With new makes of all-electric and hybrid automobiles seeming to emerge as fast as the colors of fall, it is easy to overlook another alternative to gasoline engines that could prove to be a major player in reduced-carbon transportation - cars powered by natural gas. Natural gas, which consists primarily of methane (CH4) is an abundant, cheaper and cleaner burning fuel than gasoline, but its low energy density at ambient temperature and pressure has posed a severe challenge for on-board fuel storage in cars. Help may be on the way.

Researchers with the U.S. Department of Energy (DOE)'s Lawrence Berkeley National Laboratory (Berkeley Lab) have developed a variety of metal-organic frameworks (MOFs) - sponge-like 3D crystals with an extraordinarily large internal surface area - that feature flexible gas-adsorbing pores. This flexibility gives these MOFs a high capacity for storing methane, which in turn has the potential to help make the driving range of an adsorbed-natural-gas (ANG) car comparable to that of a typical gasoline-powered car.

"Our flexible MOFs can be used to boost the usable capacity of natural gas in a tank, reduce the heating effects associated with filling an ANG tank, and reduce the cooling effects upon discharging the gas from the ANG tank," says Jeffrey Long, a chemist with Berkeley Lab's Materials Sciences Division and the University of California (UC) Berkeley who is leading this research.

"This ability to maximize the deliverable capacity of natural gas while also providing internal heat management during adsorption and desorption demonstrates a new concept in the storage of natural gas that provides a possible path forward for ANG applications where none was envisioned before."

Long is the corresponding author of a Nature paper that describes this work entitled, "Methane storage in flexible metal-organic frameworks with intrinsic thermal management." The lead author is Jarad Mason, a member of Long's research group. (See below for a complete list of co-authors.)

The United States holds a vast amount of proven natural gas reserves - some 360 trillion cubic feet and climbing. While compressed natural gas-fueled vehicles are already on the road, the widespread use of natural gas as a transportation fuel has been hampered by cumbersome and expensive on-board gas storage tanks and the cost of dispensing compressed natural gas to vehicles.

The storage issue is especially keen for light-duty vehicles such as cars, in which the space available for on-board fuel storage is limited. ANG has the potential to store high densities of methane within a porous material at ambient temperature and moderate pressures, but designing such high-capacity systems while still managing the thermal fluctuations associated with adsorbing and desorbing the gas from the adsorbent has proven to be difficult.

The key to the success of the MOFs developed by Long, Mason and their colleagues is a "stepped" adsorption and desorption of methane gas.

"Most porous materials that would be used as adsorbents exhibit classical Langmuir-type isotherm adsorption, where the amount of methane adsorbed increases continuously but with a decreasing slope as the pressure is raised so that, upon discharging the methane down to the minimum delivery pressure, much of it remains in the tank," Long says.

"With our flexible MOFs, the adsorption process is stepped because the gas must force its way into the MOF crystal structure, opening and expanding the pores. This means the amount of methane that can be delivered to the engine, i.e., the usable capacity, is higher than for traditional, non-flexible adsorbents."

In addition, Long says, the step in the adsorption isotherm is associated with a structural phase change in the MOF crystal that reduces the amount of heat released upon filling the tank, as well as the amount of cooling that takes place when methane is delivered to accelerate the vehicle.

"Crystallites that experience higher external pressures will have a greater free energy change associated with the phase transition and will open at higher pressures," Long says. "Our results present the prospect of using mechanical pressure, provided, for example, through an elastic bladder, as a means of thermal management in an ANG system based on a flexible adsorbent."

To test their approach, Long and his colleagues used a cobalt-based MOF hybrid that goes by the name "cobalt-bdp" or Co(bdp) for cobalt (benzenedipyrazolate). In its most open form, cobalt-bdp features square-shaped pores that can flex shut like an accordion when the pores are evacuated.

Combined gas adsorption and in situ powder X-ray diffraction experiments performed under various pressures of methane at 25 C (77 F)showed that there is minimal adsorption of methane by the cobalt-bpd MOF at low pressures, then a sharp step upwards at 16 bar, signifying a transition from a collapsed, non-porous structure to an expanded, porous structure. This transition to an expanded phase was reversible. When the methane pressure decreased to between 10 bar and 5 bar, the framework fully converted back to the collapsed phase, pushing out all of the adsorbed methane gas.

Long says that it should be possible to design MOF adsorbents of methane with even stronger gas binding sites and higher-energy phase transitions for next generation ANG vehicles. He and his group are working on this now and are also investigating whether the strategy can be applied to hydrogen, which poses similar storage problems.

Moreover, Long says, "Improved compaction and packing strategies should also allow further reductions to external thermal-management requirements and optimization of the overall natural gas storage-system performance."

In addition to Long and Mason, other authors of the Nature paper that describes this study were Julia Oktawiec, Mercedes Taylor, Matthew Hudson, Julien Rodriguez, Jonathan Bachman, Miguel Gonzalez, Antonio Cervellino, Antonietta Guagliardi, Craig Brown, Philip Llewellyn and Norberto Masciocchi.

- SPACE STORY - physics slug1 225 22-DEC-49 Seeing sound Seeing sound diagram-voice-encoding-scheme-lg.jpg diagram-voice-encoding-scheme-bg.jpg diagram-voice-encoding-scheme-sm.jpg Depiction of the vOICe encoding scheme. A camera mounted on glasses records video that is converted to sound by a computer and transmitted to headphones in real time. Image courtesy Shimojo Lab and Caltech. For a larger version of this image please go here. California Institute of Technology
by Staff Writers Pasadena CA (SPX) Oct 29, 2015 A busy kitchen is a place where all of the senses are on high alert - your brain is processing the sound of sizzling oil, the aroma of spices, the visual aesthetic of food arranged on a plate, the feel and taste of taking a bite. While these signals may seem distinct and independent, they actually interact and integrate together within the brain's network of sensory neurons.

Caltech researchers have now discovered that intrinsic neural connections - called crossmodal mappings - can be used by assistive devices to help the blind detect their environment without requiring intense concentration or hundreds of hours of training.

This new multisensory perspective on such aids (called sensory substitution devices) could make tasks that were previously attention-consuming much easier, allowing nonsighted people to acquire a new sensory functionality similar to vision. The work is described in a paper published in the October 22 issue of the journal Scientific Reports.

"Many neuroscience textbooks really only devote a few pages to multisensory interaction," says Shinsuke Shimojo, the Gertrude Baltimore Professor of Experimental Psychology and principal investigator on the study.

"But 99 percent of our daily life depends on multisensory - also called multimodal - processing." As an example, he says, if you are talking on the phone with someone you know very well, and they are crying, you will not just hear the sound but will visualize their face in tears. "This is an example of the way sensory causality is not unidirectional - vision can influence sound, and sound can influence vision."

Shimojo and postdoctoral scholar Noelle Stiles have exploited these crossmodal mappings to stimulate the visual cortex with auditory signals that encode information about the environment.

They explain that crossmodal mappings are ubiquitous; everyone already has them. Mappings include the intuitive matching of high pitch to elevated locations in space or the matching of noisy sounds with bright lights. Multimodal processing, like these mappings, may be the key to making sensory substitution devices more automatic.

The researchers conducted trials with both sighted and blind people using a sensory substitution device, called a vOICe device, that translates images into sound.

The vOICe device is made up of a small computer connected to a camera that is attached to darkened glasses, allowing it to "see" what a human eye would. A computer algorithm scans each camera image from left to right, and for every column of pixels, generates an associated sound with a frequency and volume that depends upon the vertical location and brightness of the pixels.

A large number of bright pixels at the top of a column would translate into a loud, high-frequency sound, whereas a large number of lower dark pixels would be a quieter, lower-pitched sound. A blind person wearing this camera on a pair of glasses could then associate different sounds with features of their environment.

In the trials, sighted people with no training or instruction were asked to match images to sounds; while the blind subjects were asked to feel textures and match them to sound. Tactile textures can be related to visual textures (patterns) like a topographic map - bright regions of an image translate to high tactile height relative to a page, while dark regions are flatter.

Both groups showed an intuitive ability to identify textures and images from their associated sounds. Surprisingly, the untrained (also called "naive") group's performance was significantly above chance, and not very different from the trained.

The intuitively identified textures used in the experiments exploited the crossmodal mappings already within the vOICe encoding algorithm. "When we reverse the crossmodal mappings in the vOICe auditory-to-visual translation, the naive performance significantly decreased, showing that the mappings are important to the intuitive interpretation of the sound," explains Stiles.

"We found that using this device to look at textures - patterns of light and dark - illustrated 'intuitive' neural connections between textures and sounds, implying that there is some preexisting crossmodality," says Shimojo. One common example of crossmodality is a condition called synesthesia, in which the activation of one sense leads to a different involuntary sensory experience, such as seeing a certain color when hearing a specific sound.

"Now, we have discovered that crossmodal connections, preexisting in everyone, can be used to make sensory substitution intuitive with no instruction or training."

The researchers do not exactly know yet what each sensory region of the brain is doing when processing these various signals, but they have a rough idea. "Auditory regions are activated upon hearing sound, as are the visual regions, which we think will process the sound for its spatial qualities and elements.

The visual part of the brain, when processing images, maps objects to spatial location, fitting them together like a puzzle piece," Stiles says. To learn more about how the crossmodal processing happens in the brain, the group is currently using functional magnetic resonance imaging (fMRI) data to analyze the crossmodal neural network.

These preexisting neural connections provide an important starting point for training visually impaired people to use devices that will help them see. A sighted person simply has to open their eyes, and the brain automatically processes images and information for seamless interaction with the environment.

Current devices for the blind and visually impaired are not so automatic or intuitive to use, generally requiring a user's full concentration and attention to interpret information about the environment. The Shimojo lab's new finding on the role of multimodal processing and crossmodal mappings starts to address this issue.

Beyond its practical implications, Shimojo says, the research raises an important philosophical question: What is seeing?

"It seems like such an obvious question, but it gets complicated," says Shimojo. "Is seeing what happens when you open your eyes? No, because opening your eyes is not enough if the retina [the light-sensitive layer of tissue in the eye] is damaged. Is it when your visual cortex is activated? But our research has shown that the visual cortex can be activated by sound, indicating that we don't really need our eyes to see. It's very profound - we're trying to give blind people a visual experience through other senses."

The paper is titled "Auditory Sensory Substitution Is Intuitive and Automatic with Texture Stimuli" and was funded by grants from the National Science Foundation, the Della Martin Fund for Discoveries in Mental Illness, and the Japan Science and Technology Agency, Core Research for Evolutional Science and Technology.