Duncan G.J.,The University of California |
Magnuson K.,University of Wisconsin - Madison |
Votruba-Drzal E.,University of Pittsburgh
Future of Children | Year: 2014
Families who live in poverty face disadvantages that can hinder their children's development in many ways, write Greg Duncan, Katherine Magnuson, and Elizabeth Votruba-Drzal. As they struggle to get by economically, and as they cope with substandard housing, unsafe neighborhoods, and inadequate schools, poor families experience more stress in their daily lives than more affluent families do, with a host of psychological and developmental consequences. Poor families also lack the resources to invest in things like high-quality child care and enriched learning experiences that give more affluent children a leg up. Often, poor parents also lack the time that wealthier parents have to invest in their children, because poor parents are more likely to be raising children alone or to work nonstandard hours and have inflexible work schedules. Can increasing poor parents' incomes, independent of any other sort of assistance, help their children succeed in school and in life? The theoretical case is strong, and Duncan, Magnuson, and Votruba-Drzal find solid evidence that the answer is yes-children from poor families that see a boost in income do better in school and complete more years of schooling, for example. But if boosting poor parents' incomes can help their children, a crucial question remains: Does it matter when in a child's life the additional income appears? Developmental neurobiology strongly suggests that increased income should have the greatest effect during children's early years, when their brains and other systems are developing rapidly, though we need more evidence to prove this conclusively. The authors offer examples of how policy makers could incorporate the findings they present to create more effective programs for families living in poverty. And they conclude with a warning: if a boost in income can help poor children, then a drop in income-for example, through cuts to social safety net programs like food stamps-can surely harm them.
Home > Press > Seeing the big picture in photosynthetic light harvesting: Berkeley Lab researchers create first multiple antennae model of photosystem II Abstract: To understand what goes on inside a beehive you can't just study the activity of a single bee. Likewise, to understand the photosynthetic light-harvesting that takes place inside the chloroplast of a leaf, you can't just study the activity of a single antenna protein. Researchers with the U.S. Department of Energy (DOE)'s Lawrence Berkeley National Laboratory and the University of California (UC) Berkeley have created the first computational model that simulates the light-harvesting activity of the thousands of antenna proteins that would be interacting in the chloroplast of an actual leaf. The results from this model point the way to improving the yields of food and fuel crops, and developing artificial photosynthesis technologies for next generation solar energy systems. The new model simulates light-harvesting across several hundred nanometers of a thylakoid membrane, which is the membrane within a chloroplast that harbors photosystem II (PSII), a complex of antennae made up of mostly of chlorophyll-containing proteins. The antennae in PSII gain "excitation" energy when they absorb sunlight and, through quantum mechanical effects, almost instantaneously transport this extra energy to reaction centers for conversion into chemical energy. Previous models of PSII simulated energy transport within a single antenna protein. "Our model, which looked at some 10,000 proteins containing about 100,000 chlorophyll molecules, is the first to simulate a region of the PSII membrane large enough to represent behavior in a chloroplast while respecting and using both the quantum dynamics and the spatial structure of the membrane's components," says chemist Graham Fleming, who oversaw the development of this model. Fleming is a world authority on the quantum dynamics of photosynthesis. He holds appointments with Berkeley Lab, the University of California (UC) Berkeley, and the Kavli Energy NanoScience Institute at Berkeley. "We use insights from structural biology, advanced spectroscopy and theory to reproduce observed phenomena spanning from one nanometer to hundreds of nanometers, and from ten femtoseconds to one nanosecond," Fleming says. "This enables us to explain the mechanisms underlying the high quantum efficiency of PSII light harvesting in ideal conditions for the first time." Fleming is the corresponding author of a paper describing this research in the Proceedings of the National Academy of Sciences. The paper is titled "Multiscale model of photosystem II light harvesting in the thylakoid membrane of plants." Co-authors are Kapil Amarnath, Doran Bennett and Anna Schneider. The ability of green plants to thrive in sunlight stems in part from the flexibility that PSII displays in harvesting solar energy. At low levels of light, through quantum processes that have been modeled by Fleming and coworkers, a photon of sunlight can be utilized for creation of chemical energy with more than 90-percent probability. Thanks to a protective mechanism known as "energy-dependent quenching," PSII is able to ensure that a plant absorbs only the amount of solar energy it needs while excess energy that might damage the plant is safely dissipated. Earlier work by Fleming and his research group revealed a molecular mechanism by which PSII is able to act as a sort of photosynthetic "dimmer switch" to regulate the amount of solar energy transported to the reaction center. However, this work was done for a single PSII antenna and did not reflect how these mechanisms might affect the transport of energy across assemblies of antennae, which in turn would affect the photochemical yield in the reaction centers of a functional thylakoid membrane. "Our new model shows that excitation energy moves diffusively through the antennae with a diffusion length of 50 nanometers until it reaches a reaction center," Fleming says. "The diffusion length of this excitation energy determines PSII's high quantum efficiency in ideal conditions, and how that efficiency is altered by the membrane morphology and the closure of reaction centers. Ultimately, this means that the diffusion length of this excitation energy determines the photosynthetic efficiency of the host plant." Given that the ability of PSII to regulate the amount of solar energy being converted to chemical energy is essential for optimal plant fitness in natural sunlight, understanding this ability and learning to manipulate it is a prerequisite for systematically engineering the light-harvesting apparatus in crops. It should also be highly useful for designing artificial materials with the same flexible properties. "Our next step is to learn now to model a system of PSII's complexity over timescales ranging from femtoseconds to minutes, and lengthscales ranging from nanometers to micrometers," Fleming says. ### This research was supported by the DOE Office of Science. Computational work was carried out at the National Energy Research Scientific Computing Center (NERSC), a DOE Office of Science User Facility hosted at Berkeley Lab. About Berkeley Lab Lawrence Berkeley National Laboratory addresses the world's most urgent scientific challenges by advancing sustainable energy, protecting human health, creating new materials, and revealing the origin and fate of the universe. Founded in 1931, Berkeley Lab's scientific expertise has been recognized with 13 Nobel prizes. The University of California manages Berkeley Lab for the U.S. Department of Energy's Office of Science. For more, visit www.lbl.gov. The DOE Office of Science is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time. For more information, please visit science.energy.gov. For more information, please click If you have a comment, please us. Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.
Home > Press > New form of electron-beam imaging can see elements that are 'invisible' to common methods: Berkeley Lab-pioneered 'MIDI-STEM' produces high-resolution views of lightweight atoms Abstract: Electrons can extend our view of microscopic objects well beyond what's possible with visible light--all the way to the atomic scale. A popular method in electron microscopy for looking at tough, resilient materials in atomic detail is called STEM, or scanning transmission electron microscopy, but the highly-focused beam of electrons used in STEM can also easily destroy delicate samples. This is why using electrons to image biological or other organic compounds, such as chemical mixes that include lithium--a light metal that is a popular element in next-generation battery research--requires a very low electron dose. Scientists at the Department of Energy'sc Lawrence Berkeley National Laboratory (Berkeley Lab) have developed a new imaging technique, tested on samples of nanoscale gold and carbon, that greatly improves images of light elements using fewer electrons. The newly demonstrated technique, dubbed MIDI-STEM, for matched illumination and detector interferometry STEM, combines STEM with an optical device called a phase plate that modifies the alternating peak-to-trough, wave-like properties (called the phase) of the electron beam. This phase plate modifies the electron beam in a way that allows subtle changes in a material to be measured, even revealing materials that would be invisible in traditional STEM imaging. Another electron-based method, which researchers use to determine the detailed structure of delicate, frozen biological samples, is called cryo-electron microscopy, or cryo-EM. While single-particle cryo-EM is a powerful tool--it was named as science journal Nature's 2015 Method of the Year --it typically requires taking an average over many identical samples to be effective. Cryo-EM is generally not useful for studying samples with a mixture of heavy elements (for example, most types of metals) and light elements like oxygen and carbon. "The MIDI-STEM method provides hope for seeing structures with a mixture of heavy and light elements, even when they are bunched closely together," said Colin Ophus, a project scientist at Berkeley Lab's Molecular Foundry and lead author of a study, published Feb. 29 in Nature Communications, that details this method. If you take a heavy-element nanoparticle and add molecules to give it a specific function, conventional techniques don't provide an easy, clear way to see the areas where the nanoparticle and added molecules meet. "How are they aligned? How are they oriented?" Ophus asked. "There are so many questions about these systems, and because there wasn't a way to see them, we couldn't directly answer them." While traditional STEM is effective for "hard" samples that can stand up to intense electron beams, and cryo-EM can image biological samples, "We can do both at once" with the MIDI-STEM technique, said Peter Ercius, a Berkeley Lab staff scientist at the Molecular Foundry and co-author of the study. The phase plate in the MIDI-STEM technique allows a direct measure of the phase of electrons that are weakly scattered as they interact with light elements in the sample. These measurements are then used to construct so-called phase-contrast images of the elements. Without this phase information, the high-resolution images of these elements would not be possible. In this study, the researchers combined phase plate technology with one of the world's highest resolution STEMs, at Berkeley Lab's Molecular Foundry, and a high-speed electron detector. They produced images of samples of crystalline gold nanoparticles, which measured several nanometers across, and the super-thin film of amorphous carbon that the particles sat on. They also performed computer simulations that validated what they saw in the experiment. The phase plate technology was developed as part of a Berkeley Lab Laboratory Directed Research and Development grant in collaboration with Ben McMorran at University of Oregon. The MIDI-STEM technique could prove particularly useful for directly viewing nanoscale objects with a mixture of heavy and light materials, such as some battery and energy-harvesting materials, that are otherwise difficult to view together at atomic resolution. It also might be useful in revealing new details about important two-dimensional proteins, called S-layer proteins, that could serve as foundations for engineered nanostructures but are challenging to study in atomic detail using other techniques. In the future, a faster, more sensitive electron detector could allow researchers to study even more delicate samples at improved resolution by exposing them to fewer electrons per image. "If you can lower the electron dose you can tilt beam-sensitive samples into many orientations and reconstruct the sample in 3-D, like a medical CT scan. There are also data issues that need to be addressed," Ercius said, as faster detectors will generate huge amounts of data. Another goal is to make the technique more "plug-and-play," so it is broadly accessible to other scientists. ### Berkeley Lab's Molecular Foundry is a DOE Office of Science User Facility. Researchers from the University of Oregon, Gatan Inc. and Ulm University in Germany also participated in the study. About Berkeley Lab Lawrence Berkeley National Laboratory addresses the world's most urgent scientific challenges by advancing sustainable energy, protecting human health, creating new materials, and revealing the origin and fate of the universe. Founded in 1931, Berkeley Lab's scientific expertise has been recognized with 13 Nobel prizes. The University of California manages Berkeley Lab for the U.S. Department of Energy's Office of Science. For more, visit www.lbl.gov. The DOE Office of Science is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time. For more information, please visit science.energy.gov. For more information, please click If you have a comment, please us. Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.
Home > Press > Scientists push valleytronics 1 step closer to reality: Berkeley Lab and UC Berkeley researchers control a promising new way to encode electrons Abstract: Scientists with the U.S. Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab) have taken a big step toward the practical application of "valleytronics," which is a new type of electronics that could lead to faster and more efficient computer logic systems and data storage chips in next-generation devices. As reported online April 4 in the journal Nature Nanotechnology, the scientists experimentally demonstrated, for the first time, the ability to electrically generate and control valley electrons in a two-dimensional semiconductor. Valley electrons are so named because they carry a valley "degree of freedom." This is a new way to harness electrons for information processing that's in addition to utilizing an electron's other degrees of freedom, which are quantum spin in spintronic devices and charge in conventional electronics. More specifically, electronic valleys refer to the energy peaks and valleys in electronic bands. A two-dimensional semiconductor called transition metal dichalcogenide (TMDC) has two distinguishable valleys of opposite spin and momentum. Because of this, the material is suitable for valleytronic devices, in which information processing and storage could be carried out by selectively populating one valley or another. However, developing valleytronic devices requires the electrical control over the population of valley electrons, a step that has proven very challenging to achieve so far. Now, Berkeley Lab scientists have experimentally demonstrated the ability to electrically generate and control valley electrons in TMDCs. This is an especially important advance because TMDCs are considered to be more "device ready" than other semiconductors that exhibit valleytronic properties. "This is the first demonstration of electrical excitation and control of valley electrons, which will accelerate the next generation of electronics and information technology," says Xiang Zhang, who led this study and who is the director of Berkeley Lab's Materials Sciences Division. Zhang also holds the Ernest S. Kuh Endowed Chair at the University of California (UC) Berkeley and is a member of the Kavli Energy NanoSciences Institute at Berkeley. Several other scientists contributed to this work, including Yu Ye, Jun Xiao, Hailong Wang, Ziliang Ye, Hanyu Zhu, Mervin Zhao, Yuan Wang, Jianhua Zhao and Xiaobo Yin. Their research could lead to a new type of electronics that utilizes all three degrees of freedom--charge, spin, and valley, which together could encode an electron with eight values of information instead of two in today's electronics. This means future computer chips could process more information with less power, enabling faster and more energy efficient computing technologies. "Valleytronic devices have the potential to transform high-speed data communications and low-power devices," says Ye, a postdoctoral researcher in Zhang's group and the lead author of the paper. The scientists demonstrated their approach by coupling a host ferromagnetic semiconductor with a monolayer of TMDC. Electrical spin injection from the ferromagnetic semiconductor localized the charge carriers to one momentum valley in the TMDC monolayer. Importantly, the scientists were able to electrically excite and confine the charge carriers in only one of two sets of valleys. This was achieved by manipulating the injected carrier's spin polarizations, in which the spin and valley are locked together in the TMDC monolayer. The two sets of valleys emit different circularly polarized light. The scientists observed this circularly polarized light, which confirmed they had successfully electrically induced and controlled valley electrons in TMDC. "Our research solved two main challenges in valleytronic devices. The first is electrically restricting electrons to one momentum valley. The second is detecting the resulting valley-polarized current by circular polarized electroluminescence," says Ye. "Our direct electrical generation and control of valley charge carriers, in TMDC, opens up new dimensions in utilizing both the spin and valley degrees of freedom for next-generation electronics and computing." ### The research was supported by the Office of Naval Research Multidisciplinary University Research Initiative program, the National Science Foundation, China's Ministry of Science and Technology, and the National Science Foundation of China. The paper, "Electrical generation and control of the valley carriers in a monolayer transition metal dichalcogenide" is scheduled for Advance Online Publication on Nature Nanotechnology's website at 11 am ET on April 4 About Lawrence Berkeley National Laboratory Lawrence Berkeley National Laboratory addresses the world's most urgent scientific challenges by advancing sustainable energy, protecting human health, creating new materials, and revealing the origin and fate of the universe. Founded in 1931, Berkeley Lab's scientific expertise has been recognized with 13 Nobel prizes. The University of California manages Berkeley Lab for the U.S. Department of Energy's Office of Science. For more, visit http://www.lbl.gov. DOE's Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit science.energy.gov. For more information, please click If you have a comment, please us. Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.
« Researchers developing solvent-based method for lithium recovery from brine with purity up to 99.9% | Main | Audi summarizes electric driving utilization from 4-year Electric Mobility Showcase; 1.4M km for A1 e-tron and A3 Sportback e-tron » The California Energy Commission approved nearly $9 million in grants for the installation of DC fast chargers along major state freeways and highways to allow electric vehicle drivers to travel from San Diego to the Oregon border without worrying about running out of energy. The grants went to four companies—Chargepoint Inc.; EV Connect Inc.; NRG EV Services LLC; and Recargo, Inc.—which will install 61 DC fast chargers at 41 sites along major routes on Interstate 5, Highway 99 and Highway 101. Fast chargers allow vehicles to fully charge in 20 to 30 minutes. Additionally, 40 sites will have one Level 2 charger, and one site will have two Level 2 chargers. Level 2 chargers allow most vehicles to go from zero to full charge in four to eight hours. Several plug-in electric vehicle charging networks currently operate in metropolitan areas. However, private industry has been hesitant to develop sites along highway corridors. Commissioners also approved an additional $12.6 million in funding to the Natural Gas Vehicle Incentive Project (NGVIP), which offers incentives for the purchase of natural gas vehicles. This funding will help reduce the current wait list as well as fund future applications. The University of California, Irvine, administers the program. Last year the Energy Commission allocated more than $11 million to recipients to purchase natural gas vehicle for use in California for at least three years. These incentives can help fleet managers replace aging gasoline and diesel vehicles with cleaner alternatives. The grants for both the chargers and the natural gas vehicle incentives are funded through the Alternative and Renewable Fuel and Vehicle Technology Program (ARFVTP), which aims to reduce California’s use and dependence on petroleum transportation fuels and increase the use of alternative and renewable fuels and advanced vehicle technologies. Energy Commission also approved funding from the Electric Program Investment Charge (EPIC) Program, which develops, demonstrates, and brings to market technologies and best practices that support California’s energy policy goals. Grants approved include: Incubating technologies. Three grants totaling nearly $15 million will expand incubator-type services and facilities available to clean energy entrepreneurs in the Bay Area, Central Valley, and San Diego regions. The recipients are Physical Science Innovations, Inc., California State University, Fresno Foundation, and Cleantech San Diego Association. Zero net energy. A grant for nearly $3 million will maximize energy efficiency and help achieve zero net energy. The recipient, Prospect Silicon Valley, will fund the demonstration of energy efficiency improvements in a Bay Area grocery store. Environmental and public health impacts of electricity generation. Nine grants totaling more than $6 million will focus on air quality, aquatic resources, terrestrial resources and climate change related to energy generation. Energy efficiency in plug loads. Two grants totaling nearly $2 million will fund research and development projects for the next generation of plug load efficiency technologies and strategies for the building sector. The two recipients are Fisher-Nickel, Inc. and Electric Power Research Institute.