Monthly Archives: January 2015
A mouse is a pointing device that detects two-dimensional motion relative to a surface. This motion is typically translated into the motion of a pointer on a display, which allows for fine control of a graphical user interface.
Physically, a mouse consists of an object held in one’s hand, with one or more buttons. Mice often also feature other elements, such as touch surfaces and “wheels”, which enable additional control and dimensional input.
The history of the mouse starts with the trackball, a related pointing device, which was invented in 1946 by Ralph Benjamin as part of a post-World War II-era radar plotting system called Comprehensive Display System (CDS). Benjamin was then working for the British Royal Navy Scientific Service. Benjamin’s project used analog computers to calculate the future position of target aircraft based on several initial input points provided by a user with a joystick. Benjamin felt that a more elegant input device was needed and invented a ball tracker called roller ball for this purpose.
The device was patented in 1947, but only a prototype using a metal ball rolling on two rubber-coated wheels was ever built and the device was kept as a military secret.
Douglas Engelbart at the Stanford Research Institute (now SRI International) invented his first mouse prototype in the 1960s with the assistance of his lead engineer Bill English. They christened the device the mouse as early models had a cord attached to the rear part of the device looking like a tail and generally resembling the common mouse. Engelbart never received any royalties for it, as his employer SRI held the patent, which ran out before it became widely used in personal computers.
Modern mice are now available wired or wireless. Such a simple device changed the way we interacted with computers. Modern laptops have built in track pads but many users still prefer a mouse.
|Inventor Douglas Engelbart’s computer mouse, showing the wheels that make contact with the working surface.|
|Modern wireless mouse|
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Walter Frederick “Fred” Morrison (January 23, 1920 – February 9, 2010) was an American inventor and entrepreneur, best known as the inventor of the Frisbee.
|Walter Frederick Morrison|
How does a Frisbee fly?
Two factors influence the flight of a Frisbee, gravity and air. Gravity acts on all objects the same way, accelerating their mass towards the center of the Earth at 10 meters/second. Once in the air, lift and angular momentum act on the Frisbee giving it a ballet-type performance. Lift is generated by the Frisbee’s shaped surfaces as it passes through the air. Maintaining a positive angle of attack, the air moving over the top of the Frisbee flows faster than the air moving underneath it.
Under the Bernoulli Principle, there is then a lower air pressure on top of the Frisbee than beneath it. The difference in pressure causes the Frisbee to rise or lift. This is the same principle that allows planes to take off, fly and land. Another significant factor in the Frisbee’s lift is Newton’s Third Law which states that for every action there is an equal and opposite reaction. The Frisbee forces air down (action) and the air forces the Frisbee upward (reaction). The air is deflected downward by the Frisbee’s tilt, or angle of attack.
Spinning the Frisbee when it is thrown, or giving it angular momentum (gyroscopic inertia), provides it with stability. Angular momentum is a property of any spinning mass. Throwing a Frisbee without any spin allows it to tumble to the ground. The momentum of the spin also gives it orientational stability, allowing the Frisbee to receive a steady lift from the air as it passes through it. The faster the Frisbee spins, the greater its stability.
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Arsenic atoms can assume several different bonding patterns which are the basis of its allotropes, each of which has a different colour; metallic grey, yellow and black arsenic. Interestingly, using a hammer to bang on arsenide minerals releases a garlic-like odour, which is the result of toxic fumes created by the oxidation of arsenic to arsenic trioxide.
Historically, Arsenic was commonly used as a rodent poison in English households, and it was also a convenient murder weapon, particularly amongst the ruling classes as you may have read in various novels and non-fiction books. However, Victorian England used arsenic in a number of ways; it was incorporated into wallpaper to prevent the growth of mould during the dark, damp English winters, it was used as the green colouring in paints, candies and candles, and as a preservative in lace.
The main use of metallic arsenic is for alloying with lead. Lead components in car batteries are strengthened by the presence of a very small percentage of arsenic.
Widespread arsenic contamination of groundwater has led to a massive epidemic of arsenic poisoning in Bangladesh and neighbouring countries. It is estimated that approximately 57 million people in the Bengal basin are drinking groundwater with arsenic concentrations elevated above the World Health Organization’s standard of 10 parts per billion (ppb).
More recently arsenic has been in the news for being found in rice. Rice holds higher levels of arsenic than other grains and acts as one of nature’s “great scavengers of metallic compounds.” Unlike, millet or polenta, rice planted in arsenic-contaminated fields acts as a vacuum for the toxin.
Rice from different countries contain differing levels of arsenic. It’s recommended that rice is washed before cooking and rinsed afterwards to lessen the effects.
Currently, the FDA in America doesn’t have safety levels for arsenic in rice. They’ve cautioned against making state-by-state or country-by country comparisons in Inorganic Arsenic levels for rice, citing the varying factors that can influence arsenic concentrations, such as soil composition, fertilizers, seasonal variability, and water-use practices.
Evidence-based public health advocates also recommend that, given the lack of regulation or labelling for arsenic in the U.S., children should eat no more than 1 to 1.5 servings per week of rice and should not drink rice milk as part of their daily diet before age 5. They also offer recommendations for adults and infants on how to limit arsenic exposure from rice, drinking water, and fruit juice.
A 2014 World Health Organization advisory conference will consider limits of 200–300 ppb for rice. The proposed new EU recommendations will limit 200 parts of arsenic per billion for adults and just 100 ppb for children and babies.
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On 8th January 1868, Søren Peder Lauritz Sørensen was born in Havrebjerg, Denmark. He died on 12th February 1939. He was a Danish chemist famous for the introduction of the concept of pH, a scale for measuring acidity and basicity.
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