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Your third grader will continue to build on basic math skills such as addition and subtraction, telling time, and counting money, but will also start to learn how to multiply, measure, and understand fractions. You can help your child master these skills simply by playing games in and around the house. Leave the flashcards and worksheets to the teacher; if you want your child to love numbers, show your child how math is part of everyday life and he'll be eager to learn more.
Here are 12 fun ways to introduce your child to the world of math. Because children learn in different ways, we've arranged these activities by learning style.
For the visual learner
Estimate the weight of a household object. Ask your child to guess the weight of the family cat, a dictionary, a glass of water. Then use the scale to find out the real weight. Have him estimate his own weight, and that of other family members. Were his estimates on target?
Buy your child a watch with an hour and second hand. Periodically ask him to tell you what time it is. Ask questions like: "If Arthur comes on at 4 p.m., how many more minutes do you have to wait?" "It takes me 15 minutes to drive to the store. Do I have time to get there before it closes at 5 p.m.?"
Use M&M's to teach fractions. Have your child count the M&M pieces in a bag. Then sort them by color. Count the number of green M&M's to find out what fraction of all of the candy is that color. Do the same with the other colors. Eat the results.
Fold a napkin. An idea from the U.S. Department of Education: Fold paper towels or napkins into large and small fractions. Start with halves, then move to quarters, then eighths, and finally 16ths. Use magic markers to label the fractions.
For the physical learner
Play card games. War and Go Fish are classic card games that reinforce basic math concepts such as greater and less than, as well as grouping by category.
Host a book or toy exchange party. Have each child bring along four or five used books or toys to sell; price all the books under one dollar (24 cents, 60 cents, etc.). Give each child one dollar in play money to spend and let them sort through the selection for about 15 minutes. When it's time to pay for the books, help the children count out the money and determine whether they have any left over or have gone over their budget. This activity reinforces making change and money skills.
Measure your family. The National PTA recommends this family activity: Use a tape measure or ruler to record the heights of everyone in your family. Total the inches to see how "tall" you are all together. Try it again with everyone's weight. A good way to practice adding two-digit numbers.
Play board games that use counting and paper money. Games such as Monopoly Junior are aimed at ages 5 through 8 but are still fun for parents or older siblings.
Play with money. This is a family game: The goal is to be the first player to win a set amount of money (75 cents, 50 cents). Roll a pair of dice. Each person gets the number of pennies shown on the dice. As each player gets five pennies, replace them with a nickel. Replace ten pennies with a dime, and so on. The first player to reach the set amount wins. This game reinforces grouping skills, and counting by fives.
Plan and shop for a meal. Give your child the grocery circular from the newspaper. Give him a budget ($30, $50) and have him plan a dinner for your family. If he goes over the budget, what can he subtract? If he has money left over, what else can he buy? Then go to the store and shop for the items together. Did his estimates match the real total?
For the auditory learner
Play a guessing game. A good one for a car trip: Have your child think of a number between one and 100. Try to guess the number by asking questions such as "Is it greater than 50?" "Is it between 35 and 55?" Then switch roles and have your child do the guessing.
Make a recipe with your child. Give your child the measuring cups, measuring spoons, and bowls and read him the directions as he does the work. An easy — and delicious — way to introduce concepts such as volume, weight, and fractions.
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Spiral galaxy NGC 4921 presently is estimated to be 320 million light years distant.
This image, taken by the Hubble Space Telescope, is being used to identify key stellar distance markers known as Cepheid variable stars.
The magnificent spiral NGC 4921 has been informally dubbed anemic because of its low rate of star formation and low surface brightness.
Visible in the image are, from the center, a bright nucleus, a bright central bar, a prominent ring of dark dust, blue clusters of recently formed stars, several smaller companion galaxies, unrelated galaxies in the far distant universe, and unrelated stars in our Milky Way Galaxy.
Explore further: Hubble Snaps Images of a Pinwheel-Shaped Galaxy
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Shingles (herpes zoster) is a painful, blistering skin rash. It is caused by the varicella-zoster virus. This is the virus that also causes chickenpox.
After you get chickenpox, the virus remains inactive (becomes dormant) in certain nerves in the body. Shingles occurs after the virus becomes active again in these nerves after many years.
The reason the virus suddenly becomes active again is not clear. Often only one attack occurs.
Shingles can develop in any age group. You are more likely to develop the condition if:
If an adult or child has direct contact with the shingles rash and did not have chickenpox as a child or the chickenpox vaccine, they can develop chickenpox, not shingles.
The first symptom is usually pain, tingling, or burning that occurs on one side of the body. The pain and burning may be severe and are usually present before any rash appears.
Red patches on the skin, followed by small blisters, form in most people:
Other symptoms may include:
You may also have pain, muscle weakness, and a rash involving different parts of your face if shingles affects a nerve in your face. The symptoms may include:
Your health care provider can make the diagnosis by looking at your skin and asking about your medical history.
Tests are rarely needed, but may include taking a skin sample to see if the skin is infected with the virus.
Blood tests may show an increase in white blood cells and antibodies to the chickenpox virus. But the tests cannot confirm that the rash is due to shingles.
Your health care provider may prescribe a medicine that fights the virus, called an antiviral drug. This drug helps reduce pain, prevent complications, and shorten the course of the disease.
The medicines should be started within 72 hours of when you first feel pain or burning. It is best to start taking them before the blisters appear. The medicines are usually given in pill form. Some people may need to receive the medicine through a vein (by IV).
Strong anti-inflammatory medicines called corticosteroids, such as prednisone, may be used to reduce swelling and pain. These medicines do not work in all patients.
Other medicines may include:
Follow your health care provider's instructions about how to care for yourself at home.
Other measures may include:
Stay away from people while your sores are oozing to avoid infecting those who have never had chickenpox -- especially pregnant women.
Herpes zoster usually clears in 2 to 3 weeks and rarely returns. If the virus affects the nerves that control movement (the motor nerves), you may have temporary or permanent weakness or paralysis.
Sometimes the pain in the area where the shingles occurred may last from months to years. This pain is called postherpetic neuralgia.
It occurs when the nerves have been damaged after an outbreak of shingles. Pain ranges from mild to very severe. Postherpetic neuralgia is more likely to occur in persons over age 60.
Complications may include:
Call your health care provider if you have symptoms of shingles, particularly if you have a weakened immune system or if your symptoms persist or worsen. Shingles that affects the eye may lead to permanent blindness if you do not receive emergency medical care.
Do not touch the rash and blisters on persons with shingles or chickenpox if you have never had chickenpox or the chickenpox vaccine.
A herpes zoster vaccine is available. It is different than the chickenpox vaccine. Older adults who receive the herpes zoster vaccine are less likely to have complications from shingles.
Cohen J. Varicella-zoster virus (chickenpox, shingles). In: Goldman L, Schafer AI, eds. Goldman’s Cecil Medicine. 24th ed. Philadelphia, Pa.: Elsevier Saunders; 2011:chap 383.
Habif TP.Clinical Dermatology. 5th ed. St. Louis, MO: Elsevier Mosby; 2009:chap 12.
Updated by: Jatin M. Vyas, MD, PhD, Assistant Professor in Medicine, Harvard Medical School; Assistant in Medicine, Division of Infectious Disease, Department of Medicine, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Bethanne Black, and the A.D.A.M. Editorial team.
The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed physician should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. Copyright 1997-2014, A.D.A.M., Inc. Duplication for commercial use must be authorized in writing by ADAM Health Solutions.
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Civil Rights Movement Teacher Resources
Find Civil Rights Movement educational ideas and activities
Showing 201 - 220 of 1,588 resources
Montgomery Bus Boycott
It's December 1, 1955, and a tired African American woman refuses to give up her seat for a white man on a bus in Montgomery. This woman is Rosa Parks. While she wasn't the first person to stay seated despite the current laws, her arrest...
3 mins 9th - 12th Social Studies & History
Individuals Making a Difference
The focus of this, the third in a five-lesson unit study of human rights, is on individuals who made a difference. Billy Bowlegs, Dr. Sun Yat Sen, Fannie Lou Hamer, Michi Weglyn, and Yuri Koshiyama are some of the people class members...
9th - 12th Social Studies & History CCSS: Adaptable
Strength and Voices: Engaging Scenario – Lights camera, action! Day 1
This task is somewhat incomplete, yet if matched with the larger unit, it could be a helpful way to start off a great project. Learners work in groups to create and research a film documentary on civil rights. This project is based on...
7th English Language Arts CCSS: Designed
Centers of the Storm: The Lyceum and the Circle at the University of Mississippi
Greek Revival architecture and the Civil Rights Movement? Sure! Examine how the Lyceum and Circle, two historic buildings located on the campus of the University of Mississippi, relate to integration and the 1962 riot on the university...
9th - 12th English Language Arts CCSS: Designed
Perspectives and Point of View: Engaging Scenario Unit 1
In groups Middle schoolers work together to analyze texts and author's perspective across media types. They read the Langston Hughes poem, "I Look at the World" and speeches from JFK and MLK. They create a multi-media presentation...
6th English Language Arts CCSS: Designed
Freedom Songs of the Civil Rights Movement
Fifth graders analyze freedom songs sung during the Civil Rights Movement. In this historical music lesson plan, 5th graders sing and understand the musical concepts within freedom songs. Students also analyze the songs' meanings and...
5th Visual & Performing Arts
Leaders in the Civil Rights Movement
Students investigate who Rosa Parks and Martin Luther King Jr. were. They study the impact of the Civil Rights Movement and the Montgomery Bus Boycott. Each student designs through pictures and/or words how they make a better place.
9th - 12th Social Studies & History
Making More Places at the Table: The American Civil Rights Movement of the 50's and 60's
Eleventh graders examine the biography of Henry B. Gonzalez. They examine primary source documents from Congressman Gonzalez's personal papers related to his contributions to the Civil Rights Movement.
11th Social Studies & History
Civil Rights Movement in America
Eleventh graders explore the Civil Rights movement as a culmination of history and cultural perspectives developed from the Slave Trade and Reconstruction. They identify leading persons and organizations and their personal philosophy to...
11th Social Studies & History
Let Freedom Ring: The Life & Legacy of Martin Luther King, Jr.
Students use text and photos to visualize the delivery of Dr. Martin Luther King, Jr.'s historic "I Have A Dream" speech. They analyze Dr. King's speech for examples of imagery and allusion and create original poetry and illustrations...
3rd - 5th Social Studies & History
Martin Luther King Jr. and Nonviolence
Using the book, Martin's Big Words, learners will discover the life of Dr. Martin Luther King Jr. Vocabulary is identified throughout the story by using several his famous protest speeches as examples. Class discussions on racism, during...
K - 5th Social Studies & History
Martin Luther King Jr's "I Have A Dream" Speech
Invite your class to investigate racism and civil rights by analyzing the great Dr. Martin Luther King's speech. Your learners will read the words from the "I Have a Dream" speech and analyze the political and racial overtones. They will...
6th - 8th Visual & Performing Arts
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A natural disaster is a major adverse event resulting from natural processes of the Earth; examples include floods, volcanic eruptions, earthquakes, tsunamis, and other geologic processes. A natural disaster can cause loss of life or property damage, and typically leaves some economic damage in its wake, the severity of which depends on the affected population's resilience, or ability to recover.
An adverse event will not rise to the level of a disaster if it occurs in an area without vulnerable population. In a vulnerable area, however, such as San Francisco, an earthquake can have disastrous consequences and leave lasting damage, requiring years to repair.
In 2012, there were 905 natural disasters worldwide, 93% of which were weather-related disasters. Overall costs were US$170 billion and insured losses $70 billion. 2012 was a moderate year. 45% were meteorological (storms), 36% were hydrological (floods), 12% were climatological (heat waves, cold waves, droughts, wildfires) and 7% were geophysical events (earthquakes and volcanic eruptions). Between 1980 and 2011 geophysical events accounted for 14% of all natural catastrophes.
- 1 Avalanches
- 2 Earthquakes
- 3 Volcanic eruptions
- 4 Hydrological disasters
- 5 Meteorological disasters
- 6 Wildfires
- 7 Health disasters
- 8 Space disasters
- 9 Protection by international law
- 10 See also
- 11 References
- 12 External links
During World War I, an estimated 40,000 to 80,000 soldiers died as a result of avalanches during the mountain campaign in the Alps at the Austrian-Italian front, many of which were caused by artillery fire.
An earthquake is the result of a sudden release of energy in the Earth's crust that creates seismic waves. At the Earth's surface, earthquakes manifest themselves by vibration, shaking and sometimes displacement of the ground. The vibrations may vary in magnitude. Earthquakes are caused mostly by slippage within geological faults, but also by other events such as volcanic activity, landslides, mine blasts, and nuclear tests. The underground point of origin of the earthquake is called the focus. The point directly above the focus on the surface is called the epicenter. Earthquakes by themselves rarely kill people or wildlife. It is usually the secondary events that they trigger, such as building collapse, fires, tsunamis (seismic sea waves) and volcanoes, that are actually the human disaster. Many of these could possibly be avoided by better construction, safety systems, early warning and planning. Some of the most significant earthquakes in recent times include:
- The 2004 Indian Ocean earthquake, the third largest earthquake recorded in history, registering a moment magnitude of 9.1-9.3. The huge tsunamis triggered by this earthquake killed at least 229,000 people.
- The 2011 Tōhoku earthquake and tsunami registered a moment magnitude of 9.0. The earthquake and tsunami killed 15,889 and injured 6,152. 2,609 were still missing as of 2014.
- The 8.8 magnitude February 27, 2010 Chile earthquake and tsunami cost 525 lives.
- The 7.9 magnitude May 12, 2008 Sichuan earthquake in Sichuan Province, China. Death toll at over 61,150 as of May 27, 2008.
- The 7.7 magnitude 2006 Pangandaran earthquake and tsunami.
- The 6.9 magnitude 2005 Azad Jammu & Kashmir and KPK province Earthquake, which killed or injured above 75,000 people in Pakistan.
Volcanoes can cause widespread destruction and consequent disaster in several ways. The effects include the volcanic eruption itself that may cause harm following the explosion of the volcano or the fall of rock. Second, lava may be produced during the eruption of a volcano. As it leaves the volcano, the lava destroys many buildings and plants it encounters. Third, volcanic ash generally meaning the cooled ash - may form a cloud, and settle thickly in nearby locations. When mixed with water this forms a concrete-like material. In sufficient quantity ash may cause roofs to collapse under its weight but even small quantities will harm humans if inhaled. Since the ash has the consistency of ground glass it causes abrasion damage to moving parts such as engines. The main killer of humans in the immediate surroundings of a volcanic eruption is the pyroclastic flows, which consist of a cloud of hot volcanic ash which builds up in the air above the volcano and rushes down the slopes when the eruption no longer supports the lifting of the gases. It is believed that Pompeii was destroyed by a pyroclastic flow. A lahar is a volcanic mudflow or landslide. The 1953 Tangiwai disaster was caused by a lahar, as was the 1985 Armero tragedy in which the town of Armero was buried and an estimated 23,000 people were killed .
A specific type of volcano is the supervolcano. According to the Toba catastrophe theory 75,000 to 80,000 years ago a super volcanic event at Lake Toba reduced the human population to 10,000 or even 1,000 breeding pairs creating a bottleneck in human evolution. It also killed three quarters of all plant life in the northern hemisphere. The main danger from a supervolcano is the immense cloud of ash which has a disastrous global effect on climate and temperature for many years.
It is a violent, sudden and destructive change either in quality of earth's water or in distribution or movement of water on land below the surface or in atmosphere.
A flood is an overflow of an expanse of water that submerges land. The EU Floods directive defines a flood as a temporary covering by water of land not normally covered by water. In the sense of "flowing water", the word may also be applied to the inflow of the tide. Flooding may result from the volume of water within a body of water, such as a river or lake, which overflows or breaks levees, with the result that some of the water escapes its usual boundaries. While the size of a lake or other body of water will vary with seasonal changes in precipitation and snow melt, it is not a significant flood unless the water covers land used by man like a village, city or other inhabited area, roads, expanses of farmland, etc.
Some of the most notable floods include:
- The Johnstown Flood of 1889 where over 2200 people lost their lives when the South Fork Dam holding back Lake Conemaugh broke.
- The Huang He (Yellow River) in China floods particularly often. The Great Flood of 1931 caused between 800,000 and 4,000,000 deaths.
- The Great Flood of 1993 was one of the most costly floods in United States history.
- The North Sea flood of 1953 which killed 2251 people in the Netherlands and eastern England
- The 1998 Yangtze River Floods, in China, left 14 million people homeless.
- The 2000 Mozambique flood covered much of the country for three weeks, resulting in thousands of deaths, and leaving the country devastated for years afterward.
- The 2005 Mumbai floods which killed 1094 people.
- The 2010 Pakistan floods directly affected about 20 million people, mostly by dispolacement, destruction of crops, infrastructure, property and livelihood, with a death toll of close to 2,000.
- The 2014 India–Pakistan floods
A limnic eruption occurs when a gas, usually CO2, suddenly erupts from deep lake water, posing the threat of suffocating wildlife, livestock and humans. Such an eruption may also cause tsunamis in the lake as the rising gas displaces water. Scientists believe landslides, volcanic activity, or explosions can trigger such an eruption. To date, only two limnic eruptions have been observed and recorded:
- In 1984, in Cameroon, a limnic eruption in Lake Monoun caused the deaths of 37 nearby residents.
- At nearby Lake Nyos in 1986 a much larger eruption killed between 1,700 and 1,800 people by asphyxiation.
Tsunamis can be caused by undersea earthquakes as the one caused by the 2004 Indian Ocean Earthquake, or by landslides such as the one which occurred at Lituya Bay, Alaska.
- The 2004 Indian Ocean Earthquake created the Boxing Day Tsunami.
- On March 11, 2011, a tsunami occurred near Fukushima, Japan and spread through the Pacific.
Blizzards are severe winter storms characterized by heavy snow and strong winds. When high winds stir up snow that has already fallen, it is known as a ground blizzard. Blizzards can impact local economic activities, especially in regions where snowfall is rare.
Significant blizzards include:
- The Great Blizzard of 1888 in the United States in which many tons of wheat crops were destroyed.
- The 2008 Afghanistan blizzard
- The North American blizzard of 1947
- The 1972 Iran blizzard resulted in approximately 4,000 deaths and lasted for 5 to 7 days.
Cyclone, tropical cyclone, hurricane, and typhoon are different names for the same phenomenon, which is a cyclonic storm system that forms over the oceans. The deadliest hurricane ever was the 1970 Bhola cyclone; the deadliest Atlantic hurricane was the Great Hurricane of 1780 which devastated Martinique, St. Eustatius and Barbados. Another notable hurricane is Hurricane Katrina which devastated the Gulf Coast of the United States in 2005.
Extratropical cyclones, sometimes called mid-latitude cyclones, are a group of cyclones defined as synoptic scale low pressure weather systems that occur in the middle latitudes of the Earth (outside the tropics) not having tropical characteristics, and are connected with fronts and horizontal gradients in temperature and dew point otherwise known as "baroclinic zones". As with tropical cyclones, they are known by different names in different regions (Nor'easter, Pacific Northwest windstorms, European windstorm, East Asian-northwest Pacific storms, Sudestada and Australian east coast cyclones). The most intense extratropical cyclones cause widespread disruption and damage to society, such as the storm surge of the North Sea flood of 1953 which killed 2251 people in the Netherlands and eastern England, the Great Storm of 1987 which devastated southern England and France and the Columbus Day Storm of 1962 which struck the Pacific Northwest.
Drought is unusual dryness of soil, resulting in crop failure and shortage of water for other uses, caused by significantly lower rainfall than average over a prolonged period. Hot dry winds, high temperatures and consequent evaporation of moisture from the ground can contribute to conditions of drought.
Well-known historical droughts include:
- 1900 India killing between 250,000 to 3.25 million.
- 1921–22 Soviet Union in which over 5 million perished from starvation due to drought
- 1928–30 Northwest China resulting in over 3 million deaths by famine.
- 1936 and 1941 Sichuan Province China resulting in 5 million and 2.5 million deaths respectively.
- The 1997–2009 Millenium Drought in Australian led to a water supply crisis across much of the country. As a result many desalination plants were built for the first time (see list).
- In 2006, Sichuan Province China experienced its worst drought in modern times with nearly 8 million people and over 7 million cattle facing water shortages.
- 12-year drought that was devastating southwest Western Australia, southeast South Australia, Victoria and northern Tasmania was "very severe and without historical precedent".
- In 2011, the State of Texas lived under a drought emergency declaration for the entire calendar year. The drought caused the Bastrop fires.
Hailstorms are falls of rain drops that arrive as ice, rather than melting before they hit the ground. A particularly damaging hailstorm hit Munich, Germany, on July 12, 1984, causing about 2 billion dollars in insurance claims.
A heat wave is a period of unusually and excessively hot weather. The worst heat wave in recent history was the European Heat Wave of 2003.
A summer heat wave in Victoria, Australia, created conditions which fuelled the massive bushfires in 2009. Melbourne experienced three days in a row of temperatures exceeding 40°C (104°F) with some regional areas sweltering through much higher temperatures. The bushfires, collectively known as "Black Saturday", were partly the act of arsonists.
The 2010 Northern Hemisphere summer resulted in severe heat waves, which killed over 2,000 people. It resulted in hundreds of wildfires which causing widespread air pollution, and burned thousands of square miles of forest.
Heat waves can occur in the ocean as well as on land with significant effects (often on a large scale) e.g. coral bleaching.
A tornado is a violent, dangerous, rotating column of air that is in contact with both the surface of the earth and a cumulonimbus cloud or, in rare cases, the base of a cumulus cloud. It is also referred to as a twister or a cyclone, although the word cyclone is used in meteorology in a wider sense, to refer to any closed low pressure circulation. Tornadoes come in many shapes and sizes, but are typically in the form of a visible condensation funnel, whose narrow end touches the earth and is often encircled by a cloud of debris and dust. Most tornadoes have wind speeds less than 110 miles per hour (177 km/h), are approximately 250 feet (80 m) across, and travel a few miles (several kilometers) before dissipating. The most extreme tornadoes can attain wind speeds of more than 300 mph (480 km/h), stretch more than two miles (3 km) across, and stay on the ground for dozens of miles (perhaps more than 100 km).
Well-known historical tornadoes include:
- The Tri-State Tornado of 1925, which killed over 600 people in the United States;
- The Daulatpur-Saturia Tornado of 1989, which killed roughly 1,300 people in Bangladesh.
Wildfires are large fires which often start in wildland areas. Common causes include lightning and drought but wildfires may also be started by human negligence or arson. They can spread to populated areas and can thus be a threat to humans and property, as well as wildlife.
An epidemic is an outbreak of a contractible disease that spreads through a human population. A pandemic is an epidemic whose spread is global. There have been many epidemics throughout history, such as the Black Death. In the last hundred years, significant pandemics include:
- The 1918 Spanish flu pandemic, killing an estimated 50 million people worldwide
- The 1957–58 Asian flu pandemic, which killed an estimated 1 million people
- The 1968–69 Hong Kong water flu pandemic
- The 2002-3 SARS pandemic
- The AIDS pandemic, beginning in 1959
- The H1N1 Influenza (Swine Flu) Pandemic 2009–2010
Other diseases that spread more slowly, but are still considered to be global health emergencies by the WHO, include:
- XDR TB, a strain of tuberculosis that is extensively resistant to drug treatments
- Malaria, which kills an estimated 1.6 million people each year
- Ebola virus disease, which has claimed hundreds of victims in Africa in several outbreaks
|This section requires expansion. (December 2010)|
Asteroids that impact the Earth have led to several major extinction events, including one that created the Chicxulub crater 64.9 million years ago and associated with the demise of the dinosaurs. Scientists estimate that the likelihood of death for a living human from a global impact event is comparable to death from airliner crash. One of the notable impact events in modern times was the Tunguska event in June 1908.
A solar flare is a phenomenon where the sun suddenly releases a great amount of solar radiation, much more than normal. Some known solar flares include:
- An X20 event on August 16, 1989
- A similar flare on April 2, 2001
- The most powerful flare ever recorded, on November 4, 2003, estimated at between X40 and X45
- The most powerful flare in the past 500 years is believed to have occurred in September 1859
Protection by international law
International law, for example Geneva Conventions defines International Red Cross and Red Crescent Movement the Convention on the Rights of Persons with Disabilities, requires that "States shall take, in accordance with their obligations under international law, including international humanitarian law and international human rights law, all necessary measures to ensure the protection and safety of persons with disabilities in situations of risk, including the occurrence of natural disaster." And further United Nations Office for the Coordination of Humanitarian Affairs is formed by General Assembly Resolution 44/182. People displaced due to natural disasters are currently protected under international law (Guiding Principles of International Displacement, Campala Convention of 2009).
- Act of God
- Effects of climate change on humans
- Emergency management
- Environmental disaster
- Environmental emergency
- Gamma ray burst
- List of countries by natural disaster risk
- List of natural disasters by death toll
- Property insurance
- World Conference on Disaster Reduction
- G. Bankoff, G. Frerks, D. Hilhorst (eds.) (2003). Mapping Vulnerability: Disasters, Development and People. ISBN 1-85383-964-7.
- Luis Flores Ballesteros. "What determines a disaster?" 54 Pesos Sep 2008:54 Pesos 11 Sep 2008. <http://54pesos.org/2008/09/11/what-determines-a-disaster/>
- D. Alexander (2002). Principles of Emergency planning and Management. Harpended: Terra publishing. ISBN 1-903544-10-6.
- B. Wisner, P. Blaikie, T. Cannon, and I. Davis (2004). At Risk - Natural hazards, people's vulnerability and disasters. Wiltshire: Routledge. ISBN 0-415-25216-4.
- Natural Catastrophes in 2012 Dominated by U.S. Weather Extremes Worldwatch Institute May 29, 2013
- Lee Davis (2008). "Natural Disasters". Infobase Publishing. p.7. ISBN 0-8160-7000-8
- ^ "USGS Earthquake Details". United States Geological Survey. http://earthquake.usgs.gov/earthquakes/eqinthenews/2010/us2010tfan/. Retrieved February 27, 2010
- Gibbons, Ann (19 January 2010). "Human Ancestors Were an Endangered Species". ScienceNow.
- MSN Encarta Dictionary. Flood. Retrieved on 2006-12-28. Archived 2009-10-31.
- Directive 2007/60/EC Chapter 1 Article2
- Glossary of Meteorology (June 2000). Flood. Retrieved on 2009-01-09.
- Wurman, Joshua (2008-08-29). "Doppler On Wheels". Center for Severe Weather Research. Retrieved 2009-12-13.
- "Hallam Nebraska Tornado". National Weather Service. National Oceanic and Atmospheric Administration. 2005-10-02. Retrieved 2009-11-15.
- Roger Edwards (2006-04-04). "The Online Tornado FAQ". National Weather Service. National Oceanic and Atmospheric Administration. Retrieved 2006-09-08.
- "Sun Unleashes Record Superflare, Earth Dodges Solar Bullet". ScienceDaily. April 4, 2011. Retrieved 2011-08-27.
- "Biggest Solar Flare ever recorded". National Association for Scientific and Cultural Appreciation. 2004. Retrieved 2011-08-27.
- "A Super Solar Flare". NASA. May 6, 2008. Retrieved 2011-08-27.
- Article 11 of the Convention on the Rights of Persons with Disabilities
- Terminski, Bogumil, Towards Recognition and Protection of Forced Environmental Migrants in the Public International Law: Refugee or IDPs Umbrella (December 1, 2011). Policy Studies Organization (PSO) Summit, December 2011.
|Wikiquote has quotations related to: Natural disasters|
- "Natural Disasters News". Ubyrisk. Worldwide news site focused on natural disasters, mitigation and climate changes news
- "Global Risk Identification Program (GRIP)". GRIP.
- "BioCaster Global Health Monitor". National Institute of Informatics (NII).
- "World Bank's Hazard Risk Management". World Bank.
- "Disaster News Network". Retrieved 2006-11-05. US news site focused on disaster-related news.
- "EM-DAT International Disaster Database". Retrieved 2006-11-05. Includes country profiles, disaster profiles and a disaster list.
- "Global Disaster Alert and Coordination System". European Commission and United Nations website initiative.
- "Natural Disaster and Extreme Weather. Searchable Information Center". Ebrary.
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How 3D works
How We See
The fact that our left eye and right eye see objects from different angles is the basis of 3D photography. If you try looking at an object through one eye and then the other, you will notice that it slightly changes position. However, with both eyes open, the two images that each eye observes separately are fused together as one in our brain. It is the fusion of these two images that creates normal binocular (3D) sight and allows our brain to understand depth and distance.
To capture images in 3D two camera lenses are used in place of our eyes, set about 2 ½ inches apart, which is the same distance between your eyes (called the interocular or interaxial distance). The two lenses each capture onto separate pieces of film. To review the image in 3D a stereoscopic viewer is needed. This is made of 2 eye pieces, each one feeds only one of the images to each eye, (the right image to the right eye and the left image to the left eye) tricking your brain into fusing the images into a single 3D image (as it would with normal vision).
To project a 3D film, two individual images representing the perspective of the left and right eye are simultaneously projected on screen. Without special glasses during the presentation, it will seem like you are seeing double, because in actual fact you are seeing two separate images. Fortunately the 3D glasses correct this problem. Each lens of the 3D glasses has a special filter (either red and cyan as in the old style glasses or the more modern polarized lenses) which blocks out the opposing image, allowing each eye only to see one image. Your brain perceives the fusion of the two separate images as one three-dimensional image.
The IMAX 3D Experience
In IMAX to recreate the 3D effect on screen we project two separate films through the same projector, one for the right eye and one for the left, at the same time. The film is projected through a set of passive linear polarized lenses, which match the lenses in the special glasses that the customers wear. The polarized lenses separate out the images making sure that your right eye only sees the right film and the left eye sees the left film. When this information is passed from your eyes to your brain it fuses them together to create the world's best 3D experience.
Want to book tickets? Easy!
Just come down and rock up to
the front door, or call 0141 420 5000.
See you soon.
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Common Core Standards: ELA
- The Standard
- Teach With Shmoop
- Sample Assignments
- Aligned Resources
RL.9-10.9. Analyze how an author draws on and transforms source material in a specific work (e.g., how Shakespeare treats a theme or topic from Ovid or the Bible or how a later author draws on a play by Shakespeare).
Just as there are no new literary devices or ways to arrange a story (see Question 5), there are no new stories. Yes, that’s right—we just said that. There weren’t even any new stories four hundred years ago, when Shakespeare was repackaging used goods for the amusement of King James’s court. The good news is that the “old” stories provide endless ways to rearrange their parts, plots, and themes so as to create new work. This Standard takes a closer look at how borrowing turns old news into new art.
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Using this Standard
- 1984 Teacher Pass
- A Raisin in the Sun Teacher Pass
- A Rose For Emily Teacher Pass
- Adventures of Huckleberry Finn Teacher Pass
- Animal Farm Teacher Pass
- Antigone Teacher Pass
- Beowulf Teacher Pass
- Brave New World Teacher Pass
- Death of a Salesman Teacher Pass
- Fahrenheit 451 Teacher Pass
- Fences Teacher Pass
- Frankenstein Teacher Pass
- Grapes Of Wrath Teacher Pass
- Great Expectations Teacher Pass
- Hamlet Teacher Pass
- Heart of Darkness Teacher Pass
- Julius Caesar Teacher Pass
- King Lear Teacher Pass
- Macbeth Teacher Pass
- Moby Dick Teacher Pass
- Narrative of Frederick Douglass Teacher Pass
- Oedipus the King Teacher Pass
- Of Mice and Men Teacher Pass
- One Flew Over the Cuckoo's Nest Teacher Pass
- Romeo and Juliet Teacher Pass
- The Aeneid Teacher Pass
- The As I Lay Dying Teacher Pass
- The Bluest Eye Teacher Pass
- The Canterbury Tales General Prologue Teacher Pass
- The Canterbury Tales: The Miller's Tale Teacher Pass
- The Canterbury Tales: The Wife of Bath's Prologue Teacher Pass
- The Cask of Amontillado Teacher Pass
- The Catch-22 Teacher Pass
- The Catcher in the Rye Teacher Pass
- The Crucible Teacher Pass
- The Great Gatsby Teacher Pass
- The House on Mango Street Teacher Pass
- The Iliad Teacher Pass
- The Lottery Teacher Pass
- The Metamorphosis Teacher Pass
- The Odyssey Teacher Pass
- The Old Man and the Sea Teacher Pass
- Their Eyes Were Watching God Teacher Pass
- Things Fall Apart Teacher Pass
- To Kill a Mockingbird Teacher Pass
- Twilight Teacher Pass
- Wide Sargasso Sea Teacher Pass
- Wuthering Heights Teacher Pass
Sample Questions for Use in Class
1. Shakespeare and Stoppard: Different Plays, Same Body Count
Tom Stoppard’s Rosencrantz and Guildenstern are Dead is based on Shakespeare’s Hamlet in both obvious and not-so-obvious ways. Obviously, Stoppard borrows two of Shakespeare’s minor characters and gives them top billing. But the two plays also have similar themes – both dwell on the futility of human action and the inevitability of death. Have students compare the two passages below (or others from the plays, if you so choose), discussing how each deals with the ideas of death and action/ inaction:
To be, or not to be: that is the question:
Whether 'tis nobler in the mind to suffer
The slings and arrows of outrageous fortune,
Or to take arms against a sea of troubles,
And by opposing end them? To die: to sleep;
No more; and by a sleep to say we end
The heart-ache and the thousand natural shocks
That flesh is heir to, 'tis a consummation
Devoutly to be wish'd. To die, to sleep;
To sleep: perchance to dream: ay, there's the rub;
For in that sleep of death what dreams may come
When we have shuffled off this mortal coil,
Must give us pause: there's the respect
That makes calamity of so long life;
For who would bear the whips and scorns of time,
The oppressor's wrong, the proud man's contumely,
The pangs of despised love, the law's delay,
The insolence of office and the spurns
That patient merit of the unworthy takes,
When he himself might his quietus make
With a bare bodkin? who would fardels bear,
To grunt and sweat under a weary life,
But that the dread of something after death,
The undiscover'd country from whose bourn
No traveller returns, puzzles the will
And makes us rather bear those ills we have
Than fly to others that we know not of?
Thus conscience does make cowards of us all;
And thus the native hue of resolution
Is sicklied o'er with the pale cast of thought,
And enterprises of great pith and moment
With this regard their currents turn awry,
And lose the name of action.
Rosencrantz: Do you ever think of yourself as actually dead, lying in a box with the lid on it? Nor do I really. Silly to be depressed by it. I mean, one thinks of it like being alive in a box. One keeps forgetting to take into account that one is dead. Which should make all the difference. Shouldn't it? I mean, you’d never know you were in a box would you? It would be just like you were asleep in a box. Not that I’d like to sleep in a box, mind you. Not without any air. You'd wake up dead for a start and then where would you be? In a box. That's the bit I don't like, frankly. That’s why I don’t think of it. Because you'd be helpless wouldn't you? Stuffed in a box like that. I mean, you'd be in there forever. Even taking into account the fact that you're dead. It isn't a pleasant thought. Especially if you're dead, really. Ask yourself: if I asked you straight off I'm going to stuff you in this box now – would you rather to be alive or dead? Naturally you’d prefer to be alive. Life in a box is better than no life at all. I expect. You'd have a chance at least. You could lie there thinking, well, at least I’m not dead. In a minute, somebody’s going to bang on the lid and tell me to come out. (knocks) "Hey you! What's your name? Come out of there!"
2. Unintentional Borrowing
Even though there are no new stories, storytellers can end up borrowing from previous stories without knowing it because the sheer number of tales is so vast that no one can possibly be expected to know them all. Have students compare and contrast the two summaries below. What’s the same, and what’s different? How do these similarities and differences shed new light on both the old tale and the new one?
8 C.E.: Philomela Weaves a Tale
In Metamorphoses, the Roman writer Ovid tells the tale of Tereus and Philomela. Tereus is a strapping young soldier married to Philomela’s sister, Procne - but he’s still got the hots for Philomela. When Philomela tells him to get lost, Tereus assaults her, then cuts out her tongue so she can’t tell her sister what he did. Undaunted, Philomela weaves a tapestry showing the assault, then presents it to her sister. (We’re never told what Procne thinks of this fabulous “gift”.)
2008 C.E.: A Story in Pictures
In 2008, police in Los Angeles, California, arrested a 24-year-old man on suspicion of drug charges. While they were taking his booking photos, they noticed that he had an elaborate scene tattooed across his chest and shoulders. On closer inspection, the police discovered that it was a scene that exactly matched the scene of an unsolved liquor store murder that had happened a few years before - right down to the name of the liquor store, which appeared in the tattooed version. The tattoo’s owner later confessed that he had committed the murder, then had the event made into a tattoo. Needless to say, no one but the man’s prison mates are likely to see him show off his story for a long time.
Quiz 1 QuestionsHere's an example of a quiz that could be used to test this standard.
Quiz 2 QuestionsHere's an example of a quiz that could be used to test this standard.
Questions 1-10 are based on the following information:
One classic Greek myth is the story of Pygmalion. Pygmalion was a sculptor who didn’t love much of anything except carving things out of stone all day long. That is, he didn’t love much of anything until he started carving a lovely lady out of marble, whom he named Galatea. The more he carved, the more he fell in love with the lady he was carving, until the statue was finally finished and Pygmalion was so madly in love with it that he stared at it all day long. Taking pity on him lest he waste away to nothing, the gods turned Galatea-the-statue into Galatea-the-woman so that Pygmalion could marry her and maybe even start eating and sleeping again instead of staring at her all the time. (We’re not told how Galatea felt about this arrangement.)
In 1913, George Bernard Shaw wrote Pygmalion, a play based on the myth. In the play, linguist and English gentleman Henry Higgins makes a bet with his friend that he can pick a lower-class flower seller at random off the street, teach her to speak “proper” English, and dupe all his upper-class friends into thinking she’s a duchess instead of a poor person. To do this, Higgins enlists a flower girl named Eliza Doolittle, gives her several speech and etiquette lessons, and then successfully passes her off as an upper-class lady at a local ball, making a rich young man fall in love with her.
Eliza, however, is furious that Higgins has only been “helping” her in order to win a bet and that, now that she has all these upper-class manners, her friends at home laugh at her. They get into a fight and she storms out, only coming back later to tell Higgins off and announce that she’s going to marry the rich young man with the crush on her, which for some reason Higgins thinks is hilarious - probably to conceal the fact that he’s in love with the upper-class lady he “created,” but not the lower-class flower girl she started as.
In 1972, Richard Huggett wrote the play The First Night of Pygmalion. The play focuses on the events backstage at the very first production of Shaw’s play. The three main characters are Shaw, Mrs. Campbell (who plays Eliza) and Herbert Beerbohm Tree (who plays Higgins). The play is mostly about the fight the three have over what the characters would and wouldn’t say on stage, including the infamous line “not bloody likely,” which Shaw, Campbell, and Tree each have a passionate reason for leaving in the play or taking out. As far as we know, no one falls in love with anyone, but the play does deal to some extent with Shaw’s belief that he can turn Mrs. Campbell, who has never been a particularly good actress, into one of the best on stage by shaping her to fit Eliza’s role.
- Teaching A Raisin in the Sun: Costume Design
- Teaching A Rose for Emily: Write an Epitaph
- Teaching A Rose for Emily: Put Miss Emily On Trial
- Teaching A Rose for Emily: Dramatizing "A Rose for Emily"
- Teaching The Adventures of Huckleberry Finn: Rollin' on the River: Mapping Huck's Journey
- Teaching The Adventures of Huckleberry Finn: Is Mark Twain is the Original Jon Stewart?
- All Quiet on the Western Front: War is Awesome… When it’s Fake!
- All Quiet on the Western Front: Eggnog in a Trench
- An Occurrence at Owl Creek Bridge: Write What You Know
- Teaching Animal Farm: Don't Wanna Be Your Beast of Burden: Animal Farm Music
- Teaching Animal Farm: You Say You Want A (R)evolution?
- Teaching Antigone: The First Three Letters of Funeral
- As I Lay Dying: Dysfunction Junction: Somebody, Help These Bundrens!
- As I Lay Dying: Telling a Story from All Sides: Experimenting with Multiple-Perspective Narration
- Teaching 1984: From Doublethink to Doublespeak
- Teaching 1984: This Is Why I Write
- Teaching 1984: It's Not Over Until the Fat Lady Sings
- A Christmas Carol: From Victorian England to Modern America
- Teaching Twilight: "The Cullen Cars"
- Teaching Twilight: Judging a Book by its Cover
- Teaching Wide Sargasso Sea: Hollywood Needs Your Help! Make a Movie of Wide Sargasso Sea
- Teaching Wuthering Heights: Timing is Everything
- Teaching Wuthering Heights: Isn't It Byronic?
- Teaching Wuthering Heights: Remix Time on the Moors
- Beloved: Back to the Source
- Teaching Beowulf: Speaking Beowulf
- Teaching Beowulf: Wise Guys in Beowulf: Gnomic Verse
- Teaching Brave New World: Aldous Huxley: Oracle or Alarmist?
- Catch-22: Waiting for Yossarian: Bureaucracy in Catch-22 and in Schools
- Catch-22: Oops, I Satirized It Again
- Catch-22: Achilles’ Heel: Antiheroes in Catch-22 and the Iliad
- Teaching Death of a Salesman: It's Just an Expressionism
- Teaching Death of a Salesman: Selling the American Dream
- Teaching Fahrenheit 451: Burn, Baby, Burn: Censorship 101
- Teaching Fahrenheit 451: Internet Censorship
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To calculate the area of a triangle you need to know its height. If this information is not given to you, you can easily calculate it based on what you do know! This article will teach you two different ways to find the height of a triangle, depending on what information you have been given.
Method 1 of 2: Using Base and Area
(You may also use the side lengths as the height)
1Recall the formula for the area of a triangle. The formula for the area of a triangle is A=1/2bh.
- A = Area of the triangle
- b = Length of the base of the triangle
- h = Height of the base of the triangle
2Look at your triangle and determine which variables you know. In this case, you already know the area, so assign that value to A. You should also know the value of one side length; assign that value to "'b'". If you do not know both the Area and the length of one side, you will need to try a different method.
- Any side of a triangle can be the base, regardless of how the triangle is drawn. To visualize this, just imagine rotating the triangle until the known side length is at the bottom.
- For example, if you know that the area of a triangle is 20, and one side is 4, then: A = 20 and b = 4.
3Plug your values into the equation A=1/2bh and do the math. First multiply the base (b) by 1/2, then divide the area (A) by the product. The resulting value will be the height of your triangle!
- In our example: 20 = 1/2(4)h
- 20 = 2h
- 10 = h
Method 2 of 2: Equilateral Triangle
1Recall the properties of an equilateral triangle. An equilateral triangle has three equal sides, and three equal angels that are each 60 degrees. If you cut an equilateral triangle in half, you will end up with two congruent right triangles.
- In this example, we will be using an equilateral triangle with side lengths of 8.
2Recall the Pythagorean Theorem. The Pythagorean Theorem states that for any right triangle with sides of length a and b, and hypotenuse of length c: a2 + b2 = c2. We can use this theorem to find the height of our equilateral triangle!
3Break the equilateral triangle in half, and assign values to variables a, b, and c. The hypotenuse c will be equal to the original side length. Side a will be equal to 1/2 the side length, and side b is the height of the triangle that we need to solve.
- Using our example equilateral triangle with sides of 8, c = 8 and a = 4.
4Plug the values into the Pythagorean Theorem and solve for b2. First square c and a by multiplying each number by itself. Then subtract a2 from c2.
- 42 + b2 = 82
- 16 + b2 = 64
- b2 = 48
5Find the square root of b2 to get the height of your triangle! Use the square root function on your calculator to find Sqrt(2. The answer is the height of your equilateral triangle!
- b = Sqrt (48) = 6.93
We could really use your help!
In other languages:
Italiano: Trovare l'Altezza di un Triangolo, Português: Achar a Altura de um Triângulo, Deutsch: Die Höhe eines Dreiecks bestimmen, Español: encontrar la altura de un triángulo, Русский: найти высоту треугольника, 中文: 求三角形的高, Français: calculer la hauteur d'un triangle, Bahasa Indonesia: Mencari Tinggi Segitiga, Nederlands: De hoogte van een driehoek berekenen
Thanks to all authors for creating a page that has been read 464,744 times.
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Earth's companion is so large and fascinating that geologists count the Moon as one of the solar system's "terrestrial planets." In fact, it was probably born from Earth, after a Mars-sized body collided with the proto-Earth, in a collision so violent that the Moon that coalesced from the leftover fragments was entirely (or almost entirely) molten. We can tell this story of Earth and the Moon's creation thanks to our analysis of the rocks returned to Earth by the Apollo astronauts, Luna landers, and chance discoveries of lunar meteorites. New laboratory techniques yield new discoveries every year even though no samples have been collected from the surface of the Moon since 1972.
In the years since the end of the space race between the United States and Russia, many other nations have sent robotic spacecraft to orbit the Moon as a first step in their planetary exploration: Japan, the European Space Agency, India, and China. Likewise, many people see a staging station on the Moon as a necessary first stepping stone toward sending humans on missions to asteroids or Mars. Thanks to the combined data from lunar orbiters from all nations we know that there is water stored in lunar soil and that there are permanently sunlit peaks at the lunar poles, providing for two basic needs of human settlements: water and power. We can go back to the Moon; but who will make the effort?
Recent Blog Articles About the Moon
Learn about the Planetary Society’s newest project: PlanetVac, with Honeybee Robotics, aims to prototype and test in a huge vacuum chamber a new way to sample planetary surfaces that could be used for sample return or for in situ instruments.
Posted by Emily Lakdawalla on 2013/01/31 02:00 CST
We welcomed Sarah Noble to our weekly Google+ Hangout. Sarah is a lunar geologist and a civil servant working in the Research & Analysis program at NASA Headquarters, and has recently been named Program Scientist for the LADEE lunar mission.
Posted by Emily Lakdawalla on 2003/11/14 12:00 CST
New observations reported this week in the journal Nature have cast doubt on the theory that thick deposits of ground ice lie conveniently close to the surface in permanently shadowed crater floors at the lunar poles.
Posted by Emily Lakdawalla on 2012/03/14 08:47 CDT
It is always thrilling to see relics of human exploration out there on other worlds. Today, the Lunar Reconnaissance Orbiter Camera team posted some new photos of two defunct spacecraft: the Luna 17 lander and the Lunokhod 1 rover. I've posted images of the two craft before, but the ones released today are much better.
Posted by Emily Lakdawalla on 2014/01/21 05:02 CST
A higher-resolution version of the Chang'e 3 lander's panoramic view of the lunar surface has appeared on the Web, and artist Don Davis has cleaned it of artifacts to make a beautiful, seamless view. In other news, the mission has been reorganized to accommodate a possibly year-long adventure on the lunar surface.
Posted by Jason Davis on 2011/09/08 11:58 CDT
On September 6, NASA released new high-resolution photos from the Lunar Reconnaissance Orbiter (LRO) showing the Apollo 12, 14 and 17 landing sites from vantage points as close as 21 kilometers.
Fifteen years ago, Society members and passionate space advocates like you helped save the Pluto mission. Now we can do the same for missions to Europa and Mars.
Join over 19,000 people who have completed their petition and consider a donation to support advocacy efforts.
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This session introduces the idea that there are different meanings of "more" and distinguishes between relative and absolute comparisons. To familiarize ourselves with the idea of equivalent ratios, we will use both additive and multiplicative methods to explore different ways of making similar figures. We will look at mixture problems and explore ratios without using algorithms to convert them to common denominators. Finally, we will examine characteristics of equations and graphs that represent direct variation.
Materials Needed: Graph paper, rulers, handouts of Quadperson, blank overheads
Groups: Discuss any questions about the homework. If time allows, take a few minutes to try out the number games with a partner. Pairs should show their networks to one another. One partner can choose a (secret) input, run it through the network, and reveal only the output. Then the other partner can use the "undoing" network to find the original number.
Groups: Take a minute and discuss iteration, along with Problems H4 and H5 from Session 3. It is likely to be a new idea.
<< back to Session 4 index
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The phylum Mollusca includes snails, clams, chitons, slugs, limpets, octopi, and squid. As mollusks develop from a fertilized egg to an adult, most pass through a larval stage called the trocophore. The trocophore is a ciliated, free-swimming stage. Mollusks also have a radula or file-like organ for feeding, a mantle that may secrete a shell, and a muscular foot for locomotion. Clams are marine mollusks with two valves or shells. Like all mollusks, a clam has a mantle which surrounds its soft body. It also has a muscular foot which enables the clam to burrow itself in mud or sand. The soft tissue above the foot is called the visceral mass and contains the clam's body organs.
Kingdom - Animalia
Phylum - Mollusca
Class - Bivalvia or Pelecypoda
To study the internal and external anatomy of a bivalve mollusk.
Dissecting pan, dissecting kit, screwdriver, lab apron, plastic gloves, safety glasses, preserved clam
Put on your lab apron, safety glasses, and plastic gloves.
Place a clam in a dissecting tray and identify the anterior and posterior ends of the clam as well as the dorsal, ventral, & lateral surfaces. Figure 1
Locate the umbo, the bump at the anterior end of the valve. This is the oldest part of the clam shell. Find the hinge ligament which hinges the valves together and observe the growth rings.
Turn the calm with its dorsal side down and insert a screwdriver between the ventral edges of the valves. Carefully work the tip of the screwdriver between the valves so you do not jab your hand.
Turn the screwdriver so that the valves are about a centimeter apart. Leave the tip of the screwdriver between the valves and place the clam in the pan with the left valve up.
Locate the adductor muscles. With your blade pointing toward the dorsal edge, slide your scalpel between the upper valve & the top tissue layer. Cut down through the anterior adductor muscle, cutting as close to the shell as possible.
Repeat step 6 in cutting the posterior adductor muscle. Figure 2
Bend the left valve back so it lies flat in the tray.
Run your fingers along the outside and the inside of the left valve and compare the texture of the two surfaces.
Examine the inner dorsal edges of both valves near the umbo and locate the toothlike projections. Close the valves & notice how the toothlike projections interlock.
Locate the muscle "scars" on the inner surface of the left valve. The adductor muscles were attached here to hold the clam closed.
Identify the mantle, the tissue that lines both valves & covers the soft body of the clam. Find the mantle cavity, the space inside the mantle.
Locate two openings on the posterior end of the clam. The more ventral opening is the incurrent siphon that carries water into the clam and the more dorsal opening is the excurrent siphon where wastes & water leave.
With scissors, carefully cut away the half of the mantle that lined the left valve. After removing this part of the mantle, you can see the gills, respiratory structures.
Observe the muscular foot of the clam, which is ventral to the gills. Note the hatchet shape of the foot used to burrow into mud or sand.
Locate the palps, flaplike structures that surround & guide food into the clam's mouth. The palps are anterior to the gills & ventral to the anterior adductor muscle. Beneath the palps, find the mouth.
With scissors, cut off the ventral portion of the foot. Use the scalpel to carefully cut the muscle at the top of the foot into right and left halves.
Carefully peel away the muscle layer to view the internal organs.
Locate the spongy, yellowish reproductive organs.
Ventral to the umbo, find the digestive gland, a greenish structure that surrounds the stomach.
Locate the long, coiled intestine extending from the stomach.
Follow the intestine through the calm. Find the area near the dorsal surface that the intestine passes through called the pericardial area. Find the clam's heart in this area.
Continue following the intestine toward the posterior end of the clam. Find the anus just behind the posterior adductor muscle.
Use your probe to trace the path of food & wastes from the incurrent siphon through the clam to the excurrent siphon.
Answer the questions on your lab report & label the diagrams of the internal structures of the clam. Also, use arrows on the clam diagram to trace the pathway of food as it travels to the clam's stomach. Continue the arrows showing wastes leaving through the anus.
When you have finished dissecting
the clam, dispose of the clam as your teacher advises and clean, dry, and return
all dissecting equipment to the lab cart. Wash your hands thoroughly with soap.
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LEWIS AND CLARK EXPEDITION
Ambrose, S.E. Undaunted Courage (Simon & Schuster, 1996).
United States citizens knew little about western North America when the Lewis and Clark Expedition set out in 1804. Twelve years earlier Captain Robert Gray, an American navigator, had sailed up the mouth of the great river he named the Columbia. Traders and trappers reported that the source of the Missouri River was in the mountains in the Far West. No one, however, had yet blazed an overland trail.
President Thomas Jefferson was interested in knowing more about the country west of the Mississippi and in finding a water route to the Pacific Ocean. In 1803, two years after he became president, he asked Congress for $2,500 for an expedition.
To head the expedition, Jefferson chose his young secretary, Captain Meriwether Lewis. Lewis invited his friend Lieutenant William Clark to share the leadership. Both were familiar with the frontier and with Native Americans through their service in the army.
Before Lewis and Clark set out, word came that Napoleon had sold an immense tract of land to the United States. Therefore, part of the region the expedition would be exploring was United States territory.
Plans for the expedition were carefully laid. The party was to ascend the Missouri to its source, carry canoes across the Continental Divide, and descend the Columbia River to its mouth. In preparation for the historic journey, Lewis studied natural history and learned how to fix latitude and longitude by the stars. In the winter of 1803-04 the expedition was assembled in Illinois, near St. Louis. The permanent party consisted of the two leaders, Lewis and Clark; three sergeants; 22 privates; the part-Native American frontiersman George Drouillard; and Clark's African American slave, York. They called themselves the Corps of Discovery.
On May 14, 1804, the explorers started up the Missouri in a 55-foot (17-meter) covered keelboat and two small canoes, paddled by French boatmen and a small temporary escort. On August 3 they held their first meeting with Native Americans at a place the explorers named Council Bluff, across the river and downstream from present-day Council Bluffs, Iowa. In late October they reached the earth-lodge villages of the Mandan, near the present site of Bismarck, N.D.
Across the river from the Mandan villages, the explorers built Fort Mandan and spent the winter. It was here that they hired Toussaint Charbonneau, a French interpreter, and his Native American wife, Sacagawea, the sister of a Shoshone chief. While at Fort Mandan, Sacagawea gave birth to a baby boy. This did not stop her from participating in the group. She carried the child on her back for the rest of the trip. As an interpreter she proved invaluable.
In the spring of 1805 the keelboat was sent back to St. Louis with dispatches for President Jefferson and with natural history specimens. Meanwhile, canoes had been built. On April 7 the party continued up the Missouri. On April 26 it passed the mouth of the Yellowstone, and on June 13 reached the Great Falls of the Missouri. Carrying the laden canoes 18 miles (29 kilometers) around the falls caused a month's delay. In mid-July the canoes were launched again above the falls. On the 25th the expedition reached Three Forks, where three rivers join to form the Missouri. They named the rivers the Madison, the Jefferson, and the Gallatin, after presidents James Madison and Thomas Jefferson, and Albert Gallatin, who was secretary of treasury under Jefferson.
For some time the explorers had been within sight of the Rocky Mountains. Crossing them was to be the hardest part of the journey. The expedition decided to follow the Jefferson River, the fork that led westward toward the mountains.
On August 12 the group climbed to the top of the Continental Divide, where they hoped to see the headwaters of the Columbia close enough to let them carry their canoes and proceed downstream toward the Pacific. Instead they saw mountains stretching endlessly into the distance. The water route Jefferson had sent them to find did not exist.
They were now in the country of the Shoshone, Sacagawea's people. Sacagawea eagerly watched for her tribe, but it was Lewis who found them. The chief, Sacagawea's brother, provided the party with horses and a guide for the difficult crossing of the lofty Bitterroot Range.
It took the Corps of Discovery most of September to cross the mountains. Hungry, sick, and exhausted, they reached a point on the Clearwater River where Nez Perce helped them make dugout canoes. From there they were able to proceed by water. They reached the Columbia River on October 16.
On Nov. 7, 1805, after a journey of nearly 18 months, Clark wrote in his journal, "Great joy in camp. We are now in view of the Ocean." The explorers had traveled more than 4,100 miles (6,600 kilometers) since they started up the Missouri. They were disappointed to find no ships at the mouth of the Columbia. A few miles from the Pacific shore, south of present-day Astoria, Ore., they built a stockade, Fort Clatsop. There they spent the rainy winter.
On March 23, 1806, the entire party started back. They crossed the mountains in June with Nez Perce horses and guides. Beside the Bitterroot River the two leaders separated to learn more about the country.
Clark headed for the Yellowstone River and followed it to the Missouri. Lewis, with nine men, struck off toward the northeast to explore a branch of the Missouri that he named the Marias. On this trip he had a skirmish with Native Americans that left two Blackfoot dead, the only such incident of the entire journey. Later, while out hunting, he was accidentally shot by one of his own men. He recovered after the party was reunited and had stopped at the Mandan villages. There they left Sacagawea and her family.
The party reached St. Louis on Sept. 23, 1806. Their arrival caused great rejoicing, for they had been believed dead. They had been gone two years, four months, and nine days.
Lewis, Clark, and several other members of the expedition kept detailed journals. They brought back much new material for cartographers and specimens of previously unknown wildlife. American settlers and traders soon began to travel over the route they had blazed. The expedition also provided useful support for the United States claim to the Oregon country.
A project by History World International
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Why are the stars in the Orion constellation different colors?
In this view of Orion you can see that the stars are different colors. The red star in the upper left is Betelgeuse (pronounced BET-ul-juice). The blue star in the lower right is Rigel. The fuzzy patch in the sword is the Orion nebula. The nebula will be discussed in the concept, Star Formation.
With a quick look, stars look the same. Look closer, though, and you can see differences. The most obvious differences are in size and color.
Color and Temperature
Think about the coil of an electric stove as it heats up. The coil changes in color as its temperature rises. When you first turn on the heat, the coil looks black. The air a few inches above the coil begins to feel warm. As the coil gets hotter, it starts to glow a dull red. As it gets even hotter, it becomes a brighter red. Next it turns orange. If it gets extremely hot, it might look yellow-white, or even blue-white. Like a coil on a stove, a star’s color is determined by the temperature of the star’s surface. Relatively cool stars are red. Warmer stars are orange or yellow. Extremely hot stars are blue or blue-white.
Star temperatures are measured in degrees kelvin. The lowest temperature on the kelvin scale is absolute zero. That means molecules have no motion. Kelvin is related to Celsius and Fahrenheit in these ways:
[°C] = [K] − 273.15
[°F] = [K] × 9/5 − 459.67
A graph of the brightness (absolute magnitude) of stars versus their color (temperature) is pictured below ( Figure below ). This is called Hertzsprung-Russell diagram.
The Hertzsprung-Russell diagram plots luminosity (absolute magnitude) against the color of the stars ranging from the high-temperature blue-white stars on the left side of the diagram to the low temperature red stars on the right side.
Most stars fall along the main sequence curve. Stars in the main sequence fuse hydrogen into helium in the core. The horizontal branch also has many stars. These fuse helium in the core and burn hydrogen surrounding the core. Other stars are found in other regions.
Relative sizes of stars of different masses.
This illustration ( Figure above ) shows the relative sizes of stars and their mass compared to the sun. Red dwarfs are less massive and much smaller in size than the sun. This means they have a very long lifetime. Our sun is a fairly common type of star and has an average lifespan. Red giants are what some main sequence stars (like our sun) become near the end of their lives. They are much larger than our sun. Supergiants are very massive stars and are larger than our sun, but have a smaller radius than red giants. Supergiants have very short lifetimes.
- red dwarf : A relatively cool small star.
- red giant : A relatively cool, large star.
- supergiant : An enormous star that is near the end of its life.
- Stars are classified by color, which correlates with temperature. Red stars are the coolest and blue are the hottest.
- Stars are plotted on a Hertzsprung-Russell diagram.
- Star temperatures are found in a continuum ranging from 2000 K to more than 30,000 K.
- Kelvin is a temperature measure in which the lowest temperature is absolute zero.
Use the resource below to answer the questions that follow.
- Star Classification - Sixty Symbols at http://www.youtube.com/watch?v=R6_dZhE-4bk (7:57)
- What characteristics of a star does a classification system need to tell?
- What is the classification of our star?
- What is the problem with the classification system set up for stars?
- What number is assigned to the brightest stars? Originally what did astronomers think that was referring to, which was thought to indicate temperature?
- Why wasn't this a very good way to measure that characteristic?
- What is the current letter classification, in order from hottest to coldest? What is the mnemonic device to remember that?
- Why is the temperature of a star a really important thing to know?
- What identified on each axis of the Hertzsprung-Russell diagram?
- Why are stars different colors?
- Where do most stars fall on the Hertzsprung-Russel diagram? Why?
- Why do stars that are different colors appear in the same constellation?
- If a cluster of stars is all the same color, what could that mean?
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Reading Skills Teacher Resources
Find Reading Skills educational ideas and activities
Showing 1 - 20 of 3,767 resources
Students practice their fluency skills. In this fluency lesson, students read aloud stories to their peers and they help to coach one another on their fluency, pronunciation, phrasing, and inflection. They discuss what makes a good reader enjoyable to listen to and easy to understand.
In this reading skills worksheet, students read about skills to use while reading and then fill out a Venn Diagram. Students choose which items to go into their Venn Diagram.
In this reading skills learning exercise, students fill in a graphic organizer, writing an article name, prediction, vocabulary words, main idea, values and a reflection.
In this reading skills worksheet, students read a selection entitled "Hurricane Warning!" and then respond to 5 questions regarding the main idea and supporting details.
In this graphic aids reading skills worksheet, learners read a 3 paragraph piece and examine the graphic aid accompanying it. Students respond to 4 short answer questions and use the graphic aid provided to think of their own labels and captions.
In this fact and opinion activity, middle schoolers sharpen their reading skills as they read a 1 page article titled "Culture Control" and identify the facts and opinions in the piece. Students list 2 facts and 2 opinions about an issue that matters to them.
In this cause and effect reading skills activity, students read a 5 paragraph selection about the Antarctic ice and identify causes and effects noted in the piece. Students give examples of cause and effect pertaining to an issue of their choice.
In this reading skills and strategies worksheet, learners look for sequence in the provided reading selection as they complete a graphic organizer. Students also identify the sequence of events about a day that especially memorable for them.
Students read articles related to local, state, national, and world events using word maps.
Seventh graders master the SQ3R method. They begin reading for a purpose and organize thoughts through categorizing them. They write in their notebooks what they think about the lesson and the classroom for the day and write a paragraph about their own culture.
In this problem and solution reading strategies learning exercise, students read a 2 page selection about renewable energy and then identify the problems and solutions noted in the essay.
In this reading skills worksheet, students use clues from a story to make predictions about what will happen next and continue to revise their predictions as they read.
In this reading skills worksheet, students look for clues about the author's purpose in a 3 paragraph selection. Students decide whether the author's main purpose is to inform, entertain, or persuade.
In this reading skills and strategies worksheet, learners look for sequence in the provided reading selection as they complete a graphic organizer. Students also identify a sequence of events pertaining to goals they have set for themselves and achieved.
In this reading skills and strategies learning exercise, students read a 1 page passage titled " A Few Good Noses" and identify important details about the piece as they complete a graphic organizer.
Students explore the rhythm of words. For this reading skills lesson, students read Bedtime at the Swamp and use rhythm instruments to find the cadence in the words of the story. Students listen for rhythm in other written text as they listen to more stories, rhymes, and songs.
In this reading skills worksheet, learners look for the main idea and details that support it as they respond to questions about to the 1 page reading selection. Students also identity the main idea and supporting details of an interesting job that they might write about.
Students sharpen their reading skills and learn about the character trait of generosity through the book, "The Rainbow Fish." They describe characters in the story, explain cause and effect, make simple predictions, and compare characters.
Students compare a map of the Roman Empire in 44 BC with one of the Roman Empire in 116 AD. Using these two maps as a reference, students use critical reading skills to explore the expansion of the Roman Empire during that time period.
Students observe and listen to nonfiction books about the life cycle of pumpkins. They practice early reading skills in a shared reading related to pumpkins. They observe the life cycle of a pumpkin including growth and decay.
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© 2008 Zachary S Tseng B-3 - 1
A mass m is suspended at the end of a spring, its weight stretches the spring
by a length L to reach a static state (the equilibrium position of the system).
Let u(t) denote the displacement, as a function of time, of the mass relative
to its equilibrium position. Recall that the textbook’s convention is that
downward is positive Then, u > 0 means the spring is stretched beyond its
equilibrium length, while u < 0 means that the spring is compressed. The
mass is then set in motion (by any one of several means).
© 2008 Zachary S Tseng B-3 - 2
The equations that govern a mass-spring system
At equilibrium: (by Hooke’s Law)
mg = kL
While in motion:
m u″ + γ u′ + k u = F(t)
This is a second order linear differential equation with constant coefficients.
It usually comes with two initial conditions: u(t0) = u0, and u′(t0) = u′0.
Summary of terms:
u(t) = displacement of the mass relative to its equilibrium position.
m = mass (m > 0)
γ = damping constant (γ ≥ 0)
k = spring (Hooke’s) constant (k > 0)
g = gravitational constant
L = elongation of the spring caused by the weight
F(t) = Externally applied forcing function, if any
u(t0) = initial displacement of the mass
u′(t0) = initial velocity of the mass
© 2008 Zachary S Tseng B-3 - 3
Undamped Free Vibration (γ = 0, F(t) = 0)
The simplest mechanical vibration equation occurs when γ = 0, F(t) = 0.
This is the undamped free vibration. The motion equation is
m u″ + k u = 0.
The characteristic equation is mr2
+ k = 0. Its solutions are i
r ±= .
The general solution is then
u(t) = C1 cos ω0t + C2 sin ω0t.
=0ω is called the natural frequency of the system. It is the
frequency at which the system tends to oscillate in the absence of any
damping. A motion of this type is called simple harmonic motion.
Comment: Just like everywhere else in calculus, the angle is measured in
radians, and the (angular) frequency is given in radians per second. The
frequency is not given in hertz (which measures the number of cycles or
revolutions per second). Instead, their relation is: 2π radians/sec = 1 hertz.
The (natural) period of the oscillation is given by
© 2008 Zachary S Tseng B-3 - 4
To get a clearer picture of how this solution behaves, we can simplify it with
trig identities and rewrite it as
u(t) = Rcos (ω0 t − δ).
The displacement is oscillating steadily with constant amplitude of
1 CCR += .
The angle δ is the phase or phase angle of displacement. It measures how
much u(t) lags (when δ > 0), or leads (when δ < 0) relative to cos(ω0 t),
which has a peak at t = 0. The phase angle satisfies the relation
More explicitly, it is calculated by:
=δ , if C1 > 0,
πδ += −
, if C1 < 0,
δ = , if C1 = 0 and C2 > 0,
δ −= , if C1 = 0 and C2 < 0,
The angle is undefined if C1 = C2 = 0.
© 2008 Zachary S Tseng B-3 - 5
An example of simple harmonic motion:
Graph of u(t) = cos(t) − sin(t)
Phase angle: δ = −π/4
© 2008 Zachary S Tseng B-3 - 6
Damped Free Vibration (γ > 0, F(t) = 0)
When damping is present (as it realistically always is) the motion equation
of the unforced mass-spring system becomes
m u″ + γ u′ + k u = 0.
Where m, γ, k are all positive constants. The characteristic equation is mr2
γr + k = 0. Its solution(s) will be either negative real numbers, or complex
numbers with negative real parts. The displacement u(t) behaves differently
depending on the size of γ relative to m and k. There are three possible
classes of behaviors based on the possible types of root(s) of the
Case I. Two distinct (negative) real roots
> 4mk, there are two distinct real roots, both are negative. The
displacement is in the form
21)( += .
A mass-spring system with such type displacement function is called
overdamped. Note that the system does not oscillate; it has no periodic
components in the solution. In fact, depending on the initial conditions the
mass of an overdamped mass-spring system might or might not cross over
its equilibrium position. But it could cross the equilibrium position at most
© 2008 Zachary S Tseng B-3 - 7
Figures: Displacement of an Overdamped system
Graph of u(t) = e−t
Graph of u(t) = − e−t
© 2008 Zachary S Tseng B-3 - 8
Case II. One repeated (negative) real root
= 4mk, there is one (repeated) real root. It is negative:
The displacement is in the form
u(t) = C1 e rt
+ C2 te rt
A system exhibits this behavior is called critically damped. That is, the
damping coefficient γ is just large enough to prevent oscillation. As can be
seen, this system does not oscillate, either. Just like the overdamped case,
the mass could cross its equilibrium position at most one time.
Comment: The value γ2
= 4mk → mk2=γ is called critical damping. It
is the threshold level below which damping would be too small to prevent
the system from oscillating.
© 2008 Zachary S Tseng B-3 - 9
Figures: Displacement of a Critically Damped system
Graph of u(t) = e−t / 2
+ t e− t / 2
Graph of u(t) = e−t / 2
− t e− t / 2
© 2008 Zachary S Tseng B-3 - 10
Case III. Two complex conjugate roots
< 4mk, there are two complex conjugate roots, where their common
real part, λ, is always negative. The displacement is in the form
u(t) = C1 e λt
cos µt + C2 e λt
A system exhibits this behavior is called underdamped. The name means
that the damping is small compares to m and k, and as a result vibrations will
occur. The system oscillates (note the sinusoidal components in the
solution). The displacement function can be rewritten as
u(t) = Reλ t
cos (µt − δ).
The formulas for R and δ are the same as in the previous (undamped free
vibration) section. The displacement function is oscillating, but the
amplitude of oscillation, Reλ t
, is decaying exponentially. For all particular
solutions (except the zero solution that corresponds to the initial conditions
u(t0) = 0, u′( t0) = 0), the mass crosses its equilibrium position infinitely
Damped oscillation: u(t) = e−t
© 2008 Zachary S Tseng B-3 - 11
The displacement of an underdamped mass-spring system is a quasi-periodic
function (that is, it shows periodic-like motion, but it is not truly periodic
because its amplitude is ever decreasing so it does not exactly repeat itself).
It is oscillating at quasi-frequency, which is µ radians per second. (It’s just
the frequency of the sinusoidal components of the displacement.) The peak-
to-peak time of the oscillation is the quasi-period:
In addition to cause the amplitude to gradually decay to zero, damping has
another, more subtle, effect on the oscillating motion: It immediately
decreases the quasi-frequency and, therefore, lengthens the quasi-period
(compare to the natural frequency and natural period of an undamped
system). The larger the damping constant γ, the smaller quasi-frequency and
the longer the quasi-period become. Eventually, at the critical damping
threshold, when mk4=γ , the quasi-frequency vanishes and the
displacement becomes aperiodic (becoming instead a critically damped
Note that in all 3 cases of damped free vibration, the displacement function
tends to zero as t → ∞. This behavior makes perfect sense from a
conservation of energy point-of-view: while the system is in motion, the
damping wastes away whatever energy the system has started out with, but
there is no forcing function to supply the system with additional energy.
Consequently, eventually the motion comes to a halt.
© 2008 Zachary S Tseng B-3 - 12
Example: A mass of 1 kg stretches a spring 0.1 m. The system has a
damping constant of γ = 14. At t = 0, the mass is pulled down 2 m and
released with an upward velocity of 3.5 m/s. Find the displacement function.
What are the system’s quasi-frequency and quasi-period?
m = 1, γ = 14, L = 0.1;
mg = 9.8 = kL = 0.1 k → 98 = k.
The motion equation is u″ + 14u′ + 98u = 0, and
the initial conditions are u(0) = 2, u′(0) = −3.5.
The roots of characteristic polynomial are r = −7 ± 7i:
u(t) = C1 e −7t
cos 7t + C2 e −7t
Therefore, the quasi-frequency is 7 (rad/sec) and the quasi-period is
Apply the initial condition and we get C1 = 2, and C2 = 3/2. Hence
u(t) = 2e −7t
cos 7t + 1.5e −7t
© 2008 Zachary S Tseng B-3 - 13
Summary: the Effects of Damping on an Unforced Mass-Spring System
Consider a mass-spring system undergoing free vibration (i.e. without a
forcing function) described by the equation:
m u″ + γ u′ + k u = 0, m > 0, k > 0.
The behavior of the system is determined by the magnitude of the damping
coefficient γ relative to m and k.
1. Undamped system (when γ = 0)
Displacement: u(t) = C1 cosω0 t + C2 sinω0 t
Oscillation: Yes, periodic (at natural frequency
Notes: Steady oscillation with constant amplitude
1 CCR += .
2. Underdamped system (when 0 < γ2
Displacement: u(t) = C1 e λ t
cos µt + C2 e λ t
Oscillation: Yes, quasi-periodic (at quasi-frequency µ)
Notes: Exponentially-decaying oscillation
3. Critically Damped system (when γ2
Displacement: u(t) = C1 e rt
+ C2 te rt
4. Overdamped system (when γ2
© 2008 Zachary S Tseng B-3 - 14
Displacement: u(t)= C1 ert
+ C2 tert
Mass crosses equilibrium at most once.
Mechanical Vibrations, F(t)=0
System oscillates with amplitude decreasing
Displacement: u(t)= C1e
cos µt + C2 e
Oscillation quasi periodic: Tq = 2π/µ
Displacement: u(t)= C1 e
+ C2 e
Mass crosses equilibrium at most once.
γ = 0, Displacement: u(t)= C1 cos ω0t + C2 sin ω0t
Natural frequency: ω0 = , Steady oscillation with constant amplitude
© 2008 Zachary S Tseng B-3 - 15
Undamped Forced Vibration (γ = 0, F(t) ≠ 0)
Now let us introduce a nonzero forcing function into the mass-spring system.
To keep things simple, let damping coefficient γ = 0. The motion equation is
mu″ + ku = F(t).
In particular, we are most interested in the cases where F(t) is a periodic
function. Without the losses of generality, let us assume that the forcing
function is some multiple of cosine:
mu″ + ku = F0 cosωt.
This is a nonhomogeneous linear equation with the complementary solution
uc(t) = C1 cosω0 t + C2 sinω0 t.
The form of the particular solution that the displacement function will have
depends on the value of the forcing function’s frequency, ω.
Case I. When ω ≠ ω0
If ω ≠ ω0 then the form of the particular solution corresponding to the
forcing function is
Y = Acosωt + Bsinωt.
Solving for A and B using the method of Undetermined Coefficients, we find
Therefore, the general solution of the displacement function is
© 2008 Zachary S Tseng B-3 - 16
An interesting instance of such a forced vibration occurs when the initial
conditions are u(0) = 0, and u′(0) = 0. Applying the initial conditions to the
general solution and we get
C , and C2 = 0.
Again, a clearer picture of the behavior of this solution can be obtained by
rewriting it, using the identity:
sin(A)sin(B) = [cos(A − B) − cos(A + B)]/2.
The displacement becomes
The behavior exhibited by this function is that the higher-frequency, of
(ω0 + ω)/2, sine curve sees its amplitude of oscillation modified by its
lower-frequency, of (ω0 − ω)/2, counterpart.
This type of behavior, where an oscillating motion’s own amplitude shows
periodic variation, is called a beat.
© 2008 Zachary S Tseng B-3 - 17
An example of beat:
Graph of u(t) = 5sin(1.8t)sin(4.8t)
© 2008 Zachary S Tseng B-3 - 18
Case II. When ω = ω0
If the periodic forcing function has the same frequency as the natural
frequency, that is ω = ω0, then the form of the particular solution becomes
Y = Atcos ω0 t + Btsin ω0 t.
Use the method of Undetermined Coefficients we can find that
A = 0, and
B = .
The general solution is, therefore,
The first two terms in the solution, as seen previously, could be combined to
become a cosine term u(t) = Rcos (ω0 t − δ), of steady oscillation. The third
term, however, is a sinusoidal wave whose amplitude increases
proportionally with elapsed time. This phenomenon is called resonance.
Resonance: graph of u(t) = tsin(t)
© 2008 Zachary S Tseng B-3 - 19
Technically, true resonance only occurs if all of the conditions below are
1. There is no damping: γ = 0,
2. A periodic forcing function is present, and
3. The frequency of the forcing function exactly matches the
natural frequency of the mass-spring system.
However, similar behaviors, of unexpectedly large amplitude of oscillation
due to a fairly low-strength forcing function occur when damping is present
but is very small, and/or when the frequency of forcing function is very
close to the natural frequency of the system.
© 2008 Zachary S Tseng B-3 - 20
1 – 4 Solve the following initial value problems, and determine the natural
frequency, amplitude and phase angle of each solution.
1. u″ + u = 0, u(0) = 5, u′(0) = −5.
2. u″ + 25u = 0, u(0) = −2, u′(0) = 310 .
3. u″ + 100u = 0, u(0) = 3, u′(0) = 0.
4. 4u″ + u = 0, u(0) = −5, u′(0) = −5.
5 – 10 Solve the following initial value problems. For each problem,
determine whether the system is under-, over-, or critically damped.
5. u″ + 6u′ + 9u = 0, u(0) = 1, u′(0) = 1.
6. u″ + 4u′ + 3u = 0, u(0) = 0, u′(0) = −4.
7. u″ + 6u′ + 10u = 0, u(0) = −2, u′(0) = 9.
8. u″ + 2u′ + 17u = 0, u(0) = 6, u′(0) = −2.
9. 4u″ + 9u′ + 2u = 0, u(0) = 3, u′(0) = 1.
10. 3u″ + 24u′ + 48u = 0, u(0) = −5, u′(0) = 6.
11. Consider a mass-spring system described by the equation
2u″ + 3u′ + ku = 0. Give the value(s) of k for which the system is under-,
over-, and critically damped.
12. Consider a mass-spring system described by the equation
4u″ + γu′ + 36u = 0. Give the value(s) of γ for which the system is under-,
over-, and critically damped.
13. One of the equations below describes a mass-spring system undergoing
resonance. Identify the equation, and find its general solution.
(i.) u″ + 9u = 2cos9t (ii.) u″ + 4u′ + 4u = 3sin 2t
(iii.) 4u″ + 16u = 7cos2t
© 2008 Zachary S Tseng B-3 - 21
14. Find the value(s) of k, such that the mass-spring system described by
each of the equations below is undergoing resonance.
(a) 8u″ + ku = 5sin6t (b) 3u″ + ku = −πcost
1. u = 5cost − 5sint, ω0 = 1, R = 25 , δ = −π/4
2. u = −2cos5t + 32 sin5t, ω0 = 5, R = 4, δ = 2π/3
3. u = 3cos10t, ω0 = 10, R = 3, δ = 0
4. u = −5cost/2 − 10sint/2, ω0 = 1/2, R = 55 , δ = π + tan−1
5. u = e −3t
+ 4te −3t
, critically damped
6. u = 2e −3t
− 2e −t
7. u = −2e −3 t
cost + 3e −3 t
sin t, underdamped
8. u = 6e − t
cos4t + e − t
9. u = 4e −t/4
− e −2t
10. u = −5e −4t
− 14te −4t
, critically damped
11. Overdamped if 0 < k < 9/8, critically damped if k = 9/8, underdamped
if k > 9/8.
12. Underdamped if 0 < γ < 24, critically damped if γ = 24, overdamped if
γ > 24. When γ = 0, the system is undamped (rather than underdamped).
13. (iii), tttCtCu 2sin
2sin2cos 21 ++=
14. (a) k = 288 (b) k = 3
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|Part of the Politics series|
|Basic forms of government|
A confederation (also known as confederacy or league) is a union of political units for common action in relation to other units. Usually created by treaty but often later adopting a common constitution, confederations tend to be established for dealing with critical issues (such as defense, foreign affairs, or a common currency), with the central government being required to provide support for all members.
The nature of the relationship among the states constituting a confederation varies considerably. Likewise, the relationship between the member states, the central government, and the distribution of powers among them is highly variable. Some looser confederations are similar to intergovernmental organizations and even may permit secession from the confederation. Other confederations with stricter rules may resemble federations. A unitary state or federation may decentralize powers to regional or local entities in a confederal form.
In a non-political context, confederation is used to describe a type of organization which consolidates authority from other autonomous (or semi-autonomous) bodies. Examples include sports confederations or confederations of pan-European trades unions.
In the context of the history of the indigenous peoples of the Americas, a confederacy may refer to a semi-permanent political and military alliance consisting of multiple nations (or "tribes", "bands", or "villages") which maintained their separate leadership. One of the most well-known is the Iroquois Confederacy, but there were many others during different eras and locations across North America; these include the Wabanaki Confederacy, Western Confederacy, Powhatan Confederacy, Seven Nations of Canada, Pontiac's Confederacy, Illinois Confederation, Tecumseh's Confederacy, Great Sioux Nation, Blackfoot Confederacy, Iron Confederacy and Council of Three Fires.
Many scholars have proposed that Belgium has some characteristics of a confederation. For example, C. E. Lagasse declared that Belgium was "near the political system of a Confederation" regarding the agreements between Belgian regions and communities, while Centre de recherche et d'information socio-politiques (CRISP) director Vincent de Coorebyter called Belgium "undoubtedly a federation...[with] some aspects of a confederation" in Le Soir. Also in Le Soir, Professor Michel Quévit of the Catholic University of Leuven wrote that the "Belgian political system is already in dynamics of a Confederation".
Nevertheless, the Belgian regions and communities lack the necessary autonomy to leave the Belgian state. As such, the federal aspects seem to dominate. Also for fiscal policy and public finances, the federal state dominates the other levels of government.
The limited confederal aspects appear to be a meager political reflection of the profound sociological, cultural and economic differences between Flemings and Walloons (or French-speaking Belgians). As an example, in the last several decades, over 95% of the Belgians have voted for political parties that represent voters from only one community. Parties that advocate Belgian unity and appeal to voters of both communities systematically get only a few percent of the votes.
This makes Belgium fundamentally different from federal countries like Switzerland, Canada, Germany and Australia. In those countries, national parties get over 90% of the votes. The only comparable places with Belgium are Catalonia, the Basque Country, Northern Ireland and Scotland, where there is majority voter turnout for local political parties, while national parties draw less (sometimes much less) than half of the votes.
In modern terminology, Canada is a federation and not a confederation. However, at the time the Constitution Act, 1867, confederation was the normal British and Canadian term for a single sovereign nation-state of federating provinces. Canadian Confederation generally refers to the Constitution Act, 1867 which formed the Dominion of Canada from three of the colonies of British North America, and to the subsequent incorporation of other colonies and territories. Therefore on July 1, 1867, Canada became a self-governing dominion of the British Empire with a federal structure under the leadership of Sir John A. Macdonald. The provinces involved were the Province of Canada (comprising Canada West, now Ontario, formerly Upper Canada; and Canada East now Quebec, formerly Lower Canada), Nova Scotia, and New Brunswick. Later participants were Manitoba, British Columbia, Prince Edward Island, Alberta and Saskatchewan (the latter two created as provinces from the Northwest Territories in 1905), and finally Newfoundland (now Newfoundland and Labrador) in 1949. Canada is an unusually decentralized federal state and not a confederate association of sovereign states, (the usual meaning of confederation in modern terms). A Canadian law, the Clarity Act, and a court ruling, Reference re Secession of Quebec, set forth the conditions for negotiations to allow Canadian provinces (though not territories) to leave the Canadian federal state; however, as this would require a constitutional amendment, there is no current "constitutional" method for withdrawal.
Due to its unique nature, and the political sensitivities surrounding it, there is no common or legal classification for the European Union (EU). However, it does bear some resemblance to both a confederation (or "new" type of confederation) and a federation. The EU operates common economic policies with hundreds of common laws, which enable a single economic market, open internal borders, a common currency and allow for numerous other areas where powers have been transferred and directly applicable laws are made. However, unlike a federation, the EU does not have exclusive powers over foreign affairs, defence and taxation. Furthermore, laws sometimes must be transcribed into national law by national parliaments; decisions by member states are taken by special majorities with blocking minorities accounted for; and treaty amendment requires ratification by every member state before it can come into force.
However, academic observers more usually discuss the EU in the terms of it being a federation. As international law professor Joseph H. H. Weiler (of the Hague Academy and New York University) wrote, "Europe has charted its own brand of constitutional federalism". Jean-Michel Josselin and Alain Marciano see the European Court of Justice as being a primary force behind building a federal legal order in the Union with Josselin stating that a "complete shift from a confederation to a federation would have required to straightforwardly replace the principality of the member states vis-à-vis the Union by that of the European citizens...As a consequence, both confederate and federate features coexist in the judicial landscape". Rutgers political science professor R. Daniel Kelemen observed: "Those uncomfortable using the 'F' word in the EU context should feel free to refer to it as a quasi-federal or federal-like system. Nevertheless...the EU has the necessary attributes of a federal system. It is striking that while many scholars of the EU continue to resist analyzing it as a federation, most contemporary students of federalism view the EU as a federal system".[when?] Thomas Risse and Tanja A. Börzel claim that the "EU only lacks two significant features of a federation. First, the Member States remain the 'masters' of the treaties, i.e., they have the exclusive power to amend or change the constitutive treaties of the EU. Second, the EU lacks a real 'tax and spend' capacity, in other words, there is no fiscal federalism."
The Iroquois League, historically the Iroquois Confederacy, is a group of Native Americans (in what is now the United States) and First Nations (in what is now Canada) that consists of six nations: the Mohawk, the Oneida, the Onondaga, the Cayuga, the Seneca and the Tuscarora. The Iroquois have a representative government known as the Grand Council. The Grand Council is the oldest governmental institution still maintaining its original form in North America. The League has been functioning since prior to major European contact. Each tribe sends chiefs to act as representatives and make decisions for the whole nation.
Serbia and Montenegro
Serbia and Montenegro (2003–06) was a confederation that was formed by the two remaining republics of the Socialist Federal Republic of Yugoslavia (SFR Yugoslavia): Montenegro and neighboring Serbia were sole legal successors to FR Yugoslavia, which consequently ceased to exist. The country was reconstituted as a very loose political union called the State Union of Serbia and Montenegro. It was established on February 4, 2003.
As a confederation, Serbia and Montenegro were united only in very few realms, such as defense, foreign affairs and a very weak common president of the confederation. The two constituent republics functioned separately throughout the period of its short existence, and continued to operate under separate economic policies, as well as using separate currencies (the euro was and still is the only legal tender in Montenegro, while the dinar was still the legal tender in Serbia). On 21 May 2006, the Montenegrin independence referendum was held. Final official results indicated on 31 May that 55.5% of voters voted in favor of independence. The state union effectively came to an end after Montenegro's formal declaration of independence on June 3rd 2006, and Serbia's formal declaration of independence on June 5th.
Switzerland, officially known as the Swiss Confederation, is an example of a modern country that refers to itself as a confederation. However, at the time Switzerland adopted the Latin name "Confoederatio Helvetica", no distinction existed in Europe between the words "confederation" and "federation" regarding the strength of federal authority. After the Swiss civil war of 1847, when some of the Catholic cantons tried to set up a separate alliance (the Sonderbundskrieg), the resulting political system acquired all the characteristics of a federation. It had been a confederacy since its inception in 1291 as the Old Swiss Confederacy, originally created as an alliance among the valley communities of the central Alps, and retains the confederal name. The confederacy facilitated management of common interests (free trade) and ensured peace in the important mountain trade.
Historical confederations (especially those predating the 20th century) may not fit the current definition of a confederation, may be proclaimed as a federation but be confederal (or the reverse), and may not show any qualities that 21st-century political scientists might classify as those of a confederation.
Arabia during Muhammad era
Early in 627 during the Battle of the Trench a confederation of tribes was formed to fight the Islamic Prophet Muhammad. The Jews of Banu Nadir met with the Arab Quraysh of Makkah. Huyayy ibn Akhtab, along with other leaders from Khaybar, traveled to swear allegiance with Safwan at Makkah.
The Banu Nadir began rousing the nomads of Najd. The Nadir enlisted the Banu Ghatafan by paying them half of their harvest. This contingent, the second largest, added a strength of about 2,000 men and 300 horsemen led by Unaina bin Hasan Fazari. The Bani Assad also agreed to join, led by Tuleha Asadi. From the Banu Sulaym, the Nadir secured 700 men, though this force would likely have been much larger had not some of its leaders been sympathetic towards Islam. The Bani Amir, who had a pact with Muhammad, refused to join.
Other tribes included the Banu Murra, with 400 men led by Hars ibn Auf Murri, and the Banu Shuja, with 700 men led by Sufyan ibn Abd Shams. In total, the strength of the Confederate armies, though not agreed upon by scholars, is estimated to have included around 10,000 men and six hundred horsemen. At the end of March 627 the army, which was led by Abu Sufyan, marched on Medina.
In accordance with the plan the armies began marching towards Medina, Meccans from the south (along the coast) and the others from the east. At the same time horsemen from the Banu Khuza'a left to warn Medina of the invading army.
Some have more the characteristics of a personal union, but appear here because of their self-styling as a "confederation":
- a Confederated personal union.
- b De facto confederation.
- Oxford English Dictionary
- "How Canadian Govern Themselves, First Edition, 1980 by Eugene Forsey, Ch. on A Federal State p.1". .parl.gc.ca. Retrieved 2011-02-19.
- French Le confédéralisme n'est pas loin Charles-Etienne Lagasse, Les nouvelles institutions politiques de la Belgique et de l'Europe, Erasme, Namur 2003, p. 405 ISBN 2-87127-783-4
- Belgian research center whose activities are devoted to the study of decision-making in Belgium and in Europe[dead link]
- French: "La Belgique est (...) incontestablement, une fédération : il n’y a aucun doute (...) Cela étant, la fédération belge possède d’ores et déjà des traits confédéraux qui en font un pays atypique, et qui encouragent apparemment certains responsables à réfléchir à des accommodements supplémentaires dans un cadre qui resterait, vaille que vaille, national." Vincent de Coorebyter "La Belgique (con)fédérale" in Le Soir 24 June 2008
- French: "Le système institutionnel belge est déjà inscrit dans une dynamique de type confédéral." Michel Quévit Le confédéralisme est une chance pour les Wallons et les Bruxellois, Le Soir, 19 September 2008
- Robert Deschamps, Michel Quévit, Robert Tollet, "Vers une réforme de type confédéral de l'État belge dans le cadre du maintien de l'union monétaire," in Wallonie 84, n°2, pp. 95-111
- P.W. Hogg, Constitutional Law of Canada (5th ed. supplemented), para. 5.1(b).
- How Canadians Govern Themselves, 7th ed
- Kiljunen, Kimmo (2004). The European Constitution in the Making. Centre for European Policy Studies. pp. 21–26. ISBN 978-92-9079-493-6.
- Burgess, Michael (2000). Federalism and European union: The building of Europe, 1950–2000. Routledge. p. 49. ISBN 0-415-22647-3. "Our theoretical analysis suggests that the EC/EU is neither a federation nor a confederation in the classical sense. But it does claim that the European political and economic elites have shaped and moulded the EC/EU into a new form of international organization, namely, a species of "new" confederation."
- Josselin, Jean Michel; Marciano, Alain (2006). "The Political Economy of European Federalism". Series: Public Economics and Social Choice. Centre for Research in Economics and Management, University of Rennes 1, University of Caen. p. 12. WP 2006-07; UMR CNRS 6211.
A complete shift from a confederation to a federation would have required to straightforwardly replace the principalship of the member states vis-à-vis the Union by that of the European citizens.... As a consequence, both confederate and federate features coexist in the judicial landscape.
- "How the Court Made a Federation of the EU" [referring to the European Court of Justice]. Josselin (U. de Rennes-1/CREM) and Marciano (U. de Reims CA/CNRS).
- J.H.H. Weiler (2003). "Chapter 2, Federalism without Constitutionalism: Europe's Sonderweg". The federal vision: legitimacy and levels of governance in the United States and the European Union. Oxford University Press. ISBN 0-19-924500-2.
Europe has charted its own brand of constitutional federalism. It works. Why fix it?
- How the [ECJ] court made a federation of the EU Josselin (U de Rennes-1/CREM) and Marciano (U de Reims CA/CNRS).
- Josselin, Jean Michel; Marciano, Alain (2006). "The political economy of European federalism" (PDF). Series: Public Economics and Social Choice. Centre for Research in Economics and Management, University of Rennes 1, University of Caen. p. 12. WP 2006-07; UMR CNRS 6211.
- Bednar, Jenna (2001). A Political Theory of Federalism. Cambridge University. pp. 223–270.
- Thomas Risse and Tanja A. Börzel, Who is Afraid of a European Federation? How to Constitutionalise a Multi-Level Governance System, Section 4: The European Union as an Emerging Federal System, Jean Monnet Center at NYU School of Law
- Evans-Pritchard, Ambrose (2003-07-08). "Giscard's 'federal' ruse to protect Blair". The Daily Telegraph. Retrieved 2008-10-15.
- Jennings, p.94
- "Startseite". admin.ch. 2011-02-13. Retrieved 2011-02-19.
- "Federal Chancellery - The Swiss Confederation – a brief guide". Bk.admin.ch. 2010-03-01. Retrieved 2011-02-19.
- swissconfederationinstitute Resources and Information. This website is for sale!. swissconfederationinstitute.org. Retrieved on 2013-07-12.
- Haller/Kölz, p. 147
- Lings, Muhammad: his life based on the earliest sources, pp. 215f.
- al-Halabi, al-Sirat al-Halbiyyah, p. 19.
- Nomani, Sirat al-Nabi, p. 368-370.
- Watt, Muhammad at Medina, p. 34-37.
- Rodinson, Muhammad: Prophet of Islam, p. 208.
|Look up confederation in Wiktionary, the free dictionary.|
- P.-J. Proudhon, The Principle of Federation, 1863.
- The Fathers of Confederation
- Confederation: The Creation of Canada
- South Africa at worldstatesmen.org.
- United Confederation of Taino People
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A painting by Rudolf Bohunek depicting a man and a barrel of whiskey entitled "Ould Irish Whiskey. This image was painted during the Prohibition Era around 1910. Learn more »
In the early twentieth century, Louisiana reluctantly became subject to the abolition, or prohibition, of alcoholic drinks as a result of the federal law.The ban on alcohol mandated by the 18th amendment to the US Constitution, commonly known as the Volstead Act, was approved by Congress in December 1917, ratified with the approval of thirty-six of the forty-eight states in January 1919, and became law on January 16, 1920.
The effort to eliminate alcohol, or the “dry” movement, as it was often known, actually began in earnest in the 1840s. In 1869 an official Prohibition Party emerged to coordinate dry efforts. By 1873 the Women’s Christian Temperance Union (WCTU) eclipsed other national antialcohol movements, emerging as a potent political force across much of the South and Midwest. The Louisiana branch of the WCTU boasted a large membership of politically active “drys.” During the Progressive era (1890–-1920), the Anti-Saloon League established itself as an umbrella organization to coordinate prohibition efforts.
Attitudes about Prohibition
Louisiana proved an uneasy partner in the “noble experiment.” Much of north central Louisiana, portions of the Florida Parishes, the Black Belt parishes along the Mississippi River, and the western Sabine River parishes were dominated by strongly pro-prohibition Baptist and Methodist adherents. Yet the majority of Louisiana residents opposed the prohibition of alcohol. Many Roman Catholics, Episcopalians, and German Lutherans across the southern part of the state intensely resisted the new law. Business interests in New Orleans and other southern Louisiana urban areas also opposed prohibition due to the economic implications it entailed. Many “wets” enjoyed the opportunity to consume alcohol, while others resisted the law in the belief that government had no right to legislate morality.
Unlike some states that exhibited near homogeneity in their stance on drinking hard liquor, Louisiana endured deeply entrenched divisions. Many residents accepted prohibition arguments that alcohol contributed to moral depravity and illicit behavior. Others believed it advanced the misery and debauchery of the poor, especially among newly freed African Americans. Still others claimed alcohol served as a root cause of Louisiana’s exceptionally high rates of violence. Yet, alcohol had always played a prominent role in Louisiana life. Whether celebrating Mardi Gras, joining in a corn shucking, or enjoying an elegant meal at a New Orleans restaurant, alcoholic drinks proved a normal concomitant to Louisiana culture.
Prohibition Takes Effect
When the law took effect in January 1920, Louisianans quickly perfected numerous methods to circumvent it. Indeed, some have argued that drinking liquor became even more popular in Louisiana after it was declared illegal. Rumrunning became a major industry; smugglers brought so many shiploads of illegal liquor to Louisiana that the price actually began to decline. A 1926 survey of social workers nationwide identified New Orleans as the “wettest” city in America. A similar 1924 report issued by the US Attorney General’s office declared southern Louisiana to be 90 percent wet. In rural upstate parishes, illicit stills concealed in the vast woodlands provided customers with prodigious quantities of moonshine liquor, ranging from “Blind Tiger” to “Busthead” whiskey.
The political atmosphere of the state facilitated Louisianans’ ability to resist prohibition. Some members of the New Orleans city council sought to have alcohol declared a food supplement in order to circumvent the law. When asked by the mayor of Atlanta what his administration was doing to enforce prohibition, Louisiana governor Huey P. Long famously responded “not a damn thing.” Scores of Louisiana residents, whether they consumed alcohol or not, simply resented the intrusion of government into what they perceived as private affairs. Thus, they refused to support enforcement of the law.
Despite such obstacles, federal agents worked aggressively to enforce their mandate. Coast Guard cutters stepped up interdiction of rumrunning throughout the 1920s, even firing on and sinking some runners such as the Canadian-registered schooner, I’m Alone, in the Gulf of Mexico. Liquor raids peaked in New Orleans in 1925 when 200 agents uncovered and destroyed more than 10,000 cases of liquor. By December 1926, New Orleans had more padlocked speakeasies or saloons illegally selling alcohol than any city in the nation. When repeal of the prohibition law occurred in April 1933, more than nine hundred retail beer permits were issued in the Crescent City in the first week.
In Louisiana, as elsewhere, prohibition did reduce the overt consumption of alcohol. Yet it also contributed to social degradation by promoting multiple forms of criminal behavior such as rumrunning, moonshining, and violent turf wars, not to mention increasing hostility toward government agents and the legal authority they represented. In the end, prohibition may have been a noble experiment, but its legacy was short lived in Louisiana. As recently as the 1980s, the Louisiana legislature proved willing to temporarily forgo federal highway construction appropriations rather than raise the drinking age to twenty-one. Consuming alcoholic beverages has proven a deeply ingrained dynamic of Louisiana culture that even the federal government cannot mitigate.
Cite This Entry
Chicago Manual of Style
Hyde, Samuel C. "Prohibition." In KnowLA Encyclopedia of Louisiana, edited by David Johnson. Louisiana Endowment for the Humanities, 2010–. Article published February 7, 2011. http://www.knowla.org/entry/847/.
Hyde, Samuel C. "Prohibition." KnowLA Encyclopedia of Louisiana. Ed. David Johnson. Louisiana Endowment for the Humanities, 7 Feb 2011. Web. 5 Feb. 2016.
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Apollo Space Freighter (1963)
When first proposed in 1959, the spacecraft that would eventually become known as the Apollo Command and Service Module (CSM) was envisioned as a three-man Earth-orbital vehicle upgradable to lunar-orbital capability. On November 15, 1960, NASA awarded six-month feasibility study contracts for just such an Apollo spacecraft to the Martin Company, the Convair Division of General Dynamics, and the General Electric (GE) Company Defense Electronic Division, Missile and Space Vehicle Department. The CSM at that time was to include a Command Module (CM), a Service Module (SM), and an orbital module, a kind of mini-space station. The three companies submitted their final study reports on May 15, 1961.
Ten days later, President John F. Kennedy redirected Apollo – and, indeed, the entire U.S. civilian space program – toward the goal of landing a man on the moon by the end of the 1960s. On November 28, 1961, NASA awarded North American Aviation (NAA) the contract to build the Apollo CSM, the initial design of which included two modules: the conical CM and the drum-shaped SM. At the time, the method by which NASA would carry out the President’s mandate remained uncertain, though it was widely assumed that it would soon award a contract for a third Apollo spacecraft module: a landing propulsion module for lowering the CSM to the lunar surface. NAA went so far as to design the Service Propulsion System (SPS) main engine, mounted at the base of the SM, with enough thrust to launch the CSM off the moon using the propulsion module as a launch pad.
The Apollo CSM would never land on the moon, however. On July 11, 1962, as part of an ongoing debate that was not finally settled until November of that year, NASA selected the Lunar-Orbit Rendezous (LOR) mode for accomplishing the Apollo mission. A contract for a third Apollo module was indeed awarded (to Grumman, on November 7, 1962), but it was for the Lunar Excursion Module (LEM), a bug-like two-man lander that would detach from the CSM in lunar orbit and land. The Apollo CSM thus became the mother ship for delivering astronauts and LEM to lunar orbit and returning astronauts and moon rocks to Earth.
If some within NASA had had their way, then the Apollo CSM would also have become the primary crew and cargo delivery vehicle for a 24-man Earth-orbiting space station beginning as early as 1968. In April 1963, NASA’s Manned Spacecraft Center (MSC) awarded NAA a contract for a seven-month, two-phase study of a Modified Apollo (MODAP) Logistics Spacecraft. At the time, MSC personnel, who had moved from NASA’s Langley Research Center in Virginia beginning in early 1962, were housed in temporary offices scattered across Houston, Texas. By the time NAA completed the MODAP study in November 1963, MSC had officially opened its new facilities on Houston’s southern outskirts.
Not surprisingly, the Apollo CSM design in 1963 had yet to reach its final form. No docking unit design had been selected, for example, though the probe-and-drogue system eventually chosen was already the leading candidate. A peculiar phased-array high-gain antenna had yet to be replaced by the familiar four-dish Apollo high-gain. The overall layout and many other details were, however, firmly in place, giving NAA a meaningful point of departure for its MODAP design.
The Apollo CSM’s crew-carrying CM included three astronaut couches, a control panel, small windows at strategic locations, a side-mounted hatch, a docking tunnel and parachutes in its nose, and a bowl-shaped heatshield and thrusters for orienting it for atmosphere reentry at its base. An umbilical linked the CM to the SM. The SM included seven major internal compartments. A central cylindrical compartment housed helium pressurant tanks for pushing rocket propellants to the SPS main engine. Arrayed around the central compartment were six triangular compartments containing tanks of fuel and oxidizer for the SPS and four attitude-control thruster quads, fuel cells for making electricity and water, and tanks of liquid oxygen and liquid hydrogen for supplying the fuel cells.
The MODAP CSM would have a stripped-down SM and a beefed-up CM. Because it would spend a limited amount of time in free flight before docking with an Earth-orbiting space station that could supply it with air, electricity, and cooling, it could dispense with or downgrade many lunar mission SM systems. Batteries would replace the lunar SM’s fuel cells, for example, and a compact, less powerful LEM descent engine would replace the SPS. The LEM engine would draw propellants from a pair of spherical tanks in the central cylindrical compartment. This would free up the triangular compartments for cargo containers.
NAA assumed that the MODAP CSM would launch on a two-stage Saturn IB rocket capable of placing 32,500 pounds into a 105-nautical-mile-high circular parking orbit (NAA also looked at launching the MODAP CSM on a four-stage Titan-IIIC). Pre-launch preparations, launch operations, and ascent to parking orbit would need from five to 10 days, from five to eight hours, and 11 minutes, respectively. The spacecraft would remain in parking orbit for less than five hours before igniting the LEM descent engine to place itself into an elliptical transfer orbit with a 260-mile apogee (highest point above the Earth). Upon reaching this apogee 45 minutes later, it would again ignite its engine to circularize its orbit. Rendezvous and docking with the space station in 260-mile-high orbit would need up to 17.5 hours.
Though MSC was on the move throughout the MODAP study and busy with Apollo moon program preparations, its engineers had already found time to design the 24-man space station to which the MODAP CSM would deliver crews and cargo. Designed for launch on a single two-stage Saturn V rocket, MSC’s station would reach orbit unmanned and unfold three “arms” from a central hub. The hub would included a docking port for MODAP CSM spacecraft and three berthing ports for MODAP CMs without their SMs.
NAA calculated that a 24-man space station with full crew rotation every six months would need to receive a MODAP CSM bearing six astronauts and 5855 pounds of cargo eight times per year, or once every 45 days. The cargo manifest would include 1620 pounds of food, 1035 pounds of breathing oxygen, 505 pounds of buffering nitrogen, 1450 pounds of propellants, and 1245 pounds of spare parts. Water would not be carried because the space station was expected to recycle all of its water.
The company estimated that containers for solid and liquid cargo – which it called Cargo Modules, or CAMs – would have a combined empty mass of 1970 pounds. The volume required to accommodate the cargo and containers would total 202.4 cubic feet, meaning that all necessary cargo could be carried in four of the SM’s six triangular compartments. NAA noted that the MODAP CSM launched on a Saturn IB would have surplus cargo capacity equal to 1302 pounds of mass and 52 cubic feet of volume that might be applied to additional cargo, such as science instruments. In all, one MODAP CSM could transport 9127 pounds of cargo and CAMs.
NAA proposed that the MODAP SM include hinged doors for unloading cargo at the space station, a process that would have to be completed in 44 days or less to make way for the next MODAP CSM to dock. Small doors near the top of the SM, where it joined the CM, would provide access to four CAMs holding liquid cargo, while large doors below those would expose four solid-cargo CAMs.
NAA envisioned that the three-armed MSC space station would include a hangar for either the MODAP CM alone or for the entire MODAP CSM. If the hangar housed the CM alone, then the SM would protrude into open space following docking. A robot arm on the station would grip each CAM in turn and transfer it to a pipe-like loading chute on the station’s exterior. After all cargo was transferred, the MODAP SM would be cast off and the hangar closed to protect the MODAP CM, which would remain attached to the station for up to six months. If, on the other hand, the hangar accommodated the entire MODAP CSM, then cargo transfer would occur within the hangar. The SM would still be cast off within 44 days of docking to make room for the next MODAP CSM.
After the MODAP SM was discarded, the MODAP CM would be pivoted using a manipulator arm to a berthing port to free up the main docking port. It would remained parked there, undergoing periodic inspection and maintenance but otherwise dormant, for up to six months.
Discarding the MODAP SM meant that the MODAP CM would need to carry a separate de-orbit propulsion module. NAA proposed a cluster of six solid-propellant retrorocket motors, any five of which would be adequate to deorbit the MODAP CM. The retro package would also include batteries for powering the MODAP CM during free flight prior to reentry. NAA expected that, under normal conditions, the MODAP CM would need 30 minutes for checkout and undocking, after which the retro motors would fire immediately. Twenty-five minutes later, shortly after de-orbit module separation, it would reenter Earth’s atmosphere. Because the MODAP CM would encounter the atmosphere moving at about half the speed of the lunar CM, its heat shield could be about half as thick. Descent and splashdown would need 11 minutes. The MODAP CM would be heavier than the lunar CM, so would lower on four parachutes; that is, one more than the lunar CM. Its crew could splash down safely if one parachute failed.
Under normal circumstances, the MODAP CM would splash down in the Gulf of Mexico, not far from Houston, and crew recovery would take place within a few hours. NAA acknowledged, however, that emergencies might occur. Because of this, the MODAP CM could fly free of the space station for up to 10.5 hours while its orbit carried it into position for reentry and splashdown at any of three landing sites. These were the prime site in the Gulf of Mexico, a site near Okinawa in the western Pacific Ocean, and a site near Hawaii. To cut costs, fleets of recovery ships would not remain on standby at the landing sites; because of this, recovery might be delayed for up to 24 hours following an emergency splashdown near Okinawa or Hawaii.
An abort during ascent to orbit could cause the MODAP CM to land in southern Africa; that is, on land. To protect its three-man crew during a land landing, the lunar CM would include shock absorbers in its supporting seat struts. These would enable the crew couches to move vertically up to five inches to dissipate the force of impact.
Because the MODAP CM would carry six men arrayed in two rows of three couches, one row above the other, vertical couch movement was not an option. Insufficient room would exist within the MODAP CM to permit vertical movement totaling at least 10 inches (five inches per row). The lunar CM would also rely on crushable material in the CM heatshield; this would be inadequate to soften the blow for the greater mass of six men.
NAA proposed to solve this problem by, in effect, moving the shock absorbers from the seat supports to the MODAP CM’s heat shield and by adding four solid-propellant landing rockets. In the event of a land landing, the heat shield would deploy downward on shock absorbing struts and the landing rockets would ignite and pivot out from behind the shield.
NAA assumed a MODAP CSM design and test program spanning from early 1964 to mid-1968, and that operational MODAP CSMs would deliver crews and cargoes to the 24-man space station from mid-1968 through 1973. The company anticipated that five MODAP CSMs would be used in ground tests and unmanned test flights, and that 40 MODAP CSMs would fly during the five-year space station program. Of these, perhaps two would fail, requiring assembly of at least two backup spacecraft. NAA placed the total cost of the MODAP CSM program (including $861 million for Saturn IB rockets) at $1,881,350,000.
Final Technical Presentation: Modified Apollo Logistics Spacecraft, Contract NAS 9-1506, North American Aviation, Inc., Space and Information Systems Division, November 1963.
Beyond Apollo chronicles space history through missions and programs that didn’t happen.
I research and write about the history of space exploration and space technology with an emphasis on missions and programs planned but not flown (that is, the vast majority of them). Views expressed are my own.
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Introduce or review geometric shapes such as circles, triangles, squares, rectangles, etc. with students. Hold a class discussion of the similarities and differences between the shapes. Have students use construction paper and Crayola® Construction Paper™ Crayons to illustrate mastery of each of the discussed shapes.
Students collect clean, recycled boxes, such as shoes boxes milk cartons, etc. Remind students that each box needs to have an attached lid.
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Focus on historic achievements and positive role models with this collaborative monument making project.
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The Early Cases
The Supreme Court adopted its present law of affirmative action after an extended period of experimentation. In a series of plurality decisions, various justices and coalitions of justices toyed with a variety of legal standards to govern the use of racial classifications for the benefit of racial minorities. In the course of the deliberations that occurred among the justices, a number of legal issues emerged as having potential constitutional significance. Finally, after a series of Reagan and Bush appointments, the Supreme Court was able to speak through majority opinions in issuing its formula for constitutionally acceptable affirmative action. Under current law, most forms of race-conscious affirmative action now appear to be unconstitutional.
The Court's constitutional decisions are directly applicable only to governmental use of affirmative action programs because the state-action requirement of the Fourteenth Amendment—the legal provision on which the Court's decisions are based—does not apply to purely private action. Private affirmative action programs, however, must comply with the congressional statutes that govern the private use of racial classifications, such as the Civil Rights Act of 1964, which prohibits, inter alia, discrimination in education, employment, and public accommodations. It is unclear whether the Supreme Court will ultimately adopt the same standards for statutory and constitutional analysis of affirmative action.1
The problems posed by affirmative action are directly traceable to Brown v. Board of Education.2 In Brown I, the Supreme Court invalidated the separate-but-equal doctrine of Plessy v. Ferguson,3 and held that, under the equal protection clause of the Fourteenth Amendment, governmental use of racial classifications was constitutionally suspect.4 Then, in Brown II and its progeny, the Court not only held that the Constitution required a remedy for the continuing effects of past discrimination but stressed that the use of racial classifications was constitutionally compelled where necessary to provide an effective remedy for the prior constitutional violation. As a result,
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You may have heard of the Richter scale used to study earthquakes. In 1935 Charles Richter developed a system to measure the magnitude --or amount of energy released--of an earthquake. Each whole number on the Richter scale indicates a tenfold increase in amplitude (greatness in size). Thus, a 7.5 earthquake on the Richter scale actually has ten times the amplitude of a 6.5 earthquake. There is no upper limit on the Richter scale, meaning that it could be used to measure earthquakes of a ten or more magnitude if one ever occurred. The most devastating earthquakes we know of are 8 or 9 on the Richter scale.
Scientists also measure seismic waves, or movements in the earth's crust. Special machines called seismographs record movement in the earth, including earthquakes that are so low in magnitude that people cannot feel them. You can make a simple seismograph to demonstrate how this machine works.
Fill a 2-liter soda bottle with water and use wire to suspend it about 1' above the surface of a table, using a sturdy stick or ruler set across stacks of heavy books. (The bottle should hang freely between the books.)
Tape a sheet of paper with aluminum foil underneath it to the table, beneath the bottle.
Roll a felt-tip pen in a piece of paper, and tape it loosely enough for the pen to slide up and down.
Tape this roll to the side of the bottle so that the pen's tip touches the paper.
Shake the table back and forth, gently at first and then a little harder. (Don't move the table's legs; shaking is enough.)
When you're done, examine the paper. What kind of record is there of the 'quake'?
There's another measurement used for earthquakes: the Modified Mercalli Scale is used to measure intensity, or how strong the effects of the quake are. The intensity varies based on position relative to the epicenter of the earthquake, so one earthquake does not have a set number from the scale assigned to it as with the Richter scale. Intensity is measured in Roman numerals I-XII. For a list of effects at each level, visit www.geo.mtu.edu/UPSeis/Mercalli.html
If it isn't confusing enough with so many things to measure, there's one more method for determining magnitude. The Moment Magnitude scale is more accurate than the Richter scale for measuring large earthquakes. In the world's worst recorded earthquake--the 1960 one in Chile--the magnitude on the Richter scale was 8.5, but on the Moment Magnitude (Mw) scale it was 9.5.
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Collecting rocks and minerals is a fun way to learn about geology! Most kids are naturally inclined to pick up any "pretty" rock that they see, which provides a great learning opportunity. Start by keeping the interesting rocks you find on walks and hikes. You might want to wrap larger specimens in newspaper and put small ones in plastic ziplocks until you get home.
You can use a brush (old toothbrushes work well) to "clean" your specimens: brush the dirt off carefully, so that fragile rocks or minerals are not damaged.
Sort through the specimens that you've collected, putting similar stones together. Once you have done that, use a rocks and minerals guide and try to identify each rock. Match up color and description as best as possible. If you don't have a good guide, check one out at a local library. Use the tests in the next section for more properties that will help you identify a rock or mineral.
As you identify each specimen, make a label for it. If possible, write down the location and the date when the rock or mineral was collected. For rocks, you might also want to note information such as what minerals it is made of and whether it is igneous, sedimentary, or metamorphic. For minerals, note the elements that they are composed of: for example, Galena is PbS (lead sulfide).
Keep your specimens in a compartmentalized box or in cardboard egg cartons. If you want to number your specimens, use a permanent marker to mark each one consecutively. Write the number on each label as well. That way you won't worry about getting the rocks confused with each other.
Identifying Specimens: Testing Rocks & Minerals
There are many tests you can perform to help you identify your rock and mineral specimens. The first step is to examine your specimen with a magnifying glass and take note of its outside appearance. Look for the mineral's transparency. If you can see through the specimen, it is transparent. If light can pass through, but the specimen cannot be seen through, your mineral is translucent. Minerals that do not let light through are called opaque.
Next, test your specimen for hardness. Mineral hardness is measured on the Mohs Hardness Scale. On each level of the scale a mineral can be scratched by something of the same or higher level, but nothing lower. Number one on the Mohs scale is talc, because it is soft and very easy to scratch. Number ten is the diamond, because it is the hardest natural substance and can only be scratched by another diamond. Test your mineral specimen by trying to scratch it with your fingernail. Next try a copper penny, and then a steel nail. A fingernail has a hardness of 2.5, a penny is 3.5, and a steel nail is 5.5. If you are able to scratch your specimen with the penny but not with your fingernail, it has a hardness between 2.5 and 3.5. Also try scratching your specimen with another rock to see which one is harder.
One last test that is commonly used is called a streak test. A mineral's "streak," or color when it is finely powdered, is always the same, even when the color of the mineral varies. (Sometime the streak can be very different from the color of the mineral itself.) Rub your specimen across a piece of porcelain tile (called a streak plate) and examine the color it leaves behind. You can also rub it across smooth cement if you don't have a tile.
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This educational guide focuses on whether or not the American Space Program should send a manned Mission to Mars. Students are invited to examine the arguments on both sides of the debate, developing critical thinking skills as they work through the activities. Students will learn how to support their arguments with evidence and reason. It is expected that at the end of this guide students will determine where they stand on this controversial issue.
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Establishing Borders: The Expansion of the United States, 1846-48
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A healthy ear emits soft sounds in response to the sounds that travel in. Detectable with sensitive microphones, these otoacoustic emissions help doctors test newborns' hearing. A deaf ear doesn't produce these echoes.
New research involving the University of Michigan and Oregon Health and Science University shows that, contrary to the current scientific thought, the emissions don't leave the ear the same way they entered. The findings give new insight into a phenomenon that researchers study to better understand hearing loss, and they reinforce a previous controversial study that came to a similar conclusion.
A paper on the research is published in the current issue of Proceedings of the National Academy of Sciences.
"The former wisdom on how otoacoustic emissions left the ear was that there was a backward-traveling wave going along the structure of the cochlea in the same way as the forward-traveling sound wave," said Karl Grosh, a professor in the U-M departments of Mechanical Engineering and Biomedical Engineering and an author of the paper. "These measurements show that is not the case."
Grosh said the next step is to develop tools to find out where hearing damage is occurring. "If we want to try to infer from the emission what's wrong with the ear, we have to understand how the emission is produced," Grosh said.
The experiment, performed at the Oregon Health and Science University in associate professor Tianying Ren's lab, showed that the sound waves coming out travel through the fluid of the inner ear, rather than rippling along the basilar membrane of the cochlea.
The cochlea, located deep in the ear, is shaped like a snail. The basilar membrane essentially cuts the inner channel of the cochlea diametrically in half into two chambers. Both chambers are filled with liquid.
Sound waves going into the ear undulate along the basilar membrane through the cochlea and eventually excite the organ of Corti, which senses and sends the sound signals to the brain through the auditory nerve.
Sounds coming out of the ear, according to results from this experiment, likely travel through the fluid on either side of the basilar membrane.
For this experiment, the researchers used laser interferometers, which detect waves, to measure vibrations of the basilar membrane in response to sound at two locations in the cochlea of gerbils. They detected evidence of sound waves traveling forward on the membrane, but they found no evidence of backward-traveling waves.
"Our new method can detect vibrations of less than a picometer, 1,000 times smaller than the diameter of an atom. The new data demonstrate that there is no detectable backward-traveling wave at physiological sound levels across a wide frequency range," said Ren, principal investigator of this project. "This knowledge will change scientists' fundamental thinking on how waves propagate inside the cochlea, or how the cochlea processes sounds."
The paper is called "Reverse wave propagation in the cochlea."
Source: University of Michigan
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(Phys.org)—Two teams working independently have succeeded in entangling a single electron spin with a single photon in a solid-state platform. Both teams describe their process and results in papers they've had published in the journal Nature. The two teams used laser pulses fired at quantum dots to entangle pairs of electrons and photons then used different techniques to remove either the shared color that resulted or their polarization.
To create a quantum computer, scientists believe it will be necessary to combine or connect stationary quantum bits (qubits) with mobile or "flying" qubits. Thus, research has been focused on building a system in which this is possible. In this new research, quantum dots were used to represent the stationary particles while photons were used to represent those that fly. To connect them, the researchers relied on entanglement between pairs of particles and the properties they share.
In their labs, both teams used very small semiconductors to trap a single electron, e.g. a quantum dot. They then both fired a laser at the dot to set its spin state to either up or down (representing "0" or "1"). Next both teams also fired another laser pulse at the dot to force it to a higher energy level. Doing so caused an entangled photon to be released as the energy decayed. The photon was emitted as either horizontally or vertically polarized with a wavelength that was demonstrated by either a red or blue color. It was at this stage that the work between the two teams diverged. To use the information from a (qubit) in a quantum system, only one of the two properties can be allowed to exist; thus the other must be removed. The first team's work involved removing the color, the second, the polarization.
To remove the color the first team ran the photon through a crystal that was also shot with a laser beam. Doing so caused the colors to smear which was enough to remove that property from the entangled particles. The second team removed the polarization by allowing the photon to pass through a polarizing filter which forced it into an anticlockwise state which effectively erased the shared property from the particles.
More information: 1. Quantum-dot spin–photon entanglement via frequency downconversion to telecom wavelength, Nature, 491, 421–425 (15 November 2012) doi:10.1038/nature11577
Long-distance quantum teleportation and quantum repeater technologies require entanglement between a single matter quantum bit (qubit) and a telecommunications (telecom)-wavelength photonic qubit. Electron spins in III–V semiconductor quantum dots are among the matter qubits that allow for the fastest spin manipulation and photon emission, but entanglement between a single quantum-dot spin qubit and a flying (propagating) photonic qubit has yet to be demonstrated. Moreover, many quantum dots emit single photons at visible to near-infrared wavelengths, where silica fibre losses are so high that long-distance quantum communication protocols become difficult to implement. Here we demonstrate entanglement between an InAs quantum-dot electron spin qubit and a photonic qubit, by frequency downconversion of a spontaneously emitted photon from a singly charged quantum dot to a wavelength of 1,560 nanometres. The use of sub-10-picosecond pulses at a wavelength of 2.2 micrometres in the frequency downconversion process provides the necessary quantum erasure to eliminate which-path information in the photon energy. Together with previously demonstrated indistinguishable single-photon emission at high repetition rates, the present technique advances the III–V semiconductor quantum-dot spin system as a promising platform for long-distance quantum communication.
2. Observation of entanglement between a quantum dot spin and a single photon, Nature, 491, 426–430 (15 November 2012) doi:10.1038/nature11573
Entanglement has a central role in fundamental tests of quantum mechanics1 as well as in the burgeoning field of quantum information processing. Particularly in the context of quantum networks and communication, a main challenge is the efficient generation of entanglement between stationary (spin) and propagating (photon) quantum bits. Here we report the observation of quantum entanglement between a semiconductor quantum dot spin and the colour of a propagating optical photon. The demonstration of entanglement relies on the use of fast, single-photon detection, which allows us to project the photon into a superposition of red and blue frequency components. Our results extend the previous demonstrations of single-spin/single-photon entanglement in trapped ions, neutral atoms and nitrogen–vacancy centres to the domain of artificial atoms in semiconductor nanostructures that allow for on-chip integration of electronic and photonic elements. As a result of its fast optical transitions and favourable selection rules, the scheme we implement could in principle generate nearly deterministic entangled spin–photon pairs at a rate determined ultimately by the high spontaneous emission rate. Our observation constitutes a first step towards implementation of a quantum network with nodes consisting of semiconductor spin quantum bits.
© 2012 Phys.org
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Oxidation and Reduction
Oxidation is the loss of electrons or loss of hydrogen and addition of oxygen.
Reduction is the gain of electrons or gain of hydrogen and loss of oxygen.
Redox refers to a reaction where both of these happens. Remember it with OIL RIG (Oxidation Is Loss, Reduction Is Gain)
The oxidation state of simple ions is simply its charge. For example, the oxidation state of Mg2+ is +2. However, we also assign oxidation states to other compounds and is the charge it would have if it were a simple ion and not bonded. In order to work out the oxidation states of some compounds we need to use some rules.
|Oxidation state of an atom in element is 0||Br in Br2 is 0|
|The oxidation state of Fluorine is always -1; O is nearly always -2 and Cl is usually -1.||no example.|
|The sum of the oxidation states in a polyatomic ions is always the charge on the ion.||In PO43- the Oxygens make -8 so P should be +8 - 3 (the overall charge) meaning its oxidation state here is +5.|
The oxidation gives a compound its name, for example Iron (IV) oxide means the oxidation state of iron is 4 so therefore there must be two oxygen atoms bonded to it.
S-block metals loose their electrons in a reaction so are good reductants (they are oxidised easily).
And then there are p-block elements which can have different oxidation states; and those in group VII gain electrons in reactions so are good oxidants (they gain electrons easily).
Have a look at the reaction below.
Fe2O3 + 2Al ® Al2O3 + 2Fe
In this reaction iron is reduced (is an oxidant) because it gains electrons and goes from ion to element, and the reverse is true for aluminium which is oxidised (is a reductant). To show this we use half equations as below.
Fe3+ + 3e- ® Fe
Al ® Al3+ + 3e-
Another skill you need is to combine half equations. Use the following example where concentrated nitric acid is added to copper. To do this you simply need to have the same number of electrons in each equation and then add combine, the same electrons means they will cancel.
Remember that in acid, you can balance with H+ ions as well.
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Kids learn the appearance and value of pennies, count pennies, and write the number of cents for the pennies on this first grade math worksheet.
Counting quarters is simple once you learn how. Practice counting quarters with your child using this math worksheet.
Let's go shopping! In this math worksheet, your kid will add up the value of groups of coins, then draw lines from coins to the items that cost the same amount.
Let your first grader flex his financial savvy with this fun worksheet. Your child must circle the coins that add up to the value of each present.
This worksheet features a piggy bank and is a fun, familiar way to help preschoolers begin counting money.
Your child is shopping for gifts, and it's time to make her purchases. This fun worksheet asks your child to circle the coins she needs to purchase each gift.
Exact change only, please! In this first grade worksheet, your child will match each group of coins to an item with a price tag of equal value.
Being able to identify and count coins is a valuable skill for kids. In this worksheet, your child will count coins, then write their total values on the lines.
Kids learn the appearance and value of dimes, count dimes, and write the number of cents for the dimes on this first grade math worksheet.
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Analyze Air Quality with Lichens
Lichens are composite organisms consisting of a fungus (the mycobiont) and a photosynthetic partner (the photobiont or phycobiont) growing together in a symbiotic relationship. The photobiont is usually either a green alga (commonly Trebouxia) or cyanobacterium (commonly Nostoc).
The morphology, physiology and biochemistry of lichens are very different from those of the isolated fungus and alga in culture. Lichens occur in some of the most extreme environments on Earth—arctic tundra, hot deserts, rocky coasts, and toxic slag heaps.
However, they are also abundant as epiphytes on leaves and branches in rain forests and temperate woodland, on bare rock, including walls and gravestones, and on exposed soil surfaces (e.g., Collema) in otherwise mesic habitats.
The roofs of many buildings have lichens growing on them. Lichens are widespread and may be long-lived; however, many are also vulnerable to environmental disturbance, and may be useful to scientists in assessing the effects of air pollution, ozone depletion, and metal contamination.
Lichens are informally classified by growth form into:
Lichens are sensitive to air pollution, specially the air's acidity. Therefore, the presence or absence can be used to see how clean the air is. Shrubby and leafy lichens only survive in clean air, and when an area is really polluted you will not find anyone.
The goal of this application is to help to analyze, classify and measure the size of the lichens in order to study the quality of air in different areas of the cities.
Look for lichens on walls, stones and trees take pictures with your phone and submit the data using this EpiCollect Plus Lichens project. Then, you can help in measuring the size of the lichen in this web application!
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In living and past peoples, there is wide range of variability. Despite this variability, our bones
have features that can be clues to ancestry. Many of these features reflect evolutionary processes, including adaptation to the environment.
Bone cells retain "biogeographical" information that is found in our DNA. These inherited markers are due to mutational changes that gradually accumulate and differentiate populations over time. DNA can help associate an individual with a region of the world.
We can also assess ancestral origins by looking at the skeleton itself. The bones of the skull express inherited features from one generation to the next. Measuring the cranium gives us information that is similar to that from DNA. By comparing a skull's measurements with data from populations worldwide, scientists can statistically evaluate that individual's relationship to a world group.
Identifying Ancestry in the Colonial Chesapeake
The archaeological cases in the Written in Bone exhibition focus on identifying skeletal remains from only three groups who were here in the 1600s and early 1700s — individuals of American Indian, European, and African origins.
- Individuals with American Indian ancestry have proportionately wider faces and shorter, broader cranial vaults.
- Individuals with European ancestry tend to have straight facial profiles and narrower faces with projecting, sharply angled nasal bones.
- Individuals with sub-Saharan African ancestry generally show greater facial projection in the area of the mouth, wider distance between the eyes, and a wider nasal cavity.
Illustrations by Diana Marques
- The color of a bone does not reveal ancestry. Bone color has more to do with what happens to a body after death than in life.
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Oh no! The mayor finally finished building the city, but all the signs got mixed up! Can your child help him sort out the mess?
Help your second grader learn how to read a math table by using this math farm table to answer a set of questions.
Can your second grader make her own bar chart? Use this pretend survey of 38 people and their favorite cities to find out!
Give your second grader some practice working with data with this fun-to-complete favorite veggie survey.
Kids practice making a Venn diagram about kinds of gift wrap by sorting the gifts in their correct spaces in this 2nd grade math worksheet.
If your second grader is stumped by bar graphs, clear up the confusion with this worksheet that helps kids learn how to read and interpret a bar graph.
Celebrate the winter Olympics with this 2nd grade math worksheet in which children practice reading, analyzing, and computing data in a bar graph.
Pictographs are a great introduction to working with data and graphs. Kids help the hamburger cafe compare the number of hamburgers they sold using pictographs.
If your child has ever played Battleship, chances are he's familiar with grids. Can your child help build a new town by drawing buildings on the grid map?
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Primary Sources and Research – 4
Students’ research will use the History Detective Form to examine artifacts and primarysource documents, making observations about them and generalizing about what theymight mean. And how they might be used by historians. The primary source documentsare authentic and come from the life of Elizabeth K. Steen, anthropologist and explorer whose life is largely forgotten (this in itself is a good history lesson—about how historyis written and the odd quirks that influence what is recorded for future generations). Thislesson takes two 50 minute long sessions to accomplish
Grade State Standards 4
Grade Information Literacy StandardsObjectives
1.Students will recognize primary sources and secondary sources and be able to describe the difference.2.Students will experience how historians conduct their research.3.Students will have the opportunity to learn collaboratively fromtheir peers as they examine primary sources items in teams.4.Students will select one primary source and one secondary sourceto use in their own slide show teaching other students the difference between primary and secondary sources.5.Students will produce a three slide powerpoint presentation aboutwhat they know about primary and secondary sources with illustrations of the two. Using the template.
Materials and Resources
1.Letters, artifacts, old photographs, newspaper articles, postcards,and other items which offer clues to about Elizabeth k. Steen’s life.2.Secondary resources for comparison purposes.3.White gloves for the junior archivists to touch the aged documents.-- explain4.Students come equipped with worksheets and pencils5.Graphic resources provided on the web for students to select fromfor their slide presentations. Including a template for PowerPoint.
Students will assemble as
the Media Specialist begins the overview PowerPoint
and describes the housekeeping aspects of the lesson.Embedded in this lesson is a film from the National Parks Service – DownMobile Way from 1935 which the Media Specialist will use to work through thePrimary/Secondary Resource Inquiry Form as an example of how it should be
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Multiplying Decimals Teacher Resources
Find Multiplying Decimals educational ideas and activities
Showing 101 - 120 of 1,224 resources
Developing the Concept: Exponents and Powers of Ten
Here is an exponents lesson which invites learners to examine visual examples of multiplication and division using powers of 10. They also practice solving problems that their instructors model. If you are new to teaching these skills,...
5th - 7th Math CCSS: Adaptable
Graphing Calculator Activity: Multiplying and Dividing Mixed Numbers
In this graphing calculator worksheet, students explore necessary steps to multiply and divide mixed numbers using a graphing calculator. In groups, students measure objects in their classroom and write equations using their collected...
8th - 9th Math
New Review Fraction Equivalence, Ordering, and Operations
Need a unit to teach fractions to fourth graders? Look no further than this well-developed and thorough set of lessons that take teachers through all steps of planning, implementing, and assessing their lessons. Divided into eight...
3rd - 5th Math CCSS: Designed
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Fossil galaxy reveals clues to early universe
A tiny galaxy has given astronomers a glimpse of a time when the first bright objects in the universe formed, ending the dark ages that followed the birth of the universe.
Astronomers from Sweden, Spain and the Johns Hopkins University used NASA's Far Ultraviolet Spectroscopic Explorer (FUSE) satellite to make the first direct measurement of ionizing radiation leaking from a dwarf galaxy undergoing a burst of star formation. The result, which has ramifications for understanding how the early universe evolved, will help astronomers determine whether the first stars -- or some other type of object -- ended the cosmic dark age.
The team presented its results Jan. 12 at the American Astronomical Society's 207th meeting in Washington, D.C.
Considered by many astronomers to be relics from an early stage of the universe, dwarf galaxies are small, very faint galaxies containing a large fraction of gas and relatively few stars. According to one model of galaxy formation, many of these smaller galaxies merged to build up today's larger ones. If that is true, any dwarf galaxies observed now can be thought of as "fossils" that managed to survive -- without significant changes -- from an earlier period.
Led by Nils Bergvall of the Astronomical Observatory in Uppsala, Sweden, the team observed a small galaxy, known as Haro 11, which is located about 281 million light years away from Earth in the southern constellation of Sculptor. The team's analysis of FUSE data produced an important result: between 4 percent and 10 percent of the ionizing radiation produced by the hot stars in Haro 11 is able to escape into intergalactic space.
Ionization is the process by which atoms and molecules are stripped of electrons and converted to positively charged ions. The history of the ionization level is important to understanding the evolution of structures in the early universe, because it determines how easily stars and galaxies can form, according to B-G Andersson, a research scientist in the Henry A. Rowland Department of Physics and Astronomy at Johns Hopkins and a member of the FUSE team.
"The more ionized a gas becomes, the less efficiently it can cool. The cooling rate in turn controls the ability of the gas to form denser structures, such as stars and galaxies," Andersson said. The hotter the gas, the less likely it is for structures to form, he said.
The ionization history of the universe therefore reveals when the first luminous objects formed, and when the first stars began to shine.
The Big Bang occurred about 13.7 billion years ago. At that time, the infant universe was too hot for light to shine. Matter was completely ionized: atoms were broken up into electrons and atomic nuclei, which scatter light like fog. As it expanded and then cooled, matter combined into neutral atoms of some of the lightest elements. The imprint of this transition today is seen as cosmic microwave background radiation.
The present universe is, however, predominantly ionized; astronomers generally agree that this reionization occurred between 12.5 and 13 billion years ago, when the first large-scale galaxies and galaxy clusters were forming. The details of this ionization are still unclear, but are of intense interest to astronomers studying these so-called "dark ages" of the universe.
Astronomers are unsure if the first stars or some other type of object ended those dark ages, but FUSE observations of "Haro 11" provide a clue.
The observations also help increase understanding of how the universe became reionized. According to the team, likely contributors include the intense radiation generated as matter fell into black holes that formed what we now see as quasars and the leakage of radiation from regions of early star formation. But until now, direct evidence for the viability of the latter mechanism has not been available.
"This is the latest example where the FUSE observation of a relatively nearby object holds important ramifications for cosmological questions," said Dr. George Sonneborn, NASA/FUSE Project Scientist at NASA's Goddard Space Flight Center, Greenbelt, Md.
This result has been accepted for publication by the European journal Astronomy and Astrophysics.
Bergvall will be available to answer questions from the media about this research at poster #175.21, during the poster-viewing sessions at the AAS meeting on Thursday, January 12. A high resolution image is available from http://www.jhu.edu/news/home06/jan06/haro.html or from Lisa De Nike at [email protected] or 443-287-9960.
The FUSE project is a NASA Explorer mission developed in cooperation with the French and Canadian space agencies by the Johns Hopkins University, Baltimore, Md., the University of Colorado, Boulder, and the University of California, Berkeley. The mission is operated out of Johns Hopkins University's Homewood campus in Baltimore. NASA Goddard manages the program for NASA's Science Mission Directorate. For more information about the FUSE mission, visit http://fuse.pha.jhu.edu
Last reviewed: By John M. Grohol, Psy.D. on 21 Feb 2009
Published on PsychCentral.com. All rights reserved.
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The first printing press designed to use the newly invented Cherokee alphabet arrives at New Echota, Georgia.
The General Council of the Cherokee Nation had purchased the press with the goal of producing a Cherokee-language newspaper. The press itself, however, would have been useless had it not been for the extraordinary work of a young Cherokee named Sequoyah, who invented a Cherokee alphabet.
As a young man, Sequoyah had joined the Cherokee volunteers who fought under Andrew Jackson against the British in the War of 1812. In dealing with the Anglo soldiers and settlers, he became intrigued by their “talking leaves”-printed books that he realized somehow recorded human speech. In a brilliant leap of logic, Sequoyah comprehended the basic nature of symbolic representation of sounds and in 1809 began working on a similar system for the Cherokee language.
Ridiculed and misunderstood by most of the Cherokee, Sequoyah made slow progress until he came up with the idea of representing each syllable in the language with a separate written character. By 1821, he had perfected his syllabary of 86 characters, a system that could be mastered in less than week. After obtaining the official endorsement of the Cherokee leadership, Sequoyah’s invention was soon adopted throughout the Cherokee nation. When the Cherokee-language printing press arrived on this day in 1828, the lead type was based on Sequoyah’s syllabary. Within months, the first Indian language newspaper in history appeared in New Echota, Georgia. It was called the Cherokee Phoenix.
One of the so-called “five civilized tribes” native to the American Southeast, the Cherokee had long embraced the United States’ program of “civilizing” Indians in the years after the Revolutionary War. In the minds of Americans, Sequoyah’s syllabary further demonstrated the Cherokee desire to modernize and fit into the dominant Anglo world. The Cherokee used their new press to print a bilingual version of republican constitution, and they took many other steps to assimilate Anglo culture and practice while still preserving some aspects of their traditional language and beliefs.
Sadly, despite the Cherokee’s sincere efforts to cooperate and assimilate with the Anglo-Americans, their accomplishments did not protect them from the demands of land-hungry Americans. Repeatedly pushed westward in order to make room for Anglo settlers, the Cherokee lost more than 4,000 of their people (nearly a quarter of the nation) in the 1838-39 winter migration to Oklahoma that later became known as the Trail of Tears. Nonetheless, the Cherokee people survived as a nation in their new home, thanks in part to the presence of the unifying written language created by Sequoyah.
In recognition of his service, the Cherokee Nation voted Sequoyah an annual allowance in 1841. He died two years later on his farm in Oklahoma. Today, his memory is also preserved in the scientific name for the giant California redwood tree, Sequoia.
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The conquest of Central America is primarily the story of the conquest of the Maya states in northern Central America (1551–1697). There were, however, other tribes further south. Rodrigo de Bastidas established Spain's claim to the isthmus of Panama. He sailied along the Darién coast (March 1501). Christopher Columbus, on his fourth voyage, sailed along the Caribbean coast of Central America from the Bay of Honduras to Panama. The next forays to Central America were launched from the growing Spanish colony of Cuba. Vasco Núñez de Balboa was the firstv European to cross the Isthmus of Panama. Balboa claimed the Pacific Ocean and all the lands adjoining it for the Spanish Crown. The next Spanish expedition from Cuba on the Yucatán Peninsula looking for slaves to work the Cuban plantations as the Native American population on the island had been desimated.
The focus of the Spanishm howevere turned north to the Aztec Empire. After defeating the Aztecs, the Spanish turned their attention south. The first Conquistador to lead an expedition south was Pedro de Alvarado, one of the most ambutious and cruel of the Conquistadores. The principal campaigns to control CentraL America were fought in the north by Alvarado. The strongrst tribes were located in the highlands of Guatemala and El
Salvador. These were the Maya and related states. Alvarado reached Guatemala traveling down the Pacific coast (1523). He commanded a relatively small force made up of a few hundred Spanish horsemen and soldiers, but backed with Native American allies he prevailed in a bloody campaign.
The Maya are one of the best studied of the major pre-Colombian native American civilizations. Unlike the Aztecs and Incas, the Maya were a much older civilization which had passed its peak by the time of the encounter with the Europeans. The Maya first appear in the Yucatan Peninsula about 2600 B.C. They became a civiization of major importance about 250 AD in what is now southern Mexico, Guatemala, western Honduras, El Salvador, and northern Belize. Unlike the Inda and Aztecs, the Maya were not a centralized imperial state. There virtually independent city states were connected by extensive trade routes. The Maya show evidence of assimilating the technology and culture of previous civilizations which had developed to the north in moden Mexic, especially the Olmecs. The Maya are especially noteworthy for their achievements in astronomy, mathematics, accurate calendars, hieroglyphics, and archectecture. Mayan hieroglyphics,probably of Olmec origins, was the most sophisticated writing system in Meso-America. The Mayan archetectural heritage is especially impressive. Many sites in the Yucantan and northerm Central America include temple-pyramids, palaces, and observatories. The Maya especially venerated the jaguar and built temple-pyramids to the being they saw as the Lord of the Underworld. As with the other Meso-American civilizations, these edifaces were built without metal tools, beasts of burden, or even the wheel. Mayan agriculture was especially impressive as methods such as storing rainwater in underground reservoirs dealt with the limited available groundwater. The Maya were also accomplished weavers and potters. The Spanish encountered the Maya centuries after their classical era, unlike the Aztec and Inca who were in their acendancy. The decline of the Maya is one of the great mysteries in archeology. There are numerous theories. Increasingly archelogists are coming to believe that the decline was a more gradual process than was once believed. The process appears to have involved expanding populations which required overcultivation of available land resulting in decling yields that could not support dense populations.
Rodrigo de Bastidas established Spain's claim to the isthmus of Panama. He sailied along the Darién coast (March 1501). Christopher Columbus, on his fourth and last voyage, sailed along the Caribbean coast of Central America from the Bay of Honduras to Panama (1502-03). When after sime difficulty, hecfinally made it back to Spain, he reported seeing natives wearuing gold ornamnts in Costa Rica. The first effort at colonization occurred in what is now Costa Rica, but faoled (1506). The next forays to Central America were launched from the growing Spanish colony of Cuba. Vasco Núñez de Balboa was the first European to cross the Isthmus of Panama and view the Pacific Ocean (1513). Balboa claimed the Pacific and all the lands adjoining it for the Spanish Crown. The next Spanish expedition from Cuba on the Yucatán Peninsula looking for slaves to work the Cuban plantations as the Native American population on the island had been desimated. The focus of the Spanishm howevere turned north to the Aztec Empire. Only gradually did the conquest of Central America take place where no rich empires were found.
Spain then colonized the Caribbean and then hearing rumors of a rich inland empire began to plan to colonize the mainland. The Aztec were a war-like people located in the central valley of Mexico and dominated much of southern Mexico during the 15th and early 16th centuries until the arrival of the Spanish conquistadores. Their capital Tenochtitlan was unknown to Europe, but was one of the great cities of the world. Diego Velasquez, Spanih Governor of Cuba, put a trusted soldier, Hernando Cortez, in charge of an expedition to the mainland. Hernando Cortés sailed from Cuba in 1519. Cortez's campaign against the Aztec's is one of the most dramatic events of history, brilliantly told by several historians. The golden booty helped make Spain the leading European power. It also provided a secure base for the further conquest of the Americas and this meant Central America.
The Spanish encountered the Maya centuries after their classical era, unlike the Aztec and Inca who were in their acendancy. The conquest of Central America is primarily the story of the conquest of the Maya states in northern Central America. There were, however, other tribes further south. After defeating the Aztecs, the Spanish turned their attention south. The first Conquistador to lead an expedition south was Pedro de Alvarado, one of the most ambutious and cruel of the Conquistadores. The principal campaigns to control CentraL America were fought in the north by Alvarado. The strongrst tribes were located in the highlands of Guatemala and El
Salvador. These were the Maya and related states. Alvarado reached Guatemala traveling down the Pacific coast (1523). He commanded a relatively small force made up of a few hundred horsemen, soldiers and Native American allies.
Although Yucatan is a part of modern Mexico it was at the time of Cotrez's conquest of Mexico (the Aztecs) not a part of the Aztec Empire, but rather populated by the Maya. When the Spaniards first reached Yucatan (1517-19), much of peninsula was controled by ruling castes of central-Mexican origin. They rebuilt Chichén Itzá into a powerful Early Postclassic center. During the Late Postclassic period (1250-1520) the center of Maya leadership in Yucatán had shifted to Mayapán which briefly reunified the region. Mayapán was defeated (1441).. As a result, northern Yucatán split nto sixteen small city-states. This fragmentation meant that the Spanish did not dencounter a strongly, centrally organized Mayan state. Francisco de Montejo, a Cotrz ally, became a wealty nobelman in Mexico. He lobbied the crown to grant him a Capitulación (royal contract) to raise an army and conquer Yucatán. The Crown hesitated for several years and finally issued the Capitulación (1526). The Spanish conquest consisted of three campaigns (1527-46).
The pre-Conquest population of Nicaragua is not known with any certainty. Some estimates suggest it may have been as high as 1 million people. One report speculates about an Aztec trading post. Columbus passed along the Caribbean coast (1502). The Spanish made no attempt to colonize what is now modern Nicaragua untill two decaded later. Gil Gonzalez Davila led the first Spanish expedition (1520). Francisco Fernandez de Cordoba conquered the area (1524). He founded the modern cities of Granada and Leon. The Native American population was descimated by the Spanish conquest. The Spanish killed some Native Americans in the conquest. European duseases killed even more. The population was largely enslaved. As many as 0.2 million were sent to work in Spanish mines in the new South American colony carved about of the Inca lands. The royal govenor in Nicaragua, Francisco de Castañeda, favored slave hunting. Rodrigo de Contreras became governor of Nicaragua (1532). Reformer Bartolomé de Las Casas and Emperor Carlos V forced Contreras to cancel a slave tradeing expedition (1536). The Governor expelled the reformer. A Spanish Census about three decades after the conquest showed only 11,137 Native Americans left in the country’s heartland of western Nicaragua (1548).
The Maya dominated western Honduras, but declined (early 9th century). The most important Mayan city-state was Copán. Christopher Columbus landed on the coast of modern Honduras near modern Trujillo on his fourth and last voyage (1502). He named the country Honduras because the waters was so deep along the coast. Conquistador Hernán Cortés landed in Honduras (1525). He left 6 months later after failing to find another rich Native American empire to plunder, returning to Spain. Spanish planters on Cuba raided the northern coast attempting to capture Native Americans they could enslave. Pedro de Alvarado began the actual conquest of Honduras. He defeated the resistance led by Çiçumba near Ticamaya (1536). Alvarado divided the conquered native lands among his men. The natives living their essentially became slaves in the repartimiento system. Native resistancde to Spanish britality flared up in Gracias a Dios, Comayagua, and Olancho (1537-38). Lempira led the uprising in Gracias a Dios.
Northern central America including Belize was dominated by the Mayan. The Maya appeared to have begun to move into coastal Belize from the Guatelan Highlands (about 1500 BC). The highpoint of Mayan civilization in Belize was a few centuries before the arival of the Spanish (1200 AD). Important Maya sites include: Caracol, Lamanai, Lubaantun, Altun Ha, and Xunantunich. Archeologists describe Maya cites with high population densities. Columbus sailed along the coast of Central America, including Belize (1502). There was for a long time even after Spanish settlement of Mexico and elsewhere in Central America, no settlement along the coast of what is now Belize. The first European settlement seems to have been inadvertant--shipwrecked English seamen (1638). More English settlements followed, but the English hold on the coast was precarious.
Christopher Columbus was the first European to find what is now Costa Rica. He landed near modern Puerto Limón during his fourth and last voyage (1502). He found a friendly population and noted the gold decorations that some of the local population wore. This was the origin of the name Costa Rica (rich coast). Columbus speculated thst their might be a rich empire farther inland. Spanish King Ferdinand, as a result, appointed Diego de Nicuesa governor of the region and disparched him to colonize it (1506). The Native Americans this time were not friendly. The diseases the Spanish brought may have been a factor. De Nicuesa was contronted by the tropical jungle, disease, and unfriendly natives. With half his party dead, he returned to Spain. The Spanish persisted. The major effort led by Gil González Dávila founded a colony on the Golfo de Nicoya (1522).
He launched a bloody conquest of the natives, killing and torturing them into submision. González returned with some gold, but many in his expedition died and there was still not settlmebt in Costa Rica. Juan Vásquez de Coronado arrived as another royal governor (1562). He decided that to found a permanent settlment that he needed to move inland to the central higlands. Here he founded Cartago which became the first permanent Spanish colony in Costa Rica (1563). The Spanish tended to found cities along the coat where they could be supported by their navy. Tropical diseases and the fertility if the central highlands with its rich volcanic soil caused Vásquez to move inland.
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Nibbling by herbivores can have a greater impact on the width of tree rings than climate, new research has found. The study, published this week in the British Ecological Society's journal Functional Ecology, could help increase the accuracy of the tree ring record as a way of estimating past climatic conditions.
Many factors in addition to climate are known to affect the tree ring record, including attack from parasites and herbivores, but determining how important these other factors have been in the past is difficult.
Working high in the mountains of southern Norway, midway between Oslo and Bergen, a team from Norway and Scotland fenced off a large area of mountainside and divided it into different sections into each of which a set density of domestic sheep was released every summer.
After nine summers, cross sections of 206 birch trees were taken and tree ring widths were measured. Comparing these with local temperature and the numbers of sheep at the location where the tree was growing allowed the team to disentangle the relationship between temperature and browsing by sheep and the width of tree rings.
According to lead author Dr James Speed of the NTNU Museum of Natural History and Archaeology: "We found tree ring widths were more affected by sheep than the ambient temperature at the site, although temperatures were still visible in the tree ring records. This shows that the density of herbivores affects the tree ring record, at least in places with slow-growing trees."
The impact of large herbivores on tree rings has, until now, been largely unknown, so these findings could help increase the accuracy of the tree ring record as a way of estimating past climatic conditions, says Dr Speed: "Our study highlights that other factors interact with climate to affect tree rings, and that to increase the accuracy of the tree ring record to estimate past climatic conditions, you need to take into account the history of wild and domestic herbivores. The good news is that past densities of herbivores can be estimated from historic records, and from the fossilised remains of spores from fungi that live on dung."
"This study does not mean that using tree rings to infer past climate is flawed as we can still see the effect of temperatures on the rings, and in lowland regions tree rings are less likely to have been affected by herbivores because they can grow out of reach faster," he explains.
Tree rings give us a window into the past, and have been widely used as climate recorders since the early 1900s. The growth rings are visible in tree trunk cross sections, and are formed in seasonal environments as the wood is laid down faster in summer than winter. In years with better growing conditions (in cool locations this usually means warmer) tree rings are wider, and because trees can be very long-lived and wood is easily preserved, for example in bogs and lakes, this allows very long time-series to be established, and climatic conditions to be estimated from the ring widths.
Explore further: Ecuador seizes 200,000 shark fins
More information: James D. M. Speed, Gunnar Austrheim, Alison J. Hester and Atle Mysterud (2011), 'Browsing interacts with climate to determine tree ring increment', doi: 10.1111/j.1365-2435.2011.01877.x, is published in Functional Ecology on 27 July 2011.
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