Category: AQA Unit 5 Nuclear/ Thermal

Synchrotron yields ‘safer’ vaccine

Synchrotron yields ‘safer’ vaccine

Producing vaccines against viral threats is a potentially hazardous business and that’s why manufacturers have to operate strict controls to ensure that no pathogens escape.

British scientists have developed a new method to create an entirely synthetic vaccine which doesn’t rely on using live infectious virus, meaning it is much safer.

What’s more the prototype vaccine they have created, for the animal disease foot-and-mouth, has been engineered to make it more stable.

That means it can be kept out of the fridge for many hours before returning to the cold chain – overcoming one of the major hurdles in administering vaccines in the developing world.

The research, published in the journal PLOS pathogens, was a collaboration between scientists at Oxford and Reading Universities, the Pirbright Institute, and the UK’s national synchrotron facility, the Diamond Light Source near Oxford.

Diamond is a particle accelerator which sends electrons round a giant magnetic ring at near light speeds.

The electrons emit energy in the form of intense X-rays which are channelled along “beamlines” – into laboratories where they are used to analyse structures in extraordinary detail.


Synchrotrons have been used before to analyse viruses at the atomic level, but the technology has advanced considerably to enable scientists to create a stable synthetic vaccine.

“What we have achieved here is close to the holy grail of foot-and-mouth vaccines.

Unlike traditional vaccines, there is no chance that the empty shell vaccine could revert to an infectious form,” said Dave Stuart, Life Sciences Director at Diamond, and MRC Professor of Structural Biology at the University of Oxford.

“This work will have a broad and enduring impact on vaccine development, and the technology should be transferable to other viruses from the same family, such as poliovirus and hand-foot-and-mouth disease, a human virus which is currently endemic in South-East Asia.”

These human disease threats, like foot-and-mouth, are all picornaviruses.

Viruses are inherently unstable and fragile, but picornaviruses can be studied using X-ray crystallography.

Diamond Light Source The Crystal Lab uses robots

This enables the protein shell of the virus to be analysed at the atomic level – something a billion times smaller than a pinhead.

As with any vaccine, the aim is to prompt the immune system to recognise this outer shell and destroy the pathogen before it has time to lock onto cells and infect them with its genetic material.

In this research the scientists created a synthetic viral shell, but lacking its pathogenic RNA interior – the genetic material the virus uses to replicate itself.

Crucially they were able to reinforce the structure of the viral shell to make it stronger, to improve the stability of the vaccine.

Pre-clinical trials have shown it to be stable at temperatures up to 56C for at least two hours. Foot-and-mouth is endemic in central Africa, parts of the Middle East and Asia, so this would be a significant improvement over existing vaccines.

With current foot-and-mouth vaccines it is difficult to distinguish between immunised livestock and those which have been infected.

That proved to be a major hurdle in controlling the foot-and-mouth outbreak in the UK in 2001 because it would have prevented the export of livestock.

But the synthetic vaccine should allow scientists to show the absence of infection in vaccinated animals.

“The foot-and-mouth-disease virus epidemic in the UK in 2001 was disastrous and cost the economy billions of pounds in control measures and compensation,” explained Dr Bryan Charleston, Head of Livestock Viral Diseases Programme at the Pirbright Institute.

“This important work has been a direct result of the additional funding that was provided as a result of the 2001 outbreak to research this highly contagious disease.”

The potential hazards of working with viruses was underlined in 2007 when the Pirbright laboratory site was identified as the source of a leak which led to an outbreak of foot-and-mouth disease.

Polio, another picornavirus, which exclusively affects humans, has been eliminated from nearly every country in the world, although it stubbornly persists in Nigeria, Pakistan and Afghanistan.

The need for secure vaccine production will become even more vital should polio be wiped out.

“Current polio vaccines, which use live virus for their production, pose a potential threat to the long-term success of eradication if they were to re-establish themselves in the population.

“Non-infectious vaccines would clearly provide a safeguard against this risk”, said Dr Andrew Macadam, a virologist specialising in polio at the National Institute for Biological Standards and Control in Hertfordshire.

“This technology has great potential in terms of cost and biosafety.

“Any design strategy that minimises the chances of accidental virus release would not only make the world a safer place but would lower the bio-containment barriers to production allowing vaccines to be made more cheaply all over the world.”

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Star is Caught Devouring a Planet

Star is caught devouring planet (from the BBC)

Artist's impression of a planet's destruction

Astronomers have found evidence for a planet being devoured by its star, yielding insights into the fate that will befall Earth in billions of years.

The team uncovered the signature of a planet that had been “eaten” by looking at the chemistry of the host star.

They also think a surviving planet around this star may have been kicked into its unusual orbit by the destruction of a neighbouring world.

Details of the work have been published in Astrophysical Journal Letters.

The US-Polish-Spanish team made the discovery when they were studying the star BD+48 740 – which is one of a stellar class known as red giants. Their observations were made with the Hobby Eberly telescope, based at the McDonald Observatory in Texas.

Rising temperatures near the cores of red giants cause these elderly stars to expand in size, a process which will cause any nearbyHobby-Eberly telescope planets to be destroyed.

“A similar fate may await the inner planets in our solar system, when the Sun becomes a red giant and expands all the way out to Earth’s orbit some five billion years from now,” said co-author Prof Alexander Wolszczan from Pennsylvania State University in the US.

Lithium boost

The first piece of evidence for the missing planet comes from the star’s peculiar chemical composition.

Spectroscopic analysis of BD+48 740 revealed that it contained an abnormally high amount of lithium, a rare element created primarily during the Big Bang 14 billion years ago.

 The discovery was made using the Hobby-Eberly telescope in Texas

Lithium is easily destroyed in stars, so its high abundance in this ageing star is very unusual.

“Theorists have identified only a few, very specific circumstances, other than the Big Bang, under which lithium can be created in stars,” Prof Wolszczan explained.

“In the case of BD+48 740, it is probable that the lithium production was triggered by a mass the size of a planet that spiralled into the star and heated it up while the star was digesting it.”

The second piece of evidence discovered by the astronomers is the highly elliptical orbit of a newly discovered planet around the red giant star. The previously undetected world is at least 1.6 times as massive as Jupiter.

Co-author Andrzej Niedzielski of Nicolaus Copernicus University in Torun, Poland, said that orbits as eccentric as this one are uncommon in planetary systems around evolved stars.

“In fact, the BD+48 740 planet’s orbit is the most elliptical one detected so far,” he added.

Because gravitational interactions between planets are often responsible for such peculiar orbits, the astronomers suspect that the dive of the missing planet toward its host star before it became a giant could have given the surviving massive planet a burst of energy.

This boost would have propelled it into its present unusual orbit.

Team member Eva Villaver of the Universidad Autonoma de Madrid in Spain commented: “Catching a planet in the act of being devoured by a star is an almost improbable feat to accomplish because of the comparative swiftness of the process, but the occurrence of such a collision can be deduced from the way it affects the stellar chemistry.

“The highly elongated orbit of the massive planet we discovered around this lithium-polluted red giant star is exactly the kind of evidence that would point to the star’s recent destruction of its now-missing planet.”

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France expands nuclear power plans despite Fukushima

BBC News Update……… People look at the construction site of the third-generation European Pressurised Water nuclear reactor (EPR) in Flamanville, north-western France, in this file picture taken in April 2011

With dwindling fossil fuel supplies, France is increasingly reliant on its nuclear power plants which now provide it with three-quarters of its electricity

In the aftermath of Japan’s nuclear crisis at Fukushima, some European nations are rethinking their atomic plans. But France, home to 58 of 143 reactors in the EU, remains nuclear energy’s champion, and plans not to retire its power stations but to expand them. Emma Jane Kirby examines why.

For many tourists visiting the tranquil north Normandy coast, the giant EPR reactor at Flamanville is little more than a lamentable industrial scar on a rather beautiful landscape.

But to the French government, Flamanville’s European Pressurised Reactor (EPR) is the embodiment of the future.

Following the disaster at Japan’s Fukushima nuclear power station – which was heavily damaged by the deadly 11 March quake and tsunami – President Nicolas Sarkozy announced there would be an audit of all nuclear facilities.

But he added firmly that France would not be rethinking its nuclear energy policy as neighbours Germany, Italy and Switzerland have.

Unlike Germany’s reversal of policy on Monday that will see it phase out the country’s 17 nuclear power stations by 2022, Mr Sarkozy said France was confident that nuclear energy was safe and it was “out of the question” to end nuclear power.

The EPR being constructed in Flamanville is marketed as the most secure power station yet.

A protester wearing a gas mask stands in front of the construction site of the third-generation European Pressurised Water nuclear reactor (EPR) in Flamanville, during an anti-nuclear demonstration, on 23 April, 2011Anti-nuclear protesters have made their thoughts about the Flamanville expansion abundantly clear. It is built by EDF, a company which is 80% owned by the French government. The system is organised into four sub-systems (current plants in operation only have two), each located in separate rooms away from the reactor building.

Simultaneous failure of the systems is regarded as almost impossible; the idea is that if an incident were to occur on one of the systems, the reactor could continue to operate safely during repairs, as at least two other systems would remain available.

In the event of a meltdown, the core would be isolated by the reactor building’s dual-wall containment which has one wall in pre-stressed concrete designed to withstand significant increases in pressure, and the second in reinforced concrete, known as the concrete shell. But many French people – including Didier Anger, an anti-nuclear campaigner and former MEP – are not convinced.

Tsunami breaching the power plant's defences (Image: TEPCO)Fukushima was heavily damaged by the 11 March quake and tsunami. “That’s just propaganda,” Mr Anger told the BBC at his home a few miles inland from Flamanville. He pointed to the strong ties between EDF and the French government and asked how we could trust the government’s word about nuclear safety when it owns such a massive stake in the company that builds the reactors? It was all, he insisted, the “same club”.

“France claims to be a democracy,” he laughed. “But in terms of the nuclear industry we are yet to prove that! “A few weeks ago, after Fukushima, the current director of our nuclear safety authority announced in front of MPs that perhaps we should stop the EPR reactor to look at any possible problems.

“A few hours later he was made to back-pedal… he was silenced… because the power of the old boys’ network is formidable in France.”

Two years ago, cracks were found in the concrete base of the reactor dome at Flamanville and welding proved to be sub-standard. Addressing those safety issues has meant the project is now at least two years behind schedule and way over budget.

This week, European nuclear watchdogs must start safety checks – or stress tests – on their nuclear facilities to make sure they could withstand an earthquake or tsunami like that at Fukushima. Although a 9m (30 ft) wave is unlikely on the North Normandy coast at Flamanville, Prof Jacques Foos, one of France’s most respected nuclear scientists, says all precautions must be taken. “The accident at Fukushima proved completely extraordinary events can happen,” he told me. “So what would happen if a giant wave did hit one of our nuclear power plants? We need to check that out. “I’m not saying we need to think about every eventuality such as what would happen if we were struck by a meteorite… but I am saying that when we build nuclear power plants now, we have to think the unthinkable.” The high-tech EPR reactor at Flamanville has been designed to withstand disasters such as a plane crash – but older reactors will not have such sophisticated security systems. Claude Birraux, an MP with President Sarkozy’s governing UMP party, has been chairing the official French parliamentary inquiry into the Fukushima accident, and hopes that the EU stress tests coupled with the separate French audit will help to reassure a nervous French public.

Environmentalist group Greenpeace activists are suspended next to protest banner on one of the cooling towers of the nuclear plant of Belleville-sur-Loire, central France, in March 2007Critics say businesses are scared off by the EPR reactor

“There will be a review made by the safety authorities and if one nuclear power plant is not able to answer to those questions (set by the EU), it can maybe be shut down,” he said. “Maybe.”

Nuclear technology is one of France’s major exports. Three years ago, France struck a deal with the UK to build four new EPR reactors in Britain but in December 2009 it lost a $40bn (£24bn) reactor deal with Abu Dhabi amid recriminations that it was too costly.

President Sarkozy insisted that the deal was lost because its high safety standards drove up the cost. Professor Jacques Foos hopes that in a post-Fukushima world its “safety first” EPR reactors will bring in more business for France. “We will see a boost in sales now,” he said confidently. “Because who would baulk at paying for safety these days? You can’t have a reactor these days that’s thought of as being too safe.” A boost in sales should result in a boost in jobs but that’s not an argument that holds much sway with anti-nuclear campaigner Didier Anger. Building on a second EPR reactor on the Normandy coast at Penly begins next year but Mr Anger doubts it will boost employment.

“In Flamanville, we thought the EPR would bring a lot of employment… but 50% of the workers are from Poland or Romania, or at least not from here,” he complained. He pointed to the high 9.7% unemployment rate in the Cherbourg area and asked me why I thought the jobless total was so high. “It’s because a lot of businesses are scared off by the EPR reactor,” said Mr Anger. “They think what if there was an accident? The exclusion zone would be 20km [12 miles] or more. That’s no good for business… so they don’t set up here.”

Nuclear landscape? But if France is to make more sales with the EPR reactor, who will the new customers be when most of Europe appears to be pulling out of the nuclear energy game and mothballing their old reactors? Could nuclear technology be sold to countries which simply aren’t ready to deal with the potential risks?

Chernobyl's Number Four Reactor - 20 April 2011Memories of the disaster at Chernobyl linger in France quarter of a century later. MP Claude Birraux insists that France will only sell nuclear technology to responsible countries. “There are three rules: safety, safety and safety, whatever the cost,” he said. “You need to have regulation, legislation and you need an independent safety authority… otherwise no… you can’t have it.”

France began developing its civilian nuclear programme as a response to oil shortages in the 1970s. With dwindling fossil fuel supplies, the country is increasingly reliant on its nuclear power plants which now provide it with three-quarters of its electricity.

Nuclear energy, said Claude Birraux, was essential for “French independence”. With 58 nuclear reactors already in operation here, sites like Flamanville look likely to be part of the French landscape for many years to come.

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UK’s atomic clock ‘is world’s most accurate’

This is an article from BBC Science, really useful for how we work out units!

By Jason Palmer Science and technology reporter, BBC News, Teddington

Caesium clock at NPL (NPL)An atomic clock at the UK’s National Physical Laboratory (NPL) has the best long-term accuracy of any in the world, research has found.

Studies of the clock’s performance, to be published in the journal Metrologia, show it is nearly twice as accurate as previously thought.

The clock would lose or gain less than a second in some 138 million years.

The UK is among the handful of nations providing a “standard second” that keeps the world on time.

However, the international race for higher accuracy is always on, meaning the record may not stand for long.

The NPL’s CsF2 clock is a “caesium fountain” atomic clock, in which the “ticking” is provided by the measurement of the energy required to change a property of caesium atoms known as “spin”.

By international definition, it is the electromagnetic waves required to accomplish this “spin flip” that are measured; when 9,192,631,770 peaks and troughs of these waves go by, one standard second passes.

Matching colours

Inside the clock, caesium atoms are gathered into bunches of 100 million or so, and passed through a cavity where they are exposed to these electromagnetic waves.

The colour, or frequency, is adjusted until the spins are seen to flip – then the researchers know the waves are at the right frequency to define the second.

The NPL-CsF2 clock provides an “atomic pendulum” against which the UK’s and the world’s clocks can be compared, ensuring they are all ticking at the same time.

That correction is done at the International Bureau of Weights and Measures (BIPM) in the outskirts of Paris, which collates definitions of seconds from six “primary frequency standards” – CsF2 in the UK, two in France, and one each in the US, Germany and Japan.

For those six high-precision atomic pendulums, absolute accuracy is a tireless pursuit.

At the last count in 2010, the UK’s atomic clock was on a par with the best of them in terms of long-term accuracy: to about one part in 2,500,000,000,000,000.

What time is it, exactly?

World clock

  • The international time standard is maintained by a network of over 300 clocks worldwide
  • These are sent by satellite and averaged at BIPM, a measurement institute in France
  • But the “tick” of any one of them could drift out of accuracy, so BIPM corrects the average using six “primary frequency standards” in Europe, the US and Japan
  • Their corrected result, “International Atomic Time”, is occasionally compared with the time-honoured measure of time by astronomical means
  • Occasionally a “leap second” is added or subtracted to correct any discrepancy

But the measurements carried out by the NPL’s Krzysztof Szymaniec and colleagues at Pennsylvania State University in the US have nearly doubled the accuracy.

The second’s strictest definition requires that the measurements are made in conditions that Dr Szymaniec said were impossible actually to achieve in the laboratory.

“The frequency we measure is not necessarily the one prescribed by the definition of a second, which requires that all the external fields and ‘perturbations’ would be removed,” he explained to BBC News.

“In many cases we can’t remove these perturbations; but we can measure them precisely, we can assess them, and introduce corrections for them.”

The team’s latest work addressed the errors in the measurement brought about by the “microwave cavity” that the atoms pass through (the waves used to flip spins are not so far in frequency from the ones that flip water molecules in food, heating them in a microwave oven).

A fuller understanding of how the waves are distributed within it boosted the measurement’s accuracy, as did a more detailed treatment of what happens to the measurement when the millions of caesium atoms collide.

Without touching a thing, the team boosted the known accuracy of the machine to one part in 4,300,000,000,000,000.

But as Dr Szymaniec said, the achievement is not just about international bragging rights; better standards lead to better technology.

“Nowadays definitions for electrical units are based on accurate frequency measurements, so it’s vital for the UK as an economy to maintain a set of standards, a set of procedures, that underpin technical development,” he said.

“The fact that we can develop the most accurate standard has quite measurable economic implications.”

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Exam Past Papers Unit 5 & 5D

Here is a zipped file structure to download to your PC. It contains all the exam questions from AQA for Unit 5 from 2002 to 2010. Remember this includes the legacy or old spec papers from 2002-8 which are very similar.

Turning Points Exam Papers 2002_10

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The Electron a “charged particle”

The story of cathode rays begins in 1855. In that year, Heinrich Geissler invented the mercury vacuum pump. With the pump he could remove almost all of the air from a sealed glass tube.  Geissler’s friend Julius Plucker used the pump to evacuate a special kind of tube. Inside the tube were two electrodes. Plucker attached one electrode, called the anode, to the positive terminal of a battery. He attached the other electrode, the cathode, to the negative terminal. He noticed that the glass near the cathode glowed with greenish light. When Plucker held a magnet near the tube, the glowing spot moved.  Plucker’s student, Johann Wilhelm Hittorf, put solid objects inside the tube between the cathode and the glow. The objects cast shadows. Hittorf concluded that the cathode was emitting something that travelled in straight lines, like light rays. The German physicist Eugen Goldstein named them “cathode rays.”

The English scientist William Crookes thought cathode rays were streams of molecules that had picked up a negative electric charge. Crookes knew from the laws of electricity and magnetism that a charged particle in a magnetic field would move in a circle. Since a magnetic field caused cathode rays to move in a circle, Crookes reasoned, they must be made of charged particles.

If cathode rays were streams of charged particles, an electric field also should have deflected their path. The German physicist Heinrich Hertz tested this hypothesis. He set a cathode ray tube between two metal plates. One plate was positively charged and the other was negatively charged. Negatively charged molecules should have been attracted to the positive plate. When Hertz connected his tube to the battery, the cathode rays kept going in a straight line. Hertz concluded that the cathode rays were a new kind of electromagnetic wave.  Hertz’s student, Philipp Lenard, designed a cathode ray tube with a thin foil at one end. The cathode rays went right through the foil. Since molecules of gas could not go through the foil, Lenard knew that cathode rays could not be charged molecules. He agreed with his teacher that they must be electromagnetic waves.

Then Jean-Baptiste Perrin conducted a very simple but very clever experiment. He accelerated a beam of electrons in a glass tube. You can see at the start of my video how the spot on the glass tube is the impact of the electrons causing fluorescent on paint on the inside of the tube. He then setup a magnetic field at 90 degrees to the beam using coils of wire (Helmholz coils). As you increase the current flow inside the coils the field becomes stronger causing the beam to curve according to Flemings LH rule of FBI. Now as the beam is directed down to a collector which is connected to a gold leaf electroscope the leaf rises. This shows us that the beam is in fact charged. Further experiments show the charge is also negative. This is evidence that cathode rays are in not part of the EM Spectrum.

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