This week in science is a review of the most interesting scientific news of the week.
Science community in mourning.
Mildred Dresselhaus, MIT Institute professor emerita of physics and of electrical engineering and computer science, died Monday at the age of 86. Professor Dresselhaus was one of the first scientists to consider the possibility of carbon nanotubes manufacturing and was among the pioneers of nanoscience. Furthermore, she was responsible for launching a new field of energy research by exploring the thermoelectric effect at the nanoscale.
Dresselhaus was the first woman to attain the rank of full, tenured professor at MIT, where she kept working for 50 years even after retiring. Also, she was the first woman to receive the National Medal of Science in Engineering. Finally, in 2014, she was awarded the Presidential Medal of Freedom from President Obama.
Source: MIT Technology Review
Scientists have been searching for years for the reason why graphite turns into hexagonal diamond instead of the more common cubic diamond when exposed to high pressures, what contradicts the theory. But this search now seems to be over, according to a publication by a team of researchers from Fudan University and Shanghai University in China.
Both the cubic and the hexagonal types of diamond and the graphite are carbon allotropes, which means they are made of carbon atoms, but differ on the spatial arrangement. This difference has several consequences to the resulting materials and are responsible for the softness of the graphite, which makes it possible to be used in pencils, but also responsible for the hardness of both kinds of diamond.
The team of researchers has studied all the possible pathways in the graphite-to-diamond transition by using a new type of simulation, called stochastic surface walking. This new simulation allows the identification of the pathways which have the lowest-energy intermediate structures. Instead, old simulations would consider only the prediction that less energy is required to start forming the cubic diamond than to start forming the hexagonal diamond.
According to one of the scientists, Zhi-Pan Liu, the outcomes of their work goes far beyond answering this question:
"This work resolves the long-standing puzzle of why hexagonal diamond is preferentially produced from graphite instead of the cubic diamond at the onset of diamond formation. Considering that graphite-to-diamond is a prototype solid-to-solid transition, the knowledge learned from this work should greatly benefit the understanding of high-pressure solid physics and chemistry.”
The researchers have added that both kinds of diamond structures are of great value, even though the cubic structure is the one present in jewelry diamonds. For example, the hexagonal diamond is predicted to be even harder than the cubic one. Unfortunately, it can only be found in meteorites and it is not yet possible to produce large versions of it.
Researchers from the University of Melbourne in Australia have announced the creation of the first magnetic resonance microscope. Magnetic resonance imaging techniques can produce noninvasive 3-D images using harmless magnetic fields and radio waves, therefore they have many possible applications for human medicine.
Also, by using magnetic resonance spectroscopy, physicians and researchers can study the biochemistry of any specific tissue. For example, one can record metabolic changes in tumors, in the brain, and in muscles. Unfortunately, the resolution of this technique is only about 10 micrometers, but that is where the magnetic resonance microscope enters.
David Simpson and his colleagues, from the University of Melbourne, have stated the resolution of the new microscope is far better: “We demonstrate imaging resolution at the diffraction limit (~300 nm)”. Furthermore, this resolution was achieved at room temperature.
The breakthrough of the project was the development of a diamond film sensor, resembling the light sensitive CCD chip in a camera, to create the magnetic resonance images. This diamond film is embedded with nitrogen atoms, which can fluoresce in various colors indicating changes in the sample being analyzed.
Finally, because of its high resolution and sensitivity to changes in the samples, the magnetic resonance microscope has the potential to revolutionize studies in biochemistry.
Source: MIT Technology Review
Astronomers using several telescopes around the world have now confirmed the existence of at least seven Earth-sized planets orbiting the dwarf star TRAPPIST-1, which is at “just” 40 light-years from our solar system. The planets are designated TRAPPIST-1b, c, d, e, f, g and h, in order of increasing distance from the dwarf star.
Also, three of those planets, TRAPPIST-1e, f, and g, lie in the habitable zone, where liquid water could be found at the surface. As stated by Michaël Gillon, from the STAR Institute at the University of Liège in Belgium:
"This is an amazing planetary system—not only because we have found so many planets, but because they are all surprisingly similar in size to the Earth!"
Finally, this discovery has made the TRAPPIST-1 system a new target for astronomers, with the NASA/ESA Hubble Space Telescope already collecting more data about the atmospheres of those planets. These results were presented in the paper "Seven temperate terrestrial planets around the nearby ultracool dwarf star TRAPPIST-1", by M. Gillon et al., published in the journal Nature.
Those living in South America and southern Africa, but mainly in Chile, Argentina, Angola, Zambia and the Democratic Republic of Congo, will have the privilege of watching an annular solar eclipse on Sunday, February 26. This kind of eclipse occurs when the Earth, Moon, and Sun line up and results in the beautiful image above.
The annular effect will last just about one minute, but the Moon will take about two hours to move from one side to the other of Earth’s view of the Sun. The eclipse can be seen in southern Chile starting at 12:21 GMT and it will reach Angola around 15:15 GMT.
Finally, a warning: one should not look directly at the Sun unless using special glasses! So be careful! Also, if you will be located anywhere the eclipse can be seen, don’t forget to check if the weather will allow a clear view of the event.