Stichtng Weet wat je besteedt : Hoe omgaan met je geld
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De Stichting wil jongeren advies geven over het goed omgaan met geld met het doel financieel zelfredzaam te worden. Door middel van de crowd-sourced film Edgie waarin Wouter Bos, voormalig Nederlands minister van …


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Chocoladetraject : Educatief Pakket
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Het chocoladetraject is een gratis educatief pakket voor lessen over transport en logistiek.

Het betreft materiaal voor een vakoverschrijdend project waarin de vakken aardrijkskunde, techniek en Nederlands aan bod komen en er ook …


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Educatief gsm-gebruik : Lespakket
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Gsm's en school: het is niet altijd een goed huwelijk. Ze kunnen soms ordeverstorend zijn. Maar anderzijds heeft bijna elke leerling er één en zou het een gemiste kans zijn om er op school geen aandacht aan te besteden. …


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Verantwoord omgaan met Wi-Fi en gsm-straling op school
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Computers, gsm’s en allerhande moderne communicatietechnologie zijn niet meer weg te denken uit de leefwereld van kinderen en jongeren. Kinderen en jongeren en in toenemende mate ook hun ouders, verwachten dat ze hun toestellen ook op school …


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French Naughts and Crosses
French Naughts and Crosses.
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Activation and information in working memory and attention

Bradley R. Postle, recorded 12/5/12


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Excitonics

An exciton is an excitation that mediates the absorption and emission of light, especially in low-cost disordered solar cell and LED materials. In the Center for Excitonics, we seek to supersede traditional electronics with devices that use excitons to mediate the flow of energy. In my presentation, I’ll describe two applications of excitonics in devices: high-brightness quantum dot-based LEDs, and exciton fission in high efficiency solar cells.


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Liquid Biofuels: An International Solution to an International Challenge

Concerns about national security issues and global warming have kindled interest in production of liquid biofuels. In order to minimize the conflict between food and fuel use, it is increasingly important to establish systems for the efficient production of biofuels from non-food polysaccharides such as renewable lignocellulosic biomass or directly from carbon dioxide and other gases. Ethanol, typically used as “biofuel” in cars— alcohol refined from grain or sugar cane &mda
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How Far Can a Shirt See: The Birth of a Revolution in Fibers and Fabrics

Fibers and fabrics are among the earliest forms of human expression; these materials shield us from the environment and play an important role in defining who we are. Surprisingly, in sharp contrast to other areas of our existence, fibers have remained practically unchanged for thousands of years.

Can fibers become highly functional objects similar to computers and smartphones? Can they see, hear, sense, and communicate? Our research focuses on extending the f
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Acknowledgements

The content acknowledged below is Proprietary (see terms and conditions). This content is made available under a Creative Commons Attribution-NonCommercial-ShareAlike 2.0 Licence

Grateful acknowledgement is made to the following sources for permission to reproduce material in this unit:

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5 Summary

  1. Eutrophication is a process in which an ecosystem accumulates mineral nutrients. It can occur naturally, but is usually associated with human activity that releases nutrients into the environment.

  2. Anthropogenic eutrophication has caused a widespread loss of biodiversity in many systems. Recent attempts to reverse the process are proving difficult and expensive.

  3. Symptoms of eutrophication are most readily seen in aquatic sys
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4.4 Reducing nutrient availability

Once nutrients are in an ecosystem, it is usually much harder and more expensive to remove them than tackle the eutrophication at source. The main methods available are:

  • precipitation (e.g. treatment with a solution of aluminium or ferrous salt to precipitate phosphates);

  • removal of nutrient-enriched sediments, for example by mud pumping; and

  • removal of biomass (e.g. harvesting of common reed) and using it for thatchi
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3.2 Anthropogenic sources of nutrients

In addition to the natural sources of nutrients referred to above, nitrogen and phosphorus enter the environment from a number of anthropogenic sources. These are considered below.


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3.1.1 Phosphorus

Phosphorus has a number of indispensable biochemical roles and is an essential element for growth in all organisms, being a component of nucleic acids such as DNA, which hold the code for life. However, phosphorus is a scarce element in the Earth's crust and natural mobilization of phosphorus from rocks is slow. Its compounds are relatively insoluble, there is no reservoir of gaseous phosphorus compounds available in the atmosphere (as there is for carbon and nitrogen), and phosphorus is also
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2.7 A gene ‘for’ obesity?

So far we have mostly emphasized the way in which different environmental factors may affect body weight and provide a partial explanation of both individual cases of obesity and the increase in average body weight that has been so clearly documented in both North America and Western Europe during the last two decades. There is also marked individual variability in body weight. For example, any weight between about 58 and 78 kg would be regarded as ‘desirable’ for a person of height 1.77
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Acknowledgements

The material acknowledged below is contained in Chapter 3 of An Introduction to Galaxies and Cosmology (eds Mark H Jones and Robert J Lambourne), published by the Press Syndicate of The University of Cambridge  in association with The Open University. Copyright © The Open University, 2003, 2004.

This publication forms part of an Open University course S282 Astronomy.


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5.1 Introduction

So far we have seen how the properties of the central engine of the AGN can be accounted for by an accreting supermassive black hole. Though there are many questions still to be resolved, this model does seem to be the best available explanation of what is going on in the heart of an AGN. But of course all AGNs are not the same. We have identified four main classes and in this section we will attempt to construct models that reproduce the distinguishing features of these four classes.


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