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U.S. Morning Call: Markets look to Fed for more stimulus
Dec 12 - The U.S. Federal Reserve is expected to announce a fresh round of bond buying as part of its efforts to support an economic recovery with low interest rates.
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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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4.3 Reducing the nutrient source

Europe is the continent that has suffered most from eutrophication, and increasing efforts are being made to restore European water bodies damaged by nutrient enrichment. If the ultimate goal is to restore sites where nature conservation interest has been damaged by eutrophication, techniques are required for reducing external loadings of nutrients into ecosystems.

Although algal production requires both nitrogen and phosphorus supplies, it is usually sufficient to reduce only one major
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2.1 Effects on primary producers in freshwater ecosystems

Plant species differ in their ability to compete as nutrient availability increases. Some floating and submerged macrophyte species are restricted to nutrient-poor waters, while others are typical of nutrient-rich sites (see Table 2.2). Figure 2.2 shows turbid water in a polluted drainage ditch associated with localized growth of algae. There are no aquatic plants present.

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1.2 Resource availability and species diversity

A wide range of ecosystems has been studied in terms of their species diversity and the availability of resources. Each produces an individual relationship between these two variables, but a common pattern emerges from most of them, especially when plant diversity is being considered. This pattern has been named the humped-back relationship and suggests diversity is greatest at intermediate levels of productivity in many systems (Figure 1.5).

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8.2 Chromosome scaffolds

Most of the chromosomal DNA chains within the interphase nucleus are believed to be held on a scaffold or backbone structure made from various proteins, with loops of between 20 and 200 kb extruding from attachment sites. This chromosome structure is shown schematically in Figure 40. The scaffold, as well as permitting further compaction, serves to bring the DNA together in organised regions. There are many different protein components of these scaffolds, amongst them DNA topoisomerases.


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Nucleosomal DNA packaging into a 30 nm fibre: the role of histone H1

When chromatin is isolated from the nucleus and examined under the electron microscope, it can be seen as a 30 nm fibre. This fibre is formed through the action of the histone H1 on the nucleosomal DNA in the 10 nm fibre. In contrast to the other histone proteins, H1 does not contain the histone fold motif.

Compaction of the 10 nm fibre to give the 30 nm fibre is achieved by interaction of the H1 protein with both the linker DNA and the histone octamers, as shown in Figure 31
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DNA supercoiling and protein binding in the E. coli chromosome

As discussed earlier, the DNA of the E. coli chromosome is highly negatively supercoiled due to the action of the DNA gyrase enzyme (Section 3.2). This negative supercoiling serves to assist in compaction of the DNA, with the repulsive forces of the sugar-phosphate backbones being counteracted by polyamines. Many of the proteins
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7.2 The eubacterial chromosome

Some of the diverse roles of chromatin components can be illustrated by examining the E. coli chromosome. Like most prokaryotes, E. coli has a single chromosome consisting of a single double-stranded circular DNA molecule. There is no nucleus present, but the E. coli DNA is within a discrete entity in the cytoplasm called the nucleoid. The nucleoid contains a multitude of proteins and is in close proximity to the ribosomes, where translation occurs. In addition to
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7.1 Introduction

Until now, we have discussed DNA primarily as a double helix, but in its natural state within the cell it is found packaged as a complex mixture with many different proteins and other components. You have already seen examples of proteins with specific roles to play, such as topoisomerases and the proteins with various DNA binding domains, but in this section we will turn our attention to the proteins that serve to pack and organise the DNA into what we call chromatin.

The packaging of
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6.3 The recognition of specific DNA sequences by proteins

Transcription factors act by binding to specific DNA regions, dependent upon the recognition of particular sequences of bases, usually through direct interactions in the major groove. They are known to use certain motifs for DNA binding and many contain the helix–turn–helix (HTH) or zinc finger motifs. We will now discuss the molecular properties of these two protein motifs that confer DNA binding ability on the proteins that contain them.

The classical HTH motif consists of two
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Acknowledgements

Acknowledgements

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

The material acknowledged below is Proprietary and used under licence (not subject to Creative Commons Licence). See Terms and Conditions.


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4.1 Natural stores of carbon

The major natural stores of carbon (called ‘reservoirs’) are shown below in Figure 1.9.

4 Fossil fuels

Part of the incoming solar energy becomes stored in fossil fuels (oil, gas and coal:
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2.3 Global power demand

In Section 2.2 we calculated a value of 14.3 TW for the average global requirement for primary power in 2002
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7.6 Questions

Question 15

Suppose that a galaxy has emission lines in its optical spectrum. A line of wavelength 654.3 nm is broadened by 2.0 nm. Estimate the velocity dispersion of the gas giving rise to the broadened spectral line. Is it likely to
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7.1 The spectra of galaxies

  • The spectrum of a galaxy is the composite spectrum of the objects of which it is composed.

  • The optical spectrum of a normal galaxy contains contributions from stars and HII regions. An elliptical galaxy has no HII regions and has an optical spectrum that looks somewhat like a stellar spectrum but with rather fainter absorption lines. A spiral galaxy has both stars and star-forming regions, and its optical spectrum is the composite of its st
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6.2 Do supermassive black holes really exist?

One outstanding feature of the black-hole model is that the black hole must be supermassive. Can one at least detect the presence of a massive central object?

  • How might a massive central object be detected using information from galactic rotation curves?

  • By measuring rotation speeds near the nucleus of the galaxy. The faster the rotation speeds, the greater the enclosed mass.

So the answer is yes. In NGC 4151
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Radio-loud AGNs

The second model (Figure 36b) is similar to the first, but now the engine is producing a pair of jets that will eventually end in a pair of lobes, as seen in radio galaxies and some quasars.

Looking at the model from the side, one expects to see narrow lines in the spectrum (but not broad lines) and two
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