The earliest pipe organs were water organs, which were powered by the flow of water, sometimes from a natural resource or using a pump. Later ones used foot pedals or hand cranks to pump a bellows, which in turn produces the air that goes through the pipes. These kinds of organs are still made today, and are called harmoniums. Today's pipe organs ones use an electric motor to move air, and some, like those in theaters, play different instruments as well. The Wurlitzer company was well known for making instruments that make different sounds.
Mechanical organs have a mechanism that controls which notes are played and when they are played. One type of mechanical organ is the barrel organ, which usually get their music printed on cardboard sheets, although some use piano rolls or a barrel similar to that of a carillon or music box.
Mechanical organs can be all shapes and sizes. The smaller barrel organs are often heard on streets in Europe and is a common way of getting money from people who pass by. These types are sometimes called hurdy gurdies, but this is not true. Larger barrel organs can be found on fairgrounds and are loud so that they can be heard above all the other noise at a fair. Meanwhile, smaller barrel organs can be found indoors, and play songs when someone puts in a coin, similar to a slot machine. Some clocks have barrel organ mechanisms that play music at certain times, such as every hour.
The electronic organ is one of the newest types of organ. They use electronics to simulate the sound of a pipe organ and many other instruments. Because of this, they do not need to be very big and many are no bigger than a piano so that they can fit in homes, schools, or can be moved around as needed. They also do not go out of tune because it holds all its sounds on computerized chips. Many organists think they do not feel as good to play as a traditional, mechanical pipe-organ.
There are electronic organs that look and sound like those played in churches, and even many churches use electronic organs when they do not have the money or space for a full pipe organ. The best-known electronic organs include the Hammond organ heard in jazz, and other organs, like those made by the Japanese company Yamaha, are in fact synthesizers that can sound like a whole orchestra playing together. These types of organs are often used for music education, especially in Asia.
Twin
Twins are (including human) offspring that are born
"Human twins" are two people that shared the during a single pregnancy, and one is normally born quickly after the first. Because of the size of the uterus,
There are 2 types of twins. They are:
Fraternal twins are also known as "non-identical twins" or "dizygotic twins". They happen when two ova are released from the ovary at the same time, and each is fertilized by a different sperm. This results in the birth of fraternal twins. They can be of different sexes. Genetically, they are no more similar than any two siblings.
Identical twins or "monozygotic twins": A single ovum is fertilized to form one zygote. This zygote later splits, and each half of the zygote becomes a twin. The twins have the same genes.
There are five variations of twinning that occur commonly. The frequency varies in different populations. The three most common variations are all fraternal, meaning the two twins are not from the same egg:
The last two variations are identical twins, which means they come from one single egg that split later:
Twinning is common in many other species, such as cats, sheep, and ferrets. Twinning occurs in cattle about 1-4% of the time, and research is being done to improve the chances of twins being born. If an animal has twins it can be more profitable for the breeder, especially if there is a smaller chance of miscarriage.
Ceiling
A ceiling is the surface that covers the upper limit of a room. It is not generally considered a structural element, as it does not hold anything up. It simply conceals the underside of the floor or roof above it.
There are many different types of ceilings in architecture. In religious buildings, the ceilings are often decorated with frescos, mosaic tiles and other surface treatments. Perhaps the most famous example is the ceiling of the Sistine Chapel, painted by Michelangelo.
Column
A column in architecture is a vertical element that transmits the weight of the structure above to the structure below. Columns can be either a single piece or several pieces put together. Columns are frequently used to support beams or arches on which the upper parts of walls or ceilings rest.
Stone columns were already used in the architecture of ancient Egypt as early as 2600 BC.
Identical twins
Identical twins start out as genetically identical: they have the same alleles. They are formed by a fertilised egg dividing into two separate individuals. They are always of the same sex, and are monozygotic or MZ twins (mono = one; zygote = fertilised egg). This contrasts with "fraternal twins", who are formed by two separate eggs fertilised by two separate sperms, and who are not always the same sex (DZ = dizygotic). Both types of twin are carried in the same uterus at the same time, so their birth environment is the same.
Research shows that the frequency of monozygotic twinning is one in 240 births. Fraternal twins are twice as common. In vitro fertilization (IVF) techniques are more likely to create dizygotic twins. For IVF deliveries, there are nearly 21 pairs of twins for every 1,000.
Identical twins are natural clones. Because they start out with the same genes, they can be used to investigate how much heredity contributes to individual people. This is the nature vs nurture question.
Studies with twins have been quite interesting. If we make a list of characteristic traits, we find that they vary in how much they owe to heredity. For example:
The way the studies are done is like this. Take a group of identical twins and a group of fraternal twins, and a group of siblings from the population. Measure them for various traits. Do a statistical analysis (such as analysis of variance). This tells you to what extent the trait is inherited. You will find that all those traits which are partly inherited will be significantly more similar in identical twins.
Studies like this may be carried further, by comparing identical twins brought up together with identical twins brought up in different circumstances. That gives a handle on how much circumstances can alter the outcomes of genetically identical people.
Modern research has shown quite clearly that genetic inheritance does influence psychological aspects of life (how people behave), not just physical aspects.
The person who first did twin studies was Francis Galton, Darwin's half-cousin, who was a founder of statistics. His method was to trace twins through their life-history, making many kinds of measurement. Unfortunately, though he knew about mono and dizygotic twins, he did not appreciate the real genetic difference. Twin studies of the modern kind did not appear until the 1920s.
Wilhelm Weinberg made the first estimate of the rate of twinning. Realizing that identical twins would have to be the same sex, while non-identical twins could be either same or opposite sex, Weinberg derived a formula for estimating the frequency of MZ and DZ twins from the ratio of same and opposite sex twins to the total of maternities. Weinberg also estimated that the heritability of twinning itself was close to zero. That means the capacity to have twins is not hereditary.
Monozygotic twins are genetically "nearly identical" and they are always the same sex unless there has been a mutation during development. Monozygotic twins always have different phenotypes. Twins may express different sexual phenotypes, normally from an XXY Klinefelter's syndrome zygote splitting unevenly.