They can be deployed as additional surveillance resources during major events, or as high-resolution 3D street-imaging systems. Intelligent swarms of aerial drones are a universally useful tool for police, crisis managers and urban planners. Special 3D sensors developed by Fraunhofer researchers ensure flawless aerobatics and prevent collisions.

Like a well-rehearsed formation team, a flock of flying robots rises slowly into the air with a loud buzzing noise. A good two dozen in number, they perform an intricate dance in the sky above the seething hordes of soccer fans. Rowdy hooligans have stormed the field and set off flares. Fights are breaking out all over, smoke is hindering visibility, and chaos is the order of the day. Only the swarm of flying drones can maintain an overview of the situation. These unmanned aerial vehicles (UAVs) are a kind of mini-helicopter, with a wingspan of around 2m. They have a propeller on each of their two variable-geometry side wings, which lends them rapid and precise manoeuvrability. In operation over the playing field, their cameras and sensors capture urgently needed images and data, and transmit them to the control centre. Where are the most seriously injured people? What is the best way to separate the rival gangs? The information provided by the drones allows the head of operations to make important decisions more quickly, while the robots form up to go about their business above the arena autonomously – and without ever colliding with each other, or with any other obstacles.

A CMOS sensor developed by researchers at the Fraunhofer Institute for Microelectronic Circuits and Systems IMS in Duisburg lies at the heart of the anti-collision technology. ‘The sensor can measure three-dimensional distances very efficiently,’ says Werner Brockherde, head of the development department. Just as in a black and white camera, every pixel on the sensor is given a grey value. ‘But on top of that,’ he explains, ‘each pixel is also assigned a distance value.’ This enables the drones to determine their position accurately in relation to other objects around them.

Sensor has a higher resolution than radar

The distance sensor developed by the IMS offers significant advantages over radar, which measures distances using reflected echoes. ‘The sensor has a much higher local resolution,’ says Brockherde. ‘Given the near-field operating conditions, radar images would be far too coarse.’ The flying robots are capable of identifying even small objects measuring 20x15m at ranges of up to 7.5m. Moreover, this distance information is then transmitted at the very impressive rate of 12 images per second.

Even when there is interfering light, for example when a drone is flying directly into the sun, the sensor will deliver accurate images. It operates according to the time-of-flight (TOF) process, whereby light sources emit short pulses that are reflected by objects and bounced back to the sensor. In order to prevent over-bright ambient light from masking the signal, the electronic shutter only opens for a few nanoseconds. In addition, the sensor also takes differential measurements, in which the first image is captured using ambient light only, a second is taken using the light pulse as well, and the difference between the two determines the required output signal.  ‘All of this happens in real time,’ adds Brockherde.

New challenges, but many benefits and uses

The 3D distance sensors are built into cameras manufactured by TriDiCam, a spin-off company of Fraunhofer IMS. Jochen Noell, TriDiCam’s managing director, admits: ‘This research project has presented us with new challenges as regards ambient operating conditions and the safety of the sensor technology.’ The work falls under the AVIGLE project, one of the winners of the ‘Hightech.NRW’ cutting-edge technology competition that receives funding from both the Land of North Rhine-Westphalia and the EU. The IMS engineers will be presenting their sensor technology at the Fraunhofer CMOS Imaging Workshop in Duisburg on June 12 and 13 this year.

Conducting intelligent aerial surveillance of major events is not the only intended use for flying robots. They could also be of benefit to disaster relief workers, and likewise to urban planners, who could utilise them to produce detailed 3D models of streets or to inspect roofs in order to establish their suitability for solar installations. Whether deployed to create virtual maps of difficult-to-access areas, to monitor construction sites or to measure contamination at nuclear power plants, these mini UAVs could potentially be used in a wide range of applications, obviating the need for expensive aerial photography and/or satellite imaging.

The 3D camera in the flying robot can identify small objects measuring 20 x 15cm from 7m away. (Image: Fraunhofer IMS)

Source: Fraunhofer-Gesellschaft

The photovoltaics industry is booming, and the market for solar farms is growing quickly all over the world. Yet, the task of planning PV power plants to make them as efficient as possible is far from trivial. Fraunhofer researchers, working with Siemens Energy Photovoltaics, have developed software that simplifies conceptual design.

The share of renewable energies in the overall energy mix is rising rapidly worldwide. With three-figure growth rates, photovoltaics (PV) play a major role. According to market research organisations, the PV market grew by 139% in the year 2010. Germany is among the world‘s leaders in this technology that uses solar cells to convert sunlight straight into electrical energy. Yet the task of planning large-scale PV power plants spanning several square kilometres is a complex one. With customer specifications, regulations and government subsidy programs to consider, designers must also account for numerous other factors including weather, climate, topography and location.

These factors, in turn, influence the selection and placement of the individual components that include the PV arrays with their solar modules, inverters and wiring, not to mention access roads. Until now, engineers have designed solar power plants using CAD programs, with every layout and every variation painstakingly generated separately. This is a very time-consuming approach. To improve a planned power plant in terms of certain criteria, or to compare different concepts with one another, oftentimes the entire planning process has to be repeated.

Several hundred plant designs at the push of a button

In the future, this approach will be improved considerably: researchers at the Fraunhofer Institute for Industrial Mathematics ITWM in Kaiserslautern, in collaboration with Siemens Energy Photovoltaics, have developed new planning software that makes it possible to build solar power plants better and more quickly. ‘Our algorithms programmed exclusively for the Siemens PVplanet (PV Plant Engineering Toolbox) software provide engineers with several hundred different plant designs in a single operation. It takes less than a minute of computation time,’ ITWM researcher Dr. Ingmar Schüle points out.

The only user inputs are parameters such as the topography of the construction site and the module and inverter types that will be used. The user can also change a number of parameters – such as the orientation, spacing and inclination of the solar arrays – to study the impact on the quality of the planning result.

Cost estimates and income calculations included

To evaluate the designed PV power plants, an income calculation is performed that includes a simulation of the weather in the region in question, the course of the sun throughout the year and the physical module performance including shading effects. With the results of this computation and an estimate of the investment and operating costs, the planning tool can come up with a figure for the LCOE (‘levelised’ cost of energy). By comparing the plant with a large number of similar configurations, the planners can investigate the sensitivity of the various parameters to find the right solution from a large array of options.

‘The software assists the expert with decision-making and helps with the design of the best possible PV power plant for the site involved. Which one is ‘best‘ depends on a number of aspects – from the customer’s objectives to the site and environmental conditions, but also on the financing concept and the financial incentives for photovoltaics in the target region. All of these criteria are taken into account.’ Schüle points out. Dr. Martin Bischoff, project manager at Siemens AG, Energy Sector, is also convinced of this approach: ‘Aside savings, more than anything else the planning tool provides an overview of the scope for optimisation. This provides the best possible support for planning the most cost-efficient systems. There has been no other planning software with this scope or level of detail until now.’

In the future, large PV plants such as the Siemens solar farm that went into operation in 2011 in Le Mées, France, can be planned quickly and efficiently using the PVplanet software solution. (Image: Siemens AG)

Source: Fraunhofer-Gesellschaft

Gaming system a new step for telepathology and other telemedicine fields.

Wileen Wong Kromhout

Online crowd sourcing  -  in which a task is presented to the public, who respond, for free, with various solutions and suggestions  -  has been used to evaluate potential consumer products, develop software algorithms and solve vexing research-and-development challenges. But what about diagnosing infectious diseases?

Working on the assumption that large groups of public non-experts can be trained to recognise infectious diseases with the accuracy of trained pathologists, researchers from the UCLA Henry Samueli School of Engineering and Applied Science and the David Geffen School of Medicine at UCLA have created a crowd-sourced online gaming system in which players distinguish malaria-infected red blood cells from healthy ones by viewing digital images obtained from microscopes.

The UCLA team found that a small group of non-experts playing the game (mostly undergraduate student volunteers) was collectively able to diagnosis malaria-infected red blood cells with an accuracy that was within 1.25% of the diagnostic decisions made by a trained medical professional.

The game, which can be accessed on cell phones and personal computers, can be played by anyone around the world, including children.

Getting people involved

‘The idea is, if you carefully combine the decisions of people  -  even non-experts  -  they become very competitive,’ said Aydogan Ozcan, an associate professor of electrical engineering and bioengineering and the corresponding author of the crowd-sourcing research. ‘Also, if you just look at one person’s response, it may be OK, but that one person will inevitably make some mistakes. But if you combine 10 to 20, maybe 50 non-expert gamers together, you improve your accuracy greatly in terms of analysis.’

Crowd sourcing, the UCLA researchers say, could potentially help overcome limitations in the diagnosis of malaria, which affects some 210 million people annually worldwide and accounts for 20% of all childhood deaths in sub-Saharan Africa and almost 40% of all hospitalisations throughout that continent.

The current gold standard for malaria diagnosis involves a trained pathologist using a conventional light microscope to view images of cells and count the number of malaria-causing parasites. The process is very time-consuming, and given the large number of cases in resource-poor countries, the sheer volume presents a big challenge. In addition, a significant portion of cases reported in sub-Sahara Africa are actually false positives, leading to unnecessary and costly treatments and hospitalisations.

Speedy diagnoses from the crowd

By training hundreds, and perhaps thousands, of members of the public to identify malaria through UCLA’s crowd-sourced game, a much greater number of diagnoses could be made more quickly  -  at no cost and with a high degree of collective accuracy.

‘The idea is to use crowds to get collectively better in pathologic analysis of microscopic images, which could be applicable to various telemedicine problems,’ said Sam Mavandadi, a postdoctoral scholar in Ozcan’s research group and the study’s first author.

Ozcan and Mavandadi emphasised that the same platform could be applied to combine the decisions of minimally trained health care workers to boost the accuracy of diagnosis significantly, which is especially promising for telepathology, among other telemedicine fields.

The new UCLA study, ‘Distributed Medical Image Analysis and Diagnosis Through Crowd-Sourced Games,’ has been accepted for publication in the journal PLoS ONE. More information is available at http://biogames.ee.ucla.edu.

Automated algorithm

In addition to developing the crowd-sourced gaming platform that allows players to assist in identifying malaria in cells imaged under a light microscope, Ozcan’s research group created an automated algorithm for diagnosing the same images using computer vision, as well as a novel hybrid platform for combining human and machine resources toward efficient, accurate and remote diagnosis of malaria.

‘The most exciting aspect is that this is an entirely novel approach in the area of visual diagnostics, which really challenges diagnostic algorithms used to date,’ said Karin Nielsen, a professor of infectious diseases in the department of paediatrics at the Geffen School of Medicine. ‘It is diagnostics outside the box  -  that is, the study introduces an entirely new concept in diagnostics with the use of games for this purpose. The potential applications of this new approach are immense.’

How the game works:

Before playing the game, each player is given a brief online tutorial and an explanation of what malaria-infected red blood cells typically look like using sample images. After completing a short training phase, players go through the actual game, in which they are presented with multiple frames of red blood cell images and can use a ‘syringe’ tool to ‘kill’ the infected cells one-by-one and use a ‘collect-all’ tool to designate the remaining cells in the frame as ‘healthy.’

Within each frame, there are a certain number of cells whose status (i.e., infected or not) is known by the game but not by the players. These control cell images allow Ozcan’s team to dynamically estimate the performance of gamers as they go through each frame and also helps the team assign a score for every frame the gamer passes through.

‘I believe that, similar to other very innovative ideas, one of the major challenges will be the scepticism of traditional microscopists, pathologists and clinical laboratory personnel, not to mention malaria experts, who will initially view with suspicion a gaming approach in malaria diagnostics,’ said Nielsen, also an author of the study. ‘It is a very revolutionary proposal and it might take a few clinical studies in the field to document the efficacy of this platform in order to convince traditional microbiologists and other infectious disease colleagues.’

Potential benefits for developing countries

‘Scaling up accurate, automated and remote diagnosis of malaria through a crowd-sourced gaming platform may lead to significant changes for developing countries,’ Ozcan said.

‘It could eliminate the current overuse and misuse of anti-malarial drugs, improve management of non-malaria fevers by ruling malaria out, lead to better use of existing funds, and reduce risks due to long-term side-effects of anti-malarial drugs on patients who don’t need treatment,’ Mavandadi added.

Ozcan’s team hopes to bring the platform into the field through clinical trials to help validate its use and facilitate implementation of the technology worldwide. Nielsen and Ozcan plan to implement it at clinical sites in countries such as Mozambique, Malawi and Brazil.

In addition, the same crowd-sourcing and gaming-based micro-analysis and medical diagnosis platform could be further scaled up for a variety of other biomedical and environmental applications in which microscopic images need to be examined by experts, the researchers said.

Other authors of the study included Stoyan Dimitrov, Steve Feng, Frank Yu, Uzair Sikora, Oguzhan Yaglidere and Swati Padmanabhan, all with the UCLA Department of Electrical Engineering.

Funding for Ozcan Research Group is provided by the Presidential Early Career Award for Scientists and Engineers (PECASE), the Army Research Office Young Investigator Award, the NSF CAREER Award (BISH Program), the Office of Naval Research Young Investigator Award 2009 and the NIH Director’s New Innovator Award.

For more information on the Ozcan Research Group, visit http://innovate.ee.ucla.edu and http://biogames.ee.ucla.edu.

A sample malaria-diagnosis game screen.

This photograph depicted a female Anopheles albimanus mosquito while she was feeding on a human host, thereby, becoming engorged with blood. Like other species in the genus Anopheles, A. albimanus adults hold the major axis of the body more perpendicularly to the surface of the skin when blood feeding. Anopheles spp. adults also generally feed in the evening, or early morning when it is still dark. This species is a vector of malaria, predominantly in Central America. (Image: Wikimedia Commons)

Source: UCLA

Amy Albin

It seems improbable that a baby born underweight would be prone to obesity, but it is well documented that these children tend to put on weight in youth if they are allowed free access to calories. Now, researchers believe they understand why this happens.

A new animal model study at UCLA has found that in low–birth-weight babies whose growth was restricted in the womb, the level of appetite-producing neuropeptides in the brain’s hypothalamus  -  the central control of the appetite  -  is higher, resulting in a natural tendency among these children to consume more calories.

‘Other studies have shown that neuronal processes that signal the brain to eat were wired differently in the hypothalamus if a hormonal gene, such as leptin, was missing,’ said the study’s lead author, Dr. Sherin Devaskar, professor of paediatrics and executive chair of the department of paediatrics at Mattel Children’s Hospital UCLA. ‘What we found is that appetite-producing genes in the hypothalamus are completely programmed toward eating more to make up for the relative decrease in nutrition while in the womb. Therefore, the natural tendency for a child born with low birth weight is to eat more and try to catch up in growth. But if this is not curbed, it can result in childhood obesity.’

The findings appear in the June issue of the Journal of Neuroscience Research and are currently available online.

Rodent models used in the study

The study was undertaken in rodent models that mimicked small human babies. This was accomplished by reducing rodent mothers’ intake of calories, which in turn led to the birth of small, low–birth-weight and growth-restricted babies. The rodent babies were then examined at an early age to see how much milk they consumed and to monitor their energy expenditure. In addition, the researchers examined the effect that being growth-restricted in the womb had on hypothalamic neuropeptides that control appetite when the babies were weaned.

The researchers observed that those neuropeptides that bring increased appetite with decreased energy expenditure were increased in the hypothalamus, while the neuropeptides that reduce appetite and increase energy expenditure were decreased. Therefore, the homeostatic balance of appetite-controlling neuropeptides was disrupted. The hypothalamus was poised to consume as many calories as were available, with no sense of satisfaction.

These findings expand on recent research published by Devaskar and colleagues in the June issue of the journal Diabetes, which found that if small babies are placed on a diet of moderately regulated calories during infancy, their propensity to become obese decreases. Because this was an early animal study, the UCLA researchers do not recommend that mothers of low–birth-weight infants start restricting their children’s nutrition and suggest they consult with a paediatrician regarding any feeding questions.

About 10% of babies in the United States are born ‘small’  -  defined as less than the 10th percentile by weight for a given gestation period. Some organisations define low birth weight as less than 2 500g at term.

Low birth weight can be caused by malnutrition due to a mother’s homelessness or hunger or her desire not to gain too much weight during pregnancy. Additional causes include illness or infection, a reduction in placental blood, smoking, or use of alcohol or drugs during pregnancy.

Growth restriction before birth may cause lasting changes in genes in certain insulin-sensitive organs like the pancreas, liver and skeletal muscle. Before birth, these changes may help the malnourished foetus use all available nutrients. After birth, however, these changes may contribute to health problems such as obesity and diabetes.

Devaskar said the next phase of research would look at an intervention to reverse the hypothalamic neuropeptide changes that cause the central control of appetite to be set too high.

(Image: Wikimedia Commons)

Melody Pupols

The overwhelming majority of proteins and other functional molecules in our bodies display a striking molecular characteristic: They can exist in two distinct forms that are mirror images of each other, like your right hand and left hand. Surprisingly, each of our bodies prefers only one of these molecular forms.

This mirror-image phenomenon  -  known as chirality or ‘handedness’  -  has captured the imagination of a UCLA research group led by Thomas G. Mason, a professor of chemistry and physics and a member of the California NanoSystems Institute at UCLA.

Mason has been exploring how and why chirality arises, and his newest findings on the physical origins of the phenomenon were published 1 May in the journal Nature Communications.

‘Objects like our hands are chiral, while objects like regular triangles are achiral, meaning they don’t have a handedness to them,’ said Mason, the senior author of the study. ‘Achiral objects can be easily superimposed on top of one another.’

Why many of the important functional molecules in our bodies almost always occur in just one chiral form when they could potentially exist in either is a mystery that has confounded researchers for years.

‘Our bodies contain important molecules like proteins that overwhelmingly have one type of chirality,’ Mason said. ‘The other chiral form is essentially not found. I find that fascinating. We asked, ‘Could this biological preference of a particular chirality possibly have a physical origin?’‘

How does chirality occur in the first place?

In addressing this question, Mason and his team sought to discover how chirality occurs in the first place. Their findings offer new insights into how the phenomenon can arise spontaneously, even with achiral building blocks.

Mason and his colleagues used a manufacturing technique called lithography, which is the basis for making computer chips, to make millions of microscale particles in the shape of achiral triangles. In the past, Mason has used this technique to ‘print’ particles in a wide variety of shapes, and even in the form of letters of the alphabet.

Using optical microscopy, the researchers then studied very dense systems of these lithographic triangular particles. To their surprise, they discovered that the achiral triangles spontaneously arranged themselves to form two-triangle ‘super-structures,’ with each super-structure exhibiting a particular chirality.

In the image that accompanies this article, the coloured outlines in the field of triangles indicate chiral super-structures having particular orientations.

So what is causing this phenomenon to occur? Entropy, says Mason. His group has shown for the first time that chiral structures can originate from physical entropic forces acting on uniform achiral particles.

Bizarre

‘It’s quite bizarre,’ Mason said. ‘You’re starting with achiral components  -  triangles  -  which undergo Brownian motion and you end up with the spontaneous formation of super-structures that have a handedness or chirality. I would never have anticipated that in a million years.’

Entropy is usually thought of as a disordering force, but that does not capture its subtler aspects. In this case, when the triangular particles are diffusing and interacting at very high densities on a flat surface, each particle can actually maximise its ‘wiggle room’ by becoming partially ordered into a liquid crystal (a phase of matter between a liquid and a solid) made out of chiral super-structures of triangles.

‘We discovered that just two physical ingredients  -  entropy and particle shape  -  are enough to cause chirality to appear spontaneously in dense systems,’ Mason said. ‘In my 25 years of doing research, I never thought that I would see chirality occur in a system of achiral objects driven by entropic forces.’

As for the future of this research, ‘we are very interested to see what happens with other shapes and if we can eventually control the chiral formations that we see occurring here spontaneously,’ he said.

‘To me, it’s intriguing, because I think about the chiral preference in biology,’ Mason added. ‘How did this chiral preference happen? What are the minimum ingredients for that to occur? We are learning some new physical rules, but the story in biology is far from complete. We have added another chapter to the story, and I’m amazed by these findings.’

Achiral triangles form chiral super-structures. The coloured patches in the field of triangles indicate newly formed chiral structures. Coloured patches represent parallelogram outlines around pairs of triangles that have formed chiral super-structures. Parallelograms having different ‘handedness’ and orientations are colour-coded and superimposed over each other. (Image: Thomas G. Mason and Kun Zhao)

Source: UCLA

To celebrate its 22nd anniversary in orbit, the Hubble Space Telescope released a dramatic new image of the star-forming region 30 Doradus, also known as the Tarantula Nebula because its glowing filaments resemble spider legs. A new image from all three of NASA’s Great Observatories – Chandra, Hubble, and Spitzer – has also been created to mark the event.

The nebula is located in the neighbouring galaxy called the Large Magellanic Cloud, and is one of the largest star-forming regions located close to the Milky Way. At the centre of 30 Doradus, thousands of massive stars are blowing off material and producing intense radiation along with powerful winds. The Chandra X-ray Observatory detects gas that has been heated to millions of degrees by these stellar winds and also by supernova explosions. These X-rays, coloured blue in this composite image, come from shock fronts – similar to sonic booms – formed by this high-energy stellar activity.

The Hubble data in the composite image, coloured green, reveals the light from these massive stars along with different stages of star birth, including embryonic stars a few thousand years old still wrapped in cocoons of dark gas. Infrared emission data from Spitzer, seen in red, shows cooler gas and dust that have giant bubbles carved into them. These bubbles are sculpted by the same searing radiation and strong winds that comes from the massive stars at the centre of 30 Doradus.

(Image: X-ray: NASA/CXC/PSU/L. Townsley et al; Optical: NASA/STScI; Infrared: NASA/JPL/PSU/L. Townsley et al)

Source: NASA

New data from the Herschel Space Observatory shows that galaxies with the most powerful, active, supermassive black holes at their cores produce fewer stars than galaxies with smaller black holes.

Supermassive black holes are believed to reside in the hearts of all large galaxies. When gas falls upon these monsters, the materials are accelerated and heated around the black hole, releasing great torrents of energy. In the process, active black holes often generate colossal jets that blast out twin streams of heated matter.

Inflows of gas into a galaxy also fuel the formation of new stars. In a new study of distant galaxies, Herschel helped show that star formation and black hole activity increase together, but only up to a point. Astronomers think that if an active black hole flares up too much, it starts spewing radiation that prevents raw material from coalescing into new stars.

This artist concept of the local galaxy Arp 220, captured by the Hubble Space Telescope, helps illustrate the Herschel results. The bright core of the galaxy, paired with an overlaid artist’s impression of jets emanating from it, indicate that the central black hole’s activity is intensifying. As the active black hole continues to rev up, the rate of star formation will, in turn, be suppressed in the galaxy. Astronomers want to study further how star formation and black hole activity are intertwined.

Herschel is a European Space Agency cornerstone mission, with science instruments provided by consortia of European institutes, with important participation by NASA. (Image: NASA/JPL-Caltech)

Source: NASA

Researchers determine that although glaciers continue to increase in velocity, the rate at which they can dump ice into the ocean is limited

Changes in the speed that ice travels in more than 200 outlet glaciers indicates that Greenland’s contribution to rising sea level in the 21st century could be significantly less than the upper limits some scientists thought possible.

The finding comes from a paper funded by the National Science Foundation (NSF) and NASA and published in the journal Science.

While the study indicates that a melting Greenland’s contributions to rising sea levels could be less than expected, researchers concede that more work needs to be done before any definitive trend can be identified.

Studies like this one are designed to examine more closely and in greater detail what is actually happening with the ice sheets, often using newer and more precise tools and thereby better defining the parameters that scientists use to make predictions, such as the upper limits of sea-level rise.

Some good news

‘This study provides more evidence that the rate at which these glaciers can dump ice into the ocean is indeed limited,’ said Ian Howat, assistant professor of Earth sciences and member of the Byrd Polar Research Centre at Ohio State University, a co-author on the paper. ‘What remains to be seen is how long the acceleration will continue – but it appears that our worst-case scenarios aren’t likely.’

The fate of the Earth’s ice sheets and their potential contributions to sea-level rise as the globe warms are among the major scientific uncertainties cited in the Fourth Assessment of the Intergovernmental Panel on Climate Change (IPCC). This is in part because the Greenland and Antarctic ice sheets have historically been, and in large measure continue to be, relatively sparsely monitored, as compared to other parts of the globe.

The faster the glaciers move, the more ice and melt water they release into the ocean.

In previous studies, scientists trying to understand the contribution of melting ice to rising sea level in a warming world considered a scenario in which the Greenland glaciers would either double or increase by as much as 10-fold their velocity between 2000 and 2010 and then stabilise at the higher speed.

A small rise in mean sea level

This new study shows Greenland ice would likely move at the lower rate – a doubling of its speed – and contribute about 100mm to rising sea level by 2100. The previous studies used the higher speed and estimated the glaciers would contribute nearly 475mm by the end of this century.

In the new study, the scientists extracted a decade-long record of changes in Greenland outlet glaciers by producing velocity maps using data from the Canadian Space Agency’s Radarsat-1 satellite, Germany’s TerraSar-X satellite and Japan’s Advanced Land Observation Satellite. They started with the winter of 2000-01 and then repeated the process for each winter from 2005-06 through 2010-11 and found that the outlet glaciers had not increased in velocity as much as had been speculated.

‘So far, on average we’re seeing about a 30% speedup in 10 years [of Greenland glaciers, which gives new insight for rising sea level],’ said Twila Moon, a University of Washington doctoral student in Earth and space sciences and lead author of the paper documenting the observations.

It is important to look at as much data as possible

‘This study is a great example of the power of high-resolution data sets in both space and time, and the importance of looking carefully at as much data as possible in helping make the best predictions we can of future changes’, said Henrietta Edmonds, program director for Arctic Natural Sciences in NSF’s Office of Polar Programs.

The scientists saw no clear indication in the new research that the glaciers will stop gaining speed during the rest of the century, and so by 2100 they could reach or exceed the scenario in which they contribute 100mm to sea level rise.

The record showed a complex pattern of behaviour. Nearly all of Greenland’s largest glaciers that end on land move at top speeds of 10-100m a year, and their changes in speed are small because they are already moving slowly. Glaciers that terminate in fjord ice shelves move at 200-1 000m a year, but did not gain speed appreciably during the decade.

In the East, Southeast and Northwest areas of Greenland, glaciers that end in the ocean can travel 11km or more in a year. Their changes in speed varied (some even slowed), but on average the speeds increased by 28% in the Northwest and 32% in the Southeast during the decade.

Moon said she was drawn to the research from a desire to take the large store of data available from the satellites and put it into a usable form to understand what is happening to Greenland’s ice. ‘We don’t have a really good handle on it and we need to have that if we’re going to understand the effects of climate change,’ she said.  ‘We are going to need to continue to look at all of the ice sheet to see how it’s changing, and we are going to need to continue to work on some tough details to understand how individual glaciers change.’

The north branch of Jakobshavn Isbrae is in the upper left corner of the image, with several newly calved icebergs in front of it. The larger, faster moving, south branch is located near the upper right corner. Prior to about 2003, both branches merged to create a large floating ice tongue that extended beyond the iceberg covered area visible in this image. Since the 1990, the glacier calving front (terminus) has retreated about 18km. Now, it is only in the winter that both branches sometimes merge to form a much smaller seasonal ice tongue, which breaks up in the spring. (Image: Polar Science Centre, Applied Physics Laboratory, University of Washington)

Source: National Science Foundation

Sacrificial beams and stress-dependent materials – concepts of interest to modern engineering – are critical in keeping webs strong

While researchers have long known of the incredible strength of spider silk, the robust nature of the tiny filaments cannot alone explain how webs survive multiple tears and winds that exceed hurricane strength.

Now, a study that combines experimental observations of spider webs with complex computer simulations shows that web durability depends not only on silk strength, but also on how the overall web design compensates for damage and the response of individual strands to continuously varying stresses.

Reporting in the cover story of the 2 February 2012, issue of Nature, researchers from the Massachusetts Institute of Technology (MIT) and the Politecnico di Torino in Italy show how spider web-design localises strain and damage, preserving the web as a whole.

How does the web actually work?

‘Multiple research groups have investigated the complex, hierarchical structure of spider silk and its amazing strength, extensibility and toughness,’ says Markus Buehler, associate professor of civil and environmental engineering at MIT. ‘But, while we understand the peculiar behaviour of dragline silk from the ‘nanoscale up’ – initially stiff, then softening, then stiffening again – we have little insight into how the molecular structure of silk uniquely improves the performance of a web.’

The spider webs found in gardens and garages are made from multiple silk types, but viscid silk and dragline silk are most critical to the integrity of the web. Viscid silk is stretchy, wet and sticky, and it is the silk that winds out in increasing spirals from the web centre. Its primary function is to capture prey. Dragline silk is stiff and dry, and it serves as the threads that radiate out from a web’s centre, providing structural support. Dragline silk is crucial to the mechanical behaviour of the web.

Some of Buehler’s earlier work showed that dragline silk is composed of a suite of proteins with a unique molecular structure that lends both strength and flexibility. ‘While the strength and toughness of silk has been touted before – it is stronger than steel and tougher than Kevlar by weight – the advantages of silk within a web, beyond such measures, has been unknown,’ Buehler adds.

The study’s subjects

The common spiders represented in the recent study, including orb weavers (Nephila clavipes), garden spiders (Araneus diadematus) and others, craft familiar, spiralling web patterns atop a scaffolding of radiating filaments. Building each web takes energy the spider cannot afford to expend often, so durability is key to the arachnid’s survival.

Through a series of computer models matched to laboratory experiments with spider webs, the researchers were able to tease apart what factors play what role in helping a web endure natural threats that are either localised, such as a twig falling on a filament, or distributed, such as high winds.

‘For our models, we used a molecular dynamics framework in which we scaled up the molecular behaviour of silk threads to the macroscopic world. This allowed us to investigate different load cases on the web, but more importantly, it also allowed us to trace and visualise how the web fractured under extreme loading conditions,’ says Anna Tarakanova, who developed the computer models along with Steven Cranford, both graduate students in Buehler’s laboratory.

Building ‘synthetic’ webs

‘Through computer modelling of the web,’ Cranford adds, ‘we were able to efficiently create ‘synthetic’ webs, constructed out of virtual silks that resembled more typical engineering materials such as those that are linear elastic, like many ceramics, and elastic-plastic materials, which behave like many metals. With the models, we could make comparisons between the modelled web’s performance and the performance seen in the webs made from natural silk. In addition, we could analyse the web in terms of energy, and details of the local stress and strain,’ which are traits experiments were able to reveal.

The study showed that, as one might expect, when any part of a web is perturbed, the whole web reacts. Such sensitivity is what alerts a spider to the struggling of a trapped insect. However, the radial and spiral filaments each play different roles in attenuating motion, and when stresses are particularly harsh, they are sacrificed so that the entire web may survive.

‘The concept of selective, localised failure for spider webs is interesting since it is a distinct departure from the structural principles that seem to be in play for many biological materials and components,’ adds Dennis Carter, the NSF program director for biomechanics and mechanobiology who helped support the study.

‘For example, the distributed material components in bone spread stress broadly, adding strength. There is no ‘wasted’ material, minimising the weight of the structure. While all of the bone is being used to resist force, bone everywhere along the structure tends to be damaged prior to failure.’

A clever strategy

In contrast, a spider’s web is organised to sacrifice local areas so that failure will not prevent the remaining web from functioning, even if in a diminished capacity, says Carter. ‘This is a clever strategy when the alternative is having to make an entire, new web,’ he adds. ‘As Buehler suggests, engineers can learn from nature and adapt the design strategies that are most appropriate for specific applications.’

Specifically, when a radial filament in a web is snagged, the web deforms more than when a relatively compliant spiral filament is caught. However, when either type fails – under great stress – it is the only filament to fail.

The unique nature of the spider-silk proteins enhances that effect. When a filament is pulled, the silk’s unique molecular structure – a combination of amorphous proteins and ordered, nanoscale crystals – unfurls as stress increases. This leads to a stretching effect that has four distinct phases: an initial, linear tugging; a drawn out stretching as the proteins unfold; a stiffening phase that absorbs the greatest amount of force; and then a final, stick-slip phase before the silk breaks.

According to the researchers’ findings, the failure of silk threads occurs at points where the filament is disturbed by that external force, but after failure, the web returns to stability – even in simulations using broad forces, like hurricane-force winds.

‘Engineered structures are typically designed to withstand large loads with limited damage, but extreme loads are more difficult to account for,’ says Cranford. ‘The spider has uniquely solved this problem by allowing a sacrificial member to fail under high load. One of the first questions a structural engineer must ask is ‘what is the design load?’ For a spider web, however, it does not matter if the load is just strong enough to cause failure, or one hundred times higher – the net effect is the same. Allowing a sacrificial member to fail removes the unpredictability of ‘extreme’ loads from the design equation.’

This hierarchical depiction shows how a spider web responds to stress, spanning from the web scale to the scale of protein molecules only nanometres, or billionths of a meter, across. When a force strikes the web, such as that from a trapped fly, the web deforms in distinct ways at multiple scales yet fails only where silk threads are under the most stress. The web manages that feat because of slipping that takes place within the spider-silk protein molecules. The result is compensation for some stress, yet sacrificial failure when stress becomes extreme, preserving the web as a whole. (Illustration: Zina Deretsky, National Science Foundation, in collaboration with S. Cranford, G. Bratzel and M.J. Buehler (all three from Massachusetts Institute of Technology, and Rihcard C. Yu and Andaluz Yu of Green Pacific Biologicals)

(Image: Michael Hartl, via Wikimedia Commons)

Source: National Science Foundation

Researchers release findings on who benefits from nature tourism

Using nature’s beauty as a tourist draw can boost conservation in China’s valued panda preserves, but it is not an automatic ticket out of poverty for the humans who live there, a unique long-term study shows. This study can also have relevance here in South Africa, where there are many projects to assist local communities in benefiting from local tourism attractions.

Often those who benefit most from nature-based tourism are people who already have resources. The truly impoverished have a harder time breaking into the tourism business, according to the paper, ‘Drivers and Socioeconomic Impacts of Tourism Participation in Protected Areas,’ published in the 25 April edition of PLoS One.

The study looks at nearly a decade of burgeoning tourism in the Wolong Nature Reserve in Southwestern China. China, like many areas in the world, relies on tourism over farming for economic viability, while attempting to preserve fragile animal habitat.

However, until now, no one has taken a close look at the long-term implications for people economically.

‘Long-term studies like this one give us a birds-eye view into the multifaceted connections between people and the environments they occupy,’ said Thomas Baerwald, a program director for the Geography and Spatial Sciences Program at the National Science Foundation (NSF), which partially funded the study.

Finding the right balance

‘Finding the right balance between economics that lift people from poverty and habitat management is an important role for social and environmental scientists and will be important into the future.’

Lead researcher Wei Liu is a Ph.D. candidate in the Centre for Systems Integration and Sustainability (CSIS) at Michigan State University (MSU). He and his colleagues took advantage of the centre’s 15-year history of work in Wolong, which they call an excellent laboratory to study the complex interactions of humans and nature.

‘This study shows the power of having comprehensive long-term data to understand how everything works together,’ Liu said. ‘This is the first time we’ve been able to put it together to understand how changes are being made.’

The PLoS One paper is co-authored by Christine Vogt, MSU professor of community, agriculture, recreation and resource studies; Junyan Luo, research associate; Guangming He, research assistant; Kenneth Frank, professor of measurement and quantitative methods and fisheries and wildlife; and Jianguo ‘Jack’ Liu, Rachel Carson Chair in Sustainability. All but Vogt are members of CSIS; Jack Liu is director.

Watching families ride the wave of change

Wei Liu and his colleagues followed 220 families in Wolong from 1999 to 2007 as they rode the wave of change in an area shifting from farming to bringing in tourists, who wanted to see the land of the giant pandas as well as experience its beauty.

That wave abruptly stopped in 2008 with the massive Sichuan earthquake that measured 8.0 on the moment magnitude scale used by seismologists to calculate the size of earthquakes. Damage to roads and buildings from Sichuan still impedes business development today.

Wei Liu and team studied the impact of having resources in Wolong. Residents who already had money, were educated, and had relationships with governmental officials had a much greater chance of being successful with the arrival of nature-based tourism.

Lacking these resources made it harder, which is significant since many of China’s programs and initiatives aim to lift people out of poverty.

‘The policies haven’t yet reached their full potential,’ Wei Liu said. ‘But now we have the data to show what’s happening.

Seeing the downside of tourism

An interesting piece of the research was learning that people who are engaged in the tourism trade were more likely to acknowledge the tradeoffs between tourism development and conservation. Wei said they acknowledged that tourism increased noise, traffic congestion and disturbance to wildlife.

Wei Liu said this research could help China – and other countries around the world – with the next steps of developing policies to balance tourism with habitat management. The area is working hard to rebuild from the earthquake, just as other developing tourism areas are challenged by natural disasters. The study, he and his colleagues say, can point to opportunities to improve policies.

The research was funded by NSF and NASA. Research on the interactions between human behaviour and the environment can help guide policy, and are an important focus of NSF’s Directorate for Social, Behavioural and Economic Sciences

Research shows nature tourism is not an automatic ticket out of poverty for people who transition from farming to tourism for economic improvement. Here, tourists watch pandas at China's Conservation and Research Centre for the Giant Panda (CCRCGP) in Wolong Nature Reserve, May 2005. (Image: Wei Liu, Department of Fisheries and Wildlife, Michigan State University)

Source: National Science Foundation