Archive | January 2013

wake up in fisheries

Can Hurricane Dean “Wake” Up Fisheries?


perfectstormdvdcover.jpgChris just mentioned Hurricane Dean’s cold wake, and I’m reminded that there may be some potentially helpful implications for the fisheries of the region. I recently explained the concept of “dead zones”: oxygen-free ocean regions characterized by a dense layer of warm water settled on top of colder water. This stratification, called a thermocline, keeps oxygen from filtering through the water column–resulting in massive areas of oceans devoid of marine life. The Gulf of Mexico has been experiencing an enormous dead zone every year, exacerbated by runoff from fertilizers and animal waste in the Mississippi and Atchafalaya River Basins.

In the wake of Hurricane Katrina, however, scientists found dissolved oxygen in areas that had none the preceding week. Coincidence?

As Chris’s post hints, the winds of strong hurricanes create gigantic waves and help mix surface waters downwards while bringing colder nutrient rich waters upward (similar to a natural process called upwelling). So it’s possible that Hurricane Dean has helped get rid of stratification, meaning that dissolved oxygen will be redistributed throughout the water column from top to bottom.

Whether this helps out the Gulf, of course, will depend upon how much of the cold wake lingers in the Caribbean, rather than extending further northward.



Experts’ Shocking Warning: Don’t Let Fish Chew on Your Feet


The next time fish-pedicure enthusiasts dunk their feet in a vat of squirming, skin-nibbling, toothless carp, they may get more than they bargained for—especially if those fish just feasted on diseased skin. Health officials, fearing the spread of infections, have now launched a major investigation into this allegedly fishy beauty technique.

In the UK, fish pedicures are booming, which is great for beauty clinics because the procedure costs upwards of £50 ($81 U.S.).  Visitors place their feet in a tank full of Garra rufa fish—a variety of Turkish toothless carp—and sit back while the fish eat away their dead skin. These foot-fetishistic fish have been nicknamed “doctor fish,” and though more and more UK citizens are dunking their feet, the UK’s Health Protection Agency (HPA) has a hunch that this procedure may be doing more harm than good.

Over the past six months, several environmental health officers have contacted the HPA about the dangers of fish pedicures, leading to the present investigation, which hopes to discover whether fish spa pedicures spread infections. Quoting an HPA agency member,  BBC News reports:

“Alongside colleagues in environmental health, Health Protection Scotland and the Health and Safety Laboratory, the HPA will examine the most up to date evidence of any possible risks associated with Garra rufa fish pedicures and will publish guidelines that will be available UK-wide.”

If commercial fish pedicures are banned, the UK would be following the lead of 14 U.S. states that have already outlawed the procedure. In the U.S., the major concern was how spas reuse the fish on many customers—a practice they’re forced to do because Garra rufa fish are pricey.

But salons are defending their practices by pointing out that diseases don’t stand a chance in their UV-lit, filtered tanks. And their position is buffered by the little fact that there are as yet no known cases—at least to the HPA’s knowledge—of fish-spa-induced infections in the UK. Despite this fact, just the thought of dunking one’s feet in the same vat of fish as countless other people is enough to make them squeamish.


Stickleback Fish Learn Like Humans, Despite Tiny Little Fish Brains


ImageA tiny fish common in European streams may learn in a more sophisticated way than has ever been recorded among animals and which mimics human learning. In a study published in the journal Behavioral Ecology, scientists found that the nine-spined stickleback fish used the success and failures of their peers to gauge where they should seek food.

The fish were shown to display a type of learning known as “hill-climbing,” in which an entity continually looks for a better solution to a problem; in this case, one fish copied others that were more successful in finding food. Researchers caught 270 nine-spined sticklebacks in Leicester, England. The fish were organized into experimental groups. These fish groups then took turns as either free swimmers in a tank with worm-yielding feeders at the end, or as “learners” in a transparent, partitioned-off area of the specially designed tank. One of the two feeders released more worms than the other [Discovery News].

The first group of free-swimming fish quickly learned which feeder was full of worms, and were then put into the observers’ chamber. Next, researchers switched which feeder held the worms, and the fish in the observation tank watched the next fish group identify the new worm-filled feeder. After switching the two groups of fish again, the original group made a beeline for the feeder full of worms that their peers had fed from.

This experiment shows that many of [the fish in the experiment] could compare the behaviour of other sticklebacks with their own experience and choose which fish to copy in order to find more food [BBC]. Scientists say that this learning method is optimal for humans, too, and this skill might be expected in animals more closely related to humans.

Co-author Jeremy Kendal said: “Small fish may have small brains but they still have some surprising cognitive abilities. These fish are obviously not at all closely related to humans, yet they have this human ability to only copy when the pay off is better than their own [Telegraph]. Researchers say it’s likely that these fish developed this learning ability as an adaptation to their local environment, and may have become so clever simply because they need to be in order to survive. The small fish, which measures less than three inches long, has had to evolve to be cleverer than other fish because it is a prime target for predators, making the journey to find food precarious [Telegraph].

DNA Mimic Brewed in Lab


Artificial DNA that can encode information just like the real thing.


In a remarkable act of biological mimicry, researchers in Europe and the United States announced in April that they had created six types of artificial DNA—synthetic genetic material that can encode information just like the real thing. The invention suggests that the earliest life on Earth did not necessarily rely on DNA or its cousin, RNA, since other molecules can also perform the same tricks. The artificial DNA, or XNAs, are “simple chemical alternatives to store and propagate genetic information,” says team leader Philipp Holliger of the Medical Research Council Laboratory of Molecular Biology in Cambridge, England.

Natural DNA consists of a ladder frame of ring-shaped deoxyribose molecules (which form the backbone of the double helix) and rungs of bases (which spell out the genetic alphabet). To create XNAs, Holliger and his team replaced the deoxyribose with alternative synthetic chemical ring structures such as arabinose or cyclohexene. Like DNA, XNAs can hold genetic information that specifies how to build a protein. And XNAs can evolve: When the researchers subjected billions of unique XNA strands to selective pressure in a test tube—in this case binding to a provided target molecule—out came XNA sequences folded up into 3-D structures that could bind.

XNAs may also have medical applications. Short strands of nucleic acids, called aptamers, can target a disease-inducing gene or protein and, for example, block it from activating. Natural aptamers are quickly degraded by the body, but because XNA aptamers are foreign, they will last longer—long enough, Holliger hopes, to have therapeutic value.


Single-Atom Transistor Created

What could this tiny electronic switch mean for the future of computing?



In the ever-shrinking world of electronics, vacuum tubes long ago gave way to solid-state component transistors, then to transistors in integrated circuits. Last year an international team achieved the next astonishing milestone in downsizing: They devised a way to make a single-atom transistor, the smallest possible electronic switch. By controlling electrons, that atom can modulate the flow of information and so be the foundation of a new kind of ultrafast, ultracompact computer. The team was led by physicist Michelle Simmons of the University of New South Wales and electrical engineer Gerhard Klimeck of Purdue University.

The single-atom transistor is made by carving a slot in a hydrogen-coated silicon wafer with a tunneling electron microscope and depositing a single phosphorus atom in the hole. The phosphorus atom acts as an electrical bucket, holding one electron—representing a single bit of information—until it is jolted with an external voltage. The phosphorus switch has been tested and in the future could form the basis for both traditional and quantum computing.

Airborne Telescope Sees Matter Falling into A Black Hole

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Ring of material around a black hole

SOFIA image of a ring of dust that appears to be feeding material into the Milky Way’s central supermassive black hole. That sentence was entirely too much fun to type.

I see a lot of amazing astronomical images, of course, so it takes a lot for one to surprise me. But the when I saw this one, I literally whispered “wow” out loud.

What you’re seeing there is a ring of dust circling the supermassive black hole in the center of the Milky Way! It’s about nine light years across, and heavily inclined, so it looks like an oval. The upside-down T is, quite possibly, material falling in from the ring toward the black hole itself.


Here’s the scoop. We live in a flat spiral galaxy, about 100,000 light years across. In the very center of the galaxy (and, so we think, in every big galaxy in the Universe) is a black hole, 26,000 light years from Earth. It’s huge: It has four million times the mass of the Sun. That’s big for a black hole, but I’ll note it’s teeny compared to the total mass of the galaxy, which is 400 billion or so times the mass of the Sun.

Still, it’s beefy, with a commensurate powerful gravitational field. There’s a lot of stuff in the galactic center that swirls around it, including stars, and clouds of gas and dust. That ring and fingers of material stretching on to the center seen above have been known for some time, but this is one of the best images I’ve seen of both together at the same time.

The picture was taken by the SOFIA telescope, which is—get this—a telescope with a 2.5 meter (9 foot) mirror mounted inside a Boeing 747 aircraft with a gigantic hole cut out of the side. Yes, seriously. At cruising altitude it gets above most of the water vapor in our atmosphere, which is critical: Water absorbs far-infrared light, which is what SOFIA is designed to detect. It actually has very sophisticated engineering to keep it pointed and stable, and the proof is in the pudding. Or in the image of the galactic circumnuclear ring, I suppose. And it’s still a lot cheaper than launching a telescope into space, so there’s that, too.

Two images of the center of the Milky Way.

The ring of dust around the Milky Way’s black hole by SOFIA (left) and the same area as seen by an infrared camera on Hubble (right)


By looking so far into the infrared it can peer through a lot of the dust and junk floating around in our galaxy that might otherwise block the view. The image above shows the SOFIA picture on the left, and on the right is the same view, but this time using the Hubble Space Telescope NICMOS infrared camera. It cannot see the ring because the material simply isn’t putting out light that Hubble can detect. All NICMOS sees are stars…though if you look, you can see places where there are fewer stars that correspond to places in the SOFIA image where the dust is. What SOFIA sees as bright actually blocks light for Hubble.

SOFIA image of the Quintuplet Cluster, the site of new star formation.

SOFIA image of the Quintuplet Cluster, the site of new star formation


So why is that ring glowing in the far infrared? We think that a few million years ago there was a burst of star formation in the gas near the galactic center. A lot of high-mass, hot stars were born, and they energized the gas and dust in the region. Just 100 light years from the ring is the Quintuplet Cluster, seen here by SOFIA, suspected of being one of the sites of this stellar fecundity. In Hubble images you can see many stars that make up this cluster, but SOFIA sees the warm dust choking the cluster, heated by the newborn stars within. Each little blob is a thick cocoon of dust enshrouding hot young stars; the bigger circular feature is a shell of dust expelled by a very massive star that will soon end its life in a tremendous supernova explosion.

These pictures really amaze me. I tend to think of our galactic downtown as a busy place, but still, relatively quiet. I’ve written about what happens when these supermassive black holes actively gobble down matter: You get chaos, beams of matter blasting out at nearly the speed of light, bursts of high energy X- and gamma rays, and pretty much annihilation for anything with a few hundred light years. Our central supermassive black hole is (happily) pretty quiet as these things go, but that doesn’t mean it’s boring!

But then, black holes rarely are.

Saturn’s Moon Has a Hidden Ocean

Smog-covered Titan passes in front of Saturn’s thin rings; their shadow makes stripes on the planet.

Titan, the largest of Saturn’s moons, is a remarkable place. Bigger than the planet Mercury, it has a thick, opaque atmosphere; complex weather; and lakes of liquid natural gas. Last June astronomers added another wild detail to the profile: a global ocean buried beneath the icy surface.

The discovery came from six flybys of Titan that NASA’s Cassini spacecraft, orbiting Saturn since 2004, made between 2006 and 2011. During those passes, astronomers measured how the intense pull of Saturn’s gravity deforms Titan during its 16-day revolution around the ringed planet. If Titan were a solid body, it would barely be affected, bulging only about 3 feet during its closest approach to Saturn. Cassini’s measurements revealed that Titan actually bulges a substantial 30 feet, indicating that the moon’s surface rides on top of a sloshing layer of water of unknown depth. Scientists suspect that Jupiter’s moons Europa and Ganymede also have hidden oceans. But Titan is particularly intriguing because it has abundant organic molecules on its surface. Organics and liquid water are crucial ingredients for life.

So far, Cassini’s observations hint at a disappointingly cold and inhospitable ocean floor. A dedicated Titan probe could give a real answer. In an era of diminished budgets, though, that may not happen for many years.