Tuesday, April 18, 2017

Constance and Nano: Engineering Adventure!

The Society of Women Engineers (SWE)'s has the SWENext program , which offers great resources and outreach for students through the age of 18. They hold engineering events designed for girls, provide scholarships, hold events to meet women engineers, have cool engineering projects, and great contests.

One of their newer outreach endeavors is "Constance and Nano Engineering Adventure!" This is a comic book about friends Constance and Nano and their engineering adventures, solving problems with science, engineering, technology and math! You can even download the first issue for free HERE.

Wednesday, April 12, 2017

Flyfocals: Vision and Vectors Help Hunting Robber Flies

Image credit: Thomas Shahan

Robber flies (Asilidae family) are not your typical house flies. They are small, predatory insects that feed on a vast array of other arthropods. While they are small in size (10 times smaller than a dragonfly), these guys are serious hunters. For example, Mallophora omboides is known as the “Florida bee killer” for its taste for honey bees. Other robber flies hunt down wasps, dragonflies, spiders, or grasshoppers, just to name a few. Perhaps almost as impressive as the types of prey is how they are subdued. Typically, robber flies will perch out in an open sunny place and wait, seizing their prey in flight and injecting it with neurotoxic or proteolytic enzymes that both immobilizes it and liquefies its insides.

A recent study in Current Biology took a closer look at the robber fly’s “aerial attack strategy.” The authors focused on the genus Holcocephala, a group native to the Americas. Let’s start by going over something you know about but probably never realized had an actual term: constant bearing angle (CBA) strategy. Initially, I tried to describe this just using text, but it is really best visualized with the help of a supplemental graphic from the paper.

Figure S1 from Wardill et al. (2017). Diagram showing how the constant bearing angle strategy (CBA) and proportional navigation can be used to intercept targets. It looks like an eye, but you are actually looking down on the "Human" and seeing the top of the head (black) and shoulders (white). 
Visualize this: You are walking along and ahead of you a ball is rolling along the ground from your left. But you decide that you want to get to the ball before it would intercept your path. If you want to catch the ball you can’t run straight for where you see it or it will have rolled past that spot before you get there. If you want to intercept that ball while it is still on your left, you will technically have to turn to backward, changing your “bearing angle.” You must anticipate where it will be and run in a straight line to that spot. This line is a “parallel range vector.” There are several of these vectors, depending on when you choose to change course.

The study considered whether the flies were using this CBA strategy to catch their prey. To do this, the researchers went out to a field and hung up a big white sheet as a backdrop for their high-speed video cameras. Next, they set up their “fly teaser,” a custom made plastic frame that housed a stepper motor and several pulleys to move taut fishing line. This allowed for precise, computer controlled movements of the beads they attached to the fishing line. When a robber fly perched on a blade of grass in their study area, they “teased” it with a bead (a.k.a. dummy prey item for the fly). They included several variations including bead size and direction. They recorded the fly with two synchronized cameras running at 1000 fps to get a 3D view of the attack. For each attack video, they analyzed the frame at which the flies started to take off and until it began a terminal deceleration on final approach of the target. Then: measure, measure, measure, math, math, math.

They found that the flies were fairly consistent with the CBA model. If they decelerated or reversed the bead during the attack, the robber flies compensated, actively keeping the range vectors parallel. One unexpected finding occurred in cases where the bead moved in front of the fly and it took off with a head-on collision course. They found that the fly still intercepted the bead while flying at a backward angle, meaning that the latter part of its trajectory was distinctly curved. When they took a closer look, the found the results to reflect a “lock-on” process “during which the fly has a new heading and the speed is fixed to a value slightly higher than that of the prey.” This lock-on strategy has not been described in any other flying animal. The flies were able to compensate for unexpected changes in the target’s velocity and uncertainties in the location, size, and speed of the target.

Adapted from paper's graphical abstract
This type of hunting relies very heavily on vision. So each robber fly was captured for later, high detailed analysis of the head and eyes. It is important to remember that insects have compound eyes. Repeating units (the ommatidia, which have hexagonal faces called facets) that make up the eyes function as separate receptors that, when put together, assemble view of the environment. The researchers measured several parts and angles within the eyes, and once again math, math, math. This revealed the ommatidia in the front, center portion of each eye (colored red in the picture) to be nearly double the size of those in other areas, have extended focal lengths and smaller receptors. This means that the flies can reduce diffraction, focus incident light, and optimize resolution in this area. This results in a frontal fovea, or area within the eye that provides greater visual acuity than the rest of the eye. Sort of like the embedded lens of bifocal glasses; while that is an incredibly simplified way to look at it, it tells you a lot about how the flies might strategize prey capture. Also, they could be judging distance using stereopsis. This is when they use both eyes in combination to depth and 3D structure. The authors sum things up nicely, so I'll leave it in their words: "[It is kind of amazing the] accurate performance that a miniature brain can achieve in highly demanding sensorimotor tasks."

Interested in more details? Here’s a video summary put together by the researchers:


Wardill, T., Fabian, S., Pettigrew, A., Stavenga, D., Nordström, K., & Gonzalez-Bellido, P. (2017). A Novel Interception Strategy in a Miniature Robber Fly with Extreme Visual Acuity Current Biology, 27 (6), 854-859 DOI: 10.1016/j.cub.2017.01.050

Read more about robber flies at University of Florida's Featured Creatures page.

Wednesday, April 5, 2017

The Universe is Your Sandbox

Lately I've been catching up on The Weekly Space Hangout podcast. A few weeks ago, they featured an interview with Dan Dixon, a developer of Universe Sandbox. This is an incredibly cool, scientifically accurate, interactive space and gravity game/simulator.

"Create and destroy on an unimaginable scale... with a space simulator that merges real-time gravity, climate, collision, and material interactions to reveal the beauty of our universe and the fragility of our planet."

Want to add a moon or two to a solar system and see how those moons will be ripped apart by a planet? How about seeing what happens when you fling planets into or out of a solar system? What about modeling Earth's climate, watching sea ice grow and recede based on the planets tilt? Oh! And go ahead and terraform Mars while you are tinkering with climates. The scenarios of creation and destruction you can do are endless!

Perhaps most importantly, it uses real science, real physics. And it runs on your home computer. The latest version even has VR mode. It only costs $24.99 (USD), which, for a video game of this complexity is pretty good.

Check it out:

A moon colliding with Earth.

Orbiting bodies and their trails colored by their velocity.

A supernova within our solar system.

Neptune pulling apart Saturn's rings.

All images from Universe Sandbox.

Tuesday, March 14, 2017

Thursday, March 9, 2017

Women of Science

This is a wonderful video about some important women of science and the sexism that they faced then as well as today.

Monday, March 6, 2017

Dart Art: Science and Nature

I know Kevin Dart's work through his movie art (e.g., Interstellar). This is his Science and Nature series, which features prints that focus "on the wonder that is space and our surroundings."

You can see more of his art at his tumblr page.

SCIENCE & NATURE - Teaser Trailer from Chromosphere on Vimeo.

Thursday, March 2, 2017

Women of NASA Legos!

Legos! I don't know about you, but I love all things Lego. When Lego goes sciency, I love it even more. Now, five female NASA pioneers will soon me immortalized in Lego form in the new Women of NASA set created by Maia Weinstock, a science editor and writer at MIT news. It beat out 11 other projects in a Lego Ideas competition. And with the recent success of the movie "Hidden Figures," this set is sure to be a hit.

Margaret Hamilton
The set includes figures of:

  • Margaret Hamilton - A computer scientist that worked at MIT under contact with NASA in the 1960s. She developed the on-board flight software for the Apollo missions and was awarded the Presidential Medal of Freedom for her work in the Apollo 11 moon landing. She poplarized the modern concept of software.

Katherine Johnson
  • Katherine Johnson - A  mathematician and space scientists that is best known for calculating and verifying trajectories for the Mercury and Apollo programs. She is one of the women portrayed in the movie Hidden Figures.

Nancy Grace Roman
  • Nancy Grace Roman - A chief astronomer for NASA and one of the first female executives at NASA. She is known as the "Mother of Hubble" because she was instrumental in the realization of the Hubble Space Telescope. She also developed NASA's astonomy research program.

    Sally Ride
  • Sally Ride - Best known as the first American woman in space (1983), she was also a physicist. She later focused on education, founding an educational company focusing on encouraging children, especially girls, to pursue the sciences.

  • Mae Jemison - Best known as the first African-American woman in space (1992), she's also a mediacal physician and an entrepreneur. She established a company that develops new technologies and encourages students in the sciences.

It also includes a desktop frame that displays the figures and their names as well as vignettes detailing their accomplishments.

Keep up to date with this at the Lego Ideas Project Page for Women of NASA

Read more at:

Tuesday, February 28, 2017

Rap Battle: Mitosis vs. Meiosis

We all love a good rap battle. Watch mitosis take on meiosis!


Friday, February 24, 2017

Symbiote Separation: Coral Bleaching and Climate Change

It’s been a while since I’ve broken down some studies for you, so I took on a big one.

I’m sure you’ve heard of coral bleaching. What is it? Why does it happen? Why does it matter? To start off, you need to know a little bit more about the individuals that make up a coral head (fan, whip, etc.): the polyp. Coral polyps look like tiny plants but are actually tiny animals (less than ½ an inch in diameter). They produce calcium carbonate to create a protective shell or skeleton that, when thousands are living together, make up what you see as a single coral head. Really, only the outer-most layer of a coral head is actually alive (yes, they build their houses on top of the skeletons of their ancestors). Lots of individual corals make up a reef. Polyps have stinging cells (nematocysts) on their tentacles that capture any prey that swims a little too close. But a polyp does not live alone inside of its skeleton-house; it is actually in a symbiotic relationship with dinoflagellates (a.k.a. marine algae) called zooxanthellae (zo-o-zan-THELL-ee). Zooxanthellae live inside the tissues of the polyp and photosynthesize, passing some of the energy they make to the polyp. They get a place to live and the polyp gets some energy, it’s a win-win. And, it is the zooxanthellae that give the corals much of their color.

When the coral gets stressed, it expels the zooxanthellae, causing them to turn completely white. Not dead, but very stressed and more likely to die. This is coral bleaching. All sorts of things can stress a coral and cause them to eject their zooxanthellae: temperature, light, tides, salinity, or nutrients. A polyp has cemented itself in its skeleton-house so it isn’t able to relocate when conditions change. Coral reefs are one of the most diverse ecosystems on the planet, definitely in the oceans. Coral serves as both food and/or shelter for many other species, up to ¼ of all ocean species. And their location means they protect shorelines too. That is a lot of responsibility.

Now let’s look at those stressors. Remember middle school chemistry? Yeah, me neither. Here’s a little refresher: water reacts with carbon dioxide to make carbonic acid (H2O + CO2 = H2CO3). Rising atmospheric carbon dioxide (yes, we’re talking climate change here) both increases surface water temperature and makes water more acidic. That’s two stressors, y’all. And more than 30 percent of human emitted CO2 gets taken up by the oceans. A paper published by Anthony et al. (2008) in PNAS did a nice experiment looking at what happens to different coral species when the ocean acidifies and/or warms. They collected three of the most important “framework builders” in Heron Reef in the Indo-Pacific and transferred them to lab aquaria: Porolithon onkodes (common crustose coralline algae [CCA] species), Acropora intermedia (a fast growing, branching species), and Porites lobata (a massive species). Next, they used a custom-built CO2 dosing (bubbling) and temperature control system to test different acidification and temperature regimes that simulate doubling and 3- to 4-fold CO2 level increases as projected by the Intergovernmental Panel on Climate Change (IPCC). Then, they waited, they watched, and they took pictures for 8 weeks. From these digital images, they measured the amount of color and reduction in luminance of the corals. They also measured net rates of photosynthesis, respiration and calcification.

They found that increased CO2 (i.e., acidification) led to 40-50 percent bleaching in Porolithon and Acropora. For both of these species, the effect of increased CO2 on bleaching was stronger than the effect of temperature. Porites was less sensitive to increased CO2 alone, but was most sensitive in both stressors. High temperature amplified the bleaching by 10-20 percent in Porolithon and Acropora and 50 percent in Porites. In Porolithon, increased CO2 lead to a severe decline in productivity and calcification that was exacerbated by warming. Acropora’s productivity actually maximized with intermediate increases in CO2, but dropped at higher levels. Porites's productivity dropped with high CO2 but not like that of the Acropora. These species had similar calcification responses to each other, each much less than Porolithon. Overall, the authors proposed that CO2 induces bleaching through its impact on photoprotective mechanisms. Porolithon was the most sensitive to acidification, which is concerning because it is a primary reef-builder and serves as a settlement cue for invertebrate larvae (including other corals).

A very recent study by Perry and Morgan (2017) in Scientific Reports zoomed out to look at corals at a large scale. They looked at magnitude of changes that followed the El Niño/Southern Oscillation (ENSO)-induced Sea Surface Temperature (SST) warming anomaly that affected the central Indian Ocean region in mid-2016, sort of a natural warming experiment. The ENOS-induced SST warming was above the NOAA “bleaching threshold,” defined as the point where SST is 1°C warmer than the highest monthly mean temperature. To do this they went to reefs in the southern Maldivian atoll of Gaafu Dhaalu, ran transects (basically, a line along which you measure stuff), and collected data on coral mortality, substrate composition, reef rugosity (a measure of complexity), and gross carbonate production and erosion. Then they determined carbonate budgets for the 3-dimensional surface of the reefs (there are equations…I won’t go into it…you’re welcome).

They found extensive, overall coral mortality - over 70 percent. This was mostly driven by branching and tabular Acropora species (remember them from the last study?), which declined by an average of 91 percent! All of this coral death resulted in a decline in the net carbonate budgets. This decline reflected both reduced coral carbonate production and increased erosion by parrotfish as they graze on the algal film that grows on coral rock. Pre-coral bleaching, carbonate production was dominated by branching, corymbose and tabular species of Acropora; post-bleaching production by non-Acropora increased, with massive and sub-massive taxa (e.g., Porites species) more than doubling. Together, carbonate budgets were reduced by an average of 157 percent! All of this equates to a rapid loss in coral cover, growth potential, and structural complexity. The overall impact of the carbonate budget was profound and has major ecological implications. These habitats have gone from a state of strong growth potential to one of net framework erosion and breakdown; basically, the reefs are eroding faster than they are growing. And it may take 10-15 years for a full recovery, depending on the frequency of similar anomalies.

So what’s the take-away from all of this? Corals are sensitive to their environment, but not all species of corals respond equally. Climate change is a huge factor in health and recovery of coral reefs, and steps need to be taken soon if we want to keep these little guys and the phenomenal habitats that they create.

Here are the studies:

Anthony KR, Kline DI, Diaz-Pulido G, Dove S, & Hoegh-Guldberg O (2008). Ocean acidification causes bleaching and productivity loss in coral reef builders. Proceedings of the National Academy of Sciences of the United States of America, 105 (45), 17442-6 PMID: 18988740

Perry CT, & Morgan KM (2017). Bleaching drives collapse in reef carbonate budgets and reef growth potential on southern Maldives reefs. Scientific reports, 7 PMID: 28084450

Also check out the NOAA Coral Reef Conservation Program and The Smithsonian Ocean Portal for Corals

Images from (in order of appearance): NOAA Coral Reef Information SystemSmithsonian Ocean Portal, and NOAA Ocean Service

Tuesday, February 14, 2017

Like a Tardigrade, My Love For You Will Never Die

How could I pass up a Valentine's Day without posting some wonderfully sciency V-day cards and comics?

From: Tiny Snek Comics

via FB; credit unknown

From: Sketching Science

From: National Geographic Channel

From: Trust me, I'm a "Biologist"; comic credit: Nick Uhlig

From: Trust me, I'm a "Biologist"; comic credit unknown

From: Entomology Memes

From: Fake Science

From: The Upturned Microscope

From: Gomer Blog

From: Science Friday

From: Science Friday

From: xkcd

I'm Back!

It has been awhile. A long long while. I know, I know. My New Year's resolution was to starting writing regularly on the blog again. Better late than never.

My only excuse for my excessively long absence is that I have been writing. So, I'll take a little me-moment to catch you up on what I've been up to:

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