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March 2011 Elements that contain unstable nuclei are radioactive; they are called radionuclides. They decay by releasing mostly alpha and beta particles accompanied by gamma rays. An alpha particle has low-energy, is positively charged and consists of two protons and two neutrons, i.e., a helium atom without its 2 electrons; it can be stopped by tissue paper or human skin.  A beta particle is a high-energy, negatively charged electron (negatron) or a positively charged positron; it can be stopped by a sheet of aluminum. Gamma rays are high energy, short-wavelength, electromagnetic radiation; they can be stopped by concrete or lead. The energy released by radionuclides may knock electrons out of their orbits around an atom’s nucleus. This process is called ionizing radiation. Ionizing radiation damages living tissues, leads to changes in constituents of the cell, including the DNA of chromosomes, and results in changes in structure and function of the cells and organ syst...

Pakistani currency has a rich timeline and all these years changes have been made for the convenience of public and to strengthen the economy. Until 1971, Pakistani currency was printed in two languages i.e. Bengali and Urdu. 'Paisa' coins were used till 80s that were discontinued and replaced by notes which again got discontinued and replaced by new coins. Here is history and some of the interesting facts about Pakistani currency. 1) Word 'rupiya' is a Sanskrit word which means 'a coin of silver' 2) Concept of Coins that are used in Pakistan, begun thousands years ago in India 3) First coin with name 'Rupee' was introduced by Sher Shah Suri in 1545 4) The coins issued after 1840 bore the portrait of Queen Victoria 5) Acute shortage of silver during the First World War, led to the introduction of paper currency of One Rupee 6) A new "Anna Series" was introduced in 1940s  7) Hyderabad State had its own curr...