Nutrition

November 17, 2011 by · Leave a Comment 

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A diagrammatic guide to daily eating (figure 27a). The food guide pyramid has been adopted by the US Department of Agriculture and the Department of Health and Human Services to encourage people to eat healthily. Six major groups of food are arranged in a pyramid shape to indicate the number of recommended daily servings of each group: the food group with the highest number of recommended daily servings (bread, cereal, and pasta group) form the base of the pyramid; the group with the lowest recommended number of servings (fats, oils, and sweets) form the apex of the pyramid. The guidelines are for the average person. All active people should have at least the lowest number of servings recommended for each food group. Very active people, especially serious athletes and those in physically demanding jobs, may need more than the larger number of recommended servings.

In the UK an alternative diagrammatic guide to the food guide pyramid has been introduced. It is called the ‘plate model’ (figure 27b). This diagram takes the form of a plate divided into five sections representing the main food groups: bread, other cereals, and potatoes; milk and dairy foods; fatty and sugary foods; meat, fish, and alternatives; and fruit and vegetables. Market research found that the public preferred this approach to the pyramid.

The Pyramid includes five major food groups, each of which provides nutrients needed for good health. By making healthful choices within these food groups, like selecting low-fat and high-fiber foods, people can promote good health and reduce their risk of disease. The placement of foods within the Pyramid shows that foods of plant origin should supply most of the servings of food in the daily diet.

The Breads, Cereals, Rice, and Pasta Group forms the base of the Pyramid, with the largest number of servings recommended (six to eleven servings recommended daily). The next layer up includes the Fruit Group (two to four servings) and the Vegetable Group (three to five servings). At the third level are the Milk, Yogurt, and Cheese Group (two to three servings) and the Meat, Poultry, Fish, Dry Beans, Eggs, and Nuts Group (two to three servings). At the tip of the Pyramid are Fats, Oils, and Sweets. These foods and food ingredients should be used “sparingly” to avoid excess calories and/or fat. It is not necessary to completely avoid foods such as salad dressing, butter, margarine, candy, soft drinks, and sweet desserts, but they should be consumed infrequently.

The Pyramid includes symbols that represent the fats and added sugars found in foods. These are most concentrated at the tip of the Pyramid, but are also found in foods from the five major food groups. This reveals that some foods within the five food groups are high in fat and/or sugar. People can limit their fat and sugar intake, as suggested by the Dietary Guidelines for Americans, by selecting foods low in fat and added sugars most of the time.

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Holograms

January 28, 2010 by · Leave a Comment 

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A hologram is a flat surface that, under proper illumination, appears to contain a three-dimensional image. A hologram may also project a three-dimensional image into the air—a lifelike image that can be photographed although it cannot be touched. Because they cannot be copied by ordinary means, holograms are widely used to prevent counterfeiting of documents such as credit cards, driver’s licenses, and admission tickets. The word hologram comes from the Greek roots holos meaning whole and gramma meaning message. The process of making a hologram is called holography. When a hologram is made, light from a laser records an image of the desired object on film or a photographic plate.

There are basically two types of holograms. A reflection hologram is viewed when lit from the front, while a transmission hologram is viewed by shining a light through it from the back side. An embossed hologram is made by backing a transmission hologram with a mirror-like substance, which allows it to be viewed when lit from the front. Holograms can also be made that show moving objects; these sequences, called stereograms, are typically three to 20 seconds long.

Although a hologram is a visual image of a physical object, it is quite different from a photograph. For instance, when an object is photographed, each portion of the photo contains an image of the corresponding portion of the original object. Each section of a hologram, however, contains a complete image of the original object, viewed from a vantage point that corresponds to the section’s position on the hologram. Thus, if the transparent plate containing a transmission hologram is broken, each piece will still be able to project the entire image, albeit from a different point of view. Using a piece from near the top of the holographic plate will produce an image as seen from above, while using a piece from near the bottom of the plate will create the impression of looking upward toward the object.

Another interesting property of holograms is that they preserve the optical properties of objects such as lenses. For instance, consider making a hologram of a magnifying glass placed in front of a butterfly. When viewing the holographic image of those objects, an observer will find that the portions of the butterfly seen through the image of the magnifying glass will be enlarged.

Holographic packaging has been shown to increase the sales of certain products. Projection holograms are especially eye-catching and are used at trade shows and retail stores. They can be used to display extremely delicate or valuable objects. A classic example was an image of a diamond-adorned hand that was projected over the sidewalk outside the Cartier jewelry store in New York City in 1970. Not only did it catch the attention of people walking by it, it attracted television news crews. In fact, it was even attacked by an umbrella-wielding pedestrian who thought it was the “work of the devil.” In another instance, rather than repeatedly handling the fragile skull of the 2,300 year old Lindow Man, researchers studied its holographic image. Scotland Yard’s Forensic Science Department used this holographic image to construct a physical model of the remains of the prehistoric man. As yet another application of holography, former Chicago Bears football coach Mike Ditka displayed a holographic portrait of himself in his restaurant to create a somewhat personal image when he could not be there in person.

Holograms can be made at home by hobbyists for a modest investment in equipment. The process requires a laser and an isolation table to prevent movement of the equipment while the film is being exposed. Holograms are also produced commercially and can be reproduced in large quantities. Using stock artwork, a master hologram for mass production can be created for as little as $2,500, whereas using custom artwork can cost $5,000 to $10,000. Reproducing the image costs from 1 to 4 cents per inch (2.5 cm), depending on the volume; this represents a 40% decrease since embossed holograms were first marketed in the late 1970s. Finished holograms can be attached to other objects as pressure-sensitive labels (0.5 to 1.5 cents each) or by hot stamping (2 to 5 cents each). Once the artwork is finalized, it takes about three months to create and reproduce a batch of commercial holograms. It is estimated that more than $200 million worth of embossed holograms were manufactured in 1995.

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Celluloid

January 7, 2010 by · Leave a Comment 

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English photographer John Carbutt founded the Keystone Dry Plate Works in 1879 with the intention of producing gelatin dry plates. The Celluloid Manufacturing Company was contracted for this work by means of thinly slicing layers out of celluloid blocks and then removing the slice marks with heated pressure plates. After this, the celluloid strips were coated with a photosensitive gelatin emulsion. It is not certain exactly how long it took for Carbutt to standardize his process, but it occurred no later than 1888. A 15 inch-wide sheet of Carbutt’s film was used by William Dickson for the early Edison motion picture experiments on a cylinder drum Kinetograph. However, the celluloid film base produced by this means was still considered too stiff for the needs of motion picture photography.

By 1889, more flexible celluloids for photographic film were developed, and both Hannibal Goodwin and the Eastman Kodak Company obtained patents for a film product (Ansco, which purchased Goodwin’s patent when he died, was eventually successful in an infringement suit against Kodak). This ability to produce photographic images on a flexible material (as opposed to a glass or metal plate) was a crucial step toward the advent of motion pictures.

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