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One Entrepreneur’s Plan to Transform Africa
Fred Swaniker’s African Leadership Academy and his African Leadership Network are already helping thousands of young people become entrepreneurs, activists and professionals. His latest effort, the African Leadership Universities, could multiply that exponentially.
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6.637 Optical Signals, Devices, and Systems (MIT)
6.637 covers the fundamentals of optical signals and modern optical devices and systems from a practical point of view. Its goal is to help students develop a thorough understanding of the underlying physical principles such that device and system design and performance can be predicted, analyzed, and understood. Most optical systems involve the use of one or more of the following: sources (e.g., lasers and light-emitting diodes), light modulation components (e.g., liquid-crystal light modulato
Author(s): Warde, Cardinal

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Content within individual OCW courses is (c) by the individual authors unless otherwise noted. MIT OpenCourseWare materials are licensed by the Massachusetts Institute of Technology under a Creative C

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2.7 Fluorine (F)

Fluoride ions (F) are rare in foods, though some are found in tea and in seafood. However, fluoride does occur naturally in some water supplies, derived from the rocks through which the water flows. Its only role in the body appears to be to help to protect teeth from decay.

The stages of tooth decay are as follows:

  • bacteria live in saliva on teeth (form plaque)

  • produce lactic acid → dissolves calcium salts in tooth
    Author(s): The Open University

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    Copyright © 2013 The Open University

Demise of the Anasazi
A climate change resulted in the Anasazi being driven by hunger from their homes and their civilization collapses. Lessons that are explained are too many people and not enough resources.

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Commercial-Refrigerator-Freezer-Combo

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