted for crimes against humanity and incitement of genocide. The security situation did not improve during June–August 2013 and there were reports of over 200,000 internally displaced persons (IDPs) as well as human rights abuses and renewed fighting between Séléka and Bozizé supporters.


How many people were displaced in the unrests?


What faction was fighting against the remaining Bozize loyalists?


What national part is located in the South West?

In the southwest, the Dzanga-Sangha National Park is located in a rain forest area. The country is noted for its population of forest elephants and western lowland gorillas. In the north, the Manovo-Gounda St Floris National Park is well-populated with wildlife, including leopards, lions, cheetahs and rhinos, and the Bamingui-Bangoran National Park is located in the northeast of CAR. The parks have been seriously affected by the activities of poachers, particularly those from Sudan, over the past two decades.[citation needed]


What large animals reside in the national park?


Which Primate can be found in the national park?


What National Park can be found in the North?


What has threatened the wildlife in this park?


There are many missionary groups operating in the country, including Lutherans, Baptists, Catholics, Grace Brethren, and Jehovah's Witnesses. While these missionaries are predominantly from the United States, France, Italy, and Spain, many are also from Nigeria, the Democratic Republic of the Congo, and other African countries. Large numbers of missionaries left the country when fighting broke out between rebel and government forces in 2002–3, but many of them have now returned to continue their work.


Where do most of the missionaries come from?


What caused most of the missionaries to leave the country?


What African country bordering CAR are some of these missionaries from?


Due to fighting, what threatened people in the NorthWest?

In 2006, due to ongoing violence, over 50,000 people in the country's northwest were at risk of starvation but this was averted due to assistance from the United Nations.[citation needed] On 8 January 2008, the UN Secretary-General Ban Ki-Moon declared that the Central African Republic was eligible to receive assistance from the Peacebuilding Fund. Three priority areas were identified: first, the reform of the security sector; second, the promotion of good governance and the rule of law; and third, the revitalization of communities affected by conflicts. On 12 June 2008, the Central African Republic requested assistance from the UN Peacebuilding Commission, which was set up in 2005 to help countries emerging from conflict avoid devolving back into war or chaos.


Who assisted in saving the people from starvation?


Who headed the UN effort to rebuild CAR?


When did CAR request assistance directly to prevent war?


When was the new Government seated in CAR?

A new government was appointed on 31 March 2013, which consisted of members of Séléka and representatives of the opposition to Bozizé, one pro-Bozizé individual, and a number representatives of civil society. On 1 April, the former opposition parties declared that they would boycott the government. After African leaders in Chad refused to recognize Djotodia as President, proposing to form a transitional council and the holding of new elections, Djotodia signed a decree on 6 April for the formation of a council that would act as a transitional parliament. The council was tasked with electing a president to serve prior to elections in 18 months.


What did the former opposition parties declare?


How long did the parliament have until the next election?


The per capita income of the Republic is often listed as being approximately $400 a year, one of the lowest in the world, but this figure is based mostly on reported sales of exports and largely ignores the unregistered sale of foods, locally produced alcoholic beverages, diamonds, ivory, bushmeat, and traditional medicine. For most Central Africans, the informal economy of the CAR is more important than the formal economy.[citation needed] Export trade is hindered by poor economic development and the country's landlocked position.[citation needed]


How is the per capita income compared to the world?


Which item that poachers kill elephants for can be obtained in CAR?


What type of agriculture is popular in the CAR?

Agriculture is dominated by the cultivation and sale of food crops such as cassava, peanuts, maize, sorghum, millet, sesame, and plantain. The annual real GDP growth rate is just above 3%. The importance of food crops over exported cash crops is indicated by the fact that the total production of cassava, the staple food of most Central Africans, ranges between 200,000 and 300,000 tonnes a year, while the production of cotton, the principal exported cash crop, ranges from 25,000 to 45,000 tonnes a year. Food crops are not exported in large quantities, but still constitute the principal cash crops of the country, because Central Africans derive far more income from the periodic sale of surplus food crops than from exported cash crops such as cotton or coffee.[citation needed] Much of the country is self-sufficient in food crops; however, livestock development is hindered by the presence of the tsetse fly.[citation needed]


The economy grows at what rate in the last few years?


How many tonnes of Cassave is produced per year?


What product is produced that is exported?


Which insect hinders livestock development?


What is the major telecommunications provider in CAR?

Presently, the Central African Republic has active television services, radio stations, internet service providers, and mobile phone carriers; Socatel is the leading provider for both internet and mobile phone access throughout the country. The primary governmental regulating bodies of telecommunications are the Ministère des Postes and Télécommunications et des Nouvelles Technologies. In addition, the Central African Republic receives international support on telecommunication related operations from ITU Telecommunication Development Sector (ITU-D) within the International Telecommunication Union to improve infrastructure.


Who assists CAR with telecommunications?


What does the CAR get help with with regards to communication from ITU-D?


The 2009 Human Rights Report by the United States Department of State noted that human rights in CAR were poor and expressed concerns over numerous government abuses. The U.S. State Department alleged that major human rights abuses such as extrajudicial executions by security forces, torture, beatings and rape of suspects and prisoners occurred with impunity. It also alleged harsh and life-threatening conditions in prisons and detention centers, arbitrary arrest, prolonged pretrial detention and denial of a fair trial, restrictions on freedom of movement, official corruption, and restrictions on workers' rights.


What concerns are there regarding to human rights?


What punishment is a human rights violation per the US state Dept?


What right in a court is denied and considered a human right violation?


Asthma is thought to be caused by a combination of genetic and environmental factors. Environmental factors include exposure to air pollution and allergens. Other potential triggers include medications such as aspirin and beta blockers. Diagnosis is usually based on the pattern of symptoms, response to therapy over time, and spirometry. Asthma is classified according to the frequency of symptoms, forced expiratory volume in one second (FEV1), and peak expiratory flow rate. It may also be classified as atopic or non-atopic where atopy refers to a predisposition toward developing a type 1 hypersensitivity reaction.


What medications can also trigger asthma?


What patterns are used to diagnose asthma?


There is no cure for asthma. Symptoms can be prevented by avoiding triggers, such as allergens and irritants, and by the use of inhaled corticosteroids. Long-acting beta agonists (LABA) or antileukotriene agents may be used in addition to inhaled corticosteroids if asthma symptoms remain uncontrolled. Treatment of rapidly worsening symptoms is usually with an inhaled short-acting beta-2 agonist such as salbutamol and corticosteroids taken by mouth. In very severe cases, intravenous corticosteroids, magnesium sulfate, and hospitalization may be required.


What is taken by mouth to treat rapidly worsening symptoms?


What happens in very severe cases of asthma?


Asthma is characterized by recurrent episodes of wheezing, shortness of breath, chest tightness, and coughing. Sputum may be produced from the lung by coughing but is often hard to bring up. During recovery from an attack, it may appear pus-like due to high levels of white blood cells called eosinophils. Symptoms are usually worse at night and in the early morning or in response to exercise or cold air. Some people with asthma rarely experience symptoms, usually in response to triggers, whereas others may have marked and persistent symptoms.


When are symptoms of asthma normally worse?


What is produced in the lungs by coughing?


Is asthma worst during the day or at night time?


Does everyone have horrible episodes of asthma?


Do other health concerns happen less frequently or more frequently with asthma?

A number of other health conditions occur more frequently in those with asthma, including gastro-esophageal reflux disease (GERD), rhinosinusitis, and obstructive sleep apnea. Psychological disorders are also more common, with anxiety disorders occurring in between 16–52% and mood disorders in 14–41%. However, it is not known if asthma causes psychological problems or if psychological problems lead to asthma. Those with asthma, especially if it is poorly controlled, are at high risk for radiocontrast reactions.


What are three of the other health conditions that occur more frequently with asthma?


What other type of disorders are frequent in asthma sufferers?


What are those with asthma that is poorly controll more susceptable to?


What are some of the enviromental factors that have been linked to asthma?

Many environmental factors have been associated with asthma's development and exacerbation including allergens, air pollution, and other environmental chemicals. Smoking during pregnancy and after delivery is associated with a greater risk of asthma-like symptoms. Low air quality from factors such as traffic pollution or high ozone levels, has been associated with both asthma development and increased asthma severity. Exposure to indoor volatile organic compounds may be a trigger for asthma; formaldehyde exposure, for example, has a positive association. Also, phthalates in certain types of PVC are associated with asthma in children and adults.


What two things are associated with a greater risk of asthma-like symptoms?


What can cause symptoms and asthma serverity to change?


Exposure to what compounds can also trigger asthma?


What hypothesis tries to explain the increased amount of asthma world wide?

The hygiene hypothesis attempts to explain the increased rates of asthma worldwide as a direct and unintended result of reduced exposure, during childhood, to non-pathogenic bacteria and viruses. It has been proposed that the reduced exposure to bacteria and viruses is due, in part, to increased cleanliness and decreased family size in modern societies. Exposure to bacterial endotoxin in early childhood may prevent the development of asthma, but exposure at an older age may provoke bronchoconstriction. Evidence supporting the hygiene hypothesis includes lower rates of asthma on farms and in households with pets.


How does the hygiene hypothesis explain the increase in asthma?


What has caused the reduced exposure in childhood?


What is some of the evidence backing the hygiene hypothesis?


Family history is a risk factor for asthma, with many different genes being implicated. If one identical twin is affected, the probability of the other having the disease is approximately 25%. By the end of 2005, 25 genes had been associated with asthma in six or more separate populations, including GSTM1, IL10, CTLA-4, SPINK5, LTC4S, IL4R and ADAM33, among others. Many of these genes are related to the immune system or modulating inflammation. Even among this list of genes supported by highly replicated studies, results have not been consistent among all populations tested. In 2006 over 100 genes were associated with asthma in one genetic association study alone; more continue to be found.


If one identical twin has asthma, what are the odds of the other twin having asthma?


How many genes were associated with asthma by the end of 2005?


How many genes were associated with asthma in 2006?


What else are these genes closely related to?


Asthma is the result of chronic inflammation of the conducting zone of the airways (most especially the bronchi and bronchioles), which subsequently results in increased contractability of the surrounding smooth muscles. This among other factors leads to bouts of narrowing of the airway and the classic symptoms of wheezing. The narrowing is typically reversible with or without treatment. Occasionally the airways themselves change. Typical changes in the airways include an increase in eosinophils and thickening of the lamina reticularis. Chronically the airways' smooth muscle may increase in size along with an increase in the numbers of mucous glands. Other cell types involved include: T lymphocytes, macrophages, and neutrophils. There may also be involvement of other components of the immune system including: cytokines, chemokines, histamine, and leukotrienes among others.


What two airways are most effected by asthma?


What other cell types are involced with the changing of airways?


What other components of the immune systems are included?


Is there a universal definition of astham?

While asthma is a well recognized condition, there is not one universal agreed upon definition. It is defined by the Global Initiative for Asthma as "a chronic inflammatory disorder of the airways in which many cells and cellular elements play a role. The chronic inflammation is associated with airway hyper-responsiveness that leads to recurrent episodes of wheezing, breathlessness, chest tightness and coughing particularly at night or in the early morning. These episodes are usually associated with widespread but variable airflow obstruction within the lung that is often reversible either spontaneously or with treatment".


What main components play a role in asthma?


What does hyper-responsiveness of the airways cause?


What are two ways to reverse an asthma attack?


Is there a test to determine asthma in an individual?

There is currently no precise test with the diagnosis typically based on the pattern of symptoms and response to therapy over time. A diagnosis of asthma should be suspected if there is a history of: recurrent wheezing, coughing or difficulty breathing and these symptoms occur or worsen due to exercise, viral infections, allergens or air pollution. Spirometry is then used to confirm the diagnosis. In children under the age of six the diagnosis is more difficult as they are too young for spirometry.


What is used to confirm the diagnosis of asthma?


What age is too young to use spirometry to determine asthma?


What is recommended to help in the diagnosis of asthma?

Spirometry is recommended to aid in diagnosis and management. It is the single best test for asthma. If the FEV1 measured by this technique improves more than 12% following administration of a bronchodilator such as salbutamol, this is supportive of the diagnosis. It however may be normal in those with a history of mild asthma, not currently acting up. As caffeine is a bronchodilator in people with asthma, the use of caffeine before a lung function test may interfere with the results. Single-breath diffusing capacity can help differentiate asthma from COPD. It is reasonable to perform spirometry every one or two years to follow how well a person's asthma is controlled.


Why is spirometry so commonly used to diagnose asthma?


What helps support the evidence of asthma?


What substance can skew the results of an asthma test?


What test can tell the difference between asthma and COPD?


What is the rate that is used in most of the evidence?

Other supportive evidence includes: a ≥20% difference in peak expiratory flow rate on at least three days in a week for at least two weeks, a ≥20% improvement of peak flow following treatment with either salbutamol, inhaled corticosteroids or prednisone, or a ≥20% decrease in peak flow following exposure to a trigger. Testing peak expiratory flow is more variable than spirometry, however, and thus not recommended for routine diagnosis. It may be useful for daily self-monitoring in those with moderate to severe disease and for checking the effectiveness of new medications. It may also be helpful in guiding treatment in those with acute exacerbations.


What is more variable than spirometry but not recommended?


Asthma is clinically classified according to the frequency of symptoms, forced expiratory volume in one second (FEV1), and peak expiratory flow rate. Asthma may also be classified as atopic (extrinsic) or non-atopic (intrinsic), based on whether symptoms are precipitated by allergens (atopic) or not (non-atopic). While asthma is classified based on severity, at the moment there is no clear method for classifying different subgroups of asthma beyond this system. Finding ways to identify subgroups that respond well to different types of treatments is a current critical goal of asthma research.


When asthma is caused by allergens that is called what?


What is asthma usually classified based on?


What is a important goal of asthma research?


Although asthma is a chronic obstructive condition, it is not considered as a part of chronic obstructive pulmonary disease as this term refers specifically to combinations of disease that are irreversible such as bronchiectasis, chronic bronchitis, and emphysema. Unlike these diseases, the airway obstruction in asthma is usually reversible; however, if left untreated, the chronic inflammation from asthma can lead the lungs to become irreversibly obstructed due to airway remodeling. In contrast to emphysema, asthma affects the bronchi, not the alveoli.


What are examples of chronic obstructive pulmonary disease?


Is the airway obstuction reversable in asthma?


What part of the airway does emphysema affect?


What part of the airway does asthma affect?


Exercise-induced bronchoconstriction is common in what profession?

Exercise can trigger bronchoconstriction both in people with or without asthma. It occurs in most people with asthma and up to 20% of people without asthma. Exercise-induced bronchoconstriction is common in professional athletes. The highest rates are among cyclists (up to 45%), swimmers, and cross-country skiers. While it may occur with any weather conditions it is more common when it is dry and cold. Inhaled beta2-agonists do not appear to improve athletic performance among those without asthma however oral doses may improve endurance and strength.


What professions has the highest rate of Exercise-induced bronchoconstriction?


What conditions are more likely to cause Exercise-induced bronchoconstriction?


What does not appear to help athletic performance that do not have asthma?


Asthma that is the result of or made worse by workplace exposure is reported as what?

Asthma as a result of (or worsened by) workplace exposures, is a commonly reported occupational disease. Many cases however are not reported or recognized as such. It is estimated that 5–25% of asthma cases in adults are work–related. A few hundred different agents have been implicated with the most common being: isocyanates, grain and wood dust, colophony, soldering flux, latex, animals, and aldehydes. The employment associated with the highest risk of problems include: those who spray paint, bakers and those who process food, nurses, chemical workers, those who work with animals, welders, hairdressers and timber workers.


What percent of asthma cases in adults are work-related?


What are some of the most common agents?


What professions normally have the highest risk of problems?


What is a condition that can cause symptoms of astham in children?

Many other conditions can cause symptoms similar to those of asthma. In children, other upper airway diseases such as allergic rhinitis and sinusitis should be considered as well as other causes of airway obstruction including: foreign body aspiration, tracheal stenosis or laryngotracheomalacia, vascular rings, enlarged lymph nodes or neck masses. Bronchiolitis and other viral infections may also produce wheezing. In adults, COPD, congestive heart failure, airway masses, as well as drug-induced coughing due to ACE inhibitors should be considered. In both populations vocal cord dysfunction may present similarly.


What are some other causes of airway obstruction?


What other conditions can cause wheezing?


In adults, what conditions can cause the symptoms of asthma?


What is a complication of chronic asthma?

Chronic obstructive pulmonary disease can coexist with asthma and can occur as a complication of chronic asthma. After the age of 65 most people with obstructive airway disease will have asthma and COPD. In this setting, COPD can be differentiated by increased airway neutrophils, abnormally increased wall thickness, and increased smooth muscle in the bronchi. However, this level of investigation is not performed due to COPD and asthma sharing similar principles of management: corticosteroids, long acting beta agonists, and smoking cessation. It closely resembles asthma in symptoms, is correlated with more exposure to cigarette smoke, an older age, less symptom reversibility after bronchodilator administration, and decreased likelihood of family history of atopy.


If you are 65 years old and have an obstructive airway disesase, you are more likely to have what other conditions?


Why is this not determined in a patient with COPD?


What are the principles of management for asthma and COPD?


What is weak that is not helping prevent the development of asthma?

The evidence for the effectiveness of measures to prevent the development of asthma is weak. Some show promise including: limiting smoke exposure both in utero and after delivery, breastfeeding, and increased exposure to daycare or large families but none are well supported enough to be recommended for this indication. Early pet exposure may be useful. Results from exposure to pets at other times are inconclusive and it is only recommended that pets be removed from the home if a person has allergic symptoms to said pet. Dietary restrictions during pregnancy or when breast feeding have not been found to be effective and thus are not recommended. Reducing or eliminating compounds known to sensitive people from the work place may be effective. It is not clear if annual influenza vaccinations effects the risk of exacerbations. Immunization; however, is recommended by the World Health Organization. Smoking bans are effective in decreasing exacerbations of asthma.


What preventative measures always work to prevent asthma?


What has been determined about dietry restrictions during pregnancy and when breast feeding?


What is a key component of control and preventing asthma attacks?

Avoidance of triggers is a key component of improving control and preventing attacks. The most common triggers include allergens, smoke (tobacco and other), air pollution, non selective beta-blockers, and sulfite-containing foods. Cigarette smoking and second-hand smoke (passive smoke) may reduce the effectiveness of medications such as corticosteroids. Laws that limit smoking decrease the number of people hospitalized for asthma. Dust mite control measures, including air filtration, chemicals to kill mites, vacuuming, mattress covers and others methods had no effect on asthma symptoms. Overall, exercise is beneficial in people with stable asthma. Yoga could provide small improvements in quality of life and symptoms in people with asthma.


What are some of the more common triggers?


What can reduce the effectiveness of medications?


What did law that limit smoking accomplish?


What type of exercise can provide small improvements?


What type of person would use bronchial thermoplasty as an option?

For those with severe persistent asthma not controlled by inhaled corticosteroids and LABAs, bronchial thermoplasty may be an option. It involves the delivery of controlled thermal energy to the airway wall during a series of bronchoscopies. While it may increase exacerbation frequency in the first few months it appears to decrease the subsequent rate. Effects beyond one year are unknown. Evidence suggests that sublingual immunotherapy in those with both allergic rhinitis and asthma improve outcomes.


What does bronchial thermoplasty consist of?


What effect does bronchial thermoplasty have?


What treatment helps improve those with allergic rhinitis and asthma?


The prognosis for asthma is generally good, especially for children with mild disease. Mortality has decreased over the last few decades due to better recognition and improvement in care. Globally it causes moderate or severe disability in 19.4 million people as of 2004 (16 million of which are in low and middle income countries). Of asthma diagnosed during childhood, half of cases will no longer carry the diagnosis after a decade. Airway remodeling is observed, but it is unknown whether these represent harmful or beneficial changes. Early treatment with corticosteroids seems to prevent or ameliorates a decline in lung function.


What has caused the mortality rate to decrease?


Worldwide, how many people suffer from asthma?


How many cases that are diagnosed in childhood make it past 10 years with asthma?


By 2011, how many people were affected by asthma?

As of 2011, 235–330 million people worldwide are affected by asthma, and approximately 250,000–345,000 people die per year from the disease. Rates vary between countries with prevalences between 1 and 18%. It is more common in developed than developing countries. One thus sees lower rates in Asia, Eastern Europe and Africa. Within developed countries it is more common in those who are economically disadvantaged while in contrast in developing countries it is more common in the affluent. The reason for these differences is not well known. Low and middle income countries make up more than 80% of the mortality.


How many people die per year from asthma?


What countries is asthma more commonly seen?


Why are different countries effected differently?


How much was the average cost of hospital stays for asthma-related issues for children??

From 2000 to 2010, the average cost per asthma-related hospital stay in the United States for children remained relatively stable at about $3,600, whereas the average cost per asthma-related hospital stay for adults increased from $5,200 to $6,600. In 2010, Medicaid was the most frequent primary payer among children and adults aged 18–44 years in the United States; private insurance was the second most frequent payer. Among both children and adults in the lowest income communities in the United States there is a higher rates of hospital stays for asthma in 2010 than those in the highest income communities.


How much was the average cost of hospital stays for asthma-related issues for adults?


Who was the most frequent primary payer amount children and adults?


Who was more likely to seek hospital help in the US for asthma reasons?


When was the first paper written about asthma?

In 1873, one of the first papers in modern medicine on the subject tried to explain the pathophysiology of the disease while one in 1872, concluded that asthma can be cured by rubbing the chest with chloroform liniment. Medical treatment in 1880, included the use of intravenous doses of a drug called pilocarpin. In 1886, F.H. Bosworth theorized a connection between asthma and hay fever. Epinephrine was first referred to in the treatment of asthma in 1905. Oral corticosteroids began to be used for this condition in the 1950s while inhaled corticosteroids and selective short acting beta agonist came into wide use in the 1960s.


What was first used as a cure for asthma?


In 1880 what was used intraveniously for asthma?


When did inhaled corticosteroids and short acting beta agonist start being used?


Did LaserDisks offer higher or lower quality sound and picture than VHS?

Although the format was capable of offering higher-quality video and audio than its consumer rivals, the VHS and Betamax videocassette systems, LaserDisc never managed to gain widespread use in North America, largely due to high costs for the players and video titles themselves and the inability to record TV programming. It also remained a largely obscure format in Europe and Australia. By contrast, the format was much more popular in Japan and in the more affluent regions of Southeast Asia, such as Hong Kong, Singapore, and Malaysia, being the prevalent rental video medium in Hong Kong during the 1990s. Its superior video and audio quality did make it a somewhat popular choice among videophiles and film enthusiasts during its lifespan.


Why didn't LaserDisk gain popularity in North America?


With whom was LaserDisk a popular choice for it's picture and sound quality?


In what city was LaserDisk used as a popular rental medium in the 1990s?


LaserDisc was first available on the market, in Atlanta, Georgia, on December 15, 1978, two years after the introduction of the VHS VCR, and four years before the introduction of the CD (which is based on laser disc technology). Initially licensed, sold, and marketed as MCA DiscoVision (also known as simply "DiscoVision") in North America in 1978, the technology was previously referred to internally as Optical Videodisc System, Reflective Optical Videodisc, Laser Optical Videodisc, and Disco-Vision (with a dash), with the first players referring to the format as "Video Long Play".


How many years after VHS was LaserDisk released?


Under what name was LaserDisc originally marketed?


How did the first viewers refer to the media?


Who purchased the majority stake and re-marketed the product in 1980?

Pioneer Electronics later purchased the majority stake in the format and marketed it as both LaserVision (format name) and LaserDisc (brand name) in 1980, with some releases unofficially referring to the medium as "Laser Videodisc". Philips produced the players while MCA produced the discs. The Philips-MCA cooperation was not successful, and discontinued after a few years. Several of the scientists responsible for the early research (Richard Wilkinson, Ray Dakin and John Winslow) founded Optical Disc Corporation (now ODC Nimbus).


Was Laserdisk officially or unofficially reffered to as "Laser Videodisc"?


Did MCA produce the disc or the players after being bought out?


Who were the scientists that worked on the early research for Laserdiscs?


What company did the early Laserdisc researchers later found?


What product replaced LaserDisc in North America by the early 2000s?

By the early 2000s, LaserDisc was completely replaced by DVD in the North American retail marketplace, as neither players nor software were then produced. Players were still exported to North America from Japan until the end of 2001. The format has retained some popularity among American collectors, and to a greater degree in Japan, where the format was better supported and more prevalent during its life. In Europe, LaserDisc always remained an obscure format. It was chosen by the British Broadcasting Corporation (BBC) for the BBC Domesday Project in the mid-1980s, a school-based project to commemorate 900 years since the original Domesday Book in England. From 1991 up until the early 2000s, the BBC also used LaserDisc technology to play out the channel idents.


Who chose LaserFisc for their Domesday Project in the mid-1980s?


Which country still exported players to North America until 2001?


The standard home video LaserDisc was 30 cm (12 in) in diameter and made up of two single-sided aluminum discs layered in plastic. Although appearing similar to compact discs or DVDs, LaserDiscs used analog video stored in the composite domain (having a video bandwidth approximately equivalent to the 1-inch (25 mm) C-Type VTR format) with analog FM stereo sound and PCM digital audio. The LaserDisc at its most fundamental level was still recorded as a series of pits and lands much like CDs, DVDs, and even Blu-ray Discs are today. However, while the encoding is of a binary nature, the information is encoded as analog pulse width modulation with a 50% duty cycle, where the information is contained in the lengths and spacing of the pits. In true digital media the pits, or their edges, directly represent 1s and 0s of a binary digital information stream. Early LaserDiscs featured in 1978 were entirely analog but the format evolved to incorporate digital stereo sound in CD format (sometimes with a TOSlink or coax output to feed an external DAC), and later multi-channel formats such as Dolby Digital and DTS.


What numbers are used in Binary information coding?


Were the ealiest LaserDiscs in 1978 analog or digitally formatted?


What was the length capacity of the CAA55 format?

As Pioneer introduced Digital Audio to LaserDisc in 1985, they further refined the CAA format. CAA55 was introduced in 1985 with a total playback capacity per side of 55 minutes 5 seconds, reducing the video capacity to resolve bandwidth issues with the inclusion of Digital Audio. Several titles released between 1985 and 1987 were analog audio only due to the length of the title and the desire to keep the film on one disc (e.g., Back to the Future). By 1987, Pioneer had overcome the technical challenges and was able to once again encode in CAA60, allowing a total of 60 minutes 5 seconds. Pioneer further refined CAA, offering CAA45, encoding 45 minutes of material, but filling the entire playback surface of the side. Used on only a handful of titles, CAA65 offered 65 minutes 5 seconds of playback time per side. There are a handful of titles pressed by Technidisc that used CAA50. The final variant of CAA is CAA70, which could accommodate 70 minutes of playback time per side. There are not any known uses of this format on the consumer market.


Why was Back to the Future released with analog sound?


What was the maximum length of the CAA60 format?


How many works were released to the public with the CAA70 format?


What was the difference between LaserDisc and LaserVision in the UK?

Sound could be stored in either analog or digital format and in a variety of surround sound formats; NTSC discs could carry two analog audio tracks, plus two uncompressed PCM digital audio tracks, which were (EFM, CIRC, 16-bit and 44.056 kHz sample rate). PAL discs could carry one pair of audio tracks, either analog or digital and the digital tracks on a PAL disc were 16-bit 44.1 kHz as on a CD; in the UK, the term "LaserVision" is used to refer to discs with analog sound, while "LaserDisc" is used for those with digital audio. The digital sound signal in both formats are EFM-encoded as in CD. Dolby Digital (also called AC-3) and DTS—which are now common on DVD titles—first became available on LaserDisc, and Star Wars: Episode I – The Phantom Menace (1999) which was released on LaserDisc in Japan, is among the first home video releases ever to include 6.1 channel Dolby Digital EX Surround. Unlike DVDs, which carry Dolby Digital audio in digital form, LaserDiscs store Dolby Digital in a frequency modulated form within a track normally used for analog audio. Extracting Dolby Digital from a LaserDisc required a player equipped with a special "AC-3 RF" output and an external demodulator in addition to an AC-3 decoder. The demodulator was necessary to convert the 2.88 MHz modulated AC-3 information on the disc into a 384 kbit/s signal that the decoder could handle. DTS audio, when available on a disc, replaced the digital audio tracks; hearing DTS sound required only an S/PDIF compliant digital connection to a DTS decoder.


The Phantom Menace was one of the first home videos to use what sound format?


What competition caused LaserDisc sales to decline?

In the mid to late 1990s many higher-end AV receivers included the demodulator circuit specifically for the LaserDisc players RF modulated Dolby Digital AC-3 signal. By the late 1990s with LaserDisc players and disc sales declining due to DVD's growing popularity the AV receiver manufacturers removed the demodulator circuit. Although DVD players were capable of playing Dolby Digital tracks, the signal out of DVD player were not in a modulated form and not compatible with the inputs designed for LaserDisc AC-3. Outboard demodulators were available for a period that convert the AC-3 signal to standard Dolby Digital signal that was compatible with the standard Dolby Digital/PCM inputs on capable AV receivers. Another type marketed by Onkyo and others converted the RF AC-3 signal to 6-channel analog audio.


Did all AV receivers carry the demodulator circuits necessary for LaserDiscs, or only high-end models?


What did the Onkyo outboard demodulator covert the RF AC-2 signal to?


Was sound quality from disc to disc and between players consistent or varied?

At least where the digital audio tracks were concerned, the sound quality was unsurpassed at the time compared to consumer videotape, but the quality of the analog soundtracks varied greatly depending on the disc and, sometimes, the player. Many early and lower-end LD players had poor analog audio components, and many early discs had poorly mastered analog audio tracks, making digital soundtracks in any form most desirable to serious enthusiasts. Early DiscoVision and LaserDisc titles lacked the digital audio option, but many of those movies received digital sound in later re-issues by Universal, and the quality of analog audio tracks generally got far better as time went on. Many discs that had originally carried old analog stereo tracks received new Dolby Stereo and Dolby Surround tracks instead, often in addition to digital tracks, helping boost sound quality. Later analog discs also applied CX Noise Reduction, which improved the signal-noise ratio of their audio.


Was analog or digital formatting more popular with enthusiasts?


What result did adding CX Noise Reduction have on analog discs?


Which company added digital sound option when re-releasing movies?


Which channel would not work in conjunction with AC-3 audio?

Both AC-3 and DTS surround audio were clumsily implemented on LaserDiscs, leading to some interesting player- and disc-dependent issues. A disc that included AC-3 audio forfeited the right analog audio channel to the modulated AC-3 RF stream. If the player did not have an AC-3 output available, the next most attractive playback option would be the digital Dolby Surround or stereo audio tracks. The reason for this is the RF signal needs to bypass the audio circuitry in order to be properly processed by the demodulator. If either the player did not support digital audio tracks (common in older players), or the disc did not include digital audio tracks at all (uncommon for a disc which is mastered with an AC-3 track), the only remaining option was to fall back to a monophonic presentation of the left analog audio track. However, many older analog-only players not only failed to output AC-3 streams correctly, but were not even aware of their potential existence. Such a player will happily play the analog audio tracks verbatim, resulting in garbage (static) output in the right channel.


What audio playback options were available if an AC-3 output was not present?


What happens to the right channel in a player that doesn't recognize AC-3?


Are integrated AC-3 demodulators common in LaserDisc players or a rare find?

Only one 5.1 surround sound option exists on a given LaserDisc (either Dolby Digital or DTS), so if surround sound is desired, the disc must be matched to the capabilities of the playback equipment (LD Player and Receiver/Decoder) by the purchaser. A fully capable LaserDisc playback system includes a newer LaserDisc player that is capable of playing digital tracks, has a digital optical output for digital PCM and DTS audio, is aware of AC-3 audio tracks, and has an AC-3 coaxial output; an external or internal AC-3 RF demodulator and AC-3 decoder; and a DTS decoder. Many 1990s A/V receivers combine the AC-3 decoder and DTS decoder logic, but an integrated AC-3 demodulator is rare both in LaserDisc players and in later A/V receivers.


How many 5.1 surround sound options exist in LaserDiscs?


What type of decoder logic is common in 1990s A/V receivers?


Which has a longer playing time: PAL LaserDiscs or NTSC discs?

PAL LaserDiscs have a slightly longer playing time than NTSC discs, but have fewer audio options. PAL discs only have two audio tracks, consisting of either two analog-only tracks on older PAL LDs, or two digital-only tracks on newer discs. In comparison, later NTSC LDs are capable of carrying four tracks (two analog and two digital). On certain releases, one of the analog tracks is used to carry a modulated AC-3 signal for 5.1 channel audio (for decoding and playback by newer LD players with an "AC-3 RF" output). However, older NTSC LDs made before 1984 (such as the original DiscoVision discs) only have two analog audio tracks.


How many audio tracks do PAL LaserDiscs have?


Which two audio options are available on PAL LaserDiscs?


What was the name of the first solid-state laser consumer LaserDisc player?

In March 1984, Pioneer introduced the first consumer player with a solid-state laser, the LD-700. It was also the first LD player to load from the front and not the top. One year earlier Hitachi introduced an expensive industrial player with a laser diode, but the player, which had poor picture quality due to an inadequate dropout compensator, was made only in limited quantities. After Pioneer released the LD-700, gas lasers were no longer used in consumer players, despite their advantages, although Philips continued to use gas lasers in their industrial units until 1985.


Besides a solid-state laser, what else was unique about the LD-700?


Which company continued to use gas-lasers in industrial models of LD players although they were no longer used in consumer models?


Which three names did MCA use for LaserDisc technology during its development?

During its development, MCA, which co-owned the technology, referred to it as the Optical Videodisc System, "Reflective Optical Videodisc" or "Laser Optical Videodisc", depending on the document; changing the name once in 1969 to Disco-Vision and then again in 1978 to DiscoVision (without the hyphen), which became the official spelling. Technical documents and brochures produced by MCA Disco-Vision during the early and mid-'70s also used the term "Disco-Vision Records" to refer to the pressed discs. MCA owned the rights to the largest catalog of films in the world during this time, and they manufactured and distributed the DiscoVision releases of those films under the "MCA DiscoVision" software and manufacturing label; consumer sale of those titles began on December 15, 1978, with the aforementioned Jaws.


To what did MCA change the name to in 1969?


When did MCA remove the hyphen from the name Disco-Vision?


Which company owned the rights to the world's largest collection of films during the 1970s?


Consumer sales of MCA films began in 1978 with what movie?


What did VLP stand for in English-speaking countries?

Philips' preferred name for the format was "VLP", after the Dutch words Video Langspeel-Plaat ("Video long-play disc"), which in English-speaking countries stood for Video Long-Play. The first consumer player, the Magnavox VH-8000 even had the VLP logo on the player. For a while in the early and mid-1970s, Philips also discussed a compatible audio-only format they called "ALP", but that was soon dropped as the Compact Disc system became a non-compatible project in the Philips corporation. Until early 1980, the format had no "official" name. The LaserVision Association, made up of MCA, Universal-Pioneer, IBM, and Philips/Magnavox, was formed to standardize the technical specifications of the format (which had been causing problems for the consumer market) and finally named the system officially as "LaserVision".


Which group officially chose the name "Laservision"?


The Laservision Association was comprised of which companies?


Which company joined a 50/50 partnership with MCA in 1977?

Pioneer Electronics also entered the optical disc market in 1977 as a 50/50 joint-venture with MCA called Universal-Pioneer and manufacturing MCA designed industrial players under the MCA DiscoVision name (the PR-7800 and PR-7820). For the 1980 launch of the first Universal-Pioneer player, the VP-1000 was noted as a "laser disc player", although the "LaserDisc" logo displayed clearly on the device. In 1981, "LaserDisc" was used exclusively for the medium itself, although the official name was "LaserVision" (as seen at the beginning of many LaserDisc releases just before the start of the film). However, as Pioneer reminded numerous video magazines and stores in 1984, LaserDisc was a trademarked word, standing only for LaserVision products manufactured for sale by Pioneer Video or Pioneer Electronics. A 1984 Ray Charles ad for the LD-700 player bore the term "Pioneer LaserDisc brand videodisc player". From 1981 until the early 1990s, all properly licensed discs carried the LaserVision name and logo, even Pioneer Artists titles.


In what year was the first Universal-Pioneer player released?


What was the name of the first Universal-Pioneer player?


Which singer did an ad for the LD-700 player in 1984?


What other companies did MCA manufacture discs for?

During the early years, MCA also manufactured discs for other companies including Paramount, Disney and Warner Bros. Some of them added their own names to the disc jacket to signify that the movie was not owned by MCA. After Discovision Associates shut down in early 1982, Universal Studio's videodisc software label, called MCA Videodisc until 1984, began reissuing many DiscoVision titles. Unfortunately, quite a few, such as Battlestar Galactica and Jaws, were time-compressed versions of their CAV or CLV Disco Vision originals. The time-compressed CLV re-issue of Jaws no longer had the original soundtrack, having had incidental background music replaced for the video disc version due to licensing cost (the music would not be available until the THX LaserDisc box set was released in 1995). One Universal/Columbia co-production issued by MCA Disco Vision in both CAV and CLV versions, The Electric Horseman, is still not available in any other home video format with its original score intact; even the most recent DVD release has had substantial music replacements of both instrumental score and Willie Nelson's songs. An MCA release of Universal's Howard the Duck, sees only the start credits shown in widescreen before changing to 4:3 for the rest of the film. For many years this was the only disc-based release of the film, until widescreen DVD formats were released with extras. Also, the LaserDisc release of E.T. the Extra-Terrestrial is the only format to include the cut scene of Harrison Ford playing the part of the school headmaster telling off Elliott for letting the frogs free in the biology class.


What quirk is present in MCA's release of Howard the Duck?


What is unique about the LaserDisc release of E.T.?


Which film is only available with its original score in LD format , even today?


How many horizontal TVL lines did LaserDisc have in comparison to VHS's 240?

LaserDisc had a number of advantages over VHS. It featured a far sharper picture with a horizontal resolution of 425 TVL lines for NTSC and 440 TVL lines for PAL discs, while VHS featured only 240 TVL lines with NTSC. It could handle analog and digital audio where VHS was mostly analog only (VHS can have PCM audio in professional applications but is uncommon), and the NTSC discs could store multiple audio tracks. This allowed for extras like director's commentary tracks and other features to be added onto a film, creating "Special Edition" releases that would not have been possible with VHS. Disc access was random and chapter based, like the DVD format, meaning that one could jump to any point on a given disc very quickly. By comparison, VHS would require tedious rewinding and fast-forwarding to get to specific points.


Which medium was chapter based like DVD format, Laserdisc or VHS?


Which medium allowed for multiple audio tracks, Laserdisc or VHS?


Were Laserdiscs initially cheaper or more costly to produce than their VHS counterparts?

LaserDiscs were initially cheaper than videocassettes to manufacture, because they lacked the moving parts and plastic outer shell that are necessary for VHS tapes to work, and the duplication process was much simpler. A VHS cassette has at least 14 parts including the actual tape while LaserDisc has one part with five or six layers. A disc can be stamped out in a matter of seconds whereas duplicating videotape required a complex bulk tape duplication mechanism and was a time-consuming process. However, by the end of the 1980s, average disc-pressing prices were over $5.00 per two-sided disc, due to the large amount of plastic material and the costly glass-mastering process needed to make the metal stamper mechanisms. Due to the larger volume of demand, videocassettes quickly became much cheaper to duplicate, costing as little as $1.00 by the beginning of the 1990s.


How many parts does a VHS tape have that must be manufactured?


How much did LaserDiscs cost to produce by the end of the 1980s?


How much did VHS cost to produce by the 1990s?


Were Laserdiscs or VHS more durable in the long run?

LaserDiscs potentially had a much longer lifespan than videocassettes. Because the discs were read optically instead of magnetically, no physical contact needs to be made between the player and the disc, except for the player's clamp that holds the disc at its center as it is spun and read. As a result, playback would not wear the information-bearing part of the discs, and properly manufactured LDs would theoretically last beyond one's lifetime. By contrast, a VHS tape held all of its picture and sound information on the tape in a magnetic coating which is in contact with the spinning heads on the head drum, causing progressive wear with each use (though later in VHS's lifespan, engineering improvements allowed tapes to be made and played back without contact). Also, the tape was thin and delicate, and it was easy for a player mechanism, especially on a low quality or malfunctioning model, to mishandle the tape and damage it by creasing it, frilling (stretching) its edges, or even breaking it.


Why is physical contact with a VHS tape less desirable than an optical reading?


Where do VHS tapes store their information?


LaserDisc was a composite video format: the luminance (black and white) and chrominance (color) information were transmitted in one signal, separated by the receiver. While good comb filters can do so adequately, these two signals cannot be completely separated. On DVDs, data is stored in the form of digital blocks which make up each independent frame. The signal produced is dependent on the equipment used to master the disc. Signals range from composite and split, to YUV and RGB. Depending upon which format is used, this can result in far higher fidelity, particularly at strong color borders or regions of high detail (especially if there is moderate movement in the picture) and low-contrast details like skin tones, where comb filters almost inevitably smudge some detail.


What device seperated the black and white and color signals in LaserDiscs?


In what areas are comb filters most likely to lose detail?


Are comb filters exact, or is some data smudged?


In contrast to the entirely digital DVD, LaserDiscs use only analog video. As the LaserDisc format is not digitally encoded and does not make use of compression techniques, it is immune to video macroblocking (most visible as blockiness during high motion sequences) or contrast banding (subtle visible lines in gradient areas, such as out-of-focus backgrounds, skies, or light casts from spotlights) that can be caused by the MPEG-2 encoding process as video is prepared for DVD. Early DVD releases held the potential to surpass their LaserDisc counterparts, but often managed only to match them for image quality, and in some cases, the LaserDisc version was preferred. However, proprietary human-assisted encoders manually operated by specialists can vastly reduce the incidence of artifacts, depending on playing time and image complexity. By the end of LaserDisc's run, DVDs were living up to their potential as a superior format.


What step of the DVD production process causes contrast banding?


How does LaserDisc operation vary from DVD?

LaserDisc players can provide a great degree of control over the playback process. Unlike many DVD players, the transport mechanism always obeys commands from the user: pause, fast-forward, and fast-reverse commands are always accepted (barring, of course, malfunctions). There were no "User Prohibited Options" where content protection code instructs the player to refuse commands to skip a specific part (such as fast forwarding through copyright warnings). (Some DVD players, particularly higher-end units, do have the ability to ignore the blocking code and play the video without restrictions, but this feature is not common in the usual consumer market.)


What are "User Protected Options" on DVDs?


Where are User Protected Options commonly found on DVDs?


Which format, LaserDisc or DVD, gives the user the most control over playback?


What does the repair+skip feature on newer DVD players do?

Damaged spots on a LaserDisc can be played through or skipped over, while a DVD will often become unplayable past the damage. Some newer DVD players feature a repair+skip algorithm, which alleviates this problem by continuing to play the disc, filling in unreadable areas of the picture with blank space or a frozen frame of the last readable image and sound. The success of this feature depends upon the amount of damage. LaserDisc players, when working in full analog, recover from such errors faster than DVD players. Direct comparison here is almost impossible due to the sheer size differences between the two media. A 1 in (3 cm) scratch on a DVD will probably cause more problems than a 1 in (3 cm) scratch on a LaserDisc, but a fingerprint taking up 1% of the area of a DVD would almost certainly cause fewer problems than a similar mark covering 1% of the surface of a LaserDisc.[citation needed]


Which format, DVD or Laserdisc, can become unreadable with damage?


Will the same size scratch cause more problems for a DVD or LaserDisc?


Which format is considered to look most realistic, LaserDisc or DVD?

Similar to the CD versus LP sound quality debates common in the audiophile community, some videophiles argue that LaserDisc maintains a "smoother", more "film-like", natural image while DVD still looks slightly more artificial. Early DVD demo discs often had compression or encoding problems, lending additional support to such claims at the time. However, the video signal-to-noise ratio and bandwidth of LaserDisc are substantially less than that of DVDs, making DVDs appear sharper and clearer to most viewers.


Which format, LaserDisc or DVD, is said to appear sharper and clearer to most viewers?


What features do LaserDiscs lack in, causing DVDs to appear sharper and clearer?


What was the vertical blanking interval used for in LaserDiscs, preventing Macrovision signal to be implemented?

Another advantage, at least to some consumers, was the lack of any sort of anti-piracy technology. It was claimed that Macrovision's Copyguard protection could not be applied to LaserDisc, due to the format's design. The vertical blanking interval, where the Macrovision signal would be implemented, was also used for the internal timing on LaserDisc players, so test discs with Macrovision would not play at all. There was never a push to redesign the format despite the obvious potential for piracy due to its relatively small market share. The industry simply decided to engineer it into the DVD specification.


Why wasn't there a need to redesign the LaserDisc format to prevent piracy?


What protection could not be applied to LaserDiscs, making them prone to piracy?


LaserDisc was the first format to provide what type of releases to consumers?

LaserDisc's support for multiple audio tracks allowed for vast supplemental materials to be included on-disc and made it the first available format for "Special Edition" releases; the 1984 Criterion Collection edition of Citizen Kane is generally credited as being the first "Special Edition" release to home video,[citation needed] and for setting the standard by which future SE discs were measured. The disc provided interviews, commentary tracks, documentaries, still photographs, and other features for historians and collectors.


What was the first "Special Edition" film to be released to home video?


What bonus features were available on the first home video "Special Edition"?


What feature, unique to LaserDisc, made bonus content possible?


What was required of a LaserDisc to continue playback after 60 minutes?

The space-consuming analog video signal of a LaserDisc limited playback duration to 30 minutes (CAV) or 60 minutes (CLV) per side because of the hardware manufacturer's refusal to reduce line count for increased playtime. After one side was finished playing, a disc has to be flipped over in order to continue watching a movie, and some titles fill two or more discs. Many players, especially units built after the mid-1980s, can "flip" discs automatically by rotating the optical pickup to the other side of the disc, but this is accompanied by a pause in the movie during the side change. If the movie is longer than what could be stored on two sides of a single disc, manually swapping to a second disc is necessary at some point during the film. One exception to this rule is the Pioneer LD-W1, which features two disc platters. In addition, perfect still frames and random access to individual still frames is limited only to the more expensive CAV discs, which only had a playing time of approximately 30 minutes per side. In later years, Pioneer and other manufacturers overcame this limitation by incorporating a digital memory buffer, which "grabbed" a single frame from a CLV disc.


Which LaserDisc player solves the disc switching dilemma?


What must be reduced in order to allow LaserDisc playback time to increase?


Which format allows for more playback tie per side, CLV or CAV?


What video problems on a LaserDisc can be caused by dust or scratches?

The analog information encoded on LaserDiscs does not include any form of built-in checksum or error correction. Because of this, slight dust and scratches on the disc surface can result in read-errors which cause various video quality problems: glitches, streaks, bursts of static, or momentary picture interruptions. In contrast, the digital MPEG-2 format information used on DVDs has built-in error correction which ensures that the signal from a damaged disc will remain identical to that from a perfect disc right up until the point at which damage to the disc surface is so substantial that it prevents the laser from being able to identify usable data.


Which format used in DVDs has built-in error correction?


What type of encoding, analog or digital, causes LaserDiscs to be succeptable to damages?


In addition, LaserDisc videos sometimes exhibit a problem known as "crosstalk". The issue can arise when the laser optical pickup assembly within the player is out of alignment or because the disc is damaged or excessively warped, but it could also occur even with a properly functioning player and a factory-new disc, depending on electrical and mechanical alignment problems. In these instances, the issue arose due to the fact that CLV discs require subtle changes in rotating speed at various points during playback. During a change in speed, the optical pickup inside the player might read video information from a track adjacent to the intended one, causing data from the two tracks to "cross"; the extra video information picked up from that second track shows up as distortion in the picture which looks reminiscent of swirling "barber poles" or rolling lines of static.


What problem can be caused by a player becoming out of alignment?


How does "crosstalk" appear to the viewer?


In which format does crosstalk generally not occur?

Assuming the player's optical pickup is in proper working order, crosstalk distortion normally does not occur during playback of CAV format LaserDiscs, as the rotational speed never varies. However, if the player calibration is out of order or if the CAV disc is faulty or damaged, other problems affecting tracking accuracy can occur. One such problem is "laser lock", where the player reads the same two fields for a given frame over and over again, causing the picture to look frozen as if the movie were paused.


Why does the CAV format prevent crosstalk?


Is LaserDisc quality consistent or inconsistent between player brands?

Another significant issue unique to LaserDisc is one involving the inconsistency of playback quality between different makers and models of player. On most televisions, a given DVD player will produce a picture that is visually indistinguishable from other units. Differences in image quality between players only becomes easily apparent on large televisions and substantial leaps in image quality are generally only obtained with expensive, high-end players that allow for post-processing of the MPEG-2 stream during playback. In contrast, LaserDisc playback quality is highly dependent on hardware quality. Major variances in picture quality appear between different makers and models of LD players, even when tested on a low to mid-range television. The obvious benefits of using high quality equipment has helped keep demand for some players high, thus also keeping pricing for those units comparably high. In the 1990s, notable players sold for anywhere from US$200 to well over $1,000, while older and less desirable players could be purchased in working condition for as little as $25.


What is LaserDisc playback quality dependent on?


How cheaply could an older LaserDisc player be purchased in the 1990s?


What range of prices were high-end LaserDisc players in the 1990s?


What substandard product was used in LD manufacturing that caused "laser rot"?

Many early LDs were not manufactured properly; sometimes a substandard adhesive was used to sandwich together the two sides of the disc.[citation needed] The adhesive contained impurities that were able to penetrate the lacquer seal layer and chemically attack the metalized reflective aluminium layer, causing it to oxidize and lose its reflective characteristics. This was a problem that was termed "laser rot" among LD enthusiasts, also called "color flash" internally by LaserDisc-pressing plants. Some forms of laser rot could appear as black spots that looked like mold or burned plastic which cause the disc to skip and the movie to exhibit excessive speckling noise. But, for the most part, rotted discs could actually appear perfectly fine to the naked eye.


What was the internal name for "laser rot" within LD processing plants?


What problems could occur with laser rot?


Why didn't LaserDiscs become popular in North America?

LaserDisc did not have high market penetration in North America due to the high cost of the players and discs, which were far more expensive than VHS players and tapes, and due to marketplace confusion with the technologically inferior CED, which also went by the name Videodisc. While the format was not widely adopted by North American consumers, it was well received among videophiles due to the superior audio and video quality compared to VHS and Betamax tapes, finding a place in nearly one million American homes by the end of 1990. The format was more popular in Japan than in North America because prices were kept low to ensure adoption, resulting in minimal price differences between VHS tapes and the higher quality LaserDiscs, helping ensure that it quickly became the dominant consumer video format in Japan. Anime collectors in every country the LD format was released, which includes both North America and Japan, also quickly became familiar with this format, and sought the higher video and sound quality of LaserDisc and the availability of numerous titles not available on VHS. LaserDiscs were also popular alternatives to videocassettes among movie enthusiasts in the more affluent regions of South East Asia, such as Singapore, due to their high integration with the Japanese export market and the disc-based media's superior longevity compared to videocassette, especially in the humid conditions endemic to that area of the world.


By 1990, how many American homes were estimated to use LD?


Why were LaserDiscs more popular in Japan?


Which format was more popular in high humidity areas such as Singapore?


How much did a LD cost in Hong Kong in the 1990s?

The format also became quite popular in Hong Kong during the 1990s before the introduction of VCDs and DVD; although people rarely bought the discs (because each LD was priced around USD100), high rental activity helped the video rental business in the city grow larger than it had ever been previously. Due to integration with the Japanese export market, NTSC LaserDiscs were used in the Hong Kong market, in contrast to the PAL standard used for broadcast (This anomaly also exists for DVD). This created a market for multi-system TVs and multi-system VCRs which could display or play both PAL and NTSC materials in addition to SECAM materials (which were never popular in Hong Kong). Some LD players could convert NTSC signals to PAL so that most TVs used in Hong Kong could display the LD materials.


Broadcast in Hong Kong used which standard formatting?


In contrast to broadcast, which format did consumers use in Hong Kong?


By what year had DVD taken over the LaserDisc market?

Although the LaserDisc format was supplanted by DVD by the late 1990s, many LD titles are still highly coveted by movie enthusiasts (for example, Disney's Song of the South which is unavailable in the US in any format, but was issued in Japan on LD). This is largely because there are many films that are still only available on LD and many other LD releases contain supplemental material not available on subsequent DVD versions of those films. Until the end of 2001, many titles were released on VHS, LD, and DVD in Japan.


Which collector group highly values LaserDisc for their rareness?


Until the end of what year were movies released in VHS, LD, and DVD in Japan?


What country was the only to receive a LD release of Disney's Song of the South?


In what decade did Philips produce a "professional" LD model for computer?

In the early 1980s, Philips produced a LaserDisc player model adapted for a computer interface, dubbed "professional". In 1985, Jasmine Multimedia created LaserDisc Juke Boxes featuring music videos from Michael Jackson, Duran Duran, and Cyndi Lauper. When connected to a PC this combination could be used to display images or information for educational or archival purposes, for example thousands of scanned medieval manuscripts. This strange device could be considered a very early equivalent of a CD-ROM.


Which musical artists were featured on LD Jukeboxes in 1985?


How many EditDroid systems were ever built?

In the mid-1980s Lucasfilm pioneered the EditDroid non-linear editing system for film and television based on computer-controlled LaserDisc players. Instead of printing dailies out on film, processed negatives from the day's shoot would be sent to a mastering plant to be assembled from their 10-minute camera elements into 20-minute film segments. These were then mastered onto single-sided blank LaserDiscs, just as a DVD would be burnt at home today, allowing for much easier selection and preparation of an Edit Decision List. In the days before video assist was available in cinematography, this was the only other way a film crew could see their work. The EDL went to the negative cutter who then cut the camera negative accordingly and assembled the finished film. Only 24 EditDroid systems were ever built, even though the ideas and technology are still in use today. Later EditDroid experiments borrowed from hard-drive technology of having multiple discs on the same spindle and added numerous playback heads and numerous electronics to the basic jukebox design so that any point on each of the discs would be accessible within seconds. This eliminated the need for racks and racks of industrial LaserDisc players since EditDroid discs were only single-sided.


Were EditDroid discs single or multi-sided?


Which production company engineered the EditDroid machines in the 1980s?


In what year did the Doomsday project occur?

In 1986, a SCSI-equipped LaserDisc player attached to a BBC Master computer was used for the BBC Domesday Project. The player was referred as an LV-ROM (LaserVision Read Only Memory) as the discs contained the driving software as well as the video frames. The discs used the CAV format, and encoded data as a binary signal represented by the analog audio recording. These discs could contain in each CAV frame video/audio or video/binary data, but not both. "Data" frames would appear blank when played as video. It was typical for each disc to start with the disc catalog (a few blank frames) then the video introduction before the rest of the data. Because the format (based on the ADFS hard disc format) used a starting sector for each file, the data layout effectively skipped over any video frames. If all 54,000 frames are used for data storage an LV-ROM disc can contain 324 MB of data per side. The Domesday Project systems also included a genlock, allowing video frames, clips and audio to be mixed with graphics originated from the BBC Master; this was used to great effect for displaying high resolution photographs and maps, which could then be zoomed into.


Which equipment was used for the Doomsday Project?


The Doomsday Project discs used which formatting?


Which of Apple's programming languages allowed users to ceatively manipulate LaserDiscs?

Apple's HyperCard scripting language provided Macintosh computer users with a means to design databases of slides, animation, video and sounds from LaserDiscs and then to create interfaces for users to play specific content from the disc through software called LaserStacks. User-created "stacks" were shared and were especially popular in education where teacher-generated stacks were used to access discs ranging from art collections to basic biological processes. Commercially available stacks were also popular with the Voyager company being possibly the most successful distributor.


What did LaserStacks software enable Mac users to do?


Where were "stacks" created with the LaserStack software used?


Which commercial company was LaserStack's most successful distributor?


A combination computer/LD player was comissioned by what government entity?

Under contract from the U.S. Military, Matrox produced a combination computer/LaserDisc player for instructional purposes. The computer was a 286, the LaserDisc player only capable of reading the analog audio tracks. Together they weighed 43 lb (20 kg) and sturdy handles were provided in case two people were required to lift the unit. The computer controlled the player via a 25-pin serial port at the back of the player and a ribbon cable connected to a proprietary port on the motherboard. Many of these were sold as surplus by the military during the 1990s, often without the controller software. Nevertheless, it is possible to control the unit by removing the ribbon cable and connecting a serial cable directly from the computer's serial port to the port on the LaserDisc player.


How much did Matrox's computer/LD combo weigh?


How could Matrox's computer unconventionally be controlled?


What quality made LDs a consideration for videogames in the 1980s and 1990s?

The format's instant-access capability made it possible for a new breed of LaserDisc-based video arcade games and several companies saw potential in using LaserDiscs for video games in the 1980s and 1990s, beginning in 1983 with Sega's Astron Belt. American Laser Games and Cinematronics produced elaborate arcade consoles that used the random-access features to create interactive movies such as Dragon's Lair and Space Ace. Similarly, the Pioneer Laseractive and Halcyon were introduced as home video game consoles that used LaserDisc media for their software.


What was the first game to use LaserDiscs?


In what year was Sega's AStron Belt released?


With what operating ratio would MUSE Discs operate?

In 1991, several manufacturers announced specifications for what would become known as MUSE LaserDisc, representing a span of almost 15 years until the feats of this HD analog optical disc system would finally be duplicated digitally by HD DVD and Blu-ray Disc. Encoded using NHK's MUSE "Hi-Vision" analogue TV system, MUSE discs would operate like standard LaserDiscs but would contain high-definition 1,125-line (1,035 visible lines) (Sony HDVS) video with a 5:3 aspect ratio. The MUSE players were also capable of playing standard NTSC format discs and are superior in performance to non-MUSE players even with these NTSC discs. The MUSE-capable players had several noteworthy advantages over standard LaserDisc players, including a red laser with a much narrower wavelength than the lasers found in standard players. The red laser was capable of reading through disc defects such as scratches and even mild disc rot that would cause most other players to stop, stutter or drop-out. Crosstalk was not an issue with MUSE discs, and the narrow wavelength of the laser allowed for the virtual elimination of crosstalk with normal discs.


What benefits did the MUSE narrow wavelength red laser have?


In addition to scratches and rot, what other common LaserDisc issue was to be eliminated by MUSE discs?


How many years did it take Blu-ray and HD-DVD players to duplicate MUSE technology?


In order to view MUSE encoded discs, it was necessary to have a MUSE decoder in addition to a compatible player. There are televisions with MUSE decoding built-in and set top tuners with decoders that can provide the proper MUSE input. Equipment prices were high, especially for early HDTVs which generally eclipsed US$10,000, and even in Japan the market for MUSE was tiny. Players and discs were never officially sold in North America, although several distributors imported MUSE discs along with other import titles. Terminator 2: Judgment Day, Lawrence of Arabia, A League of Their Own, Bugsy, Close Encounters of the Third Kind, Bram Stoker's Dracula and Chaplin were among the theatrical releases available on MUSE LDs. Several documentaries, including one about Formula One at Japan's Suzuka Circuit were also released.


Did MUSE have a large or small target market, even in Japan?


What were some movies that were released on MUSE LaserDiscs?


With the release of 16:9 televisions in the mid-1990s, Pioneer and Toshiba decided that it was time to take advantage of this aspect ratio. Squeeze LDs were enhanced 16:9-ratio widescreen LaserDiscs. During the video transfer stage, the movie was stored in an anamorphic "squeezed" format. The widescreen movie image was stretched to fill the entire video frame with less or none of the video resolution wasted to create letterbox bars. The advantage was a 33% greater vertical resolution compared to letterboxed widescreen LaserDisc. This same procedure was used for anamorphic DVDs, but unlike all DVD players, very few LD players had the ability to unsqueeze the image for 4:3 sets, and very few if any 4:3 sets could be set to play them properly either. If the discs were played on a standard 4:3 television the image would be distorted. Since very few people owned 16:9 displays, the marketability of these special discs was very limited.


With what aspect ratio did Squeeze LDs operate?


Why did Squeeze LDs have a very limited market?


Could the 16:9 aspect ratio be easily resized by a normal LD player, or was the image significantly distorted?


What percent vertical resolution increase did Squeeze LDs feature over regular widescreen LDs?


Which movie was released twice on Squeeze LD?

There were no anamorphic LaserDisc titles available in the US except for promotional purposes. Upon purchase of a Toshiba 16:9 television viewers had the option of selecting a number of Warner Bros. 16:9 films. Titles include Unforgiven, Grumpy Old Men, The Fugitive, and Free Willy. The Japanese lineup of titles was different. A series of releases under the banner "SQUEEZE LD" from Pioneer of mostly Carolco titles included Basic Instinct, Stargate, Terminator 2: Judgment Day, Showgirls, Cutthroat Island, and Cliffhanger. Terminator 2 was released twice in Squeeze LD, the second release being THX certified and a notable improvement over the first.


What improvement was added to Terminator 2's second Squeeze LD release?


What Warner Brothers films were available in 16:9 aspect ratio Squeeze LDs?


What films were available for Japanese market Squeeze LDs?


Another form of recordable LaserDisc that is completely playback-compatible with the LaserDisc format (unlike CRVdisc with its caddy enclosure) is the RLV, or Recordable LaserVision disc. It was developed and first marketed by the Optical Disc Corporation (ODC, now ODC Nimbus) in 1984. RLV discs, like CRVdisc, are also a WORM technology, and function exactly like a CD-R disc. RLV discs look almost exactly like standard LaserDiscs, and can play in any standard LaserDisc player after they have been recorded.


Which company originally developed and marketed the RLV?


In what year did ODC develop the Recordable LaserVision Disc?


What is the difference in appearance between an RLV disc and a regular LD?

The only cosmetic difference between an RLV disc and a regular factory-pressed LaserDiscs is their reflective purple-violet (or blue with some RLV discs) color resulting from the dye embedded in the reflective layer of the disc to make it recordable, as opposed to the silver mirror appearance of regular LDs. The purplish color of RLVs is very similar to DVD-R and DVD+R discs. RLVs were popular for making short-run quantities of LaserDiscs for specialized applications such as interactive kiosks and flight simulators.


Why do RLV discs have a blue or purple reflective color?


What color were regular LaserDiscs, in contrast to RLVs blueish purple hues?


In contrast to large LD disks, what is the size of a standard CD?

There were also 12 cm (4.7 in) (CD size) "single"-style discs produced that were playable on LaserDisc players. These were referred to as CD Video (CD-V) discs, and Video Single Discs (VSD). A CD-V carried up to five minutes of analog LaserDisc-type video content (usually a music video), as well as up to 20 minutes of digital audio CD tracks. The original 1989 release of David Bowie's retrospective Sound + Vision CD box set prominently featured a CD-V video of Ashes to Ashes, and standalone promo CD-Vs featured the video, plus three audio tracks: "John, I'm Only Dancing", "Changes", and "The Supermen".


What were CD size "single"-style discs called that were compatible with LaserDisc players?


How much video content could be stored on a CD-V disk?


What were CD-V's video capacities usually used for?


Which artist released a music video and three audio tracks on CD-V in 1989?


What were VSDs lacking that CD-Vs included?

CD-Vs are not to be confused with Video CDs (which are all-digital and can only be played on VCD players, DVD players, CD-i players, computers, and later-model LaserDisc players, such as the DVL series from Pioneer that can also play DVDs). CD-Vs can only be played back on LaserDisc players with CD-V capability. VSDs were the same as CD-Vs, but without the audio CD tracks. CD-Vs were somewhat popular for a brief time worldwide, but soon faded from view. VSDs were popular only in Japan and other parts of Asia, and were never fully introduced to the rest of the world.


In what areas of the world were VSDs popular?


Were VSDs or CD-Vs all digital and also playable on DVD players?


The annelids are bilaterally symmetrical, triploblastic, coelomate, invertebrate organisms. They also have parapodia for locomotion. Most textbooks still use the traditional division into polychaetes (almost all marine), oligochaetes (which include earthworms) and leech-like species. Cladistic research since 1997 has radically changed this scheme, viewing leeches as a sub-group of oligochaetes and oligochaetes as a sub-group of polychaetes. In addition, the Pogonophora, Echiura and Sipuncula, previously regarded as separate phyla, are now regarded as sub-groups of polychaetes. Annelids are considered members of the Lophotrochozoa, a "super-phylum" of protostomes that also includes molluscs, brachiopods, flatworms and nemerteans.


Which subtype of annelids includes most marine worms?


Which subtype of annelids includes earthworms?


Since 1997, what are leeches seen as a subgroup of?


The basic annelid form consists of multiple segments. Each segment has the same sets of organs and, in most polychaetes, has a pair of parapodia that many species use for locomotion. Septa separate the segments of many species, but are poorly defined or absent in others, and Echiura and Sipuncula show no obvious signs of segmentation. In species with well-developed septa, the blood circulates entirely within blood vessels, and the vessels in segments near the front ends of these species are often built up with muscles that act as hearts. The septa of such species also enable them to change the shapes of individual segments, which facilitates movement by peristalsis ("ripples" that pass along the body) or by undulations that improve the effectiveness of the parapodia. In species with incomplete septa or none, the blood circulates through the main body cavity without any kind of pump, and there is a wide range of locomotory techniques – some burrowing species turn their pharynges inside out to drag themselves through the sediment.


What end of annelids with well-developed segmentation has muscles that act like hearts?


What movement method do some burrowing annelids use?


Although many species can reproduce asexually and use similar mechanisms to regenerate after severe injuries, sexual reproduction is the normal method in species whose reproduction has been studied. The minority of living polychaetes whose reproduction and lifecycles are known produce trochophore larvae, that live as plankton and then sink and metamorphose into miniature adults. Oligochaetes are full hermaphrodites and produce a ring-like cocoon around their bodies, in which the eggs and hatchlings are nourished until they are ready to emerge.


What can asexual reproduction techniques help annelids do?


What annelids make a cocoon in a ring around themselves?


How do earthworms help the soil they live in?

Earthworms are Oligochaetes that support terrestrial food chains both as prey and in some regions are important in aeration and enriching of soil. The burrowing of marine polychaetes, which may constitute up to a third of all species in near-shore environments, encourages the development of ecosystems by enabling water and oxygen to penetrate the sea floor. In addition to improving soil fertility, annelids serve humans as food and as bait. Scientists observe annelids to monitor the quality of marine and fresh water. Although blood-letting is no longer in favor with doctors, some leech species are regarded as endangered species because they have been over-harvested for this purpose in the last few centuries. Ragworms' jaws are now being studied by engineers as they offer an exceptional combination of lightness and strength.


How much of near-shore marine annelids are burrowing?


How do burrowing marine annelids help ocean ecosystems?


What annelids' jaws are being studied by engineers?


Since annelids are soft-bodied, their fossils are rare – mostly jaws and the mineralized tubes that some of the species secreted. Although some late Ediacaran fossils may represent annelids, the oldest known fossil that is identified with confidence comes from about 518 million years ago in the early Cambrian period. Fossils of most modern mobile polychaete groups appeared by the end of the Carboniferous, about 299 million years ago. Palaeontologists disagree about whether some body fossils from the mid Ordovician, about 472 to 461 million years ago, are the remains of oligochaetes, and the earliest indisputable fossils of the group appear in the Tertiary period, which began 65 million years ago.


What fossil signs of annelids are found?


What types of annelids appeared 299 million years ago?


What period started around 472 million years ago?


What externally divides annelids' segments?

No single feature distinguishes Annelids from other invertebrate phyla, but they have a distinctive combination of features. Their bodies are long, with segments that are divided externally by shallow ring-like constrictions called annuli and internally by septa ("partitions") at the same points, although in some species the septa are incomplete and in a few cases missing. Most of the segments contain the same sets of organs, although sharing a common gut, circulatory system and nervous system makes them inter-dependent. Their bodies are covered by a cuticle (outer covering) that does not contain cells but is secreted by cells in the skin underneath, is made of tough but flexible collagen and does not molt – on the other hand arthropods' cuticles are made of the more rigid α-chitin, and molt until the arthropods reach their full size. Most annelids have closed circulatory systems, where the blood makes its entire circuit via blood vessels.


What divides annelids' segments internally?


What do the segments of an annelid share?


What language does the term 'chaetae' come from?

Most of an annelid's body consists of segments that are practically identical, having the same sets of internal organs and external chaetae (Greek χαιτη, meaning "hair") and, in some species, appendages. However, the frontmost and rearmost sections are not regarded as true segments as they do not contain the standard sets of organs and do not develop in the same way as the true segments. The frontmost section, called the prostomium (Greek προ- meaning "in front of" and στομα meaning "mouth") contains the brain and sense organs, while the rearmost, called the pygidium (Greek πυγιδιον, meaning "little tail") or periproct contains the anus, generally on the underside. The first section behind the prostomium, called the peristomium (Greek περι- meaning "around" and στομα meaning "mouth"), is regarded by some zoologists as not a true segment, but in some polychaetes the peristomium has chetae and appendages like those of other segments.


Which parts of annelids are different from true segments?


What language does 'prostomium' come from?


How are the layers arranged in annelids' cuticles?

Annelids' cuticles are made of collagen fibers, usually in layers that spiral in alternating directions so that the fibers cross each other. These are secreted by the one-cell deep epidermis (outermost skin layer). A few marine annelids that live in tubes lack cuticles, but their tubes have a similar structure, and mucus-secreting glands in the epidermis protect their skins. Under the epidermis is the dermis, which is made of connective tissue, in other words a combination of cells and non-cellular materials such as collagen. Below this are two layers of muscles, which develop from the lining of the coelom (body cavity): circular muscles make a segment longer and slimmer when they contract, while under them are longitudinal muscles, usually four distinct strips, whose contractions make the segment shorter and fatter. Some annelids also have oblique internal muscles that connect the underside of the body to each side.


What are annelids' cuticles made out of?


What do non-cuticle annelids use to protect their skin?


The setae ("hairs") of annelids project out from the epidermis to provide traction and other capabilities. The simplest are unjointed and form paired bundles near the top and bottom of each side of each segment. The parapodia ("limbs") of annelids that have them often bear more complex chetae at their tips – for example jointed, comb-like or hooked. Chetae are made of moderately flexible β-chitin and are formed by follicles, each of which has a chetoblast ("hair-forming") cell at the bottom and muscles that can extend or retract the cheta. The chetoblasts produce chetae by forming microvilli, fine hair-like extensions that increase the area available for secreting the cheta. When the cheta is complete, the microvilli withdraw into the chetoblast, leaving parallel tunnels that run almost the full length of the cheta. Hence annelids' chetae are structurally different from the setae ("bristles") of arthropods, which are made of the more rigid α-chitin, have a single internal cavity, and are mounted on flexible joints in shallow pits in the cuticle.


What hair-like extensions do chetoblasts make?


Nearly all polychaetes have parapodia that function as limbs, while other major annelid groups lack them. Parapodia are unjointed paired extensions of the body wall, and their muscles are derived from the circular muscles of the body. They are often supported internally by one or more large, thick chetae. The parapodia of burrowing and tube-dwelling polychaetes are often just ridges whose tips bear hooked chetae. In active crawlers and swimmers the parapodia are often divided into large upper and lower paddles on a very short trunk, and the paddles are generally fringed with chetae and sometimes with cirri (fused bundles of cilia) and gills.


What kind of parapodia do burrowing annelids often have?


What type of annelids have limb-like parapodia?