Friday, December 31, 2010
Thursday, December 30, 2010
With the help of Beau Lotto from University College London, 30 kids from Blackawton Primary School designed and conducted experiments on bees, and then analyzed the results. The resulting paper was published in Biology Letters.
The eight to ten year old kids were interested in whether bees could solve problems in the way that humans could. In particular, they tested whether bees could learn to distinguish a blue flower surrounded by yellow flowers from a yellow flower surrounded by blue. Doing so correctly would lead the bees to a treat of sugar water rather than salt water. The children also wanted to know whether all the bees performed in the same way, or if some bees had distinct learning capacities.
To answer these questions, the kids first taught the bees to enter a plexiglass box containing four panels of 16 circles each, each containing a little tube of sugar water. Later, these tubes might contain salt water or nothing at all. For the experimentation phase, the circles surrounding the tubes were colored in varying patterns of yellow or blue. After being trained which colors within each pattern would yield the sugar water, the bees went to the correct colors over 90% of the time.
Figure 1. Conditions and responses to ‘test 1’ (control). (a) The pattern of colours that the bees were trained to and tested on in their first test (see text for explanation). (b) The selections made by all the bees tested (dots show where each bee landed and tried to get sugar water). (c) A table showing the preferences of each bee during testing (see text for explanation).
Interestingly, while all the bees went to the sugar-rewarding tubes most of the time, many bees clearly preferred blue over yellow, or vice versa. For example, one bee went to 31 correct yellow circles and 4 incorrect yellow circles, but never bothered to visit any blue circles.The bigger point, of course, is that anyone can learn to enjoy and participate in science!
Wednesday, December 29, 2010
Sea scorpion fossil (Mixopetrus kjaeri).
Credit: Ghedoghedo, June 2009
Sea scorpions, also known as eurypterids, were gigantic ancient arthropods. Despite their name, they did not have venomous stingers. However, with their huge spine-covered claws, they were long thought to be one of the top predators of the Paleozoic period. A closer look at the mechanical constraints on those claws tells a different story. Richard Laub, Victor Tollerton and Richard Berkof wrote in the Bulletin of the Buffalo Society of Natural Sciences that sea scorpions would have been able to exert no more than half the force needed to crush horseshoe crabs, a common prey item of that era. To make matters worse, the sea scorpions lacked the necessary joints to allow them to grasp prey.Present day arthropods are often predators, so sea scorpions, which were the largest arthropods ever, were expected to be equally carnivorous. This new evidence suggests that despite their fearsome appearance, they may have been predominantly scavengers. Laub even entertains the possibility that the creatures may have been vegetarians.
Tuesday, December 28, 2010
Sonya Kahlenberg from Bates College and Richard Wrangham from Harvard University have been studying wild chimpanzees in Uganda for the past 14 years. During that time, they’ve discovered numerous examples of young chimps treating sticks like dolls.
In all, the researchers counted over a hundred examples of chimps carrying around sticks, taking them into their nests at night, playing with the sticks, and even making separate nests for those sticks. Most of this play was done by juvenile females, and was rarely practiced by males or adults. Also, the stick-carrying behavior ended as soon as the females had babies of their own. Taken together, the data certainly seems to suggest that the females were using the sticks as practice babies. In other words, as dolls.This is interesting for two reasons. First, this behavior seems to indicate the kind of complex representational view of objects that was thought to be the purview of humans alone. Second, because the use of the sticks as dolls was present mainly in females, this indicates that sexual preference for types of toys may predate human evolution.
Monday, December 27, 2010
Researchers from Imperial College London are working on a way to sequence entire genomes in a matter of minutes. When perfected, their device should be able to read 10 million bases/second. To put that in perspective, current methods have a sequencing rate of about 10 bases/second. Each human genome has about three billion bases, which currently takes about 3.5 days to sequence. The new device will sequence an entire human genome in about five minutes.
The new device relies on the fact that each base has its own unique electrical signal. A single strand of DNA is fed through a 50 nanopore opening in a silicon chip. As it goes through the tiny gap, a tunneling electrode junction on the other side reads each base's distinct electrical signal.
Although using electrical signatures to read DNA is not a new idea, no one has been able create a small enough electrode junction until now. The Imperial College team successfully constructed a prototype with a small enough gap to read DNA bases. The next step will be to calibrate the device to identify individual bases. The scientists expect their method to be in wide use within the next ten years.
Sunday, December 26, 2010
It’s easy to measure the magnetic field on the surface of the Earth, but not so easy to do so deep in Earth’s interior. In fact, until now, that’s never been done. Bruce Buffett and his team from UC Berkeley used distant quasars to work out the strength of the magnetic field 1800 miles underground.
To find the field strength, Buffett relied on the fact that the moon’s tug makes the axis of the solid inner core of the Earth precess, or spin slowly in the opposite direction to that of the moon. The magnetic field of the fluid outer core damps the affect on the inner core. The distant quasars provide a measuring stick to see how much the axis of spin is offset.
The magnetic field strength has repercussions for conditions inside the Earth’s core. In addition to the residual heat left over from the formation of the Earth, more heat is generated inside the Earth by convection currents as heavier elements sink, or by radioactive decay. The higher the magnetic field, the greater the contribution of radioactive decay to the total heat budget of the planet.
It turns out that the interior of the Earth has a magnetic field strength of 25 Gauss. To put that in perspective, the magnetic field strength on the surface of the Earth is only about 0.5 Gauss. 25 Gauss is actually right in the middle of the range of values geophysicists had predicted. This means that about 60% of the power generated at the core comes from convection.
Saturday, December 25, 2010
A team of Cambridge undergraduates participating in the annual International Genetically Engineered Machines (IGEM) competition, has come up with a concept for creating bioluminescent street lamps. The students took genes from fireflies and inserted them into E. coli bacteria, where they produced enough light to read by. The researchers hope to someday use the same technique to insert genes into trees, which can then replace electric streetlights. Not to mention the benefit to Christmas tree decorators.
The team used a technique called ‘Gibson assembly’ to insert the genes. You can see how this was done below.
For those interested in more specifics, the following video may help.
Friday, December 24, 2010
The tired, confused, grouchy state that is jet lag just got a little bit worse. Lance Kriegsfeld and his team from the University of California, Berkeley have found that repeated jet lag may have permanent effects on brain function and memory.
Jet lag occurs when our personal circadian rhythm (the internal clock that tells us when it’s time to eat and sleep) is out of sync with our environment. For example, right after you fly from London to Los Angeles you'd like to get up and have breakfast around midnight. Most people recover from jet lag in a few days. Kriegsfeld and his colleagues wondered if there were any hitherto unrecognized long term effects of jet lag.
To find out, the scientists subjected hamsters (creatures with stopwatch precise circadian rhythms) to six-hour time shifts twice a week for a month. This is the equivalent of flying back and forth from New York to Paris. During the last two weeks and again a month later, the hamsters were given memory and learning tests.
Not surprisingly, the hamsters did poorly while feeling the affects of jet lag. What was surprising was that the animals still showed cognitive impairment a month later. Even more chilling, the hamsters that had experienced prolonged jet lag had only half as many new neurons in their hippocampus (a region of the brain critical for long-term memory) as the control hamsters. This new data correlates with other health risks associated with jet lag, such as an increased incidence of diabetes, heart disease and cancer.The scientists don’t believe that an occasional flight could have long-term effects. Remember, the hamsters had been subjected to the equivalent of 8 long flights in one month. Kriegsfeld does suggest that people who must routinely shift their days and nights do their best to maintain their daily rhythms. For example, he suggested that when required to sleep during the day they used blackout curtains to darken the room.
Thursday, December 23, 2010
The atomic weights of ten elements will no longer be expressed as a single number. Instead, those atomic weights will be expressed as a range. According to chemists at the International Union of Pure and Applied Chemistry’s Commission on Isotopic Abundancies and Atomic Weights, this should more accurately reflect the way the elements are found in nature.
The atomic weight of an element is the ratio of the mass of one atom of that element to 1/12th the mass of a carbon-12 atom. Some elements, such as gold, only come in one isotope, whereas others, such as hydrogen, can have a variable number of neutrons. This means that while every sample of pure gold weighs the same as any other sample, this is not true of hydrogen samples. Therefore, giving a single atomic weight for an element like hydrogen was misleading.
The elements with the new designations are hydrogen, lithium, boron, carbon, nitrogen, oxygen, silicon, sulfur, chlorine and thallium. These elements will now have their atomic weights listed as a range with upper and lower limits. That should make chemistry problems so much more fun for undergrads.
By the way, 2011 is the International Year of Chemistry, so start working on your costumes.
Wednesday, December 22, 2010
It has been known since 1992 that babies as young as five months can do simple arithmetic (1+1=2). However, it was not thought that young children could compare more fluid amounts of things, such as quantities of water or sand. Kristy VanMarie from the University of Missouri and Karen Wynn of Yale have found that babies as young as ten months old can tell a larger amount of cereal from a lesser amount.
The experiment was very simple. The researchers poured cereal into cups and let the babies choose which cup they preferred. Starting at about ten months, as long as one cup had at least three times as much as the other, the babies would consistently choose the larger amount. At around 14 months, the babies could even remember which cup held more when the amounts were poured into opaque cups.
As an aside, the arithmetic experiments (also run by Karen Wynn) relied on the babies’ attention spans, rather than on their ability to choose an object. As an example, the five-month old babies were shown one doll on a table. A screen was lowered in front of that doll. The babies then watched as an experimenter added one more doll behind the screen. When the curtain was raised, there were either one or two dolls there. If there was only one doll, the babies stared for a lot longer than if there were two dolls. In other words, the babies appeared to be nonchalant about the fact that 1+1=2 but surprised to find that 1+1=1. The same results were found with subtraction: babies stared longer when removing one doll from behind a screen did not appear to decrease the total number of dolls from 2 to 1.
Tuesday, December 21, 2010
As everyone knows, the two key components to maintaining healthy weight are diet and exercise. But what happens to people who don’t exercise? Are they doomed to suffer weight gain and diabetes? In order to answer that question, researchers have created mice that are incapable of exercising. Surprisingly, the mice are not at greater risk for diabetes than their calisthenics-practicing counterparts.
The mice in question are lacking the transcription coactivator PGC-1. Briefly, PGC-1 is responsible for regulating genes involved in energy metabolism. Without PGC-1, mitochondria cannot function normally, leading to cells that garner much less energy from the fuel they take in. That limited energy is funneled strictly into cell maintenance and growth, leaving little for exercise. The afflicted mice can develop normally, but cannot run on their exercise wheels.Even though the PGC-1 negative mice were not exercising, they did not suffer from either obesity or insulin resistance. This surprised many scientists, who expected the lack of exercise to lead directly to such health risks. The new thinking is that the insulin resistance came first, and that this triggered the decline in mitochondrial function, rather than the other way around. In other words, it isn’t the sedentary lifestyle that leads to diabetes, but rather diabetes that leads to being sedentary. More specifically, obesity may trigger a decline in PGC-1, which makes it more difficult for people to exercise.
Monday, December 20, 2010
Red dwarfs are small (less than half the size of our sun), cool stars (less than 4000 K). Taken together, these properties make the stars difficult to find from any distance. Until recently, all the red dwarfs that had been identified were within our own galaxy. Not unreasonably, astronomers assumed that other galaxies would have a similar number of red dwarfs. This did not turn out to be the case.
Pieter van Dokkum of Yale University and Charlie Conroy of the Harvard-Smithsonian Center for Astrophysics have found that some nearby elliptical galaxies have as many as 20 times more red dwarfs than does our Milky Way galaxy.
Filtering out the light from brighter stars, astronomers detected the faint signature of small, dim red dwarf stars in nearby elliptical galaxies (right), and found these are much more numerous than in our own Milky Way (left). This finding suggests that the total number of stars in the universe could be up to three times higher than previously thought.
Illustration by Yale UniversityOne reason scientists are interested in red dwarfs is that they burn through their fuel at an extremely slow rate, maintaining constant heat and luminosity all the while. This means that any planet with the potential to develop life that happens to be orbiting a red dwarf would have hundreds of billions of years to do so. Life on such a planet would have more than enough time to go from single-celled to civilization. And now we know there are lots more of these stars around.
Sunday, December 19, 2010
Weather permitting, North Americans will be able to see a total lunar eclipse tomorrow night. Depending on where you live, you’ll be able to see the eclipse sometime between 10:30 pm on December 20th (West coast denizens) to 5 am on the 21st (for those on the East coast).
Caption: Path of the Moon through Earth's umbral and penumbral shadows during the Total Lunar Eclipse of Dec. 21, 2010.
Credit: Fred Espenak/NASA's Goddard Space Flight Center
Lunar eclipses occur when the Earth moves directly between the sun and the moon. In this position, the Earth casts a shadow over the moon. If you get a chance to observe the lunar eclipse, you should see the moon change colors from gray through orange to deep red as the Earth’s shadow passes over it. And, by the way, you can safely observe these color changes with your own eyes, no special equipment required.
There won’t be another total lunar eclipse visible in North America for over three and a half years. So if there’s nice weather in your area, take the opportunity to see this one.
Saturday, December 18, 2010
One of the major causes of death and injury after hurricanes or bomb attacks is the resultant flying shards of glass. A team of engineers from the University of Missouri and from the University of Sydney, Australia has just developed a new type of blast-resistant glass. One of the major benefits of the new version is that, unlike current blast-proof glass, it will fit in standard window frames.
Currently, blast-proof windows are made of layers of polymers and are at least an inch thick. This means that they cannot be swapped into standard window frames. The new type of glass is actually a sandwich of various components. On the outside are two thin sheets of regular glass. Between those sheets are long glass fibers, woven together and soaked in liquid plastic. The three components are bonded together with clear adhesive. The resultant glass panes are expected to cost about the same as standard blast-proof panes. However, the new panes are only one quarter inch thick, easily thin enough to fit within standard window frames.
Thus far, small prototypes of the new glass panes have tested well. The engineers hope to bring full sized windows to market within the next three or four years.
Caption: An engineer from the University of Missouri studies the glass pane after a test explosion.Credit: DHS S&T
Friday, December 17, 2010
Image is a stack of 100 x 2 minute exposures @ ISO1600 taken on 10/8/10 by zAmboni.
Thursday, December 16, 2010
Researchers from the University of Oregon and from Oregon State University have been studying the leaf cutter ants Atta cephalotes. In doing so, they’ve made two interesting discoveries. One is that the tiny creatures have incredibly sharp and durable cutting blades on their mandibles. The second is that the ants have a retirement program for older workers.
Leaf cutter ants make their living by cutting up leaves and carrying them back to their nests. The ants don’t eat the leaves, rather, they use the leaves to feed a crop of fungus which the ants actually eat. Yes, leaf cutter ants are tiny farmers. It takes a lot of effort to slice through those thick leaves (in comparison to the ants) and a sharper slicing blade makes the job that much easier. Robert Schofield, lead author of the paper in Behavioral Ecology and Sociobiology, and his team have found that the slicing blade on the ants mandibles is made of a zinc-rich biomaterial that starts out as sharp as any man-made knife edge. These biomaterials have been found in the sharp parts (stings and claws) of other small invertebrates.
You can watch some leaf cutter ants at work below.
Even this sharp, durable substance does get dull over time, and the ants have no way of sharpening them. The video below shows an ant with a dull cutting blade. Notice how inefficient the ant is at cutting through the leaf.
Once the ants are taking three times as long to cut the same number of leaves, they retire from leaf-cutting and become leaf carriers. Their new job is to carry the leaf pieces back to the nest. Thus, they continue to perform useful tasks even after they are too old to continue at their previous jobs.
Wednesday, December 15, 2010
For the past decade, women have been cautioned about using hormone replacement therapy (estrogen and/or progestin) to combat the symptoms of menopause. Karla Kerlikowske of the University of California, San Francisco and her colleagues wondered what effect that advice has had on cancer rates. Their conclusion: cancer rates have dropped due to the cessation of hormone replacement therapy.
The scientists examined the mammography records of nearly 700,000 women, aged 40 to 79, over a ten-year period from 1997 to 2007. The first large studies showing the risks of hormone replacement were done in 2002, resulting in an immediate and precipitous decrease in the number of women using the hormones. Among women who were old enough to have started using hormone therapy prior to 2002 (aged 50 to 69), the breast cancer rate dropped by over 20% between 2002 and 2005. This strongly suggests that the cessation of hormone replacement therapy was responsible for the decrease in cancer.
Although it seems clear that hormone replacement therapy should be avoided if possible, I’d like to put the actual risks in perspective. Even in 2002, the peak of hormone usage, there were only 40 cases of breast cancer out of every 10,000 women in the study. In other words, stopping the hormone treatment dropped each woman’s risk of cancer from about 0.4% to about 0.3%. While this reduction is a worthy goal, those who need hormone replacement should not panic.
Tuesday, December 14, 2010
Iapetus is one of Saturn’s largest moons. Thanks to the Cassini Mission, we’ve known for the past five years that Iapetus has a unique equatorial ridge that’s up to 20 kilometers high and 100 kilometers wide. William McKinnon of the University of Washington and Andrew Dombard of the University of Illinois have proposed one way that ridge could have been created: impact with a moon of its own.
Caption: A ridge that follows the equator of Saturn's moon Iapetus gives it the appearance of a giant walnut. The ridge, photographed in 2004 by the Cassini spacecraft, is 100 kilometers (62 miles) wide and at times 20 kilometers (12 miles) high. (The peak of Mount Everest, by comparison, is 5.5 miles above sea level.)
The astronomers propose that Iapetus once had its own satellite. Over time, this satellite’s orbit deteriorated to the point where it was torn apart by Iapetus’ tidal forces. The resulting chunks formed an unstable ring that eventually slammed into the equatorial surface of Iapetus, creating the ridge.
Caption: In 2007 Cassini flew within a few thousand kilometers of Iapetus's surface to take this dramatic picture of the ridge.
Other scientists disagree, arguing that internal activity like volcanoes was responsible for the formation of the ridge. While McKinnon and Dombard haven’t been able to rule out this possibility, they claim that the crashing satellite hypothesis is the better one. Most compellingly, for reasons of energy conservation, a ring of debris would have to form around a stellar body’s equator. In contrast, volcanoes and earthquakes can occur anywhere on a planetary body, making it much less likely that they could be responsible for a ridge encircling the equator.
Monday, December 13, 2010
Scientists led by Richard Behringer of the M.D. Anderson Cancer Center have successfully produced mice that had two male parents. Here’s how they did it.
First, the researchers took cells from a male mouse (Dad #1, or D1) and induced them into becoming pluripotent stem cells. They next grew these D1 cells in culture until some of them spontaneously lost their Y chromosome (which occurs somewhere between 1 and 3% of the time. The geneticists now had their hands on cells containing only a single X chromosome (XO cells) that were female despite having been derived from a male.
In humans, having only one X chromosome (Turner’s syndrome) causes sterility. Not so in mice. The D1-derived female cells were mixed with the normal XX cells in an early stage female embryo. This resulted in a chimeric mouse, with some cells containing the two X chromosomes of the female embryo and others only the one X chromosome of the D1 cells. All the cells developed inside a female body however, meaning that any D1 cells that happened to be in the ovaries could develop into egg cells.
Finally, Dad #2, an ordinary male, was called upon to fertilize the D1 eggs. Genetic testing confirmed that the resulting offspring got their DNA only from D1 and D2, and not from the female host that housed the D1 cells.
To be clear, this technique is not yet possible in humans for a couple of reasons. First, as stated above, women with Turner’s syndrome are sterile. Thus, there wouldn’t be any XO eggs. Second, we haven’t been able to create pluripotent cells from somatic (non-sperm or egg) cells in humans. And of course, even if these problems could be solved there are many ethical questions, not least of which is getting host women to supply the D1 eggs. Remember, these women would have been made into D1 chimeras from an early embryonic stage, a rather objectionable prospect. So don’t expect to see babies born from two fathers any time soon, if ever.
Sunday, December 12, 2010
Vertebrate embryos follow a very specific developmental pathway from single cells to entire organisms. Anna Keyte and Kathleen Smith of Duke University have found that marsupial embryos do not adhere to this strictly controlled timeline, but instead have limbs that jump the queue.
In all other vertebrates, the internal organs mature before the limbs appear. By the time the limbs have muscles or bones, the rest of the fetus is fairly well developed. Marsupials, however, are born at an early embryonic state and finish gestating in their mother’s pouch rather than in her uterus or in an egg like other vertebrates. The tiny creatures must make their way unassisted to their mothers’ pouches, which can be a considerable distance in some species. Thus, marsupial embryos require strong forelimbs far earlier than other vertebrates do.
An embryonic short-tailed opossum finishing its development outside the womb.
Credit: Anna KeyteKeyte and Smith found that the genes for limb expression were turned on much earlier in marsupials than in other vertebrates, and that more cells from the early embryos were slated for limb development. As you can see from the picture, these embryos are little more than slugs with weightlifters' arms. Once the task of getting into the pouch in completed, the embryos can continue their development like any other vertebrate.