There is a vaccine against chickenpox. Usually, the vaccine is given to children if they did not have the disease before the start of puberty, that is aged 9–13 years old. Sometimes to help your child not to scratch when they have chicken pox, you can get a special cream for it such as e45.
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Tonality
Music has tonality if it uses the notes of a major or minor scale. Such music is tonal. It is in a particular "key". Nearly all Western music is tonal.
All tonal music is based on a major or minor scale. If the tune “Twinkle, twinkle little star” is played starting on the note C, the notes of a C major scale will be used. The note C will sound like the home note (the “tonic”) and, indeed, the tune finishes on a C. The tune could have started on any other note (C sharp, D, E flat, E etc.) but a knowledge of scales would be needed as some sharps or flats (black notes) will be required. When singing the tune there is no need to think about the sharps and flats: the singer does them quite naturally.
A piece of tonal music will usually modulate after a while. This means that it changes key. But the music will not sound finished until it goes back to the original key. If one sings The Star-Spangled Banner and stops after the words “our flag was still there” the song sounds as if it has stopped in mid-air. It will not sound finished until it goes back to the first key in the last two lines.
Most Western music from about 1600 onwards is based in a major or minor key. This system of tonality was used by all the great composers up to the 20th century and in popular music and most folk music. Listening to a symphony by Beethoven is like going on a journey through various key areas, always returning to the original tonic at the end. In some cases, such as Beethoven’s "Fifth Symphony", it may start in the minor and finish in the major. This is because minor keys can sound disturbed, full of tension, but major keys sound happier and more relaxed.
The opposite of “tonality” is atonality. An atonal piece is one where there is no feeling of a home key. Playing lots of random notes will sound atonal. Schoenberg was one of the most famous composers of atonal music. Of course, his music is not just random notes (although it may sound like it to the listener at first), so he had to find another way of giving his music shape. That is why he invented the twelve-tone system.
Toucan
The toucan is a South American bird in the family Ramphastidae. This social bird lives in small flocks in lowland rainforests in countries such as Costa Rica. It flies short distances between trees. Toucans rest in holes in trees. They mostly eat fruit, but sometimes they also eat insects and small lizards.
They are brightly marked and have large, often-colorful bills. The family includes five genera and over forty different species.
Toucans are resident breeders and do not migrate. Toucans are usually found in pairs or small flocks. They sometimes fence with their bills and wrestle, which scientists think is to find out who is the top bird amongst them.
Toucans are known for their huge beaks, which can grow larger than their bodies. They use their beaks for reaching over and plucking fruit from branches of trees. The bright colors (usually orange) on the beak may help the toucans to recognize each other, and to scare off other birds.
Elbow
The elbow is a hinge-joint between the bones of the upper and lower arm. It joins the humerus of the upper arm and the radius and ulna of the forearm together. Everyone has 2 elbows. It allows the lower arm to be extended or retracted (moved in). The elbow also allows the arm to turn. It moves by using three ligaments: the "anterior, posterior, ulnar collateral" and "radial collateral" ligaments.
Wrist
The wrist is the joint that links together the lower arm and the hand.
Knee
The knee is the joint that links 4 of the upper and lower bones of the leg, which are called the femur, tibia, fibula and the patella. The knee joint is the largest joint in the body and is an extensive network of ligaments and muscles. Basically, it is a hinge which allows movement of the lower leg in only one direction. The lower leg (tibia+fibula+foot) can swing back from the knee, and that is all.
The knee is held together by ligaments which connect the bones and produces fluid which lubricates the movement at the joint. The meniscus is a cartilage
that lies on the inner and outer edges of the upper surface of the tibia. These are the shock
absorbers of the knee and supply proper weight distribution.
Atomic theory
In chemistry and physics, the atomic theory explains how our understanding of the atom has changed over time. Atoms were once thought to be the smallest pieces of matter. However, it is now known that atoms are made up of protons, neutrons, and electrons. These subatomic particles are made up of quarks. The first idea of the atom came from the Greek philosopher Democritus. A lot of the ideas in the modern theory came from John Dalton, a British chemist and physicist.
The theory applies to solids, liquids and gases, but it does not apply in way analogous to plasmas or neutron stars.
Democritus thought that if you cut something in half again and again, you would at last have to stop. He said that this last piece of matter could not be cut any smaller. Democritus called these small pieces of matter atoms, which means "indivisible". He thought that atoms would last forever, never change and could not be destroyed. Democritus thought that there was nothing between the atoms and that everything around us could be explained if we could understand how atoms worked.
Some other philosophers agreed, and others disagreed. They had no way to experiment to show whether his theory was true or not.
In 1758, Roger Joseph Boscovich described a precursor of the atomic theory.
In 1803, the English scientist John Dalton, born in Cumberland, reworked Democritus' theory, as follows:
Dalton defined the atom as the "basic unit of an element that can take part in a chemical combination".
In 1850, Sir William Crookes constructed a 'discharge tube', that is a glass tube with the air removed and metallic electrodes at its ends, connected to a high voltage source. When creating a vacuum in the tube, a light discharge can be seen that goes from the cathode (negatively-charged electrode) to the anode (positively-charged electrode). Crookes named the emission 'cathode rays'.
After the cathode ray experiments, Sir Joseph John Thomson established that the emitted ray was formed by negative charges, because they were attracted by the positive pole. Thomson knew that the atoms were electrically neutral, but he established that, for this to occur, an atom should have the same quantity of negative and positive charges. The negative charges were named "electrons" ("e"-).
According to the assumptions established about the atoms neutral charge, Thomson proposed the first atomic model, that was described as "a positively-charged sphere in which the electrons were inlaid (with negative charges)". It is known as the "plum pudding model".
In 1906, Robert Millikan determined that the electrons had a Coulomb (C) charge of -1.6 * 10, something that allowed calculation of its mass as tiny, equal to 9.109 * 10 kg.
In the same time, experiments by Eugene Goldstein in 1886 with cathode discharge tubes allowed him to establish that the positive charges had a mass of 1.6726 * 10 kg and an electrical charge of +1,6 * 10 C. Lord Ernest Rutherford later named these positively charged particles "protons"
In 1910, the New Zealand physicist Ernest Rutherford put forward the idea that the positive charges of the atom were found mostly in its center, in the nucleus, and the electrons ("e"-) around it.