Wednesday, May 31, 2017

Amazon Rainforest May Be More Resilient to Deforestation Than Previously Thought

Taking a fresh look at evidence from satellite data, and using the latest theories from complexity science, researchers at the University of Bristol have provided new evidence to show that the Amazon rainforest is not as fragile as previously thought. The research is published in Nature Communications.

The Amazon forest stores about half of the global tropical forest carbon and accounts for about a quarter of carbon absorption from the atmosphere by global forests each year. As a result, large losses of Amazonian forest cover could make global climate change worse.

In the past, researchers have found that a large part of the Amazon forest is susceptible to a tipping point. The tell-tail sign is satellite data showing areas of savannah and rainforest coexisting under the same environmental conditions. 

Credit: University of Bristol 

Theories from nonlinear dynamics would then suggest that both states are alternative stable outcomes. This so called bistability means that shocks such as forest clearance or drought could lead to a dramatic increase of fire occurrence and tip an area of rainforest into savannah. Areas that have experienced this transition would then remain locked into this savannah state until large enough increases of rainfall and release of human pressures allow forests to regrow faster than they are lost by intermittent fires.

Bert Wuyts, a fourth year PhD student in the Bristol Centre for Complexity Sciences and lead author on the paper, said: “I decided to take a fresh look at the data and a very different picture emerged when I controlled for seasonality and took out all the data points from satellite images that represented locations that had been subjected to human influence. Suddenly the property of bistability disappeared almost completely.”

Bert, who made this discovery in the first year of his PhD, thought it seemed most puzzling, so he teamed up with Professor Alan Champneys, a theorist in the Department of Engineering Mathematics, and Dr Jo House, an expert on land use change from the School of Geographical Sciences. For the past two years they have been examining these findings rigorously.

Alan Champneys, Professor of Applied Non-linear Mathematics, added: “When I first agreed to co-supervise Bert’s PhD, I was worried that I had no expertise in the mathematics required to study the observed effects in the satellite data. Fortunately Bert is a superbly independent student and Jo was on hand as a field expert.

“Little did I realise though that the key to understanding Bert’s observations was the same pattern formation theory I have used extensively before. To me this shows the power of interdisciplinary collaboration and also the ubiquity of mathematics and data science in explaining seemingly unrelated phenomena.”

Previous research appears to have failed to take into account spatial interaction and edge effects between neighbouring zones, typically through naturally occurring forest fires. Taking such terms into account leads to reaction-diffusion theory, used widely in predicting the formation of spatial patterns within physics and chemistry. According to the theory, there should be a distinct boundary between forest and savannah predictable from climate and soils.

The key was to recognise that proximity to human cultivations acts as a third determining factor. Forests closer to human cultivations are subject to logging and erosion by fires originating from the open cultivated areas. This causes a shift of the forest-savanna boundary towards wetter areas.

The good news is that as long as there is some forest left, deforestation will not lock currently forested areas into a savannah state. This means that recovery of the forest in deforested areas should happen as soon as these areas are released from human pressures. Nevertheless, there exists a second mechanism that could lead to bistability of Amazonian forest cover, which was not taken into account in this research.

Previous research has shown via simulations that the Amazon forest can have a positive effect on regional rainfall. Through this mechanism, forest loss may lead to decreased rainfall causing further forest loss. Whether climate change or deforestation may still permanently transform the Amazon forest into a savannah depends on the importance of this second mechanism and is subject of further research.


Contacts and sources:
University of Bristol

Citation: ‘Amazonian forest-savanna bistability and human impact’ by Bert Wuyts, Alan R. Champneys and Joanna I. House in Nature Communica

Exactly How Old Are Animals: Half a Billion, a Billion, or 1.5 Billion Years?

The origin of animals was one of the most important events in the history of Earth. Beautifully preserved fossil embryos suggest that our oldest ancestors might have existed a little more than half a billion years ago.

Yet, fossils are rare, difficult to interpret, and new, older fossils are constantly discovered.

An alternative approach to date the 'tree of life' is the molecular clock, which was introduced in the early 1960s by twice Nobel Laureate Linus Pauling which uses genetic information. 

Detail from an embryo of the scalidophoran Markuelia from the Middle Cambrian of Australia.
Credit: Philip Donoghue - University of Bristol

Early molecular clock studies assumed that mutation accumulated at a fixed rate across all species and concluded that our oldest ancestor might have existed around 1.5 billions of years ago, a date that is almost three-times as old as the oldest fossil evidence of animal life.

These results sparked heated, scientific debates that only eased off in the last decade when a new generation of more realistic 'relaxed' clock methods, that do not assume constancy of the mutation rate, started to close the gap between molecules and fossils indicating that animals are unlikely to be older than around 850 million of years.

However, using a recently developed relaxed molecular clock methods called RelTime a team of scientists at Oakland (Michigan) and Temple (Philadelphia) dated the origin of animals at approximately 1.2 billion years ago reviving the debate on the age of the animals.

Puzzled by the results of the American team, researchers from the University of Bristol and Queen Mary University of London decided to take a closer look at RelTime and found that it failed to relax the clock. Their findings are published today in the journal Genome Biology and Evolution.

Professor Philip Donoghue from the University of Bristol's School of Earth Sciences, said: "What caught our attention was that results obtained using RelTime were in strong disagreement with a diversity of different studies, from different research groups and that used different software and data, all of which broadly agreed that animals are unlikely to be older than approximately 850 million years."

Dr Mario dos Reis, a co-author from London, added: "Generally scientists use Bayesian methods to relax the clock. These methods use explicit probability models to account for the uncertainty in the fossil record and in the mutation rate.

"Bayesian methods borrow tools from financial mathematics to model variation in mutation rate in a way that is similar to that used to model the stochastic variation in stock prices with time.

"By applying these sophisticated mathematical tools, Bayesian methods relax the clock and estimate divergence times. However, RelTime is not a Bayesian method."

Dr Jesus Lozano-Fernandez, also from the University of Bristol, added: "Estimating divergence times is difficult and different relaxed molecular clock methods use different approaches to do so. However, we discovered that the RelTime algorithm failed to relax the clock along the deepest branches of the animal tree of life."

Bristol’s Professor Davide Pisani concluded: "Current Bayesian methods date the last common animal ancestor to less than approximately 850 millions of years ago, in relatively good agreement with the fossil record.

"RelTime suggested that animals are much older but it turned out that it suffers from the same problems of the early clock methods.

"This clearly indicates that older ideas suggesting that animals might be twice or three times as old as the oldest animal fossil are erroneous and only emerge when changes in mutation rate are incorrectly estimated.

"RelTime results sounded like a blast from the past, but their provably erroneous nature ended up blasting these same old ideas that they were trying to revive."

Contacts and sources:
University of Bristol

Citation: 'RelTime rates collapse to a strict clock when estimating the timeline of animal diversification' by J. Lozano-Fernandez, M. dos Reis, P. Donoghue and D. Pisani in Genome Biology and Evolution

Gecko-Inspired Multipurpose Gripper Has Load Sharing Mechanism

An elastic membrane covered with tiny fibres paired with a pressure differential enables a new soft gripper system with a high adhesion performance even on curved surfaces

Robots generally need a gripper that adapts to three-dimensional surfaces. Such a gripper needs to be soft to adapt to a great variety of geometries, but not too soft, as it will detach easily and not be able to bear weight for very long. Researchers working with Metin Sitti at the Max Planck Institute for Intelligent Systems in Stuttgart developed a membrane equipped with microscopic fibres inspired by the fine hairs on a gecko's foot and attached it to a suction cup-like flexible body. 

An internal pressure differential ensures perfect conformation of the flexible gripper to a wide variety of surfaces and equally distributes the load over the entire contact interface. As a result, the researchers suppressed load induced stress concentrations at the edges, which strongly reduced the adhesion. The gripper demonstrates a 14-times higher adhesion than grippers without this load sharing mechanism.

Demonstration of the proposed soft adhesion-based gripping system holding various 3D objects such as (A) a rounded glass flask filled with 200 mL of liquid (total weight of 307 g), (B–D) a 118-g coffee cup, (E) a 41-g pair of of cherry tomatoes, and (F) a 139-g plastic bag. (Scale bar, 10 cm.)
Credit: © PNAS

The gecko can easily move along smooth walls or upside down on the ceiling. Owing to the millions of tiny hairs on the underside of its toes. The tiny hairs adhere to almost any surface by means of van der Waals forces. While the force of a single hair is extremely weak, their individual contributions add up to a total force that can carry a multiple of the little lizard's body weight.

Simplified mimics of nature’s adhesives can now be technologically fabricated, for example in polymers, having gecko inspired adhesive hairs on their surface. However, up to now, their rigid backing restricted the adhesive membrane to adapt to curved surfaces. Even a soft backing would be of little use: it would peel off from the contact edges, where the forces concentrate, similar to a piece of Sellotape that is pulled off.

“Our goal therefore was to distribute the load equally over the entire membrane,” explains Sukho Song, first author of the study, from the Max Planck Institute for Intelligent Systems in Stuttgart. The key: The researchers attached an adhesive membrane to a flexible gripper body allowing the membrane to adapt to complex shapes. Then, they applied a gentle pressure differential inside the gripper chamber, causing its adaptation to the object surface. The pressure differential distributes the load across the entire contact interface of the membrane. This prevents the formation of load concentrations at the gripper edges, which can induce an easy releasing of the object. 

“Another advantage is that the gripper can accommodate the deformation of an object. As a result, the surfaces do not peel off, which would lead to a loss of adhesive force,” says co-author Dirk-Michael Drotlef. This is not possible with a rigid backing.

The scientists in Stuttgart overcame another weakness of previous systems. On the gecko’s foot, millions of tiny hairs adhere far less than a million individual hairs. Because many hairs are not optimally aligned or do not make contact with the surface. This in turn means that the adhesive force does not proportionally increase with the surface area. Up to now, the performance of most reversible technical adhesive systems has been significantly poorer on curved surfaces compared to the gecko. 

“Up to now, only 1.8 percent of the maximum adhesive force was achieved by similar systems without the new load sharing mechanism,” says Drotlef. “Our gripper achieves a 14 times increase, which is around 26 percent.”

This is very close to the natural model and meets important requirements for real-world gripping applications. In tests, a coin-sized gripper could hold a roughly 300-gram glass flask filled with liquid, a cup at different holding points, including its handle, as well as tomatoes and a 140-gram plastic bag. Therefore, it is truly a multipurpose gripper.

Another advantage is the residue-free adhesion, which is important for the microchip manufacturing where even the smallest contamination has to be avoided. Robots, on the other hand, could move on differently shaped surfaces using this technology, irrespective of how narrow these are. Adhesion to very rough surfaces is the only aspect that continues to cause problems for researchers, but the team in Stuttgart is about to address this issue.

Contacts and sources:
Christian J. Meier
Professor Dr. Metin Sitti
Max Planck Institute for Intelligent Systems

Citation: Sukho Song, Dirk-Michael Drotlef, Carmel Majidi and Metin Sitti
Controllable load sharing for soft adhesive interfaces on three-dimensional surfaces PNAS, DOI: 10.1073/pnas.1620344114

Reptile Vocalization Is Surprisingly Flexible and Complex

Phenotypic plasticity of gecko calls reveals the complex communication of lizards

It has now been shown for the first time that non-avian reptiles are able to adjust their calls in relation to environmental noise as is known for the complex vocal communication systems of birds and mammals. 

In Tokays, night active geckos of South East Asia, researchers of the Max Planck Institute for Ornithology in Seewiesen found an increase in the duration of brief call notes in the presence of broadcast noise compared to quiet conditions. 

The geckos did not adjust the amplitude of their calls, however, under noisy conditions the animals produced more of the louder syllables. This discovery shows that the communication systems of non-avian reptiles are much more complex than previously thought and that they already possess faculties that are typical of sophisticated signaling of birds and mammals.

Geckos have a sophisticated vocal communication systems similar to mammals and birds.
Credit: © Henrik Brumm

The sophisticated vocal communication systems of birds and mammals are characterized by a high degree of plasticity in which signals are individually adjusted in response to changes in the environment. One mechanism of such vocal plasticity is the Lombard effect, in which the call amplitude increases depending on the level of ambient noise. This Lombard effect is often accompanied by an increase in the duration of the call, which further helps to detect the signals in noise.

In non-avian reptiles some species do have vocal communication, like for example the Tokay, a night active gecko from South East Asia. Within his repertoire, especially the loud GECK-O call stands out and led to his scientific name Gekko gecko. The GECK-O call has important functions for the communication of Tokay males to attract females and to repel rival males. This call is often preceded by low-amplitude cackles. 

For their study, Henrik Brumm and Sue Anne Zollinger of the Max Planck Institute for Ornithology exposed Tokays to noise of about 65 dB(A) which corresponds to the traffic noise of a busy street. They wanted to find out if the Lombard effect could also be found in a reptile. And in fact, the Tokays increased the duration of the GECK-calls by 7 percent and the O-calls by 37 percent compared to the control group in quiet conditions. Therefore, the Tokays, and probably also other vocally-communicating reptiles, are able to adjust their calls depending on the ambient conditions.

However, the researchers could not find a Lombard effect in the calls, as the Tokays did not increase the amplitude of their call syllables in relation to the background noise level. "The study suggests that the Lombard effect evolved independently in birds and mammals", says Henrik Brumm, first author of the study and research group leader in Seewiesen. 

However, the Tokays employed another strategy to increase the overall signal-to-noise ratio of their calls: Instead of increasing the amplitude of each call component, they produced more of the loud GECK-O syllables and fewer of the softer cackle calls in noise. "We think that the fact that signals will reach the intended recipient is a driving force for the evolution of a communication system, independently of the animal group", says Sue Anne Zollinger, co-author of the study.

Contacts and sources:
Dr. Henrik Brumm
Max Planck Institute for Ornithology, Seewiesen

Citation: Vocal plasticity in a reptile
Henrik Brumm, Sue Anne Zollinger
Published 24 May 2017.DOI: 10.1098/rspb.2017.0451

Relatives of Ancient Egyptians Revealed in First Genetic Study of Egypt’s Mummies

An international team of scientists, led by researchers from the University of Tuebingen and the Max Planck Institute for the Science of Human History in Jena, successfully recovered and analyzed ancient DNA from Egyptian mummies dating from approximately 1400 BCE to 400 CE, including the first genome-wide nuclear data from three individuals, establishing ancient Egyptian mummies as a reliable source for genetic material to study the ancient past. 

The study, published in Nature Communications, found that modern Egyptians share more ancestry with Sub-Saharan Africans than ancient Egyptians did, whereas ancient Egyptians were found to be most closely related to ancient people from the Near East.

Egyptian mummy

Credit: Dada/Wikimedia Commons

Egypt is a promising location for the study of ancient populations. It has a rich and well-documented history, and its geographic location and many interactions with populations from surrounding areas, in Africa, Asia and Europe, make it a dynamic region. Recent advances in the study of ancient DNA present an intriguing opportunity to test existing understandings of Egyptian history using ancient genetic data.

However, genetic studies of ancient Egyptian mummies are rare due to methodological and contamination issues. Although some of the first extractions of ancient DNA were from mummified remains, scientists have raised doubts as to whether genetic data, especially nuclear genome data, from mummies would be reliable, even if it could be recovered. 

“The potential preservation of DNA has to be regarded with skepticism,” confirms Johannes Krause, Director at the Max Planck Institute for the Science of Human History in Jena and senior author of the study. 

“The hot Egyptian climate, the high humidity levels in many tombs and some of the chemicals used in mummification techniques, contribute to DNA degradation and are thought to make the long-term survival of DNA in Egyptian mummies unlikely.” The ability of the authors of this study to extract nuclear DNA from such mummies and to show its reliability using robust authentication methods is a breakthrough that opens the door to further direct study of mummified remains.

For this study, an international team of researchers from the University of Tübingen, the Max Planck Institute for the Science of Human History in Jena, the University of Cambridge, the Polish Academy of Sciences, and the Berlin Society of Anthropology, Ethnology and Prehistory, looked at genetic differentiation and population continuity over a timespan of around one and a half millennia, and compared these results to modern populations. 

Verena Schünemann carrying out paleogenetic examinations at the University of Tuebingen.
Credit: © Johannes Krause

The team sampled 151 mummified individuals from the archaeological site of Abusir el-Meleq, along the Nile River in Middle Egypt, from two anthropological collections hosted and curated at the University of Tübingen and the Felix von Luschan Skull Collection at the Museum of Prehistory of the Staatliche Museen zu Berlin, Stiftung Preussischer Kulturbesitz.

In total, the authors recovered mitochondrial genomes from 90 individuals, and genome-wide datasets from three individuals. They were able to use the data gathered to test previous hypotheses drawn from archaeological and historical data, and from studies of modern DNA. “In particular, we were interested in looking at changes and continuities in the genetic makeup of the ancient inhabitants of Abusir el-Meleq,” said Alexander Peltzer, one of the lead authors of the study from the University of Tübingen. 

Map of Egypt, showing the archaeological site of Abusir-el Meleq (orange X), and the location of the modern Egyptian samples used in the study (orange circles). 
Map of Egypt, showing the archaeological site of Abusir-el Meleq (orange X), and the location of the modern Egyptian samples used in the study (orange circles). Graphic: Annette Guenzel.
Graphic: Annette Guenzel. Credit: Nature Communications, DOI: 10.1038/NCOMMS15694

The team wanted to determine if the investigated ancient populations were affected at the genetic level by foreign conquest and domination during the time period under study, and compared these populations to modern Egyptian comparative populations. “We wanted to test if the conquest of Alexander the Great and other foreign powers has left a genetic imprint on the ancient Egyptian population,” explains Verena Schünemann, group leader at the University of Tübingen and one of the lead authors of this study.

Close genetic relationship between ancient Egyptians and ancient populations in the Near East

The study found that ancient Egyptians were most closely related to ancient populations in the Levant, and were also closely related to Neolithic populations from the Anatolian Peninsula and Europe. “The genetics of the Abusir el-Meleq community did not undergo any major shifts during the timespan of around one and a half millennia we studied, suggesting that the population remained genetically relatively unaffected by foreign conquest and rule,” says Wolfgang Haak, group leader at the Max Planck Institute for the Science of Human History in Jena. 

The data shows that modern Egyptians share approximately 8% more ancestry on the nuclear level with Sub-Saharan African populations than with ancient Egyptians. “This suggests that an increase in Sub-Saharan African gene flow into Egypt occurred within the last 1,500 years,” explains Stephan Schiffels, group leader at the Max Planck Institute for the Science of Human History in Jena. Possible causal factors may have been improved mobility down the Nile River, increased long-distance trade between Sub-Saharan Africa and Egypt, and the trans-Saharan slave trade that began approximately 1,300 years ago.

This study counters prior skepticism about the possibility of recovering reliable ancient DNA from Egyptian mummies. Despite the potential issues of degradation and contamination caused by climate and mummification methods, the authors were able to use high-throughput DNA sequencing and robust authentication methods to ensure the ancient origin and reliability of the data. The study thus shows that Egyptian mummies can be a reliable source of ancient DNA, and can greatly contribute to a more accurate and refined understanding of Egypt’s population history.


Contacts and sources:
Prof. Dr. Johannes Krause
Max Planck Institute for the Science of Human History in Jena and University of Tübingen

Dr. Dr. Verena Schünemann
University of Tübingen

Citation:  Verena J. Schuenemann, Alexander Peltzer, Beatrix Welte, W. Paul van Pelt, Martyna Molak, Chuan-Chao Wang, Anja Furtwangler, Christian Urban, Ella Reiter, Kay Nieselt, Barbara Tessmann, Michael Francken, Katerina Harvati, Wolfgang Haak, Stephan Schiffels & Johannes Krause: Ancient Egyptian mummy genomes suggest an increase of Sub-Saharan African ancestry in post-Roman periods. Nature Communications, DOI: 10.1038/ncomms15694

Tuesday, May 30, 2017

3D Printer Inks from the Woods Can Even Print Jawbones

Empa researchers have succeeded in developing an environmentally friendly ink for 3D printing based on cellulose nanocrystals. This technology can be used to fabricate microstructures with outstanding mechanical properties, which have promising potential uses in implants and other biomedical applications.

In order to produce 3D microstructured materials for automobile components, for instance, Empa researchers have been using a 3D printing method called “Direct Ink Writing” for the past year. During this process, a viscous substance – the printing ink – is squeezed out of the printing nozzles and deposited onto a surface, pretty much like a pasta machine. 

The big advantage of “Direct Ink Writing” (DIW) lies in the almost unlimited selection of materials available for inks. The cartridges can be filled with any kind of ink with differing compositions and these can then be printed directly and alternately. The printer has one high and one low temperature cartridge. This means that if certain polymers need to be melted, this can be done directly in the printer. The temperature can also be set for the substrate to be printed on, so that the hot liquid will, for example, immediately cool as soon as it hits the substrate. This offers a large degree of freedom in the development of new kinds of inks with tailor-made properties.

A jaw bone printed with the cellulose ink - the outstanding mechanical properties have promising potential uses in implants and other biomedical applications
Credit: Empa

Empa researchers Gilberto Siqueira and Tanja Zimmermann from the Laboratory for Applied Wood Materials have now succeeded, together with colleagues from Harvard University and ETH Zürich, in developing a new, environmentally friendly 3D printing ink made from cellulose nanocrystals (CNC).

Rod-like cellulose nanocrystals (CNC) approximately 120 nanometers long and 6.5 nanometers in diameter under the microscope. 
Credit: Empa

Cellulose, along with lignin and hemicellulose, is one of the main constituents of wood. The biopolymer consists of glucose chains organized in long fibrous structures. In some places the cellulose fibrils exhibit a more ordered structure. 

"The places with a higher degree of order appear in a more crystalline form. And it is these sections, which we can purify with acid, that we require for our research", explains Siqueira. The final product is cellulose nanocrystals, tiny rod-like structures that are 120 nanometers long and have a diameter of 6.5 nanometers. And it is these nanocrystals that researchers wanted to use to create a new type of environmentally friendly 3D printing ink. 

Previous inks contained a rather small proportion of “biological” materials, with a maximum of 2.5 percent CNC. The Empa team wished to increase this proportion, as they have now succeeded in doing – their new inks contain a full 20 percent CNC.

"The biggest challenge was in attaining a viscous elastic consistency that could also be squeezed through the 3D printer nozzles", says Siqueira. The ink must be “thick” enough so that the printed material stays “in shape” before drying or hardening, and doesn't immediately melt out of shape again. The first CNC mixtures were water-based. This did work in principle, but yielded a very brittle material. Therefore, Siqueira and his colleagues developed a second, polymer-based recipe that had a decisive advantage: after printing and hardening using UV radiation, the CNC “cross-linked” with polymer building blocks, which gave the composite material a significantly higher degree of mechanical rigidity.

Bringing things together despite resistance

What sounds quite simple in retrospect caused the Empa team a great deal of head-scratching. Siqueira: "Most polymers are water-repellent or hydrophobic, whereas cellulose attracts water – it is hydrophilic. As a result they are not very compatible." So the researchers first of all had to chemically modify the CNC surface.

After the first attempts at printing and X-ray analysis of the obtained microstructures, the researchers noticed that the CNC in the printed object had aligned itself almost perfectly in the direction it was printed in. They concluded that the mechanical strength used to push the ink through the printing nozzle was sufficient to align it. "It is pretty interesting that one can so easily control the direction of the nanocrystals, for example, if you want to print something that should have a specific mechanical rigidity in a certain direction", says Siqueira.

Lots and lots of possibilities

These outstanding mechanical properties represent a decisive advantage compared to other materials such as carbon fibers, which are also used in DIW inks. In addition, the new kind of ink from the Empa lab is made from a renewable material – cellulose. "Cellulose is the most frequently occurring natural polymer on Earth", says Siqueira. It is not just found in trees, but also in other plants and even in bacteria. 

The crystals, which are isolated from various cellulose sources, are morphologically different from each other and differ in size, but not in their properties. And they may also be of interest to, for example, the automobile industry or for packaging of any kind. "However, the most important area of application for me is in biomedicine", says Siqueira, "for example in implants or prostheses". The Empa researcher is convinced that the CNC material is suitable for a wide variety of different applications due to its outstanding mechanical properties, as well as the possibility of chemical modification and alignment during printing.

These possibilities are currently being investigated further at Empa. A PhD student is currently focusing on the further development of the materials and the printing method for other applications. In addition, a Master’s student intends to develop other “biological” inks. "Research in this field is only just beginning", says Gilberto Siqueira. "Printing with biopolymers is currently a very hot topic."

Contacts and sources:
Dr. Gilberto de Freitas Siqueira
Applied Wood Materials

 Citation: Cellulose Nanocrystal Inks for 3D Printing of Textured Cellular Architectures, G. Siqueira, D. Kokkinis, R. Libanori, M.K. Hausmann, A.S. Gladman, A. Neels, P. Tingaut, T. Zimmermann, J.A. Lewis, A.R. Studart, Advanced Functional Materials, DOI: 10.1002/adfm.201604619

World-First Technology Reduces Harmful Diesel Emissions

An industry-first technology developed by Loughborough University has the potential to significantly cut nitrogen oxide (NOx) emissions in diesel engines.

In 2015 the Government estimated that exposure to NOx and particulate matter emissions from diesel engines lead to around 52,000 additional deaths in the UK. NOx emissions are also the primary cause of smog in major cities around the world and a growing public health concern.

This has led to growing pressure on vehicle manufacturers to reduce engine emissions, with new European NOx reduction targets for on-highway and heavy-duty diesel vehicles now so low they are almost impossible to meet.

The Ammonia Creation and Conversion Technology (ACCT) created by academics from the University’s School of Mechanical, Electrical and Manufacturing Engineering effectively increases the capacity of existing on engine after treatment systems.

Currently almost all new diesel vehicles are fitted with a Selective Catalytic Reduction (SCR) system to try and remove NOx produced by combustion. This system uses AdBlue™ to safely provide the ammonia required to reduce NOx into harmless nitrogen and water.

The drawback is that AdBlue™ only functions well at high exhaust temperatures, typically in excess of 250ºC. Therefore, the SCR does not necessarily operate at all engine conditions, for example, during short, stop-start commutes, particularly in urban areas or on construction sites.

What’s more, use of AdBlue™ at these problematic lower temperatures can result in severe exhaust blockages and subsequent engine damage.

Credit: Loughborough University

ACCT is an AdBlue™ conversion technology that uses waste energy to modify AdBlue™ to work effectively at these lower exhaust temperatures. By greatly extending the temperature range at which SCR systems can operate the new technology significantly enhances existing NOx reduction systems.

ACCT is the only technology of its kind in the world.

Loughborough’s Professor Graham Hargrave, an internationally acclaimed expert on the optimisation of combustion engines, developed the technology with Research Associate Jonathan Wilson.

“We are all familiar with the ‘cold start’, where diesel vehicles spew out plumes of toxic emissions before their catalytic systems are up to temperature and able to work effectively,” explains Professor Hargrave.

“Unfortunately with many vehicles doing short stop/start journeys, such as buses and construction vehicles, many engines never reach the optimal temperature required for the SCR systems to operate efficiently. The result is excessive NOx being released into the urban environment, especially in large cities.

“Our system enables the SCR systems to work at much lower temperatures – as low as 60oC. This means that the NOx reduction system remains active through the whole real world driving cycle, leading to significant reductions in tailpipe emissions.”

Currently the Loughborough technology has been tailored for HGV’s, however the same system is fully scalable for use in all diesel vehicles.

“No viable alternative to the diesel engine currently exists for the heavy duty market and is going to be in use for many more years,” added Jonathan Wilson. “Systems are needed now that tackle NOx emissions, to help reduce the number of air pollution related deaths and enable vehicle manufactures to meet the ever reducing emissions targets set by the Government. ACCT is the answer.”

The Energy Technology Institute's (ETI) Chief Technology Officer for Heavy Duty Vehicles, Chris Thorne said: “Based upon a brief review, the ACCT technology recently developed by Loughborough has the potential to viably produce gaseous ammonia at temperatures significantly below 190°C, thus enabling increased conversion efficiency and lower NOx emissions.

“It is likely that emissions legislation will become even tighter and vehicle manufacturers will need to develop technologies to address this, and it is our belief that the ACCT technology should be further developed as it could help address this challenge in the real world.”

Contacts and sources:

Do Stars Fall Quietly into Black Holes, Or Crash into Something Utterly Unknown?

Astronomers in the United States, at the University of Texas at Austin and Harvard University, have put a basic principle of black holes to the test, showing that matter completely vanishes when pulled in. Their results, published in Monthly Notices of the Royal Astronomical Society, constitute another successful test for Albert Einstein's General Theory of Relativity.

Most scientists agree that black holes, cosmic entities of such great gravity that nothing can escape their grip, are surrounded by a so-called event horizon. Once matter or energy gets close enough to the black hole, it cannot escape — it will be pulled in. Though widely believed, the existence of event horizons has not been proved.

"Our whole point here is to turn this idea of an event horizon into an experimental science, and find out if event horizons really do exist or not," said Pawan Kumar, a professor of astrophysics at The University of Texas at Austin.

This artist’s impression shows a star crossing the event horizon of a supermassive black hole located in the centre of a galaxy. The black hole is so large and massive that tidal effects on the star are negligible, and the star is swallowed whole. The effects of gravitational lensing distorting the light of the star are not shown here.
Credit: Mark A. Garlick/CfA.  

Supermassive black holes are thought to lie at the heart of almost all galaxies. But some theorists suggest that there's something else there instead — not a black hole, but an even stranger supermassive object that has somehow managed to avoid gravitational collapse to a singularity surrounded by an event horizon. The idea is based on modified theories of General Relativity, Einstein's theory of gravity.

While a singularity has no surface area, the noncollapsed object would have a hard surface. So material being pulled closer — a star, for instance — would not actually fall into a black hole, but hit this hard surface and be destroyed.

Kumar, his graduate student Wenbin Lu, and Ramesh Narayan, a theorist from the Harvard-Smithsonian Center for Astrophysics, have come up with a test to determine which idea is correct.

This is the first in a sequence of two artist’s impressions that shows a huge, massive sphere in the centre of a galaxy, rather than a supermassive black hole. Here a star moves towards and then smashes into the hard surface of the sphere, flinging out debris. The impact heats up the site of the collision. 
Credit: Mark A. Garlick/CfA

In this second artist’s impression a huge sphere in the centre of a galaxy is shown after a star has collided with it. Enormous amounts of heat and a dramatic increase in the brightness of the sphere are generated by this event. The lack of observation of such flares from the centre of galaxies means that this hypothetical scenario is almost completely ruled out. 
Credit: Mark A. Garlick/CfA

"Our motive is not so much to establish that there is a hard surface," Kumar said, "but to push the boundary of knowledge and find concrete evidence that really, there is an event horizon around black holes."

The team figured out what a telescope would see when a star hit the hard surface of a supermassive object at the centre of a nearby galaxy: The star's gas would envelope the object, shining for months, perhaps even years.

Once they knew what to look for, the team figured out how often this should be seen in the nearby universe, if the hard-surface theory is true.

"We estimated the rate of stars falling onto supermassive black holes," Lu said. "Nearly every galaxy has one. We only considered the most massive ones, which weigh about 100 million solar masses or more. There are about a million of them within a few billion light-years of Earth." 

They then searched a recent archive of telescope observations. Pan-STARRS, a 1.8-meter telescope in Hawaii, recently completed a project to survey half of the northern hemisphere sky. The telescope scanned the area repeatedly during a period of 3.5 years, looking for "transients" — things that glow for a while and then fade. Their goal was to find transients with the expected light signature of a star falling toward a supermassive object and hitting a hard surface.

"Given the rate of stars falling onto black holes and the number density of black holes in the nearby universe, we calculated how many such transients Pan-STARRS should have detected over a period of operation of 3.5 years. It turns out it should have detected more than 10 of them, if the hard-surface theory is true," Lu said.

They did not find any.

"Our work implies that some, and perhaps all, black holes have event horizons and that material really does disappear from the observable universe when pulled into these exotic objects, as we've expected for decades," Narayan said. "General Relativity has passed another critical test."

Now the team is proposing to improve the test with an even larger telescope: the 8.4-meter Large Synoptic Survey Telescope (LSST, now under construction in Chile). Like Pan-STARRS, LSST will make repeated surveys of the sky over time, revealing transients — but with much greater sensitivity.

Contacts and sources:
Rebecca Johnson,UT Austin Astronomy Program
Dr Peter Edmonds, Harvard-Smithsonian Center for Astrophysics
Wenbin Lu, The University of Texas at Austin
Citation: "Stellar disruption events support the existence of the black hole event horizon", Wenbin Lu, Pawan Kumar and Ramesh Narayan, Monthly Notices of the Royal Astronomical Society, Oxford University Press, vol. 468 (1): pp. 910-919.

How Did Dinosaurs 'Proto Fly'? Possibly Like This

Tiny parrotlets take wing like Archaeopteryx might have, and how future robots still could.

How often does research reveal not only how dinosaurs could have moved in the past, but how robots might move in the future?

If a Pacific parrotlet (Forpus coelestis) needs to get to a nearby branch, it uses its legs to jump. If a target falls just outside of its jump range, however, it can add a "proto-wingbeat," a small flapping motion that allows it to travel farther without using as much energy as full flight.

That method of "long jumping" by using a combination of wings and legs may have been how the parrotlets' distant ancestors -- dinosaurs -- moved through trees to forage, according to a Stanford University research team supported by the National Science Foundation's (NSF) Biological Sciences Directorate.

Pacific parrotlet uses energy-efficient "proto-wingbeat" to get to a branch beyond its jump range
Pacific parrotlet
Credit: Diana Chin, Lentink Lab

Researchers Diana D. Chin and David Lentink write in a new Science Advances paper that with a single proto-wingbeat, a bird-like dinosaur like Archaeopteryx or Microraptor could jump 20 percent farther than if it had just used its legs. The boost would only cost the proto-flier the amount of energy needed to support 30 percent of its bodyweight. That meant they could save more energy for other activities necessary for survival and reproduction -- and gain an edge over competitors.

If a Pacific parrotlet needs to get to a branch beyond its jump range, it uses an energy-efficient wingbeat that isn't as taxing as full flight. Research by NSF-funded scientists Diana D. Chin and David Lentink, of Stanford University, found that bird-like dinosaurs like Archaeopteryx or Microraptor might have used similar proto-wingbeats to maneuver through branches. Parrotlets also select takeoff angles that conserve energy when jumping from branch-to-branch. That insight could help future researchers design robots with wings and legs that can conserve energy when traversing cluttered environments.

Credit: Diana Chin, Lentink Lab

The paper focused on more than the distant past, however. Another key finding of the study was that parrotlets select takeoff angles that help them reduce the energy they need to jump and fly. Depending on the distance or incline, the parrotlets will change that angle.

Conserving energy is important for living beings and also for bimodal robots that have legs and wings. When traversing cluttered environments, these robots could optimize their takeoff angles like the parrotlets and use the conserved energy for other purposes, including longer operations.

Credit: Restoration by Heinrich Harder, 1906/Wikimedia Commons

To measure the forces parrotlets generate using their legs and wings, the researchers equipped the birds' perches with force sensors and developed a new flight chamber that measures the aerodynamic forces of their wings. Measuring the forces exerted on the perch is relatively standard. To measure how the birds' wings generate aerodynamic lift forces, the researchers outfitted the bottom floor and ceiling of the flight chamber with sensors. This new method, an innovation from Lentink's lab, allowed the researchers to measure the pressure forces induced by the wing's lift. The researchers found the leg and wing forces combined allow parrotlets to forage efficiently by making wing-assisted long jumps.

In future work, the research team plans to further study these short flights using a new method of recording bird flight in 3-D developed with support from NSF and the U.S. Army Research Laboratory. The method involves projecting customized patterns of light on birds as they fly. The projected patterns deform on the birds' bodies, and a high-speed camera catches the action. Information from the footage is then used to create a 3-D reconstruction of how the birds' bodies move.

Contacts and sources:
Robert J. Margetta, National Science Foundation
David Lentink, Stanford University

'Halos' Discovered on Mars Widen Time Frame for Potential Life

Lighter-toned bedrock that surrounds fractures and comprises high concentrations of silica — called “halos”— has been found in Gale crater on Mars, indicating that the planet had liquid water much longer than previously believed. The new finding is reported in a new paper published today in Geophysical Research Letters, a journal of the American Geophysical Union.

“The concentration of silica is very high at the centerlines of these halos,” said Jens Frydenvang, a scientist at Los Alamos National Laboratory and the University of Copenhagen and lead author of the new study. “What we’re seeing is that silica appears to have migrated between very old sedimentary bedrock and into younger overlying rocks.

A mosaic of images from the navigation cameras on the NASA Curiosity rover shows “halos” of lighter-toned bedrock around fractures. These halos comprise high concentrations of silica and indicate that liquid groundwater flowed through the rocks in Gale crater longer than previously believed.

Credit: NASA/JPL-Caltech.

The goal of NASA’s Curiosity rover mission has been to find out if Mars was ever habitable, and it has been very successful in showing that Gale crater once held a lake with water that we would even have been able to drink, but we still don’t know how long this habitable environment endured. What this finding tells us is that, even when the lake eventually evaporated, substantial amounts of groundwater were present for much longer than we previously thought—thus further expanding the window for when life might have existed on Mars.”

Whether this groundwater could have sustained life remains to be seen. But this new study buttresses recent findings by another Los Alamos scientist who found boron on Mars for the first time, which also indicates the potential for long-term habitable groundwater in the planet’s past.

The halos were analyzed by the rover’s science payload, including the laser-shooting Chemistry and Camera (ChemCam) instrument, developed at Los Alamos National Laboratory in conjunction with the French space agency. Los Alamos’s work on discovery-driven instruments like ChemCam stems from the Laboratory’s experience building and operating more than 500 spacecraft instruments for national security.

Curiosity has traveled more than 16 kilometers (10 miles) over almost 1,700 Martian days as it has traveled from the bottom of Gale crater part way up Mount Sharp in the center of the crater. Scientists are using all the data collected by ChemCam to put together a more complete picture of the geological history of Mars.

The elevated silica in halos was found over approximately 20 to 30 meters (66 to 100 feet) in elevation near a rock-layer of ancient lake sediments that had a high silica content.

“This tells us that the silica found in halos in younger rocks close by was likely remobilized from the old sedimentary rocks by water flowing through the fractures,” Frydenvang said. Specifically, some of the rocks containing the halos were deposited by wind, likely as dunes. Such dunes would only exist after the lake had dried up. The presence of halos in rocks formed long after the lake dried out indicates that groundwater was still flowing within the rocks more recently than previously known.

Contacts and sources:
Lauren Lipuma, The American Geophysical Union
Laura Mullane, Los Alamos National Laboratory

Citation: "Diagenetic silica enrichment and late-stage groundwater activity in Gale crater, Mars"

New Species Discovered: New Glassfrog Species with Transparent Skin Reveals Their Hearts and Other Organs

In the Neotropics, there is a whole group of so-called glassfrogs that amaze with their transparent skin covering their bellies and showing their organs underneath. A recently discovered new species from Amazonian Ecuador, however, goes a step further to fully expose its heart thanks to the transparent skin stretching all over its chest as well as tummy.

The new amphibian is described by a team of scientists led by Dr. Juan M. Guayasamin, Universidad San Francisco de Quito, Ecuador, in the open access journal ZooKeys.

The new glassfrog species (Hyalinobatrachium yaku) in life.

Credit: Jaime Culebras and Ross Maynard

It can also be distinguished by the relatively large dark green spots at the back of its head and the foremost part of the body. Additionally, the species has a characteristic long call.

The new frog is named Hyalinobatrachium yaku, where the species name (yaku) translates to 'water' in the local language Kichwa. Water and, more specifically, slow-flowing streams are crucial for the reproduction of all known glassfrogs.

The reproductive behaviour is also quite unusual in this species. Males are often reported to call from the underside of leaves and look after the egg clutches.

Juvenile of the new glassfrog species (Hyalinobatrachium yaku) in life.

Credit: Ross Maynard

Having identified individuals of the new species at three localities, the researchers note some behavioural differences between the populations. Two of them, spotted in the riverine vegetation of an intact forest in Kallana, have been calling from the underside of leaves a few metres above slow-flowing, relatively narrow and shallow streams. Another frog of the species has been observed in an area covered by secondary forests in the Ecuadorian village of Ahuano. Similarly, the amphibian was found on the underside of a leaf one metre above a slow-flowing, narrow and shallow stream.

However, at the third locality - a disturbed secondary forest in San José de Payamino - the studied frogs have been perching on leaves of small shrubs, ferns, and grasses some 30 to 150 cm above the ground. Surprisingly, each of them has been at a distance greater than 30 metres from the nearest stream.

The researchers note that, given the geographic distance of approximately 110 km between the localities where the new species has been found, it is likely that the new species has a broader distribution, including areas in neighbouring Peru.

The uncertainty about its distributional range comes from a number of reasons. Firstly, the species' tiny size of about 2 cm makes it tough to spot from underneath the leaves. Then, even if specimens of the species have been previously collected, they would be almost impossible to identify from museum collection, as many of the characteristic traits, such as the dark green marks, are getting lost after preservation. This is why the conservation status of the species has been listed as Data Deficient, according to the IUCN Red List criteria.

Nevertheless, the scientists identify the major threats to the species, including oil extraction in the region and the related water pollution, road development, habitat degradation and isolation.

"Glassfrogs presumably require continuous tracts of forest to interact with nearby populations, and roads potentially act as barriers to dispersal for transient individuals," explain the authors.

Contacts and sources:
Juan M. Guayasamin
Pennsoft Publishers

Citation: Guayasamin JM, Cisneros-Heredia DF, Maynard RJ, Lynch RL, Culebras J, Hamilton PS (2017) A marvelous new glassfrog (Centrolenidae, Hyalinobatrachium) from Amazonian Ecuador. ZooKeys 673: 1-20.

Sunday, May 28, 2017

Nano Fiber Feels Forces and Hears Sounds Made by Cells

Engineers at the University of California San Diego have developed a miniature device that’s sensitive enough to feel the forces generated by swimming bacteria and hear the beating of heart muscle cells.

The device is a nano-sized optical fiber that’s about 100 times thinner than a human hair. It can detect forces down to 160 femtonewtons — about ten trillion times smaller than a newton — when placed in a solution containing live Helicobacter pylori bacteria, which are swimming bacteria found in the gut. In cultures of beating heart muscle cells from mice, the nano fiber can detect sounds down to -30 decibels — a level that’s one thousand times below the limit of the human ear.

An artist’s illustration of nano optical fibers detecting femtonewton-scale forces produced by swimming bacteria. 
nano optical fibers
Credit: Rhett S. Miller/UC Regents

“This work could open up new doors to track small interactions and changes that couldn’t be tracked before,” said nanoengineering professor Donald Sirbuly at the UC San Diego Jacobs School of Engineering, who led the study.

Some applications, he envisions, include detecting the presence and activity of a single bacterium; monitoring bonds forming and breaking; sensing changes in a cell’s mechanical behavior that might signal it becoming cancerous or being attacked by a virus; or a mini stethoscope to monitor cellular acoustics in vivo.

The work is published in Nature Photonics on May 15.

The optical fiber developed by Sirbuly and colleagues is at least 10 times more sensitive than the atomic force microscope (AFM), an instrument that can measure infinitesimally small forces generated by interacting molecules. And while AFMs are bulky devices, this optical fiber is only several hundred nanometers in diameter. “It’s a mini AFM with the sensitivity of an optical tweezer,” Sirbuly said.

The device is made from an extremely thin fiber of tin dioxide, coated with a thin layer of a polymer, called polyethylene glycol, and studded with gold nanoparticles. To use the device, researchers dip the nano optical fiber into a solution of cells, send a beam of light down the fiber and analyze the light signals it sends out. These signals, based on their intensity, indicate how much force or sound the fiber is picking up from the surrounding cells.

“We’re not just able to pick up these small forces and sounds, we can quantify them using this device. This is a new tool for high resolution nanomechanical probing,” Sirbuly said.

Here’s how the device works: as light travels down the optical fiber, it interacts strongly with the gold nanoparticles, which then scatter the light as signals that can be seen with a conventional microscope. These light signals show up at a particular intensity. But that intensity changes when the fiber is placed in a solution containing live cells. Forces and sound waves from the cells hit the gold nanoparticles, pushing them into the polymer layer that separates them from the fiber’s surface. Pushing the nanoparticles closer to the fiber allows them to interact more strongly with the light coming down the fiber, thus increasing the intensity of the light signals. Researchers calibrated the device so they could match the signal intensities to different levels of force or sound.

The key to making this work is the fiber’s polymer layer. It acts like a spring mattress that’s sensitive enough to be compressed to different thicknesses by the faint forces and sound waves produced by the cells. And Sirbuly says the polymer layer can be tuned — if researchers want to measure larger forces, they can use a stiffer polymer coating; for increased sensitivity, they can use a softer polymer like a hydrogel.

Moving forward, researchers plan to use the nano fibers to measure bio-activity and the mechanical behavior of single cells. Future works also includes improving the fibers’ “listening” capabilities to create ultra-sensitive biological stethoscopes, and tuning their acoustic response to develop new imaging techniques.

Contacts and sources:
Liezel LabiosUniversity of California, San Diego

Paper title: “Nanofibre optic force transducers with sub-piconewton resolution via near-field plasmon-dielectric interactions” by Qian Huang*, Joon Lee*, Fernando Teran Arce*, Ilsun Yoon, Pavimol Angsantikul, Justin Liu, Yuesong Shi, Josh Villanueva, Soracha Thamphiwatana, Xuanyi Ma, Liangfang Zhang, Shaochen Chen, Ratnesh Lal and Donald J. Sirbuly at UC San Diego.

*These authors contributed equally to this work.

This work was supported by the National Science Foundation (ECCS 1150952) and the University of California, Office of the President (UC-LFRP 12-LR-238415). 

3-D Printed Ovaries Produce Healthy Offspring

Bioprosthetic ovaries produced mouse pups in otherwise infertile mice. 

The new world of 3-D printed organs now includes implanted ovary structures that, true to their design, actually ovulate, according to a study by Northwestern University Feinberg School of Medicine and McCormick School of Engineering.

By removing a female mouse’s ovary and replacing it with a bioprosthetic ovary, the mouse was able to not only ovulate but also give birth to healthy pups. The moms were even able to nurse their young.

The bioprosthetic ovaries are constructed of 3-D printed scaffolds that house immature eggs, and have been successful in boosting hormone production and restoring fertility in mice, which was the ultimate goal of the research.

“This research shows these bioprosthetic ovaries have long-term, durable function,” said Teresa K. Woodruff, a reproductive scientist and director of the Women’s Health Research Institute at Feinberg. “Using bioengineering, instead of transplanting from a cadaver, to create organ structures that function and restore the health of that tissue for that person, is the holy grail of bioengineering for regenerative medicine.”

The paper was published May 16, in Nature Communications.

How is this research different from other 3-D printed structures?

What sets this research apart from other labs is the architecture of the scaffold and the material, or “ink,” the scientists are using, said Ramille Shah, assistant professor of materials science and engineering at McCormick and of surgery at Feinberg.

That material is gelatin, which is a biological hydrogel made from broken-down collagen that is safe to use in humans. The scientists knew that whatever scaffold they created needed to be made of organic materials that were rigid enough to be handled during surgery and porous enough to naturally interact with the mouse’s body tissues.

Credit: Northwestern University

“Most hydrogels are very weak, since they’re made up of mostly water, and will often collapse on themselves,” Shah said. “But we found a gelatin temperature that allows it to be self-supporting, not collapse, and lead to building multiple layers. No one else has been able to print gelatin with such well-defined and self-supported geometry.”

That geometry directly links to whether or not the ovarian follicles, organized hormone-producing support cells surrounding an immature egg cell, will survive in the ovary, which was one of the bigger findings in the study.

“This is the first study that demonstrates that scaffold architecture makes a difference in follicle survival,” Shah said. “We wouldn’t be able to do that if we didn’t use a 3-D printer platform.”
How does this impact humans?

The scientists’ sole objective for developing the bioprosthetic ovaries was to help restore fertility and hormone production in women who have undergone adult cancer treatments or those who survived childhood cancer and now have increased risks of infertility and hormone-based developmental issues.

“What happens with some of our cancer patients is that their ovaries don’t function at a high enough level and they need to use hormone replacement therapies in order to trigger puberty,” said Monica Laronda, co-lead author of this research and a former post-doctoral fellow in the Woodruff lab. “The purpose of this scaffold is to recapitulate how an ovary would function. We’re thinking big picture, meaning every stage of the girl’s life, so puberty through adulthood to a natural menopause.”

Laronda is now an assistant professor at the Stanley Manne Children’s Research Institute at the Ann & Robert H. Lurie Children’s Hospital.

Additionally, the successful creation of 3-D printed implants to replace complex soft tissue could significantly impact future work in soft tissue regenerative medicine.

Technically, how does biological 3-D printing work?

3-D printing an ovary structure is similar to a child using Lincoln Logs, said Alexandra Rutz, co-lead author of the study and a former biomedical engineering graduate fellow in Shah’s Tissue Engineering and Additive Manufacturing (TEAM) lab at the Simpson Querrey Institute. Children can lay the logs at right angles to form structures. Depending on the distance between the logs, the structure changes to build a window or a door, etc.

“3-D printing is done by depositing filaments,” said Rutz, who is now a Whitaker International Postdoctoral Scholar at École Des Mines De Saint-Étienne in Gardanne, France. “You can control the distance between those filaments, as well as the advancing angle between layers, and that would give us different pore sizes and different pore geometries.”

In Northwestern’s lab, the researchers call these 3-D printed structures “scaffolds,” and liken them to the scaffolding that temporarily surrounds a building while it undergoes repairs.

“Every organ has a skeleton,” said Woodruff, who also is the Thomas J. Watkins Memorial Professor of Obstetrics and Gynecology and a member of the Robert H. Lurie Comprehensive Cancer Center of Northwestern University. “We learned what that ovary skeleton looked like and used it as model for the bioprosthetic ovary implant.”

In a building, the scaffolding supports the materials needed to repair the building until it’s eventually removed. What’s left is a structure capable of holding itself up. Similarly, the 3-D printed “scaffold” or “skeleton” is implanted into a female and its pores can be used to optimize how follicles, or immature eggs, get wedged within the scaffold. The scaffold supports the survival of the mouse’s immature egg cells and the cells that produce hormones to boost production. The open structure also allows room for the egg cells to mature and ovulate, as well as blood vessels to form within the implant enabling the hormones to circulate within the mouse bloodstream and trigger lactation after giving birth.

The all-female McCormick-Feinberg collaboration for this research was “very fruitful,” Shah said, adding that it was motivational to be part of an all-female team doing research towards finding solutions to female health issues.

“What really makes a collaboration work are the personalities and being able to find the humor in the research,” Shah said. “Teresa and I joked that we’re grandparents of these pups.”

Contacts and sources: 
Kristin Samuelson
Northwestern University

Baboons at the Leading Edge of a Pack, Eat First, Take the Most Risks

Are you the kind of person who, at a party, tends to be surrounded by friends in the middle of the crowd, or do you prefer to find a quiet corner where you can sit and talk? Recent work by scientists at University of California Davis shows that wild baboons behave similarly to humans — with some animals consistently found in the vanguard of their troop while others crowd to the center or lag in the rear.

An adult male baboon and an adult female with clinging infant forage for food. Adult male baboons are larger than females and have impressive weaponry (i.e. larger teeth). This means that they are not only socially dominant but also less vulnerable to predators, influencing the costs and benefits of being on the edge of the group versus the center.
Photo by Margaret Crofoot

Using high-resolution GPS tracking, UC Davis Assistant Professor Margaret Crofoot and her team of researchers continuously monitored the movements of nearly an entire baboon troop in central Kenya to discover how interactions among group-mates influenced where in the troop individuals tended to be found.

“How animals position themselves within their social group can have life or death consequences,” explained Crofoot, an anthropologist. “Individuals at the front of their group may get the first crack at any food their group encounters, but they are also more vulnerable to being picked off by predators.”

Interestingly, the team’s work suggests that very simple behavioral rules may explain baboons’ apparent preferences for particular spatial positions. “Animals who pay attention to more of their group-mates when deciding where to move will inevitably end up at the center of their group,” said Crofoot. Differences in social sensitivity may therefore explain why younger baboons end up in the safest positions at the center of their troop, while adult males find themselves exposed on the leading edge.

Researchers have long noted that spatial positioning has important fitness implications, but where an animal is positioned in its group depends not only on its own behavior, but also on the behavior of its group-mates. “How natural selection shapes such emergent properties is fundamental to understanding the evolutionary dynamics of social organisms,” Crofoot said.

The findings were published in April in the journal Proceedings of the Royal Society.

The study was funded by the National Science Foundation, Office of Naval Research, Army Research Office and Human Frontiers Science Program.
More information

Contacts and sources:
Karen Nikos-Rose/Andy Fell
University of California Davis  (UC Davis)

Read the study

Baboons on the Move Practice Democracy

Interactive Touchscreen for Dolphins Created, They Play Games Like Whack-a-Mole with Training

Dolphins are highly intelligent and social animals, but can they use a smartphone built just for them? Yes, scientists have discovered—they can even play games like Whack-a-Mole with little training.

Researchers at Rockefeller University and Hunter College, working with the National Aquarium in Baltimore, MD, have developed a touchpad for dolphins, the first of its kind, using optical technology. The system, essentially an underwater computer touchscreen through which dolphins are able to interact and make choices, will be used to investigate dolphin intelligence and communication by providing them choice and control over a number of activities.

Observing dolphins interact with a specially-made touchscreen could open new windows into dolphin cognition. 
Dolphin eye
Credit: The M2C2 Research Collaborative

The eight-foot underwater touchscreen features specialized dolphin-friendly “apps” and a symbolic keyboard to provide the dolphins with opportunities to interact with the system. To make the system safe for the dolphins, the touchscreen has been installed outside an underwater viewing window, so that no parts of the device are in the pool: the animals’ touch is detected optically. 

 While the research is still in its early stages, the team has embarked on studies aimed at understanding dolphin vocal learning and communication, their capacity for symbolic communication, and what patterns of behavior may emerge when the animals have the ability to request items, videos, interactions, and images.

A dolphin’s version of touchscreen Whack-a-Mole.

 Credit: The M2C2 Research Collaborative

The interdisciplinary research team is comprised of biophysicist Marcelo Magnasco, professor and head of the Laboratory of Integrative Neuroscience at Rockefeller University, and Diana Reiss, a dolphin cognition and communication research scientist and professor in the department of psychology at Hunter College. Also involved are Ana Hocevar, a postdoctoral research scientist; and Sean Woodward, a doctoral student, both in Magnasco’s lab.

“It was surprisingly difficult to find an elegant solution that was absolutely safe for the dolphins, but it has been incredibly rewarding to work with these amazing creatures and see their reactions to our system,” says Magnasco. “It has always been hard to keep up with dolphins, they are so smart; a fully interactive and programmable system will help us follow them in any direction they take us.”

In addition to the touchscreen itself, the dolphin’s habitat at the National Aquarium has been outfitted with equipment to record their behavior and vocalizations as they encounter and begin to use the technology.

“We hope this technologically-sophisticated touchscreen will be enriching for the dolphins and also enrich our science by opening a window into the dolphin mind,” says Reiss. “Giving dolphins increased choice and control allows them to show us reflections of their way of thinking and may help us decode their vocal communication.”

Already, the scientists have begun to introduce the dolphins to some of the system’s interactive apps, so the animals can explore on their own how touching the screen results in specific contingencies. Without any explicit training or encouragement, one of the younger dolphins, Foster, spontaneously showed immediate interest and expertise in playing a dolphin version of Whack-a-Mole, in which he tracks and touches moving fish on the touchscreen.

The researchers believe this technology will help extend the high-throughput revolution in biology that has brought us whole genome sequencing and the BRAIN project, into the field of animal cognition. They also hope that the information gleaned from this research will result in increased empathy toward dolphins and inspire global policies for their protection.

Contacts and sources:
Katherine Fenz
Rockefeller University

In a Drought, Over-Irrigated Lawns Lose 70 Billion Gallons of Water a Year

In the summer of 2010, Los Angeles lost about 100 gallons of water per person per day to the atmosphere through evaporation, mostly from overwatering of lawns and trees.

Lawns accounted for 70 percent of the water loss, while trees accounted for 30 percent, according to a study published today in the journal Water Resources Research. The research was funded by the National Science Foundation (NSF) and conducted by Diane Pataki and Elizaveta Litvak of the University of Utah.

The scientists found that 70 percent of Los Angeles' evapotranspiration comes from irrigated lawns.
The scientists found that 70 percent of Los Angeles' evapotranspiration comes from irrigated lawns.
Credit: Diane Pataki

The results, based on measurements taken before Los Angeles mandated watering restrictions in 2014, show a pattern of systemic overwatering of the city's lawns, and a surprising water efficiency of its tree cover. The researchers also found a correlation between water loss and household income.

The water loss that Pataki and Litvak measured is called evapotranspiration (ET), the evaporation of water from the soil and the transpiration, or release of water vapor, from plants. ET rates depend on several factors, including plant type, temperature, humidity and the amount of water in the soil.

According to the scientists' measurements, Los Angeles' soils were an abundant source of water during the drought, largely a result of lawn overwatering. Imagine placing a soaking wet towel out to dry on a hot summer day: it's a thoroughly wet surface, and should evaporate quickly. Water loss from an over-irrigated lawn is similar because transpiration from the grass pumps water from the soil to the atmosphere.

For the study, the researchers took measurements in the urban tree canopy throughout Los Angeles.

Credit: Diane Pataki

"California's recent drought highlights the need for urban water conservation," says Tom Torgersen, program director in the Division of Earth Sciences in NSF's Geosciences Directorate, which funded the research. NSF's directorates for Biological Sciences and Social, Behavioral and Economic Sciences also funded the research.

Torgersen says that for Los Angeles, the greatest ET was due to turf grass and seed-producing trees. Palm trees made very small contributions.

"Both provide an alleviation of the urban heat island effect and reduce the need for air conditioning," Torgersen says. "However, the benefit is not evenly shared. The higher the median income, the greater the local ET, with cooler temperatures in wealthier areas and higher temperatures in poorer sections of the city."

To measure ET from lawns, Litvak devised a shoebox-size chamber that measured rapid changes of the temperature and humidity above the grass.

Pataki, Litvak and their colleagues traveled around Los Angeles in the summer of 2010 and the winter of 2011 taking measurements to develop a mathematical model of ET rates from lawns under different conditions.

Researchers estimated the flow of water vapor from the soil to the atmosphere in Los Angeles landscapes.

Credit: Diane Pataki

They tested the hypothesis that wealthier neighborhoods had more plant cover and cooler temperatures than poorer areas.

ET rates in the wealthiest neighborhoods, they found, were roughly twice those of poorer neighborhoods. That's probably due to a variety of factors, Pataki and Litvak say, including the larger lot sizes of more expensive properties.

Trees emerged as the water-saving heroes of the study, using far less water than grassy lawns.

Trees have a much lower leaf surface area and don't directly irrigate their leaves, so they are less prone to evaporation. Also, trees regulate their transpiration rate in response to the surrounding humidity. Under dry conditions, trees will rein in transpiration so they can retain water.

"It's surprising that we can maintain the tree canopy of L.A. with relatively little water," Pataki says. "There's this assumption that we need abundant irrigation to support trees. But we can drastically reduce water use and still have trees."

This spring, Los Angeles' watering restrictions were lifted after California's very wet winter.

Pataki says it's too early to tell whether Los Angeles residents' watering patterns and landscaping choices will return to pre-drought excesses.

"Whether the drought changed people's landscape preferences in a lasting way, that's something we still need to find out," she says.

Contacts and sources:
Cheryl Dybas, National Science Foundation (NSF)
Paul Gabrielsen, University of Utah

World’s Most Sensitive Dark Matter Detector Releases First Results

Scientists behind XENON1T, the largest dark matter experiment of its kind ever built, are encouraged by early results, describing them as the best so far in the search for dark matter.

Dark matter is one of the basic constituents of the universe, five times more abundant than ordinary matter. Several astronomical measurements have corroborated the existence of dark matter, leading to an international effort to observe it directly. Scientists are trying to detect dark matter particle interacting with ordinary matter through the use of extremely sensitive detectors. Such interactions are so feeble that they have escaped direct detection to date, forcing scientists to build detectors that are more and more sensitive and have extremely low levels of radioactivity.

On May 18, the XENON Collaboration released results from a first, 30-day run of XENON1T, showing the detector has a record low radioactivity level, many orders of magnitude below surrounding material on earth.

XENON1T installation in the underground hall of Laboratori Nazionali del Gran Sasso. The three story building on the right houses various auxiliary systems. The cryostat containing the LXeTPC is located inside the large water tank on the left.
XENON1T Installation
Photo by Roberto Corrieri and Patrick De Perio

“The care that we put into every single detail of the new detector is finally paying back,” said Luca Grandi, assistant professor in physics at the University of Chicago and member of the XENON Collaboration. “We have excellent discovery potential in the years to come because of the huge dimension of XENON1T and its incredibly low background. These early results already are allowing us to explore regions never explored before.”

The XENON Collaboration consists of 135 researchers from the United States, Germany, Italy, Switzerland, Portugal, France, the Netherlands, Israel, Sweden and the United Arab Emirates, who hope to one day confirm dark matter’s existence and shed light on its mysterious properties.

Located deep below a mountain in central Italy, XENON1T features a 3.2-ton xenon dual-phase time projection chamber. This central detector sits fully submersed in the middle of the water tank, in order to shield it from natural radioactivity in the cavern. A cryostat helps keep the xenon at a temperature of minus-95 degrees Celsius without freezing the surrounding water. The mountain above the laboratory further shields the detector, preventing it from being perturbed by cosmic rays.

But shielding from the outer world is not enough, since all materials on Earth contain tiny traces of natural radioactivity. Thus extreme care was taken to find, select and process the materials making up the detector to achieve the lowest possible radioactive content. This allowed XENON1T to achieve record “silence” necessary to detect the very weak output of dark matter.

A particle interaction in the one-ton central core of the time projection chamber leads to tiny flashes of light. Scientists record and study these flashes to infer the position and the energy of the interacting particle—and whether it might be dark matter.

Scientists assembling the XENON1T time projection chamber.
Photo by Enrico Sacchetti

Despite the brief 30-day science run, the sensitivity of XENON1T has already overcome that of any other experiment in the field probing unexplored dark matter territory.

“For the moment we do not see anything unexpected, so we set new constraints on dark matter properties,” Grandi said. “But XENON1T just started its exciting journey and since the end of the 30-day science run, we have been steadily accumulating new data.”
UChicago central to international collaboration

Grandi’s group is very active within XENON1T, and it is contributing to several aspects of the program. After its initial involvement in the preparation, assembly and early operations of the liquid xenon chamber, the group shifted its focus in the last several months to the development of the computing infrastructure and to data analysis.

“Despite its low background, XENON1T is producing a large amount of data that needs to be continuously processed,” said Evan Shockley, a graduate student working with Grandi. “The raw data from the detector are directly transferred from Gran Sasso Laboratory to the University of Chicago, serving as the unique distribution point for the entire collaboration.”

The framework, developed in collaboration with a group led by Robert Gardner, senior fellow at the Computation Institute, allows for the processing of data, both on local and remote resources belonging to the Open Science Grid. The involvement of UChicago’s Research Computing Center including Director Birali Runesha allows members of the collaboration all around the world to access processed data for high-level analyses.

Grandi’s group also has been heavily involved in the analysis that led to this first result. Christopher Tunnell, a fellow at the Kavli Institute for Cosmological Physics, is one of the two XENON1T analysis coordinators and corresponding author of the result. Recently, UChicago hosted about 25 researchers for a month to perform the analyses that led to the first results.

“It has been a large, concentrated effort and seeing XENON1T back on the front line makes me forget the never-ending days spent next to my colleagues to look at plots and distributions,“ Tunnell said. “There is no better thrill than leading the way in our knowledge of dark matter for the coming years.”

U.S. federal funding for the research comes from the National Science Foundation.

Contacts and sources:
University of Chicago

The Lively Garden of the Ediacaran 635 to 540 Million Years Ago

The Garden of the Ediacaran was a period in the ancient past when Earth’s shallow seas were populated with a bewildering variety of enigmatic, soft-bodied creatures. Scientists have pictured it as a tranquil, almost idyllic interlude that lasted from 635 to 540 million years ago. But a new interdisciplinary study suggests that the organisms living at the time may have been much more dynamic than experts have thought.

Artist’s conception of a scene from the Garden of the Ediacaran. The new study suggests a number of these strange species which predate animals may have been capable of moving about 
Credit: Franz Anthony / Studio 252MYA

Scientists have found It extremely difficult to fit these Precambrian species into the tree of life. That is because they lived in a time before organisms developed the ability to make shells or bones. As a result, they didn’t leave much fossil evidence of their existence behind, and even less evidence that they moved around. So, experts have generally concluded that virtually all of the Ediacarans—with the possible exception of a few organisms similar to jellyfish that floated about—were stationary and lived out their adult lives fixed in one place on the sea floor.

Fossil imprint of Parvancorina, which may have been the first species capable of orienting itself to face into an ocean current.

Credit: Masahiro Miyasaka / Wikimedia Commons

The new findings concern one of the most enigmatic of the Ediacaran genera, a penny-sized organism called Parvancorina, which ischaracterized by a series of ridges on its back that form the shape of a tiny anchor. By analyzing the way in which water flows around Parvancorina’s body, an international team of researchers has concluded that these ancient creatures must have been mobile: specifically, they must have had the ability to orient themselves to face into the current flowing around them. That would make them the oldest species known to possess this capability, which scientists call rheotaxis.

“Our analysis shows that the amount of drag produced with the current flowing from front to back is substantially less than that flowing from side to side,” said Simon Darroch, assistant professor of earth and environmental sciences at Vanderbilt University, who headed the study. “In the strong currents characteristic of shallow ocean environments, that means Parvancorina would have benefited greatly from adjusting its position to face the direction of the flow.”

Simon Darroch 
Credit: Steve Green / Vanderbilt

The analysis, which used a technique borrowed from engineering called computational fluid dynamics (CFD), also showed that when Parvancorina faced into the current, its shape created eddy currents that were directed to several specific locations on its body. “This would be very beneficial to Parvancorina if it was a suspension feeder as we suspect because it would have concentrated the suspended organic material making it easier to consume,” Darroch said.

Details of the analysis are described in a paper titled “Inference of facultative mobility in the enigmatic Ediacaran organismParvancorina” published online May 17 by the Royal Society journal Biology Letters.

These conclusions are reinforced by an independent study performed by a team of Australian researchers published March 30 in the journal Scientific Reports. Analyzing an Ediacaran site in South Australia, they found that the Parvancorina fossils were preferentially aligned in the direction of the prevailing current and determined that this alignment was not passive but represented a rheotactic response at some point in the organism’s life history.

Top and side views produced by computer simulations show how water flows around the body of Parvancorina when the current is coming from the front (a), side (b) and rear (c). The arrows show the direction of the water flow and the colors represent its velocity (red and yellow are fast, blue and green are slow). It demonstrates that the flow patterns differ dramatically with each orientation. This implies that the organism had to have been mobile to feed effectively.
Credit: Simon Darroch / Vanderbilt

This is only the second time that CFD has been applied to study Ediacarans. In 2015, the same team of researchers applied this technique to analyze flow patterns around an organism called Tribrachidium heraldicum. This is a disk-shaped organism characterized by three spiraling ridges on its back. In this case, their analysissupported the conclusion that it was the oldest known suspension feeder, dating back to 555 million years.

“We decided to stop trying to figure out where these species fit in the tree of life and to try to determine how they were shaped by evolutionary forces,” said Darroch. “We wanted to understand how their weird architectures affected how they ate, reproduced and moved. Because they lived in a shallow sea environment, strong currents must have played a major role in their evolution. So computational fluid dynamics is the perfect tool for addressing this question.”

According to team member Imran Rahman, research fellow at the Oxford University Museum of Natural History, CFD has been used to analyze the design and optimize the performance of a wide variety of structures and machines, ranging from nuclear reactors to aircraft, but it is only in the last few years that they have begun applying it to study the fossil record: “CFD has the potential to transform our understanding of how ancient organisms fed and moved, so I would anticipate that many more paleontologists will start making use of the method in coming years.”

“When you sit back and think about it, we are virtually recreating ancient oceans, and populating them with digital representations of long extinct organisms that have defied our understanding for over 50 years in order to gain insight on how they lived their day to day lives,” added co-author Marc Laflamme, assistant professor of earth science at the University of Toronto Mississauga. “This kind of work would not have been feasible even a decade ago, and I believe it represents the direction that modern paleontology is forging.”

Model of a Parvancorina organism.

Credit: Matteo De Stefano/MUSE/Wikimedia Commons

“The fact that we have now established that one Ediacaran species could move around suggests that our picture of this period may be fundamentally wrong,” said Darroch. “There may have been a lot more movement going on than we thought and we intend to apply this technique to other Ediacaran fossils to determine if that was the case.”

Vanderbilt graduate student Brandt Gibson and Rachel Racicot at the Natural History Museum of Los Angeles County also contributed to the study.

CThe research was supported by National Science Foundation grants DEB 1331980 and PLR 134175 and by National Science and Engineering Research Council of Canada grant RGPIN 435402.

Contacts and sources:  
David Salisbury 
Vanderbilt University