2.3.2 Fast breeder reactors

If fast neutrons produced in the chain reactions are not moderated or absorbed, the rate of conversion of uranium-238 into plutonium-239 (Equation 3) can exceed the fission rate of plutonium-239. Reactors that use fast neutrons in this way are called fast breeder reactors.

Their main fuel is
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3.2 Uranium occurrence and ore deposits

In igneous rocks, uranium is more abundant in granites (~3.5 ppm) than in basalts (~1 ppm). The large size of the uranium atom prevents it from easily entering the structures of common rock-forming minerals, so it is an incompatible element that tends to remain in magmas until a late stage of crystallisation, when it enters minor minerals, or even the uranium oxide, uraninite (UO2). In suitable circumstances, following fractional crystallisation of uranium-rich granitic magm
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Virtual Maths, Shapes, Space and Measure, Demonstration of a Theodolite Survey in action
Using a theodolite to calculate the height of a building, demonstration 'in the field', includes interactive simulation tools and formulae
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4.3.5 Domestic campaigns

An important aspect of efforts to reduce nutrient inputs to water bodies is the modification of domestic behaviour. Public campaigns in Australia have encouraged people to:

  • wash vehicles on porous surfaces away from drains or gutters

  • reduce use of fertilizers on lawns and gardens

  • compost garden and food waste

  • use zero- or low-phosphorus detergents

  • wash only full loads in washing machines


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2.4.1 Electromagnetism and fields

When Newton wrote about 'The System of the World' in Part 3 of Principia, the only forces he could discuss in any detail were the contact forces that arose when one object touched another, and gravity, which acted at a distance. Even so, Newton thought that there were other forces at work in the world, and hoped they might eventually be brought within his overall scheme just as gravity had been. In fact, Newton wrote:


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7.8 Summary of Section 7

This section has sought to illustrate the formation of connections between neurons and their targets by exploring a few examples. The picture that emerges is one of cells at different stages of development subjected to a vast array of signals. These signals are the medium through which environmental factors exert their effects. To some of these signals, some cells respond; to other signals, other cells respond. What a cell, a neuroblast, a growth cone actually does is dependent on the combina
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18.417 Introduction to Computational Molecular Biology (MIT)
This course introduces the basic computational methods used to understand the cell on a molecular level. It covers subjects such as the sequence alignment algorithms: dynamic programming, hashing, suffix trees, and Gibbs sampling. Furthermore, it focuses on computational approaches to: genetic and physical mapping; genome sequencing, assembly, and annotation; RNA expression and secondary structure; protein structure and folding; and molecular interactions and dynamics.
Author(s): Lippert, Ross

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20.440 Analysis of Biological Networks (BE.440) (MIT)
This class analyzes complex biological processes from the molecular, cellular, extracellular, and organ levels of hierarchy. Emphasis is placed on the basic biochemical and biophysical principles that govern these processes. Examples of processes to be studied include chemotaxis, the fixation of nitrogen into organic biological molecules, growth factor and hormone mediated signaling cascades, and signaling cascades leading to cell death in response to DNA damage. In each case, the availability o
Author(s): Essigmann, John,Sasisekharan, Ram

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1 Natural groups

Darwin made extensive observations on a great many creatures, including mammals, and noticed that species fell into natural groups, e.g. lions, tigers and leopards have many similarities, and resemble cats. On the basis of his observations, he was able to place mammals in distinct groups.

His work has continued, and we now recognise that mammals have evolved from a common ancestor, and have branched into many different groups, or ‘Orders’. The animation below shows the different O
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6.2.4 The speed and direction of the Earth's motion

The first significant claim to have detected the motion of the Earth relative to the ‘frame of isotropic 3 K radiation’ came in 1977 from a group at Berkeley, California. They concluded that the Earth is moving at a speed of (390 ± 60) km s−1, in a direction towards the constellation Leo, relative to a frame in which the 3 K radiation is isotropic. Their conclusion resulted from observations of a variation of intensity with angle of the form predicted by Equation 14, which w
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5.3 The redshift of the 3 K radiation

The temperature, T, of the radiation is proportional to the most probable photon energy, E, which as we have said is proportional to f, and hence inversely proportional to the wavelength λ. Thus,

According to Equation 1, we have for the
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FOAMCARP closed cell aluminium foam
Additions such as SiC are made to molten aluminium or aluminium alloy to modify the melt viscosity and make it suitable for foaming. Calcium carbonate is then added to the melt which is solidified to form a precursor which can be foamed in a controlled manner by a subsequent heat treatment. The resulting foam has a fine and relatively uniform cell structure.
Author(s): DoITPoMS, University of Cambridge,D C Curran, Depa

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Socially Responsible Investing
The Center for Leadership Ethics presented the 2014 Executive Ethics Symposium August 29, 2014 at The Lodge on the Desert
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Radio Lingua Network News: 5 September 2008
The latest news from Radio Lingua including details of Coffee Break Spanish arrangements, new podcasts launched this autumn and the Radio Lingua video contest in which you can win an iPod.
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Husky Football Legend Napoleon Kaufman
Get caught up with the UW's all-time rushing yards leader, Napoleon Kaufman - from his time as part of the Husky national championship team, through his pro football career, to his current role as a senior pastor for the Well Christian Community Church in Livermore, California. Napoleon Kaufman, former Husky football player, senior pastor, Well Christian Community Church 04/26/2015 uwtv.org/uw360
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3.5.1 Final arousal

Emergence can be viewed as the final step in the series of periodic arousals. Instead of re-entering hibernation, the animal maintains the euthermic condition. The cue for maintaining this final arousal is probably not temperature, as some species emerge when T a is well below zero. It is also difficult to see how arousal could be affected by daylength, since the hibernating animal is usually underground in a cavity or a burrow. Perhaps fat or food stores reach a minimum lev
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Las células eucariotas
OpenStax College
Al final de esta sección serás capaz de: Describir la estructura de las células (eucariotas) de plantas y animales. Puntualizar el papel de la membrana plasmática. […]

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An introduction to energy resources

Understanding energy resources involves considering all types of energy source from various sci
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Learn to Write the Upper Case Letters of the Alphabet
This video demonstrates how to write the 26 letters of the alphabet in capitals. Each capital letter's name is read by the narrator, while the correct pen stroke is illustrated via animation. (4:13)
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7.343 Protein Folding, Misfolding and Human Disease (MIT)
This course is one of many Advanced Undergraduate Seminars offered by the Biology Department at MIT. These seminars are tailored for students with an interest in using primary research literature to discuss and learn about current biological research in a highly interactive setting. The instructor for this course, Dr. Kosinski-Collins, is a member of the HHMI Education Group. Maintenance of the complex three-dimensional structure adopted by a protein in the cell is vital for function. Oftentimes
Author(s): Kosinski-Collins, Melissa

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