University of Washington (UW) scientists have built a new nanometer-sized laser — using the thinnest semiconductor available today — that is energy efficient, easy to build, and compatible with existing electronics.
The UW nanolaser, developed in collaboration with Stanford University, uses a tungsten-based semiconductor only three atoms thick as light emitter.
The technology is described in a paper published in the March 16 online edition of Nature.
Nanolasers — which are so small they can’t be seen with the eye — have the potential to be used in a wide range of applications from next-generation computing to implantable microchips that monitor health problems.
But current nanolaser designs use materials that are either much thicker or that are embedded in the structure of the cavity that captures light. That makes them difficult to build and to integrate with modern electronic circuits and computing technologies.
The UW version, instead, uses a flat sheet that can be placed directly on top of a commonly used optical cavity, a tiny cave that confines and intensifies light. The ultrathin nature of the semiconductor — made from a single layer of a tungsten-based molecule — yields efficient coordination between the two key components of the laser.
The UW nanolaser requires only 27 nanowatts, which is very energy efficient, can be easily fabricated, and it can potentially work with silicon components common in modern electronics.
Researchers at Tianjin University in China, Oak Ridge National Laboratory, the University of Tennessee, Humboldt University in Berlin and the University of Hong Kong where also involved.
Primary funding came from the Air Force Office of Scientific Research. Other funders include the National Science Foundation, the state of Washington through the Clean Energy Institute, the Presidential Early Award for Scientists and Engineers administered through the Office of Naval Research, the U.S. Department of Energy, and the European Commission.
How to bend light around ultra-tiny corners
Another problem with using photonics (light-based electronics), in interconnects between chips, for example, is the difficulty in steering light around corners in tiny spaces.
Sending information on light beams instead of electrical signals allows data to be transmitted thousands of times more quickly, but controlling the light beams without losing their energy has been the challenge. Conventional light waveguides, like optical fibers, can be used to steer light through turns. But the turns must be gradual. If the turn is too quick, the light beams escape and energy is lost.
So researchers at the University of Texas El Paso (UTEP) and the University of Central Florida (UCF) developed a plastic honeycomb-like device that can steer light beams around tighter curves than ever before possible, opening up new possibilities for high-speed light-based data transmission in computers, smartphones, and other devices.
The device is based on “spatially variant photonic crystals” (SVPCs), in which the orientation of the 3D-printed “honeycomb” cell gradually changes. This allows for directing the flow of infrared light around a 90 degree bend.
The work was published in an open-access article in the journal Optics Express and was supported by NSF CAREER Awards, NSF grants, and DARPA.
Abstract of Monolayer semiconductor nanocavity lasers with ultralow thresholds
Ellis, B. et al. Ultralow-threshold electrically pumped quantum-dot photonic-crystal nanocavity laser. Nature Photon. 5, 297-300 (2011)”>Engineering the electromagnetic environment of a nanometre-scale light emitter by use of a photonic cavity can significantly enhance its spontaneous emission rate, through cavity quantum electrodynamics in the Purcell regime. This effect can greatly reduce the lasing threshold of the emitter, providing a low-threshold laser system with small footprint, low power consumption and ultrafast modulation. An ultralow-threshold nanoscale laser has been successfully developed by embedding quantum dots into a photonic crystal cavity (PCC). However, several challenges impede the practical application of this architecture, including the random positions and compositional fluctuations of the dots, extreme difficulty in current injection, and lack of compatibility with electronic circuits. Here we report a new lasing strategy: an atomically thin crystalline semiconductor—that is, a tungsten diselenide monolayer—is non-destructively and deterministically introduced as a gain medium at the surface of a pre-fabricated PCC. A continuous-wave nanolaser operating in the visible regime is thereby achieved with an optical pumping threshold as low as 27 nanowatts at 130 kelvin, similar to the value achieved in quantum-dot PCC lasers. The key to the lasing action lies in the monolayer nature of the gain medium, which confines direct-gap excitons to within one nanometre of the PCC surface. The surface-gain geometry gives unprecedented accessibility and hence the ability to tailor gain properties via external controls such as electrostatic gating and current injection, enabling electrically pumped operation. Our scheme is scalable and compatible with integrated photonics for on-chip optical communication technologies.
Abstract of Tight control of light beams in photonic crystals with spatially-variant lattice orientation
Spatially-variant photonic crystals (SVPCs), in which the orientation of the unit cell changes as a function of position, are shown to be capable of abruptly controlling light beams using just low index materials and can be made to have high polarization selectivity. Multi-photon direct laser writing in the photo-polymer SU-8 was used to fabricate three-dimensional SVPCs that direct the flow of light around a 90 degree bend. The lattice spacing and fill factor were maintained nearly constant throughout the structure. The SVPCs were characterized at a wavelength of 2.94 μm by scanning the faces with optical fibers and the results were compared to electromagnetic simulations. The lattices were shown to direct infrared light of one polarization through sharp bends while the other polarization propagated straight through the SVPC. This work introduces a new scheme for controlling light that should be useful for integrated photonics.
Researchers at University of Texas at Dallas (UT Dallas) have created a material made from nanofibers that can stretch to up to seven times its length while remaining tougher than Kevlar.
These structures absorb up to 98 joules per gram. Kevlar, often used to make bulletproof vests, can absorb up to 80 joules per gram. The researchers hope the structures will one day form material that can reinforce itself at points of high stress and could potentially be used in military airplanes or other defense applications.
In a study published by ACS Applied Materials and Interfaces, a journal of the American Chemical Society, researchers twisted nanofiber into yarns and coils. The electricity generated by stretching the twisted nanofiber formed an attraction ten times stronger than a hydrogen bond, which is considered one of the strongest forces formed between molecules.
Researchers sought to mimic their earlier work on the piezoelectric action (how pressure forms electric charges) of collagen fibers found inside bone in hopes of creating high-performance materials that can reinforce itself, said Dr. Majid Minary, an assistant professor of mechanical engineering in the University’s Erik Jonsson School of Engineering and Computer Science and senior author of the study.
“We reproduced this process in nanofibers by manipulating the creation of electric charges to result in a lightweight, flexible, yet strong material,” said Minary, who is also a member of the Alan G. MacDiarmid NanoTech Institute. “Our country needs such materials on a large scale for industrial and defense applications.”
For their experiment, researchers first spun nanofibers out PVDF and its co-polymer, polyvinvylidene fluoride trifluoroethylene (PVDF-TrFE). Researchers then twisted the fibers into yarns, and then continued to twist the material into coils.
Researchers then measured mechanical properties of the yarn and coils, such as how far it can stretch and how much energy it can absorb before failure.
“Our experiment is proof of the concept that our structures can absorb more energy before failure than the materials conventionally used in bulletproof armors,” Minary said. “We believe, modeled after the human bone, that this flexibility and strength comes from the electricity that occurs when these nanofibers are twisted.”
The next step in the research is to make larger structures out of the yarns and coils, Minary said.
A Texas A&M University engineer also participated in the work, which was funded by the Air Force Office of Scientific Research Young Investigator Research Program and the National Science Foundation.
Abstract of High-Performance Coils and Yarns of Polymeric Piezoelectric Nanofibers
We report on highly stretchable piezoelectric structures of electrospun PVDF-TrFE nanofibers. We fabricated nanofibrous PVDF-TrFE yarns via twisting their electrospun ribbons. Our results show that the twisting process not only increases the failure strain but also increases overall strength and toughness. The nanofibrous yarns achieved a remarkable energy to failure of up to 98 J/g. Through overtwisting process, we fabricated polymeric coils out of twisted yarns that stretched up to ∼740% strain. This enhancement in mechanical properties is likely induced by increased interactions between nanofibers, contributed by friction and van der Waals interactions, as well as favorable surface charge (Columbic) interactions as a result of piezoelectric effect, for which we present a theoretical model. The fabricated yarns and coils show great promise for applications in high-performance lightweight structural materials and superstretchable piezoelectric devices and flexible energy harvesting applications.
High-performance computing and genetic engineering could boost crop photosynthetic efficiency enough to feed a planet expected to have 9.5 billion people on it by 2050, researchers report in an open-access paper in the journal Cell.
“We now know every step in the processes that drive photosynthesis in plants such as soybeans and maize,” said University of Illinois plant biology professor Stephen P. Long, who wrote the report with colleagues from Illinois and the CAS-MPG Partner Institute of Computational Biology in Shanghai.
“We have unprecedented computational resources that allow us to model every stage of photosynthesis and determine where the bottlenecks are, and advances in genetic engineering will help us augment or circumvent those steps that impede efficiency. Long suggested several strategies.
Add pigments. “Our lab and others have put a gene from cyanobacteria into crop plants and found that it boosts the photosynthetic rate by 30 percent. ” But Long says we could improve that. “Some bacteria and algae contain pigments that utilize more of the solar spectrum than plant pigments do. If added to plants, those pigments could bolster the plants’ access to solar energy.
Add the blue-green algae system. Some scientists are trying to engineer C4 photosynthesis in C3 plants, but this means altering plant anatomy, changing the expression of many genes and inserting new genes from C4 plants, Long said.
“Another, possibly simpler approach is to add to the C3 chloroplast the system used by blue-green algae,” he said. This would increase the activity of Rubisco, an enzyme that catalyzes a vital step of the conversion of atmospheric carbon dioxide into plant biomass. Computer models suggest adding this system would increase photosynthesis as much as 60 percent, according to Long.
More sunlight for lower leaves. Computer analyses of the way plant leaves intercept sunlight have revealed other ways to improve photosynthesis. Many plants intercept too much light in their topmost leaves and too little in lower leaves; this probably allows them to outcompete their neighbors, but in a farmer’s field such competition is counterproductive, Long said. Studies headed by U. of I. plant biology professor Donald Ort aim to make plants’ upper leaves lighter, allowing more sunlight to penetrate to the light-starved lower leaves.
Eliminate traffic jams. “The computer model predicts that by altering this system by up-regulating some genes and down-regulating others, a 60 percent improvement could be achieved without any additional resource — so 60 percent more carbon could be assimilated for no more nitrogen,” Long said.
In silico simulation. “The next step is to create an in silico plant to virtually simulate the amazingly complex interactions among biological scales,” said U. of I. plant biology professor Amy Marshall-Colon, a co-author on the report. “This type of model is essential to fill current gaps in knowledge and better direct our engineering efforts.”
30 years lead time
The work should be undertaken now, Long said. “If we have a success today, it won’t appear in farmers’ fields for 15 years at the very earliest,” he said. “We have to be doing today what we may need in 30 years.”
Funding for this work was provided by the Bill & Melinda Gates Foundation, the U.S. Department of Agriculture, the National Science Foundation, and the Chinese Academy of Sciences.
Abstract of Meeting the Global Food Demand of the Future by Engineering Crop Photosynthesis and Yield Potential
Increase in demand for our primary foodstuffs is outstripping increase in yields, an expanding gap that indicates large potential food shortages by mid-century. This comes at a time when yield improvements are slowing or stagnating as the approaches of the Green Revolution reach their biological limits. Photosynthesis, which has been improved little in crops and falls far short of its biological limit, emerges as the key remaining route to increase the genetic yield potential of our major crops. Thus, there is a timely need to accelerate our understanding of the photosynthetic process in crops to allow informed and guided improvements via in-silico-assisted genetic engineering. Potential and emerging approaches to improving crop photosynthetic efficiency are discussed, and the new tools needed to realize these changes are presented.
…Young Entrepreneur award. Karoli is also an alumnus of Singularity University. The American industrialist Henry Ford, regarding diminishing customer…
Researchers at MIT and Stanford University have developed a new kind of solar cell that combines two different layers of sunlight-absorbing material to harvest a broader range of the sun’s energy. The development could lead to photovoltaic cells that are more efficient than those currently used in solar-power installations, the researchers say.
The new cell uses a layer of silicon — which forms the basis for most of today’s solar panels — but adds a semi-transparent layer of a material called perovskite*, which can absorb higher-energy particles of light. Unlike an earlier “tandem” solar cell reported by members of the same team earlier this year — in which the two layers were physically stacked, but each had its own separate electrical connections — the new version has both layers connected together as a single device that needs only one control circuit.
The new findings are reported in the open-access paper in the journal Applied Physics Letters by MIT graduate student Jonathan Mailoa; associate professor of mechanical engineering Tonio Buonassisi; Colin Bailie and Michael McGehee at Stanford; and four others.
Simpler to make and install
“Different layers absorb different portions of the sunlight,” Mailoa explains. In the earlier tandem solar cell, the two layers of photovoltaic material could be operated independently of each other and required their own wiring and control circuits, allowing each cell to be tuned independently for optimal performance.
By contrast, the new combined version should be much simpler to make and install, Mailoa says. “It has advantages in terms of simplicity, because it looks and operates just like a single silicon cell,” he says, with only a single electrical control circuit needed.
Perovskites have been studied for potential electronic uses including solar cells, but this is the first time they have been successfully paired with silicon cells in this configuration, a feat that posed numerous technical challenges.
Now the team is focusing on increasing the power efficiency — the percentage of sunlight’s energy that gets converted to electricity — that is possible from the combined cell. In this initial version, the efficiency is 13.7 percent, but the researchers say they have identified low-cost ways of improving this to about 30 percent — a substantial improvement over today’s commercial silicon-based solar cells — and they say this technology could ultimately achieve a power efficiency of more than 35 percent.
They will also explore how to easily manufacture the new type of device, but Buonassisi says that should be relatively straightforward, since the materials lend themselves to being made through methods very similar to conventional silicon-cell manufacturing.
One hurdle is making the material durable enough to be commercially viable: The perovskite material degrades quickly in open air, so it either needs to be modified to improve its inherent durability or encapsulated to prevent exposure to air — without adding significantly to manufacturing costs and without degrading performance.
The research was supported by the Bay Area Photovoltaic Consortium and the U.S. Department of Energy.
* As KurzweilAI has noted, the versatile perovskite material has also been used for harvesting hydrogen fuel from sunlight and water at lower cost, in lower-cost high-brightness LEDs, as an infrared superlens, and in future chips that operate at atomic dimensions.
Abstract of A 2-terminal perovskite/silicon multijunction solar cell enabled by a silicon tunnel junction
With the advent of efficient high-bandgap metal-halide perovskite photovoltaics, an opportunity exists to make perovskite/silicon tandem solar cells. We fabricate a monolithic tandem by developing a silicon-based interband tunnel junction that facilitates majority-carrier charge recombination between the perovskite and silicon sub-cells. We demonstrate a 1 cm2 2-terminal monolithic perovskite/silicon multijunction solar cell with a V OC as high as 1.65 V. We achieve a stable 13.7% power conversion efficiency with the perovskite as the current-limiting sub-cell, and identify key challenges for this device architecture to reach efficiencies over 25%.
In a broad new assessment of the status and prospects of solar photovoltaic technology, MIT researchers say that it is “one of the few renewable, low-carbon resources with both the scalability and the technological maturity to meet ever-growing global demand for electricity.”
Use of solar photovoltaics has been growing at a phenomenal rate: Worldwide installed capacity has seen sustained growth averaging 43 percent per year since 2000. To evaluate the prospects for sustaining such growth, the MIT researchers look at possible constraints on materials availability, and propose a system for evaluating the many competing approaches to improved solar-cell performance.
The analysis is presented in the journal Energy & Environmental Science. A broader analysis of solar technology, economics, and policy will be incorporated in a forthcoming assessment of the future of solar energy by the MIT Energy Initiative.
The team comprised MIT professors Vladimir Bulović, Tonio Buonassisi, and Robert Jaffe, and graduate students Joel Jean and Patrick Brown. One useful factor in making meaningful comparisons among new photovoltaic technologies, they conclude, is the complexity of the light-absorbing material.
The report divides the many technologies under development into three broad classes: wafer-based cells, which include traditional crystalline silicon, as well as alternatives such as gallium arsenide; commercial thin-film cells, including cadmium telluride and amorphous silicon; and emerging thin-film technologies, which include perovskites, organic materials, dye-sensitized solar cells, and quantum dots.
With the recent evolution of solar technology, says Jean, the paper’s lead author, it’s important to have a uniform framework for assessment. It may be time, he says, to re-examine the traditional classification of these technologies, generally into three areas: silicon wafer-based cells, thin-film cells, and “exotic” technologies with high theoretical efficiencies.
“We’d like to build on the conventional framework,” says Jean, a doctoral student in MIT’s Department of Electrical Engineering and Computer Science. “We’re seeking a more consistent way to think about the wide range of current photovoltaic technologies and to evaluate them for potential applications. In this study, we chose to evaluate all relevant technologies based on their material complexity.”
Under this scheme, traditional silicon — a single-element crystalline material — is the simplest material. While crystalline silicon is a mature technology with advantages including high efficiency, proven reliability, and no material scarcity constraints, it also has inherent limitations: Silicon is not especially efficient at absorbing light, and solar panels based on silicon cells tend to be rigid and heavy. At the other end of the spectrum are perovskites, organics, and colloidal quantum dots, which are “highly complex materials, but can be much simpler to process,” Jean says.
The authors make clear that their definition of material complexity as a key parameter for comparison does not imply any equivalency with complexity of manufacturing. On the contrary, while silicon is the simplest solar-cell material, silicon wafer and cell production is complex and expensive, requiring extraordinary purity and high temperatures.
By contrast, while some complex nanomaterials involve intricate molecular structures, such materials can be deposited quickly and at low temperatures onto flexible substrates. Nanomaterial-based cells could even be transparent to visible light, which could open up new applications and enable seamless integration into windows and other surfaces. The authors caution, however, that the conversion efficiency and long-term stability of these complex emerging technologies is still relatively low.
As they write in the paper: “The road to broad acceptance of these new technologies in conventional solar markets is inevitably long, although the unique qualities of these evolving solar technologies — lightweight, paper-thin, transparent — could open entirely new markets, accelerating their adoption.”
The study does caution that the large-scale deployment of some of today’s thin-film technologies, such as cadmium telluride and copper indium gallium diselenide, may be severely constrained by the amount of rare materials that they require. The study highlights the need for novel thin-film technologies that are based on Earth-abundant materials.
Future R&D themes
The study identifies three themes for future research and development:
- Increasing the power-conversion efficiency of emerging photovoltaic technologies and commercial modules.
- Reducing the amount of material needed per cell. Thinner, more flexible films and substrates could reduce cell weight and cost, potentially opening the door to new approaches to photovoltaic module design.
- Reducing the complexity and cost of manufacturing. Here the researchers emphasize the importance of eliminating expensive, high-temperature processing, and encouraging the adoption of roll-to-roll coating processes for rapid, large-scale manufacturing of emerging thin-film technologies.
“We’ve looked at a number of key metrics for different applications,” Jean says. “We don’t want to rule out any of the technologies,” he says — but by providing a unified framework for comparison, he says, the researchers hope to make it easier for people to make decisions about the best technologies for a given application.
Martin Green, a professor at the Australian Centre for Advanced Photovoltaics at the University of New South Wales who was not involved in this work, says the MIT team has produced “some interesting new insights and observations.” He says the paper’s main significance “lies in the attempt to take a unifying look at the issues involved in choosing between PV technologies.”
“The issues involved are complex,” Green adds, “and the authors abstain from betting on any particular PV technology.”
Abstract of Pathways for solar photovoltaics
Solar energy is one of the few renewable, low-carbon resources with both the scalability and the technological maturity to meet ever-growing global demand for electricity. Among solar power technologies, solar photovoltaics (PV) are the most widely deployed, providing 0.87% of the world’s electricity in 2013 and sustaining a compound annual growth rate in cumulative installed capacity of 43% since 2000. Given the massive scale of deployment needed, this article examines potential limits to PV deployment at the terawatt scale, emphasizing constraints on the use of commodity and PV-critical materials. We propose material complexity as a guiding framework for classifying PV technologies, and we analyze three core themes that focus future research and development: efficiency, materials use, and manufacturing complexity and cost.
Rice University scientists have found that the carbon nanotube fibers they developed for aerospace are superior to metal and plain-carbon electrodes for deep brain stimulation for neurological disorders such as Parkinson’s and for brain-machine interfaces to neural circuits in the brain.
The individual nanotubes measure only a few nanometers across, but when millions are bundled in a process called wet spinning, they become thread-like fibers about a quarter the width of a human hair.
Strong as metal but soft as silk and highly conductive
“We developed these fibers as high-strength, high-conductivity materials” for aerospace applications, where strength, weight and conductivity are paramount, said co-developer Matteo Pasquali, a chemist and chemical engineer.
“Yet, once we had them in our hand, we realized that they had an unexpected property: They are really soft, much like a thread of silk. Their unique combination of strength, conductivity and softness makes them ideal for interfacing with the electrical function of the human body.”
Pudding-compatible design may revolutionize brain implants
“The brain is basically the consistency of pudding and doesn’t interact well with stiff metal electrodes,” said Caleb Kemere, a Rice assistant professor who brought expertise in animal models of Parkinson’s disease. “The dream is to have electrodes with the same consistency [as the brain], and that’s why we’re really excited about these flexible carbon nanotube fibers and their long-term biocompatibility.”
Tests on cells and then in rats with Parkinson’s symptoms proved several advantages for the fibers:
- They are stable and as efficient as commercial platinum electrodes at only a fraction of the thickness.
- The soft fibers caused little inflammation, which helped maintain strong electrical connections to neurons by preventing the body’s defenses from scarring and encapsulating the site of the injury.
- The highly conductive carbon nanotube fibers show much more favorable impedance (similar to resistance) than state-of-the-art metal electrodes, allowing for use of lower voltages.
- The working end of the fiber is the exposed tip, which is about the width of a neuron. The rest is encased with a three-micron layer of a flexible, biocompatible polymer with excellent insulating properties.
- Doctors who implant deep brain stimulation devices start with a recording probe able to “listen” to neurons that emit characteristic signals depending on their functions, Kemere said. Once a surgeon finds the right spot, the probe is removed and the stimulating electrode gently inserted, but it’s “too big to detect any spiking activity, so basically the clinical devices send continuous pulses regardless of the response of the brain.” The new carbon nanotube fibers simplify implantation because they can do both functions (send and receive signals),
Kemere foresees a closed-loop system that can read neuronal signals and adapt stimulation therapy in real time. He anticipates building a device with many electrodes that can be addressed individually to gain fine control over stimulation and monitoring from a small, implantable device.
The Welch Foundation, the National Science Foundation, and the Air Force Office of Scientific Research supported the research.Abstract of Neural Stimulation and Recording with Bidirectional, Soft Carbon Nanotube Fiber Microelectrodes
The development of microelectrodes capable of safely stimulating and recording neural activity is a critical step in the design of many prosthetic devices, brain machine interfaces and therapies for neurologic or nervous-system-mediated disorders. Metal electrodes are inadequate prospects for the miniaturization needed to attain neuronal-scale stimulation and recording because of their poor electrochemical properties, high stiffness and propensity to fail due to bending fatigue. Here we demonstrate neural recording and stimulation using carbon nanotube (CNT) fiber electrodes. In vitro characterization shows that the tissue contact impedance of CNT fibers is remarkably lower than state-of-the-art metal electrodes, making them suitable for recording single neuron activity without additional surface treatments. In vivo chronic studies in parkinsonian rodents show that CNT fiber microelectrodes stimulate neurons as effectively as metal electrodes with ten times larger surface area, while eliciting a significantly reduced inflammatory response. The same CNT fiber microelectrodes can record neural activity for weeks, paving the way for the development of novel multifunctional, dynamic neural interfaces with long-term stability.
In a letter of commitment presented to President Barack Obama at the White House Science Fair Monday, more than 120 U.S. engineering schools announced plans to educate a new generation of engineers expressly equipped to tackle some of the most pressing issues facing society in the 21st century.
These “Grand Challenges,” identified through initiatives such as the White House Strategy for American Innovation, the National Academy of Engineering (NAE) Grand Challenges for Engineering, and the United Nations Millennium Development Goals, include complex yet critical goals such as engineering better medicines, making solar energy cost-competitive with coal, securing cyberspace, and advancing personalized learning tools to deliver better education to more individuals.
Each of the 122 signing schools has pledged to graduate a minimum of 20 students per year who have been specially prepared to lead the way in solving such large-scale problems, with the goal of training more than 20,000 formally recognized “Grand Challenge Engineers” over the next decade.
Grand Challenge Engineers will be trained through special programs at each institution that integrate five educational elements: (1) a hands-on research or design project connected to the Grand Challenges; (2) real-world, interdisciplinary experiential learning with clients and mentors; (3) entrepreneurship and innovation experience; (4) global and cross-cultural perspectives; and (5) service-learning.
The training model was inspired by the National Academy of Engineering-endorsed Grand Challenge Scholars Program (GCSP), established in 2009 by Duke’s Pratt School of Engineering, Olin College, and the University of Southern California’s Viterbi School of Engineering in response to the NAE’s 14 Grand Challenges for Engineering in the 21st century.
There are currently 20 active GCSPs and more than 160 NAE-designated Grand Challenge Scholars have graduated to date. Half of the graduates are women—compared with just 19 percent of U.S. undergraduate engineering students—demonstrating the program’s appeal to groups typically underrepresented in engineering.
Examples of GCSP participants working on Grand Challenges include: Alex Caven at the State University of New York (SUNY), who is involved in efforts to provide access to clean water in Haiti; Michaela Rikard, who is working on engineering better medicines at North Carolina State University; Allison Kindig at Iowa State, who is creating sustainable engineering projects in developing countries; and Olin College’s Luke Metz, who is engineering computerized writing aids to advance personalized learning.
More information on this initiative, including a copy of the letter of commitment, is available here.
Imagine being able to download a full-length 8GB HD movie to your phone in six seconds (versus seven minutes over 4G or more than an hour on 3G) and video chats so immersive that it will feel like you can reach out and touch the other person right through the screen.
That’s the vision for the 5G concept — the next generation of wireless networks — presented at the Mobile World Congress show last week, according to re/code. Here’s what it will offer:
- Significantly faster data speeds: 10Gbps, compared to one gigabit per second (max) with 4G.
- Ultra-low latency (time to send a packet): one millisecond vs. 50 with 4G — particularly important for industrial applications and driverless cars.
- A more “connected world”: The Internet of Things (wearables, smart home appliances, connected cars) will need a network that can accommodate billions of connected devices. Part of the goal behind 5G is to provide that capacity, and also to be able to assign bandwidth depending on the needs of the application and user.
“Ulrich Dropmann, head of industry environment networks at Nokia, gave a scenario where you might be cruising in your driverless car when, unbeknownst to you, a crash has just occurred up the road,” says re/code. “With 5G, sensors placed along the road would be able to instantly relay that information back to your car (this is where having low latency is important), so it could brake earlier and avoid another accident.”
So when might it be here? “The most optimistic targets would see the first commercial network up and running by 2020, but even that may be too optimistic. As with LTE, it will take years for the network to become widespread.”
Scientists have coaxed stem cells to grow the first three-dimensional human mini lungs, or organoids, to help scientists learn more about lung diseases and test new drugs.
Previous research has focused on deriving lung tissue from flat (2D) cell systems or growing cells onto scaffolds made from donated organs.
“These mini lungs can mimic the responses of real tissues and will be a good model to study how organs form, change with disease, and how they might respond to new drugs,” says senior study author Jason R. Spence, Ph.D., assistant professor of internal medicine and cell and developmental biology at the University of Michigan Medical School.
In an open-access study published in the online journal eLife, the scientists decscribe how they succeeded in growing structures resembling both the large airways known as bronchi and small lung sacs called alveoli.
Since the mini lung structures were developed in a dish, they lack several components of the human lung, including blood vessels, which are a critical component of gas exchange during breathing. But the organoids may still serve as a discovery tool for researchers as they turn basic science ideas into clinical innovations. The idea is to use the 3D structures as a next step up from (or complement to) animal research.
Cell behavior has traditionally been studied in the lab in 2D situations where cells are grown in thin layers on cell-culture dishes. But most cells in the body exist in a three-dimensional environment as part of complex tissues and organs. The advantage of growing 3-D structures of lung tissue, Spence says, is that their organization bears greater similarity to the human lung.
How to make a human lung organoid in a dish
To make these lung organoids, researchers at the U-M’s Spence Lab and colleagues from the University of California, San Francisco; Cincinnati Children’s Hospital Medical Center; Seattle Children’s Hospital, and University of Washington manipulated several of the signaling pathways that control the formation of organs:
- Stem cells were instructed to form a type of tissue called endoderm, found in early embryos and that gives rise to the lung, liver and several other internal organs.
- Scientists activated important development pathways that are known to make endoderm form three-dimensional tissue while inhibiting two other key development pathways at the same time.
- The endoderm became tissue that resembles the early lung found in embryos.
- This early lung-like tissue spontaneously formed three-dimensional spherical structures as it developed.
- To make these structures expand and develop into lung tissue, the team exposed the cells to additional proteins that are involved in lung development.
- The resulting lung organoids survived in the lab for more than 100 days.
“We expected different cells types to form, but their organization into structures resembling human airways was a very exciting result,” says lead study author Briana Dye, a graduate student in the U-M Department of Cell and Developmental Biology.
The research is supported by the National Heart, Lung and Blood Institute (NHLBI), the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), the March of Dimes and the U-M’s Center for Organogenesis and Biological Sciences Scholars Program (BSSP).
Abstract of In vitro generation of human pluripotent stem cell derived lung organoids
Recent breakthroughs in 3-dimensional (3D) organoid cultures for many organ systems have led to new physiologically complex in vitro models to study human development and disease. Here, we report the step-wise differentiation of human pluripotent stem cells (hPSCs) (embryonic and induced) into lung organoids. By manipulating developmental signaling pathways hPSCs generate ventral-anterior foregut spheroids, which are then expanded into human lung organoids (HLOs). HLOs consist of epithelial and mesenchymal compartments of the lung, organized with structural features similar to the native lung. HLOs possess upper airway-like epithelium with basal cells and immature ciliated cells surrounded by smooth muscle and myofibroblasts as well as an alveolar-like domain with appropriate cell types. Using RNA-sequencing, we show that HLOs are remarkably similar to human fetal lung based on global transcriptional profiles, suggesting that HLOs are an excellent model to study human lung development, maturation and disease.
Physicists from MIT and the University of Belgrade have developed a new technique that can entangle 2,910 atoms using only a single photon — the largest number of particles that have ever been mutually entangled experimentally (previous record: 100).
The researchers say the technique provides a realistic method to generate large ensembles of entangled atoms, which are key components for realizing more-precise atomic clocks and more powerful computers.
“You can make the argument that a single photon cannot possibly change the state of 3,000 atoms, but this one photon does — it builds up correlations that you didn’t have before,” says Vladan Vuletic, the Lester Wolfe Professor in MIT’s Department of Physics, and the paper’s senior author. “We have basically opened up a new class of entangled states we can make, but there are many more new classes to be explored.”
The entanglement concept was first proposed in a 1935 paper by Albert Einstein, Boris Podolsky and Nathan Rosen: two or more particles may be correlated in such a way that any change to one will simultaneously change the other, no matter how far apart they may be. For instance, if one atom in an entangled pair were somehow made to spin clockwise, the other atom would instantly be known to spin counterclockwise, even though the two may be physically separated by thousands of miles.
The idea was dismissed by Einstein as “”spooky action at a distance,” but in a paper published yesterday (March 24) in Nature Communications, researchers at Griffith University and the University of Tokyo reported measurements that confirm non-local collapse of a particle’s wave function. The scientists used homodyne detectors — which measure wave-like properties — to confirm splitting of a single photon between two laboratories.
Scientists have been searching for ways to entangle large numbers of atoms, which could be the basis for powerful quantum computers and more-precise atomic clocks.
Picking up quantum noise
Scientists have so far been able to entangle large groups of atoms, although most attempts have only generated entanglement between pairs in a group. Only one team has successfully entangled 100 atoms — the largest mutual entanglement to date, and only a small fraction of the whole atomic ensemble.
Now Vuletic and his colleagues have successfully created a mutual entanglement among 2,910 atoms, virtually all the atoms in the 3,100 atoms ensemble, using very weak laser light — down to pulses containing a single photon. The weaker the light, the better, Vuletic says, as it is less likely to disrupt the cloud. “The system remains in a relatively clean quantum state,” he says.
The researchers first cooled a cloud of atoms, then trapped them in a laser trap, and sent a weak laser pulse through the cloud. They then set up a detector to look for a particular photon within the beam. Vuletic reasoned that if a photon has passed through the atom cloud without event, its polarization, or direction of oscillation, would remain the same.
If, however, a photon has interacted with the atoms, its polarization rotates just slightly — a sign that it was affected by quantum “noise” in the ensemble of spinning atoms, with the noise being the difference in the number of atoms spinning clockwise and counterclockwise.
“Every now and then, we observe an outgoing photon whose electric field oscillates in a direction perpendicular to that of the incoming photons,” Vuletic says. “When we detect such a photon, we know that must have been caused by the atomic ensemble, and surprisingly enough, that detection generates a very strongly entangled state of the atoms.”
Vuletic and his colleagues are currently using the single-photon detection technique to build a state-of-the-art atomic clock* that they hope will overcome what’s known as the “standard quantum limit” — a limit to how accurate measurements can be in quantum systems. Vuletic says the group’s current setup may be a step toward developing even more complex entangled states.
“This particular state can improve atomic clocks by a factor of two,” Vuletic says. “We’re striving toward making even more complicated states that can go further.”
This research was supported in part by the National Science Foundation, the Defense Advanced Research Projects Agency, and the Air Force Office of Scientific Research.
* Today’s best atomic clocks are based on the natural oscillations within a cloud of trapped atoms. As the atoms oscillate, they act as a pendulum, keeping steady time. A laser beam within the clock, directed through the cloud of atoms, can detect the atoms’ vibrations, which ultimately determine the length of a single second.
The accuracy of atomic clocks improves as more and more atoms oscillate in a cloud. Conventional atomic clocks’ precision is proportional to the square root of the number of atoms: For example, a clock with nine times more atoms would only be three times as accurate. If these same atoms were entangled, a clock’s precision could be directly proportional to the number of atoms — in this case, nine times as accurate. The larger the number of entangled particles, then, the better an atomic clock’s timekeeping.
UPDATE 3/25/2015: Added mention of research confirming the entanglement theory.
Abstract of Entanglement with negative Wigner function of almost 3,000 atoms heralded by one photon
Quantum-mechanically correlated (entangled) states of many particles are of interest in quantum information, quantum computing and quantum metrology. Metrologically useful entangled states of large atomic ensembles have been experimentally realized, but these states display Gaussian spin distribution functions with a non-negative Wigner quasiprobability distribution function. Non- Gaussian entangled states have been produced in small ensembles of ions, and very recently in large atomic ensembles. Here we generate entanglement in a large atomic ensemble via the interaction with a very weak laser pulse; remarkably, the detection of a single photon prepares several thousand atoms in an entangled state. We reconstruct a negative-valued Wigner function—an important hallmark of non-classicality—and verify an entanglement depth (the minimum number of mutually entangled atoms) of 2,910 ± 190 out of 3,100 atoms. Attaining such a negative Wigner function and the mutual entanglement of virtually all atoms is unprecedented for an ensemble containing more than a few particles. Although the achieved purity of the state is slightly below the threshold for entanglement- induced metrological gain, further technical improvement should allow the generation of states that surpass this threshold, and of more complex Schrödinger cat states for quantum metrology and information processing. More generally, our results demonstrate the power of heralded methods for entanglement generation, and illustrate how the information contained in a single photon can drastically alter the quantum state of a large system.
A method of using light to activate or suppress neurons without requiring genetic modification (as in optogenetics) has been developed by scientists from the University of Chicago and the University of Illinois at Chicago.
The new technique, described in the journal Neuron, uses targeted, heated gold nanoparticles. The researchers says it’s a significant technological advance with potential advantages over current optogenetic methods, including possible use in the development of therapeutics for diseases such as macular degeneration.
“This is effectively optogenetics without genetics,” said study senior author Francisco Bezanilla, PhD, Lillian Eichelberger Cannon Professor of biochemistry and molecular biology at the University of Chicago. “Many optogenetic experimental designs can now be applied to completely normal tissues or animals, greatly extending the scope of these research tools and possibly allowing for new therapies involving neuronal photostimulation.”
How it works
Optogenetics, the use of light to control neural activity, is a powerful technique with widespread use in neuroscience research. It involves genetically engineered neurons that express a light-responsive protein originally discovered in algae. This process allows scientists to stimulate individual neurons as well as neural networks with precise flashes of light. However, since optogenetics is reliant on genetic modification, its use is primarily limited to relatively few model organisms.
Bezanilla and his colleagues have previously shown that normal, non-genetically modified neurons can be activated by heat generated from pulses of near-infrared light. But this method lacked specificity and can damage cells.
To improve the technique, they used gold nanoparticles — spheres only 20 nanometers in diameter. When stimulated with visible light, spherical gold nanoparticles absorb and convert light energy into heat. This heating effect can activate unmodified neurons. However, nanoparticles must be extremely close to a cell to produce any effect. Since the nanoparticles diffuse quickly, or get washed away in a neuron’s immediate environment, their efficacy is short-lived.
Making gold nanoparticles sticky
To get nanoparticles to stick, Bezanilla and his team coupled them to a synthetic molecule based on Ts1, a scorpion neurotoxin, which binds to sodium channels without blocking them. Neurons treated with Ts1-coupled nanoparticles in culture were readily activated by light. Untreated neurons were non-responsive.
Importantly, treated neurons could still be stimulated even after being continuously washed for 30 minutes, indicating that the nanoparticles were tightly bound to the cell surface. This also minimized potentially harmful elevated temperatures, as excess nanoparticles were washed away.
Neurons treated with Ts1-coupled nanoparticles could be stimulated repeatedly with no evidence of cell damage. Some individual neurons, targeted with millisecond pulses of light, produced more than 3,000 action potentials (spikes) over the span of 30 minutes, with no reduction in efficacy. In addition to cultured cells, Ts1-coupled nanoparticles were tested on complex brain tissue using thin slices of mouse hippocampus. In these experiments, the researchers were able to activate groups of neurons and then observe the resulting patterns of neural activity.
“The technique is easy to implement and elicits neuronal activity using light pulses. Therefore, stimulating electrodes are not required,” Bezanilla said. “Furthermore, with differently-shaped nanoparticles it can work in near-infrared as well as in visible wavelengths, which has many practical advantages in living animals. Thus far, most optogenetic tools have been limited to visible wavelengths.”
While Ts1 was effective, it did not allow the stimulation of non-Ts1-responsive neuronal populations. To develop a more general strategy of cell targeting, the researchers coupled nanoparticles to antibodies that target other highly expressed proteins in neurons. They chose two antibodies that bind the ion channels TRPV1 and P2X3. Similar to Ts1, neurons treated with these antibody-coupled nanoparticles were activated by light even after continuous washing.
That nanoparticles can be coupled to different antibodies and retain efficacy suggests flexibility for future applications, including human therapeutic development. In retinal diseases such as age-related macular degeneration, for example, photoreceptor cells that absorb light signals are damaged or dead.
However, the retinal nerve cells that carry visual information to the brain often remain intact and healthy. Nanoparticles targeted to these cells could potentially absorb light and directly stimulate the neurons, bypassing defective photoreceptors, according to the authors.
“While much additional research must be done to determine the feasibility of this nanoparticle approach as a vision restoration therapy, our results encourage further effort aimed at achieving this critical clinical objective,” said study co-author David Pepperberg, PhD, Searls-Schenk Professor of ophthalmology and visual sciences at UIC.
Although no harmful effects were observed, the team notes that toxicity is a possibility. However, many live-animal tests and human clinical trials have already been completed using formulations of gold nanoparticles without serious side effects. The researchers are now testing the efficacy of the technique in animal models to verify its potential for therapeutic use.
Abstract of Photosensitivity of Neurons Enabled by Cell-Targeted Gold Nanoparticles
Unmodified neurons can be directly stimulated with light to produce action potentials, but such techniques have lacked localization of the delivered light energy. Here we show that gold nanoparticles can be conjugated to high-avidity ligands for a variety of cellular targets. Once bound to a neuron, these particles transduce millisecond pulses of light into heat, which changes membrane capacitance, depolarizing the cell and eliciting action potentials. Compared to non-functionalized nanoparticles, ligand-conjugated nanoparticles highly resist convective washout and enable photothermal stimulation with lower delivered energy and resulting temperature increase. Ligands targeting three different membrane proteins were tested; all showed similar activity and washout resistance. This suggests that many types of ligands can be bound to nanoparticles, preserving ligand and nanoparticle function, and that many different cell phenotypes can be targeted by appropriate choice of ligand. The findings have applications as an alternative to optogenetics and potentially for therapies involving neuronal photostimulation.
Harvard scientists have demonstrated a new way to detect and extract biomolecules from fluid mixtures, using an ingenious microfluidic design combining chemical and mechanical properties.
The approach requires fewer steps, uses less energy, and achieves better performance than several techniques currently in use. It could lead to better technologies for medical diagnostics and chemical purification.
For example, it could provide a means of removing contaminants from water, and even be tailored to enable energy-efficient desalination of seawater, the researchers say. It could also be used to capture valuable minerals from fluid mixtures.
The biomolecule sorting technique was developed in the laboratory of Joanna Aizenberg, Amy Smith Berylson Professor of Materials Science at Harvard School of Engineering and Applied Sciences (SEAS) and Professor in the Department of Chemistry and Chemical Biology.
How it works
The new microfluidic device, described in a paper appearing Monday March 23 in the journal Nature Chemistry, is composed of microscopic “fins” embedded in a hydrogel that is able to respond to different stimuli, such as temperature, pH, and light.
Special DNA strands called aptamers, that under the right conditions bind to a specific target molecule, are attached to the fins, which move the cargo between two chemically distinct environments. Modulating the pH levels of the solutions in those environments triggers the aptamers to “catch” or “release” the target biomolecule.
After using computer simulations to test their novel approach, in collaboration with Prof. Anna C. Balazs from the University of Pittsburgh, Aizenberg’s team conducted proof-of-concept experiments in which they successfully separated thrombin, an enzyme in blood plasma that causes the clotting of blood, from several mixtures of proteins.
Their research suggests that the technique could be applicable to other biomolecules, or used to determine chemical purity and other characteristics in inorganic and synthetic chemistry.
“Our adaptive hybrid sorting system presents an efficient chemo-mechanical transductor, capable of highly selective separation of a target species from a complex mixture — all without destructive chemical modifications and high-energy inputs,” Aizenberg said. “This new approach holds promise for next-generation, energy-efficient separation and purification technologies and medical diagnostics.”
Tunable, repeatable, reusable
The system is dynamic; its integrated components are highly tunable. For example, the chemistry of the hydrogel can be modified to respond to changes in temperature, light, electric and magnetic fields, and ionic concentration. Aptamers, meanwhile, can target a range of proteins and molecules in response to variations in pH levels, temperature, and salt.
“The system allows repeated processing of a single input solution, which enables multiple recycling and a high rate of capture of the target molecules,” said lead author Ximin He, Assistant Professor of Materials Science and Engineering at Arizona State University and formerly a postdoctoral research fellow in Aizenberg’s group at Harvard.
Conventional biomolecule sorting systems rely on external electric fields, infrared radiation, and magnetic fields, and often require chemical modifications of the biomolecules of interest. That means setups can be used only once or require a series of sequential steps.
Aizenberg is also co-director of the Kavli Institute for Bionano Science and Technology and a core faculty member at Harvard’s Wyss Institute for Biologically Inspired Engineering, leading the Adaptive Materials Technologies platform there.
Other contributors to the work include researchers from the University of Pittsburgh, Arizona State University, and the Wyss Institute. The research was supported by the U.S. Department of Energy.
Abstract of An aptamer-functionalized chemomechanically modulated biomolecule catch-and-release system
The efficient extraction of (bio)molecules from fluid mixtures is vital for applications ranging from target characterization in (bio)chemistry to environmental analysis and biomedical diagnostics. Inspired by biological processes that seamlessly synchronize the capture, transport and release of biomolecules, we designed a robust chemomechanical sorting system capable of the concerted catch and release of target biomolecules from a solution mixture. The hybrid system is composed of target-specific, reversible binding sites attached to microscopic fins embedded in a responsive hydrogel that moves the cargo between two chemically distinct environments. To demonstrate the utility of the system, we focus on the effective separation of thrombin by synchronizing the pH-dependent binding strength of a thrombin-specific aptamer with volume changes of the pH-responsive hydrogel in a biphasic microfluidic regime, and show a non-destructive separation that has a quantitative sorting efficiency, as well as the system’s stability and amenability to multiple solution recycling.
UT Southwestern Medical Center neuroscientists have identified key cells in the brain that control 24-hour circadian rhythms (sleep and wake cycles) as well as functions such as hormone production, metabolism, and blood pressure.
The discovery may lead to future treatments for jet lag and other sleep disorders and even for neurological problems such as Alzheimer’s disease, as well as metabolism issues and psychiatric disorders such as depression.
It’s been known since 2001 that circadian rhythms are generated within a specific area of the brain called the suprachiasmatic nucleus (SCN), a tiny region located in the hypothalamus. But that region contains about 20,000 neurons that secrete more than 100 identified neurotransmitters, neuropeptides, cytokines, and growth factors, so researchers have not been able to pinpoint which neurons control circadian rhythms.
Neuromedin S: master controller of circadian rhythms
Now UT Southwestern neuroscientists report in the journal Neuron that they have found “a group of SCN neurons that express a neuropeptide called neuromedin S (NMS) is both necessary and sufficient for the control of circadian rhythms,” according to Dr. Joseph Takahashi*, Chairman of Neuroscience and Howard Hughes Medical Institute (HHMI) Investigator at UT Southwestern, who holds the Loyd B. Sands Distinguished Chair in Neuroscience.
NMS is a neuropeptide — a protein made of amino acids that neurons use to communicate. The researchers found in a mouse study that modulating the internal clock in just the NMS neurons altered the circadian period throughout the whole animal. The study also provided new insights into the mechanisms by which light synchronizes body clock rhythms.
“This study marks a significant advancement in our understanding of the body clock” said senior author Dr. Masashi Yanagisawa**, Adjunct Professor of Molecular Genetics, former HHMI Investigator at UT Southwestern, and current Director of the World Premier International Institute for Integrative Sleep Medicine at the University of Tsukuba in Japan.
The research was supported by the National Institute of Health and the Howard Hughes Medical Institute.
Overexposure to artificial light: don’t use TV, iPads and e-readers before sleeping
So what’s causing these neuropeptide changes? Scientists have found that modern life — a cycle of inadequate exposure to natural light during the day and overexposure to artificial light at night — can mess with the body’s natural sleep pattern.
The solution may be to change our lighting, says University of Connecticut Health cancer epidemiologist Richard Stevens, who has been studying the effects of artificial lighting on human health for three decades.
“It’s become clear that typical lighting is affecting our physiology,” Stevens says. “We’re learning that better lighting can reduce these physiological effects.
“By that we mean dimmer and longer wavelengths [yellow, orange, red] in the evening, and avoiding the bright blue of e-readers, tablets, and smart phones.”
Stevens and co-author Yong Zhu from Yale University explain this in an open-access paper published in the British journal Philosophical Transactions of the Royal Society B.
The paper summarizes what we know up to now on the effect of lighting on our health, Stevens says. While short-term effects can be seen in [disrupted] sleep patterns, “there’s growing evidence that the long-term implications of this have ties to obesity, diabetes, depression, breast cancer, and possibly other cancers.”
The major culprit is electronic devices, which emit enough blue light when used in the evening to suppress the sleep-inducing hormone melatonin and disrupt the body’s circadian rhythm.
(Blue light wakes us up in the morning, and reddish light, such as in a sunset, puts us to sleep.)
A recent study comparing people who used e-readers to those who read old-fashioned books in the evening showed a clear difference: those using e-readers showed delayed melatonin onset, Stevens said.
“It’s about how much light you’re getting in the evening,” Stevens says. “It doesn’t mean you have to turn all the lights off at eight o’clock every night, it just means if you have a choice between an e-reader and a book, the book is less disruptive to your body clock. At night, the better, more circadian-friendly light is dimmer and … redder, like an incandescent bulb.”
Stevens was on the scientific panel whose work led to the classification of shift work as a “probable carcinogen” by the International Agency on Cancer Research in 2007.
* Takahashi previously identified and cloned the first mammalian gene — called Clock—related to circadian rhythms. Since then, the Takahashi lab has determined that disruptions in the Clock and Bmal1 genes in mice can alter the release of insulin by the pancreas, resulting in diabetes, and they determined the 3-D structure of the CLOCK-BMAL1 protein complex, which are considered to be the batteries of the biological clock.
** Yanagisawa first identified the important role that endothelin plays on the cardiovascular system, and later, with his discovery of orexin, showed that sleep/wakefulness is controlled by a single neuropeptide. His lab has since identified numerous receptors involved in the regulation of appetite and blood pressure, as well as other neuropeptides that play an important role in the regulation of energy metabolism, stress responses, emotions, and other functions.
Abstract of Neuromedin S-Producing Neurons Act as Essential Pacemakers in the Suprachiasmatic Nucleus to Couple Clock Neurons and Dictate Circadian Rhythms
Circadian behavior in mammals is orchestrated by neurons within the suprachiasmatic nucleus (SCN), yet the neuronal population necessary for the generation of timekeeping remains unknown. We show that a subset of SCN neurons expressing the neuropeptide neuromedin S (NMS) plays an essential role in the generation of daily rhythms in behavior. We demonstrate that lengthening period within Nms neurons is sufficient to lengthen period of the SCN and behavioral circadian rhythms. Conversely, mice without a functional molecular clock within Nms neurons lack synchronous molecular oscillations and coherent behavioral daily rhythms. Interestingly, we found that mice lacking Nms and its closely related paralog, Nmu, do not lose in vivo circadian rhythms. However, blocking vesicular transmission from Nms neurons with intact cell-autonomous clocks disrupts the timing mechanisms of the SCN, revealing that Nms neurons define a subpopulation of pacemakers that control SCN network synchrony and in vivo circadian rhythms through intercellular synaptic transmission.
Abstract of Electric light, particularly at night, disrupts human circadian rhythmicity: Is that a problem?
Over the past 3 billion years, an endogenous circadian rhythmicity has developed in almost all life forms in which daily oscillations in physiology occur. This allows for anticipation of sunrise and sunset. This physiological rhythmicity is kept at precisely 24 h by the daily cycle of sunlight and dark. However, since the introduction of electric lighting, there has been inadequate light during the day inside buildings for a robust resetting of the human endogenous circadian rhythmicity, and too much light at night for a true dark to be detected; this results in circadian disruption and alters sleep/wake cycle, core body temperature, hormone regulation and release, and patterns of gene expression throughout the body. The question is the extent to which circadian disruption compromises human health, and can account for a portion of the modern pandemics of breast and prostate cancers, obesity, diabetes and depression. As societies modernize (i.e. electrify) these conditions increase in prevalence. There are a number of promising leads on putative mechanisms, and epidemiological findings supporting an aetiologic role for electric lighting in disease causation. These include melatonin suppression, circadian gene expression, and connection of circadian rhythmicity to metabolism in part affected by haem iron intake and distribution.
As NASA astronaut Scott Kelly launches for the International Space Station Friday, March 27, Northwestern University scientists will be watching with more than a passing interest. Scott Kelly is half of their experiment.
A Northwestern-led research team is one of 10 NASA-funded groups across the country studying identical twins Scott and Mark Kelly to learn how living in space for a long period of time — such as a mission to Mars — affects the human body. While Scott spends a year in space, his brother, Mark, also a veteran NASA astronaut, will remain on Earth, as a ground-based control.
“What we really want to know is what is going to happen to the human body with prolonged time in space and after a return to Earth?” said Fred W. Turek, who is leading the study of how the space environment affects the microbiota “ecosystem” in the human gastrointestinal (GI) tract.
Turek is the Charles E. and Emma H. Morrison Professor of Biology in the Weinberg College of Arts and Sciences at Northwestern. His research team includes Northwestern colleague Martha H. Vitaterna and collaborators from Rush University Medical School and the University of Illinois Chicago.
The same interdisciplinary research team also is planning a parallel study in mice. NASA recently selected Turek’s team as one of 16 new life science projects to be carried out onboard the International Space Station at a future time.
Using biological samples collected from the Kelly brothers before, during and after Scott Kelly’s year in space, the researchers will use DNA sequences to identify the microbes inhabiting the gastrointestinal tracts of the twin astronauts.
The study is one of the first to examine how living at zero gravity for a year affects a human’s gut microbiota. The findings will help scientists better understand the role of microbiota in human health and disease.
“Identical twins provide unique advantages,” Vitaterna said. “We can directly compare the space twin with the Earth twin because they are a genetic match. Fred and I are thrilled to be part of this unprecedented research.”
The complex ecological microbiology community that inhabits the human GI tract influences normal physiology and behavior and susceptibility to disease. Despite the clear importance of the GI microbiota for maintaining overall health and influencing disease state, the effects of the spaceflight environment on the human microbiome remains unknown.
“It is imperative that studies be carried out on long-term missions in space so that any adverse changes can be identified and countermeasures can be developed to insure the safety and health of our astronauts on extended spaceflight missions, such as to Mars,” Turek said.
In the mouse study, the researchers will study genetically identical mice in space and on Earth. They will examine the effects of long-term spaceflight on hundreds of different microbes in the animals’ gastrointestinal tract as well as the impact of any microbiota changes on physiology and behavior. Ground-based experiments will complement those carried out onboard the International Space Station.
This study will allow the researchers to look at physiological systems they are not investigating in the study of the Kelly twins.
“The results of these studies are going to give us some surprises but ultimately they will teach us how to keep a healthy microbiota and, therefore, a healthy human,” Vitaterna said. She is director of Northwestern’s Sleep, Circadian and Other Rhythm Experiments (SCORE) Core research facility.
Turek and Vitaterna are faculty members in Weinberg’s department of neurobiology and the Center for Sleep and Circadian Biology. Turek also has appointments in the departments of neurology and psychiatry in the Northwestern University Feinberg School of Medicine.
Completing the research team are Chicago-area colleagues Dr. Ali Keshavarzian and Christopher Forsyth of Rush University Medical School and Stefan Green of the University of Illinois Chicago. This team previously published findings on the effects of “jet lag” on microbiota in mice.
Astronomers have expanded the search for extraterrestrial intelligence into a new realm with detectors tuned to infrared light.
The idea was first proposed by Charles Townes, the late UC Berkeley scientist whose contributions to the development of lasers led to a Nobel Prize, in a paper  published in 1961.
Pulses from a powerful near-infrared laser could outshine a star, if only for a billionth of a second. Interstellar gas and dust is almost transparent to near-infrared, so these signals can be seen from greater distances. It also takes less energy to send the same amount of information using infrared signals than it would with visible light.
Scientists have searched for radio signals for more than 50 years and expanded their search to the optical realm more than a decade ago. But instruments capable of capturing pulses of infrared light have only recently become available.
“We had to wait for technology to catch up,” said Shelley Wright, an Assistant Professor of Physics at the University of California, San Diego who led the development of the new instrument while at the University of Toronto’s Dunlap Institute for Astronomy & Astrophysics.
The new instrument, called NIROSETI (near-infrared optical SETI), will also gather more information than previous optical detectors by recording levels of light over time so that patterns can be analyzed to for potential signs of other civilizations.
NIROSETI has been installed at the University of California’s Lick Observatory on Mt. Hamilton east of San Jose and saw first light on March 15. Lick Observatory has been the site of several previous SETI searches, including an instrument to look in the optical realm, which Wright built as an undergraduate student at UC Santa Cruz.
Near-infrared dramatically extends search for ET
Because near-infrared light penetrates farther through gas and dust than visible light, this new search will extend to stars thousands rather than merely hundreds of light years away.
Also, the success of the Kepler Mission, which has found habitable planets orbiting stars both like and unlike our own, has prompted the new search to look for signals from a wider variety of stars. Last week, researchers from the Australian National University and the Niels Bohr Institute in Copenhagen announced that new calculations show that billions of the stars in the Milky Way will have one to three planets in the habitable zone (where there is the potential for liquid water and thus where life could exist).
NIROSETI could uncover new information about the physical universe as well. “This is the first time Earthlings have looked at the universe at infrared wavelengths with nanosecond time scales,” said SETI scientist and optical SETI pioneer Dan Werthimer of UC Berkeley, a key NIROSETI researcher. “The instrument could discover new astrophysical phenomena, or perhaps answer the question of whether we are alone.”
The group also includes famed SETI pioneer Frank Drake of the SETI Institute and UC Santa Cruz, who serves as a senior advisor to both past and future projects and is an active observer at the telescope.
Drake pointed out several additional advantages to a search in this new realm. “The signals are so strong that we only need a small telescope to receive them. Smaller telescopes can offer more observational time, and that is good because we need to search many stars for a chance of success.” he said. The receivers are also much more affordable that those used on radio telescopes.
“There is only one downside: the extraterrestrials would need to be transmitting their signals in our direction,” Drake said, though he sees a positive side to that limitation. “If we get a signal from someone who’s aiming for us, it could mean there’s altruism in the universe. I like that idea. If they want to be friendly, that’s who we will find.”
Or perhaps it could mean there’s someone out there looking to harm us, as Stephen Hawking has warned.
Funding for the project is from Bill and Susan Bloomfield.
How NIROSETI works
The search for extraterrestrial signals (SETI) began in 1960, when Frank Drake searched for microwave radio waves at a microwave “waterhole” frequency of 1,420 MHz (21 cm). In 1997, Werthimer’s group at UC Berkeley extended the search, testing the first pulsed multiple detector system in the optical (light) domain and launching “optical SETI” (OSETI).
NIROSETI has now taken the next step. NIROSETI is a telescope designed to detect pulsed laser signals emitted at specific near-infrared wavelengths (900 to 1700 nm, longer than visible light). The assumption is that a distant civilization could signal its existence by transmitting a code consisting of two or more extremely short laser pulses in a period less than .5 nanosecond and at extremely high power (enough to exceed the light emitted from their sun for that very brief period of time to rule out the sun as a source).
The NIROSETI project is described in detail in the journal SPIE Proceedings  and in an open-access arXiv version  of the paper.
Abstract of A near-infrared SETI experiment: probability distribution of false coincidences
A Search for Extraterrestrial Life (SETI), based on the possibility of interstellar communication via laser signals, is being designed to extend the search into the near-infrared spectral region (Wright et al, this conference). The dedicated near-infrared (900 to 1700 nm) instrument takes advantage of a new generation of avalanche photodiodes (APD), based on internal discrete amplification. These discrete APD (DAPD) detectors have a high speed response (< 1 GHz) and gain comparable to photomultiplier tubes, while also achieving significantly lower noise than previous APDs. We are investigating the use of DAPD detectors in this new astronomical instrument for a SETI search and transient source observations. We investigated experimentally the advantages of using a multiple detector device operating in parallel to remove spurious signals. We present the detector characterization and performance of the instrument in terms of false positive detection rates both theoretically and empirically through lab measurements. We discuss the required criteria that will be needed for laser light pulse detection in our experiment. These criteria are defined to optimize the trade between high detection efficiency and low false positive coincident signals, which can be produced by detector dark noise, background light, cosmic rays, and astronomical sources. We investigate experimentally how false coincidence rates depend on the number of detectors in parallel, and on the signal pulse height and width. We also look into the corresponding threshold to each of the signals to optimize the sensitivity while also reducing the false coincidence rates. Lastly, we discuss the analytical solution used to predict the probability of laser pulse detection with multiple detectors.
Augmented reality start-up Magic Leap has released a mind-boggling video that dramatically dissolves the boundary between real and virtual. In the video, we look from the user’s POV as he manipulates virtual objects — such as a monitor playing a YouTube video and a rolodex — in the air with his fingers, Minority Report-style. He then picks up a real toy ray gun and plays a shooter video game, zapping virtual robots projected onto the real world.
It’s unclear whether the video is actual footage from an unannounced future augmented-reality product or a concept demo. But Magic Leap raised $542 million funding last October from investors led by Google, so we can probably expect some form of augmented magic soon.
They also found that manipulating these signals can repair genetic defects and induce development of healthy brain tissue in locations where it would not ordinarily grow.
In their research with Xenopus laevis frog embryos (which share many evolutionary traits with humans), they found that bioelectric signaling regulates the activity of two cell reprogramming factors (proteins that can turn adult cells into stem cells).
Their results appear in the March 11, 2015 edition of The Journal of Neuroscience.
How cells use bioelectrical signals to communicate and control
“We’ve found that cells communicate, even across long distances in the embryo, using bioelectrical signals, and they use this information to know where to form a brain and how big that brain should be,” says the paper’s corresponding author Michael Levin, Ph.D., who holds the Vannevar Bush Chair in biology and directs the Center for Regenerative and Developmental Biology in the School of Arts and Sciences at Tufts University. “The signals are not just necessary for normal development; they are instructive.”
The research expands on previous work by Levin at Tufts, in which biologists were able to cause tissue to grow a new organ by simply altering the membrane voltage gradients of cells, causing tadpoles to grow eyes outside of the head area, as KurzweilAI reported in 2011.
But the concept actually dates back to 1932, when Dr. Harold S. Burr, Professor Emeritus, Anatomy at Yale University School of Medicine, found that electrical gradients across tissue can direct growth and form of organisms. He later discovered in 1937 that abnormal growth (such as cancer) was preceded by the appearance of abnormal voltage gradients in an organ.
These bioelectric signals are implemented by changes in the voltage difference across cell membranes — called the cellular resting potential — and the differential voltage (different voltage level) across anatomical regions.
Bioelectric signaling involves different cell types, including mature somatic cells and stem cells.
Overriding Genetic Defects
“This latest research also demonstrated molecular techniques for ‘hijacking’ this bioelectric communication to force the body to make new brain tissue at other locations and to fix genetic defects that cause brain malformation,” says Levin. “This means we may be able to induce growth of new brain tissue to address birth defects or brain injury, which is very exciting for regenerative medicine.”
A case in point is the Notch signaling pathway, a protein signaling system that plays a role in neural cell growth and differentiation in mammals and most other multicellular organisms. Defects in Notch signaling disrupt brain development and are also associated with disorders such as T-cell acute lymphoblastic leukemia and multiple sclerosis.
The research team found that using molecular techniques to force proper bioelectrical states in cells enabled them to override the defects induced by Notch malfunction, resulting in a much more normal brain despite a genetically defective Notch protein.
Bioelectricity and reprogramming factors work together to regulate tissue fate, says Levin. “Additional study is needed to understand more fully the mechanisms by which electric signaling interacts with genetic networks. However, here we show two such steps, involving calcium signaling and cell-cell communication via electrical synapses known as gap junctions.
“We are working on applying these techniques in biomedical contexts, especially ion channel modulating drugs — electroceuticals — to repair defects and induce brain regeneration.”
The research was supported by the National Institutes of Health, the National Science Foundation, and the G. Harold and Leila Y. Mathers Charitable Foundation.
Abstract of Endogenous Gradients of Resting Potential Instructively Pattern Embryonic Neural Tissue via Notch Signaling and Regulation of Proliferation
Biophysical forces play important roles throughout embryogenesis, but the roles of spatial differences in cellular resting potentials during large-scale brain morphogenesis remain unknown. Here, we implicate endogenous bioelectricity as an instructive factor during brain patterning in Xenopus laevis. Early frog embryos exhibit a characteristic hyperpolarization of cells lining the neural tube; disruption of this spatial gradient of the transmembrane potential (Vmem) diminishes or eliminates the expression of early brain markers, and causes anatomical mispatterning of the brain, including absent or malformed regions. This effect is mediated by voltage-gated calcium signaling and gap-junctional communication. In addition to cell-autonomous effects, we show that hyperpolarization of transmembrane potential (Vmem) in ventral cells outside the brain induces upregulation of neural cell proliferation at long range. Misexpression of the constitutively active form of Notch, a suppressor of neural induction, impairs the normal hyperpolarization pattern and neural patterning; forced hyperpolarization by misexpression of specific ion channels rescues brain defects induced by activated Notch signaling. Strikingly, hyperpolarizing posterior or ventral cells induces the production of ectopic neural tissue considerably outside the neural field. The hyperpolarization signal also synergizes with canonical reprogramming factors (POU and HB4), directing undifferentiated cells toward neural fate in vivo. These data identify a new functional role for bioelectric signaling in brain patterning, reveal interactions between Vmem and key biochemical pathways (Notch and Ca2+ signaling) as the molecular mechanism by which spatial differences of Vmem regulate organogenesis of the vertebrate brain, and suggest voltage modulation as a tractable strategy for intervention in certain classes of birth defects.
A new diet known by the acronym MIND (Mediterranean-DASH Intervention for Neurodegenerative Delay) could significantly lower a person’s risk of developing Alzheimer’s disease (AD) — even if the diet is not meticulously followed, according to a paper published in the journal Alzheimer’s & Dementia: The Journal of the Alzheimer’s Association.
This finding comes from a longitudinal study by Rush University Medical Center and Harvard School of Public Health of 923 volunteers (144 of them developed AD) shows that the MIND diet lowered the risk of AD by as much as 53 percent in participants who adhered to the diet rigorously, and by about 35 percent in those who followed it moderately well.
Developed by nutritional epidemiologist Martha Clare Morris, PhD, and colleagues at Rush University Medical Center in Chicago, the MIND diet is a hybrid of the Mediterranean and DASH (Dietary Approaches to Stop Hypertension) diets, both of which have been found to reduce the risk of cardiovascular conditions, like hypertension, heart attack, and stroke. Some researchers have found that these two older diets provide protection against dementia as well.
Morris and her colleagues developed the MIND diet based on information that has accrued from years’ worth of past research about what foods and nutrients have good, and bad, effects on the functioning of the brain over time. This is the first study to relate the MIND diet to Alzheimer’s disease.
Easier to follow than the Mediterranean diet
In the latest study, the MIND diet was compared with the two earlier diets. People with high adherence to the DASH and Mediterranean diets also had reductions in AD — 39 percent with the DASH diet and 54 percent with the Mediterranean diet — but got negligible benefits from moderate adherence to either of the two other diets.
The MIND diet is also easier to follow than, say, the Mediterranean diet, which calls for daily consumption of fish and three to four daily servings of each of fruits and vegetables, Morris said.
The MIND diet has 15 dietary components, including 10 “brain-healthy food groups” — green leafy vegetables, other vegetables, nuts, berries, beans, whole grains, fish, poultry, olive oil and wine — and (because it was tracking what people actually eat, rather than what they should) five unhealthy groups that comprise red meats, butter and stick margarine, cheese, pastries and sweets, and fried or fast food.
The MIND diet includes at least three servings of whole grains, a salad and one other vegetable every day — along with a glass of wine. It also involves snacking most days on nuts and eating beans every other day or so, poultry and berries at least twice a week and fish at least once a week. Dieters must limit eating the designated unhealthy foods, especially butter (less than 1 tablespoon a day), cheese, and fried or fast food (less than a serving a week for any of the three), to have a real shot at avoiding the devastating effects of Alzheimer’s, according to the study.
Berries are the only fruit specifically to make the MIND diet. “Blueberries are one of the more potent foods in terms of protecting the brain,” Morris said, and strawberries have also performed well in past studies of the effect of food on cognitive function.
Participants in study were assigned points if they ate brain-healthy foods frequently and avoided unhealthy foods. The one exception was that participants got one point if they said olive oil was the primary oil used in their homes.
The study enlisted volunteers already participating in the ongoing Rush Memory and Aging Project (MAP), which began in 1997 among residents of Chicago-area retirement communities and senior public housing complexes. An optional “food frequency questionnaire” was added from 2004 to February 2013.
Food more important than genetic risk factors
“With late-onset AD, with that older group of people, genetic risk factors are a small piece of the picture,” she said. Past studies have yielded evidence that suggests that what we eat may play a significant role in determining who gets AD and who doesn’t, Morris said.
When the researchers in the new study left out of the analyses those participants who changed their diets somewhere along the line — say, on a doctor’s orders after a stroke — they found that “the association became stronger between the MIND diet and [favorable] outcomes” in terms of AD, Morris said. “That probably means that people who eat this diet consistently over the years get the best protection.”
In other words, it looks like the longer a person eats the MIND diet, the less risk that person will have of developing AD, Morris said. As is the case with many health-related habits, including physical exercise, she said, “You’ll be healthier if you’ve been doing the right thing for a long time.”
Morris said, “We devised a diet and it worked in this Chicago study. The results need to be confirmed by other investigators in different populations and also through randomized trials.” That is the best way to establish a cause-and-effect relationship between the MIND diet and reductions in the incidence of Alzheimer’s disease, she said.
The study was funded by the National Institute on Aging.
Abstract of MIND diet associated with reduced incidence of Alzheimer’s disease
Background: In a previous study, higher concordance to the MIND diet, a hybrid Mediterranean- Dietary Approaches to Stop Hypertension diet, was associated with slower cognitive decline. In this study we related these three dietary patterns to incident Alzheimer’s disease (AD).
Methods: We investigated the diet-AD relations in a prospective study of 923 participants, ages 58 to 98 years, followed on average 4.5 years. Diet was assessed by a semiquantitative food frequency questionnaire.
Results: In adjusted proportional hazards models, the second (hazards ratio or HR 5 0.65, 95% confidence interval or CI 0.44, 0.98) and highest tertiles (HR 5 0.47, 95% CI 0.26, 0.76) of MIND diet scores had lower rates of AD versus tertile 1, whereas only the third tertiles of the DASH (HR 5 0.61, 95% CI 0.38, 0.97) and Mediterranean (HR 5 0.46, 95% CI 0.26, 0.79) diets were associated with lower AD rates.
Conclusion: High adherence to all three diets may reduce AD risk. Moderate adherence to the MIND diet may also decrease AD risk.
A software update will give Tesla Model S cars the ability to start driving themselves in “autopilot” mode on “major roads” like highways this summer, Tesla Motors chief executive Elon Musk announced today (March 19).
He also said Tesla had been testing its autopilot mode on a route from San Francisco to Seattle, largely unassisted, and that the cars will be able to park themselves in a private garage and be summoned by smart phone.
Via Verge Video/Jalopnik/Bureau Oberhaeuser: Riding in the insane Tesla Model S
Taking it a step further, Musk predicted at NVidia’s annual developers conference on Tuesday (March 17) that humans driving cars will eventually be outlawed. “It’s too dangerous,” he said. “You can’t have a person driving a two-ton death machine.” But he admitted that “the hardest part of helping cars drive themselves is what happens when vehicles are traveling between 15 and 50 miles per hour.”
Automatic downloaded car software updates
Other updates announced today were Automatic Emergency Braking (will engage in the event of an unavoidable collision in order to reduce risk of impact), Blind Spot Warning (alerts you when drivers behind you are dangerously close), Side Collision Warning, and Valet Mode (limits its speed, locking the glove box and trunk and hiding personal information). In addition, the software will update the audio system sound quality, improved radio tuning, and refined active cruise control. Other luxury cars have most of these features, but updates are not possible.
“We really designed the Model S to be a very sophisticated computer on wheels,” Musk said.
“With Tesla’s regular over-the-air software updates, Model S actually improves while you sleep, the Tesla blog explains. “When you wake up, added functionality, enhanced performance, and improved user experience make you feel like you are driving a new car.”
The software update also includes two apps to eliminate “range anxiety.” The Range Assurance app scans the Tesla charging network and routes drivers to the best one, and Trip Planner integrates the best charging options into a route.
“Tesla is a software company as much as it is a hardware company. … We view this the same as updating your phone or your laptop,” Musk said.