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News Bulletin : ADA News Bulletin October 2011
44 OCTOBER 2011 Compiled by Associate Professor Barrie Gillings clinical hints COMMUnICATIOnS At the time of writing, there have been none, which is a surprise, because there was an error in the last column which remained undetected by the ever vigilant CH proofing police. Your Wordsmith stated that the TV program ‘Letters and Numbers’ was on the ABC. This is incorrect. You will find it on SBS, and on every weeknight. If you do crossword puzzles, this is the pre- dinner TV viewing for you! Yesterday the Gillings clan came up with a ‘full monty’, a nine letter word, our first! It must have been easy as one of the contestants got the same word. David Astel, the adjudicator (and crossword puzzle writer), found the same word, and to finesse our ace, found two more, an astonishing achievement. CLInG fILM When this product first came on the market, it was called Saran-Wrap, and was a sensation. It was a film of polyvinylidine chloride (PVDC), and food wrapped in it retained moisture and flavour, and was protected against spoilage through exposure to oxygen. Because of possible environmental problems with the halogen component, PVDC has been superseded by the less effective polyethylene film, called ‘Cling Film’ or ‘Glad Wrap’. This film, which can be made microwave-safe, is now almost universal as a cover for packaged fresh foods, and few shops, or kitchens, industrial or domestic, are without it. One of its useful qualities is the ability to cling. This is because when it is unwound from the roll, it acquires a static charge which allows it to adhere tenaciously to most surfaces. But don’t be mislead when the TV advertisement shows the bowl of liquid staying sealed when the bowl is inverted. This is because of air pressure, not because the film clings so tenaciously. The advertisers are misleading you, but ‘in the most delightful way’, as the Mary Poppins song explains. A fLASH In THE bULb This is not to be confused with a flash bulb. Many years ago, before the electronic flash became so common in or on cameras, night-time pictures were taken using ‘photoflash’ bulbs. These were bulbs which contained magnesium foil or wire, and were filled with oxygen. The camera shutter provided a contact when open, which ignited the bulb using current from a small battery. Some problems arose because the magnesium took a little time to ignite, so a suitable delay had to be introduced so that the flash was at its brightest when the shutter was fully open. The modern electronic flash, a discharge of high voltage in an inert gas, such as xenon, solved the timing problem. Before the flashbulb, the flash was produced by igniting an open tray filled with magnesium powder, as sometimes seen in old or period-type movies. This is dangerous but effective. The open-tray method of illumination is still used to illuminate large static objects for photography, such as caves, and was probably how Frank Hurley illuminated the famous pictures he made of the ill-fated ‘Endurance’, trapped in the winter ice in Antarctica. But there is another ‘flash in a bulb’ that bears explaining. The well-known incandescent bulb was patented by Sir Joseph Swan in 1878, closely followed by Thomas Alva Edison. They combined forces in producing the Ediswan bulb and socket, the latter used to this day, but not for much longer, as the energy-efficient light bulbs are replacing the incandescent filament bulbs. The incandescent bulb uses a tungsten filament in a glass envelope containing an inert gas. Eventually, the tungsten filament, which is commonly a coil, or a coiled coil, becomes excessively hot in one area because of increased local electrical resistance, and thus glow more brightly, causing more loss of metal, increasing the resistance and a vicious circle occurs. The electrical current flowing through the filament when the bulb is subsequently switched on is higher than when the filament is hot, and this high current can raise the temperature of the hot-spot in the filament so high that the bulb ‘fuses’. This fusing can cause arcing and a bright flash, like a flash bulb, and the extra current flow can cause a fuse to blow or a circuit breaker to trip. You are unlikely to see this effect repeated again, so enjoy it while you can. TO SLEEP, PERCHAnCE TO dREAM Hamlet knew all about it. But getting to sleep can be difficult. Dr Laura Pearce gives advice to dentists in the ADA NSW newsletter, and offered the following for getting to sleep: Lie with mouth and jaw relaxed, tip of tongue on your incisal papilla, mouth slightly open. Exhale fully. Close mouth and inhale for four seconds. Hold your breath for seven seconds. Exhale over eight seconds. Repeat the sequence three times. She made no mention of an alternative technique: drink three whiskeys. bUGATTI For non-car persons, this is a make of motor car with a long history. Bugatti owners are fanatical, and a breed apart. Some Bugattis have small and closely-set brake and clutch pedals, and it is said that a true aficionado binds the feet of his male children so that, when adult, their feet will fit the pedals. All models are expensive. If you come across a ‘barn find’ Bugatti, which has been there for years, and can buy it for a song, do so. One such, a 1937 Bugatti Type 57S with 262,854 miles on the clock, sold at auction in February 2009 for $11.8 million.
ADA News Bulletin September 2011
ADA News Bulletin November 2011