Science-- there's something for everyone

Monday, March 31, 2014

Diagnosing concussion with a blood sample

File:Concussion Anatomy.png
Image by Concussion mechanics.svg, 5/18/2012

There’s been a lot of attention paid of late to the problem of diagnosing concussions. How can you tell if an athlete has suffered a concussion, in which case he should be removed from play? One way is to look for biochemical markers. For example, boxers have increased levels of total tau proteins (T-tau) in their cerebrospinal fluid that correlate with the number and severity of the head blows they receive. Unfortunately, you can only analyze cerebrospinal fluid by doing lumbar punctures, which require a certain level of expertise.

Therefore, it would be nice to be able to detect a concussion biomarker with a simple blood draw. Luckily, there is now an ultra sensitive digital immunoassay that can measure T-tau in blood samples. Scientists led by Pashtun Shahim of Sahlgrenska Academy at the University of Gothenburg used the new method to quantify levels T-tau in the blood serum of hockey players.

Out of 288 players in the Swedish Hockey League, researchers took blood tests from 47 prior to the start of their professional season. During the season, 35 athletes suffered concussions (based on current guidelines), and 28 of them provided blood samples at 1, 12, 36, and 48 hours and 144 hours after the injury. It should be noted that these 28 were not necessarily the same men who had given the pre-concussion samples.

T-tau was significantly increased in all the post-concussion samples with the highest levels measured during the first hour. T-tau was also higher in players with more severe concussions, like those who had lost consciousness. This means that T-tau levels immediately after concussion could be used to predict when an athlete could safely return to play.

Obviously, these results are mere correlations at this point. And of course, we don’t have baseline measurements of the same people pre and post-concussion. However, if the results do pan out, measuring blood levels of T-tau could be a valuable tool in determining which athletes should be cleared for competition.

Shahim, P., Tegner, Y., Wilson, D., Randall, J., Skillbäck, T., Pazooki, D., Kallberg, B., Blennow, K., & Zetterberg, H. (2014). Blood Biomarkers for Brain Injury in Concussed Professional Ice Hockey Players JAMA Neurology DOI: 10.1001/jamaneurol.2014.367.

Friday, March 28, 2014

An argument for the environmental cause of autism

Although we still don’t have a definitive cause for autism spectrum disorders (ASD), we know there is a strong genetic component. Cases of ASD tend to cluster in families and many specific genes have been implicated. However, that doesn’t mean that those genetic changes weren’t caused by environmental factors that acted during fetal development.

Researchers led by Andrey Rzhetsky of the University of Chicago scoured the insurance claims of roughly one third of the U.S. population looking for incidences of ASD. They compared those rates, county by county across the country, with the rate of birth defects in the reproductive systems of baby boys. The idea was that the birth malformations would indicate whether the parents had been exposed to environmental toxins like pesticides.

Sure enough, regions with higher rates of congenital malformations also had higher rates of ASD. For every 1% increase in birth defects there was a 283% higher incidence of ASD. This suggests that whatever is causing the increase in birth defects is also causing ASD.

To be clear, this is no more than an association. We don’t know for sure that environmental toxins are responsible for causing ASD, let alone which toxins. It is interesting that the male genetic structures form in the fetus at about the same time as neurons appear within the developing brain. Thus, exposure at that time could affect both or either developing organs.

If there is a an environmental factor causing ASD, it is felt prenatally, and perhaps even before conception (if the parents' germ cells were affected). By the time the baby is born, the damage has already been done.

Rzhetsky, A., Bagley, S., Wang, K., Lyttle, C., Cook, E., Altman, R., & Gibbons, R. (2014). Environmental and State-Level Regulatory Factors Affect the Incidence of Autism and Intellectual Disability PLoS Computational Biology, 10 (3) DOI: 10.1371/journal.pcbi.1003518.

Thursday, March 27, 2014

Internal food webs

This is the parasite food web containing 10 groups of clustered parasites, tissues, and immune responses.
Credit: Dr. Griffiths

Last year, I wrote about researchers adding parasites to food web diagrams. You can’t really understand the dynamic interactions within an ecosystem if you don’t take parasites into account. Well, that’s just as much true inside a body as out. We play host to a complex community of microorganisms. Understanding how different parasites interact with each other within our bodies could play a key roll in defeating them.

In particular, does the presence of one type of virus or fungi inhibit or promote the growth of another? Would treating a bacterial infection give protozoans free reign to roam the body?

To begin to answer those questions, Emily Griffiths, formerly at University of Sheffield but currently at North Carolina State University, and her colleagues pored through published papers to find cases of multiple infection. From those reports, the researchers constructed a network of interactions showing links between parasites, immune system components that could attack those parasites, and the host resources that the parasites could consume.

The authors found that most parasites are only indirectly linked to each other. In other words, they don’t care what other parasites are doing or even whether they are present at all. This is not different from most free-living species, who also do not care what other organisms are doing, so long as those creatures don’t try to eat them. Where parasites did interact, it was more likely to be by sharing food resources rather than by eliciting the same immune responses.

Like in real estate, the most important thing in parasitism seems to be location. The scientists found ten tightly bound communities of parasites, eight of which were associated with particular body parts. You can
see a cartoon of this finding at the top.  

Griffiths, E., Pedersen, A., Fenton, A., & Petchey, O. (2014). Analysis of a summary network of co-infection in humans reveals that parasites interact most via shared resources Proceedings of the Royal Society B: Biological Sciences, 281 (1782), 20132286-20132286 DOI: 10.1098/rspb.2013.2286.

Wednesday, March 26, 2014

Just for fun: The peacock spider

Do you like peacock spiders? Then you'll want to visit the YouTube channel Peacockspiderman maintained by cinematographer Jürgen Otto. Do you not know what peacock spiders are? Then you'll definitely want to visit that channel. Here's a sample:

Here's Dr. Otto's narration of the events. Note how tiny the spiders are:

More about peacock spiders here, by Gwen Pearson, aka Bug Girl.

Tuesday, March 25, 2014

Healthy food choices don’t hurt concession stands

food and brand lab, concession stand makeoverWe’re all well aware of the obesity epidemic our nation is facing and of the accompanying health risks. We also know that an important part of combatting childhood obesity is to offer healthy food choices. That being the case, why not sell nutritious items at high school concession stands during games? That’s the question that Helena Laroche of the University of Iowa and her colleagues set out to answer.

To begin with, it’s important to note that concession stands make up a very important source of revenue for their schools, helping to fund student organizations and sports teams. Clubs running the food stands can be reluctant to change the menu for fear of hurting sales. Not only could spectators fail to buy healthier snacks, but seeing them on the menu might drive people away from the concession stand all together. 

To see if that was the case, researchers collected data from concession stands in one Iowa High School (1700 students) over two seasons. The first year, the stand offered its usual menu. The second year, the usual foods were sold along with some healthier variations (nachos made without trans fats, for example) plus some new items including fruits and vegetables. None of the new items contained trans fats, and all had been selected from a preference survey given to students and parents.

Profits from the concession stands did not differ between the two years. In other words, having healthy choices did not deter people from buying snacks. So far so good. But were people selecting the healthier options? They were. About 9% of the total revenue was due to the purchase of the new, healthier items. More importantly, sales for those healthier choices continued to increase game after game, indicating that the public liked having them on the menu.

Author Brian Wansink of Cornell University exuberantly explains:

Laroche, H., Ford, C., Hansen, K., Cai, X., Just, D., Hanks, A., & Wansink, B. (2014). Concession stand makeovers: a pilot study of offering healthy foods at high school concession stands Journal of Public Health DOI: 10.1093/pubmed/fdu015.

Monday, March 24, 2014

Young children can understand natural selection

Suppose you read a picture book about some mythical trunked mammals called ‘pilosas’. The pilosas are evenly divided between those with skinny trunks and those with fat trunks, and their diet consists of insects. However, the climate where the pilosas live changes so that insects move deep underground where only thin-trunked pilosas can reach them. After some time, there are very few fat-trunked pilosas around, virtually all the pilosas now have thin trunks.

What would you conclude from reading that story? If you are a 5 to 8 year old child, you would come away with a pretty good understand of natural selection.

Researchers led by Deborah Kelemen of Boston University assessed how well 28 five and six year olds and 33 seven and eight year olds understood evolution by natural selection on a scale of zero to four. The children were then given (or read to from) the pilosa picture book and retested. Only if the kids understood that individual pilosas were not changing, but rather that the makeup of the population of pilosas was changing because some groups were out-reproducing others were they given full points for understanding natural selection.

The results are below. The top panel is for the five and six year old kids, the bottom for the 7 and 8 year olds. As you can see, before the picture book (pretest), the younger kids had almost no familiarity with the concept of natural selection. Afterwards, most of them had at least some understanding and nearly a fifth of them could apply the concept to new populations of animals (generalization test). For the older kids, the results were even more impressive. Nearly all of them came away with a very good idea of natural selection works.

Fig. 2.
(a) younger and (b) older children classified into the five levels of natural-selection understanding as a function of assessment. Because of rounding, percentages do not always add up to 100. Level 0 = no isolated facts; Level 1 = isolated facts but no natural-selection understanding; Level 2 = foundation for natural-selection understanding; Level 3 = natural-selection understanding in one generation; Level 4 = natural-selection understanding for multiple generations.
Psychological science PMID: 24503874.

This is significant because natural selection is not usually taught before age 13, and often not until 18, if at all. By that time, incorrect ideas can become entrenched in students’ minds. It was thought that children wouldn’t be able to understand complex ideas like natural selection until they were in their teens. Not so much.

As Kelemen explains:

It turns out that if you put the facts into the context of a theory, the kids learn not only the facts, but they also understand the full explanation. And they get it beyond a level we ever imagined they would, given how young they are. 

Kelemen D, Emmons NA, Seston Schillaci R, & Ganea PA (2014). Young Children Can Be Taught Basic Natural Selection Using a Picture-Storybook Intervention. Psychological science PMID: 24503874.

Friday, March 21, 2014

Do your medicines get along?

When we get into our senior years, chances are we’ll be regularly taking medications, either as a treatment or as a preventative measure for chronic ailments. Unfortunately, the chances that some of those drugs will interfere with each other is quite high. Researchers from the Yale School of Medicine found that about a fifth of older Americans receive medications that can worsen some of their conditions.

About 75% of older adults have more than one treatable chronic condition. For example, a person might have high blood pressure (hypertension) and diabetes. The medications for some ailments can be detrimental for other conditions. Beta blockers taken to treat heart disease can worsen pulmonary disease.

To look for drug interactions, the scientists recruited close to 6000 medicare recipients, who provided health and medication histories. Fourteen different ailments (hypertension, osteoporosis, etc) treated by 27 different classes of medication were included in the study.

Nearly 80% of the participants had at least two chronic conditions and almost a third of the patients had ten different conditions! Given those statistics, it’s not at all surprising that that 23% of the patients were receiving at least one medication that could have worsened one of their conditions. And that doesn’t even include nonprescription medications like aspirin.

The matter is complicated by the fact that patients may be better off taking two competing medications that are only somewhat effective than in skipping the treatment for one of their medical conditions. This makes it even more critical to be sure that your doctor knows all the medications you are taking so he or she can evaluate the cost/benefit of them in combination.

Lorgunpai, S., Grammas, M., Lee, D., McAvay, G., Charpentier, P., & Tinetti, M. (2014). Potential Therapeutic Competition in Community-Living Older Adults in the U.S.: Use of Medications That May Adversely Affect a Coexisting Condition PLoS ONE, 9 (2) DOI: 10.1371/journal.pone.0089447.

Thursday, March 20, 2014

Solar cells as art

Sure, solar panels are nice if you just want nonpolluting renewable energy. But what if you want to add a designer touch to your building? You can’t expect the fashion conscious home owner to be satisfied with plain black solar panels on their roof.

I might interject here to say that I have plain black solar panels on my roof, and I’m totally satisfied. But on with the story.

University of Michigan researchers led by Jae Yong Lee have found a way to make colored photovoltaic cells. The prototypes are able to convert 2% of the sun’s energy into usable energy. That's quite a bit worse than the 10% efficiency achieved by the top of the line solar cells. But those cells don’t have pretty pictures on them.

Professon Jay Guo holds up a prototype.
Image courtesy of University of Michigan

The colors on the solar cells aren’t pigments, but rather are created by varying the thickness of the silicon within the cells. Blue areas are six nanometers thick, whereas red areas are 31 nanometers thick. This means that the colors are not dependent on the viewing angle. The different structures capture and transmit different wavelengths of light.

Lead author Jay Guo explains:

Lee, J., Lee, K., Seo, S., & Guo, L. (2014). Decorative power generating panels creating angle insensitive transmissive colors Scientific Reports, 4 DOI: 10.1038/srep04192.


Wednesday, March 19, 2014

Just for fun: Lumpsuckers

Lumpsuckers actually are a lot more fun than the name sounds. Why, you can celebrate your children's birthday with these little fish, assuming the party takes place in a salt water aquarium.

Balloon Lumpsuckers Displayed In Tokyo

Balloon lumpsuckers at the Epson Shinagawa Aqua Stadium in Tokyo, Japan in 2008.

These little round fish have modified pelvic fins that have evolved into adhesive discs that will stick to... well, just about anything.

Toad Lumpsuckers (Eumicrotremus phrynoides - middle two) and Pacific Spiny Lumpsuckers (Eumicrotremus orbis - top and bottom), demonstrating adhesive pelvic discs. Credit: NOAA's Alaska Fisheries Science Center

More on these creatures by Bec Crew at Scientific American Blogs.

Tuesday, March 18, 2014

How preschoolers outsmart college students

Child playing with a blicketness machine.
Credit: Image courtesy of University of California - Berkeley
In what should be no surprise to anyone, young children can be better learners than adults. What’s interesting is that one reason for this is that children are more open-minded in picking up connections. They’re more flexible in their thinking than adults are. Christopher Lucas from the University of Edinburgh and colleagues from the University of California, Berkeley explored this by letting children and college students play with a light-up toy box.

Preschoolers (age 4 and 5) and college students were presented with a ‘blicketness machine’, a box that lights up when certain combinations of clay shapes (‘blickets’) are placed upon it. After watching a demonstration, the participants then have to figure out what configuration of blickets made the machine light up. 

When the machine lit up after two objects were placed on it, participants could infer that those objects had a disjunctive relationship with each other (either A or B alone would have been sufficient) or a conjunctive relationship (both A and B were required).

Adults were much more likely to assume that the clay pieces operated independently. That is, they had a bias toward disjunctive relationships. This was true even when it ran contrary to the evidence presented. In contrast, the preschoolers were more readily able to switch to a conjunctive viewpoint.

Of course, no one is saying that small children are smarter than college students. However, young kids do seem to have more cognitive flexibility, especially when it comes to figuring out cause and effect.

Lucas, C., Bridgers, S., Griffiths, T., & Gopnik, A. (2014). When children are better (or at least more open-minded) learners than adults: Developmental differences in learning the forms of causal relationships Cognition, 131 (2), 284-299 DOI: 10.1016/j.cognition.2013.12.010.

Monday, March 17, 2014

Elephants discriminate between human voices

If you’re a wild African elephant of mature age, you’ve probably had a number of encounters with humans, some of which you undoubtedly regret. Of course, not all humans pose the same threat to your little band, so it would be useful if you could distinguish potential predators from mere passersby. The good news is that you can!

Two groups of people that elephants commonly encounter are the Maasai and the Kamba. The former are much more likely to come into deadly conflict with the elephants than the latter. Consequently, elephants show more fear when exposed to either the scent or red color of garments worn by Maasai men than to clothes worn by Kamba men.

Researchers from the University of Sussex and Amboseli Trust for Elephants investigated whether elephants could also distinguish between human voices. To that end, they recorded Maasai and Kamba men and women saying “Look, look over there, a group of elephants is coming” in their own languages. The recordings were played back to groups of female elephants (females and juveniles typically travel separately from adult males).

All the groups displayed more fearful, defensive behavior after hearing male Maasai voices than they did for Kamba voices or for female Maasai voices. They bunched together and spent more time carefully sniffing the air. It should be noted that Maasai women are not involved in hunting elephants and thus pose no real threat to the animals.

Interestingly, when the recordings were acoustically altered to make men sound like women and vice versa, the elephants still showed fear only when hearing what were originally male voices. In other words, the elephants could tell the men from the women even when the men sounded like women to our ears.

I don’t find it that surprising that elephants can distinguish men from women by their voices, though it is a bit odd that they seem to be better at it than we are. I do find it amazing that African elephants can tell the men from two different tribes apart by their voices. This suggests that elephants can discriminate between human languages, a remarkable ability.

By the way, aural perspicacity goes both ways. Another new study shows that humans can tell how old elephants are by listening to their vocal calls. 

McComb, K., Shannon, G., Sayialel, K., & Moss, C. (2014). Elephants can determine ethnicity, gender, and age from acoustic cues in human voices Proceedings of the National Academy of Sciences DOI: 10.1073/pnas.1321543111.

Friday, March 14, 2014

Where’s our second Earth?

To date, we’ve found over 1500 exoplanets and have detected more than two thousand possible candidates for that status that have yet to be confirmed. So where’s our second Earth? Unfortunately, we haven’t found it yet. And according to researchers led by Helmut Lammer of the Space Research Institute of the Austrian Academy of Sciences, that planet may be even more elusive than we thought.

Two of the main criteria for whether are planet could harbor life are its size and its location. The planet must be small enough to have a rocky surface, as opposed to being a giant ball of gas like Jupiter. It must also be located at a distance from its star that allows the presence of liquid water. That orbital distance is often referred to as ‘the habitable zone’ or sometimes ‘the goldilocks zone’.

Lammer and his team think we should add internal composition, or more specifically, density to that list of requirements. 

The mass of the initial rocky core determines whether the final planet is potentially habitable.
Top: The core has a mass of more than 1.5 times that of the Earth. The result is that it holds on to a thick atmosphere of hydrogen (H), deuterium (H2) and helium (He).
Bottom: The evolution of a smaller mass core, between 0.5 and 1.5 times the mass of the Earth. It holds on to far less of the lighter gases, making it much more likely to develop an atmosphere suitable for life.
Credit: NASA / H. Lammer

As it’s being formed from the dust and gas around a young star, a protoplanet captures a hydrogen envelope around it. Depending on conditions, most or all of that hydrogen can be stripped away, as was the case with the Earth. However, if a planet is dense enough, it will retain a thick blanket of hydrogen. If so, the pressure on the surface of that planet will be too great to sustain life. Thus, a planet might appear similar to the Earth and even orbit within the habitable zone, but be completely inhospitable. 

Lammer, H., Stokl, A., Erkaev, N., Dorfi, E., Odert, P., Gudel, M., Kulikov, Y., Kislyakova, K., & Leitzinger, M. (2014). Origin and loss of nebula-captured hydrogen envelopes from 'sub'- to 'super-Earths' in the habitable zone of Sun-like stars Monthly Notices of the Royal Astronomical Society DOI: 10.1093/mnras/stu085.

Thursday, March 13, 2014

Virtual Reality versus phantom limb pain

The majority of people who have had a limb amputated, regardless of the reason for that amputation, suffer from ‘phantom limb pain’. As the name suggests, phantom limb pain is the phenomenon in which a person feels persistent pain or itching coming from a limb that has been amputated. Sufferers will sometimes insist that the missing hand or foot is extremely painful to them. Understandably, this has been difficult for physicians to treat, since there is no hand or foot. Painkillers can be ineffective, and the discomfort can last years or even a lifetime.

At first, phantom pain was thought to be triggered by crushed or damaged nerves at the amputation site. Now, it is known that the discomfort originates directly in the brain. The part of the brain responsible for the missing limb now has no job, and begins to fire when other parts of the body are stimulated. In some cases, stroking part of a patient’s face will create the sensation of touching a missing limb.

That being the case, doctors have had some success at curing phantom limb pain by using mirror boxes to trick the brain into thinking the limb has been resurrected.

There are a couple of drawbacks to this treatment. For one thing, not all patients respond to the visual cues provided by the mirror. Perhaps more importantly, a person must have one completely sound and functional limb for the mirror to work.

Researchers from Chalmers University of Technology and Sahigrenska University Hospital in Gothenburg, Sweden have been experimenting with virtual and enhanced reality systems to get around both of these drawbacks. They use computer algorithms to turn signals from the muscles left at the amputation site into instructions for moving a virtual limb. Because the signals originate in the amputated limb, rather than the opposite side of the body, the sensation is more vivid. Also, no intact limb is required for the therapy.

In the augmented reality environment, the patient can see himself with a superimposed virtual arm, which is controlled by muscle signals from his arm stump.
Credit: Ortiz-Catalan et al., Frontiers in Neuroscience

So far, the scientists were able to bring relief to one patient who had suffered from phantom limb pain since losing his arm nearly 50 years ago. After working with the system once or twice a week for ten weeks, the patient reported his first moments of being completely pain free:
These pain-free periods are something almost new to me and it is an extremely pleasant sensation.
I'm sure it is. And let's hope he and others like him can enjoy many more pain-free moments thanks to this technology.

Ortiz-Catalan, M., Sander, N., Kristoffersen, M., Håkansson, B., & Brånemark, R. (2014). Treatment of phantom limb pain (PLP) based on augmented reality and gaming controlled by myoelectric pattern recognition: a case study of a chronic PLP patient Frontiers in Neuroscience, 8 DOI: 10.3389/fnins.2014.00024.


Wednesday, March 12, 2014

Just for fun: Bird flight paths

If you could film birds flying with long dotted lines trailing behind them, what would you see? Luckily, Professor Dennis Hlynsky of the Rhode Island School of Design has provided the answer. And it's even more fascinating than you think. 

Is it just me, or do the birds look like they're writing in the sky?

More of Professor Hlynsky's videos here.

Tuesday, March 11, 2014

The ocean that might have been

You’re familiar with the Atlantic Ocean, but have you ever heard of the Saharan Atlantic Ocean? No? That’s because there is no Saharan Atlantic Ocean. But there might have been.

From 510 to 180 million years ago, South America and Africa were fused together in a supercontinent called Gondwana.

After that time, rifts in the Earth’s crust broke Gondwana apart, separating the Americas from Africa and resulting in the formation of the Atlantic Ocean. However, Christian Heine and Sascha Brune of the University of Sydney and the German Research Centre for Geosciences found that such an eventuality was far from certain. Instead, Africa itself could have split apart with the western half remaining attached to South America. You can see a model of what that might have looked like below.

A hypothetical model of the circum-Atlantic region at present-day, if Africa had split into two parts along the West African Rift system. Here, the north-west part of present day Africa would have moved with the South American continent, forming a "Saharan Atlantic ocean".
Credit: Sascha Brune/Christian Heine

For a while (some 20 million years), it looked like either scenario could have played out. Gondwana could have been split between Africa and South America or between Eastern and Western Africa.

Obviously, the former rift proved more powerful and the African rift was eventually abandoned. Thus we ended up with the Earth we have today.

Heine, C., & Brune, S. (2014). Oblique rifting of the Equatorial Atlantic: Why there is no Saharan Atlantic Ocean Geology, 42 (3), 211-214 DOI: 10.1130/G35082.1.

Monday, March 10, 2014

Rafting on a baby ant float

If your community was escaping from a flood by building a living raft, would you use babies as floatation devices? What if those babies turned out to be much more buoyant than adults? If you’re an ant of the species Formica selysi, that’s exactly what you would do.

University of Lausanne researchers led by Jessica Purcell tested the rafting strategies of F. selysi. To do so, they first had to address a few questions, like how long can a worker ant survive being submerged in water? And just how buoyant is an ant larva? These questions were handily answered by holding worker ants under water and by floating larvae in increasing concentrations of detergent. Fun for everyone.

Next, the scientists encouraged colonies of ants to build rafts by slowly flooding the platform they were living on. The ant rafts are built solely of ant bodies, they used no other construction materials. As the rafts were constructed, the researchers observed their building strategies.

If there were larvae or pupae (brood) available, the workers would put them in a pile and climb on top. If present, the queen would then take a lofty position on top of the workers and float away in relative ease and safety. 

You can observe this in the following video, which is shot from underneath. Note how pillowy and comfortable the large yellow ant brood looks.

As odd as it seems to our sensibilities, floating away on a pile of babies gives everyone a higher chance of success. Worker ants have a 79% survival rate after being submerged for eight hours, but ant brood fare even better. In addition, ant larvae and pupae are significantly more buoyant than the adult workers. Putting the brood on the bottom means that the adults stay drier and have subsequently shorter post-rafting recovery times, which could be crucial if the colony has to quickly establish a beachhead at the new location.

For your viewing pleasure: an unsinkable raft of fire ants, which employ a similar raft building strategy. And you thought magnets were fun to play with.  

Purcell, J., Avril, A., Jaffuel, G., Bates, S., & Chapuisat, M. (2014). Ant Brood Function as Life Preservers during Floods PLoS ONE, 9 (2) DOI: 10.1371/journal.pone.0089211.

Friday, March 7, 2014

Bad news about water usage

An average person could fulfill all her indoor water needs (drinking, food preparation, sanitation and hygiene) with about thirteen gallons per day. In the U.S., we don’t believe in being average however. In 2005, we each used about 98 gallons per day. As climate change reworks the planetary precipitation levels, that could prove to be a big problem. Unfortunately, most people have little idea of how to solve that problem.

Shahzeen Attari from Indiana University asked 1000 people two questions in random order: What’s the most effective thing you can do to reduce your own water consumption; and what’s the most effective thing other Americans can do.

The responses were divided into two categories: curtailment (take shorter showers, eat less meat) or efficiency (switch to water-saving appliances). Most people chose curtailment options for themselves and others by a seven to one ratio. Yet, the single most effective thing a person can do to conserve water is to retrofit an older toilet. Sure, turning the water off while you brush your teeth is good, but replacing an aged clothes washing machine with a newer, much more efficient model would make a much bigger difference.

People were also terrible at estimating how much water different activities used, which no doubt plays into their inability to make the smartest conservation choices. Of course, it’s also true that, while you might save money in the long run, changing out your appliances can be pretty expensive. Meanwhile, taking shorter showers doesn’t cost anything.

Attari, S. (2014). Perceptions of water use Proceedings of the National Academy of Sciences DOI: 10.1073/pnas.1316402111.

Thursday, March 6, 2014

Revenge of the Crazy Ants

This is a fire ant (Solenopsis invicta). 

Solenopsis invicta

Although it originated in South America, there’s a good chance you are more familiar with it than you want to be. Fire ants are now pests throughout much of the world. Among their charms is an extremely painful venom and a willingness to attack.

If you live in the southern United States, you may be pleased to hear that fire ants have met their match in another invader from South America, the crazy ant (Nylanderia fulva). 

Nylanderia fulva
Photographed by April Nobile, 6/8/07
Fire ants easily dispatch most other ant species from their territories, but the crazy ants are not only holding their own, they’re actually displacing the fire ants. How?

Edward LeBrun, Nathan Jones and Lawrence Gilbert of The University of Texas at Austin found that the crazy ants can detoxify the venom of the fire ants, rendering the latter weaponless in the ensuing battle. The crazy ants do this by daubing themselves with their own abdominal secretions.

Crazy ants that were permitted to detoxify the fire ant venom had a 98% survival rate. That rate dropped in half when the crazy ants' own venom glands were sealed, preventing them from applying the antidote. With the arrival of crazy ants, it looks like fire ants' days may be numbered.

The news isn't all good. While crazy ants are likely to spread more slowly than fire ants did, they will eventually cause many of the same problems, devastating native populations of insects, and, in turn, the animals that depend on those insects.

You can read more about this here

Lebrun EG, Jones NT, & Gilbert LE (2014). Chemical Warfare Among Invaders: A Detoxification Interaction Facilitates an Ant Invasion. Science (New York, N.Y.) PMID: 24526314.

Wednesday, March 5, 2014

Just for fun: Science demos!

Get Set Demonstrate is a Youtube channel for science teachers. Or anyone who likes to set up experiments and see cool results.

Below are step by step instructions for making a 'pearls of water' demonstration using standard high school lab equipment.

Just remember not to put your students into epileptic fits.

Tuesday, March 4, 2014

Wallabies don't see like quokkas

Wiebke Ebeling from Curtin University and Jan Hemmi from The University of Western Australia have discovered that the color vision of wallabies is more similar to that of dogs than of quokkas. If you’re like me, the first thing you thought upon reading that sentence was, ‘what the hell is a quokka?’

Here it is:

Quokka, photographed by Loetifuss, 9/23/2005

I know, I know. So cute!

The important point is that like wallabies, quokkas are marsupials. This means that wallabies are much more closely related to quokkas than they are to placental mammals, like dogs. However most placental mammals (except for some primates) have only two types of cones and thus have limited color vision (they're dichromates). In contrast, many marsupials, including quokkas, are trichromatic, having three types of cones. Yet, the closely related wallaby is a dichromate.

How do we know? Well, by training the critters to indicate whether two light panels appeared to be the same color.

Light stimuli were projected onto diffuser flaps that also served as the trigger when the animal pushed to indicate a stimulus choice. If correct, a food reward was delivered into a feeder bowl under the stimuli.
Photo copyright: W. Ebeling.

It’s pretty clear that the wallabies are dichromatic. What’s not clear is why they differ in this fundamental way from other, closely related marsupials. 

Wiebke Ebeling, & Jan M. Hemmi (2014). Dichromatic Colour Vision in Wallabies as Characterised by Three Behavioural Paradigms PLOS ONE DOI: 10.1371/journal.pone.0086531.

Monday, March 3, 2014

Gripping without fingers

Researchers from the University of Chicago, Cornell and iRobot have designed a new robotic gripper that you are definitely going to want to play with.
Credit: John Amend, Cornell University

You’ll notice something striking about this particular robotic arm. Unlike other models, this design has no fingers or claw. In fact, it’s just a bag. Yet, it can somehow grip any kind of object. How?

The bag is filled with small grains. For their prototype, the authors used a balloon filled with coffee grounds. The bag is then attached to a vacuum. When that vacuum is turned off, the coffee grounds are packed loosely enough to mold around objects. Then, when the vacuum is turned on, the air is evacuated from the balloon leaving the coffee grounds rigidly compressed in place around the gripped object.

You can see a demonstration below:

Didn’t I tell you you were going to want one? Well, the good news is that you can make your own universal gripper! Here’s one tutorial:


Eric Brown, Nicholas Rodenberg, John Amend, Annan Mozeika, Erik Steltz, Mitchell R. Zakin, Hod Lipson, & Heinrich M. Jaeger (2010). Universal Robotic Gripper based on the Jamming of Granular Material Proceedings of the National Academy of Sciences 107, (44) 18809-18814 (2010) arXiv: 1009.4444v2.