More recently, the meaning of the pentagram was discussed in "The Da Vinci Code" by Dan Brown. According to the book, the pentagram actually belonged to the ancient religion of Pagan Sun Worship, and was tied to the female planet Venus: every 8 years Venus traces a perfect pentagram across the sky. The book says that the pentagram was a symbol for the sacred female, but was later taken by Christianity and said to mean the devil in order to destroy beliefs that females were sacred.
A pentacle is on the flag of Morocco, as well as Ethiopia's.
Benzene
Benzene, also known as benzol, is an organic chemical compound with the formula CH. It is a colorless and flammable liquid with a sweet smell. Benzene molecules are a ring of six carbon atoms that are each bonded to one hydrogen atom. It is an "aromatic" compound, meaning the ring has alternating double bonds.
Benzene is carcinogenic, which means it can cause cancer. It has many real-world uses. It is used as an additive in gasoline, plastics, synthetic rubber, dyes and it is an industrial solvent, which means it can dissolve many other chemical molecules. Benzene is also a natural part of crude oil and is therefore present in gasoline. Many medicines contain parts made from benzene.
Benzene has special properties called aromaticity. All six carbon atoms in the ring are on the same flat plane. To account for all the bonds on a six carbon ring, there must be alternating double carbon bonds (Conjugated system):
If benzene had three double bonds, three sides of its ring would be shorter than the other three sides. X-ray diffraction shows that all of six carbon-carbon bonds in benzene are of the same length of 140 picometres (pm). The C–C bond lengths are greater than a double bond (135 pm) but shorter than a single bond (147 pm). This intermediate distance is consistent with electron delocalization: the electrons for C–C bonding are distributed equally between each of the six carbon atoms. The molecule is planar. One representation is that the structure exists as a superposition of so-called resonance structures, rather than either form individually. (In other words, the molecule's double bonds switch quickly between pairs of carbon atoms.) The delocalization of electrons is one explanation for the thermodynamic stability of benzene and related aromatic compounds. It is likely that this stability contributes to the peculiar molecular and chemical properties known as aromaticity. To indicate the delocalized nature of the bonding, benzene is often depicted with a circle inside a hexagonal arrangement of carbon atoms.
As is common in organic chemistry, the carbon atoms in the diagram above have been left unlabeled. Realizing each carbon has 2p electrons, each carbon donates an electron into the delocalized ring above and below the benzene ring. It is the overlap of p-orbitals both above and below the ring that produces the pi clouds.
In 1986, some chemists disputed the delocalized view of benzene in an article published in the journal "Nature". They showed that the electrons in benzene are almost certainly localized to particular carbon atoms. They showed the aromatic properties of benzene come from spin coupling rather than electron delocalization. Other scientists wrote articles to support this view in "Nature" in 1987. But, chemists are slow to switch from the delocalized electrons view.
Derivatives of benzene occur sufficiently often as a component of organic molecules that there is a Unicode symbol in the Miscellaneous Technical block with the code U+232C (⌬) to represent it with three double bonds, and U+23E3 (⏣) for a delocalized version.
Tasmanian devil
The Tasmanian devil ("Sarcophilus harrisii") is a meat eating mammal. It is a marsupial, which means it has a small pouch to carry its babies. It is the largest meat eating marsupial in the world. It is nocturnal, which means it sleeps during the day and is awake during the night. Tasmanian devils now live only in Tasmania, an island state of Australia.
The devil is the same size as a small dog with a wide head and a short tail. Male devils can weigh 12 kg and be 30 cm tall. It has black fur and makes a loud and very scary screeching noise. It will hunt other animals and also feed on dead animals. The devil has strong teeth and jaws and will eat all its prey, even bones and fur.
The Tasmanian devil became extinct on the Australian mainland about 3,000 years ago - before European settlement in 1788. They were hunted in Tasmania. In the 1930s the Van Dieman's Land Company offered 25 cents for each male and 35 cents for each female killed. In 1941 they became officially protected.
In 1996 the devils began to get very sick and then die with large tumours on their faces. Devil facial tumour disease has greatly reduced the number of devils and now threatens their survival. In some areas 85% of devils have been found with the disease. In the places where the tumours were seen first, devil numbers have dropped by 95%. The tumour is spread by biting. Because the devils are all closely related (not enough genetic diversity), the tumour cells are not seen as new; so the devil's immune system does not fight it. In May 2008 the Tasmanian devil was listed as endangered. Programs are being tried by the Tasmanian government to reduce the impact of the disease. About 60 devils without the disease have been captured and are to be kept as a tumour free group for rebreeding. Scientists have been looking at ways to give the devils immunity but so far this has not worked.
New research is showing the devils are having babies earlier, they use to breed at two years, but now are breeding at one year old. Devils used to have babies every year for three years, but they are now dying before they can produce a second litter (family).
The devils have a low genetic diversity which is consistent with a 'founder effect'. What this means is: a small number colonised Tasmania from Australia at some stage. So their genetic variety was much less than the parent population. Disease like the present may have happened before, and reduced the population to a small number. These events are called 'population bottlenecks'. A small population which carries less variation is always vulnerable to extinction, because none of the animals may be resistant to the infection.
Its genome was sequenced in 2010 by the Wellcome Trust Sanger Institute. There is some hope for their survival because, since 2005, three females have been found that are partially resistant to the disease.
Joseph Haydn
Joseph Haydn (also known as Franz Joseph Haydn) was an Austrian composer. He was born on March 31 or April 1, 1732, and died on May 31, 1809. He was one of the most famous composers in the Classical music period. He is often called the "Father of the Symphony."
Haydn's father made wheels for a living, and had the skills of a blacksmith, stonemason, and carpenter. He used that skill in his spare time to make musical instruments for his family to play. The Haydn family would give informal weekend concerts. One of Joseph's relatives thought that Joseph had a great singing voice and should go with him to a boarding school where he would start studying to become a priest.
Haydn did not like it very much at the boarding school, but his voice developed to a point where he was selected to be a part of the Boy's Choir of the Vienna Cathedral. He stayed there until his voice changed.
Haydn made a living teaching lessons and playing in the streets for handouts until he met Nicolai Porpora, who hired Haydn as an accompanist and general servant.
Eventually Haydn got a job working for Nicholas Esterhazy. He worked for the Esterhazys for over 30 years. He wrote symphonies, string quartets, operas, piano sonatas, and other pieces.
After he was released from his duties with the Esterhazys, Haydn travelled to London. Even at the age of 60 he was still active and wrote some of his most famous symphonies there.