To Know About Pioneers of Atomic Age

Antoine Henri Becquerel (1852-1908) was a French Physicist who discovered radioactivity.

Some substances, when they have been exposed to bright sunlight, glow in the dark for some time afterwards. This effect is called Phosphorescence. Henri Becquerel followed in the footsteps of his father and grandfather who had both been well-known physicists. He was interested in crystals which glow (fluoresce) after absorbing sunlight. When Roentgen discovered X-rays in 1895, Becquerel was fascinated. In the meanwhile a Frenchman named Henri poincare, who later became famous as a brilliant mathematician, suggested that phosphorescent substances might give off X-rays. In 1896, a friend and fellow-countryman of Poincare, Antoine Henri Becquerel, decided to put the matter to the test. He exposed crystals of a Uranium compound to sunlight to make them phosphorescent and placed them on thickly wrapped photographic plates. On developing the plates he found that the plates had been blackened by rays from the uranium compounds. It looked as if Poincare had been correct. A few days later Becquerel happened to be developing some old photographic plates to see if they were still good enough to use. The plates had been kept in a drawer in which there were traces of the uranium compounds. He found to his astonishment that those plates had been blackened by the uranium, even though they had been kept in the dark. The blackening had nothing to do with phosphorescence after all. Becquerel had discovered what came to be called radioactivity. He found that the uranium ore pitchblende was more intensely radioactive that even uranium itself. His enthusiasm influenced Pierre and Marie Curie.

The Curies

Becquerel was friendly with Pierre Curie, a lecturer in Physics at the University of Sorbonne in Paris, and his wife Marie, who was a chemist. He mentioned his discovery regarding Pitchblende to them, and they resolved to try to isolate the unknown, powerfully radioactive element that must be present in the ore.

The Curies obtained loads of Pitchblende ‘waste’ from the Austrian government from which the uranium had already been extracted. They worked in an old wood shed in the Sorbonne purifying and separating the ore. In July 1898 they announced that there were not one, but two unknown radioactive elements in pitchblende. They isolated one, which Marie Curie named polonium, after Poland, where she was born. They did not succeed in isolating the second one, which they called radium, until 1902.

For their pioneering work on radioactivity, Becquerel and the Curies were jointly awarded the 1903 Nobel Physics Prize.

The radium the Curies had prepared so far was in the form of a compound. Therefore, they set about producing pure radium. Pierrie, however, was killed in a street accident in 1906, and Marie continued alone. Breaking with all tradition, the Sorbonne offered Pierre’s position to Madame Curie. In 1910 Marie succeeded at last in preparing a minute amount of pure radium. This brought her a second Nobel Prize in 1911. Soon afterwards she helped to found, and became the first director of the Radium institute of Paris.

Marie Curie died of leukemia, a disease of white blood cells. It has since been shown that radiation can cause leukemia, so it is more than likely that Madame Curie died as a result of excessive exposure to the intense radiation from the elements she had discovered. 

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Know great about Mosquitoes its causes and varieties

Mosquito, a two-winged ‘little fly’ is a menace to humankind. It causes blood loss, transmits diseases like malaria, filaria, dengue, chikungunya, and Japanese encephalitis. There is incredible diversity in the mosquito family. Weighing only about 2.5 milligrams, mosquitoes have survived through the ages. Fossil and zoogeographic evidence suggest that these insects evolved during the dinosaur period of Jurassic Age around 250 million years ago. Though dinosaurs are long gone, these small winged creatures have adapted and evolved to produce extensive taxonomic, genetic and ecological diversity.

Where are they found?

Mosquitoes are found throughout the world except in places that are permanently frozen. They are found amply in the tropics and subtropics. The largest population of individual species occurs in the Arctic Tundra. Out of the 3500 mosquito species, about 350 species have been reported in India.

The diseases they transmit

It is estimated that over 700 million people are affected by the diseases transmitted by mosquitoes. Some of the major diseases are: malaria, filaria, dengue, chikugunya, Japanese Encephalitis (JE), yellow fever, Western Nile Fever (WNF), Western Equine Encephalitis (WEE), Eastern Equine Encephalitis (EEE), Venezuelan Equine Encephalitis (VEE), and California Encephalitis (CE).

Varieties of Mosquitoes Anopheles

Anophelinae comprises 450 species. Sixty-six of these are medically crucial for their plasmodium-carrying capacity. In our country, 58 Anopheline species have been recorded of which 10 are known to be malarial vectors.

How to identify Anopheles

Anopheles can be identified by the three to four black spots on the upper edge of the wing. It has grayish brown body and pale bands on maxillary pulp. Male mosquitoes have antennae that look like brush. In females, antennae do not have such dense hairs. The Primary vector An Culicifacies has widespread distribution and can efficiently transmit both ordinary and cerebral malaria. It breeds proficiently during monsoon and causes incidence of malaria intensify.

The other varieties are: An. Stehensi, an urban vector; An.fluviatilis that inhabits hilly regions; An.minimus found in tea garden belts and foothill regions; An.dirus, mainly confined to the forest and forest fringe areas; An.minimus, dirus and fluviatilis maintain stable malaria in the northeastern states. An.Sundaicus is at present restricted to Andaman Nicober islands, though it was earlier prevalent in Odisha. Besides malaria transmission An.gambiae, An. Funestus etc. carry the filarial parasite in some parts of the world including East Africa, Papua New Guinea. An.barbirostris and An.hycranus can transmit Japanese encephalitis virus also.

Why they feed on: Major Anopheline vectors are anthropophilic and feed on the blood of humans inside the house. The biting hours vary through night (depending on the species) with a flight range of two to three kilometers. Their flight sound is not audible.

Where they breed: Anopheles breed in fresh water bodies like riverside, lakes, cisterns, wells, paddy fields etc. But few species can breed even in foul water, muddy ponds and marshlands.

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