Diffusion essay

Rogers and Karyn L. I still consider good information to be the best medicine. DeBakey, Chair, Board of Regents, National Library of Medicine Introduction The purpose of the present essay is to derive lessons learned from past research on the diffusion of innovations that could be utilized in medical library outreach.

Diffusion essay

RUBY Ruby is corundum whose Diffusion essay coloring derives from chromium impurities, all other color varieties of this mineral species being referred to as sapphire.

The ruby color range includes pinkish, purplish, orangey and brownish red gems depending on the chromium and iron content.

Diffusion essay

The trace mineral content tends to vary with the geologic formation which produced the ruby, so that original place adjectives, such as Burmese and Thai, have come, in later years, to be sometimes used in describing color.

The stone below is an example of a corundum gem that some would call a ruby and for which some, more conservatively. The old saying about questionable stones goes: Unless the seller specifically states the stone is unheated you should assume that some kind of heat treatment has been used.

Generally, high temperature heating and controlled cooling is done Diffusion essay clarify the stones, especially by dissolving "silk" rutile ; but it can also improve tone and saturation of color. Such treatments can only be detected in stones whose residual inclusions, or surfaces, show signs of heat stress; so completely flawless stones will give no clues, and cannot be positively verified as unheated.

For this reason such enhancement does not radically lower the value of ruby gems. Not so for gems treated with traditional dyeing red ruby oil or other, more recently invented, treatments such as surface or lattice diffusion, or glass infilling.

With the possible exception of some of the latest diffusion processes routine gemological tests can detect the treatments. These stones are both the easiest to identify and the least expensive to produce.

Such stones often show diagnostic growth features called "curved striae", never seen in natural gemstones. More complex processes have been developed in recent years such as flux melting and hydrothermal synthesis. These so closely simulate natural formation conditions that colors, and even inclusions, look extremely natural, and such stones are difficult for all but the most highly skilled professionals to identify as man-made.

Luckily there are several diagnostic inclusions such as "fingerprints" which identify a gem as natural ruby, and others which in many cases, can provide evidence for or against heating. Ruby simulants are many and varied including natural gems such as red spinel, rubellite tourmaline and garnet, and man made or enhanced materials like glass and dyed quartz.

Historically, various assembled stones such as garnet and glass doublets have been used as well. Of course, a heavily included or fractured stone will be less stable. For reasonably clean stones, no special wear or care precautions are necessary.

Ruby shows pleochroism, which means that the color varies with the direction of viewing. Gemologists use a simple tool called a dichroscope to test for this property, which will easily discriminate ruby from its natural simulants like red spinel, garnet and also from glass.

Most rubies show distinct purplish red and orangey red colors pleochroic colors, and the dichroscope displays them side by side for easy comparison.

Burmese rubies often fluoresce so strongly that the effect is noticeable even in sunlight. Such stones seem literally to glow, and are greatly admired. Thai and African stones generally lack this property due to their higher iron content.The "traditional" view is that Eastern European Jews descend almost entirely from French and German Jews.

This essay presents the pros and cons of the controversial "Khazar theory" of Eastern European Jewish origins and will attempt to provide a likely middle-ground solution to the question.

Published: Mon, 5 Dec Water scarcity is the major problem that is faced all across the world.

Diffusion of Innovations Model -- Rogers and Scott Report

Although 2/3rd of the earths crust is made up of water but all this water is not available for drinking and for other human activities as either it is locked in the form of ice or present in the form of vast saline oceans and seas.

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Studies have shown that when people have too many options, they avoid making a decision. ENVIRONMENTALISM AND EUROCENTRISM: A REVIEW ESSAY. J. M. BLAUT "Environment molds history," says Jared Diamond in _Guns, Germs, and Steel: The Fates of Human Societies_ (p.

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