RESEARCH in Jülich

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:: INTO OBLIVION

Jülich Researchers Pursue New Lead in Alzheimer’s Case :: Black Carbon: The Underrated Climate Threat

:: Pedestrian Simulation: Pushing and Shoving for Science

The Magazine from Forschungszentrum Jülich 03|2013

RESEARCH

in Jülich

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:: IN THE PICTURE

Is it a globe that’s deflating? No, not at all. This blue sphere measures about a twentieth of a millimetre and consists of pure tungsten. The sphere was produced in the electron beam test facility JUDITH, where Jülich researchers expose materials to high thermal loads. Inside JUDITH, even tungsten – the metal with the high- est melting point of all the elements – can melt and then solidify again within a fraction of a millisecond, forming bizarre shapes. What appear to be ‘continents’

under a scanning electron microscope clearly show that the crystal lattice created in this process is not uniform. Tungsten is currently the material of choice for an envisaged extreme application: it will be used to cover particularly vulnerable parts of the wall in the future fusion reactor ITER – where it will enclose a plasma with a temperature of up to 100 million°C.

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6 16 22

3 | 2013 Research in Jülich

3 :: NEWS IN BRIEF 4

:: COVER STORY 6

6 New Suspect in Alzheimer’s Case Hot on the heels of what is causing the disease

11 What Good is Diagnosis Without Treatment?

Interview with Prof. Dieter Sturma

:: RESEARCH AT THE CENTRE 12

12 Long-Haul Trucks: Engine Off – Fuel Cell On Clean energy source in the driver’s cabin

14 The Underrated Climate Threat Soot particles put climate and health at risk

15 On the Road to Recovery Arctic ozone layer is on the mend

16 Two Thousand’s a Crowd Volunteers push and shove for science

18 Tyres, Friction, and Clever Calculations Computers calculate the perfect mix

20 The Voice as a Door Opener Where our brain judges others

:: LAST BUT NOT LEAST 22

22 Fact-Finding in the Forest

Scientists examine ecological restoration in Eifel National Park 23 Publication Details

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Research in Jülich 3 | 2013

4 Ultrafast Pulses for Computers of the Future

Soil Moisture Data Improve Weather Forecasts

Fuel Cells Successful in Endurance Test

Institute of Bio- and Geosciences | Jülich researchers and their partners from the German Aerospace Center (DLR) took to the air to determine soil moisture in the catchment area of the river Rur this spring. Soil moisture influences the exchange of energy and water between the soil and the atmosphere, and is a parameter that will help to improve weather forecasts and flood predictions. During their measurements, the researchers tested a combination of two different types of microwave probes. This combination is currently being optimized for a planned NASA satellite mission in 2015. ::

Peter Grünberg Institute/Insti- tute for Advanced Simula- tion | Jülich researchers and their international colleagues have succeeded in generating extremely short and fast spin current pulses in a controlled manner. Using such pulses in the terahertz fre- quency range, future computers could process data faster and with greater energy efficiency than presently possible. The scientists exploited the electrons’

‘spin’ to produce these ultrafast pulses. This, in addition to their charge, can be used for informa- tion processing. The team of researchers present the experimental procedures used in the journal Nature Nanotechnology. ::

Measuring soil moisture over Blaustein- see lake near Eschweiler

Forklift truck with direct methanol fuel cell

Institute of Energy and Climate Research | With a new world record of over 20,000 hours in continuous operation, Forschungszentrum Jülich’s direct methanol fuel cells (DMFCs) have once again demonstrated their suitability for practical ap- plications. DMFCs run on liquid methanol instead of the gas- eous hydrogen used in conventional fuel cells. Methanol offers certain advantages: it allows a great deal of energy to be stored in a small space and can be refilled quickly. The in- crease in the lifetime of DMFCs from a few hours to the 20,000 now achieved is the result of systematic development efforts.

Jülich researchers are testing them as battery re- placements for use in electric forklift trucks

for large warehouses. Other possible ap- plications are auxiliary power units

for uninterruptable power supply, as required, for ex-

ample, in mobile base stations and computing centres. ::

The theme of Science Year 2013 is ‘The Demographic Opportunity’. One aspect of demographic change is that we’re growing older. In Ger- many, for example, life expec- tancy increases by about three months every year. This is a gift, but it also presents science with new challenges. One of them is basic research on Alzheimer’s – one of the issues we address at Jülich. In this issue, researchers present new findings on the causes of the disease, and also report on options for early diagnosis and treatments that could be developed as a result of their research. You will also read the latest news on the ozone layer, discover why fuel cells could become attractive for truck drivers, and learn that pushing and shoving can actually be a good thing when it ad- vances the cause of science.

I hope that this issue makes for interesting reading.

Yours sincerely, Prof. Achim Bachem

Chairman of the Board of Directors of Forschungszentrum Jülich

:: EDITORIAL

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NEWS IN BRIEF

Mexican Wave Drives Unicellular Organisms

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Institute of Complex Systems/Institute for Advanced Simulation | Injuries heal because cells divide over and over again until the open wound is eventually cov- ered with new tissue. What’s surprising about this process is that the new cells don’t push the adjacent ones aside, but pull each other in one direction – a process comparable to a game of tug-of- war. All cells join in the process, even those situated at a large distance from the wound. Simulations now offer an ex- planation for this coordinated action: the cells pull in a random direction, and if they come upon an obstacle in that direction, they will try a different one. This creates tension in the new tissue that may accelerate the healing process and hold the wound together. An international research team including scientists from Jülich have published their findings in the journal Proceedings of the National Academy of Sciences (PNAS). ::

Institute of Complex Systems/Institute for Advanced Simulation | Motile cilia propel unicellular organisms such as Paramecia through water and sweep mucus and dirt out of the human respiratory tract. While doing so, the eyelash-like cilia, which are up to ten micrometres long, exhibit a movement pattern similar to a Mexican wave. Up to now, it had been unclear whether this fulfils a function, and how the patterns come about. A simulation of several thousand cilia in liquid has now shown that the movement of the surrounding liquid plays the key role. It produces a synchronized, self-organized wave motion. Jülich researchers have found out that the wavelike movements of the cilia, similar to a synchronized ‘rowing movement’, enable them to propel cells twice as fast and ten times as efficiently.

Their findings were published in the journal Proceedings of the National Academy of Sciences (PNAS). They could help us to gain a better under- standing of diseases involving cilia or to construct artificial swimmers. ::

No plaster required! New cells are cre- ated when a wound closes, evidently holding the tissue beneath together like an adhesive bandage.

Microscopic Mexican wave: cilia in liquids propel cells by means of organized wave motions.

The Tug-of-War of

Wound Healing

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6 New Suspect in

Alzheimer’s Case

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COVER STORY | Alzheimer’s

7 In Alzheimer’s research, there is growing evidence that it is not deposits in the brain but small soluble aggregates of the beta-amyloid peptide that destroy neurons and synapses – and are thus the real cause of the disease. Jülich researchers are working on a way to render these aggregates harmless, and have succeeded in using them as a biomarker for the diagnosis of Alzheimer’s.

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o those affected by the disease and their relatives, it seems as though progress has been slow in Alzheimer’s research for years. A number of promising drugs that were suc- cessfully tested on animals failed miser- ably in clinical trials. “It’s certainly very disappointing that none of the active substances developed so far has proven effective,” says Prof. Dieter Willbold. He is a director at Jülich’s Institute of Com- plex Systems (ICS), where he is head of Structural Biochemistry. “However, in basic research, there is no sign at all of a standstill – quite the opposite,” he says.

“There’s so much to do that the only lim- its on research are the funding available and the number of scientists at hand.”

The fact that his team has acquired fresh funding for their two most important work packages therefore comes in very handy. € 2 million from the Helm- holtz Validation Fund has been ear- marked for Jülich Alzheimer’s research for the next two years. “With this funding, we are hoping to get our active substance through phase I clinical trials,”

Willbold says, brimming with optimism.

Ten years of intensive research have already been invested in the precursor substance D3, and a further three in its improved derivative. This peptide is made up of a relatively short chain of amino acids. It is able to destroy beta-amyloid oligomers in particular, which consist of a few dozen beta-amyloid molecules.

These beta-amyloid oligomers have a particularly lethal property: in con- trast to the very large and much better known fibrils, they are water-soluble – which means that bodily fluids can spread them throughout the entire body. They are suspected of being the real ‘bad guys’ that cause the damage to synapses and entire neurons.

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Forschen in Jülich 3 | 2013

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Cell membrane

Beta-amyloid molecules Protein residue

Neuron

Synapses

Calcium ions

Ca ²⁺

Insoluble protofibrils Soluble beta-amyloid oligomers

Gamma-secretase Beta-secretase

APP

8 Hot on the heels of what

is causing the disease

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3 | 2013 Forschen in Jülich

B

Plaques

Beta-amyloid oligomers

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A large piece is cut off outside the cell membrane by beta-secretase.

Gamma-secretase cuts further into the membrane and produces beta amyloid.

Beta-amyloid molecules are formed. It seems that these are not harmful in their monomeric form. In fact, it is assumed that they fulfil a protective role in the nervous system. However, as we grow older, it becomes more likely that several beta-amyloid molecules will join up to form larger molecule clusters.

Smaller aggregates consisting of between two and a few dozen beta-amyloid molecules are soluble in bodily fluids. These ‘beta-amyloid oligomers’ are suspected of damaging neurons and the connections between them, and thus ultimately of causing Alzheimer’s disease. Two possible mechanisms are being discussed:

The oligomers are deposited in the membrane of neurons, where they form pores. This allows calcium ions to flood the cells in an uncontrolled manner, causing them to die.

The beta-amyloid oligomers bind to the cells’ own receptors, which may send a signal that damages the cells.

At the same time, the well-known beta-amyloid plaques are formed from insoluble protofibrils.

Recent research findings suggest that these cause far less damage to cells than the oligomers, but are a reservoir for the toxic beta-amyloid oligomers.

Simple (‘monomeric’) beta-amyloid molecules are formed from the cells’ own amyloid precursor protein (APP) throughout our lives. They are cut from this larger protein by enzymes known as secretases in two steps.

COVER STORY | Alzheimer

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CHANNELS OF OBLIVION

Junior Professor Dr. Birgit Strodel from the Institute of Complex Systems is using computer models to investigate how this process unfolds. She found out that aggregates comprising four or six beta-amyloid molecules are able to form stable channels in cell membranes.

“These channels allow calcium ions to flood the cell in an uncontrolled manner, which spells death for these cells,” says the researcher. Her results are support- ed by electron micrographs of synapses in brain slices affected by Alzheimer’s.

These show pores that do not occur in the healthy brain.

Birgit Strodel and her team have also studied the possible mode of action of D3 in computer models. “We have been able to show where D3 docks onto the beta amyloid and how it must bind to it in order to dissolve the toxic amyloid aggregates,” says Strodel. The weak point is a series of negative charges at one end of the beta-amyloid molecules.

This is where the molecules bind to other beta-amyloid molecules when the disease sets in, enabling them to ar- range themselves into larger aggregates like pleated sheets. D3 in turn Prof. Birgit Strodel uses mathematical models to support the quest for an active substance.

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has corresponding positive charges that dock onto this precise location – the binding site situated in the ‘pleat’ of the sheet – shielding it and destroying the aggregate. In future, Strodel’s computer models will be used to further optimize D3.

In order to understand why the days in Willbold’s and Strodel’s laboratories should have more than 24 hours, it is important to know the effects D3 has shown to have in animal experiments.

The substance was tested on ‘Alzheim- er’s mice’ that produce human beta-amyloid, form the typical plaques in the brain, and later demonstrate a notice- ably reduced ability to learn. For example, these mice forget how to get to a platform immersed in a pool of murky water, where they can take a rest from swimming. When the mice were admin- istered D3 with their drinking water or by infusion, three things happened: the amyloid plaques and typical inflamma- tion processes in the brain were reduced and, at the same time, their ability to learn improved.

Dieter Willbold pleads for patience:

“The phase I clinical trials that are about to begin will only show whether the substance can be safely used in humans.

Whether it has the same effect as in animal experiments will only be clarified in phases II and III.”

TEST TO BRING CLARITY

One of the decisive factors in these clinical studies is selecting the right patients. Current test procedures do not yield exact results: about 30 % of patients actually suffer from a different form of dementia. “On the one hand, several radiopharmaceuticals are available as of this year for better diagnosis and monitoring,” says Willbold thought- fully (see ‘What Good is Diagnosis With- out Treatment?’, p. 11), “but on the other hand, they involve rather expensive ex- aminations. Moreover, we’re more inter- ested in the amyloid oligomer load in bodily fluids than in the amyloid plaques in the brain.” In a recently published study, his team presented a new test that is extremely sensitive to amyloid oligomers in spinal fluid. In healthy individ- uals, almost no oligomers were detect- ed. In those suffering from Alzheimer’s and even in patients with initial cognitive impairments, a large number of the toxic aggregates were found.

The degree of dementia could be clearly read from the oligomer concen- tration in the cerebrospinal fluid. Only one patient diagnosed with Alzheimer’s, who suffered from severe dementia, puzzled the scientists. He did not have elevated oligomer levels. “Although there are a couple of other possible reasons for this, I assume that he was in- correctly diagnosed with Alzheimer’s.

As the diagnostic method currently used is not 100 % accurate, an improved method based on biomarkers is bound to return different results,” says Prof.

Willbold. “Unfortunately, for a number of different reasons, we couldn’t examine the patient again to clarify this,” he says. In order to standardize the test and refine it further for clinical application, the Federal Ministry of Education and Research (BMBF) is making funds available as part of the so-called V.I.P.

programme. Willbold is convinced: “A test of this kind will accelerate numerous clinical studies and make them more reliable, which will lead to the faster development of an effective drug against Alzheimer’s.” ::

Brigitte Stahl-Busse Prof. Dieter Willbold and his team devel-

op new methods for the diagnosis and treatment of patients with Alzheimer’s.

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COVER STORY | Alzheimer’s

Question: What does an early diagnosis of Alzheimer’s entail?

Prof. Sturma: Considerable problems, but also a great deal of options. Long- term perspectives, which can be ex- pressed in the form of advance health care directives, for example, can clash dramatically with present interests, which arise from experiencing the world in a certain way. This is illustrated by the example of Walter Jens, a writer and university professor who recently passed away. Before being diagnosed with Alzheimer’s, he had made the decision to refuse life-sustaining treatment should he lose his mental capacity. But then, when he was already in a late stage of Alzheimer’s, he used what was left of his ability to communicate to make it clear that he didn’t want to die. In Walter Jens’

case, he uttered the words: “Don’t kill, please don’t kill.” No doctor or relative in this situation would undertake to let life end here.

Question: Is there a right to know?

Prof. Sturma: Of course there are a number of people who say they want to know, for example in order to make certain arrangements and to put their af- fairs in order. On the other hand, there’s also the right not to know. If you’re diagnosed with a disease a dozen or even fifteen years before it manifests itself, then you won’t be able to live those fifteen years as if you didn’t know. And quite a few patients with amyloid plaques in the brain do not develop any

dementia at all. But these people would live with the sword of Damocles hanging over them for many years. This has a fundamental impact on people’s options to live a self-determined life. Of course, all of this would change were it plausible to believe that treatment will be available soon.

Question: Are doctors well prepared to deal with these ethical conflicts?

Prof. Sturma: No, usually not. Several semesters of ethics studies should, in my opinion, be an indispensable part of medical training. Today, life-and-death decisions must be confronted in every phase of life, from the embryo to life-sustaining treatment for patients in a coma. There is far too little debate on these multifaceted situations in professional circles. This should also involve

developing rules for communicating risks and diagnoses to patients with some form of dementia. ::

This interview was conducted by Brigitte Stahl-Busse.

What Good is Diagnosis Without Treatment?

The diagnosis of Alzheimer’s is about to undergo radical change: new tracers make amyloid plaques visible ten to twenty years before the disease first manifests itself.

However, this diagnosis presents doctors and patients with enormous conflicts, be- cause an effective treatment will not be available in the short term and the role of plaques has not yet been fully explained. Prof. Dieter Sturma from Jülich’s Institute of Neuroscience and Medicine, Ethics in the Neurosciences (INM-8), comments on this dilemma in an interview.

The new radiopharmaceuticals that track down beta-amyloid plaques in the living brain with the help of positron emission tomography (PET) are referred to as flor- betapir, florbetaben, and flutemetamol.

For research, an additional substance known as PiB (Pittsburgh compound B) is also available. Thanks to these new developments, potential drugs can now be tested much earlier and on the right group of patients.

New diagnostic methods support research

Previous methods had a 30 % error rate in the diagnosis of Alzheimer’s disease.

Forschungszentrum Jülich was involved in the licensing study for florbetaben.

The new tracers also make it possible to monitor the disease at the same time. In future, florbetaben will also be used to trace how Jülich’s peptide D3 reduces the amyloid plaques in the brains of living Alzheimer’s mice.

Prof. Dieter Sturma, head of Ethics in the Neurosciences

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12 F

or many truck drivers, their vehicle is not only their workplace, but also a bedroom and living room at the same time. During breaks in particular, they do not want to go without air conditioning, communications technology, and a stove. There’s a simple solution to meeting the demand for electricity:

idling the engine. According to a 2007 study, the idling time of a single average

US truck is a whopping 1,700 hours per year – that’s around 70 days. This requires on average 11,000 litres of diesel and produces noise, soot, and climate-damaging exhaust fumes.

A number of US states have decided to put an end to this by passing anti - idling laws. They are also aware of the fact that idling the engine is very ineffec- tive when it comes to converting diesel into electric power. The energy yield, referred to as ‘efficiency’ by experts, is only about 10 %. In Europe, the issue of on-

board power supply is not of quite as much importance because the distances are usually shorter, a dense network of service areas is available, and the climate is more temperate. Nevertheless, even in these parts there is a demand for environmentally friendly and energy-efficient auxiliary power systems.

Jülich scientists have developed such a system based on fuel cells. It delivers an electric power of five kilowatts, which is sufficient for most trucks. In test operation, it has demonstrated that it is able to convert diesel and run entirely independently.

CLEAN PERFORMANCE

The system is about 1.10 metres wide, 1 metre high, and 70 cm deep. It compris- es several components (see diagram):

the reformer converts diesel, steam, and air into a gas rich in hydrogen. However, the gas also contains about 10 % carbon monoxide that could bring the fuel cell to a standstill; experts refer to this process as ‘poisoning’. The downstream

Conventional engines waste energy and pollute the en- vironment when idling so that they can produce elec- tricity for air conditioning and other electrically pow- ered devices in trucks. A fuel cell system developed by Jülich scientists that runs independently of the engine utilizes diesel more efficiently.

Power on board

A reformer and a shift reactor produce hydrogen-rich gas for the fuel cell from diesel. In the fuel cell, the hydrogen reacts with oxygen from the air to form water, producing electric current in the process. The re- maining off-gases are burned in the downstream catalytic burner. This produces waste heat, which in turn produces steam for the reformer. The type of fuel cell shown here is a high-temperature polymer electrolyte fuel cell (HT-PEFC) with a thin polymer membrane doped with phos- phoric acid as the electrolyte, sepa- rating the anode from the cathode.

Kerosene or diesel

Reformate

Air

Off-gas Water

Hydrogen

Air

Cathode off-gas Cooling medium Steam

Anode off-gas

HT-PEFC

Shift reactor Reformer

Catalytic burner

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RESEARCH AT THE CENTRE | Fuel Cells

shift reactor is therefore responsible for reducing the share of carbon monoxide to less than 1%. While doing so, it produces additional hydrogen that fuel cells can utilize as fuel gas.

“The high-temperature polymer electrolyte fuel cells (HT-PEFCs) we’re using in the system can tolerate carbon monoxide levels of about 1% without major performance losses,” says Prof. Ralf Pe- ters from Jülich’s Institute of Energy and Climate Research, Electrochemical Pro- cess Engineering (IEK-3). This means that the system can manage without additional components that would have to cleanse the gas further after the shift reaction – which would mean greater weight and require more space.

Each component of the system is the result of intensive development work and know-how at Jülich. The reformer, for example, is a ninth-generation device developed at Jülich and is able to mix diesel with air and steam in a particularly efficient manner. “We faced two major challenges in achieving the performance required for a truck when

developing the fuel cell system. Firstly, we had to construct cells with a large area – 320 cm² – and secondly, we had to connect 70 of these cells to a stack that worked reliably,” says Prof. Werner Leh- nert, also from IEK-3.

RACE OF THE SYSTEMS

The high tolerance of HT-PEFCs for carbon monoxide is due to the temperatures of 160 °C to 180 °C at which this type of fuel cell is operated. This is also the reason it is referred to as a

‘high-temperature’ cell, as conventional PEFCs have an operating temperature of just 60 °C to 80 °C.

On the other hand, the term

‘high-temperature’ is somewhat mislead- ing, because there are other types of fuel cells that run at much higher temperatures. One of these is the solid oxide fuel cell (SOFC), with an operating temperature of 700 °C. This technology is also in the running for use in auxiliary power units in trucks; Jülich scientists are involved in a project in which companies and research institutions jointly develop relevant systems to market maturity. It is

uncertain whether HT-PEFCs or SOFCs will ultimately come out on top. “One point in favour of HT-PEFCs is that they only have to be preheated for ten min- utes, whereas SOFCs take much longer to reach the operating temperature,”

says Lehnert. The researchers are aiming to build a HT-PEFC demonstration system that is smaller and more compact than the current system, if possible with industry partners.

Both types of systems are expected to reach efficiency levels of 35 % to 40 % in the future. This will make them more efficient and climate-smart than diesel generators, and in addition, they are ex-

tremely quiet. ::

Dr. Frank Frick

The driver’s cabin as a haven: during breaks, it serves as a kitchen, office, and bedroom.

Prof. Werner Lehnert and Prof. Ralf Pe- ters are already planning the next, more compact on-board power supply with fuel cells.

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14 S

oot is produced almost all over the world. It is the result of an incom- plete combustion of fossil fuels such as wood and coal. In industrialized countries, it is primarily diesel engines that produce soot emissions. Heating stoves and simple fireplaces in rural areas of Asia and Africa also contribute to these emissions. These fireplaces are fuelled not just with wood, but also with plant residues and cow dung. “Indeed, it’s traditional primitive domestic fires that cause the majority of emissions, in addition to the burning of forests and sa- vannahs,” says Dr. Martin Schultz from the Institute of Energy and Climate Re- search (IEK-8). His work as part of this study concentrated on emissions from the combustion of biomass.

Over a period of four years, the scientists studied the complex role played by black carbon in the climate system, re- fined climate models, and compared them to different measurement results.

The Underrated Climate Threat

Black carbon has a much stronger impact on global warming than previously assumed – soot particles heat the air about twice as much as previously estimated. However, this knowledge may lead to new opportunities for mitigating climate change. These are the results of an international group of researchers including scientists from Jülich.

Their findings have been included in the United Nations’ report on climate change, the 2013 IPPC Report.

Their work was complicated by the fact that soot particles have a number of different effects on the climate. When they are dispersed in the atmosphere by wind, for example, they absorb and scat- ter solar radiation and influence the formation of clouds. When black carbon later falls on ice and snow, this acceler- ates the melting process. In addition, soot can also alter the climate impact of pollutants formed along with it, such as sulphur dioxide.

SHORT-TERM MITIGATION

Some of these processes have a cooling effect, while others cause the climate to heat up. On the whole, however, scientists have come to the conclusion that soot has a greater impact on anthropo- genic global warming than methane or nitrous oxide. Carbon dioxide alone is ranked ahead of black carbon. “However, it’s important to carefully consider which of the possible measures will protect the

climate and which won’t,” says the Jülich researcher. The scientists therefore recommend that not all sources of soot be taken on at once, but that soot emissions from diesel engines as well as domestic wood and coal fires be reduced initially. They estimate that this could mitigate global warming at least in the short term – by up to half a degree Celsi- us, in the most optimistic of scenarios.

For the purposes of comparison: the objective of international climate policy is to limit global warming to no more than two degrees Celsius above pre-in- dustrial levels. Moreover, a reduction of soot emissions would also benefit human health. Diesel soot, for example, has been identified as a cause of lung

cancer. ::

Christian Hohlfeld

Research focus: diesel vehicle emissions as well as primitive stoves and woodburners

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RESEARCH AT THE CENTRE | Climate Research

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n the EU project RECONCILE, researchers from 14 countries studied the chemical process of ozone depletion over a period of four years. They were able to demonstrate that it is indeed chlorine compounds that are responsible for this process. These results refute a study published in 2007 that in- directly questioned the role of chloro- fluorocarbons (CFCs) in ozone depletion.

“The Montreal Protocol is delivering results,” says Jülich environmental chemist Dr. Marc von Hobe. In the Protocol, signed in 1987, more than 190 countries pledged to reduce the emission of chem- icals containing chlorine, such as CFCs.

The amount of chlorine in the stratosphere has since fallen significantly. This is demonstrated by analyses of air samples taken as part of the RECONCILE programme. However, these compounds remain in the atmosphere longer than previously thought.

And now climate change represents the next challenge for the ozone layer.

Climate change could alter the temperature, circulation patterns, and chemical composition of the stratosphere. This also influences the ozone layer, the thick- ness of which in turn has an effect on temperature. Marc von Hobe believes that this is yet another reason to reduce the emission of greenhouse gases con- siderably and thus stop climate change.

The ozone layer above the Arctic is currently on the mend. An international group of scientists including researchers from Jülich predict that it could make a full recovery by the end of the century. However, a new threat is already looming: climate change.

NEW UNDERSTANDING

Thanks to RECONCILE, researchers now know more about ozone depletion and the formation of holes in the ozone layer.

For example, the findings have com- pletely changed our understanding of polar stratospheric clouds (PSCs). These clouds form in the stratosphere under certain conditions at temperatures of below -80 °C. At their surface, chlorine reactions are set in motion that deplete ozone. The scientists found out that PSCs are formed at a much faster rate and at higher temperatures than previously assumed. The scientists used the new insights to improve existing climate models. These models facilitate more reliable predictions of how the ozone layer will develop in future – and of the possible consequences of climate change for

the stratosphere. ::

Christian Hohlfeld

Beginning in 2009, the European Union provided RECONCILE with funding of

€ 3.5 million under its 7^th Framework Pro- gramme. The researchers performed numerous laboratory experiments, on-site measurements, and computer simulations. Important findings are based on data and samples the scientists collected above the Arctic with the research aircraft M55 Geophysica. The project, which was coordinated by Forschungszentrum Jülich, was brought to a successful close in 2013.

RECONCILE

Two specialists: Marc von Hobe and M55 Geophysica. The Russian plane is one of three aircraft worldwide that can reach altitudes of up to 21 kilometres.

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Pushing and shoving was explicitly allowed during an experiment that was one of the largest of its kind. At the Messe Düsseldorf exhibition hall, Jülich researchers guided a total of 2,000 pedestrians through different scenarios over four days. Their goal was to achieve a better understanding of the in- ternal dynamics of crowds of people in order to improve safety at large public events.

The experiments were part of the BaSiGo project, which aims to develop new safety concepts for large-scale events. In the project funded by the Fed- eral Ministry of Education and Research (BMBF), Jülich researchers are col- lecting data, for example for a model that will calculate pedestrian trajectories in advance by means of computer simulations. It will be part of a concept comprising various safety modules that can be applied individually to any large event and is being developed in cooperation with nine project partners from science, the fire brigade, the police force, and industry.

Two Thousand’s a Crowd

PROF. ARMIN SEYFRIED AND STEFAN HOLL watch hundreds of pedestrians walking through their experimental set-up from an elevating work platform. The two Jülich scientists conducted the BaSiGo experiments at Messe Düsseldorf over several days. These were among the largest experiments ever performed with crowds of people. Holl says that their goal was to measure “basic data on pedestrian dynamics”.

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DURING THE JUNCTION EXPERI- MENT, the test subjects came to- wards a junction from four sides and tried to walk across it in a straight path. As soon as there were about 100 participants in the middle of the junction, movement was no longer possible, and the experiment had to be broken off with the blow of a whistle.

THE SCIENTISTS OBSERVED the experiments from all angles on nine monitors. Their work doesn’t end with the experiments, however. “We collected 42 terabytes of data, which will form the basis of a number of PhD theses,” says Jülich researcher Stefan Holl. One of the scientists’ objectives is to create a model that will enable the simulation of large crowds of people at major events. This will allow dangerous situations to be predicted – and therefore prevented.

THE WHITE SUN HATS worn by the participants played a vital role: using the QR code printed on top, the trajectory of each person could be tracked with an accuracy of a few centimetres. In- stalled on the ceiling were 24 cameras that re- corded the experiments.

ONE OF 30 EXPERIMENTAL SET-UPS:

the barrier. The test subjects in this pho- to are flocking into a closed-off area and then leaving it again. In this set-up, the researchers measured the crowd density at which pedestrians can still move individually. They increased the density in stages. From a density of six people per square metre, it became almost im- possible to leave the crowd – and that’s despite the fact that the experiments took place under ideal conditions. The researchers therefore recommend that organizers prevent such high densities.

A FINDING of project partner the University of Siegen was also eye-opening. Gebhard Rusch, professor of media sciences, tried to optimize the pedestrian trajectories “through minimally invasive interven- tions”. A roundabout sign was displayed on a screen before participants entered the junction. At first, the participants ig- nored the sign, but as soon as they were made aware of it,

“we entered a whole new world”, says Rusch. The pedestrians passed through the junction, and the flow was uninter- rupted even at higher densities.

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RESEARCH AT THE CENTRE | Simulation

Christoph Mann

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18 A

fter tyres exploded spectacularly on no less than four cars at the Silverstone Formula One race on 30 June, news agencies cited Paul Hem- bery, the tyre manufacturer’s motor sport director: “We’ve seen something new, a different type of problem. We’re currently performing our analysis. We’ve got to go away and understand what has happened today.” Indeed, developing tyres for special purposes – not just For- mula One racing – is still characterized by sophisticated test series rather than an understanding of the complicated relationships between rubber mixtures and tyre properties. Jülich scientists Dr.

Bo Persson and Dr. Boris Lorenz are well

Tyres, Friction, and Clever Calculations

Motorists want tyres that save fuel, keep them safe in any weather, and wear as slowly as possible. And car manufacturers would like to specifically develop such tyres on computers, without having to produce thousands and thousands of rubber mixtures and test tyres. Jülich researchers are working on a way to make this vision a reality.

effectiveness of technical seals, for example. Persson’s guiding principle is as follows: to calculate the actual contact area between two bodies, the roughness of the respective surfaces must be taken into account on numerous length scales – from a thousandth of a millimetre to a centimetre. In concrete terms this means that, analogously to microscopy, Persson integrated a ‘magnification factor’ into his theory in order to look at roughness in ever smaller dimensions.

PROGRAM CALCULATES FRICTION Persson then incorporated his consider- ations on contact mechanics into a theory of rubber friction, which was also new, and transferred it to a computer model. The program runs on a standard PC because it is an analytical model instead of a numerical model, i.e. one with systems of equations that can be solved exactly and do not require ap- proximation. The scientists feed the computer with data on the roughness of the road, which can be measured easily, as well as on the elasticity and temperature behaviour of the rubber mixture under investigation. From this informa- tion, the program calculates the friction between the tyre and the road surface, for instance as a function of the ‘slip’.

When the driver steps on the brakes, for example, the tyre turns a little more slowly than would correspond to the speed of the vehicle. The tyre therefore slides across the road surface, and this sliding part of the movement is referred to as slip.

on their way to changing this. Prestig- ious tyre manufacturers worldwide have already taken notice of their work.

This interest is also fuelled by a new EU directive in force since November 2012. It stipulates that tyres must bear a label enabling consumers to identify at a glance the tyres’ fuel efficiency, wet grip, and external rolling noise. “This of course means that manufacturers are stepping up their efforts to optimize their products with a view to these crite- ria,” says engineer Lorenz. And the key to such an optimization is to be able to explain the static friction of rubber and calculate it from basic data.

This was Persson’s goal when he first started to work on this topic 15 years ago. At the time, the physicist was developing a novel theory on the size of the actual con-

tact area between two bodies when they

touch. In this specific case, this

means the contact between

the tyre and the road. This question is also relevant for the

Dr. Boris Lorenz de- veloped an apparatus to determine the fric- tion of tyre rubber.

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RESEARCH AT THE CENTRE | Materials Research

A theory such as Persson’s is contin- gent on whether the calculated values correspond to those measured in the field. The Jülich researchers have therefore developed an apparatus that measures the friction of rubber tyres on the tarmac at different speeds. Their latest results, which they obtained in cooperation with scientists from tyre manufacturer Bridgestone, were recently published.

THEORY CONFIRMED

The results fit right in with Persson’s theory. Different factors determine friction and therefore tyre grip depending on the speed. “Below a slip velocity of about one centimetre per second, tyre grip is primarily determined by the actual contact area. At higher speeds, the viscoelasticity of the rubber is the domi- nant factor instead,” says Lorenz, sum- marizing a key finding. In everyday life, both factors are relevant for rubber friction on the road. When an anti-lock braking system is actuated, for example, the tyre briefly grips the road first at the lowest slip velocity before it begins to slide at a slip velocity of up to one metre per second.

Viscoelastic materials are elastic like solids and, at the same time, exhibit vis- cous characteristics like liquids. Why this property of rubber has an impact on tyre grip at all is explained by the researchers as follows: the tyre is exposed to impacts from small irregularities in the tarmac. When as a result the tyre yields and is dented, the molecules in the rubber move against each other and for a short time consume energy. Ulti- mately, this energy loss decelerates the movement of the tyre on the road and gives it better grip.

In future, the Jülich scientists are planning to use different rubber mixtures to verify their theoretical predictions of grip on wet roads and at high slip velocities. And then, one day, chance may cease to play a decisive role in the world of tyres – including those used in

Formula One racing. ::

Dr. Frank Frick

In motor sport as well as in other areas, tyre development requires sophisticated tests. In the future, computer models could calculate the perfect rubber mixture.

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B

arack Obama, Meryl Streep, and German newsreader Claus Kleber all have voices that many people perceive as pleasant. Prof. Simon Eick- hoff knows that this is a priceless advan- tage. “A voice that exudes trustworthiness and attractiveness is a door opener, both at work and in our private lives,”

says the medical scientist, who performs research at the Institute of Neurosci- ence and Medicine at Jülich and is also a professor for cognitive neurosciences at Heinrich Heine University Düsseldorf.

To date, the primary focus of scientific study has been the influence of faces.

As part of a research project, the neuroscientist and his team therefore asked 44 healthy adults to evaluate different male and female voices. In the function- al magnetic resonance imaging (fMRI) scanner, they were played simple everyday sentences, such as “Excuse me, have you got the time please?”, and then asked to judge the speakers in terms of their trustworthiness, cheerfulness, attractiveness, and age.

At the same time, images were taken of their brain activity at two-second intervals. Interestingly enough, it was always the same area of the brain that was active: the dorsomedial prefrontal cortex. “This is also the area with which we assess facial expressions,” says Si- mon Eickhoff. “Our finding that voices are also assessed in this area confirmed our hypothesis that this must be a key region for social judgements in the human brain.”

The Voice as a Door Opener

There are some people to whom we’d lend our lawn mower or car without a second thought. To others we wouldn’t. Trust is created by impressions that are processed in the brain as quick as a flash. A smile or a look can make all the difference. So can a sentence, as Jülich neuroscientists recently found out in a research project on judging voices. Apparently, the brain has a kind of central key region for social judge- ments that is activated when faces – and voices – are judged.

Trustworthy or undependable?

Attractive or un- appealing? A look or a word is often enough for us...

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Knowledge of the different areas in the brain responsible for making judgements helps scientists to achieve deep- er insights into psychiatric diseases such as depression and autism. Autism, a disorder classified by the World Health Organization as a pervasive de- velopmental disorder that is still considered incurable, is characterized by im- paired social interaction. “For example, it is difficult for autists to put themselves in somebody else’s shoes. Often, they do not return a smile, or have diffi- culty recognizing feelings such as anger or sadness in others,” explains Eickhoff.

Scientists have found out that this fac- ulty of empathizing with someone else is also located in the dorsomedial prefrontal cortex.

In order to better understand the neurobiological causes of this and other psychiatric disorders, the medical scien- VITAL CONTROL

What seems important for private and professional contacts and relationships in the 21^st century is also important from the point of view of evolutionary history. “Social cognitive judgements – about a person’s trustworthiness, for example – constitute warning signs that, in addition to basic emotions such as fear or disgust, are a decisive factor for survival,” says Eickhoff. Whether caveman or CEO: choosing the right partner is and always has been crucial for people’s own futures – this hasn’t changed from the hunter-gatherer era to the 21^st century.

The evaluations by the dorsomedial prefrontal cortex, which remain relevant in the long term, are opposed by the as- sessments of spontaneous emotions in other regions of the brain. “Whether someone is happy or sad at any given moment is judged in our amygdala,” says Simon Eickhoff. He adds that there have already been numerous studies on the processing of these basic emotions. Re- search on social cognitive decision-making processes – for example, whether we trust a person or not – is still in its infan- cy, however.

tist is already planning follow-up pro- jects to analyse the brain structure and the networking of different brain areas in patients. “We want to discover whether the brain structure as such is abnor- mal, whether the interaction of the dorsomedial prefrontal cortex with other brain regions deviates from the norm, or whether both explanations are true,”

says the neuroscientist. The results could contribute to improving treatment methods in a specific manner. ::

Ilse Trautwein

Prof. Simon Eickhoff has investigated which areas of the brain are active when people judge voices.

... to make a judgement on others – as if their characteristic traits were writ- ten on their faces.

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RESEARCH AT THE CENTRE | Neuroscience

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22 Fact-Finding in the Forest I

n a forest, the quantity of trees cut down

should not exceed the quantity of trees growing back. What sounds like a recent recommen- dation from an environmental protection organization is actually a demand put forward as many as 300 years ago. Hans Carl von Carlowitz, who was in charge of mining in Freiberg in the Elec- torate of Saxony, laid down this principle in 1713 in his treatise Sylvicultura oeconomica, the first comprehensive work on forestry. He is therefore considered to be the father of the principle of sustainability.

Many a forest fell victim to people’s demand for wood until the end of the 19^th century. Never- theless, in time, the idea of counteracting this with targeted forest management and reforesta- tion gained acceptance – for example, in what is today the Eifel National Park. However, the forest administrators decided not to replant native deciduous trees but spruces, because they grow faster. Yet today we know that the deciduous trees offer native plants and animals more fa- vourable living conditions. The Eifel National Park administration therefore recently started to convert its spruce forest back into mixed deciduous forest.

Jülich researchers and their colleagues are ex- amining the renaturation process with scientific methods in the area around the Wüstebach, a small stream. For the first time, they are performing long-term, continuous analyses of the consequences of such a process on the water, carbon, and nitrogen balances. They took soil samples at about 175 locations before restoration measures began in order to be able to compare them with future measurements. The results will also be of interest for nature conservation and climate protection in other countries where coniferous forests are cut down. The investigations are part of the large-scale project TERENO (Terrestrial Envi- ronmental Observatories), in which Jülich scientists from the Institute of Bio- and Geo- sciences (Agrosphere) together with other colleagues from Germany are investigating the re-

gional impact of climate change. ::

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LAST BUT NOT LEAST

PUBLICATION DETAILS Research in Jülich Magazine of Forschungszentrum Jülich, ISSN 1433- 7371 Published by: Forschungs- zentrum Jülich GmbH | 52425 Jülich

| Germany Conception and editorial work: Annette Stettien, Dr. Barbara Schunk, Dr. Anne Rother (responsible according to German press law) Authors: Dr. Frank Frick, Chris- tian Hohlfeld, David Kreienbruch, Christoph Mann, Tobias Schlößer, Dr. Barbara Schunk, Brigitte Stahl- Busse, Ilse Trautwein, Angela Wenzik Translation: Language Services | Forschungszentrum Jülich Graph- ics and layout: SeitenPlan GmbH, Corporate Publishing, Dortmund Images: CHEN WS/Shutterstock.com (19), DenisNata/Shutterstock.com (13 bottom mug), erichon/Shutterstock.

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Large-scale operation in the forest: Jülich scientists take soil sam- ples before the spruce trees at the Wüstebach site, a small stream in the Eifel National Park, make way for native deciduous trees.

1. Alexander Graf (left) and François Jonard forcefully drive a soil sampling device into the soil. | 2. All samples are packed up in bags and labelled. | 3. Lutz Weihermüller fills ‘Kopecky rings’ by hand in order to determine physical parameters of the soil. | 4. Werner Küpper delivers samples for registration. | 5. Nina Gottselig holding a sample tube – referred to as a ‘liner’ – with a fresh sam- ple. | 6. The scientists dig deep to take samples from depths of up to one metre. Shown here are Anne Berns (left) and Lutz Weihermüller. | 7. Soup kitchen: the researchers take a well-deserved break. They took samples at depths of up to one metre at about 175 locations.

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