Squid supplies blueprint for printable thermoplastics

This is a whimsical image of a squid creating 3-D printed devices. Credit: Adriás Bago

Squid, what is it good for? You can eat it and you can make ink or dye from it, and now a Penn State team of researchers is using it to make a thermoplastic that can be used in 3-D printing.

"Most of the companies looking into this type of material have focused on synthetic plastics," said Melik C. Demirel, professor of engineering science and mechanics. "Synthetic plastics are not rapidly deployable for field applications, and more importantly, they are not eco-friendly."

Demirel and his team looked at the protein complex that exists in the squid ring teeth (SRT). The naturally made material is a thermoplastic, but obtaining it requires a large amount of effort and many squid.

"We have the genetic sequence for six squid collected around the world, but we started with the European common squid," said Demirel, who with his team collected the cephalopods.

The researchers looked at the genetic sequence for the protein complex molecule and tried synthesizing a variety of proteins from the complex. Some were not thermoplastics, but others show stable thermal response, for example, the smallest known molecular weight SRT protein was a thermoplastic. The results of their work were published in today's (Dec. 17) issue of Advanced Functional Materials and illustrates the cover.

Most plastics are currently manufactured from fossil fuel sources like crude oil. Some high-end plastics are made from synthetic oils. Thermoplastics are polymer materials that can melt, be formed and then solidify as the same material without degrading materials properties.

This particular thermoplastic can be fabricated either as a thermoplastic, heated and extruded or molded, or the plastic can be dissolved in a simple solvent like acetic acid and used in film casting. The material can also be used in 3D printing machines as the source material to create complicated geometric structures.

To manufacture this small, synthetic SRT molecule, the researchers used recombinant techniques. They inserted SRT protein genes into E. coli, so that this common, harmless bacteria could produce the plastic molecules as part of their normal activity and the thermoplastic was then removed from the media where the E. coli lived. Wayne Curtis, professor of chemical engineering and Demirel collaborating on this project together with their students worked on this aspect of the project.

"The next generation of materials will be governed by molecular composition -- sequence, structure and properties," said Demirel.

The thermoplastic the researchers created is semi-crystalline and can be rigid or soft. It has a very high tensile strength and is a wet adhesive; it will stick to things even if it is wet.

This thermoplastic protein has a variety of tunable properties, which can be adjusted to individual requirements of manufacturing. Because it is a protein, it can be used for medical or cosmetic applications.

"Direct extraction or recombinant expression of protein based thermoplastics opens up new avenues for materials fabrication and synthesis, which will eventually be competitive with the high-end synthetic oil based plastics," the researchers report.

Source: Penn State

The science behind swimming: From whales to larvae, common principles at work in swimming

Whale and diver (stock illustration). Using simple hydrodynamics, researchers were able to show that a handful of principles govern how virtually every animal -- from the tiniest fish to birds to gigantic whales propel themselves though the water. Credit: © James Thew / Fotolia

At nearly 100 feet long and weighing as much as 170 tons, the blue whale is the largest creature on the planet, and by far the heaviest living thing ever seen on Earth. So there's no way it could have anything in common with the tiniest fish larvae, which measure millimeters in length and tip the scales at a fraction of a gram, right?

Not so fast, says L. Mahadevan, the Lola England de Valpine Professor of Applied Mathematics, of Organismic and Evolutionary Biology, and of Physics.

Using simple hydrodynamics, a team of researchers led by Mahadevan was able to show that a handful of principles govern how virtually every animal -- from the tiniest fish to birds to gigantic whales propel themselves though the water. The study is described in a September 14 paper in Nature Physics.

"What we wanted to investigate was how the speed of an organism changes as a function of how large it is, how quickly it moves and how much it moves," Mahadevan said. "To resolve that in detail, however, is very complex, because there is a great deal of differences in morphology and what parts of the body different creatures use to swim. The question is: Is there anything in common across all these organisms? The answer, we found, is yes."

In an effort to uncover those common principles, Mahadevan working with a postdoctoral fellow in his group , Mattia Gazzola, and a colleague Mederic Argentina from the University of Nice, began by trying to unpack the physics of how different creatures swim.

"The traditional approach to swimming phenomena is to take a certain specimen and accurately characterize it via experiments and/or simulations, and try to generalize from there, but it is very hard to strip out specific biological effects from general principles," Gazzola said. "We instead thought that while swimmers exhibit a huge diversity in shapes and kinematics, at the end of the day they all live in the same media, water.

"Therefore we thought that if a unifying mechanistic principle existed, it had to lie in the constraints that the flow environment poses to all its inhabitants," he continued. "And this is a purely physical problem, much easier to solve since it is not affected by biological vagaries. What I like about this paper is that in one line of algebra we derived a compact formula that accounts for 50 years of experiments. This is an example of how powerful minimal modeling can be."

"The basic relationship we wanted to understand was how the input variables -- namely the size of the organism, the amount an organism moves and how quickly it moves -- control the output variable, which is effectively the speed at which it moves," Mahadevan explained. "What we found is that there is a specific relationship, which can be described by in terms of a simple scaling law with two limits."

The first, which corresponds to creatures moving at intermediate speeds, describes situations where the bulk of the resistance is caused by skin friction, because water "sticks" to the organism's body. At faster speeds, Mahadevan said, the resistance organisms face largely comes from pressure that builds up in front of and around them, which is described by the second limit.

"While it wasn't a surprise that the resistance changed at organisms moved faster, the fact that those challenges could be so simply described was interesting and provocative, because we are talking about organisms that range in size from a few millimeters to the size of a blue whale," Mahadevan said.

Armed with those observations, Mahadevan and colleagues turned to a host of empirical observations that had been made over the past 50-plus years. When those data were plotted on a graph, the researchers found that the swimming speed of virtually every organism, from fish larvae to frogs to birds, amphibians and even whales, could be described by one of the two equations.

The same also held true, Mahadevan said, when Gazzola created complex computer models to solve the governing equations of fluid dynamics to describe how different organisms swim.

"What is particularly interesting is that all the organisms essentially reach the hydrodynamic limits of performance," he said. "Our simple theory, which doesn't distinguish in any detailed way between something like a blue whale and fish larvae, except in the parameters of how large you are, much you move and how quickly you move, can describe all this diversity. That suggests there are general principles at work here."


Source: Harvard University

Predicting the predator threatening a squirrel by analyzing its sounds and tail movements

Thaddeus McRae poses in the Gifford Arboretum with his remote-controlled cat, after being interviewed by WSVN. Credit: University of Miami College of Arts and Sciences

Everyone has watched squirrels playfully climbing trees, gracefully leaping from branch to branch, and scurrying across parks. Thaddeus McRae, Ph.D '12, adjunct assistant research professor of biology in the University of Miami College of Arts Sciences, has taken these observations to a scientific level.

McRae studied squirrel colonies on the Coral Gables campus to see how their sounds and tail movements differ in response to different kinds of threats. He is looking to discover why squirrels interact using both vocalizations and gestures.

"These multimodal signals, which simultaneously send information via two or more sensory modalities to communicate, are ubiquitous," McRae said, adding that people and other mammals, birds, insects and spiders -- and even some plants -- communicate in this manner.

The different sounds, expressions and gestures might "reinforce each other, or maybe they contain different information, or maybe they reach different audiences," he said.

To conduct his research -- the basis of his Ph.D. dissertation -- McRae designed a unique tool: a remote-controlled cat, which he used to chase squirrels while recording their reactions to ground-based predators. Gliders painted to resemble hawks showed the squirrels' responses to threats from the air.

McRae has become somewhat of a local celebrity scientist, with recent and upcoming stories about his study appearing on the Miami New Times "Riptide" blog, and WSVN. He sees three reasons for this media attention.

Squirrels "are often most abundant in the same places people are most abundant," McRae said, adding that they're "cute and fuzzy with a bushy tail, which for some people goes a long way toward earning goodwill."

He also conducted his research in a "very public setting, outdoors on UM's campus in the middle of the city." McRae believes that this helps to breakdown the "mysterious aura" of science, "putting scientific curiosity out there where passersby can see it and become curious themselves."

Finally, he admits that "there's something a little bit humorous" about his research process and his unusual tools.

"To me, this squirrel study isn't cool because I used remote control cats, although enjoying whatever tools you use is nice, it's cool because we learned something about squirrels that we didn't know before," McRae said.

Over two years of observation McRae, working closely with Professor of Biology Steven Green, found that he could quite accurately predict what type of predator was threatening a squirrel by analyzing its sounds and tail movements.

He measured the response of three distinct squirrel sounds: the "kuk" (a short bark), the "quaa" (a longer squeal) and the "moan" (a whistling sound).

He also looked for specific patterns for tail motions in combination with these noises. The "twitch" involves a controlled movement in an arc shape, while the "flag" can take the shape of an arc, figure eight, circle or squiggle.

McRae theorizes that the squirrels use the vocal and tail alarm calls for two purposes -- to let predators know that they have been spotted, and to warn other squirrels of danger in the area. To this end, he is now conducting follow-up research to determine how squirrels react to distress signals from their peers.

For both his current study and his dissertation research, McRae has worked extensively with undergraduate research assistants.

"I try to give them a taste of various steps in the process, from thinking about the organisms and asking questions, to collecting data, to the sometimes tedious task of converting those data into analyzable form, to drawing conclusions. I share with them the joy of discovery," he said.

"Even a small, fast research project can show us something we never knew before. It may not shake the earth, but it's another tiny piece of understanding. ... For a young student to be one of the first handful of people on Earth to share even a small discovery is, frankly, freaking awesome."

Source: University of Miami

In a rapidly changing north, new diseases travel on the wings of birds

When polar bears (Ursus maritimus) meet glaucous gulls (Larus hyperboreaus) over the remains of a bowhead whale (Balaena mysticetus), they may be sharing more than a meal. As the warming climate brings animals into new proximity, parasites, viruses, and bacteria can find opportunities to spread to new and naïve hosts, sometimes jumping from birds to mammals, and from marine ecosystems to land ecosystems. Credit: USGS

When wild birds are a big part of your diet, opening a freshly shot bird to find worms squirming around under the skin is a disconcerting sight. That was exactly what Victoria Kotongan saw in October, 2012, when she set to cleaning two of four spruce grouse (Falcipennis canadensis) she had taken near her home in Unalakleet, on the northwest coast of Alaska. The next day, she shot four grouse and all four harbored the long, white worms. In two birds, the worms appeared to be emerging from the meat.

Kotongan, worried about the health of the grouse and the potential risk to her community, reported the parasites to the Local Environmental Observer Network, which arranged to have the frozen bird carcasses sent to a lab for testing. Lab results identified the worms as the nematode Splendidofilaria pectoralis, a thinly described parasite previously observed in blue grouse (Dendragapus obscurus pallidus) in interior British Columbia, Canada. The nematode had not been seen before so far north and west. Though S. pectoralis is unlikely to be dangerous to people, other emerging diseases in northern regions are not so innocuous.

Animals are changing their seasonal movements and feeding patterns to cope with the changing climate, bringing into close contact species that rarely met in the past. Nowhere is this more apparent than the polar latitudes, where warming has been fastest and most dramatic. Red foxes are spreading north into arctic fox territory. Hunger is driving polar bears ashore as sea ice shrinks. Many arctic birds undertake long migratory journeys and have the mobility to fly far beyond their historical ranges, or extend their stay in attractive feeding or nesting sites.

With close contact comes a risk of infection with the exotic parasites and microorganisms carried by new neighbors, and so disease is finding new territory as well. Clement conditions extend the lifecycles of disease carrying insects, and disease-causing organisms. Migratory birds can take infectious agents for rides over great distances. In November 2013, Alaska Native residents of St. Lawrence Island, in the Bering Sea, alerted wildlife managers to the deaths of hundreds of crested auklets, thick-billed murres, northern fulmars and other seabirds, caused by an outbreak of highly contagious avian cholera (Pasteurella multocida).

"It's the first time avian cholera has shown up in Alaska," said Caroline Van Hemert, a wildlife biologist with the U.S. Geological Survey in Anchorage, Alaska. "St. Lawrence Island is usually iced in by November, but last year we had a warm fall and winter in Alaska. We don't know for sure that open water, climate, and high-densities of birds contributed to the outbreak, but it coincided with unusual environmental conditions."

Circumstantial evidence collected by researchers and local observers is pointing toward a surge of infectious disease in the northern latitudes, but scanty baseline data makes interpretation of current trends uncertain. Van Hemert and colleagues review the state of our knowledge of emerging disease in northern birds and effects on wildlife and human health, discussing strategies for cooperative programs to fill in information gaps in the December issue of Frontiers in Ecology and the Environment.

Source:  Ecological Society of America