Published: Tuesday, September 29, 2015 – 06:04 in Biology & Nature
MIT scientists, working with colleagues in Spain, have discovered and mapped a light-sensing protein that uses vitamin B12 to perform key functions, including gene regulation. The result, derived from studying proteins from the bacterium Thermus thermophilus, involves at least two findings of broad interest. First, it expands our knowledge of the biological role of vitamin B12, which was already understood to help convert fat into energy, and to be involved in brain formation, but has now been identified as a key part of photoreceptor proteins — the structures that allow organisms to sense and respond to light.

Second, the research describes a new mode of gene regulation, in which the light-sensing proteins play a key role. In so doing, the scientists observe, the bacteria have repurposed existing protein structures that use vitamin B12, and put them to work in new ways.

“Nature borrowed not just the vitamin, but really the whole enzyme unit, and modified it … and made it a light sensor,” says Catherine Drennan, a professor of chemistry and biology at MIT.

The findings are detailed this week in the journal Nature. The paper describes the photoreceptors in three different states: in the dark, bound to DNA, and after being exposed to light.

“It’s wonderful that we’ve been able to get all the series of structures, to understand how it works at each stage,” Drennan says.

The paper has nine co-authors, including Drennan; graduate students Percival Yang-Ting Chen, Marco Jost, and Gyunghoon Kang of MIT; Jesus Fernandez-Zapata and S. Padmanabhan of the Institute of Physical Chemistry Rocasolano, in Madrid; and Monserrat Elias-Arnanz, Juan Manuel Ortiz-Guerreo, and Maria Carmen Polanco, of the University of Murcia, in Murcia, Spain.

The researchers used a combination of X-ray crystallography techniques and in-vitro analysis to study the bacteria. Drennan, who has studied enzymes that employ vitamin B12 since she was a graduate student, emphasizes that key elements of the research were performed by all the co-authors.

Jost performed crystallography to establish the shapes of the structures, while the Spanish researchers, Drennan notes, “did all of the control experiments to show that we were really thinking about this right,” among other things.

By studying the structures of the photoreceptor proteins in their three states, the scientists developed a more thorough understanding of the structures, and their functions, than they would have by viewing the proteins in just one state.

Microbes, like many other organisms, benefit from knowing whether they are in light or darkness. The photoreceptors bind to the DNA in the dark, and prevent activity pertaining to the genes of Thermus thermophilus. When light hits the microbes, the photoreceptor structures cleave and “fall apart,” as Drennan puts it, and the bacteria start producing carotenoids, which protect the organisms from negative effects of sunlight, such as DNA damage.

The research also shows that the exact manner in which the photoreceptors bind to the DNA is novel. The structures contain tetramers, four subunits of the protein, of which exactly three are bound to the genetic material — something Drennan says surprised her.

“That’s the best part about science,” Drennan says. “You see something novel, then you think it’s not really going to be that novel, but you do the experiments [and it is].”

Drennan adds that in the long run, the finding could have practical applications, such as the engineering of light-directed control of DNA transcription, or the development of controlled interactions between proteins.

“I would be very interested in … thinking about whether there could be practical applications of this,” Drennan says.

Source: Massachusetts Institute of Technology

http://esciencenews.com/articles/2015/09/29/a.natural.light.switch

Microsoft’s continued focus on making its products available cross-platform continues today with the launch of its communications apps, Skype for Android Wear smartwatches. The app, which rolls out with the latest version of Skype 6.4 for Android, allows you to receive notifications and read your messages on Android Wear devices including the Moto 360, Huawei Watch, LG Watch Urbane, or the ASUS ZenWatch, Microsoft says.

Similar to its previously-released Apple Watch counterpart, the new Skype for Android Wear app lets you respond to incoming messages from your wrist, either by speaking into the device and having your message transcribed from voice to text, or by choosing from a selection of pre-written responses. You can also draw on the watch’s screen with a finger to send an emoji, as well as accept or decline incoming calls with a tap.

In the case you want to take a call, you can accept the call from the watch but then use Skype on your Android smartphone along with your microphone, headphones, or wireless Bluetooth speaker or headset in order to continue the conversation. The Watch app additionally lets you mute, hang up, pause or switch to another incoming call, as need be.

While the Android app update itself is largely focused on bringing the new Android Wear features to Skype users, the new version of the app also includes the recently released Skype Mojis, which are Skype’s own version of emojis that let you share clips from favorite movies and TV shows through messaging.

You Can Now Skype From Your Android Wear Smartwatch

Relaxnews
Published Tuesday, September 29, 2015 6:30AM EDT
At first glance, there isn’t much to tell the iPhone 6 apart from the 6s. And yet, Apple’s latest smartphone does offer a few significant improvements, especially on the photo and video side.
3D Touch technology
Just like its predecessor, the iPhone 6s has a 4.7 inch Retina HD display (1334×750 pixels), now equipped with 3D Touch technology. This proprietary tech, a derivative of the Force Touch found on the Macbook and Apple Watch, allows users to control various functions depending on the pressure applied to the screen.
New cameras
Apple needed to take a giant step forward with its photo capabilities, so the iPhone 6s now has a 12MP main camera (iSight) that is a significant step up from the iPhone 6’s 8MP. It also now includes the Live Photos feature that captures the moments just before and after your picture and sets it in motion with just the press of a finger. As for the front-facing camera (the FaceTime camera), it’s been upgraded to 5MP and can film in 1080p.

4K video
As for video, Apple has introduced 4K filming (3840×2160 pixels) as well as slow motion capture at a rate of 120 frames per second in HD (1080p). You can also take 8MP photos while filming in 4K.
A new color
In addition to silver, space grey and gold, the iPhone 6S (as well as the 6S Plus) is also available in a new color, pink gold.

http://www.ctvnews.ca/5things/iphone-6-vs-6s-four-main-differences-1.2581333

Jessie is here? Who’s Jessie? Wasn’t she the cowgirl doll in “Toy Story 2” – you know, the one who got abandoned in a park to that Sarah McLachlan song, resulting in at least one software engineer finding he had something in his eye at that point…?

Yes, it is that Jessie, but not in that context. The Raspbian operating system is based on Debian Linux, and the different versions of Debian are named after characters from the “Toy Story” films. Recent versions of Raspbian have been based on Debian Wheezy (the penguin who’s lost his squeaker in “Toy Story 2”), but Raspbian has now been updated to the new stable version of Debian, which is called Jessie.

So what’s new?

Many of the changes between Wheezy and Jessie are invisible to the end-user. There are modifications to the underlying system to improve performance and flexibility, particularly as regards the control of system processes, and as with any update, there are numerous bug fixes and tweaks. And at the same time as the upgrade to Jessie, we’ve added a bunch of changes and improvements to the desktop user interface.

Look and feel

The first thing anyone starting the new Jessie image from scratch will notice is that the default behaviour is to boot straight to the desktop GUI, not to the Linux command line. This was a decision taken because this is the expected behaviour for all modern computers; the default interface for a personal computer in 2015 is a desktop GUI, not just text on a screen. It is still possible to set the Pi to boot to the command line for people who prefer that – just toggle the relevant setting in the Raspberry Pi Configuration application described below.

When the desktop launches, you might notice some slight tweaks to the appearance of things like menus, check boxes and radio buttons. This is because the appearance of Raspbian is now based on version 3 of GTK+, the user interface toolkit used for the LXDE desktop environment. The older version 2 of GTK+ is slowly being replaced with version 3 in many applications, so this change was inevitable at some point – the new appearance isn’t a huge change, but does look slightly more modern. Many of the applications in Raspbian are still using GTK+ version 2, but the PiX theme for GTK+2 has been changed to bring it into line with that for GTK+3.

You’ll notice on the menu bar that there is now an eject icon at the top right – this is a new plug-in that allows USB drives and the like to be safely ejected without the risk of losing data. It’s slightly risky to just pull out a USB drive, particularly if you have just copied a file to it, as the system manages the write to a drive in the background, and the write takes a finite amount of time. If you pull the drive out before the write has finished, you’ll corrupt the file and lose data – clicking the eject icon and then selecting the drive to remove waits for any pending writes to complete and then prompts that it is safe to remove the drive.

Office applications

One of our main aims with regard to Raspberry Pi is not just to make it a great cheap computer for education, but also to make it a great cheap computer in its own right. To this end, we want to make it possible to use a Pi to do the sort of things you’d do on a Mac or a PC, so we’re including some more applications that we think people will find useful. In this release, we have added the LibreOffice suite and Claws Mail.

LibreOffice is a full-featured office suite which is compatible with Microsoft Office files – it includes a word processor, spreadsheet, presentation graphics, vector drawing and database programs, all of which should feel familiar to anyone used to using Office. It has had some optimisation for Pi, and runs pretty well, particularly on Pi 2.

Claws Mail is an email client for those of us who are old-fashioned enough to prefer not to do email through a browser – it supports all common email protocols, and offers all the functionality of a standalone mail client like Windows Mail or Thunderbird.

Java tools

There are also two new applications in the Programming category – these are two new environments for writing Java applications, called BlueJ and Greenfoot (from the University of Kent and Oracle). If you’re interested in learning Java, or already a Java programmer, have a look at them. There are some sample projects for both in the /home/pi/Documents directory.

Settings and configuration

There are a couple of new settings dialogs in this release, found under the Preferences entry in the main menu. The first is Raspberry Pi Configuration – this is a GUI version of the old raspi-config command-line application, which provides all the same functionality in a nicer interface. (The old raspi-config is still on the system and can be accessed from the command line by typing “sudo raspi-config”, but it shouldn’t be necessary to do so any more.)

The new Raspberry Pi Configuration allows you to enable and disable interfaces, tweak performance and configure internationalisation options, such as timezone and keyboard. It also allows some more control over boot options than was available in the past, with the option to automatically log in as the “pi” user available when booting to both CLI and desktop.

There is a new keyboard setting dialog, accessed from the Localisation tab, but hopefully many people won’t need this – the system will detect some common keyboards sold for use with Pi and set up the GUI keyboard driver correctly. If that doesn’t happen, it’s now easy to choose the right country and keyboard type in this dialog.

The other new setting dialog is the Main Menu Editor. This is a Pi version of a menu editor called Alacarte, written in Python – this should make it easier for people to add or remove items to the main menu. (And, by popular demand, the Other menu is back on the system – but it will now only appear if applications are installed that don’t appear in any other categories…)

Updated applications

There are updates to several of the applications that used to come with Raspbian. There are new versions of Scratch, Sonic Pi, and the Epiphany web browser; none of these have changed fundamentally in operation, but they all include bug fixes and performance improvements.

Support has been added for some of the new Pi peripherals that have been released recently, including the Sense HAT as used in Astro Pi – this is now supported under Scratch and Python.

Python users used to have to launch Python with sudo in order to allow access to the GPIO lines – Python can now access GPIOs as a standard user. Also for Python, the Pygame Zero game environment is installed by default – have a look at pygame-zero.readthedocs.org for information on what it can do.

One final small thing – if you want to get a screenshot of your Pi, just press the Print Screen button on your keyboard. A PNG file will be put in your home directory, thanks to the (slightly strangely named) scrot utility.

Where can I get it?

This is a major version upgrade – due to the large number of changes to the underlying operating system, we strongly recommend using Jessie from a clean image, so you’ll need to download a new Jessie image from the downloads page on our site.

Starting with a clean image is the recommended way to move to Jessie. If you really need to update a Wheezy image, we have tried an unsupported upgrade path which is documented on the forums here. This has been shown to work on a vanilla Wheezy image, but we can’t predict what effect it may have on any packages or data that you have installed, so this is very much at your own risk. Feel free to add your experiences and improvements to the upgrade process to the forum so others can benefit.

As ever, your feedback on the release is very much welcome – do add a comment below, and I’ll try to respond to as many as I can.

https://www.raspberrypi.org/blog/raspbian-jessie-is-here/

A fully wraparound, ultrathin invisibility cloak at the microscale
September 28, 2015
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This image shows a 3-D illustration of a metasurface skin cloak made from an ultrathin layer of nanoantennas (gold blocks) covering an arbitrarily shaped object. When activated, light reflects off the cloak (red arrows) as if it were reflecting off a flat mirror. (credit: Image courtesy of Xiang Zhang group, Berkeley Lab/UC Berkeley)

An ultra-thin invisibility “skin” cloak that can conform to the shape of an object and conceal it from detection with visible light has been developed by scientists at Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of California (UC) Berkeley.

Working with blocks of gold nanoantennas, the Berkeley researchers created a “skin cloak” just 80 nanometers in thickness that was wrapped around a three-dimensional object about the size of a few biological cells and shaped with multiple bumps and dents. The surface of the skin cloak was meta-engineered to reflect light waves, making the object invisible to optical detection when the cloak is activated.

“This is the first time a 3D object of arbitrary shape has been cloaked from visible light,” said Xiang Zhang, director of Berkeley Lab’s Materials Sciences Division. “Our ultra-thin cloak now looks like a coat. It is easy to design and implement, and is potentially scalable for hiding macroscopic objects.”

Zhang, who holds the Ernest S. Kuh Endowed Chair at UC Berkeley and is a member of the Kavli Energy NanoSciences Institute at Berkeley (Kavli ENSI), is the corresponding author of a paper describing this research in the journal Science.

Click to see an animation of an invisibility cloak that makes a 3-D object disappear (credit: Zhang group)

It is the scattering of light from its interaction with matter that enables us to detect and observe objects. The rules that govern these interactions in natural materials can be circumvented in metamaterials, whose optical properties arise from their physical structure rather than their chemical composition.

For the past ten years, Zhang and his research group have been pushing the boundaries of how light interacts with metamaterials, managing to curve the path of light or bend it backwards, phenomena not seen in natural materials, and to render objects optically undetectable. In the past, their metamaterial-based optical carpet cloaks were bulky and hard to scale up, and entailed a phase difference between the cloaked region and the surrounding background that made the cloak itself detectable, though what it concealed was not.

Now you see it, now you don’t

In the new study, the researchers used red light to illuminate an arbitrarily shaped 3-D sample object about 1,300 square micrometers in area and wrapped in the gold nanoantenna skin cloak. The light reflected off the surface of the skin cloak was identical to light reflected off a flat mirror, making the object underneath it invisible even by phase-sensitive detection. The cloak can be turned “on” or “off” simply by switching the polarization of the nanoantennas.

“A phase shift provided by each individual nanoantenna fully restores both the wavefront and the phase of the scattered light so that the object remains perfectly hidden,” says co-lead author Zi Jing Wong, also a member of Zhang’s research group.

According the researchers. the ability to manipulate the interactions between light and metamaterials offers future prospects for technologies such as high-resolution optical microscopes and superfast optical computers, and for hiding the detailed layout of microelectronic components or for security encryption purposes.

At the macroscale, among other applications, invisibility cloaks could prove useful for 3D displays, they add.

Abstract of An ultrathin invisibility skin cloak for visible light

Metamaterial-based optical cloaks have thus far used volumetric distribution of the material properties to gradually bend light and thereby obscure the cloaked region. Hence, they are bulky and hard to scale up and, more critically, typical carpet cloaks introduce unnecessary phase shifts in the reflected light, making the cloaks detectable. Here, we demonstrate experimentally an ultrathin invisibility skin cloak wrapped over an object. This skin cloak conceals a three-dimensional arbitrarily shaped object by complete restoration of the phase of the reflected light at 730-nanometer wavelength. The skin cloak comprises a metasurface with distributed phase shifts rerouting light and rendering the object invisible. In contrast to bulky cloaks with volumetric index variation, our device is only 80 nanometer (about one-ninth of the wavelength) thick and potentially scalable for hiding macroscopic objects.

references:
Xingjie Ni, Zi Jing Wong, Michael Mrejen, Yuan Wang, Xiang Zhang. An ultrathin invisibility skin cloak for visible light. Science, 2015 DOI: 10.1126/science.aac9411
related:
Making 3-D objects disappear

http://www.kurzweilai.net/how-to-make-3-d-objects-totally-disappear

Allows for high-resolution and scalability for engineering tissue scaffolds and implants
September 28, 2015

Illustration of laser-based micropatterning of silk hydrogels. The transparent gels enable the laser’s photons (pink) to be absorbed more than 10 times deeper than with other materials without damaging the cells (green) surrounding the letters (credit: M.B. A)

Tufts University biomedical engineers have developed low-energy, ultrafast laser technology for micropatterning high-resolution, 3-D structures in silk-protein hydrogels.

Micropatterning is used to bring oxygen and nutrients to rapidly proliferating cells in an engineered tissue scaffold. The goal is “to controllably guide cell growth and create an artificial vasculature (blood vessel system) within an already densely seeded silk hydrogel,” said Fiorenzo G. Omenetto, Ph.D., senior author of a paper on the work in PNAS Early Edition published September 15 online before print.

Current patterning techniques allow for the production of random, micrometer-scale pores and also the creation of larger channels that are hundreds of micrometers in diameter, but there is little in between.

The Tufts researchers used the ultrafast femtosecond laser to generate scalable, high-resolution 3-D pores (voids) within silk protein hydrogel, a soft, transparent biomaterial that supports cell growth and allows cells to penetrate deep within it. The researchers were able to create pores at multiple scales as small as 10 micrometers and as large at 400 micrometers over a large volume.

The transparent silk gels also enabled the laser’s photons to be absorbed nearly 1 cm below the surface of the gel — more than ten times deeper than with other materials — without damaging adjacent material.

The laser treatment can be done while keeping the cell culture sealed and sterile. Unlike most 3-D printing, this technique does not require photoinitiators (compounds that promote photoreactivity but are typically not biocompatible).

Omenetto is associate dean for research, professor of biomedical engineering and Frank C. Doble professor at Tufts School of Engineering and also holds an appointment in physics in the School of Arts and Sciences.

The research team reported similar results in vitro and in a preliminary in vivo study in mice.

Abstract of Laser-based three-dimensional multiscale micropatterning of biocompatible hydrogels for customized tissue engineering scaffolds

Light-induced material phase transitions enable the formation of shapes and patterns from the nano- to the macroscale. From lithographic techniques that enable high-density silicon circuit integration, to laser cutting and welding, light–matter interactions are pervasive in everyday materials fabrication and transformation. These noncontact patterning techniques are ideally suited to reshape soft materials of biological relevance. We present here the use of relatively low-energy (< 2 nJ) ultrafast laser pulses to generate 2D and 3D multiscale patterns in soft silk protein hydrogels without exogenous or chemical cross-linkers. We find that high-resolution features can be generated within bulk hydrogels through nearly 1 cm of material, which is 1.5 orders of magnitude deeper than other biocompatible materials. Examples illustrating the materials, results, and the performance of the machined geometries in vitro and in vivo are presented to demonstrate the versatility of the approach.

references:
Matthew B. Applegate, Jeannine Coburn, Benjamin P. Partlow, Jodie E. Moreau, Jessica P. Mondia, Benedetto Marelli, David L. Kaplan, Fiorenzo G. Omenetto. Laser-based three-dimensional multiscale micropatterning of biocompatible hydrogels for customized tissue engineering scaffolds. Proceedings of the National Academy of Sciences, 2015; 201509405 DOI: 10.1073/pnas.1509405112
related:
Ultrafast lasers offer 3-D micropatterning of biocompatible hydrogels

http://www.kurzweilai.net/ultrafast-lasers-enable-3-d-micropatterning-of-biocompatible-hydrogels

As an array of billions of carbon nanotubes, they could efficiently capture solar energy
September 28, 2015

This schematic shows the components of the optical rectenna developed at the Georgia Institute of Technology (credit: Thomas Bougher, Georgia Tech)

Using nanometer-scale components, Georgia Institute of Technology researchers have demonstrated the first optical rectenna, a device that combines the functions of an antenna and a rectifier diode to convert light directly into DC current.

Based on multiwall carbon nanotubes and tiny rectifiers fabricated onto them, the optical rectennas could provide a new technology for energy harvesters, including photodetectors that would operate without the need for cooling, convert waste heat to electricity, and ultimately, efficiently capture solar energy.

In the new devices, the carbon nanotubes act as antennas to capture light from the Sun or other sources. As the waves of light hit the nanotube antennas, they create an oscillating charge that moves through rectifier devices attached to them. The rectifiers switch on and off at record high petahertz speeds, creating a small direct current.

The efficiency of the devices demonstrated so far remains below one percent, but the researchers hope to boost that output by using billions of rectennas in an array, which could produce significant current. They believe a rectenna with commercial potential may be available within a year.

“We could ultimately make solar cells that are twice as efficient at a cost that is ten times lower, and that is to me an opportunity to change the world in a very big way” said Baratunde Cola, an associate professor in the George W. Woodruff School of Mechanical Engineering at Georgia Tech. “As a robust, high-temperature detector, these rectennas could be a completely disruptive technology if we can get to one percent efficiency. If we can get to higher efficiencies, we could apply it to energy conversion technologies and solar energy capture.”

A carbon nanotube optical rectenna converts green laser light to electricity in the laboratory of Baratunde Cola at the Georgia Institute of Technology (credit: Rob Felt, Georgia Tech)

“A rectenna is basically an antenna coupled to a diode, but when you move into the optical spectrum, that usually means a nanoscale antenna coupled to a metal-insulator-metal diode,” Cola explained. “The closer you can get the antenna to the diode, the more efficient it is. So the ideal structure uses the antenna as one of the metals in the diode – which is the structure we made.”

The rectennas fabricated by Cola’s group are grown on rigid substrates, but the goal is to grow them on a foil or other material that would produce flexible solar cells or photodetectors.

Cola sees the rectennas built so far as simple proof of principle. “We think we can reduce the resistance by several orders of magnitude just by improving the fabrication of our device structures,” he said. “Based on what others have done and what the theory is showing us, I believe that these devices could get to greater than 40 percent efficiency.”

The research, supported by the Defense Advanced Research Projects Agency (DARPA), the Space and Naval Warfare (SPAWAR) Systems Center and the Army Research Office (ARO), is reported September 28 in the journal Nature Nanotechnology.

* Developed in the 1960s and 1970s, rectennas have operated at wavelengths as short as ten micrometers, but for more than 40 years researchers have been attempting to make devices at optical wavelengths. There were many challenges: making the antennas small enough to couple optical wavelengths, and fabricating a matching rectifier diode small enough and able to operate fast enough to capture the electromagnetic wave oscillations. But the potential of high efficiency and low cost kept scientists working on the technology.

Fabricating the rectennas begins with growing forests of vertically-aligned carbon nanotubes on a conductive substrate. Using atomic layer chemical vapor deposition, the nanotubes are coated with an aluminum oxide material to insulate them. Finally, physical vapor deposition is used to deposit optically-transparent thin layers of calcium then aluminum metals atop the nanotube forest. The difference of work functions between the nanotubes and the calcium provides a potential of about two electron volts, enough to drive electrons out of the carbon nanotube antennas when they are excited by light.

In operation, oscillating waves of light pass through the transparent calcium-aluminum electrode and interact with the nanotubes. The metal-insulator-metal junctions at the nanotube tips serve as rectifiers switching on and off at femtosecond intervals, allowing electrons generated by the antenna to flow one way into the top electrode. Ultra-low capacitance, on the order of a few attofarads, enables the 10-nanometer diameter diode to operate at these exceptional frequencies.

Georgia Tech | Using nanometer-scale components, researchers have demonstrated the first optical rectenna, a device that combines the functions of an antenna and a rectifier diode to convert light directly into DC current.

Abstract of A carbon nanotube optical rectenna

An optical rectenna—a device that directly converts free-propagating electromagnetic waves at optical frequencies to direct current—was first proposed over 40 years ago, yet this concept has not been demonstrated experimentally due to fabrication challenges at the nanoscale. Realizing an optical rectenna requires that an antenna be coupled to a diode that operates on the order of 1 pHz (switching speed on the order of 1 fs). Diodes operating at these frequencies are feasible if their capacitance is on the order of a few attofarads, but they remain extremely difficult to fabricate and to reliably couple to a nanoscale antenna. Here we demonstrate an optical rectenna by engineering metal–insulator–metal tunnel diodes, with a junction capacitance of ∼2 aF, at the tip of vertically aligned multiwalled carbon nanotubes (∼10 nm in diameter), which act as the antenna. Upon irradiation with visible and infrared light, we measure a d.c. open-circuit voltage and a short-circuit current that appear to be due to a rectification process (we account for a very small but quantifiable contribution from thermal effects). In contrast to recent reports of photodetection based on hot electron decay in a plasmonic nanoscale antenna, a coherent optical antenna field appears to be rectified directly in our devices, consistent with rectenna theory. Finally, power rectification is observed under simulated solar illumination, and there is no detectable change in diode performance after numerous current–voltage scans between 5 and 77 °C, indicating a potential for robust operation.

references:
Asha Sharma, Virendra Singh, Thomas L. Bougher and Baratunde A. Cola. A carbon nanotube optical rectenna. (Nature Nanotechnology, 2015). DOI: 10.1038/nnano.2015.220
related:
First Optical Rectenna – Combined Rectifier and Antenna – Converts Light to DC Current

http://www.kurzweilai.net/first-optical-rectenna-converts-light-to-dc-current

September 28, 2015

NASA says these dark, narrow, 100 meter-long streaks called recurring slope lineae flowing downhill on Mars appear to have been formed by contemporary flowing water (credit: NASA/JPL/University of Arizona)

New findings from NASA’s Mars Reconnaissance Orbiter (MRO) provide the strongest evidence yet that liquid water flows intermittently on present-day Mars, NASA announced today.

Researchers detected darkish signatures of hydrated minerals on slopes in several locations that appear to ebb and flow over time, based on spectrometer data. The signatures darken and appear to flow down steep slopes during warm seasons, and then fade in cooler seasons.

“This is a significant development, as it appears to confirm that water — albeit briny — is flowing today on the surface of Mars,” said John Grunsfeld, astronaut and associate administrator of NASA’s Science Mission Directorate in Washington.

“We found the hydrated salts only when the seasonal features were widest, which suggests that either the dark streaks themselves or a process that forms them is the source of the hydration. In either case, the detection of hydrated salts on these slopes means that water plays a vital role in the formation of these streaks,” said Lujendra Ojha of the Georgia Institute of Technology in Atlanta, lead author of a report on these findings published Sept. 28 by Nature Geoscience.

Ojha and his co-authors interpret the spectral signatures as caused by hydrated minerals called perchlorates. On Earth, naturally produced perchlorates are concentrated in deserts, and some types of perchlorates can be used as rocket propellant.

Other co-authors are affiliated with NASA Ames Research Center, Johns Hopkins University Applied Physics Laboratory, University of Arizona Lunar and Planetary Laboratory, Southwest Research Institute, and Laboratoire de Planétologie et Géodynamique.

JPL | Animation of Site of Seasonal Flows in Hale Crater, Mars

references:
Jeffrey A. Hawkes et al. Efficient removal of recalcitrant deep-ocean dissolved organic matter during hydrothermal circulation. Nature Geoscience (2015) doi:10.1038/ngeo2543. Sept. 28, 2015
L. Ojha et al. Spectral Evidence for Hydrated Salts in Seasonal Brine Flows on Mars. EPSC Abstracts Vol. 10, EPSC2015-838-1, 2015. European Planetary Science Congress 2015 (open access)
related:
NASA Confirms Evidence That Liquid Water Flows on Today’s Mars

http://www.kurzweilai.net/liquid-water-flows-on-todays-mars-nasa-confirms

A flat tire can leave you feeling defeated and deflated. It is nearly impossible to get enough torque on those small wrenches that come with the car to put on the spare and, once the full-size tire comes off, chances are it is never going back on. Often, the only good long-term solution is to replace the tire.

But that may be soon be a thing of the past. Scientists from Germany and Finland have developed rubber than self-heals after being punctured. This rubber doesn’t require vulcanization, an essential step that allows it to be durable and elastic.

“Invented by Charles Goodyear, chemical cross-linking of rubbers by sulfur vulcanization is the only method by which modern automobile tires are manufactured,” reads the study abstract. This new method involves “converting commercially available and widely used bromobutyl rubber into a highly elastic material with extraordinary self-healing properties without using conventional cross-linking or vulcanizing agents.”

The researchers presented their findings in Applied Materials and Interfaces, a journal of the American Chemical Society, along with a video which describes how the process works.

In the experiment, a cut in the rubber healed itself at room temperature and heat, especially when applied in the first 10 minutes after the tear, sped up the process.

“After eight days, the rubber can withstand pressures of more than 750 psi, that’s about 20 times the normal amount of pressure on a tire,” the narrator says in the video uploaded by the American Chemical Society.

This means a tire could repair itself while sitting in a garage, which beats having to take it to the shop.

http://www.theglobeandmail.com/globe-drive/news/trans-canada-highway/self-healing-rubber-means-your-flat-tire-can-fix-itself/article26563614/

Water – a key necessity for life as we know it – still flows sometimes on the surface of Mars, a new study suggests.

Strong evidence for seasonal flows of liquid salty water have been detected by NASA’s Mars Reconnaissance Orbiter, report scientists in a paper published Monday in the journal Nature Geoscience.

Summary of the paper
“It suggests that it would be possible for life to be on Mars today,” said John Grunsfeld, NASA’s associate administration for science, at a news conference detailing the discovery.

PHOTOS | Mars rovers’ coolest pics
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Previously, scientists have found ample evidence that Mars was once much warmer and wetter billions of years ago than it is now, and could have supported life then. It hasn’t been clear whether the colder, drier Red Planet of today could still support microbial life. Many scientists think life could still survive deep underground, but not necessarily on the surface where it could be more easily detected.

Dark narrow streaks called recurring slope lineae appear on the walls of Garni crater on Mars. The dark streaks here are up to few hundred metres in length and contain chemical signatures for water-logged salts or brines. (NASA/JPL/University of Arizona)

‘These results strongly support the hypothesis that seasonal warm slopes are forming liquid water on contemporary Mars.’

– Ojha et al., Nature Geoscience
The new study looked at streaks that form on some slopes on Mars during warmer times of the year. Scientists previously suspected they might be caused by flowing, salty water. The streaks, which are less than five metres wide and called “recurring slope lineae,” appear in the summer when temperatures can get above the freezing point of even fresh water and well above the freezing point of salty water – between -23 C and +27 C. They disappear during colder seasons.

But no salt or water had previously been detected in those streaks.

Now, Lujendra Ojha, a PhD candidate in planetary sciences at the Georgia Institute of Technology, and his colleagues are reporting they have detected the chemical signatures of brines in the streaks that suggest those streaks form as the result of “water activity on Mars” that’s still happening today.

The Mars Reconnaissance Orbiter spacecraft has been orbiting that planet since 2006, taking detailed images of the surface and scanning it for the chemical signatures of water and minerals associated with water.

What Ojha and his colleagues did was tease out the chemical signatures from individual pixels in images of the slope lineae. They found signatures for water-logged salts in the streaks, but not in the surrounding soil.

“These results strongly support the hypothesis that seasonal warm slopes are forming liquid water on contemporary Mars,” the researchers wrote.

The brine forming the streaks would be far saltier than the Earth’s oceans — perhaps five per cent water and 95 per cent salt, suggested Alfred McEwen, a University of Arizona in Tuscon researcher who co-authored the paper.

They would likely appear as thin layers of wet soil, not more than a centimetre deep — “not standing water,” he said at the news conference.

But because the streaks are visible over large areas of the surface of Mars, “if you add it all up, it could be a significant volume.”

In fact, said Mary Beth Wilhelm of NASA’s Ames Research Center, another co-author of the paper, that water could potentially be used as a resource by future human explorers, decreasing the cost and increasing the resilience of human missions to Mars.

The types of salts found — sodium perchlorate, magnesium chlorate and magnesium perchlorate — can lower the freezing point of water by 40 to 70 degrees and reduce its evaporation at higher temperatures, making it stable on the surface of Mars under a wider range of conditions than usual. That’s what made it detectable even during the mid-afternoon – the driest time of day on Mars, but the time of day that the Mars Reconnaissance Orbiter scans the surface.

Similar brines support life in Atacama Desert

In the paper, the researchers noted that on Earth, similar brines offer “the only known refuge for active microbial communities” in the driest parts of Chile’s Atacama Desert.

This image was taken by the Mars Reconnaissance Orbiter spacecraft, which has been orbiting the planet since 2006, taking detailed images of the surface and scanning it for the chemical signatures of water and minerals associated with water. (Greg Shirah/NASA)

On Mars, such brines could provide “transiently wet conditions near surface,” the researchers said. However, they cautioned that the amount of water may be too low to support known organisms that exist on Earth.

Grunsfeld added that the brine streaks aren’t the most likely place on Mars to find life – better conditions for microbes would likely be underground, near a source of fresh water, rather than salty water.

The researchers said they still don’t know where the water supplying the brine might be coming from. Most likely, Wilhelm said, the salts are absorbing water from the atmosphere until they dissolve, through a process called deliquescence. But researchers aren’t sure if there’s enough water vapour in Mars’s atmosphere for that to happen.

Signs of similar salts have previously also been found by the Curiosity rover that is currently still exploring the surface, as well as the Phoenix mission in 2008 and possibly the Viking landers in the 1970s.

http://www.cbc.ca/news/technology/mars-nasa-science-finding-1.3246527