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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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4.4.2 Phosphate stripping

It has been estimated that up to 45% of total phosphorus loadings to freshwater in the UK comes from sewage treatment works. This input can be reduced significantly (by 90% or more) by carrying out phosphate stripping. The effluent is run into a tank and dosed with a product known as a precipitant, which combines with phosphate in solution to create a solid, which then settles out and can be removed. It is possible to use aluminium salts as a precipitant, but the resulting sludge contains tox
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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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Summary of Section 7

  1. Packaging of DNA serves to protect against damage, to compact the DNA helix into a suitable size within the cell, and to act as both a platform for and an intrinsic part of the structural and regulatory machinery involved in DNA metabolism.

  2. DNA compaction in prokaryotes achieved through a combination of supercoiling and interactions with proteins that aid DNA bending.

  3. Compaction of the eubacterial chromosome is facilitated
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Core histone tail modification regulates DNA compaction

SAQ 34

What effect would neutralising the positive charges on the octamer N-terminal tails have upon the compaction of DNA by H1?

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2.8 Treatments for obesity

At this point you may be wondering what the range of studies that we have examined might suggest in terms of treatment for obesity. As you have seen, weight gain essentially arises from an imbalance of energy supply and energy expenditure. Therefore it is not surprising that dieting (restriction of energy input) and exercise (increased energy output) are recommended both to reduce body weight and also for their additional health benefits. However, even a quick survey of the research literatur
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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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2.6 Obesity and ageing

So, it seems that a part of the explanation for Ron's obesity, and the health problems that have led him to seek medical advice, may relate to the environment in which he is living, and more specifically the diet that he has chosen. It may also be a diet that is especially effective in activating the reward circuits in Ron's brain. However, Ron is also in his later middle age. A longitudinal study of people of this age in the USA suggests that average body weight increases by 1–2 kg per dec
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2.4 Obesity – an evolutionary perspective

If you were now to take a broader biological approach to the data discussed in the previous section you might still be puzzled. Excess body weight leads to a variety of diseases, including diabetes, osteoarthritis and so on – surely this must reduce overall biological fitness.

SAQ 21

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1.5 Obesity

At the time of writing (2004) 20% of the adult population of the UK is classified as obese. The number of obese children has doubled since 1982, 10% of six year olds and 17% of fifteen year olds are now classified as obese. As shown in Table 4, obesity is recognized when the BMI exceeds 30 and occurs quite simply wh
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1.3 Balanced energy intake

There is a need for a certain daily energy intake to allow metabolism to occur in the body. Metabolism means all the chemical reactions occurring in the body and there are two types of process involved: catabolism breaks down larger molecules into smaller ones often with energy release and anabolism is the building up of larger molecules from smaller precursors, often requiring energy. The body requires energy to power anabolic, mechanical (for example, muscle contraction
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2.4 Summary of Section 2

  1. The water cycle involves the movement of water, in all its forms, over, on and through the rocks near the surface of the Earth in a cycle. This cycle is driven by the Sun's energy and the Earth's gravity. The total volume of water in the cycle is virtually co
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