Science Sunday #27
Posted by Don McLenaghen on December 18, 2011
– and on the seventh day we learn.
Each week I hope to give a synopsis of the interesting science stories I have heard on my plethora of science podcasts I listen to each week plus anything I pick up scanning the inter-web. This week’s top stories:
This week’s top stories:
Gold 2.0, valuable and harder than steel –
EPFL scientists have created 18-karat gold that’s harder than tempered steel and virtually unscratchable.
By combining a gold alloy with boron carbide, an extremely hard ceramic that’s used in bulletproof vests, a team of EPFL researchers has succeeded in making the world’s toughest 18-karat gold (75% gold). With a Vickers hardness number of 1000, it’s harder than most tempered steels (600 Vickers) and thus almost impossible to scratch, except with a diamond. This discovery is the result of a three-year collaboration between the Mechanical Metallurgy Laboratory in EPFL’s Institute of Materials, under the leadership of Professor Andreas Mortensen, and the Swiss watchmaking company Hublot.
The process for developing this material is relatively complicated. Powdered boron carbide is heated to almost 2000°C, where it forms a rigid, porous structure by a process called sintering. A liquid molten alloy of gold is infiltrated under very high pressure into the pores of this structure, and then solidified, yielding a pore-free composite material. The final material is thus made up of two kinds of crystals that are intimately interconnected in space, like two three-dimensional labyrinths. Because the molten gold used is a previously-made alloy based on 24-karat gold and aluminum (3%) for strength, the final gold is thus 3% aluminum, 75% gold and 22% boron carbide.
By definition, gold is very soft. Managing to harden it to this degree while still maintaining 18-karat purity was a real challenge for the EPFL scientists. They overcame the obstacle by taking the ceramic-metal composite approach. Composite materials are created by artificially combining several materials that conserve their individual characteristics even after they’re assembled. In this they are different from alloys, in which atoms mix together to form a new, homogeneous, material.
New rules for ethical treatment of research primates –
Given that chimpanzees are so closely related to humans and share similar behavioral traits, the National Institutes of Health should allow their use as subjects in biomedical research only under stringent conditions, including the absence of any other suitable model and inability to ethically perform the research on people, says a new report from the Institute of Medicine and National Research Council. In addition, use of these animals should be permissible only if forgoing their use will prevent or significantly hinder advances necessary to prevent or treat life-threatening or debilitating conditions, said the committee that wrote the report. Based on these criteria, chimpanzees are not necessary for most biomedical research.
“The report’s recommendations answer the need for a uniform set of criteria for assessing the scientific necessity of chimpanzees in biomedical, comparative genomics, and behavioral research,” said committee chair Jeffrey Kahn, senior faculty member, Johns Hopkins Berman Institute of Bioethics, Baltimore. “The committee concluded that research use of animals that are so closely related to humans should not proceed unless it offers insights not possible with other animal models and unless it is of sufficient scientific or health value to offset the moral costs. We found very few cases that satisfy these criteria”.
The committee would not close the door on the possibility that chimpanzees may be needed in future research to develop treatments or preventive tools against as yet unknown diseases or disorders. It is impossible to say in advance whether other animal models or research tools will always serve effectively and quickly enough in the face of a novel health threat.
The report’s recommendations focus on the scientific necessity of the chimpanzee as a research subject, but also take ethical issues into account. Chimpanzees’ genetic closeness to humans and their similar biological and behavioral characteristics not only make chimpanzees a uniquely valuable species for certain types of research but also demand greater justification for conducting research with them, the committee said.
Should Vesta be reclassified a planet? –
On Vista “we’re seeing enormous mountains, valleys, hills, cliffs, troughs, ridges, craters of all sizes, and plains,” says Chris Russell, Dawn principal investigator from UCLA. “Vesta is not a simple ball of rock. This is a world with a rich geochemical history. It has quite a story to tell!”
In fact, the asteroid is so complex that Russell and members of his team are calling it the “smallest terrestrial planet.” Vesta has an iron core, notes Russell, and its surface features indicate that the asteroid is “differentiated” like the terrestrial planets Earth, Mercury, Mars, and Venus.
Researchers believe this process also happened to Vesta. The story begins about 4.57 billion years ago, when the planets of the Solar System started forming from the primordial solar nebula. As Jupiter gathered itself together, its powerful gravity stirred up the material in the asteroid belt so objects there could no longer coalesce. Vesta was in the process of growing into a full-fledged planet when Jupiter interrupted the process.
Although Vesta’s growth was stunted, it is still differentiated like a true planet. “We believe that the Solar System received an extra slug of radioactive aluminum and iron from a nearby supernova explosion at the time Vesta was forming,” explains Russell. “These materials decay and give off heat. As the asteroid was gathering material up into a big ball of rock, it was also trapping the heat inside itself.”
As Vesta’s core melted, lighter materials rose to the surface, forming volcanoes and mountains and lava flows. “We think Vesta had volcanoes and flowing lava at one time, although we’ve not yet found any ancient volcanoes there,” says Russell. “We’re still looking. Vesta’s plains seem similar to Hawaii’s surface, which is basaltic lava solidified after flowing onto the surface.
The real Star War’s Midichloria –
The work, published in this month’s issue of Molecular Biology and Evolution, challenges traditional explanations of how the ancestors of mitochondria first entered our cells between one and a half and two billion years ago. It also sheds new light on a process recognised as one of the major transitions in the history of life on earth.
“Our results challenge the paradigm – shown in every biology textbook – that mitochondria were passive bacteria gobbled up by a primordial cell,” says co-author Dr Nathan Lo from the University of Sydney’s School of Biological Sciences.
“We have found instead that the mitochondrial ancestor most likely had a flagellum, so was able to move, and possibly acted as a parasite, rather than prey, on early eukaryotic cells,” added Dr Lo, who collaborated with scientists from Italy and Spain on the research.
“We studied M. mitochondrii because its genome has never been analysed and because it is the only bacterium known to be able to enter into the mitochondria of living cells,” said Dr Lo.
After determining the DNA sequence of M. mitochondrii’s entire genome, Dr Lo and collaborators found the bacterium contained 26 genes coding for an entire flagellum – including all the key components such as hook, filament and basal body.
He also found a second set of genes which coded for enzymes that would allow the bacterium to survive in low-oxygen environments. These genes have never been seen before in bacterial relatives of mitochondria.
Dr Lo says: “We found these two sets of genes were inherited from the common ancestor shared by M. mitochondrii and our own mitochondria. Mitochondria’s ancestor most likely possessed a flagellum, which is a key characteristic of many parasitic bacteria.
“Our results show the ancestor of mitochondria probably played a much more active, even parasitic, role in the early interactions with its eukaryotic host than previously thought. They also explain how the relationship could have evolved in the low-oxygen environments of two billion years ago.
“This should cause a rethink of how the symbiosis between mitochondria and eukaryotic cells originally developed – one of the most controversial topics in biology.”
Women are worse at math than men, really? –
A major study of recent international data on school mathematics performance casts doubt on some common assumptions about gender and math achievement — in particular, the idea that girls and women have less ability due to a difference in biology.
“We tested some recently proposed hypotheses that try to explain a supposed gender gap in math performance and found they were not supported by the data,” says Janet Mertz, lead author in a new study published in Notices of the American Mathematical Society. The study looked at data from 86 countries, which the authors used to test the “greater male variability hypothesis” famously expounded in 2005 by Lawrence Summers, then president of Harvard, as the primary reason for the scarcity of outstanding women mathematicians.
That hypothesis holds that males diverge more from the mean at both ends of the spectrum and, hence, are more represented in the highest-performing sector. But, using the international data, the Wisconsin authors observed that greater male variation in math achievement is not present in some countries, and is mostly due to boys with low scores in some other countries, indicating that it relates much more to culture than to biology.
The Wisconsin study also debunked the idea proposed by Steven Levitt of “Freakonomics” fame that gender inequity does not hamper girls’ math performance in Muslim countries, where most students attend single-sex schools. Levitt claimed to have disproved a prior conclusion of others that gender inequity limits girls’ mathematics performance. He suggested, instead, that Muslim culture or single-sex classrooms benefit girls’ ability to learn mathematics.
To measure the status of females relative to males within each country, the authors relied on a gender-gap index, which compares the genders in terms of income, education, health and political participation. Relating these indices to math scores, they concluded that math achievement at the low, average and high end for both boys and girls tends to be higher in countries where gender equity is better. In addition, in wealthier countries, women’s participation and salary in the paid labor force was the main factor linked to higher math scores for both genders.
“We found that boys — as well as girls — tend to do better in math when raised in countries where females have better equality, and that’s new and important,” says Kane. “It makes sense that when women are well-educated and earn a good income, the math scores of their children of both genders benefit.”
Feet before lungs –
Extensive video analysis, published in the Proceedings of the National Academy of Sciences, reveal that the African lungfish can use its thin pelvic limbs to not only lift its body off the bottom surface but also propel itself forward. Both abilities were previously thought to originate in early tetrapods, the limbed original land-dwellers that appeared later than the lungfish’s ancestors.
The observation reshuffles the order of evolutionary events leading up to terrestriality, the adaptation to living on land. It also suggests that fossil tracks long believed to be the work of early tetrapods could have been produced instead by lobe-finned ancestors of the lungfish.
“In a number of these trackways, the animals alternate their limbs, which suggested that they must have been made by tetrapods walking on a solid substrate,” said Melina Hale, PhD, associate professor of Organismal Biology and Anatomy. “We’ve found that aquatic animals with fundamentally different morphologies and that aren’t tetrapods could potentially make very similar track patterns”.
The discovery suggests that many of the developments necessary for the transition from water to land could have occurred long before early tetrapods, such as Tiktaalik, took their first steps on shore. Lobe-finned ancestors of the lungfishes as well as tetrapods could have evolved hind limb propulsion and the ability to walk on the substrate at the bottom of a lake or marsh millions of years before limbs with digits and land-dwelling animals appeared.
“This shows us — pardon the pun — the steps that are involved in the origin of walking,” Shubin said. “What we’re seeing in lungfish is a very nice example of how bottom-walking in fish living in water can easily come about in a very tetrapod-like pattern”.
What makes a buttercup Yellow? –
The researchers discovered that the buttercup petal’s unique bright and glossy appearance is the result of the interplay between its different layers. In particular, the strong yellow reflection responsible for the chin illumination is mainly due to the epidermal layer of the petal that reflects yellow light with an intensity that is comparable to glass.
Scientists have been interested in how the buttercup flower works for over a century. They have previously shown that the reflected colour is yellow due to the absorption of the colours in the blue-green region of the spectrum by the carotenoid pigment in the petals. As the blue-green light is absorbed, the light in the other spectral regions (in this case, primarily yellow) is reflected. It has also been known for many years that the epidermal layer of the petals is composed of very flat cells, providing strong reflection.
This new study shows how the buttercup’s exceptionally bright appearance is a result of a special feature of the petal structure. The epidermal layer of cells has not one but two extremely flat surfaces from which light is reflected. One is the top of the cells, the other exists because the epidermis is separated from the lower layers of the petal by an air gap. Reflection of light by the smooth surface of the cells and by the air layer effectively doubles the gloss of the petal, explaining why buttercups are so much better at reflecting light under your chin than any other flower.
The researchers also found that the buttercup reflects a significant amount of UV light. As many pollinators, including bees, have eyes sensitive in the UV region, this provides insight into how the buttercup uses its unique appearance to attract insects.