Tau ceti: The next Earth? Probably not

How would an alien world like this look? That's the question that ASU undergraduate art major Joshua Gonzalez attempted to answer. He worked with Professor Patrick Young's group to learn how to analyze stellar spectra to find chemical abundances, and inspired by the scientific results, he created two digital paintings of possible unusual extrasolar planets, one being Tau Ceti for his Barrett Honors Thesis

As the search continues for Earth-size planets orbiting at just the right distance from their star, a region termed the habitable zone, the number of potentially life-supporting planets grows. In two decades we have progressed from having no extrasolar planets to having too many to search. Narrowing the list of hopefuls requires looking at extrasolar planets in a new way. Applying a nuanced approach that couples astronomy and geophysics, Arizona State University researchers report that from that long list we can cross off cosmic neighbor Tau Ceti.

The Tau Ceti system, popularized in several fictional works, including Star Trek, has long been used in science fiction, and even popular news, as a very likely place to have life due to its proximity to Earth and the star's sun-like characteristics. Since December 2012 Tau Ceti has become even more appealing, thanks to evidence of possibly five planets orbiting it, with two of these -- Tau Ceti e and f -- potentially residing in the habitable zone.
Using the chemical composition of Tau Ceti, the ASU team modeled the star's evolution and calculated its habitable zone. Although their data confirms that two planets (e and f) may be in the habitable zone it doesn't mean life flourishes or even exists there.
"Planet e is in the habitable zone only if we make very generous assumptions. Planet f initially looks more promising, but modeling the evolution of the star makes it seem probable that it has only moved into the habitable zone recently as Tau Ceti has gotten more luminous over the course of its life," explains astrophysicist Michael Pagano, ASU postdoctoral researcher and lead author of the paper appearing in the Astrophysical Journal. The collaboration also included ASU astrophysicists Patrick Young and Amanda Truitt and mineral physicist Sang-Heon (Dan) Shim.
Based upon the team's models, planet f has likely been in the habitable zone much less than 1 billion years. This sounds like a long time, but it took Earth's biosphere about 2 billion years to produce potentially detectable changes in its atmosphere. A planet that entered the habitable zone only a few hundred million years ago may well be habitable and even inhabited, but not have detectable biosignatures.
According to Pagano, he and his collaborators didn't pick Tau Ceti "hoping, wanting, or thinking" it would be a good candidate to look for life, but for the idea that these might be truly alien new worlds.
Tau Ceti has a highly unusual composition with respect to its ratio of magnesium and silicon, which are two of the most important rock forming minerals on Earth. The ratio of magnesium to silicon in Tau Ceti is 1.78, which is about 70% more than our sun.
The astrophysicists looked at the data and asked, "What does this mean for the planets?"
Building on the strengths of ASU's School of Earth and Space Exploration, which unites earth and space scientists in an effort to tackle research questions through a holistic approach, Shim was brought on board for his mineral expertise to provide insights into the possible nature of the planets themselves.
"With such a high magnesium and silicon ratio it is possible that the mineralogical make-up of planets around Tau Ceti could be significantly different from that of Earth. Tau Ceti's planets could very well be dominated by the mineral olivine at shallow parts of the mantle and have lower mantles dominated by ferropericlase," explains Shim.
Considering that ferropericlase is much less viscous, or resistant to flowing, hot, yet solid, mantle rock would flow more easily, possibly having profound effects on volcanism and tectonics at the planetary surface, processes which have a significant impact on the habitability of Earth.
"This is a reminder that geological processes are fundamental in understanding the habitability of planets," Shim adds.
"Tau Ceti has been a popular destination for science fiction writers and everyone's imagination as somewhere there could possibly be life, but even though life around Tau Ceti may be unlikely, it should not be seen as a letdown, but should invigorate our minds to consider what exotic planets likely orbit the star, and the new and unusual planets that may exist in this vast universe," says Pagano.

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The above story is based on materials provided by Arizona State University. Note: Materials may be edited for content and length.

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Journal Reference:

1. Michael Pagano, Amanda Truitt, Patrick A. Young, Sang-Heon Shim. THE CHEMICAL COMPOSITION OFτCETI AND POSSIBLE EFFECTS ON TERRESTRIAL PLANETS. The Astrophysical Journal, 2015; 803 (2): 90 DOI: 10.1088/0004-637X/803/2/90

Ultra-sensitive sensor detects individual electrons

A silicon chip was used for the design of the gate sensor.

A Spanish-led team of European researchers at the University of Cambridge has created an electronic device so accurate that it can detect the charge of a single electron in less than one microsecond. It has been dubbed the 'gate sensor' and could be applied in quantum computers of the future to read information stored in the charge or spin of a single electron.

In the same Cambridge laboratory in the United Kingdom where the British physicist J.J. Thomson discovered the electron in 1897, European scientists have just developed a new ultra-sensitive electrical-charge sensor capable of detecting the movement of individual electrons.
"The device is much more compact and accurate than previous versions and can detect the electrical charge of a single electron in less than one microsecond," M. Fernando González Zalba, leader of this research from the Hitachi Cambridge Laboratory and the Cavendish Laboratory,said.
Details of the breakthrough have been published in the journal Nature Communications and its authors predict that these types of sensors, dubbed 'gate sensors', will be used in quantum computers of the future to read information stored in the charge or spin of a single electron.
"We have called it a gate sensor because, as well as detecting the movement of individual electrons, the device is able to control its flow as if it were an electronic gate which opens and closes," explains González Zalba.
The researchers have demonstrated the possibility of detecting the charge of an electron with their device in approximately one nanosecond, the best value obtained to date for this type of system. This has been achieved by coupling a gate sensor to a silicon nanotransistor where the electrons flow individually.
In general, the electrical current which powers our telephones, fridges and other electrical equipment is made up of electrons: minuscule particles carrying an electrical charge travelling in their trillions and whose collective movement makes these appliances work.
However, this is not the case of the latest cutting-edge devices such as ultra-precise biosensors, single electron transistors, molecular circuits and quantum computers. These represent a new technological sector which bases its electronic functionality on the charge of a single electron, a field in which the new gate sensor can offer its advantages.

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Story Source:
The above story is based on materials provided by Plataforma SINC. Note: Materials may be edited for content and length.

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Journal Reference:

1. M. F. Gonzalez-Zalba, S. Barraud, A. J. Ferguson, A. C. Betz. Probing the limits of gate-based charge sensing. Nature Communications, 2015; 6: 6084 DOI: 10.1038/ncomms7084

Full-color moving holograms in high resolution

A new way of streaming high-resolution, full-color full-parallax three-dimensional (3D) hologram videos may have applications in the entertainment and medical imaging industries.

Three-dimensional (3D) movies, which require viewers to wear stereoscopic (i.e. Related to the technique of creating an impression of depth by showing two slightly offset flat images to each eye) glasses, have become very popular in recent years. However, the 3D effect produced by the glasses cannot provide perfect depth cues. Furthermore, it is not possible to move one's head and observe that objects appear different from different angles -- a real-life effect known as motion parallax. Now, A*STAR researchers have developed a new way of generating high-resolution, full-color, 3D videos that uses holographic technology [1].

Holograms are considered to be truly 3D, because they allow the viewer to see different perspectives of a reconstructed 3D object from different angles and locations (see image). Like a photograph, a hologram contains information about the size, shape and color of an object. Where holograms differ from photographs is that they are created using lasers, which can produce the complex light interference patterns, including spatial data, required to re-create a complete 3D object.
However, generating high-resolution, moving holograms to replace current 3D imaging technology has proved difficult. To enhance the resolution of their holographic videos, Xuewu Xu and colleagues at the Data Storage Institute in Singapore used an array of spatial light modulators (SLMs).
"SLMs are devices used in current two-dimensional projectors to alter light waves and generate projections," explains Xu. "In a 3D holographic display, SLMs are used to display hologram pixels and create 3D objects by light diffraction. Each SLM in our system can display up to 1.89 billion hologram pixels every second, but this resolution is not high enough for a seamless large video display."
To address this challenge, Xu and his team divided every frame of their hologram video into 288 sub-holograms. They then streamed the sub-holograms through 24 high-speed SLMs stacked together in an array. This technique was combined with optical scan tiling, which uses a scanning mirror to combine the signals from the SLMs, thus filling in any gaps in the physical tiling array. Finally, the researchers sped up the full-color video playback using powerful graphics processing units. This combination of technologies produced one high-resolution, full-parallax moving hologram displaying 45 billion pixels per second.
"We increased the resolution of the holographic display system by 24 times," states Xu. "The full-color 3D holographic video plays at a rate of 60 frames per second, so it appears seamless to the human eye."
Potential applications of the new technique include 3D entertainment and medical imaging. However, new SLM devices with a smaller pixel size, higher resolution and faster frame rate are required before large-scale 3D holographic video displays can become reality.

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Story Source:
The above story is based on materials provided by The Agency for Science, Technology and Research (A*STAR). Note: Materials may be edited for content and length.

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Journal Reference:

1. Xuewu Xu, Xinan Liang, Yuechao Pan, Ruitao Zheng, Zhiming Abel Lum. Spatiotemporal multiplexing and streaming of hologram data for full-color holographic video display. Optical Review, 2014; 21 (3): 220 DOI: 10.1007/s10043-014-0032-y

Picture this: Graphene brings 3-D holograms clearer and closer

From mobile phones and computers to television, cinema and wearable devices, the display of full colour, wide-angle, 3D holographic images is moving ever closer to fruition, thanks to international research featuring Griffith University.

Led by Melbourne's Swinburne University of Technology and including Dr Qin Li, from the Queensland Micro- and Nanotechnology Centre within Griffith's School of Engineering, scientists have capitalised on the exceptional properties of graphene and are confident of applications in fields such as optical data storage, information processing and imaging.
"While there is still work to be done, the prospect is of 3D images seemingly leaping out of the screens, thus promising a total immersion of real and virtual worlds without the need for cumbersome accessories such as 3D glasses," says Dr Li.
First isolated in the laboratory about a decade ago, graphene is pure carbon and one of the thinnest, lightest and strongest materials known to humankind. A supreme conductor of electricity and heat, much has been written about its mechanical, electronic, thermal and optical properties.
"Graphene offers unprecedented prospects for developing flat displaying systems based on the intensity imitation within screens," says Dr Li, who conducted carbon structure analysis for the research.
"Our consortium, which also includes China's Beijing Institute of Technology and Tsinghua University, has shown that patterns of photo-reduced graphene oxide (rGO) that are directly written by laser beam can produce wide-angle and full-colour 3D images.
"This was achieved through the discovery that a single femtosecond (fs) laser pulse can reduce graphene oxide to rGO with a sub-wavelength-scale feature size and significantly differed refractive index.
"Furthermore, the spectrally flat optical index modulation in rGOs enables wavelength-multiplexed holograms for full colour images."
Researchers say the sub-wavelength feature is particularly important because it allows for static holographic 3D images with a wide viewing angle up to 52 degrees.
Such laser-direct writing of sub-wavelength rGO featured in dots and lines could revolutionise capabilities across a range of optical and electronic devices, formats and industry sectors.
"The generation of multi-level modulations in the refractive index of GOs, and which do not require any solvents or post-processing, holds the potential for in-situ fabrication of rGO-based electro-optic devices," says Dr Li.
"The use of graphene also relieves pressure on the world's dwindling supplies of indium, the metallic element that has been commonly used for electronic devices.
"Other technologies are being developed in this area, but rGO looks by far the most promising and most practical, particularly for wearable devices. The prospects are quite thrilling."
The findings are published in the esteemed journal Nature Communications.

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The above story is based on materials provided by Griffith University. Note: Materials may be edited for content and length.

Study links brain anatomy, academic achievement, and family income

Many years of research have shown that for students from lower-income families, standardized test scores and other measures of academic success tend to lag behind those of wealthier students.

In middle-schoolers, neuroscientists find differences in brain structures where knowledge is stored.

A new study led by researchers at MIT and Harvard University offers another dimension to this so-called "achievement gap": After imaging the brains of high- and low-income students, they found that the higher-income students had thicker brain cortex in areas associated with visual perception and knowledge accumulation. Furthermore, these differences also correlated with one measure of academic achievement -- performance on standardized tests.

"Just as you would expect, there's a real cost to not living in a supportive environment. We can see it not only in test scores, in educational attainment, but within the brains of these children," says MIT's John Gabrieli, the Grover M. Hermann Professor in Health Sciences and Technology, professor of brain and cognitive sciences, and one of the study's authors. "To me, it's a call to action. You want to boost the opportunities for those for whom it doesn't come easily in their environment."

This study did not explore possible reasons for these differences in brain anatomy. However, previous studies have shown that lower-income students are more likely to suffer from stress in early childhood, have more limited access to educational resources, and receive less exposure to spoken language early in life. These factors have all been linked to lower academic achievement.

In recent years, the achievement gap in the United States between high- and low-income students has widened, even as gaps along lines of race and ethnicity have narrowed, says Martin West, an associate professor of education at the Harvard Graduate School of Education and an author of the new study.

"The gap in student achievement, as measured by test scores between low-income and high-income students, is a pervasive and longstanding phenomenon in American education, and indeed in education systems around the world," he says. "There's a lot of interest among educators and policymakers in trying to understand the sources of those achievement gaps, but even more interest in possible strategies to address them."

Allyson Mackey, a postdoc at MIT's McGovern Institute for Brain Research, is the lead author of the paper, which appears the journal Psychological Science. Other authors are postdoc Amy Finn; graduate student Julia Leonard; Drew Jacoby-Senghor, a postdoc at Columbia Business School; and Christopher Gabrieli, chair of the nonprofit Transforming Education.

Explaining the gap

The study included 58 students -- 23 from lower-income families and 35 from higher-income families, all aged 12 or 13. Low-income students were defined as those who qualify for a free or reduced-price school lunch.

The researchers compared students' scores on the Massachusetts Comprehensive Assessment System (MCAS) with brain scans of a region known as the cortex, which is key to functions such as thought, language, sensory perception, and motor command.

Using magnetic resonance imaging (MRI), they discovered differences in the thickness of parts of the cortex in the temporal and occipital lobes, whose primary roles are in vision and storing knowledge. Those differences correlated to differences in both test scores and family income. In fact, differences in cortical thickness in these brain regions could explain as much as 44 percent of the income achievement gap found in this study.

Previous studies have also shown brain anatomy differences associated with income, but did not link those differences to academic achievement.

In most other measures of brain anatomy, the researchers found no significant differences. The amount of white matter -- the bundles of axons that connect different parts of the brain -- did not differ, nor did the overall surface area of the brain cortex.

The researchers point out that the structural differences they did find are not necessarily permanent. "There's so much strong evidence that brains are highly plastic," says Gabrieli, who is also a member of the McGovern Institute. "Our findings don't mean that further educational support, home support, all those things, couldn't make big differences."

In a follow-up study, the researchers hope to learn more about what types of educational programs might help to close the achievement gap, and if possible, investigate whether these interventions also influence brain anatomy.

"Over the past decade we've been able to identify a growing number of educational interventions that have managed to have notable impacts on students' academic achievement as measured by standardized tests," West says. "What we don't know anything about is the extent to which those interventions -- whether it be attending a very high-performing charter school, or being assigned to a particularly effective teacher, or being exposed to a high-quality curricular program -- improves test scores by altering some of the differences in brain structure that we've documented, or whether they had those effects by other means."

Story Source:

The above story is based on materials provided by Massachusetts Institute of Technology. The original article was written by Anne Trafton. Note: Materials may be edited for content and length.